Experiments on the practical I/O efficiency of geometric algorithms: Distribution sweep versus plane sweep

We present an extensive experimental study comparing the performance of four algorithms for the following orthogonal segment intersection problem: given a set of horizontal and vertical line segments in the plane, report all intersecting horizontal-vertical pairs. The problem has important applications in VLSI layout and graphics, which are large-scale in nature. The algorithms under evaluation are our implementations of distribution sweep and three variations of plane sweep. Distribution sweep is specifically designed for the situations in which the problem is too large to be solved in internal memory, and theoretically has optimal I/O cost. Plane sweep is a well-known and powerful technique in computational geometry, and is optimal for this particular problem in terms of internal computation. The three variations of plane sweep differ by the sorting methods (external versus internal sorting) used in the preprocessing phase and the dynamic data structures (B-tree versus 2-3-4-tree) used in the sweeping phase. We generate the test data by three programs that use a random number generator while producing some interesting properties that are predicted by our theoretical analysis. The sizes of the test data range from 250 thousand segments to 2.5 million segments. The experiments provide detailed quantitative evaluation of the performance of the four algorithms, and the observed behavior of the algorithms is consistent with their theoretical properties. This is, to the best of our knowledge, the first experimental algorithmic study comparing the practical performance between external-memory algorithms and conventional algorithms with large-scale test data.     

p型Se的电沉积及其转化为n型CdSe的机理研究

利用线性电位扫描光伏安法等技术研究钛基体上Se半导体薄膜的电化学形成及转化过程.实验结果表明,在H_2SeO_3溶液中进行电沉积可获得p型Se薄膜,它可在酸性CdSO_4溶液中阴极转化为n型CdSe.讨论了Se的电沉积动力学及其转化为CdSe的可能机理.所述原理可望用于p-n异质结的电化学制备.     

搅拌下吸附富集时不可逆过程峰电流方程式

线性变势吸附伏安法是一种简便的痕量分析方法。本文讨论了此方法中不可逆过程的峰电流方程式,并对其作了验证。仪器与试剂 83-2.5型多阶自动新极谱仪(各档灵敏度已校正),LZ_3-100型函数记录仪,Metrohm E410型悬汞电极,所用试剂同文献[1]。实验方法在含0.1mol/dm~3NH_3/NH_4Cl,1×10~(-4)mol/dm~3丁二肟,pH=9.2的Co(Ⅱ)溶液中用氮气除氧并搅拌。由于配合物的稳定常数很大(β=10~(17)),可以认为Co(Ⅱ)A_2的浓度等于Co(Ⅱ)的浓度。由于电势负于-1.20V时Co(Ⅱ)A_2在电极上不吸附,因此先将电极置于-1.5V,一当从悬汞电极中旋出新的汞滴,立即将电势恒定于-0.8V,富集一定时间,然后关闭搅拌器,30秒后,电势以100mV/s的速度向负方向扫描至-1.3V,同时     

Evaluation of the current function in linear sweep voltammetry by Pade approximation and epsilon convergence

Two procedures, viz., the epsilon convergence algorithm and Pade approximation scheme, are used to evaluate the current function values, graphical representation of the output, and verification of the model using existing data are carried out. For theoretical simulations of voltammograms, closed form of rational expressions using Pade approximant for the response of various reactions schemes involving soluble reactant and product, as well as coupled chemical process to an imposed linear scans were derived. Similarly, it was demonstrated epsilon convergence as an alternative procedure is much easier and elegant to use by an electroanalytical chemist with extreme ease.__________From Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 482–500.Original English Text Copyright © 2005 by Sivakumar, Basha.This article was submitted by the authors in English.     

Adsorptive stripping voltammetric determination of netilmicin in the presence of formaldehyde

A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde has been proposed for the first time. In the presence of 3.0×10⁻³ g ml⁻¹ formaldehyde, netilmicin exhibits a sensitive cathodic peak at −1.30 V (vs. the saturated calomel electrode, SCE) in a medium of Britton–Robinson buffer (pH 8.7) with a scan rate of 100 mV s⁻¹ after a preconcentration period of 120 s at −1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin concentration over the range 4.2×10⁻⁹–1.0×10⁻⁷ g ml⁻¹. The achieved limits of detection and quantitation were 1.0×10⁻¹⁰ and 3.3×10⁻¹⁰ g ml⁻¹ netilmicin, respectively. It was deduced from the experiments that the amine–aldehyde condensation product formed between netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable formulations and spiked human urine and serum samples.      

Optimal control and stability analysis of an online game addiction model with two stages

In this paper, we establish a mathematical model of online game addiction with two stages to research the dynamic properties of it. The existence of all equilibria is obtained, and the basic reproduction number is calculated by the method of next-generation matrix. The global asymptotic stability of disease-free equilibrium (DFE) is proved by comparison principle, and the global asymptotic stability of endemic equilibrium (EE) is proved by constructing an appropriate Lyapunov function. Then we use the Pontryagin's maximum principle to find the optimal solution of the model, so that the number of infected people can be minimized. In numerical simulation, firstly, we validate the global stability of DFE and EE. Secondly, we consider three kind of control measures (treatment, isolation, and education) and divide them into four cases. The models with control and without control are solved numerically by using forward and backward sweep Runge-Kutta method. In order to achieve the best control effect, we suggest that three kind of measures should be used simultaneously according to the optimal control strategy.     

Phase Transitions in Emulsions Formed by Aqueous Emulsifier and its Action on Improving Mobility in Oil Recovery

Transition from oil-in-water (O/W) emulsions to water-in-oil (W/O) emulsions and its action on enhanced oil recovery was investigated by viscosity, morphology, and simulated flooding experiments. This transition can be realized by increasing the volume ratio of oil to water or decreasing the emulsifier concentration. At a mass concentration of 0.3 wt%, the self-developed emulsifier FJ-1 mainly forms O/W emulsions at a volume ratio (oil to water) of 1:1. The emulsions behave as O/W emulsions with a low viscosity when the volume ratio of oil to water is below 2:1. Above 2:1, increasing volume ratio leads to the O/W emulsions transferring into W/O emulsions with high viscosity. For example, at a volume fraction of 4:1, the viscosity of W/O emulsions reaches 229.1 mPa · s, and separated water can hardly be detected. Transition from O/W emulsions to W/O emulsions with high viscosity can also be realized by decreasing the concentration of emulsifier to 0.05 wt% or lower at a volume ratio of 1:1. These may be the critical factors leading to transition from O/W emulsions to W/O emulsions at core conditions. Simulated flooding experiments show that emulsifier fluids can act as an in situ mobility improver and make an improvement of oil recovery even by 20.4%. The results indicate that the water-in-crude-oil emulsions possess great potential in enhancing oil recovery.     

A New Indicator Reaction and Its Application-Catalytic Determination of Ultratrace Amounts of Rhodium with Linear Sweep Voltammetry

Introduction Sensitive linear sweep voltammetry to have been applied to the catalytic kinetic analysis may be helpful for the application of some organic reagents to the analysis of inorganic ones by voltammetry, The catalytic reaction-linear sweep voltammetric method for the determination of noble metals, such as Ag, Os, Ru and Ir has been developed, but no report about the method for the determination of rhodium has been published so far.     

环己烯电化学环氧化的研究

The electrochemical epoxidation of cyclohexene on smooth platinum was investigated by means of convolution potential sweep voltammetry and potential step in H₂O-NaBr-MeCN-(这里有图片19891223-1260-1.gif) system.It is further proved that the electrochemical oxidation of Br^- is irreversible in the system, and the electrochemical epoxidation of cyclohexene shows a characteristic of ECcatatytic mechanism.Based on the analysis of data, some kinetic parameters were determined.     

Time-domain sweeplets for acoustic measurements

This paper proposes new types of time-domain generated sine sweeps for impulse response measurements. A general time-domain analytical formulation method, combined with numeric phase alignment and frequency-domain inverse filtering is presented. It is applied to derive three new families of controllable spectrum sine sweeps called sweeplets, capable of matching 1/f^β background noises, producing finite band defocusing and single frequency focusing shapes. Mathematical properties concentrating on practical control of the signal shapes are examined. Effects of various perturbations, such as stationary and transient background noise, harmonic distortion and finite length are presented. Applicability of the proposed method is experimentally verified by a room acoustic measurement example.