• The Journal of Korean Association of Computer Education
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• v.17 no.2
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• pp.77-86
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• 2014

By PISA 2007, TIMSS 2011, Korean high school students had high academic achievement to science and mathematics, while they had low attitude. Prospective college students are increasingly avoiding natural science and engineering. Moreover, the opportunities to learn to computer science in middle and high school are disappeared rapidly. The necessity of STEAM program based on Physical computing arise under these situation. Therefore, we developed STEAM program and studied the effects of the program in 2012. The result showed that students' scientific interests and attitude, scientific problem solving ability, scientific creative problem solving ability, personality test for children, and satisfaction of school life were enhanced. This study is follow-up study for the same students who improved every domain of the measurements. They were administerd pre-test at start of 2012, post-test at end of 2012, and delayed post-test at the end of 2013, on same test. The result of the study showed that only attitude to Scientific Inquiry was enhanced, but there was no significant result on the other domain of the test in comparison with start of 2012. But this result demonstrate the effect of STEAM education conversely.

• Journal of Korean Society of Forest Science
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• v.77 no.4
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• pp.389-400
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• 1988

The recent trend in multiple-use land management planning is using Model I and Model II formulations designed for timber activity scheduling problems. Numerous models hate been developed, with MUSYC(Johnson and Jones, 1979) being the first to incorporate both model structures. Currently the most popular computer program using both Model I and Model II is FORPLAN(Johnson and others, 1986). A Model I formulation requires fewer rows and provides more direct information on what happens to an acre from rotation to rotation. In some problems, Model II provides a much more compact problem matrix with much fewer columns and only a moderate increase in row number. In this paper we examined and evaluated their usefulness in comprehensive multiresource forest management planning.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.365-372
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• 2012

Recently, regional society requires engineers to understand the international affairs and to be global experts endowed with leadership. General education appropriate to engineers should fulfill these needs and provide wide understandings in humanity. General sciences education should be also reinforced for the students taking low level science courses under 7th education program to improve learning ability of the major subjects in college. A general education component including humanity for the engineers could be trained continuously from primary school to college under the 2009 revised education program. Various opportunity for education should be provided through the special curriculum development at the college or department level, which trains experts who fulfill the need of community. Multi-major program is a substitute for offering the educational opportunity to the students in environmental engineering, one of multidisciplinary programs. Emphasized criteria of the curriculum requirements and adequate contents of general education need be also developed for supporting the students to take advanced courses in major.

• Journal of Convergence for Information Technology
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• v.9 no.7
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• pp.1-7
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• 2019

With the recent commercialization of the next generation of wireless 5G in everyday life, many changes have been made to organizations, industries and businesses of various sizes in various fields. However, although the improved speed and latency of 5G has improved, improvements in encryption, authentication and privacy are still required. In this paper, multiple groups of information management techniques are proposed to efficiently protect users' privacy in the heterogeneous environment of 5G. The proposed technique aims to allow distributed management of users' privacy links by clouding the privacy information generated by different heterogeneous devices to efficiently interface with different groups. Suggestion techniques process user-specific privacy information independently in a virtual space so that users can periodically synchronize their privacy information.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.2
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• pp.109-120
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• 2017

A discounted cost model for preventive maintenance of armor units of rubble-mound breakwaters is mathematically derived by combining the deterioration model based on a discrete-time stochastic process of shock occurrence with the cost model of renewal process together. The discounted cost model of condition-based maintenance proposed in this paper can take into account the nonlinearity of cumulative damage process as well as the discounting effect of cost. By comparing the present results with the previous other results, the verification is carried out satisfactorily. In addition, it is known from the sensitivity analysis on variables related to the model that the more often preventive maintenance should be implemented, the more crucial the level of importance of system is. However, the tendency is shown in reverse as the interest rate is increased. Meanwhile, the present model has been applied to the armor units of rubble-mound breakwaters. The parameters of damage intensity function have been estimated through the time-dependent prediction of the expected cumulative damage level obtained from the sample path method. In particular, it is confirmed that the shock occurrences can be considered to be a discrete-time stochastic process by investigating the effects of uncertainty of the shock occurrences on the expected cumulative damage level with homogeneous Poisson process and doubly stochastic Poisson process that are the continuous-time stochastic processes. It can be also seen that the stochastic process of cumulative damage would depend directly on the design conditions, thus the preventive maintenance would be varied due to those. Finally, the optimal periods and scale for the preventive maintenance of armor units of rubble-mound breakwaters can be quantitatively determined with the failure limits, the levels of importance of structure, and the interest rates.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.379-386
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• 2005

Among various kinds of hearing aids which have been developed so far. the conventional air conduction hearing aids have some problems such as the acoustic distortion, an howling effect due to acoustic feedback. Another type of hearing aid. the cochlear implant system can be applied to the profound imparied person. However. it shows the disadvantage that there is no possibility of recovery of the acoustic organ such as ossicle. On the other hand. the implantable middle ear heaving device directly vibratos the ossicular chain and has better sound qualify. good cosmetics for appearance. and wide frequency responses so that it can overcome the defects or the conventional hearing aids. In this paper, a mathematical modeling and a momentum equation derivation of the DET has been performed. For the optimization of the structure dimension generating maximal vibrating force of the DET. the computer simulation using a finite element analysis (FEA) software has been performed. Also. the vibrating transducer has been designed to make the frequency characteristics or the transducer be similar to those of the normal middle ear. Through the experimental results, the measured vibration characteristics of the DET has been evaluated to verify the performance for the application to implantable middle ear hearing devices.

• Journal of the Korea Convergence Society
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• v.7 no.6
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• pp.13-21
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• 2016

In this paper we are trying to explain the effect of temperature on polymer membrane exchange water electrolysis (PEMWE) and polymer membrane exchange fuel cell (PEMFC) simultaneously. A comprehensive studying approach is proposed and applied to a 50Watt PEM fuel cell system in the laboratory. The monitoring process is carried out through wireless LoRa node and gateway network concept. In this experiment, temperature sensor measure the temperature level of electrolyzer, fuel cell stack and $H_2$ storage tank and transmitted the measured value of data to the management control unit (MCU) through the individual node and gateway of each PEMWE and PEMFC. In MCU we can monitor the temperature and its effect on the performance of the fuel cell system and control it to keep the lower heating value to increase the efficiency of the fuel cell system. And we also proposed a mathematical model and operation algorithm for PEMWE and PEMFC. In this model, PEMWE gives higher efficiency at lower heating level where as PEMFC gives higher efficiency at higher heating value. In order to increase the performance of the fuel cell system, we are going to monitor, communicate and control the temperature and pressure of PEMWE and PEMFC by installing these systems in a building of university which is located in the southern part of Korea.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2058-2062
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• 2009

1992년 한강수계법이 제정되면서 우리나라에 도입된 오염총량관리제는 현재 2차총량관리 시행계획수립 단계에 이르렀다. 오염총량제에서 수질모델은 수계구간별로 설정된 기준유량과 목표수질 조건을 달성하는 지를 판단할 수 있는 도구로 사용되며, 다양한 모델들이 사용되고 있다. 그 중 하천수질모형으로는 주로 QUAL2E, QUALKO, QUALKO2 모형으로 압축할 수 있다. QUAL2E 모형은 1980년대에 개발되어 국내외로 널리 이용하고 있으나 SOD를 0차나 일정량으로 처리하였고, 부착조류에 의한 용존산소 변화와 부유 조류 사멸시 발생하는 유기물이 고려되지 않았다. 또한 용존산소가 부족한 상태에서 반응이 활발한 탈질화과정이 포함되지 않아 이들 반응에 의해 수질이 영향을 받는 하천에 적용하기에는 한계가 있었다. 그리고 QUAL2E 모델은 여러 개의 지류를 가진 대형 하천에는 적용하기 어려운 단점이 있다. 국내에서는 1999년 QUAL2E 모델에 WASP5의 장점을 접목시켜 QUALKO 모델을 개발하였다. 이 모델은 QUAL2E에 부유성 조류의 사멸로 인한 유기물의 내부증가, 탈질화 반응 및 부착식물의 광합성 호흡 과정을 추가한 것이다. 또한 QUAL2E 모델에서 BOD는 CBOD로 입력되고 모의되므로 bottle BOD의 개념이 결여되어 있으므로 이러한 문제점을 보완하고, 조류의 생산 및 사멸에 의한 내부생산 유기물 증가와 탈질화 반응 과정을 추가한 것이다. 우리나라에서 진행되고 있는 총량관리 대상물질은 2010년까지는 $BOD_5$이며, 2011년부터는 일부 지역에 총인이 포함될 예정이다. 2007년에 실험실에서 측정하는 BOD5나 유기성 질소 또는 유기성 인을 그대로 입력하여 계산되고 출력할 수 있으며, 향후 오염총량제의 관리대상항목으로 논의되고 있는 TOC를 모의할 수 있는 QUALKO2가 개발되었다. 이에 본 연구에서는 향후 활용도가 클 것으로 기대되는 QUALKO2 모형에 기존 QUAL2E-UNCAS 모형에 서 수행할 수 있는 불확실성 해석 기법인 Monte Carlo 모의를 가능하도록 모형을 수정하고자 한다. 실제 하천에서의 수질해석에 대한 단순한 표현인 수학적 모형은 불확실성을 내포하고 있으며, Monte Carlo 해석을 사용하여 모형의 불확실도 정량화와 매개변수의 불확실성을 통계학적으로 기술할 수 있다. 또한 각 지점에 대한 계산결과치들에 대해 빈도 및 누가빈도분포 값을 제시함으로서 모형 예측치들의 전반적인 분포경향을 평가할 수 있으며, 하천수질에 대해서 환경기준치를 위배할 가능성을 산정하는데 활용할 수 있다. 우리나라 실정에 맞는 QUALKO2 모형에 Monte Carlo 모의를 통해 신뢰도 기반의 수질해석을 수행하게 된다면 수질정책의 기초자료 제공에 기여할 것으로 판단된다.

• The KIPS Transactions:PartC
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• v.14C no.6
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• pp.519-524
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• 2007

One of the most important issues on the sensor network with resource limited sensor nodes is prolonging the network lifetime by effectively utilizing the limited node energy. The most representative mechanism to achieve a long lived sensor network is the clustering mechanism which can be further classified into the single hop mode and the multi hop mode. The single hop mode requires that all sensor nodes in a cluster communicate directly with the cluster head(CH) via single hop md, in the multi hop mode, sensor nodes communicate with the CH with the help of other Intermediate nodes. One of the most critical factors that impact on the performance of the existing multi hop clustering mechanism is the cluster size and, without the assumption on the uniform node distribution, finding out the best cluster size is intractable. Since sensor nodes in a real sensor network are distributed non uniformly, the fixed size mechanism may not work best for real sensor networks. Therefore, in this paper, we propose a new dynamic size multi hop clustering mechanism in which the cluster size is determined according to the distance from the sink to relieve the traffic passing through the CHs near the sink. We show that our proposed scheme outperforms the existing fixed size clustering mechanisms by carrying out numerical analysis and simulations.

• Journal of Korea Technology Innovation Society
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• v.20 no.3
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• pp.732-753
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• 2017

Recently, when evaluating the technology values in the fields of biotechnology, pharmaceuticals and medicine, we have needed more to estimate those values in consideration of the period and cost for the commercialization to be put into in future. The existing discounted cash flow (DCF) method has limitations in that it can not consider consecutive investment or does not reflect the probabilistic property of commercialized input cost of technology-applied products. However, since the value of technology and investment should be considered as opportunity value and the information of decision-making for resource allocation should be taken into account, it is regarded desirable to apply the concept of real options, and in order to reflect the characteristics of business model for the target technology into the concept of volatility in terms of stock price which we usually apply to in evaluation of a firm's value, we need to consider 'the continuity of stock price (relatively minor change)' and 'positive condition'. Thus, as discussed in a lot of literature, it is necessary to investigate the relationship among volatility, underlying asset values, and cost of commercialization in the Black-Scholes model for estimating the technology value based on real options. This study is expected to provide more elaborated real options model, by mathematically deriving whether the ratio of the present value of the underlying asset to the present value of the commercialization cost, which reflects the uncertainty in the option pricing model (OPM), is divided into the "no action taken" (NAT) area under certain threshold conditions or not, and also presenting the estimation logic for option values according to the observation variables (or input values).