首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The piezoresisitive effect of p type diamond films is analyzed by deformation potential theory and valence bands split off model.It is found that the great difference of the efficient mass between the heavy and light hole of diamond is one of the main factors which are responsible for the piezoresistive effect in the p type diamond films.The gauge factor calculation formula is obtained according to the strain induced heavy and light hole band splitting off model,and the calculation results are in accordance with the experimental results.  相似文献   

2.
The mechanism of electron field emission from CVD diamond films is investigated while analyzing its structure. The results indicate that there is some graphite in CVD diamond films and the coefficient which electrons tunneled through the diamond grains is enhanced because the electrons obtained energy from the electric field in graphite. Based on the results, a mechanism is put forward that enhancement of the electrons tunneled through diamond grains by graphite resulted in improvement electron emission from CVD diamond films. Some experimental results are well explained by the mechanism.  相似文献   

3.
Diamond nucleation is the key of synthesizing diamond films. At present, the negative bias is the most effective method of enhancing diamond nucleation. In this work, the forming energy is emphatically calculated that a diamond nucleus is built up on a micro defect (pit) produced on the substrate surface by ion bombardment in the process of negative bias enhanced diamond nucleation. The analytic function between nucleation energy of diamond, nucleation density, nucleation speed and pit density is given in some reasonable formulas. The results indicate that descent of the nucleation energy of diamond with the pit density resulted in enhancement of nucleation density and nucleation speed, and the results are in agreement with experimental results in conferences. The reason of the pit reduced the nucleation energy is analyzed.  相似文献   

4.
The STM three dimensions surface shape appearance figure and scanning tunneling spectrum(STS) of nano-meter diamond are obtained by STM.IPC-205B developed by the authors.Insulator diamond films being transacted into nano-meter diamond particles,the STM three dimensions surface shape appearance figure of nano-meter diamond is gotten under a certain bias voltage.Then nano-meter diamond microstructure is observed.And the STS of nano-meter diamond is gained.Also it exhibits the energy gap breadth of nano-meter diamond.At the same time,the STS and conductive mechanism are analyzed.STM/STS studies can not only explain the spectrum study mechanism of conductive capability of nano-meter diamond and expand application field of STM,but also they may act as the important study means for nanometer crystal particles structure and energy spectrun character analyse after insulated material turns into nanometer crystal particles.  相似文献   

5.
The divagation of the internal stress in diamond films is analyzed .It's found that due to the unknown directions of the stress and crystallographic axes , the proportional parameter to express the relationship between the stress and the shift of Raman spectrum is hard to obtain precisely , resulting in the divagation of the internal stresses which are calculated from the shift of Raman spectrum.  相似文献   

6.
The authors discusss exciton energies in a thin film with d thickness and influence of the edge polarization upon the excitons.The polarization is described as interaction between electron(hole) and its image charge.It is found that the interaction decreases the exciton energies to some extent and the influence of the interaction upon the films possessing different dielectric constants and with different thickness are different.  相似文献   

7.
Summary Total seed proteins of 24 common buckwheat cultivars and cultivated populations within a molecular weight range of 30 to 54 kDa were analysed by SDS-PAGE. Single seed analysis of six cultivars identified a total of 18 alternative protein bands with different mobilities. Differences of individual protein band frequencies extracted from single seeds among six buckwheat cultivars varied distinctively, indicating high intravarietal polymorphism. The relation between frequencies of protein bands revealed by single seed analysis and their appearance on the bulk seed analyses was demonstrated. Regarding to band mobility rate and relative band intensity among 24 bulk samples analysed, 14 had distinctive electrophoregrams while the other 10 were ranged into four distinct groups. Analysis of endosperm and cotyledon proteins showed that proteins stored in these main seed parts are tissue specific. The observed electrophoretic polymorphism related to proteins stored in the cotyledons while there was no apparent variability with endosperm proteins.  相似文献   

8.
In order to protect the copyright of digital audio and video in Internet, we propose a novel audio blind watermarking scheme combined discrete wavelets transform, discrete cosine transform, QR decomposition and audio characteristics. In this algorithm, the audio are split into blocks, and each block are decomposed on two dimensional discrete wavelet transform (DWT), then the approximate sub band coefficients are decomposed on discrete cosine transform (DCT), and the first quarter of the DCT coefficients are decomposed on QR decomposition and get a triangle matrix. At last, the watermarking information is embedded into the triangle matrix. The experiments show that the algorithm can get better balance between transparency and robustness of watermark, and it has strong robustness against the common audio signal processing such as additive white Gaussian noise, re sampling, re quantization, low pass filter, MP3 compression and cutting replacement.  相似文献   

9.
The influence of blasting vibration on the adjacent buildings is inevitable if blasting is employed for excavation. Daping station tunnel of Chongqing light railway project, on which there is dense with population and buildings, has a minimum buried depth of only four meters and maximum span length of 26.3 meters. The stepped excavation mode with short hole, multi round and V shaped cut are adopted. The maximum charge weight of one delayed interval is determined by the permitted vibration velocity. The smooth blasting technology with adding vibration reduction holes is used. Meanwhile, the charge weight per hole is strictly controlled. With the simulation and on site test, it is found that the proposed technology for tunnel construction is feasible.  相似文献   

10.
弱光胁迫对不同基因型玉米籽粒发育和碳氮代谢的影响   总被引:1,自引:0,他引:1  
周卫霞  董朋飞  王秀萍  李潮海 《作物学报》2013,39(10):1826-1834
以不耐阴型玉米豫玉22和耐阴型玉米郑单958为试验材料,设置自然光照和弱光胁迫2个处理,研究弱光胁迫对不同基因型玉米籽粒建成和碳氮代谢的影响,探求弱光胁迫下碳氮代谢与籽粒建成的关系。结果表明,弱光胁迫下,玉米籽粒生长发育减缓,败育数增加,体积和干重降低;果穗顶部籽粒可溶性糖、蔗糖含量和全氮含量升高, 淀粉含量和碳氮比降低;豫玉22胚乳细胞中淀粉粒密度降低,郑单958与对照相近。弱光胁迫下,不耐阴型玉米豫玉22果穗籽粒的生长发育减缓程度大于耐阴型玉米郑单958,同一基因型果穗顶部籽粒生长发育减缓程度大于中部籽粒,耐阴型玉米郑单958在恢复自然光照后籽粒体积、干重、籽粒碳氮含量和碳氮比与对照之间的差异均小于豫玉22,表现出更强的补偿效应。淀粉合成能力和碳氮比的下降可能是弱光胁迫条件下籽粒发育不良以致最终造成败育的主要原因。  相似文献   

11.
氮磷钾平衡施用对花椰菜经济产量及品质的影响   总被引:2,自引:0,他引:2  
应用311-A拟饱和最优回归设计和{3,2}单形格子饱和设计,通过氮磷钾肥配比和氮肥分期施用田间试验,拟建花椰菜施用氮磷钾肥对经济产量、施肥利润及氮肥分期施用比例的效应函数。寻优结果表明:花椰菜最高产量的氮、磷、钾优化施肥组合为N 249.28、P2O554.33和K2O 238.83kg/hm2,其最高经济产量达54.877t/hm2;最佳施肥利润的氮、磷、钾优化施肥组合为N 243.52、P2O552.22和K2O 234.09kg/hm2,其最佳施肥利润达63784.89元/hm2,经济产量也达54.853t/hm2;较佳施氮分配比例为基肥 :前期追肥 :后期追肥为0.3135:0.4500:0.2365,其对应的氮肥用量分别为N76.49、109.80和57.71kg/hm2,期望较高的经济产量可达55.313 t/hm2。在同等肥底下,花椰菜维生素C、还原糖和总糖含量与施氮量之间呈一定程度上的负相关,与磷、钾施用量之间呈不同程度的正相关;而硝酸盐含量则与氮施用量呈一定程度的正相关,与磷、钾施用量之间相当程度的负相关。在磷钾用量相同的情况下,氮肥越迟施用或后期施用量越大,花椰菜维生素C、还原糖和总糖含量越低,但硝酸盐含量则越高。  相似文献   

12.
According to tribochemical reaction and modeling of action mechanism ,the action mechanism optimized by nanoparticles in oil lubricating under friction is studied .The surface of a couple material is optimized by the together action of three approach stated as follows: Firstly, the thickness and intensity of lubricating layers or films provided with the action improving tribological properties increase because of enrichment of nanoparticles on the surface or near surface of couple-material arising from short force. Secondly, new lubricating film is built because of tribochemical reaction concerned with nanoparticles enriched in surface under friction and wear. Thirdly, the surface of couple-material is optimized by nanoparticles, for instance machine polishing, filling and leveling up the tiny hole and crackle on surface.  相似文献   

13.
旱麦草属物种高分子量麦谷蛋白亚基的检测与鉴定   总被引:1,自引:0,他引:1  
利用SDS-PAGE方法对旱麦草属4个种10份材料的高分子量谷蛋白进行了检测和鉴定.结果显示,旱麦草物种具有的高分子量谷蛋白亚基与普通小麦中发现的不一样,其迁移率存在较大差异,多数为1条高分子量谷蛋白亚基,迁移率比Ax1基迁移率小;有的材料中没有检测到高分子量谷蛋白,在10份材料中检测到6种亚基变异.  相似文献   

14.
为了探究彩叶观赏竹叶片结构与颜色之间的关系,以白纹阴阳竹(Hibanobambusa.tranquillans f. shiroshima H. Okaura)和白纹椎谷笹(Sasaella.glabra f. albo-striata Muroi)2种观赏竹的叶片为材料,制作叶表皮制片、叶片石蜡切片和超薄切片,通过光学显微镜和电子显微电镜对其形态结构进行观察。结果显示:2种竹子叶片表皮结构相似,均属于稻型叶,且二者叶片绿、白条带区域的表皮细胞之间无明显差异;而叶肉细胞则呈现不同程度的叶绿体变异(基粒片层降解、产生大量嗜锇颗粒等)。其中,叶色为浅绿色的条纹中有1层或2层叶肉细胞叶绿体发生变异;叶色为白色或浅黄色的细胞内叶绿体全部变异;而叶色为绿色的细胞中叶绿体结构均正常。表明叶肉细胞中叶绿体变异的程度可能是影响竹子叶片色度的重要原因之一,从而使叶片呈现不同的颜色。  相似文献   

15.
To assess relationships between the life cycle of the seagrass Zostera noltii and light conditions in its habitat, the seasonal dynamics of a seagrass-dominated community on a tidal flat off Terschelling were studied. The main components of this community were seagrass, periphyton and the periphyton grazing mudsnail Hydrobia ulvae. Total biomass of the seagrass stand showed a unimodal curve with a maximum of more than 110 gADW·m−2 in August and a minimum of less than 10 gADW·m−2 in January. Chlorophyll density of periphyton on the seagrass leaves followed a more or less similar pattern, ranging from 0.4 μg chlorophyll·cm−2 in May to more than 3 μg chlorophyll·cm−2 at the end of August. Periphyton biomass was, however, already maximal in May with almost 1.6 mgADW·cm−2 and subsequently decreased to less than 0.6 mgADW·cm−2 in August. The total weight of H. ulvae was more or less stable, varying between more than 150 and less than 400 gDW·m−2, although significant changes were observed within size classes.Light is assumed to be the primary limiting factor for seagrass distribution in the Wadden Sea. The light conditions of seagrass in the study area were influenced by periphyton and mudsnails. Leaf growth rates and biomass development appeared to be related with light conditions in the seagrass habitat. Shading caused by periphyton during the growing season was estimated at 10 to 90% of incident light, resulting in a reduction of about 2 to 80% of the yearly period during which the light compensation point (LCP) of the seagrass is exceeded. The mudsnails were found to be theoretically able to ingest daily 25 to 100% of the standing stock of periphyton and microphytobenthos. It is concluded that shading by periphyton and grazing by mudsnails play an important role in the seasonal biomass development and survival of Z. noltii in the seagrass-dominated community on a tidal flat off Terschelling.  相似文献   

16.
以云烟87为研究对象,于2018-2019年连续2年研究了烟草还苗期常规灌溉、轻度补灌和重度补灌3种灌溉方式与白膜、转光膜、配色膜和黑膜4种覆膜颜色互作对前期垄体膜下土温、土壤含水率,揭膜时烟株农艺性状、干物质积累量和烤后烟产质量的影响。结果表明:在不同补灌条件下,补灌方式对垄体膜下土温影响较小;在相同补灌条件下,白膜和转光膜升温效果优于配色膜和黑膜;垄体膜下0~15cm土壤含水率表现为黑膜>配色膜>转光膜>白膜,15~30cm土层土壤含水率表现为白膜>转光膜>配色膜>黑膜。在相同覆膜处理下,移栽后1~7d土壤含水率随补灌量的增加呈上升趋势,0~15cm土层上升较显著。互作处理M-Z(轻度补灌+转光膜)揭膜时烟株、根茎叶干物质积累量最高,烤后烟的产质量表现最好。在襄阳山区采用轻度补灌+转光膜方式可促进烟株大田生育期前期生长发育,提升烟叶产量和质量。  相似文献   

17.
A wheeled vehicle to be fitted with common rubber - tire do not adapt to the desert area because of the wheel slip sinkage. It is important for improving the mobility of vehicle in sand to develop a new running gear of vehicles . Based on the mathematical models and mechanical models for interaction effect between wheel and sand. the influence on the interaction effect between running gear of vehicles and sand on traction performance are analyzed by using the theory of granular limit equilibrium. The results show that the interaction modes between wheel and sand is charged and the mobility of vehicle in sand is improrld.  相似文献   

18.
In the light of development of integrating AutoCAD menu on architectural structure footing series which can integrate computing with drawing, this paper studies the interface between AutoCAD and advanced languages and presents a kind of interface suitable to menu. In combination SCR file with Defun fuction. this paper solves the problem of insufficient node space and the problem that function can not be recursively called while making use off AutoLISP language.  相似文献   

19.
双转光膜对棚温及烟苗生长与生理特性的影响   总被引:3,自引:1,他引:2  
3年大棚烟草漂浮育苗试验表明:采用单基双能转光剂、光质和光强可以调控的双转光膜能同时将日光中对光合作用无效或低效的紫外光和绿黄光转变为对光合作用高效的蓝光、红光,具有显著的增温效应和促进烟苗生长的作用。双转光膜能显著提高叶片叶绿素含量和净光合速率,增加烟苗根、茎、叶干重及其淀粉、可溶性糖和粗纤维素含量;在冬季和早春,双转光膜能提高大棚温度1.7℃。采用双转光膜育苗有利于提高烟苗的抗逆性,培育壮苗。  相似文献   

20.
ABSTRACT A growing literature has accumulated that points to the stability of industrial location patterns. Can this be reconciled with spatial dynamics? This article starts with the premise that demonstrable regularities exist in the manner in which individual industries locate (and relocate) over space. For Canada, spatial distributions of employment are examined for seventy‐one industries over a thirty‐year period (1971–2001). Industry data is organized by “synthetic regions” based on urban size and distance criteria. “Typical” location patterns are identified for industry groupings. Industrial spatial concentrations are then compared over time using correlation analysis, showing a high degree of stability. Stable industrial location patterns are not, the article finds, incompatible with differential regional growth. Five spatial processes are identified, driving change. The chief driving force is the propensity of dynamic industries to start up in large metro areas, setting off a process of diffusion (for services) and crowding out (for manufacturing), offset by the centralizing impact of greater consumer mobility and falling transport costs. These changes do not, however, significantly alter the relative spatial distribution of most industries over time.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号