Advanced Materials Research Vols. 455-456

Abstract: Rock damage and breaking mechanism with water jet has been as yet a difficult problem due to jet high turbulence and complicacy of rock material. According to fluid-structure interaction (FSI) theory, the standard k-epsilon two equations and control volume method for water jet, and the elastic orthotropic continuum and finite element method for rocks, are employed respectively to establish a numerical analyzing model of high pressure water jet impinging on rock. A damage criterion, with non-dimensional coefficient to characterize rock damage, is also set up for analyzing rock failure mechanism with water jet. The process of jet impact on the rock is simulated, by using the FSI model, Micro failure mechanism test and analysis with scanning electron microscope (SEM) for rock failure surface by jets cutting were performed, whose results show that the micro-mechanism of rock failure due to water jet impingement is a brittle fracture in the condition of tensile and shearing stress. The test results also agree well with the numerical simulating analysis, which constructs a bridge between the micro-failure and macro-breaking mechanism of rock with water jets impact. The investigation affords a new method for studying the mechanism of rock failure underhigh pressure water jet impingement.

Abstract: Various methods have been introduced to predict postweld hardness of the heat affected zone (HAZ) for 9% Ni steel which is a primary steel adopted in the construction of liquefied natural gas (LNG) storage facilities. Two models were derived for the evaluation of the HAZ hardness, and then validated. The formulae developed in this investigation are sufficient to predict the hardness of the HAZ for 9% Ni steel . For the model using a rule of mixture, it is suggested that the morphology of martensite should be taken into consideration. Since the prediction of hardness depends on the calculation of the critical cooling time and hardness of microstructural constituents, a formula to estimate the hardness of martensite in HAZ was given. For empirical equation relating welding parameters, calculation results were found to give a fairly good description of the postweld HAZ hardness.

Abstract: In order to improve thermal to-electric energy conversion efficiency of the micro gas turbine power generation system, a novel micro porous media combustor is designed and experimental investigation on the H₂/air diffusion combustion is performed to obtain its combustion characteristics. High efficiency diffusion combustion of H₂/air can be stabilized in the very wide operating range, especially at higher excess air ratio. Exhaust gas temperature is markedly improved and meanwhile heat loss ratio is evidently decreased. Moreover, in the certain operating ranges, the greater the combustion thermal power and excess air ratio, the smaller heat loss of the micro combustor will be. The micro porous media combustor should be a preferred micro combustor for developing the micro gas turbine power generation system.

Abstract: The photoelectrical responsibility of single photo-electronic devices makes it difficult to achieve the high efficiency under light intensity range. The key to overcome limits is to develop the system consisting of a set of solar cells. In this work, we predict the model parameters under various conditions combination of three model parameters change with the relationship between light and temperature and then predict the value of the model parameters under various conditions and thus predict the components of the output characteristics under 0.5S UN--6.0 SUN. The results given in this work will provide a way to realize a high photo-electric conversion efficiency of the solar system in application.

Abstract: In order to improve capacitance in supercapacitors application, activated carbon (AC) was modified by nitric acid oxidizing treatment. Oxygen-containing functional groups (OCFG) were detected by using FTIR techniques. Cyclic voltammetry and constant current charge-discharge were used to characterize the electrochemical performance of the samples in 6 mol/L KOH solution. FTIR studies showed that chemical modification promoted the formation of OCFG on the surface of AC. It was found that the contribution rate of pseudo-capacitance to the total capacitance increased significantly with the extent of oxidization treatment. When oxidized by 50% HNO3, AC achieved a specific capacitance of 197.26F/g at a current density of 20mA/cm2 corresponding to an increasing rate up to 20%.

Abstract: . This study introduces support vector regression (SVR) approach to model the relationship between the glass transition temperature (Tg) and multipole moments for polymers. SVR was trained and tested via 60 samples by using two quantum chemical descriptors including the molecular traceless quadrupole moment and the molecular average hexadecapole moment Φ. The prediction performance of SVR was compared with that of reported quantitative structure property relationship (QSPR) model. The results show that the mean absolute error (MAE), mean absolute percentage error (MAPE) and root mean square error (RMSE) of training samples and test samples achieved by SVR model, are smaller than those achieved by the QSPR model, respectively. This investigation reveals that SVR-based modeling is a practically useful tool in prediction of the glass transition temperature of polymers.

Abstract: . Based on two quantum chemical descriptors (the thermal energy Ethermal and the total energy of the whole system EHF) calculated from the structures of the repeat units of polyacrylamides by density functional theory (DFT), the support vector regression (SVR) approach combined with particle swarm optimization (PSO), is proposed to establish a model for prediction of the glass transition temperature (Tg) of polyacrylamides. The prediction performance of SVR was compared with that of multivariate linear regression (MLR). The results show that the mean absolute error (MAE=4.65K), mean absolute percentage error (MAPE=1.28%) and correlation coefficient (R2=0.9818) calculated by leave-one–out cross validation (LOOCV) via SVR models are superior to those achieved by QSPR (MAE=14.25K, MAPE=4.39% and R2=0.9211) and QSPR-LOO (MAE=17.01K, MAPE=5.66% and R2=0.8823) models for the identical samples, respectively. The prediction results strongly demonstrate that the modeling and generalization abilities of SVR model consistently surpass those of QSPR and QSPR-LOO models. It is revealed that the established SVR model is more suitable to be used for prediction of the Tg values for unknown polymers possessing similar structure than the conventional MLR approach. These suggest that SVR is a promising and practical methodology to predict the glass transition temperature of polyacrylamides.

Abstract: Anthocyanins are the main pigments in flowers and fruits. In most cases, anthocyanin accumulation in fruit is highly controlled by the developmental level. In this study, the cDNA fragments of three genes, chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), and anthocyanidin synthase (ANS), which are involved in the flavonoid pathway, were isolated from total RNA of strawberry ripe fruit by using polymerase chain reaction technique and labeled as probes to determine the expression of anthocyanin biosynthetic genes. Northern analysis showed that a correlation between anthocyanin accumulation and expression of the flavonoid pathway genes during the ripening of strawberry fruits. At the early stages of fruit development, the mRNA levels encoding CHS, DFR, ANS were high probably responsible for the accumulation of condensed tannins, but the levels decreased dramatically when fruits turned white from green. During the stage of pigment accumulation, their mRNA levels increased strongly to be involved anthocyanin biosynthesis. Difference of CHS in mRNA abundance was correlated with differential accumulation of anthocyanins throughout the process of fruit development. Therefore, CHS could be a key structure gene involved in anthocyanin synthesis. Furthermore, the co-ordination of expression of anthocyanin biosynthetic genes implied a common regulatory mechanism controlling the expression of structural genes in the flavonoid pathway.

Abstract: . Aloe, an important folk herbal drug, includes abundant polysaccharides and secondary metabolites which bringing about the difficulty of isolating high-quality DNA or RNA. In this paper, one and two improved methods were used to isolate the genomic DNA and RNA from the leaf of Aloe, respectively. The obtained samples presented good quality and integrality, and thus, they could be further used for many downstream molecular experiments. This reported protocols on extraction of DNA and RNA offered a valuable reference for other related studies.

Abstract: . Antibacterial proteins/peptides are important parts of the innate immune system in Clarias gariepinus. To examine potential antibacterial proteins/peptides in organs and mucus of C. gariepinus, crude protein/peptide extracts were isolated with ammonium sulfate precipitation from mucus, skin, gill, suprabranchial organ and intestine. Following further extraction using Sephadex G-50 gel filtration chromatography, the proteins/peptides associated with two absorption peaks (AP1 and AP2) were pooled, respectively, and assayed for their antibacterial activities against Escherichia coli, Aeromonas hydrophila and Edwardsiella tarda. The results showed that AP1 and AP2 from all the sampled tissues and mucus at concentration of 100 mg mL-1 exhibited antibacterial activity against the tested bacterial strains. Differences in antibacterial activity were observed among sample extracts. The protein profiles of AP1 obtained by Tricine-SDS-PAGE gel showed a broad range of peptides/proteins, and molecular weight of the mutual abundant peptide obtained was about 27 kDa. Antibacterial activity of AP2 extracted from intestine was due to peptide with molecular weight of 5.5 kDa.