• Advances in aircraft and spacecraft science
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• v.10 no.4
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• pp.369-391
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• 2023

In our research we have offered a solid solution for aeronautical analysis. which can guarantee the asymptotic stability of coupled nonlinear facilities. According to the theoretical solutions and methods presented, the engine of this aircraft is a small high-bypass turbofan engine. using the non-linear aero-motor control approach and this paper focuses on the power management function of the aero-motor control system. These include static controls and transient controls. A mathematical model of the high-bypass-ratio two-spool unmixed-flow aeroengine was developed through a set of nonlinear dynamic equations verified by experimental data. A single actuator using the displacement method is designed to maintain a certain level of thrust under steady-state conditions. and maintains repeatable performance during transient operation from the requested thrust phase to the next. A single controller can compensate for the effects of noise and harmonic noise at many performance points. And the dynamic performance of a single controller is satisfactory during the transient. for fairness Numerical and computer experiments are described in the perfection of the methods we offer in research.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.5
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• pp.881-893
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• 2020

CFI(Control Flow Integrity) is a mitigation mechanism that protects programs by verifying control flows. IFCC(Indirect Function Call Checks) and SCS(Shadow Call Stack), CFI supported by LLVM Clang compiler, were introduced to protect applications in Android. IFCC protects function calls and SCS protects function returns. In this paper, we propose attacks to bypass CFI on the application environment with IFCC and SCS. Even if IFCC and SCS were applied to user applications, it was confirmed that there were many code segments not protected by IFCC and SCS in the application memory. We execute code in CFI unprotected segments to construct 1) bypassing IFCC to call a protected function, 2) modulating return address via SCS bypass. We identify code segments not protected by IFCC and SCS in Android10 QP1A. 191005.007.A3. We also implement proof-of-concept exploits to demonstrate that modulation of control flow is possible in an environment where IFCC and SCS are applied.

• Journal of Mechanical Science and Technology
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• v.19 no.5
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• pp.1158-1168
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• 2005

A shunt from the left ventricle to the left anterior descending artery is being developed for coronary artery occlusive disease, in which the shunt or conduit connects the the left ventricle (LV) with the diseased artery directly at a point distal to the obstruction. To aid in assessing and optimizing its benefit, a computational model of the cardiovascular system was developed and used to explore various design conditions. Computational fluid dynamic analysis for the shunt hemodynamics was also done using a commercial finite element package. Simulation results indicate that in complete left anterior descending artery (LAD) occlusion, flow can be returned to approximately 65% of normal, if the conduit resistance is equal for forward and reverse flow. The net coronary flow can increase to 80% when the backflow resistance is infinite. The increases in flow rate produced by asymmetric flow resistance are enhanced considerably for a partial LAD obstruction, since the primary effect of resistance asymmetry is to prevent leakage back into the ventricle during diastole. Increased arterial compliance has little effect on net flow with a symmetric shunt, but considerably augments it when the resistance is asymmetric. The computational results suggest that an LV-LAD conduit will be beneficial when the resistance due to artery stenosis exceeds 27 PRU, if the resistance is symmetric. Fluid dynamic simulations for the shunt flow show that a recirculating region generated near the junction of the coronary artery with the bypass shunt. The secondary flow is induced at the cutting plane perpendicular to the axis direction and it is in the attenuated of coronary artery.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.65-71
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• 2017

This work presents a comparative work on the ride comfort of a quarter car suspension system between two different magneto-rheological (MR) dampers; one is conventional type without bypass hole and the other is featured by several bypass holes in the piston. As a first step, two different MR dampers are designed on the basis of the governing equation and manufactured with same geometric dimensions except the bypass holes. After investigating the field-dependent damping properties, two dampers are installed to the quarter car suspension system. The suspension model is then derived and a sky-hook controller is implemented to identify vibration control performance under random road. It is shown that the suspension system with MR damper featured by the bypass holes can provide much better ride quality than the case without the bypass holes. This is validated via experimental implementation.

• Nuclear Engineering and Technology
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• v.33 no.3
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• pp.315-326
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• 2001

Direct ECC bypass phenomena that occur in a reactor vessel downcomer with a Direct Vessel Injection (DVI) system during the reflood phase of a Large Break Loss-of-Coolant Accident (LBLOCA) are experimentally investigated using a transparent l/7.5 scaled down test facility of the Upper Plenum Test Facility (UPTF). A series of separate effect tests are peformed in order to investigate the mechanisms of direct ECC bypass and to find out its scaling parameters. Various flow regimes and phasic distribution in downcomer are identified and mapped, and the fraction of direct ECC bypass is measured under a wide range of air and water injection conditions. From the counterpart test of the UPTF Test 21-D, the dimensionless gas velocity ( $j^{*}$$_{g,eff}$) is derived experimentally, which is believed to be a major scaling parameter for the fraction of direct ECC bypass. And it is found out that the direct ECC bypass is greatly affected by the spreading width of ECC water film and the geometric configuration of the downcomer.r.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.539-543
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• 2009

When the suction pressure of compressor decreases under its limit, the compression ratio is increased causing the malfunctions of compressor. As the method to decrease the compression ratio, hot gas bypass system is usually adopted in heat pump system. In the hot gas bypass system, the discharged gas from the compressor is bypassed into the compressor suction, which causes the increase of suction pressure and the decrease of compression ratio. In this study, the characteristics and performances of the hot gas bypass system in heat pump was investigated experimentally with a variation of the bypass flow rate ratio. With the increase of the bypass rate ratio, the compressor suction pressure was increased, even though the total capacity and COP was decreased. From the analysis of the experimental results, the optimum pressure control algorithm was suggested in this study.

• Journal of Chest Surgery
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• v.25 no.12
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• pp.1399-1403
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• 1992

The evaluation of the effectivess of ongoing cardiopulmonary resucitation efforts is dependent on the commonly used methods, such as the presence of femoral or carotid artery pulsations, arterial blood gas determinations, peripheral arterial pressure and intracardiac pressure monitoring. But recent studies suggest that end-tidal carbon dioxide tension serves as a non-invasive measurement of pulmonary blood flow and therefore cardiac output under constant ventilation. A prospective clinical study was done to determine whether end-tidal carbon dioxide monitoring in open heart surgery under cardiopulmonary bypass could be used as a prognostic indicator of bypass weaning. We monitored end-tidal PCO2 values continuously during cardiopulmonary bypass in 30 patients. "Ohmeda 5210 CO-2 monitor" under infrared absorption method were incorperated into the ventilator circuit by means of a side point adaptor between endotracheal tube and ventilator tubing. 18 patients[Group I ] were res-ucitated from partial bypass followed by aorta cross clamp off and 12 patients[Group II ] from aorta cross clamp off followed by partial bypass. But there was no difference between two groups[p>0.05]. The value of end-tidal carbon dioxide tension during ventricular fibrillation or nearly arrest state was 6.6$\pm$2.9 mmHg, and at the time of spontaneous beating was 19.3$\pm$5.6 mmHg[Mean$\pm$Standard deviation], In conclusion end-tidal carbon dioxide tension monitoring provides clinically useful, continous, noninvasive and supplementary prognostic indicator during cardiopulmonary bypass weaning procedures.rocedures.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.4
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• pp.390-396
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• 2004

A double-inlet pulse tube refrigerator was fabricated as a U-shape with $\Phi$19.0 mm${\times}$125 mm regenerator packed by #200 stainless steel mesh and $\Phi$12.7 mm${\times}$125 mm pulse tube. A pressure sensor was installed at the inlet of the regenerator and a differential pressure sensor was installed across the bypass. Amplitude of the pulsating pressure was independent of the opening of the orifice and the bypass valves. Helium flow through the orifice and the bypass was calculated based on the measured pressure. Energy loss through the orifice and the bypass was evaluated with the measured pressure and the calculated helium flow rate. The energy loss, which is equivalent to the refrigeration capacity at the cold end of the ideal pulse tube refrigerator, was mainly generated through the orifice. It was proportional to the opening of the orifice valve, but the real refrigerator displayed the best performance at the optimized opening of the orifice valve. This optimized performance of the tested pulse tube refrigerator can be explained by additional refrigeration losses. As an example, the shuttle heat transfer loss of the pulse tube was calculated from the measured experimental data.

• Journal of Chest Surgery
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• v.28 no.7
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• pp.671-677
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• 1995

Skeletonization of the internal mammary artery [IMA during myocardial revascularization procedures may provide some advantages, compared with the pedicle graft of the artery. In 17 patients undergoing IMA grafting by skeletonization technique, flow through the artery was measured on mean arterial pressure of 50-55 mmHg immediately after cardiopulmonary bypass started [first flow and just before its anastomosis to left anterior descending artery [second flow . In 16 patients except 1 patient whose graft was injured during mobilization, the first flow of IMA graft was 32.3 $\pm$ 7.4 ml/min and the second flow increased to 59.6$\pm$25.9 ml/min without any treatment and the site for anastomosis of the IMA graft was more than 1.0 cm above the bifurcation. On the basis of previous clinical studies, the flow of the skeletonized IMA was greater than that of the pedicle graft [59.6 $\pm$ 25.9 ml/min versus 37.7$\pm$ 14.1 ml/min, p < 0.05 . In comparison between the skeletonized IMA and the IMA graft intraluminally dilated with papaverine solution, there was no significant difference between two flows[59.6 $\pm$25.7 ml/min versus 74.7 $\pm$31.4 ml/min, not significant , but the former showed longer graft and anastomosis of more proximal portion of the graft to left anterior descending artery. In conclusion, the technique of internal mammary artery skeletonization has consistently produced a satifactory conduit for myocardial revascularization procedures. We have adopted IMA skeletonization not only because of the flow, diameter, and vessel length obtained but also because of limited perivascular tissue disruption that occurs during the dissection.

• Journal of Chest Surgery
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• v.38 no.1 s.246
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• pp.13-22
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• 2005

It has been known that pulsatile flow is physiologic and more favorable to tissue perfusion than nonpulsatile flow. The purpose of this study is to directly compare the effect of pulsatile versus nonpulsatile blood flow to renal tissue perfusion in extracorporeal circulation by using a tissue perfusion measurement system. Material and Method: Total cardiopulmonary bypass circuit was constructed to twelve Yorkshire swines, weighing 20$\~ $30 kg. Animals were randomly assigned to group 1 (n=6, non pulsatile centrifugal pump) or group 2 (n=6, pulsatile T-PLS pump). A probe of the tissue perfusion measurement system $(QFlow^{TM}-500)$ was inserted into the renal pa­renchymal tissue. Extracorporeal circulation was maintained for an hour at a pump flow of 2 L/min after aortic cross-clamping. Tissue perfusion flow of the kidney was measured at baseline (before bypass) and every 10 minutes after bypass. Serologic parameters were collected at baseline and 60 minutes after bypass. Result: Baseline parameters were not different between the groups. Renal tissue perfusion flow was substantially higher in the pulsatile group throughout the bypass (ranged 48.5$\~$ 64 in group 1 vs. 65.8$\~$88.3 mL/min/100 g in group 2, p=0.026$\~$ 0.45) The difference was significant at 30 minutes bypass $(47.5{\pm}18.3\;in\;group\;1\;vs.\;83.4{\pm}28.5$ mL/min/100 g in group 2, p=0.026). Serologic parameters including plasma free hemoglobin, blood urea nitrogen, and creatinine showed no differences between the groups at 60 minutes after bypass (p=NS). Conclusion: Pulsatile flow is more beneficial to tissue perfusion of the kidney in short-term extracorporeal circulation. Further study is suggested to observe the effects to other vital organs or long-term significance.