A review of the photovoltaic industry and its development in Africa

This article presents an overview of the commercialisation experiences of photovoltaics and draws some conclusion from the past and applies them to the future. In particular, the development for this industry in Africa is examined to identify the areas of strength and potential as well as the necessary infrastructure—for production, distribution and installation in order to support its growth. The question of capital requirement versus the efficiency of photovoltaics is highlighted and the reliabilty factor is analysed. As a result of examining the past, three issues seem crucial for the future development of photovoltaics, especially in Africa: (1) technology development; (2) education; (3) finance. These issues are addressed and their interdependence and impact on the use of photovoltaics are explored. The success stories of several photovoltaic companies in Africa, in spite of their problems, can be a source of optimism for the future contribution of this industry to the improved quality of life and economic growth as well as the employment opportunities on this continent. Finally, a method of co-operation between research in photovoltaics at the universities and local industry is proposed as part of the Research and Development (R&D) infrastructure necessary for the technical support of this field.     

Influence of long- term aging and superimposed creep

In an effort to understand the effects of long-term aging at high temperatures and those of the superimposed creep stresses on the microstructural variations in a 0.50Cr-0.50Mo-0.25V steel, the shoulder and gage portions of the specimens subjected to stress rupture tests at 500 °C and 540 °C have been studied by transmission electron microscopy. The optical microstructure, in the normalized and tempered condition, consists of about 95 pct ferrite with the remainder bainite. The ferrite has an extremely fine precipitation of vanadium carbide (VC) as interphase precipitate as well as in random distribution. In the bainitic area, M₃C is present in the globular as well as plate-like morphology. Specimens ruptured at 500 °C and 540 °C were selected for transmission electron microscopic study. Both the interphase precipitates and randomly distrib- uted precipitates of VC coarsen considerably due to prolonged exposure at elevated tempera- tures, and ultimately fine M₂C platelets nucleate and grow on either side of these precipitates, resulting in the formation of the so-called H-carbides. The superimposed creep stress has a marginal effect on the coarsening kinetics of VC but has enhanced its precipitation along dis- locations and has promoted the formation of H-carbides.     

Experimental and theoretical study on amino acid derivatives as eco-friendly corrosion inhibitor on mild steel in hydrochloric acid solution

Amino acid derivatives, namely, 2-(2-oxo-2-phenothiazin-10-yl)ethylamino)-3-mercaptopropanoic acid (OPEM) and 2-(2-oxo-2-phenothiazin-10-yl)ethylamino)acetic acid (OPEA) were synthesized and investigated as inhibitors for mild steel corrosion in 15% HCl solution using the weight loss, polarization, and electrochemical impedance spectroscopy (EIS) techniques. The inhibition efficiency of both the inhibitors increased with increasing the temperature and concentration of inhibitor. The inhibitors OPEM and OPEA show corrosion inhibition efficiency of 97.5 and 95.8%, respectively, in 200?ppm concentration, at 333?K. Polarization studies showed that both studied inhibitors were of mixed type in nature. The adsorption of inhibitors on the mild steel surface obeys Langmuir adsorption isotherm and the surface of inhibited and uninhibited specimens were analyzed by scanning electron microscopy (SEM). The semiempirical AM1 method was employed for theoretical calculations and the obtained results were found to be consistent with the experimental findings.     

Multi-party semi-quantum key distribution-convertible multi-party semi-quantum secret sharing

This paper proposes a multi-party semi-quantum secret sharing (MSQSS) protocol which allows a quantum party (manager) to share a secret among several classical parties (agents) based on GHZ-like states. By utilizing the special properties of GHZ-like states, the proposed scheme can easily detect outside eavesdropping attacks and has the highest qubit efficiency among the existing MSQSS protocols. Then, we illustrate an efficient way to convert the proposed MSQSS protocol into a multi-party semi-quantum key distribution (MSQKD) protocol. The proposed approach is even useful to convert all the existing measure–resend type of semi-quantum secret sharing protocols into semi-quantum key distribution protocols.     

Influence of long-term aging at 520 °C and 560 °C and the superimposed creep stress on the microstructure of 1.25Cr-0.5Mo steel

In order to understand the influence of high-temperature aging effects and those of the superimposed creep stress on the microstructural variations in a 1.25Cr-0.5Mo steel, the shoulder as well as gage portions of specimens subjected to stress-rupture tests at 520 °C and 560 °C have been studied by transmission electron microscopy. In the normalized and tempered condition, the microstructure of the steel consists of 90 pct ferrite and 10 pct bainite, and M₃C is the only carbide present in bainite and at a few ferrite grain boundaries. On aging at 520 °C for 5442 hours, Cr₂N precipitates in a fibrous form at ferrite-bainite interfaces, and the creep stress has enhanced this mode of precipitation. On holding for 13,928 hours at 520 °C, fibrous carbide is still present but its composition has changed to Mo₂C, while the superimposed creep stress has promoted the precipitation of Mo₂C needles with fine globular precipitates of M₂₃C₆. Aging at 560 °C for 1854 or 10,338 hours has resulted in the precipitation of longer Mo₂C needles and ellipsoidal M₂₃C₆ carbide precipitation; the superimposed creep stress has resulted in a more dense precipitation of shorter needles in both cases. There is some recovery of bainitic ferrite at 560 °C, though the cementite coarsening is negligible.     

PFC-CTR,PFC-OCB: Efficient stream cipher modes of authencryption

Authencryption is a cryptographic process of providing confidentiality and integrity protection of messages in a single pass, simultaneously, without any support of conventional checksum, MAC, or hash function. This article encompasses the process to construct the stream cipher-based authencryption environment, where the keystream is generated from any secure block algorithm like AES. Accordingly, in order to demonstrate the working principle of authencryption in the stream cipher environment, the authors introduce two stream cipher modes of authencryption, namely, PFC-CTR and PFC-OCB. PFC-CTR denotes the counter-based authencryption environment, and PFC-OCB specifies the authencryption environment built upon the underlying foundation of OCB. They argue that both of the proposed stream cipher modes of authencryption are quite robust against several active attacks (e.g., message stream modification attacks, known-plain-text attacks, and chosen-plain-text attacks). At the same time, they can efficiently deal with other issues like “limited error propagation,” and so on, existing in several conventional stream cipher modes of operation like CFB, OFB, and CTR.     

Affine invariant comparison of point-sets using convex hulls and hausdorff distances

Many object recognition or identification applications involve comparing features associated with point-sets. This paper presents an affine invariant point-set matching technique which measures the similarity between two point-sets by embedding them into an affine invariant feature space. The developed technique assumes no a priori knowledge of reference points, as is the case in many identification problems. Reference points of a point-set are obtained based on its convex hull. An enhanced version of the Modified Hausdorff Distance is also introduced and used in the feature space for comparing two point-sets. It should be noted that the technique does not attempt to obtain correspondences between the point-sets. The introduced technique is applied to two real databases and its performance is found favorable as compared to three other affine invariant matching techniques.     

Provably Secure Mutual Authentication and Key Exchange Scheme for Expeditious Mobile Communication Through Synchronously One-Time Secrets

The Universal Mobile Telecommunication Standard (UMTS) is continuously evolving to meet the increasing demand of modern mobile and Internet applications for high capacity and advanced features in security and quality of service. Although admittedly enhanced in terms of security as compared to GSM (2G) systems, UMTS still has some weaknesses that may often lead to several security incidents. In this article, we come up with a novel authentication mechanism based on the one-time-secret security capabilities, which can assure an expeditious mobile communication environment and simultaneously be able to deal with the several issues related to security vulnerabilities (Redirection Attack, Man-in-the-Middle-Attack) and others like the excessive bandwidth consumption, storage overhead in VLR etc. existing in the current mobile communication (UMTS). In addition, here we also introduce a new concept called “Neighborhood Policy”, where several VLRs can form groups among themselves and carry out significant responsibilities in order to authenticate a User without interfering HLRs even though the User moves to a new VLR (belongs to the same group). We argue that the proposed solution not only achieves the mutual authentication in a secure manner, but at the same time, it also greatly reduces the computation and communication cost of the mobile User as compared to the existing state of the art authentication schemes.     

Effect of filler addition and strain rate on the compressive strength of silica styrene‐butadiene rubber‐filled epoxy composites

The compressive failure of nanoparticle silica and styrene‐butadiene rubber (SBR)‐filled epoxy composites has been investigated. Significant increase in compressive strength, compressive modulus, work of yielding, and work of fracture was noted for the cases of composites containing low weight fraction of silica and SBR. The compressive strength is about 4–10 times of the tensile strength for composite material containing different weight percent of SBR. Increase in compressive yield strength and decrease in compressive ultimate strength have been observed with crosshead speed 0.1–100 mm/s over all weight content of SBR and silica. The material shows increased elastic region with increasing crosshead speed. This indicates that the material is expected to behave more elastically and less plastically over all the crosshead speeds. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers