Sources and nature of secondary school teachers’ education in computer-related ergonomics

Teachers’ knowledge of computer-related ergonomics in education will have an effect on the learning process and the work practices of their students. However little is known about teacher education in this area. The study aimed to investigate the sources and nature of secondary school teachers’ education about computer-related ergonomics. It also investigated the use of computers by secondary school children. The study included all secondary schools in the Republic of Ireland. The findings suggest that computers are widely available and are used frequently by students and teachers. However, there is evidence that teachers are not receiving information on computer-related ergonomics. Teachers were generally dissatisfied with this and would welcome information on the subject. The study discusses the implications of the findings and makes recommendations to meet the needs of the teachers.     

A predictive model of the effects of genotypic,pre‐ and postharvest stages on barley β‐glucan levels

BACKGROUND: β‐Glucan is a bioactive component of cereal grains that has many potential uses and health‐promoting benefits. Recent research has focused on improving the nutritional value of food by increasing human exposure to β‐glucan. This study looks at the development of a farm‐level baseline model (including scenario analysis) to evaluate the impact of pre‐ and postharvest stages (including genotypic factors, environmental conditions, agronomic factors and storage) on β‐glucan levels in barley. Monte Carlo simulation techniques were employed to model various stages in pre‐ and postharvest processes and to simulate the factors influencing the level of β‐glucan content in both hulled barley (H_B) and hull‐less barley (H_LB) genotypes. RESULTS: The baseline model found that the mean simulated level of β‐glucan was 40.99 and 56.77 g kg^?1 for H_B and H_LB genotypes respectively. A sensitivity analysis highlighted that genotype was the most important parameter in determining the final β‐glucan content (correlation coefficients of 0.66 and 0.78 for H_B and H_LB respectively), more so than any of the agronomic factors analysed. The scenario analysis highlighted the importance of harvest date (scenario 2) and storage conditions (scenario 3), with a potential 32.6 and 32.7% decrease in β‐glucan (compared with the baseline model) if harvesting is carried out early during physiological maturity (i.e. at growth stage 92) and a potential 20.1 and 19.5% increase in β‐glucan for H_B and H_LB respectively if storage time is minimised. CONCLUSION: This study predicted the influence of genotypic, pre‐ and postharvest operations on β‐glucan content and thus allows strategies to be identified to influence β‐glucan content in barley products. Copyright © 2008 Society of Chemical Industry     

基于异构集成技术的相控阵T/R组件微系统

基于硅基微电子机械系统(MEMS)工艺和三维异构集成技术,研制了一款硅基X波段2×2相控阵T/R组件.该组件采用收发一体多功能芯片方案,将所有器件封装于两层硅基中.其中上层硅基集成了低噪声放大器、功率放大器、开关、电源调制驱动器和PMOSFET等芯片,下层硅基集成了多功能芯片、串/并转换芯片以及逻辑运算芯片;两层硅基封装之间通过植球进行堆叠.最终样品尺寸仅为20 mm×20 mm×3 mm.实测结果显示,在8～ 12 GHz内,该T/R组件饱和输出功率约为29 dBm,接收增益约为21 dB,接收噪声系数小于3 dB,在具备优良射频性能的同时实现了组件的小型化.     

A catalyst-free and facile route to periodically ordered and c-axis aligned ZnO nanorod arrays on diverse substrates

In this work we present a method for the deposition of periodically ordered, c-axis aligned ZnO nanorod arrays. By using chemical bath deposited films in conjunction with silica templating through nanosphere monolayers, masks suitable for high temperature deposition are created. A vapour phase transport technique is then used to deposit ordered arrays, quickly and inexpensively in a manner ideal for low cost, scalable and reproducible growth on a diverse range of substrates.     

Enhancing the Spectrum Sensing Performance of Cluster-Based Cooperative Cognitive Radio Networks via Sequential Multiple Reporting Channels

In cluster-based cooperative cognitive radio networks (CCRNs), spectrum sensing and decision making processes to determine whether the primary user (PU) signal is present or absent in the network are very important and vital issues to the utilisation of the idle spectrum. The reporting time delay is a very important matter to make quick and effective global decisions for the fusion center (FC) in a cluster-based CCRNs. In this paper, we propose the concept of multiple reporting channels (MRC) for cluster-based CCRNs to better utilize the reporting time slot by extending the sensing time of secondary users (SUs). A multiple reporting channels concept is proposed based on frequency division multiple access to enhance the spectrum sensing performance and reduce the reporting time delay of all cluster heads (CHs). In this approach, we assign an individual reporting channel to each cluster for reporting purposes. All the SUs in each cluster sequentially pass their sensing results to the corresponding cluster head (CH) via the assigned single reporting channel, which extends the sensing time duration of SUs. Each CH uses the dedicated reporting channel to forward the cluster decision to the FC that makes a final decision by using the “K-out-of-N” rule to identify the presence of the PU signal. This approach significantly enhances the sensing time for all SUs than the non-sequential as well as minimize the reporting time delay of all CHs than sequential single channel reporting approach. These two features of our proposed approach increase the decision accuracy of the FC more than the conventional approach. Simulation results prove that our proposed approach significantly enhances the sensing accuracy and mitigate the reporting time delay of CH compared to the conventional approach.

     

The effect of remodelling and contractility of the actin cytoskeleton on the shear resistance of single cells: a computational and experimental investigation

The biomechanisms that govern the response of chondrocytes to mechanical stimuli are poorly understood. In this study, a series of in vitro tests are performed, in which single chondrocytes are subjected to shear deformation by a horizontally moving probe. Dramatically different probe force–indentation curves are obtained for untreated cells and for cells in which the actin cytoskeleton has been disrupted. Untreated cells exhibit a rapid increase in force upon probe contact followed by yielding behaviour. Cells in which the contractile actin cytoskeleton was removed exhibit a linear force–indentation response. In order to investigate the mechanisms underlying this behaviour, a three-dimensional active modelling framework incorporating stress fibre (SF) remodelling and contractility is used to simulate the in vitro tests. Simulations reveal that the characteristic force–indentation curve observed for untreated chondrocytes occurs as a result of two factors: (i) yielding of SFs due to stretching of the cytoplasm near the probe and (ii) dissociation of SFs due to reduced cytoplasm tension at the front of the cell. In contrast, a passive hyperelastic model predicts a linear force–indentation curve similar to that observed for cells in which the actin cytoskeleton has been disrupted. This combined modelling–experimental study offers a novel insight into the role of the active contractility and remodelling of the actin cytoskeleton in the response of chondrocytes to mechanical loading.     

Gas-liquid mass transfer in two and three-phase upflows through a vertical tube

Oxygen absorption rates were measured to determine volumetric coefficients of gas-liquid mass transfer coefficients k_La in gas-liquid and gas-liquid-solid upward flows through a vertical tube. The liquid was deionized water or aqueous glycerol solution, and the solids were glass beads or polystyrene beads. The dependencies of k_La on gas velocity, liquid velocity, temperature, solid material, and solid concentration were examined. The experimental results were correlated with empirical equations. The mechanisms of the solid loading effect are discussed.     

Unsupervised learning with hierarchical feature selection for DDoS mitigation within the ISP domain

A new Mirai variant found recently was equipped with a dynamic update ability, which increases the level of difficulty for DDoS mitigation. Continuous development of 5G technology and an increasing number of Internet of Things (IoT) devices connected to the network pose serious threats to cyber security. Therefore, researchers have tried to develop better DDoS mitigation systems. However, the majority of the existing models provide centralized solutions either by deploying the system with additional servers at the host site, on the cloud, or at third party locations, which may cause latency. Since Internet service providers (ISP) are links between the internet and users, deploying the defense system within the ISP domain is the panacea for delivering an efficient solution. To cope with the dynamic nature of the new DDoS attacks, we utilized an unsupervised artificial neural network to develop a hierarchical two‐layered self‐organizing map equipped with a twofold feature selection for DDoS mitigation within the ISP domain.