Bifurcation analysis in a predator–prey system with a functional response increasing in both predator and prey densities

Poor dispersion characteristics of rockets, due to the orientation of the launcher for multiple launch rocket system (MLRS) departing from that intended, have always restricted the MLRS development for several decades. Orienting control is a key technique to improve the dispersion characteristics of rockets. The purpose of this paper is to propose an orienting control method for launcher of the MLRS in a salvo firing. Because the MLRS is a typical nonlinear system, the major difficulty in designing the orienting controller lies in the nonlinearity. To deal with the nonlinearity, the concept of computed torque control is introduced. The MLRS equation of motion is established using Lagrange method. The inner loop feedforward and the outer loop feedback are adopted to design the controllers for the azimuth and elevation axes of MLRS. By combining the inner and outer control loops together, the PID-computed torque controller is designed. The numerical simulation is implemented to show the control performance, and then, the effectiveness and applicability of the proposed controller are demonstrated by the firing experiment of a salvo of three rockets.     

Macroeconomic labour productivity and its impact on firm's profitability

The construction industry is one of the largest sectors in the US economy, yet little is known about the key macroeconomic parameters that affect its industry’s structure and performance. The main objectives of this research are (1) to analyse the macroeconomic performance of construction industry as a whole and at 14 of its sub-sectors in terms of labour productivity, gross margin, and worker's wages; and (2) to develop a quantitative model that predicts a firm's profitability by analysing various levels of labour productivity. The results of a non-linear regression analysis based on the comprehensive US Economic Census data show that the construction industry’s sub-sectors with the highest productivity are the most profitable with regard to the gross margins that they are able to generate. This study and its model will help decision makers better assess macroeconomic performance and conduct trend analysis of the construction industry to serve as a basis for developing strategic roadmap for the future.     

An Amphiphilic Polymer‐ and Carbon Nanotube‐Modified Indium Tin Oxide Electrode for Sensitive Electrochemical DNA Detection with Low Nonspecific Binding

We herein report an amphiphilic polymer‐, carboxylated multiwalled carbon nanotube (CNT)‐, silane polymer‐, and streptavidin‐modified indium tin oxide (ITO) electrode that allows low nonspecific binding and efficient immobilization of DNA, along with good electrocatalytic activities and low background‐current levels. The low nonspecific binding results from the well‐covering of the CNT and ITO surface with the amphiphilic polymer and silane polymer, as well as the poly(ethylene glycol) groups of the polymers. The streptavidin for DNA immobilization is covalently attached to the carboxylic acid groups of the amphiphilic polymer and CNT. A low surface coverage of CNT on the ITO electrode provides the good electrocatalytic activities and low background‐current levels. The fabricated electrode enables us to achieve a detection limit of 100 pM in DNA detection.     

Nonlinear electrostatic waves in inhomogeneous dense dusty magnetoplasmas

The nonlinear electrostatic drift waves are studied using quantum hydrodynamic model in dusty quantum magnetoplasmas. The dissipative effects due to collisions between ions and dust particles have also been taken into account. The Korteweg-de Vries Burgers (KdVB) like equation is derived and analytical solution is obtained using tanh method. The limiting cases of KdV type solitary waves, Burger type monotonic shock waves and oscillatory shock solutions are also presented. It is found that both hump and dip type solitary structures are possible in quantum dusty plasmas. However, amplitude and width of the nonlinear structure depend on the dust charge polarity and its concentration in electron-ion quantum plasmas. The monotonic shock like structure is independent of the quantum parameter. It is found that shock strength is increased in the presence of positively charged particles in comparison with negatively charged dust particles. The oscillatory shock structures are also obtained and it is found that change in dust charge polarity only shifts the phase of the oscillatory shock in plasmas. The numerical results are also presented for illustration.     

Alternatively modified bingel reaction for efficient syntheses of C60 hexakis-adducts

It was found that the C60 hexakis-adduct (Th) bearing 12 electron-donating N,N-dimethylaniline moieties could not be synthesized by the Bingel-Hirsch method with either classical or deviated experimental parameters in a one-pot reaction. A different modification to the original Bingel reaction without the use of any templating agent was necessary for high-yield synthesis of the compound. The generalization of this alternatively modified Bingel method to the preparation of other C60 hexakis-adducts is demonstrated. [structure: see text].     

Liquid-liquid extraction coupled with LC/MS/MS for monitoring of malonyl-CoA in rat brain tissue

The formation of malonyl-CoA is catalyzed by acetyl-CoA carboxylase (ACC), the rate-limiting enzyme of de novo fatty acid synthesis. Monitoring the changes of malonyl-CoA concentration in the brain in response to treatments such as pharmaceutical intervention (via ACC inhibitors) or different dietary conditions (such as varied feeding regimes) is of great interest and could help increase the understanding of how this molecule contributes to feeding behavior and overall energy balance. We have developed a sensitive analytical method for the determination of malonyl-CoA levels in rat brain tissue. The assay involved removal of tissue lipids by liquid-liquid extraction followed by LC/MS/MS analysis of the aqueous layer for malonyl-CoA. The method was sensitive enough (limit of quantitation = 50 ng/mL, or approximately 0.018 nmol/g brain tissue) to determine malonyl-CoA in individual rat brain preparations. The assay performance was sufficiently rugged to support drug discovery screening efforts and provided an additional analytical tool for monitoring brain malonyl-CoA levels.     

CFD analysis of an oscillating wing at various reduced frequencies

The effect of various reduced frequencies has been examined for an oscillating aspect ratio 10 NACA 0015 wing. An unsteady, compressible three‐dimensional (3D) Navier–Stokes code based on Beam and Warming algorithm with the Baldwin–Lomax turbulence model has been used. The code is validated for the study against published experimental data. The 3D unsteady flow field is simulated for reduced frequency values of 0.1, 0.2 and 0.3 for a fixed mean angle of attack position and fixed amplitude. The type of motion is sinusoidal harmonic. The force coefficients, pressure distributions and flow visualization show that at the given conditions the flow remains attached to the wing surface even at high angles of attack with no clear separation or typical light‐to‐deep category of dynamic stall. Increased magnitude of hysteresis and higher gradients are seen at higher reduced frequencies. The 3D effects are even found at midspan locations. In addition, the rate of decrease in lift near the wing tips compared with the wing root is not much like in the static cases. Copyright © 2008 John Wiley & Sons, Ltd.     

In-plane thermal conductance measurement of one-dimensional nanostructures

We present a new analytical model for thermal conductivity measurement of one-dimensional nanostructures on substrates. The model expands the capability of the conventional 3ω technique, to make it versatile with both in and out of plane thermal conductivity measurement on specimens either freestanding or attached to substrates. We demonstrate the model on both conducting (aluminum) and semi-conducting (focused ion beam deposited platinum) specimens. The agreement with the established values in the literature suggests the superiority of this technique in terms of convenience and robustness of measurement.     

Control of charge recombination dynamics in dye sensitized solar cells by the use of conformally deposited metal oxide blocking layers

We report herein a methodology for conformally coating nanocrystalline TiO2 films with a thin overlayer of a second metal oxide. SiO2, Al2O3, and ZrO2 overlayers were fabricated by dipping mesoporous, nanocrystalline TiO2 films in organic solutions of their respective alkoxides, followed by sintering at 435 degrees C. These three metal oxide overlayers are shown in all cases to act as barrier layers for interfacial electron transfer processes. However, experimental measurements of film electron density and interfacial charge recombination dynamics under applied negative bias were vary significantly for the overlayers. A good correlation was observed between these observations and the point of zero charge of the different metal oxides. On this basis, it is found that the most basic overlayer coating, Al2O3 (pzc = 9.2), is optimal for retarding interfacial recombination losses under negative applied bias. These observations show good correlation with current/voltage analyses of dye sensitized solar cell fabricated from these films, with the Al2O3 resulting in an increase in V(oc) of up to 50 mV and a 35% improvement in overall device efficiency. These observations are discussed and compared with an alternative TiCl4 posttreatment of nanocrystalline TiO2 films with regard to optimizing device efficiency.