Prediction of Bubble Size Distribution in Aluminium Foam as a Function of %Titanium Hydride Addition

Foaming of liquid aluminium by addition of foaming agent (TiH₂ particles) is numerically simulated using population balance equations. Phenomena such as hydrogen release by the TiH₂ particles, heterogeneous nucleation of bubbles in oxide surface cavities, and diffusion based bubble growth are modelled. A simple mass transfer coefficient, which varies inversely with the bubble size is used to estimate the bubble growth rate. Simulation is performed to study the effect of TiH₂ content on the final bubble size distribution, total number of bubbles and average bubble size. In general, the average properties of the predicted distributions are close to the experimental values, whereas the spread in the bubble size is observed to be considerably narrower for the predicted values. The deviation in the spread of the distributions is attributed to the inverse bubble size dependent growth rate and non-inclusion of bubble coalescence in the model.     

Empirical relations for the propagation characteristics of diffused channel waveguides

Empirical relations for the propagation constant and the field profile parameters of integrated optical diffused channel waveguides have been developed. The field profile used is the evanescent secant-hyperbolic field, which has been shown earlier to be a very good approximation for diffused channel-waveguide modes. Least-square fitting has been used to obtain the empirical relations. The results show that the error in empirical relations for the propagation constant is within 2% for a broad range of waveguide parameters. The obtained empirical relations for the field profile and the propagation constant have been used, as an example, to calculate the coupling length of diffused channel-waveguide-based directional couplers.     

Response of growing Japanese quails to dietary concentration of L‐threonine

The influence of dietary levels of L ‐threonine (Thr) on growth and immune response was investigated in growing (0–5 weeks of age) Japanese quails (n = 288). Three dietary treatments were formulated using three levels of Thr [9.6, 10.2 and 11.2 kg^?1 diet dry matter (DM)] at a fixed protein level of 233 g kg^?1 and an energy level of 12.15 MJ (2900 kcal) metabolizable energy (ME) kg^?1 feed dry matter. A metabolism trial with a 3‐day collection period was conducted at the third week of age employing all the birds. The cell‐mediated (using PHA‐P) and humoral (SRBC response) immune responses were measured at the fourth week of age. Carcass traits were assessed at the end of fifth week of age. Body weight gain was lower (P < 0.01) in birds received 9.6 g Thr kg^?1 DM than in groups fed 10.2 g or 11.2 g kg^?1 DM in the diet, but there was no significant difference in gain between the groups fed 10.2 or 11.2 g Thr kg^?1 DM in the diet. Feed intake differed significantly owing to Thr levels being lowest (P < 0.05) at 9.6 g Thr kg^?1 DM in the diet. Feed conversion ratio (FCR), protein efficiency and energy efficiency improved at the 11.2 g kg^?1 level from 0 to 3 weeks of age; however, from 3 to 5 weeks of age, better FCR emanated from a diet with 9.6 g Thr kg^?1 DM. The nitrogen balance did not differ (P > 0.05) with Thr level. Carcass traits, relative weight of immune organs and cell‐mediated (PHA‐P) and humoral (SRBC response) immune responses did not differ significantly (P > 0.05) as a result of the dietary treatments. Copyright © 2006 Society of Chemical Industry     

Room-temperature ferromagnetism in graphitic petal arrays

We report room-temperature ferromagnetism of graphitic petal arrays grown on Si substrates by microwave plasma chemical vapor deposition without catalyst. The samples have been characterized by Raman and X-ray photoelectron spectroscopy to confirm the absence of possible ferromagnetic impurities. The petals exhibit ferromagnetic hysteresis with saturation magnetization of ～4.67 emu cm(-3) and coercivity of ～105 Oe at 300 K, comparable to the reported behavior of few-layer graphene. Upon O2 annealing the saturation magnetization and coercivity decreased to 2.1 emu cm(-3) and ～75 Oe respectively. The origin of ferromagnetism is believed to arise from the edge defects and vacancies in the petals.     

Ultra Wideband Co-planer Microstrip Patch Antenna for Wireless Applications

In this paper, a comparative study of co-planar gap coupled rectangular and elliptical microstrip patch antenna is presented. It is analyzed by using circuit theory concept. The proposed antennas show ultra wideband operations which depend on dimensions of the patches, gap between them as well as air gap thickness. It is observed that the performance of gap coupled elliptical patch antenna is better than that of rectangular patch antenna while the area of rectangular and elliptical patches is same. The bandwidth of proposed rectangular patch antenna is found to be 50.7 % with average gain of 6.5 dBi while for elliptical patch antenna the bandwidth and gain further improves up to 57.6 % and 9.5 dBi respectively. The theoretical results are in good agreement with the simulated results obtained from IE3D simulation software.     

Analysis of L-Shaped Slot Loaded Circular Disk Patch Antenna for Satellite and Radio Telecommunication

In the present paper a dual frequency resonance antenna is achieved by introducing L- shaped slot in circular disk patch. It is analysed by using circuit theory concept. The resonance frequency is found to be 5.087 and 8.455 GHz and the 10 dB bandwidth of the proposed antenna for lower and upper resonance frequency is found to be 4.39 and 4.66 % respectively. It is easy to adjust the higher and lower band by changing the dimensions of notch and slot introduced in the antenna. The frequency ratio is found to be 1.6621. The gain and efficiency of the proposed antenna is found to be 9.50 dB at lower resonance however it is 7.0 dB at upper resonance frequency whereas the efficiency at lower and upper resonance is found to be 94.6 and 88.2 %.The theoretical results are compared with IE3D simulation results which are in good agreement.     

Controls for microgrids with storage: Review,challenges, and research needs

The interest on microgrid has increased significantly triggered by the increasing demand of reliable, secure, efficient, clean, and sustainable electricity. More research and implementation of microgrid will be conducted in order to improve the maturity of microgrid technology. Among different aspects of microgrid, this paper focuses on controls of microgrid with energy storage. A comprehensive review on current control technology is given with a discussion on challenges of microgrid controls. Basic simulation results are also presented to enhance and support the analysis. Finally, research needs and roadmap for microgrid control are also described.     

A novel approach for analyzing severe crash patterns on multilane highways

This study presents a novel approach for analysis of patterns in severe crashes that occur on mid-block segments of multilane highways with partially limited access. A within stratum matched crash vs. non-crash classification approach is adopted towards that end. Under this approach crashes serve as units of analysis and it does not require aggregation of crash data over arterial segments of arbitrary lengths. Also, the proposed approach does not use information on non-severe crashes and hence is not affected by under-reporting of the minor crashes. Random samples of time, day of week, and location (i.e., milepost) combinations were collected for multilane arterials in the state of Florida and matched with severe crashes from the corresponding corridor to form matched strata consisting of severe crash and non-crash cases. For these cases, geometric design/roadside and traffic characteristics were derived based on the corresponding milepost locations. Four groups of crashes, severe rear-end, lane-change related, pedestrian, and single-vehicle/off-road crashes, on multilane arterials segments were compared separately to the non-crash cases. Severe lane-change related crashes may primarily be attributed to exposure while single-vehicle crashes and pedestrian crashes have no significant relationship with the ADT (Average Daily Traffic). For severe rear-end crashes speed limit, ADT, K-factor, time of day/day of week, median type, pavement condition, and presence of horizontal curvature were significant factors. The proposed approach uses general roadway characteristics as independent variables rather than event-specific information (i.e., crash characteristics such as driver/vehicle details); it has the potential to fit within a safety evaluation framework for arterial segments.     

Bio‐diesel lubricity: correlation study with residual acidity

Bio‐diesel has been accepted as a renewable liquid biofuel worldwide. In order to ensure customers' acceptance, standardisation and quality assurance are the key factors to the market introduction of bio‐diesel as a transport fuel. Lubricity of bio‐diesel is an important issue and it is well reported that 1–2% bio‐diesel is sufficient to maintain the lubricity of diesel even of very poor lubricity. However, a wide variation in lubricity performance of bio‐diesel from different vegetable oils and sources has been noticed. In addition, on critical examination, it was noticed that the variation in the lubricating performance of bio‐diesel could be better linked to its residual acidity than to variation in fatty acid composition. Copyright © 2007 John Wiley & Sons, Ltd.     

Solar assisted method for recovery of bitumen from oil sand

A novel concept for the recovery of bitumen from oil sands in a natural gas limited environment with and without CO₂ constraints is presented. We suggest a feasible method for the recovery of unconventional oil in an environmentally friendly and sustainable way that has the potential of eliminating the need of natural gas as a process fuel. The proposed concept involves mid temperature steam generation for stimulating an oil sand formation. The steam is generated by utilizing solar radiation. The method uses the thermal mass of the oil sand formation to allow for cyclic steam injection during solar availability while still yielding continuous bitumen recovery. Feasibility assessments of the concept from both a thermodynamic and financial point of view are presented for a scenario of development in the Athabasca region in Alberta, Canada.