• Title/Summary/Keyword: Implicit Modeling

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VIV simulation of riser-conductor systems including nonlinear soil-structure interactions

  • Ye, Maokun;Chen, Hamn-Ching
    • Ocean Systems Engineering
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    • v.9 no.3
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    • pp.241-259
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    • 2019
  • This paper presents a fully three-dimensional numerical approach for analyzing deepwater drilling riser-conductor system vortex-induced vibrations (VIV) including nonlinear soil-structure interactions (SSI). The drilling riser-conductor system is modeled as a tensioned beam with linearly distributed tension and is solved by a fully implicit discretization scheme. The fluid field around the riser-conductor system is obtained by Finite-Analytic Navier-Stokes (FANS) code, which numerically solves the unsteady Navier-Stokes equations. The SSI is considered by modeling the lateral soil resistance force according to nonlinear p-y curves. Overset grid method is adopted to mesh the fluid domain. A partitioned fluid-structure interaction (FSI) method is achieved by communication between the fluid solver and riser motion solver. A riser-conductor system VIV simulation without SSI is firstly presented and served as a benchmark case for the subsequent simulations. Two SSI models based on a nonlinear p-y curve are then applied to the VIV simulations. Also, the effects of two key soil properties on the VIV simulations of riser-conductor systems are studied.

Agenda Setting between the Public and Government on Weibo: The Case of Shanghai Lockdown during the COVID-19 Epidemic

  • Weiwen Yu
    • Journal of Contemporary Eastern Asia
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    • v.22 no.2
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    • pp.39-58
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    • 2023
  • This study examined China's public and government agenda setting in response to the Shanghai lockdown due to the COVID-19 pandemic. It employed content analysis, correlation, and Granger's causality tests to analyze 1,717 Weibo posts published by the public and the Shanghai Municipal Government from March 12 to June 1, 2022. The results showed that (1) pandemic statistics were the central attribute in the government agenda, while civil life, community management, and government and policies were the central attributes in the public agenda; (2) the government's agenda unidirectionally influenced the public agenda in terms of government policy attributes; and (3) the government and public agendas reciprocally influenced each other in terms of economic attributes. This study contributed to the existing literature by examining agenda-setting dynamics in a city closure event during the COVID-19 epidemic. It also extended existing methods by modeling implicit relationships between attributes in the public and government agendas.

An Algorithm for Referential Integrity Relations Extraction using Similarity Comparison of RDB (유사성 비교를 통한 RDB의 참조 무결성 관계 추출 알고리즘)

  • Kim, Jang-Won;Jeong, Dong-Won;Kim, Jin-Hyung;Baik, Doo-Kwon
    • Journal of the Korea Society for Simulation
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    • v.15 no.3
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    • pp.115-124
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    • 2006
  • XML is rapidly becoming technologies for information exchange and representation. It causes many research issues such as semantic modeling methods, security, conversion far interoperability with other models, and so on. Especially, the most important issue for its practical application is how to achieve the interoperability between XML model and relational model. Until now, many suggestions have been proposed to achieve it. However several problems still remain. Most of all, the exiting methods do not consider implicit referential integrity relations, and it causes incorrect data delivery. One method to do this has been proposed with the restriction where one semantic is defined as only one same name in a given database. In real database world, this restriction cannot provide the application and extensibility. This paper proposes a noble conversion (RDB-to-XML) algorithm based on the similarity checking technique. The key point of our method is how to find implicit referential integrity relations between different field names presenting one same semantic. To resolve it, we define an enhanced implicity referentiai integrity relations extraction algorithm based on a widely used ontology, WordNet. The proposed conversion algorithm is more practical than the previous-similar approach.

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A Mathematical Modeling of Two-Dimensional Unsteady Flow for Long Waves in a Harbor (항내(港內) 장주기파(長週期波) 해석(解析)을 위한 2차원(二次元) 부정류(不定流)의 수학적(數學的) 모형(模型))

  • Lee, Jong Tae;Lee, Won Hwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.3 no.1
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    • pp.13-24
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    • 1983
  • A mathematical model for the two-dimensional unsteady flow was developed by introducing Abbott's implicit finite difference operator and double sweep algorithm, which could be applied to simulate the respose of a harbor against the intrusion of long waves through the entrance connected to open sea. In order to improve its accuracy corresponding to the field phenomena, bottom resistance, Coriolis force, wind effect terms were included and wave direction and radiating effect was considered. The result of seiche test was always stable and the amplitude was accurate. Some phase shift was occured, but it could be reduced by using small values of Courant number and many points per a wave length as well. A comparision with the Ippen and Goda's theoritical and hydraulic experimental works was fulfilled.

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Comparison and Analysis of Implicit and Explicit Collaboration Process Languages (암시적/명시적 협업 프로세스 언어의 비교분석)

  • Jo, Myung-Hyun;Park, Jung-Up;Sul, Joo-Young;Baeg, Moon-Hong;Son, Jin-Hyun
    • The KIPS Transactions:PartD
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    • v.13D no.5 s.108
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    • pp.671-682
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    • 2006
  • Until now, a variety of the standard and research activities are progressed in the business process management. However, since the common standard of the collaboration process language has not been determined, the research activities could not be well-systemized. We would present the guide-line to select and use the collaboration process language straightly through comparing different collaboration process languages (BPEL4WS, BPML, WSCI, WS-CDL, BPSS, etc). In this regard, we define the implicit and the explicit collaboration as the collaboration method in advance and present the result acquired according to compare and analyze the features of the collaboration process languages. First, the necessary elements the collaboration process languages have are extracted through the framework of the inter-organizational workflow proposed by Bernauer and the collaboration process modeling procedure(CPMP). Second, we analyze the properties of the collaboration process language based the essential elements. Finally, we show the complete example that the collaboration business process really reflects the characteristics of the collaboration business process languages

Study on Modeling the Spectral Solar Radiation Absorption Characteristics in Determining the surface Temperature of a Ground Object (지상물체의 표면온도 계산을 위한 파장별 태양복사 흡수특성 모델링 연구)

  • Choi, Jun-Hyuk;Gil, Tae-Jun;Kim, Tae-Kuk
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.1
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    • pp.33-39
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    • 2007
  • This paper is aimed at the development of a software that predicts the surface temperature profiles of three-dimensional objects on the ground by considering the spectral solar radiation through the atmosphere. The spectral solar radiation through the atmosphere is modeled by using the well-known LOWTRAN7 code which analyzes the detailed spectral transmission characteristics by considering the atmospheric gas layers. In this paper, the transient temperature distribution over a cylinder is calculated by using the semi-implicit method. The spectral radiative surface properties such as the absorptivity and emissivity of the objects are used to model the effects of the solar irradiation and the surface emission. Both the detailed spectral modeling and the simple total modeling for the solar radiation absorption show fairly good agreement with each other by showing less than 3% difference in surface temperature.

Recent Reseach in Simulation Optimization

  • 이영해
    • Proceedings of the Korea Society for Simulation Conference
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    • 1994.10a
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    • pp.1-2
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    • 1994
  • With the prevalence of computers in modern organizations, simulation is receiving more atention as an effectvie decision -making tool. Simualtion is a computer-based numerical technique which uses mathmatical and logical models to approximate the behaviror of a real-world system. However, iptimization of synamic stochastic systems often defy analytical and algorithmic soluions. Although a simulation approach is often free fo the liminting assumption s of mathematical modeling, cost and time consiceration s make simulation the henayst's last resort. Therefore, whenever possible, analytical and algorithmica solutions are favored over simulation. This paper discussed the issues and procedrues for using simulation as a tool for optimization of stochastic complex systems that are dmodeled by computer simulation . Its emphasis is mostly on issues that are speicific to simulation optimization instead of consentrating on the general optimizationand mathematical programming techniques . A simulation optimization problem is an optimization problem where the objective function. constraints, or both are response that can only be evauated by computer simulation. As such, these functions are only implicit functions of decision parameters of the system, and often stochastic in nature as well. Most of optimization techniqes can be classified as single or multiple-resoneses techniques . The optimization of single response functins has been researched extensively and consists of many techniques. In the single response category, these strategies are gradient based search techniques, stochastic approximate techniques, response surface techniques, and heuristic search techniques. In the multiple response categroy, there are basically five distinct strategies for treating the responses and finding the optimum solution. These strategies are graphica techniqes, direct search techniques, constrained optimization techniques, unconstrained optimization techniques, and goal programming techniques. The choice of theprocedreu to employ in simulation optimization depends on the analyst and the problem to be solved. For many practival and industrial optimization problems where some or all of the system components are stochastic, the objective functions cannot be represented analytically. Therefore, modeling by computersimulation is one of the most effective means of studying such complex systems. In this paper, after discussion of simulation optmization techniques, the applications of above techniques will be presented in the modeling process of many flexible manufacturing systems.

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Dispute of Part-Whole Representation in Conceptual Modeling (부분-전체 관계에 관한 개념적 모델링의 논의에 관하여)

  • Kim, Taekyung;Park, Jinsoo;Rho, Sangkyu
    • Journal of Intelligence and Information Systems
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    • v.18 no.4
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    • pp.97-116
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    • 2012
  • Conceptual modeling is an important step for successful system development. It helps system designers and business practitioners share the same view on domain knowledge. If the work is successful, a result of conceptual modeling can be beneficial in increasing productivity and reducing failures. However, the value of conceptual modeling is unlikely to be evaluated uniformly because we are lack of agreement on how to elicit concepts and how to represent those with conceptual modeling constructs. Especially, designing relationships between components, also known as part-whole relationships, have been regarded as complicated work. The recent study, "Representing Part-Whole Relations in Conceptual Modeling : An Empirical Evaluation" (Shanks et al., 2008), published in MIS Quarterly, can be regarded as one of positive efforts. Not only the study is one of few attempts of trying to clarify how to select modeling alternatives in part-whole design, but also it shows results based on an empirical experiment. Shanks et al. argue that there are two modeling alternatives to represent part-whole relationships : an implicit representation and an explicit one. By conducting an experiment, they insist that the explicit representation increases the value of a conceptual model. Moreover, Shanks et al. justify their findings by citing the BWW ontology. Recently, the study from Shanks et al. faces criticism. Allen and March (2012) argue that Shanks et al.'s experiment is lack of validity and reliability since the experimental setting suffers from error-prone and self-defensive design. They point out that the experiment is intentionally fabricated to support the idea, as such that using concrete UML concepts results in positive results in understanding models. Additionally, Allen and March add that the experiment failed to consider boundary conditions; thus reducing credibility. Shanks and Weber (2012) contradict flatly the argument suggested by Allen and March (2012). To defend, they posit the BWW ontology is righteously applied in supporting the research. Moreover, the experiment, they insist, can be fairly acceptable. Therefore, Shanks and Weber argue that Allen and March distort the true value of Shanks et al. by pointing out minor limitations. In this study, we try to investigate the dispute around Shanks et al. in order to answer to the following question : "What is the proper value of the study conducted by Shanks et al.?" More profoundly, we question whether or not using the BWW ontology can be the only viable option of exploring better conceptual modeling methods and procedures. To understand key issues around the dispute, first we reviewed previous studies relating to the BWW ontology. We critically reviewed both of Shanks and Weber and Allen and March. With those findings, we further discuss theories on part-whole (or part-of) relationships that are rarely treated in the dispute. As a result, we found three additional evidences that are not sufficiently covered by the dispute. The main focus of the dispute is on the errors of experimental methods: Shanks et al. did not use Bunge's Ontology properly; the refutation of a paradigm shift is lack of concrete, logical rationale; the conceptualization on part-whole relations should be reformed. Conclusively, Allen and March indicate properly issues that weaken the value of Shanks et al. In general, their criticism is reasonable; however, they do not provide sufficient answers how to anchor future studies on part-whole relationships. We argue that the use of the BWW ontology should be rigorously evaluated by its original philosophical rationales surrounding part-whole existence. Moreover, conceptual modeling on the part-whole phenomena should be investigated with more plentiful lens of alternative theories. The criticism on Shanks et al. should not be regarded as a contradiction on evaluating modeling methods of alternative part-whole representations. To the contrary, it should be viewed as a call for research on usable and useful approaches to increase value of conceptual modeling.

Entitymetrics Analysis of the Research Works of Dong-ju Yun using Textmining (텍스트마이닝을 이용한 윤동주 연구의 개체계량학적 분석)

  • Park, Jinkyeun;Kim, Taekyoun;Song, Min
    • Journal of the Korean BIBLIA Society for library and Information Science
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    • v.28 no.1
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    • pp.191-207
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    • 2017
  • This paper employs entitymetrics analysis on the research works of Dong-ju Yun. He was a Korean poet who was studied by many researchers on his works, religion and life. We collected 1,076 papers about Dong-ju Yun and conducted various approaches including co-author citation analysis, topic modeling analysis to identify the topic trend in the study of Dong-ju Yun. Also we extracted entities like person's name and literature's title from abstract to examine the relationship among them. The result of this paper enables us to objectively identify the topic trend and infer implicit relationships between key concept associated with Dong-ju Yun based on text data. Moreover, we observed sub-research topics such as life, poem, aesthetic existence, comparative literature, literary translation, and religious beliefs. This paper shows how entitymetrics can be utilized to study intellectual structures in the humanities.

Topic modeling and topic change trend analysis for advanced construction technologies (건설신기술에 대한 토픽 모델링 및 토픽 변화추이 분석)

  • Jeong, Seong Yun;Kim, Nam Gon
    • Smart Media Journal
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    • v.10 no.4
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    • pp.102-110
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    • 2021
  • Currently, the advanced construction technology endorsement system is being operated to promote the development of domestic construction technology. We tried to examine the implicit meanings inherent in advanced construction technologies by analyzing the relationship between emerging vocabularies with high importance in relation to the advanced construction technologies endorsed through this system. For this purpose, 918 cases of advanced construction technology information were collected. Based on the endorsed year and summary of the advanced construction technologies, the importance of the emerging vocabularies was measured for each advanced construction technology. And, based on the LDA model, the degree of influence between related vocabularies was evaluated for each of the four topic areas. Topics according to the technical application fields were analyzed. From 1990 to 2021, the trend of changes in highly influential vocabularies by each topic was inferred. In the future, changes in the degree of influence of the topics of environment, machinery, facilities, and maintenance and reinforcement of structures and related technology fields were predicted.