• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.40.4-41
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• 2010

Using magnetic field and plasma moment data obtained by THEMIS satellites(A, D, and E), we selected 203 fast flow events accompanied by dipolarization in the near-Earth region( X(GSM) = -7 ~ -12 RE) and statistically examined their properties. It was found that most of the fast flows show the maximum velocity between 1 minute before dipolarization onset and 2 minutes after onset and proceed earthward and duskward. We also found that only the flows with low velocity of less than 400 km/s are observed at X > -8 RE, while the high velocity flows(as well as low velocity flows) are observed at the further tailward region(X < -8 RE). And most of the tailward flows are slow regardless of distance at X(GSM) = -7 ~ -12 RE. On the other hand, if we consider the fast flow as a bubble (Pontius and Wolf, 1990), the entropy parameter, PV5/3 is an important factor to describe the plasma sheet dynamics. Thus we investigated the relationship between the flow velocity and the amount of change in PV5/3 before and after dipolarization onset and found out that the dipolarizations with more depleted entropy parameter tend to show higher flow velocity. Also we examined how the magnetic field at geosynchronous orbit responds to the fast flow accompanied by dipolarization in the near-earth plasma sheet, using the measurements from GOES 11 and 12 statellites. We found that most of the fast flows do not reach geosynchronous orbit as suggested by Ohtani et al. (2006).

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.236-245
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• 2021

In this study, direct numerical and large eddy simulations of transitional flows around studs were conducted to investigate the effectiveness of turbulence stimulators at very low speeds for the minimum propulsion power condition of four knots. For simplicity, the studs were assumed to be installed on a flat plate, while the wake was observed up to 0.23 m downstream behind the second stud. For applicability to a model ship, we also studied the flow characteristics behind the first and second studs installed on a curved plate, which was designed to describe the geometry of a bulbous bow. A laminar-to-turbulent transition was observed in the wake at Re_D ≥ 921 (U_∞≥0.290 m/s), and the wall shear stress at Re_D = 1162 (U_∞ = 0.366 m/s) in the second wake was similar to that of the fully developed turbulent boundary layer after a laminar-to-turbulent transition in the first wake. At Re_D = 581 (U_∞ = 0.183 m/s), no turbulence was stimulated in the wake behind the first and second studs on the flat plate, while a cluster of vortical structures was observed in the first wake over the curved plate. However, a cluster of vortical structures was revealed to be generated by the reattachment process of the separated shear layer, which was disturbed by the first stud rather than directly initiated by the first stud. It was quite different from a typical process of transition, which was observed at relatively high Re_D that the spanwise scope of the turbulent vortical structures expanded gradually as it went downstream.

• 생명과학회지
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• 제8권2호
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• pp.223-233
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• 1998

Molecular chaperone의 발견은 생명과학자들에게 살아있는 세포 내에서 어떻게 생체활성단백질이 만들어지고 유지되는지에 대한 자극과 함께 그것을 증명하기 위한 실험동기를 부여하였다. 초기에는 Molecular chaperone이 nucleosomes의 assembly에 관여하는 단백질을 설명하기 위하여 사용되었으나, 지금은 기본적인 세포생리기능의 하나인 단백질의 folding과 assembly를 돕는 assistant protein으로 주로 사용된다. 단백질합성 뿐만 아니라 단백질수송, oligomeric structure의 assembly와 disassembly, heat shock을 포함한 각종 내, 외부스트래스에 의해서 변성된 단백질의 세로내분화와 회복에도 Molecular chaperone이 관여하고 있다. 그러나 아직까지는 Molecular chaperone들의 3차구조와 그들간의 상호작용에 관한 정보가 부족하여 크게 진전되지 못하고 있지만, 많은 연구자에 의한 정보축적으로 인하여 빠른 시일 내에 Molecular chaperone에 세포내역할이 분명하게밝혀질 것이다.

• Perspectives in Nursing Science
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• 제9권2호
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• pp.83-93
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• 2012

Purpose: The purpose of this study was to describe the post-traumatic stress experiences of firefighters and paramedics. Methods: The participants were 20 fire fighters and paramedics who belong to the Busan Fire Department. Data were collected through in-depth, unstructured audio-taped interviews by the investigator over a six-month period. The participants were asked to describe their post-traumatic stress. The data were analyzed according to Giorgi's method for phenomenological analysis. Results: The interview data were organized by theme into 7 categories that emerged from the analysis. Participants faced various post-traumatic stresses working as fire fighters or paramedics. The categories were suffering from disastrous situations, feeling of fear and helplessness in the face of death, re-experiencing vividly the past traumatic situation, avoiding painful reminders of the trauma, emotional numbing as time passes, suffering from emotional arousal and increased anxiety, and struggling to cope with the post-traumatic stress. Conclusion: This study provides a better understanding of post-traumatic stress experiences from fire fighters and paramedics and the knowledge gained from this study will help in developing appropriate post-traumatic stress management programs.

• Educational Technology International
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• 제9권2호
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• pp.97-121
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• 2008

The purposes of the present study are to describe the design of mobile learning scenarios based on learning sciences theories, and to discuss implications for the future research in this area. To move beyond mere speculations about the abundant possibilities of mobile learning and to make real impact in K-12 school settings, it is critical to conduct school-based research grounded on the learning sciences theories. Towards this end, this paper describes school-based mobile learning projects conducted by a research team at the Learning Sciences Lab in Singapore, and then discusses the possibilities and challenges of mobile learning to further inform future research. Specifically, this paper explores the affordances of mobile technology, such as portability, connectivity and context-sensitivity, to design seamless learning scenarios that bridge formal and informal learning experiences. The authors present a framework for re-conceptualizing different types of learning based on physical settings and intentionality, and then describe two seamless learning scenarios, namely 3Rs and Chinatown Trail, which were implemented in one primary school in Singapore. In conclusion, the authors discuss the affordances of seamless mobile learning for enhancing one's lived experiences to build a living ecological relationship between the person and the environment, and how mobile technology can play a critical role for enabling such lived experiences.

• 항공우주기술
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• 제4권2호
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• pp.163-170
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• 2005

국가 우주개발 중장기계획에 따라 향후 10년간 다양한 발사체 및 위성을 개발할 필요가 있다. 그러므로 이러한 발사체 및 위성 개발과정에 있어 ReTF나 PTA-II 시험설비와 같은 시험설비가 다수 필요할 것으로 예상된다. 이에 우리연구원은 KSLV 추진기관에 대한 종합 시험을 수행할 수 있는 대형 연소시험설비 구축을 계획 중이다. 본 논문에서는 해당 시험설비의 기본 설계안에 따른 시설 배치 레이아웃과 위험물 저장량을 기초로 하여 시험설비에서 화재 또는 폭발 발생 시 그 피해가 어떻게 전파되는지 모델 해석을 통해 알아보았다. 논문에 포함되어진 안전성 평가, 피해정도, 피해범위를 바탕으로 기 수행된 설계 결과를 보완함으로써 좀 더 안전한 시험설비를 구축할 수 있도록 하는 것이 목적이다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.788-793
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• 2004

Internet-based distribution of digital contents provides great opportunities for producers, distributors and consumers, but it may seriously threaten users' privacy. The Digital Rights Management (DRM) systems which one of the major issues, concern the protection of the ownership/copyright of digital content. However, the most recent DRM systems do not support the protection of the user's personal information. This paper examines the lack of privacy in DRM systems. We describe a privacy policy and user's privacy preferences model that protect each user's personal information from privacy violation by DRM systems. We allow DRM privacy agent to automatically negotiate between the DRM system policy and user's privacy preferences to be disclosed on behalf of the user. We propose an effective negotiation algorithm for the DRM system. Privacy rules are created following the negotiation process to control access of the user's personal information in the DRM system. The proposed privacy negotiation algorithm can be adapted appropriately to the existing DRM systems to solve the privacy problem effectively.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.279-287
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• 2009

Magnetic resonance electrical impedance tomography (MREIT) is a new medical imaging modality providing cross-sectional images of a conductivity distribution inside an electrically conducting object. MREIT has rapidly progressed in its theory, algorithm and experimental technique and now reached the stage of in vivo animal and human experiments. Conductivity image reconstructions in MREIT require various steps of carefully implemented numerical computations. To facilitate MREIT research, there is a pressing need for an MREIT software package with an efficient user interface. In this paper, we present an example of such a software, called CoReHA which stands for conductivity reconstructor using harmonic algorithms. It offers various computational tools including preprocessing of MREIT data, identification of boundary geometry, electrode modeling, meshing and implementation of the finite element method. Conductivity image reconstruction methods based on the harmonic $B_z$ algorithm are used to produce cross-sectional conductivity images. After summarizing basics of MREIT theory and experimental method, we describe technical details of each data processing task for conductivity image reconstructions. We pay attention to pitfalls and cautions in their numerical implementations. The presented software will be useful to researchers in the field of MREIT for simulation as well as experimental studies.

• Journal of Communications and Networks
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• 제12권2호
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• pp.174-180
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• 2010

Automatic Repeat reQuest (ARQ) is a very effective technique against transmission error at the medium access control (MAC) layer. An erroneous MAC protocol data unit can be typically retransmitted within a given limit. In order to improve the IP-level performance, which directly affects the user-perceived quality-of-service (QoS), we propose a new truncated ARQ strategy, called MAC service data unit-based ARQ (S-ARQ), where the finite number of opportunities for retransmissions are shared by multiple fragments out of an IP datagram. We describe how SARQ can be implemented in a practical system, and then propose another variant of S-ARQ employing a functionality called early detection of failure. Basically, we evaluate the performance of SARQ in two different manners. First, assuming i.i.d. error process, we analyze both the probability of the delivery failure and the average delay of IP datagram. Then, we assess the performance of S-ARQ via simulation over a 2-state Markov channel.

• Advances in aircraft and spacecraft science
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• 제4권4호
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• pp.449-465
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• 2017

The aim of the present work is to present a computational study of the non-linear aero-elastic behavior of a multi-layered Thermal Protection System (TPS). The severity of atmospheric re-entry conditions is due to the combination of high temperatures, high pressures and high velocities, and thus the aero-elastic behavior of flexible structures can be difficult to assess. In order to validate the specific computational model and the overall strategy for structural and aerodynamics analyses of flexible structures, the simplified TPS sample tested in the 8' High Temperature Tunnel (HTT) at NASA LaRC has been selected as a baseline for the validation of the present work. The von $K{\acute{a}}rm{\acute{a}}n^{\prime}s$ three dimensional large deflection theory for the structure and a hybrid Raleigh-Ritz-Galerkin approach, combined with the first order Piston Theory to describe the aerodynamic flow, have been used to derive the equations of motion. The paper shows that a good description of the physical behavior of the fabric is possible with the proposed approach. The model is further applied to investigate structural and aero-elastic influence of the number of the layers and the stitching pattern.