With the extensive recent development of communication methods and resulting increase in data surveillance and espionage, the need for reliable data encryption methods is greater than ever. Conventional encryption calculations, for example, DES and RSA, are not beneficial in the field of picture encryption because of some inherent characteristics of pictures such as bulk data size and high redundancy, which are problematic for conventional encryption. Many researchers have proposed different image encryption schemes to overcome image encryption problems. In the last two decades, more and more studies have looked to incorporate conventional encryption methods and the complex behavior of chaotic signals. In this paper, a novel image encryption algorithm is proposed based on pixel chaotic permutation. A chaotic logistic map and Ikeda map are used to design a new pseudo-random bit generator, and a novel permutation scheme is used to modify pixel values. Then, a new permutation algorithm based on a traditional Japanese game called Amidakuji is used for pixel scrambling. Different statistical manners, such as correlation coefficient, NPCR (Number of Pixels Change Rate), UACI (Unified Average Changing Intensity), and entropy, are used to provide analysis of the effectiveness of the proposed encryption methods. Our example reveals that the proposed encryption method can obtain highly secure encrypted images using a novel chaotic permutation method based on Amidakuji.

Wireless sensor networks, which have been used in many applications in recent years, consist of tiny sensor nodes with restriction in processing ability and the battery unit. Because of that, one of the crucial problems in this field is power consumption and network lifetime. Geographic Adaptive Fidelity is a routing protocol which tries to reduce energy consumption by powering off unnecessary nodes. In this paper, we proposed a new backbone algorithm for this protocol to saving more energy which causes to improving the lifetime and performance of the networks. The results of simulation show that active grids will be halved approximately.

One of the most important concepts in multi programming Operating Systems is scheduling. It helps in choosing the processes for execution. Round robin method is one of the most important algorithms in scheduling. It is the most popular algorithm due to its fairness and starvation free nature towards the processes, which is achieved by using proper quantum time. The main challenge in this algorithm is selection of quantum time. This parameter affects on average Waiting Time and average Turnaround Time in execution queue. As the quantum time is static, it causes less context switching in case of high quantum time and high context switching in case of less quantum time. Increasing context switch leads to high average waiting time, high average turnaround time which is an overhead and degrades the system performance. With respect to these points, the algorithms should calculate proper value for the quantum time. Two main classes of algorithms that are proposed to calculate the quantum time include static and dynamic methods. In static methods quantum time is fixed during the scheduling. Dynamic algorithms are one of these methods that change the value of quantum time in each cycle. For example in one method the value of quantum time in each cycle is equal to the median of burst times of processes in ready queue and for another method this value is equal to arithmetic mean of burst times of ready processes.
In this paper we proposed a new method to obtaining quantum time in each cycle based on arithmetic-harmonic mean (HARM). Harmonic mean is calculated by dividing the number of observations by the reciprocal of each number in the series. With examples we show that in some cases it can provides better scheduling criteria and improves the average Turnaround Time and average Waiting Time.