• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.522-526
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• 2012

New experimental method to measure solid descending velocity in a vertical downcomer was presented and effects of downcomer diameter and particle properties on descending velocities for Geldart group A, B, and D particle have been measured and investigated. The effect of initial solid inventory on solid descending velocity was negligible. However, solid flow rate, solid circulation rate and solid descending velocity increased as the downcomer diameter increased. Moreover, solid descending velocity increased linearly as the downcomer diameter increased and showed distinguishable trend for Geldart group D particle from Geldart group A and B particles. Empirical correlations of solid descending velocity for Geldart group D and Geldart group A and B particles have been derived based on the measured values. The correlations could predict well the solid descending velocities.

• Resources Recycling
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• v.32 no.2
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• pp.33-42
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• 2023

Metal emulsions have been studied for several decades as a method of increasing the efficiency of the steelmaking process. This study was performed using a water model, observable at room temperature, to compensate for the disadvantages of the high-temperature experiment, the results of which are difficult to observe visually. As a substitute for metal-in-slag emulsions, experiments were conducted by dropping distilled water into silicone oil and comparing the results with the results of a calculation by momentum balance equations. The descending velocity of the water droplet decreased as the diameter of the droplet and viscosity of the fluid (silicon oil) increased. To simulate the descending velocity of a water droplet in silicon oil under stirring conditions, the flow rate of the fluid (silicon oil) was measured by particle image velocimetry (PIV) methods. The calculation of the descending velocity of the water droplet was in good agreement with the measured values, with and without stirring a viscous silicone oil.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.249-250
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• 2015

This study contemplated the descending air current from the smoke layers related to the smoke logging phenomenon in the Water Mist applied design for effective evacuation safety design. As a result, database on the average particle diameter, particle velocity and distribution of sprinkling was obtained and the relationship between the water amount and particle diameter was obtained. Also Descending smoke velocity was significantly faster to 9.8m/s, it is determined that appeared rapidly by a high water pressure.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.121-122
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• 2014

This study contemplated the descending air current from the smoke layers related to the smoke logging phenomenon in the sprinkler applied design for effective evacuation safety design. As a result, database on the average particle diameter, particle velocity and distribution of sprinkling was obtained and the relationship between the water amount and particle diameter was obtained. Also, in relation to descending air current, the movement of smoke layer to the bottom at the descending air current velocity of 0.6m/s was observed and stable descending air current was observed in existence of fire source over 100kW in size.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.9
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• pp.1165-1173
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• 1997

The steady state close-contact melting phenomenon occurring between a phase change material and an isothermally heated flat plate with relative motion is investigated analytically, in which the effects of vertical convection in the liquid film and solid-liquid density difference are incorporated simultaneously. Not only the scale analysis is conducted to estimate a priori qualitative dependence of system variables on characteristic parameters, but also an analytical solution to a set of simplified model equations is obtained to specify the effects under consideration. These two results are consistent with each other, in that the vertical convection affects both the solid descending velocity and the film thickness, and that the density difference alters only the solid descending velocity. While the effect of vertical convection can be characterized conveniently by a newly introduced temperature gradient factor which asymptotically approaches the unity/zero with decreasing/increasing the Stefan number, that of density difference is represented by the liquid-to-solid density ratio. It is shown that the solid descending velocity depends linearly on the density ratio, and that the ratios of solid descending velocity, film thickness and friction coefficient to the conduction solution are proportional to 3/4, 1/4 and -1/4 powers of the temperature gradient factor, respectively. Also, established is the fact that the effect of convection can be legitimately neglected in the analysis for the range of the Stefan number less than 0.1.

• Journal of Oriental Neuropsychiatry
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• v.15 no.2
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• pp.173-180
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• 2004

Objectives : The purpose of this study is to investigate the change of cerebral blood flow velocity by different types of suggestion in normal subject. Methods : Suggestion of ascending qi inducement and descending qi inducement which were recomposed from autogenic training, was operated on 60 normal subjects individually. Then cerebral blood flow velocity was examined by Transcranial doppler ultrasonography(TCD) each 5 minutes before and after suggestion. Results : The result shows that cerebral blood flow(CBF) velocity was increased significantly in suggestion of ascending qi inducement and CBF velocity was decreased significally after 1 minute in suggestion of descending qi inducement. Conclusion : Suggestion could have affected to CBF velocity, and also different types of suggestion could have affected to the change of brain blood flow. Various clinical studies should be completed on patients in the future.

• Advances in aircraft and spacecraft science
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• v.5 no.5
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• pp.551-579
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• 2018

This work is concerned with the motion of propeller driven airplanes, flying at constant velocity on ascending or descending rectilinear trajectories. Its purpose is to provide important features of rectilinear flights that are required for airplane trajectory planning but that cannot be found already published. It presents a method for calculating the amount of fuel used, the restrictions on the trajectory parameters, as inclination and speed, which result from the load factor, the lift coefficient, the positivity and upper boundedness of the power available. It presents a complete discussion of both ascending and descending flights, including gliding. Some original remarks are made about the parameters of gliding. It shows how to construct tables of parameters allowing to identify rapidly flyable trajectories. Sample calculations are shown for the Cessna 182 and a Silver Fox like unmanned aerial vehicle.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.12
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• pp.3970-3979
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• 1996

A fluid flow inside a circular cylinder subject to horizontal, circular oscillation is analyzed numerically and experimentally. The steady streaming velocities at the edges of the boundary layers on the bottom and side surfaces of the cylinder obtained in the previous paper are used as the boundary conditions in the governing equations for the steady flow motion in the interior region. The Stokes' drift velocity obtained in the previous paper also constitutes the Lagrangian velocity which is used in the momentum equations. It turns out that the interior steady flow is composed of one cell, ascending at the center and descending near the side surface, at the streaming Reynolds number 2500. However, at the streaming Reynolds number 25, the flow field is divided into two cells resulting in a descending flow at the center. The experimentally visualized flow patterns at the bottom surface agree well with the analytical solutions. The visualization experiment also confirms the flow direction as well as the center position of the cell obtained by the numerical solutions.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.797-807
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• 2008

For this study, the semi-adiabatic temperature rising test is accomplished by using ternary system cement (OPC, BFS, FA) reducing temperature crack. Two tests are conducted; one is for the paste test, and the other is for the concrete test. As the results of paste tests, using fly ash is better to reduce hydration temperature than doing blast furnace slag. In the case of the paste mixed ternary system cement, the more fly ash is mixed and the less blast furnace slag is used, the lower the temperature is. The less the mixture ratio of blast furnace slag is and the more the mixture ratio of fly ash is, the later the temperature rising velocity and descending velocity are. Besides, the temperature is lower if water/binder ratio is high. The use of ternary system cement has the retardation effect of temperature rising because the time to reach the maximum temperature is in the order of OPC100, binary system cement, and ternary system cement. From the test, the maximum temperature of concrete used ternary system cement is $8{\sim}11^{\circ}C$ lower than that of concrete used OPC100. Moreover, temperatures rising velocity and descending velocity of ternary system cement range $47{\sim}51%$ and $37{\sim}42%$ compared with OPC100. The specimen of concrete shows remarkable low internal temperature and slow temperature rising velocity and descending velocity compared with the specimen of paste because it is that temperature loss of concrete is much more than paste specimen according to aggregates.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.12
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• pp.1710-1719
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• 1997

An approximate analytical solution for the initial transient process of close-contact melting occurring between a phase change material kept at its melting temperature and an isothermally heated flat surface is derived. The model is so developed that it can cover both rectangular and circular cross-sectional solid blocks. Normalization of simplified model equations in reference to the steady solution enables the solution to be expressed in a generalized form depending on the liquid-to-solid density ratio only. A selected result shows an excellent agreement with the previously reported numerical data, which justifies the present approach. The solution appears to be capable of describing all the fundamental characteristics of the transient process. In particular, dependence of the solid descending velocity oft the density ratio at the early stage of melting is successfully resolved. The effects of other parameters except the density ratio on the transient behaviors are efficiently represented via the steady solution implied in the normalized result. A simple approximate method for estimating the effect of convection on heat transfer across the liquid film is also proposed.