• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.275-282
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• 2004

The engine bearing transmits the powers from cylinder to crankshaft with small clearance between con-rod and crankpin. The minimum oil film thickness is a significant parameter in the operation of bearing. The contact pressure of bearing should be considered for the reason that elastic deformation of bearing be caused by contact pressure of bearing. There are important factors which are maintaining of minimum oil film thickness expecting of the length of maximum and minimum oil film thickness with changing of the loads to keep running normally. Furthermore, this study is very crucial to develop the design of engine bearing and crankshaft system.

• Journal of the Korean Operations Research and Management Science Society
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• v.24 no.1
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• pp.39-48
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• 1999

An economic procedure of selective assembly is proposed when a product is composed of two mating components. The major qualify characteristic of the product is the clearance between the two components. The components are divided into several classes prior to assembly. The component characteristics are assumed to be independently and normally distributed with equal variance. The procedure is designed so that the proportions of both components in their corresponding classes are the same. A cost model is developed based on a quadratic loss function and methods of obtaining the optimal class limits as well as the optimal number of classes are provided. Formulas for obtaining the proportion of rejection and the unavailability of mating components are also provided. The proposed model is compared with the equal width and the equal area partitioning methods using a numerical example.

• 유체기계공업학회:학술대회논문집
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• 2003.12a
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• pp.404-411
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• 2003

Three-dimensional vortical flow and separated flow topology near the casing wall in an axial flow fan having two different tip clearances have been investigated by a Reynolds-averaged Wavier-Stokes (RANS) flow simulation. The simulation shows that the tip leakage vortex formed close to the leading edge of the blade tip on suction side grows in the streamwise direction. On the casing wall, a separation line is formed upstream of the leakage vortex center due to the interference between the leakage vortex and main flow. The reverse flow is observed between the separation line and the attachment line generated downstream of the trailing edge, and increased with enlarging tip clearance. The patterns of a leakage velocity vector including a leakage flow rate are also analyzed according to two tip clearances. It is noted that the understanding of the distribution of a limiting streamline on the casing wall is very important to grasp the characteristics of the vortical flow in the axial flow fan.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.585-592
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• 2009

The performance of screw compressor depends on lots of design parameters of rotor profile, such as length of seal line, wrap angle, blow hole, suction and discharge port size, number of rotor lobe, etc. The optimum rotor profile makes it possible to increase the compression efficiency with low energy consumption, and to minimize the loss of power. In this research, a new rotor profile design and performance analysis are done by computer simulation. It is expected that the volumetric efficiency is improved because the internal leakage is reduced due to the minimization of blow hole and clearance, and the stiffness of rotors is increased due to the reduction of length to diameter ratio. Also, the specific power consumption will be secured for use ranging from low to high operation speed.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.303-309
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• 2019

A hybrid control of a rectifier/regulator of wireless power transfer systems for electric vehicles is studied. A combined rectifier/regulator is used for charging control. The hybrid control comprises integral cycle control and pulse width modulation control to cope with the variations in the induced voltage due to clearance and alignment. The hybrid control has good control capability and does not cause severe switching loss. A 22 kW prototype of the Wireless Power Transfer class 4 charging system defined by the Society of Automotive Engineers is constructed and tested to verify the proposal.

• Tribology and Lubricants
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• v.34 no.3
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• pp.107-114
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• 2018

This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.

• The Korean Journal of Malacology
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• v.21 no.1
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• pp.47-56
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• 2005

A series of radiotracer experiments were employed to quantitatively compare the biokinetics of uptake from the dissolved phase (influx rates), uptake from the various types of food source (assimilation efficiency), and loss (efflux) of Ag between Potamocorbula amurensis and Macoma balthica. Simultaneously, influx rates of dissolved Cd in both clams were determined to compare with those of Ag. Effects of salinity on influx rates were evaluated in these 2 euryhaline species, as were effects of clam size. Influx rate of Ag and Cd (${\mu}g g^{-1}$ [dry wt.] $d^{-1}$) increased linearly with metal concentrations. Influx rates of Ag in both clams were 3 to 4 times those of Cd. Absolute influx rates of the 2 metals were 4 to 5 times greater in P. amurensis than M. balthica, probably because of differences in biological attributes (i.e. clearance rate or gill surface area). As salinity was reduced from 20 to 2.5 psu, the influx rate of Cd in P. amurensis increased 4-fold and that of Ag increased 6-fold, consistent with expected changes in speciation. Weight-specific metal influx rates (${\mu}g g^{-1}$ [dry wt.] $d^{-1}$) were negatively correlated with the tissue dry weight of the clams, but most rate constants determining physiological turnover of assimilated metals were not affected by clam size.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.33-41
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• 2014

In a supersonic turbine, A rotor overlap technique reduced the chance of chocking in the rotor passage, and made the design pressure ratio satisfied. However, the technique also made additional losses, like a pumping loss, expansion loss, etc. Therefore, an approximate optimization technique was appled to find the optimal shape of overlap which maximizes the improvement of the turbine performance. The design variables were shape factors of a rotor overlap. An optimal design for rotor overlap reduces leakage mass flow rate at tip clearance by about 50% and increases about 4% of total-static efficiency compared with the base model. It was found that the most effective design variable is the tip overlap and that the hub overlap size is the lowest.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.22
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• pp.9985-9996
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• 2014

Background and Aim: Laparoscopic and open rectum surgery for rectal cancer remains controversial. This systematic review compared the short-term and long-term efficiency and complications associated with laparoscopic and open resection for rectal cancer. Materials and Methods: We searched PubMed, Embase, Cochrane Library, ISI Web of Knowledge and the China Biology Medicine Database to identify potential randomized controlled trials from their inception to March 31, 2014 without language restriction. Additional articles were identified from searching bibliographies of retrieved articles. Two reviewers independently assessed the full-text articles according to the pre-specified inclusion and exclusion criteria as well as the methodological quality of included trials. The meta-analysis was performed using RevMan 5.2. Results: A total of 16 randomized controlled trials involving 3,045 participants (laparoscopic group, 1,804 cases; open group, 1,241 cases) were reviewed. Laparoscopic surgery was associated with significantly lower intraoperative blood loss, earlier return of bowel movement and reduced length of hospital stay as compared to open surgery, although with increased operative time. It also showed an obvious advantage for minimizing late complications of adhesion-related bowel obstruction. Importantly, there were no significant differences in other postoperative complications, oncological clearance, 3-year and 5-year or 10 year recurrence and survival rates between two procedures. Conclusions: On the basis of this meta-analysis we conclude that laparoscopic surgery has advantages of earlier postoperative recovery, less blood loss and lower rates of adhesion-related bowel obstruction. In addition, oncological outcome is comparable after laparoscopic and open resection for rectal cancer.

• Clinical and Experimental Pediatrics
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• v.46 no.9
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• pp.921-925
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• 2003

Intestinal lymphangiectasia, one of the protein-losing gastroenteropathies, is an uncommon disease characterized by dilated intestinal lymphatics, enteric protein loss, edema, hypoalbuminemia, and lympocytopenia. Small bowel biopsy and CT have been used to confirm the diagnosis of intestinal lymphangiectasia. Small bowel biopsy shows collections of abnormal dilated lacteals in submucosa with distortion of villi and CT findings have been described as diffuse nodular thickening of the small bowel and as linear hypodense streaking densities in the small bowel caused by dilated lymphatic channels. Demonstration of increased enteric protein loss using $^{51}Cr-$, $^{131}I-$ or $^{99m}Tc-labeled$ albumin, timed measurement of fecal excretion of radioactivity or by measuring fecal clearance of alpha 1-antitrypsin can also help the diagnosis. We experienced a rare case of intestinal lymphangiectasia in an eight year old boy who presented with facial edema, abdominal distension and intermittent diarrhea. We report a patient with intestinal lymphangiectasia, in whom abdominal CT, $^{99m}Tc-labeled$ albumin scintitigraphy, and stool alpha 1-antitrypsin measurement played key roles in determining the diagnosis. A brief review of literature was made.