High-velocity impact damage behavior of plain-woven SiC/SiC composites after thermal loading

This study investigates characteristics of foreign-object damage in plain-woven SiC/SiC composites after thermal loading. High-speed impact tests were conducted on virgin specimens, thermally exposed specimens, and thermally shocked specimens, in which the maximum temperature during thermal loading was 600 °C or 1000 °C. An oxide layer was generated on the specimen surface by thermal loading at 1000 °C. Damaged areas on the front and back surfaces induced by particle impact were independent of thermal loading. However, in specimens thermally loaded at 1000 °C, brittle failure, i.e. cone cracking without fiber pull-out, occurred due to oxidation of the fiber/matrix interfaces, and the ballistic limit velocity significantly decreased. Finally, the ballistic limit is predicted using static strength properties, and the effect of thermal loading on impact resistance is discussed.     

Application of particle simulation methods to composite materials: a review

Particle simulation methods represent deformation of an object by motion of particles, and their Lagrangian and discrete nature is suitable for explicit modeling of the microstructure of composite materials. They also facilitate handling of large deformation, separation, contact, and coalescence. Mesh-free particle methods will thus be appropriate for a part of issues throughout the lifecycle of composite materials despite their high calculation cost. This study focuses on three particle simulation methods, namely, smoothed particle hydrodynamics, moving particle semi-implicit method, and discrete element method, and reviews approaches for modeling composite materials through these methods. Applicability of each method as well as advantages and drawbacks will be discussed from the viewpoint of engineering of composite materials. This reviewing study suggests capability of particle simulation methods to handle multiphysics and to predict various complex phenomena that necessitate explicit modeling of the material’s microstructure consisting of reinforcements (inclusions), matrix, and voids.     

Executing optimized throwing motion on robot arm with free joint

We address the throwing motion optimization for robot. In order to pursue the best throwing motion, we may need heuristics/intuition free methods. We propose a throwing method that is composed of rapid semi-optimal motion-planning and output zeroing method. So as to execute the optimized trajectories in real rigid body systems, we need some compensations for the noises around the optimized trajectories. We introduce a compensation method for the optimized throwing motions of a robot arm with a free joint. To validate the effectiveness of the proposed method, we conducted a throwing experiment using a two-link arm. As a result of the experiment, the robot arm threw a ball with 63.7 km/h, which was the best record through the past experiments of this arm.     

Superconductivity in New Pb-Based 1222 Layered Cuprates of (Pb0.75W0.25)Sr2(Eu2.0−x Ce x )Cu2O z

New Pb-based 1212 cuprates of (Pb_0.8W_0.2)Sr₂(Nd_1?x Ca _x )Cu₂O_7?δ were synthesized. The sample with x=0.6 was reported to show superconductivity with an onset temperature up to 82 K. Interestingly, in order to obtain superconductivity of the sample, synthesis in N₂ was necessary, then synthesis in air or post-treatment in O₂ led to the disappearance of superconductivity. Recently, we have successfully synthesized new Pb-based 1222 cuprates for the composition range of 0.3≤x≤1.0 in the (Pb_0.75W_0.25)Sr₂(Eu_2.0?x Ce _x )Cu₂O _z system. The samples have a tetragonal crystal structure; the typical lattice parameters are a=0.3850 nm and c=2.889 nm. Among them, a sample with x=0.3 is discovered to show superconductivity with an onset of about 15 K. These cuprates have the same (Pb, W)O monolayers as the Pb-based 1212 cuprates described above. In these new cuprates, superconductivity appears when the samples are annealed not in air and under He atmosphere, but under high-pressure O₂.     

Smoothed particle hydrodynamics in a generalized coordinate system with a finite‐deformation constitutive model

This study proposes smoothed particle hydrodynamics (SPH) in a generalized coordinate system. The present approach allocates particles inhomogeneously in the Cartesian coordinate system and arranges them via mapping in a generalized coordinate system in which the particles are aligned at a uniform spacing. This characteristic enables us to employ fine division only in the direction required, for example, in the through‐thickness direction for a thin‐plate problem and thus to reduce computation cost. This study provides the formulation of SPH in a generalized coordinate system with a finite‐deformation constitutive model and then verifies it by analyzing quasi‐static and dynamic problems of solids. High‐velocity impact test was also performed with an aluminum target and a steel sphere, and the predicted crater shape agreed well with the experiment. Furthermore, the numerical study demonstrated that the present approach successfully reduced the computation cost with marginal degradation of accuracy. Copyright © 2015 John Wiley & Sons, Ltd.     

Humidity dependence of microwear characteristics of amorphous carbon films on silicon substrates

Influences of environmental humidity on various scanning-scratched wear characteristics, such as long-term stability of wear resistance and load dependence, scratch number dependence and scratch velocity dependence of wear depth, are evaluated by using an atomic force microscope and diamond tips. Amorphous carbon (a-C) films are deposited on silicon substrates by the electron cyclotron resonance plasma (ECR) sputtering method and the RF sputtering method combined with CVD using argon gas containing methane (CH₄) as a sputtering gas. In carbon samples with a higher hydrogen content, clear influences of the humidity on various wear characteristics are observed and their wear resistances decrease with increase of the humidity. In the ECR sputtered carbon film with low hydrogen content, wear resistance is stable during long-term exposure to an environment of high temperature and high humidity. In this film, the influences of humidity on the wear resistance and adhesion forces between the films and the substrates are not observed, since it is highly wear resistant and the wear depths are shallow in each test. Thus, amorphous carbon films with low hydrogen content are suitable as wear resistant protective overcoats from the point of view of the wear resistance, in particular the influence of the humidity on the wear resistance including its long-term stability.     

From needs to aspirations in information technology for development

ABSTRACT

“Needs” figure prominently both in the technology sector and in international development. Both fields refer frequently to people’s needs and perform needs assessments. But, the two groups differ on what needs are. The technologist’s conception is represented in such statements as, “the user needs to see shoes in various colors on an e-commerce website.” Development focuses on more basic needs such as nutrition, health, and employment. We argue that conflating these two classes of needs is a subtle but underlying cause of myopic technological interventions. While development is increasingly understood to require changes in human capital, institutional capacity, and mass values – traits internal to people and societies – the technologist’s conception of needs suggests solutions that change external context through technological artifacts. We propose an approach to ICT and development that is focused less on needs, and more on aspirations. We rationalize aspirations as a basis for action, and present preliminary evidence in the form of a survey and three brief case studies for the viability of aspiration-based approaches to development.     

DomainProfiler: toward accurate and early discovery of domain names abused in future

Domain names are at the base of today’s cyber-attacks. Attackers abuse the domain name system (DNS) to mystify their attack ecosystems; they systematically generate a huge volume of distinct domain names to make it infeasible for blacklisting approaches to keep up with newly generated malicious domain names. To solve this problem, we propose DomainProfiler for discovering malicious domain names that are likely to be abused in future. The key idea with our system is to exploit temporal variation patterns (TVPs) of domain names. The TVPs of domain names include information about how and when a domain name has been listed in legitimate/popular and/or malicious domain name lists. On the basis of this idea, our system actively collects historical DNS logs, analyzes their TVPs, and predicts whether a given domain name will be used for malicious purposes. Our evaluation revealed that DomainProfiler can predict malicious domain names 220 days beforehand with a true positive rate of 0.985. Moreover, we verified the effectiveness of our system in terms of the benefits from our TVPs and defense against cyber-attacks.