平板冻结器超压事故的原因分析     

李敏  李湛 《广东海洋大学学报》2002,22(6):49-53

平板冻结器超压事故的发生主要由于使用设备时操作不当和设备质量不过关而引起。对设备超压原理分析和平板冻结器在不同温度条件下的充液比例进行理论计算 ,结果表明 ,停机时 ,在室温 35℃的条件下 ,蒸发器中的充液比例达到 0 .86 0 5时 ,会引起蒸发器发生超压而爆炸。当蒸发器中充液比例在 0 .86 0 5以下时发生的超压事故 ,肯定存在设备质量不过关的因素 ;而当充液比例在 0 .86 0 5或以上时发生的超压事故 ,则是由误操作引起。。  相似文献   

Suspended sediment and phosphorus in proglacial rivers: bioavailability and potential impacts upon the P status of ice‐marginal receiving waters     

Andy Hodson  Paul Mumford  Debbie Lister 《水文研究》2004,18(13):2409-2422

This paper adopts standard tests developed in temperate catchment research to determine the total phosphorus (TP) and the algal available (base‐extractable) phosphorus (NaOH–P) content of a wide range of glaciofluvial sediments from the Northern Hemisphere. We find that the TP content of these sediments is broadly similar to the P content of major rock types in Earth's crust (230–670 µgP/g) and so the TP yields of glacier basins may be high owing to the efficacy of suspended sediment evacuation by glacial meltwaters. We show that this is best achieved where subglacial drainage systems are present. The NaOH–P pool of the sediments is found to be low (1–23 µgP/g) relative to the TP pool and also to the NaOH–P pool of suspended sediments in temperate, non‐glacierized catchments. This most probably reflects the restricted duration of intimate contact between dilute meltwaters and glacial suspended sediments during the ablation season. Thus, despite the high surface‐area:volume ratio of glacial suspended sediments, the potential for P adsorption to mineral surfaces following release by dissolution is also low. Further, sorption experiments and sequential extraction tests conducted using glacial suspended sediments from two Svalbard catchments indicate that the generation of reactive secondary minerals (e.g. Fe‐ and other hydroxides) with a strong capacity to scavenge P from solution (and thereby promote the continued dissolution of P) may also be limited by the short residence times. Most P is therefore associated with poorly weathered, calcite/apatite‐rich mineral phases. However, we use examples from the Svalbard glacier basins (Austre Brøggerbreen and Midre Lovénbreen) to show that the high sediment yields of glaciers may result in appreciable NaOH–P loading of ice‐marginal receiving waters. Again, the importance of subglacial drainage is highlighted, as it produces a major, episodic release of NaOH–P at Midre Lovénbreen that results in a yield (8·2 kg NaOH–P/km²/year) more than one order of magnitude greater than that at Austre Brøggerbreen (where subglacial drainage is absent and the yield is 0·48 kg NaOH‐P/km²/year). Therefore, as since both detrimental and beneficial effects of sediment‐bound P loading in ice marginal receiving waters are possible (i.e. either reduced primary productivity owing to increased turbidity or P fertilization following desorption) there is a pressing need to assess the ambient P status of such environments and also the capacity for ice‐marginal ecosystems to adapt to such inputs. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

X Per新发射相的不寻常变化     

刘庆忠  杭恒荣 《天文学报》1997,38(4):434-440

对ＸＰｅｒ新发射相连续四年的光学光谱和近红外光度监测结果，ＸＰｅｒ近两年的变化不同寻常，主要表现以下两点：（１）尽管它的光学光度Ｖ星等只恢复至失去气壳前的亮度，但Ｈａ发射线等值宽度和近红外，Ｊ，Ｈ和Ｋ光度地超过了历史记录的最大值，分别达到了１６．３４Ａ和５．３＾ｍ，５．３＾ｍ和５．１＾ｍ，表明ＸＰｅｒ新发射相气南的密度和尺度较都大，（２）我们首次观测到ＸＰｅｒ近红外光度和Ｈα发射线等值宽度变化趋势  相似文献   

步进电机步距角的正余弦细分原理     

张竹恒  周尊源  孙淑琴 《时间频率学报》1997,(1)

步进电机的步距角由于受到机械结构和经典细分驱动电路的限制，只能适量的减小，但对于许多精密设备的控制及高精度的定位系统，其步距角的分辨率还应提高，正金弦细分驱动电路很好地解决了这一问题。它的主要特点是和计算机或单片机的接口简单、转速连续可调；增减EPROM的地址线可灵活改变细分数；电机运行平稳、振动小、噪声低。  相似文献   

基于B/S架构的城市车辆指挥调度系统     

范志龙  陈雪丰 《测绘信息与工程》2009,34(6):36-37

提出了基于B/S架构的WebGIS城市车辆指挥调度系统框架,综合利用了GPS、GPRS等技术,实现了对城市车辆的指挥调度功能。  相似文献   

6种鱼类肌肉组织肌苷酸的检测分析          下载免费PDF全文

刘旭  王军  张纹  杜佳莹  苏永全 《海洋科学》2008,32(2):22-24

采用高效液相色谱技术,在国内首次测定了条纹斑竹鲨(Chilocsyllium plagiosum)、大黄鱼(Pseudosci-aena crocea)、鳜(Siniperca chuatsi)、青石斑鱼(Epinephelus awoara)、牙鲆(Paralichthys olivaceus)和乌塘鳢(Bostrichthys sinensis)等6种鱼类新鲜和冻存肌肉组织中肌苷酸含量。结果表明:(1)不同鱼类肌肉组织中肌苷酸质量比不同,牙鲆新鲜肌肉组织中肌苷酸质量比最高,为4.214 mg/g,其余5种鱼类为2.365~3.634 mg/g。(2)10 d冻存试验中,经-70℃超低温冻存,6种鱼类冻存肌肉组织中肌苷酸质量比均高于新鲜肌肉组织,大黄鱼肌肉组织冻存1 d肌苷酸质量比达最大值,鳜肌肉组织冻存10 d肌苷酸质量比呈上升态势未出现最大值,其余5种鱼类肌肉组织肌苷酸质量比均在冻存第5天达到最大值。长时间的冻存将会降低食用鱼肉中肌苷酸质量比,导致鲜味下降,但经1周左右短时间的冻存后可明显提高鱼肉中肌苷酸质量比,增加鲜味,提高食用价值。  相似文献   

The τ Herculid meteor shower and Comet 73P/Schwassmann–Wachmann 3     

P. A. Wiegert  P. G. Brown  J. Vaubaillon  H. Schijns 《Monthly notices of the Royal Astronomical Society》2005,361(2):638-644

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Orbital Elements of 2004 Perseid Meteoroids Perturbed by Jupiter     

Josep Maria Trigo-Rodriguez  Jeremie Vaubaillon  José Luís Ortiz  Alberto Castro-Tirado  Jordi Llorca  Esko Lyytinen  Martin Jelínek  Antonio de Ugarte Postigo  Pablo Santos Sanz  Francisco J. Aceituno Castro  Albert Sánchez Caso  Antonio Bernal González  Juan Pastor Erades  Francisco Ocaña 《Earth, Moon, and Planets》2005,97(3-4):269-278

Jupiter and Saturn produce important gravitational impulses on meteoroids released by comet 109P/Swift-Tuttle. The meteoroids from this comet once released follow retrograde orbits that during their periodic approaches to these planets (within 1.6 and 0.9 A.U., respectively) are impulsed gaining orbital energy. This perturbation effect is translated into a net inward shift in the node of the perturbed meteoroids. Such geometry with Jupiter occurred in 2004 over a meteoroid trail ejected by this comet during the 1862 A.D. return of the comet to perihelion. In order to study the predicted outburst produced by one-revolution meteoroids, the Spanish Photographic Meteor Network (SPMN) performed an extensive campaign. As a part of this observational effort here are presented 10 accurate meteoroid orbits. We discuss their origin by comparing them with the theoretical orbital elements of the dust trails intercepting the Earth during the 2004 Perseid return.  相似文献   

会计电算化在测绘单位管理中的组织与实施     

孙毅 《地理信息世界》2002,(2)

会计基础工作是财会工作的基本环节 ,是经济管理的重要基础。实现会计电算化对于加强会计基础工作 ,保证财会工作科学有效地进行 ,减少工作误差 ,实现会计工作现代化操作及现代化管理具有现实意义  相似文献   

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高永刚  郭金运  黄金维  岳建平 《大地测量与地球动力学》2008,28(1):45-49

??TOPEX/Poseidon????????????Χ???????ν??з??????ó?????:?????????????Χ???????????ε?????;????????????????????ζ??????????,?????????????????????????????????????????????  相似文献