• Journal of Welding and Joining
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• v.29 no.3
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• pp.51-57
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• 2011

Bead shape control with gas force process has been developed to overcome the concave back bead in pipe orbital welding. However, It is impossible to make a convex back bead using the existing gas nozzle, because it has high gas-consuming and low gas force. The purpose of this paper, to develop optimum shape of nozzle which to reduce the consumption of gas, maximizing the shield gas force with low cost and high productivity coincide the Green welding. In this paper venturi-type nozzle was designed by using the Venturi meter and compared velocity, pressure, arc shape in the flat position with existing CP-nozzle. As a result, Venturi-type nozzle's maximum velocity and pressure was improved at the same flow rate. Also heat input was increased by the arc contraction in the flat position.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.202-208
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• 2001

A Switched Reluctance Motor(SRM) has double salient poles structure and the phase windings are wound in stator. SRM hase more simple structure that of other motor, thus manufacture cost is low, mechanically strong, reliable to a poor environment such as high temperature, and maintenance cost is low because of brushless. SRM needs position detector to get rotator position information for phase excitation and tachometer or encoder for constant speed operation. But, this paper doesn\`s use an encoder of high cost for velocity measurement of rotator. Instead of it, the algorithm for position detection and velocity estimation from simple slotted disk has been proposed and developed. To implement variable speed digital control system with velocity estimation algorithm, the TMS320F240-20MIPS fixed point arithmetic processor of TI corporation is used. The experimental results of the developing system are enable to control speed with wide range, not only single pulse, hard chopping mode and soft chopping, ut also variable speed control, and advance angle control.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.155-164
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• 2011

In the case of impact loading test, measurement of the test data has difficulties due to fast loading velocity. In addition, the dynamic behaviors of specimens are distorted by ignoring local fracture. In this study, therefore, finite element analysis which considers local fracture and strain rate effect on impact load was performed by using LS-DYNA, an explicit analysis program. The one-way and two-way specimens strengthened with FRP Sheets and steel fibers were considered as analysis models. The results showed that the impact resistance of steel fiber reinforced concrete (SFRC) and ultra high performance concrete (UHPC) was enhanced. In the case of specimens strengthened with FRP Sheets, GFRP was superior to CFRP in the performance of impact resistance, and there was little effect of the FRP Sheet orientation. The reliability of this analysis model was verified by comparing with previous experimental results.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.33.1-33.1
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• 2016

Dwarf elliptical galaxies (dEs), the most abundant galaxy type in clusters, were recently shown to exhibit a wide variety in their properties. Particularly, the presence of blue cores in some dEs, what we call dE(bc), supports the scenario of late-type galaxy infall and subsequent transformation into red, quiescent dEs. While several transformation mechanisms for these dE(bc)s within cluster environment have been proposed, all these processes are able to explain only some of the observational properties of dEs. In this context, internal kinematic properties of dE(bc)s provide the most crucial evidence to discriminate different processes for the formation of these galaxies. We present Gemini Multi Object Spectrograph (GMOS) long-slit spectroscopy of two dE(bc)s in the Virgo cluster. We obtained radial profiles of velocity and velocity dispersion out to ~1.3 effective radius. We found that two dE(bc)s exhibit kinematically decoupled components as well as distinct peculiar features in velocity profiles, supporting the scenario of mergers. We also found that these galaxies are structurally compatible with low surface brightness component of blue compact dwarf galaxies. We suggest that a part of dE(bc)s in the Virgo Cluster were formed through galaxy merger in low density environment such as galaxy group or outskirt of the cluster, and then were quenched by subsequent effects within cluster environment.

• Nutrition Research and Practice
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• v.11 no.4
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• pp.327-333
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• 2017

BACKGROUND/OBJECTIVES: Complications of diabetes, such as cardiovascular disease, are associated with increased mortality among type 2 diabetes mellitus patients. Homocysteine has been recently identified as a predictor of cardiovascular disease-related complications in diabetes. We investigated whether or not supplementation with folic acid tablets can lower homocysteine levels and improve parameters related with vascular complications. SUBJECTS/METHODS: We conducted a non-randomized 8-week trial involving postmenopausal diabetic women (n = 25) supplemented with $800{\mu}g$ of folic acid ($400{\mu}g$ twice a day) daily. Subjects' serum levels of folate, homocysteine, and vitamin $B_{12}$ were measured, along with vascular function and brachial-ankle pulse wave velocity. RESULTS: Folic acid supplementation significantly increased serum folate levels (P < 0.0001), reduced homocysteine levels (P < 0.0001), and increased vitamin $B_{12}$ levels (P = 0.0063). There were significant decreases in low-density lipoprotein cholesterol levels as well as the ratios of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol and total cholesterol to high-density lipoprotein cholesterol. Brachial-ankle pulse wave velocities were not altered by supplementation. Changes in serum vitamin $B_{12}$ after folic acid supplementation were negatively correlated with changes in brachial-ankle pulse wave velocity. CONCLUSIONS: In this study on postmenopausal Korean women with type 2 diabetes mellitus, folic acid supplementation reduced serum homocysteine levels, increased serum folate and vitamin $B_{12}$ levels, and lowered lipid parameters.

• Smart Structures and Systems
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• v.7 no.4
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• pp.241-262
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• 2011

Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.

• The KSFM Journal of Fluid Machinery
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• v.16 no.2
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• pp.48-53
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• 2013

This paper presents a numerical investigation of the influence of the blade back sweep angle on the performance and flow characteristics in a centrifugal compressor with a vaneless diffuser. Five impellers with different back sweep angles were tested in the flow simulations. It was found that a low back sweep angle could improve the total-to-total pressure ratio and the work coefficient over whole operating ranges. However, the flow field in an impeller with a low back sweep angle produced a more non-uniform velocity distribution at the impeller exit because the wake region was significantly increased. As a consequence, the impeller with a low back sweep angle caused a low diffuser performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.77-80
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• 1998

Recently, extending the local broadcasting and increasing lots of informations. The low-loss communication cable is required in proportion as frequency .The reason of transportation loss causes to using the high frequencies like hundreds of MHz or decades of GHz. For the low transportation loss. It is required the developing-technology of foaming and the high foamed insulator with the dielectric ratio of the nearest to 1. Therefor, there is the purpose of developing the insulating materials for the low dielectric ratio. Also it is important to measure the attenuation, which is one of the important parameters.sa the evaluation of transportation characteristic with frequency in the communication cable. In this paper,the result showed that the dielectric ratio(1.4) of the nearest to 1 and low attenuation with high frequency were very related to the transportation and reflection characteristics such as propagation velocity (82.27%). Delay time and voltage standing wave ratio(VSWR).

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.7
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• pp.1840-1850
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• 1994

Enhancement of numerical algorithms for low speed compressible flow will be considered. Contemporary time-marching algorithm has been widely accepted and applied as the method of choice for transonic, supersonic and hypersonic flows. In the low Mach number regime, time-marching algorithms do not fare as well. When the velocity is small, eigenvalues of the system of compressible equations differ widely so that the system becomes very stiff and the convergence becomes very slow. This characteristic can lead to difficulties in computations of many practical engineering problems. In the present approach, the time-derivative preconditioning method will be used to control the eigenvalue stiffness and to extend computational capabilities over a wide range of flow conditions (from very low Mach number to supersonic flow). Computational capabilities of the above algorithm will be demonstrated through computation of a variety of practical engineering problems.

• Journal of agricultural medicine and community health
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• v.24 no.1
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• pp.1-11
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• 1999

This study was carried out to find out if peripheral neuropathy was resulting from exposed to pesticides in farmers. Thirty four male farmers in rural area of Chungju were selected as a study group. According to the farm type and area, the group was subdivided into two groups: the high exposed group(n=20) and the low exposed group(n=14). Nerve conduction velocity tests were done on four nerves of the dominant arm(median motor, median sensory, ulnar sensory, and ulnar motor) and three nerves of the dominant leg(peroneal motor, sural sensory, and posterior tibial motor). On the nerve conduction study, all of the results were included normal range. But comparing to reference mean values, most of results were significantly decreased(P < 0.01 by t-test). And the median motor conduction velocity and the peroneal nerve latency were significantly increased in the high exposed group than the low exposed group and reference values. But we concluded that these findings are caused by age difference not pesticide exposure. In conclusion, we cannot find any abnormality of nerve conduction velocity caused by exposure to pesticide in this study group.