Post micromachining of MPW based CMOS–MEMS comb resonator and its mechanical and thermal characterization

In recent years micro electro mechanical system (MEMS) based micro resonant sensors have been given a lot of attention due to their potential as a platform for the development of many novel physical, chemical, and biological sensors. That is why this paper covers post processing of the structures fabricated through Multi-Project-Wafer using 0.35 µm MIMOS CMOS technology with particular focus on dry etching of Si and SiO₂ from the front side of CMOS–MEMS chip that is optimized using aluminum coated carrier wafer and achieved results are debris free as compared to photoresist coated carrier wafer. The device is etched through from the front side to avoid parasitic capacitances and squeeze film damping by keeping minimum size of the die. The etching of SiO₂ as well as deep Si etch-through using the same plasma etcher (SS110A Tegal) is successfully demonstrated in this work. Finally, after the successful post CMOS micromachining of the device, resonance frequency i.e. 8164 Hz and quality factor i.e. 51.34, is determined. The joule heating effect due to the passing of current through the central shuttle of the device is characterized. The maximum temperature close to the anchors of the comb resonator where the piezoresistors are located is determined through temperature coefficient of resistance measurement using PE-4RF type probe station and it is found to be 37.62 °C.     

Simulation-based dynamic traffic assignment for short-term planning applications

Evaluation of Intelligent Transportation Systems (ITS) at the planning level requires the use of appropriate tools that can capture the dynamic and stochastic interactions between demand and supply. The objective of this paper is to present a methodological simulation-based framework for such applications and implement it in the context of dynamic traffic assignment. The framework consists of a mesoscopic supply simulator and a demand simulator that combines OD estimation capabilities with discrete travel behavior models. Simulation-based DTA systems are particularly suited to evaluate a wide range of Advanced Traffic Management Systems (ATMS) and Advanced Traveler Information Systems (ATIS). The simulation model performance is illustrated through two large-scale case studies in Irvine, California, and Lower Westchester County, NY.     

Structural and optical characterization of (Sn/Li) co-doped ZnO thin films deposited by spray pyrolysis technique

(Sn/Li) co-doped ZnO (LTZO) thin films have been deposited by spray pyrolysis technique and their structural, morphological and optical properties have been investigated. The films were characterized by X-ray diffractometer (XRD), field-emission scanning electron micrograph (FESEM), (UV–Vis) spectroscopy and photoluminescence spectroscopy. XRD results revealed that all thin films (LTZO) are polycrystalline with à hexagonal wurtzite structure, moreover when the Li reach (5 at.%) content, the surface thin films of (LTZO5) become covered with bigger and clear nano-sized crystallites and the average value of grain size is 147 nm with mainly hexagonal grains. The (UV–Vis) spectroscopy showed high transmittance in the visible region, which varied between 84% and 93% and the doping of 5 at.% for all the films of Li content thin films (LTZO5) red shifted. The doping ZnO with lithium and tin were eliminates the deep-level emission in orange/red bands (around to 600 nm).     

Depth-of-Interaction Compensation Using a Focused-Cut Scintillator for a Pinhole Gamma Camera

Preclinical SPECT offers a powerful means to understand the molecular pathways of drug interactions in animal models by discovering and testing new pharmaceuticals and therapies for potential clinical applications. A combination of high spatial resolution and sensitivity are required in order to map radiotracer uptake within small animals. Pinhole collimators have been investigated, as they offer high resolution by means of image magnification. One of the limitations of pinhole geometries is that increased magnification causes some rays to travel through the detection scintillator at steep angles, introducing parallax errors due to variable depth-of-interaction in scintillator material, especially towards the edges of the detector field of view. These parallax errors ultimately limit the resolution of pinhole preclinical SPECT systems, especially for higher energy isotopes that can easily penetrate through millimeters of scintillator material. A pixellated, focused-cut (FC) scintillator, with its pixels laser-cut so that they are collinear with incoming rays, can potentially compensate for these parallax errors and thus improve the system resolution. We performed the first experimental evaluation of a newly developed focused-cut scintillator. We scanned a Tc-99m source across the field of view of pinhole gamma camera with a continuous scintillator, a conventional "straight-cut" (SC) pixellated scintillator, and a focused-cut scintillator, each coupled to an electron-multiplying charge coupled device (EMCCD) detector by a fiber-optic taper, and compared the measured full-width half-maximum (FWHM) values. We show that the FWHMs of the focused-cut scintillator projections are comparable to the FWHMs of the thinner SC scintillator, indicating the effectiveness of the focused-cut scintillator in compensating parallax errors.     

The potential role of renewable energy in Moldova

The European Union (EU) is developing an increasingly close relationship with Moldova, going beyond cooperation, to gradual economic integration and a deepening of political cooperation. This fact indicates that eventually the adoption of EU legislation in the energy sector is a necessity. Therefore, the provision of a clear picture of the country’s renewable energy potential is considered essential, bearing in mind the new EU Renewable Energy Directive, which sets a mandatory target of 20% of renewable energy sources by 2020 for each member state. The aim of this paper is to discuss the perspective of renewable energy in Moldova taking into account the current energy framework and to analyze, whether it is suitable to adopt similar methodologies and policy frameworks applied in other EU countries.     

Simulation of an efficient silicon heterostructure solar cell concept featuring molybdenum oxide carrier‐selective contact

Transition metal oxides/silicon heterocontact solar cells are the subject of intense research efforts owing to their simpler processing steps and reduced parasitic absorption as compared with the traditional silicon heterostructure counterparts. Recently, molybdenum oxide (MoO_x, x < 3) has emerged as an integral transition metal oxide for crystalline silicon (cSi)‐based solar cell based on carrier‐selective contacts (CSCs). In this paper, we physically modelled the CSC‐based cSi solar cell featuring MoO_x/intrinsic a‐Si:H/n‐type cSi/intrinsic a‐Si:H/n⁺‐type a‐Si:H for the first time using Silvaco technology computer‐aided design simulator. To analyse the optical and electrical properties of the proposed solar cell, several technological parameters such as work function and thickness of MoO_x contact layer, intrinsic a‐Si:H band gap, interface recombination, series resistance, and temperature coefficient have been evaluated. It has been shown that higher work function of MoO _x induces the formation of a favourable Schottky barrier height as well as an inversion at the front interface, stimulating least resistive path for holes. Utilising thinner MoO_x layer implies reduced tunnelling of minority charge carriers, thus enabling the device to numerically attain 25.33% efficiency. With an optimised interface recombination velocity and reduced parasitic absorption, the proposed device exhibited higher V_oc of 752 mV, J_sc of 38.8 mA/cm², fill‐factor of 79.0%, and an efficiency of 25.6%, which can be termed as the harbinger for industrial production of next‐generation efficient solar cell technology.     

Mechanical,morphological, thermal properties and hydrolytic degradation behavior of polylactic acid/polypropylene carbonate blends prepared by solvent casting

The preparation of polylactic acid (PLA) and polypropylene carbonate (PPC) blend films by using the solvent casting method is to improve the properties of pure PLA. The blends' mechanical and thermal properties, morphological as well as hydrolytic degradation behavior are evaluated. The tensile test proved that the increase of PPC from 0 wt% to 75 wt% could improve the elongation of pure PLA when the graph showed a significant increase of the elongation from 10% to 1000%. Scanning Electron Microscopy (SEM) supported the significant increase in elongation of the blends when it shows a definite phase separation in 75/25 PLA/PPC, where 25% of PPC has formed islands in the PLA matrix. Differential scanning calorimetry indicates the partial miscibility of the blends where two peaks of the glass transition temperature moved towards each other when the amount of PPC increases. Fourier transform infrared (FTIR) spectroscopy revealed a possible intermolecular interaction between two polymers, which affects the miscibility of the blends. Finally, the hydrolytic degradation test indicates that the degradation started from the PLA phase and the blends' degradation rate decrease as wt% of PPC increase.     

Bioethanol production from biomass: carbohydrate vs syngas fermentation

Environmental problems associated with the use of fossil fuels as well as their expected scarcity in the near future requires a search for new alternative fuels produced from renewable sources. Bioethanol is a biofuel that can be obtained from biomass and waste as feedstocks through fermentation. Two major routes allow conversion of the feedstocks to fermentable substrates, i.e. the hydrolytic route and the thermochemical route. In the hydrolytic route, the feedstock undergoes a pretreatment stage first, aimed at facilitating the subsequent hydrolytic treatment. Chemical, physical or biological pretreatments can be applied. Lignocellulosic feedstocks are mainly composed of cellulose, hemicellulose and lignin. The pretreatment attacks the lignin and hemicellulose polymers and makes cellulose more accessible in the next, hydrolytic, stage. The hydrolytic treatment uses enzymes to convert the cellulose polymer to simple, fermentable, sugars, mainly glucose. Simple sugars obtained from hemicellulose and cellulose are then fermented by yeasts to bioethanol. In the thermochemical alternative, the feedstock is gasified, yielding syngas – a mixture largely composed of CO, CO₂ and H₂ – which can be fermented anaerobically, usually by clostridia, to ethanol or other products. In both cases, downstream processes are then applied to recover and purify the biofuel. The different stages involved in both alternatives are described, and both processes are compared in terms of their main characteristics and development stage. © 2015 Society of Chemical Industry     

Arsenic Bioaccessibility in Cooked Rice as Affected by Arsenic in Cooking Water

Abstract: Rice can easily accumulate arsenic (As) into its grain and is known to be the highest As‐containing cereal. In addition, the As burden in rice may increase during its processing (such as when cooking using As‐polluted water). The health risk posed by the presence of As in cooked rice depends on its release from the matrix along the digestive system (bioaccessibility). Two types of white polished long‐grain rice, namely, nonparboiled and parboiled (total As: 202 and 190 μg As kg^?1, respectively), were cooked in excess of water with different levels of As (0, 10, 47, 222, and 450 μg As L^?1). The bioaccessibility of As from these cooked rice batches was evaluated with an in vitro dynamic digestion process. Rice cooked with water containing 0 and 10 μg As L^?1 showed lower As concentrations than the raw (uncooked) rice. However, cooking water with relatively high As content (≥47 μg As L^?1) significantly increased the As concentration in the cooked rice up to 8‐ and 9‐fold for the nonparboiled and parboiled rice, respectively. Parboiled rice, which is most widely consumed in South Asia, showed a higher percentage of As bioaccessibility (59% to 99%) than nonparboiled rice (36% to 69%) and most of the As bioaccessible in the cooked rice (80% to 99%) was released easily during the first 2 h of digestion. The estimation of the As intake through cooked rice based on the As bioaccessibility highlights that a few grams of cooked rice (less than 25 g dry weight per day) cooked with highly As contaminated water is equivalent to the amount of As from 2 L water containing the maximum permissible limit (10 μg As L^?1). Practical Application: Studies on As bioaccessibility are needed for determining human As intake from rice for use in accurate risk assessments to establish updated legislation regarding maximum level of As in food. High As bioaccessibility from parboiled rice (consumed by the majority of the people in South Asia), and the findings of high As levels in discarded rice gruel (fed to livestock), has implications for human and animal health.