Enhancing the carbonation of MgO cement porous blocks through improved curing conditions

The use of reactive magnesia (MgO) as the binder in porous blocks demonstrated significant advantages due to its low production temperatures and ability to carbonate, leading to significant strengths. This paper investigates the enhancement of the carbonation process through different curing conditions: water to cement ratio (0.6-0.9), CO2 concentration (5-20%), curing duration (1-7 days), relative humidity (55-98%), and wet/dry cycling frequency (every 0-3 days), improving the carbonation potential through increased amounts of CO2 absorbed and enhanced mechanical performance. UCS results were supported with SEM, XRD, and HCl acid digestion analyses. The results show that CO2 concentrations as low as 5% can produce the required strengths after only 1 day. Drier mixes perform better in shorter curing durations, whereas larger w/c ratios are needed for continuous carbonation. Mixes subjected to 78% RH outperformed all the others, also highlighting the benefits of incorporating wet/dry cycling to induce carbonation. © 2014 Elsevier Ltd.

Numerical study on NOx/CO emissions in the diffusion flames of high-temperature off-gas of steelmaking converter

The combustion of high-temperature off-gas of steelmaking converter with periodical change of temperature and CO concentration always leads to CO and NOx over-standard emissions. In the paper, high-temperature off-gas combustion is simulated by adopting counterflow diffusion flame model, and some influencing factors of CO and NOx emissions are investigated by adopting a detailed chemistry GRI 3.0 mechanism. The emission index of NOx (EINOx) decreases 1.7–4.6% when air stoichiometric ratio (SR) increase from 0.6 to 1.4, and it dramatically increases with off-gas temperature at a given SR when the off-gas temperature is above 1500 K. High-concentration CO in off-gas can result in high NOx emissions, and NOx levels increase dramatically with CO concentration when off-gas temperature is above 1700 K. Both SR and off-gas temperature are important for the increase of CO burnout index (BICO) when SR is less than 1.0, but BICO increase about 1% when off-gas temperature increases from 1100 K to 1900 K at SR > 1.0. BICO increases with CO concentration in off-gas, and the influence of off-gas temperature on BICO is marginal. BICO increases with the relative humidity (RH) in air supplied, but it increases about 0.5% when RH is larger than 30%.

增温对川西亚高山针叶林不同光环境下几种幼苗生长的影响

由于人类活动所引起的地球大气层中温室气体的富集已导致全球地表平均温度在20 世纪升高了0.6 ¡æ，并预测在本世纪将上升1.4-5.8 ¡æ。气候变暖对陆地植物和生态系统产生深远影响，并已成为全球变化研究的重要议题。位于青藏高原东部的川西亚高山针叶林是研究气候变暖对陆地生态系统影响的重要森林类型。森林采伐迹地和人工云杉林下作为目前该区人工造林和森林更新的两种重要生境，二者截然不同的光环境对亚高山针叶林不同物种更新及森林动态有非常重要的影响。 本文以青藏高原东部亚高山针叶林几种主要森林树种为研究对象，采用开顶式增温法（OTCs）模拟气候变暖来研究增温对生长在两种不同光环境下（全光条件和林下低光环境）的几种幼苗早期生长和生理的影响，旨在从更新角度探讨亚高山针叶林生态系统不同树种对气候变暖在形态或生理上的响应差异，其研究结果可在一定程度上为预测气候变暖对亚高山针叶林物种组成和演替动态提供科学依据，同时也可为未来林业生产管理者提供科学指导。 1、与框外对照相比，OTCs 框内微环境发生了一些变化。OTCs 框内与框外对照气温年平均值分别为5.72 ¡æ和5.21 ¡æ，而地表温度年平均值分别为5.34 ¡æ和5.04 ¡æ，OTCs 使气温和地表年平均温度分别提高了0.51 ¡æ和0.34 ¡æ；OTCs框内空气湿度年平均值约高于框外对照，二者分别为90.4 %和85.3 %。 2、增温促进了三种幼苗生长和生物量的积累，但增温效果与幼苗种类及所处的光环境有关。无论在全光或林下低光条件下，增温条件下云杉幼苗株高、地径、分支数、总生物量及组分生物量（根、茎、叶重）都显著地增加；增温仅在全光条件下使红桦幼苗株高、地径、总生物量及组分生物量（根、茎、叶重）等参数显著地增加，而在林下低光条件下增温对幼苗生长和生物量积累的影响效果不明显；冷杉幼苗生长对增温的响应则与红桦幼苗相反，增温仅在林下低光条件下对冷杉幼苗生长和形态的影响才有明显的促进作用。 增温对三种幼苗的生物量分配模式产生了不同的影响，并且这种影响也与幼苗所处的光环境有关。无论在全光或林下低光环境下，增温都促使云杉幼苗将更多的生物量分配到植物地下部分，从而导致幼苗在增温条件下有更高的R/S 比；增温仅在林下低光条件下促使冷杉幼苗将更多的生物量投入到植物叶部，从而使幼苗R/S 比显著地降低；增温在全光条件下对红桦幼苗生物量分配的影响趋势与冷杉幼苗在低光条件下相似，即增温在全光条件下促使红桦幼苗分配更多的生物量到植物同化部分—叶部。 3、增温对亚高山针叶林生态系统中三种幼苗气体交换和生理表现的影响总体表现为正效应（Positive），即增温促进了几种幼苗的生理活动及其表现：（i）无论在全光或林下低光环境下，增温使三种幼苗的光合色素含量都有所增加；（ii）增温在一定程度上提高了三种使幼苗的PSII 光系统效率（Fv/Fm），从而使幼苗具有更强的光合电子传递活性；增温在一定程度使三种幼苗潜在的热耗散能力（NPQ）都有所增强，从而提高幼苗防御光氧化的能力；（iii）从研究结果来看，增温通过增加光合色素含量和表观量子效率等参数而促进幼苗的光合作用过程。总体来说增温对幼苗生理过程的影响效果与幼苗种类及所处的光环境有关，增温仅在全光条件下对红桦幼苗光合过程的影响才有明显的效果，而冷杉幼苗则相反，增温仅在低光条件下才对幼苗的生理过程有显著的影响。 4、增温对三种幼苗的抗氧化酶系统产生了一定的影响。从总体来说，增温使几种幼苗活性氧含量及膜脂过氧化作用降低，从而在一定程度上减轻了该区低温对植物生长的消极影响；增温倾向表明使三种幼苗体内抗氧化酶活性和非酶促作用有所提高，从而有利于维持活性氧代谢平衡。但增温影响效果与幼苗种类所处的光环境及抗氧化酶种类有关，增温对冷杉幼苗抗氧化酶活性的影响仅在林下低光环境下效果明显，而对红桦幼苗抗氧化酶活性的影响仅在全光条件下才有明显的效果。 总之，增温促进了亚高山针叶林生态系统中三种幼苗的生长和生理表现，但幼苗生长和生理对增温的响应随植物种类及所处的光环境不同而变化，这种响应差可能异赋予了不同植物种类在未来气候变暖背景下面对不同环境条件时具有不同的适应力和竞争优势，从而对亚高山针叶林生态系统物种组成和森林动态产生潜在的影响。 Enrichment of atmospheric greenhouse gases resulted from human activities suchas fossil fuel burning and deforestation has increased global mean temperature by 0.6¡æ in the 20th century and is predicted to increase it by 1.4-5.8 ¡æ. The globalwarming will have profound, long-term impacts on terrestrial plants and ecosystems.The ecoologcial consequences arising from global warming have also become thevery important issuses of global change research. The subalpine coniferous forests inthe eastern Qinghai-Tibet Plateau provide a natural laboratory for the studying theeffects of climate warming on terrestrial ecosystems. The light environment differssignificantly between clear-outs and spruce plantations, which is particularlyimportant for plant regeneration and forest dynamics in the subalpine coniferous forests. In this paper, the short-term effects of two levels of air temperature (ambient andwarmed) and light (full light and ca. 10% of full light regimes) on the early growthand physiology of Picea asperata, Abies faxoniana and Betula albo-sinensis seedlingswas determined using open-top chambers (OTCs). The aim of the present study wasto understand the differences between tree species in their responses to experimentalwarming from the perspective of regeneration. Our results could provide insights intothe effects of climate warming on community composition and regeneration behavior for the subalpine coniferous forest ecosystem processes, and provide scientificdirection for the production and management under future climate change. 1. The OTCs manipulation slightly altered thermal conditions during the growingseason compared with the outside chambers. The annual mean air temperature andsoil surface temperature was 5.72 and 5.34 ¡æ (within the chambers), and 5.21 and5.04 ¡æ (outside the chambers), respectively. The OTCs manipulation increased airtemperature and soil surface temperature by 0.51 and 0.34 ¡æ on average, respectively.Air relative humidity was slightly higher inside the OTCs compared with the controlplots, with 90.4 and 85.3 %, respectively. 2. Warming generally stimulated the growth and biomass accumulation of thethree tree species, but the effects of warming on growth and development variedbetween light conditions and species. Irrespective of light regimes, warmingsignificantly increased plant height, root collar diameter, total biomass, componentbiomass (stem, foliar and root biomass) and the number of branches in P. asperataseedlings; For A. faxoniana seedlings, significant effects of warming on all the tested parameters (plant height, root collar diameter, total biomass, and component biomass) were found only under low light conditions; In contrast, the growth responses of B.albo-sinensis seedlings to warming were found only under full light conditions. Warming had pronounced effects on the pattern of carbon allocation. Irrespectiveof light regimes, the P. asperata seedlings allocated relatively more biomass to rootsin responses to warming, which led to a higher R/S. Significant effects of warming onbiomass allocation were only found for the A. faxoniana seedlings grown under lowlight conditions, with significantly increased in leaf mass ratio (LMR) and decreasedin R/S in responses to warming manipulation. The carbon allocation responses of B.albo-sinensis seedling to warming under full light conditions were similar with theresponse of A. faxoniana seedlings grown under low light conditions. Warmingsignificantly decreased root mass ratio (RMR), and increased leaf mass ratio (LMR)and shoot/root biomass ratio (S/R) for the B. albo-sinensis seedlings grown under full light conditions. 3. Warming generally had a beneficial effect on physiological processes of dominant tree species in subalpine coniferous forest ecosystems: (i) Warming markedincreased the concentrations of photosynthetic pigments in both tree species, but theeffects of warming on photosynthetic pigments were greater under low lightconditions than under full light conditions for the two conifers; (ii) Warming tended toenhance the efficiency of PSII in terms of increase in Fv/Fm, which was related tohigher chloroplast electron transport activity; and enhance non-radiative energydissipation in terms of in increase in NPQ, which may reflect an increased capacity inpreventing photooxidation; (iii) Warming may enhance photosynthesis and advancephysiological activity in plants by increasing photosynthetic pigment concentration,the efficiency of PSII and apparent quantum yield (Φ) etc. From the results, theeffects of warming on seedlings’ physiological performance varied between lightenvironment and species. The effects of warming on photosynthesis performance of B.albo-sinesis seedlings were pronounced only under full light conditions, while thephysiological responses of A. faxoniana seedlings to warming were found only underthe 60-year plantation. These results provided further support for the observationsabove on growth responses of seedlings to warming. 4. Warming had marked effects on antioxidative systems of the three seedlings.Warming generally decreased H2O2 accumulation and the rate of O2- production, andalleviated degree of lipid peroxidation in terms of decreased MDA content, whichalleviated to some extent the negative effects of low temperature on the plant growthand development in this region; Warming tended to increase the activities ofantioxidative enzymes and stimulate the role of non-enzymatic AOS scavenging,which helped to create an balance in maintaining AOS metabolites for the threeseedlings. Nevertheless, the effects of warming on antioxidative defense systems werepronounced only under the 60-year plantation for the A. faxoniana seedlings. Incontrast, the marked effects of warming on antioxidative defense systems for the B.albo-sinesis seedlings were found only under the full light conditions. In sum, warming is considered to be generally positive in terms of growth andphysiological process. However, the responses of growth and physiology performanceto warming manipulation varied between species and light regimes. Competitive and adaptive relationships between tree species may be altered as a result of responsedifferences to warming manipulation, which is one mechanism by which globalwarming will alter species composition and forest dynamics of subalpine coniferousforest ecosystems under future climate change.

Novel hydrophilic-hydrophobic multiblock copolyimides as proton exchange membranes: Enhancing the proton conductivity

A series of novel multiblock copolymers based on sulfonated copolyimides were developed and evaluated for use as proton exchange membranes (PEMs). In these multiblock copolyimides, the hydrophilic blocks were composed of the sulfonated dianhydride and the sulfonated diamine, with sulfonic acid groups on every aromatic ring (i.e., fully sulfonated). This molecular design was implemented to effectively enhance the proton conductivity. The properties of the multiblock copolyimides with varying IEC values or block lengths were investigated to obtain a better understanding of the relationship between molecular structure and properties of proton exchange membranes. The water uptake and proton conductivity were found to be highly dependent upon their structure. The block copolymers displayed significantly higher proton conductivities, especially at low relative humidity than the random copolymers with a similar IEC.

Perfectly Hydrophobic Silicone Nanofiber Coatings: Preparation from Methyltrialkoxysilanes and Use as Water-Collecting Substrate

Perfectly hydrophobic (PHO) coatings consisting of silicone nanofibers have been obtained via a solution process using methyltrialkoxysilanes as precursors. On the basis of thermal gravimetry and differential thermal analysis (TG-DTA) and Fourier transform infrared spectroscopy (FTIR) results, the formula of the nanofibers was tentatively given and a possible growth mechanism of the nanofibers was proposed. Because of the low affinity between the coatings and the small water droplet, when using these coatings as substrate for collecting water vapor, the harvesting efficiency could be enhanced as compared with those from bare glass substrate for more than 50% under 25 degrees C and 60-90% relative humidity. By removing the surface methyl group by heat treatment or ultraviolet (UV) irradiation, the as-prepared perfectly hydrophobic surface can be converted into a superhydrophilic surface.

Water resistant sulfonated polyimides based on 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianhydride (BNTDA) for proton exchange membranes

A series of sulfonated polyimides (SPIs) were synthesized in in-cresol from 4,4'-binaphthyl- 1,11,8,8'-tetracarboxylic dianhydride (BNTDA), 4.4'-diaminodiphenylether-2,2-disulfonicacid (ODADS), and 4.4'-diamino-diphenyl ether (ODA) in the presence of triethylamine and benzoic acid. The resulted polyimides showed much better water resistance than the corresponding sulfonated polyimides from 1,4,5,8-naphthatenetetracarboxylic dianhydride (NTDA) and ODADS, which is contributed to the higher electron density in the carbonyl carbon atoms of BNTDA. Copolyimides S-75 and S-50 maintained their mechanical properties and proton conductivities after aging in water at 100 degrees C for 800 h. The proton conductivity of these SPIs was 0.0250-0.3565 S/cm at 20 degrees C and 100% relative humidity (RH), and increased to 0.11490.9470 S/cm at 80 degrees C and 100% RH. The methanol permeability values of these SPIs were in the range of 0.99-2.36 x 10(-7) cm(2)/S, which are much lower than that of Nafion 117 (2 x 10(-6) cm(2)/s).

The influencing factors on the macroporous formation in polymer films by water droplet templating

Regular micrometer-size porous polystyrene film is prepared by water droplet templating, i.e. breath figures are stabilized by the polymer in solution and thermocapillary flow arranges them into ordered packing. The influences of polystyrene molecular weight, solvent properties, and the relative humidity of atmosphere on the pattern formation and hole sizes are investigated. Two different kinds of hole packing fashion are also observed and their formation mechanisms are discussed.

Barrier properties of vinylidene chloride methyl acrylate copolymer

A series of vinylidene dichloride (VDC) copolymers with methyl acrylate (MA) as comonomer (3-12wt%), was prepared by free-radical suspension copolymerization. The permeability coefficients of the copolymers to oxygen and carbon dioxide were measured at 1.0 MPa and at 30 degrees C, and those to water vapor were measured at 30 degrees C and 100% relative humidity. All the VDC/MA copolymers studied are semicrystalline. As the MA content increases, the permeability coefficients of the copolymers to oxygen, carbon dioxide, and water vapor are progressively increased, caused by decrease in crystalline fraction and increase in free volume of VDC/MA copolymers.

Barrier property and structure of acrylonitrile/acrylic copolymers

A series of acrylonitrile (AN) copolymers with methyl acrylate (MA) or ethyl acrylate (EA) as comonomer (5-23 wt%) was prepared by free-radical copolymerisation. The permeability coefficients of the copolymers to oxygen and carbon dioxide were measured at 1.0 MPa and at 30 degrees C, and those to water vapor also measured at 100% relative humidity and at 30 degrees C. All the AN/acrylic copolymers are semicrystalline. As the acrylate content increase, the permeability coefficients of the copolymers to oxygen and carbon dioxide are increased progressively, but those to water vapor are decreased progressively. The gas permeability coefficients of the polymers were correlated with free-volume fractions or the ratio of free volume to cohesive energy.

Barrier properties of vinylidene chloride copolymers

The permeability coefficients of a series of copolymers of vinylidene chloride (VDC) with methyl acrylate (MA), butyl acrylate (BA) or vinyl chloride (VC) (as comonomer) to oxygen and carbon dioxide have been measured at 1.0 MPa and 30 degrees C, while those to water vapor have been measured at 30 degrees C and 100% relative humidity. All the copolymers are semicrystalline. VDC/MA copolymers have lower melting temperature compared with VDC/BA copolymers, while that melting temperature of VDC/VC copolymer is higher than that of VDC/acrylate copolymers with the same VDC content. The barrier property of the copolymers is predominantly controlled by crystallite, free volume fraction, and cohesive energy. The permeability coefficients of VDC/MA copolymers to oxygen, carbon dioxide, and water vapor were successfully correlated with the ratio of free volume to cohesive energy.

Electrochemical investigations of micro-droplets formed on metals during the deliquescence of salt particles in atmosphere

CORROSION; WATER; SPECTROSCOPY; CHLORIDE; ZINC; NUCLEATION; INTERFACE; ELECTRODE; SURFACES; GROWTH

Phenomenon of micro-droplets formation on metals during the deliquescence of salt particles in atmosphere

CORROSION; MECHANISM; WATER; ZINC

Neural network retrieval of ocean surface parameters from SSM/I data

A new algorithm based on the multiparameter neural network is proposed to retrieve wind speed (WS), sea surface temperature (SST), sea surface air temperature, and relative humidity ( RH) simultaneously over the global oceans from Special Sensor Microwave Imager (SSM/I) observations. The retrieved geophysical parameters are used to estimate the surface latent heat flux and sensible heat flux using a bulk method over the global oceans. The neural network is trained and validated with the matchups of SSM/I overpasses and National Data Buoy Center buoys under both clear and cloudy weather conditions. In addition, the data acquired by the 85.5-GHz channels of SSM/I are used as the input variables of the neural network to improve its performance. The root-mean-square (rms) errors between the estimated WS, SST, sea surface air temperature, and RH from SSM/I observations and the buoy measurements are 1.48 m s(-1), 1.54 degrees C, 1.47 degrees C, and 7.85, respectively. The rms errors between the estimated latent and sensible heat fluxes from SSM/I observations and the Xisha Island ( in the South China Sea) measurements are 3.21 and 30.54 W m(-2), whereas those between the SSM/ I estimates and the buoy data are 4.9 and 37.85 W m(-2), respectively. Both of these errors ( those for WS, SST, and sea surface air temperature, in particular) are smaller than those by previous retrieval algorithms of SSM/ I observations over the global oceans. Unlike previous methods, the present algorithm is capable of producing near-real-time estimates of surface latent and sensible heat fluxes for the global oceans from SSM/I data.