String Assembly Research Articles

Mechanical Calculation for Workover String in Highly-Deviated and Horizontal Well

Force analysis and calculation of workover string in the highly-deviated and horizontal well is the basis of designing and checking string strength, selecting tools and determining operation parameters, which determines the operation safety and success of engineering accidence treatment. In this paper, by comprehensive consideration of wellbore structure, string assembly, string load and workover operation conditions, the workover string mechanical model has been built under three kinds of working states of lifting, lowering and rotating. The downhole string mechanics has been analyzed and calculated. By field verification, the string assembly, tool selection and operation parameter optimization can be achieved, which can improve the safety and success rates of workover engineering accident treatment.

Electrical field computation of polymeric insulator using reduced dimension modeling

In recent years, electrical field distribution is the area of major concern in the service life of Polymeric Insulators. Several methodologies are proposed to analyze the electrical field along the insulators both experimentally and numerically of which the former might be very time consuming requiring a number of trial-error tests to determine the optimum dimensions. The advent of super computers makes numerical analyses feasible on any complex geometry modeled in 3-D and the overall optimization techniques to control the electrical field become quite easier. However, the main drawbacks in 3-D analyses are the more computation time and memory, making it desirable to simplify the structure. Hence a methodology based on relationship between electrical field profiles of 2-D (axi-symmetry model of insulator with corona ring) and 3-D model (insulator with corona ring, tower, 3 phase hardware fittings and conductors) for a dimension and location of corona/grading rings is proposed. Based on the relationship, electrical field profiles of 3-D models are predicted for different dimension and location of rings using its equivalent 2-D model electrical field profile. Commercially available 2-D and 3-D finite element based electrostatic field computation program is used. A 220 kV suspension type I string assembly is used for this study. Later, the approach is validated for 132 kV and 400 kV insulators. The type of tower, string configuration is kept constant throughout the analyses.

Workover String Mechanical Model and Calculation of Slanted and Horizontal Well

Force analysis and calculation of workover string in the slanted and horizontal well are the basis of designing and checking string strength, selecting tools and determining operation parameters, which determine the operation safety and success of engineering accidence treatment. In this paper, by comprehensive consideration of wellbore structure, string assembly, string load and workover operation conditions, the workover string mechanical model has been built under three kinds of working states of lifting, lowering and rotating. The downhole string mechanics has been analyzed and calculated. By field verification, the string assembly, tool selection and operation parameter optimization can be achieved, which can improve the safety and success rates of workover engineering accident treatment.

String model for the dynamics of glass-forming liquids.

We test the applicability of a living polymerization theory to describe cooperative string-like particle rearrangement clusters (strings) observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy Sconf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near Tg and a low T residual entropy, thus avoiding a Kauzmann "entropy crisis."

Investigations of Different Soldering Failure Modes and their Impact on Module Reliability

Future Photovoltaic is being increasingly forced to reduce costs and increase module power by constant or better module reliability [1]. So over the last years a radical decrease of module prices is observed on the contrary the module power changes to higher classes. This indicates that the common used materials (e.g. frames, solder ribbon, wafer, metallization etc.) join their physical limits. This contains different challenges due to reliability. For future applications such requirements will be e.g.:•Smaller frames vs. high loads•Thinner glass substrates vs high impacts•Smaller interconnection area vs. higher current density and higher thermal dissipation•Smaller ribbons vs higher cell breakage rate & higher soldering challengesThis represents only a small number of the challenges facing the Photovoltaic industry in the future. The aim and role of PV industry is to realize efficient and reliable modules. This paper will present detailed data on soldering failure modes during string assembly and reliability testing, and the long-term mechanical and electrical stability of the solder joints and their impact on the long-term efficiency of the modules. The data will show that different failure modes have different effects on the quality of interconnections as well as on the reliability of the modules.

Quantitative Model for Clusters of String-like Cooperative Motion in a Coarse-Grained Glass-Forming Polymer Melt

ABSTRACTWe apply a living polymerization theory to describe cooperative string-like particle rearrangement clusters observed in simulations of a coarse-grained polymer melt. The theory quantitatively describes the interrelation between the average string length L, configurational entropy Sconf, and the order parameter for string assembly Φ without free parameters. Combining this theory with the Adam-Gibbs (AG) model allows us to predict the relaxation time τ in a lower temperature T range than accessible by current simulations. In particular, the combined theories suggest a return to Arrhenius behavior near Tg and a low T residual entropy, thus avoiding a Kauzmann ‘entropy crisis’.

Influence of Interlayer Exchanges on Vorticity-Aligned Colloidal String Assembly in a Simple Shear Flow

Hard spheres in Newtonian fluids serve as paradigms for Non-Newtonian materials phenomena exhibited by colloidal suspensions. A recent experimental study (Cheng et al. 2011 Science, 333, 1276) showed that upon application of shear to such a system, the particles form string-like structures aligned in the vorticity direction. We explore the mechanism underlying this out-of-equilibrium organization with Steered Transition Path Sampling, which allows us to bias the Brownian contribution to rotations of close pairs of particles and alter the dynamics of the suspension in a controlled fashion. Our results show a strong correlation between the string structures and the rotation dynamics. Specifically, the simulations show that accelerating the rotations of close pairs of particles, not increasing their frequency, favors formation of the strings. This insight delineates the roles of hydrodynamics, Brownian motion, and particle packing, and, in turn, informs design strategies for controlling the assembly of large-scale particle structures.

ACTIVE VIBRATION CONTROL FOR SUBTERRANEAN DRILLING OPERATIONS

An active vibration control device improves drilling by actively applying a dampening profile and/or a controlled vibration to a drill string and/or bottomhole assembly (BHA). Embodiments of the present invention control the behavior of a drill string and/or BHA in order to prevent or minimize the occurrence of harmful drill string/BHA motion and/or to apply a vibration to the drill string/BHA that improves one or more aspects of the drilling process. Measurements of one or more selected parameters of interest are processed to determine whether the undesirable vibration or motion is present in the drill string or BHA and/or whether the drill string and/or BHA operation can be improved by the application of a controlled vibration. If either or both conditions are detected, corrective action is formulated and appropriate control signals are transmitted to one or more devices in the drill string and/or BHA.

A new method of forecasting initial formation temperature during the whole drilling process based on proportional-integral control principle

A strategy based on proportional-integral feedback control was applied to gradually feedback the error between simulation of transient heat transfer model and logged date to forecast initial formation temperature. In this study, based on the each control unit of mass, momentum and energy conservation principles in a wellbore, the transient heat transfer model was developed between circulation and shut-in stages under real casing program and drilling string assembly condition, which were solved by full implicit finite difference method. Meanwhile, the proportional-integral control principle was introduced to compare the error range between measured temperature and prediction temperature, which can precisely and quickly obtain initial formation temperature. Combined with a deep well basic data, the results show that the heat exchange efficiency of wellbore and formation was changed by the casing pipe depth, thus affecting formation temperature distribution of the near-well zone. What’s more, the initial and boundary conditions of each control unit in the down-hole was also changed by circulation and shut-in operating time during the drilling process, leading to the variation of distribution distance of the initial formation temperature of the near-well zone. Development of the numerical models and the research methods can provide accurately, economically and quickly to obtain theoretical basis for oil drilling, geothermal well exploiting and the initial formation temperature information.

Power circuit breaker using micro-mechanical switches

The objective of this research is to investigate innovative power distribution components based on micro-electromechanical systems technologies integrated with advanced optimisation methods to improve the performance of electric power distribution systems. A novel medium voltage circuit breaker using two switching string assemblies has been developed. The building block is a switching unit, which includes micro-switch shunted by a diode and a resistance. Several switching units are connected in series to form the switching string and several strings are connected in parallel to form the switching string assembly. A magnetic coil activates the switches. The circuit breaker contains two switching string assemblies connected in series. One of them interrupts the current in the positive the other in the negative cycle. The opening of the mechanical switches transfers the current to the diodes, without any arcing. The diodes interrupt the current at zero crossing. The project objective includes an educational component: to bring innovative topics in power distribution engineering to practising engineers (e.g., continuing education) as well as engineering students. The design appears to be a logical step in innovative power circuit breaker design that allows better control of circuit interruption than conventional breakers.

Novel Concept for Medium Voltage Circuit Breakers Using Microswitches

This letter presents a new concept for circuit breakers (CBs) using microelectromechanical switches (MEMS). The building block is a switching unit, including a micro-switch shunted by a diode. Several switching units are connected in series and in parallel to form a switching string assembly. The opening of the mechanical switches transfers the current to the diodes. The diodes interrupt the current at the first zero crossing. The use of micro-switches miniaturizes the CB and assures arc less current interruption by the end of the first half cycle.

The Utilization of Micromechanical Devices in a Power Circuit Breaker

This article relates to the investigation of innovative power distribution components based on microelectromechanical technologies integrated with advanced optimization methods to improve the performance of electric power distribution systems. A novel medium voltage class circuit breaker using two switching string assemblies has been designed and implemented in a laboratory prototype. The building block is a switching unit, which includes microelectromechanical switch shunted by a diode. Several switching units are connected in series to form the switching string, and several strings are connected in parallel to form the switching string assembly. A magnetic coil activates the switches. A circuit breaker is comprised of two switching string assemblies connected in series. One string interrupts the current in the positive half cycle, and the other interrupts current in the negative half cycle. The opening of the mechanical switches transfers the current to the diodes, without arcing. In this way, the circuit breaker is a hybrid between a solid-state circuit breaker and a true microelectromechanical switch circuit breaker. The study shows the feasibility of building a full-scale unit.

Channel-forming, self-assembling, bishelical amphiphilic peptides: design, synthesis and crystal structure of Py(Aibn)2, n=2,3,4.

The design, synthesis, characterization and self-assembling properties of a new class of amphiphilic peptides, constructed from a bifunctional polar core attached to totally hydrophobic arms, are presented. The first series of this class, represented by the general structure Py(Aibn)2 (Py=2,6-pyridine dicarbonyl unit; Aib=alpha, alpha'-dimethyl glycine; n=1-4), is prepared in a single step by the condensation of commercially available 2,6-pyridine dicarbonyl dichloride with the methyl ester of homo oligoAib peptide (Aibn-OMe) in the presence of triethyl amine. 1H NMR VT and ROESY studies indicated the presence of a common structural feature of 2-fold symmetry and an NH...N hydrogen bond for all the members. Whereas the Aib3 segment in Py(Aib3)2 showed only the onset of a 3(10)-helical structure, the presence of a well-formed 3(10)-helix in both Aib4 arms of Py(Aib4)2 was evident in the 1H NMR of the bispeptide. X-ray crystallographic studies have shown that in the solid state, whereas Py(Aib2)2 molecules organize into a sheet-like structure and Py(Aib3)2 molecules form a double-stranded string assembly, the tetra Aib bispeptide, Py(Aib4)2, is organized to form a tetrameric assembly which in turn extends into a continuous channel-like structure. The channel is totally hydrophobic in the interior and can selectively encapsulate lipophilic ester (CH3COOR, R=C2H5, C5H11) molecules, as shown by the crystal structures of the encapsulating channel. The crystal structure parameters are: 1b, Py(Aib2)2, C25H37N5O8, sp. gr. P2(1)2(1)2(1), a=9.170(1) A, b=16.215(2) A, c=20.091(3) A, R=4.80; 1c, Py(Aib3)2, C33H51N7O10H2O, sp. gr. P1, a=11.040(1) A, b=12.367(1) A, c=16.959(1) A, alpha =102.41 degrees, beta =97.29 degrees, gamma =110.83 degrees, R1=6.94; 1 da, Py(Aib4)2.et ac, C41H65N9O12.1.5H2O.C4H8O2, sp. gr. P1, a=16.064(4) A, b=16.156 A, c=21.655(5) A, alpha =90.14(1)degrees, beta=101.38(2) degrees, gamma=97.07(1)degrees, Z=4, R1=9.03; 1db, Py(Aib4)2.amylac, C41H65N9O12.H2O.C7H14O2, P2(1)/c, a=16.890(1) A, b=17.523(1)A, c=20.411(1) A, beta=98.18 degrees, Z=4, R=11.1 (with disorder).

Vibratory Power Delivery to Rock During Rotary-Vibratory Drilling

This paper outlines the theoretical description of the vibratory portion of the rotary-vibratory drilling process. A multiple mechanical element model is used to describe the drill string and rock-rock bit assembly. The drill string model has continuously distributed properties of mass, stiffness, and external drilling-mud damping. A closed form solution is developed using boundary condition matching at the end of each mechanical element. The solution is used to compute the power input to the system by a vibratory unit, the power delivered to the rock, and the power lost to the drilling mud through vibratory losses. From these data, efficiencies are computed. The analytical solution has been checked in parallel with a transfer matrix computer solution. The results are identical within computer precision. The analytical model is then applied to the study of the Drilling Research Incorporated (DRI) prototype drilling system and its test drilling parameters for the 1957 test drilling. Explanations of the limits of the increase in drilling rates to 2:1 are explored. The results are explored relative to the potential for increasing the drill penetration rates by system redesign. Conclusions are drawn concerning the most productive routes to be taken for rotary-vibratory drilling systems and for the vibratory driver. It has become clear that successful future downhole rotary-vibratory drilling rigs will require a complete system understanding, a complete system design, and a new concept in vibratory driver.