Safety Evaluation of Water Environment Carrying Capacity of Five Cities in Ningxia Based on Ecological Footprint of Water Resources

[Objectives]To make safety evaluation of water environment carrying capacity of five cities in Ningxia based on ecological footprint of water resources.[Methods]With the help of the grey relational model,15 indicators were selected from the natural,economic,and social aspects,and the most influential factors in the three fields were selected.Based on the concept of ecological priority,the water resources carrying capacity of the five cities in Ningxia from 2010 to 2019 was calculated with the help of the water resources ecological footprint model.Then,the indicators of the water resources ecological footprint model were coupled with the existing indicators to establish a comprehensive evaluation indicator system.Finally,the changes of the water environment carrying capacity of the five cities in Ningxia were analyzed with the help of the principal component analysis(PCA).[Results]The ecological pressure of water resources and the ecological deficit of water resources in the five cities were relatively large.Specifically,Yinchuan City had the most obvious deficit of water resources but good carrying capacity;Zhongwei City had a large ecological deficit of water resources,poor carrying capacity,and the largest ecological pressure index of water resources;Guyuan City had low water resources ecological deficit,water resources ecological carrying capacity and water resources ecological pressure index.[Conclusions]Through the analysis of the coupling indicator system,it can be seen that the water environment carrying capacity of the five cities is in an upward trend,indicating that the water environment in each region tends to become better.

Research on dynamic matching model of electric vehicles and charging facilities in China:A case study of taxis in Beijing

Charging infrastructure supports the rapid development of China's new energy vehicle industry.It not only plays a decisive role in providing accessible and convenient services for electric vehicle(EV)users but also,in one of the seven new infrastructure areas,plays an important role in stabilizing growth and unleashing economic potential during the new coronavirus(COVID-19)pandemic,impacting China's economy.In this study,the system dynamics model was used to predict the development of the EV industry and the demand for charging infrastructure,while considering the influence of policy,increase in EV mileage,and consumer purchase intention index.Furthermore,using the matching of EVs and charging infrastructure in Beijing and policy oriented sensitivity analysis,a simulation of the construction of battery swap taxis and power stations under three policy scenarios was conducted.This research shows that with policies implemented to support charging infrastructure and swapping compatible taxis,Beijing can achieve its goal of replacing all EVs with fast-swap batteries and fast-charging functions within three years.

一种L/C 双频段盘锥和微带阵列的天线综合设计

设计了一种工作于L、C频段的复合天线,天线采用盘锥天线和微带阵列叠层复合设计。盘锥天线通过加载金属短路柱实现小型化和宽频化,在0.95~1.6 GHz辐射水平全向电磁波;微带天线采用2×2小型化阵列,在4.25~4.35 GHz实现高增益定向电磁波辐射。该复合天线内嵌安装于金属腔体内,腔体直径为200 mm,高度为26.5 mm,易与蒙皮共形,能够同时满足L频段多种数据链功能和C频段无线电测高功能需求,可广泛应用于航空航天领域。

一种降低机体对天线方向图影响的多天线应用方案

针对机载超短波通信的需求,为降低机体对超短波天线方向图的影响,提出了一种机载超短波多天线应用方法。通过多天线的使用和天线优化布局,改善天线装机后带来的辐射畸变的影响,保证天线空域覆盖率,提升超短波通信能力。

一种新型高增益小型化四臂螺旋天线

针对卫星通信、卫星导航设备中四臂螺旋天线低仰角增益低、馈电网络尺寸不能满足安装要求的问题,设计了一种新型四臂螺旋天线,采用折叠式威尔金森(Wilkinson)移相馈电网络馈电,采用类八臂渐变式螺旋臂的方法提升天线低仰角增益。天线仿真和测试结果吻合良好,结果显示,在±60°~±90°低仰角范围内天线增益提高了1~2dB,天线轴比保持在2以内,馈电网络高度降低了1.5cm。该四臂螺旋天线具有低仰角高增益、圆极化特性良好、尺寸小等特点。

直升机测向天线阵装机影响分析

针对直升机信号侦查测向需求,分析了6元T型测向天线阵装机后受机身及周围遮挡物的影响,以及天线的幅度一致性和相位一致性的变化。针对分析结果,给出了优化布局设计建议,提高天线阵元之间的幅度和相位一致性,提升信号测向的性能。

三伸缩杆驱动的光伏板视日追踪系统设计与研究

视日追踪系统能够显著地提高光伏板接收太阳能的效率。相较于串联式,并联式视日追踪系统以其追踪精度高、功耗小和耗材少等优点在太阳能追踪中具有很大的应用潜力,但相关研究尚属起步阶段且并不能满足实际需求。基于3-RPS并联机构,提出了一种新型三伸缩杆驱动的光伏板视日追踪系统。其中,三根伸缩杆结构相同,且呈正三角形布置;每根伸缩杆的上端通过复合铰链与光伏板相连,下端通过转动铰链与基座相连;通过改变三根伸缩杆的长短驱动光伏板运动,实现对太阳的实时追踪。首先,结合太阳运动规律和3-RPS的机构性质,根据空间几何学,建立了追日过程中的相关数学模型。在此基础上,针对特定的追踪地点、日期和机构尺寸,对系统分别在夏至日和冬至日当天进行了仿真分析。进而,针对每条支链所需伸缩杆节数过多的问题,提出了动平台质心高度可动的控制策略。对于目前商业化球铰转动范围不足的问题,采用虎克铰链加转动铰链组成的复合铰链代替球铰的结构方案,同时,得到了复合铰链绕其各转动轴线的转动角度。然后,由于追日过程是一个缓慢的过程,通过建立系统的瞬时静力学模型,仿真得到了系统所需的驱动力和驱动功率,最大驱动力为164.65 N,总的最大驱动功率为2.94×10–3 W。最后,实施了系统的追日实验,验证了理论和仿真分析的正确性,同时得到了系统的追踪精度在±0.4°以内。

3D打印种植导板在前牙区不同术式的精度比较

目的比较3D打印种植导板引导前牙牙种植在不同术式下的精度。方法选择21例(32个牙位)牙缺失患者,制作仿真翻瓣与不翻瓣颌骨模型,分为翻瓣组(FP组)与不翻瓣组(FPS组),分别设计制作牙种植导板,比较两组牙种植体实际位置与术前规划在顶端、底端、垂直向距离的偏差值和角度偏差值。采用SPSS 19.0软件对数据进行统计学分析。结果FPS组与FP组种植体顶端、底端、垂直向距离偏差值和角度偏差值的差异均有统计学意义(P<0.05);与FPS组相比,FP组偏差值更小,精度更高。结论3D打印种植导板可提高牙种植的精确性,翻瓣与不翻瓣的不同术式对牙种植精度有一定的影响,临床医生可根据实际情况合理选择术式。

CAD/CAM导板在后牙区种植精度的体外研究

目的后牙区利用计算机辅助设计和制作(computer aided design and computer aided manufacture,CAD/CAM)导板种植时,比较翻瓣与不翻瓣两种术式的精度。方法选取20名后牙种植患者的锥形束CT(cone beam CT,CBCT)资料和石膏模型,采用3D打印技术制作翻瓣与不翻瓣树脂模型,运用导板在两种模型上模拟牙种植术,分别计算术前术后种植体位置偏差进而比较两种术式的精度。结果 CAD/CAM导板在后牙区辅助种植时,翻瓣与不翻瓣术式种植体顶端偏差分别为(0.95±0.36) mm、(1.33±0.43) mm;底端偏差分别为(1.53±0.56) mm、(1.94±0.30) mm;角度偏差分别为3.45°±1.10°、3.31°±1.55°;深度偏差分别为(0.75±0.47) mm、(1.43±0.41) mm。翻瓣与不翻瓣两种术式在种植体距离偏差上有统计学差异,角度偏差上没有统计学差异。结论 CAD/CAM导板引导的种植翻瓣术式比不翻瓣术式在种植体距离偏差上更准确。

The Switching Fractional Order Chaotic System and Its Application to Image Encryption

Many studies on fractional order chaotic systems and secure communications have been carried out, however,switching fractional order chaotic system and its application to image encryption have not been explored yet. In this paper,a new switching fractional order chaotic system is proposed,containing fractional order Chen system and the other two fractional order chaotic systems. Chaotic attractors and dynamical analysis including Lyapunov exponent, bifurcation diagram,fractal dimension, dissipation, stability and symmetry are shown firstly. After that, some circuit simulations through Multisim are presented. By controlling switch k_1 and k_2, switching among the three fractional order chaotic subsystems can be realized. Finally,we apply the switching fractional order chaotic system to image encryption using exclusive or(XOR) encryption algorithm. The encryption scheme could increase randomness and improve speed of encryption.

机载垂尾超短波一体化天线的设计

设计了一种适用于机载垂尾顶部安装的超短波一体化天线,实现了天线与天线罩结构和性能上一体化。对一体化和分离式两种形式的超短波天线进行了研究,采用曲流和匹配加载技术实现了天线的宽频带工作特性,在工作频带内实测驻波比≤2.5,相较于分离式天线,一体化天线解决了天线与天线罩之间的加载耦合效应而导致天线增益下降的问题,在全频带增益提高了约2 dB,重量降低了1.9 kg,天线性能得到全面提升。

Design and Optimization of Planting Process Parameters for 2ZYX-2 Type Green Onion Ditching and Transplanting Machine

Considering the current low level of mechanization for domestic green onion planting and the high labor intensity of artificial planting,a 2ZYX-2 green onion ditching and transplanting machine,which can complete ditching,ridging,transplanting,repression,soil covering and other operations,is designed in this study.The Central Composite test design method was carried out with the speed of the transplanting machine,the depth of the opener and the horizontal position of the opener as the experimental factors and with the qualification ratio of perpendicularity,the variation coefficient of the plant spacing and the qualification ratio of the planting depth as the test index.Through the analysis of the model interaction and response surface,the change laws that the influence the machine’s forward speed,the depth of the opener and the horizontal position of the opener were studied.The regression model was optimized by Design-Expert 8.0.6 software,and the accuracy of the predicted results was verified by experiments.The optimal working parameters showed that the forward speed of the machine was 0.06 m/s,the depth of the opener was 102 mm,and the horizontal position of the opener was 29 mm.Under conditions of optimal working parameters,the qualification rate of the verticality was 86.83%,the coefficient of variation for the plant spacing was 2.77,and the pass rate of planting depth was 88.26%.The research related to the thesis can provide a reference for the mechanized planting of green onion,which is of great significance to the cost-effectiveness of the green onion industry.

Improvement of tensile superelasticity by aging treatment of NiTi shape memory alloys fabricated by electron beam wire-feed additive manufacturing

For the first time,this work comprehensively studied the effectiveness of precipitation hardening achieved by aging treatment in improving the tensile superelasticity of NiTi alloys fabricated by elec-tron beam wire-feed additive manufacturing(EBAM),which possesses inherent advantages in producing dense and oxidation-free structures.Aging treatments under three temperatures(450,350,and 250℃)and different durations were conducted,and the resultant performance of tensile superelasticity,together with the corresponding evolution of precipitation and phase transformation behavior were investigated for the EBAM-fabricated NiTi alloys.Results showed that by appropriate aging treatment,EBAM fabricated NiTi alloys could achieve excellent recovery rates of approximately 95%and 90%after the 1st and 10th load/unload cycle for a maximum tensile strain of 6%,which were almost the highest achieved so far by AM processed NiTi alloys and close to those of some conventional NiTi alloys.The improvement of tensile superelasticity benefited from the fine and dispersive Ni4Ti3 precipitates,which could be introduced by aging at 350℃ for 4 h or at 250℃ for 200 h.Moreover,the large amount of Ni4Ti3 precipitates would promote the intermediate R-phase transformation and bring a two-stage or three-stage transformation sequence,which depended on whether the distribution of the precipitation was homogeneous or not.This work could provide guidance for the production of NiTi alloys with good tensile superelasticity by EBAM or other additive manufacturing processes.

Size effect on the microstructure, phase transformation behavior, and mechanical properties of NiTi shape memory alloys fabricated by laser powder bed fusion

In this work,NiTi samples with different thicknesses(0.15-1.00 mm)were fabricated by laser powder bed fusion(LPBF)under variable scanning speeds(500-1200 mm s^(-1)).The densification behavior,phase transformation behavior,and mechanical properties of the sample with different thicknesses are studied.The results indicate a strong size effect in the LPBF-fabricated NiTi alloy.The decrease of the sample thickness results in(i)the increase of porosity,(ii)the decrease of the number of adhered NiTi powder particles at the surface,(iii)the monotonous decrease of the martensitic transformation temperatures(MTTs),and(iv)the decrease of the shape recovery temperature.The influence of sample thickness on the melt-pool behavior,and thus the microstructure and performance of NiTi alloys are discussed.It is suggested that the melt-pool is deeper and narrower in the thin samples than in the thick samples.We conclude that,apart from the LPBF process conditions,the sample dimensions have also to be considered to fabricate NiTi structures with predictable properties.

第479例——认知功能下降,呼吸衰竭,结肠占位

患者男,78岁,因发热伴双下肢乏力、言语减少、记忆力下降于北京协和医院住院治疗。病程中抗菌药物治疗后体温恢复正常,但认知障碍及意识障碍快速进展,继发重症肺部感染、呼吸衰竭、感染性休克。粪便潜血阴性,血癌胚抗原阴性,抗核抗体阳性,PET-CT提示乙状结肠代谢增高灶,双侧额叶、颞叶、顶叶、后部扣带回代谢减低,结肠镜活检明确乙状结肠中分化腺癌,考虑乙状结肠癌继发神经系统副肿瘤综合征。经神经科、消化内科、基本外科、重症医学科、风湿免疫科、临床营养科等多科协作,完成全麻下腹腔镜乙状结肠癌根治切除术及围术期并发症诊治,患者最终神志明显改善,体温、氧合恢复正常。

武夷山国家公园及其周边鱼类多样性

武夷山国家公园是中国正式设立的第一批国家公园之一,其所处的武夷山脉在动物地理区划上是东洋区南亚亚区华南小区、东洋区东亚亚区华东小区的分界线。为查明武夷山国家公园及其周边的鱼类区系和多样性现状,本研究在梳理历史研究资料的基础上,对调查区域内的崇阳溪、麻阳溪、九曲溪、北溪和铅山河5条河流进行了实地调查,从物种多样性和功能多样性两个层面对武夷山国家公园及其周边地区鱼类多样性水平进行了分析。结合历史数据,武夷山国家公园及其周边地区分布的土著鱼类为113种,隶属于5目17科61属,其中以鲤形目鱼类为主,共82种,占物种总数的72.6%,其次为鲈形目,共16种,占总数的14.2%。受威胁鱼类3种,包括2种国家Ⅱ级野生水生保护动物,即胭脂鱼(Myxocyprinusasiaticus)和花鳗鲡(Anguillamarmorata)。武夷山国家公园的第一优势种为拟腹吸鳅(Pseudogastromyzonfasciatus),与其周边地区以点纹银鮈(Squalidus wolterstorffi)为第一优势种不同。多样性分析结果显示武夷山国家公园的鱼类物种丰富度指数、多样性指数和均匀度指数均低于周边区域。通过比较调查区域内5条河流的鱼类多样性,麻阳溪鱼类多样性显著高于其他河流,铅山河的多样性显著低于其他河流。位于国家公园内的九曲溪鱼类多样性比周边地区的崇阳溪要低。鱼类功能多样性结果显示,武夷山国家公园的功能丰富度指数显著低于周边地区,功能离散度和功能均匀度均高于周边地区;在河流方面,北溪的功能丰富度显著高于其他河流,崇阳溪的功能均匀度较高,九曲溪的功能离散度显著高于其他河流。综合鱼类多样性分析结果,武夷山国家公园鱼类多样性低主要是自然生境异质性低和人为活动共同作用形成,而周边地区的河流受到捕捞、水利设施、水质污染等因素的影响。这些干扰改变了鱼类的群落结构,使得鱼类多样性降低。因此应该加强对该区域的鱼类多样性保护工作,未来还应进一步开展针对公园内鱼类多样性的调查工作。

牙周炎与非牙周炎患者行牙种植同期GBR术后种植体周围骨吸收量对比

目的:对比分析牙周炎患者与非牙周炎患者行牙种植同期引导骨再生(guided bone regeneration,GBR)术后骨吸收差异。方法:选取2014年6月~2015年6月期间在我院接受牙种植同期引导骨再生术的35例患者,分为牙周炎组(15例,共32枚种植体)和非牙周炎组(20例,共30枚种植体),对比两组患者负载2年期间种植体周围骨吸收情况及随访期间的牙周情况。结果:牙周炎患者经牙周治疗及牙周维护后牙周情况良好,随访期间牙周检查结果与非牙周炎组差异无统计学意义(P>0.05);两组患者在负载2年后,牙周炎组种植体周围骨吸收量为(1.28±0.68)mm,大于非牙周炎组(0.72±0.62)mm,差异有统计学意义(P<0.05)。结论:经牙周治疗与维护后,牙周炎患者牙周情况与非牙周炎患者无统计学差异;但牙周炎患者牙种植同期GBR术后的种植体周围骨吸收较多。

芒果采收车的结构设计及有限元力学分析

中国是农业大国,海南是中国热带水果芒果的主要产地,当前芒果的采摘主要以人工为主,导致芒果采摘劳动强度大、收集效率低,随着人工收集成本的不断提高,亟需实现芒果采收机械化、智能化。合理高效的机械化设备能很大提高芒果采收的效率,减轻人的工作量。主要基于Workbench对所设计的新型智能式芒果采摘车在极限位置的工作情况建立整车分析相应的静力学方程,进行静力学分析,论证采摘臂质量设计的安全性。

Early changes of procalcitonin predict bacteremia in patients with intensive care unit-acquired new fever

Background Rapid detection of bacteremia is important for critically ill patients. Procalcitonin （PCT） has emerged as a marker of sepsis, but its characterization for predicting bacteremia is still unclear. This study aimed to investigate the role of change of PCT within 6 to 12 hours after new fever in predicting bacteremia. Methods An observational study was conducted in the ICU of our hospital from January 2009 to March 2010. Adult patients with new fever were included and grouped as bacteremia and non bacteremia group. Serum PCT concentration was measured at admission and within 6 to12 hours after new fever （designated PCT0 and PCT1）. Other results of laboratory tests and therapeutic interventions were recorded. Multivariate Logistic regression analysis was used to identify the risk factors of bacteremia. The area under the ROC curve （AUC） was constructed to evaluate the discriminative power of variables to predict bacteremia. Results Totally 106 patients were enrolled, 60 of whom had bacteremia and 46 did not have bacteremia,. The acute physiology and chronic health evaluation II （APACHE II） and sequential organ failure assessment （SOFA） scores were 13.1±7.8 and 5.0±2.2 at admission, respectively. There was no significant difference in PCT0 between the bacteremia group and nonbacteremia group; 1.27μg/L （range, 0.10-33.3） vs. 0.98μg/L （range, 0.08-25.7）, （P=0.157）. However, the PCT1 and the rate of change of PCT were significantly higher in bacteremia group; PCT1 was 6.73μg/L （1.13-120.10） vs. 1.17μg/L （0.10-12.10） （P=0.001）, and the rate of change was 5.62 times （1.05-120.6） vs. 0.07 times （-0.03-0.18） （P〈0.001）. The area under the ROC curve （AUC; 95% confidence interval） of the rate of change of PCT was better for predicting bacteremia than that of PCT1; 0.864 （range, 0.801-0.927） vs. 0.715 （range, 0.628-0.801）, （P〈0.05）. The AUCs of PCT0 and other parameters （such as WBC count, granulocyte percentage and temperature） were not significantly different （all P〉0.05）. The best cut-off value for the rate of change was 3.54 times, with a sensitivity of 88.5% and a specificity of 98.0%. It was also an independent predictor of bacteremia （odds ratio 29.7, P〈0.0001） and wasn＇t correlated with the presence or absence of co-infection, neutropenia or immunodeficiency （P〉0.05）. Conclusion The rate of change of PCT is useful for early detection of bacteremia during new fever and superior to the PCT absolute value and other parameters in non-selected ICU patients.

Unconventional Weyl exceptional contours in non-Hermitian photonic continua

Unconventional Weyl points with topological charges higher than 1 can transform into various complex unconventional Weyl exceptional contours under non-Hermitian perturbations.However,theoretical studies of these exceptional contours have been limited to tight-binding models.Here,we propose to realize unconventional Weyl exceptional contours in photonic continua—non-Hermitian anisotropic chiral plasma,based on ab initio calculation by Maxwell’s equations.By perturbing in-plane permittivity,an unconventional Weyl point can transform into a quadratic Weyl exceptional ring,a type I Weyl exceptional chain with one chain point,a type II Weyl exceptional chain with two chain points,or other forms.Realistic metamaterials with effective constitutive parameters are proposed to implement these unconventional Weyl exceptional contours.Our work paves a way toward exploration of exotic physics of unconventional Weyl exceptional contours in non-Hermitian topological photonic continua.