Mg-6%Zn-10%β-Ca3(PO4)2 composite was prepared through powder metallurgy methods with different chitosan coatings on its surface. The properties of the chitosan coatings on the surface of Mg-6%Zn-10%β-Ca3(PO4)2 compo...Mg-6%Zn-10%β-Ca3(PO4)2 composite was prepared through powder metallurgy methods with different chitosan coatings on its surface. The properties of the chitosan coatings on the surface of Mg-6%Zn-10%β-Ca3(PO4)2 composite, such as the adhesion ability, the corrosion behavior and the cytotoxicity properties, were investigated, and the microstructure of the chitosan coating was observed by scanning electron microscope(SEM). The results show that chitosan coating improves the corrosion resistance of the magnesium composite specimens significantly. Mg-6%Zn-10%β-Ca3(PO4)2 composite specimens exhibit good corrosion resistance and low p H values in simulated body fluid(SBF) at 37 °C in the immersion test with 7-layer chitosan coating whose relative molecular mass is 30×104 Da. The cytotoxicity tests indicate that Mg-6%Zn-10%β-Ca3(PO4)2 with chitosan coating is nontoxic with a cytotoxicity grade of zero against L-929 cells, which is better than that of uncoated composites.展开更多
The corrosion behavior study was conducted on a novel Fe77 Mo5P9C7.5 B1.5 in-situ metallic glass matrix composite （MGMC）. This composite sample was developed by introduction of bcc a-Fe dendrites as reinforcing phas...The corrosion behavior study was conducted on a novel Fe77 Mo5P9C7.5 B1.5 in-situ metallic glass matrix composite （MGMC）. This composite sample was developed by introduction of bcc a-Fe dendrites as reinforcing phase. The corrosion behavior of this composite was compared to its monolithic counterpart and other Fe-based alloys such as 304L and 2304L stainless steels. The corrosion resistance of MGMCs in H2SO4 solution shows inferior to that of other Fe-based alloys. Experiments suggest that Fe-BMGs samples possess better corrosion resistance property than that of Fe-MGMCs. The possible underlying reasons can be the inhomogeneity induced by the precipitation of a-Fe dendrites in the MGMCs.展开更多
AIM:To assess the effects of bile and pancreatic juice on structural and mechanical resistance of extracellular matrices(ECMs) in vitro.METHODS:Small-intestinal submucosa(SIS),porcine dermal matrix(PDM),porcine perica...AIM:To assess the effects of bile and pancreatic juice on structural and mechanical resistance of extracellular matrices(ECMs) in vitro.METHODS:Small-intestinal submucosa(SIS),porcine dermal matrix(PDM),porcine pericardial matrix(PPM) and bovine pericardial matrix(BPM) were incubated in human bile and pancreatic juice in vitro.ECMs were examined by macroscopic observation,scanning electron microscopy(SEM) and testing of mechanical resistance.RESULTS:PDM dissolved within 4 d after exposure to bile or pancreatic juice.SIS,PPM and PDM retained their integrity for > 60 d when incubated in either digestive juice.The effect of bile was found to be far more detrimental to mechanical stability than pancreatic juice in all tested materials.In SIS,the loss of mechanical stability after incubation in either of the digestive secretions was less distinct than in PPM and BPM [mFmax 4.01/14.27 N(SIS) vs 2.08/5.23 N(PPM) vs 1.48/7.89 N(BPM)].In SIS,the extent of structural damage revealed by SEM was more evident in bile than in pancreatic juice.In PPM and BPM,structural damage was comparable in both media.CONCLUSION:PDM is less suitable for support of gastrointestinal healing.Besides SIS,PPM and BPM should also be evaluated experimentally for gastrointestinal indications.展开更多
An efficient method for helicopter rotor fault diagnosis was proposed using diagnostic matrix and its software framework was developed.The diagnostic matrix was extracted by the way of simulating the quantitative mode...An efficient method for helicopter rotor fault diagnosis was proposed using diagnostic matrix and its software framework was developed.The diagnostic matrix was extracted by the way of simulating the quantitative models of damaged and undamaged rotor systems.The conflicts were recognized by the virtual symptom sensor based on the dependencies between symptoms and faults.Diagnostic candidates were generated by the Boolean hitting algorithm.The proposed method provides multi-fault real-time diagnostic capability and it is suitable for the synthetic health monitoring of complex systems.展开更多
In this paper, a statistical analysis method is proposed to research life characteristics of products based on the partially accelerated life test. We discuss the statistical analysis for constant-stress partially acc...In this paper, a statistical analysis method is proposed to research life characteristics of products based on the partially accelerated life test. We discuss the statistical analysis for constant-stress partially accelerated life tests with Lomax distribution based on interval censored samples. The EM algorithm is used to obtain the maximum likelihood estimations(MLEs) and interval estimations for the shape parameter and acceleration factor.The average relative errors(AREs), mean square errors(MSEs), the confidence intervals for the parameters, and the influence of the sample size are discussed. The results show that the AREs and MSEs of the MLEs decrease with the increase of sample size. Finally, a simulation sample is used to estimate the reliability under different stress levels.展开更多
AIM: To validate accuracy of a novel chair-side test for matrix metalloproteinase(MMP)-8 as compared to enzyme-linked immunosorbent assay(ELISA) in Periodontal health and disease.METHODS: Gingival crevicular fluid was...AIM: To validate accuracy of a novel chair-side test for matrix metalloproteinase(MMP)-8 as compared to enzyme-linked immunosorbent assay(ELISA) in Periodontal health and disease.METHODS: Gingival crevicular fluid was collected from 150 subjects, Group 1(healthy)- 50 subjects, Group 2(gingivitis)- 50 subjects and Group 3(chronic periodontitis)- 50 subjects. A chair-side test strip was indigenously prepared using polyclonal antibodies(principle of immunochromatography) to detect the MMP-8 levels. The detection accuracy(sensitivity and specificity) of the MMP-8 levels by chair-side test kit were compared with ELISA at baseline and 3 mo after scaling and root planing among the study population.RESULTS: The novel chair side test detected MMP-8 levels in accordance with ELISA which at baseline were higher in Group 2 and Group 3 as compared to controls(P < 0.05), and these enzyme levels decreased after therapy(P < 0.05). The chair-side test could differentiate healthy, gingivitis and periodontitis. The detection accuracy of the chair-side test strip were on par with ELISA(sensitivity 92.9% and specificity of 100%) which were statistically significant(P < 0.05). A desire to arouse interest about periodontal health and maintenance in the Indian population provided a strong rationale for us to develop our chair-side test strips to suit our economy. Moreover, this was the first ever effort to develop and validate a chair-side test strip to detect MMP-8 levels in the Indian population. This test can be used on a large scale in private dental practice for the early detection of disease, tapping the sites at risk for disease, alongside helps in patient education and motivation for maintenance.CONCLUSION: This study shows that the novel chair side test kit detects MMP-8 levels a biomarker of periodontal disease progression accurately making it a good chair side diagnostic tool. Further, it is cost effective and time saving which can make it applicable in private dental practice on a large scale for the early detection of periodontal disease.展开更多
Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical propert...Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical properties MMCs was done by many researchers;however in depth study on the oxidation behavior of cenosphere, reinforced MMCs are required, since the application of Aluminum-based MMCs is extensively used in applications like automobile, navigation and aviation, where the demand on light weight corrosion resistance material is very much required. In the present work varied compositions of Al7075 grade Aluminum-cenosphere composites use liquid metallurgy route adopting stir casting approach. The experimental study was aimed at experimental investigations of developed composites under different corrosive environments. The corrosion tests were carried out as per ASTM standards. Salt spray test using NaCl was carried out as per ASTM B117 and immersion tests using NaCl and NaOH as corrodents were carried out by following ASTM G31 standards. The results obtained from the tests revealed that as increase in weight % of reinforcement, corrosion resistance increases up to 7.5% reinforcement, and further the corrosion resistance decreases marginally. Solution heat treated samples exhibited higher resistance to oxidation than cast samples in all corrosive environments. The SEM images show the presence of micro cracks and occurrence of pitting corrosion on the corrosion tested specimens.展开更多
Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size ...Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size n is available from each population. This paper presents a likelihood ratio test criterion for testing equality of K multiple correlation matrices and extends the results to the testing of equality of K partial correlation matrices.展开更多
The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave tha...The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave that propagated in the sample were collected. The damage parameter was defined by ultrasonic parameter and the wave signals were analyzed by correlation method. The results show that with the increase of tensile load, the damage parameter increases and the correlation coefficient decreases. The fracture section morphologies of PMMC under tensile load were observed by SEM. It is found that there are many concaves in the metal matrix. Therefore the damage evolution can be concluded. The initial damage is induced by void nucleation, growth and subsequent coalescence in the matrix or interface separation.展开更多
In this paper we compare recently developed preliminary test estimator called Preliminary Test Stochastic Restricted Liu Estimator (PTSRLE) with Ordinary Least Square Estimator (OLSE) and Mixed Estimator (ME) in the M...In this paper we compare recently developed preliminary test estimator called Preliminary Test Stochastic Restricted Liu Estimator (PTSRLE) with Ordinary Least Square Estimator (OLSE) and Mixed Estimator (ME) in the Mean Square Error Matrix (MSEM) sense for the two cases in which the stochastic restrictions are correct and not correct. Finally a numerical example and a Monte Carlo simulation study are done to illustrate the theoretical findings.展开更多
Ridge type estimators are used to estimate regression parameters in a multiple linear regression model when multicolinearity exists among predictor variables. When different estimators are available, preliminary test ...Ridge type estimators are used to estimate regression parameters in a multiple linear regression model when multicolinearity exists among predictor variables. When different estimators are available, preliminary test estimation procedure is adopted to select a suitable estimator. In this paper, two ridge estimators, the Stochastic Restricted Liu Estimator and Liu Estimator are combined to define a new preliminary test estimator, namely the Preliminary Test Stochastic Restricted Liu Estimator (PTSRLE). The stochastic properties of the proposed estimator are derived, and the performance of PTSRLE is compared with SRLE in the sense of mean square error matrix (MSEM) and scalar mean square error (SMSE) for the two cases in which the stochastic restrictions are correct and not correct. Moreover the SMSE of PTSRLE based on Wald (WA), Likelihood Ratio (LR) and Lagrangian Multiplier (LM) tests are derived, and the performance of PTSRLE is compared using WA, LR and LM tests as a function of the shrinkage parameter d with respect to the SMSE. Finally a numerical example is given to illustrate some of the theoretical findings.展开更多
This investigation deals with the intelligent system for parallel fault-tolerant diagnostic tests construction. A modified parallel algorithm for fault-tolerant diagnostic tests construction is proposed. The algorithm...This investigation deals with the intelligent system for parallel fault-tolerant diagnostic tests construction. A modified parallel algorithm for fault-tolerant diagnostic tests construction is proposed. The algorithm is allowed to optimize processing time on tests construction. A matrix model of data and knowledge representation, as well as various kinds of regularities in data and knowledge are presented. Applied intelligent system for diagnostic of mental health of population which is developed with the use of intelligent system for parallel fault-tolerant DTs construction is suggested.展开更多
基金Project(2012zzts068) supported by the Fundamental Research Funds for the Central Universities of Central South University,ChinaProject(2010fj3091) supported by the Open Funding of State Key Laboratory of Powder Metallurgy and Science&Technology Foundation,China
文摘Mg-6%Zn-10%β-Ca3(PO4)2 composite was prepared through powder metallurgy methods with different chitosan coatings on its surface. The properties of the chitosan coatings on the surface of Mg-6%Zn-10%β-Ca3(PO4)2 composite, such as the adhesion ability, the corrosion behavior and the cytotoxicity properties, were investigated, and the microstructure of the chitosan coating was observed by scanning electron microscope(SEM). The results show that chitosan coating improves the corrosion resistance of the magnesium composite specimens significantly. Mg-6%Zn-10%β-Ca3(PO4)2 composite specimens exhibit good corrosion resistance and low p H values in simulated body fluid(SBF) at 37 °C in the immersion test with 7-layer chitosan coating whose relative molecular mass is 30×104 Da. The cytotoxicity tests indicate that Mg-6%Zn-10%β-Ca3(PO4)2 with chitosan coating is nontoxic with a cytotoxicity grade of zero against L-929 cells, which is better than that of uncoated composites.
基金Item Sponsored by National Natural Science Foundation of China(51401141)Science Foundation of Shanxi Province of China(2013011010-1)Youth Science Foundation of Shanxi Province of China(2014021017-3)
文摘The corrosion behavior study was conducted on a novel Fe77 Mo5P9C7.5 B1.5 in-situ metallic glass matrix composite （MGMC）. This composite sample was developed by introduction of bcc a-Fe dendrites as reinforcing phase. The corrosion behavior of this composite was compared to its monolithic counterpart and other Fe-based alloys such as 304L and 2304L stainless steels. The corrosion resistance of MGMCs in H2SO4 solution shows inferior to that of other Fe-based alloys. Experiments suggest that Fe-BMGs samples possess better corrosion resistance property than that of Fe-MGMCs. The possible underlying reasons can be the inhomogeneity induced by the precipitation of a-Fe dendrites in the MGMCs.
文摘AIM:To assess the effects of bile and pancreatic juice on structural and mechanical resistance of extracellular matrices(ECMs) in vitro.METHODS:Small-intestinal submucosa(SIS),porcine dermal matrix(PDM),porcine pericardial matrix(PPM) and bovine pericardial matrix(BPM) were incubated in human bile and pancreatic juice in vitro.ECMs were examined by macroscopic observation,scanning electron microscopy(SEM) and testing of mechanical resistance.RESULTS:PDM dissolved within 4 d after exposure to bile or pancreatic juice.SIS,PPM and PDM retained their integrity for > 60 d when incubated in either digestive juice.The effect of bile was found to be far more detrimental to mechanical stability than pancreatic juice in all tested materials.In SIS,the loss of mechanical stability after incubation in either of the digestive secretions was less distinct than in PPM and BPM [mFmax 4.01/14.27 N(SIS) vs 2.08/5.23 N(PPM) vs 1.48/7.89 N(BPM)].In SIS,the extent of structural damage revealed by SEM was more evident in bile than in pancreatic juice.In PPM and BPM,structural damage was comparable in both media.CONCLUSION:PDM is less suitable for support of gastrointestinal healing.Besides SIS,PPM and BPM should also be evaluated experimentally for gastrointestinal indications.
文摘An efficient method for helicopter rotor fault diagnosis was proposed using diagnostic matrix and its software framework was developed.The diagnostic matrix was extracted by the way of simulating the quantitative models of damaged and undamaged rotor systems.The conflicts were recognized by the virtual symptom sensor based on the dependencies between symptoms and faults.Diagnostic candidates were generated by the Boolean hitting algorithm.The proposed method provides multi-fault real-time diagnostic capability and it is suitable for the synthetic health monitoring of complex systems.
基金Supported by National Natural Science Foundation of China(11271039)
文摘In this paper, a statistical analysis method is proposed to research life characteristics of products based on the partially accelerated life test. We discuss the statistical analysis for constant-stress partially accelerated life tests with Lomax distribution based on interval censored samples. The EM algorithm is used to obtain the maximum likelihood estimations(MLEs) and interval estimations for the shape parameter and acceleration factor.The average relative errors(AREs), mean square errors(MSEs), the confidence intervals for the parameters, and the influence of the sample size are discussed. The results show that the AREs and MSEs of the MLEs decrease with the increase of sample size. Finally, a simulation sample is used to estimate the reliability under different stress levels.
文摘AIM: To validate accuracy of a novel chair-side test for matrix metalloproteinase(MMP)-8 as compared to enzyme-linked immunosorbent assay(ELISA) in Periodontal health and disease.METHODS: Gingival crevicular fluid was collected from 150 subjects, Group 1(healthy)- 50 subjects, Group 2(gingivitis)- 50 subjects and Group 3(chronic periodontitis)- 50 subjects. A chair-side test strip was indigenously prepared using polyclonal antibodies(principle of immunochromatography) to detect the MMP-8 levels. The detection accuracy(sensitivity and specificity) of the MMP-8 levels by chair-side test kit were compared with ELISA at baseline and 3 mo after scaling and root planing among the study population.RESULTS: The novel chair side test detected MMP-8 levels in accordance with ELISA which at baseline were higher in Group 2 and Group 3 as compared to controls(P < 0.05), and these enzyme levels decreased after therapy(P < 0.05). The chair-side test could differentiate healthy, gingivitis and periodontitis. The detection accuracy of the chair-side test strip were on par with ELISA(sensitivity 92.9% and specificity of 100%) which were statistically significant(P < 0.05). A desire to arouse interest about periodontal health and maintenance in the Indian population provided a strong rationale for us to develop our chair-side test strips to suit our economy. Moreover, this was the first ever effort to develop and validate a chair-side test strip to detect MMP-8 levels in the Indian population. This test can be used on a large scale in private dental practice for the early detection of disease, tapping the sites at risk for disease, alongside helps in patient education and motivation for maintenance.CONCLUSION: This study shows that the novel chair side test kit detects MMP-8 levels a biomarker of periodontal disease progression accurately making it a good chair side diagnostic tool. Further, it is cost effective and time saving which can make it applicable in private dental practice on a large scale for the early detection of periodontal disease.
文摘Aluminum-based metal matrix composites (MMCs) are considered in several technological applications owing to their enhanced mechanical properties when compared with monolithic metals. Research on the mechanical properties MMCs was done by many researchers;however in depth study on the oxidation behavior of cenosphere, reinforced MMCs are required, since the application of Aluminum-based MMCs is extensively used in applications like automobile, navigation and aviation, where the demand on light weight corrosion resistance material is very much required. In the present work varied compositions of Al7075 grade Aluminum-cenosphere composites use liquid metallurgy route adopting stir casting approach. The experimental study was aimed at experimental investigations of developed composites under different corrosive environments. The corrosion tests were carried out as per ASTM standards. Salt spray test using NaCl was carried out as per ASTM B117 and immersion tests using NaCl and NaOH as corrodents were carried out by following ASTM G31 standards. The results obtained from the tests revealed that as increase in weight % of reinforcement, corrosion resistance increases up to 7.5% reinforcement, and further the corrosion resistance decreases marginally. Solution heat treated samples exhibited higher resistance to oxidation than cast samples in all corrosive environments. The SEM images show the presence of micro cracks and occurrence of pitting corrosion on the corrosion tested specimens.
文摘Coutsourides derived an ad hoc nuisance paratmeter removal test for testing equality of two multiple correlation matrices of two independent p variate normal populations under the assumption that a sample of size n is available from each population. This paper presents a likelihood ratio test criterion for testing equality of K multiple correlation matrices and extends the results to the testing of equality of K partial correlation matrices.
基金Project(104014) supported by Fok' Ying Tong Education Foundation, China Project(05B008) supported by the Scientific Research Fund of Hunan Provincial Education Department, China
文摘The damage characteristic of particle reinforced metal matrix composite (PMMC) was studied by ultrasonic non-destructive evaluation method. After the sample was damaged induced by tensile load, the ultrasonic wave that propagated in the sample were collected. The damage parameter was defined by ultrasonic parameter and the wave signals were analyzed by correlation method. The results show that with the increase of tensile load, the damage parameter increases and the correlation coefficient decreases. The fracture section morphologies of PMMC under tensile load were observed by SEM. It is found that there are many concaves in the metal matrix. Therefore the damage evolution can be concluded. The initial damage is induced by void nucleation, growth and subsequent coalescence in the matrix or interface separation.
文摘In this paper we compare recently developed preliminary test estimator called Preliminary Test Stochastic Restricted Liu Estimator (PTSRLE) with Ordinary Least Square Estimator (OLSE) and Mixed Estimator (ME) in the Mean Square Error Matrix (MSEM) sense for the two cases in which the stochastic restrictions are correct and not correct. Finally a numerical example and a Monte Carlo simulation study are done to illustrate the theoretical findings.
文摘Ridge type estimators are used to estimate regression parameters in a multiple linear regression model when multicolinearity exists among predictor variables. When different estimators are available, preliminary test estimation procedure is adopted to select a suitable estimator. In this paper, two ridge estimators, the Stochastic Restricted Liu Estimator and Liu Estimator are combined to define a new preliminary test estimator, namely the Preliminary Test Stochastic Restricted Liu Estimator (PTSRLE). The stochastic properties of the proposed estimator are derived, and the performance of PTSRLE is compared with SRLE in the sense of mean square error matrix (MSEM) and scalar mean square error (SMSE) for the two cases in which the stochastic restrictions are correct and not correct. Moreover the SMSE of PTSRLE based on Wald (WA), Likelihood Ratio (LR) and Lagrangian Multiplier (LM) tests are derived, and the performance of PTSRLE is compared using WA, LR and LM tests as a function of the shrinkage parameter d with respect to the SMSE. Finally a numerical example is given to illustrate some of the theoretical findings.
文摘This investigation deals with the intelligent system for parallel fault-tolerant diagnostic tests construction. A modified parallel algorithm for fault-tolerant diagnostic tests construction is proposed. The algorithm is allowed to optimize processing time on tests construction. A matrix model of data and knowledge representation, as well as various kinds of regularities in data and knowledge are presented. Applied intelligent system for diagnostic of mental health of population which is developed with the use of intelligent system for parallel fault-tolerant DTs construction is suggested.
