• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권6호
• /
• pp.3273-3308
• /
• 2017

Building appropriate trust evaluation models is an important research issue for security guarantee in social networks. Most of the existing works usually consider the trust values at the current time slot, and model trust as the stochastic variable. However, in fact, trust evolves over time, and trust is a stochastic process. In this paper, we propose a novel time-variant stochastic trust evaluation (TSTE) model, which models trust over time and captures trust evolution by a stochastic process. Based on the proposed model, we derive the time-variant bound of untrustworthy probability, which provides stochastic trust guarantee. On one hand, the time-variant trust level of each node can be measured by our model. Meanwhile, by tolerating nodes with relatively poor performance, our model can effectively improve the node resource utilization rate. Numerical simulations are conducted to verify the accuracy and consistency of the analytical bounds on distinguishing misbehaved nodes from normal ones. Moreover, simulation results on social network dataset show the tradeoff between trust level and resource utilization rate, and verify that the successful transmission rate can be improved by our model.

• 한국태양에너지학회 논문집
• /
• 제39권6호
• /
• pp.113-125
• /
• 2019

With the opening of the small power brokerage business market in December 2018, the small power trading market has started in Korea. Operators must submit the day-ahead estimates of power output and receive incentives based on its accuracy. Therefore, the accuracy of power generation forecasts is directly affects profits of the operators. The forecasting process for power generation can be divided into two procedure. The first is to forecast solar irradiation and the second is to transform forecasted solar irradiation into power generation. There are two methods for transformation. One is to simulate with physical model, and another is to use regression model. In this study, we found the best-fit regression model by analyzing hourly data of PV output and solar irradiation data during three years for 242 PV plants in Korea. The best model was not a linear model, but a sigmoidal model and specifically a Gompertz model. The combined linear regression and Gompertz curve was proposed because a the curve has non-zero y-intercept. As the result, R² and RMSE between observed data and the curve was significantly reduced.

• 대한임베디드공학회논문지
• /
• 제18권6호
• /
• pp.319-325
• /
• 2023

In this study, we proposed a method for hyperparameter optimization in the building and training of a deep learning model designed to process point cloud data collected by a millimeter-wave radar system. The primary aim of this study is to facilitate the deployment of a baseline model in resource-constrained IoT devices. We evaluated a RadHAR baseline deep learning model trained on a public dataset composed of point clouds representing five distinct human activities. Additionally, we introduced a coarse-to-fine hyperparameter optimization procedure, showing substantial potential to enhance model efficiency without compromising predictive performance. Experimental results show the feasibility of significantly reducing model size without adversely impacting performance. Specifically, the optimized model demonstrated a 3.3% improvement in classification accuracy despite a 16.8% reduction in number of parameters compared th the baseline model. In conclusion, this research offers valuable insights for the development of deep learning models for resource-constrained IoT devices, underscoring the potential of hyperparameter optimization and model size reduction strategies. This work contributes to enhancing the practicality and usability of deep learning models in real-world environments, where high levels of accuracy and efficiency in data processing and classification tasks are required.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제11권9호
• /
• pp.4197-4219
• /
• 2017

Cloud computing is a new service to provide dynamic, scalable virtual resource services via the Internet. Cloud market is available to multiple cloud computing resource providers and users communicate with each other and participate in market transactions. However, since cloud computing is facing with more and more security issues, how to complete the allocation process effectively and securely become a problem urgently to be solved. In this paper, we firstly analyze the cloud resource allocation problem and propose a mathematic model based on combinatorial double auction. Secondly, we introduce a trust evaluation mechanism into our model and combine genetic algorithm with simulated annealing algorithm to increase the efficiency and security of cloud service. Finally, by doing the overall simulation, we prove that our model is highly effective in the allocation of cloud resources.

• 자원ㆍ환경경제연구
• /
• 제13권4호
• /
• pp.735-761
• /
• 2004

해외자원개발사업은 성공할 경우 높은 수익률을 보장하지만 장기적인 투자기간과 높은 시장위험부담으로 인하여 사업의 가치분석에 있어서 사업기간 동안의 여러 가지 변수들을 분석할 수 있는 유연성을 요구하고 있다. 기업의 투자 의사결정과정에서 가장 널리 이용되는 평가방법인 전통적 기존의 현금흐름할인법의 단점을 보완할 대안으로서 제시된 옵션가격 결정모형(Option Pricing Model)을 여타의 다른 자산의 평가 및 사업성 평가에 응용하고자 하는 연구 분야인 실물옵션(Real Options)은 특히 위험도가 큰 자원개발사업의 가치를 평가할 좋은 방법론으로 주목받아왔으나, 다양한 현실적 상황을 도입하게 되면 확률과정이 난해한 형태로 변하여 수학적 처리가 용이하지 않아 실용화에 가장 큰 걸림돌로 작용하고 있다. 따라서 기존의 연구들은 확률과정의 선정과정에서 자원개발사업의 특성이나 실용성을 고려하여 확률과정을 선정하지 않고 기초적인 확률과정을 적용하여 왔다. 본 연구에서는 해외자원개발사업을 대상으로 옵션가격 결정모형을 활용하는 경우를 산정하여, 해외자원개발사업의 평가에 쉽게 활용될 수 있는 단순화된 함수의 형태로 표현된 옵션가격 결정모형을 제시해 보았다. 즉, 이론적인 정교한 확률과정을 도출하기보다는 자원개발사업의 특징을 충분히 반영하면서도 사업평가실무에 손쉽게 이용될 수 있는 현실적이면서도 단순한 확률과정을 선정하고자 하였다. 이를 위하여 구리, 연, 아연의 국제시장가격의 특성과 연-아연광 개발사업의 사례를 활용하여 기존의 모형연구들과 달리 실제의 위험을 모두 분석하되, 분석하는 모형을 최대한 단순화하여가는 과정을 통하여 Gibson-Schwartz가 제안한 Two-Factor Model과 Long-Term Asset Model을 적절한 모형으로 선정하고, 이를 바탕으로 운영옵션과 투자개시옵션의 두 가지 경영옵션을 분석하여 그 결과를 제시하였다. 본 연구에서 분석, 제안한 단순화 과정은 앞으로 옵션가격 결정이론을 바탕으로 한 가치평가모형의 실제사례 적용연구에서 활용될 수 있을 것으로 기대한다.

• 한국시뮬레이션학회:학술대회논문집
• /
• 한국시뮬레이션학회 2003년도 추계학술대회 및 정기총회
• /
• pp.185-192
• /
• 2003

Digital Manufacturing-based production could be very effective in shipbuilding in order to save costs and time, to increase safety for workers, and to prevent bottleneck processes in advance. Digital shipbuilding system, a simulation-based production tool, is being developed to achieve such aspects in Korea. To simulate material flow in a subassembly line at a shipyard, the product, process and resources was modeled for the subassembly process which consisted of several sub-processes such as tack welding, piece alignment, tack welding, and robot welding processes. The analysis and modeling were carried out by using the UML(Unified Modeling Language), an object-oriented modeling method as well as IDEF(Integration DEFinition), a functional modeling tool. Initially, the characteristics of the shop resources were analyzed using the shipyard data, and the layout of the subassembly line was designed with the resources. The production process modeling of the subassembly lines was performed using the discrete event simulation method. Using the constructed resource and process model, the productivity and efficiency of the line were investigated. The number of workers and the variations In the resource performance such as that of a new welding robot were examined to simulate the changes in productivity. The bottleneck process floated according to the performance of the new resources. The proposed model was viewed three-dimensionally in a digital environment so that interferences among objects and space allocations for the resources could be easily investigated

• 한국경영과학회지
• /
• 제24권4호
• /
• pp.81-94
• /
• 1999

Organization change projects such as Business Process Redesign(BPR) have been implemented by many firms for enhancing their organizational performance. However, management is reluctant to initiate these projects due to enterprise-wide impact and steeper project cost than the traditional system development projects. Thus, there emerges a need to accurately assess the value of the redesigned organizational process for the successful implementation of BPR projects. The purpose of this study is to assess the value of process redesign in the point of resource utilization and allocation, and cycle time and cost reduction. The candidate process and the design alternatives are identified from organizational requirements analysis. The variables and their relations are defined to perform task activity analysis, bottleneck analysis, cycle cost analysis, and resource utilization analysis. A Case study of a manufacturing company indicates that the assessments method proposed in this study is a promising approach to identify the business alternative process that lead to the highest organizational performance.

• 한국전자거래학회지
• /
• 제17권1호
• /
• pp.53-74
• /
• 2012

본 연구에서는 비즈니스 프로세스 관리(Business Process Management, BPM) 환경에서 자원의 성능에 영향을 미치게 되는 여러 요소를 고려하여 인적자원을 선택하는 방법론을 개발한다. 스케줄링에 있어서 자원의 선택 문제는 작업 수행도에 직접적인 영향을 미치기 때문에 중요한 문제로 인식되어져 왔다. 비록 많은 문제에 있어서 전통적인 자원선택 방법론이 의미를 가져왔으나, 인적자원을 다루는데 있어서는 가장 좋은 방법론이라고 볼 수 없다. 인적자원은 작업부하, 작업소요시간, 작업간 시간 등의 다양한 요소에 의해서 영향을 받는 특이한 요소이며 본 연구는 이러한 다양한 요소를 고려하여 작업자를 선택하는 방법론을 제시한다. 이를 위해서 베이지안 네트워크를 사용하며, 앞서 기술한 여러 요소들을 한꺼번에 고려하기 위한 베이지안 선택규칙(Bayesian Selection Rule, BSR)을 도입하였다. 또한, 시뮬레이션을 통해서 본 연구에서 개발된 방법론이 대기시간, 작업수행시간과 사이클 타임을 줄일 수 있음을 보였다.

• 한국건설관리학회논문집
• /
• 제24권2호
• /
• pp.37-49
• /
• 2023

본 연구에서는 제조업 분야에서 보편적으로 활용되어 온 제약이론을 바탕으로 강교 제작공장의 생산성을 향상시키기 위한 자원할당 방법론을 제안한다. 이를 위해 도장 공정을 병목공정으로 정의한 후, 공정 전용 자원할당(OSRA), 제품 전용 자원할당(PSRA), 범용 자원할당(GRA) 등 3가지의 자원할당 방법론을 개발하였다. 강교 공급사슬 시뮬레이션 모델을 활용한 성능평가 실험 결과, GRA 방법론이 재공재고수(NWIP)와 대기시간(WT) 측면에서 가장 우수한 성능을 보였다. 특히, 강교 제작공장의 부하와 부하 변동성이 증가할수록 다른 두 전용 자원할당 방식과의 성능 격차는 더욱 커졌다. 평균적으로 GRA는 NWIP과 WT를 OSRA 대비 36.2%, 34.6%, PSRA 대비 71.0%, 70.4% 감소시켰다. 재공재고수와 대기시간의 감소는 병목현상의 완화를 의미하며, 이는 결국 강교 제작공장의 생산성이 향상되었음을 의미한다.

• 한국전자거래학회지
• /
• 제5권2호
• /
• pp.81-99
• /
• 2000

Nowadays, many commercial ERP products, such as Oracle, SAP, and Baan, etc, are designed based on large-scaled companies. It is difficult for small and medium-size companies with weakness in budgets and resources(e.g., human, organization, technique, and so on) to use them as it was. So, new ERP system need to be provided for small and medium-size companies. In this paper, we model and provide a conceptual ERP model for small and medium-size companies by using "4＋1 View" architecture model of Unified Modeling Language(UML). The conceptual ERP model consists of five subsystems： Manufacturing, Sales, HumanResource and Payroll, Accounting, and Trading. Especially, we describe the conceptual ERP model focusing on "Manufacturing" subsystem by using several diagrams of UML. By using the conceptual ERP model, the ERP system′s developers of small and medium-size companies can obtain many benefits： improving the efficiency of software developing process and helping user requirements gathering and description of ERP system′s nonfunctional aspect as well as functional aspect.