Optimal early refill rules for Danjiangkou Reservoir

Water levels in reservoirs are generally not allowed to exceed the flood-limited water level during the flood season, which means that huge amounts of water spill in order to provide adequate storage for flood prevention and that it is difficult to fill the reservoir fully at the end of year. Early reservoir refill is an effective method for addressing the contradiction between the needs of flood control and of comprehensive utilization. This study selected the Danjiangkou Reservoir, which is the water source for the middle route of the South-North Water Diversion Project （SNWDP） in China, as a case study, and analyzed the necessity and operational feasibility of early reservoir refill. An early reservoir refill model is proposed based on the maximum average storage ratio, optimized by the progressive optimality algorithm, and the optimal scheduling schemes were obtained. Results show that the best time of refill operation for the Danjiangkou Reservoir is September 15, and the upper limit water level during September is 166 m. The proposed early refill scheme, in stages, can increase the annual average storage ratio from 77.51% to 81.99%, and decrease spilled water from 2.439 × 109 m^3 to 1.692×109 m^3, in comparison to the original design scheme. The suggested early significant comprehensive benefits, which decision-making. reservoir refill scheme can be easily operated with may provide a good reference for scheduling

Effect of tool plunge depth on the microstructure and fracture behavior of refill friction stir spot welded AZ91 magnesium alloy joints

We used refill friction stir spot welding(RFSSW)to join 2-mm-thick AZ91D-H24 magnesium alloy sheets,and we investigated in detail the effect of tool plunge depth on the microstructure and fracture behavior of the joints.A sound joint surface can be obtained using plunge depths of 2.0 and 2.5 mm.Plunge depth was found to significantly affect the height of the hook,with greater plunge depths corresponding to more severe upward bending of the hook,which compromised the tensile-shear properties of the joints.The hardness reached a minimum at the thermo-mechanically affected zone due to the precipitation phases of this zone as it dissolved into theα-matrix during the welding process.The fracture modes of RFSSW joints can be divided into three types:shear fracture,plug fracture,and shear–plug fracture.Of these,the joint with a shear–plug fracture exhibited the best tensile-shear load of 6400 N.

Effect of refilling time on microstructure and mechanical properties of friction spot welded LY12 aluminum alloy

Friction spot welding （FSpW） was successfully used to produce joints of LY12 aluminum alloy. The effects of refilling time on microstructure and mechanical properties of FSpW joints were systematically studied. Results show that the cross-section of FSpW joint presents a basin-like morphology. A white bonding ligament exists in the center of the joint. The stir zone can be clarified into sleeve affected zone and pin affected zone based on different grain sizes. With increasing the refilling time from 2. 0 s to 3.5 s, grains in the stir zone become coarser, microhardness of the joint decreases and tensile shear failure load of the joint firstly increases and then decreases. The maximum tensile shear failure load of 8 130 N is attained when the refilling time is 3.0 s. Shear-plug fracture mode and shear fracture mode can be observed in the tensile shear tests. The maximum hardness of 169. 7 HV is attained in the joint center when the refilling time is 2. 0 s.

Refill Friction Stir Spot Welding Al Alloy to Copper via Pure Metallurgical Joining Mechanism

The current investigation of refill friction stir spot welding(refill FSSW)Al alloy to copper primarily involved plunging the tool into bottom copper sheet to achieve both metallurgical and mechanical interfacial bonding.Compared to conventional FSSW and pinless FSSW,weld strength can be significantly improved by using this method.Nevertheless,tool wear is a critical issue during refill FSSW.In this study,defect-free Al/copper dissimilar welds were successfully fabricated using refill FSSW by only plunging the tool into top Al alloy sheet.Overall,two types of continuous and ultra-thin intermetallic compounds(IMCs)layers were identified at the whole Al/copper interface.Also,strong evidence of melting and resolidification was observed in the localized region.The peak temperature obtained at the center of Al/copper interface was 591℃,and the heating rate reached up to 916℃/s during the sleeve penetration phase.A softened weld region was produced via refill FSSW process,the hardness profile exhibited a W-shaped appearance along middle thickness of top Al alloy.The weld lap shear load was insensitive to the welding condition,whose scatter was rather small.The fracture path exclusively propagated along the IMCs layer of Cu_(9)Al_(4) under the external lap shear loadings,both CuAl_(2) and Cu_(9)Al_(4) were detected on the fractured surface on the copper side.This research indicated that acceptable weld strength can be achieved via pure metallurgical joining mechanism,which has significant potential for the industrial applications.

Capillary refill time as a guide for operational decision-making process of autoimmune pancreatitis:Preliminary results

AIM: To investigate the efficacy of a novel intraoperative diagnostic technique for patients with preliminary diagnosis of autoimmune pancreatitis(AIP).METHODS: Patients with pancreatic surgery were reviewed to identify those who received a preliminary diagnosis of AIP between January 2010 and January 2014. The following data were collected prospectively for patients with a pathological diagnosis of AIP: clinical and demographic features, radiological and operative findings, treatment procedure, and intraoperative capillary refill time(CRT) in the pancreatic bed.RESULTS: Eight patients(six males, two females; mean age: 51.4 years) met the eligibility criteria of pathologically confirmed diagnosis. The most frequent presenting symptoms were epigastric pain and weight loss. The most commonly conducted preoperative imaging studies were computed tomography and endoscopic retrograde pancreaticodoudenography. The most common intraoperative macroscopic observations were mass formation in the pancreatic head and diffuse hypervascularization in the pancreatic bed. All patients showed decreased CRT(median value: 0.76 s, range: 0.58-1.35). One-half of the patients underwent surgical resection and the other half received medical treatment without any further surgical intervention. CONCLUSION: This preliminary study demonstrates a novel experience with measurement of CRT in the pancreatic bed during the intraoperative evaluation of patients with AIP.

Material flow behavior and microstructural evolution during refill friction stir spot welding of alclad 2A12-T4 aluminum alloy

In this study, we used the stop-action technique to experimentally investigate the material flow and microstructural evolution of alclad 2A12-T4 aluminum alloy during refill friction stir spot welding.There are two material flow components, i.e., the inward-or outward-directed spiral flow on the horizontal plane and the upward-or downward-directed flow on the vertical plane.In the plunge stage, the flow of plasticized metal into the cavity is similar to that of a stack, whereby the upper layer is pushed upward by the lower layer.In the refill stage, this is process reversed.As such, there is no obvious vertical plasticized metal flow between adjacent layers.Welding leads to the coarsening of S(Al2CuMg) in the thermo-mechanically affected zone and the diminishing of S in the stir zone.Continuous dynamic recrystallization results in the formation of fine equiaxed grains in the stir zone, but this process becomes difficult in the thermo-mechanically affected zone due to the lower deformation rate and the pinning action of S precipitates on the dislocations and sub-grain boundaries, which leads to a high fraction of low-angle grain boundaries in this zone.

5A06/AZ31异质合金RFSSW接头组织及性能研究

采用不同的焊具搅拌转速和扎入深度开展了5A06铝合金上板/AZ31镁合金下板的回填式搅拌摩擦点焊试验,观察了焊点的宏观形貌,采用显微硬度及拉剪性能测试手段获得了焊点横截面的硬度分布和拉剪承载性能,并对搅拌套下方界面的晶粒、金属间化合物(IMC)层进行了微观表征和成分分布定量分析。结果表明,焊点表面成形均较好,当搅拌速度、扎入深度过大时焊点表面出现较多飞边。当焊具搅拌速度为1900 r/min,扎入深度为1.6 mm时,拉剪强度最大,但也仅为57.65 MPa。在拉剪载荷下,焊点沿着界面水平方向断裂,断口呈现脆性断裂特征。随着焊接热输入增大,界面金属间化合物反应层变厚,反应产物为β-Al3Mg2和γ-Al12Mg17。因脆性相与合金基体之间存在热应力,界面位置出现微裂纹。搅拌套下方焊点界面两侧金属产生塑性变形并逐渐累积,促进动态再结晶形核,形成再结晶晶粒。

Al/Ti异质合金回填式搅拌摩擦点焊数值模拟

采用耦合的欧拉-拉格朗日(CEL)算法对2 mm厚的5A02铝合金/TC4钛合金板异质金属回填式搅拌摩擦点焊过程展开模拟研究,分析了旋转速度和停留时间对焊点成型过程中温度场、等效塑性应变场以及材料流动的影响。结果表明,在扎入初期,热累积作用明显,升温速率相对较快,随焊接过程进行,产热会由摩擦产热转变为摩擦和塑性变形共同产热,升温速率放缓。当搅拌头转速为2000 r/min、扎入速度为1 mm/s、扎入深度为1.9 mm、回填速度为1mm/s、停留时间为0 s时,铝合金焊核区温度峰值达到558℃,等效塑性应变峰值达到120。在模拟的工艺区间内,焊核区峰值温度与旋转速度呈正相关,停留时间对温度的影响并不明显。

面向新时期新需求的三峡水库运行方案研究

本文回顾三峡水库设计洪水、特征水位、运行方案变化调整过程,综述三峡水库运行调度关键技术研究进展和分析来水来沙变化情况。分别采用最可能洪水地区组成法和非一致性洪水频率分析两种途径,推求考虑上游水库群调蓄影响的三峡水库运行期设计洪水及特征水位。结果表明:近10年三峡入库泥沙量比初设成果减少了84.4%,宜昌站水文情势IHA-RVA综合指标为74%、发生了重度改变,三峡水库运行期1000年一遇7~15 d洪量减少了约81.5亿~142.8亿m^(3),初设确定汛限水位的主要制约因素(防洪、泥沙)发生了很大的变化。原单站设计洪水及确定的三峡水库175-155-145 m运行方案,已无法满足新时期水资源高效利用和生态环境保护的新需求。建议把三峡水库运行方案调整为175-160-155 m,主汛期水位在155~160 m区间动态控制运行,长江中下游梅雨结束后应考虑提前蓄水,8月底蓄至163 m左右,9月底蓄至165 m,10月底蓄满。该方案在保证大坝和下游防洪安全的前提下,汛期减少弃水并增加枯水期补水量,预计可增发10%左右的发电量;抬高运行水位也有利于库区航运和减少消落带;9月份尽量不蓄水或少蓄水,可减少蓄水期对下游河道及两湖生态环境的不利影响,具有巨大的经济、社会和生态环境等综合利用效益。当预测预报长江流域可能发生流域性大洪水时,尽快将库水位消落至汛限水位145 m,确保大坝和下游防洪安全。

参附注射液联合血必净注射液对脓毒症心肌病患者循环和毛细血管充盈时间的影响

目的 评价参附注射液加血必净注射液对(脓毒症心肌病SIC)患者循环和毛细血管充盈时间的影响。方法 将87例SIC患者随机分为治疗组和对照组,对照组44例,治疗组43例。对照组患者给予脓毒症集束化治疗;治疗组在对照组的基础上给予血必净注射液加参附注射液静脉滴注,两组疗程均为3 d。评估病情和预后指标(APACHEⅡ评分、SOFA评分)、心肌损伤标志物(cTnT、NT-ProBNP)、血流动力学指标(MAP、CVP、CI)、微循环指标(Lac、24 h Lac清除率、CRT)。结果 治疗后,两组APACHEⅡ评分、SOFA评分、cTnT、NT-ProBNP、Lac、CRT均降低(P<0.05),均以治疗组更明显(P<0.05),24 h Lac清除率治疗组高于对照组(P<0.05)。治疗后两组患者MAP、CVP较治疗前均升高,治疗后24、48、72 h,治疗组CI高于照组;治疗后第6、24 h,治疗组患者Lac低于对照组(P<0.05);治疗后第3、6、24 h,治疗组患者CRT低于对照组(P<0.05)。结论 在西医常规集束化治疗的基础上,加用参附注射液和血必净注射液治疗,可改善微循环及血流动力学,抑制心肌损伤,有利于改善SIC患者的心功能。

基于射流补水的水泵水轮机S特性改善研究

针对水泵水轮机的“S”特性提出了在导叶顶盖位置无叶区处加装注水管的解决方案,并模拟了注水管安装在不同位置时的“S”特性曲线,分析了加装注水管后转轮区域内流线及转轮各叶道流量的分布规律。结果表明,于导叶顶盖加装注水管可以有效改善转轮内部流动,减轻转轮和导叶内部流动的相互影响,减小叶道涡的尺寸,同时有效缓解了转轮各叶道流量分布不均的现象。在注水管处于无叶区中段和活动导叶附近时,对“S”特性的改善效果明显。

铝合金回填式搅拌摩擦点焊研究现状

回填式搅拌摩擦点焊作为一种先进的固相焊接技术,能够有效避免液相焊接的固有缺陷,同时消除搅拌摩擦点焊带来的匙孔,因此,在铝合金、镁合金等轻质金属点连接领域有着无可替代的优势,受到了国内外学者的广泛关注。经过多年的发展,回填式搅拌摩擦点焊已经不再局限于早期的套筒下扎模式,而是出现了多种不同的类型和模式,如额外填充式搅拌摩擦点焊、两阶段回填式搅拌摩擦点焊等。本文综述了近年来回填式搅拌摩擦点焊在铝合金焊接领域的研究现状,涉及点焊过程的基本工作原理,焊接工艺及接头组织性能研究,以及焊接接头的常见失效行为分析。本文对工程中回填式搅拌摩擦点焊接头性能的优化、工艺参数的合理选择提供一定的借鉴作用。

中心到外周的体温梯度和毛细血管再充盈时间对患者术中组织灌注的预测价值

目的探讨中心到外周的体温梯度(Tc-toe)和毛细血管再充盈时间(CRT)对患者术中组织灌注的预测价值。方法采用回顾性病例对照研究方法,选取2023年4月至7月于上海交通大学医学院附属同仁医院外科重症监护室收治的148例患者为研究对象,按照乳酸水平是否异常将其分为对照组(91例,乳酸水平<2.0 mmol/L)和病例组(57例,乳酸水平≥2.0 mmol/L)。比较两组相关指标。将乳酸作为因变量,将单因素分析结果中P<0.2的因素进行多因素logistic回归分析。受试者操作特征(ROC)曲线评估患者术中组织灌注的预测价值。结果两组手术时间、术中失血量、Tc-toe、CRT、意识和急诊手术情况比较,差异有统计学意义(P<0.05)。单因素logistic回归分析显示,Tc-toe、CRT、年龄、意识、术中失血量和急诊手术与乳酸水平有关(P<0.05)。多因素logistic回归分析显示,Tc-toe(OR=5.97,95%CI:1.55~23.04,P<0.05)、CRT(OR=38.48,95%CI:7.68~192.78,P<0.05)、肌酐(OR=0.07,95%CI:0.01~0.79,P<0.05)和冠心病/心律失常(OR=0.15,95%CI:0.03~0.83,P<0.05)是患者术中组织灌注的独立影响因素。ROC曲线分析显示,Tc-toe预测组织灌注的曲线下面积为0.876,截断值为1.05℃,灵敏度为80.22%,特异度为87.72%;CRT预测组织灌注的曲线下面积为0.919,截断值为2.5 s,灵敏度为74.73%,特异度为96.49%。结论Tc-toe和CRT可通过预测血乳酸水平,从而预测患者术中组织灌注情况。

大型沉井流塑状粉质黏土地基固结排水分析

为了探究一种加快沉井地基土体固结排水效率的施工方法及其对沉井结构受力安全性影响,基于南京长江河段某过江通道悬索桥锚碇大型沉井基础,开展实测和数值模拟分析,研究换填沙袋处理配合沉井对角浇筑方法在流塑状粉质黏土地基基础施工过程中的影响。结果表明:在沉井井壁和隔墙底部采取换填沙袋处理后,沉井浇筑和接高施工进度可不受粉质黏土排水固结过程控制,而主要取决于沉井结构混凝土强度的增长情况。换填沙袋地基处理可以提升固结排水效率,但容易出现地基不均匀现象,从而产生沉井结构受力安全性问题。

铝-钢异种材料回填式搅拌摩擦点焊接头界面连接机制与力学性能研究

以5754铝合金与DC04钢为研究对象,进行了铝板在上的回填式搅拌摩擦点焊试验,研究了搅拌套下扎深度对铝-钢界面微观组织特征与接头力学性能的影响。结果表明,当搅拌套未扎入下层钢板时,冶金结合为铝-钢界面的主要连接机制。当搅拌套扎入下层钢板时,铝-钢界面同时发生机械咬合与冶金结合,其中,机械咬合主要发生在搅拌套作用区。通过工艺优化得出最优工艺参数为:转速2000 r/min、焊速0.5 mm/s,搅拌套下扎深度1.45 mm,此时接头最大拉剪失效载荷达5105 N。

华北土石山区油松生长季夜间液流分配特征

【目的】通过对油松生长季夜间液流特征和环境驱动因素的研究,揭示夜间液流组分拆分特征,探讨夜间液流的组分与气象因子之间的相关关系,以及茎干补水对气象因子的响应,为华北土石山区水资源和水源涵养林管理决策提供理论依据。【方法】以华北土石山区的油松作为研究对象,根据径阶大小选取18棵样树,在2014年生长季运用Granier热扩散探针技术(TDP)持续观测夜间液流,结合称重式蒸渗仪和自制微型蒸渗仪来计算蒸腾量,解析夜间液流的去向;并进行夜间液流与土壤含水量、大气温度、湿度及光合有效辐射等气象因子的相关分析,以确定主要驱动因素。【结果】在6—9月典型晴天,夜间液流速率都呈逐渐降低趋势,18:00—24:00的夜间液流速率高于00:00—05:00,夜间液流主要用于对白天失水过多的茎干进行补水,以至于在24:00时油松茎干储水量基本达到饱和,因此,00:00—05:00夜间液流速率趋于稳定;油松夜间液流用于茎干补水的比例(95.34%)显著高于用于夜间蒸腾量的比例(4.66%);油松夜间茎干补水量与饱和水汽压差呈极显著正相关(R^(2)=0.793,P<0.01),而对土壤含水量变化响应不敏感(R^(2)=0.105,P>0.05),表明夜间液流主要受饱和水汽压影响。【结论】华北土石山区的油松生长季夜间液流随着夜间时间的进行呈现逐渐降低的趋势;绝大部分的夜间液流用于夜间茎干补水,在气象因子中,饱和水汽压是驱动夜间茎干补水及夜间液流的重要因子(P<0.01)。

Refill friction stir spot welding (RFSSW): a review of processing, similar/dissimilar materials joining, mechanical properties and fracture mechanism

Refill friction stir spot welding(RFSSW)provides a novel method to join similar and/or dissimilar metallic materials without a key-hole in the center of the joint.Having the key-hole free characterization,the similar/dissimilar RFSSW joint exhibits remarkable and endurable characteristics,including high shear strength,long fatigue life,and strong corrosion resistance.In the meanwhile,as the key-hole free joint has different microstructures compared with conventional friction stir spot welding,thus the RFSSW joint shall possess different shear and fatigue fracture mechanisms,which needs further investigation.To explore the underlying failure mechanism,the similar/dissimilar metallic material joining parameters and pre-treatment,mechanical properties,as well as fracture mechanisms under this novel technology will be discussed.In details,the welding tool design,welding parameters setting,and the influence of processing on the lap shear and fatigue properties,as well as the corrosion resistance will be mainly discussed.Moreover,the roadmap of RFFSW is also discussed.

Effect of thermo-mechanical conditions during constrained friction processing on the particle refinement of AM50 Mg-alloy phases

Constrained Friction Processing(CFP)is a novel solid-state processing technique suitable for lightweight materials,such Mg-and Al-alloys.The technique enables grain size refinement to fine or even ultrafine scale.In this study,the effect of CFP on the microstructural refinement of AM50 rods is investigated in terms of particle size and morphology of the eutectic and secondary phases originally present in the base material,in particular the eutecticβ-Mg_(17)Al_(12)and Al-Mn phases.For that purpose,as-cast and solution heat-treated base material and processed samples were analyzed.The Al_(8)Mn_(5) intermetallic phase was identified as the main secondary phase present in all samples before and after the processing.A notorious refinement of these particles was observed,starting from particles with an average equivalent length of a few micrometers to around 560 nm after the processing.The refinement of the secondary phase refinement is attributed to a mechanism analogous to the attrition comminution,where the combination of temperature increase and shearing of the material enables the continuous breaking of the brittle intermetallic particles into smaller pieces.As for the eutectic phase,the results indicate the presence of the partially divorcedβ-Mg_(17)Al_(12)particles exclusively in the as-cast base material,indicating that no further phase transformations regarding the eutectic phase,such as dynamic precipitation,occurred after the CFP.In the case of the processed as-cast material analyzed after the CFP,the thermal energy generated during the processing led to temperature values above the solvus limit of the eutectic phase,which associated with the mechanical breakage of the particles,enabled the complete dissolution of this phase.Therefore,CFP was successfully demonstrated to promote an extensive microstructure refinement in multiple aspects,in terms of grain sizes of theα-Mg phase and presence and morphology of the Al-Mn and eutecticβ-Mg_(17)Al_(12).

金沙江下游梯级水库提前蓄水策略

随着长江上游水库群汛末集中蓄水问题日益突出,在确保防洪安全的前提下,提前抬升水库运行水位,有序衔接防洪与蓄水调度显得尤为重要。以金沙江下游乌东德、白鹤滩、溪洛渡、向家坝梯级水库为研究对象,选取发电量和水资源利用率为评价指标,探究汛期7—8月份梯级水库提前蓄水策略。研究结果表明:①平水(50%频率)、枯水(75%频率)和特枯(90%频率)来水条件下,乌东德、白鹤滩梯级水库应尽可能提前抬升运行水位,且优先抬升乌东德库水位。②7月份平水、8月份平水或枯水条件下,应优先将乌东德库水位抬升至960 m以上;7月份枯水、8月份平水或枯水条件下,应优先将乌东德库水位抬升至954 m以上。③不同来水条件下,溪洛渡水库应尽可能抬升库水位,但最高不超过585 m。

6082铝合金回填式搅拌摩擦点焊对接接头的组织和性能研究

将回填式搅拌摩擦点焊首次应用到铝合金的对接过程中。本文研究了搅拌头转速对2 mm厚的6082铝合金对接接头显微组织和性能的影响。结果表明,使用1.6 mm的搅拌头下压量可有效避免接头底部未焊合。但当转速为1950 r/min时,搅拌套筒回抽路径的外沿形成热裂纹。焊核区晶粒明显细化,当转速为1350 r/min时,焊核区平均晶粒尺寸由母材的30.84μm减小至8.43μm;热机影响区和焊核区的织构也发生明显变化。焊缝的硬度整体上高于母材的,这与焊缝中较小的晶粒有关。当转速为1650 r/min时接头的强度最高,达到190 MPa;当转速为1950 r/min时,因热机影响区/焊核区截面的裂纹缺陷影响,接头的抗拉强度仅为121 MPa。