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| 1 | Effectiveness of a Passive-active Vibration Isolation System with Actuator Constraints显示文摘In the prediction of active vibration isolation performance,control force requirements were ignored in previous work.This may limit the realization of theoretically predicted isolation performance if control force of large magnitude cannot be supplied by actuators.The behavior of a feed-forward active isolation system subjected to actuator output constraints is investigated.Distributed parameter models are developed to analyze the system response,and to produce a transfer matrix for the design of an integrated passive-active isolation system.Cost functions comprising a combination of the vibration transmission energy and the sum of the squared control forces are proposed.The example system considered is a rigid body connected to a simply supported plate via two passive-active isolation mounts.Vertical and transverse forces as well as a rotational moment are applied at the rigid body,and resonances excited in elastic mounts and the supporting plate are analyzed.The overall isolation performance is evaluated by numerical simulation.The simulation results are then compared with those obtained using unconstrained control strategies.In addition,the effects of waves in elastic mounts are analyzed.It is shown that the control strategies which rely on unconstrained actuator outputs may give substantial power transmission reductions over a wide frequency range,but also require large control force amplitudes to control excited vibration modes of the system.Expected power transmission reductions for modified control strategies that incorporate constrained actuator outputs are considerably less than typical reductions with unconstrained actuator outputs.In the frequency range in which rigid body modes are present,the control strategies can only achieve 5–10 dB power transmission reduction,when control forces are constrained to be the same order of the magnitude as the primary vertical force.The resonances of the elastic mounts result in a notable increase of power transmission in high frequency range and cannot be attenuated by active control.The investigation provides a guideline for design and evaluation of active vibration isolation systems. | SUN Lingling SUN Wei SONG Kongjie HANSEN Colin H | 2014 | Chinese Journal of Mechanical Engineering2014，27，3： | 5 |
| 2 | Experimental investigation of transient characteristics of mild surge and diffuser rotating stall in a centrifugal compressor with vaned diffuser显示文摘The centrifugal compressor is widely used for gas compression in various industrial fields such as aero-engine, gas turbine and turbocharger. However, the stable operating range is usually restricted by the occurrence of flow instability such as stall and surge. The paper experimentally examines the developing process of surge and stall occurring in a centrifugal compressor to advance the understanding on flow mechanism of flow instability. It is found that three types of pressure fluctuation can be observed at low flowrate region. At the critical point, the local stall firstly occurs in some specific diffuser passages and the enlarged local diffuser stall eventually induces the mild surge of compression system indicated by the sinusoidal pressure fluctuation. At lower mass flow rate, the diffuser stall cell begins to circumferentially propagate along the impeller rotating direction at 11% of rotor speed with the existence of mild surge. In comparative analysis of IGV pre-swirl angle on the occurrence of mild surge, the mild surge still occurs at the operating condition when the slope of the characteristic map of test stage is still obviously negative, in which the compression system is supposed to be stable in previous study. And a new suggested criterion for the prediction of mild surge is demonstrated that the occurrence of mild surge depends on the destabilization effect of downstream components about diffuser and volute. Combined with the experimental data, the streamwise distribution characteristic of diffuser stall can be used to develop the simplified model of lumped parameters for the analysis on the generation mechanism of the diffuser rotating stall. The quantitative investigation on the relation between the pressure-rise characteristic of subcomponents and the occurrence of mild surge and diffuser rotating stall not only advances the prediction of stability limit but also lays the theoretic foundation for controlling these unsteady behaviors to improve the operating range. | ZHAO Yang XI Guang ZOU HanSen SUN Ya Wei WANG ZhiHeng | 2020 | Science China(Technological Sciences)2020，63，7： | 2 |
| 3 | Better parameters of ventilation-CO2 output relationship predict death in CHF patients显示文摘Objective: Measures of ventilation-co_2 output relationship have been shown to be more prognostic than peak O_2 uptake in assessing life expectancy in patients with chronic heart failure(CHF). Because both the ratios(V4e/V4co_2) and slopes(V4e-vs-V4co_2) of ventilation-co_2 output of differing durations can be used, we aim to ascertain which measurements best predicted CHF life expectancy. Methods: Two hundred and seventy-one CHF patients with NYHA class II-IV underwent incremental cardiopulmonary exercise testing(CPET) and were followed-up for a median duration of 479 days. Four different linear regression V4e-vsV4co_2 slopes were calculated from warm-up exercise onset to: 180 s, anaerobic threshold(AT), ventilatory compensation point(VCP); and peak exercise. Five V4e/V4co_2 ratios were calculated for the following durations: rest(120 s), warm-up(30 s), AT(60 s), lowest value(90 s), and peak exercise(30 s). Death or heart transplant were considered end-points. Multiple statistical analyses were performed. Results: CHF patients had high lowest V4e/V4co_2(41.0±9.2, 141±30%pred), high V4e/V4co_2 at AT(42.5±10.4, 145±35%pred), and high V4e-vs-V4co_2 slope to VCP(37.6±12.1, 126±41%pred). The best predictor of death was a higher lowest V4e/V4co_2(≥42, ≥141%pred), whereas the V4e-vs-V4co_2 slope to VCP was less variable than other slopes. For death prognosis in 6 months, %pred values were superior: for longer times, absolute values were superior. Conclusion: The increased lowest V4e/V4co_2 ratio easily identifiable and simply measured during exercise, is the best measurement to assess the ventilation-co_2 output relationship in prognosticating death in CHF patients. | You-xiu YAO Xing-guo SUN Zhe ZHENG Gui-zhi WANG James E. Hansen William W.Stringer Karlman Wasserman Sheng-shou HU | 2015 | 中国应用生理学杂志2015，31，6： | 2 |
| 4 | Carbon dioxide pressure- concentration relationship in arterial and mixed venous blood during exercise显示文摘 | Sun XG Hansen JE Stringer WW | 2001 | J Appl Pbysiol2001，90，： | 1 |
| 5 | Oscillatory breathing and exercise gas exchange abnormalities prognosticate early mortality and morbidity in heart failure显示文摘 | Sun XG Hansen JE Beshai JF | 2010 | J Am Coil Cardiol2010，55，： | 1 |
| 6 | Chronic kidney disease after nephrectomy in patients with small renal masses: a retrospective observational analysis 显示文摘 | SUN M BIANCHI M HANSEN J | 2012 | Eur Urol2012，62，4： | 1 |
| 7 | Oxygen uptake efficiency plateau (OUEP) best predicts early death in heart failure显示文摘 | Sun XG Hansen JE Stringer WW | 2012 | Chest2012，141，5： | 1 |
| 8 | Chronic kidney disease after nephrectomy in patients with small renal masses: a retrospective ob- servational analysis显示文摘 | Sun M Bianchi M Hansen J | 2012 | Eur Urol2012，62，4： | 1 |
| 9 | Ventilatory efficiency during exercise in healthy subjects 显示文摘 | Sun XG Hansen JE Garatachea N | 2002 | Am J Respir Crit Care Med2002，166，11： | 1 |
| 10 | Gas exchange detection of exercise-induced right-to-left shunt in patients with primary pulmonary hypertension显示文摘 | Sun XG Hansen JE Oudiz RJ | 2002 | Cir- culation2002，105，： | 1 |
| 11 | Exercise pathophysiology in patients with primary pulmonary hypertension 显示文摘 | Sun XG Hansen JE Oudiz R J | 2001 | Circulation2001，104，： | 1 |
| 12 | Exercise pathophysiology in patients with primary pulmonary hypertension显示文摘 | Sun X G Hansen J E Oudiz R J | 2001 | Circulation2001，104，4： | 1 |
| 13 | Comparison of exercise cardiac output by the Fiek principle using O2 and CO2显示文摘 | Sun XG Hansen J E Ting H | 2000 | Chest2000，118，： | 1 |
| 14 | Reproducibil- ity of cardiopulmonary exercise gas exchange parame- ters in patients with pulmonary arterial hypertension显示文摘 | Hansen JE Sun XG Yasunobu Y | 2004 | Chest2004，126，： | 1 |
| 15 | Carbon dioxide pressure-concentration relationship in arterial and mixed venous blood during exercise显示文摘 | Sun XG Hansen JE Stringer WW | 2001 | J Appl Physiol2001，90，： | 1 |
| 16 | Adaptive evolution of drug targets in producer and non-producer organisms显示文摘 | HANSEN BG SUN XE GENEE HG | 2012 | Biochem J2012，441，1： | 1 |
| 17 | Oxygen uptake efficiency plateau best predicts early death in heart failure 显示文摘 | Sun XG Hansen JE Stringer WW | 2012 | Chest2012，141，5： | 1 |
| 18 | Oxygen uptake efficiency plateau: physiology and reference value 显示文摘 | Sun XG Hansen JE Stringer WW | 2012 | Eur J Appl Physiol2012，112，： | 1 |
| 19 | Oxygen uptake efficiency plateau best prediets early death in heart failure 显示文摘 | Sun XG Hansen JE Stringer WW | 2012 | Chest2012，141，： | 1 |
| 20 | Effect of biventricular pacing on the exercise pathophysiology of heart failure 显示文摘 | Wasserman K Sun XG Hansen JE | 2007 | Chest2007，132，： | 1 |
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