• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.379-388
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• 2006

This paper presents a model for evaluating the contribution by arch action to shear resistance in shear-critical reinforced concrete beams. Based on the relationship between shear and bending moment in beams subjected to combined shear and bending, the behavior of a beam is explicitly divided into two base components of the flexural action and the tied arch action. The compatibility condition of the shear deformation that deviates from Bernoulli bending plane is formulated utilizing the smeared truss idealization with an inclined compression chord. The Modified Compression Filed Theory is employed to calculate the shear deformation of the web, and the relative axial displacements of the compression and the tension chord by the shear flow are also calculated. From this shear compatibility condition in a beam, the shear contribution by the arch action is numerically decoupled. Then the validity of the model is examined by applying the model to some selected test beams in literatures. The results may confirm the rationale of the proposed behavioral model.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.6
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• pp.699-706
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• 2007

The cooling heat transfer coefficient and pressure drop of $CO_2$(R-744) in helical coil copper tubes were investigated experimentally The main components of the refrigerant loop are a receiver, a variable-speed pump, a mass flow meter. a pre-heater and a inclined helical coil type gas cooler (test section). The test section consists of a smooth copper tube of 2.45 and 4.55mm inner diameter The refrigerant mass fluxes were varied from 200 to $600 [kg/m^2s]$ and the inlet pressures of 9as cooler were 7.5 to 10.0 [MPa]. The heat transfer coefficients of $CO_2$ in helical coil tubes increase with the increase of mass flux and gas cooling pressure of $CO_2$. The pressure drop of $CO_2$ in the gas cooler shows a relatively food agreement with those Predicted by Ito's correlation developed for single-phase in helical coil tubes. Though a few correlation available with the data. the local heat transfer coefficient of $CO_2$ agrees well with those presented by Pitla et al. among the predictions. However at the region near pseudo-critical temperature. the experiment data indicate higher values than the Pitla et al. correlation.

• Journal of Mechanical Science and Technology
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• v.18 no.2
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• pp.185-192
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• 2004

The aeroacoustic characteristics of a centrifugal fan for a vacuum cleaner and its noise reduction method are studied in this paper. The major noise source of a vacuum cleaner is the centrifugal fan. The impeller of the fan rotates at over 30000 rpm, and generates very high-level noise. It was revealed that the dominant noise source is the aerodynamic interaction between the rotating impeller and stationary diffuser. The directivity of acoustic pressure showed that most of the noise propagates backward direction of the fan-motor assembly. In order to reduce the high tonal sound generated from the aerodynamic interaction, unevenly pitched impeller and diffuser, and tapered impeller designs were proposed and experiments were performed. Uneven pitch design of the impeller changes the sound quality while the overall sound power level (SPL) and the performance remains similar. The effect of the tapered design of impeller was evaluated. The trailing edge of the tapered fan is inclined. This reduces the flow interaction between the rotating impeller and the stationary diffuser because of some phase shifts. The static efficiency of the new impeller design is slightly lower than the previous design. However, the overall SPL is reduced by about 4 dB(A). The SPL of the fundamental blade passing frequency (BPF) is reduced by about 6 dB (A) and the 2$\^$nd/ BPF is reduced about 20 dB (A). The vacuum cleaner with the tapered impeller design produces lower noise level than the previous one, and the strong tonal sound was dramatically reduced.

• Journal of Korea Water Resources Association
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• v.47 no.12
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• pp.1165-1176
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• 2014

In a river bend the water surface is inclined by the centrifugal force toward the transverse section. If channel slope and flow rate increase, the gradient is rising generally. There are lots of the flood damage at the bends of mountain river because the flood water levels have exceeded frequently the levee levels which are added a free board to the design flood water level. Therefore the superelevation should be considered in designing the mountainous river bend. In present study it was proposed to estimate the superelevation at the bend of mountain river and the superelevation coefficient defined from multiplying the sub-factors. The values of the influence factors for the superelevation coefficient were suggested from analyzing the superelevation measured at the bends in Yangyangnamdae river and the hydraulic experiments in gravel-bed channel with a $90^{\circ}$ bend. The applicability of these methods to estimate the superelevation at the bends in mountain river was verified by the superelevation measured at the bend in Naerin river.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.1
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• pp.105-113
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• 2009

The performance of a direct-injection type diesel engine often depends on the strength of swirl or squish, shape of combustion chamber, the number of nozzle holes, etc. This is of course because the combustion in the cylinder was affected by the mixture formation process. In this paper, combustion process of biodiesel fuel was studied by employing the piston which has several grooves with inclined plane on the piston crown to generate swirl during the compression stroke in the cylinder in order to improve the atomization of high viscosity fuel such as biodiesel fuel and toroidal type piston generally used in high speed diesel engine. To take a photograph of flame, single cylinder, four stroke diesel engine was remodeled into two stroke visible engine and high speed video camera was used. The results obtained are summarized as follows; (1) In the case of toroidal piston, when biodiesel fuel was supplied to plunger type injection system which has very low injection pressure as compared with common-rail injection system, the flame propagation speed was slowed and the maximum combustion pressure became lower. These phenomena became further aggravated as the fuel viscosity gets higher. (2) In the case of swirl groove piston, early stage of combustion such as rapid ignition timing and flame propagation was activated by intensifying the air flow in the cylinder. (3) Combustion process of biodiesel fuel was improved by the reason mentioned in paragraph (2) above. Consequently, the swirl grooves would also function to improve the combustion of high viscosity fuel.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.4
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• pp.879-892
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• 2003

This thesis makes a review of symptoms and cause of the numbness in the literature. clinical case are studied and classified according to the Hyungsang of the patients. The followings are the conclusions: In case of Dam type persons, numbness is mainly caused by Fire with blood deficiency and so cured by tonifying the Jung and blood. In case of Bang Kwang type persons. it is generally caused by the deficiency of Ki and damp-phlegm and treated by reinforcing Ki and removing dampness. Persons of Jung and Hyal types are apt to be afflicted with numbness of deficiency symptoms which can be cured by tonifying the Jung and blood. Those of Ki and Shin types are inclined to get numb from the congestion and stagnancy and so treated by promotion the flow of Ki, dispelling stagnancy, resolving phlegm and promoting digestion. Numbness is common to the old people and women. The deficiency of blood and primordial energy is a cause of old people's numbness. Women get numb due to the pent-up feelings and emotional disturbance. The function disharmony of five Jang and six Bu makes the body lose the control of heat and cold or deficiency and excessiveness, which can be a cause of numbness. Especially the deficiency of the spleen results in numbness. When the special parts of the body become numb treatment must be decided after due consideration on which of the Jang and Bu or meridians is related to that affected area. In case of person with six meridian types. unbalance of Ki and blood leads the six atmospheric influences(wind, cold, heat, dampness, dryness and fire) get into the body through the most developed meridian and brings in numbness.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.323-331
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• 2019

In this study, a computational model approach for the modeling of hydrodynamic pressures acting on radial gates during strong earthquakes is proposed. The use of the dynamic layering method with the Arbitrary Lagrangian Eulerian (ALE) algorithm and the SIMPLE method for simulating free reservoir surface flow in addition to moving boundary interfaces between the fluid domain and a structure due to earthquake excitation are suggested. The verification and validation of the proposed approach are realized by comparisons performed using the renowned formulation derived by the experimental results for vertical and inclined dam surfaces subjected to earthquake excitation. A parameter study for the truncated lengths of the two-dimensional fluid domain demonstrates that twice the water level leads to efficient and converged computational results. Finally, numerical simulations for large radial gates with different curvatures subjected to two strong earthquakes are successfully performed using the suggested computational model.

• Journal of The Korean Society of Agricultural Engineers
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• v.64 no.2
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• pp.37-45
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• 2022

In-situ pilot experiment was carried out to establish a countermeasure on the soil loss from the hill side uplands that was rehabilitated by soil remediation method nearby abandoned mine sites for 2 years. It was considered that the affect of an inclination of cover surface, a stabilization treatment of cover layer by lime and steel refining slag (SRS) and a vegetation of soil surface as an effect factors in the experiment. It was constructed 4 lysimeters (plots, 22 m long, 4 m width) on the hilly side (37% inclination). One plot was control and two plots was treated by 1% lime and SRS. A remind one plot was modified a inclination to 27% to compare the affect of inclination on the amount of cover soil loss. It was attached a reservior tank and water level gauge in the end of lysimeters to measure the amount of the surface water flow and soil loss. It was also installed the automated sensors that could be collect the precipitation, soil moisture content, tension of cover layer in each plots. It was observed that the event of precipitation were caused the soil loss and it were related the physical and chemical properties of cover soil and inclination of surface layer of plots. During the experiment, it was exceeded the national regulation (50 t/ha/yr) in 37% inclination plots even though it was vegetated on the cover soil surface. However, in 27% inclination plot, it was shown that the amount of soil loss was maintained below the national regulation and, more ever, vegetation could reduce the the amount of soil loss. Therefore it was expected that such results could be applied to the future design of rehabilitation projects on the polluted farmland nearby abandoned mine sites.

• Transactions of the Korean hydrogen and new energy society
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• v.34 no.1
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• pp.8-16
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• 2023

In this work, we report basic performance test results of a lab-scale three phase alternative current (AC) arc plasma torch system for plasma gas reforming applications. The suggested system primarily consists of three graphite electrodes inclined at 12.5° to the central axis, a 𝞥 150 mm cylindrical gas path and a three phase-60 Hz AC power supply. At air flow rate of 50 Lpm and arc currents of 100-175 A, test results revealed that plasma resistances were decreasing from 1.08 Ω to 0.53 Ω with the increase of plasma power from 9.3 kW to 13.8 kW, causing the decrease of power factor and increase of the line voltages. However, the injected air can be heated quickly up to the temperatures of >1,200℃ when injecting AC arc plasma powers of >10 kW.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2B
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• pp.171-178
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• 2006

The finite element model based on the 2-D advection-dispersion equation incorporating the dispersion tensor that is calculated using velocity field data was developed in order to analyze more accurately 2-D mixing of pollutants for meandering streams. The proposed model was tested using the straight channel that inclined at 45o in the Cartesian coordinate system. The simulation results showed that dispersion tensor model using velocity field data gives an accurate solution. The suitability of the proposed model in analyzing actual pollutant mixing in meandering channels was demonstrated by comparing the simulation results with experimental data obtained from the tracer tests in the laboratory flume. Comparison results showed that the proposed model with dispersion tensor can represents more accurately the mixing phenomena of the pollutants in the meandering channels in which the direction of the primary flow is varying periodically along the channel.