含水量增加时湿陷性黄土变形特性研究

本文通过湿陷性黄土变含水量情况下的室内试验，结合试验曲线提出了变形分界含水量、变形分界压力的概念，将它们与湿陷起始含水量、湿陷起始压力作了比较，对变形分界含水量、变形分界压力的应力阐明了初步设想。

Seasonal changes of soil respiration in Betula platyphylla forest in Changbai Mountain, China

A stdudy was conducted to determine the seasonal changes of soil respiration and the contribution of root respiration to soil respiration in Betula plaophylla forest in Changbai Mountain from May to September in 2004. Results indicated that the total soil respiration, root-severed soil respiration and the root respiration followed a similar seasonal trend, with a high rate in summer due to wet and high temperature and a low rate in spring and autumn due to lower temperature. The mean rates of total soil respiration, root-severed soil respiration and root respiration were 4.44, 2.30 and 2.14 μmol.m^-2.s^-1, respectively during the growing season, and they were all exponentially correlated with temperature. Soil respiration rate had a linear correlation with soil volumetric moisture. The Q10 values for total soil respiration, root-severed soil respiration and root respiration were 2,82, 2.59 and 3. 16, respectively. The contribution rate of root respiration to the total soil respiration was between 29.3% and 58.7% during the growing season, indicating that root is a major component of soil respiration. The annual mean rates of total soil respiration, root-severed soil respiration and root respiration were 1.96, 1.08, and 0.87 μmol.m^-2.s^-1, or 741.73 408.71, and 329.24 g.m^-2.a^-1, respectively. Root respiration contributed 44.4% to the annual total soil respiration. The relationship proposed for soil respiration with soil lemperature was useful for understanding and predicting potential changes in Changbai Mountain B. platyphylla forest ecosystem in response to forest management and climate change.

Effects of Forest Gaps on Some Microclimate Variables in Castanopsis kawakamii Natural Forest

The objective of this study was to understand the effects of forest gap and variations in different seasons, gap size, locations and diurnal variations on forest microclimate and soil water content. Spatial and temporal distribution features oi air temperature （TA）, soil temperature （Ts）, relative humidity （h） and soil water content （ψ） were measured in Castanopsis kawakamii natural forest gaps created by a severe typhoon or fallen dead trees. The results showed that： （1） the variations of TA, h, and Tsin four seasons were extremely significant. The variations of ψ in four seasons were extremely significant except for those between spring and summer. （a） The diurnal variations of TA and Tswere expressed with a single peak curve. The diurnal variations of h and ψ presented a high-low-high trend （3） The variations of TA, h, and Ts were extremely significant among the large, medium and small gaps in C. kawakamii natural forest. Medium gaps had the highest TA and the lowest h while small gaps were jusl contrary to medium gaps. The variations of T were extremely significant for large, medium and small gaps except those between the medium and large gaps （4） The TA, h, Ts and ψ were decreased from the gap center, canopy gap, expanded gap to understory. These results will help further our understanding of the abiotic and consequent biotic responses to gaps in the mid-subtropical broadleaved forests, which also provide a theoretical basis for the scientific management and population restoration of C. kawakamii natural forest.

Variation characteristics of aquifer parameters induced by groundwater source heat pump operation under variable flow

The variation characteristics of aquifer parameters,induced by groundwater source heat pump(GWSHP) operation under variable flow,were theoretically analyzed through a case study,in which the characteristics of building air conditioning load were considered.The results,compared with the constant flow operation,indicate that the influence on the variations of porosity,hydraulic conductivity and confined water head is decreased by 48%,51% and 71%,respectively,under variable flow operation.The security of variable flow operation is superior to that of constant flow.It is also concluded that the climate region and function of the buildings are primary factors which affect the suitability of variable flow operation in GWSHP.

Physiological and Biochemical Response of Artificial Wetland Plant under Electric Field

By measuring wetland plants chlorophyll content,malondialdehyde(MDA) content and superoxide dismutase(SOD) enzyme activity,the changes of wetland plant physiological characeristics under different power strength were studied,and the mechanism of electric field on plant physiological characteristics was analyzed to provide a theoretical basis for the pollutant removal ability strengthening of artificial wetland under electricfield.The results showed that compared with the control plants,low-intensity-voltage(1 V and 3 V) had no significant effect on the normal physiological and biochemical indexes of the plants,and the growth trend was better than the control group;with the voltage increasing,plant chlorophyll content,MDA content and SOD activity were greatly affected,indicating that plants were under strong oxidative stress,and the growth was damaged.Therefore,a suitable electric field could enhance the sewage treatment effect of constructed wetland.

Global Water Vapor Content Decreases from 2003 to 2012： An Analysis Based on MODIS Data

Water vapor in the earth′s upper atmosphere plays a crucial role in the radiative balance, hydrological process, and climate change. Based on the latest moderate-resolution imaging spectroradiometer(MODIS) data, this study probes the spatio-temporal variations of global water vapor content in the past decade. It is found that overall the global water vapor content declined from 2003 to 2012(slope b = –0.0149, R = 0.893, P = 0.0005). The decreasing trend over the ocean surface(b = –0.0170, R = 0.908, P = 0.0003) is more explicit than that over terrestrial surface(b = –0.0100, R = 0.782, P = 0.0070), more significant over the Northern Hemisphere(b = –0.0175, R = 0.923, P = 0.0001) than that over the Southern Hemisphere(b = –0.0123, R = 0.826, P = 0.0030). In addition, the analytical results indicate that water vapor content are decreasing obviously between latitude of 36°N and 36°S(b = 0.0224, R = 0.892, P = 0.0005), especially between latitude of 0°N and 36°N(b = 0.0263, R = 0.931, P = 0.0001), while the water vapor concentrations are increasing slightly in the Arctic regions(b = 0.0028, R = 0.612, P = 0.0590). The decreasing and spatial variation of water vapor content regulates the effects of carbon dioxide which is the main reason of the trend in global surface temperatures becoming nearly flat since the late 1990 s. The spatio-temporal variations of water vapor content also affect the growth and spatial distribution of global vegetation which also regulates the global surface temperature change, and the climate change is mainly caused by the earth's orbit position in the solar and galaxy system. A big data model based on gravitational-magmatic change with the solar or the galactic system is proposed to be built for analyzing how the earth's orbit position in the solar and galaxy system affects spatio-temporal variations of global water vapor content, vegetation and temperature at large spatio-temporal scale. This comprehensive examination of water vapor changes promises a holistic understanding of the global climate change and potential underlying mechanisms.

Stress-strain relationship of unsaturated cohesive soil

A moisture-content based constitutive model was proposed based on the hyperbolic model as an attempt to move towards the implementation of unsaturated soil mechanics into routine geotechnical engineering practice. The stress-strain behavior of in-situ soil at a depth of 5 m was investigated by conducting undrained triaxial compression tests using the remolded soil samples. The test results show that the stress-strain relationship of unsaturated cohesive soil is still hyperbolic. The values of parameters a and b given in the model decrease with increasing the confining pressure for soil samples with the same moisture content and increase with increasing the moisture content for soil samples under the same confining pressure. The relationships between parameters a, b and moisture content were studied for confining pressures of 100, 150, 200 and 250 kPa. The comparison between the measured and predicted stress-strain curves for an additional group of soil samples, having a moisture content of 25.4%, shows that the proposed moisture content-dependent hyperbolic model provides a good prediction of stress-strain behavior of unsaturated cohesive soil.

Moisture effect on compressive behavior of concrete under dynamic loading

The effect of moisture content upon compressive mechanical behavior of concrete under impact loading was studied. The axial rapid compressive loading tests of over 50 specimens with five different saturations were executed. The technique "split Hopkinson pressure bar"(SHPB) was used. The impact velocity was 10 m/s with corresponding strain rate of 50 s-1. The compressive behavior of materials was measured in terms of stress-strain curves, dynamic compressive strength, dynamic increase factor(DIF) and critical strain at a maximum stress. The data obtained from test indicate that both ascending and descending portions of stress-stain curves are affected by moisture content. However, the effect is noted to be more significant in ascending portion of the stress-strain curves. Dynamic compressive strength is higher at lower moisture content and weaker at higher moisture content.Furthermore, under nearly saturated condition, an increase in compressive strength can be found. The effect of moisture content on the average DIF of concrete is not significant. The critical compressive strain of concrete does not change with moisture content.

Analysis of Soil Water Dynamics in a Tropical Rain Forest Soil （Arinic lixisol）, Abeokuta, Nigeria

Soil water dynamics in the dominant lwo soil series （Arinic lixisol） were evaluated at the Federal University of Agriculture, Alabata, Abeokuta, Nigeria. Field capacity, infiltration and water retention characteristics were evaluated in situ for a period of 161 d in the dry season for two root zone depths. Results show that the Iwo soil series has a field capacity ranging from 2.6%-5.5% at 0-45 cm and 45-90 cm root zone depths, respectively. The soil is quick draining with high infiltration rate and very poor water retention capacity confirming that the soil will require a short irrigation interval of about 2-3 d since available water for plant growth in predominantly sandy soils ranges between 2%-8%. Based on the foregoing, sprinkler irrigation is best suited for the lwo soil series, it should, however, be noted that the water application rate must be less than the infiltration rate of the soil in order to prevent surface ponding and runoff. A multivariate model relating soil moisture content with soil moisture tension and soil temperature calibrated within the study had very low model accuracy of 56% and 45% for the two root zone depths, respectively, implying the need for further studies.

Temporal and Spatial Variability of Dissolved Organic Carbon Concentration in the Xijiang River, South China

A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological seasons. The DOC level during the flood season (1.18 mg L-1) was less than that during the non-flood season (1.40 mg L-1). Owing to the concomitance of the flushing and dilution effects of the runoff during the high-water period, the variation of riverine DOC concentration with discharge in the XJR differed from that reported in many other major rivers. The DOC export flux above the city of Wuzhou was about 0.62× 106 g C km-2 yr-1. The DOC transported during the "056" Massive Flood period comprised 30.35% of the annual total, while the discharge accounted for 36.32% of the total annual flow. The characteristics in riverine DOC concentration in the XJR were attributed to the combined effect of the geomorphologic, monsoon climatic and hydrological processes as well as land-use within the drainage basin.

Thermal and Textural Changes of Turkish Delight with Storage Relative Humidity

Lokum （Turkish delight） is a high sugar and starch containing food. Since the major deterioration factor affecting the storability of lokum is moisture gain or loss, the effect of the possible ambient conditions （32%, 53%, 75% RH and 15, 25, 35 ℃） on weight change and firmness of tokum was determined to estimate its structural changes. The variations in thermal properties of lokurn samples stored at different RH （32, 53, 65, 75, and 85% RH） were also determined. Increasing RH decreased glass transition of lokum samples, and two glass transitions （Tg） were observed at 75 and 85% RH. The presence of the second Tg could be related with phase separation which was increased with increasing moisture content and RH. Lokum should be kept at around 50% RH and 15℃, higher storage RH＇s and temperatures will cause the product to become unacceptable by the consumer within 20 days.

Comparison of steam-gasification characteristics of coal char and petroleum coke char in drop tube furnace

The steam-gasification reaction characteristics of coal and petroleum coke （PC） were studied in the drop tube furnace （DTF）. The effects of various factors such as types of carbonaceous material, gasification temperature （1100- 1400 ℃） and mass ratio of steam to char （0.4：1, 0.6：1 and 1：1 separately） on gasification gas or solid products were investigated. The results showed that for all carbonaceous materials studied, H2 content exhibited the largest part of gasification gaseous products and CH4 had the smallest part. For the two petroleum cokes, CO2 content was higher than CO, which was similar to Zun-yi char. When the steam/char ratio was constant, the carbon con- version of both Shen-fu and PC chars increased with increasing temperature. When the gasification temperature was constant, the carbon conversions of all char samples increased with increasing steam/char ratio. For all the steam/char ratios, compared to water gas shift reaction, char-H2O and char-CO2 reaction were further from the thermodynamic equilibrium due to a much lower char gasification rate than that of water gas shift reaction rate. Therefore, kinetic effects may play a more important role in a char gasification step than thermodynamic effects when the gasification reaction of char was held in DTF, The calculating method for the equilibrium shift in this study will be a worth reference for analysis of the gaseous components in industrial gasifier. The reactivity of residual cokes decreased and the crystal layer （L002/d002） numbers of residual cokes increased with increasing gasification temperature. Therefore, L002/d002, the carbon crystallite structure parameter, can be used to evaluate the reactivity of residual cokes.

Experimental and theoretical study on thermal and moisture characteristics of new-type bamboo structure wall

Thermal and moisture characteristics of the bamboo structure wall were tested in natural climate and three representative variation processes of heat and moisture： heating from solar radiation in summer at normal temperature and humidity, heating from solar radiation in summer at normal temperature and high humidity after rain, humidifying from brash in summer at high temperature and normal humidity. The results show that, in summer, the largest temperature difference between external and internal surface of the 28 mm-thick bamboo plywood wall is 11.73℃ （at 15：40） and the largest strain difference is 136 μm/m （at 18：50）, both in ambient and indoor conditioned environment. In heating process, lengthways of the wall surface are in contracting strain while transverse ways are in expanding strain at initial stage and in contracting strain during later period. When the high temperature wall is humidified by rain, the surface temperature drops, moisture content increases and the expanding strain is presented on the surface during the whole process. Temperature and moisture content are two important factors which affect thermal and moisture stress （TMS） of the bamboo structure wall. The TMS is not only related to temperature and moisture content, but also greatly affected by temperature gradient, moisture content gradient and rates of changing.

Soil Respiration in a Subtropical Mangrove Wetland in the Jiulong River Estuary, China

The diurnal and seasonal variations of soil respiration （SR） were studied at a subtropical mangrove wetland in the Jiulong River Estuary from May 2010 to April 2011. SR rates were measured continuously from 08：00 to 06：00 local time （24-h time system） on July 8-9 and October 3-4, 2010; and January 15-16 and April 11-12, 2011. Similar patterns in the diurnal variation of SR were observed on October 2-3 and April 11-12, with the maximum values at 14：00 and the minimum at 00：00. However, the diurnal dynamics of SR on July 8-9, 2010 and January 15-16, 2011 showed different patterns, with the maximum values at 08：00-10：00 on above sampling dates and the minimum at 22：00 on July 8 and at 04：00 on January 16. The daily mean values of SR approximated to the values measured at 08：00. SR fluctuated with distinct seasonal patterns. The seasonal variation was characterized by a mono-peak pattern, with the highest rate （6.18 ~mol CO2 m-2 s-1） in July and the lowest rate （0.36 ~tmol CO2 m-2 s-1） in December. The results showed that the variation of SR in mangrove wetland was mainly controlled by soil temperature, and there was no significant correlation between SR and soil water content. It also implied that the model of SR in mangrove wetland should not only consider the effect of soil temperature, but also incorporate other factors, such as water level, precipitation, microbial activity and photosynthesis, which also could affect SR.

Temporal Variations in Soil CO_2 Efflux Under Diferent Land Use Types in the Black Soil Zone of Northeast China

The quantification of soil CO2 effiux is crucial for better understanding the interactions between driving variables and C losses from black soils in Northeast China and for assessing the function of black soil as a net source or sink of atmospheric CO2 depending upon land use. This study investigated responses of soil CO2 effiux variability to soil temperature interactions with different soil moisture levels under various land use types including grassland, bare land, and arable （maize, soybean, and wheat） land in the black soil zone of Northeast China. The soil CO2 effiuxes with and without live roots, defined as the total CO2 efftux （FtS） and the root-free CO2 ei^lux （FrfS）, respectively, were measured from April 2009 to May 2010 using a static closed chamber technique with gas chromatography. The seasonal soil CO2 fluxes tended to increase from the beginning of the measurements until they peaked in summer and then declined afterwards. The mean seasonal FtS ranged from 20.3=h7.8 to 58.1~21.3 mg CO2-C m-2 h-1 for all land use types and decreased in the order of soybean land ~ grassland 〉 maize land ~ wheat land ） bare land, while the corresponding values of FrfS were relatively lower, ranging from 20.3~7.8 to 42.3~21.3 mg CO2-C m-2 h-1. The annual cumulative FtS was in the range of 107-315 g CO2-C m-2 across all land uses types. The seasonM CO2 effiuxes were significantly （P 〈： 0.001） sensitive to soil temperature at 10 cm depth and were responsible for up to 62% of the CO2 effiux variability. Correspondingly, the temperature coefficient Q10 values varied from 2.1 to 4.5 for the seasonal FtS and 2.2 to 3.9 for the FrfS during the growing season. Soil temperature interacting with soil moisture accounted for a significant fraction of the CO2 flux variability for FtS （up to 61%） and FrfS （up to 67%） via a well-defined multiple regression model, indicating that temperature sensitivity of C02 flux can be mediated by water availability, especially under water stress.

Water-enhanced plastic deformation in felsic rocks

Using Fourier transform infrared spectroscopy(FTIR),we measured water contents in quartz and feldspar for four kinds of felsic rocks,i.e.,undeformed granite,banded granitic gneiss,fine-grained felsic mylonite,and fine-grained quartz-mica schist,collected from Pengguan Complex and Kangding Complex in the Longmenshan tectonic zone,Sichuan,China.The absorbance spectra suggest that water in coarse-grained quartz and feldspar of undeformed granite and banded granitic gneiss occurs mainly as hydroxyl in crystal defects,and water in most of fine-grained quartz and feldspar of felsic mylonite is molecular water in inclusions and liquid-type water in grain boundaries,but in some cases it still occurs as hydroxyl in crystal defects.Water content of quartz in undeformed granite is 0.001 wt%-0.009 wt %,and that of feldspar 0.005 wt%-0.02 wt%.The banded granitic gneiss shows water contents of 0.002 wt%-0.011 wt% in quartz and 0.012 wt%-0.036 wt% in feldspar.Quartz ribbon and feldspar ribbon in fine-grained felsic mylonite show that their water contents are similar to those of coarse-grained quartz and feldspar in granite,0.002 wt%-0.011 wt%,and 0.004 wt%-0.02 wt%,respectively.Water contents of fine-grained quartz and feldspar are respectively 0.004 wt%-0.02 wt% and 0.012 wt%-0.06 wt%.Water content of quartz in fine-grained quartz-mica schist is 0.007 wt%-0.15 wt%.Water-bearing minerals display much higher water contents than those of nominally anhydrous minerals,and the percentage of water-bearing minerals in felsic rocks increases with the strain of rocks.These new data indicate that hydroxyl in crystal defects has basically not been released during the shear deformation,and on the contrary,the increase in molecular water in inclusions and liquid-type water in grain boundaries as well as water-bearing minerals after shear deformation leads to a significant increase of the water content in deformed rocks.Based on data of creep tests,it is inferred here that the fine-grained mylonites with more water have much lower strength than that of the weakly deformed coarse-grained rocks in the middle crust,and this indicates that trace amount of water significantly helped develop the ductile shear zone.

New insights into the effects of molecular weight and end group on the temperature-induced phase transition of poly(N-isopropylacrylamide) in water

In an attempt to clarify issues related to the molecular weight dependence of the phase transition of poly(N-isopropylacrylamide) (PNIPAM) in water,we prepared a library of PNIPAM samples of well-controlled molecular weight (7000 to 45000 g/mol) bearing identical groups on each chain end.The polymers were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) with a bifunctional chain tranfer agent and further end group modification.The effects of the end group chemical structure,hydroxyethyl (HE),propargyl (Pr),chloroethyl (CE),n-butyl (nBu),n-hexyl (nHe),and isobutylsulfanylthiosulfanyl (IBS) on the phase transition temperature of aqueous PNIPAM solutions were investigated by high-sensitivity differential scanning calorimetry (HS-DSC),yielding the enthalpy ΔH and the endotherm maximum temperature (T M),and turbidimetry,providing the cloud point (T CP) of each solution.The T CP and T M of the PNIPAM sample of lowest molar mass (M n 7,000 g/mol,0.5 g/L) ranged,respectively,from 38.8 to 22.5 °C and 42.2 to 26.0 °C,depending on the structure of the end-group,whereas H showed no strong end-group dependence.The phase transition of all polymers,except,-di(n-butyl-PNIPAM),exhibited a marked dependence on the polymer molar mass.