Time-resolved characteristics of a nanosecond pulsed multi-hollow needle plate packed bed dielectric barrier discharge

In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.

Wear mechanism and serious wear position of casing pipe in vertical backfill drill-hole

Vertical backfill drill-hole is usually a key project in an underground mine with backfill method and can be easily damaged by impact of backfill slurry.Observation of the damaged vertical backfill drill-holes in Jinchuan Nonferrous Metal Corporation（JNMC）,Gansu Province,China,given by a digital drill-hole video camera,indicated that there usually exist serious wear zones in casing pipe in vertical backfill drill-hole（CVBH）.It was suggested that serious wear position of CVBH should be located at an interface between air and solid-liquid mixture within CVBH.Backfill slurry falls freely and impacts the wall of CVBH near the interface with great momentum and energy coming from high speed free fall of backfill slurry.The depth of serious wear position of CVBH,i.e.,free fall height of backfill slurry in CVBH,can be estimated by the height of vertical backfill drill-hole,the length of horizontal pipeline,the density of slurry and the hydraulic gradient of pipeline system.A case study indicated that the estimation equation of serious damage depth of CVBH was of enough accuracy and was helpful for daily maintenance and management of vertical backfill drill-hole.

Effect of Working Position on Vertical Motion Straightness of Open Hydrostatic Guideways in Grinding Machine

Hydrostatic guideways have various applications in precision machine tools due to their high motion accuracy. The analysis of motion straightness in hydrostatic guideways is generally ignoring the external load on the slider. A variation force also exists, caused by the different working positions, together with the dead load of the slider and that of other auxiliary devices. The effect of working position on vertical motion straightness is investigated based on the equivalent static model, considering the error averaging effort of pressured oil film in open hydrostatic guideways. Open hydrostatic guideways in LGF1000 are analyzed with this approach. The theoretical results show that the slider has maximum vertical motion straightness when the working position is closer the guiderail of Y axis. The vertical motion straightness reaches a minimum value as the working position is located at the center of the two guiderails on the Y axis. The difference between the maximum and minimum vertical motion straightness is 34.7%. The smaller vertical motion straightness is attributed to the smaller spacing of the two pads centers, along the Y direction. The experimental results show that the vertical motion straightness is 4.15 μm/1200 mm, when the working position is located in the middle of the Xbeam, and 5.08 pro/1200 mm, when the working position is approaching the Y guiderails, denoting an increase of 18.3%. The changing trends of the measured results validate the correctness of the theoretical model. The research work can be used to reveal the variation law of accuracy of the open hydrostatic guideways, under different working positions, to predict the machining precision, and provides the basis for an error compensation strategy for gantry type grinding machines.

Role of subjective visual vertical in patients with posterior canal benign paroxysmal positional vertigo as a prognostic marker after canalith repositioning maneuver

Objective:To study the potential role of subjective visual vertical(SVV)as a prognostic marker for canalith repositioning maneuver(CRM)in patients with posterior canal benign paroxysmal positional vertigo(PC-BPPV)for the Indian population.Methods:SVV was examined in 30 patients with PC-BPPV before and after canalith repositioning maneuver and after complete resolution of PC-BPPV.Study parameters included the mean of 10 angular tilt readings and direction of deviation,which were compared before and after CRM and following complete resolution of PC-BPPV.Results:The angle of SVV tilt was greater and deviated towards the affected ear before CRM in all patients,which decreased significantly shortly after CRM and continued to decrease after complete resolution of PC-BPPV(p<0.0001).Conclusions:SVV can be used to test utricular dysfunction in PC-BPPV.The angle of tilt improves in response to CRM,which may be used as a prognostic marker in patients with PC-BPPV receiving CRM.

H_∞Loop Shaping Control for Plasma Vertical Position Instability on QUEST

QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils （HCU and HCL） outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative （PD） controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does.

Studies on Performance of Distributed Vertical Axis Wind Turbine under Building Turbulence

As a part of the new energy development trend,distributed power generation may fully utilize a variety of decentralized energy sources.Buildings close to the installation location,besides,may have a considerable impact on the wind turbines’operation.Using a combined vertical axis wind turbine with an S-shaped lift outer blade and-shaped drag inner blade,this paper investigates how a novel type of upstream wall interacts with the incident wind at various speeds,the influence region of the turbulent vortex,and performance variation.The results demonstrate that the building’s turbulence affects the wind’s horizontal and vertical direction,as well as its speed,in downstreamplaces.The wall’s effect on wind speed changing in the downstreamarea is thoroughly investigated.It turns out that while choosing an installation location,disturbing flow areas or low disturbing flow zones should be avoided to have the least impact on wind turbine performance.

深硅刻蚀晶圆位置偏移分析与研究

晶圆位置偏移过大是导致深硅刻蚀设备发生传片报警问题的主要原因之一,尤其是在采用静电卡盘的设备中。阐述了晶圆位置发生偏移原因,重点研究了解吸附配方、顶针驱动和片间清洗方案。研究表明,静电吸盘的表面聚合物残留是导致静电释放不充分的主要因素,表面聚合物的清除有助于优化晶圆位置偏移。电动三针在固有残留静电力的情况下,通过缓慢连续升针方案缓解了跳片现象。优化片间清洗方案大幅减小表面聚合物残留。实验结果表明:优化后的解吸附配方为工艺时长90 s、电极功率1000 W、气压20 mTorr(1 mTorr≈0.133 Pa)、氩气体积流量250 mL/min,电动三针接触晶圆前、接触中、脱离静电吸盘后的升针速度分别为3、2和6 mm/s,在上述工艺条件下,通过进一步优化片间清洗方案,使得晶圆位置偏移量从初始的2~6 mm降至0.2 mm以内。

针片状骨料含量对沥青混凝土骨料级配的影响研究

为研究针片状骨料含量对沥青混凝土骨料级配的影响,本文采用逐级填充法,选用骨架稳定性为衡量骨架级配优劣的唯一指标,考虑针片状含量为0%、20%、25%、30%、35%,利用垂直振动压实仪成型试件。结合加州承载比(CBR)值、骨架密度与空隙率综合评价骨架稳定性,以此确定各组粗骨料级配。采用合成级配的设计方法,将粗细集料进行全粒径骨料级配设计。结果表明,随着针片状骨料含量的增加,全粒径骨料骨架稳定性呈现先增后减的趋势,其中针片状骨料含量为30%的骨架稳定性最优,针片状骨料含量35%的稳定性最劣。

浅圆仓不同运行方式对粮堆通风调温效果影响

浅圆仓在粮食储藏中有着广阔的应用前景,探究垂直通风与径向通风系统不同运行方式的通风降温效果,有助于为粮食的安全储存提供支持。文章以浅圆仓内粮堆(大豆)为研究对象,通过有限体积法,数值模拟了3种不同风道在正压上行通风和负压下行通风为期14 d的调温过程,获得了粮堆内部的气流和温度分布情况,并对比分析了通风降温速率、均匀性与能耗等。结果表明:各通风方式下均无通风死角,形式差异导致流向与涡团的位置差异;垂直风道正、负压方式下通风7 d后仓内无高温区域,其他两种风道出现高温区域,14 d时各种工况均无高温区域;只有径向风道的负压通风的降温速率与最终温度低于正压通风;径向风道的通风均匀性优于其他两种风道,正压通风的均匀性优于负压通风的;而正压通风的能耗普遍低于负压通风。

基于Langer线的穿刺体位对肿瘤化疗患者输液港难免性医用黏胶相关皮肤损伤的预防效果研究

目的探究基于Langer线的无损伤针穿刺体位对肿瘤化疗患者输液港难免性黏胶相关皮肤损伤的预防效果。方法通过平行胸部Langer线对床头抬高60~90°和平卧位穿刺进行皮肤软组织力学、表皮屏障功能理论分析,然后选取2019年5月至2020年5月南京医科大学第一附属医院肿瘤科79例植入胸壁输液港、既往应用Ⅳ3000及液体敷料皮肤保护性屏障仍出现输液港黏胶相关性皮肤损伤的患者为研究对象。采用前瞻性自身前后对照,干预前采用平卧位穿刺,干预后床头抬高60~90°穿刺,比较两种穿刺体位对输液港黏胶相关性皮肤损伤预防效果和带针期间舒适度的影响。结果干预后患者输液港黏胶相关性皮肤相关性损伤总发生率较干预前显著降低(P<0.001),机械性损伤发生率、接触性皮炎发生率较干预前显著降低(均P<0.05),输液港带针期间舒适度较干预前明显提高(P<0.001),且不增加患者穿刺时的疼痛感(P=0.692)。结论床头抬高60~90°穿刺可降低肿瘤化疗患者输液港难免性黏胶相关皮肤损伤,提高患者带针期间的舒适度。

叉车发动机舱散热特性及空间布局优化仿真研究

叉车速度较低且发动机舱内部复杂,在叉车研发设计阶段,如何提高发动机舱散热能力,优化散热器性能已成为工程师关注的焦点。以某型号叉车发动机舱的散热特性为研究对象,建立了叉车发动机舱的实体模型,利用计算流体动力学方法,分析了发动机舱内温度场和流场。研究了风扇竖直方向位置、风扇相对聚风罩轴向嵌入度、风扇与散热器距离这3个关键因素对发动机舱散热性能的影响规律。利用多指标分析综合平衡法进行正交试验分析,获得了散热机舱内空间布局的最优方案,即上移风扇10 mm、风扇轴向嵌入度60%、风扇与散热器距离增加20 mm。该优化方案可以使水散热器散热量提高11.76%,液压油散热器散热量提高7.16%。

2种栽培模式对酿酒葡萄马瑟兰果际微域环境和果实发育的影响

【目的】研究2种栽培模式对新疆吐哈盆地产区酿酒葡萄马瑟兰果际微域环境和果实发育的影响,为产区酿酒葡萄栽培模式选择提供参考。【方法】以新疆吐哈盆地产区酿酒葡萄马瑟兰为试材,采用低‘厂’字形(结果高度40 cm,处理组)和高‘厂’字形(结果高度80 cm,对照组)2种模式栽培,比较分析2种栽培模式下果实生育期果际微域环境指标和果实发育指标变化及采收期果实品质、花色苷组分。【结果】与高‘厂’字形栽培相比,低‘厂’字形栽培果实生育期果际日最高温、日均温度分别降低1.66和2.21℃,月均超过35℃温差总和与月均≥35℃高温时长分别减小39.25℃和40.12 h;日最大湿度、日最小湿度和日均湿度分别提高2.89%、1.70%和2.64%,日均低湿时长减小11.56 h;叶幕透射辐射、土壤反射辐射和总辐射分别降低36.94%、50.38%和44.91%。低‘厂’字形栽培相比高‘厂’字形栽培更有利于果实发育,转色期浆果具有更高的酒石酸、苹果酸和抗坏血酸质量浓度,采收期果穗质量和果粒质量分别增大38.74%和25.61%,萎蔫率降低14.20%,可溶性固形物减小2.67°Brix,总酸质量浓度提高0.83 g/L,皮总黄烷醇含量和总花色苷含量分别提高23.83%和5.80%,但低‘厂’字形栽培降低了3′,5′-羟基取代类花色苷比例、花色苷甲基化修饰比例和花色苷总修饰比例。【结论】新疆吐哈盆地产区酿酒葡萄马瑟兰采用低‘厂’字形栽培能够改善果际微域环境,提高果实品质。

错[牙合]畸形患者髁突位置及正畸治疗前后髁突位置变化的CBCT评估

口颌系统的功能健康、稳定是口腔正畸治疗的基本目标之一。健康人群的下颌处于牙尖交错位(in-tercuspal position,ICP)时髁突位置基本位于关节窝的中央,颞下颌关节功能稳定。错[牙合]畸形患者由于正畸牙齿移动及咬合改变,可能发生颞下颌关节的相关改建,特别是髁突位置的改变。传统的髁突位置的评估方法是通过架来转移下颌位置,然后在髁突位置测量仪上进行测量,但此方法得到的髁突位置变化缺乏一致性。近年来,锥形束CT(cone beam computed tomography,CBCT)成为正畸治疗检查的首选,CBCT可精准地测量关节间隙,确定髁突位置的改变。本文对髁突位置的CBCT评估及正畸治疗前后的错[牙合]畸形髁突位置变化的研究进行综述。文献复习结果表明,不同错[牙合]畸形患者的髁突位置存在差异,正畸治疗前后髁突位置也可能发生变化,使用CBCT可以较低的辐射剂量和更高的精确度评价错[牙合]畸形的髁突位置,有助于进一步研究错畸[牙合]形患者髁突位置变化的机制,并为患者治疗提供更准确、个性化的指导。

穿刺活检单针阳性前列腺癌术后病理升级的危险因素分析及列线图模型构建

目的:对穿刺活检单针阳性前列腺癌术后病理升级的危险因素进行分析,并尝试构建预测穿刺单针阳性前列腺癌患者术后病理升级的数学模型。方法:回顾分析2015年1月至2020年8月期间于北京大学第一医院诊断为前列腺癌且接受根治性前列腺切除术的患者1 349例,选取其中穿刺活检单针阳性患者的临床资料,将其分为术后病理较穿刺病理升级组及未升级组,比较两组的年龄、体重指数、临床分期、前列腺影像报告和数据系统(prostate imaging reporting and data system, PI-RADS)评分、磁共振成像(magnetic resonance imaging, MRI)报告的前列腺体积、前列腺穿刺活检的Gleason评分、穿刺前及术前血清前列腺特异性抗原(prostate specific antigen, PSA)、手术方式、术后病理分期的差异,将单因素分析中P<0.1的术前变量纳入多因素Logistic回归并绘制列线图,通过受试者工作特征曲线对模型进行评价。结果:共有71例患者符合纳入排除标准,其中术后病理升级组34例,未升级组37例,两组患者的年龄(P=0.585)、体重指数(P=0.165)、手术方式(P=0.08)、MRI前列腺体积(P=0.067)、临床分期(P=0.678)、PI-RADS评分(P=0.203)、穿刺前PSA(P=0.359)、术前PSA(P=0.739)、PSA密度差(P=0.063)、穿刺Gleason评分(P=0.068)差异均无统计学意义,两组患者穿刺阳性针中肿瘤组织占比(P=0.007)、术后病理分期(P<0.001)及术后Gleason评分(P<0.001)差异有统计学意义。将单因素分析中P<0.1的术前变量,即MRI前列腺体积、PSA密度差、穿刺阳性针中的肿瘤组织占比、穿刺Gleason评分纳入多因素Logistic回归分析,只有MRI前列腺体积组间差异有统计学意义。进一步根据多因素Logistic回归结果绘制列线图,受试者工作特征曲线的曲线下面积为0.773。结论:对于穿刺病理单针阳性的前列腺癌患者,若前列腺体积较小或穿刺阳性针中肿瘤组织占比较少,需警惕术后病理较穿刺病理升级的可能;对于可能出现病理升级的患者,需谨慎考虑术前的危险分层。本模型可初步用于预测穿刺活检单针阳性前列腺癌患者术后病理升级的可能性。

基于推进器偏置的半潜式平台动力定位模型试验研究

半潜式平台在进行动力定位作业时,由于其水线面面积较小而初稳性高较低,其垂向运动(横摇、纵摇、垂荡)易受到推进器法向力作用的影响。基于此,提出一种基于推进器偏置的推力分配模式,旨在合理利用推进器的法向力抑制平台垂向运动,而不影响平台水平面定位功能。在海洋工程水池开展半潜式平台的动力定位模型试验,对比和分析不同载荷工况及推进器偏置模式下平台的六自由度运动响应。结果表明,推进器偏置策略能够基本保证水平面定位精度,并显著减小平台垂向运动在其固有频率附近的响应幅值,在该试验工况下,功率谱密度(PSD)峰值减小高达54.7%,对波频区间的运动影响则较小。该研究结果可为半潜平台垂向运动抑制提供新思路。

基于490 nm垂直外腔面发射激光器的长距离水下激光通信系统

水下无线光通信技术为深海勘探和海洋资源开发利用带来了一种效率高且可靠性强的通信新方案.本文采用490 nm垂直外腔面发射激光器作为光源,基于声光外调制技术,采用脉冲位置调制方式(pulseposition modulation,PPM)搭建了长距离水下无线光通信系统.结合光源的优势并经过软判决算法优化PPM解调来提升水下通信性能,采用64 PPM调制,成功实现了96 m的水下传输距离,在50 MHz时隙频率下得到传输的误码率为1.9×10^(-5).同时测量到采用软判决解调相较于硬判决解调在性能增益上有着大约2 dB的提升,验证了软判决算法在提升水下通信性能方面相比硬判决算法的显著优势.

工艺参数对立向分体等离子弧增材制造过程的影响

【目的】为探究分体等离子弧增材制造过程中工艺参数对立向增材成形的影响,以单道熔覆层宽度和高度为评价指标对其展开研究。【方法】基于构建的立向分体等离子弧增材制造系统,通过单因素变量法研究了立向位置时丝/总电流比、离子气流量、丝材端部位置等工艺参数对熔覆层成形的影响,分析了工艺参数与基板热输入和熔敷率的关联机制。【结果】结果表明,当总电流保持不变时,丝材电流的增加会显著改善熔覆层成形,熔覆层宽度减小、高度增加;当离子气流量增加时,电弧等离子流力增强,使熔覆层宽度增加、高度减小;当送丝速度增加时,丝材端部靠近电弧中心,传质增加、传热减小,使熔覆层宽度减小、高度增加;丝材电流增加时,通过改变系统热、质、力的传输使熔覆层尺寸变化,而基板电流增加时,仅通过改变热、力传输使熔覆层尺寸变化。【结论】当总电流不变时,可采用提高丝/总电流比、减小离子气流量、丝材端部位置远离基板等措施减小基板的热输入并提高熔覆率,或直接增加丝材电流以提高熔覆率,进而实现高效增材制造。该研究将为分体等离子弧增材制造工艺在空间位置增材制造领域的拓展应用提供一定的理论指导。

安全型无损伤针二步结构式垂直固定法在输液港插针中的应用

目的:探讨安全型无损伤针二步结构式垂直固定法在输液港插针中的应用效果。方法:采用便利抽样法,选取南京市某三级甲等医院130例应用输液港的病人,按入院时间进行分组,2021年1月—3月入院的65例应用输液港病人作为对照组,采用常规固定方式进行插针;2021年4月—5月入院的65例应用输液港病人作为试验组,采用安全型无损伤针二步结构式垂直固定法进行插针。比较两组病人一次插针成功率、垂直插针率、穿刺时疼痛评分和插针用时等。结果:试验组一次插针成功率(96.92%)高于对照组(76.92%);试验组垂直插针率(95.38%)高于对照组(66.15%),差异均有统计学意义(P<0.05)。试验组疼痛评分[(1.26±0.44)分]低于对照组[(1.58±0.68)分],差异有统计学意义(P<0.05)。两组插针用时比较,差异无统计学意义(P>0.05)。结论:安全型无损伤针二步结构式垂直固定法能提高输液港一次插针成功率及垂直插针率,降低病人疼痛程度。

80 MN压剪试验机竖向加载模糊PID控制系统的设计

为了稳定、精确、可靠地实施超大力值竖向加载,以80 MN压剪试验机为对象,对其竖向加载装置的机械结构、液压系统以及控制系统进行总体设计;建立位置-压力双闭环PID控制算法的数学模型,并设计模糊PID控制器;最后,通过AMESim-Simulink对控制系统进行耦合仿真,获取位移与试验力的时域响应曲线,并在80 MN压剪试验机上进行竖向加载试验以验证控制系统的可靠性。结果表明:竖向加载模糊PID控制系统使竖向加载在220 s后达到稳态,位移误差与试验力误差均小于0.05%,此控制系统的稳定性、精确性和可靠性得到验证。

女性良性阵发性位置性眩晕患者SVV/SVH结果分析

目的分析女性良性阵发性位置性眩晕(BPPV)患者主观视觉垂直线(subjective visual vertical,SVV)和主观视觉水平线(subjective visual horizontal,SVH)结果。方法回顾性纳入符合BPPV诊断标准的40~60岁女性患者310例为围绝经组,年龄<40岁的同期女性BPPV患者110例为青年组,年龄>60岁的同期女性BPPV患者332例为老年组,分析不同年龄组女性BPPV患者SVV/SVH特点。结果(1)女性BPPV患者SVV/SVH总异常率为42.29%;(2)围绝经组和青年组SVV/SVH异常率在不同罹患管型中无显著差异(P均>0.05);(3)老年组SVV/SVH异常率在不同罹患管型中分别为,水平半规管嵴帽BPPV 58.62%、水平半规管管石BPPV 48.65%、后半规管BPPV 36.68%,差异有统计学意义(P<0.05);(4)围绝经组、青年组、老年组BPPV患者SVV/SVH总异常率分别为41.94%、46.36%、41.27%,三组间无显著差异(P>0.05)。结论约40%女性BPPV患者伴有SVV/SVH异常,且随年龄增长在不同罹患管型中有所差异。