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The use of coat-hanger dies is prevalent in the plastic film and sheet extrusion industry. The product quality and the power of the extrusion machine depend on the uniformities of the fluid velocity at the exit and the pressure drop. Die manufacturers face the challenge of producing coat-hanger dies that can extrude materials uniformly and with a minimal pressure drop. Previous studies have analyzed the die outlet's flow homogeneity and pressure drop using various numerical simulations. However, the combination of the scheme programming language together with the Adjoint Method of Optimization has yet to be attempted. The adjoint optimization method has been demonstrated to be beneficial in addressing issues related to shape optimization problems and it may also be beneficial in optimizing the design of dies used in polymer melt extrusion. In this study, the proposed innovations involve incorporating both the Scheme programming language and Adjoint solver to examine and optimize the coat hanger's flow homogeneity and pressure drop. Before optimization, the outlet velocity was almost 10 times higher at the die center than at the edges but after optimization, it became more uniform. The proposed optimized coat-hanger die geometry results in more uniform melt flow as demonstrated by the velocity contour plot and the outlet velocity graph in the die slit area, reducing the deviation value from 0.097 to 0.015. Additionally, the mass flux variance across the die outlet decreased by 71.6% from 0.015069 kg m−2 s−1 to 0.004281 kg m−2 s−1. Therefore, using this method reduces the amount of time wasted on trial and error or other optimization techniques that may be limited by design constraints. [ABSTRACT FROM AUTHOR]

In interactive theorem provers (ITPs), extensible syntax is not only crucial to lower the cognitive burden of manipulating complex mathematical objects, but plays a critical role in developing reusable abstractions in libraries. Most ITPs support such extensions in the form of restrictive "syntax sugar" substitutions and other ad hoc mechanisms, which are too rudimentary to support many desirable abstractions. As a result, libraries are littered with unnecessary redundancy. Tactic languages in these systems are plagued by a seemingly unrelated issue: accidental name capture, which often produces unexpected and counterintuitive behavior. We take ideas from the Scheme family of programming languages and solve these two problems simultaneously by proposing a novel hygienic macro system custom-built for ITPs. We further describe how our approach can be extended to cover type-directed macro expansion resulting in a single, uniform system offering multiple abstraction levels that range from supporting simplest syntax sugars to elaboration of formerly baked-in syntax. We have implemented our new macro system and integrated it into the new version of the Lean theorem prover, Lean 4. Despite its expressivity, the macro system is simple enough that it can easily be integrated into other systems. [ABSTRACT FROM AUTHOR]

The capability of proactive in-network caching and sharing of content is one of the most important features of an information-centric network (ICN). We describe an ICN model featuring autonomous agents controlling the content routers. Such agents are unlikely to share cached content with other agents without an incentive to do so. To stimulate cooperation between agents, we adopt a reputation and trust building scheme that is able to explicitly account for both objective current content availability and subjective willingness to cooperate. The scheme is further complemented with a so-called one-time goodwill mechanism introduced to avoid penalizing agents failures to provide temporarily unavailable content. In a simulated ICN environment under a modified Random Waypoint user mobility model, we investigate the resiliency of the reputation and trust building scheme to subversion, that is, strategic (selfish or malicious) agents acquiring higher trust values than honest ones, for varying user mobility scenarios. The scheme proves resilient in low-mobility scenarios, while increased user mobility is shown to have a negative effect. The one-time goodwill mechanism partly remedies this for high-mobility scenarios. We validate the results by comparison with an existing reputation and trust building scheme and with an alternative user mobility model. [ABSTRACT FROM AUTHOR]

We propose two new authentication schemes for the cloud that support private attribute-based authentication services. The basic scheme is non-anonymous attribute-based authentication scheme. The extended scheme of the basic scheme is fully anonymous attribute-based authentication scheme to realize full anonymity and unlinkability services. In the proposed schemes, a user is authenticated by the remote server if the intersection of the set of his/her assigned attributes and the server’s required attributes exceeds a satisfactory predefined level. Unlike existing attribute-based encryption and signature schemes that require the user to perform significant amount of elliptic curve bilinear pairings and modular exponentiations, and require the user to hold a significantly long decryption/signature key, in our schemes the user is not required to perform any bilinear pairings. With a fixed length private key, independent of the number of attributes, the cloud user performs only few exponentiations by which he/she is able to authenticate himself/herself to the remote server and establish a session key with the server with the condition that he/she satisfies a predefined level of the server’s attributes requirement. Therefore, our schemes are suitable for implementation on devices with limited resources. We provide the rigorous security of the proposed schemes and complexity analysis of our schemes. Finally, the security and performance comparisons of our schemes with the existing related schemes show that our schemes outperform other existing schemes. [ABSTRACT FROM AUTHOR]

Passive knee prostheses require a significant amount of additional metabolic energy to carry out a gait cycle, therefore affecting the natural human walk performance. Current active knee prostheses are still limited because they do not reply with accuracy of the natural human knee movement, and the time response is relatively large. This paper presents the design and control of a new biomimetic-controlled transfemoral knee prosthesis based on a polycentric-type mechanism. The aim was to develop a knee prosthesis able to provide additional power and to mimic with accuracy of the natural human knee movement using a stable control strategy. The design of the knee mechanism was obtained from the body-guidance kinematics synthesis based on real human walking patterns obtained from computer vision and 3D reconstruction. A biomechanical evaluation of the synthesized prosthesis was then carried out. For the activation and control of the prosthesis, an echo-control strategy was proposed and developed. In this echo-control strategy, the sound side leg is sensed and synchronized with the activation of the knee prosthesis. An experimental prototype was built and evaluated in a test rig. The results revealed that the prosthetic knee is able to mimic the biomechanics of the human knee. [ABSTRACT FROM AUTHOR]

As is well known, the additional low-order harmonic currents and the huge computation amount of the cost function value with all available control sets are the two special issues of finite-control-set model predictive current control (FCS-MPCC) for multiphase inverters. Thus, this paper proposes a FCS-MPCC scheme with duty-ratio optimization for five-phase inverters. First, a group of the reconstructed virtual voltage vectors (V3) with low-order harmonic elimination is defined and employed as the control sets in FCS-MPCC scheme. Thus, it leads to no requirement for harmonic items and weighting factors existing in the cost function. Then, a combination of zero vectors and the selected V3 during each control horizon is adopted to rearrange the pulse sequence, which can realize constant switching frequency. In addition, the durations of the selected V3 and zero vectors during each control horizon are also estimated to minimize the steady-state current ripples in different subspaces based on the cost function optimization. Finally, a comparison of the proposed V3-FCS-MPCC scheme and the other FCS-MPCCs are presented in simulation and experimental test. Simulation and experimental results verify that the proposed V3-FCS-MPCC scheme can remain the simplified structure, fast dynamic performance, constant switching frequency, and achieve minimum current ripples in different subspaces. [ABSTRACT FROM PUBLISHER]

The modular multilevel converter (MMC) is attractive for medium- or high-power applications because of the advantages of its high modularity, availability, and high power quality. Reliability is one of the most important challenges for the MMC consisting of a large number of power electronic devices. The diode open-circuit fault in the submodule (SM) is an important issue for the MMC, which would affect the performance of the MMC and disrupt the operation of the MMC. This paper analyzes the impact of diode open-circuit failures in the SMs on the performance of the MMC and proposes a protection scheme for the MMC under diode open-circuit faults. The proposed protection scheme not only can effectively eliminate the possible caused high voltage due to the diode open-circuit fault but also can quickly detect the faulty SMs, which effectively avoids the destruction and protects the MMC. The proposed protection scheme is verified with a downscale MMC prototype in the laboratory. The results confirm the effectiveness of the proposed protection scheme for the MMC under diode open-circuit faults. [ABSTRACT FROM PUBLISHER]

For tidal range power plants to be sustainable, the environmental impacts caused by the implement of various tidal barrage schemes must be assessed before construction. However, several problems exist in the current researches: firstly, evaluation criteria of the tidal barrage schemes environmental impact assessment (EIA) are not adequate; secondly, uncertainty of criteria information fails to be processed properly; thirdly, correlation among criteria is unreasonably measured. Hence the contributions of this paper are as follows: firstly, an evaluation criteria system is established from three dimensions of hydrodynamic, biological and morphological aspects. Secondly, cloud model is applied to describe the uncertainty of criteria information. Thirdly, Choquet integral with respect to λ -fuzzy measure is introduced to measure the correlation among criteria. On the above bases, a multi-criteria decision-making decision framework for tidal barrage scheme EIA is established to select the optimal scheme. Finally, a case study demonstrates the effectiveness of the proposed framework. [ABSTRACT FROM AUTHOR]

This work investigates secure cluster-aided multi-hop randomize-and-forward networks. We present a hop-by-hop multi-hop transmission scheme with relay selection, which evaluates for each cluster the relays that can securely receive the message. We propose an analytical model to derive the secure connectivity probability ( SCP) of the hop-by-hop transmission scheme. For comparison, we also analyze SCPs of traditional end-to-end transmission schemes with two relay-selection policies. We perform simulations, and our analytical results verify that the proposed hop-by-hop scheme is superior to end-to-end schemes, especially with a large number of hops or high eavesdropper channel quality. Numerical results also show that the proposed hop-by-hop scheme achieves near-optimal performance in terms of the SCP. [ABSTRACT FROM AUTHOR]

This paper presents a novel generalized quadrature spatial modulation ( GQSM) transmission scheme using antenna grouping. The proposed GQSM scheme combines QSM and conventional spatial multiplexing ( SMux) techniques in order to improve the spectral efficiency ( SE) of the system. Analytical and simulation results show that the proposed transmission scheme has minimal losses in terms of the average bit error probability along with the advantage of an increased SE compared with previous SM and QSM schemes. For the case studies, this advantage represents a reduction of up to 81% in terms of the number of required transmit antennas compared with QSM. In addition, a detection architecture based on the ordered successive interference cancellation scheme and the QR decomposition is presented. The proposed QRD- M adaptive algorithm showed a near-maximum-likelihood performance with a complexity reduction of approximately 90%. [ABSTRACT FROM AUTHOR]

Recently, Multi-Database Mining (MDBM) for association rules has been recognized as an important and timely research area in the Knowledge Discovery Database (KDD) community. It consists of mining different databases in order to obtain frequent patterns which are forwarded to a centralized place for global pattern analysis. Various synthesizing models [8, 9,13,14,15,16] have been proposed to build global patterns from the forwarded patterns. It is desired that the synthesized rules from such forwarded patterns must closely match with the mono-mining results, ie., the results that would be obtained if all the databases are put together and mining has been done. When the pattern is present in a site but fails to satisfy the minimum support threshold value, it is not allowed to take part in the pattern synthesizing process. Therefore this process can lose some interesting patterns which can help the decision maker to make the right decisions. To adress this problem, we propose to integrate the users knowledge in the local and global mining process. For that we describe the users beliefs and expectation by the rule schemas multi-level and integrate them in both the local association rules mining and in the synthesizing process. In this situation we get true global patterns of select items as there is no need to estimate them. Furthermore, a novel Condensed Patterns Tree (CP-TREE)structure is defined in order to store the candidates patterns for all organization levels which can improve the time processing and reduce the space requirement. In addition CP-TREE structure facilitate the exploration and the projection of the candidates patterns in differents levels. finally We conduct some experimentations in real world databases which are the production field and demonstrate the effectivlness of the CP-TREE structure on time processing and space requirement. [ABSTRACT FROM AUTHOR]

Attribute based encryption (ABE) is a good way to achieve flexible and secure access control to data, and attribute revocation is the extension of the attribute-based encryption, and the keyword search is an indispensable part for cloud storage. The combination of both has an important application in the cloud storage. In this paper, we construct a searchable attribute-based encryption scheme with attribute revocation in cloud storage, the keyword search in our scheme is attribute based with access control, when the search succeeds, the cloud server returns the corresponding cipher text to user and the user can decrypt the cipher text definitely. Besides, our scheme supports multiple keywords search, which makes the scheme more practical. Under the assumption of decisional bilinear Diffie-Hellman exponent (q-BDHE) and decisional Diffie-Hellman (DDH) in the selective security model, we prove that our scheme is secure. [ABSTRACT FROM AUTHOR]

Next generation wireless networks will carry traffic from a wide range of applications, and many of them may require packets to be delivered before their respective deadlines. In this paper, we investigate using inter-session network coding to send packets wirelessly for two deadline-constrained unicast sessions. In particular, each unicast session aims to transmit a file, whose packets have hard sequential deadline constraints. We first characterize the corresponding deadline-constrained capacity region under heterogeneous channel conditions and heterogeneous deadline constraints. We show that this deadline-constrained capacity region can be achieved asymptotically by modifying the existing generation-based (G-B) schemes. However, despite its asymptotic optimality, the G-B scheme has very poor performance for small and medium file sizes. To address these problems, we develop a new immediately-decodable network coding (IDNC) scheme that empirically demonstrates much better performance for short file sizes, and we prove analytically its asymptotic optimality when used to send large files. Our analysis uses a novel version of drift analysis, which could also be of independent interest to other IDNC schemes. [ABSTRACT FROM PUBLISHER]

Dense wireless networks are a promising solution to meet the huge capacity demand in 5G wireless systems. However, there are two implementation issues, namely, the interference and backhaul issues. To resolve these issues, we propose a novel network architecture called the backhaul-limited cached dense wireless network (C-DWN), where a physical layer (PHY) caching scheme is employed at the base stations (BSs), but only a fraction of the BSs have wired payload backhauls. The PHY caching can replace the role of wired backhauls to achieve both the cache-induced multiple-input-multiple-output (MIMO) cooperation gain and cache-assisted multihopping gain. Two fundamental questions are addressed. Can we exploit the PHY caching to achieve linear capacity scaling with limited payload backhauls? If so, how much cache is needed? We show that the capacity of the backhaul-limited C-DWN indeed scales linearly with the number of BSs if the BS cache size is larger than a threshold that depends on the content popularity. We also quantify the throughput gain due to cache-induced MIMO cooperation over conventional caching schemes (which exploit purely the cached-assisted multihopping). Interestingly, the minimum BS cache size needed to achieve a significant cache-induced MIMO cooperation gain is the same as that needed to achieve the linear capacity scaling. [ABSTRACT FROM PUBLISHER]

Encryption using vector decomposition problem (VDP) on higher dimensional vector spaces is a novel method in cryptography. Yoshida has shown that the VDP on a two-dimensional vector space is at least as hard as the computational Diffie-Hellman problem on a one-dimensional subspace under certain conditions. Steven Galbraith has shown that for certain curves, the VDP is at most as hard as the discrete logarithm problem on a one-dimensional subspace. Okomoto and Takashima proposed encryption scheme and signature schemes using VDP. An authenticated key agreement scheme using vector decomposition problem is proposed in this paper. [ABSTRACT FROM AUTHOR]

Public key cryptosystems are secure only when the authenticity of the public key is assured. Shao proposed a new scheme to overcome the problems of the existing schemes, which suffers from two major drawbacks. The first drawback is the availability of users' passwords in plaintext format in key server which are prone to attacks by ill-minded users. The second one is depending on the key server blindly for certificate generation, without further verification by the user. To overcome these severe drawbacks, we proposed an improved key authentication scheme based on Chinese remainder theorem and discrete logarithms. Our scheme allows the user to generate his/ her certificate without the help of any trusted third party. This scheme is intended for online services, military and defense applications to exchange keys securely. [ABSTRACT FROM AUTHOR]

In this paper, we show that large annotated data sets have great potential to provide strong priors for saliency estimation rather than merely serving for benchmark evaluations. To this end, we present a novel image saliency detection method called saliency transfer. Given an input image, we first retrieve a support set of best matches from the large database of saliency annotated images. Then, we assign the transitional saliency scores by warping the support set annotations onto the input image according to computed dense correspondences. To incorporate context, we employ two complementary correspondence strategies: a global matching scheme based on scene-level analysis and a local matching scheme based on patch-level inference. We then introduce two refinement measures to further refine the saliency maps and apply the random-walk-with-restart by exploring the global saliency structure to estimate the affinity between foreground and background assignments. Extensive experimental results on four publicly available benchmark data sets demonstrate that the proposed saliency algorithm consistently outperforms the current state-of-the-art methods. [ABSTRACT FROM PUBLISHER]

Predicate encryption is a public-key encryption that supports attribute-hiding as well as payload-hiding and achieves high flexibility in terms of access control. Since Katz, Sahai, and Waters first proposed the predicate encryption scheme in 2008, several predicate encryption schemes have been published. Unfortunately these are impractical as they require O(n) pairing computations for decryption with considerably large sized public parameters, secret key, and ciphertext, where n is the dimension of the attribute/predicate vectors. In this paper, we propose a very efficient predicate encryption scheme that requires only n exponentiation plus three pairing computations for decryption with shorter sized public parameters, secret key, and ciphertext. The proposed scheme is proven selective attribute-secure against chosen-plaintext attacks in the standard model under the Asymmetric Decisional Bilinear Diffie-Hellman assumptions. [ABSTRACT FROM AUTHOR]

The growing demand on the performance of transparent computing systems requires good cache schemes in order to overcome the prolonged network latency. However, evaluating cache schemes, especially measuring the performance of a transparent computing system with particular cache scheme remains challenging. This is because neither method is available to evaluate the effectiveness and efficiency of the cache schemes in transparent computing, nor the simulator has been developed to measure the system performance under particular cache schemes. In this paper, we propose TranSim, a full-featured, high-performance simulation framework for transparent computing. For the first time, TranSim introduces a methodology to evaluate the performance of multi-level cache hierarchies in transparent computing under different cache configurations and cache replacement policies. TranSim can also demonstrate the behavior and performance of the entire transparent computing system rather than only the cache miss/hit rate. Using TranSim, the system designer can quickly evaluate the effectiveness of cache schemes along with the system performance. We construct several experiments to evaluate the effectiveness and efficiency of TranSim. Results show that TranSim can accurately output the performance of both the cache hierarchy and the entire transparent computing system. [ABSTRACT FROM AUTHOR]

Continuous scaling of process technology increases variations in transistors. The process variations cause large fluctuations in the access times of static random-access memory (SRAM) cells. Caches made of those SRAM cells cannot be accessed within the target clock cycle time, which reduces the yield of processors. Many schemes have been proposed to combat these access time failures in caches. However, these schemes are limited in their coverage and do not scale well at high failure rates. We propose a new level one (L1) cache architecture employing multi-cycle cell access (MCCA) and subarray-level parallel access (SLPA). MCCA eliminates all access-time failures in L1 caches. SLPA minimizes the performance impact of cache bandwidth loss due to MCCA. For further performance improvement, architectural techniques are proposed. Our experimental results show that our proposed L1 cache architecture incurs a performance hit of less than 1.2 percent compared to the conventional cache architecture with no access time failure. Our proposed architecture is not sensitive to access time failure rates and has a low overhead compared with previously proposed competitive schemes. [ABSTRACT FROM AUTHOR]

Provisioning buffer management mechanism is especially crucial in resource-constrained delay tolerant networks (DTNs) as maximum data delivery ratio with minimum overhead is expected in highly congested environments. However, most DTN protocols do not consider resource limitations (e.g., buffer, bandwidth) and hence, results in performance degradation. To strangle and mitigate the impact of frequent buffer overflows, this paper presents an adaptive and efficient buffer management scheme called size-aware drop (SAD) that strives to improve buffer utilization and avoid unnecessary message drops. To improve data delivery ratio, SAD exactly determines the requirement based on differential of newly arrived message(s) and available space. To vacate inevitable space from a congested buffer, SAD strives to avoid redundant message drops and deliberate to pick and discard most appropriate message(s) to minimize overhead. The performance of SAD is validated through extensive simulations in realistic environments (i.e., resource-constrained and congested) with different mobility models (i.e., Random Waypoint and disaster). Simulation results demonstrate the performance supremacy of SAD in terms of delivery probability and overhead ratio besides other metrics when compared to contemporary schemes based on Epidemic (DOA and DLA) and PRoPHET (SHLI and MOFO). [ABSTRACT FROM AUTHOR]

As new network applications have arisen rapidly in recent years, it is becoming more difficult to predict the exact traffic pattern of a network. In consequence, a routing scheme based on a single traffic demand matrix often leads to a poor performance. Oblivious routing (Racke in Proceedings of the 43rd annual IEEE symposium on foundations of computer science 43-52, 2002) is a technique for tackling the traffic demand uncertainty problem. A routing scheme derived from this principle intends to achieve a predicable performance for a set of traffic matrixes. Oblivious routing can certainly be an effective tool to handle traffic demand uncertainty in a wireless mesh network (WMN). However, a WMN has an additional tool that a wireline network does not have: dynamic bandwidth allocation. A router in a WMN can dynamically assign bandwidth to its attached links. This capability has never been exploited previously in works on oblivious routing for a spatial time division multiple access (STDMA) based WMN. Another useful insight is that although it is impossible to know the exact traffic matrix, it is relatively easy to estimate the amount of the traffic routed through a link when the routing scheme is given. Based on these two insights, we propose a new oblivious routing framework for STDMA WMNs. Both analytical models and simulation results are presented in this paper to prove that the performance-in terms of throughput, queue lengths, and fairness-of the proposed scheme can achieve significant gains over conventional oblivious routing schemes for STDMA based WMNs. [ABSTRACT FROM AUTHOR]

Mobile ad hoc networks (MANETs) rely on the benevolence of nodes within the network to forward packets from a source node to a destination node. This network construction allows for the forwarding nodes, whether they are selfish or malicious, to drop packets hindering end-to-end communication. In this paper, a new scheme is proposed against collusion black hole and slander attacks in MANETs, named E2EACK. A novel method is used to detect collusion attacks due to collusive malicious nodes which cooperate in the route discovery, but refuse to forward data packets and do not disclose the misbehavior of each other. Contrary to existing methods that detect only collusion black hole attacks, the E2EACK also detects slander attacks and framing attacks. Moreover, the E2EACK uses ACKnowledgment packet to detect malicious nodes on the path and Message Authentication Code (MAC) to authenticate the sender of each data packet. Analytical and simulation results show that the proposed scheme considerably decreases the routing overhead and increases the packet delivery ratio compared to the existing methods. [ABSTRACT FROM AUTHOR]

Nodes in a wireless sensor network (WSN) are generally deployed in unattended environments making them susceptible to attacks. Therefore, the need of defending such attacks is of utmost importance. The challenge in providing security in this network is that the securing mechanism must be lightweight to make it implementable for such resource-constrained nodes. A robust security solution for such networks must facilitate authentication of sensor nodes. So far, only data authentication has drawn much attention from the research community. In this paper, a digital watermark based low-overhead solution (LoWaNA) is proposed for node authentication. The proposed watermarking technique consists of three modules viz. watermark generation, embedding and detection. The robustness of the algorithm is measured in terms of cracking probability and cracking time. This robustness analysis helps us to set the design guideline regarding size of watermark. Performance of the scheme is analyzed in terms of storage, computation and communication overhead. The analytical results are compared with two of the existing schemes and that show significant reduction of all such overheads. Thus it proves the suitability of the proposed scheme for resource-constrained networks like WSN. Finally the entire scheme is simulated in Cooja, the Contiki network simulator to make it readily implementable in real life mote e.g. MICAz. [ABSTRACT FROM AUTHOR]

In mobile social networks, forwarding is a challenging problem since there may be no end-to-end paths. Existing schemes using overlays are not applicable to pure mobile social networks since they use environments different from the mobile social networks. To resolve this problem, we propose a novel forwarding scheme that considers the common neighbor similarity and contact probability. In the proposed scheme, the more nodes have in common, the more likely they are to be friends, and higher contact probabilities between nodes increase the chances they will arrive at the destination. The proposed scheme constructs an overlay using two layers with the common neighbor similarity and the contact probability and forwards messages to the destinations through the overlay. Experimental results show that the proposed scheme outperforms most known forwarding schemes in terms of balancing the network traffic and transmission delay. [ABSTRACT FROM AUTHOR]

In this paper, we propose an XML data placement scheme by optimally partitioning XML data among multiple broadcast channels in such a way that it minimizes the average response time of mobile clients in processing of different XML queries. By performing several experiments, we have shown that our proposed XML data placement scheme improves the performance of XML query processing of mobile clients in terms of access time without increasing the tuning time. [ABSTRACT FROM AUTHOR]

Conventional feedback control systems cannot perform well under strong disturbances. Cascade control is an alternative approach to the classical single-input single output-control systems to improve the performance of the control system, especially in the case of disturbances. The general approach to identify the tuning parameters of the controllers used in the inner and the outer loop of the cascade controller structure is to tune the inner and the outer loop in a strict sequence. Here, simultaneous tuning of the inner and outer loop controllers is given. Tuning parameters of the inner and outer loop controllers are determined using a genetic algorithm. Simulation results for stable, unstable and integrating processes in the cascade control scheme are provided to illustrate the performance of the proposed controller design method. [ABSTRACT FROM AUTHOR]

This paper investigates the operation of a smart distribution system comprised of multiple microgrids during emergency conditions. It proposes a two-stage hierarchical scheme for outage management in such a system to enhance the security of supply during contingencies. This goal is achieved through sharing the available generation and storage capacities among different microgrids. In doing so, a well-organized framework is devised in order to introduce the roles and tasks of each player in operation stage of a multi-microgrids system. Based on this framework, the general optimization model that needs to be evaluated at each stage of the proposed outage management scheme is formulated. In this regard, a model predictive control (MPC)-based approach is proposed to determine the optimal scheduling policy of microgrids in the first stage. In the second stage, distribution system operator (DSO) as an independent entity coordinates the operation of different microgrids and schedules their unused generation/storage capacities for minimizing load curtailments in the whole system. This method captures the inherent uncertainties of outage duration and significantly increases the resilience of resulting schedule against prediction errors of load and renewable resources. Various features of this scheme are studied through implementation on a test system. The results verify the effectiveness of the proposed scheme in enhancing the reliability of distribution systems and demonstrate the benefits it will bring to both customers and DSOs. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Methods for solving the multidimensional multiextremal optimization problems using the nested optimization scheme are considered. A novel approach for solving the multidimensional multiextremal problems based on the adaptive nested optimization has been proposed. This approach enables to develop methods of the global optimum search which are more efficient in comparison with the ones on the base of the traditional nested optimization scheme. The new approach provides advantages due to better usage of the information on the problem in the course of optimization. A general scheme of a adaptive nested optimization is described. A theoretical substantiation of the method convergence is given for the case when for solving the univariate subproblems within the nested scheme an information algorithm of global search is used. Results of numerical experiments on the well-known classes of the test multiextremal functions confirming the efficiency of the proposed scheme are presented. [ABSTRACT FROM AUTHOR]

In this paper, a simplified network model based on fluid flow theory and stochastic differential equations is derived. Based on the linearized TCP/AQM model, the modified adaptive strategy is applied to adjust the traditional Smith predictor for reducing the dependency on the mathematical model. Then, an Adaptive Modified Smith-PI controller (AMS-PI) is introduced as a new AQM scheme. According to historical data, this algorithm can dynamically modify the output, compensate for the influence of time delay, and reduce effectively the sensitivity to the actual model. The simulation results demonstrate that the performance of the proposed AMS-PI scheme are clearly superior to those of the PI scheme under both cases involving long delay and burst data flow. [ABSTRACT FROM AUTHOR]

This article investigates the operation of a microgrid system through a novel control scheme. The proposed microgrid system employs various autonomous generation systems, including photovoltaic, wind, a diesel engine, a fuel cell, an aqua electrolyzer, and a battery. A simulation model for this microgrid system was developed using MATLAB/SIMULINK (The MathWorks, Natick, Massachusetts, USA). A proportion-integral-derivative control scheme is employed, and the parameters of proportion-integral-derivative controllers for various controllable sources are tuned with a firefly algorithm. This is done using a new proposed weighted goal attainment method for achieving improved and fault-tolerant operation. The proposed control scheme shows better performance over the classical proportion-integral-derivative and bacterial foraging–proportion-integral-derivative controller in both transient and steady-state conditions. The firefly algorithm–proportion-integral-derivative controller also shows stronger robustness properties against system perturbations, disturbances, and faults than that with other controller structures. The robustness is a highly desirable property in such a scenario since many components of the microgrid may be switched on/off or may run at lower/higher power output at different time instants. [ABSTRACT FROM AUTHOR]

The Variable-Sized Bin Packing Problem (abbreviated as VSBPP or VBP) is a well-known generalization of the NP-hard Bin Packing Problem (BP) where the items can be packed in bins of M given sizes. The objective is to minimize the total capacity of the bins used. We present an asymptotic approximation scheme (AFPTAS) for VBP and BP with performance guarantee $A_{\varepsilon }(I) \leq (1+ \varepsilon )OPT(I) + \mathcal {O}\left ({\log ^{2}\left (\frac {1}{\varepsilon }\right )}\right )$ for any problem instance I and any ε>0. The additive term is much smaller than the additive term of already known AFPTAS. The running time of the algorithm is $\mathcal {O}\left ({ \frac {1}{\varepsilon ^{6}} \log \left ({\frac {1}{\varepsilon }}\right ) + \log \left ({\frac {1}{\varepsilon }}\right ) n}\right )$ for BP and $\mathcal {O}\left ({ \frac {1}{{\varepsilon }^{6}} \log ^{2}\left ({\frac {1}{\varepsilon }}\right ) + M + \log \left ({\frac {1}{\varepsilon }}\right )n}\right )$ for VBP, which is an improvement to previously known algorithms. Many approximation algorithms have to solve subproblems, for example instances of the Knapsack Problem (KP) or one of its variants. These subproblems - like KP - are in many cases NP-hard. Our AFPTAS for VBP must in fact solve a generalization of KP, the Knapsack Problem with Inversely Proportional Profits (KPIP). In this problem, one of several knapsack sizes has to be chosen. At the same time, the item profits are inversely proportional to the chosen knapsack size so that the largest knapsack in general does not yield the largest profit. We introduce KPIP in this paper and develop an approximation scheme for KPIP by extending Lawler's algorithm for KP. Thus, we are able to improve the running time of our AFPTAS for VBP. [ABSTRACT FROM AUTHOR]

This paper presents a novel space vector modulation (SVM) method combined with a modified four-step commutation to achieve a perfect zero common-mode voltage (CMV) for matrix converters (MCs). The new SVM method was developed by using only rotating input voltage vectors, which results in the CMV for MCs being zero. However, it causes some noise in practical applications that drive MCs with traditional four-step commutation. In order to solve this noise problem, a modified four-step commutation is also proposed to perfectly eliminate the CMV for MCs without any noise. In the modified four-step commutation, a delay time is designed to deal with misjudgment of input voltages. The proposed SVM method and four-step commutation are easily implemented via software and achieve good performance in input/output current waveforms. Prototype experiments were carried out to evaluate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

Time-division multiplexing (TDM) is a mature scheme for the readout of arrays of transition-edge sensors (TESs). TDM is based on superconducting-quantum-interference-device (SQUID) current amplifiers. Multiple spectrometers based on gamma-ray and X-ray microcalorimeters have been operated with TDM readout, each at the scale of 200 sensors per spectrometer, as have several astronomical cameras with thousands of sub-mm or microwave bolometers. Here we present the details of two different versions of our TDM system designed to read out X-ray TESs. The first has been field-deployed in two 160-sensor (8 columns $$\times $$ 20 rows) spectrometers and four 240-sensor (8 columns $$\times $$ 30 rows) spectrometers. It has a three-SQUID-stage architecture, switches rows every 320 ns, and has total readout noise of 0.41 $$\mu \Phi _{\mathrm {0}} / \surd $$ Hz. The second, which is presently under development, has a two-SQUID-stage architecture, switches rows every 160 ns, and has total readout noise of 0.19 $$\mu \Phi _{\mathrm {0}} / \surd $$ Hz. Both quoted noise values are non-multiplexed and referred to the first-stage SQUID. In a demonstration of this new architecture, a multiplexed 1-column $$\times $$ 32-row array of NIST TESs achieved average energy resolution of $$2.55\pm 0.01$$ eV at 6 keV. [ABSTRACT FROM AUTHOR]

In high frequency induction heating systems, the effective load parameters change during the different operating conditions. It is necessary to maintain constant input voltage to the induction heating load to improve the quality of the heating. The resonant based high frequency converter is generally used for these applications for the reduction of switching losses. The resonant condition is also affected during the variation in load parameters. The controller should provide a good voltage regulation with less response time and less overshoot during the loading conditions. In this paper, a load adaptive fuzzy logic control scheme is proposed to perform the voltage control of the high frequency inverter under variable load conditions. A frequency tracking control system is also employed for the inverter system using the phase lock loop. The phase lock loop ensures the resonant frequency operation of the inverter during the change in load parameters. The state space model of the system is discussed to study the inverter during different operating conditions. The fuzzy logic controller based closed loop control scheme is developed using the MATLAB simulation tool. The responses of the conventional and fuzzy logic controllers are studied for load voltage regulation and the effectiveness of the control schemes is verified. The dynamic behavior of the system is studied under no load and loaded conditions with the two controllers. The fuzzy based closed loop control scheme improves the dynamic response of the system compared to the conventional controller. The response of the induction heating system is validated with a hardware prototype. The results are presented in order to confirm the proposed control strategy. [ABSTRACT FROM AUTHOR]

A peak-to-average power ratio (PAPR) reduction method for an orthogonal frequency division multiplexing (OFDM) system based on a combination of a partial transmit sequence (PTS) scheme with the backtracking search optimization algorithm (BSA) is proposed. The PTS scheme shows good PAPR reduction performance; however, it requires a complex computation to search the set of optimum phase factors, especially for high-speed data transmissions. To minimize the complexity of the search for optimum phase factors, the PTS scheme is combined with the BSA. The BSA is a new and efficient population-based evolutionary search algorithm for real-valued optimization problems. A set of simulations is conducted for the PAPR reduction performance and computational complexity comparisons of the BSA-PTS scheme with different PTS schemes. Simulation results indicate that the BSA-PTS scheme yields an effective PAPR reduction performance with low computational complexity. [ABSTRACT FROM AUTHOR]

The problem of finding similar strings is very important in most real life applications including spell-checking, data cleaning, next generation sequencing, and alignment. In order to query and manage string data online, scalable algorithms and frameworks are essential. Scalable frameworks and algorithms have been introduced in the past few years. However, these frameworks mainly deal with caching and querying structured data. They do not deal with fuzzy queries, where we need to search for an approximate string. In this paper, we propose an edit distance aware filtering algorithm for all kinds of approximate string search problems. We also propose a novel name spell-check engine mainly for social networks. Our experiments show that our edit distance aware filtering mechanism alone improves the query processing time and throughput by almost 30%. Additionally, our name spell-check engine improved the name spell-check response time and throughput almost 10 times by using our filtering scheme and some domain specific observations. [ABSTRACT FROM AUTHOR]

In this paper we propose a novel Lamarckian Hybrid Grouping Genetic Algorithm (LHGGA) with repair heuristics for a problem of resources assignment to mobile terminals (or, simply, users) in Wide-band Code Division Multiple Access (WCDMA) networks. We propose a novel problem formulation that takes into account all the interference terms, which strongly depend on the assignment to be done. The second contribution is a cost function (to be minimized) with weighted components, which is composed of not only the load factors (including the mentioned interference terms) but also other utilization ratios for aggregate capacity, codes, power, and users without service. The second group of contributions is related to the LHGGA approach. On the one hand, we propose a novel encoding scheme, suitable for the novel problem formulation. On the other hand, we present fully tailored operators. We emphasize the proposal of a repair operator of unphysical candidates (which are substituted by their repaired versions), and a crossover operator, able to acts on groups (users assigned to a base station) in a very efficient way. The proposed LHGGA exhibits a superior performance than that of the conventional method, since most of users receive the demanded services along with a more efficient use of resources per user. The LHGGA approach has been successfully applied to a variety of scenarios: different number of users, distributions, or users profiles. [ABSTRACT FROM AUTHOR]

Energy consumption is an important index in mobile ad hoc networks. Data packet transmission increases among nodes, particularly in big data communication. However, nodes may be unable to transmit data packets because of energy over-consumption. Consequently, information may be lost and network communication may block. While opportunistic network is a kind of mobile ad hoc networks, researchers do not focus on energy consumption in opportunistic network communication. This study proposed an effective sensor energy supply scheme that can be applied in opportunistic networks. This scheme considers nodes sensor requests and communication model. In this scheme, nodes do not only accomplish energy supply in communication, but also extend communication time in opportunistic networks. Compared with the Spray and Wait algorithm and the Binary Spray and Wait algorithm in simulations, the proposed scheme extends communication time, increases data packet transmission, and accomplishes energy supply among nodes. [ABSTRACT FROM AUTHOR]

A group signature scheme allows any member to sign on behalf of a group. It is applied to practical distributed security communication environments, such as privacy-preserving, data mining. In particular, the excellent features of group signatures, including membership joining and revocation, anonymity, traceability, non-frameability and controllable linkability, make group signature scheme more attractive. Among these features, non-frameability can guarantee that a member's signature cannot be forged by any other (including issuer), and controllable linkability supports to confirm whether or not two group signatures are created by the same signer while preserving anonymity. Until now, only Hwang et al.'s group schemes (proposed in 2013 and 2015) can support all of these features. In this paper, we present a new dynamic group signature scheme which can achieve all of the above excellent features. Compared with their schemes, our scheme has the following advantages. Firstly, our scheme achieves more efficient membership revocation, signing and verifying. The cost of update key in our scheme is two-thirds of them. Secondly, the tracing algorithm is simpler, since the signer can be determined without the judging step. Furthermore, in our scheme, the size of group public key and member's private key are shorter. Lastly, we also prove security features of our scheme, such as anonymity, traceability, non-frameability, under a random oracle model. [ABSTRACT FROM AUTHOR]

Key agreement is paramount in secure wireless communications. A promising approach to address key agreement schemes is to extract secure keys from channel characteristics. However, because channels lack randomness, it is difficult for wireless networks with stationary communicating terminals to generate robust keys. In this paper, we propose a Robust Secure Key Agreement (RSKA) scheme from Received Signal Strength (RSS) in stationary wireless networks. In order to mitigate the asymmetry in RSS measurements for communicating parties, the sender and receiver normalize RSS measurements and quantize them into q-bit sequences. They then reshape bit sequences into new l-bit sequences. These bit sequences work as key sources. Rather than extracting the key from the key sources directly, the sender randomly generates a bit sequence as a key and hides it in a promise. This is created from a polynomial constructed on the sender's key source and key. The receiver recovers the key by reconstructing a polynomial from its key source and the promise. Our analysis shows that the shared key generated by our proposed RSKA scheme has features of high randomness and a high bit rate compared to traditional RSS-based key agreement schemes. [ABSTRACT FROM AUTHOR]

In this paper, we investigate joint power allocation and relay selection (PARS) schemes in non-orthogonal cooperative protocol (NOCP) based cognitive relay networks. Generally, NOCP outperforms the orthogonal cooperative protocol (OCP), since it can provide more transmit diversity. However, most existing PARS schemes in cognitive relay networks focus on OCP, which are not suitable for NOCP. In the context of NOCP, we first derive the joint constraints of transmit power limit for secondary user (SU) and interference constraint for primary user (PU). Then we formulate optimization problems under the aforementioned constraints to maximize the capacity of SU in amplify-and-forward (AF) and decode-and-forward (DF) modes, respectively. Correspondingly, we derive the closed form solutions with respect to different parameters. Numerical results are provided to verify the performance improvement of the proposed PARS schemes. [ABSTRACT FROM AUTHOR]

In this paper, we propose a hybrid routing scheme that utilizes location information to support reliable data transmission in mobile ad hoc networks. The proposed scheme determines and maintains routing path by considering the directionality and connectivity of nodes using grid zones and information on neighbor nodes. In addition, it generates alternative paths with consideration for node distance and reliability. To show the superiority of the proposed routing scheme, a performance evaluation was conducted using simulations. The performance evaluation results show that the proposed scheme offers faster and more reliable data transmission than the existing routing schemes, and the number of messages decreases by approximately 31% compared to the existing schemes on average. [ABSTRACT FROM AUTHOR]

This paper considers a channel estimation scheme for millimeter-wave multiuser multiple-input multiple-output systems. According to the proposed method, parts of the beams are selected and the channel parameters are estimated according to the sparsity of channels and the orthogonality of the beams. Since the beams for each channel become distinct and the signal power increases with the increased number of antennas, the proposed approach is able to achieve good estimation performance. As a result, the sum rate can be increased in comparison with traditional approaches, and channels can be estimated with fewer pilot symbols. Numerical results verify that the proposed approach outperforms traditional approaches in cases with large numbers of antennas. [ABSTRACT FROM AUTHOR]

Cooperative spectrum sensing (CSS) for vacant licensed bands is one of the key techniques in cognitive radio networks. Currently, sequential probability ratio test scheme (SPRT) is considered as a powerful soft decision approach to improve the sensing result for CSS. However, SPRT assumes all secondary users (SU) are honest, and thus offering opportunities for malicious SUs to launch the spectrum sensing data falsification attack (SSDF attack). To combat such misbehaved behaviors, recent efforts have been made to trust mechanism. In this paper, we argue that powering SPRT with traditional trust mechanism is not enough. Dynamic SSDF attackers can maintain high trust in an alternant process of submitting honest or false sensing data, resulting in difficultly detecting them. Noting that the trust value of dymamic SSDF attackers behave highly volatile, a novel trusted SPRT scheme (VSPRT) based on volatility decay analysis is proposed in this paper to mitigate the harmful effect of dynamic SSDF attackers in the process of the soft-decision data fusion, and thus improving the accuracy of the final sensing result. Simulation results show that the VSPRT scheme outperforms the conventional SPRT schemes. [ABSTRACT FROM AUTHOR]

Buildings account for nearly 40 percent of the total energy consumption in the United States. As a critical step toward smart cities, it is essential to intelligently manage and coordinate the building operations to improve the efficiency and reliability of overall energy system. With the advent of smart meters and two-way communication systems, various energy consumptions from smart buildings can now be coordinated across the smart grid together with other energy loads and power plants. In this paper, we propose a comprehensive framework to integrate the operations of smart buildings into the energy scheduling of bulk power system through proactive building demand participation. This new scheme enables buildings to proactively express and communicate their energy consumption preferences to smart grid operators rather than passively receive and react to market signals and instructions such as time varying electricity prices. The proposed scheme is implemented in a simulation environment. The experiment results show that the proactive demand response scheme can achieve up to 10 percent system generation cost reduction and 20 percent building operation cost reduction compared with passive demand response scheme. The results also demonstrate that the system cost savings increase significantly with more flexible load installed and higher percentage of proactive customers participation level in the power network. [ABSTRACT FROM AUTHOR]