• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.6 s.261
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• pp.531-538
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• 2007

In this study, an air conditioning system using carbon dioxide as a refrigerant was developed for automotive cabin cooling. Experiments have been carried out to examine the steady state and dynamic characteristics of this system. The system consists of a compressor, a gas cooler, an evaporator, an expansion device, an internal heat exchanger and an accumulator. The compressor is a variable displacement type, driven by the electric motor, and the gas cooler and the evaporator are aluminum extruded heat exchangers of micro channel type. The $CO_2-refrigerant$ charge, the compressor speed, the air inlet temperature of the gas cooler, the air inlet temperature and the air flow rate of the evaporator and the cooling load are varied and the performance of the system is experimentally investigated. As the compressor speed increased, cooling capacity increased, but the coefficient of performance was deteriorated. As the cabin air temperature or the air flow rate to the cabin was set high, both the cooling capacity and the COP increased. In the cool down experiment with 1.0 or 2.0 kW of heat load, the dynamic characteristics of the air-conditioning system were investigated. For a given capacity of compressor, cool down speed was monitored, and the temperature change was acceptable fur low heat load condition.

• Restorative Dentistry and Endodontics
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• v.43 no.1
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• pp.2.1-2.10
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• 2018

Objectives: To determine the effect of size and insertion depth of irrigation needle on the amount of apical extruded debris and the amount of penetration depth of sealer using a confocal laser scanning microscope (CLSM). Materials and Methods: Twenty maxillary premolars were assigned to 2 groups (n = 10), according to the size of needle tip, 28 G or 30 G. Buccal roots of samples were irrigated with respective needle type inserted 1 mm short of the working length (WL), while palatal roots were irrigated with respective needle type inserted 3 mm short of the WL. Prepared teeth were removed from the pre-weighed Eppendorf tubes. Canals were filled with F3 gutta-percha cone and rhodamine B dye-labeled AH 26 sealer. Teeth were transversally sectioned at 1 and 3 mm levels from the apex and observed under a CLSM. Eppendorf tubes were incubated to evaporate the irrigant and were weighed again. The difference between pre- and post-weights was calculated, and statistical evaluation was performed. Results: Inserting needles closer to the apex and using needles with wider diameters were associated with significantly more debris extrusion (p < 0.05). The position of needles and level of sections had statistically significant effects on sealer penetration depth (p < 0.05 for both). Conclusions: Following preparation, inserting narrower needles compatible with the final apical diameter of the prepared root canal at 3 mm short of WL during final irrigation might prevent debris extrusion and improve sealer penetration in the apical third.

• Journal of Haehwa Medicine
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• v.19 no.1
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• pp.119-128
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• 2010

Objective : Lower back pain is the most common pain in our life, and Heniated Intervetebral Disk(HIVD) of L-spine is one of the most common disease that cause lower back pain. This study is designed to invertigate the general distributions for HIVD patients. Subjects and Methods : The 193 patients who had taken diagnosis of HIVD by L-spine CT or L-spine MRI and admitted to Cheonan oriental medical hospital in Daejon university from January 2008 to December 2009 were reviewed. They were analyzed according to sex, age, prevalent duration, and causing factor. They were treated with acupuncture, herbal medicine and physical therapy. And treatment efficacy was evaluated according to each distribution respectively. Result 1. Among 193 patients, males were more than females in the ratio of 1.47:1. 2. According to age, 33.2% patients were thirties. 3. According to causing factor, 39.9% patients with unknown origin were most. 4. According to prevalent duration, 49.7% patients were on acute stage and 20.2% patients were on 6-10days. 5. According to HIVD types, patients with protruded disc type and with lesion of L4-5 were most common respectively 45.1%, 63.3%. 6. When effective rates were analyzed according to each distribution, patients on twenties, acute stage and with extruded disc type were showed good effective rates, respectively 92.7%, 90.6%, 89.3%. Conclusion: Total effect rate was 87.5%. Prevalence of HIVD is the highest in the age of 30 to 40, L4-5 occupy the most. And early treatment was better than late treatment.

• Journal of Acupuncture Research
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• v.23 no.3
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• pp.21-35
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• 2006

Objectives : Herniation of Nucleus Pulposus(HNP) of Cervical is the most important reason that causes Cervical pain. The aim of this study is to investigate the effectiveness of Carthmi-Flos Herbal acua-acupuncture therapy for Cervical disc Herniation patients. Methods : To evaluate the effectiveness of Carthmi-Flos Herbal acua-Acupuncture Therapy, 20 patients were treated by Carthmi-Flos Herbal acua-acupuncture therapy. To estimate the efficacy of treatment, we used Quardruple Visual Analog Scale (QVAS). Results & Conclusion : 1. As a objectivity treatment record, they test treatment record good 35%, fair 35%, excellent 30%. 2. After Carthmi-Flos acua-acupuncture therapy, pain rate changed from 8.80 to 5.40 3. By the results which puts out the statistics in sex , a pain rate of male changed from 8.57$({\pm}1.51)$ to 2.71$({\pm}2.63)$, a pain rate of female 8.92$({\pm}0.95)$ to 3.77$({\pm}2.09)$. Intentional difference is none as a therapy. 4. By the results which puts out the statistics in age, after forties changed from 9.07$({\pm}0.88)$ to 3.80$({\pm}2.43)$ and before forties changed from 8.00$({\pm}1.58)$ to 2.20$({\pm}1.30)$. Intentional difference is none as a therapy. 5. By the results which puts out the statistics in Duration, pain rate of the acutest group changed from 8.36$({\pm}1.12)$ to 2.18$({\pm}1.08)$, pain rate of the subacute group changed from 9.80$({\pm}0.45)$, to 5.20$({\pm}2.68)$, pain rate of the chronic group changed from 8.67$({\pm}1.53)$ to 3.33$({\pm}1.53)$. Intentional difference is none as a therapy. 6. By the results which puts out the statistics in the reading of Lumbar MID, pain rate of the Bulging type changed from 9.00$({\pm}1.05)$ to 4.30$({\pm}2.67)$, pain rate of the Protruded type changed from 8.50$({\pm}1.00)$, to 3.50$({\pm}1.29)$, pain rate of the Extruded type changed from 6.00 to 1.00, pain rate of the Mixed type changed from 9.20$({\pm}0.84)$ to 2.00$({\pm}1.23)$, Intentional difference is none as a therapy.

• Composites Research
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• v.26 no.4
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• pp.254-258
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• 2013

Polypropylene films reinforced with multi-walled carbon nanotubes and exfoliated graphite nanoplatelets were fabricated by extrusion, and the effects of filler type and take-up speed on the mechanical properties and microstructure of composite films were investigated. Differential scanning calorimetry revealed that the addition of carbon nanomaterials resulted in increased degree of crystallinity. However, increasing the take-up speed reduced the degree of crystallinity, which indicates that tension-induced orientations of polymer chains and carbon nanomaterials and the loss of degree of crystallinity due to rapid cooling at high take-up speeds act as competing mechanisms. These observations were in good agreement with tensile properties, which are governed by the degree of crystallinity, where the C-grade exfoliated graphite nanoplatelet with a surface area of $750m^2/g$ showed the greatest reinforcing effect among all types of carbon nanomaterials used. Scanning electron microscopy was employed to observe the carbon nanomaterial dispersion and orientation, respectively.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.112-119
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• 2020

In this study, cellulose-based bacterial pellets was used for the self-healing concrete manufacturing. The pellet is composed of complex cultured bacterial spore powder, methyl cellulose, two kinds of PVA nutrients and water, and is extruded through a hydraulic press to have a shape of 2mm in diameter to 3 to 4mm in length. Cellulose pellets expand at neutral pH, release bacteria and nutrients, and do not react in a basic environment, increasing the long-term survival rate of bacteria in cement mortar. In addition, pellet self-healing performance of pellet mortar was significantly higher than that of control mortar. Cellulose-based pellets are a new type of bacterial carrier system that will help develop self-healing concrete in the future by improving and optimizing pellets.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.1 s.94
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• pp.227-237
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• 1999

As the interface bonding phenomenon between the matrix and the reinforcements has a large effect on the mechanical properties of MMCs, a sugestion of the strength analysis technique considering the residual stress and the interface bonding phenomenon is very important for the design of pans and the estimation of fatigue behavior. In this paper the three dimensional finite element anaysis is performed during the elasto-plastic deformation of the particulate reinforced metal matrix composites. It was analyzed with the volume fractions in view of microscale. Bonding strength. interface separation and matrix void growth between the matrix and the reinforcements will be predicted on deformation under tensile loading. An interface seperation is estimated by the fracture criterion which is a critical value of generalized plastic work per unit volume. The shape of the reinforcement is assumed to be a perfect sphere. And the type of the reinforcement distribution is assumed as FCC array. The thermal residual stress in MMCs is induced by the heat treatment. It is included at the simulation as an initial residual stress. The element birth and death method of the ANSYS program is used for the estimation of the interface bonding strength, void generation and propagation. It is assumed that the fracture in the matrix region begin to occur under the external loading when the plastic work per unit volume is equal to the critical value. The fracture strain will be defined. The experimental data of the extruded $SiC_p$>/606l Al composites are compared with the theoretical results.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.662-667
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• 2009

Porous SiC candle filter preforms were fabricated by extrusion and ramming process. To fabricate SiC candle filter preform, commercially available 85 ${\mu}m\;{\alpha}-$-SiC powder and 44 ${\mu}m$ mullite, CaC$O_3$ powder were used as the starting materials. The candle type preforms were fabricated by vacuum extrusion and ramming process, and sintered at $1400{^{\circ}C}$ 2 h in air atmosphere. The effect of forming method on porosity, density, strength (flexural and compressive strength) and microstructure was investigated. Also, corrosion test of the sintered candle filter specimens as forming method was performed at $600{^{\circ}C}$ in IGCC syngas atmosphere. The sintered SiC filter which was formed by ramming process has more higher density and exhibit higher strength than extruded filter. Its maximum density and 3-point bending strength were 2.00 g/$cm^3$ and 45 MPa, respectively.

• Journal of Biosystems Engineering
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• v.22 no.4
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• pp.439-450
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• 1997

Most of Korean feed mill has a pregrind system which was suitable for the processing of less number of ingredients and finished products, and good for the mash type feed product. But industries has been changed in production volume and cost, and also from mash to further processed products such as pelleted and extruded. Therefore, Korea feed industries now should change the process, especially the grinding system from the current pregrind to other grind system, but this change will cost a lot of investment and also loosing current grinding system, and should have production shut down during the construction period. To solve these problems, combined grinding system based on a new model mill has been developed. The combined grind system is combination of pregrind and postgrind system, which has the advantages of those two grind systems, and also which can allow to utilize existing pregrind system continuously without any production interruption due to new postgrind system construction. This newly developed model has been applied to the feed mill expansion project of `B`feed company in 1994, and it was very successful application and showed excellent results as we intended. The new model mill, combined grind system applied can save fixed asset investment because old pregrind system can be used as is, and also can reduce production cost and improve product quality. And the possibility of critical production shut down can be much lowered. Within this new grinding model development, multi-screen combination system has been developed for the better grinding texture quality and safer operation. This new model mill with combined grind system will be applied by most feed manufacturing plant and may enhance their production competitiveness, and the further study and development should be continued.

• Applied Biological Chemistry
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• v.25 no.3
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• pp.119-125
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• 1982

Using piston type extruder, barley flour was extruded at various processing conditions, The used variables were three shear rates (apparent shear rate 118, 534, $1169sec^{-1}$), four extrusion temperatures(90, 120, 150, $180^{\circ}C$) and three moisture contents (15, 25, 35%). The rheological properties and the extrudate quality were monitored in extrusion. Barley flour showed pseudoplastic behavior having average power law index 0.28 in used shear rate range. When viewed from general appearance, die swell, density, water uptake, rehydration swell and gelatinization degree of extrudate, $25{\sim}35%$ moisture and $120^{\circ}C$ temperature was suitable processing condition for noodle-like product, and 25% moisture and $150^{\circ}C$ temperature was good for snack or flake product. Moisture content of the extrudate can be pretty well estimated from energy balance at higher temperature and higher moisture content.