The Fourth Element: Characteristics, Modelling, and Electromagnetic Theory of the Memristor

In 2008, researchers at HP Labs published a paper in {\it Nature} reporting the realisation of a new basic circuit element that completes the missing link between charge and flux-linkage, which was postulated by Leon Chua in 1971. The HP memristor is based on a nanometer scale TiO$_2$ thin-film, containing a doped region and an undoped region. Further to proposed applications of memristors in artificial biological systems and nonvolatile RAM (NVRAM), they also enable reconfigurable nanoelectronics. Moreover, memristors provide new paradigms in application specific integrated circuits (ASICs) and field programmable gate arrays (FPGAs). A significant reduction in area with an unprecedented memory capacity and device density are the potential advantages of memristors for Integrated Circuits (ICs). This work reviews the memristor and provides mathematical and SPICE models for memristors. Insight into the memristor device is given via recalling the quasi-static expansion of Maxwell's equations. We also review Chua's arguments based on electromagnetic theory.Comment: 28 pages, 14 figures, Accepted as a regular paper - the Proceedings of Royal Society

V/STOL maneuverability and control

Maneuverability and control of V/STOL aircraft in powered-lift flight is studied with specific considerations of maneuvering in forward flight. A review of maneuverability for representative operational mission tasks is presented and covers takeoff, transition, hover, and landing flight phases. Maneuverability is described in terms of the ability to rotate and translate the aircraft and is specified in terms of angular and translational accelerations imposed on the aircraft. Characteristics of representative configurations are reviewed, including experience from past programs and expectations for future designs. The review of control covers the characteristics inherent in the basic airframe and propulsion system and the behavior associated with ontrol augmentation systems. Demands for augmented stability and control response to meet certain mission operational requirements are discussed. Experience from ground-based simulation and flight experiments that illustrates the impact of augmented stability and control on aircraft design is related by example

The 'tumble' departure mode in weightshift-controlled

The cost of private or recreational flying is high for most conventional aircraft types. During the last 25 years, however, an alternative has become available in the form of the microlight aircraft. It has a relatively low cost of ownership and has opened up flying to a greater audience. However, there have been a number of accidents, usually fatal, to this class of aircraft, which could not be explained through any conventional understanding. The reason for these accidents, which involve a departure from controlled flight followed by aircraft structural failure (generally including mechanical failure of the basebar, wingtips and leading edge), has become known as the `tumble’, owing to the basic motion of the aircraft. This paper analyses the tumble mode, from its initiation through to the steady rotation condition. History has shown that the tumble mode has always resulted in the destruction of an aircraft. In consequence, it is the authors’ opinion that consideration of the tumble during the approval of new designs should concentrate upon avoidance, since there is no identi®able recovery mechanism from the established mode without the use of an external safety device. A programme of research into this phenomenon was initiated in 1997. The peculiar nature of the tumble motion has required the aerodynamic modelling to address the effects of a high pitch rate, which has led to the introduction of unsteady aerodynamic effects. This paper sets out to describe and explain the mode, leading to a model that might reasonably be developed to produce relatively tumble resistant aircraft. Finally, the methods of possible entry are explained; it is intended that this information may be used in pilot training to ensure the avoidance ofthe tumble instability

Flight evaluation of advanced controls and displays for transition and landing on the NASA V/STOL systems research aircraft

Flight experiments were conducted on Ames Research Center's V/STOL Systems Research Aircraft (VSRA) to assess the influence of advanced control modes and head-up displays (HUD's) on flying qualities for precision approach and landing operations. Evaluations were made for decelerating approaches to hover followed by a vertical landing and for slow landings for four control/display mode combinations: the basic YAV-8B stability augmentation system; attitude command for pitch, roll, and yaw; flightpath/acceleration command with translational rate command in the hover; and height-rate damping with translational-rate command. Head-up displays used in conjunction with these control modes provided flightpath tracking/pursuit guidance and deceleration commands for the decelerating approach and a mixed horizontal and vertical presentation for precision hover and landing. Flying qualities were established and control usage and bandwidth were documented for candidate control modes and displays for the approach and vertical landing. Minimally satisfactory bandwidths were determined for the translational-rate command system. Test pilot and engineer teams from the Naval Air Warfare Center, the Boeing Military Airplane Group, Lockheed Martin, McDonnell Douglas Aerospace, Northrop Grumman, Rolls-Royce, and the British Defense Research Agency participated in the program along with NASA research pilots from the Ames and Lewis Research Centers. The results, in conjunction with related ground-based simulation data, indicate that the flightpath/longitudinal acceleration command response type in conjunction with pursuit tracking and deceleration guidance on the HUD would be essential for operation to instrument minimums significantly lower than the minimums for the AV-8B. It would also be a superior mode for performing slow landings where precise control to an austere landing area such as a narrow road is demanded. The translational-rate command system would reduce pilot workload for demanding vertical landing tasks aboard ship and in confined land-based sites

Gain scheduling control and loop interactions in dual duct HVAC system

This research focuses on gain scheduling control of a dual duct system and its local loop interactions. To reach these objectives, experiments were conducted in a dual duct system. The test facility consists three control loops. (cold air temperature control, hot air temperature control, and mixed air temperature control). The steady state and dynamic characteristics of the dual duct system were studied. Two control strategies were employed to improve the system performance: (i) conventional PI control, and (ii) gain scheduling control. The experimental results subject to load disturbances (set-point changes and initial condition changes) showed that the performance of the gain scheduling controller is better than the conventional PI controller. However, it was found that the gain scheduling control method caused significant oscillations and took nearly 25 minutes to reach a stable final value under low load conditions. Therefore, an adaptive gain scheduling (AGS) controller was developed to improve the disturbance rejection properties of the controller. Experimental and simulation results show that the adaptive gain scheduling controller has dramatically increased controller performance under low load conditions. The prioritization of control loops due to loop interactions was evaluated and the gain scheduling-adaptive controller was applied to the entire system to minimize loop interactions. The experimental results showed that, compared to conventional PI controller, the dynamic responses of adaptive gain scheduling controller are better

Single-Pass Drying of Rough Rice Using Glass Transition Principles

The objective of this research was to study the drying characteristics, milling quality, and functional properties of rough rice subjected to single-pass drying while controlling kernel material states. Drying experiments were conducted at 60, 70, and 80C and relative humidities ranging from 13 to 83%. High drying air relative humidities (greater than 63%) maintained both the kernel surface and core in a rubbery state during drying, whereas low drying air relative humidities caused rapid transitioning of the surface layers from a rubbery to a glassy state. Long-grain pureline cultivar, Wells, medium-grain pureline cultivar, Jupiter, and long-grain hybrid cultivar, CL XL729, were dried from harvest moisture content to 12.5% moisture content in a single-pass. Immediately after drying, samples were tempered in the drying container or in sealed plastic bags at the drying air temperature for 0, 30, and 60 min, after which they were spread in thin layers and cooled to ambient conditions. For all drying air temperatures and tempering conditions, milling quality was not significantly different from the controls when the relative humidity of the drying air was maintained above 63% (both the kernel core and surface maintained in a rubbery state during drying) and rice was tempered immediately after drying in sealed plastic bags and at the drying air temperature for at least 60 min. Minimal reduction to milling quality was observed at the low drying-air relative humidities when samples were tempered immediately after drying in sealed plastic bags and at the drying air temperature for at least 60 min: tempering in containers having large headspaces or for shorter durations failed to reduce the intra-kernel stresses created during drying due to differences in material state between the surface and the core, thereby causing kernel fissuring and breakage during subsequent milling. The high-temperature conditions did not affect color, degree of milling, and thermal properties. However, pasting viscosity profile was significantly affected

STOVL Control Integration Program

An integrated flight/propulsion control for an advanced vector thrust supersonic STOVL aircraft, was developed by Pratt & Whitney and McDonnell Douglas Aerospace East. The IFPC design was based upon the partitioning of the global requirements into flight control and propulsion control requirements. To validate the design, aircraft and engine models were also developed for use on a NASA Ames piloted simulator. Different flight control implementations, evaluated for their handling qualities, are documented in the report along with the propulsion control, engine model, and aircraft model

A ground-simulator investigation of helicopter longitudinal flying qualities for instrument approach

A ground-simulation experiment was conducted to investigate the direct and interactive influences of several longitudinal static and dynamic stability parameters on helicopter flying qualities during terminal-area operations in instrument conditions. Variations that were examined included five levels of static control-position gradients ranging from stable to unstable; two levels of dynamic stability for the long-period oscillation; two levels of the steady-state pitch speed gradient; two levels of angle-of-attack stability and pitch-rate damping; and two levels of stability and control augmentation. These variations were examined initially in calm air and thin in simulated light-to-moderate turbulence and wind shear. Five pilots performed a total of 223 evaluations of these parameters for a representative microwave landing system precision approach task conducted in a dual-pilot crew-loading situation

Mission-oriented requirements for updating MIL-H-8501. Volume 1: STI proposed structure

The structure of a new flying and ground handling qualities specification for military rotorcraft is presented. This preliminary specification structure is intended to evolve into a replacement for specification MIL-H-8501A. The new structure is designed to accommodate a variety of rotorcraft types, mission flight phases, flight envelopes, and flight environmental characteristics and to provide criteria for three levels of flying qualities, a systematic treatment of failures and reliability, both conventional and multiaxis controllers, and external vision aids which may also incorporate synthetic display content. Existing and new criteria were incorporated into the new structure wherever they could be substantiated

The Fifth NASA/DOD Controls-Structures Interaction Technology Conference, part 1

This publication is a compilation of the papers presented at the Fifth NASA/DoD Controls-Structures Interaction (CSI) Technology Conference held in Lake Tahoe, Nevada, March 3-5, 1992. The conference, which was jointly sponsored by the NASA Office of Aeronautics and Space Technology and the Department of Defense, was organized by the NASA Langley Research Center. The purpose of this conference was to report to industry, academia, and government agencies on the current status of controls-structures interaction technology. The agenda covered ground testing, integrated design, analysis, flight experiments and concepts