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排序方式: 共有257条查询结果,搜索用时 234 毫秒
31.
Shaik Jeelani 《Wear》1981,68(2):191-202
A review of various techniques employed in measuring cutting temperatures is presented and it is pointed out that the method of IR photography is certainly better than other techniques for the accurate measurement of the temperature distribution in the cutting region. The thermal sensitivity of high speed IR film has increased significantly in the past two decades. It is now possible to use IR photography for measuring cutting temperatures without preheating the workpiece and the cutting tool.Temperature measurements in the surface region of annealed 18% Ni maraging steel were made at cutting speeds of 80 and 160 ft min?1. It was observed that the temperature is very high at the surface and decreases with depth beneath the surface. The cutting temperature increases with an increase in the wear land or dullness of the tool. 相似文献
32.
Avula Edukondalu T. Sripathi Shaik Kareem Ahmmad Syed Rahman K. Sivakumar 《Journal of Electronic Materials》2017,46(2):808-816
Glass with compositions xK2O-(30 ? x)Li2O-10WO3-60B2O3 for 0 ≤ x ≤ 30 mol.% have been prepared using the normal melt quenching technique. The optical reflection and absorption spectra were recorded at room temperature in the wavelength range 300–800 nm. From the absorption edge studies, the values of the optical band gap (E opt) and Urbach energy (ΔE) have been evaluated. The values of E opt and ΔE vary non-linearly with composition parameter, showing the mixed alkali effect. The dispersion of the refractive index is discussed in terms of the single oscillator Wemple Di-Domenico model. 相似文献
33.
We present a MMI-based photonic crystal all-optical logic gate structure for logic functions such as XNOR, XOR, OR and NAND with square-type lattice of Si rods in air host. Phase-based logic inputs produce intensity-based logic outputs with high contrast ratio. The calculated ON to OFF contrast ratio for the logic functions XNOR/XOR and OR/NAND is 40.41 and 37.40 dB, respectively. Further, it is improved by 11.53 and 12.46% for XNOR/XOR and OR/NAND logic functions, respectively, by reducing the back reflection with the introduction of absorbing waveguides. The structure in both the forms has a fast response period that is less than or equal to 0.131 ps. The size of the structure is quite compact with dimension \(6.4\,\upmu \hbox {m} \times 8.8\,\upmu \hbox {m}\). 相似文献
34.
Function Follows Form: Correlation between the Growth and Local Emission of Perovskite Structures and the Performance of Solar Cells 下载免费PDF全文
M. Ibrahim Dar Alexander Hinderhofer Gwenole Jacopin Valentina Belova Neha Arora Shaik Mohammed Zakeeruddin Frank Schreiber Michael Grätzel 《Advanced functional materials》2017,27(26)
Understanding the relationship between the growth and local emission of hybrid perovskite structures and the performance of the devices based on them demands attention. This study investigates the local structural and emission features of CH3NH3PbI3, CH3NH3PbBr3, and CH(NH2)2PbBr3 perovskite films deposited under different yet optimized conditions using X‐ray scattering and cathodoluminescence spectroscopy, respectively. X‐ray scattering shows that a CH3NH3PbI3 film involving spin coating of CH3NH3I instead of dipping is composed of perovskite structures exhibiting a preferred orientation with [202] direction perpendicular to the surface plane. The device based on the CH3NH3PbI3 film composed of oriented crystals yields a relatively higher photovoltage. In the case of CH3NH3PbBr3, while the crystallinity decreases when the HBr solution is used in a single‐step method, the photovoltage enhancement from 1.1 to 1.46 V seems largely stemming from the morphological improvements, i.e., a better connection between the crystallites due to a higher nucleation density. Furthermore, a high photovoltage of 1.47 V obtained from CH(NH2)2PbBr3 devices could be attributed to the formation of perovskite films displaying uniform cathodoluminescence emission. The comparative analysis of the local structural, morphological, and emission characteristics of the different perovskite films supports the higher photovoltage yielded by the relatively better performing devices. 相似文献
35.
Habibuddin Shaik S. N. Rachith K. J. Rudresh Abdul Sattar Sheik K. H. Thulasi Raman P. Kondaiah G. Mohan Rao 《Journal of Polymer Research》2017,24(3):35
This work aimed towards the study on variations in the percentage of β-phase in Poly vinylidene fluoride (PVDF) thin films deposited by spin coating technique. PVDF is a semi-crystalline polymer which exhibits α, β, γ and δ polymorphs. Among these polymorphs, generally it crystallizes in a non-polar α-phase, which is of little importance as far as its applications are concerned. However, the β-phase, which exhibits spontaneous polarity created tremendous interest and showed a path towards the devices based on its pyro- and piezoelectric properties. Fourier Transform Infrared (FTIR) spectroscopy and XRD techniques were used to study the percentage of formation of β-phase in spin coated PVDF thin films at different processing conditions viz. spin rotation speed (rpm), solution concentration and annealing temperature. We identified the β-phase percentage in PVDF thin films, which are (i) Deposited with different rotation speeds ranging from 1000 to 9000 rpm, (ii) Annealed at different temperatures viz.; room temperature to 100C, and (iii) Deposited at various solution concentrations. It is identified that percentage of formation of β-phase is high in the films deposited with 15(w/v)% solution concentration which is annealed at 100C. The films deposited at higher rpm is showing low enhancement in the β-phase with annealing temperature. 相似文献
36.
Snaith HJ Humphry-Baker R Chen P Cesar I Zakeeruddin SM Grätzel M 《Nanotechnology》2008,19(42):424003
The solar to electrical power conversion efficiency for dye-sensitized solar cells (DSCs) incorporating a solid-state organic hole-transporter can be over 5%. However, this is for devices significantly thinner than the optical depth of the active composites and by comparison to the liquid electrolyte based DSCs, which exhibit efficiencies in excess of 10%, more than doubling of this efficiency is clearly attainable if all the steps in the photovoltaic process can be optimized. Two issues are currently being addressed by the field. The first aims at enhancing the electron diffusion length by either reducing the charge recombination or enhancing the charge transport rates. This should enable a larger fraction of photogenerated charges to be collected. The second, though less actively investigated, aims to improve the physical composite formation, which in this instance is the infiltration of mesoporous TiO(2) with the organic hole-transporter 2,2',7,7'-tetrakis(N,N-di-p-methoxypheny-amine)-9,9'-spirobifluorene (spiro-MeOTAD). Here, we perform a broad experimental study to elucidate the limiting factors to the solar cell performance. We first investigate the charge transport and recombination in the solid-state dye-sensitized solar cell under realistic working conditions via small perturbation photovoltage and photocurrent decay measurements. From these measurements we deduce that the electron diffusion length near short-circuit is as long as 20?μm. However, at applied biases approaching open-circuit potential under realistic solar conditions, the diffusion length becomes comparable with the film thickness, ~2?μm, illustrating that real losses to open-circuit voltage, fill factor and hence efficiency are occurring due to ineffective charge collection. The long diffusion length near short-circuit, on the other hand, illustrates that another process, separate from ineffective charge collection, is rendering the solar cell less than ideal. We investigate the process of TiO(2) mesopore infiltration with spiro-MeOTAD by examining the cross-sectional images of and performing photo-induced absorption spectroscopy on devices with a range of thickness, infiltrated with spiro-MeOTAD with a range of concentrations. We present our interpretation of the mechanism for material infiltration, and by improving the casting conditions demonstrate efficient charge collection through devices of over 7?μm in thickness. This investigation represents an improvement in our understanding of the limiting factors to the dye-sensitized solar cell. However, much work, focused on composite formation and improved kinetic competition, is required to realize the true potential of this concept. 相似文献
37.
Shadab Md Nabil A. Alhakamy Waleed S. Alharbi Javed Ahmad Rasheed A. Shaik Ibrahim M. Ibrahim Javed Ali 《International journal of molecular sciences》2021,22(24)
In the present work, novel modality for lung cancer intervention has been explored. Primary literature has established the potential role of cyclooxygenase-2 (COX-2) inhibitor in regression of multiple forms of carcinomas. To overcome its poor water solubility and boost anticancer activity, etoricoxib (ETO) was chosen as a therapeutic candidate for repurposing and formulated into a nanoemulsion (NE). The prepared ETO loaded NE was characterized for the surface charge, droplet size, surface morphology, and in vitro release. The optimized ETO loaded NE was then investigated for its anticancer potential employing A549 lung cancer cell line via cytotoxicity, apoptotic activity, mitochondrial membrane potential activity, cell migration assay, cell cycle analysis, Caspase-3, 9, and p53 activity by ELISA and molecular biomarker analysis through RT-PCR test. The developed ETO-NE formulation showed adequate homogeneity in the droplet size distribution with polydispersity index (PDI) of (0.2 ± 0.03) and had the lowest possible droplet size (124 ± 2.91 nm) and optimal negative surface charge (−8.19 ± 1.51 mV) indicative of colloidal stability. The MTT assay results demonstrated that ETO-NE exhibited substantial anticancer activity compared to the free drug. The ETO-NE showed a substantially potent cytotoxic effect against lung cancer cells, as was evident from the commencement of apoptosis/necrotic cell death and S-phase cell cycle arrests in A549 cells. The study on these molecules through RT-PCR confirmed that ETO-NE is significantly efficacious in mitigating the abundance of IL-B, IL-6, TNF, COX-2, and NF-kB as compared to the free ETO and control group. The current study demonstrates that ETO-NE represents a feasible approach that could provide clinical benefits for lung cancer patients in the future. 相似文献
38.
Kuang D Klein C Snaith HJ Moser JE Humphry-Baker R Comte P Zakeeruddin SM Grätzel M 《Nano letters》2006,6(4):769-773
A Li+ coordinating sensitizer, NaRu(4-carboxylic acid-4'-carboxylate)(4,4'-bis[(triethylene glycol methyl ether) methyl ether]-2,2'-bipyridine)(NCS)2 (coded as K51), has been synthesized, and the effect of Li+ coordination on its performance in mesoscopic titanium dioxide dye-sensitized solar cells has been investigated. Fourier transform infrared spectra suggest that Li+ coordinates to the triethylene oxide methyl ether side chains on the dye molecules. With the addition of Li+ to a nonvolatile liquid electrolyte, we observe a significant increase in the photocurrent density, with only a small decrease in the open-circuit voltage, contrary to a non ion coordinating dye which displays a large drop in potential with the addition of Li+. For a solar cell incorporating an organic hole-transporter, we find the potential rises with increasing the Li+ concentration in the hole-transporter matrix. For the liquid electrolyte and solid-state cells, we obtain power conversion efficiencies of 7.8% and 3.8%, respectively, under simulated sunlight. 相似文献
39.
Yuanxin Zhou Mahesh Hosur Shaik Jeelani P. K. Mallick 《Journal of Materials Science》2012,47(12):5002-5012
In this study, dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and flexural tests were performed on unfilled,
1, 2, 3, and 4 wt% clay filled SC-15 epoxy to identify the effect of clay weight fraction on thermal and mechanical properties
of the epoxy matrix. The flexural results indicate that 2.0 wt% clay filled epoxy showed the highest improvement in flexural
strength. DMA studies also revealed that 2.0 wt% system exhibit the highest storage modulus and T
g as compared to neat and other weight fraction. However, TGA results show that thermal stability of composite is insensitive
to the clay content. Based on these results, the nanophased epoxy with 2 wt% clay was then utilized in a vacuum assisted resin
transfer molding set up with carbon fabric to fabricate laminated composites. The effectiveness of clay addition on thermal
and mechanical properties of composites has been evaluated by TGA, DMA, tensile, flexural, and fatigue test. 5 °C increase
in glass transition temperature was found in nanocomposite, and the tensile and flexural strengths improved by 5.7 and 13.5 %,
respectively as compared to the neat composite. The fatigue strength was also improved significantly. Based on the experimental
result, a linear damage model combined with the Weibull distribution function has been established to describe static failure
processing of neat and nanophased carbon/epoxy. The simulated stress–strain curves from the model are in good agreement with
the test data. Simulated results show that damage processing of neat and nanophased carbon/epoxy described by bimodal Weibull
distribution function. 相似文献
40.
Mingkui Wang Soo‐Jin Moon Mingfei Xu Kethineni Chittibabu Peng Wang Ngoc‐Le Cevey‐Ha Robin Humphry‐Baker Shaik M. Zakeeruddin Michael Grätzel 《Small (Weinheim an der Bergstrasse, Germany)》2010,6(2):319-324
The high‐molar‐extinction‐coefficient heteroleptic ruthenium dye, cis‐Ru (4,4′‐bis(5‐octylthieno[3,2‐b] thiophen‐2‐yl)‐2,2′‐bipyridine) (4,4′‐dicarboxyl‐2,2′‐bipyridine) (NCS)2, exhibits an AM 1.5 solar (100 mW cm?2)‐to‐electric power‐conversion efficiency of 4.6% in a solid‐state dye‐sensitized solar cell (SSDSC) with 2,2′, 7,7′‐tetrakis‐(N,N‐di‐p‐methoxyphenylamine)9,9′‐spirobifluorene (spiro‐MeOTAD) as the organic hole‐transporting material. These SSDSC devices exhibit good durability during accelerated tests under visible‐light soaking for 1000 h at 60 °C. This demonstration elucidates a class of photovoltaic devices with potential for stable and low‐cost power generation. The electron recombination dynamics and charge collection that take place at the dye‐sensitized heterojunction are studied by means of impedance and transient photovoltage decay techniques. 相似文献