Small-scale fire tests in the underwater tunnel section model with new sidewall smoke extraction

The Shenzhen–Zhongshan Bridge is a 24‐km‐long bridge and tunnel system,including a 6.8-km-long super cross section subsea tunnel.To solve the smoke exhaust problem of a super large cross-section subsea tunnel,the tunnel has a new smoke exhaust system that combines a horizontal smoke exhaust cross section at the top and sidewall smoke exhaust holes.In order to evaluate the potential fire hazards of this type of tunnel,a 1:30 tunnel model was established and 140 smallscale experiments on underwater tunnel fires were conducted.By changing the fire power,fire location,and fan operation mode,different scenarios of submarine immersed tunnel fire were simulated and the related key parameters such as fire smoke diffusion behavior and smoke temperature distribution were studied.On this basis,the optimal smoke control strategy was proposed for different fire scenarios.The research results indicate that the new smoke exhaust system can fully utilize the smoke flow characteristics,significantly improve smoke exhaust efficiency,and increase available evacuation time,thus further enhancing the fire safety of super large cross-section subsea tunnels.

31.38 Gb/s GaN-based LED array visible light communication system enhanced with V-pit and sidewall quantum well structure

Although the 5G wireless network has made significant advances,it is not enough to accommodate the rapidly rising requirement for broader bandwidth in post-5G and 6G eras.As a result,emerging technologies in higher frequencies including visible light communication(VLC),are becoming a hot topic.In particular,LED-based VLC is foreseen as a key enabler for achieving data rates at the Tb/s level in indoor scenarios using multi-color LED arrays with wavelength division multiplexing(WDM)technology.This paper proposes an optimized multi-color LED array chip for high-speed VLC systems.Its long-wavelength GaN-based LED units are remarkably enhanced by V-pit structure in their efficiency,especially in the“yellow gap”region,and it achieves significant improvement in data rate compared with earlier research.This work investigates the V-pit structure and tries to provide insight by introducing a new equivalent circuit model,which provides an explanation of the simulation and experiment results.In the final test using a laboratory communication system,the data rates of eight channels from short to long wavelength are 3.91 Gb/s,3.77 Gb/s,3.67 Gb/s,4.40 Gb/s,3.78 Gb/s,3.18 Gb/s,4.31 Gb/s,and 4.35 Gb/s(31.38 Gb/s in total),with advanced digital signal processing(DSP)techniques including digital equalization technique and bit-power loading discrete multitone(DMT)modulation format.

Fungal corneal ulcer after repair of an overhanging filtering bleb:A case report

BACKGROUND Overhanging filtering bleb is a common complication after trabeculectomy and surgical repair is an effective treatment when the patient presents with apparent symptoms.Filtering bleb relevant infection including in the filtering bleb itself and even endophthalmitis in some severe cases has been reported.However,corneal fungal infection after filtering bleb repair is rarely reported.CASE SUMMARY A 57-year-old Chinese man who had sensations of redness and foreign body sensations in the left eye 3 wk after repair of overhanging filtering bleb.3 wk ago,due to sensations of a foreign body in the left eye for 3 years with worsening for 3 mo.The patient was diagnosed as overhanging filtering bleb and underwent a repair of overhanging filtering bleb.Postoperative,the filtering bleb formed well and the intraocular pressure is normal.But the patient gradually develop redness,pain and a grey infiltrate of the cornea in the eye.Finally it developed into fungal corneal ulcer.Through asking the medical history,we found the patient had irregularly self-medicated for years with glucocorticoid eye drops for years to relieve the foreign body sensation in the eye caused by filtering bleb overhanging.Because the glucocorticoid eye drops he used years ago had provide normal sensation to the eye.After 3 mo of anti-fungal treatment,the inflammation was controlled.CONCLUSION In addition to avoiding the development of overhanging filtering bleb after trabeculectomy,the present case report also suggests that clinicians should pay more attention to the patient’s ocular self-medication history.Particularly in patients with a history of glaucoma or eye surgery.Because these patients may be exposed to more types of eye drops than other individuals,they may select the wrong medi-cations for long-term use,based on their previous experience.

ANALYSIS OF INTERNAL WAVERIDER INLET AND TYPICAL SIDEWALL COMPRESSION INLET PERFORMANCE

A new internal waverider inlet with a rectangular shape of entrance and exit in front view is designed at Ma=6.0.The design is based on a better basic flowfield ICFC than traditional one and derived with the technology of stream tracing and shock cutting.Comparison between the newly designed inlet and a typical sidewall compression inlet is given.The design Mach number and entrance shape of this new inlet are chosen according to the sidewall compression inlet.Numerical results show that most of the performance parameters of the internal waverider inlet are a bit higher than the sidewall inlet,such as the flow capture coefficient,total pressure recovery and the kinetic efficiency.The performances of these two inlets at off-design points are compared.The internal waverider inlet can capture more than 91% of incoming flow under all simulated conditions.Results show that internal waverider inlet using 3-D compression and high flow capture coefficient is a kind of fixed-geometry inlet with better performance.

Experimental study on thermal environment in large-space building with low sidewall air supply

The thermal environmental characteristics are experim-entally studied in terms of different air supply volumes and outdoor meteorological parameters in a large-space building which is air conditioned with a low sidewall air supply.The experimental results show that the indoor vertical temperature distributions under different condition are similar.The maximum vertical temperature difference（MVTD）is up to about 20 ℃,and it linearly changes with the sol-air temperature.The indoor vertical temperature gradients（VTGs）in the upper,central and lower zones are different.The influence of the sol-air temperature on the VTGs in the upper and the lower zones is greater than that in the central zone.The characteristics of the VTGs in the three zones affected by the air supply volume are the same as those affected by the sol-air temperature.Besides,because of the small air velocity,the predicted mean vote（PMV）on comfort in the occupied zone is slightly high and the air temperature difference between the head and the ankle is usually more than 3 ℃.

Thermal stratification level of low sidewall air supply with air-conditioning system in large space

The thermal stratification level of low sidewall air supply system in large space was defined. Depending on the experiment of low sidewall air supply in summer 2008,the thermal stratification level was studied by simulation. Based on the simulation of experiment condition,the air velocity and vertical temperature distribution in a large space were simulated at different air-outlet velocities,and then the thermal stratification level line was obtained. The simulation results well match with the experimental ones and the average relative error is 3.4%. The thermal stratification level is heightened by increasing the air-outlet velocity with low sidewall air supply mode. It is concluded that when air-outlet velocity is 0.29 m/s,which is the experimental case,a uniform thermal environment in the higher occupied zone and a stable stratification level are formed. When the air-outlet velocity is low,such as 0.05 m/s,the thermal stratification level is too low and the air velocity is too small to meet the human thermal comfort in the occupied zone. So,it would be reasonable that the air-outlet velocity may be designed as 0.31 m/s if the height of the occupied zone is 2 m.

A New Arrangement with Nonlinear Sidewalls for Tanker Ship Storage Panels

Sloshing phenomenon in a moving container is a complicated free surface flow problem. It has a wide range of engineering applications, especially in tanker ships and Liquefied Natural Gas (LNG) carriers. When the tank in these vehicles is partially filled, it is essential to be able to evaluate the fluid dynamic loads on tank perimeter. Different geometric shapes such as rectangular, cylindrical, elliptical, spherical and circular conical have been suggested for ship storage tanks by previous researchers. In this paper a numerical model is developed based on incompressible and inviscid fluid motion for the liquid sloshing phenomenon. The coupled BEM-FEM is used to solve the governing equations and nonlinear free surface boundary conditions. The results are validated for rectangular container using data obtained for a horizontal periodic sway motion. Using the results of this model a new arrangement of trapezoidal shapes with quadratic sidewalls is suggested for tanker ship storage panels. The suggested geometric shape not only has a maximum surrounded tank volume to the constant available volume, but also reduces the sloshing effects more efficiently than the existing geometric shapes.

Research and application of sidewall stability predic-tion method based on analytic hierarchy process and fuzzy integrative evaluation method

As a difficult problem, sidewall instability has been beset drilling workers all the time. Not only does it cause huge economic losses, but also it determines the success or failure of drilling engineering. Due to complex relationship between various factors which influence sidewall stability, it hasn’t been found a widely applied method to predicate sidewall stability so far. Therefore, in order to formulate corresponding measures to ensure successful drilling, searching for a kind of better method to forecast sidewall stability before drilling becomes an imperative and significant topic for drilling engineering. On the basis of traditional sidewall stability analytical method, we have put forward the Fuzzy Comprehensive Evaluation Method to forecast sidewall stability regulation using physico-chemical performance parameters of the clay mineral. This method has been improved by introducing the Analytic Hierarchy Process (AHP) and the Maximum Subjection Principle in the application process. After introducing Analytic Hierarchy Process to identify weight, and Maximum Subjection Principle to obtain evaluation results, it has reduced the influence of human factors and enhanced the accuracy of the fuzzy evaluation results. The application in Hailaer Area indicates that this method can predict sidewall stability of gas-oil well with high credibility and strong practicability.

Numerical Simulation of PMM Tests for A Ship in Close Proximity to Sidewall and Maneuvering Stability Analysis

As the maneuverability of a ship navigating close to a bank is influenced by the sidewall, the assessment of ship maneuvering stability is important. The hydrodynamic derivatives measured by the planar motion mechanism （PMM） test provide a way to predict the change of ship maneuverability. This paper presents a numerical simulation of PMM model tests with variant distances to a vertical bank by using unsteady RANS equations. A hybrid dynamic mesh technique is developed to realize the mesh configuration and remeshing of dynamic PMM tests when the ship is close to the bank. The proposed method is validated by comparing numerical results with results of PMM tests in a circulating water channel. The first-order hydrodynamic derivatives of the ship are analyzed from the time history of lateral force and yaw moment according to the multiple-run simulating procedure and the variations of hydrodynamic derivatives with the ship-sidewall distance are given. The straight line stability and directional stability are also discussed and stable or unstable zone of proportional-derivative （PD） controller parameters for directional stability is shown, which can be a reference for course keeping operation when sailing near a bank.

Study on mechanical principle of reinforcing sidewalls and corners of roadway to control floor heave by anchors

The movement principle of sidewalls and floor of extraction opening is analyzed, it is found that floor heave not only has something to do with the floor strata, but sidewalls. The effect of sidewall anchor and corner anchor is studied, the mechanical principle of reinforcing sidewalls and corners is put forward and applied in engineering practice.

Experimental Investigation of Flame Structure and Combustion Limit During Premixed Methane/Air Jet Flame and Sidewall Interaction

The effects of inlet gas parameters and sloping sidewall angle on the flame structure and combustion limit with and without sidewall were experimentally investigated.Flame height and impact angle were obtained by chemiluminescence intensity analysis of CH*distribution.First,the combustion characteristics of flame with and without sidewall at different equivalence ratios were explored;then,the influence of Reynolds number and inlet gas temperature on flame structure and combustion limit of v-shaped flame with sidewall were analyzed,and the results with sidewall were compared with those without sidewall.Finally,the variation trend of flame parameters with different sloping sidewall angles was analyzed.The experimental results show that the existence of sidewall makes flame shape change from“M-shaped”to“inverted N-shaped”,and conical shape to trapezoidal shape.The inhibition effect of sidewall on flame stretching downstream is strengthened with the increase in Reynolds number;but as the temperature of the inlet gas increases,the inhibitory effect is obviously weakened.When sloping sidewall angle decreases from 90°to 55°at 5°intervals,flame height and impact angle of v-shaped flame reach the extreme value whenβ=80°.Compared with the case without sidewall,the range of v-shaped flame with sidewall has no obvious trend of broadening or shrinking when inlet gas temperature is increased;however,as sloping sidewall angle decreases,the range of the v-shaped flame shrinks obviously and flammability limit increases significantly.

SIDEWALL FLOW STABILITY IN THE MHD CHANNEL FLOWS

The velocity distribution between two sidewalls is; M-shaped for the MHD channel flows with rectangular cross section and thin conducting walls in a strong transverse magnetic field. Assume that the dimensionless numbers R(m) much less than 1, M, N much greater than 1, and sigma* much less than 1 and that the distance between two perpendicular walls is very long in comparison with the distance between two sidewalls. First, the equation for steady flow is established, and the solution of M-shaped velocity distribution is given. Then, an equation for stability of small disturbances is derived based on the velocity distribution obtained. Finally, it is proved that the stability equation for sidewall how can be transformed into the famous Orr-Sommerfeld equation, in addition, the following theorems are also proved, namely, the analogy theorem, the generalized Rayleigh's theorem, the generalized Fjortoft's theorem and the generalized Joseph's theorems.

Axial segregation characteristics and size-induced flow behavior of particles in a novel rotary drum with curved sidewalls

Particle mixing and segregation are common phenomena in rotary drums,which are challenging to be controlled and driven artificially in powder technology.In this work,the discrete element method(DEM)was applied to construct the novel rotary drum composed of different shaped curved sidewalls.By varying the operation parameters of particle and sidewall shapes as well as the length-to-diameter(L/D)ratio of drums,the axial mixing and segregation processes of binary size-induced particles were investigated.The results show that the axial flow velocity of the particle mixtures is noticeably weakened once the particle angularity increases,making the non-spherical particles to mix better in rotary drums compared to the spherical particles.Besides,in the short drums with size-induced spherical particles,the axial segregation characteristics are significantly enhanced by the convex sidewalls while suppressed by the concave sidewalls.However,for size-induced non-spherical particles,the axial segregation structure can be present in rotary drums with plane and concave sidewalls while not in drums with convex sidewalls.Moreover,the axial segregation band structure of spherical particles eventually increases proportionally with the increased drum L/D ratios.In contrast,the non-spherical particles cannot form obvious multi-proportional segregation bands.

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway stations

A disadvantage of the conventional quasi-static test method is that it does not consider the soil restraint effect.A new method to test the seismic performance of prefabricated specimens for underground assembled structures is proposed,which can realistically reflect the strata restraint effect on the underground structure.Laboratory work combined with finite element(FE)analysis is performed in this study.Three full-scale sidewall specimens with different joint forms are designed and fabricated.Indices related to the seismic performance and damage modes are analyzed comprehensively to reveal the mechanism of the strata restraint effect on the prefabricated sidewall components.Test results show that the strata restraint effect effectively improves the energy dissipation capacity,load-bearing capacity,and the recoverability of the internal deformation of the precast sidewall components.However,the strata restraint effect reduces the ductility of the precast sidewall components and aggravates the shear and bending deformations in the core region of the connection joints.Additionally,the strata restraint effect significantly affects the seismic performance and damage mode of the prefabricated sidewall components.An FE model that can be used to conduct a seismic performance study of prefabricated specimens for underground assembled structures is proposed,and its feasibility is verified via comparison with test data.

Research on conductive-material-filled electrodes for sidewall insulation performance in micro electrochemical machining

In micro electrochemical machining(ECM)processes,stray corrosion causes undesired metal dissolution and the deterioration of shape accuracy.Adopting a sidewall-insulated electrode is an effective approach to suppressing stray corrosion.Most sidewall-insulated electrodes are made of metal substrate and non-metallic thin films.Nevertheless,the thin-film insulating materials attached to a metal substrate are susceptible to damage in an electrolytic environment.This study presents a novel concept of the conductive-material-filled electrode for better sidewallinsulation performance.The micro-scale quartz tube serves as the insulating substrate.Commercially available conductive fillers including metal wire,molten metals,and silver powder are filled inside the working cathode of the quartz tube.Consequently,the metal-wire-filled electrode,moltenmetal-filled electrode,and nano-powder-filled electrode are designed and fabricated.From the verification results of electrode toughness,material removal rate,and surface topography,the metal-wire-filled electrode and moltenmetal-filled electrode exhibit the same performance as a traditional metal-based electrode and much better durability.By contrast,the nano-powder-filled electrode is unable to withstand long-term ECM processes because of the loss of cured powder particles.In ECM experiments,microstructures with steep sidewalls(taper angle<9.7°)were machined using the metal-wire-filled electrode and molten-metal-filled electrode,which could replace the traditional electrode,achieving a longer service life and superior sidewall-insulation performance.

Interactive Effects of Wind Tunnel Sidewalls on Flow Structures around 2D Airfoil Model

This paper presents the effect of wind tunnel sidewalls on the wind turbine airfoils with experimental and numerical methods.The test is carried out in a low-speed wind tunnel at Re=2.62×10^(5).Pressures acting on the airfoil surface are measured by a multiport pressure device.And,the oil flow visualization technique is used to investigate the flow field characteristics of the airfoil surface.Then,a numerical simulation was conducted with the measurement results.As a result,it is clarified the flow structures on the airfoil surface depend strongly on the angles of attack and the sidewalls.At small angles of attack,the three-dimensional separation caused by the interaction between the sidewall boundary layer and the airfoil boundary layer is very small,and only appears near the junction of the airfoil model and the sidewall.This corner separation becomes large with the increase of the angle of attack.At the middle part of the testing model,the boundary layer flow evolves into three-dimensional separation,i.e.,stall cell,when the separation develops to an appreciate extent.The stall phenomenon will further spread from the center line to sidewalls with the increase of the angle of attack;and then,its development will be limited by the sidewall boundary layer separation.Comparably,the simulation shows that the sidewall make the pressure coefficient Cpdecrease,and proper boundary condition can maintain two-dimensional flow at large angles of attack by eliminating the influence of corner vortices.

基于极限平衡法的危岩倾覆稳定性三维计算方法

目前危岩防治工作中,危岩稳定性评价主要以简化后的二维剖面作为计算模型。由于自然界中的危岩形态极不规则,采用二维剖面计算模型并不能真实反映危岩受力情况。为了研究危岩稳定性三维计算方法,在前人研究基础上,基于极限平衡理论,提出了由后缘裂缝抗拉强度控制的危岩倾覆稳定性三维计算公式,采用数值积分和空间几何方法给出了在危岩单体三维模型基础上求解危岩后缘岩体抗拉力、水压力及其力矩计算公式和实现流程。以三峡库区瞿塘峡吊嘴危岩为实例开展了应用,并通过数值分析进行了验证。通过不同形态危岩的三维稳定性分析,讨论了三维与二维稳定性计算结果的关系,对比发现危岩形态对稳定性计算结果有明显影响,三维计算较二维计算更准确和实用。

Differences and Correlations of Morphological and Hemodynamic Parameters between Anterior Circulation Bifurcation and Side-wall Aneurysms

Objective:The objective of this research was to explore the difference and correlation of the morphological and hemodynamic features between sidewall and bifurcation aneurysms in anterior circulation arteries,utilizing computational fluid dynamics as a tool for analysis.Methods:In line with the designated inclusion criteria,this study covered 160 aneurysms identified in 131 patients who received treatment at Union Hospital of Tongji Medical College,Huazhong University of Science and Technology,China,from January 2021 to September 2022.Utilizing follow-up digital subtraction angiography(DSA)data,these cases were classified into two distinct groups:the sidewall aneurysm group and the bifurcation aneurysm group.Morphological and hemodynamic parameters in the immediate preoperative period were meticulously calculated and examined in both groups using a three-dimensional DSA reconstruction model.Results:No significant differences were found in the morphological or hemodynamic parameters of bifurcation aneurysms at varied locations within the anterior circulation.However,pronounced differences were identified between sidewall and bifurcation aneurysms in terms of morphological parameters such as the diameter of the parent vessel(Dvessel),inflow angle(θF),and size ratio(SR),as well as the hemodynamic parameter of inflow concentration index(ICI)(P<0.001).Notably,only the SR exhibited a significant correlation with multiple hemodynamic parameters(P<0.001),while the ICI was closely related to several morphological parameters(R>0.5,P<0.001).Conclusions:The significant differences in certain morphological and hemodynamic parameters between sidewall and bifurcation aneurysms emphasize the importance to contemplate variances in threshold values for these parameters when evaluating the risk of rupture in anterior circulation aneurysms.Whether it is a bifurcation or sidewall aneurysm,these disparities should be considered.The morphological parameter SR has the potential to be a valuable clinical tool for promptly distinguishing the distinct rupture risks associated with sidewall and bifurcation aneurysms.

高温小井眼大直径岩心旋转井壁取心仪研制及应用

随着油气勘探开发难度增大,特别是海洋油气勘探开发的不断加大,以及深水井、高温井越来越多,地质方面对电缆测井技术所获取的参数要求也越来越高。为了更好地获取小井眼尺寸井壁岩心样本,助力油气田高效探勘开发,通过对取心仪井下仪器关键零部件电子控制短节和机械液压短节的创新设计与模拟分析,研制了适用于高温、高压、小尺寸井眼的大直径旋转井壁取心仪(MRCT-dumpy)。通过功能测试和5口井作业应用表明,大直径旋转井壁取心仪钻头性能及取心电机性能均得到充分验证,其热管理系统满足作业需要,符合设计要求;该取心仪取心功能正常,最高单趟收获岩心43颗,满足小井眼大直径取心作业要求。该仪器的设计与应用可为后期同类技术的发展提供指导。

随州公共活动中心结构设计

随州公共活动中心是体型复杂的多馆合一式综合性城市公共建筑,具有平面单向超长、质量分布明显不对称、大跨度、大悬挑、顶板大开洞等特点。在对该结构体系进行了重难点分析的基础上,采用现浇预应力钢筋混凝土框架+屈曲约束支撑的减震结构体系,利用屈曲约束支撑解决平面单向超长造成的扭转,同时使结构形成多道抗震防线;大跨度楼盖采用预应力密肋楼盖控制结构高度;针对顶板大开洞的嵌固端问题提出了具体的加强措施。提出了针对该类结构的BRB布置及减震参数设计,通过有限元数值仿真分析论证了BRB的减震效果。针对超限情况提出了抗震性能目标及抗震措施。