Dynamic Reliability Evaluation and Life Prediction of Transmission System of Multi-Performance Degraded Wind Turbine

Wind power is a kind of important green energy.Thus,wind turbines have been widely utilized around the world.Wind turbines are composed of many important components.Among these components,the failure rate of the transmission system is relatively high in wind turbines.It is because the components are subjected to aerodynamic loads for a long time.In addition,its inertial load will result in fatigue fracture,wear and other problems.In this situation,wind turbines have to be repaired at a higher cost.Moreover,the traditional reliability methods are difficult to deal with the above challenges when performing the reliability analysis of the transmission system of wind turbines.To solve this problem,a stress-strength interference model based on performance degradation is introduced.Based on considering the strength degradation of each component,the improved Monte Carlomethod simulation based on the Back Propagation neural network is used to obtain the curve of system reliability over time.Finally,the Miner linear cumulative damage theory and the Carten-Dolan cumulative damage theory method are used to calculate the cumulative damage and fatigue life of the gear transmission system.

Corrigendum to“Anthraquinone derivatives supported by Ti_(3)C_(2)(MXene)as cathode materials for aluminum-organic batteries”[J.Energy Chem.74(2022)174–183]

The authors regret that the printed version of the above article contained an error reference.We hope to correct it here.[14]B.J.M.Christophe Legein,Franck Fayon,Angew.Chem.Int.Ed.,132(2020)19409–19415.

Engineering the spectra of photon triplets generated from micro/nanofiber

Quantum light sources are the core resources for photonics-based quantum information processing.We investigate the spectral engineering of photon triplets generated by third-order spontaneous parametric down-conversion in micro/nanofiber.The phase mismatching at one-third pump frequency gives rise to non-degenerate photon triplets,the joint spectral intensity of which has an elliptical locus with a fixed eccentricity of√6/3.Therefore,we propose a frequency-division scheme to separate non-degenerate photon triplets into three channels with high heralding efficiency for the first time.Choosing an appropriate pump wavelength can compensate for the fabrication errors of micro/nanofiber and also generate narrowband,non-degenerate photon triplet sources with a high signal-to-noise ratio.Furthermore,the long-period micro/nanofiber grating introduces a new controllable degree of freedom to tailor phase matching,resulting from the periodic oscillation of dispersion.In this scheme,the wavelength of photon triplets can be flexibly tuned using quasi-phase matching.We study the generation of photon triplets from this novel perspective of spectrum engineering,and we believe that this work will accelerate the practical implementation of photon triplets in quantum information processing.

云南屏边苗族地区农村中学生生活行为方式与抑郁症状的相关性

目的探讨云南屏边苗族地区农村中学生生活行为方式与抑郁症状的关联,为改变青少年不健康生活行为方式和改善抑郁症状提供数据支持。方法在云南屏边县随机整群选取2所中学的819名初中生,通过调查问卷面对面收集中学生生活行为方式数据,使用抑郁-焦虑-压力量表(Depression Anxiety Stress Scale,DASS-21)评估抑郁症状,使用广义线性模型分析生活行为方式与抑郁症状的关联。结果中学生抑郁症状检出率为33.21%,女生抑郁症状检出率高于男生(39.20%vs26.72%),差异有统计学意义(P<0.05)。学习日视屏时间(β=0.283,95%CI=0.114~0.452)、白天户外活动时间(β=-0.292,95%CI=-0.512~-0.071)、早餐行为(β=-0.263,95%CI=-0.455~-0.071)、新鲜食物消费(β=-0.291,95%CI=-0.529~-0.053)、零食消费(β=0.294,95%CI=0.019~0.569)均与中学生抑郁症状关联(P值均<0.05)。学习日视屏时间(β=0.297,95%CI=0.074~0.520)、白天户外活动时间(β=-0.369,95%CI=-0.673~-0.065)、早餐行为(β=-0.288,95%CI=-0.567~-0.010)、新鲜食物消费(β=-0.423,95%CI=-0.735~-0.110)与男生抑郁症状关联(P值均<0.05)。学习日视屏时间(β=0.306,95%CI=0.056~0.557)、抽烟(β=0.679,95%CI=0.044~1.314)、早餐行为(β=-0.304,95%CI=-0.576~-0.031)、西式快餐消费(β=-1.278,95%CI=-2.425~-0.131)与女生抑郁症状关联(P值均<0.05)。结论屏边苗族地区农村中学生抑郁症状检出率较高,并与不健康生活行为方式相关,改变不健康生活行为方式是预防青少年抑郁症状的关键。

Full scale experimental study of a small natural draft dry cooling tower for concentrating solar thermal power plant

Concentrating solar thermal power system can provide low carbon,renewable energy resources in countries or regions with strong solar irradiation.For this kind of power plant which is likely to be located in the arid area,natural draft dry cooling tower is a promising choice.To develop the experimental studies on small cooling tower,a 20 m high natural draft dry cooling tower with fully instrumented measurement system was established by the Queensland Geothermal Energy Centre of Excellence.The performance of this cooling tower was measured with the constant heat input of 600 kW and 840 kW and with ambient temperature ranging from 20 ℃ to 32 ℃.The cooling tower numerical model was refined and validated with the experimental data.The model of 1 MW concentrating solar thermal supercritical CO2 power cycle was developed and integrated with the cooling tower model.The influences of changing ambient temperature and the performance of the cooling tower on efficiency of the power system were simulated.The differences of the mechanism of the ambient temperature effect on Rankine cycle and supercritical CO2 Brayton cycle were analysed and discussed.

High-performance supercapacitors based on free-standing SiC@PEDOT nanowires with robust cycling stability

Conductive polymers as one of the candidate materials with pseudocapacitor behavior have inspired wide attentions,because of their high conductivity,fexibility,low cost and excellent processability.However,the intrinsically poor cycling stability induced by the volume change over the doping/dedoping redox process limits their practical applications.Herein,we report the exploration of electrodes with robust cycling capacity for supercapacitors(SCs),which are rationally designed by coating conductive poly(3,4-ethylenedioxythiophene)(PEDOT)around free-standing SiC nanowires using an all-dry oxidative chemical vaper deposition(oCVD)method.The as-constructed SiC@PEDOT nanowire architecture enables a specific capacitance of 26.53 m F/cm^(2)at 0.2 m A/cm^(2),which is~370%to that of SiC nanowire counterpart(7.04 m F/cm^(2)).Moreover,their aqueous-based SCs exhibit robust cycling stability with104%capacity retention after 10000 cycles,which is among the highest values achieved for PEDOTbased SCs.

A High Spectral Efficient Frequency-Domain Channel-Estimation Method for the Polarization-Division-Multiplexed CO-OFDM-OQAM System

Contrary to the other multi-carrier modulation systems, the coherent optical orthogonal frequency division multiplexing communication system with an offset quadrature amplitude modulation (CO-OFDM-OQAM) possesses inherent imaginary interference (IMI). This has an important impact on the channel estimation process. Currently, a variety of frequency-domain channel estimation methods have been proposed. However, there are various problems that still exist. For instance, in order to reduce the influence of IMI, it is necessary to insert more guard intervals between the training sequence and the payload, leading to the occupation of excessive spectrum resources. In order to address this problem, this work designs a high spectral efficient frequency-domain channel estimation method for the polarization-division-multiplexing CO-OFDM-OQAM systems. First, the working principle of the proposed method is described in detail. Then, its spectral efficiency, power peak-to-average ratio, and channel estimation performance are studied based on simulations. The simulation results show that the proposed method improves the spectral efficiency without worsening the power peak-to-average ratio. The channel estimation capability of this method is verified in three scenarios of long-distance transmissions, including back-to-back, 100 km, and 200 km transmissions. .

热辐射强度对5种橡胶生胶燃烧和热解特性的影响

为探究热辐射强度对橡胶生胶燃烧和热解特性的影响,以天然橡胶(NR)、三元乙丙橡胶(EPDM)、顺丁橡胶(BR)、丁腈橡胶(NBR)和丁苯橡胶(SBR)为研究对象,利用锥形量热仪测定生胶的燃烧行为,发现在不同强度热辐射作用下,NR和EPDM的热释放速率(HRR)曲线均为后单峰型,但BR,NBR和SBR的HRR曲线会从35 kW/m^(2)热辐射强度下的后单峰型转变为15 kW/m^(2)热辐射强度下的双峰型。该双峰型曲线的形成可以通过着火前样品的外观变化和热解特性演化进行解释。在15 k W/m^(2)热辐射作用下,BR,NBR和SBR样品的上半部分出现了多分层现象,表面形成了较多的硬质炭层,且至少有1个分层的残碳率和热解反应活化能均大于35 kW/m^(2)热辐射作用下样品表层的残碳率和热解反应活化能。该分层现象和热解特性演化可能与低强度热辐射作用下生胶较长时间处于交联反应温度区间有关,而NR和EPDM的交联作用因为返原现象而大幅削弱,故而在15 kW/m^(2)热辐射强度下没有出现双峰型HRR曲线。

A pair of nuclear factor Y transcription factors act as positive regulators in jasmonate signaling and disease resistance in Arabidopsis

The plant hormone jasmonate(JA)regulates plant growth and immunity by orchestrating a genome-wide transcriptional reprogramming.In the resting stage,JASMONATE-ZIM DOMAIN(JAZ)proteins act as main repressors to regulate the expression of JA-responsive genes in the JA signaling pathway.However,the mechanisms underlying de-repression of JA-responsive genes in response to JA treatment remain elusive.Here,we report two nuclear factor Y transcription factors NF-YB2 and NF-YB3(thereafter YB2 and YB3)play key roles in such de-repression in Arabidopsis.YB2 and YB3 function redundantly and positively regulate plant resistance against the necrotrophic pathogen Botrytis cinerea,which are specially required for transcriptional activation of a set of JA-responsive genes following inoculation.Furthermore,YB2 and YB3 modulated their expression through direct occupancy and interaction with histone demethylase Ref6 to remove repressive histone modifications.Moreover,YB2 and YB3 physically interacted with JAZ repressors and negatively modulated their abundance,which in turn attenuated the inhibition of JAZ proteins on the transcription of JA-responsive genes,thereby activating JA response and promoting disease resistance.Overall,our study reveals the positive regulators of YB2 and YB3 in JA signaling by positively regulating transcription of JA-responsive genes and negatively modulating the abundance of JAZ proteins.

Interface-induced polymerization strategy for constructing titanium dioxide embedded carbon porous framework with enhanced chemical immobilization towards lithium polysulfides

The shuttle effect induced by soluble lithium polysulfides(LiPSs)is known as one of the crucial issues that limit the practical applications of lithium-sulfur(Li-S)batteries.Herein,a titanium dioxide nanoparticle embedded in nitrogen-doped porous carbon nanofiber(TiO_(2)@NCNF)composite is constructed via an interface-induced polymerization strategy to serve as an ideal sulfur host.Under the protection of the nanofiber walls,the uniformly dispersed TiO_(2) nanocrystalline can act as capturing centers to constantly immobilize LiPSs towards durable sulfur chemistry.Besides,the mesoporous microstructure in the fibrous framework endows the TiO_(2)@NCNF host with strong physical reservation for sulfur and LiPSs,sufficient pathways for electron/ion transfer,and excellent endurance for volume change.As expected,the sulfur-loaded TiO_(2)@NCNF composite electrode presents a fabulous rate performance and long cycle lifespan(capacity fading rate of 0.062%per cycle over 500 cycles)at 2.0 C.Furthermore,the assembled Li-S batteries harvest superb areal capacity and cycling stability even under high sulfur loading and lean electrolyte conditions.

血管介入治疗对中晚期肿瘤患者凝血功能影响的回顾性研究

目的:研究中晚期肿瘤患者血管介入治疗前后凝血功能的变化。方法:回顾性分析2018年1月至2018年10月于首都医科大学附属北京中医医院行血管介入治疗的174例中晚期肿瘤患者,观察血管介入治疗前后血小板及相关凝血指标的变化。血管介入治疗后1周内行相关指标检测的63例患者设为A组,血管介入治疗后1个月(30±7天)行相关指标检测的111例患者设为B组。数据采用SPSS 22.0软件进行统计学分析。结果:A组纤维蛋白原(FIB)、D-D二聚体(D-D)值较治疗前显著升高,活化部分凝血活酶时间(APTT)缩短,血小板(PLT)值较治疗前降低(均P<0.05);B组FIB、D-D、PLT值较治疗前降低,凝血酶原时间(PT)、APTT较治疗前延长(P>0.05);血管介入治疗前,共58例患者伴有血液高凝状态,其中A组28例(48.3%),B组30例(51.7%);血管介入治疗后,共71例(40.8%)患者伴有血液高凝状态,其中A组40例(56.3%),B组31例(43.7%)。结论:血管介入治疗在短期内可影响相关凝血指标,加剧中晚期肿瘤患者的血液高凝状态,但随着时间延长,对患者凝血功能的影响逐渐降低,相关血凝指标可逐渐恢复至治疗前水平,建议在血管介入治疗后密切监测患者凝血功能变化。

白内障术后黄斑囊样水肿的OCTA研究

目的:使用光学相干断层扫描血管造影术(Optical Coherence Tomography Angiography, OCTA)对白内障术后黄斑囊样水肿患者的黄斑区视网膜厚度及血流情况进行研究。材料:本研究为前瞻性研究,收集2017年4月到2018年2月期间就诊于青岛大学附属医院眼科的白内障术后黄斑囊样水肿患者20例20只眼,正常白内障术后患者20例20只眼,利用OCTA测量白内障术后黄斑囊样水肿患者治疗前后、正常白内障术后患者的黄斑区视网膜厚度,黄斑的灌注、血管密度并进行分析。结果:正常组黄斑血管密度为19.23 &#177;1.88,灌注密度为0.429 &#177;0.039,黄斑区视网膜厚度为254.12 &#177;22.02 μm,白内障术后黄斑囊样水肿组黄斑血管密度为18.66 &#177;2.911,灌注密度为0.408 &#177;0.045,黄斑区视网膜厚度为482.15 &#177;19.23 μm,黄斑囊样水肿组黄斑血管、灌注密度较正常组减少(P <0.05),黄斑区视网膜厚度增加(P <0.01)。经过曲安奈德治疗后,白内障术后黄斑囊样水肿组黄斑血管密度为19.06 &#177;2.911,灌注密度为0.418 &#177;0.031,黄斑区视网膜厚度为268.34 &#177;17.14 μm,较治疗前血管密度、灌注密度增加(P <0.05),黄斑区视网膜厚度减少(P <0.01)。结论:白内障术后黄斑水肿患者黄斑区视网膜厚度增加,血流密度及灌注密度减少。经曲安奈德治疗后,白内障术后黄斑水肿患者黄斑区视网膜厚度较治疗前减少,血管密度及灌注密度较治疗前增加。

Review on heterophase/homophase junctions for efficient photocatalysis: The case of phase transition construction

Semiconductor photocatalysts are extensively applied in environmental treatment and energy conversion.However,one of their major disadvantages is their relatively low photocatalytic performance owing to the recombination of generated electron-hole pairs.The presence of the phase junction is an effective way to promote the photocatalytic activity by increasing the separation efficiency of the electron-hole pairs.Accordingly,extensive research has been conducted on the design of phase junctions of photocatalysts to improve their charge transfer properties and efficiencies.Therefore,for the design of an appropriate phase junction and the understanding of the mechanism of electron-hole separation,the development of the photocatalytic phase junction,including the preparation methods of the heterogeneous materials,is tremendously important and helpful.Herein,the commonly used,externally induced phase transformation fabrication techniques and the primary components of the semiconductors are reviewed.Future directions will still focus on the design and optimization of the phase junction of photocatalytic materials according to the phase transition with higher efficiencies for broadband responses and solar energy utilization.Additionally,the most popular phase transformation fabrication techniques of phase junctions are briefly reviewed from the application viewpoint.

Comparison of yield performance between direct-seeded and transplanted double-season rice using ultrashort-duration varieties in central China

Labor scarcity requires double-season rice to be planted by direct seeding as an alternative to transplanting. Only ultrashort-duration varieties can be used in direct-seeded, double-season rice(DSD) in central China where thermal time is limited. Whether ultrashort-duration varieties grown in DSD can be as productive and efficient in nitrogen(N) use as transplanted double-season rice(TPD) remains unclear. Field experiments were conducted in Hubei province, central China with two establishment methods(DSD,TPD) and three N rates in the early and late seasons of 2017 and 2018. Nitrogen treatments included zero-N control(N0), total N rate of 60 kg N ha;with equal splits at basal, midtillering, and panicle initiation(N1), and weekly N application at 15 kg ha;from seeding/transplanting to heading(N2). Both early-and late-season rice under DSD matured within 95 days, on average 9 days shorter than rice under TPD. The grain yield of DSD was comparable to or higher than that of TDP in both seasons, although the daily yield was significantly higher under DSD than under TDP. Before heading, DSD had higher leaf area,stem number, intercepted radiation, and radiation use efficiency than TPD, which compensated for the negative effect of short growth duration on biomass production. Total dry weight and harvest index under DSD were comparable to or higher than those under TDP. In general, the recovery efficiency of fertilizer-N under DSD was higher than that under TPD, but the reverse was true for physiological N use efficiency. Thus, there was no significant difference in agronomic N use efficiency between DSD and TPD. These results suggested that DSD with ultrashort-duration varieties is a promising alternative to TPD in central China for maintaining high grain yield and N fertilizer use efficiency with less labor input.

高度近视合并白内障患者三焦点人工晶体植入的临床效果观察

目的:观察高度近视合并白内障患者植入三焦点人工晶状体的临床疗效。方法:回顾性研究。收集2016年11月至2017年10月在我院行人工晶体植入术的白内障患者70例70眼,根据患者术前屈光状态及植入晶体类型分为三组,分析其术后3月的裸眼远、中、近视力及最佳矫正远视力下的中、近视力,客观视觉质量、视觉不良症状、脱镜率及手术满意度。结果:术后3月,A、B组裸眼中、近视力,远矫下的中、近视力差异有统计学意义(P 0.05);A组MTF cutoff高于B组,SR、OSI、100%、20%、9%OVs低于B组,但差异无统计学意义(P >0.05);A、C组裸眼远、中、近视力、MTF cutoff、SR、100%、20%、9%OVs差异无统计学意义(P <0.05);A组眩光、光晕的发生率略高于B组;三组患者的脱镜率分别为90%、32%、100%。结论:高度近视合并白内障患者术中植入三焦点人工晶体可以获得较好的全程视力和良好的视觉质量,术后对框架眼镜的依赖显著降低,患者满意度高。

THE QUASI-BOUNDARY VALUE METHOD FOR IDENTIFYING THE INITIAL VALUE OF THE SPACE-TIME FRACTIONAL DIFFUSION EQUATION

In this article,we consider to solve the inverse initial value problem for an inhomogeneous space-time fractional diffusion equation.This problem is ill-posed and the quasi-boundary value method is proposed to deal with this inverse problem and obtain the series expression of the regularized solution for the inverse initial value problem.We prove the error estimates between the regularization solution and the exact solution by using an a priori regularization parameter and an a posteriori regularization parameter choice rule.Some numerical results in one-dimensional case and two-dimensional case show that our method is efficient and stable.

A Review of the Design and Architecture of Starch-Based Dietary Foods

Carbohydrates,which are mostly present in sugar,starch,and fiber,are one of the main ingredients of food and the primary source of energy in the human diet.Among these three main sources,starch stands out as one of the most abundant reserves of carbohydrates.Investigating starch would not only enhance our understanding of the functionality of starch in the human body but also aid in the design of novel starch-based dietary foods.The present review first provides a state-of-the-art understanding of the various classifications of dietary starches,including rapidly digesting starch(RDS),slowly digesting starch(SDS),and resistant starch(RS).Moreover,both the in vivo and in vitro determination methods of the digestibility of starch-based dietary foods are discussed.Based on the current understanding,present research strategies to design novel starch-based dietary foods through either the direct addition of modified starch or the alteration of processing conditions are highlighted.Furthermore,certain perspectives related to the future research directions of starch-based foods are also included.

3D placement of unmanned aerial vehicles and partially overlapped channel assignment for throughput maximization

This paper investigates a wireless system with multi-Unmanned Aerial Vehicles(UAVs)for improving the overall throughput.In contrast to previous studies that optimize the locations of UAVs and channel assignment separately,this paper considers the two issues jointly by exploiting Partially Overlapped Channels(POCs).The optimization problem of maximizing network throughput is formulated as a non-convex and non-linear problem.In order to find a practical solution,the problem is decomposed into two subproblems,which are iteratively optimized.First,the optimal locations of UAVs are determined under a fixed channel assignment scheme by solving the mixed-integer second-order cone problem.Second,an efficient POC allocation scheme is determined via the proposed channel assignment algorithm.Simulation results show that the proposed approach not only significantly improves system throughput and service reliability compared with the cases in which only orthogonal channels and stationary UAVs are considered,but also achieves similar performance using the exhaustive search algorithm with lower time complexity.

高校共青团组织在大学生双创教育中的地位——以山西部分高校为例

现如今,面对严峻的就业形势以及创新型国家建设的需要,各大高校对于我们广大大学生的创新创业教育显得尤为重要。本文根据目前山西部分高校在创新创业教育中存在的问题,通过走访调查、查阅文献资料等方式,对高校共青团组织在创新创业教育中的作用进行了深入了解和全面分析,提出高校共青团组织在大学生创新创业教育工作顺利开展和高效进行的建议。

TWO REGULARIZATION METHODS FOR IDENTIFYING THE SOURCE TERM PROBLEM ON THE TIME-FRACTIONAL DIFFUSION EQUATION WITH A HYPER-BESSEL OPERATOR

In this paper,we consider the inverse problem for identifying the source term of the time-fractional equation with a hyper-Bessel operator.First,we prove that this inverse problem is ill-posed,and give the conditional stability.Then,we give the optimal error bound for this inverse problem.Next,we use the fractional Tikhonov regularization method and the fractional Landweber iterative regularization method to restore the stability of the ill-posed problem,and give corresponding error estimates under different regularization parameter selection rules.Finally,we verify the effectiveness of the method through numerical examples.