• Journal of Korean Neurosurgical Society
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• v.54 no.4
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• pp.280-288
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• 2013

Objective : Perfusion computed tomography (PCT) has the ability to measure quantitative value and produce maps of mean transit time (MTT), cerebral blood flow (CBF), and cerebral blood volume (CBV). We assessed cerebral hemodynamics by using these parameters and acetazolamide (ACZ) challenge for pre- and post-procedural evaluation in patients with unilateral cerebrovascular stenotic disease. Methods : Thirty patients underwent pre-procedural PCT with ACZ challenge, and 24 patients (80%) was conducted follow up PCT after angioplasty with same protocol. The mean MTT, CBF, and CBV were measured and compared in both middle cerebral arterial (MCA) territories before and after ACZ challenge. Hemispheric ratio and percent change after ACZ challenge were calculated before and after angioplasty. Results : The mean stenosis rate was 76.6%. Significant increases in MTT (32.6%, p=0.000) and significant decreases in CBF (-14.2%, p=0.000) were found in stenotic side MCA territories. After ACZ challenge, there were significant changes in MTT (37.4%, p=0.000), CBF (-13.1%, p=0.000), and CBV (-10.5%, p=0.001) in pre-procedural perfusion study. However, no significant increases were found in MTT, or decreases in CBF and CBV in post-procedural study. There were no significant changes after ACZ challenge also. In addition, the degrees of these changes (before and after ACZ challenge) were highly correlated with the stenotic degrees in pre-procedural perfusion study. Conclusion : PCT with ACZ challenge appears to be a useful tool to assess the cerebral perfusion status especially in patients with unilateral symptomatic stenotic disease.

• Korean Journal of Biological Psychiatry
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• v.7 no.1
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• pp.80-84
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• 2000

Background : Hypersalivation can be a troublesome side effect of clozapine, limiting its usefulness in the management of some cases of schizophrenia. But the pharmacodynamic basis of clozapine-induced hypersalivation remains obscure. Object : The aim of this study was to evaluate the effect of the ${\alpha}_2$-adrenergic agonist clonidine on clozapine-induced hypersalivation in the patients who were receiving clozapine. Method : Twenty one schizophrenic inpatients on clozapine participated in the study. The amount of saliva was measured on the 7th day at 8pm after starting clozapine treatment. Of them, 15 patients who had experienced hypersalivation was treated with 0.1mg/day of clonidine. Result : Of 21 schizophrenic patients treated with clozapine in the psychiatric inpatient clinic, 15(71.4%) complained hypervalivation. After clonidine treatment, mean salivary flow-rate was decreased significantly in these patients. Conclusion : Clozapine-induced hypersalivation could be decreased by administration of ${\alpha}_2$-adrenergic agonist clonidine and compliance could be improved. Also our study supports the notion that increased adrenergic tone contributes to clozapine-induced hypersalivation.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.12
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• pp.1681-1691
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• 2002

The heat transfer and pressure drop characteristics of heat exchangers with louver fins were experimentally investigated. The samples had small fin pitches (1.0 mm to 1.4 mm), and experiments were conducted up to a very low frontal air velocity (as low as 0.3 m/s). At a certain Reynolds number (critical Reynolds number), the flattening of the heat transfer coefficient curve was observed. The critical Reynolds number was insensitive to the louver angle, and decreased as the louver pitch to fin pitch ratio (L$_{p}$F$_{p}$) decreased. Existing correlations on the critical Reynolds number did not adequately predict the data. It is suggested that, for proper assessment of the heat transfer behavior, the louver pattern in addition to the flow characterization need to be considered. The heat transfer coefficient increased as the fin pitch decreased. At low Reynolds numbers, however, the trend was reversed. Possible explanation is provided considering the louver pattern between neighboring fins. Different from the heat transfer coefficient, the friction factor did not show the flattening characteristic. The reason may be attributed to the form drag by louvers, which offsets the decreased skin friction at a low Reynolds number. The friction factor increased as the fin pitch decreased and the louver angle increased. A new correlation predicted 92% of the heat transfer coefficient and 90% of the friction factor within $\pm$10%.10%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.361-365
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• 2003

Planar Inductively Coupled Plasma (PICP) etching of InGaP was performed in $BCl_3,\;BCl_3/Ar\;and\;BCl_3/Ne$ plasmas as a function of ICP source power ($0\;{\sim}\;500\;W$), RIE chuck power ($0\;{\sim}\;150\;W$), chamber pressure ($5\;{\sim}\;15\;mTorr$) and gas composition of $BCl_3/Ar\;and\;BCl_3/Ne$. Total gas flow was fixed at 20 sccm (standard cubic centimeter per minute). Increase of ICP source power and RIE chuck power raised etch rate of InGaP, while that of chamber pressure reduced etch rate. We also found that some addition of Ar and Ne in $BCl_3$ plasma improved etch rate of InGaP. InGaP etch rate was varied from $1580\;{\AA}/min$ with pure $BC_3\;to\;2800\;{\AA}/min$ and $4700\;{\AA}/min$ with 25 % Ar and Ne addition, respectively. Other process conditions were fixed at 300 W ICP source power, 100 W RIE chuck power and 7.5 mTorr chamber pressure. SEM (scanning electron microscopy) and AFM (atomic force microscopy) data showed vertical side wall and smooth surface of InGaP at the same condition. Proper addition of noble gases Ar and Ne (less than about 50 %) in $BCl_3$ inductively coupled plasma have resulted in not only increase of etch rate but also minimum preferential loss and smooth surface morphology by ion-assisted effect.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.89-99
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• 2001

In the present paper, Helmholtz resonator, which is widely used as a sound-amplification device, is applied to the development of seawater-exchanging breakwater. The incident waves can induce a large response in the resonator when incident wave frequency is close to one of natural modes of the resonator. Largely amplified potential energy due to the resonance supplies clean seawater into the harbor side throughout the channel. Flow supplied by the resonator circulates the seawater of harbor and helps to improve water quality. Within the framework of linear potential theory, matched asymptotic expansion method is employed to analyze the wave responses in a resonator. The semi-circular shape of the resonator has been chosen as an analytic model for mathematical simplicity. The wave responses of both single and arrays of Helmholtz resonator are investi¬gated. To validate an analytic solution, model test is conducted at 2-dimensional wave tanle Wave hcights in the resonator and velocity at the channel are measured for the state of valve-on and valve-off.

• The Korean Journal of Physiology and Pharmacology
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• v.22 no.5
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• pp.481-491
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• 2018

Allergic asthma is one of the most enduring diseases of the airway. The T-helper cells and regulatory T-cells are critically involved in inflammatory responses, mucus hypersecretion, airway remodelling and in airway hyper-responsiveness. Cigarette smoke (CS) has been found to aggravate inflammatory responses in asthma. Though currently employed drugs are effective, associated side effects demand identification and development of novel drugs with negligible or no adverse effects. Rutin, plant-derived flavonoid has been found to possess antioxidant and anti-inflammatory effects. We investigated the ability of rutin to modulate T-cells and inhibit inflammation in experimentally-induced asthma in cigarette smoke exposed mice. Separate groups of neonatal mice were exposed to CS for 10 days from post-natal days 2 to 11. After 2 weeks, the mice were sensitized and challenged with ovalbumin (OVA). Treatment group were given rutin (37.5 or 75 mg/kg body weight) during OVA sensitization and challenge. Rutin treatment was found to significantly inhibit cellular infiltration in the airways and Th2 and Th17 cytokine levels as well. Flow cytometry revealed effectively raised $CD4^+CD25^+Fox3^+$ Treg cells and supressed Th17 cell population on rutin treatment. Airway hyper-responsiveness observed following CS and OVA challenge were inhibited by rutin. $NF-{\kappa}B$ and iNOS, chief regulators of inflammatory responses robustly activated by CS and OVA were down-regulated by rutin. Rutin also inhibited the expression of matrix metalloproteinase 9, thereby aiding in prevention of airway remodelling in asthma thereby revealing to be a potent candidate in asthma therapy.

• Journal of Energy Engineering
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• v.24 no.2
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• pp.72-78
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• 2015

In the present study, a recuperator to improve the thermal efficiency of a micro gas turbine is considered. The counter flow plate-fin heat exchanger with offset strip fins is chosen as the type of the recuperator. From the optimization study as varying design parameters of the recuperator determined from the ideal cycle analysis, the internal structure of the recuperator is determined. The recuperator is made from stainless steel 304. In order to evaluate performance of the recuperator, experimental investigation is performed. The effects of inlet temperature of hot-side of the recuperator on the thermal performance of the recuperator are investigated. As a result, effectiveness of the recuperator obtained from the experiments is well consistent with that obtained from the correlations.

• Progress in Superconductivity
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• v.8 no.1
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• pp.81-86
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• 2006

We investigated resistance development in $Au/YBa_2Cu_3O_7(YBCO)$ thin film meander lines during high-power faults. The meander lines were fabricated by patterning 300 nm thick YBCO films coated with 200 nm thick gold layers into meander lines. A gold film grown on the back side of the substrate was also patterned into a meander line. The front meander line was connected to a high-power fault-test circuit and the back line to a DC power supply. Resistance of both lines was measured during the fault. They were immersed in liquid nitrogen during the experiment. Behavior of the resistance development prior to quench completion could be understood better by comparing resistance of the front meander lines with that of the back. Quench completion point could be determined clearly. Resistance and temperature at the quench completion point were not affected by applied field strength. The experimental results were analyzed quantitatively with the concept of heat transfer within the meander lines/substrate and to the surrounding liquid nitrogen. In analysis, the fault period was divided into three regions: flux-flow region, region prior to quench completion, and region after quench completion. Resistance was calculated for each region, reflecting the observation for quench completion. The calculated resistance in three regions was joined seamlessly and agreed well with data.

• Tribology and Lubricants
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• v.33 no.1
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• pp.23-30
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• 2017

The electric controlled marine diesel engine has fuel pump generating the high pressurized fuel for fuel injection to combustion chamber via a common rail. Fuel pump consists of a cam-roller system. Journal bearing installed between a roller and a cam-roller pin is subjected to fluctuating heavy and instant loads by cam lift. First, Kinematic analysis is carried out to predict bearing loads during one cycle acting on the journal bearing. Second, flexible multi-body dynamic analysis and transient elasto-hydrodynamic(EHD) lubrication analysis for journal bearing considering elastic deformation of cam-roller pin, roller and bearing are conducted using AVL EXCITE/PU software to predict lubrication performance. The clearance ratio and journal groove shape providing lubrication oil are important parameter in bearing design having good performance and can be changed easier than other design parameters such as diameter, width, oil supply pressure and bearing material grade. Generally, journal bearing performance is represented by the minimum oil film thickness(MOFT) and peak oil film pressure(POFP). As well as the traditional design parameters(MOFT, POFP), in this study, temperature rise of lubrication oil is also evaluated through the side leakage flow of supplied oil. By the evaluating MOFT, POFP and temperature rise, the optimum bearing clearance ratio is decided.

• Journal of Veterinary Clinics
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• v.15 no.2
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• pp.346-351
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• 1998

As an antitumor agents cyclophosphamide (CPA) is frequently used in animal clinic. Important adverse effects of its administration are leukopenia, thrombocytopenia and anemia. We investigated the effects of chicken egg white derivatives (EWD and EF-203) on the changes of blood cells and the neutrophil phagocytosis of rats administered with CPA. Rats were administered CPA peritoneally at dose of 50 mgag once a day far 3 days plus either EWD or EF-203 orally at dose of 200 mg/kg once a day far 3 days. Thereafterl the changes of blood cells by automatic blood cell counter and the phagocytosis of neutrophils by flow cytometry were examined far 7 days. There was no change in RBC values regardless of administration of either EWD or EF-203 throughout experimental period. But rats receiving CPA plus either EWD or EF-203 showed a significant higher PCV values than those of CPA alone (p<0.01). The numbers of peripheral blood platelets and WBC and the differential count of neutrophils in the ra% receiving CPA plus either EWD or EF-203 were significantly higher (p<0.05 to 0.01) than those of CPA alone. Moreover, these rats showed significanly enhanced phagocytoses of neutrophils when compared to rats with CPA alone (p<0.01). These result suggested that chicken egg white derivatives including EWD and EF-2% have immunomodulatory effects in regard to the increase of platelets, WBC, differential count of neutrophils, PCV, and the enhancement of phagocytic activity of neutrophils in immunosuppressed rats by CPA. Thus, co-adminstration of chicken egg white derivatives will be able to reduce the side effects in the animals treated with antitumor agents.