Determination method of mesh size for numerical simulation of blast load in near-ground detonation

In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.

Mesh Size Effect in Numerical Simulation of Blast Wave Propagation and Interaction with Structures

Numerical method is popular in analysing the blast wave propagation and interaction with structures.However,because of the extremely short duration of blast wave and energy trans-mission between different grids,the numerical results are sensitive to the finite element mesh size.Previous numerical simulations show that a mesh size acceptable to one blast scenario might not be proper for another case,even though the difference between the two scenarios is very small,indicating a simple numerical mesh size convergence test might not be enough to guarantee accu-rate numerical results.Therefore,both coarse mesh and fine mesh were used in different blast scenarios to investigate the mesh size effect on numerical results of blast wave propagation and interaction with structures.Based on the numerical results and their comparison with field test re-sults and the design charts in TM5-1300,a numerical modification method was proposed to correct the influence of the mesh size on the simulated results.It can be easily used to improve the accu-racy of the numerical results of blast wave propagation and blast loads on structures.

Cost effective use of mosquito net mesh in inguinal hernia repair

Mesh hernia repair is one of the commonest open techniques of inguinal hernia repair.The main limiting factor in the use of new meshes is the cost.We carried out a prospective randomized double blind study and comprising of a hundred patients with 100 inguinal hernias admitted consecutively for elective surgery,divided into the polypropylene mesh(PPM)group and the mosquito net mesh(MNM)group each containing fifty patients.All cases were completed successfully and results revealed no difference in two groups.The results of the present study,in consistent with the published literature,reveal that the cheap indigenous mosquito mesh,which has similar properties of an imported mesh,can be safely used for tension-free inguinal hernia repair in adults.Further trials with a larger number of patients and longer follow-ups are justified and recommended.

Influence Predictions of Contact Effects on Mesh Stiffness of Face Gear Drives with Spur Gear

Mesh stiffness is one of important base parameters of face gear dynamic studies.However,a calculation solution of mesh stiffness of face gear drives is not to be constructed due to complex geometric flakes of face gear teeth.Thus,a calculation solution of mesh stiffness of face gear drives with a spur gear,which is based on the proposed equivalent face gear teeth and Ishikawa model,is constructed,and the influence of contact effects on mesh stiffness of face gear drives is investigated.The results indicate the mesh stiffness of face gear drives is sensitive to contact effects under heavy loaded operating conditions,specially.These contributions will benefit to improve dynamic studies of face gear drives.

Cost-effectiveness analysis comparing robotic sacrocolpopexy to a vaginal mesh hysteropexy for treatment of uterovaginal prolapse

Objective: To compare costs and QoL associated with 2 minimally invasive operations to treat uterovaginal prolapse. Study Design: A decision analytic cost-effectiveness model comparing vaginal mesh hysteropexy to robotic-assisted sacrocolpopexy. Costs were derived from a hospital perspective. QoL estimates focused on: recurrent prolapse;erosion;infection;transfusion;cystotomy;chronic pain;lower urinary tract symptoms;and mortality. Actual procedural costs at our institution were calculated. Costs and quality adjusted life years were examined over 1 year. Results: The costs ($21,853) and QALYs (0.9645) for robotic sacrocolpopexy produced a CE Ratio of $22,657 per QALY. The costs ($14,890) and QALYs (0.9309) for vaginal mesh produced a CE Ratio of $15,995 per QALY. The incremental cost per QALYs for robotic surgery was $207,232. Sensitivity analysis on all utilities, cost estimates, and complication estimates didn’t cross any thresholds. Conclusion: Vaginal mesh was more cost-effective than robotic sacrocolpopexy even when the cost of the robot was not factored.

奥法妥木单抗治疗视神经脊髓炎谱系疾病疗效分析

目的探讨奥法妥木单抗治疗视神经脊髓炎谱系疾病(NMOSDs)的疗效及安全性。方法纳入2022年4月至2023年3月郑州大学第一附属医院采用奥法妥木单抗治疗方案的25例NMOSDs患者,分为定期给药组(A组,12例)及按CD19+B细胞百分比给药组(B组,13例),计算用药前和用药1年时年化复发率(ARR)、复发例数、复发次数和时间、复发症状,采用扩展残疾状态量表(EDSS)评估神经功能,记录用药期间药物不良反应。结果奥法妥木单抗治疗1年时3例(12%)复发,A组1例患者复发2次,分别为用药后1和5个月;B组2例患者复发,1例复发2次,为用药后2和6个月,1例复发1次,为用药后2个月。两组用药1年时与用药前仅ARR变化幅度差异具有统计学意义(F=29.061,P=0.000),A组用药1年时ARR较用药前下降(t=13.215,P=0.001),B组用药1年时ARR亦较用药前下降(t=19.259,P=0.000)。有8例出现注射部位疼痛、3例注射后发热、1例注射后头痛,其中1例诊断为细菌性脑膜炎;14例感染新型冠状病毒,其中1例因新型冠状病毒感染致肺炎入住重症监护病房;均无残疾、死亡等严重不良反应,EDSS评分均未增加。结论奥法妥木单抗定期给药或依据CD19+B细胞百分比给药均可减少患者复发风险,改善EDSS评分;早期与糖皮质激素联用需警惕感染风险。

混杂网格增强超高性能混凝土双向板的弯曲性能

网格增强超高性能混凝土(ultra-high performance concrete,UHPC)具有轻质、高强、耐久性好等特性,已应用于薄壁结构和工程加固领域,但单一网格很难实现高效的增强增韧效应.为研究混杂网格增强UHPC双向板的抗弯性能,对3个钢丝网格与玻璃纤维网格混杂增强UHPC板、3个钢丝网格与玄武岩纤维网格混杂增强UHPC板、6个单一网格增强UHPC板和1个无网格UHPC对照板进行弯曲试验,研究网格种类、总层数及铺层方式对其破坏形态、承载能力和弯曲韧性的影响.结果表明:与单一钢丝网格板和单一玻璃纤维网格板相比,钢-玻璃纤维网格混杂板开裂后表现更显著的硬化现象,在连续网格与混杂短纤维协同效应下,板呈现多裂缝破坏模式,延性较理想.铺设2层网格时,钢-玻璃纤维网格混杂板的承载能力较单一钢丝网格板提升23.7%,且其在20 mm挠度处的残余承载力较单一玻璃纤维网格板提升28.2%;钢-玄武岩纤维网格混杂板峰前阶段的能量吸收值和20 mm挠度处的残余承载力均优于单一玄武岩纤维网格板.网格总层数为3层时,与单一玄武岩纤维网格板相比,2层钢丝网格与1层玄武岩纤维网格混杂增强板在峰前挠度为2 mm时的能量吸收值提高了21.6%,20 mm挠度处的残余承载力提高了42.6%.钢-玻璃纤维网格混杂板的网格强度利用率最理想,其承载能力、能量吸收值及弯曲韧性指标均高于钢-玄武岩纤维网格混杂板.最后,考虑网格强度有效利用率建立了混杂网格增强UHPC双向板抗弯承载力理论公式,适用性良好.

双尾鳍船舶纵倾节能及其尺度效应的数值研究

纵倾节能是一种高效易行的船舶节能手段,针对纵倾节能应用,采用基于RANS求解的数值模拟方法,对不同缩尺比与纵倾角度工况下的双尾鳍内河船型绕流场进行了数值模拟。本文分析纵倾角度对阻力及其成分的影响规律;分析阻力随纵倾角度变化规律的原因并对纵倾节能相关的尺度效应进行探讨。结果表明,双尾鳍船舶以设计航速航行时,纵倾角度为首倾1.5°左右时阻力最小,且纵倾节能存在明显的尺度效应。

复刻与迭代:第一代大学生同胞教育辐射现象探究

第一代大学生身处家庭、学校、社会等多重环境中,但既有研究鲜少对个体间长期的深层作用机制进行深入研究,也并未对“多子女家庭”给予充分关注,难以回应新时代的生育政策。本研究以16个来自“985”或“211”高校的第一代大学生家庭为研究对象,采用质的研究方法从个人时间纵向视角考察同胞教育辐射呈现出的显性支持与隐性规程两种作用路径。研究发现,兄姐通过情感与物质扶持、关键信息传递等显性支持向弟妹提供了一种弥补性资源;兄姐所示范的参照轨迹与目标边界成为一种隐性规程,分别提升了弟妹对“如何考上好大学”的结果期待及“我能考上好大学”的功效期待。在应试惯习的培养与养育经验的迭代之外,不同家庭养育造就了共生或竞逐的同胞关系,导致同胞教育辐射现象分化。本土研究突破了传统的资源稀释假设。

增强型的无线mesh网络信道分配方法

为更可靠地实行无线mesh网络的资源分配,将干扰模型引入mesh网络的节点流量模型中,提出改进型的基于流量感知的固定C-HYA信道分配方法,采用一种更贪婪的算法规避波纹效应,降低网络干扰。之后对算法进行实现仿真,建立相应网络拓扑结构,对在mesh网络中采用传统算法及改进算法对抗波纹效应及信道干扰的情况进行了对比分析。

免疫检查点抑制剂相关抗神经元抗体阳性副肿瘤神经综合征临床特征分析

目的 分析抗神经元抗体阳性免疫检查点抑制剂相关副肿瘤神经综合征(ICI-PNS)的临床特征。方法与结果 纳入2012年1月至2024年3月中国医学科学院北京协和医院诊断与治疗的5例抗神经元抗体阳性ICI-PNS患者,肿瘤类型包括小细胞肺癌(2例)、恶性黑色素瘤(1例)、霍奇金淋巴瘤(1例)、宫颈癌(1例),免疫检查点抑制剂包括程序性死亡蛋白-1抑制剂(3例)、程序性死亡蛋白配体-1抑制剂(1例)、程序性死亡蛋白-1/细胞毒性T细胞相关抗原4双抑制剂(1例)。5例患者均出现副肿瘤神经综合征的高风险表型,其中4例表现为边缘性脑炎,1例表现为快速进展的小脑综合征。血清和(或)脑脊液中检出的抗神经元抗体包括抗Hu、γ-氨基丁酸B型受体、Y染色体性别决定区相关高迁移率组盒蛋白1、代谢型谷氨酸受体5型、Yo抗体。4例神经系统症状出现在应用免疫检查点抑制剂2周内。4例病情达峰时改良Rankin量表评分为3分,1例为5分。5例患者常见不良事件评价标准分级(CTCAE)均为3级。治疗方面,停用免疫检查点抑制剂,给予糖皮质激素联合静脉注射免疫球蛋白治疗,神经系统症状均有改善。结论 中高风险抗神经元抗体是ICI-PNS的诊断标志物,可依据ICI-PNS临床表型及CTCAE分级等综合制定免疫治疗方案,停用免疫检查点抑制剂,应用糖皮质激素、静脉注射免疫球蛋白可以改善患者预后。

Resistance of full-scale beams against close-in explosions.Numerical modeling and field tests

This paper explores the performances of a finite element simulation including four concrete models applied to a full-scale reinforced concrete beam subjected to blast loading. Field test data has been used to compare model results for each case. The numerical modelling has been, carried out using the suitable code LS-DYNA. This code integrates blast load routine(CONWEP) for the explosive description and four different material models for the concrete including: Karagozian & Case Concrete, Winfrith, Continuous Surface Cap Model and Riedel-Hiermaier-Thoma models, with concrete meshing based on 10, 15, and 20 mm. Six full-scale beams were tested: four of them used for the initial calibration of the numerical model and two more tests at lower scaled distances. For calibration, field data obtained employing pressure and accelerometers transducers were compared with the results derived from the numerical simulation. Damage surfaces and the shape of rupture in the beams have been used as references for comparison. Influence of the meshing on accelerations has been put in evidence and for some models the shape and size of the damage in the beams produced maximum differences around 15%. In all cases, the variations between material and mesh models are shown and discussed.

个性化钛网联合浓缩生长因子修复前牙槽嵴缺损的临床疗效

目的:探究个性化钛网联合浓缩生长因子修复前牙槽嵴缺损的临床疗效。方法:纳入105例前牙槽嵴缺损患者作为研究对象,均行种植修复。根据随机数字表法分为研究组(52例)和对照组(53例),对照组采用个性化钛网覆盖,研究组在对照组基础上联合浓缩生长因子。随访1年,分析2组种植成功率、牙槽嵴高度、骨增量、牙槽骨骨密度、骨厚度、美学效果及并发症情况。结果:术后1年,2组研究对象中发生种植体松动或脱落例数均为0,种植成功率100%。研究组牙槽嵴的高度、骨增量、牙槽骨骨密度、骨厚度均大于对照组(P<0.05)。研究组红色美学指数与白色美学指数评分高于对照组(P<0.05)。研究组出现术后肿痛、牙周感染各2例,牙龈出血、过敏各1例,对照组出现术后肿痛、牙龈出血、过敏各1例,牙周感染2例(P>0.05)。结论:个性化钛网联合浓缩生长因子修复前牙槽嵴缺损能改善牙槽嵴高度及骨代谢,提升美学效果。

家庭状况对青少年发展的影响——同胞的调节作用

生育政策变迁凸显了同胞在青少年发展中的作用。基于家庭系统视角和中国教育追踪调查(CEPS)数据,文章探讨了同胞在家庭中影响青少年发展的内在机制。研究发现,家庭状况对青少年发展的影响在独生子与非独生子之间存在差异,同胞对青少年发展具有“缓冲效应”,即同胞的存在难以让青少年从家庭社会经济地位的提高、非忽视型教养方式、非吵闹型夫妻关系、亲密的亲子关系中获取更多的“发展红利”,但也不会更多地遭遇家庭社会经济地位弱势、忽视型教养方式、吵闹型夫妻关系、疏离的亲子关系导致的“发展赤字”。同胞对青少年发展的影响更趋近于“雪中送炭”,而非“锦上添花”。这一发现有助于回应“越穷越生”“有条件生二孩却不生”等社会现象,同时预示“少子化”可能会加剧青少年发展的两极分化。

经腹壁人工网片无张力双侧顶端悬吊盆底重建术的疗效分析

目的观察经腹壁人工网片无张力双侧顶端悬吊盆底重建术的临床疗效。方法选取2021年3月1日至2023年10月31日在河南省人民医院因盆腔脏器脱垂行经腹壁人工网片无张力双侧顶端悬吊盆底重建术的患者作为观察组,共85例,同期行腹腔镜下骶骨固定术后的患者40例作为对照组,并分为保留子宫组、切除子宫组两个亚组。随访至2024年4月30日,分析其手术情况和术后并发症,并采用盆腔器官脱垂定量分期法(POP-Q)、盆底功能障碍性疾病症状问卷及其分量表(PFDI-20)、排尿困扰量表(UDI-6)、结直肠肛门困扰量表(CRADI-8)和盆腔器官脱垂困扰量表(POPDI-6)、盆底疾病生活质量影响问卷短表(PFIQ-7),盆腔器官脱垂/尿失禁性生活问卷(PISQ-12)对患者术前、术后治疗效果和生活质量进行组内及组间比较。结果观察组患者中位随访时间13.13个月,客观治愈率96.47%,再次手术率1.18%,围手术期并发症发生率为6.45%(切除子宫)、4.35%(保留子宫),网片暴露率1.61%(切除子宫)。对照组患者中位随访时间13.76个月,客观治愈率92.5%,再次手术率2.5%,围手术期并发症发生率为14.71%(切除子宫)、33.33%(保留子宫),网片暴露率8.82%(切除子宫)。观察组与对照组相比,客观治愈率、再次手术率无差异,观察组的手术时间短、出血少、术后排气快、住院时间短、围手术期并发症发生率低、网片暴露率低,尤其是保留子宫的患者,优势更明显。观察组和对照组患者组内比较时,术后1年与术前POP-Q的各指示点均明显改善(P<0.05),术后PFDI-20、UDI-6、CRADI-8、POPDI-6、PFIQ-7、PISQ-12量表评分均较术前明显降低,差异有统计学意义(P<0.05),但在进行组间比较时,差异无统计学意义(P>0.05)。结论经腹壁人工网片无张力双侧顶端悬吊盆底重建术是治疗前、中盆腔脱垂的一种有效手术方案,可明显改善患者脱垂症状,提高患者生活质量,与骶骨固定术有相似的临床效果,尤其适用于保留子宫的患者。

面向网状指标体系的强化学习型作战效能评估方法

作战效能评估在作战筹划与战斗力建设等领域具有重要应用价值。作为效能评估的核心要素,评估指标在体系对抗条件下必然存在高度关联,打破了独立性原则。针对现有作战效能评估方法面临此类评估场景时在功能或性能上的局限,提出了一种面向网状指标体系的作战效能评估方法。该方法从强化学习视角看待评估问题,将评估指标和指标间关联分别视作状态和状态迁移,通过合理构造策略函数和环境特性函数,可求解基于状态价值的指标综合权重,并借助经典指标聚合法评估作战效能,并通过实验证实了方法的有效性。

基于数值包络法的谐波齿轮传动共轭齿廓设计方法

针对谐波齿轮传动中S形齿廓存在的啮合区域优化问题,提出一种有效边缘点共轭齿廓的设计方法,避免了S形齿廓方程复杂导致的无法求解问题。以S形齿廓的凸齿廓为啮合副基础齿廓,分别以传统间隙调整法与有效边缘共轭点法设计了柔轮、刚轮的齿廓,并在平面数值分析、有限元模型中对比分析了两种设计方法所得齿廓的啮合特性与接触应力。研究结果表明,有效边缘共轭点齿廓设计方法可以同时实现二次啮合和两点啮合,增大了啮合角度以及啮合弧长;整圈啮合齿对数增加了15.78%,有55%的柔轮齿参与啮合,提升了谐波齿轮传动负载性能;有效增大了接触区域,齿廓间的最大接触应力降低了24.36%,可有效降低柔轮和刚轮齿面间的磨损。

三种不同腹股沟疝手术修补方案的临床有效性及安全性分析

目的 比较平片无张力疝修补术(Lichtenstein)、疝环充填式疝修补术(Rutkow)、腹膜前修补术(Kugel)三种修补方案治疗腹股沟疝的疗效及安全性。方法 60例成人腹股沟疝患者,根据修补方案的不同分为Lichtenstein组、Rutkow组、Kugel组,各20例。比较三组临床指标(手术时间、术后下床时间、住院时间)、术后早期并发症发生情况、术后不同时间疼痛程度及随访2年的术后复发率、异物感。结果 Lichtenstein组、Rutkow组、Kugel组手术时间分别为(65.2±10.3)、(58.6±9.5)、(72.1±11.2)min,术后下床时间分别为(12.8±3.1)、(10.4±2.6)、(14.2±3.5)h,住院时间分别为(5.6±1.2)、(4.9±1.0)、(6.2±1.4)d,三组比较有显著差异(P<0.05)。Kugel组术后早期并发症发生率5.00%略低于Lichtenstein组的10.00%和Rutkow组的10.00%,但并无显著差异(P>0.05)。术后1 d, Lichtenstein组、Rutkow组、Kugel组视觉模拟评分法(VAS)评分分别为(4.13±1.02)、(4.22±1.33)、(3.91±1.40)分,比较无显著差异(P>0.05)。术后1个月, Lichtenstein组、Kugel组VAS评分分别为(2.31±0.41)、(2.26±0.57)分,均低于Rutkow组的(3.16±0.92)分;术后6个月, Lichtenstein组、Kugel组VAS评分分别为(1.02±0.97)、(0.97±0.82)分,均低于Rutkow组的(1.91±1.55)分,有显著差异(P<0.05)。在术后2年的随访中,三组复发率比较,无显著差异(P>0.05);但Rutkow组的异物感占比60.00%明显高于Lichtenstein组的5.0%和Kugel组的10.0%,有显著差异(P<0.05)。结论 Lichtenstein、Rutkow、Kugel治疗腹股沟疝的疗效及并发症几乎接近,宜根据不同病例采用不同方案。

Effects of Heaving Motion on the Aerodynamic Performance of a Double-Element Wing in Ground Effect

The broad implication of the paper is to elucidate the significance of the dynamic heaving motion in the aerodynamic performance of multi-element wings,currently considered as a promising aspect for the improvement of the aerodynamic correlation between CFD,wind tunnel and track testing in race car applications.The relationship between the varying aerodynamic forces,the vortex shedding,and the unsteady pressure field of a heaving double-element wing is investigated for a range of mean ride heights,frequencies,and amplitudes,using a two-dimensional(2D)unsteady Reynolds-averaged Navier-Stokes(URANS)approach and an overset mesh method for modelling the moving wing.The analysis of the results shows that at high frequencies,i.e.,k≥5.94 and amplitudes a/c≥0.05 the interaction of the shear vorticity between the two elements results in the generation of cohering leading and trailing edge vortices on the flap,associated to the rapid variation of thrust and downforce enhancement.Both the occurrence and intensity of these vortices are dependent upon the frequency,amplitude,and mean ride height of the heaving wing.The addition of the flap significantly alters the frequency of the shed vortices in the wake and maintains the generation of downforce for longer time in ground proximity.The comparison with the static wing provides evidence that the dynamic motion of a race car wing can be beneficial in terms of performance,or detrimental in terms of aerodynamic correlation.

DPM dispersion inside a single straight entry using dynamic mesh model

Three-dimensional simulations of diesel particulate matter （DPM） distribution inside a single straight entry for the Load-Haul-Dump loader （LHD）-truck loading and truck hauling operations were conducted by using ANSYS FLUENT computational fluid dynamics software. The loading operation was performed for a fixed period of 3 min. The dynamic mesh technique in FLUENT was used to study the impact of truck motion on DPM distribution. The resultant DPM distributions are presented for the cases when the truck were driving upstream and downstream of the loading face. Interesting phenomena were revealed in the study including the piston effect, layering of DPM in the roof region, and backflow of diesel exhaust against ventilation. The results from the simulation can be used to determine if the areas inside the face area and straight entry exceed the current U.S. regulatory requirement for DPM concentration （〉160 pg/m3）. This research can guide the selection of DPM reduction strategies and improve the working practices for the underground miners.