Helicopter Anti-Torque System Using Strakes

A helicopter is disclosed with a system for controlling main-rotor torque which reduces the power and size requirements of conventional anti-torque means. The torque countering forces are generated by disrupting the main rotor downwash flowing around the fuselage. The downwash flow is separated from the fuselage surface by a strake positioned at a specified location on the fuselage. This location is determined by the particular helicopter wash pattern and fuselage configuration, generally being located between 20 deg before top dead center (TDC) and 80 deg from TDC on the fuselage side to which the main rotor blade approaches during rotation. The strake extends along the fuselage from the cabin section to the aft end and can be continuous or separated for aerodynamic surfaces such as a horizontal stabilizer

A research program in determination of heavy metals in sediments and benthic species in relation to nuclear power plant operation

Heavy metals in the estuarine environment can be toxic to fish and shellfish early life history stages and concentrations build up to levels of concern in marketable shellfish. The present survey was begun just before startup in 1974 of the 1900 megawatt Calvert Cliffs Nuclear Power Plant on the Chesapeake Bay in order to assess and understand factors relating to heavy metal accumulation in estuarine biota. Oysters were collected in large numbers at test and reference sites in June 1974 to 77 and individually analyzed for copper and zinc. Oyster copper and zinc concentrations were correlated with salinity read at time of collection. The relationship of oyster age to metal concentration was examined with two sets of oysters of known age and genetic origin (laboratory spawned). Copper sorption by typical mid Bay sediments, and field studies on cadmium concentrations in sediments were examined

An adaptive maneuvering logic computer program for the simulation of one-on-one air-to-air combat. Volume 1: General description

A technique for computer simulation of air combat is described. Volume 1 decribes the computer program and its development in general terms. Two versions of the program exist. Both incorporate a logic for selecting and executing air combat maneuvers with performance models of specific fighter aircraft. In the batch processing version the flight paths of two aircraft engaged in interactive aerial combat and controlled by the same logic are computed. The realtime version permits human pilots to fly air-to-air combat against the adaptive maneuvering logic (AML) in Langley Differential Maneuvering Simulator (DMS). Volume 2 consists of a detailed description of the computer programs

Complexity-based learning and teaching: a case study in higher education

This paper presents a learning and teaching strategy based on complexity science and explores its impacts on a higher education game design course. The strategy aimed at generating conditions fostering individual and collective learning in educational complex adaptive systems, and led the design of the course through an iterative and adaptive process informed by evidence emerging from course dynamics. The data collected indicate that collaboration was initially challenging for students, but collective learning emerged as the course developed, positively affecting individual and team performance. Even though challenged, students felt highly motivated and enjoyed working on course activities. Their perception of progress and expertise were always high, and the academic performance was on average very good. The strategy fostered collaboration and allowed students and tutors to deal with complex situations requiring adaptation

Free energy density for mean field perturbation of states of a one-dimensional spin chain

Motivated by recent developments on large deviations in states of the spin chain, we reconsider the work of Petz, Raggio and Verbeure in 1989 on the variational expression of free energy density in the presence of a mean field type perturbation. We extend their results from the product state case to the Gibbs state case in the setting of translation-invariant interactions of finite range. In the special case of a locally faithful quantum Markov state, we clarify the relation between two different kinds of free energy densities (or pressure functions).Comment: 29 pages, Section 5 added, to appear in Rev. Math. Phy

Wearing Quality of Reused Wool

This cooperative study between the South Dakota and Minnesota stations, was undertaken to determine the effect of combining various amounts of reused wool with new wool upon the serviceability of wool flannels made of these two types of fiber. Since the wear life of a garment necessarily must include cleaning and aging as well as wear the study was designed to measure the physical changes in these flannels which resulted from those three factors

Compact millimetre wave and terahertz radiation sources driven by pseudospark-generated electron beam

A pseudospark (PS) plasma sourced electron beam was both computationally and experimentally studied for generation of millimetre wave and terahertz radiation. The beam-wave interaction region is a sinusoidal rippled-wall slow wave structure of a backward wave oscillator (BWO) in G-band. An electron beam of ∼1 mm diameter carrying a current of up to 10 A with a sweeping voltage of 42 to 25 kV and pulse duration of 25 ns propagated through the interaction region in a plasma environment without the need for a guiding magnetic field, which resulted in broadband millimetre radiation generation over a frequency range of 186-202 GHz with a maximum power of 20 W

Experiments on W-band extended interaction oscillator with pseudospark sourced post-accelerated electron beam

The experimental study of a pseudospark discharge sourced electron beam with post acceleration (PA) is presented. The PA circuit was used to drive a W-band extended interaction oscillator (EIO). The experiments showed a significant increase in the output power, with 200 Watts at 94 GHz measured corresponding to a 5 times increase in the output power as compared to when post acceleration is not used. The microwave device developed has the advantage of not requiring an external magnetic field making it a low cost, compact and portable sub-terahertz radiation source

Study of the beam profile and position instability of a post-accelerated pseudospark-sourced electron beam

A pseudospark-sourced electron beam is a promising candidate for driving a THz millimeter wave radiation source. However, the physics governing the electron beam density profile and the beam center deviation from the axis of the structure, which may be caused by the randomness in the pseudospark discharge process, remains still unclear especially for the high energy component of the pseudospark-sourced electron beam which is usually non-mono-energetic. It is essential to study the electron beam density profile and the beam center position distribution for optimizing the pseudospark discharge configuration. In this paper, images of some single-shot electron beam pulses have been captured using a 50 μm thickness stopping copper foil and a phosphor screen coated with P47 scintillator to study the electron beam density profile and the beam center position distribution of the high energy component of the electron beam. The experiments have been carried out on two pseudospark discharge configurations with two different size hollow cathode cavities. The influence of the cathode aperture of each configuration has also been studied according to the beam images. Experimental results show that the beam profile of the high energy component has a Lorentzian distribution and is much smaller than the axial aperture size with the beam centers dispersing within a certain range around the axis of the discharge structure. The pseudospark-sourced electron beam with the larger hollow cathode cavity shows smaller full width at half maximum (FWHM) radius and a more concentrated beam center distribution