• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2004.04a
• /
• pp.424-429
• /
• 2004

The high speed machining center(HMC) has been widely applied to manufacture a die and trial product in many machine industry. Because the evaluation for HMC is not sufficiently performed and the efficient cutting conditions can't be selected, a peat loss has been caused in the cost aspect. In this study, the need of preliminary running time and unstable spindle speed is presented by the analysis of acceleration in idling. The Machinability for the TiA1N coated flat end mill and STD11 (H$\sub$R/C60) is evaluated from the trends of tool wear and cutting force according to cutting conditions . The resonance spindle speed is identified through the tool wear and natural frequency test.

• Journal of Mechanical Science and Technology
• /
• v.16 no.6
• /
• pp.776-784
• /
• 2002

We have performed experimental studies for the improvements of pneumatic brake systems of freight trains. Currently, most of the freight trains operated by the Korean National Railroad have either empty-load or diaphragm type brake systems. In this study, appropriate methods that the air pressure characteristics in both type of brake systems are in accordance with each other have been investigated. We have also performed running tests using a 30 car-train set to design optimum capacity of a quick release valve. The test results show that the quick release valve is considerably effective in shortening the release time of the diaphragm type brake system. In the case of a normal brake application, the diaphragm type brake system with the quick release valve reduces the release time to 34% of that of the system without the quick release valve. This release time is almost equivalent to that of the empty-load type brake system. Accordance of braking performance in different types of brake systems in a train set is expected to prevent wheel flats and to reduce maintenance costs.

• 한국신재생에너지학회:학술대회논문집
• /
• 2011.05a
• /
• pp.61.2-61.2
• /
• 2011

The spanwise aerodynamic loads of the wind turbine blade are investigated numerically. The blade shape such as twist and chord length along the blade span is obtained from the procedure of aerodynamically optimal design. The rated tip speed ratio and the rated wind velocity are set to 7 and 12m/s respectively. The BEM method is applied to obtain both the aerodynamic performance of the wind turbine (Fig.1) and the spanwise aerodynamic loads along the blade span including Prandtl's tip loss factor. The maximum running power coefficient is occurred around 90% radial position from hub (Fig.2). The distributed aerodynamic loads along the blade span can be used for structure analysis.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.12
• /
• pp.1233-1240
• /
• 2004

Condition monitoring and fault diagnosis of machines are gaining importance in the industry because of the need to increase reliability and to decrease possible loss of production due to machine breakdown. By comparing the nitration signals of a machine running in normal and faulty conditions, detection of faults like mass unbalance, shaft misalignment and bearing defects is possible. This paper presents a novel approach for applying the fault diagnosis of rotating machinery. To detect multiple faults in rotating machinery, a feature selection method and support vector machine (SVM) based multi-class classifier are constructed and used in the faults diagnosis. The results in experiments prove that fault types can be diagnosed by the above method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2004.11a
• /
• pp.275-282
• /
• 2004

The engine bearing transmits the powers from cylinder to crankshaft with small clearance between con-rod and crankpin. The minimum oil film thickness is a significant parameter in the operation of bearing. The contact pressure of bearing should be considered for the reason that elastic deformation of bearing be caused by contact pressure of bearing. There are important factors which are maintaining of minimum oil film thickness expecting of the length of maximum and minimum oil film thickness with changing of the loads to keep running normally. Furthermore, this study is very crucial to develop the design of engine bearing and crankshaft system.

• Journal of Power System Engineering
• /
• v.10 no.2
• /
• pp.62-67
• /
• 2006

The maintenance of continuity on food processing has created a need for the rapid reinstatement of many types of frozen fish to an ambient temperature and good condition. A number of thawing methods are in current use have also several disadvantages in thawing time. discoloration mass loss caused by drying, capital and running cost. These damages are, it is claimed, either eliminated or improves by the vacuum system. An experimental study on the thawing for hair tail and Yellow croaker by the vacuum system were carried out. The Yellow croaker thawing time with this vacuum system took out 170 minutes to reach from $-10.3^{\circ}C\;to\;-0.8^{\circ}C$ at 20mmHg abs. and hair tail thawing time 220 minutes to reach from $-12.2^{\circ}C\;to\;0^{\circ}C$ at 20mmHg abs.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.692-697
• /
• 2007

The current collection system, pantograph, is one of the important subsystems in electric train system, because of it's fatal function and role of supplying power to the train system. Generally, the function of current collection system is evaluated by loss of contact rate between pantograph and contact wire in catenary by measuring arcs, or by statistical method of evaluating minimum mean contact force. The Korean Tiling Train(TTX) has been manufactured by KRRI and Korean domestic companies and is preparing the trial running test of itself. In this paper, we introduce our successful achievement, measuring system and applied methods of dynamic characteristics for the tilting pantograph, developed of by our own technology.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.3
• /
• pp.175-180
• /
• 2008

Flow quantity to supply to a coil in floor heating system is important to achieve comfortable indoor air condition in the winter season. The hot water header is used to distribute the water into the coil. Experimental study has been performed using the water header that have 5 branches consisted of flow control valves and automatic shut-off valves. Each branch line connected it with X-L pipe. Experimental tests accomplished it to investigate the flow distribution characteristics of the hot water header. Experimental results show that the selection of the pump head and differential pressure are very important to save running energy of the system, and high differential pressure needs more friction loss in the case of suitable differential pressure for balancing of the header.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.537-543
• /
• 2003

Condition monitoring and fault diagnosis of machines are gaining importance in the industry because of the need to increase reliability and to decrease possible loss of production due to machine breakdown. By comparing the vibration signals of a machine running in normal and faulty conditions, detection of faults like mass unbalance, shaft misalignment and bearing defects is possible. This paper presents a novel approach for applying the fault diagnosis of rotating machinery. To detect multiple faults in rotating machinery, a feature selection method and support vector machine (SVM) based multi-class classifier are constructed and used in the faults diagnosis. The results in experiments prove that fault types can be diagnosed by the above method.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2000.10a
• /
• pp.466-470
• /
• 2000

Externally pressurized air journal bearing has been widely used in high-speed spindle system and precision machinery because of its characteristics such as substantially low frictional loss, low heat generation and averaging effect leading better running accuracy. But air journal bearing have a disadvantage of the low load capacity due to the low viscosity. In this paper, The air journal bearing design to overcome the defects of air bearing such as low stiffness and dimping coefficients was investigated theoretically.