Oil Spill Cleanup from Sea Water by Sorbent Materials

Three sorbents were compared in order to determine their potential for oil spill cleanup. Polypropylene nonwoven web, rice hull, and bagasse with two different particle sizes were evaluated in terms of oil sorption capacities and oil recovery efficiencies. Polypropylene can sorb almost 7 to 9 times its weight from different oils. Bagasse, 18 to 45 mesh size, follows polypropylene as the second sorbent in oil spill cleanup. Bagasse, 14 to 18 mesh size, and rice hull have comparable oil sorption capacities, which are lower than those of the two former sorbents. It was found that oil viscosity plays an important role in oil sorption by sorbents. All adsorbents used in this work could remove the oil from the surface of the water preferentially.     

Infrared thin layer drying of saffron (Crocus sativus L.) stigmas: Mass transfer parameters and quality assessment

Saffron is the most precious and expensive agricultural product. A dehydration treatment is necessary to convert Crocus sativus L. stigmas into saffron spice. To the best of our knowledge, no information on mass transfer parameters of saffron stigmas is available in the literature. This study aimed at investigating the moisture transfer parameters and quality attributes of saffron stigmas under infrared treatment at different temperatures(60,70, …, 110 °C). It was observed that the dehydration process of the samples occurred in a short accelerating rate period at the start followed by a falling rate period. The effective moisture diffusivity and convective mass transfer coefficient were determined by using the Dincer and Dost model. The diffusivity values varied from1.1103 × 10~(-10)m~2·s~(-1)to 4.1397 × 10~(-10)m~2·s~(-1) and mass transfer coefficient varied in the range of 2.6433 × 10~(-7)–8.7203 × 10~(-7)m·s~(-1). The activation energy was obtained to be 27.86 k J·mol~(-1). The quality assessment results showed that the total crocin content increased, when the temperature increased up to90 °C but, in higher temperatures, the amount of crocin decreased slightly. The total safranal content of the samples decreased slightly when drying temperature increased from 60 °C to 70 °C and then continuously increased up to 110 °C. Also, the amount of picrocrocin increased from 83.1 to 93.3 as the drying temperature increased from 60 °C to 100 °C.     

Integral equation formulation of radiation from rectangular waveguides and horns

The radiation field patterns of rectangular waveguides and horns of finite dimensions are obtained numerically. The electric field integral equation is formulated to relate their radiation patterns to the surface current distribution. These currents are determined numerically by reducing the integral equation to a matrix equation, using the moment method. The computed currents are then used to calculate the radiation patterns and cross-polar fields of the finite wavegiudes and horns. The method is numerically efficient and can be applied to the computation and optimization of the antenna feed configurations.     

Experimental Study and Mathematical Modeling of NO Removal Using the UV/H2O2 Advanced Oxidation Process

An experimental study on NO removal via UV/H₂O₂ process was conducted in a semi‐continuous bubble‐column reactor and the effect of some operation parameters including NO initial concentration and gas flow rates on removal efficiency was investigated. Applying UV light increased the efficiency significantly. The steady‐state removal efficiency was found to be higher at the lower gas flow rates. The bubble size as an important factor in mass transfer calculations and modeling procedure was determined at different gas flow rates using bubble photographs and image processing technique. In the ranges of flow rates studied here, the gas flow rate had no significant effect on the bubble diameter. A mathematical model was developed to describe the NO removal process. The model predictions were compared with existing experimental data, confirming a good agreement of the data.     

Separation of Ethylene Glycol/Water Mixtures using NaA Zeolite Membranes

Inorganic membranes and particularly zeolite membranes are usually used for the dehydration of organic solvents by pervaporation (PV). This work reports an experimental study on the PV dehydration of ethylene glycol (EG)/water mixtures using commercial nanoporous NaA zeolite membranes. The concentration range investigated (C_EG > 70 wt %) was selected according to existing industrial requirements. The recirculation flow rate was kept at a value of 1.5 L/min. The fluxes and separation factors were monitored as the dehydration proceeded. In addition, the activation energy of permeation (E_a) was calculated. The effect of temperature was investigated in the range 50–70 °C. The results obtained demonstrated the successful performance of the membrane for the dehydration of EG/water mixtures. It was observed that at 70 °C and with 70 wt % initial EG concentration, larger fluxes and separation factors could be obtained, i.e., 0.94 kg m^–2h^–1 and 1177, respectively. The Pervaporation Separation Index (PSI) of the membrane was found to be high compared to that of polymeric membranes.     

An empirical evaluation of three regional growth models

There exist a variety of models pertaining to the explanation of the regional growth process. Some empirical evidence exists in support of some of these models. It is not possible, however, to evaluate the relative merits of the models on the basis of the evidence, for the data base used for each differ from that used for the others. Yet, in view of the large number of models available, and the tendency to develop new ones, it is crucial that such an empirical evaluation be made.In this paper we consider the three most widely accepted demand models of regional growth, and examine the ability of each to explain the variation of growth experience among the different regions of the U.S. We also examine the degree to which the empirical evidence support or contradict the implicit assumptions and implications of each.Because a common data base is used for the estimation of all three models (cross-section samples on the 48 contiguous states and the District of Columbia, 1947, 1958 and 1963), we are able to assess the relative merits of the models and their dynamic behavior.The results reported in this study are based on those of a research project on regional growth sponsored jointly by the Japan-American Institute of Management Science, Hawaii and Fujitsu Ltd., Japan. Mr. M. Akiyama and M. J. Fujiwara of Fujitsu Ltd., collaborated with the author in that project. Their contribution as well as the support of JAIMS and Fujitsu are gratefully acknowledged. The views expressed in this paper, however, are solely the author's.     

Lateral‐Polarity Structure of AlGaN Quantum Wells: A Promising Approach to Enhancing the Ultraviolet Luminescence

Aluminum‐gallium‐nitride alloys (Al _x Ga_{1– x} N, 0 ≤ x ≤ 1) can emit light covering the ultraviolet spectrum from 210 to 360 nm. However, these emitters have not fulfilled their full promise to replace the toxic and fragile mercury UV lamps due to their low efficiencies. This study demonstrates a promising approach to enhancing the luminescence efficiency of AlGaN multiple quantum wells (MQWs) via the introduction of a lateral‐polarity structure (LPS) comprising both III and N‐polar domains. The enhanced luminescence in LPS is attributed to the surface roughening, and compositional inhomogeneities in the N‐polar domain. The space‐resolved internal quantum efficiency (IQE) mapping shows a higher relative IQE in N‐polar domains and near inversion domain boundaries, providing strong evidence of enhanced radiative recombination efficiency in the LPS. These experimental observations are in good agreement with the theoretical calculations, where both lateral and vertical band diagrams are investigated. This work suggests that the introduction of the LPS in AlGaN‐based MQWs can provide unprecedented tunability in achieving higher luminescence performance in the development of solid state light sources.     

Lateral polarity control of Ⅲ-nitride thin film and application in GaN Schottky barrier diode

N-polar and Ⅲ-polar GaN and AIN epitaxial thin films grown side by side on single sapphire substrate was reported.Surface morphology,wet etching susceptibility and bi-axial strain conditions were investigated and the polarity control scheme was utilized in the fabrication of Schottky barrier diode where ohmic contact and Schottky contact were deposited on N-polar domains and Ga-polar domains,respectively.The influence of N-polarity on on-state resistivity and I-V characteristic was discussed,demonstrating that lateral polarity structure of GaN and A1N can be widely used in new designs of optoelectronic and electronic devices.     

Numerical modeling of natural convection in an open cavity with two vertical thin heat sources subjected to a nanofluid

This paper presents a numerical study of natural convection cooling of two heat sources vertically attached to horizontal walls of a cavity. The right opening boundary is subjected to the copper–water nanofluid at constant low temperature and pressure, while the other boundaries are assumed to be adiabatic. The governing equations have been solved using the finite volume approach, using SIMPLE algorithm on the collocated arrangement. The study has been carried out for the Rayleigh number in the range 10⁴ ≤ Ra ≤ 10⁷, and for solid volume fraction 0 ≤ φ ≤ 0.05. In order to investigate the effect of heat source location, three different placement configurations of heat sources are considered. The effects of both Rayleigh numbers and heat source locations on the streamlines, isotherms, Nusselt number are investigated. The results indicate that the flow field and temperature distributions inside the cavity are strongly dependent on the Rayleigh numbers and the position of the heat sources. The results also indicate that the Nusselt number is an increasing function of the Rayleigh number, the distance between two heat sources, and distance from the wall. In addition it is observed that the average Nusselt number increases linearly with the increase in the solid volume fraction of nanoparticles.