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41.
This paper reports an investigation in which the performance of plain and metakaolin (MK)-modified concretes were studied
under two different curing regimes. The purpose of this study is to evaluate the effectiveness of MK in enhancing the strength
and permeation properties of concrete. MK was used to replace 0–20% of Portland cement by weight in concrete with two water-binder
(w/b) ratios of 0.35 and 0.55. The change in compressive strength, sorptivity, and chloride ingress with age at all cement
replacement levels under both air and water curing are compared with those of the control concrete. The results indicated
that the inclusion of MK greatly reduced sorptivity and chloride permeability of concrete in varying magnitudes, depending
mainly on replacement level of MK, w/b ratio, curing condition, and chloride exposure period. It was found that under the
inadequate or poor curing, MK-modified concretes suffered a more severe loss of compressive strength and permeability-related
durability than the plain concretes. 相似文献
42.
In this study, the effect of TiO2 addition as a nucleating agent on the crystallization and machinability of potassium mica and fluorapatite base glass ceramics
were investigated. Glass compositions were prepared and casted at predetermined temperatures. Differential thermal analysis
and XRD methods were applied to characterize phase precipitation sequence and identification of phases. Disc and cylindrical
shaped samples were prepared to determine microstructural and mechanical properties in terms of microhardness and machinability.
FEG-SEM was used to characterize variation of microstructural constituents depending on the amount of nucleating agent. The
results indicate that optimum microstructure and machinability can be obtained in machinable glass-ceramic by the addition
of 1 wt% TiO2 for the composition having 3:7 weight ratio of fluorapatite to potassium mica. 相似文献
43.
The spin-1 model is studied on the Bethe lattice by including the bilinear J and biquadratic K exchange interactions into the Hamiltonian. The effects of J is randomized by using a bimodal random distribution with an adjustable parameter α which allows to study the cases of ±J-model and bond-dilution. The thermal variations of the order-parameters are studied to obtain the possible phase diagrams of the model. It is found that second-order phase transitions lines separate the ordered-phases, ferromagnetic, or antiferromagnetic, from the disordered one, i.e., the paramagnetic phase. The staggered quadrupolar phase lines are also found and only seen for higher negative K values for coordination number q=4 and 6, only. The reentrant behavior is also found for some of the phase transitions lines. 相似文献
44.
Technological forecasting is a tool for organizations to develop their technology strategies. The quality of forecasting is extremely important for the accuracy of the results and in turn company future. Therefore a proper selection methodology of forecasting technique that considers the characteristics of technology and resources needed such as cost, time is essential. On the other hand, although many forecasting techniques are available, there is a high uncertainty in choosing the most appropriate technique among a set of available techniques. In this paper interval valued intuitionistic fuzzy technique for order preference by similarity to ideal solution (TOPSIS) method is proposed for the solution of technological forecasting technique selection problem. The proposed method includes seven selection criteria and twelve forecasting technique alternatives. The methodology is applied for 3D TV technology. The results revealed that Fisher Pry method is found as the most appropriate method for forecasting since it has the highest closeness coefficient. 相似文献
45.
Martin Oberringer Erhan Akman Juseok Lee Wolfgang Metzger Cagri Kaan Akkan Elif Kacar Arif Demir Hashim Abdul-Khaliq Norbert Pütz Gunther Wennemuth Tim Pohlemann Michael Veith Cenk Aktas 《Materials science & engineering. C, Materials for biological applications》2013,33(2):901-908
In-stent restenosis is a common complication after stent surgery which leads to a dangerous wall narrowing of a blood vessel. Laser assisted patterning is one of the effective methods to modify the stent surface to control cell–surface interactions which play a major role in the restenosis. In this current study, 316LS stainless steel substrates are structured by focusing a femtosecond laser beam down to a spot size of 50 μm. By altering the laser induced spot density three distinct surfaces (low density (LD), medium density (MD) and high density (HD)) were prepared. While such surfaces are composed of primary microstructures, due to fast melting and re-solidification by ultra-short laser pulses, nanofeatures are also observed as secondary structures. Following a detailed surface characterization (chemical and physical properties of the surface), we used a well-established co-culture assay of human microvascular endothelial cells and human fibroblasts to check the cell compatibility of the prepared surfaces. The surfaces were analyzed in terms of cell adherence, proliferation, cell morphology and the differentiation of the fibroblast into the myofibroblast, which is a process indicating a general fibrotic shift within a certain tissue. It is observed that myofibroblast proliferation decreases significantly on laser treated samples in comparison to non-treated ones. On the other hand endothelial cell proliferation is not affected by the surface topography which is composed of micro- and nanostructures. Such surfaces may be used to modify stent surfaces for prevention or at least reduction of restenosis. 相似文献
46.
Shu Wei Goh Michelle Akin Zhanping You Xianming Shi 《Construction and Building Materials》2011,25(1):195-200
This paper reports on the potential benefits of micro- or nano-sized materials for asphalt mixtures used on pavements, specifically when they are exposed to water or deicing solutions. Asphalt mixtures were prepared with various amount of nanoclay and/or carbon microfiber, and compacted using the Superpave? gyratory compactor. Moisture susceptibility and deicer impacts were assessed by exposing the samples to water or deicing chemicals (NaCl, MgCl2 and CaCl2), and seven freeze–thaw cycles, in a modified AASHTO T283 test. Comparisons of micro- or nano-modified asphalt mixtures exposed to deicers are made based on results of indirect tensile strength tests, which preliminarily demonstrate the great potential of using microfibers and nanoclays in asphalt mixture for improved performance. Based on the results, it was found that the addition of nanoclay and carbon microfiber would improve a mixture’s moisture susceptibility performance or decrease the moisture damage potential in most cases. The detailed effects of deicing solutions on the tensile strength of micro- or nano- modified asphalt mixture are discussed in this paper. 相似文献
47.
Serdar Kara Bülent Keskinler Elif Erhan 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(4):511-518
BACKGROUND: A biochemical oxygen demand (BOD) sensor, based on an immobilized Pseudomonas syringae in highly porous micro‐cellular polymer (MCP) in combination with a dissolved oxygen electrode, has been developed for the analysis of biodegradable organic compounds in aqueous samples. Microorganisms were immobilized in a molded MCP disk and a wastewater sample was injected into the biocomposite disk by a flow injection system. Dissolved oxygen (DO) changes as a measure of soluble BOD was read with a DO probe placed into a flow cell carrying biocatalytically activated disk. RESULTS: Optimal response of the MCP BOD sensor was obtained at pH 6.8 and 25 °C with a typical response time of 3–5 min for a 2 mm thick molded polymeric disk. The sensor showed detection linearity over the range 5–100 mg L?1 BOD5 (r2 > 0.99) at a flow rate of 0.6 mL min?1. The repeatability and reproducibility of the sensor response were found to be 3.08% and 7.77%, respectively. BOD values produced with this biosensor for various municipal and industrial wastewaters correlated well with those determined by the conventional 5‐day BOD test. CONCLUSION: This new biosensor was different from present amperometric BOD biosensor configurations in which the biocatalyst (microbial/enzymatic) is placed between cellulose and Teflon membranes installed on a DO probe. The use of a molded MCP disk coniainng microbial activity offers better stability and lifetime for commercial use in environmental monitoring. Copyright © 2008 Society of Chemical Industry 相似文献
48.
Jingyuan Xu Zengshe Liu Sevim Z. Erhan 《Journal of the American Oil Chemists' Society》2008,85(3):285-290
Hydrogels formed from biopolymers or natural sources have special advantages because they may have biodegradable and biocompatible
properties. The viscoelastic properties of a newly developed biological hydrogel made from epoxidized soybean oil (ESO) were
investigated. The material called HPESO is a hydrolytic product of polymerized ESO (PESO). HPESO exhibited viscoelastic solid
or gel behavior above 2% (wt. %) concentration at room temperature and viscous liquid behavior at 55 °C. The thermal assembly
disassembly reassembly function of the HPESO hydrogel was completely reversible. The viscoelastic properties of HPESO were
dependent on concentration. Analysis of modulus and concentration dependence and stress relaxation measurement indicated that
HPESO was a physical gel where the cross-linkers between the molecules were physical junctions. HPESO hydrogel also exhibited
fast initial recovery of its viscoelastic properties after being subjected to mechanical shear disruption. The function and
behavior of the HPESO hydrogel suggest that this biomaterial may be suitable for applications in drug delivery and scaffolds
of bioengineering and tissue engineering.
Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard
of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may
also be suitable. 相似文献
49.
Multirelational k-Anonymity 总被引:1,自引:0,他引:1
Nergiz Mehmet Ercan Clifton Christopher Nergiz Ahmet Erhan 《Knowledge and Data Engineering, IEEE Transactions on》2009,21(8):1104-1117
k-Anonymity protects privacy by ensuring that data cannot be linked to a single individual. In a k-anonymous data set, any identifying information occurs in at least k tuples. Much research has been done to modify a single-table data set to satisfy anonymity constraints. This paper extends the definitions of k-anonymity to multiple relations and shows that previously proposed methodologies either fail to protect privacy or overly reduce the utility of the data in a multiple relation setting. We also propose two new clustering algorithms to achieve multirelational anonymity. Experiments show the effectiveness of the approach in terms of utility and efficiency. 相似文献
50.