On-site vibration test and dynamic response analysis of wind turbine of intertidal zone

In our study, the vibration signal of impulse response and attenuation response are extracted using the correlation function and power spectrum, and the natural frequency of wind turbine is determined. Compared with the rotation frequency of the blades of wind turbine which are 1p (one blade) and 3p (three blades), and wind vibration performance of the wind turbine is determined. The natural frequency of wind turbine is between the frequencies of one blade and three blades of wind turbine, which can avoid resonance phenomenon and meet the precision requirement for engineering application. The laws of acceleration and strain response along the wind turbine under ordinary wind load are obtained by installing acceleration sensor and strain gauge along the wind turbine. We found that the acceleration at the wind turbine top increases 10 times than that at the bottom. The acceleration influenced by tide is 1.14 times than that with no tide. The strain produced maximum value at the opening place of wind turbine and near the top, it should be paid attention in the engineering design

A Novel High Linearity and Low Power Folded CMOS LNA for UWB Receivers

© 2017 World Scientific Publishing Company. Electronic version of an article published as Journal of Circuits, Systems and Computers, Vol. 27, No. 03, 1850047, https://doi.org/10.1142/S0218126618500470.This paper presents a high linearity and low power Low-Noise Amplifier (LNA) for Ultra-Wideband (UWB) receivers based on CHRT 0.18μm CMOS technology. In this work, the folded topology is adopted in order to reduce the supply voltage and power consumption. Moreover, a band-pass LC filter is embedded in the folded-cascode circuit to extend bandwidth. The transconductance nonlinearity has a great impact on the whole LNA linearity performance under a low supply voltage. A post-distortion (PD) technique employing an auxiliary transistor is applied in the transconductance stage to improve the linearity. The post-layout simulation results indicate that the proposed LNA achieves a maximum power gain of 12.8dB. The input and output reflection coefficients both are lower than -10.0dB over 2.5~11.5GHz. The input third-order intercept point (IIP3) is 5.6dBm at 8GHz and the noise figure (NF) is lower than 4.0dB. The LNA consumes 5.4mW power under a 1V supply voltage.Peer reviewe

Distillation of Gaussian Einstein-Podolsky-Rosen steering with noiseless linear amplification

Einstein-Podolsky-Rosen (EPR) steering is one of the most intriguing features of quantum mechanics and an important resource for quantum communication. The inevitable loss and noise in the quantum channel will lead to decrease of the steerability and turn it from two-way to one-way. Despite an extensive research on protecting entanglement from decoherence, it remains a challenge to protect EPR steering due to its intrinsic difference from entanglement. Here, we experimentally demonstrate the distillation of Gaussian EPR steering in lossy and noisy environment using measurement-based noiseless linear amplification. Our scheme recovers the two-way steerability from one-way in certain region of loss and enhances EPR steering for both directions. We also show that the distilled EPR steering allows to extract secret key in one-sided device-independent quantum key distribution. Our work paves the way for quantum communication exploiting EPR steering in practical quantum channels

Model Hamiltonian for Topological Insulators

In this paper we give the full microscopic derivation of the model Hamiltonian for the three dimensional topological insulators in the $Bi_2Se_3$ family of materials ($Bi_2Se_3$, $Bi_2Te_3$ and $Sb_2Te_3$). We first give a physical picture to understand the electronic structure by analyzing atomic orbitals and applying symmetry principles. Subsequently, we give the full microscopic derivation of the model Hamiltonian introduced by Zhang {\it et al} [\onlinecite{zhang2009}] based both on symmetry principles and the ${\bf k}\cdot{\bf p}$ perturbation theory. Two different types of $k^3$ terms, which break the in-plane full rotation symmetry down to three fold rotation symmetry, are taken into account. Effective Hamiltonian is derived for the topological surface states. Both the bulk and the surface models are investigated in the presence of an external magnetic field, and the associated Landau level structure is presented. For more quantitative fitting to the first principle calculations, we also present a new model Hamiltonian including eight energy bands.Comment: 18 pages, 9 figures, 5 table

Evaluating the structure characteristics of epikarst at a typical peak cluster depression in Guizhou plateau area using ground penetrating radar attributes

Epikarst, defined as the “skin” of karst environment, is widely developed in southwest China, largely as a result of the subtropical monsoon climate. Typical SW China karst accommodates a dual hydrogeological structure, with surface and subsurface hydrological systems. The epikarst ecosystem of karst environments plays a key role in biogeochemical cycling and energy and material storage and transport. Due to low rates of soil-formation derived from carbonate rock weathering, the soil layer is shallow and scattered, presenting interlocked features within carbonate rock. Research on epikarst structure is primarily based on section field survey with semi-quantitative characterization, often lacking a fully quantitative description of soil-rock structural characteristics. We utilized ground penetrating radar (GPR) attributes to interpret the structure of epikarst at a peak cluster depression in the Guizhou karst plateau. Two typical types of epikarst slope profiles and one peak cluster depression in Maguan Town, Puding County were selected for study. We used MALA GPR equipment with 500 MHz and 50 MHz antennas to acquire data. GPR data was processed conventionally and then average energy attributes, average amplitude attributes and coherence attributes were extracted to interpret the structure of the two epikarst profiles and the soil depth of the depression. The results show that: (i) energy and coherence attributes can highlight the soil-rock structure of the epikarst profiles with relative ease; (ii) compared to the original returned image, the energy attributes visualise the soil and rock medium more effectively; and (iii) the coherence attributes can identify the reflection interface between complete bedrock and bedrock containing fissure and grikes (epikarst). In addition, using the 50 MHz antenna we were able to determine the soil depth in depression with coherence attributes indicating a depth of 3.6 m, very close to the real depth (3.58 m) measured by our auger verification work. GPR attributes provide evidence that the epikarst has developed a large number of fissures filled with soil or other materials, but that the bedrock under the epikarst has few fractures. GPR attributes are therefore helpful for increasing our confidence of studying the structure of slope epikarst structure and depression soil depth