Steering in computational science: Mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.     

Optimal pricing and ordering policy for non-instantaneous deteriorating items under inflation and customer returns

This paper deals with an economic production quantity inventory model for non-instantaneous deteriorating items under inflationary conditions considering customer returns. We adopt a price- and time-dependent demand function. Also, the customer returns are considered as a function of both price and demand. The effects of time value of money are studied using the Discounted Cash Flow approach. The main objective is to determine the optimal selling price, the optimal replenishment cycles, and the optimal production quantity simultaneously such that the present value of total profit is maximized. An efficient algorithm is presented to find the optimal solution. Finally, numerical examples are provided to solve the presented inventory model using our proposed algorithm, which is further clarified through a sensitivity analysis. The results of analysing customer returns provide important suggestions to financial managers who use price as a control to match the quantity sold to inventory while maximizing revenues. The paper ends with a conclusion and an outlook to future studies.     

空气中激光烧蚀Cu产生等离子体发射光谱的研究

利用Q-开关Nd:YAG激光器产生的1.06 μm、10 ns的脉冲激光聚焦在空气中的Cu靶上,观测了激光诱导的Cu等离子体发射光谱.采用不同的激光能量,分析了波长范围为440 nm到540 nm的空间分辨发射光谱.在局部热力学平衡(LTE)条件近似下,根据谱线的相对强度,得到了等离子体电子温度约在104 K以上,给出了靶面附近电子温度的空间演化规律,并探讨了N(Ⅱ)500.52 nm谱线的谱线强度和半高全宽随激光能量的变化规律.     

Mesoporous phosphated and sulphated silica as solid acid catalysts for glycerol acetylation

Sulphate- and phosphate-loaded silicas were synthesised using the sol-gel method with different sulphate and phosphate loadings. These catalysts were characterised using Fourier transform infrared spectroscopy (FT-IR), the Brunauer-Emmett-Teller (BET) method and X-ray photoelectron spectroscopy (XPS). Acidity was measured using the temperature-programmed desorption of ammonia (TPD-NH3) method. The results showed that glycerol esterification with acetic acid conversion decreased as follows: α(H₂SO₄) (100 %) > α(H₃PO₄) (99 %) > α(silica loaded with 20 % sulphuric acid) (SS-20; 98 %) > α(silica loaded with 20 % phosphoric acid) (PS-20; 83 %). These studies suggest that the solid acid catalytic activity in the esterification of glycerol is highly dependent on catalyst acidity strength, pore size and surface area.     

Solid Phase Extraction of Uranium by Naphthalene‐Methyltrioctylammonium Chloride and Arsenazo(III) Adsorbent and Subsequent Spectrophotometric Determination

A simple and effective method has been presented for the preconcentration of uranium by solid phase extraction. For this purpose arsenazo(III) supported on naphthalene‐methyltrioctylammonium chloride was used as an adsorbent and uranium solution at pH 3.5 with flow rate of 1 mL·min⁻¹ was passed through the column. Therefore, uranium‐arsenazo(III) complex was formed onto column. Uranium was quantitatively eluted with 5 mL of a 0.1% ammonium tetraphenylborate and determined by spectrophotometric method at 652 nm. Several parameters such as pH, amount of reagents, sample volume, etc. were investigated. The effect of diverse ions on the preconcentration has also been studied and the optimized conditions developed have been utilized for the trace determination of uranium. A preconcentration factor of 100 was achieved. The relative standard deviation (N=8) was 0.5% for 3 ng· mL⁻¹ of uranium. The three sigma detection limit (36) was 0.045 ng·mL⁻¹     

A Dynamic Crystal‐to‐Amorphous Transformation Microporous ZnII Mixed Neutral‐ligand Metal‐organic Polymer {[Zn(bpp)2(μ‐4,4′‐bipy)(H2O)2](ClO4)2·H2O}n

A new rarely reported Zn^II mixed‐polypyridine coordination polymer with both rigid and flexible spacers, {[Zn(bpp)₂(μ‐4,4′‐bipy)(H₂O)₂](ClO₄)₂ · H₂O}_n ( 1 ), has been synthesized and characterized by elemental analysis, IR‐, ¹H NMR‐, ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction. The thermal stability of compound 1 was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The single‐crystal X‐ray structure of 1 shows that the complex has been formed from a 1D polymer as a result of bridging by the 4,4′‐bipy ligands. Solution and solid‐state luminescent spectra of the compound 1 indicate intense fluorescent emissions at ca. 353.6 and 468.8 nm, respectively. Removal of the interstitial water guest molecules results in a loss of crystallinity, but exposure to water vapor reestablishes the original structure, thus constituting 1 as a third‐generation porous framework.     

Stability analysis and approximate solution of SIR epidemic model with Crowley-Martin type functional response and Holling type-II treatment rate by using homotopy analysis method

In this paper, SIR epidemic model with Crowley-Martin type functional response and Holling type-II treatment rate is investigated. The analysis of the model shows that it has two equilibria, namely disease-free and endemic. We investigate the existence and stability results of equilibria by using LaSalle''s invariant principle and Lyapunov function. $\mathfrak{R}_{0}$ has been found to ensure the extinction or persistence of the infection. Furthermore, homotopy analysis method is employed to obtain the series solution of the proposed model. By using the homotopy solutions, firstly, several $\hbar$-curves are plotted to demonstrate the regions of convergence, then the residual and square residual errors are obtained for different values of these regions. Secondly, the numerical solutions are presented for various iterations and the absolute error functions are applied to show the accuracy of the applied homotopy analysis method.     

Electro-deposition of gold nanostructures on carbon paste electrode: a platform with signal amplification for voltammetric study and determination of pyridoxine (vitamin B<Subscript>6</Subscript>)

For the first time, the electrochemical synthesis of gold nanostructures was done at the surface of carbon paste electrode. This device was used as a simple and sensitive electrochemical sensor for measurement of pyridoxine (Vitamin B₆, VB₆). The diffusion coefficient (D) and the kinetic parameters such as electron transfer coefficient (α) and catalytic rate constant (k) for VB₆ were also determined using electrochemical approaches. The cyclic voltammetry method showed VB₆ oxidation reaction with irreversible characteristics was diffusion-controlled at low scan rates. Using differential pulse voltammetry (DPV), the peak current was linearly dependent on VB₆ concentration in the ranges of 1.9–110.8 and 110.8–257.0 μM, with detection limit of 74.0 nM, respectively. Results showed there is no interference of other vitamins in oxidation of VB₆. DPV was used to quantify of VB₆ in some real samples by the standard addition method. The modified electrode showed good sensitivity and stability.     

Synthesis and Characterization of [Zn2(4,4′‐bipy)n(AcO)4] – One‐dimensional Chain (n = 1) and One‐dimensional Double‐Chain (n = 2) Coordination Polymers

Two new Zn^II(μ‐4,4′‐bipy) coordination polymers with acetate anions, [Zn(4,4′‐bipy)(AcO)₂] ( 1 ) and [Zn₂(4,4′‐bipy)(AcO)₄] ( 2 ), have been synthesized. The compounds were characterized with elemental analysis, IR‐, ¹H NMR‐, ¹³C NMR spectroscopy and studied by thermal analysis, fluorescence measurements and x‐ray crystallography. The structural studies of compound 1 suggest the structure is a coordination polymer of zinc(II) consisting of linear double chains formed by bridging 4,4′‐bipy ligand and connection of the acetate‐bridged centrosymmetric [Zn₂(OAc)₂]²⁺ nodes.     

A copper ion-selective electrode with high selectivity prepared by sol-gel and coated wire techniques

A sol-gel electrode and a coated wire ion-selective poly(vinyl chloride) membrane, based on thiosemicarbazone as a neutral carrier, were successfully developed for the detection of Cu (II) in aqueous solutions. The sol-gel electrode and coated electrode exhibited linear response with Nernstian slopes of 29.2 and 28.1 mV per decade respectively, within the copper ion concentration ranges 1.0×10^–5–1.0×10^–1 M and 6.0×10^–6–1.0×10^–1 M for coated and sol-gel sensors. The coated and sol-gel electrodes show detection limits of 3.0×10^–6 and 6.0×10^–6 M respectively. The electrodes exhibited good selectivities for a number of alkali, alkaline earth, transition and heavy metal ions. The proposed electrodes have response times ranging from 10–50 s to achieve a 95% steady potential for Cu²⁺ concentration. The electrodes are suitable for use in aqueous solutions over a wide pH range (4–7.5). Applications of these electrodes for the determination of copper in real samples, and as an indicator electrode for potentiometric titration of Cu²⁺ ion using EDTA, are reported. The lifetimes of the electrodes were tested over a period of six months to investigate their stability. No significant change in the performance of the sol-gel electrode was observed over this period, but after two months the coated wire copper-selective electrode exhibited a gradual decrease in the slope. The selectivity of the sol-gel electrode was found to be better than that of the coated wire copper-selective electrode. Based on these results, a novel sol-gel copper-selective electrode is proposed for the determination of copper, and applied to real sample assays.