Application of the Box-Wilson experimental design method for the spherical oil agglomeration of coal

In this study, the Box-Wilson statistical experimental design method was employed to evaluate the effects of important variables such as bridging liquid (oil) concentration, salt (CaCl₂·2H₂O) concentration and stirring speed on the agglomeration of bituminous coal. Response function coefficients were determined by the regression analysis of experimental data and the predictions were found to be in good agreement with the experimental results. The optimum kerosene concentration, CaCl₂·2H₂O concentration and stirring speed were determined as 30 wt%, 1 M and 1683 rpm, respectively, when considering combustible recovery and ash content.In addition, contact angle and solution surface tension measurements were carried out to evaluate of agglomeration success with the contact angle values and surface tension values. The surface tension of CaCl₂ 2H₂O solutions and the average contact angle increased with increasing CaCl₂·2H₂O concentration.     

Pumping with electroosmosis of the second kind in mesoporous skeletons

This paper presents the use of mesoporous silica skeletons as substrates for electroosmotic (EO) micropumps. Mesoporous silica skeletons have bimodal pore size distributions consisting of macropores and cation-permselective mesopores. These materials have the potential for high flow rate per power because the cation-permselective mesopores can generate an induced charge layer (ICL) and electroosmosis of the second kind (EO-2) under high applied electric fields. The diffuse charge layers induced by the electric field result in an EO-2 flow rate that increases quadratically with increasing electric field. In contrast, the flow rate of the more common electroosmosis of the first kind (EO-1) is linearly proportional to electric field. Here, we investigate the impact of finite pressure loads on the EO-2 flow rate with experiments and an engineering model to evaluate the potential of mesoporous skeletons for micropumping applications. Our results include analyses of maximum flow rate, maximum pressure, and flow rate with intermediate pressure loads. The results indicate the existence of a critical pressure load at which reverse pressure-driven flow significantly diminishes the EO-2 flow. We also investigate the scaling of flow rate per power with respect to substrate thickness and area, demonstrating significant increases in flow rate per power with thinner substrates and favorable scaling for miniaturization of EO-2 pumps.     

Automatic detection of coastal plumes using Landsat TM/ETM+ images

Riverine fresh water outflows create coastal plumes that are distinguished from surrounding sea water by their specific spectral signature. Coastal waters are unique ecosystems, and they are very important in terms of living resources and oceanographic processes. River plumes and coastal turbid waters have important effects on coastal marine ecosystems, and they also influence marine life cycles, sediment distribution, and pollution. Remote sensing and digital image-processing techniques provide an effective tool to detect and monitor these plume zones over large areas. The primary goal of this study was automatic detection and monitoring of coastal plume zones using multispectral Landsat Thematic Mapper/Enhanced Thematic Mapper Plus (TM/ETM+) imagery. For that purpose, the proposed algorithm exploits spectral features of the multispectral images by using feature extraction and decision-making steps. The procedure has two main stages: (1) some pre-processing operations were applied to the images in order to extract the plume core reflectance values with maximum turbidity and offshore water mass reflectance values; (2) a k-means algorithm was applied with initial seed values of reflectance computed from the pre-processing stage to classify coastal plume zones. Spatial pattern and variability of optical characteristics of coastal plume zones were then defined following the results of the classification process. The algorithm was automatically applied in three different regions with three multispectral Landsat images acquired on different dates, and yielded a very high classification accuracy in detecting coastal plume zones.     

A preferred approach to the linearization of turbulent boundary-layer equations

An efficient procedure for solving the fully linearized form of the boundary-layer equations is described for turbulent flows. The procedure makes use of the so-called bordering algorithm and is applicable to problems in which the structure of the linearized system of equations deviates from the block triagonal matrix form which may be caused by boundary conditions.     

A study of wing-fuselage interaction

Summary The problem addressed is that of the initial profile appropriate for the calculation of the boundary layer on the wing at a wing-body junction. The geometry considered is such that the fuselage boundary layer reaches the interaction region still attached and it is shown that when the wing has curvature the boundary-layer component of velocity normal to the wing is turned inviscidly through a right angle to provide a (in general) non-zero profile to initiate the wing calculation.     

Reaction Mechanism and Kinetics of 1,8‐Diazabicyclo[5.4.0]undec‐7‐ene and Carbon Dioxide in Alkanol Solutions

Carbon dioxide‐binding organic liquids (CO₂BOL) are a new class of solvents with advantageous properties such as high boiling points, low specific heats, high absorption capacities, and easily reversible reactions. In order to implement these solvents in processes, the reaction characteristics must be determined a priori. This work presents an analysis of the rate constants and activation energies of the reaction between carbon dioxide and 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in 1‐hexanol and 1‐propanol. The reactions were found to comply with a termolecular reaction mechanism and exhibited pseudo‐first‐order behavior in the presence of excess DBU and 1‐alkanol. It was concluded that DBU‐based CO₂BOL are environmentally friendly and easy‐to‐handle solvents that may provide great flexibility and improvements over conventional carbon dioxide absorption processes.     

Turbulent boundary layers with assigned wall shear

In this paper we consider the problem of computing the external velocity distribution on a two-dimensional body in an incompressible boundary-layer flow for a specified wall shear. This leads to an ‘overdetermined’ boundary-value problem for a partial differential equation containing the edge velocity as an unknown parameter. A numerical procedure for determining the external velocity is given, together with several examples for laminar and turbulent boundary layers.     

Fabrication of two-layered Al-B4C composites by conventional hot pressing uuder nitrogen atmosphere and their characterization

In this study, we describe the conventional hot pressing (CHP) of layered Al-B₄C composites and their characterization. The matrix alloy A1-5 wt.%Cu was prepared from elemental powder mixtures. The metal and B₄C powders were mixed to produce either Al-Cu-10vol.%B₄C or Al-Cu-30vol.%B₄C combinations. Then, these powder mixtures were stacked as layers in the hot pressing die to form a two-layered composite. Hot pressing was carried out under nitrogen atmosphere to produce 30×40×5 mm specimens. Microstructural features and age hardening characteristics of composites were determined by specimens cut longitudinally. The flexural strength of both layered composites and their monolithic counterparts were investigated via three point bending tests. In the case of layered specimens of both 10vol.%B₄C and 30vol.%B₄C containing layers were loaded for three-point test. The results show that a homogeneous distribution of B₄C particles in the matrix alloy which is free of pores, can be obtained by CHP method. The ageing behavior of the composites was found to be influenced by the reinforced materials, i.e. higher hardness values were reached in 8 hrs for the composites than that for the matrix alloy. Flexural strength test showed that two-layered composites exhibited improved damage tolerance depending on layer arrangement. Microstructural investigation of the fracture surfaces of the bending specimens was performed by means of scanning electron microscope (SEM). While layer with lower reinforcement content exhibited large plastic deformation under loading, the other with higher reinforcement content exhibited less plastic deformation.