Search

Class imbalance is a serious problem that plagues the semantic segmentation task in urban remote sensing images. Since large object classes dominate the segmentation task, small object classes are usually suppressed, so the solutions based on optimizing the overall accuracy are often unsatisfactory. In the light of the class imbalance of the semantic segmentation in urban remote sensing images, we developed the concept of the Down-sampling Block (DownBlock) for obtaining context information and the Up-sampling Block (UpBlock) for restoring the original resolution. We proposed an end-to-end deep convolutional neural network (DenseU-Net) architecture for pixel-wise urban remote sensing image segmentation. The main idea of the DenseU-Net is to connect convolutional neural network features through cascade operations and use its symmetrical structure to fuse the detail features in shallow layers and the abstract semantic features in deep layers. A focal loss function weighted by the median frequency balancing (MFB_Focalloss) is proposed; the accuracy of the small object classes and the overall accuracy are improved effectively with our approach. Our experiments were based on the 2016 ISPRS Vaihingen 2D semantic labeling dataset and demonstrated the following outcomes. In the case where boundary pixels were considered (GT), MFB_Focalloss achieved a good overall segmentation performance using the same U-Net model, and the F1-score of the small object class “car” was improved by 9.28% compared with the cross-entropy loss function. Using the same MFB_Focalloss loss function, the overall accuracy of the DenseU-Net was better than that of U-Net, where the F1-score of the “car” class was 6.71% higher. Finally, without any post-processing, the DenseU-Net+MFB_Focalloss achieved the overall accuracy of 85.63%, and the F1-score of the “car” class was 83.23%, which is superior to HSN+OI+WBP both numerically and visually.

With the rapid growth of the Internet, the scale of graphs has increased dramatically, which poses special challenges in representing both web graphs and social network graphs. In the adjacency matrix of web and social network graphs, only a very small proportion of the elements is “1” s. Furthermore, we find that using the aggregation of scattered 1 s to form a high density of adjacency matrices is beneficial to the compression of storage space. Based on these findings, we propose the DGC-K2-tree compression approach based on K2-tree, which can greatly increase the density of 1 s among the existing algorithms and adequately compress the blank area in the adjacency matrix. Then, we design a query algorithm for this mechanism to support the operation on the graph. The experimental results show that compared with the state-of-the-art algorithms, including the K2-tree based on a diagonal clustering mechanism (K2-BDC), the K2-tree, Re-Pair, and LZ78, our approach achieves better compression ratio and shorter time consumption. In terms of storage efficiency, our approach reduces the space by an average of 34.07% compared to the best performing algorithm K2-BDC. In terms of query efficiency, our approach reduces the time by an average of 80.63% compared to the best performing algorithm LZ78.

A joint operation of renewable energy with energy storage devices and the development of multi-energy market transactions are effective ways to accommodate renewable energy such as wind power. This paper addresses issues of joint equilibrium analysis of the wholesale electricity market (WEM) and the gas market (GM) in which wind power producers (WPPs), power-to-gas (P2G) equipment, natural gas generating unit (NGGU) and gas storage device (GSD) constitute a joint operator (JO) to participate in bidding competition. First, a new coupled electricity and gas markets trading framework is presented, in which WPP can use P2G equipment, NGGU and GSD to tackle the surplus and deficit of its actual output. In addition, P2G equipment and NGGU have arbitrage behavior in the multi-energy market. Second, based on this framework, a multi-period stochastic game equilibrium model in which the JO, conventional generators (CGs) and gas companies participate in the multi-energy market bidding competition is established, and the equilibrium model is solved by the nonlinear complementarity method. Finally, simulation results show that the presented multi-energy trading framework can tackle the deviation of the WPP participating in the multi-period WEM competition, reduce the market power of CGs, and improve the market competitiveness of WPP and the social welfare.

Prognostics and health management (PHM) is an important topic of rolling bearing, so partition of healthy stage and different degree of fault states are equally important as fault types. This study uses a multi-label learning method, Binary Relevance (BR) algorithm, for fault diagnosis of bearing data based on both of states partition and fault types judgment. The Binary Relevance algorithm simplifies the classification process by transforming the multi-classification problem into multiple binary classification problems. Using extreme learning machine ensures the classification speed and effect. By comparative experiments on XJTU-SY bearing datasets, the effectiveness of our method is proved to be superior.

When wind power producers (WPPs) bid in the day-ahead market, how to address the deviation between the bid output and the actual output is one of the important topics in the design of electricity markets with WPPs. Under the background of the Energy Internet, the complementarity between power system and natural gas system provides an alternative solution for mitigating the adverse effects of random fluctuations in renewable energy sources. First, a multi-energy trading framework is presented to tackle WPP’s bid deviations. In the framework, the WPP is considered to bid in the day-ahead electricity market (DAEM). In order to compensate the bid deviations of WPP, power to gas (P2G) equipment, natural gas generating unit (NGGU) and gas storage devices can be used by the WPP when it has excess/deficit electricity, and the rest deviation can be compensated by the gas market (GM). Second, based on the trading framework, a multi-period joint game equilibrium model of the DAEM and GM is proposed. In this model, the Cournot bid form is applied by both WPP and conventional power producers in the DAEM and gas producers in the GM. Furthermore, a nonlinear complementary method is applied to solve the equilibrium model. Finally, the numerical examples show that the proposed multi-energy trading model can completely compensate the WPP’s bid deviation in the DAEM, help to improve the market competitiveness of WPP and the accommodation of wind power, and also smooth the price fluctuations in the DAEM and GM.

In this paper, we propose a conditional privacy-preserving authentication scheme based on pseudonyms and (t,n) threshold secret sharing, named CPPT, for vehicular communications. To achieve conditional privacy preservation, our scheme implements anonymous communications based on pseudonyms generated by hash chains. To prevent bad vehicles from conducting framed attacks on honest ones, CPPT introduces Shamir (t,n) threshold secret sharing technique. In addition, through two one-way hash chains, forward security and backward security are guaranteed, and it also optimize the revocation overhead. The size of certificate revocation list (CRL) is only proportional to the number of revoked vehicles and irrelated to how many pseudonymous certificates are held by the revoked vehicles. Extensive simulations demonstrate that CPPT outperforms ECPP, DCS, Hybrid and EMAP schemes in terms of revocation overhead, certificate updating overhead and authentication overhead.

Evaluating the reliability of weighted networks is an NP-hard problem. In this paper, a symbolic algorithm evaluating the reliability of network under capacity and delay constraints is proposed. First, the weighted network is converted to a symbolic algebraic decision diagrams (ADD) by encoding the vertices of the network, and the variable ordering are computed by breadth-first search and priority function in order to reduce the size of ADD. Then, edges in minimal paths (MPs) which does not meet the constraint formula of quickest path problem are not visited, leading to a low complexity of the network traversal. Finally, ADD constructed by two custom operators is traversed to compute the network reliability. The computational performance of the proposed algorithm is illustrated through some experimentation with different weighted networks.

Position-based cryptography has attracted lots of researchers' attentions. In mobile Internet, there are lots of position based security applications. For the first time, one new conception, position-based proxy signcryption is proposed. Based on a secure positioning protocol, one model of position-based proxy signcryption is proposed. In the model, positioning protocol is tightly bound to proxy signcryption, not loosely. Further, we propose one concrete position-based proxy signcryption scheme, its correctness is proved, and its security is also analyzed. As far as we know, it is the first position-based proxy signcryption scheme.

Position-based cryptography has attracted lots of researchers' attention. In the mobile Internet, there are many position-based security applications. For the first time, one new conception-proxy multi-signature binding positioning protocols, is proposed. Based on one secure positioning protocol, one model of the proxy multi-signature binding positioning protocols is proposed. In the model, positioning protocols are bound to proxy multi-signature tightly, not loosely. Further, we propose one scheme of proxy multi-signature binding positioning protocols. As far as we know, it is the first scheme of proxy multi-signature binding positioning protocols.

Kalman filter (KF) is widely used in SINS + GPS-guided combination method, but the sensor's mathematical model of the transporter is generally nonlinear, so the complexity and computation of the model are large. In this paper, we present an Kalman filter algorithm based on error state variables in SINS + GPS navigation application. The mathematical model of the errors of GPS data and inertial navigation data is linear, so the errors are taken as the states, which avoids the complexity caused by nonlinear and makes the design difficulty reduced significantly. This paper also gives the design process and the mathematical model of navigation system, and sets the state parameters of the model. Finally, simulation results show the effectiveness of the algorithm.

Taihu Lake is an important ecosystem in east China, and also an ecologically vulnerable region. Pesticide residues can be detected in Taihu Lake. Although the environmental concentrations are not high enough to harm the ecosystem acutely, the residues can pose potential risk to the ecosystem and human health because of their chronic impacts. It is necessary to assess the ecological risk induced by pesticide residues' chronic impacts. Based on the integration of risk quotient method and probabilistic risk assessment method, this paper proposes a methodology of ecological risk assessment of pesticide residues' chronic impacts. It indicates that dichlorvos posed quite high chronic risk to the ecosystem, while risks posed by other pesticides are acceptable. Whereas combined ecological risk posed by the mixture is 24.08% in average, which exceeds the acceptable 5% level. Temporal variations of each pesticide's contribution to the total ecological risk are also presented. This analysis shows that risk alleviation actions should be made taking account of the pesticide residues' chronic impacts in Taihu Lake.

Nowadays, most proxy signature schemes are based on the difficulty of DLP (Discrete Logarithm Problem) or ECDLP (Elliptical Curve Discrete Logarithm Problem). As though many proxy signature schemes based on DLP or ECDLP have been proposed, it makes us discouraged that some disadvantages can be found after a new or modified proxy signature scheme was designed after short time. How to solve the question? How to design secure and valid proxy signature scheme? How to prove them secure? Now, it is too difficult for us to prove one scheme secure, but if we can have some principles to conform to when designing some proxy signature schemes based on DLP or ECDLP, it will be helpful. It will be able to make the scheme designer to make few mistakes, that's to say, by these principles, they can judge their schemes meet basic secure conditions. If designers don't conform to these principles, it can easily be seen that their schemes are definitely insecure. It is all known by us that until now there are not these principles in the real life. By some hints from some attacks, especially forgery attacks, it seems to us that we have found three basic principles which should be conformed to when proxy signature schemes are proposed. The first principle is that the existent forms of public parameters in proxy signatures in the proxy signature verification congruence make a key role on the security property of unforgeability. The second principle is that any public parameter in the proxy signature can't lonely exist in the proxy signature verification congruence in the form of bases or exponents. The third principle is that any public parameter in the proxy signature should exist in the proxy signature verification equation in the form of not only exponents and bases, but also hashes. In addition, some examples are given.

In order to represent the production knowledge more integrally and to receive more efficient knowledge reasoning, an OBDD based production knowledge representation model is presented. Then, OBDD based knowledge reasoning rule and its associated algorithms are implemented. Finally, an example is taken to illustrate feasibility and efficiency of the OBDD based model and reasoning rules.

In a (t, n) threshold proxy signature scheme, one original signer delegates a group of n proxy signers to sign on behalf of the original signer. When the proxy signature is created, at least t proxy signers cooperate to produce valid proxy signatures and any less than t proxy signers can't cooperatively generate valid proxy signatures. Self-certified public key systems have attracted more and more attention because of its advantages. In 2005, Hsu and Wu designed a self-certified threshold proxy signature scheme with message recovery, nonrepudiation and traceability, which is based on Hsu et al.'s self-certified public key system. Park et al. showed that Hsu and Wu's self-certified threshold proxy signature scheme is insecure against the malicious original signer in 2006. That is, Hsu and Wu's scheme suffers from the cheat attack, where a malicious original signer can cheat CA into extracting a proxy signing key of a proxy signer. We analyzed Park et al's security analysis for Hsu and Wu's scheme and pointed out that the cheat attack proposed by Park et al. can't succeed. In one hand, in self-certified public system, users cannot freely change their private or public keys. If users want to change their private or public keys, CA has some corresponding strategy to limit users' behaviors. In the other hand, if some disagreement about the forged threshold proxy signature occurs, there are two solutions to deal with it. One solution depends on the help of CA and the other solution relies on the help of the delegated proxy signer.

Water environmental risk identification (WERI) is a basic step for industrial parks in the regional water environmental risk (WER) management. It is an effective means to control risk damage in advance and help find out the regional hazard sources. It will be helpful for putting forward corresponding countermeasures to avoid water pollution accidents. Depending on the features of risk sources, control system, as well as regional risk receptors, and taking the enterprise and its surrounding area away from 1 kilometre as the evaluation unit, integrated evaluation index system (IEIS) was developed to identify the region WER. The analytic hierarchy process (AHP) was applied to determine the weight of each factor. Taixing Economic Development Zone (TEDZ) was taken as a case study for the application of the model. The results showed that 3.57%, 50% and 46.4% of the enterprises in TEDZ had high, medium and low risks, respectively. Countermeasures were provided for the decision-makers on the risk management.

In a (t,n) threshold proxy signature scheme, an original signer delegates a group of n proxy signers to sign messages on behalf of him or her. When the proxy signature is created, t or more proxy signers cooperate to generate valid proxy signatures and any less than t proxy signers can't cooperatively produce valid proxy signatures. In 2003, Hwang et al. proposed a practical threshold proxy signature scheme (HLL-scheme) which is based on RSA crypto system for the first time. In 2004, Wang et al. had provided some comments on HLL-scheme. They showed that some mistakes of equations had made HLL-scheme become insecure. Moreover, in 2005, Kuo and Chen also showed two security weaknesses in Hwang et al.'s scheme: one is similar to RSA reblocking problem and the other is that the value of Li is not clearly defined. In addition, to overcome the second shortcoming of HLL-scheme, Kuo and Chen also provided a modified threshold proxy signature scheme (KC-scheme) based on HLL-scheme. By observation, we find that KC-scheme cannot still work. In other words, in KC-scheme, the value of Li cannot still be worked out, as makes KC-scheme not workable. To design a workable threshold proxy signature scheme, based on KC-scheme, an improved scheme is proposed