多孔介质中晶体的结晶压力分析

孔隙溶液中结晶体产生的结晶压力是多孔材料宏观上形成介质变形、冻胀破坏的重要因素之一。以溶液–晶体的化学势平衡为基础,考虑了溶液中的粒子相互作用,分别对以过饱和比为驱动的盐分结晶体和以温度为驱动的冰结晶体进行了理论分析,建立了非理想溶液中晶体对孔壁产生的最大结晶压力模型,并对溶液的冰点温度进行了分析。以NaCl溶液和Na2SO4溶液为例,分别对不同浓度和不同温度下的盐、水结晶压力及冰点温度进行了参数分析。结果表明:对于盐分结晶体,其结晶压力与溶液的过饱和比、溶液活度以及结晶盐的类型密切相关;对于冰晶体,其结晶压力与环境温度以及溶液的活度相关。     

The biodegradability of two primary alcohol ethoxylate nonionic surfactants under practical conditions,and the toxicity of the biodegradation products to rainbow trout

A field trial has been performed to measure the biodegradability of two typical alcohol ethoxylate nonionic surfactants, “Dobanol” 45-7 and “Dobanol” 45-11, by dosing them to biological filters in a mixture with domestic sewage. Influent levels were 10 and 25 mg l^?1 of each surfactant and 96–98% degradation was achieved within a temperature range of 5–10°C. The surfactants had no adverse effects on the filters in terms of the usual sanitary parameters (BOD, COD, TOC and ammoniacal nitrogen). Tests on the effluents indicated no residual acute lethal toxicity to rainbow trout Salmo gairdneri).     

Experimental Characterisation of the Fire Behaviour of Thermal Insulation Materials for a Performance-Based Design Methodology

A novel performance-based methodology for the quantitative fire safe design of building assemblies including insulation materials has recently been proposed. This approach is based on the definition of suitable thermal barriers in order to control the fire hazards imposed by the insulation. Under this framework, the concept of “critical temperature” has been used to define an initiating failure criterion for the insulation, so as to ensure there will be no significant contribution to the fire nor generation of hazardous gas effluents. This paper proposes a methodology to evaluate this “critical temperature” using as examples some of the most common insulation materials used for buildings in the EU market, i.e. rigid polyisocyanurate foam, rigid phenolic foam, rigid expanded polystyrene foam and low density flexible stone wool. A characterisation of these materials, based on a series of ad-hoc Cone Calorimeter and thermo-gravimetric experiments, serves to establish the rationale behind the quantification of the critical temperature. The temperature of the main peak of pyrolysis, obtained from differential thermo-gravimetric analysis under a nitrogen atmosphere at low heating rates, is proposed as the “critical temperature” for materials that do not significantly shrink and melt, i.e. charring insulation materials. For materials with shrinking and melting behaviour it is suggested that the melting point could be used as “critical temperature”. Conservative values of “critical temperature” proposed are 300°C for polyisocyanurate, 425°C for phenolic foam and 240°C for expanded polystyrene. The concept of a “critical temperature” for the low density stone wool is examined in the same manner and found to be non-applicable due to the inability to promote a flammable mixture. Additionally, thermal inertia values required for the performance-based methodology are obtained for PIR and PF using a novel approach, providing thermal inertia values within the range 4.5 to 6.5 × 10³ W² s K^?2 m^?4.     

Speciation of iodine in solid environmental samples by iodine K-edge XANES: application to soils and ferromanganese oxides

A method was developed for speciation of iodine in solid materials using X-ray absorption near-edge structure (XANES). This method was used to identify the iodine species (mainly inorganic iodine) in environmental samples. It was shown that the XANES spectra of iodide and iodate sorbed within solid materials can be simulated by the linear combination of the spectra of iodide and iodate ions in water. The distribution coefficient (Kd) between soil and water was obtained independently for iodide and iodate, based on iodine speciation both in the solid phase, by XANES, and in the aqueous phase, by HPLC-ICP-MS. It was found that the Kd of iodate is larger than that of iodide by a factor of more than six, showing the more soluble nature of iodide. It was suggested that iodate can form in soil even when iodide is injected into the soil-water system under conditions within the iodide-stable field of the Eh-pH diagram of iodine. This is caused by the much higher affinity of iodate for solid surfaces than iodide. In soil samples under various water saturation conditions, or various Eh conditions, the iodide fraction in water increases with decreasing Eh, which results in an increase in the dissolved total iodine fraction in soil water. The speciation method using XANES was also applied to iodine in a natural soil sample and marine ferromanganese oxides. It is suggested that iodine K-edge XANES is a promising tool for determining the iodide/iodate ratio in natural solid samples, which contributes to better understanding of the behavior of iodine at the Earth's surface.     

Laboratory study and interpretation of mechanical behavior of frozen clay through state concept

Towards the development of a mechanical model that can be part of multi-physical analysis of frozen soils, a program of systematic frozen-unfrozen parallel triaxial tests at different temperatures and strain rates was conducted. The mechanical behavior of the reconstituted high-plasticity clay samples was investigated and interpreted through a state concept based on Ladanyi and Morel’s (1990) postulate on the unique relationship between the inter-particle “effective” stress and the strain path. The Critical State Lines (CSLs) for clay specimens frozen undrained were mapped by referring to the shear behavior of unfrozen specimens sharing the same strain history. With other conditions set identical, the shear strength linearly increased with a decrease in the temperature for the range from ?10 °C to ?2 °C, and log-linearly increased with an increase in the strain rate for the range from 0.001%/min to 0.1%/min. Direct comparison of the strain-rate effects between frozen and unfrozen specimens with identical strain paths and states in the soil skeleton clearly indicates that the viscoplasticity derives from that of pore ice. A conceptual interpretative framework invoking temperature- and strain rate-dependent state bounding surfaces and CSLs was proposed to describe the behavior of frozen soils under steady and non-steady temperature and strain rate. The above observations of the behavioral features of frozen and unfrozen soils, with further experimental work, are expected to lead to the construction of a unified framework for describing the behavior under both states and the transition between them.     

The effect of temperature on the removal of non-ionic surfactants during small-scale activated-sludge sewage treatment—II. Comparison of a linear alkyl phenol ethoxylate with branched-chain alkyl phenol ethoxylates

The biodegradability of a linear alkyl phenol ethoxylate surfactant has been compared with the biodegradabilities of two branched-chain alkyl phenol ethoxylates during sewage treatment in small-scale activated-sludge plants. In addition, a linear alkyl benzene sulphonate (LAS) anionic surfactant was tested to study its removal during treatment in the “porous-pot” equipment. Tests were carried out at ≈ 20°, 12°, 8° and 5°C to study the effect of temperature on the removal of the different materials.Very little difference was found between the degrees of removal of any of the alkyl phenol ethoxylates. They were well degraded at 20°C, but a stable degree of removal could not be maintained at reduced temperatures. At 8°C and 5°C the percentage removals fluctuated between 60 and 90 per cent. This appears to be a feature of the behaviour of alkyl phenol ethoxylates during this type of treatment. The LAS surfactant, after a period of acclimatization, was consistently degraded by more than 90 per cent at all temperatures of operation.     

Residual behavior of steel rebars and R/C sections after a fire

The mechanical properties of various steel bars exposed to high temperature (“residual” properties) are experimentally investigated up to 850 °C, with reference to a number of steel and bar types (carbon and stainless steel; quenched and self-tempered bars; hot-rolled and cold-worked bars; smooth and deformed bars). The aim is to clarify to what extent the thermal sensitivity of the different bars affects the ultimate capacity of a typical R/C section subjected to an eccentric axial force, past a fire (“residual” capacity). As usual in the design of R/C sections under combined bending and axial loading, the ultimate behavior is represented through the “M–N envelopes”, where the materials strength decay due to high temperature is taken into account. The results show that quenched and self-tempered bars (QST), very popular in Europe, are more temperature-sensitive above 600 °C than the carbon-steel bars extensively used in the States and nowadays rarely used in Europe. Furthermore, the best response is exhibited by the stainless-steel bars, provided that they are hot rolled, as it is generally the case for medium- and large-diameter bars. Similar conclusions can be drawn for the sections reinforced with the different bar types.     

Linking the mechanical properties of frozen sandstone to phase composition of pore water measured by LF-NMR at subzero temperatures

Water-bearing porous rocks can be greatly strengthened by freezing; its microscopic mechanisms lie in how subzero temperature modifies pore structure but have not yet been clearly defined. In this study, we link the mechanical properties of frozen sandstone to phase composition of pore water (i.e., relative amount of unfrozen water and ice). Both the strength (uniaxial compressive strength and tensile strength) and the phase composition of pore water (tested through the nuclear magnetic resonance (NMR) method) of frozen sandstone at nine subzero temperatures were measured. The results showed the following: (1) subzero temperature strengthened saturated sandstone significantly, both the strengths increased in a three-stage mode and each stage showed an approximately linear trend as temperature decreased from 0 to – 20 °C; and (2) change of phase composition with freezing displayed two distinct stages: the rapid decreasing stage of unfrozen water content (0 to – 4 °C), when bulk water and capillary water froze almost completely, and the slow decreasing stage (? 4 to – 20 °C), when adsorbed water froze partially. Based on direct observations on microscopic pore structure of sandstone and detailed discussion on the mechanical interactions between water, ice, and pore wall, phase composition may modify the mechanical properties of frozen rocks through the following effects: the supporting effect of ice under compression, the crack-filling effect of ice, the cementing effect of unfrozen water film under tension or under shearing load, and the frost damage effect. The former three are strengthening effects, while the latter one is weakening effect.

     

Experimental Study on Residual Mechanical Properties of Bolt-Sphere Joints After a Fire

Through tensile testing of 15 steel bolt-sphere joints and 15 aluminum alloy bolt-sphere joints, influencing rules of material type, high temperature and cooling mode on tensile properties of post-fire bolt-sphere joints were studied, and then failure modes of the joints were determined. According to experimental data, the calculation formula of residual tension capacity of post-fire bolt-sphere joints was presented. Experimental data indicated that (1) decreased extension on the mechanical properties of aluminum alloy bolt-sphere joints after high temperature in the fire was significantly higher than that of the steel bolt-sphere joints; (2) when fire temperature was lower than 800 °C, the tension capacity of steel bolt-sphere joints could be restored by more than 90% after cooling; (3) when fire temperature was lower than 500 °C, the tension capacity of aluminum alloy bolt-sphere joints could be restored by more than 50% after cooling; (4) bolt-sphere joints could still satisfy the requirement of “strong node and weak member” after a fire; and (5) material type and fire temperature were the main factors that influenced post-fire mechanical properties of bolt-sphere joints.     

Investigating the raveling test for full-depth reclamation

Full-Depth Reclamation (FDR) is a sustainable method of building pavement structure compared to more traditional rehabilitation methods. Traffic is generally returned to an FDR project before a surface course is applied, as water in the FDR needs time to evaporate from the structure. This should not be done too quickly or raveling occurs. Currently, there is no test to quantify the timing of return to traffic. In this study, the “Raveling test of cold mixed bituminous emulsion samples” (ASTM D7196) was used to compare asphalt emulsion and asphalt foam FDR. Asphalt emulsion samples were cured at ambient and 40 °C temperatures, while asphalt foam samples were cured at ambient temperatures. Raveling test data was collected from 0 to 48 hours of curing, however, samples were often not able to withstand fifteen minutes of testing. Therefore, the “time lasted” (the time the raveling head loses contact with the surface of the sample) was recorded. In general, the asphalt emulsion samples that were cured in the oven at 40 °C had a longer time lasted and showed higher potential for determination of return to traffic. In addition, the asphalt emulsion samples had a longer time lasted than the asphalt foam samples at ambient temperatures.     

湍流中微小冰晶融化时间的理论研究

为了消除过冷水连续制冰系统中的微小冰晶，通过建立模型，分析了湍流中微小冰晶的融化过程，提出了计算融化时间的方法，分析了融化时间与最小旋涡尺度和水温的关系。指出通过增大湍流程度，使最小旋涡尺度小于某一数值(与水温有关，可通过计算确定)，从而可以在较低的水温、较短的时间内融化水中的微小冰晶。     

Regulation of sensory nerve conduction velocity of human bodies responding to annual temperature variations in natural environments

The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being.     

Formation of methyl iodide on a natural manganese oxide

This paper demonstrates that manganese oxides can initiate the formation of methyl iodide, a volatile compound that participates to the input of iodine into the atmosphere. The formation of methyl iodide was investigated using a natural manganese oxide in batch experiments for different conditions and concentrations of iodide, natural organic matter (NOM) and manganese oxide. Methyl iodide was formed at concentrations ≤1 μg L⁻¹ for initial iodide concentrations ranging from 0.8 to 38.0 mg L⁻¹. The production of methyl iodide increased with increasing initial concentrations of iodide ion and Mn sand and when pH decreased from 7 to 5. The hydrophilic NOM isolate exhibited the lowest yield of methyl iodide whereas hydrophobic NOM isolates such as Suwannee River HPOA fraction produced the highest concentration of methyl iodide. The formation of methyl iodide could take place through the oxidation of NOM on manganese dioxide in the presence of iodide. However, the implication of elemental iodine cannot be excluded at acidic pH. Manganese oxides can then participate with ferric oxides to the formation of methyl iodide in soils and sediments. The formation of methyl iodide is unlikely in technical systems such as drinking water treatment i.e. for ppt levels of iodide and low contact times with manganese oxides.     

Hydration of high-calcium quicklime with methanol–water mixtures

In this study, hydration of quicklime was accomplished with different methanol–water mixtures. The greater the percentage of methanol, the more intense was the suppression of the hydration conditions. The reactivity was not greatly affected by the presence of methanol up to 20%, while for hydration mixtures with 30 to 60% methanol a great reduction of reactivity was observed. In all cases of hydration the complete conversion of CaO into Ca(OH)₂ was established by the XRD method. From the SEM study it was ascertained that in a percentage of up to 20% methanol, a normal hydration was observed, expressed by aggregates of hydrated lime grains, whereas the hydration in mixtures of 30–60% methanol, progressively leads to the formation of tabular crystals, the size of which increases with the methanol percentage. What is more important is that the maximum hydration temperature decreases up to 12.5 °C for hydration mixtures up to 20% methanol without the quality of the produced hydrated lime being affected.     

Determination of iodide,iodate and organo-iodine in waters with a new total organic iodine measurement approach

The dissolved iodine species that dominate aquatic systems are iodide, iodate and organo-iodine. These species may undergo transformation to one another and thus affect the formation of iodinated disinfection byproducts during disinfection of drinking waters or wastewater effluents. In this study, a fast, sensitive and accurate method for determining these iodine species in waters was developed by derivatizing iodide and iodate to organic iodine and measuring organic iodine with a total organic iodine (TOI) measurement approach. Within this method, organo-iodine was determined directly by TOI measurement; iodide was oxidized by monochloramine to hypoiodous acid and then hypoiodous acid reacted with phenol to form organic iodine, which was determined by TOI measurement; iodate was reduced by ascorbic acid to iodide and then determined as iodide. The quantitation limit of organo-iodine or sum of organo-iodine and iodide or sum of organo-iodine, iodide and iodate was 5 μg/L as I for a 40 mL water sample (or 2.5 μg/L as I for an 80 mL water sample, or 1.25 μg/L as I for a 160 mL water sample). This method was successfully applied to the determination of iodide, iodate and organo-iodine in a variety of water samples, including tap water, seawater, urine and wastewater. The recoveries of iodide, iodate and organo-iodine were 91–109%, 90–108% and 91–108%, respectively. The concentrations and distributions of iodine species in different water samples were obtained and compared.     

单次升温条件下硫酸盐渍土的融沉试验研究

硫酸盐渍土具有明显的随季节温度变化而发生土体结构改变的特性,给工程造成较大危害。为研究单次升温条件下硫酸盐渍土的融沉特性,在室内配置压实度分别为90%、95%和98%,含盐量分别为0%、2%、5%、8%和10%的硫酸盐渍土试样,采用高低温试验箱进行单次升温试验。结果表明:单次升温条件下,硫酸盐渍土的融沉过程可大致分为4个阶段,温度于-15 ℃~-10 ℃(±5)区间为“结构融沉”阶段,-10 ℃~0 ℃区间为“融沉调整”阶段,0 ℃~15 ℃区间为“冰消融沉”阶段,15 ℃~25 ℃区间为“结晶融沉”阶段。0%含盐量时,其融沉率随压实度增大而减小,不同含盐量条件下的融沉率均大于0%含盐量时的融沉率,且当压实度在90%~95%范围内变化时,融沉率与压实度呈反比例变化趋势;98%压实度土体的融沉率在2%~8%含盐量时总体呈减小趋势,10%时又骤然增大;压实度为95%和98%时,在15 ℃~20 ℃区间融沉率增量最大,并在20 ℃达到最大值;而压实度为90%时,达到该状态时的温度为25 ℃;综合分析认为处理硫酸盐渍土地基的压实度以95%为宜。该研究可为硫酸盐渍土地区工程建设提供借鉴和参考。     

Disparities of indoor temperature in winter: A cross-sectional analysis of the Nationwide Smart Wellness Housing Survey in Japan

The WHO Housing and health guidelines recommend a minimum indoor temperature of 18°C to prevent cold-related diseases. In Japan, indoor temperatures appear lower than in Euro-American countries because of low insulation standards and use of partial intermittent heating. This study investigated the actual status of indoor temperatures in Japan and the common characteristics of residents who live in cold homes. We conducted a nationwide real-world survey on indoor temperature for 2 weeks in winter. Cross-sectional analyses involving 2190 houses showed that average living room, changing room, and bedroom temperatures were 16.8°C, 13.0°C, and 12.8°C, respectively. Comparison of average living room temperature between prefectures revealed a maximum difference of 6.7°C (Hokkaido: 19.8°C, Kagawa: 13.1°C). Compared to the high-income group, the odds ratio for living room temperature falling below 18°C was 1.38 (95% CI: 1.04-1.84) and 2.07 (95% CI: 1.28-3.33) for the middle- and low-income groups. The odds ratio was 1.96 (95% CI: 1.19-3.22) for single-person households, compared to households living with housemates. Furthermore, lower room temperature was correlated with local heating device use and a larger amount of clothes. These results will be useful in the development of prevention strategies for residents who live in cold homes.     

Modified Critical Temperatures for Steel Design Based on Simple Calculation Models in Eurocode 3

Critical temperature is defined as the temperature at which failure is expected to occur in a structural steel member given a uniform temperature distribution and load level. Determination of the critical temperature is a simple but efficient way for structural fire design. This paper proposed a new model which incorporated the buckling, load levels and non-dimensional slenderness to calculate the critical temperature of steel member under fire based on the simple calculation models in Eurocode 3. To advance the application of this new model, design charts for determining the critical temperatures were developed. The design charts showed that the critical temperature decreases with increasing load level, and increases as the buckling curve varies from “a₀” to “d”. It is also recommended to use higher grade steel in both normal and fire situations. The accuracy of this model was ascertained by comparing with the test results in available literature. The new model gave an average prediction-to-test ratio of 0.980 with a standard deviation of 0.077, indicating conservative and less scattered predictions. The percentage of over-prediction (i.e., prediction-to-test ratio >1.0) was less than 5.8% when the nominal yield strength of steel rather than its test strength was used for predictions. In general, reasonable agreements were obtained between the test results and the predictions.     

A “marker” technique to monitor treated industrial wastewater effluents

In toxicological research with hazardous substances (e.g. carcinogens), wastewater effluent from the test facility must be free of such substances before discharge into the environment. An industrial wastewater processing plant employing adsorbers of carbon and XAD-2 resin is described; however, chemical assays of each batch of treated effluent must certify the absence of all test agents. Elution profiles and adsorption isotherm tests with the test agents vs. the two adsorbents provided the basis for a “marker” technique which should eliminate the necessity to assay for all test agents in each batch of processed effluent. A rationale is presented for periodic introduction of a “marker” (gentian violet) into the primary adsorbers. If detected in the effluent, the “marker”, which elutes from the adsorbers before most of the test agents would signal impending depletion of the adsorbent which could then be replaced. Recommendations to modify the industrial wastewater treatment plant and to implement the “marker” technique are presented as cost-effective alternatives to extensive and laborious chemical assays.     

Temperature,cyanide and phenolic nitrification inhibition

Laboratory evaluations were conducted of the rate of ammonia biooxidation to nitrite by an autotrophic culture of nitrifiers. Ammonia oxidation biokinetics were found to follow Michaelis-Menten-type relationships. Alterations in Michaelis-Menten kinetics were quantified with elevated temperatures and selected trace organics typical of steel industry type wastewaters. Based on data obtained, the toxic inhibition to biological nitrification decreased in the order of free cyanide, coal tar acid phenolics (derived from a coke plant), phenol, 2,3,6-trimethylphenol, 2-ethylpyridine, 2,4,6-trimethylphenol, complexed cyanides and thiocyanate. All substances except free cyanide appear to follow a “shoulder effect” where low levels of inhibitor had no influence on rates of biological nitrification while higher levels had profound effects. Upper temperature limits for stable optimum nitrification is about 30°C with decreasing rates of nitrification on either side of this optimum. Nitrification rates approach zero as temperatures of wastewater approach 45°C.