On the use of multi-path inductorless TIAs for larger transimpedance limit

This paper discusses the use of mutli-path inductorless transimpedance amplifiers (TIAs), consisting of several different second-order shunt-feedback sub-TIAs (SF-sTIAs) driven by the photodiode, to break the single-stage technology-dependent transimpedance limit. The advantage of the MP-TIA that is explored in this work is in its third-order transfer function, which provides additional degrees of freedom in tailoring the performance. Pole and zero locations of the MP-TIA transfer function are examined and verified with behavioural simulations. The theoretical transimpedance limit for MP-TIAs based on two SF-sTIAs is derived. The possibility of further increasing the transimpedance limit vs bandwidth trade-off by combining three and four sub-TIAs is investigated with simulations. A transistor-level design example of an MP-TIA is presented. The 0.13-μm CMOS MP-TIA achieves the largest figure-of-merit among published TIAs.     

Memory for emotional trait adjectives in clinically depressed youth

An experiment was conducted to examine memory for emotional trait adjectives in depressed children and adolescents. Two groups of children and adolescents, clinically depressed participants and non-clinical controls, were compared on computerized versions of recall and recognition memory tasks. Three groups of words (positive trait adjectives, negative trait adjectives, and categorized neutral words) were used in the experiment. Results showed that the depressed group recalled significantly more negative adjectives than positive adjectives, whereas the control group recalled the same number of positive and negative adjectives. This effect was predicted by the association between age and level of depression, with the depression-related bias becoming stronger with age. Signal detection analysis revealed that the depressed group did not show any bias in the recognition task. The findings are discussed with respect to cognitive theories of depression with consideration of the developmental implications.     

Information processing in recovered depressed children and adolescents

Previous research into subjective probability estimates for negative events revealed that depressed children estimated events as equally likely to happen to themselves as to other children. In contrast, both controls and anxious children estimated that negative events were more likely to happen to others than to themselves. The present study followed up this finding by investigating the subjective probability judgements concerning future negative events generated by children and adolescents who have recovered from depression. Subjects generated probability estimates either for themselves or for other children for a range of negative events on a visual analogue scale. The results revealed that both recovered depressed and matched control groups estimated negative events as significantly more likely to happen to others than to themselves. It was also found that the recovered depressed subjects estimated that negative events were less likely overall, compared to the controls. These results are discussed in the context of the adult literature.     

A Novel Approach for Prediction of Monthly Ground Water Level Using a Hybrid Wavelet and Non-Tuned Self-Adaptive Machine Learning Model

Water Resources Management - In recent decades, due to groundwater withdrawal in the Kabodarahang region, Iran, Hamadan, hazardous events such as sinkholes, droughts, water scarcity, etc., have...     

Estimation of mixing volumes in buoyant miscible displacement flows along near‐horizontal pipes

We present a methodological framework for estimating the degree of mixing between successive miscible fluids pumped along a near‐horizontal pipe. Either or both of the fluids can be non‐Newtonian, of Herschel–Bulkley type. Overall it is considered that the objective is to minimise mixing. In laminar regimes our estimates are based on front velocity of the leading displacement front. In turbulent regimes the spreading mechanism is dispersion. In addition to the estimates of mixing volumes/lengths, we also predict a minimal flow rate necessary in order to achieve a successful displacement of the residual fluid. © 2013 Canadian Society for Chemical Engineering     

Simulation of gas separation using partial element stage cut modeling of hollow fiber membrane modules

A mathematical model is developed to simulate a gas separation process using a hollow fiber membrane module. In particular, a new numerical technique is introduced based on flash calculation. Such analysis allows identifying the required membrane properties needed to reach module performance of interest. This model is validated for six different gas separation cases taken from literature. Then, the validated model is used to investigate the effect of O₂ and N₂ permeances on O₂ recovery and O₂ mole fraction in the permeate stream. A realistic two‐stage air enrichment process is also proposed for O₂ production using an industrial module with different fibers numbers. Moreover, this model is used to simulate a natural gas purification process using a single unit to determine the required membrane separation area and CH₄ loss. Finally, a two‐stage process is proposed to equally enhance CH₄ retentate mole fraction and decrease CH₄ loss. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1766–1777, 2018     

Economic investigation on the use of internal coating for natural gas trunk-lines

Natural gas transmission through pipeline is the most common method for high capacity gas transmission especially when LNG technology is impossible or uneconomical. These systems are too cost intensive mainly due to fuel consumption of compressor stations. To cope with this problem, internally coated pipeline is considered as an effective approach. A mathematical model was developed in previous study and a visual program was compiled to reach optimum design of natural gas trunk-lines. Effect of different parameters such as pressure, diameter, and material grade can be investigated by developed model. This paper aims to study the effect of surface roughness from economic viewpoint. Results show that internal coating has an insignificant effect on pipeline Life Cycle Cost while it has a considerable decreasing effect on pressure drop and consequently fuel consumption cost. This study shows a coated pipeline is not ever profitable. Internal coating is disadvantageous before breakeven flow rate and breakeven point is a function of other operating conditions. The profitability will increase by increasing flow rate especially at high flow rates. This behavior is a direct result of decrease in laminar sublayer's thickness. Therefore, a detailed economic research seems indispensable over the whole project's lifetime before making any decision about using of internal coating.     

Effect of cigarette smoke exposure on the growth of Streptococcus mutans and Streptococcus sanguis: an in vitro study.

The aim of the present study was to determine the effect of cigarette smoke on the growth of Streptococcus mutans and Streptococcus sanguis. The standard strains of S. mutans (ATCC 25175) and S. sanguis (ATCC 10556) were cultured on blood agar and incubated for 48 hr in three main environments: atmospheric air, carbon dioxide, and cigarette smoke. Kent gold 1(nicotine: 0.1 mg, tar: 1 mg), Kent lights (nicotine: 0.8 mg, tar: 9 mg) and Bahman (nicotine: 1 mg, tar: 13 mg) were the brands used in the present study. Afterwards, digital photographs of the colonies were taken and the diameter of colonies was measured. Data were analyzed using Post Hoc and General Linear Model statistical tests. Cigarette smoke and carbon dioxide environments significantly increased the growth of S. mutans. However, high nicotine/tar content cigarette smoke (Bahman) had the greatest impact on S. mutans and S. sanguis. The mutans/sanguis ratio, which was 0.71 in atmospheric air, increased to 1.07 in the presence of carbon dioxide. Kent gold 1, Kent lights, and Bahman demonstrated a mutans/sanguis ratio of 1, 0.84, and 0.98 respectively. In conclusion, it seems that the growth of S. sanguis and S. mutans is accelerated in the vicinity of cigarette smoke.     

Magnetohydrodynamic (MHD) flows of viscoelastic fluids in converging/diverging channels

The present work is a theoretical investigation of the applicability of magnetic fields for controlling hydrodynamic separation in Jeffrey-Hamel flows of viscoelastic fluids. To achieve this goal, a local similarity solution was found for laminar, two-dimensional flow of a viscoelastic fluid obeying second-order/second-grade model as its constitutive equation with the assumption being made that the flow is symmetric and purely radial. These assumptions enabled a third-order nonlinear ODE to be obtained as the single equation governing the MHD flow of this particular fluid in flow through converging/diverging channels. With three physical boundary conditions available, Chebyshev collocation-point method was used to solve this ODE numerically. Results are presented in terms of parameters such as Reynolds number, Weissenberg number, channel half-angle, and the magnetic number. It was found that these parameters all have a profound effect on the velocity profiles in Jeffrey-Hamel flows. The effect of magnetic field was found to be more striking in that it is predicted to force fluid elements near the wall to exceed centerline velocity in converging channels and to suppress separation in diverging channels. Interestingly, the effect of the magnetic field in delaying flow separation is predicted to become more pronounced the higher the fluid’s elasticity.