• International Journal of Internet, Broadcasting and Communication
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• 제16권1호
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• pp.29-35
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• 2024

TCP is considered as one of the major candidate transport protocols even for constrained IoT networks..In our previous work, we investigated the congestion control mechanism of the uIP TCP. Since the uIP TCP sets the window size to one segment by default, managing the retransmission timer is the primary approach to congestion control. However, the original uIP TCP sets the retransmission timer based on the fixed RTO, it performs poorly when a radio duty cycling mechanism is enabled and the hidden terminal problem is severe. In our previous work, we proposed a TCP retransmission timer adjustment scheme for uIP TCP which adopts the notion of weak RTT estimation of CoCoA, exponential backoffs with variable limits, and dithering. Although our previous work showed that the proposed retransmission timer adjustment scheme can improve performance, we observe that the scheme often causes a node to set the retransmission timer for an excessively too long time period. In this work, we show that slightly modifying the dithering mechanism of the previous scheme is effective for improving TCP fairness.

• 디지털융복합연구
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• 제16권6호
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• pp.197-204
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• 2018

3D 컴퓨터그래픽에서 유체를 이용한 사실적인 시각효과(Visual Effects)는 영상의 질적 완성도를 높이는데 중요한 요소로 작용한다. 유체의 각 속성을 제어하여 물, 불, 폭발 등의 사실적인 움직임을 생성시키는 과정을 유체 시뮬레이션(Fluid Simulation)이라 한다. 일반적으로 유체 시뮬레이션의 제작은 주 시뮬레이션(Main simulation) 작업단계에 집중되지만, 이를 위한 사전준비 단계(Initial set up)인 초기 방출자에 대한 효과적인 생성방법이 중요하다. 이에 본 연구의 목적은 유체의 초기 방출 운동과 형태에 관여하는 요소들을 분석하고 이를 초기 제작공정에 적용할 수 있는 효과적인 방법을 제시하고자 한다. 이를 위한 연구의 전개는 첫째, 기존 관련 연구에 대해 분석 및 문제점을 제기하고, 둘째, 보다 효과적인 유체효과 시뮬레이션 진행을 위해, Dynamic Fluid Emitter Creation과 User Design Type Emission Velocity Solution에 대한 두가지 실험을 진행한다. 본 연구를 통해, 사용자 설계형의 방출 제어 솔루션을 통해 효율적인 초기단계의 유체 시뮬레이션 제작방법을 제시한다.

• 한국전자파학회논문지
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• 제16권1호
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• pp.102-112
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• 2005

본 논문에서는 CSP(Chip Size Package)를 이용하여 정합소자 및 모든 바이어스소자, ESD(Electrostatic Dis-charge) 보호소자를 MMIC상에 완전집적한 K/Ka밴드 광대역 MMIC chip set에 관하여 보고한다. CSP에 대해서는 이방성 도전필름인 ACF(Anisotropic Conductive Film)를 이용하였으며, 그 결과 MMIC 패키지 프로세스가 간략화 되었고, CSP MMIC의 저 가격화가 실현되었다. MMIC상에 집적하기 위한 DC 바이어스 용량소자로서는 고유전율의 $STO(SrTi_{3})$ 필름 커패시터가 이용되었으며, DC 피드소자와 ESD 보호소자로서는 LC 병렬회로가 사용되었다. 그리고, K/KA 밴드 광대역에 걸친 MMIC의 정합과 안정도를 위해서는 프리매칭회로와 RC 병렬회로가 이용되었으며, 제작된 CSP MMIC는 광대역(K/Ka) 밴드에서 양호한 RF 특성을 보였다. 본 논문은 K/Ka 밴드의 주파수 대역에 있어서의 완전집적화 CSP MMIC 칩셋에 관한 최초의 보고이다.

• Safety and Health at Work
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• 제14권1호
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• pp.43-49
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• 2023

Background: Messaging surrounding skin cancer prevention has previously focused on the general public and emphasized how or when activities should be undertaken to reduce solar ultraviolet radiation (UVR) exposure. Generic messages may not be applicable to all settings, and should be tailored to protect unique and/or highly susceptible subpopulations, such as outdoor workers. The primary objective of this study was to develop a set of tailored, practical, harm-reducing sun safety messages that will better support outdoor workers and their employers in reducing the risk of solar UVR exposure and UVR-related occupational illnesses. Methods: We adapted a core set of sun safety messages previously developed for the general population to be more applicable and actionable by outdoor workers and their employers. This study used an integrated knowledge translation approach and a modified Delphi method (which uses a survey-based consensus process) to tailor the established set of sun safety messages for use for outdoor worker populations. Results: The tailored messages were created with a consideration for what is feasible for outdoor workers, and provide users with key facts, recommendations, and tips related to preventing skin cancer, eye damage, and heat stress, specifically when working outdoors. Conclusion: The resulting tailored messages are a set of evidence-based, expert- approved, and stakeholder-workshopped messages that can be used in a variety of work settings as part of an exposure control plan for employers with outdoor workers.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2013년도 추계학술대회
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• pp.722-725
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• 2013

본 연구에서는 열처리를 하지 않은 소자와 열처리 소자의 기본 특성을 비교, 분석하고 온도에 따른 특성 변화를 확인하였다. 사용된 소자는 상부전극이 Pt/Ti(150nm), 하부전극은 Pt(150nm), 산화층은 $HfO_2$(70nm)이고, 열처리 온도는 $500^{\circ}C$, $850^{\circ}C$ 이다. 측정 소자 성능은 Set/Reset 전압, sensing window(저항상태 차이)다. 측정결과 세 종류의 소자의 기본 특성은 열처리별 온도가 높을수록 Set/Reset전압과 sensing window가 증가하였다. 온도에 따른 기본특성 분석 실험 결과 온도가 증가함에 따라 Set/Reset전압과 sensing window가 감소하였다. Set/Reset 전압의 온도에 따른 변화율은 $850^{\circ}C$ 열처리한 소자가 제일 작았고, sensing window의 변화율은 $500^{\circ}C$ 열처리 소자에서 가장 작은 변화율을 보였다. Set/Reset 전압의 변화율 과 sensing window를 고려했을 때 $500^{\circ}C$ 열처리 소자가 좋은 메모리 특성을 보였다.

• 디지털산업정보학회논문지
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• 제14권4호
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• pp.189-204
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• 2018

The purpose of this study is to examine an organizational performance difference by individual utilization level of the smart work. The Smart work help minimizing business process and improving organization productivity based on information technology. This new technology provides a flexible way of the task through smart-work center, videoconferencing, telecommuting, mobile(remote control) and business-only messenger. This investment changes organizational culture, institutions and behavior by new technology applying. The organization system change due to smart work has trouble between alteration preferences and existing maintains a group. In response, the organization should make investment justification of smart work for institutional and culture stabilized by a new system in organization. I set up the analytical process of four stages for empirical research. It will analyze an operation difference of the smart work between pre and post investment in the first-step analysis. The two-step analysis will conduct a text mining analysis of smart work operations. The three-step analysis will identify organization performance differences among individual levels in smart work. The four-step analysis will identify a factor difference in organizational performance by individual utilization level on smart work. According to the study, It has been revealed a difference between the pre and post investment performance on smart work. The text mining analyses many appeared an improvement opinion of organizational culture. Next, there is a difference in organization performance among utilize groups of smart work. Furthermore, the factors of organizational performance among groups appeared differently. The theoretical contribution of this study provided to expand the organizational theory of organization change and resistance. The practical implications provided to require a strong guideline an organizational culture and institution for smart work.

• International Journal of Quality Innovation
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• 제9권3호
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• pp.71-91
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• 2008

The definition of cycle time is the time from the wafer start to the wafer output. It usually takes one or two months to get the product since customer decides to produce it. The cycle time is a critical factor for customer satisfaction because it represents the response time to the market. Long cycle time reflects the ineffective investment for the capital. The cycle time is very important for foundry because long cycle time will cause customer unsatisfied and the order loss. Consequently, all of the foundries put lots of human source in the cycle time improvement. Usually, we make decisions based on the experience in the cycle time management. We have no mechanism or theory for cycle time management. We do work-in-process (WIP) management based on turn rate and standard WIP (STD WIP) set by experiences. But the experience didn't mean the optimal solution, when the situation changed, the cycle time or the standard WIP will also be changed. The experience will not always be applicable. If we only have the experience and no mechanism, management will not be work out. After interview several foundry fab managers, all of the fab can't reflect the situation. That is, all of them will have an impact period after product mix or utilization varied. In this study, we want to develop a formula for standard WIP and use statistical process control (SPC) concept to set WIP upper/lower limit level. When WIP exceed the limit level, it will trigger action plans to compensate WIP Profile. If WIP Profile balances, we don't need too much WIP. So WIP level could be reduced and cycle time also could be reduced.

• Tribology and Lubricants
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• 제30권5호
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• pp.271-277
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• 2014

Hydraulic reciprocating seals have been widely used to prevent fluid leakage and to provide lubricant film on counter surface in various hydraulic system. The degradation of the seal may cause the catastrophic failure of the hydraulic system. To assess the durability of the seals and the compatibility with counter surface, accelerated life testing (ALT) has been typically employed from industry. However, ALT often takes up to a few months to cause a failure of the seals, and therefore, there is a need to develop more efficient ALT methods. In this work, the degradation characteristics of polyurethane (PU) seals from field test are investigated and they are compared to those from the component and bench tests, with an aim to contribute to the development of ALT method. From the comparison of the cross-sectional profiles of the sealing surface of the PU specimens before and after the tests, both wear and compression set are found to be responsible for degradation of the PU seals. It is also shown that the major wear mechanisms of the PU seals from the field is abrasive wear and formation of pits. The component and bench tests performed in this work are shown to reproduce such wear mechanisms, and therefore, those test methods can be used as an ALT method for PU seals. In particular, the bench test proposed in this work may be effectively utilized to assess the durability and the compatibility of the seals with the counter surface. The results of this work are expected to aid in the design of ALT for PU seal.

• Asian Journal for Public Opinion Research
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• 제5권2호
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• pp.143-174
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• 2018

A cultural exchange program widens the horizons of students. It gives them the opportunity to associate with other societies and learn their cultures at the same time. This program also serves as a training ground where students enhance their skills, acquire learnings, and gain experiences that will help them in their future careers and make them more competitive than others. Hence, the objective of this study is to come up with an output from a set of guidelines established and gathered from the different "work and travel" experiences of the participants. This study adopted the phenomenological and was conducted in places that are relatively quiet for recording, and suitable and convenient for both the researchers and participants. The researchers gathered data through in-depth interviews of samples gathered through snowball sampling. Cellphones were used to record interviews. At the end of the thematic analysis of information, the researchers came up with three major categories which included: (1) 'having the opportunity to know the industry well and improve one's capability', 'undergoing different cultural exchange experiences for better development', and 'being able to practice intercultural immersion'. Some of the researchers' recommendations would be to institute a feedback mechanism such as personal interviews, monitoring visits, etc. and use the output, a set of guidelines, that would help the future 'work and travel' participants to prepare and anticipate the program they would undergo.

• 디지털융복합연구
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• 제12권3호
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• pp.317-323
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• 2014

본 연구는 슬링운동이 근골격계질환자들의 근체형 변화에 미치는 영향을 알아보기 위하여 D광역시 H산업체 근로자 20명을 대상으로 실험군(10명)과 대조군(10명)으로 나누어, 12주간 실험군에게 슬링운동 적용 전 후의 근체형을 비교분석하였다. 통계프로그램은 SPSS 18.0 을 이용하였고, 12주간 슬링운동 전 후의 집단 간 비교는 대응 t-test를 이용하였다. 12주간 슬링운동을 실시한 결과, 실험군(10명)의 흉부, 요부 및 배부에서 모두 유의한 효과를 나타내었으나 대조군(10명)에서는 유의한 효과가 나타나지 않았다. 따라서 12주간의 슬링운동이 작업관련성 근골격계 질환자들의 근체형 변화에 도움을 주는 의미 있는 운동으로 사료된다.