排序方式: 共有71条查询结果,搜索用时 0 毫秒
61.
Dorman SC O'Brien RA Lewis AT Salter EA Wierzbicki A Hixon PW Sykora RE Mirjafari A Davis JH 《Chemical communications (Cambridge, England)》2011,47(32):9072-9074
A boronium-based paraquat analog undergoes reductions at more negative potentials than paraquat itself, making it a promising building block for electroactive materials. 相似文献
62.
Iraj Mohammadpoor‐Baltork Ahmad Reza Khosropour Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Mohammad Soltani Arsalan Mirjafari 《Journal of heterocyclic chemistry》2011,48(6):1419-1427
An efficient method for the synthesis of a series of 2,3‐disubstituted‐2,3‐dihydroquinazolin‐4(1H)‐ones is described via one‐pot condensation reaction of isatoic anhydride, aryl aldehydes, and primary amines using a Brønsted acidic ionic liquid, [Hmim][NO3], as a catalyst and medium. The present protocol enjoys convenient reaction and simple work‐up, greenness, short reaction times, and reusable catalyst as well as mild reaction conditions. J. Heterocyclic Chem., (2011). 相似文献
63.
We present a pore-scale network model of two- and three-phase flow in disordered porous media. The model reads three-dimensional pore networks representing the pore space in different porous materials. It simulates wide range of two- and three-phase pore-scale displacements in porous media with mixed-wet wettability. The networks are composed of pores and throats with circular and angular cross sections. The model allows the presence of multiple phases in each angular pore. It uses Helmholtz free energy balance and Mayer–Stowe–Princen (MSP) method to compute threshold capillary pressures for two- and three-phase displacements (fluid configuration changes) based on pore wettability, pore geometry, interfacial tension, and initial pore fluid occupancy. In particular, it generates thermodynamically consistent threshold capillary pressures for wetting and spreading fluid layers resulting from different displacement events. Threshold capillary pressure equations are presented for various possible fluid configuration changes. By solving the equations for the most favorable displacements, we show how threshold capillary pressures and final fluid configurations may vary with wettability, shape factor, and the maximum capillary pressure reached during preceding displacement processes. A new cusp pore fluid configuration is introduced to handle the connectivity of the intermediate wetting phase at low saturations and to improve model’s predictive capabilities. Based on energy balance and geometric equations, we show that, for instance, a gas-to-oil piston-like displacement in an angular pore can result in a pore fluid configuration with no oil, with oil layers, or with oil cusps. Oil layers can then collapse to form cusps. Cusps can shrink and disappear leaving no oil behind. Different displacement mechanisms for layer and cusp formation and collapse based on the MSP analysis are implemented in the model. We introduce four different layer collapse rules. A selected collapse rule may generate different corner configuration depending on fluid occupancies of the neighboring elements and capillary pressures. A new methodology based on the MSP method is introduced to handle newly created gas/water interfaces that eliminates inconsistencies in relation between capillary pressures and pore fluid occupancies. Minimization of Helmholtz free energy for each relevant displacement enables the model to accurately determine the most favorable displacement, and hence, improve its predictive capabilities for relative permeabilities, capillary pressures, and residual saturations. The results indicate that absence of oil cusps and the previously used geometric criterion for the collapse of oil layers could yield lower residual oil saturations than the experimentally measured values in two- and three-phase systems. 相似文献
64.
Here Darcy–Forchheimer 3D stretching flow of nanoliquid in the presence of convective condition and homogeneous–heterogeneous reactions is analyzed. Impacts of thermophoresis, Brownian diffusion and zero nanoparticles mass flux condition are considered. Adequate transformation procedure give rise to system in terms of ordinary differential equations. The governing mathematical system has been tackled by optimal homotopic technique. Graphical results have been presented for temperature and concentration dsitributions. Numerical benchmark is provided to study the values of skin friction coefficients and local Nusselt number. Skin friction coefficients are declared increasing functions of porosity and Forchheimer parameters. Furthermore the local Nusselt number is reduced for larger values of porosity and Forchheimer parameters. 相似文献
65.
Arsalan Wares 《International Journal of Mathematical Education in Science & Technology》2019,50(2):315-321
These notes discuss several related propositions in geometry that can be explored in a dynamic geometry environment. The propositions involve an unexpected property of quadrilaterals. 相似文献
66.
Arsalan Wares Iwan Elstak 《International Journal of Mathematical Education in Science & Technology》2019,50(5):800-805
The purpose of these notes is to provide examples of large-scale geometry problems that have the potential to promote constructive struggling in high-school geometry classrooms. These problems are suitable for being explored in a dynamic geometry environment. The notes also contain brief sketches of solutions to the two problems. 相似文献
67.
Arsalan Wares 《International Journal of Mathematical Education in Science & Technology》2018,49(3):437-441
These notes discuss several related problems in geometry that can be explored in a dynamic geometry environment. The problems involve an interesting property of hexagons. 相似文献
68.
Syed Arsalan Jawed Davide Cattin Nicola Massari Massimo Gottardi Andrea Baschirotto 《Analog Integrated Circuits and Signal Processing》2011,67(3):395-405
A single-package digital MEMS Capacitive Microphone (MCM) system is presented. The system consists of a MCM, which is wire-bonded
with its readout interface (RI). The MCM sensor is fabricated using a combination of surface and bulk micromachining, employing
diaphragm-stiffening to achieve piston-like diaphragm-movement and attaining required sensitivity with a smaller diaphragm-area.
The RI is designed in 0.35 μm CMOS and it consists of a preamplifier (PAMP), a sigma-delta modulator (SDM), integrated biasing
and digital control, converting the MCM capacitive variations into a single-bit over-sampled digital bitstream. The PAMP employs
a two-terminal bootstrapped source-follower buffer to make the readout insensitive to the MCM parasitics, subsequently feeding
a third-order single-loop single-bit modulator running at 2.5 MHz. The electrical measurements of the standalone RI demonstrate
55 dB A-weighted @ 1 Pa SNDR at the analog PAMP output and 80 dB A-weighted dynamic-range at the digital output, which corresponds
to a conversion range from 40 to 120 dB SPL. The SNDR for acoustic measurements is 33 dB A-weighted @ 1 Pa, limited by the
higher MCM thermal noise floor and reduced sensitivity (−53 dB V @ 1 Pa). The frequency characterization of the system for
the complete audio-band demonstrates the effect of the system package towards higher frequencies (>9 kHz), giving rise to
Helmholtz resonance, and reduction in sensitivity for low-frequencies (<400 Hz) because of acoustic short-circuiting inside
the MCM due to flow-by slots. The complete system consumes 460 μA of total current for a 1.8 V single-supply. The total system
dimensions are 4.5 × 2 mm2 (excluding the package), demonstrating the viability of a low-area, low-power and high dynamic-range implementation of digital
MCM. 相似文献
69.
Shamim A. Arsalan M. Roy L. Shams M. Tarr G. 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2008,55(7):643-647
70.
Syed Arsalan Jawed Junaid Ali Qureshi Moaaz Ahmed Atia Shafique Abdul Hameed Waqar Ahmed Qureshi Muhammad Irfan Kazim 《Analog Integrated Circuits and Signal Processing》2012,73(1):273-289
This paper presents a low-noise and high dynamic-range CMOS readout-IC (ROIC) for a 64?×?64 array of opto-electrical sensors. The readout chain comprises a pixel preamplifier array, correlated-double-sampling based switched-capacitor gain blocks, class-AB output buffer for driving off-chip loads and a 12-bit pipeline ADC for on-chip digitization. The pixel preamplifiers array, occupying an area of 30???m?×?30???m per pixel, can either be hybridized to a separate IR or UV sensor or can be used as monolithic visible-light active CMOS pixel-array after exposing (by etching the pad) the embedded photodiode under the bonding pads. The ROIC is designed and fabricated in 0.25???m 1P/5?M CMOS technology with 5?mm?×?5?mm of total dimensions. The integrated readout chain, in integrate-then-read mode, demonstrates a dynamic range of 72?dB for electrically emulated sensor currents from 25?pA to 100?nA. It can support a frame rate of 700?fps, with single fully-differential analog as well as 12-bit digital output, at 10?MHz while consuming 17?mW with on-chip biases. 相似文献