• Journal of ILASS-Korea
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• v.9 no.1
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• pp.8-14
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• 2004

future exhaust emission limits for diesel-driven passenger cars will force the automotive company to significantly develop of the new technologies of diesel engine respectively of the drive assemblies. As we know, the contributions of soot and nitrogen oxide is the main problems in diesel engine. Recently, as a result, the pilot injection of common-rail fuel injection system recognizes an alternative function to solve an environmental problem. This study describes the effect of the nozzle structure and driven characteristic of injector on pilot injection fur a passenger car common-rail system. The pilot spray structure such as spray tip penetration, spray speed and spray angle were obtained by high speed images, which is measured by the Mie scattering method with optical system fur high-speed temporal photography. Also the CFD analysis was carried out for fuel behavior under high pressure in between needle and nozzle of injector for common-rail system to know the condition of initial injection at experiment test. It was found that solenoid-driven injector with 5-hole was faster than 6-hole injector in spray speed at same conditions and piezo-driven injector showed faster response than solenoid injector.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.4
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• pp.285-292
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• 2009

In this paper, when ac motors are driven by the diode rectifier/Z-source inverter system, the common-mode voltages of system are analyzed in details under both the shoot-through state and non-shoot-through state through equivalent circuits. Then a modified space vector modulation strategy is suggested for attenuating the negative common-mode voltage by eliminating the zero voltage vector, and also controlling the shoot-through time. Through the simulation studies with PSIM and experiments with 32-bit DSP, it is verified that the negative common-mode voltage can be reduced by more than 50%.

• Journal of Power Electronics
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• v.18 no.3
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• pp.923-930
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• 2018

Based on the application of an integrated dynamic brake (IDB) system that uses a PWM inverter fed-AC motor drive to operate the piston, a new active zero state PWM (AZSPWM) is proposed to improve the stability and reliability of the IDB system by suppressing the conducted electro-magnetic interference (EMI) noise under a wide range of load torque. The new AZSPWM reduces common-mode voltage (CMV) by one-third when compared to that of the conventional space vector PWM (CSVPWM). Although this method slightly increases the output current ripple by reducing the CMV, like the CSVPWM, it can be used within the full range of the load torque. Further, unlike other reduced common-mode voltage (RCMV) PWMs, it does not increase the switching power loss. A theoretical analysis is presented and experiments are performed to demonstrate the effectiveness of this method.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.251-256
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• 2003

The capability of pilot injection with small fuel quantity at all engine operating conditions is one of the main feature of the common rail system. The purpose of the pilot injection is to lower the engine noise and to reduce the NOx emissions. This study describes the pilot spray structure characteristics of the common-rail diesel injectors, solenoid-driven and piezo-driven type, with different electric driving characteristics So, three common-rail injectors with different electric current wave were used in this study. The pilot spray characteristics such as spray speed, spray tip penetration, and spray angle were obtained by spray images, which is measured by the back diffusion light illumination method with optical system for high-speed temporal photography. Also the CFD analysis was carried out for fuel behavior under high pressure in between needle and nozzle of solenoid-driven injector to know the condition of initial injection at experiment test. It was found that pilot injection of common-rail system was effected by rate of injection and temperature of injected fuel and electrical characteristic of the driven injector.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.17 no.3
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• pp.155-161
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• 2014

Purpose: Constipation is a common pediatric problem worldwide. This study aims to describe the clinical characteristics of pediatric constipation in south Jordan according to gender and age group. Methods: All patients with constipation managed at our pediatric gastroenterology service between September 2009 and December 2012 were included. Hospital charts were reviewed. Demographic data, clinical characteristics, and final diagnosis were recorded. Data were analyzed according to gender and the following age groups: infants, pre-school, school age, and adolescents. Results: During the study period, 126 patients were enrolled. The number (percentage) of patients according to age were the following infants: 43 (34.1%), pre-school: 55 (43.7%), school age: 25 (19.8%), and adolescents: 3 (2.4%). Males made up 54.8% of the study population. There were no statistical gender differences in any age group. The most common symptom in all age groups was dry, hard stool. Infrequent defecation was found in almost one-half of the patients. Fecal incontinence was more common in school-aged children compared to pre-school-aged children and adolescents. Abdominal pain was seen in almost 40% of the constipated children. Abdominal pain was more prevalent in girls and older children. Fecal mass in the rectum was the most common physical finding, with constipated boys exhibiting higher rates. Functional constipation was the most common etiology. Conclusion: Clinical characteristics of constipation in children vary according to age group and gender. Older children had less frequent bowel motions, a longer duration of symptoms, and a higher prevalence of long-standing constipation compilations (fecal incontinence and abdominal pain).

• Journal of Physiology & Pathology in Korean Medicine
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• v.22 no.1
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• pp.234-245
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• 2008

Yeonkyopaedok-san(YPS) extract is widely used to treat the common cold. The purpose of this study was to evaluate the efficacy of YPS on the common cold. Two hundred Patients with common colds of recent onset were randomized to the double blind, placebo-controlled study. They received 800 mg YPS extract or placebo in capsules, orally dissolved 3 times a day for 7 days. The total symptom score was assessed by the physician, using a 5-point scale on start and finish. Resolution of cold symptoms based on subjective daily symptoms. Total symptom score was significantly decreased in YPS groups in comparison to that in placebo group (p=0.027). Headache (p=0.012), loss of appetite (p=0.037), eyeball discomfort (p=0.002) were more affected. Time to resolution of cold symptoms did not show significant effect (p=0.592). Adverse effects were less in the YPS group than placebo group (2% vs 3%). In this community-based, randomized controlled trial, YPS were effective in treating cold symptoms in college students.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.109-114
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• 2006

The reformed bio-diesel fuel irradiated by the ultrasonic wave is applied to the diesel engine of common rail in common use recently. This study has the object to examine the properties of engine performance and discharged materials. The bio-diesel fuel is mixed and used with the diesel fuel in common use at the ratio of $20\%\;or\; 100\%$. The ultrasonic energy is irradiated to the individually mixed fuel in order to reform the fuel. This fuel is applied to the engine in this experiment. And It is compared and analyzed from the experimental results with two cases irradiating the ultrasonic wave and no irradiating.

• Korean Journal of Head & Neck Oncology
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• v.15 no.2
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• pp.211-216
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• 1999

We analyzed retrospectively the 74 patients with salivary tumors who were treated surgically at Chonbuk National University Hospital. The following results were obtained: 1) The most prevalent site was parotid gland and minor salivary gland is second in order. The most prevalent site of minor salivary gland tumor was palate. 2) Slow-growing painless mass was the most common chief complaints. 3) The most frequnet age incidence was 4th and 6th decades. 4) Sex ratio of male to female was 1:1.1, but in minor salivary gland tumor, female was more prevalent and sex ratio of male to female was 1:1.5. 5) Histopathologically, the most common salivary gland tumor was pleomorphic adenoma. Among the benign tumors, the pleomorphic adenoma was most common and Warthin's tumor was next. Among the malignant tumors, the mucoepidermoid carcinoma was most common and adenoid cystic carcinoma, adenocarcinoma were the next. 6) 59 patients with benign tumor and 15 patients with malignant tumor were treated with operative therapy. Among patients with malignant tumor, 12 patients were treated with postoperative radiation therapy. 7) Overall incidence of postoperative complication was 14.9% and the most common complication was transient facial nerve weakness and hematoma.

• Journal of The Korean Association For Science Education
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• v.17 no.4
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• pp.405-413
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• 1997

High school common science is introduced by the sixth national curriculum. It consists of physics, chemistry, biology and earth science like the secondary school science. In this paper, textbooks are analyzed by the science teachers and the status of the present teaching and learning methods is reported. The detailed results are as follows; 1. Almost high school teachers choose textbook that included little the STS material. More than two teachers are teaching the high school common science and when they are chosen, they are independent with their major. 2. According to the national curriculum, they evaluated the textbooks as it is below the middle level. This evaluations are not dependent on teachers' comparement and textbook's class except the several matters based on STS (science-technology-society). 3. The teacher teaching the high school common science thought that teaching the textbook in school is worse than analysizing it. they must have emphasised on learning of inquire method than system of knowledge, introduction to material connected with real life and STS in the high school common science.

• Journal of electromagnetic engineering and science
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• v.15 no.2
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• pp.89-96
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• 2015

This paper describes the application of a passive noise cancellation method to a prototype inductor-inductor-capacitor (LLC) resonant converter by placing a compensation winding in a transformer to reduce common mode noise. The connection method for the compensation winding is investigated. A circuit analysis is implemented for the displacement currents between the primary and secondary windings in the transformer. The analyzed displacement currents are verified by performing a circuit simulation and a proper compensation winding connection that reduces common mode noise is found. The measurement results show that common mode noise is reduced effectively up to 20 dB in the 1 to 7 MHz frequency region for the prototype LLC resonant converter by using the proposed passive noise cancellation method.