• Transactions of the Korean Society of Mechanical Engineers
• /
• v.19 no.7
• /
• pp.1780-1786
• /
• 1995

The main goal of the present study is to establish the techniques and methodolgies of turbine performance test through evaluating the objective turbine test piece, and checking the reliability of the self-developed test facility by performing a series of turbine tests under ambient temperature condition. A high speed coupling, a lubrication system and a test bed of the test facility were modified through a series of preliminary test in order to reduce the vibration and oil leakage. The flowrate control of the test facility and data acquisition were accomplished by using a software called "Labview" The measurement of shaft horse power and control of rotational speed according to the conditions of turbine rotation were performed by a separate system. The preliminary evaluation of the measured data suggests that the developed test facility and the test technique can be used reliably for the performance test of turbines with the minor improvement.provement.

• Tribology and Lubricants
• /
• v.27 no.1
• /
• pp.25-33
• /
• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.5
• /
• pp.866-873
• /
• 2001

The governing partial differential equations of a helical spring with a circular section were derived from Frenet formulas and Timoshenko beam theory. These were solved to give the dispersion relationship between wave number and frequency along with wave form. Wave motions of helical springs are categorized by 4 regimes. In the first regime, the lower frequency area, the torsional and extensional waves of the spring are predominant and two waves are composite wave motions involving lateral motion of the coils and rotation of the coils about a horizontal axis. All waves are propagating in the second regime. The wave of the extensional motion of the spring and one wave of transverse motion of a wire change from travelling waves to near field waves in the third regime. Both waves excited by both axial and transverse motion are predominant in the fourth regime.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.11a
• /
• pp.159-165
• /
• 2001

The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive(HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss from factor of HDD can be obtained from this analysis at each operation conditions.

• Journal of Chest Surgery
• /
• v.14 no.3
• /
• pp.218-224
• /
• 1981

Acute gastric volvulus is one of the most fatal complications of the eventration of diaphragm and require emergency surgical treatment unless it is possible to pass a nasogatric tube. This 10 year old female patient was admitted because of severe abdominal pain and marked abdominal distention before about 3 days. On chest P-A and plain abdomen, there were the elevation of the left hemidiaphragm and marked dilatation of stomach and the triad of symptoms emphasized by Bochdalek in 1904 was present. Emergency operation [wedge resection of necrotic area of stomach and gastropexy after gastric decompression and plication of diaphragm] was performed. The type of gastric volvulus was organo-axial rotation, in which the stomach rotated around the line that connects the cardia with the pylorus [Fig. 4].

• Applied Microscopy
• /
• v.46 no.1
• /
• pp.14-19
• /
• 2016

Currently, focused ion beams (FIB) are widely used for specimen preparation in atom probe tomography (APT), which is a three-dimensional and atomic-scale compositional analysis tool. Specimen preparation, in which a specific region of interest is identified and a sharp needle shape created, is the first step towards successful APT analysis. The FIB technique is a powerful tool for site-specific specimen preparation because it provides a lift-out technique and a controllable manipulation function. In this paper, we demonstrate a general procedure containing the crucial points of FIB-based specimen preparation. We introduce aluminum holders with moveable pin and an axial rotation manipulator for specimen handling, which are useful for flipping and rotating the specimen to present the backside and the perpendicular direction. We also describe specimen preparation methods for nanowires and nanopowders, using a pick-up method and an embedding method by epoxy resin, respectively.

• International Journal of Fluid Machinery and Systems
• /
• v.8 no.4
• /
• pp.304-310
• /
• 2015

Numerical simulation was applied to investigate the Taylor vortex flow inside the concentric cylinders with a constant radial temperature gradient. The reliability of numerical simulation method was verified by the experimental results of PIV. The radial velocity and temperature distribution in plain and 12-slit model at different axial locations were compared, and the heat flux distributions along the inner cylinder wall at different work conditions were obtained. In the plain model, the average surface heat flux of inner cylinder increased with the inner cylinder rotation speed. In slit model, the slit wall significantly changed the distribution of flow field and temperature in the annulus gap, and the radial flow was strengthen obviously, which promoted the heat transfer process at the same working condition.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2007.04a
• /
• pp.698-703
• /
• 2007

A simplified model which incorporates the moment-axial tension interaction of the double-span beams in a column-removed steel frame is presented in this paper. To this end, material and geometric nonlinear parametric finite element analyses were conducted for the double-span beams by changing the beam span to depth ratio and the beam size within some practical ranges. The beam span to depth ratio was shown to be the most influential factor governing the catenary action of the double-span beams. Based on the parametric analysis results, a simplified piecewise linear model which can reasonably describe the vertical, resisting force versus the beam chord rotation relationship was proposed. It was also shown that the proposed method can readily be used for the energy-based progressive collapse analysis of steel moment frames.

• Structural Engineering and Mechanics
• /
• v.55 no.1
• /
• pp.205-228
• /
• 2015

The results of a numerical investigation pertaining to the hysteretic behaviour of concrete filled steel tubular (CFT) column to I-beam connections are discussed in detail. Following the verification of the numerical results against the available experimental tests, the nonlinear finite element (FE) analysis was implemented to evaluate the effects of different parameters including the column axial load, beam lateral support, shape and arrangement of stiffeners, stiffness of T-stiffeners, and the number of shear stiffeners. Pursuing this objective, an external CFT column to beam connection, tested previously, was selected as the case-study. The lateral forces on the structure were simulated, albeit approximately, using an incremental cyclic loading reversal applied at the beam tip. The results were compared in terms of hysteretic load-displacement curves, stress distributions in connection, strength, rotation, and energy dissipation capacity. It was shown that external T-stiffeners combined with internal shear stiffeners play an important role in the hysteretic performance of CFT columns to I-beam connections.

• Proceedings of the KSME Conference
• /
• 2001.06b
• /
• pp.116-120
• /
• 2001

In swash plate type axial piston hydraulic pump and motor, the piston shoe is periodically pressurized with square function shape by supply pressure load as rotation of cylinder barrel. Therefore the recess pressure on bottom part of piston shoe is suddenly increase through orifice in the piston shoe. In this study, we simulated that the frequency response of the recess pressure against with change of supply pressure with analysis tool. Also, we evaluate the dynamic response characteristics of overbalanced hydrostatic bearing with change of the orifice diameter.