Showing papers by "University of Huddersfield published in 1999"
TL;DR: In this paper, a double-blind, randomized controlled trial of a novel educational booklet compared with a traditional booklet for patients seeking treatment in primary care for acute or recurrent low back pain was conducted.
Abstract: Study Design. A double-blind, randomized controlled trial of a novel educational booklet compared with a traditional booklet for patients seeking treatment in primary care for acute or recurrent low back pain.
Objective. To test the impact of a novel educational booklet on patients' beliefs about back pain and functional outcome.
Summary of Background Data. The information and advice that health professionals give to patients may be important in health care intervention, but there is little scientific evidence of their effectiveness. A novel patient educational booklet, The Back Book, has been developed to provide evidence-based information and advice consistent with current clinical guidelines.
Methods. One hundred sixty-two patients were given either the experimental booklet or a traditional booklet. The main outcomes studied were fear-avoidance beliefs about physical activity, beliefs about the inevitable consequences of back trouble, the Roland Disability Questionnaire, and visual analogue pain scales. Postal follow-up response at 1 year after initial treatment was 78%.
Results. Patients receiving the experimental booklet showed a statistically significant greater early improvement in beliefs which was maintained at 1 year. A greater proportion of patients with an initially high fear-avoidance beliefs score who received the experimental booklet had clinically important improvement in fear-avoidance beliefs about physical activity at 2 weeks, followed by a clinically important improvement in the Roland Disability Questionnaire score at 3 months. There was no effect on pain.
Conclusion. This trial shows that carefully selected and presented information and advice about back pain can have a positive effect on patients' beliefs and clinical outcomes, and suggests that a study of clinically important effects in individual patients may provide further insights into the management of low back pain.
Nonspecific low back pain is a common and recurring symptom that most people usually deal with themselves and for which there is no effective cure. Hence, the information and advice that health professionals give to patients may be a potent element of the health care intervention. Von Korff and Saunders 36 and Bush et al 12 found that one of the main reasons patients consult physicians is to seek information and reassurance. Bush et al 12 suggested that these patients have practical and realistic desires to learn about their low back pain, what to expect, and what they can do about it. There is some evidence that greater congruence among the patient's and clinician's perception of the problem, the prognosis for the disorder, and its long-term management is associated with higher patient satisfaction and better short-term outcomes. 14
Qualitative studies 8,33 have demonstrated the complexity and heterogeneity of patients' perceptions of back pain, which may raise questions about how easily these can be modified by simple information and advice. Deyo and Diehl 18 and Bush et al 12 found that, for patients in the United States, the most frequent reason for dissatisfaction with medical care was failure to receive an adequate explanation of their back pain. Patients who believed that the physician's explanation was inadequate wanted more diagnostic tests, did not cooperate as well with treatment, and had poorer clinical outcomes at 3 weeks. Skelton et al 33 found that patients in the United Kingdom were skeptical of medical explanations for their back pain either because they doubted its validity or because it did not fit their own understanding of the problem. Borkan et al 8 found that Israeli patients also were quite critical of the medical system and more interested in what works.
The first U.S. and U.K. clinical guidelines for acute low back pain 3,16 recommended that patients should be given accurate and up-to-date information and advice about back pain and its management; however, that recommendation was based on theoretical considerations and general clinical consensus rather than on any firm scientific evidence that such information improves outcomes. These guidelines gave few practical details on precisely what the content of that information and advice should be, apart from general reassurance about the absence of serious disease and that most back pain improves quickly with simple symptomatic measures and activity modification. There has been a progressive shift in subsequent international guidelines. 10 Based on additional evidence that is now available, 40 the more recent U.K. 31 and New Zealand 2 guidelines suggest that the physician provide more positive advice to stay active and continue ordinary activities as normally as possible. The New Zealand guidelines also provide a detailed assessment of psychosocial yellow flags (risk factors for chronic pain and disability) and suggest general behavioral principles for how patients with these features should be managed. 23
Discussion at the Second International Forum for Primary Care Research on Low Back Pain 9 identified the continuing need for a simple and convincing explanation of back pain that is acceptable to patients and that would form a logical basis for active management. Most guidelines recommend that printed educational material should be made available, though this recommendation is based on limited evidence. 10 There are hundreds of leaflets and booklets about back pain, but remarkably few have been submitted to any sort of scientific evaluation. 11 Roland and Dixon 28 reported on the only randomized controlled trial (RCT) of a traditional clinical booklet that showed any significant impact on patients: those receiving the booklet consulted less frequently and had fewer specialist referrals for back pain over the next year. Cherkin et al 15 reported on an RCT that compared a 15-minute session with an educational nurse with a booklet that was similar to the material accompanying the Agency for Health Care Policy and Research (AHCPR) guidelines. 3 The nurse intervention yielded higher patient satisfaction, perceived knowledge, and exercise participation in the short term. The booklet showed similar trends, but they did not reach statistical significance compared with the outcomes of usual care. Neither of these trials showed any effect of a booklet on pain or functional status.
The aim of the current study was to determine the impact of a novel educational booklet on the beliefs and functional outcome of patients seeking treatment in primary care for an acute or recurrent episode of low back pain.
537 citations
TL;DR: In this paper, the attenuation length of photoelectrons was found to vary from a minimum of ∼5 A at an electron kinetic energy (E) of 100 eV up to ∼23 A at a kinetic energy of 1000 eV and can be described by the expression λ = 0.3E0.64 in the range 300−1000 eV.
Abstract: The interaction of both photoelectrons and X-rays with self-assembled monolayers of n-alkanethiols on gold has been measured using synchrotron radiation as the photon source in the energy range 140−1100 eV. The attenuation length of photoelectrons (λ) was found to vary from a minimum of ∼5 A at an electron kinetic energy (E) of 100 eV up to ∼23 A at a kinetic energy of 1000 eV and can be described by the expression λ = 0.3E0.64 in the range 300−1000 eV. Exposure of the self-assembled monolayer to X-rays leads to fission of the C−S bond with a cross section of the order of 10-17 cm2 which diplays no apparent dependence on the incident photon energy.
199 citations
TL;DR: The results from both instrumental and sensory data suggest that it may not be the amount of polysaccharide that is important to rheological properties, but the type of exopolysaccharid (EPS)-producing strains and consequently the interaction of the polymer with the milk proteins during the fermentation.
Abstract: Summary Rheological and sensory properties of yoghurts prepared from commercially available cultures that had ropy and non-ropy characteristics were compared. Our results from both instrumental and sensory data suggest that it may not be the amount of polysaccharide that is important to rheological properties, but the type of exopolysaccharide (EPS)-producing strains and consequently the interaction of the polymer with the milk proteins during the fermentation. Data also suggest that the interaction and co-operative growth that occurs in mixed cultures also influences the yield of EPS production in the fermentation, as combining two ropy strains does not lead to an increase in total polysaccharide, although the viscosity can be improved. Texture measurements for viscosity correlated with sensory evaluation of viscosity and with slipperiness.
180 citations
TL;DR: In this paper, fine sediment deposits were mapped at two sites on the falling limb of the hydrograph at monthly intervals between May and September, 1995, and the sampling period coincided with one of the driest periods in England since records began in the 17th century.
Abstract: Fine sediment deposition is a widespread phenomenon encountered in rivers and streams as a result of both natural and anthropogenic activities. The Little Stour (Kent, UK) has a history of low-flow problems owing to drought and groundwater abstraction. Fine sediment deposits were mapped at two sites on the falling limb of the hydrograph at monthly intervals between May and September, 1995. The sampling period coincided with one of the driest periods in England since records began in the 17th century. The area of the channel bed covered by fine sediments increased from approximately 10 to 20% at the upstream site and from 20 to 40% at the downstream site during the study period. The benthic macroinvertebrate communities from different substrate mesohabitats were distinct, with riffle taxa (i.e. Agapetus fuscipes and Simuliidae) confined to areas of clean gravel. This suggests that an expansion of fine sediment deposits may result in impoverishment of the community. The implications of these findings are discussed with particular reference to the timing of management activities within lowland streams. Copyright © 1999 John Wiley & Sons, Ltd.
156 citations
TL;DR: In this paper, the authors propose a congruence model for examining what entrepreneurs and entrepreneurial managers must achieve strategically in order to create and sustain organisational effectiveness and success, and conclude that entrepreneurship is a process which is essential for establishing winning strategic positions and, as such, is relevant and vital for all types and size of organisation.
Abstract: Contends that the E‐V‐R (environment‐values‐resources) congruence model provides an ideal framework for examining what entrepreneurs and entrepreneurial managers must achieve strategically in order to create and sustain organisational effectiveness and success. E‐V‐R shows how the environment is a source of opportunities and threats ‐ external key success factors; and that resources constitute strengths and weaknesses, strategic competencies which either match, or fail to match, environmental needs. Sustaining and changing this strategic fit is dependent on leadership, culture and values. Goes on to show that entrepreneurship is a process which is essential for establishing winning strategic positions and, as such, is relevant and vital for all types and size of organisation. Concludes with a summary model which relates the characteristics of successful strategic leadership with the key issues of risk and crisis management.
144 citations
TL;DR: In this paper, a dual-plane Electrical Resistance Tomography (ERT) system was used for measuring the local solids volume fraction distribution and axial velocity distribution in liquid flows.
135 citations
TL;DR: In this paper, the authors discuss the terms entrepreneur and entrepreneurship, emphasise the economic and social importance of entrepreneurs and summarise key research findings to produce a model of outcomes and capital created by entrepreneurs.
Abstract: Discusses the terms entrepreneur and entrepreneurship, emphasises the economic and social importance of entrepreneurs and summarises key research findings to produce a model of outcomes and capital created by entrepreneurs. Shows how entrepreneurs can be found in many walks of life, not just business, and explains that they are responsible for creating social and artistic capital as well as financial wealth. Concludes with reflections on the challenges faced, in part by educationalists, in trying to develop both more entrepreneurs and more enterprise in organisations.
130 citations
TL;DR: A review of the literature and guidance provided for businesses considering responses to the environmental aspects and impacts of their tourist activities can be found in this article, where the authors make recommendations for improving both the provision of tourism services through supply chain management and destination management, and the education of the consumer in ways which make tourism more consistent with sustainable development.
Abstract: This paper reviews some of the literature and guidance provided for businesses considering responses to the environmental aspects and impacts of their tourist activities. It concentrates on the role of individual business organizations within the tourism industry and examines both supply-side (production) and demand-side (consumption) policies. In its review of a number of guidelines the paper attempts to make recommendations for improving both the provision of tourism services through supply chain management and destination management, and the education of the consumer in ways which make tourism more consistent with the concept of sustainable development. This emphasizes the need for businesses involved in tourism provision not only to look at the supply side and the demand side of their activities but also to provide stronger signals between the two parts so that more meaningful progress is made towards sustainable tourism. It places considerable emphasis on the role of intermediaries in bridging the gap between demand and supply. Copyright © 1999 John Wiley & Sons, Ltd and ERP Environment.
122 citations
TL;DR: In this article, the impacts of drought on the macroinvertebrate community of the Little Stour River, Kent, were investigated and the results indicated the importance of winter groundwater recharge in sustaining summer flows in chalk streams.
Abstract: Chalk streams are characterised by naturally regulated flow regimes but their headwaters (winterbourne streams), are typified by periods of desiccation alternating with periods of high flow. This paper describes the impacts of drought on the macroinvertebrate community of the Little Stour River, Kent. Following the 1988-1992 drought, riverine habitats were severely degraded and some dewatering of previously perennial reaches occurred. Large volumes of fine sediment were deposited at the channel margins and on the river bed. In the summer of 1992 the relative abundance of macroinvertebrates was low. However, recovery was dramatic in the following three years. In 1995 a severe summer rainfall deficit had no detectable deleterious impact on the macroinvertebrate community, reflecting the importance of winter groundwater recharge in sustaining summer flows in chalk streams. Few taxa were eliminated as a result of the drought, suggesting the presence of refugia from which recolonisation of taxa could take place. The results are discussed in relation to the reported impact of drought on other groundwater fed rivers.
94 citations
TL;DR: In this article, the authors examined the decision making of one ethical unit trust operating in the United Kingdom and described the development of the ethical criteria and the ways in which their implementation was monitored.
Abstract: Although ethical investment is a growing phenonenon which attracts a signficant amount of media interest, relatively little has been written about the internal operations of ethical investment funds. Using a variety of sources, including interviews with a fund manager and participant observation at meetings of the fund’s ethical advisory committee, this paper examines the decision making of one ethical unit trust operating in the United Kingdom. In particular, it describes the development of the ethical criteria and the ways in which their implementation was monitored. Several significant parallels between publicly stated ethical investment criteria and corporate codes of ethics are then discusssed.
74 citations
TL;DR: In this article, the authors investigated the relationship between the bacterial quality of stream waters and the intensity of adjacent agricultural land-use in a small upland catchment in north Derbyshire, England.
TL;DR: In this paper, the authors set out some common manufacturing classification systems, then attempted to map them against accepted paradigms for production planning and control approaches, and confirmed the need for a more rigorous approach to software selection, and the need to complete underspecification.
Abstract: Since the early 1970s, production planning systems have evolved from material requirements planning (MRP) through manufacturing resource planning (MRPII) into enterprise resource planning (ERP) with simultaneous development of related control systems such as theory of constraints (epitomised by OPT), just‐in‐time (JIT), etc. One key area for all manufacturing companies is the planning and control function. There is a wide range of generic proprietary software available that aims to meet a company’s planning and scheduling requirements. The difficulty experienced by many companies is not only in examining available software, but also in understanding the match between business needs and the capabilities of that software. This paper first sets out some common manufacturing classification systems, then attempts to map them against accepted paradigms for production planning and control approaches. Analysis confirms the need for a more rigorous approach to software selection, and the need for a complete unders...
TL;DR: In the presence of chiral thiourethane ligands [Cu(MeCN) 4 ]BF 4 forms active catalysts for the conjugate addition of MeMgBr, ZnEt 2 and AlR 3 (R = Me, Et) to non-3-en-2-one, hept-3in-en2-1, and 5-methylhex-3en-1-one.
01 Apr 1999
TL;DR: In this paper, the authors introduce the concept of top contact in spur and helical gear transmission systems, and compare the theoretical results with experimental measurements using a single flank tester and a back-to-back dynamic test rig.
Abstract: This paper is devoted to a phenomenon known as corner contact, or contact outside the normal path of contact, which can occur in spur and helical gear transmission systems under certain conditions. In this case, a change in position of the driven gear with respect to its theoretical position takes place, thus inducing a transmission error referred to here as the transmission error outside the normal path of contact (TEo.p.c).The paper deals with spur gears only, but the results are directly applicable to helical gears. It systematizes previous knowledge on this subject, suggests some further developments of the theory and introduces the novel phenomenon of top contact. The theoretical results are compared with experimental measurements using a single flank tester and a back-to-back dynamic test rig for spur and helical gears, and they are in good agreement.Convenient approximate equations for calculation of TEo.p.c suggested here are important for analysis of experimental data collected in the for...
TL;DR: This study suggests that young men may be willing to participate in an aspect of personal health surveillance and if this is the case then low cost strategies to increase impact on the target audience should be considered.
Abstract: Testicular cancer remains the most commonly occurring cancer in young men (aged 20–45 years) and recent trends suggest an increase throughout the western world. Whilst testicular cancer is highly treatable late diagnosis resulting in poorer treatment outcomes remains a problem. Testicular self-examination (TSE) a procedure whereby young men can routinely systematically examine their testicles has been advocated as a particularly effective health education intervention. This study aimed to establish the knowledge of testicular cancer and prevalence of TSE practice amongst young men. A descriptive survey approach using a 16-item self-report questionnaire was administered to a convenience sample of 203 male undergraduate and postgraduate students at the University of Huddersfield. Results indicated that the majority of the respondents were either uninformed or misinformed about the risks and symptoms of testicular cancer although 78% indicated an interest in accessing information. Only 32% had prior knowledge of TSE, 22% practiced TSE, and worryingly only a single respondent was able to recognize the correct procedure and indicated he regularly practiced TSE. Sixty-eight per cent indicated that TSE should be a part of general health assessments for men. Although some critics of TSE argue the cost of teaching TSE outweighs the benefits in terms of early diagnosis this study suggests that young men may be willing to participate in an aspect of personal health surveillance. If this is the case then low cost strategies to increase impact on the target audience should be considered.
TL;DR: In this article, the authors considered reactions to actual victimisations experienced in the past year and found that only assault victims experience other reactions more than that of anger, whereas non-fear and non-anger responses were more frequent.
Abstract: A previous article demonstrated, from an analysis of data derived from a quantitative survey of 1,629 adult Scottish residents, that being 'angry', rather than being 'afraid', was the reaction most respondents thought they would feel when imagining crime victimisation, irrespective of age, gender or victim-status. This article plumbs the same data base, but here considers reactions to actual victimisations experienced in the past year. When initial reactions are considered, only assault victims experience other reactions more than that of anger. When later reactions are examined, respondents report less anger (except for assault), much less fear (particularly for assault) and many more non-fear and non-anger responses. These results are placed in the context of other research, and against a qualitative background derived from interviews conducted with an initial sample of different respondents. Some possible reasons for the relative neglect of victim-anger are discussed.
TL;DR: In this article, the ring closing metathesis of N,N-diallylanilines and a related 1,2-dihydroquinoline, catalysed by Grubbs' catalyst, occurs in good yield at room temperature furnishing 3-pyrrolines and 3piperidines.
TL;DR: In this article, the authors evaluated the effectiveness of cognitive-behavioral group counseling provided to behaviorally disruptive elementary school children by the first author, a school social worker, and found that the intervention can be effective in reducing the behavior of children with disruptive behavior.
Abstract: The objective was to evaluate the effectiveness of cognitive–behavioral group counseling provided to behaviorally disruptive elementary school children Fifty-two referred children received protocol-based cognitive–behavioral group counseling provided by the first author, a school social worker Students were randomly assigned to receive either immediate (IT) group counseling or delayed treatment (DT) The two groups were roughly equivalent on most demographic and outcome measures at the first assessment Following group counseling, the IT groups' self-esteem, perceived self-control, teacher, and teacher aide grades of classroom comportment significantly improved, while similar measures of the DT children did not appreciably change The DT children then received the same group program the IT group was exposed to three months earlier, and when group counseling was completed (third assessment) the IT groups' gains had been maintained, and the DT group gained improvements similar to those obtained by the IT group In conclusion, cognitive–behavioral group work can be an effective intervention with behaviorally disruptive elementary school students Copyright © 1999 John Wiley & Sons, Ltd
01 Jan 1999
TL;DR: Measurement of the femoral heads and acetabular cups is carried out to demonstrate the applicability of the characterization technique for the three-dimensional surface topography of orthopaedic joint prostheses.
Abstract: This study attempts to investigate a range of ‘better’ methods for the characterization of the three-dimensional (3D) surface topography of orthopaedic joint prostheses In this paper, a new characterization tool for the comprehensive identification and evaluation of functional features of these surface topographies is presented For identification, the surface topography is investigated in a space-scale space, by employing wavelet analysis The roughness, waviness and form involved in surface topography are consequently separated and recovered respectively The multiscalar topographical features are identified and captured The errors caused as a consequence of three-dimensional measurement methods can be reduced After identification, the three-dimensional surface assessment techniques previously reported by Stout and co-workers are used for the quantitative evaluation of various surface roughness features of the or topaedic joint prostheses Moreover, the functional properties, such as bearing
01 Jan 1999
TL;DR: It has been shown that machine tool thermal distortion can account for 75 percent of the total machining error as mentioned in this paper, and there has been a great deal of interest in techniques for reduc...
Abstract: It has been shown that machine tool thermal distortion can account for 75 per cent of the total machining error. As a result there has been a great deal of interest in techniques for reduci...
01 Jun 1999
TL;DR: In this article, a systematic approach to profile relief design of low and high contact ratio spur gears and its effects on transmission error (TE) and tooth loads is introduced. But this approach is based on a number of simplifying assumptions to ease the understanding of the relief design and useful relief cases determined during the simplified analysis are further investigated.
Abstract: This is the first of a series of papers on the design of the tooth profile relief of both low and high contact ratio spur gears and its effects on transmission error (TE) and tooth loads. A systematic approach to profile relief design is introduced. The process of profile relief analysis is based on a number of simplifying assumptions to ease the understanding of the relief design. Useful relief cases determined during the simplified analysis are further investigated, with realistic parameter values such as variable stiffness, manufacturing tolerances and so on, in other papers of the series. Experimental validation of the cases proven to be good are also given in forthcoming papers.In the present paper, the systematic approach is applied to low contact ratio (LCR) spur gears first with some design regions and to high contact ratio (HCR) spur gears with some new and promising design regions and rules. Several smooth transmission error curves at different loads are shown to be possible for the reli...
TL;DR: In the absence of an oxidant, tetrapropylammonium perruthenate is reduced by 2-undecanol to a low-valent ruthenium species that efficiently catalyzes the isomerization of a wide range of allylic alcohols into the corresponding saturated carbonyl derivatives.
Abstract: In the absence of an oxidant, tetrapropylammonium perruthenate (TPAP) is reduced by 2-undecanol to a low-valent ruthenium species that efficiently catalyzes the isomerization of a wide range of allylic alcohols into the corresponding saturated carbonyl derivatives [Eq. (1)]. R1, R2, R3, R4=alkyl, aryl, H.
TL;DR: A questionnaire survey of 120 diploma students in one university investigated several aspects of part-time work: incidence, nature, motivating factors, and effects on their professional and personal lives.
TL;DR: In this paper, the authors focus on ethical investment and discuss the broad direction in which they would like their own work, and the work of others, to go in the future.
Abstract: It is common for professors to base inaugural lectures on work that they have already done, perhaps thereby giving a hint of why they have been appointed. One topic that has been an interest of mine over many years is ethical investment. The word `inaugural' suggests a degree of looking forward. Therefore, in addition to outlining some of the work that has brought me to this point, I would like to indicate the broad direction in which I would like my own work, and I hope the work of others, to go in the future. As I am focusing on ethical investment it would seem sensible to give an introductory indication of what is meant by that term. So the first question is:
TL;DR: In this article, the authors investigate how women experience the transition to programs of professional higher education and highlight issues which appear to assist the transition and highlight the issues that help women cope with the transition.
Abstract: The aim of the research described in this article was to investigate how women experience the transition to programmes of professional higher education. The investigation took place in a school of a British university where the professional areas chosen were social work and health care education. Most of the participants were new to the higher education system and were entering as mature students, but a few were making educational transitions and had previous involvement in higher education. As the central focus was an investigation of subjective accounts, a phenomenological perspective was adopted and the methods used were mainly qualitative. A multiple methods approach to data collection was taken. The investigation took place over two phases, covering the period of transition to programmes over two consecutive years. Anxieties were commonly experienced by participants in the transition to their programme. Breakwell's (1986) theory of threatened identities seems useful in understanding the emerging issues. Anxieties could be explained in terms of threats to identity ‘principles’; however, these arose from the social context and coping with them is not always psychologically based. Issues which appear to assist the transition are highlighted. Copyright © 1999 John Wiley & Sons, Ltd.
Journal Article•
TL;DR: In this article, the authors compared the stereochemical consequences of tetrahedral and trigonal bipyramidal intermediates for b-Lactam degradation and phosphonylation.
Abstract: Four membered b-Lactam rings do not show unusual reactivity compared with their acyclic amide analogues and there is no evidence of concerted mechanisms for nucleophilic substitution reactions at the carbonyl centre. The identity of the general base/acid catalyst in the serine b-Lactamases, which catalyse the hydrolysis of b-Lactams, is unknown. There are no ideal transition state analogue inhibitors for these enzymes which involve several intermediates and transition states. The class C serine b-Lactamase enhances the rate of phosphonylation of its active site serine residue by a similar magnitude to the enzyme rate enhancement factor for the hydrolysis of b-Lactams. Comparisons are made between the stereochemical consequences of tetrahedral and trigonal bipyramidal intermediates for hydrolysis and phosphonylation respectively. Class B zinc b-Lactamases are inhibited by thiol dipeptides with a D configuration at the cysteine centre analogous to the L configuration at C6 in penicillins. The mechanism of hydrolysis catalysed by the metallo-b-Lactamases probably involves a di-anionic tetrahedral intermediate stabilised by zinc(II).
TL;DR: A highly diastereoselective method for the synthesis of 3-substituted isoindolin-1-ones has been developed through application of a tricyclic lactam substrate as an N-acyliminium ion precursor.
TL;DR: A flow microcalorimetric technique for characterising the acidities of polystyrene resins by ammonia adsorption from the gas phase has been applied to a series of macroporous and gel-type resin catalysts.
Abstract: A flow microcalorimetric technique for characterising the acidities of sulphonated polystyrene resins by ammonia adsorption from the gas phase has been applied to a series of macroporous and gel-type resin catalysts. The relationship between acidities measured using this technique and catalytic activities towards liquid phase reactions has been examined using two acid-catalysed test reactions. Results show that catalytic activities are not related in a simple way to the concentrations of acid sites measured by ammonia adsorption, but there is a useful correlation between the strengths of the acid sites measured in this way and catalytic activities of the resins. We conclude that acid site strength, based on ammonia adsorption and used alone, can be a useful indicator of activity for this type of acid catalyst.
10 Oct 1999
TL;DR: In this paper, it was shown that the preferred frequencies of excitation of any disc brake system may be related directly to the free mode frequency of the disc and that the interface geometry of the pad, the effective rubbing diameter, and the effective working length of a pad are all important features regarding the frequency generated.
Abstract: The mode of vibration of a noisy disc brake is always diametral with a noise frequency marginally less than the free mode of vibration of the disc. Wheel speed does not affect the frequency but if brake pressure is altered then the noise frequency changes accordingly~an increasing pressure resulting in an increasing frequency over a specified range. Such observations have been made of a variety of different disc brake designs from single piston sliding fist type calipers to four piston opposed rigid calipers with it being possible to relate the noise frequency to the free mode of vibration of the disc in all cases. If the characteristics controlling this behavior can be identified then the same principles and criteria may be used to predict the noise propensity of any brake at the design stage.
The paper proposes, and shows, that the preferred frequencies of excitation of any disc brake system may be related directly to the free mode frequency of the disc. In addition it is shown that the interface geometry of the pad, the effective rubbing diameter of the disc and the effective working length of the pad are all important features regarding the frequency generated. It is demonstrated that this relationship allows the probable instability frequencies of a disc brake to be predicted and shows that the frequency will vary over a computable range as a result of the brake pressure. The principle is successfully extended to consider a braking system arrangement employing two calipers working on one wheel. The proposal suggests that brake noise be as much a basic design problem as a material selection problem and answers questions such as why chamfers on pads changes the propensity of a noisy brake to generate noise.
A case study of a heavy vehicle using a four opposed piston caliper on the rear and a pair of four opposed piston calipers on each front wheel goes some way to validate the proposal. The study and tests show that angular positioning of the front wheel caliper pair has a significant influence on the propensity of the brake to generate noise and the frequencies that were subsequently emitted