Tracing post-limit-point paths with reduced basis technique

A reduced basis technique and a problem-adaptive computational algorithm are presented for predicting the post-limit-point paths of structures. In the proposed approach the structure is discretized by using displacement finite element models. The nodal displacement vector is expressed as a linear combination of a small number of vectors and a Rayleigh-Ritz technique is used to approximate the finite element equations by a small system of nonlinear algebraic equations.To circumvent the difficulties associated with the singularity of the stiffness matrix at limit points, a constraint equation, defining a generalized arc-length in the solution space, is added to the system of nonlinear algebraic equations and the Rayleigh-Ritz approximation functions (or basis vectors) are chosen to consist of a nonlinear solution of the discretized structure and its various order derivatives with respect to the generalized arc-length. The potential of the proposed approach and its advantages over the reduced basis-load control technique are outlined. The effectiveness of the proposed approach is demonstrated by means of numerical examples of structural problems with snap-through and snap-back phenomena.     

Measurement and Analysis of Thermophysical Properties of Diorites in the Temperature Range from 253 to 333 K

Thermal conductivity and thermal diffusivity are simultaneously measured for a collection of diorite samples taken from Shewa-Shahbaz Garhi volcanic complex near Mardan, Pakistan by using the transient plane source (TPS) technique. The temperature dependence of the transport properties of these samples is studied in the temperature range from 253 to 333 K. Different relationships for the temperature dependence of the thermal conductivity and thermal diffusivity are tested. The samples are also characterized by their chemical composition, density, porosity, and specific gravity at room temperature and atmospheric pressure. Theoretical calculation of the specific gravity parameter based on the chemical composition is in good agreement with the experimental observation. No correlation was found for the temperature dependence of the thermal transport behavior on porosity, chemical composition, and density.     

Recombination effects with high-pressure Langmuir probes

With increasing ion density, the ion current collected by a negatively biased electric probe is eventually dominated by ions produced by reactive processes in the vicinity of the probe. Here, we derive an expression for the probe current to a cylindrical probe when all the ions collected to the probe are assumed to be generated within the sheath which surrounds the probe. Measurements of probe current in a seeded atmospheric-pressure flame are in good agreement with the theory. The significance of reaction processes is reinforced by the fact that the maximum probe current is found to be approximately three times the total current that the flame would produce with frozen chemistry, i.e. the saturation current.     

Islam and Online Imagery on Malaysian Tourist Destination Websites

In December 1996, TIME magazine published an article titled "Finding God on the Web," which projected how the Internet would shape information seeking on faith and religion. A decade later, the Web has become a popular tool for gathering religious information as well as information and imagery related to religious travel. Yet there is little research on religious destination imagery online. Imagery—positive or negative, pictographic or narrative—influences the selection of tourism destinations. This study explored online Muslim images in Malaysia via interviews and content analyses of pictures and text on tourism destination websites' homepages. The results reveal minimal portrayal of Muslim images by Malaysian tourism destination organizations. This study adds to the small body of research, especially in Muslim countries, on online religious imagery and suggests avenues for tourism operators in Malaysia and elsewhere to improve their online image with both Muslim and non-Muslim travelers.     

Power Law Velocity Profile in Fully Developed Turbulent Pipe and Channel Flows

The power law velocity profile has been analyzed in terms of the envelope of the friction factor which gives the friction factor log law. The power law index α and prefactor C are shown as the function of the friction Reynolds number, as well as the function of the alternate variable the nondimensional friction velocity. The fully developed turbulent superpipe flow data of McKeon et al. and fully developed channel flow data of Zanoun et al. have been analyzed and the power law index α and prefactor C data have been estimated, first as a function of the friction Reynolds number and second as function of the nondimensional friction velocity. Based on analysis, several correlations have been proposed that have been supported by the data.     

Build-Operate-Transfer in Infrastructure Projects in the United States

While the infrastructure in the United States is in need of large and immediate investment, the funds provided by public agencies are not nearly sufficient to face such a challenge. Build-operate-transfer (BOT) is a delivery/financing system that can be a solution to this problem. In this system, a private sponsor finances the design, construction, maintenance, and operation of a public project for a specified concession period, at the end of which it transfers ownership to the government agency, hopefully after recouping its costs and achieving profits. A questionnaire survey of large municipalities and state departments of transportation was conducted to determine the extent to which they are using BOT in their large projects, to investigate the implementation of BOT, and the reasons why some government agencies avoid using BOT. The findings indicate that very few agencies use BOT. The reasons why most do not use BOT were reported by the respondents to be the availability of proven alternatives and enough funds, the existence of political barriers, and resistance to change both on the part of government agencies and private sponsors. When government agencies and private sponsors explore the use of BOT, they should avoid the pitfalls perceived by the respondents in this study.     

A Carrier-Based Unipolar PWM Current Controller That Minimizes the PWM-Cycle Average Current-Error Using Internal Feedback of the PWM Signals

A carrier-based unipolar pulsewidth modulation (PWM) current controller is described using a one-phase PWM rectifier bridge as a test circuit. The controller PWM signal generator uses a sawtooth carrier signal to obtain both synchronized PWM waveforms and a constant switching frequency. A current-error signal and an amplitude modulation depth signal are used to create the input reference signal to the PWM signal generator. The amplitude modulation depth signal is obtained from the PWM-cycle average of the PWM signal generator output signals. This internal feedback is illustrated using a second-order low pass Butterworth filter. With an appropriately designed low-pass filter, the current-error signal is forced to be centered on zero over a PWM cycle. The maximum peak-peak magnitude of the current-error signal is used as a design guideline for deciding an appropriate gain constant in the controller current feedback loop. The low pass filter design is examined to determine a suitable gain and 20-dB attenuation frequency to minimize the current-error signal. The steady-state and transient operation of the proposed current controller is compared with a proportional-integral controller and an average current-error controller. SPICE simulations and experimental results are used to demonstrate the characteristics of the controller.     

Study of Half-Metallic Ferromagnetism in Be0.75Ti0.25Y (Y = S,Se, and Te) Using Ab Initio Calculations: Potential Candidate for Spintronic Devices

The structural, elastic, electronic, and magnetic properties of Be_0.75Ti_0.25Y (Y = S, Se, and Te) have been investigated to understand their potential applications in spintonic devices. Crystals of BeS, BeSe, and BeTe, individually doped with Ti with a dopant concentration of x = 0.25, have been evaluated by using full-potential linearized augmented plane-wave plus local orbital method within the framework of density functional theory. We employed the Wu–Cohen generalized gradient approximation for optimizing the crystal structure and evaluating elastic properties. In order improve bandgap values and optical parameters, the modified Becke and Johnson (mBJ) potential has been employed. The theoretical investigation of band structure and density of states confirms the half-metallic ferromagnetic nature of these compounds. The elastic constants are calculated by the charpin method which shows that the compounds under consideration are brittle and anisotropic. Moreover, it is noted that tetrahedral crystal field splits the 3d state of Ti into triple degenerate t_2g and double degenerate e_g states. The exchange splitting energies Δ _x (d) and Δ _x (pd) and exchange constants (N ₀ α) and (N ₀ β) are predicted from triple degenerate t_2g states, and negative values of N ₀ β justify that the nature of effective potential is more attractive in spin down case rather than that in the spin up case. We also find the crystal field splitting (ΔE _crystal = E _t2g?E _eg) energy and reduction of the local magnetic moment of Ti from its free space charge value and creation of small local magnetic moments on the non-magnetic Be, S, Se, and Te sites by p–d hybridization.     

Evolving Recurrent Neural Network using Cartesian Genetic Programming to Predict The Trend in Foreign Currency Exchange Rates

Forecasting the foreign exchange rate is an uphill task. Numerous methods have been used over the years to develop an efficient and reliable network for forecasting the foreign exchange rate. This study utilizes recurrent neural networks (RNNs) for forecasting the foreign currency exchange rates. Cartesian genetic programming (CGP) is used for evolving the artificial neural network (ANN) to produce the prediction model. RNNs that are evolved through CGP have shown great promise in time series forecasting. The proposed approach utilizes the trends present in the historical data for its training purpose. Thirteen different currencies along with the trade-weighted index (TWI) and special drawing rights (SDR) is used for the performance analysis of recurrent Cartesian genetic programming-based artificial neural networks (RCGPANN) in comparison with various other prediction models proposed to date. The experimental results show that RCGPANN is not only capable of obtaining an accurate but also a computationally efficient prediction model for the foreign currency exchange rates. The results demonstrated a prediction accuracy of 98.872 percent (using 6 neurons only) for a single-day prediction in advance and, on average, 92% for predicting a 1000 days’ exchange rate in advance based on ten days of data history. The results prove RCGPANN to be the ultimate choice for any time series data prediction, and its capabilities can be explored in a range of other fields.     

Microwave-assisted urea-modified sorghum biomass for Cr (III) elimination from aqueous solutions

The present study concentrated on the use of an agro-waste biodegradable sorghum biomass in its simple and modified forms for the binding of Cr (III) ions. A relatively new method of modification was adopted using urea under microwave irradiation. FTIR analysis showed the presence of oxygen and nitrogen bearing functional groups in unmodified (UMS) and modified (MS) sorghum biomass. The appearance of new bands and shifts in the peaks confirmed the modification. The influence of different process parameters such as the adsorbent dose, solution pH, contact time, agitation speed and initial metal ion concentration was studied thoroughly to evaluate optimum conditions for adsorption. Maximum adsorption for Cr (III) ions occurred at pH 5.0–6.0 using UMS and MS. Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models in a non-linear fashion were used to explain the phenomenon. Maximum adsorption capacity was 7.03 and 16.36 mg of Cr (III) per gram of UMS and MS, respectively. Adsorption mechanism was explored by pseudo-first- and pseudo-second-order kinetic models, and it was found that the process followed pseudo-second-order kinetics. Thermodynamic study indicated the process favorability. The study concluded that urea modification under microwave irradiation produces a non-toxic and more effective adsorbent for Cr (III) remediation by inducing new nitrogen bearing functional groups to sorghum biomass.