Computational Simulation of the Joint Shape after as-Reflowed Soldering

2010 ◽  
Vol 177 ◽  
pp. 651-656
Author(s):  
Ning Zhang ◽  
Li Tian ◽  
Yao Wu Shi ◽  
Jian Lin ◽  
Yong Ping Lei ◽  
...  

Using the interactive software, this study was mainly focused on developing a 3-D joint shape after the as-reflowed soldering which is the one of chief factors affecting the reliability. From the results, the soldering process can be simulated and observed directly. By changing the various conditions and constraints, such as surface tension, wetting angle and specific gravity, it makes a comparison between the simulated result and the experimental one. The simulated parameters are based on those of the traditional eutectic Sn-Pb solder. After slicing and comparing the different profiles of the simulated shape, the 3-D simulated geometry fits well with the experimental one.

Water Waves ◽  
2021 ◽  
Author(s):  
M. D. Groves

AbstractIn the applied mathematics literature solitary gravity–capillary water waves are modelled by approximating the standard governing equations for water waves by a Korteweg-de Vries equation (for strong surface tension) or a nonlinear Schrödinger equation (for weak surface tension). These formal arguments have been justified by sophisticated techniques such as spatial dynamics and centre-manifold reduction methods on the one hand and variational methods on the other. This article presents a complete, self-contained account of an alternative, simpler approach in which one works directly with the Zakharov–Craig–Sulem formulation of the water-wave problem and uses only rudimentary fixed-point arguments and Fourier analysis.


2019 ◽  
Vol 239 (4) ◽  
pp. 661-701 ◽  
Author(s):  
Sandra Dummert ◽  
Ute Leber ◽  
Barbara Schwengler

AbstractThe current situation in the German apprenticeship market is characterized by two contradictory developments. On the one hand, establishments are experiencing increasing problems filling the training positions they offer, and the number of vacant training positions is climbing. On the other hand, the transition into training is still difficult for many young people, and the number of unsuccessful vocational training applicants is rising. Hence, matching supply with demand is becoming increasingly difficult in the German job market for training positions. Using the Linked Employer-Employee dataset (LIAB) from the Institute for Employment Research (IAB), our paper provides a closer examination of the phenomenon of unfilled training positions. It presents an overview of the evolution of vacant training positions in eastern and western Germany and attempts to explain the number of vacancies by investigating the factors responsible for the establishments’ inability to fill their training positions. We assume that training position vacancies are due not only to internal company reasons such as firm size or the wage offer for apprentices but also to external conditions such as general regional factors. Therefore, our analysis also considers the situation on the demand side of the labor market within a region. The results of our multilevel mixed-effects estimations show that in addition to characteristics on the enterprise level, regional determinants also affect the share of vacant apprenticeships. With respect to establishment-related factors, mainly characteristics that describe the attractiveness of the firm prove to be important. With regard to regional-specific factors, we find that the availability of school leavers in a region in addition to the level of regional-sectoral competition impacts the recruiting success of establishments. Our analysis also shows that there are remarkable differences between eastern and western Germany concerning both the quantitative importance of unfilled training positions and the factors affecting them.


Antiquity ◽  
1936 ◽  
Vol 10 (39) ◽  
pp. 306-324 ◽  
Author(s):  
F. W. Morgan

The distribution of woodland and the stages of its gradual disappearance were of fundamental importance in the early historical geography of England. Wood was a valuable element in medieval economy and one of the chief factors affecting the nature of settlement, The evidence concerning the extent of the woodland in early England is of two kinds : (1) the surface geology, which provides a basis for the reconstruction of the original extent ; (2) the statistics of the Domesday Book: these refer to the eleventh century, but they may have some retrospective value. The present essay is an attempt to examine the Domesday evidence for the south and south-western counties of Berkshire, Hampshire, Wiltshire, Dorset, Somerset, Devon and Cornwall.


2016 ◽  
Vol 78 (5) ◽  
pp. 396-403 ◽  
Author(s):  
Samuel Potter ◽  
Rebecca M. Krall ◽  
Susan Mayo ◽  
Diane Johnson ◽  
Kim Zeidler-Watters ◽  
...  

With the looming global population crisis, it is more important now than ever that students understand what factors influence population dynamics. We present three learning modules with authentic, student-centered investigations that explore rates of population growth and the importance of resources. These interdisciplinary modules integrate biology, mathematics, and computer-literacy concepts aligned with the Next Generation Science Standards. The activities are appropriate for middle and high school science classes and for introductory college-level biology courses. The modules incorporate experimentation, data collection and analysis, drawing conclusions, and application of studied principles to explore factors affecting population dynamics in fruit flies. The variables explored include initial population structure, food availability, and space of the enclosed population. In addition, we present a computational simulation in which students can alter the same variables explored in the live experimental modules to test predictions on the consequences of altering the variables. Free web-based graphing (Joinpoint) and simulation software (NetLogo) allows students to work at home or at school.


2021 ◽  
Vol 12 (8) ◽  
pp. 2161-2179
Author(s):  
Daiane Maria de Genaro Chiroli ◽  
Raíza Conde Coradazi ◽  
Fabio Jose Ceron Branco ◽  
Yslene Rocha Kachba ◽  
Franciely Velozo Aragão ◽  
...  

Healthcare logistics play an important role in management, being attributed the activities of acquisition, distribution and movement of materials, professionals and patients. This work aims to develop a study, using the healthcare logistics in the movement of patients in the third health region of Paraná, proposing a linear programming problem that will pass through a computational simulation, considering the existing demands and constraints in the system, aiming to optimize the flow of patients from this region. The present study developed four mathematical models, based on demands and constraints followed by linear programming in order to find the best possible solution for the flow of patients from the third health region of the state of Paraná. The study developed reached its goal of optimization, generating an economy in the transportation of patients. Through the analysis of the results, it is concluded that the model that best suits the presented problem is the one of costs minimization, since the one of vehicles presented higher costs. Possibly the model that minimizes the vehicles would bring better results if the vehicles were not outsourced, but of the Ponta Grossa City Hall (PMPG). Was possible to verify the importance of the theme, especially when referring to the flow of patients in the health services due to the lack of studies with this specific approach. Even with the scarcity of data, it is possible to notice the potential for improvements on this patient transport system.


2020 ◽  
Vol 1 (4) ◽  
pp. 25-37
Author(s):  
A.E. Yesakov ◽  
◽  
A.V. Kretov ◽  
P.A. Krasavin ◽  
◽  
...  

Variators of different operating principles and designs are of interest as components of automatic transmissions for ground transport and traction machines. At the same time, one of the most popular types of variators are the variators built on the basis of continuously variable transmissions with flexible links. The main reasons for the use of such variators in the transmissions of a number of modern passenger vehicles are, on the one hand, the emergence of flexible link designs with high durability, and, on the other hand, the widespread introduction of programmable electronic devices into automatic control systems for continuously variable transmissions. A direct consequence of the latter circumstance was the need for in-depth research aimed at synthesizing such control algorithms that would make it possible to fully use the advantages inherent in continuously variable transmissions with flexible links and minimize the operational consequences of their shortcomings. This paper makes an attempt to solve the problem of synthesizing the algorithm in a preliminary form, based on the goal of providing the vehicle with the best traction and speed properties. The presence of such an attempt will allow, having set the main parameters of a continuously variable transmission for some reason, to develop the hardware of the automatic control system. In turn, this will make it possible to synthesize a refined algorithm that takes into account the dynamics of the system, errors of meters and signal conversion devices, as well as other factors affecting work pro-cesses. When considering the described problem, various variants of the geometry of the contact surfaces of the continuously variable transmission links were taken into account and the corre-sponding mathematical apparatus were formed. The results of calculations, obtained by computer program that implements these devices, are selectively presented in the materials of the paper.


Author(s):  
Harius Eko saputra

Almost every day, in various mass media, especially in newspapers, it is found that there are so many complaints and unsatisfactory opinions from the community, as the customer, towards the current implementation of public service. These complaints and unsatisfactory opinions can describe how bad the quality of the current public service is, which is benefited by the community. It may be the right time for the community to be treated as citizens, who will have rights and give priority to their rights for being served afterwards. They are not anymore being considered as clients who previously have no any choice in choosing and in determining what kind of service that they really want to. There are so many results from research, seminar and writings that are conducted by experts in which their works talk about the implementation of a good and qualified public service. Currently, however, the qualified public service has not yet implemented as should have been. The implementation of public service still acts as however it please to be and only emphasize on its own interest without considering the consumer’s importance as the party that should really be served as well as possible. For this reason, a research, which is done in Service Integrated Unit of the Jember Regency, tries to find out any factors affecting quality of the public services. The main core of the public service implementation is the quality of norm of the service executor. The matter that should be realized is that the executor is the person who should serve for the community, and the community is the one who should be served as well as possible.Keywords: Implementation of public service, legislatif


2018 ◽  
Vol 159 ◽  
pp. 02058
Author(s):  
Deddy Chrismianto ◽  
Kiryanto ◽  
Berlian Arswendo Adietya

Ship resistance is one of the main factors affecting the design of a ship. Catamaran boat is a ship with small wet surface area that able to reduce drag and improve ship power. Generally, a bulbous bow is implemented to reduce wave resistance because the bulbous shape is believed to attenuate the bow wave system. Additionally, the bulbous bow also tends to reduce viscous resistance. When the flow around the body is smooth, the total ship resistance can be reduced significantly if the optimum bulbous bow is obtained. In this study, the main purpose is to get the bulbous bow shape in catamaran boat which produces the smallest ship resistance by using computational fluid dynamic (CFD). Generating the variation of the bulbous bow shapes apply the one-to-one correspondence of the cross section parameter (ABT) and lateral parameter (ABL). The result of investigation shows that application of bulbous bow on catamaran boat can reduce about 11-13% of total resistance of ship.


2017 ◽  
Vol 38 (6) ◽  
pp. 3563
Author(s):  
Rosana Aparecida da Silva-Buzanello ◽  
Daneysa Lahis Kalschne ◽  
Silmara Maisa Heinen ◽  
Claudete Pertum ◽  
Alexia Francielli Schuch ◽  
...  

Pork consumption in Brazil is still low despite its productive importance. Relevant issues such as swine breeding, meat quality, and evaluation of aspects and attributes considered important by pork consumers at the time of purchase allows identifying consumer market demands. Moreover, physical parameters evaluation or pork cuts are suggested to certify the meat quality. The aim of this study was to identify the current situation of pig farming and determine the main aspects considered by consumers when buying pork in the Western region of Paraná state, Brazil. Furthermore, the physical properties of five pork chop brands marketed in the region were determined. Initially, an exploratory research was conducted involving ten pig farming sector professionals. This research allowed identifying that professionals understand the factors affecting meat quality and that some municipalities in the region are beyond their absorption capacity for pig production market. A descriptive research involving one hundred pork consumers showed that, although most prefer beef, 41% reported to consume pork 2 to 3 times a week. Pork chops and ribs are the preferred cuts, either fried or roasted. Details such as expiration date and federal inspection register were considered the most important aspects at the time of purchase, while price was the least important one. The meat color was the most mentioned sensory attribute. The physical analyses of five pork chop brands showed no pH difference (p > 0.05), water holding capacity, and cooking loss results, distinctive from the one observed for color (L*, a* and b*) and shearing force, which showed differences among the brands (p ? 0.05). Comparing pH and L*, it can be suggested that two brands showed normal meat characteristics, one DFD meat (pH > 6.0 and L* < 45), and other two brands PSE (pH < 5.8 and L* > 50). The research contributed to identifying features considered important by pork consumers, suggesting strategic actions to achieve greater preference and consumption index. The evaluation of physical parameters showed there is variability involved in pork chop quality as the samples were obtained from commercially different origins and under different processing and storage conditions.


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