• 한국분무공학회지
• /
• 제13권4호
• /
• pp.180-186
• /
• 2008

The aim of this work is to investigate the effect of ambient conditions on the spray behavior of biodiesel-ethanol blended fuels. In order to analyze the spray behavior, spray tip penetration and spray cone angle were obtained from the visualization system and the effects of ethanol blending are compared macroscopic characteristics with the numerical results. It was reveled that the ethanol contents in biodiesel-ethanol blended fuels affect the spray tip penetration a little and increased the spray cone angle. Increased ambient pressure induced the decrease of the spray tip penetration, and the increased ambient temperature lead to the increase of the spray tip penetration. In addition, the increased ambient temperature promoted the vaporization and atomization of spray with the effect of increasing ethanol fuel.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.628-632
• /
• 2000

In the recent day, shielding can was made of permalloy materials for automobile display instrument. The good roundness has an effect on magnetic property such as the low coercivity and the high permeability. But the products having the roundness is transformed by the heat treatment, the sending to the company and the assembly process. So for the stiffness of the edge, it is necessary for hemming process to be added in the deep drawing process. And it has the good appearance to create a smooth edge rather than a razor edge with urr. In this paper, it is controlled to get the best hemming product by the Pre-hemming angle($105^{\circ}$, $120^{\circ}$, $135^{\circ}$). And Possible process and tool design modification, which may lead to quality improvement in hemming were tested experimentally and using FEM. The commercial finite element program PAM-STAMPTM was used to simulate the pre-hemming process and hemming process, and the predictions were compared with experimental results according to the pre-hemming angle.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2009년도 정보 및 제어 심포지움 논문집
• /
• pp.396-398
• /
• 2009

Scoliosis is a three-dimensional deformity caused by lateral curvature of the spine. The existing braces used to correct the posture were some drawbacks such as inconvenience, tightness as well as unfitness to wear. In this study, we devised a posture guidance system in order to monitor a posture continuously and lead to pose correctly and a new method fur measuring a Cobb's angle value in third dimension based on two 3-axis accelerometers. As a result, the correlation coefficients between desired and measured angles were and standard error between desired and measured angles were 0.99, 1.32(x-axis), 0.99 and 1.10(y-axis), respectively. The devised system showed good potential for the optimal posture guide and an early detection of scoliosis.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2000년도 추계학술대회 논문집
• /
• pp.810-813
• /
• 2000

Burr makes trobles on manufacturing process due to deburring cost, quality of products and productivity. This paper described the results of experimental study on the influence of the cutting parameters on the formation of exit burrs in face milling. The cutting parameters were investigated changing exit angle, rake nagle , lead angle in tool geometry as well as feed per tooth. Also we carried out experimets on several materials. Using the result of experimental study, burr types are classified according to appearance and formation mechanism in exit burr and we are considered the burr formation in each type of burr.

• 설비공학논문집
• /
• 제12권7호
• /
• pp.623-631
• /
• 2000

Effects of the taper angle and the angular velocity of a pulse tube on the enthalpy flow loss associated with the steady mass streaming were analysis by two-dimensional analysis of a pulse tube with variable cross-section. It was shown that the steady mass flux can lead to a large steady second-order temperature. The enthalpy flow loss associated with the steady mass streaming increases as the angular velocity increases. For a pulse tube where the viscous penetration depth is far thinner than the inner radius, the enthalpy flow loss can be significantly reduced by tapering the pulse tube since both the steady mass flux and the steady second-order temperature decrease as the taper angle increase.

• 소음진동
• /
• 제8권3호
• /
• pp.477-484
• /
• 1998

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the prewist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and prewist angles, lead to the coupled motions of the shaft and the bladed disk.

• 한국응용과학기술학회지
• /
• 제20권4호
• /
• pp.296-308
• /
• 2003

The capacity and long life of gel electrolyte batteries is connected with gas recombination producting $PbO_2$ and Pb electrode. We were prepared with phosphoric acid gel electrolyte to know gel characteristics per density to assemble VRLA batteries. We studied by measuring electrolyte dispersion using Brewster-angle microscope(BAM), charge-discharge cycle and electrode structure using scanning election microscope(SEM) per electrolyte density. As a results, phosphoric acid density 1.210 was excellent gel dispersion in sol condition, electrode condition after fifty cycles in this study.

• Journal of Welding and Joining
• /
• 제18권6호
• /
• pp.74-82
• /
• 2000

The fluxless wetting properties of UBM-coated Si-wafer to the binary lead-free solders(Sn-Ag, Sn-Sb, Sjn-In, Sn0Bi) were estimated by wetting balance method. With the new wettability indices from the wetting curves of one side coated specimen, the wetting property estimation of UBM-coated Si-wafer was possible. For UBM of Si-chip, Au/Cu/Cr UBm was better than au/Ni/TI in the point of wetting time/ At general reflow process temperature, the wettability of high melting point solders(Sn-Sb, Sn-Ag) was better than that of low melting point one(Sn-Bi, Sn-In). The contact angle of the one side coated Si-plate to the solder could be calculated from the force balance equation by measuring the static state force and the tilt angle.

• 대한기계학회논문집A
• /
• 제20권12호
• /
• pp.3822-3827
• /
• 1996

In this study, the ways of calculating the efficiency of ball screws are presented to fix the design variables effectively. To calculate the efficiency of ball screws, the frection coefficient is needed to be deduced. Therefore it is deduced measuring the preload torque of double nut ball screws of which the preload can be varied by springs. The efficieny of ball screws and the mazimum efficiency condition are calculated with the deduced friction coefficient. In addition, the characteristic of friction and lubrication is considered.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
• /
• pp.101-109
• /
• 1997

An analytical procedure on the base of the substructure synthesis and assumed modes method is developed to investigate the flexibility effect of bladed disk assembly on vibrational modes of flexible rotor system. In modeling the system, Coriolis forces, gyroscopic moments, and centrifugal stiffening effects are taken into account. The coupled vibrations between the shaft and bladed disk are then extensively investigated through the numerical simulation of simplified models, with varying the shaft rotational speed and the pretwist and stagger angles of the blade. It is found that the Coriolis and inertia forces and the inertia torque, which are induced by the one nodal diameter modes of the bladed disk and vary depending upon the stagger and pretwist angles, lead to the coupled motions of the shaft and the bladed disk.