Interest-Based Access Control for Content Centric Networks (extended version)

Content-Centric Networking (CCN) is an emerging network architecture designed to overcome limitations of the current IP-based Internet. One of the fundamental tenets of CCN is that data, or content, is a named and addressable entity in the network. Consumers request content by issuing interest messages with the desired content name. These interests are forwarded by routers to producers, and the resulting content object is returned and optionally cached at each router along the path. In-network caching makes it difficult to enforce access control policies on sensitive content outside of the producer since routers only use interest information for forwarding decisions. To that end, we propose an Interest-Based Access Control (IBAC) scheme that enables access control enforcement using only information contained in interest messages, i.e., by making sensitive content names unpredictable to unauthorized parties. Our IBAC scheme supports both hash- and encryption-based name obfuscation. We address the problem of interest replay attacks by formulating a mutual trust framework between producers and consumers that enables routers to perform authorization checks when satisfying interests from their cache. We assess the computational, storage, and bandwidth overhead of each IBAC variant. Our design is flexible and allows producers to arbitrarily specify and enforce any type of access control on content, without having to deal with the problems of content encryption and key distribution. This is the first comprehensive design for CCN access control using only information contained in interest messages.Comment: 11 pages, 2 figure

Effect of Soil Moisture and Tillage Depth on Some Mechanical Properties for Tillage Machines Type (Moldboard Plow)

  نفذت تجربة لدراسة  تأثير رطوبة التربة وعمق الحراثة على بعض الصفات الميكانيكية والفيزيائية للتربة تحت مستويين من رطوبة التربة 10 – 12% و وثلاثة مستويات للأعماق 14، 16، 18 سم باستعمال  RCBD المحراث المطرحي. نفذت التجربة وفق التجارب العاملية تحت تصميم القطاعات العشوائية الكاملة  بثلاثة مكررات. اشارت النتائج الى تفوق المستوى الرطوبي 10 – 12% معنويا على المستوى الرطوبي 12 – 14%، بينما تفوق عمق الحراثة 14 سم معنويا على المستويين 16 و 18 سم في جميع الصفات المدروسة. كانت النتائج المسجلة، استهلاك الوقود 11.348 و 10.77 لتر.هكتار-1، نسبة النزلاق 9.291 و9.111% ، القدرة المفقودة بالانزلاق  2.689 و 2.414 كيلو واط، الكفاءة الحقلية 68.967 و 68.358% ، القدرة على ذراع السحب 12.226 و12.001 كليو واط، والمقاومة النوعية 8.553 و 9.045 نيوتن.سم-2 على التوالي عند المستوى الرطوبي 10 – 12% وعمق حراثة 14 سم.The effect of soil moisture and tillage depth was studied based on some mechanical properties for type tillage machine (moldboard plow)  and soil physical characteristics wene tested two soil moisture levels of 10-12%and 12-14% and three levels tillage depth of 14,16 and 18 cm. The experiments were conducted in a factorial experiment under a randomized complete block design with three replications. The results showed that the soil moisture 10-12 % was significantly better than the soil moisture 12-14% as while tillage depth at range 14cm was significantly superior to the other two levels 16 and 18 cm in all studied conditions. The results showed fuel consumption of 11.348 and 10.777 L.ha-1 , slippage percentage of 9.291 and 9.111 % power losses due to slippage of 2.689 and 2.414 kW, field efficiency of 68.358 and 68.967 %, drawbar power 12.226 and 12.001kw and specific resistance 9.045 and 8.553 N.cm-2 for soil moisture 10-12% and tillage depth 14 cm , respectively

Energy Distribution in disordered elastic Networks

Disordered networks are found in many natural and artificial materials, from gels or cytoskeletal structures to metallic foams or bones. Here, the energy distribution in this type of networks is modeled, taking into account the orientation of the struts. A correlation between the orientation and the energy per unit volume is found and described as a function of the connectivity in the network and the relative bending stiffness of the struts. If one or both parameters have relatively large values, the struts aligned in the loading direction present the highest values of energy. On the contrary, if these have relatively small values, the highest values of energy can be reached in the struts oriented transversally. This result allows explaining in a simple way remodeling processes in biological materials, for example, the remodeling of trabecular bone and the reorganization in the cytoskeleton. Additionally, the correlation between the orientation, the affinity, and the bending-stretching ratio in the network is discussed

Magnetic superlens-enhanced inductive coupling for wireless power transfer

We investigate numerically the use of a negative-permeability "perfect lens" for enhancing wireless power transfer between two current carrying coils. The negative permeability slab serves to focus the flux generated in the source coil to the receiver coil, thereby increasing the mutual inductive coupling between the coils. The numerical model is compared with an analytical theory that treats the coils as point dipoles separated by an infinite planar layer of magnetic material [Urzhumov et al., Phys. Rev. B, 19, 8312 (2011)]. In the limit of vanishingly small radius of the coils, and large width of the metamaterial slab, the numerical simulations are in excellent agreement with the analytical model. Both the idealized analytical and realistic numerical models predict similar trends with respect to metamaterial loss and anisotropy. Applying the numerical models, we further analyze the impact of finite coil size and finite width of the slab. We find that, even for these less idealized geometries, the presence of the magnetic slab greatly enhances the coupling between the two coils, including cases where significant loss is present in the slab. We therefore conclude that the integration of a metamaterial slab into a wireless power transfer system holds promise for increasing the overall system performance

Optimizing community detection in social networks using antlion and K-median

Antlion Optimization (ALO) is one of the latest population based optimization methods that proved its good performance in a variety of applications. The ALO algorithm copies the hunting mechanism of antlions to ants in nature. Community detection in social networks is conclusive to understanding the concepts of the networks. Identifying network communities can be viewed as a problem of clustering a set of nodes into communities. k-median clustering is one of the popular techniques that has been applied in clustering. The problem of clustering network can be formalized as an optimization problem where a qualitatively objective function that captures the intuition of a cluster as a set of nodes with better in ternal connectivity than external connectivity is selected to be optimized. In this paper, a mixture antlion optimization and k-median for solving the community detection problem is proposed and named as K-median Modularity ALO. Experimental results which are applied on real life networks show the ability of the mixture antlion optimization and k-median to detect successfully an optimized community structure based on putting the modularity as an objective function

Acetylcysteine for prevention of contrast-induced nephropathy after intravascular angiography: A systematic review and meta-analysis

BACKGROUND: Contrast-induced nephropathy is an important cause of acute renal failure. We assess the efficacy of acetylcysteine for prevention of contrast-induced nephropathy among patients undergoing intravascular angiography. METHODS: We conducted a systematic review and meta-analysis of randomized controlled trials comparing prophylactic acetylcysteine plus hydration versus hydration alone in patients undergoing intravascular angiography. Studies were identified by searching MEDLINE, EMBASE, and CENTRAL databases. Our main outcome measures were the risk of contrast-induced nephropathy and the difference in serum creatinine between acetylcysteine and control groups at 48 h. RESULTS: Fourteen studies involving 1261 patients were identified and included for analysis, and findings were heterogeneous across studies. Acetylcysteine was associated with a significantly reduced incidence of contrast-induced nephropathy in five studies, and no difference in the other nine (with a trend toward a higher incidence in six of the latter studies). The pooled odds ratio for contrast-induced nephropathy with acetylcysteine relative to control was 0.54 (95% CI, 0.32–0.91, p = 0.02) and the pooled estimate of difference in 48-h serum creatinine for acetylcysteine relative to control was -7.2 μmol/L (95% CI -19.7 to 5.3, p = 0.26). These pooled values need to be interpreted cautiously because of the heterogeneity across studies, and due to evidence of publication bias. Meta-regression suggested that the heterogeneity might be partially explained by whether the angiography was performed electively or as emergency. CONCLUSION: These findings indicate that published studies of acetylcysteine for prevention of contrast-induced nephropathy yield inconsistent results. The efficacy of acetylcysteine will remain uncertain unless a large well-designed multi-center trial is performed