Fluorescence spectroscopy of complex aromatic mixtures

The contribution of two- to seven-ring polycyclic aromatic hydrocarbons (PAH) and of larger aromatic structures contained in complex PAH-laden mixtures collected in flames was evaluated by fluorescence spectroscopy. A composition procedure of the fluorescence spectra of individual PAHs, analyzed by gas chromatography/mass spectrometry (GC/MS) was applied for the evaluation of their contribution to the fluorescence spectra of PAH-laden mixtures. In this way, it was possible to put in evidence the contribution to the total fluorescence spectrum of high molecular weight aromatic species present in the PAH-laden mixtures and not detectable by GC/MS. Qualitative and quantitative interpretation of synchronous and conventional fluorescence spectra of PAH-laden mixtures formed in combustion processes was proposed. The composition procedure was showed to be reliable in the UV-visible region for samples dissolved in cyclohexane solutions, but failed in the UV region when the solvent contained heavy atoms, as in the case of dichloromethane. However, the heavy-atom solvent effect was not sufficient to explain the depression of the UV fluorescence signal. Energy transfer interaction between fluorene and other fluorescing PAHs was suggested to be also responsible for this effect on the basis of fluorescence studies performed on single PAHs and their mixtures in cyclohexane, methanol, and dichloromethane.     

Using biological motion to enhance the conspicuity of roadway workers

This study examined whether the conspicuity of road workers at night can be enhanced by distributing retroreflective strips across the body to present a pattern of biological motion (biomotion). Twenty visually normal drivers (mean age = 40.3 years) participated in an experiment conducted at two open-road work sites (one suburban and one freeway) at night-time. At each site, four road workers walked in place wearing a standard road worker night vest either (a) alone, (b) with additional retroreflective strips on thighs, (c) with additional retroreflective strips on ankles and knees, or (d) with additional retroreflective strips on eight moveable joints (full biomotion). Participants, seated in stationary vehicles at three different distances (80 m, 160 m, 240 m), rated the relative conspicuity of the four road workers. Road worker conspicuity was maximized by the full biomotion configuration at all distances and at both sites. The addition of ankle and knee markings also provided significant benefits relative to the standard vest alone. The effects of clothing configuration were more evident at the freeway site and at shorter distances. Overall, the full biomotion configuration was ranked to be most conspicuous and the vest least conspicuous. These data provide the first evidence that biomotion effectively enhances conspicuity of road workers at open-road work sites.     

Supramolecular aromatic interactions to enhance biodegradable film properties through incorporation of functionalized cellulose nanocrystals

Cellulose nanocrystals (CNC) were grafted with an aliphatic and an aromatic isocyanate (octadecyl and 4-phenylbutyl isocyanate) and composites of poly(butyleneadipate-co-terephthalate) – PBAT – with 5 and 10 wt% of modified and non-modified CNC were prepared through solvent casting. Rheological analysis confirmed that the degree of grafting contributed to CNC dispersion and allowed the formation of a percolated structure. The treated-CNC reinforced composites displayed improved mechanical properties, namely: an increase by 120% and 40% in the elastic modulus and the tensile strength, respectively. The best results were obtained with 4-phenylbutyl isocyanate-modified CNC, due to the π–π interactions between the phenyl rings grafted onto the CNC molecules and the aromatic rings of the polymeric chain, as indicated by Raman spectroscopy. To the best of our knowledge, it is the first time that the CNC incorporation is studied in a PBAT pure matrix.     

Permeation of aromatic solvent mixtures through nitrile protective gloves

The permeation of binary and ternary mixtures of benzene, toluene, ethyl benzene and p-xylene through nitrile gloves were investigated using the ASTM F739 test cell. The more slowly permeating component of a mixture was accelerated to have a shorter breakthrough time than its pure form. The larger differences in solubility parameter between a solvent mixture and glove resulted in a lower permeation rate. Solubility parameter theory provides a potential approach to interpret the changes of permeation properties for BTEX mixtures through nitrile gloves. Using a one-dimensional diffusion model based on Fick's law, the permeation concentrations of ASTM F739 experiments were appropriately simulated by the estimated diffusion coefficient and solubility. This study will be a fundamental work for the risk assessment of the potential dermal exposure of workers wearing protective gloves.     

Using reflective clothing to enhance the conspicuity of bicyclists at night

Bicycling at night is more dangerous than in the daytime and poor conspicuity is likely to be a contributing factor. The use of reflective markings on a pedestrian's major joints to facilitate the perception of biological motion has been shown to greatly enhance pedestrian conspicuity at night, but few corresponding data exist for bicyclists. Twelve younger and twelve older participants drove around a closed-road circuit at night and indicated when they first recognized a bicyclist who wore black clothing either alone, or together with a reflective bicycling vest, or a vest plus ankle and knee reflectors. The bicyclist pedalled in place on a bicycle that had either a static or flashing light, or no light on the handlebars. Bicyclist clothing significantly affected conspicuity; drivers responded to bicyclists wearing the vest plus ankle and knee reflectors at significantly longer distances than when the bicyclist wore the vest alone or black clothing without a vest. Older drivers responded to bicyclists less often and at shorter distances than younger drivers. The presence of a bicycle light, whether static or flashing, did not enhance the conspicuity of the bicyclist; this may result in bicyclists who use a bicycle light being overconfident of their own conspicuity at night. The implications of our findings are that ankle and knee markings are a simple and very effective approach for enhancing bicyclist conspicuity at night.     

Preparation of thermosensitive gold nanoparticles by plasma pretreatment and UV grafted polymerization

This work is to develop an easy method of plasma treatment and graft polymerization to prepare thermosensitive gold nanoparticles. Gold nanoparticles (Nano-Au) were reduced by trisodium citrate combined with hydrogen tetrachloroaurate(III) tetrahydrate (chloroauric acid) and modified with 11-mercaptoundecanoic acid (MUA) by the self-assembly monolayers (SAM). The surface graft polymerization of N-isopropylacrylamide (NIPAAm) was carried out by two steps, using O₂ plasma pretreatment of the surface on MUA SAM modified Nano-Au to form the peroxide groups on Nano-Au(MUA), and then subsequently using UV light to induce grafting with thermosensitive polymer. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to direct investigation of the particle size and morphology in situ. The diameters of the gold nanoparticles measured from the TEM images are in good agreement with data measured at room temperature which is about 15 nm. The thermosensitive gold nanoparticles were characterized by chemical structure of surface (ESCA) and Fourier-transform infrared spectroscopy (FTIR). ESCA result suggests that plasma treatments can be employed to generate peroxides on the Nano-Au(MUA) for the subsequent UV graft polymerization of PNIPAAm.     

Using hybrid reinforcement methodology to enhance overall mechanical performance of pure magnesium

In the present study, magnesium based composites containing galvanised iron wire mesh and carbon fibres as continuous reinforcement were fabricated using the disintegrated melt deposition technique followed by hot extrusion. Microstructural characterisation of the extruded composite samples showed minimal porosity and good interfacial integrity between iron wire mesh and the matrix. The penetration of magnesium in between carbon fibres remains limited. Mechanical characterization revealed that the addition of reinforcements lead to an increase in hardness, dynamic modulus and 0.2%YS, did not affect the UTS and reduced the ductility. The overall mechanical performance of the composite with hybrid reinforcement synthesized in this study remained superior when compared to conventional composite formulations with comparatively higher volume fraction of reinforcement.     

聚氨酯脲和聚氨酯酰亚胺膜的制备与渗透汽化芳烃/烷烃分离性能研究

通过两步聚合的方法,成功制备了以聚己二酸乙二醇酯(PEA)为软段的聚氨酯脲(PUU)和聚氨酯酰亚胺(PUI)膜材料,用FT-IR,NMR和DSC等方法对两种膜材料的分子结构及性质等进行了表征,并考察了两种膜对芳烃/烷烃混合物的渗透汽化分离性能.结果表明,两种膜都对芳烃表现出良好的选择渗透性,在相同的条件下,PUU膜的渗透通量比PUI膜更大而分离因子更小.对于苯的浓度为50%的苯/环己烷混合物分离体系,45℃时PUI膜的渗透通量为18.6 kg·μm/(m2·h),分离因子为7.3;而对于苯/正己烷混合物分离体系,渗透通量则为22.4 kg·μm/(m2·h),分离因子为15.2.     

Using support vector machine and dynamic parameter encoding to enhance global optimization

This study presents an approach which combines support vector machine (SVM) and dynamic parameter encoding (DPE) to enhance the run-time performance of global optimization with time-consuming fitness function evaluations. SVMs are used as surrogate models to partly substitute for fitness evaluations. To reduce the computation time and guarantee correct convergence, this work proposes a novel strategy to adaptively adjust the number of fitness evaluations needed according to the approximate error of the surrogate model. Meanwhile, DPE is employed to compress the solution space, so that it not only accelerates the convergence but also decreases the approximate error. Numerical results of optimizing a few benchmark functions and an antenna in a practical application are presented, which verify the feasibility, efficiency and robustness of the proposed approach.     

Using forecasts and managerial accounting information to enhance closed-loop supply chain management

This paper develops a generic forecasting framework for product returns that combines concepts used in different disciplines. If more-step ahead forecasts of product returns are required, estimating sales data is necessary. This is accomplished by adopting growth curve models based on the extended Kalman filter. In order to capture the process generating product returns more adequately than in the literature, we propose an adaptive Bayesian approach to forecast future returns. The combination of these two concepts enables us to conduct more-step ahead forecasts. We evaluate the robustness of this approach against Holts approach, a Kalman filter based approach, and the model by Toktay et al. (Manag Sci 46:1412–1426, 2000) for varying degrees of misspecification. In addition, we create a link between forecasting accuracy and the economic value added. This enables the user to choose the economically worthwhile forecasting method that trades-off additional operating costs and savings in working capital. Our theoretical and numerical results indicate that our approach operates on high accuracy even in situations when the underlying assumptions are obviously violated.     

Transport properties of nonelectrolyte liquid mixtures—VI. Viscosimetric study of binary mixtures of hexafluorobenzene with aromatic hydrocarbons

Viscosity coefficients for binary mixtures of hexafluorobenzene with benzene, toluene, para-xylene, and mesitylene have been measured along the saturation line at temperatures from 15 to 120°C using specially designed capillary viscometers. Densities were measured using a pyknometer and volume-change apparatus. Deviations of the viscosities from a rectilinear dependence on mole fraction are consistent with enhanced interactions between unlike species, which increase with increasing number of methyl groups on the aromatic hydrocarbon and decrease with increasing temperature. The application of the Grunberg and Nissan equation, the Hildebrand equation, and energy of activation theories to these results is examined.     

Concentration dependence in the spectra of polycyclic aromatic hydrocarbon mixtures by front-surface fluorescence analysis

Polycyclic aromatic hydrocarbons (PAHs) are a challenge for fluorescence analysis. Inner-filter quenching effects and energy transfers of PAHs in petroleum differ with concentration, leading to characteristically different fluorescence. At high concentrations of single PAH molecules and petroleum mixtures the classic rectangular quartz cell presents a particular challenge due to inner filter effects from right-angle illumination. While quite a few instrumental and mathematical corrections for these effects are reported throughout the literature, for researchers with standard instrumental sample compartments a triangular fluorometer cell can be used to emulate front-surface fluorescence analysis. This work presents concentration study results from the single PAH molecules fluoranthene and azulene dissolved in spectral-grade cyclohexane and also seeks to correct an aspect of our past work on the fluorescence of petroleum mixtures.     

Using acoustic cavitation to enhance chemotherapy of DOX liposomes: experiment in vitro and in vivo

Experiments in vitro and in vivo were designed to investigate tumor growth inhibition of chemotherapeutics-loaded liposomes enhanced by acoustic cavitation. Doxorubicin-loaded liposomes (DOX liposomes) were used in experiments to investigate acoustic cavitation mediated effects on cell viability and chemotherapeutic function. The influence of lingering sensitive period after acoustic cavitation on tumor inhibition was also investigated. Animal experiment was carried out to verify the practicability of this technique in vivo. From experiment results, blank phospholipid-based microbubbles (PBM) combined with ultrasound (US) at intensity below 0.3 W/cm(2) could produce acoustic cavitation which maintained cell viability at high level. Compared with DOX solution, DOX liposomes combined with acoustic cavitation exerted effective tumor inhibition in vitro and in vivo. The lingering sensitive period after acoustic cavitation could also enhance the susceptibility of tumor to chemotherapeutic drugs. DOX liposomes could also exert certain tumor inhibition under preliminary acoustic cavitation. Acoustic cavitation could enhance the absorption efficiency of DOX liposomes, which could be used to reduce DOX adverse effect on normal organs in clinical chemotherapy.     

Generalization and analytic description of thermal conductivity of paraffin and aromatic hydrocarbons and their mixtures

Experimental data on thermal conductivity of liquid binary mixtures of aromatic hydrocarbons with n-hexane are generalized.     

Using perforated ventilation ducts to enhance the cooling effect of crushed-rock interlayer on embankments in permafrost regions

A previous laboratory test carried out by the authors proved that the addition of ventilation ducts can efficiently enhance the cooling effect of crushed-rock interlayer. The mechanism revealed by the laboratory test was that, the ventilation ducts intensified natural convection and thus enhanced cooling effect of the crushed-rock interlayer by decreasing its upper boundary temperature. In this study, to further enhance the cooling effect of the crushed-rock interlayer, the ventilation ducts were perforated and then positioned at the upper boundary of the crushed-rock interlayer. Two crushed-rock interlayer embankments with perforated and imperforated (ordinary) ventilation ducts were tested under the same test conditions. The analysis of the temperature characteristics of the two test crushed-rock interlayer embankments with perforated and imperforated ventilation ducts showed that the crushed-rock interlayer embankment performed a more efficient cooling effect when the ventilation ducts were perforated. The effect was straightforward: the addition of the perforation on the ventilation duct wall let the air that was flowing through ventilation ducts partially penetrated into the crushed-rock interlayer. The result was that, during negative air temperature period, the upper boundary temperature of crushed-rock interlayer was decreased to a great extent, and consequently natural convection in the crushed-rock interlayer was intensified. The cooling effect during negative air temperature was efficient enough to restrict the heat injected into the embankment during positive air temperature period. On the whole, the crushed-rock interlayer embankment with perforated ventilation ducts has a good cooling effect to the underlying permafrost. Based on these, the new type of embankment is recommended in the construction of large-width highways in permafrost regions in the future.     

Using supply chain management to enhance industry—university collaborations in IT higher education in Korea

Facing such serious problems in cultivating IT engineers as a mismatch in supply and demand of IT workers, shortage of globally competitive IT professionals, and insufficient education and training of university graduates, the Korean government has decided to adopt a new paradigm in national IT engineering education, based on supply chain management (SCM) in manufacturing. SCM weights improving competitiveness of the supply chain as a whole via a long-term commitment to supply chain relationships and a cooperative, integrated approach to business processes. These characteristics of SCM are believed to provide insight into a more effective IT education and industry-university relationship. On the basis of the SCM literature, a model for industry-oriented IT higher education is designed, and then applied in the field of computer-software engineering in Korea.     

紫外线(UV)固化技术在数字成像材料中的应用(四)UV固化技术在立体光刻中的应用

近年来，数字成像技术不断提高和应用范围的迅速推广，也推动了UV固化技术在这一领域的融合和应用，取得了极大的成效，由于UV固化材料具有快速固化、高效、低污染、节能、优质等特点，很快发展成为一种新型的数字成像材料，目前已实现产业化的主要有UV喷墨打印、计算机直接制版CTP、印刷电路版数字化制作、立体光刻等四种技术，作者拟分为四个专题予以阐述，本文主要讨论其第四个专题：UV固化技术在立体光刻中的应用。