Complexity of increasing the secure connectivity in wireless ad hoc networks

We consider the problem of maximizing the secure connectivity in wireless ad hoc networks, and analyze complexity of the post-deployment key establishment process constrained by physical layer properties such as connectivity, energy consumption and interference. Two approaches, based on graph augmentation problems with nonlinear edge costs, are formulated. The first one is based on establishing a secret key using only the links that are already secured by shared keys. This problem is in NP-hard and does not accept polynomial time approximation scheme PTAS since minimum cutsets to be augmented do not admit constant costs. The second one extends the first problem by increasing the power level between a pair of nodes that has a secret key to enable them physically connect. This problem can be formulated as the optimal key establishment problem with interference constraints with bi-objectives: (i) maximizing the concurrent key establishment flow, (ii) minimizing the cost. We prove that both problems are NP-hard and MAX-SNP with a reduction to MAX3SAT problem

Why don't they answer? Unit non-response in the IAB Establishment Panel

"With the IAB Establishment Panel the Institute for Employment Research (Institut für Arbeitsmarkt- und Berufsforschung - IAB) has conducted a large-scale annual establishment survey in western Germany since 1993 and also in eastern Germany since 1996, covering some 15,500 establishments in the meantime. In this panel survey the establishments are asked in face-to-face interviews1 to provide information on key determinants of employment. The IAB Establishment Panel is a survey in which the same establishments are contacted each year. New establishments are added to the sample each year in order to depict structural change. Furthermore additional establishments have to be included in the sample to replace those which have dropped out of the sample in the course of time. For despite all efforts, one problem arises in every survey: individual establishments' unwillingness to participate, which leads to so-called non-response. Two forms of non-response can be distinguished. First, an establishment may refuse to participate in the survey at all (unit non-response). Second, participating establishments may fail to answer individual questions in the questionnaire (item non-response). Both types of non-response can lead to biased results if the cases of non-response are not random. Unit non-response leads to greater problems, however, as no interview is available for these establishments and it is not just the case that individual questions are not answered. Experience made with the IAB Establishment Panel shows that the willingness of establishments surveyed for the first time to participate in the survey is clearly lower, at 36 percent, than that of establishments which have already been included in the survey at least once. Furthermore the unit non-response of establishments surveyed for the first time has increased in the past few years. The willingness of the panel establishments, in other words the repeat respondents from previous years, to complete the questionnaire is considerably higher at about 80 percent. There is no indication that the willingness to participate is declining over the years. The advantage of panel surveys is also that a wealth of establishment information is available from previous years for the establishments which have been surveyed repeatedly but which no longer respond and this can be used to model the non-response process. On the other hand little information is available about the establishments which are included in the survey for the first time. It is important to analyse the non-response processes in order to gain the most precise insight possible into the survey process. The findings obtained in this way make it possible to optimise the fieldwork management, thus contributing to quality improvements and possibly to cost reductions. In addition to this, the analyses can reveal any selectivities that may lead to biased estimates. The representativeness of the projection of all variables can also be jeopardised by possible selectivities. Furthermore, in panel surveys selectivities may intensify over time. The aim of this paper is to examine the unit non-response of establishments which have already taken part in the survey at least once and are approached again. On the basis of an extended conceptual framework for establishment surveys, determinants that influence the non-response process are to be brought out. For the first time for establishment surveys the interviewer's influence on the success of the interview is taken into account both in the conceptual framework and in the analyses." (Author's abstract, IAB-Doku) ((en))Datengewinnung, Antwortverhalten, IAB-Betriebspanel, Befragung, Non Response

Predicting the potential geographical distribution of the harlequin ladybird, Harmonia axyridis, using the CLIMEX model - BioControl

Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) is a ladybird beetle native to temperate and subtropical parts of Asia. Since 1916 populations of this species have been introduced throughout the world, either deliberately, or by accident through international transport. Harmonia axyridis was originally released as a classical biological control agent of aphid and coccid pests in orchards and forests, but since 1994 it is also available as a commercial product for augmentative control in field and greenhouse crops. It is a very voracious and effective natural enemy of aphids, psyllids and coccids in various agricultural and horticultural habitats and forests. During the past 20 years, however, it has successfully invaded non-target habitats in North America (since 1988), Europe (1999) and South America (2001) respectively in a short period of time, attacking a wide range of non-pest species in different insect orders. Becoming part of the agricultural commercial pathway, it is prone to being introduced into large areas across the world by accident. We use the CLIMEX programme (v2) to predict the potential geographical distribution of H. axyridis by means of matching the climate of its region of origin with other regions in the world and taking in account biological characteristics of the species. Establishment and spread seem likely in many regions across the world, including those areas which H. axyridis has already invaded (temperate Europe, North America). Based on the CLIMEX prediction a large part of Mediterranean Europe, South America, Africa, Australia and New Zealand seem highly suitable for long-term survival of H. axyridis as well. In addition we evaluate CLIMEX as a strategic tool for estimating establishment potential as part of an environmental risk assessment procedure for biological control agents we discuss biological and ecological aspects necessary to fine-tune its establishment and spread in areas after it has been introduce

The development of ASEAN from historical approach

Since ASEAN was established in 8 August 1967, ASEAN organization was only joined by five countries.Now ASEAN has become a successful regional organization in bringing the attention of the other countries in rest of the world. Generally, ASEAN has successfully nurtures the cooperation in political, economical, social and cultural with establishment in exercise and research facilities for shared interest.Nowadays, ASEAN roles and influence has strong base in Southeast Asia and South Asia regions.ASEAN has taken place as important body in Asia Pacific political stream through Asian Regional Forum (ARF), where it is successful to create attention of various countries not only in Asia region but also United States of America and Europe involvement.Nevertheless, beside the successful story and prosperity achieved by ASEAN at this moment it has uniqueness when it has to face challenges at the early stage of ASEAN establishment. This journal will touch on history and ASEAN life story and explain What and How ASEAN able to strengthen its role and existence at the time Southeast Asia countries need an organization with the ability to unite all the countries in Southeast Asia region

Google QUIC performance over a public SATCOM access

Google QUIC accounts for almost 10% of the Internet traffic and the protocol is not standardized at the IETF yet. We distinguish Google QUIC (GQUIC) and IETF QUIC (IQUIC) since there may be differences between the two. Both Google and IETF versions run over UDP and cannot be split the way satellite systems usually do with TCP connections. The need for adapting any-QUIC parameters needs to be evaluated. Since GQUIC is available, we analyze its behavior over a satellite communication system. In our evaluations, GQUIC quick connection establishment does not compensate an inappropriate congestion control. The resulting page downloading time doubles when using GQUIC as opposed to the performance with optimized split TCP connections. This paper concludes that specific tuning are required when any-QUIC runs over a high BDP network.Comment: To appear in International Journal of Satellite Communications and Networking. 13 pages, 8 figure

\u3ci\u3eHippodamia Variegata\u3c/i\u3e (Goeze) (Coleoptera: Coccinellidae) Detected in Michigan Soybean Fields

Since its initial detection near Montreal, Canada in 1984, the variegated lady beetle Hippodamia variegata (Goeze) (Coleoptera:Coccinellidae) has spread throughout the northeastern United States. In 2005, this immigrant Old World species was detected in Michigan for the first time. Twenty-nine adults were found in soybean fields in 4 counties: Ingham, Gratiot, Kalamazoo, and Saginaw.The first individuals were found in Gratiot County on 22 June 2005; we continued to detect individuals until 18 Aug 2005 (2 individuals collected in Saginaw Co.) when sampling ended. Prior to this study, H. variegata had not been known to prey on the soybean aphid, Aphis glycines Matsumura (Homoptera: Aphididae). The establishment of soybean aphid throughout the north-central U.S. may aid the spread of H. variegata throughout the region

A First Look at QUIC in the Wild

For the first time since the establishment of TCP and UDP, the Internet transport layer is subject to a major change by the introduction of QUIC. Initiated by Google in 2012, QUIC provides a reliable, connection-oriented low-latency and fully encrypted transport. In this paper, we provide the first broad assessment of QUIC usage in the wild. We monitor the entire IPv4 address space since August 2016 and about 46% of the DNS namespace to detected QUIC-capable infrastructures. Our scans show that the number of QUIC-capable IPs has more than tripled since then to over 617.59 K. We find around 161K domains hosted on QUIC-enabled infrastructure, but only 15K of them present valid certificates over QUIC. Second, we analyze one year of traffic traces provided by MAWI, one day of a major European tier-1 ISP and from a large IXP to understand the dominance of QUIC in the Internet traffic mix. We find QUIC to account for 2.6% to 9.1% of the current Internet traffic, depending on the vantage point. This share is dominated by Google pushing up to 42.1% of its traffic via QUIC

Interaction of Seed Dispersal and Environmental Filtering Affects Woody Encroachment Patterns in Coastal Grassland

Encroachment of woody plants into grasslands has occurred worldwide and includes coastal ecosystems. This conversion process is mediated by seed dispersal patterns, environmental filtering, and biotic interactions. As spatiotemporally heterogeneous, harsh environments, barrier islands present a unique set of challenges for dispersal and establishment. Environmental conditions act as filters on dispersed seeds, thereby influencing encroachment and distribution patterns. Seldom have patterns of propagule dispersal been considered in the context of woody encroachment. We quantified dispersal and post‐dispersal processes of an encroaching woody population of Morella cerifera relative to directional rate of encroachment and observed distribution patterns on an Atlantic coastal barrier island with strong environmental filtering. We analyzed historic foredune elevation as a proxy for reduced interior environmental stress. The dispersal kernel was leptokurtic, a common characteristic of expanding populations, but rate of encroachment has slowed since 2005. Expansion pattern was related to foredune elevation, which limits encroachment below a threshold elevation. This difference between dispersal kernel behavior and encroachment rate is due to limited availability of suitable habitat for Morella and temporal variability in chlorides during the time of germination. Our results demonstrate that processes mediating seeds and seedling success must be accounted for to better understand establishment patterns of encroaching woody plants

Establishment Exits in Germany: The Role of Size and Age

Using comprehensive data for West Germany, this paper investigates the determinants of establishment exit. We find that between 1975 and 2006 the average exit rate has risen considerably. In order to test various "liabilities" of establishment survival identified in the literature, we analyze the impact of establishment size and put a special focus on differences between young and mature establishments. Our empirical analysis shows that the mortality risk falls with establishment size, which confirms the liability of smallness. The probability of exit is substantially higher for young establishments which are not more than five years old, thus confirming the liability of newness. There also exists a liability of aging since exit rates first decline over time, reaching a minimum at ages 15 to 18, and then rise again somewhat. The determinants of exit differ substantially between young and mature establishments, suggesting that young establishments are more vulnerable in a number of ways.firm exits, Germany

Globalization and productivity : a survey of firm-level analysis

Recent empirical studies which utilize plant- or establishment-level data to examine globalization's impact on productivity have discovered many causal mechanisms involved in globalization's impact on firms' productivity. Since these pathways have been broad, there have been few attempts to summarize the several and detailed mechanisms of self-selection and learning at the same time. This paper examines seven pathways so that the clear-cut consequences of the broad picture of globalization become visible. This strategy is useful for detecting missing links within and across the existing studies as well as for finding possible synergy effects among different mechanisms. Insightful policy implications may be derived from the comprehensive comparisons between the seven different pathways of globalization.Firm-level data, Globalization, Productivity, International trade, Foreign investments, Developing countries, Developed countries