• The KSFM Journal of Fluid Machinery
• /
• v.17 no.3
• /
• pp.19-24
• /
• 2014

Development of long-term mobile energy sources for mobile robots or small-sized unmanned vehicles are actively increasing. The micro gas turbine generator (MTG) is a good candidate for this purpose because it has both of high energy density and high power density, and 500W class MTG is under development. The designed MTG can be divided into 2 main parts. One part consists of motor/ generator and compressor, and the other one consists of combustor, recuperator and turbine. 500W class MTG is designed to operate at ultra-high speed of 400,000 rpm in high turbine temperature over $700^{\circ}C$ to improve the efficiency. Because the magnetism of NdFeB permanent magnet for the motor/generator could be degraded if the temperature is over $150-200^{\circ}C$, MTG needs the thermal insulation to block the heat transfer from combustor/turbine side to motor/generator side. Moreover, the motor/generator is allocated to get the cooling effect from the rapid air flow by the compressor. This study presents the experimental results to verify whether the thermal insulator and air flow are effective enough to keep the motor/generator part in the low temperature less than $100^{\circ}C$. From the motoring test by using the high temperature test rig, it was confirmed that the motor/generator part could maintain the temperature less than $50^{\circ}C$ under the condition of 1.0 bar compressed air.

• Tribology and Lubricants
• /
• v.31 no.4
• /
• pp.141-147
• /
• 2015

Gas foil thrust bearings (GFTBs) have attractive advantages over rolling element bearings and oil film thrust bearings, such as oil-free operation, high speed stability, and high-temperature operation. However, GFTBs have lower load carrying capacity than the other two types of bearings owing to the inherent low gas viscosity. The load carrying capacity of GFTBs depends mainly on the compliance of the foil structure and the formed hydrodynamic wedge, where the gas pressure field is generated between the top foil and the thrust runner. The load carrying capacity of the GFTBs is very important for the suitable design of oil-free turbomachinery with high performance. The aim of the present study is to identify the characteristics of the load carrying performance of GFTBs. A new test rig for the experimental measurements is designed to provide static loads up to 800 N using a pneumatic cylinder. The maximum operating speed of the driving motor is 30,000 rpm. A series of experimental tests—lift-off test, static load performance test, and maximum load capacity test—estimate the performance of a six-pad GFTB, in terms of the static load, driving torque, and temperature. The maximum load capacity is determined by increasing the static load until the driving torque rises suddenly with a sharp peak. The test results show that the torque and temperature increase linearly with the static load. The estimated maximum load capacity per unit area is approximately 80.5 kPa at a rotor speed of 25,000 rpm. The test results can be used as a design guideline for GFTBs for realizing oil-free turbomachinery.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.37 no.12
• /
• pp.1483-1487
• /
• 2013

Water injection pump outputs oil with high pressure during this process, seawater is injected into the well to recover the well pressure and maintain high productivity. A water injection pump has high productivity, and therefore, it serves as a key piece of equipment in marine plants. In this light, water injection pumps are being studied widely in industry. In this study, the rotor dynamics is analyzed to determine the natural frequency according to the bearing stiffness and operation speed change. This study aims to establish the pump reliability through critical speed, stability, and unbalance response analysis.

• Structural Engineering and Mechanics
• /
• v.66 no.6
• /
• pp.749-759
• /
• 2018

Aiming at widely used high-pier bridges in Sichuan-Tibet Railway, this paper presents an investigation to design and evaluate the seismic vibration reduction effects of several measures, including viscous damper (VD), friction pendulum bearing (FPB), and tuned mass damper (TMD). Primarily, according to the detailed introduction of the concerned bridge structure, dynamic models of high-pier bridges with different seismic vibration reduction (SVR) measures are established. Further, the designs for these SVR measures are performed, and the optimal parameters of these measures are investigated. On this basis, the vibration reduction effects of these measures are analyzed and assessed subject to actual earthquake excitations in Wenchuan Earthquake (M=8.0), and the most appropriate SVR measure for high-pier bridges in Sichuan-Tibet Railway is determined at the end of the work. Results show that the height of pier does not obviously affect the performances of the concerned SVR measures. Comprehensively considering the vibration absorption performance, installation and maintenance of all the employed measures in this paper, TMD is the best one to absorb vibrations induced by earthquakes.

• Asian-Australasian Journal of Animal Sciences
• /
• v.22 no.8
• /
• pp.1107-1112
• /
• 2009

The separation of X and Y chromosome-bearing sperm is of use in many aspects of livestock maintenance. In this study, we sought to determine the difference in DNA content between X- and Y-bearing sperm, separate sperm into X- and Y-enriched pools, and assess the efficacy of sorting. Sperm collected from Duroc and miniature pigs were stained with 20.8 $\mu{M}$ Hoechst 33342 and analyzed using a high-speed cell sorter. Measurement of the fluorescence intensity of stained sperm nuclei revealed that the X-bearing sperm of Duroc and miniature pigs respectively contain 2.75% and 2.88% more DNA than Y-bearing sperm. In total, 50.18% of the sperm were assigned to the X-sorted sample and 49.82% was assigned to the Y-sorted sample for Duroc pigs. For miniature pigs, the Xsorted sample represented 50.19% of the population and the Y-sorted represented 49.81% of the population. Duplex PCR was used to evaluate accuracy of sorting. A fast and reliable method for porcine sexing was developed through amplification of the sex-determining region of the Y chromosome gene (SRY). Oligonucleotide primers were designed to amplify the conserved porcine SRY high motility group (HMG) box sequence motif. We found that the primer pair designed in this study was 1.46 times more specific than previously reported primers. Thus, this study shows that the present method can be applied in porcine breeding programs to facilitate manipulation of the sex ratio of offspring and to achieve precise sexing of porcine offspring by amplification of the HMG box of the SRY gene.

• Journal of Biosystems Engineering
• /
• v.25 no.3
• /
• pp.213-220
• /
• 2000

Grafting of fruit-bearing vegetables has been widely used to increase the resistance to soil-borne diseases, to increase the tolerance to low temperature or to soil salinity, to increase the plant vigor, and to extend the duration of economic harvest time. After grafting, it is important to control the environment around grafted seedlings for the robust joining of a scion and rootstock. Usually the shading materials and plastic films are used to keep the high relative humidity and low light intensity in greenhouse or tunnel. It is quite difficult to optimally control the environment for healing and acclimation of grafted seedlings under natural light. So the farmers or growers rely on their experience for the production of grafted seedling with high quality. If artificial light is used as a lighting source for graft-taking of grafted seedlings, the light intensity and photoperiod can be easily controlled. The purpose of this study was to develop a prototype system for the graft-taking enhancement of grafted seedlings using artificial lighting and to investigate the effect of air current speed on the distribution of air temperature and relative humidity in a graft-taking enhancement system. A prototype graft-taking system was consisted by polyurethane panels, air-conditioning unit, system controller and lighting unit. Three band fluorescent lamps (FL20SEX-D/18, Kumho Electric, Inc.) were used as a lighting source. Anemometer (Climomaster 6521, KANOMAX), T-type thermocouples and humidity sensors (CHS-UPS, TDK) were used to measure the air current speed, air temperature and relative humidity in a graft-taking system. In this system, air flow acted as a driving force for the diffusion of heat and water vapor. Air current speed, air temperature and relative humidity controlled by a programmable logic controller (UP750, Yokogawa Electric Co) and an inverter (MOSCON-G3, SAMSUNG) had an even distribution. Distribution of air temperature and relative humidity in a graft-taking enhancement system was fairly affected by air current speed. Air current speed higher than 0.1m/s was required to obtain the even distribution of environmental factors in this system. At low air current speed of 0.1m/s, the evapotranspiration rate of grafted seedlings would be suppressed and thus graft-taking would be enhanced. This system could be used to investigate the effects of air temperature, relative humidity, air current speed and light intensity on the evaportranspiration rate of grafted seedlings.

• Journal of Power System Engineering
• /
• v.3 no.4
• /
• pp.79-85
• /
• 1999

The magnetic levitation system is utilized in the magnetic bearing of high-speed rotor system because of little friction, no lubrication, no noise and so on. The magnetic levitation system needs the feedback controller for the stabilization of system, and gap sensors are generally used to measure the gap. The use of sensor easily goes into troublesome caused by sensor failure discord between the measurement point and the control point etc. This paper gives a controller design method of magnetic levitation system which satisfies the given $H_{\infty}$ control performance and the robust stability of the presence of physical parameter perturbations. To the end, we investigated the validity of the designed controller through results of simulation.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.8 s.173
• /
• pp.50-56
• /
• 2005

This paper is described a development of an optical fiber displacement sensor. The optical fiber sensor using an intensity modulated measures the displacement between target and sensor. A prototype sensor is composed of a transmitting part, a receiving part and a signal processing circuit. The experiment was conducted not only the sensor performance but also factors that affect intensity. The main performance of this sensor is resolution of 0.37um and the non-linearity $0.7\%$ FS and the dynamic bandwidth of about 6.3kHz. As a result of rotation test, the prototype sensor showed an equivalent performance to a commercial eddy current sensor.

• Journal of KSNVE
• /
• v.8 no.1
• /
• pp.195-203
• /
• 1998

The magnetic levitation system is utilized in the magnetic bearing of high-speed rotor because of little friction, no lubrication, no noise and so on. The magnetic levitation system need the feedback controller for the stabilization of system, and gap sensors are generally used to measure the gap. The use of sensor easily goes into troublesome caused by sensor failure discord between the measurement point and the control point etc. This paper presents the design of robust stabilizing contoller by $H_{\infty}$ control theory using the sensorless method proposed by authors in the magnetic levitation system. And we investigated both the validity of the designed controller and the usefulness of the sensorless magnetic levitation system through results of actual experiment.

• Journal of the Korean Society for Railway
• /
• v.9 no.3 s.34
• /
• pp.298-304
• /
• 2006

An active application of concrete track is being expected for the future constructions of Korean railroad. For the successful concrete track construction and design in earthwork areas, the roadbed behavior should be reasonably estimated using the proper analysis method. In this paper, behaviors of concrete track on the reinforced roadbed constructed with the standard stiffness and depth were estimated thorough numerical analyses and field measurements. A three dimensional finite difference method was employed to model the concrete tracks and subground. The settlement and vertical pressures caused by train load were estimated by the numerical method and compared with the field measurement results. The bearing characteristics of roadbed were presented and the proper method for the analysis of concrete track was proposed.