• 로봇학회논문지
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• 제8권4호
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• pp.256-265
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• 2013

A local map-based exploration algorithm for mobile robots is presented. Segmented frontiers and their relative transformations constitute a tree structure. By the proposed efficient frontier segmentation and a local map management method, a robot can reduce the unknown area and update the local grid map which is assigned to each frontier node. Although this local map-based exploration method uses only local maps and their adjacent node information, mapping completion and efficiency can be greatly improved by merging and updating the frontier nodes. Also, we suggest appropriate graph search exploration methods for corridor and hall environments. The simulation demonstrates that the entire environment can be represented by well-distributed frontier nodes.

• 경영과학
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• 제29권3호
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• pp.157-168
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• 2012

In this study, we consider an order promising problem at parallel machine shops where orders arrive dynamically. We develop methods for the problem, which instantly quote the due-dates of arrived orders. In this study, we first propose methods which can estimate flow times of orders, in which the current and future inventory status as well as the specific scheduling scheme used in the shop are taken into account, and then the due-dates are set by the order promising methods using the estimation results. The quoted due-dates of orders are compared with the actual completion times of those which are obtained from the simulation runs. The series of computational experiments show that the superior performance of the proposed methods in terms of the accuracy of due-date quotation.

• International Journal of Air-Conditioning and Refrigeration
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• 제7권
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• pp.101-111
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• 1999

The effect of various conditions of frosting and defrosting on the defrosting behavior of a fin-tube heat exchanger has been examined experimentally. An electric heater is used for defrosting in a fin-tube heat exchanger. There are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of frost irrespective of the frosting condition. The defrosting behavior is affected by frosting density as well as frost accumulation, both of which vary with the experimental operating conditions. The heat loss to the surrounding air decreases, and melting and defrosting efficiencies show high values with decreasing heat input.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2008년도 학술발표회 논문집
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• pp.823-828
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• 2008

In accordance with the Cambodian government's poverty reduction policy, the Krang Ponley Water Resources Development Project was selected and has been carried out as a priority to develop the northwest areas of Phnom Penh since early 2003. Rehabilitation and new construction of water supply system such as embankments, canals and hydraulic structures are urgently needed for stable water supply, hydropower generation and flood damage reduction within the project area. The completion of the project is expected to be extremely helpful in the economic development of Cambodia as well as to improving the economic conditions of the residents in the project area.

• 한국국방경영분석학회지
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• 제9권1호
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• pp.63-68
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• 1983

The ideal way of eliminating errors in a large scale software system is to test the software with all possible inputs, providing sufficiently large amount of execution time. However, in practice, the test must be performed within given budget and time limits. Therefore, to perform the test under given constraints, we have to properly select inputs and determine the execution time for each selected inputs. This paper studies the distribution of number of errors at a given time as well as the distribution of time required to reduce the number of errors to a certain level. We assumed that error occurrence times are distributed exponentially (not necessarily identical) and the number of errors at the initial stage is known or estimable.

• 대한인간공학회지
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• 제18권3호
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• pp.73-86
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• 1999

Nowadays, VCR(Video Cassette Recorder) has various functions, but users use to fail operating these function because of the complexity of operation. The process of operating VCR contains user's cognitive characteristics. It is necessary for designing it that we must identify a user's mental process in the behind of operational behaviors. This effort, as well as considering physical dimensions and layout, can make VCR easy to use. In this research, VCR remote controller are analyzed by the cognitive method and experiments. Three types of VCR remote controllers, cognitive VCR models and two non-cognitive(typical) VCR models, are adopted as experimental objects to test the validation of the suggested user's cognitive mode of VCR. As results, when VCR was operated by the cognitive prototype of remote controller, task completion time was reduced to 80.5%, and the number of errors was reduced to 96.8%.

• 산업기술연구
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• 제13권
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• pp.3-17
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• 1993

The composting process is a suitable to dispose the livestock manure in terms of resources recovery. However the performence of composting process is greatly affected by the environmental conditions such as characteristics of manure, type of the bulking agent, initial moisture contents, temperature, recycle and so on. The purpose of this study is to evaluate the optimum environmental conditions of composting process for livestock manures. The analytical results indicated that no bulking agent was necessary for the cow manure because of the proper C/N ratio. However the pig manure required a bulking agent since the pig manure had not only low in C/N ration but poor ventilation characteristics. In addtion, the initial miosture content for optimum composting appeared to be about 60%. The temperature control was also an essential factor to enhance the activity of thermophilic microorganisms in the laboratory composting unit. It was further found that the recycle of composts may contributed the completion of composting precess as well as C/N ratio reduction and moisture control.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1256-1263
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• 2010

Suction Drain Method is soft ground improvement technique, in which a vacuum pressure can be directly applied to the Vertical Drain Board to promote consolidation and strengthening the soft ground. This method does not require a surcharge load, different to embankment or Preloading Method. In this study, ground improvement efficiency of suction drain method was estimated when duplex loading pressure with vacuum and pressure. During suction drain method process, surface settlement and pore pressure were monitored, and cone resistance test as well as water content were also measured after the completion of Suction Drain Method treatment.

• Journal of Information Technology Applications and Management
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• 제16권4호
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• pp.263-283
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• 2009

Although some CASE tools supported conceptual data design, they required for users too much preliminary knowledge to learn how to use and handle them. In addition, in a number of studies on conceptual data design with natural language, they claimed passive participation for users with conforming to messages predefined by CASE tools. As an alternative to these traditional CASE tools, we proposed an ERD formulator for automated data design tool, called ERDF, so that even ordinary users, not necessarily data modeler, are capable of formulating ERD on business requirements by use of ERDF. We, first of all, introduced NSM as the standard methodology. We also designed the structure of ERDF including main controller, input controller, operation controller, regulation controller, schema controller, and output controller. We then defined conceptual domains and basic operations to lay down schema operations as well as sentence rules to handle input sentence in natural language. To get an ERD that is faithful to business requirements, we laid out supplementary design for dialogue and confirmation of soundness and completion.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.57-60
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• 2006

The purpose of this study is to explain the importance of Vibration Monitoring Device by introducing an example of Predictive Maintenance System using Condition Monitoring System of Hydro-turbine generator. Confirming vibration of generation equipment is commissioning procedure during equipment completion for checking guaranteed items. Data from Generator output range are used to determine output band to continue the performance of equipment. The Vibration Monitoring System is not absolute method of maintenance, but if it is used well with expert, it will be visible, data-analyzed, scientific maintenance more than others. And also, Condition Monitoring System is very important for remote controlled small hydro-power plant although most of it is installed in Large hydro-power plant.