• Journal of Korean Society of Water and Wastewater
• /
• v.29 no.4
• /
• pp.519-531
• /
• 2015

It has been widely accepted that the pressure management of water distribution systems using pressure reducing valves(PRVs) would be an effective method for controlling leakages. A pressure reducing valve (PRV) regulates outlet pressure regardless of fluctuating flow and varying inlet pressure, thereby reducing leakage and mitigating the stress on the water distribution system. However, the operation of a PRV is vulnerable to its mechanical condition and hydraulic operability. In this research, the effect of PRVs installed in water distribution system are evaluated in terms of hydraulic pressure reduction and mechanical performance by analyzing measured pressure data with statistical approach. A statistical approach using the moving average filter and frequency analysis based on fourier transform is presented to detect abnormally operated PRVs that have been densely installed in water distribution system. The result shows that the proposed approach can be a good performance evaluation method by simply measuring pressures for the PRVs.

• Korean Journal of Microbiology
• /
• v.24 no.3
• /
• pp.308-316
• /
• 1986

Vertical distribution of heterotrophic bacteria and physico-chemical characteristics were measuted in Kum River estuarine sediments. And interrelationship between heterotrophic bacterka and environmental factors was also studied. The type of sediment of Site 1 was silty clay, and sand at Site 2. Annual pH ranges were between 7.1 and 7.7 in the clay type sediment (Site 1) and 6.9-7.2 in the sand type sediment (Site 2). It was shown that organic matter contents were higher in the clay type sediment than those of sand type sediment. Redox potential values of sediments were decreased rapidly with depth at Site 1, but those of Sete 2 showed vertical fluctuation. Nitrogens(ammonia+amino acid-N, nitrate-N, nitrite-N) and phosphate in the clay type sediment showed higher values than those of sand type sediment. Annual distribution of heterotrophic bacteria were ranged $6.71{\times}10^4$ cells/g dry wt. $-2.50{\times}10^6$ cells/g dry wt. In the clay type sediment and $2.67{\times}10^3$ cells/g dry wt. $-1.94{\times}10^6$ cells/g dry wt. in the sand type sediment. Distribution of proteolytic, lipolytic, and amylolytic bacteria were decreased with the depth and the highest density was found in April and the lowest in January. Bacterial populations in sediments were closely correlated with such environmental factors as pH, redox potential, moisture content, organic matter contents, and inorganic nutrients such as nitrite-N and phosphate-P.

• Journal of Energy Engineering
• /
• v.14 no.2 s.42
• /
• pp.123-132
• /
• 2005

An economic feasibility study is performed for the wind power generation with the examination of the wind speed and its distribution at Daekwanryung at which a wind fm is under construction. In this analysis, the distribution of wind speed is the key issue. The wind distribution which is usually expressed in terms of Weibull distribution with shape factor and scale factor needs to be reexamined to find the proper values of them according to the empirical wind speed data. After this kind of analysis is done, annual power generation of wind is calculated. Due to the lack of cost information, we applied EWEA data instead or the actual information from the site. The result would be of use to determine the 'reference price' of wind power under the current system of 'compensating subsidy for renewable power generation'.

• The Korean Journal of Applied Statistics
• /
• v.23 no.6
• /
• pp.1057-1065
• /
• 2010

In this paper we discuss some cautionary notes in using the Pearson chi-squared test statistic for the goodness-of-fit of the ordinal response model. If a model includes continuous type explanatory variables, the resulting table from the t of a model is not a regular one in the sense that the cell boundaries are not fixed but randomly determined by some other criteria. The chi-squared statistic from this kind of table does not have a limiting chi-square distribution in general and we need to be very cautious of the use of a chi-squared type goodness-of-t test. We also study the limiting distribution of the chi-squared type statistic for testing the goodness-of-t of cumulative logit models with ordinal responses. The regularity conditions necessary to the limiting distribution will be reformulated in the framework of the cumulative logit model by modifying those of Moore and Spruill (1975). Due to the complex limiting distribution, a parametric bootstrap testing procedure is a good alternative and we explained the suggested method through a practical example of an ordinal response dataset.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.4 no.1
• /
• pp.93-103
• /
• 2001

A reflection signal in an active sonar using a high frequency is mainly formed of a specular reflection from the surface of an object along with several equivalent scatters inside, which are characterized by the spatial distribution of the highlight on the object. This study analyze the existing echo signal synthesis models eq, random distribution model, equivalent interval distribution model & MUTAHID(Modified Underwater TArget by HIlight Distribution) model for simulated target, and compare the characteristics of the reflected signal synthesis results for each model in various conditions. These highlight distribution models can be efficiently applied to the simulated target signals synthesis of various real systems requiring the echo signal synthesis on the underwater target.

• Journal of Navigation and Port Research
• /
• v.29 no.10 s.106
• /
• pp.897-906
• /
• 2005

The purpose of this research is to verify the strategic fitness and relevance of the distribution park for a hub port in Northeast Asia and to find a method to be a hub-port with a competitive edge. The strategic factor of distribution park development are policy, methodology and promotion method So these factors are analysed by structural equation model. The essential results of the research show that distribution park should be actually developed to produce value-added and to be port cluster.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.48 no.6
• /
• pp.59-67
• /
• 2006

Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between $93.38{\sim}107.67$. Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.

• Journal of the Korea Safety Management & Science
• /
• v.9 no.3
• /
• pp.95-102
• /
• 2007

Nowadays, globally high-grade companies have done their best for increasing their competitive power through a many kinds of method in incisive competition for making certain of a pacesetting position. Among the rest, Six Sigma have been the best methodology of improving process and have proven to be effective by the result of improving process in many of manufacturing business, however, it has not obtained excellent results in the transaction business. In transaction business, a $30\sim50%$ costs in total costs is generated by slow-speed working and reworking. The slow processes decrease the quality and increase the cost, which decreases customer satisfaction, and finally the income is decreased. All of them are so called wastes in processes. For this, adopting of lean six sigma methodology in process management can eliminate the wastes and reduce the variation. This study focuses on distribution with the domains like capacity, layout, amount of location, assignment of product, operation procedure and operation rule in order to improve these domains, we make a further application of eight analysis ways based on DMAIC method for improving operation of processes of distribution center as the third profit source. The goal of this study is to trace an approach that can easily adopt of Lean Six Sigma in operational management of distribution center by a kind of data, analysis method and template.

• Journal of Ocean Engineering and Technology
• /
• v.23 no.6
• /
• pp.105-110
• /
• 2009

The objective of this paper is to investigate the statistical properties of Vickers hardness (HV) for friction welded parts in a Ni-based super alloy (Alloy718). In the case of post weld heat treatment (PWHT) parts, hardness tests were repeated for three different applied loads, 100, 200, and 300 g, with a duration time of 10 seconds. The arithmetic means of the Vickers hardness in heat affected zone (HAZ) materials were smaller than those of the base metal (BM) in all of the applied loads. The coefficient of variation (COV) for the BM and HAZ decreased by increasing the applied load. The probability distribution of the Vickers hardness followed the Weibull distribution well. The distribution of the Vickers hardness was not found to be symmetric. The shape parameter and scale parameter increased by increasing the applied load at both the BM and HAZ.

• Korean Journal of Human Ecology
• /
• v.17 no.3
• /
• pp.469-483
• /
• 2008

Body image is important as it is related to self-esteem and can be enhanced by clothing and the degree of enhancement is related to clothing fit. The purpose of the paper is to find the adequate ease distribution of jacket pattern for the obese women who want to slenderize their shape by optical illusion. Subjective evaluation of the visual appearance we collected and, at the same time, 3D clothing air volume was observed for the nine types of experimental jackets with different ease distribution. As results it was found that jacket pattern for the obese women is that the front width of pattern is wider than what of back width in waist and abdomen. It was also noted that there was distance between clothing and skin in the girth around hip of jacket. 3D scanner clearly demonstrated the distribution of ease is useful to find the pattern variables responsible for the slender appearance of the obese women. The ready-to-made clothes for the obese women's clothing should be manufactured systematically in due consideration of the diversity and scarcity of the obese women's body shape.