• Archives of Reconstructive Microsurgery
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• v.13 no.1
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• pp.1-6
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• 2004

Advances in microvascular techniques and refinements in microsurgical tissue transfers have enabled surgeons to combine different tissue components and reconstruction into a single-stage operation in extensive or composite defect following injury. Some problems and consideration for extensive or composite defects are form, shape, function, and dimension of the defect sites. Therefore combination of two or more flaps is required to reconstruct extensive or composite defect. This paper presents our clinical experience of four cases of combined free flaps with or without sequential microanastomosis in reconstruction of upper extremity based on peroneal flowthrough, thoracodorsal, and dorsalis pedis vascular system. Satisfactory results were obtained without flap loss and complications. The free flaps were combined in th following fashion; two cases by bridge fashion, one by chimeric microanastomosis and one by simple chimeric fashion. The median follow-up time on all patients was 21.7 months. Donor site morbidity was minimal. Extensive soft tissue or composite defects can be effectively covered by various combined flaps. Even though the risk for complication exists, the options of combination with or without sequential microanastomosis can add a functional or sensory dimension to reconstruction of complex wounds.

• Journal of Korea Society of Industrial Information Systems
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• v.18 no.5
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• pp.51-58
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• 2013

A clock duty-cycle corrector (DCC) which is an essential device of clocking circuits for high-speed system-on-chip (SoC) design is introduced in this paper. The architectures and operation of conventional analog feedback DCCs and digital feedback DCCs are compared and analyzed. A new mixed-mode feedback DCC that combines the advantages of analog DCCs and digital DCCs to achieve a wider duty-cycle correction range, higher operating frequency, and higher duty-cycle correction accuracy is presented. Especially, the architectures and design of a mixed-mode duty-cycle amplifier (DCA) which is a core unit circuit of a mixed-mode DCC is presented in detail. Two mixed-mode DCCs based on a single-stage DCA and a two-stage DCA were designed in a 0.18-${\mu}m$ CMOS process, and it is proven that the two-stage DCA-based DCC has a wider duty-cycler correction range and smaller duty-cycle correction error.

• Journal of Electrical Engineering and Technology
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• v.13 no.2
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• pp.648-658
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• 2018

Regarding the fact that wind power forecast accuracy is gradually improved as time is approaching, this paper proposes a two-stage rolling dispatch approach based on model predictive control (MPC), which contains an intra-day rolling optimal scheme and a real-time rolling base point tracing scheme. The scheduled output of the intra-day rolling scheme is set as the reference output, and the real-time rolling scheme is based on MPC which includes the leading rolling optimization and lagging feedback correction strategy. On the basis of the latest measured thermal unit output feedback, the closed-loop optimization is formed to correct the power deviation timely, making the unit output smoother, thus reducing the costs of power adjustment and promoting wind power accommodation. We adopt chance constraint to describe forecasts uncertainty. Then for reflecting the increasing prediction precision as well as the power dispatcher's rising expected satisfaction degree with reliable system operation, we set the confidence level of reserve constraints at different timescales as the incremental vector. The expectation of up/down reserve shortage is proposed to assess the adequacy of the upward/downward reserve. The studies executed on the modified IEEE RTS system demonstrate the effectiveness of the proposed approach.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.4
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• pp.503-508
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• 2007

Small scale D-water treatment plant(WTP) where has slow sand filtration was using raw water containing high concentration of manganese (> 2mg/l). The raw water was pre-chlorinated for oxidation of manganese and resulted in difficulty for filtration. Thus, sometimes manganese concentration and turbidity were over the water quality standard. Two stage rapid manganese sand filtration pilot plant which can treat $200m^3/d$ was operated to solve manganese problem in D-WTP. The removal rate of manganese and turbidity were about 38% and 84%, respectively without pH control of raw water. However, when pH of raw water was controlled to average 7.9 with NaOH solution, the removal rate of manganese and turbidity increased to 95.0% and 95.5%, respectively and the water quality of filtrate satisfied the water quality standard. Manganese content in sand was over 0.3mg/g which is Japan Water Association Guideline. The content in upper filter was 5~10 times more than that of middle and lower during an early operation but the content in middle and lower filter was increased more and more with increase of operation time. This result means that the oxidized manganese was adsorbed well in sand. Rapid manganese sand filter was backwashed periodically. The water quality of backwash wastewater was improved by sedimentation. Thus, turbidity and manganese concentration decreased from 29.4NTU to 3.09NTU and from 1.7mg/L to 0.26mg/L, respectively for one day. In Jar test of backwash wastewater with PAC(Poly-aluminum chloride), optimum dosage was 30mg/L. Because the turbidity of filtrate was high as 0.76NTU for early 5 minute after backwash, filter-to-waste should be used after backwash to prevent poor quality water.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1015-1026
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• 2018

A family of dual-DC-input (DI) dual-buck inverters (DBIs) is proposed by employing a DI switching cell as the input of traditional DBIs. Three power ports, i.e. a low voltage DC input port, a high voltage DC input port and an AC output port, are provided by the proposed DI-DBIs. A low voltage DC source, whose voltage is lower than the peak amplitude of the AC side voltage, can be directly connected to the DI-DBI. This supplies power to the AC side in single-stage power conversion. When compared with traditional DBI-based two-stage DC/AC power systems, the conversion stages are reduced, and the power rating and power losses of the front-end Boost converter of the DI-DBI are reduced. In addition, five voltage-levels are generated with the help of the two DC input ports, which is a benefit in terms of reducing the voltage stresses and switching losses of switches. The topology derivation method, operation principles, modulation strategy and characteristics of the proposed inverter are analyzed in-depth. Experimental results are provided to verify the effectiveness and feasibility of the proposed DI-DBIs.

• Journal of Chest Surgery
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• v.17 no.4
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• pp.620-624
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• 1984

The optimal surgical management of the coarctation of the aorta associated with ventricular septal defect is still debated. Sixteen patients with the coarctation of the aorta and VSD were operated upon between November, 1980 and September 1984 at Seoul National University Hospital. They were 11 males and 5 females. All presented between 5 months and 11.5 years of age [mean= 5.5 years]. Presenting symptoms were congestive heart failure in 11 [69%], cyanosis on crying in 3 [19%], and frequent upper respiratory infection in 2 [13%]. In all cases two-stage operation was applied except one in which one stage procedure was taken. Resection and end-to-end anastomosis was used in 3, Dacron graft in 5, Gortex graft in 1, and left subclavian flap angioplasty in 4. Remaining two were missed on the operating table before correction of the coarctation of the aorta. Overall operative death in repair of the coarctation of the aorta were 3[20%]. Among the 12 survivors after repair of the coarctation of the aorta, 4 required patch closure of VSD, 2 required primary closure, 2 showed spontaneous closure [17%], one [8%] showed decrease in its size, 3 were under observation. It might be safe to approach the coarctation of aorta plus VSD with initial repair of the coarctation of the aorta without banding of main pulmonary artery and later management of VSD as usual manner in simple VSD.

• Journal of the Korean Operations Research and Management Science Society
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• v.35 no.1
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• pp.83-95
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• 2010

This paper considers a firm that operates make-to-stock and make-to-order facilities in successive stages. The make-to-stock facility produces components which are consumed by the external market demand as well as the internal make-to-order operation. The make-to-order facility processes customer orders with the option of acceptance or rejection. In this paper, we address the problem of coordinating how to allocate the capacity of the make-to-stock facility to internal and external demands and how to control incoming customer orders at the make-to-order facility so as to maximize the firm's profit subject to the system costs. To deal with this issue, we formulate the problem as a Markov decision process and characterize the structure of the optimal inventory allocation and customer order control. In a numerical experiment, we compare the performance of the optimal policy to the heuristic with static inventory allocation and admission control under different operating conditions of the system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.425-432
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• 2009

In this study, the improvement of cooling capacity by applying gas injection technique in a two-stage heat pump using R410A was experimentally investigated. A twin rotary type compressor with gas injection was applied to the heat pump system. The optimum refrigerant charge for the injection and the non-injection cycles was selected to achieve the maximum COP at the cooling standard condition. The injection cycle showed less optimum refrigerant charge than that of the non-injection cycle. The cooling performances of the injection and the non-injection cycles were measured and compared by varying compressor frequency from 40 to 90 Hz. The cooling capacity of the gas injection cycle was 1.6% -11.3% higher than that of the non-injection cycle. The COP of the gas injection cycle was 13.7% to 28.9% higher than that of the non-injection cycle at the same cooling capacity. The heat pump system showed stable operation after 30% of the injection valve opening.

• Speech Sciences
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• v.11 no.2
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• pp.193-210
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• 2004

In this paper, we develop a real time lip-synch system that activates 2-D avatar's lip motion in synch with an incoming speech utterance. To realize the 'real time' operation of the system, we contain the processing time by invoking merge and split procedures performing coarse-to-fine phoneme classification. At each stage of phoneme classification, we apply the support vector machine (SVM) to reduce the computational load while retraining the desired accuracy. The coarse-to-fine phoneme classification is accomplished via two stages of feature extraction: first, each speech frame is acoustically analyzed for 3 classes of lip opening using Mel Frequency Cepstral Coefficients (MFCC) as a feature; secondly, each frame is further refined in classification for detailed lip shape using formant information. We implemented the system with 2-D lip animation that shows the effectiveness of the proposed two-stage procedure in accomplishing a real-time lip-synch task. It was observed that the method of using phoneme merging and SVM achieved about twice faster speed in recognition than the method employing the Hidden Markov Model (HMM). A typical latency time per a single frame observed for our method was in the order of 18.22 milliseconds while an HMM method applied under identical conditions resulted about 30.67 milliseconds.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.192-194
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• 2018

In this paper a new single-stage ac-dc converter with high frequency isolation and low components count is introduced. The proposed converter is constructed using two interleaved boost circuits in the grid side and non-regulating full bridge in the DC side. An optimized switching is implemented on the two interleaved boost circuits resulting in a ripple-free grid current without a ripple cancellation network; hence very small filter inductors are used. A simple and reliable closed-loop control system is easily implemented, since the phase-shift angle is the only independent variable. Moreover, current imbalance is avoided in the presented topology without current control loop in each phase. The proposed charger charges the battery with a sinusoidal-like current instead of a constant direct current. ZVS turn on of all switches is achieved throughout the operation in both directions of power flow without any additional components.