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排序方式: 共有238条查询结果,搜索用时 453 毫秒
71.
72.
Wenhua Yu David M. France David S. Smith Dileep Singh Elena V. Timofeeva Jules L. Routbort 《International Journal of Heat and Mass Transfer》2009,52(15-16):3606-3612
Heat transfer experiments were performed with a water-based nanofluid containing 170-nm silicon carbide particles at a 3.7% volume concentration and having potential commercial viability. Heat transfer coefficients for the nanofluid are presented for Reynolds numbers ranging from 3300 to 13,000 and are compared to the base fluid water on the bases of constant Reynolds number, constant velocity, and constant pumping power. Results were also compared to predictions from standard liquid correlations and a recently altered nanofluid correlation. The slip mechanisms of Brownian diffusion and thermophoresis postulated in the altered correlation were investigated in a series of heating and cooling experiments. 相似文献
73.
74.
Spatial logics have been proposed to reason locally and modularly on algebraic models of distributed systems. In this paper
we define the spatial equational logic A
π
L whose models are processes of the applied π-calculus. This extension of the π-calculus allows term manipulation and records communications as aliases in a frame, thus augmenting the predefined underlying
equational theory. Our logic allows one to reason locally either on frames or on processes, thanks to static and dynamic spatial
operators. We study the logical equivalences induced by various relevant fragments of A
π
L, and show in particular that the whole logic induces a coarser equivalence than structural congruence. We give characteristic
formulae for some of these equivalences and for static equivalence. Going further into the exploration of A
π
L’s expressivity, we also show that it can eliminate standard term quantification. 相似文献
75.
76.
Nanomaterials are promising candidates to improve the delivery efficiency and control of active agents such as DNA or drugs directly into cells. Here we demonstrate cell-culture platforms of nanotemplated "nanostraws" that pierce the cell membrane, providing a permanent fluidic pipeline into the cell for direct cytosolic access. Conventional polymeric track-etch cell culture membranes are alumina coated and etched to produce fields of nanostraws with controllable diameter, thickness, and height. Small molecules and ions were successfully transported into the cytosol with 40 and 70% efficiency, respectively, while GFP plasmids were successfully delivered and expressed. These platforms open the way for active, reproducible delivery of a wide variety of species into cells without endocytosis. 相似文献
77.
Measured values of process variables are subject to measurement noise. The presence of measurement noise can result in detuned controllers in order to prevent excessive adjustments of manipulated variables. Digital filters, such as exponentially weighted moving average (EWMA) and moving average (MA) filters, are commonly used to attenuate measurement noise before controllers. In this article, we present another approach, a dynamic data reconciliation (DDR) filter. This filter employs discrete dynamic models that can be phenomenological or empirical, as constraints in reconciling noisy measurements. Simulation results for a storage tank and a distillation column under PI control demonstrate that the DDR filter can significantly reduce propagation of measurement noise inside control loops. It has better performance than the EWMA and MA filters, so that the overall performance of the control system is enhanced. 相似文献
78.
The presence of measurement bias and random noise significantly deteriorates the information quality of plant data. Data reconciliation techniques for steady-state processes have been widely applied to processing industries to improve the accuracy and precision of the raw measurements. This paper develops an algorithm for simultaneous bias correction and data reconciliation for dynamic processes. The algorithm considers process model error as an important contributing factor in the estimation of the measurement bias and process state variables. It employs black-box models for the process as would be done when phenomenological models are difficult or impractical to obtain. Simulation results of a distillation column demonstrated that this algorithm effectively compensates constant and non-constant measurement biases yielding much improved reconciled values of process variables. It has computational advantages over previously proposed algorithms based on non-linear dynamic data reconciliation because an analytical solution is available when using linear process models to approximate the process. 相似文献
79.
Jiun-Chan John V. Dale Jules L. Dileep Prabir K. 《Sensors and actuators. B, Chemical》2008,131(2):448-454
Simultaneous measurement of total NOx and O2 using two electrochemical methods are demonstrated using metal/metal oxide internal oxygen reference electrode-based sensors at high temperatures. The Pd/PdO-containing reference chamber was sealed within a stabilized zirconia superstructure by a high pressure/temperature plastic deformation bonding method exploiting grain boundary sliding between the ceramic components. Amperometric and potentiometric NOx sensing devices were assembled on the outside of the sensor. Pt-loaded zeolite Y was used to obtain total NOx capability. Both the amperometric and potentiometric type sensors showed total NOx response, with the potentiometric device showing better NOx/O2 signal stability and lower NOx–O2 cross-interference. Since these sensors do not require plumbing for reference air, there is more flexibility in the placement of such sensors in a combustion stream. 相似文献
80.
This paper provides an overview of current electric energy consumption of full-scale municipal MBR installations based on literature review and case studies. Energy requirements of several MBRs were linked to operational parameters and reactor performance. Total and specific energy consumption data were analysed on a long-term basis with special attention given to treated flow, design capacity, membrane area and effluent quality. The specific energy consumption of an MBR system is dependent on many factors, such as system design and layout, volume of treated flow, membrane utilization and operational strategy. Operation at optimal flow conditions results in a low specific energy consumption and energy efficient process. Energy consumption of membrane related modules was in the range of 0.5-0.7 kWh/m(3) and specific energy consumption for membrane aeration in flat sheet (FS) was 33-37% higher than in a hollow fibre (HF) system. Aeration is a major energy consumer, often exceeding 50% share of total energy consumption. In consequence, coarse bubble aeration applied for continuous membrane cleaning remains the main target for energy saving actions. Also, a certain potential for energy optimization without immediate danger of affecting the quality of the produced effluent was observed. 相似文献