以钾长石为原料制备的白榴石对牙科玻璃陶瓷性能的影响

实验采用了化工原料来合成SiO2-Al2O3-K2O系统玻璃陶瓷,结果发现合成的玻璃陶瓷主要为玻璃相,只有很少量的白榴石晶体;在玻璃相陶瓷中添加白榴石后,其显微结构表明白榴石晶体呈柱状或颗粒状与玻璃相基质紧密结合,并均匀地分布于玻璃相基质中;添加白榴石可明显提高玻璃陶瓷的强度。     

胸部创伤致大量血胸的急救及护理体会

胸部创伤致大量血胸在胸外科较为常见,而胸膜腔内积血是胸外伤后常见的并发症,易造成有效循环血量骤减甚至休克,病情危急凶猛,常导致死亡。我们认为,在胸部创伤致大量血胸患者的急救过程中,护理人员要做到早期准确评估伤情和出血量,及时纠正休克,能为手术抢救和后继治疗争取时间并创造有利条件。而规范化、程序化的护理措施,能够使急救工作急而有序,行之有效;快速、敏捷的应急能力与急救技术是提高急救效果的根本保证,护士应根据病情制订规范化的预检抢救程序,保证护理工作准确无误,确保抢救成功。     

Analysis of The Working Performance of Large Curvature Prestressed Concrete Box Girder Bridges

Based on numerical shape functions and the structural stressing state theory, the mechanical properties of the curved prestressed concrete box girder (CPCBG) bridge model under different loading cases are presented. First, the generalized strain energy density (GSED) obtained from the measured strain data is used to represent the stressing state pattern of the structure; then, the stressing state of the concrete section is analyzed by plotting the strain and stress fields of the bridge model. The stressing state pattern and strain fields of the CPCBG are shown to reveal its mechanical properties. In addition, the measured concrete strain data are interpolated by the non-sample point interpolation (NPI) method. The strain and stress fields of the bridge model have been plotted to analyze the stressing state of the concrete cross-section. The internal forces in the concrete sections are calculated by using interpolated strains. Finally, the torsional effects are simulated by measuring the displacements to show the torsional behavior of the cross-section. The analysis and comparison of the internal force and strain fields reveal the common and different mechanical properties of the bridge model. The results of the analysis of the curved bridge model provide a reference for the future rational design of bridge projects.     

Predicting Compressive and Splitting Tensile Strengths of Silica Fume Concrete Using M5P Model Tree Algorithm

Compressive strength (CS) and splitting tensile strength (STS) are paramount parameters in the design of reinforced concrete structures and are required by pertinent standard provisions. Robust prediction models for these properties can save time and cost by reducing the number of laboratory trial batches and experiments needed to generate suitable design data. Silica fume (SF) is often used in concrete owing to its substantial enhancements of the engineering properties of concrete and its environmental benefits. In the present study, the M5P model tree algorithm was used to develop models for the prediction of the CS and STS of concrete incorporating SF. Accordingly, large databases comprising 796 data points for CS and 156 data records for STS were compiled from peer-reviewed published literature. The predictions of the M5P models were compared with linear regression analysis and gene expression programming. Different statistical metrics, including the coefficient of determination, correlation coefficient, root mean squared error, mean absolute error, relative squared error, and discrepancy ratio, were deployed to appraise the performance of the developed models. Moreover, parametric analysis was carried out to investigate the influence of different input parameters, such as the SF content, water-to-binder ratio, and age of the specimen, on the CS and STS. The trained models offer a rapid and accurate tool that can assist the designer in the effective proportioning of silica fume concrete.     

Microstructure and Mechanical Properties of Metal Foams Fabricated via Melt Foaming and Powder Metallurgy Technique: A Review

Metal foams possess remarkable properties, such as lightweight, high compressive strength, lower specific weight, high stiffness, and high energy absorption. These properties make them highly desirable for many engineering applications, including lightweight materials, energy-absorption devices for aerospace and automotive industries, etc. For such potential applications, it is essential to understand the mechanical behaviour of these foams. Producing metal foams is a highly challenging task due to the coexistence of solid, liquid, and gaseous phases at different temperatures. Although numerous techniques are available for producing metal foams, fabricating foamed metal still suffers from imperfections and inconsistencies. Thus, a good understanding of various processing techniques and properties of the resulting foams is essential to improve the foam quality. This review discussed the types of metal foams available in the market and their properties, providing an overview of the production techniques involved and the contribution of metal foams to various applications. This review also discussed the challenges in foam fabrications and proposed several solutions to address these problems.     

Correlation of Bone Material Model Using Voxel Mesh and Parametric Optimization

The authors present an algorithm for determining the stiffness of the bone tissue for individual ranges of bone density. The paper begins with the preparation and appropriate mechanical processing of samples from the bovine femur and their imaging using computed tomography and then processing DICOM files in the MIMICS system. During the processing of DICOM files, particular emphasis was placed on defining basic planes along the sides of the samples, which improved the representation of sample geometry in the models. The MIMICS system transformed DICOM images into voxel models from which the whole bone FE model was built in the next step. A single voxel represents the averaged density of the real sample in a very small finite volume. In the numerical model, it is represented by the HEX8 element, which is a cube. All voxels were divided into groups that were assigned average equivalent densities. Then, the previously prepared samples were loaded to failure in a three-point bending test. The force waveforms as a function of the deflection of samples were obtained, based on which the global stiffness of the entire sample was determined. To determine the stiffness of each averaged voxel density value, the authors used advanced optimization analyses, during which numerical analyses were carried out simultaneously, independently mapping six experimental tests. Ultimately, the use of genetic algorithms made it possible to select a set of stiffness parameters for which the error of mapping the global stiffness for all samples was the smallest. The discrepancies obtained were less than 5%, which the authors considered satisfactory by the authors for such a heterogeneous medium and for samples collected from different parts of the bone. Finally, the determined data were validated for the sample that was not involved in the correlation of material parameters. The stiffness was 7% lower than in the experimental test.     

Ternary Blends for Self-Compacting Mortars Production Composed by Electric Arc Furnace Dust and Other Industrial by-Products

This study is framed within the circular economy model through the valorisation of industrial by-products. This research shows the results of producing self-compacting mortars (SCMs) with electric arc furnace dust (EAFD) and other industrial by-products such as fly ash, conforming (FA) or not conforming (NcFA), from coal-fired power plants, or recovery filler (RF) from hot-mix asphalt plants. Three batches of SCMs, each with one industrial-by product (FA, NcFA, or RF), and three levels of EAFD ratio incorporation (0%, 10%, 20%), were tested. An extra batch with a greater amount of FA was manufactured. When the incorporation ratio of EAFD rose, the mechanical strength decreased, due to the presence of a calcium zinc hydroxide dihydrate phase; nevertheless, this decrease diminished over time. All SCM mixes, except the 40C 40FA 20 EAFD mix, were above 20 MPa at 28 days. All mixes named 70C and 40C reached 40 and 30 MPa, respectively, at 90 days. Mixes with EAFD showed less capillarity and no difference in water absorption by immersion with respect to mixes without EAFD after 91 days. The SCMs designed proved to be stable in terms of leaching of the heavy metals contained in EAFD, where all the hardened SCMs were classified as inert.     

Omega-9 Modifies Viscoelasticity and Augments Bone Strength and Architecture in a High-Fat Diet-Fed Murine Model

The influence of diet on the development of osteoporosis is significant and not fully understood. This study investigated the effect of diets of varying lipid profiles and ω-3, ω-6 and ω-9 composition on the structural and mechanical properties of bone. The hypothesis studied was that a diet high in saturated fat would induce osteoporosis and produce an overall increased detrimental bony response when compared with a diet high in unsaturated ω-6, or ω-9. Male C57BL/6J mice were fed either a control diet, 50:50 mix (saturated:unsaturated) high in ω-9 (HFD^50:50), a diet high in saturated fat (HSF) or a polyunsaturated fat diet high in ω-6 (PUFA) over an 8-week duration. Tibiae were retrieved and evaluated using DMA, 3-point-bending, histomorphometry, and microCT. Mice fed a HSF diet displayed key features characteristic of osteoporosis. The loss tangent was significantly increased in the HFD^50:50 diet group compared with control (p = 0.016) and PUFA-fed animals (p = 0.049). HFD^50:50-fed mice presented with an increased viscous component, longer tibiae, increased loss modulus (p = 0.009), and ultimate stress, smaller microcracks (p < 0.001), and increased trabecular width (p = 0.002) compared with control animals. A diet high in ω-9 resulted in an overall superior bone response and further analysis of its role in bone health is warranted.     

特发性黄斑裂孔患者术后裂孔愈合形态与视功能恢复的研究

目的探讨特发性黄斑裂孔患者术后裂孔愈合形态与视功能恢复的关系。方法选择特发性黄斑裂孔1次性术后裂孔愈合患者36例(38只眼)的连续临床资料,进行回顾性分析。应用相干光断层扫描(OCT)观察裂孔愈合形态,采用激光扫描检眼镜(SLO)测定患者术前,术后1、3、6个月黄斑区光敏度、绝对暗点、相对暗点平均面积及中心视力,并对检测结果进行分析。结果根据OCT图像,裂孔形态分为完全愈合型(22只眼)、部分愈合型(10只眼)及未愈合型(6只眼)。术后6个月,完全愈合型和部分愈合型眼的中心视力、光敏度、绝对暗点和相对暗点的平均面积均较术前有明显改善(均P<0.05);未愈合型眼的中心视力、光敏度虽较术前改善,但绝对暗点、相对暗点差异则无显著意义(P>0.05);完全愈合型眼的视力、光敏度、绝对暗点改善程度与部分愈合型和未愈合型眼比较,差异有显著意义(P<0.05)。Ⅱ期裂孔眼术后黄斑中心凹形态可完全恢复。结论术后黄斑区中心凹部视网膜正常形态的恢复与视功能改善程度呈正相关(P<0.05)。术后中心凹的形态恢复越好,视功能改善程度越高。裂孔早期阶段(Ⅱ期裂孔)行手术,更有机会获取良好的视功能。(中华眼科杂志,2004,40:443-447)     

儿童无创通气的局限性及气管插管介入时机选择

近年来,无创通气在儿童呼吸支持领域有了较快发展。无创通气无需气管插管,操作简便,对部分呼吸道疾病有较为满意的疗效。但是,无创通气不能完全替代有创机械通气。在有些疾病无创通气不仅有着较高的失败率,而且会因气管插管的延误导致病情恶化,增加患儿的病死率。在行无创通气之前需评估患儿是否适宜进行无创通气治疗。对于进行无创通气治疗的患儿需严密监护,动态观察生理指标和监测数据的变化,掌握好气管插管的时机,以免造成有创机械通气治疗的延误。