Comprehending Kademlia Routing - A Theoretical Framework for the Hop Count Distribution

The family of Kademlia-type systems represents the most efficient and most widely deployed class of internet-scale distributed systems. Its success has caused plenty of large scale measurements and simulation studies, and several improvements have been introduced. Its character of parallel and non-deterministic lookups, however, so far has prevented any concise formal analysis. This paper introduces the first comprehensive formal model of the routing of the entire family of systems that is validated against previous measurements. It sheds light on the overall hop distribution and lookup delays of the different variations of the original protocol. It additionally shows that several of the recent improvements to the protocol in fact have been counter-productive and identifies preferable designs with regard to routing overhead and resilience.Comment: 12 pages, 6 figure

A Lightweight Approach for Improving the Lookup Performance in Kademlia-type Systems

Discovery of nodes and content in large-scale distributed systems is generally based on Kademlia, today. Understanding Kademlia-type systems to improve their performance is essential for maintaining a high service quality for an increased number of participants, particularly when those systems are adopted by latency-sensitive applications. This paper contributes to the understanding of Kademlia by studying the impact of \emph{diversifying} neighbours' identifiers within each routing table bucket on the lookup performance. We propose a new, yet backward-compatible, neighbour selection scheme that attempts to maximize the aforementioned diversity. The scheme does not cause additional overhead except negligible computations for comparing the diversity of identifiers. We present a theoretical model for the actual impact of the new scheme on the lookup's hop count and validate it against simulations of three exemplary Kademlia-type systems. We also measure the performance gain enabled by a partial deployment for the scheme in the real KAD system. The results confirm the superiority of the systems that incorporate our scheme.Comment: 13 pages, 8 figures, conference version 'Diversity Entails Improvement: A new Neighbour Selection Scheme for Kademlia-type Systems' at IEEE P2P 201

S-PRAC: Fast Partial Packet Recovery with Network Coding in Very Noisy Wireless Channels

Well-known error detection and correction solutions in wireless communications are slow or incur high transmission overhead. Recently, notable solutions like PRAC and DAPRAC, implementing partial packet recovery with network coding, could address these problems. However, they perform slowly when there are many errors. We propose S-PRAC, a fast scheme for partial packet recovery, particularly designed for very noisy wireless channels. S-PRAC improves on DAPRAC. It divides each packet into segments consisting of a fixed number of small RLNC encoded symbols and then attaches a CRC code to each segment and one to each coded packet. Extensive simulations show that S-PRAC can detect and correct errors quickly. It also outperforms DAPRAC significantly when the number of errors is high

Properties of Recycled Aggregate in Concrete and Road Pavement Applications

This paper highlights the results of the performed testing program which aimed at investigating the possibility of utilizing the recycled crushed aggregates of the construction and demolition wastes (CDW) in engineering applications in Gaza Strip. The characteristics of the crushed aggregates were determined and compared to international standards. The reuse alternative is investigated in concrete mixes and road construction throughout the testing program. Eight representative samples were selected from different locations in Rafah and Khan Younis. A Technical team supervised the collection process, crushing, transporting, handling and testing program. In general, the test results showed that the recycling of the CDW aggregates and its use in both concrete and road sub-base give acceptable results. Most of the characteristic test results were within the standard limits. The results of the tests that concern road applications were good and verified the adequacy of materials. The results of the tests for concrete applications were also desirable and proved that these materials, CDW, could be used in some concrete applications. The values of the CBR ratio at 100% were 186.6 for demolition samples and 186.1 for crushed concrete samples. Comparably with the CBR of the local base course that is ranged between 100 and 130, the CBR values were high due to the large quantity of cementious materials, and achieved the minimum required value (80) for base course at 100% compaction according to AASHTO (T180-D) and (T 193). A local concrete mix design was used for testing CDW use in concrete . This mix gave a compressive strength of about 250 kg/cm2 of compressive strength at 28 days at water to cement ratio of 0.6 and 290 kg cement content. The results of the testing program of the recycled CDW were above expectations and showed, to some extent, good indications. Two testing labs were used to prepare and test the samples. Most tests at 7 and 28 days, showed high results compared to the control samples of natural materials. The results of the compressive strength of all samples at the same water to cement ratio were close to each other

Influence of the Butt Joint Design of TIG Welding on the Thermal Stresses

The aim of this paper is to demonstrate the influence of the single butt joint design of TIG welding on the thermal stresses for carbon steel type St-37. The butt welding was performed by V angles 30°,45°,60° and 90° and the thermal stresses analysis is based on the local moving heat flux. The numerical model developed by ANSYS12 software based on solving the three dimensional energy equation, considering moving heat source and temperature dependent material properties. Temperature and stresses distributions were obtained function of time. From the results, it is evident that the joint design has an important role in the welding process, when the edge angle of the welding region gets bigger, the faults get less due to increase of heat flux in the welding region. It can be concluded that the specimen with less than 6mm thickness can be welded without edge angle preparation, due to increase the thermal stresses when edge angle is evident and higher thermal stresses distribution was at edge angle 60° and lowest thermal stresses distribution was at 90°

Helosciadium crassipes Koch (Apiaceae) extracts as natural sunscreen and preservative additives

Recently, ingredients derived from natural sources have gained increasing interest in the cosmetic field due to their low toxicity. Therefore, this study was designed to explore the cosmetic potential of Helosciadium crassipes Koch (Apiaceae) species growing in Algeria as a promising natural preservative and broad-spectrum UV protection additive. In our study, the in-vitro antioxidant effect was assessed via DPPH radical scavenging and total antioxidant capacity by phosphomolybdenum method (TAC), while the protection against UVB radiation was evaluated according to the sun protection factor (SPF) by using UV spectroscopic technic at wavelengths ranging from 290 to 320 nm and Mansur’s equation, for the photoprotective effect against long-wavelength UVA, UVA/UVB and critical wavelength (λc) parameters were evaluated. The outcomes showed that among the tested extracts, the methanolic extract (MeOH) contains high levels of phenolics and flavonoids, and possesses a significant antioxidant effect, particularly in DPPH radical scavenging assay. Similarly, this last one exhibited high photoprotective activity in UVB and UVA ranges. The gathered results reveal the possibility of using this extract as a good natural additive to be incorporated into cosmetic formulations as a broad-spectrum UV protection candidate and as a preservative agent

Applying Geographic Information System to Locate the Residential burglary Hotspots in Penang Island, Malaysia

Identifying the geographic areas with a high concentration of house break-in incidents is crucial in policing and prevention initiations. Despite the popularity of geographic information system in mapping residential burglary, not many studies have explored the significance level of the areas comprising crime to understand the severity of the hot spots. Hence, this study sought to identify the geographic location of the residential burglary hotspotsin Penang Island and explores their spatial configuration. The latest available (2011 to 2013) police-recorded incidents of house break-in for day and night were collected from Penang Islands Headquarters, Georgetown. Geocoding technique was used to map the exact postal address of the houses in GIS. This study applied two spatial analysis tools, namely ‘Getis-Ord or Gi*’ and ‘Average Nearest Neighbor’ to detect the locations of the hotspots of residential burglary hotspots. The results demonstrated a high clustering value for the residential burglary hotspotsin the year 2013. The study concludes that even though most of the subdistricts of Penang Island have low or average-value clusters, but the increasing claustration value of the hotspot from 2011 to 2013 proofs that there is a persistent underlying physical or socioeconomic issue in these areas. Therefore, detection of the relatively in more vulnerable areas in this study makesthe decision of resource allocation for further exploration and immediate treatment by the authorities easier. Overlapping of the hotspot maps generated in this study with other maps such as various crime types, land use, and socio-demographic maps will help in deeper scrutinization of the reasons behind the occurrence of house break-in of the hotspot

Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

Mapping 123 million neonatal, infant and child deaths between 2000 and 2017

Since 2000, many countries have achieved considerable success in improving child survival, but localized progress remains unclear. To inform efforts towards United Nations Sustainable Development Goal 3.2—to end preventable child deaths by 2030—we need consistently estimated data at the subnational level regarding child mortality rates and trends. Here we quantified, for the period 2000–2017, the subnational variation in mortality rates and number of deaths of neonates, infants and children under 5 years of age within 99 low- and middle-income countries using a geostatistical survival model. We estimated that 32% of children under 5 in these countries lived in districts that had attained rates of 25 or fewer child deaths per 1,000 live births by 2017, and that 58% of child deaths between 2000 and 2017 in these countries could have been averted in the absence of geographical inequality. This study enables the identification of high-mortality clusters, patterns of progress and geographical inequalities to inform appropriate investments and implementations that will help to improve the health of all populations