New approach for SOI pixel sensor:analysis and implementation

Silicon on Insulator (SOI) is an interesting alternative to bulk silicon for the fabrication of integrated circuits due to its advantages with respect to the junction leakage, low switching noise coupling, high temperature immunity, low voltage and low power applications. Recently, SOI transistors have also been used in high speed CPU's due to their high switching performances and their reduced power consumption. Another application where high performances and even higher densities are needed are dynamic memories (DRAM) where floating body SOI MOSFETS were used as an 1T memory node. Using the floating body as a charge storage reduces the unit cell size and drastically increases the bit density and the storage capacity. However, despite technical advances in SOI technology, it has rarely been exploited in optical sensing and imagery. The main reasons are the expected low optical conversion efficiency due to the relatively thin silicon film thicknesses, well below 1 µm and the slow time constants due to slow recombinations at the junctions. In addition, the slim active region reduces the optical bandwidth of such sensors as longer wavelengths are absorbed deeper (and in the case of SOI probably in the buried oxide layer). Despite these major handicaps, it was shown recently that an SOI MOSFET based phototransistor could detect light intensities as low as 5 mW/m2. However, previous work addressed only low light intensities neglecting the slow transients drawbacks. Moreover, as for most fully and partially depleted SOI MOSFET's based photodetectors, it is the drain current variation due to light absorption that was used as a measure of photon densities (for instance the 5 mW/m2 generates 50 fA of photocurrent). Such variations are hard to measure with the needed resolution as such currents are close to the noise levels of any amplifier. This research project proposes a new measurement technique that does not rely on direct quantification of the photocurrent and hence overcomes the problems inherent to noise and low current variations. In addition to that, this novel technique solves the problem of slow drain current recovery time inherent to the slow recombinations at the junctions. This technique relies on the transient charge pumping used to remove continuously photogenerated charges from the electrically insulated body of the MOSFET. Then, since the transistor is always maintained in equilibrium conditions, this approach will get rid of any transient effect occurring in the partially depleted SOI MOSFET. Also presented in this work is an extension of this technique to any floating body MOSFET. We presented also measurement of bulk P-MOSFET whose n-well was left floating and showed that the behaviour was similar to that of a floating body SOI MOSFET. Still using the transient charge pumping to remove extra charge from the floating n-well. Finally, An SOI circuit implementation of this technique was presented. This circuit takes advantage of some of the properties of the floating body SOI MOSFET to implement a first order delta sigma modulator at the pixel level without substantially reducing the fill factor. The first order delta sigma modulator in each pixel, can improve the resolution and offer a direct digital output without the need of an ADC

Measurement and Performance Evaluation of a Silicon On Insulator Pixel Matrix

A new technique for driving silicon-on-insulator pixel matrixes has been proposed in [1], which was based on transient charge pumping for evacuating the extra photogenerated charges from the body of the transistor. An 8x8 pixel matrix was designed and fabricated using the above technique. In this paper, the measurement set-up is described and the performance evaluation procedure is given, together with results of its implementation on the fabricated pixel matrix. The results show the applicability of the charge pumping technique and the effective operation of the image sensor

Five‐Year Hospital Readmission After Coronary Artery Bypass Surgery and the Association With Off‐Pump Surgery and Sex

Background Limited data exist on long‐term readmission and its association with patient and procedural characteristics after coronary artery bypass grafting. We aimed to investigate 5‐year readmission after coronary artery bypass grafting and specifically focus on the role of sex and off‐pump surgery. Methods and Results We performed a post hoc analysis of the CORONARY (Coronary Artery Bypass Grafting [CABG] Off or On Pump Revascularization) trial, involving 4623 patients. The primary outcome was all‐cause readmission, and the secondary outcome was cardiac readmission. Cox models were used to investigate the association of outcomes with sex and off‐pump surgery. Hazard function for sex was studied over time using a flexible, fully parametric model, and time‐segmented analyses were performed accordingly. Rho coefficient was calculated for the correlation between readmission and long‐term mortality. Median follow‐up was 4.4 years (interquartile range, 2.9–5.4 years). The cumulative incidence rates of all‐cause and cardiac readmission were 29.4% and 8.2% at 5 years, respectively. Off‐pump surgery was not associated with either all‐cause or cardiac readmission. The hazard for all‐cause readmission in women over time was constantly higher than the hazard for men (hazard ratio [HR], 1.21 [95% CI, 1.04–1.40]; P=0.011). Time‐segmented analyses confirmed the higher risk for all‐cause (HR, 1.21 [95% CI, 1.05–1.40]; P<0.001) and cardiac (HR, 1.26 [95% CI, 1.03–1.69]; P=0.033) readmission in women after the first 3 years of follow‐up. All‐cause readmission was strongly correlated with long‐term all‐cause mortality (Rho, 0.60 [95% CI, 0.48–0.66]), whereas cardiac readmission was strongly correlated with long‐term cardiovascular mortality (Rho, 0.60 [95% CI, 0.13–0.86]). Conclusions Readmission rates are substantial at 5 years after coronary artery bypass grafting and are higher in women but not with off‐pump surgery. Registration URL: http://www.clinicaltrials.gov/; Unique identifier: NCT00463294

Hybrid Evolutionary Algorithms: Methodologies, Architectures, and Reviews

Evolutionary computation has become an important problem solving methodology among many researchers. The population-based collective learning process, self-adaptation, and robustness are some of the key features of evolutionary algorithms when compared to other global optimization techniques. Even though evolutionary computation has been widely accepted for solving several important practical applications in engineering, business, commerce, etc., yet in practice sometimes they deliver only marginal performance. Inappropriate selection of various parameters, representation, etc. are frequently blamed. There is little reason to expect that one can find a uniformly best algorithm for solving all optimization problems. This is in accordance with the No Free Lunch theorem, which explains that for any algorithm, any elevated performance over one class of problems is exactly paid for in performance over another class. Evolutionary algorithm behavior is determined by the exploitation and exploration relationship kept throughout the run. All these clearly illustrates the need for hybrid evolutionary approaches where the main task is to optimize the performance of the direct evolutionary approach. Recently, hybridization of evolutionary algorithms is getting popular due to their capabilities in handling several real world problems involving complexity, noisy environment, imprecision, uncertainty, and vagueness. In this chapter, first we emphasize the need for hybrid evolutionary algorithms and then we illustrate the various possibilities for hybridization of an evolutionary algorithm and also present some of the generic hybrid evolutionary architectures that has evolved during the last couple of decades. We also provide a review of some of the interesting hybrid frameworks reported in the literature