Strong asymmetrical vortices appear on the leeward of slender body at high angles of attack, which has very unfavorable effect on the stability and control of the aircraft. A method is developed to control the side fo...Strong asymmetrical vortices appear on the leeward of slender body at high angles of attack, which has very unfavorable effect on the stability and control of the aircraft. A method is developed to control the side force of slender body at high angles of attack, and is verified in wind tunnel. A thin-film triangular self-excited oscillation flag is fixed at the tip of the slender body model whose semi-apex angle is 10°. Side force is approximately linearly proportional to roll-setting angle of self-excited oscillation flag at high angles of attack, and the slop of fitting straight line obtained by the least square method is -0.158. The linear relationship between side force and roU-setting angle provides convenience for developing side force control law of slender body at high angles of attack. Experimental data shows that the side force coefficients vary linearly with roll-setting angles when a specific plastic self-excited oscillation flag is used as the control flag. The range of side force coefficient and roll-setting angle are, respectively, -3.2 to 3.0 and -20° to 20°. The device is simple, effective, and is of great potential in engineering application.展开更多
The paper focuses on the design and Field Programmable Gate Array (FPGA) implementation of embedded system for time based dual encryption scheme with Delay Compulsion Function (DCF) and also illustrates the applicatio...The paper focuses on the design and Field Programmable Gate Array (FPGA) implementation of embedded system for time based dual encryption scheme with Delay Compulsion Function (DCF) and also illustrates the application of DCF in time based cryptography. Further, the strength of the time based FPGA encryption algorithm with and without using DCF is analyzed using a Nios II processor. This proposed scheme enhances the security of vital data against Brute force attack by incorporating a temporal key distribution where two different keys encrypt the data simultaneously, one being the regular key and the other being the time. The time is included using a dynamically varying number of shifts thereby allowing the system to wait for the duration and this forms the second dimension of the key. Presently, available encryption systems suffer from Brute Force attack in which all the key combinations are tried in order to find the correct key. In such a case, the time taken for breaking the key depends on the speed of the system used for cryptanalysis. The proposed system adds complexity by using dynamically varying sequence of operations, by including the time as a second dimension of the key besides minimizing the possibility of Brute Force attack and increasing the time required for cryptanalysis irrespective of the system capability. As the proposed system needs concurrent execution and real time processing, the system is implemented using Altera Stratix II FPGA and the results are presented.展开更多
基金supported by the ‘‘National Natural Science Foundation-Outstanding Youth Foundation’’
文摘Strong asymmetrical vortices appear on the leeward of slender body at high angles of attack, which has very unfavorable effect on the stability and control of the aircraft. A method is developed to control the side force of slender body at high angles of attack, and is verified in wind tunnel. A thin-film triangular self-excited oscillation flag is fixed at the tip of the slender body model whose semi-apex angle is 10°. Side force is approximately linearly proportional to roll-setting angle of self-excited oscillation flag at high angles of attack, and the slop of fitting straight line obtained by the least square method is -0.158. The linear relationship between side force and roU-setting angle provides convenience for developing side force control law of slender body at high angles of attack. Experimental data shows that the side force coefficients vary linearly with roll-setting angles when a specific plastic self-excited oscillation flag is used as the control flag. The range of side force coefficient and roll-setting angle are, respectively, -3.2 to 3.0 and -20° to 20°. The device is simple, effective, and is of great potential in engineering application.
文摘The paper focuses on the design and Field Programmable Gate Array (FPGA) implementation of embedded system for time based dual encryption scheme with Delay Compulsion Function (DCF) and also illustrates the application of DCF in time based cryptography. Further, the strength of the time based FPGA encryption algorithm with and without using DCF is analyzed using a Nios II processor. This proposed scheme enhances the security of vital data against Brute force attack by incorporating a temporal key distribution where two different keys encrypt the data simultaneously, one being the regular key and the other being the time. The time is included using a dynamically varying number of shifts thereby allowing the system to wait for the duration and this forms the second dimension of the key. Presently, available encryption systems suffer from Brute Force attack in which all the key combinations are tried in order to find the correct key. In such a case, the time taken for breaking the key depends on the speed of the system used for cryptanalysis. The proposed system adds complexity by using dynamically varying sequence of operations, by including the time as a second dimension of the key besides minimizing the possibility of Brute Force attack and increasing the time required for cryptanalysis irrespective of the system capability. As the proposed system needs concurrent execution and real time processing, the system is implemented using Altera Stratix II FPGA and the results are presented.
