• International Journal of Contents
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• v.16 no.4
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• pp.39-49
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• 2020

The goal of this research was to understand the patterns of multidimensional engagement in MOOCs. An email with an online survey link was sent to enrollees in an MOOC course. The survey included 35 questions asking about engagement, teaching presence, and learning persistence. The items were validated in the literature, revised for the MOOC setting, reviewed by four professionals in the field of educational technology, and used in the study. A heterogeneous group of 170 individuals gathered through convenience sampling participated in the study. With cluster analysis of the engagement data, three groups were identified: Cluster1, 2, and 3. Cluster 1 scored high on behavioral, emotional, and cognitive engagement. Cluster 2 scored high on behavioral aspects but low on emotional and cognitive engagement. Cluster 3 scored low on behavioral and cognitive engagement but high on emotional aspects. The study addressed cluster-specific learner characteristics and differences in perceived teaching presence and learning persistence. Design strategies pertaining to each cluster were further discussed. These strategies may guide instructors and practitioners in the design and management of MOOCs and should be further validated through future studies.

• Electronics and Telecommunications Trends
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• v.39 no.4
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• pp.10-20
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• 2024

Recent advancements in autonomous flight technologies for Unmanned Aerial Vehicles (UAVs) have greatly expanded their applicability for various tasks, including delivery, agriculture, and rescue. This article presents a comprehensive survey of path planning techniques in autonomous navigation and exploration that are tailored for UAVs. The robotics literature has studied path and motion planning, from basic obstacle avoidance to sophisticated algorithms capable of dynamic decision-making in challenging environments. In this article, we introduce popular path and motion planning approaches such as grid-based, sampling-based, and optimization-based planners. We further describe the contributions from the state-of-the-art in exploration planning for UAVs, which have been derived from these well-studied planners. Recent research, including the method we are developing, has improved performance in terms of efficiency and scalability for exploration tasks in challenging environments without human intervention. On the basis of these research and development trends, this article discusses future directions in UAV path planning technologies, illustrating the potential for UAVs to perform complex tasks with increased autonomy and efficiency.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.1
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• pp.63-70
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• 1999

The optimum sampling area which can be applied to the benthic community study is estimated from large survey data in the Songdo tidal flat and subtidal zone of Youngil Bay, Korea. A total of 250 samples by 0.02 $m^2$ box corer for the benthic fauna in Songdo tidal flat and 50 samples by 0.1 $m^2$ van Veen grab in Youngil Bay were taken from the total sampling area of 5 $m^2$. It was assumed that the sampling area could contain sufficient information on sediment fauna, if cumulative number of species, ecological indices, and similarity index by cluster analysis reflect the similarity level of 75% to those found at total sampling area (5 $m^2$). A total of 56 and 60 species occurred from Songdo tidal flat and Youngil Bay, respectively. The cumulative curve of the species number ($N_{sp}$) as a function of the sampling area (A in $m^2$ ) was fitted as $N_{sp}=37.379A^{0.257}$ ($r^2=0.99$) for intertidal fauna and $N_{sp}=40.895A^{0.257}$ ($r^2=0.98$) for subtidal fauna. Based on these curves and 75% of similarity to the total sampling area (5 $m^2$), the optimum sampling area was proposed as 1.6 $m^2$ for the intertidal and 1.5 $m^2$ for the subtidal fauna. Ecological indices (species diversity, richness, evenness and dominance indices) were again calculated on the basis of species composition in differently simulated sample sizes. Changes in ecological indices with these sample sizes indicated that samplings could be done by collecting fauna from < 0.5 $m^2$-1.5 $m^2$ on the Songdo tidal flat and from < 0.5 $m^2$-1.2 $m^2$ in Youngil Bay. Changes in similarity level of all units of each simulated sample size showed that sampling area of 0.3 $m^2$ (Songdo tidal flat) and 0.6 $m^2$ (Youngil Bay) should be taken to obtain a similarity level of 75%. In conclusion, sampling area which was determined by cumulative number of species, ecological indices and similarity index by cluster analysis could be determined as 1.5 $m^2$ (0.02 $m^2$ box corer, n=75) for Songdo tidal flat and 1.2 $m^2$ (0.1 $m^2$ van Veen grab, n=12) for Youngil Bay. If these sampling areas could be covered in the field survey, population densities of seven dominant species comprising 68% of the total faunal abundance occurring on Songdo tidal flat and six species comprising 90% in Youngil Bay can be estimated at the precision level of P=0.2.

• Journal of the Korean housing association
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• v.20 no.1
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• pp.1-10
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• 2009

This paper documents research carried on the University students who are potential residents of the city to find out their preference for the ubiquitous residential functions, and categorize based on the life style to find out difference of their preference on ubiquitous residential functions. A survey was conducted on 324 university students in Gwangju city. The students were selected through purposive sampling and quota sampling by self-administered questionnaire sheets. The analysis analyzing methods using SPSS/PC 12.0 are frequency, percentage, factor analysis, cluster analysis, $x^2$(chaisquare)-test and one-way ANOVA (analysis of variance). For the survey, lifestyle types were categorized as: These are classified based on the analysis of facts regarding characteristics of student's lifestyles that are divided into nine types of facts and then make the four types through the cluster analysis as below. Energetic life type, Inactive life type, Family-oriented life type, Thrifty and Personality-oriented life type. The residential function of Ubiquitous is classified as Safety, Convenience, Comfortableness, Information, Health, Leisure and the residential space is divided into bedroom, livingroom, kitchen, bathroom. Considering the preference aspects for Ubiquitous residential function, among the bedroom, living room, kitchen, and bathroom, University student seek for safety from the living room, Convenience from the kitchen and Comfortableness from the living room, bedroom and kitchen. For Information, bedroom is most preferred among the bedroom, living room, and kitchen. For Health and Leisure, bedroom is preferred between bedroom and living room. In terms of the difference about the preferences for ubiquitous functions based on the four types of lifestyles; The Thrift-oriented type is commonly preferred to the Inactive type among the bedroom, living room and kitchen. The Family-oriented and the Thrift-oriented type were preferred to the Energetic and Inactive types in the bathroom. Also, in the entire residential space, the Ubiquitous functions is most preferred by the Thrifty and Personality-oriented life type.

• Journal of Environmental Science International
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• v.6 no.6
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• pp.563-578
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• 1997

The purpose of this study is to suggest the estimation model of' amenity environment' by Perceived Envionmental Quality Index(PEQI) model. A questionnaire survey was carried out for 연e study area of Taegu-Kyungbuk region. Sampling size was 838(427 of Taegu and 411 of Kyungbuk residents by stratified sampling of each region's(7 Gu for Tae-gu, 7 Cities 61 Gun far Kyungbuk) population. The survey was done during Sep. to Nov, of 1996. The suggested model was composed of four estimation categories and 16 Indicators. The four categories were 'Cleanness 61 Quietness', 'Naturalness & Harmony', 'Beauty 61 Comfort' and 'Environmental Conservation Efforts'. And each category has several individual Indicators. The weighted means of satisfaction were different by each region. Suseong-gu, Dalseogu, Joong-gu(Taegu), Bumcheon, Andong, and Cheondo(Kyungbuk) showed high enoronmental satisfaction, but Dong-gu. Seo-gu(taegu), Youngcheon, and Pohang(Kyungbuk) showed lower environmental satisfaction. By Analytic Hierarchy Process(AHP) of weighting values for each categorirs, 'Enoronmental Conservation Efforts' was estimated as the most Important(value of 0.367), and 'Naturalness 61 Harmony'(0. 242),'Clenness & guletness'(0.225), and 'Beauty & Comfort'(0.166) were Important respectively. Total PEQI's were estimated as 48.0 for Taegu, and 53.3 for Kyungbuk. PEQI's for each regions were between 46.2(Dong-gu) and 59.9(Kimcheon). The validity of the suggested model was verined by factor analysis. The four factors were identnied as the same categories and indicators. Finally, The LISREL+7 model was suggested as estimauon model of 'Amenity Environment' for Taegu-Kyungbuk region.

• The Korean Journal of Applied Statistics
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• v.19 no.1
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• pp.57-67
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• 2006

In sampling survey, nonresponse tend to occur inevitably. If we use information from respondents only, the estimates will be baised. To overcome this, various non-response imputation methods have been studied. If there are few auxiliary variables for replacing missing imputation or spatial autocorrelation exists between respondents and nonrespondents, spatial autocorrelation can be used for missing imputation. In this paper, we apply several nonresponse imputation methods including spatial imputation for the analysis of farm household economy data of the Gangwon-Do in 2002 as an example. We show that spatial imputation is more efficient than other methods through the numerical simulations.

• KIEAE Journal
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• v.10 no.2
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• pp.39-48
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• 2010

PAJU Book City Plan was designed to integrate two concepts of "Publishing Productive City" and "Ecological City" with the goal of "bringing of human being and nature together". This research on the post occupancy evaluation on PAJU Book City has two aims; One is to define how people, mainly working there rather than living, recognize the city and the other is to identify the problems resulted from the first phase of planning process and to suggest feasible solutions at the same time. It would be desirable that the outcome of this research should be used as data sources to improve the second phase of the plan. The evaluation criteria were created by the pre-survey on the basis of previous researches and "Pa Ju publishing city architectural design guide book (1999)". With those criteria, on-site questionnaire was conducted among people who work in PAJU Book City and stratified sampling was used for the proper sampling. The result is as follows; the visual-aesthetic criteria had positive response, which also closely related to a city satisfaction. Considering this result, construction type, circumferential environment of the building and a place of building form were found appropriate. The evaluation on the physical-ecological criteria was relatively low. Respondents were unsatisfied with green space and required better ecological waterway and more roadside tree. As green space was given a lot of weight in satisfaction survey, more green urban areas should be planned in the next phase. The evaluation on the social-behavior criteria got the lowest score. Particularly, the accessibility and convenient facilities were remarkably low. Nonetheless, the self-conceit about PAJU Book City was highly evaluated and played a crucial role in a city satisfaction. In order to achieve the goal, physical beauty, characteristics as a publication city as well as an ecologically sustainable city should be main agenda in the second phase of Paju Book City Plan. Consequently, it is important to strike a balance between the external environment and image media in order that PAJU Book City should be re-born as a culture city.

• Smart Media Journal
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• v.5 no.4
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• pp.103-110
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• 2016

This study aims to establish the standards to give the design weight in case when developing equipment designs, by classifying products with similar purposes in accordance with the morphological characteristics and also extracting the typicality. Limiting the sampling group for the extraction of the typicality to a pendant-type and a ceiling buried-type through the preceding case study and consultation with experts, the survey was conducted for majors and relevant workers in six cities, sampling products released in Korea and Japan before May 2016. The 1st survey was about the Morphological classification, and the 2nd times about the extraction of the typicality while the 3rd one was about the classification of the morphological attributes. By drawing the design attributes based on the functional/morphological classification and formative principles, it aimed to establish the base of the future research on the measurement of design weight. The results of this study aim to efficiently establish the roles of design technology in accordance with changes in the lighting fixture market caused by the substitution of light sources, and also to draw the development direction to rapidly cope with the accelerated changes in lighting design types and corporate R&D.

• Korean Journal of Agricultural Science
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• v.43 no.3
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• pp.299-319
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• 2016

The National Forest Inventory (NFI) is important for providing fundamental data for basic forest planning and the establishment of forest policies for the purpose of implementing sustainable forest management. The purpose of this study is to present the development of Korea's NFI including legal basis, sampling design, and measured variables and to review the usage of NFI data. The survey methods and forestry statistics among the Unites States, Canada, Japan, China, and European countries were briefly compared. Total 140 publications utilizing NFI data between 2008 and 2015 were categorized with 15 subjects. Korea has conducted the NFI 6 times since 1971, but only the $6^{th}$ NFI is comparable with the fifth, the previous NFI, because the permanent sampling plots have been shared between the periods. The Korean Forestry Statistics contains only half as many variables as that of advanced countries in Forestry. More researches were needed to improve consistent measurement of diverse variables through implementation of advanced technologies. Additional data for Forest Health Monitoring since the NFI $6^{th}$ must be under quality control which will be an essential part of the inventories for providing the chronological change of forest health.

• Korea journal of population studies
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• v.11 no.1
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• pp.1-13
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• 1988

This study examines the sampling bias that may have resulted from the large number of missing observations. Despite well-designed and reliable sampling procedures, the observed sample values in DSFH(Demographic Survey on Changes in Family and Household Structure, Japan) included many missing observations. The head administerd survey method of DSFH resulted in a large number of missing observations regarding characteristics of elderly non-head parents and their children. In addition, the response probability of a particular item in DSFH significantly differs by characteristics of elderly parents and their children. Furthermore, missing observations of many items occurred simultaneously. This complex pattern of missing observations critically limits the ability to produce an unbiased analysis. First, the large number of missing observations is likely to cause a misleading estimate of the standard error. Even worse, the possible dependency of missing observations on their latent values is likely to produce biased estimates of covariates. Two models are employed to solve the possible inference biases. First, EM algorithm is used to infer the missing values based on the knowledge of the association between the observed values and other covariates. Second, a selection model was employed given the suspicion that the probability of missing observations of proximity depends on its unobserved outcome.