Twin roll casting and melt conditioned twin-roll casting of magnesium alloys

Recently, BCAST at Brunel University has developed a MCAST (melt conditioning by advanced shear technology) process for conditioning liquid metal at temperature either above or bellow the alloy liquidus using a high shear twin-screw mechanism. The MCAST process has now been combined with the twin roll casting (TRC) process to form an innovative technology, namely, the melt conditioned twin roll casting (MC-TRC) process for casting Al-alloy and Mg-alloy strips. During the MC-TRC process, liquid alloy with a specified temperature is continuously fed into the MCAST machine. By intensive shearing under the high shear rate and high intensity of turbulence, the liquid is transformed into conditioned melt with uniform temperature and composition throughout the whole volume. The conditioned melt is then fed continuously into the twin-roll caster for strip production. The experimental results show that the AZ91D MC-TRC strips with different thicknesses have fine and uniform microstructure. The strip consists of equiaxed grains with a mean size of 60-70μm. The strip displays extremely uniform grain size and composition throughout the whole cross-section. Investigation also shows that both TRC and MC-TRC processes with reduced deformation are effective to reduce the formation of defects, particularly the formation of the central line segregations

Can green LED light do a magical thing to plants?

Red and blue light are the most important in driving photosynthesis to produce adequate yield. It is also believed that green light may contribute to the adaptation to growth. However, the effects of the green light which may trigger specific and necessary responses in plant growth have been underestimated in the past. In this study, lettuce (Lactuca sativa L.) was exposed to different continuous light (CL) conditions for 48 h by combination of red and blue light emitting diodes (LEDs) supplied with/without green LEDs in an environmental controlled growth chamber. Green light supplementation enhanced photosynthetic capacity by increasing net photosynthetic rate (P n), maximal photochemical efficiency (Fv/Fm), electron transport for carbon fixation (JSPII) and chlorophyll content, which led to increases of plant fresh and dry weight under CL treatment. Green light decreased malondialdehyde and H2O2 accumulation by increasing superoxide dismutase (SOD) enzyme, catalase (CAT) enzyme and ascorbate peroxidase (APX) activities after 24 h CL. Supplementary green light was also shown to lead to a significant increase in the expression of the photosynthetic genes Lhcb and psbA from 6 to 12 h and retained higher level compared with other light conditions between 12 and 24 h. The results indicate that the effects of green light on the lettuce plant growth via promoting psbA and Lhcb expression to maintain higher photosynthetic capacity and green light could alleviate the negative effects caused by CL

Single-Shot Refinement Neural Network for Object Detection

For object detection, the two-stage approach (e.g., Faster R-CNN) has been achieving the highest accuracy, whereas the one-stage approach (e.g., SSD) has the advantage of high efficiency. To inherit the merits of both while overcoming their disadvantages, in this paper, we propose a novel single-shot based detector, called RefineDet, that achieves better accuracy than two-stage methods and maintains comparable efficiency of one-stage methods. RefineDet consists of two inter-connected modules, namely, the anchor refinement module and the object detection module. Specifically, the former aims to (1) filter out negative anchors to reduce search space for the classifier, and (2) coarsely adjust the locations and sizes of anchors to provide better initialization for the subsequent regressor. The latter module takes the refined anchors as the input from the former to further improve the regression and predict multi-class label. Meanwhile, we design a transfer connection block to transfer the features in the anchor refinement module to predict locations, sizes and class labels of objects in the object detection module. The multi-task loss function enables us to train the whole network in an end-to-end way. Extensive experiments on PASCAL VOC 2007, PASCAL VOC 2012, and MS COCO demonstrate that RefineDet achieves state-of-the-art detection accuracy with high efficiency. Code is available at https://github.com/sfzhang15/RefineDetComment: 14 pages, 7 figures, 7 table

Continuous light-emitting Diode (LED) lighting for improving food quality

Lighting-emitting diodes (LEDs) have shown great potential for plant growth and development, with higher luminous efficiency and positive impact compared with other artificial lighting. The combined effects of red/blue or/and green, and white LED light on plant growth and physiology, including chlorophyll fluorescence, nitrate content and phytochemical concentration before harvest, were investigated. The results showed that continuous light (CL) exposure at pre-harvest can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants, and the former is dependent on the spectral composition and continuous light duration. Lettuce plants grown under continuous combined red and blue (with or without green) LED light with a photosynthetic photon flux density (PPFD) at 200 μ mol m-2-s-1 exhibited a remarkable decrease of nitrate contents at 24 h compared to other light treatments. In addition, red and blue light (R:B=4:1) was more effective in facilitating lettuce growth than white LED light at the same PPFD. Moreover, continuous LED light for 24 h significantly enhanced the free-radical scavenging activity and increased phenolic compound concentrations. In this study, we suggest that a period of continuous LED (R/B) with green (G) light exposure is needed in order to decrease nitrate concentrations and enhance lettuce quality. 24 h appears to be the best, but this period should not exceed 48 h. It appears that continuous light could enhance the activity of nitrate reductase leading to a low level of nitrate content in the leaf. However, the reduction of nitrate is considered to be associated with the circadian clock and the light-signaling pathway as well

Adversarial Sparse-View CBCT Artifact Reduction

We present an effective post-processing method to reduce the artifacts from sparsely reconstructed cone-beam CT (CBCT) images. The proposed method is based on the state-of-the-art, image-to-image generative models with a perceptual loss as regulation. Unlike the traditional CT artifact-reduction approaches, our method is trained in an adversarial fashion that yields more perceptually realistic outputs while preserving the anatomical structures. To address the streak artifacts that are inherently local and appear across various scales, we further propose a novel discriminator architecture based on feature pyramid networks and a differentially modulated focus map to induce the adversarial training. Our experimental results show that the proposed method can greatly correct the cone-beam artifacts from clinical CBCT images reconstructed using 1/3 projections, and outperforms strong baseline methods both quantitatively and qualitatively

Effects of continuous LED lighting on reducing nitrate content and enhancing edible quality of lettuce during pre-harvest stage

Lettuce easily accumulates higher nitrate content during production, especially in hydroponic system, and higher ni trate content poses a threat to human health. Light condition (light quality, intensity and duration) significantly affects nitrate content in plants. Lighting -emitting diodes (LEDs) have showed the great potential for plant growth and development with the higher luminous efficiency and positive impact compared with other artificial light. The effects of combination of red (R)/ blue (B) or/and green (G), and white (W) LED lights on the plant growth, plant physiological 8th 45 International Symposium on Light in Horticulture changes, including chlorophyll fluorescence, nitrate contents and phytochemical concentration before harvest were investigated. The results showed that Pre-harvest continuous light exposure can effectively reduce nitrate accumulation and increase phytochemical concentrations in lettuce plants, and the reduction in nitrate content is dependent on the spectral composition and light intensity of the applied light sources and continuous light duration. Lettuce plants grown under the continuous combined red, green and blue LED light (RGB) with a PPFD at 200 μmol·m-2·s -(RGB-200) and RB-200 treatments exhibited a remarkable decrease of nitrate contents at 24 h compared to other LED light treatments. Moreover, continuous LED light at 24 h significantly enhanced the DPPH free-radical scavenging activity and increase phenolic compound concentrations. In this study, we suggest that a period of continuous LED light (RGB-200 or RB -200) exposure is needed in order to decrease nitrate concentrations and enhance lettuce quality. The period of 24 h continuous LED light exposure appears to be the best, and this period should not exceed 48 h

Flux measurements in the near surface layer over a non-uniform crop surface in China

International audienceEddy covariance measurements were conducted on fluxes of moisture, heat and CO2 in a near-surface layer over a non-uniform crop surface in an agricultural ecosystem in the central plain of China from 10 June to 20 July 2002. During this period, the mean canopy height was about 0.50 m. The study site consisted of grass (10% of area), bean (15%), corn (15%) and rice (60%). Based on footprint analysis, we expected >90% of the measured flux (at a height of 4 m above ground surface) to occur within the nearest 600 m of upwind area. We examined interdiurnal variations in the components of the surface energy balance and in CO2 flux. Results show that the pattern of energy partition had no obvious variation during the season. Daytime absorption of CO2 flux by the crop canopy suddenly increased after thunderstorm events. We examined the energy budget closure and found it to be around 0.85. We compared energy partitioning for all rain-free days, and found energy imbalance was more significant for the 1~3 days after rainy events and energy components almost achieve balance for the other rain-free days. It indicated that the cold or warm rainwater infiltrating into soil made problems