• Industrial Engineering and Management Systems
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• 제9권2호
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• pp.70-79
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• 2010

Makespan and cost minimization are two important factors in project investment. This paper considers a multi-mode resource-constrained project scheduling problem with the objective of minimizing costs, subject to a deadline constraint. A number of studies have focused on minimizing makespan or resource availability cost with a specified deadline. This problem assumes a fixed cost for the availability of each renewable resource per period, and the project cost to be minimized is the sum of the variable cost associated with the execution mode of each activity. The presented memetic algorithm (MA) consists of three features: (1) a truncated branch and bound heuristic that serves as effective preprocessing in forming the initial population; (2) a strategy that maintains two populations, which respectively store deadline-feasible and infeasible solutions, enabling the MA to explore quality solutions in a broader resource-feasible space; (3) a repair-and-improvement local search scheme that refines each offspring and updates the two populations. The MA is tested via ProGen generated instances with problem sizes of 18, 20, and 30. The experimental results indicate that the MA performs exceptionally well in both effectiveness and efficiency using the optimal solutions or the current best solutions for the comparison standard.

• 산경연구논집
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• 제9권1호
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• pp.25-38
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• 2018

Purpose - The purpose of this study is to empirically investigate the impact of donor's fiscal status on aid decisions before and after the 2008 global financial crisis. The effects on aid can change depending on the donor country's fiscal status and the period of financial crisis. Research design, data, and methodology - A fixed effect regression and dynamic panel GMM is conducted using a comprehensive dataset combining 31 donor and 167 recipient countries during 1996-2015. The key explanatory variable is central government debt-to-GDP ratio of donor country. Recipient countries' GNI per capita, population, governance indicators, and bilateral trade-to-GDP ratio between donor and recipient countries are included as control variables. Results - We can confirm the relationship between donor country's fiscal status and aid flow. The cyclical component of government debt is found to have a negative impact on grant decisions particularly after the 2008 global financial crisis. This effect becomes larger in the countries with high government debt-to-GDP ratio. ODA decisions from the countries with low financial constraint do not significantly affected by the recipient countries' factors such as GNI, population, and governance indicator. Conclusions - Based on the empirical results of this study, the source of aid should be diversified by incorporating private sector and innovative financing sources.

• Journal of Microbiology and Biotechnology
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• 제28권5호
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• pp.831-838
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• 2018

Trophic interactions of introduced biocontrol fungi with soil animals can be a key determinant in the fungal proliferation and activity. This study investigated the trophic interaction of an introduced biocontrol fungus with soil nematodes. The biocontrol fungus Trichoderma harzianum ThzID1-M3 and the fungivorous nematode Aphelenchoides sp. (10 per gram of soil) were added to nonsterile soil, and microbial populations were monitored for 40 days. Similar results were obtained when the experiment was duplicated. ThzID1-M3 stimulated the population growth of indigenous nematodes (p < 0.05), regardless of whether Aphelenchoides sp. was added. Without ThzID1-M3, indigenous nematodes did not increase in number and the added Aphelenchoides sp. nematodes almost disappeared by day 10. With ThzID1-M3, population growth of nematodes was rapid between 5 and 10 days after treatment. ThzID1-M3 biomass peaked on day 5, dropped at day 10, and then almost disappeared at day 20, which was not influenced by the addition of nematodes. In contrast, a large quantity of ThzID1-M3 hyphae were present in a heat-treated soil in which nematodes were eliminated. Total fungal biomass in all treatments peaked on day 5 and subsequently decreased. Addition of nematodes increased the total fungal biomass (p < 0.05), but ThzID1-M3 addition did not affect the fungal biomass. Hyphae of total fungi when homogenously distributed did not support the nematode population growth; however, hyphae of the introduced fungus did when densely localized. The results suggest that soil fungivorous nematodes are an important constraint on the hyphal proliferation of fungal agents introduced into natural soils.

• 한국잡초학회지
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• 제18권4호
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• pp.364-370
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• 1998

1981 및 1992년도 우리 나라 논잡초 조사자료를 이용한 생태학적 종합우점도 분석과 GIS에 의한 분석결과에 대한 요약을 하여 보면 다음과 같다. 1. 1981년 생태학적 종합우점도 분석에 의하여 가장 우점도가 높았던 잡초는 물달개비이었으며, 이는 전국적인 논에 걸쳐 가장 발생밀도가 높은 것으로 이해되지만 GIS분석에 의한 전국지역에 걸친 발생밀도는 이와 큰 차이가 나타났다. 2. 1981년 GIS분석에 의한 일년생 광엽잡초 물달개비의 발생우점 지역으로서는 경기의 시흥, 여주지역, 충남의 당진, 예산, 아산, 공주, 청양, 부여, 논산, 천안, 금산 등이었으며, 경북지방은 점촌, 청도, 영천, 봉화, 영풍 등이 상대적으로 매우 높은 발생량을 보였다. 3. 1992년 우점도가 가장 높았던 잡초는 다년생 사초과 잡초인 올방개이었으며. GIS분석에 의한 지역별 발생밀도는 현저한 차이를 보였으며, 주로 경기남부지역과 충남 중 서부지역, 전남 남 서부지역 등이 상대적으로 발생밀도가 높았다. 4. 1992년 올방개 발생이 극심한 지역은 경기 용인, 안성, 화성, 평택, 이천, 여주 일원과 충남의 서산, 당진, 태안, 천안, 공주, 아산, 청양, 예산, 대전일원, 전북의 장수, 전남의 무안, 나주, 해남 등으로 나타났다.

• 한국정보과학회논문지:시스템및이론
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• 제36권4호
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• pp.239-246
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• 2009

각 계층 네트워크가 세마포에 의하여 용량제한을 갖는 중첩형 대기행렬 네트워크의 평균대기시간에 관하여 연구하였다. 중첩형 대기행렬 네트워크는 고객의 대기시간 관점에서 보다 간단한 대기행렬 네트워크로 변환될 수 있다. 이러한 중첩형 대기행렬 네트워크의 가장 중요한 특성은 하위계층의 흐름이 상위 계층의 상태에 의존적이며, 제한을 받는다는 것이다. 이러한 형태의 대기행렬 네트워크는 성능분석을 정확히 할 수 없기 때문에, 변환된 중첩형 대기행렬 네트워크를 이용하여 평균대기시간에 대한 하한과 상한을 분석하고자 한다. 모의실험에 관한 측정은 도착분포가 단계형태 분포로서 포아송, 얼랑 그리고 초지수분포에 관하여 조사하였다. 이렇게 구한 범위는 추후에 좀 더 근접한 근사치를 구하는데 이용할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제31권6호
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• pp.815-822
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• 2021

Indigenous fungus-feeding nematodes may adversely affect the growth and activity of introduced biocontrol fungi. Alginate pellets of the biocontrol fungus Trichoderma harzianum ThzID1-M3 and sclerotia of the fungal plant pathogen Sclerotinia sclerotiorum were added to nonsterile soil at a soil water potential of -50 or -1,000 kPa. The biomass of ThzID1-M3, nematode populations, and extent of colonization of sclerotia by ThzID1-M3 were monitored over time. The presence of ThzID1-M3 increased the nematode population under both moisture regimes (p < 0.05), and fungivores comprised 69-75% of the nematode population. By day 5, the biomass of ThzID1-M3b and its colonization of sclerotia increased and were strongly correlated (R² = 0.98), followed by a rapid reduction, under both regimes. At -50 kPa (the wetter of the two environments), fungal biomass and colonization by ThzID1-M3 were less, in the period from 5 to 20 days, while fungivores were more abundant. These results indicate that ThzID1-M3 stimulated the population growth of fungivorous nematodes, which in turn, reduced the biocontrol ability of the fungus to mycoparasitize sclerotia. However, colonization incidence reached 100% by day 5 and remained so for the experimental period under both regimes, although hyphal fragments disappeared by day 20. Our results suggest that indigenous fungivores are an important constraint for the biocontrol activity of introduced fungi, and sclerotia can provide spatial refuge for biocontrol fungi from the feeding activity of fungivorous nematodes.

• 음성과학
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• 제10권2호
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• pp.35-43
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• 2003

General speaker verification systems improve their recognition performances by normalizing log likelihood ratio, using a speaker model and its background speaker model that are required to be verified. So these systems rely heavily on the availability of much speaker independent databases for background speaker model design. This constraint, however, may be a burden in practical and portable devices such as palm-top computers or wireless handsets which place a premium on computations and memory. In this paper, new approach for the GMM-based background model design used in portable speaker verification system is presented when the enrollment data is available. This approach is to modify three parameters of GMM speaker model such as mixture weights, means and covariances along with reduced mixture order. According to the experiment on a 20 speaker population from YOHO database, we found that this method had a promise of effective use in a portable speaker verification system.

• 대한산업공학회지
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• 제22권1호
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• pp.3-15
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• 1996

An approximation algorithm is presented for cyclic queueing networks with finite buffers. The algorithm decomposes the queueing network into individual queues with revised arrival and service process and revised queue capacity. Then, each queue is analyzed in isolation. The service process reflects the additional delay a unit might undergo due to blocking and the arrival process is described by a 2-phases Coxian ($C_2$) distribution. The individual queues are modelled as $C_2/C_2$/1/B queues. The parameters of the individual queues are computed approximately using an iterative scheme. The population constraint of the closed network is taken into account by ensuring that the sum of the average queue lengths of the individual queues is equal to the number of customers of the network. Extensive numerical experiments show that this method provides a fairly good estimation of the throughput.

• 한국시뮬레이션학회:학술대회논문집
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• 한국시뮬레이션학회 1999년도 춘계학술대회 논문집
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• pp.47-52
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• 1999

In this paper we propose new approximate method for the performance analysis of closed-loop production system with unreliable machines and random processing times. The approximate method decomposes the production system consisting of K machines into a set of K subsystems, each subsystem consisting of two machines separated by a finite buffer. Then, each subsystem is analyzed by analyzing method n isolation. The population constraint of the closed-loop production system is taken into account by prescribing that the sum of average buffer level in the subsystems is equal to the number of customers in the closed-loop production system,. We establish a set of equations that characterizes unknown parameters of the servers in the subsystems. An iterative procedure is then used to determine the unknown parameters. Experimental results show that these methods provide a good estimation of the throughput.

• International Journal of Aeronautical and Space Sciences
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• 제3권1호
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• pp.50-60
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• 2002

A new co-evolutionary algorithm, of which the convergence speed is accelerated by neural networks, is proposed and verified in this paper. To reduce computational load required for co-evolutionary optimization processes, the cost function and constraint information is stored in the neural networks, and the extra offspring group, whose cost is computed by the neural networks, is generated. It increases the offspring population size without overloading computational effort; therefore, the convergence speed is accelerated. The proposed algorithm is applied to attitude control design of flexible satellites, and it is verified by computer simulations and experiments using a torque-free air bearing system.