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991.
R. Krishna D. Velmurugan S. Shanmuga Sundara Raj H.‐K. Fun P. C. Srinivasan 《Crystal Research and Technology》2001,36(11):1295-1301
The title compound crystallizes in monoclinic system with space group P21 /n. The cell parameters are a = 12.3824(3) Å, b = 8.9255(1) Å, c = 19.9188(4) Å, V = 2181.75(7) Å3 , α = γ = 90.0° and β = 97.663(1)°. The structure has an indole moiety and an imidazolidine ring connected together. The phenyl sulfonyl group is attached to the indole moiety and the dichlorophenyl ring to the imidazolidine ring. The structure has a C‐H … Cl intra molecular hydrogen bond and C‐H … π type intermolecular interactions. 相似文献
992.
Motor fans used for cooling electric motors have long been recognized as one of the major noise sources. Current paper focuses on design of motor fan for electric motors that are used in submarines for pumping sea water. Noise reduction at source is very important and the critical task, for under water applications. An attempt has been made for reduction of motor fan noise by modification of noise sources. For this purpose computational fluid dynamics and computational aeroacoustics code FLUENT package is used to identify the noise sources and to know the overall sound pressure level of motor fan. From these results it is observed that aerodynamic noise is the dominate fan noise source. Aerodynamic noise of motor fan can be reduced by modifying fan geometry. The aerodynamic noise level of motor fan has been reduced by replacing the straight blades with various digits of NACA (National Advisory Committee for Aeronautics) 65 series airfoil sections. From the numerical results it is observed that the minimum sound pressure level for NACA 65-010 is 65.4 dB(A). These numerical results are compared with measurements in a semi-anechoic chamber. It is found that there is good agreement between numerical and experimental results. 相似文献
993.
Koduru Hajarathaiah Murali Krishna Enduri Satish Anamalamudi Tatireddy Subba Reddy Srilatha Tokala 《Entropy (Basel, Switzerland)》2022,24(5)
Computing influential nodes gets a lot of attention from many researchers for information spreading in complex networks. It has vast applications, such as viral marketing, social leader creation, rumor control, and opinion monitoring. The information-spreading ability of influential nodes is greater compared with other nodes in the network. Several researchers proposed centrality measures to compute the influential nodes in a complex network, such as degree, betweenness, closeness, semi-local centralities, and PageRank. These centrality methods are defined based on the local and/or global information of nodes in the network. However, due to their high time complexity, centrality measures based on the global information of nodes have become unsuitable for large-scale networks. Very few centrality measures exist that are based on the attributes between nodes and the structure of the network. We propose the nearest neighborhood trust PageRank (NTPR) based on the structural attributes of neighbors and nearest neighbors of nodes. We define the measure based on the degree ratio, the similarity between nodes, the trust values of neighbors, and the nearest neighbors. We computed the influential nodes in various real-world networks using the proposed centrality method. We found the maximum influence by using influential nodes with SIR and independent cascade methods. We also compare the maximum influence of our centrality measure with the existing basic centrality measures. 相似文献
994.
The Raman spectra of 2-fluoroacetamide, trifluoroacetamide and 2-iodoacetamide were recorded and their infrared spectra as mulls were measured in the range 4000–200 cm−1. The Fourier transform far-infrared spectra of the same samples, in the region 500–50 cm−1, were also obtained. The frequencies were assigned to various fundamental modes of the molecules on the basis of qualitative considerations. 相似文献
995.
Enhanced Photocatalytic Performance of ZnO Nanorods Coupled by Two‐Dimensional α‐MoO3 Nanoflakes under UV and Visible Light Irradiation
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Prof. Da‐Ren Hang Krishna Hari Sharma Prof. Chun‐Hu Chen Sk Emdadul Islam 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(36):12777-12784
We exploit the utilization of two‐dimensional (2D) molybdenum oxide nanoflakes as a co‐catalyst for ZnO nanorods (NRs) to enhance their photocatalytic performance. The 2D nanoflakes of orthorhombic α‐MoO3 were synthesized through a sonication‐aided exfoliation technique. The 2D MoO3 nanoflakes can be further converted to substoichiometric quasi‐metallic MoO3?x by using UV irradiation. Subsequently, 1D–2D MoO3/ZnO NR and MoO3?x/ZnO NR composite photocatalysts have been successfully synthesized. The photocatalytic performances of the novel nanosystems in the decomposition of methylene blue are studied by using UV‐ and visible‐illumination setup. The incorporated 2D nanoflakes show a positive influence on the photocatalytic activity of the ZnO. The obtained rate constant values follow the order of pristine ZnO NR<MoO3/ZnO NR<MoO3?x/ZnO NR composites. The enhancement of the photocatalytic efficiency can be ascribed to a fast charge carrier separation and transport within the heterojunctions of the MoO3/ZnO NRs. In particular, the best photocatalytic performance of the MoO3?x/ZnO NR composite can be additionally attributed to a quasi‐metallic conductivity and substoichiometry‐induced mid‐gap states, which extend the light absorption range. A tentative photocatalytic degradation mechanism was proposed. The strategy presented in this work not only demonstrates that coupling with nanoscale molybdenum oxide nanoflakes is a promising approach to significantly enhance the photocatalytic activity of ZnO but also hints at new type of composite catalyst with extended applications in energy conversion and environmental purification. 相似文献
996.
997.
We consider the discrete versions of the well-known Borg’s theorem and use simple linear algebraic techniques to obtain new versions of the discrete Borg-type theorems. To be precise, we prove that the periodic potential of a discrete Schrödinger operator is almost a constant if and only if the possible spectral gaps of the operator are of small width. This result is further extended to more general settings and the connection to the well-known Ten Martini problem is also discussed. 相似文献
998.
Kinetics of Stripping Ni(II) from the Ni‐BTMPPA Complex/BTMPPA/Kerosene System by Sulfate‐Acetato Solution
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The kinetics of stripping of Ni2+ from a Ni‐BTMPPA complex, dissolved in a kerosene solution of BTMPPA (H2A2, Cyanex 272), by acidic sulfate‐acetato solution, was studied using the single (falling) drop technique and flux (F) method of data treatment. The empirical flux equation at 303 K is Fb (kmol/m2s) = 10?4.35 [Ni2+] (1+10?3.42 [H+]?1)?1 ([H2A2](o)0.5+2.50 [H2A2](o))?1 (1+6[SO42?]) (1+3.20 [Ac?]). Activation energy (Ea), entropy change in activation (ΔS±), and enthalpy change in activation (ΔH±) were measured under different experimental conditions. Based on the empirical flux equation, Ea and ΔS±, the mechanism of Ni2+ stripping is provided. In a low [H+] region, the stripping reaction steps appear as [NiA+] → Ni2+ + A? and [Ni(HA2)2](int) → [NiHA2]+(int) + HA2(int)? in lower and higher concentration regions of free BTMPPA, respectively, provided [SO42?] and [Ac?] are kept low. However, at higher [H+] concentrations, the stripping is under diffusion control. With increasing [SO42?] and [Ac?], the enhancement of the rate is attributed to the attack of the Ni(II) complex by SO42? or HSO4? and Ac? to form NiSO4 or NiHSO4+ and NiAc+ complexes. Negative ΔS± values indicate that the rate‐determining stripping reaction steps occur via an substitution nucleophilic, bimolecular (SN2) mechanism. 相似文献
999.
LaMaire R.O. Krishna A. Ahmadi H. 《Selected Areas in Communications, IEEE Journal on》1994,12(8):1299-1313
We analyze an efficient medium access control (MAC) protocol for use in a single cell of a wireless local area network (LAN). A fixed frame structure with two periods is used; one period for making reservations using a slotted Aloha protocol and a second period for data transmission. The MAC protocol operates in a centralized manner in which a single station, the base station, accepts reservations (transmission or data requests) that are made by the remote stations, and then schedules the times in which they will transmit or receive data. We consider two different types of client-server traffic models, an open-loop and a closed-loop model. In the open-loop model, a remote station can generate reservation requests for the base station whether or not it has received a response from the base station. In the closed-loop case, the remote station waits for a response before generating a new request. The performance of the MAC protocol was analyzed exactly for both the open and closed-loop traffic models and for cases in which transmission errors and a mean-value type of radio capture model are included. In addition, different policies were considered for the transmission strategy that is used by the remote stations when they attempt to make reservations. We derive exact results for the mean throughput and waiting times as well as for the queue length distributions. We also derive an approximate Markov chain to treat a case in which a fixed-position capture model is used. Several types of behavior are illustrated through the use of numerical examples 相似文献
1000.
To enhance the throughput of a slotted random access protocol in a radio communication system, we describe the use of a scheme
in which multiple power levels are used at the transmitters. We first consider a situation in which n transmitters are simultaneously trying to send a packet to a central receiving station using a time‐slotted access protocol,
like slotted ALOHA. Each of these transmitters randomly chooses one of m discrete power levels during each attempt to send a packet. One of the simultaneously sent packets can often be successfully
received due to the power capture effect. We consider two types of capture models: (1) one in which the transmitter with the
largest received power captures the channel, and (2) one in which the transmitter captures the channel only if its signal‐to‐interference
ratio is above some threshold when received at the central station. In this paper, we determine the optimal transmit probabilities
for the power levels as well as the optimal values of the power levels themselves, when their range is constrained and for
cases both with and without Rayleigh fading. After determining the precise optimal power levels and probabilities for maximizing
the capture probabilities (i.e., for a given n), we propose a less complex, but nearly optimal, approximate approach based on using logarithmically equi‐spaced levels.
After demonstrating the closeness of our suboptimal results to the optimal results, we apply our approach to the problem of
optimizing the throughput of the slotted ALOHA protocol for a case in which the input traffic is generated according to a
Poisson process. Several numerical examples are presented along with a demonstration of how the optimal choice of power levels
and probabilities can enhance throughput relative to previous ad hoc methodologies.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献