• Coupled systems mechanics
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• 제11권2호
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• pp.151-166
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• 2022

Peltier cells have low efficiency, but they are becoming attractive alternatives for affordable and environmentally clean cooling. In this line, the current article develops closed-form and semianalytical solutions to improve the temperature distribution of Bi₂Te₃ thermoelements. From the distribution, the main objective of the current work-the optimal electric intensity to maximize cooling-is inferred. The general one-dimensional differential coupled equation is integrated for linear and quadratic geometry of thermoelements, under temperature constant properties. For a general shape, a piece-wise solution based on heat flux continuity among virtual layers gives accurate analytical solutions. For variable properties, another piece-wise solution is developed but solved iteratively. Taking advantage of the formulae, the optimal intensity is directly derived with a minimal computational cost; its value will be of utility for more advanced designs. Finally, a parametric study including straight, two linear, barrel, hourglass and vase geometries is presented, drawing conclusions on how the shape of the thermoelement affects the coupled phenomena. A specially developed coupled and non-linear finite element research code is run taking into account all the materials of the cell and using symmetries and repetitions. These accurate results are used to validate the analytical ones.

• Nuclear Engineering and Technology
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• 제55권9호
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• pp.3388-3400
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• 2023

Detailed analysis of the neutron pathway through matter inside the nuclear reactor core is exceedingly needed for safety and economic considerations. Due to the constant development of high-performance computing technologies, neutronics analysis using computer codes became more effective and efficient to perform sophisticated neutronics calculations. In this work, a commercial pressurized water reactor (PWR) presented by Virtual Environment for Reactor Applications (VERA) Core Physics Benchmark are modeled and simulated using a high-fidelity simulation of OpenMC code in terms of criticality and fuel pin power distribution. Various problems have been selected from VERA benchmark ranging from a simple two-dimension (2D) pin cell problem to a complex three dimension (3D) full core problem. The development of the code capabilities for reactor physics methods has been implemented to investigate the accuracy and performance of the OpenMC code against VERA SCALE codes. The results of OpenMC code exhibit excellent agreement with VERA results with maximum Root Mean Square Error (RMSE) values of less than 0.04% and 1.3% for the criticality eigenvalues and pin power distributions, respectively. This demonstrates the successful utilization of the OpenMC code as a simulation tool for a whole core analysis. Further works are undergoing on the accuracy of OpenMC simulations for the impact of different fuel types and burnup levels and the analysis of the transient behavior and coupled thermal hydraulic feedback.

• Steel and Composite Structures
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• 제49권4호
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• pp.393-405
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• 2023

In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cells' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.

• 전자통신동향분석
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• 제38권6호
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• pp.62-74
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• 2023

In response to diverse external stimuli, sensory receptors generate spiking nerve signals. These generated signals are transmitted to the brain along the neural pathway to advance to the stage of recognition or perception, and then they reach the area of discrimination or judgment for remembering, assessing, and processing incoming information. We review research trends in neuromorphic sensory perception technology inspired by biological sensory perception functions. Among the various senses, we consider sensory nerve decoding technology based on sensory nerve pathways focusing on touch and smell, neuromorphic synapse elements that mimic biological neurons and synapses, and neuromorphic processors. Neuromorphic sensory devices, neuromorphic synapses, and artificial sensory memory devices that integrate storage components are being actively studied. However, various problems remain to be solved, such as learning methods to implement cognitive functions beyond simple detection. Considering applications such as virtual reality, medical welfare, neuroscience, and cranial nerve interfaces, neuromorphic sensory recognition technology is expected to be actively developed based on new technologies, including combinatorial neurocognitive cell technology.

• 한국인터넷방송통신학회논문지
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• 제24권1호
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• pp.207-212
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• 2024

수소연료전지의 중요성은 계속 강조되며, 이 분야에서의 교육 및 훈련 수요가 증가하고 있다. 다양한 교육 환경 중에서 메타버스 교육은 특히 원격 학습에 대응하기 위해 글로벌 교육산업에서 새로운 변화의 시대를 열고 있다. 메타버스가 교육에 가져온 가장 중요한 변화는 단방향, 강사 중심 및 정적인 가르침 접근에서 다방향 및 동적인 접근으로의 전환이다. 메타버스는 수소 연료전지 엔지니어 교육에서도 효과적으로 활용될 것으로 예상되며, 교육과 훈련이 언제 어디서나 가능하게 함으로써 교육의 효과를 향상시킬 뿐만 아니라 엔지니어링 교육에 관련된 비용을 줄일 수 있을 것으로 기대된다. 본 연구에서는 이러한 아이디어에 영감을 받아 연료 전지 교육 플랫폼을 설계하고 있다. 메타버스를 활용하여 이론 학습 및 훈련을 결합한 플랫폼을 만들었다. 본 연구에서는 학습 참여자의 참여도를 높이기 위한 교육 훈련 콘텐츠 개발, 사용성 향상을 위한 사용자 인터페이스 구성, 가상 세계에서 물체와 상호 작용하는 환경 생성, 디지털 트윈 형태의 수렴 서비스 지원 등의 주요 요소를 개발했다.

• 대한전자공학회논문지TC
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• 제39권1호
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• pp.20-33
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• 2002

패킷을 이용한 음성 서비스는 무선 망을 통한 음성 서비스 등으로 구현되고 있으며, 미래의 모든 음성 서비스는 패킷 기반형으로 진화할 것이다. 이러한 측면에서 ATM의 AAL2를 이용한 음성 패킷의 전달은 백본 망에서 음성 패킷의 전달 효율을 증가시키는 대표적인 방법이다. AAL2를 이용한 음성 서비스의 경우, 망의 자원이 허락되면 새로운 호의 연결을 수락한다. 하지만 새로운 호에 의해 발생되는 패킷으로 기존의 AAL2 연결의 전송 지연이 급격하게 증가할 가능성이 존재한다. 따라서 본 논문에서는 AAL2를 이용한 음성 서비스를 제공하는데 있어, AAL2 버퍼 관리 매카니즘으로 N개의 호에 대해 N개의 가상 버퍼를 통하여 각각의 호에 대한 전송지연변이를 계산하고, 전송 지연 변이에 따른 패킷 폐기 알고리즘을 제시한다. 이러한 패킷 폐기 알고리즘은 새로운 호의 수락으로 인해 발생하는 전송지연변이의 증가때문에 기존의 호의 QoS가 급격하게 악화되는 것을 방지한다. 그리고 종단 대 종단 지연에 영향을 미치는 AAL2 패킷 구성과 ATM 셀 구성의 요소를 분석하고, 음성 서비스를 ATM 셀로 만드는 과정을 K-정책을 갖는 M/D/1 큐잉시스템과 MIN(K, Tc) 정책을 갖는 M/D/1 큐잉 시스템으로 모델링함으로써, AAL2 패킷을 ATM 셀로 만드는 과정에서의 ATM 셀 밀집도와 AAL2 버퍼에서의 지연시간을 분석하였다. 제안하는 알고리즘을 모의 실험하여서 큐잉 시스템 모델링 결과와 비교하고 성능 결과를 분석하였다. 성능 분석 결과, AAL2 패킷 생성 시간과 ATM셀 생성 시간은 음성 소스의 갯수가 증가할 경우 전송 지연에 영향을 미치지 못하였으며, 제안하는 알고리즘은 음성 소스의 QoS를 저하하지 않은 수준에서 전송 지연을 낮게 유지할 수 있었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.48-48
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• 2010

Sound quality and NVH-issues(Noise, Vibration and Harshness) of vehicles has become very important for car manufacturers. It is interpreted as among the most relevant factors regarding perceived product quality, and is important in gaining market advantage. The general sound quality of vehicles was gradually improved over the years. However, today the development cycles in the automotive industry are constantly reduced to meet the customers' demands and to react quickly to market needs. In addition, new drive and fuel concepts, tightened ecological specifications, increase of vehicle classes and increasing diversification(increasing market for niche vehicles), etc. challenge the acoustic engineers trying to develop a pleasant, adequate, harmonious passenger cabin sound. Another aspect concerns the general pressure for reducing emission and fuel consumption, which lead to vehicle weight reductions through material changes also resulting in new noise and vibration conflicts. Furthermore, in the context of alternative powertrains and engine concepts, the new objective is to detect and implement the vehicle sound, tailored to suit the auditory expectations and needs of the target group. New questions must be answered: What are appropriate sounds for hybrid or electric vehicles? How are new vehicle sounds perceived and judged? How can customer-oriented, client-specific target sounds be determined? Which sounds are needed to fulfil the driving task, and so on? Thus, advanced methods and tools are necessary which cope with the increasing complexity of NVH-problems and conflicts and at the same time which cope with the growing expectations regarding the acoustical comfort. Moreover, it is exceedingly important to have already detailed and reliable information about NVH-issues in early design phases to guarantee high quality standards. This requires the use of sophisticated simulation techniques, which allow for the virtual construction and testing of subsystems and/or the whole car in early development stages. The virtual, testing is very important especially with respect to alternative drive concepts(hybrid cars, electric cars, hydrogen fuel cell cars), where complete new NVH-problems and challenges occur which have to be adequately managed right from the beginning. In this context, it is important to mention that the challenge is that all noise contributions from different sources lead to a harmonious, well-balanced overall sound. The optimization of single sources alone does not automatically result in an ideal overall vehicle sound. The paper highlights modern and innovative NVH measurement technologies as well as presents solutions of recent NVH tasks and challenges. Furthermore, future prospects and developments in the field of automotive acoustics are considered and discussed.

• 한국항해항만학회지
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• 제27권3호
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• pp.283-288
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• 2003

Recently, the growth of applications and services over high-speed Internet increases, ATM networks as wide area back-bone has been a major solution. As the conventional TCP/IP suite is still the standard protocol used to support upper application on current. Internet, the issues regarding whether TCP/IP will operate efficiently on top of an ATM infrastructure and how to control its QoS still remain for studies. TCP uses a window-based protocol for flow control in the transport layer. When TCP uses the UBR service in ATM layer, the control method is only buffer management. If a cell is discarded in ATM layer, one whole packet of TCP will be lost; this fact occur the most TCP performance degradation. Several dropping strategies, such as Tail Drop, EPD, PPD, SPD, FBA, have been proposed to improve the TCP performance over ATM. In this paper, to improve the TCP performance, we propose a packet dropping scheme that is based on comparison with EPD, SPD and FBA. Our proposed scheme is applied to schemes discussed in the previous technology. Our proposed scheme does not need to know each connection's mean packet size. When the buffer exceeds the given threshold, it is based on comparison between the number of dropped packet and the approved packet. Our results are reported and discussed for comparing these discarding schemes under similar conditions. Although the number of virtual channel (VC) is increased, the simulation results showed that the proposed scheme can allocate more fairly each VC than other scheme.

• 대한방사선기술학회지:방사선기술과학
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• 제38권1호
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• pp.17-21
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• 2015

소아백혈병의 치료방법 인 조혈모세포이식법의 전처치 방법으로서 항암제와 함께 대표적으로 사용되고 있는 전신방사선조사에 대하여 치료를 시행하기 전 정량적인 인체장기에 대한 선량을 평가하고자 하였다. 모의실험 프로그램 MCNPX를 사용하여 가상의 공간에서 소아용 모의피폭체를 대상으로 조직보상체의 재질을 변화시켜 실험을 진행하였다. 그 결과 첫째, 평균피부선량은 조직보상체의 재질에 따라 Plexiglass는 74.60 mGy/min, Al은 73.96 mGy/min, Cu는 72.26 mGy/min, Pb의 경우 67.90 mGy/min을 보였다. 둘째, 심부선량은 조직보상체 재질에 상관없이 갑상선, 생식선, 소화기계, 머리, 폐, 신장의 순으로 높게 나타났다. 끝으로 조직보상체와 환자와의 거리는 50 cm 이격시켰을 때가 이상적인 것으로 분석되었다. 본 연구결과를 토대로 할 때, 조직보상체 Al, Cu, Pb은 현재 사용되고 있는 Plexiglass 재질을 대체할 수 있을 것으로 판단된다.

• 한국의류학회지
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• 제44권4호
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• pp.573-593
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• 2020

This study analyzes consumers' responses toward chatbot services in a fashion retail context. Anthropomorphism and personalization of chatbots are proposed as critical features of a chatbot service that attract positive behavioral intentions from consumers. Social presence, trust, and enjoyment are expected to mediate associations among chatbot characteristics and consumers' acceptance of the service. The experiment was conducted in a controlled laboratory; participants were instructed to engage with a virtual shopping chatbot service via their cell phone and complete a questionnaire online. A total of 189 participants participated in this study along with and four experimental groups of 2 (anthropomorphism: high / low) × 2 (personalization: high / low) were formed with between-subject design. The collected data were analyzed using SPSS 25.0 and SPSS PROCESS Macro programs. The results show that the effect of anthropomorphism and personalization of chatbots on consumers' service acceptance intention when using fashion shopping chatbot service were mediated sequentially by social presence, trust, social presence and enjoyment. This study provides meaningful evidence on the effects of chatbots characterized by anthropomorphism and personalization on consumer responses, acceptance intention and associated psychological mechanisms by expanding the field of consumer behavior into chatbot services.