• Journal of Power Electronics
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• 제1권2호
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• pp.71-77
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• 2001

This paper proposes a new zero-current switching (ZCS) pulse-width modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero current condition. The diodes commutate softly and the reverse recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of DC to DC PWM converters is derived. The new family of ZCS PWM converters is suitable for the high power applications employing IGBTs. Among the new family of DC to DB PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype converter operating at 40 kHz.

• The Korean Journal of Physiology and Pharmacology
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• 제10권5호
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• pp.223-229
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• 2006

The emerging concept of the 'neurovascular unit' may enable a powerful paradigm shift for neuroscience. Instead of a pure focus on the 'neurobiology' of disease, an opportunity now exists to return to a more integrative approach. The neurovascular unit emphasizes that signaling between vascular and neuronal compartments comprise the basis for both function and dysfunction in brain. Hence, brain disorders are not just due to death of neurons, but instead manifested as cell signaling perturbations at the neurovascular interface. In this mini-review, we will examine 3 examples of this hypothesis: neurovascular mechanisms involved in the thrombolytic therapy of stroke, the crosstalk between neurogenesis and angiogenesis, and the link between vascular dysfunction and amyloid pathology in Alzheimer's disease. An understanding of cell-cell and cell-matrix signaling at the neurovascular interface may yield new approaches for targeting CNS disorders.

• 정보보호학회논문지
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• 제6권3호
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• pp.3-10
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• 1996

ATM 망과 같은 초고속 네트워크에서 전송 에러의 주요 원인은 과잉밀집 상태에 있어서의 버퍼 오버플로우이며 이로 인해 셀손실을 야기한다. 본 논문은 이러한 문제를 줄이기 위해 연속적인 셀손실을 회복할 수 있는 방법을 제안하며 이 방법은 18개의 연속적인 셀손실을 회복할 수 있다. 또한 인터리빙 기법을 이용한 FEC 기법의 수치적인 성능 분석을 하였으며 이 결과 셀 손실율을 상당히 절감할 수 있었다.

• 한국식품위생안전성학회지
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• 제24권4호
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• pp.368-372
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• 2009

본 연구에서는 우리나라에서 2-3번째로 자주 발생하는 식중독 원인균인 S. aureus를 대상으로 불충분한 열처리와 NaCl처리에 따른 각각의 생존균수 변화와 불충분한 열처리 후 다양한 NaCl농도(0%, 2%, 4%, 6%)하에서 sublethal injured cell의 회복 정도를 조사하였다. 그 결과, 불충분한 열처리 정도가 증가함에 따라 생존균수가 유의적인 감소를 하였으나, NaCl 처리시 NaCl 농도가 6%까지 증가함에 따라서 생존균수의 변화가 거의 없었다. 그리고 $55^{\circ}C$나 $60^{\circ}C$에서 30분간 열처리하는 기간 동안에 sublethal injured cell들이 발생하였으며, 그들의 회복 정도는 높은 염농도에 노출될수록 회복 정도가 감소하였다. 또한 이와 같은 현상은 같은 온도에서 열처리 시간이 증가할수록 더욱 명확히 나타났다. 그리고 동일한 온도에서 sublethal heating 후 노출된 NaCl 농도가 증가함에 따라서 D-value가 감소하는 경향을 나타내었다. 이와 같은 결과는 불충분한 열처리 과정에 의하여 생성된 sublethal injured cell들이 열처리 후 회복되는 과정에서 배지의 NaCl 농도가 증가함에 따라서 회복 정도가 감소하였음을 의미한다.

• Journal of Korean Neurosurgical Society
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• 제50권3호
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• pp.209-215
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• 2011

Objective : The authors investigated the changes of cortical sensorimotor activity in functional MRI (fMRI) and functional recovery in spinal cord injury (SCI) patients who had been treated by bone marrow cell transplantation. Methods : Nineteen patients with SCI were included in this study; ten patients with clinical improvement and nine without. The cortical sensorimotor activations were studied using the proprioceptive stimulation during the fMRI. Results : Diagnostic accuracy of fMRI with neurological improvement was 70.0% and 44.4% for sensitivity and specificity, respectively. Signal activation in the ipsilateral motor cortex in fMRI was commonly observed in the clinically neurological improved group (p-value=0.002). Signal activation in the contralateral temporal lobe and basal ganglia was more commonly found in the neurological unimproved group (p-value<0.001). Signal activation in other locations was not statistically different. Conclusion : In patients with SCI, activation patterns of fMRI between patients with neurologic recovery and those without varied. Such plasticity should be considered in evaluating SCI interventions based on behavioral and neurological measurements.

• Journal of Applied Biological Chemistry
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• 제43권2호
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• pp.109-111
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• 2000

Effect of the two-stage operation and cell concentration on indirubin production was investigated using bioreactor culture of Polygonum tinctorium. Two-stage culture was operated successfully for 110 days without any adverse effects on continuous indirubin production. Maximum indirubin concentration was found to be at 80 mg/bioreactor. Initial cell concentration significantly affected indirubin production. The indirubin production at 29.2% PCV was improved by 845%, compared to that at 5% PCV. For high-density bioreactor culture of P. tinctorium, a maximum production rate of 10.2 mg indirubin/L day was obtained. Indirubin recovery for bioreactor operation was also examined using XAD-2, XAD-4, XAD-7, and solid silicon. XAD-4 was 1.6-fold more effective than that for solid silicon in indirubin recovery.

• ETRI Journal
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• 제38권6호
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• pp.1153-1162
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• 2016

This paper addresses the resource allocation (RA) problem in multi-cell cognitive radio networks. Besides the interference power threshold to limit the interference on primary users PUs caused by cognitive users CUs, a proportional fairness constraint is used to guarantee fairness among multiple cognitive cells and the impact of imperfect spectrum sensing is taken into account. Additional constraints in typical real communication scenarios are also considered-such as a transmission power constraint of the cognitive base stations, unique subcarrier allocation to at most one CU, and others. The resulting RA problem belongs to the class of NP-hard problems. A computationally efficient optimal algorithm cannot therefore be found. Consequently, we propose a suboptimal RA algorithm composed of two modules: a subcarrier allocation module implemented by the immune algorithm, and a power control module using an improved sub-gradient method. To further enhance algorithm performance, these two modules are executed successively, and the sequence is repeated twice. We conduct extensive simulation experiments, which demonstrate that our proposed algorithm outperforms existing algorithms.

• 한국막학회:학술대회논문집
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• 한국막학회 2004년도 Proceedings of the second conference of aseanian membrane society
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• pp.55-58
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• 2004

Cell separation from peripheral blood was investigated using surface-modified polyurethane (PU) membranes with different functional groups. Both red blood cells and platelets could pass through unmodified PU and PU-SO$_3$H membranes, while the red blood cells preferentially passed through PU-N(C$_2$H$_{5}$ )$_2$ and PU-NHC$_2$H$_4$OH membranes. The permeation ratio of T and B cells was less than 25% for the surface-modified and unmodified PU membranes. CD34$^{+}$ cells have been recognized as various kinds of stem cells including hematopoietic and mesenchymal stem cells. The adhesiveness of CD34$^{+}$ cells on the PU membranes was found to be higher than that of red blood cells, platelets, T cells or B cells. Overall, the adhesiveness of blood cells on the PU membranes increased in the following order: red blood cells $\leq$ platelets ＜ T cells $\leq$ B cells ＜ CD34$^{+}$ cells. Treatment of PU-COOH membranes with a human albumin solution to detach adhered blood cells, allowed recovery of mainly CD34$^{+}$ cells in the permeate, while both red blood cells and platelets could be isolated in the permeate using unmodified PU membranes. The PU membranes showed different permeation and recovery ratios of specific cells depending on the functional groups attached to the membranes.mbranes.

• 한국통신학회논문지
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• 제27권10C호
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• pp.987-992
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• 2002

본 논문에서는 ㎓대역의 고속 클럭 신호를 필요로 하는 데이터 통신 시스템 분야에 응용될 수 있는 새로운 구조의 클럭 및 데이터 복원회로를 구현하였다. 구현된 회로는 고속 데이터 전송시 주로 사용되는 NRZ형태의 데이터 복원에 적합한 구조로서 위상동기 회로에 발생하는 high frequency jitter를 방지하기 위한 새로운 위상 검출 구조를 갖추고 있다. 또 가변적인 지연시간을 갖는 delay cell을 이용한 위상검출기를 이용하여 위상 검출기가 갖는 dead zone 문제를 해결하고, 항상 최적의 동작을 수행하여 빠른 동기 시간을 갖는다. 수십 Gbps급 대용량을 수신할 수 있도록 다채널 확장에 용이한 구조를 사용하였으며, 1.25Gbps급 데이터를 복원하기 위한 클럭 생성을 목표로 하여 CMOS 0.25$\mu\textrm{m}$ 공정을 사용하여 구현한 후 그 동작을 측정을 통해 검증하였다.

• Restorative Dentistry and Endodontics
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• 제12권2호
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• pp.73-80
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• 1987

The present study was designed to help elucidate the effect of glass ionomer cements on the exposed dental pulp by means of histologic examination. A total of 40 cavities of class V were prepared on the teeth of 4 dogs with exposure of 1mm in diameter on the bases of them. 20 cavities were filled with glass ionomer cement as the experimental group and the other 20 cavities were filled with zinc oxide eugenol cement as the control group. The dogs were sacrificed at one, two, three, and four weeks after filling, and the specimens were routinely prepared and stained with Hematoxylin-Eosin. The obtained microscopic findings were as follows: Inflammatory cell infiltrations were observed in control in 1 week, which decreased markedly with time. In all control groups, hemorrhage around exposed pulp tissue and coagulation change of pulp were observed. Secondary dentin formation and thickened predentin were observed in 4 week cases, and the recovery of pulp tissue was favorable on the whole. Inflammatory cell infiltration was observed in all GIC groups. Proliferation of blood vessel and congestion were observed with coagulation changes around the exposed pulp tissue. Secondary dentin formation and thickened predentin were observed in 3 weeks. In the experimental 4 week case, secondary dentin formation was evident. On the whole, pulpal irritation of glass ionomer cement was relatively severe. Recovery of pulp tissue in GIC groups was less favorable compared with that of ZOE groups.