• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.10 no.1
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• pp.66-78
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• 1998

Adequate ventilation with the proper amount of air to the right place is important factor to achieve a good Indoor air climate. Thus it is of prime importance that the ventilation system is working properly. This requires reliable pressure loss calculation to balance the air flow through duct systems. So a computer program for balancing CAV duct system is developed In this study. The results of CAV duct system is compared with the "Balans" code developed by Larsen from Norway. To obtain the pressure drop characteristics of damper at duct terminal, some experiments are performed using DPM(Dual Pressure Measurement) system. To adjust the resistance of damper, present study suggests that some special diffusers should be designed and damper producers should give the data of air flow vs. pressure drop to the customs when they manufacture the damper. One of the results concludes that the working time can be reduced from several minutes to several seconds per damper in the present experimental site, if the DPM system and the air volume adjusting process are used.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.915-916
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• 2015

The main sensor of AGV is the guide sensor in order to detect the path, and the sensor consists of 8 or 16-magneto resistance devices arranged by with 10mm. In controlling the AGV posture by using the sensor, AGV is occurred left/right shaking frequently. So, for driving stability of AGV, An accuracy of the sensor should be improved. Therefore, this study proposed sensor signal processing method to improve accuracy of guide sensor, and implemented. The accuracy of sensor in experimentation showed 2.84[mm]. In designing the sensor for controlling AGV posture, the proposed method will be effective.

• International Journal of Contents
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• v.11 no.4
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• pp.56-69
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• 2015

This paper proposes an efficient image encryption scheme based on quintuple encryption using two chaotic maps. The encryption process is realized with quintuple encryption by calling the encrypt(E) and decrypt(D) functions five times with five different keys in the form EDEEE. The decryption process is accomplished in the reverse direction by invoking the encrypt and decrypt functions in the form DDDED. The keys for the quintuple encryption/decryption processes are generated by using a Tent map. The chaotic values for the encrypt/decrypt operations are generated by using a Gumowski-Mira map. The encrypt function E is composed of three stages: permutation, pixel value rotation and diffusion. The permutation stage scrambles all the rows and columns to chaotically generated positions. This stage reduces the correlation radically among the neighboring pixels. The pixel value rotation stage circularly rotates all the pixels either left or right, and the amount of rotation is based on chaotic values. The last stage performs the diffusion four times by scanning the image in four different directions: Horizontally, Vertically, Principal diagonally and Secondary diagonally. Each of the four diffusion steps performs the diffusion in two directions (forward and backward) with two previously diffused pixels and two chaotic values. This stage ensures the resistance against the differential attacks. The security and performance of the proposed method is investigated thoroughly by using key space, statistical, differential, entropy and performance analysis. The experimental results confirm that the proposed scheme is computationally fast with security intact.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.279-285
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• 2018

Graphene is an interesting material because it has remarkable properties, such as high intrinsic carrier mobility, good thermal conductivity, large specific surface area, high transparency, and high Young's modulus values. It is produced by mechanical and chemical exfoliation, chemical vapor deposition (CVD), and epitaxial growth. In particular, large-area and uniform single- and few-layer growth of graphene is possible using transition metals via a thermal CVD process. In this study, we utilize polystyrene and boron oxide, which are a carbon precursor and a doping source, respectively, for synthesis of pristine graphene and boron doped graphene. We confirm the graphene grown by the polystyrene and the boron oxide by the optical microscope and the Raman spectra. Raman spectra of boron doped graphene is shifted to the right compared with pristine graphene and the crystal quality of boron doped graphene is recovered when the synthesis time is 15 min. Sheet resistance decreases from approximately $2000{\Omega}/sq$ to $300{\Omega}/sq$ with an increasing synthesis time for the boron doped graphene.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.10
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• pp.1984-1991
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• 2011

Among ground impedance measurement methods, the fall-of-potential method is the most thorough and reliable method. In the fall-of-potential method, ground electrode and auxiliary probes are placed in a straight line, and then, auxiliary potential probe is moved away from the ground electrode. The point at which plotted resistance curve flattens out is taken as right position of auxiliary potential probe. However, in some cases, it is hard to place ground electrode and auxiliary probes in a straight line. Therefore, we provided alternative placement method in this research. The method can be easily applicable to placing auxiliary probes. Also, this paper analyzed and compared ground impedance measurement standards of large grounding systems. Based on the analysis, practical measurement method using an earth tester was proposed. The proposed methods presented in this paper will be useful when determining locations of auxiliary probes in alternative positions, and the methods can be applied practically and easily.

• Korean Journal of Cleft Lip And Palate
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• v.4 no.2
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• pp.45-50
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• 2001

Recents reports have demonstrated that force and direction is important during mandibular distraction osteogenesis. The purpose of this study was to evaluate the resistant force of internal pterygoid muscles and inquire into relationship between internal pte'Ygoid muscles and cephalometric parameters. Eighty four patients with class III malocclusion underwent bilateral sgittal splitting of ramus with intraoral vertico-sagittal ramal osteotomy. A spring scale were used for measuring for resistence of internal pterygoid mescles after splitting of ramus. Skeletal-dental cephalometric analysis was made following statistic package was used for correlation between resistence and cephalometric parameters. The resistant force of right internal pterygoid muscle was greater than left muscle in Korean with class III malocclusion and the force had a linear regression relationship with facial depth (distance between nasion and gonion). The results suggested that facial depth has significant correlation of the resistance of internal pterygoid muscle (p<0.05).

• The Korean Society of Law and Medicine
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• v.12 no.1
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• pp.69-98
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• 2011

Asbestos has been used for roofing, walling and the like for the constructions since 60's~70's owing to its excellent fire resistance and heat insulative nature. However, it has banned to be used in major countries all over the world since WHO-affiliated International Agency for Research on Cancer (IARC) stipulated asbestos by a top carcinogen causing lung cancer, malignant mesothelioma and so on in 1986. Therefore, we had prohibited the use of asbestos on brakes for automobile since 2007 and on most of the products other than some cases of having no alternatives such as munitions from 2009. Nevertheless, diseases from asbestos have a long incubation period of 10~40 years, therefore, even if being exposed to asbestos, preliminary prevention is rather more important than instant possible damage as damages can be greater decades later. Accordingly, this thesis has a purpose to seek a plan in order to guarantee the rights of national health from harmfulness of asbestos by comparing and reviewing the policies on asbestos in advanced countries such as France, Japan, Netherlands and such like.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.1034-1040
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• 2003

Tension mask is a part of CRT type devices, which is installed right behind glass-made front panel. Numerous slits on the thin metal sheet enable the electron beams emitted from posterior gun to be focused, resulting in enhanced definition. Flattened and enlarged displays necessitate the imposition of pretension on the masks, in order to improve the robustness of display quality against vibration or impact. High temperature assembly process subsequent to pretensioning, however, degenerates creep resistance of mask material, and common mask may become susceptible to undesirable elongation due to creep. Once tensile stress becomes high enough to induce creep deformation, pretension is substantially loosened. In this study, tension mask assembly is modeled as a combined structure of beams and wire array, and a numerical simulation is attempted for pretensioning followed by high temperature process. Based on a model study, creep occurrence is found to be probable and its adverse influence is quantified. As fur maintaining high tensile force, simply increasing pretension does not seem to be helpful. Instead, the structure of frame needs to be modified somehow, or material for mask needs to be selected properly.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.277-280
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• 1999

We fabricated a resistive superconducting fault current limiter of two stripe meander type based on a YBCO film, and performed current limitation experiments. In order to disperse the heat generated at hot spots in the YBCO film the film was coated with a gold shunt layer. At $0^{\circ}$ fault angle the minimum quench current was $9.6 A_{peak}$(meander line cross section: $5{\times}10^{-6}cm^2$) and the fast quench time was 0.63 msec. The resistance of the limiter continued to increase for three cycles due to heat generation in the gold layer and was stabilized afterwards. At $45^{\circ}$ and $90^{\circ}$ the fast quench time were 0.56 msec and 0.26 msec, respectively. The quench time is believed to be reduced because faults occurred when the current was increasing or was at the peak value. With the limiter we could effectively limit the fault current about 1/5 times right after the fault and about 1/8.5 times three cycles after.

• Journal of Chest Surgery
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• v.20 no.1
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• pp.22-29
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• 1987

From Sep. 1978 to Aug. 1986, 44 cases of Fontan operation were performed at Seoul National University Hospital. 1] The diagnoses were TA in 13 [38.6%], UVH in 21 [47.79`], DORV in 3 [6.8%], TGA in 2 [4.5%] and C-ECD with DORY in 1[2.3%]. 2] There were 20 operative deaths [44.5%]. 3] The operative risk factors were early date of operation between 1978 and 1983, young age below 3 years old, direct atriopulmonary anastomosis without roofing, and postoperative high CVP above 25cmH,O. But the relation between operative mortality and various cardiac diseases was absent. 4] survived patients were followed from 1 to 54 months except 3 patients who were lost to follow up. 16 patients were in functional class I and 1 in class II, 2 of the above 17 patients were reoperated due to residual right to left shunt. In remained 4 patients, 3 patients persisted cyanosis after operation and 1 patients died 1 month postoperatively due to pulmonary embolism. 5] As 4 result, the Fontan procedure can be done with a good result for tricuspid atresia and other complex lesions. The operative mortality can be reduced further with a correct anatomical diagnosis preoperatively, rigid operative criteria to pulmonary vascular resistance, direct atriopulmonary anastomosis with roofing, and use of `Venous Assist Device` postoperatively in low cardiac output patients.