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In this paper, we propose an adaptive feedforward compensator using parameter estimation to compensate for the communication time delay in cooperative adaptive cruise control (CACC). When CACC uses a feedforward controller to improve tracking performance and satisfy the string stability, it should take into account the communication delay between vehicles. Pade approximation of the time delay can be used for the design of feedforward compensator, but there is a limitation since the approximated system becomes the non-minimum system. To cope with this inherent non-causality problem, we propose an approximated causal transfer function for the feedforward compensator. Then, we apply extended Kalman filter as one of parameter estimation methods with a nonlinear model from the state augmented by a parameter of the approximated causal transfer function. Numerical simulation results show that the proposed system not only mitigates spacing error in time-varying communication delay but also satisfies string stability in a platoon.

Recently, researches on key management scheme for user access control in outsourced databases have been actively done. Because outsourced databases require dealing with a lot of users and data resources, an efficient key management scheme for reducing the number of authentication keys is required. However, the existing schemes have a critical problem that the cost of key management is rapidly increasing as the number of keys becomes larger. To solve the problem, we propose an efficient key management scheme for user access control in outsourced databases. For this, we propose an Resource Set Tree(RST)-based key generation algorithm to reduce key generation cost by merging duplicated data resources. In addition, we propose a hierarchical Chinese Remainder Theorem(CRT)-based key assignment algorithm which can verify a user permission to gain accesses to outsourced databases. Our algorithm can reduce key update cost because the redistribution of authentication keys is not required. We also provide the analytic cost models of our algorithms and verify the correctness of the theoretical analysis by comparing them with experiment results. Finally, we show from the performance analysis that the proposed scheme outperforms the existing schemes in terms of both key generation cost and update cost.

Objective To determine the synergistic effect of parathyroid hormone (PTH) [1-34] in combination with hyperbaric oxygen (HBO) on bone graft in a rat calvarial bone defect model under impaired osteogenic conditions. Materials and methods Twenty-four rats were divided into three groups. Localized radiation with a single 12 Gy dose was administered to the calvaria. Four weeks after radiation, calvarial circular defects were created in the parietal bones. All defects were filled with biphasic calcium phosphate. After the bone graft, PTH [1-34] was injected subcutaneously, and HBO was administered. At 6 weeks after the bone graft, the rats were sacrificed, and specimens were harvested. Results Histomorphometric evaluation showed that the percentage of new bone area was higher in the PTH and PTH/HBO groups than in the control group. The percent residual material area was decreased in the PTH/HBO group compared with the control group. The percentage blood vessel number was highest in the PTH group. Micro-CT evaluation showed that the new bone volume was highest in the PTH/HBO group. The residual material volume was lowest in the PTH/HBO group. Conclusion Within the limitations of this study, our data indicate that PTH combined with HBO may reverse radiation-induced impairment of bone healing.

Due to the popularity of location-based services, the amount of generated spatial data in daily life has been dramatically increasing. Therefore, spatial database outsourcing has become popular for data owners to reduce the spatial database management cost. The most important consideration in database outsourcing is meeting the privacy requirements and guarantying the integrity of the query result. However, most of existing database transformation techniques do not support both of the data privacy and integrity of the query result. To solve this problem, we propose a spatial data transformation scheme that utilizes the shearing transformation with rotation shifting. In addition, we described the attack models to measure the data privacy of database transformation schemes. Finally, we demonstrated through the experimental evaluations that our scheme provides high level of data protection against different kinds of attack models, compared to the existing schemes, while guaranteeing the integrity of the query result sets.

As the outsourcing of mobile sensitive data has been highlighted, data encryption schemes are required to protect the mobile sensitive data. Accordingly, it is necessary to develop not only a distributed index structure to efficiently manage the large amount of encrypted data, but also a query processing scheme over the encrypted data. To the best of our knowledge, there has been no research on index structure for the encrypted data. Meanwhile, the existing query processing schemes over the encrypted data can support limited types of queries. Also, without decrypting data, the existing schemes cannot support operations among data between different columns because they use different types of encryption schemes depending on their attribute types. To solve the problems, in this paper, we propose a bitmap-based distributed index structure and a query processing scheme for the encrypted data. The proposed distributed index structure guarantees data privacy preservation and performance improvement for the various types of queries. In addition, by processing a query over the encrypted data without data decryption, the proposed query processing scheme provide both high query performance and 100% accuracy while preserving the data privacy. Finally, we show from our performance analysis that our proposed index structure and query processing scheme are suitable for protecting the data privacy of the mobile sensitive data.

Cloud computing has emerged as a new platform for storing and managing databases. As a result, a database outsourcing paradigm has gained much interests. To prevent the contents of outsourced databases from being revealed to cloud computing, databases must be encrypted before being outsourced to the cloud. Therefore, various Top-k query processing techniques have been proposed for encrypted databases. However, there is no existing work that can not only hide data access patterns, but also preserve the privacy of user query. To solve the problems, in this paper, we propose a new privacy-preserving Top-k query processing algorithm. Our algorithm protects the user query from the cloud and conceals data access patterns during query processing. A performance analysis shows that the proposed scheme provide good scalability without any information leakage.

Because much interest in spatial database for cloud computing has been attracted, studies on preserving location data privacy have been actively done. However, since the existing spatial transformation schemes are weak to a proximity attack, they cannot preserve the privacy of users who enjoy location-based services in the cloud computing. Therefore, a transformation scheme is required for providing a safe service to users. We, in this paper, propose a new transformation scheme based on a line symmetric transformation (LST). The proposed scheme performs both LST-based data distribution and error injection transformation for preventing a proximity attack effectively. Finally, we show from our performance analysis that the proposed scheme greatly reduces the success rate of the proximity attack while performing the spatial transformation in an efficient way.

Outsourcing database to a third-party data provider is becoming a common practice for data owners to avoid the cost of managing and maintaining the database. Meanwhile, because of the popularity of location-based services, the need for spatial data is increasing dramatically. However, the most important challenge in database outsourcing is how to meet privacy requirements and guarantee the integrity of the query result as well. Unfortunately, most of the existing techniques support either data privacy or integrity on spatial databases. To carry on both privacy and integrity for outsourced spatial data, we propose a spatial transformation scheme that makes use of shearing transformation with rotation shifting. We describe attack models measuring the data privacy of our transformation scheme. Finally, our extensive experiments have demonstrated that our scheme has adequate strength for data privacy by showing outstanding performance against different kinds of attack models and efficiently handles the query integrity of the query result sets. Copyright © 2013 John Wiley & Sons, Ltd.

Recent development of wireless communication technologies and the popularity of smart phones are making location-based services (LBS) popular. However, requesting queries to LBS servers with users’ exact locations may threat the privacy of users. Therefore, there have been many researches on generating a cloaked query region for user privacy protection. Consequently, an efficient query processing algorithm for a query region is required. So, in this paper, we propose k-nearest neighbor query (k-NN) processing algorithms for a query region in road networks. To efficiently retrieve k-NN points of interest (POIs), we make use of the Island index. We also propose a method that generates an adaptive Island index to improve the query processing performance and storage usage. Finally, we show by our performance analysis that our k-NN query processing algorithms outperform the existing k-Range Nearest Neighbor (kRNN) algorithm in terms of network expansion cost and query processing time.

With the growth of cloud computing, database outsourcing has attracted much interests. Due to the serious privacy threats in cloud computing, databases needs to be encrypted before being outsourced to the cloud. Therefore, various Top-k query processing algorithms have been studied for encrypted databases. However, existing algorithms are either insecure or inefficient. Therefore, in this paper we propose an efficient and secure Top-k query processing algorithm. Our algorithm guarantees the confidentiality of both the data and a user query while hiding data access patterns. Our algorithm also enables the query issuer not to participate in the query processing. To achieve a high level of query processing efficiency, we use new secure protocols using Yao's garbled circuit and a data packing technique. A performance analysis shows that the proposed algorithm outperforms the existing works in terms of query processing costs.

Because a wide range of professionals utilize Social Network Service (SNS), the SNS users have recently required an expert recommendation service to enable users to perform both cooperation and technical communication with experts. A content-boosted collaborative filtering (CBCF) provides various prediction algorithms which support effective recommendations. However, the CBCF cannot calculates the similarity of items (or users) when the calculation condition is not clearly provided. To solve the problem, we propose a content-aware hybrid collaborative filtering scheme for expert recommendation in SNSs. Finally, we show from a performance analysis that our scheme outperforms the existing method in terms of recommendation accuracy.

Because much interest in spatial database for cloud computing has been attracted, studies on preserving location data privacy have been actively done. However, since the existing spatial transformation schemes are weak to a proximity attack, they cannot preserve the privacy of users who enjoy location-based services in the cloud computing. Therefore, a transformation scheme is required for providing a safe service to users. We, in this chapter, propose a new transformation scheme based on a line symmetric transformation (LST). The proposed scheme performs both LST-based data distribution and error injection transformation for preventing a proximity attack effectively. Finally, we show from our performance analysis that the proposed scheme greatly reduces the success rate of the proximity attack while performing the spatial transformation in an efficient way.

Research on secure range query processing techniques in outsourced databases has been spotlighted with the development of cloud computing. The existing range query processing schemes can preserve the data privacy and the query privacy of a user. However, they fail to hide the data access patterns while processing a range query. So, in this paper we propose a secure range query processing algorithm which hides data access patterns. Our method filters unnecessary data using the encrypted index. We show from our performance analysis that the proposed range query processing algorithm can efficiently process a query while hiding the data access patterns.

Secure range query processing algorithms have been studied as the range query can be used as a baseline technique in various fields. However, when processing a range query, the existing methods fail to hide the data access patterns which can be used to derive the actual data items and the private information of a querying issuer. The problem is that the data access patterns can be exposed even though the data and query are encrypted. So, in this paper we propose a new range query processing algorithm on the encrypted database. Our method conceals the data access patterns while supporting efficient query processing by using our proposed encrypted index search scheme. Through the performance analysis, we show that the proposed range query processing algorithm can efficiently process a query while hiding the data access patterns.

Recent development in wireless communication technology like GPS as well as mobile equipments like PDA and cellular phone makes location-based services (LBSs) popular. However, because users request a query to LBS servers by using their exact locations while moving on the road network, users' privacy may not be protected in the LBSs. Therefore, a mechanism for users' privacy protection is required for the safe and comfortable use of LBSs by mobile users. For this, we, in this paper, propose a road network distance based cloaking scheme supporting user privacy protection in location-based services. The proposed scheme creates a cloaking area by considering road network distance, in order to support the efficient and safe LBSs on the road network. Finally, we show from our performance analysis that our cloaking scheme outperforms the existing cloaking scheme in terms of cloaking area and service time.

Background The prevalence of hepatitis C virus (HCV) infections in elderly patients has been increasing in a number of countries. A few reports concerning pegylated interferon-α (PEG-IFN-α)-based combination treatment in elderly chronic hepatitis C (CHC) patients have been published, with slightly different treatment outcomes. Objectives We investigated the treatment response and safety of PEG-IFN-α plus ribavirin combination therapy in elderly patients with CHC. Patients and Methods Among a total of 181 treatment-naïve CHC patients (60 patients with genotype 1, 121 patients with genotype 2 or 3), 38 were aged ≥ 65 years (defined as the elderly group) and 143 were aged < 65 years (defined as the non-elderly group). Results The overall sustained virologic response (SVR) was lower in the elderly group than in the non-elderly group, but it was not significantly different (65.8 % vs. 76.2 %, P = 0.15). In a subgroup analysis, among patients with genotype 1, the elderly group had a significantly lower SVR rate than the non-elderly group (30.8 % vs. 66.0 %, P = 0.03). However, the SVR rate in patients with HCV genotype 2 or 3 was comparable between the two groups (84.0 % vs. 81.3 %, P = 0.85). HCV genotype was significantly associated with SVR in the elderly patients (genotype 1 vs. 2 or 3, odds ratio: 0.18, 95% confidence interval: 0.000-0.869, P = 0.03). The incidence of premature discontinuation of treatment (21.1 % vs. 9.1 %, P = 0.05) and dose modification (52.6 % vs. 31.5 %; P = 0.02) due mainly to adverse events or laboratory abnormalities, were higher in the elderly group than in the non-elderly group. Conclusions PEG-IFN-α plus ribavirin combination therapy might be considered for elderly CHC patients, especially for genotype 2 or 3, with vigilant monitoring of adverse events.