New public-key cryptosystem

The development of a new public-key cryptosystem is discussed. This system is a hybrid combination of the RSA (Rivest-Shamir-Adleman) and knapsack crypto-systems. The message is encrypted in two stages using the knapsack algorithm followed by the RSA algorithm, and then decrypted in reverse order. The mathematics of the knapsack and RSA algorithms, a security analysis of the hybrid system, and a small computer simulation example are all included. The major advantages of this system, when compared with the knapsack and RSA crypto-systems, are higher speed and greater security.     

Stress analysis of clamped-free grid composite cylindrical shell under various end loadings

Stress analysis of cylindrical grid-stiffened composite shells was conducted under transverse loading,pure bending,torsion and axial compression under clamped-free boundary condition.Electrical strain gauges were employed to measure the strains in transverse loading case to validate the finite element analysis which was conducted using ANSYS software.Good agreement was obtained between the two methods.It was observed that stiffening the composite shell with helical ribs decreased the average equivalent Von Mises stress on the shell.The reduction of the stress seemed to be higher in the intersection of two ribs.It was also seen that the stress reduction ratio was higher when the structure was under bending compared to torsion and axial compression.The reduction ratio was approximately 75% in pure bending in the intersection point of the ribs,while it was approximately 25% in torsion.Therefore,it is concluded that the presence of the ribs is more effective under bending.Failure analysis was done using Tsai-Wu criterion.The ribs were observed to result in maximum and minimum increase in the failure load of the structure under transverse bending and torsional loading,respectively.     

Automatic diagnosis from electrocardiograms (ECGs)

This paper deals with the development of a new algorithm for electrocardiogram (ECG) analysis for automatic diagnostic purposes. The frequency characteristic of each segment of the ECG signal is computed via a fast Fourier transform. The phase characteristic of the segments is used to identify the cardiac abnormalities. The accuracy, reliability, and consistency of the algorithm have been verified by carrying out a classification of various normal and abnormal ECG waveforms. This work is a useful step towards the goal of automatic and computerized ECG interpretation and diagnosis.     

New multistage knapsack public-key cryptosystem

A new public-key cryptosystem is presented. This system is a multistage trapdoor knapsack cryptosystem. In this system the message is encrypted and decrypted in multistage using a knapsack algorithm. The knapsack algorithm, a security analysis of the multistage system, and a small computer simulation example are presented. The main advantage of the proposed system is that it provides higher security than a single-stage knapsack cryptosystem of the same length.     

Generation of gaussian pseudo-random process with specific correlation properties

A new method for the generation of a correlated pseudo-random gaussian process with a desired power spectral density or auto-correlation function is presented. Samples of the pseudo-random process are generated at the output of the cascade connection of a pseudo-random number (PN) generator and correlation-shaping finite impulse response filter. The proposed method generates a pseudo-random gaussian process, having arbitrary correlation properties, with a high degree of accuracy. Computer simulation examples are given to demonstrate the performance of the method.     

Fat and protein contents, acidity and somatic cell counts in bulk milk of Holstein cows in the Khorasan Razavi Province, Iran

Relationships between total bulk milk somatic cell score (SCS) and milk fat and protein contents and acidity were investigated in the Khorasan Razavi Province, a region that contributes 6.83% of total milk production in Iran. A total of 1476 samples were analysed. Data were obtained by randomly collecting 123 samples of bulk tank milk from 41 dairy farms during April 2006 to March 2007, every month. Milk was analysed for titratable acidity, protein and fat contents and somatic cell counts (direct microscopic cell count and with Somatos, Russia). Microscopic and Somatos somatic cell counts were comparable. Results showed that the season of raw milk production did not have a significant effect on acidity. Milk fat content increased gradually from spring to winter and there were significant differences ( P <  0.05) between spring and other seasons. Higher levels of milk protein fractions were observed during the autumn and winter than in other seasons. The highest total bulk milk somatic cell counts were observed in July. Total bulk milk SCS had significant effects ( P <  0.05) on acidity and fat and protein contents. Moreover, the level of acidity and fat in milk decreased with increasing SCS. A significant positive relationship was observed between total bulk milk SCS and the protein content of milk. Elevated SCS were associated with lowered milk quality in Holsteins in the Khorasan Razavi Province.     

New technique for detection and height estimation of buried metallic objects

A new technique for the detection and height estimation of buried metallic objects is developed. This technique is bused on the phase characteristics of both transmitted and received signals. A discrete Fourier transform via a fast Fourier transform algorithm is used to compute the phase characteristic. The height of the buried metallic object is estimated by detecting the transition frequency and measuring the phase difference between the transition frequency and the next frequency component in the spectrum of the received signal. Computer simulation studies show that this technique is efficient, reliable, and provides sufficient accuracy.