• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.5 s.176
• /
• pp.1314-1322
• /
• 2000

The acoustic property of reactive type single expansion chamber can be analyzed by traditional plane wave theory. This theory can be applied in low frequency range and has good performance. But this theory can't include higher order modes, therefore another method is essential to analyze acoustic filter in high frequency range. Many researcher suggested the method that can concern higher order modes, and their methods are using mode matching technique. But there is no method that can be applied to the analysis of single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber. In this paper, the method which can analyze single expansion chamber with arbitrary inlet/outlet duct position and numbers of higher order modes of inlet/outlet duct and middle chamber using fundamental mode matching technique, was suggested and the predictions by this method was compared with those by the finite element method, and the influence of inlet/outlet location to acoustic performance of single expansion chamber is investigated and explained by higher order mode effects.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.08a
• /
• pp.72-82
• /
• 2004

The deformation mechanism of hexagonal close-packed materials is quite complicate including slips and twins. A deformation mechanism, which accounts for both slip and twinning, was investigated for polycrystalline hop materials. The model was developed in a finite element polycrystal model formulated with initial strain method where the stiffness matrix in FEM is based on the elastic modulus. We predicted numerically the texture of Mg alloy(AZ31B) sheet by using FEM based on crystal plasticity theory. Also, we introduced the recrystallized texture employed the maximum energy release theory after rolling. From the numerical study, it was clarified that the shrink twin could not be the main mechanism for shortening of c-axis, because the lattice rotation due to twin rejects fur c-axis to become parallel to ND(normal direction of plate). It was showed that the deformation texture with the pyramidal slip gives the ring type pole figure having hole in the center.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2008.05a
• /
• pp.369-373
• /
• 2008

This case analyze the point of trouble and reform processing construction on input design to resolve the problem for setting tower in front of narrow base at the 154kV OO Transmission Line substaion. Hereafter the input design are presented for the basic reference data which the case a point of trouble and reform contents, input design of special shape tower and the foundation on substation input design cannot be setted by standard type of tower because of narrow base and cannot keep clerance overhead transmission conductor input to the substion.

• Journal of Power Electronics
• /
• v.11 no.1
• /
• pp.37-44
• /
• 2011

In this paper, a four-phase 8/6-pole 4-kW SR motor drive model is presented. Based on experimental data, the model allows an accurate simulation of a drive in dynamic operation. Simulations are performed and a laboratory type set-up is built based on a TI TMS320F2812 platform to experimentally verify the theoretical results obtained for a SR motor. To reduce acoustic noise and to correct the power factor of this drive, a two-stage power converter is proposed that uses a current source rectifier (CSR) as the input stage for the asymmetrical converter of the studied SRM. Employing the space-vector modulation (SVM) method in matrix converters, the CSR switching allows the dc link's capacitors to be eliminated and the power factor of the SRM drive to be improved. As the electrical motive force (emf) is directly proportional to the rotor speed, the input voltage to the machine can be programmed to be a function of the speed with the modulation index of the CSR, leading to a reduction in the acoustic noise of the SRM drive. Simulation of the whole SRM drive system is performed using MATLAB-Simulink. The results fully comply with the required conditions such as power factor correction with an improvement in the THD.

• Proceedings of the KIEE Conference
• /
• 2002.04a
• /
• pp.55-57
• /
• 2002

In industry, A pallet truck is drived mainly by d.c motor, because it use to battery for input power. However, d.c motor has a brush, this is the disadvantage of the d.c motor for a pallet truck. Though a brushless d.c motor has a permanent magnet, it is for low torque. Switched reluctance motors(SRM) have the advantage a high torque/weight ratio, as the large reluctance torque is made by salient poles of both start and rotor, and a high reliability, this paper design the shape of the switched reluctance motor that will replace a d.c motor for A pallet truck. First of all, designed parameter of SRM, outer diameter, diameter of rotor and stock length, from the outputr equation considering electric loading and magnetic loading. Next, design diameter of stator and rotor, depth of slot pole width, air gap as inner size of motor. The design of SRM certify the torque, the efficiency and the output power by a simulation.

• The Journal of the Korean life insurance medical association
• /
• v.3 no.1
• /
• pp.149-162
• /
• 1986

We had experienced very rare a case of renal cell carcinoma through ultrasonic diagnosis, september, 1985 at medical dept. Dae Han Kyoyuk Ins. Company. The conclusions that we gained, making a comparative-analysis of operation's view and ultrasonic view are as follows; 1. Echolucent area which was $0.6cm^2$ size in the center of tumor was shown by ultrasonography, we noticed it occured necrosis or cystic change and the extracts grossly after. operation accorded with ultrasonic view. 2. Tumor was 65mm in diameter on ultrasonography and made clear 55mm in diameter after operation 3. There was not fever, anemia, even typical triad of renal cell carcinoma, blood pressure was within normal limits. 4. The case was stage I by Robson's Modification method. 5. The case was clear cell type by classifying of histology. 6. The affected site was left side and origin was lower pole of the kidney. 7. After radical nephrectomy, until present prognosis was favorable and he exists.

• Applied Microscopy
• /
• v.27 no.4
• /
• pp.417-432
• /
• 1997

The structures of the fertilized egg envelope in three species of cichlidae, golden severum (Cichlasoma severum var.), convic cichlid (Cichlasoma nigrofasciatum) and discus (Symphysodon aequifasciatus) were investigated by routine light and electron microscopies. The fertilized eggs of all three species were of the non-transparent, ellipsoidal, adhesive and non-floted type. The egg envelopes have a single micropyle, which is thought to the pathway of sperm in the area of the animal pole. In golden severum, an outer surface of egg envelope was covered by a reticular layer, that of convic cichlid was covered by an amorphous reticular layer and that of discus was covered by a branched reticular layer. The fertilized egg envelopes consisted of two distinct layers, an adhesive outer layer and an inner layer, consisted of lamellae alternating with interlamellae of lower electron density, in all three species; an inner layer of golden severum was $15\sim17$ layers, that of convic cichlid was $14\sim16$ layers, and that of discus was $18\sim19$ layers.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.7
• /
• pp.315-322
• /
• 2001

High speed brushless permanent magnet(PM) machines need a key technology to minimize the iron core losses in stator and the eddy current losses in the retained sleeve and magnets caused by slotting harmonics. Thus, slotless or iron-coreless brushless PM machines have been applied for a very high rotational speed and/or the ripple-free torque. Unfortunately, slotless or coreless PM machines have lower open-circuit field than slotted and/or iron-cored types, which cause to reduce power density. Fortunately, Halbach array can generate the strong magnetic field systems without additional magnetic materials. In this paper, the 4-pole Halbach array is applied to the high speed machine and is compared with the radial magnetized PM array in field system. The iron-/air-cored stator of PM machine is constructed with/without winding slots. Open circuit magnetic fields of each type are presented from the analytical method and finite element method. Consequently, it is confirmed that the Halbach array field system with slotless stator is more suitable to the high speed motor because it has high flux density, sinusoidal flux distribution than others.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.2
• /
• pp.111-117
• /
• 1990

This paper investigated the effect of the zero on the right-half-plane on stability in the buck-boost DC-DC converter which is one type of the switching regulator, and the stability region in connection with the output current was shown by evaluating the feed-back gain. From the result it is shown that the stability decreases by the existence of the zero on the right-half-plane. We carried out a compensation by a pole in the feedback circuit and obtained the available stability region in relation to the gain band-width product. These results proved to be the validity by experiment.

• Journal of the Korean Magnetics Society
• /
• v.2 no.1
• /
• pp.50-55
• /
• 1992

Numerical method for analyzing the reading process in magnetic recording system is described. Hysteresis characteristics must be included in numerical analysis not only recording process but also reading process because of hysteretic behavior of recording media. Algorithm which is consisted of finite clement method for numerical analysis and Preisach model considered to be more appropriate method than Stoner-Wohlfarth model with spin curling mode for describing hysteresis characteristics is constructed. Equations to calculate waveform of reproduced voltage is proposed. Then, this is applied to perpendicular magnetic recording systems with pole type head and double layer media. Waveform of magnetic flux density and reproduced voltage induced in head coil is obtained. If the recording current increase in recording process, magnitude of reproduced voltage in reproducing process saturates. From this saturation curve, value of current which produce maximum voltage can be obtained.