Anisotropic lattice Boltzmann-phase-field modeling of crystal growth with melt convection induced by solid-liquid density change

Density change is ubiquitous in phase transformation, and it can induce melt convection which strongly influences the crystal growth. Here, an anisotropic lattice Boltzmann-phase-field method was extended to predict the dendritic growth under the shrinkage or expansion melt convection by density change induced. A novel LB equation with an anisotropic coefficient was constructed to model the advancement of ordering parameter, coupling with the passive scalar LB equation for convective and diffusive heat transfer during phase transition. We studied dendritic growth and shape selection with melt convection induced by density change in crystal growth. Results show that the melt convection induced by density change affects strongly the dendritic growth. The shrinkage flow results in a higher tip velocity while the expansion flow leads to a slower one. Predicted Péclet number with respect to the relative density change was compared with an analytical solution. Moreover, the modified selection parameter has been verified by numerical simulations.

The changes of preoperative bone mineral density of patients with nonfunctional pituitary adenoma

Objective To evaluate the bone mineral density (BMD) alteration of patients with nonfunctional pituitary adenoma in Chinese mainland and further to investigate the relevant factors of BMD changes. Methods 31 patients with nonfunctional adenoma and 255 healthy controls were enrolled in this study between December 2007 and May 2008.

A New Kind of Shape-stabilized Phase Change Materials

Based on the lowest melting point and Schroeder’s theoretical calculation formula,nano- modified organic composite phase change materials（PCMs）were prepared.The phase transition temperature and the latent heat of the materials were 24℃and 172 J/g,respectively.A new shape-stabilized phase change materials were prepared,using high density polyethylene as supporting material.The PCM kept the shape when temperature was higher than melting point.Thus,it can directly contact with heat transfer media.The structure,morphology and thermal behavior of PCM were analyzed by FTIR,SEM and DSC.

Analysis of Dynamic Variations of Crustal Density in the Longmenshan Area before the Wenchuan M_S8.0 Earthquake

Based on the repeated gravity observation data from 1996 to 2007 from the Longmenshan gravity network, which has been dealt with by adjustment processing, the benchmark interference removal and impact of elevation changes removal, and by using the 3-D inversion method to reflect underground density, we analyze the characteristics of Longmenshan regional dynamic crustal density at depths of 25km, 20km and 15kin. The results show that in the Wenchuan earthquake preparation process, the regional density field showed marked characteristics both in time and space distribution. From the point of time process, the density change trend in the ten years before the earthquake presents a periodic change pattern： steady phase, dramatic stage, slow reducing phase and slow increase phase. The degree of density changes is from large to small, which means that earthquake gestation has reached the final stage. From the point of space distribution, density change distribution has a tendency of ＂dispersion--relative concentration＂, this shows that before the earthquake, the entropy of the underground density field was decreased. In addition, dramatic density changes often occur in the Longmenshan fault zone and western Sichuan plateau. Also, with the increase of depth, the trend of density change is more and more obvious. Through comparative analysis, the influence of density change on gravity is much bigger than that from height change.

Disturbance and forest recovery in the Monarch Butterfly Biosphere Reserve,Mexico

Analysis of the change in forest cover is important to determine stand dynamics and the processes involved in disturbance and recovery.Forests of the core zone of the Monarch Butterfly Biosphere Reserve were studied using photo interpretation techniques,considering biennial changes between 1999 and 2013 and changes over the whole period of study 1999–2013.Error matrices were elaborated to determine the processes of change involved in both recovery and disturbance.The biennial changes for the whole period amounted to 2274 ha;343 ha accounted as degraded in more than one biennial period.The total changes in forest cover between 1999 and 2013 involved 4902 ha,out of which,2912 ha were affected by disturbance,and 1990 ha were recovered.For density and 2013 vegetation cover maps,the overall accuracy was 95.6%and 90.2%,respectively.By combining both maps,gradual processes were revealed that were not evident in separate analyses.This methodology is useful for the management and conservation of natural protected areas.

Effects of Forest Type and Urbanization on Carbon Storage of Urban Forests in Changchun, Northeast China

Rapid urbanization has led to dramatic changes in urban forest structures and functions, and consequently affects carbon(C) storage in cities. In this study, field surveys were combined with high resolution images to investigate the variability of C storage of urban forests in Changchun, Northeast China. The main objectives of this study were to quantify the C storage of urban forests in Changchun City, Northeast China and understand the effects of forest type and urbanization on C storage of urban forests. The results showed that the mean C density and the total C storage of urban forests in Changchun were 4.41 kg/m2 and 4.74 × 108 kg, respectively. There were significant differences in C density among urban forest types. Landscape and relaxation forest(LF) had the highest C density with 5.41 kg/m2, while production and management forest(PF) had the lowest C density with 1.46 kg/m2. These differences demonstrate that urban forest type is an important factor needed to be considered when the C storage is accurately estimated. Further findings revealed significant differences in different gradients of urbanization, and the mean C density decreased from the first ring(6.99 kg/m2) to the fourth ring(2.87 kg/m2). The total C storage increased from the first ring to the third ring. These results indicate that C storage by urban forests will be significantly changed during the process of urbanization. The results can provide insights for decision-makers and urban planners to better understand the effects of forest type and urbanization on C storage of urban forests in Changchun, and make better management plans for urban forests.

The relationships between land use change and demographic dynamics in western Jilin province

Demographic change was thought to although there were several interacting factors be the most major driver of land use change involved, especially in the developing coun- tries. In this paper, we selected western Jilin province in China as the study area to provide a case study for understanding the relationship between spatial-temporal pattern of the land use change and population dynamics from 1975 to 2010. The results showed that the change of farmland area percentage could be modeled well by using a quadratic function, the least area percentage of farmland was 15.4% in areas where the population density was 0 peo- ple/km2, and farmland area percentage had a greatest value of 94.8% when population den- sity was 199.25 people/km2. The area percentage of grassland, water body and wetland de- creased exponentially with population density increased. The relationship between land use degree and population density could be modeled well by using a logistic regression models. Due to economic growth and technological progress and the existence of Hollow Village phenomenon, land use degree still increased in areas where population density was negative growth. In addition, land use dynamics increased exponentially with population density change. Land use relative change of woodland, grassland, built-up land and wetland were proportional to population density change. According to the simulation results of the land use structure and land use degree, Da＇an and Zhenlai had the greatest possibility to be further reclaimed. As sensitive and fragile areas, it was of significance to study environmental pro- tection and ecologic construction on Tongyu and Qian＇an.

Prediction of density and volume variation of hematite ore particles during in-flight melting and reduction

HIsarna is a promising ironmaking technology to reduce CO2 emission.Information of phase transformation is essential for reaction analysis of the cyclone reactor of the HIsarna process.In addition,data of density and volume of the ore particles are necessary for estimation of the residence time of the particles in the cyclone reactor.Phase transformation of iron ore particles was experimentally studied in a drop-tube furnace under simulated cyclone conditions and compared with thermodynamic calculation.During the pre-reduction process inside the reactor,the mineralogy of iron ore particles transforms sequentially from hematite to sub-oxides.The density changes of the particles during the melting and reduction can be predicted based on the phase composition and temperature.Therefore,density models in the studies were evaluated with reported experimental data of slag.As a result,a more reliable density model was developed to calculate the density of the formed slag containing mainly FeO–Fe2O3.The density and volume of the partially reduced ore particles or melt droplets were estimated based on this model.The results show that the density of the ore particles decreases by 15.1%at most along the progressive reduction process.Furthermore,the model results also indicate that heating,melting and reduction of the ore could lead to 6.63%–9.37%swelling of the particles,which is mostly contributed by thermal expansion.It would result in corresponding variation in velocity of the ore particles or melt droplets during the flight inside the reactor.