基于Y-shaped路网的早高峰拼车定价策略

针对交通资源配置有限导致的早高峰通勤拥堵问题,借鉴共享经济理论,引入拼车出行概念,充分考虑通勤者出行方式和Y-shaped路网特点,建立了基于通勤者出行效益的拼车定价模型.模型结合费用补偿机制,讨论了以平台利润最大化和系统负效用最小化为目标的拼车定价策略,并给出了定价策略有效的阈值条件.研究结果表明,当通勤者都参与到拼车服务中时,拼车平台利润和交通系统负效用在其相应拼车定价策略下均能达到最优值,并且以交通系统负效用最小化为目标的拼车定价策略能消除Y-shaped路网中瓶颈处的交通拥堵.

Flow Regimes in Bubble Columns with and without Internals: A Review

Hydrodynamics characterization in terms offlow regime behavior is a crucial task to enhance the design of bubble column reactors and scaling up related methodologies.This review presents recent studies on the typicalflow regimes established in bubble columns.Some effort is also provided to introduce relevant definitions pertaining to thisfield,namely,that of“void fraction”and related(local,chordal,cross-sectional and volumetric)variants.Experimental studies involving different parameters that affect design and operating conditions are also discussed in detail.In the second part of the review,the attention is shifted to cases with internals of various types(perfo-rated plates,baffles,vibrating helical springs,mixers,and heat exchanger tubes)immersed in the bubble columns.It is shown that the presence of these elements has a limited influence on the global column hydrodynamics.However,they can make the homogeneousflow regime more stable in terms of transition gas velocity and transi-tion holdup value.The last section is used to highlight gaps which have not beenfilled yet and future directions of investigation.

Visual experimental study of nanofluids application to promote CO_(2) absorption in a bubble column

The addition of dispersed-phase nanoparticles in the liquid phase can enhance the gas-liquid transfer process as the suspended nanoparticles affect the transfer process inside the fluid through microdisturbance or micro-convection effects.In this article,a high-speed digital camera was used to visualize the bubble behavior of CO_(2) in pure water and nanofluids to examine the effects of CO_(2) gas flow rate,nanoparticle solid content and type on the bubble behavior in the fluids.The CO_(2) absorption performance in three water-based nanofluids were compared in a bubbler.And the mass transfer characteristics during CO_(2) bubble absorption and the reasons for the enhanced gas-liquid mass transfer effect of nanoparticles were analyzed.The results showed that the presence of nanoparticles affected the formation process of bubbles in the fluid,shortened the bubble detachment time,reduced the detachment diameter,effectively increased the gas-liquid contact area,and improved the bubbles detachment frequency.The system with MCM-41 corresponded to a higher overall mass transfer coefficient.Uncalined MCM-41 contained surfactant that enhanced foaming behavior in water.This prevented the transfer of CO_(2) to some extent,and the CO_(2) absorption by uncalined MCM-41/H_(2)O was 5.34%higher than that by pure water.Compared with SiO_(2) nanoparticles with the same particle size and the same composition,MCM-41 had a higher adsorption capacity and better hydrophilicity due to its larger specific surface area and rich porous structure,which was more favorable to accelerate the collision between nanoparticles and CO_(2) bubbles to cause micro-convection.Under the condition of 0.1%(mass)solid content,the enhancement of CO_(2) absorption process by MCM-41 nanoparticles was more significant and improved by 16.9%compared with pure water.

Numerical Analysis of Cold-Formed Thin-Walled Steel Short Columns with Pitting Corrosion during Bridge Construction

Pitting corrosion is harmful during bridge construction,which will lead to uneven roughness of steel surfaces and reduce the thickness of steel.Hence,the effect of pitting corrosion on the mechanical properties of cold-formed thin-walled steel stub columns is studied,and the empirical formulas are established through regression fitting to predict the ultimate load of web and flange under pitting corrosion.In detail,the failure modes and load-displacement curves of specimens with different locations,area ratios,and depths are obtained through a large number of non-linear finite element analysis.As for the specimens with pitting corrosion on the web,all the specimens are subject to local buckling failure,and the failure mode will not change with pitting corrosion,but the failure location will change with pitting corrosion location;the size,location,and area ratio of pitting corrosion have little influence on the ultimate load of cold-formed thin-walled steel short columns,but the loss rate of pitting corrosion section area has a greater impact on the ultimate bearing capacity.As for the specimen with flange pitting corrosion,the location and area ratio of pitting corrosion have less influence on the ultimate load of cold-formed thin-walled steel short columns,and the section area loss rate has greater influence on the ultimate bearing capacity;the impact of web pitting corrosion on the ultimate load is greater than that of flange pitting corrosion under the same condition of pitting corrosion section area.The prediction formulas of limit load which are suitable for pitting corrosion of web and flange are established,which can provide a reference for performance evaluation of corroded cold-formed thin-walled steel.

An Affordable and Easily Accessible Approach for Acrylonitrile Monomer Purification through a Simple Column Technique

This manuscript presents a dataset detailing a method for purifying monomers. Purification plays a crucial role in every chemical process, as it leads to an improvement in product quality through the removal of impurities. The primary method for monomer purification, like acrylonitrile (AN), is the distillation technique. However, this technique is unsafe and hard to set up or handle. A straightforward, risk-free, low-cost method like the column technique resolves these issues. A simple column technique demonstrated the successful execution of purifying AN. Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed that AN was successfully purified, with purity reaching 99.8%. FTIR spectra revealed changes in the position and intensity of the stretching vibration peaks after purification. Also, the functional groups of the inhibitor monomethyl ether of hydroquinone (MeHQ) were undetected after purification. Furthermore, after purification, NMR spectra revealed the absence of aromatic protons and carbons associated with MeHQ. In conclusion, the column technique is a successful and inexpensive way to purify AN monomers. This makes it useful for a wide range of applications, especially in polymerization reactions where MeHQ needs to be removed to prevent self-polymerization during the initiation process.

Gastrotracheal fistula:Treatment with a covered self-expanding Y-shaped metallic stent

A 67-year-old man had a sev-ere cough and pulmonary infection for 1 wk before seeking evaluation at our hospital.He had undergone esophagectomy with gastric pull-up and radiotherapy for esophageal cancer 3 years previously.After admission to our hospital,gastroscopy and bronchoscopy revealed a fistulous communication between the posterior tracheal wallnear the carina and the upper residual stomach.We measured the diameter of the trachea and bronchus and determined the site and size of the fistula using multislice computed tomography and gastroscopy.A covered self-expanding Y-shaped metallic stent was implanted into the trachea and bronchus.Subsequently,the fistula was closed completely.The patient tolerated the stent well and had good palliation of his symptoms.

Y-shaped block copolymers of poly(ethylene glycol) and poly(N-isopropylacrylamide) synthesized by ATRP

Novel Y-shaped block copolymers of poly（ethylene glycol） and poly（N-isopropylacrylamide）, PEG-b-（PNIPAM）2, were successfully synthesized through atom transfer radical polymerization （ATRP）. A difunctional macroinitiator was prepared by esterification of 2,2-dichloroacetyl chloride with poly（ethylene glycol） monomethyl ether （PEG）. The copolymers were obtained via the ATRP ofN-isopropylacrylamide （NIPAM） at 30℃ with CuCl/Me6TREN as a catalyst system and DMF/H2O （v/v = 3：1） mixture as solvent. The resulting copolymers were characterized by gel permeation chromatography （GPC） and ^1H NMR. These block copolymers show controllable molecular weights and narrow molecular weight distributions （PDI 〈 1.15）. Their phase transition temperatures and the corresponding enthalpy changes in aqueous solution were measured by differential scanning calorimetry （DSC）. As a result, the phase transition temperature of PEG45-b-（PNIPAM55）2 is higher than that of PNIPAM, however, the corresponding enthalpy change is much lower, indicating the significant influence of the macromolecular composition and architecture on the phase transition.

Binary collision approximation for solitary waves in a Y-shaped granular chain

We implement a binary collision approximation to study solitary wave propagation in a two-dimensional double Y- shaped granular chain. The solitary wave was transmitted and reflected when it met the interface of the bifurcated branches of the Y-shaped granular chains. We obtain the analytic results of the ratios of the transmitted and reflected speeds to the incident speed of the solitary wave, the maximum force between the two neighbor beads in a solitary wave, and the total time taken by the pulse to pass through each branch. All of the analytic results are in good agreement with the experimental observations from Daraio et al. [Phys. Rev. E 82 036603 （2010）]. Moreover, we also discuss the delay effects on the arrival of split pulses, and predict the recombination of the split waves traveling in branches in the final stem of asymmetric systems. The prediction of pulse recombination is verified by our numerical results.

Evaluation of ultimate bearing capacity of Y-shaped vibro-pile

Based on Mindlin stress solution, a numerical computational method was proposed to calculate the stresses in the ground induced by side friction and the resistance of Y-shaped vibro-pile. The improved Terzaghi's and ЪерезанцевВГ's methods for ultimate bearing capacity evaluation were proposed by considering the stress strength induced by friction resistance at pile head level of Y-pile. A new method to calculate the ultimate bearing capacity of Y-pile was also proposed based on the assumptions of soil failure mode at the tip of Y-pile and the use of Mohr-Coulomb soil yield criterion and Vesic compressive correction coefficient with the induced stresses in the ground. Based on the comparisons with the field static load test results, it is found that the improved Terzaghi's method gives higher ultimate capacity, while the other two methods shows good agreement with the field results.

Prediction of column failure modes based on artificial neural network

To implement the performance-based seismic design of engineered structures,the failure modes of members must be classified.The classification method of column failure modes is analyzed using data from the Pacific Earthquake Engineering Research Center(PEER).The main factors affecting failure modes of columns include the hoop ratios,longitudinal reinforcement ratios,ratios of transverse reinforcement spacing to section depth,aspect ratios,axial compression ratios,and flexure-shear ratios.This study proposes a data-driven prediction model based on an artificial neural network(ANN)to identify the column failure modes.In this study,111 groups of data are used,out of which 89 are used as training data and 22 are used as test data,and the ANN prediction model of failure modes is developed.The results show that the proposed method based on ANN is superior to traditional methods in identifying the column failure modes.

Transfer characteristics of dynamic biochemical signals in non-reversing pulsatile flows in a shallow Y-shaped microfluidic channel: signal filtering and nonlinear amplitude-frequency modulation

The transports of the dynamic biochemical signals in the non-reversing pulsatile flows in the mixing microchannel of a Y-shaped microfluidic device are ana- lyzed. The results show that the mixing micro-channel acts as a low-pass filter, and the biochemical signals are nonlinearly modulated by the pulsatile flows, which depend on the biochemical signal frequency, the flow signal frequency, and the biochemical signal transporting distance. It is concluded that, the transfer characteristics of the dynamic biochemical signals, which are transported in the time-varying flows, should be carefully considered for better loading biochemical signals on the cells cultured on the bottom of the microfluidic channel.

Y-Shaped Intra-Scleral Fixated Lens versus Retro-Pupillary Iris Claw Lens in the Treatment of Aphakia

Background: Many reasons can lead to an aphakia without adequate capsular support for implantation of a posterior chamber intraocular lens (IOL), such as intraoperative unintentional rupture of posterior capsule during phacoemulsification, planned intracapsular cataract extraction, ocular trauma and lens dislocation due to congenital and acquired causes. Purpose: To compare Y-shaped intra-scleral fixation of a posterior chamber IOL with retro pupillary fixation of an iris-claw intraocular lens (IOL) for Aphakic eyes without sufficient capsular support as respects safety, visual recovery and complications of both methods. Patients and Methods: One hundred Aphakic eyes were arbitrarily distributed between two groups. Group A included 50 eyes treated with retropupillary fixation of iris claw lens and group B included 50 eyes treated with Y-shaped intra-scleral fixation technique. Preoperative, intraoperative and postoperative data were analysed including best corrected visual acuity (BCVA), intraocular pressure (IOP), surgical time, intraoperative problems, IOL malposition and postoperative complications. Following up on patients was carried out for at least six months. Results: The mean duration of surgery was 21 ± 5.3 min in group A and was 53.4 ± 6.9 min in group B (p-value 0.05). IOL tilt was found in 0 (0%) eyes in group A and in 5 (10%) eyes in group B (p 0.05). Conclusion: The results of our study indicated that both methods are satisfactory in correcting aphakia without sufficient capsular support as regards postoperative best corrected visual acuity (BCVA);however the surgical technique of retropupillary iris claw lens is easier, shorter, with low intra- and postoperative complications and safer than those used for intra-scleral fixation of IOL. But for eyes which lack both iris and capsular support, a scleral fixation of a posterior chamber IOL remains the only option.

Comparison of lag screws and double Y-shaped miniplates in the fixation of anterior mandibular fractures

BACKGROUNDMandibular fractures constitute about 80.79% of maxillofacial injuries inAlexandria University, either as isolated mandibular fractures or as a part ofpanfacial fractures. The combination of symphyseal and parasymphyseal fracturesrepresent 47.09% of the total mandibular fractures.AIMTo compare the effectiveness of lag screws vs double Y-shaped miniplates in thefixation of anterior mandibular fractures.METHODSThis study is a prospective randomized controlled clinical trial, performed onsixteen patients with anterior mandibular fractures. Patients were divided equallyinto two groups, each consisting of eight patients. Group 1: Underwent openreduction and internal fixation using two lag screws. Group 2: Underwent openreduction and internal fixation using double Y-shaped plates. The followingparameters were assessed: operating time in minutes, pain using a visual analogscale, edema, surgical wound healing for signs and symptoms of infection,occlusion status and stability, maximal mouth opening, and sensory nervefunction. Cone beam computed tomography was performed at 3 and 6 mo tomeasure bone density and assess the progression of fracture healing.RESULTSThe study included 13 males (81.3%) and 3 females (18.8%) aged 26 to 45 years(mean age was 35.69 ± 6.01 years). The cause of trauma was road traffic accidentsin 10 patients (62.5%), interpersonal violence in 3 patients (18.8%) and othercauses in 3 patients (18.8%). The fractures comprised 10 parasymphyseal fractures(62.5%) and 6 symphyseal fractures (37.5%). The values of all parameters were comparable in both groups with no statistically significant difference except forthe mean bone density at 3 mo postoperatively which was 946.38 ± 66.29 in group 1 and 830.36 ± 95.53 in group 2 (P = 0.015).CONCLUSIONBoth lag screws and double Y-shaped miniplates provide favorable means offixation for mandibular fractures in the anterior region. Fractures fixed with lagscrews show greater mean bone density at 3 mo post-operation, indicative ofhigher primary stability and faster early bone healing. Further studies with largersample sizes are required to verify these conclusions.

Numerical simulation of gas–liquid flow in the bubble column using Wray–Agarwal turbulence model coupled with population balance model

In this paper,an improved computational fluid dynamic(CFD)model for gas-liquid flow in bubble column was developed using the one-equation Wary-Agarwal(WA)turbulence model coupled with the population balance model(PBM).Through 18 orthogonal test cases,the optimal combination of interfacial force models,including drag force,lift force,turbulent dispersion force.The modified wall lubrication force model was proposed to improve the predictive ability for hydrodynamic behavior near the wall of the bubble column.The values simulated by optimized CFD model were in agreement with experimental data,and the errors were within±20%.In addition,the axial velocity,turbulent kinetic energy,bubble size distribution,and the dynamic characteristic of bubble plume were analyzed at different superficial gas velocities.This research work could provide a theoretical basis for the extension of the CFD-PBM coupled model to other multiphase reactors..

An optimization method for enhancement of gas–liquid mass transfer in a bubble column reactor based on the entropy generation extremum principle

In this study,an optimization method is proposed to enhance the gas–liquid mass transfer in bubble column reactor based on the entropy generation extremum principle.The mass transfer–induced entropy generation can be maximized with the increase of mass transfer rate,based on which the velocity field can be optimized.The oxygen gas–liquid mass transfer is the major rate–limiting step of the toluene emissions biodegradation process in bubble column reactor,so the entropy generation due to oxygen mass transfer is used as the objective function,and the conservation equations of the gas–liquid flow and species concentration are taken as constraints.This optimization problem is solved by the calculus of variations,the optimal liquid flow pattern is obtained and the relationship of the maximum mass transfer enhancement on viscous dissipation is revealed,which can be used to improve the design of internal structure of the bubble column reactor.

Pressure drop of structured packing in pilot column and comparison to common correlations

Packed columns are widely used in the chemical industry such as absorption,stripping,distillation,and extraction in the production of e.g.organic chemicals,and pharmaceuticals.Pressure loss and pressure drop correlations are of special interest when it comes to the hydrodynamic properties of a column.The pressure loss across the column is of interest in the design phase when the size of the blower to drive the gas stream through the column has to be decided.The loading point and flooding point are also influenced by the pressure loss and the area of operation is determined from these points.This work examines four different correlations on pressure drop.The correlations are(i)Ergun’s equation(1952),(ii)an improved version of Ergun’s equation by Stichlmair,Bravo,and Fair(1989),(iii)an equation developed by Billet and Schultes(1999),and(iv)an equation by Rocha,Bravo,and Fair(1993).The complexity of the correlations is increasing in the mentioned order,Ergun’s equation being the simplest one.This study investigates if the more complicated correlations give better predictions to pressure drop in packed columns.This is determined by comparing the correlations to experimental data for pressure drop in a packed column with 8.2 m of structured packing using water as the liquid and atmospheric air as the gas.Seven experiments were carried out for determining the pressure drop in the column with liquid flows varying from 0 to 500 kg·h^(-1).At constant liquid flow,the gas flow was varied from approximately 10 to 70 kg·h^(-1).The pressure drop across the non-wetted column was best described by the correlation by Rocha et al.while the pressure drop for liquid flows from 100 to 500 kg·h^(-1)was,in general,best described by Stichlmair’s equation.For an irrigated column,the highest deviation was a predicted pressure drop 69.6%lower than measured.The best prediction was 0.1%higher than the measured.This study shows,surprisingly,that for a system of water and atmospheric air,complicated correlations on pressure drop determination do not provide better estimates than simple equations.

Rapid Analysis of Four Alkaloids in Uncaria rhynchophylla by Core-Shell Column HPLC and Quantitative Analysis of Multi-Components by Single Marker(QAMS)

As a traditional herbal medicine,the major alkaloids in Uncaria rhynchophylla have been proven to have blood pressure-lowering and sedative effects.It is essential to develop an effective method for the determination of the major alkaloids in U.rhynchophylla.In this research,a rapid quantitative analysis involving multi-components analysis by a single marker strategy coupled with core-shell column HPLC was adopted to analyse four alkaloids(corynoxeine,isocorynoxeine,isorhynchophylline,rhynchophylline)in U.rhynchophylla.Isorhynchophylline was selected as the internal reference substance,the content of which was determined by the traditional external standard method.Relative correction factors(RCF)between isorhynchophylline and the other three alkaloids were calculated respectively.The results showed that the QAMS method had good robustness under different HPLC instruments.Nineteen batches of U.rhynchophylla were tested.No significant difference was observed between the results by QAMS and EMS(Correlation coefficient>0.99,p>0.05).The QAMS method could be employed as a rapid,effective technique for the quality control of U.rhynchophylla.

Automatic segmentation of gas plumes from multibeam water column images using a U-shape network

Cold seeps are widely developed on the seabed of continental margins and can form gas plumes due to the upward migration of methane-rich fluids.The detection and automatic segmentation of gas plumes are of great significance in locating and studying the cold seep system that is usually accompanied by hydrate layers in the subsurface.A multibeam echo-sounder system(MBES)can record the complete backscatter intensity of the water column,and it is one of the most effective means for detecting cold seeps.However,the gas plumes recorded in multibeam water column images(WCI)are usually blurred due to the interference of the complicated water environment and the sidelobes of the MBES,making it difficult to obtain the effective segmentation.Therefore,based on the existing UNet semantic segmentation network,this paper proposes an AP-UNet network combining the convolutional block attention module and the pyramid pooling module for the automatic segmentation and extraction of gas plumes.Comparative experiments are conducted among three traditional segmentation methods and two deep learning methods.The results show that the AP-UNet segmentation model can effectively suppress complicated water column noise interference.The segmentation precision,the Dice coefficient,and the recall rate of this model are 92.09%,92.00%,and 92.49%,respectively,which are 1.17%,2.10%,and 2.07%higher than the results of the UNet.

A dynamic control structure of liquid-only transfer stream distillation column

The intention of this fundamental work is to explore the manipulation of a mixture of benzene,toluene and o-xylene separated from liquid-only transfer divided-wall column(LTS-DWC).First,two control structures are clearly proposed,including seven component control loops(CS1)and seven temperature control loops(CS2).However,two control structures can handle ±10% feed disturbances rather than larger feed disturbances.Subsequently,an equivalent four-column model by introducing withdraw ratio is developed to discuss the effect of two liquid-only side-stream on the overall reboiler duty.It is indicated that the second liquid-only side-stream withdraw ratio strongly affects the overall energy consumption.Hence,six-component control loops within the fixed second liquid-only side-stream withdraw ratio(CS3)is proposed and the purity of products returns to set value even as facing ±20% feed disturbances.Finally,based on the above results,it is established a temperature control structure(CS4)for controlling fixed second liquid-only side-stream withdraw ratio,which can cope with ±15% disturbances.Inspired by these findings,an insight into the dynamic control of LTS-DWC promotes the industrial implementation of DWC through new liquid-only side-stream configurations.

Modeling of Fixed Bed Adsorption Column Parameters of Iron(II) Removal Using Ferrihydrite Coated Brick

Fixed-bed operating experimental column conditions were studied to evaluate the performance of brick from Bangui Region (in Central African Republic), coated with iron oxyhydroxide (ferrihydrite) for the removal of iron(II) from aqueous solution. The prediction of theoretical breakthrough profiles using Bohart and Adams sorption model was employed to achieve characteristic parameters such as depth of exchange zone, time required for exchange zone to move vertically, moving rate for the exchange zone and adsorption capacity useful for fixed-bed column reactor was investigated under varying operating conditions. The effects of bed depth and flow rate on iron(II) adsorption were studied. Our finding revealed that the Brick from Bangui Region (in Central African Republic), coated with ferrihydrite was a very efficient media for the removal of Fe(II) ions from water. The experimental data showed that the depth and the moving rate (10.3 ± 0.6 cm) and (0.208 ± 0.006 cm/min) respectively of the exchange zone (adsorption zone) were independent of variability of the height of the adsorbent bed column, however the variations of the flow rate affect the moving rate of the exchange zone. The bed depth service time (BDST) model was used and permitted us to predict the service times of columns operated at various flow rates and bed depths and these predicted values were compared with the experimental values.