• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.866-870
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• 2001

Measurement techniques for in-duct acoustic source parameters can be classified into the direct method and the load method, according to whether it utilizes an extra external source or not. It is reported that the load methods yield the negative source resistance and the purpose of this paper is to clarify that the time-varying nature of the source is the main cause of this physically implausible result. For this purpose, the direct and load methods for measuring the source characteristics of a simplified fluid machine are simulated using the time domain numerical analysis. In the numerical simulations, the method of characteristics is employed and the source characteristics are calculated from the resultant data. It is shown that the load method results in negative source resistance for some frequencies, whereas the direct method yields positive values for all frequencies considered. It is found that the result of load method is quite sensitive to the change of cylinder pressure or valve profile in contrast to the direct method.

• 한국IT서비스학회지
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• 제5권1호
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• pp.149-164
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• 2006

The companies are trying to apply to software development approach by utilizing open-source components. The open-source components are new alternatives to solve limits of the previous software developments such as quality of software, time and cost of development. Accordingly, various analysis of open-source components were performed. However, the researches about the detailed procedures and methods to utilize open-source components in practical industry are immature. In this paper, we propose the procedures and cases for identifying, validating, selecting of suitable open-source components and for applying to change and modification. Proposed procedures and cases will be a great contribution to spread of utilizing the open-source.

• 한국대기환경학회지
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• 제13권4호
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• pp.285-296
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• 1997

The suspended particulate matters had been collected on quartz fiber fiters by a cascade impactor having 9 size stages for 4 years (Sep. 1991 to Dec. 1995) in Kyung Hee University-Suwon Campus. Membrane filters were used to collected the particulate matters on each stage. The weight concentration on each stage was obtained by a microbalance and further chemical element levels were determined by an x-ray fluorescence system. Based on these chemical information, our study focused on applying the target transformation factor analysis (TTFA), a receptor model, to identify aerosol sources and to apportion quantitatively their mass contribution. There are total of 63 ambient data sets. Each data set consists of the 8 size-ranged subdata sets characterized by 16 elemental variables. By the results, four to five sources were extracted from each size range and some sources reappeared in other size ranges. Then total of 8 source profiles were statistically generated from all the ranges, such as oil burning source, soil source, field burning source, gasoline related source, coal burning source, marine source, glass related source, and unknown sources. Apportioning aerosol mass to each source was intensively examined by investigating emission inventories near the study area. The results showed that soil particle source was the most significant contributor. However, coal and oil burning sources were the major anthropogenic ones. The study finally proposed some air quality control strategies to achieve the clean air quality in Suwon area.

• Journal of Communications and Networks
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• 제3권4호
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• pp.365-373
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• 2001

We propose a new channel reservation protocol which can reduce message delay by using a counter for detection of d source conflict in a WDM single-hop network with non-equivalent propagation delay. A source convict occurs when a source node has the right to transmit more than or equal to two messages simultaneously, which are transmitted using different wavelengths. In such a case, the source node has to newly obtain the right to transmit the message. In the proposed protocol, by using a source conflict counter a source node can detect a source conflict before a wave-length assignment is performed. Therefore, the source node can start a procedure to newly obtain the right to transmit the message which cannot be transmitted due to a source conflict. We analyse the throughput performance by taking the effect of a source conflict into account, and show that the approximate analysis and the computer simulated results are close. Also, from computer simulated results, we show that our proposed protocol can reduce mean message delay dramatically without degrading throughput performance as the offered load becomes large.

• 소음진동
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• 제8권3호
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• pp.542-552
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• 1998

The noise sources, structure-borne and/or air-borne, in machinery can be defined by their locations and strengths. However the locations of that noise sources are well known in many cases. In those cases, the problem can be defined as an inverse problem to known the strengths of the noise sources in the frequency domain, the modeling scheme is classified by thecoherent or incoherent source. This paper expands the basic concept to the case of the complex noise sources, in which the set of coherent and incoherent noise sources are matched with the noise of a real vehicle. The error factors in the experiment and the optimal number of the monopole sources to match the real suond filed are also investigated. The results of the noise source modeling of heavy machinery show that the incoherent and coherent/incoherent source models are applicable to the high frequency and the low frequency region, respectively. The noise source model also enables the noise source analysis to rank the contribution of real source group such as engine, T/M, exhuast, etc.

• 한국대기환경학회지
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• 제31권6호
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• pp.508-519
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• 2015

The objective of this study was to quantitatively estimate $PM_{2.5}$ source contribution in Gyeongsan. Ambient $PM_{2.5}$ samples have been collected on zefluor, quartz and nylasorb filter by $PM_{2.5}$ samplers of cyclone method from September 2010 to December 2012. Collected samples were analyzed for determining 17 inorganic elements, 8 ions, and 8 carbon components after pretreatment. Based on these chemical information, the PMF model was applied to estimate the quantitative contribution of air pollution sources. The results of the PMF modeling showed that the sources were apportioned by biomass burning source (15.5%), secondary sulfate source (16.0%), industry source (10.4%), soil source (7.0%), gasoline source (9.1%), incinerator source (10.4%), diesel emission source (11.0%), and secondary nitrate source (20.6%), respectively. To analyze local source impacts from various wind directions, the CPF analysis were performed using source contribution results with the wind direction values measured at the site.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.452-452
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• 2006

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권3호
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• pp.348-363
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• 2013

The use of I-Core sandwich panel has increased in cruise ship deck structure since it can provide similar bending strength with conventional stiffened plate while keeping lighter weight and lower web height. However, due to its thin plate thickness, i.e. about 4~6 mm at most, it is assembled by high power $CO_2$ laser welding to minimize the welding deformation. This research proposes a volumetric heat source model for T-joint of the I-Core sandwich panel and a method to use shell element model for a thermal elasto-plastic analysis to predict welding deformation. This paper, Part I, focuses on the heat source model. A circular cone type heat source model is newly suggested in heat transfer analysis to realize similar melting zone with that observed in experiment. An additional suggestion is made to consider negative defocus, which is commonly applied in T-joint laser welding since it can provide deeper penetration than zero defocus. The proposed heat source is also verified through 3D thermal elasto-plastic analysis to compare welding deformation with experimental results. A parametric study for different welding speeds, defocus values, and welding powers is performed to investigate the effect on the melting zone and welding deformation. In Part II, focuses on the proposed method to employ shell element model to predict welding deformation in thermal elasto-plastic analysis instead of solid element model.

• 한국과학교육학회지
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• 제38권6호
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• pp.813-823
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• 2018

본 연구의 목적은 빛에 대한 초등학생들의 이미지 스키마를 통해 이들의 개념적 은유 유형을 분석하는 것이다. 연구 참여자는 경상남도 G시의 한 개 초등학교 6학년 학생 162명이다. 이 연구를 위해 분석틀이 고안되었으며, 그 분석틀은 이미지 스키마 분석틀과 체계적 기능 문법 분석틀이다. 학생들의 빛 개념을 묻는 질문지도 개발되었다. 연구 결과는 다음과 같다. 첫째, 광원에 대해 학생들은 빛에 대해 두 가지의 구조를 가지고 있음을 보였으며, 그 두 가지는 빛이 광원으로부터 나와 직선으로 공간에 퍼져나간다는 것과 빛이 광원 주위에 정지해 있다는 것이다. 둘째, 물체를 보는 과정에 대한 이해에서는, 학생들은 과학자적 개념을 포함하여 5개의 구조를 나타냈다. 셋째, 빛의 반사에 대한 이해에서는 학생들은 과학자적 개념을 포함하여 4가지의 개념 구조를 나타냈다.

• 한국항공우주학회지
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• 제49권6호
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• pp.473-480
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• 2021

소형 무인비행체 드론의 비행제어기(Flight Controller) 소프트웨어로 널리 사용되고 있는 오픈소스(Open Source)에 대한 정적분석(Static Analysis)을 통해 소프트웨어 품질의 문제점을 분석하고 개선 방안을 제시한다. 소프트웨어 품질 기준으로는 국제적으로 널리 적용되고 있는 MISRA 코딩 규칙을 선정하였으며, 정적분석 도구는 국제 도구인증(Tool Certification)을 받아 항공분야 뿐만 아니라 안전성(Safety)이 요구되는 자동차, 철도, 원자력, 의료 등 모든 산업에서 활용되고 있는 LDRA Tool을 사용하였다. 오픈소스 모듈의 구조, 사용 데이터 분석, 코딩 규칙 준수, 품질 지표(복잡도 및 시험성) 등 소프트웨어의 품질 전반에서 안전성을 위협하는 문제점들을 발견하였으며, 이에 대한 개선 방안을 제시하였다.