A subgradient procedure for the solution of minimax location problems

Unconstrained planar minimax location problems are typically convex but not everywhere differentiable, thus precluding their solution by gradient techniques. We employ subgradients, which always exist, to the solution of some planar minimax location problems. A heuristic subgradient algorithm is presented for the solution of minimax location problems involving Euclidean and rectilinear distances. An attractive feature of the method is the ease of implementation on any size computer. We give a computational comparison of the algorithm with existing methods.     

The preparation and characterisation of polymer latices formed in the absence of surface active agents

Methods have been devised for the formation of monodisperse polystyrene latices in the absence of added surface active agents. The particles are stabilised, as a colloidal dispersion, by surface groupings which are an integral part of the particle and are not removed by dialysis. By suitable variation of the ionic strength of the aqueous phase, the initiator concentration and the polymerisation temperature, the final particle size obtained in single-stage reactions was varied between c. 0.15 and 1.0 μm. The coefficient of variation on particle diameters was usually less than 5%. The ionic strength of the aqueous phase was found to play an important part in determining particle size; this was explained in terms of a limited coagulation process occurring at the stage involving the nucleation of polymer particles. Conductometric titration experiments revealed the presence of sulphate, carboxyl and hydroxyl groups on the particle surfaces. Molecular weight determination of the polystyrene formed showed that this was lower than that formed in conventional emulsion polymerisation.     

Properties of hot photoexcited holes in Cu-doped germanium at low temperature

A theoretical study is made of the properties of hot photoexcited holes in Cu-doped Germanium as a function of the lattice temperature and compensation density (N_d). Numerical solutions of the rate equation, obtained by an iterative technique, give the steady-state energy distribution of hot photoexcited holes due to aproximately blackbody room temperature radiation. Considering only a spherical heavy-hole band, simple acoustic deformation scattering and instantaneous optical phonon emission it is found that for the lowest values of N_d the energy distribution function is approximately Maxwellian and gives a good fit with experimental photohall mobilities. For higher values of N_d, a spherical light hole band is included in the calculations and this involves the use of a two-parameter deformation potential for inter- and intra-valley transverse and longitudinal scattering, and also instantaneous inter- and intra-valley optical scattering. The experimental photohall mobilities can then be used to give information on the deformation potential parameters for the valence band of Ge which cannot be derived from equilibrium transport measurements.     

Need achievement training with grade-nine students.

To examine the effect of achievement motivation training on academic achievement, 81 students were given a 15-wk need achievement training course as part of their regular curriculum during the 1st semester of Grade 9. They were compared with 108 Grade-9 students in another school who did not receive the course. The difference in mean change in language arts and science was not significant, while the mean change in need achievement, mathematics, social studies, and academic average was significant and in the predicted direction. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of membrane filtration rates and hydrophobic grid membrane filter coliform and Escherichia coli counts in food suspensions using paddle-type and pulsifier sample preparation procedures

Food suspensions prepared by Pulsifier contained less debris and filtered 1.3x to 12x faster through hydrophobic grid membrane filters (HGMFs) than those prepared by Stomacher 400. Coliform and Escherichia coli counts made by an HGMF method yielded 84 and 36 paired samples, respectively, positive by both suspending methods. Overall counts of pulsificates and stomachates did not differ significantly for either analysis, though coliform counts by Pulsifier were significantly higher in mushrooms and significantly lower in ground pork (P = 0.05). Regression equations for log10 counts of coliform and E. coli by Pulsifier and Stomacher were: Pulsifier = 0.12 + 0.97 x Stomacher, and Pulsifier = 0.01 + 1.01 x Stomacher, respectively.     

食品中着色剂的检测方法研究进展

着色剂是食品添加剂中的一大类分支,在食品加工和生产中有着广泛的应用。由于食品的基质类型复杂多样,着色剂的种类也非常多、性质差异大,给分析检测工作带来挑战。本文对近年来的食品中着色剂的检测方法进行综述,包括样品前处理和分析检测技术,并根据应用方法和适用的食品基质及检测目标物进行分类总结,为进一步开展食品中着色剂的检测方法的研究工作提供参考。     

一种判定RDX热分解机理函数与热安全性的方法

将DSC、TG数据与Malek法相结合研究了RDX的热分解,得到外延起始温度Le0、拐点温度T、峰顶温度Tp、分解终止温度Tf、分解焓变ΔH、表观活化能E、指前因子A、反应级数n、热爆炸临界温度Tb和自加速分解温度TSADT;利用TG热分析得到RDX热分解的起始分解温度T0、质量损失Δm%、最大质量损失速率及对应的温度...     

智能交通信息物理融合云控制系统

针对现代智能交通信息物理融合路网建设中的对象种类复杂、采集数据量大、传输及计算需求高以及实时调度控制能力弱等问题,基于云控制系统理论,以现代智能交通控制网络为研究对象,设计了智能交通信息物理融合云控制系统方案,包括智能交通边缘控制技术和智能交通网络虚拟化技术.基于智能交通流大数据,在云控制管理中心服务器上利用深度学习和超限学习机等智能学习方法对采集的交通流数据进行训练预测计算,能够预测城市道路的短时交通流和拥堵状况.进一步在云端利用智能优化调度算法得到实时的交通流调控策略,用于解决拥堵路段交通流分配难题,提高智能交通控制系统动态运行性能.仿真结果表明了本文方法的有效性.     

Pre-stack basis pursuit seismic inversion for brittleness of shale

Brittleness of rock plays a significant role in exploration and development of shale gas reservoirs. Young’s modulus and Poisson’s ratio are the key parameters for evaluating the rock brittleness in shale gas exploration because their combination relationship can quantitatively characterize the rock brittleness. The highvalue anomaly of Young’s modulus and the low-value anomaly of Poisson’s ratio represent high brittleness of shale. The technique of pre-stack amplitude variation with angle inversion allows geoscientists to estimate Young’s modulus and Poisson’s ratio from seismic data. A model constrained basis pursuit inversion method is proposed for stably estimating Young’s modulus and Poisson’s ratio. Test results of synthetic gather data show that Young’s modulus and Poisson’s ratio can be estimated reasonably. With the novel method, the inverted Young’s modulus and Poisson’s ratio of real field data focus the layer boundaries better, which is helpful for us to evaluate the brittleness of shale gas reservoirs. The results of brittleness evaluation show a good agreement with the results of well interpretation.