• Nuclear Engineering and Technology
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• v.49 no.6
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• pp.1172-1180
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• 2017

The application of Monte Carlo (MC) to large-scale fixed-source problems has recently become possible with new hybrid methods that automate generation of parameters for variance reduction techniques. Two common variance reduction techniques, weight windows and source biasing, have been automated and popularized by the consistent adjoint-driven importance sampling (CADIS) method. This method uses the adjoint solution from an inexpensive deterministic calculation to define a consistent set of weight windows and source particles for a subsequent MC calculation. One of the motivations for source consistency is to avoid the splitting or rouletting of particles at birth, which requires computational resources. However, it is not always possible or desirable to implement such consistency, which results in inconsistent source biasing. This paper develops an original framework that mathematically expresses the coupling of the weight window and source biasing techniques, allowing the authors to explore the impact of inconsistent source sampling on the variance of MC results. A numerical experiment supports this new framework and suggests that certain classes of problems may be relatively insensitive to inconsistent source sampling schemes with moderate levels of splitting and rouletting.

• Journal of Environmental Impact Assessment
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• v.20 no.1
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• pp.71-78
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• 2011

This paper aims to assessing impact of reduction of non-point source pollution in the Bokha Stream watershed. The BASINS/HSPF model was calibrated and verified for water flow and water qualities using Total Maximum Daily Load 8days data from 2006 to 2007. Accuracy of the BASINS/HSPF models in simulating hydrology and water quality was compared and there were somewhat differences of statistical results, but water flow and water quality were simulated in good conditions over the study period. The applicability of models was tested to evaluate non-point source control scenarios to response hydrology and water quality in the Bokha stream using various measures which include BMPs approach and change of landuse. The evaluation of reduction of non-point source pollution was developed using load-duration curve. Despite strong reduction of non-point source, there are not satiated target quality at low flow season.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.2
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• pp.93-99
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• 2001

A new type geometric and mathematical network reduction model is introduced. Large-scale network is analyzed with analytic approach. The graph has many nodes, branches and loops. Circuit equation are obtained from these elements and connection rule. In this paper, the analytic relation between voltage source has a mutual different graphic property. Node-reduction procedure is achieved with this circuit property. Consequently voltage source value is included into the adjacent node-analyzing equation. A resultant model equations are reduced as much as voltage source number. Matrix rank is (n-1-k), where n, k is node and voltage source number. The reduction procedure is described and verified with geometric principle and circuit theory. Matrix type circuit equation can be composed with this technique. The last results shall be calculated by using computer.

• Particle and aerosol research
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• v.16 no.4
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• pp.73-94
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• 2020

Particulate infectious sources, including infectious viruses, can float in the air, causing airborne infections. To prevent indoor airborne infection, dilution control by ventilation and indoor air cleaners are frequently used. In this study, the risk of airborne infection by the operation of these two techniques was evaluated. In case of dilution control by ventilation, a high efficiency air filter was embedded at the inlet of supply air. In this study, infectious source reduction devices such as indoor air cleaner include all kinds of mechanical-filters, UV-photo catalysts and air ionizers through which air flow is forced by fans. Two mathematical models for influenza virus were applied in an infant care room where infants and young children are active, and the risk reduction efficiency was compared. As a result, in the case of individually operating the ventilator or the infectious source reduction device, the airborne infection risk reduction efficiencies were 55.2~61.2% and 53.8~59.9%, respectively. When both facilities were operated, it was found that the risk of airborne infection was reduced about 72.2~76.8%. Therefore, simultaneous operation of ventilation equipment and infectious source reduction device is the most effective method for safe environment that minimizes the risk of airborne infection of respiratory infectious diseases. In the case of a space where sufficient ventilation operation is difficult, it was found that the operation of an infectious source reduction device is important to prevent the spread of infectious diseases. This study is meaningful in that it provides an academic basis for strategies for preventing airborne infection of respiratory infectious diseases.

• Journal of Korean Society on Water Environment
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• v.36 no.5
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• pp.405-422
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• 2020

Land use change by urbanization has significantly affected the hydrological process including the runoff characteristics. Due to this situation, it has been becoming more complicated to manage non-point source pollutions caused by rainfall. In order to effectively control non-point sources, it is necessary to identify the reduction efficiency of the various management method based on land use characteristics. Thus, the purpose of this study is to analyze the reduction efficiency of non-point source pollution management practices targeting three different watersheds with the different land use characteristics using the Soil and Water Assessment Tool (SWAT). To do this, the vulnerable subwatersheds to non-point source pollution occurrence within each watershed were selected based on the streamflow and water quality simulation results. Then, considering the land use, low impact development (LID) or best management practices (BMPs) were applied to the selected subwatersheds and the efficiency of each management was analyzed. As a result of analysis of the non-point source pollution reduction efficiency, when LID was applied to urban areas, the average reduction efficiencies of SS, NO₃-N, and TP were 5.92%, 4.62%, and 10.35%, respectively. When BMPs were applied to rural areas, the average reduction efficiencies of SS, TN and TP were 35.45%, 4.37%, and 10.16%, respectively. The results of this study can be used as a reference for determining appropriate management methods for non-point source pollution in urban, rural, and complex watersheds.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.1
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• pp.63-73
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• 1988

In this paper, an algorithm is proposed to evaluate the source-to-terminal reliability, the probability that a source node can communicate with a terminal node, in a probabilistic derected graph. By using Satyanaratana's factoring $theorem^{(7)}$, the original graph can be partitioned into two reduced graphs obtained by contracting and deleting the edge connected to the source node in the probabilistic directed graph. The edge removal proposed in this paper and the general series-parallel reduction can then be applied to the reduced graph. This edge reduction can be applied recursively to the reduced graphs until a source node can be connected to a terminal node by one edge. A computer program which can be applied to evaluating the source-to-terminal reliability in a complex and large network has also been developed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.156-160
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• 2005

The radiated noise of the excavator is composed of the various noise sources such as the diesel engine, cooling fan and hydraulic system, so the noise reduction for each noise source is required. In this study, the source contribution analysis for these principal noise sources is performed by using the noise source removal method. And to reduce the noise due to each one, the various experiments and analyses are studied. On the basis of these results, the proper reduction countermeasures are derived to develop the excavator satisfied the $2^{nd}$ noise regulation of EU.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2005.10a
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• pp.637-642
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• 2005

The objective of this study is to evaluate design parameters of free water surface constructed wetland for the reduction of agricultural nonpoint source pollution. From literature review, the key design parameters were selected as influent concentration, influent water volume, hydraulic retention time and wetland system arrangement. The design value for each parameter was established after pilot study. Full-scale constructed wetland on the basis of the designed values was constructed to evaluate those reasonableness. The results of this study showed that the designed values for free water surface constructed wetland were appropriate for the reduction of agricultural nonpoint source pollution.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.57-61
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• 2006

In the single-phase switched reluctance motor (SRM) drive, the required DC source is generally supplied by the circuit consisting of bridge rectifier and large filter capacitor connected with DC line terminal. Due to the large capacity of the capacitor, the charged time of capacitor is very short from the AC source. Lead to the bridge rectifiers draws pulsating current from the AC source side, which results in reduction of power factor and low system efficiency. Therefore a novel single-phase SRM drive system is presented in this paper, which includes drive circuit realizing reduction of torque ripple and improvement of power factor with a novel switching topology. The proposed drive circuit consists of one switching part and diode, which can separate the output of AC/DC rectifier from the large capacitor and supply power to SRM alternately, in order to realize the torque ripple reduction and power factor improvement through the switching scheme. In addition, the validity of the proposed method is tested by some simulations and experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.983-990
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• 2011

This paper investigates active noise control(ANC) of a rectangular cavity using single channel filtered-x least mean square(FXLMS) algorithms to globally reduce the interior noise. To obtain the global reduction of the interior noise, multichannel active control should be incorporated in general. We, however, examined firstly the optimal location of the secondary source that produces a global reduction of the interior noise field using single channel control. We then investigated the frequency characteristics of the reduction to yield the effective frequency band of the active control system. It follows that the secondary source should be located as close to the primary source as possible in order to obtain the global reduction.