229,356 research outputs found
Method of Correcting Wind Tunnel Data for Omitted Parts of Airplane Models
Wind tunnel models do not have complete similarity to the full scale airplane. Part of the dissimilarity is due to the difference between the stationary model in the artificial wind stream of the tunnel and the moving airplane in still air. There are a number of other reasons for departing from exact geometrical similitude. For reasons of accuracy and economy, all minor parts of the full scale airplane, such as struts, wires, fittings, control horns and other parts whose scale corrections are large are removed from wind tunnel models. By omitting the minor parts of the airplane in the wind tunnel model and adding to the forces and moments of the model those omitted parts measured full scale and properly reduced, the scale effects of such parts disappear from the model data. Scale effects due to major parts of the airplane, particularly the fuselage and wings, can be corrected by omitting the propeller and making the surface of the model as smooth as possible, two further departures from geometrical similitude between model and full scale that add considerably to the accuracy and economy of model tests
Lightweight, high-strength, reinforced plastic tube-franging die
Dies of a phenolic molding compound with chopped glass fibers as fill material possess a flexural strength of 20,000 psi and a compressive strength of 28,500 psi
A simulator study of the interaction of pilot workload with errors, vigilance, and decisions
A full mission simulation of a civil air transport scenario that had two levels of workload was used to observe the actions of the crews and the basic aircraft parameters and to record heart rates. The results showed that the number of errors was very variable among crews but the mean increased in the higher workload case. The increase in errors was not related to rise in heart rate but was associated with vigilance times as well as the days since the last flight. The recorded data also made it possible to investigate decision time and decision order. These also varied among crews and seemed related to the ability of captains to manage the resources available to them on the flight deck
The Arecibo Galaxy Environment Survey VIII : Discovery of an Isolated Dwarf Galaxy in the Local Volume
The Arecibo Galaxy Environment Survey (AGES) has detected a nearby HI source
at a heliocentric velocity of +363 km/s . The object was detected through its
neutral hydrogen emission and has an obvious possible optical counterpart in
Sloan Digital Sky Survey (SDSS) data (though it does not have an optical
redshift measurement). We discuss three possible scenarios for the object : 1)
It is within the Local Group, in which case its HI properties are comparable
with recently discovered ultra-compact high velocity clouds; 2) It is just
behind the Local Group, in which case its optical characteristics are similar
to the newly discovered Leo P galaxy; 3) It is a blue compact dwarf galaxy
within the local volume but not associated with the Local Group. We find the
third possibility to be the most likely, based on distance estimates from the
Tully-Fisher relation and its velocity relative to the Local Group.Comment: 5 pages, 6 figures, accepted for publication in MNRAS. Minor
correction to institution and addres
Abundances of Na, Sc, Cr, Mn, Fe, Co, and Cu in 92 meteorites, 9 terrestrial specimens, and 90 individual chondrules Quarterly progress report, 1 Sep. - 30 Nov. 1963
Elemental abundancies in individual chondrules, chondrites and terrestrial matter, whole rock- type meteorites, and carbonaceous chondrite
Quantum clocks observe classical and quantum time dilation
At the intersection of quantum theory and relativity lies the possibility of
a clock experiencing a superposition of proper times. We consider quantum
clocks constructed from the internal degrees of relativistic particles that
move through curved spacetime. The probability that one clock reads a given
proper time conditioned on another clock reading a different proper time is
derived. From this conditional probability distribution, it is shown that when
the center-of-mass of these clocks move in localized momentum wave packets they
observe classical time dilation. We then illustrate a quantum correction to the
time dilation observed by a clock moving in a superposition of localized
momentum wave packets that has the potential to be observed in experiment. The
Helstrom-Holevo lower bound is used to derive a proper time-energy/mass
uncertainty relation.Comment: Updated to match published versio
Active social location in schools: professional development for the whole school workforce?
The workforce in English schools has changed over recent years; there are more categories of staff to be found in English schools and the relative sizes of the categories have altered. Alongside these changes, the Every Child Matters reform programme implies the need to pay attention to the importance of all categories of staff to the welfare of children. However, there has not hitherto been an adequate characterisation of the nature of the practice of workers other than teachers . This paper attempts to characterise the position of school workers other than teachers to better understand the distinctive nature of their practice. We focus on Teaching Assistants, Caretakers and Lunchtime Supervisors as three groups which are sufficiently different to enable us to develop a richer theoretical account of identity in the school workforce than has hitherto been available. We have argued elsewhere (Coldron and Smith, 1999) that a teacher’s practice and his or her development of that practice can best be understood as a process of active social location. In this paper, we apply the same theoretical understanding of practice to the work identities of these three groups of school staff. By better understanding the identities that their different positions and associated resources make available, we aim to provide a richer picture and a way of thinking of the work identities of staff in school who are not teachers, one that is not colonised by the ways of thinking about the higher status teacher group.</p
The efficiency and the demagnetization field of a general Halbach cylinder
The maximum magnetic efficiency of a general multipole Halbach cylinder of
order is found as function of . The efficiency is shown to decrease for
increasing absolute value of . The optimal ratio between the inner and outer
radius, i.e. the ratio resulting in the most efficient design, is also found as
function of and is shown to tend towards smaller and smaller magnet sizes.
Finally, the demagnetizing field in a general -Halbach cylinder is
calculated, and it is shown that demagnetization is largest either at or . For the common case of a Halbach cylinder
the maximum values of the demagnetizing field is either at at
the outer radius, where the field is always equal to the remanence, or at at the inner radius, where it is the magnitude of the field in the
bore. Thus to avoid demagnetization the coercivity of the magnets must be
larger than these values.Comment: 5 pages, 5 figure
Digital computing cardiotachometer
A tachometer is described which instantaneously measures heart rate. During the two intervals between three succeeding heart beats, the electronic system: (1) measures the interval by counting cycles from a fixed frequency source occurring between the two beats; and (2) computes heat rate during the interval between the next two beats by counting the number of times that the interval count must be counted to zero in order to equal a total count of sixty times (to convert to beats per minute) the frequency of the fixed frequency source
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