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Energy saving rates for a multistage centrifugal pump with variable speed drive

Rakibuzzaman M., Kim K., Kim H.-H., Suh S.-H.

Journal of Power Technologies

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2017

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Vol. 97, nr 2

163--168

EN

Multistage centrifugal pumps with variable speed drives are currently widely used in a variety of industrial and commercial applications. However, there are limitations to defining the efficiency of variable speed drive pumps. As an alternative method, energy saving rates can be evaluated with flow patterns and mean duty cycles. Computational fluid dynamics (CFD) is being used as a good tool to understand this and is less time consuming in terms of analyzing performances the experimental method. Research attention was focused on the energy saving rates of a multistage centrifugal pump for variable flow with variable speed drive through numerical and experiment methods. For this investigation Reynolds-averaged Navier-Stokes (RANS) equations were discretized by the finite volume method and a two equations SST model was used to account for three dimensional steady state flows. In the experimental system, an experimental set-up of a variable flow system was made to obtain energy saving rates and computational results were validated. The energy saving rates of the pumps depend on the flow patterns and specific mean duty cycles on which the machine or system operates. Mean duty cycles were divided into different flow operating conditions and a weighting for the mean value was given for each segment according to interval time. The pump system was operated at 50_70% of maximum flow rates. The energy saving rates were obtained from input power through CFD simulation and experimentally, and the mean duty cycle was obtained from flow patterns in the field of the pump. Energy saving rates were evaluated as a function of mean duty cycle and input power of the system operation. The total energy consumed for the constant speed drive was 25,922 kWh and for the variable speed drive pump was 17,687 kWh through CFD. The total annual energy saving rates were annually 33.81% through computational and 31.77% through experimental method with the variable speed drive system when compared to the constant speed drive system.

2

Effects Of Combinations Of Patternmaking Methods And Dress Forms On Garment Appearance

Fujii C., Takatera M., Kim K.

Autex Research Journal

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2017

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Vol. 17, no. 3

277--286

EN

We investigated the effects of the combinations of patternmaking methods and dress forms on the appearance of a garment. Six upper garments were made using three patternmaking methods used in France, Italy, and Japan, and two dress forms made in Japan and France. The patterns and the appearances of the garments were compared using geometrical measurements. Sensory evaluations of the differences in garment appearance and fit on each dress form were also carried out. In the patterns, the positions of bust and waist darts were different. The waist dart length, bust dart length, and positions of the bust top were different depending on the patternmaking method, even when the same dress form was used. This was a result of differences in the measurements used and the calculation methods employed for other dimensions. This was because the ideal body shape was different for each patternmaking method. Even for garments produced for the same dress form, the appearances of the shoulder, bust, and waist from the front, side, and back views were different depending on the patternmaking method. As a result of the sensory evaluation, it was also found that the bust and waist shapes of the garments were different depending on the combination of patternmaking method and dress form. Therefore, to obtain a garment with better appearance, it is necessary to understand the effects of the combinations of patternmaking methods and body shapes.

3

Effect of Patternmaker’s Proficiency On the Creation of Clothing

Kim K., Otani T., Takatera M.

Autex Research Journal

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2017

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Vol. 17, no. 2

120--128

EN

The effect of the patternmaker’s proficiency on the creation of clothing was investigated by the observation of the patternmaking process for clothing that satisfies the designer. We asked Japanese and French patternmakers to make a clothing pattern for the same design. The reasons for the differences in resultant clothing patterns and toiles made by the two patternmakers are discussed. Although the patternmaking processes used by the proficient patternmakers were similar, the resultant patterns were different owing to different recognition of the design. In particular, the shape and size of the collar that the designer emphasized in the illustration were different in the resultant patterns. Differences in patternmaking originated from differences in the patternmakers′ levels of expertise in terms of education, experience, and proficiency. However, the designer was satisfied with both patterns.

4

Numerical analysis of cavitation phenomena with variable speed centrifugal pump

Rakibuzzaman M., Kim K., Suh S.-H.

Journal of Power Technologies

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2016

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Vol. 96, nr 4

306--311

EN

Cavitation is an abnormal physical phenomenon which can be generated in relatively low pressure regions in centrifugal pumps. In predicting and understanding cavitation in the pumps, it is important to secure their efficiency and reliability. The purpose of this study is to analyze the cavitation flows in centrifugal pumps with variable speeds through numerical methods. The Rayleigh–Plesset cavitation model was adapted as the source term for inter-phase mass transfer in order to predict and understand the cavitation performances. The Reynolds-average Navier-Stokes (RANS) equations were discretized by the finite volume method. The two-equation SST turbulence model was accounted for turbulent flows. The numerical analysis results were validated with experimental data and it was found that both results were in good accordance. The cavitation performances were obtained for variable speeds with different temperatures and the effects on cavitation were described according to different cavitation numbers. Cavitation performances were also observed for different centrifugal pump stages (1st and 2nd). The performances of cavitation decreased with the increase of rotational speed. In addition, the development of cavitation is elucidated according to the different temperatures, and the effects of water vapor volume fraction are discussed.

5

Relationship between the Physical Properties and Hand of Jean Fabric

Kawamura A., Zhu C., Peiffer J., Kim K., Li Y., Takatera M.

Autex Research Journal

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2016

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Vol. 16, no. 3

138--145

EN

We investigated the distinctive characteristics of jean fabrics (denim fabrics obtained from jeans) and compared the physical properties and the hand. We used 13 kinds of jean fabric from commercial jeans and 26 other fabric types. The physical properties were measured using the Kawabata evaluation system, and the fabric hand was evaluated by 20 subjects using a semantic differential method. To characterise the hand of jean fabrics compared with other fabrics, we used principal component analysis and obtained three principal components. We found that jean fabrics were characterised by the second principal component, which was affected by feelings of thickness and weight. We further characterised the jean fabrics according to ‘softness & smoothness’ and ‘non-fullness’, depending on country of origin and type of manufacturer. The three principal components were analysed using multiple linear regression to characterise the components according to the physical properties. We explained the hand of fabrics including jean fabrics using its association with physical properties.

6

Shear force allowance in lumbar spine under follower load in neutral standing posture

Kim K., Kim Y. H., Lee S.

Acta of Bioengineering and Biomechanics

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2010

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Vol. 12, no. 4

49-53

EN

It has been shown experimentally that the load carrying capacity of the spine significantly increases when compressive loads are carried along the follower load (FL) direction. However, it is necessary to modify the current FL concept because a certain amount of shear force is produced during activities in daily life. In this study, a clinically allowable range of shear force was investigated using the modified FL concept. The shear force allowance was defined as the maximum ratio of the shear force to the follower force at each vertebral body center. Then, it was shown that the appropriate shear force allowance was within approximately 0.2 ~ 0.5 from the investigation of the follower forces, the shear forces, and the muscle force coordination. The predicted shear force allowance indicated that the resultant joint force is directed to a certain inside region between a half vertebral body and whole vertebral body.

7

Molecular Clusters to Nanomaterials

Singh N., Lee H., Suh S., Kołaski M., Kim K.

Polish Journal of Chemistry

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2007

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Vol. 81, nr 5-6

1021-1035

EN

Theoretical investigations of gas phase clusters enable the evaluation of intrinsic molecular properties and intermolecular interactions. Based on the microscopic determination of the properties of individual atoms, molecules, or clusters, one can predict the macroscopic properties of bulk matter. With the aid of theoretical insights into the interaction forces holding these clusters and subsequent properties of a large number of cluster systems (ranging from simple water clusters to large pi-systems), we have investigated the properties of various novel molecular systems including endo/exohedral fullerenes, nanotori, nonlinear optical materials, ionophores/receptors, polypeptides, enzymes, organic nanotubes, nanowires, and electronic and nano-mechanical molecular devices. This mini-review highlights some of the interesting results obtained in the course of our extensive theoretical investigations of clusters toward the molecular design approach of nanomaterials.