• The korean journal of orthodontics
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• v.54 no.6
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• pp.346-358
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• 2024

Objective: Miniscrew-assisted maxillary expansion devices are frequently used for patients with calcified midpalatal sutures. This study aimed to evaluate the effects of two bone-borne maxillary expansion appliances on the cranial and circummaxillary sutures by comparing cone-beam computed tomography (CBCT) images before and after transverse maxillary expansion. Methods: A total of 81 patients (women = 58, men = 23) were treated with either a C-expander (n = 44) or an ATOZ expander (n = 37). CBCT images were obtained before (T0) and after (T1) maxillary expansion, and the widths of 10 circummaxillary sutures were measured in the sagittal, coronal, and axial planes. The Wilcoxon signed-rank test was used to compare the changes in suture width between the C-expander and ATOZ groups, and statistical significance was set at P < 0.05. Results: The frontonasal, frontomaxillary, pterygomaxillary, nasomaxillary, internasal, intermaxillary, and midpalatal suture widths increased significantly after maxillary expansion in both the ATOZ and C-expander groups (both P < 0.05). The frontozygomatic, zygomaticomaxillary, and temporozygomatic suture widths decreased in the C-expander group (P < 0.05), whereas the frontozygomatic suture width increased significantly in the ATOZ group (P < 0.05). The width changes of the frontozygomatic, zygomaticomaxillary, temporozygomatic, pterygomaxillary, internasal, intermaxillary, and midpalatal sutures differed significantly between the two groups (P < 0.05). Conclusions: Both the C- and ATOZ expanders affected the suture width in the naso-maxillozygomatic region. The C-expander decreased the circum-zygomatic suture widths, whereas the ATOZ expander widened the frontozygomatic suture with no effect on other circummaxillary sutures.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.230-235
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• 2014

In this study, performances of the vane expander protype for micro organic Rankine cycle with refrigerant R134a as a working fluid have been analyzed. While operating organic Rankine cycle for analysing expander efficiencies such as overall efficiencies, volumetric efficiencies and mechanical efficiencies under $110^{\circ}C$ of expander inlet temperature, the power of the expander, inlet temperature of expander, inlet pressure of expander and the flow rate of the working fluid(refrigerant R134a) have been measured while varying the rotational speed of the expander. It was found that the more the expander revolution speed is high, the more the expander power, overall efficiencies and volumetric efficiencies are higher. In case of 500 rpm of rotational speed, overall efficiencies are 6~7% and in case of 1000 rpm, overall efficiencies are 11~12%. We have found that low volumetric efficiencies result in poor overall efficiencies.

• Journal of Power System Engineering
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• v.20 no.2
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• pp.17-25
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• 2016

In this paper, the feasibility study on a gerotor type expander as a power converting device in a small scale power generation ORC system was made by performance analysis of the gerotor expander. Design of a 1kW-class gerotor expander was carried out and its performance was numerically simulated. For a R134a Rankine system with about 20 kW solar heat source, the gerotor expander efficiency was calculated to be 35~75% for the operating conditions of $Te=80{\sim}100^{\circ}C$ and $Tc=30{\sim}60^{\circ}C$. Maximum expander efficiency was obtained at an expansion ratio somewhat higher than the design expansion ratio due to pre-expansion during suction process inside the outer and inner rotor mate. If the operating expansion ratio is not far from the design expansion ratio, the gerotor expander performance can be well compared to that of a scroll type.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.237-242
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• 2009

A steam Rankine cycle was considered to recover waste heat from the exhaust gas of an automobile. Conceptual design of a swash plate type expander was practiced to convert steam heat to shaft power. With the steam pressure and temperature of 35 bar and $300^{\circ}C$ at the expander inlet, respectively, the expander was estimated to produce the shaft power output of about 1.93 kW from the exhaust gas waste heat of 20 kW. The expander output increased linearly accordingly to the amount of exhaust gas waste heat in the range of from 10-40 kW, and the Rankine cycle efficiency was more or less constant at about 9.6% regardless of the waste heat amount.

• Archives of Plastic Surgery
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• v.36 no.4
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• pp.422-427
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• 2009

Purpose: Breast cancer is second most common cancer in women. Almost of patients with breast cancer treated with mastectomy undergoes breast reconstruction. Nipple reconstruction is an important step in breast reconstruction. Many surgeons have investigated of nipple reconstruction using the flap technique after breast reconstruction with the autologous tissue. The objective of this study is to evaluate the results of nipple reconstruction using the C - V flap technique after breast reconstruction with the only breast expander. Methods: From April 2006 to May 2008, the authors treated 17 patients of nipple reconstruction using C - V flap technique, who were received breast reconstruction with the only breast expander. We have predicted decrease of the size of reconstructed nipple and designed flap a little larger than wanted nipple size. Nipple splint was applied for 4 - 6 months for minimizing decrease of the size of reconstructed nipple. The diameter and height of the reconstructed nipple were measured and patient's satisfaction score was assessed. Results: Mean follow-up duration was 12.5 months. Among the 17 patients, the average absorption rate by height of nipple was 47.0%. Partial necrosis was noted in 1 case, and treated well with conservative management. There was no other significant complications noted. Patient's satisfactory score was assessed by the height, design and location of the nipple. The average of satisfaction score was 85%, 68%, 62% and total average was 83%. Conclusion: The authors experienced 17 patients of nipple reconstruction using the C - V flap technique after breast reconstruction with the only breast expander. The absorption rate of the size of the nipple, complications and patient's satisfactory score of this study were similar to those of nipple reconstruction after breast reconstruction with the autologous tissue. It is expected that nipple reconstruction after breast reconstruction with the only breast expander is safe and reliable. It is considered that a long - term study is necessary.

• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.397-403
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• 2007

In this paper, conceptual design of scroll expander-compressor for Stirling engine utilizing solar energy as heat source has been carried out. Orbiting scroll member was designed to have a double-sided structure to reduce the overall scroll size and to cancel out the axial forces on the orbiting scroll base plate. Diameter of designed scroll base plate was about 251 mm for the expander, and it was about 218 mm for the compressor. With operating condition such as temperature range of $400^{\circ}C/20^{\circ}C$, pressure range of 6 MPa/2 MPa, and shaft speed of 2700 rpm, the shaft output of the designed scroll expander was calculated to be 49.8 kW, while input power for the scroll compressor was 38.6 kW, yielding 11.2 kW for the output power of the Stirling engine. Overall efficiencies of the scroll expander and compressor were 93.73% and 92.87%, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.5
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• pp.313-320
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• 2011

For a steam Rankine cycle to recover waste heat from the exhaust gas of an Internal combustion engine, a swash plate type of expander as a power conversion unit has been designed. Numerical simulation has been carried out to estimate the performance of the designed expander. With the steam pressure and temperature of 35 bar and $300^{\circ}C$ at the expander inlet, respectively, the expander was estimated to produce the shaft power output of about 2.67 kW from the exhaust gas waste heat of 25.2 kW. The expander output increased almost linearly with the amount of exhaust gas waste heat in the range of from 5~40 kW, and the expander and Rankine cycle efficiencies showed gradual decreases in the ranges of 72.2%~69.5% and 10.8%~10.4%, respectively.

• Journal of Power System Engineering
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• v.16 no.4
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• pp.30-36
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• 2012

A scroll expander has been designed to produce a shaft power from a R134a Rankine cycle for electricity generation. Heat was supplied to the Rankine cycle through a heat exchanger, which received heat from another cycle of water. In the water cycle, water was heated up in a boiler using biogenic solid fuel. The designed scroll expander was a horizontal type, and a trochoidal oil pump was employed for oil supply to bearings and Oldham-ring keys. For axial compliance, a back pressure chamber was created on the backside of the orbiting scroll base plate. Numerical study has been carried out to estimate the performance of the designed scroll expander. The expander was estimated to produce the shaft power of about 2.9 kW from a heat supply of 36 kW, when the temperature of R134a was $80^{\circ}C$ and $35^{\circ}C$ at the evaporator and condenser of the Rankine cycle, respectively. The expander efficiency was about 70.5%. When the amount of heat supply varied in the ranges of 7.5~55 kW, the expander efficiency changed in the range of 45.6~70.5%, showing a peak efficiency of 70.5% at the design shaft speed.

• Journal of the Korean Institute of Gas
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• v.19 no.4
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• pp.41-48
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• 2015

The performance characteristics of a scroll expander is the most important variable for the performance of organic Rankine cycle system. In this paper, the performance characteristics of a scroll expander was identified using 1kW class organic Rankine cycle system with various operating conditions. The ORC system is composed of an evaporator, a scroll expander, a condenser and a working fluid feed pump that uses R245fa as working fluid. The hot water temperature was controlled from $80^{\circ}C$ to $115^{\circ}C$ by the 50kW-class electric water-heater. The maximum isentropic efficiency of the scroll expander was measured about 77%, and the shaft power was measured from 0.5 kW to 1.8 kW according to heat source temperatures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.26 no.4
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• pp.151-157
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• 2014

An algebraic scroll expander has been fabricated and tested in a R134a Rankine cycle with heat source of 20 kW. For the operating conditions of 20~26 bar and $90{\sim}93^{\circ}C$ at the expander inlet and 8~9 bar at the outlet, the expander produced the shaft output power of about 0.6~0.7 kW in the operating speed range of 1500~2000 rpm. These correspond to the expander efficiency of 40~45%. The volumetric efficiency increased with increasing of the expander speed, reaching to 80% at 2000 rpm. Comparing to numerical simulation results, mechanical efficiency from the test data was found to be considerably low by as much as 30%, indicating that reduction in the frictional loss should be made to improve the scroll expander efficiency.