• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권6호
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• pp.359-367
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• 2004

The switched reluctance motor(SRM) has considerable potential for industrial applications because of its high result lily as a result of the absence of rotor windings. In some applications with SRM, paralleling strategy is often used for cost saving, increasing of current capacity and system reliability. A SRM inverter has very low ,switching frequency. This results in reducing the burden for a high-speed of the gate-amp interface circuit. and the linearity of optocoupler is used to protect the instantaneous peak current for the stable operation. In this paper, series resistor is used to equal the current sharing of each switching device and a linear gate-amp is proposed to protect the instantaneous peak current which occurs in transient state. The proposed paralleling strategy is verified by experimental results.

• 치과방사선
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• 제20권2호
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• pp.315-333
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• 1990

This study was performed to measure the skin absorbed doses from full mouth standard intraoral radiography (l4 exposures) in bisecting angle and paralleling techniques. Thermoluminescent dosimeters were used in a phantom. Circular tube collimator(60㎜ in diameter, 20㎝ in length) and rectangular collimator(35㎜ × 44㎜, 40㎝ in length) were set for bisecting angle and paralleling techniques respectively. All measurement sites were classified into 8 groups according to distance from each point of central rays. The results were as follows: 1. The skin absorbed doses from the paralleling technique were significantly decreased than those from the bisecting technique in both points at central ray and points away from central ray. The percentage rates of decrease were greater at points away from central ray than those at central ray. 2. The skin absorbed doses at the lens of eye, parotid gland, submandibular gland and thyroid region were significantly decreased in paralleling techniuqe, but those of the midline of palate remained similar in both techniques. 3. The highest doses were measured at the site 20mm above the point of central ray for the mandibular premolars in bisecting angle technique and at the point of central ray for the mandibular premolars in paralleling techniques. The lowest doses were measured at the thyroid region in both techniques.

• 치위생과학회지
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• 제11권3호
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• pp.155-161
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• 2011

본 연구는 치근단 필름 촬영에 있어서 촬영법에 따른 실책율을 살펴봄으로써 향후 효율적인 촬영기술 습득과 학생의 지도를 위한 기초 자료를 얻고자 시행되었다. 2009년 3월부터 2010년 12월까지 D 보건대학 및 S 보건대학 치위생과 학생들을 대상으로 촬영한 필름 14,402매를 분석하고, 등각촬영법과 평행촬영법의 촬영 실습수업을 이수한 학생 263명을 대상으로 현상과정에서 가장 어려웠던 점에 관한 설문조사를 실시하여 다음과 같은 결과를 얻었다. 1. 등각촬영법으로 촬영한 경우 상 하악 모두 대구치부에서 실책율이 가장 높았다. 2. 평행촬영법으로 촬영한 경우 상악에서는 소구치부, 하악에서는 대구치부에서 실책율이 가장 높았다. 3. 촬영기술상의 실책은 등각촬영법과 평행촬영법 모두 필름위치의 부정확이 가장 높게 나타났으며, 등각촬영법이 평행촬영법에 비해 실책율이 높게 나타났다. 4. 현상기술상의 실책은 등각촬영법과 평행촬영법 모두 어두운 상과 밝은 상이 가장 높게 나타났으며, 등각 촬영법이 평행촬영법에 비해 실책율이 높게 나타났다. 5. 학생들은 현상과정에서 현상의 정도를 파악하는 것을 가장 어려워하는 것으로 나타났다. 이상의 결과로 살펴볼 때, 치근단 촬영 시 실책율을 줄이기 위해서는 구강 내 형태학적, 해부학적 구조의 이해가 필요하며, 충분한 시간을 가지고 여러 번 반복 촬영하여 숙련도를 높이는 것이 중요하다고 생각된다.

• 치과방사선
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• 제28권2호
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• pp.471-489
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• 1998

For the successful endodontic treatment, root canal should be cleaned thoroughly by accurate mechanical and chemical canal preparation and sealed completely with canal filling material without damaging the periapical tissues. The accuracy of the root canal length measurement is a prerequisite for the success of the endodontic treatment, and the root canal length is often determined by the standard periapical radiographs and digital tactile sense. In this study, the accuracy and the clinical usefulness of Digora/sup (R)/, an intraoral digital imaging processor and the conventional standard radiographs were compared by measuring the length from the top of the file to the root apex. 30 single rooted premolars were invested in a uniformly sized blocks and No.25 K-file was inserted into and fixed in each canal. Each block was placed in equal distance and position to satisfy the principle of the bisecting angle and paralleling techniques and Digora/sup (R)/ system's image and standard periapical radiographs were taken. Each radiograph was examined by 3 different observers by measuring the length from top of the file to the root apex and each data was compared and analyzed. The results were as follows; 1. In the bisecting angle technique, the average difference between the Digora/sup (R)/ system and standard periapical radiograph was 0.002 mm and the standard deviation was 0.341 mm which showed no statistically significant difference between the two systems(p>0.05). Also, in the paralleling technique, the average difference between these two system was 0.007 mm and the standard deviation was 0.323 mm which showed no statistically significant difference between the two systems(p>0.05). 2. In Digora/sup (R)/ system, the average difference between the bisecting angle and paralleling technique was -0.336 mm and the standard deviation was 0.472 mm which showed a statistically significant difference between the two techniques(p<0.05). Also, in the standard periapical radiographs, the average difference between the bisecting angle and paralleling technique was 0.328 mm and the standard deviation was 0.517 mm which showed a statistically significant difference between these two techniques(p<0.05). 3. In Digora/sup (R)/ system and the standard periapical radiographs. there was a statistically significant difference between the measurement using the bisecting angle technique and the actual length(p<0.05), But there was no statistically significant difference between the measurement using the paralleling technique and the actuallength(p>0.05). In conclusion. the determination of the root canal length by using the Digora/sup (R)/ system can give us as good an image as the standard periapical radiograph and using the paralleling technique instead of the bisecting angle technique can give a measurement closer to the actual canal length. thereby contributing to a successful result. Also. considering the advantages of the digital imaging processor such as decreasing the amount of exposure to the patient. immediate use of the image. magnification of image size. control of the contrast and brightness and the ability of storing the image can give us good reason to replace the standard periapical radiographs.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2004년도 학술대회 논문집
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• pp.237-240
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• 2004

For the paralleled operation of DC/DC converters, the current sharing between each modules is the most important for the reliability of the power system. Interleaving method is commonly used with many paralleling schemes for the reduction of the ripple in the output voltage of paralleled converters and there are many commercial IC for interleaving application appliable. But for all of them, it is impossible to detect the number of module in operating and then change the phase of them automatically. In this paper, a novel paralleling method is proposed for the converter parallel operation, which detects the number of modules in active and sets the phases of PWM signals applied to each modules autonomously. This can greatly improve the output voltage ripple and reliability of the system. The expandibility of modular number can be done very easily by just adding several parts.

• 조명전기설비학회논문지
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• 제24권9호
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• pp.62-70
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• 2010

Fuel cell system which can solve the environmental problem is receiving attention. To use utility power necessary power conversion system from low voltage that is generated by fuel cell system. because fuel cell has special characteristic of low voltage high current. To improve PCS's efficiency the paralleling method is used. Available the method could reduce the switching loss. But the existing research could not be found optimal result and accompanying several effects. In this study analysis several effects causing the parallel method. The effects have been demonstrated through simulations and experiments.

• Journal of Power Electronics
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• 제14권4호
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• pp.788-795
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• 2014

This paper demonstrates the dynamic behaviors of paralleled high power IGBTs using trench and fieldstop technologies. Four IGBTs are paralleled and standard deviation is adopted to represent the imbalance. Experiments are conducted under three different operation conditions and at different temperatures ranging from $-25^{\circ}C$ to $125^{\circ}C$. The experimental results show that operation at very low and very high temperatures usually aggravates the switching behaviors. There is a trade-off between the balance and the losses at low temperatures. These results can help in the design of heat sinks in paralleling applications confronting very low temperatures.

• 치위생과학회지
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• 제4권3호
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• pp.97-102
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• 2004

구내표준방사선사진의 촬영에 있어서 촬영법에 따라 어떤 실책을 얼마나 범하는지를 파악하여 앞으로의 학생지도에 필요한 자료를 얻고자 D보건대학 치위생과 학생들을 대상으로 수업한 결과 필름 3251매를 분석하고, 등각촬영법과 평행촬영법의 촬영실습수업을 이수한 학생 120명을 대상으로 설문조사를 하여 아래와 같은 결과를 얻었다. 1. 등각촬영법으로 촬영한 경우에는 상 하악 모두 견치부에서 실책률이 가장 높았다. 2. 평행촬영법으로 촬영한 경우에는 상 하악 모두 소구치부에서 실책률이 가장 높았다. 3. 촬영기술상의 실책은 상의 연장이 가장 빈도가 높았다. 4. 실책률과 왜곡량 모두 평행촬영법에 비해 등각촬영법에서 높게 나타났다. 5. 필름처리과정에서의 실책은 저현상이 가장 빈도가 높았다. 6. 학생들은 등각촬영법에서는 중심방사선의 수직각 조절을, 평행촬영법에서는 필름고정기구를 구강내에 고정시키는 것을 가장 어렵게 느끼고 있었다. 7. 학생들은 현상과정에서는 현상정도 파악을 가장 어려워하는 것으로 나타났다. 이상의 결과를 종합해 볼 때 구내표준촬영법을 익힘에 있어서 학생들은 수직각조절 미숙으로 인한 실책을 가장 많이 범하며, 현상과정에서 현상정도 파악을 가장 어려워하는 것으로 나타났다. 따라서 학생들이 실책을 줄이고 수면 효율을 높이기 위해서는 해부학적 구조를 충분히 이해하고 공간적인 개념을 가지고 접근할 수 있도록 하는 지도와 함께 각자의 기준을 설정할 수 있도록 개인의 선행 학습 수준에 맞는 1:1 지도가 요구된다. 이를 위해서는 충분한 시간과 보조인력의 확충이 필요하다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2011년도 전력전자학술대회
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• pp.271-272
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• 2011

The rising popularity of renewable energy sources resulted in development of the units of higher rated powers. As a result of the limited power handling capacity of individual devices, paralleling is the choice to increase the equipment rating, while keeping the THD of the current at the PCC within the agency specified standards. And their typical power circuit configuration limits the stress on individual devices to an appreciable extent. The main scope of this paper is the analysis of filter structure in paralleling inverter system's operation. Simulation results are shown to verify the theoretical analysis.

• 한국치위생학회지
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• 제12권5호
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• pp.987-997
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• 2012

Objectives : This study was carried out in order to obtain basic data for students' efficient acquirement and instruction of radiography technology in the future by surveying dental hygiene students' recognition of periapical radiography. Methods : This study carried out a questionnaire survey targeting dental hygiene students from December 2009 to December 2010, and obtained the following results. Results : 1. As a result of examining recognition on periapical radiography, the bisecting angle technique was indicated to be averagely $3.84{\pm}0.566$ points. The paralleling technique was indicated to be $2.66{\pm}0.701$ points. 2. As a result of examining about problems given the bisecting angle technique, what had been most difficult given the bisecting angle technique was indicated to be the highest in cone positioning with 34.2%. The most difficulty given deciding on the X-ray vertical-angel irradiation direction was indicated to be the highest with 66.9% in adjusting the cone direction on the virtual bisector. 3. As a result of examining about problems given the paralleling technique, what had been most difficult in the process of the paralleling technique was indicated to be the highest with 56.7% in fixing the film immobilization device inside the mouth. Conclusions : Examining the above results, it is considered that there is a need of understanding morphological and anatomical structure inside the mouth in order to reduce the mistake rate given the periapical radiography, and that it is important to increase skill level by repetitively shooting several times with having enough time.