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931.
The empirical Complex Model developed by the US Environmental Protection Agency (EPA) is used by refiners to predict the toxic emissions of reformulated gasoline with respect to gasoline properties. The difficulty in implementing this model in the blending process stems from the implicit definition of Complex Model through a series of disjunctions assembled by the EPA in the form of spreadsheets. A major breakthrough in the refinery-based Complex Model implementation occurred in 2008 and 2010 through the use of generalized disjunctive and mixed-integer nonlinear programming (MINLP). Nevertheless, the execution time of these MINLP models remains prohibitively long to control emissions with our online gasoline blender. The first objective of this study is to present a new model that decreases the execution time of our online controller. The second objective is to consider toxic thresholds as hard constraints to be verified and search for blends that verify them. Our approach introduces a new way to write the Complex Model without any binary or integer variables. Sigmoid functions are used herein to approximate step functions until the measurement precision for each blend property is reached. By knowing this level of precision, we are able to propose an extremely good and differentiable approximation of the Complex Model. Next, a differentiable objective function is introduced to penalize emission values higher than the threshold emissions. Our optimization module has been implemented and tested with real data. The execution time never exceeded 1 s, which allows the online regulation of emissions the same way as other traditional properties of blended gasoline. 相似文献
932.
Jie Dang Farzin Fatollahi-Fard Petrus Christiaan Pistorius Kuo-Chih Chou 《Metallurgical and Materials Transactions B》2018,49(1):123-131
In this study, reaction steps of a process for synthesis of titanium oxycarbide from titanium slag were demonstrated. This process involves the reduction of titanium slag by a methane-hydrogen-argon mixture at 1473 K (1200 °C) and the leaching of the reduced products by hydrofluoric acid near room temperature to remove the main impurity (Fe3Si). Some iron was formed by disproportionation of the main M3O5 phase before gaseous reduction started. Upon reduction, more iron formed first, followed by reduction of titanium dioxide to suboxides and eventually oxycarbide. 相似文献
933.
Fuh-Der Chou Hui-Mei Wang Tzu-Yun Chang 《The International Journal of Advanced Manufacturing Technology》2009,43(7-8):810-821
This paper considers the problem of scheduling n jobs on a single machine to minimize the total weighted completion time in the presence of sequence-dependent setup times and release times. To the best of our knowledge, little research has been devoted to this scheduling problem. Therefore, we developed two exact algorithms, including a constraint programming model and a branch-and-bound method for small problems. The obtained optimal solutions can be used as a benchmark for evaluating the performance of heuristics. With the complexity in mind, two heuristics, including a best index dispatch (BID) and a modified weighted shortest processing time (MWSPT) based on non-delay concepts are also proposed for large problems. The time complexities of the two proposed heuristics are O(n 4) and O(n 3), respectively. The computational results showed that the branch-and-bound method could solve most instances with 40 jobs under the time limit of 7,200 s. The BID heuristic is superior to the MWSPT in solution quality, although both can efficiently and effectively obtain near-optimal solutions for large instances. 相似文献
934.
935.
分析了温度漂移对声表面波谐振器(SAWR)及其声表面波振荡器(SAWO)频率特性、以及对SAW加速度计测量准确性的影响,探讨了提高SAW加速度计测量准确度的方法,提出了一种基于浮动零点原理抑制温度共模干扰的双对SAWR加速度计设计方案.本方案不仅通过设置浮动零点SAWR抑制了SAWO频率-温度漂移对SAW加速度计测量准确度的干扰,还在一定程度上降低了对SAWR表面制造工艺的要求. 相似文献
936.
937.
Yuh‐Shyan Hwang Dong‐Shiuh Wu Jiann‐Jong Chen Chun‐Chi Shih Wen‐Shou Chou 《International Journal of Circuit Theory and Applications》2009,37(3):397-411
In this paper, third‐order current‐mode MOSFET‐C filters that use operational transresistance amplifiers (OTRAs) with little parasitic capacitance effects are presented. On the basis of the proposed systematic method and design procedure, we can efficiently synthesize third‐order active filters with OTRAs along with simplified MOSFET resistor circuits, and all virtually grounded capacitors. Third‐order current‐mode Chebychev low‐pass and high‐pass filters are realized to verify the validity of the theoretical analysis. Experimental results employing commercially available current feedback amplifiers are also given. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
938.
939.
940.
CO2 laser annealing induced effects of dehydrogenation, Si nanocrystal precipitation, ablation, and optical refinement in PECVD grown SiO1.25 film are investigated. Dehydrogenation shrinks SiO1.25 thickness by 40 nm after annealing at laser intensity (Plaser) of 4 kW/cm(2) for 1.4 ms. As Plaser increases to 6 kW/cm(2), the photoluminescence (PL) red-shifts to 806 nm due to the size enlargement of Si nanocrystals, while a reduced optical bandgap energy from 3.3 to 2.43 eV and an enlarged refractive index from 1.57 to 1.87 are also observed. Transmission electron microscopy analysis reveals that the randomly oriented Si nanocrystals exhibit an average diameter of 5.3 nm and a volume density of 1.9 x 10(18) cm(-3). CO2 Laser ablation initiates at intensity higher than 7 kW/cm(2), which introduces numerous structural defects with a strong PL at 410 nm. Such an ablation inevitably leads to a blue-shifted optical bandgap energy from 2.43 to 2.76 eV as Plaser enlarges from 6 to 12 kW/cm(2) are concluded. 相似文献