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Aerodynamic characteristics of an Ejection Seat System at different angles of attack are studied by the numerical method and the flow mechanisms for such flows are carefully analyzed. The governing equations are Reynolds-averaged Navier-Stokes equations which are solved by the unstructured finite volume method. Upwind Osher scheme is used for spatial discretization and five-stage Runge-Kutta scheme is applied for temporal discretization. The DES model based on S-A one equation turbulence model is adopted. Parallel computation is based on the domain decomposition method and multi-block is achieved by using METIS system. The experimental data is used to validate this method. This research is helpful to understand the aerodynamic characteristics and flow mechanisms of Ejection Seat System at different angles of attack and Mach numbers, and can provide reasonable reference for Ejection Seat System design.

The improving technology and the ubiquity of the Internet have allowed more and more people to transmit data via the Internet. The contents of the transmission can be in the form of words, voices, images, or even computer animation. To protect the contents from interceptors' attention, the image hiding technology thus emerged. Some contents transmitted via the Internet can be confidential data such as highly valued product design blueprints or war plans, so it is important to pay more attention to the security of the transmitted data, or what we called secret image in this paper. The point of this paper is to enhance the security of the secret image without causing too much distortion to the host image and in the meantime to shorten the image hiding process time. For better protection, we adopted encryption process DES. In addition, we used greedy algorithm to shorten hiding process and to protect the host image from being severely distorted.

To test our proposed method to see whether it indeed achieved its objective, we used two sets of images in our experiment. The results of the experiments showed, when k = 2, our PSNR is close to that of Wang et al.'s optimal LSB substitution, but is not significantly different from that of simple LSB substitution. However, our method took approximately only 1/7 of the time consumed by Wang et al. When k = 3, our PSNR is significantly higher than that of simple LSB substitution. The experimental results confirmed that our method could effectively protect host image quality and shorten the overall hiding time when it enhanced the security of the secret image.

In the past, most image hiding techniques have been applied only to gray scale images. Now, many valuable images are color images. Thus, it has become important to be able to apply image-hiding techniques to hide color images. In this paper, our proposed scheme can not only be applied to "a color host image hiding a color secret image", but also to "a color host image hiding a gray scale secret image". Our scheme utilizes the rightmost 3, 2 and 3 bits of the R, G, B channels of every pixel in the host image to hide related information from the secret image. Meanwhile, we utilize the leftmost 5, 6, 5 bits of the R, G, B channels of every pixel in the host image and set the remaining bits as zero to generate a palette. We then use the palette to conduct color quantization on the secret image to convert its 24-bit pixels into pixels with 8-bit palette index values. DES encryption is then conducted on the index values before the secret image is embedded into the rightmost 3, 2, 3 bits of the R, G, B channels of every pixel in the host image.

The experimental results show that even under the worst case scenario our scheme guarantees an average host image PSNR value of 39.184 and an average PSNR value of 27.3415 for the retrieved secret image. In addition to the guarantee of the quality of host images and retrieved secret images, our scheme further strengthens the protection of the secret image by conducting color quantization and DES encryption on the secret image in advance. Therefore, our scheme not only expands the application area of image hiding, but is also practical and secure.

In this paper, a novel gray-level image-hiding scheme is proposed. The goal of this scheme is to hide multiple important gray-level images into another meaningful gray-level image. The secret images to be protected are first compressed using the vector quantization scheme. Then, the DES cryptosystem is conducted on the VQ indices and related parameters to generate the encrypted message. Finally, the encrypted message is embedded into the rightmost two bits of each pixel in the cover image.

According to the experimental results, average image qualities of 44.320 dB and 30.885 dB are achieved for the embedded images and the retrieved secret images, respectively. In other words, multiple secret images can be effectively hidden into one host image of the same size. In addition, the proposed scheme strengthens the protection of the secret images by conducting the DES cryptosystem on the related parameters and the VQ indices of the compressed secret images. Therefore, the proposed scheme provides a secure approach to embed multiple important images into another meaningful image of the same size.

The smart card is being used all over the world, because of its power to store data securely and execute calculations confidentially. This paper proposes an easy way to implement the strategy which can guarantee data integrity and privacy in the transmission path between the terminal application of the smart card and the smart card. This strategy consists of cryptographic functions of message and methods for transmitting APDU and managing secret keys. Some cryptographic functions of message are defined and developed for transmitting APDU confidentially. These cryptographic functions can keep the byte length of input and output messages identical. This strategy for transmitting APDU points out how to call cryptographic functions to encode or decode the data body of APDU, and how to construct a modified APDU message structure according to the original APDU message structure, which will be sent to its intended recipient instead of the original APDU message structure. With the proper secret keys, the authorized party can recover this modified APDU to its corresponding original APDU properly, without any information leakage. The transfer of secret keys to other parties is the most difficult aspect of secure APDU transmission, whereas data encryption/decryption is relatively straightforward. Two distinct strategies for managing secret keys, namely the static and the dynamic are introduced and compared. The dynamic strategy is preferred for a terminal application and smart card which do not need to authenticate each other. The implementation of this dynamic strategy has been detailed.

An efficient and secure platform is needed for data storage and transmission, specially for the multimedia content like audio, image and video. In this paper, a new methodology is proposed for the secured medical image compression. Initially, Bandelet transform is applied to the input medical image to obtain the coefficients. Using unequal error protection (UEP) method, the obtained coefficients are prioritized. These coefficients are encrypted using data encryption standard (DES) and will be encoded using listless set partitioning embedded block (Listless SPECK) technique. For the performance evaluation, peak signal-to-noise ratio (PSNR), mean square error (MSE), structural similarity index (SSIM), image quality index (IQI), average difference (AD), normalized cross-correlation (NK), structural content (SC), maximum difference (MD), Laplacian mean squared error (LMSE) and normalized absolute error (NAE) are taken. From the experimental results and performance evaluation, it is shown that the proposed approach is producing good results.

In this study, heat transfer characteristics and flow structures over periodically dimple-protrusion patterned walls in a turbulent channel flow were systematically investigated using Detached Eddy Simulation method. The periodically patterned surface is applied to the bottom wall only in the test channel. It is found that larger depth/height induces higher friction factor and heat transfer. Furthermore, the highest Nusselt number is found to be located at the upstream portion of protrusion and the downstream portion of dimple. Additionally, the distributions of Nusselt number exhibit symmetrical features for the small depth/height configuration and asymmetric characteristics for the large depth/height configuration.

The unsteady aerodynamics computational fluid dynamics simulations of the flow-field around a three-bladed Rutland 503 horizontal axis wind turbine rotor have been conducted in this paper to provide information needed to predict the three-dimensional aerodynamics behavior. In the CFD analysis, the variation of wind velocity between 9.3m/s and 15m/s is investigated. The Detached Eddy Simulation method is used with the turbulence model SST. A multiblock structured mesh is used for the discretization of the study domain. The solutions are obtained by using the Solver Fluent 6.3 which uses the method of finites volumes. The results of simulations obtained are compared with the experimental data [1] obtained in Wind Tunnel Laboratory LMA Arts and Métiers Paris-Tech in order to validate these results. Results of the numerical simulation in three dimensions of the unsteady field of flow around the blade are presented.

A reconfigurable cipher chip has higher security and flexibility than a conventional one. Therefore, it will be an important part of the future security mechanisms. For designing such kind of chips, the challenge is to improve the throughput rate. In this paper, the reconfiguration of DES, 3DES and AES is analyzed firstly. Then, it proposes a new reconfigurable architecture based on pipelining and paralleling which can implement the three algorithms with a high-speed. The results show that the operating frequency is 100MHz and the throughput rate is 7Gbps for DES, 2.3Gbps for 3DES and 1.4Gbps for AES. Compared with the similar existing implementations, our design can achieve a higher performance.

A new method of fast image encryption based on image characteristics and DES is presented. This paper introduces the basic characteristics of image, and analyzes the essence of DES. The image is first transformed based on rows and columns. Then a left-top part of the image is encrypted by DES. Most of the image data are encrypted using DES XOR operation. Experimental results show that this method has better safety, efficiency and is easily implemented.

While designing an encryption algorithm, apart from security, one of the most important parameter that are required to be considered is it's performance and cost analysis. Here we have tried to highlight the performance of some well known data encryption algorithms like DES, 3DES, AES ( Rijndael ) and compare them with the MODDES. Based on the experiment, it can be said that the MODDES algorithm is one of the best performing partially symmetric key algorithm among the algorithms chosen for implementation, particularly for the text message with limited size.