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排序方式: 共有582条查询结果,搜索用时 62 毫秒
41.
The interconnected, molecular sized pores of microporous materials as well as of nonporous materials are of great interest for absorption, separation and catalytic applications because of their large accessible surface area. Swift heavy ion (SHI) irradiation is a useful technique for the physical and chemical modifications of the polymers. To obtain calibrated pores in cylindrical shape the etching rate along the tracks should be essentially higher than the etching rate of undamaged polymer. Multiple pores, due to overlapping of the pores and inhomogeneous pore distribution, may arise due to high pore density and non-uniform target thickness. The shape of the pores in the polymers is affected by the conditions of chemical etching used for enlarging the latent track. It is well-established that pore size is the determining parameter for hydrogen storage as well as for nanofiltration. Slow positron beam in addition to Doppler Broadening Spectroscopy (DBS) is a useful technique to evaluate the nanoporosity of polymers. 相似文献
42.
An improved method for the synthesis of 3,4-dihydropyrimidinones by one pot cyclocondensation of aldehyde, β-dicarbonyl compound
and urea with significant enhancement in reaction rates using room temperature ionic liquid [bmim] BF4 immobilized Cu(acac)2 as recyclable catalytic system is described. 相似文献
43.
Suman Roy Janardan Misra Indranil Saha 《Software Testing, Verification and Reliability》2016,26(8):548-571
We revisit the problem of real‐time verification with dense‐time dynamics using timeout and calendar‐based models and simplify this to a finite state verification problem. We introduce a specification formalism for these models and capture their behaviour in terms of semantics of timed transition systems. We discuss a technique, which reduces the problem of verification of qualitative temporal properties on infinite state space of a large fragment of these timeout and calender‐based transition systems into that on clock‐less finite state models through a two‐step process comprising of digitization and finitary reduction. This technique enables us to verify safety invariants for real‐time systems using finite state model checking avoiding the complexity of infinite state (bounded) model checking and scale up models without applying techniques from induction‐based proof methodology. In the same manner, we verify timeliness properties. Moreover, we can verify liveness for real‐time systems, which are not possible by using induction with infinite state model checkers. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
44.
K.A. Dubey C.V. Chaudhari S.K. Suman N. Raje R.K. Mondal V. Grover S. Murali Y.K. Bhardwaj L. Varshney 《Polymer Composites》2016,37(3):756-762
Flexible lead‐free high energy radiation shielding material was developed through internal compounding. Polymer‐filler interaction, crosslinking density, specific gravity, physicomechanical characteristics, percentage attenuation, and thermal stability of the crosslinked composites were estimated. It was found that even at very high filler loading composites can be crosslinked; however, the crosslinking density was composition dependent and was highest in 10–50 wt% loading range at 100 kGy and 200 kGy. The Nielsen model was applied to understand the micromechanics of the system. Attenuation of gamma radiation from Am241 was not affected by the crosslinking density. Thermal stability of the composites was found to be significantly affected with bismuth oxide loading. POLYM. COMPOS., 37:756–762, 2016. © 2014 Society of Plastics Engineers 相似文献
45.
Patwari Neal Croft Jessica Jana Suman Kasera Sneha K. 《Mobile Computing, IEEE Transactions on》2010,9(1):17-30
Secret keys can be generated and shared between two wireless nodes by measuring and encoding radio channel characteristics without ever revealing the secret key to an eavesdropper at a third location. This paper addresses bit extraction, i.e., the extraction of secret key bits from noisy radio channel measurements at two nodes such that the two secret keys reliably agree. Problems include 1) nonsimultaneous directional measurements, 2) correlated bit streams, and 3) low bit rate of secret key generation. This paper introduces high-rate uncorrelated bit extraction (HRUBE), a framework for interpolating, transforming for decorrelation, and encoding channel measurements using a multibit adaptive quantization scheme which allows multiple bits per component. We present an analysis of the probability of bit disagreement in generated secret keys, and we use experimental data to demonstrate the HRUBE scheme and to quantify its experimental performance. As two examples, the implemented HRUBE system can achieve 22 bits per second at a bit disagreement rate of 2.2 percent, or 10 bits per second at a bit disagreement rate of 0.54 percent. 相似文献
46.
Dajun Yuan Rui Guo Yaguang Wei Wenzhuo Wu Yong Ding Zhong Lin Wang Suman Das 《Advanced functional materials》2010,20(20):3484-3489
A simple two‐step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm2, with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA‐patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site‐selective growth of the ZnO nanowires. The method demonstrates high application potential for wafer‐scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices. 相似文献
47.
T. R. Vijaybabu T. Ramesh Suman Pandipati Sujit Mishra G Sridevi C Pradeep Raja Rhoda Afriyie Mensah Oisik Das Manjusri Misra Amar Mohanty Karthik Babu NB 《大分子材料与工程》2023,308(7):2300001
The lifespan and the performance of flexible electronic devices and components are affected by the large accumulation of heat, and this problem must be addressed by thermally conductive polymer composite films. Therefore, the need for the development of high thermal conductivity nanocomposites has a strong role in various applications. In this article, the effect of different particle reinforcements such as single and hybrid form, coated and uncoated particles, and chemically treated particles on the thermal conductivity of various polymers are reviewed and the mechanism behind the improvement of the required properties are discussed. Furthermore, the role of manufacturing processes such as injection molding, compression molding, and 3D printing techniques in the production of high thermal conductivity polymer composites is detailed. Finally, the potential for future research is discussed, which can help researchers to work on the thermal properties enhancement for polymeric materials. 相似文献
48.
Alessandro Bedini Valentina Zanolli Sandro Zanardi Ugo Bersellini Enrico Dalcanale Michele Suman 《Food Analytical Methods》2013,6(1):17-27
The food industry has a direct interest into bitter-tasting substances either for the identification of negative off-flavors or for the monitoring of a desired organoleptic quality. A rapid technique, based on Fourier transform-near infrared (FT-NIR) spectroscopy and able to detect taste molecular markers in bakery commodities, was developed, focusing the attention on biscuits category. Xanthines (caffeine, theobromine, and theophylline) and polyphenols (catechins and epicathechins), considered as mainly responsible for the bitter-taste of coffee\cocoa\chocolate based products, were firstly checked using a confirmatory liquid chromatography (LC)-ESI\mass spectrometry (MS)-MS procedure after hot methanol–water extraction. Correspondent data were used for the calibration of the FT-NIR through PLS regression. Values of the standard errors of prediction (lower than 10 %) were comparable to the values of the standard errors of cross-validation. Coefficients of determination indicated a good predictive power in the calibration model (R 2 xanthines?=?0.97, R 2 polyphenols?=?0.96) and a satisfying discriminating power among different contents in the validation models (R 2 xanthines?=?0.96, R 2 polyphenols?=?0.96). A testing phase on the generated model was executed by a comparison of LC-MS and sensory panel data with FT-NIR responses recorded on unknown biscuits: differences between found and predicted levels were generally below 5 % and the best predictability was achievable in chocolate-based biscuits. This methodology is able to work directly on solid products, has the potential to be expanded on other categories of gustative molecular markers (like sugars) and can be conceived as applicable for a routine control of a standardized bitter taste quality in a real industrial production. 相似文献
49.
Conoidal shells are very popular roofing units owing to their aesthetic elegance and stiffness. Many parts of the globe, which were earlier assumed to be seismologically stable, are now being considered as earthquake prone. Hence the necessity to build light structures using composites has become very important. In this paper an eight-noded isoparametric shell element is applied for analyzing the bending behavior of delaminated composite conoidal shells under a uniformly distributed load with different practical boundary conditions. To ensure compatibility of deformation and equilibrium of forces and moments at the delamination crack front, a multipoint constraint algorithm is incorporated, which leads to an unsymmetrical stiffness matrix. This formulation is validated through the solution of benchmark problems. Lamination, curvature, and extent of delamination area are varied to compare the performances of delaminated conoidal shells against those with no damage. The results are carefully observed, and a set of conclusions is presented at the end of the paper. 相似文献
50.
Development of a Liposome Based Contraceptive System for Intravaginal Administration of Progesterone 总被引:2,自引:0,他引:2
Sanjay K. Jain Ranjit Singh Balram Sahu 《Drug development and industrial pharmacy》1997,23(8):827-830
Progesterone bearing liposomes were prepared by the cast film method and characterized for various physical attributes. The liposomes could encapsulate nearly 98% of the drug. The progesterone bearing liposomes were incorporated into polyacrylamide gel and the drug content was determined. The in vitro drug dqfusion across she-goat vaginal membrane from the liposomal formulation was found to follow near zero order kinetics. The progestational activity of liposomal and control gel was assessed by monitoring the effect on the formation of corpora lutea. It was observed that both the formulations inhibit the formation of corpora lutea and thus, exhibited progestationul activity but the efsect of liposomal preparation was found to be greater and prolonged as compare to control gel. 相似文献