• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1743-1753
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• 2017

Since there are multiple random variables in the probabilistic load flow (PLF) calculation of distribution system containing distributed generation (DG) and electric vehicle charging load (EVCL), a Monte Carlo method based on composite sampling method is put forward according to the existing simple random sampling Monte Carlo simulation method (SRS-MCSM) to perform probabilistic assessment analysis of voltage quality of distribution system containing DG and EVCL. This method considers not only the randomness of wind speed and light intensity as well as the uncertainty of basic load and EVCL, but also other stochastic disturbances, such as the failure rate of the transmission line. According to the different characteristics of random factors, different sampling methods are applied. Simulation results on IEEE9 bus system and IEEE34 bus system demonstrates the validity, accuracy, rapidity and practicability of the proposed method. In contrast to the SRS-MCSM, the proposed method is of higher computational efficiency and better simulation accuracy. The variation of nodal voltages for distribution system before and after connecting DG and EVCL is compared and analyzed, especially the voltage fluctuation of the grid-connected point of DG and EVCL.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.4
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• pp.369-379
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• 1993

Using a successive removal approach the mechanism of sampling capture efficiency of blue crabs by dredges was studied in Chesapeake Bay during winter 1992. For the twenty-six field experiments no significant statistical differences were detected in dredge efficiency using general linear model analysis by factors including bottom sediments, water depths, and sampling vessels. Dredge efficiency (i.e., catchability) was estimated by two methods, Leslie (Leslie and Davis, 1939) and a simple revised method. Mean catchability was estimated at 0.26 (SE=0.03), indicating that only $26\%$($95\%\;C. I.=20{\sim}32\%$) of crabs present in the path of the dredge of a given sampling area are caught with a single dredge tow. Dredge efficiency declined exponentially as crab density increased.

• Bulletin of the Korean Chemical Society
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• v.34 no.8
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• pp.2353-2357
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• 2013

The objective of this study was to develop a simple, less time-consuming and accurate sampling technique based on solid-phase sorption with activated carbon as the sorbents. The results from solid-phase sorption techniques were compared to that from a conventional solvent impinger-based technique to confirm the efficacy of the proposed method. The laboratory results indicated that the solid-phase sorption method was suitable for the determination of siloxanes as the measured concentrations were similar to that from a solvent impinge method. The data from solid-phase sorption method showed excellent recovery and reproducibility while the sampling was less labor intensive and less time consuming than the solvent impinge method. Following the laboratory tests, the solid-phase sorption technique was successfully applied to sampling biogas from a field site. This study shows that the activated carbon-based solid-phase sorption can be a reliable and less time-consuming option for the sampling and collection of siloxanes under various different landfill conditions.

• Journal of the Korean Chemical Society
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• v.29 no.3
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• pp.220-225
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• 1985

An attempt was made to determine some trace metals in highly concentrated samples using micro sampling technique in flame atomic absorption spectrophotometry. Major instrumental parameters and optimun analytical conditions investigated were the measuring time of instrument (the speed of electronics), sample volume, burner height, aspiration rate, and fuel to oxidant ratio. Advantages of the present technique are not only rapid, simple, and sensitive with good precision but also capability of analyzing small volume of sample and ability to handle highly concentrated samples without serious burner clog-up problem compared to conventional flame atomic absorption.

• Journal of Electrical Engineering and Technology
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• v.8 no.4
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• pp.872-878
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• 2013

In industrial control systems, flow measurement is a very important issue. It is frequently needed to calculate how much total fluid or gas flows through a cross-section. Flow volume measurement tools use simple sampling or rectangle methods. Actually, flow volume measurement process is an integration process. For this reason, measurement systems using instantaneous sampling technique cause considerably high errors. In order to make more accurate flow measurement, numerical integration methods should be used. Literally, for numerical integration method, Rectangular, Trapezoidal, Simpson, Romberg and Gaussian Quadrature methods are suggested. Among these methods, trapezoidal rule method is quite easy to calculate and is notably more accurate and contains no restrictive conditions. Therefore, it is especially convenient for the portable flow volume measurement systems. In this study, the volume measurement of air which is flowing through a cross-section is achieved by using PLC ladder diagram. The measurements are done using two different approaches. Trapezoidal rule method is proposed to measure the flow sensor signal to minimize measurement errors due to the classical sampling method as a different approach. It is concluded that the trapezoidal rule method is more effective than the classical sampling.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.51-59
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• 2007

A reliability-based approach that can systematically model various sources of uncertainty is presented in the context of slope stability. Expressions for characterization of soil properties are developed in order to incorporate sampling errors, spatial variability and its effect of spatial averaging. Reliability analyses of slope stability with different statistical representations of soil properties show that the incorporation of sampling error, spatial correlation, and conditional simulation leads to significantly lower probability of failure than that obtained by using simple random variable approach. The results strongly suggest that the spatial variability and sampling error have to be properly incorporated in slope stability analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.13 no.3
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• pp.179-185
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• 2008

In this paper, an advanced torque control scheme of SRM using DITC(Direct Instantaneous Torque Control) and PWM(pulse width modulation) is presented. Different from conventional DITC method, proposed method uses one or two switching modes at every sampling time, instead of only one switching mode. The duty ratio of the phase switch is regulated according to the torque error and simple control rules of DITC. Moreover the sampling time of control can be extended, which allows implementation on low cost micro-controllers. A simple calculation of PWM can assure a constant switching frequency with an excellent control performance. The proposed control method is verified by the simulations and experimental results.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.10a
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• pp.248-255
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• 1993

Recently, due to the increasing attention to the structural safety under uncertain environments, many researches on the structural reliability analysis have been peformed. Some useful methods are available to evaluate performance reliability of structures with explicit limit states. However, for large structures, in which structural behaviors can be analyzed with finite element models and the limit states are only expressed implicitly, Monte-Carlo simulation method has been mainly used. However, Monte-Carlo simulation method spends too much computational time on repetitive structural analysis. Many alternative methods are suggested to reduce the computational work required in Monte-Carlo simulation. Response surface method is widely used to improve the efficiency of structural reliability analysis. Response surface method is based on the concept of approximating simple polynomial function of basic random variables for the limit state which is not easily expressed in explicit forms of design random variables. The response surface method has simple algorithm. However, the accuracy of results highly depends on how properly the stochastic characteristics of the original limit state has been represented by approximated function, In this study, an improved response surface method is proposed in which the sampling points for creating response surface are modified to represent the failure surface more adequately and the combined use of a linear response surface function and Rackwitz-Fiessler method has been employed. The method is found to be more effective and efficient than previous response surface methods. In addition more consistent convergence is achieved, Accuracy of the proposed method has been investigated through example.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2373-2379
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• 2023

In sodium systems, leakage is one of the safety concerns; it can cause chemical reactions, which may result in fires. There are contact and non-contact types of leak detectors, and the conventional method of non-contact type detection is by gas sampling. Because of the complexity of this method, there has always been a need for a simple gas sensor, and the resistive-type nanostructure ZnO sensor is a promising option with various advantages. In this study, a ZnO sensor was fabricated, and the concept was tested as a leak detector using a dedicated experiment facility. The experiment results showed distinctive changes in resistance with the presence of sodium aerosol under various conditions. Replacing the conventional gas sampling with the ZnO sensors is expected to enable identification of the leakage location if used as a point-wise instrumentation and to greatly reduce the total cost, making the system simple, light, and effective. For further study, more tests will be performed to evaluate the sensitivity of key parameters under various conditions.

• International Journal of Industrial Entomology and Biomaterials
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• v.8 no.1
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• pp.17-26
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• 2004

Pest monitoring through field surveys and surveillance helps in forecasting the population build up of pest. It reduces the load of pesticides application and forms the basis of Integrated Pest Management in sericulture. Common sampling techniques for quantifying pest populations and damage caused by them are reviewed emphasizing the need for quick and simple sampling methods. Various direct and indirect sampling methods for establishing pest populations are discussed and methods have been discussed to use indirect sampling method under IPM programme in sericulture. The use of pheromone lures and traps forms one of the important ingredients of integrated pest management, which calls for integration of all available methods in a cost effective and environmental friendly manner offering consistent efficacy. Silk-worms feed on the variety of silk host plants and spin cocoons. Each silk host plant is attacked in the field by number of insect pest species. Several pests are common to mulberry, tasar, oak tasar, muga and eri host plant but pest status and seasonal abundance differs from each crop. The key pests are serious perennially occurring persistent species which cause considerable yield loss every year on large areas and require control measure. Regular occurrence of minor pest is noticed but sudden increase in its population is not known. The occasional pests are sporadic but potential causing sufficient damage. Silk losses due to attack of all the pests have not been calculated. However, information on pest biology and ecology, and control practices being practiced is available but the period of outbreak of major pests and predators on silkworms and its host plant needs to be reinvestigated. Pest and predators forecasting based on surveillance information may provide an opportunity to minimize the losses, particularly to reduce expenditure involved in pest management.