• 한국방재학회 논문집
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• 제9권5호
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• pp.15-21
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• 2009

AASHTO LRFD 설계 기준에 따른 합성형 교량 전단연결재 설계는 주로 강도보다는 피로에 의해 지배되는 것으로 알려져 있다. 이 피로 설계는 1966년 Slutter와 Fisher의 연구에 근거하고 있다. 당시의 시험은 1면으로 수행되었기 때문에 편심이 작용하였고, 이로 인하여 전단연결재에 별도의 인장력이 가해지게 되어 피로 강도가 감소되는 결과를 낳은 것으로 보인다. 또한, 피로 S-N 곡선은 응력변동폭과 하중반복 횟수 각각의 로그 스케일에 대하여 선형 관계를 보이는 것으로 Fisher에 의해 후에 밝혀졌으나, 전단연결재의 경우에 대해서만은 아직도 응력변동폭에 로그를 취하지 않고 있다. 이 연구는 현재 미국, 영국, 유럽, 일본에서 사용 중인 피로 설계 곡선을 비교 검토한 결과 미국 설계 기준이 비교적 보수적인 설계를 하고 있음을 확인하였다. 나아가, 당시의 실험 세팅과 데이터를 재분석하고 최근까지 전 세계에 공개된 피로 실험 데이터를 수집하여 분석 비교하고, 이를 바탕으로 적절한 설계식을 추천하고자 한다.

• 한국정밀공학회지
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• 제19권12호
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• pp.64-69
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• 2002

In this study, the optimal dynamic isolation system for gas operated combat weapon has been investigated. For this purpose, firstly, the dynamic behavior of human induced by firing operations has been analyzed through a series of experimental works using the devised test setup. The characteristics of linear impulse has been compared under some conditions of support system. In order to design the optimal dynamic isolation system, parameter optimization process has been performed based on the simplified isolation system under constraints of moving displacement and transmitted force. Finally, the performance of the designed dynamic absorbing system has been evaluated by simulation.

• 한국의상디자인학회지
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• 제4권2호
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• pp.31-45
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• 2002

The purpose of this study was designed to investigate if self-monitoring variable among various individual trait theories and demographic variable would be variables which can explain about the importance differences of consumer service level of retailing in the garment product. The survey was conducted from Feb, 6 to 16, 2002. For this survey, the 118 data were analysed with spss window 9.0 version and Cronbach's, Factor analysis, one-way ANOVA, Duncan test, Frequency, mean, percentage were applied. The results of this study were as follows; 1. Consumer service was classified in attitude/confidence/expert knowledge of salesperson, product display, product information, product assortment, shopping environment, lighting setup. 2. As a result of analyzing the importance differences per consumer service dimension depending on self-monitoring levels, it was not significant differences. 3. As a result of analyzing the importance differences per consumer service dimension depending on demographic variables, it was not significant differences.

• International Journal of Precision Engineering and Manufacturing
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• 제4권6호
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• pp.38-43
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• 2003

In this study, the optimal dynamic absorbing system for the gas operated HIF (high implusive force) device has been investigated. For this purpose, firstly, the dynamic behavior of human body induced by impulsive disturbances has been analyzed through a series of experimental works using the devised test setup. The characteristics of linear impulse has been compared under some conditions of support system. In order to design the optimal dynamic absorbing system, the parameter optimization process has been performed based on the simplified isolation system model under constraints of moving displacement and transmitted force. Finally, the performance of the designed dynamic absorbing system has been evaluated by simulation in the actual operating condition.

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 춘계학술대회 논문집
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• pp.200-207
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• 1999

The purpose of this research is to setup the design procedure of low noise rolling stocks. Noise sources are identified at a field test, and the contribution of noise sources to each part of car interior is ensured by sound intensity measurement technique. Added material to each section of the carbody makes it possible to identify absorption or reflection performance of each part to the anterior random noise. Such experimental tests to the exterior noise intruding through the floor represent that the best countermeasure on the floor is to implement reflecting material which can properly interfere noise. Design procedure of low noise rolling stocks is set through several experiments.

• 한국소음진동공학회논문집
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• 제14권9호
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• pp.801-810
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• 2004

Parameter modification of a linear finite element model(FEM) based on modal sensitivity matrix is usually performed through an effort to match FEM modal data to experimental ones. However, there are cases where this method can't be applied successfully; lack of reliable modal data and ill-conditioning of the modal sensitivity matrix constitute such cases. In this research, a novel concept of introducing feedback loops to the conventional modal test setup is proposed. This method uses closed-loop natural frequency data for parameter modification to overcome the problems associated with the conventional method based on modal sensitivity matrix. We proposed the whole procedure of parameter modification using the closed-loop natural frequency data including the modal sensitivity modification and controller design method. Proposed controller design method is efficient in changing modes. Numerical simulation of parameter estimation based on time-domain input/output data is provided to demonstrate the estimation performance of the proposed method.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3580-3596
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• 2021

An integral test facility, PILLAR, was commissioned, aiming to provide valuable experimental results which can be referenced by system and component designers and used for the performance demonstration of liquid-metal-cooled, passive small modular reactors (SMRs) toward their licensing. The setup was conceptualized by a scaling analysis which allows the vertical arrangements to be conserved from its prototypic reactor, scaled uniformly in the radial direction achieving a flow area reduction of 1/200. Its final design includes several heater rods which simulate the reactor core, and a single heat exchanger representing the steam generators in the prototype. The system behaviors were characterized by its data acquisition system implementing various instruments. In this paper, we present not only a detailed description of the facility components, but also selected experimental results of both steady-state and transient cases. The obtained steady-state test results were utilized for the benchmark of a system code, achieving a capability of accurate simulations with ±3% of maximum deviations. It was followed by qualitative comparisons on the transient test results which indicate that the integral system behaviors in passive LBE-cooled systems are able to be predicted by the code.

• 공학교육연구
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• 제22권5호
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• pp.56-62
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• 2019

This paper suggests the necessity of design education to engineering majors through qualitative research on the characteristics of intelligent artifacts. Robot cleaner is one of intelligent artificial objects that can approach people's life without awkwardness. How do people think of robot cleaners and define their personality, these days? In this experiment, subjects use and observe four different robot cleaners that have different appearances, behaviors and sounds in an experimental setup where is similar to actual use environment. We measure subjects' preferences and assessments for four different robot cleaners' personality. The test subjects were 11 designers who frequently collaborated with engineers and were able to express and express opinions about products. Experimental results showed that robot cleaners with the highest scores in appearance, behavior, and sound had the highest preference. In contrast, robot cleaners with low scores in three factors showed different results in the preference ranking.

• Tribology and Lubricants
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• 제36권6호
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• pp.332-341
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• 2020

High-speed turbomachinery implements gas foil bearings (GFBs) due to their distinctive advantages, such as high efficiency, lesser part count, and lower weight. This paper provides the test results of the static structural stiffnesses and loss factors of bump-type foil thrust bearings with increasing preload and bearing deflection. The focus of the current work is to experimentally quantify variability in structural stiffnesses and loss factors among the four test thrust bearings with identical design values and material of the bump and top foil geometries using the same (open-source) fabrication method. A simple test setup, using a rigidly mounted non-rotating shaft and thrust disk, measures the bearing bump deflections with increasing static loads on the test bearing. The inner and outer diameters of the test bearings are 41 mm and 81 mm, respectively. The loss factor, best-representing energy dissipation in the test bearings, is estimated from the area inside the local hysteresis loop of the load versus the bearing deflection curve. The measurements show that structural stiffnesses and loss factors of the test bearings significantly rely on applied preloads and bearing deflections. Local structural stiffnesses of the test bearings increase with applied preloads but decrease with bearing deflections. Changes of loss factors are less sensitive to applied preloads and bearing deflections compared to those of structural stiffnesses. Up to 35% variability in static load structural stiffnesses is found between bearings, while up to 30% variability in loss factors is found between bearings.

• 대한치과교정학회지
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• 제48권4호
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• pp.268-280
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• 2018

Resistance to sliding (RS) between the bracket, wire, and ligature has been largely debated in orthodontics. Despite the extensive number of published studies, the lack of discussion of the methods used has led to little understanding of this phenomenon. The aim of this study was to discuss variables affecting RS in orthodontics and to suggest an operative protocol. The search included $PubMed^{(c)}$, $Medline^{(c)}$, and the Cochrane $Library^{(c)}$. References of full-text articles were manually analyzed. English-language articles published between January 2007 and January 2017 that performed an in vitro analysis of RS between the bracket, wire, and ligature were included. Study methods were analyzed based on the study design, description of materials, and experimental setup, and a protocol to standardize the testing methods was proposed. From 404 articles identified from the database search and 242 records selected from published references, 101 were eligible for the qualitative analysis, and six for the quantitative synthesis. One or more experimental parameters were incompatible and a meta-analysis was not performed. Major factors regarding the study design, materials, and experimental setup were not clearly described by most studies. The normal force, that is the force perpendicular to the sliding of the wire and one of the most relevant variable in RS, was not considered by most studies. Different variables were introduced, often acting as confounding factors. A protocol was suggested to standardize testing procedures and enhance the understanding of in vitro findings.