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101.
Anindya Chakraborty Arun K. Majumdar Shamik Sural 《International Journal of Information Security》2010,9(1):51-67
Even state of the art database protection mechanisms often fail to prevent occurrence of malicious attacks. Since in a database
environment, the modifications made by one transaction may affect the execution of some of the later transactions, it leads
to spreading of the damage caused by malicious (bad) transactions. Following traditional log-based recovery schemes, one can
rollback (undo) the effect of all the transactions, both malicious as well as non-malicious. In such a scenario, even the
unaffected transactions are also rolled back. In this paper, we propose a column dependency-based approach to identify the
affected transactions which need to be compensated along with the malicious transactions. To ensure durability, committed
non-malicious transactions are then re-executed in a manner that retains database consistency. We present a static recovery
algorithm as well as an on-line version of the same and prove their correctness. A detailed performance evaluation of the
proposed scheme with TPC-C benchmark suite is also presented. 相似文献
102.
Novel sol-gel derived calcium phosphate coatings on Mg4Y alloy 总被引:1,自引:0,他引:1
Abhijit RoySatish S. Singh Moni Kanchan DattaBoeun Lee J. OhodnickiPrashant N. Kumta 《Materials Science and Engineering: B》2011,176(20):1679-1689
Calcium phosphates (CaPs) and silicon containing calcium phosphates (Si-CaPs) coatings on a biodegradable magnesium yttrium alloy (Mg4Y) were prepared by a sol-gel technique to improve the bioactivity of the alloy surface. The experimental results show that thick porous coatings comprised of nano-sized calcium phosphate particles can be prepared by heating the as dip coated substrates at 450 °C. The in vitro degradation results show that the coatings do not alter the degradation kinetics of the substrates significantly and the release of magnesium and yttrium ions at initial time points was very similar for both the coated and bare substrates. The cyto-compatibility studies using MC3T3-E1 osteoblasts show that the coated substrates were more bioactive than the uncoated substrates as the cells begin to grow and form a matrix on the coated substrates more easily than on the bare metal. These preliminary results collectively show the potential of use of sol-gel derived calcium phosphate coatings on magnesium based degradable scaffolds to improve their surface bioactivity. 相似文献
103.
P. Monash Abhijit Majhi Dr G. Pugazhenthi 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2010,85(4):545-554
BACKGROUND: Ceramic membranes have received more attention than polymeric membranes for the separation and purification of bio‐products owing to their superior chemical, mechanical and thermal properties. Commercially available ceramic membranes are too expensive. This could be overcome by fabricating membranes using low‐cost raw materials. The aim of this work is to fabricate a low‐cost γ‐Al2O3–clay composite membrane and evaluate its potential for the separation of bovine serum albumin (BSA) as a function of pH, feed concentration and applied pressure. To achieve this, the membrane support is prepared using low‐cost clay mixtures instead of very expensive alumina, zirconia and titania materials. The cost of the membrane can be further reduced by preparing a γ‐alumina surface layer on the clay support using boehmite sol synthesized from inexpensive aluminium chloride instead of expensive aluminium alkoxide using a dip‐coating technique. RESULTS: The pore size distribution of the γ‐Al2O3‐clay composite membrane varied from 5.4–13.6 nm. The membrane was prepared using stable boehmite sol of narrow particle size distribution and mean particle size 30.9 nm. Scanning electron microscopy confirmed that the surface of the γ‐Al2O3–clay composite membrane is defect‐free. The pure water permeability of the support and the composite membrane were found to be 4.838 × 10?6 and 2.357 × 10?7 m3 m?2 s?1 kPa?1, respectively. The maximum rejection of BSA protein was found to be 95%. It was observed that the separation performance of the membrane in terms of flux and rejection strongly depends on the electrostatic interaction between the protein and charged membrane. CONCLUSION: The successively prepared γ‐Al2O3‐clay composite membrane proved to possess good potential for the separation of BSA with high yield and could be employed as a low cost alternate to expensive ceramic membranes. Copyright © 2009 Society of Chemical Industry 相似文献
104.
105.
This work presents the absorptance of high-temperature superconducting YBa2Cu3O7-delta (YBCO) films, deposited on Si substrates, in the far infrared from 15 to 95 cm - 1 (wavelength from 667 to 105 mu m) at temperatures of 100, 200, and 300 K (i.e., in the normal state). Our experiments show a significant difference in the absorptance for radiation incident on the film side as compared to radiation incident on the substrate side. Interference fringes associated with the Si substrate are observed from the measurement and used to analyze the interaction of radiation with the film - substrate composite at the interface. The film thickness is found to have a strong effect on the absorptance of the film - substrate composite, especially for radiation incident on the substrate side. 相似文献
106.
R. S. Dutta S. Majumdar P. K. Limaye U. D. Kulkarni G. K. Dey 《Transactions of the Indian Institute of Metals》2011,64(1-2):31-36
Ni-Cr-Fe based superalloy 690 substrate, pack aluminized at 1273 K, revealed formation of multilayer comprising (NiCr)Al + Cr5Al8, Ni2Al3 + Cr5Al8, NiAl and γ phases. Knoop hardness number varied from 225 to 1142 along the cross-section. Wear and friction tests on aluminized specimen were performed in dry medium using reciprocating sliding wear and friction machine with tungsten carbide ball at 15 N load with frequencies at 10, 15 and 20 Hz. The coefficient of friction, the static ones were obtained in the vicinity of 0.2, 0.3 and 0.5, while dynamic ones were 0.3, 0.4 and 0.4 respectively. For the ball, the wear rate was 1.9 × 10?6, 1.2 × 10?5 and 1.5 × 10?5 mm3/Nm, whereas the wear rate was 5.8 × 10?5, 3.8 × 10?4 and 4.6 × 10?4 mm3/Nm respectively for the aluminized specimen indicating good adherent surface coating. 相似文献
107.
Polycrystalline undoped and indium-doped CdS0.2Se0.8 thin films were deposited on FTO-coated glass substrates by spray pyrolysis. The cell configurations CdS0.2Se0.8/1 M (Na2S + S + NaOH)/C and In:CdS0.2Se0.8/1 M (Na2S + S + NaOH)/C were used to study a wide range of photoelectrochemical characteristics including capacitance–voltage in the dark, current–voltage characteristics in the dark and under illumination, photovoltaic power output and spectral response and to perform electrochemical impedance spectroscopy studies. The study reveals that the films exhibit n-type conductivity. Various PEC parameters such as the junction ideality factor under illumination, series and shunt resistances, fill factor and efficiency have been estimated for the PEC cells formed with CdS0.2Se0.8 and indium-doped CdS0.2Se0.8 thin films. The efficiency and fill factor of these PEC cells are found to be improved from 0.79% and 0.46 to 2.12% and 0.49, respectively, with indium doping in CdS0.2Se0.8 thin films. Electrochemical impedance spectroscopy studies show that doping of indium into CdS0.2Se0.8 thin film improves the performance of resulting PEC cells. 相似文献
108.
Anton V. Polotai Tae-Hee Jeong Gai-Ying Yang Elizabeth C. Dickey Clive A. Randall Pascal Pinceloup Abhijit S. Gurav 《Journal of Electroceramics》2009,23(1):6-12
Multilayer ceramic capacitors based on BaTiO3 dielectric compositions and Ni inner electrodes have complex interfacial reactions that impact the continuity of the inner
electrode microstructure. Previously we demonstrated that through the addition of Cr to Ni, a significant improvement in the
continuity of ultra-thin Ni electrodes in Ni–BaTiO3 multilayer capacitors could be achieved. Here, the effect of the Cr addition to the nickel electrode pastes is studied with
regard to the electrical properties. Low-field electrical measurements demonstrate no major differences between Cr doped Ni
and undoped Ni. However, high-field measurements show a significant decrease to the total capacitor resistance. Under a critical
electrical bias the conductivity significantly increases due to a Fowler–Nordheim tunneling conduction though the interfacial
Schottky barrier at the dielectric–electrode interface; the onset voltage of this conduction is much lower than with the undoped
nickel. Based on these results, we evaluate criteria for the selection of an appropriate refractory metal in order to improve
the Ni electrode continuity. 相似文献
109.
Summary The drag experienced in a micropolar fluid is investigated by considering uniform streaming past a flat plate. Some recent results on the fundamental solution of the Oseenlinearization of the micropolar flow equations are used to reduce the problem to that of solving a scalar integral equation. The integral equation is analyzed by the application of both asymptotic and variational methods. Results indicate that the drag experienced in a micropolar fluid always exceeds that found in the absence of any micropolarity; however one of the parameters which characterizes a micropolar fluid can be used to minimize the drag.With 2 Figures 相似文献
110.
The lung is comprised of about 40 different cell types, of which only 15% are type II cells. These are the major, if not the sole, source of synthesis and secretion of lung surfactant. To date a large number of methods have been described for the isolation of pure populations of type II cells using a wide variety of techniques, but most of these have employed differential centrifugation methods and have used adult rodents. The present study reports the isolation of type II cells from fetal rabbit lungs by the immunoglobin G plating method. Pure populations of fetal type II cells in high yield and with good viability were obtained by the procedure for the first time from rabbit fetal tissue. 相似文献