Bubble formation at two adjacent submerged orifices in inviscid fluids

A theoretical model has been developed as an extension of single orifice bubble formation to investigate the growth and detachment of vapor/gas bubbles formed at two adjacent submerged orifices in inviscid fluids. The mathematical model treats the two bubbles as an expanding control volume moving to the line of centers above a wall. The movement of the bubbles is obtained by application of force balance acting on the bubble and accounts for surface tension, buoyancy, steam momentum and liquid inertia effects. The liquid inertia effects are determined by applying inviscid and irrotational flow assumptions to allow potential flow theory to calculate the liquid velocity field which then allows the pressure distribution to be calculated. The model is extended to include the mass and energy equations to model the steam bubble formation in sub-cooled water. The theoretical results are compared with the available experimental data of bubble formation during constant mass flow steam bubble formation at two submerged upward facing orifices in sub-cooled water. The model was validated by available experimental data for the growth and detachment processes of two adjacent 1 mm orifices at system pressures of 2 and 3 bars, flow rates of 1.2-4 g/min at sub-cooling of 3.5-35 ºC. The comparisons of theory and experiments indicate that the model successfully predicts the bubbles growth and detachment for the range of conditions studied

Investigation of a Rotating Shaft with a Novel Integrated Wireless Accelerometer

Rotating shafts are the most critical components of rotating machines such as motors, pumps, engines and turbines. Due to their heavy workloads, defects are more likely to develop during operation. There are many techniques used to monitor shaft defects by analysing the vibration of the shaft as well as the instantaneous angular speed (IAS) of the shaft. The signals are measured either using non-contact techniques such as laser-based measurement or indirect measurement such as the vibration on bearing housings. The advancement in low cost and low power Micro Electro Mechanical Systems (MEMS) make it possible to develop an integrated wireless sensor mounted on rotating shafts directly. This can make the fault diagnosis of rotating shafts more effective as it is likely to capture more details of shaft dynamics. This paper presents a novel integrated wireless accelerometer mounted directly on a rotating shaft and demonstrates that it can effectively monitor different degree of misalignments occurring commonly in a shaft system

Endoscopy : an evolving speciality

The practice of endoscopy has been rapidly changing due to new emerging technologies and novel techniques. There has been more focus on colonoscopy training with the development of structured programmes including simulators. Chromoendoscopy and magnification endoscopy have enabled improved diagnosis of small neoplastic lesions and will be important for the success of colorectal cancer screening programmes. The small bowel is now accessible to diagnostic modalities like capsule endoscopy and to therapeutic tools through the double balloon enteroscope. Endoscopic therapy has also become more sophisticated with endoscopic therapy of reflux disease now possible. Excision of large colorectal adenomatous polyps by endoscopic mucosal resection and dissection of submucosal tumours may reduce the need for surgical intervention. The practice of endoscopy has rapidly changed over the past few years. What was once a simple diagnostic procedure made possible by the development of fibre optics has become a speciality in its own right. This article will highlight some aspects of endoscopic practice that have undergone major changes over the past few years and that will shape endoscopy practice in the future.peer-reviewe

Investigation of Wireless Sensor Deployed on a Rotating Shaft and Its Potential for Machinery Condition Monitoring

Rotating shafts are the most critical component of rotating machines such as motors, pumps, engines and turbines. Due to their heavy duties, defects are more like developed during operation. There are many techniques used to monitor shaft defects by analysing the vibration of the shaft as well as the instantaneous angular speed (IAS) of the shaft. The signal are measured either using non-contact techniques such as laser-based measurement or indirect measurement such as the vibration on bearing housings. The advancement in low cost and low power Micro Electro Mechanical Systems (MEMS) make it possible to develop an integrated wireless sensor which can be mounted on the shaft. This can make the fault diagnosis of rotating shafts more effective because the sensor can be mounted on the shaft directly. This paper presented a novel integrated wireless accelerometer for rotational parameter measurement. Its performance is benchmarked with that from a shaft encoder. Experimental results show that the wireless acceleration signal has less noise and hence it is more possible for small fault detection. Keywords: Wireless sensor, Rotating shaft, Instantaneous angular speed, Condition monitorin

A 22-year-old woman with recurrent gastrointestinal bleeding since childhood

CASE PRESENTATIONA 22-year-old woman was referred to our unit for capsule endoscopy because of recurrent iron deficiency anaemia and gastrointestinal bleeding since childhood. Cutaneous vascular lesions had been surgically removed when she was a child.During the preceding year she required blood transfusions every month and had a total of 9 iron infusions. Gastroscopy and colono-scopy at another hospital had shown small vascular lesions in the stomach, duodenum and colon. Clinical examination revealed pallor. Blood investigations showed a haemoglobin level of 9.6 g/dl and a MCV of 67 fl.The capsule endoscopy (PillCam, Given Imaging) was performed. Fifteen lesions similar to those shown in figures 1 and 2 were noted through-out small bowel. She underwent a laparotomy with intra-operative entero-scopy; the lesions were removed and the histology is shown in Figure 3

The use of passive telemetry in rotor fault diagnosis

The sensors most commonly used for monitoring machine health are wired accelerometers because of their high performances and good stability. However, these transducers are usually large in size; require an external power source. Hence, there is a need for cheaper and reliable alternative for the conventional accelerometers. This thesis reports the development of a wireless accelerometer based on Micro-Electro-Mechanical System (MEMS) inertial sensor and off-the-shelf digital RF communication modules. It is small enough to be installed on the rotating shaft of a machine. In addition, it has a high enough resolution to be used to analyse the dynamic behaviour of rotating shaft. The wireless sensor is mounted with its sensitive axis in the tangential direction with respect to the centre of the rotor. This position allows the sensor to perform high resolution tangential acceleration measurements and nullifies the centripetal acceleration. To assist in the validation of the wireless sensor, a mathematical model was derived to simulate the vibration signals from the test rig. Experimental and simulated results both confirmed the effectiveness of the wireless sensor in detecting different degrees of misalignments and unbalance of a flexible rotor system. The wireless sensor has been confirmed to possess the capability of detecting small degrees of misalignment using the spectral amplitude of the peak at 2X running speed compared to other conventional sensors (wired accelerometers, laser vibrometers). In addition, the results of the experiment and simulation have also confirmed the capacity of the wireless sensor to detect different shaft unbalance grades at 1X running speed using spectral and order magnitudes. However, the wired sensors used for comparison failed to show any clear separation of the different grades of shaft unbalance. Moreover, it has been observed that the instantaneous angular speed (IAS) derived directly from the wireless sensor correlates well with that obtained from a shaft encoder and showed the capacity to detect the main features of rotor dynamics. An advanced algorithm has been developed to remove the gravity effect. The application of the algorithm has made the IAS computed from the wireless sensor more indicative to that obtained by a shaft encoder

Higgs ptp_t distribution in Higgs + jet production at hadron colliders within the non-commutative Higgs effective standard model

We use the non-commutative Higgs effective standard model to make a phenomenological prediction for the transverse momentum distribution of the Higgs boson produced in association with a jet at hadron colliders. We calculate at leading order in the non-commutative parameter $\Theta$ as well as leading order in the strong coupling $\alpha_s$, the one-loop $p_t$ distribution of the Higgs boson. As in the standard model, the fixed-order distribution suffers from large logarithms at small $p_t$ which require an all-orders resummation. We find that the large-$p_t$ region of the distribution is strongly affected by the non-commutativity, while small-$p_t$ region is not. Following this observation, we propose a simple matching method that allows us to compute a result that is also valid at small $p_t$ obtained with standard-model parton showers such as Pythia 8.Comment: 9 pages, 3 figure

Organic and conventional sweetpotato production in the Southeastern of United States: a comparative analysis

Background There has been a piqued interest in alternative agricultural production systems that are environmentally friendly due to concerns on how sustainable it is to grow conventionally. However, in the producer’s point of view, economic returns are an important issue in decision-making in adaptation. The purpose of this study is to assess the economic risk of conventional and organic sweetpotato production in the Southeastern US. The primary and secondary data were used for the analysis. We identified risk variables in stochastic profit function and performed Monte Carlo simulation in analyzing profitability and economic risk of conventional and organic production systems. Results Findings from the meta-analysis suggest lower sweetpotato yields and higher selling prices, are to be expected in the organic sweetpotato production systems compared with the conventional. A higher probability of having positive net return from organically grown sweetpotato compared to conventional production systems was observed. Conclusions Increase in unit cost leads to a decrease in net profit in both conventional and organic production systems. Sweetpotato price has more effect on net return compared to its yield in conventional production systems. The higher selling price, lower yield and lower unit costs provide a higher net profit return for the organic sweetpotato production systems. Unit cost in conventional production was noted to be higher in general, inferring conventional sweetpotato production could potentially experience a higher variability in net farm income. Despite the high production cost, however, farmers are encouraged to go into sweetpotato production as it appears to be profitable. Further studies should be conducted on conventional treatments without synthetic pesticides and fertilizers as these systems perhaps, may display lower external input costs that might make them more profitable similar to organic systems

Endoscopy: An Evolving Speciality

Abstract The practice of endoscopy has been rapidly changing due to new emerging technologies and novel techniques. There has been more focus on colonoscopy training with the development of structured programmes including simulators. Chromoendoscopy and magnification endoscopy have enabled improved diagnosis of small neoplastic lesions and will be important for the success of colorectal cancer screening programmes. The small bowel is now accessible to diagnostic modalities like capsule endoscopy and to therapeutic tools through the double balloon enteroscope. Endoscopic therapy has also become more sophisticated with endoscopic therapy of reflux disease now possible. Excision of large colorectal adenomatous polyps by endoscopic mucosal resection and dissection of submucosal tumours may reduce the need for surgical intervention. The practice of endoscopy has rapidly changed over the past few years. What was once a simple diagnostic procedure made possible by the development of fibre optics has become a speciality in its own right. This article will highlight some aspects of endoscopic practice that have undergone major changes over the past few years and that will shape endoscopy practice in the future. Clinical Updat