scholarly journals Microscopic characterization and strength characteristics of cemented backfill under different humidity curing conditions

2019 ◽  
Vol 6 (12) ◽  
pp. 191227
Author(s):  
Jianhua HU ◽  
Fengwen Zhao ◽  
Qifan Ren ◽  
Ye Kuang ◽  
Tan Zhou ◽  
...  
Keyword(s):  
Pore Size ◽  
Strength Characteristics ◽  
Curing Conditions ◽  
Factors Affecting ◽  
Exponential Functional ◽  
Cemented Backfill ◽  
Small Pore ◽  
Microscopic Features ◽  
Paste Backfill ◽  
Powder Content

Under different exploitive conditions, the humidity levels of the backfill stopes are not the same. Humidity greatly affects the strength and microscopic characterization of the backfill. Cemented paste backfill (CPB) specimens were cured using 0, 30, 70% and standard curing (20°C, 99%) under four different humidity conditions. At 28 days, nuclear magnetic resonance (NMR) and scanning electron microscopy (SEM) techniques were used to obtain the microscopic features of the CPB specimens. The relationships between the permeability and uniaxial compressive strength (UCS) of the CPB specimens, and the microscopic characteristics of the CPB specimens, were established. The results showed the following: (i) The permeability of the CPB had an exponential functional relationship with its stone powder content. (ii) The stone powder content of CPB and the peak area of the T 2 spectrum are negatively correlated with the UCS. However, there was a T 2 peak area corresponding to the worst UCS with the same stone powder content. (iii) The peak area of the T 2 spectrum showed that the proportion of area of a small pore size was more than 80%, indicating that the pore size was mainly small. The pore diameter of small pores was linearly and inversely proportional to the UCS of the specimens. It can be found that the factors affecting the strength characteristics of CPB include not only the stone powder content, but also the curing conditions of different humidity.

Novel Lightweight Metal Foam Heat Exchangers

2001 ◽  
Author(s):  
David P. Haack ◽  
Kenneth R. Butcher ◽  
T. Kim ◽  
T. J. Lu
Keyword(s):  
Heat Exchange ◽  
Pore Size ◽  
Heat Exchangers ◽  
Metal Foam ◽  
Heat Removal ◽  
Random Orientation ◽  
Flow Rates ◽  
Small Pore ◽  
Complex Heat Exchange ◽  
Flow Through

Abstract An overview of open cell metal foam materials with application to advanced heat exchange devices is presented. The metal foam materials considered consist of interconnected cells in a random orientation. Metal foam materials, manufacture and fabrication into complex heat exchange components are described. Experiments with flat foam panels brazed to copper sheets shows increasing heat removal effectiveness with decreasing product pore size at equivalent coolant flow rates. However, the high-pressure drop associated with flow through small pore-size material makes the use of larger pore size material more attractive.

Tailoring the Pore Size of Hypercrosslinked Polymer Foams

1996 ◽  
Vol 431 ◽  
Author(s):  
W. P. Steckle ◽  
M. A. Mitchell ◽  
P. G. Apen
Keyword(s):  
Pore Size ◽  
Polyaromatic Hydrocarbons ◽  
Crosslinking Agent ◽  
Nitrogen Adsorption ◽  
Total Surface Area ◽  
Pore Sizes ◽  
Surface Areas ◽  
Small Pore ◽  
High Resolution Tem ◽  
Cure Time

AbstractOrganic analogues to inorganic zeolites would be a significant step forward in engineered porous materials and would provide advantages in range, selectivity, tailorability and processing. Rigid molecular foams or “organic zeolites” would not be crystalline materials and could be tailored over a broader range of pore sizes and volumes. A novel process for preparing hypercrosslinked polymeric foams has been developed via a Friedel-Crafts polycondensation reaction. A series of rigid hypercrosslinked foams have been prepared using simple rigid polyaromatic hydrocarbons including benzene, biphenyl, m-terphenyl, diphenylmethane, and polystyrene, with p-dichloroxylene (DCX) or divinylbenzene (DVB) as the crosslinking agent. Transparent gels are formed suggesting a very small pore size. After drying the foams are robust and rigid. Densities of the resulting foams can range from 0.15g/cc to 0.75g/cc. Nitrogen adsorption studies have shown that by judiciously selecting monomers and crosslinking agent along with the level of crosslinking and the cure time of the resulting gel, the pore size, pore size distribution, and the total surface area of the foam can be tailored. Surface areas range from 160 to 1,200 m2/g with pore sizes ranging from 6Å to 2,000Å. Further evidence of the uniformity of the foams and their pore sizes has been confirmed by high resolution TEM.

scholarly journals Early-Age Cracking in Concrete: Causes, Consequences, Remedial Measures, and Recommendations

2018 ◽  
Vol 8 (10) ◽  
pp. 1730 ◽  
Author(s):  
Md. Safiuddin ◽  
A. Kaish ◽  
Chin-Ong Woon ◽  
Sudharshan Raman
Keyword(s):  
Service Life ◽  
Concrete Structures ◽  
Real Life ◽  
Early Age ◽  
Structural Elements ◽  
Remedial Measures ◽  
Curing Conditions ◽  
Factors Affecting ◽  
Different Types ◽  
Service Conditions

Cracking is a common problem in concrete structures in real-life service conditions. In fact, crack-free concrete structures are very rare to find in real world. Concrete can undergo early-age cracking depending on the mix composition, exposure environment, hydration rate, and curing conditions. Understanding the causes and consequences of cracking thoroughly is essential for selecting proper measures to resolve the early-age cracking problem in concrete. This paper will help to identify the major causes and consequences of the early-age cracking in concrete. Also, this paper will be useful to adopt effective remedial measures for reducing or eliminating the early-age cracking problem in concrete. Different types of early-age crack, the factors affecting the initiation and growth of early-age cracks, the causes of early-age cracking, and the modeling of early-age cracking are discussed in this paper. A number of examples for various early-age cracking problems of concrete found in different structural elements are also shown. Above all, some recommendations are given for minimizing the early-age cracking in concrete. It is hoped that the information conveyed in this paper will be beneficial to improve the service life of concrete structures. Concrete researchers and practitioners may benefit from the contents of this paper.

scholarly journals The nylon bag technique in the determination of ruminal feed protein degradation

1983 ◽  
Vol 55 (1) ◽  
pp. 1-78 ◽  
Author(s):  
Jouko Setälä
Keyword(s):  
Particulate Matter ◽  
Pore Size ◽  
Control Sample ◽  
Sample Treatment ◽  
Sample Weight ◽  
Factors Affecting ◽  
Experimental Animals ◽  
Incubation Periods ◽  
Feed Protein

The investigation included experiments in which factors affecting the reliability of the nylon bag method were studied. The possibility of applying the feed protein degradabilities to practical feeding conditions was also examined. In the experiments concerning reliability, such factors as bag porosity, sample weight, sample treatment, washing procedure, diets, and differences between animals and incubation days were studied. The feed protein degradabilities were also determined by using as incubation periods the ruminal retention times for particulate matter of different feeds, evaluated as a function of DM intake/100 kg liveweight in different diets. A nylon bag, with a pore size of 40 µm and internal dimensions of 6 X 12 cm was selected for the degradability determinations. The sample weight used in incubations was 57 —60  mg DM/cm2. In the determination of feed protein degradability, when sheep are used as experimental animals, it is recommended that for routine determinations only one animal be used, analyzing the contents of two bags for each incubation period during two successive days. A control sample of which degradability is determined in advance in many sheep, should be used in all incubations in order to control the digestive processes in the rumen of the experimental sheep. The actual degradabilities analyzed by the bag method are applicable in practise, if they are determined using animals at similar feeding levels and on diets similar to those prevailing under the conditions in which the degradabilities are going to be used.

scholarly journals The effect of curing conditions on the expansion efficiency of MgO expansion agent

2021 ◽  
Vol 233 ◽  
pp. 03047
Author(s):  
Yu Fang ◽  
Li Yongchao
Keyword(s):  
Curing Temperature ◽  
Obvious Effect ◽  
Curing Conditions ◽  
Factors Affecting ◽  
Temperature Conditions ◽  
Low Humidity ◽  
Humidity Environment

In order to further promote the research and application of MgO expansion agent in concrete field, this paper carried out the effect of different humidity and temperature conditions on the expansion properties of mortar and mortar specimens mixed with MgO expansion agent. In addition, the mechanism of the factors affecting the sensitivity of the MgO expansion agent is revealed by combining microscopic technology. The results show that the higher the curing temperature and the greater the curing humidity, the greater the expansion efficiency of the MgO expansion agent. The temperature of 20~40°C has no obvious effect on the efficiency of the MgO expansion agent, but the expansion value of the specimen doubles as the temperature rises to 40~80°C. Besides, the higher the curing humidity, the better the expansion efficiency of the MgO expansion agent, but the MgO expansion agent is more sensitive to the low humidity environment, and the specimen shrinks in the lower humidity environment (RH=60%).

Effect of crosslinking agents on the strength characteristics of cellulosic fabrics using 23 32 mixed level factorial

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Farhana Naeem ◽  
Fareha Asim ◽  
Muhammad Tufail
Keyword(s):  
High Strength ◽  
Strength Characteristics ◽  
Blend Ratio ◽  
Tear Strength ◽  
Content Type ◽  
Factors Affecting ◽  
Acrylate Copolymer ◽  
Curing Method ◽  
Crosslinking Agents ◽  
Significant Factors

Purpose Low pilling and wrinkle-free appearance of cellulosic fabrics are always demanded. Resin finishes are applied to improve these properties, but there is an adverse effect of the resin finish as it tends to reduce the strength of the fabrics. Therefore, the effect of the two most important finishes; anti-pilling and resin finish, on the strength characteristics of 100% viscose and 50:50 Viscose/cotton plain and satin fabrics were investigated in this paper. The purpose of this study is to identify significant factors affecting the strength of fabrics finished with crosslinking agents [non-ionic acrylate copolymer and (dimethyloldihydroxyethyleneurea)]. Design/methodology/approach A statistical model of 23 32 mixed level factorial design was used for the study. Appratan N9211 (A) and Arkofix NF (B) were tested at three concentrations, whereas three factors fabric; weave (C), blend ratio (D) and curing method (E) were tested at two levels. The performance of the finish was evaluated by two response variables, which were tensile and tear strength. Findings The various conditions of high strength values of the fabrics were presented in this paper. It was found that the tear strength of the fabrics increased after finishing except for 50:50 viscose/cotton plain fabric, whereas the tensile strength of plain fabrics is better at shock cure and for a satin normal cure is better. The model adequacy plots exhibit that the assumptions of normality and independence are not desecrated. Moreover, the values of “predicted R2” are in reasonable agreement with the “adjusted R2,” which confirms that models have been accounted for most of the inconsistency. Originality/value This paper is a part of my PhD dissertation. Unlike the previous studies, this paper investigated the effect of two crosslinking agents, Appretan N9211 as anti-pilling and Arkofix NF as wrinkle resistant agents on 100% viscose and 50:50 viscose/cotton plain and satin. Three different concentrations of both the crosslinking agents were used. Also, fixation of the finishes was carried out at a normal cure and shock cure.

scholarly journals Challenges in Fabrication of Tissue-Engineered Cartilage with Correct Cellular Colonization and Extracellular Matrix Assembly

2018 ◽  
Vol 19 (9) ◽  
pp. 2700 ◽  
Author(s):  
Mikko Lammi ◽  
Juha Piltti ◽  
Juha Prittinen ◽  
Chengjuan Qu
Keyword(s):  
Extracellular Matrix ◽  
Articular Cartilage ◽  
Pore Size ◽  
Cartilage Tissue ◽  
Cellular Interactions ◽  
Matrix Assembly ◽  
Small Pore ◽  
Culture Models ◽  
Open Question ◽  
Engineered Cartilage

A correct articular cartilage ultrastructure regarding its structural components and cellularity is important for appropriate performance of tissue-engineered articular cartilage. Various scaffold-based, as well as scaffold-free, culture models have been under development to manufacture functional cartilage tissue. Even decellularized tissues have been considered as a potential choice for cellular seeding and tissue fabrication. Pore size, interconnectivity, and functionalization of the scaffold architecture can be varied. Increased mechanical function requires a dense scaffold, which also easily restricts cellular access within the scaffold at seeding. High pore size enhances nutrient transport, while small pore size improves cellular interactions and scaffold resorption. In scaffold-free cultures, the cells assemble the tissue completely by themselves; in optimized cultures, they should be able to fabricate native-like tissue. Decellularized cartilage has a native ultrastructure, although it is a challenge to obtain proper cellular colonization during cell seeding. Bioprinting can, in principle, provide the tissue with correct cellularity and extracellular matrix content, although it is still an open question as to how the correct molecular interaction and structure of extracellular matrix could be achieved. These are challenges facing the ongoing efforts to manufacture optimal articular cartilage.

ChemInform Abstract: C2-C4 OLEFINS BY REACTION OF METHANOL ON ZEOLITES OF SMALL PORE SIZE

1982 ◽  
Vol 13 (42) ◽  
Author(s):  
U. DETTMEIER ◽  
H. LITTERER ◽  
H. BALTES ◽  
W. HERZOG ◽  
E. I. LEUPOLD ◽  
...  
Keyword(s):  
Pore Size ◽  
Small Pore Size ◽  
Small Pore
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