Kinetic parameter estimation for cooling crystallization process based on cell average technique and automatic differentiation

In this paper, a cell average technique(CAT) based parameter estimation method is proposed for cooling crystallization involved with particle growth, aggregation and breakage, by establishing a more efficient and accurate solution in terms of the automatic differentiation(AD) algorithm. To overcome the deficiency of CAT that demands high computation cost for implementation, a set of ordinary differential equations(ODEs) entailed from CAT based discretized population balance equation(PBE) are solved by using the AD based high-order Taylor expansion. Moreover, an AD based trust-region reflective(TRR) algorithm and another interior-point(IP) algorithm are established for estimating the kinetic parameters associated with particle growth, aggregation and breakage. As a result, the estimation accuracy can be further improved while the computation cost can be significantly reduced, compared to the existing algorithms. Benchmark examples from the literature are used to illustrate the accuracy and efficiency of the AD-based CAT, TRR and IP algorithms in comparison with the existing algorithms. Moreover, seeded batch cooling crystallization experiments of β form L-glutamic acid are performed to validate the proposed method.     

Temperature-insensitive reading of a flash memory cell

The temperature characteristics of the read current of the NOR embedded flash memory with a 1.5T-per-cell structure are theoretically analyzed and experimentally verified. We verify that for a cell programmed with a “10” state, the read current is either increasing, decreasing, or invariable with the temperature, essentially depending on the reading overdrive voltage of the selected bitcell, or its programming strength. By precisely controlling the programming strength and thus manipulating its ...     

Application of nano-patterned InGaN fabricated by self-assembled Ni nano-masks in green InGaN/GaN multiple quantum wells

The nano-patterned InGaN film was used in green InGaN/GaN multiple quantum wells(MQWs) structure, to relieve the unpleasantly existing mismatch between high indium content InGaN and GaN, as well as to enhance the light output. The different self-assembled nano-masks were formed on InGaN by annealing thin Ni layers of different thicknesses. Whereafter,the InGaN films were etched into nano-patterned films. Compared with the green MQWs structure grown on untreated InGaN film, which on nano-patterne...     

Modeling and analysis of landing collision dynamics for a shipborne helicopter

A Lagrange dynamic model is established based on small-angle approximation to improve the simulation model for shipborne helicopter landing collision. To describe fuselage motion effectively, the proposed model considers ship motion, the interaction of the tires with the deck, and tire slippage. A mechanism of sliding motion is built, and a real-time reliability analysis of the algorithm is implemented to validate the proposed model. Numerical simulations are also conducted under different operation conditions. Results show that the proposed dynamic model can simulate the collision motion of helicopter landing in real time. Several suggestions for helicopter pilot landing are likewise provided.     

Influence of gas atmosphere on synergistic control of mercury and dioxin by nonthermal plasma

In this paper, narrow-pulse power discharge is used to study the synergistic control of mercury and dioxins, in which 1,2,4-trichlorobenzene (TCB) was used as a dioxin analog, by using a self- designed experimental system. The competitive effects of NO, SO₂ and HCl on the TCB removal by non-thermal plasma are discussed. The influence of acid gas on TCB degradation is reflected in the competitive effect. NO has the greatest influence on TCB degradation efficiency. The oxidation efficiency of Hg⁰ decreased by about 10% in all three acidic gas atmospheres, and the effect of each gas component on Hg⁰ oxidation is complex. In the flue gas atmosphere of ‘acid gas+Hg⁰ +TCB’, the mechanism of the synergistic control of Hg⁰ and TCB by the non- thermal plasma is different, which has competition and promotion relationship between each other. The contribution of various flue gas components to the results was complicated, but the overall experimental results show that the synergistic control effect of the system can continue to improve. According to the generated product backstepping, ·OH plays an important role in the synergistic control of the degradation of Hg⁰ and TCB. Through this study, we hope to provide basic research data for the collaborative control of flue gas in the incineration industry.     

Atmospheric polycyclic aromatic hydrocarbons in north China: a winter-time study

The contamination and outflow of atmospheric polycyclic aromatic hydrocarbons (PAHs) in the Chinese Northern Plain, a region with a total area of 300 000 km2 and a high PAH emission density, were investigated. Polyurethane foam (PUF) and PM10 samples were collected at 46 sites located in urban, rural (towns or villages), and control (remote mountain) areas in the winter from November 2005 to February 2006. The observed concentrations of atmospheric PAHs were generally higher than those reported for developed countries and southern Chinese cities. It was found that there was no significant difference in air PAH concentrations between the urban and the rural areas (514 +/- 563 ng/m3 and 610 +/- 645 ng/ m3, respectively), while the PAH concentrations at the control sites (57.1 +/- 12.6 ng/m3) were 1 order of magnitude lower than those at the other sites. The primary reason for the similarity in PAH concentrations between urban and rural areas was the fact that the predominant sources of biomass and domestic coal combustion were widely spread over the study area. The partition constants (K(PM10)) of PAHs were significantly correlated to the corresponding values of subcooled liquid-vapor pressure (pL0). However, the regression slopes of log K(PM10) versus log pL0 were much steeper than -1, indicating adsorption dominated over absorption. Three distinct patterns of outflow from the study area were identified by forward trajectory and cluster analysis.     

Fate modeling of phenanthrene with regional variation in Tianjin,China

A multimedia fate model with spatially resolved air and soil phases was developed and evaluated. The model was used for calculation of phenanthrene concentrations in air, water, soil, and sediment in Tianjin area and transport fluxes between the adjacent bulk phases under steady-state assumption. Both air and soil phases were divided into 3113 individual compartments of 4 km2 each to assess the spatial variation of phenanthrene concentrations and fluxes. Independently measured phenanthrene concentrations in air, water, and soil were used for model validation. The spatial variation in soil was validated using a set of measured phenanthrene concentrations of 188 surface soil samples collected from the area. Most data used either for model calculation or for model validation were collected during the last 5 years. As the results of the model validation, the calculated mean values for phenanthrene concentrations in various bulk phases are in fair agreement with those independently observed and are very close to those calculated using the model without spatial variation. The absolute difference between the calculated and the measured mean concentrations are 0.14, 0.48, and 0.13 log-units (mol/m3) for air, water, and soil, respectively. The spatial distribution patterns of phenanthrene in both air and soil were well modeled. Spatially, however, the model overestimated the soil phenanthrene level at low concentration range and underestimated it at high concentration range. The calculated distribution of phenanthrene in the air matches well with the emission from fossil fuel combustion, while the calculated distribution pattern in the soil is similar to that observed.     

Organochlorine pesticides in agricultural soil and vegetables from Tianjin, China

Samples of eight types of vegetables, the rhizosphere soils, and bulk soils were collected from two sites (A and B) in Tianjin, China for the determination of hexachlorocyclohexane isomers (HCHs) and dichlorodiphenyltrichloroethane and metabolites (DDXs). The average concentrations of total HCHs and DDXs in the bulk soils were 3.6 and 80.1 ng/g for site A and 102 and 235 ng/g for site B, respectively. Relative accumulations of HCHs and DDXs in the rhizosphere soil from site A but not site B were demonstrated. The concentrations of total HCHs and DDXs in vegetable roots were 3.6-60 and 4.2-73 ng/g for site A and 15-152 and 7.1-136 ng/g for site B, respectively. Difference in bioaccumulation among various vegetables, especially between tuber and fibrous vegetables was significant. DDXs in spinach and cauliflower from site B and lindane (gamma-HCH) in cauliflower from both sites and violet from site B exceeded the maximum residual limits. Linear correlation of log-transformed HCHs and DDXs contents between the vegetable roots and the rhizosphere soils suggests the direct uptake of HCHs and DDXs.     

央视新台址主楼悬臂钢结构安装技术

央视新台址主楼悬臂结构具有悬挑跨度大、重量大、结构双向倾斜高空折形对接、多接头异形构件多、安装风险大等施工特点,使得施工中结构稳定性、安全性、精度控制、结构反变形预调处理和变形控制困难.指出了施工中需要考虑的问题,并采用两塔悬臂分离安装、逐步阶梯延伸、空中阶段合拢的安装方法,介绍了安装流程和安装工艺,并采用计算机全过程模拟来保证安装步骤、分区分跨、阶梯延伸、阶段合拢的可行性和安全性.