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1.
In the hostile and highly corrosive marine environment,advanced composite materials can be used in marine current turbines due to their high strength-to-weight ratios and excellent resistance to corrosion.A composite material marine current turbine(CMMCT),which has significant advantages over traditional designs,has been developed and investigated numerically.A substantial improvement in turbine performance is achieved by placement of a duct to concentrate the energy.Computational fluid dynamics(CFD) results show that the extracted power of a ducted CMMCT can be three to four times the power extracted by a bare turbine of the same turbine area.The results provide an insight into the hydrodynamic design and operation of a CMMCT used to shorten the design period and improve technical performance. 相似文献
2.
以DMF、丙酮、二氯甲烷和丙酮／二氯甲烷为溶剂,通过静电纺丝方法制备PCL亚微米纤维．通过SEM观察纤维形貌及其孔径大小,通过N2吸附一脱附曲线计算纤维的比表面积,通过拉伸实验测试纤维的力学性能．实验结果表明：以单-DMF、丙酮为溶剂制备得到表面光滑无孔亚微米纤维．而以二氯甲烷为溶剂无法制备连续的纤维．以丙酮／二氯甲烷为溶剂制备得到直径为0．86±0．14／μm、孔径大小为65．0±17．5nm,比表面积为21．15m2／g的亚微米纤维．相比较无孔纤维,多孔PCL亚微米纤维的拉伸强度和杨氏模量略有下降,而断裂伸长率有所增加,主要是因为拉伸过程中,多孔纤维发生一定程度的收缩．PCL亚微米纤维表面的多孔结构有利于细胞的黏附与生长,因而有望作为组织工程支架材料． 相似文献
3.
不同速度高速列车车外噪声的调查研究 总被引：1，自引：1，他引：0
Bin HE Xin-biao XIAO Qiang ZHOU Zhi-hui LI Xue-song JIN 《浙江大学学报(A卷英文版)》2014,(12):1019-1033
研究目的：基于声源识别,得出车外噪声分布特性及场点主要噪声源。创新要点：1．研究高速列车噪声源强特性及频谱特性;2．揭示不同速度下不同声源频谱变化规律;3．分析车外声场场点噪声变化规律及主要声源。研究方法：1．利用车外声源识别系统（图2）分析高速列车声源分布规律及频谱特性;2．利用声源的垂向（图10）分布研究不同声源在各频率下垂向分布规律;3．利用场点声源与速度的拟合关系（图16）研究场点主要噪声源。重要结论：1．高速列车车外噪声源主要分布在轮轨区域、受电弓和车间连接区域;2．轮轨区域噪声包括滚动噪声和气动噪声,在各频率均为最显著声源;3．在整个列车高度,轮轨滚动噪声对总噪声贡献率大于气动噪声;4．车外场点噪声主要频率为630-2500Hz,主要来自轮轨滚动噪声。 相似文献
4.
The structural change of the oviduct of freshwater shrimp （Macrobrachium nipponense） during spawning was examined by electron microscopy. The oviduct wall structural characteristics seem to be influenced significantly by the spawning process. Before the parturition and ovulation, two types of epithelial cells （types Ⅰ and Ⅱ） are found in the epithelium. The free surfaces of type Ⅰ and type Ⅱ cells have very dense long microvilli. Under the type Ⅰ and type Ⅱ cells, are a relatively thick layer of secreting material and a layer of mostly dead cells. After ovulation, two other types of epithelial cells （types Ⅲ and Ⅳ） are found in the oviduct wall epithelium. The free surface of type Ⅲ cells only has short microvilli scattered on the surface. The thick layer with secreting material and the dead cell layer disappeared at this stage. In some type Ⅲ cells, the leaking out of cytoplasm from broken cell membrane led to the death of these type Ⅲ cells. The transformation of all four types of epithelial cells was in the order： Ⅳ→Ⅰ→Ⅱ→Ⅲ. 相似文献
5.
对于《楚辞·离骚》中的"薋菉葹"三字是恶草还是普通的草,诸家各有自己不同的说法,并未达成一致。今就从"薋菉葹"到底是什么以及女嬃劝说的人之常情上两个方面,尝试着探究"薋菉葹"三字。 相似文献
6.
Rate-dependent constitutive model of poly（ethylene terephthalate） for dynamic analysis 总被引：1，自引：0，他引：1
Uniaxial tensile testing at strain rates ranging from 10-3 to 10-1 s-1 was carried out to study the rate-dependent me-chanical behavior for poly（ethylene terephthalate） （PET） used in the packaging industry. The experimental results show that a rate-dependent plastic behavior exists for PET material. The value of the yield strength was found to increase with the increasing strain rate. A new constitutive model based on the improved Cowper-Symonds rate-dependent constitutive model is proposed to describe the mechanical behavior of PET material in the strain rate ranging from 10-3 to 10-1 s-1, providing more accurate material data for the subsequent simulation analysis of drop test and dynamic buckling. The predictions obtained using the proposed model are compared with experimental results of the improved Cowper-Symonds model. The simulating results of the proposed model agree well with the experimental data. For a low strain rate, the predictions of this model are more precise than those obtained using the improved Cowper-Symonds model. This confirms that the new constitutive model is suitable for describing the me-chanical behavior of PET material at a low strain rate and modeling impact problem. 相似文献
7.
Cun-jian MIAO Jin-yang ZHENG Xiao-zhe GAO Ze HUANG A-bin GUO Du-yi YE Li MA 《浙江大学学报(A卷英文版)》2013,14(1):31-37
Cold-stretched pressure vessels from austenitic stainless steels(ASS) are widely used for storage and transportation of liquefied gases,and have such advantages as thin wall and light weight.Fatigue is an important concern in these pressure vessels,which are subjected to alternative loads.Even though several codes and standards have guidelines on these pressure vessels,there are no relevant design methods on fatigue failure.To understand the fatigue properties of ASS 1.4301(equivalents include UNS S30400 and AISI 304) in solution-annealed(SA) and cold-stretched conditions(9% strain level) and the response of fatigue properties to cold stretching(CS),low-cycle fatigue(LCF) tests were performed at room temperature,with total strain amplitudes ranging from -.4% to -.8%.Martensite transformations were measured during the tests.Comparisons on cyclic stress response,cyclic stress-strain behavior,and fatigue life were carried out between SA and CS materials.Results show that CS reduces the initial hardening stage,but prolongs the softening period in the cyclic stress response.Martensite transformation helps form a stable regime and subsequent secondary hardening.The stresses of monotonic and cyclic stress-strain curves are improved by CS,which leads to a lower plastic strain and a much higher elastic strain.The fatigue resistance of the CS material is better than that of the SA material,which is approximately 1?03 to 2?04 cycles.The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels.However,considering the CS material has a better fatigue resistance,the S-N curve will be more conservative.The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels. 相似文献
8.
The failure mode and adhesion of thermal barrier coating (TBC) 8YSZ (ZrO2+8% (w/w) Y2O3) deposited on NiCoCrAlTaY bond coat by atmospheric plasma spraying were investigated. A grooved modified three-point bending specimen that can generate a single interface crack to facilitate the control of crack growth was adopted for testing, which was conducted at the ambient temperature of 100 °C. The morphology and composition of fractured surfaces were examined by means of a scanning electron microscopy (SEM) and an energy disperse spectroscopy (EDS). Images and spectrum show that cracks are initiated and propagated exclusively within YSZ layer adjacent to top/bond coat interface. The load-displacement curves obtained exhibit similar shapes that indicate two distinct stages in crack initiation and stable crack growth. Finite element analyses were performed to extract the adhesion strength of the TBCs. The delamination toughness of the plasma-sprayed 8YSZ coatings at 100 °C, in terms of critical strain energy release rate Gc, can be reliably obtained from an analytical solution. 相似文献
9.
目的：探讨复方丹参片早期干预对APP/PS1转基因小鼠学习记忆的影响及作用机制。方法：4月龄野生型小鼠和APP/PS1转基因小鼠分别灌胃给予溶剂或药物8周后,采用新物体识别实验和跳台实验评价复方丹参片对小鼠行为学表现的影响;应用ELISA检测小鼠海马β淀粉样蛋白（β-amyloid protein,Aβ）Aβ40、Aβ42的含量;采用Real time PCR和Western blot分别检测胰岛素分解酶（insulin degrading enzyme,IDE）/脑啡肽酶（neprilysin,NEP）m RNA和蛋白水平的变化。结果：新物体识别实验结果显示,复方丹参片720 mg·kg-1显著性增加APP/PS1转基因小鼠对新物体的识别指数。跳台实验结果显示,复方丹参片720、360 mg·kg-1显著性减少APP/PS1转基因小鼠学习次数,此外,复方丹参片720 mg·kg-1明显增加小鼠在平台的停留时间。ELISA结果显示,复方丹参片720、360 mg·kg-1显著性降低APP/PS1转基因小鼠海马Aβ40、Aβ42水平。Real-time PCR结果显示,复方丹参片720 mg·kg-1显著性上调APP/PS1转基因小鼠海马IDE和NEP m RNA的表达。Western blot结果显示,复方丹参片720 mg·kg-1显著性增加小鼠海马IDE蛋白表达。结论：复方丹参片可改善APP/PS1转基因小鼠学习记忆能力,可能与减少海马Aβ水平和增加IDE的表达有关。 相似文献
10.
陈毓述 《安徽师范大学学报(人文社会科学版)》2015,(1):98-104
大革命时期,党组织建设面临严重困难,兼任中央组织部部长的中共最高领导人陈独秀,果断采取措施,加强党的组织建设。使党组织短期内获得了迅速发展,实现了从宣传小团体向群众性革命政党的转变;在中国政党史上,首次使用了民主集中制的概念;党的基层组织以支部取代小组,为中共现行的基层组织体制奠定了基础;开始了党的组织纪律建设,树立了防范与惩治意识。党组织的发展与壮大,为大革命失败后党领导土地革命准备了组织条件。 相似文献
11.
汉语被动句中＂被＂的属性问题一直存在着争议,有学者认为＂被＂是表示遭受意义的动词,＂被＂字句是以＂被＂为主动词的主动句。但是我们分析失语症患者的语言理解后发现,他们对实意动词和主动句的理解与正常人没有差异,但是对功能语类的理解却出现巨大的偏差和缺失,这一特征与失语症患者被动句的理解偏差和缺失表现出一致性,说明＂被＂不是实意语类而应当归属于功能语类。 相似文献
12.
Heparin was grafted onto polycarbonate urethane (PCU) surface via a three-step procedure utilizing α, ωdiamino-poly(ethylene glycol) (APEG, M n =2 000) as a spacer. In the first step, isocyanate functional groups were introduced onto PCU surface by the treatment of hexamethylene diisocyanate (HDI) in the presence of di-n-butyltin dilaurate (DBTDL) as a catalyst. In the second step, APEG was linked to the PCU surface to obtain the APEG conjugated PCU surface (PCU-APEG). In the third step, heparin was covalently coupled with PCU-APEG in the presence of N-hydroxysuccinimide (NHS) and 1-ethyl-3-(3-dimethylamidopropyl) carbodiimide (EDAC). The amount of heparin (1.639 μg/cm 2 ) covalently immobilized on the PCU-APEG surface was determined by the toluidine blue method. The modified surface was characterized by water contact angle, attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The hemocompatibility was preliminarily studied by platelet adhesion test. The results indicated that heparin was successfully grafted onto the PCU surface, and meanwhile the hydrophilicity and hemocompatibility of the modified PCU surface were improved significantly compared with the blank PCU surface. 相似文献
13.
OFDM电力线通信系统抗噪性能分析 总被引：1，自引：0，他引：1
基于电力线通信（ PLC ）系统的实测噪声,分析OFDM系统的电力线通信系统性能。通过Matlab和嵌入数字信号处理（ DSP ）系统进行虚拟发送和接收,在传输信道中加入噪声（加性白高斯噪声、电力线有色背景噪声等）仿真操作来干扰发送信号,以达到系统性能分析的目的。同时,在OFDM系统中分析卷积编码的前向纠错（ FEC ）的应用。结果表明,低阶调制可使系统性能改善,前向纠错技术通过解码可以自动纠正传输误码,降低接收信号的误码率（ BER）。 相似文献
14.
15.
使用第一性原理计算方法对Al和N极性AlN表面和生长特性的差异开展了研究.构建未吸附和吸附一个原子或原子层的Al和N极性AlN表面结构进行模拟和理论计算.结果表明：Al极性AlN比N极性AlN更稳定,并且在生长时将具有更高的生长速率;在富N的生长环境下,N极性AlN的生长容易在表面形成双N原子层而出现反型畴;Al和N原子在Al极性表面上更容易扩散,所以外延生长的Al极性面AlN将会具有更加平整的表面形貌. 相似文献
16.
Edwin Coate 《Higher Education》1993,25(3):303-320
Oregon State University became one of the first research universities in the United States to introduce the Total Quality Management methodology into its administrative structure in 1989. Beginning with finance and administration, quality improvement teams were introduced and achieved significant improvement in process effectiveness and efficiency. Improved quality was also achieved and measured by customer satisfaction.TQM was expanded to all administrative areas — including student affairs, research, and faculty administration — over the next four years. TQM has also been used in curriculum development, teaching improvement, and research proposal development.This paper describes the implementation strategy used by Oregon State University and presents some of the results achieved. Particular attention is paid to implementation barriers found in university settings.Today, Oregon State University has over 85 process improvement teams working in both administrative and academic areas and has received many awards for its work in Total Quality Management. 相似文献
17.
许迅雷 《西安文理学院学报》2011,(2):57-60
在高斯噪声环境下,由于扩展卡尔曼滤波（EKF）在目标跟踪应用中精度低和可能出现的滤波发散,将无迹卡尔曼滤波（UKF）应用于非线性系统的目标跟踪.通过UKF在目标跟踪中的应用和仿真结果的分析比较表明,与EKF相比较,UKF收敛快、对噪声适应能力强,算法实现简单. 相似文献
18.
《天津大学学报(英文版)》2015,(4)
To understand the vibration noise behaviors of amorphous metal alloy core distribution transformer(AMACDT), a 10 k VA prototype was tested under no-load and short-circuit conditions, respectively. The vibration characteristics were described when rated voltage was applied to the secondary side, and the primary side was connected with different load resistances. The largest amplitude positions on the upper bracket and tank surfaces were recorded by vibration sensors arranged on the surface. A data-acquisition platform was set up for signal measurement. The vibration amplitude related to frequency was discussed, and experimental results indicated that the position with the largest amplitude accrued in the middle of the upper bracket and tank surface, at phases a and c, respectively. The experimental results suggest that magnetostrictive and electrodynamic forces play a major role in exciting the vibration noise. At the same time, some rib-reinforcements were welded on the upper bracket and tank surfaces to lessen the vibration energy, which reduced the noise. 相似文献
19.
近代汉语被动标记“吃”与“被”、“叫”、“让”、“给”等被动标记语音发展方向迥异,汉语方言和人类语言被动标记的共性也表明了“吃”在清代突然消失存在某种语音动因,这种语音动因体现了语音在语法化过程中的制约和选择作用。 相似文献
20.
脉冲噪声的自适应滤除方法 总被引：1，自引：0，他引：1
武英 《南京晓庄学院学报》2005,21(5):25-27
为了在滤除图像噪声的同时更好的保护图像的细节,文中提出了一种基于非线性自适应滤波结构的改进算法。用中心加权中值滤波算法代替原方法中的中值滤波算法以及中值滤波代替均值滤波作为最终滤波结果输出。这种算法与同类算法相比,具有更好的滤波性能并能更好的保护细节,其效果明显优于中值滤波算法。 相似文献