scholarly journals Compaction and Breakage Characteristics of Crushed Stone Used as the Backfill Material of Urban Pavement Subsidence

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Zhongbing Cai ◽  
Dan Zhang ◽  
Lang Shi ◽  
Zhong Chen ◽  
Biao Chen ◽  
...  
Keyword(s):  
Particle Breakage ◽  
Crushed Stone ◽  
Compaction Process ◽  
Backfill Material ◽  
Loading Mode ◽  
Compaction Behavior ◽  
Direct Loading ◽  
Primary Means ◽  
The Difference ◽  
Stepwise Loading

The subsidence of urban pavement is becoming frequent accidents, and backfill is the primary means of remedy. Crushed stone is a commonly used aggregate for backfill material in engineering, and its compaction behavior under load needs to be well understood. In this work, a series of compaction tests were carried out on the same batch of crushed stone samples with the same gradation. The content changes of particles with different sizes were analyzed, the particle breakage characteristics during the compaction process were discussed, and the difference in particle breakage caused by loading speed and loading mode was examined. It shows the following: (1) For all samples, the content of particles that were crushed during compaction was always less than 40%. The particles with the strongest breakage varied with sample gradation. (2) The particle breakage could be divided into four categories: complete fragmentation, complete rupture, local fragmentation, and surface grinding. They affected the particle size distribution after compaction to varying degrees. (3) The particle breakage could be expressed as a cubical parabola of loading speed, whose coefficients are related to the sample gradation. (4) Stepwise loading rendered stronger particle breakage than direct loading, and the increase of particle breakage due to loading mode was more evident for continuous grading samples than discontinuous grading samples. This study will provide an experimental basis and reference for the selection and use of backfill aggregate in urban subsidence areas.

scholarly journals The Bearing and Breakage Characteristics of Crushed Stone Aggregates in the Bedding Course of Permeable Roads

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Zhongbing Cai ◽  
Chengchun Qiu
Keyword(s):  
Particle Size ◽  
Smart Cities ◽  
Important Application ◽  
Particle Breakage ◽  
Crushed Stone ◽  
Urban Flooding ◽  
Particle Crushing ◽  
Compaction Process ◽  
Two Stages ◽  
The Impact

The current study of permeable roads helps address urban flooding in Chinese cities caused by frequent heavy rainfall and build smart cities with sponge-like functionality. Crushed stone is widely used in constructing the bedding course of permeable roads because it has good water permeability. Experiments on the compaction of crushed stone were carried out by considering the impact of particle size and gradation to examine the strength and particle breakage characteristics of crushed stone and evaluate its use as the aggregate in the bedding course of permeable roads. The compaction process can be divided into two stages, i.e., the preliminary compaction stage and the particle crushing and intensive compaction stage. The latter consists of an alternating cycle of compacting and crushing. The particle size distribution after crushing can be described analogously to the Talbot continuous gradation equation. Single particle size samples are subject to earlier and stronger particle breakage than the mixed particle size sample, which are affected by both compaction level and loading speed. This study has important application value, and it provides experimental support for the study of materials for urban permeable roads.

A Hybrid Model to Predict the Gyratory Compaction of Hot Mixed Asphalt

2019 ◽  
Author(s):  
Teng Man
Keyword(s):  
Hybrid Model ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Aggregate Size ◽  
Asphalt Mixtures ◽  
Compaction Process ◽  
Particle Rearrangement ◽  
Compaction Behavior ◽  
Grain Size Distributions ◽  
Gyratory Compaction

The compaction of asphalt mixture is crucial to the mechanical properties and the maintenance of the pavement. However, the mix design, which based on the compaction properties, remains largely on empirical data. We found difficulties to relate the aggregate size distribution and the asphalt binder properties to the compaction behavior in both the field and laboratory compaction of asphalt mixtures. In this paper, we would like to propose a simple hybrid model to predict the compaction of asphalt mixtures. In this model, we divided the compaction process into two mechanisms: (i) visco-plastic deformation of an ordered thickly-coated granular assembly, and (ii) the transition from an ordered system to a disordered system due to particle rearrangement. This model could take into account both the viscous properties of the asphalt binder and grain size distributions of the aggregates. Additionally, we suggest to use the discrete element method to understand the particle rearrangement during the compaction process. This model is calibrated based on the SuperPave gyratory compaction tests in the pavement lab. In the end, we compared the model results to experimental data to show that this model prediction had a good agreement with the experiments, thus, had great potentials to be implemented to improve the design of asphalt mixtures.

Mismatch Effect on the Mixed Mode Type Creep Crack within Weldment

2016 ◽  
Vol 853 ◽  
pp. 281-285
Author(s):  
Jun Hui Zhang ◽  
Yan Wei Dai
Keyword(s):  
Mixed Mode ◽  
Stress Triaxiality ◽  
Crack Tip ◽  
Crack Tip Field ◽  
Creep Crack ◽  
Loading Mode ◽  
The Difference ◽  
Engineering Practices ◽  
Mismatch Effect ◽  
Transient And Steady State

Creep crack within weldments are very common in engineering practices, and the cracking location in these welding structures always appears at the HAZ location. The mismatch effect on the mixed mode creep crack is still not clear in these available literatures. The aim of this paper is to investigate the mismatch influence on the creep crack of mixed mode thoroughly. A mixed mode creep crack within HAZ is established in this paper. The leading factor that dominates the creep crack tip field under mixed loading mode is studied. The influences of mismatch effect on mode mixity, stress distribution and stress triaxiality are proposed. The difference of mixed mode creep crack and normal mode I or mode II creep crack are compared. The influence of mixity factor on the transient and steady state creep of crack tip are also analyzed.

scholarly journals Batteries in a vehicle – conditions, capabilities and limitations

2018 ◽  
Vol 180 ◽  
pp. 03001
Author(s):  
Piotr Julian Biczel ◽  
Maciej Kwiatkowski
Keyword(s):  
Specific Energy ◽  
Electric Motor ◽  
Combustion Engine ◽  
Mass Range ◽  
Electrochemical Cells ◽  
Charging Time ◽  
Vehicle Mass ◽  
Primary Means ◽  
The Difference ◽  
Basic Features

Electric buses are now seen as the primary means of public transport in cities. However, their exploitation is associated with a number of limitations. The article presents the problem of battery use in buses. The design differences between the vehicle with the internal combustion engine and the electric motor are discussed. In particular, authors compared the number of passengers that both types of buses can take, as well as the difference in vehicle mass and range, and the reasons for these differences. The types of electrochemical cells that can be used to power vehicles and their basic features are presented. The article focuses on the NMC, LFP, LTO and LIC type cells. Next, the battery pack structure and its components were described. The specific energies of cells and batteries constructed from these cells were compared. Next, the most important features of the vehicle equipped with batteries with various types of cells are discussed. The mass, range, charging time and cycle lifetime of the batteries were compared. The basic dependence was noted: the greater the specific energy, the smaller the number of battery cycles. So if the bus has to take more passengers, it must have light batteries, which should be frequently charged, which requires high cyclic lifetimes.

scholarly journals HOPS-dependent endosomal fusion required for efficient cytosolic delivery of therapeutic peptides and small proteins

2018 ◽  
Author(s):  
Angela Steinauer ◽  
Jonathan R. LaRochelle ◽  
Rebecca Wissner ◽  
Samuel Berry ◽  
Alanna Schepartz
Keyword(s):  
Cell Penetrating Peptides ◽  
Correlation Spectroscopy ◽  
Confocal Imaging ◽  
Endocytic Pathway ◽  
Endosomal Escape ◽  
Stapled Peptides ◽  
Critical Determinant ◽  
Small Proteins ◽  
Primary Means ◽  
The Difference

AbstractProtein therapeutics represent a significant and growing component of the modern pharmacopeia, but their potential to treat human disease is limited because most proteins fail to traffic across biological membranes. Recently, we discovered that cell-permeant miniature proteins (CPMPs) containing a precisely defined, penta-arginine motif traffic readily to the cytosol and nucleus with efficiencies that rival those of hydrocarbon-stapled peptides active in animals and man. Like many cell-penetrating peptides (CPPs), CPMPs enter the endocytic pathway; the difference is that CPMPs are released efficiently from endosomes while other CPPs are not. Here, we seek to understand how CPMPs traffic from endosomes into the cytosol and what factors contribute to the efficiency of endosomal release. First, using two complementary cell-based assays, we exclude endosomal rupture as the primary means of endosomal escape. Next, using a broad spectrum of techniques, including an RNA interference (RNAi) screen, fluorescence correlation spectroscopy (FCS), and confocal imaging, we identify VPS39—a gene encoding a subunit of the homotypic fusion and protein sorting (HOPS) complex—as a critical determinant in the trafficking of CPMPs and hydrocarbon-stapled peptides to the cytosol. Although CPMPs neither inhibit nor activate HOPS function, HOPS activity is essential to efficiently deliver CPMPs to the cytosol. Subsequent multi-color confocal imaging studies identify CPMPs within the endosomal lumen, particularly within the intraluminal vesicles (ILVs) of Rab7+ and Lamp1+ endosomes that are the products of HOPS-mediated fusion. These results suggest that CPMPs require HOPS to reach ILVs—an environment that serves as a prerequisite for efficient endosomal escape.

Manufacture of road stone and respective quality requirements in the pre-revolutionary Russia

2020 ◽  
pp. 47-52
Author(s):  
E. E. Kameneva ◽  
◽  
E. V. Kamenev ◽  
Keyword(s):  
Quality Indicators ◽  
Physical And Mechanical Properties ◽  
Road Construction ◽  
Crushed Stone ◽  
Scale Production ◽  
Experimental Conditions ◽  
Quality Requirements ◽  
The Difference ◽  
Temperature Loads

The paper studies the establishment and development history for road stone quality requirements and covers its manufacture in the pre-revolutionary Russia. It is shown that industrial-scale production of road stone was first initiated in Russia as late as at the end of the 19 century. Due to the development of road construction technologies, it became requisite to assess the quality of rocks used to produce crushed stone. The first speculative conclusions on the effect of moisture, mechanical and temperature loads on the quality of crushed stone were made in the middle of the 19 century; however, at the time, there was no uniformity in how to establish the material quality. Crushed stone quality indicators (strength, abrasion, grain shape, and some others) were formulated at the beginning of the 20 century, when mechanized crushed stone manufacturing methods were being first introduced in Russia. In the same period, methods were developed for establishing certain crushed stone quality indicators in laboratory conditions. The underlying principles for these methods, in fact, correspond to the current methods of testing physical and mechanical properties of rocks. The difference lies in the equipment design, experimental conditions, and quantitative assessments of the indicators studied. In general, the late 19 – early 20 centuries may be referred to as the period when the scientific approach was first applied to crushed stone quality studies in Russia and the foundations for its standardization were laid.

Strength Analysis of MEMS Micromirror Devices - Effects of Loading Mode and Etching Damage

2005 ◽  
Vol 297-300 ◽  
pp. 527-532 ◽  
Author(s):  
Satoshi Izumi ◽  
Chan Wee Ping ◽  
Makoto Yamaguchi ◽  
Shinsuke Sakai ◽  
Atsushi Suzuki ◽  
...  
Keyword(s):  
Evaluation Method ◽  
Combined Loading ◽  
Strength Analysis ◽  
Load Factor ◽  
Pure Bending ◽  
Loading Test ◽  
Loading Mode ◽  
Safe Side ◽  
The Difference ◽  
Torsion Strength

Strength evaluation method for MEMS micromirror has been proposed. Pure bending and combined loading tests have been performed and torsion strength has been estimated from those results. Two-parameter Weibull distribution was used to evaluate the fractured stresses estimated from FEM model. There exists the difference in strength between pure bending and combined loading. From the load factor analysis, it is found that both geometry and stress distribution have to be considered to estimate the strength of MEMS since flaw population is non-uniformly distributed. It is also found torsional strength can be estimated on the safe side by using the result of combined loading test. From the comparison between two kinds of specimen fabricated by different etching conditions, it is found that the fracture strength is greatly affected by the amount of etching damage (notching).

scholarly journals DEM investigation of the effect of particle breakage on compact properties

2021 ◽  
Vol 249 ◽  
pp. 07004
Author(s):  
Dazhao Gou ◽  
Xizhong An ◽  
Runyu Yang
Keyword(s):  
Pore Size ◽  
Numerical Study ◽  
Sphere Packing ◽  
Particle Breakage ◽  
Density Distributions ◽  
Compaction Behavior ◽  
Stress Strain Relation ◽  
Pore Properties ◽  
Breakage Behavior

Particle breakage during compaction affects compaction behavior and the quality of the formed compact. This work conducted a numerical study based on the discrete element method (DEM) to investigate the effect of particle breakage on compaction dynamics and compact properties, including particle size and density distributions, and pore properties. A force-based breakage criterion and Apollonian sphere packing algorithm were employed to characterize particle breakage behavior. The pore structures of the compacts were characterized by the watershed pore segmentation method. Calibrated with experimental data, the model was able to simulate the stress-strain relation comparable with experimental observation. During compaction, the particles were gradually broken from top to bottom with increasing pressure. Both density and pore size of the compacts had relatively uniform distribution at larger stress, while the pore size decreased sharply when the particles started to break, indicating that the smaller fragments in the compact system have a significant effect on the pore size distribution.

scholarly journals The mobility gap: estimating mobility levels required to control Canada’s winter COVID-19 surge

2021 ◽  
Author(s):  
Kevin A. Brown ◽  
Jean-Paul R. Soucy ◽  
Sarah A. Buchan ◽  
Shelby L. Sturrock ◽  
Isha Berry ◽  
...  
Keyword(s):  
Growth Rate ◽  
Residential Mobility ◽  
Rate Ratio ◽  
Herd Immunity ◽  
Primary Means ◽  
Low Levels ◽  
The Difference ◽  
Canadian Provinces ◽  
Pharmaceutical Interventions ◽  
Mobility Gap

AbstractBackgroundNon-pharmaceutical interventions remain a primary means of suppressing COVID-19 until vaccination coverage is sufficient to achieve herd immunity. We used anonymized smartphone mobility measures in seven Canadian provinces to quantify the mobility level needed to suppress COVID-19 (mobility threshold), and the difference relative to current mobility levels (mobility gap).MethodsWe conducted a longitudinal study of weekly COVID-19 incidence from March 15, 2020 to January 16, 2021, among provinces with 20 COVID-19 cases in at least 10 weeks. The outcome was weekly growth rate defined as the ratio of current cases compared to the previous week. We examined the effects of average time spent outside the home (non-residential mobility) in the prior three weeks using a lognormal regression model accounting for province, season, and mean temperature. We calculated the COVID-19 mobility threshold and gap.ResultsAcross the 44-week study period, a total of 704,294 persons were infected with COVID-19. Non-residential mobility dropped rapidly in the spring and reached a median of 36% (IQR: 31,40) in April 2020. After adjustment, each 5% increase in non-residential mobility was associated with a 9% increase in the COVID-19 weekly growth rate (ratio=1.09, 95%CI: 1.07,1.12). The mobility gap increased through the fall months, which was associated with increasing case growth.InterpretationMobility strongly and consistently predicts weekly case growth, and low levels of mobility are needed to control COVID-19 through winter 2021. Mobility measures from anonymized smartphone data can be used to guide the provincial and regional implementation and loosening of physical distancing measures.

scholarly journals The Influence of Bleeding of Cement Suspensions on Their Rheological Properties

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1609 ◽  
Author(s):  
Tabea von Bronk ◽  
Michael Haist ◽  
Ludger Lohaus
Keyword(s):  
Rheological Properties ◽  
Cement Paste ◽  
Great Influence ◽  
Compaction Process ◽  
Measuring Procedure ◽  
Sedimentation Behavior ◽  
Segregation Phenomenon ◽  
The Difference ◽  
Mixing Water

Flowable concretes tend to segregate. The risk of segregation is particularly high when the concrete is vibrated during the compaction process. A well-known segregation phenomenon is the so-called “bleeding”. This is a rise of water to the surface of the freshly poured concrete due to the difference in density between the mixing water and the concrete’s denser solid components (aggregates, cement and additives). This type of segregation occurs particularly within the paste. The focus of this paper is, therefore, on the sedimentation behavior at the microscale of concrete and especially on the influence of this process on rheological properties of the cement paste. In addition to common bleeding tests of cement suspensions using standing cylinders, rheometric measurements were performed on the suspensions during the bleeding process. A measuring procedure was developed for the rheometric measurements of the sedimenting cement suspensions. The rheological properties of the investigated cement suspensions were determined at four specific measuring times and at four specific measuring heights (i.e., positions) each. With this method it could be shown that the cement suspensions are not homogeneous over their height and that bleeding has a great influence on the rheological properties of cement suspension.

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