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单层球面和柱面网壳结构的承载能力已有不少研究,但双层球面网壳的力学特性和失效机理的研究很少涉及。基于此,系统地研究了4种不同矢跨比双层凯威特球面网壳的失效机理和破坏过程,考察了多个力学指标来评估网壳的力学性能,如变形能力、总应变能、总弹/塑性应变能和屈服杆件数等。捕捉了4种矢跨比网壳的杆件失效过程和失效机理的差异。计算结论可为双层球面网壳结构的设计提供参考与借鉴。

以4个矢跨比（1/3、1/4、1/5、1/6）的双层凯威特型球面网壳为研究对象,重点考察了网壳结构的可靠度、敏感性和相关性随荷载等级提高的变化规律。为了深入研究外荷载、杆件的物理属性和几何参数的随机性分别对网壳结构可靠度的影响程度,根据随机变量类型,分别将杆件的横截面面积、弹性模量和屈服强度定义为一个随机变量,继而研究了功能函数对各类型随机变量的敏感性程度;为了全面深入地探讨网壳结构在各等级荷载作用下的受力性能,定义了4种类型的功能函数,包括最大挠度、总塑性应变能、屈服杆件数目和总塑性应变,考察了4种类型功能函数对各随机变量的敏感性程度及功能函数间的相关性;最后,研究了各随机变量敏感性随不同矢跨比的变化规律。

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Shallow groundwater or narrow-deep lined canals have suffered the vertical frost heave at the top of the canal in cold regions. The lining fracture and whole uplift frost damage are also prone to occur, leading to the low stability of the canal at low temperature. However, the existing engineering models of canal frost heave have focused only on the normal one of the canal slope. This study aims to consider the combined effect of vertical frost heave on the top of the canal and normal frost heave on the slope. A mechanical engineering model was established to consider the canal frost heave. Sensitive soil was selected to simulate the moisture-heat-mechanical coupling numerical models in the canal. The frost heave was then used under different dip angles of the slope, width-to-depth ratios, and groundwater levels. The maximum tensile stress was calculated to locate the different freezing depths and dip angles of the slope during frost-jacking. The specific mechanism of canal lining was then explored to clarify the distribution of vertical and normal frost heave during frost-jacking. The internal force of canal lining plate and frost-jacking strength of canal slope were evaluated to calculate the critical slope length, critical groundwater level, and dangerous location of frost-jacking failure. Finally, the engineering mechanics model was proposed to test the actual case. The experimental data was in agreement with the field observation. The results show that the freezing counterforce was failed to offset the upper tangential frost-jacking force, particularly for the lower lining with the short slope length. The lining was also suffered from the jacking disease as a whole. Otherwise, a frost-jacking force was formed inside the lining. The greater the freezing depth and the dip angles of the slope were, the larger the area of the lining bearing the upward tangential force was, and the greater the frost-jacking tensile stress was. The position of the maximum tensile stress caused by jacking was shifted to the lower part of the canal with the increase of freezing depth and inclination angle of the canal slope. The maximum tensile stress was negatively related to the groundwater level. The critical water level of the lining was the critical groundwater level of the original ground frost heave. At the same time, the frost heave of the original ground was a necessary and insufficient condition for the canal to produce the frost pull. The numerical fitting indicated that the minimum curvature radius of the frost depth line at the top of the canal increased with the increase of frost depth and dip angles of the slope. The depth of frost shared a linear relationship with the minimum curvature radius. The dip angles of the slope exhibited a greater impact on the fitting slope. The maximum error of tensile stress was verified by the numerical model to be 1.5%. The frost-jacking position error was within 16.01%. Therefore, the slope range of the freezing line radius function was 1.047 to 4.040 in the soil conditions of the Ningxia irrigation area. There were the overall uplift pattern of small canal and the cracking failure pattern of large canal linings. The damage mechanism was then clarified to prevent and control the anti-frost heave of canal lining. The finding can also provide a strong reference for engineering design and code revision. [ABSTRACT FROM AUTHOR]

Copyright of Engineering Mechanics / Gongcheng Lixue is the property of Engineering Mechanics Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Metal structure and equipment are scattered and diverse in hydropower and water conservancy projects. There are many participants and a large amount of information in the whole process of metal structure mid equipment design and manufacturing. "Information islands" exist among project participants, mid the level of informatization and digitization needs to be further improved. Relying on Lidi, 'Wudongde Hydropower Station mid other projects, with the help of BIM technology, research was carried out in the aspects of model database construction, engineering drawing expression, digital design and handover of metal structure equipment. The simulation function of knowledge engineering and ergonomics was deeply applied in the aspects of virtual product experience, virtual manufacturing, operation and maintenance, in order to provide a reference for the application of BIM technology for the similar engineering metal structures. [ABSTRACT FROM AUTHOR]

An elastic foundation beam theory can be used to properly and effectively deal with the interaction between soil and structure. The theory application has also been gradually promoted in the frost-heaving mechanical analysis of frozen soil engineering structures in recent years. However, the existing Winkler model cannot consider the continuity of frozen soil. It is very necessary to presuppose the distribution of tangential freezing force. In this study, the governing differential equations were presented for the normal and tangential directions. The Pasternak shear layer was also introduced to connect the adjacent soil springs and contact interface layer between the frozen soil and concrete lining plate. Then, the frost-heaving mechanical model of the trapezoidal concrete lining canal was established using the two-parameter Pasternak elastic frozen soil foundation. The model was effectively connected with the SL23-2006“Specification for Design of Anti-freeze of Canal Engineering”. The frost-heaving mechanical analysis was applied to the concrete lining canals with the deep groundwater table. The computational accuracy of the frost-heaving mechanical model was improved significantly, where the shear layer was introduced to describe the interaction between the Winkler soil springs. The distribution of tangential freezing force was incorporated into the elastic foundation beam theory through the introduction of the contact interface layer. As such, there was no need for an improved model for the distribution of tangential freezing force. Taking the trapezoidal main canal of the Jinghui irrigation area in Gansu Province of China as the prototype, the improved model was applied to calculate the normal frost-heaving displacement of each point on the concrete lining plate. A comparison was then made on the Winkler model, the Finite Element Model (FEM) and test values. The comparative analysis indicated that there was consistent overall variation and tendency in the presented model, Winkler model, and FEM simulation. The critical test points were set on the concrete lining plates. The two-parameter elastic foundation beam model was much more consistent with the test values than those in the Winkler model and FEM. Furthermore, the two-parameter elastic foundation beam model was reduced to the Winkler model, when the shearing factor of frozen soil g was equal to 0. These results demonstrated the rationality and reliability of the presented model. The presented model was also applied to calculate the tangential displace and tangential freezing force of each section of the concrete lining plate. A parameter analysis was then carried out for the tangential contact stiffness. Among them, different tangential contact stiffness was set as the contact surface layer between concrete lining plates and frozen soil. Consequently, there was a nonlinear distribution in the section tangential displace and tangential freezing force along the concrete lining plates. A general decreasing trend was found in the tangential displace of each section with the increment of tangential contact stiffness. The distribution of tangential freezing force showed that “when one side is relatively large, then the other side is small”. In addition, there was a linear and uniform distribution of tangential freezing force, when the tangential contact stiffness was smaller. By contrast, the more nonlinear and non-uniform distribution was observed with the increase of tangential contact stiffness. The finding can provide a strong reference to designing the frost heave damage resistance of canals. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Theoretical Studies of Literature & Art / Wenyi Lilun Yanjiu is the property of Editorial Board of Theoretical Studies in Literature & Art and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Canals, as the preferred form of water conveyance, play an important role in the agricultural irrigation and long-distance water diversion projects in arid regions. However, the arid regions are mainly distributed in the seasonal permafrost regions in China, namely arid-cold regions. Due to the interaction between the canal seepage and frost heave, the freeze-thaw aging damages are more severe and common. The field investigation shows that the failure forms of canals include seepage, swelling, uplift, overhead, instability and collapse, and limit the safe operation and performance of canals seriously. In this study, the research progresses of the theories and technologies of anti-seepage and anti-frost heave for canals in arid-cold areas were summarized. Firstly, the mechanism of freeze-thaw failure and failure mode for canals was analyzed by indoor unit experiments, model experiments and field monitoring. Secondly, the engineering mechanical models of canal frost heaving failure were introduced based on limit equilibrium theory, such as material mechanics model and elastic mechanics model. Thirdly, multi-field coupling numerical models were developed including coupled heat-mechanics model, heat-water-mechanics model and the interaction model between frozen soil and canal lining. Lastly, the development processes of anti-seepage and anti-frost heave technologies for canals were expounded from four aspects: 1) the thermal insulation and preservation technologies against the external low temperature on soil and heat loss; 2) the anti-seepage and drainage technologies to reduce water content and water migration in soil; 3) soil replacement with sand or gravel technologies; 4) force release technologies by section structure optimization. With the increase of canal scale and upgrading demand for disrepair canals in harsh environment, the frost heaving failure mode was complex. The research frontiers and technical difficulties in this study mainly included: 1) the multi-field coupling failure mechanism and failure mode in the complex environment, such as solar radiation, freeze-thaw cycles and salinization, and operation conditions, such as water conveyance in winter with or without ice cover and water level dropping; 2) further development of multi-field coupling simulation model based on coupled heat-water-mechanics model covered the following aspects: canal thermal boundary with solar radiation and convective heat transfer model considering section form; canal damage model of freeze-thaw deterioration considering frost heaving and thawing of soil to analyze canal slope collapse; viscoplastic damage model for contact surface according to experiment on interfacial strength and stress-strain characteristics of lining-separated ice-frozen soil under freeze-thaw cycles; effects of salt on parameters of moisture field, thermal field and mechanical field and coupled heat-water-mechanics-salt model; 3) the canal failure criterion determination including strength, stiffness and stability of structures combined with field monitoring and numerical model, then modified the engineering mechanical model from the aspects of frost heaving force and adfreezing force distribution and foundation coefficient, and eventually formed a set of design method using engineering mechanical model to design and numerical model to check; 4) moisture, temperature and displacement changes under different anti-seepage and anti-frost heave measures of canals and standardization design combined with experiments, failure criterion and numerical model; 5) the dynamic disaster process and prevention and control technologies of canals determination by the following methods: classified variables such as environmental factors, operating conditions, section forms and failure forms of canals based on the field monitoring data and numerical simulation results, and then established the relationship between the variables by neural network and other algorithms. Finally, the future research directions were discussed and included: 1) complement of the design theory and method for anti-seepage and anti-frost heave; 2) establishment of dynamic evolution forecasting model for disaster chain in the whole life cycle. These may help to provide guidance to scientific design and efficient operation of water conveyance canals in arid-cold areas. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the rapid increase of water consumption by living and industry in cities, the operation of the water-delivery canal is becoming common during the icy period in winter. However, there is still a lack of quantitative method for evaluation of freezing damage that could seriously threaten the normal operation of water-delivery canal. In this paper, the ice and frost damage of ice-covered water-delivery canal was defined as the result of the coupling effect of the static ice pressure on the lining plate and the frost heave of the canal subsoil. In this regard, this study deduced an analytical expression of internal force, stress calculation and anti-crack criterion of lining structure under operating conditions of ice cover. The process of derivation was based on elastic foundation beam theory model for no water delivery canal, and the interaction of ice thrust, ice constraint and frost heaving force of foundation were considered. Through the change of the influence coefficient of static ice load, hydrostatic pressure and the coupling coefficient of freezing load, the internal force and stress distribution of lining structure could be unified under the conditions with or without ice cover and water supply in winter, and thus a unified mechanical model of freezing damage for lining structure of water-delivery canal in cold region could be established to provide a quantitative analysis method for the freezing damage of ice-covered water-delivery canal. In order to ensure the practicability of this study, a trapezoidal lined canal of Xinjiang Manas River Diversion Hydropower Station was took as a prototype. In this area, the lowest temperature was -19°C, the foundation soil of canal was loam, the thickness of concrete lining slope plate was 0.20 m, the concrete strength of slope plate was C20. The distribution of internal force, stress and ice pullout force of lining slabs was analyzed, and then the distribution of maximum bending moment along lining slabs and the location of dangerous section were determined with ice and frost damage. The comparative analysis of internal force and stress calculation of the 3 typical trapezoidal canal freezing damage mechanical models showed that the maximum tensile stress of the cross section was 4.186, 2.447 and 2.208 MPa, respectively. The freezing damage in the case that water delivery canal was ice-free was the most serious, and in the case that the canal of no water delivery was the lightest, while the ice-covered water delivery case was in the middle of the former 2 cases, and there was a big difference among the 3 cases, and the location of lining where freezing damage began to occur was totally different. Therefore, 3 typical operating conditions should be considered comprehensively in the anti-ice and freezing design of trapezoidal canal of water delivery in winter and security under the 3 conditions should be evaluated according to failure law and mechanical model. Based on the minor deformation hypothesis of materials, and a unified mechanical model was established here to calculate and analyze the frost heaving of canal foundation soil and ice load acting on concrete canal. In the future, mechanical model of ice and freezing damage of canal under ice cover should be researched deeply for coupling effect of ice cover life cycle. This study can provide theoretical support for the design of water-delivery canal in cold region, for effectively predicting canal frost failure under different conditions, and has important guiding significance for ensuring the normal operation of water-delivery canal. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water delivery canals play an important role in highly efficient water use in arid and semi-arid regions in China. Those regions mostly belong to cold region widely distributed with seasonal frozen soils. Thus, canal lining is susceptible to frost damage because of the heave of freezing soil and the adfreezing constraint between foundation and lining. Double geo-membranes between lining and foundation soil have an advantage in relieving adfreezing strength and adjusting lining displacement to adapt nonuniform frost heave but reduce the stiffness and stability of lining structure. To find the best layout of double geo-membranes and quantitative analysis on the adaptation of the double geo-membranes, a heat-moisture-stress coupling model of frost heave for arc bottom trapezoidal canal was established by finite element method. A bilinear interaction model between layers of cushion was considered by thin elastic layer element, of which the friction force was expressed as reaction force relating to its shear stiffness. A total of 3 different layout forms of composite cushion (membrane-membrane, membrane-fabric and fabric-fabric) were simulated by various shear stiffness parameters. The lining stress and deformation were compared by different canal sections and layout forms of double membranes cushion under lining. The result showed that: 1) For narrow and deep lined canals, the smaller the friction between membranes would result in the more uniform frost heave but the worse overall structure stability. While for wide and shallow canals, it was disadvantageous for neither frost heave uniformity nor overall stability when reducing the friction between membranes. Hence considering the requirements of frost heave uniformity and stability, the membrane-fabric form was suitable for both narrow and deep lined canals and wide and shallow lined canals. 2) The arch structure at the bottom of canal had an arch effect that could increase the axial compressive force along lining when bearing the heave force at the lower surface of lining. But as decreasing friction by double membranes, the arch effect was weaken, causing the extra tensile stress in the slope of canal lining. Therefore, considering the requirements of structure strength, the membrane-fabric and fabric-fabric form was suitable for anti-frost damage of canal lining. Double membranes cushion with less adfreezing strength such as membrane-membrane and membrane-fabric combinations could relieve the freezing constraint and adjust lining uneven frost heave deformation, but may lead to large displacement and damage tensile stress as a result of the release of arch effect at the bottom of the canal. Therefore, double membranes cushion with some small friction could not ensure the safety of strength and stiffness of lining structure. In addition, proper adfreezing strength was helpful in adjusting uneven frost heave by partly slip and limiting overall deformation. Furthermore, the arch effect should be rationally utilized to produce compressive stress along lining. In consequence, when membrane-fabric was used as interface between membranes, the displacement variance of lining decreased by 25% and the frost heave stress reduced by more the 50%, while the overall displacement increased by 0.2 cm or less. This double membranes form, which was suitable for narrow and deep canals as well as wide and shallow canals, could meet the requirements of strength, stiffness and stability for lining structure, and could improve the adaptive ability for frost heave damage. The results could provide information for selecting reasonable layout of double membranes cushion lining canals in cold region. [ABSTRACT FROM AUTHOR]

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Sprinkler irrigation is one of the main water-saving irrigation methods at home and abroad. As a common water-saving irrigation equipment, impact sprinkler is widely used in landscaping and agricultural irrigation fields. The traditional impact sprinkler with circle spray filed has the disadvantages of overlap spray, excessive spray and missing spray. In response to above disadvantages, impact sprinkler with square spray field has been improved but it remains facing many problems such as complicated mechanical structure, excessive head loss, and it’s spray shape deviates from square. In order to reduce the local head loss, the inner passageway of spray’s flow regulator consist of hollow shaft and threaded pipe was optimized with streamline. To achieve the goals of accurate square spray field, the docking port between hollow shaft and threaded pipe was reshaped with diamond shape as entry end connect to threaded pipe and star shape as export end connect to hollow shaft. The improvement above can effectively reduced the head loss that was unfavorable to the spray shape, and improved the range and spray shape factor. To evaluate the drag reduction effect in passageway of sprinkler, the flow regulator was divided into four part according to it’s inner flow state. Then the head loss formulas for each part were derived by energy equation and momentum equation of hydrodynamics. The whole head loss of the optimized flow regulator was expressed as sum of the four parts head loss related to their flow velocity and loss coefficient effected by passageway’s shape at last. The flow velocity of each part could be obtained by simulating which was conducted in this paper. This work provided a theoretical basis for the selection of the flow regulator inlet and outlet and flow passage optimization of the square spray field impact sprinkler. For global flow analysis and provide flow velocity result for head loss calculation, the three-dimensional unsteady numerical simulation of the inner flow path of the square spray field impact sprinkler was carried out. The 3D geometric model of flow regulator was established using Pro/E software. The distribution regularities of velocity and pressure were simulated by FLUENT software with the RNG k-ε turbulence model. Pressure inlet was set as the inlet boundary condition in the model, with the working pressure 250, 300, 350, 400, 450 and 500 kPa respectively. According to the relationship between the flow rate and the range of the same type of Rain Bird impact sprinkler without the flow regulator, the range of four corners of a square spray field sprinkler with optimized flow regulator was calculated. According to the working equation of the square spray impact sprinkler, the variation rule of the range under different rotation angles can be obtained. Finally, comparting with the same type of Rain Bird sprinkler, the optimization effect of the square sprinkler was evaluated by the variation of the head loss, flow rates, range change and spray shape, and the reliability of the results was verified. The results show that the new type of square spray field sprinkler is simple in structure, hydraulic automatic control, energy saving, durable and convenience, and has standard spraying shape with small head loss. Compared with the square spray field sprinkler before optimized, the head loss of the optimized square spray field sprinkler in the rated working pressure reduced by 25.8%. The flow regulator range of the improved sprinkler is enlarged, with maximum flow rate increasing by 12.87% and minimum decreasing by 12.83% respectively. In addition, the spray shape factor is 86.89% which rises 15.5% and the out spray reduces 9.85%. This provides a theoretical reference for the design, manufacture and application of the square spray field sprinkler. [ABSTRACT FROM AUTHOR]

Ｉｎ ｏｒｄｅｒ ｔｏ ａｃｃｕｒａｔｅｌｙ ｍａｓｔｅｒ ｔｈｅ ｅｆｆｉｃｉｅｎｃｙ⁃ｉｍｐｒｏｖｉｎｇ ａｎｄ ｃａｐａｃｉｔｙ⁃ｅｘｐａｎｄｉｎｇ ｐｏｔｅｎｔｉａｌ ｏｆ ｒｕｒａｌ ｈｙｄｒｏｐｏｗｅｒ ｓｔａｔｉｏｎ ａｎｄ ｏｐｔｉｍｉｚｅ ｔｈｅ ｔｒａｎｓｆｏｒｍｅｄ ｕｎｉｔ ｏｐｅｒａｔｉｏｎ ｃｏｍｂｉｎａｔｉｏｎ， ｂａｓｅｄ ｏｎ ｃｏｒｒｅｌａｔｉｏｎ ｆｕｎｃｔｉｏｎ ｏｆ ｈｙｄｒａｕｌｉｃ ｆａｃｔｏｒｓ ｗｉｔｈ ｒｕｎｏｆｆ ｄａｔａ ａｎｄ ｃｏｍｂｉｎｅｄ ｔｈｅ ｍｅａｎ ａｎｎｕａｌ ｐｏｗｅｒ ｇｅｎｅｒａｔｉｏｎ ｔｏ ｂａｃｋ ｃａｌｃｕｌａｔｅ ｔｈｅ ｒｕｎｏｆｆ， ｔｈｅ ｈｙｄｒｏｐｏｗｅｒ⁃ｃｈｅｃｋｉｎｇ， ｉｎｓｔａｌｌｅｄ ｃａｐａｃｉｔｙ ａｎｄ ｔｕｒｂｉｎｅ ｔｙｐｅ ｏｆ Ｘｉａｋｏｕ Ｈｙｄｒｏｐｏｗｅｒ Ｓｔａｔｉｏｎ ｈａｓ ｂｅｅｎ ｃｏｎｆｉｒｍｅｄ． Ｄｅｓｉｇｎｉｎｇ ａｐｐｌｉｃａｔｉｏｎ ｓｈｏｗｓ ｔｈａｔ ｔｈｒｏｕｇｈ ｔｈｅ ｃａｌｃｕｌａｔｉｏｎ ａｎｄ ｂａｃｋ⁃ｃａｌｃｕｌａｔｉｏｎ ｏｆ Ｙｉｎｇｇｅ Ｓｔａｔｉｏｎ ｒｕｎｏｆｆ ｄａｔａ ｏｆ Ｓｈａｎｃｈａ Ｒｉｖｅｒ ａｎｄ ｓｔａｔｉｓｔｉｃａｌ ｄａｔａ ｏｆ ｐｏｗｅｒ ｓｔａｔｉｏｎ’ｓ ｙｅａｒｓ ｏｆ ｒｕｎｎｉｎｇ ｐｏｗｅｒ ｇｅｎｅｒａｔｉｏｎ， ｔｈｅ ａｃｃｕｒａｔｅ ｄａｔａ ｏｆ ｗａｔｅｒ ｅｎｅｒｇｙ ｉｎｄｅｘ ｗｈｉｃｈ ｃａｎ ｔｒｕｌｙ ｒｅｆｌｅｃｔ ｔｈｅ ｏｐｅｒａｔｉｏｎ ｃｈａｒａｃｔｅｒｉｓｔｉｃ ｏｆ ｐｏｗｅｒ ｓｔａｔｉｏｎ ａｎｄ ｅｎｓｕｒｅｄ ｔｈｅ ｄｅｓｉｇｎｉｎｇ ｓｃｈｅｍｅ ｗｉｔｈ ｔｅｃｈｎｉｃａｌ ｆｅａｓｉｂｉｌｉｔｙ ａｎｄ ｅｃｏｎｏｍｙ ｈａｓ ｂｅｅｎ ｏｂｔａｉｎｅｄ． Ａｆｔｅｒ ｒｅａｓｏｎａｂｌｅ ｔｅｃｈｎｏｌｏｇｉｃａｌ ｔｒａｎｓｆｏｒｍａｔｉｏｎ， ｔｈｅ ｗａｔｅｒ ｕｔｉｌｉｚａｔｉｏｎ ａｎｄ ｃｏｎｖｅｒｓｉｏｎ ｅｆｆｉｃｉｅｎｃｙ ｈａｖｅ ｂｅｅｎ ｉｍｐｒｏｖｅｄ， ｔｈｅ ａｂａｎｄｏｎｅｄ ｗａｔｅｒ ａｎｄ ｏｐｅｒａｔｉｎｇ ｅｎｅｒｇｙ ｃｏｎｓｕｍｐｔｉｏｎ ｈａｖｅ ｂｅｅｎ ｒｅｄｕｃｅｄ． Ｔｈｅ ｓｔａｔｉｏｎ ｃａｎ ｒｅａｌｉｚｅ ｔｈｅ ａｉｍｓ ｏｆ ｅｎｅｒｇｙ ｃｏｎｓｅｒｖａｔｉｏｎ ａｎｄ ｃｏｎｓｕｍｐｔｉｏｎ ｒｅｄｕｃｔｉｏｎ ａｔ ｔｈｅ ｓａｍｅ ｔｉｍｅ ｏｆ ｅｆｆｉｃｉｅｎｃｙ⁃ｉｍｐｒｏｖｉｎｇ ａｎｄ ｃａｐａｃｉｔｙ⁃ｅｘｐａｎｄｉｎｇ ａｎｄ ｉｔ ｈａｓ ｎｏ ｎｅｅｄ ｆｏｒ ａｄｄｉｔｉｏｎａｌ ｍｅａｓｕｒｅｓ． [ABSTRACT FROM AUTHOR]

To ensure reasonable stress states of branching structures,and to determine the relationship between their form layout and stability, a branching structures geometric model was established based on inverse-hang recursive method. The relationship between the branching structure forms and stability was analyzed by using finite element method considering initial imperfection and geometrical-material nonlinearities. The effects of varying parameters, including tubular diameter, diameter ratio of adjacent grade members and branch node location, on structural stability and failure mode were discussed. The results show that the structural stability is not sensitive to codified initial imperfection values ; however, geometrical-material nonlinearities have remarkable influence on the stability of branching structures. Structural stability capacity reaches its maximum value when the ratio of stem diameter to structure height equals to 0. 045, structural capacity per unit mass is increased first and then generally maintains unchanged with increasing in the diameter. The diameter ratio influences structural failure mode, where structural stability increases first and decreases, and structural capacity per unit mass reaches its maximum value when the diameter ratio equals to 0. 8. The effect of branch angle (form layout of branching structures) on the structural stability is significant, when the angle between branch and stem axis equals to 30°, structural material utilization ratio of reaches its maximum value, and the form layout of branching structures is optimal. Structural stability is remarkably improved with increase in lateral member stiffness. [ABSTRACT FROM AUTHOR]

In vast and cold permafrost regions, concrete lining canals are highly vulnerable to frost heave damage because of the freezing and expansion of foundation soil. Frost heave deformation of canal foundation frozen soil is orthotropic, namely bi-directional frost heave. Bi-directional frost heave of foundation soil consists of frost heave both parallel to temperature gradient direction and perpendicular to temperature gradient direction. As large-sized concrete lining trapezoidal canals have larger cross-section dimension and longer canal slope lining plate than ordinary canals, the mechanism of frost heave damage of large-sized canals is different from medium or small sized ones. Both storage effect of tangential frost heave force along canals concrete lining plates and frozen shrinkage stress of canals concrete lining plates are significant. The reasons for frost heave damage of canals concrete lining plates in cold regions consist of frost heave of canal foundation frozen soil and frozen shrinkage of canals concrete lining plates. As low rainfall and no water diversion in winter in north-western cold and arid regions in China, initial moisture content of canal foundation soil is extremely low. In specific regions with specific meteorological conditions and soil quality conditions, groundwater replenishment becomes dominant influence factor which determines frost heave intensity of each point on canal concrete lining plates. By combining Winkler elastic foundation assumption for canal foundation frozen soil and considering orthotropy of frost heave deformation of frozen soil namely bi-directional frost heave of frozen soil, calculating methods to determine distribution of normal frost heave force and tangential frost heave force on canals concrete lining plates in open-system conditions were proposed. Eventually calculation formulas of internal force of canal concrete lining plates were carried out. Analytic formulas to calculate frozen shrinkage stress of canal lining plates were deduced based on elastic foundation beam theory, and methods for crack resistance checking computations of canal lining plates of large-sized concrete lining trapezoidal canal were proposed. By taking a trapezoidal canal in Gansu Jinghui irrigation district as prototype, the distribution of internal force and frozen shrinkage stress of each section of lining plates were determined. Then the distribution of maximum tensile stress (namely, tensile stress on upper surface of canal lining plates) on canal lining plates and the position coordinate of the most dangerous section were calculated. Contrast analysis results between the situation considering both bi-directional frost heave and frozen shrinkage stress and the situation only considering normal frost heave force irrespective of frozen shrinkage stress showed that the calculated value of maximum section tensile stress according to the latter was notably less than the previously calculated value. Therefore, taking no consideration of the effects caused by bi-directional frost heave of canal foundation frozen soil and lining plate frozen shrinkage in mechanics analysis and frost heave resistance designs of large-sized concrete lining canal was unsafe. While considering both bi-directional frost heave and frozen shrinkage stress, the maximum cross-section tensile stress on shady-slope plate was 2.134 MPa. While considering normal frost heave only and irrespective frozen shrinkage stress, the maximum cross-section tensile stress on shady-slope plate was 1.494 MPa. Thus it can be seen that the calculated values would be smaller if considering normal frost heave only and irrespective frozen shrinkage stress. The research results can provide references for mechanics analysis and frost heave resistance designs of large-sized concrete lining canal. [ABSTRACT FROM AUTHOR]

As a result of the largeamount of frost heave in winter and the serious collapse in spring which attributed to the shallow underground water table of arenosol's foundation, a foundation replacement measure with block stone in the main canal of Jingtai irrigation was proposed for anti-frost heave and anti-thaw settlement. According to the relationship between groundwater depth and frost thawing sink strength of canal base, it got frozen soil's constitutive equation and it calculated the displacement field and stress field of canal lining that before and after replacement of block stone by using the COMSOL finite element software. The results show that the replacement of canal slope, the canal bottom lining plate method to the maximum displacement value relative to replacement before are reduced by 53.8% and 78.0% respectively; after replacement, the maximum method to frost heaving force of lining and cut to a freezing stress compared to change before filling are reduced by 73.2% and 82.8% respectively and the overall distribution is more uniform. In the condition of shallow groundwater or soil softening encountering water, the effects of freezing-thawing resistance by the block-stone replacement measure for canal are excellent. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The precast concrete slab lining trapezoidal canal is widely applied in cold regions of northern China, but the calculation method of frost heaving force distribution and the mechanics model of frost heaving damage under high groundwater level conditions have not yet been set up. Due to similar weather condition and soil texture in the specific region, the strength capacity of groundwater supply on each point of the concrete lining slab becomes the decisive factor of the strength of frost heaving on each point. Through Winkler assumption for mechanic characteristics of soil, the strength of frost heaving on each point of the concrete lining slab is only related to the capacity of water supply on the corresponding point; according to the functional relations between frost heaving force, frost heaving strength and groundwater depth, the article proposed a method to calculate the frost heaving force distribution on the concrete lining slab. By applying the idea to a type of precast concrete slab lining trapezoidal channel whose precast concrete slab size was moderate, a mechanics model of frost heaving damage in open system was established. The article divided precast concrete slab lining canal into 2 types. One had large precast concrete slabs, and as caulking material was cement mortar with weak bond strength, the integrality of the type was worse; the other had moderate precast concrete slab size and caulking material was usually flexible material with strong bond strength such as polyurethane, plastic waterproof ointment, so the integrality of the type was excellent and it was the main research object of this article. With the preceding model the distribution of axial-tension, shear force and moment in the canal slope lining plate can be calculated, respectively. Combining mechanical analysis with engineering practices, the manifestations and the reasons of frost heaving damage of precast concrete slab lining trapezoidal channel were classified as axial-crack, shear failure and bending rupture of joints between precast concrete slabs. According to different forms and reasons of frost heaving damage, the controlled sections for checking the possibility of frost heaving damage were confirmed, and the corresponding judge rules were proposed. The method to check normal displacement caused by frost heaving on joints between precast concrete slabs was put forward based on the unit-load method. The calculation method and the mechanics model discussed in the article were based on different groundwater supply intensity of different point on canal lining, so it had great commonality, and it could calculate the distribution of frost heaving force on concrete lining canal with different types of cross-section. Finally, an engineering example was carried out, and the results showed that the model was reasonable and reliable and can serve as reference and theoretical basis for engineering designs. [ABSTRACT FROM AUTHOR]

The great latent heat of the water transfer and phase transformation in the winter has a significant effect on the temperature field of the canal base soil. The researches on the freezing-thawing of frozen soil with moisture phase change are mostly based on the road foundation, buried pipe, and so on. The study on frost heave damage of lining canal is relatively less. As the canal is in water-carrying condition for a long time, the moisture content of canal foundation soil is high, especially in excavation canal because of the high groundwater table caused by moisture convergence. Under the preceding special geological conditions, as the canal foundation soil is freezing, not only is the water frozen in situ, but also the unfrozen water migrates to the freezing front and changes phase, and then the temperature field and displacement field in canal foundation are influenced by reason of tremendous latent heat of phase change. Although in some past thermal-mechanics coupling calculations the latent heat of moisture phase change is in consideration, the source of moisture with phase change is not completely considered, the computed results of temperature field are not precise enough, and the inaccuracy of the results can lead to the error of frost heave deformation calculated by thermal-mechanics coupling models. So the article established a frost heave model for canal foundation frozen soil, and the water migration and phase change were taken into account in this model. The model regarded the permafrost as cryogenic expansion material, in which the latent heat was added to the conduction equation, and the latent heat is equivalent heat capacity. According to Clapeyron equation and Darcy’s law, the article established the expression of moisture migration of freezing fronts in saturated freezing soil, and the latent heat of moisture migration was as the source term of conduction equation. In order to verify the reasonableness of the model, the COMSOL was used, which is a kind of large-scale software for multi-physics fields coupling for numerical calculation. Results showed that in the temperature and displacement field the phase change produced a great influence. After considering the phase change, the freezing depth of the soil advanced slowly, the maximum frozen depth was 1.5 m, and it was near to the actual value which was 1.8 m. But if the moisture phase change was not in consideration, the calculation value of maximum frozen depth was 3 m, and it was much greater than the actual value. As the moisture phase change was in consideration, the maximum normal displacements on the shady slope, sunny slop and canal bottom were 9.65, 4.81 and 2.0 cm, respectively. Compared with the model not considering phase change, the frost heave model proposed in this article is more in line with the actual situation. So in order to make the calculation results accord well with actual value, the influence of moisture phase change on temperature fields and displacement fields can’t be neglected. The present results can provide reference to engineering design for frost heave resistance in cold region. [ABSTRACT FROM AUTHOR]

目的探討基層醫院冠心病監護病房(CCU)專科護士培養模式。方法 2013年4月至2014年3月,對26名在心血管內科從事護理工作滿2年的執業護士進行CCU專科方面的系統培訓。聘請院內外專家給予理論授課6個月240學時,之后在CCU和ICU各輪轉3個月,由該CCU和ICU臨床教師1:2帶教,1年后進行效果評價。結果培訓后,CCU專科護士的理論成績、操作成績、CCU病房質量評分、特一級護理評分、護理安全評分、消毒隔離評分及護理文書評分均明顯高于培訓前,差異均有統計學意義(P<0.01)。結論 CCU專科護士在基層醫院的培訓模式具有可行性,CCU專科護士的綜合素質和CCU護理質量均明顯提高,但護士的護理科研能力相對薄弱,應根據需求開展有效可行的護理科研規范化培訓。 [ABSTRACT FROM AUTHOR]