DH

DH, Dh or dh may refer to:

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0-6-0

Under the Whyte notation for the classification of steam locomotives, 0-6-0 represents the wheel arrangement of no leading wheels, six powered and coupled driving wheels on three axles, and no trailing wheels. This was the most common wheel arrangement used on both tender and tank locomotives, in versions with both inside and outside cylinders.

In Britain the Whyte notation of wheel arrangement was also often used for the classification of electric and diesel-electric locomotives with side-rod coupled driving wheels.

Other equivalent classifications are:

In the UIC classification popular in Europe, the same arrangement is written as C if the wheels are coupled with rods or gears, or Co if they are independently driven.

Overview

History

The 0-6-0 configuration was the most widely used wheel arrangement for both tender and tank steam locomotives. The type was also widely used for diesel switchers (shunters). Because they lack leading and trailing wheels, locomotives of this type have all their weight pressing down on their driving wheels and consequently have a high tractive effort and factor of adhesion, making them comparatively strong engines for their size, weight and fuel consumption. On the other hand, the lack of unpowered leading wheels have the result that 0-6-0 locomotives are less stable at speed, so they are mostly used on trains where high speed is unnecessary.

(385250) 2001 DH47

(385250) 2001 DH₄₇, also written as 2001 DH47, is a small asteroid orbiting near the L₅ point of Mars (60 degrees behind Mars on its orbit).

Discovery, orbit and physical properties

2001 DH₄₇ was discovered on February 1, 2001 by the Spacewatch program, observing from Steward Observatory, Kitt Peak and classified as Mars-crosser by the Minor Planet Center. Its orbit is characterized by low eccentricity (0.035), moderate inclination (24.4º) and a semi-major axis of 1.52 AU. Its orbit is well determined as it is currently (March 2013) based on 45 observations with a data-arc span of 3,148 days. It has an absolute magnitude of 19.7 which gives a characteristic diameter of 562 m.

Mars trojan and orbital evolution

It was identified as Mars trojan by H. Scholl, F. Marzari and P. Tricarico in 2005 and its dynamical half-lifetime was found to be of the order of the age of the Solar System. Recent calculations confirm that it is indeed a stable L₅ Mars trojan with a libration period of 1365 yr and an amplitude of 11°. These values as well as its short-term orbital evolution are very similar to those of 5261 Eureka.