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991.
The results of the analysis of variations in the radiative recombination coefficient with varying doping level and concentration of excess electron-hole pairs are reported. It is shown that, along with the effect of narrowing of the band gap calculated in the many-electron approximation, the effect of screening of the Coulomb interaction responsible for the decrease in the excition binding energy should be taken into account. Both effects produce similar trends and decrease the radiative recombination coefficient with increasing levels of doping or injection. The contributions of excitonic radiative recombination and band-to-band radiative recombination to the total radiative recombination coefficient are separated from each other. It is shown that, in the region of room temperature, both contributions are comparable, while at liquid-nitrogen temperature, the excitonic component dominates over the band-to-band component. The results obtained by refined calculations of the limiting value of the internal quantum yield of electroluminescence for the silicon diodes and p-i-n structures are presented. It is shown that the internal quantum yield of electroluminescence can be as high as 14%. However, this values sharply decreases with increasing surface recombination rate and decreasing lifetime of excess charge carriers in the bulk. 相似文献
992.
A Low-Power CMOS Linear-in-Decibel Variable Gain Amplifier With Programmable Bandwidth and Stable Group Delay 总被引:1,自引:0,他引:1
Tsou S.-C. Li C.-F. Huang P.-C. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2006,53(12):1436-1440
This brief presents a new circuit architecture for linear-in-decibel, constant-bandwidth variable gain amplifier (VGA). To obtain high linearity under low-voltage operation, this VGA is a closed-loop structure. In loop amplifier design, two techniques are applied: first, the loop amplifier is given finite input impedance. This arrangement keeps the VGA bandwidth constant under different gain setting. Second, a current-buffered compensation is applied for loop stability. Compared to the Miller compensation, this method achieves wider bandwidth. The prototype chip using 0.18-mum CMOS technology demonstrates that -10- to 20-dB gain and 0.5- to 30-MHz bandwidth can be programmed independently. The group delay difference within 30-dB gain control range is smaller than 1%. The total circuit dissipates 1.35 mA from a 1.8-V supply 相似文献
993.
P. Acedo H. Lamela G. Villaseca R. Santos J.P. Vilcot M. Pessa 《Photonics Technology Letters, IEEE》2006,18(6):755-757
In this letter, we demonstrate the possibility of using two monolithically integrated laterally coupled diode lasers for data transmission beyond the intrinsic relaxation oscillation frequency of semiconductor lasers. The resonance of the lateral modes of such structure provides a peak in the small signal modulation response of the device above the relaxation oscillation frequency of the intrinsic emitters that is studied in terms of relative intensity noise and phase noise to characterize this new, simple, and compact device. Optical transmission of a 64-Mb/s pseudorandom bit sequence signal using a microwave carrier over this resonance peak of the lateral modes above the relaxation oscillation is demonstrated for the first time to our knowledge. 相似文献
994.
Thermal treatment applied in association with a biological system allows for a significant reduction in excess sludge production (approximately 50%). In general, heat treatment is described as a sludge disintegration technique. This paper offers a thorough study on the impact of heat treatment, at temperatures below 100 degrees C, on the solubilisation of the sludge COD and its biodegradability. Discontinuous heating experiments were performed on activated and digested sludge. At all temperatures tested the released COD for digested sludge was systematically higher than that for activated sludge (15 and 40%, respectively, at 95 degrees C for 40 min of contact time). For the first 30 min, a 1st order kinetic, with respect to the residual COD, was systematically found. In the range of 40-95 degrees C, digested sludge had a lower activation energy than activated sludge (26 kcal/mol compared to 70-160 kcal/mol). COD solubilisation is thus more positively influenced by temperature in the case of activated sludge. This may be due to the significant difference in the ratio of protein/carbohydrate in digested and activated sludge (1-5 and 0.2-0.7, respectively). The increase in the COD/TKN ratio in the solubilised fraction after thermal treatment of activated sludge suggests a preferential solubilisation of proteins over carbohydrates. Respirometric tests performed on the solubilised COD showed that whatever the sludge origin, only 40-50% of released COD is biodegradable at a conventional hydraulic retention time (i.e., 24 h). Hence, heat treatment would act more through organic matter solubilisation rather than by a biodegradability increase. 相似文献
995.
A. P. Vasil’ev V. P. Vasyukhno M. E. Netecha V. L. Vysotskii R. I. Kalinin A. A. Sarkisov A. Yu. Kazennov Yu. V. Sivintsev A. M. Chernyaev 《Atomic Energy》2006,101(1):506-511
The radioecological conditions which developed on the territory over the long operating time of the object of the naval fleet
in Guba Andreev are described. The results of an analysis of the sources of the real and potential danger and measures to
prevent dangerous effects for the environment and the workers at the time remediation work is performed are discussed.
__________
Translated from Atomnaya énergiya, Vol. 101, No. 1, pp. 49–55, July, 2006. 相似文献
996.
Joel P. Martin J. Edward Swan II Robert J. Moorhead II Zhanping Liu Shangshu Cai 《Computer Graphics Forum》2008,27(3):991-998
We present the results from a user study looking at the ability of observers to mentally integrate wind direction and magnitude over a vector field. The data set chosen for the study is an MM5 (PSU/NCAR Mesoscale Model) simulation of Hurricane Lili over the Gulf of Mexico as it approaches the southeastern United States. Nine observers participated in the study. This study investigates the effect of layering on the observer's ability to determine the magnitude and direction of a vector field. We found a tendency for observers to underestimate the magnitude of the vectors and a counter‐clockwise bias when determining the average direction of a vector field. We completed an additional study with two observers to try to uncover the source of the counter‐clockwise bias. These results have direct implications to atmospheric scientists, but may also be able to be applied to other fields that use 2D vector fields. 相似文献
997.
Florian Matthes 《Informatik-Spektrum》2008,31(6):527-536
Zusammenfassung Anwendungslandschaften in Unternehmen sind langlebige hoch-komplexe Strukturen bestehend aus hunderten bis tausenden von miteinander
vernetzten betrieblichen Informationssystemen, die von Personen mit sehr unterschiedlichen Interessen und Erfahrungshintergrund
konzipiert, erstellt, modifiziert, betrieben, genutzt und finanziert werden. Die Softwarekartographie zielt darauf ab, die
Kommunikation zwischen diesen Personen durch zielgruppenspezifische verst?ndliche graphische Visualisierungen zu unterstützen,
die Gesch?fts- und Informatik-Aspekte gleicherma?en berücksichtigen, und die speziell für langfristige und strategische Management-Betrachtungen
geeignet sind.
In diesem Beitrag fassen wir zun?chst die in der betrieblichen Praxis wohlbekannten Probleme beim Management von Anwendungslandschaften
zusammen und diagnostizieren erhebliche Kommunikationsdefizite. Da Anwendungslandschaften als Systeme von Systemen mit Menschen
als integrale Systembestandteile zu verstehen sind, werden Karten als attraktiver L?sungsansatz identifiziert und die wesentlichen
Konzepte der Softwarekartographie anhand von Beispielen vorgestellt. Dabei werden Querbezüge zu anderen Fachgebieten der Informatik
und Wirtschaftsinformatik hergestellt, und die bisherige Nutzung der Forschungsergebnisse in der Praxis gezeigt. 相似文献
998.
A fine-grained reconfigurable architecture based on double gate technology is proposed and analyzed. The logic function operating on the first gate of a double-gate (DG) transistor is reconfigured by altering the charge on its second gate. Each cell in the array can act as logic or interconnect, or both, contrasting with current field-programmable gate array structures in which logic and interconnect are built and configured separately. Simulation results are presented for a fully depleted SOI DG-MOSFET implementation and contrasted with two other proposals from the literature based on directed self-assembly. 相似文献
999.
Sebastián López Gustavo M. Callicó Félix Tobajas Valentín de Armas José F. López Roberto Sarmiento 《ETRI Journal》2008,30(6):862-864
This letter presents a novel approach for organizing computational resources into groups within H.264/AVC motion estimation architectures, leading to reductions of up to 75% in the equivalent gate count with respect to state‐of‐the‐art designs. 相似文献
1000.
Phenylbutazone was recrystallized from its solutions by using a supercritical fluid antisolvent process. It was dissolved
in acetone and supercritical carbon dioxide was injected into the solution, thereby inducing supersaturation and particle
formation. Variation in the physical properties of the recrystallized phenylbutazone was investigated as a function of the
crystallizing temperature and the carbon dioxide injection rate. The recrystallized particles showed cleaner surfaces and
more ordered morphology compared to the particles obtained by other methods such as solvent evaporation. X-ray diffraction
patterns indicated that the crystallinity of the particles had been modified upon the recrystallization. Differential scanning
calorimetry measurement revealed that the crystallizing temperature influenced the thermal stability of the resulting crystals.
Larger crystals were produced when the carbon dioxide injection rate was reduced. 相似文献