Design Trade-Offs and Feasibility Assessment of a Novel One-Body, Laminated-Rotor Flywheel Switched Reluctance Machine

In a bid to respond to the challenges being faced in the installation of flywheel-based electric energy storage systems (EESSs) in customer-side facilities, namely high safety, high energy/power densities and low cost, research work towards the development of a novel, one-body, laminated-rotor flywheel, based on a switched reluctance machine (OBOLAR-Fly SR machine) is presented, where the laminated rotor provides both the energy storage and motor/generator functions. The one-body architecture improves compactness and robustness. Besides, the rotor’s laminated body ensures inherently high safety. From the design perspective, the rotor’s dual purpose causes the traditional electrical machines design aspects, such as power development, cooling, losses, torque ripple, etc., to clash with the typical requirements of a flywheel, namely in-vacuum operation and moment of inertia. This results in six main trade-offs to be addressed during the design process: rotor material, speed ratio, number of drive phases, split ratio, optimal vacuum level, and controller hysteresis band. A 60 kW, 2.2 kWh OBOLAR-Fly SR system is developed with a twofold objective: (1) provide an in-depth description of the six bespoke design trade-offs and give some useful guidelines to tackle them; (2) prove the OBOLAR-Fly concept and compare the prototype’s performance with the current state of the art flywheels. Preliminary experimental results prove the viability of the OBOLAR idea and show its competitiveness in terms of efficiency and power density. On the other hand, a gap in energy density to be filled in future research works is highlighted

Design of Control Moment Gyros for Agile Small Satellites.

Since the beginning of space history new innovative ideas have been driving space scientists to develop state of the art systems to get their satellites further into space, enable them to handle huge amounts of data connecting the Earth’s continents, produce imagery with sufficiently high detail to help governments and companies to plan, protect and develop their interests. These systems, or more accurately satellite subsystems, are the building blocks of complicated machines which the current modem world relies upon heavily for now and the future. This study presents the successful attempt to develop a new multi purpose actuator part of a very important satellite system, the ADCS (Attitude Determination and Control System). The ADCS is a very crucial subsystem for every spacecraft as it provides the necessary control, very often determining the possible capabilities of each mission. Focused on small Earth Observation (EO) satellites, a highly agile ADCS can greatly increase the satellite’s performance by capturing more images during a single orbital pass, while enabling new types of images to be captured such as stereoscopic ones. A new actuator TW-ECMG (Twin Energy Control Moment Gyro) is developed to further improve the current state of the art by increasing the satellite’s power efficiency, attitude control capabilities, attitude resolution, along with considerable mass savings. While decreasing development costs, launch costs, development time and spacecraft complexity the new TW-ECMG actuator can also be used as an energy storage device. The thesis will start by a detailed reference to the current state of the art introducing the reader to the basic principles behind attitude control, followed by the development steps of a range of air-bearing platforms which are used to test the newly developed TW-ECMG, a cluster of four TW-ECMGs and an additional new actuator, the Modular Control Moment Gyro (M-CMG). The entire hardware development process is described accompanied with extended hardware and software simulations developed using CAD and MATLAB software packages. As the actuator has been developed with the potential of storing energy in its flywheels a chapter has been dedicated to test this principle by combining the ADCS with the power subsystem to create a demonstration of a Combined Energy and Attitude Control System which is called for sort CEACS. Although none of these systems have been used as part of an actual satellite mission to date, they clearly demonstrate the capabilities of such technologies and the substantial benefits it can offer to any spacecraft that will employ them. With some further improvement and the integration of these systems, current small satellite platforms can become more capable than ever before

Design of Control Moment Gyros for Agile Small Satellites.

Since the beginning of space history new innovative ideas have been driving space scientists to develop state of the art systems to get their satellites further into space, enable them to handle huge amounts of data connecting the Earth’s continents, produce imagery with sufficiently high detail to help governments and companies to plan, protect and develop their interests. These systems, or more accurately satellite subsystems, are the building blocks of complicated machines which the current modem world relies upon heavily for now and the future. This study presents the successful attempt to develop a new multi purpose actuator part of a very important satellite system, the ADCS (Attitude Determination and Control System). The ADCS is a very crucial subsystem for every spacecraft as it provides the necessary control, very often determining the possible capabilities of each mission. Focused on small Earth Observation (EO) satellites, a highly agile ADCS can greatly increase the satellite’s performance by capturing more images during a single orbital pass, while enabling new types of images to be captured such as stereoscopic ones. A new actuator TW-ECMG (Twin Energy Control Moment Gyro) is developed to further improve the current state of the art by increasing the satellite’s power efficiency, attitude control capabilities, attitude resolution, along with considerable mass savings. While decreasing development costs, launch costs, development time and spacecraft complexity the new TW-ECMG actuator can also be used as an energy storage device. The thesis will start by a detailed reference to the current state of the art introducing the reader to the basic principles behind attitude control, followed by the development steps of a range of air-bearing platforms which are used to test the newly developed TW-ECMG, a cluster of four TW-ECMGs and an additional new actuator, the Modular Control Moment Gyro (M-CMG). The entire hardware development process is described accompanied with extended hardware and software simulations developed using CAD and MATLAB software packages. As the actuator has been developed with the potential of storing energy in its flywheels a chapter has been dedicated to test this principle by combining the ADCS with the power subsystem to create a demonstration of a Combined Energy and Attitude Control System which is called for sort CEACS. Although none of these systems have been used as part of an actual satellite mission to date, they clearly demonstrate the capabilities of such technologies and the substantial benefits it can offer to any spacecraft that will employ them. With some further improvement and the integration of these systems, current small satellite platforms can become more capable than ever before

The Effect of the Preoperative Fasting Regimen on the Incidence of Gastro-Oesophageal Reflux in 90 Dogs

This study aimed to investigate the effect of three different preoperative fasting regimens on the incidence of gastro-oesophageal reflux (GOR) in dogs under general anaesthesia. Ninety dogs undergoing non-abdominal and non-thoracic elective surgery were included in the study and equally allocated to three groups. Dogs received canned food providing half the daily resting energy requirements (RER) 3 h prior to premedication (group 3H), a quarter of the daily RER 3 h before premedication (group 3Q), and half the daily RER 12 h before premedication (group 12H). The animals were premedicated with acepromazine and pethidine, anaesthesia was induced with propofol and maintained with isoflurane vaporised in oxygen. Oesophageal pH was monitored throughout anaesthesia. Demographic and surgery-related parameters were not different among groups. The incidence of GOR was 11/30 in group 3H (36.7%), 9/30 in group 3Q (30.0%) and 5/30 in group 12H (16.7%), which was not statistically different (p = 0.262). Reduction of the amount of the preoperative meal from half to a quarter of the daily RER did not reduce the incidence of GOR but resulted in a lower oesophageal pH (p = 0.003). The results of this study suggest that the administration of a meal 3 h before anaesthesia does not have any beneficial effect in the reduction of GOR incidence in dogs compared to the administration of a meal 12 h before anaesthesia

The Effect of the Preoperative Fasting Regimen on the Incidence of Gastro-Oesophageal Reflux in 90 Dogs

This study aimed to investigate the effect of three different preoperative fasting regimens on the incidence of gastro-oesophageal reflux (GOR) in dogs under general anaesthesia. Ninety dogs undergoing non-abdominal and non-thoracic elective surgery were included in the study and equally allocated to three groups. Dogs received canned food providing half the daily resting energy requirements (RER) 3 h prior to premedication (group 3H), a quarter of the daily RER 3 h before premedication (group 3Q), and half the daily RER 12 h before premedication (group 12H). The animals were premedicated with acepromazine and pethidine, anaesthesia was induced with propofol and maintained with isoflurane vaporised in oxygen. Oesophageal pH was monitored throughout anaesthesia. Demographic and surgery-related parameters were not different among groups. The incidence of GOR was 11/30 in group 3H (36.7%), 9/30 in group 3Q (30.0%) and 5/30 in group 12H (16.7%), which was not statistically different (p = 0.262). Reduction of the amount of the preoperative meal from half to a quarter of the daily RER did not reduce the incidence of GOR but resulted in a lower oesophageal pH (p = 0.003). The results of this study suggest that the administration of a meal 3 h before anaesthesia does not have any beneficial effect in the reduction of GOR incidence in dogs compared to the administration of a meal 12 h before anaesthesia

The Effect of the Preoperative Fasting Regimen on the Incidence of Gastro-Oesophageal Reflux in 90 Dogs

This study aimed to investigate the effect of three different preoperative fasting regimens on the incidence of gastro-oesophageal reflux (GOR) in dogs under general anaesthesia. Ninety dogs undergoing non-abdominal and non-thoracic elective surgery were included in the study and equally allocated to three groups. Dogs received canned food providing half the daily resting energy requirements (RER) 3 h prior to premedication (group 3H), a quarter of the daily RER 3 h before premedication (group 3Q), and half the daily RER 12 h before premedication (group 12H). The animals were premedicated with acepromazine and pethidine, anaesthesia was induced with propofol and maintained with isoflurane vaporised in oxygen. Oesophageal pH was monitored throughout anaesthesia. Demographic and surgery-related parameters were not different among groups. The incidence of GOR was 11/30 in group 3H (36.7%), 9/30 in group 3Q (30.0%) and 5/30 in group 12H (16.7%), which was not statistically different (p = 0.262). Reduction of the amount of the preoperative meal from half to a quarter of the daily RER did not reduce the incidence of GOR but resulted in a lower oesophageal pH (p = 0.003). The results of this study suggest that the administration of a meal 3 h before anaesthesia does not have any beneficial effect in the reduction of GOR incidence in dogs compared to the administration of a meal 12 h before anaesthesia

The Use of Stromal Vascular Fraction in Long Bone Defect Healing in Sheep

The objectives of the present study were to evaluate (a) the feasibility of using stromal vascular fraction (SVF) and nanocrystalline hydroxyapatite (nHA) paste in combination for the treatment of segmental bone defect, (b) the quality of the callus produced, (c) the potential improvement of the autograft technique, and (d) the direct comparison of the biomaterial to the use of autogenous cancellous bone. Unilateral, segmental mid-diaphyseal bone defect was created on the right metatarsus of skeletally mature sheep animals (n = 24) under anesthesia (D0). Residual segments were stabilized by stainless-steel plates and appropriate screws. Defects were managed as follows: group A: use of nHA paste to filling, group B: use of autogenous bone graft mixed with nHA bone paste, placed in defect, group C: use of SVF mixed with nHA bone paste injected into defect, group D: use of bone graft and SVF with nHA paste before apposition in bone defect. SVF had been previously isolated from adipose tissue of the animals intra-operatively after digestion with collagenase solution and neutralization. Animals were evaluated clinically and by X-raying and ultrasonographic examination of the defect, at regular intervals, until D90. Ultrasonographic assessment performed along the length of the defect included calculation of the length of the bone defect and assessment of vascularization. SVF was successfully isolated from group C and D animals, with the average yield being 1.77 × 106 cells. The comparison of clinical scores (based on the ‘Kaler scale’) on each post-operative day indicated significant differences between the four groups on D1 to D30 (p p = 0.07) and 0 (p = 0.033). Differences in radiographic assessment scores were significant for scores obtained on D60 (p = 0.049) and D90 (p = 0.006). There was a significant difference between the four groups in the length of the bone defect, as assessed ultrasonographically, for the entire length of the study; median values were 8, 8.5, 6, and 8 mm for groups A, B, C, and D, respectively (p = 0.008). There was a significance in the differences between median scores obtained during the histopathological examination: 2, 11, 13.5, and 12 for group A, B, C, and D (p = 0.022). There was an inverse correlation between the overall scores of histopathological evaluations and the length of the bone defect (observed on D90) (p p < 0.0001). This is the first study in which the efficacy of fresh autologous Stromal Vascular Fraction (SVF) from adipose tissue in enhancing bone healing in a long, weight-bearing, diaphyseal bone was evaluated. It is concluded that the lumbosacral region was an attractive site for harvesting adipose tissue, the use of SVF contributed to faster rehabilitation post-operatively, and SVF significantly enhanced bone formation; in general, the results indicated an osteogenic potential of SVF comparable to the gold standard autologous bone graft