Drill string vibrations have resulted in an increase in nonproductive time, drilling cost, and a need for drill string system optimization in the oil and gas industry. Higher vibrations can lead to washout, blow-out p...
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ISBN:
(纸本)9780791859414
Drill string vibrations have resulted in an increase in nonproductive time, drilling cost, and a need for drill string system optimization in the oil and gas industry. Higher vibrations can lead to washout, blow-out phenomena, and a rapid wear and tear of drill string components. An in-depth understanding of the root causes of the drill string vibrations is of utmost importance. The effects of mass imbalance, bottom hole assembly (BHA) design, weight on bit, hole angle, hole size, RPM, drilling fluid viscosity, bit and formation type on drill string vibrations have been studied in the past. The main objective of this paper is to propose a novel drill string vibration model taking into consideration the effects of axial compression load, borehole clearance, and contact force in conjunction with Euler-Bernoulli, Rayleigh, and Shear beam theories. The proposed model studies the effects of axial compression load, borehole clearance, and stiffness on the natural frequency and frequency response of drill string. The drill string is considered as a cantilever beam with a circular cross-sectional area in a horizontal drilling condition, while the fluid (water) around it is considered as a spring and dashpot model. Drill string vibrations are modeled based on a distributed system approach. The forces acting on the cantilever beam element are axial compression load, shear forces, bending moment, fluid stiffness and damping forces. A fourth order partial differential equation is derived and the solution is obtained based on the assumed modes approach to obtain the characteristic equation and mode shapes. Natural frequency is determined using the eigen values obtained from the characteristic equation. The orthogonality conditions are further derived to decouple the derived equation. The drill string is initially assumed unbounded, hence the amount of contact force required to restrict the drill string within the borehole is determined. An iterative process is employed to restri
Grapevine winter pruning is a complex task, that requires skilled workers to execute it correctly. The complexity of this task is also the reason why it is time consuming. Considering that this operation takes about 8...
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The framework of the peanut shelling machine functions as a supporting structure for the components of the peanut shelling machine, namely the top funnel, funnel retaining frame, the lid on the peeler shaft, pulley, s...
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The latest advances in topological physics have yielded a rich toolset to design highly robust wave transfer systems, for overcoming issues like beam steering and lateral diffraction in surface acoustic waves (SAWs). ...
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Benefit from the high payload-to-weight ratio, parallel robots are expected to have a high potential for energy savings. However,it is a challenging issue to evaluate the energy efficiency of parallel robots with a qu...
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Benefit from the high payload-to-weight ratio, parallel robots are expected to have a high potential for energy savings. However,it is a challenging issue to evaluate the energy efficiency of parallel robots with a quantitative method. Quantitative energy efficiency evaluation methods include energy efficiency evaluation models and indices which mathematically describe the relationship between energy consumers in models and design variables of robots, such as geometry, mass and inertia *** the structural features of parallel robots, the chains and the end effectors are identified as two separated energy consumers. Besides, the chains in parallel robots are identified as a transmission system which transfers energy from drives to the end effectors. On this basis, an energy efficiency evaluation model considering the change rate of kinetic energy stored in chains is built. The kinetic energy change rate of chains is influenced by design variables of robots as well as motion of the end *** order to give a quantitative description of energy efficiency performance of parallel robots, indices considering arbitrary velocity vector of the end effector are proposed. The evaluation method is suitable for all kinds of parallel robots with various motion conditions. Furthermore, the method can be used to optimize machining parameters and guide the design of energyefficient machines.
Indium-doped cadmium oxide (In:CdO) thin films exhibit tunable epsilon-near-zero (ENZ) modal frequencies across a wide spectral range, bridging the mid-wave and near-infrared (IR). In:CdO thin films are prepared by re...
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Indium-doped cadmium oxide (In:CdO) thin films exhibit tunable epsilon-near-zero (ENZ) modal frequencies across a wide spectral range, bridging the mid-wave and near-infrared (IR). In:CdO thin films are prepared by reactive cosputtering from metallic Cd and In targets using high-power impulse magnetron sputtering (HiPIMS) and radio frequency sputtering, respectively. Using this approach, CdO thin films with carrier concentrations ranging from 2.3×1019 to 4.0×1020cm–3 and mobilities ranging from 300 to 400cm2/Vs are readily achieved. UV-VIS absorption spectra are used to measure optical bandgap, revealing a Burstein-Moss shift of 0.58 eV across the doping range investigated. Optical measurements demonstrate the tunability of near-perfect plasmonic ENZ absorption across the mid-wave and into the near-IR spectral ranges by controlling the carrier concentration through doping, while tuning the film thickness for impedance matching. In comparison to other dopants that can be introduced to HiPIMS-deposited CdO, In offers the largest range of carrier concentrations while maintaining high mobility, thus allowing for the widest accessibility of the IR spectrum of a single plasmonic material grown by sputtering.
We examine the tuning of cooperative behavior in repeated multi-agent games using an analytically tractable, continuous-time, nonlinear model of opinion dynamics. Each modeled agent updates its real-valued opinion abo...
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Nowadays, an important robot in education as a strategy is the meaningful integration of technology to encourage the students to think and connect to a real-world situation. Moreover, robots offer an excellent tool fo...
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Grapevine winter pruning is a complex task, that requires skilled workers to execute it correctly. The complexity makes it time consuming. It is an operation that requires about 80-120 hours per hectare annually, maki...
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Complex tasks require human collaboration since robots do not have enough dexterity. However, robots are still used as instruments and not as collaborative systems. We are introducing a framework to ensure safety in a...
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