scholarly journals Study on the Relationship between Mechanical Properties and Mesostructure of Microbial Cemented Sand Bodies

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Yue Yan ◽  
Yang Tang ◽  
Guobin Xu ◽  
Jijian Lian ◽  
Dengfeng Fu
Keyword(s):  
Compressive Strength ◽  
Spatial Distribution ◽  
Network Structure ◽  
Ground Improvement ◽  
Influential Factors ◽  
Spatial Network ◽  
Cemented Sand ◽  
Multiple Parameters ◽  
Improvement Method ◽  
The Relationship

Microbial-induced calcite precipitation (MICP) is a novel ground improvement method to effectively increase the strength of sandy soil. However, the relationship between the compressive strength of cemented sand and mesostructure of the cemented structure has not been addressed adequately. In this paper, a suite of microbial cementing experiments were conducted, considering multiple parameters controllable in testing. Twenty-two cementing columns were examined by uniaxial compressive strength (UCS) tests to explore the response of variations in compressive strength. The correlation of compressive strength with mesostructure of cemented samples was investigated using the X-ray computed tomography (XCT) method. Three main influential factors—the uniform spatial distribution, increasing contents, and increasing size of the crystals—were found to contribute positively to the strength behavior. Under relatively uniform spatial distribution, increasing the contents of crystals facilitated the initial construction of “spatial network” structure, and further stacks of calcium carbonate crystals promote the complete construction of the “spatial network” structure, and thus helped to increase compressive strength. The spatial distribution curves of crystals are in good agreement with the destructive characteristic curves of structures.

scholarly journals Improvement of Unconfined Compressive Strength of Soft Clay using Microbial Calcite Precipitates

2021 ◽  
Vol 27 (3) ◽  
pp. 67-75
Author(s):  
Nawar Aqeel Ali ◽  
Mahdi O. Karkush
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Unconfined Compressive Strength ◽  
Ground Improvement ◽  
Soft Clay ◽  
Undrained Shear Strength ◽  
Soil Particles ◽  
Improvement Method ◽  
Bacillus Sonorensis ◽  
Undrained Shear

The precipitation of calcite induced via microorganisms (MICP) is a technique that has been developed as an innovative sustainable ground improvement method utilizing ureolytic bacteria to soil strengthening and stabilization. Locally isolated Bacillus Sonorensis from Iraqi soil samples were found to have high abilities in producing urease. This study aims to use the MICP technique in improving the undrained shear strength of soft clay soil using two native urease producing bacteria that help in the precipitation of calcite to increase the cementation between soil particles. Three concentrations of each of the locally prepared Bacillus sonorensis are used in this study for cementation reagent (0.25M, 0.5M, and 1M) during the period of treatment. The results showed that the native isolated bacteria have high activity in bindings the soil particles together. The results of unconfined compressive strength tests showed that using MICP helps increase the undrained shear strength of soil by (3-5 times) for C11 types of native isolates, but the D11 was (1.5-2 times) because two types have different activity. This study's main finding is using the native urease-producing bacteria isolated from Iraqi soil in the MICP technique for the biocementation of soil, which is considered one of the sustainable techniques in the construction industry.

scholarly journals Thermal Cracking Analysis of Microbial Cemented Sand under Various Strains Based on the DEM

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Yang Tang ◽  
Guobin Xu ◽  
Yue Yan ◽  
Dengfeng Fu ◽  
Chunlai Qu ◽  
...  
Keyword(s):  
Ground Improvement ◽  
Thermal Cracking ◽  
Heating Process ◽  
Cemented Sand ◽  
X Ray ◽  
Thermal Cracks ◽  
Temperature Load ◽  
Calibration Algorithm ◽  
Improvement Method ◽  
Strength And Stiffness

Microbial-induced calcite precipitation (MICP) is a novel ground improvement method to increase the strength and stiffness of sand. However, the influences of temperature load on the internal microstructure of microbial cemented sand (MCS) material under the experimented strain have always been a key concern for the extensive application. Three kinds of experiments, X-ray diffraction (XRD), X-ray computed tomography (XCT), and scanning electron microscopy (SEM), were conducted to explore the composition, shape, and bonding characteristics of physical assemblies in this paper. A precision DEM modelling of MCS, mainly composed of irregular particle modelling and a mesoparameter calibration algorithm, has been proposed for the thermal cracking analysis under various strains (i.e., 1.0‰–3.0‰). Research results indicate that three kinds of bonding (that is sand-calcite, calcite-calcite, and sand-sand) are present in the MCS material. The application of temperature has a superposition effect on the damage of MCS material with increasing strain. Moreover, as the heating duration gradually increases, the effect of thermal rupture produces a distinct quiet period. The length of thermal cracks in the transverse direction increases throughout the heating process.

The Study on the Relationship between Spatial Network Structure of Teaching Architecture and Students' Flow Behavior Based on Complex Network Analysis

2018 ◽  
Vol 878 ◽  
pp. 183-196
Author(s):  
Ke Xie ◽  
Fang Wu ◽  
Jia Li Wu ◽  
Sheng Li ◽  
Jia Hui Wang ◽  
...  
Keyword(s):  
Higher Education ◽  
Network Analysis ◽  
Informal Learning ◽  
Complex Network ◽  
Network Structure ◽  
Flow Behavior ◽  
Spatial Network ◽  
Learning Space ◽  
Complex Network Analysis ◽  
The Relationship

Informal learning is an important part of active learning in higher education. It is of great significance to create a good informal learning space for higher education. However, the current design of university buildings is lack of quality informal learning space. This paper analyzes the relationship between complex network analysis and student behavior, and finds that there exists a close relationship between them. The spatial structure has the essential impact on the distribution of the informal learning. The construction of streamline system places an important role in the formation of learning space network. The density of the network relationship is not a key factor, but the relationship model presents more important. The cohesion of network plays an important role in the formation of spatial network of learning. In the network structure, since the groups with cohesion power are capable to convey the information even faster, the regeneration inside the groups can be achieved through the flow of resource/information.

scholarly journals Spatiotemporal evolution of COVID-19 infection and detection within night light networks: comparative analysis of USA and China

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Christopher Small ◽  
Daniel Sousa
Keyword(s):  
Spatial Distribution ◽  
Network Structure ◽  
Population Distribution ◽  
Spatial Network ◽  
Size Distributions ◽  
Spatial Networks ◽  
Spatiotemporal Evolution ◽  
Low Luminance ◽  
Wide Range ◽  
The Usa

AbstractThe spatial distribution of population affects disease transmission, especially when shelter in place orders restrict mobility for a large fraction of the population. The spatial network structure of settlements therefore imposes a fundamental constraint on the spatial distribution of the population through which a communicable disease can spread. In this analysis we use the spatial network structure of lighted development as a proxy for the distribution of ambient population to compare the spatiotemporal evolution of COVID-19 confirmed cases in the USA and China. The Visible Infrared Imaging Radiometer Suite (VIIRS) Day/Night Band sensor on the NASA/NOAA Suomi satellite has been imaging night light at ~ 700 m resolution globally since 2012. Comparisons with sub-kilometer resolution census observations in different countries across different levels of development indicate that night light luminance scales with population density over ~ 3 orders of magnitude. However, VIIRS’ constant ~ 700 m resolution can provide a more detailed representation of population distribution in peri-urban and rural areas where aggregated census blocks lack comparable spatial detail. By varying the low luminance threshold of VIIRS-derived night light, we depict spatial networks of lighted development of varying degrees of connectivity within which populations are distributed. The resulting size distributions of spatial network components (connected clusters of nodes) vary with degree of connectivity, but maintain consistent scaling over a wide range (5 × to 10 × in area & number) of network sizes. At continental scales, spatial network rank-size distributions obtained from VIIRS night light brightness are well-described by power laws with exponents near −2 (slopes near −1) for a wide range of low luminance thresholds. The largest components (104 to 105 km2) represent spatially contiguous agglomerations of urban, suburban and periurban development, while the smallest components represent isolated rural settlements. Projecting county and city-level numbers of confirmed cases of COVID-19 for the USA and China (respectively) onto the corresponding spatial networks of lighted development allows the spatiotemporal evolution of the epidemic (infection and detection) to be quantified as propagation within networks of varying connectivity. Results for China show rapid nucleation and diffusion in January 2020 followed by rapid decreases in new cases in February. While most of the largest cities in China showed new confirmed cases approaching zero before the end of February, most of these cities also showed distinct second waves of cases in March or April. Whereas new cases in Wuhan did not approach zero until mid-March, as of December 2020 it has not yet experienced a second wave of cases. In contrast, the results for the USA show a wide range of trajectories, with an abrupt transition from slow increases in confirmed cases in a small number of network components in January and February, to rapid geographic dispersion to a larger number of components shortly before mobility reductions occurred in March. Results indicate that while most of the upper tail of the network had been exposed by the end of March, the lower tail of the component size distribution has only shown steep increases since mid-June.

An evaluation of ECT sample height for small flute board grades and Box Manufacturer’s Certification compliance

TAPPI Journal ◽  
2009 ◽  
Vol 8 (6) ◽  
pp. 24-28
Author(s):  
CORY JAY WILSON ◽  
BENJAMIN FRANK
Keyword(s):  
Compressive Strength ◽  
Compressive Load ◽  
Test Sample ◽  
Test Methods ◽  
Test Method ◽  
Initial Development ◽  
Sample Height ◽  
Relationship Of ◽  
The Relationship ◽  
Corrugated Fiberboard

TAPPI test T811 is the specified method to ascertain ECT relative to box manufacturer’s certification compliance of corrugated fiberboard under Rule 41/ Alternate Item 222. T811 test sample heights were derived from typical board constructions at the time of the test method’s initial development. New, smaller flute sizes have since been developed, and the use of lighter weight boards has become more common. The T811 test method includes sample specifications for typical A-flute, B-flute, and C-flute singlewall (and doublewall and triplewall) structures, but not for newer thinner E-flute or F-flute structures. This research explores the relationship of ECT sample height to measured compressive load, in an effort to determine valid E-flute and F-flute ECT sample heights for use with the T811 method. Through this process, it identifies challenges present in our use of current ECT test methods as a measure of intrinsic compressive strength for smaller flute structures. The data does not support the use of TAPPI T 811 for ECT measurement for E and F flute structures, and demonstrates inconsistencies with current height specifi-cations for some lightweight B flute.

Determinant Factors of Student's Perception Toward Educational Loan Repayment

2018 ◽  
Vol 15 (1) ◽  
pp. 73-83
Author(s):  
Siti Zulaika Zolkeplee ◽  
Abu Bakar Hamed ◽  
Ahamad Faosiy Ogunbado
Keyword(s):  
Parental Influence ◽  
Student Loan ◽  
Influential Factors ◽  
Ministry Of Education ◽  
Loan Repayment ◽  
Education Fund ◽  
Relationship Of ◽  
The Relationship ◽  
Universiti Utara Malaysia ◽  
Survey Approach

The issue of unpayable educational loan that lead to student’s defaults has become a worrying trend all over the world. This research aims to examine the relationship of anxiety, parental influence, media awareness, and religiosity on student’s perception on educational loan repayment. A survey approach has been adopted to investigate student’s perception on educational loan repayment in Universiti Utara Malaysia. The data for this study were collected via structured questionnaires which were completed by 359 undergraduate Muslim’s students who acquire their financial loan from National Higher Education Fund Corporation (NHEFC). The data were then quantitatively analyzed using SPSS program. The findings of Pearson’s correlation showed a positive correlation between student’s perception towards educational loan repayment and religiosity, parental influence, media awareness, and anxiety. Further analysis using a multiple regression indicated that all independent variables explained 32.9 per cent of student’s perception on educational loan repayment. The result again indicated that religiosity and parent’s influence are most influential factors on student’s perception towards educational loan repayment. Whilst, media awareness slightly contributed to student’s perception towards educational loan repayment and anxiety gave no impact. The result implied that the Ministry of Education may design the syllabus in school and university curricular by adding the value of responsibility in loan repayment especially in religious and moral subjects. Besides, the Ministry Education of Malaysia are also urged to use media to disseminate the information regarding the importance for students to make loan repayment to parents as well as students. The collection of student loan then can be used for the next generation in financing their study which could result the prosperity of nation.

scholarly journals Insights Into the Correspondence Between Land Use Pattern and Spatial Distribution of Rail Transit Services

2021 ◽  
Author(s):  
Zhongqi Wang ◽  
Qi Han ◽  
Bauke de Vries ◽  
Li Dai
Keyword(s):  
Land Use ◽  
Spatial Distribution ◽  
Operations Management ◽  
Latent Variable ◽  
Structural Equation ◽  
Equation Modeling ◽  
Rail Transit ◽  
Land Use Patterns ◽  
Transit Services ◽  
The Relationship

AbstractThe identification of the relationship between land use and transport lays the foundation for integrated land use and transport planning and management. This work aims to investigate how rail transit is linked to land use. The research on the relationship between land use and rail-based transport is dominated by the impacts of rail projects on land use, without an in-depth understanding of the reverse. However, it is important to note that issues of operation management rather than new constructions deserve greater attention for regions with established rail networks. Given that there is a correspondence between land use patterns and spatial distribution of heavy railway transit (HRT) services at such regions, the study area (i.e., the Netherlands) is partitioned by the Voronoi diagram of HRT stations and the causal relationship between land use and HRT services is examined by structural equation modeling (SEM). The case study of Helmond (a Dutch city) shows the potential of the SEM model for discussing the rail station selection problem in a multiple transit station region (MTSR). Furthermore, in this study, the node place model is adapted with the derivatives of the SEM model (i.e., the latent variable scores for rail service levels and land use characteristics), which are assigned as node and place indexes respectively, to analyze and differentiate the integration of land use and HRT services at the regional level. The answer to whether and how land use affects rail transit services from this study strengthens the scientific basis for rail transit operations management. The SEM model and the modified node place model are complementary to be used as analytical and decision-making tools for rail transit-oriented regional development.

scholarly journals Visual evaluation of relative deep mixing method type of ground-improvement method

2021 ◽  
pp. 100233
Author(s):  
Koki Nakao ◽  
Shinya Inazumi ◽  
Toshiaki Takaue ◽  
Shigeaki Tanaka ◽  
Takayuki Shinoi
Keyword(s):  
Ground Improvement ◽  
Visual Evaluation ◽  
Deep Mixing ◽  
Improvement Method ◽  
Mixing Method

scholarly journals Double parton distributions in the pion from lattice QCD

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Gunnar S. Bali ◽  
Luca Castagnini ◽  
Markus Diehl ◽  
Jonathan R. Gaunt ◽  
Benjamin Gläßle ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Matrix Elements ◽  
Parton Distributions ◽  
Almost All ◽  
The Relationship

Abstract We perform a lattice study of double parton distributions in the pion, using the relationship between their Mellin moments and pion matrix elements of two local currents. A good statistical signal is obtained for almost all relevant Wick contractions. We investigate correlations in the spatial distribution of two partons in the pion, as well as correlations involving the parton polarisation. The patterns we observe depend significantly on the quark mass. We investigate the assumption that double parton distributions approximately factorise into a convolution of single parton distributions.

scholarly journals Statistical Law and Predictive Analysis of Compressive Strength of Cemented Sand and Gravel

2020 ◽  
Vol 27 (1) ◽  
pp. 291-298
Author(s):  
Shoukai Chen ◽  
Yongqiwen Fu ◽  
Lei Guo ◽  
Shifeng Yang ◽  
Yajing Bie
Keyword(s):  
Compressive Strength ◽  
Back Propagation ◽  
Back Propagation Neural Network ◽  
Predictive Analysis ◽  
Distribution Law ◽  
Data Set ◽  
Cemented Sand ◽  
Mix Proportion ◽  
Kolmogorov Smirnov ◽  
Sand And Gravel

AbstractA data set of cemented sand and gravel (CSG) mix proportion and 28-day compressive strength was established, with outliers determined and removed based on the Boxplot. Then, the distribution law of compressive strength of CSG was analyzed using the skewness kurtosis and single-sample Kolmogorov-Smirnov tests. And with the help of Python software, a model based on Back Propagation neural network was built to predict the compressive strength of CSG according to its mix proportion. The results showed that the compressive strength follows the normal distribution law, the expected value and variance were 5.471 MPa and 3.962 MPa respectively, and the average relative error was 7.16%, indicating the predictability of compressive strength of CSG and its correlation with the mix proportion.

Sign in / Sign up

Export Citation Format

Share Document