Modelling the physics of high speed product-weighing

Compac Sorting Equipment Auckland (Compac) manufactures and exports high-speed, accurate sorting systems for fruit and vegetables. Their sizers operate at between 10-15 pieces of fruit per second per lane. They weigh each piece of fruit individually, using a pair of cantilever loadcells, in less than 1/10 of a second. Compac wanted a mathematical model of the weighing process, that will help them to accurately weigh heavier fruit (more than 250g) at higher speeds (in less than a tenth of a second). They also asked for help with easing back on the size and stability of the weighing assembly, which would reduce the physical size and manufacturing cost of the overall system

Analysis of coil slumping

Steel strip is usually stored as a coil, which will slump to some degree after the removal of the mandrel. More often than not, the amount of slumping is so minor that it is assumed not to have occurred. Occasionally, the amount, though minor, is sufficient to compromise the integrity of the cylindrical bore which compromises subsequent handling of the coil. In extreme situations, the slumping progresses to a complete collapse of the coil. Such a collapse is rare. It occurs when a coil cannot hold up its own mass and loses its circular cross-section. It is thought to be principally associated with the size and weight of the coil, inappropriate coiling tensions and/or poor re-coiler equipment design. Strip properties, especially inter-strip contact characteristics, have been demonstrated experimentally to be crucial determinants of whether or not coil collapse is likely to occur. The particular kind of slumping/collapse of interest to BlueScope Steel, who proposed this Study Group problem, is the minor slumping that compromises cylindrical bore integrity. It is referred to as coil slump. The Study Group was asked to investigate and model the phenomenon of coil slumping, and, if possible, to quantify the effect of critical parameters, especially coil mass, strip thickness and inter-strip friction. In particular, it was suggested that deliberations should aim to characterize the geometry of slumping and to predict the deformation profile at the innermost and outermost wraps. For BlueScope Steel, the long term objectives are: (1) the formulation of the governing equations for the stresses in a coil under self-weight, (2) the identification of analytical solutions and/or numerical schemes for the final coil shape after slumping, and (3) the formulation of exclusion rules-of-thumb which predict when a particular form of slump (oval or triangular) is likely to occur. The Study Group made some progress with (1), limited progress with (2) and most progress with (3). Though various computer programs were written to explore different force and energy balance scenarios, they only scratched the surface with regards to (2). Success with it is heavily dependent in substantial progress being made with (1). As explained in detail in the sequel, the Study Group’s deliberations resulted in an improved understanding of the coil slumping/collapse problem by identifying a number of specific issues that should be of direct assistance to BlueScope Steel’s future management of coil slumping/collapse. In particular, such issues included the need, from a modelling perspective, to draw a clear distinction between minor slumping and major slumping which can subsequently lead to collapse; the formulation of a heuristic hypothesis about the dynamics of coil slumping/collapse which can be compared with historical data and act act as a conceptualization guide for further investigations; the identification of a “tension-weight ratio” (R) as the relevant dimensionless group which represents an indicative rule-of-thumb which can be applied in practice; and proposed, on the basis of the hypothesis, an efficient procedure for recording collapse events and statistically identifying possible collapse situations

People, Penguins and Petri Dishes: Adapting Object Counting Models To New Visual Domains And Object Types Without Forgetting

In this paper we propose a technique to adapt a convolutional neural network (CNN) based object counter to additional visual domains and object types while still preserving the original counting function. Domain-specific normalisation and scaling operators are trained to allow the model to adjust to the statistical distributions of the various visual domains. The developed adaptation technique is used to produce a singular patch-based counting regressor capable of counting various object types including people, vehicles, cell nuclei and wildlife. As part of this study a challenging new cell counting dataset in the context of tissue culture and patient diagnosis is constructed. This new collection, referred to as the Dublin Cell Counting (DCC) dataset, is the first of its kind to be made available to the wider computer vision community. State-of-the-art object counting performance is achieved in both the Shanghaitech (parts A and B) and Penguins datasets while competitive performance is observed on the TRANCOS and Modified Bone Marrow (MBM) datasets, all using a shared counting model.Comment: 10 page

Increased Susceptibility of Arterial Tissue to Wire Perforation with the Application of High Frequency Mechanical Vibrations

High frequency mechanical vibrations (20–50 kHz), delivered via small diameter flexible wire waveguides represent a minimally invasive technology for the treatment of chronic total occlusions (CTOs) and in other tissue ablation applications. Tissue disruption is reported to be caused by repetitive mechanical contact and cavitation. This work focuses on the effects of vibrating wire waveguides in contact with arterial tissue. An apparatus with clinically relevant parameters was used, characterized as operating at 22.5 kHz and delivering amplitudes of vibration of 17.8 - 34.3 µm (acoustic intensity, ISATA: 1.03 - 3.83 W/cm2) via 1.0 mm diameter waveguides. Inertial cavitation (in water at 370C) was determined to occur above amplitudes of vibration greater than 31.4 µm (ISATA = 3.21 W/cm2). The energized waveguides were advanced through tissue samples (porcine aorta) and the force profiles were measured for a range of acoustic intensities. The results show that the tissue perforation initiation force, perforation initiation energy and total energy required to perforate the tissue reduces with increasing acoustic intensity. No significant reduction in perforation force or energy was observed in the inertial cavitation region. Multistage perforation was evident through the force profile and histological examination of the tissue samples post wire waveguide perforation

Perforation of Arterial Tissue Using Kilohertz Frequency Ultrasound Delivered via Wire Waveguides

An emerging technology proposes the use of low frequency-high power ultrasound transmitted via wire waveguides for the disruption and ablation of atherosclerotic lesions, more specifically advanced fibrous or calcified plaques such as chronic total occlusions (CTO). This energy delivery selectively ablates rigid diseased tissue by means of direct mechanical contact, cavitation and other forces generated by the intense dynamic pressure fields generated. The first clinical device using this energy delivery was granted FDA approval in 2007 [1] for the ablation of CTOs and most research to date has focused on ablation and disruption of hard, fibrous or calcified tissues [2]. This work, however, investigates the affects this energy delivery has on the perforation of soft healthy tissue (porcine aorta). Materials and methods An ultrasonic apparatus has been developed with operational characteristics similar to clinical devices reported in the literature i.e. frequency of operation (22.5kHz) and distal-tip ultrasonic amplitudes of vibration (~15-50μm). This apparatus delivers ultrasound via 1mm nitinol wire waveguides (132mm in length) with flat distal tips. An experimental test rig was developed to perform controlled tests (ultrasonic power delivery and feedrates) on tissue samples in a thermostatic tank (37oC). Perforation force measurement was achieved by means of a strain gauge arrangement on a cantilever tissue holder. A miniature hydrophone was also incorporated for the detection of cavitation by analysing the acoustic spectrum while the device was activated. Sub, super and ultra harmonics of the fundamental are all considered indicative of stable cavitation, whereas an increase in the broadband noise, in regions absent of significant harmonics, are indicative of inertial cavitation [3]. Porcine aorta was exhumed, stored in saline and tested less then 24 hours after death. Connective tissue was removed and samples (10x20mm) were cut from the descending aorta. Wires were advanced towards the tissue at a constant feedrate of 38 mm/min until perforation. Results As shown in Figure 1, an increase in distal tip amplitudes of vibration reduced the perforation force. It was found that stable cavitation occurred at all power settings (\u3e 15μm). At the high power displacement amplitude setting of 34.3μm the perforation force was 1.2N when compared with 5.5N with no ultrasonic activation. The inertial cavitation threshold was crossed at distal-tip amplitudes of vibration greater than 30μm. However, no significant decrease in perforation force was evident in the inertial cavitation region. At the macro level, the tissue appears to fail in a similar manner for all distal-tip amplitudes of vibration. Discussion Perforation force of soft arterial tissue does not appear to be significantly effected by the onset of inertial cavitation. Further histological examination may be required to determine residual tissue damage from cavitation. Additional studies are needed to determine to what extent tissue is ablated, cut or removed at various power levels. It is suggested, however, that tissue removal using this energy on soft tissue is minimal when compared to that of hard brittle tissue ablation

Ablation of Chronic Total Occlusions Using Kilohertz-Frequency Mechanical Vibrations in Minimally Invasive Angioplasty Procedures.

Certain minimally invasive cardiology procedures, such as balloon angioplasty and stent implantation, critically require that the site of an arterial blockage be crossed by an intraluminal guidewire. Plaques resulting in near or totally occluded arteries are known as chronic total occlusions (CTOs), and crossing them with conventional guidewires is a significant challenge. Among the most promising proposed solutions is the delivery of high power, low frequency ultrasonic vibrations to the occlusion site via an intraluminal wire waveguide. The vibrating distal-tip of the ultrasound wire waveguide is used to transmit energy to the surrounding plaques, tissues and fluids in order to ablate or weaken atherosclerotic plaque. Potential mechanisms of interaction with the plaque and adjacent fluids identified in the literature include; (i) direct contact with the waveguide distal tip, (ii) subcavitational acoustic fluid pressure fluctuations, (iii) cavitation, and (iv) acoustic streaming. This article will summarize developments in this area over more than two decades, describing experimental methods for device performance characterization, preclinical tests, early clinical investigations and, later, full clinical trials. The article will also review theoretical foundations, and numerical models suitable for device design and analysis. Finally, important issues for future research and for the development of this technology will be considered

Soft Tissue Cutting with Ultrasonic Mechanical Waveguides

The use of ultrasonic vibrations transmitted via small diameter wire waveguides represents a technology that has potential for minimally invasive procedures in surgery. This form of energy delivery results in distal tip mechanical vibrations with amplitudes of vibration of up to 50 μm and at frequencies between 20-50 kHz commonly reported. This energy can then be used by micro-cutting surgical tools and end effectors for a range of applications such as bone cutting, cement removal in joint revision surgery and soft tissue cutting. One particular application which has gained regulatory approval in recent years is in the area of cardiovascular surgery in the removal of calcified atherosclerotic plaques and chronic total occlusions. This paper builds on previous work that was focused on the ultrasonic perforation of soft vascular tissue using ultrasonically activated mechanical waveguides and the applied force required to initiate failure in soft tissue when compared with non-ultrasonic waveguides. An ultrasonic device and experimental rig was developed that can deliver ultrasonic vibrations to the distal tip of 1.0 mm diameter nickel-titanium waveguides. The operation of the ultrasonic device has been characterized at 22.5 kHz with achievable amplitudes of vibration in the range of 16 – 40μm. The experimental rig allows the ultrasonically activated waveguide to be advanced through a tissue sample over a range of feedrates and the waveguide-tissue interaction force can be measured during perforation into the tissue. Preliminary studies into the effects of feedrate on porcine aortic arterial tissue perforation forces are presented as part of this work. A range of amplitudes of vibration at the wire waveguide distal tip were examined. The resulting temperature increase when perforating artery wall when using the energized wire waveguides is also examined. Results show a clear multistage failure of the tissue. The first stage involves a rise in force up to some critical force and tissue displacement whereby the cut is initiated. The results show that with increasing ultrasonic amplitude of vibration the perforation force decreases considerably. The current results show that for the range of feedrates investigated 19-95 mm/min at an amplitude of vibration of 34.3 μm there was no significant effect on the perforation initiation force. The ΔT in the tissue 3.0 mm from the point of entry is also presented for a range of amplitudes of vibration

Ultrasonic Angioplasty: Assessing the Risk of Arterial Perforation

Atherosclerosis is a cardiovascular disease that effects large and medium muscular arteries (such as coronary and iliac) and also large elastic arteries (such as aorta) [1]. It causes thickening of the arterial wall and over time can result in a completely blocked artery or chronic total occlusion (CTO). While the majority of atherosclerotic lesions can be attempted by typical Percutaneous Transluminal Coronary Angioplasty (PTCA) such as balloon and stent implantation, calcified CTOs are often problematic as they do not lend themselves to be accessed by the guidewire which is required to implant the balloon and stent. Excessive guidewire pushing force may result in arterial perforation with CTOs often requiring invasive by-pass surgery. An alternative method proposes the use of low frequency high power ultrasound transmitted through wire waveguides for the removal of the calcified material from advanced atherosclerotic lesions. This type of energy manifests itself as a mechanical vibration at the distal tip of the wave guide with amplitudes of up to 100 microns and frequencies ranging between 20-45 kHz commonly reported. The ultrasound acts to disrupt calcified diseased tissue by means of direct contact ablation, cavitation, acoustic steaming and other pressure wave components while the elastic tissue remains largely unaffected [2]. In this study the effects of this form of ultrasound on healthy arterial tissue (porcine aorta) is examined. Experiments were carried out to determine the force required to perforate healthy porcine arterial tissue both with and without ultrasound at various distal tip displacements

Slowly westward: A journey through a folded landscape

My thesis, Slowly Westward: A Journey Through A Folded Landscape, is made up of two distinct parts. The first part contains three essays which recount some of my journeys through the Irish landscape. The second part is a photobook which is made up of images taken during my time spent travelling through the island of Ireland. During the 19th century Ireland became the first country in the world to have a detailed map made of its entire surface. As this map was made by a colonial power, it led to a number of issues regarding representation, translation and construction. The first text, Bull Island, looks at the unintended physical consequences that colonial surveys had on Dublin bay with the construction of a sea wall which inadvertently led to the development of Bull Island. This text also refers to Allan Sekula and his approach of Critical Realism. The second text, Croghan, deals with the construction of contemporary Ireland and looks at artists including Sean Keating, who dealt with ideas of national self-representation in a post-independence Ireland. The third text, Inishark, recounts a journey to the abandoned island of Shark which was initially only partially mapped. Here I was looking for a space beyond the effects of the maps. This essay includes references to Tim Robinson’s remapping of the Irish west coast and John Berger’s thoughts on the connection between photography and time. The accompanying photobook is my personal response to my time spent travelling through this deeply layered space. The book is not sequenced chronologically or geographically. Rather it is made up of images reconfigured into a sequence which draws into question the contested nature of Ireland, and its numerous histories, representations and interpretations