Super Operations Research Articles

Nonlinear simulations of the peeling-ballooning instability of super H-modes in the HL-3 tokamak

As the newly built tokamak in China, HL-3 will explore high-performance operation scenarios, such as super H-mode. The energy confinement and core parameters in the super H-mode can be much larger than that in the normal H-mode. Based on the pedestal simulation code EPED, the operation space of the super H-mode is obtained in HL-3. Magnetic shear decreases with increasing triangularity; consequently, a super H-mode can be achieved. The threshold of triangularity for accessing a super H-mode in HL-3 is around 0.4. By using BOUT++, a nonlinear simulation study of the pedestal instabilities in the super H-mode equilibrium is executed for the first time. As expected, the low n peeling mode, which can cause much of the energy loss (17%) from the pedestal region, is dominant in the super H-mode. Such a large collapse in the pedestal region would lead to a transition from super H-mode to H-mode. It is crucial to expand the parameter space of the super H-mode or mitigate the edge-localized mode (ELM) size for sustaining the super H-mode operations. The E × B velocity shear is found to play an important role in controlling the ELMs in HL-3. The small E × B velocity shear leads to a large growth rate but results in a small ELM size around the peeling boundary. The ELM size is closely related to both the growth rate of peeling-ballooning mode and the duration time of the linear phase. In contrast, a large E × B velocity shear can stabilize the instabilities near the ballooning boundary. Next, the parameter space of the super H-mode can be enlarged.

Experimental investigation of aluminium 2024 alloy using cylindrical magnetic abrasive finishing process

In super finishing operations, the magnetic abrasive finishing (MAF) method is being researched as the Predominant finishing method. A cylindrical MAF (CMAF) method that was developed internally has undergone experimental investigation to improve the surface qualities of the aluminium 2024 alloy (Al 2024). For the machining process, a mixed abrasive of Al2O3 and SiC was utilized. Variable process factors for the experimental investigation include voltage, speed, and the percentage of abrasives. Based on results, the surface finish of the workpiece had improved to 94.12 % from its initial surface finish with a maximum of 11.5 mg of metal removed from the surface. Nevertheless, throughout the experimentation, the temperature that develops on the work surface as a result of the abrasives' shearing action is less than 57 °C.

Super Multi-Frequency Oscillations at Fundamental Harmonics With a Complex Cavity Gyrotron

Two resonators with different radii were separately excited in a complex cavity to demonstrate super multi-frequency operations of a gyrotron. A demountable gyrotron was constructed and driven by 15-kV, 0.4-A annular electron beams. The magnetic field strength was varied from 4 to 8 T to excite a series of transverse electric modes in each resonator. In the frequency range of 120 – 220 GHz, 13- and 9-mode oscillations at the fundamental harmonics were identified in the first and second resonators, respectively. Furthermore, backward wave oscillations of these modes allowed continuous frequency variation. Even if two resonators oscillate at the same time with different frequencies, most of them can be independently excited by regulating the velocity pitch and/or injection radius of the electron beam. As a result, 27% of frequencies from 120 to 220 GHz became available with a single gyrotron. This is the largest frequency occupation reported so far in this frequency range. The frequency gaps between neighboring modes were less than 10 GHz. The maximum output power obtained for each mode was more than 28 W.

Super short operations on both gene order and intergenic sizes

BackgroundThe evolutionary distance between two genomes can be estimated by computing a minimum length sequence of operations, called genome rearrangements, that transform one genome into another. Usually, a genome is modeled as an ordered sequence of genes, and most of the studies in the genome rearrangement literature consist in shaping biological scenarios into mathematical models. For instance, allowing different genome rearrangements operations at the same time, adding constraints to these rearrangements (e.g., each rearrangement can affect at most a given number of genes), considering that a rearrangement implies a cost depending on its length rather than a unit cost, etc. Most of the works, however, have overlooked some important features inside genomes, such as the presence of sequences of nucleotides between genes, called intergenic regions.Results and conclusionsIn this work, we investigate the problem of computing the distance between two genomes, taking into account both gene order and intergenic sizes. The genome rearrangement operations we consider here are constrained types of reversals and transpositions, called super short reversals (SSRs) and super short transpositions (SSTs), which affect up to two (consecutive) genes. We denote by super short operations (SSOs) any SSR or SST. We show 3-approximation algorithms when the orientation of the genes is not considered when we allow SSRs, SSTs, or SSOs, and 5-approximation algorithms when considering the orientation for either SSRs or SSOs. We also show that these algorithms improve their approximation factors when the input permutation has a higher number of inversions, where the approximation factor decreases from 3 to either 2 or 1.5, and from 5 to either 3 or 2.

Static Stiffness Parametric Studies of Newly Conceptualized Inter Shaft Squeeze Film Damper (ISSFD) Rings

Most of the modern gas turbine engine designs requiring super critical operations will often have squeeze film dampers (SFDs) on the high pressure spool bearing as an inevitable feature. However, Squeeze Film Dampers are not very common for inter-shaft bearing applications and are still in the research and development stage. The current effort concentrates on static stiffness parametric studies based on newly conceptualized intershaft squeeze film damper (ISSFD) ring design suitable for space constrained intershaft bearing application of a typical two spool configured system. The work involves static stiffness evaluation of three and four grooves ISSFD rings by varying the groove angle/groove length/subtended angle of groove & hence the overlapping angle of grooves by conducting static tests on a dedicated static stiffness evaluation test rig designed and fabricated for the purpose. The pattern of circumferential variation of stiffness of each ring is studied and the results revealed a typical trend of decreasing stiffness in ISSFD ring with the increase in groove angle and hence the overlapping angle of grooves. The static stiffness parametric studies has resulted in developing an ideal profile of ISSFD ring having six grooves that exhibited axisymmetric pattern of circumferential variation of stiffness. When used in a space constrained intershaft bearing plane of a typical two spool gas turbine engine, the ideal ISSFD ring profile would exhibit the best damping performance. 
 Keywords: Inter Shaft Squeeze Film Damper (ISSFD), Gas Turbine Engine, Static stiffness, two spools, grooves.

Sorting signed circular permutations by super short operations

BackgroundOne way to estimate the evolutionary distance between two given genomes is to determine the minimum number of large-scale mutations, or genome rearrangements, that are necessary to transform one into the other. In this context, genomes can be represented as ordered sequences of genes, each gene being represented by a signed integer. If no gene is repeated, genomes are thus modeled as signed permutations of the form pi =(pi _1 pi _2 ldots pi _n), and in that case we can consider without loss of generality that one of them is the identity permutation iota _n =(1 2 ldots n), and that we just need to sort the other (i.e., transform it into iota _n). The most studied genome rearrangement events are reversals, where a segment of the genome is reversed and reincorporated at the same location; and transpositions, where two consecutive segments are exchanged. Many variants, e.g., combining different types of (possibly constrained) rearrangements, have been proposed in the literature. One of them considers that the number of genes involved, in a reversal or a transposition, is never greater than two, which is known as the problem of sorting by super short operations (or SSOs).Results and conclusionsAll problems considering SSOs in permutations have been shown to be in mathsf {P}, except for one, namely sorting signed circular permutations by super short reversals and super short transpositions. Here we fill this gap by introducing a new graph structure called cyclic permutation graph and providing a series of intermediate results, which allows us to design a polynomial algorithm for sorting signed circular permutations by super short reversals and super short transpositions.

Investigation of TiAlN coated roller burnishing on Al-(B4C)p MMC workpiece material

ABSTRACTBurnishing avoids the need for super finishing operations after the conventional turning process, to enhance the surface quality. This paper deals with the surface modifications of Al(B4C)p Metal Matrix Composites (MMC) workpiece material after burnishing with a TiAlN coated WC roller. The burnishing speed, lubrication type, burnishing passes, and coating were the input parameters. Surface hardness and roughness after the burnishing were studied. It was found that the coating on the WC roller had enhanced the hardness in the workpiece after burnishing in the case of Al-5 wt.% (B4C)p, under all conditions. The effect of the coating on the work piece surface hardness was not significant with Al-10 wt.% (B4C)p. While burnishing Al-5 wt.% (B4C)p, the minimum surface roughness combined with maximum surface hardness was obtained, during the third pass under dry condition using uncoated rollers. The number of passes to achieve the desired surface conditions reduced, on using coated rollers with kerosene as the lubricant.

Cutting forces, surface roughness and tool life in high-speed milling of hardened steel convex surface

This paper presents a contribution to hardened tool steel milling studies. High-speed milling is largely utilized to substitute some EDM and polishing operations, mainly in finish machining of dies and molds made of hardened tool steel. Tool path and tool inclination are parameters used to identify adequate milling strategies, mainly to super finishing operations. Tool strategy is a very important variable in this kind of operations, since it may generate either long or short tool life, either low or high workpiece surface roughness. In this work, several milling experiments were performed in a circular convex AISI D6 hardened steel workpiece, having as input variables feed direction (upward and downward following the circular form of the surface) and tilt angle (tool inclination). Downward tool path resulted in longer tool lives, regardless the tilt angle utilized. Moreover, in upward tool path, workpiece surface roughness was not adequate to a process which aims to replace EDM. In downward tool path and tilt angle 0°, workpiece surface roughness values were adequate to EDM substitution along the whole tool life and the ratio of axial and radial cutting force components was higher than in upward tool path, which was determinant to the generation of low values of surface roughness.

New Formula (22/17) for Calculation of the Total Amount of Intravenous Fluids Given for Pediatric & Neonatal Surgical Operations Weighing up to 20 Kg or 5 Years Age

Introduction: A new formula(RH) for calculation of intra operative fluids given in neonatal & pediatric life threatening surgical operations from 1 kg – 2o kg body weight (or 1 day – 5 yrs age) was explained in this study. Aim of the Study : To find a simple , correct, & easily applicable formula to avoid any unwanted dangerous faults in calculation of fluid requirements in all types of neonatal& pediatric surgical operations from 1 kg – 20 kg body weight (or 1 day – 5 years age) especially for juniors or early post graduated doctors dealing with these age group (or weights). Patients: (5000 Patients) including neonates, infants & pediatric age group presented to CWTH/Medical city/Baghdad for different types of surgical operations were enrolled in this study divided to 3 groups (Group A) Life threatening and emergency conditions 2300 patients, (Group B) Major& super major elective operations 700 patients & (Group C) Different types of minor to moderate elective surgical operations 2000 patients. Methods: In this new formula intra operative fluid requirements calculated as: a) *Pre existing deficit (Fasting): 20 ml/kg this amount is divided over 3 hours: ½ the amount given in the 1st hour of operation and ¼ the amount is given for each the 2nd& 3rd hours of operations. b) *Maintenance fluid requirements: 4 ml/kg/hr for all weights up to 20 kg. c) *3rd Space replacement: 8 ml/kg/hr for major& super major operations & 4 ml/kg/hr for minor operations. Results: By comparison of this new formula with most of other references and other anesthesia text books fluid formulas regarding this aspect the results is that the difference in the total amounts of fluid requirements per hour was minute and regarded as negligible difference. Conclusion: *This new(RH) formula has been used for years(2005-2015) in neonatal & pediatric anesthetic department in CWTH/ Baghdad Medical City for 5000 neonates, infants & pediatric patients without any complications. a. This new formula is correct, safer, simpler & easily applicable than other formulas. b. The most important point in this new formula, is that it can be summarized by just 2 numbers (22- 17), 22ml/kg for the 1st hr. & 17 ml for the 2nd& 3rd hrs of operation time for major operation.

The Effect of Belt Finishing Process Variables on the Topography of Finished Surfaces

The high performance of industrial applications requires increasingly technical functional surfaces, particularly from the point of view of topography and micro texture. Belt finishing is one of the finest machining processes widely used to improve surface texture and to increase wear resistance and fatigue life. It modifies the surface topography in a wide range of roughness and waviness scales, and consequently modifies the functionality of the surface in terms of the bearing area, local plasticity, and durability. In this paper, the topographic signature of the belt finishing process on a wide range of wavelengths of surface topography is analyzed to track the effect of each working parameter, and makes it possible then to understand the principal physical mechanisms activated during the super finishing operations (cutting, ploughing, and friction). To this aim, a multiscale decomposition of the surface topography before and after finishing by using a 2D continuous wavelet transform is introduced.