High speed and high temperature operation capabilities are desirable features of integrated circuits. Due to their innate electrical and physical properties, silicon carbide based devices greatly outperform silicon based devices in this regard. Unlike MOSFETs, SiC bipolar transistors do not have an oxide layer under high electric field, and hence are not prone to reliability issues at high temperatures. This work presents an optimized 4H-SiC BJT with high current gain that is capable of high speed operations at elevated temperatures. Optimized emitter coupled logic circuits based on this device demonstrate robust operation over wide range of temperatures.
This work aims at devising an uncertainty quantification strategy for MEMS that will allow a processguided variability-aware design process. A reference case of Monte Carlo simulations using MEMS+ will first be set up followed by generalized polynomial chaos implementation of uncertainty quantification of MEMS. Models of vibrational energy harvesters are used to show case the techniques which will be validated against devices fabricated in collaboration with IME, Singapore.
Energy can be harvested from ambient sources such as vibration, wireless, thermal and solar. Using energy harvesting in running ultra-low power systems could potentially enable battery-free operation in many applications, especially in wearable and implantable biomedical devices. A special energy efficient interface circuit, which transfers harvested energy to be utilized by the load, is an essential part in the overall harvesting system. Traditionally, power converters such as DC-DC converters were entirely based on analog circuit design. This paper presents detailed implementation of a zero current detection technique for the inductor-based DC-DC converter using digital ASIC design flow. The proposed design was implemented using 65 nm Global Foundries Low Power CMOS process. It occupied an area of 209.88 um^2 and consumed 8.07 uW. Furthermore, the proposed design maximum frequency was 925.96 MHz. By using the ASIC design flow, the design is all-digital, portable and technology independent.
Nano metal-semiconductor contacts in sub 20 nm range have showed a deviation in the electrical characteristics compared to conventional diode. New devices based on nano schottky junction have been proposed to overcome the limitations of CMOS devices. We propose a new theoretical approach to study the enhancements of the electric field at the interface, and then the total current along the junction. The results revealed a dominant tunneling current at the reverse bias for a low n-dope semiconductor substrates. Whereas thermionic current was dominant at forward bias, in the case of high n-dope semiconductor substrates. We have used finite element simulation software (COMSOL), to analyze and compare the electrical characteristics of nano schottky diode with the existing experimental data.
Random pore polymeric flow model (RPPFM) is developed to describe the dynamic evolution (i.e., particle growth rate, average molecular properties, etc.) of supported Ziegler Natta (Z-N) catalysts in gas-phase olefin co-polymerization. A multi-site kinetic scheme is considered to describe the olefin copolymerization over a Z-N catalyst. Moreover, a comprehensive diffusion-reaction model is employed to calculate the transfer rate(s) of monomer(s) from the gas phase to the catalyst metal active sites dispersed in the polymer particle. Based on the above model considerations, a detailed simulation analysis is carried out to assess the effects of monomer/co-monomer concentrations, particle size, catalyst metal concentration, initial catalyst morphology (i.e. porosity), etc. on the polymerization rate, particle growth, spatial-temporal monomer(s) concentration(s) and temperature profiles, particle overheating in a growing polymer particle. It is shown that larger particle sizes result in lower polymerization rates but higher particle overheating.
Volatile organic compounds (VOCs) are considered as major contributors to air pollution due to their toxicity and their contribution to ozone depletion. Catalysts based on noble metal particles as well as metal oxides have been widely studied for the oxidative degradation of (VOCs) as a promising method for their emission control and removal. While supported noble metal catalysts exhibit, generally, higher catalytic activities as compared with metal oxide catalysts, they have some disadvantages including: (a) their higher costs, (b) deactivation due to their sensitivity to poisons, and (c) sintering at higher temperatures [1]. On the other hand, transition metal oxide catalysts have several advantages including ability to promote redox reactions, high thermal stability, low costs, and the possibility of fabrication in high surface area porous powders. Therefore, transition metal oxides have been studied extensively as appropriate catalysts for the total catalytic combustion of VOCs [2,3].
This study gauges the viability of using alginate (hydrogel sphere form) bio-sorbent in removing heat stable salts (total organic acid; TOA anions) and heavy metal ions present in the industrial lean amine (MDEA) solution used in the natural gas sweetening process. Their adsorption properties at varying conditions of the middle-east were also investigated. The maximum adsorption capacities of hydrogel sphere adsorbents for TOA anions ranged from 909.09 to 666.66 mg/g. Langmuir model fits well to the experimental data and revealed the surface heterogeneity of the adsorbents. The resulting alginate hydrogel sphere adsorbents had selectivity to metal ions (Cr and Fe) along with TOA anions. Regeneration studies were carried out using double distilled water for seven cycles of adsorptiondesorption. The high HSS and metal ion removal ability even at high temperature conditions and the regeneration efficiency of this bio-sorbent suggest its applicability in natural gas industrial processes as a promising adsorbent.
A improved lag method was proposed to study the permeation of gas mixtures or vapor-gas mixtures. This technology, which is based on the difference in the boiling points of the components, can simultaneously measure the mass transport properties of each component. The permeation of a binary mixture of H2O(v)/CO2 was measured on a composite polymer membrane to demonstrate the feasibility of the technology. The method is low-cost and convenient for the future study of the permeation
In the Shipyard profile of Lingshan Island, soft-sediment deformation structures(SSDS) are well exposed. The lithology unites consist mainly of sandstone and interbedded sandstone-shale. Sandstones are recognized to be formed by sandy debris flow and turbidity current . Interbedded sandstone and shale contain sole marks and graded bedding. Slump folds, syngenetic faults, asymmetrical pillow structure and boudinage structure are the main SSDS. Along the direction of shear, stretches of hinges of folds become parallel to the slump direction. Syngenetic faults consist of both normal faults and reverse faults. Asymmetrical pillow structures are formed by sandy debris flow moving along a slope. Boudinage structures are result of stretch stress between layers with different competence. Three slump complexes are recognized based on space distribution of SSDS. Based on soft-sediment deformation along a slope, massive sandstone, abundance of graded bedding and absent of vertical liquefied structures, rapid sedimentation is suggested for SSDS.
Nuclear Magnetic Resonance (NMR) measurements of selected core plugs from different carbonate fabrics were obtained from an offshore Abu Dhabi oilfield to complement the previous reservoir rock typing (RRT) scheme. Former RRT was done on a standard workflow integrating lithofacies description from cores, petrographic analysis from thin sections, poro-perm from conventional core analysis (CCAL) and capillary pressure and pore throat sizes from MICP data. In this study, we used NMR data to validate the previous RRT grouping. NMR T2 distributions by depth and carbonate fabrics are presented and compared with previous MICP and petrographic data and interpretations. The paper aims to present the methodology and results of the NMR spectrometer laboratory measurements conducted on water-saturated plugs retrieved from two offshore wells. The approach of plug selection ensures that each previous RRT group was covered by a representative plug from each oil bearing zone.
