Time-based, Low-power, Low-offset 5-bit 1 GS/s Flash ADC Design in 65nm CMOS Technology

Low-power, medium resolution, high-speed analog-to-digital converters (ADCs) have always been important block which have abundant applications such as digital signal processors (DSP), imaging sensors, environmental and biomedical monitoring devices. This study presents a low power Flash ADC designed in nanometer complementary metal-oxide semiconductors (CMOS) technology. Time analysis on the output delay of the comparators helps to generate one more bit. The proposed technique reduced the power consumption and chip area substantially in comparison to the previous state-of-the-art work. The proposed ADC was developed in TSMC 65nm CMOS technology. The offset cancellation technique was embedded in the proposed comparator to decrement the static offset of the comparator. Moreover, one more bit was generated without using extra comparators. The proposed ADC achieved 4.1 bits ENOB at input Nyquist frequency. The simulated differential and integral non-linearity static tests were equal to +0.26/-0.17 and +0.22/-0.15, respectively. The ADC consumed 7.7 mW at 1 GHz sampling frequency, achieving 415 fJ/Convstep Figure of Merit (FoM)

Characteristics of density current dynamics over rough channel beds

Density currents occur in a variety of natural and man-made scenarios, and this emphasises the importance of studying them. The density-driven currents are the main agent for sediment transportation in many dam reservoirs. In most cases, these currents flow over surfaces which are not smooth; nevertheless, the effect of bottom roughness on the body of these currents has not been fully understood. Hence, this study mainly aims to examine the structure of density currents propagating over rough beds. To achieve this, alterations in the velocity and concentration profiles of the density currents in the presence of different bottom roughness configurations are investigated. The influence of various bottom roughness configurations on entrainment of ambient fluid into these currents is also quantified. Initially, laboratory experiments were carried out with density currents flowing over a smooth surface to analyse the dynamics of the currents with a range of experimental conditions; this provided a baseline for comparison. Then, seven bed roughness configurations (λ/Kr=1, 4, 8, 16, 32, 64 and 128 where λ denotes the downstream spacing between each two subsequent roughness elements and Kr denotes the roughness height) were chosen to encompass both dense and sparse bottom roughness. The rough beds consisted of square cross-section beams which cover the full channel width and are perpendicular to the flow direction in a repeated array. The primary results of this research reveal that the bottom roughness causes deceleration of the currents, reduction of their excess densities and enhancement of water entrainment into them. A critical spacing of the roughness elements (λ/Kr=8) is found for which the currents demonstrate the lowest velocities. For the spacings which are more than the critical value, the controlling influence of the roughness is reduced, and the velocities are increased by expanding the cavities between the elements. The rough bed with λ/Kr=128 roughness has very little influence on the currents and maintained velocities resembling those of the smooth bed. The magnitude of the entrainment rates also varies depending on the roughness configurations with the most substantial entrainment rate occurring for the λ/Kr=8, which is 5.26 times higher than that of the plane surface. Using dimensional analysis, equations are proposed for estimating the mean velocities of the currents and their entrainment rates for various configurations of the bottom roughness. The findings of this research contribute towards a better parameterisation and improved knowledge of density currents flowing over non-plane surfaces. This can lead to a better prediction of the evolution of these currents in many practical cases as well as improved planning and design measures related to the control of such currents

Experiments on density currents dynamics over conic roughness elements

Density currents are flows driven by density differences caused by suspended fine solid material, dissolved contents, temperature gradient or a combination of them. Reservoir sedimentation is often related to sediment transport by density currents. This sedimentation can block bottom outlets, reduce the capacity of reservoir and harms the dam power plants. The head is the leading edge of density currents. In this paper, the influences of artificially roughened beds on dynamics of the frontal region of density currents are investigated experimentally. Three rough beds using conic roughness elements and a smooth bed were tested. The observed trend is that as the surface roughness increases the head concentration and velocity decreases

Experiments on the dynamics of density currents

Density currents occur when fluid of one density propagates along a horizontal boundary into fluid of a different density. In dam reservoirs, density currents are the main transport mechanism for the incoming sediments and they play an important role in redistribution of existing sediments. This paper aims to investigate velocity structure in the body of density currents. To this end, laboratory experiments were performed on density currents having various initial conditions and bottom slopes. Then, vertical velocity profiles were recorded in the body of density currents. The velocity structure of the currents was investigated by fitting equations to the wall and jet regions of the measured profiles, and the constants of the equations were yielded with R2 more than 0.80. Temporal and spatial evolution of density currents were also analysed to study the dynamics of the frontal region of the currents. It was observed that the currents having more bottom slope travel at a further distance. It was also found that 400% increase in the initial concentration of the currents can increase their frontal velocity up to 97%

Nanotechnology-based electrochemical biosensors for monitoring breast cancer biomarkers

Breast cancer is categorized as the most widespread cancer type among women globally. On-time diagnosis can decrease the mortality rate by making the right decision in the therapy procedure. These features lead to a reduction in medication time and socio-economic burden. The current review article provides a comprehensive assessment for breast cancer diagnosis using nanomaterials and related technologies. Growing use of the nano/biotechnology domain in terms of electrochemical nanobiosensor designing was discussed in detail. In this regard, recent advances in nanomaterial applied for amplified biosensing methodologies were assessed for breast cancer diagnosis by focusing on the advantages and disadvantages of these approaches. We also monitored designing methods, advantages, and the necessity of suitable (nano) materials from a statistical standpoint. The main objective of this review is to classify the applicable biosensors based on breast cancer biomarkers. With numerous nano-sized platforms published for breast cancer diagnosis, this review tried to collect the most suitable methodologies for detecting biomarkers and certain breast cancer cell types

Effective Removal of Hexavalent Chromium from Aqueous Solutions Using Ionic Liquid Modified Graphene Oxide Sorbent

Ionic liquid modified reduced graphene oxide (IL-rGO) was prepared and examined for chromate removal. The sorbent was characterized by N2 adsorption-desorption measurement (BET), transmission electron microscopy (TEM), powder X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The sorption behavior of chromate on the ionic liquid modified reduced graphene oxide sorbent from an aqueous medium was studied by varying the parameters such as contact time, initial chromate concentration, pH, and agitation speed. The results showed that sorption kinetics of chromate by IL-rGO follows the pseudo second order, which indicates that the sorption mechanism is both chemical and physical interaction. The sorption isotherm studies revealed that Langmuir model provided the best fit to all the experimental data with an adsorption capacity of 232.55 mg g–1 for IL-rGO. Thermodynamic parameters, such as Gibbs free energy (–2.85 kJ mol–1 at 298 K), enthalpy (55.41 kJ mol–1), and entropy (11.64 J mol–1 K–1) of sorption of the chromate on ionic liquid modified reduced graphene oxide was evaluated, and it was found that the reaction was spontaneous and endothermic in nature. This work is licensed under a Creative Commons Attribution 4.0 International License

A sub-threshold differential cmos schmitt trigger with adjustable hysteresis based on body bias technique

This paper presents a sub-threshold differential CMOS Schmitt trigger with tunable hysteresis, which can be used to enhance the noise immunity of low-power electronic systems. By exploiting the body bias technique to the positive feedback transistors, the hysteresis of the proposed Schmitt trigger is generated, and it can be adjusted by the applied bias voltage to the bulk terminal of the utilized PMOS transistors. The principle of operation and the main formulas of the proposed circuit are discussed. The circuit is designed in a 0.18-μm standard CMOS process with a 0.6 V power supply. Post-layout simulation results show that the hysteresis width of the Schmitt trigger can be adjusted from 45.5 mV to 162 mV where the ratio of the hysteresis width variation to supply voltage is 19.4%. This circuit consumes 10.52 × 7.91 μm2 of silicon area, and its power consumption is only 1.38 μW, which makes it a suitable candidate for low-power applications such as portable electronic, biomedical, and bio-implantable systems

The influence of roughness on the propagation of density currents

Density currents occur when fluid of one density propagates along a horizontal boundary into fluid of a different density. They are also called turbidity currents when the main driving mechanism is from suspended sediments. Reservoir sedimentation is often related to sediment transport by turbidity currents. The leading edge of a density current is deeper than the following current and is called head or front. In this paper, the effects of bed roughness on density currents propagation were studied. Experiments were carried out over a smooth bed as well as three artificially roughened beds by cylindrical roughness elements. Temporal and spatial evolutions of the current front were analyzed. In experiments performed over rough beds, the measured head velocities were smaller than that of smooth bed. The observed trend is that as the surface roughness increases the front velocity decreases

The Satisfaction Level of Participants of the 5th Medical Students' Scientific Olympiad in Iran in 2013

Background & Objective: It is attempted to identify creative and talented individuals and to ensure the satisfaction of volunteers through creating a joyful atmosphere in scientific Olympiads. The aim of the present study was to assess the level of satisfaction of candidates with the quality of the 5th National Medical Sciences Olympiad in Iran. Methods: This cross-sectional study was conducted in the summer of 2013. The study population consisted of the candidates of the 5th National Medical Sciences Olympiad among the medical universities of Iran. The subjects were selected through census method. The data collection tool was a questionnaire designed by the researcher and its validity and reliability were confirmed. Data were analyzed using SPSS software at a significance level of P < 0.050. Results: Of the 222 studied candidates around the country, 67 individuals (30.2%) studied Basic Sciences, 52 (23.4%) Clinical Reasoning, 67 (30.2%) Management of Health Systems, and 36 (16.2%) Art in Medical Education. The mean satisfaction level of candidates with the quality of this national Olympiad was 3.2 ± 1.1, and with the content and functionality of this Olympiad was 3.3 ± 1.2. There was a significant relationship between gender and satisfaction with the quality of the Olympiad (P = 0.002). There was a significant relationship between age (P = 0. 010, r = 0. 131), semester (P = 0. 019, r = 0.122), and academic type (P = 0. 019) and satisfaction with content and functionality of this Olympiad. Conclusion: Satisfaction with quality, content, and functionality of the 5th Olympiad was at a moderate level, and thus, requires improvements. Key Words: Satisfaction, Scientific Olympiad, Talent, 5th Olympiad, Medical student