If I have seen further, it is by standing on the shoulders of giants Essay

If I have seen further, it is by standing on the shoulders of giants - Essay Example Leonardo’s father was one of the traders who traded in Bugia; a Mediterranean port found in North Eastern Algeria. He always accompanied his father on his journeys across North Africa, and through travelling, he gained valuable knowledge of the mathematical systems that were popular in the countries they visited. After travelling for fifteen years, he quit his long travels and went back to his hometown (Robertson & O’Connor, www-history.mcs.st-and.ac.uk). While in Pisa, his hometown; Leonardo decided to write books based on his mathematical foundation. Examples of these books include; Liber Abaci, Practica Geometricae, Flos, Liber Quadratorum, among others. Influences from Indian, Arabian and Greek mathematicians can be detected in his methods. Therefore, it is correct to say that Leonardo’s works represents the developments of results he acquired from his predecessors. Leonardo’s published his first work, Liber Abaci (Book of Abacus), in 1202. The Book of Abacus was based on algebra and calculations that he accumulated during his several voyages. The book introduced the use of Arabic numerals and the Hindu-Arabic place value system into Europe: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 (Robertson & O’Connor, www-history.mcs.st-and.ac.uk). Prior to this time, Roman numerals were being used in Europe, and they were extremely awkward for arithmetic. For example, I =1, V=5, X =10, among others. Leonardo also described in Latin the rules being learnt at elementary schools for subtracting, adding, dividing and multiplying numbers. Several arithmetic problems handled in the book were similar to the ones that appeared in the Arab sources. Liber Abaci’s second section contained several mathematical problems faced by merchants. These problems related to the pricing of goods, how profit calculations were to be conducted, how currencies used in the Mediterranean countries were to be converted, and problems that had originated from China. The third section

UAE Culture and Society Research Paper Example | Topics and Well Written Essays - 2500 words - 2

UAE Culture and Society - Research Paper Example trong implications on the culture and social life of people living in a country, during the pre-oil days the culture and economy of United Arab Emirates can be classified as a desert economy marked by Bedouin lifestyle and culture. Farming was very scarce due to unavailability of water and was only done near oasis. Pearling and sea trading were the most important sources of income of the people living in this area of the world in the middle of the 20th century. The various aspects of Arab culture were very prominent in the culture of the United Arab Emirates because of strong bondage with the other countries of the Arab world. In order to analyze the culture of a country, we have to know the location and geography of the country because these things have strong implications on the culture and lifestyle of the people of a country. United Arab Emirates is located on the Persian Gulf and shares borders with Saudi Arabia, Qatar and Oman. The area of the country is distributed among the seven emirates in a very non-uniform way. 85% of the total area of United Arab Emirates falls in Abu Dhabi and Ajman has a size of equal to a small city. Oases are randomly scattered throughout the desert area of United Arab Emirates and mountains of Hajar which run throughout the country also have a barren topography. The overall climate of UAE can be classified as hot and dry in winter and very hot and humid in summer. United Arab Emirates has a very small population and thus the income and resources per capita are very high. The health care conditions, nutrition levels and living conditions were very poor during the pre-oil times, therefore a marked increase in population was observed after the discovery of oil. Better facilities not only resulted in an increase in the population growth rate of the native population, the development of infra structure created a lot of job opportunities and labor class from various countries of Asia moved to United Arab Emirates, resulting in a mild

The Apostle Paul Essay Example for Free

The Apostle Paul Essay This report paper will be on the life of Paul. We will look at many various different facts about this influential man of God. We all know the apostle Paul was used of God in a miraculous way, but this paper will take a behind the scenes look at some areas. I also endeavor to make this paper come alive and reveal things about the apostle Paul that maybe have never been discovered by the average reader and possibly forgotten by the veteran Christian. The Author of Acts First, let me begin by saying that in Acts class we learned the importance of Acts for the local New Testament church today. When the church is of course if we would just be reminded to get back to the book of Acts then we would see many of our church problems disappear in no time at all. Contrary to what many baby Christians believe the Apostle Paul did not write the Book of Acts, but rather we learn that Luke wrote it. This was Luke’s second treatise as it is written. Paul’s Transition The Apostle Paul that we know at the end of his Epistles is not the same as when we first meet him in the Scriptures. The Apostle Paul came a long way from where he was to where he ended up. The Bible tells us that he would persecute the Church passionately and without regard for the Believers. The Apostle Paul was arguably the world’s most influential missionary (obviously not counting the Lord Jesus) to ever walk planet earth. Paul was not always his name but actually he was called Paul only after his conversion. Paul’s first and original name was Saul. Saul was a terror to the church and a modern day widow maker in his heyday. We even see Saul there early on when Stephen the martyr was being slain by his adversaries. We read the account firsthand in Acts the seventh chapter verse fifty-eight the Bible says: Act 7:58 And cast him out of the city, and stoned him: and the witnesses laid down their clothes at a young mans feet, whose name was Saul. Paul’s Childhood Before we get to far ahead in the story let me give a little bit of history of Saul from Tarsus. Saul was born either very close to the same time that Jesus was born or within a few years of His birth. He was born and lived in the city of Tarsus. Tarsus was a roman providence in the southeast of Asia Minor. This undoubtedly was beautiful lush gardens and beautiful scenery for Saul to enjoy growing up. Paul’s Schooling Saul enjoyed great scenery growing up but more importantly because of where he lived he received the best education of that day that money could buy. Saul from an early age was already leaps and bounds ahead of his peers academically. Saul had a sharp mind and we will see he used that later on his ministry, and the writing of Romans which I believe was written by the Apostle Paul. Paul was living the all around Jewish dream people would say as they heard about all he had. Paul’s Family We do not know much about the history and background of Saul’s family. We do however know that his dad was of one of the strictest tribe of the Jews. He was a Pharisee and also of the tribe of Benjamin. He had nothing but pure unmixed non tainted blood in their thinking. Paul’s Religion Act 23:6 But when Paul perceived that the one part were Sadducees, and the other Pharisees, he cried out in the council, Men and brethren, I am a Pharisee, the son of a Pharisee: of the hope and resurrection of the dead I am called in question. His father was a Roman citizen, but we do not read in the Scriptures if the apostle Paul was wed or not. Saul grew up and finished his preliminary studies approximately at the age of thirteen. After this beginning he would gone to a prominent Jewish school to study law. Saul was privileged to have been able to study under the significant rabbi Gamaliel. It was here that he spent an immense amount of time pouring himself into his studies and where he learned many things. Historians tell us that Saul was already gaining political prowess and prestige rapidly ahead of his peers. Many people believe that Saul was already heavily involved in the Sanhedrin. Saul became an extreme activist and zealous about persecuting the church. This was partially ironic because we already know that Saul trained and learned from Gamaliel who taught the exact opposite of that. We see him standing up as one of the council saying: Act 5:34-35 Then stood there up one in the council, a Pharisee, named Gamaliel, a doctor of the law, had in reputation among all the people, and commanded to put the apostles forth a little space; And said unto them, Ye men of Israel, take heed to yourselves what ye intend to do as touching these men. Act 5:38-39 And now I say unto you, Refrain from these men, and let them alone: for if this counsel or this work be of men, it will come to nought: But if it be of God, ye cannot overthrow it; lest haply ye be found even to fight against God. Paul as a Persecutor Now that Saul was intent on persecuting the church he looked for Christians everywhere. Saul was a man that did no task half way. Saul would give everything in life one hundred and ten percent as we see evident all though the study of his life. Saul discovered one way or another that there were Christians in Damascus and so after a discussion with the chief priest he received orders or permission to take care of business. Saul was so dedicated that we see he is willing to make the one hundred and thirty mile trek to persecute the church. The chief priest gave him permission to go to Damascus and bring both men and women bound back to Jerusalem. Paul’s Conversion On this trip to Damascus is where Saul gets confronted with the truth and converted to the truth. The Lord stops him in his tracks and on his path by shining a bright light around him. The Lord asks him a question from Heaven,† Saul, Saul, why persecutest thou me? Saul falls to the ground under the power of the light and asks, â€Å"Who art thou, Lord?† and Jesus replies to him by saying,† I am Jesus whom thou persecutest: it is hard for thee to kick against the pricks. Right away Saul falls under intense conviction was converted and immediately asks the Lord what He would have him to do. On a brief side note this is an incredible testimony to the conversion and character of Saul. He would do everything one hundred percent and never give up until the Lord moved him and we see that every time he goes through a difficult situation (which was quite often) in his ministry. Saul’s name was eventually changed to Paul later on (which is the Gentile name) and he is temporarily blinded by the bright light. He fasts and goes without food or drink for three days. Scholars speculate it was there that he agonized and struggled but returned victoriously. A few days later he received his sight after Ananais put his hands on him and he was baptized. Paul’s Ministry He writes and informs us in Galatians that after his salvation experience he spent some time alone in the desert area of Arabia. After a period of some three years Paul is now charged up and ready to go. Many people speculate as to what exactly Paul did for those three years. We believe with research that is it safe to say that the Apostle Paul was deep in studying and learning more and more. Paul was a Pharisaical man before, but now after dealings with the Lord we see him as dry sponge soaking up the wisdom of the Word and becoming reading to dispense of it. Three years later he returned to Damascus and was ready to now preach boldly. Unfortunately they did not receive him kindly and he was forced to flee for his own personal safety. He left and went unto Jerusalem only to face the same result three weeks later. Paul was beginning to face the beatings and persecutions and torture that he had so readily dished out to the people to whom now he was called to minister. Paul was undergoing life altering events that did not even seem to faze him in the least possible way. The Apostle Paul was starting to really emerge and became quickly one of the leading missionaries for the faith. We see the church at Antioch catch spiritual fire and become burden for missions and those around them. They decided to send John Mark, Barnabas, and Paul on their very first missionary trip. This would revolutionize missions for ever after. Paul’s First Missionary Trip These three men would begin sailing from Seleucia across to Cyprus which was approximately eighty miles to the southwest. It was on this journey that Saul would no longer be called Saul but rather the Apostle Paul. The Apostle Paul took the lead role on this trip and took charge. They trekked across the mainland, and unfortunately for whatever reason John Mark left the missions field. The absence of John Mark would become a sore spot between Barnabas and the Apostle Paul in the future. However, the trip continued and they passed though Pamphylia, Pisidia, and Lycaonia. They turned the world upside down with their passion and mission trip. As they returned back home they retraced their steps visiting babes in Christ along the way and encouraged many churches. They would ordain elders within the church to act as an overseer in their presence to make sure all things would continue as they were. From the city of Perga they sailed unto Antioch. Paul’s Division After a while being in Antioch the Apostle Paul proposed that they return and check up on their brethren to see how they fared. The planning was going great and the trip was sure to be even bigger and better than the first until it came to a screeching halt. For the aforementioned reasons there was a sharp division between the two. Barnabas wanted to take John Mark, his cousin, and give him another chance, but the Apostle Paul was quick to remember what happened last time when John Mark bailed on them. The division was so sharp that they parted company Paul’s Second Missionary Trip Paul began his second missionary journey with a new missionary partner, Silas. Barnabas took his cousin and went on a missionary journey separate. The Apostle Paul began this missionary trip about A.D. 51. Each missionary tour that Paul took he wanted to stay out a little longer and go a little further in to the mission field. After each missionary trip he would return to Antioch give reports to the churches and check up on and encourage the brethren. Paul’s Third Missionary Trip On this third missionary trip he toured the upper coast of Asia Minor as he made his way slowly to Ephesus. As we said earlier each trip the apostle Paul wanted to stay longer and longer on the mission field and this trip was no different. He tarried there with the brethren for three years ministering to them. Like the other trips he suffered much persecution here as well. It seems that this trip might have had the most severe torture as Paul was getting older the beatings were becoming more severe and the hurled rocks would only hurt that much more against his bare sun beat back. Paul suffered so much on his mission’s trips yet he always wanted to do more and he maintained a joyful attitude despite his circumstances. Conclusion The Apostle Paul was a man that experienced great transformation in his life. He was a Pharisee of the Pharisee’s and Hebrew and on his way to Hell. God miraculously saved him on his way to persecute the church and turned his life around. Paul was a zealous man with a lot of passion whatever he did and the ministry was no different. Paul went on multiple missionary trips leading many people to Jesus. He challenged the churches, established order when necessary and revolutionized missions. The Apostle Paul is someone we should model our missions after. He had a desire to please God and did whatever it took to lead the churches in the way of truth. Paul truly lived a life that daily was â€Å"back to Acts†. And He was a real man because he preached Christ and Him crucified. May we all be as dedicated to the cause of Christ as we saw in this paper that The Apostle Paul was to Jesus Christ his Lord and Saviour.

Effect Of Vibration On Solder Joint Reliability Engineering Essay

Effect Of Vibration On Solder Joint Reliability Engineering Essay CHAPTER 01 INTRODUCTION SOLDER JOINT IN ELECTRONIC ASSEMBLIES Circuit boards range from simple single moulded plastic boards with copper conductors on one or both sides to multilayer boards with copper conductors, each layer being separated by a dielectric and interconnected by metal conductors. Minimum line width and spacing between lines is less than 100  µm. The board typically is made from a composite such as an epoxy with layered sheets of woven fibreglass. The dielectric material between layers of conductors is usually a polymer, for example polyimide. To maintain solder ability, the exposed copper may be coated with an inhibitor such as benzotriazole or with a solder overcoat. Components are attached to the board with solder or metal-filled conductive adhesives. Fully assembled boards may be further protected against moisture, contamination, and mechanical damage by a cover coat. 1.2 SOLDER JOINT RELIABILITY AND FAILURE Solder joints are widely used in the electronic packaging industry to produce good electrical, thermal, and mechanical connections between the package and the printed circuit board. Eighty percentage of the mechanical failure in airborne and automation electronic caused by vibration and shock. Design appropriate measure to ensure the survival equipment in the shock and vibration environment is necessary to do so. Remaining 20 percentage of mechanical failure related to thermal stresses resulting from high thermal gradients, coefficient of thermal expansion and high coefficient of elasticity. Solder joint failure occur in several reasons: Poor design of the solder joint A bad solder joint treatment Solder material Excessive stress applied to solder joints. In general, however, the solder joint failure are simply ranked according to the ature of stress that have caused. Most joint failure fall into three major categories: Fatigue failure due to cyclic stress application Due to the implementation of a long term or permanent load The stress is due to overloading in the short term Reflow profile also has a significant role on solder joint reliablity. because It also has a high influence micro structure of the solder joint. Vibration failure of solder joints is often assessed for reliability using high accelerated life test, which is represented by a GRMS- time curve. For surface mount microelectronic components, an approximation of printed circuit board (PCB) model analysis can be made by assuming PCB as a bare unpopulated thin plate because the increase in stiffness of PCB due to the mounting of the components is approximately offset by the increase in total mass of the populated PCB [2]. However, this approximation can lead to errors in natural frequency prediction for different package profiles, for flip-chip-on-board (FCOB) and plastic-ball-grid-array (PBGA) assemblies [3,4]. When the component has small profile, the approximation of PCB assembly as a bare PCB can provide satisfactory modal analysis results because the stiffness and mass contribution of small component to PCB assembly is not significant. In this study, varying G-level random vibration tests for PCB assembly were conducted. In order to assess the reliability of PCB assembly, it is necessary to conduct the dynamic analysis. A global-local modeling approach [4-6] was used. The analyses by Basaran [7,8], Chandaroy [9] and Zhao et al. [10] show that solder joint deformation is in the elastic range for vibration loading. The global-local or submodeling method [11-13] has been used for the board level FE simulation. In this study, four different model cases were investigated for FEA modal analysis to calculate the first order natural frequency of the FCOB assembly. A quasi-static analysis approach was conducted for the FCOB assembly to evaluate the stress strain behavior of the solder joints. A harmonic analysis was also investigated to study the dynamic response of the FCOB assembly subjected to vibration load. Fatigue life prediction results from the quasi-static analysis and harmonic analysis approaches were compared to the test results. 1.3 PROJECT PURPOSE In this modern world due to the causes of health and environmental issues the electronic manufacturing industries facing a challenging problem of necessity to produce reliable solder products in very high density with very low cost. Solder joints are very important to the reliability of Printed Circuit Boards (PCB). This is a one of the leading factor in transmission of electrical and thermal connections. In case of every PCB even a smaller solder joints are very important. So this project investigates the Effect of Vibration on Solder Joint Reliability in Electronics Assembly Applications. Solder joint of a Electronic assembly is very important measurement because of This model based study might help engineers effectively improve the PCB mechanical design and thus improve reliability of electronics attached to the PCB by considering realistic uncertainties and adverse vibration environments. CHAPTER 02 LITERATURE REVIEW 2.1 SINE ON RANDOM VIBRATION TESTING Vibration sine on random testing is performed by superimposing a sine wave on top of a random environment. A sine on random vibration test duplicates the combined environment of a spinning helicopter blade with its distinct resonant levels and the rest of the aircraft which generates random engine and aerodynamic induced vibration. Gunfire on board an aircraft causes sine vibration while the rest of the aircraft generates random excitations. These types of tests are duplicating vibration characterized by dominant peaks (sinusoids) superimposed on a broadband background Another variation would be a swept sine on random test. 2.2 SINUSOIDAL VIBRATION TESTING Dynamic deflections of materials caused by vibration can cause a host of problems and malfunctions including failed electrical components, deformed seals, optical and mechanical misalignment, cracked or broken structures, excessive electrical noise, electrical shorts, chafed wiring. Because sine vibration is basically a certain fundamental frequency and the harmonics of that fundamental, in its pure state, this type of vibration is generated by a limited but significant number of sources. Expressed as amplitude versus frequency, sine vibration is the type of vibration generated in the field by sources such as engine rotational speeds, propeller and turbine blade passage frequencies, rotor blade passage and launch vehicles. While much of real world vibration is random, sine vibration testing accomplishes several important goals in product qualification and testing. Much material and finished product was modeled on some type of sine vibe signature. A sine sweep of frequencies will determine whether the assumptions were correct and if the deviations are significant enough to cause design changes. In other words, sweep will establish if the anticipated frequency has been met and/or discovers the test item fundamental frequency. Similarly, a sweep will help identify the test subject resonance frequencies, which may be the points at which the item experiences particularly stressful deflections. By dwelling at those frequencies in subsequent tests, premature failures due to the properties of the material may come to light before the items sees field use. Some of the following tests include fixed frequency at higher levels of the controlling variable (displacement, velocity, acceleration), and random vibration . Per customer request, NTS will run sweeps in one direction, decreasing, increasing or bi-directionally and can change frequency logarithmically or linearly. Another typical sinusoidal vibration test, sine burst such as the teardrop, goes rapidly to peak pulse and then decays at lower rate (to prevent damage to the unit). The burst test puts a maximum load into an article at a rapid rate and particularly stresses joints and seams to identify workmanship and design issues. 2.3RANDOM VIBRATION TESTING The legitimacy of random vibration s an effective tool of screening work man ship defects came about during manufacturing. Up until that limited hertz sine was applied during reliability testing. Pure sinusoidal vibration is composed of a single frequency at any given time. Comparisons tests revealed that to equal the effectiveness of random vibration. The test item will have to be subjected to many sine frequencies over a longer period of time, and may unintentionally fatigue the test item. Random vibrations undercover defect faster. 2.4 Real world simulation. Most vibration in real world is random for example a vehicle travelling over road experience random vibration from the road irregularities. A ground launched rocket vehicle experiences non stationary vibration during its flight the motor ignites the rocket travel through the atmosphere , the motor burn ends and so forth even in wing when subjected to turbulent air flow, undergoes random vibration. Random vibration is composed of multitude of continues spectrum of frequencies. Motion varies randomly with time. It can be presented in the domain by a power spectral density function [G2/Hz]. HIGHLY-ACCELERATED LIFE TESTING (HALT) Exposes the product to a step-by-step cycling in environmental variables such as temperature, shock and vibration. HALT involves vibration testing in all three axes using a random mode of frequencies. Finally, HALT testing can include the simultaneous cycling of multiple environmental variables, for example, temperature cycling plus vibration testing. This multi-variable testing approach provides a closer approximation of real-world operating environments. Unlike conventional testing, the goal of HALT testing is to break the product. When the product fails, the weakest link is identified, so engineers know exactly what needs to be done to improve product quality. After a product has failed, the weak component(s) are upgraded or reinforced. The revised product is then subjected to another round of HALT testing, with the range of temperature, vibration, or shock further increased, so the product fails again. This identifies the next weakest link. By going through several iterations like this, the product can be made quite robust. With this informed approach, only the weak spots are identified for improvement. This type of testing provides so much information about the construction and performance of a product, that it can bequite helpful for newer engineers assigned to a product with which they are not completely familiar. HALT testing must be performed during the design phase of a product to make sure the basic design is reliable. But it is important to note that the units being tested are likely to be hand-made engineering prototypes. At Trace, we have found that HALT testing should also be performed on actual production units, to ensure that the transition from engineering design to production design has not resulted in a loss of product quality or robustness. Some engineers may consider this approach as scientifically reasonable, but financially unrealistic. However, the cost of HALT testing is much less than the cost of field failures HIGHLY-ACCELERATED STRESS SCREENING (HASS) HASS testing is an on-going screening test, performed on regular production units. Here, the idea is not to damage the product, but rather to verify that actual production units continue to operate properly when subjected to the cycling of environmental variables used during the HASS test. The limits used in HASS testing are based on a skilled interpretation of the HALT testing parameters. The importance of HASS testing can be appreciated when one considers todays typical manufacturing scenario. Circuit boards are purchased from a vendor who uses materials purchased from other vendors. Components and sub-assemblies are obtained from manufacturers all over the world. Often, the final assembly of the product is performed by a subcontractor. This means that the quality of the final product is a function of the quality (or lack thereof) of all the components, materials, and processes which are a part of that final product. These components, materials, and processes can and do change over time, thereby affecting the quality and reliability of the final product. The best way to ensure that production units continue to meet reliability objectives is through HASS testing. RELIABILITY Reliability is defined as the probability that a device will perform its required function under stated conditions for a specific period of time. Predicting with some degree of Confidence is very dependent on correctly defining a number of parameters. For instance, choosing the distribution that matches the data is of primary importance. If a correct distribution is not chosen, the results will not be reliable. The confidence, which depends on the sample size, must be adequate to make correct decisions. Individual component failure rates must be based on a large enough population and relevant to truly reflect present day normal usages. There are empirical considerations, such as determining the slope of the failure rate and calculating the activation energy, as well as environmental factors, such as temperature, humidity, and vibration. Lastly, there are electrical stressors such as voltage and current. Reliability engineering can be somewhat abstract in that it involves much statist ics; yet it is engineering in its most practical form. Will the design perform its intended mission? Product reliability is seen as a testament to the robustness of the design as well as the integrity of the quality and manufacturing commitments of an organization. One of the fundamentals of understanding a products reliability requires an understanding of the calculation of the failure rate. The traditional method of determining a products failure rate is through the use of accelerated vibration operating life tests performed on a sample of devices. The failure rate obtained on the life test sample is then extrapolated to end-use conditions by means of predetermined statistical models to give an estimate of the failure rate in the field application. Although there are many other stress methods employed by electronic assembly manufacturers to fully characterize a products reliability, the data generated from operating life test sampling is the principal method used by the industry for estimating the failure rate of a electronic assembly in field service. Failure Rate (ÃŽÂ ») Measure of failure per unit of time. The useful life failure rate is based on the exponential life distribution. The failure rate typically decreases slightly over early life, then stabilizes until wear-out which shows an increasing failure rate. This should occur beyond useful life. Failure In Time (FIT) Measure of failure rate in 109 device hours; e. g. 1 FIT = 1 failure in 109 device hours. Total Device Hours (TDH) The summation of the number of units in operation multiplied by the time of operation. Mean Time between failures (MTBF) Reliability is quantified as MTBF (Mean Time Between Failures) for repairable product and MTTF (Mean Time To Failure) for non-repairable product. A correct understanding of MTBF is important. A power supply with an MTBF of 40,000 hours does not mean that the power supply should last for an average of 40,000 hours. According to the theory behind the statistics of confidence intervals, the statistical average becomes the true average as the number of samples increase. An MTBF of 40,000 hours, or 1 year for 1 module, becomes 40,000/2 for two modules and 40,000/4 for four modules. Sometimes failure rates are measured in percent failed per million hours of operation instead of MTBF. The FIT is equivalent to one failure per billion device hours, which is equivalent to a MTBF of 1,000,000,000 hours. The formula for calculating the MTBF is ÃŽÂ ¸ = T/R. ÃŽÂ ¸ = MTBF T = total time R = number of failures MTTF is stands for Mean Time To Failure. To distinguish between the two, the concept of suspensions must first be understood. In reliability calculations, a suspension occurs when a destructive test or observation has been completed without observing a failure. MTBF calculations do not consider suspensions whereas MTTF does. MTTF is the number of total hours of service of all devices divided by the number of devices. It is only when all the parts fail with the same failure mode that MTBF converges to MTTF. ÃŽÂ ³= T/N ÃŽÂ ³ = MTTF T = total time N = Number of units under test. If the MTBF is known, one can calculate the failure rate as the inverse of the MTBF. The formula for (ÃŽÂ ») is: where r is the number of failures. Once a MTBF is calculated, probability can derive from following equation: R(t) = e-t/MTBF Confidence Level or Limit (CL) Probability level at which population failure rate estimates are derived from sample life test. The upper confidence level interval is used. Acceleration Factor (AF) A constant derived from experimental data which relates the times to failure at two different stresses. The AF allows extrapolation of failure rates from accelerated test conditions to use conditions. Since reliability data can be accumulated from a number of different life tests with several different failure mechanisms, a comprehensive failure rate is desired. The failure rate calculation can be complicated if there are more than one failure mechanisms in a life test, since the failure mechanisms are thermally activated at different rates. Equation 1 accounts for these conditions and includes a statistical factor to obtain the confidence level for the resulting failure rate. THE BATHTUB CURVE The life of a population of units can be divided into three distinct periods. Figure 1 shows the reliability bathtub curve which models the cradle to grave instantaneous failure rates vs. time. If we follow the slope from the start to where it begins to flatten out this can be considered the first period. The first period is characterized by a decreasing failure rate. It is what occurs during the early life of a population of units. The weaker units die off leaving a population that is more rigorous. This first period is also called infant mortality period. The next period is the flat portion of the graph. It is called the normal life. Failures occur more in a random sequence during this time. It is difficult to predict which failure mode will manifest, but the rate of failures is predictable. Notice the constant slope. The third period begins at the point where the slope begins to increase and extends to the end of the graph. This is what happens when units become old and begin to fail at an increasing rate. Reliability Predictions Methods A lot of time has been spent on developing procedures for estimating reliability of electronic equipment. There are generally two categories: (1) predictions based on individual failure rates, and (2) demonstrated reliability based on operation of equipment over time. Prediction methods are based on component data from a variety of sources: failure analysis, life test data, and device physics. For some calculations (e.g. military application) MIL-HDBK-217 is used, which is considered to be the standard reliability prediction method. A simple failure rate calculation based on a single life test would follow equation 1. ÃŽÂ »Ã¢â€š ¬Ã‚  = failure rate. TDH = Total Device Hours = Number of units x hours under stress. AF = Acceleration factor, see Equation 3. Since reliability data can be accumulated from a number of different life tests with several different failure mechanisms, a comprehensive failure rate is desired. The failure rate calculation can be complicated if there are more than one failure mechanisms in a life test, since the failure mechanisms are thermally activated at different rates. Equation 1 accounts for these conditions and includes a statistical factor to obtain the confidence level for the resulting failure rate where, ÃŽÂ » = failure rate in FITs (Number fails in 109 device hours) ÃŽÂ ² = Number of distinct possible failure mechanisms k = Number of life tests being combined xi = Number of failures for a given failure mechanism i = 1, 2, ÃŽÂ ² TDHj = Total device hours of test time for life test j, j = 1, 2, k AFij = Acceleration factor for appropriate failure mechanism, i = 1, 2, k M = ÃŽ2 (ÃŽÂ ±, 2r +2) / 2 where, ÃŽ2 = chi square factor for 2r + 2 degrees of freedom r = total number of failures (ÃŽÂ £ xi) ÃŽÂ ± = risk associated with CL between 0 and 1. 2.2 SOLDER PASTE 2.1.1 ROLE OF SOLDER PASTE IN REFLOWING Solder paste is a combination mixture of a flux composition and a highly grinded, powdered solder metal alloy that is normally used in the electronics industry to soldering processes. And also it is call as a attachment medium between the device interconnection features and the PCB itself. The components of a solder paste are specially designed for excellent printing and reflow characteristics. In normal case of the surface mount soldering process involves placing the substrate and a small amount of solder paste in a printed circuit board. After that the system will be heated until the solder reflows, forms an electrical connection between the solder pad and the electrical contact of electronics part. After this reflow finished it forms both an electrical and mechanical connection between the electronics components and the printed circuit board. 2.1.2 SELECTION CRITERIA OF A SOLDER PASTE Selection of a solder paste is very important factor for reflowing process, reliability its quality. The following factors are considerable for a good solder paste [6]. The size of the solder alloy particles which are in the solder paste The tendency to form voids The properties of the flux medium of the solder paste Alpha particle emission rate The design of the stencil to be used for printing Thermal properties of the solder paste Electrical properties of the solder paste CHAPTER 03 EXPERIMENTS 3.1 MATERIALS AND METHODOLGY SOLDER PASTE Basically I used solder paste in same procedure. The details of solder paste used in the experiment are given in the following table TYPE OF SOLDER PASTE ALLOYS CODING PARTICLE SIZE METAL LOADIND S1 Sn95.5Ag4Cu0.5 S2 Sn42Bi57Ag1 Table 3.1.1 types of solder paste used in experiment For this project all above solder paste should be in a container with appropriate labelling and identification on it to distinguish it from the Tin lead solder paste. The solder paste should be stored in a refrigerator between 35 45 F. and should be allowed to come room temperature for minimum four hours before doing the solder paste printing. Once it has finished the using solder paste must replace to the refrigerator since it can not be at room temperature over 24 hours. The self life of the lead free solder pastes may be reducing from the typical six month. The above guidelines are strictly followed in this project. Because it is not only for guarantee the quality of solder paste but also a good way to reduce the errors that may affect the final results of the project. SOLDER PASTE PRINTING IMPORTANT OF SOLDER PASTE PRINTING Surface mount technology (SMT) is used extensively in the electronics industry. Surface mount components are potentially more reliable products can be designed and manufactured using the SMT. The solder paste stencil printing process is very critical and important step in the surface mount manufacting process. Most of all the soldering defects are due to problems dealing with the screening process. So we want to a major consideration in operation and set up steps in stencil printing process. When we are monitoring these factors carefully we can minimize the defects. The main purpose of printing solder paste on PCB is to supply solder alloy to solder joint to correct amount. That only print must be aligned correctly and can get a perfect component placement. PRINTING PROCESS PARAMETERS Some of the following parameters are very important to printing process. STENCIL Stencils are using for the solder paste slip easily off the aperture edges and thereby secures a uniform print. For this process we using electro formed stencils. Because of these stencils have very shape edge and slightly conic. Generally a stencil is mading from cupper or nickel [12]. ENVIRONMENTAL Dust and dirt from the air that will reach the PCBs and stencils can be defects poor wet ability in the reflow soldering process. So PCBs should be stored in sealed packages and cleaned before use. SOLDER PASTE Solder paste characterise must be controlled to achieve a maximum production results. Some of the factors are given below [12]. Percent of metal Viscosity Slump Solder balls Flux activity working life and shelf life STENCIL PRINTING PARAMETERS Stencil printing parameters are very important factors in printing processes to achieve a best yield. The following parameters must be monitors and controlled in a printing process. Squeegee pressure = 8kg Squeegee speed = 20 mm/s Separation speed = 100% Printing gap = 0.0 mm These factors and limit can be adjust for our project purpose SOLDER PASTE PRINTING EQUIPMENT AND PROCESS Figure 3.2.4.1 DEK 260 stencil printing machine The DEK 260 stencil printing machine is used to print solder paste on the circuit board. This DEK 260 stencil printing machine has two main functions. Registers the position of the product screen with in the print head Positioning the circuit board below the stencil, to ready for the print cycle. The boards to be print are supported on magnetic tooling and held by vacuum caps arranged on the plate to guarantee the board steady during the printing on to the board. The first step of the experiment is to do the solder paste printing on to the board. In this project unable to get metal stencil, so circuit boards are printed by hand, below procedure followed to print PCB Put weights onto the stencil to fix it roll the squeegee over the stencil solder paste presses through the aperture onto PCB separate stencil two circuit boards are printed with solder paste for each solder paste types. Totally 4 circuit boards printed. SOLDER PASTE REFLOWPROCESS/PROFILE Figure 3.3.1 reflow oven To achieve a good reliable solder joint the reflow process is very important. When doing the reflow with sn-pb solder paste often performed at minimum peak temperature of about 203. It is 20k above the sn pb liquid state temperature. When doing the reflow process with lead free solder paste it has to be performed at a minimum peak temperature of 230. It is just 13K above the melting temperature. It is generally accepted that lead free solders requires a higher reflow temperature up to 220 230. Reflow profile will be affecting the reliability of a solder joint. Because it is a major factor that influence the formation of the intermettallic layers in a solder joint. Intermettalic layer is a critical part of a solder joint. An intermettalic bond thickness should be thin. Therefore a good reflow profile must produce solder bumps with a thin intermetallic layer. PREHEAT ZONE In this zone indicates how the temperature is changing fast on the printed circuit board. The ramp-up rate is usually between 1-3 per second. If this rate exceeds there will be damage to components from thermal shock. Only In this preheat zone the solder paste begins to evaporate. So if the rise rate is too low the evaporation of flux is not incomplete. This will affect the quality of the solder joint. THERMAL SOAK ZONE It is also called the flux activation zone. In this thermal soak zone it will take 60-120 seconds for removal of solder paste and activation of fluxes. Solder spattering and balling will be happen if the temperature is too high or too low. End of this thermal shock zone a thermal equilibrium will complete the entire circuit board. REFLOW ZONE In this reflow zone only the maximum temperature will be reached. In this zone we have to consider about the peak temperature that is the maximum allowable temperature of entire process. It is very important to monitor this maximum temperature exceeds the peak temperature in this zone. It may cause damage to the internal dies of SMT components and a block to the growth of intermetalic bonds. we have to consider the profile time also. If time exceeds than the manufactures specification it also affect the circuit boards quality. 3.3.4 COOLING ZONE In the reflow process the last zone is cooling zone. A proper cooling inhabits excess intermetallic formation or thermal shock to the components. Generally the cooling zone temperature range is 30 100. In this project I selected the following temperature profiles. This temperature profile is stranded reflow profile for lead free soldering. Zone 1 220 Zone 2 180 Zone 3 170 Zone 4 190 Zone5 233 Zone 6 233 Totally 4 circuit boards were printed. Choosing of good reflow profile was not involves any defects or damages in the printed circuit board. Figure 3.3.4.1a printed circuit board after reflow SET UP EVENT DETECTOR The constructed PCBs were connected with event detector by ribbon data cable. Ribbon cable addressed according to `Analysis tech STD series event detectors manual . pins 1 to 32 function as source point and pins 33 to 37 function as ground point. To obtain closed loop circuit to monitor the behaviour of PCB components, PCB boards 1, 2, 3 and 4 connected to channel 1,2,33 and 34 respectively. Ribbon cable After connected ribbon cable with event detector and enviromenrt chamber, channels are assigned in WIN DATA LOG software which supplied with event detector. For this test following settings define for data acquisition INVESTICATING RELIABILITY OF SOLDER JOINT UNDER VIBRATION CHAMER In this study, PCBs were used in Variable Frequency Vibration Test to analyse the dynamic response of PCB assembly subjected to random vibration loading. The PCB specimens were tested at different acceleration levels to assess the solder joint reliability subjected varying G-level vibration loads(G is the gravitational acceleration), respectively. Vibration tests were accomplished by using an electro dynamic Shaker

Advocating Elderly Americans Essay -- Advocates Senior Citizens

The elderly in America have many needs that can range from transportation, a little more money, and even just a little companionship but one of their major needs is advocacy. They need someone to stand up and fight with them for what the need. The elderly of today did so much for this country such things as fight both world wars and the Korean Conflict, they fought for equality, and the escalated this country to the greatness we have today.   Ã‚  Ã‚  Ã‚  Ã‚  So what is an advocate? Advocate is a person or group that represents a common interest and goes to great lengths to see that their cause is not neglected. So why does our elderly need advocates? Our elderly need advocates for various reasons. They need someone to fight with congress over healthcare cost and issues, they need someone to defend them against neglect and abuse, and most of all they need someone to make them aware of the services and programs available to make their lives easier. Advocates are very important to our elderly as well as they should be no one wants to be alone, we all want someone to fight beside us. So who does stand up and fight for our elderly?   Ã‚  Ã‚  Ã‚  Ã‚  In all parts of the United States there are Offices for the Aging to assist our elderly with obtaining the services they deserve. The Office for the Aging was created to promote self-determination, self-promotion and self-sufficiency among the elderly. They also wanted to make seniors aware of the services available to them and their families. Over the years that Offices for the Aging has existed they have created networks of connections in many aspects with in each of their communities. Through their broad range of connections they can assist any one with any problems. Most people feel as though the Office for the Aging is nothing more than a referral agency. There could be nothing further from the truth, Office for the Aging offers a wide variety of services but if they do not offer a service that you need they can and will refer you to an agency that can. One of the services that the Office for the Aging offers is Social Security counseling. This is a big servi ce because of the changing laws and the complexity of the laws it is tough for many elderly to understand properly obtain all of the money they are entitled to. Office for the Aging can also go to your Social Security hearing for you if you wish that they do so. The Office for ... ...as quoted as saying, â€Å"It’s virtually impossible to take back the House or win the presidency without taking back the seniors. That makes them the key battleground†¦Ã¢â‚¬  In the upcoming decade there will be over 76 million baby boomers that will be over 65 that mean they will have more power then any other voting cohort in America. This means the attention that the senior vote is getting will become stronger and stronger. Older people are more likely to vote that are younger people this means that seniors can be their own advocate. Seniors can be their own advocates by voting people into office that will vote their way on important issues. Voting is a powerful instrument for all people but is often overlooked.   Ã‚  Ã‚  Ã‚  Ã‚  Advocacy is an important in order for voices to be heard. Seniors citizens have various needs and as fellow humans it is our obligation to protect them. They paved the way for our country’s prosperity who are we to put them out pasture. Works Cited www.aarp.org www.americangeriatrics.org www.carie.org www.commoncause.org www.ncscinc.org www.senior.org The gerontologist. â€Å"Older People and Voting Participation: Past and Future† by Robert Binstock. February 2000.

The Decline of Aristocracy in The Communist Manifesto Essay -- Communi

The Decline of Aristocracy in The Communist Manifesto The decline of aristocracy in The Communist Manifesto began with Karl Marx’s statement, â€Å"The history of all hitherto existing societies is the history of class struggles.†1 Marx recognized the ideals of the social rank, which has influenced every society throughout history. The two social classes described by Marx were the Bourgeoisie, or the upper class, and the Proletariats, or the lower class. Before the Bourgeoisie came to social power, landowners and corporate organizations ran the society. Marx believed that the severe separation of the two classes greatly troubled society and that the two classes must coexist as one with each other.2 The Bourgeoisie were the landowners, employers, and those who received capital in the society. They had other people work under them and controlled labor in order to increase personal capital. â€Å"Marx delineates his vision of history, focusing on the development and eventual destruction of the bourgeoisie, the dominant class of his day.†3 The Bourgeoisie came up with the idea to create a new social class known as the Proletariats, which were the laborers for the production of Bourgeoisie industry. The Proletariat was composed of the lower class of individuals as well as the lower region of the middle class; which eventually fell into the classification of Proletariat. This class is identified by hard individual efforts. The Proletariats lived to work, and the only way that they were hired was if the business owners believed they could increase capital. Marx described the worker as a sort of soldier or a slave for their labor.4 Similar to slaves, the working class was exploited by their superiors, or the Bou... ... 1. Marx, Karl and Frederick Engels, Manifesto of the Communist Party (Dayton: U Dayton P, 1999), 38. 2. Smith, J.N. "ClassicNote on Communist Manifesto." ClassicNotes by Gradesaver. 2000. Gradesaver. 22 March 2001 < http://www.gradesaver.com/ClassicNotes/Titles/communist/ >. 3. Smith, J.N., ClassicNotes by GradeSaver 4. Lukacs, George. History and Class Consiousness (Massachusetts: The MIT Press, 1968), 46. 5. Smith, J.N., ClassicNotes by GradeSaver 6. McIntosh, Ian. Classical Sociological Theory (New York: New York University Press, 1997), 17. 7. Lukacs, George, 46. 8. Smith, J.N., ClassicNotes by GradeSaver 9. Hoselitz, Ben F. "Karl Marx on Secular and Social Development: A Study in the Sociology of Nineteenth Century 10. Marx, Karl and Frederick Engels, Manifesto of the Communist Party

Human Resources Management Essay

Human Resources Management (HRM) is a new concept. It is a combination of HR, Accounting, Management, Financial Management and Economics. Globalization to would economy has exposed the corporate business organization to worldwide competition, mobilization of professional manpower and modern quantitative management practice. So, there are growing realization cannot achieve its goal effectively and efficiently. To face this complex management challenge, effective objectively measurable database system to measure and apply HRM information. Now-a-days, in Bangladesh, every year, and huge amount of money and talented HRM are being engaged by corporate to improve the productivity or skills o f their workforce across the country. Such huge expenditures are made with the expectation of future returns in terms of improved services to be rendered by skilled employees. In other words, organizations by investing human resources development definitely increase the service potentials embodied in human resources and these investments thus create economic assets for the organizations. Human resource (or personnel) management, in the sense of getting things done through people, is an essential part of every manager’s responsibilities, but many organizations find it advantageous to establish a specialist division to provide an expert service dedicated to ensuring that the human resource function is performed efficiently. â€Å"People are our most valuable asset† is a cliche which no member of any senior management team would disagree with. Yet, the reality for many organizations are that their people remain under valued, under trained and under utilized. The rate of change facing organizations has never been greater and organizations must absorb and manage change at a much faster rate than in the past. In order to implement a successful business strategy to face this challenge, organizations, large or small, must ensure that they have the right people capable of delivering the strategy. There is a long-standing argument about where HR-related functions should be organized into large organizations, e. g. , â€Å"should HR be in the Organization Development department or the other way around? The HRM function and HRD profession have undergone tremendous change over the past 20-30 years. Many years ago, large organizations looked to the â€Å"Personnel Department,† mostly to manage the paperwork around hiring and paying people. More recently, organizations consider the â€Å"HR Department† as playing a major role in staffing, training and helping to manage people so that people and the organization are performing at maxim um capability in a highly fulfilling manner. Company Profile History of Partex Group: Partex Group is among the large Bangladesh private sector manufacturing and service based enterprises, owning and operating over twenty units giving value for money to all customers. The group started modestly in 1959 in tobacco trading and with prudent entrepreneurship of our Founder Chairman Mr. M. A. Hashem today we have a stake in tobacco, food, water, soft drinks, steel container, edible oil, wooden board, furniture, cotton yarn and the IT sector. After Bangladesh was established our Chairman set up M/S Hashem Corporation (Pvt) Ltd. n Chittagong city meeting the large demand of food and materials needed for sustaining the needs of a new nation through imports. From importing to import substitution was the next logical step and the stepping stone into the manufacturing sector, which has matured to the multi million dollar diverse investment of the Partex Group today. A dedicated work force and committed board members led by our Chairman and backed by a market oriented corporate strategy has been the cornerstone of our success. Today the group has over twenty family owned private limited companies with a sizable turnover. Ours is a dynamic organization always exploring new ideas and avenues to expand and grow further. Long before environment came to dominate the development agenda. Star Particle Board Mills in the sixties pioneered an eco-friendly industry to reduce pressure on our scarce forest recourses. It is a unique combination of environmental protection and commerce; belaying most doomsayers who claim the two to be at odds. The one score and ten year successful perpetuation of our timber substitute products not only speak volumes of the foresight of Partex’s founders but also their vision of the future. They make particle board from agro-waste, mostly jute stalks, and ensure greater value to the jute growers of Bangladesh. Products are processed using modern technology to produce homogenous and strong particle board that can withstand seasonal change and are free from termite and fungal attack. These particle boards go on to produce veneered boards of various design and texture. Also door panels both plains and decorative in various finishes and sizes. In addition their produce special furniture boards, stylish furniture and even various plywood on our range of products. Beside, in house and outside training, recruits business graduates from reputed universities as management training for mainstream banking to enrich quality of human resources contributing towards operations effective and long-term sustainable results. Vision Statement: The Sky is not the limit for us, but their expectation is within limits. Therefore, their imagination soars beyond conventional barriers. Partex Group share or destiny with their beloved motherland. They want to serve her in the greater quest for national uplift. Mission statement: To sincere traveler, the way is never too long. Partex Group believes in â€Å"progress in diversity and service through entrepreneur†. They are merchants and missionaries, doers and dreamers, entrepreneurs and professionals. They are futuristic with emphasis on creating thinking and dynamic action. High quality financial services with the help the latest technology. Fast and accurate customer services Balance growth strategy High standard business ethics Steady return on shareholders equity. Innovative banking at a competitive price. Attract and retain quality human resource. Firm commitment to the society and the growth of national economy. The spirit: Enterprise is Partex Group’s spirit. Partex Group manufactures superior import-substitute consumer and industrial products. Their cutting edge precision leads to greater public utility and hygiene, with a great care for the environment and human inhabitation. It is the very ingredient that gives their organization the integrity upon which their reputation is built and we zealously guard it everyday. Many a thousand minds of their group contributed to their gathered knowledge to keep the wheels rolling that in turn leads them to goal. This cumulative strength of knowledge is required, today, to find new solutions for the manifold problems of fast- changing economic cultural and ecological milieu. Objectives: Partex Group is a customer focused modern banking institution thriving fast in both earning and ability to stand out as a leading banking institution in Bangladesh. They deliver unparalleled financial services with the touch of heart to Retail, Small and Medium Scale Enterprises (SMEs), corporate, institutional and governmental clients through the outlets of branches across the country. Their business initiatives center on the emerging need of the clients. Partex Groups’ client commitments are the following: Provided services with high degree of professionalism and use of most modern technology. Create life-long relationship based on mutual trust and respect. Respond to customer needs with speed and accuracy.