A semi-quantitative approach to risk analysis, as an alternative to QRAs

In quantitative risk analysis (QRA) risk is quantified using probabilities and expected values, for example expressed by PLL values, FAR values, IR values and F–N curves. The calculations are tedious and include a strong element of arbitrariness. The value added by the quantification can certainly be questioned. In this paper, we argue that such analyses often are better replaced by semi-quantitative analyses, highlighting assessments of hazards and barriers, risk influencing factors (RIFs) and safety improvement measures. The assessments will be based on supporting information produced by risk analysts, including hard data and analyses of failure causes and mechanisms, barrier performance, scenario development, etc. The approach acknowledges that risk cannot be adequately described and evaluated simply by reference to summarising probabilities and expected values. There is a need for seeing beyond the standard probabilistic risk results of a QRA. Key aspects to include are related to uncertainties in phenomena and processes, and manageability factors. Such aspects are often ignored in standard QRAs.     

Exploring Web keyword analysis as an alternative to link analysis: a multi-industry case

The study explored the feasibility of using Web keyword analysis as an alternative to link analysis and tested the feasibility in a multi-industry environment. The keyword is the organization??s name, in this case the company name. American companies from five industries were included in the study. The study found that the Web visibility of a company as measured by the number of Webpages on which the company name appears correlates with the company??s business measures (revenue, profits, and assets). The correlation coefficients are similar to that between the inlink counts and the business measures. This suggests that the keyword count (searched by the company name) could replace inlink count as an alternative indicator of some commonly used business measures. The co-word (the co-occurrence of the names of two companies on Webpages) count was used as a measure of the relatedness of the two companies. Multidimensional scaling (MDS) analysis was applied to the co-word matrices and generated MDS maps that showed relationships among companies in a multi-industry context. Keyword data were collected from three different types of Websites (general Websites, blog sites, and Web news sites) and results were compared. The study found blog sites to be the better source to collect data for this type of study. The comparison of MDS maps generated from co-link data and the blog co-word data showed that the co-word analysis is as effective as co-link analysis in mapping business relationships. The value of the study is not limited to the business sector as the co-word method could be applied to analysing relationships among other types of organizations.     

Pervaporation as an alternative to headspace

The use of pervaporation as an alternative to headspace is proposed. The analytical system involves the speciation of organomercury compounds in solid samples using pervaporation, which has been coupled for the first time to gas chromatography. The speciation of mercury as Me(2)Hg, Et(2)Hg, and MeHgCl has been carried out without any derivatization of the analytes, which, after separation from the solid matrix, are preconcentrated on a Tenax minicolumn prior to desorption and chromatographic separation on a semicapillary column (HP-1) prior to atomic fluorescence detection. No column degradation was observed. Linear ranges and detection limits slightly better than those obtained by headspace GC were observed for mercury species in solid samples. Excellent recoveries (between 95 and 107%) for mercury species added to complex solid samples were obtained by this extremely simple and easily automated setup.     

竹材废弃物作为工业锅炉燃料的研究

我国竹材资源在传统制作和工业加工过程中的重量利用率低于40%,有60%以上的竹材成为加工剩余物,竹材生物资源量巨大.竹材的硫和灰分含量仅为洁净煤质燃料的1/5~1/3,是一种非常洁净的燃料.竹材作为工业锅炉燃料时,含水量应控制在20%以下.燃煤锅炉改烧竹材燃料时,需对配风方案、进料机构和局部结构进行改进.竹材废弃物代油燃烧,具有明显的价格优势和环保效益.经济性分析结果表明,在竹材废弃物丰富的地区,开发燃用竹材废弃物的工业锅炉具有良好的经济性.     

Fog water as an alternative and sustainable water resource

As the world’s population and demand for fresh water increases, new water resources are needed. One commonly overlooked aspect of the water cycle is fog, which is an important part of the hydrology of coastal, high-altitude, and forested regions. Fog water harvesting is being investigated as a sustainable alternative water resource for drinking water and reforestation. Fog water harvesting involves using mesh nets to collect water as fog passes through them. The materials of these nets, along with environmental factors such as wind speed, influence the volume of water collected. In this article, a review of current models for fog collection, designs, and applications of fog water harvesting is provided. Aspects of fog water harvesting requiring further research and development are identified. In regions with frequent fog events, fog water harvesting is a sustainable drinking water resource for rural communities with low per capita water usage. However, an analysis of fog water harvesting potential for the coastal areas of northern California (USA) showed that fog yields are too small for use as domestic water in areas with higher household water demands. Fog water shows particular promise for application in reforestation. Fog water irrigation can increase growth rates and survivability of saplings in reforestation efforts in regions with frequent fog events. Using fog collectors, denuded areas once dependent on natural fog drip can be restored, benefiting local hydrology and ecosystem recovery. Improvement in fog collector designs, materials, and models to increase collection efficiency, perhaps by inclusion of ideas from natural systems, will expand the regions where fog harvesting can be applied.     

An extended techno-economic analysis of the utilization of glycerol as an alternative feedstock for methanol production

Glycerol is a by-product of biodiesel production and may become an environmental problem. This paper investigates the utilization of glycerol as alternative feedstock for methanol production. A mathematical model of the methanol plant encompassing the steam reforming and methanol synthesis units is employed to generate data for an economic analysis involving two comparative cases: the conventional operation of the plant using only natural gas and the operation with partial substitution of the natural gas by glycerol. The results indicate that the glycerol injection can reduce the total natural gas consumption by about 11% for a given fixed methanol production. A breakeven analysis procedure is applied to determine the limit price of glycerol that makes this operation economically feasible. Based on a natural gas price of 10.13 US$/MMbtu, this analysis demonstrates that glycerol injection is feasible if its price is lower than 78.5 US$/t. Additionally, a sensitivity analysis indicates that a variation of 10% on the natural gas price causes a 26% variation on the glycerol breakeven point. The complete set of data indicates that it is possible to explore periods of glycerol low prices to reduce the operational costs of methanol plants that suffer from high natural gas prices.     

Enzymatic tissue digestion as an alternative sample preparation approach for quantitative analysis using liquid chromatography-tandem mass spectrometry

Compound extraction from biological tissue often presents a challenge for the bioanalytical chemist. Labor-intensive homogenization or sonication of whole or powdered tissue is performed before compounds can be extracted and analyzed. Enzymatic digestion is commonly used for tissue dissociation and cell harvesting and offers the advantages of unattended sample preparation, potential automation, and low cost. The feasibility of enzymatic digestion as an alternate tissue preparation technique was evaluated for bioanalysis of drugs in conjunction with LC/MS/MS. Two different enzymes (collagenase and proteinase K) that are known to degrade connective tissues to allow tissue dissolution were chosen for evaluation, employing well-known antidepressants desipramine and fluoxetine as test compounds in dog and rat brain tissue. Comparison between enzymatic digestion and conventional homogenization tissue preparation was performed, including investigation of matrix ionization suppression of both methods using a postcolumn infusion system. Results showed that enzymatic digestion has extraction efficiency comparable to homogenization. Matrix ionization suppression was not observed for either the test compounds evaluated or the sample extraction method. Test compound levels of incurred tissue samples prepared by enzymatic digestion were in good agreement with the values obtained by the conventional homogenization tissue preparation, indicating that enzymatic digestion is an appropriate tissue sample preparation method.     

UF as an alternative pretreatment step for producing drinking water

This article describes membrane research which focuses on exploring the use of open ultrafiltration as an alternative to conventional separation technologies used for producing drinking water. Four different water types, originating from three water sources, are investigated. Four open ultrafiltration membranes are used, of which three are of a hollow-fibre configuration while one is tubular. On the one hand it was found that permeate quality was always very good, compared with conventional techniques — no bacteria, suspended solids or turbidity were present. Moreover, the quality was independent of operational conditions or the membrane type. On the other hand, it was found that operational conditions strongly differ in terms of ‘raw’ water quality, or the membrane type used.     

Experimental study on HFC-161 mixture as an alternative refrigerant to R502

Ternary near-azeotropic mixture of HFC-161 as an alternative refrigerant to R502 is firstly presented in this paper. The physical characteristics of this new refrigerant are similar to those of R502. Its environment performance is friendly. It has an ODP of zero and a GWP smaller than those of R502, R404A and R507. Without any modification to system components, drop-in experimental tests are performed on a vapor compression refrigeration plant with a reciprocating compressor, which was originally designed to use R404A, a major substitute for R502. Experimental results under two different rated working conditions indicate that the pressure ratios of this new refrigerant are nearly equal to those of R404A. Under lower evaporative temperature, its COP is almost equal to that of R404A and its discharge temperature is slightly higher than that of R404A, while under higher evaporative temperature, its COP is greater than that of R404A and its discharge temperature is lower than that of the latter. This new refrigerant can achieve a high level of COP and can be considered as a promising retrofit refrigerant to R502.     

Sustainability considerations of biodiesel based on supply chain analysis

Developing clean and renewable energy resources ranks as one of the greatest challenges facing mankind in the medium to long term. The issues associated with developing non-fossil energy are intimately connected with economic development and prosperity, quality of life and global stability, and require smart strategies for sustainable development. This study presents a relative sustainability assessment of biodiesel, taking into account its full life cycle with the main goal of comparing alternative feedstocks, either currently used or promising for future use such as microalgae. A set of sustainability metrics relevant for biodiesel is identified using only the data available in the literature and taking into account all the three dimensions of sustainability: environmental, societal, and economic. Although this study does not attempt to identify which feedstock or process is the best, its procedural suggestions may be valuable to practitioners and policy makers seeking to identify the best alternatives. The conclusions, however, are limited by the availability and the quality of the data used in the analyses.     

PEDOT-PSSA as an alternative support for Pt electrodes in PEFCs

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT-PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H⁺-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT-PSSA composite also helps reducing Nafion content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT-PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT- PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT-PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm⁻² at a load current-density of 1800 mA cm⁻² with Nafion content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes.     

R404A在螺杆制冷机组中替代R22性能研究

在比较分析HFC非共沸混合制冷剂R404A(R125/R143a/R134a,44/52/4wt%)和R22物性特点的基础上,理论和试验研究了R404A在螺杆制冷机组中替代R22的可行性和适用性.研究结果表明,只要将原为R22设计的螺杆制冷机组稍加改动,直接加入R404A制冷剂,机组便完全能够正常运行,其各主要性能指标与R22较为接近.     

Ionic liquids as an attractive alternative solvent for thermal lens measurements

The use of ionic liquids (ILs) as a solvent for thermal lens measurements has been investigated. It was found that ILs provide a better medium for thermal lens measurements than water. Specifically, not only the ILs offer at least 20 times higher sensitivity than water but that the enhancement can be appropriately adjusted by changing either the cation or the anion of the ILs. For example, the sensitivity in [BMIm]+[Tf2N]- is approximately 26 times higher than in water. It can be increased up to 31 times by changing the anion to [PF6]- (i.e., [BMIm]+[PF6]-) or to 35 times by changing the cation to [OMIm]+ (i.e., [OMIm]+[Tf2N]-). In fact, the sensitivity of thermal lens measurements in ILs is comparable to those in volatile organic solvents such as benzene, carbon tetrachloride, and hexane. However, the ILs are more desirable as they have virtually no vapor pressure. Furthermore, additional sensitivity enhancement (up to 42 times higher than that in water) can be achieved by simply adding surfactants into the ILs. Based on the thermal conductivity (k) and dn/dT values, calculated from the measured thermal time constant tc and thermal lens strength theta, it is evident that the observed sensitivity enhancement by the ILs is due to their relatively better thermooptical properties. More specifically, the enhancement is due not to the relatively modest lowering of the thermal conductivity but rather to the substantial increase in their dn/dT values. Because of the relationship between dn/dT and drho/dT, it is expected that ILs can serve as an attractive and superior solvent not only for thermal lens measurements but also for other photothermal and photoacoustic techniques as well. Also equally important is the fact that the thermal lens technique in particular and photothermal techniques, in general, can offer a unique means to determine themooptical and thermal physical properties of the ILs (e.g., thermal conductivity, thermal diffusivity, and phase transition temperatures). This type of data is currently lacking but is of extreme importance for implementing ILs as a solvent in various industrial applications.     

Emulsion/solvent evaporation as an alternative technique in pellet preparation

Paracetamol/Eudragit RS, paracetamol/ethylcellulose, and paracetamol/cellulose acetate pellets of different drug/polymer ratios (w/w) were prepared by the dissolution/solvent evaporation technique. These pellets were then characterized by particle size distribution analysis, ultraviolet (UV) spectroscopy, differential thermal analysis, and scanning electron microscopy (SEM). Hard gelatin capsules were filled with each particle size fraction of these pellets, and in vitro dissolution studies were performed to verify the capability of each series of pellets to control drug release. Pellets were spherical, presented a polynucleated microcapsule structure, and under certain experimental conditions, the yield of the preparation process reached very high values. The dissolution studies pointed out the slow paracetamol release from these pellets.     

Dynamic analysis in solid mechanics by an alternative boundary element procedure

A new procedure for eigenvalue and transient dynamic analyses in solid mechanics is presented here using a boundary integral approach. Contrary to previous work, it is shown in this paper that by applying a special class of co-ordinate functions one can obtain the mass matrix using boundary values. As a consequence, the free vibration case is reduced to an algebraic eigenvalue problem, while transient vibrations can be solved by using a direct time integration procedure.     

Effects of dimethyl or diethyl carbonate as an additive on volatility and flash point of an aviation fuel

Vapor pressures and flash points for several mixtures of an aviation fuel with dimethyl carbonate (DMC) or diethyl carbonate (DEC) have been measured, respectively, over the entire composition range. Correlation between the experimental vapor pressures and the equilibrium temperatures by the Antoine equation is performed for each mixture. The bubble-point lines of pressure versus composition at different temperatures and those of temperature versus composition at different pressures are then obtained from the Antoine correlations. It is found that DMC and DEC are the oxygenated hydrocarbon additives that can adjust effectively the volatility and flash point of the aviation fuel. The correlation of the flash points with the vapor pressure data for the pseudo-binary mixtures of the fuel and DMC or DEC gives satisfactory results.