The main result of this paper is that a Lorentzian manifold is locally conformally equivalent to a manifold with recurrent lightlike vector field and totally isotropic Ricci tensor if and only if its conformal tractor holonomy admits a 2-dimensional totally isotropic invariant subspace. Furthermore, for semi-Riemannian manifolds of arbitrary signature we prove that the conformal holonomy algebr...

The aim of this paper and its sequel is to introduce and classify the holonomy algebras of the projective Tractor connection. After a brief historical background, this paper presents and analyses the projective Cartan and Tractor connections, the various structures they can preserve, and their geometric interpretations. Preserved subbundles of the Tractor bundle generate foliations with Ricci-f...

Two fully loaded (80,000 pounds nominal weight) tractor semi-trailer trucks were impacted into an instrumented wall at 55 miles per hour and an oblique angle of 15 degrees to the wall. This effort was conducted under two separate contracts, one under FHWA and the other NHTSA. The objective of the FHWA contract was to determine lateral impact forces in heavy vehicle collisions with an instrument...

Between 1920 and 1939 a nearly six-fold increase occurred in the number of tractors on American farms, from 246,000 tractors in 1920 to 1,445,000 tractors in 1939 [5]. This substantial growth in tractor usage occurred during a period where the role of the tractor in agricultural production was changing. In 1920, the tractor was primarily viewed as the supplier of the peak power needs in spring ...

soil compaction has become a widespread problem in the world and it is considered as one of the main factors affecting land degradation in arid and semi-arid agricultural land. the aim of this study was to investigate the effects of soil compaction on soil carbon and nitrogen sequestration, physical (aggregate stability, saturated soil moisture content, bulk density, and porosity) and chemical ...

Introduction Direct energy expenses (diesel, gasoline, propane, electricity) total more than $1 billion annually for Iowa’s farmers. Day-to-day farm management techniques such as adjusting tractor gear and throttle settings, making use of front-wheel-drive, and other strategies can reduce diesel fuel consumption for row crop production and general tractor operations. This study is being conduct...

Introduction Direct energy expenses (diesel, gasoline, propane, electricity) total more than $1 billion annually for Iowa’s farmers. Day-to-day farm management techniques such as adjusting tractor gear and throttle settings, reducing tillage depths, and monitoring tractor tire inflation pressures can reduce diesel fuel consumption for row crop production. This study is being conducted over mult...

Soil compaction has become a widespread problem in the world and is one of the factors involved in land degradation and declining crop yields, especially in the arid and semi-arid agriculture. The purpose of this study was to investigate the effects of subsoil compaction on morphological, physiological and agronomic aspects of wheat .The research was carried out in the experimental farms of Anb...

Articulation angle sensing is an essential component of manoeuvrability and stability control systems for articulated heavy goods vehicles, particularly long combination vehicles. Existing solutions to this task are limited by reliance on trailer modifications or information measurement accuracy, both, restricting commercial adoption. In paper we present a purely tractor-based sensor concept co...