Implementation of Single-Precision Floating-Point Trigonometric Functions with Small Area

Meso-level Comparison of Mental Health Service Availability and Use in Chile and Spain

Objective:To examine the urban and rural variation in walking patterns and pedestrian crashes.Design:The rates of pedestrians being struck by motor vehicles was estimated according to miles walked and resident years.Setting:New...

Projection of the cochlea onto the cochlear nuclei was studied by lesioning the spiral ganglion and tracing degenerating fibers and terminals by the Nauta‐Gygax and Fink‐Heimer methods. Basal turn lesions result in degeneration in the medial portion of anterior ventral cochlear nucleus (AVCN) including globular cell area, small spherical cell area, and a small portion of the large spherical cell area; in dorsomedial portion of posterior ventral cochlear nucleus (PVCN) including globular cell area and octopus cell area; and in the medial extreme of the central region of dorsal cochlear nucleus (DCN). Apical turn lesions result in degeneration in the lateral portion of AVCN including globular cell area, small spherical cell area, and a substantial amount of the large spherical cell area; in the ventrolateral portion of PVCN including globular cell area and multipolar cell area; and in the lateral extreme of the central region of DCN. Lesions in intermediate turns of the cochlea result in degeneration in correspondingly intermediate regions of the cochlear nuclear complex. The basal portion of the cochlea (high frequency) projects most strongly to the small spherical cell area and the octopus cell area. The apical turns (low frequency) project most strongly to the large spherical cell area and the multipolar cell area.

Using Composite Estimators to Improve both Domain and Total Area Estimation

The four-level Hybrid Clamped Converter (4L-HCC) is emerging as a promising DC/AC converter topology for high-efficiency medium-voltage drives. However, without proper control, the voltage fluctuation of the DC-link capacitors will be excessive, resulting in distorted AC current and stability issue in low frequency operation. In reality, the distorted current makes it impractical for motor drive during the rotor speed ramp up. This paper presents a control method of the HCC to reduce the DC link capacitor voltage fluctuations at very low frequency. Simulation results show that the proposed method can significantly reduce the capacitor fluctuation from 43% to 4.3% at 5 Hz and allow the HCC to operate at high steady-state frequency (60Hz). Meanwhile, a comparison study is conducted between the 4L-HCC and an equivalent 4-level Modular Multilevel Converter (4L-MMC). Compared to the equivalent MMC converter at very low frequency, the properly controlled HCC has more margin in DC bus voltage to generate high AC output voltage with a lower AC output current in THD and lower switching losses in power switches.

Bayesian ranking of sites for engineering safety improvements: Decision parameter, treatability concept, statistical criterion, and spatial dependence

Energy harvesting of environmental vibrations has been an intensive research field for several years, but there are lingering challenges regarding low frequency applications. Building off our recent invention of a multi-stable, broadband electromagnetic harvester relying on a dual resonant, rectilinear-to-rotary motion converter, research detailed in this paper outlines the creation of theoretical models for the dual resonator and systematically examines these models through experiments to further understand the interrelation of key design parameters and to optimize the harvester's performance. More specifically, the dual resonant system converts broadband rectilinear vibrations to rotational motions via magnetic coupling, while frequency up-conversion via magnetic plucking converts low frequency vibrations into high frequency rotations. By combining the advantages of multi-stable nonlinearity, the invented dual resonant energy harvester possesses high power density at low operating frequencies. In this paper, a nonlinear electromechanical model of the dual resonant harvester is established, and the parametric study is conducted for various repulsive magnets configurations. Subsequent experiments validate the theoretical analysis. Systematic analysis of both theoretical and experimental results shows that the initial rotation angle and the configurations among the coupling magnets are critical to determining the operating patterns of the rotor and fully exploiting the potential of magnetic plucking to increase voltage output. The optimized dual resonator is advantageous over the linear harvesters by providing wider low frequency bandwidth via the inherent nonlinear dynamics.

With the direct-drive wind power system, full-power converter technology has been developed and applied. However, most of wind generators operate at rated voltage of 690 V in wind field at present while direct-drive power system needs the full-scale power converter. For the high-power output, power devices must support higher current. Before the breakthrough of the present level of the current rating, multi converters can meet the low-voltage, high-current condition under the parallel operation. In full-scale power converters of direct-drive wind power system, we combine carrier phase shifted technique and parallel converters successfully, and realize the normal operation in low frequency. More and more multilevel converter used in the larger wind power plant. With the development of multilevel converter , multi-pulse generator is needed. In this paper, a twelve-pair PWM generator based on FPGA is designed for three-phase voltage source 5-level inverters. Carrier phase shifted SPWM (CPS-SPWM) is applied as switch modulation strategy. CPS- SPWM can achieve a high equivalent switching frequency effect at rather low real device switching frequency, which is very suitable for high power equipments. A three-phase voltage source 5-level cascade inverters prototype is accomplished by this twelve-pair PWM generator. The experimental results verify the correctness of the design. Other modulation strategies, such as multilevel space vector modulation and sample time staggered space vector modulation, can also be accomplished by FPGA. This is of much significance to the further application of multi-modular converters and multilevel converters.

This study applied existing methods of landslide susceptibility modelling of the mountainous area of the Cordillera Blanca (Peru), which is prone to landslides. In heterogeneous regions as in the Cordillera Blanca, the performance of a physically based approach Stability Index Mapping (SINMAP) was compared to empirical statistical models using logistic regression and a landslide density model. All models were applied to three different digital elevation models (DEMs): ASTER GDEM, SRTM (both 30-m spatial resolution), and TanDEM-X (12-m spatial resolution). Obtained results were evaluated using the area under the receiver operating characteristic curve (AUC) approach, once for a landslide inventory which extends over the whole study area and once using an inventory of a smaller area. The physically based approach (AUCs between 0.567 and 0.625) performed worse than the statistical models (AUCs from 0.672 to 0.759) over the large area. Additionally, all models received higher performances within the small area. This coincided with differences of the variability of the DEM-derived characteristics (e.g. slope angle and curvature) from the small to the large evaluation area. Using the smaller evaluation area, all models received higher AUC values (0.743–0.799), and the impact of the DEMs was less visible. The analysis of the susceptibility showed that mainly the same slopes are considered as most or least susceptible by all models, but SINMAP is classifying larger areas as unstable or stable. Overall, this study showed that regional-scale landslide susceptibility modelling can lead to reasonable results even in regions with scarce model input data, but performances of different DEMs and models need to be evaluated carefully.

The characteristic of constant-current output (CCO) and constant-voltage output (CVO) on full-bridge topology can be realized by using a traditional double-sided LCC compensation network. The switching from CCO mode to CVO mode can be realized by switching the operating frequency in CCO mode ( f CC) to the operating frequency in CVO mode ( f CV). However, the operating frequency is generally high, the value of L P, L S, and M in the loosely coupled transformer will have a significant influence on the operating frequency of the circuit, which makes it difficult to carry out a long-distance transmission at a lower operating frequency, otherwise, the self-inductance of the coils will be high, even though it is used to transfer low-power. Therefore, in this article, a novel P- CLCL compensation topology based on a single-switching circuit (SSC) is proposed to address these problems. The switching from CCO to CVO can also be realized by changing the operating frequency from f CC to f CV, and a relatively lower operating frequency and a relatively farther transmission distance than full-bridge topology are realized. The calculation method of circuit parameters, implementation of zero-voltage-switching, sensitivity analysis, and load-independent output are discussed. Finally, the simulation and experiment are carried out to verify the correctness of the analysis.

BCH code is adopted as a part of the Forward Error Correction subsystem of DVB-S2 system, which is the next generation digital video broadcast system based on satellite wireless communication system. As DVB-S2 system uses very long code length and multiple code modes, full compatible BCH decoder is high area cost. In order to reduce the area cost of the full compatible DVB-S2 BCH decoder, we have modified the VLSI implementation of Berlekamp Massey Algorithm for key equation solver which is the main part of BCH decoder, rebuilt the Galois Filed Multiplications including the constant Galois Field Multiplications and the general Galois Field Multiplications. In order to support all the code modes and Adaptive Coded Modulation, a novel duo-pipeline reconfigurable architecture have been proposed, which can support code mode switching without stalling the symbol stream. We have implemented the decoder with verilog HDL, and have evaluated it by FPGA platform and ASIC library. The results show that the logic area of the decoder is at least 13% fewer than other existing decoders.

Low switching frequency operation is preferred to improve the system efficiency as well as for optimal use of inverter rating in variable speed drive systems. Low switching frequency operation presents stability and performance issues during transition from lower to higher speed operations using asynchronous to synchronous programmed pulse width modulation (PWM) operation of the inverter. The paper presents a sensorless vector control strategy for the permanent magnet synchronous motor (PMSM) drive operating at low switching frequency with programmed PWM methods. Specifically for the reduced switching frequency operation, the analysis, design and implementation of the key control subsystems consisting of the current controller, back EMF observer and position tracking controller in the drive system are developed and presented. Experimental results validate the design methodology, system performance including the efficiency improvement with the proposed control strategy.

Geometrical effects of wick structures on the maximum phase change capability

The successful launch of GF3 satellite has achieved long-term, sustained and stable acquisition of DOM product all over the China, however, it is a difficult project to deploy angle transmitter or select the same image points between SAR image and optical image manually, which only suitable for SAR image in some small areas, and cannot meet the needs of production and engineering application in large areas. In order to reduce the cost and improve the efficiency of surveying and mapping, a new approach of DOM product generation in large areas was proposed in this paper, which can automatically achieve the process of heterogeneous data matching of SAR data based on the optical DOM reference map and the process of dodging and mosaic line editing. 100 scenes of SLC image of GF3 satellite with the FSII imaging mode covering a large area and Beijing-Tianjin-Hebei region were selected as experimental image, by the heterogeneous data matching, high-precise control points and link points were automatically acquired, and the block adjustment of GF3 data in the experimental area was completed. The RMSE of all control points and link points in azimuth direction was better than 0.41 pixels, the RMSE in range direction was better than 0.85 pixels, and the maximum error was better than 3 pixels. According to the requirement of quality examination, based on the ZY3-DOM data, 5 checkpoints were well-distributed selected for each scene of image. The experimental results showed that the horizontal accuracy of 66% of image orthorectification result were better than 1 pixel (10 m), and 34% of image orthorectification result were better than 2 pixels (20 m), in which the accuracy between 10 and 20 meters were mountain or high-mountain terrain. And the GF3 orthorectification result can meet the horizontal accuracy requirement of 1:50000 scale surveying and mapping in China. At the same time, for the orthorectification result of 100 scenes of GF3 data, dodging and mosaic line were automatically generated and processed, and appropriate dodging points were added to adjust the grey value of one or both sides of image. It can be seen from this article that the hue transition of whole experimental area was more natural, there was no obvious hue difference, and the amount of manual editing was not big. Therefore, the degree of automation of this approach proposed in this paper was very high, which can meet the needs of dodging process in large areas of GF3 data.

In radar sounding, it is highly desirable to operate at low frequencies to improve the depth of penetration. For a spaceborne sounder that is orbiting a planet with an ionosphere, the lowest operating frequency is limited by the plasma frequency of the ionosphere. The ionosphere affects the radar signal through dispersion which changes the shape of the signal and introduces a propagation time delay. The impact on the operation of the sounder is twofold by 1) introducing an unknown delay which makes the surface tracking difficult, and 2) degrading the range compression by changing the chirp shape and duration. In this paper, the authors first demonstrate the effect of the ionosphere on the radar signal through development of an approximate model for the ionosphere of Mars and then present a scheme to compensate for the ionospheric dispersion by taking advantage of the strong specular surface reflection which is expected at low frequencies on Mars. Although the example which is presented in this paper is limited to Mars, the technique is generic and can be used for low frequency radar sounding in general.