• 환경위생공학
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• 제23권4호
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• pp.1-11
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• 2008

The goal of today's environmental education is to enhance the understanding of the serious of environmental problems and the interactions among environment. With this perspectives people need to be aware that environmental education is no longer a liberal arts in university education, but play a vital role within the socio-cultural context. This study was performed to assess the changes in the university student's attitudes and consciousness in real life after the education of a point at issues of environmental problems. For this study 11 questionnaires which were composed of large scale environmental problems(water and air pollution), and small scale environmental problems(food additives, GMO, endocrine disrupter) were performed with self-administered by university students(n=781) who made a application for liberal arts related to environmental subjects. According to the analysis the most student's consciousness of a point at issue of environmental problems(water pollution, air pollution, additives, GMO, endocrine disrupter), and practical attitudes(i.e., practical attendant at congregation and internet voting) were change statistically significant(p<0.01) after the education of a point at issue of environmental problems rather than before. Specially, the score for the item of the large scale problem of environmental issues(water pollution, air pollution) were decreased significantly(p<0.01), but the score for the small scale problems, such as food additives, GMO, endocrine disrupter were increased significantly(p<0.01) after the education of a point at issue of environmental problems(p<0.01). And among the students that participated, 97.7% responded that such a point at issues of environmental problem is needed at the university. With this educational improvements supports the states that the education of a point at issue of environmental problems were more essential, practical and needed to students at university rather than that of an existing instruction. Thus, further studies are required to develop the education of environmental issues at universities like STSE programme.

• 한국시뮬레이션학회논문지
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• 제7권2호
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• pp.115-123
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• 1998

A simulation is performed to investigate the effect of the pipe supports on the change of the natural frequencies of curved pipe systems containing fluid flow, for different elbow angles and geometry of the pipe systems. Based upon the Hamilton's principle, the equations of motions are derived, and the finite element equation is constructed to solve the corresponding eigenvalue problem. The angles of elbows do not affect the change of the fundamental natural frequency, but affect the change of the third or higher natural frequencies. Without any support, the change of the fundamental natural frequency due to the geometric change is smaller than the change of the second or higher natural frequencies. The more curve parts exist in the pipe system, the less change of lower frequency range, compared with the change of higher frequency range, is observed. Spring supports can be used to reduce the fundamental natural frequency, without change of the second or higher natural frequencies. To avoid resonance, which is critically dangerous from the view point of structural dynamics, the mechanical properties such as stiffness or the location of pipe supports are need to be changed to isolate the natural frequencies from the frequency range of dominant vibration modes.

• 한국유체기계학회 논문집
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• 제3권4호
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• pp.15-21
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• 2000

An anemometer employing the bulk PTC thermistor as the sensing element is investigated in this study. The numerical and experimental works are carried out to improve the sensitivity problem of the element by focusing fluid dynamics point of view. The typical shape of the sensing element has been used as a rectangular type, but this shape has a sensitivity problem because of flow separations on the sharp edge when the flow direction is different from that of the sensing element. In order to reduce the reading error, the installer has to be very careful about the flow direction. The reading error fluctuation by time as well as the sensitivity problem can be improved considerably through this study. It can be concluded that the small change of the sensor shape can improve the performance of the flow sensor.

• 한국안광학회지
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• 제14권4호
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• pp.45-51
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• 2009

목적: 본 연구는 단초점렌즈와 VDT 증후군 개선을 위해 설계된 기능성렌즈를 착용하고 4시간 동안 VDT 작업 전과 후의 임상성능과 시각적인 문제에 대하여 설문조사를 비교 분석하자 한다. 방법: 20~45세의 남 여 30명을 대상으로 단초점렌즈와 기능성렌즈(ad Plus, HANDOK OPTEC Co.)를 각각 착용시킨 후 4시간 동안 VDT 작업 전과 후의 근거리 및 원거리시력, 등가구면굴절력의 변화, 조절근점, 폭주근점, AC/A ratio, 조절용이성 등을 검사하고, 시각적인 문제에 대한 자각증상을 설문조사하였다. 결과: 단초점렌즈와 비교하여 기능성렌즈를 착용했을 때 근거리시력, 조절근점, 폭주근점, 조절용이성이 유의하게 개선되었다. 4시간 동안 VDT 작업 후의 시각적 문제점에 대한 항목의 평균 점수는 단초점렌즈에서 3.63 ${\pm}$ 0.75이고, 기능성렌즈에서 4.69 ${\pm}$ 0.83으로 기능성렌즈가 유의하게 개선된 것으로 조사되었다. 결론: 기능성렌즈가 단초점렌즈보다 4시간 동안 VDT 작업 후의 조절기능 및 시각적 문제점 개선에 도움이 되는 우수한 렌즈로 생각된다.

• 한국항공우주학회지
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• 제47권11호
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• pp.795-802
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• 2019

본 논문에서는 인공위성의 근접운용에서 발생할 수 있는 위치-자세 결합운동을 정의하고, 이를 듀얼 쿼터니언 기반의 운동방정식을 통해 접근한다. 인공위성의 위치-자세 결합운동은 두 위성의 상대운동에서 목표 지점이 무게 중심이 아닌 위성체 위의 임의의 점에 위치할 때 발생하며, 특히 근거리 운용에서 명확히 보여진다. 듀얼 쿼터니언 기반의 운동방정식은 각속도 상태를 직접 반영하여, 자세의 변화가 위치에 영향을 미치는 위치-자세 결합운동을 간결하게 정의할 수 있다. 여기에서는 위치-자세 결합운동의 해결을 위해 기존의 접근방법과 함께 듀얼 쿼터니언 기반의 운동방정식을 새롭게 제시한다. 수치 시뮬레이션에서는 두 위성의 상대운동에서 위치-자세 결합운동으로 목표 지점에 대한 위치 오차가 발생함을 보이고, 듀얼 쿼터니언 기반의 운동방정식이 이를 해결할 수 있음을 검증한다.

• 환경위생공학
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• 제8권2호
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• pp.49-64
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• 1993

The present waste problems require a change of thinking with regard to conventional economics. It has been generally believed that competitive markets maximize social welfare. But, the other hand, a few economists argue that "the competitive markets cannot always be relied on to provide all goods in the efficient amount." One of the best examples of the latter contention is the environmental problem. What is the basic thinking of the conventional economics that causes this problems \ulcorner What is the present problem that requires the change of conventional economic thinking \ulcorner The environmental problem result from the conventional economic thinking such as pursuing the limitless of the Gross National Product(GNP), believing the increasing returns in economics of scale and the efficiency of competitive market. This economic principles, howe- ver, does not apply currently to public goods, especially environmental amenity and natural resource because the price of markets does not reflect the natural goods of services. We call this eternality. Externalizes are no considered by either buyers or sellers of goods of which production or use results in an eternality. This leads to market failure are causes an waste problem in the economic activities. Today, it is almost impossible to say in a word what the solution for waste problems is because they are by-products complicated and entangled human activities. In this paper, I have introduced the causes of environmental problems only from the economic point of view. I have also described the needs of conversion of conventional economic thinking. Firstly, sustainable development, maintaining the natural resources, should be the basis of the economic growth rather that pursuing the limitless growth of GNP. Secondly, an appropriate scale of human's production activity should be taken into account to reduce the impact to the natural environment. Thirdly, internalization of eternality is asked to correct the market failure. This requires the public policy such as imposing a talsubsidy, assigning a property right or implement a more detailed environmental quality standard through, because use of the natural resources can be. allocated optimally by the intervention of government or social associations.

• 한국항행학회논문지
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• 제24권4호
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• pp.291-298
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• 2020

본 연구는 입자 무리 최적화 (PSO; particle swarm optimization) 알고리즘을 이용하여 기존의 MPPT 알고리즘보다 신속하게 MPP를 추적할 수 있는 모델을 제안하였다. 제안 모델은 PSO 알고리즘에서 gbest 및 pbest의 가속 상수를 높게 설정하여 신속하게 MPP 지점을 추적하고 이로 인한 전력 불안정 문제점을 제거하였다. 또한, 일사량의 급격한 변화에 따른 태양광 패널의 전력 변화를 감지하여 알고리즘을 다시 실행하였다. 실험결과, 일사량이 691.5W/m2에 대해서 MPPT 시간이 0.03초와 전력이 131.65로서 기존의 P&O와 INC 알고리즘보다 높은 전력과 빠른 속도로 MPP를 추적하였으며, 일사량 변화에 따라 신속하게 MPP를 추적하였다. 제안 모델은 태양광 패널이 병렬로 연결되어 있는 태양광 발전소에서 부분적인 음영에 의해 전력량의 변화를 감지하였을 경우에도 적용할 수 있다. 본 연구는 MPPT 알고리즘을 개선하기 위해 MFO (moth flame optimization) 및 WOA (whale optimization algorithm)와 같은 최적화 알고리즘에 대한 비교 연구가 필요하다.

• 한국응용과학기술학회지
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• 제14권1호
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• pp.45-52
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• 1997

It is the problem point of stability for this study to produce cosmetics and to occur in the circulation process, and specially in a case of alcoholic toilet water the precipitation materials to float on content materials has study on the solubility of perfume, and it has practiced in order to examine the problem point whether the raw materials of plastic vessel is or not harmful in content materials. In testing result, A study on stability of alcoholic toilet water is above all the precipitation materials which floats in content materials, and It is appeared by combination ratio to the raw materials of perfume, ethanol, solubilizer and refining water etcs, and in second the alkali degree which has gushed out of glass vessel can understand the thing that the change of PH is largely increased following to the passage of time, and in third the harmful component of content materials out of raw material in plastics vessel must certainly consider a stability and a safety in quality control of products.

• 한국항해학회지
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• 제13권1호
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• pp.55-61
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• 1989

Nowadays much efforts for evaluating the productivity of port physical distribution system to meet the rapid change of the port and shipping circumstances has been made continuously all over the world. The major part of these efforts is the improvement of the productivity of cargo handling system. The cargo equipment system as infrastructure in the cargo handling system is organized well in some degrees, but the management system of manpower as upper structure is still remained in an insufficient degree. There is little study, so far, on a systematic research for the management of port labor gang, and even those were mainly depended on rule of thumb. The object of this study is to introduce the method of optimal allocation and assignment for the labor gang in single ship, which was suggested as a first stage in dealing with them generally. The problem of optimal allocation and assignment of the labor gang can be (I) formalized with multi-stage allocation and assignment of the labor gang can be. (II) dealt with two stages in form of hierarchic structure and moreover, (III) The optimal size of labor gang was obtained through dynamic programming from the point of minimizing the summation of labor gang in every stage, (IV) For the problem of optimal assignment, the optimal policy was determined at the point of minimizing the summation of movement between hatches.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2001년도 추계종합학술대회
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• pp.295-299
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• 2001

1912년 4월 14일 타이타닉호의 해난사고로 인하여 세계 각국이 해상에 있어서의 안전을 위한 조약을 국제 협약으로 규정한 뒤 모든 선박에 있어서 안전항해를 위한 무선통신설비를 설치하고 있다. 또한 우리나라에서도 선박안전법 제 4호의 규정에 의하여 무선통신 설비를 설치하도록 하였다. 그러나 GMDSS라는 새로운 통신제도의 도입에 따라 선박 통신 시스템에 일대 변화가 초래되어 많은 문제점이 발생되고 있다. 이에 따른 우리나라의 해상통신의 문제점에 대하여 연구하고자 한다.