• 한국대기환경학회지
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• 제32권4호
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• pp.384-393
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• 2016

In this study, two kinds of industrial filter bags were tested for their filtration performance to apply the existing bag filter systems. Experimental variables were examined for pressure drop, cleaning interval, residual pressure drop, cleaning efficiency, fractional grade efficiency, total collection efficiency according to the filter bag structure. According to these results, the filter bags tested in this study demonstrated good performance in dust collection. This was also true for the double surface filter bag. The lifetime was longer than the round type filter bag because the filtration area was more than 1.6 times wider and the filter quality factor was much higher. Therefore, double surface filter bags are suggested to be used in order to increase filtration performance of the bag filter systems.

• Smart Structures and Systems
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• 제3권2호
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• pp.133-146
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• 2007

This paper addresses a new type of broad and stage-based hybrid carbon fiber reinforced polymer (HCFRP) sensor that is suitable for the sensing of infrastructures. The HCFRP sensors, a type of composite sensor, are fabricated with three types of carbon tows of different strength and moduli. For all of the specimens, the active materials are carbon tows by virtue of their electrical conductivity and piezoresistivity. The measurement principles are based on the micro- and macro-fractures of different types of carbon tows. A series of experiments are carried out to investigate the sensing performances of the HCFRP sensors. The main variables include the stack order and volume fractions of different types of carbon tows. It is shown that the change in electrical resistance is in direct proportion to the strain/load in low strain ranges. However, the fractional change in electrical resistance (${\Delta}R/R_0$) is smaller than 2% prior to the macrofractures of carbon tows. In order to improve the resistance changes, measures are taken that can enhance the values of ${\Delta}R/R_0$ by more than 2 times during low strain ranges. In high strain ranges, the electrical resistance changes markedly with strain/load in a step-wise manner due to the gradual ruptures of different types of carbon tows at different strain amplitudes. The values of ${\Delta}R/R_0$ due to the fracture of high modulus carbon tows are larger than 36%. Thus, it is demonstrated that the HCFRP sensors have a broad and stage-based sensing capability.

• 대한기계학회논문집B
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• 제26권5호
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• pp.666-674
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• 2002

A rapid expansion of the moist air or stream through transonic nozzle often leads to not-equilibrium condensation shock, causing a considerable amount of energy loss to the entire flow field. Depending on amount of heat released, condensation shock wave occurs in the nozzle and interacts with the boundary layer flow. In the current study, a passive control technique using a porous wall with a plenum cavity underneath is applied for purpose of alleviation the condensation shock wave in a transonic nozzle. A droplet growth equation is incorporated into two-dimensional wavier-Stokes equation systems. Computations are carried out using a third-order MUSCL type TVD finite-difference scheme with a second-order fractional time step. An experiment using an indraft transonic wind tunnel is made to validate the present computational results. The results obtained show that the magnitude of condensation shock wave is reduced by the current passive control method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권1호
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• pp.269-286
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• 2018

Signal detection in symmetric alpha-stable ($S{\alpha}S$) distributed noise is a challenging problem. This paper proposes a detector based on a decreasing exponential function (DEF). The DEF detector can effectively suppress the impulsive noise and achieve good performance in the presence of $S{\alpha}S$ noise. The analytical expressions of the detection and false alarm probabilities of the DEF detector are derived, and the parameter optimization for the detector is discussed. A performance analysis shows that the DEF detector has much lower computational complexity than the Gaussian kernelized energy detector (GKED), and it performs better than the latter in $S{\alpha}S$ noise with small characteristic exponent values. In addition, the DEF detector outperforms the fractional lower order moment (FLOM)-based detector in $S{\alpha}S$ noise for most characteristic exponent values with the same order of magnitude of computational complexity.

• 한국시뮬레이션학회논문지
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• 제24권3호
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• pp.89-96
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• 2015

무기체계를 보다 효과적으로 사용하기 위해 다양한 표적 유형별로 무기효과 평가방법이 발전되었다. 본 연구에서는 3차원 건물표적에 대한 공격시 파괴효과를 평가할 수 있는 가장 효과적인 방법론을 찾고자 하였다. 가능한 건물표적에 대한 파괴효과 평가 방법에는 기대손실파괴확률(EFD)과 단발명중파괴확률(SSPD)이 있다. 여기에 건물표적의 크기, 무기체계 원형공산오차(CEP), 건물평균유효파괴면적(MAE_bldg), 건물표적과 유도무기 조우조건인 입사각을 입력변수로 하여 무기체계의 파괴효과를 계산하였다. 무기체계 특성 CEP와 MAE_bldg의 변화에 따른 EFD와 SSPD 결과를 비교하고 입사각의 변화량과 표적건물 높이에 따른 파괴효과를 비교함으로써 3차원 건물표적에 대한 적합성을 분석하였다.

• 한국전산구조공학회논문집
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• 제27권3호
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• pp.173-182
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• 2014

동역학의 새로운 변분이론인 혼합 합성 변분이론은 수학물리학을 비롯한 공학에 있어 초기치-경계치 문제해석에 광범위하게 적용될 수 있는 기반을 제공하는 것으로, 본 논문은 이 이론을 토대로 시간에 대한 이차의 형상함수가 적용된 시간 유한요소해석법을 개발하고 그 해석법의 수치특성 확인을 통해 향후 다양한 동적시스템 해석의 적용에 대한 가능성을 살펴보았다. 이를 위해 가장 기본적인 선형탄성의 단자유도계가 고려되었다. 에너지 보존시스템의 경우(비감쇠 시스템에 외력이 작용치 않는 경우), 제안된 알고리즘 모두는 time-step에 관계없이 안정적이며 수치감쇠가 없이 에너지와 모멘텀이 보존되는 symplecticity property를 가지고 있음을 확인할 수 있었고, 감쇠시스템인 경우, time-step이 점점 작아질수록 정확한 해에 빠르게 수렴하는 것을 확인하였다.

• 대한인간공학회지
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• 제28권4호
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• pp.1-7
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• 2009

The purpose of this study was to evaluate the legibility of one-syllable Korean characters with the participation of sixteen subjects. The experiment considered nine factors including age (young and old), gender (male and female), illuminance (150lx and 600lx), viewing distance (50cm and 200cm), material type (paper and LCD), typeface (Ming and Gothic), thickness (plain and bold), color contrast (black letter/white background and white letter/black background), and complexity (simple, complex, and number) to examine main effects with a $2^{6-3}\times3$ fractional factorial design. The dependent variables were minimum character size of 100% correctness, maximum character size of 0% correctness, and minimum character size of comfortable reading preference. The results of analysis of variance (ANOVA) revealed that age, illuminance, viewing distance and complexity were significant for all dependent variables, except gender which was significant only for the minimum character size of comfortable reading preference. In general, the young could see twofold smaller size letters than the elderly. The subjects could see smaller sized letters with the illuminance of 600lx and viewing distance of 50cm than 150lx and 200cm, respectively and also with numbers, simple characters, and complex characters in that order. The findings of this study could be characterized about the legibility of Korean characters and be good resources for developing its standard.

• 동력기계공학회지
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• 제17권3호
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• pp.72-81
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• 2013

Many articles have been published about a 2-degree of freedom model that includes the lateral and yaw motions for controller synthesis in intelligent transport system applications. In this paper, a 3-degree of freedom linear model that includes the roll motion is developed to design a robust steering controller for lane following maneuvers using ${\mu}$-synthesis. This linear perturbed system includes a set of parametric uncertainties in cornering stiffness and unmodelled dynamics in steering actuators. The state-space model with parametric uncertainties is represented in linear fractional transformation form. Design purpose can be obtained by properly choosing the frequency dependent weighting functions. The objective of this study is to keep the tracking error and steering input energy small in the presence of variations of the cornering stiffness coefficients. Furthermore, good ride quality has to be achieved against these uncertainties. Frequency-domain analyses and time-domain numerical simulations are carried out in order to evaluate these performance specifications of a given vehicle system. Finally, the simulation results indicate that the proposed robust controller achieves good performance over a wide range of uncertainty for the given maneuvers.