• Steel and Composite Structures
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• 제24권5호
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• pp.549-559
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• 2017

As few multi-tower single-box multi-cell cable-stayed bridges with corrugated steel webs have been built, analysis is mostly achieved by combining single-girder model, beam grillage model and solid model in support of the design. However, such analysis methods usually suffer from major limitations in terms of the engineering applications: single-girder model fails to account for spatial effect such as shear lag effect of the box girder and the relevant effective girder width and eccentric load coefficient; owing to the approximation in the principle equivalence, the plane grillage model cannot accurately capture shear stress distribution and local stress state in both top and bottom flange of composite box girder; and solid model is difficult to be practically combined with the overall calculation. The usual effective width method fails to provide a uniform and accurate "effective length" (and the codes fail to provide a unified design approach at those circumstance) considering different shear lag effects resulting from dead load, prestress and cable tension in the construction. Therefore, a novel spatial grid model has been developed to account for shear lag effect. The theoretical principle of the proposed spatial grid model has been elaborated along with the relevant illustrations of modeling parameters of composite box girder with corrugated steel webs. Then typical transverse and longitudinal shear lag coefficient distribution pattern at the side-span and mid-span key cross sections have been analyzed and summarized to provide reference for similar bridges. The effectiveness and accuracy of spatial grid analysis methods has been finally validated through a practical cable-stayed bridge.

• Journal of Korea Trade
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• 제26권1호
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• pp.99-112
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• 2022

Purpose - This paper empirically investigates via a spatial lag model from the perspective of space economy to find the influencing factors of South Korea's OFDI along with 60 countries. Design/methodology - In the study of regional economic phenomena, we must first test the corresponding spatial correlation, and on this basis, complete the construction of the spatial model. For the target research object, after testing the spatial correlation, if there is spatial correlation, a spatial measurement model is needed. This paper uses the global Moran's I index for calculation. Based on the characteristics and research needs of the research object, this paper selects the spatial lag model to verify the existence of the spatial effect and factors affecting OFDI. Findings - Our results show that export scale, infrastructure, technology level, political stability, resource endowment, market size, distance and labor cost have a certain impact on Korea's OFDI, but at present the distance and market size factors are the most important influencing factors for South Korea's OFDI, The technical level and political stability have little effect on South Korea's OFDI, and are not main factors determining South Korea's OFDI. Originality/value - Through spatial measurement verification, it was found that the spatial effect has a significant impact on OFDI, along with more than 60 countries. On this basis, relevant suggestions are put forward, which have strong practical significance for South Korea's OFDI to achieve healthy and sustainable development.

• Journal of Biosystems Engineering
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• 제39권4호
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• pp.377-388
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• 2014

Purpose: Determining the spatial structure of data is important in understanding within-field variability for site-specific crop management. An understanding of the spatial structures present in the data may help illuminate interrelationships that are important in subsequent explanatory analyses, especially when site variables are correlated or are a combined response to multiple causative factors. Methods: In this study, correlation, principal component analysis, and single and nested variogram models were applied to soil electrical conductivity and chemical property data of two fields in central Missouri, USA. Results: Some variables that were highly correlated, or were strongly expressed in the same principal component, exhibited similar spatial ranges when fitted with a single variogram model. However, single variogram results were dependent on the active lag distance used, with short distances (30 m) required to fit short-range variability. Longer active lag distances only revealed long-range spatial components. Nested models generally yielded a better fit than single models for sensor-based conductivity data, where multiple scales of spatial structure were apparent. Gaussian-spherical nested models fit well to the data at both short (30 m) and long (300 m) active lag distances, generally capturing both short-range and long-range spatial components. As soil conductivity relates strongly to profile texture, we hypothesize that the short-range components may relate to the scale of erosion processes, while the long-range components are indicative of the scale of landscape morphology. Conclusion: In this study, we investigated the effect of changing active lag distance on the calculation of the range parameter. Future work investigating scale effects on other variogram parameters, including nugget and sill variances, may lead to better model selection and interpretation. Once this is achieved, separation of nested spatial components by factorial kriging may help to better define the correlations existing between spatial datasets.

• 응용통계연구
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• 제23권3호
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• pp.609-619
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• 2010

Geostatistical data among spatial data is analyzed in three stages: (1) variogram estimation, (2) model fitting for the estimated variograms and (3) spatial prediction using the fitted variogram model. It is very important to estimate the variograms properly as the first stage(i.e., variogram estimation) affects the next two stages. In general, the variogram is estimated with the moment estimator. To estimate the variogram, we have to decide the 'lag increment' or the 'number of lags'. However, there is no established rule for selecting the number of lags in estimating the variogram. The present paper proposes a method of choosing the optimal number of lags based on the PRESS statistic. To show the usefulness of the proposed method, we perform a small simulation study and show an empirical example with with air pollution data from Korea.

• Journal of the Korean Data and Information Science Society
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• 제26권3호
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• pp.561-568
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• 2015

이 연구에서는 공간회귀모형 중 공간시차모형과 공간오차모형을 이용하여 대구 경북 지역 단위면적당 아파트 매매가격을 예측하였다. k-최근접이웃 (k-nearest neighbours)을 이용하여 공간가중행렬을 구축하였으며, 이를 이용해 2012년 3월의 단위면적당 아파트 매매가격에 대한 모형을 적합시켰다. 적합시킨 공간시차모형, 공간오차모형을 이용하여 2013년 3월의 단위면적당 아파트 매매가격을 예측하였으며 RMSE (root mean squared error), RRMSE (root relative mean squared error), MAE (mean absolute error)를 통해 두 모형의 성능을 비교하였다.

• 한국측량학회지
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• 제32권3호
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• pp.225-231
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• 2014

When a spatial regression model that uses kernel density values as a dependent variable is applied to retail business data, a unique model cannot be selected because kernel density values change following kernel bandwidths. To overcome this problem, this paper suggests how to use the point pattern analysis, especially the L-index to select a unique spatial regression model. In this study, kernel density values of retail business are computed by the bandwidth, the distance of the maximum L-index and used as the dependent variable of spatial regression model. To test this procedure, we apply it to meeting room business data in Seoul, Korea. As a result, a spatial error model (SEM) is selected between two popular spatial regression models, a spatial lag model and a spatial error model. Also, a unique SEM based on the real distribution of retail business is selected. We confirm that there is a trade-off between the goodness of fit of the SEM and the real distribution of meeting room business over the bandwidth of maximum L-index.

• 경영과정보연구
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• 제37권1호
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• pp.155-175
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• 2018

우리나라 아파트 가격 결정 요인에 대한 선행연구 중 공간적 의존성을 반영한 연구가 많이 있으나 공간시차변수의 내생성 문제를 고려한 연구는 거의 없는 실정이다. 이에 따라 본 연구는 공간시차변수를 포함한 2단계 분위수 회귀분석으로 부산의 아파트 가격 결정 요인을 분석하였다. 실증분석 결과, 공간시차변수의 회귀계수는 0.5 이상으로 1% 수준에서 통계적으로 유의적이어서, 인근아파트 가격이 다른 아파트 가격에 미치는 영향이 매우 큰 것이 확인되었다. 그리고 아파트 구입자는 면적이 넓고, 총층수와 거주층수가 높으며, 거실의 방향이 남향이고 바다가 보이는, 지하철역, 고등학교 및 해안에 인접한 아파트를 선호하는 것으로 나타났다. 예상과는 다르게, 산조망은 빌딩조망 보다 덜 선호하는 것으로 나타났는데, 이것은 산조망 아파트는 거실이 북향으로 저가 아파트 지역에 주로 위치하고 있기 때문인 것으로 추정된다. 또한 분위수 회귀분석이 OLS 추정보다도 아파트가격에 대한 주택특성의 효과를 더 잘 설명하였다. 예컨대 아파트 거실이 남향인 것은 저가 아파트에 비하여 고가 아파트에서 아파트 가격에 2배 정도 더 큰 정의 영향을 미치고, 해안에 인접한 아파트에 대한 가격효과도 고가 아파트가 저가 아파트에 비하여 10배 정도 큰 정의 영향을 미치는 것으로 나타났다.

• 대한지리학회지
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• 제48권6호
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• pp.978-993
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• 2013

공간회귀모형은 공간가중행렬을 통해 공간관계를 명시적으로 정량화한다는 점에서 타 모형과 뚜렷하게 구별되는 강점이 있는 동시에, 공간가중행렬 구성에 자의성이 개입된다는 약점을 가지고 있기도 하다. 본 연구에서는 공간가중행렬의 구성에 따라 모형 적합도가 어떻게 변화하는지 인천시를 사례로 실증적으로 검토하였다. 또한 인근지역 범위 설정에 따라 공간시차모형(spatial lag model) 또는 공간오차모형(spatial error model) 중 어떠한 모형이 보다 우수하게 나타는지 검토하였다. 분석 결과, 토지가격 추정에 있어 인근지역 범위를 좁게 파악하는 공간가중행렬을 구성할수록 모형 적합도가 전반적으로 개선되는 것이 확인되었다. 또한, 공간적 이질성이 심한 지역은 공간오차모형의 적합도가 보다 우수한 것으로 파악되었다. 공간적 이질성이 심한 지역은 동질적 성격을 갖는 하부 인근지역으로 세분함으로써 그러한 이질성을 완화시킬 수 있었고, 그 결과 공간오차모형보다 공간시차모형의 적합도가 우수하게 나타날 수 있음을 밝혔다.

• 디지털융복합연구
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• 제16권11호
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• pp.45-55
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• 2018

본 연구에서는 소비자단체의 공간적 분포와 그 특성을 살펴보고, 소비자단체의 발전 방안을 모색하는 데 필요한 근거 자료를 마련하고자 하였다. 이를 통해 지역을 기반으로 한 소비자단체가 소비자문제를 보다 효과적으로 해결할 수 있는 구체적인 방안을 제안할 수 있기 때문이다. 본 연구에서는 11개 소비자단체, 815개소 지부 및 지회 자료를 수집하여 국지적 자기상관과 공간시차모델을 활용하여 분석하였다. 첫째, 소비자단체의 공간적 분포는 지리적인 특성에 따른 패턴을 찾기 어려웠다. 둘째, 소비자단체는 인구와 사업체 수가 많고 면적이 큰 지역일수록 더 많이 분포하고 있는 것으로 나타났다. 셋째, 소비자단체의 공간적 분포는 소비자상담 건수와 비교할 때, 소비자단체의 수요와 공급 간 불일치가 발생한다는 것을 나타낸다. 후속 연구에서는 소비자단체의 활동에 관한 질적 자료를 보충하여 분석함으로써, 소비자단체의 구체적인 발전방안을 지속적으로 모색할 필요가 있다.

• 한국철도학회논문집
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• 제7권2호
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• pp.155-162
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• 2004

In order to account for a price variation of apartment that places near a newly constructed subway station, a spatial hedonic model was developed to examine spacial characteristics that affect a purchasing price of an apartment using a White Estimator. In particular, the paper aims to examine various effects of subway 7 construction on an apartment price in Seoul Metropolitan Area. As explanatory variables, an apartment size, distance to a closest subway station, distance to the Central Business District (CBD) of Seoul, the number of years after building, and a lagged variable of the apartment purchasing price were used. The lagged variable plays a role of representing a spatial weighted average of previous prices of other apartments that locate within 3 km from the apartment. For a precise study, an entire sample was divided into two sets, southern area and southwestern area of Seoul, and two different spatial hedonic models were estimated. Not only before and after analysis, but also with and without analysis were conducted to compare with different effects of the spatial characteristics of two areas. The results show that before the construction of the subway 7, the prices of the apartments in the southern area were more sensitive to the apartment size, the distance to a closest subway station, the distance to the CBD, and the prices of the other apartments locating within 3km rather than those in the southwestern area. After the construction, on contrast, it is found that the apartment purchasing prices in the southwestern area are more sensitive than those in the southern area due to people's expectation regarding a new development around the subway station. In addition, the prices of the apartments locating closely with a transfer station are more likely to go up by increase in the apartment size, the distance to the station, and the prices of the other apartments within 3 km. Compared with the negative effects of the distance to the station on the prices in the other models, the positive effect of the distance to the transfer station might be caused by the characteristics of commercial area in which people are not likely to live.