Estimation of Bearing Forces in Rotating Machinery: A Problem Revisited

Development of a new ship machinery installation may require combinations of prime movers, electric motors, generators, gearboxes and other items that have not been used previously. Large items of this type are expensive to develop, so that only existing production items are likely to be affordable. Modern quiet ship design requires careful attention to the source characteristics of the individual machinery items as well as the dynamic characteristics of any new combination, so that fluctuating forces transmitted to the hull via mounting systems and flexible connectors in the final installation are within acceptable limits. Almost periodic components, which arise at multiples of machine rotational frequency, are of particular concern. Machine source properties are often known only in terms of the vibration characteristics of previous installations, not in terms of the disturbing forces that cause that vibration. The aim of the techniques described in this paper is to allow deduction of those disturbing forces from a matrix of transfer functions at each frequency of interest, measured with an existing machine in operation. The number of forces to be estimated must be less than the number of structural degrees of freedom. Those degrees of freedom arise from rigid body motions and machine flexural properties, which may change significantly when shafts are rotating. Also, the matrices must be redundant in order to allow estimation of the accuracy of derived force estimates. The larger the machine, the greater the number of degrees of freedom that are likely to arise at a given frequency. A first use of the methodology was to establish the bearing forces in a marine turbo generator (TG) set with plain journal bearings. Measurements of transfer functions were made with the machine stationary and then with the machine in normal operation. Direct and reciprocal measurements in different directions were made for a large number of locations on the machine structure and bearings, covering the frequency range up to more than twice shaft rotational frequency. There were large differences in some frequency ranges between the static and operational conditions. Vibration due to machine operation was then measured to allow deduction of bearing forces using the transfer function matrices. Repeat measurements were made to establish whether machine source properties changed significantly with time, while statistical techniques were also used to identify and eliminate any suspect measurements. Those early experiments are described in this paper with a view to future application of similar techniques

Estimation of Bearing Forces in Rotating Machinery: A Problem Revisited

Development of a new ship machinery installation may require combinations of prime movers, electric motors, generators, gearboxes and other items that have not been used previously. Large items of this type are expensive to develop, so that only existing production items are likely to be affordable. Modern quiet ship design requires careful attention to the source characteristics of the individual machinery items as well as the dynamic characteristics of any new combination, so that fluctuating forces transmitted to the hull via mounting systems and flexible connectors in the final installation are within acceptable limits. Almost periodic components, which arise at multiples of machine rotational frequency, are of particular concern. Machine source properties are often known only in terms of the vibration characteristics of previous installations, not in terms of the disturbing forces that cause that vibration. The aim of the techniques described in this paper is to allow deduction of those disturbing forces from a matrix of transfer functions at each frequency of interest, measured with an existing machine in operation. The number of forces to be estimated must be less than the number of structural degrees of freedom. Those degrees of freedom arise from rigid body motions and machine flexural properties, which may change significantly when shafts are rotating. Also, the matrices must be redundant in order to allow estimation of the accuracy of derived force estimates. The larger the machine, the greater the number of degrees of freedom that are likely to arise at a given frequency. A first use of the methodology was to establish the bearing forces in a marine turbo generator (TG) set with plain journal bearings. Measurements of transfer functions were made with the machine stationary and then with the machine in normal operation. Direct and reciprocal measurements in different directions were made for a large number of locations on the machine structure and bearings, covering the frequency range up to more than twice shaft rotational frequency. There were large differences in some frequency ranges between the static and operational conditions. Vibration due to machine operation was then measured to allow deduction of bearing forces using the transfer function matrices. Repeat measurements were made to establish whether machine source properties changed significantly with time, while statistical techniques were also used to identify and eliminate any suspect measurements. Those early experiments are described in this paper with a view to future application of similar techniques

Response to Crocetti et al.

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Luxury retailers’ entry and expansion strategies in China

Purpose The purpose of this paper is to examine internationalising luxury fashion retailers’ entry and post-entry expansion strategies in mainland China. Design/methodology/approach The study adopts a pragmatic mixed-methods research approach, including a quantitative mail survey and qualitative face-to-face in-depth executive interviews. Findings Different from initial single entry methods, multiple methods are increasingly popular for luxury fashion retailers’ post-entry expansion in mainland China. Although directly controlled expansion strategies have become significant, local partnerships are still important and omnichannel distribution strategies are rapidly growing. Research limitations/implications The findings were generated in mainland China only. Originality/value This work provides an understanding of luxury fashion retailers’ activities in the Chinese market from both macro and micro perspectives. It examines luxury fashion retailers’ initial entry strategies, as well as their post-entry expansion strategies in mainland China. Few studies in the area of international luxury fashion retailing have employed a mixed-methods approach with this number of participants

Reduction in jejunal fluid absorption in vivo through distension and cholinergic stimulation not attributable to enterocyte secretion

Jejunal fluid absorption in vivo was reduced by distension and by hydrostatic pressure and further declined on adding E. coli STa enterotoxin but no net fluid secretion was detected. Luminal atropine reduced pressure mediated reductions in fluid absorption to normal values but intravenous hexamethonium was without effect. A neural component to inhibition of absorption by pressure (though not stretch) may be mediated by axon reflexes within cholinergic neurons.Perfusion of cholinergic compounds also reduced net fluid absorption but did not cause secretion. In order to show that these actions were not secretory processes stimulated by cholinergic compounds that offset normal rates of absorption, these compounds were tested for their ability to cause net secretion in loops that were perfused with solutions in which choline substituted for sodium ion. In addition, these perfusates additionally contained E. coli STa enterotoxin or EIPA (ethyl-isopropyl-amiloride) to minimize absorption.In these circumstances, where it might be expected to do so if it were acting through a secretory rather than an absorptive mechanism, carbachol did not cause net fluid secretion. Cholinergic stimulation and pressure induced distension are thought to reduce net fluid absorption through inducing secretion but are found only to reduce fluid absorption.In conclusion, distension and cholinergic stimulation of the small intestine are two further circumstances in which fluid secretion is assumed to explain their action on fluid movement, as required by the enterocyte secretion model of secretion but, which like STa enterotoxin, instead are only able to reduce fluid absorption. This casts further doubt on the widespread validity of the enterocyte secretion model for fluid appearance in the lumen in diarrhoeal diseases

Hong Kong, a Gateway for Mainland China? An examination of the impact of luxury fashion retailers’ ownership structures on expansion strategies

Purpose: The purpose of this paper is to examine luxury fashion retailers’ ownership structures at their internationalisation strategies in Hong Kong and mainland China. Design/methodology/approach: This study adopts a pragmatic mixed methods approach, comprising a quantitative mail survey and ten qualitative executive interviews. Findings: This study found that group-owned luxury fashion retailers usually encounter fewer difficulties when internationalising into mainland China than their individually owned counterparts because of parenting advantage, particularly functional and service support. However, the success of some individually owned brands has demonstrated that branding strategies, management culture, international experience, financial power and local partners’ know-how are as important as parent company support and although the luxury market in mainland China has become developed, many foreign luxury fashion retailers still enter Hong Kong prior to mainland China. However, in relation to post-entry management and expansion strategies, the importance of Hong Kong has weakened because the emergence of capital cities, the growth of the middle class and fewer political restrictions. Research limitations/implications: The research findings are generated in the context of Hong Kong and mainland China, they are therefore limited in explaining luxury fashion retailers’ internationalisation strategies in other markets. Despite the challenge of the sample size, 63 out of 130 survey respondents (48.5 per cent response rate) and ten interview participants are felt to be sufficient to represent the market. Practical implications: This research can be used by practitioners when assessing appropriate entry strategies to the Chinese luxury fashion market. Originality/value: This is a pioneering study of the Chinese luxury market from the perspective of international retail strategies. It differentiates between Greater China (including Hong Kong, Macau and Taiwan) and mainland China, and examines the impact of luxury fashion retailers’ ownership structures on their internationalisation strategies

Contextual influences on social enterprise management in rural and urban communities

The idea that difference exists between rural and urban enterprise activity is not new, the obvious comparators are measures such as social architecture, resource availability and accessibility. However, when the concept and practice of management in social enterprise is compared in these two contexts then there is opportunity to further our understanding of the contextual challenges encountered by social enterprise. In this paper six cases studies are compared and analysed: three cases are urban social enterprises and three classified as remote rural social enterprises. The urban cases are social enterprises located around Glasgow in the west of Scotland and are compared with three remote rural location studies, one on the Scottish mainland peninsula, the other in northern Scotland and the final case on a Scottish western island. We conclude that the main differences between remote rural and urban management of social enterprise are heavily nuanced by in-migration levels in both rural and urban locations, leadership and community needs and therefore deserving of context relevant policy

The gastric acid pocket is attenuated in H. pylori infected subjects

Objective Gastric acid secretory capacity in different anatomical regions, including the postprandial acid pocket, was assessed in Helicobacter pylori positive and negative volunteers in a Western population. Design We studied 31 H. pylori positive and 28 H. pylori negative volunteers, matched for age, gender and body mass index. Jumbo biopsies were taken at 11 predetermined locations from the gastro-oesophageal junction and stomach. Combined high-resolution pH metry (12 sensors) and manometry (36 sensors) was performed for 20 min fasted and 90 min postprandially. The squamocolumnar junction was marked with radio-opaque clips and visualised radiologically. Biopsies were scored for inflammation and density of parietal, chief and G cells immunohistochemically. Results Under fasting conditions, the H. pylori positives had less intragastric acidity compared with negatives at all sensors >1.1 cm distal to the peak lower oesophageal sphincter (LES) pressure (p<0.01). Postprandially, intragastric acidity was less in H. pylori positives at sensors 2.2, 3.3 and 4.4 cm distal to the peak LES pressure (p<0.05), but there were no significant differences in more distal sensors. The postprandial acid pocket was thus attenuated in H. pylori positives. The H. pylori positives had a lower density of parietal and chief cells compared with H. pylori negatives in 10 of the 11 gastric locations (p<0.05). 17/31 of the H. pylori positives were CagA-seropositive and showed a more marked reduction in intragastric acidity and increased mucosal inflammation. Conclusions In population volunteers, H. pylori positives have reduced intragastric acidity which most markedly affects the postprandial acid pocket

Combination of gastric atrophy, reflux symptoms and histological subtype indicates two distinct aetiologies of gatric cardia cancer.

<b>INTRODUCTION</b> Atrophic gastritis is a risk factor for non-cardia gastric cancer, and gastro-oesophageal reflux disease (GORD) for oesophageal adenocarcinoma. The role of atrophic gastritis and GORD in the aetiology of adenocarcinoma of the cardia remains unclear. We have investigated the association between adenocarcinoma of the different regions of the upper gastrointestinal tract and atrophic gastritis and GORD symptoms. <b>METHODS</b> 138 patients with upper GI adenocarcinoma and age and sex matched controls were studied. Serum pepsinogen I/II was used as a marker of atrophic gastritis and categorised to five quintiles. History of GORD symptoms, smoking and H.pylori infection was incorporated in logistic regression analysis. Lauren classification of gastric cancer was used to subtype gastric and oesophageal adenocarcinoma. <b>RESULTS</b> Non-cardia cancer was associated with atrophic gastritis but not with GORD symptoms; 55% of these cancers were intestinal subtype. Oesophageal adenocarcinoma was associated with GORD symptoms, but not with atrophic gastritis; 84% were intestinal subtype. Cardia cancer was positively associated with both severe gastric atrophy [OR, 95% CI: 3.92 (1.77 – 8.67)] and with frequent GORD symptoms [OR, 95% CI: 10.08 (2.29 – 44.36)] though the latter was only apparent in the nonatrophic subgroup and in the intestinal subtype. The association of cardia cancer with atrophy was stronger for the diffuse versus intestinal subtype and this was the converse of the association observed with non-cardia cancer. <b>CONCLUSION</b> These findings indicate two distinct aetiologies of cardia cancer, one arising from severe atrophic gastritis and being of intestinal or diffuse subtype similar to non-cardia cancer, and one related to GORD and intestinal in subtype, similar to oesophageal adenocarcinoma. Gastric atrophy, GORD symptoms and histological subtype may distinguish between gastric versus oesophageal origin of cardia cancer

A study of blood contamination of Siqveland matrix bands

AIMS To use a sensitive forensic test to measure blood contamination of used Siqveland matrix bands following routine cleaning and sterilisation procedures in general dental practice. MATERIALS AND METHODS: Sixteen general dental practices in the West of Scotland participated. Details of instrument cleaning procedures were recorded for each practice. A total of 133 Siqveland matrix bands were recovered following cleaning and sterilisation and were examined for residual blood contamination by the Kastle-Meyer test, a well-recognised forensic technique. RESULTS: Ultrasonic baths were used for the cleaning of 62 (47%) bands and retainers and the remainder (53%) were hand scrubbed prior to autoclaving. Overall, 21% of the matrix bands and 19% of the retainers gave a positive Kastle-Meyer test, indicative of residual blood contamination, following cleaning and sterilisation. In relation to cleaning method, 34% of hand-scrubbed bands and 32% of hand-scrubbed retainers were positive for residual blood by the Kastle-Meyer test compared with 6% and 3% respectively of ultrasonically cleaned bands and retainers (P less than 0.001). CONCLUSIONS: If Siqveland matrix bands are re-processed in the assembled state, then adequate pre-sterilisation cleaning cannot be achieved reliably. Ultrasonic baths are significantly more effective than hand cleaning for these items of equipment