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排序方式: 共有735条查询结果,搜索用时 15 毫秒
101.
Seth D. Silverstein 《Energy and Buildings》1977,1(1):51-56
The design of a simple energy conserving window management system is described, and its heat transfer characteristics are calculated. The device serves as a quasi-active solar collector during winter daytime, provides added insulation comparable with that of vented storm windows during winter nighttime, and rejects solar heat during summer cooling periods. The problem of avoiding the intensity of direct sun through windows while obtaining essentially all the associated heat is effectively solved with a window system of this type. The results of the numerical modeling show that the dual shade:will be approximately 90% as energy efficient as an unshaded window while intercepting direct sunlight;will save about 40% on energy losses through a single pane window during winter nighttime;will reduce solar heat gain by about 70% during peak-power summer air conditioning periods. 相似文献
102.
The influences of impurity levels, grain size, and tensile strength on in-service temper embrittlement of CrMoV steels have
been investigated. The samples for this study were taken from several steam turbine CrMoV rotors which had operated for 15
to 26 years. The effects of grain size and tensile strength on embrittlement susceptibility were separated by evaluating the
embrittlement behavior of two rotor forgings, which were made from the same ingot, after giving an extended step-cooling treatment.
The results reveal that among the residual elements in the steels, only P produces a significant embrittlement. The variation
of P and tensile strength of the steels in the ranges investigated has no effect on in-service temper embrittlement susceptibility,
as measured by the shift in fracture appearance transition temperature (FATT). However, the prior austenite grain size plays
a major role on in-service embrittlement. The fine grain steels with a grain size of ASTM No. 9 or higher are virtually immune
to in-service embrittlement. In steels having duplex grain sizes, the embrittlement susceptibility is controlled by the size
of coarser grains. For a given steel chemistry, the coarse grain steel is more susceptible to in-service embrittlement, and
a decrease in ASTM grain size number from 4 to 0/1 increases the shift in FATT by 61°C (110°F). It is demonstrated that long-term
service embrittlement can be simulated, except in very coarse grain steels, by using the extended step-cooling, treatment.
The results of step-cooling studies also show that the coarse grain rotor steels take longer time during service to reach
a fully embrittled state than the fine grain rotor steels. This difference in the kinetics of embrittlement is believed to
be related to the variations in Mo content in the matrix and the grain size of the steels. 相似文献
103.
104.
UNStudio Ben van Berkel Hannes Pfau Astrid Piber Jin Xing Hufton+Crow Seth Powers 《中国建筑装饰装修》2018,(4)
正UNStudio由Ben van Berkel和Caroline Bos创立,是一个国际性的建筑设计网络。拥有三个全方位服务的国际事务所,分别位于阿姆斯特丹、香港和上海。专于建筑、室内建筑、产品设计、城市发展和基础设施项目。地址:浙江省杭州市钱江新城富春路业主方:凯德集团建筑面积:392526m~2项目年份:2017醒目的裙楼之上坐落着两座流线型的高楼,从中可以饱览钱塘江和西湖的迷人风光。 相似文献
105.
106.
Fernando Perez Rojo Sumedha Seth William Erskine Parwinder Kaur 《International journal of molecular sciences》2021,22(8)
Subterranean clover (Trifolium subterraneum) is the most widely grown annual pasture legume in southern Australia. With the advent of advanced sequencing and genome editing technologies, a simple and efficient gene transfer protocol mediated by Agrobacterium tumefaciens was developed to overcome the hurdle of genetic manipulation in subterranean clover. In vitro tissue culture and Agrobacterium transformation play a central role in testing the link between specific genes and agronomic traits. In this paper, we investigate a variety of factors affecting the transformation in subterranean clover to increase the transformation efficiency. In vitro culture was optimised by including cefotaxime during seed sterilisation and testing the best antibiotic concentration to select recombinant explants. The concentrations for the combination of antibiotics obtained were as follows: 40 mg L−1 hygromycin, 100 mg L−1 kanamycin and 200 mg L−1 cefotaxime. Additionally, 200 mg L−1 cefotaxime increased shoot regeneration by two-fold. Different plant hormone combinations were tested to analyse the best rooting media. Roots were obtained in a medium supplemented with 1.2 µM IAA. Plasmid pH35 containing a hygromycin-resistant gene and GUS gene was inoculated into the explants with Agrobacterium tumefaciens strain AGL0 for transformation. Overall, the transformation efficiency was improved from the 1% previously reported to 5.2%, tested at explant level with Cefotaxime showing a positive effect on shooting regeneration. Other variables in addition to antibiotic and hormone combinations such as bacterial OD, time of infection and incubation temperature may be further tested to enhance the transformation even more. This improved transformation study presents an opportunity to increase the feeding value, persistence, and nutritive value of the key Australian pasture. 相似文献
107.
Lianfeng Zhao Kwangdong Roh Sara Kacmoli Khaled Al Kurdi Samik Jhulki Stephen Barlow Seth R. Marder Claire Gmachl Barry P. Rand 《Advanced materials (Deerfield Beach, Fla.)》2020,32(25):2000752
The performance of lead-halide perovskite light-emitting diodes (LEDs) has increased rapidly in recent years. However, most reports feature devices operated at relatively small current densities (<500 mA cm−2) with moderate radiance (<400 W sr−1 m−2). Here, Joule heating and inefficient thermal dissipation are shown to be major obstacles toward high radiance and long lifetime. Several thermal management strategies are proposed in this work, such as doping charge-transport layers, optimizing device geometry, and attaching heat spreaders and sinks. Combining these strategies, high-performance perovskite LEDs are demonstrated with maximum radiance of 2555 W sr−1 m−2, peak external quantum efficiency (EQE) of 17%, considerably reduced EQE roll-off (EQE > 10% to current densities as high as 2000 mA cm−2), and tenfold increase in operational lifetime (when driven at 100 mA cm−2). Furthermore, with proper thermal management, a maximum current density of 2.5 kA cm−2 and an EQE of ≈1% at 1 kA cm−2 are shown using electrical pulses, which represents an important milestone toward electrically driven perovskite lasers. 相似文献
108.
Cameron H. Feriante Samik Jhulki Austin M. Evans Raghunath R. Dasari Kaitlin Slicker William R. Dichtel Seth R. Marder 《Advanced materials (Deerfield Beach, Fla.)》2020,32(2):1905776
Imine-linked 2D covalent organic frameworks (COFs) form more rapidly than previously reported under Brønsted acid-catalyzed conditions, showing signs of crystallinity within a few minutes, and maximum crystallinity within hours. These observations contrast with the multiday reaction times typically employed under these conditions. In addition, vacuum activation, which is often used to isolate COF materials significantly erodes the crystallinity and surface area of the several isolated materials, as measured by N2 sorption and X-ray diffraction. This loss of material quality during isolation for many networks has historically obscured otherwise effective polymerization conditions. The influence of the activation procedure is characterized in detail for three COFs, with the commonly used 1,3,5-tris(4-aminophenyl)benzene-terephthaldehyde network (TAPB-PDA COF), the most prone to pore collapse. When the networks are activated carefully, rapid COF formation is general for all five of the imine-linked 2D COFs studied, with all exhibiting excellent crystallinity and surface areas, including the highest surface areas reported to date for three materials. Furthermore, to simplify the workup of COF materials, a simple nitrogen flow method provides high-quality materials without the need for specialized equipment. These insights have important implications for studying and understanding how 2D COFs form. 相似文献
109.
Seth R. Goldstein Thomas Hubin Scott Rosenthal Clayton Washburn 《Journal of microscopy》1990,157(1):29-38
A no-moving-parts, 30 frames/s, laser-beam scanning confocal reflected-light microscope has been developed. In principle, the technique can be extended to fluorescence and transmission light microscopy. Acousto-optic beam deflectors controlled by digital electronics move a laser beam in a 512-line interlaced 8·5 times 8·5-mm raster. The light passes through a beam splitter, enters an inverted microscope through the side camera port, and is imaged at the object by the microscope objective. Reflected light returns through the objective, exits the camera port, is reflected off the beam splitter, and is imaged on to the photocathode of an image dissector tube (IDT). Confocality is provided by raster scanning the IDT aperture coincident with the congruent image of the laser beam incident on the object. Real-time jitter-free reflected light images of a variety of biological objects have been produced. Computer-controlled alignment of the laser scan and IDT is performed in several seconds. 相似文献
110.
Thomas Seth Davis Fiona B. Horne Jens C. Yetter Jane E. Stewart 《Journal of chemical ecology》2018,44(6):601-610
Conifer secondary metabolites play a key role in mechanisms of resistance to biotic disturbance, especially by bark beetles and beetle-associated microorganisms. Here, we describe variation in constitutive monoterpenes isolated from Engelmann spruce, Picea engelmannii, phloem across fourteen high-elevation populations in the Rocky Mountains of Colorado, and test interactions between phloem monoterpenes and an endophloedic symbiotic fungus, Leptographium abietinum, associated with the North American spruce beetle, Dendroctonus rufipennis. We consistently identified ten monoterpenes in Engelmann spruce phloem, and the trees in our samples could be classified into two geographically interspersed chemical phenotypes, or ‘chemotypes’: one in which α- and β-pinene were the most abundant monoterpenes, and one in which 3-carene was the most abundant monoterpene. Media amended with low concentrations of α-pinene, β-pinene, 3-carene, myrcene, and terpinolene stimulated growth of L. abietinum. Increasing monoterpene concentrations uniformly retarded fungal growth. Linalool completely suppressed fungal growth at all concentrations, while terpinolene completely suppressed growth at low and intermediate concentrations, indicating relatively high toxicity of these compounds. Tests with monoterpene blends representing the ‘average’ monoterpene composition of each chemotype indicated that representative chemotypes are equivalent in fungistatic activity, with chemotype blends being inhibitory even at low concentrations. Total constitutive monoterpene abundances in Engelmann spruce phloem ranged from 42 to 1796 μg/g. Induction of Engelmann spruce phloem monoterpenes in response to L. abietinum or other biotic agents has yet to be quantified, but is important for further understanding Engelmann spruce resistance to the D. rufipennis-L. abietinum complex. 相似文献