Sharif Digital Repository

A new methodology has been proposed to model and predict the pilot rating of a typical aircraft for flights through turbulences. The main idea here is to correlate the so-called "pilot rating" to the pilot physical energy demanded by the aircraft in a given flight condition and flying task. The proposed methodology, in addition to the other known factors, accepts the level of the human pilot physical energy consumed in each suitable period of time as well as the rate of energy consumption in the same period. These two, form the prime factors to predict the pilot rating in flying tasks that have a reasonable duration. Different case studies conducted by the authors show that for cases like... 

The subject of the present paper is the investigation of the sharp edged gust effects on the aeroelastic behavior of a flexible wing. It is important to determine the response of the wing to the atmospheric turbulences during normal flight. So, linear modal analysis technique and linear quasi-steady aerodynamic are used for structural modeling and aerodynamic loading, respectively. Also, Lagrange method is used to obtain the system of equations of motion. Using the normal modes of free vibration, structural and aerodynamic matrices can be constructed. Then the aeroelastic instability of the system is determined using p method. Kussner function is used to model the sharp gust effects on the... 

We present a novel optical code division multiple access (OCDMA) scheme based on spatial optical heterodyning for free-space optical communication systems. In this technique, in particular, the decoding process is established by means of a spatial optical heterodyne receiver. The spatial heterodyning OCDMA introduced can be considered to be in the class of spread-space techniques, which implies that there is no structural limitation on the shape of time domain signals, e.g., digital or analog modulation. For the sake of simplicity and practicality we considered onoff keying modulation. However, there is no limitation on using more advanced modulation schemes such as pulse position... 

In this paper, the problem of designing optimal conflict-free maneuvers for planar multiple aircraft encounters is studied. The maneuvers propose suitable heading changes for aircraft in a cooperative manner. The new mathematical approach provides optimal trajectories to resolve a wide variety of conflicts, especially in the presence of high-altitude Clear Air Turbulence (CAT). The proposed approach effectively uses Genetic Algorithms (GA), together with modified webs, to quickly find conflict-resolving maneuvers. Different case studies show the method is fast enough to be used for real-time applications when resolving conflicts involving two aircraft. It is also efficient enough to resolve... 

Context. We show the benefits of using electron-multiplying CCDs and the shift-and-add technique as a tool to minimise the effects of atmospheric turbulence, such as blending between stars in crowded fields, and to avoid saturated stars in the fields observed. We intend to complete, or improve on, the census of the variable star population in globular cluster NGC 6715. Aims. Our aim is to obtain high-precision time-series photometry of the very crowded central region of this stellar system via the collection of better angular resolution images than has been previously achieved with conventional CCDs on ground-based telescopes. Methods. Observations were carried out using the Danish 1.54-m... 

Fading and path loss are the major challenges in practical deployment of free space optical communication systems. In this paper, a cooperative free space communication via an optical amplify-and-forward relay is considered to deal with these challenges. We use photon counting approach to investigate the system bit error probability (BEP) performance and study the effects of atmospheric turbulence, background light, amplified spontaneous emission, and receiver thermal noise on the system performance. We compare the results with those of the multiple-transmitter (MT) system. The results indicate that the performance of the relay-assisted system is much better than that of the MT system in... 

In this work, we derive a few new advective flux approximation expressions, apply them in a hybrid finite-volume-element (FVE) formulation, and solve the turbulent reacting flow governing equations in the cylindrical frame. To derive these advective-kinetic-based expressions, we benefit from the advantages of a physical influence scheme (PIS) basically, extend it to the cylindrical frame suitably, and approximate the required advective flux terms at the cell faces more accurately. The present numerical scheme not only respects the physics of flow correctly but also resolves the pressure–velocity coupling problem automatically. We also suggest a bi-implicit algorithm to solve the set of... 

Reliability evaluation is a key factor in serviceability and safety analysis of air vehicles. Structural health monitoring methods have grown to a degree of maturity in many industries. However, there is a challenging interest to tie in SHM with reliability assessment. In this respect, consideration of stochastic structural dynamics with SHM data and random loadings opens a new chapter in failure prevention. The current study focuses on the stochastic behavior of structures as a way to relate SHM data with reliability. In this respect, uncertain factors such as atmospheric turbulence, structural parameters, and sensor outputs are considered in the process of reliability assessment. Firstly,...