Phase Transformations in ZrO_2 after Shock Loading

The effects of shock loading on the morphology,grain growth during heating and phase transforma- tion of ZrO_2 have been investigated.It is shown that shock loading may be efficiently used to modify submicron ceramic powders with nanocrystalline structure.After shock loading,the critical diameter of ZrO_2 particles transformed from tetragonal to monoclinic decreased due to stored strain energy. Annealing of powders resulted in reversible transformation to the tetragonal without considerable grain growth up to 1200℃.

Redistribution of Trace Elements During Shock-inducd Melting and Phase Tranzition of Minerals in the Suizhou l6 Chondrite

The Suizhou meteorite is an L6 chondrite. This meteorite is consisted of olivine, low-Ca pyroxene, plagioclase, FeNi metal, troilite, whitlockite, chlorapatite, chromite and ilmenite. Olivine and pyroxene grains display shock-induced mosaic texture, and most plagioclase grains were melted and transformed to maskelynite. This meteorite contains a few very thin shock-produced melt veins ranging from 20 to 100 μm in width. They are chondritic in composition and contain abundant high-pressure minerals in two assemblages. One is the coarse-grained assemblage of ringwoodite, majorite, lingunite with minor amount of tuite, xieite, the CF-phase, akimotoite and amorphized perovskite, and the fine-grained assemblage (the melt vein matrix) composed of majorite-pyrope garnet, magnesiowüstite. FeNi metal and troilite in the Suizhou shock veins were molten and occur as small intergrowth grains or veinlets filling the interstices of garnet crystals or cracks in the vein matrix. It was revealed that olivine, pyroxene and plagioclase in the Suizhou shock veins have transformed in solid state to their high-pressure polymorphs ringwoodite, majorite, and lingunite, respectively, without change in their chemical compositions.

Numerical study of dynamic phase transitions in shock tube

Shock tube problem of a van der Waals fluid with a relaxation model was investigated. In the limit of relaxation parameter tending towards zero, this model yields a specific Riemann solver. Relaxing and relaxed schemes were derived. For an incident shock in a fixed tube, numerical simulations show convergence toward the Riemann solution in one space dimension. Impact of parameters was studied theoretically and numerically. For certain initial shock profiles, nonclassical reflecting wave was observed. In two space dimensions, the effect of curved wave fronts was studied, and some interesting wave patterns were exposed.

Analysis of Culture Shock In Intercultural Communication

Culture shock can be easily encountered in intercultural communication.This paper illustrates the causes of culture shock,and also provides solutions to deal with culture shock and try to reduce its influence.

A Phase-Dependent Hypothesis for Locomotor Functions of Human Foot Complex

The human foot is a very complex structure comprising numerous bones, muscles, ligaments and synovial joints. As the only component in contact with the ground, the foot complex delivers a variety of biomechanical functions during human locomotion, e.g. body support and propulsion, stability maintenance and impact absorption. These need the human foot to be rigid and damped to transmit ground reaction forces to the upper body and maintain body stability, and also to be compliant and resilient to moderate risky impacts and save energy. How does the human foot achieve these apparent conflicting functions？ In this study, we propose a phase-dependent hypothesis for the overall locomotor functions of the human foot complex based on in-vivo measurements of human natural gait and simulation results of a mathematical foot model. We propse that foot functions are highly dependent on gait phase, which is a major characteristics of human locomotion. In early stance just after heel strike, the foot mainly works as a shock absorber by moderating high impacts using the viscouselastic heel pad in both vertical and horizontal directions. In mid-stance phase （-80% of stance phase）, the foot complex can be considered as a springy rocker, reserving external mechanical work using the foot arch whilst moving ground contact point forward along a curved path to maintain body stability. In late stance after heel off, the foot complex mainly serves as a force modulator like a gear box, modulating effective mechanical advantages of ankle plantiflexor muscles using metatarsal-phalangeal joints. A sound under- standing of how diverse functions are implemented in a simple foot segment during human locomotion might be useful to gain insight into the overall foot locomotor functions and hence to facilitate clinical diagnosis, rehabilitation product design and humanoid robot development.

On some problems of seismic crustal phase

In this paper, some practical problems in seismological observations are discussed on the identification of seismiccrustal phase, such as: “whether P (Pg) and S(Sg) are direct waves or not?”; “whether S(Sg) and Lg as well asng and P (Pg) are two kinds of waves or identical wave?”;“on seismoiogicai phases in regional travel-timetable”;“on the symbols and identifications of phases in seismological observation repors”;“on the relation between mLg and ML”, and so on. Some confused ideas on these problems are clarified.

Global structure stability of impact-induced tensile waves in phase-transforming materials

The global structure stability of the impact-induced tensile waves mentioned by Huang （Huang, S. J. Impact-induced tensile waves in a kind of phase-transforming materials. IMA Journal of Applied Mathematics, 76, 847-858 （2011）） is considered. By introducing Riemann invariants, the governing equations of motion are reduced into a 2 ~ 2 diagonally strictly hyperbolic system. Then, with the aid of the theory on the typical free boundary problem and maximally dissipative kinetics, the global structure stability of the impact-induced tensile waves propagating in a phase-transforming material is proved.

Shock-induced migration of asymmetry tilt grain boundary in iron bicrystal: A case study of Σ3 [110]

Many of our previous studies have discussed the shock response of symmetrical grain boundaries in iron bicrystals.In this paper, the molecular dynamics simulation of an iron bicrystal containing Σ3 [110] asymmetry tilt grain boundary(ATGB) under shock-loading is performed. We find that the shock response of asymmetric grain boundaries is quite different from that of symmetric grain boundaries. Especially, our simulation proves that shock can induce migration of asymmetric grain boundary in iron. We also find that the shape and local structure of grain boundary(GB) would not be changed during shock-induced migration of Σ3 [110] ATGB, while the phase transformation near the GB could affect migration of GB. The most important discovery is that the shock-induced shear stress difference between two sides of GB is the key factor leading to GB migration. Our simulation involves a variety of piston velocities, and the migration of GB seems to be less sensitive to the piston velocity. Finally, the kinetics of GB migration at lattice level is discussed. Our work firstly reports the simulation of shock-induced grain boundary migration in iron. It is of great significance to the theory of GB migration and material engineering.

Effect of metallic phase content on mechanical properties of (85Cu-15Ni)/(10NiO-NiFe_2O_4) cermet inert anode for aluminum electrolysis

(85Cu-15Ni)/(10NiO-NiFe2O4) cermets were prepared with Cu-Ni mixed powders as toughening metallic phase and 10NiO-NiFe2O4 as ceramic matrix. The phase composition, microstructure of composite and the effect of metallic phase content on bending strength, hardness, fracture toughness and thermal shock resistance were studied. X-ray diffraction analysis indicates the coexistence of (Cu-Ni), NiO and NiFe2O4 phases in the cermets. Within the content range of metallic phase from 0% to 20% (mass fraction), the maximal bending strength (176.4 MPa) and the minimal porosity (3.9%) of composite appear at the metallic phase content of 5%. The fracture toughness increases and Vickers’ hardness decreases with increasing metal content. When the thermal shock temperature difference (△t) is below 200 ℃, the loss rate of residual strength for 10NiO-NiFe2O4 ceramic is only 8%, but about 40% for (85Cu-15Ni)/(10NiO-NiFe2O4) cermets. As △t is above 200 ℃, the residual strength sharply decreases for sample CN0 and falls slowly for samples CN5-CN20.

High Order Relaxation Schemes on Phase Transition Equations

Formal analysis of the bubble phenomena of the second order relaxation scheme is presented when this method is applied to phase transition equations. The reason of oscillations is that the second order scheme can’t find the discontinuities on the phase boundary. Based on this realization, a second order relaxation scheme is derived to eliminate it. This new method finds all components and characteristic discontinuities, thus the phase boundary is found exactly. The difference of presented new method and the well-known Nessyahu-Tadmor(NT) scheme is also studied. From the numerical experiment, the new derived scheme is shown much better to compute the phase transition equations.

Structure Transformations in the Polycrystalline (Ti,Nb)₃Al Alloy under Shock-Wave Loading

Structure transformations in the two-phase (Ti, Nb)3Al alloy, induced by shock-wave loading, were studied. The samples were subjected to an impact of a steel plate. The maximum pressure on the samples’ surfaces was 100 GPa, while the maximum temperature was 573 K. The β0→α2 phase transformation occurred during strong deformations. High temperature rectilinear dislocations (such types of dislocations usually could arise at 1073 K) with the c-component, which occasionally formed slip bands, were located at the α2-phase grains after the shock. The deformation α2-phase twins were not observed.

THE FLOW STRUCTURE OF DILUTE GAS-PARTICLE SUSPENSIONS BEHIND A SHOCK WAVE MOVING ALONG A FLAT SURFACE

The asymptotic and numerical investigations of shock-induced boundary layers in gas-particle mixtures are presented. The Saffman lift force acting on a particle in a shear flow is taken into account. It is shown that particle migration across the boundary layer leads to intersections of particle trajectories. The corresponding modification of dusty gas model is proposed in this paper.The equations of two-phase sidewall boundary layer behind a shock wave moving at a constant speed are obtained by using the method of matched asymptotic expansions. The method of the calculation of particle phase parameters in Lagrangian coordinates is described in detail. Some numerical results for the case of small particle concentration are given.

Two-way coupling model for shock-induced laminar boundary-layer flows of a dusty gas

The present paper describes a numerical two-way coupling model for shock-induced laminar boundary-layer flows of a dust-laden gas and studies the transverse migration of fine particles under the action of Saffman lift force. The governing equations are formulated in the dilute twophase continuum framework with consideration of the finiteness of the particle Reynolds and Knudsen numbers. The full Lagrangian method is explored for calculating the dispersedphase flow fields （including the number density of particles） in the regions of intersecting particle trajectories. The computation results show a significant reaction of the particles on the two-phase boundary-layer structure when the mass loading ratio of particles takes finite values.

射流参数对双孔液态CO_(2)相变冲击岩石裂纹扩展的影响

液态CO_(2)相变作用时的射流形状与冲击方向影响着破岩效果。基于自行构建的试验系统,结合LS-DYNA数值模拟,研究了双孔液态CO_(2)在不同气流释放方向组合下的岩石裂纹扩展规律。结果表明:双孔X方向相背冲击时,岩石裂纹并不能在两孔之间扩展贯通。双孔X方向相对冲击时,两孔之间形成贯穿裂纹。双孔Y方向同向冲击时,裂纹沿初始冲击方向扩展,并在孔周围扩展形成多条裂纹。数值模拟结果表明:在不同释放口组合冲击作用下,X方向相对冲击时裂纹在两孔之间形成贯穿,初始裂纹继续扩展贯穿至前后侧面。X方向相背冲击下的试样裂隙主要向预留孔四周扩展。Y方向同向冲击下试样内部裂隙沿初始气流冲击方向的反方向扩展,并未形成贯穿裂纹。从裂纹定向扩展效果而言,双孔X方向相对冲击效果最好,Y方向同向冲击次之,X方向相背冲击最差。从顶面主裂纹扩展数量而言,X方向相背冲击最多,Y方向同向冲击次之,X方向相对冲击最少。研究结果可为CO_(2)冲击致裂技术应用提供指导。

重度烧伤患者非休克期两种输血治疗策略的对比研究

目的浅析重度烧伤患者(非休克期)应用两种输血治疗方案的临床效果。方法选择2020年4月至2023年4月郑州市第一人民医院收治的重度烧伤患者88例进行回顾性分析,依据输血策略的不同分为A组(限制性输血)与B组(开放性输血),各44例,就两组患者输血量,输血有效性[输血前后计算每单位红细胞输注前后的变化量,Δ红细胞(RBC)、Δ血红蛋白(Hb)和Δ红细胞压积(HCT)],电解质变化,凝血功能,不良反应风险进行组间比较。结果A组患者输入RBC、血浆及总血量均低于B组,差异有统计学意义(P<0.05);A组输血有效性ΔRBC、ΔHb指标均高于B组,差异有统计学意义(P<0.05);A组治疗后钠离子(Na^(+))、钙离子(Ca^(2+))指标均高于于B组,且钾离子(K^(+))指标低于B组,差异有统计学意义(P<0.05);A组治疗后凝血酶原时间(PT)、凝血酶时间(TT)、活化部分凝血活酶时间(APTT)指标高于B组,纤维蛋白原浓度(FIB)指标低于B组,差异有统计学意义(P<0.05);A组不良反应风险(9.09%)与B组(20.45%)比较,差异无统计学意义(P>0.05)。结论在治疗重度烧伤患者的非休克期输血过程中,采取限制性输血与开放性输血两种治疗策略均可达到良好的治疗效果,但限制性输血治疗可减少输血的频率,从而降低输血可能带来的风险,并节约血液资源,这对于临床合理安全使用血液具有重要意义。

应用于新型环路热管的两相引射器数值模拟

环路热管是一种高效被动式相变传热装置,广泛应用于高热流电子器件散热等领域。前期研究发现将小型两相引射器与平板式环路热管耦合,可大幅提高传热性能。然而,小型两相引射器内部流动及传热机理尚不清晰,难以对新型环路热管进行正向设计与理论建模。通过数值模拟研究了汽水参数和混合腔结构对两相引射器性能及内部流场分布的影响。结果表明,喉部下游存在凝结激波,随着背压增加,其位置逐渐向喉部移动;其强度与背压、蒸汽产量、混合腔长度呈正相关,与水温呈负相关。引射器最大工作背压在40~125 kPa,与蒸汽产量和水温呈正相关,与混合腔长度呈负相关。通过大量模拟,得到了设计功率下水温和混合腔长度对引射器工作模式和压比的影响规律。

电磁冲击处理对TC11钛合金冲击韧性及其微观组织的影响

通过夏比冲击实验、金相显微镜、扫描电镜和透射电镜表征手段,研究了电磁冲击处理对TC11钛合金冲击韧性及其微观组织的影响。分析讨论了电磁冲击处理过程中处理时间对TC11钛合金冲击韧性的影响规律。结果表明,相比于未处理试样,处理时间为0.44、0.88和1.32 s的电磁冲击处理使得试样的冲击吸收功分别提升13.2%、20.3%和3.1%。且随着处理时间的延长,TC11钛合金中α相含量不断上升。α相含量增加不利于TC11钛合金冲击韧性的提升,但电磁冲击处理引起的界面润湿和界面桥接对试样冲击功的提升起着决定性影响。

霍尔辛赫煤矿可控冲击波强化增透试验研究

为了改善CO_(2)气爆致裂对煤层的增透效果,本文以霍尔辛赫煤矿五盘区集中回风大巷为研究背景,应用可控冲击波增透技术对使用过CO_(2)气爆致裂的煤层进行了强化增透试验研究。在五盘区集中回风大巷共布置7个强化增透钻孔。通过增透孔、观测孔抽采效果的观察分析,表明在已实施CO_(2)措施的区域,可控冲击波增透可以在一定程度上提高钻孔瓦斯流量,具有二次强化增透效果。

烧伤休克期家兔丁胺卡那霉素药动学的改变

５０只家兔烫伤前和烫伤后静脉注射丁胺卡那霉素（１０ｍｇ／ｋｇ）的药动学资料比较结果表明，２０～３０％体表面积三度烫伤后６ｈ、１２ｈ、２４ｈ和３６ｈ给药的４０只补液家兔的丁胺卡那霉素药动学参数均表现为，半衰期（ｔ＿１／２）延长、表观分布容积（Ｖｄ）增加，清除率（ＣＬ）和曲线下面积（ＡＵＣ）改变不明显；１０只烫后６ｈ给药的不补液家兔的药动学参数则为：ｔ＿１／２会延长、Ｖｄ改变不明显、ＣＬ下降和ＡＵＣ增加。本研究揭示了烧伤休克期丁胺卡那霉素药动学变化的特点，为临床合理用药提供实验依据。

蒸汽喷射制冷系统中喷射器内特殊流动现象的研究

本文通过求解二维N-S方程来模拟蒸汽喷射器内复杂的流动混合过程,模拟时使用了蒸汽的真实物性公式。与理想气体假设不同,真实物性的带入,真实地反映了蒸汽经缩放喷嘴时,温度递减,喷嘴出口后温度场波动变化的特征．模拟时,通过对节点焓值的计算,得出了喷射器内发生相变的蒸汽的百分含量,实现了相变现象的定量分析。在激波捕捉方面,验证了喷射器内喷嘴出口后,膨胀波(压缩波)经混合层反复折射、转化、衰减的过程,以及在扩压室入口会产生斜激波的理论预测。