Harnessing optical micro-combs for microwave photonics

In the past decade, optical frequency combs generated by high-Q micro-resonators, or micro-combs, which feature compact device footprints, high energy efficiency, and high-repetition-rates in broad optical bandwidths, have led to a revolution in a wide range of fields including metrology, mode-locked lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum optics. Among these, an application that has attracted great interest is the use of micro-combs for RF photonics, where they offer enhanced functionalities as well as reduced size and power consumption over other approaches. This article reviews the recent advances in this emerging field. We provide an overview of the main achievements that have been obtained to date, and highlight the strong potential of micro-combs for RF photonics applications. We also discuss some of the open challenges and limitations that need to be met for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference

Deformation Twin Formed By Self-Thickening, Cross-Slip Mechanism In Nanocrystalline Ni

We report the observation of a deformation twin formed by a recently proposed self-thickening, cross-slip twinning mechanism. This observation verifies one more twinning mechanism, in addition to those reported before, in nanocrystalline face-centered-cubic metals. In this mechanism, once the first Shockley partial is emitted from a grain boundary, and cross slips onto another slip plane, a deformation twin could nucleate and grow in both the primary and cross-slip planes without requiring the nucleation of additional Shockley partials from the grain boundary

Microstructural evolution and formation of nanocrystalline intermetallic compound during surface mechanical attrition treatment of cobalt

Nanocrystalline intermetallic Co3Fe7 was produced on the surface of cobalt via surface mechanical attrition (SMA). Deformationinduced diffusion entailed the formation of a series of solid solutions. Phase transitions occurred depending on the atomic fraction of Fe in the surface solid solutions: from hexagonal close-packed (11% Fe). Nanoscale compositional probing suggested significantly higher Fe contents at grain boundaries and triple junctions than grain interiors. Short-circuit diffusion along grain boundaries and triple junctions dominate in the nanocrystalline intermetallic compound. Stacking faults contribute significantly to diffusion. Diffusion enhancement due to high-rate deformation in SMA was analyzed by regarding dislocations as solute-pumping channels, and the creation of excess vacancies. Non-equilibrium, atomic level alloying can then be ascribed to deformation-induced intermixing of constituent species. The formation mechanism of nanocrystalline intermetallic grains on the SMA surface can be thought of as a consequence of numerous nucleation events and limited growth. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Stress effects on stability and diffusion behavior of sulfur impurity in nickel: A first-principles study

A systematic investigation regarding the effect of stress on the stability and diffusion behavior of S impurity in Ni was carried out via first-principles methods. A comparison of the formation energy of S in Ni indicated that S more easily forms as a solution atom with increasing S concentration in Ni supercells, but the binding energy showed that as the concentration of S that dissolved into Ni increased, the structure became less stable. The diffusion barrier via the octahedral-tetrahedral-octahedral site path was always lower than that via the octahedral-octahedral site path. The diffusion barrier of single S decreased with increase in tensile stress. S diffusion accelerated under applied tensile stress, which was disadvantageous in suppressing S retention in Ni. These results implied that even at a low concentration, dissolved S still had a tendency of precipitating from the Ni matrix, to further increase the stability of the system. (C) 2014 Elsevier B. V. All rights reserved

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

Company innovativeness measurement: Development of an assessment tool to measure the innovation performance of companies

Technology, Policy and Managemen

Effects of Transients on High Voltage Cable Insulation

Occasionally sporadic defects in high voltage cable insulation may escape from detection by commissioning or maintenance tests. Usually these tiny defects will not initiate significant partial discharges or cause breakdown in the cable insulation system under normal AC operating condition and normal transient situations. However, nowadays more often complex transient’s behaviour occurs in power systems. For example, in a mixed line and cable system, superimposed transients with large overvoltage can occur due to switching operations. Such transients may have unexpected influences on the partial discharge behaviour and degradation of the cable insulation. This thesis aims to investigate which potential effects such transients have on the insulation condition of the HV cable system, in particular in one of its weakest links, the cable joint.DC systems, Energy conversion & Storag

A Tool for the Design of Facilities for the Sustainable Production of Knowledge

The aim of the study is to develop a ‘design tool’, that is a method to enhance the design and planning of facilities for the sustainable production of new knowledge. More precisely, the objective is to identify a method to support the conception of building complexes related to the long-term production of new knowledge. The tool is focused on the necessary spatial conditions pertaining to this end, especially the topological networks. Today, with profound developments in what has been called the Knowledge Economy and consequent changes in our society, new challenging design problems have to be faced. It appears that one of the most crucial of these is to design Sustainable Innovation Facilities which can meet the new needs and exploit the potential of the New Environment of our time.To solve this new problem, a new set of design methods is needed, in the form of a design tool. The concept of ‘Sustainable Development’ in the economy and the environment is applied to the production of new knowledge. The basic feature of ‘Sustainable Development’ is generalized as: the process of increasing or at least maintaining output in a changing environment by means of adaptation. One condition contributing significantly to such adaptation is knowledge ‘diversity’ of people interacting within what have been called ‘clusters’. There are two possibilities of achieving such clusters of high diversity: 1) through ‘virtual’ media and 2) through face-to-face interaction in ‘real’ places. Both are seen to be of value. Hence, facilities for sustainably producing new knowledge have to combine the advantages of both virtual and physical means. In certain situations, over-reliance on virtual media may to lead to ‘Cyberbalkanization’. This study thus concentrates on enhancing interaction in the ‘real places’ that exist in built environments. To measure physical diversity in clusters, three steps are suggested: 1. The identification of clustering locations in innovation facilities; 2. The identification of users interacting in such clustering locations; 3. The measurement of the diversity of the agents interacting in such clusters. To provide a better understanding of the concepts of diversity and cluster formation related to the physical spatial organization of a facility, the campus of TU Delft was chosen as a case study. The study shows that the possibility for physical interaction between knowledge agents in clusters from diverse academic backgrounds is very low, which forces us to think about conditions that may increase them. As a result, the study is concerned with the necessary conditions to allow the formation of clusters of high diversity in knowledge production facilities. These conditions are represented in terms of topological networks consisting of nodes, which represent places for potential encounters, and links between nodes, which represent accessibility between such places. We use the term ‘Archigraph’ for these networks. To construct the design tool, three examples of applications are considered to explore how the tool can be constructed. The three examples illustrate how to compare diversity of interacting groups in clusters for schemes in three different situations as follows: different network structure but similar allocation; different allocation but the same network structure; and different allocation with different network structure. To test the tool, two design options from a real design competition are used in another case study. We compare the ‘diversity index’ of the schemes using the design tool. Possible modifications to the tool are suggested as a result of this case study. Starting from methodologies developed by the Design Knowledge Systems Research Center (DKS) for the development of design tools, the research is also innovative in the following respects: 1. The transfer of concepts and techniques from the domains of economics, regional science, environmental sustainability, and sociology to the domain of spatial design, on the scale of building complexes; 2. The development of a model representing spatial attributes constraining face-to-face group interaction in the built environment; 3. The development of a design tool which can help in evaluating and optimizing the potential diversity of groups communicating within building complexes. The design tool proposed here is not intended for use as a deterministic design machine but as an aid to providing a better understanding in comparing alternative building plans when the topological network is taken as a necessary condition for enhancing physical interaction among diverse agents.ArchitectureArchitectur

Microstructure evolution in pearlitic rail steel due to rail/wheel interaction

The microstructural aspects of rolling contact fatigue in rails were studied. The rail track is a critical component of the railway system and its long-term performance contributes crucially to the sustainable development of the railway system. The increasing demands of trains with a higher speed/capacity impose more severe load conditions on the steel rail tracks. Steels with improved performance are needed to meet such demands because the current rail steels are reaching their limit. Moreover, the understanding of the root cause of damage in rails is still insufficient. This hinders the development of new rail steels that perform better.MSE-