食品双螺杆挤出机内物料停留时间及其分布研究

应用流体分析软件对熔体在食品双螺杆挤出机中的三维等温流场进行了模拟计算，给出了粒子的运动轨迹，在此基础上作出了物料在挤出机内的停留时间分布曲线。这种模拟方法与传统的实验方法相比有着极大的优越性，为食品双螺杆挤出机挤出机理的研究提供了一个新思路，并可将该方法推广到与之相近的流体分析中。     

Tropical Tree Growth and Longevity: Validation of Growth Simulation,a Bootstrapping Model

ABSTRACT

Growth Simulation, an analytical modeling technique, has been increasingly used in ecological studies and practical forestry applications where dendrochronology is not applicable. The technique uses randomly sampled diameter increments from tagged trees over a known time interval to assemble a statistical sample of lifetime growth trajectories. We carried out a validation of Growth Simulation using a temperate species in order to compare indirect model outputs with direct tree ring analysis. Rings were measured on sample disks cut from 55 pine branches ranging in age from 8–36 years. Assessments included lifetime growth rates, growth rate with respect to diameter and age, periodic annual increment (PAI), cross-referencing of rings by date, and autocorrelation of growth over successive periods. Tree ring analysis and Growth Simulation showed close correspondence for all parameters tested (maximum, median, and minimum growth rates; longevity estimates). Growth Simulation is found to be a robust and informative technique for studies of tropical tree growth, and is especially useful where analysis of tree rings is not feasible or when bootstrapping analysis of ring data is of interest.     

Using ecological trajectories to track long-term taxonomic and functional changes in benthic shallow soft-bottom communities (Bay of Saint-Brieuc,English Channel)

1. Taxonomic and functional trajectories of benthic assemblages were studied in shallow soft-bottom sediments in the bay of Saint-Brieuc (Western English Channel). Changes were assessed at different spatial and temporal scales using a macrobenthic dataset based on 38 stations sampled in 1987 and 2019, coupled with data from one station sampled annually between 2005 and 2019 as part of the European Water Framework Directive monitoring programme.
2. Taxonomic trajectories indicated 1) changes in the structure and distribution of benthic assemblages, 2) an homogenization of the assemblages, and 3) significant functional shifts.
3. Fishing activities and nutrient enrichment are probably strong drivers of the observed changes, as suggested by the higher mortality rate of fragile, flexible, tubiculous and burrowing species, and the increase in the abundance of opportunistic species in the assemblages. Certain populations of macroinvertebrates seem jointly controlled by climate change and by the aforementioned local factors of disturbance.
4. The Community Trajectory Analysis framework appears as a new and interesting method to track ecological changes in marine ecosystems by measuring change with respect to a baseline state, to help define ecological recovery (station returning to the initial ecological state) and departure (station presenting increased changes over time), and to analyse trajectory similarity.
5. According to the degradation of habitat over time, we identify the need for the implementation of knowledge-based conservation strategies, especially within Natura 2000 sites.

     

渔用浮标定位监视系统

介绍了几种常用的渔用浮标定位监视系统的基本组成、工作原理及各自的特点。着重对GPS渔用浮标定位监视系统的模式及各组成部分的功能和设计的关键技术进行了讨论。采取适当方法解决关键技术后,使GPS渔用浮标定位系统具有较强的抗干扰能力和信息自动交换能力,特别适合在海洋中容易漂移的渔具、航行器等设备中作位置监视、搜寻之用。     

Measurement of the Motion of Fertilizer Particles Leaving a Centrifugal Spreader Using a Fast Imaging System

Although mechanically simple, centrifugal spreaders used for mineral fertilization involve complex physics that cannot be fully characterized at the present time. We are developing sensors to evaluate the spatial distribution of the fertilizer on the ground based on the measurement of initial flight conditions of fertilizer granules after their ejection by the spreading disk. The techniques developed are based on the analysis of images of the area around the disk showing the granule ejection. A high resolution – low cost imaging system for the analysis of high speed particle projection developed for this specific purpose is presented in this paper. The system, based on a camera and a sequence of flashes, is used to characterize the centrifugal spreading of fertilizer particles ejected at speeds of approximately 30ms^–1. It automatically computes the direction of ejection and velocity of each granule observed in the image. Multi-exposure images collected with the camera installed perpendicular to the output flow of granules are analyzed to estimate the trajectories of the fertilizer granules, using different motion estimation methods.     

一种新型振荡水柱式波浪能发电装置的设计

随着全球能源危机的加深,寻找替代传统能源的新能源成为能源发展的必由之路,针对此问题,设计了一种利用海洋波浪能发电的新型振荡水柱式发电装置。文章介绍了装置的基本组成及其结构设计,并对其工作原理和工作过程进行说明。结合海浪理论和计算原理、波浪发电系统的水动力匹配准则、波浪能转换效率理论、空气动力学等理论,分析和计算装置的能量及其转化效率。设装置在线性波浪的作用下,波浪周期为4 s,波浪高度为0.5 m,浮子边长为0.3 m,输风管道直径为0.05 m,通过理论计算,装置的整体理论效率为0.364,相比常见的波浪能发电装置,本装置具有更高的发电效率。     

一种新型振荡浮子式海洋波浪能发电装置的设计

针对目前出现的全球能源短缺危机,设计并研制了一种新型的运用海洋波浪能进行发电的振荡浮子式波浪能发电装置。简要介绍该装置的基本组成和确定转换装置的方案,完成转换装置的结构设计,并对装置的工作过程进行了说明。结合海浪理论与计算原理、海洋波浪能转换以及机械设计等知识并运用MATLAB软件编程计算装置的整机理论效率。假设装置在规则线性波浪的作用下,通过理论计算,该装置在波浪周期为5 s,波浪高度为1.5 m,浮子直径为0.2 m,长度为0.3 m的条件下,整机理论效率可达0.393。该装置具有很好的发电效率,并且装置的结构可靠性高,具有广阔的发展前景。     

Abandonment of traditional terraced landscape: A change detection approach (a case study in Costa Viola,Calabria, Italy)

This paper presents the results of a change‐detection study of the historical agricultural terraced landscape in “Costa Viola” (Calabria, South Italy). During the last century, because of the loss of economic competitiveness, it has undergone progressive abandonment, followed by landscape degradation. Taking into consideration the very steep slopes of Costa Viola and the need to analyse with high precision the historical evolution of the terraced landscape, research methods were implemented coupling advanced geomatic techniques with in situ detailed surveys. Based on historical aerial photographs, orthophotos, and numeric cartography, we analysed the land use/land cover change in the period 1955–2014 using photogrammetric and geoprocessing techniques, focusing particularly on trajectories in agricultural terraces. Area covered by active terraces decreased dramatically between 1955 and 2014, from 813.25 to 118.79 ha (−85.4%). The implemented spatial database was built in a free open‐source software taking into consideration spatial accuracies and completeness. Spatial comparison among land use/land cover maps was carried out using a postclassification comparison technique that can provide complete cross‐tabulation matrices. These data were compared with socio‐economic statistics concerning demography and trends of farms with vineyards. The evolutionary dynamics of the active agricultural terraces were also analysed trough the definition of 6 types of spatio‐temporal patterns recognised in the analysed period. These methods allowed to highlight the ongoing dynamics of abandonment of agricultural terraces in relation to their main causes and effects. Although tailored for the specific case study, they can be applied to many other terraced agricultural landscapes presenting similar characteristics and problems.     

Regionalisation of the muscle fascicle architecture in the equine longissimus dorsi muscle

REASON FOR PERFORMING STUDY: The longissimus dorsi is the largest muscle in the equine back and plays an important role in locomotor ability and performance in the horse. In vivo studies suggest that the mechanical function varies between different muscle segments, in part determined by anatomy. It is possible therefore that variations in function reflect variations in the anatomy of the longissimus dorsi along its length. OBJECTIVES: To identify if there are regional variations in muscle architecture of the longissimus dorsi. METHODS: Computed tomography scans were obtained from 8 cadaver backs to identify the cross-sectional area and volume of the muscle. The 3D orientations of the muscle fascicles were quantified in situ by their direction cosines using a magnetic digitisation system. RESULTS: Mean +/- s.e. volume of the muscle was 2.34 +/- 0.18 l for each side and mean length of the vertebral column from T4 to L6 dorsal spinous processes was 56.57 +/- 2.0 cm. There were significant differences in the cross-sectional area and the moment arm lengths between muscle segments (P<0.05). In the lumbar region, the mediolateral moment arms were 2-3 times greater than the dorsoventral moment arms. There were significant variations in the direction cosines (n = 7129) between muscle segments and between different regions within each segment (P<0.05). POTENTIAL RELEVANCE: These observations indicate that the muscle fascicle architecture predisposes the longissimus dorsi to different functions both along its length and between different regions within each segment. Detailed 3D anatomical measures of the structure with in vivo measures of function (back motion and muscle activity) will be investigated in further studies.     

渔用声纳电子示位标防盗技术研究

针对我国金枪鱼捕捞渔船上的无线电示位标装备现状,特别是为了防止盗取设备强占渔场的现象发生,对带有预警防盗功能的声纳示位标技术展开研究与试验,系统将渔用声纳与卫星电子浮标整体集成,利用水声数据采集技术与卫星数据通信技术,通过水下拾音器采集柴油机噪声的音频信息,该系统集成了卫星定位、声纳探测、无线电与卫星通讯,并开发出了嵌入式防盗设备,系统实现了示位标常规功能的同时增加了有效的预警防盗功能。可以提高我国金枪鱼鱼群探测信息化水平并保证设备的安全性。初步试验结果显示试验选用的渔民标准配备的挂机螺旋桨启动时的频率值稳定在8.5 kHz左右,且空蚀效应明显,在海洋噪声普遍高于10.3 kHz的环境下,嵌入式防盗系统在50~100 m范围内可准确实现设备的预警防盗,且抗干扰能力强,相比于其它防盗方式更为实时有效。