Stability and Startup of Non Linear Loop Circuits

The reliable analysis of DC operating point in circuits with positive feedback topology is often challenging, and frequently performed with ad hoc methods. These techniques are often error prone and lead to the frequent use of sub-optimal or unnecessary additional circuits for the stabilization or determination of the operating point (startup circuits). We present a simple and reliable technique for the determination of “stable” circuit solutions, that is based on the use of available circuit simulators and hence takes advantage of accurate device models. The method has been experimentally validated on a self-biasing current generator fabricated with a standard 0.18 μm CMOS process

Modeling of Hydrogen Storage Materials: A Reactive Force Field for NaH

Parameterization of a reactive force field for NaH is done using ab initio derived data. The parameterized force field(ReaxFFNaH) is used to study the dynamics governing hydrogen desorption in NaH. During the abstraction process of surface molecular hydrogen charge transfer is found to be well described by the parameterized force field. To gain more insight into the mechanism governing structural transformation of NaH during thermal decomposition a heating run in a molecular dynamics simulation is done. The result shows that a clear signature of hydrogen desorption is the fall in potential energy surface during heating

Perturbing singular systems and the correlating of uncorrelated random sequences

A stochastic process may be used to combine sequences with zero autocorrelation to give an autocorrelated sequence. We study this simple paradigm of irreversible mixing. © 2007 American Institute of Physics

A Practical Method for Mapping of Pesticide Loss Risk in Cultivated Soils of Greece

In an attempt to map the soil factors controlling pesticide losses, surface soil samples were collected from 196 sites in the cultivated area of Trifyllia, SW Peloponnese, Greece. Up to now, the pesticide losses risk in the studied area is unknown. For this aim, the following key characteristics that affect movement or binding have been taken into consideration: soil texture, slope and soil organic matter content. A GIS map was compiled from discrete soil variables that affect pesticide losses (leaching and/or runoff). According to soil texture, 3 moderate leaching risk classes, 2 high and 1 low were defined, and the respective classes based on Soil Organic Matter (SOM) content were 3 low risk classes, 2 moderate and 1 class of high risk. The study area consists of two soil slope classes 0-2% and 2-6% which were used to calculate the leaching potential of pesticides. The compiled maps can be used by local authorities in order to minimize the potential negative environmental impacts of pesticide usage at farm level, and to suggest various mitigation strategies. Appropriate farming practices must be applied to decrease leaching or losses by runoff in order to mitigate the pollution of shallow aquifers and surface waters in SW Peloponnese. Rational irrigation management is of high importance as it increases the pesticide effectiveness and reduces off site movement. Moreover, runoff of pesticides can be reduced by using minimum tillage techniques to mitigate soil erosion. Finally, farming systems and practices that increase soil organic matter content (e.g. no tillage) can reduce substantially the risk of water pollution by pesticides

Spanish Ketogenic Mediterranean diet: a healthy cardiovascular diet for weight loss

<p>Abstract</p> <p>Background</p> <p>Ketogenic diets are an effective healthy way of losing weight since they promote a non-atherogenic lipid profile, lower blood pressure and decrease resistance to insulin with an improvement in blood levels of glucose and insulin. On the other hand, Mediterranean diet is well known to be one of the healthiest diets, being the basic ingredients of such diet the olive oil, red wine and vegetables. In Spain the fish is an important component of such diet. The objective of this study was to determine the dietary effects of a protein ketogenic diet rich in olive oil, salad, fish and red wine.</p> <p>Methods</p> <p>A prospective study was carried out in 31 obese subjects (22 male and 19 female) with the inclusion criteria whose body mass index and age was 36.46 ± 2.22 and 38.48 ± 2.27, respectively. This Ketogenic diet was called "Spanish Ketogenic Mediterranean Diet" (SKMD) due to the incorporation of virgin olive oil as the principal source of fat (≥30 ml/day), moderate red wine intake (200–400 ml/day), green vegetables and salads as the main source of carbohydrates and fish as the main source of proteins. It was an unlimited calorie diet. Statistical differences between the parameters studied before and after the administration of the "Spanish Ketogenic Mediterranean diet" (week 0 and 12) were analyzed by paired Student's <it>t </it>test.</p> <p>Results</p> <p>There was an extremely significant (p < 0.0001) reduction in body weight (108.62 kg→ 94.48 kg), body mass index (36.46 kg/m²→31.76 kg/m²), systolic blood pressure (125.71 mmHg→109.05 mmHg), diastolic blood pressure (84.52 mmHg→ 75.24 mmHg), total cholesterol (208.24 mg/dl→186.62 mg/dl), triacylglicerols (218.67 mg/dl→113.90 mg/dl) and glucose (109.81 mg/dl→ 93.33 mg/dl). There was a significant (p = 0.0167) reduction in LDLc (114.52 mg/dl→105.95 mg/dl) and an extremely significant increase in HDLc (50.10 mg/dl→54.57 mg/dl). The most affected parameter was the triacylglicerols (47.91% of reduction).</p> <p>Conclusion</p> <p>The SKMD is safe, an effective way of losing weight, promoting non-atherogenic lipid profiles, lowering blood pressure and improving fasting blood glucose levels. Future research should include a larger sample size, a longer term use and a comparison with other ketogenic diets.</p

Ultra wideband, low-power, 3-5.6 GHz, CMOS voltage-controlled oscillator

In this paper, a low-power inductorless ultra wideband (UWB) CMOS voltage-controlled oscillator is designed in TSMC 0.18 mu m CMOS technology as a part of a ultra wideband FM (UWBFM) transmitter. The VCO includes a current-controlled oscillator (CCO) which generates output frequencies between 1.5 and 2.8 GHz and a voltage-to-current (V-to-I) converter. A low-power frequency doubler based on a Gilbert cell, which operates in weak inversion, doubles the VCO tuning range achieving oscillation frequencies between 3 and 5.6 GHz. Thus, the well-known proportionality between the oscillation frequency and the bias tuning current in CCOs is avoided for the entire achieved tuning range, resulting in a lower power design. The employed architecture provides high suppression, over 45 dB, of the 1st and 3rd harmonics, while enabling high-frequency operation and conversion gain due to the unbalanced structure and the single-ended output. The current consumption is 5 mA at a supply voltage of 1.8 V. The VCO exhibits a phase noise of -80.56 dBc/Hz at 1 MHz frequency offset from the carrier and a very high ratio of tuning range (60.4%) over power consumption equal to 8.26 dB which is essential for a UWBFM transmitter. (C) 2009 Elsevier Ltd. All rights reserved

Ultra-Wideband, Low-Power, Inductorless, 3.1-4.8 GHz, CMOS VCO

A low-power, inductorless, UWB CMOS voltage controlled oscillator is designed in 0.18 mu m CMOS technology targeting to a UWBFM transmitter application. The VCO is a Double-Cross-Coupled Multivibrator and generates output frequencies ranging from 1.55 GHz to 2.4 GHz. A low-power frequency doubler based on a Gilbert cell, which operates in weak inversion, doubles the VCO tuning range from 3.1 GHz to 4.8 GHz. The proportionality between the oscillation frequency and the bias current is avoided in this case for the entire achieved tuning range resulting in a low-power design. The selected architecture provides high suppression, over 45 dB, for the 1(st) and 3(rd) harmonics, while enabling high-frequency operation and conversion gain due to the unbalanced structure and the single-ended output. The proposed VCO draws 4 mA from a 1.8 V supply, it has a phase noise of -76.7 dBc/Hz at 1 MHz offset from the center frequency, while it exhibits a very high ratio of tuning range (43%) over power consumption equal to 7.76 dB

Cubic Spline Approximation of Transfer Functions for Speeding Neural Networks Performances

We propose the approximation of transfer function tanh (i.e. the Hyperbolic tangent) by cubic splines. Thus we save many multiplications and a division required for the standard double precision evaluation of this function. The cost we have to pay is to admit at most 2 decimal digits of inaccuracy in the final result. It is hopped to be small enough for implementation of this new approximants with neural networks