Simulating hypervelocity impact effects on structures using the smoothed particle hydrodynamics code MAGI

Analysis of interaction occurring between space debris and orbiting structures is of great interest to the planning and survivability of space assets. Computer simulation of the impact events using hydrodynamic codes can provide some understanding of the processes but the problems involved with this fundamental approach are formidable. First, any realistic simulation is necessarily three-dimensional, e.g., the impact and breakup of a satellite. Second, the thickness of important components such as satellite skins or bumper shields are small with respect to the dimension of the structure as a whole, presenting severe zoning problems for codes. Thirdly, the debris cloud produced by the primary impact will yield many secondary impacts which will contribute to the damage and possible breakup of the structure. The problem was approached by choosing a relatively new computational technique that has virtues peculiar to space impacts. The method is called Smoothed Particle Hydrodynamics

Space debris characterization in support of a satellite breakup model

The Space Kinetic Impact and Debris Branch began an ambitious program to construct a fully analytical model of the breakup of a satellite under hypervelocity impact. In order to provide empirical data with which to substantiate the model, debris from hypervelocity experiments conducted in a controlled laboratory environment were characterized to provide information of its mass, velocity, and ballistic coefficient distributions. Data on the debris were collected in one master data file, and a simple FORTRAN program allows users to describe the debris from any subset of these experiments that may be of interest to them. A statistical analysis was performed, allowing users to determine the precision of the velocity measurements for the data. Attempts are being made to include and correlate other laboratory data, as well as those data obtained from the explosion or collision of spacecraft in low earth orbit

Homogenization of composites with extended general interfaces: comprehensive review and unified modeling

Abstract Interphase regions that form in heterogeneous materials through various underlying mechanisms such as poor mechanical or chemical adherence, roughness, and coating, play a crucial role in the response of the medium. A well- established strategy to capture a finite-thickness interphase behavior is to replace it with a zero-thickness interface model characterized by its own displacement and/or traction jumps, resulting in different interface models. The contributions to date dealing with interfaces commonly assume that the interface is located in the middle of its corresponding interphase. We revisit this assumption and introduce a universal interface model, wherein a unifying approach to the homogenization of heterogeneous materials embedding interfaces between their constituents is developed. The proposed novel interface model is universal in the sense that it can recover any of the classical interface models. Next, via incorporating this universal interface model into homogenization, we develop bounds and estimates for the overall moduli of fiber-reinforced and particle-reinforced composites as functions of the interface position and properties. Furthermore, we elaborate on the computational implications of this interface model. Finally, we carry out a comprehensive numerical study to highlight the influence of interface position, stiffness ratio and interface parameters on the overall properties of composites, where an excellent agreement between the analytical and computational results is observed. The developed interface-enhanced homogenization framework also successfully captures size effects, which are immediately relevant to emerging applications of nano-composites due their pronounced interface effects at small scales

HIDROID: prototyping a behavioral host-based intrusion detection and prevention system for android

Previous research efforts on developing an Intrusion Detection and Prevention Systems (IDPS) for Android mobile devices rely mostly on centralized data collection and processing on a cloud server. However, this trend is characterized by two major limitations. First, it requires a continuous connection between monitored devices and the server, which might be infeasible, due to mobile network's outage or partial coverage. Second, it increases the risk of sensitive information leakage and the violation of user's privacy. To help alleviate these problems, in this paper, we develop a novel Host-based IDPS for Android (HIDROID), which runs completely on a mobile device, with a minimal computation burden. It collects data in run-time, by periodically sampling features reflecting the utilization of scarce resources on a mobile device (e.g. CPU, memory, battery, bandwidth, etc.). The detection engine exploits statistical and machine learning algorithms to build a data-driven model for the benign behavior. Any observation failing to match this model triggers an alert, and the preventive agent takes proper countermeasure(s) to minimize the risk. HIDROID requires no malicious data for training or tuning, which makes it handy for day-to-day usage. Experimental test results, on a real-life device, show that HIDROID is well able to learn and discriminate normal from malicious behavior, with very promising accuracy of up to 0.9, while maintaining false positive rate by 0.03

The effect of green chemistry education based on practical activity on learning and attitude of pre-service chemistry teachers

Background and Objective:Chemistry plays a fundamental role in human civilization and its place in economics, politics and life is becoming more and more prominent and covers a wide range of chemical products such as drugs, dyes, fertilizers, etc. However, the environmental damage caused by it is a major human concern. Many of us today take steps to reduce environmental impact, for example by participating in chemical recycling programs and using energy-saving light bulbs; we buy local products and maybe drive hybrid cars. But what if "we could somehow prevent pollution from the start?" Thus, with a new approach called green chemistry, chemists are being led to a new phase of research activities to develop green reactions and use them instead of the old methods, to help human health and society by eliminating toxins from chemical processes. The purpose of this research is education of green chemistry through the curriculum related to the principles of green chemistry in General Chemistry Lab 1and the effect of this educational course on learning and attitude of the pre-service chemistry teachers toward green chemistry principles. Methods: This educational course involves two green experiments implemented according to green chemistry principles. The experiments include determination of molar mass relation in a chemical reaction and determination of the amount of ascorbic acid in a tablet of vitamin C. The research methods are practical, experimental and quasi-experimental and the used instruments were the researcher-constructed tests in the field of learning and attitude domain. Statistic population of this study consists of experimental group (N=30) and control group (N=30) of the student teachers at Shahid Rajaee Teacher Training University in the academic year 2017-2018. Data analysis was done using descriptive and inferential statistics with SPSS software. Findings: The obtained results show that among12 principles of Green Chemistry, students have learned the principles of 1 to 4 and 7 to 12 of these 12 principles and they have been attracted to them. In addition, the implementation of a curriculum related to the principles of green chemistry has had a positive impact on the attitude of the pre-service chemistry teachers. Conclusion: Findings from the research show that teaching the principles of green chemistry can be done based on the activity-oriented approach in the chemistry curriculum as in most developed countries. Student-teacher education can lead them to develop a positive attitude towards green chemistry and to have more motivation and desire to study chemistry based on the principles of green chemistry and to pass this attitude on to their students in the teaching process. Also, in designing the curriculum, it should be noted that in the sequence of practical activities, it should be done in such a way that it includes all the principles of green chemistry so that education based on it can give all the principles of green chemistry to learners or give them a positive attitude.   ===================================================================================== COPYRIGHTS  ©2019 The author(s). This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, as long as the original authors and source are cited. No permission is required from the authors or the publishers.  ====================================================================================

Striae gravidarum: Associated factors

Background: Striae gravidarum (SG) is the most common change in connective tissue of pregnant women and may cause cosmetic concerns. Objectives: To determine the frequency of SG in Iranian pregnant women and its possible associations with the characteristics of themselves and their newborns. Methods: One hundred and eighteen primigravid pregnant women were included in this prospective observational study at their first prenatal visit, among them 114 completed the study and gave birth. Results: One hundred (87.7) of 114 women developed SG with a mean Davey's score of 4.04±2.47. The mean gestational age at which SG first appeared was 27.57±5.38 weeks. Family history of SG in mother, baseline and delivery body mass index, greatest abdominal and hip girths, newborn weight, height and head circumference were significantly associated with the presence of SG. All of these factors were also correlated with Davey's score. Conclusion: Genetic and physical risk factors may be involved in the development of SG in primigravid women. © 2007 The Authors Journal compilation © 2007 European Academy of Dermatology and Venereology

Towards an autonomous host-based intrusion detection system for android mobile devices

In the 5G era, mobile devices are expected to play a pivotal role in our daily life. They will provide a wide range of appealing features to enable users to access a rich set of high quality personalized services. However, at the same time, mobile devices (e.g., smartphones) will be one of the most attractive targets for future attackers in the upcoming 5G communications systems. Therefore, security mechanisms such as mobile Intrusion Detection Systems (IDSs) are essential to protect mobile devices from a plethora of known and unknown security breaches and to ensure user privacy. However, despite the fact that a lot of research effort has been placed on IDSs for mobile devices during the last decade, autonomous host-based IDS solutions for 5G mobile devices are still required to protect them in a more efficient and effective manner. Towards this direction, we propose an autonomous host-based IDS for Android mobile devices applying Machine Learning (ML) methods to inspect different features representing how the device’s resources (e.g., CPU, memory, etc.) are being used. The simulation results demonstrate a promising detection accuracy of above 85%, reaching up to 99.99%

Veni Vidi Dixi: Reliable Wireless Communication with Depth Images

The upcoming industrial revolution requires deployment of critical wireless sensor networks for automation and monitoring purposes. However, the reliability of the wireless communication is rendered unpredictable by mobile elements in the communication environment such as humans or mobile robots which lead to dynamically changing radio environments. Changes in the wireless channel can be monitored with frequent pilot transmission. However, that would stress the battery life of sensors. In this work a new wireless channel estimation technique, Veni Vidi Dixi, VVD, is proposed. VVD leverages the redundant information in depth images obtained from the surveillance cameras in the communication environment and utilizes Convolutional Neural Networks CNNs to map the depth images of the communication environment to complex wireless channel estimations. VVD increases the wireless communication reliability without the need for frequent pilot transmission and with no additional complexity on the receiver. The proposed method is tested by conducting measurements in an indoor environment with a single mobile human. Up to authors best knowledge our work is the first to obtain complex wireless channel estimation from only depth images without any pilot transmission. The collected wireless trace, depth images and codes are publicly available.Comment: Accepted for publication in CoNext 2019 with reproducibility badges. The measurements and the processing codes are available at https://gitlab.lrz.de/lkn_measurements/vvd_measurements for your evaluatio

Treatment of female pattern hair loss

Female pattern hair loss (FPHL) as a distinctive entity was first described about 30 years ago. The objective of this study was to perform a systematic review of all randomized controlled trials for treatment of FPHL. A preliminary search was carried out in several databases up to August 2008 to identify all randomized controlled trials on nonsurgical interventions for treatment of FPHL. Studies reporting fewer than 10 patients and non-English articles were excluded. Additionally, references of relevant articles and reviews were checked manually in search for additional sources. Among 238 citations found in the preliminary search, 12 fulfilled all criteria to be included in the systematic review. Topical minoxidil 1 to 5 for 24 to 48 weeks was shown to be effective in FPHL and its effect was not related to age or androgen level of patients. In addition, it may be effective in women with FPHL, both with and without hyperandrogenism, and in young and old premenopausal or postmenopausal. In patients with increased serum androgens, oral flutamide but not finasteride or cyproterone acetate was more effective than no treatment. Topical minoxidil is effective in patients with FPHL, with or without hyperandrogenism, but there is limited evidence for the efficacy of antiandrogens. © 2012 Pulse Marketing & Communications, LLC