• Journal of Advanced Marine Engineering and Technology
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• v.39 no.6
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• pp.609-613
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• 2015

In this study, the experiments are performed to investigate the local heat transfer and pressure drops of developed turbulent flows in the diverging square channels along the axial distance. The square divergent channels are manufactured with a fixed rib height (e) = 10 mm. Four different parallel angled ribs ($a=30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) are placed on the channel's one-sided wall only. TThe measurement are conducted within the range of Reynolds numbers from 22,000 to 79,000. The results show that a rib angle-of-attack of $45^{\circ}$ produces the best heat-transfer performance.

• Journal of Power System Engineering
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• v.19 no.5
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• pp.32-37
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• 2015

The present study is to investigates the convective heat transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The divergent rectangular channel is fabricated with V-shaped ribs on one wall only and the inlet hydraulic diameter to outlet hydraulic diameter ratio($D_{ho}/D_{hi}$) of 1.49 is used. The current investigation has covered a Reynolds number (Re) range of 22,000~75,000, relative roughness height ($e/D_h$) of 0.1~0.2, and rib angle of attack (a) of $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$ for a fixed relative pitch of 10. Results show that the Nusselt numbers are the greatest in the $60^{\circ}$-angled ribs; however, the total friction factors are the highest in the $30^{\circ}$-angled ribs.

• Korean Journal of Acupuncture
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• v.38 no.1
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• pp.1-7
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• 2021

Objectives : In the meridian pathway system, 5 yang meridians excluding bladder meridian pass ST12. In this study, we tried to find out why 5 yang meridians pass ST12. Methods : 15 classics of acupuncture and moxibustion literature - 『Huangdimingtangjingjixiao』, 『Zhenjiujiayijing』, 『Huangdineijingtaisu』, 『Beijiqianjinyaofang』, 『Waitaimiyaofang』, 『Ishimpo』, 『Taipingshenghuifang』, 『Tongrenshuxue-zhenjiutujing』, 『Zhenjiuzishengjing』, 『Shisijingfahui』, 『Zhenjiujuying』, 『Yixuerumen』, 『Zhenjiudacheng』, 『Leijing』, and 『Leijingtuyi』- were reviewed and compared. Results : Five yang meridians passed ST12, and large intestine meridian and triple energizer meridian were closely related to ST12 in divergent channels. Stomach meridian and gall bladder meridian were related to ST12 in meridian muscles. ST12 was related to small intestine meridian in main cure effect. ST12 is in the best position to enter the body cavity. Conclusions : It can be seen that ST12 is closely related to all internal organs through the characteristics of stomach meridian. Therefore, it is thought that ST12's various characteristics largely explains a pathway to enter the body cavity in the hand and foot three yang meridians.

• Ocean and Polar Research
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• v.24 no.3
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• pp.189-196
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• 2002

A multichannel seismic survey was conducted in the southern Ayu Trough which is the only spreading boundary between the Philippine Sea and Caroline plates. The seismic system used in this study comprises of 2.46-l sleeve gun and a 12-channel streamer with a group interval of 6.25m. Migration technique was used to analyze seismic velocity, and poststack depth migration was applied to the stacked data. The sediment thickness obtained from the depth section tends to increase with distance from the spreading axis. Sedimentation rates are poorly constrainted in the study area. The apparent half-spreading rates estimated from the sediment thickness and sedimentation rate from DSDP hole on the caroline plate are 4.7mm/yr and 7.9mm/yr at $1^{\circ}24'N\;and\;0^{\circ}42'N$, respectively, which are fester than Previously suggested. On the basis of new oblique spreading geometry, the recalculated spreading rates are 5.4mm/yr and 9.1mm/yr at $1^{\circ}24'N\;and\;0^{\circ}42'N$, respectively. Seismic sections show that the topography is asymmetric across the Ayu Trough and the acoustic basement is rough. These features are consistent with the earlier suggestion that the Ayu Trough is a slow-spreading divergent boundary. A detailed examination of seismic profiles away from the axis shows that sediments can be divided into two layers which implies a possible change in the spreading rate anuor sedimentation condition during the formation of the trough.

• Membrane Journal
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• v.7 no.3
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• pp.142-149
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• 1997

The extended analysis on the diverging flow through asymmetric membrane pores has been performed in this study. Afore rigorous equations of velocity profile relevant to the divergent slit and cone shaped channels, which are widely used as a general pore model, have been obtained by employing a creeping flow approach of Newtonian fluids. As a degree of asymmetry (i.e., diverging angle) is increased, the predicted flow function shifts Toward the center region due to the incorporated wall effect, so that the overall velocity profile becomes decreased. It is true, as expected, that when the divergent channel is in the low diverging angle limit, the channel flow results in the Poiseuillean fashion by utilizing a lubrication approximation. The flow rate equation of each type of channel has been developed from the combined solution of velocity profile and pressure fields. The effect of diverging flow on the flow rate enhancement has been remarkably predicted, in which the flow rate increases with the increase of pore asymmetry. The advantage of our theoretical results lies in the analytical expression for the diverging flow behavior through pore channels as well as its ability to play a fundamental role on the related membrane filtrations such as microfiltration and ultrafiltration.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.262-270
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• 2004

Basic experiments were carried out using the THT-IV low-power Hall thruster to examine the influences of magnetic field shape and strength, and acceleration channel length on thruster performance and to establish guidelines for design of high-performance Hall thrusters. Thrusts were measured with varying magnetic field and channel structure. Exhaust plasma diagnostic measurement was also made to evaluate plume divergent angles and voltage utilization efficiencies. Ion current spatial profiles were measured with a Faraday cup, and ion energy distribution functions were estimated from data with a retarding potential analyzer. The thruster was stably operated with a highest performance under an optimum acceleration channel length of 20 mm and an optimum magnetic field with a maximum strength of about 150 Gauss near the channel exit and with some shape considering ion acceleration directions. Accordingly, an optimum magnetic field and channel structure is considered to exist under an operational condition, related to inner physical phenomena of plasma production, ion acceleration and exhaust plasma feature. A new Hall thruster was designed with basic research data of the THT-IV thruster. With the thruster with many considerations, long stable operations were achieved. In all experiments at 200-400 V with 1.5-3 mg/s, the thrust and the specific impulse ranged from 15 to 70 mN and from 1100 to 2300 see, respectively, in a low electric power range of 300~1300 W. The thrust efficiency reached 55 %. Hence, a large map of the thruster performance was successfully made. The thermal characteristics were also examined with data of both measured and calculated temperatures in the thruster body. Thermally safe conditions were achieved with all input powers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.364-367
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• 2005

A series of computational simulations have been carried out for non-reacting and reacting flows in channel-type and divergent scramjet combustor configurations with and without a cavity. Transverse injection of hydrogen is considered with the injection pressure varying from 0.5 to 1.5 MPa. The detailed resolution of the oscillatory flow and flame dynamics are captured at sufficient scale to identify the underlying physical mechanisms, and the role of combustor configuration, cavity and amount of heat addition could be understood.

• The Journal of Korean Academy of Prosthodontics
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• v.43 no.3
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• pp.352-362
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• 2005

Statement of problem. Accurate impression is essential to success of implant prostheses. But there have been few studies about the accuracy of fixture-level impression techniques in internal connection implant systems. Purpose. The purpose of this study was to compare the accuracy of two fixture-level impression techniques in two conditions (parallel and divergent) and to assess the effect of tightening sequences and forces on stresses generated on superstructures in internal connection implant system (Astra Tech). Material and methods. Two metal master frameworks made from two abutments (Cast-to Abutment ST) each and a corresponding, passively fitting, dental stone master cast with four fixture replicas (Fixture Replica ST) were fabricated. Ten dental stone casts for each impression techniques (direct unsplinted & splinted technique) were made with vinyl polysiloxane impressions from the master cast. Strain gauges for each framework were fixed midway between abutments to measure the degree of framework deformation on each stone cast. Pairs of strain gauges placed opposite each other constituted one channel (half Wheatstone bridge) to read deformation in four directions (superior, inferior, anterior, and posterior). Deformation data were analyzed using one-way ANOVA and the Tukey test at the .01 level of significance. And the effect of tightening sequences (right-to-left and left-to-right) and forces (10 Ncm and 20 Ncm) were assessed with ten stone casts made from parallel condition by the splinted technique. Deformation data were analyzed using paired t-test at the .01 level of significance. Conclusions. Within the limitations of this study, the following conclusions could be drawn. 1. Frameworks bent toward the inferior side on all casts made by both direct unsplinted and splinted impression techniques in both parallel and divergent conditions. 2. There was no statistically significant difference of accuracy between the direct unsplinted and splinted impression techniques in both parallel and divergent conditions (P>.01). 3. There was no statistically significant difference of stress according to screw tightening sequences in casts made by the splinted impression technique in parallel condition (P>.01). 4. Greater tightening force resulted in greater stress in casts made by the splinted impression technique in parallel condition (P<.01).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.7
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• pp.380-394
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• 2015

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.