调查能证实猜疑和揭示令人惊讶的问题

各地区的受访者都指出了工作量增大及缩短设计周期以将产品推向市场的问题. 我们EDN每年都要开展几项重大的调查.我们通过这些调查来对以后要报导的内容、以及如何向读者和网友提供信息等做出决策.每隔18个到24个月,就进行一次名为"工程师所关注的问题"的调查.该调查旨在了解读者所从事工作、工作压力、流行的可行技术、工程学科技能及信息资源和互连网使用等.整个调查的量十分大,但在这里我将展示几个选段给读者,在未来的栏目中也许会刊登更多选段.     

从以太中提取能量并为轻便系统供电的采集器 热、振动和射频源都具有为低功耗设备供电的潜力

世上没有免费的午餐,你的父母可能是这么教你的.当然,我们不可能从稀薄的空气中取得能量,是吗?但事实上,人体,工厂机器,各种型号的收音机,以及很多其它东西都在以热、振动或射频电波形式辐射能量.     

Preparation and investigation of sodium alginate nanocapsules by different microemulsification devices

Numerous techniques of preparation have been reported for the encapsulation of the core material, but the microemulsion technique is the most effective and commonly used for encapsulation. In this article, three microemulsification devices including ultrasonic stirrer, labo ratory reactor, and mechanical stirrer were used to produce the alginate nanocapsules containing peppermint oil. The effect of different parameters on surface morphology, mean particle size, and size distributions were investigated. The results indicated that the ultrasonic stirrer is the best device to make the nanocapsules containing essential oils prepared by microemulsion method, so that the size of nanocapsules prepared by ultrasonic stirrer was about 56 nm. Also, the results of GC‐MS, FTIR, and TGA show that quantities of the remaining compounds in nanocapsules prepared by ultrasonic stirrer are higher than other devices. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41904.     

Mechanical behavior of recycled reinforced polyamide railway fasteners

Modern railway tracks use short‐fiber glass reinforced polyamide to inject insulating and mechanically resistant fasteners to connect the rails to the sleepers. Some of this material is later withdrawn, due either to defective production or to breakage in service. The recovery of the material for its later re‐use would lead to a great saving, from both an environmental and an economic viewpoint. Mechanical recycling is a simple, economic process that only requires the crushing of the material and its subsequent molding, without the need for any chemical treatments. However, it has some drawbacks; as with any kind of recycling, there is a certain loss of material quality with some degradation of its properties. In this work, the physical and mechanical results for fasteners injected with recycled material are compared to others injected with pure material. The results show that the use of recycled fasteners is limited in‐service by working conditions that increase the thermoplastic material temperature above its critical glass transition temperature, T_g. POLYM. COMPOS., 31:1142–1149, 2010. © 2009 Society of Plastics Engineers     

Characterization of different promoters for designing a new expression vector in Saccharomyces cerevisiae

The widely used pESC vector series (Stratagene, La Jolla, CA, USA) with the bidirectional GAL1/GAL10 promoter provides the possibility of simultaneously expressing two different genes from a single vector in Saccharomyces cerevisiae. This system can be induced by galactose and is repressed by glucose. Since S. cerevisiae prefers glucose as a carbon source, and since its growth rate is higher in glucose than in galactose‐containing media, we compared and evaluated seven different promoters expressed during growth on glucose (pTEF1, pADH1, pTPI1, pHXT7, pTDH3, pPGK1 and pPYK1) with two strong galactose‐induced promoters (pGAL1 and pGAL10), using lacZ as a reporter gene and measuring LacZ activity in batch and continuous cultivation. TEF1 and PGK1 promoters showed the most constant activity pattern at different glucose concentrations. Based on these results, we designed and constructed two new expression vectors which contain the two constitutive promoters, TEF1 and PGK1, in opposite orientation to each other. These new vectors retain all the features from the pESC–URA plasmid except that gene expression is mediated by constitutive promoters. Copyright © 2010 John Wiley & Sons, Ltd.     

Evaluation of Models for Spinach Respiratory Metabolism Under Low Oxygen Atmospheres

Anaerobic respiration is a major problem that causes the deterioration of fresh produce packaged under low O₂ atmospheres. The problem becomes more severe and causes high losses in the packages handling at ambient conditions, especially in developing countries. In designing modified atmosphere packaging, the risk of anaerobic development greatly depends upon the accuracy of respiration rate prediction; therefore, the respiration rate model for a particular produce has to be identified. In this study, different atmospheric storage conditions in a closed system were realized to examine the adaptability of respiration rate models for spinach storage under low O₂ at an expected ambient temperature of 25 °C. Six models were applied and it was found that, for aerobic conditions, the respiration rate could be described with a constant respiratory quotient by three models, viz., (a) Michaelis–Menten model without inhibition, (b) Michaelis–Menten model with uncompetitive inhibition, and (c) Langmuir adsorption model, whereas three other models, viz. (d) Michaelis–Menten model with competitive inhibition, (e) Michaelis–Menten model with noncompetitive inhibition, and (f) Michaelis–Menten with mixed inhibition could not be fitted. Among the three successful models, the Michaelis–Menten with uncompetitive inhibition was found to be the most suitable model for practical applications in developing countries where cold-chain systems are lacking. This model can be applied for the prediction of gas composition and optimize the packages, particularly to ensure the aerobic respiration.     

Determination and evaluation of acceptable force limits in single-digit tasks

Acceptable limits derived from psychophysical methodologies have been proposed, measured, and employed in a range of applications. There is little existing work, however, on such limits for single-digit exertions and relatively limited evidence on several fundamental issues related to data collection and processing of a sequence of self-regulated exertion levels. An experimental study was conducted using 14 male and 10 female participants (age range 18-31 years) from whom maximal voluntary exertions and maximal acceptable limits (MALs) were obtained using the index finger and thumb. Moderate to high levels of consistency were found for both measures between sessions separated by one day. Single MAL values, determined from a time series of exertions, were equivalent across three divergent processing methods and between values obtained from 5- and 25-min samples. A critical interpretation of these and earlier results supports continued use of acceptable limits but also suggests that they should be used with some caution and not equated with safe limits. This research can be applied toward future development of exertion limits based on perceived acceptability.     

Evaluation of circumferential pressure as an intervention to mitigate postural instability induced by localized muscle fatigue at the ankle

Pressure application via taping reportedly improves proprioception, and localized muscle fatigue (LMF) increases postural sway, which may be due to a loss of position sense acuity (PSA). This exploratory study investigated the effects of circumferential pressure (CP) and induced ankle LMF on sway. Fourteen young participants performed fatiguing sub-maximal isotonic plantarflexion exercises. Ankle PSA was determined, and used to categorize participants (i.e. high and low groups). Postural sway during quiet standing was assessed using a force platform, both pre- and post-LMF. CP was applied unilaterally to the dominant leg above the ankle joint. Both CP and LMF resulted in greater sway in the low PSA group. CP did not mitigate LMF effects on sway in the low PSA group, but reduced sway among the high PSA group. Reduced PSA may thus indicate less reliance on somatosensation for balance maintenance.

Relevance to industry

Potential benefits of circumferential pressure were indicated. Specifically, CP at the ankle led to improved postural control in certain individuals, which suggests that pressure application might thereby improve balance maintenance and help reduce occupational fall incidents. Results might help to design occupational interventions (specifically CP or taping) differently for individuals with low vs. high PSA.     

Fatigue during prolonged intermittent overhead work: reliability of measures and effects of working height

Shoulder pain is prevalent among industrial workers and existing evidence supports that overhead work is an important specific risk factor. Existing guidelines are limited, with overhead work typically recommended to be avoided, and research on overhead work has been mixed in terms of the effects of increasing arm reach. A laboratory-based simulation of overhead work was conducted, at three working heights, in order to facilitate improved guidelines and to identify potential non-linear effects of overhead work height. Several indicators of shoulder fatigue served as outcome measures and a preliminary study was performed to assess the reliability of several of these measures. Fatigue measures based on electromyography (EMG) generally had low reliability, whereas excellent reliability was exhibited for ratings of perceived discomfort (RPD). Consistent with this, no effects of overhead work height were found on EMG-based measures, yet clear non-linear effects were found on RPD and task performance. The source of the effects of work height appeared to be related to a combination of muscle activation levels and demands on precision/control at the highest location. These results support the utility of subjective measures for relatively low-level intermittent exertions and demonstrate increasingly detrimental fatigue and performance effects at extremes in reach during overhead work.     

Estimation of forces exerted by the fingers using standardised surface electromyography from the forearm

Determination and integration of human force capabilities and requirements is an essential component of ergonomic evaluation. With regard to hand-intensive tasks, direct force measurements can be cumbersome and intrusive. Here, the use of surface electromyography (EMG) was evaluated. EMG was obtained from three standardised electrode sites on the forearms of 30 individuals. Linear regression models were generated to estimate finger force levels from normalised electromyographic measures, while forces were generated in several finger couplings. The results suggest that standardised procedures for obtaining electromyographic data and simple linear models can be used to accurately estimate finger forces during a variety of finger exertions in fixed postures, although the level of accuracy depends on the type of model. Such models begin to overcome the limitations of direct finger strength measurements of individuals.