Digital Signal Processing for Optical Communications and Coherent LiDAR

Internet data traffic within data centre, access and metro networks is experiencing unprecedented growth driven by many data-intensive applications. Significant efforts have been devoted to the design and implementation of low-complexity digital signal processing (DSP) algorithms that are suitable for these short-reach optical links. In this thesis, a novel low-complexity frequency-domain (FD) multiple-input multiple-output (MIMO) equaliser with momentum-based gradient descent algorithm is proposed, capable of mitigating both static and dynamic impairments arising from the optical fibre. The proposed frequency-domain equaliser (FDE) also improves the robustness of the adaptive equaliser against feedback latencies which is the main disadvantage of FD adaptive equalisers under rapid channel variations. The development and maturity of optical fibre communication techniques over the past few decades have also been beneficial to many other fields, especially coherent light detection and ranging (LiDAR) techniques. Many applications of coherent LiDAR are also cost-sensitive, e.g., autonomous vehicles (AVs). Therefore, in this thesis, a low-cost and low-complexity single-photodiode-based coherent LiDAR system is investigated. The receiver sensitivity performance of this receiver architecture is assessed through both simulations and experiments, using two ranging waveforms known as double-sideband (DSB) amplitude-modulated chirp signal and single-sideband (SSB) frequency-modulated continuous-wave (FMCW) signals. Besides, the impact of laser phase noise on the ranging precision when operating within and beyond the laser coherence length is studied. Achievable ranging precision beyond the laser coherence length is quantified

Study on Barriers and Countermeasures of Technological Innovation of Ecological Service Function Assessment of Urban Greenbelt

AbstractAs the main body of the natural productivity, the urban greenbelt, an irreplaceable comprehensive ecological service system, plays a leading role in beautifying the urban appearance, improving the quality of the urban ecological environment, adjusting the urban ecological balance. The research of ecological service function assessment is a hot research of many domains in recent times, such as ecology, environmental science, sociology, science of culture, economics, etc. Technological innovation is not only the urgent need and significant support system of technological development, but also the urgent need of solving the existing problems of the ecological service function assessment of urban greenbelt. This paper analyzes the main barriers and corresponding countermeasures of the technological innovation, such as unsound innovation mechanism, dated technological means, fault information transform, unsound assessment system, etc., which provides enlightenment and reference for the assessment, planning, construction, management and sustainable development of the ecological service function of urban greenbelt

Impact of Laser Phase Noise on Ranging Precision Within and Beyond Laser Coherence Length in FMCW LiDAR

We study the impact of laser phase noise on ranging precision in a frequency modulated continuous-wave (FMCW) LiDAR system, demonstrating ranging of 384.72 m with ∼15 cm precision at 7× intrinsic laser coherence length

Research on the Artificial Intelligence Attribution Analysis and the Reasons for Decline of Physical Fitness of College Students in the Tropical Area under the Background of "Sunshine Sports"

In 2010, the research team conducted a survey on the physical quality of 1600 college students in Hainan Province, and analyzed the changes in the physical quality of college students in Hainan from 2000 to 2010, and learned about the impact of sunshine sports on the physical quality of college students in Hainan Province. Based on this, a targeted intervention was proposed, which can provide reference for the sports workers and decision-makers in Hainan Province and improve the physical quality of students

Secure Decentralized Access Control Policy for Data Sharing in Smart Grid

Smart grid has improved the security, efficiency of the power system and balanced the supply and demand by intelligent management, which enhanced stability and reliability of power grid. The key point to achieve them is real-time data and consume data sharing by using fine-grained policies. But it will bring the leakage of the privacy of the users and losing of control over data for data owners. The reported solutions can not give the best trade-off among the privacy protection, control over the data shared and confidentiality. In addition, they can not solve the problems of large computation overhead and dynamic management such as users’ revocation. This paper aims at these problems and proposes a decentralized attribute-based data sharing scheme. The proposed scheme ensures the secure sharing of data while removing the central authority and hiding user’s identity information. It uses attribute-based signcryption(ABSC) to achieve data confidentiality and authentication. Under this model, attribute-based encryption gives the access policies for users and keeps the data confidentiality, and the attribute-based signature is used for authentication of the primary ciphertextintegrity. It is more efficient than ”encrypt and then sign” or ”sign and then encrypt”. In addition, the proposed scheme enables user’s revocation and public verifiability. Under the random oracle model, the security and the unforgeability against adaptive chosen message attack are demonstrated

Refined Qingkailing Protects MCAO Mice from Endoplasmic Reticulum Stress-Induced Apoptosis with a Broad Time Window

In the current study, we are investigating effect of refined QKL on ischemia-reperfusion-induced brain injury in mice. Methods. Mice were employed to induce ischemia-reperfusion injury of brain by middle cerebral artery occlusion (MCAO). RQKL solution was administered with different doses (0, 1.5, 3, and 6 mL/kg body weight) at the same time of onset of ischemia, and with the dose of 1.5 mL/kg at different time points (0, 1.5, 3, 6, and 9 h after MCAO). Neurological function and brain infarction were examined and cell apoptosis and ROS at prefrontal cortex were evaluated 24 h after MCAO, and western blot and intracellular calcium were also researched, respectively. Results. RQKL of all doses can improve neurological function and decrease brain infarction, and it performed significant effect in 0, 1.5, 3, and 6 h groups. Moreover, RQKL was able to reduce apoptotic process by reduction of caspase-3 expression, or restraint of eIF2a phosphorylation and caspase-12 activation. It was also able to reduce ROS and modulate intracellular calcium in the brain. Conclusion. RQKL can prevent ischemic-induced brain injury with a time window of 6 h, and its mechanism might be related to suppress ER stress-mediated apoptotic signaling

Using proper orthogonal decomposition to solve heat transfer process in a flat tube bank fin heat exchanger

Proper orthogonal decomposition (POD) reduced-order model can save computing time by reducing the dimension of physical problems and reconstructing physical fields. It is especially suitable for large-scale complex problems in engineering, such as ground heat utilization, sea energy development, mineral exploitation, multiphase flow and flow and heat transfer with complex structure. In this paper, the POD reduced-order model was used to calculate the heat transfer in a flat tube bank fin heat exchanger. The calculating results of the finite volume method (FVM) were adopted as the snapshot samples. Singular value decomposition method was used to decompose the samples to obtain a series of bases and corresponding coefficients on sampling conditions. With these coefficients, interpolation method was used to calculate the coefficients on predicting conditions. And the physical field has been reconstructed using the bases and the interpolated coefficients directly. In the calculation of heat transfer unit of flat tube fin heat exchanger, air-side Reynolds number, transverse tube spacing and the fin spacing were chosen as the variables. The results obtained by the POD method are in good agreement with the results calculated by the FVM. Moreover, the POD reduced-order model presented in this paper is more advantageous in comparison with the FVM in terms of accuracy, suitability, and computational speed.Cited as: Wang, Y., Xia, X., Wang, Y., et al. Using proper orthogonal decomposition to solve heat transfer process in a flat tube bank fin heat exchanger. Advances in Geo-Energy Research, 2017, 1(3): 158-170, doi: 10.26804/ager.2017.03.0