Center for the Arts Dedication

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Study on multi-axis sine vibration test control techniques

This paper describes several key aspects about multi-axis sine vibration test control techniques including the identification of the system frequency response function, synchronization of the input and output signals, the generation of the sinewave, the control algorithm, etc. A multi-axis sine vibration controller is developed based on these key techniques and the major framework of the controller is introduced. Finally, a dual axial experiment is carried out by the controller. The test results show the feasibility of the control algorithm and the good control strategy of the multi-axis sine vibration controller in which the key techniques are realized

New Stabilization for Dynamical System with Two Additive Time-Varying Delays

This paper provides a new delay-dependent stabilization criterion for systems with two additive time-varying delays. The novel functional is constructed, a tighter upper bound of the derivative of the Lyapunov functional is obtained. These results have advantages over some existing ones because the combination of the delay decomposition technique and the reciprocally convex approach. Two examples are provided to demonstrate the less conservatism and effectiveness of the results in this paper

Current Perspectives on Role of MSC in Renal Pathophysiology

In the course of the development and worsening of kidney disease, the treatments available are expensive and may cause adverse effects such as immune rejection, inadequate renal resources, or post-operative complications. Therefore, there is an urgent to develop more effective treatments. The advent of mesenchymal stem cells (MSCs) represents a new direction in this context. The current use of MSCs for the treatment of kidney disease has mostly involved experimental studies on animals and only a few clinical trials have been conducted. This review focused on the mechanisms of MSC involvement from different sources in the improvement of renal pathophysiology in recent years. These mechanisms include homing to damaged kidney tissue, and differentiating into or fusing with the innate cells of the kidney. The paracrine or endocrine action through secreting protective cytokines and/or releasing microvesicle from MSCs also plays a critical role in amelioration of kidney disease. With modern engineering technology like microRNA delivery and a combinational therapy approach such as reduction of renal fibrosis in obstructive nephropathy with MSCs and serelaxin, MSC may make great contribution to the improvement of renal pathophysiology. However, the therapeutic effects of MSC are still controversial and several problems remain unsolved. While it is too early to state that MSCs are useful for the treatment of renal diseases in clinic, it is thought that solutions to the existing problems will enable effective modulation of the biological characteristics of MSCs, thereby providing new and effective approaches for the treatment of renal diseases

Tumor-reactive CD4+ T cells develop cytotoxic activity and eradicate large established melanoma after transfer into lymphopenic hosts

Adoptive transfer of large numbers of tumor-reactive CD8+ cytotoxic T lymphocytes (CTLs) expanded and differentiated in vitro has shown promising clinical activity against cancer. However, such protocols are complicated by extensive ex vivo manipulations of tumor-reactive cells and have largely focused on CD8+ CTLs, with much less emphasis on the role and contribution of CD4+ T cells. Using a mouse model of advanced melanoma, we found that transfer of small numbers of naive tumor-reactive CD4+ T cells into lymphopenic recipients induces substantial T cell expansion, differentiation, and regression of large established tumors without the need for in vitro manipulation. Surprisingly, CD4+ T cells developed cytotoxic activity, and tumor rejection was dependent on class II–restricted recognition of tumors by tumor-reactive CD4+ T cells. Furthermore, blockade of the coinhibitory receptor CTL-associated antigen 4 (CTLA-4) on the transferred CD4+ T cells resulted in greater expansion of effector T cells, diminished accumulation of tumor-reactive regulatory T cells, and superior antitumor activity capable of inducing regression of spontaneous mouse melanoma. These findings suggest a novel potential therapeutic role for cytotoxic CD4+ T cells and CTLA-4 blockade in cancer immunotherapy, and demonstrate the potential advantages of differentiating tumor-reactive CD4+ cells in vivo over current protocols favoring in vitro expansion and differentiation

High‐Efficiency, Vacuum‐Deposited, Small‐Molecule Organic Tandem and Triple‐Junction Photovoltaic Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109903/1/aenm201400568.pd

Global Temperature Sensing for an Operating Power Transformer Based on Raman Scattering

Traditional monitoring methods cannot obtain the overall thermal information for power transformers. To solve this problem, a distributed fiber optic sensor (DFOS) was creatively applied inside an operating 35 kV power transformer by highly integrating with the electromagnetic wires. Then, the transformer prototype with totally global sensing capability was successfully developed and it was qualified for power grid application through the strict ex-factory tests. The as designed optical fiber sensor works stably all the time with a temperature accuracy of ±0.2 °C and spatial positioning accuracy of 0.8 m. Based on the obtained internal temperature distribution, Gaussian convolution was further applied for the signal processing and hereby, the hotspots for all the windings and iron cores could be accurately traced. The hottest points were located at 89.1% (55 °C) of the high voltage winding height and 89.7% (77.5 °C) of the low voltage winding height. The actual precise hotspot location corrected the traditional cognition on the transformer windings and it would serve as an essential reference for the manufactures. This new nondestructive internal sensing and condition monitoring method also exhibits a promising future for the DFOS applying in the high-voltage electrical apparatus industry

Design and Performance Test of Transformer Winding Optical Fibre Composite Wire Based on Raman Scattering

Winding overheating is a common fault in a transformer. To detect the temperature, the most widely used method is a point-type measurement, but traditional measurement methods cannot obtain the whole temperature distribution in a transformer. Taking this into consideration, a new method with which to measure the temperature of transformer windings was proposed. Based on Raman scattering, a new fibre-optic composite winding model was developed. The feasibility of the model was verified by electrical as well as temperature, field simulation and power frequency resistance testing. To assess the practicality and accuracy of the new model, a distributed optical fibre temperature measurement platform was built, and a series of experiments were designed. According to the data collected, the temperature measurement error based on the method could be limited to 1 °C while the positioning accuracy error was within 1 m, which meant that the new approach can satisfy the requirements of transformer winding temperature measurement and locate hot spots in the winding

Effects of Degraded Optical Fiber Sheaths on Thermal Aging Characteristics of Transformer Oil

With the development of fiber optic sensing technology, optical fiber sensors have been widely used in online monitoring of power transformers. To investigate the influence of aging fiber sheaths on transformer oil, two kinds of special optical fibers with thermoplastic polyester elastomer (TPEE) and poly tetra fluoroethylene (PTFE) as sheaths underwent thermally accelerated aging in transformer oil at 130 °C. The volume resistivity, dielectric dissipation factor (DDF), and breakdown voltage of the oil were measured to indicate insulation strength. The water content and acid value of the oil were measured and fitted to predict the aging tends. The thermal aging characteristics of the oil were quantitatively compared and results showed two kinds of optical fibers could exacerbate all the physical and chemical parameters of oil, and the TPEE sheath had a more significant impact on the oil. The reasons contributing to such phenomenon were analyzed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Both TPEE and PTFE were depolymerized in high-temperature transformer oils, producing water and small molecule hydrocarbon groups. The accumulation of small hydrocarbon groups promoted positive feedback of pyrolysis in the oil. The free hydrogen produced by oil pyrolysis increased the acidity of the oil, which in turn increased the solubility of the water produced by sheath depolymerization. The chain depolymerization of TPEE was more severe than that of PTFE, further exacerbating the deterioration of TPEE-containing oil