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Showing papers by "University of Waterloo published in 1983"


Journal ArticleDOI
TL;DR: In this article, the requirements for functions synthesizing judgements (quantities or their ratios), in particular separability, associativity or bisymmetry, cancellativity, consensus, reciprocal or homogeneity properties are investigated and all functions satisfying them are determined.

785 citations


Journal ArticleDOI
TL;DR: In this paper, the sensitivity to disturbances and robustness under plant perturbations are measured in a weighted H^{\infty} norm, and the results are extended to unstable plants, and explicit formulas for the general situation of a finite number of right halfplane (RHP) plant zeros or poles are provided.
Abstract: In this paper, we look for feedbacks that minimize the sensitivity function of a linear single-variable feedback system represented by its frequency responses. Sensitivity to disturbances and robustness under plant perturbations are measured in a weighted H^{\infty} norm. In an earlier paper, Zames proposed an approach to feedback design involving the measurement of sensitivity by "multiplicative seminorms," which have certain advantages over the widely used quadratic norm in problems where there is plant uncertainty, or where signal power-spectra are not fixed, but belong to sets. The problem was studied in a general setting, and some H^{\infty} examples were solved. Here, a detailed study of the single-variable case is undertaken. The results are extended to unstable plants, and explicit formulas for the general situation of a finite number of right half-plane (RHP) plant zeros or poles are provided. The Q or "approximate-inverse" parametrization of feedbacks that maintain closed-loop stability is extended to the ease of unstable plants. The H^{\infty} and Wiener-Hopf approaches are compared.

562 citations


Journal ArticleDOI
TL;DR: In this paper, the authors explored the validity of the claim by considering data from a recent study of 77 adult women who were victimized as children: survivors of father-daughter incest and found that finding meaning in one's victimization facilitated long term adjustment to the event.
Abstract: A critical feature of many undesirable life events is that they often shatter the victim's perception of living in an orderly, meaningful world. Many authors have suggested that following such outcomes, the search for meaning is a common and adaptive process. This paper explores the validity of that claim by considering data from a recent study of 77 adult women who were victimized as children: survivors of father-daughter incest. In the process, several central questions regarding the search for meaning are addressed. How important is such a search years after a crisis? Over time, are people able to make sense of their aversive life experiences? What are the mechanisms by which individuals find meaning in their negative outcomes? Does finding meaning in one's victimization facilitate long term adjustment to the event? Finally, what are the implications of an inability to find meaning in life's misfortunes?

529 citations


Journal ArticleDOI
TL;DR: Arguments are presented to support the concept that walking speed is largely controlled by gain and that the timing of the motor patterns, which is extremely tightly synchronized with the anatomical position, is under major afferent control.
Abstract: Motor patterns in normal human gait are evident in several biomechanical and EMG analyses over the stride period. Some of these patterns are invariant over the stride period with changes of cadence, whole others are closely correlated with speed changes. The findings for slow, natural, and fast walking are summarized: 1. Joint angle patterns over the stride period are quite invariant, and do not change with cadence; 2. Moment of force patterns at the ankle are least variable and quite consistent at all speeds; 3. A recently defined support moment is quite consistent at all speeds. 4. Moments at the knee and hip are highly variable at all cadences but decrease their variability as cadence increases; 5. Mechanical power patterns at all joints show consistent timing over the stride period; 6. EMG profiles of 5 muscles show consistent timing over the stride, but the amplitude increases as walking speed increases. Arguments are presented to support the concept that walking speed is largely controlled by gain and that the timing of the motor patterns, which is extremely tightly synchronized with the anatomical position, is under major afferent control.

504 citations


Journal ArticleDOI
TL;DR: A natural-gradient tracer test using a chloride solution with an initial injection volume of 0.7 m 3 was performed in the sandy aquifer at the Borden site as mentioned in this paper.

424 citations


Journal ArticleDOI
TL;DR: A saggital plane biomechanical analysis of 11 slow jogging trials yielded joint moments of force, power curves and positive and negative work at each of the joints of the lower limb indicating the dual role of hip flexors and extensors relative to the trunk and lower limb stability.

377 citations


Journal ArticleDOI
TL;DR: Several characterizations of the class of strongly chordal graphs are presented, including a forbidden induced subgraph characterization and two characterizations in terms of totally balanced matrices, which yields a polynomial recognition algorithm.

349 citations


Journal ArticleDOI
TL;DR: A landfill-derived contaminant plume with a maximum width of ∼600 m, a length of ∼700 m and a maximum depth of 20 m in an unconfined sand aquifer was delineated by means of a monitoring network that includes standpipe piezometers, multilevel point-samplers and bundle-piezometers as discussed by the authors.

303 citations


Journal ArticleDOI
TL;DR: In this paper, it was suggested that stream ecologists should learn much more than they now know about groundwater, and it seems probable that it is an important source of organic matter to the stream ecosystem.
Abstract: In the light of findings in recent years about the extent and nature of the hyporheal zone, the rate of uptake of organic matter by stream beds, and the fact that groundwater contains dissolved organic matter, it is suggested that stream ecologists should learn much more than they now know about groundwater. It seems probable that it is an important source of organic matter to the stream ecosystem which has escaped consideration to date.

269 citations


Journal ArticleDOI
TL;DR: It is suggested that differences in complementary and noncomplementary specialization may underlie individual differences in cognitive skills, and that complementary specialization exists only as a statistical norm.

269 citations


Journal ArticleDOI
TL;DR: It is argued that this adds uncontrolled variance to the observed right-ear advantage and indicates that laterality effects are simply attentional bias, but this effect can be attributed to an asymmetry of perceptual discrimination.

Journal ArticleDOI
TL;DR: In this article, different interpretations of tourism capacity are discussed, including inherent assumptions and potential applications, and a strategic planning model is recommended which includes the establishment of goals, ongoing evaluation of impacts, and the optional use of limits.

Journal ArticleDOI
TL;DR: In this paper, the authors used classical probability theory to derive expressions for the expected (or mean) value of quantities such as the irradiation on inclined surfaces, collector output, and net gain through windows.

Journal ArticleDOI
TL;DR: The significant alterations in peak torque outputs with both legs suggest that neural adaptations play a prominent role in strength performance with training and detraining.
Abstract: To investigate biochemical, histochemical and contractile properties associated with strength training and detraining, six adult males were studied during and after 10 weeks of dynamic strength training for the quadriceps muscle group of one leg, as well as during and after a subsequent 12 weeks of detraining Peak torque outputs at the velocities tested (0-270 degrees X s-1) were increased (p less than 005) by 39-60% and 12-37% after training for the trained and untrained legs, respectively No significant changes in peak torques were observed in six control subjects tested at the same times Significant decreases in strength performance of the trained leg (16-21%) and untrained leg (10-15%) were observed only after 12 weeks of detraining Training resulted in an increase (p less than 005) in the area of FTa (21%) and FTb (18%) fibres, while detraining was associated with a 12% decrease in FTb fibre cross-sectional area However, fibre area changes were only noted in the trained leg Neither training nor detaining had any significant effect on the specific activity of magnesium-activated myofibrillar ATPase or on the activities of enzymes of phosphagen, glycolytic or oxidative metabolism in serial muscle biopsy samples from both legs In the absence of any changes in muscle enzyme activities and with only modest changes in FT fibre areas in the trained leg, the significant alterations in peak torque outputs with both legs suggest that neural adaptations play a prominent role in strength performance with training and detraining

Journal ArticleDOI
01 Jul 1983
TL;DR: Using a restricted form of quintic Hermite interpolation, it is possible to allow distinct bias and tension parameters at each joint without destroying geometric continuity, which provides a new means of obtaining local control of bias and pressure in piecewise polynomial curves and surfaces.
Abstract: The Beta-spline introduced recently by Barsky is a generalization of the uniform cubic B-spline: parametric discontinuities are introduced in such a way as to preserve continuity of the unit tangent and curvature vectors at joints (geometric continuity) while providing bias and tension parameters, independent of the position of control vertices, by which the shape of a curve or surface can be manipulated. Using a restricted form of quintic Hermite interpolation, it is possible to allow distinct bias and tension parameters at each joint without destroying geometric continuity. This provides a new means of obtaining local control of bias and tension in piecewise polynomial curves and surfaces.

Journal ArticleDOI
TL;DR: PBQ ratings of 123 preschoolers were correlated with observations of in-class social and cognitive play behaviors, sociometric status, and social problem-solving skills and indicated that children rated highly on the PBQ's Anxious-Fearful, Hostile-Aggressive, and Hyperactive-Distractible factors appeared to be a useful instrument for identifying children with social problems.
Abstract: Behar and Stringfield (1974) have suggested that the Preschool Behavior Questionnaire (PBQ) is a reliable index of young children's social competence. However, there are few extant data in which teacher ratings of children on the PBQ have been correlated with independent assessments of social competence. In this study PBQ ratings of 123 preschoolers were correlated with observations of in-class social and cognitive play behaviors, sociometric status, and social problem-solving skills. Analyses indicated that children rated highly on the PBQ's Anxious-Fearful, Hostile-Aggressive, and Hyperactive-Distractible factors (a) displayed less mature and more aggressive in-class behaviors, (b) were less popular among their peers, and (c) were more likely to suggest negative affect strategies on the social problem-solving measure. Thus, the PBQ appears to be a useful instrument for identifying children with social problems.

Journal ArticleDOI
TL;DR: The plume contains above-background concentrations of dissolved zinc and manganese, with maximum concentrations of 400, 2000 and 1200 mg l−1, respectively as discussed by the authors, with a range of values from 30 mg l − 1 beneath the landfill to 5mg l− 1 near the front of the plume.

Journal ArticleDOI
TL;DR: It was found that the average relative contributions of the ankle and hip muscles were approximately 23 and 28% respectively, with the remaining 49% of the work being done by the muscles acting at the knee joint.
Abstract: A work-energy approach was used to determine the contributions of the muscles crossing the hip, knee and ankle joints to the total positive work done during maximal vertical jumps. It was found that the average relative contributions of the ankle and hip muscles were approximately 23 and 28% respectively, with the remaining 49% of the work being done by the muscles acting at the knee joint. The efficiency of jumping, i.e. the ratio of potential energy gained to the net mechanical work done by the muscles acting at the three lower limb joints was nearly 1.0. These results stress the importance of all three major leg extensor muscle groups to the performance of an explosive activity such as vertical jumping. It is suggested that the work-energy approach supplies useful information concerning joint contributions without the problems associated with other techniques.

Journal ArticleDOI
TL;DR: In this paper, the authors used a systematic elimination procedure to find three atomic property expressions which could be used to distinguish the crystal structures of AB intermetallic compounds and used them to predict the structure type of unknown AB phases with high accuracy.
Abstract: We used a systematic elimination procedure to find three atomic property expressions which could be used to distinguish the crystal structures of AB intermetallic compounds We started from 182 sets of tabulated physical properties and calculated atomic properties and combined them for the binary phases of A and B elements according to the modulus sums, differences, products and ratios The three expressions giving the best separation are the magnitude Δ(r s + r p ) Z AB = ¦(r s + r p ) Z A −(r s + r p ) Z B ¦ of the difference of Zunger's pseudopotential radii sums, the magnitude Δ MB AB = ¦X MB A −X MB B ¦ of the Martynov-Batsanov electronegativity difference and the sum ∑ZVEAB of the number of valence electrons We used these three axes in a three-dimensional structural stability diagram to separate 20 AB structure types representing 998 compounds into distinct regions with only 22 violations However, the diagram allows, as it must, an overlap of two (three) different structure types in regions that contain phases which have two (three) polymorphic structural forms The use of this diagram in conjunction with Miedema's model (for positive or negative ΔHfo) is a powerful tool for predicting the structure type of unknown AB phases with high accuracy

Journal ArticleDOI
TL;DR: A function diagram (f-diagram) D consists of the family of curves obtained from n continuous functions f"i:[0,1]->R(1=1) and on the other side of the diagonal R is the graph of the integers.

Journal ArticleDOI
TL;DR: It is shown that for arbitrary real edge costs the travelling salesman problem can be polynomially solved for such a graph, and an explicit linear description of the travelled salesman polytope is given.
Abstract: A Halin graphH=T∪C is obtained by embedding a treeT having no nodes of degree 2 in the plane, and then adding a cycleC to join the leaves ofT in such a way that the resulting graph is planar. These graphs are edge minimal 3-connected, hamiltonian, and in general have large numbers of hamilton cycles. We show that for arbitrary real edge costs the travelling salesman problem can be polynomially solved for such a graph, and we give an explicit linear description of the travelling salesman polytope (the convex hull of the incidence vectors of the hamilton cycles) for such a graph.

Journal ArticleDOI
14 Oct 1983-Science
TL;DR: Most of the newly recalled material was incorrect, especially for highly hypnotizable subjects in the hypnosis condition, which can have profound implications for forensic investigations.
Abstract: The forensic use of hypnosis is increasing. A hypermnesic procedure was used in an experiment that calls this practice into question. Subjects tried for a week to recall 60 previously presented pictures. They were then either hypnotized or not and encouraged to recall even more pictures. Most of the newly recalled material was incorrect, especially for highly hypnotizable subjects in the hypnosis condition. Such errors in recall can have profound implications for forensic investigations.

Journal ArticleDOI
TL;DR: In this article, a line-tunable CO 2 laser was used in conjunction with supersonic beams of dilute mixtures of SF 6 or CH 3 F in Ar to obtain the infrared spectra of Ar clusters containing these molecules.

Journal ArticleDOI
TL;DR: Split beams of varying separations from a helium-neon laser were directed through the crystalline lenses of a number of vertebrates to indicate the extent to which the refractive index variation of the lens and lens shape control spherical aberration.

Journal ArticleDOI
TL;DR: In this paper, six types of devices for groundwater monitoring were used on an experimental basis in the investigation of the plume of contamination in the unconfined sandy aquifer at the Borden landfill.

Journal ArticleDOI
01 May 1983-Planta
TL;DR: Production of superoxide ion radicals by chloroplasts from senescing leaves ofPhaseolus vulgaris L. vulgaris coincides temporally with the initiation of lipid peroxidation and the formation of gel-phase lipid in chloroplast membranes, phenomena known to be induced by this reactive species of oxygen.
Abstract: The formation of superoxide ion radicals (\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \)) by chloroplasts from senescing leaves ofPhaseolus vulgaris L. was determined by electron-spin-resonance measurements of Tiron (1,2-dihydroxybenzene-3,5-disulfonic acid) semiquinone, a radical species formed when Tiron reacts with\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \). The Tiron radical signal obtained from chloroplasts is sensitive to superoxide dismutase (EC 1.15.1.1) confirming that it is derived from\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \), oxygen-dependent and unaffected by 3-(3,4-dichlorophenyl)-1,1-dimethyl urea and hydroxylamine. Further confirmation of the identity of the radical was obtained by using the diagnostic spin trap 5,5′-dimethyl-1-pyrroline-1-oxide. The production of\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) by illuminated chloroplasts increases by about fourfold during the early stages of leaf senescence; it declines again as senescence intensifies. A similar pattern of\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) production was noted during aging of isolated chloroplasts in buffer. In addition, heat denaturation of freshly isolated chloroplasts greatly increases their ability to form\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) upon illumination, indicating that the radical is formed through a photochemical reaction involving chlorophyll, rather than enzymatically. Accordingly, the rise in\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) production during senescence may reflect deteriorative molecular rearrangements in the thylakoid membranes, which expose chlorophyll molecules normally inaccessible to oxygen. The propensity of chloroplasts to produce increased levels of\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) with advancing senescence is not counterbalanced by an augmented enzymatic radical-scavenging capability. Moreover, the peak in\(O_2^{\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{ - } } \) production during leaf senescence coincides temporally with the initiation of lipid peroxidation and the formation of gel-phase lipid in chloroplast membranes, phenomena that are known to be induced by this reactive species of oxygen.

Journal ArticleDOI
TL;DR: Multivariate central and local limit theorems are proved for a n (k) as n → ∞ that are based on examining the generating function that are shown to apply to permutations with rises and falls, ordered partitions of sets, Tutte polynomials of recursive families, and dissections of polygons.


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the class of shear-free expanding (or contracting) irrotational perfect fluids obeying an equation of state $p=p(ensuremath{\mu})$ and satisfying the field equations of general relativity.
Abstract: We investigate the class of shear-free expanding (or contracting) irrotational perfect fluids obeying an equation of state $p=p(\ensuremath{\mu})$ and satisfying the field equations of general relativity. It is shown that these space-times are either Friedmann-Robertson-Walker, or spherically symmetric Wyman solutions, or a special class of plane-symmetric models. This last class, which is given in exact form, is apparently new; the metrics are locally either spatially or temporally homogeneous. We show that the spherically symmetric Wyman solutions and the new class of plane-symmetric models are inconsistent with the additional requirement of a comoving surface of zero pressure, and thereby obtain a coordinate-free proof and a generalization of a result of Mansouri, concerning shear-free spherically symmetric gravitational collapse. Some properties of our solutions, and further generalizations of our results, are considered.

Journal ArticleDOI
TL;DR: Alkali treatment of corn stover improves the avaliability of cellulose and hemicellulose for enzymatic attack and saccharificatin (g sugar/g stover) of the residue and dissolved solids byenzymatic hydrolysis was achieved compared to 20% for untreatedcorn stover.
Abstract: Alkali treatment of corn stover improves the availability of cellulose and hemicellulose for enzymatic attack. Treatments were carried out for 1 to 60 min at temperatures and NaOH concentrations ranging from 100 to 150 degrees C and 0 to 2%, respectively. Solubilization of the stover and sugar production by enzymatic hydrolysis (Trichoderma viride cellulase) of the solid residue and the dissolved solids were used to measure the effect of caustic treatment. At 150 degrees C and 2% NaOH concentration, 65% of the original stover was dissolved after 5 min and 52% saccharification (g sugar/g stover) of the residue and dissolved solids by enzymatic hydrolysis was achieved compared to 20% for untreated corn stover. (6 Refs.)