Revisiting free riding and the Tit-for-Tat in BitTorrent: A measurement study

In this paper we report new results of our continuous effort on analyzing the impact of incentive mechanisms on user behavior in BitTorrent. In this second measurement and analysis study we find that free riders’ population has significantly increased comparing to our previous measurement study. We relate this increase to the advance in end-users’ connection speeds and to users’ increased knowledge in BitTorrent. We also categorize free riders based on the behavior they exhibit in multiple-torrent system into three types: cheaters, strategic and lucky peers. Furthermore, refuting the findings of other studies, we show that peers who exploit the system in BitTorrent are both high bandwidth capacity peers and low bandwidth capacity peers. Moreover, we argue that the Tit-for-Tat mechanism does not discriminate peers based on their bandwidth capacities and that it reacts successfully against inter-class bandwidth capacity strategic peers. Finally, we propose a memory-backoff approach to the optimistic unchoke policy that reduces the volume of free riding in BitTorrent.

A SiGe BiCMOS analog SISO decoder with I/O interface

Although recent implementations of analog iterative decoders have proven their potential for higher decoding speed and less power consumption than their digital counterparts, the CMOS or conventional BiCMOS technologies used so far seem to be incapable to cope with the need for high throughput that high-speed applications require. Within this context this work presents the design and test results of a high-speed analog SISO (Soft-Input Soft-Output) channel decoder for an 8-bit trellis code by exploiting the high-speed features of SiGe heterojunction bipolar transistors (HBTs). It is one of the first successful implementations of an error-correcting decoder in SiGe BiCMOS technology, which incorporates a high-speed I/O interface. A high-level model of the mismatch effects indicates that there is no significant performance penalty. Moreover, simulations and performance evaluations of an analog Turbo decoder based on the designed SISO decoder are provided. Even though the IC of the SISO module was tested at a throughput up to 3 Mbps, simulation results show that the decoder is capable to operate at 50 Mbps. The measured power consumption is 860 mW and the die area is 3.4 × 3 mm².     

An Evaluation of Tricalcium Phosphate Excipients Particularly Using Instrumented Rotary and Single Station Tablet Presses

Two direct compression grades of tricalcium phosphate, Tri-Compress^R (Edward Mendell Co., Inc.) and Tri-Tab^R (Stauffer Chemical Co.), and a product containing tricalcium phosphate, D locust bean gum and citric acid, Loco-Tab^R (Ingredient Technology Corp.), were studied. Loco-Tab is composed of smaller particles having more irregularly shaped surfaces than the others. It is also less dense and somewhat less flowable than the other materials. None of these excipients lost weight at elevated temperature and none can be considered to be hygroscopic. Compressibility in formulations was studied using instrumented rotary and single station tablet presses. In all cases, the single station press yielded harder tablets at a given compression force. Dissolution of an insoluble drug was affected to a degree by the press used. Drug dissolution from Loco-Tab formulations was excellent at all tablet hardnesses, a highly desirable property for tablets to be coated using fluidized bed equipment. Loco-Tab would seem to be the calcium phosphate excipient of choice while recognizing that it is not a single entity and that it is acidic, in contrast to the neutral to slightly basic pH of the others.     

A Lottery-based pricing scheme for peer-to-peer networks

Users in Peer-to-Peer (P2P) networks tend to exploit the maximum resources they are able to obtain, offering minimum resources in response. This behavior undermines the goal of P2P systems in spreading files through the network and imposes the concept of free-riding. In this paper we propose a Lottery-based pricing mechanism to enhance the sharing level in P2P networks and help increase the number of objects disseminated. The scheme is an extension of the traditional micropayment mechanism. Our scheme provides higher payoff for peers who contribute to the P2P network and higher cost for peers who act selfishly and choose not to share resources. We present simulation results to demonstrate the performance of the proposed mechanism.     

Implicit Numerical Integration of Nonsmooth Multisurface Yield Criteria in the Principal Stress Space

Plasticity models employing multiple yield surfaces are frequently met in plasticity theory and engineering practice. The multiple yield surfaces may or may not intersect in a smooth manner, with the latter case being a superset of the former, typically encountered more often in engineering problems and covered within this work. Prominent members of this class of plasticity models can be found in a wide range of applications in Soil Mechanics, Rock Mechanics, Damage Mechanics, metal plasticity, concrete modeling or in the modeling of brittle or cohesive/frictional materials. While the importance of these models is widely acknowledged, difficulties arising from the singularities induced by the nonsmooth intersections of the yield surfaces, introduce severe algorithmic and numerical complexities that usually require specific treatment of each model. Three main problems can be identified, originating mainly from the application of the normality hypothesis, namely that (a) the elastic domain is subdifferential with respect to the stress vector at the intersections of the yield surfaces, (b) severe numerical errors are present in the vicinity of intersections since the derivatives of the yield surfaces are not always defined in these areas and (c) the set of the yield surfaces considered to be ultimately active is not known a priori. The objectives of this article are (a) to provide a comprehensive review of the related literature and an extensive overview of the solution techniques proposed by different researchers, (b) to present the formulation and propose the algorithmic treatment for the problem of nonsmooth multisurface plasticity models and finally (c) to give implementation details for some of the most widely used nonsmooth multisurface plasticity models. The proposed algorithm is based on a spectral representation of stresses and strains for the case of infinitesimal deformation plasticity and the reformulation of the return mapping scheme in principal stress directions. The determination of the set of the yield surfaces that will remain ultimately active is identified by involving a systematic enforcement of the Karush–Kuhn–Tucker conditions, providing in this way a surface agnostic implementation. Four representative examples of nonsmooth, multisurface plasticity models, are extensively presented and examined within the framework of the proposed algorithm. These are the Tresca, the Mohr–Coulomb, the Hoek–Brown and the Drucker–Prager (in the case that it is accompanied with a tension cut–off type surface) yield criteria, all of which are well established in the related literature and engineering practice. The efficiency, robustness and accuracy of the proposed algorithm is demonstrated through a series of numerical examples with excellent results.     

Regulations and Audit Opinions: Evidence from EU Banking Institutions

In this study, we empirically investigate the relationship between financial and auditing requirements, capital requirements, official supervisory power, and the likelihood of receiving a qualified audit opinion. The sample consists of 71 qualified financial statements and 17,526 unqualified ones, from 3,642 banking institutions operating in 15 old and new EU countries over the period 1999–2006. The results indicate that financial and auditing requirements have a negative influence, while supervisory power has a positive impact, on the likelihood of qualified audit opinions. Concerning capital requirements, we find that only initial stringency has an impact on audit opinions.     

The effect of basil (Ocimum basilicum L.) on soil organic matter biodegradation and other soil chemical properties

The effects of basil (Ocimum basilicum L.) on soil organic matter biodegradation, nutritional mineral elements and bacterial colonies were studied in the laboratory. The air‐dried basil plant tissues incorporated at five different rates (0, 1, 2, 3, and 4 g per 50 g of soil) resulted in increases in organic carbon mineralization, mineral nitrogen forms in organic phosphorus and available potassium. The level of available forms of manganese and zinc was increased at all the rates of added basil whereas copper was increased at the two upper rates. Also, the addition of basil resulted in a decrease in soil bacterial colonies. The results of this study indicated that the basil could be used as a cover crop for suppressing weed or pathogens in organic soils, with a positive effect on soil productivity. In addition, the incorporation of basil in soil could reduce the number of bacterial colonies. Copyright © 2007 Society of Chemical Industry     

Broadband in India: Strategic investment opportunities

India is one of the top five mobile communications markets in the world. A wave of structural reforms in the Indian telecommunications industry during the past decade has fueled this growth. Following the introduction of competition, removal of entry barriers, and increasing foreign direct investment, the mobile sector has enjoyed unparalleled success. In contrast, broadband Internet services have not witnessed similar development, and the spread of broadband services in India is slow compared to some of the developing nations in the same region. This paper outlines the success factors (social, economic, and technological) that have contributed to the growth of the mobile communications industry. Based on its success, this paper proposes strategic investment opportunities for service providers, governments, and corporate organizations in the field of broadband services. It also touches on major areas that are outside the telecom arena but contribute to its success.