Experimental and Numerical Investigation of Local Scour Around Submarine Piggyback Pipeline Under Steady Current

As a new type of submarine pipeline, the piggyback pipeline has been gradually adopted in engineering practice to enhance the performance and safety of submarine pipelines. However, limited simulation work and few experimental studies have been published on the scour around the piggyback pipeline under steady current. This study numerically and experimentally investigates the local scour of the piggyback pipe under steady current. The influence of prominent factors such as pipe diameter, inflow Reynolds number, and gap between the main and small pipes, on the maximum scour depth have been examined and discussed in detail. Furthermore, one formula to predict the maximum scour depth under the piggyback pipeline has been derived based on the theoretical analysis of scour equilibrium. The feasibility of the proposed formula has been effectively calibrated by both experimental data and numerical results. The findings drawn from this study are instructive in the future design and application of the piggyback pipeline.

Full-Scale Numerical Simulation of the Local Scour Under Combined Current and Wave Conditions Based on Field Data

The monopile is the most common foundation to support offshore wind turbines.In the marine environment,local scour due to combined currents and waves is a significant issue that must be considered in the design of wind turbine foundations.In this paper,a full-scale numerical model was developed and validated based on field data from Rudong,China.The scour development around monopiles was investigated,and the effects of waves and the Reynolds number Re were analyzed.Several formulas for predicting the scour depth in the literature have been evaluated.It is found that waves can accelerate scour development even if the KC number is small(0.78<KC<1.57).The formula obtained from small-scale model tests may be unsafe or wasteful when it is applied in practical design due to the scale effect.A new equation for predicting the scour depth based on the average pile Reynolds number(Rea)is proposed and validated with field data.The equilibrium scour depth predicted using the proposed equation is evaluated and compared with those from nine equations in the literature.It is demonstrated that the values predicted from the proposed equation and from the S/M(Sheppard/Melville)equation are closer to the field data.

Mechanical behaviour analysis and support system field experiment of confined concrete arches

Soft rock control is a big challenge in underground engineering.As for this problem,a high-strength support technique of confined concrete(CC)arches is proposed and studied in this paper.Based on full-scale mechanical test system of arch,research is made on the failure mechanism and mechanical properties of CC arch.Then,a mechanical calculation model of circular section is established for the arches with arbitrary section and unequal rigidity;a calculation formula is deduced for the internal force of the arch;an analysis is made on the influence of different factors on the internal force of the arch;and a calculation formula is got for the bearing capacity of CC arch through the strength criterion of bearing capacity.With numerical calculation and laboratory experiment,the ultimate bearing capacity and internal force distribution is analyzed for CC arches.The research results show that:1)CC arch is 2.31 times higher in strength than the U-shaped steel arch and has better stability;2)The key damage position of the arch is the two sides;3)Theoretical analysis,numerical calculation and laboratory experiment have good consistency in the internal force distribution,bearing capacity,and deformation and failure modes of the arch.All of that verifies the correctness of the theoretical calculation.Based on the above results,a field experiment is carried out in Liangjia Mine.Compared with the U-shaped steel arch support,CC arch support is more effective in surrounding rock deformation control.The research results can provide a basis for the design of CC arch support in underground engineering.

Experimental and Numerical Study on the Gas Explosion in Urban Regulator Station

Regulator station is an important part in the urban gas transmission and distribution system.Once gas explosion occurs,the real explosion process and consequences of methane gas explosion in the regulator station were not revealed systematically.In this study,a full-scale experiment was carried out to simulate the regulator station explosion process,and some numerical simulations with a commercial CFD software called FLACS were conducted to analyze the effect of ignition and vent conditions on the blast overpressure and flame propagation.The experimental results demonstrated that the peak overpressure increased as the distance from the vent increased within a certain distance.And the maximum overpressure appeared 3 m away from the door,which was about 36.6 kPa.It was found that the pressure-time rising curves obtained from the simulation are basically the same as the ones from the experiment,however,the time of reaching the peak pressure was much shorter.The numerical simulation results show that the peak overpressures show an increase trend as the ignition height decreased and the vent relief pressure increased.It indicates that the damage and peak overpressure of gas explosion could be well predicted by FLACS in different styles of regulator station.In addition,the results help us to understand the internal mechanism and development process of gas explosion better.It also offers technical support for the safety protection of the urban regulator station.

Large scale sand saltation over hard surface:a controlled experiment in still air

Saltation is the major particle movement type in wind erosion process.Saltating sand grains can rebound up to tens of times larger in length and height over hard surface(such as gravel surface)than over loose sand surface.Gravels usually have different faces,causing distinct response of the impacting grains,but the effects of the grain and gravel-surface contact angle on grain rebound are not yet well quantified.We performed full-range controlled experiments of grain saltation using different contact angles,grain sizes and impact speeds in still air,to show that contact angle increases the height of representative saltation path but decreases particle travel length.The results were compared with outputs from the COMprehensive numerical model of SALTation(COMSALT).Large saltation height of 4.8 m and length of 9.0 m were recorded.The maximum and representative saltation height over the gravel surface were found to be about 4.9 times and 12.8 times those over the loose sandy surface,respectively.The maximum saltation length may be reduced by 58%and the representative saltation height may be increased by 77%as contact angle increases from 20°to 40°.We further showed that the collision inertia contributes 60%of the saltation length,and wind contributes to the other 40%.These quantitative findings have important implications for modeling saltation trajectory over gravel surface.

Error Model of Curves in GIS and Digitization Experiment

A stochastic error process of curves is proposed as the error model to describe the errors of curves in GIS. In terms of the stochastic process, four characteristics concerning the local error of curves, namely, mean error function, standard error function, absolute error function, and the correlation function of errors , are put forward. The total error of a curve is expressed by a mean square integral of the stochastic error process. The probabilistic meanings and geometric meanings of the characteristics mentioned above are also discussed. A scan digitization experiment is designed to check the efficiency of the model. In the experiment, a piece of contour line is digitized for more than 100 times and lots of sample functions are derived from the experiment. Finally, all the error characteristics are estimated on the basis of sample functions. The experiment results show that the systematic error in digitized map data is not negligible, and the errors of points on curves are chiefly dependent on the curvature and the concavity of the curves.

Experiments on Large-Diameter Welded Hollow Spherical Joint

We experimented on welded hollow spherical joint of a stadium steel roof to investigate the stress and strain distributions on the surface of the joint and determine the ultimate bearing capacity. Then, finite element analysis was made to experimental results. When the test load was 140% of the design load, the stress at the bottom of the fourth wimble pipe reached the yield point. The experimental results agree with the analytical results well.

Investigation on the Concept of Local Aesthetic Experience in Chinese Context

Aesthetic anthropology is a new paradigm of the modem aesthetic research of China. Professor Wang Jie and his research team put forward the concept of local aesthetic experience in the process of research. The concept is used to summarize and refer to the existing way and existing form of non-westem mainstream culture in aesthetic dimension under global context. Local aesthetic experience converges many important problems in the research on aesthetic anthropology

Experimental Research and Finite Element Analysis on Setting Stiffening Rib of Corner Joints in Gabled Frames

In order to clear constructional design of corner joint, it is necessary to further investi-gate mechanical property of corner joint in gabled frames. Through static test and finite element software analysis of comparing the panel zone with and without inclined stiffener. Some conclusions are given in the article. The load displacement curves show that the capacity of oblique nodes installed within stiffening rib components is enhanced i.e. 40% more than those without stiffening rib nodes. The results reveal that in the gabled frames, the corner node with the inclined stiffening rib can improve the bearing capacity of the specimens. When the extraterritorial flange is tension, the erection of the inclined stiffening rib can prevent structural failure and improve effectually the ductility of the structure.

农业数字化转型的国际经验、本土实践和政策启示

农业数字化转型通过智能化、高效化生产,能够更好地适应市场需求和资源环境变化,实现农业可持续发展。在实现农业数字化发展中,欧盟以“共享”的信息传递系统建设、“开放”的区域集群构建以及“绿色”要素的反向驱动为主,美国以集约化和规模化农业生产方式、市场机制引入和社会资本引导以及数字技术推广体系建设为主,日本以发展精细化数字农业、政府和农协协同推进以及数字技术创新驱动为主。中国摸索出了“政府主导+多主体融合”“农业龙头企业主导+政策扶持”“科研机构主导+产学研融合”和“能人带动+示范引领”4种适合中国农情的发展路径,但也面临政府主导的数字化项目缺乏可持续性、未能充分发挥社会组织的潜力与功能、农业规模化程度低和绿色消费市场信任缺失等问题。为此,应构建各地区的数据信息获取的联动机制、制定市场普遍严格遵循的绿色生产监管机制、推动农业组织向规模化和集约化方向发展、推动农业科研机构市场化运营以及充分发挥农业协会等社会组织的作用。

局部麻醉下机器人辅助经皮椎体后凸成形伤椎注入骨水泥的患者体验分析

背景:局部麻醉下传统C臂辅助经皮椎体后凸成形手术需多次透视以调整穿刺方向,工作通道建立时间较长,患者术中疼痛刺激较大;而机器人辅助经皮椎体后凸成形手术可一次性精准穿刺成功,明显改善患者术中体验,同时减少骨水泥渗漏风险。目的:比较局部麻醉下机器人辅助和传统C臂辅助经皮椎体后凸成形手术的患者体验和其他疗效。方法:选择四川省医学科学院·四川省人民医院(电子科技大学附属医院)收治的单节段骨质疏松性椎体压缩骨折患者241例,其中132例在局部麻醉下进行机器人辅助经皮椎体后凸成形手术治疗(机器人辅助组),109例在局部麻醉下进行传统C臂辅助经皮椎体后凸成形手术治疗(传统透视组),记录患者术中体验评价、骨水泥注射量、手术时间、工作通道建立时间、住院费用及并发症,术后1 d通过影像学评估穿刺偏差与骨水泥渗漏。结果与结论:(1)机器人组59例患者术中体验评价为“非常好”,43例为“好”,16例为“一般”,10例为“差”,4例为“非常差”;传统透视组30例患者术中体验评价为“非常好”,44例为“好”,21例为“一般”,9例为“差”,5例为“非常差”,两组间术中体验评价比较差异有显著性意义(Z=-2.546,P=0.011);机器人组患者术中目测类比评分低于传统透视组(t=-9.513,P=0.000);机器人组、传统透视组愿意在必要时再次接受经皮椎体后凸成形手术的患者分别为84例和47例,组间比较差异有显著性意义(Z=-2.730,P=0.006);(2)机器人组患者手术时间、住院费用均多于传统透视组(t=2.860,P=0.003;t=36.522,P=0.000),工作通道建立时间短于传统透视组(t=-27.066,P=0.000),穿刺精度优于传统透视组(Z=-3.656,P=0.000),骨水泥渗漏率低于传统透视组(χ^(2)=7.284,P=0.007);(3)结果表明,局部麻醉后在机器人辅助行经皮椎体后凸成形手术患者的手术体验较好,具有穿刺精确、工作通道建立时间短、骨水泥渗漏率低的优势。

小鼠颈肌前庭诱发肌源性电位实验中的胸锁乳突肌定位研究

目的 设计重测信度高的小鼠颈肌前庭诱发肌源性电位(cVEMP)实验方法以验证定位胸锁乳突肌的准确性。方法 选用2月龄ICR雄性小鼠3只,1只解剖定位小鼠胸锁乳突肌,其余2只设计实验方案验证定位准确性。结果 记录电极定位到小鼠胸锁乳突肌上可重复引出清晰的cVEMP波形。结论 根据2只实验小鼠均可测得重测信度高的cVEMP波形,提示本研究定位胸锁乳突肌位置准确。

国内新一轮零基预算改革的地方经验与启示

零基预算是对现有财政支出格局的深度调整,是进一步优化财政资源配置、提高财政资金使用效益的关键之举。本文梳理了自2014年以来国内实施零基预算改革的地方实践,归纳出新一轮零基预算改革呈现出地方对改革的认识不统一、改革措施不尽相同,改革所涉资金范围以及对编报项目预算的要求不同,改革的具体措施存在差异但又有共通之处等特点,且实践中推进改革面临突破利益固化藩篱具有挑战性,编报与审核工作量大、专业性强以及对不同的支出项目进行优先级排序难度高等困难,在总结广西、重庆、广州、江苏、浙江等地区亮点经验的基础上,提出了地方深化零基预算改革的思路与举措。

地方政府推进全民健身公共服务数字化转型——基于浙江省的经验考察

推进全民健身公共服务数字化转型是构建更高水平全民健身公共服务体系的应有之义,也是实现体育治理现代化的关键基石。以“十四五”期间国家级体育数字化改革试点浙江省为实体考察对象,基于TOE理论分析框架,归纳浙江省推进全民健身公共服务数字化转型的实践经验;基于“浙江经验”,提出地方政府推进全民健身公共服务数字化转型应加强数字技术科研攻关、建立一盘棋一体化推进机制、构建适宜的政策推进环境、坚持先试点后推广的基层探索方法,助力我国构建更高水平全民健身公共服务体系。

师范专业认证背景下无机化学实验教学改革探索与实践——以溶液的配制为例

无机化学实验可以培养化学专业学生的实验操作技能,强化和训练学生逻辑能力和创新思维。首先对我校化学专业的无机化学实验课程概况及教学中存在的问题进行了阐述,然后对“溶液的配制”实验项目的教学现状进行了分析,最后在此基础上提出了相应的教学改革措施,分别从挖掘课程思政元素、优化课堂教学内容、加大安全教育力度、改进教学模式与方法、变革课程考核形式等方面进行了实践探索。通过改革实践提高了学生的实验操作技能,培养了学生严谨认真的实验态度与实事求是的做事风格,取得了较好的教学效果,可为其他高校无机化学实验教学改革和人才培养提供一定的借鉴与参考。

Comparison of perceived pain and patients’ satisfaction with traditional local anesthesia and single tooth anesthesia: A randomized clinical trial

BACKGROUND Contemporary innovations in the area of local anesthesia have attempted to provide an absolutely pain free experience for patients.Since the introduction of Computer-Controlled Local Anesthetic Delivery Systems to dentistry,many studies have compared its efficacy and safety to conventional anesthesia.However,very few studies have compared single tooth anesthesia(STA)and traditional local anesthesia.AIM To compare pain rating,changes in blood pressure,and heart rate during the local anesthetic injection.The secondary objectives were to measure the patients’level of satisfaction and the differences in anesthetic efficiency between the STA system and traditional local infiltration.METHODS A randomized controlled trial was conducted and a total of 80 patients with dental restorative needs were enrolled for the study.The patients were evaluated for their general physical status and oral clinical findings before enrollment.Information regarding perceived pain,changes in heart rate and blood pressure,and patients’satisfaction was collected using an electronic data form and was analyzed using paired and unpaired t-tests.RESULTS No significant difference was noted in perceived pain(P=0.59)and systolic blood pressure(P=0.09)during anesthetic injection using both traditional and STA techniques.STA patients had a significantly higher heart rate during anesthesia,although a statistically significant difference was noted among the traditional anesthesia and the STA groups even before anesthesia.During the restorative procedure,less pain was perceived by STA patients on the Wong-Baker FACES pain scale,which was statistically significant(P<0.001).Analyses of post-procedure patient responses showed that STA patients had a significantly better treatment experience and preferred to have the same method of injection in the future(P=0.04).CONCLUSION STA system can provide less painful and more comfortable restorative treatment procedures in comparison to the traditional infiltration technique.

Full-scale experiment for segmental linings of deep-buried shield tunnels bearing high inner water pressure:Comparison of mechanical behaviors of continuous-and stagger-jointed structures

Full-scale loading tests were performed on shield segmental linings bearing a high earth pressure and high inner water pressure,focus-ing on the effects of the inner water load and assembly manner on the mechanical properties of the segmental linings.The test results indicate that the deep-buried segmental linings without inner pressure have a high safety reserve.After the action of high inner water pressure,the lining deformation will increase with the reduction of the safety reserve,caused by the significant decrease in the axial force in the linings.Because the bending moment at the segmental joints is transferred to the segment sections in the adjacent ling rings,the convergence deformation,openings of segmental joints,and bolt strains are smaller for the stagger-jointed lining than those for the continuous-jointed lining;however,dislocations appear in the circumferential joints owing to the stagger-jointed assembly.Although it significantly improves the mechanical performance of the segmental lining,stagger-jointed assembly results in compromising the water-proofing safety of circumferential joints.The stagger-jointed assembly manner can be considered to improve the service performance of shield tunnels bearing high inner water pressure on the premise that circumferential joint waterproofing is satisfied.

Multi-Innovation Gradient Iterative Locally Weighted Learning Identification for A Nonlinear Ship Maneuvering System

This paper explores a highly accurate identification modeling approach for the ship maneuvering motion with fullscale trial. A multi-innovation gradient iterative(MIGI) approach is proposed to optimize the distance metric of locally weighted learning(LWL), and a novel non-parametric modeling technique is developed for a nonlinear ship maneuvering system. This proposed method’s advantages are as follows: first, it can avoid the unmodeled dynamics and multicollinearity inherent to the conventional parametric model; second, it eliminates the over-learning or underlearning and obtains the optimal distance metric; and third, the MIGI is not sensitive to the initial parameter value and requires less time during the training phase. These advantages result in a highly accurate mathematical modeling technique that can be conveniently implemented in applications. To verify the characteristics of this mathematical model, two examples are used as the model platforms to study the ship maneuvering.

Locally Resonant Gaps of Phononic Beams Induced by Periodic Arrays of Resonant Shunts

Periodic arrays of shunted piezoelectric patches are employed to control the propagation of elastic waves in phononic beams.Each piezo-patch is connected to a single resistance-inductance-capacitance shunting circuit.Therefore,the resonances of the shunting circuits will produce locally resonant gaps in the phononic beam.However,the existence of locally resonant gaps induced by resonant shunts has not been clearly proved by experiment so far.In this work,the locally resonant gap in a piezo-shunted phononic beam is investigated theoretically and verified by experiment.The results prove that resonances of shunting circuits can produce locally resonant gaps in phononic beams.

Prediction of the Local Scour at the Bridge Square Pier Using a 3D Numerical Model

In this paper, the problem on local scour around a single square pier was studied by using both the numerical and physical models. The numerical model for the study is FSUM based on a finite-difference method to solve the Reynolds averaged Navier-Stokes equations (RANS) and the equations for suspended sediment concentration and bed morphology. The computed result was verified through data measured in the experimental flume with a sand bed. In general, the typical features of local scour around the pier were successfully simulated by FSUM, such as stream flow, bow flow, down flow, horseshoe vortex. The comparison between the computation and experiment data shows a quite good fitness. Both numerical model and experiment results show that the maximum scour depth occurs at two front edges of the pier. Although the computed result shows a little bigger scour depth in comparison with the measurement in the physical model, it still confirms the reliability of numerical model in some measure.