An extended social force model on unidirectional flow considering psychological and behavioral impacts of hazard source

An accurate assessment of the evacuation efficiency in case of disasters is of vital importance to the safety design of buildings and street blocks.Hazard sources not only physically but psychologically affect the pedestrians,which may further alter their behavioral patterns.This effect is especially significant in narrow spaces,such as corridors and alleys.This study aims to integrate a non-spreading hazard source into the social force model following the results from a previous experiment and simulation,and to simulate unidirectional pedestrian flows over various crowd densities and clarity–intensity properties of the hazard source.The integration include a virtual repulsion force from the hazard source and a decay on the social force term.The simulations reveal(i)that the hazard source creates virtual bottlenecks that suppress the flow,(ii)that the inter-pedestrian push forms a stabilisation phase on the flow-density curve within medium-to-high densities,and(iii)that the pedestrians are prone to a less orderly and stable pattern of movement in low clarity–intensity scenarios,possibly with lateral collisions passing the hazard source.

Tailoring the texture and mechanical properties of 3%Y_(2)O_(3)p/ZGK200 composites fabricated by unidirectional and cross rolling followed by annealing

3%Y_(2)O_(3)p/ZGK200 composites were subjected to unidirectional rolling(UR)and cross rolling(CR)at 400℃and 350℃followed by annealing at 300℃for 1 h.The microstructure,texture and mechanical properties of rolled and annealed composites were systematically studied.The rolled composites exhibited a heterogeneous microstructure,consisting of deformed grains elongated along rolling direction(RD)and Y_(2)O_(3)particles bands distributed along RD.After annealing,static recrystallization(SRX)occurred and most deformed grains transformed into equiaxed grains.A non-basal texture with two strong T-texture components was obtained after UR while a non-basal elliptical/circle texture with circle multi-peaks was obtained after CR,indicating that rolling path had great influences on texture of the composites.After annealing process,R-texture component disappeared or weakened,as results,a non-basal texture with double peaks tilting from normal direction(ND)to transverse direction(TD)and a more random non-basal texture with circle multi-peaks were obtained for UR and CR composites,respectively.The yield strength of rolled composites after UR showed obvious anisotropy along RD and TD while a low anisotropic yield strength was obtained after CR.Some Y_(2)O_(3)particles broke during rolling.The fracture of the composites was attributed to the existence of Y_(2)O_(3)clusters and interfacial debonding between particles and matrix during tension,as a result,the ductility was not as superior as matrix alloy.

Frost deformation and microstructure evolution of porous rock under uniform and unidirectional freeze-thaw conditions

The frost deterioration and deformation of porous rock are commonly investigated under uniform freeze-thaw(FT)conditions.However,the unidirectional FT condition,which is also prevalent in engineering practice,has received limited attention.Therefore,a comparative study on frost deformation and microstructure evolution of porous rock under both uniform and unidirectional FT conditions was performed.Firstly,frost deformation experiments of rock were conducted under cyclic uniform and unidirectional FT action,respectively.Results illustrate that frost deformation of saturated rock exhibits isotropic characteristics under uniform FT cycles,while it shows anisotropic characteristics under unidirectional FT condition with both the frost heaving strain and residual strain along FT direction much higher than those perpendicular to FT direction.Moreover,the peak value and residual value of cumulative frost strain vary as logarithmic functions with cycle number under both uniform and unidirectional FT conditions.Subsequently,the microstructure evolution of rock suffered cyclic uniform and unidirectional FT action were measured.Under uniform FT cycles,newly generated pores uniformly distribute in rock and pore structure of rock remains isotropic in micro scale,and thus the frost deformation shows isotropic characteristics in macro scale.Under unidirectional FT cycles,micro-cracks or pore belts generate with their orientation nearly perpendicular to the FT direction,and rock structure gradually becomes anisotropic in micro scale,resulting in the anisotropic characteristics of frost deformation in macro scale.

Unidirectional Negative Refraction at an Exceptional Point of Acoustic P T-Symmetric Systems

We demonstrate a method to realize unidirectional negative refraction in an acoustic parity-time(P T)-symmetric system, which is composed of a pair of metasurfaces sandwiching an air gap. The pair of metasurfaces possesses loss and gain modulations. The unidirectional negative refraction, which is strictly limited to the case of incident wave imposing on the loss end of the metasurface, is demonstrated at the exception point(EP) in this P T-symmetric system, while the incidence from the other side leads to strong reflection. Based on rigorous calculations, we explicitly show the underlying mechanism of this model to achieve unidirectional wave scatterings around the EP in the parametric space. In addition, the perfect imaging of a point source in the three-dimensional space, as a signature of negative refraction, is simulated to provide a verification of our work. We envision that this work may sharpen the understanding of P T-symmetric structures and inspire more acoustic functional devices.

Absorbable and unidirectionally compressible intestine-intestine stapler

Inventors:Xiujun Cai,Mingyu Chen,Chen Lu,Yifan Wang,Diyu Huang,Hepan Zhu,Yibin Zhu,Bin Zhang Applicant:Zhejiang University,Zhejiang,China Patent No.:US 10,980,541 B2 Date of Patent:Apr.20,2021 An absorbable and unidirectionally compressible intestinal anastomosis device includes a first through pipe portion and a second through pipe portion including large ends and small ends,respectively;the large ends are used for fixing an intestinal canal,and the small end of the second through pipe portion is inserted into the small end of the first through pipe portion.The two large ends are drawn close to each other to achieve an intestineeintestine anastomosis.The outer sides of circular rings at the ends of the small ends of the first through pipe portion and the second through pipe portion are provided with gradually expanded elastic horn-shaped openings.The device can make two stapled intestinal canals rest relatively,thereby avoiding adjustments required in other assembly modes.

Effect of melt superheat on structural uniformity of lotus-type porous metals prepared by unidirectional solidification

Structural uniformity is an important parameter influencing physical and mechanical properties of lotus-type porous metals prepared by directional solidification of metal-gas eutectic (Gasar). The effect of superheat on structural uniformity as well as average porosity, pore morphology of porous metals was studied. The experimental results show that, when the superheat is higher than a critical value (ΔTc), the bubbling or boiling phenomenon will occur and the gas bubbles will form in the melt and float out of the melt. As a result, the final porosity will decrease. In addition, a higher superheat will simultaneously cause a non-uniform porous structure due to the pores coalescence and bubbling phenomenon. Finally, a theoretical model was developed to predict the critical superheat for the hydrogen to escape from the melt and the corresponding escapement ratio of hydrogen content. Considering the escapement of hydrogen, the predicted porosities are in good agreement with the experimental results.

RELAXATION BEHAVIOUR OF GFRP UNIDIRECTIONAL LAMINATES

In this paper two set of GFRP specimens are manufactured and tested to investigate the relaxation behaviour under cyclic loading in the longitudinal and transversel direction. The relaxation of GFRP unidirectional laminates is evident for both cyclic loadings. Under longitudinal cyclic loading the relaxation is dependent on the number of loading cycles. Under transverse loading the relaxation depends on the loading cycles as well as the time of loading. Two expressions are set up to describe the relaxation for the longitudinal and transverse loading, and the predictions agree well with the experimental data.

Hydrogen diffusion coefficient in liquid metals evaluated by solid-gas eutectic unidirectional solidification

Based on the solid-gas eutectic unidirectional solidification technique and the principle of unidirectional solidification of single-phase alloy, a new method for evaluating the diffusion coefficient of hydrogen in liquid metals was proposed. Taking Cu-H2 system for example, the influences of argon partial pressure and superheat degree of melt on the diffusion coefficient of hydrogen in liquid metal were studied and the predicted values were similar to each other. The obtained temperature-dependent equation for diffusion coefficient of hydrogen in liquid copper is comparable with experimental data in literature, which validates the effectiveness of this method. The temperature-dependent equations for diffusion coefficient of hydrogen in liquid Mg, Si and Cu-34.6%Mn alloy were also evaluated by this method, along with the values at the melting point of each metal and alloy.

Textural Evolution of AZ31B Magnesium Alloy Sheets Undergoing Repeated Unidirectional Bending at Room Temperature

In this paper, repeated unidirectional bending （RUB）, was applied to improve the texture of AZ31B magnesium alloy sheets so as to enhance their stamping properties. The samples undergoing RUB were annealed at different temperatures. The mechanical properties, formability, textural components and microstructure of the samples before and after RUB were characterized and compared. It was found that the basal textural component was reduced dramatically by RUB, and that （1212） and （1211） textural components appeared. Annealing has a great effect on the mechanical properties of samples undergoing RUB. The plasticity and stamping formability of samples were greatly improved by RUB and annealing at 260℃ for 1 h, and elongation to fracture and Erichsen value were increased to 38% and 67%, respectively.

Continuous unidirectional solidification of QAl9-4 Cu-Al alloy

A continuous unidirectional solidification equipment with the advantages of electric slag remelting, induction heating, continuous casting and unidirectional solidification was built to study the QAl9 4 Cu Al alloy. The results show that the electro slag induction continuous unidirectional solidification process can be used for the steady continuous unidirectional solidification of QAl9 4, and revitalizes the down pulling continuous unidirectional solidification process; that the temperature distribution in the mold wall reflects that of the molten metal in the mold, thus the temperature distribution in the mold wall can be used to control the electric slag induction continuous unidirectional solidification process; and that the mutual matching of the technological parameters is the key to stabilize the solidification process.

Mechanism of reduction of columnar dendrite spacing in unidirectional solidification caused by electric current passing through solid liquid interface

Considering the S L interface morphology stability, the S L interface energy, the Joule heat produced by electric current at the S L interface, and the change of solute concentration at the S L interface indirectly caused by electric current, the mechanism of reduction of columnar dendrite spacing in unidirectional solidification caused by electric current passing through solid liquid interface was studied. The following conclusions can be drawn that: 1) under sub rapid solidification condition, increasing electric current density will improve the stability of S L interface, thus decreasing the columnar dendrite spacing; 2)there are two ways by which the increase of electric current decreases the columnar dendrite spacing, one is promoting the splitting of the protruding tips at the S L interface, the other is promoting the forming of new convex parts at the bottom of the concave interface.[

Fabrication of pure copper rods containing continuous columnar crystals by continuous unidirectional solidification technology

Pure copper rods containing continuous columnar crystals were fabricatedusing the downward CUS (Continuous Unidirectional Solidification) equipment. When the technologicalparameters were set as the ranges of mould temperature 1100-1300℃, cooling distance (the distancefrom the exit of the cast mould to the start point of cooling) 10-20 mm, casting speed 0.2-2.5 mm/s,cooling water (20-25℃) volume 1000-1320 L/h, and when these parameters matched reasonably, the CUSprocess was performed stably, and pure copper rods containing continuous columnar crystals withbright and smooth surface were produced. The dendritic arm spacing of the crystals in copper rodsdecreased with increasing the casting speed. The results of the texture by X-ray diffractionanalysis showed that the rods has strong <100> fiber texture.

WAYS OF STABILIZING CONTINUOUS UNIDIRECTIONAL SOLIDIFICATION PROCESS AND VERIFICATION TESTS

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A simple method for solving unidirectional methane gas flow in coal seam based on similarity solution

The equation used to model the unidirectional flow of methane gas in coal seams is usually formulated as a nonlinear partial differential equation, which needs to be solved numerically with a computer program.Nevertheless, for people without access to the computer program, the conventional numerical method may be inconvenient. Thus, the objective here is to seek some method simpler than the conventional one for solving the flow problem. A commonly used model of the unidirectional methane gas flow is considered, where the methane adsorption is described by the Langmuir isotherm and the free gas is treated as real gas. By introducing the similarity solution, a simple method for solving the flow model is proposed, which can be done on a hand calculator. It is shown by two examples that the gas pressure profile obtained by the proposed method agrees well with the direct numerical solution of the flow model.

Macrostructure and properties of thin walled copper tubes prepared by the downward continuous unidirectional solidification method

The macrostructure and properties of the thin walled copper tube prepared by the downward continuous unidirectional solidification （DCUS） method were studied. The result shows that the macrostructure is closely related to the solid-liquid interface profile, which is influenced by the distance between the cooling water location and the solidification front. The mechanical properties of the thin walled copper tube prepared by the DCUS method are near those of the normal cast copper, and it has good relative density, electrical conductivity, and elongation, which are not greatly affected by casting speed. The thin walled copper tube prepared by the DCUS method also has good processing properties that can be taken to further drawing procedures directly without an intermediate process, and obtains good mechanical properties with the total processing rate of 89.8%.

Structure and properties of AZ31B magnesium alloy sheets processed by repeatedly unidirectional bending at different temperatures

Repeatedly unidirectional bending(RUB) was applied to the magnesium alloy sheet to improve the basal texture.The effect of RUB temperature on resulting structure and room temperature properties was investigated.The texture components of the sheet undergoing RUB at recovery temperature were similar to those of the sheet undergoing RUB at room temperature(RT).As the RUB temperature increased to above recrystallization temperature,the texture components became more disperse and the pyramidal components increased.With the increase of RUB temperature,the grain size near the surface of the sheets undergoing RUB tended to grow up.When the sheets were processed by RUB at medium-high temperature followed by annealing at 533 K,the yield strength and fracture elongation were lower than those of the cold rolled sheet;however,the Erichsen value was slightly higher than that of the cold rolled sheet.The sheet undergoing RUB at RT followed by annealing at 533 K represented the best mechanical properties.

Driving Mechanism of Cotton Comber's Detaching Roller Based on Time-Sharing Unidirectional Drive

The high-speed reciprocating motion of a detaching roller limits the velocity of a cotton comber and affects the quality of comber slivers. The article has proposed a controllable time-sharing unidirectional hybrid drive mechanism after analyzing detaching roller's current numerical control drive method. The analysis focuses on the detaching roller motion required according to cotton comber's velocity and process. The double-servo motors of the mechanism consists of differential gear trains. The mechanism addresses the problem of increased servo motor power,and failure of promptly responded to the positive inversion process of mechanism driven by servo motors. A velocity calculation model of the detaching roller controllable drive mechanism will be generated by using superposition method and design of differential gear trains. The accuracy of the model will be verified using the test platform. This study has presented a reliable and practical high-speed drive mechanism and can be a reference to future studies on high-speed reciprocating motion drive.

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion—Effect of Fluidic Diode on the Performance

As a system using a conventional unidirectional air turbine in oscillating water column (OWC) based on a wave energy plant, a twin unidirectional impulse turbine topology has been suggested in previous studies. However, the average efficiency of the suggested twin turbine is considerably lower than that of a conventional unidirectional turbine in this topology because reciprocating air flow can’t be rectified adequately by a unidirectional turbine. In order to improve the efficiency, using fluidic diode is discussed. In this study, two different fluidic diodes were discussed by computational fluid dynamics (CFD) and a wind tunnel test. Further, its usefulness is discussed from a view point of the turbine efficiency. The fluidic diode was shown to improve rectification of the topology. However, it needs more improvement in regards to its energy loss in order to enhance the turbine efficiency.

Formation of twinned dendrites during unidirectional solidification of Al-32%Zn alloy

The present study focused on the formation and crystallographic orientation of twinned dendrites coexisting with equiaxed grains in unidirectional solidification of Al-32%Zn(mass fraction)alloy.The morphology was investigated by optical metallograph and electron back-scattered diffraction technique.Results showed that the macrostructure of the alloy exhibited a typical feathery and fan-like structure while the microstructures were elongated lamellas,which were separated by coherent and incoherent twin boundaries.Both the primary trunk and all lateral arms of twinned dendrites grew along〈110〉directions,unlike regular〈100〉α(Al)dendrites.The facet growth of crystals at solid/liquid interface was responsible for the origin of twinned dendrites during the weak local convection,and high thermal gradient and medium solidification velocity had significant contribution to the formation of twinned dendrites.The formation mechanism of twinned dendrites which consisted of three multiplication ways of new twin boundaries formation and one way of dendrite evolution in twin plane was shown schematically.

A new matrix-based mathematical model for determining unidirectional circuits in a ventilation network

The occurrence of local circulating ventilation can be caused by many factors, such as the airflow reversion during mine fire,the improper arrangement of local fan or underground fan station and the man-made error input of raw data before network solving. Once circulating ventilations occur,the corresponding branches in the ventilation network corresponding to the relevant airways in ventilation system form circuits,and all the direc- tions of the branches in the circuits are identical,which is the unidirectional problem in ventilation network.Based on the properties of node adjacent matrix,a serial of mathe- matical computation to node adjacent matrix were performed,and a mathematical model for determining unidirectional circuits based on node adjacent matrix was put forward.