• 유체기계공업학회:학술대회논문집
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• 2001.11a
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• pp.469-474
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• 2001

The feasibility of a oil-free motor-driven two-stage centrifugal compressor supported by air bump bearings is investigated. This centrifugal compressor is driven by 75kW motor at an operating speed of 39,000RPM md a pressure ratio of the compressor is up to 4. The analysis is performed, based upon bearing equilibrium position, bearing stiffness, Campbell diagram, unbalance response and stability. It is demonstrated in this paper that air bump bearings can be adopted well to a oil-free motor-driven centrifugal compressor.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.4
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• pp.11-18
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• 2007

A moving object detection algorithm for surveillance video is here proposed which employs background initialization based on two-stage median filtering and a background updating method based on state transition diagram. In the background initialization, the spatiotemporal similarity is measured in the subinterval. From the accumulated difference between the base frame and the other frames in a subinterval, the regions affected by moving objects are located. The median is applied over the subsequence in the subinterval in which regions share similarity. The outputs from each subinterval are filtered by a two-stage median filter. The background of every frame is updated by the suggested state transition diagram The object is detected by the difference between the current frame and the updated background. The proposed method showed good results even for busy, crowded sequences which included moving objects from the first frame.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.4
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• pp.278-283
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• 2013

This paper presents a design and fabrication of 0.5 V two stage operational amplifier. The proposed operational amplifier utilizes body-driven differential input stage and self-cascode current mirror structure. Cadence Virtuoso is used for layout and the layout data is verified by LVS through Mentor Calibre. The proposed two stage operational amplifier is fabricated using $0.13{\mu}m$ CMOS process and operation at 0.5 V is confirmed. Measured low frequency small signal gain of operational amplifier is 50 dB, power consumption is $29{\mu}W$ and chip area is $75{\mu}m{\times}90{\mu}m$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.7
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• pp.1487-1504
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• 1997

In this paper, the two-stage variable block-size multiresolution motion algorithm is proposed for an interframe coding scheme in the wavelet decomposition. An optimal bit allocagion between motion vectors and the prediction error in sense of minimizing the total bit rate is obtained by the proposed algorithm. The proposed algorithm consists of two stages for motion estimatation and only the first stage can be separated and run on its own. The first stage of the algorithm introduces a new method to give the lower bit rate of the displaced frame difference as well as a smooth motion field. In the second stage of the algorithm, the technique is introduced to have more accurate motion vectors in detailed areas, and to decrease the number of motion vectors in uniform areas. The algorithm aims at minimizin gthe total bit rate which is sum of the motion vectors and the displaced frame difference. The optimal bit allocation between motion vectors and displaced frame difference is accomplished by reducing the number of motion vectors in uniform areas and it is based on a botom-up construction of a quadtree. An entropy criterion aims at the control of merge operation. Simulation resuls show that the algorithm lends itself to the wavelet based image sequence coding and outperforms the conventional scheme by up to the maximum 0.28 bpp.

• Journal of Chest Surgery
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• v.30 no.11
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• pp.1121-1124
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• 1997

This is a report of a successful, rapid two-stage arterial switch operation in an infant with dextrotransposition of great arteries with an intact ventricular septum beyond the appropriate time for arterial switch operation.'A 4-month-old female infant was admitted due to severe cyanosis, respiratory insufficiency, and frequent dia rhea secondary to ischemic colitis. Echocardiographic examination presented marked leftward deviation of the interventricular septum, and left and right ventricular pressures as measured by cardiac catheterization were 40/4 mmHg and 85/2 mmHg, respectively. Fifteen days after a preparatory operation (pulmonary artery band with modified right Blalock-Taussig shunt), left ventricular-right ventricular systolic pressure ratio increased to 105/90. Arterial switch operation associated with the division of the right Blalock-Taussig shunt and the removal of pulmonary artery band was performed. A(leer the operation, the infant showed normal cardiac function with no postoperative complication.

• Transactions of Materials Processing
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• v.32 no.4
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• pp.199-207
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• 2023

The stainless steel basket-bowl, a critical component of washing machines, is characterized by its unique two-tiered circular shape. This study explores the potential of a draw-bead free die design to address tearing concerns in the prospective plastic layer during the drawing operation. In order to prevent wrinkles that may arise from the absence of a draw-bead, a two-stage punch configuration is proposed. The influence of the blank holder force on wrinkle reduction is also examined. Finite element analysis is employed to evaluate the proposed die design by analyzing the wrinkle shape and strain mode. The results confirm that the stainless steel basket-bowl can be successfully drawn without wrinkles utilizing the proposed two-stage punch without a draw-bead on the blank holder. These findings contribute to the development of more efficient and reliable manufacturing processes for the stainless steel basket-bowl production.

• Journal of Korean Neurosurgical Society
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• v.60 no.2
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• pp.257-261
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• 2017

Objective : This study was conducted to assess the surgical results of one-stage posterior minimal laminectomy and video-assisted thoracoscopic surgery (VATS) for the treatment of thoracic dumbbell tumor and to describe its precise technique. In addition, we investigated the technique's usefulness and limitations. Methods : Seven cases of thoracic dumbbell tumor (two men and five women, mean age, 43 years) were analyzed retrospectively. Pathological findings included schwannoma in four patients, neurofibroma in two patients, and hemangioma in one patient. The location of tumors varied from T2/3 to T12/L1. Dumbbell tumors were resected by one-stage operation using posterior laminectomy followed by VATS without instrumentation. Clinical data were reviewed. Results : The mean follow-up period was 25 months (range, 3-58 months), and the operative time ranged from 255 to 385 min (mean, 331 min), with estimated blood loss ranging from 110 to 930 mL (mean, 348 mL). The tumor was completely resected without instrumentation and postoperative instability in all cases. Postoperative complications included atelectasis and facial anhydrosis in one case each. Conclusion : One-stage posterior minimal laminectomy and VATS may be a safe and less invasive technique for removal of thoracic dumbbell tumor without instability. This method has the advantage of early ambulation and rapid recovery because it reduces blood loss and postoperative pain.

• Archives of Reconstructive Microsurgery
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• v.19 no.2
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• pp.101-107
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• 2010

Purpose: The free flap has been widely used as one stage reconstructive procedure the skin and soft tissue defect. The secondary adjuvant operations are often needed for better results as functional and aesthetic compartment. Therefore, we focus on the secondary adjuvant surgeries for better outcome after free flaps. Methods: One hundred ninety six consecutive patients underwent free flaps between January, 2002 and February 2009. The cases constituted ninety two male patients and one hundred four female patients. For the patients who got free flap operation, we investigated secondary adjuvant operations what type of procedures was applied according to the reconstructed sites. All clinical data were based on the patient's medical records. Results: Of one hundred ninety six patients in whom free flap was performed, a total of eighty two patients(41.8%) received the secondary adjuvant operation. Because of many patients got multiple secondary adjuvant operations, the number of the secondary adjuvant operation become one hundred fifty five cases. The most common used procedure is a liposuction, and the second one is a lipoinjection. Conclusion: As the secondary adjuvant operation like a liposuction, lipoinjection, etc., satisfaction for operative result was increased in the aspects of function and aesthetics. So the secondary adjuvant operation in free flap surgeries contributed in raising the patient's quality of life.

• Journal of Microbiology and Biotechnology
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• v.10 no.1
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• pp.75-80
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• 2000

An improved method of refolding recombinant human proinsulin from E. coli was presented. It was based on a two-stage stirred tank reactor in which denatured proinsulin-s-sulfonate was mixed instantaneously with a reaction buffer in the first stage reactor, and then fed to the second stage reactor. The mixture was stirred further for a total of 30h in the second stage reactor. In this system, unfavorable effects present due to the increase in reaction volume and protein concentration for protein refolding, which becomes significant in a large-scale operation, were avoided. Refolding yields of over 80% was obtained for achieving reaction volume of upto 50 l at protein concentration of 1 mg/ml. The optimum urea concentration was 1M. Refolding yield at the 1-1 reaction volume and protein concentration of 0.5mg/ml was increased about 2.5-fold, compared to that in a batch reactor. By increasing protein concentration in a two-stage refolding reaction, the cost for insulin production could be reduced, therefore, making this process economical.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.271-278
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• 2016

Recently, reverse osmosis (RO) is the most common process for seawater desalination. A common problem in both RO and thermal processes is the high energy requirements for seawater desalination. The one energy saving method when utilizing the osmotic power is utilizing pressure retarded osmosis (PRO) process. The PRO process can be used to operate hydro turbines for electrical power production or can be used directly to supplement the energy required for RO desalination system. This study was carried out to evaluate the performance of both single-stage PRO process and two-stage PRO process using RO concentrate for a draw solution and RO permeate for a feed solution. The major results, were found that increase of the draw and feed solution flowrate lead to increase of the production of power density and water permeate. Also, comparison between CDCF and CDDF configuration showed that the CDDF was better than CDCF for stable operation of PRO process. In addition, power density of two-stage PRO was lower than the one of single-stage. However, net power of two-stage PRO was higher than the one of single-stage PRO.