A new structure for capacitor-mismatch-insensitive multiply-by-two amplification

A new approach to achieve a switched-capacitor multiply-by-two gain-stage with reduced sensitivity to capacitors' mismatches is presented in this paper. It is based on sampling fully differential input signals onto both plates of the input capacitors rather than sampling onto one plate of the capacitors with the other tied to a reference. It uses one operational amplifier (op-amp) in two phases to produce the gain of two (/spl times/2). Comparing to the conventional multiply-by-two gain-stage, the mismatches between the capacitors has a much smaller influence on the accuracy of the gain of two (/spl times/2). Analytical and circuit-level analysis of the architecture and the conventional structure are presented using a generic 0.35/spl mu/m CMOS technology

Modeling of switched-capacitor delta-sigma Modulators in SIMULINK

Precise behavioral modeling of switched-capacitor /spl Delta//spl Sigma/ modulators is presented. Considering noise (switches' and op-amps' thermal noise), clock jitter, nonidealities of integrators and op-amps including finite dc-gain (DCG) and unity gain bandwidth, slew-limiting, DCG nonlinearities and the input parasitic capacitance, quantizer hysteresis, switches' clock-feedthrough, and charge injection, exhaustive behavioral simulations that are close models of the transistor-level ones can be performed. The DCG nonlinearity of the integrators, which is not considered in many /spl Delta//spl Sigma/ modulators' modeling attempts, is analyzed, estimated, and modeled. It is shown that neglecting this parameter would lead to a significant underestimation of the modulators' behavior and increase the noise floor as well as the harmonic distortion at the output of the modulator. Evaluation and validation of the models were done via behavioral and transistor-level simulations for a second-order modulator using SIMULINK and HSPICE with a generic 0.35-/spl mu/m CMOS technology. The effects of the nonidealities and nonlinearities are clearly seen when compared to the ideal modulator in the behavioral and actual modulator in the circuit-level environment

Investigating the hindrances of implementation of occupational health and safety among small medium enterprise’s in the Gauteng Province of South Africa

Abstract: A positive safety culture requires participation of all stakeholders in construction industry, and is shown through the safety-related knowledge, attitudes, beliefs, behaviour and practices of each worker. Therefore, the study is investigating the hindrances in the implementation of occupational health and safety (OHS) among small medium enterprises (SME’S) in the construction industry in the Gauteng Province of South Africa. A structured questionnaire was distributed to different construction companies and construction workers. From the 70 questionnaires distributed, 42 were brought back and they were all valid and usable. Findings from the survey results obtained from the chosen respondents revealed health safety was known and practiced, however, there are hindrances in the implementation such as poor regular inspections and audits, poor management, poor supervision, lack of material and components, lack of management commitment, equipment and tools, poor communication between workers, poor employers involvement, lack of training and risk education to name a few were the major hindrance in the implementation of occupational health and safety among SME’s. Furthermore, if the challenges could be addressed appropriate and effectively result could manifest such as increased productivity; improve quality work; contractors growth and reduced claims; reduced accidents; reduced rework; improved schedule performance. Management and leadership at all levels are therefore encourage to improve construction OH&S in South Africa among SME’s. Moreover, occupational health and safety of the workers is not negotiable, is all pervasive, increases productivity, and leads to better performance, improve the company image, reduced claims and accidents also reduce lost times spent on injuries. The concept of OHS implementation must be emphasized by the client and the consulting team by way of having occasional not once off, a major workshop to be held three times in a year, to increase the awareness and the seriousness of the implementation of OHS

Environmentally sustainable facile synthesis of nanocrystalline holmium hafnate (Ho2Hf2O7): Promising new oxide-ion conducting solid electrolyte

A2B2O7 oxides with defect-fluorite structure are one of the potential candidates for solid oxide fuel cell electrolyte material due to their excessive thermodynamic stability in oxygen potential gradient at elevated temperature between 500 and 900 °C. Holmium hafnate nanoparticles have been synthesised through the Leeds Alginate Process (LAP) using inorganic salts of holmium and hafnium as starting materials immobilized in alginate beads. Ion exchange with sodium alginate and its subsequent thermal treatment have been used to prepare the nanopowder of Ho2Hf2O7. Thermal decomposition of dried beads is carried out at 700 °C for 2 h and 6 h to obtain the nanoparticles of Ho2Hf2O7. This calcination temperature was determined after carrying out simultaneous thermogravimetric analysis and differential scanning calorimetry (TGA/DSC). High Temperature X-ray Diffraction (HT-XRD) was carried out to gain further insight into the thermal decomposition process in static ambient environment. HT-XRD analysis corroborated with the results obtained from TGA/DSC. Nano-crystalline powder of single phase Ho2Hf2O7 has been obtained by calcination of oven dried ion-exchanged alginate beads in relatively low temperature range of 500–700 °C. Rietveld refinement of X-ray diffraction (XRD) data confirmed the formation of single phase defect fluorite structure of Ho2Hf2O7. The crystallographic parameters calculated from TEM and XRD analysis are in excellent agreement with each other. Furthermore, TEM–EDX analysis confirms that the Ho2Hf2O7 synthesised by the facile alginate process is nearly stoichiometric. Raman spectroscopy gives evidence of the presence of oxide-ion vacancy in holmium hafnate which is supported with ac-impedance spectroscopy measurement at selected three temperatures. The present study suggests that the LAP has the capability of yielding on a large scale single phase defect-fluorite nanoparticles of electrolyte materials for solid oxide fuel cells in environmentally sustainable, economical and energy efficiently manner

Experimental Study of Darcy and Non-Darcy Flow in Porous Media

A simple experimental set-up is used to validate capillary-tube models of flow in porous media for (non-) spherical particles and coarse grains of particular/specific mesh sizes. Of the two models used, one model characterizes the structure of the media apart from particle diameter or equivalent particle diameter for non-spherical objects compared to the other model. The magnitude of computed tortuosity for particles/grains studied is in order, however, that of the spherical particles was slightly higher than published values for spheres. Likewise, the ratio of dynamic to static specific surface area was below anticipated and known results in literature. For the non-spherical particle that was approximated as a half-oblate spheroid, the possible error in computed volume and surface area may be the reason for the deviation of computed equivalent diameter from the effective diameter obtained by fitting Ergun correlation to experimental result. The deviation of computed results based on the conducted experiment may in fact be due to error in appropriately fitting straight line to plotted data and precision error of gauges, and possible hysteresis at low flow velocity due to experimental procedur

Assessing and Improving Science Student #SciComm Skills

As the population becomes increasingly connected online, there is a growing need for effective science communication on social media platforms (referred to here as #SciComm). We deployed a survey to all FHSU undergraduate and graduate science students to gauge their experiences with #SciComm. Questions included what training students already receive on communicating science to non-scientists and which classes incorporate building these skills. Our survey found that most students have not received any formal training in online science communication. However, many students reported that they wanted more hands-on #SciComm training. Results were used to develop and implement a workshop for FHSU students to provide a primer on #SciComm during the Spring 2023 semester. Ultimately, we hope to encourage more classroom- and workshop-based activities to better prepare the next generation of scientists for science communication in a digital world

Changes in Cigarette Smoking and Vaping in Response to the COVID-19 Pandemic in the UK: Findings from Baseline and 12-Month Follow up of HEBECO Study

This study investigated UK adults’ changes in cigarette smoking and vaping during the COVID-19 pandemic and factors associated with any changes. Data were from an online longitudinal study. A self-selected sample (n = 332) of 228 smokers and 155 vapers (51 participants were both smokers and vapers) completed 5 surveys between April 2020 and June 2021. Participants self-reported data on sociodemographics, COVID-19-related, and smoking/vaping characteristics. During the 12 months of observations, among smokers, 45% self-reported a quit attempt (27.5% due to COVID-19-related reasons) since the onset of COVID-19 pandemic and the quit rate was 17.5%. At 12 months, 35.1% of continuing smokers (n = 174) reported smoking less and 37.9% the same, while 27.0% reported an increase in the number of cigarettes smoked/day. Among vapers, 25.0% self-reported a quit attempt (16.1% due to COVID-19-related reasons) and the quit rate was 18.1%. At 12 months, 47.7% of continuing vapers (n = 109) reported no change in the frequency of vaping/hour, while a similar proportion reported vaping less (27.5%) and more (24.8%). Motivation to quit smoking and being younger were associated with making a smoking quit attempt and smoking cessation. Being a cigarette smoker was associated with vaping cessation. Among a self-selected sample, COVID-19 stimulated more interest in reducing or quitting cigarette smoking than vaping

MODELING AND OPTIMIZATION OF SURFACE ROUGHNESS IN END MILLING OF ALUMINIUM USING LEAST SQUARE APPROXIMATION METHOD AND RESPONSE SURFACE METHODOLOGY

In end milling, accurate setting of process parameters is extremely important to obtained enhanced surface roughness (SR). Due to a recent innovation in mechanization made it possible to produce high quality manufacturing products. The perceptions of quality in mechanical products are their physical look that is the surface roughness (SR). The aim of this research work is to develop mathematical expression (M.E) and mathematical model using least square approximation method and Response Surface Methodology (RMS) to predict the SR for end milling of Al 6061 alloy. The process parameters that were selected as predictors for the SR are Spindle speed (V), axial depth of cut (a), feed rate (f) and radial depth of cut (d). 30 samples of Al 6061 alloy were carried out using SIEG 3/10/0010 CNC machines and each of the experimental result was measured using Mitutoyo surface roughness tester and Presso- firm. The minimum SR of 0.5 μm were obtained at a spindle speed of 2034.608 rpm, feed rate of 100 mm/min, axial depth of cut of 20 mm, and radial depth of cut 1.5 mm. Analysis of variances shows that the most influential parameters was feed rate. Afte

Effect of aluminum oxide nanoparticles on the rheology and stability of a biopolymer for enhanced oil recovery.

Uncommon and untested biopolymers in field pilot studies, but applied in laboratory studies are combined with Al2O3 nanoparticles to form nanocomposites for enhanced oil recovery (EOR) performance evaluation. Core plug samples of the Niger Delta region and Berea sandstone were used as the porous media for EOR experiments. Incremental oil recovery sequel to waterflooding (secondary recovery) was 5–12% and 5–7% for potato starch nanocomposite (PSPNP) and gum Arabic nanocomposite (GCNP) respectively. The biopolymer nanocomposites showed improved viscosity over the biopolymers. Thus, the nanoparticle served as a viscosity modifier on one-hand and stability enhancer on the other. EOR was affected by biopolymer and nanoparticle concentration with the attendant catch-22 situation of permeability impairment. The overall higher incremental recovery of applying PSPNP came by an intermediate potato starch (PSP) flooding between waterflooding and PSNP flooding. Consequently, slugs of biopolymer and biopolymer nanocomposite may be the way forward knowing that the biopolymers studied have surface-active constituents

Associations between vaping and Covid-19: Cross-sectional findings from the HEBECO study

AIMS: To explore i) associations between vaping and self-reported diagnosed/suspected Covid-19; ii) changes in vaping since Covid-19 and factors associated with these changes; iii) whether Covid-19 motivated current or recent ex-vapers to quit. METHODS: Cross-sectional online survey of 2791 UK adults recruited 30/04/2020-14/06/2020. Participants self-reported data on sociodemographic characteristics, diagnosed/suspected Covid-19, vaping status, changes in vaping and motivation to quit vaping since Covid-19. RESULTS: There were no differences in diagnosed/suspected Covid-19 between never, current and ex-vapers. Bayes factors indicated there was sufficient evidence to rule out small negative (protective) associations between vaping status and diagnosed/suspected Covid-19. Among current vapers (n = 397), 9.7 % (95 % CI 6.8-12.6 %) self-reported vaping less than usual since Covid-19, 42.0 % (37.2-46.9 %) self-reported vaping more, and 48.3 % (43.4-53.2 %) self-reported no change. In adjusted analyses, vaping less was associated with being female (aOR = 3.40, 95 % CI 1.73-6.71), not living with children (aOR = 4.93, 1.15-21.08) and concurrent smoking (aOR = 8.77, 3.04-25.64), while vaping more was associated with being younger (aOR = 5.26, 1.37-20.0), living alone (aOR = 2.08, 1.14-3.85), and diagnosed/suspected Covid-19 (aOR = 4.72, 2.60-8.62). Of current vapers, 32.2 % (95 % CI 27.5-36.8 %) were motivated to quit vaping since Covid-19, partly motivated by Covid-19, and 21.0 %, (10.5-31.4 %) of recent ex-vapers quit vaping due to Covid-19. CONCLUSIONS: Among UK adults, self-reported diagnosed/suspected Covid-19 was not associated with vaping status. Half of current vapers changed their vaping consumption since Covid-19, with the majority reporting an increase, and a minority was motivated to quit due to Covid-19. REGISTRATION: The analysis plan was pre-registered, and it is available at https://osf.io/6j8z3/