End Of String Research Articles

Introduction to and Benefits of Tubing-Conveyed Perforating

Summary Tubing-conveyed perforating (TCP) technology has grown dramatically duringthe past 5 years. This paper presents a general overview of state-of-the-artTCP systems and operating techniques and discusses the TCP benefits and thetradeoffs involved in the use of conventional wireline perforating. The TCP gunstring, with spacers and selected accessories, is run into the well on the endof a testing or completion string, and the guns are positioned across the zonesof interest (Fig. 1). When the TCP string is positioned with a nuclear-typelogging device, the surface well-control equipment installed, and the desiredpressure underbalance established, the guns are fired. The result is pressureunderbalance established, the guns are fired. The result is simultaneousperforation of all selected intervals with high-performance gun systems in anoptimal pressure environment. Benefits of TCP Operational Efficiency. TCP allows the well operator to perforate long, orwidely spaced, intervals simultaneously on a single trip into the well ratherthan having to make multiple runs on wireline. The difference between TCP andwireline-perforating rig time depends on interval length and the number ofwireline descents vs. the additional time to position the string and to readythe well for TCP operations. However, TCP exposes the gun to the wellenvironment longer than wireline perforating, a concern in high-temperatureoperations. TCP gives the well operator an opportunity to perform a flow testimmediately after perforating. Impulse type testing techniques can be used toidentify the extent of wellbore damage before large investments in stimulationor gravel packing are made. In addition to impulse testing, a variety of othertesting and completion equipment can be combined with the TCP string to providefor comprehensive reservoir evaluation immediately after perforating. Underbalanced Perforating. An underbalance, established between theformation and wellbore pressures before the TCP guns are fired, creates aninstantaneous and controlled surge of formation fluids into the well, whichcleans the perforations and enhances the well's productivity andinjectivity. Safety. Surface well-control equipment is installed and tested beforeperforating, guaranteeing complete safety throughout all phases of the TCPoperation. phases of the TCP operation. High-Performance Perforating Systems. Gun size is limited by the ID of the casing, permitting use of the largestpossible charges permitting use of the largest possible charges (either deeplypenetrating or big-entry-hole type) and high shot densities. Guns can beconfigured to provide the optimum shot density and pattern for the specificapplication. TCP Completion Types Temporary TCP Completions. In a temporary TCP completion, the guns are runinto the well at the end of a workstring. After the guns are fired, and time isallowed for cleanup and testing, the well is killed with a nondamagingcompletion fluid and the TCP string is removed. Completionprocedures-backwashing, acidizing, procedures-backwashing, acidizing, fracturing, or gravel packing then be implemented. Large Intervals or MultizoneWells. Large intervals or wells where several widely spaced zones arecommingled into a single production string are completed efficiently productionstring are completed efficiently on a temporary workstring. After perforating, the well is killed with a nondamaging perforating, the well is killed with anondamaging completion fluid and the gun string is removed. This system affordsthe benefits of TCP while providing an alternative to leaving the gun string inthe well where it could interfere with future operations. Gravel-Packed Wells. High-shot-density TCP guns loaded with big-entry-hole charges shotunderbalanced are used to perforate a zone to be gravel packed. After perforatea zone to be gravel packed. After cleanup, the well is killed with anondamaging completion fluid and the guns are retrieved to permit the runningof screens and installation of the gravel pack. Testing. A well-control valvecan be used in conjunction with TCP to provide a quick look at thenear-wellbore region by impulse testing. A longer-duration drillstem test (DST)provides for a more detailed analysis of the commercial potential of thereservoir through observation of the types of fluids recovered and the flowrates. The DST/TCP combination ensures optimum perforation cleanup and providesreservoir performance characteristics. The system involves TCP guns run below aretrievable packer and a set of DST tools. Immediately after firing, the wellis tested by alternately flowing and shutting in to develop the desiredreservoir information. Permanent TCP Completions. In a Permanent TCP Completions. In a permanentTCP completion, the guns are run of permanent TCP completion, the guns are runof the end of the final completion string. The wellhead and safety equipmentare installed before firing. The guns remain in the well after the perforatingoperation and may be dropped into the rathole if desired.

Longitudinal vibration of a pipe string designed for mining manganese nodules in the deep ocean.

This paper presents a theoretical analysis of longitudinal vibrations of a long pipe string with a buffer attached to its free bottom end. Natural frequencies and modes are evaluated. Furthermore, supposing the heaving motion of the ship to be sinusoidal, the steady-state responses of the pipe string are determined. It is found that the natural frequencies decrease with the buffer mass, and the steady-state response can be affected considerably by the buffer aspect-ratio as well as its mass. Because the oscillation amplitude at the bottom end of the pipe string can be amplified to several times that at the top end, this problem may be important in the design and operation of such mining systems.

Portrep: A portable repeated string finder

AbstractIn recent years, several authors have presented algorithms that locate instances of a given string, or set of strings, within a text. Recently, authors have given less consideration to the complementary problem of processing a text to find out what strings appear in the text, without any preconceived notion of what strings might be present. A system called PATRICIA, which was developed two decades ago, is an implementation of a solution to this problem. The design of PATRICIA is very tightly bound to the assumptions that individual string elements are bits and that the user of the system can provide complete lists of starting and stopping places for strings. This paper presents an approach that drops these assumptions. Our method allows different definitions of indivisible string elements for different applications, and the only information the user provides for the determination of the beginning and ends of strings is a specification of a maximum length for output strings.This paper also describes a portable C implementation of the method, called PORTREP. The primary data structure of PORTREP is a trie represented as a ternary tree. PORTREP has a method for eliminating redundancy from the output, and it can function with a bounded number of nodes by employing a heuristic process that reuses seldom‐visited nodes. Theoretical analysis and empirical studies, reported here, give confidence in the efficiency of the algorithms. PORTREP has the ability to form the basis for a variety of text‐analysis applications, and this paper considers one such application, automatic document indexing.

Acoustical properties of drill strings: Application

Analysis has demonstrated a viable data transmission system for communicating by acoustical carrier waves in drill strings used to drill wells. Because of the periodic structure of this waveguide, complex transmission characteristics exist. Two experiments have been used to study these phenomena. In the first experiment, a scale laboratory model was constructed to examine the acoustical response of this system. A longitudinal impulse was produced with a hammer and the resulting signal was measured at several locations with semiconductor strain gauges. In the second experiment, the impulse response of a 1500‐ft drill string suspended in a mudfilled well was tested. The data exhibit all of the phenomena predicted by the theory. Measured attenuation is about 2 dB per thousand feet. Both the comb filter phenomena produced by the periodic structure of the pipe and tool joints, and the standing‐wave interference pattern caused by echos between opposite ends of the drill string are present. [This work was supported by the U. S. Department of Energy at Sandia National Laboratories under Contract DE‐AC04‐76DP00789.]

Tremolo device for a guitar

A tremolo device for a stringed instrument such as a guitar in which a reelable member is provided to which the ends of the instrument strings are connected. Said reelable device includes a tremolo arm for oscillating the reelable device in one direction and return springs for restoring the reelable device in the opposite direction to provide a tremolo effect under the control of the operator. The reelable device comprises a plurality of arcuate members, each individual to one of the strings with the radius of curvature of each arcuate member being smaller for the largest diameter spring and larger for the smallest diameter string and varying appropriately in between. Other effects may also be produced in that the arcuate curvature may be other than a simple arc.

Group theory from “quarks” at the ends of strings

We add D fermionic variables to the ends of open strings, generating the combinatoric and group theory factors of SO(2 [ D/2] ). Thus 10 variables give SO(32). The results are illustrated by a one-loop calculation, giving the partition function of the theory. We discuss boundary conditions, and the modifications of the Feynman rules needed for obtaining the groups U(2 [ D 2 ] ) and USp(2 [ D 2 ] ) .

下端にバッファを持つ揚鉱管の縦振動

In order to aid the design and safety control of a pipe-string in the deep oceanmining system, the transient longitudinal vibration of the pipe-string which hasa buffer at the lower end has been theoretically analysed for the most crucial case where the upper end of the pipe-string was caught after it fell downwards.The analyses of the displacement and axial stress produced in the pipe-string indicate the following results:(1) If the mass-ratio, which is defined as the ratio of the buffer mass to the total mass of the pipe-string, increases, the maximum displacement of the buffer increases and then becomes constant after themass-ratio exceeds 0.75. Furthermore, the displacement pertaining to the larger mass-ratio takes more time to reach the maximum value.(2) The maximum displacement of the buffer slightly decreases as the outer diameter of the buffer increases.(3) The peak value of the reduced displacement, which is defined as the ratio of the displacement of the buffer to the falling distance, slightly decreases as this distance increases.(4) The tensile stress in the axial direction produced at the upper end of the pipe-string decreases immediately after the end falls downwards. As soon as the end is stopped from falling, the tensile stress almost recovers up to the static value of the initial state and then it becomes larger periodically because of the propagation of the stress wave.(5) Ifthe yield strength of the pipe material is assumed as 80×106 Kgf/m2, the limit for the falling distance of the upper end of the pipe string in this study is about 0.8m in case that the mass-ratio, M, is 0.75, about 1.6m in case thatM=0.5, and about 2.0m in case thatM=0.25.(6) Once the upper end of the pipe-string falls downwards, the softness of the receiving part to prevent the end from further falling is not so helpful forthe reduction of the tensile stress.

A model of bacterial DNA segregation based upon helical geometry

A new mechanism to segregate daughter genomes in bacterial cells is suggested that is based upon the rules of geometry governing the helix clock (Mendelson, 1982a). The reorientation of cell surface string arrays used as a timing reference in the helix clock is capable of drawing apart the initial products of DNA replication. Physically linking the sister DNA replication origins to the ends of the initial cell surface string inserted into the cell surface at the start of a helix clock cycle, and linking the DNA terminus to a point along the length of the same string provides a means to mark the locations to which the genomes will segregate as well as the place where cell division will occur. The parallel packing of additional cell surface strings into an array which includes the string to which DNA is attached provides the necessary spatial rearrangements. The helical segregation model can account for the precise registration of cell divisions with the completion of replication forks in a multifork replication system, provides a basis for determining the relationship of sister cell sizes at division, and can also accommodate the asymmetrical divisions associated with minicell production and sporulation. Examination of the helical segregation theory under multifork DNA replication conditions moreover reveals that adjacent helical clocks are physically linked to one another although totally independent in terms of their progression through the clock cycle. A relationship between the initiation of DNA replication forks and the insertion of the first cell surface string associated with the start of a helix clock cycle is predicted by the model.

Real‐time shuffle stack automaton

AbstractAs models to describe concurrent systems, Petri net, shuffle stack automaton (SSA), flow expression, event expression, and shuffle grammar have been proposed. SSA is an automaton which is obtained by adding to the finite automaton a stack with shuffle function. Its descriptive power has already been discussed. This paper discusses the real‐time shuffle stack automaton (RSSA, which is an SSA without λ‐transition in regard to the input), which is a subclass of SSA. It is shown that RSSA has the same descriptive power, independently of the accepting mode (empty‐stack acceptance or final‐state acceptance), and of whether or not a terminating symbol is provided at the end of the input string. It is also shown that the descriptive power of RSSA is incomparable to that of the push‐down automaton, but is properly contained in that of the linear bounded automaton. If a language is bounded and if the set obtained by applying Parikh mapping to that language is semi‐linear, the language is accepted by RSSA. Another property of the language accepted by RSSA is that if it is a bounded context‐free language, it is accepted by RSSA.

Piano string‐hammer interaction

Only in textbooks does a hammer deliver a delta‐function impulse to a string. A real hammer generally remains in contact with the string until one or more reflections from the string ends return to kick it free. The spectrum of the string vibration that finally results depends on the relative mass of hammer and string as well as on the striking point. Some results for the idealized case of a point mass hammer will be presented. The problem of generalizing the theory to lossy, compliant hammers will be discussed.

Remarks on multihead pushdown automata and multihead stack automata

It is shown that k + 1 heads are better than k for one-way multihead pushdown (resp. stack) automata if they do not have endmarkers on the input tape and accept by final state with at least one input head at the right end of the input string. In addition, for two-way multihead pushdown (resp. stack) automata, “hardest languages” are described. It is also shown that for two-way multihead pushdown (resp. stack) automata there is a language with the hardest time and space complexity which can be written as L + for some one-way multihead pushdown (resp. stack) automaton language L, where L + = {w|w n is in L for some n ⩾ 1}. A representation theorem for recursively enumerable languages is also given.

“I give you the end of a golden string”

“I give you the end of a golden string”

Criticism in the Woods: Fairy Tales as Poetry

Criticism in the Woods:Fairy Tales as Poetry Roderick McGillis Perseus turned to Fable and gave her the spindle. "In your hands this spindle will delight us forever and out of yourself you will spin for us an unbreakable thread." Novalis The fairy tale, a short epic form, tends to embrace the entire world. Max Lüthi I give you the end of a golden string, Only wind it into a ball,It will lead you in at Heaven's gate Built in Jerusalem's wall. William Blake The fairy tale and the riddle are essentially related. Max Lüthi [End Page 2] I offer a formidable list of epigraphs, but they structure my theme: the world of the fairy tale.1 This world is essentially metaphoric, and therefore it invites literary critics to examine it. Since the critic cannot locate all tales in time or establish an author for each, he ought to prefer a synchronic approach to the diachrony of late nineteenth century folklore or to the extra-literary synchrony of many psychological approaches. To speak of synchrony, however, is misleading. We find ourselves in a structuralist cell inside the prison-house of language, chained to the same pillar with Vladimir Propp, Claude Levi-Strauss, Michel Butor, and Eleazar Meletinsky.2 This is impressive company, but the hermeneutic models it represents—for example, the Proppian functions of dramatis personae in fairy tales—are as reductive as most models so far advanced as interpretive keys to traditional tales. Propp himself had a diachronic intention; he sought a historical explanation for the structures he perceived in fairy tales as his The Historical Roots of the Fairy Tale (1946) reveals. Literary critics know that the origin of the fairy tale is Fable, and it is her "unbreakable thread" I hope to follow. My epigraphs plot both sections of this essay. The first section is a brief review of recent criticism of fairy tales. What I hope to suggest is the inadequacy, from a literary perspective, of this criticism. Currently, criticism of fairy tales is in the woods. Section two argues for the phenomenological unity of the tales and explains their liberating potential. In this section I provide readings of "Hans in Luck," and "The Fisherman and his Wife." What I wish to establish is the validity of a "poetic" reading of fairy tales. As poetry, the tales are closer to riddle than they are to charm, two other forms of oral literature. I Anglo-American literary criticism has been unkind to the fairy tale. Traditionally, this unkindness has consisted either in an insistence on the unsuitability of the tales for children or in an insistence on their suitability for children and hence their unsuitability for serious literary criticism. We all know the irritation "that cursed Barbauld Crew" caused Charles Lamb one hundred and eighty years ago. Mrs. Barbauld and Mrs. Trimmer failed to see much of value in fairy tales. In the Barbauld Trimmer tradition, defenders of the child's right to tedium, literal-minded readers, continue to disparage the fairy tale, and in a spirit similar to Lamb's, although from a dramatically different standpoint, Bruno Bettelheim has felt the impetus to defend the child's right to enchantment.3 But perhaps more regrettable is the tacit assumption by literary criticism, at least until recently, that the traditional fairy tale is too simple to deserve scrutiny. The fairy tale formed no tradition great or small. New Criticism, strangely, ignored it; archetypal criticism nodded in its direction, but turned quickly to the pursuit of fairy tale motifs in Dickens and other mainstream writers; structuralist criticism acknowledges the importance of Propp and turns, as usual, to more important texts; and post-structuralist criticism (deconstructionism) has so far shown little interest in approaching the abyss that awaits the attentive reader of fairy tales. That there is an "abyssing"4 for the interpreter of fairy tales was clear to those nineteenth century writers closest to the spirit of the fairy tale. In Heinrich von Ofterdingen (1801), Novalis articulates something of the deconstructionist enterprise: "You meditate and meditate and guess at a meaning now and then and get all the more eager to unravel the...

Torsional wave generator

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Line segment singular configurations with instantonic topological charge

The importance of instanton (1) and monopole (2) solutions of the Yang-Mills (YM) equations seems to be out of question nowadays (3). While monopoles may exist as physical objects (as already speculated by DIRAC}, the physical meaning of instanton solutions is not so clear, although they seem to be very relevant in the problem of quark confinement. Nevertheless, using only regular solutions of the YM equations, one cannot get a sufficiently convincing explanation of the experimental fact that quarks are confined. This has brought many people to the search for singular solutions as merons (4) and singular monopoles, located at the zeros of the fourth component of the gauge field A~ (which in this formulation replaces the Higgs field)(5). ADLER has recently obtained monopolelike solutions of the YM equations in the presence of quark sources hut ignoring spin currents. He has derived configurations which display various geometries for the zero set, namely points, strings, spheres and 3-dimensional sets. Of greatest importance are finite-string configurations carrying the topological charge at the extremes, where quark insertion is possible {remember that topological charge density is maximum in the vicinity of quarks). To be noticed is the fact that, in 2and 3-dimensional extended zero sets, a topological density can appear on surfaces. But in strings {including Dirac's monopole string) the topological charge is always calculated as a local integral over the string ends, the contribution of the string itself being null or unphysical (5.6). Moreover, explicit string solutions of the YM equations have been always obtained in the limit of no t ime dependence (static limit). In the present paper we construct exact, string-singular solutions of the YM equations without external sources, but in the full 4-dimensional Euclidean space E 4.

On The Origin, significance, and Minimization of Nonuniform Contamination Along HVDC Insulator Strings

it is shown theoretically and experimentally that the electric force on charged airborne contaminants can cause the distribution of contaminant along the length of an insulator string energized by HVDC to be nonuniform. This nonuniformity causes a nonlinear voltage distribution along the string. As a result, some sections of the insulator string may be subject to electrical stresses high enough to initiate insulator failure. Comparative flashover tests between insulators with uniform and nonuniform contamination distributions confirm this hypothesis (i.e. that nonuniform contamination along the insulator string degrades HVDC insulator performance). It is also shown that grading rings can be attached to each end of an insulator string without creating air gaps less than those needed to protect against transient overvoltages. The grading rings modify the electric field in the vicinity of the string and cause the distribution of contamination along the string to be more uniform. This in turn may lead to improved insulator performance

String set and string securing apparatus for musical instruments

Disclosed are guitars having quick attach, quick release string securing mechanisms for use with string sets of measured lengths. A first embodiment of strings has loops formed on both ends, while a second embodiment of strings has a loop formed on one end and an anchor ball secured on the other. Each guitar disclosed has tuning mechanism including transversely extending string holding posts over which the string loops may be hooked. Guitars utilizing the first string embodiment have crosspiece structure carrying upwardly projecting posts around which the loops of the other strings ends can be hooked. The guitar utilizing the second string embodiment has crosspiece structure defining slotted rearwardly opening sockets for receiving the anchor balls secured on the other string ends. The string holding ends of each of the string holding posts are preferably formed as ball-shaped members and may be formed by screwing a ball on a treaded shaft.

Stringed instrument bridge

A bridge for an electric string bass or other stringed musical instrument includes a base adapted for attachment to the body of the instrument and a number of saddles for individually supporting the strings, the saddles being adjustably movable to different positions relative to the base, in the direction along the length of the strings, to adjust the string intonation. The saddles may include piezoelectric elements for providing electrical signals and, in this case, the base may further include a covered recess for housing a plurality of volume controls each associated with a respective one of the strings. The saddles are designed and arranged on the base to support the strings with a given curvature matching that of the fret board and an adjustment means is provided for raising, lowering and/or tilting the base relative to the body to bring the strings into proper height adjustment relative to the frets. The bridge base also provides an easy-loading tailpiece for anchoring the adjacent ends of strings to the base and a housing for a mute mechanism located forwardly of the saddles.

Flavour and spin structure of linear baryons

Based on the string picture, we construct a phenomenological model for baryons and study their flavour symmetry, exchange degeneracy pattern and spin structure. Baryons on leading trajectories are assumed to have the configuration of two quarks being attached to the ends of a linear string and the third sitting in the middle, called linear baryons. For such linear baryons, a unitarization scheme can be constructed in a manner similar to the dual unitarity scheme for mesons but without recourse to the 1 N expansion. We find that the interchange interaction of the middle quark with one of the other two quarks at the ends of the string can give rise to a large exchange degeneracy breaking of the baryon spectrum. With this non-planar correction, the model of linear baryons can account for the observed pattern of leading baryon states.

Studies on Corona Performance of Insulator Assemblies for UHV Transmission Lines

This paper describes the results of a series of investigation into corona performance of proto type insulator assemblies for UHV transmission lines. For the shielding rings of UHV insulator assemblies, satisfactory RIV characteristics under wet condition was found not to be obtained by simply extrapolating the design practice of EHV insulator assemblies. By the best use of the shielding function of conductors, if relatively small shielding rings are installed at the energized end of the insulator string, the RIV can be restricted below a target value. The insulator assemblies equipped with such shielding rings showed a satisfactory performance from AN point of view.