Effect of leading-edge tubercles on the flow over low-aspect-ratio wings at low Reynolds number

Two-dimensional time-resolved particle image velocimetry(TR-PIV)and stereographic particle image velocimetry(SPIV)techniques were used to investigate the effect of leading-edge tubercles on the flow over low-aspect-ratio wing models.The angle of attack is fixed at 10°,and the Reynolds number based on chord length is 5.8×10^(3).It is shown that the leading-edge tubercles can effectively mitigate flow separation in the model and also reduce the contribution of wake vortex to the fluctuating energy of flow.Counter-rotating vortex pairs(CVPs)initiated from the peak of leading-edge tubercles can promote nearby momentum exchange,enhance mixing of the flow and increase the energy contained in the boundary layer,which results in resisting the larger adverse pressure gradient.Therefore,it is concluded that CVPs play an important role in mitigating the flow separation for wings with leading-edge tubercles.

Follow-up strategy for early detection of delayed pseudoaneurysms in patients with blunt traumatic spleen injury: A single-center retrospective study

BACKGROUND The spleen is the most commonly injured solid organ in blunt abdominal trauma,and splenic pseudoaneurysm rupture is associated with a high risk of mortality.Nonoperative management has become the standard treatment for hemodynam-ically stable patients with splenic injuries.On the other hand,delayed splenic pseudoaneurysms can develop in any patient,and at present,there are no known risk factors that may reliably predict their occurrence.Furthermore,there is a lack of consensus regarding the most appropriate strategies for monitoring and mana-ging splenic injuries,especially lower-grade(I-III).AIM To determine the predictors of pseudo-aneurysm formation following splenic injury and develop follow-up strategies for early detection of pseudoaneurysms.METHODS We retrospectively analyzed patients who visited the Level I Trauma Center bet-ween January 2013 and December 2022 and were diagnosed with spleen injuries after blunt abdominal trauma.RESULTS Using the American Association for the Surgery of Trauma spleen injury scale,the splenic injuries were categorized into the following order based on severity:Grade I(n=57,17.6%),grade II(n=114,35.3%),grade III(n=89,27.6%),grade IV(n=50,15.5%),and grade V(n=13,4.0%).Of a total of 323 patients,35 underwent splenectomy and 126 underwent angioembolization.19 underwent delayed angioembolization,and 5 under-went both initial and delayed angioem-bolization.In 14 patients who had undergone delayed angioembolization,no extravasation or pseudoaneurysm was observed on the initial computed tomography scan.There are no particular patient-related risk factors for the formation of a delayed splenic pseudoaneurysm,which can occur even in a grade I spleen injury or even 21 days after the injury.The mean detection time for a delayed pseudoaneurysm was 6.26±5.4(1-21,median:6,inter-quartile range:2-9)days.CONCLUSION We recommend regular follow-up computed tomography scans,including an arterial and portal venous phase,at least 1 week and 1 month after injury in any grade of blunt traumatic spleen injury for the timely detection of delayed pseudoaneurysms.

Pelvic fractures in blunt trauma patients:A comparative study

BACKGROUND Pelvic fractures(PF)with concomitant injuries are on the rise due to an increase of high-energy trauma.Increase of the elderly population with age related comorbidities further complicates the management.Abdominal organ injuries are kindred with PF due to the proximity to pelvic bones.Presence of contrast blush(CB)on computed tomography in patients with PF is considered a sign of active bleeding,however,its clinical significance and association with outcomes is debatable.AIM To analyze polytrauma patients with PF with a focus on the geriatric population,co-injuries and the value of contrast blush.METHODS This retrospective cohort study included 558 patients with PF admitted to level 1 trauma center(01/2017-01/2023).Analyzed variables included:Age,sex,mechanism of injury(MOI),injury severity score(ISS),Glasgow coma scale(GCS),abbreviated injury scale(AIS),co-injuries,transfusion requirements,pelvic angiography,embolization,laparotomy,orthopedic pelvic surgery,intensive care unit and hospital lengths of stay,discharge disposition and mortality.The study compared geriatric and non-geriatric patients,patients with and without CB and abdominal co-injuries.Propensity score matching was implemented in comparison groups.RESULTS PF comprised 4%of all trauma admissions.89 patients had CB.286(52%)patients had concomitant injuries including 93(17%)patients with abdominal co-injuries.Geriatric patients compared to non-geriatric had more falls as MOI,lower ISS and AIS pelvis,higher GCS,less abdominal co-injuries,similar CB and angio-embolization rates,less orthopedic pelvic surgeries,shorter lengths of stay and higher mortality.After propensity matching,orthopedic pelvic surgery rates remained lower(8%vs 19%,P<0.001),hospital length of stay shorter,and mortality higher(13%vs 4%,P<0.001)in geriatric patients.Out of 89 patients with CB,45(51%)were embolized.After propensity matching,patients with CB compared to without CB had more pelvic angiography(71%vs 12%,P<0.001),higher embolization rates(64%vs 22%,P=0.02)and comparable mortality.CONCLUSION Half of the patients with PF had concomitant co-injuries,including abdominal co-injuries in 17%.Similarly injured geriatric patients had higher mortality.Half of the patients with CB required an embolization.

Stability analysis and transition prediction of hypersonic boundary layer over a blunt cone with small nose bluntness at zero angle of attack

Stability and transition prediction of hypersonic boundary layer on a blunt cone with small nose bluntness at zero angle of attack was investigated. The nose radius of the cone is 0.5 mm; the cone half-angle is 5°, and the Mach number of the oncoming flow is 6. The base flow of the blunt cone was obtained by direct numerical simulation. The linear stability theory was applied for the analysis of the first mode and the second mode unstable waves under both isothermal and adiabatic wall condition, and e^N method was used for the prediction of transition location. The N factor was tentatively taken as 10, as no experimentally confirmed value was available. It is found that the wall temperature condition has a great effect on the transition location. For adiabatic wall, transition would take place more rearward than those for isothermal wall. And despite that for high Mach number flows, the maximum amplification rate of the second mode wave is far bigger than the maximum amplification rate of the first mode wave, the transition location of the boundary layer with adiabatic wall is controlled by the growth of first mode unstable waves. The methods employed in this paper are expected to be also applicable to the transition prediction for the three dimensional boundary layers on cones with angle of attack.

Leading-edge receptivity of boundary layer to three-dimensional free-stream turbulence

The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on external disturbances such as sound waves and vortices in the free stream, whereas those on the leading-edge receptivity to the three-dimensional free-stream turbulence (FST), which is more general in the nature, are rarely reported. In consideration of this, this work is devoted to investigating the receptivity process of three-dimensional Tollmien-Schlichting (T-S) wave packets excited by the three-dimensional FST in a flat-plate boundary layer numerically. The relations between the leading-edge receptivity and the turbulence intensity are established, and the influence of the FST directions on the propagation directions and group velocities of the excited T-S wave packets is studied. Moreover, the leading-edge receptivity to the anisotropic FST is also studied. This parametric investigation can contribute to the prediction of laminar-turbulent transition.

On the mechanism by which nose bluntness suppresses second-mode instability

A physical mechanism by which nose bluntness suppresses second-mode instability is proposed.Considered are 7 degree half-angle straight cones with nose bluntness radii of 0.15 mm, 3.556 mm,5 mm, 9.525 mm, 12.7 mm and 25.4 mm at tunnel conditions relevant to the AFOSR-Notre Dame Large Mach 6 Quiet Tunnel. It is shown that second-mode suppression is achieved via entropy layer modulation of the basic state density gradient. A weakening of the density gradient disrupts the acoustic resonance necessary to sustain second-mode growth. These results are consistent with the thermoacoustic interpretation which posits that second-mode instability can be modeled as thermoacoustic resonance of acoustic energy trapped within an acoustic impedance well.Furthermore, the generalized inflection point criterion of Lees and Lin is applied to develop a criterion for the existence of second-mode instability based on the strength of the basic state density gradient.

Panscleritis After Blunt Ocular Trauma in A Child with Epididymitis

We reported an 8-year-old boy with panscleritis in left eye and right epididymitis after falling on the ground.Etiologic diagnosis played a key role in this case.Systemic examinations ruled out systemic autoimmune diseases,tumors,and infections as the cause of scleritis and suggested that the disease was caused by a local delayedtype hypersensitivity(DTH)induced by ocular trauma and was non-infectious.Still,the right epididymitis was infectious.Both conditions were treated successfully using steroids and antibiotics,respectively.Thus,early etiologic diagnosis and reasonable treatment are crucial to prevent visual loss.

Necroptosis plays a crucial role in the exacerbation of retinal injury after blunt ocular trauma

Retinal injury after blunt ocular trauma may directly affect prognosis and lead to vision loss.To investigate the pathological changes and molecular mechanisms involved in retinal injury after blunt ocular trauma,we established a weight drop injury model of blunt ocular trauma in male Beagle dogs.Hematoxylin-eosin staining,immunofluorescence staining,western blotting,and TUNEL assays were performed to investigate retinal injury within 14 days after blunt ocular trauma.Compared with the control group,the thicknesses of the inner and outer nuclear layers,as well as the number of retinal ganglion cells,gradually decreased within 14 days after injury.The number of bipolar cells in the inner nuclear layer began to decrease 1 day after injury,while the numbers of cholinergic and amacrine cells in the inner nuclear layer did not decrease until 7 days after injury.Moreover,retinal cell necroptosis increased with time after injury;it progressed from the ganglion cell layer to the outer nuclear layer.Visual electrophysiological findings indicated that visual impairment began on the first day after injury and worsened over time.Additionally,blunt ocular trauma induced nerve regeneration and Müller glial hyperplasia;it also resulted in the recruitment of microglia to the retina and polarization of those microglia to the M1 phenotype.These findings suggest that necroptosis plays an important role in exacerbating retinal injury after blunt ocular trauma via gliosis and neuroinflammation.Such a role has important implications for the development of therapeutic strategies.

局部外形参数对高速飞行器的RCS影响

为了降低高速飞行器的雷达散射截面(radar cross section,RCS),采用多层快速多极子算法和物理光学法研究局部外形参数对飞行器雷达散射特性的影响。在此基础上,提出一种变半径弧形的边缘钝化形式,以提高飞行器仰视对抗能力。所提出的变半径弧形钝化外形具有良好的RCS减缩能力,与传统圆弧钝化外形相比,在前向重点角域内,RCS对数均值降低了22.88%;随着仰角的增大,变半径弧形钝化形式还具备全向RCS减缩能力,在全向角域内RCS对数均值降低了13.37%。最后,研究所提出的变半径弧形钝化方式在不同雷达波频段下的RCS特性,结果表明这种钝化方式对于频率较高时仰视对抗能力更好。

深空再入飞行器烧蚀粗糙表面高超声速转捩预测

深空再入飞行器为提高气动减速效率,一般采用大钝度迎风外形以及烧蚀降热型防热结构。而扁平的前体外形与气动加热烧蚀导致表面粗糙度急剧增加等因素,极易造成飞行器迎风面流动失稳,流动出现转捩甚至演化为湍流,使表面热流分布发生巨大变化,给飞行器安全带来极大挑战。国内以往对大钝头再入器微观形貌变化下高超声速边界层失稳机制和转捩模拟的研究开展很少。以大钝头防热罩与沙粒式分布粗糙元为研究对象,分别利用基于高超声速与粗糙元修正的γ-Reθ转捩模式和k-ω-γ转捩模式,分析了高超声速来流条件下分布粗糙元等效粗糙高度、来流Reynolds数、攻角以及化学非平衡基本流对大钝头迎风表面的间歇因子分布和边界层转捩位置以及热流分布的影响,研究了深空再入飞行器烧蚀粗糙表面的高超声速边界层转捩发展规律与气动热影响规律。

局部凸起在V形钝前缘模型中的降热特性研究

三维内转式进气道的唇口结构通常存在复杂的激波干扰及严酷的气动热载荷,严重威胁高超声速飞行器的性能与安全.在6.0马赫的高超声速流动中,以V形钝前缘模型为研究对象,设计了局部凸起的被动流动控制降热方案.采用数值模拟手段,首先研究了局部凸起方案的降热能力以及降热原理,然后初步优化了局部凸起的位置、高度以及宽度等关键设计参数,最后分析了优化后的局部凸起方案的攻角、侧滑角及马赫数的适用性.研究结果表明:上游凸起边缘形成的斜激波与主马赫反射结构形成的透射激波发生干扰,能够减弱其冲击壁面的强度,实现降热的目的;驻点凸起通过改变超声速射流的对撞角度,能够降低其对撞的强度,实现降热的目的.原始方案的降热能力约为37.75%,在对局部凸起的关键设计参数进行初步优化后,优化方案的降热能力将提升至44.60%.设计工况下的优化方案具有良好的攻角适用性,而高度可变的优化方案可以较好地适用于有侧滑角及高马赫数的流动.在研究范围内,高度可变的优化局部凸起方案的降热能力均高于20%.

丙三醇联合防腐剂对半干武昌鱼贮藏期间品质的影响

为改善半干武昌鱼货架期短、难以常温流通等问题,以半干武昌鱼为对象,通过测定菌落总数(total viable counts,TVC)、酵母菌和霉菌总数、微生物组成、总挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸反应物(thiobarbituric acid reactive substances,TBARS)值、pH值等指标,并结合感官评分,研究丙三醇联合防腐剂对半干武昌鱼贮藏过程中品质的影响。结果表明,随着贮藏时间的延长,丙三醇联合复合防腐剂(0.075%山梨酸钾+0.025%脱氢乙酸钠)处理和对照组半干武昌鱼的感官评分均不断下降,TVC、酵母菌总数、乳杆菌属相对丰度、TVB-N含量、TBARS值、pH值均不断升高。与对照组相比,丙三醇联合防腐剂处理可以减缓半干武昌鱼感官评分下降,抑制细菌和酵母菌生长,减少细菌多样性,降低乳杆菌属细菌相对丰度,减少TVB-N的积累,减缓脂肪氧化速率,并将半干武昌鱼在25、15、4℃下的货架期分别延长2、4、7 d。本研究可为半干武昌鱼的质量控制与货架期延长提供参考。

弹道冲击下石墨烯和聚乙烯改性芳纶织物的钝伤防护性能

芳纶凭借其轻质高强的特点广泛应用于防弹领域。为提高单层芳纶织物的抗钝伤能力,采用热塑性树脂聚乙烯(Polythene,PE)与石墨烯纳米粒子表面改性方法提升芳纶织物的抗钝伤性能。以背衬凹陷为标准,对不同质量配比改性芳纶织物的抗钝伤能力和能量吸收特性进行测试对比。对比结果表明:石墨烯和PE两种改性方法均可提升芳纶织物的抗钝伤能力,其中PE改性方法使得改性织物面密度增加较小但抗钝伤能力显著提升,10%PE的防弹能力和比吸能值较纯芳纶分别提升了18.0%和30.8%;石墨烯改性织物刚性的增加使其低速抗钝伤能力增强,但是过大的纱线间摩擦使其高速防护能力减弱,2%石墨烯粉体为石墨烯改性织物的最佳配比。此外,优化验证得到了2层10%PE和13层的6层正交超高分子量PE无纬布防弹衣组合设计。

水分活度降低剂对半干武昌鱼品质的影响

以半干武昌鱼为研究对象,通过测定水分活度(water activity,a_(w))、水分状态、菌落总数(total viable counts,TVC)、酵母菌总数、总挥发性盐基氮(total volatile basic nitrogen,TVB-N)含量、硫代巴比妥酸反应物(thiobarbituric acid reactive substances,TBARS)值及感官评分,研究不同a_(w)降低剂对半干武昌鱼水分状态及品质的影响。结果表明:a_(w)降低剂种类和添加量对半干武昌鱼的a_(w)、水分状态及理化指标有显著影响,且添加量的影响大于种类;海藻糖、山梨糖醇和丙三醇对半干武昌鱼的a_(w)均有一定的降低作用,丙三醇对a_(w)的降低效果最好,添加6%丙三醇时,可将半干武昌鱼的a_(w)从0.917降低至0.873;随着海藻糖、山梨糖醇和丙三醇添加量的增加,半干武昌鱼肉的T_(22)显著减小(P<0.05),T_(23)无显著差异(P>0.05),其不易流动水比例显著增加(P<0.05),而自由水比例显著降低(P<0.05);相对于对照组,随着a_(w)降低剂添加量的增加,半干武昌鱼的TVC、酵母菌总数、TVB-N含量、TBARS值均显著降低(P<0.05),其中6%丙三醇组的各项指标最优。a_(w)降低剂的添加可有效降低水分自由度和流动性,减缓半干武昌鱼品质劣变。

创伤性胰腺损伤12例外科治疗分析

目的探讨外伤所致闭合性腹部损伤中胰腺损伤的外科治疗方法。方法回顾性收集2018年1月至2023年8月西安交通大学第一附属医院收治并行外科治疗的12例创伤性胰腺损伤病人的临床资料,从受伤原因、诊断方法、外科治疗方法、并发症等方面进行分析。结果12例胰腺损伤病人的受伤方式:交通伤8例,撞击伤4例。胰腺损伤分级:Ⅱ级2例,Ⅲ级6例,Ⅳ级1例,Ⅴ级3例。8例病人术前行血清淀粉酶测定,其中6例血清淀粉酶升高。10例病人术前CT检查诊断胰腺损伤。所有病人均行手术治疗,其中行腹腔积血清除1例,腹腔积血清除术加胰腺修补术1例,胰体尾切除术6例(其中同时行脾脏切除4例),行胰腺坏死组织清除加胰液外引流术并于1年后行二期胰肠吻合术1例,胰十二指肠切除2例,行肠系膜上静脉修补加胰腺坏死组织清除加腹腔置管通畅引流术1例。所有病人中,死于多器官功能衰竭1例,发生术后并发症4例,其中胰瘘2例,腹腔感染2例。结论闭合性腹部损伤病人行CT检查是早期诊断胰腺损伤的重要方式,早期进行分级有助于手术方式的选择决策。经术前检查提示胰腺高级别损伤者应在生命体征维持平稳的前提下及时行手术治疗,选择合理的手术方式及术后通畅引流是防止术后并发症的关键。

步枪弹侵彻背部穿硬防护人体靶标钝击效应研究

针对枪弹侵彻穿防弹衣人体背部产生脊柱脊髓钝性损伤,建立了DBP10式5.8 mm步枪弹侵彻NIJⅢ级SiC/UHMWPE防弹插板的数值模型,采用JHB本构和基于Abaqus二次开发的VUMAT本构分别模拟SiC陶瓷和UHMWPE层合板;开展了5.8 mm步枪弹侵彻NIJⅢ级SiC/UHMWPE防弹插板的数值模拟,通过基于高速摄影的弹道实验结果对比验证了数值模型的准确性;基于枪弹侵彻防弹插板的数值模拟结果,开展了5.8 mm步枪弹以910 m/s入靶速度侵彻背部穿硬防护人体躯干靶标的数值模拟,明确了步枪弹击中防弹衣后压力波在肌肉-脊柱内的传导规律,还原了枪弹侵彻过程中人体典型器官(心、肝、肺、胃等)的应力波传递过程。结果表明:人体背部在枪弹钝击作用下会在脊椎椎骨上产生瞬时高应力,可能导致椎骨骨折、椎间盘突出和脊柱不稳定;致伤点T10椎体后方脊髓最大应力为1.04 MPa,可能导致脊髓改变;对脊髓上应力与加速度线性回归分析表明,压力与加速度呈正相关。

Imaging characteristics and treatment strategies for carotid artery occlusion caused by skull base fracture:Three case reports

BACKGROUND Traumatic internal carotid artery(ICA)occlusion is a rare complication of skull base fractures,characterized by high mortality and disability rates,and poor prognosis.Therefore,timely discovery and correct management are crucial for saving the lives of such patients and improving their prognosis.This article retrospectively analyzed the imaging and clinical data of three patients,to explore the imaging characteristics and treatment strategies for carotid artery occlusion,combined with severe skull base fractures.CASE SUMMARY This case included three patients,all male,aged 21,63,and 16 years.They underwent plain film skull computed tomography(CT)examination at the onset of their illnesses,which revealed fractures at the bases of their skulls.Ultimately,these cases were definitively diagnosed through CT angiography(CTA)examinations.The first patient did not receive surgical treatment,only anticoagulation therapy,and recovered smoothly with no residual limb dysfunction(Case 1).The other two patients both developed intracranial hypertension and underwent decompressive craniectomy.One of these patients had high intracranial pressure and significant brain swelling postoperatively,leading the family to choose to take him home(Case 2).The other patient also underwent decompressive craniectomy and recovered well postoperatively with only mild limb motor dysfunction(Case 3).We retrieved literature from PubMed on skull base fractures causing ICA occlusion to determine the imaging characteristics and treatment strategies for this type of disease.CONCLUSION For patients with cranial trauma combined with skull base fractures,it is essential to complete a CTA examination as soon as possible,to screen for blunt cerebrovascular injury.

超声造影诊断血流动力学稳定的钝性腹部实质脏器创伤患者的临床价值

目的 探讨超声造影(CEUS)在血流动力学稳定的钝性腹部实质脏器创伤诊断中的临床价值。方法 选取我院急救部收治的血流动力学稳定的疑似钝性腹部实质创伤患者42例,均行对比增强计算机断层扫描(CECT)、常规超声及CEUS检查,并评估脏器损伤分级。以CECT诊断结果为标准,计算常规超声及CEUS诊断钝性腹部实质脏器创伤的灵敏度、特异度、阳性预测值、阴性预测值和准确率;比较CEUS与CECT评估各脏器损伤分级的差异。结果 42例疑似钝性腹部实质脏器创伤患者中,CECT诊断阳性患者30例,CEUS诊断阳性患者29例;CEUS诊断灵敏度为93.33%,特异度为91.67%,阳性预测值96.55%,阴性预测值为84.62%,准确率为92.86%。CEUS与CECT在评估各脏器损伤分级方面比较差异无统计学意义。结论 CEUS在血流动力学稳定的钝性腹部实质脏器创伤患者诊断中有一定的临床价值。

战斗部头部形状对侵彻钢板影响的试验与理论研究

[目的]旨在探究战斗部头部形状对其侵彻匀质金属板性能的影响。[方法]利用92 mm滑膛炮发射平头型战斗部和尖头型战斗部侵彻Q345B与921A钢材料的靶板,通过测速靶网以及高速摄像方法对战斗部侵彻钢板前后的速度进行测量,分析侵彻靶板后战斗部与靶板的毁伤模式,从而建立起不同头部形状战斗部侵彻下的理论评估方法。[结果]结果表明:战斗部头部形状对侵彻靶板后的毁伤模式以及对不同类型钢板的等效换算均具有重要影响;尖头型战斗部对靶板的毁伤以花瓣型为主,平头型战斗部以剪切冲塞为主;与贝尔金公式相比,采用改进Thomoson公式计算战斗部侵彻靶板后的剩余速度所得结果与试验结果吻合更好。[结论]所提方法及结果可用于后续对战斗部穿甲性能的评估,并可为后续大质量战斗部侵彻金属板研究提供相关依据。

超声引导肾锥体精准穿刺钝性分离法在无积水肾盂造瘘术中的临床应用:一种无积水肾盂造瘘新方法

目的:探讨超声造影辅助下超声引导肾锥体精准穿刺钝性分离法在无积水肾盂造瘘术中的临床应用情况。方法:回顾性分析2022年5月至2024年4月在解放军总医院第一医学中心进行超声引导下无积水肾盂造瘘的患者11例,其中单侧肾盂造瘘6例,双侧肾盂造瘘5例,共16例次无积水肾盂穿刺造瘘术。均在超声引导下徒手穿刺目标肾锥体并采用钝性分离法置入导丝。统计穿刺过程中的首次穿刺成功率、平均穿刺针数、穿刺时间、总置管时间、并发症情况。结果:所有患者均穿刺成功,首针穿刺成功率为81.25%,平均穿刺针数为1.19±0.4、平均穿刺时间为(122.19±22.55)s、平均置管时间为(674.19±46.61)s;所有肾盂穿刺造瘘均未出现活动性出血及其他严重并发症,2例次术后第2天引流不畅重新调整引流管。结论:超声造影辅助下超声引导肾锥体精准穿刺钝性分离法在无积水肾盂造瘘术中应用效果良好,具有较高的安全性和可行性,为泌尿系损伤无法行输尿管支架的患者提供了安全有效的治疗方法,值得推广。