The stable flight posture that affects sports performance during flight is usually formed by the multiple angles of the athlete-ski posture. At present, research on the flight phase is mainly based ...on the single-factor impact analysis based on computational fluid dynamics simulation technology, but studies on the multi-factor coupling relationship of two or more factors is less. This study aims to determine the best optimal-level combination based on the simulation model of this work through comprehensive evaluation from the optimisation perspective of multi-factor coupling. Here, a refined model of the athlete-ski system with the characteristics of ski jumping was established. Reynolds time-averaged method was used for the simulation. A three-factor and five-level simulation test was conducted on the relative inclination between skis, the angle between the body and the ski and the ski V-angle through orthogonal experiment design. Our results show that the optimal-level combination of the relative inclination between skis of 120°, the angle between the body and the ski of 20°, and the ski V-angle of 30° is relatively best in terms of aerodynamic characteristics. Simulation results were similar to the results of the winter field data from video analysis, and the results were effective.
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Efficient performance modeling is an extremely important task for yield analysis and design optimization of analog circuits. In this paper, a novel regression modeling method based on hierarchical ...shrinkage priors is proposed to construct hybrid performance models with both high accuracy and low computational cost. In particular, the user-defined model templates derived from design equations and the general-purpose orthogonal polynomials are combined together to set up a hybrid dictionary. Next, in order to avoid over-shrinking large model coefficients, a novel regression method based on hierarchical shrinkage priors and variational Bayesian inference is adopted for model fitting. A rail-to-rail operational amplifier example demonstrates that the proposed method achieves up to 40% error reduction over other state-of-the-art approaches without increasing the modeling cost.
We reported a novel HIV-1 circulating recombinant form (CRF) among three epidemiologically unlinked patients through men having sex with men in Hebei Province, China. It was named CRF103_01B (this is ...temporary as we have not received the CRF number from HIV databases). A near full-length genome phylogenetic tree showed that CRF103_01B was generated by three B (Western origin) segments and CRF01_AE that was described as cluster 5 lineage of CRF01_AE (CRF01-5). The emergence of CRF103_01B increased the complexity of the HIV-1 epidemic in China.
This paper presents a wideband fractional-N synthesizer whose loop bandwidth is controlled adaptively. A fast automatic frequency-control (AFC) technique which selects the subband of the VCO is ...proposed to reduce the residual fractional error to 1/16 of the reference frequency f ref . A new 4/4.5 prescaler is adopted to lower the quantization noise by reducing the quantization step size to 0.5.
A differential high linearity low-noise amplifier (LNA) based on a capacitor-cross-coupled topology is presented in this paper. An off-chip balun is used for providing DC-bias and canceling the ...channel thermal noise of the transconductance MOS transistors. The LNA uses NMOS load and provides an extra signal feed-forward and noise-canceling path. Analysis shows that the noise contribution of the transconductance MOST is only gamma/20 and the noise figure (NF) of the proposed LNA is 1 + 0.2gamma. The chip is implemented in a 0.18-mum MMRF CMOS process. Measured results show that in 50 M-860 MHz frequency range, the LNA achieved 15 dB gain, 2.5 dB NF, 8.3 dBm IIP3 and consumes only 4 mA current from a 1.8-V supply.
A wideband CMOS variable gain low noise amplifier (VGLNA) used for TV tuner is presented. A single-to-differential (S2D) circuit other than an off-chip balun is applied for high gain mode and a ...resistive attenuator is for five steps (6 dB per step) attenuation in low gain mode. The performance of S2D, especially the noise factor is analyzed. The chip is implemented in a 0.18-mum 1P6M mixed-signal CMOS process. Measurements show that in the 50-860 MHz frequency range, the VGLNA achieves 15 dB maximum gain, 31 dB variable gain range, a minimum 3.8 dB noise figure and 2.6 dBm 11P3 at 15 dB gain while consumes 5.7 mA from a 1.8 V supply.
In this paper, a wide-band CMOS low-noise amplifier (LNA) is presented, in which the thermal noise of the input MOSFET is canceled exploiting a noise-canceling technique. The LNA is designed under ...input/output impedance matching condition. And its noise figure (NF) and linearity analysis are investigated particularly. The LNA chip is implemented in a 0.25-mum 1P5M RF CMOS process. Measurement results show that in 50-860 MHz, the gain is about 13.4 dB, the NF is from 2.4 dB to 3.5 dB, and the input-referred third-order intercept point (IIP3) is 3.3 dBm. The chip consumes 30 mW at 2.5-V power supply and the core size is only 0.15 mm times 0.18 mm.
A 12 th order active-RC filter for DVB Tuner applications with automatic frequency tuning (AFT) is presented in this paper. The filter is implemented in Butterworth biquad structure. The AFT circuit ...is introduced to compensate the frequency variation by a 7-bits switched-capacitor array. The measurement results indicate that the precision of tuning circuit can be controlled less than plusmn2.3%, the in-band group delay variation is 70 ns, and the in-band IM3 achieves -60 dB with -27 dbm input power. This proposed filter circuit, fabricated in a SMIC 0.18 mum CMOS process, consumes 6 mA current with 1.8 V power supply.
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