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1.
Organic electroluminescent devices are light-emitting diodes in which the active materials consist entirely of organic materials. Here, the fabrication of a white light-emitting organic electroluminescent device made from vacuum-deposited organic thin films is reported. In this device, three emitter layers with different carrier transport properties, each emitting blue, green, or red light, are used to generate white light. Bright white light, over 2000 candelas per square meter, nearly as bright as a fluorescent lamp, was successfully obtained at low drive voltages such as 15 to 16 volts. The applications of such a device include paper-thin light sources, which are particularly useful for places that require lightweight illumination devices, such as in aircraft and space shuttles. Other uses are a backlight for liquid crystal display as well as full color displays, achieved by combining the emitters with micropatterned color filters. 相似文献
2.
我国水稻白叶枯病抗性遗传的评价和利用 总被引：31，自引：1，他引：30
70年代以来我国水稻对白叶枯病抗性遗传的评价和利用取得相当进展,评价了大量包括地方品种、野生稻和国外引进的种质对水稻白叶枯病的抗性,鉴定了许多抗源。其中有些具有基因Xa-3和Xa-4的抗源广泛地用作杂交计划中的供体,选育出一批优良的品种（系）,进行了成株抗性和全生育期抗性的评价,同时,广泛地进行了白叶枯病抗性遗传的研究,包括不同抗性类型的品种、亚种间杂交后代和杂交稻育种后代的抗性遗传行为。并就系统研究抗性基因,培育包括1-2个有利基因的改良抗源等方面提出建议。 相似文献
3.
碳源是低碳氮比废水反硝化过程的限制性因素之一,外加固体碳源可以强化微生物反硝化脱氮效果。为筛选出合适的外加碳源,本研究选用廉价的农业废弃物(稻草和锯木屑)和水生植物(绿狐尾藻和梭鱼草)作为固体碳源材料,分析不同固体碳源材料的释碳特征,比较其对反硝化过程的脱氮效果。结果表明,4种材料的释碳过程均符合二级动力学方程,其释碳能力大小为:稻草(25.64 mg/(g·L))梭鱼草(23.64 mg/(g·L))锯木屑(22.37 mg/(g·L))绿狐尾藻(20.45 mg/(g·L)),其中,绿狐尾藻的释放速率最快,其COD释放浓度达饱和浓度一半时所用时间仅为3.56 h。4种材料作为外加固体碳源可显著提高反硝化脱氮效率,其对水体硝态氮的去除率均达80%以上。由于梭鱼草在试验后期出现氨氮的大量积累,会造成水体二次污染。因此,稻草、锯木屑和绿狐尾藻适合作为外加碳源材料利用。 相似文献
4.
Utterback JM 《Science (New York, N.Y.)》1974,183(4125):620-626
The varied definitions used in the sources that have been discussed make any aggregate analysis difficult. A simple three-stage analysis of flows to, from, and within the firm was used to facilitate comparisons. Even so, each of the generalizations is drawn from relatively small and unrepresentative samples. Case studies may continue to be a source of ideas and hypotheses for further research, but do not appear to offer a means for deeper understanding of the innovation process. The retrospective nature of nearly all of the sources discussed probably means that the process has been viewed as much more rational and well-ordered than it is in fact. This failing is partially overcome in firsthand accounts such as those of Suites and Bueche (63) and Frey and Goldman (64). Each of these accounts involves a successful innovation according to technical or commercial criteria, or both. However, many of the characteristics of innovations that have failed commercially (10) appear to be similar to those of successful cases. The few longitudinal studies, and studies comparing more and less successful cases, do support the main conclusions drawn above (10, 32, 38). More serious problems are raised by the distinctly nonrepresentative nature of the samples used. There are few cases (17, 33, 65) in which the contributions of more than one organization, or details of interactions over a significant period of time, are discussed. There is a wide variation in the importance of the innovations included, ranging from those affecting the economy as a whole to cases involving production in a single firm, albeit with significant commercial results (66). In addition to questions of comparability and sampling, a central problem for further research on innovation will be to devise an operational model to account for interfirm and interindustry differences. Polar definitions used in past studies, "high technology" and "mature industry," for example, are insufficient. One possibility is to use the strategy for growth or competition evident in a firm or an industry, such as sales maximization (automotive), cost minimization (transportation, communications), performance maximization (aircraft, chemicals), or control of materials resources (mining, petroleum), as a basis for drawing distinctions (67). For example, in an industry that seeks to maximize sales, one would expect innovations that would be highly visible to consumers to be developed rapidly (68). In a cost-minimizing situation, production, as opposed to product technology, would be a major source of uncertainty, while the reverse might be the case in a performance-maximizing situation. Greater uncertainty arising from technical sources would imply greater sophistication in effective firms' product planning approaches, while a more stable technology would imply greater sophistication in market research and market-oriented strategies for innovation, and so forth. Much more work is needed along these lines if outcomes of interventions in the innovative process are to be predicted with any accuracy. Some implications for providing incentives and reducing barriers do seem clear from the work to date. Effective directions for federal action lie in strategies such as creating new markets through purchases or procurement policies; aggregating or focusing markets through regulation and other means; providing for market entry by contracts to smaller firms, venture capital, stronger patent protection, and so on; and providing for mobility and informal contacts within the technical community. Technology "push" strategies (such as tax incentives) to increase most research spending, prizes for new technology, and documentation and information retrieval systems would probably be less important in stimulating innovation. Definitive answers will require the most difficult kind of research-experiments in the field. Since the interventions required are difficult and expensive in most cases, they will not be under the researcher's control. Nor will the effect of policy changes be visible over a short period. Thus it seems imperative to take advantage of interventions that occur fortuitously to construct "quasi-experiments" (69) with as great a degree of control over other factors as possible. For example, have recent changes in policy regarding federally held patents increased the commercial use of these patents? Have changes in the capital gains laws retarded the development and growth of "spin-off" enterprises? Has the identification of technology gaps (3) and competitive opportunities stimulated innovation? The effects of such actions on technical innovation could be carefully observed with a modest but sustained research effort, which promises to yield valuable information beyond that available from largely historical sources. 相似文献
5.
L Hesselink SS Orlov A Liu A Akella D Lande RR Neurgaonkar 《Science (New York, N.Y.)》1998,282(5391):1089-1094
Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. It is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species. 相似文献
6.
Cole T 《Science (New York, N.Y.)》1983,221(4614):915-920
The alkali metal thermoelectric converter (AMTEC) is a device for the direct conversion of heat to electrical energy. The sodium ion conductor beta"- alumina is used to form a high-temperature regenerative concentration cell for elemental sodium. An AMTEC of mature design should have an efficiency of 20 to 40 percent, a power density of 0.5 kilowatt per kilogram or more, no moving parts, low maintenance requirements, high durability, and efficiency independent of size. It should be usable with high-temperature combustion, nuclear, or solar heat sources. Experiments have demonstrated the feasibility of the AMTEC and confirmed the theoretical analysis of the device. A wide range of applications from aerospace power to utility power plants appears possible. 相似文献
7.
李晖 《厦门水产学院学报》2011,(3):212-217
对喷淋式MOCVD反应器中的传质过程进行了数理分析,并提出了该类型反应器的结构设计原则.数理分析显示,基片上方各点的轴向速度仅是垂直距离的函数,与径向距离无关;顶壁高度对反应室内的传质有重要影响.设计喷淋式反应器结构时,应重点考虑顶壁高度和反应室半径的选取、基片加热方式以及喷淋头结构的柔性设计. 相似文献
8.
近十年中国土壤重金属污染源解析研究进展 总被引：33，自引：9，他引：24
基于不同源解析方法中所采用的数据类型的差异性,归纳总结了常用于土壤中重金属来源解析的源排放清单法以及不同受体模型,结果表明:现阶段我国土壤中的重金属源解析研究仍主要以定性的传统多元统计方法为主,且不同源解析方法得到的源解析结果基本一致,能够相互印证、互相支持。现阶段,我国土壤中的主要重金属污染元素为Cd,同时也普遍存在Cu、Zn、Pb、Hg的污染。其中,Cd、Cu、Zn主要来自于施肥等农业活动,部分地区还来源于工业活动,甚至以其为主;Hg则主要来源于工业活动及其产生的大气沉降,局部地区叠加高Hg农药的贡献;Pb的来源则比较复杂多样;As、Cr、Ni则主要受土壤母质控制。总体看来,源排放清单法具有适用于不同尺度的优势,应加强源排放量数据和重金属土壤淋滤量数据的收集,以便计算重金属浓度在土壤中的动态变化;先进的统计学方法在土壤重金属源解析中的应用研究应进一步开展,以便探讨这些方法的应用前景。将上述多种源解析方法联用并加强污染源贡献的定量研究仍是未来开展土壤重金属源解析工作的方向。此外,大气沉降作为很多重金属的重要来源,应加强对不同区域大气沉降中重金属初始来源的解析研究,为进一步从源头控制土壤重金属污染提供理论支持。 相似文献
9.
陈地光 《福建农林大学学报(自然科学版)》1982,(2)
本工艺是应用氧乙炔火焰为热源,喷焊耐磨复合合金粉末。使机器零件表面层获得耐磨、耐腐蚀、抗高温氧化等功能,从而提高零件和机械的服役寿命。本文简述耐磨复合合金粉末研制特点、涂层性能的试验研究、模拟及田间试验结果、喷焊工艺要领和提高喷焊层耐磨粒磨损机理的初步剖析。复合合金粉末Pygt-801是我们研制成功的新粉末。它具有廉价和优异的性能。与类似商品比较,可获得显著的经济效果。经较长时间的喷焊实践和工艺的不断改进,已获得硬度高、耐磨和良好冲击韧性的喷焊层。喷焊层硬质相的显微硬度HV=1450～1800(相当HRC76—81),粘结相(机体)HV=805～965(HRC 63.2～68)。经过模拟试验与田间试验,其耐磨性是65Mn钢的二倍。 相似文献
10.
L Green 《Science (New York, N.Y.)》1967,156(781):1448-1450
In this article I have presented, for discussion, a proposed system for energy generation by which the principal sources of environmental pollution by power plants could be eliminated. For stationary power plants the concept appears feasible technically and, according to my " horseback estimates," perhaps economically as well, depending upon the economic value of the by-products of sulfur, CO(2), water, and possibly nitrogen, and upon the price we are willing to pay for a clean environment .Thus, a more thorough engineering and economic analysis to explore these and other factors in greater depth seems warranted. In the case of turbine-driven vehicles, the technical and economic feasibility of widespread distribution and handling of the fuel constitutes a serious question, but one which deserves equally serious consideration before the possibility is discounted. The reports of the cited study panels notwithstanding, the technology required for the proposed system exists today, with one exception. This exception (which is not essential for trial of the system but will be required for its complete fruition) is the development of a nuclear reactor for the prime purpose of delivering process heat for the steam reforming of natural gas and, ultimately, for gas production from coal in a continuous process, such as those discussed by Pieroni et al. (16). Today's intermittent processes of coking and gas production are both archaic and themselves large sources of atmospheric pollution, and a development program aimed at advancing the technology of the coal industry in this regard would seem long overdue. The report of the PSAC Environmental Pollution Panel recommended "demonstration of the feasibility and economy of new developments for abating or controlling pollution through their use at Federal installations" and suggested the coalburning TVA power plants as a likely place for such demonstration. This suggestion is doubly appropriate since the TVA is in a region of subnormal " atmospheric ventilation" (8). By design these plants are adjacent to the AEC's Oak Ridge National Laboratory, and such a location would seem ideal for an experiment on the wedding of nuclear and fossil sources of energy. In comments on a preliminary draft of this article, proponents of "conventional " nuclear power pointed out that such power is hard to beat on the basis of cost, and that dissipation of heat to the air by way of cooling towers can also be accomplished in conventional plants (17). These observations are individually correct but not compatible: the low power costs cited are for very large plants [of the order of 1000 mega-watts lectrical) and larger], and the costs of cooling towers and associated equipment needed to dissipate such large amounts of heat [of the order of 2000 megawatts (thermal)] to air from a closed cycle would offset the power cost advantage of the large plant. In regard to the proposed use of nuclear process heat, Weinberg (20) has expressed doubt that much advantage can be derived from this approach because the temperatures involved are too high for low-cost reactors, and heat transfer from surfaces could involve materials problems. In the case of gas production, this is indeed an anticipated problem-not a technologically insuperable one, but a problem of reducing the cost of the materials required (16). Indeed, Weinberg himself has mentioned this possible use of nuclear heat in a recent publication discussing the steam reforming of coal to liquid fuel(21). Also, an improved process for synthesizing methane from lignitec has recently been reported (22). Since the earlier studies date back a decade, a new look at the problems and costs involved relative to the benefits to be derived (not the least of which could be new vigor for the coal industry) would seem to be in order. In the case of steam reforming of natural gas, the temperature level (about 1500 degrees F) is such that the technology is available today, and a process-heat-reactor design study could be initiated without awaiting further developments. 相似文献
11.
日光温室卷帘机自动接缝装置设计 总被引：1，自引：0，他引：1
日光温室卷帘机在设施农业中非常重要。传统的日光温室大棚存在中间保温覆盖材料无法被同步卷放或跑偏褶皱等缺陷。本研究针对传统日光温室卷帘机的设计缺陷,设计了一种用于日光温室中间覆盖材料自动卷放的自动接缝装置,它能使卷帘轴与自动接缝装置能够同步运行,具有可折叠性。装置中心与卷帘轴保持1m左右的距离,能够随着卷帘机的升降轻松的打开和收起。运行时装置顶端始终与大棚表面保持150°,能够避免接缝装置与大棚表面的碰撞。试验表明,设备运行良好,收放自如,能很好解决日光温室中间覆盖材料不能够被卷放的难题,运行效率较高,卷起或铺开10m长的棉被仅需5~8min。 相似文献
12.
Organic field-effect transistors have been developed that function as either n-channel or p-channel devices, depending on the gate bias. The two active materials are alpha-hexathienylene (alpha-6T) and C(60). The characteristics of these devices depend mainly on the molecular orbital energy levels and transport properties of alpha-6T and C(60). The observed effects are not unique to the two materials chosen and can be quite universal provided certain conditions are met. The device can be used as a building block to form low-cost, low-power complementary integrated circuits. 相似文献
13.
水稻胚乳RNA定量RT-PCR分析中参照基因选择 总被引：8，自引：0，他引：8
以6个籼粳稻品种胚乳总RNA为研究材料,检测包括eEF-la、eIF-4a、UBC、GAPDH、UBQ-5、TBL和ACTl在内的7个常用管家基因的表达稳定性情况,通过geNorm软件分析选择最佳参照基因.结果表明:不同的品种间,eEF-la和ACT1的表达最为稳定,UBC的表达变化最为明显.当利用多基因作为内参基因时,使用两个最稳定表达的管家基因即可达到准确校正的目的.该结果为水稻等植物中基因表达分析时内参基因的选择提供了参考. 相似文献
14.
【目的】硒作为人体必不可少的元素之一,在疾病预防与抗氧化方面具有重要作用。小麦作为主要作物之一,是人类获取植物性硒源的主要来源,因此,提高小麦籽粒硒含量是人体补充硒的一条高效、低廉、简单易行的途径。拟通过对已定位到的SNP位点开发KASP标记用于开展高硒小麦选育。【方法】利用已经完成的660K小麦SNP标记的人工合成小麦SHW-L1重组自交系（recombinant inbred lines,RILs）群体,将前期定位的籽粒硒含量相关的QTL区间进一步缩小,开发稳定基因内的SNP位点为KASP标记。【结果】成功开发出2个KASP标记AX-1和AX-2,标记能够在群体中进行基因型分型和鉴定材料籽粒硒含量的相对高低。2个标记都可将供试材料按照基因型分为2类,即高硒和低硒材料,符合1:1的等位基因分离比例。但按照表现型来划分,标记对低硒材料的筛选率（大于90%）要远高于高硒材料（小于30%）。具有高硒含量的表现型材料中,有81%的材料具有高硒的基因型,表明了标记的可靠性。同时,在以人工合成小麦SHW-L1为亲本的其他衍生后代株系中也能用该KASP标记进行基因型分型,分型结果与表型结果一致,说明了标记的有效性,也表明可通过开发到的KASP标记来提升选择效率。【结论】AX-1和AX-2可作为一个实用的分子标记用于SHW-L1为亲本的高硒小麦品种选育和种质资源创制。 相似文献
15.
Josephson superconducting devices of the tunnel-junction type have exciting potential for use in building ultrahigh-speed computers. We consider the properties of superconducting metals that are needed for such devices that would be used in integrated computer circuits operated at a temperature near absolute zero. Recent advances in lead-alloy thin-film materials are described that have led to substantial improvements in lead-alloy Josephson device reliability. The properties of a Pb(0.84)In(0.12)Au(0.04) alloy, of Nb, and of Nb(3)Sn are discussed as examples of three different groups of materials that are of interest. Investigations of lead-alloy and niobium devices have progressed to the point that it is evident that they have good potential for fabricating integrated circuits containing large numbers of devices. 相似文献
16.
Due to increasing regulations and restrictions,there is an urgent need to develop effective alternatives to chemical-dependent fumigation control of soilborne pests and pathogens. Anaerobic soil disinfestation(ASD) is one such alternative showing great promise for use in the control of soilborne pathogens and pests. This method involves the application of a carbon source,irrigation to field capacity,and covering the soil with a plastic tarp. While the mechanisms of ASD are not completely understood,they appear to be a combination of changes in the soil microbial community composition,production of volatile organic compounds,and the generation of lethal anaerobic conditions. The variety of materials and options for ASD application,including carbon sources,soil temperature,and plastic tarp type,influence the efficacy of pathogen suppression and disease control. Currently,both dry(e.g.,rice bran) and liquid(e.g.,ethanol) carbon sources are commonly used,but with different results depending on environmental conditions. While solarization is not an essential component of ASD,it can enhance efficacy. Understanding the mechanisms that mediate biological changes occurring in the soil during ASD will facilitate our ability to increase ASD efficacy while enhancing its commercial viability. 相似文献
17.
Ahn JH Kim HS Lee KJ Jeon S Kang SJ Sun Y Nuzzo RG Rogers JA 《Science (New York, N.Y.)》2006,314(5806):1754-1757
We developed a simple approach to combine broad classes of dissimilar materials into heterogeneously integrated electronic systems with two- or three-dimensional layouts. The process begins with the synthesis of different semiconductor nanomaterials, such as single-walled carbon nanotubes and single-crystal micro- and nanoscale wires and ribbons of gallium nitride, silicon, and gallium arsenide on separate substrates. Repeated application of an additive, transfer printing process that uses soft stamps with these substrates as donors, followed by device and interconnect formation, yields high-performance heterogeneously integrated electronics that incorporate any combination of semiconductor nanomaterials on rigid or flexible device substrates. This versatile methodology can produce a wide range of unusual electronic systems that would be impossible to achieve with other techniques. 相似文献
18.
针对西北地区胡麻播种机旋耕取土装置取土不均匀导致膜上覆土不均匀的问题,设计一款带有蓄土装置的胡麻精量穴播联合作业机。该机具由旋耕装置、地膜覆土装置、滴灌带铺设装置、地膜铺设装置和播种装置组成。根据农艺种植要求对机具的关键装置进行理论分析和功率计算,确定满足覆土工作时运土带线速度、双向螺旋输送器转速、双排取种勺式穴播器的半径及整机配套拖拉机功率。采用EDEM软件对地膜覆土装置覆土过程进行仿真,验证蓄土装置的可行性。田间试验结果表明:机具前进速度为0.6 m/s时,其空穴率为1.2%、穴粒数合格率89.3%、播种深度合格率86.5%、膜孔错位率5.1%、膜边覆土厚度合格率95.7%、邻接行距合格率92.4%。田间播种性能试验相关指标均达到覆膜穴播机作业质量要求,田间试验覆土结果与仿真结果基本一致。 相似文献
19.
针对具体的工程实例,对高强砼材料的经济性问题进行分析比较。结果表明,高强砼材料具有投入高,产出更高,经济效益更趋合理的特点,其经济性优于普通低强砼材料。 相似文献
20.
[目的]构建了负责运输苏氨酸至胞外的转运蛋白的关键基因rhtB过表达的苏氨酸发酵菌M122,考察不同的碳源、氮源及pH对该重组菌产L-苏氨酸的影响。[方法]选用不同的碳、氮源对L-苏氨酸生产菌株的发酵过程进行分析,对发酵培养基的碳、氮源及pH进行优化。[结果]定向改造后苏氨酸发酵菌对营养物质的利用效率增加,使用蔗糖作为碳源发酵时,摇床培养L-苏氨酸产量为28.1g/L;以(NH4)2SO4或酵母粉作为氮源发酵时,L-苏氨酸产量分别为27.8和28.2g/L,均优于使用其他氮源时苏氨酸的产量。对发酵的最适pH研究表明,中性条件下更有利于菌体的生长和L-苏氨酸的产生。[结论]确定了苏氨酸发酵菌M122的最佳碳源为蔗糖,最佳氮源为(NH4)2SO4或酵母粉,最适pH为7.0。 相似文献