scholarly journals TIDAL ASYMMETRY IN MANGROVE CREEKS

2011 ◽  
Vol 14 (4) ◽  
pp. 86-92
Author(s):  
Phuoc Luong Hong Vo ◽  
Phuc Tran Duy Le
Keyword(s):  
Friction Coefficient ◽  
Great Influence ◽  
Biosphere Reserve ◽  
Current Speed ◽  
Ho Chi Minh City ◽  
Tidal Asymmetry ◽  
Simple Analytical Model ◽  
Friction Coefficients ◽  
Mangrove Swamp ◽  
Can Gio Mangrove

A simple analytical model for flow in the creeks is formulated, built up and applied in the real conditions in Nang Hai creek, Can Gio mangrove Biosphere Reserve (Ho Chi Minh city).Observed data of current speed and water level in the creek in the year of 2005 were used to find the friction coefficients in the mangrove swamp and to apply in the model. Results from calculated modeling show obviously the tidal asymmetry in mangrove creek. The peaks of current speed at flood and ebb tides are not equal as the swamp is inundated. The friction coefficients have the great influence in the tidal asymmetry. The friction coefficient in the creek can change remarkably the current speed in the creek, inducing the changes of the current speed peaks. The friction coefficient in the swamp has much less influenced to the current speed in the creeks.

scholarly journals BENTHIC DIATOM COMMUNITIES OF MANGROVE FORESTS OF CAN GIO BIOSHPERE RESERVE, HO CHI MINH CITY

2009 ◽  
Vol 12 (7) ◽  
pp. 72-78
Author(s):  
Hang Thi Gia Nguyen ◽  
Triet Tran ◽  
Tung Thanh Nguyen
Keyword(s):  
Mixed Forest ◽  
Biosphere Reserve ◽  
Root Surface ◽  
Benthic Diatom ◽  
Ho Chi Minh City ◽  
Mangrove Forests ◽  
Surface Sampling ◽  
Diatom Communities ◽  
The Difference ◽  
Can Gio Mangrove

This study investigated benthic diatom communities of mangrove forests at Can Gio Mangrove Biosphere Reserve, Ho Chi Minh City, Vietnam. Samples were collected on two substrates: mud surface and living root surface. Sampling locations were placed in four types of mangrove vegetation: mud flat (without vegetation), Rhizophora forests, mixed forest of Avicennia-Rhizophora and Avicennia forest along three tidal creeks during wet and dry seasons of 2004-2005. A total of 348 taxa were identified, of which 100 taxa belong to the Order Centrales and 238 belong to the Order Pentales. There were significant differences in benthic diatom species richness and species composition between two types of substrates and among different mangrove forest types. The difference between wet and dry season was not significant.

scholarly journals Studying the meeting of practical requirements of ecotourism in the Can Gio Mangrove World Biosphere Reserve, Ho Chi Minh City

2016 ◽  
Vol 19 (4) ◽  
pp. 95-103
Author(s):  
Loan Thanh Ngo
Keyword(s):  
Human Resources ◽  
Cultural Values ◽  
Biosphere Reserve ◽  
Ho Chi Minh City ◽  
Can Gio Mangrove

Ecotourism is considered as a pre-eminent form of tourism that helps to balance economic purpose and conservation of natural and cultural values of the area. However, in order to conduct efficient ecotourism activities, besides a specific ecosystem, the locality must have proper human resources as well as responsible tourists. This paper presents some findings from our research on how the labors’ planning and working for ecotourism spots in Can Gio to meet the requirements of ecotourism. A survey with tourists was also realized. The result raises some concerns about the sustainability of ecotourism in Can Gio.

scholarly journals New Equation for Predicting Pipe Friction Coefficients Using the Statistical Based Entropy Concepts

Entropy ◽  
2021 ◽  
Vol 23 (5) ◽  
pp. 611
Author(s):  
Yeon-Woong Choe ◽  
Sang-Bo Sim ◽  
Yeon-Moon Choo
Keyword(s):  
Friction Coefficient ◽  
Accurate Determination ◽  
Mean Velocity ◽  
Friction Coefficients ◽  
Flow Discharge ◽  
Comparison Results ◽  
Flow Loss ◽  
Key Variables ◽  
New Equation

In general, this new equation is significant for designing and operating a pipeline to predict flow discharge. In order to predict the flow discharge, accurate determination of the flow loss due to pipe friction is very important. However, existing pipe friction coefficient equations have difficulties in obtaining key variables or those only applicable to pipes with specific conditions. Thus, this study develops a new equation for predicting pipe friction coefficients using statistically based entropy concepts, which are currently being used in various fields. The parameters in the proposed equation can be easily obtained and are easy to estimate. Existing formulas for calculating pipe friction coefficient requires the friction head loss and Reynolds number. Unlike existing formulas, the proposed equation only requires pipe specifications, entropy value and average velocity. The developed equation can predict the friction coefficient by using the well-known entropy, the mean velocity and the pipe specifications. The comparison results with the Nikuradse’s experimental data show that the R2 and RMSE values were 0.998 and 0.000366 in smooth pipe, and 0.979 to 0.994 or 0.000399 to 0.000436 in rough pipe, and the discrepancy ratio analysis results show that the accuracy of both results in smooth and rough pipes is very close to zero. The proposed equation will enable the easier estimation of flow rates.

scholarly journals Theoretical Studies of the Interaction between Screw Surface and Material in the Mixer

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 962
Author(s):  
Andrzej Marczuk ◽  
Vasily Sysuev ◽  
Alexey Aleshkin ◽  
Petr Savinykh ◽  
Nikolay Turubanov ◽  
...  
Keyword(s):  
Friction Coefficient ◽  
High Efficiency ◽  
Animal Feed ◽  
Structural Features ◽  
Power Demand ◽  
Friction Coefficients ◽  
Length Unit ◽  
Mixing Chamber ◽  
Size Of Particles ◽  
The Impact

Mixing is one of the most commonly used processes in food, animal feed, chemical, cosmetic, etc., industries. It is supposed to provide high-quality homogenous, nutritious mixtures. To provide appropriate mixing of materials while maintaining the process high efficiency and low energy consumption it is crucial to explore and describe the material flow caused by the movement of mixing elements and the contact between particles. The process of mixing is also affected by structural features of the machine components and the mixing chamber, speed of mixing, and properties of the mixed materials, such as the size of particles, moisture, friction coefficients. Thus, modeling of the phenomena that accompany the process of mixing using the above-listed parameters is indispensable for appropriate implementation of the process. The paper provides theoretical power calculations that take into account the material speed change, the impact of the material friction coefficient on the screw steel surface and the impact of the friction coefficient on the material, taking into account the loading height of the mixing chamber and the chamber loading value. Dependencies between the mixer power and the product degree of fineness, rotational speed of screw friction coefficients, the number of windings per length unit, and width of the screw tape have been presented on the basis of a developed model. It has been found that power increases along with an increase in the value of these parameters. Verification of the theoretical model indicated consistence of the predicted power demand with the power demand determined in tests performed on a real object for values of the assumed, effective loading, which was 65–75%.

scholarly journals Comparison of Microplastic Pollution in Beach Sediment and Seawater at UNESCO Can Gio Mangrove Biosphere Reserve

2021 ◽  
pp. 2100044
Author(s):  
Vo Thi Kim Khuyen ◽  
Dinh Vu Le ◽  
Axel René Fischer ◽  
Christina Dornack
Keyword(s):  
Biosphere Reserve ◽  
Beach Sediment ◽  
Can Gio Mangrove

Effect of the Friction Coefficient on Large Strain Extrusion Machining

2013 ◽  
Vol 273 ◽  
pp. 138-142 ◽  
Author(s):  
Ping Lin ◽  
Zi Chun Xie ◽  
Qing Li
Keyword(s):  
Finite Element ◽  
Friction Coefficient ◽  
Nanostructured Materials ◽  
Deformation Behavior ◽  
Large Strain ◽  
Effective Strain ◽  
Finite Element Simulations ◽  
Friction Coefficients ◽  
Simulation Results

The present study focused on the influence of the friction coefficient on the deformation behavior in large strain extrusion machining (LSEM). A series of simulation results of effective strain were obtained under different friction coefficients by conducting finite element simulations with a FEM code. The results show that LSEM can produce different effective strains by changing the friction coefficients, thus enabling the fabrication of bulk nanostructured materials. An analysis of the variation of effective strain through the chip demonstrated that the chip deformed much more inhomogeneously when the friction coefficient became larger. The obtained results can offer valuable guidelines for later LSEM studies.

Experimental study on friction coefficient and temperature rise of heavy-load grease-lubricated spherical plain bearings with surface texture

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Jinlong Shen ◽  
Tong Zhang ◽  
Jimin Xu ◽  
Xiaojun LIU ◽  
Kun Liu
Keyword(s):  
Friction Coefficient ◽  
Temperature Rise ◽  
Surface Texture ◽  
Tribological Performance ◽  
Textured Surface ◽  
Textured Surfaces ◽  
Roughness Parameters ◽  
Heavy Load ◽  
Friction Coefficients ◽  
Content Type

Purpose This paper aims to improve the tribological performance of grease-lubricated spherical plain bearings (SPBs) under heavy load, dimple-type textures were prepared by laser on the outer surface of the inner ring. The influence of roughness parameters of a textured surface on reducing friction coefficient and temperature rise was also explored. Design/methodology/approach This study adopts a laser processing method to fabricate dimple-type textures. Three-dimensional roughness parameters were used to characterize the textured surfaces. The friction coefficients of five SPBs with surface texture and one original commercially available SPB without surface texture under different nominal loads were measured on a self-established test rig. The data of temperature rise were obtained by nine embedded thermal couples. Findings The results indicate that SPBs with textures generally exhibit lower friction coefficients than the original SPB without textures. The dimple depth has a significant influence on improving the tribological performance, which coincides with the analysis by surface roughness parameters. A textured surface with negative Ssk and high Vvc has the minimum temperature rise. Originality/value As it is too difficult to arrange sensors into heavy-load SPBs, there are few reports about the temperature characteristics. Through nine embedded thermal couples, the distribution of temperature rise on the inner ring of SPBs was given in this study. The positive effect of surface texture on reducing temperature rise and friction coefficient was verified, which is beneficial for the design of heavy-load SPBs.

Experimental investigation on Stribeck curves of different elastic modulus materials under oil and water lubrication conditions

2020 ◽  
Vol 72 (6) ◽  
pp. 805-810
Author(s):  
Hua Zhang ◽  
Guangwu Zhou ◽  
Ping Zhong ◽  
Kepeng Wu ◽  
Xingwu Ding
Keyword(s):  
Elastic Modulus ◽  
Friction Coefficient ◽  
Friction Pair ◽  
Water Lubrication ◽  
Contact Friction ◽  
Friction Coefficients ◽  
Content Type ◽  
Low Viscosity ◽  
Stribeck Curves ◽  
Lubrication Conditions

Purpose The purpose of this paper is to study the influence of friction coefficient of materials with different elastic modulus on the variation of velocity and load under water lubrication and oil lubrication conditions. Design/methodology/approach Low-viscosity lubricating oil and water were used as lubricants to test the friction performance of the ball-disc contact friction pair in the lubrication state on the universal micro-tribometer multi-functional friction and wear test system. Findings In the same speed range, the lubrication states from soft to rigid materials are not necessarily similar to each other. Generally, the material with low elastic modulus is suitable in low-viscosity lubricant environments, while the material with high elastic modulus has relatively smaller friction coefficients in oil-lubricated environments compared with water lubrication. However, the coefficients of polyethylene, polytetrafluoroethylen and polyoxymethylene are exceeded by rubber’s coefficients under water lubrication in the same experiment environments, and their lubrication states are not affected by lubricants. The friction coefficient of the friction pair decreases with the increase of loads; however, it does not apply to all materials. The friction coefficients of materials with smaller elastic modulus such as rubber under high loads are rather large. Therefore, the elastic modulus of the material under high loads is a factor to be considered. Originality/value The Stribeck curves study of the ball-disk contact friction pair comprising soft and rigid materials, whose elastic modulus is from hundreds of GPa to a few of MPa, was carried out. The influence of different speeds, loads and lubricants on the friction coefficient of the friction pair was revealed, which provided a research basis for the selection and matching of friction pair materials.

scholarly journals Trophic relationships and basal resource utilisation in the Can Gio Mangrove Biosphere Reserve (Southern Vietnam)

2019 ◽  
Vol 145 ◽  
pp. 35-43 ◽  
Author(s):  
Frank David ◽  
Cyril Marchand ◽  
Nguyen Thành-Nho ◽  
Vinh Truong Van ◽  
Pierre Taillardat ◽  
...  
Keyword(s):  
Biosphere Reserve ◽  
Trophic Relationships ◽  
Resource Utilisation ◽  
Southern Vietnam ◽  
Can Gio Mangrove

Friction and Adhesion of Copper in Vacuum

1967 ◽  
Vol 89 (4) ◽  
pp. 425-431 ◽  
Author(s):  
R. D. Brown ◽  
R. A. Burton
Keyword(s):  
Friction Coefficient ◽  
Contact Duration ◽  
Friction Coefficients ◽  
Dry Air ◽  
Very High

Friction and adhesion coefficients of copper on copper were measured in vacuum (5 × 10−10 to 4 × 10−7 torr) at temperatures ranging from −270 to 1000 F, and in controlled pressures of dry air ranging from 10−9 to 760 torr at 75 F. The effects of duration of exposure of surfaces to vacuum, and the effects of contact duration on adhesion were studied. Friction coefficients were very high (2.2 to over 16) and increased greatly with temperature; adhesion coefficients also increased with temperature, but at given temperatures, were about one-tenth the magnitudes of the friction coefficient.

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