Global dust density in two-dimensional complex plasma

The driven-dissipative Langevin dynamics simulation is used to produce a two-dimensional(2D) dense cloud, which is composed of charged dust particles trapped in a quadratic potential. A 2D mesh grid is built to analyze the center-to-wall dust density. It is found that the local dust density in the outer region relative to that of the inner region is more nonuniform,being consistent with the feature of quadratic potential. The dependences of the global dust density on equilibrium temperature, particle size, confinement strength, and confinement shape are investigated. It is found that the particle size, the confinement strength, and the confinement shape strongly affect the global dust density, while the equilibrium temperature plays a minor effect on it. In the direction where there is a stronger confinement, the dust density gradient is bigger.

Two-Dimensional Euler Adaptive Mesh Method on Detonation

The adaptive mesh refinement （AMR） method is applied in the 2-D Euler multi-component elasticplastic hydrodynamics code （MEPH2Y）. It is applied on detonation. Firstly, the AMR method is described, including a conservative spatial interpolation, the time integration methodology with the adapitve time increment and an adaptive computational region method. The advantage of AMR technique is exhibited by numerical examples, including the 1-D C-J detonation and the 2-D implosion ignited from a single point. Results show that AMR can promote the computational efficiency, keeping the accuracy in interesting regions.

Two-dimensional numerical research on effects of titanium target bombarded by TEMPⅡ accelerator

Two-dimensional numerical research has been carried out on the ablation effects of titanium target irradiated by intense pulsed ion beam （IPIB） generated by TEMP Ⅱ accelerator. Temporal and spatial evolution of the ablation process of the target during a pulse time has been simulated. We have come to the conclusion that the melting and evaporating process begin from the surface and the target is ablated layer by layer when the target is irradiated by the IPIB. Meanwhile, we also obtained the result that the average ablation velocity in target central region is about 10 m/s, which is far less than the ejection velocity of the plume plasma formed by irradiation. Different effects have been compared to the different ratio of the ions and different energy density of IPIB while the target is irradiated by pulsed beams.

Two-dimensional titanium carbonitride MXene as a highly efficient electrocatalyst for hydrogen evolution reaction

In this paper,we report,for the first time,on the electrochemical catalytic activity of 2D titanium carbonitride MXene for hydrogen evolution reaction(HER).According to our study,2D titanium carbonitride exhibited much higher electrocatalytic activity than its carbide analogues,achieving an onset overpotential of 53 mV and Tafel slope of 86 mV dec^(-1),superior to the titanium carbide with onset overpotential of 649 mV and Tafel slope of 303 mV dec^(-1).The obtained onset overpotential for 2D titanium carbonitride is lower than those of all the reported transition metal carbides MXene catalysts without additives,so far.Density functional theory calculations were conducted to further understand the electrochemical performance.The calculation results show that a greater number of occupied states are active for Ti_(3)CNO_(2),revealing free energy for the adsorption of atomic hydrogen closer to 0 than that of Ti_(3)C_(2)O_(2).Both experimental and calculation studies demonstrate the excellent electrocatalytic behavior of titanium carbonitride.The investigation of 2D titanium carbonitride opens up a promising paradigm for the conscious design of high-performance non-precious metal catalyst for hydrogen generation.

Titanium mesh for bone augmentation in oral implantology: current application and progress

Guided bone regeneration(GBR)is an effective and simple method for bone augmentation,which is often used to reconstruct the alveolar ridge when the bone defect occurs in the implant area.Titanium mesh has expanded the indications of GBR technology due to its excellent mechanical properties and biocompatibility,so that the GBR technology can be used to repair alveolar ridges with larger bone defects,and can obtain excellent and stable bone augmentation results.Currently,GBR with titanium mesh has various clinical applications,including different clinical procedures.Bone graft materials,titanium mesh covering methods,and titanium mesh fixing methods are also optional.Moreover,the research of GBR with titanium mesh has led to multifarious progresses in digitalization and material modification.This article reviews the properties of titanium mesh and the difference of titanium mesh with other barrier membranes;the current clinical application of titanium mesh in bone augmentation;common complications and management and prevention methods in the application of titanium mesh;and research progress of titanium mesh in digitization and material modification.Hoping to provide a reference for further improvement of titanium mesh in clinical application and related research of titanium mesh.

Hard tissue stability after guided bone regeneration: a comparison between digital titanium mesh and resorbable membrane

Guided bone regeneration(GBR)uses resorbable and non-resorbable membranes as biological barriers.This study compared the differences in hard tissue stability between GBR using evidence-based digital titanium mesh and resorbable collagen membranes during implant placement.A total of 40 patients(65 implant sites)were enrolled and divided into two groups:resorbable membrane and digital titanium mesh groups.The alveolar bone was analyzed at two-and three-dimensional levels using conebeam computed tomography and by reconstructing and superimposing the hard tissues at four time points:preoperatively,postoperatively,before second-stage surgery,and 1 year after loading.The use of digital titanium mesh showed less alveolar bone resorption in vertical and horizontal directions two-dimensionally before the second-stage surgery and 1 year after loading.Regarding volumetric stability,the percentage of resorption after 6 months of healing with resorbable membrane coverage reached 37.5%.However,it was only 23.4%with titanium mesh.Although postoperative bone volume was greater at all labial sites with resorbable membrane than with digital titanium mesh,after substantial bone resorption within 1 year of loading,the labial bone thickness at the upper part of implants was thinner with resorbable membrane than with digital titanium mesh.Furthermore,digital titanium meshes made according to ideal bone arch contour reduced soft tissue irritation,and the exposure rate was only 10%.Therefore,although both resorbable membrane and digital titanium mesh in GBR were able to successfully reconstruct the bone defect,digital titanium meshes were better at maintaining the hard tissue volume in the osteogenic space.

Surgical Resection of Sternal Tumors and Reconstruction with Titanium Mesh

Objective To evaluate the use of titanium mesh reconstruction after sternal tumor resection. Methods From January 2007 to January 2011, 14 patients with sternal tumors were admitted into Peking Union Medical Hospital. The clinical characteristics, surgical resection, and technique of reconstruction were reviewed. Results Of the 14 patients, 3 had a metastatic sternal tumor, the primary sites of which were as follows: hepatic carcinoma in one case (metastasis 19 years after operation), breast carcinoma in another case (metastasis 5 years after operation), and renal carcinoma in the other case (found simultaneously). Two patients showed local involvement of the sternum: 1 had thymic carcinoma, and the other had myofibrosarcoma. The remaining 9 patients had primary tumors: 4 were osteochondroma, 3 chondrosarcoma, 1 eosinophilic granuloma, 1 non-Hodgekin's lymphoma. En bloc resection of the sternal tumor was performed in all the 14 patients. The defect was repaired with the titanium mesh adjusted to the shape of the defect and fixed with the stainless steel wire. Eleven patients were followed up for a period from 2 months to 4 years, during which no translocation or broken of the titanium mesh was observed. Conclusions Radical en bloc excision remains the treatment of choice for sternal tumors. Sternum defect reconstruction using titanium mesh as a rigid replacement proves appropriate and effective.

High Scalp Tension after Three-Dimensional Titanium Mesh Repair for Skull Defect: 2 Case Reports

Rationale: The three-dimensional (3D) computer-made titanium mesh is widely used in the skull repair for those patients receiving decompression of the bone flap. It can restore normal anatomy to a greater extent and make a better appearance. Case Presentation: We reported two cases of patients admitted to our hospital who have experienced high scalp tension after skull repair. At first, these two patients underwent decompression of the bone flap, and the physical examination results showed a defect of skull. No neurological symptoms and signs were found. The 3D computed tomography (CT) reconstruction of skull was performed, and then the skull repair with 3D titanium mesh was conducted. But because of high scalp tension, they underwent a second operation, during which we re-trimmed and reduce the arc of the titanium mesh. The scalp incision of both patients healed well and no titanium mesh was exposed. Both patients have a good prognosis. Lessons: We highlight that the high tension of scalp due to overstretching after 3D titanium mesh repair for skull defect should be paid much attention to. Trimming and reducing the arc of titanium mesh is an effective treatment for this situation.

Computer-Assisted Surgery for Mandibular Reconstruction Using a Patient-Specific Titanium Mesh Tray and Particulate Cancellous Bone and Marrow

Craniomaxillofacial surgery is difficult due to the complexity of the regional anatomy. Computer-assisted surgery is a promising tool aiming to improve the safety and precision of such surgery. A computer-assisted surgical navigation approach for reconstruction of mandibular defects using a patient-specific titanium mesh tray and particulate cancellous bone and marrow (PCBM) harvested from bilateral anterior ilia is proposed. This case report involves a large multicystic ameloblastoma affecting the right mandible of a 31-year-old male patient. Following detailed clinical examination, radiological interpretation, and histopathological diagnosis, computer-assisted surgical simulation with a virtual 3-dimensional (3-D) model was designed using surgical planning software based on the pre-operative computed tomography data. Long-span segmental resection of the mandible was planned, and the defect was analyzed for reconstruction using a patient-specific reconstruction titanium mesh tray mediated with computer-aided design and manufacturing (CAD/CAM) techniques. During the actual surgery, the ultrasonic bone cutting instrument in the surgeon’s hand was connected to the navigation system to touch an anatomical position on the patient. Therefore, osteotomies were performed finely and smoothly according to the navigation images of the cutting bone line by sequentially moving the instrument. Finally, a CAD/CAM-mediated titanium mesh tray condensed by PCBM was adapted to the remaining mandibular fragments. Six months postoperatively, the patient had a good mandibular configuration and facial contour. Integration of different technologies, such as software planning and 3-D surgical simulation, combined with intraoperative navigation and CAD/CAM techniques, provides safe and precise mandibular reconstruction surgery.

Research Progress of Titanium Polypropylene Mesh in Breast Reconstruction

To investigate the application of titanium polypropylene mesh in breast reconstruction.In this study,we selected the literature data in recent 4 years to analyze the application of titanium polypropylene mesh in breast reconstruction.Using the keywords of"breast reconstruction,""titanium polypropylene mesh,^^"application"and"research progress,we analyzed and summarized the related research progress of titanium polypropylene mesh in breast reconstruction.The research was conducted using the analysis of titanium polypropylene mesh,titanium polypropylene mesh in breast reconstruction surgery advantages,adverse complications related to titanium polypropylene mesh in breast reconstruction surgery and preventive measures.By constantly improving these aspects in the research process,the current study has certain value,and may guide the research work of titanium mesh in breast reconstruction.

Repair of infectious scalp defects with titanium mesh exposure by scalp rotation flap

Objective To explore the application of scalp rotation flap in reconstruction of infectious scalp defect with titanium mesh exposure. Methods Twelve patients were treated in this group including 4 males and 8 female. S The defective size ranged from 2. 0 cm × 5. 0 cm to 0.

Anatomy-related risk factors in Harm's mesh subsidence in cervical reconstruction after one-level corpectomy

Objective:To clarify anatomy-related factors in the cervical spine with subsidence of titanium mesh cage (TMC) after one-level cervical corpectomy and fusion. The effect of the cervical posture, segmental curvature and endplate gradient on this postoperative phenomenon was evaluated. Methods: Between August 2003 and March 2006, a total of the 236 patients underwent one-level corpectomy and TMC fusion. Their radiological examinations were reviewed and clinical outcomes evaluated. Results: In the patients who were followed up for 12 months, TMC subsidence occurred in 54 (28.6%) cases. C6 corpectomy had a significant higher risk (26/60, 43.3%) for TMC subsidence, which was correlated with the variation of the gradient of the vertebral endplates against cervical levels. Although the clinical outcome was comparable with those in the literature, the patients may have subsidence-related problems such as neck-shoulder pain, neurological deterioration and instrumental failure. Conclusion: To decrease the incidence of subsidence, TMC design should be optimized to be in line with anatomic characteristics of the cervical spine.

钛网上CdS纳米微球的制备及可见光下产氢性能研究

为了提高催化剂的光催化产氢能力,本文采用简单的水热法,在处理后的钛网表面生长了CdS纳米微球。利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和X射线光电子能谱(XPS)等测试手段对样品的成分、结构、形貌进行了表征,并研究了其光电化学性能及可见光下光催化性能。结果表明,钛网上生长的CdS微球由纳米棒组装而成,通过缺陷调控,Cd/S物质的量之比为1∶1(CdS-1)的样品具有良好的光电响应,在零偏压下最大光电流约为140μA,可见光下的产氢率可达212.6μmol·h^(-1)·cm^(-2),并且方便回收,是一种理想的光催化产氢材料。

Mimics软件三维重建技术行钛网形态优化设计在颅骨成形术中的应用

目的探讨应用Mimics软件三维重建技术进行钛网形态优化设计在颅骨成形术中的应用效果。方法2017年5月至2022年5月前瞻性进行颅骨成形术60例,其中30例应用Mimics软件三维重建技术进行钛网形态优化设计(优化组),30例应用常规设计的钛网(对照组)。结果与对照组比较,优化组手术切口供血良好率明显增高(80.0%vs.53.3%;P=0.028),术后切口甲级愈合率明显增高(70.0%vs.40.0%;P=0.020),术后拆线时间明显缩短[(7.07±0.95)d vs.(7.83±1.12)d;P=0.006],术后大量硬膜外积液发生率明显降低(10.0%vs.36.7%;P=0.015)。优化组术后无颅内出血、钛网外露情况。结论应用Mimics软件三维重建技术对钛网形态进行优化设计,可有效降低颅骨成形术中切口缝合的张力,术后切口供血和愈合更佳,缩短术后拆线时间,降低大量硬膜外积液的发生率,有效减少颅内出血和钛网外露。

旋转超声加工对TiBw网状钛基复合材料表面残余应力的影响

为研究不同切削条件下旋转超声加工对材料表面残余应力的影响,选取硼化钛晶须(TiB whiskers,TiBw)网状钛基复合材料为实验对象,使用镍基电铸金刚石砂轮进行旋转超声加工,并分析了加工后材料的表面残余应力。结果表明:由于钛基复合材料具有网状结构和优异的高温性能,使切削热和微观相变产生的残余应力较小,磨粒机械作用产生的残余应力更大。随着超声振动的引入,磨粒高频冲击工件表面,使旋转超声加工工件表面残余应力均大于普通磨削。在主轴转速n=9000 r/min,进给速度v f=8 mm/min,加工深度a p=25μm的加工参数下,旋转超声加工工件表面存在-540 MPa的残余压应力,随着主轴转速增大,残余应力显著减小,并且残余应力的影响层深度逐渐减小。超声振动的引入增大工件表面残余压应力,提高材料抗疲劳性能。

大型复杂钛合金铸件有限差分网格快速生成算法

钛合金以其卓越的耐腐蚀性、轻质和高强度特性,成为航空航天工业中的核心材料。随着现代装备制造技术的飞速发展,钛合金铸件的制造技术也达到了新的高度,不仅复杂程度显著提升,而且铸件的规模也趋向于大型化。钛合金铸件大型化、薄壁化、复杂化的趋势,无疑对铸造过程的数值模拟带来了挑战。网格是数值模拟过程的计算域,因此首要问题就是如何高效生成高质量的网格。为应对这一问题,本文提出了一种算法,旨在高效生成适用于有限差分方法的六面体均匀网格。该算法结合了具有空间划分优势的八叉树数据结构和经典的射线法。首先利用八叉树数据结构对钛合金铸件的三维模型进行精细空间划分,通过与有限差分网格的映射关系,快速生成精确的表面网格。然后采用射线法,以表面网格为基础,依据射线与铸件内部的交点信息,精准构建内部网格。经过测试验证,该算法能够高效、准确地生成高质量的有限差分六面体均匀网格,为后续的数值计算提供了精确、可靠的计算域。

3D打印金属椎体替代物力学性能评价

目的 对钛网及3D打印金属椎体替代物力学性能进行研究,为临床中人工椎体选择与结构优化设计提供指导。方法 通过压缩力学测试,对钛网及3D打印多孔型、桁架型与拓扑型椎体替代物的等效力学属性与结构破坏形式进行系统研究。结果 钛网等效弹性模量[(2 908.73±287.39) MPa]仅次于拓扑型椎体替代物,但其结构强度与稳定性较差,等效屈服强度[(46.61±4.85) MPa]高于多孔型椎体替代物,且在压缩中率先屈服;多孔型椎体替代物结构强度[(18.14±0.17)~(25.79±0.40) MPa]不足,难以满足脊柱重建力学要求;桁架型椎体替代物等效弹性模量[(2 477.86±55.19)~(2 620.08±194.36)MPa]与等效屈服强度[(77.61±0.50)~(88.42±1.07) MPa]良好但稳定性不足,在压缩过程中容易出现失稳现象;拓扑型椎体替代物具有最高的等效弹性模量[(3 746.28±183.80) MPa]与等效屈服强度[(177.43±3.82) MPa],可为人工椎体在体服役安全稳定提供更强保障。结论 拓扑优化方法可实现椎体替代物高强度、高稳定性设计,提供更大的设计空间与安全余量,为人工椎体轻量化与新材料设计提供更多可能。

自制负压封闭引流装置联合扩张头皮皮瓣修复钛网外露创面一例

目的探讨自制负压封闭引流装置联合扩张头皮皮瓣修复钛网外露创面的可行性。方法对颅骨修复术后钛网外露、钛网下窦道存在患者采用自制负压封闭引流装置培养肉芽肿组织,至创面感染控制后,行钛网外头皮皮瓣扩张术。待钛网下肉芽完全生长填塞,钛网外扩张皮瓣达到能够无张力覆盖钛网创面,再行扩张头皮皮瓣移植覆盖钛网创面,创面外VSD持续负压吸引,观察皮瓣存活情况,皮瓣张力以及切口恢复情况。结果术后扩张皮瓣完全无张力覆盖钛网创面,皮瓣无缺血淤血,皮瓣切口无明显张力,皮瓣存活良好。结论自制负压封闭引流装置联合扩张头皮皮瓣修复钛网外露创面效果较好,继续扩展病例数量,观察疗效,如能继续保持较好疗效,临床可以考虑推广使用。

钛网植骨联合上颌窦底提升术改善上颌磨牙区严重骨缺损病例1例

目的面对上颌磨牙区偏离牙弓曲线水平向严重缺损伴骨高度不足,本病例尝试选用钛网作为支架,联合上颌窦底提升术实现局部区域的水平向和垂直向骨增量。方法患者术前CBCT显示,26牙位处剩余骨宽度约3.3 mm,高度约4.9 mm,27牙位处剩余骨宽度约5.2 mm,高度约5.1 mm。病例治疗采用了钛网维持颊侧水平向成骨空间,采集自体骨混合人工骨植骨,并应用富血小板纤维蛋白,同时联合侧壁开窗上颌窦底提升术改善垂直向骨量。结果术后5个月,取出钛网,CBCT显示,26牙位处较术前骨宽度增加了2.0 mm,高度增加了3.2 mm;27牙位处较术前骨宽度增加了1.2 mm,高度增加了4.0 mm,获得了理想的骨增量效果。术后6个月,进行经牙槽嵴顶上颌窦底提升术和种植体植入术,种植体初期稳定性良好。术后1年,种植修复完成,CBCT显示,26牙位处较术前骨宽度增加了2.9 mm,高度增加了4.5 mm;27牙位处较术前骨宽度增加了0.9 mm,高度增加了6.6 mm,结果显示骨增量效果稳定,恢复了正常的咬合功能,并取得一定的美学效果改善。结论该病例结果表明,钛网植骨联合上颌窦底提升术可以获得较为充分稳定的骨增量效果,是一种可靠的用来改善上颌磨牙区骨量不足的方法。

双曲抛物面形态和传统近似牙槽嵴形态3D打印钛网的力学性能研究

目的探究双曲抛物面空间结构对个性化钛网的力学性能影响。方法使用3-Matic 15软件为牙槽嵴吸收患者的下颌骨三维模型进行虚拟骨增量,分别增量为双曲抛物面结构和近似牙槽嵴结构,并制作孔隙为圆形、三角形、四边形和六边形,厚度为0.2 mm、0.3 mm、0.4 mm的个性化钛网,构建有限元分析模型,施加力和约束,分析各组钛网的应力和位移。结果同一厚度下,不同孔隙结构的双曲抛物面钛网应力和位移均明显低于近似牙槽嵴形态的钛网;随厚度减小,各组钛网的应力和位移显著增加。结论双曲抛物面这一空间结构可以均匀的分散应力,减少个性化钛网的应力集中,减少钛网受力后的位移,使钛网兼具了良好的力学性能和较薄的厚度,降低了对软组织的刺激,减少钛网暴露的可能。