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Punchthrough transit-time diodes have been constructed with both Schottky-barrier and diffused-junction emitters. The microwave and d.c. characteristics of these devices are strikingly similar. Either construction technique appears to be suitable for the future development of low-noise microwave sources. 相似文献
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Runge K. Gimlett J.L. Clawin D. Way W. Cheung N.K. Kipnis I. Snapp C. 《Electronics letters》1989,25(20):1346-1347
The authors have designed and implemented a submicron silicon bipolar master-slave D-type flip-flop integrated circuit which can be used either as a decision circuit or a demultiplexer, operating at data rates as high as 8.1 and 11.2 Gbit/s, respectively. The circuit was fabricated using a 0.6 mu m, nonpolysilicon emitter technology, occupying an area of 0.8 mm*0.9 mm, and dissipating 410 mW of power.<> 相似文献
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Flexible, architectured, photonic nanostructures such as colloidal photonic crystals (CPCs) can serve as colorimetric strain sensors, where external applied strain leads to a noticeable color change. However, CPCs' response to strain is difficult to quantify without the use of optical spectroscopy. Integration of flexible electrical readout of CPCs' color change is a challenge due to a lack of flexible/stretchable electrical transducers. This work details a colorimetric strain sensor with optoelectrical quantification based on an integrated system of CPCs over a crumpled graphene phototransducer, which optoelectrically quantifies CPCs, response to strain. The hybrid system enables direct visual perception of strain, while strain quantification via electrical measurement of the hybrid system outperforms that of crumpled graphene strain sensors by more than 100 times. The unique combination of a photonic sensing element with a deformable transducer will allow for the development of novel, electrically quantifiable colorimetric sensors with high sensitivity. 相似文献
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Kurt B. Waldman David L. Ortega Robert B. Richardson Daniel C. Clay Sieglinde Snapp 《Food Security》2016,8(6):1087-1099
Adoption rates of leguminous crops remain low in sub-Saharan Africa despite their potential role in improving nutrition, soil health, and food security. In this study we explored Malawian farmers’ perceptions of various legume attributes and assessed how these perceptions affected allocation of land to legume crops using a logit link model. We found high regional variation in both consumption- and production-related preferences, but relatively consistent preferences across samples. While scientific understanding and farmer perceptions were aligned on some topics and for some legumes, there were discrepancies elsewhere, particularly in terms of soil fertility and nutrition. Understanding why these discrepancies exist and where there were potential biases are critical in explaining the extent of adoption. In many cases perceptions of legume attributes may be influenced by the cultural role of the crop in the household, particularly in terms of food security or market-orientation. The findings also suggest that researchers need to look beyond both the agronomic properties and farmers’ preferences to fully understand the extent of adoption. Socioeconomic factors, biases, and marketing concerns may also influence integration of legumes into maize-based cropping systems. 相似文献
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This article demonstrates how unique local factors affect implementation of commitment statutes and, consequently, the extent to which implementation supports fundamental treatment philosophies. Four local variations in the implementation of Ohio's commitment statute are examined with a methodology designed to describe commitment processes. Qualitative case studies highlight factors that appear to contribute to variability across these sites. The authors contend that this information can be used as a system management tool at the state and local levels to (1) suggest needed changes in local service systems, (2) identify specific options/interventions for effecting change in desired directions and (3) assess the extent to which changes affect commitment processes in predictable ways that are consistent with philosophical principles. 相似文献
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Winter cover crops are capable of supplying multiple economic and environmental benefits in temperate environments of North America, but the lack of adapted populations for specific environmental and agricultural contexts has resulted in cover crops that are unreliable and perform ecosystem functions unevenly. To maximize the benefits provided by winter cover crops, we argue for trait selection by crop scientists that is cognizant of desired ecosystem functions, with the goal of providing commercially available populations that have variable functions. We illustrate this approach through a case study of a promising winter annual legume cover crop, hairy vetch (Vicia villosa). Six key traits and associated functions are considered within specific agroecological contexts. We discuss tradeoffs that may occur among desired plant traits and illustrate how over‐selection for a particular trait could negatively affect performance and overall benefits from a cover crop. Intraspecific combinations of complementary cover crops are suggested as means to achieve multiple agroecosystem functions. Copyright © 2008 Society of Chemical Industry 相似文献
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Jorgenson R. D. Sorensen L. Leet D. Hagedorn M. S. Lamb D. R. Friddell T. H. Snapp W. P. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2010,98(2):299-314
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Sieglinde Zelzer Harald Mangge Sabine Pailer Herwig Ainoedhofer Petra Kieslinger Tatjana Stojakovic Hubert Scharnagl Florian Prüller Daniel Weghuber Christian Datz Johannes Haybaeck Barbara Obermayer-Pietsch Christian Trummer Johanna Gostner Hans-Jürgen Gruber 《International journal of molecular sciences》2015,16(5):11689-11698
Metabolic dysfunctions might play a crucial role in the pathophysiology of thyroid dysfunctions. This study aimed to investigate the impact of a controlled diet (normal versus high fat feeding) on hypothyroid and hyperthyroid Sprague Dawley rats. Female Sprague Dawley rats (n = 66) were grouped into normal diet (n = 30) and high-fat diet (n = 36) groups and subdivided into controls, hypothyroid and hyperthyroid groups, induced through propylthiouracil or triiodothyronine (T3) treatment, respectively. After 12 weeks of treatment metabolic parameters, such as oxidized LDL (oxLDL), malondialdehyde (MDA), 4-hydroxynonenal (HNE), the lipid profile, body weight and food intake parameters were analyzed. Successfully induced thyroid dysfunctions were shown by T3 levels, both under normal and high fat diet. Thyroid dysfunctions were accompanied by changes in calorie intake and body weight as well as in the lipid profile. In detail, hypothyroid rats showed significantly decreased oxLDL levels, whereas hyperthyroid rats showed significantly increased oxLDL levels. These effects were seen under high fat diet and were less pronounced with normal feeding. Taken together, we showed for the first time in female SD rats that only hyper-, but not hypothyroidism, is associated with high atherogenic oxidized LDL irrespective of normal or high-fat diet in Sprague Dawley rats. 相似文献
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Microwave amplification has been obtained from silicon diodes operated in avalanche-resonance pumped modes. D.C.-r.f. conversion efficiencies were 25% at 1.3GHz for a saturation gain of 12dB and a bandwidth of 3%. 相似文献