3D建模与快速成型技术在个体化膝关节假体术中的应用

目的探讨3D建模与快速成型技术在个体化膝关节肿瘤假体手术治疗中的新方法,评价3D建模与快速成型技术的应用价值.方法选取3例膝关节骨肿瘤患者,术前均对膝关节周围病损区行CT扫描,获得原始数据后,导入Mimics19.0软件,在软件中模拟手术规划,并且设计与切除后剩余的骨组织相契合的钛合金"植物.随访期间应用国际骨与软组织肿瘤保肢(Musculoskeletal Tumor Society,MSTS)功能评分系统对患者的术后功能情况进行评价.结果 3例患者均获随访,随访时间5~26个月,平均16个月.末次随访MSTS得分为18~29分,平均24.3分,其中优2例,良1例,优良率达100%.结论通过3D建模与快速成型技术在膝关节肿瘤手术中的应用,可精确指导截骨界限,设计个体化膝关节假体,韧带附丽点接近生理结构,为膝关节骨肿瘤治疗提供新方法.     

自体腓骨长肌腱和腘绳肌腱在关节镜下重建膝关节前交叉韧带临床研究

目的探讨关节镜下自体腓骨长肌腱和腘绳肌腱重建膝关节前交叉韧带的临床疗效.方法选取47例前交叉韧带损伤患者,应用随机数字表法将患者分为两组,分别行关节镜下腓骨长肌腱(A组)与腘绳肌腱(B组)重建膝关节交叉韧带,比较两组患者术后一般情况;分析两组患者术前、术后3个月、术后6个月的膝关节功能、稳定性,分析腓骨长肌腱组足弓的静力学变化.结果术后随访时,A组大腿周长减小与B组比较差异无统计学意义(P0.05);两组患者术后Tegner评分、Lysholm评分、IKDC评分结果差异无统计学意义(P0.05);A,B两组患者术后胫骨前移比较差异无统计学意义(P0.05);A组患者足弓情况与术前比较,术后6个月、术后1 a足弓的静力学指标无明显变化(P0.05).结论自体腓骨长肌腱重建膝关节前交叉韧带断裂与自体腘绳肌腱取得的临床效果相当.     

京津冀协同视角下区域大气污染现状及综合防治研究

京津冀区域大气污染已成为全国空气污染的重灾区,目前京津冀区域大气污染合作治理共识已基本形成。本文在对京津冀大气污染区域合作治理现状进行系统研究的基础上,以SO2、NO2、PM10、PM2.5四种污染物为指标,对京津冀目前大气质量状况以及15年来的大气质量变化趋势做了全面梳理分析。对存在的问题进行了探讨,并针对当前京津冀区域大气污染防治措施提出了建议,以期为破解区域大气污染治理困境提供借鉴参考。     

Shear-thickening behavior of Fe-ZSM5 zeolite slurry and its removal with alumina/boehmites

A cryogenic scanning electron microscopy (cryo-SEM) technique was used to explore the shear-thickening behavior of Fe-ZSM5 zeolite pastes and to discover its underlying mechanism. Bare Fe-ZSM5 zeolite samples were found to contain agglomerations, which may break the flow of the pastes and cause shear-thickening behaviors. However, the shear-thickening behaviors can be eliminated by the addition of halloysite and various boehmites because of improved particle packing. Furthermore, compared with pure Fe-ZSM5 zeolite samples and its composite samples with halloysite, the samples with boehmite (Pural SB or Disperal) additions exhibited network structures in their cryo-SEM images; these structures could facilitate the storage and release of flow water, smooth paste flow, and avoid shear-thickening. By contrast, another boehmite (Versal 250) formed agglomerations rather than network structures after being added to the Fe-ZSM5 zeolite paste and resulted in shear-thickening behavior. Consequently, the results suggest that these network structures play key roles in eliminating the shear-thickening behavior.     

Solid-phase synthesis of Cu<Subscript>2</Subscript>MoS<Subscript>4</Subscript> nanoparticles for degradation of methyl blue under a halogen-tungsten lamp

The Cu₂MoS₄ nanoparticles were prepared using a relatively simple and convenient solid-phase process, which was applied for the first time. The crystalline structure, morphology, and optical properties of Cu₂MoS₄ nanoparticles were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and UV-vis spectrophotometry. Cu₂MoS₄ nanoparticles having a band gap of 1.66 eV exhibits good photocatalytic activity in the degradation of methylene blue, which indicates that this simple process may be critical to facilitate the cheap production of photocatalysts.     

Preparation and performance of a cold gas dynamic sprayed high-aluminum bronze coating

By mixing preheated high-aluminum bronze powders with different amounts of Al₂O₃ powder, a low-pressure cold-sprayed coating was prepared and sprayed onto a Cr12MoV steel substrate. The hardness of the coating and the bonding strength between the coating and the substrate were tested with a HV-1000 microhardness tester and a mechanical universal testing machine. The surface microstructure, cross-section and tensile fracture surface of the coating were observed with a scanning electron microscope (SEM). Correspondingly, the influences of the preheat treatment temperature of the bronze powder and the Al₂O₃ content on the coating performance were investigated. The results indicate that the hardness of bronze powders decreased and the coating deposition rate increased after the preheating treatment of the bronze powder. The Al₂O₃ content in the mixed powders contributed to the deformation of bronze powders during the spraying process. This trend resulted in varied performance of the coating.     

Process mineralogy characteristics of acid leaching residue produced in low-temperature roasting-acid leaching pretreatment process of refractory gold concentrates

To provide a theoretical basis for a suitable process to extract gold from refractory gold concentrates, process mineralogy on the acid leaching residue of gold calcine was studied by chemical composition, X-ray diffraction, scanning electron microscopy-energy spectrum, and mineral dissociation analysis. The results showed that the acid leaching residue contained Au 68.22 g/t, Ag 92.71 g/t, Fe 0.44%, As 0.10%, and S 0.55%. Gold and silver minerals existed as native gold, argentite, and proustite. Quartz, the main gangue mineral, accounted for 78.33wt/%. The dissociation degree analysis showed that the proportions of monomer and exposed gold in acid leaching residue were 96.66wt%. The cyanidation results showed that the cyanide gold leaching rate of acid leaching residues was close to 100wt%. However, the maximum cyanide gold leaching rate of gold calcine was only 85.31wt%. This suggests that acid leaching can increase the gold dissolution rate in the cyanide process.     

Thermal performance and reduction kinetic analysis of cold-bonded pellets with CO and H_2 mixtures

Cold-bonded pellets, to which a new type of inorganic binder was applied, were reduced by H2–CO mixtures with different H2/CO molar ratios(1:0, 5:2, 1:1, 2:5, and 0:1) under various temperatures(1023, 1123, 1223, 1323, and 1423 K) in a thermogravimetric analysis apparatus. The effects of gas composition, temperature, and binder ratio on the reduction process were studied, and the microstructure of reduced pellets was observed by scanning electron microscopy–energy-dispersive spectrometry(SEM-EDS). The SEM-EDS images show that binder particles exist in pellets in two forms, and the form that binder particles completely surround ore particles has a more significant hinder effect on the reduction. The reduction equilibrium constant, effective diffusion coefficient, and the reaction rate constant were calculated on the basis of the unreacted core model, and the promotion effect of temperature on reduction was further analyzed. The results show that no sintering phenomenon occurred at low temperatures and that the increasing reaction rate constant and high gas diffusion coefficient could maintain the promotion effect of temperature; however, when the sintering phenomenon occurs at high temperatures, gas diffusion is hindered and the promotion effect is diminished. The contribution of the overall equilibrium constant to the promotion effect depends on the gas composition.     

Experimental investigation and thermodynamic assessment of the yttriumhydrogen binary system

A coupled experimental investigation and thermodynamic study of the yttrium-hydrogen(Y-H) binary system were carried out to provide more comprehensive and quantitative insights into the key thermodynamic properties of this system. Y-H system in the full range of H/Y = 0–3.0 was investigated by accurate pressure composition isotherm(PCI) measurement to provide credible phase equilibria information and thermodynamic data.The phase boundaries obtained were in agreement with previous experimental data but with improved accuracy.With the guide of the crystal structures, all the solid phases were modelled using the three sublattice model. The Y-H phase diagram and thermodynamic parameters were calculated and assessed with the CALPHAD technique.The obtained results are in very good agreement with our experimental data and the published data reported in literature. The obtained thermodynamic database of Y-H system can be used to predict the hydrogenation behavior and decomposition temperatures of hydrides.     

Damage evolution and failure mechanism of thermal barrier coatings under Vickers indentation by using acoustic emission technique

Acoustic emission(AE) technique was adopted to monitor the damage evolution of air plasma-sprayed(APS) yttria-partially-stabilized zirconia(YSZ) thermal barrier coatings(TBCs) during instrumented indentation testing, and then the failure mechanisms were investigated by cluster analysis and wavelet transform methods.The results of cluster analysis showed that there were three classes associated with distinct failure types for the 8YSZ coatings under Vickers indentation. Based on wavelet transform, these three clusters could be clearly distinguished from their dominant frequency bands, which were concentrated on levels A5(0–156.25 kHz), D5(156.25–312.5 kHz) and D4(312.5–625 kHz), respectively. Thus, the failure mechanism of 8YSZ coatings under Vickers indentation could be clarified by the distribution of different failure types in indentation depth. To sum up, as indentation load increases, the 8YSZ coatings can accommodate the indenter by elastic or little plastic deformation, microcracks propagation and then debonding at the splat boundaries. By comparing the distribution of AE signals induced by different failure types in indentation depth for samples with different thermal exposure time, it can be inferred that thermal exposure treatment can accelerate the degradation of APS 8YSZ TBCs.