Rapid Design and Manufacture of Ultralight Cellular Materials

This paper details the design, manufacture and testing of regular metallic lattice structures with unit cell sizes in the range 0.8mm to 5mm and truss elements of 100-500 µm in diameter [1]. The structures were manufactured using Selective Laser Melting (SLM) technology from 316L stainless steel. Compression tests have shown yield loadings of over 3.5kN despite being only 18mm by 18mm by 10mm in height, the results are favourably comparable to current commercially available metallic foams. Software has been developed that creates slice files without the use of CAD software or STL files and is capable of producing lattices within a volume defined by a STL file.Mechanical Engineerin

High velocity impact resistance of fibre metal laminates

The high velocity impact resistance of fibre metal laminates (FMLs) based on combinations of three different aluminium alloys (6161-O, 6061-T6, 7075-T6) and a glass fibre reinforced epoxy resin have been investigated both experimentally and numerically. A series of perforation tests on multilayer configurations, ranging from a simple 2/1 lay-up to a seven ply 4/3 laminate. High velocity impact was conducted using a projectile gas-gun launcher, operating in the velocity range between 119 m/s and 252 m/s.[1] The impact response of fibre metal laminates samples was characterised by determining the energy required to perforate the panels. A stereoscopic Digital Image Correlation (DIC) method was adopted to measure full-field deformations and strain for FMLs which providing the full field strain history and 3D measurements up to sample perforation. The perforation resistance of the panels was predicted using the finite element analysis package Abaqus/Explicit. A vectorized user-defined material subroutine (VUMAT) was employed to define Hashin’s 3D rate-dependant damage criteria for the composite layers. The subroutine was implemented into the commercial finite element software ABAQUS/Explicit to simulate the deformation and failure of FMLs. Agreement between the predictions of the finite element models and the experimental data was good across the range of configurations. Ballistic limit of those FMLs was obtained from both the experimental tests and numerical approaches

Use of conventional optical fibers and fiber Bragg gratings for damage detection in advanced composite structures: A review

Structurally integrated sensors which are capable of continuous structural health monitoring represent an attractive option in view of their potential for providing real-time assessment/ warning of structural damage. In recent years, optical fiber systems have attracted a considerable amount of attention and have been shown to be a very attractive option for health monitoring in advanced composite materials. These sensors have either been embedded or surfacebonded to the host material thereby allowing continuous assessment of the health of the structure. Structural health assessment takes the form of damage detection and/or monitoring of specific health indicators. In the former approach, the optical fiber systems are generally optimized to increase their sensitivity to the presence of damage in the composite structure, while the latter approach relies on the examination of characteristic changes in the monitored parameter to infer a loss in structural integrity. To this end, many investigators have demonstrated the potential of optical fiber sensors, most particularly intensity-based optical fiber systems and fiber Bragg grating sensors for structural health monitoring of advanced composite materials. The initial part of this paper provides an up-to-date review of the applications of optical fiber sensors in composite materials, focussing particularly on the use of intensitybased optical fiber systems and fiber Bragg grating sensors for damage detection. These optical fiber systems have been shown to be capable of detecting impact damage, transverse cracking, and delamination, and have the ability to monitor strain in structures. The introduction of optical fiber sensors into a composite material can inadvertently produce a geometrical discontinuity in the vicinity of the sensor. Numerous experimental investigations have also been performed to assess the possible reduction in the properties of the host structure. A review of the findings of these investigations reported in the literature is also given. This review article cites 161 references

LR characterization of chirotopes of finite planar families of pairwise disjoint convex bodies

We extend the classical LR characterization of chirotopes of finite planar families of points to chirotopes of finite planar families of pairwise disjoint convex bodies: a map \c{hi} on the set of 3-subsets of a finite set I is a chirotope of finite planar families of pairwise disjoint convex bodies if and only if for every 3-, 4-, and 5-subset J of I the restriction of \c{hi} to the set of 3-subsets of J is a chirotope of finite planar families of pairwise disjoint convex bodies. Our main tool is the polarity map, i.e., the map that assigns to a convex body the set of lines missing its interior, from which we derive the key notion of arrangements of double pseudolines, introduced for the first time in this paper.Comment: 100 pages, 73 figures; accepted manuscript versio

Scaling the Non-linear Impact Response of Flat and Curved Composite Panels

The application of scaling laws to thin flat and curved composite panels exhibiting nonlinear response when subjected to low-velocity transverse impact is investigated. Previous research has shown that the elastic impact response of structural configurations exhibiting geometrically linear response can be effectively scaled. In the present paper, a preliminary experimental study is presented to assess the applicability of the scaling laws to structural configurations exhibiting geometrically nonlinear deformations. The effect of damage on the scalability of the structural response characteristics, and the effect of scale on damage development are also investigated. Damage is evaluated using conventional methods including C-scan, specimen de-plying and visual inspection of the impacted panels. Coefficient of restitution and normalized contact duration are also used to assess the extent of damage. The results confirm the validity of the scaling parameters for elastic impacts. However, for the panels considered in the study, the extent and manifestation of damage do not scale according to the scaling laws. Furthermore, the results indicate that even though the damage does not scale, the overall panel response characteristics, as indicated by contact force profiles, do scale for some levels of damage

From Acting What’s next to Speeding Trap: Co-Evolutionary Dynamics of an Emerging Technology-Leader

JEL Classifications: O33, O53, L63[[abstract]]How does technological innovation emerge and evolve? We approach such an inquiry by synthesizing the perspectives of dynamic capabilities and co-evolutionary dynamics to portray organizational routines and multi-phase strategic renewals of an emerging technology-leader. To untangle the emergence of technological innovation, we conducted a longitudinal case study on the first and the largest dedicated semiconductor foundry, TSMC, located in the emerging economy of Taiwan. The firm-case of TSMC illustrates two unique co-evolutionary paths, that is, transforming from industry-latecomer to technology-leader and from process innovation to product innovation. We found multi-motor co-evolutionary dynamics between TSMC and the semiconductor industry, where its co-evolutionary mechanism of managed selection in its creating phase of mature process-innovation (1987-1998) has migrated to hierarchical renewal in its extending phase of advanced process-innovation (1999-2001), and then to holistic renewal in its modifying phase of product-innovation (2002-2007). During such paths, our research discovered a unique type of organizational routines, acting what’s next because TSMC has proactively searched for potential problems sooner than its competitors. However, such routines, although driving technological innovation, also lead to a unique type of success-trap, that is, speeding trap. When an emerging technology-leader fundamentally changes the industrial structures to over-specs, the growth driven by technology speeding may trap such a leader in a loop of over-exploration.[[sponsorship]]The authors are grateful to the research grant from the National Science Council (NSC) in Taiwan. The earlier manuscript of this paper was presented at the 2009 Annual Meeting of Academy of International Business (AIB) in San Diego, USA.[[notice]]補正完畢[[journaltype]]國外[[ispeerreviewed]]Y[[booktype]]紙本[[booktype]]電子版[[countrycodes]]CA

Measuring attitude towards Buddhism and Sikhism : internal consistency reliability for two new instruments

This paper describes and discusses the development and empirical properties of two new 24-item scales – one measuring attitude toward Buddhism and the other measuring attitude toward Sikhism. The scale is designed to facilitate inter-faith comparisons within the psychology of religion alongside the well-established Francis Scale of Attitude toward Christianity. Data were obtained from a multi-religious sample of 369 school pupils aged between 13 and 15 in London. Application of the two scales demonstrated that adolescents had a more positive attitude to Buddhism than Sikhism. The findings confirm the reliability of the scales and commend them for further use

A Multi-telescope Campaign on FRB 121102: Implications for the FRB Population

We present results of the coordinated observing campaign that made the first subarcsecond localization of a Fast Radio Burst, FRB 121102. During this campaign, we made the first simultaneous detection of an FRB burst by multiple telescopes: the VLA at 3 GHz and the Arecibo Observatory at 1.4 GHz. Of the nine bursts detected by the Very Large Array at 3 GHz, four had simultaneous observing coverage at other observatories. We use multi-observatory constraints and modeling of bursts seen only at 3 GHz to confirm earlier results showing that burst spectra are not well modeled by a power law. We find that burst spectra are characterized by a ~500 MHz envelope and apparent radio energy as high as $10^{40}$ erg. We measure significant changes in the apparent dispersion between bursts that can be attributed to frequency-dependent profiles or some other intrinsic burst structure that adds a systematic error to the estimate of DM by up to 1%. We use FRB 121102 as a prototype of the FRB class to estimate a volumetric birth rate of FRB sources $R_{FRB} \approx 5x10^{-5}/N_r$ Mpc$^{-3}$ yr$^{-1}$, where $N_r$ is the number of bursts per source over its lifetime. This rate is broadly consistent with models of FRBs from young pulsars or magnetars born in superluminous supernovae or long gamma-ray bursts, if the typical FRB repeats on the order of thousands of times during its lifetime.Comment: 17 pages, 7 figures. Submitted to AAS Journal

Self-similarity and Reynolds number invariance in Froude modelling

This review aims to improve the reliability of Froude modelling in fluid flows where both the Froude number and Reynolds number are a priori relevant. Two concepts may help to exclude significant Reynolds number scale effects under these conditions: (i) self-similarity and (ii) Reynolds number invariance. Both concepts relate herein to turbulent flows, thereby excluding self-similarity observed in laminar flows and in non-fluid phenomena. These two concepts are illustrated with a wide range of examples: (i) irrotational vortices, wakes, jets and plumes, shear-driven entrainment, high-velocity open channel flows, sediment transport and homogeneous isotropic turbulence and (ii) tidal energy converters, complete mixing in contact tanks and gravity currents. The limitations of self-similarity and Reynolds number invariance are also highlighted. Many fluid phenomena with the limitations under which self-similarity and Reynolds number invariance are observed are summarised in tables, aimed at excluding significant Reynolds number scale effects in physical Froude-based models

Evaluating Tuberculosis Case Detection in Eritrea

We used results from a national tuberculosis prevalence survey in Eritrea to calculate case detection rate (CDR) and compared it with the published CDR. The CDR obtained from the survey was ≈40%, whereas the CDR published by the World Health Organization was 3× lower (14%)