移动式推土台的使用及效益分析

林业公路的养护,在没有装载机与其它养路机具配套的情况下,砂料的装车工艺只能靠木制的固定式推土台通过推土机来完成。本文就结合松岭林业局研制的移动式推土台在使用和效益上进行了分析。     

More than eating dirt: a review of avian geophagy‡

Geophagy, the ingestion of earth varying in particle size from stones to soils rich in clay, is a relatively widespread behaviour across avian taxa. We reviewed its occurrence in birds and its hypothesised adaptive functions in birds. Of the ～30 avian orders, 23 exhibit geophagy. However, it has only been documented in ～260 species (～2% of birds) and therefor is relatively uncommon. Ingestion of stones and other large particles (grit) is recorded in 54 extant families across the avian phylogeny and appears to be ancient in birds and has evolved several times. Clay ingestion is recorded in 14 phylogenetically scattered families and might have evolved repeatedly. Furthermore, at least nine families exhibit both clay and grit ingestion. Six hypothesised functions of avian geophagy involve digestion and nutrition. Ingested grit might provide (1) essential minerals, particularly sodium or calcium, but it appears to primarily (2) improve mechanical digestion of food in the gizzard, where ingested stones and sand particles are known as gastroliths. Consistent with this gastrolith hypothesis, ～86% of species ingesting grit consume “hard” food: seeds, leaves, insects or other animals. In contrast, ingested clay appears to be for sodium or other nutrient intake and/or protecting birds from ingested plant secondary compounds, by (3) protecting the digestive tract and (4) adsorbing these compounds. Consistent with this, ～88% of species ingesting clay eat fruit that is often rich in secondary compounds and low in sodium, and clay ingestion is associated with frugivory in a representative sample of genera of which many have been shown to source sodium. The other two hypotheses are buffering gastric pH (5) and acquiring antidiarrheal agents (6), but no documentation of this in birds was found. We suggest additional tests of these hypotheses and additional investigation of these proposed benefits of geophagy in birds.     

干喷钢砂的工艺研究

分析了影响干喷钢砂效果的因素,应用正交试验方法研究了干喷钢砂工艺参数对喷砂效果的影响。对于高硬度试件,通过测定涂层与基体的结合强度,验证了优化干喷钢砂预处理具有较好的实用性,同时可改善零件的疲劳强度。粗造度测试结果表明,采用该工艺处理的表面符ＧＢ１１３７３－８９的要求,可满足电喷涂的需要。     

Potential use of abrasive air-propelled agricultural residues for weed control

A potential new post-emergence physical weed control tactic is described. It entails plant abrasion and death upon assault from abrasive grits propelled by compressed air. Grit derived from granulated walnut shells was delivered by a sand blaster at 517 kPa at distances of 300–600 mm from seedlings of Chenopodium album in glasshouse pots. Control was influenced by size of plants at time of treatment. Seedlings at the cotyledon to 2-leaf stages of growth were mostly destroyed by a single split-second blast of grit of <1 s duration, but were unaltered by compressed air alone. Plants at the 4- to 6-leaf growth stages required up to 10 blasts of grit to be killed. These results indicate that small weed seedlings of susceptible species might be physically controlled by abrasion from air-propelled grit derived from suitable agricultural residues.     

干喷钢砂在电弧喷涂修复曲轴中的应用

表面粗化在电弧喷涂中具有重要作用,涂层质量很大程度上取决于表面粗化预处理的效果。应用正交试验法对干喷钢砂工艺参数对喷砂效果和结合强度的影响进行了试验研究,确定了优化的干喷钢砂电喷涂工艺规范。粗糙度测试结果表明,采用优化的工艺规范处理表面,粗化质量符合国家标准要求。发动机台架试验结果表明,优化干喷钢砂电喷涂工艺规范用于修复曲轴是可行的。     

接触轮式强力平面砂带磨削及其磨损试验研究

砂带磨损是影响加工精度、表面质量、加工效率和生产成本的重要因素之一。以往的研究只局限于普通砂带磨削的磨损，而强力砂带磨削磨损研究尚未见诸报导。本文对接触轮式强力平面砂带磨削的砂带磨损过程、砂带磨损形式、磨损机理及磨削参数对磨损的影响作了大量的实验研究。测定了此种磨削上的相对金属切除率、磨削法向力、磨削条件下砂带的金属去除机理和磨损机理，得出了一些重要结论。     

Dental microwear of sympatric rodent species sampled across habitats in southern Africa: Implications for environmental influence

Dental microwear textures have proven to be a valuable tool for reconstructing the diets of a wide assortment of fossil vertebrates. Nevertheless, some studies have recently questioned the efficacy of this approach, suggesting that aspects of habitat unrelated to food preference, especially environmental grit load, might have a confounding effect on microwear patterning that obscures the diet signal. Here we evaluate this hypothesis by examining microwear textures of 3 extant sympatric rodent species that vary in diet breadth and are found in a variety of habitat types: Mastomys coucha, Micaelamys namaquensis and Rhabdomys pumilio. We sample each of these species from 3 distinct environmental settings in southern Africa that differ in rainfall and vegetative cover: Nama‐Karoo shrublands (semi‐desert) and Dry Highveld grasslands in the Free State Province of South Africa, and Afromontane (wet) grasslands in the highlands of Lesotho. While differences between habitat types are evident for some of the species, inconsistency in the pattern suggests that the microwear signal is driven by variation in foods eaten rather than grit‐level per se. It is clear that, at least for species and habitats sampled in the current study, environmental grit load does not swamp diet‐related microwear signatures.     

Effects of Dietary Fiber and Grit on Performance,Gastrointestinal Tract Development,Lipometabolism, and Grit Retention of Goslings

This study investigated effects of dietary ifbre and grit on growth performance, gastrointestinal tract （GIT） development, serum indexes and grit retention of Sichuan white goslings in China. The experiment was a 3×2 factorial design consisting of dietary crude ifbre （CF） at 2.0, 4.0 and 6.0%levels by adding grass meal and with or without grit supplementation. A total of 720 1-d-old male goslings were randomly allocated into 36 pens of 20 goslings/pen （n=6 pens/treatment）. At 21 d of age, GIT, blood samples and grit in gizzards were collected. Body weight （BW）, empty BW （without GIT）, average daily gain （ADG） and average daily feed intake （ADFI） were affected by CF levels and the medium （4.0%） had the highest value. Adding grit improved BW, empty BW, ADG and ADFI. CF affected relative weight or length of proventriculus, gizzard and duodenum. Increasing CF levels decreased jejunum villus height and affected caecal crypt depth and villus height to crypt depth ratio. Higher CF levels decreased serum triglyceride. Adding grit increased relative weight of abdominal fat. Grit addition increased grit weight in gizzard and the ratio of grit in 0.45-1 and 1-2 mm while decreasing the ratio of grit〈0.45 and 2-3 mm. In conclusion, moderate CF level and grit addition increased performance of goslings without interaction. Dietary CF levels affected the development of upper GIT and serum triglyceride. Grit needed by goslings should be less than 2 mm. Goslings’ gizzard would accumulate grit from feed when other grit could not be acquired.     

高速公路桥涵台背回填方法的探讨

介绍了京沪高速公路化临段工程桥涵台背回填砂砾料的质量标准和砂砾料最大干密度试验方法，对试验中的一些问题提出了处理意见；分析了砂砾级配、粗细程度、含泥量对回填质量的影响；讨论了几种常用压实度检测方法对砂砾料压实度检测的可行性。     

无琼脂培养诱导非洲菊无菌生根研究

培养成本高,移栽成活率较低一直是植物组织培养中的两大难题。为降低组织培养中琼脂培养的成本,提高移栽成活率,需寻求一种廉价而操作简便的基质取代琼脂。以非洲菊的无菌芽为试材,分别接种在以砂砾、海绵、琼脂为支撑材料的培养基中诱导生根,并统计移栽成活率。结果显示,以砂砾为支撑基质诱导非洲菊生根快,且生根率高(分别为96.55%、89.47%、94.11%),幼苗长势最好,移栽成活率最高(分别为97.63%、96.25%、78.18%)。同时,营养液体积及支撑材料处理等细节技术对生根也有影响。说明砂砾与海绵等无机基质可以取代琼脂作组织培养的支撑物,该技术将具有较强的推广价值。