Local calibration of rigid pavement performance models using resampling methods

The performance prediction models in the Pavement-ME design software are nationally calibrated using in-service pavement material properties, pavement structure, climate and truck loadings, and performance data obtained from the Long-Term Pavement Performance programme. The nationally calibrated models may not perform well if the inputs and performance data used to calibrate those do not represent the local design and construction practices. Therefore, before implementing the new M-E design procedure, each state highway agency (SHA) should evaluate how well the nationally calibrated performance models predict the measured field performance. The local calibrations of the Pavement-ME performance models are recommended to improve the performance prediction capabilities to reflect the unique conditions and design practices. During the local calibration process, the traditional calibration techniques (split sampling) may not necessarily provide adequate results when limited number of pavement sections are available. Consequently, there is a need to employ statistical and resampling methodologies that are more efficient and robust for model calibrations given the data related challenges encountered by SHAs. The main objectives of the paper are to demonstrate the local calibration of rigid pavement performance models and compare the calibration results based on different resampling techniques. The bootstrap is a non-parametric and robust resampling technique for estimating standard errors and confidence intervals of a statistic. The main advantage of bootstrapping is that model parameters estimation is possible without making distribution assumptions. This paper presents the use of bootstrapping and jackknifing to locally calibrate the transverse cracking and IRI performance models for newly constructed and rehabilitated rigid pavements. The results of the calibration show that the standard error of estimate and bias are lower compared to the traditional sampling methods. In addition, the validation statistics are similar to that of the locally calibrated model, especially for the IRI model, which indicates robustness of the local model coefficients.     

Interface Engineering and Controlling the Friction and Wear of Ultrathin Carbon Films: High sp3 Versus High sp2 Carbons

Understanding and engineering interfaces, and controlling the friction and wear of materials, are extremely important for many technological applications, particularly for magnetic storage technologies and micro‐ and nanoelectromechanical systems (MEMS and NEMS), where one sliding/moving surface comes into contact with another. Ultrathin carbon films are generally employed in most of these technologies. However, their wear and friction mechanisms are not well understood, especially the role of the film–substrate (FS) interface has not been deeply explored and discussed to date. This limits further developments in this field. Through experimental and theoretical experiments, we are able to report on the engineering of a FS interface consisting of high sp³‐ and high sp²‐bonded ultrathin carbon films on Al₂O₃–TiC substrates by introducing a silicon nitride (SiN_x) interlayer and tuning the carbon ion energy. All carbon‐based overcoats show a low coefficient of friction (COF) in the range of 0.08–0.16; however, the high sp³‐bonded C/SiN_x bilayer overcoat reveals the lowest and most stable friction. The friction mechanism is explained using an integrated framework of surface passivation, rehybridization, material transfer, tribolayer formation, and interfaces. We discover that FS interface engineering substantially reduces the wear of ultrathin carbon films while maintaining/reducing the friction. In general, this approach can be applied to control the friction and wear of ultrathin films of diverse materials.     

Facile Preparation of Lightweight and Flexible PVA/PEDOT:PSS/MWCNT Ternary Composite for High-Performance EMI Shielding in the X-Band Through Absorption Mechanism

Journal of Electronic Materials - Electromagnetic safeguards are key factors for electronic devices. Lightweight and highly flexible polymer composite films with high electrical conductivity are...     

Energy Balanced Model for Lifetime Maximization in Randomly Distributed Wireless Sensor Networks

In this paper, an energy balanced model (EBM) for lifetime maximization for a randomly distributed sensor network is proposed. The lifetime of a sensor network depends on the rate of energy depletion caused by multiple factors, such as load imbalance, sensor deployment distribution, scheduling, transmission power control, and routing. Therefore, in this work, we have developed a mathematical model for analysis of load imbalance under uniform and accumulated data flow. Based on this analysis, we developed a model to rationalize energy distribution among the sensors for enhancing the lifetime of the network. To realize the proposed EBM, three algorithms—annulus formation, connectivity ensured routing and coverage preserved scheduling have been proposed. The proposed model has been simulated in ns-2 and results are compared with Energy-Balanced Transmission Policy and Energy Balancing and unequal Clustering Algorithm. Lifetime has been measured in terms of the time duration for which the network provides satisfactory level of coverage and data delivery ratio. EBM outperform both the existing models. In our model the variance of residual energy distribution among the sensors is lower than other two models. This validated the essence of energy rationalization hypothesized by our model.     

Development of MMIC-based modules for multichannel RF/opticalsubcarrier multiplexed communications applications

We present a C-band monolithic microwave integrated circuit (MMIC) transmitter module development for multichannel RF/optical subcarrier multiplexed (OSCM) communication applications. The C-band MMIC transmitter module consists of one fully monolithic four-channel OSCM transmitter IC and four coupled-line filters. This MMIC is designed and implemented in a commercial GaAs MESFET process and coupled line bandpass filters are fabricated on the module board. We present the design and performance of the first fully monolithic IC transmitter module for OSCM packet switched applications     

Analytical approach towards available bandwidth estimation in wireless ad hoc networks

Wireless Networks - Since 1999 IEEE 802.11 has become a dominating wireless technology for providing WLAN in both public and private places. The protocol has evolved with time and the current...     

Parameterized key assignment for confidential communication in wireless networks

Predistribution of cryptographic keys is a widely used approach for establishing secure communication between severely resource-constrained nodes with limited or no access to network infrastructure. Many proposed key predistribution schemes make the implicit assumption that message contents need not be kept private from nodes other than the intended recipient. Messages in such schemes are not guaranteed to be confidential—they may be read by nodes within the network other than the intended recipient. In this paper, we present TASK—a symmetric key predistribution scheme that enables secure and confidential communication within wireless networks. TASK distributes keys by generating and reinforcing a series of template key assignment instances. It is parameterized, which allows it to make use of key storage capacities that other recently proposed schemes cannot. We show, through analysis and simulation, that TASK can achieve a level of security superior to that of two recently proposed schemes that also provide confidentiality. We also demonstrate that the techniques used in TASK (namely parameterization, templatization, and selective reinforcement) can be applied to other key assignment schemes for star or bipartite networks.     

BIIR: A Beacon Information Independent VANET Routing Algorithm with Low Broadcast Overhead

Most of the existing VANET routing protocols rely on information collected from beacons for making routing decisions such as next neighbor selection. Beacons are very small size hello messages that each vehicle broadcasts periodically. Owing to very small payload size of beacons as compared to the payload size of a data message, they can easily pass through even very weak links, through which a data message could never pass. Therefore, the use of beacon information for making routing decisions in a highly dynamic scenario such as VANETs may cause selection of routes through which data message can never be sent. Several researchers have given solutions that do not use beacon information for making routing decisions. But most of these solutions incorporate a large number of broadcasts to forward the data packets, causing wastage of bandwidth. In this paper, we present a beacon information independent geographic routing algorithm called BIIR, which reduces the number of broadcasts to forward the data packets by making intelligent use of information collected by the vehicle during previous route discovery attempts for a destination. Our simulation results have shown that the proposed algorithm outperforms the existing beacon less routing protocols in terms of the average number of broadcasts per data packet forwarding, packet delivery ratio and end to end delay experienced by the data messages.     

Efficient revocable ID‐based encryption with cloud revocation server

The capability to efficiently revoke compromised/misbehaving users is important in identity‐based encryption (IBE) applications, as it is not a matter of if but of when that one or more users are compromised. Existing solutions generally require a trusted third party to update the private keys of nonrevoked users periodically, which impact on scalability and result in high computation and communication overheads at the key generation center. Li et al proposed a revocable IBE scheme, which outsources most of the computation and communication overheads to a Key Update Cloud Service Provider (KU‐CSP). However, their scheme is lack of scalability since the KU‐CSP must maintain a secret value for each user. Tseng et al proposed another revocable IBE scheme with a cloud revocation authority, seeking to provide scalability and improve both performance and security level. In this paper, we present a new revocable IBE scheme with a cloud revocation server (CRS). The CRS holds only one secret time update key for all users, which provides the capability to scale our scheme. We demonstrate that our scheme is secure against adaptive‐ID and chosen ciphertext attacks under the k‐CAA assumption and outperforms both schemes mentioned above, in terms of having lower computation and communication overheads.