Influence of climatic factors on tree-ring maximum latewood density of Picea schrenkiana in Xinjiang, China

The influence of temperature and precipitation on maximum latewood density （MXD） was mainly discussed in this paper, based on the samples of Picea schrenkiana from the Manas River Basin, Xinjiang, China. The correlation analysis between MXD and instrumental records from the Shihezi Meteorological Station showed that the MXD was positively related to the mean maximum temperature throughout the growing season at high elevations. Comparatively, the ring-width at low altitudes was limited by the precipitation in May-June. The composite chronology by MXD sequences was highly correlated with the mean maximum temperature in July- August （r = 0.54,p 〈 0.001）, which was then reconstructed by the composite chronology. The comparative analysis on the reconstructed temperatures, observed values, and drought indices （Is） revealed that precipitation would affect MXD when the absolute value of Is was greater than 1.5a （i.e., ｜Is｜ 〉 2.5） in the period of 1953-2008 A.D. or close to 1.5σ for 2-3 consecutive years. The response characteristics are linked with the semiarid climate in the study area. In a single year or consecutive years of extreme dryness, the lack of precipitation would limit the thickening oflatewood cell walls and thus impact the MXD. All in all, if a MXD chronology is aimed to reconstruct temperature history, the moisture conditions at the sampling site should be considered prudently.

A NUMERICAL STUDY OF INDENTATION WITH SMALL SPHERICAL INDENTERS

The finite element method for the conventional theory of mechanism-based strain gradient plasticity is used to study the indentation size effect. For small indenters （e.g., radii on the order of 10μm）, the maximum allowable geometrically necessary dislocation （GND） density is introduced to cap the GND density such that the latter does not become unrealistically high. The numerical results agree well with the indentation hardness data of iridium. The GND density is much larger than the density of statistically stored dislocations （SSD） underneath the indenter, but this trend reverses away from the indenter. As the indentation depth （or equivalently, contact radius） increases, the GND density decreases but the SSD density increases.

Performance evaluation of cement-stabilized pond ash-rice husk ashclay mixture as a highway construction material

This paper reports the results of an investigation carried out on clay soil stabilized with pond ash(PA),rice husk ash(RHA) and cement. Modified Proctor compaction tests were performed in order to investigate the compaction behavior of clay, and California bearing ratio(CBR) tests were performed to determine the strength characteristics of clay. For evaluation purpose, the specimens containing different amounts of admixtures were prepared. Clay was replaced with PA and RHA at a dosage of 30%e45% and5%e20%, respectively. The influence of stabilizer types and dosages on mechanical properties of clay was evaluated. In order to study the surface morphology and crystallization characteristics of the soil samples, scanning electron microscopy(SEM) and X-ray diffraction(XRD) analyses were carried out,respectively. The results obtained indicated a decrease in the maximum dry density(MDD) and a simultaneous increase in the optimum moisture content(OMC) with the addition of PA and RHA.Multiple linear regression analysis(MLRA) showed that the predicted values of CBR tests are in good agreement with the experimental values. Developed stabilized soil mixtures showed satisfactory strength and can be used for construction of embankments and stabilization of sub-grade soil. The use of locally available soils, PA, RHA, and cement in the production of stabilized soils for such applications can provide sustainability for the local construction industry.

General expression of double ellipsoidal heat source model and its error analysis

In order to analyze the maximum power density error with different heat flux distribution parameter values for double ellipsoidal heat source model, a general expression of double ellipsoidal heat source model was derived .front Goldak double ellipsoidal heat source model, and the error of maximum power density was analyzed under this foundation. The calculation error of thermal cycling parameters caused by the maximum power density error was compared quantitatively by numerical simulation. The results show that for guarantee the accuracy of welding numerical simulation, it is better to introduce an error correction coefficient into the Goldak double ellipsoidal heat source model expression. And, heat flux distribution parameter should get higher value for the higher power density welding methods.

Effects of Soil-Cement Stabilization on the Index Properties of Subgrades of Three Selected Roads in the Niger Delta Region of Nigeria

In this study, the impact of soil-cement stabilization on the index properties of the subgrade of roads was investigated. Efforts were on the means of improving the bearing capacity of the subgrade of a flexible pavement structure. Three selected roads (Ogbia-Nembe, section of the East-West Road and section of Port Harcourt-Aba Road) in the Niger Delta Region of Nigeria were examined to determine the effect of sand-cement stabilization on the compaction index property of their undisturbed subgrade and the optimal ratio of soil-cement on the expansive soils at which the California Bearing Ratio (CBR) is optimized. Disturbed soil samples were collected from twenty trial pits on each of the three study roads using a hand ulger and tested for their respective compaction index properties. It was discovered that their California Bearing Ratio (CBR) was very low. Some of the collected specimen materials were stabilized with varying percentages of soil-cement contents ranging from 6% - 14% in order to ascertain its effects on the compaction index properties of the sample soils. Results of the various stabilization test procedures show that: Stabilization of the soil using Soil-Cement Stabilization affected the Compaction Index properties of the soil and further improved the California Bearing Ratio (CBR). On the Ogbia-Nembe Road;Soil-Cement stabilization improved the CBR and is optimized at a 10% sand-cement ratio with optimum moisture content ranging from 6.2% - 14%, maximum dry density ranges from 1700 - 1780 kg/m3, yielding an average CBR of 42.7% for soaked samples. On the section of East-West Road from Eleme Junction to Etteh Junction;Soil-Cement stabilization improved the CBR and is optimized at a 14% sand-cement ratio with optimum moisture content ranging from 6.2% - 14.2%, maximum dry density ranges from 1660 - 1800 kg/m3, yielding an average CBR of 43.9% for soaked samples. On the section of Port Harcourt-Aba Express Road from Eleme Junction to Osisioma Junction;Soil-Cement stabilization improved the CBR and is optimized at a 12% sand-cement ratio having an optimum moisture content ranging from 5.4% - 17.3%, maximum dry density ranges from 1610 - 1740 kg/m3, and an average California Bearing Ratio for soaked samples at 40%.

Soil Improvement Using Waste Materials:A Review

With the industrialisation,industrial byproducts are produced in large quantities and create nuisance to natural habitats.The disposal of these wastes like fly ash,marble powder,construction and demolition(C&D)waste,brick powder,agricultural wastes etc.has become the potential threat to the ecosystem and need some real solutions.The direct disposal of such wastes into open land or water bodies causes circumambient pollution.One of the potential solutions is to utilise these wastes in the construction industry on large scale as subgrade rehab or additive to cement based materials.In the present study,the compaction and strength characteristics of stabilised soil have been studied by using various waste materials i.e.lime,cement,plastic waste,industrial waste,fibre,mushroom waste,wet olive pomace etc.and reviewed.The addition of additives improved the engineering properties of soil significantly.

Reliability analysis based on a novel density estimation method for structures with correlations

Estimating the Probability Density Function（PDF） of the performance function is a direct way for structural reliability analysis,and the failure probability can be easily obtained by integration in the failure domain.However,efficiently estimating the PDF is still an urgent problem to be solved.The existing fractional moment based maximum entropy has provided a very advanced method for the PDF estimation,whereas the main shortcoming is that it limits the application of the reliability analysis method only to structures with independent inputs.While in fact,structures with correlated inputs always exist in engineering,thus this paper improves the maximum entropy method,and applies the Unscented Transformation（UT） technique to compute the fractional moments of the performance function for structures with correlations,which is a very efficient moment estimation method for models with any inputs.The proposed method can precisely estimate the probability distributions of performance functions for structures with correlations.Besides,the number of function evaluations of the proposed method in reliability analysis,which is determined by UT,is really small.Several examples are employed to illustrate the accuracy and advantages of the proposed method.

Interaction of 80S Rat Liver Ribosome with Lipid Monolayers Studied by Electron Microscopy

The adsorption of 80S ribosome from rat liver on the surface of lipid monolayers was examined by the electron microscopy (EM) using a negative staining method. The results showed that a large number of ribosomes were adsorbed on the lipid membrane surfaces containing positively charged SA (octadecylamine), while few ribosomes were observed on surfaces of neutral or negatively charged lipid monolayers. The interaction of ribosome with positively charged monolayers was affected by the composition and ratio of the membrane lipids, and by the ionic strength and pH value of the subphase buffer. The results suggest that ribosome should be adsorbed on the membrane surface through electrostatic force.