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空气占据空间实验教学设计
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作者 薛烈龙 《中小学实验与装备》 1995年第1期40-40,共1页
空气占据空间实验教学设计江陵县教研室薛烈龙(434100)实验目的使学生知道空气的存在,认识空气是占据空间的实实在在的物体。培养学生使用实验手段认识物体的能力。实验器材水槽一个,气球一个,去底的透明塑料饮料瓶一个,水... 空气占据空间实验教学设计江陵县教研室薛烈龙(434100)实验目的使学生知道空气的存在,认识空气是占据空间的实实在在的物体。培养学生使用实验手段认识物体的能力。实验器材水槽一个,气球一个,去底的透明塑料饮料瓶一个,水。实验步骤及教学过程1.先将水槽装... 展开更多
关键词 空间实验 教学设计 饮料瓶 气球 压入水 江陵县 教学过程 认识物体 实验手段 实验器材
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矿泉水瓶在小学自然实验教学中的两则应用
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作者 姚炳会 《教学仪器与实验》 2002年第X1期24-24,共1页
关键词 实验教学 小学自然 乒乓球 矿泉水瓶 水面 河北青县 力实验 瓶盖 出水槽 压入水
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Input characteristics and risk analysis of ballast water from offshore entry ships in China 被引量:2
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作者 DU Huan ZHANG Xiao-fang +2 位作者 ZHANG Zhi-tao LIU Kai-ying LI Ri-hong 《Marine Science Bulletin》 CAS 2017年第2期20-37,共18页
Large quantities of ballast water discharge from ocean going ships in sea ports of China is one of the important factorswhich cause the spread of aquatic nonindigenous harmful species isolated geographically by waters... Large quantities of ballast water discharge from ocean going ships in sea ports of China is one of the important factorswhich cause the spread of aquatic nonindigenous harmful species isolated geographically by waters,the deteriorating environment of the near-shore water area and the frequent outbreaks of red tides.In this paper,the total amount of the ballast water input estimation model for entry ships in Chinese ports was established.The information of foreign trade shipping and the import and export goods released publicly by the State Department of Transportation and the State General Administration of Customs were investigated.And then,the input features and its ecological environment risk of ballast water in China's offshore entry ships from2007to2012were analyzed based on the established total input amounts of ballast water from entry ships to Chinese sea ports together with the ballast water input ratio of the five major port-groups in China.The results show that:the total ballast water input amounts from entry ships of the five major port-groups in China are extremely imbalanced.The most developed Yangtze River Delta in economy has the biggest total ballast water input amounts,103.61million tons in2012.The second is the Circum-Bohai Sea Region(73.66million tons)and the third is the Pearl River Delta(67.24million tons).The total ballast water input amounts of the northwest and the southwest coastal areas are less,only16.57and5.71million tons respectively.The large quantity of entry ships’ballast water discharge has been an enormous threat to ecological environment of our country's sea areas,especially to economically developed regions. 展开更多
关键词 ballast water input of ballast water marine environment and ecology risk analysis
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In situ experimental study on TBM excavation with high-pressure water-jet-assisted rock breaking 被引量:9
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作者 ZHANG Jin-liang YANG Feng-wei +2 位作者 CAO Zhi-guo XIA Yi-min LI Yong-chang 《Journal of Central South University》 SCIE EI CAS CSCD 2022年第12期4066-4077,共12页
China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system i... China’s first high-pressure hydraulically coupled rock-breaking tunnel boring machine(TBM) was designed to overcome the rock breaking problems of TBM in super-hard rock geology, where high-pressure water jet system is configured, including high-flow pump sets, high-pressure rotary joint and high-pressure water jet injection device. In order to investigate the rock breaking performance of high-pressure water-jet-assisted TBM, in situ excavation tests were carried out at the Wan’anxi Water Diversion Project in Longyan, Fujian Province, China, under different water jet pressure and rotational speed. The rock-breaking performance of TBM was analyzed including penetration, cutterhead load, advance rate and field penetration index. The test results show that the adoption of high-pressure water-jet-assisted rock breaking technology can improve the boreability of rock mass, where the TBM penetration increases by 64% under the water jet pressure of 270 MPa. In addition, with the increase of the water jet pressure, the TBM penetration increases and the field penetration index decreases. The auxiliary rock-breaking effect of high-pressure water jet decreases with the increase of cutterhead rotational speed. In the case of the in situ tunneling test parameters of this study, the advance rate is the maximum when the pressure of the high-pressure water jet is 270 MPa and the cutterhead rotational speed is 6 r/min. The technical superiority of high-pressure water-jet-assisted rock breaking technology is highlighted and it provides guidance for the excavation parameter selection of high-pressure hydraulically coupled rock-breaking TBM. 展开更多
关键词 tunnel boring machine high-pressure water jet PENETRATION advance rate field penetration index
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MECHANICAL BEHAVIOUR OF MAIN FLOOR FOR WATER INRUSH IN LONGWALL MINING 被引量:3
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作者 钱鸣高 缪协兴 黎良杰 《Journal of China University of Mining and Technology》 1995年第1期9-16,共8页
In this paper a new mechanica1 medel indicating the mechanical behaviour of main floor in longwall mining is proposed. In the medel the unfractured rnain floor is considered as an elasto plastic plate, and the combina... In this paper a new mechanica1 medel indicating the mechanical behaviour of main floor in longwall mining is proposed. In the medel the unfractured rnain floor is considered as an elasto plastic plate, and the combination of fractured blocks as a voussoir beam. Using the plastic hmit theory of plates, th limit load acting on rnain floor and the position of its largest deformation are gotten. The stability conditions for the key blocks of the voussoir beam are analysed by "S-R" stability theory. The results of the theoretical analysis are important for the study on the water inrush from seam floor. 展开更多
关键词 floor water inrush main floor fracture voussoir beam 'S-R' stability
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Fracture mechanics solution of confined water progressive intrusion height of mining fracture floor 被引量:2
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作者 Lu Haifeng Yao Duoxi +1 位作者 Shen Dan Cao Jiyang 《International Journal of Mining Science and Technology》 SCIE EI CSCD 2015年第1期99-106,共8页
In order to obtain the value of confined water progressive intrusion height of mining fracture floor, the analysis equation was deduced based on the fracture extension theory of the fracture mechanics. Further- more, ... In order to obtain the value of confined water progressive intrusion height of mining fracture floor, the analysis equation was deduced based on the fracture extension theory of the fracture mechanics. Further- more, the influence of some parameters (e.g., advancing distance of working face, water pressure, initial fracture length and its angle) on confined water progressive intrusion height were analyzed. The results indicate that tension-shearing fracture of floor is extended more easily than compression-shearing frac- ture under the same conditions. When floor fracture dip angle is less than 90% tension-shearing extension occurs more easily on the left edge of the goaf. If fracture dip angle is larger than 90% it occurs more easily on the right edge of the goal. The longer the advancing distance of working face is, the greater initial frac- ture length goes; or the larger water pressure is, the greater possibility of tension-shearing extension occurs. The confined water progressive intrusion height reaches the maximum on the edge of the goaf. Field in situ test is consistent with the theoretical analysis result. 展开更多
关键词 Tension-shearing fractureCompression-shearing fractureConfined water progressive intrusionFloor water invasion
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Robust Watermarking of Mobile Video Resistant against Barrel Distortion 被引量:2
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作者 Huawei Tian Yanhui Xiao +2 位作者 Gang Cao Jianwei Ding Bo Ou 《China Communications》 SCIE CSCD 2016年第9期131-138,共8页
In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped with barrel distortion.The copyright of the mobile video should be verified on both the orig... In head mounted display(HMD),in order to cancel pincushion distortion,the images displayed on the mobile should be prewarped with barrel distortion.The copyright of the mobile video should be verified on both the original view and the pre-warped virtual view.A robust watermarking resistant against barrel distortion for HMDs is proposed in this paper.Watermark mask is embedded into image in consideration of imperceptibility and robustness of watermarking.In order to detect watermark from the pre-warped image with barrel distortion,an estimation method of the barrel distortion is proposed for HMDs.Then,the same warp is enforced on the embedded watermark mask with the estimated parameters of barrel distortion.The correlation between the warped watermark and the pre-warped image is computed to predicate the existence of watermark.As shown in experimental results,watermark of mobile video can be detected not only from the original views,but also from the pre-warped virtual view.It also shows that the proposed scheme is resistant against combined barrel distortion and common post-processing,such as JPEG compression. 展开更多
关键词 mobile video HMD with mobile robust watermarking
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Generation and propagation characteristics of fluctuation pressure in hydraulic fracturing with unstable fluid-injection
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作者 ZHU Ge DONG Shi-min +1 位作者 JIA He-tong DONG Zi-long 《Journal of Central South University》 SCIE EI CAS CSCD 2022年第1期186-196,共11页
Different from the stable injection mode of conventional hydraulic fracturing,unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate,which is beneficial to improve the frac... Different from the stable injection mode of conventional hydraulic fracturing,unstable fluid-injection can bring significant dynamic effect by using variable injection flow rate,which is beneficial to improve the fracturing effect.Obviously,the propagation process of fracturing fluid along the pipe string is crucial.In this paper,the fluid transient dynamics model in the pipe string was established,considering the boundary conditions of variable injection flow rate and reservoir seepage,and the unsteady friction was also taken into account.The above model was solved by characteristics and finite difference method respectively.Furthermore,the influences of geological parameters and fluid injection schemes on fluctuating pressure were also analyzed.The results show that unstable fluid-injection can cause noticeable fluctuation of fracturing fluid in the pipe string.Simultaneously,there is attenuation during the propagation of pressure fluctuation.The variation frequency of unstable fluid-injection and well depth have significant effects on pressure fluctuation amplitude at the bottom of the well.This research is conducive to understanding the mechanism of unstable fluid-injection hydraulic fracturing and providing guidance for the design of fluid-injection scheme. 展开更多
关键词 hydraulic fracturing unstable injection transient flow fluctuation pressure SEEPAGE
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Research on Critical Flow of Water under Supercritical Pressures in Nozzles 被引量:3
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作者 Yuzhou Chen Minfu Zhao Chunsheng Yang Keming Bi Kaiwen Du Shuming Zhang 《Journal of Energy and Power Engineering》 2012年第2期201-208,共8页
An experiment on critical flow of water was conducted in two nozzles of 1.41 mm in diameter and 4.35 mm in length with rounded-edge and sharp-edge respectively, covering the ranges of inlet pressure of 22.1-29.1 MPa a... An experiment on critical flow of water was conducted in two nozzles of 1.41 mm in diameter and 4.35 mm in length with rounded-edge and sharp-edge respectively, covering the ranges of inlet pressure of 22.1-29.1 MPa and inlet temperature of 38-474 ℃. More than 200 data points were obtained and the characteristics and parametric trends were investigated. In the region of near and beyond pseudo-critical temperature the thermal-equilibrium is dominant, and the flow rate can be estimated by the modified homogeneous equilibrium model. In the below pseudo-critical region the results exhibit scattered feature as a result of hysteresis effect in the onset of vaporization, characterizing a bifurcation behavior. This effect is more significant in the nozzle with sharp-edge, especially at higher pressure. For temperature well below the pseudo-critical point, the flow is not at critical condition and the flow rate can be represented by the Bernoulli equation reasonably. 展开更多
关键词 Critical flow CHOKING NOZZLE supercritical pressure THERMAL-EQUILIBRIUM reactor safety.
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浅谈演示实验可见度的提高
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作者 熊惠娥 《江西教育(管理版)(A)》 北大核心 1999年第3期46-46,共1页
实验是传授自然知识的重要教学手段,也是自然教学的核心。村级小学由于实验设备不充足,开展小学自然实验的主要形式还是教师演示实验。通过教师的演示,使学生了解自然现象。但是,要达到理想的实验目的,使学生清楚地了解自然知识,... 实验是传授自然知识的重要教学手段,也是自然教学的核心。村级小学由于实验设备不充足,开展小学自然实验的主要形式还是教师演示实验。通过教师的演示,使学生了解自然现象。但是,要达到理想的实验目的,使学生清楚地了解自然知识,必须努力提高实验的可见度。今就这一... 展开更多
关键词 演示实验 实验目的 观察指导 自然教学 教师 玻璃杯 模拟实验 规范化 水蒸气 压入水
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9500克鲶鱼出水记
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作者 黄朝学 《中国钓鱼》 1999年第10期52-52,共1页
今年8月7日双休日,我与钓友到茂名青年湖钓鱼。这天天气闷热,无风,气温35℃。下午2点左右,刮起小风,湖面微翻波浪,突然我的一支3米海竿弯向水面,竿尖压入水面不弹起,我急忙提竿犹如挂底。约两分钟后,鱼缓缓要线,向湖中游去,大约游了六... 今年8月7日双休日,我与钓友到茂名青年湖钓鱼。这天天气闷热,无风,气温35℃。下午2点左右,刮起小风,湖面微翻波浪,突然我的一支3米海竿弯向水面,竿尖压入水面不弹起,我急忙提竿犹如挂底。约两分钟后,鱼缓缓要线,向湖中游去,大约游了六七米后,鱼打桩不动。我听朋友说,鱼打桩后,弹渔线可迫使鱼游动,于是我就弹了几下渔线。 展开更多
关键词 鲶鱼 双休日 广东茂名 绕线轮 压入水 拉锯战 水面 桩后 小风 天气
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浮潜的技术
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《新体育》 1999年第7期55-55,共1页
通常游泳时我们总是手脚并用,为的是能使头不时地露出水面以便呼吸,并且游得快.而当我们进行浮潜时,由于使用了潜水服、面罩、脚蹼和呼吸管等装备,就可以浮在水面头朝下看,同时不用抬头也能自如地呼吸了.动作与通常的游泳比较可以放慢很... 通常游泳时我们总是手脚并用,为的是能使头不时地露出水面以便呼吸,并且游得快.而当我们进行浮潜时,由于使用了潜水服、面罩、脚蹼和呼吸管等装备,就可以浮在水面头朝下看,同时不用抬头也能自如地呼吸了.动作与通常的游泳比较可以放慢很多,而且减少了手臂的划水动作,一旦你能克服用手划水的习惯,将会很快成为一位潜水员. 展开更多
关键词 露出水面 呼吸管 游泳 潜水服 潜水装备 潜水员 下潜 向下弯曲 入水 压入水
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池钓浮标的秘密
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作者 蔡菊明 《中国钓鱼》 1995年第4期29-30,共2页
池钓决胜的关健在浮标的调校,许多人垂钓数年,依然懵懵懂懂;这一篇探讨浮标基本原理的心得,值得大家参考。
关键词 浮标 标杆 稳定性 基本原理 线长度 搭配组合 敏感性因素 精确度误差 压入水 配合饵料
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Performance study of a water ramjet engine 被引量:5
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作者 HUANG LiYa XIA ZhiXun +1 位作者 HU JianXin ZHU QianWen 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第4期877-882,共6页
A performance study of a water ramjet engine is described.The engine is powered by the reaction of a magnesium-based propellant and ingested water.In this study,a solid propellant,which consisted of a large percentage... A performance study of a water ramjet engine is described.The engine is powered by the reaction of a magnesium-based propellant and ingested water.In this study,a solid propellant,which consisted of a large percentage of magnesium,a binder and a small amount of oxidant,was used as a hydro reactive fuel.Cold water was injected into the combustion chamber as a main oxidant.A scaled-down experimental engine was tested in a direct-connect ground testing system to characterize the factors influencing the engine performance.The results show that the increasing of total water/fuel ratio,an addition of secondary water intake along the combustion chamber,a larger magnesium content in the solid propellant,a smaller primary water injection angle towards the coming main flow,and a higher primary injection pressure were all able to promote the engine performance.The maximum engine performance was obtained in test 08,and with all tests,an appropriate set of parameters and conditions for the optimum engine performance were determined 展开更多
关键词 underwater propulsion system ramjet engine MAGNESIUM WATER COMBUSTION performance EXPERIMENT
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