scholarly journals INFLUENCE OF STIFFNESS RELATED TO THE C40 STRENGTH CLASS OF THE HARDWOOD GROUP ESTABLISHED BY THE BRAZILIAN STANDARD IN THE DESIGN OF TIMBER STRUCTURES

Wood Research ◽  
2021 ◽  
Vol 66 (4) ◽  
pp. 582-594
Author(s):  
FRANCISCO ANTONIO ROCCO LAHR ◽  
VINICIUS BORGES DE MOURA AQUINO ◽  
FELIPE NASCIMENTO ARROYO ◽  
HERISSON FERREIRA DOS SANTOS ◽  
SERGIO AUGUSTO MELLO SILVA ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Confidence Interval ◽  
Strength Characteristic ◽  
Structural Design ◽  
Strength Class ◽  
Reference Value ◽  
Timber Structures ◽  
Average Confidence ◽  
The One ◽  
Brazilian Standard

The Brazilian standard ABNT 7190 (1997) establishes the strength classes C20, C30, C40 and C60 for the proper framework of the different wood types in the group of hardwoods. Associated with the strength class, which is based on the compressive strength characteristic value parallel to the fibers (fc0,k), the standard stipulates the respective values representing the stiffness (Ec0), with 19500 MPa being the reference value for the class C40, essential variables in structural design. For being the C40 class is the one with the greatest amplitude (20 MPa), it is possible that the value 19500 MPa is not the best representation of stiffness. This work aimed to verify the representativeness the stiffness value established by the Brazilian standard for C40 wood. The result obtained from the average confidence interval indicates the value of 14110 MPa as being the most representative, which may imply structures that are supposedly more rigid than they really are.

Performance of Nano-Silica Insulation Material Enhanced by High Humidity-Reinforcement Method

2016 ◽  
Vol 697 ◽  
pp. 433-436
Author(s):  
Shi Chao Zhang ◽  
Yu Feng Chen ◽  
Wei Wu ◽  
Hao Ran Sun ◽  
Guang Hai Wang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Raw Material ◽  
High Humidity ◽  
Insulation Material ◽  
Condensation Polymerization ◽  
Drying Process ◽  
Nano Silica ◽  
Insulation Materials ◽  
The One ◽  
Strength Improvement

In this paper, fumed nano-silica as the main raw material, nano-silica insulation materials were prepared by the dry processing. Research on humidity-reinforcement of nano-Silica insulation materials has been carried out and analyzed. When hygroscopicity of samples reach to 23%, the compressive strength 1.65MPa is at twice the one without high humidity-reinforcement, while the thermal conductivities are almost the same. Then, the action mechanism of high humidity-reinforcement method was analyzed. In humidity-reinforcement method, as vapor enters, silica sol is formed in the gap between one aggregate particle and another, and various condensation polymerization occurred in the drying process, which lead to aggregates connection and compressive strength improvement.

scholarly journals Protozoa enumeration via microscope – some remarks on methodology

2018 ◽  
Vol 44 ◽  
pp. 00121
Author(s):  
Sara Nicpoń ◽  
Paula Iliaszewicz ◽  
Maciej Leoniak ◽  
Agnieszka Trusz-Zdybek
Keyword(s):  
Confidence Interval ◽  
Activated Sludge ◽  
Sharp Increase ◽  
Statistical Significance ◽  
Lower Number ◽  
Average Confidence ◽  
Statistical Results

For proper enumeration of protozoa in activated sludge good methodology is required. In this paper we present some remarks on microscopic methodology of protozoa enumeration. This remarks concern number of repetitions from one sample required to obtain good statistical results as well as influence of sample aeration on number of found protozoa. Presented data shows that at last 10 repetitions are required from each sample to obtain low average confidence interval. Lower number of repetitions leads to sharp increase in average confidence interval and loss of statistical significance while higher number does not decrease average confidence interval substantially. As measurements lasts for few hours lack of sample’s aeration during measurement leads to detection of lower by 27% number of protozoa.

scholarly journals USE OF SLUDGE FROM SANITARY SEWAGE TREATMENT PLANTS (S.T.P) AND THEIR USE AS RAW MATERIAL IN THE MANUFACTURE OF BRICKS

2019 ◽  
Vol 16 (33) ◽  
pp. 823-840
Author(s):  
M. K. TARABAI ◽  
S. G. de AZEVEDO
Keyword(s):  
Compressive Strength ◽  
Water Absorption ◽  
Sewage Treatment ◽  
Point Of View ◽  
Test Method ◽  
Raw Material ◽  
Environmental Preservation ◽  
Ceramic Block ◽  
Environmental Requirements ◽  
The One

This paper discusses a possible solution regarding the final disposal of sludge from Sanitary Sewage Treatment Stations (ET), aiming at environmental preservation. The solid waste generated after the wastewater treatment processes is highly contaminating and detrimental to the area in which it is deposited. Given this, the use of sludge with the application of reuse techniques becomes pertinent, both from the economic point of view and from the ecological point of view. By replacing the use of aggregates from mineral deposits, the main clay raw material in the manufacture of ceramic products (Vieira, 2000), by the treated sludge of WWTP we will save on the sources of granular materials. Aiming its reintegration to the production cycle through the introduction of sludge as raw material incorporated in the ceramic mass in the manufacture of hollow bricks, the viability of use was verified through performance analysis, compared to the control brick made of pottery, without the addition of sludge. Specimens were prepared with three types of samples: 90% clay and 10% sludge; 80% clay and 20% sludge; 70% clay and 30% sludge. Mass loss, water absorption index and compressive strength tests were performed. As for the tests, the specimens with 10% and 20% of sludge were the ones that had better adaptation to the technical requirements, but because it is a larger volume of the residue for the application of reuse techniques, the brick with 20% sludge dosage. is the most suitable. NBR7.171, November 1992: Ceramic Block for masonry; Specification NBR 6.461, June 1983: Masonry Ceramic Block - Compressive Strength Check: Test Method; NBR 8.947, November 1992: Ceramic Tile- Determination of Mass and Water Absorption: Test Method. As for the tests, the specimen with 20% of sludge was the one that had the best adaptation to technical and environmental requirements. The present article approaches a possible solution regarding the destination of the sludge coming from Sanitary Sewage Treatment Stations, aiming at environmental preservation. Aiming at its reintegration into the productive cycle through applications of reuse techniques, the sludge became raw material when the ceramic mass was incorporated into the brick fabrication. Three types of samples were elaborated: 90% of clay and 10% of mud; 80% clay and 20% sludge; 70% clay and 30% sludge. As for the tests, the test specimen with 20% of sludge was the one that had more adequacy to the technical and environmental requirements.

Controllable synthesis of Mo2C with different morphology and application to electrocatalytic hydrogen evolution reaction

2021 ◽  
Author(s):  
He-qiang Chang ◽  
Guo-Hua Zhang ◽  
Kuo-Chih Chou
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Structural Design ◽  
Superior Performance ◽  
Controllable Synthesis ◽  
Nitridation Reaction ◽  
Special Surface ◽  
One Step ◽  
The One ◽  
Insight Into

Abstract In order to evaluate the effect of precursors and synthesis strategies on catalytic ability of Mo2C in the hydrogen evolution reaction (HER), four kinds of Mo2C were synthesized using two kinds of MoO3 by two strategies. Compared with the one-step direct carbonization strategy, Mo2C with a large special surface area and a better performance could be synthesized by the two-step strategy composed of a nitridation reaction and a carbonization reaction. Additionally, the as-prepared porous Mo2C nanobelts (NBs) exhibit good electrocatalytic performance with a small overpotential of 165 mV (0.5 M H2SO4) and 124 mV (1 M KOH) at 10 mA cm-2, as well as a Tafel slope of 58 mV dec-1 (0.5 M H2SO4) and 59 mV dec-1 (1 M KOH). The excellent catalytic activity is ascribed to the nano crystallites and porous structure. What’s more, the belt structure also facilitates the charge transport in the materials during the electrocatalytic HER process. Therefore, the two-step strategy provides a new insight into the structural design with superior performance for electrocatalytic HER.

Investigation of Point Load Index Using Novel Discrete Based Model

2016 ◽  
Vol 846 ◽  
pp. 348-353
Author(s):  
Somayeh Behraftar ◽  
Joshua Heslin ◽  
S. Galindo Torres ◽  
Alexander Scheuermann
Keyword(s):  
Compressive Strength ◽  
Material Properties ◽  
Mechanical Model ◽  
Rock Type ◽  
Correlation Factor ◽  
Point Load ◽  
Load Test ◽  
Point Load Index ◽  
Bonded Particles ◽  
The One

In this study, a micro-mechanical model is developed to study the correlation of the point load index in rocks with uniaxial compressive strength (UCS) tests. The model is represented by an array of bonded particles simulated by a novel discrete based model, which was introduced by the authors previously. The point load test (PLT) is performed in the field on rock samples to classify and estimate the UCS of a rock type via the index-to-strength correlation factor k. Numerical analyses, such as the one presented in this work, will serve to close the knowledge gap concerning the correlation between k, UCS and other material properties of rocks.

scholarly journals Farmers’ willingness to switch to ecological agriculture: A non-parametric analysis

2014 ◽  
Vol 60 (No. 6) ◽  
pp. 273-278
Author(s):  
C.H Yu ◽  
J.C. Yoo ◽  
B. Yao S
Keyword(s):  
Contingent Valuation ◽  
Organic Agriculture ◽  
Parametric Analysis ◽  
Contingent Valuation Method ◽  
Parametric Method ◽  
Reference Value ◽  
Dichotomous Choice ◽  
Valuation Method ◽  
The One ◽  
Non Parametric

The present study estimates the farmers’ willingness to switch to organic agriculture by using the one-and-one-half-bound dichotomous choice contingent valuation method. We survey 200 farmers in the Kwangsi-myeon, Yesan-gun (Chungnam, Korea) and ask them at what revenue level (based on a 40 kg bag of eco-friendly rice) they would be willing to switch from the conventional agricultural methods to organic agricultural methods. The Turnbull model, a non-parametric method, was then used to estimate the willingness to switch to organic agriculture. The presented results show that farmers would be willing to convert to organic agriculture if their revenues were increased to 107 369–109 230 KRW per bag from the reference value of 60 000 KRW.  

Effect of Glutinous Rice Paste on Compressive Strength of Lime-Stabilized Soil

2011 ◽  
Vol 280 ◽  
pp. 5-8
Author(s):  
Hong Tao Peng ◽  
Qi Zhang ◽  
Nai Sheng Li ◽  
De Fa Wang
Keyword(s):  
Compressive Strength ◽  
Soil Sample ◽  
Experimental Results ◽  
Box Dimension ◽  
Sem Images ◽  
Sem Image ◽  
Glutinous Rice ◽  
Stabilized Soil ◽  
The Difference ◽  
The One

The lime-stabilized soil was mixed with glutinous rice paste in proper proportion to determine the difference in compressive strength caused by introduction of glutinous rice paste. The experimental results show that the unconfined compressive strengths of lime-stabilized soil specimens treated with glutinous rice paste are all higher than those without treated at different curing times (7d, 28d, 40d, and 60d). The calculated fractal box dimension value of SEM image of lime stabilized soil sample is close to and slightly less than the one treated with glutinous rice paste. The SEM images show that the microstructure of lime-stabilized soil treated with glutinous rice paste is denser than that without treated. This kind of denser microstructure should be the basis of higher unconfined compressive strengths of the specimens treated with glutinous rice paste.

Experimental Study on the Strength and Deformation Quality of Granite with Effect of High Temperature

2012 ◽  
Vol 226-228 ◽  
pp. 1275-1278 ◽  
Author(s):  
Xiao Li Xu ◽  
Feng Gao
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
High Temperature ◽  
Reference Value ◽  
Effect Of Temperature ◽  
Rock Crystal ◽  
Brittle Ductile Transition ◽  
Strength And Deformation ◽  
Temperature Strain

Experiments on granite under uniaxial compression at high temperature of 25~850°C and after high temperature of 25~1300°C were conducted to study the effect of temperature on rock strength and deformation quality. The results show that: (1) Fitting curves between temperature strain and thermal expansion coefficient with temperature are closely first order growth exponential function relation at high temperature. Temperature strain has mutagenicity after high temperature, which can not reflect rock deformation law at high temperature exactly. (2)Mechanical properties of granite weak continuously at high temperature. Compressive strength and elastic modulus show second order attenuation trend of exponential law. But mechanical properties show mutation state after high temperature, which is closely related to the alteration of rock crystal form and brittle-ductile transition. Regression curves between compressive strength and elastic modulus with temperature are closely polynomial curve. The results reflect the fundamental regulation of granite’s interior structure changing under the action of different temperature, which will provide some reference value to rock engineering involved in high temperature.

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