• 한국유체기계학회 논문집
• /
• 제4권4호
• /
• pp.37-42
• /
• 2001

In the present study, flow characteristics of turbulent oscillatory flow in an oscillator connected to square-sectional $180^{\circ}$ curved duct are investigated experimentally. In order to investigate wall shear stress and pressure distributions, the experimental studies for air flows we conducted in a square-sectional $180^{\circ}$ curved duct by using the LDV system with the data acquisitions and the processing system. The wall shear stress at bend angle of the $150^{\circ}$ and pressure distribution of the inlet (${\phi}=0^{\circ}$) to the outlet (${\phi}=180^{\circ}$) by $10^{\circ}$ intervals of the duct are measured. The results obtained from the experiment are summarized as follows : wall shear stress values in the inner wall we larger than those in an outer wall, except for the phase angle (${\omega}t/{\pi}/6$) of 3, because of the intensity of secondary flow. The pressure distributions are the largest in accelerating and decelerating regions at the bend angle(${\phi}$) of $90^{\circ}$ and pressure difference of inner and outer walls is the largest before and after the ${\phi}=90^{\circ}$.

• 대한기계학회논문집B
• /
• 제22권11호
• /
• pp.1591-1602
• /
• 1998

Simple spanwise distribution models of deviation angle and pressure loss coefficient due to the tip leakage flow are formulated for use in association with the streamline curvature method as a flow analysis. Combining these new models with the previous deviation and loss models due to secondary flow, a robust streamline curvature method is established for flow analysis of single-stage, subsonic axial turbines with wide ranges of turning angle, aspect ratio and blading type. At the exit from rotor rows, the flow variables are mixed radially according to a spanwise transport equation. The proposed streamline curvature method is tested against a forced vortex type turbine as well as a free vortex type one. The results show that the spanwise variations of flow angle, axial velocity and loss coefficients at rotor exit are predicted with good accuracy, being comparable to a steady three-dimensional Navier-Stokes analysis. This simple and fast flow analysis is found to be very useful for the turbine design at the initial design phase.

• 한국조명전기설비학회:학술대회논문집
• /
• 한국조명전기설비학회 2004년도 학술대회 논문집
• /
• pp.145-150
• /
• 2004

The LED lighting used spot-light illuminate the limited surface. So it is a key-point to condense wide emission angle of high power light emitting diodes (LEDs) to narrow that angle. In this paper, the secondary optics was designed by lens-makers formula for concentration rays of LED into specific region. So, it simulated the optics that designed by lens makers-formula in the optical design program, LightTools. And then, show the p propriety of lens design utilizing simulation result, luminous intensity, emission angle.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.944-949
• /
• 2003

This paper addresses the control of free and dynamic response of composite rotating pretwisted blade modeled as non-uniform thin-walled beam fixed at the certain presetting and pretwisted angle and incorporating piezoelectric induced damping capabilities. A distributed piezoelectric actuator pair is used to suppress the vibrations caused by external disturbances. The blade model incorporates non-uniform features such as transverse shear, secondary warping and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration and dynamic characteristics of the blade are highlighted.

• 설비공학논문집
• /
• 제15권10호
• /
• pp.787-794
• /
• 2003

The effect of inclination angle on natural convection heat transfer has been studied for water layers. The range of the Raleigh number was from the subcritical value to 1.4${\times}$10$^{7}$ , and the range of the inclination angle, $\theta$, measured from the horizontal was 0$\leq$$\theta$$\leq$180$^{\circ}$. For horizontal water layers, present results agreed well with the results of previous investigators and also showed significant departures from the results of air layers in the turbulent regime. Inclined cylindrical water layers showed secondary maxima in heat transfer, whereas rectangular air layers showed continuous decline of Nusselt number.

• 대한기계학회논문집B
• /
• 제30권12호
• /
• pp.1164-1172
• /
• 2006

Measurements of the local heat transfer coefficients on hemispherical convex and concave surfaces with a turbulent impinging jet were made. The Reynolds number used was 11000, 23000, 50000 and the nozzle- to- surface distance was L/d=2, 4, 6, 8, and 10 and the jet angle was a = $0^{\circ}$, $15^{\circ}$, $30^{\circ}$ and $40^{\circ}$. In case of concave surface, the Nusselt number at the stagnation point decreases as the jet angle increases and has the maximum value for L/d=6. The X-axis Nusselt number distributions exhibit secondary maxima at $0^{\circ}$ $\leq$ a $\leq$ $15^{\circ}$, L/d $\leq$ 4 for X/d<0(upstream) and at $0^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, L/d $\leq$ 4 and at $30^{\circ}$ $\leq$ a $\leq$ $40^{\circ}$, 4 < L/d $\leq$ 6 for X/d<0(downstream). The secondary maximum occurs at long distance from the stagnation point as the jet angle increases or the nozzle-to-surface distance decreases. In case of convex, correlations of the stagnation point Nusselt number according to Reynolds number, jet-to-surface distance ratio and dimensionless surface angle are presented. In the stagnation point, in term of Ren, n ranges from 0.43 in case of 2 $\leq$ L/d $\leq$ 6 to 0.45 in case of 6 < L/d $\leq$ 10, there agrees roughly appears to be laminar boundary layer result. The maximum Nusselt number, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. On this condition about surface curvature D/d=10, the maximum displacement is about 0.7 times of the jet nozzle diameter. The ratio of the maximum Nusselt number to the stagnation Nusselt number increases as the jet angle increases.

• Archives of Plastic Surgery
• /
• 제32권4호
• /
• pp.474-478
• /
• 2005

Craniosynostosis is a congenital anomaly characterized by premature closure of cranial sutures. Surgical intervention should be performed during infancy. However, surgical correction of craniosynostosis remains bone defect and secondary angle occasionally. Currently, publications investigating solutions to bone defect and secondary angle created by cranioplasty are getting much interest. We have used $BoneSource^{(R)}$ which is relatively safe as an implantable substance for providing solutions for this problem. From June 2002 to January 2004, five children with craniosynostosis underwent frontocalvarial contouring using $BoneSource^{(R)}$ and concurrent cranial vault remodeling. The patient ages ranged from 8.0 months to 4.9 years(mean, 2.5 years). The quantity of $BoneSource^{(R)}$ implanted ranged from 10 to 25g, with a mean of 13g. This paper presents the first series of children treated with $BoneSource^{(R)}$ for frontocalvarial contouring in the surgical correction of craniosynostosis. No patients experienced any complications. Our results shows excellent retention of contour without causing asymmetry or irregularity. No visible evidence of interference with craniofacial growth were observed. Through our experiences, $BoneSource^{(R)}$ is found to be very useful for frontocalvarial contouring in children undergoing correction of craniosynostosis.

• Archives of Plastic Surgery
• /
• 제38권4호
• /
• pp.376-382
• /
• 2011

Purpose: In patients with unilateral cleft lip and nose deformity, alar retraction is commonly seen on the non-cleft side after cleft side is corrected. Spacer graft was used to drag down the inferior border of the alar cartilage of the non-cleft side so as to match the cleft side. By performing spacer graft and septal extension graft together, symmetry and cosmetic improvements were achieved. Methods: Seven unilateral cleft lip and nose deformity patients underwent surgery for alar retraction correction. The median age was 24 years (ranged from 15 to 34 years), and the median follow-up period was 7.4 months (ranged from 6 to 12 months). The perpendicular length from the longitudinal axis of the nostril to the alar rim, the nasolabial angle and the ala-labial angle were measured in the lateral view photo. The longest perpendicular length from the cephalic border of the alar rim to the parallel line of the alar base was measured in the frontal view photo. Results: Improvement in alar retraction was seen after the surgery. There were no specific complications during the follow-up and the symmetry of both nostrils was satisfactory. No increase in the nasolabial angle or exposure of the nostrils was seen after the tip projection via tip plasty. Conclusion: The fundamental factor in correcting alar retraction with secondary cleft lip and nose deformity is repositioning the alar rim with spacer graft, which seems to be more physiologic than other methods. The method combining spacer graft with septal extension graft will bring symmetry as well as more cosmetic improvement in correction of alar retraction with secondary cleft lip and nose deformity.

• Journal of Mechanical Science and Technology
• /
• 제20권12호
• /
• pp.2284-2291
• /
• 2006

The present study investigates gas residence time and mixing characteristics for various swirl numbers generated by injection of secondary air into a lab-scale cylindrical combustor. Fine dust particles and butane gas were injected into the test chamber to study the gas residence time and mixing characteristics, respectively. The mixing characteristics were evaluated by standard deviation value of trace gas concentration at different measurement points. The measurement points were located 25 mm above the secondary air injection position. The trace gas concentration was detected by a gas analyzer. The gas residence time was estimated by measuring the temporal pressure difference across a filter media where the particles were captured. The swirl number of 20 for secondary air injection angle of 5$^{\circ}$ gave the best condition: long gas residence time and good mixing performance. Numerical calculations were also carried out to study the physical meanings of the experimental results, which showed good agreement with numerical results.

• 전기학회논문지
• /
• 제58권8호
• /
• pp.1457-1462
• /
• 2009

This paper proposes a compensating algorithm for the secondary voltage of a coupling capacitor voltage transformer (CCVT) in the time domain by considering the hysteresis characteristics of the core. The proposed algorithm estimates the three error terms i.e. the voltage across the secondary winding parameters, the voltage across the primary winding parameters, and the voltage across the capacitor and the tuning reactor. These three terms are added to the measured secondary voltage to obtain the correct voltage. The algorithm reduces the errors of the CCVT significantly both in the steady state and during a fault. The performance of the algorithm is verified under the various fault conditions by varying the fault distance, the fault inception angle, and the fault impedance with the EMTP generated data. Test results clearly indicate that the algorithm can increase the accuracy of a CCVT significantly under the fault conditions as well as in the steady state. The algorithm helps improve the performance of a protection relay or a metering device.