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排序方式: 共有91条查询结果,搜索用时 31 毫秒
31.
F. Szmulowicz H. J. Haugan G. J. Brown K. Mahalingam B. Ullrich S.R. Munshi L. Grazulis 《Opto-Electronics Review》2006,14(1):69-75
The effect of interface anisotropy on the electronic structure of InAs/GaSb type-II superlattices is exploited in the design of thin-layer superlattices for mid-IR detection threshold. The design is based on a theoretical envelope function model that incorporates the change of anion and cation species across InAs/GaSb interfaces, in particular, across the preferred InSb interface. The model predicts that a given threshold can be reached for a range of superlattice periods with InAs and GaSb layers as thin as a few monolayers. Although the oscillator strengths are predicted to be larger for thinner period superlattices, the absorption coefficients are comparable because of the compensating effect of larger band widths. However, larger intervalence band separations for thinner-period samples should lead to longer minority electron Auger lifetimes and higher operating temperatures in p-type SLs. In addition, the hole masses for thinner-period samples are on the order the free-electron mass rather than being effectively infinite for the wider period samples. Therefore, holes should also contribute to photoresponse. A number of superlattices with periods ranging from 50.6 to 21.2 Å for the 4 μm detection threshold were grown by molecular beam epitaxy based on the model design. Low temperature photoluminescence and photoresponse spectra confirmed that the superlattice band gaps remained constant at 330 meV although the period changed by the factor of 2.5. Overall, the present study points to the importance of interfaces as a tool in the design and growth of thin superlattices for mid-IR detectors for room temperature operation. 相似文献
32.
We estimate the energy loss distribution and investigate the quenching of hadron spectra in ultrarelativistic heavy-ion collisions due to the collisional energy loss of energetic partons from hard parton collisions in the initial stage. 相似文献
33.
34.
Kaladhar?Semwal Rakesh?Ranjan P.?K.?PanigrahiEmail author P.?Munshi 《Heat and Mass Transfer》2012,48(3):541-554
Mixing of jets is crucial for optimal performance of many industrial applications and there is a need to optimize both nozzle
geometry and flow conditions. The present study reports the influence of buoyancy and perforation on mixing between a jet
and its environment. Optical techniques are ideal for the study of jet mixing due to their non-intrusive and inertia free
properties. The present study gives an account of mixing between helium jet and the ambient fluid using a combination of color
schlieren deflectometry and radial tomographic mathematics. Four different perforation sizes have been used and the experiments
are performed for Reynolds numbers 21–676 and Richardson numbers 3.27–0.0015. Color schlieren images show distinct influence
of perforation and flow conditions (Richardson number). Oxygen concentration and jet width quantify effectiveness of jet mixing.
Buoyancy plays an important role in mixing at high Richardson number. Perforation improves jet mixing i.e. there is about
120% increase in jet width and the size of perforation plays an important role. 相似文献
35.
Michael D. Hargreaves Andrew D. Burnett Tasnim Munshi John E. Cunningham Edmund H. Linfield A. Giles Davies Howell G. M. Edwards 《Journal of Raman spectroscopy : JRS》2009,40(12):1974-1983
The laser excitation wavelength is an important parameter in obtaining Raman spectra from drugs‐of‐abuse. This article compares the effect of near infrared wavelengths, 785 nm, using both benchtop and portable instrumentation and benchtop 1064 nm on the Raman spectra of seized drugs‐of‐abuse, including cocaine hydrochloride, cocaine freebase (crack), methylenedioxymethamphetamine (‘ecstasy’), amphetamine, diamorphine (heroin) and cannabis. The significant benefit of using 1064 nm for the interrogation of this type of sample is highlighted. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
36.
Michael D. Hargreaves Kristian Page Tasnim Munshi Richard Tomsett Gary Lynch Howell G. M. Edwards 《Journal of Raman spectroscopy : JRS》2008,39(7):873-880
The rapid identification for drugs‐of‐abuse in airports is of critical importance. In this study we demonstrate the viability of Raman spectroscopy for the rapid identification of illicit substances in their containers in an airport environment. Raman spectra of drugs‐of‐abuse in situ were collected using portable Raman spectrometers; this technique offers distinct advantages to government agencies, first responders and forensic scientists working in the security field. We have demonstrated that the spectrometers are able to collect the spectra of suspect powders, including cocaine HCl and d‐amphetamine sulphate with unknown constituents rapidly and with a high degree of discrimination. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
37.
Sayan Sarkar Dr. Piyali Sarkar Sandip Munshi Prof. Pradyut Ghosh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(25):7307-7314
Selectivity of aryl iodo over ethynyl iodo toward the Suzuki cross coupling reaction is explored by utilizing a palladium complex of amino-ether heteroditopic macrobicycle. Subsequently, unreacted ethynyl iodide undergoes homocoupling reaction in the same catalytic atmosphere, thereby representing a cascade dual C−C coupling reaction. Furthermore, this approach is extended for novel one-pot synthesis of unsymmetrical 1,3-diynes. 相似文献
38.
39.
Summary The formation of red colour produced by the interaction of 4-(2-pyridylazo) resorcinol (PAR) and rare earths has been studied to determine the composition, stability and other characteristics of the chelates formed. The
max of all the chelates was found to be 515 nm atph 6.2 whereas the
max of the PAR reagent at this pH is 410 nm. The composition of the chelates was found to be 12 (metalPAR) and has been established by two different methods. The stability constant values have been calculated by three different methods. The values of logK, lies in the range of 9.2–10.4 for different rare earth chelates. The chelates are stable over a wide range of pH. A tentative suggestion has also been made for the position of the chelate ring.
Zusammenfassung Die rote Farbreaktion von 4-(2-Pyridylazo)-resorcin (PAR) mit Seltenen Erden wurde untersucht, um die Zusammensetzung, die Stabilität und andere Merkmale der dabei entstehenden Chelate zu bestimmen. Beiph 6,2 wurde das Absorptionsmaximum aller Chelate bei 515 nm, das Absorptionsmaximum von PAR bei 410 nm gefunden. Die Zusammensetzung entspricht dem Verhältnis Metall: PAR=12; sie wurde nach zwei verschiedenen Methoden ermittelt. Die Komplexkonstante wurde auf drei verschiedenen Wegen bestimmt. logK liegt bei den verschiedenen Seltenen Erdmetall-Chelaten zwischen 9,2 und 10,4. Die Chelate sind in einem weitenph-Bereich beständig. Die Lage des Chelatrings wurde erörtert.相似文献
40.
This paper reviews the contributions of analytical Raman spectroscopy to the non-destructive characterisation of biological materials of relevance to forensic science investigations, including the sourcing of resins and the identification of the biodegradation of art and archaeological artefacts. The advantages of Raman spectroscopy for non-destructive analysis are well-appreciated; however, the ability to record molecular information about organic and inorganic species present in a heterogeneous specimen at the same time, the insensitivity of the Raman scattering process to water and hydroxyl groups, which removes the necessity for sample desiccation, and the ease of illumination for samples of very small and very large sizes and unusual shapes are also apparent. Several examples are used to illustrate the application of Raman spectroscopic techniques to the characterisation of forensic biomaterials and for the preservation of cultural heritage through case studies in the following areas: wall-paintings and rock art, human and animal tissues and skeletal remains, fabrics, resins and ivories. 相似文献