High Rolling Research Articles

Study on Flight Safety Risk Evaluation Model Based on Flight Exceedance Events

The aim of this study is to establish the risk evaluation model for evaluating the flight safety level objectively and precisely based on flight exceedace events. The traditional risk assessment is revised. The flight quality monitoring projects which are the main factors affecting the flight safety are selected as the evaluation indices. The weights of the indices are determined by the analytic hierarchy process, the corresponding coefficients are set for different grades of exceedance events. The exceedance events rate is the frequency of occurrence. And the risk evaluation model is established. The flight safety risk is calculated with qualitative and quantitative methods. The risk level and the main risk factors affecting the flight safety risk are determined. Some specific measures are taken to improve the flight safety risk management level. The flight quality monitoring events of a certain airline’s B737 fleets during the first half of 2017 verify the validity of the model. It is found that the risks in landing and take-off are the greatest. The risk in landing contributed greatly to overweight landing, high speed during landing, vertical g high during landing and high roll during landing. The risk in the taking off phase contributed greatly to high pitch rate at rotation, low speed at rotation, high speed at rotation and low pitch rate at rotation.

Manual wheelchair users gradually face fewer postural stability and control challenges with increasing rolling resistance while maintaining a rear-wheel wheelie

Teaching manual wheelchair users to perform wheelies using various rolling resistances is expected to facilitate learning of this advanced wheelchair skill. However, limited scientific evidence is available to support this approach. This study aimed to measure and compare postural stability and control requirements when maintaining a stationary wheelie on different rolling resistances. Eighteen manual wheelchair users with a spinal cord injury performed in a random order and maintained four 30-second wheelies on four rolling resistances: natural hard floor (NAT), 5-cm thick soft foam (LOW), 5-cm thick memory foam (MOD), and rear wheels blocked by wooden blocks (HIGH). All wheelies were performed over a large instrumented force plate to continuously record the center of pressure (CoP). To quantify postural stability, resultant and directional time- and frequency-domain CoP measures were computed and compared across all four rolling resistances. All resultant time-domain measures confirmed increased postural stability from NAT to LOW and from MOD to HIGH rolling resistances. Most time-domain measures confirmed a shift in postural control from an anticipatory to a predominantly compensatory strategy, accompanied by increased reliance on proprioceptive feedback, especially from NAT to LOW and from MOD to HIGH rolling resistances. Postural stability gradually increased with various rolling resistances while maintaining a stationary wheelie, whereas the postural control strategy shifted from an anticipatory to a reactive strategy. Blocking the rear wheels is recommended when first teaching this advanced wheelchair skill. Rapid progression on foam and natural surfaces is advocated to refine learning and enhance proper postural control strategies.

Melt Conditioning Twin Roll Casting with Thermo-Mechanical Treatment of Recycled AA6111 Alloy

A high shear melt conditioning twin roll casting process with thermo-mechanical treatment was tested to increase the tolerance to high impurity levels in recycled aluminium alloy. Applying high shear melt conditioning prior to casting of recycled AA6111 alloy exhibits reduced centre-line segregation and a fine equiaxed grain structure with improved sheet quality. Homogenisation at 540°C for 8 h with annealing at 520°C for 10 min of the melt-conditioned twin roll casting strip (MC-TRC) showed a clear grain recrystallisation, which was better than the conventional twin roll casting TRC strip. The mechanical test showed a significant improvement in the hardness after applying high shear melt conditioning with thermo-mechanical treatment.

Interface strengthening and fracture behavior of multilayer TWIP/TRIP steel

Abstract Series of multilayer TWIP/TRIP steels were hot rolled at 1000 °C with different rolling reduction ratios of 25%, 50%, 60%, 70%, 80%, 90% and 94%, and some in-situ reacted Al2O3 whiskers were identified at the clad interface based on selection oxidation. The continuous oxidized films or walls were broken and separated into fine dispersed reinforcements with increasing rolling reduction ratio, which are beneficial to strengthen the interface and toughen the multilayer steels. At low rolling reduction ratio, the thick oxidation walls inhibit the grain growth and alloy element diffusion, leading to the weakness of interface bonding and interface delamination. However, at high rolling reduction ratio, the fine dispersed Al2O3 whiskers bridge the clad interface and induce grain crossing, resulting into strong interfaces and high uniform plastic deformation capacity. Moreover, the grain crossing phenomenon and inner TWIP/TRIP coordination deformation mechanism provide a novel approach for improving fracture elongation of multilayer steels.

Anomalous vibration suppression in a weak-value-emulated heterodyne roll interferometer.

We experimentally validate the vibration suppression capabilities of a weak-value-like protocol. The phase-sensitive heterodyne technique exhibits advantageous characteristics of a weak measurement including anomalous amplification in sensitivity and technical noise suppression. It does not, however, leverage the entanglement between the system and meter to amplify the signal of interest, as is typical in a weak measurement. In this formalism, we demonstrate an amplification in sensitivity to the roll angle of over 700 times. High precision roll experiments anchor numerical simulations to show that the interferometer outperforms standard interferometry by a factor of 500 in terms of peak-to-peak noise amplitude. During the measurement of a rolling stage, technical noise - primarily in the form of vibrations - is substantially attenuated. This is the first demonstration of vibration suppression capabilities that are inherent to the light from a metrology instrument instead of achieved via mechanical damping. The emulation presented in this work also identifies an avenue to achieve anomalous amplification outside of the standard weak measurement protocol.

Comminution behavior and mineral liberation characteristics of low-grade hematite ore in high pressure grinding roll

Comminution behavior and mineral liberation characteristics of low-grade hematite ore in high pressure grinding roll

Microstructural Evolution of Mechanically Deformed Polycrystalline Silicon for Kerfless Photovoltaics

Silicon wafers for photovoltaics could be produced without kerf loss by rolling, provided sufficient control of defects such as dislocations can be achieved. A study using mainly high resolution electron backscatter diffraction (HR‐EBSD) of the microstructural evolution of Siemens polycrystalline silicon feedstock during a series of processes designed to mimic high temperature rolling is reported here. The starting material is heavily textured and annealing at 1400 °C results in 90% recrystallization and a reduction in average geometrically necessary dislocation (GND) density from >1014 to 1013 m−2. Subsequent compression at 1150 °C – analogous to rolling – produce sub‐grain boundaries seen as continuous curved high GND content linear features spanning grain interiors. Post‐deformation annealing at 1400 °C facilitates a secondary recrystallization process, resulting in large grains typically of 100 μm diameter. HR‐EBSD gives the final average GND density in as 3.2 × 1012 m−2. This value is considerably higher than the dislocation density of 5 × 1010 m−2 from etch pit counting, so the discrepancy is investigated by direct comparison of GND maps and etch pit patterns. The GND map from HR‐EBSD gives erroneously high values at the method's noise floor (≈1012 m−2) in regions with low dislocation densities.

Usability of theophylline extended-release dry syrups

Objectives We examined the usability of theophylline extended-release dry syrups, including their powder fluidity and ingestibility using one branded and six generic formulations (formulations A, B, C, D, E, F, and G, respectively). Methods To evaluate the ease of handling by pharmacists, powder fluidity was evaluated by measuring the repose angle, whereas to determine ingestibility, the viewpoints of patients or caregivers were evaluated using a questionnaire survey. Results and discussion: The repose angles of formulations A, B, C, D, E, and F were approximately 30°–40°. These formulations had sufficient powder fluidity, indicating the ease of weighing for most pharmacists. However, the repose angle of formulation G was <30°. Formulation G had high fluidity, suggesting its high rolling property. Thus, powder handling for formulation G may be more difficult than that for other six formulations. The ingestibility, such as the ease of mixing the dry syrup with water and odor intensity, was different between the formulations. Conclusions The present study provides useful information for selecting branded or generic theophylline extended-release dry syrups.

Microstructural Evolution and Electrochemical Properties of HRDSR AZ61-X (X = Ca, Ti) Alloys.

The microstructure and corrosion properties of as-cast AZ61 (Mg-6%Al-1%Zn) and AZ61 alloys doped with titanium and calcium and subjected to high ratio differential speed rolling were investigated. Addition of the alloying elements to the AZ61 alloy resulted in remarkable modification of the morphology and the amount of continuous β (Mg17Al12)-phase. Addition of Ti to the as-cast AZ61 alloy causes a decrease in the volume fraction (or discontinuity of the β-phase), leading to strong anodic dissolution. In contrast, addition of Ca to the as-cast AZ61 alloy is rather effective for preventing pitting corrosion. This is attributed to the formation of a semi-continuous network β-structure. The (Mg, Al)4Ca phases dispersed between the β (Mg17Al12)-phases led to continuity in the AZ61 alloy with Ca. The AZ61 and AZ61-X(Ca, Ti) alloys subjected to severe plastic deformation via high-ratio differential speed rolling possessed a nano-composite-like microstructure in which the α-Mg matrix with an ultra-fine grain was surrounded by a large number of fine β particles. These particles were either dynamically precipitated or broken at the grain boundaries, as well as in the grain interiors, by the high ratio differential speed rolling process. The corrosion resistance of the AZ61 and AZ61-X (X = Ca, Ti) alloys subjected to high ratio differential speed rolling was largely improved by the microstructural modification. The high ratio differential speed rolling process greatly influenced the texture of the Mg alloys, which significantly affected their corrosion behavior.

Effects of Sn on microstructure and mechanical properties of as-rolled Mg–5Zn–1Mn alloy

ABSTRACTEffects of Sn on microstructure and mechanical properties of Mg–5Zn–1Mn alloy subjected to high strain rate rolling (9.1 s-1), 300°C and 80% pass reduction are investigated. With higher Sn content, the dynamic recrystallisation (DRX) grain size gradually decreases due to the stronger pinning of nano-scale precipitates at grain boundaries and the DRX fraction first increases due to the enhanced effect on DRX by decreasing stacking fault energy and then decreases due to more precipitates at grain boundaries. Ultimate tensile strength (UTS) and elongation to rupture (Er) of as-rolled alloys increase and then decrease. Alloy with 0.9 mass% Sn exhibits the highest DRX fraction (95 vol.-%), the finer DRX grain size (1.22 µm), UTS of 358 MPa and Er of 20.4%.

Effect of Reduction on Bonding Interface of Hot-rolled Wear-resistant Steel BTW1/Q345R Cladding Plate

Wear-resistant cladding plates consisting of a substrate (Q345R) and a clad layer (BTW1) were bonded through hot rolling at the temperature of 1 200 °C and a rolling speed of 0.5 m/s. The microhardness of the cladding plate was also tested after being heat treated. The microstructure evolution on the interface of BTW1/Q345R sheets under various reduction rates was investigated with a scanning electron microscope (SEM) and EBSD. It is found that the micro-cracks and oxide films on the interface disappear when the reduction is 80%, whereas the maximum uniform diffusion distance reaches 10 μm. As a result, a wide range of metallurgical bonding layers forms, which indicates an improved combination between the BTW1 and the Q345R. Additionally, it is discovered that the unbroken oxide films on the interface are composed of Mn, Si or Cr at the reductions of 50% and 65%. The SEM fractography of tensile specimen demonstrates that the BTW1 has significant dimple characteristics and possesses lower-sized dimples with the increment in reduction, suggesting that the toughness and bonding strength of the cladding plates would be improved by the increase of reduction. The results reveal that a high rolling reduction causes the interfacial oxide film broken and further forms a higher-sized composite metallurgical bonding interface. The peak microhardness is achieved near the interface.

The efficacy of “High Pick and Roll” in relation to the defence’s reaction and its effect on the result of the game

ABSTRACTThis research was conducted to find out how effective the High Pick and Roll is, according to the defence’s reaction. This survey also investigates the total impact of this offensive strategy on the game’s final result. The sample consisted of 20 randomly selected basketball games of the Olympic Games in Rio (2016). The results show that the outcome of the High Pick and Roll can affect the result of the game (p = 0.001). Furthermore, there is an important statistical difference between the effectiveness of High Pick and Roll against various defensive plays. When the defending team played Trail and Sag, the majority of the attacks were successful whereas when the team played Switch, Deny or Trap most of attacks were missed (p = 0.01). Finally, most of attacks ending with a ball handler’s Drive were successful while when the ball handler was shooting, a great percentage of Shots were missed (p = 0.01). Apart from that, the effectiveness of each defensive play and the effectiveness of the offensive outcomes were also depicted. From the data presented above, it is clear that the High Pick and Roll is a crucial factor in basketball and the information and statistics included in this paper could be useful for basketball coaches, both from theoretical and practical perspective.

Microstructure, mechanical properties and interface bonding mechanism of hot-rolled stainless steel clad plates at different rolling reduction ratios

The microstructure, interfacial characteristics, shear behavior, tensile properties and fracture morphologies of stainless steel clad plates fabricated by vacuum hot rolling at different rolling reduction ratios of 20%, 40%, 70%, 90% and 93.75% are investigated using optical microscope (OM), ultra-depth microscope, scanning electron microscope (SEM), electron probe microanalysis (EPMA) and universal testing in detail. With the increasing rolling reduction ratio, the refinement degree of microstructure is increased, while the thicknesses of interface alloy element diffusion zones including the decarburized, carburized layers and martensite zone are decreased. Due to the different interface bonding status, the shear fracture of clad plate rolled at a low reduction ratio of 40% is located at interface, while clad plates with high reduction ratios of 70% and 90% fracture at the decarburized layers. Therefore, interface shear strength is sharply and then slightly increased. Moreover, the interface bonding strength, tensile strength and interface deformation coordination are increased, while fracture elongation is increased firstly and then decreased with the increasing rolling reduction ratio, which are attributed to the competing mechanisms of grain refinement, work hardening, interface strengthening and intergranular cracks of carburized layer. Overall, the interfacial bonding mechanism can be related to the Mn-Si oxide inclusions rupture, alloying elements diffusion, phase transition and severe plastic deformation at high rolling temperature.

DNA sequence and shape are predictive for meiotic crossovers throughout the plant kingdom.

A better understanding of genomic features influencing the location of meiotic crossovers (COs) in plant species is both of fundamental importance and of practical relevance for plant breeding. Using CO positions with sufficiently high resolution from four plant species [Arabidopsis thaliana, Solanum lycopersicum (tomato), Zea mays (maize) and Oryza sativa (rice)] we have trained machine-learning models to predict the susceptibility to CO formation. Our results show that CO occurrence within various plant genomes can be predicted by DNA sequence and shape features. Several features related to genome content and to genomic accessibility were consistently either positively or negatively related to COs in all four species. Other features were found as predictive only in specific species. Gene annotation-related features were especially predictive for maize, whereas in tomato and Arabidopsis propeller twist and helical twist (DNA shape features) and AT/TA dinucleotides were found to be the most important. In rice, high roll (another DNA shape feature) and low CA dinucleotide frequency in particular were found to be associated with CO occurrence. The accuracy of our models was sufficient for Arabidopsis and rice (area under receiver operating characteristic curve, AUROC>0.5), and was high for tomato and maize (AUROC≫0.5), demonstrating that DNA sequence and shape are predictive for meiotic COs throughout the plant kingdom.

Comparison of different comminution flowsheets in terms of minerals liberation and separation properties

Comparative mineral liberation and separation tests of hematite ores were conducted for three comminution flowsheet options to produce relatively fine products at the 70% and 90% passing 74 µm: Option A uses a high pressure grinding roll (HPGR) with screening and subsequent ball milling, Option B uses an HPGR with an air classification, and Option C uses a jaw crusher with screening and subsequent ball milling.Cracks growing inwards are relatively flat along the direction of applied force during conventional crushing. However, cracks surround the weak interface during HPGR crushing, generating a large number of “mosaic-type” locked-particles. Mineral liberation was only affected after the final grinding mode, not by the crushing method before grinding. “Mosaic-type” locked-particles produced via the particle-bed breakage have no better way to liberate in downstream ball-mill grinding.Fine mineral grains are then detached from the ore under the high compressive stress, which leads to a significant and clean liberation of the mineral phases in HPGR coarse grinding. Overall, HPGR grinding is more beneficial to the quartz liberation, while ball mill grinding is more beneficial to oxidised iron minerals at a coarse grinding fineness; these advantages disappeared after the further fine grinding.The coarse-sized liberated quartz, although well-liberated, raised rejection of coarse gangue in magnetic separation during HPGR grinding. Finally, recovery of the HPGR grinding process increased by 4.4–5.2 percentage points higher than that of the ball milling process.

To improve strength and bio-corrosion resistance of Mg-4Zn alloy via high strain rate rolling combined with double aging

High strain rate rolling (HSRR) and artificial aging are conducted to improve mechanical properties and bio-corrosion resistance of Mg-4Zn alloy by modifying grain size and precipitates. The under-aged state is the most corrosion resistant among four states in single and double aging. Bio-corrosion resistance of the as-rolled alloy can be improved by double aging of 70 °C × 10 h + 160 °C × 2 h, resulting from stress relief and uniformly distributed nano-scale G.P. zones and β1′ precipitates.

Using social media for innovation – market segmentation of family firms

PurposeThe purpose of this study is to understand the strategy adopted by family firms in using social media for their business. Based on the social media usage, this paper attempts to segment family firms. To do so, a reactive – proactive – innovative (RPI) scale was developed for the study. Then, the family firms were categorised as reactive, proactive or innovative social media users. Further, based on the scale developed, clusters were created. Family firms were placed into different clusters based on the strategy that they had for using social media platforms for their business.Design/methodology/approachA pilot sample of 50 family firms and a main study of 256 Indian family firm entrepreneurs were surveyed through self-administered questionnaires. Factor analysis reduced the 12 scale-based questions to three distinct factors. Confirmatory factor analysis was then conducted on the main sample to confirm the constructs identified using exploratory factor analysis. Cluster analysis was used to build clusters of entrepreneurs who use social media as part of their digital marketing strategy.FindingsFindings reveal that the Indian family firm market is largely divided into four main segments. These segments represent distinct behaviours with respect to the use of social media. The four segments of family firm entrepreneurs were named as high rollers, ignorant inhabitants, trend-setters, combative crowd based on their social media usage behaviour. These clusters give deep insights into the strategic usage of social media by family firms.Research limitations/implicationsThe limitation of this study is that entrepreneurs from all Indian states were not considered in the sample because of cost implications. This research study has only created the segmentation of the family firms as reactive, proactive or innovative social media users and also has created the clusters as high rollers, ignorant inhabitants, trend-setters and combative crowd. Also, the reasons for their behaviour and root cause for the strategic usage have not been studied.Practical implicationsThis study reflects on current practices of family firms with respect to usage of social media and groups them into large identifiable clusters. Equipped with the findings from this study, the RPI scale developed for the study and the clusters created, entrepreneurs can now move towards better use of social media for innovation.Originality/valueAlthough past studies have advocated the use of social media to spur innovation in firms, this study segments the current market based on their practices. It allows readers to gauge the proportion of family firms using social media for innovation and paves the way for a change in behaviour amongst these firms.

Utilizing triazine/pyrimidine acceptor and carbazole-triphenylamine donor based bipolar novel host materials for highly luminescent green phosphorescent OLEDs with lower efficiency roll-off

In this work, two novel bipolar host materials were designed, synthesized and applied in green phosphorescent based OLEDs. Both the host materials, 4-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazol-9-yl)-N,N-diphenylaniline (TRZ 1) and 4-(2-(4,6-diphenylpyrimidin-2-yl)-9H-carbazol-9-yl)-N,N-diphenylaniline (PYR 1) exhibited high thermal stability, with decomposition temperatures of 425 °C and 400 °C, respectively. The triplet energy of PYR 1 (2.63 eV) was higher than that of TRZ 1 (2.44 eV), and facilitated suitable energy transfer to the green dopant. The PYR 1 based green device demonstrated an excellent maximum current efficiency of 48.7 cd/A and external quantum efficiency of 16.4%. Interestingly, the green device with PYR 1 showed an outstanding brightness of 95,870 cd/m2, which is three times greater than that of the reference CBP based device (31,370 cd/m2). The bipolar host PYR 1 is a promising material for high luminescent and low efficiency roll off applications, especially for green PhOLEDs.

A multi-field analysis of hydrodynamic lubrication in high speed rolling of metal strips

This paper presents a multi-field analysis of full hydrodynamic lubrication in high speed cold rolling of metal strips. A robust method was developed to solve the fluid field (the lubricant flow at the roll-strip interface) and solid field (the elastoplastic deformation of a metal strip) in a simple step. The elastoplastic deformation of the strip was solved by a dynamic explicit finite element method while the hydrodynamic pressure was calculated by the Reynolds equation. A cavitation boundary was introduced to determine the hydrodynamic pressure when the lubricant film breaks down. In addition, the coupled interaction between the lubricant flow and the elastoplastic deformation of the strip, which was caused by the hydrodynamic pressure and lubricant shear stress at the solid-liquid interface, were successfully treated by an additional penalty term. Both the pressure-driven term and lubricant shearing term were used to calculate the lubricant shear stress. The introduced penalty method enables a stable numerical calculation of Reynolds equation at a high hydrodynamic pressure. The method has overcome the traditional difficulties in solving the interface contact pressure within separated zones and has led to new understanding of the effects of rolling speed and pressure coefficient of the lubricant on the hydrodynamic pressure and lubricant film thickness.

Synthesis of styrene/isoprene/butadiene integrated rubber with wide glass transition temperature by reactive extrusion

In this work, styrene/isoprene/butadiene integrated rubber (SIBR) was synthesized with n-butyllithium as the initiator and tetrahydrofuran as structure modifier in a co-rotating intermeshing twin-screw extruder. The content of diene in these terpolymers reached a surprising 70 wt% by feeding the monomers in two different sites of the twin-screw extruder. 1H-NMR, GPC and TEM results showed that the molecular structures of terpolymers changed with the variation of feeding site. Dynamic mechanical analysis of the vulcanized SIBR showed that the terpolymer had a wide glass transition region, which assured an excellent combination of high antiskid properties and low rolling resistance. Different from traditional solution polymerization, the present work provides a green approach to prepare the SIBR via bulk polymerization without solvent.