Sensorless Control of Permanent Magnet Synchronous Motor Based on New Sliding Mode Observer with Single Resistor Current Reconstruction

To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer,a piecewise square root switching function with continuously varying characteristics is designed,and its stability is analyzed by using Lyapunov stability criterion.Secondly,according to the relationship among bus current,switching state and phase current,a single bus resistance sampling current reconstruction scheme without current sensors is adopted,which effectively reduces the cost of motor system.Finally,the feasibility and effectiveness of the proposed scheme are verified by simulation.

A novel 3D geometrical reconstruction method for aluminum foams and FEM modeling of the material response

A novel method for modeling cellular materials is proposed based on MATLAB image processing and synchrotron X-ray computed tomography scan- ning to obtain an accurate calculation result of aluminum foam based on finite element model. The maximum entropy algorithm is employed to obtain the bina- rization image, and the median filtering algorithm is used to reduce the noise after binarization. The external contour and internal pores boundary is extracted by the ＂edge＂ function in MATLAB, and the geometrical model is reconstructed. A two-step mesh algorithm is adopted to mesh the reconstructed geometrical model. Accordingly, the finite element model of aluminum foam is established by the proposed method based on reconstruction geometrical model. The compression behavior of aluminum foam is obtained at 25℃, 100℃, 200℃ by ABAQUS, and good agreements with experiments are achieved by applying the present recon- struction algorithm and modeling method.

Experiments on Nanosecond Optical Parametric Generation for 486.0 nm in BBO Crystal

In this paper, an injection-seeded nanosecond optical parametric generation (OPG) using BBO crystal, which combines relatively low thresholds with a simple and compact configuration, was demonstrated. By seeding externally with distributed feedback (DFB) diode laser at 1313 nm wavelength, pumped by 355 nm laser pulse, the maximum blue laser output power of 1.36 W at a rate of 100 Hz and with linewidth less than 0.13 nm were obtained, and the maximum optical to optical conversion efficiency was to 21.2%.

Comprehensive,Continuous,and Vertical Measurements of Seawater Constituents with Triple-Field-of-View High-Spectral-Resolution Lidar

Measuring the characteristics of seawater constituent is in great demand for studies of marine ecosystems and biogeochemistry.However,existing techniques based on remote sensing or in situ samplings present various tradeoffs with regard to the diversity,synchronism,temporal-spatial resolution,and depth-resolved capacity of their data products.Here,we demonstrate a novel oceanic triple-field-of-view(FOV)high-spectral-resolution lidar(HSRL)with an iterative retrieval approach.This technique provides,for the first time,comprehensive,continuous,and vertical measurements of seawater absorption coefficient,scattering coefficient,and slope of particle size distribution,which are validated by simulations and field experiments.Furthermore,it depicts valuable application potentials in the accuracy improvement of seawater classification and the continuous estimation of depth-resolved particulate organic carbon export.The triple-FOV HSRL with high performance could greatly increase the knowledge of seawater constituents and promote the understanding of marine ecosystems and biogeochemistry.

"镂空法"在胸腔镜食管癌根治术中清扫喉返神经旁淋巴结的应用价值

目的探讨在胸腔镜食管癌根治术中采用"镂空法"行喉返神经旁淋巴结清扫的临床应用价值。方法回顾性队列研究。纳入2017年1月—2020年6月厦门大学附属第一医院胸外科178例T1~T3期食管癌患者临床资料,其中男105例、女73例,年龄41~78岁。178例患者均采用微创McKeown食管癌切除术治疗,根据术中喉返神经淋巴结的清扫方式不同分为两组:采用传统方法100例纳入传统组,采用"镂空法"78例纳入镂空组。比较两组患者术中出血量、手术时间、喉返神经旁淋巴结清扫数、术后喉返神经损伤发生率及损伤程度、术后胸腔引流量、食管吻合口瘘及肺部相关并发症。结果两组患者年龄、性别、肿瘤病灶部位及临床分期等基线资料比较,差异均无统计学意义(P值均>0.05)。镂空组喉返神经旁淋巴结清扫数目左侧为(5.28±1.77)枚、右侧为(3.33±1.36)枚,传统组喉返神经旁淋巴结清扫数目左侧为(1.79±0.96)枚、右侧为(1.05±0.88)枚;同侧组间比较,镂空组均多于传统组,差异均有统计学意义(t=15.710、12.841,P值均<0.01)。镂空组78例中,喉返神经损伤共3例(3.85%),其中轻度损伤2例(2.56%)、中度损伤1例(1.28%);传统组100例中,喉返神经损伤12例(12.00%),其中轻度损伤8例(8.00%)、中度损伤4例(4.00%);镂空组喉返神经损伤的发生率及损伤程度低于传统组,但组间比较差异均无统计学意义(χ^(2)=3.775,Z=-1.936,P值均>0.05)。镂空组肺部感染7例(8.97%)、传统组为20例(20.00%),差异有统计学意义(χ^(2)=4.140,P<0.05)。两组术中出血量、手术时间、术后胸腔引流量及食管吻合口瘘发生率比较,差异均无统计学差异(P值均>0.05)。结论在胸腔镜食管癌切除术中采用"镂空法"清扫喉返神经旁淋巴结是安全、可行的,在增加喉返神经旁淋巴结清扫数目的同时不增加喉返神经损伤的发生率。

The polyketide synthase OsPKS2 is essential for pollen exine and Ubisch body patterning in rice

Lipid and phenolic metabolism are important for pollen exine formation. In Arabidopsis, polyketide synthases （PKSs） are essential for both sporopollenin biosynthesis and exine formation. Here, we characterized the role of a polyketide synthase （OsPKS2） in male reproduction of rice （Oryza sativa）. Recombinant OsPKS2 catalyzed the condensation of fatty acyl-CoA with malonyl- CoA to generate triketide and tetraketide α-pyrones, the main components of pollen exine. Indeed, the ospks2 mutant had defective exine patterning and was male sterile. However, the mutant showed no significant reduction in sporopollenin accumulation. Compared with the WT （wild type）, ospks2 displayed unconfined and amorphous tectum and nexine layers in the exine, and less organized Ubisch bodies. Like the pksb/lap5 mutant of the Arabidopsis ortholog, ospks2 showed broad alterations in the profiles of anther-related phenolic compounds. However, unlike pksb/laps, in which most detected phenolics were substantially decreased, ospks2 accumu- lated higher levels of phenolics. Based on these results and our observation that OsPKS2 is unable to fully restore the exine defects in the pksb/laps, we propose that PKS proteins have functionally diversified during evolution. Collectively, our results suggest that PKSs represent a conserved and diversified biochemical pathway for anther and pollen development in higher plants.

Bending fracture behavior of freestanding (Gd0.9Yb0.1)2Zr2O7 coatings by using digital image correlation and FEM simulation with 3D geometrical reconstruction

It is important to investigate the mechanical performances of (Gd0.9Yb0.1)2Zr2O7 (GYbZ) materials deposited on irregular substrates for improving new thermal barrier coatings. Three-point bending fracture characteristics of freestanding GYbZ coating prepared by supersonic plasma sprayed(SPS) technique were investigated with the help of digital image correlation technique. The cracking time, crack propagation path, and mechanical properties of GYbZ coating were obtained. Meanwhile, the X-ray computed tomography technique was introduced to scan the microstructure of freestanding GYbZ coatings, which are used to establish three-dimensional(3D) finite element model by using the Avizo software. The brittle cracking criterion was applied to describe the bending fracture process of GYbZ coatings. The critical cracking strain was estimated as 0.36%±0.03% by repeatedly comparing the difference between the experimental and simulated curves. The results would be extended to predict the dangerous region and failure mechanisms of GYbZ coatings deposited on irregular substrate during finite element simulations.

Digital-analog hybrid optical phase-lock loop for optical quadrature phase-shift keying

We analyze a feasible high-sensitivity homodyne coherent optical receiver for demodulating optical quadrature phase-shift keying(QPSK). A fourth-power phase-lock loop based on a digital look-up table is used. Considering the non-negligible loop delay, we optimize the loop natural frequency. Without error correction coding, a sensitivity of -37 dBm/-35 dBm is achieved, while the bit error rate is below 10-9 at 2.5 Gbaud/5 Gbaud rate.For the QPSK communication system, the bit rate is twice the baud rate. The loop natural frequency is 0.647 Mrad/s, and the minimized steady-state phase-error standard deviation is 3.83°.

1.5 J high-beam-quality Nd:LuAG ceramic active mirror laser amplifier

A 1.5 J Nd:LuAG ceramic active mirror laser amplifier with a high beam quality is demonstrated in which a 0.8%(atomic fraction)Nd-doped Nd:LuAG ceramic disk with a diameter of 64 mm and a thickness of 5.5 mm is used as a laser gain medium.A maximum single-pass small-signal gain of 2.59 is measured when the pump energy is 11.5 J,with an injected seed energy of 0.4 J;a maximum output energy of 1.5 J is obtained at the repetition rate of 10 Hz.A far-field beam spot 1.25 times the diffraction limit(DL)is achieved by using a stimulated Brillouin scattering phase conjugation mirror(SBS-PCM)for wavefront correction.

Prevalence and Correlates of Healthy Aging Among Elderly Aged 65 Years and Over-6 PLADs,China,2019

What is already known on this topic?Healthy aging among Chinese older people has low prevalence.Some sociodemographic and lifestyle factors were shown to be associated with healthy aging.What is added by this report?The age-adjusted prevalence of healthy aging in the 6 provincial-level administrative divisions(PLADs)of China is 15.8%in 2019.County-level factors,such as the prevalence of healthy communities in a county,as well as some sociodemographic variables and physical exercise,are potential factors of healthy aging.What are the implications for public health practice?These findings showed that more targeted actions,including generalizing healthy communities and individual-level interventions,may be of great importance for healthy aging.

Highly efficient electro-optically Q-switched 473 nm blue laser

An external frequency doubling electro-optically Q-switched neodymium-doped yttrium aluminum garnet (Nd:YAG) 473 nm blue laser was demonstrated. With absorbed pump energy of 48 mJ at 100 Hz repetition rate, about 2 mJ of 473 nm blue laser pulse energy was achieved by cascade frequency doubling. The second harmonic conversion efficiency was 64.5%, and overall optical-optical efficiency was 4.2%, respectively. The blue laser pulse width was less than 10 ns, and beam quality factor was less than 2.4.

Experimental study of the flow and heat transfer of a gas–water mixture through a packed channel

Waste heat recovery from the flue gas of gasfired boilers was studied experimentally by measuring the flow and heat transfer of air and water through six kinds of packing with saturated humid air as the simulated flue gas.The experiments measured the effects of inlet air temperature, inlet air velocity and circulating water flow rate on the flow and heat transfer. The results show that higher inlet air temperatures and lower inlet air velocities lower the flow resistance and increase the heat transfer coefficient. The stainless steel packing had better surface wettability and larger thermal conductivity than the plastic packing, which enhanced the heat transfer between the water and the saturated moist air. When both the flow resistance reduction and the heat transfer enhancement were considered, the experimental results gave an optimal packing-specific surface area. A packed heat exchanger tower was designed for waste heat recovery from the flue gas of gas-fired boilers based on the experimental results which had better flow and heat transfer characteristics with lower pump and fan power consumption, more stable system operation and less thermal fluctuations compared with a non-packed heat transfer system with atomized water.

Simulation and verification of pulsed laser beam propagation underwater using Markov chains [Invited]

One fast simulation method using Markov chains was introduced to simulate angular,energy,and temporal characteristics of pulsed laser beam propagation underwater.Angular dispersion of photons with a different number of collisions was calculated based on scattering function and the state transition matrix of Markov chains.Temporal distribution and energy on the receiving plane were obtained,respectively,by use of a novel successive layering model and receiving ratio.The validity of this method was verified by comparing it with the Monte Carlo ray tracing(MCRT)method.The simulation results were close to those obtained by MCRT but were less time consuming and had smoother curves.

Highly efficient H-β Fraunhofer line optical parametric oscillator pumped by a single-frequency 355 nm laser

A highly efficient laser system output at the H-13 Fraunhofer line of 486.1 nm has been demonstrated. A high pulse energy single-frequency hybrid 1064 nm master oscillator power amplifier was frequency-tripled to achieve 355 nm laser pulses, which acted as the pmnp source of the beta barium borate nanosecond pulse optical para- metric oscillator. With pump energy of 190 mJ, the laser system generated a maximum output of 62 mJ blue laser pulses at 486.1 nm, corresponding to conversion efficiency of 32.6%. The laser spectrum width was measured to be around 0.1 ran, being in conformity with the spectrum width of the solar Fraunhofer line.

Development of single-resonant optical parametric oscillator with tunable output from 410 nm to 630 nm

A single-resonant low-threshold type-Iβ-Ba_(2)BO_(4)(BBO) optical parametric oscillator (OPO) with tunable output from 410 nm to 630 nm at 5 k Hz repetition rate is reported.By taking the noncollinear phase matching method,low-threshold OPO operation could be obtained compared with the configuration of collinear phase matching,and the maximum optical–optical conversion efficiency of 11.8%was achieved at 500 nm wavelength when 0.4 m J pump pulse energy was applied.When the noncollinearity angle was preset at 1.6°,4.8°,and 6.3°,a continuously tuning output with a total spectral range of 220 nm was successfully obtained by adjusting the phase matching angle of the BBO crystal.

Iron-catalyzed cyanoalkylation of difluoroenol silyl ethers with cyclobutanone oxime esters

An iron-catalyzed coupling reaction of difluoroenol silyl ethers and cyclobutanone oxime esters is described. This protocol provides a convenient access to various previously unknown and potentially useful gem-difluoromethylenated ketonitriles inmoderate to good yields. The transformations of resulting products to other fluorinecontaining products is also documented.

Injection-seeded single frequency 2.05μm output by ring cavity optical parametric oscillator

An injection-seeded single-resonant optical parametric oscillator（SROPO） with single frequency nanosecond pulsed 2.05 μm wavelength output is presented. Based on two potassium titanyl phosphate crystals and pumped by a 1064 nm single frequency laser pulse, injection seeding is performed successfully by using the ramp-hold-fire technique in a ring cavity with a bow-tie configuration. The SROPO provides 2.65 m J single frequency signal pulse output with a 17.6 ns pulse duration at a 20 Hz repetition rate. A near-diffraction-limited beam is achieved with a beam quality factor M^2 of about 1.2. The spectrum linewidth of the signal pulse is around 26.4 MHz,which is almost the Fourier-transform-limited value.