• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.64-72
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• 2016

The coverage area of a GNSS regional ionospheric delay model is mainly determined by the distribution of GNSS ground monitoring stations. Extrapolation of the ionospheric model data can extend the coverage area. An extrapolation algorithm, which combines observed ionospheric delay with the environmental parameters, is proposed. Neural network and least square regression algorithms are developed to utilize the combined input data. The bi-harmonic spline method is also tested for comparison. The IGS ionosphere map data is used to simulate the delays and to compute the extrapolation error statistics. The neural network method outperforms the other methods and demonstrates a high extrapolation accuracy. In order to determine the directional characteristics, the estimation error is classified into four direction components. The South extrapolation area yields the largest estimation error followed by North area, which yields the second-largest error.

• Journal of the Korean Data and Information Science Society
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• 제24권6호
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• pp.1503-1520
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• 2013

For multi-line insurance companies, allocating the risk capital to each line is a widely-accepted risk management exercise. In this article we consider several applications of the Euler capital allocation. First, we propose visual tools to present the diversification and the line-wise performance for a given loss portfolio so that the risk managers can understand the interactions among the lines. Secondly, on theoretical side, we prove that the Euler allocation is the directional derivative of the marginal or incremental allocation method, an alternative capital allocation rule in the literature. Lastly, we establish the equivalence between the mean-shortfall optimization and the RORAC optimization when the risk adjusted capital is the expected shortfall, and show how to construct the optimal insurance business mix that maximizes the portfolio RORAC. An actual loss sample of an insurance portfolio is used for numerical illustrations.

• 한국운동역학회지
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• 제20권2호
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• pp.117-127
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• 2010

The axes of upper forearm coordinate system have been considered as principal axis of each segment which was component of elbow joint. The purpose of this study was to verify whether the mean direction(principal axis) of instantaneous axes of rotation for pure flexion/extension motion coincided with the flexion/extension axis of upper forearm coordinate system. The same procedure was done for pronation/supination motion. Furthermore, it was tested indirectly that there was an interaction effect between the two rotational motions. The results showed that most segment coordinate axes statistically were not consistent with the mean directions of flexion/extension and pronation/supination axes of rotation. From the results, it would be concluded that the ISB coordinate systems was proved to be a little valid for human movement analysis. There also was an effect of pronation/supination angles on flexion/extension motion.

• 한국식품조리과학회지
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• 제19권2호
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• pp.155-164
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• 2003

The purpose of this study was to examine, in a service context, construct validity and generalizability of widely used and accepted measures of perceived organizational support, job satisfaction, organizational commitment, and service duality, and to test each measures' predictive utility in this context with path analysis. Of 350 subjects, 309 subjects participated in the analysis. Descriptive statistics (frequencies), exploratory factor analysis, reliability analysis, zero-order partial correlation analysis, and confirmatory factor analysis were used for this study. The findings from this study are as follows. First, perceived organizational support significantly influenced job satisfaction, organizational commitment. and service quality. Second, Job satisfaction had a directional impact upon organizational commitment and service quality. Third, organizational commitment showed to have a predictive impart on service quality. Finally, the results of the study provide some insight into the types of internal marketing strategies that can be applied successfully by operators of hotel F & B departments.

• 한국콘텐츠학회논문지
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• 제6권10호
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• pp.107-113
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• 2006

H.264의 인트라 프레임 에러복원기법은 상하좌우 인접한 블록의 픽셀을 사용하여 거리의 가중치 평균값으로 손실된 블록을 복원한다. H.264의 인트라 프레임 에러복원기법은 주변블록 픽셀의 간단한 평균값을 이용하여 복원하므로 심각한 블러링 현상이 발생하고 화질 저하의 문제를 야기한다. 이를 개선하기 위하여 본 논문에서는 주변블록의 픽셀 정보를 이용하여 손실된 블록의 주된 에지 방향을 추정하고, 통계값을 이용한 방해함수의 결과 값으로 에지 방향 기반의 보간법과 가중치 평균 보간법을 적응적으로 선택하여 복원하는 방법을 제안한다. 에지방향 기반의 보간법에서는 선택된 주된 에지방향과 상하좌우 각각의 주변블록의 에지방향들 간의 상호관계를 고려함으로써 최종적으로 최적 에지 방향을 선택하여 성능을 향상시킨다. 제안된 방법은 영상에 따라 H.264 에러복원기법보다 객관적인 화질이 $0.5{\sim}2.0dB$ 정도의 PSNR 향상을 보였다.

• 대한토목학회논문집
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• 제29권6B호
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• pp.543-550
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• 2009

선형외삽법에 기초한 전형적인 단시간 강우예측모형은 호우를 발생하는 강우시스템의 발달과정을 모의하지 못하는 한계를 내포하고 있다. 본 연구에서는 이러한 한계를 극복하기 위하여 기상레이더로 획득할 수 있는 여러 시간대의 반사도 정보로부터 획득한 정보변화 과정과 다항 회귀식을 이용하여 x방향과 y방향의 전파속도의 성장과정과 레이더 반사도의 성장과정 모의에 기초한 단시간 강우예측 모형을 개발하였다. 검정통계량이 제시한 결과는 2-CAPPI를 이용한 기존의 단시간 강우예측모형보다 개선된 결과를 보여주었다. 그럼에도 불구하고 본 모형이 완전한 물리적 모형이 아니라 자료사이의 상관성과 다항 회귀식을 이용한 통계적인 방법에 기초하였으므로 강우의 성장과 소멸과정을 구현과 예측성 개선에도 한계가 있음을 보였다.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권4호
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• pp.31-44
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• 2014

In the present study, a few of recently developed geostatistical models are comparatively studied. The models are two-point statistics based sequential indicator simulation (SISIM) and generalized coupled Markov chain (GCMC), multi-point statistics single normal equation simulation (SNESIM), and object based model of FLUVSIM (fluvial simulation) that predicts structures of target object from the provided geometric information. Out of the models, SNESIM and FLUVSIM require additional information other than conditioning data such as training map and geometry, respectively, which generally claim demanding additional resources. For the comparative studies, three-dimensional fluvial reservoir model is developed considering the genetic information and the samples, as input data for the models, are acquired by mimicking realistic sampling (i.e. random sampling). For SNESIM and FLUVSIM, additional training map and the geometry data are synthesized based on the same information used for the objective model. For the comparisons of the predictabilities of the models, two different measures are employed. In the first measure, the ensemble probability maps of the models are developed from multiple realizations, which are compared in depth to the objective model. In the second measure, the developed realizations are converted to hydrogeologic properties and the groundwater flow simulation results are compared to that of the objective model. From the comparisons, it is found that the predictability of GCMC outperforms the other models in terms of the first measure. On the other hand, in terms of the second measure, the both predictabilities of GCMC and SNESIM are outstanding out of the considered models. The excellences of GCMC model in the comparisons may attribute to the incorporations of directional non-stationarity and the non-linear prediction structure. From the results, it is concluded that the various geostatistical models need to be comprehensively considered and comparatively analyzed for appropriate characterizations.

• The Journal of Asian Finance, Economics and Business
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• 제6권4호
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• pp.115-128
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• 2019

The study aims to investigate the pattern of relationships such as symmetric or asymmetric, between exchange rate and foreign direct investment in Bangladesh by applying Autoregressive Distributed Lagged (ARDL) and nonlinear ARDL. In this study, we employed quarterly data for the period of 1974Q1 to 2016Q4. Data were collected and aggregated from various sources namely, Bangladesh Economic Review published by Ministry of Finance and statistical yearbook published by Bangladesh Bureau of Statistics and an annual report published by Bangladesh Bank. The relationship between exchange rate and FDI inflows attract immense interest in the recent periods, especially for developing countries' perspective. The results of the study ascertain the long run relationship between FDI, exchange rate, monetary policy, and fiscal policy. Considering the asymmetric assumption, the findings from NARDL confirm the existence of a long-run asymmetric relationship in the empirical equation. In the long run, it is observed that positive change that is the appreciation of exchange rate against USD decrease FDI inflows and negative shocks results in grater inflows of FDI, however, the positive shocks produce higher intensity that negative shocks in Exchange rate. For directional causality, the coefficients of error correction term confirm long-run causality, in particular, bidirectional causality unveiled between FDI and exchange rate.

• Fisheries and Aquatic Sciences
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• 제2권2호
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• pp.210-217
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• 1999

Chemical oxygen demand (COD), phytoplankton cell number and chlorophyll-a concentration (Chl-a), sediment mean grain size and ignition loss were studied to determine their temporal trends in the study area. Historical data of COD, cell number and Chl-a were gathered from the late 1960s or early 1980s to 1997, and trends in temporal domain were obtained from a simple regression. Sediments for grain size and ignition loss (as organic contents in sediments) were sampled from the Chokchon macrotidal flat bimonthly from September 1990 to November 1996, and were analyzed using the decomposition method of time series analysis. In general, the first three data showed increasing trends based on regression analysis. The trends of sediment grain size fluctuated in a neutral pathway while those of ignition loss yielded no increasing pattern. In contrast with the suggestions from Ahn and Choi (1998) who reported a coarsening variation in sediment grain size to be a cause of the directional and remarkable changes of macrofaunal communities in this area, we could not find such a corresponding variation pattern from our samples. In diagnosing eutrophication, a paradoxical phenomenon was encountered between the trends in water column (COD, cell number and Chl-a) and sediment (ignition loss) data. In this paper, we inferred the possible processes that produce the discrepancy. Some explanations and biological responses to eutrophication were predicted and discussed.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제41권
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• pp.2.1-2.6
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• 2019

Objectives: This study was aimed to analyze the reducing pattern of decompression on mandibular odontogenic keratocyst and to determine the proper time for secondary enucleation. Materials and methods: Seventeen patients with OKC of the mandible were treated by decompression. Forty-five series of CT data were taken during decompression and measured by using InVivo software (Anatomage, San Jose, Calif) and were analyzed. Results: The expected relative volume during decompression is calculated using the following formula: V(t) = V_initial × exp.(at + 1/2bt²) (t = duration after decompression (day)). There was no significant directional indicator in the rate of reduction between buccolingual and mesiodistal widths. Conclusion: The volume reduction rate gradually decreased, and 270 days were required for 50% volume reduction following decompression of OKC. The surgeon should be aware of this pattern to determine the timing for definitive enucleation. Clinical relevance: The volume reduction rate and pattern of decompression of the OKC can be predicted and clinicians should be considered when treating OKC via decompression.