化解数字视频的技术障碍

针对安全监控系统而言,主要任务就是需要一种低成本方式,实现在几小时、几天、几周乃至几个月的时间里实现视频影像的传输、存储以及搜索.就此,随着关键技术的不断发展,安全监控行业正经历着重大技术提升.     

Holographic polymer dispersed liquid crystals (HPDLCs) containing triallyl isocyanurate monomer

The morphology and corresponding performance of holographic polymer dispersed liquid crystals (HPDLCs) based on thiol-ene polymer are dependent on a number of factors including the gel point conversion of the polymer, polymerization kinetics, and extent of liquid crystal (LC) phase separation. Previous research of HPDLC reflection gratings made from thiol-allyl ether polymer indicates that increasing polymerization rate in systems with moderate gel point conversion can improve diffraction efficiency (DE). This work examines HPDLC reflection gratings that contain the ene monomer triallyl isocyanurate (TATATO). In HPDLCs, thiol-TATATO polymerization is two times faster than the thiol-ene polymerization of triallyl ether. By substituting TATATO for triallyl ether, the LC droplet size within HPDLC reflection gratings decreases from 100 nm to 25 nm. The dramatic reduction in LC droplet size for thiol-TATATO HPDLCs increases baseline transmission from 55% in thiol-triallyl ether HPDLCs to 90% at 450 nm. Unfortunately, the DE of thiol-TATATO HPDLCs is only approximately 10% due to poorly defined lamellae in the grating morphology. As determined with real-time IR (RTIR) spectroscopy, thiol-TATATO HPDLCs have significantly faster LC demixing kinetics in comparison to thiol-allyl ether HPDLCs. During holographic photopolymerization, the increased rate of LC demixing causes formation of LC droplets throughout the grating. The low DE of thiol-TATATO HPDLCs can be improved by mixing TATATO and allyl ether monomer. The morphology of ternary thiol-ene HPDLC formulations containing TATATO and allyl ether has a well-defined grating structure due to increased LC solubility in the system, an average LC droplet size of 50 nm, and baseline transmission of nearly 85% at 450 nm.     

Tandem Chemoselective 1,2‐/1,4‐Migration of the Thio Group in Keto Thioesters: An Efficient Approach to Substituted Butenolides

We report herein an efficient and mechanistically unique tandem chemoselective 1,2‐/1,4‐migration of the thio group in keto thioesters that provides substituted butenolides in moderate to excellent yields. Thus, α‐keto thioesters in the presence of stabilized phosphonate carbanions undergo tandem 1,2‐sulfur migration; whereas 1,4‐migration of the thio group has been achieved with the same thioesters after the treatment with Wittig reagents followed by BF₃⋅OEt₂‐catalyzed tandem reaction. The crossover experiments and the isolation of intermediates reveal a stepwise mechanism for both of these transformations.

     

A new open-framework zinc arsenate [C4N3H16]2[Zn5(AsO4)4(HAsO4)2]

A three-dimensional zinc arsenate with an interrupted zeolitic framework (?IIO), [C₄N₃H₁₆]₂[Zn₅(AsO₄)₄(HAsO₄)₂], I has been synthesized solvothermally. The structure is built up from ZnO₄, AsO₄ and HAsO₄ tetrahedral units connected alternatively through their vertices forming the 3-D structure possessing one-dimensional channels bound by 10 T-atoms (T = Zn, As). The framework density of the structure is 10.4 T-atoms which indicates considerable openness in its structure.     

Simulation Based Investigation of Triple Heterojunction TFET (THJ-TFET) for Low Power Applications

Silicon - We designed a new model tunnel field-effect transistor (TFET) based on Triple Heterojunction Tunnel Field Effect Transistor (THJ-TFET) is investigated and designed in this paper. This...     

Effective Suppression of Conducted Electro Magnetic Interference in DC-DC Boost Converter Using Field Programmable Gate Array Based Chaotic Pulse Width Modulation Switching

Abstract—In recent years, electro-magnetic interference on DC-DC converters is seen as serious problem as it limits the capability of the DC-DC converter. It is popular to use analog circuits to suppress electro-magnetic interference; however, a cheap analog circuit suffers from numerous drawbacks, including inaccurate pulse generation, carrier frequency limitation, and degraded performance due to aging. Conversely, high-performance digital circuits are capable of providing accurate pulses compared to analog circuits. In this article, a field-programmable gate array is used to generate accurate chaotic pulse-width modulation pulses for DC-DC converters. A spread spectrum technique based on randomized carrier frequency modulation with fixed duty ratio is proposed for gating pulse generation, implemented using a field-programmable gate array for electro-magnetic interference suppression. A hardware prototype is built in the laboratory for the proposed method and tested. The performance of the proposed method estimated through simulation study is validated via experimental results.     

Experimental and economic analysis of energy storage-based single-slope solar still with hollow-finned absorber basin

The paucity of drinking water is an alarming glitch across the globe. The conversion of available seawater into drinking water by utilizing renewable energy is the best way to surmount this challenge. Desalination through solar still is one of the notable, monetary, and viable processes among various desalination approaches. The current research aims to augment the potable water yield of single-slope solar still by using a hollow-finned absorber basin inserted into paraffin wax—phase change material (PCM). The effect of hollow-finned absorber basin on the yield of solar still is investigated separately, with and without PCM, and compared with the results of conventional solar still (CSS). In the first set of experiments, the CSS and solar still with a hollow-finned absorber basin without PCM (SSHF) are investigated. In the second set of experiments, the CSS and solar still with a hollow-finned absorber basin inserted into PCM (SSHFP) are investigated. The experimental results reported that the CSS is having almost the same yield on the 2 days of testing. The yield of SSHF and SSHFP is increased by 15.7% and 52.4%, respectively, when compared with CSS. The results of the economic analysis proved that the payback period and cost per liter of freshwater produced from SSHFP are comparatively better than SSHF and CSS.     

Electricity generation using solar parabolic dish system with thermoelectric generator—An experimental investigation

The present electricity grid installation cost as well as the tariff is quite high in India, particularly remote rural areas, to electrify houses. These problems can be easily solved by installing standalone systems that operate on one of the clean energy sources such as solar energy. An experimental analysis of generating electricity from a thermoelectric generator (TEG) powered by a solar parabolic dish concentrator device with aperture area and focal length of 12.6 m² and 2.42 m, respectively, is presented in this article. A TEG is made up of a thermoelectric module connected to a flat receiver by an absorber layer. The studies were carried out in Indian climatic conditions at the National Institute of Technology, Puducherry. Over a spectrum of beam radiation, the system's maximum energy conversion efficiency, as well as efficient electrical output, are evaluated and presented. The proposed system's average effective electrical efficiency is 0.424%, corresponding to the TEG's average energy conversion efficiency of 2.76%.     

Evaluation of the Loading Characteristics of the EPA WINS PM2.5 Separator

The loading characteristics of the USEPA Well Impactor Ninety Six (WINS) PM_2.5 separator was an important design consideration during the separator's development. In recognition that all inertial separators eventually overload, the loading surface of the WINS was designed to be easily accessible, replaceable, and cleanable. Prior to promulgation of the method, the loading capacity of the WINS separator was evaluated by measuring its performance after repeated loading with laboratory-generated, high concentration, coarse-mode aerosol. For this purpose, a low flow rate loading wind tunnel was designed and constructed to artificially create coarse mode aerosols composed of Arizona Test Dust. This controlled test atmosphere was sampled by the PM_2.5 reference method sampling train, as specified in 40 CFR Part 50, Appendix L, at total aerosol mass concentrations averaging 332     

Quality Mapping and Positioning of Sev—A Deep Fat Fried Snack

“Sev,” savory prepared from chickpea flour is a popular snack item for its appealing flavor and texture. Mapping and positioning of market samples consisting different varieties like Small (S1, S2, S3), Medium (M1, M2, M3), and Big (B1, B2, B3, B4) were carried out using principal component analysis. Samples were subjected to sensory profiling resulting in small variety samples were crisper compared to other varieties. Texture measurement indicated breaking strength was higher in big variety samples. Color analysis showed significant difference in L*, a*, and b* values. Principal component analysis results indicated that S1 and S2 were associated with crispness, uniform texture, and typical fried oil aroma. Commercially available sev samples were significantly different in their quality parameters, which was indicated by the study. Study showed that small variety (S3) had the highest overall quality among all the samples, which also had high sensory scores for crispness.