• 한국정보과학회논문지:데이타베이스
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• 제30권5호
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• pp.429-437
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• 2003

지난 십년 동안, CPU의 발전 속도는 메모리나 디스크의 발전 속도를 훨씬 능가하였다. 이것이 압축 방법을 사용하여 데이타베이스 크기를 줄이거나 질의 비용을 줄일 수 있게 만들었다. 다양한 데이타베이스 연구 분야에서 압축 방법이 사용되고 있지만, 다차원 색인 구조를 압축하는 연구는 거의 없다. 본 논문에서는 다차원 색인 구조를 위한 HEM(Hybrid Encoding Method)이라는 압축 방법을 제안한다. HEM 압축 방법은 다차원 색인 구조의 크기뿐만 아니라, 질의 비용도 크게 줄일 수 있다. 수학적인 분석과 다양한 실험을 통하여, 우리는 HEM 압축 방법이 기존에 제안되었던 압축 방법보다 색인 크기와 질의 비용 측면에서 우수하다는 것을 보여준다.

• Journal of Information Processing Systems
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• 제20권4호
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• pp.514-523
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• 2024

In the Internet of Medical Things, due to the sensitivity of medical information, data typically need to be retained locally. The training model of heart disease data can predict patients' physical health status effectively, thereby providing reliable disease information. It is crucial to make full use of multiple data sources in the Internet of Medical Things applications to improve model accuracy. As network communication speeds and computational capabilities continue to evolve, parties are storing data locally, and using privacy protection technology to exchange data in the communication process to construct models is receiving increasing attention. This shift toward secure and efficient data collaboration is expected to revolutionize computer modeling in the healthcare field by ensuring accuracy and privacy in the analysis of critical medical information. In this paper, we train and test a multiparty decision tree model for the Internet of Medical Things on a heart disease dataset to address the challenges associated with developing a practical and usable model while ensuring the protection of heart disease data. Experimental results demonstrate that the accuracy of our privacy protection method is as high as 93.24%, representing a difference of only 0.3% compared with a conventional plaintext algorithm.

• Journal of Forest and Environmental Science
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• 제33권4호
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• pp.348-354
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• 2017

Agroforestry has been practiced in arid and semi-arid regions for the purposes of preventing desertification and to increase income for locals. However, the intended effects of such practices have been limited due to strong winds and aridity. This study undertook multi-year monitoring of the productivity of income crops associated with windbreak planting in a semi-arid region of Mongolia, and explored strategies of windbreak planning to enhance the multi-purpose effects of agroforestry practices. The tree crown density of windbreak planting was on average 40% in one year after planting and 65% 2-3 years after, and thereby windspeeds were reduced by about 30% and 54%, respectively. Average windspeed reductions at leeward distances from the windbreak planting were approximately 60% within 3H (H=tree height), 50% at 5H, and 42% at 7-9H, presenting a pattern in which the farther the distance the less the reduction in windspeeds. The windbreak planting increased crop productivity by up to 6.8 times, compared to the productivity absent of windbreaks. Increases in the crown density as stated above resulted in increases of crop productivity by up to 3.6 times. Based on such results, this study proposed a model of windbreak planning as a typical land-use system of border windbreak planting or alternate windbreak planting of combining trees and income crops. The model also included tree planting with a crown density of 60% and allocation of income crops within a leeward distance of 5 times the height of the trees to reduce windspeeds by about 50%. The results from this study are applicable to practicing agroforestry not only at the study site but also in other regions worldwide where strong winds and aridity are problematic.

• 한국환경복원기술학회지
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• 제17권4호
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• pp.57-67
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• 2014

The vigor condition of trees is an important indicator for the management of urban forested area. But difficulties in how to assess the tree vigor condition still remain. Previous efforts were limited in the 1) measurement of single indicator rather than using multiple indices, 2) purpose-oriented measurement such as for air-pollution effect or specific pathological symptom, and 3) ordinal-scale evaluations by field crews 4) despite human errors based on his/her experiences or prior knowledge. Therefore, this study attempted to develop a quantitative and objective methodology for assessing tree vigor condition, by measuring multiple modules and building the profile inventory. Furthermore, the possibility and limitations were discussed in terms of schematic frames describing tree vigor condition. The vigor condition of 56 flowering cherry plants in urban park were assessed by in-situ measurements of following eight items; growth of crown(Gc), growth of shoots, individual tree volume(Vol), plant area index, woody area index, leaf area index, leaf chlorophyll content(Lc) and leaf water content(Lw). For validation, these measurements were compared with the ranks of holistic tree vigor condition, which were visually assessed using a 4-point grading scale based on the expert's knowledge. As a result, the measures of each evaluation item successfully highlighted a variety of aspects in tree vigor condition, including the states of both photosynthetic and non-photosynthetic parts. The variation in the results depending on evaluated parts was shown within an individual tree, even though the broad agreement among the results was found. The result of correlation analysis between the tested measurements and 4-point visual assessment, demonstrated that the state of water-stressed foliage of the season (Lw) or the development of plant materials since sapling phase (Vol) could be better viewed from the outer appearance of trees than other symptoms. But only based on the visual assessment, it may be difficult to detect the quality of photosynthesis (Lc) or the recent trend in growth of trees (Gc). To make this methodology simplified for the broad-scale application, the tested eight measurements could be integrated into two components by principal component analysis, which was labelled with 'the amount of plant materials' and 'vigor trend', respectively. In addition, the use of these quantitative and multi-scale indicators underlies the importance of assessing various aspects of tree vigor condition, taking into account the response(s) on different time and spatial scale of pressure(s) shown in each evaluated module. Future study should be advanced for various species at diverse developing stages and environment, and the application to wide areas at a periodic manner.

• 한국통신학회논문지
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• 제34권10B호
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• pp.964-972
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• 2009

무선 메쉬 네트워크(Wireless Mesh Network, WMN)는 다중 인터페이스와 다중 채널을 지원함으로써 기존의 무선 네트워크에서 발생되는 여러 문제점을 해결할 수 있는 핵심적인 미래기술로 대두되고 있다. WMN에서 다중 채널의 사용은 무선 네트워크 노드들이 사용하는 대역폭을 본질적으로 증가시켜준다. 그러나 이러한 대역폭을 충분히 사용하기 위해서는 다중 채널 환경에서 발생할 수 있는 채널 간 간섭을 최소화하는 채널 할당 기법이 요구된다. 본 논문에서는 WMN의 성능 향상을 위하여 클러스터링 기반의 최소 간섭 채널 할당(Minimum Interference Channel Assignment, MI-CA) 알고리즘을 제안한다. MI-CA 알고리즘은 클러스터 간의 Inter-Cluster 채널 할당과 클러스터 내부의 Intra-Cluster 채널 할당으로 구성된다. Inter-Cluster 채널 할당에서는 전체 WMN을 위한 베어본 채널을 MST(Minimum Spanning Tree) 기반으로 클러스터 헤더와 보더 노드에 할당하고, Intra-Cluster 채널 할당에서는 클러스터 멤버들 간에 직교채널을 재 할당함으로써 간섭을 최소화 한다. 시뮬레이션 결과 본 논문에서 제안한 MI-CA 알고리즘이 채널 간섭을 최소화함으로써 WMNs의 성능을 향상시킬 수 있음을 입증하였다.

• 한국항공우주학회지
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• 제37권5호
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• pp.433-441
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• 2009

대부분의 자연현상은 다학제 특성을 갖고 표현된다. 유체-구조 연계(FSI) 문제의 경우 기존에 검증된 전산유체 해석 프로그램 및 구조해석 프로그램을 그대로 사용할 수 있다는 장점 때문에 약결합 방식이 일반적으로 이용된다. 그러나 약결합을 이용하여 해석을 수행하기 위해서는 서로 다른 특성을 갖는 격자시스템으로 발생되는 자료의 교환을 위해서 보간 및 사상이 필수적이다. 본 연구에서는 전역지지 및 국부지지 방사기저함수(RBF)를 이용한 보간 및 가상일의 원리를 적용한 사상의 성능을 단순 3차원 형상에 적용하여 검토하였다. 국부지지 RBF에 공간분할 트리의 일종으로 빠른 공간 탐색을 가능하게 해주는 kd-tree를 사용하는 경우 효과적으로 거대 구조물의 FSI에도 보간 및 사상이 적용 가능함을 여객기 형상의 항공기 모형을 이용하여 제시하였다.

• 지능정보연구
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• 제19권4호
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• pp.123-132
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• 2013

최근 스마트 폰에 다양한 센서를 내장할 수 있게 되었고 스마트폰에 내장된 센서를 이용항 동작 인지에 관한 연구가 활발히 진행되고 있다. 스마트폰을 이용한 동작 인지는 노인 복지 지원이나 운동량 측정. 생활 패턴 분석, 운동 패턴 분석 등 다양한 분야에 활용될 수 있다. 하지만 스마트 폰에 내장된 센서를 이용하여 동작 인지를 하는 방법은 사용되는 센서의 수에 따라 단일 센서를 이용한 동작인지와 다중 센서를 이용한 동작인지로 나눌 수 있다. 단일 센서를 이용하는 경우 대부분 가속도 센서를 이용하기 때문에 배터리 부담은 줄지만 다양한 동작을 인지할 때에 특징(feature) 추출의 어려움과 동작 인지 정확도가 낮다는 문제점이 있다. 그리고 다중 센서를 이용하는 경우 대부분 가속도 센서와 중력센서를 사용하고 필요에 따라 다른 센서를 추가하여 동작인지를 수행하며 다양한 동작을 보다 높은 정확도로 인지할 수 있지만 다수의 센서를 사용하기 때문에 배터리 부담이 증가한다는 문제점이 있다. 따라서 본 논문에서는 이러한 문제를 해결하기 위해 스마트 폰에 내장된 가속도 센서를 이용하여 다양한 동작을 높은 정확도로 인지하는 방법을 제안한다. 서로 다른 10가지의 동작을 높을 정확도로 인지하기 위해 원시 데이터로부터 17가지 특징을 추출하고 각 동작을 분류하기 위해 Ensemble of Nested Dichotomies 분류기를 사용하였다. Ensemble of Nested Dichotomies 분류기는 다중 클래스 문제를 다수의 이진 분류 문제로 변형하여 다중 클래스 문제를 해결하는 방법으로 서로 다른 Nested Dichotomy 분류기의 분류 결과를 통해 다중 클래스 문제를 해결하는 기법이다. Nested Dichotomy 분류기 학습에는 Random Forest 분류기를 사용하였다. 성능 평가를 위해 Decision Tree, k-Nearest Neighbors, Support Vector Machine과 비교 실험을 한 결과 Ensemble of Nested Dichotomies 분류기를 사용하여 동작 인지를 수행하는 것이 가장 높은 정확도를 보였다.

• 한국산림과학회지
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• 제111권4호
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• pp.583-593
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• 2022

우리나라의 임목수확작업은 작업자의 고령화 및 고임금의 문제에 직면하고 있으며, 위기 개선을 위해 작업체계 개선 및 고성능 임업기계를 이용한 안정성 확보 등이 필요하다. 따라서 본 연구는 경사 35% 이상의 지역에서 타워야더와 프로세서를 기반으로 한 목재수확시스템을 적용할 때 다공정작업과 단공정작업의 생산성을 비교하며, 작업시스템의 비용절감 효과를 분석하고자 하였다. 국립산림과학원 광릉시험림 15임반 모두베기 지역을 대상으로 전목(가선)집재작업을 실시하였으며, 다공정과 단공정시스템의 생산성 및 비용을 분석하였다. 다목적집재장비를 이용한 단공정시스템은 타워야더와 프로세서를 이용한 다공정시스템에 비해 cycle당 집재본수가 1본/cycle 더 많아 집재작업 생산성은 약 1.5 m³/PMH (Productive Machine Hour; PMH)이, 조재작업은 약 1.6 m³/PMH이 더 높게 산출되었다. 다목적집재장비를 이용한 단공정(36,113원/m³)시스템은 다공정작업(41,065원/m³)시스템 보다 약 12.1%의 비용이 절감되었다. 또한 유휴시간(Idle time) 감소에 따라 단공정 및 다공정시스템 비용은 각각 최대 22.6%와 15.9%가 절감되었다.

• 한국조경학회지
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• 제31권5호
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• pp.20-30
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• 2003

This study is aimed at establishing the categories and items for ecological assessment and evaluation of the environmental friendliness of golf courses in the capital region of Korea. The categories and items for the assessment have been derived based on the existing literature and interviews with golf experts. This study covers 32 golf courses in the capital region of Korea that are available in terms of data and on-site surveys. In order to conduct a comprehensive assessment of the environmental friendliness of the golf courses, the assessment area was divided into 4 categories that include a total of 14 sub-categories. The 4 categories encompass 1) location, 2) topography, 3) vegetation, and 4) construction. As its sub-categories, the location category includes current land use and zoning in the National Land Use Management Law. Topography has 2 sub-categories in the damage ratio of existing topography, gradient, cut area, and slope height. The assessment of vegetation is largely based on site surveys in the categories of preservation of the existing vegetation, the use of natural resources and existing trees, the component ratio of native tree species, the multi-layered structure of vegetation, and the utilization of water purification plants. In the aspect of construction, afforestation on tile slopes and the utilization of existing surface soil were evaluated. The examination of comparative analysis among the 10 items as a ratio measure showed that the scores were low in the sub-categories of current land we, the use of existing trees, and the multi-layered structure of vegetation. However, the rating results were satisfactory in the 2 sub-categories including cut area, and the utilization of native tree species. Those proved to be contributing factors in the ecological health of the golf courses. According to correlation analysis of the 10 items to the overall ecological rating of each golf course, the sizes of the 32 golf courses were mainly affected by the damage ratio of existing topography, gradient, preservation of vegetation and slope height. This study has the initiative to conduct an ecological assessment of golf courses in the country based on site surveys. The study results revealed that location factors such as current land use, damage ratio of topography and gradient and topographical factors were the main factors affecting the environmental friendliness of golf courses. This indicates indicating the significance of these factors in the future construction practices of golf courses. Furthermore, this study raises the need for follow-up studies to establish more detailed assessment criteria and to develop assessment techniques for areas such as slope afforestation and water purification plants that need a qualitative approach.

• KIEAE Journal
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• 제12권2호
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• pp.93-101
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• 2012

In this study, we measured the Index of Greeness(I.O.G) and analyzed factors that affect in downtown street of Seoul. The aim of this article is to provide an ways of improving I.O.G, with an emphasis on accuracy of measurement. We utilized the autimatic measurment techniques proposed by Tonosaki to solve the problem of accuracy in measurement. The result is as follows : Firstly, the average I.O.G of Gwanghwamun Plaza is 15.76%, Jongno is 11.48% and Dasanro(from Yaksu station to Beotigogae station) is 6.36%. According to the comprehensive analysis in three reseach areas, it shows that I.O.G is intimately linked with planting method, species of trees and the presence of wall planting. Secondly, it was analyzed that grass and ground-cover planting promote I.O.G better than other method. The I.O.G of photo which contains grass is 45.47%. According to the comparative analysis between tree planting and multi-planting method, the presence of lower planting showed a difference about 8.77% of I.O.G.. From the persipective of I.O.G, tree planting with two lines is more effective than one. The difference of two ways is about 3.24%. Thirdly, it is an efficint way to use the wall planting or vertical planting in order to promote I.O.G.. In Dasanro, The I.O.G of photo which contains wall planting or vertical planting is 45.47% in contrast to the average of I.O.G. is 6.36%. Fourthly, the difference of I.O.G between broadleaf tree and needleleaf tree was larger than we thought. If look closely confined to this study, the I.O.G of street planted by Pine is 3.61% and Eastern Sycamore Family Bottonwood is 12.55%.