34 research outputs found
NF-TCP: Network Friendly TCP
No full textDelay-insensitive applications such as P2P file sharing, data center backups and software updates generate substantial amounts of traffic. This traffic, transported potentially over multiple TCP connections, competes with traffic from other possibly interactive applications. Today, with TCP, they compete on an equal level for each individual connection. In this paper, we propose a new TCP variant for such delay-insensitive applications, which we call Network Friendly TCP (NF-TCP). NF-TCP is responsive to available bandwidth, seeking to quickly and efficiently utilize the same in a congestion-free situation, while backing-off more aggressively than standard TCP on encountering competing traffic in a congested network. NF-TCP uses a novel combination of utilizing measurement of available bandwidth and ECN-based congestion avoidance techniques to ensure that it is truly friendly to existing TCP connections. We evaluate the performance of NF-TCP through ns-2 simulations and present the initial results enlightening the friendly nature of NF-TCP compared to standard TCP
Intrinsic monitoring within an IPv6 network: mapping node information to network paths
No full textIn this paper, we describe a path-based intrinsic monitoring protocol that can efficiently associate SNMP based MIB information to a network path within a single administrative domain. Our method is based on intrinsic monitoring, a lightweight metric collection protocol that makes use of the IPv6 Router Alert hop-by-hop option. The main advantage of our approach is that operators can rapidly associate node specific MIB metrics to paths within the network. This can dramatically reduce the overhead associated with correlating node specific MIB information to topology information and network paths. It provides the network operator with a tool that can be used to focus on monitoring individual paths in the network, where the nodes along the path are not known beforehand. We compare the performance overhead associated with our proposed approach to conventional SNMP get/response message exchanges. The results demonstrate a dramatic reduction in the collection time of node specific metrics. Our approach also implicitly relates collected metrics to the network path, thus removing the need to correlate metrics to topology and path information
Informal regulation of industrial pollution in developing countries : evidence from Indonesia
No full textThe authors test a model of supply-demand relations in an implicit market for environmental services when formal regulation is absent. They use plant-level data from Indonesia for 1989-90, before the advent of nationwide environmental regulation. Treating pollution as a derived demand for environmental services, their model relates emissions of biological oxygen demand to the price (expected cost) of pollution; to prices of other inputs (labor,energy, materials); and to enterprise characteristics that may affect pollution demand, including scale, vintage ownership, and efficiency. The price of pollution is determined by the intersection of plant-level demand and a local environmental supply function, enforced by community pressure or informal regulation. Environmental supply is affected by community income, education, the size of the exposed population, the local economic importance of the plant, and its visibility as a polluter. Their results are strongly consistent with the existence of an informal"pollution equilibrium."Pollution intensity declines with increase in plant size, efficiency, and local materials prices. Older plants and publicly owned facilities are more pollution intensive; multinational ownership has no independent effect. The results also suggest that the price of pollution is higher when plants are particularly visible and is far lower in poorer, less-educated communities. Thus the intensity of pollution is far higher in such communities. While it would be premature to generalize from these results, they suggest that the model of optimal pollution control in environmental economics is more relevant for developing countries than many have believed. Community-factory interactions seem to reflect environmental supply-demand considerations even when formal regulation does not exist. In addition, the apparent power of informal regulation implies that cost-effective formal systems should be designed to complement, not supplant, community control. In particular: 1) Local communities should not be forced to rely so heavily on visibility when judging environmental performance. Formal regulation should include publication of audited emissions reports from factories; 2) Environmental injustice may be real and important. Many poor, uneducated communities may need extra support from national regulators.; and 3) However, appropriate regulation should strike the right balance between equity and efficiency. Uniform national standards go too far because they eliminate all the natural and legitimate regional diversity that is also reflected in informal arrangements.Public Health Promotion,Environmental Economics&Policies,Water and Industry,Sanitation and Sewerage,Water Conservation,Environmental Economics&Policies,Water and Industry,TF030632-DANISH CTF - FY05 (DAC PART COUNTRIES GNP PER CAPITA BELOW USD 2,500/AL,Sanitation and Sewerage,Urban Services to the Poor
Influence of third body evolution on tribological property of copper-matrix friction material by surface treatment
No full textA-DDPG: Attention Mechanism-based Deep Reinforcement Learning for NFV
No full textThe efficacy of Network Function Virtualization (NFV) depends critically on (1) where the virtual network functions (VNFs) are placed and (2) how the traffic is routed. Unfortunately, these aspects are not easily optimized, especially under time-varying network states with different quality of service (QoS) requirements. Given the importance of NFV, many approaches have been proposed to solve the VNF placement and traffic routing problem. However, those prior approaches mainly assume that the state of the network is static and known, disregarding real-time network variations. To bridge that gap, in this paper, we formulate the VNF placement and traffic routing problem as a Markov Decision Process model to capture the dynamic network state transitions. In order to jointly minimize the delay and cost of NFV providers and maximize the revenue, we devise a customized Deep Reinforcement Learning (DRL) algorithm, called A-DDPG, for VNF placement and traffic routing in a real-time network. A-DDPG uses the attention mechanism to ascertain smooth network behavior within the general framework of network utility maximization (NUM). The simulation results show that A-DDPG outperforms the state-of- the-art in terms of network utility, delay, and cost.Accepted Author ManuscriptEmbedded System
Increasing the robustness of active upper limb prostheses
No full textThis thesis is based on my work done at the Institute for Neurorehabilitation Systems at the University Medical Center Goettingen. My work has been partially founded by German Ministry for Education and Research (BMBF) via the Bernstein Focus Neurotechnology (BFNT) Göttingen under grant number 1GQ0810
The local ethics committee approved all studies involving human subjects, and all subjects signed informed consents prior to their participation in the studies.
The entire thesis has been originally written by me. Part of the materials used in this thesis have also been published in journals or conferences, where I am the first or corresponding author. All rights for re-use of previously published material were obtained. Reused figures and tables of IEEE publications are marked with © [Year] IEEE.
Hereby I declare that I have written this thesis independently and with no other aids and sources than quoted
Circularly polarized antenna with U-shaped strip for RFID reader operating at 902–928 MHz
No full textCorporate governance and equity prices : evidence from the Czech and Slovak Republics
No full textThe 1992 Czechoslavakia mass privatization program involving about 1,500 eneterprises and implemented through a voucher scheme with competitive bidding was a bold step in changing the ownership and governance of a large part of the economy. It represents a clear test case of one approach, and other countries may benefit from its lessons. At the time, much skepticisism was voiced about mass privatization: it would lead to diffuse ownership, and no effective corporate governance would result. But innovative forces led to the emergence of investment funds that collected much of the individuals'voucher points, leading to a much more concentrated ownership structure. It has been expected that this concentrated ownership would lead to improved corporate governance. But the jury is still out. So far, only limited and largely anecdotal evidence is available on the impact investment funds have on the way firms are being managed. Too little time has passed and too many shocks have occurred (for example, the split of the Czech and Slovak Republics) to expect to find discernible changes in corporate governance on measures of actual firm performance. An alternative approach is to investigate whether firms that ended up with more concentratedownership -- and possibly improved governance -- sell for higher prices, either in the last voucher round or in the secondary market since then. In a forward-looking financial market, one can expect prices to incorporate the effects of better ownership on future firm performance and associated dividends to shareholders. Put differently, one would expect that two firms with different shareholding structures, but otherwise identical, would trade at different prices -- with the firm with a more concentrated ownership, and presumably better corporate governance, trading at a higher price. On a cross-sectional basis, ownership structure may thus be significant in explaining (relative) share prices. The author explores this line of reasoning. Controlling for a number of firm and sector-specific variables: he finds: 1) Majority ownership by a domestic or foreign investor has a positive influence on firm prices. 2) Firms with many small owners have lower prices. 3) Ownership by many small scale investors makes it easier for any single investor to establish effective control, but such control does not necessarily translate into higher prices. The author also provides two possible explanations of why higher prices appear to be associated only with majority ownership by a single investor: he finds: 1) The corporate legal framework and the difficulty in collecting proxy votes in the Czech and Slovak Republics may prevent a small investor from making the necessary changes in the way firms are managed, thus keeping prices low; and 2) Commercial banks are both managers of invesment funds and creditors of individual firms. Funds managers may face conflicts of interest and not be interested in increasing the value of equity alone but also the value of credits. This could explain why prices are relatively lower for those firms in which investment funds have effective control.Economic Theory&Research,Payment Systems&Infrastructure,International Terrorism&Counterterrorism,Environmental Economics&Policies,Labor Policies,International Terrorism&Counterterrorism,Payment Systems&Infrastructure,Environmental Economics&Policies,Financial Intermediation,Economic Theory&Research
