分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: By studying the advantages and disadvantages of the conventional automatic linear door systems, it was found that flat permanent magnet linear synchronous motors (PMSLM) can satisfy high-speed long-stroke heavy-load door systems better than other techniques. In order to reach a long lifespan, the authors compared five possible topologies with flat PMLSM, and then designed a kind of magnetically suspended door system driven by a single-sided flat PMLSM and suspended by the normal force of the motor. The results demonstrate that the prototype door system satisfies the requirements.
分类: 生物学 >> 生物物理学 >> 神经科学 提交时间: 2016-05-05
摘要: Postoperative cognitive dysfunction (POCD) is an important complication following major surgery and general anesthesia in older patients. However, the etiology of POCD remains largely to be determined. It is unknown how surgical stress and psychological stress affect the postoperative learning and memory function in geriatric patients. We therefore established a pre-clinical model in aged C57BL/6 mice and aimed to investigate the effects of surgical stress and psychological stress on learning and memory function and the possible roles of the protein kinase B/mammalian target of rapamycin (AKT/mTOR) pathway. The surgical stress was induced by abdominal surgery under local anesthesia, and the psychological stress was induced by a communication box. Cognitive functions and markers of the AKT/mTOR pathway were assessed at 1, 3 and 7 days following the stress. The impairments of learning and memory function existed for up to 7 days following surgical stress and surgical stress plus psychological stress, whereas the psychological stress did not affect the cognitive function alone or combined with surgical stress. Analysis of brain tissue revealed a significant involvement of the AKT/mTOR pathway in the impairment of cognition. These data suggested that surgical stress could induce cognitive impairment in aged mice and perioperative psychological stress is not a constitutive factor of POCD. The AKT/mTOR pathway is likely involved as one of the underlying mechanisms of the development of POCD. (C) 2016 IBRO. Published by Elsevier Ltd. All rights reserved.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The free piston energy converter (FPEC) is a new type of power unit for hybrid electric vehicle. In a FPEC, an internal combustion engine driven permanent magnet linear generator (PMLG) may be utilized to produce electrical energy. This paper discusses the issues that are pertinent to the design of a linear permanent magnet generator for application in a FPEC. To achieve the required high power density and low moving mass, a tubular machine equipped with modular windings and axially magnetized is considered to be the most appropriate. Finite Element Analysis are adopted to analyse the PMLG. Magnetic field distribution, EMF, thrust force and No- load corl loss are obtained through the finite element method. An effective tool for design optimization is provided. It is shown that the machine design can be optimized with respect to three key dimensional ratios while satisfying other performance specifications.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Abstract. The paper presents multi-sensor image fusion and its relevant framework and technical characteristics. The image fusion is divided into three level fusions: pixel level, feature level and decision level. It mainly discusses the image fusion algorithm at all levels of fusion, and then makes the summary and comparison of these algorithms. Since the high-level algorithms are related to some relevant practical applications of the image fusion, it is in general difficult to be summarized. So this paper also presents some typical algorithms of the fea- ture and decision levels from the perspective of the applications, to provide the necessary summary of the high level image fusion algorithm. Further, the three levels of implementation schemes are described, followed by the comparison and summary for the image evaluation criteria of the fusion method. Some problems and future directions about the multi-sensor image fusion are finally given.
分类: 材料科学 >> 材料科学(综合) 提交时间: 2017-05-09
摘要: This paper proposes a novel moving-coil voice coil motor(VCM) used for driving nano-positioning device. This VCM implements bilateral Halbach array permanent magnet as the stator and three separated coils with the slotted coil skeleton as the mover.. The VCM can achieve large stroke and nano-level positioning accuracy with the support of the compliant mechanism. Equivalent magnetic circuit method and the finite element analysis (FEA) are used in this paper to analyze the performance of the VCM. The analysis results show that the VCM can achieve a force-current ratio of 90 N/A and force ripple of ±0.19 N, which are superior than the previous designs in the literatures .
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: As there is no round optical grating and magnetic grating with large diameter that is over 0.5m in the market, a measuring system adopting dual magnetic sensors based on FPGA is proposed in this paper to measure the position/displacement and velocity of the rotating outer-rotor motor. Through using strip-type magnetic grating to stick around the outer rotor over half circumstance, the proposed system is able to produce continuous position pulse signals by switching the signals of dual magnetic sensors. The system core chip distinguishes, subdivides and filters the signals from two sensors, judging the operational state of the sensor and generating the dual magnetic sensor switching signals. It can switches the sensor signals in real time during motor operation and measures the position/displacement and velocity of motor in a precise manner. Moreover, the position/displacement, operating time and positive/negative rotation can be displayed through man-machine interactive unit. The experimental results show that arc-second control accuracy of the outer-rotor torque motor can be achieved by using the proposed system to measure the speed and position/ displacement of the outer-rotor torque motor as the feedback signal through the motion control system of motor.
提交时间: 2017-05-02
摘要: Dielectric nanosphere arrays are considered as promising light-trapping designs with the capability of transforming the freely propagated sunlight into guided modes. This kinds of designs are especially beneficial to the ultrathin hydrogenated amorphous s
分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: p53 is an important tumor suppressor and stress response mediator. Proper control of p53 level and activity is tightly associated with its function. Posttranslational modifications and the interactions with Mdm2 and Mdm4 are major mechanisms controlling p53 activity and stability. As p53 protein is short-lived and hardly detectable in unstressed situations, less is known on its basal level expression and the corresponding controlling mechanisms in vivo. In addition, it also remains obscure how p53 expression might contribute to its functional regulation. In this study, we established bacterial artificial chromosome transgenic E.coli beta-galactosidase Z gene reporter mice to monitor p53 expression in mouse tissues and identify important regulatory elements critical for the expression in vivo. We revealed preferentially high level of p53 reporter expressions in the proliferating, but not the differentiated compartments of the majority of tissues during development and tissue homeostasis. In addition, tumors as well as regenerating tissues in the p53 reporter mice also expressed high level of beta-gal. Furthermore, both the enhancer box sequence (CANNTG) in the p53 promoter and the 3' terminal untranslated region element were critical in mediating the high-level expression of the reporter. We also provided evidence that cellular myelocytomatosis oncogene was a critical player regulating p53 mRNA expression in proliferating cells and tissues. Finally, we found robust p53 activation preferentially in the proliferating compartment of mouse tissues upon DNA damage and the proliferating cells exhibited an enhanced p53 response as compared with cells in a quiescent state. Together, these results suggested a highly regulated expression pattern of p53 in the proliferating compartment controlled by both transcriptional and posttranscriptional mechanisms, and such regulated p53 expression may impose functional significance upon stress by setting up a precautionary mode in defense of cellular transformation and tumorigenesis.