Showing papers by "Northampton Community College published in 1985"

The hydrodynamic stability of flow over Kramer-type compliant surfaces. Part 1. Tollmien-Schlichting instabilities

Abstract: The hydrodynamic stability of flows over Kramer-type compliant surfaces is studied. Two main types of instability are considered. First, there are those which could not exist without viscosity, termed Tollmien–Schlichting Type Instabilities (TSI). Secondly, there are Flow-Induced Surface Instabilities (FISI), that depend fundamentally on surface flexibility and could exist with an inviscid fluid flow. Part 1, the present paper, deals mainly with the first type. The original Kramer experiments and the various subsequent attempts to confirm his results are reviewed, together with experimental studies of transition in flows over compliant surfaces and theoretical work concerned with the hydrodynamic stability of such flows.The Kramer-type compliant surface is assumed to be an elastic plate supported by springs which are modelled by an elastic foundation. It is also assumed that the plate is backed by a viscous fluid substrate having, in general, a density and viscosity different from the mainstream fluid. The motion of the substrate fluid is assumed to be unaffected by the presence of the springs and is determined by solving the linearized Navier–Stokes equations. The visco-elastic properties of the plate and springs are taken into account approximately by using a complex elastic modulus which leads to complex flexural rigidity and spring stiffness. Values for the various parameters characterizing the surface properties are estimated for the actual Kramer coatings.The boundary-layer stability problem for a flexible surface is formulated in a similar way to that of Landahl (1962) whereby the boundary condition at the surface is expressed in terms of an equality between the surface and boundary-layer admittances. This form of the boundary condition is exploited to develop an approximate theory which determines whether a particular change to the mechanical properties of the surface will be stabilizing or destabilizing with respect to the TSI. It is shown that a reduction in flexural rigidity and spring stiffness, an increase in plate mass, and the presence of an inviscid fluid substrate are all stabilizing, whereas viscous and visco-elastic damping are destabilizing.Numerical solutions to the Orr–Sommerfeld equation are also obtained. Apart from Kramer-type compliant surfaces, solutions are also presented for the rigid wall, for the spring-backed tensioned membrane with damping, previously considered by Landahl & Kaplan (1965), and for some of the compliant surfaces investigated experimentally by Babenko and his colleagues. The results for the Kramer-type compliant surfaces on the whole confirm the predictions of the simple theory. For a free-stream speed of 18 m/s the introduction of a viscous substrate leads to a complex modal interaction between the TSI and FISI. A single combined unstable mode is formed in the case of highly viscous substrate fluids and in this case increased damping has a stabilizing effect. When the free-stream speed is reduced to 15 m/s the modal interaction no longer occurs. In this case the effects of combined viscous and visco-elastic damping are investigated. It is found that damping tends to have a strong stabilizing effect on the FISI, in the form of travelling-wave flutter, but a weaker destabilizing effect on the TSI. The opposing effects of damping on the two modes of instability forms the basis of a possible explanation for Kramer's empirical observation of an optimum substrate viscosity. Results obtained using the e9 method also indicate that a substantial transition delay is theoretically possible for flows over Kramer's compliant coatings.

Influence of Geology on Lake Acidification in the ILWAS Watersheds

Abstract: Three lake-watersheds in the Adirondack Mountains of New York State, underlain by similar granitic bedrock and receiving similar levels of acidic deposition, were found to have very different surface water alkalinities. The chemical differences appear to be due to differences in the unconsolidated surficial materials in the basins. Woods Lake watershed (mean lake outlet pH of 4.7) is covered by thin till with many interspersed bedrock outcrops. The thinness of these surficial deposits (average depth 2 m) limits the amount of deep percolation of water and thus contact with alkalinity-producing inorganic horizons. In contrast, Panther Lake watershed (mean lake outlet pH of 6.2) is covered by thick glacial till (average depth 24 m). Here more of the precipitation comes in contact with the alkalinity-producing materials. Sagamore Lake watershed is much larger and has areas of both thick and thin deposits and lake outlet pH values intermediate to those of Woods and Panther lakes.

Motives for arson (fire raising).

Abstract: Using a sample of imprisoned arsonists, an attempt is made to present a more refined classification of motivation than has been offered in the past. The need for psychiatric opinion on all arsonists is stressed.

Rehabilitation after severe brain injury: a special-unit approach to behaviour disorders.

Abstract: A special unit developed for the treatment and rehabilitation of patients with behaviour disorders after severe brain injury is described, and several problem areas are discussed.

Pole assignment of strictly proper and proper linear systems by constant output feedback

Abstract: A new unifying approach for the study of pole assignment by constant output feedback (CPAP) for strictly proper and proper linear systems is presented. The multilinear nature of CPAP is reduced to a linear problem and to the standard multilinear problem of decomposability of multivectors; the solvability of CPAP thus becomes a problem of finding real intersections of a linear variety with the Grassmann variety of a projective space. An alternative proof to the ml≥n(m, I, n are the numbers of outputs, inputs, states) necessary and sufficient condition for generic pole-assignability of strictly proper systems by complex output feedback is given; the above result is extended to the ml≥ n + 1 condition for the case of proper systems. Stronger necessary conditions for generic pole assignment by a real output feedback are obtained by using the recently introduced invariant, the Plucker matrix Pn such conditions are that Pn must have full rank and ml≥n (strictly proper case), or ml≥ n + 1 (proper case). It is sh...

Asperger's syndrome and non-verbal communication: a pilot study

Abstract: The study investigated the ability of 10 patients with Asperger's syndrome to recognize and produce non-verbal aspects of facial and spoken (e.g. vocal intonation) communication by use of photographs, audiotape and videotape. It also aimed to establish materials to differentiate individuals with this condition from a comparable non-Asperger group. Asperger subjects tended to be poorer than comparable patients on all subtests.

Anorexia nervosa and bulimia: an activity-oriented approach.

Abstract: In recent years, there has been a growing trend away from a dogmatic adherence to any one approach in the treatment of eating disorders. This paper adds the new element of practice in relation to cognitive change. The activity-oriented approach outlined here stresses that patients with anorexia nervosa or bulimia must maintain responsibility for their own food intake throughout treatment. The key role of the occupational therapist in the treatment team is outlined, and suggestions for assessment and management of this type of patient are given.

The effects of mean stress and stress concentration on fatigue under combined bending and twisting

Abstract: The Gough test data on fatigue under combined bending and twisting with superimposed mean bending and torsion stresses with and without stress raisers has been re-investigated in terms of the stresses acting on the plane of maximum range of shear stress. It has been shown that the allowable amplitude of shear stress on this plane can be predicted from an equation of the form τa= [t - c1 (Kt×σa)1.5−c2σ2m]/Kt where σa and σm are the normal stress amplitude and mean normal stress respectively on the plane of maximum range of shear stress, c1 and c2 are defined material constants and Kt is the theoretical stress concentration factor.

Thickeners for thickening aqueous media

Abstract: A thickener for thickening an aqueous medium comprises a water-in-oil emulsion of a water soluble polymer in which either the polymer is essentially wholly ionic in nature and is present in solution in the aqueous phase of the emulsion, or the thickener is employed in the presence of an oil soluble surfactant present in an amount of at least 15% by weight of solid polymer. Such a thickener is particularly suitable for thickening aqueous media containing large amounts of electrolyte such as printing pastes. If at least a part of the oil phase of the water-in-oil emulsion is a silicone oil, a fabric printed by a printing paste thickened by such a thickener has a softer handle.

Anaesthesia for ENT surgery in children.

Abstract: We were interested to read the article by Dr HanningtonKiff (Anaesthesia 1985; 40: 7 6 8 ) since we are involved in a study comparing the duration and quality of recovery in two groups of children undergoing ENT surgery. In part, our study to date confirms the work of Lindgren’ who demonstrated that, using a modified version of the method of Aldrete and Kroulik for assessment of recovery in children predmedicated with tricoflos and atropine,, the time from extubation to opening eyes on command can be as long as 34 minutes after spontaneous ventilation with halothane anaesthesia. We have assessed the recovery period using the simplified scoring system of Steward3 and find that this allows an objective record of the quality and duration of recovery until the child is awake and responsive. However, the assessment of recovery in children is far from simple and a child happily awake at 10 minutes may be pain free but sobbing uncontrollably for parental comfort at 12 minutes. Similarly, a child still anaesthetised a t 20 minutes, and therefore tranquil, may in fact be in great pain and distressed at 25 minutes. We, therefore. question the value of a method of assessment of recovery which consists of three very broad assessments at 10-minute intervals and would suggest that the total period of assessment should be continued until a predetermined clinical endpoint. In Dr Hannington-Kiffs study the percentage of children given nefopam and deemed ‘difficult to restrain’ was 10% at 10 minutes, 20% at 20 minutes and 25% at 30 minutes. We wonder if this trend was continued throughout the remainder of the recovery period. The analgesic requirements of children undergoing ENT surgery vary considerably. The surgical incision of myringotomy is intensely painful, but children after myringotomy with or without the insertion of grommets generally require little postoperative analgesia. Children after adenoidectomy do not generally suffer the intensity of postoperative pain as those who have had tonsillectomy and adenoidectomy. We, therefore, wonder if equal numbers of these sub-groups of otolaryngological surgery were represented in the two groups in Dr Hannington-Kiff’s study. Finally Dr Hannington-Kiff concludes that ‘this study confirms popular opinion that papaveretum is an effective analgesic when given intra-operatively to promote quiet, uneventful emergence after ENT anaesthesia in children’. A major disadvantage to the use of papaveretum in ENT surgery. however, is the high incidence of postoperative vomiting (up to 57%) in children given this drug for premedication or for postoperative analgesia or for both.4 We wish to challenge the value of a technique that resultsin overt respiratorydepressionin 15% ofpatients and, almost certainly, unacceptably high levels ofcarbon dioxide tension in the remainder. In our current series, which compares children breathing spontaneously during halothane anaesthesia with children ventilated with nitrous oxide and oxygen alone and following opiate premedication one hour pre-operatively. we have found mean end-tidal PCO, in the spontaneously ventilating group to be 7.26 kPa. Such high levels of Pco, may contribute to an increase in operative and postoperative bleeding. If nefoparn can be shown to produce a calm, sedate child throughout the postoperative period and can be shown to have a low incidence of side-effects, then its lack of respiratory depression could make it a useful analgesic for otolaryngological surgery in children.

Network therapy: an outcome study of twelve social networks.

Abstract: Twelve social networks received a course of network therapy at the Mount Tom Institute in Holyoke, Massachusetts, by the Network Therapy Project. A total of twenty-five 3-hour meetings included 201 participants. A study was conducted examining the number and type of service contacts in the clients' central medical files three months prior to the completion of network therapy and at two 3-months intervals after therapy was terminated. Entries were made in clients' charts by case managers, by crisis team staff, and by other mental health professionals. An historical comparison group was studied by randomly choosing 12 clients from the 19 referred for network therapy who did not receive this treatment. The comparison group showed an overall 17% decrease in service utilization after the date of referral, compared to a 76% decrease postnetwork therapy in the treatment group. The difference between the group outcomes was statistically significant.

Frustrated-total-internal-reflection fiber-optic pressure sensor

Abstract: In this work the design and construction of a simple fiber-optic pressure sensor based on the principle of frustrated-total-internal-reflection in a fiber cut beyond the critical angle are described. The characteristic of the device is obtained and compared with the predictions of a simple theory. Modifications to alter its sensitivity by the use of different wavelengths and fiber cut angle are discussed.

A Comparison of the OPQ and 16PF in Relation to their Occupational Application

Abstract: The OPQ (Occupational Personality Questionnaire) is a factor‐analytic‐based, self‐report questionnaire which has been developed in Britain as a wide‐band assessment device for use in selection and counselling in jobs at managerial and professional level where personality factors are often important variables in success.

Preparative HPLC. Part 2. Purification of β-lactam derivatives using laboratory-assembled equipment

Abstract: The capabilities of a preparative chromatograph assembled at moderate cost from commercially available components are examined in relation to the purification of β-lactam derivatives. It is shown that high efficiency separations can be achieved rapidly, economically, and on a scale sufficient to provide adequate quantities of material for spectroscopic identification and biological testing. In the synthesis of a large batch of aminopropyl silica for preparative HPLC purification of an impure sample of cephacetrile, three different grades of silica were investigated. The material giving the best performance was prepared on a 100 g scale and baseline separations for 0.5 g loadings of the impure cephacetrile were obtained on a 30 cm × 2.2 cm i.d. column. The pure cephalosporin was recovered in high yield by freeze drying of the eluate.

The Photostability of Fluorescent Whitening Agents on Wool

Abstract: The stabilities, both on wool and in solution, of several commercial fluorescent whitening agents (FWAs) were examined. Stability in solution was found to vary considerably. However, the photoye/lowing rates of wool whitened with these compounds were found to be similar, suggesting that the photodegradation pathway in solution is probably different to that on wool. The stabilities of two pyrazolines were also examined, and in accordance with previous results it was found that the stabilities of these compounds in solution did not relate to the photoye/lowing rates of wool whitened with them. The photoye/lowing of whitened wool was also followed by diffuse reflectance spectroscopy. The sample was illuminated by monochromatic light and the presence of FWAs on the fabric detected by an increase in transmission. This apparent increase is due to the fluorescence contributing to the reflected light. Using such a method the presence of an FWA can be easily verified and its photodegradation followed.

Stationary instability of the buoyancy-layer flow between heated vertical planes

Abstract: The critical mode of instability is obtained for the buoyancy-driven boundary-layer flow between infinite vertical planes that are subject to a constant vertical temperature gradient and a constant horizontal temperature difference. The analysis is primarily concerned with the high Prandtl number limit when the critical disturbance occurs as stationary convection. The threshold of instability is found to correspond to the situation where a temperature change comparable with that across the layer occurs in a vertical distance of O ( R -1/8 l *), where R ( ≫ 1) is a Rayleigh number based on the vertical temperature gradient and the width of the layer, l *. Unlike the travelling wave instability found by A. E. Gill & A. Davey ( J. Fluid Mech . 35, 775 (1969)) the stationary mode is not confined to the boundary layers but consists of elongated horizontal rolls that stretch across the core region between the planes. The boundary layer-core interaction leads to the determination of the critical mode from the solution of a reduced form of the boundary-layer stability equations. The vertical wavelength of the instability is O ( R -1/8 l *), which is short compared with the distance between the planes but long compared with the boundary-layer width, which is O ( R -1/4 l *).