• 한국통신학회논문지
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• 제28권4A호
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• pp.238-246
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• 2003

본 논문에서는 현재까지 셀룰라 서비스와 PCS서비스를 위해 얻어진 전파전파 측정에 대한 전체적인 요약을 하였다. 이렇게 얻어진 협대역신호 기반의 측정치와 광대역 신호에 의한 이동통신 채널 측정에 대해 고찰을 한 후 미국 캘리포니아의 오클랜드시에서 얻어진 측정치를 이용하여 불규칙한 높이의 건물로 이뤄진 도시 환경에서 쓰일 수 있는 마이크로셀용 신호 감쇄 예측 공식을 만들고, 이를 균일한 높이의 건물로 이뤄진 환경에서 얻은 신호 감쇄 예측 공식과 비교하였다.

• Journal of Mechanical Science and Technology
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• 제15권2호
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• pp.210-216
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• 2001

This paper presents an analytical study that can predict the path-dependent forming limit of anisotropic sheet materials that experience various combinations of strain paths. To predict the forming limit diagrams(FLD), the proposed analytical procedure is performed within the framework of the Marciniak and Kuczynski(M-K) approach by using the Barlat and Lians non-quadratic anisotropic yield criterion and introducing the effect of the existence of a strain gradient over a stretching punch. The predicted path-dependent forming limit of an anisotropic sheet has been compared with the published experimental results. It has been found that the predicted path-dependent forming limits are in good agreement with the experimental data.

• 한국경제지리학회지
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• 제18권1호
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• pp.60-75
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• 2015

독일 북서부에 위치한 루르지역은 1850년대부터 석탄이 채굴되면서 석탄광업과 제철공업을 중심으로 유럽 최대의 공업지역으로 발전하였다. 그러나 1950년대에 접어들면서 에너지원으로써 유류(Oil)에 비해 석탄의 가격과 품질 경쟁력이 떨어졌고 개발도상국의 부상에 따라 이 지역의 석탄광업과 제철공업이 쇠퇴하기 시작하였다. 1970년대 부터 석탄광구와 제철공장이 하나씩 폐쇄되기 시작하여 도심에 조성된 많은 공업용지가 유휴화 되었고 실업자도 크게 늘어 심각한 경제위기에 직면하였다. 루르지역의 전형적인 공업도시라 할 수 있는 오버하우젠(Oberhausen)시는 이러한 문제에 당면하여 대규모 제철공장부지를 정화하여 거대한 쇼핑몰과 여가산업지구를 조성하였고, 겔젠키르헨(Gelsenkirhen)시는 석탄광업지구를 정화하여 태양광 산업을 중심으로 신재생에너지 산업단지와 친환경 주택단지를 조성하였다. 본 연구는 경로의존론(Path Dependence Theory)에 입각하여 이 두 도시가 추진한 도시재생정책의 집행과정과 결과를 분석하고, 이론적, 정책적 시사점을 도출하였다.

• 대한기계학회논문집A
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• 제21권1호
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• pp.104-111
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• 1997

Accounting for the additional damages come out from non-proportional loading path effect, material damage according to crystal structure dependence was studied. Microscopic observations of damaged material by SEM(Scanning Electron Microscope) showed crystal structure dependence. Biaxial in-phase loaded specimens showed the slips of same direction, which pararell each other, but biaxial 90.deg. out-of-phase loaded specimens showed multiply crossed slips. S. H. Doong and D. F. Socie reported that wavy/planar or planar slip material showed the increase in the cyclic hardening level during non-proportional cycling. From these results, the additional hardening and non-proportional loading effects were related with slip mechanism, and the slip mechanism was related with crystal structure. In the present study, a damage mechanism which accounts for the non-proportional loading effect from crystal structure dependence was considered and applied to A17075-T651.

• Geomechanics and Engineering
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• 제13권5호
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• pp.743-756
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• 2017

Laboratory investigation reveals that rockfills exhibit significant stress-path-dependent behavior during shearing, therefore realistic prediction of deformation of rockfill structures requires suitable constitutive models to properly reproduce such behavior. This paper evaluates the capability of a strain hardening model proposed by the authors, by comparing simulation results with large-scale triaxial stress-path test results. Despite of its simplicity, the model can simulate essential aspects of the shear behavior of rockfills, including the non-linear stress-strain relationship, the stress-dependence of the stiffness, the non-linear strength behavior, and the shearing contraction and dilatancy. More importantly, the model is shown to predict the markedly different stress-strain and volumetric behavior along various loading paths with fair accuracy. All parameters required for the model can be derived entirely from the results of conventional large triaxial tests with constant confining pressures.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2007년도 The 1st International Symposium on Advanced Magnetic Materials
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• pp.224.2-224.2
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• 2007

• 기술경영경제학회:학술대회논문집
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• 기술경영경제학회 2003년도 제22회 동계학술발표회 논문집
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• pp.63-77
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• 2003

In this paper, we investigate the co-movements of the real GDP cycle and the telecommunications service expenditure cycle over 1980 through 2000 in Korea. We used several appropriate statistical tools to characterize and to compare the co-movements between the two aforementioned variables. The statistics presented in this paper are common, easy to Interpret and capture important visual, descriptive information and the dynamics of data that would be lost if one focused only on the unconditional correlation coefficients of de-trended data. This paper examines four possible characteristics for the co-movements of real GDP and telecommunications service expenditure in Korea. The first is that in low frequency, the cyclical movements in telecommunications service expenditure are very similar to the cyclical movements in real GDP, The second is that in the high frequency, the estimated stationary cyclical telecommunications service expenditure is not closely related to the estimated stationary cyclical real GDP. Third, according to co-spectra analysis, the strong relationships between the variables are found in the mid-term frequency and as such this empirical finding has important implications for telecommunications policy and telecommunications service implementation strategies. Finally, in the short-term period, our empirical results support telecommunications network theories such as path dependence properties, lock-in, positive feedback externality, and network externality.

• The Journal of the Acoustical Society of Korea
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• 제17권3E호
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• pp.43-46
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• 1998

Many of the active noise control system utilize a form of the least mean square(LMS) algorithm. This paper discusses the dependence of the convergence rate on the acoustic error path in the popular algorithm which is conventional "filtered-x LMS" and introduces new algorithm "constrained filtered-x LMS". The proposed method increase the convergence region regardless of the time-delay in the acoustic error path. In the algorithms, coefficients of the controller are adapted using the residuals of constrained structure which are defined in such a way that the control process become stationary. Advantages of constrained filtered-x LMS algorithm is illustrated by convergence analysis in the mean sense.

• 소음진동
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• 제8권3호
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• pp.485-493
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• 1998

Many of the adaptive noise control systems utilize a form of the least mean square (LMS) algorithms. In the active control of noise, it is common practice to locate an error microphone far from the control source to avoid the near-field effects by evanescent waves. Such a distance between the control source and the error microphone makes a certain level of time-delay inevitable and, hence, may yield undesirable effects on the convergence properties of control algorithms such as filtered-x LMS. This paper discusses the dependence of the convergence rate on the acoustic error path in these popularalgorithms and introduces new algorithms which increase the convergence region regardless of the time-delay in the acoustic error path. Performances of the new LMS algorithms are presented in comparison with those by the conventional algorithms based on computer simulations and experiments.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.457-457
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• 2013

Current-voltage (I-V) measurements of crystalline silicon solar cells was conducted under dark conditions with the temperature range of 260 K~350 K. Using the calculation method, we extracted the crucial factors of ideality factor (n) and activation energy (Ea) to investigate the carrier conducting path in the space charge region (SCR) and the quasi-neutral region (QNR). Values of n were decreased with increasing temperature in both SCR and QNR. We also conformed that the value of Ea of SCR was larger than that of QNR about 0.4 eV. The temperature dependence of n indicates that the carrier conducting path is dominated by carrier recombination-generation in the SCR region than in the QNR region.