• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.12
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• pp.2989-2994
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• 2000

A mechanical face seal is a tribo-element intended to control leakage of working fluid at the interface of a rotating shaft and its housing. Leakage of working fluid decreases drastically as the clearance between mating seal faces gets smaller. But the very small clearance may result in an increased reduction of seal life because of high wear and heat generation. Therefore, in the design of mechanical face seals a compromise between low leakage and acceptable seal life is important, ant it present a difficult and practical design problem. A fluid film or sealing dam geometry of the seal clearance affects seal lubrication performance very much, and thereby is optimization is one of the main design consideration. in this study the Reynolds equation for the sealing dam of mechanical face seals is numerically analyzed, using the Galerkin finite element method, which is readily applied to various seal geometries, to give lubrication performances, such as opening force, restoring moment, leakage, and axial and angular stiffness coefficients. Then, to improve the seal performance an optimization is performed, considering various design variables simultaneously. For the tested case the optimization ha successfully resulted in the optimal design values of outer and inner seal radii, coning, seal clearance, and balance radius while satisfying all the operation subjected constraints and design variable side-constraints, and improvements of axial and angular stiffness coefficients by 16.8% and 2.4% respectively and reduction of leakage by 38.4% have been achieved.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.426-432
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• 2006

This paper describes the concepts of Static Line Rating (SLR) and Dynamic Line Rating (DLR) and the computational methods to demonstrate them. Calculation of the line capacity needs the heat balance equation which is also used for computing the reduced tension in terms of line aging. SLR is calculated with the data from the worst condition of weather throughout the year. Even now, the utilization ratio is obtained from this SLR data in Korea. DLR is the improved method compared to SLR. A process for DLR reveals not only improved line ratings but also more accurate allowed line ratings based on line aging and real time conditions of weather. In order to reflect overhead transmission line aging in DLR, this paper proposes the method that considers the amount of decreased tension since the lines have been installed. Therefore, the continuous allowed temperature for remaining life time is newly acquired. In order to forecast DLR, this paper uses weather forecast models, and applies the concept of Thermal Overload Risk Probability (TORP). Then, the new concept of Dynamic Utilization Ratio (DUR) is defined, replacing Static Utilization Ratio (SUR). For the case study, the two main transmission lines which are responsible for the north bound power flow in the Seoul metropolitan area are chosen for computing line rating and utilization ratio. And then line rating and utilization ratio are analyzed for each transmission line, so that comparison of the present and estimated utilization ratios becomes available. Finally, this paper proves the validity of predictive DUR as the objective index, with simulations of emergency state caused by system outages, overload and so on.

• Journal of Korea Society of Waste Management
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• v.34 no.5
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• pp.518-527
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• 2017

The development of renewable energy is currently strongly required to address environmental problems such as global warming. In particular, biomass is highlighted due to its advantages. When using biomass as an energy source, the conversion process is essential. Fast pyrolysis, which is a thermochemical conversion method, is a known method of producing bio-oil. Therefore, various studies were conducted with fast pyrolysis. Most studies were conducted under a lab-scale process. Hence, scaling up is required for commercialization. However, it is difficult to find studies that address the process analysis, even though this is essential for developing a scaled-up plant. Hence, the present study carries out the process analysis of biomass pyrolysis. The fast pyrolysis system includes a biomass feeder, fast pyrolyzer, cyclone, condenser, and electrostatic precipitator (ESP). A two-stage, semi-global reaction mechanism was applied to simulate the fast pyrolysis reaction and a circulating fluidized bed reactor was selected as the fast pyrolyzer. All the equipment in the process was modeled based on heat and mass balance equations. In this study, process analysis was conducted with various reaction temperatures and residence times. The two-stage, semi-global reaction mechanism for circulating fluidized-bed reactor can be applied to simulate a scaled-up plant.

• Journal of Korean Medical classics
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• v.25 no.2
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• pp.125-139
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• 2012

Objective : This study began with a recognition of the increase in internal disorders caused by functional impairment of the Spleen-Stomach(脾胃) due to modern dietary culture and environment. Method : Way of studying is select and analysis sentences which is include 'Stomach-Yin(胃陰)', 'Stomach-Jin(胃津)', 'Spleen-Stomach-Yin(脾胃陰)', 'Stomach-Yang(胃陽)', 'Spleen-Stomach-Yang (脾胃陽)' in Imjeungjinamuian(臨證指南醫案), and organize relevant paper. Result & Conclusion : In the history of the Spleen-Stomach Theory(脾胃學說), the theoretical mainstream was focused on On-yang(溫養), which was supplemented with methods of sweeten-cool-moisturize(甘凉濡潤) and communication-descent(通降法) by Ye, Tianshi(葉天士). Ye, Tianshi followed the academic theory of Li, Dongyuan(李東垣), putting emphasis on Stomach-gi(胃氣), along with some unique developments of his own. He specifically argued that the Spleen and Stomach be treated separately, and while accepting the methods of Li Dong-yuan in Spleen treatment, asserted that the Stomach-Yin be treated with medicinals with sweet/plain and sweet/cool/moist(甘平與甘凉濡潤) characteristics, and Stomach-Yang be kept firmly, as to prevent obstruction and reflux, by means of medicinals that communicate the Yang softly(通陽柔劑). As a result, the Yin-Yang(陰陽), Dryness-Dampness(燥濕) and Cold-Heat(寒熱) balance of the Yin-Jang (陰臟), Spleen and the Yang-Bu(陽腑), Stomach, the Stomach-Yin and Stomach-Yang was achieved both theoretically and in treatment by means of both communication and supplementation, adding accuracy to clinical application of the Spleen-Stomach Theory.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.11
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• pp.1794-1805
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• 2009

This study investigates the influence of slit positions on the microclimate temperature/humidity of garments. To design the slits, a market survey was performed to indicate the method to apply the slits, in addition to a literature survey about muscles and body surface variation through body movements. Based on the survey, three positions of slits were selected, shoulder slit, lowback slit, and midback slit, a slit width of 1cm and length to 30cm was used. The results showed that microclimate temperatures/humidity on the back according to the slit positions were in the order of, lowback, midback, and the shoulder. The lowback slit showed the highest effect on the temperature/humidity of a front trunk. Lowback slits affected on localized areas of the glutaeus maximus, erector spinae, and latissimus dorsi. Midback slits affected the back muscle and deltoid. Shoulder slits showed a more significant effect on the localized area of the deltoid versus other localized areas. In the subjective sensations, the lowback slit was cooler, dryer, and more comfortable than the other slits. For the subjective sensations by fabric characteristics, the slit positions correlated at |r|${\geq}.8$ and were significant at p<.001 The results show that the lowback slit has a superior air exchange effect and thermoregulation qualities.

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
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• v.31 no.4
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• pp.65-82
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• 2018

Objectives : The purpose of this study is 1) to explore the general tendency of the herbs or herbal formula for acne treatment in clinical practice 2) and to provide a basis for explaining the principles of acne treatment in Korean Medicine in order to make patients understand more easily based on pharmacological mechanism by analyzing the herbs or herbal formula using for acne treatment in clinical practice. Methods : In the domestic databases (Oriental medicine Advanced Searching Integrated System-OASIS, Korean Traditional Knowledge Portal-KTKP, National Discovery for Science Leader-NDSL, Research Information Sharing Service-RISS), we selected among the papers published using search terms related to "acne". Reports related to sasang constitutional medicine were excluded and a total of 23 papers were finally selected. Results : 29 prescriptions were retrieved from 23 papers. Chungan-tang (淸顔湯) notified formulas ranked first by Cheongsangbangpung- tang (淸上防風湯), Hwangnyeonhaedok-tang (黃連解毒湯), Dangguijakyaksan (當歸芍藥散) and Bipachungpe-eum (枇杷淸肺飮). Commonly used herbs are Forsythiae Fructus (連翹), Scutellariae Radix (黃芩), Gardeniae Fructus (梔子), Ligustici Rhizoma (川芎), and Angelicae Gigantis Radix (當歸). In most patients with inflammatory lesions or excessive flushing, exterior-releasing medicinal (解表藥) and heat-clearing medicinal (淸熱藥) were mainly prescribed for acne treatment, while in patients with acne accompanied hyperkeratinization, Excess sebum secretion, Dysmenorrhea or indigestion, qi-tonifying medicinal (補氣藥) or blood-tonifying medicinal (補血藥) were mainly used. KAGS (Korean Acne Grading System) was the most commonly used method for acne severity assessment. Conclusions : These findings suggest that the herbs or herbal formula for acne treatment in Korean Medicine is prescribed differently according to the cause and symptoms of acne in a unique way for control the whole body balance. Also, our findings could provide a basis for explaining the principles of acne treatment in Korean Medicine in order to make patients understand more easily based on pharmacological mechanism in clinical practice.

• Culinary science and hospitality research
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• v.4
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• pp.249-269
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• 1998

What satisfies the desire of human beings about taste most easily is sweet taste, and it has seemed that the pronoun of sweet taste is sugar. Sugar is used in confectionery and bread-making essentially, and it has influence on the structure and touch of baked confectionery. In addition, if we soften the and apply heat, coloring is made. Thus, it colors good. It doesn't have a sweet taste, but it has the effect to emit fragrance variously, balance and soften the product. The kinds of sugar are very diverse, and it is sugar to be referred to as white sugar is used most frequently. In this study, this researcher examined the classification of physicochemical property and melting point etc. of sugar in confectionery and bread-making through theoretical study, about the simple classification of sugar. In addition, this researcher approached about the role of sugar in confectionery and bread-making and about the influence to have when it is more or less than proper quantity, centering around function. As the result, this researcher extracted the importance of sugar in confectionery and bread-making. It means that the increase of 5% of sugar quantity decreases the absorption quantity of moisture by 1% in bread-making and that the excess of 8% of sugar slow the action of yeast in straight method. Besides, there are the properties such as absorptive property, permeability, storage nature, aging prevention of starch, oxidation restraint of oils and fats, the gelation action of pectin, the fermentation acceleration of yeast, and the emulsification-maintaining-nautre and antiseptics effect of fat-soluble material. And in confectionery, sugar makes fragrance and peel color, increases the storage nature with moisture maintenance and has the softening effect. So, it is considered that the attitude to study and make efforts continuously on the basis of the role of sugar will have to be unfolded in confectionery and bread-making.

• Journal of Environmental Science International
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• v.16 no.3
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• pp.261-267
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• 2007

In this study, the Slab Ocean Model (SOM) is coupled with an Atmospheric General Circulation Model (AGCM) which developed in University of Kangnung based on the land surface model of Biosphere-Atmosphere Transfer Scheme (BATS). The purposes of this study are to understand radiative role of clouds considering of the atmospheric feedback, and to compare the Clouds Radiative Forcing (CRF) come from the analyses using the clear-cloud sky method and CGCM. The new CGCM was integrated by using two sets of the clouds with radiative role (EXP-A) and without radiative role (EXP-B). Clouds in this two cases show the negative effect $-26.0\;Wm^{-2}$ of difference of radiation budget at top of atmosphere (TOA). The annual global means radiation budget of this simulation at TOA is larger than the estimations ($-17.0 Wm^{-2}$) came from Earth Radiation Budget Experiment (ERBE). The work showed the surface negative effect with $-18.6 Wm^{-2}$ in the two different simulations of CRF. Otherwise, sensible heat flux in the simulation shows a great contribution with positive forcing of $+24.4 Wm^{-2}$. It is found that cooling effect to the surface temperature due to radiative role of clouds is about $7.5^{\circ}C$. From this study it could make an accurate of the different CRF estimation considering either feedback of EXP-B or not EXP-A under clear-sky and cloud-sky conditions respectively at TOA. This result clearly shows its difference of CRF $-11.1 Wm^{-2}$.

• Transactions of the KSME C: Technology and Education
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• v.5 no.2
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• pp.97-104
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• 2017

In this study, we verify the accurate numerical analysis and simplify the perforated plate of inlet and exhaust duct using porous media for the cost reduction and the efficiency improvement of thermal-fluid analysis to evaluate cooling performance of wheel-loader. The flow loss coefficient of the perforated plate is defined by the experiment result. To define analytically the flow loss coefficient of the perforated plate, we calculate the pressure drop of unit-cell and compare to experiment result. Finally, we compare the heat balance test and the simplified simulation result on the inlet and exhaust duct of wheel-loader. After this study, we verify the applicability of the simplified analysis method on the inlet and exhaust duct of wheel-loader. And, foundation which can carry out effectively the evaluation and improvement for cooling performance of wheel-loader is prepared.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.23-30
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• 2009

A new high performance and low cost unified power system is proposed through investigating conventional Power-Integrated Drive(PID) system and Power-Separated Drive(PSD) system applied to LCD TV. Since the proposed system consists of two stage, namely power and inverter stage it features high efficiency and cost effectiveness. To satisfy the safety standard of the High voltage transformer, 1:1 transformer is employed between inverter and high voltage transformer. Moreover, to ensure the Zero Voltage Switching(ZVS) of all power switches and the Pulse Count Modulation(PCM) method is employed, which controls the number of pulse at the fixed frequency and fixed duty cycle. Therefore, it features high efficiency, improved heat generation, cost effectiveness and good EMI performance including no additional current balancing coil. To confirm the validity of proposed system, comparison of conventional system, verification of experimental results are presented.