Influence of fibre steering on the bearing performance of bolted joints in 3D printed pseudo-woven CFRP composites

Aiming to improve the bearing performance of bolted joints in carbon fibre reinforced polymer (CFRP) composites, this study investigates the impact of steered fibre paths around the hole edge within pseudo-woven (interlaced) composites that are manufactured by 3D printing. The influence of fibre steering on the crack initiation and propagation was examined through double-lap bearing tests performed on four distinct cases. Parallel to the comprehensive experimental study, digital image correlation (DIC) and X-ray computed microtomography (micro-CT) scans were performed to aid in understanding and identifying the various damage mechanisms in each specimen type. Results revealed that different patterns provided varying bearing abilities, with an employed pattern improving the initial bearing strength, initial fracture energy and ultimate fracture energy of the 3D printed pseudo-woven composite by 23.5%, 363.7% and 29.6%, respectively. Consequently, fibre steering in composites is found to be a promising method to tailor the bearing behaviour of bolted joints as required

Secondary structure investigation of bovine serum albumin (BSA) by Fourier transform infrared (FTIR) spectroscopy in the amide III region

Fourier transform infrared spectroscopy is widely used to analyze protein secondary structures. The common strategy in this field is to analyze the conformation sensitive 1700-1600 cm-1 amide I region of protein FTIR spectrum. Though the amide III region of protein is also sensitive to secondary structural changes, its potential for protein secondary structural analysis is largely unexplored. In this paper, we performed a detailed investigation on the second structural analysis of bovine serum albumin by monitoring the spectral variation of the amide III band under a variety of pH conditions by FTIR spectroscopy and FTIR second derivative spectroscopy. Our results show that both acidic and basic conditions have pronounced effects on the overall secondary structures of BSA, suggesting denaturation effects. Furthermore, we observe that the amide III band profiles under acidic and basic conditions appear to be quite different. Our results clearly demonstrate that the amide III region is a promising probing region for protein secondary structural analysis

Improved interlayer performance of short carbon fiber reinforced composites with bio-inspired structured interfaces

The weak layer interfaces of 3D-printed short carbon fiber (SCF) reinforced polymer composites have remained an issue due to planar layer printing by traditional 3D printers. Recently, multi-axis 3D printing technology which can realize non-planar layer printing has been developed. This study’s aim was to evaluate and compare the bonding performance of non-planar interfaces produced by multi-axis 3D printing with that of planar interfaces. The tested non-planar interfaces were designed as bio-inspired structured interfaces (BISIs) based on microstructural interfacial elements in biological materials. The standard specimens with the 0°/90° and 0° infill line directions were printed by a robotic arm multi-axis 3D printer. Double cantilever beam (DCB) and end-notched flexure (ENF) tests were conducted to obtain Mode Ⅰ and Mode Ⅱ interlaminar toughness of SCF-reinforced composites. Test results showed that the critical energy release rates of the integrally formed BISI were significantly improved compared with the planar interface (PLAI) for both Mode I and Mode II delamination. In particular, the BISI with 0° infill line direction exhibited the greatest increase in critical energy release rate, and the damaged areas were spatially swept through the curved interfaces of the BISI with different infill line directions by scanning electron microscopy (SEM) and computed tomography (CT), which showed that the higher critical energy release rate was always accompanied with a larger damaged area. In addition, the tensile and flexural properties of 0°-infilled PLAI and BISI specimens were also measured. This work provides an in-depth investigation of the PLAI and BISI properties of SCF-reinforced composites, demonstrating the potential benefits of integrally formed BISI by multi-axis 3D printing and fostering new perspectives to enhance layer interfaces of 3D printed composites

On Optimal Neighbor Discovery

Mobile devices apply neighbor discovery (ND) protocols to wirelessly initiate a first contact within the shortest possible amount of time and with minimal energy consumption. For this purpose, over the last decade, a vast number of ND protocols have been proposed, which have progressively reduced the relation between the time within which discovery is guaranteed and the energy consumption. In spite of the simplicity of the problem statement, even after more than 10 years of research on this specific topic, new solutions are still proposed even today. Despite the large number of known ND protocols, given an energy budget, what is the best achievable latency still remains unclear. This paper addresses this question and for the first time presents safe and tight, duty-cycle-dependent bounds on the worst-case discovery latency that no ND protocol can beat. Surprisingly, several existing protocols are indeed optimal, which has not been known until now. We conclude that there is no further potential to improve the relation between latency and duty-cycle, but future ND protocols can improve their robustness against beacon collisions.Comment: Conference of the ACM Special Interest Group on Data Communication (ACM SIGCOMM), 201

Experimental and Numerical Study of Low-Velocity Impact Damage in Sandwich Panel with UHMWPE Composite Facings

This paper is concerned with the low-velocity impact (LVI) response behaviour of sandwich composite panels (SCPs) with ultra-high molecular weight polyethylene (UHMWPE) composite facings and Polyvinyl Chloride (PVC)/Polyethylene Terephthalate (PET) foam cores. A series of LVI tests with SCPs subjected to 50 J, 80 J and 110 J were conducted to examine their impact characteristics and damage mechanisms. LVI-induced internal damage in the SCPs were characterised by compute micro-tomography (μCT) analysis. The effects of UHMWPE areal density and foam type on the LVI responses and associated failure modes of the panels were also examined. The experimental results showed that the SCP with a PET foam core exhibited higher impact strength and energy absorption performance than those of the panel with a PVC foam core. In addition, a finite element (FE) model incorporating the Puck’s failure criteria, cohesive law and crushable foam plasticity model was developed and validated to predict the intra- and inter-laminar damages of SCPs. Finally, several failure mechanisms (fibre failure, matrix cracking and local delamination) of SCPs during LVI was thoroughly discussed. The results show the UH170-PET specimen has the best impact resistance and energy absorption performance. The parametric analysis of the areal density and foam type has revealed that these parameters can be optimised for the best LVI resistance of SCPs. These findings are helpful for designing lightweight foam-based sandwich composite structures with superior impact resistance

Information asymmetry, mutual funds and earnings management: Evidence from China

This paper investigates how information asymmetry and mutual fund ownership affect listed companies' earnings management. We show that (1) reducing information asymmetry improves firms' earnings management behavior; (2) relative to short-term mutual funds, long-term mutual funds promote earnings quality by adopting a monitoring role; and (3) by dividing firms into high/low information asymmetry groups, we find that the information environment significantly increases the effect of long-term mutual funds on firms' earnings management. In this paper, we provide new evidence for the role that institutional investors play in a typical emerging capital market. Our results have clear policy implications: to increase earnings quality, it is essential to improve information transparency and develop long-term institutional investors. Ó 2013 Production and hosting by Elsevier B.V. on behalf of China Journal of Accounting Research. Founded by Sun Yat-sen University and City University of Hong Kong

Spatiotemporal Scan and Age-Period-Cohort Analysis of Hepatitis C Virus in Henan, China: 2005–2012

Background: Studies have shown that hepatitis C virus (HCV) infection increased during the past decades in China. However, little evidence is available on when, where, and who were infected with HCV. There are gaps in knowledge on the epidemiological burden and evolution of the HCV epidemic in China. Methods: Data on HCV cases were collected by the disease surveillance system from 2005 to 2012 to explore the epidemic in Henan province. Spatiotemporal scan statistics and age-period-cohort (APC) model were used to examine the effects of age, period, birth cohort, and spatiotemporal clustering. Results: 177,171 HCV cases were reported in Henan province between 2005 and 2012. APC modelling showed that the HCV reported rates significantly increased in people aged > 50 years. A moderate increase in HCV reported rates was observed for females aged about 25 years. HCV reported rates increased over the study period. Infection rates were greatest among people born between 1960 and 1980. People born around 1970 had the highest relative risk of HCV infection. Women born between 1960 and 1980 had a five-fold increase in HCV infection rates compared to men, for the same birth cohort. Spatiotemporal mapping showed major clustering of cases in northern Henan, which probably evolved much earlier than other areas in the province. Conclusions: Spatiotemporal mapping and APC methods are useful to help delineate the evolution of the HCV epidemic. Birth cohort should be part of the criteria screening programmes for HCV in order to identify those at highest risk of infection and unaware of their status. As Henan is unique in the transmission route for HCV, these methods should be used in other high burden provinces to help identify subpopulations at risk