84 research outputs found
Doing Business in China: A Risk Analysis
The aim of this research is to describe the various challenges faced by western companies that plan to do business in China. In specific this document aims to explore (I) The challenges for a Western company that wishes to outsource production to China, (II) The challenges for western companies that plan to sell their products in the Chinese market and (III) The key differences and similarities in the above mentioned scenarios
Adsorption and Wetting in Model Mesoporous Silicas and in Complex Metal Oxide Catalysts
The surface of most metal oxides is covered by hydroxyl groups which influence many surface phenomena such as adsorption and wetting, catalysis and surface reactions. Surface chemistry of silica is a subject of exhaustive studies owing to a wide variety of practical applications of silica. In Chapter 1, a brief review of classification, synthesis and characterization of silica is provided. The hydroxylation of silica surface i.e the number of hydroxyl (-OH) groups on the surface is of utmost importance for its practical applications. In Chapter 2, a brief introduction to surface hydration of silica is provided followed by the gas adsorption measurements and characterization.
Pore wetting is critical to many applications of mesoporous adsorbents, catalysts, and separation materials. In the work presented in Chapter 3, we employed the combined vapor adsorption study using nitrogen (77K) and water (293K) isotherms to evaluate the water contact angles for a series of ordered mesoporous silicas (ex:SBA-15). The proposed method of contact angle relies on the statistical film thickness (t-curve) of the adsorbed water. There were no t-curves for water for dehydroxylated or hydrophobic surfaces in literature and we addressed this issue by measuring t-curves for a series of model surfaces with known and varying silanol coverage. Using the radius of menisci ((2)), statistical film thickness t(H2O) from water isotherm, and the true radius of pores ((2)), from nitrogen isotherms, the water contact angle inside pores were calculated. As it was anticipated, the results obtained showed that the silica pore contact angles were strongly influenced by the number of the surface silanol groups and, therefore, by the thermal and hydration treatments of silicas.
Phthalocyanines (Pcs) present an interesting class of catalytically active of molecules with unique spectroscopic, photoelectric, and sometimes magnetic properties. In the work presented in Chapter 4, we have undertaken a systematic study to explore the possibility of preparing a supported catalyst material i.e loading fluorinated metal phthalocyanines onto metal oxide surfaces by two other techniques in addition to solution adsorption. Techniques or procedures that have been used to immobilize MPcs include: i) physical adsorption (from solution) onto metal oxide surface, ii) deposition by pore filling and encapsulation and iii) mesopore entrapment or confinement. The MPcs are loaded on to metal oxides with an aim to: a) maximize the surface area of the Pcs by distributing it over the support, b) immobilize the Pcs so that they do not leach into the solution environment, c) improve the thermal stability of the Pcs and d) attempt to achieve single-site catalysis. All the immobilization techniques were carried out with F64PcZn as the model MPc, acetone as the immobilization solvent and silica or alumina as adsorbents (solid support).
An understanding of gas adsorption mechanisms on metal phthalocyanines (MPcs) is essential for their practical application in biological processes, gas sensing, and catalysis. In this work, the surface characteristics were probed by performing nitrogen and water adsorption on the free-form MPcs (without immobilization on solid support) and characterization of their physical properties. The combined vapor adsorption study (developed in Chapter 3) enabled in understanding the affinity of Pcs towards water vapor i.e number of water molecules adsorbed per phthalocyanine molecule was obtained. This information is very relevant towards using Pcs as catalyst since water vapor is guaranteed to be present in most of the catalytic reaction environment
Making Sense Of Software Ecosystems: A Critical Review
Visualizing software as ecosystems has been an emergent phenomenon. The objective of this paper is to analyze the field of software ecosystems (SECO) and provide a critical review of the existing literature. This research identifies domains and peripheries of a SECO; highlights architectural challenges; examines design and control mechanisms and discusses some of the learningâs from other popular paradigms that can be applied to address the key challenges in the SECO paradigm. This paper also aims to recommend future research directions for software ecosystems and its role in the broader context of information systems research
SOLVENT BEHAVIOR IN HYDROPHOBIC SILICA NANOTUBES AND NANOTUBE MEMBRANES
The development of template-synthesized silica nanotubes has created a unique opportunity for studying confined fluids by providing nanometer-scale containers in which, the inner diameter (i.d.) and surface chemistry can be systematically and independently varied. An interesting question to be answered is: Do solvents wet nanometer-scale tubes in the same way that they wet ordinary capillaries? To answer this question, we have conducted studies to explore the wettability of the hydrophobic interiors of individual nanotubes. In these studies, single nanotubes with i.d.'s of either 30 or 170 nm were investigated over a range of water/methanol mixtures. These studies provide a direct route for comparing wetting phenomena in nanotubes with conventional macroscopic theories of capillarity. Our observations reveal four important aspects of wetting in the sub-200 nm regime; (i) observation of a sharp transition between wetting and non-wetting conditions with increasing methanol concentration, (ii) invariance of this transition between nanotubes of 30 and 170 nm pore diameter (iii) failure of the Young-Laplace equation to accurately predict the methanol mole fraction for the transition and (iv) the reversibility of the observed wetting. The single nanotube measurements were complemented with membrane transport experiments that corroborate our conclusions. The first two aspects conform to conventional capillarity (Young-Laplace), but the latter two do not. The variation between the predicted and the experimental values may be associated with either our reliance on macroscopic values of contact angles and surface tensions in the Young-Laplace equation, or to liquid phase instability within the hydrophobic pore
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RF Frontend for Spectrum Analysis in Cognitive Radio
Advances in wireless technology have sparked a plethora of mobile communication standards to support a variety of applications. FCC predicts a looming crisis due to the exponentially growing demand for spectrum and it recommends to increase the efficiency of spectrum utilization. Cognitive Radio (CR) is envisioned as a radio technology which detects and exploits empty spectrum to improve the quality of communication. Spectrum analyzer for detecting spectrum holes is a key component required for implementing cognitive radio. Mitola's vision of using an RF Analog-to-Digital (ADC) to digitize the entire spectrum is not yet a reality. The traditional spectrum analysis technique based on a RF Front end using an LO Sweep is too slow, making it unsuitable to track fast hopping signals. In this work, we demonstrate an RF Frontend that can simplify the ADC's requirement by splitting the input spectrum into multiple channels. It avoids the problem of PLL settling by incorporating LO synthesis within the signal path using a concept called Iterative Down Converter. An example 0.75GHz-11.25GHz RF Channelizer is designed in 65nm Standard CMOS Process. The channelizer splits the input spectrum (10.5GHz bandwidth) into seven channels (each of bandwidth 1.5GHz). The channelizer shows the ability to rapidly switch from one channel to another (within a few ns) as well as down-converting multiple channels simultaneously (concurrency). The channelizer achieves a dynamic range of 54dB for a bandwidth of 10.5GHz, while consuming 540mW of power. Harmonic rejection mixer plays a key role in a broadband receiver. A novel order scalable harmonic rejection mixer architecture is described in this research. A proof-of-principle prototype has been designed and fabricated in a 45nm SOI technology. Experimental results demonstrate an operation range of 0.5GHz to 1.5GHz for the LO frequency while offering harmonic rejection better than 55dB for the 3rd harmonic and 58dB for the 5th harmonic across LO frequencies. While cognitive radio solves the spectrum efficiency problem in frequency domain, the electronic beam steering provides a spatial domain solution. Electronic beam forming using phased arrays have been claimed to improve spectrum efficiency by serving more number of users for a given bandwidth. A LO path phase-shifter with frequency-doubling is demonstrated for WiMAX applications
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RF Frontend for Spectrum Analysis in Cognitive Radio
Advances in wireless technology have sparked a plethora of mobile communication standards to support a variety of applications. FCC predicts a looming crisis due to the exponentially growing demand for spectrum and it recommends to increase the efficiency of spectrum utilization. Cognitive Radio (CR) is envisioned as a radio technology which detects and exploits empty spectrum to improve the quality of communication. Spectrum analyzer for detecting spectrum holes is a key component required for implementing cognitive radio. Mitola's vision of using an RF Analog-to-Digital (ADC) to digitize the entire spectrum is not yet a reality. The traditional spectrum analysis technique based on a RF Front end using an LO Sweep is too slow, making it unsuitable to track fast hopping signals. In this work, we demonstrate an RF Frontend that can simplify the ADC's requirement by splitting the input spectrum into multiple channels. It avoids the problem of PLL settling by incorporating LO synthesis within the signal path using a concept called Iterative Down Converter. An example 0.75GHz-11.25GHz RF Channelizer is designed in 65nm Standard CMOS Process. The channelizer splits the input spectrum (10.5GHz bandwidth) into seven channels (each of bandwidth 1.5GHz). The channelizer shows the ability to rapidly switch from one channel to another (within a few ns) as well as down-converting multiple channels simultaneously (concurrency). The channelizer achieves a dynamic range of 54dB for a bandwidth of 10.5GHz, while consuming 540mW of power. Harmonic rejection mixer plays a key role in a broadband receiver. A novel order scalable harmonic rejection mixer architecture is described in this research. A proof-of-principle prototype has been designed and fabricated in a 45nm SOI technology. Experimental results demonstrate an operation range of 0.5GHz to 1.5GHz for the LO frequency while offering harmonic rejection better than 55dB for the 3rd harmonic and 58dB for the 5th harmonic across LO frequencies. While cognitive radio solves the spectrum efficiency problem in frequency domain, the electronic beam steering provides a spatial domain solution. Electronic beam forming using phased arrays have been claimed to improve spectrum efficiency by serving more number of users for a given bandwidth. A LO path phase-shifter with frequency-doubling is demonstrated for WiMAX applications
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A self-calibrated, reconfigurable RF LNA
Modern wireless System-on-Chips (SoCs), such as mobile handsets, sensor networks, and mm-wave systems, integrate an entire RF system on a single CMOS chip. Such highly complex systems require significant on-chip digital signal processing to help improve the performance of highly sensitive analog/RF components. The IC
market being competitive, the ability to achieve first pass silicon success is crucial, due to very high processing and testing time cost. Unfortunately, the ability to achieve first-pass silicon success is becoming increasingly more difficult, due to higher system complexity, higher frequency of operation, increased performance requirements, and higher process skews.
This thesis presents a 2.4 GHz, reconfigurable RF Low Noise Amplifier (LNA) using on-chip peak detection and calibration, to mitigate the deleterious effects of process, voltage and temperature (PVT) variations. The LNA can reconfigure its
input impedance matching, as well as its gain. On-chip detection of optimal input/output impedance matching is performed using an amplitude peak detector. A low power, robust maximum peak point calibration scheme is proposed that calibrates the LNA to the resonant frequency of interest. Measurement results show
that the calibration of the LNA improves the input matching (Sââ) by a maximum of 5 dB , and power gain (Sââ) by 3dB, while not significantly degrading the Noise Figure (NF)
A Four-Transistor Level Converter for Dual-Voltage Low-Power Design
Power dissipation in digital circuits has become a primary concern in electronic design. With increasing usage of portable devices, there are severe restrictions being placed on the size, weight and power of batteries. In this work, we propose a design of a dual V th feedback type four-transistor level converter (DVF4) with reduced delay and power overheads. The use of DVF4 enhances the effectiveness of a dual-voltage low-power design. The level converter can be used in a circuit with multi supply voltage system where low supply gates may feed into high supply gates resulting in lower power and higher speed than with previously published level converters. The proposed level converter is based on a feedback circuit and employs multi-V th technique. To portray the advantages, we compare the proposed level converter with a previously published level converter for various supply voltages and observe 17.44% to 53% power savings and around 50% delay reduction over the best 32 nm CMOS design available in the literature. The impact of process variations is also examined. When used with dual VDD designs, the new level converter renders up to 61% more energy savings for benchmark circuits in comparison when level converters are not allowed. Furthermore, a level converter flip-flop combination performs better than an existing level converting flip-flop. A single-threshold alternative of the new level converter still remains effective, though over a reduced voltage range
Association of ACE Polymorphism and Diabetic Nephropathy in South Indian Patients
Objective: To study the association of ACE gene polymorphism and diabetic nephropathy in South Indian subjects.
Setting: Outpatient clinic of a specialized hospital.
Patients: The study included 109 South Indian type 2 diabetic patients (72 males and 37 females; age 56.7±9.0 years, mean±SD). The patients were subdivided into two groups: nephropathic (n=86) and normoalbuminuric patients (n=23).
Interventions: Genomic DNA was isolated from the peripheral blood leukocytes. To determine the ACE genotype, genomic DNA was amplified by PCR initially using a flanking primer pair and, subsequently when necessary, with a primer pair that recognizes the insertion specific sequence for confirmation of the specificity of the amplification reactions.
Main outcome measures: ACE genotype distribution in the two study groups.
Results: In the nephropathic patients, ID and DD genotypes were present in 52.3% and 27.9% of the patients, respectively as compared to 34.8% and 21.7% respectively in those with normoalbuminuria. The D allele was present in 80.2% of the nephropathic patients and 56.5% of the normoalbuminuric patients (c 2=4.28, P=0.039; odds ratio 3.12). Therefore, the higher percentage of II genotype in the normoalbuminuric group was 43.5% as compared to the 19.8% in nephropathic patients.
Conclusions: This study showed a positive association between the D allele (ID and DD genotype) of the ACE polymorphism and diabetic proteinuria in South Indian type 2 diabetic patients. Our findings are in keeping with several earlier studies showing a strong association of the D allele of the ACE gene with diabetic nephropathy
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