• 한국해양공학회지
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• 제36권2호
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• pp.91-100
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• 2022

In general, the effect of roll motion is not considered in the study on maneuverability in calm water. However, for high-speed twin-screw ships such as the DTMB 5415, the coupling effects of roll and other motions should be considered. Therefore, in this study, the estimation of maneuverability using a 4-degree-of-freedom (DOF; surge, sway, roll, yaw) maneuvering mathematical group (MMG) model was conducted for the DTMB 5415, to improve the estimation accuracy of its maneuverability. Furthermore, a study on the change in turning performance according to the fin angle was conducted. To accurately calculate the lift and drag forces generated by the fins, it is necessary to consider the three-dimensional shape of the wing, submerged depth, and effect of interference with the hull. First, a maneuvering simulation model was developed based on the 4-DOF MMG mathematical model, and the lift force and moment generated by the side fins were considered as external force terms. By employing the CFD model, the lift and drag forces generated from the side fins during ship operation were calculated, and the results were adopted as the external force terms of the 4-DOF MMG mathematical model. A 35° turning simulation was conducted by altering the ship's speed and the angle of the side fins. Accordingly, it was confirmed that the MMG simulation model constructed with the lift force of the fins calculated through CFD can sufficiently estimate maneuverability. It was confirmed that the heel angle changes according to the fin angle during steady turning, and the turning performance changes accordingly. In addition, it was verified that the turning performance could be improved by increasing the heel angle in the outward turning direction using the side fin, and that the sway speed of the ship during turning can affect the turning performance. Hence, it is considered necessary to study the effect of the sway speed on the turning performance of a ship during turning.

• 대한산업공학회지
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• 제42권2호
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• pp.80-85
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• 2016

This study suggests a process design using cognitive processes. Job characteristic model for job design and recent cognitive engineering studies for process design are reviewed briefly. By using these concepts, the lean production system is re-interpreted in terms of cognitive engineering and the latent dimensions of the lean production system are revealed as the application of cognitive engineering principles. An integrated process design framework for cognitive manufacturing system using job characteristic model is suggested for the effective design of manufacturing system. Propositions for empirical analysis of this model are also analyzed through a questionnaire survey. Propositions are (1) experiential cognition and motivation potential affect the ability, role perception, and need for achievement of the operator in the manufacturing system, (2) the ability, role perception, and need for achievement of the operator affect the job performance. Both propositions are supported by correlation analysis and path analysis.

• 한국IT서비스학회지
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• 제11권1호
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• pp.211-221
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• 2012

Many metric-based classification models have been proposed to predict fault-proneness of software module. This paper presents two prediction models using Bayesian classifier which is one of the most popular modern classification algorithms. Bayesian model based on Bayesian probability theory can be a promising technique for software quality prediction. This is due to the ability to represent uncertainty using probabilities and the ability to partly incorporate expert's knowledge into training data. The two models, Na$\ddot{i}$veBayes(NB) and Bayesian Belief Network(BBN), are constructed and dimensionality reduction of training data and test data are performed before model evaluation. Prediction accuracy of the model is evaluated using two prediction error measures, Type I error and Type II error, and compared with well-known prediction models, backpropagation neural network model and support vector machine model. The results show that the prediction performance of BBN model is slightly better than that of NB. For the data set with ambiguity, although the BBN model's prediction accuracy is not as good as the compared models, it achieves better performance than the compared models for the data set without ambiguity.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권1호
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• pp.1-14
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• 2024

Time-series forecasting is extensively used in the actual world. Recent research has shown that Transformers with a self-attention mechanism at their core exhibit better performance when dealing with such problems. However, most of the existing Transformer models used for time series prediction use the traditional encoder-decoder architecture, which is complex and leads to low model processing efficiency, thus limiting the ability to mine deep time dependencies by increasing model depth. Secondly, the secondary computational complexity of the self-attention mechanism also increases computational overhead and reduces processing efficiency. To address these issues, the paper designs an efficient multi-layer attention-based time-series forecasting model. This model has the following characteristics: (i) It abandons the traditional encoder-decoder based Transformer architecture and constructs a time series prediction model based on multi-layer attention mechanism, improving the model's ability to mine deep time dependencies. (ii) A cross attention module based on cross attention mechanism was designed to enhance information exchange between historical and predictive sequences. (iii) Applying a recently proposed sparse attention mechanism to our model reduces computational overhead and improves processing efficiency. Experiments on multiple datasets have shown that our model can significantly increase the performance of current advanced Transformer methods in time series forecasting, including LogTrans, Reformer, and Informer.

• 한국과학교육학회지
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• 제26권1호
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• pp.1-8
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• 2006

본 연구에서는 고등학교 학생들의 성취 목적(과제지향/수행 지향/수행 회피), 유능감 등의 동기 변인과 학습 전략(심층적/피상적), 자기 조절 능력 등의 인지 변인 및 화학 선다형 수리 문제 해결력 사이의 인과관계를 경로 분석을 통해 조사하였다. 연구 결과, 유능감과 과제 지향 목적은 자기 조절 능력을 통하여 화학 수리 문제 해결력에 긍정적 영향을 미쳤으며, 특히 유능감은 인지 변인을 경유하지 않고도 직접적으로 화학 수리 문제 해결력에 긍정적 영향을 주는 것으로 조사되었다. 인지 변인 중 심층적 학습 전략은 유능감과 과제 지향 목적의 영향을 받았고 피상적 학습 전략은 수행 회피 목적의 영향을 받았으나, 이러한 학습 전략과 화학 수리 문제 해결력 사이에는 인과관계가 존재하지 않았다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.58-63
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• 2005

As fuel cells approach commercialization, hydrogen production becomes a critical step in the overall energy conversion pathway. Reforming is a process that produces a hydrogen-rich gas from hydrocarbon fuels. Hydrogen production via autothermal reforming (ATR) is particularly attractive for applications that demand a quick start-up and response time in a compact size. However, further research is required to optimize the performance of autothermal reformers and accurate models of reactor performance must be developed and validated. The design includes the requirement of accommodating a wide range of experimental set ups. Factors considered in the design of the reformer are capability to use multiple fuels, ability to vary stoichiometry, precise temperature and pressure control, implementation of enhancement methods, capability to implement variable catalyst positions and catalyst arrangement, ability to monitor and change reactant mixing, and proper implementation of data acquisition. A model of the system was first developed in order to calculate flowrates, heating, space velocity, and other important parameters needed to select the hardware that comprises the reformer. Predicted performance will be compared to actual data once the reformer construction is completed. This comparison will quantify the accuracy of the model and should point to areas where further model development is required. The end result will be a research tool that allows engineers to optimize hydrogen production via autothermal reformation.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.92-96
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• 2015

Due to unique characteristics of small construction companies, safety management is comprised of complex problems (e.g., resources constraints, a lack of formalized management structures, low level of management safety commitment etc.). In order to understand causal interdependencies between safety factors at different system levels (regulation, organization, technical and individual), this paper aims to develop a system dynamics (SD) model of safety management in small construction companies. The purpose of the SD model is to better understand why small construction companies have low level of safety performance. A causal loop diagram (CLD) was developed based on literature, with an attempt to map causal relationships between variables. The CLD was then converted into stock and flow diagram for simulation. Various tests were conducted to build confidence in the model's ability to represent the reality. A number of policies were analyzed by changing the value of parameters. The value of a system dynamics approach to safety management in small construction companies is its ability to address joint effects of multiple safety risk factors on safety performance with a systems thinking perspective. By taking into account feedback loops and non-linear relationships, such a system dynamics model provides insights into the complex causes of relatively poor safety performance of small construction companies and improvement strategies.

• 대한조선학회논문집
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• 제53권3호
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• pp.217-227
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• 2016

Recent accidents of crude oil tankers have resulted in sinking, grounding of vessels and significant levels of marine pollution. Therefore, International Maritime Organization (IMO) has been strengthening the regulations of ship maneuvering performance in MSC 137. The evaluation of maneuvering performance can be made at the early design stage; it can be investigated numerically or experimentally. The main objective of this paper was to investigate the maneuvering performance of a VLCC due to the increase of rudder force at an early design stage for low speed in shallow water conditions. It was simulated in various operating condition such as deep sea, shallow water, design speed and low speed by using the numerical maneuvering simulation model, developed using MMG maneuvering motion equation and KVLCC 2 (SIMMAN 2008 workshop). The effect of increasing the rudder force can be evaluated by using numerical simulation of turning test and ZIG-ZAG test. The research showed that, increasing the rudder force of a VLCC was more effective on improving the turning ability than improving the course changing ability especially. The improvement of turning ability by the rudder force increasing is most effective when the ship is sailing in shallow water at low forward speed.

• 유통과학연구
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• 제19권6호
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• pp.29-39
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• 2021

Purpose: This study aims to measure whether market orientation, entrepreneurial orientation, and marketing capabilities affected the business performance of salted fish distribution in Kapuk warehouse, West Jakarta at the beginning of the COVID-19 pandemic. This prolonged and difficult pandemic has had an impact on the business of selling salted fish, challenging organisations' ability to maintain business performance. Research design, data and methodology: This study uses a PLS-SEM model approach using Smart PLS 3.0 and a questionnaire as the instruments. The conditions during the observation include 77 distributors who chose to keep doing business, and the research sample were measured by the number of distributors (business actors or people in charge). In this study, the variables of marketing capabilities, market orientation, and entrepreneurial orientation were used to analyse business performance. Results: Interestingly, the results of the study succeeded in explaining that during a pandemic market, both entrepreneurial orientation and marketing ability affected current business performance, although marketing ability remains an inconsistent mediator. Conclusions: This result serves as a reminder that surviving is the priority which must be focused on now, rather than crafting strategies to excel in competition that consume valuable effort and resources.

• 산업경영시스템학회지
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• 제34권3호
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• pp.115-122
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• 2011

The critical role played by manufacturing performance measurement systems in achieving competitive success is increasingly recognized. Developing an integrated performance measurement model is significant for strategic management. This study consist of several principal steps. Performance criteria from the literature and an questionnaire were utilized prior to building the performance model. The AHP(Analytic Hierarchy Process) is utilized to evaluate the weight of each criterion when generating the performance measurement model for Korea automobile parts manufacturing company. AHP analysis showed clear difference in the priority between 5 criteria and 24 sub-criteria in terms of manufacturing performance of Korean automobile parts manufacturing company. The result of priority evaluation in the 5 criteria of 2nd level was ranked quality, cost, delivery, employee, flexibility. And the critical sub-criteria in the 24 sub-criteria of 3rd level was ranked claim rate, process defect rate, outsourcing parts defect rate, ability to quality management innovation, claim cost, etc.