Simulation of the Tooth Helix Angle Influence on the Vibration of a Single Stage Helical Gearbox

2014 ◽  
Vol 658 ◽  
pp. 83-88
Author(s):  
Zoltan Iosif Korka ◽  
Vasile Cojocaru ◽  
Calin Octavian Miclosina
Keyword(s):  
Environmental Pollution ◽  
Current Trend ◽  
Dynamic Contact ◽  
Helix Angle ◽  
Single Stage ◽  
Dynamic Loads ◽  
Speed Increase ◽  
Wide Range ◽  
A Priority

The current trend in the construction of gearboxes, regarding the speed increase, favors the increase of the dynamic loads which are accompanying the operation of these kinds of machines. The phenomena of dynamic contact like frictions, collisions and shocks which are taking place in cinematic couples, engines and mechanisms during their movement, are generating vibrations in a wide range of frequencies. Vibrations produced by gearboxes became characteristically indicators for assessing their quality. Therefore, the decrease of vibrations produced in the gear transmissions became lately a priority, being one of the combat methods in the fight against environmental pollution.

Characteristics of air entrainment during dynamic wetting failure along a planar substrate

2014 ◽  
Vol 747 ◽  
pp. 119-140 ◽  
Author(s):  
E. Vandre ◽  
M. S. Carvalho ◽  
S. Kumar
Keyword(s):  
High Speed ◽  
Water Solution ◽  
Air Entrainment ◽  
Dynamic Contact ◽  
Operating Conditions ◽  
Dynamic Wetting ◽  
Glycerol Water ◽  
Planar Substrate ◽  
Wide Range ◽  
Stationary Plate

AbstractCharacteristic substrate speeds and meniscus shapes associated with the onset of air entrainment are studied during dynamic wetting failure along a planar substrate. Using high-speed video, the behaviour of the dynamic contact line (DCL) is recorded as a tape substrate is drawn through a bath of a glycerol/water solution. Air entrainment is identified by triangular air films that elongate from the DCL above some critical substrate speed. Meniscus confinement within a narrow gap between the substrate and a stationary plate is shown to delay air entrainment to higher speeds for a wide range of liquid viscosities, expanding upon the findings of Vandre, Carvalho & Kumar (J. Fluid Mech., vol. 707, 2012, pp. 496–520). A pressurized liquid reservoir controls the meniscus position within the confinement gap. It is found that liquid pressurization further postpones air entrainment when the meniscus is located near a sharp corner along the stationary plate. Meniscus shapes recorded near the DCL demonstrate that operating conditions influence the size of entrained air films, with smaller films appearing in the more viscous solutions. Regardless of size, air films become unstable to thickness perturbations and ultimately rupture, leading to the entrainment of air bubbles. Recorded critical speeds and air-film sizes compare well to predictions from a hydrodynamic model for dynamic wetting failure, suggesting that strong air stresses near the DCL trigger the onset of air entrainment.

scholarly journals Potential impacts of climate change on Mongolia’s plant protection status quo

2018 ◽  
Vol 24 (02) ◽  
pp. 26-32
Author(s):  
Batkhuyag B ◽  
Batnaran Kh
Keyword(s):  
Climate Change ◽  
Climate Modeling ◽  
Plant Protection ◽  
Current Trend ◽  
Animal Husbandry ◽  
Distribution Patterns ◽  
Agricultural Pests ◽  
Migratory Locust ◽  
Colorado Beetle ◽  
Wide Range

Mongolia’s 2030 Sustainable Development Vision set a goal to be a self-sufficient in grain, potatoes and vegetables by 2030. However, Mongolia’s pastoral animal husbandry and rain-fed agriculture are extremely sensitive to climate change. The Asian migratory locust is considered as the most harmful grasshopper in the world. Until 1970th, these locust’s distribution areas in Mongolia were confined to oasis of Gobi deserts. A study on Asian migratory locust in Russia predicts distribution and formation of new permanent habitats of the locust in Chita oblast, Krasnoyarsk territory and Republic of Tyva. The Colorado beetle is one of the world’s most infamous invasive species due to its rapid adaptation to a wide range of ecological conditions and ability to disperse long distances. The climate modeling of Colorado beetle showed that with current trend, the beetle will expand its distribution into the most eastern and north-eastern regions of the Russian Federation. In China, the Colorado beetle was first detected in Xinjiang in 1993 and subsequently spread eastward. In China the Colorado beetle is currently expanding its areas at rate of 25 kms year (12-45 kms/year). Both species’ distribution patterns in neighboring countries show eventual establishment of permanent habitats around Mongolia. Their invasion to Mongolia will threaten country’s food security due to direct destruction of cereal and potato crops, and increased application of highly toxic pesticides. In light of these threats, Mongolia should start taking serious preventive measures by increasing surveillance and dedicated risk assessment studies for potential agricultural pests and diseases.

scholarly journals Efficient and Innovative Polishing Processes for Smoothing Complex Surface Geometries and Internal Contours on Brittle-Hard Components

2020 ◽  
Vol 238 ◽  
pp. 03010
Author(s):  
Marcel Binder ◽  
Sebastian Henkel ◽  
Anne-Marie Schwager ◽  
Christoph Letsch ◽  
Jens Bliedtner ◽  
...  
Keyword(s):  
Current Trend ◽  
Glass Ceramics ◽  
Complex Surface ◽  
Fused Silica ◽  
Free Form ◽  
Resource Saving ◽  
Processing Technologies ◽  
Wide Range ◽  
Monolithic Components ◽  
Free Form Surfaces

The material fused silica, as well as other brittle-hard materials such as glass ceramics, have great potential for use in a wide range of applications due to their special material properties. The technical advantages of these materials require sophisticated processing technologies, including polishing steps, in order to be able to use these interesting materials advantageously. In addition, a current trend in modern optical manufacturing is the use of free-form surfaces and monolithic components that combine several optical and mechanical functions in one part. Novel or improved processes are needed in order to meet future requirements for resource-saving and effective production methods at the same time.

The Environmental Pollution Analysis of Aircraft

2012 ◽  
Vol 518-523 ◽  
pp. 2259-2262
Author(s):  
Xiao Jie Chen
Keyword(s):  
Environmental Factors ◽  
Environmental Pollution ◽  
Environmental Influences ◽  
Environment Pollution ◽  
Regulatory Issues ◽  
Environmental Pressure ◽  
Pressure Groups ◽  
Aircraft Flight ◽  
Engine Design ◽  
Wide Range

The Environmental factors cover a wide range of aspects but noise and emissions are the main regulatory issues which affect the design of the aircraft. Both are largely associated with engine design aspects and aircraft flight profiles. With the expected growth in air traffic at the major airports the environmental pressure groups will become more vocal. This paper shows the influence of airworthiness and environmental influences of aircraft. Both noise and emission pollution were discussed. Several methods were given to reduce these environment pollution on the base of the analysis.

scholarly journals Young voices in mental health care: Exploring children’s and adolescents’ service experiences and preferences

2016 ◽  
Vol 22 (1) ◽  
pp. 140-151 ◽  
Author(s):  
Stefan Persson ◽  
Curt Hagquist ◽  
Daniel Michelson
Keyword(s):  
Mental Health ◽  
Health Care ◽  
Mental Health Care ◽  
Children And Adolescents ◽  
Qualitative Content Analysis ◽  
Developmental Needs ◽  
Mental Health Clinics ◽  
Wide Range ◽  
Community Mental Health Clinics ◽  
A Priority

The development of ‘youth-friendly’ services has become a priority across a wide range of health-care contexts. However, relatively few studies have specifically examined users’ experiences of, and preferences for, child and adolescent mental health care. The current study investigated young service users’ views of outpatient and community mental health clinics in Sweden, based on two data sources. First, focus group interviews were conducted with seven children and adolescents (aged 10–18 years) to explore both positive and negative experiences of mental health care. Second, written suggestions about specific service improvements were obtained from 106 children and adolescents. Qualitative content analysis revealed three overarching themes: ‘Accessibility’, ‘Being heard and seen’ and ‘Usefulness of sessions’. Young people’s recommendations for improving practice included more convenient appointment times, offered in welcoming settings; opportunities to communicate more openly with clinical staff, enabling sensitive discussion of mental health and wider personal issues; and more structured treatments that offer greater credibility and relevance to young people’s mental health and developmental needs. Young people also discussed being compelled by parents and school professionals to engage in treatment. Attending to young people’s preferences must be a priority in order to overcome ambivalence about session attendance, and enhance treatment participation and outcomes.

EXPERIMENTAL INVESTIGATION OF A FOIL BEARING STRUCTURE WITH A POLYMER COATING UNDER DYNAMIC LOADS

Tribologia ◽  
2018 ◽  
Vol 281 (5) ◽  
pp. 5-12 ◽  
Author(s):  
Paweł BAGIŃSKI ◽  
Grzegorz ŻYWICA
Keyword(s):  
Excitation Frequency ◽  
Dynamic Loads ◽  
Test Rig ◽  
Static Tests ◽  
Structural Part ◽  
Foil Bearing ◽  
Wide Range ◽  
Load Tests ◽  
Excitation Force ◽  
Stiffness And Damping

This paper presents the results of research on the structural elements of a prototypical foil bearing in terms of its dynamic loads. In the framework of dynamic tests, several dozens of measurement series were carried out on a test rig specially prepared for this purpose. Dynamic excitations were applied using an electromagnetic exciter that enables changing the amplitude and frequency of the excitation force. Owing to this, it was possible to determine characteristics of the tested system in a wide range of loads and frequencies. A value of 400 Hz was assumed as the upper limit of the excitation frequency. The test rig enabled considering the direction of dynamic loads, which, as it turned out, had a significant impact on the obtained results. The research findings show that both the amplitude and frequency of an excitation force have a major impact on the stiffness and damping of the structural part of the foil bearing. The results of dynamic load tests complement the results of static tests performed earlier.

scholarly journals Separation and Recovery of Fine Particles from Waste Circuit Boards Using an Inflatable Tapered Diameter Separation Bed

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Chenlong Duan ◽  
Cheng Sheng ◽  
Lingling Wu ◽  
Yuemin Zhao ◽  
Jinfeng He ◽  
...  
Keyword(s):  
Environmental Pollution ◽  
Printed Circuit Boards ◽  
Fine Particles ◽  
Metal Recovery ◽  
Circuit Board ◽  
Circuit Boards ◽  
Recovery Rates ◽  
Operational Conditions ◽  
Printed Circuit ◽  
Wide Range

Recovering particle materials from discarded printed circuit boards can enhance resource recycling and reduce environmental pollution. Efficiently physically separating and recovering fine metal particles (−0.5 mm) from the circuit boards are a key recycling challenge. To do this, a new type of separator, an inflatable tapered diameter separation bed, was developed to study particle motion and separation mechanisms in the bed’s fluid flow field. For 0.5–0.25 mm circuit board particles, metal recovery rates ranged from 87.56 to 94.17%, and separation efficiencies ranged from 87.71 to 94.20%. For 0.25–0.125 mm particles, metal recovery rates ranged from 84.76 to 91.97%, and separation efficiencies ranged from 84.74 to 91.86%. For superfine products (−0.125 mm), metal recovery rates ranged from 73.11 to 83.04%, and separation efficiencies ranged from 73.00 to 83.14%. This research showed that the inflatable tapered diameter separation bed achieved efficient particle separation and can be used to recover fine particles under a wide range of operational conditions. The bed offers a new mechanical technology to recycle valuable materials from discarded printed circuit boards, reducing environmental pollution.

scholarly journals A health assessment tool for multiple risk factors for obesity: age and sex differences in the prediction of body mass index

2010 ◽  
Vol 104 (2) ◽  
pp. 298-307 ◽  
Author(s):  
Julie A. Chambers ◽  
Vivien Swanson
Keyword(s):  
Physical Activity ◽  
Risk Factors ◽  
Healthy Eating ◽  
Assessment Tool ◽  
Current Trend ◽  
Eating Behaviour ◽  
Physical Activity Participation ◽  
Activity Participation ◽  
Age Group ◽  
Wide Range

The aim was to establish the relative importance of multiple dietary, activity and other risk factors in determining BMI. A cross-sectional survey was conducted with 322 adults (71 % female; aged 18–79 years; BMI 16·5–40·9 kg/m2) using a previously developed, psychometrically tested, seventy-three-item questionnaire covering a wide range of obesity risk factors (consisting of five dietary, five activity and seven other risk factor subscales). Outcome was self-reported weight and height for BMI, cross-validated with items on clothes size and perceived need to lose weight. Stepwise regression analysis predicted 25–55 % of the variance in BMI with physical activity participation, current and past dieting behaviour, amount eaten, and age being the most important predictors. The association of lower BMI and younger age appeared to be due to higher activity levels, as younger participants reported much less healthy eating behaviour than the older age group. Amount eaten and physical activity participation were stronger predictors of BMI than other factors including healthy eating and use of mechanised transport. Results showed that the relationship between various risk factors and obesity may differ by both sex and age group, suggesting that different interventions may need to be targeted at different groups. The higher-risk eating behaviour observed in younger participants is of concern and needs to be addressed, if the current trend of rising obesity levels is to be halted.

scholarly journals Gait Speed Modulations Are Proportional to Grades of Virtual Visual Slopes—A Virtual Reality Study

2021 ◽  
Vol 12 ◽  
Author(s):  
Amit Benady ◽  
Sean Zadik ◽  
Gabriel Zeilig ◽  
Sharon Gilaie-Dotan ◽  
Meir Plotnik
Keyword(s):  
Virtual Reality ◽  
Gait Speed ◽  
Visual Cues ◽  
Large Scale ◽  
Dynamic Environment ◽  
Speed Increase ◽  
Actual Surface ◽  
Gravitational Forces ◽  
Speed Modulation ◽  
Wide Range

Gait is a complex mechanism relying on integration of several sensory inputs such as vestibular, proprioceptive, and visual cues to maintain stability while walking. Often humans adapt their gait to changes in surface inclinations, and this is typically achieved by modulating walking speed according to the inclination in order to counteract the gravitational forces, either uphill (exertion effect) or downhill (braking effect). The contribution of vision to these speed modulations is not fully understood. Here we assessed gait speed effects by parametrically manipulating the discrepancy between virtual visual inclination and the actual surface inclination (aka visual incongruence). Fifteen healthy participants walked in a large-scale virtual reality (VR) system on a self-paced treadmill synchronized with projected visual scenes. During walking they were randomly exposed to varying degrees of physical-visual incongruence inclinations (e.g., treadmill leveled & visual scene uphill) in a wide range of inclinations (−15° to +15°). We observed an approximately linear relation between the relative change in gait speed and the anticipated gravitational forces associated with the virtual inclinations. Mean relative gait speed increase of ~7%, ~11%, and ~17% were measured for virtual inclinations of +5°, +10°, and +15°, respectively (anticipated decelerating forces were proportional to sin[5°], sin[10°], sin[15°]). The same pattern was seen for downhill virtual inclinations with relative gait speed modulations of ~-10%, ~-16%, and ~-24% for inclinations of −5°, −10°, and −15°, respectively (in anticipation of accelerating forces). Furthermore, we observed that the magnitude of speed modulation following virtual inclination at ±10° was associated with subjective visual verticality misperception. In conclusion, visual cues modulate gait speed when surface inclinations change proportional to the anticipated effect of the gravitational force associated the inclinations. Our results emphasize the contribution of vision to locomotion in a dynamic environment and may enhance personalized rehabilitation strategies for gait speed modulations in neurological patients with gait impairments.

scholarly journals NMR Relaxivities of Paramagnetic Lanthanide-Containing Polyoxometalates

Molecules ◽  
2021 ◽  
Vol 26 (24) ◽  
pp. 7481
Author(s):  
Aiswarya Chalikunnath Venu ◽  
Rami Nasser Din ◽  
Thomas Rudszuck ◽  
Pierre Picchetti ◽  
Papri Chakraborty ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Contrast Agents ◽  
Current Trend ◽  
Image Contrast ◽  
Relaxation Rates ◽  
Wide Range ◽  
Magnetic Resonance Imaging Mri ◽  
Nmr Sensitivity ◽  
Applied Fields

The current trend for ultra-high-field magnetic resonance imaging (MRI) technologies opens up new routes in clinical diagnostic imaging as well as in material imaging applications. MRI selectivity is further improved by using contrast agents (CAs), which enhance the image contrast and improve specificity by the paramagnetic relaxation enhancement (PRE) mechanism. Generally, the efficacy of a CA at a given magnetic field is measured by its longitudinal and transverse relaxivities r1 and r2, i.e., the longitudinal and transverse relaxation rates T1−1 and T2−1 normalized to CA concentration. However, even though basic NMR sensitivity and resolution become better in stronger fields, r1 of classic CA generally decreases, which often causes a reduction of the image contrast. In this regard, there is a growing interest in the development of new contrast agents that would be suitable to work at higher magnetic fields. One of the strategies to increase imaging contrast at high magnetic field is to inspect other paramagnetic ions than the commonly used Gd(III)-based CAs. For lanthanides, the magnetic moment can be higher than that of the isotropic Gd(III) ion. In addition, the symmetry of electronic ground state influences the PRE properties of a compound apart from diverse correlation times. In this work, PRE of water 1H has been investigated over a wide range of magnetic fields for aqueous solutions of the lanthanide containing polyoxometalates [DyIII(H2O)4GeW11O39]5– (Dy-W11), [ErIII(H2O)3GeW11O39]5– (Er-W11) and [{ErIII(H2O)(CH3COO)(P2W17O61)}2]16− (Er2-W34) over a wide range of frequencies from 20 MHz to 1.4 GHz. Their relaxivities r1 and r2 increase with increasing applied fields. These results indicate that the three chosen POM systems are potential candidates for contrast agents, especially at high magnetic fields.

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