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Journal articles on the topic 'Large diameter circular knitting machine'
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1
Abdessalem, Saber Ben, Youssef Ben Abdelkader, Sofiene Mokhtar, and Saber Elmarzougui. "Influence of Elastane Consumption on Plated Plain Knitted Fabric Characteristics." Journal of Engineered Fibers and Fabrics 4, no. 4 (2009): 155892500900400. http://dx.doi.org/10.1177/155892500900400411.
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The requirements in terms of wearing comfort with sportswear underwear and outerwear are widely linked to the use of elastane fibers. Today, elastomeric plated jersey fabric is one of the most common fabrics produced with large-diameter circular knitting machine (LCKM). However, the relation between elastane proportion and fabric characteristics has not been enough studied in literature and knitters generally use experience during machines adjustments in to order reach needed fabric characteristics. The aim of this paper was to investigate the relation between Lycra® consumption and fabric dimensional and elastic behavior. The obtained results showed that Lycra® proportion inside fabric has an incidence on fabric width, weight and elasticity. The origin of this behaviour has been discussed.
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Abdessalem, Saber Ben, Salem Ben Mansour, and Helmi Khelif. "Influence of Delayed Timing on Knitted Fabric Characteristics." Journal of Engineered Fibers and Fabrics 7, no. 4 (2012): 155892501200700. http://dx.doi.org/10.1177/155892501200700401.
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Delayed timing is a complex adjustment of large-diameter circular knitting machine (LCKM). It corresponds to the delay between cylinder and dial needles knock-over. It is generally not well-known by machines users and its impact on fabric properties has not been enough studied in literature. Knitters generally use experience during delayed timing adjustment in order reach needed fabric characteristics. The aim of this paper was to investigate the relation between delayed timing intensity and yarn tension, yarn consumption, fabric weight as well as loop length and shape. The obtained results showed that delayed timing has an incidence on fabric weight and loop shape especially at fabric back side. The origin of this influence has been discussed and related to needles feeding mechanisms.
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SHCHERBAN, Volodymyr, Oksana KOLISKO, Marjana KOLISKO, Anton KIRICHENKO, and Yuryj SHCHERBAN. "COMPUTER PROCEDURES OF THE SOFTWARE COMPLEX FOR DETERMINING THE TENSION OF THE THREAD SUPPLY PROCESS ON CIRCULAR KNITTING MACHINES." Herald of Khmelnytskyi National University 305, no. 1 (2022): 256–59. http://dx.doi.org/10.31891/2307-5732-2022-305-1-256-259.
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Determining the intensity of the thread feed process on a circular knitting machine for elastic weaves allows you to initially determine the technological loads that will occur during the interaction of the thread with the guides and working bodies depending on the type of raw material, curvature of guide surfaces, thread feed rate. The tension is changed due to the interaction of the threads with the guides of the circular knitting machine for elastic weaves of large and small curvature, tensioning devices. The development of procedures for the computer determination of thread tension on a circular knitting machine for elastic weaves should be based on the use of object-oriented programming languages. Determining the tension and changes in relative tension in the refueling zones of a circular knitting machine for elastic weaves, taking into account the specifics of the design of the thread feed system, will improve the technology of processing raw materials on a circular knitting machine for elastic weaves. The improvement of technological processes of thread processing on a circular knitting machine for elastic weaves should be based on complex studies of the process of interaction of threads with combined tensioning devices, working guide surfaces of large and small curvature of the feed system. Theoretical dependences for determining the tension will allow to obtain mathematical software used in computer software to calculate the tension and change the relative tension in the refueling zones of circular knitting machine for elastic weaves, reduce the percentage of thread breakage, improve the quality of knitted fabric. You can reduce the tension of the thread feeding process and reduce the number of thread breaks on a circular knitting machine for elastic weaves by using quality raw materials and optimizing the interaction of threads with tensioning devices on a circular knitting machine for elastic weaves, where there is interaction of threads with surfaces large and small curvature. Thread tension relationships are systems of transcendental equations that require numerical methods to solve.
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Peiner, Christoph, Henning Löcken, Leon Reinsch, and Thomas Gries. "3D Knitted Preforms Using Large Circular Weft Knitting Machines." Applied Composite Materials 29, no. 1 (2021): 273–88. http://dx.doi.org/10.1007/s10443-021-09956-1.
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Abstract3D-knits are typically produced on flat knitting or special circular knitting machines in a time-consuming process. The utilisation of a sewing-like pattern opens up the potential of a 10–50 times faster production on common large circular knitting machines as compared to conventional flat knitting machines. Since common large circular knitting machines are not designed for this technology, the limitations and the stability of process conditions have been rarely studied. To further proof the feasibility and increase technological maturity, agile product development is conducted. As a concept product, a sports bra with customised cups is developed and demonstrated, which is knitted in a single step in approx. 5 min using the sewing-like pattern on a large circular knitting machine. The agile process is utilised to build process knowledge, develop a methodology for product design and to defined a descriptive process terminology. In order to further accelerate and digitize the production process, an algorithm is developed and implemented to convert CAD-data into machine readable knitting structures. The paper presents the basics of the 3D-Knit one large circular knitting machines and a defined terminology. Furthermore, process knowledge is built up and from this a sequence of development steps is derived. The development of a 3D-knitted sports bra is presented as a proof of concept of the technology. Further, the first steps for digitalising the product development process are given. The results open up application possibilities in sportswear, upholstery and aerospace with increased productivity and hence cost reduction.
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Krauledaitė, Julija, Kristina Ancutienė, Virginijus Urbelis, Sigitas Krauledas, and Virginija Sacevičienė. "Development and evaluation of 3D knitted fabrics to protect against mechanical risk." Journal of Industrial Textiles 49, no. 3 (2018): 383–401. http://dx.doi.org/10.1177/1528083718783316.
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In this research, eight different 3D weft-knitted fabrics were developed and evaluated. 3D fabrics have been knitted on circular weft-knitting machines with two different gauges: 20E gauge and 28E gauge. Three different raw materials were used for the fabric’s production: high molecular mass polyethylene (HPPE) yarn and 0.05 mm diameter steel wire in the outer layers (for the front and reverse) and polyamide yarn in the binding layer. The experiments were conducted on the developed 3D knitted fabrics to determine the fabric’s resistance to mechanical risks such as circular blade cut, puncture, abrasion, and also to evaluate the comfort parameter, such as air permeability. It was defined that 3D weft-knitted fabrics best results on tests: circular blade cut, puncture and abrasion resistant were achieved using HPPE yarn twisted with steel wire, higher mass per unit area with more significant amount of steel wire. According to the standard EN 388:2003, three samples of developed 3D weft-knitted fabrics had the highest 5th blade cut and the highest (4th) abrasion resistance level. All of them had the highest (4th) level of puncture resistance. 3D fabrics knitted on a circular weft-knitting machine of gauge 28E ensured 1.3–2.1 times greater blade cut and 4.9–12.1 times greater abrasion resistance result, than fabrics knitted on gauge 20E, due to a higher stitch density, higher mass per unit area, density and fabric’s thickness. But on the other hand, these parameters lowered air permeability by 20.2–43.0%.
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Soekoco, Asril, Ateeq Ur Rehman, Ajisetia Fauzi, et al. "Fabrication of Recycled Polycarbonate Fibre for Thermal Signature Reduction in Camouflage Textiles." Polymers 14, no. 10 (2022): 1972. http://dx.doi.org/10.3390/polym14101972.
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Thermal signature reduction in camouflage textiles is a vital requirement to protect soldiers from detection by thermal imaging equipment in low-light conditions. Thermal signature reduction can be achieved by decreasing the surface temperature of the subject by using a low thermally conductive material, such as polycarbonate, which contains bisphenol A. Polycarbonate is a hard type of plastic that generally ends up in dumps and landfills. Accordingly, there is a large amount of polycarbonate waste that needs to be managed to reduce its drawbacks to the environment. Polycarbonate waste has great potential to be used as a material for recycled fibre by the melt spinning method. In this research, polycarbonate roofing-sheet waste was extruded using a 2 mm diameter of spinnerette and a 14 mm barrel diameter in a 265 °C temperature process by using a lab-scale melt spinning machine at various plunger and take-up speeds. The fibres were then inserted into 1 × 1 rib-stitch knitted fabric made by Nm 15 polyacrylic commercial yarns, which were manufactured by a flat knitting machine. The results showed that applying recycled polycarbonate fibre as a fibre insertion in polyacrylate knitted fabric reduced the emitted infrared and thermal signature of the fabric.
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Shen, Nan Yan, Jing Li, Xue Dong Wang, Jun Ye, and Zhi Xiang Yu. "Analysis and Detection of Elastic Deformation of the Large-Scale Crankshaft in Non-Circular Grinding." Applied Mechanics and Materials 532 (February 2014): 285–90. http://dx.doi.org/10.4028/www.scientific.net/amm.532.285.
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Due to the discontinuous axis and the big ratio of length to diameter, the large-scale crankshaft is easy to generate the complex elastic deformation under the effect of the huge gravity and the clamping force on non-circular grinding machine. The distinctive deformation deteriorates the coaxiality of all the main journals and thus the grinding precision of crankpins in non-circular grinding. In this paper, the statics analysis of large-scale crankshaft has been conducted by using the finite element simulation. The overall deformation of crankshaft and the position offset of each main journal center without or with the auxiliary supports have been simulated and contrasted. The results manifest that the auxiliary support forces produced by the steady rests have the positive effect on the compensation for crankshaft deformation. On this basis, to satisfy the demand of position adjustment of the upper and lower support pads of servo-controlled open steady rest, the on-machine measurement method and device of the position of main journal center is proposed. And then the offset calculation model of the main journal center is deduced using the measured data. The measurement method and device are beneficial for the straightening of the crankshaft and the improvement of machining accuracy of crankpins in non-circular grinding.
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Dong, Xiang Min, Li Gang Cai, Yong Sheng Zhao, and Xiao Shi. "Deformation Analysis for Hydrostatic Rotary Table of Heavy Duty CNC Machine Tool." Applied Mechanics and Materials 457-458 (October 2013): 335–39. http://dx.doi.org/10.4028/www.scientific.net/amm.457-458.335.
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The deformation of constant flow and closed type hydrostatic rotary table of heavy duty CNC machine tool has a great influence on the film thickness because of its large diameter, high load-bearing. According to the circular plate deformation theory of elasticity, differential equations of worktable deformation are derived in the simply supported conditions when bearing uniform force of different locations. Displacement curves of worktable are obtained. Force and deformation weaknesses of hydrostatic rotary table are found, which can provide theory basis for supporting location of heavy workpiece machining and whether oil film is failure or not.
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Pavlović, Željka, and Zlatko Vrljičak. "Comparing double jersey knitted fabrics made of Tencel and modal yarns, spun by different spinning methods." Journal of Engineered Fibers and Fabrics 15 (January 2020): 155892502091985. http://dx.doi.org/10.1177/1558925020919854.
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A double-bed circular knitting machine with a gauge of E17 and a needle bar diameter of 200 mm (8 in) was used to make three groups of plain weft knitted Tencel fabrics and three groups of modal knitted fabrics. The yarns were spun using three spinning methods: ring, rotor, and air-jet system. Their count was 20 tex. All the knitted fabric samples were manufactured under the same conditions. One-half of each knitted fabric sample remained unfinished, while the other half was finished. Structure parameters of all finished and unfinished knitted fabrics were analyzed, and the most significant parameters were compared. Tensile properties of the knitted fabrics in wale and course directions were measured. The difference in the elasticity of the knitted fabric was analyzed in particular, and the portions of knitted fabric stretch are given. The basic conclusion is that using equal yarn fineness, but different raw material composition and structure, the produced knitted fabrics had substantially different fabric masses per unit area. The raw material composition and construction of the yarn, that is, the yarn manufacturing process and the spinning process produce yarns of different structures and properties that are manifested in the structure and properties of the knitted fabric. Thus, the finishing process must be specific for each raw material composition and yarn structure.
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Yagishita, H. "Experimental Research on Circular Milling of Bi-Layer Composite Materials Consisting of CFRP Laminates and Titanium Alloys." Key Engineering Materials 622-623 (September 2014): 1207–14. http://dx.doi.org/10.4028/www.scientific.net/kem.622-623.1207.
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Recently, to construct an airframe 2-layer composite materials consisting of carbon fiber reinforced plastic (CFRP) laminates and TiAl6V4 still need to be machined, whereby drill holes are frequently machined. Special attention has to be paid to the machining quality, which implies hole dimensional accuracy, defect free peripheral zone, edge quality at inlet and outlet of hole and so on. Machining defects often occur as a consequence of excessive mechanical and thermal loads, which are often caused by wrong process conditions or by the wrong choice of machining process itself. With respect to widely used state-of-the-art machine tools providing high performance and equipped with potent control unit, for the comparatively large drill hole, circular milling gains interest as an alternative to the drilling operation [1, 2]. In this research, in order to select suitable machining conditions for 2-layer composite materials consisting of CFRP laminates and TiAl6V4 a large number of circular milling tests of 6 mm diameter are executed by using a high performance vertical milling machine. Hole diameter deviation from 6 mm and inner surface roughness in relation to number of hole machined are measured and evaluated for CFRP laminates and TiAl6V4. Moreover, from observations of cutting edges in relation to number of hole machined it is confirmed that under wrong machining conditions the difference of heat conductivity between CFRP laminates and TiAl6V4 induces for chips of TiAl6V4 to be deposited on the end cutting edges of endmill used. In this case tool life shortens extremely.
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Yu, Chun Jian, Xiao Diao Huang, and Rong Jing Hong. "Research on Overhanging Rigidity and Auxiliary Support Characteristics of the Large and Exact NC Rotary Table." Advanced Materials Research 139-141 (October 2010): 772–76. http://dx.doi.org/10.4028/www.scientific.net/amr.139-141.772.
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According to high-frequency chattering of workpiece overhanging the support area of the NC rotary table while gear milling, overhanging rigidity of the table was analyzed and the auxiliary support program was bring up. Online test of gear milling can be used to establish dynamic model of the overhanging structure. For enhancing increase the axial rigidity and circumferential damping of the rotary table, a kind of auxiliary support apparatus with hydraulic pressure was designed to reduce the influence of high-frequency chattering on gear milling, which doesn’t affect circular division accuracy. As a result, efficiency of gear milling was increased more than 3 times and the machining diameter of workpiece was increased from 2250mm to 3200mm, so the auxiliary support equipment can be used on many kinds of NC rotary table and machine tool.
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Yao, Jun, Yu Jun Nie, and Zhi Tong Chen. "Design and Analysis of Flow Field in Electrochemical Cutting Processing by Arranged Tube Electrode." Applied Mechanics and Materials 872 (October 2017): 67–76. http://dx.doi.org/10.4028/www.scientific.net/amm.872.67.
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The large complex structure integral components composed of difficult-to-machine material (such as titanium alloy, high temperature alloy) are more and more widely applied in aerospace, weapon equipment and other industries. The material utilization rate and the processing efficiency of the milling process are very low, the cost is high. Micro copper tubes (diameter 2mm, inner diameter 1.6mm) are arranged to electrode with shape to be processed, which could cut these components with a high efficiency and low cost. The fabrication of electrode is simple and convenient, so the cost of electrode could be reduced too. The flow field design is an important problem to be solved. The model of flow field is established, and flow field of different cathodes are simulated．The analysis results show that the rectifying ring is favorable for the electrochemical machining. Finally, the cathode with rectifying ring is used in processing experiment, the edge of cutting zone is orderly, no spark and short circuit occurs. Straight line and circular hole is successfully processed. The feasibility of the scheme is proved.
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Markova, E. V., A. M. Al Darabseh, I. E. Daba’bneh, and A. R. Ahmed. "THE EXPERIMENTAL AND NUMERICAL STUDY OF THE FORCES DURING THE INCREMENTAL FORMING OF TITANIUM SHEETS." Izvestiya of Samara Scientific Center of the Russian Academy of Sciences 23, no. 1 (2021): 5–10. http://dx.doi.org/10.37313/1990-5378-2021-23-1-5-10.
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Incremental forming is a rapid prototyping process that allows sheets to be formed without using forming tools, using a numerically controlled machine tool. A wide variety of shapes can be generated with this process. The objective of this work is to study through experimental tests and numerical simulations the behavior of ASTM grade 2 titanium during incremental point forming (SPIF). A Spinner MFG850 machining center from ISET in JENDOUBA coupled to a multi-component force sensor FN7325 was used for the forming of thin sheets by this process. As the diameter of the punch and its incremental movement are parameters having a direct effect on the forming force, tests with diameters of the punches dp varying between 10 and 15 mm and various paths made up of circular movements in the horizontal plane have been carried out experimentally. Numerical simulation is carried out in large elastoplastic deformations with ABAQUS/explicit. Comparisons of the evolution of the forming force for different values of the diameter of the punch dp and of the displacement step ∆zare carried out.
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Chen, Yu-Liang, Xuan-Qi Liang, Zi-Rong Ye, and Quang-Cherng Hsu. "Development of a Rapid Optical Measurement System for Circular Workpieces with Irregular Tooth Contours after Broaching Process." Applied Sciences 10, no. 13 (2020): 4418. http://dx.doi.org/10.3390/app10134418.
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During a manufacturing process, it is essential to quickly identify whether a tool needs to be replaced or adjusted, to ensure that production quality is not compromised. Therefore, the re-inspection of the product or first article inspection is an important process. Reducing the inspection time can reduce the time spent waiting for a product in the production line. This research aimed to design a system that can automatically and rapidly measure the dimensions of irregular tooth contours in the broaching process, to ensure cutting tools are replaced when necessary. This study developed an automatic machine for measuring the irregular tooth contours of large ring parts; the tooth root, tooth height, and tooth thickness of the workpiece are measured. The measurement diameter is approximately 200 mm, and the radial inspection accuracy is within ±20 μm; we aimed to reduce the detection time considerably. An optical micrometer and an automatic rotating platform were used in the measurement system. The workpieces to be measured were easy to install, and the eccentricity was automatically corrected by the system, thus saving time that would be taken to correct Abbe errors. This research successfully developed a rapid optical measurement system that can reduce the inspection time from 30 min to 60 s. Moreover, the maximum radial measurement error is −0.02 mm, which means that the measurement accuracy is within ±20 μm (total: 40 μm).
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Lytvyn, Oleksandr, and Kalchenko Dmytro Kalchenko. "INVESTIGATION OF THE PROCESS OF DOUBLE-SIDED GRINDING OF TORCHES OF PUSHERS WITH DIFFERENT DIAMETRERS." TECHNICAL SCIENCES AND TECHNOLOG IES, no. 2 (12) (2018): 86–93. http://dx.doi.org/10.25140/2411-5363-2018-2(12)-86-93.
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Urgency of the research. In machine tools, automotive, agricultural engineering, manufacturing, where it is necessary to ensure high accuracy of surfaces of parts with different diameters of faces, it is required to adhere to high requirements for the quality of geometric sizes, roughness and accuracy of molding. Target setting. Grinding of end surfaces of parts with different diameters of faces, is carried out on two-sided end-grinding machines. The specific gravity of grinding in the total complexity of mechanical processing is constantly increasing and at the present stage it is about 30 % in the machine tool industry, in the automotive industry more than 38% of the total complexity of processing. Actual scientific researches and issues analysis. On the two-sided end-grinding machines of the Saturn company (Germany) the processing of round ends of parts is done with a circular feed to the processing area. Abrasive wheels are used without calibrating plots, which requires a lot of processing to obtain the required precision, which reduces the productivity of grinding. The disadvantage of the method is that the processing of parts with different face diameters is not considered. Uninvestigated parts of general matters defining. It is necessary to improve the processing efficiency of parts by developing the methods of two-sided polishing of the ends of pushers with different diameters oriented grinding wheels with and with-out calibrating sections, and also the rotation or without rotation of the workpiece on the calibration section, at least one revo-lution. The research objective. Improving the accuracy of finishing the end surfaces of parts of various diameters with grinding wheels, is achieved by the fact that the shaping of the ends of the smaller diameter is performed by the maximum diameter of the flat end of one circle, and the shaping of the end face of a larger diameter – the calibration section of the second circle, the length of which is equal to the diameter of the larger end and filled with diamond pencil, which moves along a radius, which coincides with the radius of the location of the axes of the parts in the feed drum. The statement of basic materials. In order to ensure the processing of parts in one pass and the necessary precision of processing, in large-scale and mass production, a grinding method oriented circles with calibrated sections with one-sided arrangement of ends of one diameter is used. The calibration sections are then made of different lengths, depending on the diameter, respectively, larger and smaller. Conclusions. The universal method of practical application of model of accuracy of shaping of ends of parts of different diameters, oriented grinding circles with and without calibration plots has been suggested. The presented method simplifies the grinding of the grinding wheel. It does not require special editing and allows to use regular editing.
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Kharchenko, Yevgen, Andrii Sharan, and Olena Yeremeeva. "Effect of flattening wheat grain on grinding modes in roller mill." Ukrainian Journal of Food Science 9, no. 2 (2021): 223–35. http://dx.doi.org/10.24263/2310-1008-2021-9-2-9.
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Introduction. The flattening process is used to intensify the grinding of grain during varietal milling of wheat, while the optimal gap between the rolls of the ivy system remains uncertain. Materials and methods. Flattening was carried out in a laboratory ivy machine with a roller diameter of 144.0 mm; 68.4 mm and a rotation speed of 14.6 s-1. Grinding of wheat grain was carried out in a roller mill. The length of the rollers is 70 mm; the number of rifts per 1 cm circle of rollers is 6, the slope of the rifts is 12%, the ratio of circular speeds is 1:2, the speed of rotation of the high-speed roller is 3.93 m/s, the diameter of the rollers is 150 mm, the interdependence of the rifts is the back on the back, the angles of exacerbation of the rifts are 35°/70°. The mode of grinding wheat grain in the ivy machine and in the roller mill was determined by sifting the products obtained through a sieve with holes of 1.0 mm. Granulometric analysis of crushed products was determined by sifting on a standard set of sieves with module Δ≈1.21. Result and discussion. When grinding ivy products in a roller mill, the total yield of intermediate products is nonlinear in nature and can be approximated by the equation of the second degree. The optimal distance between the rollers of the ivy machine is 1.4 mm, provided that small products after flattening were previously isolated from the mixture of the flattened product. The total product of intermediate products after flattening and grinding in the roller mill has a complex nonlinear nature, which did not allow to establish the optimal value of the gap value between the rollers of the ivy system. The total product of intermediate products obtained in total during flattening and grinding is 2.9 % greater than the total product product yield obtained only in the roller mill with small ivy products previously removed. Differential curves are polymodal and have 5 maximums. Integral curves have an S-shaped appearance. When grinding whole grain, the total yield of intermediate products is greater than when grinding flattened grain in a roller mill under the same conditions. When crushing flattened grain, a greater number of large fractions of products are formed due to small ones. Conclusion. In the range of the established optimal clearance between the rolls of the flattening machine, there are no significant differences between the two methods of grinding wheat.
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Krauledaitė, Julija, Kristina Ancutienė, Sigitas Krauledas, Virginijus Urbelis, and Virginija Sacevičienė. "Research of 3D weft-knitted fabrics designed to protect against mechanical risks and suitable for contact with skin." Journal of Industrial Textiles, May 28, 2020, 152808372092583. http://dx.doi.org/10.1177/1528083720925831.
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Eight different 3D weft-knitted fabrics, consisting of outer, binding, and inner layers, were designed and produced on E20 and E28 circular weft-knitting machines. First, in the outer layer, high molecular weight polyethylene multifilament yarns and steel wire (0.05 mm diameter), twisted with high molecular weight polyethylene multifilament yarns, were used because of their exceptional properties to resist the mechanical risks. Second, in the inner layer, hydrophobic polyester spun yarns were chosen for their suitability to be used in contact with skin. Finally, in the binding layer, synthetic elastic textured polyamide yarns were used to connect the outer and inner layers. Following the standard EN 388, diverse tests were conducted to determine the resistance of the developed 3D weft-knitted fabrics to mechanical risks, i.e., circular blade cut, puncture, abrasion, and tear. The analysis showed that the quantity of steel wire in knitted structure highly influences circular blade cut and abrasion resistance, and moderately influences tear resistance for all the investigated knitted fabrics. While a strong positive correlation between the quantity of steel wire and the puncture force was defined only for 3D fabrics knitted on an E20 circular weft-knitting machine. The findings of the research lead to the conclusion that the designed 3D weft-knitted fabric structures, where the outer layer ensures protection against mechanical risks, while the inner layer is designed for contact with skin, provide complex protection against diverse mechanical risks.
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Nwokocha, C. G., and C. S. Ejimadu. "Analysis of Optic Disc and Vertical Cup Disc Ratio among Glaucoma Suspects in a Black Population." Journal of Advances in Medicine and Medical Research, June 15, 2019, 1–8. http://dx.doi.org/10.9734/jammr/2019/v29i1130145.
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Aim: To analyze the optic discs and vertical cup disc ratio in a black population.
 Method: This is a retrospective study of glaucoma suspects who presented to the clinic. Medical history was recorded and comprehensive ocular examination done on each of the subjects. Ocular examination included visual acuity, visual field, tonometry and ophthalmoscopy. Instruments used during the research were Pen torch for examination of the external structures of the eyes, Keeler ophthalmoscopes for fundus examination, Snellen’s charts both literate and illiterate charts for visual acuity assessment, Reichert AT 555 Auto non-contact tonometer for measurementof the intra-ocular pressure.
 The optic discs were analyzed using Optical Coherence Tomography machine. Data was analyzed using the statistical package EPI info version 6.04d, a software package designed by the Centers for Disease Control and Prevention (CDC), USA in 2001.
 Results: This study included total of 240 optic discs of 120 participants comprising 60 males and 60 females were examined with a mean age of 42.8±13.79; the age range was 19 to 75 years. Very Small discs (<1.0mm) 3 accounted for1.3%, Small discs (1.0-1.3mm) 4 accounted for 1.7%, Medium (1.4-1.7mm) 67 accounted for 27.9%, Large (1.8-2.0mm) 58 accounted for 24.2% while Very Large (>2.0mm) 108 accounted for 45.0% in this study.
 VCDR was noticed to have increased with increasing disc diameter. Optic disc diameter increased with increasing RNFL thickness as well (p < 0.05; r = 0.18).
 All the very small as well as the small discs were cupped 3% (n = 7/240), 14.6% (n = 35/240) of the medium to very large are also cupped while the remaining 82.5% ( n = 198/240) are normal.
 Conclusion: There was no significant correlation between disc diameter and VCDR. There was also a weak positive correlation between the optic disc diameter and the retinal nerve fiber layer thickness of the subjects, such a correlation may be the result of either an increased number of nerve fibers in eyes with larger discs or a smaller distance between the circular scan and the true optic disc margin.
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Mihevc, Andrej, and Rok Mihevc. "Morphological characteristics and distribution of dolines in Slovenia, a study of a lidar-based doline map of Slovenia." Acta Carsologica 50, no. 1 (2021). http://dx.doi.org/10.3986/ac.v50i1.9462.
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Dolines are small to intermediate enclosed depressions and are the most numerous karst feature in Slovenia. They are circular in plan form and vary in diameter from a few metres to over a kilometre. They are developed in limestone, dolomite, carbonate breccia and conglomerate and occupy different geomorphic settings. They were formed by various processes like dissolution, collapse, suffosion and transformation of caves to surface features by denudation. Publicly accessible lidar data, provided by a nationwide laser scanning project of Slovenia, was used for this study. To catalogue the dolines, we manually label a fraction of the digital elevation model (DEM) with a binary mask indicating if the area is a doline or not. We then train a slightly modified u-net, a type of machine learning algorithm, on the labelled territory. Using the trained algorithm, we infer the binary mask on the entire DEM. We convert the resulting mask into an ESRI Shapefile and manually verify the results. We note that the training and inference are error prone on types of relief that were less common in the training set (e.g., the relatively uncommon collapse dolines). We believe manual verification mitigates most of these errors, so the resulting map is a good basis for the doline study. We have made our georeferenced catalogue of dolines available at https://dolines.org/ (Mihevc & Mihevc 2021). Dolines are found in most of the karst areas, except mountains where they were eroded by glacial action or covered by glacial deposits. We detected 471,192 dolines and divided them into three genetic types. Most abundant are solution dolines (470,325). The average doline is 9 m deep, has a diameter of 42 m and a volume of 14,098 m3. The density of dolines on levelled surfaces can be as high as 500/ per km2. They are absent from the floors of poljes and steeper slopes, and are less abundant on sloping surfaces. We have identified 314 dolines to be of collapse origin. The mean depth of collapse dolines is 49 m, and 20 of them are deeper than 100 m. The mean volume is 1.2 million m3, with the largest having a volume of 11.6 million m3. Most of the collapse dolines can be found close to ponors or springs or corridors where large underground rivers flow. We have detected 553 suffosion dolines formed by suffosion of sediments in blind valleys or on poljes. This basic data set for dolines enables further study and comparison of dolines with the geology and topography of the karst.
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Toledo-Marín, J. Quetzalcóatl, Geoffrey Fox, James P. Sluka, and James A. Glazier. "Deep Learning Approaches to Surrogates for Solving the Diffusion Equation for Mechanistic Real-World Simulations." Frontiers in Physiology 12 (June 24, 2021). http://dx.doi.org/10.3389/fphys.2021.667828.
Full textAbstract:
In many mechanistic medical, biological, physical, and engineered spatiotemporal dynamic models the numerical solution of partial differential equations (PDEs), especially for diffusion, fluid flow and mechanical relaxation, can make simulations impractically slow. Biological models of tissues and organs often require the simultaneous calculation of the spatial variation of concentration of dozens of diffusing chemical species. One clinical example where rapid calculation of a diffusing field is of use is the estimation of oxygen gradients in the retina, based on imaging of the retinal vasculature, to guide surgical interventions in diabetic retinopathy. Furthermore, the ability to predict blood perfusion and oxygenation may one day guide clinical interventions in diverse settings, i.e., from stent placement in treating heart disease to BOLD fMRI interpretation in evaluating cognitive function (Xie et al., 2019; Lee et al., 2020). Since the quasi-steady-state solutions required for fast-diffusing chemical species like oxygen are particularly computationally costly, we consider the use of a neural network to provide an approximate solution to the steady-state diffusion equation. Machine learning surrogates, neural networks trained to provide approximate solutions to such complicated numerical problems, can often provide speed-ups of several orders of magnitude compared to direct calculation. Surrogates of PDEs could enable use of larger and more detailed models than are possible with direct calculation and can make including such simulations in real-time or near-real time workflows practical. Creating a surrogate requires running the direct calculation tens of thousands of times to generate training data and then training the neural network, both of which are computationally expensive. Often the practical applications of such models require thousands to millions of replica simulations, for example for parameter identification and uncertainty quantification, each of which gains speed from surrogate use and rapidly recovers the up-front costs of surrogate generation. We use a Convolutional Neural Network to approximate the stationary solution to the diffusion equation in the case of two equal-diameter, circular, constant-value sources located at random positions in a two-dimensional square domain with absorbing boundary conditions. Such a configuration caricatures the chemical concentration field of a fast-diffusing species like oxygen in a tissue with two parallel blood vessels in a cross section perpendicular to the two blood vessels. To improve convergence during training, we apply a training approach that uses roll-back to reject stochastic changes to the network that increase the loss function. The trained neural network approximation is about 1000 times faster than the direct calculation for individual replicas. Because different applications will have different criteria for acceptable approximation accuracy, we discuss a variety of loss functions and accuracy estimators that can help select the best network for a particular application. We briefly discuss some of the issues we encountered with overfitting, mismapping of the field values and the geometrical conditions that lead to large absolute and relative errors in the approximate solution.