• Journal of the Korean Arthroscopy Society
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• v.2 no.1
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• pp.93-96
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• 1998

We treated 10 cases of the medial malleolar fracture of the ankle by open reduction and internal fixation from June 1997 to December 1997. After the rigid internal fixation, we measured the gap of the fracture site and the step off of the articular surface by special instrument under the ankle arthroscopy whether it was reduced anatomically or not. And we tried to know the necessity of the arthroscopically assisted reduction and fixation in the medial malleolar fracture of the ankle. Under the arthroscopic view, all 10 cases were anatomically reduced as less than 1 mm of gap of the fracture site and less than 1mm of step off of the articular surface after open reduction and internal fixation in the medial malleolar fractures. In conclusion, through the arthroscopic management, it has advantage in finding and treating the accompanying intraarticular lesion, but also has disadvantage in setting the arthroscope and prolonging the operation time.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1103-1104
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• 2008

In this paper, authors propose a novel step-up AC-DC chopper operated with power factor correction (PFC) and with high efficiency. The proposed chopper behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed chopper is got to be a discontinuous sinusoid form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC chopper, the switching devices are turned-on with the zero current switching, but turn-off of the switching devices is switched at current maximum value. To achieve a soft switching of the switching turn-off, the proposed chopper is used a new partial resonant circuit. The result is that the switching loss is very low and the efficiency of chopper is high.

• Journal of the Korean Vacuum Society
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• v.12 no.S1
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• pp.79-82
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• 2003

We present the investigation on P- and As-desorption process from the (001) InP surface in metal organic chemical vapor deposition using surface photoabsorption (SPA). The monochromatic SPA signal showed rapid initial increase to reach In-stabilized surface value after $PH_3$ was turned off, but in case of As-desorption, the signal showed clear existence of a metastable state after the $AsH_3$ was turned off. The SPA spectra at each stable surfaces were taken to confirm the interpretation. This result indicates that the As-desorption process should be understood as a two-step process, in contrast to P-desorption of one-step process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.8
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• pp.659-666
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• 1990

Curing recent years, several state-space models describing discrete two dimensional systems are proposed. In this paper, we consider the problem of pole assignment of two dimensional systems using state feedback, based on state-space model proposed by Roessser. The design procedure is seperated into two steps. in thie first step, the sufficient condition for off diagonal matrix of the input transformed system to be zero is derived and in the second step, it is shown that the pole assignment problem of two dimensional systems is divided into the one of two 1-dimensional systems. Finally, a numerical example for illustrating the technique is given.

• 전기의세계
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• v.17 no.4
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• pp.18-27
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• 1968

Analysis of the transient stability of power systems following disturbances involves many sets of non-linear differential equations. This paper attempts to analyze the transient stability of multi-machine power systems by the step by step method, using the electronic digital computer. The critical switching times and phase angles for the main 154KV transmission system in Korea, are given from the swing curves of the probable conditions. It is concluded that the system is, in general, stable if the relay is cut off within 12 cycles after the fault. However the fault of DAEGU-SANGJU branch, accompanying much real power, makes the system unstable when the raly is cut off within 4 cycles after fault or automatic voltage regulators are equipped in this branch.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.174-175
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• 2005

Initial growth stage was investigated for SiC homoepitaxial film growth using 'step controlled epitaxy' technique. When the off angel direction is located parallel along to the gas flow direction, the smoother surface can be obtained. On the on axis substrates, selective etching was detected both the etching and growth condition. It was deduced that the high ratio of C/Si in the source gas results in well developed steps and etched spiral around micropipes.

• Journal of Information Display
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• v.6 no.3
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• pp.18-21
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• 2005

A new technology for reducing photolithography process from a four step to a three step process in the fabrication of TFT LCD is introduced. The core technology for 3-mask-TFT processes is the lift-off process [1], by which the PAS and PXL layers can be formed simultaneously. A different method of the lift-off process was developed in order to enhance the performance of efficiency with conventional positive and not negative PR which is the generally used in other lift-off process. In addition, the removal capacity of the ITO/PR in lift-off process was evaluated. The evaluation results showed that the new process can be run in conventional TFT production condition. In order to apply this new process in existing TFT process, several tests were conducted to ensure stability of the TFT process. It was found that the outgases from PR on the substrate in ITO sputtering chamber do not raise any problem, and the deposited ITO film beside the PR has conventional ITO qualities. Furthemore, the particles that were produced due to the ITO chips in PR strip bath could be reduced by the existing filtering system of stripper. With the development of total process and design of the structure for TFT using this technology, 3-mask-panels were achieved in TN and IPS modes, which showed the same display performances as those with the conventional 4mask process. The applicability and usefulness of the 3-mask process has already verified in the mass production line and in fact it currently being used for the production of some products.

• Journal of Hydrogen and New Energy
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• v.21 no.5
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• pp.355-363
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• 2010

High purity hydrogen, 97-99 vol.%, with CO at just ppm levels was obtained in a fixed bed of iron oxide employing the steam-iron cycle operation with reduction at 823K and oxidation in a steam-$N_2$ mixture at 773K TGA experiments indicated that temperature of the reduction step as well as its duration are important for preventing carbon build-up in iron and the intrusion of $CO_2$ into the hydrogen product. At a reduction temperature of 823K, oxide reduction by $H_2$ was considerably faster than reduction by CO. If the length of the reduction step exceeds optimal value, low levels of methane gas appeared in the off-gas. Furthermore, with longer durations of the reduction step and CO levels in the reducing gas greater than 10 vol.%, carbidization of the iron and/or carbon deposition in the bed exhibited the increasing pressure drop over the bed, eventually rendering the reactor inoperable. Reduction using a reducing gas containing 10 vol.% CO and a optimal reduction duration gave constant $H_2$ flow rates and off-gas composition over 10 redox reaction cycles.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1445-1453
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• 2017

In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W-100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.

• The Korean Journal of Nuclear Medicine
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• v.39 no.4
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• pp.231-238
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• 2005

Purpose: We investigated prospectively whether the interpretation considering the patterns of FDG uptake and the findings of unenhanced CT for attenuation correction can improve the diagnostic accuracy for assessing malignant lymph node (LN) and N stage in non-small cell lung cancor (NSCLC) using CT-corrected FDG-PET (PET/CT). Materials & Methods: Subjects were 91 NSCLC patients (M/F 62/29, age: $60{\pm}9$ yr) who underwent PET/CT before in dissection. We evaluated the maximum SUV (maxSUV), patterns of FDG uptake, short axis diameter, and calcification of LN showing abnormally increased FDG uptake. Then we investigated criteria improving the diagnostic accuracy and correlated results with postoperative pathology. In step 1, in was classified as benign or malignant based on maxSUV only. In step 2, LN was regarded as benign if it had lower maxSUV than the cut-off value of step 1 or it had calcification irrespective of its maxSUV. In step 3, LN regarded as malignant in step 2 was classified as benign if they had indiscrete margin of FDG uptake. Results: Among 432 LN groups surgically resected (28 malignant, 404 benign), 71 showed abnormally increased FDG uptake. We determined the cut-off as maxSUV=3.5 using ROC curve analysis. The sensitivity, specificity, and accuracy for assessing malignant LN were 64.3%, 86.9%, 85.4% in step 1, 64.3%, 95.0%, 93.1% in step 2, and 57.1%, 98.0%, 95.4% in step3, respectively. The accuracy for assessing N stage was 64.8% in step 1, 80.2% in step 2, and 85.7% in step 3. Conclusion: interpreting PET/CT, consideration of calcification and shape of the FDG uptake margin along with maxSUV can improve the diagnostic accuracy for assessing malignant involvement and N stage of hilar and mediastinal LNs in NSCLC.