• 한국군사과학기술학회지
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• 제16권3호
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• pp.348-357
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• 2013

This work describes an approach that contributes to derive from mission to critical functions of the attack helicopter under future battle space environment. An existing mission of the attack helicopter is limited to the only shooter oriented functions. In the future environment, mission and its functions of the helicopter might be much expanded. The functions should be derived by the top down approach based on systems engineering approach. In this point of view, this work describes network based future battle environment. From this environment, the missions of the attack helicopter are identified and optimized functions are derived through sequential procedures like from missions to tasks, tasks to activities, and activities to functions. The selected activities are obtained from the tasks using QFD. The weighting scores of the QFD are calculated by the AHP computational procedure. Finally the critical functions are presented through the similar procedure.

• 한국태양에너지학회 논문집
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• 제32권3호
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• pp.26-32
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• 2012

A current compensation method to reduce the mismatch loss in PV systems is proposed as a way to increase the power generation efficiency. A dc-dc converter is used to supply currents to irregular modules in a PV string and is powered from the string output. The converter's voltage conversion ratio is adjusted so that all the modules in the string are operated at the maximum power point. The power rating and size of the converter can be reduced since only the current difference between the regular and irregular module may be supplied. The compensated string shows very little voltage mismatch compared to other regular strings. The validity of the proposed method is verified through a simulation and experiments in a prototype PV system.

• 산업공학
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• 제18권3호
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• pp.350-360
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• 2005

This paper considers a strategy for planning of rework in semiconductor monitoring burn-in test process. The equipment error in monitoring burn-in test process generates many defects. These defects are transformed into good products by rework process, i.e. retest. Rework has the advantage of saving production costs. But rework increases holding costs and incurs rework costs. In monitoring burn-in test process, rework depends on operator's experience with no pre-defined specification. In practice, a number of rework activities are performed with respect to the product importance and inventory quantity. Moreover, disregard for order jobs schedule have caused due date penalties. So a strategy for planning of rework by which order jobs schedule are not affected is suggested. Futhermore, production costs, rework costs and inventory costs for planning of rework are considered.

• 한국CDE학회논문집
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• 제11권6호
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• pp.422-428
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• 2006

In this paper, an NC data optimization approach for enhancing 5-axis machining speed is presented. It is usual to use expensive commercial CAD/CAM programs for NC data of 5-axis machining, since it needs very large calculations for optimal tool positioning and orientation, tool path planning, and collision-free tool path generation. Since commercial CAD/CAM systems have similar functions and efficiency based on common algorithms of reliable theories, they do not have their own unique features for machining speed and efficiency. In other words, most commercial CAD/CAM systems consider only the characteristics of part geometry to be machined, which means that they generate almost the same NC data if the part to be machined is the same, even though different machines are used for the pin. A new approach is proposed for optimizing NC data of 5-axis machining, which is based on the characteristics of the machine to be operated. As a result, the speed of 5-axis machining can increase without losing machining accuracy and surface quality.

• 한국군사과학기술학회지
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• 제20권4호
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• pp.520-527
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• 2017

In this study, the experimental methods are compared for obtaining the parameters of the Johnson-Cook constitutive model. The parameters used for numerical simulation are very important in making an accurate estimation of numerical simulation. So, the testing method of obtaining the parameters is also very important. We compared the difference of conventional method, compression method and tensile method of AISI-4340 steel at various strain rate by using MTS, SHPB and SHTB. Taylor impact test and M&S were carried out to compare differences among these three types of JC constitutive parameter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권1호
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• pp.74-96
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• 2023

At present, the smart grid has become one of the indispensable infrastructures in people's lives. As a commonly used communication method, wireless communication is gradually, being widely used in smart grid systems due to its convenient deployment and wide range of serious challenges to security. For the insecurity of the schemes based on large integer factorization and discrete logarithm problem in the quantum environment, an identity-based key management scheme for smart grid over lattice is proposed. To assure the communication security, through constructing intra-cluster and inter-cluster multi-hop routing secure mechanism. The time parameter and identity information are introduced in the relying phase. Through using the symmetric cryptography algorithm to encrypt improve communication efficiency. Through output the authentication information with probability, the protocol makes the private key of the certification body no relation with the distribution of authentication information. Theoretic studies and figures show that the efficiency of keys can be authenticated, so the number of attacks, including masquerade, reply and message manipulation attacks can be resisted. The new scheme can not only increase the security, but also decrease the communication energy consumption.

• 국제학술발표논문집
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• The 6th International Conference on Construction Engineering and Project Management
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• pp.700-701
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• 2015

Nuclear power plant construction project can be called essential to establish a systematic project management system compared to other construction projects, taking into account the size and complexity and safety. To develop into a project management system for the Korea situation with the ongoing construction of the nuclear power plant was directed to promote nuclear power project management. In this paper, we introduce a comprehensive project management system for nuclear power projects. Currently considering the nuclear life cycle design, construction, and was developed by considering the flow of information to operate, and test each step linkage. The systems in English were developed to meet owner's requirements for advancing into overseas projects. Another point is that the systems were developed by management module, so that functions of each area can be selectively applied. It is expected that the system will establish itself as one that can be used for the entire lifecycle of nuclear power plants through gradual and systematic establishment of necessary data.

• 유공압시스템학회논문집
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• 제8권4호
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• pp.24-31
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• 2011

Double-color Injection molding machine is the assembly of many kinds of mechanical, fluid power part and electric electronic control system. From in these, fluid power is a part where becomes the first core of this machine. Fluid power systems of double-color injection molding machine are modelled and analyzed using a commercial program AMESim. Partial system models which is divided according to functional operation are made and its analysis results shows how design parameters work on operational characteristics like pressure, flow rates, displacement at each node and so on. Analysis modeling and compared the data which gets from experiment and the analysis result which has a reliability got data. The results made by analysis will be used design of fluid power circuit for developing a double-color injection molding machine.

• 공업화학
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• 제31권4호
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• pp.368-376
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• 2020

본 연구에서는 SO₂를 제어하기 위한 산화 촉매에서 platinum (Pt)을 활성금속으로 하는 촉매의 반응특성에 관한 분석을 수행하였다. Titania (TiO₂) 지지체에 다양한 precursor 형태의 Pt를 사용하여 Pt/TiO₂ 촉매를 제조하여 실험에 사용하였다. Pt/TiO₂ 상의 Pt²⁺ 또는 Pt⁴⁺와 같은 Pt valence state에 따른 SO₂ 산화의 성능 차이는 나타나지 않으며, PtCl_x과 같은 Pt chloride species는 전체적으로 SO₂ 산화 성능을 감소시킨다. 또한, XPS 분석을 수행하여 SO₂ 산화 반응 전/후의 촉매상의 valence state를 분석한 결과 SO₂ 산화반응 이후 lattice oxygen의 감소 및 surface chemisorbed oxygen의 증가를 확인할 수 있다. 따라서 Pt/TiO₂ 촉매의 SO₂의 산화 반응은 PtOx에 해당하는 lattice oxygen의 반응과 oxygen vacancy에 의한 산화-환원 반응이 진행되는 Mar-Van Krevelen 메커니즘이 주요한 SO₂ 산화 반응임을 판단할 수 있으며, 이러한 결과를 통하여 촉매 상에 존재하는 PtOx (Pt²⁺ 또는 Pt⁴⁺)의 oxygen species가 주요한 활성 site로 작용함을 확인할 수 있다.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2004년도 Korea-Russia Joint Conference on Geometics
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• pp.82-94
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• 2004

This paper addresses solutions to the challenges of carrier phase integer ambiguity resolution and cycle slip detection/identification, for maintaining high accuracy of an integrated GPS/Pseudolite/INS system. Such a hybrid positioning and navigation system is an augmentation of standard GPS/INS systems in localized areas. To achieve the goal of high accuracy, the carrier phase measurements with correctly estimated integer ambiguities must be utilized to update the system integration filter's states. The occurrence of a cycle slip that is undetected is, however, can significantly degrade the filter's performance. This contribution presents an effective approach to increase the reliability and speed of integer ambiguity resolution through using pseudolite and INS measurements, with special emphasis on reducing the ambiguity search space. In addition, an algorithm which can effectively detect and correct the cycle slips is described as well. The algorithm utilizes additional position information provided by the INS, and applies a statistical technique known as the cumulative-sum (CUSUM) test that is very sensitive to abrupt changes of mean values. Results of simulation studies and field tests indicate that the algorithms are performed pretty well, so that the accuracy and performance of the integrated system can be maintained, even if cycle slips exist in the raw GPS measurements.