• 수산해양기술연구
• /
• 제29권2호
• /
• pp.152-161
• /
• 1993

This paper deals with the effect of spatial distribution of material properties on its statistical characteristics and numerical estimation method of reliability of fatigue sensitive structures with respect to the fatigue crack growth. A method is proposed to determine experimentally the probability distribution functions of material parameters of Paris law. da/dN=C(ΔK/K sub(0) ) super(m), using stress intensity factor controlled fatigue tests. The result with a high tensile strength steel shows that the distribution of the parameter m is approximately normal and that of 1/C, is a 3-parameter Weibull. The main result obtained are : (1) The theoretical autocorrelation of the resistance, 1/C, to fatigue crack growth are almost same for different lengths. (2) The variance decreases with the increasing a averaging length. When spatial correlation length is very small. the variane decreases significantly were the averaging length. (3) The probability distribution of load cycles or the number for a crack to reach a certain length can be estimated using these functions by simulation of non-Gaussian(expecially Weibull) Stochastic Process.

• 한국정밀공학회지
• /
• 제17권12호
• /
• pp.137-144
• /
• 2000

In order to achieve systematical method for improving motion accuracy of hydrostatic table, an algorithm using finite element method is proposed in this paper. Quantification of averaging effect of oil film on motion error is performed theoretically by analysis on the relationship between spacial frequency of rail form error and motion error of table. Influences of film stiffness and pocket size on the motion error of table are also analyzed theoretically. Validity of the algorithm is verified experimentally from the test on the motion error of table with three types of rail which have different form profile. Experimental results show that the algorithm is very effective to analyze theoretically the motion error of hydrostatic table.

• 한국정밀공학회지
• /
• 제19권5호
• /
• pp.139-148
• /
• 2002

Motion errors of linear motion guideway are analyzed theoretically in this paper. For the analysis, an new algorithm predicting motion errors of bearing and guideway is proposed using the Hertz's elastic deformation theory. Accuracy averaging effect can be calculated quantitatively by analyzing relationship between motion errors of guideway and spatial frequency of rail form error. Influences of design parameters on the motion errors including the number of balls, preload, ball diameter, bearing length and the number of bearings are analyzed. As it is difficult to measure the rail form error, experimental results are compared with results analyzed by the equivalent analysis method which evaluate the motion errors of guideway using the measured errors of bearing. From the experimental results, it is confirmed that the proposed analysis method it effective lo analyze the motion errors of linear motion bearing and guideway.

• 한국정보통신학회논문지
• /
• 제8권5호
• /
• pp.970-976
• /
• 2004

본 논문에서는 MRC(Maximal Ratio Combing) 결합 기법을 사용한 RAKE 수신기에서 채널 추정 알고리즘에 따른 성능을 분석한다. 채널 추정 알고리즘에는 WMSA(Weighted Multi-Slot Averaging), 동일 이득 채널 추정 (Equal Cain Estimation ; ECE), 심볼 단위 채널 추정(Symbol-to-Symbol Estimation ; SSE)의 세 가지가 있는데 상업용 시뮬레이션 틀인 HP사의 ADS를 이용하여 비동기 방식 IMT-2000시스템(3GPP)을 대상으로 성능을 분석한다. 성능 분석을 위해서 본 논문은 Jakes 페이딩 채널 모델을 사용한다. 모의실험 결과를 통하여, 저속 도플러(3Km/h)일 때 WMSA 알고리즘이 다른 알고리즘 성능보다 더 좋음을 알 수 있다. 그러나 고속 도플러(120Km/h)일 때, 간단한 구조를 갖는 ECE 알고리즘이 보다 더 유용함을 알 수 있다.

• 대한기계학회논문집B
• /
• 제22권4호
• /
• pp.417-427
• /
• 1998

The effect of secondary flow on the heat transfer of a turbulent wake generated by a flat plate was experimentally investigated. The secondary flow was induced in a curved duct in which the flat plate wake generator was installed. All three components of turbulent heat flux were measured in the plane containing the mean radius of curvature of the curved duct. The results showed that mean temperature profiles deviate from the similarity of the straight wake because of the cold fluid transported from the free-stream. The half-width of the mean temperature profile increased rapidly by upwash motion of the secondary flow. The changes to turbulence structure caused by the secondary flow show more pronounced effect on heat transport than on momentum transport. This is because the response to the variation of flow conditions is delayed in temperature field. Negative production of the turbulent heat flux is observed in the inner wake region. From the conditional averaging, it has been found that the negative production of the turbulent heat flux is generated due to a mixing process between the hot and low momentum eddies occupied in the inner wake region and the cold and high momentum eddies in the potential region.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권8호
• /
• pp.335-343
• /
• 2021

This paper investigates the effect of institutional quality on FDI inflows by using FDI outflows from Asian countries from 2009 to 2017. We used the FDI data from five major Asian economies, which are South Korea, China, Japan, Singapore, and Hong Kong. The gravity model was used to examine the effect of institutional quality on FDI flows. The regression model considers several independent variables, and we select the most appropriate variables by using the Bayesian Model Averaging (BMA) estimator. We have shown that foreign direct investment from Asian countries depends on the size of home and the partner countries, geographical distance, trade interaction between two countries, economic freedom, labor supply, tariff rate, and capacity of the government. The results of different estimation techniques emphasize that multinational enterprises prefer to invest in those countries which have a higher income, which shows the evidence for Lucas's paradox. The results also show that economic freedom and control of corruption have a positive impact on FDI inwards. The regression results show that better institutional quality in host countries encourages more FDIs from Asian economies. It suggests that the state should control corruption and create a free economic environment to attract FDIs.

• 한국콘텐츠학회논문지
• /
• 제15권10호
• /
• pp.150-159
• /
• 2015

본 연구는 지역사회 차원의 범죄연구에 있어 분석단위의 규모에 따라 결과가 달라지는 MAUP의 스케일 효과를 검증하고자 했다. 특히, 국내 최초로 전국의 모든 읍면동과 시군구를 대상으로 최근 이슈의 중심에 서있는 성범죄에 대한 공간적 자기상관, 변수들 간의 상관관계, 인과관계 분석을 시도했다. 분석 결과, 성범죄율의 자기상관은 가설과 달리 시군구의 Moran's I가 읍면동보다 큰 반면, 상관계수와 회귀분석의 결정계수는 가설에 맞게 대부분 시군구에서 더 큰 것으로 드러났다. 이는 합역수준이 높아질수록 자료의 통합으로 인해 발생하는 평균효과 때문으로 사료되었다. 성범죄의 원인에 대해서는 두 가지 특이한 점이 발견되었는바, 첫째, 비아파트거주비율이 읍면동과 시군구 단위에서 모두 성범죄를 감소시켰고, 둘째, 숙박음식업 비율은 읍면동 단위에서만 성범죄를 증가시키는 것으로 드러났다. 이는 향후 지역특성(예, 도시 vs. 시골, 풍요지역 vs. 빈곤지역)에 따른 세부적인 분석과 독립변수가 분석 단위별로 갖는 차별적 의미에 대한 추가적인 연구가 필요함을 시사한 결과였다. 본 연구가 지역사회 범죄연구를 촉진하고 성범죄에 대한 효과적인 대안 마련에 기여할 수 있기를 바란다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2002년도 추계학술발표대회 논문집
• /
• pp.292-295
• /
• 2002

In this paper, an analytical model for the prediction of the elastic properties of multi-axial warp knit fabric (MWK) composites is proposed. The geometric limitation, effect of stitching fibers and design parameters of MWK composites are considered in the model. The elastic behavior of MWK composites was conducted by using an averaging method. The predicted elastic properties are in reasonably good agreement with experimental values. Finally the effect of stitching in the MWK composites are discussed.

• 대한원격탐사학회지
• /
• 제28권6호
• /
• pp.635-651
• /
• 2012

To produce a level-3 monthly composite image from daily level-2 Sea-viewing Wide Field-of-view Sensor (SeaWiFS) chlorophyll-a concentration data set in the East Sea, we applied four average methods such as the simple average method, the geometric mean method, the maximum likelihood average method, and the weighted averaging method. Prior to performing each averaging method, we classified all pixels into normal pixels and abnormal speckles with anomalously high chlorophyll-a concentrations to eliminate speckles from the following procedure for composite methods. As a result, all composite maps did not contain the erratic effect of speckles. The geometric mean method tended to underestimate chlorophyll-a concentration values all the time as compared with other methods. The weighted averaging method was quite similar to the simple average method, however, it had a tendency to be overestimated at high-value range of chlorophyll-a concentration. Maximum likelihood method was almost similar to the simple average method by demonstrating small variance and high correlation (r=0.9962) of the differences between the two. However, it still had the disadvantage that it was very sensitive in the presence of speckles within a bin. The geometric mean was most significantly deviated from the remaining methods regardless of the magnitude of chlorophyll-a concentration values. Its bias error tended to be large when the standard deviation within a bin increased with less uniformity. It was more biased when data uniformity became small. All the methods exhibited large errors as chlorophyll-a concentration values dominantly scatter in terms of time and space. This study emphasizes the importance of the speckle removal process and proper selection of average methods to reduce composite errors for diverse scientific applications of satellite-derived chlorophyll-a concentration data.

• 지질공학
• /
• 제18권1호
• /
• pp.1-6
• /
• 2008

금강유역의 관측소로부터 수집된 강우자료와 지하수위자료를 분석하고 두 자료를 비교 분석하였다. 그리고 강우사상이 지하수위에 미치는 영향분석을 추계학적 기법인 이동평균법을 사용하여 지하수위와 강우이동평균값의 상관관계를 분석하였다. 지하수위는 강우의 계절적 분포를 대체로 따르며 대체로 12월 초부터 4월 말까지 낮은 지하수위를 형성한다. 7월과 8월의 풍수기에는 상대적으로 높은 지하수위를 형성한다. 선행강우를 고려하기 위한 강우이동평균값과 지하수위의 상관관계는 자료의 길이가 최소 2년 이상인 지하수위 관측소를 먼저 선정하였다. 강우와 지하수위 관측소 pair를 선정함에 있어 강우의 비균질한 분포를 고려해서 지하수위 관측소보다 상류에 인접한 강우관측소를 선정하여 두 자료를 분석하였다. 금강유역의 여러 관측소 자료를 분석한 결과 이동평균기간이 10일에서 150일 범위의 값을 가질 때 최대상관계수를 가졌다. 상관계수값은 자료의 질이나 결측기간 또는 융설이나 다른 요인에 의해 넓은 범위의 값을 가지는데 금강유역의 경우 최대 0.8886의 값을 가진다.