MyMedR

Displaying publications 1 - 20 of 176 in total

Abstract:

Sort:

Fulltext Characterization and phase evolution of cordierite based glass synthesis from pure oxide and minerals

Banjuraizah Johar, Hasmaliza Mohamad, Zainal Arifin Ahmad

Journal of Nuclear and Related Technologies, 2009;2009(1):237-246.
MyJurnal

α Cordierite is very important phase in MgO-Al2O3-SiO2 system because of their very outstanding thermal, chemical and electrical properties. In this presents study nonstoichiometry cordierite (MgO:Al2O3:SiO2 = 3:1.5:5) using 2 different initial raw materials ( (i)mixture of pure oxide, and ii) mainly mixture of minerals) were fabricated and compared in terms of phase transformation and physical properties. Cordierite was prepared by glass method at low melting temperature (1350°C). Low melting temperature has resulted in partly crystalline glass which has possesses higher hardness, required longer milling time and result in contamination from grinding media. However, α-cordierite has successfully crystallized and fully densified at 850°C/2h. Activation energy for densification was investigated from thermal expansion coefficient (TCE) results. Other properties that were discussed included thermal properties using DTA/TGA.

Matched MeSH terms: Hardness
Fulltext Effects of resin cements on hardness and thickness around titanium post: an intraradicular assessment

Lim, Siau Peng, Fazal Reza, Zaihan Ariffin

Archives of Orofacial Sciences, 2011;6(2):1-10.
MyJurnal

The purpose of this study was to evaluate hardness (indicator for polymerization) and thickness of two types of resin cement at coronal, middle and apical level of tooth root canal. Ten extracted maxillary incisors were instrumented and post space was prepared for cementation of titanium post. Samples were divided into two groups and each group was cemented either of the two types of resin cements; Panavia F [dual-cured (PF)] and Rely X Luting 2 [self-cured (RL)]. The teeth were longitudinally sectioned; hardness and thickness was measured using Vickers hardness tester and a microscope (Leica DMLM). SEM observations along the cement line at the 3 different root levels were performed. Statistical analysis was performed to test significance of differences in hardness and thickness of the two types of cement (t-test; p= 0.05) and at different levels of the same type (one-way ANOVA followed by multiple comparison; p= 0.05). Significant difference of hardness was found at the apical level between the two groups and between the coronal and apical level of PF (p0.05). Moreover, voids were more obvious within the dual-cured group of cement. Dual-cured resin cement was found to be less polymerized than self-cured type at apical level. Increased thicknesses of resin cements in comparison to post space size were observed in both groups. Use of metallic post with resin cements needs further evaluation.

Matched MeSH terms: Hardness
Effects of anodizing parameters and heat treatment on nanotopographical features, bioactivity, and cell culture response of additively manufactured porous titanium

Amin Yavari S, Chai YC, Böttger AJ, Wauthle R, Schrooten J, Weinans H, et al.

Mater Sci Eng C Mater Biol Appl, 2015 Jun;51:132-8.
PMID: 25842117 DOI: 10.1016/j.msec.2015.02.050

Anodizing could be used for bio-functionalization of the surfaces of titanium alloys. In this study, we use anodizing for creating nanotubes on the surface of porous titanium alloy bone substitutes manufactured using selective laser melting. Different sets of anodizing parameters (voltage: 10 or 20V anodizing time: 30min to 3h) are used for anodizing porous titanium structures that were later heat treated at 500°C. The nanotopographical features are examined using electron microscopy while the bioactivity of anodized surfaces is measured using immersion tests in the simulated body fluid (SBF). Moreover, the effects of anodizing and heat treatment on the performance of one representative anodized porous titanium structures are evaluated using in vitro cell culture assays using human periosteum-derived cells (hPDCs). It has been shown that while anodizing with different anodizing parameters results in very different nanotopographical features, i.e. nanotubes in the range of 20 to 55nm, anodized surfaces have limited apatite-forming ability regardless of the applied anodizing parameters. The results of in vitro cell culture show that both anodizing, and thus generation of regular nanotopographical feature, and heat treatment improve the cell culture response of porous titanium. In particular, cell proliferation measured using metabolic activity and DNA content was improved for anodized and heat treated as well as for anodized but not heat-treated specimens. Heat treatment additionally improved the cell attachment of porous titanium surfaces and upregulated expression of osteogenic markers. Anodized but not heat-treated specimens showed some limited signs of upregulated expression of osteogenic markers. In conclusion, while varying the anodizing parameters creates different nanotube structure, it does not improve apatite-forming ability of porous titanium. However, both anodizing and heat treatment at 500°C improve the cell culture response of porous titanium.

Matched MeSH terms: Hardness
Fulltext On the Role of Processing Parameters in Producing Recycled Aluminum AA6061 Based Metal Matrix Composite (MMC-AlR) Prepared Using Hot Press Forging (HPF) Process

Ahmad A, Lajis MA, Yusuf NK

Materials (Basel), 2017 Sep 19;10(9).
PMID: 28925963 DOI: 10.3390/ma10091098

Solid-state recycling, which involves the direct recycling of scrap metal into bulk material using severe plastic deformation, has emerged as a potential alternative to the conventional remelting and recycling techniques. Hot press forging has been identified as a sustainable direct recycling technique that has fewer steps and maintains excellent material performance. An experimental investigation was conducted to explore the hardness and density of a recycled aluminum-based metal matrix composite by varying operating temperature and holding time. A mixture of recycled aluminum, AA6061, and aluminum oxide were simultaneously heated to 430, 480, and 530 °C and forged for 60, 90, and 120 min. We found a positive increase in microhardness and density for all composites. The hardness increased approximately 33.85%, while density improved by about 15.25% whenever the temperature or the holding time were increased. Based on qualitative analysis, the composite endures substantial plastic deformation due to the presence of hardness properties due to the aluminum oxide embedded in the aluminum matrix. These increases were significantly affected by the operating temperature; the holding time also had a subordinate role in enhancing the metal matrix composite properties. Furthermore, in an effort to curb the shortage of primary resources, this study reviewed the promising performance of secondary resources produced by using recycled aluminum and aluminum oxide as the base matrix and reinforcement constituent, respectively. This study is an outline for machining practitioners and the manufacturing industry to help increase industry sustainability with the aim of preserving the Earth for our community in the future.

Matched MeSH terms: Hardness
Assessment of masticatory performance by geometric measurement of the mixing ability with 2-color chewing gum

Yousof Y, Salleh NM, Yusof F

J Prosthet Dent, 2019 Jun;121(6):916-921.
PMID: 30745100 DOI: 10.1016/j.prosdent.2018.09.005

STATEMENT OF PROBLEM: The 2-color mixing ability test has been recently introduced for objective assessment of masticatory performance. However, the ideal bicolor specimens have not yet been identified, and the color analysis of digital images requires improvement.
PURPOSE: The purpose of this clinical study was to formulate a custom-made, 2-color chewing gum for the mixing ability test and to develop an image-processing method for color mixing analysis.
MATERIAL AND METHODS: Specimens of red-green (RG) chewing gum were prepared as a test food. Twenty dentate participants (10 men, 10 women; mean age 21 years) took part in this study. Each participant masticated 1 piece of RG gum for 3, 6, 9, 15, and 25 cycles, and this task was repeated 3 times consecutively (total n=15 for each participant). The boluses were retrieved and flattened to 1-mm-thick wafers and scanned with a flatbed scanner. The digital images were analyzed using ImageJ software equipped with a custom-built plug-in to measure the geometric dispersion (GD) of baseline red segment. The predictive criterion validity of this method was determined by correlating GD to the number of mastication cycles. The hardness and mass of RG chewing gum were measured before and after mastication. Hardness loss (%) and mass loss (%) were then calculated and compared with those of a commercially available chewing gum.
RESULTS: The 2-way repeated-measures ANOVA with post hoc Bonferroni test showed that GD was able to discriminate among the groups of different numbers of mastication cycles (P

Matched MeSH terms: Hardness
Fulltext Synthesis of Radiation Curable Palm Oil-Based Epoxy Acrylate: NMR and FTIR Spectroscopic Investigations

Salih AM, Ahmad MB, Ibrahim NA, Dahlan KZ, Tajau R, Mahmood MH, et al.

Molecules, 2015;20(8):14191-211.
PMID: 26248072 DOI: 10.3390/molecules200814191

Over the past few decades, there has been an increasing demand for bio-based polymers and resins in industrial applications, due to their potential lower cost and environmental impact compared with petroleum-based counterparts. The present research concerns the synthesis of epoxidized palm oil acrylate (EPOLA) from an epoxidized palm oil product (EPOP) as environmentally friendly material. EPOP was acrylated by acrylic acid via a ring opening reaction. The kinetics of the acrylation reaction were monitored throughout the reaction course and the acid value of the reaction mixture reached 10 mg KOH/g after 16 h, indicating the consumption of the acrylic acid. The obtained epoxy acrylate was investigated intensively by means of FTIR and NMR spectroscopy, and the results revealed that the ring opening reaction was completed successfully with an acrylation yield about 82%. The UV free radical polymerization of EPOLA was carried out using two types of photoinitiators. The radiation curing behavior was determined by following the conversion of the acrylate groups. The cross-linking density and the hardness of the cured EPOLA films were measured to evaluate the effect of the photoinitiator on the solid film characteristics, besides, the thermal and mechanical properties were also evaluated.

Matched MeSH terms: Hardness
A urea precursor to synthesize carbon nitride with mesoporosity for enhanced activity in the photocatalytic removal of phenol

Lee SC, Lintang HO, Yuliati L

Chem Asian J, 2012 Sep;7(9):2139-44.
PMID: 22733646 DOI: 10.1002/asia.201200383

A urea precursor was used for the first time to prepare mesoporous carbon nitride (MCN) by a thermal polymerization process with silica nanospheres as a hard template. Although the prepared MCN samples have similar structures and optical properties, it was revealed that the specific surface area, pore-size distribution, and morphology of the MCN samples depend on the initial mass ratio of urea to silica. Compared to the bulk carbon nitride (BCN) that only gave 20% phenol removal (6 h of irradiation), the activities can be enhanced up to 74% on MCN samples for photocatalytic removal of phenol under visible-light irradiation. The highest conversion was obtained on MCN with an initial mass ratio of urea to silica of 5, which has high surface area of 191 m(2) g(-1) and a nanoporous structure with uniform pore-size distribution of 7 nm. In addition to the high activity, the MCN sample also showed high photocatalytic stability.

Matched MeSH terms: Hardness
Effect of grain size and grain content on the hardness and drillability of rock

Mou Y, Yingfeng-Meng, Gao L, Lin H, Yufei-Li

Sains Malaysiana, 2014;43:81-87.

It is well-known that the characteristics of hardness and drillability are influenced by microstructure of rock. In this study, rock properties were analyzed on grain size and grain content. Coarse-grain and fine-grain sandstones were tested under successive indentation condition. Eighteen groups of sandstone and shale were employed for the drillability test. Indentation tests results showed that grain size influenced the low point of residual hardness, the crushing depth and volume and grain content influenced the peak point of hardness. The drillability values of shale increased with increasing contents of clay and quartz. Meanwhile, drillability values of sandstone increased with increasing content of quartz, but decreased with increasing content of clay. Therefore, these preliminary studies show great potential applications for selecting suitable bit type and formulating drilling program as a function of rock microstructure and crushing rock method for bit in the oil drilling.

Matched MeSH terms: Hardness
Fulltext Densification of in-situ copper-niobium carbide composite synthesized by mechanical alloying

Zuhailawati Hussain, Yong, Tuck Leong

Journal of Nuclear and Related Technologies, 2009;2009(1):135-140.
MyJurnal

In this paper, densification of in-situ copper-niobium carbide composite using cold pressing technique was addressed. Mixtures of Cu-20vol%NbC powder were prepared by two methods.
In first method, a mixture of Cu-15.79wt%Nb-2.04wt%C powder was milled at 400 rpm for 35 hours in a planetary mill. In second method, Cu and commercial NbC powder was mixed at 100 rpm for 2 hours in a jar mill. Then, both powders were pressed at different pressure (i.e. 350 MPa, 450 MPa, 550 MPa and 650 MPa) and sintered at 900 o C for 1 hour. Sample of in-situ and ex-situ Cu-20vol%NbC composite were characterized for density, hardness, phase formation by x-ray diffraction analysis and microstructure by scanning electron microscope. Xray diffraction analysis showed that NbC phase was formed in the in-situ processed sample. Hardness of in-situ processed copper composite was higher than that of the ex-situ processed copper composite due to good interface between coper matrix and niobium carbide reinforcement particle as well as distribution of finer niobium carbide particles in copper matrix. Sintered density of in-situ composite is lower than density of ex-situ composite beacuse of work hardening of the Cu-Nb-C mixture powder during powder to ball collision. Density and hardness of the in-situ and ex-situ Cu-20vol%NbC composites increase with the increase in compaction pressure as porosity is eliminated at higher compaction pressure.

Matched MeSH terms: Hardness
Fulltext Exploration on the thermal behavior, solid fat content and hardness of rambutan fat extracted from rambutan seeds as cocoa butter replacer

Zzaman, W., Issara, U., Easa, A.M., Yang, T.A.

International Food Research Journal, 2017;24(6):2408-2413.
MyJurnal

Fat content and macroscopic properties of fat network formulation result in final products in chocolate industry. The knowledge of physical properties is required in regard to stability of final food products resulting to quality. The study was carried out to investigate the thermal behavior, solid fat content and hardness of Rambutan fat (RF), cocoa butter and mixtures between two fats. The results found that the mixtures can be compatibility; the cocoa butter indicated the higher of solid fat content at room temperature more than RF and other mixtures. The RF had the highest melting point in both non-stabilized and stabilized form among cocoa butter and their mixtures. The hardness behavior showed lower in the mixture 1 and RF. For the phase behavior of crystallization exhibited the similar for all samples whereas the time of crystallization and temperatures were different. Therefore, the RF might be possible source of cocoa butter substitute with suitable proportion in the manufacturing chocolate and confectionery products.

Matched MeSH terms: Hardness
Fulltext Physicochemical properties and sensory characteristics of sausage formulated with surimi powder

Santana P, Huda N, Yang TA

J Food Sci Technol, 2015 Mar;52(3):1507-15.
PMID: 25745219 DOI: 10.1007/s13197-013-1145-1

The objectives of this study were to determine the physicochemical properties and sensory characteristics of fish sausage made with 100 % threadfin bream (Nemipterus japonicus) surimi powder (SP100), a mix of 50 % surimi powder and 50 % frozen surimi (SP50), and a control (100 % frozen surimi). No significant differences in protein content and folding test results (P > 0.05) were detected among the SP100 and SP50 samples and the control. Gel strength of SP100 was lower (P > 0.05) than that of the control. The texture profile analysis (TPA) values (hardness, cohesiveness, springiness, and chewiness) of SP100 were significantly lower (P

Matched MeSH terms: Hardness
Fulltext Vibrational analysis of Li1+xAlxTi2-x(PO4)3 (0.0 ≤ x ≤ 0.5) glass ceramic electrolytes prepared by acetic acid-assisted sol-gel method

Hamidi, M., Mohamed, S.N., Mustapha, R.I.P.R., Hassan, O.H., Yahya, M.Z.A.

Scientific Research Journal, 2015;12(2):0-0.
MyJurnal

In this study, Li1+xAlxTi2-x(PO4)3 (0.0 ≤ x ≤ 0.5) was prepared by acetic acid-assisted sol-gel method. The structural properties of NASICON phosphates material with chemical formula LiTi2(PO4)3 were observed using the Fourier transform infrared spectroscopy. NASICON is a family of crystalline phosphate with a general network system consisting of PO4 tetrahedra, thus bands were assigned by vibrations contributed by basic phosphates, in the wavenumber region between 1300 cm-1 and 600 cm-1. Experimental spectra indicated that all Li1+xAlxTi2-x(PO4)3 (0.0 ≤ x ≤ 0.5), heat treated at 600°C and 700°C for 3 hours in air, samples showed the presence of phosphate peaks with shift in frequency as Al3+ is substituted into the structure, and with increasing temperatures. Some bands broadened and overlapped causing it hard to analyze the arising bands. It however determined the existence of NASICON structure in all of the samples under study.

Matched MeSH terms: Hardness
Fulltext Assessment of Nano-Indentation Method in Mechanical Characterization of Heterogeneous Nanocomposite Materials Using Experimental and Computational Approaches

Karimzadeh A, R Koloor SS, Ayatollahi MR, Bushroa AR, Yahya MY

Sci Rep, 2019 10 31;9(1):15763.
PMID: 31673118 DOI: 10.1038/s41598-019-51904-4

This study investigates the capacity of the nano-indentation method in the mechanical characterization of a heterogeneous dental restorative nanocomposite using experimental and computational approaches. In this respect, Filtek Z350 XT was selected as a nano-particle reinforced polymer nanocomposite with a specific range of the particle size (50 nm to 4 µm), within the range of indenter contact area of the nano-indentation experiment. A Sufficient number of nano-indentation tests were performed in various locations of the nanocomposite to extract the hardness and elastic modulus properties. A hybrid computational-experimental approach was developed to examine the extracted properties by linking the internal behaviour and the global response of the nanocomposite. In the computational part, several representative models of the nanocomposite were created in a finite element environment to simulate the mechanism of elastic-plastic deformation of the nanocomposite under Berkovich indenter. Dispersed values of hardness and elastic modulus were obtained through the experiment with 26.8 and 48.5 percent average errors, respectively, in comparison to the nanocomposite properties, respectively. A disordered shape was predicted for plastic deformation of the equilateral indentation mark, representing the interaction of the particles and matrix, which caused the experiment results reflect the local behaviour of the nanocomposite instead of the real material properties.

Matched MeSH terms: Hardness
Biomechanical characterisation of ovine spinal facet joint cartilage

Abd Latif MJ, Jin Z, Wilcox RK

J Biomech, 2012 May 11;45(8):1346-52.
PMID: 22483055 DOI: 10.1016/j.jbiomech.2012.03.015

The spinal facet joints are known to be an important component in the kinematics and the load transmission of the spine. The articular cartilage in the facet joint is prone to degenerative changes which lead to back pain and treatments for the condition have had limited long term success. There is currently a lack of information on the basic biomechanical properties of the facet joint cartilage which is needed to develop tissue substitution or regenerative interventions. In the present study, the thickness and biphasic properties of ovine facet cartilage were determined using a combination of indentation tests and computational modelling. The equilibrium biphasic Young's modulus and permeability were derived to be 0.76±0.35 MPa and 1.61±1.10×10⁻¹⁵ m⁴/(Ns) respectively, which were within the range of cartilage properties characterised from the human synovial joints. The average thickness of the ovine facet cartilage was 0.52±0.10 mm, which was measured using a needle indentation test. These properties could potentially be used for the development of substitution or tissue engineering interventions and for computational modelling of the facet joint. Furthermore, the developed method to characterise the facet cartilage could be used for other animals or human donors.

Matched MeSH terms: Hardness/physiology
Fulltext The ability of Zea mays ears (Young Corn) powder in enhancing nutritional composition and changing textural properties and sensory acceptability of yeast bread

Lim, J.Y., Wan Rosli, W.l.

International Food Research Journal, 2013;20(2):799-804.
MyJurnal

Consumption of dietary fibre-rich food has been associated with various beneficial physiological properties and health effects. Presently, different types of natural fibre-rich ingredients are added into variety of bakery-based products to improve it fibre content for health promotional purposes. However, majority of these products are frequently added with imported dietary fibre ingredients. In the present study, bread samples were prepared with Zea mays ear (young corn) powder at the levels of either 2%, 4% or 6%. The bread samples were analyzed for nutritional composition, textural properties and sensory acceptance. Addition of young corn powder (YCP) at the level of 6% increases total dietary fibre (from 3.48% to 5.26%), moisture (from 25.64% to 26.55%), fat (from 4.35% to 4.61%) and protein content (from 9.13% to 9.51%) significantly. However, with the increasing of YCP levels in the bread, the carbohydrate content was decreased significantly (from 59.93% to 58.34%) while the ash content (from 0.95% to 0.99%) was not significantly affected. Results of texture profile analysis indicated that addition of YCP up to 6% not significantly affected the springiness (1.01-1.00) but significantly decreased cohesiveness (0.95-0.82). However, the addition of YCP up to 6% has increased hardness (0.18kg-0.57kg), gumminess (0.17kg-0.47kg) and chewiness (0.18kg-0.47kg) attributes of bread samples. On the other result, the sensory evaluation shows that the flavour score was not significantly affected by addition of YCP up to 4% (4.82-4.52) while the tenderness (4.53-4.42), elasticity (4.75-4.58), aroma (4.40-4.47), colour (4.93-4.55) and overall acceptance (4.80-4.35) scores were not significant affected up to 6%. In summary, breads with 4% addition of YCP were considered to be acceptable and potentially used in improving nutritional composition without changing sensory score.

Matched MeSH terms: Hardness
E-beam sterilizable thermoplastics elastomers for healthcare devices: Mechanical, morphology, and in vivo studies

Balaji AB, Ratnam CT, Khalid M, Walvekar R

J Biomater Appl, 2018 03;32(8):1049-1062.
PMID: 29298552 DOI: 10.1177/0885328217750476

The effect of electron beam radiation on ethylene-propylene diene terpolymer/polypropylene blends is studied as an attempt to develop radiation sterilizable polypropylene/ethylene-propylene diene terpolymer blends suitable for medical devices. The polypropylene/ethylene-propylene diene terpolymer blends with mixing ratios of 80/20, 50/50, 20/80 were prepared in an internal mixer at 165°C and a rotor speed of 50 rpm/min followed by compression molding. The blends and the individual components were radiated using 3.0 MeV electron beam accelerator at doses ranging from 0 to 100 kGy in air and room temperature. All the samples were tested for tensile strength, elongation at break, hardness, impact strength, and morphological properties. After exposing to 25 and 100 kGy radiation doses, 50% PP blend was selected for in vivo studies. Results revealed that radiation-induced crosslinking is dominating in EPDM dominant blends, while radiation-induced degradation is prevailing in PP dominant blends. The 20% PP blend was found to be most compatible for 20-60 kGy radiation sterilization. The retention in impact strength with enhanced tensile strength of 20% PP blend at 20-60 kGy believed to be associated with increased compatibility between PP and EPDM along with the radiation-induced crosslinking. The scanning electron micrographs of the fracture surfaces of the PP/EPDM blends showed evidences consistent with the above contentation. The in vivo studies provide an instinct that the radiated blends are safe to be used for healthcare devices.

Matched MeSH terms: Hardness
Fulltext Comparative evaluation of application of different fluoride varnishes on artificial early enamel lesion: An in vitro study

Majithia U, Venkataraghavan K, Choudhary P, Trivedi K, Shah S, Virda M

Indian J Dent Res, 2016 Sep-Oct;27(5):521-527.
PMID: 27966511 DOI: 10.4103/0970-9290.195642

INTRODUCTION: In an attempt to manage noncavitated carious lesions noninvasively through remineralization, a range of novel fluoride varnishes with additional remineralizing agents have been made available for clinical application.

AIM AND OBJECTIVES: The aim of this study was to compare and evaluate the remineralization potential of three commercially available varnishes on artificial enamel lesions.

MATERIALS AND METHODS: This in vitro study involves eighty intact enamel specimens prepared from premolars extracted for orthodontic purposes. After specimen preparation, the eighty samples were divided randomly into two groups (n = 40) for measurement of baseline surface Vickers microhardness and baseline calcium/phosphorus ratio (% weight) through EDAX testing. Thereafter, the specimens were subjected to demineralization for 96 h to induce initial enamel lesions and the measurements were repeated. Following demineralization, each of the two groups was divided randomly into four subgroups (n = 10) from which one was used as the control group and the others three were allotted to each of the three test varnishes. After varnish application, all the specimens were subjected to a pH cycling regimen that included alternative demineralization (3 h) and remineralization (21 h) daily, for 5 consecutive days. The Vickers microhardness and EDAX measurements were then repeated.

RESULTS: One-way ANOVA and post hoc Tukey's tests were conducted for multiple group comparison. All the three commercially available varnishes were capable of remineralizing initial enamel lesions that were induced artificially. No difference was noted in the remineralizing efficacy of the varnishes despite their different compositions. MI Varnish™ (casein phosphopeptide-amorphous calcium phosphate fluoride varnish) showed slightly better recovery in surface microhardness as compared to the other two varnishes.

CONCLUSION: All the varnishes used in this in vitro study are capable of reversing early enamel lesions.

Matched MeSH terms: Hardness/drug effects
Study on the relation between mineral compositions of rock and construction characteristics of tunnel in cold regions: a case

Yanliang shang, Shouji du, Honghong gao, Tongyin han

Sains Malaysiana, 2017;46:2241-2250.

Mineral composition of rock has a very important influence on the physical and mechanical properties of tunnel surrounding rock. Take Dangjianshan tunnel in cold regions for example, the rock specimens in different parts of tunnel were taken to carry out the detection test of mineral composition. By the detail qualitative and quantitative analysis, the relationship between mineral composition and surrounding rock engineering properties was explored. First of all, the composition and content of minerals contained in in the rock specimens were detected by X ray fluorescence spectrometer and X ray powder diffraction. The detection results show that rock of tunnel contains high hardness minerals such as quartz and feldspar which were proven by initial engineering geological investigation report, in addition, it also contains several kinds of low hardness minerals including inclined chlorite and illite which may exhibit large deformation characteristic of soft rock after the tunnel excavation in case of meeting water and weathering conditions. The total content of inclined chlorite and illite accounted for a considerable component in main tunnel, inclined shaft and parallel pilot respectively and the influence on surrounding rock engineering properties cannot be ignored. Therefore, mineral composition detection must be paid attention to after tunnel excavation. Secondly, the effects of mineral composition on surrounding rock were analyzed in aspects of rock strength, weathering resistance, water softening property and excavation deformation through comparing the rock samples in different parts of tunnel. The comparative results showed that when the mineral contents is high with high hardness and poor hydrophilicity, tunnel surrounding rock plays a better performance of physical and mechanical properties, vice versa. Finally, according to the specific geological and construction parameters of the tunnel, the correlation analysis was studied about the vault settlement after tunnel excavation and the hydrophilicity mineral content in main cave. The logarithmic relationship between them was found and the correlation coefficient was 0.98. It can provide a useful reference for the settlement prediction of Dangjinshan tunnel construction.

Matched MeSH terms: Hardness
Case study on deformation control of upper-soft and lower-hard large span tunnel station using combined control technology and monitoring demonstration

Yanliang Shang, Shouji Du, Biao Shao, Tongyin Han

Sains Malaysiana, 2017;46:2091-2099.

A large number of shallow buried tunnels are built in the city nowadays and the special strata such as large upper-soft and lower-hard ground often encountered. Deformation control of strata is the focus issue related to the construction safety. Based on Dalian metro Hing Street station with the classical geological condition of upper-soft and lower-hard ground, this paper fully used a combined control method including six different support measures to control the deformation of surrounding rock. 3D finite element model was setup to analyze the construction effect of combined control measures and the monitoring in-site was carried out to verify the deformation control effect of combined control method. It shows that the maximum surface subsidence value is gradually reduced with the support measures gradually increasing. In the case of various supports the maximum sedimentation value is 2.67 cm, which is 42. 1% lower than that of not using control method and the control effect is obvious. In addition, it can be seen that the two-layer initial support and additional large arch foot have the best effect on controlling the ground surface settlement with reduction of 11.7% and 20.2%, respectively. The research results can provide practical experience for the construction of such tunnels, and guide the design and construction of the tunnel in the future.

Matched MeSH terms: Hardness
Sintering behaviour of hydroxyapatite bioceramics

Ramesh S, Tan CY, Aw KL, Yeo WH, Hamdi M, Sopyan I, et al.

Med J Malaysia, 2008 Jul;63 Suppl A:89-90.
PMID: 19024998

The sintering behaviour of a commercial HA and synthesized HA was investigated over the temperature range of 700 degrees C to 1400 degrees C in terms of phase stability, bulk density, Young's modulus and Vickers hardness. In the present research, a wet chemical precipitation reaction was successfully employed to synthesize a submicron, highly crystalline, high purity and single phase stoichiometric HA powder that is highly sinteractive particularly at low temperature regimes below 1100 degrees C. It has been revealed that the sinterability of the synthesized HA was significantly greater than that of the commercial HA. The temperature for the onset of sintering and the temperature required to achieve densities above 98% of theoretical value were approximately 150 degrees C lower for the synthesized HA than the equivalent commercial HA. Nevertheless, decomposition of HA phase upon sintering was not observed in the present work for both powders.

Matched MeSH terms: Hardness

Filters

Please provide feedback to Administrator (afdal@afpm.org.my)

External Links