In situ impact testing of a light-rail ballasted track with tyre-derived aggregate subballast layer

In this study, the dynamic behaviour of ballasted track with and without tyre-derived aggregate (TDA) as subballast layer was assessed using impulse–response (IR) test. For this purpose, a prototype of a ballasted track was established and many IR tests were carried out. The obtained results were represented in three different kinds of velocity–time, velocity–distance and velocity–frequency curves. Processing of the obtained results revealed that TDA efficiency in terms of vibration reduction was in the range of 17–46 dB when the impact was applied to the ballast and it was in the ranges of 6–32 dB and 6–47 dB while impact locations were on the sleeper and rail, respectively. Overall, it was proven that TDA with the particle size of 5–50 mm and thickness of 200 mm reduced by 6–47 dB in vertical vibrations with the dominant frequency range of 32–63 Hz.     

Enhancing phosphate removal from wastewater by using polyelectrolytes and clay injection

Aluminum sulfate, alum, is a common chemical coagulant used for coagulation. Recently, polymers have been utilized in coagulation/flocculation processes for water purification. In this study, the ability of two organic polymers, tannin (natural polyelectrolyte) and AN913 (synthetic anionic polyelectrolyte), and clay to act as coagulant aids was tested, in the removal of phosphate from synthetic wastewater. Contaminants in synthetic waters were coagulated using alum, alum+clay, alum+tannin, alum+AN913, alum+tannin+clay and alum+AN913+clay. Alum together with polymers as coagulant aids yielded a significant improvement in phosphate removal compared with alum alone, for initial phosphate concentrations of 5–15 mg/l PO₄³⁻. The use of clay and polyelectrolytes improved the efficiency of phosphate removal and lowered the required alum dose. Fourier transform infrared (FTIR) spectroscopy was used for the identification and characterization of the aluminum species formed during dephosphorization of the synthetic wastewater with and without tannin, AN913 and clay. Evidence from FTIR spectroscopy showed the formation of aluminum hydroxyphosphate, hydroxy-Al-tannate and aluminum complexes containing phosphorus, tannin and AN913.     

Effect of particle size distribution and subgrade condition on degradation of railway ballast under impact loads

Ballasted rail tracks are generally exposed to impact loads generated from abnormal wheel-rail interface as well as sudden variations in support rigidity. These induced impact loads can lead to railway ballast degradation by attrition of the angular edges of the aggregate and breakage of single particle into finer fragments. In the present study, the degradation of ballast particles under impact loads is investigated by considering various fouling and breakage indices. For this purpose, impact test is conducted on ballast aggregates obtained from different quarries (rock types of basalt, marl, dolomite and trachyte) by varying the gradation of ballast aggregates, impact energy and subgrade type. According to the obtained results, the degradation of ballast specimens under impact loading is less for more broadly-graded ballast. In addition, providing a flexible subgrade as support condition leads to reduction in ballast degradation resulted from diminishing impact energy. Furthermore, the axial strain of ballast specimens reduces with decrease in degradation of aggregates under repeated impact loads.     

The mechanical properties of pressed processed wheat material

Breakfast wheatflake materials, produced by two methods, were milled and different sieve fractions reconstituted by hot pressing into bar-shaped test pieces, to reduce the geometry and structure effects of flakes. The stiffness and fracture properties of these pressed bars of different particle size in ranges <0.5 mm, 0.5–1 mm, 1–1.4 mm, 1.4–2 mm and of different water content were compared. Dynamic mechanical thermal analysis showed that the bending modulus, E, superimposed as a function of temperature in the range -40 to 140 °C. The value of E at 20 °C decreased with increasing water content corresponding to depression of the glass transition temperature. Microscopy of the test pieces revealed that starch was the continuous phase. The stiffness properties were similar in many respects to data published for pressed starch specimens. However, the energy to break samples at 7% water content (wet weight basis) was greater when a range of particle sizes was used compared to the results of narrow particle size ranges. This is consistent with published results on fracture toughness of particulate compacts. The energy to break samples increased with increasing water content.     

Treatment of hazardous materials spills in flowing streams with floating mass transfer agents

Field studies were conducted in a Flowing Stream Test Facility to determine parameters governing application of floating media (in this case, commercially-available activated carbon) to flowing streams for the purpose of treating hazardous materials spills in situ. It was found that removal efficiency is highly dependent on prompt location of the contaminant plume, even dispersion of media over the water surface, and favorable environmental conditions. This technique is most effective for concentrated plumes in small streams, and removal efficiencies increase as the size of the spill increases. Removal efficiencies ranged from 50 to > 95%, depending upon the substance being used in the tests.Further investigation should focus on ballast and packaging techniques, methods for increasing efficiency of contact, prevention of carbon buildup along stream banks, and efficiency of spent carbon collection.     

Development and characterization of an aerosol time-of-flight mass spectrometer with increased detection efficiency

This paper describes the development and characterization studies of a more efficient aerosol time-of-flight mass spectrometer (ATOFMS), showing results for the on-line detection and determination of the size and chemical composition of single fine (100-300 nm) and ultrafine (<100 nm) particles. An aerodynamic lens inlet was implemented, replacing the converging nozzle inlet used on conventional ATOFMS instruments. In addition, the light scattering region was modified to enhance the scattering signals for smaller particles. Polystyrene latex spheres (PSL) with aerodynamic diameters ranging from 95 to 290 nm were used to characterize the particle sizing efficiency (product of particle transmission efficiency and particle scattering efficiency), particle detection efficiency (product of particle sizing efficiency and particle hit rate), and particle beam profile and perform instrument calibration. At number concentrations of <20 particles/cm(3), the particle sizing efficiencies were determined to be approximately 0.5% for 95 nm and approximately 47% for 290-nm PSL particles, while the particle detection efficiencies were measured to be approximately 0.3% for 95 nm and 44% for 290-nm PSL particles. This represents a significant increase (i.e., at least 3 orders of magnitude) in detection efficiencies for smaller particles over the conventional ATOFMS. In addition, the beam profiles for PSL particles of various sizes were measured in the ion source of the mass spectrometer and follow a Gaussian distribution with a full width at half-maximum of approximately 0.35 mm. The resulting higher detection efficiencies allow ATOFMS to obtain higher temporal resolution measurements of the composition of fine and ultrafine individual particles as demonstrated in initial ambient measurements in La Jolla, CA. At typical ambient particle number concentrations of 10(2)-10(3) particles/cm(3), approximately 30 000 particles with aerodynamic diameters of <300 nm were detected with average 24-h hit rates of 30% for particles between 50 and 300 nm. This advancement, allowing for high temporal resolution measurements of the composition of smaller particles with higher efficiency, adds to a growing number of instruments that can chemically characterize individual fine and ultrafine particles, with the goal of providing new insights into a number of areas including environmental and material sciences, health effects studies, industrial hygiene, and national security.     

Separation of flocculated ultrafine coal by enhanced gravity separator

The separation of ultrafine coal is inefficient due to the low settling velocity in centrifugal field. The feasibility of increasing particle size by flocculation to increase the separation efficiency is verified. The effect of flocculant on the size distribution of ultrafine coal was tested. The effect of flocculant dose on deash and desulfurization efficiency was studied to determine the appropriate dosage. Further, influence of the main operating parameters of the concentrator, including centrifugal force and water counter pressure on the separation performance, was studied. In addition, a comparative test was designed to verify the stability of the flocs. Results showed that the size of ultrafine coal particles could be effectively increased by the addition of flocculant, and the yield of ?0.045 µm fraction was decreased from 50% to 17% when the flocculant dosage was 10 g/t. The combustible material recovery of clean coal increased from 58% to 66%; meanwhile, the ash content reduced from 16.7% to 14.6%. In addition, combustible matter recovery and desulphurization efficiency decreased with the increase of centrifugal force, while they increased with the water counter pressure. Results of comparison tests of ultrafine coal with flocculant pretreatment and artificial coal with the same size composition showed that the latter had greater combustible recovery and desulfurization efficiency.     

Tailoring of 2D MoS2 microspheres on 3D low-cost DE for the efficient removal of hazardous cationic dyes

The primary challenge involved in the water treatment field is to treat/clean the contaminated waste dye solutions before it releases into the environment. Industrial contaminant such as dyes are released into water streams, rendering the water unfit for further use. Treatment of such dye contaminants is still a challenging tasks that has evolved as one of the leading issues in environmental remediation. Some of the significant limitations in dye adsorption include time-consuming, synthetic routes, expensive adsorbents, more contact time, less adsorption performances and use of more adsorbents. To address such problems, herein in this work, 2D MoS₂ molybdenum disulfide)-3D DE (diatomaceous earth) hybrid materials were synthesized by a facile and efficient hydrothermal route. The prepared innovative combination of 2D & 3D porous hybrid materials demonstrated to be efficient adsorbents for the efficient removal of malachite green (MG) dye from aqueous solution with superior 97 % removal efficiency within 5 mins and with an extended 60 mins of contact time possible to achieve 99.9 % of removal efficiency. Furthermore, the maximum adsorption capacity for DE was only 0.78 mg/g and developed 2D MoS₂-3D DE exhibited an outstanding 110 mg/g for MB dye which is a significant improvement when compared to pristine DE. On the other hand, the 2D MoS₂-3D DE was explored as a membrane-based filter for the removal of other important cationic pollutant methylene blue (MB) dye which showed 100 % rejection for varied MB volumes from 50 to 200 mL with average flux rate of 2200 L.m^?2.h^?1. Additionally, the 2D-3D hybrid adsorbents substantiated with better recyclability with up to 5 cycle performances which could be an excellent candidate for the removal of industrially important cationic dyes in the future.     

Processing of fine particles using closely spaced inclined channels

A Reflux Classifier consists of a set of parallel inclined channels above a conventional fluidised bed. Recently Galvin et al. (2009, 2010) [3], [2] discovered a new and powerful separation mechanism for elutriating particles on the basis of density, utilising closely spaced channels. This arrangement suppresses the effects of particle size, thus promoting the effect of particle density. A series of particle fractionation experiments was conducted in this study to examine the effects of the channel spacing. Inclined channel spacings of 1.77, 4.2, 7, 9, and 18 mm were used in the work. A continuous distribution of coal and mineral matter, consisting of particles in the size ranges from 0.25 to 2.0 mm and 0.038 to 0.25 mm were used, with the particle density ranging from 1275 to 2600 kg/m³. The results demonstrate the benefits of the new separation mechanism, with greatly improved fractionation achieved using the more closely spaced channels.     

Influence of strain range on fatigue life reduction of stainless steel in PWR primary water

The environmental effect in the pressurized water reactor (PWR) water was investigated for various applied strain range using a type 316 stainless steel. The tests were conducted using cylindrical hollow specimens at 325°C. It was shown that the ratio of the fatigue life in the PWR water environment to that in air was about 0.3 to 0.4 regardless of the strain range when the applied strain ranges were 0.8% or more. Crack growth rates identified from spacing of striations observed on fractured surfaces were used to demonstrate that the fatigue life reduction in the PWR water environment could be attributed to the crack growth acceleration. The fractured surface observations revealed that crack initiation was enhanced by the PWR water environment. On the other hand, the reduction in the fatigue life was not significant when the strain ranges were 0.5% and 0.44%, and the specimens did not fail when the strain ranges were 0.38% or less. It was deduced that the crack initiation was not enhanced for the relatively small strain range, and the crack growth was not accelerated. Since the fatigue limit of the test material was 0.4% in the strain range in air, it was concluded that the fatigue limit was not reduced in the PWR water environment.     

Surface treatment of clayey soil particles for reducing water loss through evaporation

To conserve water in crop production and landscaping, plastic mulch or sheets are commonly used. However, the environmental impact of plastic waste is a concern. Therefore, herein we report that a silane coupling agents-based coating can be applied to natural clayey soil samples to suppress water evaporation. The hydrophobicity of soils (particle sizes 200–500 µm) can be enhanced. Evaporation flux was investigated using an electronic balance placed inside a chamber by maintaining constant flow, temperature, and relative humidity. The magnitude of evaporation flux was adjusted by placing a hydrophobic-treated soil layer in the system. It is clear that the hydrophobic-treated soil particle layer interacts with water capillaries to reduce the evaporation flux, but the effect on water vapor diffusion was small.     

Experimental study on the separation performance of a novel gas–liquid separator

A novel two-stage dynamic separator called high-gravity cyclone separator (HGCS) has been designed for gas–liquid separation. It is mainly composed of a cyclone chamber and rotary drum. In this study, its performance, including the separation efficiency and pressure drop, is experimentally investigated, and the effects of the operating conditions and drum parameters are evaluated. For droplets with a mean diameter of 7 μm, the results indicate that the optimal gas inlet velocity and high-gravity factor are 12 m/s and 59.4, respectively, and the separation efficiency reaches 98 %. The effect of liquid concentration is sensitive to the high-gravity factor. At a liquid concentration of 57 g/m³, the maximum efficiency will be 98.75 % when increasing the high-gravity factor to 85.6. Furthermore, a smaller radial height is preferable when the gas inlet velocity is greater than 12 m/s, and a better separation efficiency can be obtained by increasing the drum length to 190 mm. However, when the length is 235 mm, the efficiency will be poor because of the Kelvin–Helmholtz and Rayleigh–Taylor instabilities. Compared with the predominant roles of gas inlet velocity, drum length and radial height in pressure drop, the effects of liquid concentration and high-gravity factor are small.     

基于颗粒真实几何形状的铁路道砟剪切过程三维离散元分析

铁路道床由尺寸和形状各异的道砟颗粒组成,道砟颗粒的形状对道床的强度、变形等力学特性具有显著影响,反映颗粒单一方向尺寸分布特征的级配曲线难以全面描述形状不规则的道砟颗粒的几何特征。该文利用计算机视觉成像技术获得道砟颗粒在三个相互垂直方向的投影图,提取投影图轮廓并计算其几何特征参数;基于颗粒三视图重建与真实道砟颗粒具备相同几何特征的三维模型,引入到自行开发的三维块体离散元数值模拟程序中,建立了真实道砟颗粒料的三维离散元分析模型。通过与多种竖向压力作用下的室内直剪试验结果进行对比,验证了该方法可靠性;并在此基础上对道砟颗粒料在直剪试验中的变形和细观力学特性进行了深入详细的分析。     

Investigation on impact strength of the as-soldered Sn37Pb and Sn3.8Ag0.7Cu solder joints

Charpy impact specimens of eutectic Sn37Pb and Sn3.8Ag0.7Cu solder joints with U-type notch were prepared to investigate the joint impact strength. The gap sizes of the butt joint were selected at 0.3 and 0.8 mm. Compared with the values of 0.3 mm joint gap, the impact absorbed energies of two solder joints were increased at the joint gap of 0.8 mm. The impact strengths of Sn37Pb joints were higher than those of Sn3.8Ag0.7Cu joints in both cases. From the macrographic observation of the fracture path, when the gap was 0.3 mm, the crack initiation of two solder joints located at the root of U-type notch then propagated along one interface of the joint. For the Sn37Pb joints, the fracture path was not changed at 0.8 mm gap size. However, the fracture path of Sn3.8Ag0.7Cu joint was totally changed and the fracture occurred not at the root of pre-U notch but from one side of the solder/Cu interfaces. From the micrographic observation, the crack of the Sn37Pb joints was concentrated on the Pb-rich layer in the vicinity of interfacial intermetallic (IMC) layer and the fracture morphology mainly appeared to be a ductile-like structure. Meanwhile, the fracture of Sn3.8Ag0.7Cu joints propagated along either the interface of IMC/solder or within the IMC layer and showed a brittle failure mode.     

Separation of hafnium and zirconium from ti- and fe-rich geological materials by extraction chromatography

This paper presents a new chemical separation method for Hf and Zr from rocks using extraction chromatographic resins prepared from inert polymeric supports and the liquid anionic exchangers tri-n-octylamine or trioctylmethylammonium chloride (Aliquat 336). The method was developed using basaltic and trachyandesitic rocks with high contents of Al, Fe, and Ti. A 100-mg rock sample was decomposed with HF-HNO(3)-HClO(4) and fumed with HClO(4). The residue of this process was dissolved in 10 M HCl and then loaded on the column (6 mm i.d. × 75 mm). The major elements (Al, Ca, Mg, Ti, etc.) were eluted with 10 mL of 10 M HCl, and then Hf, Zr, and Fe were eluted sequentially using 20 mL of 8 M HCl, 20 mL of 2 M HCl, and 5 mL of 1 M HNO(3). The removal efficiency of major elements (Al, Fe, Ca, Mg) was greater than 99% and that of Ti was greater than 95%. The recoveries of Hf and Zr were better than 90% and the Zr/Hf ratio decreased from the natural ratio of 45 in the rock sample to 0.3 in the Hf fraction. This method provides an alternative to the less straightforward procedures based on several stages of ion-exchange separation and might be used for sample preparation prior to (176)Hf/(177)Hf determinations by magnetic sector multicollection ICPMS.     

Thermally mendable epoxy resin strengthened with carbon nanofibres

This paper investigates the strengthening and toughening effects of carbon nanofibres (CNFs) on a self-healing thermoset/thermoplastic blend, i.e. an epoxy/poly (ε-caprolactone) (PCL) blend. The self-healing material system was prepared by polymer blending that produced a co-continuous phase-separated structure. The addition of CNFs altered the phase structures, leading to smaller domain sizes or even completely altering the phase separation mechanism, e.g. conversion from a co-continuous phase-separated structure to a particulate phase structure when the CNF content reached a certain level (0.3 wt% in this work). As the content of CNFs increased, the resulting nanocomposite became stronger and tougher, but the self-healing efficiency diminished; the optimal CNF content was found to be 0.2 wt%, which produced the highest strength, toughness and hardness, while achieving around 70% of healing efficiency.     

Numerical simulation on adsorbent injection system for mercury removal from coal-fired flue gas

Optimizing the injection system significantly reduces the cost of adsorbent injection technology for mercury removal from coal-fired flue gas. In this work, the effects of three common injection system layouts, namely single-sided four-way pipe (SFP), quadtree (QT), and long to short (L-S), on adsorbent particle concentration, mercury concentration, and mercury removal efficiency were systematically investigated by simulation calculation. It shows adsorbent coverage, and particle concentration standard deviation coefficient at the initial injection satisfies SFP > QT > L-S. The number of nozzle and injection directions affect the distribution of adsorbent particle concentration. The apparent mercury removal occurs within 2 s after adsorbent injection. The SFP arrangement has the best average coverage rate of adsorbent (86.86%), average standard deviation coefficient (2.40), and mercury removal efficiency (60.12%). The coupling degree between particle concentration and flue gas mercury concentration field is essential in determining mercury removal performance.     

导叶式旋风管入口颗粒粒度分布对分离效率的影响

为深入研究导叶式旋风管的分离机理,用不同粒度分布的SiO2颗粒对分离总效率与粒级效率进行了对比研究。实验结果表明:入口颗粒的粒度分布不但对旋风管的分离总效率有影响,而且对粒级效率也有较大影响;不同粒径大小的颗粒在旋风管中的分离机理不同。     

Copper foams in water treatment technology: Removal of hexavalent chromium

Open-cell copper foams were prepared using a space holder technique and tested as filter-beds for the uptake and reduction of Cr(VI) in drinking water. The use of raw cane sugar as a space holder provides an environmentally friendly method for the production of foams with controllable porous network characteristics. Specifically, by applying a sugar volume of 70–80% with particle sizes in the range of 0.35–0.70 mm, it was possible to obtain final porosity of 65%, high structural stability, and enhanced interconnectivity of macropores required for the free flow of treated water. Smaller sugar particles ensure a smaller pore size and a higher specific surface area, favoring the interaction of water with the effective copper surface. Column tests indicated that a realistic filtering system using the Cu-foam can operate with complete Cr(VI) removal and minimum Cu leaching in the pH 7 ± 0.2 range, capturing chromium in the form of Cr(III) and Cr(VI) oxides. Chromium is homogeneously distributed and incorporated into the copper porous network allowing an almost unlimited lifetime of effective use compared to common adsorbents.     

Electrochemical degradation of benzene in natural water using silver nanoparticle-decorated carbon nanotubes

In this study, a novel methodology for the electrochemical degradation of benzene in natural water using silver nanoparticle-decorated carbon nanotubes has been investigated. The morphology, the structure, and the electrochemical performance of the multi-walled carbon nanotubes-silver (MWCNT-Ag) nanocomposite film were characterised by transmission electron microscopy (TEM), X-ray diffraction (XRD), and cyclic voltammetry (CV), respectively. Electrocatalytic oxidation of benzene in an aqueous solution was studied to evaluate potential applications of the MWCNT-Ag modified glassy carbon (GC) electrode in environmental science. The benzene removal efficiency in natural water containing 10 mg L⁻¹ benzene yielded 77.9% at an applied potential of +2.0 V for 2 h using the MWCNT-Ag-GC electrode. In comparison, the removal efficiency reached only 8.0% with the bare GC electrode, showing the suitability of the MWCNT-Ag nanocomposite modified GC electrode for electro-oxidation of benzene in natural water.