Appraisal of digital terrain elevation data for low-altitude flight

The use of terrain elevation databases in advanced guidance and navigation systems has greatly expanded. However, the limitations and accuracies of these databases must be considered and established prior to safe system flight evaluation. A simple approach to quantify reasonable flight limits is presented and evaluated for a helicopter guidance system dependent on a terrain database. The flight test evaluated involved a helicopter equipped with a Global Positioning System (GPS) receiver and radar altimeter, and a ground station GPS receiver which provided improved helicopter positioning. The precision navigation and radar altimeter data was acquired while flying low-altitude missions in south-central Pennsylvania. The aircraft-determined terrain elevations were compared with the terrain predicted by the Defense Mapping Agency (DMA) Level 1 terrain elevation data for the same area. The results suggest a safe set clearance altitude of 220 ft for flight testing of a DMA-based guidance avionic in the same area

Nonlinear Unsteady Motions and NOx Production in Gas Turbine Combustors

Chiefly for improved efficiency, the trend to increasing use of gas turbine engines in stationary powerplants has been firmly established. The requirement for minimum NOx production has motivated operation as close as practically possible near the lean flammability limit, to reduce flame temperatures and consequently reduce formation of nitrogen oxides via the Zeldovich thermal mechanism. However, experience has shown that under these conditions, stability of the chamber is compromised, often leading to the presence of sustained oscillations in the combustor. That possibility raises the problem of the influence of oscillatory motions on the production of nitrogen oxides. Numerically calculating these influences for a complex geometry gas turbine combustor is too computationally expensive at this ?me. Nonlinear analytical methods making use of these influences are a promising direction for simplei ways to design and develop operational gas turbine combustors. However, this analysis needs results on which to base unsteady models of the interaction between nonlinear oscillations and species production within a gas turbine combustor. In this paper, two methods are explored briefly as an initial step. The first is based on a configuration of perfectly stirred and plug flow reactors to approximate the flow in a combustion chamber. A complete representation of the chemical processes is accommodated, but the geometry is simplified. The second is a full numerical simulation for a realistic geometry, but at this stage the chemistry is simplified

Wildlife Management With a Capitalistic or a Socialistic Flavor: A Comparison of Montana with Norway

Montana and Norway passed laws in 1897 and 1899, respectively, which set the stage for today’s wildlife management. These laws were part of an effort to conserve dwindling populations of large ungulates. The Montana Legislature decided that the responsibility of wildlife management would rest primarily with the State, whereas the Norwegian Parliament decided that it would rest with the landowner. These efforts to conserve native large ungulates were successful in both Montana and Norway, but the choice of philosophically different ways to accomplish it led to very different management systems. I argue that Montana chose a socialistic system, in the sense that everyone has the same right to hunt and fish. Norway chose a capitalistic system with the landowners owning the hunting and fishing rights. I will argue that this has had major implications for the differences between these two entities in political support for wildlife, hunting methods and ethics, and wildlife conservation in general

Spacecraft ram glow and surface temperature

Space shuttle glow intensity measurements show large differences when the data from different missions are compared. In particular, on the 41-G mission the space shuttle ram glow was observed to display an unusually low intensity. Subsequent investigation of this measurement and earlier measurements suggest that there was a significant difference in temperature of the glow producing ram surfaces. The highly insulating properties coupled with the high emissivity of the shuttle tile results in surfaces that cool quickly when exposed to deep space on the night side of the orbit. The increased glow intensity is consistent with the hypothesis that the glow is emitted from excited NO2. The excited NO2 is likely formed through three body recombination (OI + NO + M = NO2*) where ramming of OI interacts with weakly surface bound NO. The NO is formed from atmospheric OI and NI which is scavenged by the spacecraft moving through the atmosphere. It is postulated that the colder surfaces retain a thicker layer of NO thereby increasing the probability of the reaction. It has been found from the glow intensity/temperature data that the bond energy of the surface bound precursor, leading to the chemical recombination producing the glow, is approximately 0.14 eV. A thermal analysis of material samples of STS-8 was made and the postulated temperature change of individual material samples prior to the time of glow measurements above respective samples are consistent with the thermal effect on glow found for the orbiter surface

Building the Rule of Law in Afghanistan: The Importance of Legal Education

The ‘rule of law’ remains an elusive commodity in Afghanistan. Securing a stable Afghanistan underpinned by the rule of law has proven exceedingly difficult despite widespread consensus in the international community regarding its fundamental importance. There is broad recognition that structural flaws in the Afghan justice system and legal profession undermine access to justice and democratic governance. Lawyers are indispensible to consolidating the rule of law; they draft laws, administer justice, shape government policy, and inculcate respect for individual rights. Yet, nobody, including the Afghan government, knows how lawyers practice in Afghanistan. Even less has been written about the process of educating Afghan lawyers even though a country's system of legal education has an undeniable impact on its legal system. Lawyers' education, especially in developing or transitional countries like Afghanistan, impacts how they ‘practice their profession, both in private and government roles.’ Legal education also promotes scholarship and practical expertise among a diverse range of government officials. Legal education is, thus, essential to the rule of law. This article provides an overview of the Afghan legal education by weaving together the scant existing literature and complementing it with several interviews with Afghan law professors to illuminate important historical and recent trends. It also begins to gather the baseline information urgently needed to better inform international efforts to promote the rule of law through assistance to the Afghan legal education system

Plasma Diagnostics by Antenna Impedance Measurements

The impedance of an electrically short antenna immersed in a plasma provides an excellent in situ diagnostic tool for electron density and other plasma parameters. By electrically short we mean that the wavelength of the free-space electromagnetic wave that would be excited at the driving frequency is much longer than the physical size of the antenna. Probes using this impedance technique have had a long history with sounding rockets and satellites, stretching back to the early 1960s. This active technique could provide information on composition and temperature of plasmas for comet or planetary missions. Advantages of the impedance probe technique are discussed and two classes of instruments built and flown by SDL-USU for determining electron density (the capacitance and plasma frequency probes) are described

Laboratory investigation of visible shuttle glow mechanisms

Laboratory experiments designed to uncover mechanistic information about the spectral and spatial characteristics of shuttle glow were conducted. The luminescence was created when a pulse of O atoms traveling at orbital velocities was directed toward NO molecules previously adsorbed to aluminum, nickel, and Z306 Chemglaz (a common baffle black) coated surfaces held at various temperatures. Spectral and spatial measurements were made using a CCD imaging spectrometer. Corroborative spectral information was recorded in separate measurements using a scanning monochromator and gated photomultiplier arrangement. The e-folding distance at several temperatures was calculated from images of the surface glow using the photometrics image processing capability of the imaging spectrometer. The e-folding distance was not altered as a function of incoming O beam velocity. The results are presented and the observations provide direct evidence that the visible shuttle glow results from recombination of oxygen atoms and surface bound NO

Simulation evaluation of a low-altitude helicopter flight guidance system adapted for a helmet-mounted display

A computer aiding concept for low-altitude helicopter flight was developed and evaluated in a real-time piloted simulation. The concept included an optimal control trajectory-generation algorithm based upon dynamic programming and a helmet-mounted display (HMD) presentation of a pathway-in-the-sky, a phantom aircraft, and flight-path vector/predictor guidance symbology. The trajectory-generation algorithm uses knowledge of the global mission requirements, a digital terrain map, aircraft performance capabilities, and advanced navigation information to determine a trajectory between mission way points that seeks valleys to minimize threat exposure. The pilot evaluation was conducted at NASA ARC moving base Vertical Motion Simulator (VMS) by pilots representing NASA, the U.S. Army, the Air Force, and the helicopter industry. The pilots manually tracked the trajectory generated by the algorithm utilizing the HMD symbology. The pilots were able to satisfactorily perform the tracking tasks while maintaining a high degree of awareness of the outside world

SETTING STANDARDS FOR SUSTAINABLE TOURISM, AS A SOURCES OF ENTREPRENEURSHIP

Abstract. Tourism is no doubt one of the largest industries and sources of entrepreneurship in the world.Behind fuels, chemicals and automotive parts, it is fourth in the amount of export income it generates.Over the recent decades, a plethora of tourism certification programs have sprung up worldwide in an effort to recognize tourism businesses who truly work to reduce negative impacts by using sustainable practices. This worldwide proliferation of tourism certification programs, however, has led to consumer confusion, lack of brand recognition and widely varying standards. Here the best practice standards for tourism certification programs is used as laid out in the Mohonk Agreement, and the recently released Global Sustainable Tourism Criteria, envisioned to serve as the common set of baseline criteria by which to accredit certification programs, to evaluate four state-level tourism certification programs as case studies in the world. This paper also conjecture what the future may look like for these programs. At the end some notes have been proposed for more researches in the way of tourism standardization