An experimental study on solid-liquid flow through rectangular ducts

Reduction in energy consumption has been the main concern of the workers in the field of solid-liquid flow. Investigators have tried to achieve this objective in various ways. Two of the well-known methods are: the addition of polymer solutions to the solid-liquid mixture and the fitting of helical ribs inside regular circular pipes. In the latter case, the reduction is considerable, but it results in a very low rate of transportation. Chiu and Seman have reported considerable reduction of head loss in a square duct when compared to the flow through a circular pipe. In the present work, an experimental study has been underaken to compare the head loss for solid-liquid flow in a circular pipe, with that for rectangular ducts of four different aspects ratios (width/height ratios), keeping the cross-sectional area of each one of them to be the same. When the perforance of a circular pipe is compared with that of the other rectangular ducts, it seems that the square duct shows a better performance in the low operating range of velocity, whereas the rectangular duct of aspect ratio 1.5 presents a still better performance, from the energy requirement point of view, for practically the entire velocity-range within which the experiment was conducted.     

Monitoring forest fires over the Indian region using Defense Meteorological Satellite Program-Operational Linescan System nighttime satellite data

Monitoring and management of forest fires is very important in countries like India where 55% of the total forest cover is prone to fires annually. The present study aims at effective monitoring of forest fires over the Indian region using Defense Meteorological Satellite Program-Operational Linescan System (DMSP-OLS) nighttime satellite data and to evaluate the active fire detection capabilities of the sensor. Nightly DMSP-OLS fire products were generated from February to May 2005 (peak fire season) and analyzed to study the occurrence and behavior of fires over different forest physiognomies in Indian region. Fire products generated from DMSP-OLS were validated with ground observations of fire records from state forest departments to evaluate the accuracy of fire products. Further, inter-comparison of the DMSP-OLS derived fire products with contemporary fire products from Moderate resolution Imaging Spectroradiometer (MODIS) (both daytime and nighttime products) in addition to fires and burnt areas derived from Indian Remote sensing Satellite (IRS-P6) Advanced Wide Field Sensor (AWiFS) data has been done to analyze spatial agreement of fire locations given by the above sensors.Results from the DMSP-OLS fire products (derived from February to May 2005) over Indian region showed high forest fires in southern dry deciduous forests during February-March; central Indian dry and mixed deciduous forests during March-April; northeastern tropical forests during February-April and northern pine forests during May. Spatial pattern in fires showed a typical seasonal shift in fire activity from the southern dry deciduous forests to the northern pine forests and temperate forests as the fire season progressed. Statistical evaluation of DMSP-OLS fire products with ground observations showed an over all accuracy of 98%. Comparison of DMSP-OLS derived fires with consecutive MODIS and AWiFS derived fires for individual days indicated that 69% of the fires continued from current day (DMSP-OLS pass around ∼ 7 pm to ∼ 10 pm local time) to the next day (MODIS and AWiFS pass ∼ 10:30 am local time). Comparison of DMSP-OLS derived fires with burnt areas estimated from AWiFS showed that 98% of DMSP-OLS derived fires on the current day fell within the burnt area of AWiFS on subsequent day. Since the worst forest fires are those that extend from the current to the consecutive days, DMSP-OLS derived fires provide a valuable augmentation to the fires derived from other sensors operating in daytime.     

Effects of reactant concentration and OH ions on the formation of nanocrystalline BaTiO3 in solution

Crystalline BaTiO₃ nanoparticles were prepared in solution at low reaction temperature. The formation of crystalline BaTiO₃ and its crystallite size was strongly dependent on the concentration of the OH⁻ ion, total concentration of the reactants, reaction temperature and reaction time. The formation pathway and the variation of crystallite size were understood by several model experiments using NaOH as the additional source of OH⁻ ions. At higher OH⁻ concentrations, the crystallite size of BaTiO₃ was found to be decreased with increasing OH⁻ concentrations, while it was increased with increasing reactant concentrations.     

Image cryptosystem based on plain image correlation rate and selective chaotic maps

In this paper, a new image encryption algorithm is introduced for encrypting grayscale digital images of any size. To improve the encryption evaluation parameters, we suggested that the value of the plain image correlation coefficient be effective in the cryptographic process, so plain images with different properties and correlation coefficient rates are encrypted in different ways. According to the average absolute value of correlation coefficient of plain image, Logistic or Tent maps is selected to generate chaotic sequences to expand plain image matrix. As the first step of the diffusion phase, the plain image matrix is developed with larger size by proper selected chaotic sequences, and simultaneously a chaotic matrix with the same size is generated by chaotic Sine map sequences. In confusion phase, the modified Lorenz map changes pixel locations of new developed matrix by means of certain equations. Then bitwise XOR is applied between developed matrix include plain image and Sine map chaotic matrix, as second step of diffusion phase. Finally, encrypted image is generated after applying exchange operations on the content of pixels, as third step of diffusion phase. Experimental results and comparisons with some of the existing methods, show that the proposed image cryptosystem is able to resist common cryptanalytic attacks and can be used as a secure method for encrypting digital images.

     

Crosstalk between β-Catenin and CCL2 Drives Migration of Monocytes towards Glioblastoma Cells

Isocitrate dehydrogenase (IDH)-wildtype glioblastoma (GBM) is a fast growing and highly heterogeneous tumor, often characterized by the presence of glioblastoma stem cells (GSCs). The plasticity of GSCs results in therapy resistance and impairs anti-tumor immune response by influencing immune cells in the tumor microenvironment (TME). Previously, β-catenin was associated with stemness in GBM as well as with immune escape mechanisms. Here, we investigated the effect of β-catenin on attracting monocytes towards GBM cells. In addition, we evaluated whether CCL2 is involved in β-catenin crosstalk between monocytes and tumor cells. Our analysis revealed that shRNA targeting β-catenin in GBMs reduces monocytes attraction and impacts CCL2 secretion. The addition of recombinant CCL2 restores peripheral blood mononuclear cells (PBMC) migration towards medium (TCM) conditioned by shβ-catenin GBM cells. CCL2 knockdown in GBM cells shows similar effects and reduces monocyte migration to a similar extent as β-catenin knockdown. When investigating the effect of CCL2 on β-catenin activity, we found that CCL2 modulates components of the Wnt/β-catenin pathway and alters the clonogenicity of GBM cells. In addition, the pharmacological β-catenin inhibitor MSAB reduces active β-catenin, downregulates the expression of associated genes and alters CCL2 secretion. Taken together, we showed that β-catenin plays an important role in attracting monocytes towards GBM cells in vitro. We hypothesize that the interactions between β-catenin and CCL2 contribute to maintenance of GSCs via modulating immune cell interaction and promoting GBM growth and recurrence.     

Development and high stress abrasive wear behavior of milled carbon fiber‐reinforced epoxy gradient composites

Milled carbon fiber‐reinforced polysulfide‐modified epoxy gradient composites have been developed. Density and hardness increases with the increase of carbon fiber content in the direction of centrifugal force, which shows the formation of gradient structure in the composite. High stress abrasive wear test was conducted on the gradient composites by using a Suga Abrasion Wear Tester. Abrasive wear rate reduced on increase of milled carbon fiber content from 0.15 to 1.66 vol%. Reduction in abrasive wear rate in milled carbon fiber‐reinforced epoxy gradient composites has been attributed to the increase of hardness, presence of random milled fibers, and debris of composite materials, which gave resistance and reduced wear rate. There is a small decrease in specific wear rate on adding 0.15 vol% milled carbon fibers. Further decrease of specific wear rate is observed on adding 0.45 vol% milled carbon fibers. After 3 N load, there is a decrease in specific wear rate behavior on adding 0.45 vol% carbon fibers, which further decreases on adding 0.60 vol% of carbon fibers. There is a remarkable decrease in specific wear rate up to 5 N load for 1.66 vol% milled carbon fiber‐reinforced composite. Reduction in specific wear rate on adding milled carbon fibers is based on the formation of debris, which remained intact in their respective positions due to the interfacial adhesion between milled carbon fibers and epoxy resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers     

Sliding wear and friction characteristics of sisal fibre reinforced polyester composites: Effect of silane coupling agent and applied load

Chopped sisal fibre‐reinforced polyester composites with and without silane modification were prepared. Wear and friction measurements on the chopped sisal fibre reinforced polyester composites have been performed at different loads for different weight percentages of sisal fibre by using a pin‐on‐disc wear and friction tester. It has been found that increase of chopped sisal fibre content increased the Pressure‐Velocity (PV) limit of composites. Silane modification improved the wear resistance of untreated sisal fibre reinforced polyester composite. Coefficient of friction increased with increase of fibre content and decreased with increase of load. Wear mechanism has been discussed with the help of SEM observations. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Influence of wood flour loading on tribological behavior of epoxy composites

A series of wood flour (WF) filled epoxy composites consisting of five samples were prepared by varying the concentration of WF in step of 10 wt%. These samples were characterized for its wear behavior in abrasive and sliding wear modes to study the influence of WF. It was observed that specific wear rate (k₀) of all the composites decreased with increasing load in sliding wear mode. Specific wear rate was of the order of 10⁻¹⁰ m³/Nm in abrasive wear mode and ∼10⁻¹⁴ m³/Nm in sliding wear mode. Composite containing 40 wt% WF exhibited the lowest specific wear rate in abrasive wear mode. While composite containing 20 wt% WF exhibited lowest specific wear rate in sliding wear mode. This was attributed to the fact that in abrasive wear mode, the wear debris consisting of mainly WF particles was maximum for 10 wt% composite and minimum for 40 wt% composite. In sliding wear mode, the exposed WF particles caused maximum roughening of steel counterface in the case of composite containing higher concentration of WF particles. Hence, they exhibited a higher value of specific wear rate. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers