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71.
ZHANG GuangDi TAI HuiLing XIE GuangZhong JIANG YaDong ZHOU Yong 《中国科学:技术科学(英文版)》2013,56(10):2576-2580
A carbon monoxide gas sensor based on single-walled carbon nanotube(SWCNT)has been developed for detection of carbon monoxide(CO)at room temperature.Copper chloride(CuCl)was mixed with SWNT by mechanical blending.The thin film was deposited on interdigitated electrodes by using airbrush technology.This paper described the fabrication of the sensor for detecting carbon monoxide with concentrations from 20 ppm to 100 ppm.The performance of CO gas sensor was measured by using relevant apparatus to obtain the continuous sensor electric resistance change on exposure to CO and air atmosphere at room temperature,respectively.The results exhibited that the senor presented a larger sensitivity and a good recoverability.The experimental results suggested the potential use of CuCl doped SWCNT for CO detecting. 相似文献
72.
Many graphics applications require that 3D models automatically be presented upright and from a good view. We propose a method that simultaneously recognizes upright orientation and good view for 3D man-made models. The strategy is to determine the best base on which a 3D model can stand upright from a small set of candidate bases. Every candidate base is composed of clustered facets of the simplified convex hull of the given 3D model. Next, a proposed UV-measurement selects the best base from the candidate bases using weighted feature-based evaluation functions based on geometrical, physical, and visual aspects. Our method has been tested using a public 3D model database and compared with previous methods. As experimental results show, our method outperforms previous work in both efficiency and accuracy. 相似文献
73.
劳动力转移背景下的种植业结构调整 总被引:1,自引:0,他引:1
对1990~2010年我国农业劳动力和5种主要农作物播种面积进行的分析表明,农村劳动力转移首先对我国的粮食生产造成很大影响,粮食种植主要集中于几个劳动力流出省份,面积总体上呈下降趋势.与此同时,收益较高的经济作物种植面积比重大幅上升.可能的解释是,在经营规模普遍较小、劳动力素质偏低的情况下,作为理性的经营者,农户进行生产结构调整时往往较少考虑自身劳力的成本,而更为关注农作物的收益.粮价偏低直接影响了种粮农民的收益,进而影响其种粮积极性. 相似文献
74.
In this paper,bottom contact organic thin-film transistor(OTFT)gas sensors were prepared.Silicon dioxide(SiO2)and titanium/aurum(Ti/Au)were used as the insulating layer and the electrode for the device,respectively.The multi-walled carbon nanotubes(MWCNTs)/α-sexithiophene(α-6T)bilayer films were used as the active layer,andα-6T single layer sensitive film was also prepared for comparison purpose.The electrical and trace NO2-sening properties of these two OTFT gas sensors were tested and analyzed.The results showed that,the OTFT device based on MWCNTs/α-6T bilayer had obviously better electrical properties,better stabilities and higher NO2-sening response values than the device withα-6T single layer,in which both the carrier mobility(μ)and on/off current ratio enhanced two order of magnitude.The improved performance of bilayer OTFT can be explained that MWCNTs acted as highly conducting bridges connecting the crystalline terraces in theα-6T film.Threshold voltage(VT),carrier mobility,on/off current ratio and grid current which showed extremely similar variation trend as source-drain current,were optional parameters to reveal the gas-sensing characteristic of OTFT gas sensors.Morphology analysis showed that the special feature of MWCNTs had certain influence on the gas-sensing properties. 相似文献
75.
张羊换 《武汉理工大学学报(材料科学英文版)》2013,28(3):604-611
The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1?x Co x (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by melt quenching technology. The structures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The alloy electrodes were charged and discharged with a constant current density in order to investigate the electrochemical hydrogen storage kinetics of the alloys. The results demonstrate that the substitution of Co for Ni results in the formation of secondary phases MgCo2 and Mg instead of altering the major phase Mg2Ni. No amorphous phase is detected in the as-quenched Cofree alloy, however, a certain amount of amorphous phase is clearly found in the as-quenched alloys substituted by Co. Furthermore, both the rapid quenching and the Co substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys, for which the notable increase of the hydrogen diffusion coefficient (D) along with the limiting current density (I L ) and the obvious decline of the electrochemical impedance generated by both the Co substitution and the rapid quenching are basically responsible. 相似文献
76.
77.
讨论了16QAM调制时应用不同类型和参数的滤波器对系统性能的影响.针对16QAM的特点,采用了存储波形累加求和法来代替一般的滤波成形,提高了调制速度.并利用其相位对称的特点将波形存储表压缩为原容量的1/4,有效地节约了存储空间. 相似文献
78.
Voltage contrast (VC) has been a powerful tool for the failure analysis of integrated circuits and multichip module. As the packing density of printed circuit board (PCB) is increasing, conventional failure analysis methods to detect open or short circuit in PCBs are no longer adequate, and voltage contrast method could be a method for this purpose. However, unlike the cases of integrated circuits and multichip module, there are many areas in PCB that will produce serious charging effect when examine under the scanning electron microscope. One of the areas is the presence of solder mask on PCB.This work examines the feasibility of using voltage contrast for PCB failure analysis. Specially designed PCB is used for experimentation, and it is found that positive bias on one track and zero bias on another copper track provide a better image contrast as compared to negative and zero biases on the tracks. Also, the variation of the image contrast with different spacing between inter copper tracks has studied. It is found that the variation depends on the presence of solder mask and its location. The variation can be very different for negative bias case as compared to the positive bias case.Finite element analysis is also performed to explain the experimental observations. All the observations can be well explained by the charging effect of the solder masks. The charging effect of solder mask is indeed very significant in affecting the image contrast, and it could reduce the contrast to almost zero in some cases. 相似文献
79.
Leong Che Kan; Hau Kit Tai; Cheng Pui Wan; Tan Li Hai 《Canadian Metallurgical Quarterly》2005,97(4):591
In a 2-wave study of a cohort of 108 Chinese students (10- to 11-year-olds) learning English as a second language, the authors examined the relative effects of three Time 1 latent constructs-- orthographic knowledge, phonological sensitivity, and word identification (reading and spelling of regular and exception words)--on the respective Time 2 performance. The authors posited autoregressive effects, in which Time 1 constructs affected their matching Time 2 performance (e.g., Time 1 orthographic knowledge on Time 2 orthographic knowledge), as well as reciprocal cross-domain effects (e.g., orthographic knowledge on word identification and vice versa). The model converged to a proper solution with reasonably good fit. The results suggest (a) strong stability in the children's word identification and phonological sensitivity, (b) substantial effects of word identification on subsequent orthographic knowledge and phonological sensitivity, particularly the former; and (c) greater variations in individuals' growth of orthographic knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
80.
Tsai FC Tai LA Wang YJ Xiao JL Hsu TH Yang CS Lee CH 《Microscopy research and technique》2011,74(6):531-538
Gold nanoparticles (AuNPs) confined in liposomes of diameters around 200 nm produce strong scattering signal owing to surface plasmon resonance, and therefore bright-field optical tracking of the AuNP-encapsulating liposomes can be conducted in living cells. Using an optical profiling technique called noninterferometric wide-field optical profilometry and a bright-field tracking algorithm, the polynomial-fit Gaussian weight method, we analyze three-dimensional (3D) motion of such liposomes in living fibroblasts. The positioning accuracy in three dimensions is nearly 20 nm. We tag the liposome membranes with fibroblast growth factor-1 and reveal the intracellular transportation processes toward or away from the nucleus. On the basis of a temporal analysis of the intracellular 3D trajectories of AuNP-encapsulating liposomes, we identify directed and diffusive motions in the transportation processes. 相似文献