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121.
S. Bandyopadhyay Hina Gokhale J.K. Sarin Sundar G. Sundararajan S.V. Joshi 《Optics and Lasers in Engineering》2005,43(2):11
The numerous unique advantages afforded by pulsed Nd:YAG laser systems have led to their increasing utility for producing high aspect ratio holes in a wide range of materials. Notwithstanding the growing industrial acceptance of the technique, the increasingly tighter geometrical tolerances and more stringent hole quality requirements of modern industrial components demand that “defects” such as taper, recast, spatter etc., in laser-drilled holes are minimized. Process parameters like pulse energy, pulse repetition rate, pulse duration, focal position, nozzle standoff, type of gas and gas pressure of the assist gas are known to significantly influence hole quality during laser drilling. The present study reports the use of Taguchi design of experiments technique to study the effects of the above process variables on the quality of the drilled holes and ascertain optimum processing conditions. Minimum taper in the drilled hole was considered as the desired target response. The entire study was conducted in three phases:(a) screening experiments, to identify process variables that critically influence taper in laser drilled holes, (b) Optimization experiments, to ascertain the set of parameters that would yield minimum taper and (c) validation trials, to assess the validity of the experimental procedures and results. Results indicate that laser drilling with focal position on the surface of the material being drilled and employing low level values of pulse duration and pulse energy represents the ideal conditions to achieve minimum taper in laser-drilled holes. Thorough assessment of results also reveals that the laser-drilling process, optimized considering taper in the drilled hole as the target response, leads to very significant improvements in respect of other hole quality attributes of interest such as spatter and recast as well. 相似文献
122.
Abdul S. Khan Hina Khalid Zenab Sarfraz Maria Khan Jibran Iqbal Nawshad Muhammad 《应用光谱学评论》2017,52(6):507-540
Recently, significant advancement has occurred in vibrational (Fourier transform infrared [FTIR] and Raman) spectroscopy associated with dental materials. FTIR and Raman spectroscopies have emerged as significant breakthrough techniques and offer exciting new possibilities in the area of dental materials. These techniques have been used to obtain chemical images of formulations and allow researchers to find out the in situ structure of materials. This review summarizes the information obtained from these two techniques and their application in dental material sciences. The presented database of vibrational spectroscopy facilitated the appropriate identification of frequently used dental materials ranging from filling, obturating, adhesive, lining/luting materials, and prosthodontics materials. Spectral peaks that are related to these materials are discussed in detail, which provided crucial data in understanding the chemical structural properties. The application of vibrational spectroscopy allowed for a quick differential identification of typical dental materials composed of organic and inorganic compounds. From our study as well as the literature reviewed, it appeared that investigators uniformly confirmed the benefits of vibrational spectroscopy concerning identification of chemical functional groups of different chemical compositions. The diagnostic and prognostic tools based on these technologies have the potential to revolutionize our concepts leading to improve materials sciences and clinical application. 相似文献
123.
S. HINA M.MUSTAFA T. HAYAT F. E. ALSAADI 《应用数学和力学(英文版)》2014,35(1):73-84
" Analysis is performed to study the slip effects on the peristaltic flow of non-Newtonian fluid in a curved channel with wall properties. The resulting nonlinear partial differential equations are transformed to a single ordinary differential equation in a stream function by using the assumptions of long wavelength and low Reynolds number. This differential equation is solved numerically by employing the built-in routine for solving nonlinear boundary value problems (BVPs) through the software Mathematica. In addition, the analytic solutions for small Deborah number are computed with a regular perturbation technique. It is noticed that the symmetry of bolus is destroyed in a curved channel. An intensification in the slip effect results in a larger magnitude of axial velocity. Further, the size and circulation of the trapped boluses increase with an increase in the slip parameter. Different from the case of planar channel, the axial velocity profiles are tilted towards the lower part of the channel. A comparative study between analytic and numerical solutions shows excellent agreement. 相似文献
124.
We determine the fundamental iron oxide high solubility mechanism that drives a new electrolytic pathway to iron production, and eliminates a major CO(2) emission source, for example it is produced using wind and solar energy, in a molten carbonate electrolyte, at a high rate and a low electrolysis energy. 相似文献
125.
Muhammad Haleem Khan Syed Manzoor Hussain Bukhari Akbar Ali Khurram Liaqat Srosh Fazal 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(1):113-119
A simple, sensitive and efficient spectrophotometric method is proposed for rapid determination of uranium using arsenazo-III
in perchloric acid. The reaction between arsenazo-III and U(VI) was instantaneous in 3 mol L−1 HClO4.
N-cetyl-N,N,N-trimethylammonium bromide was used for increasing the sensitivity and selectivity of the complex. The absorbance remains
stable for over 48 h in the presence of surfactant. The method allows the determination of uranium in the range of 1–20 μg g−1 with a molar absorptivity of 3.9 × 105 dm3 mol−1 cm−1 at 681 nm. Sandell’s sensitivity of the complex was calculated to be 6.4 ng cm−2 at λmax 681 nm. A significant enhancement was achieved in the sensitivity of the proposed method whereas, Relative Standard Deviation
was reduced from 4.5 to 1.7% in the presence of surfactant. Among various diverse ions studied, fluoride, cyanide, citrate,
sulfate and phosphate interfere beyond the tolerance limit. Among cations only Cr3+ and Co2+ decreased the normal absorbance. The validity of the reported method was tested by determining uranium in the environmental
water samples and Standard Reference Material. The results agreed closely with the reported values. The proposed method is
new, easy in operation and better in sensitivity than many of the existing methods. 相似文献
126.
Ashraf Ali Sarah Alharthi Bashir Ahmad Alia Naz Idrees Khan Fazal Mabood 《Molecules (Basel, Switzerland)》2021,26(22)
The adsorptive removal of lead (II) from aqueous medium was carried out by chemically modified silica monolith particles. Porous silica monolith particles were prepared by the sol-gel method and their surface modification was carried out using trimethoxy silyl propyl urea (TSPU) to prepare inorganic–organic hybrid adsorbent. The resultant adsorbent was evaluated for the removal of lead (Pb) from aqueous medium. The effect of pH, adsorbent dose, metal ion concentration and adsorption time was determined. It was found that the optimum conditions for adsorption of lead (Pb) were pH 5, adsorbent dose of 0.4 g/L, Pb(II) ions concentration of 500 mg/L and adsorption time of 1 h. The adsorbent chemically modified SM was characterized by scanning electron microscopy (SEM), BET/BJH and thermo gravimetric analysis (TGA). The percent adsorption of Pb(II) onto chemically modified silica monolith particles was 98%. An isotherm study showed that the adsorption data of Pb(II) onto chemically modified SM was fully fitted with the Freundlich and Langmuir isotherm models. It was found from kinetic study that the adsorption of Pb(II) followed a pseudo second-order model. Moreover, thermodynamic study suggests that the adsorption of Pb(II) is spontaneous and exothermic. The adsorption capacity of chemically modified SM for Pb(II) ions was 792 mg/g which is quite high as compared to the traditional adsorbents. The adsorbent chemically modified SM was regenerated, used again three times for the adsorption of Pb(II) ions and it was found that the adsorption capacity of the regenerated adsorbent was only dropped by 7%. Due to high adsorption capacity chemically modified silica monolith particles could be used as an effective adsorbent for the removal of heavy metals from wastewater. 相似文献
127.
Yanan Zhang Junlei Chen Fazal Razq Chenyang Su Xuehan Hou Wenhuan Huang Huabin Zhang 《中国化学》2023,41(1):75-82
Metal organic frameworks have been employed as high-performance layered double hydroxide (LDH) composite supercapacitor electrode materials but have shown unsatisfactory redox ability and stability. Herein, a host-guest CuMo-based polyoxometalate-based metal organic framework (POMOF) with copious electrochemically active sites and strong electrochemical redox activities has been effectively coupled with POM-incorporated CoNi-LDH to develop a nanocomposite (NENU-5@CoNi-LDH) by a simple solvothermal method. The designed electrode shows a high specific capacity of 333.61 mAh·g–1 at 1 A·g–1. In addition, the novel hybrid symmetric supercapacitor NENU-5@CoNi-LDH/active carbon (AC) demonstrated a high energy density of 80.8 Wh·kg–1 at a power density of 750.7 W·kg–1. Interestingly, the nanocomposite of NENU-5@CoNi-LDH exhibits an outstanding capacitance retention of 79% after 5000 charge-discharge cycles at 10 A·g–1. This work provides a new strategy and will be the backbone for future energy storage research. 相似文献
128.
Mohammad Z. Rahman Fazal Raziq Huabin Zhang Jorge Gascon 《Angewandte Chemie (International ed. in English)》2023,62(48):e202305385
Transition metal oxides (TMOs) were one of the first photocatalysts used to produce hydrogen from water using solar energy. Despite the emergence of many other genres of photocatalysts over the years, TMO photocatalysts remain dominant due to their easy synthesis and unique physicochemical properties. Various strategies have been developed to enhance the photocatalytic activity of TMOs, but the solar-to-hydrogen (STH) conversion efficiency of TMO photocatalysts is still very low (<2 %), which is far below the targeted STH of 10 % for commercial viability. This article provides a comprehensive analysis of several widely used strategies, including oxygen defects control, doping, establishing interfacial junctions, and phase-facet-morphology engineering, that have been adopted to improve TMO photocatalysts. By critically evaluating these strategies and providing a roadmap for future research directions, this article serves as a valuable resource for researchers, students, and professionals seeking to develop efficient energy materials for green energy solutions. 相似文献