Improvement of the condensation heat transfer model of the MARS-KS1.3 code using a modified diffusion layer model

Lee, Jun-Yeob,Jeong, Jae Jun,Kang, Jin-Hoon,Yun, Byongjo Elsevier 2018 Progress in nuclear energy Vol.108 No.-

<P><B>Abstract</B></P> <P>The thermal-hydraulic system code, MARS-KS1.3, tends to underestimate the condensation heat transfer under the presence of non-condensable gases. To improve its condensation heat transfer model, we adopted the Herranz's diffusion layer model and further developed it, mainly focusing on thermal-hydraulic conditions in a nuclear containment during a hypothetical accident. Two key modifications include (i) the correlations to calculate heat and mass transfer on a vertical external surface for <I>various flow conditions</I> are adopted and (ii) a <I>turbulent diffusion coefficient</I> is applied to consider the effect of turbulence on mass diffusion.</P> <P>The modified diffusion layer model was implemented into MARS-KS1.3 and it has been validated using 157 condensation experiments from six different facilities. By using the turbulent diffusion coefficient in the modified diffusion layer model, the effect of turbulence on mass diffusion and then condensation was captured very well. For most cases, the results of the modified model are in a better agreement with the experimental data, resulting in a root-mean-square error of 21.3%. It is also shown that the modified diffusion layer model can predict local condensation heat transfer change along the condensation surface well.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MARS-KS1.3 under-predicts condensation in the presence of noncondensable gases. </LI> <LI> The Herranz's diffusion layer model was adopted for the MARS code improvement. </LI> <LI> We considered the effect of turbulence on mass diffusion through diffusion layer. </LI> <LI> The results of the modified model show a better agreement with experimental data. </LI> </UL> </P>

Diffusion and competitive relationship of mobile telephone service in Guatemala: An empirical analysis

Avila, Luz Angelica Pirir,Lee, Deok-Joo,Kim, Taegu Elsevier 2018 TelecommunicationsPolicy Vol.42 No.2

<P><B>Abstract</B></P> <P>The purpose of this paper is to analyze the characteristics of diffusion process of mobile telephone service and the competitive relationships between mobile and fixed-line services in Guatemalan telecommunications market. We investigated the best-suited model to explain the diffusion process of mobile telephone in Guatemala by estimating diffusion curves using empirical data. Moreover, we explored affecting factors which characterize the diffusion pattern of mobile telephony in Guatemala through statistical analysis. Finally, in order to understand the effects of competition in the diffusion process of Guatemalan mobile phone service, we attempted to clarify the competitive relationship between mobile and fixed-line services using the Lotka-Volterra model. As a result, the logistic model was found to be the best model for describing the diffusion pattern. Moreover, investment in telecommunications, the subscribers of fixed-line services, and the number of operators in mobile market were found as significant determinants of mobile diffusion process. Results from the Lotka-Volterra model showed that the relationship between mobile and fixed-line services has changed from pure competition to amensalism.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The characteristics of diffusion process of mobile telephone service and the competitive relationships between mobile and fixed-line services in Guatemalan telecommunications market are analyzed. </LI> <LI> The logistic model is the best model for describing the diffusion pattern of mobile phone in Guatemala. </LI> <LI> Investment, fixed-line subscribers, and the number of operators are significant determinants of the diffusion rate of mobile phone in Guatemala. </LI> <LI> The relationship between mobile and fixed-line services has changed from pure competition to amensalism in Guatemala. </LI> </UL> </P>

트랜스포머 오토인코더와 Diffusion 모델을 사용한 3D CAD 모델 생성 방법

정민섭,김민성,김지범 대한전자공학회 2023 전자공학회논문지 Vol.60 No.12

본 논문에서는 명령어 시퀀스로 표현되는 3D CAD 모델을 생성할 수 있는 새로운 딥러닝 모델을 제안한다. 제안하는 모델은 CAD 명령어 시퀀스를 생성하기 위하여 트랜스포머 기반 오토인코더와 diffusion 기반 생성 모델로 구성된다. 트랜스포머 기반 오토인코더는 CAD 명령어 시퀀스를 잘 생성하도록 잠재 표현을 학습하고, diffusion 기반 생성 모델은 새로운 명령어 시퀀스 생성을 위해서 잠재 변수를 생성하도록 학습한다. 실험을 통하여 제안하는 모델이 유효하고 새로운 3D CAD 모델을 성공적으로 생성할 수 있음을 보여주었다. 또한, CAD 모델에 대한 의미 있는 잠재 공간을 학습하였음을 보여주었다. In this paper, we propose a novel deep learning model that generates 3D CAD models represented as command sequences. The proposed model consists of a transformer-based autoencoder and a diffusion-based generative model. The transformer-based autoencoder learns latent representations to generate CAD command sequences effectively, and the diffusion-based generative model learns to generate latent variables for creating new command sequences. Experimental results show that the proposed model is able to successfully generate valid and new 3D CAD models. Our experiments also show that the proposed model learns the meaningful latent space for CAD models.

신제품 및 서비스에 있어 이분조각 Bass모형에 의한 확산 패턴 분석

홍석기(Seok-Kee Hong),홍정식(Jung-Sik Hong) 대한산업공학회 2010 산업공학 Vol.23 No.4

The Bass model is the most widely used model in research of new product diffusion because it presents a nice explanation on the diffusion process of new products. However, it has a limitation that its performance of fitness is lower as the available data become less and also, the diffusion curve is bell-shape and so, it can not represent the various diffusion patterns. Recently, a two-pieces Bass model is developed and applied to analyze diffusion of 10 products. The results are encouraging in terms of fitness. However, diffusion pattern is not dealt with in the paper. In this paper, analysis of diffusion pattern is in depth addressed in two-pieces Bass model. It is shown that the diffusion curves are divided into 3 types with respect to the peak adoption rate and each type is divided into 2 types further. Takeoff time of a diffusion process is analyzed by using the inflection point and regime-change time where it represents the point that imitation and innovation parameters change. Empirical studies for 68 products(28 domestic products and 40 USA products) are performed to analyze the diffusion pattern. Findings are that diffusion patterns of all products except 1 USA product show typeⅠ and regime-change time becomes shorter as the introduction time of the product is later in domestic products and regime-change time can be regarded as a takeoff time in 47% of total 68 products.

물류보안 인증 확산모델 개발 및 적용에 관한 연구 -ISO 28000 사례를 중심으로-

이슬기 ( Seulgi Lee ),민정웅 ( Jung Ung Min ),김인석 ( Insuk Kim ) 한국로지스틱스학회 2015 로지스틱스연구 Vol.23 No.2

본 연구는 ISO 28000 물류보안경영시스템인증 확산을 시스템 다이내믹스 이론에 기초하여 모델화 하고 시뮬레이션 함으로써 인증확산의 양태를 규명하였다. 인증확산에 주요하게 영향을 미치는 정부지원금, 구전효과 등과 같은 변수들을 채택하여 인증확산 모델을 구성하고, 시뮬레이션을 통하여 확산의 양태와 차이점 및 인증기업 수 변화에 대해서도 분석을 실시하였다. 정부지원금에 따른 ISO 28000 확산 예측 결과를 통해 정부지원이 인증확산에 중대한 영향을 미치며, 확산을 구체적인 지표들을 제시하였다. 본 연구는 ISO 28000 인증 확산 모델을 통한 향후 예측 시뮬레이션을 통하여 ISO 28000 인증확산 정책결정에 중요한 시사점을 제공할 것으로 기대된다. In this study, diffusion of ISO 28000 certification is modeled by system dynamics theory and diffusion model is simulated to uncover the diffusion type of ISO 28000 certification. Government funding, Word-Of-Mouth, and other parameters mainly affecting the diffusion were selected and constructed in the diffusion model. In addition, the difference was analyzed by simulation by the different model of government support and non government support. The simulation result showed that government funding in accordance with ISO 28000 diffusion simulation results government support gives significant impacts in the spread of ISO 28000. This result will help to set optimal amount of support for the spread of ISO 28000 diffusion in terms of diffusion speed and cost effectiveness. This study is significant in constructing ISO 28000 diffusion model in the first run. Therefore, This study is expected to be a good reference of the forward-looking decision making by the simulation and forecast of the diffusion.

Verification of the Time-Split Method for Higher-Order Diffusion in the Spectral Element Method Model on a Cubed-Sphere Grid

박자린,최석진 한국기상학회 2020 Asia-Pacific Journal of Atmospheric Sciences Vol.56 No.1

This study used the time-split method for higher-order diffusion in a global numerical weather prediction model of the spectral element method on a cubed-sphere grid, and verified its performance compared to those of the explicit and implicit timestep diffusion schemes. Because the spectral element method on a cubed-sphere grid involves intrinsic characteristics of eigenvalues of the Laplacian operator, allowable timestep sizes are more restricted for stable time integration in higher-order diffusion. For example, the 6th-order diffusion significantly limits the timestep size for adequate filtering of small-scale numerical noise during simulation. The time-split scheme can be an alternative to overcome the severe constraints on the timestep size and allow the model a timestep size as large as is potentially acceptable even in higher-order diffusion, while maintaining atmospheric kinetic energy compared to that of the explicit and implicit schemes. During analysis of the amplification factor and numerical simulation of the schemes, it was shown that the time-split scheme has a theoretical response comparable to that of the explicit and implicit schemes. The numerical simulations were conducted using the Korean Integrated Model (KIM) with a 6th-order diffusion operator of three different diffusion schemes at resolutions of 0.25- or 0.125-degree grid spacing. The time-split scheme yields a forecast performance similar to both the explicit and implicit timestep schemes while greatly reducing the computational time.

소셜TV 채택에 대한 통합 모델 연구: 지속사용 의도에대한 혁신확산이론, 기술수용모델, 혁신저항모델의 통합적 접근

윤승욱 ( Sung Uk Yun ) 한국지역언론학회 2016 언론과학연구 Vol.16 No.2

본 연구는 기술수용모델과 혁신확산이론, 그리고 혁신저항모델의 주요 구성개념을 통합하여 소셜TV 이용자들의 지속사용의도에 영향을 미치는 주요 요인들을 검토하였다. 분석결과에 바탕을 두고 주요 결과에 대해 간략히 제시하면 다음과 같다. 우선, 기술수용모델에 입각하여 인지된 유용성과 인지된 용이성이 소셜TV 지속사용의 도에 미치는 영향을 살펴본 결과, 인지된 용이성은 소셜TV 지속사용의도에 통계적으로 유의한 영향을 미치지 못하였으나, 인지된 유용성은 소셜TV 지속사용의도에 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 다음으로 혁신확산이론에 입각하여 적합성, 복잡성, 시험가능성, 관찰가능성이 혁신저항에 미치는 영향을 살펴본 결과, 적합성과 복잡성, 시험가능성, 그리고 관찰가능성은 혁신저항에 통계적으로 유의한 부적 영향을 미치는 것으로 나타났다. 한편, 적합성, 복잡성, 시험가능성, 관찰가능성이 소셜TV 지속사용의도에 미치는 영향을 살펴본 결과, 적합성과 복잡성, 시험가능성은 소셜TV 지속사용의도에 통계적으로 유의한 영향을 미치지 못하였으나, 관찰가능성은 소셜TV 지속사용의도에 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 그리고 혁신저항모델에 입각하여 지각된 위험이 혁신저항과 소셜TV 지속사용의도에 미치는 영향을 살펴본 결과, 지각된 위험은 소셜TV 지속사용의도에는 통계적으로 유의한 영향을 미치지 못하였으나, 혁신저항에는 통계적으로 유의한 정적 영향을 미치는 것으로 나타났다. 마지막으로 혁신저항이 소셜TV 지속사용의도에 미치는 영향을 살펴본 결과, 혁신저항은 소셜TV 지속사용의도에 통계적으로 유의한 부적 영향을 미치는 것으로 나타났다. The purpose of this study examines key factors affecting continuance intention of social TV users by combining major features of Technology Acceptance Model, Innovation Diffusion Theory and Innovation Resistance Model. A summary of this study regarding analysis on major results is as follows ; First, with regard to perceived usefulness and perceived ease of use in Technology Acceptance Model affecting intention of continuous use in social TV, perceived ease of use fails to statistically affect continuance intention of social TV while perceived usefulness has a statistically positive influence on intention of continuous use in social TV. Second, regarding the effect of compatibility, complexity, feasibility and observation probability about innovation resistance based on Innovation Diffusion Theory, compatibility, complexity, feasibility and observation probability have a statistically neg ative effect on innovation resistance. Meanwhile, as the study examines compatibility, complexity, feasibility and observation probability affecting intention of continuous use in social use, compatibility, complexity, feasibility fail to statistically affect continuance intention of social TV while observation probability has a statistically positive influence on intention of continuous use in social use. Regarding perceived risk based on Innovation Resistance Model affecting innovation resistance and continuance intention of social TV, perceived risk fails to statistically effect continuance intention of social TV, while it has a statistically positive effect on innovation resistance. Lastly, with regard to innovation resistance affecting continuance intention of social TV, innovation resistance has a statistically negative influence on intention of continuous use in social TV.

마케팅 모형의 포지셔닝 관련 시사점에 대한 고찰: Hauser and Shugan 모형을 중심으로

원지성 한국유통과학회 2016 유통과학연구 Vol.14 No.11

Purpose – Marketing scholars have developed various types of mathematical models for describing marketing phenomenon, because there is no single model comprehensive enough to incorporate all the relevant marketing phenomena. This study tries to summarize the behavioral foundations and the mathematical derivations of the most widely used marketing models and discusses their strategic implications. This study selected four representative marketing models: multinomial logit(MNL) model, elimination-by-aspects(EBA) model, Hauser and Shugan model and Bass diffusion model. Especially, this study focuses on Hauser and Shugan(1983)’s Defender model and discusses the model’s behavioral foundation and its implications. Research design, data, and methodology - Of the four selected model, the multinomial logit model is selected as the basic normative model and the other three models are described as descriptive models in contrast. Starting the discussion from the multinomial logit model, this study explains what important strategic variables are incorporated in each of the four models. The IIA(independence of irrelevant alternatives) axiom and Luce choice model is also discussed in relation to the multinomial logit model. The concept of ‘efficient frontier’ is discussed in relation to Hauser and Shugan’s model. Graphs and tables are used to represent the key implications. No empirical study is included. Results - The analyses of the mathematical marketing models are shown to be very useful in understanding the essence of positioning strategy. The multinomial logit model implies the importance of increasing utility or consumer preference level. The EBA model implies the importance of lowering the inter-brand similarity and dominating the competitors. Hauser and Shugan model implies the importance of considering customer heterogeneity distribution in selecting the target market. Conclusions - It is shown that the concepts of ‘efficient frontier’ is useful in understanding the effectiveness of positioning strategy. Market positioning can be understood as occupying some place on the efficient frontier. The important strategic implications can be summarized as follows: Always try to increase customer preference by providing what they value, and differentiate from competing alternatives as much as possible. The best positioning strategy is to dominate all the competitors and the worst is to be dominated by the competitors.

Forecasting the Growth of Smartphone Market in Mongolia Using Bass Diffusion Model

Anar Bataa,신광섭 사)한국빅데이터학회 2022 한국빅데이터학회 학회지 Vol.7 No.1

The Bass Diffusion Model is one of the most successful models in marketing research, and management science in general. Since its publication in 1969, it has guided marketing research on diffusion. This paper illustrates the usage of the Bass diffusion model, using mobile cellular subscription diffusion as a context. We fit the bass diffusion model to three large developed markets, South Korea, Japan, and China, and the emerging markets of Vietnam, Thailand, Kazakhstan, and Mongolia. We estimate the parameters of the bass diffusion model using the nonlinear least square method. The diffusion of mobile cellular subscriptions does follow an S-curve in every case. After acquiring m, p, and q parameters we use k-Means Cluster Analysis for grouping countries into three groups. By clustering countries, we suggest that diffusion rates and patterns are similar, where countries with emerging markets can follow in the footsteps of countries with developed markets. The purpose was to predict the timing and the magnitude of the market maturity and to determine whether the data follow the typical diffusion curve of innovations from the Bass model.

A Modified Diffusion Model Considering Autocorrelated Disturbances: Applications on CT Scanners and FPD TVs

차경천,김상훈 한국마케팅학회 2009 ASIA MARKETING JOURNAL Vol.11 No.1

Estimating the Bass diffusion model often creates a time-interval bias, which leads the OLS approach to overestimate sales at early stages and underestimate sales after the peak. Further, a specification error from omitted variables might raise serial correlations among residuals when marketing actions are not incorporated into the diffusion model. Autocorrelated disturbances may yield unbiased but inefficient estimation, and therefore invalid inference results. This phenomenon warrants a modified approach to estimating the Bass diffusion model. In this paper, the authors propose a modified Bass diffusion model handling autocorrelated disturbances. To validate the new approach, authors applied the method on two different data-sets: CT Scanners in the U.S, and FPD TV sales in Korea. The results showed improved model fit and the validity of the proposed model.