• International journal of advanced smart convergence
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• 제8권3호
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• pp.61-68
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• 2019

Spatial modulation (SM) is the first proposed space modulation technique. By further utilizing the quadrature spatial dimension, quadrature spatial modulation (QSM) has been developed as an amendment to SM system to enhance the overall spectral efficiency. Both techniques are capable of entirely eliminating interchannel interference (ICI) at the receiver. In this paper, we propose a simple adaptive hybrid switching transmission scheme to obtain better system performance than SM and QSM systems under a fixed transmission date rate. The presented modulator selection criterion for switching between spatial modulator and quadrature spatial modulator is based on the larger received minimum distance of spatial modulator and quadrature spatial modulator to exploit the spatial channel freedom. It is shown through Monte Carlo simulations that the proposed hybrid SM and QSM switching system yields lower error performance than the conventional SM and QSM systems under the same fixed data rate and thus can provide signal to noise ratio (SNR) gain.

• 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.

• 지역연구
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• 제31권2호
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• pp.47-61
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• 2015

이 연구의 목적은 수도권을 대상으로 입지를 변경한 기업들의 거리감쇄효과를 실증분석하는 것이다. 기업은 이전할 때 이전비용부담과 해당지역의 고객확보, 관련업체와의 협력 등으로 해당지역과 근접한 지역으로 재입지 하려는 경향을 나타낸다. 따라서 기업의 입지변경 시 이동거리는 기존 입지지역과 최대한 가까운 지역에 재입지하려는 거리감쇄효과가 발생한다. 본 연구는 수도권 소재의 서비스업과 제조업, 건설업 기업들의 기업이동 거리감쇄함수를 구축하고 그 효과를 실증분석하였다. 실증분석결과 서비스업과 제조업, 건설업 모든 기업의 거리감쇄효과가 있음을 확인하였으며, 구축한 거리감쇄함수의 설명력($R^2$)은 제조업은 .802, 서비스업은 .812, 건설업은 .728로 높은 설명력을 나타냈다. 이는 기업이동에 대한 거리감쇄효과가 있음을 실증한 것이며, 또한 건설업과 서비스업, 제조업 순서로 거리감쇄효과가 큼을 도출하였다.

• 한국물환경학회지
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• 제30권4호
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• pp.409-417
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• 2014

Spatial prediction methods have been useful to determine the variability of water quality in space and time due to difficulties in collecting spatial data across extensive spaces such as watershed. This study compares two kriging methods in predicting BOD concentration on the unmonitored sites in the Geum River Watershed and to assess its predictive performance by leave-one-out cross validation. This study has shown that cokriging method can make better predictions of BOD concentration than ordinary kriging method across the Geum River Watershed. Challenges for the application of cokriging on the spatial prediction of surface water quality involve the comparison of network-distance-based relationship and euclidean-distance-based relationship for the improvement in the predictive performance.

• 농촌계획
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• 제15권1호
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• pp.47-59
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• 2009

The aim of this study is to analyze the green-tourism centrality considering spatial interaction using Gravity Model and social network method. The degree centrality and prestige centrality were applied as green-tourism centrality index. The rural amenity resources and human resources were counted as attraction factors, and a distance among villages was used as friction factor in gravity model. The weights of rural tourism amenity resources were calculated using the analytic hierarchy process(AHP) method and applied to evaluate green-tourism potentiality. The distance was measured with the shortest path among villages using geographic information system(GIS) network analysis. The spatial interaction from gravity model were employed as link weights between nodal points; a pair villages. Using the spatial interaction, the degree-centrality and prestige-centrality indices were calculated by social network analysis and demonstrated possibility of developing integrated green-tourism region centered on high centrality villages.

• 한국정보처리학회논문지
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• 제6권1호
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• pp.32-41
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• 1999

공간 데이터베이스 시스템에서 최소 근접질의는 매우 빈번히 발생하며, 다른 유형의 공간질의에 비하여 처리비용이 많이 요구된다. 최소근접질의의 처리비용을 최적화하기 위해서는 색인에서 검색되는 노드의수를 최소화할 수 있어야 한다. 이를 위해 최소근접질의 처리시 색인에서 방문될 노드들을 정확히 선정하기 위한 검색거리 측도인 최적탐색거리가 제안되었다[13]. 본 논문에서는 최적탐색거리의 특성을 N차원으로 확장하고 최대검색거리를 이용한 방법에 비해 최적탐색거리를 이용한 방법이 질의처리 성능이 더 우수함을 실험을 통하여 입증한다.

• 융합신호처리학회논문지
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• 제16권2호
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• pp.35-39
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• 2015

Auditory and visual stimuli presented in the peripheral visual field were perceived as spatially coincident when the auditory stimulus was presented five to seven degrees outwards from the direction of the visual stimulus. Furthermore, judgments of the perceived distance between auditory and visual stimuli presented in the periphery did not increase when an auditory stimulus was presented in the peripheral side of the visual stimulus. As to the origin of this phenomenon, there would seem to be two possibilities. One is that the participants could not perceptually distinguish the distance on the peripheral side because of the limitation of accuracy perception. The other is that the participants could distinguish the distances, but could not evaluate them because of the insufficient experimental setup of auditory stimuli. In order to confirm which of these two alternative explanations is valid, we conducted an experiment similar to that of our previous study using a sufficient number of loudspeakers for the presentation of auditory stimuli. Results revealed that judgments of perceived distance increased on the peripheral side. This indicates that we can perceive discrimination between audio and visual stimuli on the peripheral side.

• 대한공간정보학회지
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• 제13권3호
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• pp.15-24
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• 2005

국토의 난개발을 방지하기 위해 도입된 토지적성평가는 공간 및 물리적인 특성이 서로 다른 육지와 도서지역의 평가기준을 일률적으로 적용하는 데 있어서 많은 문제점을 내포하고 있다. 본 연구에서는 공간적 지리적 지역적 특성이 뚜렷이 다른 도서지역의 효율적 토지적성평가방법의 연구를 위해서 생활권역을 고려한 평가단위와 이를 기반으로 한 평가지표 개발 등에 관하여 연구였다. 평가권역을 고려한 평가단위에서는 중생활권의 평가가 가장 양호하였으며 거리분석에 있어서는 해양을 고려한 거리 분석방법을 제안하여 도서간의 접근성을 고려한 평가방법을 제시하였다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.457-461
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• 2007

In many applications, received signal strength indicator is used for location tracking and sensor nodes localization. For location finding, the distances between sensor nodes can be estimated by converting received signal's power into distance using path loss prediction model. Many researches have done the analysis of power-distance relationship for radio channel characterization. In indoor environment, the general conclusion is the non-linear variation of RSSI values as distance varied linearly. This has been one of the difficulties for indoor localization. This paper presents works on indoor RSSI characterization based on statistical methods to find the overall trend of RSSI variation at different places and times within the same room From experiments, it has been shown that the variation of RSSI values can be determined by both spatial and temporal factors. This two factors are directly indicated by the two main parameters of path loss prediction model. The results show that all sensor nodes which are located at different places share the same characterization value for the temporal parameter whereas different values for the spatial parameters. Using this relationship, the characterization for location estimation can be more efficient and accurate.

• 보건행정학회지
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• 제27권4호
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• pp.315-323
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• 2017

Background: This study was purposed to analyze the effect of spatial accessibility to the psychiatry department in general hospital on the outpatient visit of mental patients. Methods: Data was provided from the Statistics Korea and Statistical Geographic Information Service, National Health Insurance Service, Health Insurance Review and Assessment Service, and Korea Transport Institute in 2015. The study regions were 103 administrative regions such as Si and Gu. The 103 regions had at least one general hospitals with a psychiatry department. The number of outpatient visit of mental patients in regions was used as the dependent variable. Spatial accessibility to mental general hospital was used as the independent variable. Control variables included such as demographic, economic, and health medical factors. This study used network analysis and multi-variate regression analysis. Network analysis by ArcGIS ver. 10.0 (ESRI, Redlands, CA, USA) was used to evaluate the average travel time and travel distance in Korea. Multi-variate regression analysis was conducted by SAS ver. 9.4 (SAS Institute Inc., Cary, NC, USA). Results: Travel distance and time had significant effects on the number of outpatient visits in mental patients in general hospital. Average travel time and travel distance had negative effects on the number of visits. Variables such as (number of total population, percentage of aged population over 65, and number of mental general hospital) had significant effects on the number of visit in mental patients. Conclusion: Health policy makers will need to consider the spatial accessibility to the mental healthcare organization in conducting regional health planning.