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Weihua Li
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Journal Articles
Wenxing Li, Haiping Du, Zhiguang Feng, Donghong Ning, Weihua Li, Shuaishuai Sun, Lixin Tu, Jumei Wei
Article Type: Research-Article
J. Dyn. Sys., Meas., Control. September 2020, 142(9): 091003.
Paper No: DS-19-1289
Published Online: May 11, 2020
Abstract
This paper proposes a singular system-based approach for active vibration control of vehicle seat suspensions, where the drivers' acceleration is augmented into the conventional seat suspension model together with seat suspension deflection and relative velocity as system states to make the suspension model as a singular system. In this novel seat suspension system, all the system states are easy to measure in real-time. A friction observer is applied to estimate the real system friction and an H ∞ controller is designed to achieve the optimal ride comfort performance with consideration of the friction compensation, actuator saturation, and time delay issues. The cone complementarity linearization (CCL) algorithm is applied to solve the nonlinear constraints. The experimental results show that good ride comfort performance can be achieved by the proposed controller in both the time and frequency domain compared with the uncontrolled seat suspension.
Journal Articles
Article Type: Research Papers
ASME J Nondestructive Evaluation. November 2019, 2(4): 041001.
Paper No: NDE-18-1042
Published Online: September 23, 2019
Abstract
Due to harsh operating environments in underground coal seams, the key components (e.g., gear pairs and bearings) in the power transmission systems of coal cutters suffer from extreme wear and functional damages. To guarantee the safe and reliable operation of the coal cutters, it is important to monitor the condition of their transmission systems and detect possible faults in a timely manner. A challenging task here is to diagnose multiple concurrent faults. A literature review indicates that the current interests lie on the decoupling of multiple co-existing faults and that the very limited work has been done to deal with the dependence/correlation between the fault signals. To address this issue, this work extends our previous work on gear crack detection using the bounded component analysis (BCA) and proposes an improved BCA-based approach for decoupling hybrid faults with high dependence/correlation in coal cutter transmission systems. The proposed approach incorporates the Vold–Kalman order tracking and spectral kurtosis into an improved BCA framework (OTBCA-SK). Owing to the uniform sampling of order tracking, the influence of background noise and rotational speed variation on vibration signals can be effectively reduced. Since BCA is capable of handling vibration sources that are statistically dependent, OTBCA-SK can decouple both independent and dependent source signals. As a result, the vibration sources excited by hybrid faults, although maybe dependent/correlated, can be fully decoupled into single-fault vibration source signals. Three specially designed case studies were used to evaluate the effectiveness of the proposed OTBCA-SK approach in decoupling hybrid gear faults. The analysis results demonstrate better performance of hybrid fault decoupling using OTBCA-SK than that of three representative techniques, i.e., Erdogan's BCA (E-BCA), joint approximate diagonalization of eigen matrices (JADE) and fast independent component analysis (FastICA). These case studies also suggest that the proposed OTBCA-SK approach can retain the physical meaning of the original vibration and is hence suitable for hybrid fault diagnosis in practical applications.
Proceedings Papers
Proc. ASME. ICONE26, Volume 3: Nuclear Fuel and Material, Reactor Physics, and Transport Theory, V003T02A047, July 22–26, 2018
Paper No: ICONE26-82244
Abstract
Heat pipe-segmented thermoelectric module converters space reactor power system (HP-SMTCs SRPS) is a promising candidate for space nuclear power system. An examination was taken to discuss the criticality safety of HP-SMTCs reactor core in several accident conditions. In the original nuclear design, the case that reactor core is submerged in wet sand while the voids inside the core are filled with sea water and the BeO reflector are dismantled is defined as the worst status with the highest risk of supercritical. However, recent Monte Carlo transport calculation result shows that reactivity in the case that the core is submerged in water while the voids inside are empty is even higher than those cases with the voids full of sea water, which means that the reactor may encounter high risk of supercritical when some particular accidents occur. Detailed analysis about the neutron energy spectrum and absorption reaction rate is made in order to find out the potential reason of these unexpected results. According to the discussion about the criticality safety issues in some accidents, further evaluations may be necessary for the neutronics design of HP-SMTCs space reactors.
Proceedings Papers
Proc. ASME. ICONE26, Volume 3: Nuclear Fuel and Material, Reactor Physics, and Transport Theory, V003T02A029, July 22–26, 2018
Paper No: ICONE26-81596
Abstract
In order to ensure the safety of fuel rods in nuclear reactor, it is necessary to consider the condition of the power ramp during reactor operation, which may cause breakage risk of fuel rod at the time of pellet-cladding interaction (PCI) appearing. To analyze this phenomenon and reduce the risk, a performance analysis model for fuel rod is developed to carry out the steady state and transient simulation using commercial software COSMOL. The full model has three main computational models, which are heat transfer model, mechanical model and internal pressure model. The calculation results show that the stress and strain of NHR200-II fuel rods has enough margins during the power ramp process, which indicates that the risks of fuel rod damage are very low.
Proceedings Papers
Proc. ASME. ICONE26, Volume 6B: Thermal-Hydraulics and Safety Analyses, V06BT08A026, July 22–26, 2018
Paper No: ICONE26-82052
Abstract
The two-phase flow instability of forced convection has been experimentally investigated in a vertical narrow channel with the hydraulic diameter of 2.857mm and aspect ratio of 20. Transparent, metallic and conductive films on external surfaces of the test section can provide visualization and uniform heating for deionized water. The heat flux is 6–18.2 kW · m −2 . When the instability occurs at low vapor quality, a series of parameters are measured and visualized images are obtained by a high-speed camera. The results show that the large amplitude of pressure drop between the inlet and outlet in the test section is due to the elongated bubble, and the value of pressure drop is positively correlated with the volume of the bubble. The oscillation period of pressure drop decreases with the increase of heat flux, and the period can be determined by the method of the Fast Fourier Transform. The backflow phenomenon is analyzed, which has a greater effect on the oscillation of pressure drop than bubble nucleation, bubble growth, bubble coalescence and recoiling of bubble boundary.
Journal Articles
Journal:
Journal of Vibration and Acoustics
Article Type: Technical Briefs
J. Vib. Acoust. June 2018, 140(3): 034502.
Paper No: VIB-17-1031
Published Online: February 9, 2018
Abstract
In this work, two model identification methods are used to estimate the nonlinear large deformation behavior of a nonlinear resonator in the time and frequency domains. A doubly clamped beam with a slender geometry carrying a central intraspan mass when subject to a transverse excitation is used as the highly nonlinear resonator. A nonlinear Duffing equation has been used to represent the system for which the main source of nonlinearity arises from large midplane stretching. The first model identification technique uses the free vibration of the system and the Hilbert transform (HT) to identify a nonlinear force–displacement relationship in the large deformation region. The second method uses the frequency response of the system at various base accelerations to relate the maximum resonance frequency to the nonlinear parameter arising from the centerline extensibility. Experiments were conducted using the doubly clamped slender beam and an electrodynamic shaker to identify the model parameters of the system using both of the identification techniques. It was found that both methods produced near identical model parameters; an excellent agreement between theory and experiments was obtained using either of the identification techniques. This follows that two different model identification techniques in the time and frequency domains can be employed to accurately predict the nonlinear response of a highly nonlinear resonator.
Proceedings Papers
Wei Li, Dingqu Wang, Yueyuan Jiang, Songyang Li, Wenli Guo, Wei Xiong, Weihua Li, Heng Xie, Xiaotian Li
Proc. ASME. ICONE25, Volume 8: Computational Fluid Dynamics (CFD) and Coupled Codes; Nuclear Education, Public Acceptance and Related Issues, V008T09A051, July 2–6, 2017
Paper No: ICONE25-67746
Abstract
The type-II 200MW nuclear heating reactor (NHR200-II) designed by Tsinghua University is a novel pressurized water reactor, whose main specifications are as follows, the heat power is 200 MW, the design pressure of major loop is 10 MPa, the inlet and outlet temperature of coolant are 230 °C and 278 °C. In this paper, a quarter three-dimensional model of the lower plenum of the reactor pressure vessel is set up for analysis. The flow velocity distribution and the pressure distribution on the core supporting structure are calculated by method of three-dimensional numerical simulation. The results show that the lower part of the core produce symmetric vortex due to the existence of support structure. The production of the symmetric vortex, to some extent, increases the instability of the flow. On the other hand, the existence of the vortex is good for uniformity of flow distribution in the outlet holes. The flow rate in the flow channel of support structure is lower at the center and larger in the margin of core inlet. The results show that the maximum of the velocity in the flow channel is 5% higher than the minimum one.
Journal Articles
Journal:
Journal of Heat Transfer
Article Type: Research-Article
J. Heat Transfer. May 2017, 139(5): 052404.
Paper No: HT-16-1162
Published Online: February 23, 2017
Abstract
Plasma is a host of numerous analytes such as proteins, metabolites, circulating nucleic acids (CNAs), and pathogens, and it contains massive information about the functioning of the whole body, which is of great importance for the clinical diagnosis. Plasma needs to be completely cell-free for effective detection of these analytes. The key process of plasma extraction is to eliminate the contamination from blood cells. Centrifugation, a golden standard method for blood separation, is generally lab-intensive, time consuming, and even dangerous to some extent, and needs to be operated by well-trained staffs. Membrane filtration can filter cells very effectively according to its pore size, but it is prone to clogging by dense particle concentration and suffers from limited capacity of filtration. Frequent rinse is lab-intensive and undesirable. In this work, we proposed and fabricated an integrated microfluidic device that combined particle inertial focusing and membrane filter for high efficient blood plasma separation. The integrated microfluidic device was evaluated by the diluted (×1/10, ×1/20) whole blood, and the quality of the extracted blood plasma was measured and compared with that from the standard centrifugation. We found that the quality of the extracted blood plasma from the proposed device can be equivalent to that from the standard centrifugation. This study demonstrates a significant progress toward the practical application of inertial microfluidics with membrane filter for high-throughput and highly efficient blood plasma extraction.
Journal Articles
Article Type: Research-Article
J. Dyn. Sys., Meas., Control. January 2017, 139(1): 011008.
Paper No: DS-15-1519
Published Online: October 17, 2016
Abstract
A nonlinearly broadband tuneable energy harvesting device has been designed, fabricated, and tested based on the nonlinear dynamical response of a parametrically excited clamped–clamped beam carrying a central point mass as the core element; a tuning mechanism in the form of an initial axial displacement applied to one of the clamped–clamped beam ends has been introduced to the system which enables tuning of device's natural frequency. Magnets have been used as the central point mass which generates a backward electromotive force (EMF) as they move through a coil when parametrically excited. The tuning parameter was set to a value for which the primary and principal nonlinear resonant regions become close to each other; hence, the frequency bandwidth is broadened substantially, leading to a larger amount of electrical power harvested; moreover, the nonlinear behavior, due to flexural/restoring-electromagnetic couplings, increased the operating bandwidth considerably. The system was parametrically excited using an electrodynamic shaker, and the corresponding motions of the magnets were measured. By increasing the tuning parameter, the fundamental natural frequency reduces and the system nonlinearity significantly increases; it has been discovered that when the initial axial displacement is approximately the thickness of the beam the fundamental and principal parametric resonance branches combine thus, the frequency bandwidth (and hence the range of the energy harvested) is significantly increased due to the parametric excitation, nonlinear behavior, and initial axial displacement.
Journal Articles
Article Type: Research-Article
J. Energy Resour. Technol. May 2017, 139(3): 032001.
Paper No: JERT-16-1076
Published Online: October 10, 2016
Abstract
In this work, for the first time, an energy harvester based on the nonlinear dynamical response of a parametrically excited cantilever beam in contact with mechanical stoppers has been fabricated and tested; a 145% increase in the bandwidth at which energy can be effectively harvested has been observed. Experimental and theoretical investigations have been performed in order to assess the increased operating bandwidth of the energy harvester fabricated; for the experimental investigations, an electrodynamic shaker connected to a shaking table has been used to parametrically stimulate the energy harvesting device. Results showed that the parametric energy harvester without stoppers displayed a weak softening-type nonlinear response; however, with the addition of mechanical stoppers the energy harvester displayed a strong hardening-type nonlinear response which is ideal for capturing kinetic energy over larger bandwidths. The addition of mechanical stoppers on a parametrically excited cantilever beam has significant qualitative and quantitative effects on the nonlinear parametric energy harvesting; the energy harvesting bandwidth was increased in the range of 35–145% by adjusting the stoppers.
Proceedings Papers
Proc. ASME. MNHMT2016, Volume 1: Micro/Nanofluidics and Lab-on-a-Chip; Nanofluids; Micro/Nanoscale Interfacial Transport Phenomena; Micro/Nanoscale Boiling and Condensation Heat Transfer; Micro/Nanoscale Thermal Radiation; Micro/Nanoscale Energy Devices and Systems, V001T01A012, January 4–6, 2016
Paper No: MNHMT2016-6717
Abstract
Plasma is a host of various analytes such as proteins, metabolites, circulating nucleic acids (CNAs), pathogens. The key process of plasma extraction is to eliminate the contamination from blood cells. Conventional methods, such as centrifugation and membrane filtration, are generally lab-intensive, time consuming and even dangerous. In this study, we report an integrated microfluidic device that combines inertial microfluidics and membrane filter. The integrated microfluidic device was evaluated by the diluted (x1/10, x1/20) whole blood, and the quality of the extracted blood plasma was tested. It was found that quality of extracted blood plasma from integrated device was equivalent to that obtained by the centrifugation. This study demonstrates a significant progress towards the practical application of inertial microfluidics with membrane filter for high-throughput and high efficient blood plasma extraction.
Journal Articles
Journal:
Journal of Medical Devices
Article Type: Research-Article
J. Med. Devices. March 2016, 10(1): 011004.
Paper No: MED-15-1203
Published Online: November 16, 2015
Abstract
There is an increasing need to incorporate an actively controlled drug delivery system (DDS) into the next generation of capsule endoscopy in order to treat diseases in the gastrointestinal tract in a noninvasive way. Despite a number of attempts to magnetically actuate drug delivery mechanisms embedded in endoscopic capsules, longer operating distances and further miniaturization of on-board components are still drawbacks of such systems. In this paper, we propose an innovative magnetic system that consists of an array of magnets, which activates a DDS, based on an overly miniaturized slider–crank mechanism. We use analytical models to compare the magnetic fields generated by cylindrical and arc-shaped magnets. Our experimental results, which are in agreement with the analytical results, show that an optimally configured array of the magnets enhances the magnetic field and also the driving magnetic torque and subsequently, it imposes a high enough force on the piston of the DDS to expel a required dose of a drug out of a reservoir. We conclude that the proposed magnetic field optimization method is effective in establishing an active DDS that is designed to deliver drug profiles with accurate control of the release rate, release amount, and number of doses.
Proceedings Papers
Proc. ASME. ICONE18, 18th International Conference on Nuclear Engineering: Volume 3, 99-104, May 17–21, 2010
Paper No: ICONE18-29272
Abstract
The recent advances in utilization of nuclear heating reactor technology are to couple with seawater desalination process, in which process steam and fresh water is combined to produce, steam turbine is used, thermal and membrane processes are joined. In this technical concept, the “zero discharge” to environment will be realized due to using nuclear energy as the heat source for process steam and seawater desalination. Combined process steam and fresh water produce will make the product’s cost lower and make the whole system economic results better. The special design features of nuclear heating reactor will ensure that any radiological contamination can be excluded from fresh water. As joining thermal process and membrane process seawater desalination, the step utilization of thermal energy and reuse of waste heat can be realized.