Cross-Scale Study of the High-Steep Reservoir Banks under Different Mechanical States

AbstractThe deformation of high-steep rocky banks is caused by the self-weight of overlying rock mass and the fluctuation of reservoir water. In this paper, the newly developed testing equipment and the particle flow code (PFC) were used to complete the cross-scale study of the high-steep rocky banks under different mechanical states. The test conditions involved the dry state, saturated state, and hydraulic coupling states under different confining pressures. Combined with the micrographs of the fractured surface under different mechanical states, it can be found that the participation of the water could reduce the bond contact and accelerate the deformation of the particles, ultimately leading to an increase in the plastic deformation and a decrease in the peak strength of the rock mass. Compared to the saturated state, the water in the hydraulic coupling state was not transferred though the storage space was compressed; thus, the water pressure would further promote the extension of the microcracks. When considering the fluctuations of the reservoir water, the changes in the mechanical state may accelerate the degradation rate of the rock mass. The related methods can provide data support and a theoretical basis to the evolution trend of high-steep rocky reservoir banks

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

PUFKEY: A High-Security and High-Throughput Hardware True Random Number Generator for Sensor Networks

Random number generators (RNG) play an important role in many sensor network systems and applications, such as those requiring secure and robust communications. In this paper, we develop a high-security and high-throughput hardware true random number generator, called PUFKEY, which consists of two kinds of physical unclonable function (PUF) elements. Combined with a conditioning algorithm, true random seeds are extracted from the noise on the start-up pattern of SRAM memories. These true random seeds contain full entropy. Then, the true random seeds are used as the input for a non-deterministic hardware RNG to generate a stream of true random bits with a throughput as high as 803 Mbps. The experimental results show that the bitstream generated by the proposed PUFKEY can pass all standard national institute of standards and technology (NIST) randomness tests and is resilient to a wide range of security attacks

A Low Power Low Phase Noise Oscillator for MICS Transceivers

A low-power, low-phase-noise quadrature oscillator for Medical Implantable Communications Service (MICS) transceivers is presented. The proposed quadrature oscillator generates 349~689 MHz I/Q (In-phase and Quadrature) signals covering the MICS band. The oscillator is based on a differential pair with positive feedback. Each delay cell consists of a few transistors enabling lower voltage operation. Since the oscillator is very sensitive to disturbances in the supply voltage and ground, a self-bias circuit for isolating the voltage disturbance is proposed to achieve bias voltages which can track the disturbances from the supply and ground. The oscillation frequency, which is controlled by the bias voltages, is less sensitive to the supply and ground noise, and a low phase noise is achieved. The chip is fabricated in the UMC (United Microelectronics Corporation) 0.18 μm CMOS (Complementary Metal Oxide Semiconductor) process; the core just occupies a 28.5 × 22 μm2 area. The measured phase noise is −108.45 dBc/Hz at a 1 MHz offset with a center frequency of 540 MHz. The gain of the oscillator is 0.309 MHz/mV with a control voltage from 0 V to 1.1 V. The circuit can work with a supply voltage as low as 1.2 V and the power consumption is only 0.46 mW at a 1.8 V supply voltage

A Sensorless Predictive Current Controlled Boost Converter by Using an EKF with Load Variation Effect Elimination Function

To realize accurate current control for a boost converter, a precise measurement of the inductor current is required to achieve high resolution current regulating. Current sensors are widely used to measure the inductor current. However, the current sensors and their processing circuits significantly contribute extra hardware cost, delay and noise to the system. They can also harm the system reliability. Therefore, current sensorless control techniques can bring cost effective and reliable solutions for various boost converter applications. According to the derived accurate model, which contains a number of parasitics, the boost converter is a nonlinear system. An Extended Kalman Filter (EKF) is proposed for inductor current estimation and output voltage filtering. With this approach, the system can have the same advantages as sensored current control mode. To implement EKF, the load value is necessary. However, the load may vary from time to time. This can lead to errors of current estimation and filtered output voltage. To solve this issue, a load variation elimination effect elimination (LVEE) module is added. In addition, a predictive average current controller is used to regulate the current. Compared with conventional voltage controlled system, the transient response is greatly improved since it only takes two switching cycles for the current to reach its reference. Finally, experimental results are presented to verify the stable operation and output tracking capability for large-signal transients of the proposed algorithm

BFWindow: Speculatively Checking Data Property Consistency against Buffer Overflow Attacks

Buffer overflow is one of the main approaches to get control of vulnerable programs. This paper presents a protection technique called BFWindow for performance and resource sensitive embedded systems. By coloring data structure in memory with single associate property bit to each byte and extending the target memory block to a BFWindow(2), it validates each memory write by speculatively checking consistency of data properties within the extended buffer window. Property bits are generated by compiler statically and checked by hardware at runtime. They are transparent to users. Experimental results show that the proposed mechanism is effective to prevent sequential memory writes from crossing buffer boundaries which is the common scenario of buffer overflow exploitations. The performance overhead for practical protection mode across embedded system benchmarks is under 1%.SCI(E)[email protected]; [email protected]

Design and Implementation of a RF Powering Circuit for RFID Tags or Other Batteryless Embedded Devices

A RF powering circuit used in radio-frequency identification (RFID) tags and other batteryless embedded devices is presented in this paper. The RF powering circuit harvests energy from electromagnetic waves and converts the RF energy to a stable voltage source. Analysis of a NMOS gate-cross connected bridge rectifier is conducted to demonstrate relationship between device sizes and power conversion efficiency (PCE) of the rectifier. A rectifier with 38.54% PCE under normal working conditions is designed. Moreover, a stable voltage regulator with a temperature and voltage optimizing strategy including adoption of a combination resistor is developed, which is able to accommodate a large input range of 4 V to 12 V and be immune to temperature variations. Latch-up prevention and noise isolation methods in layout design are also presented. Designed with the HJTC 0.25 μm process, this regulator achieves 0.04 mV/°C temperature rejection ratio (TRR) and 2.5 mV/V voltage rejection ratio (VRR). The RF powering circuit is also fabricated in the HJTC 0.25 μm process. The area of the RF powering circuit is 0.23 × 0.24 mm2. The RF powering circuit is successfully integrated with ISO/IEC 15693-compatible and ISO/IEC 14443-compatible RFID tag chips

The Evolution Characteristics of Soil Heat Storage of the Sidewalls in Subway Stations with Years

The long-term evolution characteristics of the heat reservoir of soil have been analyzed by 15 years of simulation test with periodic indoor and outdoor air temperature conditions. A scale model test of the soil in the subway station sidewalls and software ANSYS fluid-structure coupling heat transfer model are built in this study, which are complementary and mutual authentication. In 1∼15 years, the results show that the maximal temperature rise of soil at 2 m buried depth is 3.9 °C, at 7 m buried depth is 1.6 °C, and at 12 m buried depth is 1.5 °C. On the sidewalls surface the average maximal endothermic heat flow density is 6.8 W/m2 in summer, and the average maximum exothermic heat flow density is 11.3 W/m2 in winter. It provides theoretical reference for the reasonable use of heat storage of the soil in the sidewalls of subway stations