Changes in Aerosol Optical Depth over the Arctic Ocean as Seen by CALIOP, MAIAC, and MODIS C6.1

Due to the recent increase in Arctic shipping, 2006-2020 June to October Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), Moderate Resolution Imaging Spectroradiometer (MODIS) Collection 6.1 (C6.1), and Multi-Angle Implementation of Atmospheric Correction (MAIAC) retrieved aerosol optical depth (AOD) data were examined for changes in AOD from period 1 (P1, 2006-2012) to period 2 (P2, 2014-2020 (P2). Herein, AOD was statistically analyzed on a 0.25° × 0.25° grid and in the airsheds over the various ocean basins over the Arctic north of 59.75°N. According to heatmaps of the correlation between AOD and ship traffic, and AOD and fire emissions for the airsheds, all three AOD products captured the observed inter-annual variability in wildfire occurrence well, and showed wildfire emissions over Siberia were more severe in P2 than P1. Except for the Atlantic, North, and Baltic Seas, Beaufort Sea, and Barents Sea, all three AOD products indicated that AOD was higher over the various basins in P2 than P1, but disagreed on the magnitude. This fact suggests that the detection of changes in the typical low AOD over the Arctic Ocean might be rather qualitative than quantitative. While all products captured increases in AOD due to ships at berth, only MODIS C6.1 caught the elevated AOD due to shipping on the Siberian rivers. Obviously, sub-daily resolutions are required to capture increased AOD due to short-term events like a traveling ship or short-interval fire.

基于定切深和状态依赖时滞的共振冲击钻井系统动力学特性

为了研究共振冲击钻井系统的动力学特性,综合考虑钻柱的轴向动-静载复合冲击以及轴向冲击-周向扭转耦合运动,分别建立基于定切深方法和状态依赖时滞方法的钻进系统动力学模型。通过杜哈梅积分、四阶龙格-库塔方法对动力学模型求解,分析轴向简谐动载的频率和幅值对共振钻井系统动力学特性的影响;最后,基于数值求解结果和箱线图方法,对比分析两种钻进系统动力学模型特性差异。结果表明:在给定的初始条件下,当简谐动载频率从25 Hz提高到100 Hz时,钻进系统轴向方向的跳钻现象和扭转方向的黏滑效应明显减弱;当简谐动载幅值从30 kN提高到60 kN时,钻进系统轴向方向钻头跳钻现象频发,扭转方向黏滑效应加剧;在相同初始条件和简谐动载激励下,两种模型得到的动力学特性响应曲线无论是形状还是频率均存在差异,采用状态依赖时滞模型计算得到的数据点更加集中,更接近实际钻井工况;高频低幅的简谐动载能改善共振冲击钻井系统动力学特性,从而提高钻进效率。

抛浆除鳞工艺中氧化皮去除模型研究

针对抛浆除鳞缺乏精确的氧化皮去除量与工艺参数相关数学模型的问题,以Q235热轧板带表面氧化皮为研究对象,依据能量守恒分析抛浆工艺中磨粒与水的混合浆体在冲击过程中的动能变化规律,根据应变能理论分析基体表面氧化皮在浆体冲击后的应变能变化规律,建立氧化皮去除量与抛浆工艺参数之间的数学模型.利用光滑粒子流体动力学,采用有限元ANSYS/AUTODYN模块,对抛浆过程中氧化皮与基体变形的过程进行模拟,采用抛、喷浆一体化除鳞实验平台进行抛浆除鳞实验.结果表明,当基体表面氧化皮应变高于临界应变时,氧化皮会破裂剥落;磨粒粒径对冲击范围增加率的影响与冲击速度的比值为105.35%∶24.14%,磨粒粒径对冲击深度增加率的影响与冲击速度的比值为233.67%∶5.86%,冲击范围有限元计算结果与实验结果最大偏差率为8.71%,冲击深度最大偏差率为8.55%.磨粒冲击次数解析法、有限元计算结果与实验结果一致,利用304不锈钢和45钢的抛浆除鳞实验结果验证了模型的广泛适用性.

气候变暖对吉林省降雪量与新增雪深关系的影响

降雪量和积雪深度的关系是降雪预报及水文气候模拟中的重要参数。本文利用吉林省50个站点1961—2021年的降水量、积雪深度、气温、风速和天气现象等气象观测资料,分析了降雪量和新增积雪深度的关系及主要气候影响因子。结果表明,在中等及以上强度的降雪过程中,吉林省新增积雪深度(D)与降雪量(S)的比值(深量比,Rds)平均为0.96 cm·mm^(-1);该比值存在空间差异,呈西部小东部大的分布特征,且存在明显的月际、年际和年代际变化特征,其中月际变化呈现不对称的抛物线型,12月和1月为大值时段;近60年来Rds呈减小趋势,变化速率为-0.01 cm·mm^(-1)·(10a)^(-1);降雪日Rds与气温呈明显反相关关系,其中在-12~0℃的温度区间,Rds随气温上升呈明显减小趋势。气候变暖、降水量增加和风速的减小是降雪过程中降雪量与新增雪深关系年代际变化的直接原因。揭示降雪量和新增雪深的关系对于认识东北亚中高纬度降雪积雪特征及其成因具有重要意义。

种植体支抗联合闭合式牵引在颌骨内埋伏牙、阻生牙患者中的应用效果及对治疗后康复、口腔健康的影响

目的探讨种植体支抗联合闭合式牵引在颌骨内埋伏牙、阻生牙患者中的应用效果及对治疗后康复、口腔健康的影响。方法选取2019年1月—2022年5月收治的颌骨内埋伏牙、阻生牙90例,根据治疗方法不同将其分为观察组和对照组2组各45例。观察组采取种植体支抗联合闭合式牵引治疗,对照组采取闭合式开窗术加传统固定治疗。比较2组治疗后临床效果、康复情况,治疗前和治疗后4个月龈沟液细胞因子、口腔健康微生态环境、咀嚼功能,以及治疗后4个月内不良反应发生情况。结果治疗后,观察组总有效率95.56%(43/45)高于对照组80.00%(36/45),疼痛程度低于对照组(P<0.05)。治疗后4个月,2组龈沟液丝氨酸蛋白酶抑制剂、基质金属蛋白酶-3、白细胞介素-1β和牙周袋探诊深度、牙龈指数、龈沟出血指数、菌斑指数、牙齿松动度均较治疗前升高,且观察组低于对照组(P<0.01)。治疗后4个月,2组咀嚼效率、咬合力均高于治疗前,咀嚼疼痛评分低于治疗前,且观察组咀嚼效率、咬合力高于对照组,咀嚼疼痛评分低于对照组(P<0.01)。治疗后4个月内,2组不良反应发生率比较差异无统计学意义(P>0.05)。结论种植体支抗联合闭合式牵引应用于颌骨内埋伏牙、阻生牙效果显著,可促进牙齿萌出、恢复咀嚼功能,改善治疗后口腔健康微生态环境及炎症状态,具有较好安全性。

本钢板材炼钢厂氧枪喷头工作参数分析

氧枪是氧气转炉中的最重要工艺设备之一,其性能特征直接影响到冶炼效果和吹炼时间,从而影响最终的钢材性能和钢产量。氧枪通过氧气射流流股与熔池的相互作用来实现吹炼交互,这种作用取决于氧气射流达到熔池表面时的速度大小和其冲击面积、冲击深度,因此优化氧枪喷头的工艺参数和合理的结构设计非常重要。通过对本钢板材炼钢厂的氧枪喷头工作参数进行计算,结合现场的实际工况,得出最适合本钢的操作模式。

超重型液压快速夯实技术对周边环境的振动影响分析

液压快速夯实技术在地基处理中适用范围广、加固效果好,但关于超重型液压快速夯实技术对周边环境的振动影响及有效加固深度仍需进一步探讨。本文以济南国际机场二期改扩建项目为研究背景,场地浅层分布2~7 m的难压实、可液化粉土地层,极易在机场运营期间产生液化危害,因此在机场项目正式施工前,设计6种不同夯击能级的强夯、液压夯地基处理现场试验,对比研究150 kJ超重型液压快速夯实技术对周边环境的振动影响,并在150 kJ超重型液压夯试验前后分别进行标准贯入试验,分析150 kJ超重型液压夯的有效加固深度。研究表明:150 kJ超重型液压夯在距发振点10 m时满足小于等于24 mm/s的容许振动值要求,在距发振点15 m时满足小于等于12 mm/s的容许振动值要求,在距发振点超过15 m时,70 kJ、110 kJ及150 kJ液压夯均对周边环境产生的振动影响较小;150 kJ超重型液压夯在2~8 m范围内加固效果明显,在10 m时有一定的加固效果;在距发振点超过15 m时,采用150 kJ超重型液压夯既能满足对居住建筑容许振动值的要求,又能增大加固深度,提高经济效益。

Ballistic model for the prediction of penetration depth and residual velocity in adobe:A new interpretation of the ballistic resistance of earthen masonry

In this paper, a new one-dimensional phenomenological model is developed for the assessment of the ballistic performance of Adobe. Adobe is a masonry largely spread in areas of the world involved in military operations. Addressing fundamental ballistic parameters such as residual velocity or penetration depth for this building technology is necessary. The model follows the hypotheses for the ballistic response of concrete targets to high velocity impacts, provided with a dominant contribution of shear friction typical of soils. The hypotheses at the basis of the model are consistent with all experimental evidence collected by authors on Adobe. Adobe brick and mortar belong to the material class of concrete,whereas the overall mechanical parameters are determined by the internal soil mixture, including the percentage of fibre reinforcement. Despite its relative simplicity, the model is capable of well predicting ballistic test results currently available in literature for Adobe, including the data of an experimental campaign recently performed by the authors on real Adobe walls in the field.

Impact toughness of a gradient hardened layer of Cr5Mo1V steel treated by laser shock peening

Laser shock peening（LSP） is a widely used surface treatment technique that can effectively improve the fatigue life and impact toughness of metal parts.Cr5Mo1 V steel exhibits a gradient hardened layer after a LSP process.A new method is proposed to estimate the impact toughness that considers the changing mechanical properties in the gradient hardened layer.Assuming a linearly gradient distribution of impact toughness,the parameters controlling the impact toughness of the gradient hardened layer were given.The influence of laser power densities and the number of laser shots on the impact toughness were investigated.The impact toughness of the laser peened layer improves compared with an untreated specimen,and the impact toughness increases with the laser power densities and decreases with the number of laser shots.Through the fracture morphology analysis by a scanning electron microscope,we established that the Cr5Mo1 V steel was fractured by the cleavage fracture mechanism combined with a few dimples.The increase in the impact toughness of the material after LSP is observed because of the decreased dimension and increased fraction of the cleavage fracture in the gradient hardened layer.

Assessment of rapid impact compaction in ground improvement from in-situ testing

Ground improvement has been used on many construction sites to densify granular materials,in other word,to improve soil properties and reduce potential settlement.This work presents a case study of ground improvement using rapid impact compaction(RIC).The research site comprises the construction of workshop and depots as part of railway development project at Batu Gajah-Ipoh,Malaysia.In-situ testing results show that the subsurface soil comprises mainly of sand and silty sand through the investigated depth extended to 10m.Groundwater is approximately 0.5m below the ground surface.Evaluation of improvement was based on the results of pre-and post-improvement cone penetration test(CPT).Interpretation software has been used to infer soil properties.Load test was conducted to estimate soil settlement.It is found that the technique succeeds in improving soil properties namely the relative density increases from 45% to 70%,the friction angle of soil is increased by an average of 3o,and the soil settlement is reduced by 50%.The technique succeeds in improving soil properties to approximately 5.0m in depth depending on soil uniformity with depth.

Punching and Local Damages of Fiber and FRP Reinforced Concrete under Low-Velocity Impact Load

In recent years, the development and application of high performance fiber reinforced concrete or cementitious composites are increasing due to their high ductility and energy absorption characteristics. However, it is difficult to obtain the required properties of the FRCC by simply adding fiber to the concrete matrix. Many researchers are paying attention to fiber reinforced polymers (FRP) for the reinforcement of construction structures because of their significant advantages over high strain rates. However, the actual FRP products are skill-dependent, and the quality may not be uniform. Therefore, in this study, two-way punching tests were carried out to evaluate the performances of FRP strengthened and steel and polyvinyl alcohol (PVA) fiber reinforced concrete specimens for impact and static loads. The FRP reinforced normal concrete (NC), steel fiber reinforced concrete (SFRC), and PVA FRCC specimens showed twice the amount of enhanced dissipated energy (total energy) under impact loadings than the non-retrofitted specimens. In the low-velocity impact test of the two-way NC specimens strengthened by FRPs, the total dissipated energy increased by 4 to 5 times greater than the plain NC series. For the two-way specimens, the total energy increased by 217% between the non-retrofitted SFRC and NC specimens. The total dissipated energy of the CFRP retrofitted SFRC was twice greater than that of the plain SFRC series. The PVA FRCC specimens showed 4 times greater dissipated energy than for the energy of the plain NC specimens. For the penetration of two-way specimens with fibers, the Hughes formula considering the tensile strength of concrete was a better predictor than other empirical formulae.

增强剂的有效渗透深度对水工混凝土性能的影响研究

寒区水工混凝土施工时,控制不当会出现混凝土强度偏低、抗冻性能及抗冲磨性能较差的问题。为避免出现此类情况,通过对比3种不同增强剂样品在同种混凝土中的有效渗透,分析增强剂在不同混凝土中的有效渗透深度及其对混凝土抗冻性能和抗冲磨性能的影响。结果表明,不同增强剂溶液在相同混凝土中的有效渗透深度越大,其渗入量就越多,其强度提升幅度也越大,最大可使强度回弹值提高24.1%;在不同的混凝土中,水胶比越大,抗冻性能越差,增强剂在混凝土中有效渗透深度也越大,抗冻增长率最高可达到80%;随着混凝土水胶比变大,其密实度变差,抗冲磨性能下降,但增强剂有效渗透深度变大,抗冲磨增长率也变高,最高可增至28.3%。

基于磁定位技术的冲击侵彻尺度的测量

在小天体的探测任务中,探测器需要应对小行星表面特殊的风化层地貌环境。而人们目前对于风化层与探测器间的多尺度、强非线性的复杂动力学行为认知尚不充分,且对于撞击侵彻参数的测量缺乏合适的方法。为了掌握着陆过程中探测器的侵彻尺度关系,提出了一种实验室环境下基于磁偶极子模型的撞击动力学测量系统,通过迭代标定和GA-LM最优化算法提高了定位精度。将其应用于斜坡的撞击实验中,测量了撞击过程中撞击物2个方向的侵彻深度数据。结果表明:通过迭代标定算法和GA-LM算法平均提高了三轴31%的定位精度,使得最终的单轴定位误差小于3 mm;撞击斜坡过程中存在Y方向垂直穿透和Z方向横向滑动两种侵彻过程。Y方向的垂直穿透与下落高度符合1/3的幂律关系,而Z方向的滑动位移的标度规律并不稳定,原因是存在颗粒层崩塌的影响,并使得该位移与下落高度呈现非线性增加特征。

PDC钻头复合冲击井下破岩特性模拟研究

为对比各种冲击钻井技术的破岩效果,利用ABAQUS/Explicit模块建立PDC单齿-岩石冲击模型,研究PDC单齿在无冲击、轴向冲击、扭向冲击和复合冲击作用下的破岩特性,再进一步对影响复合冲击性能的因素进行分析。分析结果表明:在其他条件相同的条件下,复合冲击下的破岩比功相较于无冲击降低了28%,较轴向冲击降低了7%,以复合冲击破岩方式破岩效率最高;岩石在复合冲击作用条件下,钻压对PDC齿破岩效率影响较大,且存在明显差异,增大钻压有利于破碎岩石;转速对复合冲击破岩效率存在一个临界值,未达到这个值时,增大转速反而会降低PDC齿的破岩效率。所得结论可为复合冲击钻井工具选择合适的钻压和转速提供理论依据。

基于FEM⁃SPH自适应耦合方法的蓝宝石DOP性能研究

为了提高弹丸侵彻类高速冲击仿真的精确度,本文利用有限元法(Finite element method,FEM)⁃光滑粒子流法(Smooth particle hydrodynamics,SPH)自适应耦合模型对蓝宝石侵彻深度(Depth of penetration,DOP)实验过程开展了数值模拟研究。通过DOP实验,验证了该算法下仿真模型的准确性,并对比了传统FEM算法和FEM⁃SPH固定耦合算法仿真模型的计算结果。研究表明,FEM⁃SPH自适应耦合算法在计算精度上有明显优势。

液池深度对水滴撞击水面后形态特征影响的实验研究

用实验方法对液滴撞击液面后的形态特征及其机理进行了研究。用高速摄像机记录了不同液池深度下的液滴撞击液面过程,总结出了在不同阶段出现的液坑、液冠、中心射流和次生液滴等特征现象。基于计算机视觉算法开发了图像处理程序,实现了特征几何参数的自动提取。讨论了液池深度、韦伯数、初始液滴直径和液滴下落高度等因素对特征运动形态的影响。结果表明:在韦伯数一定的情况下,当液池深度跨越某个临界值时,液坑、液冠、中心射流和次生液滴等特征现象发生显著变化;液冠–液坑高度比随韦伯数的增大在一定范围内增大;中心射流能否分离出次生液滴与液池深度和初始液滴直径有密切的关系。

水工混凝土抗冲磨耗性能分析

文中就水胶比和PVA纤维掺量对粉煤灰混凝土耐磨性能的影响进行研究,并且分析了抗压强度与耐磨性能的关系。结果表明,混凝土的抗冲磨强度随着水胶比的增加而降低,磨损深度随着水胶比的增加而增加;PVA纤维体积掺量低于0.25%时,有助于提高混凝土的抗磨耗性能,抗磨耗性能与纤维掺量呈正相关关系;混凝土的耐磨性能与抗压强度呈正相关关系。

高压水射流煤层割缝深度数值模拟与实验研究

高压水射流割缝技术是提高低透气性煤层瓦斯抽采效率的有效措施之一,确定割缝深度是优化钻孔布置和射流参数的基础。基于Fluent软件数值模拟分析了入口压力、靶距、旋转速度对水射流流场特征的影响规律;基于高压水射流破煤实验系统,开展了淹没和非淹没条件下冲击破煤实验,并进行了现场实验。研究表明,喷嘴结构一定时,水射流速度随着入口压力的增大而增加,冲击压力随冲击距离增大而发生衰减;水射流发展过程中截面积逐渐增大,导致冲击压力集中区域的范围随靶距的增大而逐渐扩展;射流旋转会导致旋转方向一侧的应力大于另一侧,靶体表面最大切应力随旋转速度增加而增大;随着入口压力和冲蚀时间的增加,水射流对试样的冲蚀深度增大,但冲蚀深度随冲蚀时间的增加存在阈值。根据高压水射流破煤深度实验结果可知,喷嘴直径为1 mm、压力为30 MPa时,水射流割缝直径可以达到1.2 m。工程应用表明,割缝钻孔平均瓦斯抽采流量为普通钻孔的1.56~2.52倍;抽采16 d后,瓦斯抽采浓度维持在30%以上。

复合冲击相位差对破岩效率影响数值模拟研究

现有复合冲击破岩效率的研究均未考虑轴向冲击和扭转冲击载荷相位差对于破岩效率的影响,为此,进行了复合冲击载荷相位差对破岩效率影响的研究。建立了轴-扭复合冲击钻具PDC钻头单齿破岩数值模型,分析了轴向和扭转冲击应力波不同相位差对钻齿侵彻深度、切削面下岩石损伤以及钻后形成岩屑形态及数量的影响规律。研究结果表明:在轴向和扭转冲击载荷等振幅条件下,当相位差为50%时,侵彻深度最佳,切削面以下岩石损伤的程度更为明显;当轴向振幅较大,相位差为75%时,对于岩体侵彻深度效果的提升最为明显,破岩效果最佳;相位差为100%时,侵彻深度较深,且钻齿波动较小,产生的岩屑颗粒较小。研究结论可为复合冲击钻具结构的优化和运动参数的调整提供理论基础。

糯扎渡水电站不同调度下下泄低温水改善效果研究

【目的】大型水库下泄低温水影响及相应的减缓措施效果受到水库运行、取水方式等因素的影响,各因素之间彼此联系、相互作用。明晰水库运行方式对下泄水温的影响及其对叠梁门分层取水改善效果,可为大型水库的叠梁门分层取水效果评估及优化调度提供参考。【方法】以糯扎渡水电站为研究对象,建立糯扎渡立面二维水温数学模型,探讨水库运行方式对下泄水温及叠梁门分层取水效果的影响。【结果】结果显示:(1)水库修建后下泄水体存在明显的冬季高温水、夏季低温水现象,单独运行时,10月—次年2月水温较天然水温平均偏高2.0℃,4—6月偏低2.9℃。(2)与单独运行相比,糯扎渡水电站在梯级联合运行下的下泄水体升温效应更强,10月—次年2月水温平均升高2.5℃,3—8月水温平均升高1.4℃。(3)使用叠梁门后,4—8月下泄水温较单层取水时平均提高1.9℃,水温达到18℃的时间平均提前78 d。【结论】结果表明:澜沧江下游梯级联合运行对高温水产生叠加影响,对低温水表现出削弱影响;叠梁门抬高了取水流动层位置,对下泄水温有较好的改善作用,其改善效果与淹没水深、运行时段有明显的关系。