• Journal of the Korean Society for Aviation and Aeronautics
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• v.22 no.4
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• pp.93-98
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• 2014

In this study, control of oxidizer mass flow rate and verification of control system were performed for hybrid rocket thrust control application. Oxidizer flow control system consists of ball valve and stepping motor where gaseous oxygen was used for oxidizer at feeding pressure of 10, 20 and 30 bar. According to experimental results, the oxidizer mass flow rate showed a relatively linear increment as ball valve open angle increases regardless of feeding pressure. In addition, the level of the oxidizer flow rate was kept almost constant at each sequence of flow control with ball valve during the 20 seconds of operation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.413-418
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• 2008

Flow instability in the rocket turbo pump system can be caused by various reasons such as valve, orifice and venturi, etc. The inception of cavitation, especially in the propellant feeding system, is the primary cause of the mass flow and pressure oscillation due to cyclic formation and depletion of cavitation. Meanwhile, the main propellant in liquid rocket engine is the cryogenic one, which is very sensitive to temperature variation, and the variation of propellant properties caused by thermodynamic effect should be accounted for in the flow analysis. The present study focuses on the formation of cryogenic cavitations by adopting IDM model suggested by Shyy and coworkers. Also, the flow instability was investigated in the downstream of orifice by using a developed numerical code. Calculation results show that cryogenic cavitations can lead to flow instability resulting in mass flow fluctuations due to pressure oscillations. And the prediction of cavitations in cryogenic fluid is of vital importance in designing feeding system of LRE.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.34-37
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• 2007

Propellant filling and holding test was carried out using liquid oxygen as a working fluid. The feeding line system has a filter at propellant tank outlet. Vaporization of liquid oxygen during holding after completion of filling and effect of vaporization to recirculation performance in this system was observed. Filling rate and pressure of tank ullage had the effect on state of liquid oxygen in feeding line. There was no geysering in feeding line during holding because of the position of filter.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.10
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• pp.35-43
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• 1997

In this paper, we perform a mechanism analysis and optimal design of the feeding system in a industrial sewing machine. Sewing machines are classified by the transfer mechanism as (1) transferred by feeddog only (2) transferred by feeddog and needle (3) transferred by feeddog, needle and pressure bar. The sewing machine classified as (2) is studied which is more efficient in transferring fabrics than the machine classified as (1). In analyzing the mechanism, we divide the feeding mechanism as feeddog mechanism and needle bar mechanism. The two mechanisms are conneted with each other kinematically because fabrics are transferred by two needles and a feeddog simultaneously and stitched by two needles which pass through the feeddog in every stitch cycle. We define good stitch as coincidence of stitch between the forward and reverse motion of feeding. We optimize the feeding mechanism for that purpose. It is illustrated that stitching performance of the optimized mechanism is compared to original feeding mechanism.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2001.11a
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• pp.141-141
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• 2001

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2004.11a
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• pp.183-188
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• 2004

• Nutritional Sciences
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• v.2 no.2
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• pp.76-81
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• 1999

Sodium restricted diets are known to lower blood pressure in salt sensitive, hypertensive patients. Thare is increasing evidence that potassium plays an important role as a protective factor in the regulation of blood pressure. The objective of the current study was to measure parameters of sodium, potassium, and chloride utilization as affected by feeding of substantial quantities of bread made from whole ground white torn meal, whole ground yellow corn meal, and whole ground wheat flour. The breads provided 40 percent of a caloric content of the constant, measured laboratory diet. The 28-day study was divided into an introductory period of 7-days and three experimental periods of 7-days each. Order of assignment to specific treatments for 12 healthy subjects were according to a complete randomized block design. Yellow corn bread diets resulted in the highest potassium retention (243 mg/day) and the lowest urinary sodium and potassium ratio (1.53 $\pm$ 0.26) numerically in comparison to the other test breads. The excretions of sodium and chloride were higher during controlled feeding periods than during the self-selected diet period(p < 0.05). This indicates a response to the higher intake of these electrolytes from the experimental diets than from self-selected diets. There was no significant difference in the effect of white corn bread, yellow corn bread, or whole wheat bread diet on electrolyte status in humans. However, the yellow corn bread diet resulted in a somewhat more favorable urina교 sodium to potassium ratio than that from white corn bread or whole wheat bread diet.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.1
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• pp.154-162
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• 1996

Ball screws are commonly used in linear motion feeding systems of various machine tools and automated systems. They are known to have relatively little backlash, high precision and efficiency compared to ordinary lead screws. Furthermore, the effectiveness of ball screw has made it the preferred choice of many newly developed high speed precision feeding units. The motivation of this work is to establish the groove edsigh basis of ball screws for the reduction of contact fatigue failure. In most instances, fatigue failure between ball and shaft groove is due to excessive contact pressure. Especially, the excessive load is causative of plastic flow below the contact surface, which can contribute to surface failure. But, in spite of small load, if groove conformity rate is large, contact pressure is increased and internal shear stress reach the yield value of the material. In such a point, the authors deal with design procedure for deciding the permissible conformity rate of a ball screw groove with the computational evaluation of contact pressure and maximum shear stress.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.241-244
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• 2006

The analysis of propellant feeding sub-system is performed using a commercial code SINDA/FLUINT, the comprehensive finite-difference, one-dimensional, lumped parameter tool. With the code, cryogenic helium supply system, liquid oxygen supply system, helium injection cooling system are evaluated. The code gave satisfactory estimation scheme for propulsion system characterized by cryogenic temperature and high pressure, two phase flow. This paper focuses on presenting calculation scheme of propulsion sub-system using one-dimensional code like SINDA/FLUINT.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.211-215
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• 2004

For design of cryogenic propellant feeding system, one of the main requirements is to meet temperature requirement for satisfying turbo-pump NPSH requirement. In this paper improved method of estimating the thermal stratification in liquid oxygen tank is presented to help design. In the case of liquid rocket using turbo-pump, the inner pressure of liquid oxygen tank is maintained low, so vaporization of liquid oxygen is generally occurred. In this paper, inner process of LOX tank is analyzed by two phase flow modeling. The vaporization rate and required helium mass is investigated.