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721.
Tris-(8-hydroxyquinoline) metal complex Znq2, used as light-emitting layer in electroluminescent (EL) devices was synthesized and optical properties of as-deposited Znq2 in thin films were studied. Interesting phenomenon was observed while studying the ageing and degradation behavior of Znq2 films and consequently a stable form having strong blue photoluminescence (peak 465 nm) was discovered. This converted (from green to blue emitting) film has higher molecular packing density and comparable photoluminescence intensity with Znq2 film. Here, we report on the production of this blue material under controlled conditions and its optical properties.The thin films have been deposited by thermal evaporation on quartz and silicon substrates. The optical constants (n and k) of green Znq2 film and converted (to blue) thin films have been determined using spectroscopic ellipsometry. Environment induced effects on optical properties of films have been studied using ellipsometry, photoluminescence and UV–vis transmission measurements. 相似文献
722.
Float glass has immense applications such as sensor glass, micro-processor glass and decorative glass; because of its exceptional wear resistance, chemical and thermal characteristics. Nevertheless, researchers are still bearing decisive issues, which affect its application. These issues are profile inaccuracy and chipping because of its poor machining characteristics and hence high precision machining. The objective of the present study is to condemn the chipping related hindrances while using multi-shaped diamond abrasive tools to create blind holes. The tools, which applied, are named as hollow abrasive tool, pinpointed conical tool, flat cylindrical tools and concave circular tool. The experimental trials were performed by rotary ultrasonic drilling (RUD) and CNC conventional drilling (CD). The actual industrial conditions and parameters were considered throughout the experimentation. Physics behind the formation of chipping on hole periphery by RUD and CD are revealed. In addition, individual mechanisms of multi-shape tools with respect to chipping are analyzed. The results show that RUD process has attained the smallest measurement of chip radial distance as compared to CD for all types of tool. Finally, the concave circular tool is found as the best tool particularly to get least chip radial distance during drilling i.e. 0.1145?mm. 相似文献
723.
Cover Picture: Acetylcholine Promotes Binding of α‐Conotoxin MII at α3β2 Nicotinic Acetylcholine Receptors (ChemBioChem 3/2014) 下载免费PDF全文
724.
Vivek P. Khare Alan R. Greenberg Stephen S. Kelley Heidi Pilath Il Juhn Roh Jeff Tyber 《应用聚合物科学杂志》2007,105(3):1228-1236
Whereas cellulose‐derived polymers are routinely used as membrane materials, the cellulose polymer itself is not directly used to synthesize dense/porous films for membrane applications. Recently, N‐methylmorpholine N‐oxide (NMMO) and dimethylacetamide (DMAc)/lithium chloride (LiCl) have been successfully employed for dissolving unmodified cellulose. This provides a strong rationale for reexamining the possibility of cellulose membrane fabrication using these solvents. By judiciously selecting solvents, casting conditions, and solvent exchange steps, we successfully synthesized dense/asymmetric‐porous cellulose films. The pore size and porosity of the porous films decreased systematically with increasing cellulose concentration. SEM analysis of the cross sections revealed an asymmetric skinned structure with monotonically increasing pore size away from the skin. The measured pore diameters were in the range 1.8–4.8 μm. Mechanical testing indicated that the dense films possessed tensile properties comparable to those of cellulose acetate (CA) films. Though nitrogen permeability values were comparable for cellulose and CA dense films, cellulose film permeability depended upon the type of drying protocol employed. Overall, these results demonstrate that processability need not be a constraint in the use of cellulose polymer for membrane fabrication. In selected applications, cellulose membranes could become a cost‐effective, environmentally friendly alternative to other more commonly employed membrane polymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 相似文献
725.
Mechanical micromachining is increasingly finding applications in fabrication of components in various fields, such as, biomedical devices, optics, electronics, medicine, communications and avionics. In order to ensure adequate functionality, there are stringent requirements for form and finish in case of biomedical devices like cochlear implants and metallic optics. This necessitates that the post machined surface must be burr free. To address these issues in micromachining, this paper presents results of an experimental study to investigate the influence of main process parameters i.e. speed, feed rate, depth of cut, tool diameter and number of flutes on the formation of the various types of burrs i.e. exit burrs and top burrs produced during micro-end milling operation. The experiments performed using Taguchi method shows that three types of burr formation mechanisms prevail during micro-end milling operations; these are: lateral deformation of material, bending and tearing of the chip. Also, three types of burrs were observed include: Poisson burr, rollover burr in down milling and tear burr in up milling. Further, it is observed that the depth of cut and the tool diameter are the main parameters, which influence the burr height and thickness significantly. However, the speed and the feed rate have small to negligible effect on the burr thickness and height. Besides the experimental analysis, the paper presents an analytical model to predict the burr height for exit burr. The model is built on the geometry of burr formation and the principle of continuity of work at the transition from chip formation to burr formation. Note that prediction of burr height in micro-end milling is extremely challenging due to the complex geometry of material removal and microstructural effects encountered during cutting at that length scales. The model fares well and the prediction errors range between 0.65 and 25%. 相似文献
726.
ABSTRACTIn this present paper, an experimental study is carried out on a single cylinder, four-stroke variable compression ratio (VCR), direct injection diesel engine to analyse the performance characteristics of 20% karanja oil (B20) with diethyl ether, methanol and ethanol as an additives by substituting 5% and 10%, respectively. The engine is operated at the speed of 1500 rpm with VCRs 17 and 18. Analysis of performance parameters such as brake power, indicated power, brake thermal efficiency, mechanical efficiency, specific fuel consumption and indicated thermal efficiency are arrived by the IC engine analysis software which has been coupled with the VCR engine. The outcome data of these blends are to be compared with the ordinary diesel. The results are optimised by using the design of experiments (DOE) method in MINITAB 17.0 software to find out the suitable blend for the engine. 相似文献
727.
Yuqi Guo Rodney Chua Yingqian Chen Yi Cai Ernest Jun Jie Tang J. J. Nicholas Lim Thu Ha Tran Vivek Verma Ming Wah Wong Madhavi Srinivasan 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(29):2207133
Rechargeable aqueous Zn/S batteries exhibit high capacity and energy density. However, the long-term battery performance is bottlenecked by the sulfur side reactions and serious Zn anode dendritic growth in the aqueous electrolyte medium. This work addresses the problem of sulfur side reactions and zinc dendrite growth simultaneously by developing a unique hybrid aqueous electrolyte using ethylene glycol as a co-solvent. The designed hybrid electrolyte enables the fabricated Zn/S battery to deliver an unprecedented capacity of 1435 mAh g−1 and an excellent energy density of 730 Wh kg−1 at 0.1 Ag−1. In addition, the battery exhibits capacity retention of 70% after 250 cycles even at 3 Ag−1. Moreover, the cathode charge–discharge mechanism studies demonstrate a multi-step conversion reaction. During discharge, the elemental sulfur is sequentially reduced by Zn to S2− (, forming ZnS. On charging, the ZnS and short-chain polysulfides will oxidize back to elemental sulfur. This electrolyte design strategy and unique multi-step electrochemistry of the Zn/S system provide a new pathway in tackling both key issues of Zn dendritic growth and sulfur side reactions, and also in designing better Zn/S batteries in the future. 相似文献
728.