• Title/Summary/Keyword: heterogeneity

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An Approach to the Analysis of Landscape Heterogeneity in Seoul Metropolitan Suburbs (서울시 주변지역의 경관이질성 변화 분석기법 개발을 위한 기초연구)

  • 안동만;박은관;김인호;김명수;박소영
    • Journal of the Korean Institute of Landscape Architecture
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    • v.26 no.3
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    • pp.288-296
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    • 1998
  • Natural or human disturbances cause landscape changes, which may be measured by the degree of heterogeneity. In a 16km$\times$19km area, divided into 100m$\times$100m cells, of Seoul city and its suburb, land covers are classified into 6 groups in aerial photos and land use maps. The degree of heterogeneity is defined as the number of cells that surround a central cell but have different land cover from the central cell divided by 8. The value of the degree of heterogeneity is between 0 and 1. Major findings are 1) Both urban and natural areas have low degree of heterogeneity, about 0.15~0.17. 2) Suburban area under heavy pressure of development and urbanization has highest degree of heterogeneity, about 0.25. 3) The peak of the degree of heterogeneity moved about 4.5km outward in 22 years. 4) Outer suburban area has lower degree of heterogeneity as the area is a greenbelt or forest. 5) The results show the areas with higher degree of heterogeneity which may need landscape management plans, and natural areas with lower degree of heterogeneity which may need landscape conservation plans. A landscape change model may be built for a specific city when this technique is applied to multiple sectors of the city, and the model may predict future landscape changes of the city.

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A Study on the Method for Solving Data Heterogeneity in the Integrated Information System (통합 정보시스템에서의 데이터 이질성 해결 방안에 관한 연구)

  • Park, Seong-Jin;Park, Sung-Kong;Park, Hwa-Gyoo
    • Journal of Information Technology Services
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    • v.7 no.4
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    • pp.87-99
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    • 2008
  • As the technologies for telecommunication have been evolving, more enhanced information services and integrated information systems have been introduced, which can manage a variety of information from the heterogeneous systems. The major obstacle for the integrated information systems is the integrating heterogeneous databases in the systems and the heterogeneity problems can be classified into the structural and data heterogeneities. However, the previous researches have mainly highlighted into the solving structural heterogeneity problems. This paper identifies the data heterogeneity problems for multi-database schema integrations and proposes a new solving method. We analyze the semantics equivalence in data values based on the functional dependency, primary and candidate keys, and present a procedural solution of data heterogeneity in the perspective of the concept of attribute equivalence, integration key and conceptual integration table.

Beta-Meta: a meta-analysis application considering heterogeneity among genome-wide association studies

  • Gyungbu Kim;Yoonsuk Lee;Jeong Ho Park;Dongmin Kim;Wonseok Lee
    • Genomics & Informatics
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    • v.20 no.4
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    • pp.49.1-49.7
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    • 2022
  • Many packages for a meta-analysis of genome-wide association studies (GWAS) have been developed to discover genetic variants. Although variations across studies must be considered, there are not many currently-accessible packages that estimate between-study heterogeneity. Thus, we propose a python based application called Beta-Meta which can easily process a meta-analysis by automatically selecting between a fixed effects and a random effects model based on heterogeneity. Beta-Meta implements flexible input data manipulation to allow multiple meta-analyses of different genotype-phenotype associations in a single process. It provides a step-by-step meta-analysis of GWAS for each association in the following order: heterogeneity test, two different calculations of an effect size and a p-value based on heterogeneity, and the Benjamini-Hochberg p-value adjustment. These methods enable users to validate the results of individual studies with greater statistical power and better estimation precision. We elaborate on these and illustrate them with examples from several studies of infertility-related disorders.

Single cell heterogeneity in human pluripotent stem cells

  • Yang, Seungbok;Cho, Yoonjae;Jang, Jiwon
    • BMB Reports
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    • v.54 no.10
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    • pp.505-515
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    • 2021
  • Human pluripotent stem cells (hPSCs) include human embryonic stem cells (hESCs) derived from blastocysts and human induced pluripotent stem cells (hiPSCs) generated from somatic cell reprogramming. Due to their self-renewal ability and pluripotent differentiation potential, hPSCs serve as an excellent experimental platform for human development, disease modeling, drug screening, and cell therapy. Traditionally, hPSCs were considered to form a homogenous population. However, recent advances in single cell technologies revealed a high degree of variability between individual cells within a hPSC population. Different types of heterogeneity can arise by genetic and epigenetic abnormalities associated with long-term in vitro culture and somatic cell reprogramming. These variations initially appear in a rare population of cells. However, some cancer-related variations can confer growth advantages to the affected cells and alter cellular phenotypes, which raises significant concerns in hPSC applications. In contrast, other types of heterogeneity are related to intrinsic features of hPSCs such as asynchronous cell cycle and spatial asymmetry in cell adhesion. A growing body of evidence suggests that hPSCs exploit the intrinsic heterogeneity to produce multiple lineages during differentiation. This idea offers a new concept of pluripotency with single cell heterogeneity as an integral element. Collectively, single cell heterogeneity is Janus-faced in hPSC function and application. Harmful heterogeneity has to be minimized by improving culture conditions and screening methods. However, other heterogeneity that is integral for pluripotency can be utilized to control hPSC proliferation and differentiation.

RELATIONSHIP BETWEEN VIRULENCE, METABOLIC ACID AND GENETIC HETEROGENEITY OF PORPHYROMONAS GINGIVALIS (Porphyromonas gingivalis의 독성, 대사산물 및 유전자이종성과의 관련성)

  • Kim, Kang-Ju;Chung, Chong-Pyoung
    • Journal of Periodontal and Implant Science
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    • v.23 no.1
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    • pp.1-15
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    • 1993
  • P. gingivalis has been implicated as a strong pathogen in periodontal disease and known to have three serotypes of P. gingivalis. The purpose of this study is to investigate on the relationship between virulence, metabolic acids and genetic heterogeneity of P. gingivalis. P. gingivalis W50 standard strain and five strains of P. gingivalis serotype b Korean isolates were used in this study. For in vitro virulence test, lyophilized whole cell P. gingivalis were suspended, and sonicated with ultrasonic dismembranometer. Sonicated samples were applied to cultured cells derived from periodontal ligament, and cell activity was assayed with growth and survival assay. The metabolic acids were also extracted, and determined by High Performance Liquid Chromatography. Pst I-digested bacterial genomic DNA was electrophoresed, and densitometric analysis was performed to study the genetic heterogeneity. All of the P. gingivalis serotype b produced butyric acid. In cell activity study, butyric acid inhibited the cell activity irrespective of its concentration. Densitometric analysis showed restriction fragment length polymorphism. These results suggested that there existed heterogeneity of the metabolic acids and the virulence of P. gingivalis and such heterogeneity might be related to genetic heterogeneity.

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Top Management Team Heterogeneity, Interaction and Organizational Performance in Korean Hospitals (최고경영자 팀이 의료기관의 성과에 미치는 영향)

  • Jung, Moung-Suk;Lee, Se-Hoon;Kim, Kwang-Jum
    • Health Policy and Management
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    • v.20 no.1
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    • pp.137-154
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    • 2010
  • This study empirically analyzed the effects of the Top Management Team (TMT) on organizational performance. We verified whether the age heterogeneity, job heterogeneity (core career, core function and major), and process (communication and integration) of the TMT affect organizational performance (management performance and healthcare service quality evaluation level). We collected data about 473 members of the 2006 TMT in 81 medical institutions. We also utilized statistics of organizational performance from the Ministry for Health, Welfare and Family Affairs and the Korean Institute of Hospital Management. Results of the study showed that the age heterogeneity of TMT exerted a negative effect on the healthcare service quality evaluation level, while the process exerted a positive effect. However, the age heterogeneity, job heterogeneity, and process had no influence on management performance. We discussed the implications of such outcome of the investigation in comparison with the former studies on TMT and organizational performance, and presented its restrictions and future plans.

Corporate Social Responsibility and Firm Performance: the Moderating Role of Top Management Team Characteristics and Heterogeneity

  • Meng, La-Mei;Byun, Hae-Young
    • Asia-Pacific Journal of Business
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    • v.12 no.2
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    • pp.39-60
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    • 2021
  • Purpose - The purpose of this paper is exploring whether the characteristics and heterogeneity of the TMT play a moderating role in CSR and corporate value or not. Design/methodology/approach - The literature research method includes collecting, organizing, and analyzing the literature on the characteristics and heterogeneity of the TMT, the effect of corporate social responsibility (CSR), and corporate value. We analyze the contributions and limitations in existing research, grasp the current research status, and develop the research content of this article. The empirical analysis method is based on the data of Chinese A-share listed companies from 2001 to 2017. This allows us to study the moderating effect of the characteristics and heterogeneity of the TMT on CSR and corporate value. Findings - The TMT age, education degree, overseas background, and compensation have a positive moderating effect on CSR and corporate market value. The comprehensive heterogeneity of the TMT also has a positive effect on CSR and financial performance. Research implications or Originality - The research on the relationship between CSR and corporate value is still inconclusive. Some results have found a positive relationship, while others show a negative relationship. Studies exist that report mixed findings as well. This study has attempted to clarify this problem by adding potentially missing variables related on the TMT characteristics and heterogeneity, investigating causality effects.

Using Mixed Logit Model and Latent Class Model to Analyze Preference Heterogeneity in Choice Experiment Data (선택실험법 자료에서의 선호이질성 분석을 위한 혼합로짓모형 및 잠재계층모형의 활용)

  • Yoo, Byong Kook
    • Environmental and Resource Economics Review
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    • v.21 no.4
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    • pp.921-945
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    • 2012
  • Conditional Logit (CL) model is widely used since its model estimation and interpretation of results of the model is relatively easy, on the other hand, it has the limit of preference heterogeneity of respondents being not fully considered. In this study we used the two models, Mixed Logit (ML) Model and Latent Class Model (LCM) to explain preference heterogeneity of respondents for protection for Boryeong Dam wetland. As a result of the examination for heterogeneity in Boryeong city and six metropolitan areas, we found there was significant difference between two regions. While there was explicit preference heterogeneity within respondents in Boryeong city, we found little heterogeneity within respondents in six metropolitan areas. Thus in the case of six metropolitan areas, CL model can be used for parameter estimation while in the case of Boryeong city, WTP estimates are based on parameter estimates from ML model to reflect the heterogeneity within respondents. Additionally, ML model with interaction and 2-class LCM for respondents in Boryeong city were used to explain the sources of the heterogeneity. The ML model with interaction has advantage of explaining individual unobserved heterogeneity. However The comarison between these two models reflects the fact that LCM provided added information that was not conveyed in the ML model with interaction. Thus, Preference heterogeneity within respondents in this study may be better explained by class level through LCM rather than indiviual level through ML model.

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Channel Heterogeneity Aware Channel Assignment for IEEE 802.11 Multi-Radio Multi-Rate Wireless Networks (IEEE 802.11 다중 라디오 다중 전송률 무선 네트워크를 위한 채널 이질성 인지 채널 할당)

  • Kim, Sok-Hyong;Kim, Dong-Wook;Suh, Young-Joo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.11A
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    • pp.870-877
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    • 2011
  • IEEE 802.11 devices are widely used, and terminals can be equipped with multiple IEEE 802.11 interfaces as low-cost IEEE 802.11 devices are deployed. The off-the-shelf IEEE 802.11 devices provide multiple channels and multiple data rates. In practical multi-channel networks, since there is channel heterogeneity which indicates that channels have different signal characteristics for the same node, channels should be efficiently assigned to improve network capacity. In addition, in multi-rate networks, low-rate links severely degrade the performance of high-rate links on the same channel, which is known as performance anomaly. Therefore, in this paper, we propose a heterogeneity aware channel assignment (HACA) algorithm that improves network performance by reflecting channel heterogeneity and performance anomaly. Through NS-2 simulations, we validate that the HACA algorithm shows improved performance compared with existing channel assignment algorithms that do not reflect channel heterogeneity.

Inherent Random Heterogeneity Logit Model for Stated Preference Freight Mode Choice (SP 화물수단선택을 위한 Inherent Random Heterogeneity 로짓 모형 연구)

  • KIM, Kang-Soo
    • Journal of Korean Society of Transportation
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    • v.20 no.3
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    • pp.83-92
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    • 2002
  • Freight mode choice models are essential to the analysis of many areas of transport research. However, observations of actual market choices have only been made in a limited number of situations. Therefore, stated preference(SP) techniques have emerged as an alternative source of actual market choices to be used for estimating freight mode choice models. Considerable confidence exists about SP data, but little consideration has been given to the potential for estimation bias. This paper has been motivated by the theoretical side of estimating SP discrete choice models, focusing on a case study of freight mode choice. Recently developed simulation methods are used to construct inherent random heterogeneity legit models, which consider individual heterogeneity, its inheritance to the next choices and overcome the independence from irrelevant alternatives (IIA) property. This Paper contributes to the development of models dealing with heterogeneity and its inheritance, and sheds light on the heterogeneity of freight transport.