the purpose of this research was to assess the influence of several orchard systems involving trees trained to different leader numbers on growth, cropping, and fruit quality of two apple cultivars. the study was conducted during 1994-2007 at the fruit experimental station in samotwór, next to wrocław (south-western poland). one-year-old trees of ‘elstar’ and ‘jonagold’ cultivars on the m.9 roo...

Although pneumatic down-the-hole (DTH) hammers have good performance of high penetration rate and minimal deviation tendency in the vertical section oil gas wells, they not been successfully used directional drilling due to drill tool wear wellbore disturbance. Herein, we developed a novel type DTH hammer with self-propelled round bit overcome technical difficulties drilling. Nonlinear dynamic ...

The process of borehole drilling is a nonlinear and many dimensional process. During drilling it is possible occurrence of some complications (for example transition of drilling tool in layer with anomalous pressure). New method of identification of rock layers with anomalous pressure was proposed and tested on real plant data.

The deviation correction trajectory of the mechanical vertical drilling system (MVDS) is very important because it final embodiment performance. However, impossible to obtain at design stage, except when using simulation methods. In this paper, tool face angle model and other theoretical models were established, respectively, method was created through coupling. Next, used simulate MVDS under t...

For the past three decades the quantity of petroleum (both oil and oil plus gas) found per foot of drilling effort in the United States for any given year can be expressed as a secular decrease of about 2 percent per year combined with an inverse function of drilling effort for that year. Extrapolation of energy costs and gains from petroleum drilling and extraction indicates that drilling for ...

this investigation presents the effect of various parameters on foam stability and its rheological properties. the underlying idea of this experiment is generating of drilling foam with uniform bubbles. the main problem of foam using is controlling its stability during field application. the most important parameters which cause instability in foam are gravity drainage, gas diffusion and bubble...

Abstract— Due to the superior physical and mechanical properties Glass fiber-reinforced (GFRP) composite materials are very attractive for applications like aerospace and air craft structural components. This results a large number of research papers on machining of these composite laminates. Out of all the machining operations, most commonly used operation is drilling. However, drilling operat...

Because neurosurgery and orthopedic surgery often require the drilling of bones, this paper attempts to solve the problem of bone drilling. The goal is to realize a control system, which is able to drill with a contact drilling force and can automatically stop drilling at the moment of breaking through. In particular, both the de drilling mntor control and the feed rate control are driven by fo...

Bone drilling is widely used in orthopaedics and surgery; it is a technically demanding surgical procedure. Recent technological improvements in this area are focused on efforts to reduce forces in bone drilling. This study focuses on forces and a torque required for conventional and ultrasonically-assisted tool penetration into fresh bovine cortical bone. Drilling tests were performed with two...

In this research, finite element analysis of the conventional drilling and vibration assisted drilling is carried out. The ABAQUS software is employed for FE analysis. The Johnson-Cook models for both plastic deformation and damage are employed for FE simulation.The results of the FE analysis are then verified with experimental results in both conventional and vibration assisted drilling on Al ...