The Germination of Garden and Field Seeds

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What Collective Bargaining Promises and What it Does

[Excerpt] From the outset of my career in teaching, I have been deeply interested in the question of freedom. This interest is in part due to my upbringing and in part is the result of my academic training. Not only its substance but its origins, extension, and preservation have been abiding concerns. We often take freedom for granted, but quarrels and fights about its nature, conditions, and scope fill our history. Freedom had to be won. It was never, and is not now, established universally. It has had to be gained by groups who did not enjoy it. Such extensions as have been made were only by power of those who sought it. Freedom not only has had to be fought for, but, once gained, it has had to be maintained through constant defense. Eternal vigilance is the price of freedom

Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions

The effect of modifying the gas passage of hollow metal airfoils by the additIon of internal fins and partitions was experimentally investigated and comparisons were made among a basic unfinned airfoil section and two airfoil designs having metal fins attached at the leading edge of the internal gas passage. An analysis considering the effects of heat conduction in the airfoil metal was made to determine the internal modification effectiveness that may be obtained in gas-heated components, such as turbojet-inlet guide vanes, support struts, hollow propeller blades, arid. thin wings. Over a wide range of heated-gas flow and tunnel-air velocity, the increase In surface-heating rates with internal finning was marked (up to 3.5 times), with the greatest increase occurring at the leading edge where anti-icing heat requirements are most critical. Variations in the amount and the location of internal finning and. partitioning provided. control over the local rates of surface heat transfer and permitted efficient anti-icing utilization of the gas-stream heat content

Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

An empirical relation has been obtained by which the change in drag coefficient caused by ice formations on an unswept NACA 65AO04 airfoil section can be determined from the following icing and operating conditions: icing time, airspeed, air total temperature, liquid-water content, cloud droplet impingement efficiencies, airfoil chord length, and angles of attack. The correlation was obtained by use of measured ice heights and ice angles. These measurements were obtained from a variety of ice formations, which were carefully photographed, cross-sectioned, and weighed. Ice weights increased at a constant rate with icing time in a rime icing condition and at progressively increasing rates in glaze icing conditions. Initial rates of ice collection agreed reasonably well with values predicted from droplet impingement data. Experimental droplet impingement rates obtained on this airfoil section agreed with previous theoretical calculations for angles of attack of 40 or less. Disagreement at higher angles of attack was attributed to flow separation from the upper surface of the experimental airfoil model

Evaluating Drought Vulnerability of Small Community Surface Water Supply Systems in the Midwest

This report presents approaches and data availability for evaluating the drought vulnerability of small community water supply systems in the Midwest that obtain water from surface water bodies, such as rivers, streams, natural lakes, and man-made reservoirs. A description is provided of the various types of surface water sources from which 320 small community systems in the Midwest, each serving 10,000 or fewer people, obtain their water. The small community surface water system most commonly obtains its supply from one or two small impounding reservoirs. However, a substantial number of communities instead obtain their water from either direct river withdrawals or off-channel storage of water withdrawn from streams and rivers. Sixty of these 320 small community surface water systems were interviewed to gather information on the availability of data to determine the drought vulnerability of these systems. Although hydrologic and physical data exist for evaluating many of these systems, relatively few of the interviewed system managers could provide such pertinent information. A summary of selected hydrologic data is provided that can be used to determine the relative severity of major historical drought periods for various portions of the Midwest. Focus is given to historical droughts and available data for the southern portion of the Midwest where most surface water supply systems are located, comprising parts of Kansas, Missouri, Iowa, Illinois, Indiana, and Ohio. Geographic differences in drought severity are described, as is the influence of the physical characteristics of a water supply on the “critical” drought duration that a community must consider. Basic water budget analyses of water supplies and data needs are presented. Reservoir capacity measurements and estimates of inflow are the most critical data in reliable assessment of water supply adequacy. Depending on data availability, estimation of inflows may be straightforward to highly uncertain. For water supply systems that withdraw directly from a stream or river, the existence of long-term stream gage data on that river is particularly crucial to evaluate supply adequacy, and such data for larger streams and rivers are often available. With impounding reservoirs, which are typically located on smaller streams, data for that stream may often not exist; however, data from a “surrogate” gage that is considered to be hydrologically similar are often sufficient to estimate water supply yield. Systems that use off-channel reservoirs often withdraw water from smaller streams that do not have data for accurate depiction of their yield, and these systems also appear to be the most vulnerable to severe drought conditions. Case studies are presented to provide examples of yield calculations and innovative approaches that selected small communities have undertaken for addressing drought vulnerability. The role of demand management (drought response and water conservation) in evaluating drought vulnerability is also presented. If hydrologic data and basic physical data such as storage capacity are lacking, it may be difficult for either system managers or experienced professionals to estimate a community system’s yield and potential drought impacts, particularly for off-channel reservoir and low channel dam systems. However, managers should attempt to understand the type of drought period likely to test the adequacy of the available supply and can begin recording basic system observations, such as daily withdrawal records and reservoir drawdown, in a readily-accessible form that will be useful for future evaluations.published or submitted for publicationis peer reviewe

Aerodynamic Effects Caused by Icing of an Unswept NACA 65A004 Airfoil

The effects of ice formations on the section lift, drag, and pitching-moment coefficients of an unswept NACA 65A004 airfoil section of 6-foot chord were studied.. The magnitude of the aerodynamic penalties was primarily a function of the shape and size of the ice formation near the leading edge of the airfoil. The exact size and shape of the ice formations were determined photographically and found to be complex functions of the operating and icing conditions. In general, icing of the airfoil at angles of attack less than 40 caused large increases in section drag coefficients (as much as 350 percent in 8 minutes of heavy glaze icing), reductions in section lift coefficients (up to 13 percent), and changes in the pitching-moment coefficient from diving toward climbing moments. At angles of attack greater than 40 the aerodynamic characteristics depended mainly on the ice type. The section drag coefficients generally were reduced by the addition of rime ice (by as much as 45 percent in 8 minutes of icing). In glaze icing, however, the drag increased at these angles of attack. The section lift coefficients were variably affected by rime-ice formations; however, in glaze icing, lift increases at high angles of attack amounted to as much as 9 percent for an icing time of 8 minutes. Pitching-moment-coefficient changes in icing conditions were somewhat erratic and depended on the icing condition. Rotation of the iced airfoil to angles of attack other than that at which icing occurred caused sufficiently large changes in the pitching-moment coefficient that, in flight, rapid corrections in trim might be required in order to avoid a hazardous situation

Effect of Ice Formations on Section Drag of Swept NACA 63A-009 Airfoil with Partial-Span Leading-Edge Slat for Various Modes of Thermal Ice Protection

The effects of primary and runback ice formations on the section drag of a 36 deg swept NACA 63A-009 airfoil section with a partial-span leading-edge slat were studied over a range of angles of attack from 2 to 8 deg and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.39 to 1.23 grams per cubic meter and datum air temperatures from 10 to 25 F. The results with slat retracted showed that glaze-ice formations caused large and rapid increases in section drag coefficient and that the rate of change in section drag coefficient for the swept 63A-009 airfoil was about 2-1 times that for an unswept 651-212 airfoil. Removal of the primary ice formations by cyclic de-icing caused the drag to return almost to the bare-airfoil drag value. A comprehensive study of the slat icing and de-icing characteristics was prevented by limitations of the heating system and wake interference caused by the slat tracks and hot-gas supply duct to the slat. In general, the studies showed that icing on a thin swept airfoil will result in more detrimental aerodynamic characteristics than on a thick unswept airfoil

Optical and electrical activity of defects in rare earth implanted Si

A common technique for introducing rare earth atoms into Si and related materials for photonic applications is ion implantation. It is compatible with standard Si processing, and also allows high, non-equilibrium concentrations of rare earths to be introduced. However, the high energies often employed mean that there are collision cascades and potentially severe end-of-range damage. This paper reports on studies of this damage, and the competition it may present to the optical activity of the rare earths. Er-, Si, and Yb-implanted Si samples have been investigated, before and after anneals designed to restore the sample crystallinity. The electrical activity of defects in as-implanted Er, Si, and Yb doped Si has been studied by Deep Level Transient Spectroscopy (DTLS) and the related, high resolution technique, Laplace DLTS (LDLTS), as a function of annealing. Er-implanted Si, regrown by solid phase epitaxy at 600degrees C and then subject to a rapid thermal anneal, has also been studied by time-resolved photoluminescence (PL). The LDLTS studies reveal that there are clear differences in the defect population as a function of depth from the surface, and this is attributed to different defects in the vacancy-rich and interstitial-rich regions. Defects in the interstitial-rich region have electrical characteristics typical of small extended defects, and these may provide the precursors for larger structural defects in annealed layers. The time-resolved PL of the annealed layers, in combination with electron microscopy, shows that the Er emission at 1.54microns contains a fast component attributed to non-radiative recombination at deep states due to small dislocations. It is concluded that there can be measurable competition to the radiative efficiency in rare-earth implanted Si that is due to the implantation and is not specific to Er.</p