ON THE EQUIVALENCE OF STRESS INTENSITY AND ENERGY APPROACHES IN BRIDGING ANALYSIS

Abstract— Through-thickness reinforcement is effective in suppressing delamination in composite laminates. It provides bridging in the crack wake during delamination crack growth. The closure traction behind the crack tip due to this bridging increases the delamination toughness significantly. The effect of bridging may be analysed using the stress intensity approach or the Griffith energetic approach. In this paper, delamination crack growth resistance K _R,(Δa) of a double-cantilever-beam specimen, with through-thickness reinforcement, under Mode I delamination is determined using these two approaches. Additionally, the J-integral analysis is also employed. A comparison between the theoretical results predicted by these three methods is provided using the example of stitched CFRP.     

Fracture toughness and fracture mechanisms of polybutylene-terephthalate/polycarbonate/ impact-modifier blends

A series of polybutylene-terephthalate/polycarbonate (PBT/PC) blends with different compositions were prepared using a twin-screw extruder. The morphologies of the blends were revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that a 50/50 PBT/PC blend possessed a bicontinuous structure and the other blends had a dispersed phase of either PBT or PC depending on which was the minor component. A relatively strong interface was observed in the blends with 20%, 40% and 50% PBT; but poor interfacial adhesion was found in the blends with 60% and 80% PBT. The strength of the interfacial boundary was believed to depend on the composition and blending conditions of the individual blend. Fracture experiments showed that the sharp-notch fracture toughness of PC could be significantly increased by mixing with up to 50% PBT without losing its modulus and yield stress. The toughening mechanisms involved in the fracture processes of the blends were studied using both SEM and TEM together with single-edge-double-notched-bend (SEDNB) specimens. It was found that in the toughened blends the growing crazes initiated by the triaxial stress in front of the crack tip were stabilized by the PC domains. The debonding-cavitation mechanism occurred at the PBT/PC interface, which relieved the plane-strain constraint and promoted shear deformation in both PBT and PC. This plastic deformation absorbed a tremendous amount of energy. Crack-interface bridging by the PC domains was clearly verified by the TEM study. Thus, the PC domains not only stabilized the growing crazes they also bridged crack surfaces after the crack has passed by. This effect definitely caused a large plastic-damage zone and hence a high crack resistance. Poor crack resistances of the blends rich in PBT was caused by the poor interfacial adhesion between PBT and PC. In these polymer blends, the growing crazes easily developed into cracks, which subsequently passed through the weak interface of PBT/PC and finally produced fast unstable fracture.     

Early invasive colorectal carcinomas metastatic to the lymph node with attention to their nonpolypoid development

Clinicopathologic study of six cases of early invasive colorectal carcinoma metastatic to lymph node was performed in order to elucidate possible characteristics relating to the risk of metastasis, with particular attention to the growth pattern of the primary tumor. All of the cases had at least one of the well-known risk factors for lymph node metastasis, including moderately or poorly differentiated histologic characteristics, considerable degree of submucosal invasion, and lymphatic invasion. An interesting finding of the present study was the identification of a nonpolypoid growth pattern with no concomitant adenomatous tissue, which seemed to be different from that of "malignant polyps" of previously reported cases showing adenoma-carcinoma sequence. This unique growth feature was found in all of the cases. Therefore, in addition to the accepted risk factors, nonpolypoid growth pattern and absence of adenomatous component may be risk factors predictive of nodal metastasis in patients with early invasive colorectal carcinoma.     

老年脑卒中恢复期吞咽障碍的康复治疗

目的:观察老年脑卒中恢复期吞咽功能训练对吞咽障碍的疗效.方法:20例老年脑卒中恢复期吞咽障碍患者在接受吞咽功能训练后进行才藤吞咽障碍7级评定.结果:老年脑卒中恢复期吞咽障碍患者在接受吞咽功能训练后功能明显改善,治疗前、后比较有差异(P<0.01).结论:老年吞咽障碍患者经吞咽功能训练能明显提高吞咽功能,恢复了经口摄食,促进自立能力,达到援助患者生活的目的.     

对工伤患者心理干预的探讨

目的:探讨早期心理干预治疗在工伤患者致残后中的作用.方法:将130例由社会保障经办机构确认的工伤患者分为干预组(在康复治疗的同时进行心理干预治疗)和对照组(接受单纯康复治疗).用焦虑自评量表、抑郁自评量表、日常生活能力Barthel指数进行评分,出院后进行随诊半年,用量表评定疗效.结果:与对照组比较,干预组在焦虑自评量表、抑郁自评量表、日常生活能力Barthel指数的评分均有较大改善(P＜0.05).结论:越早进行心理干预,对患者的全面康复效果越好.     

Embracing non-orthogonalmultiple access in future wireless networks

This paper provides a comprehensive survey of the impact of the emerging communication technique, non-orthogonal multiple access (NOMA), on future wireless networks. Particularly, how the NOMA principle affects the design of the generation multiple access techniques is introduced first. Then the applications of NOMA to other advanced communication techniques, such as wireless caching, multiple-input multiple-output techniques, millimeter-wave communications, and cooperative relaying, are discussed. The impact of NOMA on communication systems beyond cellular networks is also illustrated, through the examples of digital TV, satellite communications, vehicular networks, and visible light communications. Finally, the study is concluded with a discussion of important research challenges and promising future directions in NOMA.     

Investigation on diffusion bonding characteristics of SiC particulate reinforced aluminium metal matrix composites (Al/SiCp-MMC)

Joining characteristics of SiC particulate reinforced aluminium metal matrix composites (Al/SiC_p-MMC) were investigated by vacuum diffusion bonding process. The joining performances of the similar and dissimilar composites were studied, and the influences of SiC_p volume percentage and the insert alloy layer on bonding quality and properties of the bonded joints were also estimated. The experimental results indicate that the strength of vacuum diffusion bonded joints decreases with increasing SiC_p volume percentage, and obtaining satisfactory bonding quality in the diffusion bonded joints of the dissimilar Al/SiC_p-MMC is much more difficult than that of the similar Al/SiC_p-MMC. Moreover, the results still manifest that the diffusion bonding either for the similar or for the dissimilar Al/SiC_p-MMC, the suitable insert alloy layer can improve evidently the joining quality of joints, and the strength of diffusion bonded joints corresponding to using the insert alloy layer is apparently higher than that of no insert layer.     

Encapsulation of Huh-7 cells within alginate-poly(ethylene glycol) hybrid microspheres

Novel calcium alginate poly(ethylene glycol) hybrid microspheres (Ca-alg-PEG) were developed and evaluated as potentially suitable materials for cell microencapsulation. Grafting 5–13% of the backbone units of sodium alginate (Na-alg) with α-amine-ω-thiol PEG maintained the gelling capacity in presence of calcium ions, while thiol end groups allowed for preparing chemically crosslinked hydrogel via spontaneous disulfide bond formation. The combination of these two gelling mechanisms yielded Ca-alg-PEG. Human hepatocellular carcinoma cells (Huh-7) were encapsulated in Ca-alg-PEG and calcium alginate beads (Ca-alg), and cultured for 2 weeks under agitation conditions. Immediately after completion of the microencapsulation, the cell viability was 60% and similar in Ca-alg-PEG and Ca-alg. The proliferation of Huh-7 encapsulated in Ca-alg-PEG was slightly higher than in Ca-alg. Accelerated proliferation after 2 weeks was observed for the encapsulation in Ca-alg-PEG. The production of albumin confirmed the functionality of the encapsulated Huh-7 cells. The study confirms the suitability of Ca-alg-PEG and the one-step technology for cell microencapsulation.     

Facile synthesis,characterization and low-temperature catalytic performance of Au/CeO2 nanorods

Au/CeO₂ nanorods of ~ 15 nm in diameter and 100–400 nm in length have been synthesized through an efficient and simple method, and subsequently the novel low-temperature catalytic performance of Au/CeO₂ nanorods for CO oxidation is found. The composites are characterized by transmission electron microscopy, X-ray diffraction as well as X-ray photoelectron spectroscopy. It is found that the Au nanoparticles with an average diameter of 8 nm are distributed uniformly on the surface of CeO₂ nanorods. The possible formation mechanism of Au/CeO₂ nanorods has been discussed. The T₅₀ depicting the catalytic activity for CO oxidation can reach 62.1 °C, which is much lower than that of CeO₂ nanorods or Au/CeO₂ powders. In addition, Au/CeO₂ nanorods exhibit excellent stability as catalysts for CO oxidation.