High pressure hydrogen adsorption apparatus: Design and error analysis

In the present work, design and operation of a high pressure gas adsorption apparatus at room temperature and at pressures up to 100 bar are discussed. A theoretical and experimental error analysis is done to determine accuracy and robustness of the measurements. For this study, activated carbon was selected as the adsorbent and hydrogen as the adsorbate gas. A sensitivity analysis was done by taking into account the effects of temperature, pressure, volume and weight of the sample. The analysis shows that the volumes of the sample and reference cells as determined by helium-free space measurements have significant effect on the accuracy of the adsorption uptake measurement. For instance, a 0.1% error in the measurement of either volume led to approximately a 3% error in hydrogen uptake measurement at 298 K and 100 bar.     

Microwave Dielectric Properties of Rutile Filled PEEK Composites

Ceramic-filled PEEK composites were prepared by sigma mixing followed by thermolamination. Rutile-grade titanium dioxide, particle size less than 5 μm, was used as the particulate filler in the PEEK matrix to tailor the dielectric properties of the composite matrix. The dispersion of the particular filler in the PEEK matrix was studied using scanning electron microscopy. The dielectric properties of the PEEK/TiO₂ composite materials were measured in the low frequency region up to 13 MHz using an impedance analyzer. Dielectric properties in the microwave region were measured using cavity perturbation technique to evaluate the use of the composites as packaging material. Experimental results were compared with theoretically predicted values using the Lichtenecker equation. The present study shows that temperature-stable packaging materials can be realized in the PEEK/TiO₂ systems by judiciously controlling the ceramic filler concentration.     

Developing an energy-efficient electrolytic cell for magnesium

About 80% of all magnesium is produced by an electrolytic process. The electrolytic route is an energy-intensive process, and many of the developed countries have realized the need to produce magnesium in a more cost-effective manner. Toward this goal, a less energy-intensive, more compact electrolytic cell has been developed at the Central Electrochemical Research Institute, India. A 2,200 A cell was operated for more than six weeks to study the feasibility of the technology. Higher current and energy efficiencies were realized, and specific energy consumption was reduced to around 11.5 kWh/kg of metal. For more information, contact N. Rajagopalan, Central Electrochemical Research Institute, Karaikudi 630 006, India; telephone 91-22368; fax 91-04565-37779; e-mail epm@cscercri.ren.nic.in.     

Juxta‐terminal Helix Unwinding as a Stabilizing Factor to Modulate the Dynamics of Transmembrane Helices

Transmembrane helices of integral membrane proteins often are flanked by interfacial aromatic residues that can serve as anchors to aid the stabilization of a tilted transmembrane orientation. Yet, physical factors that govern the orientation or dynamic averaging of individual transmembrane helices are not well understood and have not been adequately explained. Using solid‐state ²H NMR spectroscopy to examine lipid bilayer‐incorporated model peptides of the GWALP23 (acetyl‐GGALW(LA)₆LWLAGA‐amide) family, we observed substantial unwinding at the terminals of several tilted helices spanning the membranes of DLPC, DMPC, or DOPC lipid bilayers. The fraying of helix ends might be vital for defining the dynamics and orientations of transmembrane helices in lipid bilayer membranes.     

Widespread presence of naturally occurring perchlorate in high plains of Texas and New Mexico

Perchlorate (CLO4-) occurrence in groundwater has previously been linked to industrial releases and the historic use of Chilean nitrate fertilizers. However, recently a number of occurrences have been identified for which there is no obvious anthropogenic source. Groundwater from an area of 155,000 km2 in 56 counties in northwest Texas and eastern New Mexico is impacted bythe presence of ClO4-. Concentrations were generally low (<4 ppb), although some areas are impacted by concentrations up to 200 ppb. ClO4- distribution is not related to well type (public water system, domestic, agricultural, or water-table monitoring) or aquifer (Ogallala, Edward Trinity High Plains, Edwards Trinity Plateau, Seymour, or Cenozoic). Results from vertically nested wells strongly indicate a surface source. The source of ClO4- appears to most likely be atmospheric deposition. Evidence supporting this hypothesis primarily relates to the presence of ClO4- in tritium-free older water, the lack of relation between land use and concentration distribution, the inability of potential anthropogenic sources to account for the estimated mass of ClO4-, and the positive relationship between conserved anions (e.g., IO3-, Cl-, SO4(-2)) and ClO4-. The ClO4- distribution appears to be mainly related to evaporative concentration and unsaturated transport. This process has led to higher ClO4- and other ion concentrations in groundwater where the water table is relatively shallow, and in areas with lower saturated thickness. Irrigation may have accelerated this process in some areas by increasing the transport of accumulated salts and by increasing the number of evaporative cycles. Results from this study highlight the potential for ClO4- to impact groundwater in arid and semi-arid areas through long-term atmospheric deposition.     

Synthesis of manganese doped β‐FeOOH and MnFe2 O4 nanorods for enhanced drug delivery and hyperthermia application

Preparation of manganese ferrite (MnFe₂ O₄) nanorods by the reduction of akaganeite seeds in the presence of oleylamine is reported. The Mn‐doped β‐FeOOH akaganeite seeds have been processed by the hydrolysis of metal‐chloride salts in the presence of polyethylenimine (PEI) surfactant. The hydrophobic oleylamine capped nanorods are made hydrophilic using trisodium citrate as a phase transferring agent. The nanorods form with an aspect ratio of 5.47 and possess a high magnetisation value of 69 emu/g at an applied magnetic field of 1.5 T. The colloidal water dispersion of nanorods exhibits superior heating efficiency by the application of alternating magnetic field (AMF). A specific absorption rate value of 798 W/g is achieved at an applied AMF of field strength 500 Oe and frequency 316 kHz. Further, the citrate functionalised nanorods are capable of attaching with doxorubicin (DOX) electrostatically with a loading efficiency of 97% and the drug release is pH responsive. The DOX loaded nanorods show a promising effect on the apoptosis of MCF‐7 as experimented in vitro.Inspec keywords: manganese, hydrophobicity, drug delivery systems, cellular biophysics, magnetic particles, ferrites, manganese compounds, colloids, hyperthermia, pH, iron compounds, biomedical materials, cancer, nanofabrication, nanomagnetics, hydrophilicity, nanoparticles, magnetisation, nanorods, nanomedicineOther keywords: enhanced drug delivery, hyperthermia application, manganese ferrite nanorods, polyethylenimine surfactant, hydrophilic using trisodium citrate, phase transferring agent, high magnetisation, applied magnetic field, heating efficiency, absorption rate, hydrophobic oleylamine capped nanorods, reduction, akaganeite seeds, hydrolysis, trisodium citrate, hydrophilicity, colloidal water dispersion, alternating magnetic field, frequency 316.0 kHz, FeOOH:Mg, MnFe₂ O₄      

Benchmarking energy use and greenhouse gas emissions in Singapore’s hotel industry

Hotel buildings are reported in many countries as one of the most energy intensive building sectors. Besides the pressure posed on energy supply, they also have adverse impact on the environment through greenhouse gas emissions, wastewater discharge and so on. This study was intended to shed some light on the energy and environment related issues in hotel industry. Energy consumption data and relevant information collected from hotels were subjected to rigorous statistical analysis. A regression-based benchmarking model was established, which takes into account, the difference in functional and operational features when hotels are compared with regard to their energy performance. In addition, CO₂ emissions from the surveyed hotels were estimated based on a standard procedure for corporate GHG emission accounting. It was found that a hotel’s carbon intensity ranking is rather sensitive to the normalizing denominator chosen. Therefore, carbon intensity estimated for the hotels must not be interpreted arbitrarily, and industry specific normalizing denominator should be sought in future studies.     

Study of surface topography and optical properties of Ge15Bi38Se47 films

Adherent and smooth amorphous GeBiSe films deposited by vacuum evaporation at substrate temperatures less than 30 °C have been studied for their structural and optical properties. The films were crystallized by thermal annealing and they were found to be polycrystalline in nature. A correlation between X-ray diffraction (XRD) data and surface topography is reported. Optical constants calculated from reflectance and transmittance data indicate semiconducting behaviour. The optical band gap of the as-deposited film is 1.0 eV. The measured optical contrast at 0.8 m is 44%. No significant changes in the optical parameters have been observed after exposing the samples to laboratory ambient for a period of six months. © 1998 Chapman & Hall     

Towards Unrestrained Depth Inference with Coherent Occlusion Filling

Traditional depth estimation methods typically exploit the effect of either the variations in internal parameters such as aperture and focus (as in depth from defocus), or variations in extrinsic parameters such as position and orientation of the camera (as in stereo). When operating off-the-shelf (OTS) cameras in a general setting, these parameters influence the depth of field (DOF) and field of view (FOV). While DOF mandates one to deal with defocus blur, a larger FOV necessitates camera motion during image acquisition. As a result, for unfettered operation of an OTS camera, it becomes inevitable to account for pixel motion as well as optical defocus blur in the captured images. We propose a depth estimation framework using calibrated images captured under general camera motion and lens parameter variations. Our formulation seeks to generalize the constrained areas of stereo and shape from defocus (SFD)/focus (SFF) by handling, in tandem, various effects such as focus variation, zoom, parallax and stereo occlusions, all under one roof. One of the associated challenges in such an unrestrained scenario is the problem of removing user-defined foreground occluders in the reference depth map and image (termed inpainting of depth and image). Inpainting is achieved by exploiting the cue from motion parallax to discover (in other images) the correspondence/color information missing in the reference image. Moreover, considering the fact that the observations could be differently blurred, it is important to ensure that the degree of defocus in the missing regions (in the reference image) is coherent with the local neighbours (defocus inpainting).     

Velocity control of wheeled mobile robots using computed torque control and its performance for a differentially driven robot

This article presents the development of a Computed Torque Control (CTC) scheme for Cartesian velocity control of Wheeled Mobile Robots (WMRs). The literature presents extensive study on the need and suitability of the CTC scheme for robot arms. Many researchers have identified the benefits of using a CTC scheme for mobile robots. There is however very little information on CTC schemes for controlling mobile robots. The need for the CTC scheme stems from the fact that mobile robots (industrial AGVs) employing conventional velocity control schemes experience side slip due to suspended loads while negotiating curves, and the controller gains and accelerations need to be modified for changes in the dynamics. The structure of the proposed control scheme can be employed to control any mobile robot for which an inverse dynamic model exists, as a CTC scheme requires an inverse dynamic model to compute unique values for the motor current for a given trajectory. It is demonstrated that the existence of the inverse dynamic model is guaranteed for all differentially driven WMRs for all operating conditions, and is not affected by the number of castor wheels in the WMR. In the proposed CTC scheme, the linear and angular velocities of the WMR are controlled by adjusting the WMR accelerations, which are computed based on the motor torques required to follow a given trajectory. The motor torque is pre-computed based on a dynamic model of the mobile robotic system. The simulation and experimental results presented for a differentially driven WMR demonstrate that a computed-torque control scheme provides adaptive cruising and steering control for nominally tuned controller gains compared to a conventional velocity controller to achieve proper road following in the presence of changes in the dynamics. © 1997 John Wiley & Sons, Inc.