• Title/Summary/Keyword: challenging problems

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Efficient Robust Design Optimization Using Statistical Moments Based on Multiplicative Decomposition Method (곱분해 기법 기반의 통계 모멘트를 이용한 효율적인 강건 최적설계)

  • Cho, Su-Gil;Lee, Min-Uk;Lee, Tae-Hee
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.10
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    • pp.1109-1114
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    • 2012
  • The performance of a system can be affected by various variables such as manufacturing tolerances, uncertainties of material properties, and environmental factors acting on the system. Robust design optimization has attracted much attention in the design of products because it can find the best design solution that minimizes the variance of the response while considering the distribution of the variables. However, the computational cost and accuracy of optimization have thus far been a challenging problem. In this study, robust design optimization using the multiplicative decomposition method is proposed in order to solve these problems. Because the proposed method calculates the mean and variance of the system directly from the kriging metamodel using the multiplicative decomposition method, it can be used to search for a robust optimum design accurately and efficiently. Several mathematical and engineering examples are used to demonstrate the feasibility of the proposed method.

A Study on the Truncated Tribunal in International Commercial Arbitration (국제상사중재에서 불완전중재판정부에 관한 연구)

  • Yu, Byoung-Yook
    • THE INTERNATIONAL COMMERCE & LAW REVIEW
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    • v.41
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    • pp.135-165
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    • 2009
  • It is not difficult to understand from laws and practices in arbitration area that arbitrators appointed have as many rights as their duties to do their performing duties especially to participate in the proceeding and deliberations of the arbitral process. However, sometimes can be happened that an arbitrator who was appointed by a party, refuses to participate in the proceeding or resign during the arbitral process. Generally, in the case, it is provided that the arbitrator who fails to act can be replaced by a substitute arbitrator. When it is decided to change an arbitrator, the appointment of an substitute arbitrator is likely to cause time delay, high cost with inconvenience. And also it is to be considered for additional cost and delay from possible need for repeating the hearings that were held at former arbitral tribunal. Sometimes, a party want to delay intentionally the arbitration process by using right for challenging arbitrator or designing with an arbitrator who was appointed by the party. That is why the reason it has been discussed for allowing the truncated tribunal that the remaining arbitrators that is named as truncated tribunal are permitted to complete the proceeding and issue decisions or arbitral awards. Unfortunately there are uncertain views on the validity of arbitral proceeding or recognitions and enforcement of truncated tribunal decisions in international commercial arbitration. In this article it is focusing on discussing truncated tribunal's benefits or barriers and problems through comparing with famous arbitral rules of international arbitral institutes including rules of UNCITRAL, LCIA, KCAB and the revising draft arbitration rule of UNCITRAL.

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Bioprocess Control for Continuous Culture of Dunaliella Salina in Flat Panel Photobioreactor (평판형 광생물반응기의 Dunaliella Salina 연속배양을 위한 생물공정 제어)

  • Kim, Gwang Ho;Ahn, Dong-Gyu;Park, Jong Rak;Choi, Gang Hun;Kim, Jong Tye;Kim, Ki Won;Jeong, Sang Hwa
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.2
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    • pp.137-142
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    • 2013
  • The indiscriminate use of the fossil fuel has caused serious environmental pollutions such as the shortage of energy and global warming. Microalgae have being emphasized as $3^{rd}$ generation biomass which makes the carbon dioxide reduce effectively as well as produces the biofuel. Large scale production of microbial biomass by continuous culture is a quite challenging issue, because off-line optimization strategies of a microbial process utilizing a model-based scheme give rise to many difficult problems. In this paper, the static and simple control method which was able to be applied in time-variant growth environment and large scale of algae culture was studied. The significant disturbances in on-line measurement of cell density were reduced by Savitzky-Golay FIR smoothing filter. Dunaliella salina was cultivated continuously in a flat panel photobioreactor by the on-off control of the turbidostat process.

A Multi-objective Optimization Approach to Workflow Scheduling in Clouds Considering Fault Recovery

  • Xu, Heyang;Yang, Bo;Qi, Weiwei;Ahene, Emmanuel
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.10 no.3
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    • pp.976-995
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    • 2016
  • Workflow scheduling is one of the challenging problems in cloud computing, especially when service reliability is considered. To improve cloud service reliability, fault tolerance techniques such as fault recovery can be employed. Practically, fault recovery has impact on the performance of workflow scheduling. Such impact deserves detailed research. Only few research works on workflow scheduling consider fault recovery and its impact. In this paper, we investigate the problem of workflow scheduling in clouds, considering the probability that cloud resources may fail during execution. We formulate this problem as a multi-objective optimization model. The first optimization objective is to minimize the overall completion time and the second one is to minimize the overall execution cost. Based on the proposed optimization model, we develop a heuristic-based algorithm called Min-min based time and cost tradeoff (MTCT). We perform extensive simulations with four different real world scientific workflows to verify the validity of the proposed model and evaluate the performance of our algorithm. The results show that, as expected, fault recovery has significant impact on the two performance criteria, and the proposed MTCT algorithm is useful for real life workflow scheduling when both of the two optimization objectives are considered.

Nonparametric Bayesian Statistical Models in Biomedical Research (생물/보건/의학 연구를 위한 비모수 베이지안 통계모형)

  • Noh, Heesang;Park, Jinsu;Sim, Gyuseok;Yu, Jae-Eun;Chung, Yeonseung
    • The Korean Journal of Applied Statistics
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    • v.27 no.6
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    • pp.867-889
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    • 2014
  • Nonparametric Bayesian (np Bayes) statistical models are popularly used in a variety of research areas because of their flexibility and computational convenience. This paper reviews the np Bayes models focusing on biomedical research applications. We review key probability models for np Bayes inference while illustrating how each of the models is used to answer different types of research questions using biomedical examples. The examples are chosen to highlight the problems that are challenging for standard parametric inference but can be solved using nonparametric inference. We discuss np Bayes inference in four topics: (1) density estimation, (2) clustering, (3) random effects distribution, and (4) regression.

Critical Cleaning Requirements for Flip Chip Packages

  • Bixenman, Mike;Miller, Erik
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • 2000.04a
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    • pp.43-55
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    • 2000
  • In traditional electronic packages the die and the substrate are interconnected with fine wire. Wire bonding technology is limited to bond pads around the peripheral of the die. As the demand for I/O increases, there will be limitations with wire bonding technology. Flip chip technology eliminates the need for wire bonding by redistributing the bond pads over the entire surface of the die. Instead of wires, the die is attached to the substrate utilizing a direct solder connection. Although several steps and processes are eliminated when utilizing flip chip technology, there are several new problems that must be overcome. The main issue is the mismatch in the coefficient of thermal expansion (CTE) of the silicon die and the substrate. This mismatch will cause premature solder Joint failure. This issue can be compensated for by the use of an underfill material between the die and the substrate. Underfill helps to extend the working life of the device by providing environmental protection and structural integrity. Flux residues may interfere with the flow of underfill encapsulants causing gross solder voids and premature failure of the solder connection. Furthermore, flux residues may chemically react with the underfill polymer causing a change in its mechanical and thermal properties. As flip chip packages decrease in size, cleaning becomes more challenging. While package size continues to decrease, the total number of 1/0 continue to increase. As the I/O increases, the array density of the package increases and as the array density increases, the pitch decreases. If the pitch is decreasing, the standoff is also decreasing. This paper will present the keys to successful flip chip cleaning processes. Process parameters such as time, temperature, solvency, and impingement energy required for successful cleaning will be addressed. Flip chip packages will be cleaned and subjected to JEDEC level 3 testing, followed by accelerated stress testing. The devices will then be analyzed using acoustic microscopy and the results and conclusions reported.

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Meta-synthesis Exploring Barriers to Health Seeking Behaviour among Malaysian Breast Cancer Patients

  • Yu, Foo Qing;Murugiah, Muthu Kumar;Khan, Amer Hayat;Mehmood, Tahir
    • Asian Pacific Journal of Cancer Prevention
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    • v.16 no.1
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    • pp.145-152
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    • 2015
  • Barriers to health seeking constitute a challenging issue in the treatment of breast cancer. The current meta-synthesis aimed to explore common barriers to health seeking among Malaysian breast cancer patients. From the systematic search, nine studies were found meeting the inclusion criteria. Data extraction revealed that health behavior towards breast cancer among Malaysia women was influenced by knowledge, psychological, sociocultural and medical system factors. In terms of knowledge, most of the Malaysian patients were observed to have cursory information and the reliance on the information provided by media was limiting. Among psychological factors, stress and sense of denial were some of the common factors leading to delay in treatment seeking. Family member's advice, cultural beliefs towards traditional care were some of the common sociocultural factors hindering immediate access to advanced medical diagnosis and care. Lastly, the delay in referral was one of the most common health system-related problems highlighted in most of the studies. In conclusion, there is an immediate need to improve the knowledge and understanding of Malaysian women towards breast cancer. Mass media should liaise with the cancer specialists to disseminate accurate and up-to-date information for the readers and audience, helping in modification of cultural beliefs that hinder timing health seeking. However, such intervention will not improve or rectify the health system related barriers to treatment seeking. Therefore, there is an immediate need for resource adjustment and training programs among health professional to improve their competency and professionalism required to develop an efficient health system.

Information Seeking, Evaluation, and Use on the Internet: A Case Study of Science and Engineering Scholars (인터넷의 정보의 탐색, 평가 및 활용:대학 이공계 연구자의 사례를 중심으로)

  • 이해영;이수영
    • Journal of the Korean Society for information Management
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    • v.18 no.4
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    • pp.163-181
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    • 2001
  • The Internet offers a challenging information seeking environment for users due to a great amount of information, heterogeneous objects, and diverse information quality. The purpose of this study was to identify the ways of information seeking, evaluating, and using in the Internet by looking at search behaviors of science and engineering scholars in Korean university. The research problems addressed in the study include the utility of web information, information searching strategies, the extent of search engines usage, and scholarly value of information in the Internet. The data were collected through individual interviews with 28 scholars recruited from science and engineering fields at the Myongji University. It was found that the scholars in this study less likely turn to search engines for finding research information than types of information while they use search engines primarily for searching personal information such as travel and hobbies. This is partly because the scholars believe that the information, especially research-related information, in the Internet lacks the value as scholarly information. They also tend to believe that foreign literature available in the Internet is more credible, professional, and recent than domestic literature. In conclusion, the implications for search engine developers, librarians, and researchers as users and producers in the Internet are discussed.

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Management of Defects on Lower Extremities with the Use of Matriderm and Skin Graft

  • Choi, Jun-Young;Kim, Seong-Hun;Oh, Gwang-Jin;Roh, Si-Gyun;Lee, Nae-Ho;Yang, Kyung-Moo
    • Archives of Plastic Surgery
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    • v.41 no.4
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    • pp.337-343
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    • 2014
  • Background The reconstruction of large skin and soft tissue defects on the lower extremities is challenging. The skin graft is a simple and frequently used method for covering a skin defect. However, poor skin quality and architecture are well-known problems that lead to scar contracture. The collagen-elastin matrix, Matriderm, has been used to improve the quality of skin grafts; however, no statistical and objective review of the results has been reported. Methods Thirty-four patients (23 male and 11 female) who previously received a skin graft and simultaneous application of Matriderm between January 2010 and June 2012 were included in this study. The quality of the skin graft was evaluated using Cutometer, occasionally accompanied by pathologic findings. Results All 34 patients showed good skin quality compared to a traditional skin graft and were satisfied with their results. The statistical data for the measurement of the mechanical properties of the skin were similar to those for normal skin. In addition, there was no change in the engraftment rate. Conclusions The biggest problem of a traditional skin graft is scar contracture. However, the dermal matrix presents an improvement in skin quality with elastin and collagen. Therefore, a skin graft along with a simultaneous application of Matriderm is safe and effective and leads to a significantly better outcome from the perspective of skin elasticity.

A Study on Wire-rope Type Furnace Scaffolding and Its Lifting System for Large-sized Boiler (대형 보일러 와이어로프 노내비계 및 인양시스템에 관한 연구)

  • HA, Seung Woo;Lee, Tae Ho;Lee, Hae Seung;Kim, Jeung Min;You, Tai Woo;Cho, Sun Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.7
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    • pp.679-683
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    • 2016
  • Boilers of large-sized coal-fired power plants are being operated under very poor conditions such as continuous operation or repeating of start-up and shutdown for a stable supply of electricity. Thus periodic inspection and maintenance are required to ensure reliability of operation. The loads of existing scaffolding systems for the maintenance of boilers are concentrated in the lower parts structurally, which may cause a serial collapse of the overall scaffolding system when there are problems in some members. Therefore, in this study, a safe furnace scaffolding system is developed by dispersing the loads in the upper part, as well as minimizing the hazards of serial collapsing. In addition, for cases where the direct installation of furnace scaffolding is challenging owing to the structure of the boiler tube, a lifting system for the installation of furnace scaffolding is developed so that furnace scaffolding can be supported to secure the integrity of the power generating facility.