• Journal of Chest Surgery
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• 제55권6호
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• pp.435-441
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• 2022

Background: This study aimed to evaluate the impact of the treatment modality on post-procedural acute kidney injury (AKI) and other clinical outcomes in patients with advanced chronic kidney disease who underwent surgical or transcatheter aortic valve replacement (AVR). Methods: A total of 147 patients with advanced chronic kidney disease (stage 3 to 5) who underwent isolated surgical AVR (SAVR group; n=70) or transcatheter AVR (TAVR group; n=77) were retrospectively studied. Postprocedural AKI was defined according to the RIFLE definition (an acronym corresponding to the risk of renal dysfunction, injury to the kidney, failure of kidney function, loss of kidney function, and end-stage kidney disease). Factors associated with postoperative complications and mortality were analyzed using multivariable logistic regression models and Cox proportional hazard models. Results: Postprocedural AKI occurred in 17 (24.3%) and 6 (7.8%) patients in the SAVR and TAVR groups, respectively (p=0.006). Multivariable analyses demonstrated that the SAVR group had higher risks of AKI (odds ratio [OR], 5.63; 95% confidence interval [CI], 1.85-17.73; p=0.002) and atrial fibrillation (OR, 16.65; 95% CI, 4.44-62.50; p<0.001), whereas the TAVR group had a higher risk of permanent pacemaker insertion (OR, 5.67; 95% CI, 1.21-26.55; p=0.028). The Cox proportional hazard models showed that the occurrence of AKI, contrary to the treatment modality, was associated with overall survival. Conclusion: In patients with chronic kidney disease, the risk of postprocedural AKI might be higher after SAVR than after TAVR.

• International Journal of Automotive Technology
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• 제3권1호
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• pp.27-32
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• 2002

Semi-active suspension systems are greatly expected to be in the mainstream of future controlled suspensions fur passenger cars. In this study, a continuous variable damper for a passenger car suspension is developed. It is controlled actively and exhibits high performance with light weight, low cost, and low energy consumption. To get fast response of the damper, reverse damping mechanism is adapted, and to get small pressure change rate after blow-off, a pilot controlled proportional valve is designed and analyzed. The reverse continuous variable damper is designed as a HS-SH damper which offers good body control with reduced transferred input force from tire, compared with any other type of suspension system. The damper structure is designed, so that rebound and compression damping force can be tuned independently, of which variable valve is placed externally. The rate of pressure change with respect to the flow rate after blow-offbecomes smooth when the fixed orifice size increases. Damping forces are measured with the change of the solenoid current at the different piston velocities to confirm the maximum hysteresis of 20N, linearity, and variance of damping farce. The damping farce variance is wide and continuous, and is controlled by the spoof opening, of which scheme is usually adapted in proportional valves. The reverse continuous variable damper developed in this study is expected to be utilized in the semi-active suspension systems in passenger cars after its performance and simplicity of the design is confirmed through real car test.

• 대한기계학회논문집B
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• 제37권3호
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• pp.213-219
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• 2013

본 논문의 목적은 스풀 랜드(spool land)와 슬리브(sleeve) 사이의 정특성 방정식으로부터 스풀 밸브의 압력 특성과 유동특성을 구하는 것이다. 이러한 목적을 달성하기 위하여, 스풀 랜드와 슬리브 사이의 유동을 환상간극 유동과 오리피스 유동, 그 중간의 천이 영역으로 나누고, 천이 영역의 유량계수를 길이에 따른 두 영역으로 나눈 선형 일차방정식으로 가정하였다. 스풀 밸브의 압력특성방정식을 구하기 위해 스풀의 중립지점에서부터의 변위에 따른 유동을 $q_a=q_b=0$의 조건으로부터 구하였으며, 스풀 밸브의 유량특성방정식을 구하기 위하여 스풀의 중립지점에서부터의 변위에 따른 유동을 $q_a=q_b$, $p_a=p_b$의 조건으로부터 구하였다. 구해진 수식의 타당성은 수치해석을 통해 실험식 및 기존논문과의 비교를 통해 확인하였다.

• 한국시뮬레이션학회논문지
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• 제24권4호
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• pp.29-34
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• 2015

순수 기계식 시스템에 의존하던 군용차량의 전자화가 진행되고 있다. 이미 소형 군용차량의 전자화는 상당부분 상용화되었으며, 점차적으로 대형군용차량으로 확대될 것이다. 군용차량의 안정적인 주행성능을 위해서는 자동변속기용 솔레노이드 밸브의 설계가 매우 중요하다. 본 연구에서는 솔레노이드 밸브에 대해 ATF온도 변화에 의한 성능변화를 정량적으로 예측할 수 있는 해석(Simulation)수법을 개발하는 것을 목적으로 한다. 연구는 자장해석소프트웨어인 Maxwell과 유압해석프로그램인 AMESim을 연동하여 진행한다. 시뮬레이션 결과 고온($120^{\circ}C$이상)과 극저온($-20^{\circ}C$이하)을 제외한 온도 영역에서 실험결과와 매우 유사함을 보인다.

• International Journal of Control, Automation, and Systems
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• 제5권6호
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• pp.643-651
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• 2007

The various blood pressure simulators have been proposed to evaluate and improve the performance of the automatic sphygmomanometer. These have some problems such as the deviation of the actual blood pressure waveform, limitation in the blood pressure condition of the simulator, or difficulty in displaying the blood flow. An improved simulator using disturbance observer is proposed to supplement the current problems of the blood pressure simulator. The proposed simulator has an artificial arm model capable of feeding appropriate fluids that can generate the blood pressure waveform to evaluate the automatic sphygmomanometer. A controller was designed and thereafter, simulation was performed to control the output signal with respect to the reference input in the fluid dynamic model using the proposed proportional control valve. To minimize the external fluctuation of pressure applied to the artificial arm, a disturbance observer was designed on the plant. A hybrid controller combined with a proportional controller and feed-forward controller was fabricated after applying a disturbance observer to the control plant. Comparison of the simulations between the conventional proportional controller and the proposed hybrid controller indicated that even though the former showed good control performance without disturbance, it was affected by the disturbance signal induced by the cuff. The latter exhibited an excellent performance under both situations.

• 센서학회지
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• 제16권1호
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• pp.44-51
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• 2007

A hybridized simulator for generating blood pressure waveform is proposed to study the remedy and/or evaluation of the conventional sphygmomanometer utilizing the oscillometric method which is widely applied. The blood pressure of a flowing fluid was controlled for the blood vessel's condition caused by a rhythmical and periodical contraction/relaxation because of the special excitatory and conductive system of the heart. In this study, a hybridized controller composed of the PI feedback controller and the feedforward controller. The inverse dynamics function is proposed to operating the control valve while the pressure is applied in an oil pressure tank. The proposed hybrid simulator reproducing the blood pressure waveform in an artificial blood vessel has kept the control performance consistent over all range. Based on these results, the proposed simulators could be applied to the development and compensation of the non invasive sphygmomanometer type as well as to study the characteristics of the blood pressure and blood vessel.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.42-48
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• 1999

A control method for a robot hand grasping a object in a partially unknown environment will be proposed, where a proximate sensor detecting the distance between the fingertip and object was used. Particularly, the finger joints were driven servo-pneumatically in this study. Based on the proximate sensor signal the finger motion controller could plan the grasping process divided in three phases ; fast aproach, slow transitional contact and contact force control. That is, the fingertip approached to the object with full speed, until the output signal of the proximate sensor began to change. Within the perating range of the proximate sensor, the finger joint was moved by a state-variable feedback position controller in order to obtain a smooth contact with the object. The contact force of fingertip was then controlled using the blocked-line pressure sensitivity of the flow control servovalve for finger joint control. In this way, the grasping impact could be reduced without reducing the object approaching speed. The performance of the proposed grasping method was experimentally compared with that of a open loop-controlled one.

• 설비공학논문집
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• 제16권4호
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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.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2007년도 동계학술발표대회 논문집
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• pp.161-166
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• 2007

Various thermostatic valves have been used widely in Korea for conservation of heating energy and enhancement of thermal comfort in residential buildings. But heating control performances of thermostatic valves extensively vary with the design and operational conditions of the heating system, climate condition and others. An experimental method was carried out in this study to analyze heating control characteristics by temperature sensing methods of thermostatic valves for various parameters, such as supply temperatures and flow rate of hot water, the position of room thermostats and outdoor air temperatures. As a result, the heat flow rate per day of S-Valve($34^{\circ}C$-Type) of water temperature sensing method was liked that of C-Valve of indoor air temperature sensing method with stage 3.3 of room thermostat in case supply temperature of hot water was $45^{\circ}C$, flow rate was 1.3 L/min and outdoor air temperature was $7.8^{\circ}C$.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.979-984
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• 2007

This paper presents a new control mechanism for the proportional pressure control which is accomplished by electro-pneumatic regulator using two PZT actuators. The electro-pneumatic regulator of this study is 2-stage type and consists of two piezoelectric actuators, a controller and a main poppet valve. The piezoelectric actuators are multilayer bender type and are controlled by digital signal. Proportional pressure control technique is very important because that can derive improvement of product quality and driving ability in the pneumatic system. Solenoid actuator method for pressure control is widely used but this actuator has a high power consumption characteristics. So new actuator is required for the energy saving. In this study, PZT actuator for the pressure control was fabricated and experimented instead of the conventional type solenoid actuator. Experiments for the new control mechanism of the elector-pneumatic regulator were operated under the input condition of 0.4[MPa] and it was confirmed that this mechanism has a good control characteristics to the response sensitivity and hysteresis.