A secure and efficient conference scheme for mobile communications

A growing application area in mobile communications is mobile teleconferencing, in which a group of mobile users collaborate in an interactive procedure, such as a board meeting, a task force, a scientific discussion, or even a virtual classroom. Wireless communications transmit conversations via radio, making them more susceptible to eavesdropping and unauthorized access than are conversations carried via wires. Therefore, it is crucial to ensure confidentiality and authenticity in mobile teleconferencing. When deploying secure services in mobile teleconferences, it has to be taken into account that the mobility of users is usually built on portable devices with limited computing capability. A secure conference scheme for mobile communications needs to be executed efficiently on portable devices. We propose a new secure and efficient conference scheme for mobile communications. Based on a modular square root technique, this scheme is secure against eavesdropping, impersonating, and tracking attacks and allows a participant to join or quit a mobile teleconference dynamically. In addition, the scheme is particularly efficient on the mobile user's portable device because the mobile user needs to perform only single modular multiplication plus encryptions and decryptions of a secret key cryptosystem.     

改善机载预警非正侧面阵雷达主杂波区性能的研究

本文研究了机载预警雷达采用非正侧面阵时主杂波区性能改善的问题，首先对机载雷达非正侧阵上染波谱带进行了分析，其次研究了文献（１）的先滤波再自适应处理的方法，并从实用化角度提出了改进的方法，最后对改进方法进行了详细的理论分析与计算机模拟研究。     

Effect of curing moisture on the indentation force deflection of flexible polyurethane foam

The moisture effect on the indentation force deflection (IFD) of flexible polyurethane foam was examined through the curing of the foam with different moisture contents. The employed foam was cured at 30, 40, 50, 60, 70, and 80% relative humidity, and the corresponding curing temperature was constant at 23°C. The experiments showed that the measured IFD and support factor of the flexible polyurethane foam decreased, and the hysteresis increased with the curing moisture. A statistical conversion formula was generated experimentally to correct the measured IFD of the flexible polyurethane foam to eliminate the deviation caused by the moisture effect. The measured IFD was inversely exponentially proportional to the curing moisture. The accuracy of the correction formula was verified by the conditioning of the foam again with different moisture contents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1679–1682, 2007     

Catalytic epoxidation of α-pinene over bifunctional mesoporous molecular sieves

Bifunctional titanium-mesoporous molecular sieves containing different trivalent ions, e.g. B³⁺, Al³⁺ or Fe³⁺, were synthesized and characterized. These catalysts, which contain both acid and oxidizing catalytic sites, are very active in epoxidation of bulky olefins and highly selective in diol formation. A reasonably good stability and re-usability are also observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Improved Scalar Multiplication on Elliptic Curves Defined over F2mn

We propose two improved scalar multiplication methods on elliptic curves over F_qn where q = 2^m using Frobenius expansion. The scalar multiplication of elliptic curves defined over subfield F_q can be sped up by Frobenius expansion. Previous methods are restricted to the case of a small m. However, when m is small, it is hard to find curves having good cryptographic properties. Our methods are suitable for curves defined over medium‐sized fields, that is, 10 ≤ m ≤ 20. These methods are variants of the conventional multiple‐base binary (MBB) method combined with the window method. One of our methods is for a polynomial basis representation with software implementation, and the other is for a normal basis representation with hardware implementation. Our software experiment shows that it is about 10% faster than the MBB method, which also uses Frobenius expansion, and about 20% faster than the Montgomery method, which is the fastest general method in polynomial basis implementation.     

Design and development of an intelligent controller for a pole-balancing robot

In this paper, an intelligent controller capable of static balancing as well as dynamic balancing of a pole mounted on a motorized robot is designed and developed. The brain of the intelligent controller lies in the Fuzzy Inference System, which receives as its input displacement, velocity and acceleration information. An embedded instrumentation system onboard the robot measures the displacement of the robot and the angle of inclination of the pole from the vertical position. For static balancing, the controller needs to maintain the pole in an upright position while the robot is free to move on a flat surface. For dynamic balancing, the robot needs to balance the pole while performing transitions up and down a ramp. Furthermore, the robot needs to steer itself back to the center to prevent it from falling off the ramp.     

Reliability of ferrocement slabs under cyclic thermal-shock loading

The reliability of ferrocement slabs subjected to cyclic thermal-shock loading induced by raindrops during service is investigated. The data are obtained experimentally by subjecting specimens to heating and wetting cycles and monitoring the residual first-crack strength at different periods. The imposed thermal-shock loads simulate actual service conditions and are estimated by monitoring the temperature of typical roofing slabs just before the commencement of rain over a period of time. The mean deterioration in strength obtained after correcting for curing effects due to ageing and temperature, as well as the uncertainty present, are used to assess the reliability of slabs having residual first-crack strengths above some prescribed values at different periods. The results indicate that ferrocement slabs posses good flexural resistance with respect to the cyclic loadings studied and are suitable for use as roofing elements.     

Patterns of psoriatic arthritis in Orientals

OBJECTIVE: To determine the clinical features of psoriatic arthritis (PsA) in a multiethnic Oriental population and to study the effect of ethnicity on disease patterns. METHODS: A retrospective study of 80 patients with PsA seen at either a rheumatology or dermatology referral center. Patients and case records were reviewed and data abstracted according to a standard protocol. Eighty consecutive patients with psoriasis without PsA seen at the dermatology center were recruited as controls. RESULTS: Asymmetric polyarthritis developing in the 4th decade with an equal male to female ratio was the commonest pattern of arthritis among Chinese, Indians, and Malays. Clinically apparent lumbar spondylitis was significantly more common in Indians than Chinese (10/11 vs 11/20, respectively; p = 0.046), although the prevalence of lumbar spondylitis was similar in all ethnic groups. Eighty-nine percent of subjects required nonsteroidal antiinflammatory drugs and 51% required disease modifying antirheumatic drugs at some time for control of joint disease. PsA was significantly more common among Indians compared to the ethnic distribution of the Singapore population (p < 0.000001). Multiple logistic regression identified Indian ethnicity as a risk factor for the development of PsA (OR 2.39, 95% confidence interval 1.02 to 5.60). CONCLUSION: The commonest pattern of PsA in all ethnic groups was asymmetric polyarthritis. Ethnicity affected the development and presentation of PsA in our series: Indians with psoriasis had double the risk of developing PsA compared to Chinese with psoriasis, and lumbar spondylitis when present in Chinese subjects was asymptomatic in 45%, being detectable only on radiological examination.     

Generic Impedance-Based Model for Structure-Piezoceramic Interacting System

This paper describes a generic impedance-based model for predicting the electromechanical (EM) impedance of one-dimensional (1D) and two-dimensional (2D) structure-piezoceramic (PZT) interacting systems. The vibration of a PZT patch is first analyzed. The effect of the host structure is then represented by its force impedance, which is obtained by a semianalytical method. Finally, experiments are carried out on beams and plates to simulate 1D and 2D problems, respectively. It is found that the predicted EM impedance of the structure-PZT interacting system coincides very well with the experimentally measured data. The results show that the predicted peaks match the natural frequencies of the host structure. The very small shift of the peaks from the natural frequencies caused by the interaction between the host structure and the PZT patch indicates that the small size PZT patch can be permanently bonded to the structure for on-line health monitoring without changing the mechanical properties of the structure too much. It is concluded that the proposed impedance-based model for general structure-PZT interacting systems can be potentially used in structural health monitoring.