Aerodynamic shape study of supersonic surface to surface missiles with continuous flexible nose

The aerodynamic characteristics of nine configurations of supersonic continuous deflectable nose guided missiles have been investigated. The optimized geometry was achieved based on the accuracy of confliction with constant target in ground to ground mission. The studied configurations consist of a spherical nose tip, a tangent ogive, one set of stabilizing tail fines and a cylindrical body whose midsection is flexible to form an arc of a circle. So the cylindrical body consists of a fixed part in the vicinity of the nose, middle flexible part and main body with stabilizers. The effects of fixed length (Fix = 0, 1.5, 3Cal) and flexible length (Flex = 1, 2.5, 5Cal) parameters on the aerodynamics and flight dynamics of guided missile have been studied. A code has been developed to solve full Navier-Stokes equations using finite volume and Runge-Kutta time stepping techniques and modified Baldwin-Lomax turbulence model. Multi-block technique was also used to solve the main body and fin parts flow fields. Further, a 3 degree of freedom code along with a pure pursuit guidance subroutine was developed to compare planar flight dynamics of missiles. It was found that although the missiles with bigger lengths for fixed and flex parts show more maneuverability, but this is not favorable for all missile missions as sometimes it decreases the confliction accuracy. Flight dynamic analysis shows that a change in initial launch angle may shift the favorite configuration. This means only the aerodynamic defined aim functions cannot completely supersede flight dynamic analysis in geometric optimization. Further, the thrust vector moment is an important portion of total control moment as it enhances the hitting accuracy and also decreases the importance of geometry.

     

Investigation of hydrodynamic deep drawing for conical�Ccylindrical cups

Forming conical parts is one of the complex and difficult fields in sheet-metal forming processes. Because of low-contact area of the sheet with punch tip in the initial stages of forming, bursting occurs on the sheet. Moreover, since most of the sheet surface in the area between the punch tip and blank holder is free, wrinkles appear on the wall of the drawing part. Thus, these parts are normally formed in industry by spinning, explosive forming, or multi-stage deep drawing processes. In this paper, forming pure copper and St14 conical?Ccylindrical cups in the hydrodynamic deep drawing process was studied using finite element (FE) simulation and experiment. The effect of pressure path on the occurrence of defects and thickness distribution and drawing ratio of the sheet was studied. It was concluded that at low pressures, bursting occurs on the contact area of sheet with punch tip. At higher pressures, the cup was formed, but the wall thickness distribution depends on the pressure path. It was also illustrated that for the pressure path with a certain maximum amount, the workpiece was formed adequately with minimum sheet thickness reduction. Internal pressures more than this maximum amounts did not affect on the thickness distribution. By applying the desired pressure path, conical?Ccylindrical cups with high deep drawing ratio were achieved.     

Synthesis of heat exchanger networks with nonisothermal phase changes

Most literature on the synthesis of heat exchanger networks via mathematical programming methods has dealt with phase changes by assuming nearly isothermal conditions. Many multicomponent phase changes of practical interest (e.g., those in sub‐ambient processes) occur over ranges of temperatures and exhibit nonlinear temperature‐enthalpy relations (T‐H curve). In such cases, isothermal approximations may lead to inferior or unacceptable networks. In this article, we propose a mixed‐integer nonlinear programming formulation and a solution algorithm to incorporate nonisothermal phase changes in heat exchanger network synthesis. We approximate the nonlinear T‐H curves via empirical cubic correlations, and propose a procedure to ensure minimum temperature approach at all points in the exchangers. Our approach successfully solves two industry examples and shows promise for significant cost reductions when compared with existing processes. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Buckypaper fabrication by liberation of electrophoretically deposited carbon nanotubes

Free-standing films of multi-walled carbon nanotubes (MWCNTs), also known as buckypapers, have been fabricated by a two-step process using electrophoretic deposition (EPD). Films of the multi-walled carbon nanotubes were cast onto stainless steel electrodes from aqueous suspensions by EPD. Using a facile mechanical cleavage technique, the films were liberated from their underlying electrodes to yield the buckypapers. We investigated the films’ thickness, morphology, and surface topology using, respectively, profilometry, scanning electron microscopy, and atomic force microscopy. Mechanical characterization of the buckypapers revealed the average tensile strength and Young’s modulus to be 14.5 MPa and 3.3 GPa, respectively. This fabrication approach provides a cost effective, rapid, and reproducible method to make films of MWCNTs with a range of thicknesses and macroscopic lateral dimensions.     

The Effect of Nonuniform Emitter Sheet Resistance on PERC Solar Cell Performance

Silicon - The aim of this research work is to study the effects of non-uniform emitter sheet resistance on the performance of PERC solar cells. For this purpose, we used different simulation...     

Human–computer interaction using vision-based hand gesture recognition systems: a survey

Considerable effort has been put toward the development of intelligent and natural interfaces between users and computer systems. In line with this endeavor, several modes of information (e.g., visual, audio, and pen) that are used either individually or in combination have been proposed. The use of gestures to convey information is an important part of human communication. Hand gesture recognition is widely used in many applications, such as in computer games, machinery control (e.g., crane), and thorough mouse replacement. Computer recognition of hand gestures may provide a natural computer interface that allows people to point at or to rotate a computer-aided design model by rotating their hands. Hand gestures can be classified into two categories: static and dynamic. The use of hand gestures as a natural interface serves as a motivating force for research on gesture taxonomy, its representations, and recognition techniques. This paper summarizes the surveys carried out in human--computer interaction (HCI) studies and focuses on different application domains that use hand gestures for efficient interaction. This exploratory survey aims to provide a progress report on static and dynamic hand gesture recognition (i.e., gesture taxonomies, representations, and recognition techniques) in HCI and to identify future directions on this topic.     

Error Detection and Fault Tolerance in ECSM Using Input Randomization

For some applications, elliptic curve cryptography (ECC) is an attractive choice because it achieves the same level of security with a much smaller key size in comparison with other schemes such as those that are based on integer factorization or discrete logarithm. For security reasons, especially to provide resistance against fault-based attacks, it is very important to verify the correctness of computations in ECC applications. In this paper, error-detecting and fault-tolerant elliptic curve cryptosystems are considered. Error detection may be a sufficient countermeasure for many security applications; however, fault-tolerant characteristic enables a system to perform its normal operation in spite of faults. For the purpose of detecting errors due to faults, a number of schemes and hardware structures are presented based on recomputation or parallel computation. It is shown that these structures can be used for detecting errors with a very high probability during the computation of the elliptic curve scalar multiplication (ECSM). Additionally, we show that using parallel computation along with either PV or recomputation, it is possible to have fault-tolerant structures for the ECSM. If certain conditions are met, these schemes are more efficient than others such as the well-known triple modular redundancy. Prototypes of the proposed structures for error detection and fault tolerance have been implemented, and experimental results have been presented.     

Improving the performance of simulated annealing in structural optimization

This study aims at improving the performance of simulated annealing (SA) search technique in real-size structural optimization applications with practical design considerations. It is noted that a standard SA algorithm usually fails to produce acceptable solutions to such problems associated with its poor convergence characteristics and incongruity with theoretical considerations. In the paper novel approaches are developed and incorporated into the standard SA algorithm to eliminate the observed drawbacks of the technique. The performance of the resulting (improved) algorithm is investigated in conjunction with two numerical examples (a 304-member braced planar steel frame, and 132-member unbraced space steel frame) designed according to provisions of the Allowable Stress Design (ASD) specification. In both examples, curves showing the variation of average acceptance probability parameter in standard and improved algorithms are plotted to verify usefulness and robustness of the integrated approaches.     

Clear P-wave arrival of weak events and automatic onset determination using wavelet filter banks

P-wave arrivals of many weak events cannot be precisely determined manually. Difference in power levels between noise and P-wave in wavelet detail of weak events enables us to determine P-wave arrival manually. Because of this power difference, automatic onset detection and picking algorithm is introduced using the same wavelet detail. Parameter settings are not needed as algorithm will work on data generated by either short or very broad band seismometers. Application of the proposed algorithm on data of three stations of Egyptian National Seismic Network (ENSN) in Cairo region shows a maximum standard deviation of 0.14 seconds of the corresponding manual picks.