Test String Research Articles

Orbits of a string around a five-brane.

The classical orbits of a test string in the transverse space of a singular heterotic five-brane source are classified. The orbits are found to be either circular or open, but not conic because the inverse square law is not satisfied at long range. This result differs from predictions of general relativity. The conserved total angular momentum contains an intrinsic component from the five-brane source.

In vitro hydrogen production by enteric bacteria cultured from children with small bowel bacterial overgrowth.

Lactulose breath hydrogen test and Enterotest string test were carried out simultaneously on 19 children 3-5 years old. Bacteria isolated from the jejunal fluid in upper small intestines of these children were incubated with lactulose at neutral pH. Anaerobes were present in all but one child, and in 15 children they were present in numbers greater than 5 log10 organisms per ml. Most of these bacteria did not produce hydrogen in vitro. Hydrogen production (greater than 100 ppm) was observed with the following bacteria: Bacteroides (5%), clostridia (8%), anaerobic corynebacteria (5%), Escherichia coli (67%), Lactobacillus (8%), Staphylococcus (8%), and Streptococcus (9%). The following bacteria did not produce hydrogen in vitro: Actinobacter, Actinomyces, anaerobic cocci, Bifidobacterium, Fusobacterium, micrococci, Neisseria, Sarcina, and Veillonella. This study suggests that in the diagnosis of small bowel bacterial overgrowth using lactulose breath hydrogen test, it is important to consider that patients with a flat breath hydrogen response to a carbohydrate challenge during the first 60 min may be infected with enteric bacteria which are not capable of producing H2.

Design of LHC prototype dipole cryostats

The current design of the LHC prototype dipole magnet cryostat is described. An overview of the basic components and their thermal and mechanical behaviour is given. As a first step four of these prototype cryomagnets will be connected in series in a test string to allow detailed cryogenic, mechanical and magnetic measurements to be undertaken at CERN. Each cryostat vacuum vessel houses a dipole magnet cold mass assembly inside its helium vessel, roughly 10 m long, weighing about 16 tonnes and standing on two low heat inleak support posts. All cryogenic piping required for heat interception at intermediate temperature levels and interconnection to adjacent units pass through the cryostat. The cold assembly is enclosed in two thermal insulation systems, the radiative insulation and a gaseous helium-cooled thermal shield, to intercept incoming radiative and conductive heat.

Cosmic strings in a space with topology M2 � V2

For the case of a space-time with topology M2×V2, we show that the equation of motion of an infinitely thin string has solutions that can naturally be called the laws of motion of a straight string. For the case of a locally plane conical space, the solutions are written explicitly. We show that such motions of a test string are not followed by gravitational radiation.

Determination of Virgin Rock Temperature From Drillstem Tests

This paper reports on the accuracy of virgin rock temperatures determined from drillstem tests (DST's) that was investigated by examining factors that affect the temperatures recorded downhole during DST's. It is shown that virgin rock temperatures can be calculated with a standard deviation of about 1.5{degrees} C. The data base for the investigation consisted of more than 300 measurement series recorded from DST's in the Norwegian North Sea, encompassing temperature readings from 208 DST's in 112 different oil and natural gas wells.

Local and global aspects of charge-current generating world-sheet scalar potentials

The electromagnetic interactions of a test string, including in particular the intrinsic self-interactions, are governed by its charge-current two-vector density Q α ( α= τ, σ). Being locally conserved, Q α is derivable from a parent world-sheet scalar potential V( τ, σ), that is, Q α = ε αβ V β . However, to characterize the electromagnetic properties of the string does not mean a priori specifying V( τ, σ) up to a global gauge transformation. In fact, it is only when V( τ, σ) is treated as an additional canonical variable that the superconductivity integrability constraint emerges as an equation of motion. Electric charge quantization then follows, exclusively for closed strings, provided the phase e iV stays single-valued with respect to the σ-periodicity ( Δσ = 2 π) in exactly the same way as the global property of the built-in phase e iV of an order parameter dictates magnetic flux quantization. The pedagogical case of a self-interacting circular loop, for which V=ƒ(τ)+nσ ⇔ χ = g(τ) + mσ, with n(m) counting the total number of electric charges (magnetic fluxons), is studied in the framework of two reparametrization invariant models. Following a Nielsen-Olsen type model, we advocate a novel approach to unification, with V (rather than χ) serving as the fifth dimension. The alternate model, favored on field-theoretical grounds, conceptually differs from the first one by strictly forbidding the collapse of a self-interacting loop.

Abelian self-interaction of a test loop

Using dimensional reduction, we derive the reparametrization-invariant electromagnetic self-interaction of a test string. The exact non-singular solution corresponding to a stationary circular loop is specified. The collapse is dynamically prevented provided n e n m ≠ 0, where n e ( n m ) count total number of electric charges (magnetic fluxons). The selection rule n e+ n m = 2 N ( N is an integer) suggests that a fundamentally-charged loop must carry current and hence acquire spin ∼ n e n m.

Non-Abelian self-interaction of a test loop.

The classical reparametrization-invariant SU(2) self-interactions of a test string are analyzed. Dynamically noncollapsing loop configurations in real space and on the intrinsic ${S}_{2}$ manifold are shown to exist, reflecting a combined effect of non-Abelian charges and currents. The dynamics leads naturally to a double-well "Weierstrass" potential whose minima specify two discrete configurations in the internal space.

Real Time Control of the SSC String Magnets

The system described in this paper, called SECAR, was designed to control the excitation of a test string of magnets for the proposed Superconducting Super Collider (SSC) and will be used to upgrade the present Tevatron Excitation, Control and Regulation (TECAR) hardware and software . It resides in a VME crate and is controlled by a 68020/68881 based CPU running the application software under a real time operating system named VRTX.

Context effects in word identification

Word identification comprises both sense activation and sense selection. It is hypothesized that sense activation is affected by associative relationships among words, but not by the thematic context of a discourse. Experiment I confirms this prediction using a crossmodal lexical decision task. Subjects listened to a discourse containing a target word and made a word/nonword decision to a visually presented test string. If the target word was a homograph, test words that were associates of the homograph were primed irrespective of the thematic context. On the other hand, thematically appropriate test words that were not associatively related to the target word were not primed. This result was confirmed in a second experiment where the text was presented visually at a very rapid rate. In contrast, when subjects were given enough time to process each word (Experiment 3), only thematically appropriate associates were primed. No priming effects at all were obtained in a final experiment using a rapid presentation rate where the test word was separated from the target word by two other, interfering words. It is concluded that sense activation functions as a module independent of thematic context.

Typing letter strings varying in orthographic structure

Subjects typed six-letter strings varying in orthographic structure. Lexical status, word frequency, position-sensitive log bigram frequency, and regularity of letter sequencing were systematically varied. Cumulative reaction times (RTs) of the keystrokes were adequately described by a linear function of letter position in the test string. Overall, words were typed faster than nonwords, and regular strings faster than irregular strings. Although the effect of log bigram frequency was not significant, this variable interacted with regularity and word frequency. Post hoc analyses of performance on each of the 200 letter strings revealed significant effects of the number of irregularities, log bigram frequency, and log word frequency. Transition times between successive keystrokes were significantly longer for illegal than for legal letter transitions. These results are similar to previous findings on the role of orthographic structure in the perceptual recognition of letter strings and provide a more complete analysis of context effects in typing.

The Effect of Water Chemistry on the Laboratory Compression and Permeability Characteristics of Some North Sea Chalks

Summary Chalks or chalklike carbonates have been reported to fail when returned to or near in-situ reservoir stress in the laboratory. Failure of chalks during reservoir production tests has also been reported. This paper presents laboratory results showing that the compaction behavior of the chalks is dependent on the water chemistry of the saturating fluid. The chalks were found to be strong and stable under hydrostatic stress when saturated with oil. Injection of water into the oil-saturated chalks, at stress, caused immediate compaction. The weakening of chalks by water increased the compressibility values four to eight times the oil-saturated values. The chalks resisted failure when stabilized with synthesized formation water containing calcium/bicarbonate ratios equal to the calcium/ bicarbonate ratio present in the formation-water analysis. Permeabilities of the chalks saturated with oil and brines are also presented. Introduction The failure or yielding of high porosity >25 %) chalks or chalklike carbonates during the application of stress in the laboratory has been extensively reported in the literature. Meigh and Early and Carter and Mallard found that the strength of air- or oven-dried outcrop chalks was two to three times the strength of water-saturated chalks. Blanton studied both dry and oil-saturated outcrop chalks from the North Sea area and from the U.S. gulf coast. He found no significant difference in strength between dry and oil-saturated chalks. However, he found that, although the ultimate strength increased initially with increasing hydrostatic stress, the chalks eventually collapsed at higher hydrostatic stress. Marek used a simulated reservoir brine to obtain similar results on chalklike carbonates. Owen reported that brine-saturated chalks from the Ekofisk field in the Norwegian North Sea failed when subjected to only a few hundred pounds (- 1500 kPa) of pressure in a compressibility apparatus. The weakening of calcite rocks by water has also been described by Rebinder and Likhtman, Boozer et al., and Rutter. The reported chalk failure has not been restricted to laboratory tests. Voll and Holman reported that chalk flow and casing collapse had been observed in the Valhall field, Norwegian North Sea, and cited one example where 1,500 ft (457.2 m) of produced chalk was found inside a test string. This paper presents a summary of laboratory results obtained on the compaction and permeability characteristics of some chalk samples from the Danish North Sea. The studies were conducted on core material from wells in the Goren, Cora (renamed Tyra), and Dan fields. The investigation was done to confirm the reported failure of the chalks following their return to simulated reservoir stress in the laboratory. It was postulated that, even if the chalks were weak, they should be able to withstand the stresses they had been subjected to in the reservoir before removal, unless they were weakened by the recovery or testing process. Compressibility tests conducted by a service company on a suite of samples from the Gorm field showed that most of the samples failed at stresses much less than the anticipated reservoir stress. Laboratory Tests Core-Material Preparation Core plugs 2 1/8 in. (5.40 cm) in diameter and about 3 in. (7.62 cm) long were cut from water-base-mud core material from Well DNN-3, Gorm field; Well DNE-4, Cora field; and Well DNM-8X, Dan field. The samples were cut either parallel with (vertical), or perpendicular to (horizontal), the coring axis of the submitted full-diameter core. Kerosene was used as drilling fluid to cut the samples, which were extracted in toluene to remove hydrocarbons and water, vacuum-dried, and encased in a flexible Teflons sleeve. The air permeability of each sample was measured before the samples were saturated with kerosene to obtain the PV. JPT P. 976^

Complexities of the Analysis of Surface Shut-In Drillstem Tests in an Offshore Volatile Oil Reservoir

Summary A surface shut-in drillstem test (DST) procedure as used in an offshore volatile oil reservoir. Bottomhole shut-in devices were not used because of operational difficulties and anticipated hazardous problems. The type curve and Horner plots of the bottom hole pressures (BHP's) did not conform to classical theory. This paper explains the reasons and suggests a simulation procedure for the interpretation of data. Introduction The type curve plots have a very sharp flattening bend at about 15 minutes of shut-in time, which is not typical. The tubing shut-in pressures also decline while the (BHP's) increase, this is not typical either. As a consequence of these observations, we could not accept the conventional interpretations of the buildup curves. This paper describes a new theory that explains the discrepancies. The new theory relates this unusual behavior to the combined effects of these wellbore phenomena during pressure buildup testing:wellbore storage caused by rising fluid,inertial effects caused by a rising fluid column,gas/oil phase segregation in the test string.cooling of fluid in the uppermost part of the test string by seawater, andgas going back into the oil phase in the fluid column during buildup. Background The DST procedure consisted of isolating a perforated interval by a set of packers, producing the well through a tubing (drillpipe) filled with diesel oil from several minutes to 24 hours, and finally closing the well on the surface to obtain pressure buildup data. Bottom hole shut-in devices were not used because of operational difficulties and anticipated hazardous problems during inclement weather in this hostile offshore environment. BHP's were recorded for all wells; tubing pressures and temperatures were recorded for some wells. Fig. 1 is the Homer plot of BHP and tubing pressures for a typical high-flowrate DST. Table 1 contains data needed to analyze Fig. 1. Tubing pressure and temperature are shown in Fig. 2. Fig. 3 is the type-curve plot of BHP differences vs. shut-in time. The following questions have arisen.Where is the correct straight-line portion of the Homer plot?Does deviation of the Homer plot from the early straight-line segment indicate reservoir boundary effects?Why does tubing pressure decline with shut-in time?Why does the type-curve plot have an unusual sharp bend from the early unit-slope straight-line segment? This paper provides qualitative answers to these questions based on theoretical considerations that relate to a set of complex wellbore storage phenomena. These phenomena include rising fluid wellbore storage and inertia effects at early shut-in times, gas/oil phase redistribution, wellbore fluid cooling by sea water in the top portion of the tubing, and gas dissolving back into the oil phase. Some aspects of complex wellbore storage problems and other wellbore phenomena are reported in the literature. Earlougher summarized results of the work on falling and rising wellbore storage, compressive wellbore storage, and phase redistribution wellbore effects-all before 1975. Fair's recent paper provides a promising new method of quantifying phase redistribution effect. Phase change of steam (flashing) caused by wellbore cooling for geothermal wells and its effect on well transient behavior was reported by Gringarten and Miller. JPT P. 173^

Connected digit recognition using a level-building DTW algorithm

In this paper we present a novel method for recognizing a string of connected digits based upon the use of a recently proposed level-building dynamic time warping (DTW) algorithm. The recognition system attempts to build up the string, level-by-level (i.e., digit-by-digit), by comparing portions of the test string to isolated digit reference patterns. A backtracking procedure is used to find the best string (i.e., minimum accumulated distance) as well as a set of reasonable alternative candidates. The system was tested on a number of talkers speaking variable length digit strings (from two to five digits) over dialed up telephone lines. String error rates of 4.8 percent and 4.6 percent were obtained for speaker-trained and speaker-independent systems. Word error rates of 0.7 percent (for speaker-trained tests) and 0.9 percent (for speaker-independant tests) were obtained. The digit reference templates were obtained from autocorrelation averaging of a pair of isolated word templates for each digit of the speaker-trained system, and from a clustering analysis of isolated words for the speaker-independent system.

A theory of order relations in perceptual matching.

A theory of order relations in the perceptual matching task relates order manipulations to research on retrieval processes and the representation of order information in memory. In experimental tests of the theory, presentation of a study string of letters to the subject was followed by a test string to which the subject responded same or different. The data of main interest concern the case where the test string is a permutation of the study string. When adjacent letters are switched, reaction time is long and accuracy low, suggesting that, in the comparison process, a test letter is not simply compared to the letter in the same position in the study string; rather, the comparison is distributed across positions. The memory model assumes that the representation of a letter is distributed (spread) over position and that the comparison process assesses the amount of overlap between the test string and the memory representation. The amount of overlap is transformed by a power function into the drift rate in a diffusion (random walk) comparison process. The diffusion retrieval model and overlap memory model are fitted to the data and goodness-of-fit is assessed. Shortcomings of alternative models are considered and applications of the model to related matching tasks are described.

Application of dynamic time warping to connected digit recognition

A connected digit recognizer is proposed in which a set of isolated word templates is used as reference patterns and an unconstrained dynamic time warping (DTW) algorithm is used to literally spot the digits in the string. Segmentation boundaries between digits are obtained as the termination point of the dynamic path from the previous time warp. A region around the boundary is searched for the optimum starting point for the succeeding digit. At each stage the recognizer keeps track of a set of candidate digit strings for each test string. The string with the smallest accumulated distance is used as the preliminary string estimate. To help improve the recognition accuracy, two post-correction techniques were applied to the entire set of hypothesized digit strings. One technique creates a reference string by concatenating reference contours of the digits of the string, and comparing this to the test string using a constrained dynamic time warping algorithm. The second technique performs a similar comparison using voiced-unvoiced-silence contours instead of the measured features. Small but consistent improvements in recognition accuracy have been obtained using these techniques for both speaker-trained and speaker-independent systems with digit strings recorded over dialed-up telephone lines. For variable length digit strings of from 2 to 5 digits (where the recognizer was not told the length of the string), word error rates of about 2-3 percent and string error rates on the order of 8 percent were obtained for both speaker-dependent and speaker-independent systems.

Application of post‐correction techniques to connected digit recognition

A scheme is proposed for connected digit recognition in which a set of isolated word templates is used as reference patterns and an unconstrained dynamic time warping algorithm is used to literally “spot” the digits in the string. The recognizer keeps track of a set of candidate digit strings for each test string. The string with the smallest accumulated distance is used as a preliminary string estimate. To help improve the recognition accuracy, we have considered two “post‐correction” techniques applied to the entire set of hypothesized digit strings. One technique creates a reference string by concatenating reference contours of the digits of the string and compares this to the test string using a constrained dynamic warp algorithm. The other technique performs a similar comparison using voiced‐unvoiced‐silence contours instead of the measured features. Small but consistent improvements in recognition accuracy have been obtained using these techniques for both speaker‐trained and speaker‐independent systems over dialed‐up telephone lines.

Orthographic regularity, positional frequency, and visual processing of letter strings.

Previous research has demonstrated that familiarity with the orthographic structure within a letter string can facilitate the processing of the component letters. The current research was directed at discovering the psychologically relevant properties of this structure. Two fundamental descriptions were independently varied in the construction of six-letter nonword strings. A probabilistic description based on the frequency of occurrence of letters in each position was factorially combined with a rule-governed description defined in terms of graphemic and phonological constraints. College sophomores and sixth-grade readers were asked to indicate whether or not a predesignated target letter was present in these strings. For both groups of readers, orthographic regularity and summed positional frequency were found to have only a small facilitative effect on reaction time (RT). In contrast, RTs to say "no" increased dramatically with increases in the number of letters in the catch string that were physically similar to the target letter. In another experiment, the letter string was presented for a short duration, followed immediately by masking stimulus and then the target letter. College students indicated whether or not the target was present in the test string. Accuracy of performance was critically dependent on the orthographic regularity and summed positional frequencies of the letters in the test string. No effect of letter similarity was observed. The large differences that were observed between these two tasks were accounted for in terms of the stages of processing that are critical for performance in the tasks.

Orthographic regularity, positional frequency, and visual processing of letter strings.

Previous research has demonstrated that familiarity with the orthographic structure within a letter string can facilitate the processing of the component letters. The current research was directed at discovering the psychologically relevant properties of this structure. Two fundamental descriptions were independently varied in the construction of six-letter nonword strings. A probabilistic description based on the frequency of occurrence of letters in each position was factorially combined with a rule-governed description defined in terms of graphemic and phonological constraints. College sophomores and sixth-grade readers were asked to indicate whether or not a predesignated target letter was present in these strings. For both groups of readers, orthographic regularity and summed positional frequency were found to have only a small facilitative effect on reaction time (RT). In contrast, RTs to say "no" increased dramatically with increases in the number of letters in the catch string that were physically similar to the target letter. In another experiment, the letter string was presented for a short duration, followed immediately by masking stimulus and then the target letter. College students indicated whether or not the target was present in the test string. Accuracy of performance was critically dependent on the orthographic regularity and summed positional frequencies of the letters in the test string. No effect of letter similarity was observed. The large differences that were observed between these two tasks were accounted for in terms of the stages of processing that are critical for performance in the tasks.

Orthographic regularity, positional frequency, and visual processing of letter strings: a reply to Krueger's comments.

In reply to Krueger, we address the issues of lowercase versus uppercase letter strings, words versus pseudowords, repeated letters in the test string, descriptions of orthographic structure, similarity effects, apples and oranges, and interactions of age with other variables.