Frequency response and bandwidth of a spherical random array

Exact results for the expected frequency response of a spherical, sparse random array are determined, when focused at any point, including points within the sphere. Related bandwidth results are given.     

An estimation method for cover pressure re-establishment distance and pressure distribution in the goaf of longwall coal mines

Measurement of deformations and stresses in the goaf of longwall panels is difficult due to the inaccessibility of the waste area. This paper proposes a method for estimating the distance to return of the cover pressure and the stress distribution in the goaf of flat-lying longwall panels where the caving is bulking controlled. In the development of the method, it has been considered that the final subsidence on the surface is a result of deformation of the caved material and deformation of the strata over the caved zone, i.e. during both the caving and the compaction of the caved material. In this respect, the stress–strain behaviour of the caved rock pile, bending of the lowest uncaved strata depending on seam thickness, and residual expansion of fractured strata vertically over the caved zone have been described by using previous field and laboratory investigations. From the relations established between these parameters and surface subsidence, the re-establishment of cover pressure distance has been characterised with a three-parameter power function in which the independent variables are depth, excavation height, bulking factor and compressive strength of the rock fragments. It has been found that the cover pressure distance increases exponentially by increasing depth, unlike previous findings of investigations in which the cover pressure distance increases as a linear function of depth. On the other hand, the cover pressure distance for a constant depth and mining height increases if the bulking factor of the rock pile increases and/or the strength of rock fragments decreases. When the mining height increases, the bulking factor of the caved rock pile increases, and hence this result with increase in cover pressure distance. An estimation of the stress distribution curve for panels which are wide enough for the development of cover pressure has been expressed with a six-parameter Taylor series polynomial function. The general form of the stress development curves found from the proposed method has been verified with curves obtained through numerical models.     

Trans-differentiation of human adipose-derived mesenchymal stem cells into cardiomyocyte-like cells on decellularized bovine myocardial extracellular matrix-based films

In this study, we aimed at fabricating decellularized bovine myocardial extracellular matrix-based films (dMEbF) for cardiac tissue engineering (CTE). The decellularization process was carried out utilizing four consecutive stages including hypotonic treatment, detergent treatment, enzymatic digestion and decontamination, respectively. In order to fabricate the dMEbF, dBM were digested with pepsin and gelation process was conducted. dMEbF were then crosslinked with N-hydroxysuccinimide/1-Ethyl-3-(3-dimethylaminopropyl)-carbodiimide (NHS/EDC) to increase their durability. Nuclear contents of native BM and decellularized BM (dBM) tissues were determined with DNA content analysis and agarose-gel electrophoresis. Cell viability on dMEbF for 3rd, 7th, and 14th days was assessed by MTT assay. Cell attachment on dMEbF was also studied by scanning electron microscopy. Trans-differentiation capacity of human adipose-derived mesenchymal stem cells (hAMSCs) into cardiomyocyte-like cells on dMEbF were also evaluated by histochemical and immunohistochemical analyses. DNA contents for native and dBM were, respectively, found as 886.11?±?164.85 and 47.66?±?0.09?ng/mg dry weight, indicating a successful decellularization process. The results of glycosaminoglycan and hydroxyproline assay, and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), performed in order to characterize the extracellular matrix (ECM) composition of native and dBM tissue, showed that the BM matrix was not damaged during the proposed method. Lastly, regarding the histological study, dMEbF not only mimics native ECM, but also induces the stem cells into cardiomyocyte-like cells phenotype which brings it the potential of use in CTE.     

Preparation and characterization of multilayer anti-reflective coatings via sol-gel process

Single layer and multilayer films consisting of SnO₂, Ta₂O₅, SiO₂, TiO₂, indium tin oxide (ITO) and antimony tin oxide (ATO) have been prepared by sol-gel dip coating technique. All of the multilayer films contained a SiO₂ top layer, which was composed of SiO₂ nanoparticles. The other films had polymeric character. Obtained films were characterized by ellipsometry, XRD, AFM and SEM. Light transmittance values of the films were compared. Films other than SiO₂ and Ta₂O₅ were found to have crystalline structure. Thickness values of the films were in the range of 30–115 nm and roughness values were in 1.2–23 nm range. Single layer porous silica provided 95% light transmittance, whereas ITO-TiO₂-SiO₂ multilayer film provided a light transmittance of 97.2%.     

Quantum‐Tunneling Metal‐Insulator‐Metal Diodes Made by Rapid Atmospheric Pressure Chemical Vapor Deposition

A quantum‐tunneling metal‐insulator‐metal (MIM) diode is fabricated by atmospheric pressure chemical vapor deposition (AP‐CVD) for the first time. This scalable method is used to produce MIM diodes with high‐quality, pinhole‐free Al₂O₃ films more rapidly than by conventional vacuum‐based approaches. This work demonstrates that clean room fabrication is not a prerequisite for quantum‐enabled devices. In fact, the MIM diodes fabricated by AP‐CVD show a lower effective barrier height (2.20 eV) at the electrode–insulator interface than those fabricated by conventional plasma‐enhanced atomic layer deposition (2.80 eV), resulting in a lower turn on voltage of 1.4 V, lower zero‐bias resistance, and better asymmetry of 107.     

Analysis of AC Transport Loss in Conductor on Round Core Cables

Journal of Superconductivity and Novel Magnetism - The conductor on round core (CORC) cable wound with second-generation high-temperature superconducting (HTS) tapes is a promising cable candidate...     

In situ image processing capabilities of ARM-based micro-controllers

Dealing with visual data is the key for environmental monitoring tasks in Wireless Multimedia Sensor Networks (WMSNs). Tasks such as object detection, recognition, and/or tracking do require extracting and using the right information from the inherently large amount of visual data. The widely accepted solution of legacy WSNs, transmitting the acquired data to a central base station for further processing, would render a WMSN totally useless because of the unacceptable use of bandwidth and energy. Therefore, we consider the in situ processing as a viable solution for WMSNs. However, processing power and memory capacity restrictions of existing multimedia sensor nodes along with their power consumption are the limiting factors for wide-spread use of in situ processing. Nevertheless, recent technological improvements and introduction of the new ARM cores encourage us to evaluate the image processing capabilities of ARM7/ARM9/ARM11 based micro-controllers for in situ processing in WMSNs. In this work, we first discussed the architectural design differences among the various ARM cores. Then we classified image processing algorithms into three categories. Then, we evaluated the performance of each microcontroller by running a set of basic image processing algorithms necessary for object detection, recognition, and/or tracking. The test results show that ARM11 runs up to 6–30 times faster than ARM9 and ARM7, respectively. Besides, ARM11 consumes up to 5–7 times less energy than ARM9 and ARM7 for the same type of operations.