Motion-base simulator study of control of an externally blown flap STOL transport aircraft after failure of an outboard engine during landing approach

A moving-base simulator investigation of the problems of recovery and landing of a STOL aircraft after failure of an outboard engine during final approach was made. The approaches were made at 75 knots along a 6 deg glide slope. The engine was failed at low altitude and the option to go around was not allowed. The aircraft was simulated with each of three control systems, and it had four high-bypass-ratio fan-jet engines exhausting against large triple-slotted wing flaps to produce additional lift. A virtual-image out-the-window television display of a simulated STOL airport was operating during part of the investigation. Also, a simple heads-up flight director display superimposed on the airport landing scene was used by the pilots to make some of the recoveries following an engine failure. The results of the study indicated that the variation in visual cues and/or motion cues had little effect on the outcome of a recovery, but they did have some effect on the pilot's response and control patterns

Formation and properties of halogenated aluminum clusters

The fast-flow tube reaction apparatus was employed to study the halogenation of aluminum clusters. For reactions with HX (X=Cl, Br, and I), acid-etching pathways are evident, and we present findings for several reactions, whereby AlnX− generation is energetically favorable. Tandem reaction experiments allowed us to establish that for AlnCl−, AlnI−, and AlnI−2, species with n=6, 7, and 15 are particularly resistant to attack by oxygen. Further, trends in reactivity suggest that, in general, iodine incorporation leaves the aluminum clusters’ electronic properties largely unperturbed. Ab initio calculations were performed to better interpret reaction mechanisms and elucidate the characteristics of the products. Lowest energy structures for Al13X− were found to feature icosahedral Al13 units with the halogen atom located at the on-top site. The charge density of the highest occupied molecular orbital in these clusters is heavily dependent on the identity of X. The dependence of reactivity on the clusters’ charge state is also discussed. In addition, we address the enhanced stability of Al13I− and Al13I−2, arguing that the superhalogen behavior of Al13 in these clusters can provide unique opportunities for the synthesis of novel materials with saltlike structures

Structural, electronic, and chemical properties of multiply iodized aluminum clusters

The electronic structure, stability, and reactivity of iodized aluminum clusters, which have been investigated via reactivity studies, are examined by first-principles gradient corrected density functional calculations. The observed behavior of Al13I−x and Al14I−x clusters is shown to indicate that for x⩽8, they consist of compact Al−13 and Al++14 cores, respectively, demonstrating that they behave as halogen- or alkaline earthlike superatoms. For x\u3e8, the Al cores assume a cagelike structure associated with the charging of the cores. The observed mass spectra of the reacted clusters reveal that Al13I−x species are more stable for even x while Al14I−x exhibit enhanced stability for odd x(x⩾3). It is shown that these observations are linked to the formation and filling of “active sites,” demonstrating a novel chemistry of superatoms

The population of close double white dwarfs in the Galaxy

We present a new model for the Galactic population of close double white dwarfs. The model accounts for the suggestion of the avoidance of a substantial spiral-in during mass transfer between a giant and a main-sequence star of comparable mass and for detailed cooling models. It agrees well with the observations of the local sample of white dwarfs if the initial binary fraction is close to 50% and an ad hoc assumption is made that white dwarfs with mass less than about 0.3 solar mass cool faster than the models suggest. About 1000 white dwarfs brighter than V=15 have to be surveyed for detection of a pair which has total mass greater than the Chandrasekhar mass and will merge within 10 Gyr.Comment: 15 pages, 7 figures, to appear in Proc. ``The influence of binaries on stellar population studies'', Brussels, August 2000 (Kluwer, D. Vanbeveren ed.

Boy Soldier of the Confederacy: The Memoir of Johnnie Wickersham

Fact and Fiction? Two Accounts of the Civil War Experience Boy Soldier of the Confederacy: The Memoir of Johnnie WickershamEdited by Kathleen Gorman A Civil War Soldier of Christ and Country: The Selected Correspondence of John Rodgers Meigs, 1859-1864 Edited by M...

The Confederate Defense of Mobile, 1861-1865. (Volumes I-Ii).

The people of Mobile, Alabama, supported the secession of their state from the Union in January 1861, and thousands of her able-bodied men served in the Confederate army from 1861 to 1865. Recognizing the city\u27s strategic importance as a port and major railroad center connecting the eastern and western sections of the new nation, the Confederate government moved quickly to provide adequate defenses for Mobile. Confederate soldiers occupied and began to strengthen Fort Morgan and Fort Gaines, which guarded the main channels leading into Mobile Bay. The Confederate Navy Department converted several steamers into gunboats and began construction of four ironclads, all designed to support the land defenses of Mobile. As the war progressed, Union land and naval forces moved into the Gulf of Mexico, and the Confederate authorities realized that Mobile required more defensive works than the two forts at the mouth of the bay. Engineers, using slave labor, designed and constructed earthen forts along the bay shore near the city and on various islands at the mouths of the rivers which emptied into the bay. They intended all of these batteries to protect the water approaches to Mobile in the event of an enemy naval force running past Fort Morgan and Fort Gaines. To protect the city from a land attack, the engineers erected a series of earthen redoubts connected by infantry entrenchments around Mobile. By war\u27s end, three separate lines of forts and trenches surrounded the city. Mobile undoubtedly possessed fortifications as extensive and strong as almost any city in the Confederacy. Confederate President Jefferson Davis personally chose for assignment as commanding general at Mobile men whom he knew had the qualifications needed to push the construction of all of these defensive works and whom he could rely on to conduct a successful defense against an enemy attack. Confederate brigades, regiments, and artillery batteries moved in and out of the city throughout the war. Although the garrison at times shrank in size to levels which alarmed its commanders, the Confederate military authorities in Richmond made a commitment to see that enough men manned the fortifications to put up a stiff resistance to an actual enemy attack. The War Department also always made sure that the territorial command to which Mobile belonged, whether a department or a district, had the defense of the city as its objective. The Union high command did not seriously contemplate an attack against the Mobile defenses until relatively late in the war. While strategic objectives in other areas caused the Union military authorities to delay a move against Mobile, the strength of the defenses around the city played a part in the decision. A naval demonstration against an earthen fort at Grant\u27s Pass in February 1864 resulted in little damage to that work. Admiral David G. Farragut successfully led a squadron of monitors and wooden gunboats past Fort Morgan and Fort Gaines in August 1864 and captured the lower bay defenses. The commitment of land forces elsewhere prevented the Union navy from proceeding at that time in a campaign against Mobile itself. Such a campaign finally got under way in March 1865, but it had defensive works on the eastern shore as its primary objective. After brief sieges, these Confederate fortifications fell. Faced by overwhelming numbers, Mobile\u27s commander evacuated the city on April 12, 1865, and the city\u27s governmental authorities surrendered Mobile to the enemy that same day

Grant\u27s Gamble: Pemberton\u27s Blunders Allowed Grant To Crack The Gibraltar Of The Confederacy\u27

Although much more important than the Battle of Gettysburg in determining the outcome of the Civil War, the Vicksburg Campaign has been the subject of far fewer books and articles. A three-volume work by Edwin C. Bearss remains the only detailed study of the operations against the Gibraltar of the...

A Civil War Soldier of Christ and Country, the Selected Correspondence of John Rodgers Meigs, 1859-1864

Fact and Fiction? Two Accounts of the Civil War Experience Boy Soldier of the Confederacy: The Memoir of Johnnie WickershamEdited by Kathleen Gorman A Civil War Soldier of Christ and Country: The Selected Correspondence of John Rodgers Meigs, 1859-1864 Edited by M...