GENERAL SOLUTION FOR INTERACTION OF SOLITARY WAVES INCLUDING HEAD-ON COLLISIONS

A general solution of the Boussinesq equation is presented which solves the problem of interaction of any number of right-going and left-going solitary waves.The solution relies on the exact solu- tion of Gardner,Greene,Kruskal,and Miura(1967),and has the same degree of accuracy as that solution, but has a wider scope of application.It is much simpler than,but as accurate as,Hirota's exact solu- tion(1973)of the Boussinesq equation,to which the present solution is compared for the simplest case of two solitary waves in head-on collision.

ON HEAD-ON COLLISION BETWEEN TWO GKDV SOLITARY WAVES IN A STRATIFIED FLUID

In this paper,using the reductive perturbation method combined with the PLK method and two-parameter expansions,we treat the problem of head-on collision between two solitary waves described by the generalized Korteweg-de Vries equation (the gKdV equation) and obtain its second-order approximate solution.The results show that after the collision,the gKdV solitary waves preserve their profiles and during the collision,the maximum amplitute is the linear superposition of two maximum amplitudes of the impinging solitary waves.

Use of Finite Element Analysis for the Prediction of Driver Fatality Ratio Based on Vehicle Intrusion Ratio in Head-On Collisions

To estimate the aggressivity of vehicles in frontal crashes, national highway traffic safety administration (NHTSA) has introduced the driver fatality ratio, DFR, for different vehicle-to-vehicle categories. The DFR proposed by NHTSA is based on the actual crash statistical data, which makes it difficult to evaluate for other vehicle categories newly introduced to the market, as they do not have sufficient crash statistics. A finite element (FE) methodology is proposed in this study based on computational reconstruction of crashes and some objective measures to predict the relative risk of DFR associated with any vehicle-to-vehicle crash. The suggested objective measures include the ratios of maximum intrusion in the passenger compartments of the vehicles in crash, and the transmitted peak deceleration of the vehicles’ center of gravity, which are identified as the main influencing parameters on occupant injury. The suitability of the proposed method is established for a range of bullet light truck and van (LTV) categories against a small target passenger car with published data by NHTSA. A mathematical relation between the objective measures and DFR is then developed. The methodology is then extended to predict the relative risk of DFR for a crossover category vehicle, a light pick-up truck, and a mid-size car in crash against a small size passenger car. It is observed that the ratio of intrusions produces a reasonable estimate for the DFR, and that it can be utilized in predicting the relative risk of fatality ratios in head-on collisions. The FE methodology proposed in this study can be utilized in design process of a vehicle to reduce the aggressivity of the vehicle and to increase the on-road fleet compatibility in order to reduce the occupant injury out- come.

Head-on collision of ring dark solitons in Bose-Einstein condensates

The ring dark solitons and their head-on collisions in a Bose-Einstein condensates with thin disc-shaped potential are studied. It is shown that the system admits a solution with two concentric ring solitons, one moving inwards and the other moving outwards, which in small-amplitude limit, are described by the two cylindrical KdV equations in the respective reference frames. By using the extended Poincaré-Lighthill-Kuo perturbation method, the analytical phase shifts following the head-on collisions between two ring dark solitary waves are derived. It is shown that the phase shifts decrease with the radial coordinate r according to the r-1/3 law and depend on the initial soliton amplitude and radius.

HEAD-ON COLLISION BETWEEN TWO mKdV SOLITARY WAVES IN A TWO-LAYER FLUID SYSTEM

In this paper, based on the equations presented in [2], the head-on collision between two solitary waves described by the modified KdV equation (the mKdVequation, for short) is investigated by using the reductive perturbation method combined with the PLK method. These waves propagate at the interface of a two-fluid system, in which the density ratio of the two fluids equals the square of the depth ratio of the fluids. The second order perturbation solution is obtained. It is found that in the case of disregarding the nonuniform phase shift, the solitary waves preserve their original profiles after collision, which agrees with Fornberg and Whitham's numerical result of overtaking collision[6] whereas after considering the nonuniform phase shift, the wave profiles may deform after collision.

Head-on collision between two hydroelastic solitary waves with Plotnikov-Toland's plate model

Head-on collision between two hydroelastic solitary waves propagating at the surface of an incompressible and ideal fluid covered by a thin ice sheet is analytically studied by means of a singular perturbation method. The ice sheet is represented by the Plotnikov-Toland model with the help of the special Cosserat theory of hyperelastic shells and the Kirchhoff-Love plate theory,which yields the nonlinear and conservative expression for the bending forces. The shallow water assumption is taken for the fluid motion with the Boussinesq approximation. The resulting governing equations are solved asymptotically with the aid of the Poincaré-Lighthill-Kuo method,and the solutions up to the third order are explicitly presented. It is observed that solitary waves after collision do not change their shapes and amplitudes. The wave profile is symmetric before collision, and it becomes, after collision, unsymmetric and titled backward in the direction of wave propagation. The wave profile significantly reduces due to greater impacts of elastic plate and surface tension. A graphical comparison is presented with published results, and the graphical comparison between linear and nonlinear elastic plate models is also shown as a special case of our study.

Electrical characteristics of laminar propane flame during head-on quenching

The electrical characteristics of laminar propane flame during head-on quenching were investigated experimentally and computationally.A variable small electric field was applied between the burner and the quenching plate,which recorded flame current as a function of the height of the quenching plate,for both polarities,different premixed-air volume,and quenching plate materials.More detailed information of flame,such as the distribution of OH radical and main charged species(H3O+and e-)were obtained by using numerical simulation.The results showed that during the head-on quenching,the resistance of the propane flame is on the order of 108Ω,the flame current increases with the increase of the premixed-air volume,and the effect of the quenching plate materials on the flame current is negligible.In addition,it is found that the direction of the electric field has a significant influence on the flame current,indicating the"rectifier"characteristics of the flame.Moreover,it is interestingly found that the trend of flame current for burner-(burner is negative)is more consistent with the trend of the maximum OH mole concentration than for burner+(burner is positive),which indicates that the trend of flame current for burner-can more accurately reflect the combustion state during head-on quenching.And it would be a better choice to use burner as the negative electrode when diagnosing the combustion state with an applied electric field.

高温深井矿山独头掘进巷道通风降温机理研究

针对高温深井矿山独头掘进作业温度高、通风难等问题,以海南山金抱伦金矿为原型,基于气固两相流理论,采用三维流体仿真软件模拟深井井下高温环境,根据不同通风参数下主运巷及独头巷道的温度场、速度场分布特征,研究风温、风速及岩温等对气流分布、温度分布特征影响规律。结果表明:独头巷道有效通风临界距离为7 m,巷道交接处会产生“8”字型涡流,涡流交错处断面平均温度达到最低值,超过7 m,需要采取局部通风措施改善作业环境;采用制冷设备进行降温时,制冷装置距离掘进作业点距离小于30 m,入口通风温度为20~25℃时较为适宜;对于高热巷道围岩覆盖一定厚度的保温材料,减少岩壁向气流中散热,可以有效降低巷道空气温度。研究结论可为高温深井矿山通风系统设计、局部制冷降温设计提供理论支撑。

时域声波障碍反散射问题的神经网络方法

研究了一种求解时域声波移动障碍物反散射问题的神经网络方法。该方法由一维卷积模块和多头自注意力机制模块构成,其中一维卷积模块的特征提取能力有效捕捉散射数据的局部特征;多头自注意力机制模块的全局信息捕捉能力综合分析散射数据的全局特征,采用误差的反向传播进行训练,反演障碍物的运动轨迹。实验结果表明,该方法能有效反演移动障碍物的运动轨迹。

Nonreciprocal Head-on Collision Between Two Nonlinear Solitary Waves in Granular Metamaterials with an Interface

In this work,the head-on collision and transmission with nonreciprocal properties of opposite propagating solitary waves are studied,in which the interface between different granular chains is considered.Due to the discontinuity of two periodic granular systems,the transmitted and reflected solitary waves are produced.The head-on collision appears at the interface and the reductive perturbation method is applied to derive the generated solitary waves.According to the derivation and numerical simulation,we can find that the transmitted and reflected solitary waves can propagate with the same speed when they locate at the same chain.Moreover,the influences of both the arrangement and prestress are discussed.It is found that the amplitude and velocity of solitary waves become larger because of a bigger prestress,which result in the nonreciprocal collision and transmission in the granular mechanical metamaterials.This study is expected to be helpful for the design and application of elastic wave metamaterials and mechanical diodes with nonlinear solitary waves.

Head-on Collision

Chinese automaker takes historic legal action against foreign competitor to protect its product patent since hitting the roads in early 2008, the Peri, a sleek, stylish car from Chinese automaker Great Wall Motor Co. Ltd., has been a market hit across the country, selling more than 1,000 units per month on average since its release.

multi-solitons interaction multicomponent plasma extended Poincare–Lighthill–Kuo method head-on collision

The propagation and interaction between ion acoustic multi-solitons in an unmagnetized multicomponent plasma consisting of fluid hot ions, positrons and both hot and cold electrons, are investigated by employing the extended Poincare–Lighthill–Kuo（PLK） method. Two different Kortewege-de Vries（K-dV） equations are derived. The Hirota＇s method is applied to get the K-dV multi-solitons solution. The phase shift due to the overtaking and head- on collision of the multi-solitons is obtained.

大采高工作面坚硬顶板水力压裂技术

针对大采高一次采全高采煤工作面回采过程中,经常出现的机头三角区采空区坚硬顶板难垮问题。通过对上覆岩层结构及强度进行测试、分析,结合煤层顶板特性及压裂密度大小对压裂效果的影响,确定采用分段压裂式水力压裂技术方案;并在井下现场开展水力压裂控制坚硬难垮顶板试验。结果表明,采用水力压裂技术后,工作面端头采空区顶板能够及时垮落,悬顶面积大幅度降低,工作面端头采空区悬顶沿推进方向一般最大不超过9 m,沿工作面方向最大不超过6 m,降低幅度达到70%以上,在大部分情况下,顶板能够随采随垮及时垮落,效果良好。

头颈部CTA联合颅脑灌注一站式检查在预测脑梗死预后中的临床价值

目的探究头颈部计算机断层扫描血管成像(CTA)联合颅脑灌注(CTP)一站式检查在预测脑梗死预后中的临床价值。方法选取2019年11月-2022年11月广西壮族自治区民族医院和广西壮族自治区人民医院收治的脑梗死患者100例,分为预后良好组68例和预后不良组32例。2组均进行头颈部CTA联合CTP检查并比较相关参数差异;ROC曲线分析CTA、CTP相关参数对脑梗死预后的评估价值。结果预后不良组入院NIHSS评分和入院mRS评分高于预后良好组(P<0.05);预后不良组平均ASPECTS评分、脑血容量(CBV)、脑血流量(CBF)低于预后良好组,ASPECTS评分<5分人数、平均通过时间(MTT)、峰值时间(TTP)高于预后良好组(P<0.05);Pearson相关分析结果显示,ASPECTS评分、CBV、CBF均与NIHSS评分、mRS评分呈负相关,MTT、TTP均与入院NIHSS评分、mRS评分呈正相关(P<0.05);ROC曲线显示,ASPECTS评分、CBV、CBF、MTT、TTP的曲线下面积分别为0.878、0.771、0.870、0.826、0.885,上述指标联合诊断的曲线下面积为0.990(P<0.05)。结论头颈部CTA联合颅脑CTP一站式检查能更好地预测患者预后,值得推广。

一分钟教学法在耳鼻咽喉头颈外科临床教学中的应用

住院医师规范化培训要求临床教师开展多种形式的教学工作,提高住院医师的临床思维能力和操作技能水平。耳鼻咽喉头颈外科临床教师根据本学科的专业特点开展临床教学,包括病例教学法联合模块教学、病例教学法联合以问题为导向的教学法等,可提高住院医师对理论知识的掌握程度和教学满意度,但也受到时间和场地的限制。本研究在开展教学查房、小讲课、疑难病例讨论等基础上,探索将一分钟教学法应用到日常的耳鼻咽喉头颈外科临床教学中,并取得良好效果。利用一分钟教学法的五个步骤逐步开展临床教学工作,有助于在繁忙的临床工作中进行短时间的临床教学,更容易被临床医师和住院医师所接受。

低管电压联合ASiR-V算法“一站式”心脑血管CTA扫描模式的应用价值

目的:探讨低管电压联合ASiR-V算法“一站式”心脑血管CTA扫描模式在动脉粥样硬化导致的心脑血管疾病评估中的临床应用价值。方法:回顾性分析需要进行心脑血管疾病筛查扫描的120例患者。依据扫描方式不同,分为3组,每组40人。A组为低剂量一站式”心脑血管CTA扫描模式组(80 kV,管电流智能调控,前置40%ASIR-V,后置50%ASiR-V),B组为常规剂量冠状动脉CTA扫描组(100 kV,550 mA),C组为常规剂量头颈动脉CTA扫描组(100 kV, 500 mA)。对比3组扫描模式的辐射剂量和对比剂用量,同时将3组图像进行主观评价和客观评价。结果:低管电压联合ASiR-V算法“一站式”心脑血管CTA扫描模式有效辐射剂量为(1.36±0.66)mSv,B组的辐射剂量为(2.31±0.75)mSv,C组的辐射剂量为(1.12±0.04)mSv,A组辐射剂量与B组+C组辐射剂量之和差异有统计学意义(P<0.05),A组与B组的LAD近端、LCX近端、RCA近端的CT值差异均无统计学意义(P>0.05),A组与B组的SD、CNR值差异无统计学意义(P>0.05),A组与B组CTA图像质量主观评分差异无统计学意义(P>0.05);A组与C组的CT值差异均无统计学意义(P>0.05),A组与C组的SD、CNR值差异有统计学意义(P<0.05),A组与C组图像质量主观评分差异无统计学意义(P>0.05)。结论:低剂量“一站式”头颈冠脉血管成像扫描模式的图像质量能满足临床需求,能全面评估动脉粥样硬化导致的心脑血管疾病。

不结球白菜酵母杂交cDNA文库构建及BcFT上游调控因子筛选

FLOWERING LOCUS T(FT)是调控植物开花途径中的关键基因,前期研究中,在比较晚开花wym-97和早开花cx-49两个品种的BcFT启动子时,发现cx-49的BcFT启动子存在一个1577 bp的插入片段。为探索该插入片段对不结球白菜开花的影响,本研究构建不结球白菜酵母杂交cDNA文库,继而利用酵母单杂交技术筛选与BcFT启动子互作的蛋白。结果显示,本研究所得cDNA文库的库容为1.8×10^(6)CFU,重组率为100%,插入片段长度分布范围约400~2000 bp,平均长度大于1000 bp,表明不结球白菜酵母杂交cDNA文库构建成功。自激活试验表明,800 ng·mL^(-1)的金担子素(AbA)可以抑制诱饵载体的自激活。通过酵母单杂交试验筛选到结合BcFT启动子插入片段的上游蛋白BcSAP18和BcDEAR2。综上,本研究成功构建了不结球白菜酵母杂交cDNA文库并获得了BcFT启动子插入片段的互作蛋白,为进一步研究BcFT在不结球白菜开花中的调控机制奠定了基础。

耕地保护田长制的实践分析

耕地保护是我国现阶段重点工作之一,田长制的提出和实践有助于耕地保护工作得到落实。基于此,阐述了耕地保护田长制的积极作用,分析了耕地保护田长制的实践困境,探究了耕地保护田长制的实践要求和方法,并提出了相应的解决措施,以求推动耕地保护田长制的实践,使其积极作用得到进一步发挥。

入渗水头对垂直一维入渗Philip模型参数的影响

以非饱和土壤水分运动理论为基础,建立垂直一维入渗土壤水分运动的数学模型,对不同入渗水头条件下多种典型土壤垂直一维入渗特性进行模拟,模拟结果采用Philip模型拟合.结果表明:入渗水头对吸渗率、稳渗率有一定影响,提出了包括入渗水头和饱和导水率的Philip模型参数的确定方法.利用已有文献资料对所建模型进行验证,结果表明:所建模型能较简单地确定吸渗率和稳渗率,可以较准确地反映土壤水分垂直一维入渗特点.

100kW一基多体漂浮鹰式波浪能发电装置模型试验研究

一基多体漂浮鹰式波浪能装置是一种新型的利用波浪发电的离岸漂浮式波浪能装置群,该波浪能发电装置是对已经成功发电的"鹰式I号"波浪能装置的改进优化。文中介绍的一基多体漂浮鹰式波浪能装置由4个鹰头吸波浮体、浮力舱、波浪能母船(水下附体)、半潜船、能量转换系统、锚泊系统等组成。该波浪能装置特殊设计为4个鹰头吸波浮体对称安装在一个波浪能母船上,共享能量转换系统和锚泊系统。通过一系列水槽模型试验,获得匹配各个波浪要素最优负载,测得模型在不同波浪要素下的一、二级能量转换效率,以及锚泊系统的受力。试验结果表明,模型具有良好的水动力学性能,模型俘获波浪能的能力并不受入射波的来浪方向影响,锚泊系统对模型起到了稳固、提高波浪能俘获效率的作用。