• 산경연구논집
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• 제12권8호
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• pp.33-39
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• 2021

Purpose: The influence of age on time preference is not identified in the usual cross-sectional analysis. This study aims to test whether age affects time preference after controlling for the effects of individual heterogeneity including cohort effects. Research design, data and methodology: Drawing on a nationally representative panel dataset of Indonesians, we estimate the effects of age on time preference after controlling for unobserved individual heterogeneity as well as potential cohort effects. We measure time preference exploiting information on two sets of multiple price lists: one for a one-year delay, and the other for a five-year delay. Results: When we controlled for time-invariant individual characteristics, including birth cohort effects in a fixed effects model, the older men and women were more patient in a linear fashion, particularly when the delay was longer. To highlight the importance of controlling for individual fixed effects, we repeated the specification without controlling for individual fixed effects in OLS or censored maximum likelihood regression; we found no relation between age and impatience in men or women and for a one or five-year delay. Conclusions: The older men and women are more patient, and time preferences are correlated with unobserved individual heterogeneity.

• 인터넷정보학회논문지
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• 제24권6호
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• pp.1-11
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• 2023

Federated learning (FL) is a ground breaking machine learning paradigm that allow smultiple participants to collaboratively train models in a cloud environment, all while maintaining the privacy of their raw data. This approach is in valuable in applications involving sensitive or geographically distributed data. However, one of the challenges in FL is dealing with heterogeneous and non-independent and identically distributed (non-IID) data across participants, which can result in suboptimal model performance compared to traditionalmachine learning methods. To tackle this, we introduce FedGCD, a novel FL algorithm that employs Graph Neural Network (GNN)-based community detection to enhance model convergence in federated settings. In our experiments, FedGCD consistently outperformed existing FL algorithms in various scenarios: for instance, in a non-IID environment, it achieved an accuracy of 0.9113, a precision of 0.8798,and an F1-Score of 0.8972. In a semi-IID setting, it demonstrated the highest accuracy at 0.9315 and an impressive F1-Score of 0.9312. We also introduce a new metric, nonIIDness, to quantitatively measure the degree of data heterogeneity. Our results indicate that FedGCD not only addresses the challenges of data heterogeneity and non-IIDness but also sets new benchmarks for FL algorithms. The community detection approach adopted in FedGCD has broader implications, suggesting that it could be adapted for other distributed machine learning scenarios, thereby improving model performance and convergence across a range of applications.

• Asian Journal for Public Opinion Research
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• 제1권2호
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• pp.103-127
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• 2014

This study reviews existing research on the measurement of and the relationship between political diversity and political participation. It addresses the inconsistency in the arguments of existing studies researching the influence of political diversity on political participation. It attempts to find the cause in the variety of approaches to conceptualize and operationalize the two variables. As the measure of political diversity, political network heterogeneity and network attributes are discussed in detail in specific relation to political participation. As for political participation, an in-depth analysis of various ways to understand different forms of political involvement is presented. Implications for public opinion research are discussed.

• International Journal of Internet, Broadcasting and Communication
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• 제15권4호
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• pp.279-293
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• 2023

This study investigates network effects to measure how strongly the early adopters affect the brand choice of the potential consumer. By using the Gumbel-Hougaard (GH) copula, this study checks the magnitude of network effects varied from country to country. To consider consumer heterogeneity and network effects in the growth market, this study proposes the multi-brand Gamma/Shifted-Gompertz (m-G/SG) model based on the GH copula. Out of eighteen Western European cellular phone market data and South Korea smartphone data sets, the m-G/SG model provides an improvement in the estimation accuracy over the Libai, Muller, and Peres model. The results show that network effects enhance (i) the polarization of brand choice probabilities as time elapses; (ii) the dominance of the more preferred and the earlier entered brand; and (iii) the deceleration of category-level diffusion. Potential followers can analyze their relationship with earlier entrants through the m-G/SG model and also establish an optimal market entry strategy.

• 한국IT서비스학회:학술대회논문집
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• 한국IT서비스학회 2007년도 추계학술대회
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• pp.679-684
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• 2007

This paper proposes a scheme to estimate the technical efficiency of trucks in logistics as performance measure by Data Envelopment Analysis (DEA). The result of technical efficiency estimation shows that there exists a substantial opportunity for improvement in technical efficiency of trucks and also the heterogeneity in the technical efficiency among trucks.

• 응용통계연구
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• 제15권1호
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• pp.179-186
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• 2002

반응표면분석시 모든 실험이 동일한 조건 하에서 이루어지어야 하는 데 그렇지 못할 경우 우리는 블럭화를 행하게 된다. 반응 표면분석모형으로서 우리는 주로 2차 모형을 사용한다. 본 논문은 우리가 반응표면분석모형으로서 2차 모형을 사용할 때 근사직교블럭화를 평가하기 위한 간단한 측도들을 제시한다.

• 한국IT서비스학회지
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• 제9권1호
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• pp.173-197
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• 2010

Though service is recognized as not only a new driver for economy growth but also a source for sustainable value creation, it has been misunderstood in the literatures because of traditional characteristics of service such as inseparability, heterogeneity, intangibility, and perishability. This perspective can be a cause of barrier to approach a service. The purpose of this study is to develop and validate an instrument to measure of the service process. A series of statistical procedures were used to analyze the data, which proved that the instrument is valid and reliable. This study makes a contribution to both academic research and management practice. Theoretically, this study provides a measurement of service process in organizations for identifying service process. In practice, the results of this study will help organizations evaluate their service process innovation.

• 한국수자원학회논문집
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• 제51권5호
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• pp.383-393
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• 2018

지역빈도해석은 대상 지점과 수문학적 동질성을 만족하는 주변 지점을 하나의 지역으로 보고 빈도해석을 수행하는 방법이다. 따라서 동질한 지역의 구분은 지역빈도해석에 있어서 가장 중요한 가정이라고 할 수 있다. 이에 본 연구에서는 인공신경망 기법중 하나인 자기조직화지도(self-organizing map, SOM) 기법을 활용하여 강우 지역빈도해석을 위한 동질 강수 지역을 구분하였다. 지역구분 인자로는 지형 정보와 시 단위 강우 자료를 활용하였다. 최적 SOM 지도 구성을 위해 정량적 오차와 위상관계 오차를 활용하였다. 그 결과 $7{\times}6$ 배열의 42개의 노드를 갖는 모형을 선정하였고 최종적으로 강우 지역빈도해석을 위해 6개의 군집으로 구분하였다. 동질성 검토 결과 6개의 군집 모두 동질한 지역으로 나타났으며 기존의 유사하게 구분된 지역들과 이질성 척도를 비교하였을 때 좀 더 안정적인 지역 구분결과를 나타내는 것을 확인하였다.

• The Journal of Asian Finance, Economics and Business
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• 제7권12호
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• pp.853-861
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• 2020

The study aims to measure the productivity of the Saudi banking sector at the retail level using secondary data for 11 local banks from the period 2015-2019. The study uses an extended version of the Cobb-Douglas production function to account for the fact that as banks openup more retail branches, they will need to employ more labor. The extended Cobb-Douglas production function was estimated using the two-way fixed effect model to account for unobserved heterogeneity across Saudi banks resulting from differences in labor competencies and leadership style. Besides, the model accounts for unobserved heterogeneity among Saudi banks due to the advancement in electronic services over time. The results showed that labor, branches, customers' deposits, and fixed deposits have a positive effect on the total value of generated loans. Conversely, ATM has an insignificant effect on generated loans. The average scale elasticity shows that the Saudi banks at the retail level are operating under decreasing returns to scale. The average marginal rate of technical substitution shows that Saudi banks need at least one ATM to replace one unit of labor at the retail level while keeping the same level of output.

• 자원ㆍ환경경제연구
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• 제15권5호
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• pp.885-919
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• 2006

본 연구는 환경 비시장가치 평가에서 일반적으로 통용되는 두 가지 '믿음'을 재조명하고 그 단점과 해결책을 고찰한다. 이 믿음은 (1) 지불의사액(WTP)이 비시장 선호도의 타당한 추정치라는 것과, (2) WTP를 설명함에 있어 외생변수(exogenous variables)의 기여도는 인정하면서도 내생변수(endogenous variables)는 무시할 수 있다는 것이다. 하지만, 심리행동학과 후생경제학의 최근 관련 문헌조사를 통해서 평가해 볼 때 두 가지 믿음으로부터의 이탈현상이 두드러지게 발견된다, 결론적으로, 이 같은 현상의 주요 원인으로 알려져 있는 응답자 이질성(heterogeneity)에 효과적으로 대처하기 위해서는 소비자의 선택행동을 설명하는 확률효용모델의 구성에 사회경제 변수와 심리태도 변수를 함께 고려하여야 한다. 특히, 측정의 번거로움을 이유로 후자가 무시될 경우 기존 문헌에서 제기된 다양한 편중(bias)에 노출됨으로써 추정치의 신뢰도가 낮아질 수 있다.