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排序方式: 共有785条查询结果,搜索用时 31 毫秒
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This paper addresses both solid state power amplifiers (sspas) and travelling wave tube amplifiers (twtas), highlighting their capabilities, drawbacks and future developments, for space systems. These two technologies are complementary and will coexist in future pay loads. 相似文献
3.
KI el-Noueam V Giuliano ME Schweitzer BJ O''Hara 《Canadian Metallurgical Quarterly》1997,21(5):796-799
A 62-year-old female who had a complaint of palpitation was diagnosed as bicuspid aortic stenosis and left single coronary artery by the echocardiographic examination, cardiac catheterization study and coronary artery angiography. Aortic valve replacement was performed and the patient was discharged 22 days after surgery with good post-operative course. Preoperative coronary artery angiography was important in the case of aortic valvular disease. 相似文献
4.
Five studies examined the hypotheses that when people experience positive affect, those low in self-esteem are especially likely to dampen that affect, whereas those high in self-esteem are especially likely to savor it. Undergraduate participants' memories for a positive event (Study 1) and their reported reactions to a success (Study 2) supported the dampening prediction. Results also suggest that dampening was associated with worse mood the day after a success (Study 2), that positive and negative affect regulation are distinct, that self-esteem is associated with affect regulation even when Neuroticism and Extraversion are controlled (Studies 3 and 4), and that self-esteem may be especially important for certain types of positive events and positive affect regulation (Study 5). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Foutse Khomh Massimiliano Di Penta Yann-Ga?l Guéhéneuc Giuliano Antoniol 《Empirical Software Engineering》2012,17(3):243-275
Antipatterns are poor design choices that are conjectured to make object-oriented systems harder to maintain. We investigate
the impact of antipatterns on classes in object-oriented systems by studying the relation between the presence of antipatterns
and the change- and fault-proneness of the classes. We detect 13 antipatterns in 54 releases of ArgoUML, Eclipse, Mylyn, and
Rhino, and analyse (1) to what extent classes participating in antipatterns have higher odds to change or to be subject to
fault-fixing than other classes, (2) to what extent these odds (if higher) are due to the sizes of the classes or to the presence
of antipatterns, and (3) what kinds of changes affect classes participating in antipatterns. We show that, in almost all releases
of the four systems, classes participating in antipatterns are more change-and fault-prone than others. We also show that
size alone cannot explain the higher odds of classes with antipatterns to underwent a (fault-fixing) change than other classes.
Finally, we show that structural changes affect more classes with antipatterns than others. We provide qualitative explanations
of the increase of change- and fault-proneness in classes participating in antipatterns using release notes and bug reports.
The obtained results justify a posteriori previous work on the specification and detection of antipatterns and could help
to better focus quality assurance and testing activities. 相似文献
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7.
Silk fibers and membranes were acylated with octadecenylsuccinic anhydride (ODSA) at 75°C for different times. Swelling [N,N‐dimethylformamide (DMF) and dimethyl sulfoxide (DMSO)] and nonswelling (xylene) solvent media were used for the reaction. Silk membranes that reacted in DMF or DMSO displayed faster reaction kinetics and attained higher weight‐gain values than fibers. The effect of the solvent on the reaction yield was in the following order: DMSO > DMF ? xylene. The Fourier transform infrared spectra of acylated silk samples showed the characteristic absorption bands of the anhydride at 2990, 2852, 1780–1700, and 1170 cm?1. The intensity of the latter band, which increased linearly with the weight gain, was used as a marker for evaluating the reaction kinetics of the samples acylated in the nonswelling medium. The moisture regain and water retention of silk fibers acylated with ODSA decreased significantly, regardless of the solvent system used. Accordingly, the water repellency increased. Acylation induced an increase in the thermal stability of the silk fibers and membranes. Fine particles adhering to the surfaces of the silk fibers acylated in xylene were detected by scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 324–332, 2003 相似文献
8.
Masuhiro Tsukada Hiroshi Katoh Donna Wilson Bong‐Seob Shin Takayuki Arai Ritsuko Murakami Giuliano Freddi 《应用聚合物科学杂志》2002,86(5):1181-1188
The work presented here discusses a new technique for preparing silk fibers and films with persistent antimicrobial activity through use of metallic dyestuffs during the fiber dyeing process. The length of the silk fibers investigated contracted when the fibers were immersed in concentrated neutral salt solutions, such as calcium or potassium nitrate, at elevated temperature levels. The birefringence and molecular orientation of the silk fibroin molecules became less ordered by the action of the neutral salt solutions, resulting in increased dyestuff absorption. Subsequently, contracted silk fibers were dyed with metallic dyestuffs containing Cr or Cu for the purpose of obtaining silk fibers with antimicrobial activity. Silk fibers dyed with metallic dyestuffs showed significant antimicrobial activity against the plant pathogen Cornebacterium and the human pathogen Coli bacillus. Tensile strength of the silk fibers after the salt shrinking and dyeing processes did not show a significant change, whereas the elongation at break was increased slightly. The techniques described here for preparing significantly active antimicrobial silk fibers are effective and economic ways of providing new materials for industrial and biomedical applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1181–1188, 2002 相似文献
9.
This paper deals with the epoxide treatment of silk fabrics by the pad/batch method. The optimum reaction conditions, i.e., NaOH concentration, and reaction temperature were 2.5 g/L and 30°C, respectively. A weight gain of 8.5% was attained at a reaction time of 6 h. This value slightly increased to 10% after 24 h. The reactivity of tyrosine and basic amino acid residues was dependent on the reaction time and did not significantly differ from the results of epoxide-treated silk fiber by the conventional method in tetrachloroethylene. The moisture regain slightly decreased at 4% weight gain and then increased with the epoxide content, exceeding the value of the untreated control. The crease recovery of the epoxide-treated silk fabrics measured in the wet state was significantly improved, whereas that in the dry state was almost unchanged. The rate of photoyellowing of the epoxide-treated silk fabrics by the pad/batch method was reduced significantly compared with that of the untreated control. Among the mechanical properties, elongation at break and tensile modulus remained unchanged, whereas the tensile strength slightly increased following the epoxide reaction. The thermal properties were evaluated by DSC and TGA and on the basis of the dynamic viscoelastic measurements. The DSC curve of the epoxide-treated sample showed a slight increase of the decomposition temperature of silk fibroin. The rate of weight loss determined by TGA remained unchanged regardless of the chemical modification, whereas the peak of loss modulus became broader and shifted to lower temperature. The X-ray diffractograms showed that the crystalline structure of silk fibers was not affected by the reaction with epoxides. © 1993 John Wiley & Sons, Inc. 相似文献
10.
Mangrove forests as a nature-based solution for coastal flood protection: Biophysical and ecological considerations 下载免费PDF全文
Rosanna van Hespen Zhan Hu Bas Borsje Michela De Dominicis Daniel A. Friess Svetlana Jevrejeva Maarten G. Kleinhans Maria Maza Celine E. J. van Bijsterveldt Tom Van der Stocken Bregje van Wesenbeeck Danghan Xie Tjeerd J. Bouma 《水科学与水工程》2023,16(1):1-13
Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk. It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection. However, to use mangroves effectively as a nature-based measure for flood risk reduction, we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure. In this perspective, we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence. We show that the forest properties that comprise coastal flood protection are well-known, but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation. Overall, there is relatively good understanding of the ecological processes that drive forest structure and size, but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics, and on the role of combined stressors influencing forest retreat. Integrating simulation models of forest structure under changing physical (e.g. due to sea-level change) and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection. 相似文献