Utilization of fly ash concrete in marine environment for long term design life analysis

This paper presents the performance of 7-year fly ash concrete exposed to hot and high humidity climate in marine conditions. Control concrete and fly-ash concrete cube specimens of 200 mm were cast and steel bars of 12 mm in diameter and 50 mm in length were embedded at various cover depths. The concrete specimens were exposed to tidal zone of marine environment in the Gulf of Thailand. The concrete specimens were tested for chloride penetration profile, chloride content at the position of embedded steel bar, and corrosion of embedded steel bar after being exposed to tidal zone of sea water up to 7 years. Consequently, these experimental data were used to generate the empirical equation for predicting long term required cover depth of cement and fly ash concretes to protect against the initial corrosion of reinforcing steel in a marine environment.     

Efficient Key Management Protocol for Secure RTMP Video Streaming toward Trusted Quantum Network

This paper presents an achievable secure videoconferencing system based on quantum key encryption in which key management can be directly applied and embedded in a server/client videoconferencing model using, for example, OpenMeeting. A secure key management methodology is proposed to ensure both a trusted quantum network and a secure videoconferencing system. The proposed methodology presents architecture on how to share secret keys between key management servers and distant parties in a secure domain without transmitting any secrets over insecure channels. The advantages of the proposed secure key management methodology overcome the limitations of quantum point‐to‐point key sharing by simultaneously distributing keys to multiple users; thus, it makes quantum cryptography a more practical and secure solution. The time required for the encryption and decryption may cause a few seconds delay in video transmission, but this proposed method protects against adversary attacks.     

A lightweight and secure NFC‐base mobile payment protocol ensuring fair exchange based on a hybrid encryption algorithm with formal verification

During the past few years, many near‐field communication (NFC) mobile payment protocols have been widely used and received more and more attentions. This could be an essential factor for the growth of the world economy and leads to the improvement of the quality of life for human beings. The NFC mobile payment is one prominent approach in allowing m‐commerce to conduct a sales transaction. However, fair exchange and information security are significant concerns in creating trust among the parties participating in the transaction. Many NFC mobile payment protocols have been introduced by researchers. But, most of them still lack some crucial properties of information security and fair exchange, and this can be an obstacle to their uses. In this article, we propose an NFC mobile payment protocol that possesses comprehensive properties of both information security and fair exchange for sales transaction processing. The protocol employs both symmetric and asymmetric encryptions, hash function, and the technique of offline session key generation, in order to improve the security while maintaining the lightweight property. The fairness analysis shows that the proposed protocol is more competent and effective than others. It can resolve any dispute in case one party misbehaves. Finally, the proposed protocol's security has been successfully verified using both Burrows, Abadi and Needham (BAN logic) and the Scyther tool.     

Value creating construction virtual teams: A case study in the construction sector

The research explores factors influencing knowledge value creation of virtual teams in the construction industry. Collectiveness and conscientiousness emerge as important socio-cultural enablers for value creation. Collectiveness represents the degree of cohesiveness and social relationships between virtual team members and conscientiousness represents an awareness of the situation and avoidance of uncertainty and risk by team members. Moreover, technology assets, human networks, social capital, intellectual capital, and change management are identified as essential ingredients that have the potential to ensure effective knowledge value creation.     

Concrete durability presented by acceptable chloride level and chloride diffusion coefficient in concrete: 10-year results in marine site

Generally, concrete with high resistance to the marine environment should have high compressive strength, a low chloride diffusion coefficient (D _C), and a high acceptable chloride level (Ac). Considering all parameters simultaneously, this study evaluated the degree of fly ash concrete durability based on 10-year results in a marine site. Based on the concrete durability (Ac/D _C, as compared to cement concrete with a W/B ratio of 0.45) and compressive strength, the degree of concrete durability proposed in this study indicates that fly ash concretes with a W/B ratio of 0.45 and 15–35 wt % fly ash replacement exhibit high-quality performance in a marine site.     

Preserving User Anonymity in Context‐Aware Location‐Based Services: A Proposed Framework

Protecting privacy is an important goal in designing location‐based services. Service providers want to verify legitimate users and allow permitted users to enjoy their services. Users, however, want to preserve their privacy and prevent tracking. In this paper, a new framework providing users with more privacy and anonymity in both the authentication process and the querying process is proposed. Unlike the designs proposed in previous works, our framework benefits from a combination of three important techniques: k‐anonymity, timed fuzzy logic, and a one‐way hash function. Modifying and adapting these existing schemes provides us with a simpler, less complex, yet more mature solution. During authentication, the one‐way hash function provides users with more privacy by using fingerprints of users' identities. To provide anonymous authentication, the concept of confidence level is adopted with timed fuzzy logic. Regarding location privacy, spatial k‐anonymity prevents the users' locations from being tracked. The experiment results and analysis show that our framework can strengthen the protection of anonymity and privacy of users by incurring a minimal implementation cost and can improve functionality.     

Effects of W/B ratios and fly ash finenesses on chloride diffusion coefficient of concrete in marine environment

The objectives of this investigation were to study the effect of W/B ratios and fly ash finenesses on chloride diffusion coefficient (D_c) of concrete under marine environment. Original and classified fly ashes were used as a partial replacement of Portland cement type I at 0%, 15%, 25%, 35%, and 50% by weight of binder. Water to binder ratios (W/B) were varied as 0.45, 0.55, and 0.65. Concrete cube specimens of 200 mm were cast and removed from the molds after casting 1 day and then cured in fresh water for 27 days. After that, the specimens were placed to the tidal zone of marine environment in the Gulf of Thailand. Subsequently, the specimens were tested for chloride penetration profile after being exposed to the tidal zone for 2, 3, 4, and 5 years. The regression analysis of investigated data was carried out and Fick’s second law of diffusion was applied to calculate the chloride diffusion coefficient (D_c) and chloride concentration at concrete surface (C_o) based on one-dimensional analysis. The results showed that D_c of all concrete mixtures decreased with an exposure time and the decrease of W/B ratio resulted in the decrease of D_c. When the W/B ratio of concrete was reduced, the decrease of D_c in cement concrete was higher than that of the fly ash concrete. The use of fly ash with high fineness clearly reduced the rate of chloride ingress into concrete. In addition, fly ash with high fineness has more effective on reducing of D_c in concrete with higher W/B ratio than that with lower W/B ratio.