scholarly journals Frictional Performance and Temperature Rise of a Mining Nonasbestos Brake Material during Emergency Braking

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Jiusheng Bao ◽  
Zengsong Li ◽  
Dongyang Hu ◽  
Yan Yin ◽  
Tonggang Liu
Keyword(s):  
Friction Coefficient ◽  
Surface Temperature ◽  
Tribological Performance ◽  
Emergency Braking ◽  
Lubricating Film ◽  
Friction Tester ◽  
Friction Disc ◽  
Frictional Performance ◽  
The Mean ◽  
Increment Ratio

By simulating emergency braking conditions of mine hoisters, tribological experiments of a mining nonasbestos brake material sliding on E355CC steel friction disc investigated a pad-on-disc friction tester. It is shown that, under combined influence of braking velocity and pressure, the lubricating film and micro-convex-apices on wear surface would have complex physicochemical reactions which make the instant friction coefficient rise gradually while the instant surface temperature rises first and then falls. With the antifriction effect from lubricating film and the desquamating of composite materials, the mean friction coefficient decreases first, then rises, and decreases again with the increasing of initial braking velocity. And with the existence of micro-convex-apices and variation from increment ratio of load and actual contacting area, it rises first and then falls with the increasing of braking pressure. However, the mean surface temperature rises obviously with the increasing of both initial braking velocity and braking pressure for growth of transformed kinetic energy. It is considered that the friction coefficient cannot be considered as a constant when designing brake devices for mine hoisters. And special attention should be paid to the serious influence of surface temperature on tribological performance of brake material during emergency braking.

Study on HVOF Sprayed Nickel Coated MoS2 Coatings

2012 ◽  
Vol 490-495 ◽  
pp. 3574-3577
Author(s):  
Bai Lin Zha ◽  
Xiao Jing Yuan ◽  
Li Jiang ◽  
Zhi Hong Zha
Keyword(s):  
Friction Coefficient ◽  
Abrasive Wear ◽  
Uniform Distribution ◽  
Failure Mode ◽  
Bonding Strength ◽  
Dry Friction ◽  
Tribological Performance ◽  
The Self ◽  
The Mean ◽  
Mos2 Coating

The self-lubricating coating which is dense in microstructure with low porosity and degradation is sprayed by HVOF and the spray powder is Nickel coated MoS2 with 22%wt of MoS2. The mean bonding strength and hardness of Ni-MoS2 coating is respectively about 13.68 MPa and HRB94.5. Tribological performance is evaluated by the test of dry friction coefficient, which fluctuates from 0.25 to 0.32, while the wear granule is symmetry with a uniform distribution in size, moreover, the experiment results indicate the main wear failure mode of coating is abrasive wear.

scholarly journals Tribological Performance of MoS2–WS2 Composite Film under the Atomic Oxygen Irradiation Conditions

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1407 ◽  
Author(s):  
Yanlong Fu ◽  
Dong Jiang ◽  
Desheng Wang ◽  
Xiaoming Gao ◽  
Ming Hu ◽  
...  
Keyword(s):  
Composite Film ◽  
Tribological Properties ◽  
Atomic Oxygen ◽  
Film Structure ◽  
Tribological Performance ◽  
Friction Process ◽  
Friction Noise ◽  
Lubricating Film ◽  
Friction Tester ◽  
Film Making

The oxidation and erosion of atomic oxygen are considered to be the most dangerous environmental factors for materials exposed to the aerospace environment. In order to investigate the effect of atomic oxygen on the lubricating film and improve the tribological properties, MoS2–WS2 composite film was prepared by the sputtering technique. The film structure and mechanical behavior were characterized and their vacuum tribological properties were evaluated by a friction tester. The composite film possessed better atomic oxygen (AO) resistance than pure film because of the dense structure. The tribological performance of composite film was different under the conditions after AO-irradiation and sliding and during AO-irradiation. After AO-irradiation, the tribological properties of composite film were similar to those before AO-irradiation. However, high friction noise, wear rate, and reduced wear duration were observed for the composite film under the AO-irradiation/friction process because of the continuous damage of the lubricating film due to the AO-irradiation. The addition of 16 at.% WS2 to the MoS2-based film changed the composite film structure and improved the oxidation resistance of the film, making the composite film exhibit better tribological performance than pure MoS2.

Ocular surface temperature differences in glaucoma

2021 ◽  
pp. 112067212110237
Author(s):  
Ari Leshno ◽  
Ori Stern ◽  
Yaniv Barkana ◽  
Noa Kapelushnik ◽  
Reut Singer ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Thermal Imaging ◽  
Ocular Surface ◽  
Open Angle Glaucoma ◽  
Tissue Temperature ◽  
Body Temperatures ◽  
Current Thinking ◽  
Imaging Camera ◽  
The Mean ◽  
The Difference

Purpose: Accumulating evidence suggests that neuroinflammation and immune response are part of the sequence of pathological events leading to optic nerve damage in glaucoma. Changes in tissue temperature due to inflammation can be measured by thermographic imaging. We investigated the ocular surface temperature (OST) profile of glaucomatous eyes to better understand the pathophysiology of these conditions. Methods: Subjects diagnosed with glaucoma (primary open angle glaucoma [POAG] or pseudo exfoliation glaucoma [PXFG]) treated at the Sam Rothberg Glaucoma Center (11/2019–11/2020.) were recruited. Healthy subjects with no ocular disease served as controls. The Therm-App thermal imaging camera was used for OST acquisition. Room and body temperatures were recorded, and the mean temperatures of the medial cantus, lateral cantus, and cornea were calculated with image processing software. Results: Thermographic images were obtained from 52 subjects (52 eyes: 25 POAG and 27 PXFG) and 66 controls (66 eyes). Eyes with glaucoma had a significantly higher OST compared to controls (mean 0.9 ± 0.3°C, p < 0.005). The difference between the two groups remained significant after adjustment for age, sex, intraocular pressure (IOP) and room and body temperatures. Lens status and topical IOP-lowering medication did not significantly affect OST. A subgroup analysis revealed that the OST was higher among eyes with POAG compared to eyes with PXFG, but not significantly. Conclusions: Differences in the OST between glaucomatous and normal eyes strengthens current thinking that inflammation affects the pathophysiology of glaucoma. Longitudinal studies are warranted to establish the prognostic value of thermographic evaluations in these patients.

The Influence of the Addition of Ti on the Mechanical Properties of W-S-Ti Coatings

2006 ◽  
Vol 514-516 ◽  
pp. 687-691 ◽  
Author(s):  
Manuel Evaristo ◽  
Ana Nossa ◽  
Albano Cavaleiro
Keyword(s):  
Mechanical Properties ◽  
Friction Coefficient ◽  
Tribological Performance ◽  
The Self ◽  
Wear Coefficient ◽  
Gradual Loss ◽  
Order Of Magnitude ◽  
Amorphous Structures ◽  
Ti Content ◽  
Ti Films

In this work, W-S-Ti films were deposited by r.f. magnetron sputtering, using simultaneously WS2 and Ti targets. The atomic percentage of Ti in the coating was varied from 0 at.% up to 28 at.%. No significant variations in the S/W ratio with the increase of Ti content were observed. The increasing Ti contents in the films led to a gradual loss of crystallinity. Coatings with contents greater than ≈ 16 at.% only presents a broad peak characteristic of amorphous structures. Alloying the films with Ti led to significant improvements in the hardness (from 0.3 to 8.9 GPa). Also, the adhesive critical load continuously grew with the increase of the Ti content in the films. The wear coefficient of the films dropped more than one order of magnitude with the increase of Ti content whereas the friction coefficient was kept fairly constant with just a small increase in relation to single W-S film. In conclusion, to have a good tribological performance, the addition of Ti to the films should be balanced in order that the increase of the mechanical properties does not lead to severe loss of the self-lubricant properties.

Skin friction and surface temperature of an insulated flat plate fixed in a fluctuating stream

1971 ◽  
Vol 46 (1) ◽  
pp. 165-175 ◽  
Author(s):  
Hiroshi Ishigaki
Keyword(s):  
Boundary Layer ◽  
Surface Temperature ◽  
Flat Plate ◽  
Skin Friction ◽  
High Frequency ◽  
Energy Equation ◽  
Oscillation Amplitude ◽  
Flow Oscillation ◽  
Velocity Amplitude ◽  
The Mean

The time-mean skin friction of the laminar boundary layer on a flat plate which is fixed at zero incidence in a fluctuating stream is investigated analytically. Flow oscillation amplitude outside the boundary layer is assumed constant along the surface. First, the small velocity-amplitude case is treated, and approximate formulae are obtained in the extreme cases when the frequency is low and high. Next, the finite velocity-amplitude case is treated under the condition of high frequency, and it is found that the formula obtained for the small-amplitude and high-frequency case is also valid. These results show that the increase of the mean skin friction reduces with frequency and is ultimately inversely proportional to the square of frequency.The corresponding energy equation is also studied simultaneously under the condition of zero heat transfer between the fluid and the surface. It is confirmed that the time-mean surface temperature increases with frequency and tends to be proportional to the square root of frequency. Moreover, it is shown that the timemean recovery factor can be several times as large as that without flow oscillation.

Tribological performance of self-lubricated polyamide6/boric oxide composites after water conditioning

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kawaljit Singh Randhawa ◽  
Ashwin Patel
Keyword(s):  
Friction Coefficient ◽  
Abrasion Resistance ◽  
Tribological Performance ◽  
Boric Oxide ◽  
Resistance Testing ◽  
Tribological Behaviour ◽  
Content Type ◽  
Wear Rates ◽  
Water Conditioning ◽  
Oxide Composites

Purpose This paper aims to investigate the tribological performance, i.e. abrasion resistance, friction coefficient and wear rates, of self-lubricated water conditioned polyamide6/boric oxide composites. Design/methodology/approach Polyamide6 and polyamide6/boric oxide self-lubricated composites were immersed in water for 15 days to analyze the effect of water conditioning on friction, wear and abrasion resistance. Tribological testing on pin-on-disc tribometer and abrasion resistance testing on TABER abrader were performed to see the friction coefficient and wear rates of materials. The scanning electron microscopy (SEM) characterizations were performed to analyze the wear tracks. Findings Tribological testing results revealed the loss in abrasive resistance, but there was an improvement in frictional coefficient and wear rates with steel after water absorption. The SEM images clearly show less depth of wear tracks in water-conditioned materials than dry ones. Water conditioning was found supportive in the formation of smooth lubricating transfer film on steel disc during the tribological testing. Originality/value The tribological behaviour of polymer composites is different in dry and in high humidity or water conditions. Experiments were performed to investigate B2O3 solid lubricant filler effectiveness on tribological behaviour of water-conditioned polyamide composites. Bonding between polyamide6 and water molecules plus the formation of orthoboric acid was found advantageous in decreasing the friction coefficient and wear rates of composites.

scholarly journals An evapotranspiration model self-calibrated from remotely sensed surface soil moisture, land surface temperature and vegetation cover fraction: application to disaggregated SMOS and MODIS data

2019 ◽  
Author(s):  
Bouchra Ait Hssaine ◽  
Olivier Merlin ◽  
Jamal Ezzahar ◽  
Nitu Ojha ◽  
Salah Er-raki ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Energy Balance ◽  
Surface Temperature ◽  
Land Surface Temperature ◽  
Vegetation Cover ◽  
Land Surface ◽  
Surface Soil ◽  
Surface Soil Moisture ◽  
Wide Range ◽  
The Mean

Abstract. Thermal-based two-source energy balance modeling is very useful for estimating the land evapotranspiration (ET) at a wide range of spatial and temporal scales. However, the land surface temperature (LST) is not sufficient for constraining simultaneously both soil and vegetation flux components in such a way that assumptions (on either the soil or the vegetation fluxes) are commonly required. To avoid such assumptions, a new energy balance model (TSEB-SM) was recently developed in Ait Hssaine et al. (2018a) to integrate the microwave-derived near-surface soil moisture (SM), in addition to the thermal-derived LST and vegetation cover fraction (fc). Whereas, TSEB-SM has been recently tested using in-situ measurements, the objective of this paper is to evaluate the performance of TSEB-SM in real-life using 1 km resolution MODIS (Moderate resolution imaging spectroradiometer) LST and fc data and the 1 km resolution SM data disaggregated from SMOS (Soil Moisture and Ocean Salinity) observations by using DisPATCh. The approach is applied during a four-year period (2014–2018) over a rainfed wheat field in the Tensift basin, central Morocco, during a four-year period (2014–2018). The field was seeded for the 2014–2015 (S1), 2016–2017 (S2) and 2017–2018 (S3) agricultural season, while it was not ploughed (remained as bare soil) during the 2015–2016 (B1) agricultural season. The mean retrieved values of (arss, brss) calculated for the entire study period using satellite data are (7.32, 4.58). The daily calibrated αPT ranges between 0 and 1.38 for both S1 and S2. Its temporal variability is mainly attributed to the rainfall distribution along the agricultural season. For S3, the daily retrieved αPT remains at a mostly constant value (∼ 0.7) throughout the study period, because of the lack of clear sky disaggregated SM and LST observations during this season. Compared to eddy covariance measurements, TSEB driven only by LST and fc data significantly overestimates latent heat fluxes for the four seasons. The overall mean bias values are 119, 94, 128 and 181 W/m2 for S1, S2, S3 and B1 respectively. In contrast, these errors are much reduced when using TSEB-SM (SM and LST combined data) with the mean bias values estimated as 39, 4, 7 and 62 W/m2 for S1, S2, S3 and B1 respectively.

scholarly journals MEAN SURFACE TEMPERATURE OF JAPANESE QUAIL EXPOSED TO DIFFERENT LEVELS OF AIR VELOCITY AND TEMPERATURE AT START OF LAY

2020 ◽  
Vol 4 (2) ◽  
pp. 15-18
Author(s):  
Tatiany Carvalho dos Santos ◽  
Richard Stephen Gates ◽  
Ilda De Fátima Ferreira Tinôco ◽  
Sérgio Zolnier ◽  
Letícia Cibele da Silva Ramos Freitas
Keyword(s):  
Surface Temperature ◽  
Air Temperature ◽  
Japanese Quail ◽  
Systems Engineering ◽  
Air Velocity ◽  
Agricultural Engineering ◽  
Initial Stage ◽  
Different Temperatures ◽  
The Mean ◽  
Different Levels

The objective of this study was to evaluate the effect of different air velocities and temperature at the feeder on mean surface temperature of Japanese quail during the initial stage of laying. The experiment was carried out at the Center for Research in Environment and Agroindustry Systems Engineering (AMBIAGRO), Department of Agricultural Engineering, Federal University of Viçosa, Viçosa/MG, Brazil. A total of 216 Japanese quail in the initial laying phase were placed in four environmental chambers with different temperatures and air velocity, where they were housed and distributed randomly in 2 galvanized wire cages, with 3 partitions each and 27 birds/cage, and a density of approximately 155.6 cm²/bird. The experimental design consisted of randomized blocks with replications of two treatments (air velocity at the feeder: 0, 1, 2, and 3 m/s and air temperature: 17, 23, 29 and 35°C). The mean surface temperature was analyzed by Two-Way ANOVA, with treatment means separated by the Tukey test (P < 0.05). There was a significant positive correlation between air temperature and mean surface temperature (MST). Air velocity is important in removing heat from the surface of birds.

scholarly journals Effect of Graphene Oxide and Graphite on Dry Sliding Wear Behavior of Polyester Composites

2018 ◽  
Vol 55 (1) ◽  
pp. 102-110 ◽  
Author(s):  
Marian Bastiurea ◽  
Dumitru Dima ◽  
Gabriel Andrei
Keyword(s):  
Graphene Oxide ◽  
Friction Coefficient ◽  
Wear Rate ◽  
Wear Behavior ◽  
Positive Influence ◽  
Tribological Performance ◽  
Dry Sliding Wear ◽  
Melt Mixing ◽  
Polyester Composites ◽  
All Speeds

Graphene oxide and graphite filled polyester composites were prepared by using conventional melt-mixing methods in order to improve tribological performance of polyester. It was investigated friction stability, microhardness, friction coefficient, and specific wear rate of the composites in details. It was found that the presence of graphite and graphene oxide influenced friction coefficient and wear rate of the composites. Graphene oxide decreased wear rate with increasing of test speed and graphite decreased wear rate for composite for all speeds. Tribological performance of the polyester/graphene composites is mainly attributed to bigger thermal conductivity for graphene, which can easily dissipate the heat which appears during the friction process at bigger forces. The positive influence of graphite on coefficient of friction (COF) of the composites is the result of the clivage of graphite layers during the loadings due to van der Waals weak bonds between the graphite layers.

scholarly journals Comparison of Land Surface Temperature During and Before the Emergence of Covid-19 using Modis Imagery in Wuhan City, China

2020 ◽  
Vol 34 (1) ◽  
Author(s):  
Hamim Zaky Hadibasyir ◽  
Seftiawan Samsu Rijal ◽  
Dewi Ratna Sari
Keyword(s):  
Surface Temperature ◽  
Land Surface Temperature ◽  
Land Surface ◽  
Anthropogenic Activities ◽  
Temporal Analysis ◽  
The Past ◽  
Modis Imagery ◽  
Rapid Transmission ◽  
The Mean ◽  
Spatio Temporal

Coronavirus disease (COVID-19) was firstly identified in Wuhan, China. By 23rd January 2020, China’s Government made a decision to execute lockdown policy in Wuhan due to the rapid transmission of COVID-19. It is essential to investigate the land surface temperature (LST) dynamics due to changes in level of anthropogenic activities. Therefore, this study aims (1) to investigate mean LST differences between during, i.e., December 2019 to early March 2020, and before the emergence of COVID-19 in Wuhan; (2) to conduct spatio-temporal analysis of mean LST with regards to lockdown policy; and (3) to examine mean LST differences for each land cover type. MODIS data consist of MOD11A2 and MCD12Q1 were employed. The results showed that during the emergence of COVID-19 with lockdown policy applied, the mean LST was lower than the mean LST of the past three years on the same dates. Whereas, during the emergence of COVID-19 without lockdown policy applied, the mean LST was relatively higher than the mean LST of the past three years. In addition, the mean LST of built-up areas experienced the most significant differences between during the emergence of COVID-19 with lockdown policy applied in comparison to the average of the past three years.

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