A discrete model for prediction of radon flux from fractured rocks

Prediction of radon flux from the fractured zone of a propagating cave mine is basically associated with uncertainty and complexity. For instance, there is restricted access to these zones for field measure- ments, and it is quite difficult to replicate the complex nature of both natural and induced fractures in these zones in laboratory studies. Hence, a technique for predicting radon flux from a fractured rock using a discrete fracture network （DFN） model is developed to address these difficulties. This model quantifies the contribution of fractures to the total radon flux, and estimates the fracture density from a measured radon flux considering the effects of advection, diffusion, as well as radon generation and decay. Radon generation and decay are classified as reaction processes. Therefore, the equation solved is termed as the advection-diffusion-reaction equation （ADRE）. Peclet number （Pe）, a conventional dimensionless parameter that indicates the ratio of mass transport by advection to diffusion, is used to classify the transport regimes. The results show that the proposed model effectively predicts radon flux from a fractured rock. An increase in fracture density for a rock sample with uniformly distributed radon generation rate can elevate radon flux significantly compared with another rock sample with an equivalent increase in radon generation rate. In addition to Pe, two other independent dimensionless parameters （derived for radon transport through fractures） significantly affect radon dimensionless flux. Findings provide insight into radon transport through fractured rocks and can be used to improve radon control measures for proactive mitigation.

Factors affecting use of ballistics gelatin in laboratory studies of bacterial contamination in projectile wounds

Background: Ballistics gelatin is a common tissue surrogate used in bacterial contamination models for projectile wounds. Although these studies have demonstrated that bacteria are transferred from the surface of the gelatin to the wound track by a projectile, quantifiable results have been inconsistent and not repeatable in successive tests.Methods: In this study, five areas of a typical contamination model in which bacterial recovery or survival are affected were identified for optimization. The first was a contaminated "skin" surrogate, where the novel use of vacuum filtration of a bacterial culture and buffer onto filter paper was employed. The other possibly problematic areas of the bacterial distribution model included the determination of bacterial survival when the contamination model is dried, survival in solid and molten gelatin, and the effect of high-intensity lights used for recording high-speed video.Results: Vacuum filtration of bacteria and buffer resulted in a consistent bacterial distribution and recovery. The use of phosphate buffer M9(pH 7) aided in neutralizing the ballistics gelatin and improving bacterial survival in solid gelatin. Additionally, the use of high-intensity lights to record high-speed video and the use of a 42℃ water bath to melt the gelatin were found to be bactericidal for gram-positive and gram-negative bacteria.Conclusion: Multiple areas of a typical contamination model in which bacterial survival may be impeded were identified, and methods were proposed to improve survival in each area. These methods may be used to optimize the results of bacterial contamination models for medical applications, such as understanding the progression of infection in penetrating wounds and to identify possible sources of contamination for forensic purposes.

内蒙古草原挥发性有机物排放通量的研究

2 0 0 2年夏季 ,利用静态箱方法 ,对我国内蒙古草原生态系统挥发性有机物的排放进行了首次测量 ,同时观测了太阳辐射、温湿度等参数 .结果表明 ,异戊二烯是草地挥发性有机物排放中的主要成分 .异戊二烯的排放有明显的日变化、逐日变化和季节变化规律 .因子分析表明 ,可见光辐射、温度、水汽含量是影响异戊二烯排放的主要因子 ,而且可见光辐射是控制其排放过程的最主要因子 .根据相关分析 ,在考虑影响异戊二烯的排放因子时 ,不仅要考虑通常的影响因子———可见光辐射、温度 ,还要考虑水汽的作用 .箱方法的使用不可避免地造成箱内外太阳辐射、温湿度等的差别 ,因此 ,必须考虑修正采样箱对挥发性有机物排放通量带来的影响 .2 0 0 2年夏季 ,异戊二烯排放通量 (C)的最大值为 1 6 4 9 3μg/ (m2 ·h) .6、8、9月采样期间异戊二烯排放通量的日平均值分别为 886 6、70 7 0、4 2 7 2 μg/ (m2 ·h) .

西双版纳热带森林挥发性有机物的观测研究

2002年7月中旬利用异戊二烯通量测定系统对云南西双版纳热带森林异戊二烯的排放通量进行了连续测量,同时对光合有效辐射(PAR)、气温、湿度、风等参数进行了观测.结果表明,热带地区人工橡胶林区域湿季异戊二烯的排放有明显的日变化规律,中午前后为一天中的最大值,异戊二烯排放通量的日平均值在0.85～0.24mgC/(m2(h)之间.对小时值和日平均值而言,异戊二烯的排放与PAR和气温的变化规律比较一致,但它对PAR比对气温更加敏感.不同的天气状况对异戊二烯的排放有非常明显的影响.橡胶林是一个单萜烯排放者,其单萜烯的排放速率明显依赖于PAR.橡胶林和热带雨林冠层上空异戊二烯和单萜烯的浓度也有明显的日变化规律,而且橡胶林区域的异戊二烯和单萜烯的浓度均明显高于热带雨林.

内蒙古草地挥发性有机物的预研究

内蒙古草原挥发性有机物的研究在大气化学、大气环境领域具有重要的作用。2001年夏季,利用便携式光离子化检测器以及采样仪器对于内蒙古草原的一些优势草种进行了测量,得到了对内蒙古草原挥发性有机物的初步认识。

热带人工橡胶林异戊二烯排放通量的模式研究

2 0 0 2年 7月中旬 (湿季 ) ,我们利用快速异戊二烯系统对云南热带森林异戊二烯的排放通量进行了连续测量 ,同时对其影响因子光合有效辐射、气温、湿度、风等参数进行了观测 .研究表明 ,该地区人工橡胶林异戊二烯的排放有明显的日变化 ,云和降水可以明显减小异戊二烯的排放 .利用光合有效辐射守恒的观点处理与植物异戊二烯排放有关的过程 ,建立了一个计算异戊二烯排放的经验模式 ,计算值与观测值比较接近 .因此 ,以一定的物理原理和对实际大气状况观测资料的分析为基础 ,建立异戊二烯排放模式的方法是可行的 .

草地异戊二烯排放通量影响因子的研究

20 0 2年夏季对中国内蒙古草原挥发性有机物的排放通量进行的首次测量结果表明 ,其主要成分异戊二烯的排放有明显的日变化和季节变化。采样箱对太阳辐射有非常明显的衰减作用 ,其衰减率为 1 7%～ 35 %。为准确估算异戊二烯的排放通量 ,建立其排放模式是非常必要的。基于可见光辐射传输与守恒的观点 ,在观测数据的基础上建立了异戊二烯排放通量的经验模式。结果表明 ,对日变化、季节变化和日总量的模拟值与测量值比较一致。在使用箱方法时 ,应该考虑箱内外辐射、温湿度、水汽含量之差引起的排放通量的差别 ,特别是箱内外辐射之差所引起排放通量的差别。同时也说明 ,可见光辐射是影响异戊二烯排放的最主要因子。利用异戊二烯排放通量的日总量与 1 1 :0 0通量之比和可见光辐射日总量与 1 1 :0 0时累计值之比的定量关系 ,可以由某日 1 1 :0 0的排放通量来推算该日的日总量 ,其平均相对偏差小于 1 4%。

Dimensional t-factor variation and increase of stability of the ferroelectric state in(Na_(0.5)Bi_(0.5))TiO_(3)-based solid solutions

The influence of the B-site ion substitutions in(1-x)(Bi_(1/2)Na_(1/2))TiO_(3)–xBaTiO_(3)system of solid solutions on the relative stability of the antiferroelectric(AFE)and ferroelectric(FE)phases has been studied.The ions of zirconium,tin,and(In_(0.5)Nb_(0.5)),(Fe_(0.5)Nb_(0.5)),(Al_(0.5)V_(0.5))ion complexes have been used as substituting elements.An increase in the concentration of the substituting ion results in a near linear variation in the size of the crystal lattice cell.Along with the cell size variation,a change in the relative stability of the AFE and FE phases takes place according to the changes of the tolerance factor of the solid solution.An increase in the tolerance factor leads to the increase in the temperature of the FE–AFE phase transition,and vice versa.Obtained results indicate the way for raising the temperature of the FE–AFE phase transition in(Bi_(1/2)Na_(1/2))TiO_(3)-based solid solutions.

Carbon Nanofibrous Sponge Made from Hydrothermally Generated Biochar and Electrospun Polymer Nanofibers

The objective of this study was to convert biochar,a byproduct generated from the hydrothermal process(in oxygen-limited environment)of biomass(e.g.,corn stover),into value-added product.In specific,three-dimensional(3D)biochar-containing precursor sponge,which was made by using electrospun polymer nanofibers as skeleton support,was fabricated via an innovative approach.The weight ratio of biochar to polymer(in the precursor sponge)was 2/1,and it appeared that the biochar weight ratio could be further increased.Upon heat treatments(i.e.,stabilization in air and carbonization in argon),the precursor sponge was converted into carbon nanofibrous sponge that had the porosity of~90 vol%,the BET surface area of~51.7 m^(2) g^(−1),and the carbon content of~95 wt%;and it was mechanically elastic/resilient.The electrochemical study indicated that,the carbon nanofibrous sponge could be utilized for making supercapacitor electrode with excellent rate capability and high kinetic performance.This study would not only demonstrate a high-value application of hydrothermally generated biochar,but also provide a facile while novel approach for the fabrication of carbon nanofibrous sponge which could be potentially used for various applications(particularly the energy storage application).

Mechanistic insights into the selective photocatalytic degradation of dyes over TiO_(2)/ZSM-11

Photocatalytic degradation is a promising way to eliminate dye contaminants.In this work,a series of TiO2/ZSM-11(TZ)nanocomposites were prepared using a facile solid state dispersion method.Methyl orange(MO),methylene blue(MB),and rhodamine B(RhB)were intentionally chosen as target substrates in the photocatalytic degradation reactions.Compared to pristine TiO2,negative effect was observed on MO degradation while promoted kinetics were collected on MB and RhB over TZ composites.Moreover,a much higher photocatalytic rate was interestingly achieved on RhB than MB,which indicated that a new factor has to be included other than the widely accepted electrostatic interaction mechanism to fully understand the selective photodegradation reactions.Systematic characterizations showed that TiO2 and ZSM-11 physically mixed and maintained both the whole framework and local structure without chemical interaction.The different trends observed in surface area and the photo-absorption ability of TZ composites with reaction performance further excluded both as the promotion mechanism.Instead,adsorption energies predicted by molecular dynamics simulations suggested that differences in the adsorption strength played a critical role.This work provided a deep mechanistic understanding of the selective photocatalytic degradation of dyes reactions,which helps to rationally design highly efficient photocatalysts.

Life cycle assessment of low impact development technologies combined with conventional centralized water systems for the City of Atlanta, Georgia

Low-impact development （LID） technologies, such as bioretention areas, rooftop rainwater harvesting, a_nd xeris_caping can co_ntrol stormwater runoff, supply non-potable water, and landscape open space.TillS study examines a hybrid system （HS） that combines LID technologies with a centralized water system to lessen the burden on a conventional system （CS）. CS is defined as the stormwater collection and water supply infrastructure, and the conventional landscaping choices in the City of Atlanta. The study scope is limited to five single-family residential zones （SFZs）, classified R-1 through R-5, and four multi-family residential zones （MFZs）, classified RG-2 through RG-5. Population density increases from 0.4 （R-1） to 62.2 （RG-5） persons per 1,000 m2. We performed a life cycle assessment （LCA） comparison of CS and HS using TRACI 2.1 to simulate impacts on the ecosystem, human health, and natural resources. We quantified the impact of freshwater consumption using the freshwater ecosystem impact （FEI） indicator. Test results indicate that HS has a higher LCA single score than CS in zones with a low population density; however, the difference becomes negligible as population density increases. Incorporating LID in SFZs and MFZs can reduce potable water use by an average of 50%. and 25%,respectively.; however, water savings are negligible in zones with high population density （i.e., RG-5） due to the diminished surface area per capitaavailable for LID technoogies. The results demonstrate that LID technologies effectively reduce outdoor water demand and therefore would be a good choice to decrease the water consumption impact in the City of Atlanta.

Nanostructures formation in ferroelectrics in the process of phase transformation

Received 26 June 2014;Revised 13 October 2014;Accepted 20 October 2014;Published 12 November 2014 Inhomogeneous states caused by the coexistence of the ferroelectric(FE)and antiferroelectric(AFE)phases in lead–zirconate–titanate based solid solutions have been investigated.It has been found that the domains of the FE and AFE phases with sizes of the order of 20 nm to 30 nm coexist in the bulk of the samples due to a small difference in the free energies of these phases.The coherent character of the interphase boundaries(IPBs)leads to the concentration of the elastic stresses along these boundaries.These elastic stresses cause the local decomposition of the solid solution and formation of segregates near the IPBS due to the condition that equivalent positions of the crystal lattice are occupied by the ions with different sizes.The sizes of the segregates formed in this way are of the order 8 nm to 15 nm.Some physical effects caused by the presence of these segregate nanostructures are analyzed and discussed.

A Novel Approach to Fabricate Carbon Nanomaterials-Nanoparticle Solids through Aqueous Solutions and Their Applications

A better understanding of the bonding and aggregation processes occurring between carbon nanomaterials and metal oxide particles in aqueous solutions is important in the development of novel nanosolids for applications in the areas of sensor development,highly conductive paint,nanotube alignment,polymer composites,Li-ion batteries,and many other areas.The current investigation reviews these processes and presents a detailed description of the aggregation processes occurring between carbon nanomaterials and metal oxide particles(metals)in various aqueous solutions.The results indicate that the charge attraction between the particles results in a strong homogeneous bonding that occurs within the aqueous solution and for the first time demonstrate and describe the aggregation process of these nanoparticles.The relative importance of many parameters that impact the aggregation process is identified and discussed,and guidelines for controlling the aggregation process are presented.This is a simple and cost-effective process to manufacture a novel nano-solid based on carbon nanomaterial and metal oxide.In addition,the process is easy to scale up and optimize.The methodology could lead to many significant applications as well as commercialization.

Microbial calcite,a bio-based smart nanomaterial in concrete remediation

The concept of developing a biosealant in concrete remediation is based on unique microbial metabolic processes.A common soil microorganism,Sporosarcina pasteurii,can induce CaCO_(3) precipitation in the surroundings in response to environmental cues such as high pH and available nutrients and minerals.A new biomolecule,microbial calcite is introduced as a smart nanomaterial for self-healing concrete-its effects on concrete performance were evaluated with regard to surface crack remediation and durability enhancement.For crack remediation,S.pasteurii cells immobilized on porous glass beads,Siran^(TM),were applied to cracks and tested for stiffness and compressive strengths.For durability tests,cement mortar beams prepared with bacteria were subjected to freeze-thaw cycles and examined for mean expansions and weight changes.Overall performance of the concrete was significantly enhanced by treatment with microbial calcite in simulated concrete cracks and cement mortar beams.

仿生微/纳米疏水多孔膜负载亲水海绵用于高效太阳能蒸汽转化

利用光热材料吸收太阳能产生局域化的热效应实现太阳能蒸汽转化是一项环境友好型海水淡化和废水净化的技术.本文受自然界中叶片蒸腾作用的启发,设计了一种新型仿生叶片结构,以实现高效的太阳能蒸汽转化.这种新型仿生叶片结构由三个部分组成:(1)亲水性聚乙烯醇(PVA)海绵层(相当于叶子中的叶肉组织层),具有高孔隙率和低导热性;(2)聚吡咯(PPy)层(相当于叶子中的叶绿素层)负载于PVA海绵表面以吸收太阳能;(3)微/纳米尺度的多孔疏水表面层(相当于叶片中的气孔层).其中,亲水海绵的PVA聚合物网络提供了高效水传输通道的同时实现了内部水蒸发焓的降低;PPy层吸收太阳能并转化为内能加热气液蒸汽界面的水,实现热局部化,大大减小了热损耗;疏水性多孔表面层的边缘效应,为水蒸气提供了高效逃逸通道.基于仿生叶片结构的太阳能蒸汽转化装置在一倍太阳光强(1 kW m^(−2))下蒸发率高达3.09 kg m^(−2) h^(−1).在室外自然光照条件下成功地对盐水和海水进行了脱盐和净化,平均净水速率为1.4 L m^(−2) h^(−1).这种基于仿生叶片结构的太阳能蒸汽转化装置提供了一种极具潜力的高效水净化方法,有助于利用可持续能源缓解全球水危机.

Manufacturable Novel Nanogrease with Superb Physical Properties

High-performance nanogrease manufactured from carbon nanomaterials is observed to be stable and homogeneous and have superb physical properties,such as thermal and electrical conductivities,compared with current commercial greases made of lithium,calcium,and aluminum.For the first time,carbon nanomaterials have been observed to disperse well as the sole thickeners in oil systems,e.g.,polyalphaolefin and polyester(ROYCO),without the aid of any chemical surfactants.Three-dimensional percolation network structures that exist among carbon nanomaterials are easily scalable,which can be attributed to the intermolecular van der Waals forces.Moreover,the introduction of hydrogen bonding in any form to grease significantly increases its thermal and electrical conductivities and substantially reduces the weight percentage of carbon nanomaterials needed to fabricate stable grease.For example,loading of only 1.4 wt%hydroxyl-functionalized multiwalled carbon nanotube(MWNT-OH)with Krytox XHT750 oil leads to a 37.8%increase in thermal conductivity.Moreover,75%glycerol,25% water,and 4.5 wt% MWNT-OH yielded the lowest electrical resistivity of 10.0 Ω cm.This finding can be extended to hydrogen bonding materials with functional groups,such as OH,COOH,F,and NH.The nanogrease reported in this study has been manufactured using the three-roll mill method,which is an easy and cost-effective method,as the loading weight percentage of carbon nanomaterials to fabricate stable grease decreases from 12 wt% to 3-4 wt%.Furthermore,the process is easily scalable,reproduced,and optimized.This novel high-performance nanogrease has a high commercial value and numerous applications and could replace current commercial greases.