An improved low offset latch comparator for high-speed ADCs

This paper presents a new high-speed and low offset latch comparator. The proposed offset compensation technique for latch comparator enables the preamplifier design relaxation for high-speed and high-resolution analog-to-digital converters. Employing the negative resistance of regeneration latch to enhance the comparator gain in input tracking phase is the key idea to reduce the latch input referred offset voltage. The Monte-Carlo simulation results for the designed comparator in 0.18 μm CMOS process show that equivalent input referred offset voltage is 200 μV at 1 sigma while it was 26 mV at 1 sigma before offset cancellation. The comparator dissipates 600 μW from a 1.8 V supply while operating in 500 MHz clock frequency.     

RePizer: a framework for prioritization of software requirements

The standard software development life cycle heavily depends on requirements elicited from stakeholders. Based on those requirements, software development is planned and managed from its inception phase to closure. Due to time and resource constraints, it is imperative to identify the high-priority requirements that need to be considered first during the software development process. Moreover, existing prioritization frameworks lack a store of historical data useful for selecting the most suitable prioritization technique of any similar project domain. In this paper, we propose a framework for prioritization of software requirements, called RePizer, to be used in conjunction with a selected prioritization technique to rank software requirements based on defined criteria such as implementation cost. RePizer assists requirements engineers in a decision-making process by retrieving historical data from a requirements repository. RePizer also provides a panoramic view of the entire project to ensure the judicious use of software development resources. We compared the performance of RePizer in terms of expected accuracy and ease of use while separately adopting two different prioritization techniques, planning game (PG) and analytical hierarchy process (AHP). The results showed that RePizer performed better when used in conjunction with the PG technique.     

Fischer-Tropsch synthesis with an iron catalyst: Incorporation of ethene into higher carbon number alkanes

Tracer studies with C labeled ethene show that for synthesis over a doubly promoted iron catalyst at 7 atm and ca. 60% CO conversion, higher carbon number products are formed from ethene initiation. About 10% of the added ethene (ethene/CO 0.02) is incorporated into C ₅ ⁺ products and that ca. 85% of the ethene that is incorporated does so by initiating chain growth.     

Optimization of Ozonation Process for Disinfection of Dental Unit Waterlines Using Response Surface Methodology

ABSTRACT

The reduction of microbial contamination in dental unit waterlines (DUWLs) appears to be necessary because of a potential risk of infections in immunocompromised patients and medical staff, which are regularly exposed to water and aerosols generated from DUWLs. In the present study, the qualitative and quantitative microbial contamination of water in DUWLs were determined and the conventional biomedical diagnostic tests were applied to identify microorganisms. A 3-level, 2-factor central composite design was utilized to investigate the effects of chief operating parameters and optimize ozone disinfection conditions. Also, the activity of three disinfectant (ozone, NaOCl, and peracetic acid) in microbial decontamination of DUWLs were compared. The results indicated that Microbacterium laevaniformans were the most prevalent genera (21%) among both Gram-negative and positive species in all samples. Regression analysis illustrated the good fit of the experimental data to the predicted model with R² and R²_adj correlation coefficients of 0.988 and 0.980, respectively. Moreover, under the optimal circumstances (Ozone concentration = 1.2 ppm and reaction time = 13.5 min) the disinfection efficiency was 97.52%. The results also revealed that ozone was effective disinfectant to reduce prevalent genera (with the removal of 93.75%, 92.57% and 96.15% of Pseudomonas aeruginosa, Microbacterium ?laevaniformans, and Alcaligenes faecalis, respectively) and already formed biofilms under optimum conditions. Based on achieved results, ozone was highly effective on microbial decontamination compared to peracetic acid and NaOCl disinfectant and can be used for disinfection of DUWLs.     

Student Perceptions of Engineering Entrepreneurship: An Exploratory Study

This study examines students' overall perceptions of the engineering profession in a first‐year course in engineering, and the effect of a pedagogical approach aimed at exposing students to engineering entrepreneurship and their perceptions of engineering entrepreneurship. The approach featured a market game that engaged a pilot group of 20 students in forming IT companies and competing for the best design of a travel agent system. The rest of the students in the course completed the traditional class project, which involved designing and building a land sailer. A pre‐post Likert‐type survey designed to measure students' perceptions of the engineering profession was administered to all students enrolled in this course. In addition, a short answer questionnaire seeking students' pedagogical perceptions of the market game and the land sailer project was administered at the end of the course. Results indicated that students' overall perceptions of the engineering profession significantly improved by the end of the course. More importantly, the results indicated that students who participated in the market game had significantly better perceptions of engineering entrepreneurship, specifically professional skills, than students who participated in the land sailer project. These findings are of considerable interest to engineering schools that want to increase student retention and are looking for novel approaches to assist freshmen in choosing their majors.     

Biosorption of stable cesium by chemically modified biomass of Sargassum glaucescens and Cystoseira indica in a continuous flow system

Pretreatment of biosorbents have been suggested to modify the surface characteristics which could improve biosorption process. Stable cesium biosorption was studied in continuous fixed-bed column by chemically modified biosorbents. Two kinds of brown algae (Sargassum glaucescens and Cystoseira indica) were treated with chemical agents including formaldehyde (FA), glutaraldehyde (GA), potassium hexacyanoferrate (HCF), FA and HCF, and GA and HCF. The highest biosorption capacity (BC) was obtained from C. indica treated with FA (63.5 mg Cs/g biomass) and S. glaucescens treated with FA and HCF (62 mg Cs/g biomass). To study the effect of the best treatments on the BC, the concentration of each treatment agent was decreased. With decreasing FA agent for C. indica treatment, the BC dropped. Treatment of 1g S. glaucescens biomass with 2.2g FA and then 0.18 g HCF resulted in the highest BC (73.08 mg Cs/g dry biomass) which was 35.8 times higher than intact S. glaucescens.     

Oxidative and non-oxidative degradation pathways of L-ascorbic acid

L-Ascorbic acid (AA) is an essential component for organisms and is responsible for various functions in the human body. Its structure is in a way that suffering significant structural changes during storage. Herein, the stability of L-ascorbic acid aqueous solution at various thermal (25 and 90 °C ± 2) and atmospheric oxygen or argon was monitored by optical rotation changes as a function of time intervals. Under oxygen, specific optical rotation [α] of the solution was decreased from + 22.0 to + 2.0 after 32 days and under argon + 11.5 after 9 months at 25 °C. The loss of [α] increased at 90 °C under both oxygen and argon atmospheres. Subsequently, the obtained reaction mixtures were evaporated to dryness and analysed by FT-IR, ¹H-NMR and GC-MS techniques. Results of these analyses indicate that AA was decomposed to a complex mixture of reaction products.     

Thermal vibration analysis of embedded graphene oxide powder-reinforced nanocomposite plates

In this research, thermal vibration analysis of a graphene oxide powder-reinforced (GOPR) nanocomposite embedded plate is carried out once the plate is exposed to different types of thermal...     

Thermomechanical advantages of functionally graded dental posts: A finite element analysis

This study aimed to fabricate dental posts with functionally graded structures comprised of zirconia, titanium, and hydroxyapatite and compare their thermomechanical behavior with homogeneous zirconia and titanium posts in simulated models of upper central incisor. The results indicated the gradual behavior of functionally graded dental posts in terms of physical and mechanical properties. The finite element analysis revealed a more efficient equilibration to the oral environment after removing the thermal stress in functionally graded dental post compared to the homogeneous counterparts. Therefore, the functionally graded structures could reduce the stress/strain concentrations and interfacial stresses in root canal and minimize the likelihood of root fracture.     

Thermo-mechanical wave dispersion analysis of nonlocal strain gradient single-layered graphene sheet rested on elastic medium

Microsystem Technologies - Present research is mainly devoted to show the effects of temperature change on the mechanical properties of in-plane waves propagating in a single-layered graphene...