• Journal of Welding and Joining
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• 제24권1호
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• pp.43-49
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• 2006

This paper describes the friction surface modification which has been successfully developed with the friction stir welding recently There are several problems including just position control and backlash in conventional friction surface modification system. Therefore it has been developed the friction surface modification system which has been controlled precisely both position and force by driving hydraulic cylinder in this paper. The mechtrode rotation speed(N) and feeding speed(Vz), travel speed(Vx,y) are of critical importance for the width and thickness of the coating in friction surfacing process. But there is no theoretical method of determining interrelations between process parameters affect the coating width and thickness. As a result of DOE(design of experiment) with developed system, the coating thickness and width seemed to decrease according to increase the mechtrode rotation speed(N) and traveling speed(Vx,y), to decrease feeding speed(Vz) apparently. However as the result of regression analysis the main effect was only the mechtrode rotation speed in the coating thickness.

• 대한물리의학회지
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• 제18권2호
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• pp.71-82
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• 2023

PURPOSE: This study examined the effect of training using video content on abdominal muscle thickness, Oswestry disability index (ODI), and pain in college students with chronic back pain. METHODS: Twenty-nine college students with chronic back pain participated in this study. The subjects were assigned randomly to 15 experimental groups who trained using video content and 14 control groups who exercised voluntarily using back exercise leaflets. The video used for the intervention was obtained from YouTube, and the difficulty level of the video was classified into six levels. Both groups participated in the intervention for 40 minutes/day, three times a week for six weeks, and the variables of abdominal muscle thickness, ODI, and pain were compared before and after the intervention. RESULTS: In the experimental group, there were statistically significant changes in the thickness of the internal oblique and transverse abdominis muscles, ODI, and pain after the intervention, except for the external oblique muscle (p < .05). In the control group, there was no statistically significant difference in all variables after the intervention (p > .05). A statistically significant difference in all variables was observed between the experimental group and the control group after the intervention except for the external oblique muscle (p < .05). CONCLUSION: Treatment of chronic low back pain using video content is a possible alternative treatment if quality images are selected and the difficulty levels are adjusted.

• 소성∙가공
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• 제8권3호
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• pp.269-275
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• 1999

A variable blank holding force method is proposed to improve deep drawing characteristics of sheet materials. In this method, the blank holding force (BHF) is controlled throughout a drawing process so that the punch load does not exceed a critical value, which is slightly less than the conventional process with the conforming process with the variable BHF is more flexible than the conventional process with the constant BHF and it could be used for improving the product's quality and drawability. In this paper we suggest a method controlling the BHF as a function of punch travel during the forming process. The optimization BHF curves are determined theoretically and experimentally. It is concluded that for the case of optimum BHF control methods the drawn cup height and the drawing formability achieved by this method are increased than those for constant BHF method. Also, as comparing the wall thickness distribution of the cup drawn by the constant BHF and the optimum BHF control, the BHF control reduce the wall thickness variation of the drawn cup at the cup wall and make the cup thickness distribution more uniformly than the constant BHF.

• Corrosion Science and Technology
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• 제23권3호
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• pp.228-234
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• 2024

Zinc wiping is a phenomenon used to control zinc-coating thickness on steel substrate during hot dip galvanizing by equipment called air knife. Uniformity of zinc coating weight in length and width profile along with surface quality are most critical quality parameters of galvanized steel. Deviation from tolerance level of coating thickness causes issues like overcoating (excess consumption of costly zinc) or undercoating leading to rejections due to non-compliance of customer requirement. Main contributor of deviation from target coating weight is dynamic change in air knives equipment setup when thickness, width, and type of substrate changes. Additionally, cold coating measurement gauge measure coating weight after solidification but are installed down the line from air knife resulting in delayed feedback. This study presents a coating weight control model (Galvantage) predicting critical air knife parameters air pressure, knife distance from strip and line speed for coating control. A reverse engineering approach is adopted to design a predictive, prescriptive, and descriptive model recommending air knife setups that estimate air knife distance and expected coating weight in real time. Implementation of this model eliminates feedback lag experienced due to location of coating gauge and achieving setup without trial-error by operator.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제21권3호
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• pp.288-297
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• 1999

This study has been carried out in order to measure the thickness of soft-tissue on lateral cephalographs based on body mass index(BMI) and the change in soft-tissue thickness after surgical correction of mandibular protrusion. The control material in cephalometric study comprised students at The Dental College, 38 persons, aged 21~24 years and the patient material comprised 20 women and 12men, aged 19~28 years with mandibular protrusion.The thickness of the soft-tissue based on BMI in control and study groups, the comparison between them, immediate postoperative change in the thickness, 6 months after surgery, ratio of soft-tissue response and correlation was established through various statistical methods. The result were as follows : 1. The groups based on BMI showed significant differences each other as regards the linear measurements. The thickest soft-tissue was measured 13.6mm, 15.47mm, 16.76mm at Ss, the thinnest at G' 6.0mm, 6.7mm, 7.26mm respectively. 2. The differences between control and experimental groups based on BMI showed to be significant. There were no differences at G'. The soft-tissue in prognathic patients was thicker at Ss, Ls and thinner at Li, Ls, Pg', Gn', Me'. Differential gap was greater in overweight groups. 3. The immediate soft-tissue change after surgery showed the increase at Li, Ls, Pg', Gn', Me' except G', Ls in all groups. 4. The postoperative soft-tissue change 6 months after surgery was similar with immediate change. The soft-tissue shows the increase in the thickness at Li, Pg', Gn', Me' and the greatest difference occurred at Li, 1.1mm, 0.98mm, 1.2mm respectively. 5. The patients with lower BMI index showed higher soft-tissue response to bony movement at Pg'. The immediate response ratio was 91%, 87%, 81% in A,B,C groups respectively, the response 6 months after surgery showed 96%, 91%, 84%.

• Clinical and Experimental Pediatrics
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• 제54권7호
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• pp.292-297
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• 2011

Purpose: Our study aimed to evaluated sex differences in clinical features of obese high school students. Methods: One hundred three obese high school students (body mass index [BMI]${\geq}$85th percentile) and 51 control students (BMI<85th percentile) were enrolled in this study. Anthropometric measurements were performed. Fasting serum glucose, insulin, aspartate aminotransferase, alanine aminotransferase, total cholesterol, triglyceride, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and high-sensitive C-reactive protein were measured. Abdominal fat thickness, degree of fatty liver, and carotid intima-media thickness were measured by ultrasound. Results: In control and obese groups, waist circumference was significantly longer in boys but body fat mass was Significantly higher in girls. In the control group, total cholesterol and LDL-C were higher in girls. In the obese group, however, aspartate aminotransferase, alanine aminotransferase and triglyceride were higher and HDL-C was lower in boys. Preperitoneal fat thickness was significantly higher in obese girls. In obese group, the degree of fatty liver was significantly higher in boys. Carotid intima-media thickness was not significantly different between boys and girls. Conclusion: Obese adolescents had distinguishable sex differences in body measurements, metabolic abnormalities, abdominal fat thickness and fatty liver. We can infer that these characteristics may extend into adult obesity.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.175.2-175
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• 2001

The strip profile and shape control is one of the most important technologies in Hot Rolling Mill System. Because the unbalance of strip´s shape and wave appearance between stands has a bad effect on Hot Rolling Mill System by making the inferior thickness, strip´s damage and so forth in factories. Many competition Plate Mill introduced shape control system, for example, pair cross-mill, work roll bender, which includes shape measuring instruments and shape control mathematical models. Shape meter, which is equipped for flatness, only does feedback control at the top of coil. And, for crown, we depend on initial setup value and there is no feedback control. Therefore we predict the shape of strip using rolling pressure, bender force and tension of inter-stand in ...

• 한국가구학회지
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• 제17권2호
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• pp.9-23
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• 2006

Control particleboards were significantly higher in thickness swelling than wood particle-polypropylene fiber composites and their thickness swelling increased with the increase of target density. In the composites, thickness swelling did not vary significantly with the increase of target density but increased with the increase of wood particle content. And the composites with fine wood particles were significantly lower in thickness swelling than those with coarse wood particles irrespective of target density and formulation. In the scanning electron microscopy, significantly higher thickness swelling in the composites with coarse wood particles was thought to be the result of more interfacial separations by higher swelling stresses.

• Geomechanics and Engineering
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• 제15권4호
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• pp.1017-1027
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• 2018

To explore the influence of coal thickness on the mechanical behavior and the failure characteristics of rock-coal-rock (RCR) mass, the experimental investigation of uniaxial compressive tests was conducted first and then a systematic numerical simulation by particle flow code (PFC2D) was performed to deeply analyze the failure mechanical behavior of RCR specimens with different coal thicknesses in conventional compression tests. The overall elastic modulus and peak stress of RCR specimens lie between the rock and the coal. Inter-particle properties were calibrated to match the physical sample strength and the stiffness response. Numerical simulation results show that the deformation and strength behaviors of RCR specimens depend not only on the coal thickness, but also on the confining pressure. Under low confining pressures, the overall failure mechanism of RCR specimen is the serious damage of coal section when the coal thickness is smaller than 30 mm, but it is shear failure of coal section when the coal thickness is larger than 30 mm. Whereas under high confining pressures, obvious shear bands exist in both the coal section and the rock section when the coal thickness is larger than 30 mm, but when the coal thickness is smaller than 30mm, the failure mechanism is serious damage of coal section and shear failure of rock section.

• The Journal of Korean Physical Therapy
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• 제28권5호
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• pp.264-268
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• 2016

Purpose: This study was conducted to investigate the effects on muscle thickness and balance ability after performing plank exercise on various surface types. Methods: In this study, there were thirty healthy participants. Participants were randomly distributed into three groups, a control group (n=10), sling group (n=10), and ball group (n=10). All participants performed plank exercises three times a week for four weeks. Plank exercises consisted of five sets of 30 seconds each with a one minute break between each set. Muscle thickness of the transverse abdominis (TrA), internal oblique (IO), and external oblique (EO) was measured using an ultrasound diagnostic apparatus and balance was measured using I-balance. Results: Evaluation of muscle thickness revealed that the IO and EO muscle of the ball group changed significantly relative to the control group (p<0.05). However, there were no significant changes in balance. Conclusion: The results revealed that performing plank exercise on a ball is more effective among various types of surfaces.