• Ocean Systems Engineering
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• v.7 no.3
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• pp.247-273
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• 2017

Many different engagement situations require naval ships to achieve some level of effectiveness. The performance of the naval ships is very important for such effectiveness. There have been many studies that analyze the effectiveness and the performance. The former are largely related to engagement level simulations, while the latter are largely related to engineering level simulations. However, there have been few studies that consider both the engagement level and the engineering level at the same time. Therefore, this study presents three case studies using engagement simulation of the engineering level to check the performance of the related parameters. First, detection performance simulations are carried out by changing the specifications of the passive sonars of a submarine in different scenarios. Maneuvering performance simulations are carried out by changing the specification of the hydroplanes of a submarine in different scenarios. Lastly, in order to check whether or not our forces would succeed in attacking enemy forces, we perform an engagement simulation with various naval ship models that consist of several engineering level models, such as command systems, weapon systems, detection systems, and maneuver systems. As a result, the performance according to the specifications of the naval ships and weapons is evaluated.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.1
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• pp.113-120
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• 2016

Steel in a continuous reheat furnace is heated to higher temperature to be treated in the rolling steel process. Due to this reason the continuous reheat furnace system requires an optimal control system to adjust the temperature inside the furnace. Level 2 control systems for continuous reheat furnaces generate automatic heating set points for the level 1 system of the furnace based on the mathematical thermal model which can give a good estimation of steel heating inside the furnace and is used to adjust heating requirements to optimize furnace combustion. For the current study the analytic methodology based on the design procedure from the systems engineering to develop new level 2 control system of a continuous reheat furnace was proposed. The system analysis and the requirements of the level 2 control system were derived using the unified modeling language (UML) 2.0, and the design of database and the graphic user interface (GUI) for the level 2 control system were conducted.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.12
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• pp.110-115
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• 2001

In this paper, a multiple comparison was proposed to minimize the amount of coolant. And new coolant level, called "low level", was suggested to show usefulness of multiple comparison for experiments. The amount of this levee is about 1/4 of conventional coolant amount-called "high level", and dry cutting is called "none level". Using these coolant levels, the cutting temperatures of each coolant level in turning process were analyzed by analysis of variance(ANOYA)-test and a multiple comparison. As the result of ANOVA-test, we have just known that the average of temperature of each coolant level is not equal. However by Tukey's HSD, one of multiple comparison. it was analyzed that the average of temperature of low level is similar to that of high levee and different from that of none level.erent from that of none level.

• International Journal of CAD/CAM
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• v.5 no.1
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• pp.99-109
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• 2005

This paper introduces an approach to an ontology-based multi-level knowledge framework for a knowledge management system for discrete-product development. Participants in a product life cycle want to share comprehensive product knowledge without any ambiguity and heterogeneity. However, previous knowledge management approaches are limited in providing those aspects: therefore, we suggest an ontology-based multi-level knowledge framework (OBMKF). The bottom level, the axiom, specifies the semantics of concepts and relations of knowledge so ambiguity can be alleviated. The middle level is a product development knowledge map; it defines the concepts and the relations of the product domain knowledge and guides the engineer to process their engineering decisions. The middle level is then classified further into more detailed levels, such as generic product level, specific product level, product version level, and manufactured item level, according to the various viewpoints. The top level is specialized knowledge for a specific domain that gives the solution of a specific task or problem. It is classified into three knowledge types: expert knowledge, engineering function knowledge, and data-analysis-based knowledge. This proposed framework is based on ontology to accommodate a comprehensive range of knowledge and is represented with first-order logic to maintain a uniform representation.

• ETRI Journal
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• v.42 no.4
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• pp.527-533
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• 2020

High-level synthesis (HLS), which automatically synthesizes a register-transfer level (RTL) circuit from a behavioral description written in a high-level programming language such as C/C++, is becoming a more popular technique for improving design productivity. In general, HLS tools often generate a circuit with a larger area than those of hand-designed ones. One reason for this issue is that HLS tools often generate multiple instances of the same module from a function. To eliminate such a redundancy in circuit area in HLS, HLS tools are capable of sharing modules. Function-level module sharing at a behavioral description written in a high-level programming language may promote function reuse to increase effectiveness and reduce circuit area. In this paper, we present two HLS techniques for module sharing at the function level.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.79-85
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• 2021

A standard engineering model that reflects the current organization system and engineering operation process of domestic nuclear power plants was developed based on the Standard Nuclear Performance Model developed by the American Nuclear Energy Association. The level 0 screen, which is the main screen of the engineering model computer system, consisted of an object tree structure, which provided information that is phased down from a higher structure level to a lower structure level (i.e., level 3). The level 1 screen provided information related to the sub-process of the engineering operation, whereas the Level 2 screen provided information related to each engineering operation activity. In addition, the Level 2 screen provided additional functions, such as linking electronic procedures/guidelines, providing electronic performance forms, and connecting legacy computer systems (such as total equipment reliability monitoring system, configuration management systems, technical information systems, risk monitoring systems, regulatory information, and electronic drawing system). This screen level increased the convenience of user's engineering tasks by implementing them. The computerization of an engineering model that connects the entire engineering tasks of an establishment enables the easy understanding of information related to the engineering process before and after the operation, and builds a foundation for the enhancement of the work efficiency and employee capacity. In addition, KHNP developed an online training module, which operates as an e-learning process, on the overview and utilization of a standard engineering model to expand the understanding of standard engineering models by plant employees and to secure competitiveness.

• Geomechanics and Engineering
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• v.18 no.1
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• pp.71-83
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• 2019

This investigation presented conventional triaxial and creep-permeability tests on sandstones considering thermally-induced damage (TID). The TID had no visible effects on rock surface color, effective porosity and permeability below $300^{\circ}C$ TID level. The permeability enlarged approximately two orders of magnitude as TID increased to $1000^{\circ}C$ level. TID of $700^{\circ}C$ level was a threshold where the influence of TID on the normalized mass and volume of the specimen can be divided into two linear phases. Moreover, no prominent variations in the deformation moduli and peak strength and strain appeared as TID< $500^{\circ}C$ level. It is interesting that the peak strength increased by 24.3% at $700^{\circ}C$ level but decreased by 11.5% at $1000^{\circ}C$ level. The time-related deformation and steady-state creep rate had positive correlations with creep loading and the TID level, whereas the instantaneous modulus showed the opposite. The strain rates under creep failure stresses raised 1-4 orders of magnitude than those at low-stress levels. The permeability was not only dependent on the TID level but also dependent on creep deformation. The TID resulted in large deformation and complexity of failure pattern for the sandstone.

• Journal of Electrical Engineering and information Science
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• v.1 no.2
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• pp.109-118
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• 1996

This paper deals with a new multi-level high voltage source inverter with GTO Thyristors. Recently, a multi-level approach seems to be the best suited for implementing high voltage conversion systems because it leads to harmonic reduction and deals with safe high power conversion systems independent of the dynamic switching characteristics of each power semiconductor device. A conventional multi-level inverter has some problems; voltage unbalance between DC-link capacitors and larger blocking voltage across the inner switching devices. To solve these problems, the novel multi-level inverter structure is proposed.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1053-1059
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• 2009

Construction system modeling can enhance work performance by following the behaviors of a system. System behaviors may originate from physical aspects of a system, namely operation level variables, or from non-physical aspects of a system known as context level variables. However, construction system modelers usually focus on only one type of system variable (i.e., operation level or context level) which can lead to less accurate results. Hybrid modeling with System Dynamics (SD) and Discrete Event Simulation (DES) is one of the approaches that has been utilized to address this issue. In this research, an SD-DES hybrid model of a steel fabrication shop is developed, and the benefits of capturing context level variables together with operation level variables in the model are discussed.

• Nuclear Engineering and Technology
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• v.46 no.3
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• pp.373-380
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• 2014

Safety-related parameters are very important for confirming the status of a nuclear power plant. In particular, the reactor vessel water level has a direct impact on the safety fortress by confirming reactor core cooling. In this study, the reactor vessel water level under the condition of a severe accident, where the water level could not be measured, was predicted using a fuzzy neural network (FNN). The prediction model was developed using training data, and validated using independent test data. The data was generated from simulations of the optimized power reactor 1000 (OPR1000) using MAAP4 code. The informative data for training the FNN model was selected using the subtractive clustering method. The prediction performance of the reactor vessel water level was quite satisfactory, but a few large errors were occasionally observed. To check the effect of instrument errors, the prediction model was verified using data containing artificially added errors. The developed FNN model was sufficiently accurate to be used to predict the reactor vessel water level in severe accident situations where the integrity of the reactor vessel water level sensor is compromised. Furthermore, if the developed FNN model can be optimized using a variety of data, it should be possible to predict the reactor vessel water level precisely.