Experimental study on mechanical property of stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor

Stiffening-ribbed-hollow-pipe cast-in place reinforced concrete girderless floor is a new-style hollow girderless floor system. Model experimental researches of simply-supported floor and four-corners bearing floor have been done on this new kind of floor system in this paper. The experiment results show that the floor system has good mechanical property such as high bearing capacity, big rigidity and good tensility. A theoretical method is presented in this paper that the stiffening-ribbed-hollow-pipe girderless floor can be analyzed by being converted equivalently to orthotropic solid slab. It is indicated that the method is correct and reasonable according to the contrast between theoretical calculated results and experimental measured results. The theoretical results coincide with the measured results well.

Heat transfer and friction factor of Therminol liquid phase heat transfer fluid in a ribbed tube

Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch and rib height of 4.5 and 1.0 mm.respectively.Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube.The Nusselt number increase with the increase of Reynolds number.The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times.Also,the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube.Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube.The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs,which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube.The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid.

Thermal performance and entropy generation for nanofluid jet injection on a ribbed microchannel with oscillating heat flux: Investigation of the first and second laws of thermodynamics

In current numerical study,forced flow and heat transfer of water/NDG(Nitrogen-doped graphene)nanofluid in nanoparticles mass fractions(φ)of 0,2%and 4%at Reynolds numbers(Re)of 10,50,100 and 150 are simulated in steady states.Studied geometry is a two-dimensional microchannel under the influence of nanofluid jet injection.Temperature of inlet fluid equals with Tc=293 K and hot source of microchannel is under the influence of oscillating heat flux.Also,in this research,the effect of the variations of attack angle of triangular rib(15°,30°,45°and 60°)on laminar nanofluid flow behavior inside the studied rectangular geometry with the ratio of L/H=28 and nanofluid jet injection is investigated.Obtained results indicate that the increase of Reynolds number,nanoparticles mass fraction and attack angle of rib leads to the increase of pressure drop.By increasing fluid viscosity,momentum depreciation of fluid in collusion with microchannel surfaces enhances.Also,the increase of attack angle of rib at higher Reynolds numbers has a great effect on this coefficient.At low Reynolds numbers,due to slow motion of fluid,variations of attack angle of rib,especially in angles of 30°,45°and 60°are almost similar.By increasing fluid velocity,the effect of the variations of attack angle on pressure drop becomes significant and pressure drop figures act differently.In general,by using heat transfer enhancement methods in studied geometry,heat transfer increases almost 25%.

Ribbed towel gourd seed germination

The influence of different conditions on ribbed towel gourd seed germination was tested in this paper. Results showed that the seeds germinating energy and germination percentage were increased evidently under the treatment of dipping in normal water temperature for 4 hours and drying out for 1 hour at 30℃.

Experimental Investigation on Convective Heat Transfer Characteristics in Ribbed Channel

The heat transfer and pressure loss characteristics on a square channel with two opposite surfaces roughened by high blockage ratio ribs are measured by systematic experiments.Reynolds numbers studied in the channel range from 1 400 to 8 000.The ratios of rib height to hydraulic diameter (e/D) are 0.2and 0.33,respectively.The ratio of rib spacing to height (P/e) ranges from 5to 15.The rib orientations in the opposite surfaces are symmetrical and staggered arrangements.The results show that the heat transfer coefficients are increased with the increase of rib height and Reynolds number,though at the cost of higher pressure losses.When the rib spacing to height ratio is 10,it keeps the highest heat transfer coefficient in three kinds of rib spacing to height ratios 5,10 and 15.The heat transfer coefficient of symmetrical arrangement ribs is higher than that of the staggered arrangement ribs,but the pressure loss of the symmetrical arrangement ribs is larger than that of the staggered arrangement ribs.

Research on an innovative structure of an open-ribbed steel-ultra-high performance concrete composite bridge deck

To completely solve the problem of fatigue cracking issue of orthotropic steel bridge decks(OSDs),the authors proposed a steel–ultra-high performance concrete(UHPC)lightweight composite deck(LWCD)with closed ribs in 2010.Based on the successful application of that LWCD,an adaptation incorporating an innovative composite deck structure,i.e.,the hot-rolled section steel–UHPC composite deck with open ribs(SSD)is proposed in this paper,aiming to simplify the fabrication process as well as to reduce the cost of LWCD.Based on a long-span cable-stayed bridge,a design scheme is proposed and is compared with the conventional OSD scheme.Further,a finite element(FE)calculation is conducted to reflect both the global and local behavior of the SSD scheme,and it is found that the peaked stresses in the SSD components are less than the corresponding allowable values.A static test is performed for an SSD strip specimen to understand the anti-cracking behavior of the UHPC layer under negative bending moments.The static test results indicate that the UHPC layer exhibited a satisfactory tensile toughness,the UHPC tensile strength obtained from the test is 1.8 times the calculated stress by the FE model of the real bridge.In addition,the fatigue stresses of typical fatigue-prone details in the SSD are calculated and evaluated,and the influences of key design parameters on the fatigue performance of the SSD are analyzed.According to the fatigue results,the peaked stress ranges for all of the 10 fatigue-prone details are within the corresponding constant amplitude fatigue limits.Then a fatigue test is carried out for another SSD strip specimen to explore the fatigue behavior of the fillet weld between the longitudinal and transverse ribs.The specimen failed at the fillet weld after equivalent 47.5 million cycles of loading under the design fatigue stress range,indicating that the fatigue performance of the SSD could meet the fatigue design requirement.Theoretical calculations and experiments provide a basis for the promotion and application of this structure in bridge engineering.

354例Ribbed股骨柄假体置换术的中远期疗效分析

目的探讨采用Ribbed股骨柄假体行人工全髋关节置换术(total hip arthroplasty,THA)的中远期疗效。方法回顾分析2006年10月—2016年5月采用Ribbed股骨柄假体行THA且获完整随访的354例(384髋)髋关节疾病患者临床资料。男171例,女183例;年龄20~82岁,平均53.4岁。单髋324例,双髋30例。关节置换原因:股骨头缺血性坏死151例(159髋),髋关节骨关节炎134例(136髋),类风湿性关节炎43例(43髋),强直性脊柱炎20例(40髋),创伤6例(6髋)。术前患者Harris评分为(42.34±8.89)分。术后采用Harris评分评价髋关节功能;摄X线片判断双下肢是否等长、股骨侧有无透亮带、假体稳定性以及应力遮挡发生情况。结果术后切口均Ⅰ期愈合。354例患者均获随访,随访时间2~11年,平均7.4年。末次随访时Harris评分为(80.52±7.61)分,与术前比较差异有统计学意义(t=134.804,P=0.000)。术后发生2例(2髋)假体感染,3例(3髋)假体松动,4例(4髋)假体周围骨折,48例(48髋)存在轻到中度大腿疼痛。X线片示76例(78髋)股骨侧存在透亮线以及不同程度应力遮挡。按照Engh等的方法评价假体稳定性,骨长入性稳定364髋,纤维长入性稳定15髋,假体不稳定5髋。25例(25髋)发生股骨柄假体下沉,其中5例患者双下肢长度差异>10 mm。结论采用Ribbed股骨柄假体行THA具有初始稳定性好、骨长入好等优点,术后应力遮挡发生率相对较高,但对假体中远期生存率和疗效无明显影响。

CFP假体与Ribbed假体在全髋关节置换术中应用的疗效

目的比较保留股骨颈型(CFP)假体与Ribbed假体在全髋关节置换术(THA)患者中应用效果。方法77例THA患者分别采用CFP(CFP组,41例)和Ribbed假体(Ribbed组,36例)治疗。记录手术相关指标,采用Harris髋关节功能评分(HHS评分)和WOMAC评分评估髋关节功能,根据影像学上Gruen分区及DeLee分区法来评估假体周围骨溶解、皮质骨增生及异位骨化和判定股骨假体柄是否处于中心位置;采用Engh标准评估骨-假体接触面的稳定性。结果两组手术时间和术中出血量相仿(P>0.05)。两组术后随访均超过3年,术后末次随访时HHS评分和WOMAC评分较术前改善(P<0.05)。两组并发症发生情况相仿(P>0.05);CFP组双下肢长度差>10 mm者8例(19.5%),Ribbed组则仅有1例(2.8%)(P<0.05)。结论THA中采用CFP假体或Ribbed假体均可取得良好临床疗效,但相比之下采用CFP更容易出现双下肢长度不等。

Thermal test and numerical simulation of cooling stave with internal ribbed tube

A new type of cooling stave with internal ribbed tube was proposed,and the heat transfer performance of the stave was studied by means of thermal test and numerical simulation.The temperature of cooling stave was monitored in the conditions of furnace gas temperature of 200-700 C and cooling water velocity of 0.2-1.0 m/s.The thermal test results show that the internal rib structure can form swirl in the water pipe and improve the cooling capacity of the cooling stave.The higher the furnace temperature or the lower the cooling water flow rate,the more obvious the advantage of the cooling stave with internal ribbed tube.The mathematical model of the cooling stave with internal ribbed tube was established by FLUENT software,and the influence of the internal rib structure parameters on the heat transfer performance of the cooling stave was discussed.It is suggested that the parameters of the internal ribbed tube should be 4 ribs,1 mm in height,5-7 mm in width,and 20-30 mm in lead.In the same common working conditions of the cooling stave,the maximum temperature of the newly designed cooling stave with internal ribbed tube is reduced by 5.6%compared with that of common cooling stave with round tube.The water flow rate in the internal ribbed tube only needs 0.9 m/s to reach the cooling effect of 2 m/s in the common tube cooling stave,which can save 55%of water.In case of water shortage accident of cooling stave,the maximum temperature of the cooling stave with internal ribbed tube is decreased by 22.4%compared with that of common round tube,which can effectively reduce the harm of water shortage and protect the cooling stave.

Very-large eddy simulation of the rotational effects on turbulent flow in a ribbed channel

For the simplified model of the internal cooling passage in the turbine blade of an aero-engine,the present study applies a newly developed turbulence modeling method,very-large eddy simulation(VLES),for analyzing rotational effects on the characteristics of complex turbulent flow.For comparison,not only are the delayed detached eddy simulation(DDES)method(recognized as one of the most popular hybrid Reynolds-averaged Navier-Stokes–large eddy simulation(RANS-LES)methods)and the LES method used with the same numerical setup,but also three RANS turbulence models,including the k-ωshear stress transport(SST),standard k-ε,and Reynolds stress models,are applied to analyze the flow structure in the ribbed channel(whether rotating or stationary).Complex turbulent flows in a square ribbed channel at high Reynolds number of 100000 in the stationary state and different rotational numbers(Ro)between 0.1 and 0.4 are simulated and analyzed in detail.The comparisons show that when compared with the experimental data the VLES method works best in both the stationary and rotating states.It can capture unsteady flow characteristics such as wall shear layer separation and the vortex structure resulting from the rib disturbance.The DDES method can only capture the larger-scale vortex structures,and its predictions of the time-averaged velocity differ considerably from experiments,especially in the stationary state.With a relatively coarse grid,satisfactory prediction cannot be achieved in either rotating or stationary state by the LES method with wall-adapting local eddy-viscosity(WALE)and dynamic Smagorinsky models.The three RANS models perform poorly in both the stationary and rotating states.The results demonstrate the advantages of the VLES method in analyzing the unsteady flow characteristics in the ribbed channel at high Reynolds numbers for both stationary and rotating conditions.On that basis,the study uses the VLES method to analyze the flow evolution under different rotational numbers,and the rotational effects on the fluid mechanisms are analyzed.

The admittance feature representation and impact sound feature extraction in the material identification of ribbed plates

The admittance features representing the physical attributes are used as the in termediates to extract the materialattributesrelated impact sound features of ribbed plates. Firstly, the admittance feature representations of metal ribbed plates attributes are obtained and the relationship between the admittance features and the impact sound features are established via correlation analysis method. Then, materialattributesrelated impact sound features are obtained indirectly. Finally, the performances of different sound features for the material recognition of ribbedmetal plates are verified through the Support Vector Machine classifier. The results indicate that the obtained four sets of features can effectively identify the materials of the metal ribbed plates, while the accuracy of a single feature depends on the separable degree of the corresponding material attribute. And the features extracted based on admittance functions have higher average accuracy than that of timbre features. Therefore, the proposed sound feature extraction method based on admittance features is valid, and the extracted sound features can effectively reflect the physical attributes.

Investigation of Heat Transfer Augmentation between the Ribbed Plates via Taguchi Approach and Computational Fluid Dynamics

Heat transfer and turbulent flow characteristics between the ribbed plates have been numerically studied in the present paper.The ribs with the rectangular cross-section have been placed on the top and the bottom plates of the duct,symmetrically.It is assumed that the fluid at 300 K has entered the system while the walls kept at 400 K.All numerical analyses have been performed by k-ωShear Stress Transport(SST)turbulence model for Re=10000,15000 and 20000.For the fixed rib width,the dimensionless height and the dimensionless spacing have been respectively varied as 0.1≤h’≤0.3 and 0.5≤S’≤1,and the results have been compared with the ones of the smooth plate.Even though there are twenty-seven cases obtained as a result of parametric combinations,the number of various cases has been reduced from twenty-seven to only nine different variations by applying the Taguchi method.Furthermore,the effects of all the considered parameters on the heat transfer and flow characteristics have been determined in terms of the influence degree.The optimum parameters for Nusselt number and pressure loss have been ascertained individually.What is more,the almost exact values for Nusselt number and pressure loss have also been attained by the confirmation test having an error percentage of 6%.The most dominant factor has been determined as the rib height due to its effect on both heat transfer and flow characteristics.Similarly,with respect to the numerical results,increasing the rib height,the rib spacing and Reynolds number has separately increased Nusselt number.Nevertheless,symmetrical flow structure has been disturbed as a result of ascending the rib height as clearly seen for h’=0.3 from the charts.In the meantime,pressure loss has been augmented owing to the increment of the geometrical parameters and also Reynolds number.h’=0.1 with S’=0.5 at Re=10000,h’=0.2 with S’=0.5 at Re=15000 and h’=0.1 with S’=0.75 at Re=15000 can be suggested for the heat transfer enhancement since the pressure loss of the system is tolerated.

Analysis of Turbulent Heat Transfer and Fluid Flow in Channels with Various Ribbed Internal Surfaces

This paper presents results of a numerical investigation of heat transfer and flow pattern characteristics of a channel with repeated ribs on one broad wall. Numerical computations are performed for seven ribs placed on the bottom wall of a channel for Reynolds numbers ranging from 10,000 to 30,000. The newly modified ribs (the ones with convex pointing upstream/downstream rib, wedge pointing upstream/downstream rib, concave pointing upstream/downstream rib and also concave-concave rib as well as convex-concave rib), are proposed for simulation with prospect to reduce flow separation and extend reattachment area compared to the unmodified square rib. The numerical results are reported in forms of flow structure, temperature field, turbulent kinetic energy, Nusselt number, friction factor and thermal enhancement factor. The results indicate the rib with concave-concave surfaces efficiently suppresses flow separation bubble in the corner of the rib and induces large recirculation zone over those of the others, hence giving the highest Nusselt number and friction factor. On the other hand, the one with convex-concave surface provides the lowest friction factor with moderate Nusselt number. Due to the prominent effect of its low friction factor, the rib with convex-concave surface offers the highest thermal enhancement factor of 1.19.

Effect of Blockage Ratio on Heat Transfer and Pressure Drop in Rotating Ribbed Channels at High Rotation Numbers

At high rotation numbers,the rotational effects on heat transfer and flow could be diverse among the channels with different blockage ratios.However,most studies are conducted under low rotation number(less than 0.25)and selected blockage ratio.This paper experimentally investigates the effect of rib blockage ratio(ranges from 0 to 0.3)on pressure loss and heat transfer in a rotating square channel under high rotation number(up to 0.81).The ribs staggered on leading and trailing walls were oriented 90°to the mainstream flow.The Reynolds number and the wall-to-fluid temperature ratio varied from 20000 to 40000 and 0.08 to 0.2,respectively.The results showed that a larger blockage ratio resulted in a better heat transfer but a higher pressure drop.The optimum blockage ratio was 0.1 for the best thermal performance.The rotational effects were weakened in the passage with a higher blockage ratio,where the critical rotation number could not be observed.Moreover,the heat transfer enhancement induced by rotation was more significant when the temperature ratio increased.Finally,the correlations were developed for the pressure drop and the convective heat transfer on the leading and trailing edges.

旋转带肋通道流阻特性研究

With the development of aero-engines, the turbine inlet temperature continues to rise. In order to ensure the safety and reliability of the turbine blades, cooling structures must be set inside turbine blades to cool them. Heat transfer coefficient and flow resistance are the key parameters to measure the cooling characteristics of internal cooling structures. In this paper, the characteristics of flow resistance in a rotating ribbed channel is presented numerical simulation under different rib spacings, rib angles, and thermal boundary conditions. The results show that, separation and reattachment of fluid between ribs is the key effect of rib spacing on flow resistance. The flow resistance is small when the rib spacing is small, because it's difficult for the fluid to form reattachment between the ribs. With the increase of rib spacing, the reattachment phenomenon is more obvious and the flow resistance increases accordingly. In general,p: e=10 channel has the maximum flow resistance. Secondary flow caused by the ribs is the key factor affecting the flow resistance characteristics with different rib angles. The secondary flow interacts with the main flow and causes flow loss through mixing, thus affecting the flow resistance of the channel. Under static condition, the flow resistance of 60°ribbed channel is the largest. The flow resistance of channel was affected by the temperature rise ratio also. And with the increase of the Ro, the temperature rise ratio has a more obvious effect on the flow resistance of the ribbed channel.When Ro=0.45, the flow resistance of the channel with a temperature rise ratio of 0.4 is 2.4 times that of the channel without temperature rise, while when Ro=0.3, it is 1.6 times, and when Ro=0.15, it is 1.2 times.

The influence of inter-band rock on rib spalling in longwall panel with large mining height

In order to improve rib stability,failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study.A three-dimensional mechanical model is established for the rib by considering the rock layer.A safety factor is defined foy the rib,and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock.A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability.It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability.The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area.The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line,which tends to provide a good stability state for the rib.For different inter-band rock positions,two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.

Control of Nozzle Flow Using Rectangular Ribs at Sonic and Supersonic Mach Numbers

This study deals with base pressure management in a duct for various values of the Mach number(M),namely,Mach number corresponding to sonic and four supersonic conditions.In addition to the Mach number,the nozzle pressure ratio(NPR),the area ratio,the rib dimension,and the duct length are influential parameters.The following specific values are examined at M=1,1.36,1.64,and 2,and NPRs between 1.5 and 10.The base pressure is determined by positioning ribs of varying heights at predetermined intervals throughout the length of the square duct.When the level of expansion is varied,it is seen that the base pressure initially drops for overexpanded flows and increases for under-expanded flows.When ribs are present,the flow field in the duct and pressure inside the duct fluctuate as the base pressure rises.Under-expanded flows can achieve a base pressure value that is suitably high without experiencing excessive changes in the duct flow in terms of static pressure if a rib height around 10%of the duct height close to the nozzle exit is considered.Rectangular rib passive control does not negatively affect the duct’s flow field.

Bearing mechanism of roof and rib support structure in automatically formed roadway and its support design method

Non-pillar mining technology with automatically formed roadway is a new mining method without coal pillar reservation and roadway excavation.The stability control of automatically formed roadway is the key to the successful application of the new method.In order to realize the stability control of the roadway surrounding rock,the mechanical model of the roof and rib support structure is established,and the influence mechanism of the automatically formed roadway parameters on the compound force is revealed.On this basis,the roof and rib support structure technology of confined lightweight concrete is proposed,and its mechanical tests under different eccentricity are carried out.The results show that the bearing capacity of confined lightweight concrete specimens is basically the same as that of ordinary confined concrete specimens.The bearing capacity of confined lightweight concrete specimens under different eccentricities is 1.95 times higher than those of U-shaped steel specimens.By comparing the test results with the theoretical calculated results of the confined concrete,the calculation method of the bearing capacity for the confined lightweight concrete structure is selected.The design method of confined lightweight concrete support structure is established,and is successfully applied in the extra-large mine,Ningtiaota Coal Mine,China.

Study of microstructure evolution of magnesium alloy cylindrical part with longitudinal inner ribs during hot flow forming by coupling ANN-modified CA and FEA

Hot flow forming(HFF)is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs(CPLIRs)made of magnesium(Mg)alloys,which has wide applications in the aerospace field.However,due to the thermo-mechanical coupling effect and the existence of stiffened structure,complex microstructure evolution and uneven microstructure occur easily at the cylindrical wall(CW)and inner rib(IR)of Mg alloy thin-walled CPLIRs during the HFF.In this paper,a modified cellular automaton(CA)model of Mg alloy considering the effects of deformation conditions on material parameters was developed using the artificial neural network(ANN)method.It is found that the ANN-modified CA model exhibits better predictability for the microstructure of hot deformation than the conventional CA model.Furthermore,the microstructure evolution of ZK61 alloy CPLIRs during the HFF was analyzed by coupling the modified CA model and finite element analysis(FEA).The results show that compared with the microstructure at the same layer of the IR,more refined grains and less sufficient DRX resulted from larger strain and strain rate occur at that of the CW;various differences of strain and strain rate in the wall-thickness exist between the CW and IR,which leads to the inhomogeneity of microstructure rising firstly and declining from the inside layer to outside layer;the obtained Hall-Petch relationship between the measured microhardness and predicted grain sizes at the CW and the IR indicates the reliability of the coupled FEA-CA simulation results.

Current practice in autologous rib and costal-cartilage harvest for rhinoplasty:A systematic review

Background:Autologous costal grafts are used universally in clinical practice for rhinoplasty and reconstruction.However,surgeons worldwide have not agreed on the details of graft harvesting,including rib selection,side preference,operation mode,cutting methods,and handling of the periosteum and perichondrium.This study aimed to provide an overview of the novel techniques used for auto-rib harvesting in rhinoplasty within the past 5 years and identify potential avenues for future research.Methods:We searched for related articles in PubMed,Embase,and Web of Science from 2019 to 2023,summa-rized crucial but controversial steps in recent practice,and analyzed their theoretical basis and clinical feasibility.Results:Auto-rib and cartilage open harvest is still mainstream in rhinoplasty and reconstruction,with the 5th to 8th ribs and cartilage being the most used.The laparoscopic harvest is gaining attention,being second only to the open harvest,with the 9th/10th ribs and cartilages being particularly convenient.The clinical applications of full-cut and split-cut methods differ in their advantages.Except for some special reasons,almost all studies tended to preserve the periosteum and perichondrium in situ,and few surgeons chose to harvest the grafts on the left side.Conclusion:Multiple techniques have emerged,requiring surgeons to balance the benefits and risks of various strategies at each step.New theories and techniques should be fully tested promptly and in clinical practice before wide application.Overall,a professional consensus is needed for better directivity,precision,and stability in clinical practice.