• 한국기계가공학회지
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• 제20권12호
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• pp.107-112
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• 2021

The usage of electric-powered components consisting of several electrical and mechanical parts is continuously increasing in automobiles. Therefore, continuous assessment of the reliability and quality of these electric-powered parts is crucial. In this study, a noise and vibration measurement system for testing and evaluating the different electric-powered parts of automobiles was designed. Further, an FFT analysis was performed on some electric-powered steering assembly test equipment. In the FFT analysis of the noise and vibration signals for each essential fault part, the vibration FFT analysis was significantly compared with the noise analysis. The results showed that the vibration FFT analysis was more effective in determining the reliability and quality of the electric-powered parts.

• 시스템엔지니어링학술지
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• 제18권1호
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• pp.84-89
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• 2022

For system maintenance optimization, it is necessary to establish a state information system by CBM+ including CBM and RCM, and sensor selection for CBM+ application requires system process for function model analysis at the early design stage. The study investigated the contents of CBM and CBM+, analyzed the function analysis tasks and procedures of the system, and thus presented a D-FMEA based sensor selection inference methodology at the early stage of design for CBM+ application, and established it as a D-FMEA based sensor selection inference process. The D-FMEA-based sensor inference methodology and procedure in the early design stage were presented for diesel engine sub assembly.

• 대한물리치료과학회지
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• 제24권1호
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• pp.59-68
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• 2017

Purpose : The aims of this study was to conduct a systematic literature review with meta-analysis to investigate the effect of virtual reality based rehabilitation program on balance of patient with stroke in Korean studies. Method : The studies for analysis were searched in electronic databases(Research Information Sharing Service; RISS, Korean Studies Information Service; KISS, DBpia, e-articles, National Assembly Library). The key words for search were 'virtual reality', 'stroke', and 'balance' and only randomized controlled trials and clinical controlled trials were included. Of 40 studies identified in the search, 20 studies met the criteria of this study and included in this meta-analysis. Result : The results were as follows: 1) The overall effect size of virtual reality based rehabilitation program was 0.557(95% critical interval; 0.340~0.774). 2) In the analysis of sub-categorical variables, effect size was as follows; the commercial game type(0.621) > virtual environment type(0.335); the dynamic balance measurement(0.750) > static balance measurement(0.226); randomized controlled trial(0.653) > clinical controlled trial(0.275); and thesis type(0.706) > article of journal type(0.339). 3) In the analysis of sub-continuous variables, as time of program(per session) increased, the balance increased(p<0.05). Conclusion : The results of this study showed that virtual reality based rehabilitation program moderately improves the balance of stroke patient. Further studies are recommended to investigate the effect of sub-variables related to virtual reality programs on motor functions of patient with stroke.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.798-801
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• 2015

Cadmium telluride(CdTe) 나노입자의 자기조립으로 형성된 나노구조체는 독특한 특성 때문에 여러 분야에서 활발히 연구되고 있다. 나노구조체의 광학적, 물리적 특성은 물질 형태에 크게 의존하기 때문에 나노구조를 제어하는 기술은 나노과학 분야에서 가장 핵심적인 요체이다. 이번 실험에서 각 나노입자의 자기조립을 통해 나노선이 제조됨을 확인하였다. 안정제로 사용된 thioglycolic acid(TGA)와 Cd 이온의 비율을 기존의 2.4:1에서 1.3:1로 낮추어 CdTe 나노선을 합성 하였다. 자기조립을 통해 생성된 나노입자는 곧고 긴 형태였으며 다결정을 이루고 있었다. 이렇게 합성된 나노선은 투과전자현미경(TEM)과 주사전자현미경(SEM)으로 관찰하였으며, 작게는 500 nm에서 크게는 $10{\mu}m$ 이상의 곧고 긴 나노선이 합성된 것을 확인할 수 있었다.

• 한국항공우주학회지
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• 제40권5호
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• pp.461-466
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• 2012

본 논문에서는 현재 KAIST 인공위성 연구센터(SaTReC)에서 개발 진행 중인 과학기술위성3호(STSAT-3) 위성체의 탑재체 데이터 전송을 위한 X대역 송신기 비행모델 개발 및 시험에 관하여 기술한다. 과학기술위성3호의 통신시스템은 크게 상태정보, 명령 송수신을 위한 통신채널과 임무데이터 전송을 위한 통신채널로 구성되며 상태 정보 및 명령 송수신을 위하여 S대역을 사용하며 임무데이터 전송용으로 X대역 주파수를 사용하고 있다. 과학기술위성 3호에서는 대용량 메모리 유닛(MMU; Mass Memory Unit)에 저장된 탑재체 관측정보가 X대역 송신기의 QPSK 변조기에서 변조를 하고, 변조된 신호는 스위치를 거친 이후에 안테나를 통해 송신된다. 본 논문에서는 과학기술위성 3호 X대역 송신기 내부의 변조방식, 저역통과 여파기, power amp, 스위치 등에 대해서 제작된 특성을 기술한다. X-band 송신기의 비행모델은 성능시험, 환경시험(진동시험, 열진공시험)을 성공적으로 마치고 위성체 조립 단계(Assembly Integration and Test, AIT)에 납품되었다.

• 폴리머
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• 제30권6호
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• pp.453-463
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• 2006

분자 모델에 의한 전산 모사는 단백질 접힘, 미셀화, 블록공중합체의 규칙구조화 등 다양한 고분자 계의 자기조립 현상을 예측하거나 그 조립 메커니즘을 밝히는 데 특별히 유용한 연구방법이다. 자기조립 현상은 분자 수, 분자 크기 등, 계의 속성에 따라 나노미터 이하의 현상으로부터 마이크론이나 그 이상의 길이 스케일의 현상까지 조립 구조의 길이 스케일이 매우 광범위하기 때문에 다양한 계의 모든 조립 현상을 양자역학적 방법과 같은 궁극의 근본원칙에 의해 모사하는 것은 현실적인 시간 내에서 불가능하다. 이러한 문제들을 해결하기 위해 계를 기술하는 과정에서 필요 이상으로 세밀한 표현을 생략하여 모델을 다른 관점에서 재구성하는 방법이 있는데 재구성된 모델은 그 관점에 따라 크게 '원자 수준'의 모델과 '메조 스케일 수준'의 모델로 분류할 수 있다. 본 총론에서는 고분자 자기조립 현상과 관련하여 이 두 가지 관점에 따른 모델과 모사 방법들에 대해 살펴보고자 한다.

• 인간식물환경학회지
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• 제24권3호
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• pp.277-283
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• 2021

Background and objective: This study was conducted to increase understanding of agriculture through agricultural experience programs for adolescents living in self-reliance residence hall, and to investigate changes in work performance ability through changes in hand function. Methods: There were 11 subjects, and the average age was 18.2 years, all males without disabilities. The agricultural experience program consists of a total of 10 sessions including orientation and watching videos on future agriculture, creating vegetable gardens, planting, managing each crop, harvesting, visiting the processing room, and selling at a local food store. Results: The change in agricultural literacy by the agricultural experience program positively improved from a score of 113.73 to 127.91 (p = .008). The changes by sub-item are as follows. The value and safety of agri-foods (p = .020) and agriculture and natural environment (p = .007) were significantly improved. The function and value of rural areas (p = .050), production of agricultural products (p = .160), processing and distribution of agricultural products (p = .248), and agricultural policies (p = .058) were not significantly changed. The simple function of the hands was measured by the number of pegs inserted during 30 seconds, and the assembly function was measured by the number of pegs inserted during 60 seconds. In the case of simple function, the dominant hand was improved from 14.82 to 15.83 (p = .014), andthe non-dominant hand was also significantly improved from 13.79 to 15.01 (p = .002). There was no significant improvement in the simple function (p = .153) and assembly function (p = .770) of both hands. Conclusion: It is considered that the agricultural experience program will enable youths living in self-reliance residence halls to enhance their understanding of agriculture as an occupation, and enable them to play a role as wise consumers by positively affecting improvements in their agricultural literacy and simple hand functions.

• Nuclear Engineering and Technology
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• 제48권1호
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• pp.274-284
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• 2016

Purpose: The purpose of this work is to describe the spectrometric analysis of gaseous cloud formation over reactor mixed uranium-and-plutonium (UP) fuel $(U_{0.8}Pu_{0.2})O_2$ samples heated to a temperature $>2,000^{\circ}C$, and thus forecast and evaluate radiation hazards threatening humans who cope with the consequences of any accident at a fission reactor loaded by UP mixed oxide $(U_{0.8}Pu_{0.2})O_2$, such as a mixture of 80% U and 20% Pu in weight. Materials and methods: The UP nuclear fuel samples were heated up to a temperature of over $2,000^{\circ}C$ in a suitable assembly (apparatus) at out-of-pile experiments' implementation, the experimental in-depth study of metabolism of active materials in living organisms by means of artificial irradiation of pigs by plutonium. Spectrometric measurements were carried out on the different exposed organs and tissues of pigs for the further estimation of human internal exposure by nuclear materials released from the core of a fission reactor fueled with UP mixed oxide. Results: The main results of the research described are the following: (1) following the research on the influence of mixed fuel fission products (radioactive isotopes being formed during reactor operation as a result of nuclear decay of elements included into the fuel composition) on living organisms, the authors determined the quantities of plutonium dioxide ($PuO_2$) that penetrated into blood and lay in the pulmonary region, liver, skeleton and other tissues; and (2) experiments confirmed that the output speed of plutonium out of the basic precipitation locations is very small. On the strength of the experimental evidence, the authors suggest that the biological output of plutonium can be disregarded in the process of evaluation of the internal irradiation doses.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1802-1813
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• 2023

Conjugate heat transfer between liquid metal and solid is a common phenomenon in a liquid-metal-cooled fast reactor's fuel assembly and heat exchanger, dramatically affecting the reactor's safety and economy. Therefore, comprehensively studying the sophisticated conjugate heat transfer in a liquid-metal-cooled fast reactor is profound. However, it has been evidenced that the traditional Simple Gradient Diffusion Hypothesis (SGDH), assuming a constant turbulent Prandtl number (Pr_t,, usually 0.85 - 1.0), is inappropriate in the Computational Fluid Dynamics (CFD) simulations of liquid metal. In recent decades, numerous studies have been performed on the four-equation model, which is expected to improve the precision of liquid metal's CFD simulations but has not been introduced into the conjugate heat transfer calculation between liquid metal and solid. Consequently, a four-equation model, consisting of the Abe k - ε turbulence model and the Manservisi k_𝜃 - ε_𝜃 heat transfer model, is applied to study the conjugate heat transfer concerning liquid metal in the present work. To verify the numerical validity of the four-equation model used in the conjugate heat transfer simulations, we reproduce Johnson's experiments of the liquid lead-bismuth-cooled turbulent pipe flow using the four-equation model and the traditional SGDH model. The simulation results obtained with different models are compared with the available experimental data, revealing that the relative errors of the local Nusselt number and mean heat transfer coefficient obtained with the four-equation model are considerably reduced compared with the SGDH model. Then, the thermal-hydraulic characteristics of liquid metal turbulent pipe flow obtained with the four-equation model are analyzed. Moreover, the impact of the turbulence model used in the four-equation model on overall simulation performance is investigated. At last, the effectiveness of the four-equation model in the CFD simulations of liquid sodium conjugate heat transfer is assessed. This paper mainly proves that it is feasible to use the four-equation model in the study of liquid metal conjugate heat transfer and provides a reference for the research of conjugate heat transfer in a liquid-metal-cooled fast reactor.

• 한국재료학회지
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• 제17권1호
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• pp.31-36
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• 2007

Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Tow and $110^{\circ}C$. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to $170^{\circ}C$ with 0.1ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about $110^{\circ}$ of contact angle and under $20^{\circ}$ of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under $110^{\circ}$. Also the white circles were founded in LFM images under $110^{\circ}$. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at $170^{\circ}C$, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.