Mobility and dynamic erosion process of granular flow:insights from numerical investigation using material point method

In order to understand the dynamics of granular flow on an erodible base soil,in this paper,a series of material point method-based granular column collapse tests were conducted to investigate numerically the mobility and dynamic erosion process of granular flow subjected to the complex settings,i.e.,the aspect ratio,granular mass,friction and dilatancy resistance,gravity and presence of water.A set of power scaling laws were proposed to describe the final deposit characteristics of granular flow by the relations of the normalized run-out distance and the normalized final height of granular flow against the aspect ratio,being greatly affected by the complex geological settings,e.g.,granular mass,the friction and dilatancy resistance of granular soil,and presence of water in granular flow.An index of the coefficient of friction of granular soil was defined as a ratio of the target coefficient of friction over the initial coefficient of friction to quantify the scaling extent of friction change(i.e.,friction strengthening or weakening).There is a characteristic aspect ratio of granular column corresponding to the maximum mobility of granular flow with the minimum index of the apparent coefficient of friction.The index of the repose coefficient of friction of granular flow decreased gradually with the increase in aspect ratio because higher potential energy of granular column at a larger aspect ratio causes a larger kinetic energy of granular soil to weaken the friction of granular soil as a kind of velocity-related friction weakening.An increase in granular mass reduces gradually the indexes of the apparent and repose coefficients of friction of granular soil to enhance the mobility of granular flow.The mobility of granular flow increases gradually with the decrease in friction angle or increase in dilatancy angle of granular soil.However,the increase of gravity accelerates granular flow but showing the same final deposit profile without any dependence on gravity.The mobility of granular flow increases gradually by lowering the indexes of the apparent and repose coefficients of friction of granular flow while changing the surroundings,in turn,the dry soil,submerged soil and saturated soil,implying a gradually increased excessive mobility of granular flow with the friction weakening of granular soil.Presence of water in granular flow may be a potential catalyzer to yield a long run-out granular flow,as revealed in comparison of water-absent and water-present granular flows.In addition,the dynamic erosion and entrainment of based soil induced by granular flow subjected to the complex geological settings,i.e.,the aspect ratio,granular mass,gravity,friction and dilatancy resistance,and presence of water,were comprehensively investigated as well.

Sound radiation of a functionally graded material cylindrical shell in water by mobility method

Based on the fundamental dynamic equations of functionally graded material (FGM) cylindrical shell, this paper investigates the sound radiation of vibrational FGM shell in water by mobility method. This model takes into account the exterior fluid loading due to the sound press radiated by the FGM shell. The FGM cylindrical shell was excited by a harmonic line radial force uniformly distributing along the generator. The FGM shell equations of motion, the Helmholtz equation in the exterior fluid medium and the continuity equation at fluid-shell interface are used in this vibroacoustic problem. The expressions of sound radiation efficiency and sound field of the FGM shell have been derived by mobility method. Radiation efficiency, modal mobility and the directivity pattern of the sound field are solved numerically. In particular, radiation efficiency and directivity pattern with various power law index are analyzed.

Doppler shift estimation methods in mobile communication systems

Several Doppler shift estimators, including mean logarithm envelope difference (MLED) method, auto-correlation function (ACF) method, zero crossing rate (ZCR) method and mean square phase difference (MSPD) method were discussed and compared. The estimation principle and theoretical estimation bias of these estimators under Rayleigh fading channels were analyzed; furthermore, the Cramer Rao bound (CRB) of Doppler shift estimation was deduced, and a novel modification method based on two-dimensional polynomial fitting was proposed to reduce the Doppler shift estimation bias. We verified our algorithms with the Monte Carlo computer simulation; simulation results showed better variance performance of modified methods than those of the original methods. In addition, the applicable situations of these estimators were discussed.

Direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene via van der Pauw geometry

We report the direct measurements of conductivity and mobility in millimeter-sized single-crystalline graphene on SiO2/Si via van der Pauw geometry by using a home-designed four-probe scanning tunneling microscope（4P-STM）. The gate-tunable conductivity and mobility are extracted from standard van der Pauw resistance measurements where the four STM probes contact the four peripheries of hexagonal graphene flakes, respectively. The high homogeneity of transport properties of the single-crystalline graphene flake is confirmed by comparing the extracted conductivities and mobilities from three setups with different geometry factors. Our studies provide a reliable solution for directly evaluating the entire electrical properties of graphene in a non-invasive way and could be extended to characterizing other two-dimensional materials.

Mobile Equilibrium Method for Determining Composition and Stability Constant of Coordination Compounds of the Form M_mR_n

A new method is proposed for determining the composition and stability constant of coordination compounds of the form M m R n ; it can be used to differentiate mono and poly nuclear coordination compounds. The equation derived is lg( A i/(A max - A i) m)=n lg c′ R+lg( m·β(c M/A max ) ( m -1) ). The method is based on Bent French limited logarithm method. The demonstration of the proposed method has yielded correct results for Sc 3+ chlorophosphonazo Ⅲ system and Fe 3+ Chromazurol S system.

Performance Evaluation of Mobility Anchor Point with Guard Load Reservation in Hierarchical Mobile IPv6

Hierarchical mobile IPv6 （HMIPv6） introduces a mobility anchor point to reduce the signaling overhead and handoff latency. In this paper, we apply the matrix-analytical approach to explore the performance measures of the ongoing mobile nodes （MNs） drop and new MNs block probabilities of mobility anchor point with a guard bandwidth reservation scheme. We apply the Markovian arrival process （MAP） to model ongoing MNs and new MNs. Five related performance measures are derived, including the long-term new MN block and ongoing MN drop probabilities, and the three short-term measures of average length of a block period and a non-block period, as well as the conditional ongoing MN drop probability during a block period. These performance measures greatly assist the guard bandwidth reservation mechanism in determining a proper threshold guard bandwidth. The results presented in this paper can provide guidelines for designing adaptive algorithms to adjust the threshold in the guard bandwidth reservation scheme.

Mobility of large clusters on a semiconductor surface:Kinetic Monte Carlo simulation results

The mobility of clusters on a semiconductor surface for various values of cluster size is studied as a function of temperature by kinetic Monte Carlo method. The cluster resides on the surface of a square grid. Kinetic processes such as the diffusion of single particles on the surface, their attachment and detachment to/from clusters, diffusion of particles along cluster edges are considered. The clusters considered in this study consist of 150-6000 atoms per cluster on average. A statistical probability of motion to each direction is assigned to each particle where a particle with four nearest neighbors is assumed to be immobile. The mobility of a cluster is found from the root mean square displacement of the center of mass of the cluster as a function of time. It is found that the diffusion coefficient of clusters goes as D = A（T）Na where N is the average number of particles in the cluster, A（T） is a temperature-dependent constant and a is a parameter with a value of about -0.64 〈 a 〈 -0.75. The value of a is found to be independent of cluster sizes and temperature values （170-220 K） considered in this study. As the diffusion along the perimeter of the cluster becomes prohibitive, the exponent approaches a value of -0.5. The diffusion coefficient is found to change by one order of magnitude as a function of cluster size.

Easy Determination of Radiation Absorption in Brain Tissue from Mobile Phones Using Finite Element Method

Brain tissue plays a significant role in both cognitive and psychomotor behavior of humans. However, their interaction with radiation emanating from hand held mobile devices is still not fully understood. This research was aimed at investigating radiation absorption in brain tissue. Bovine brain tissues ranging from lesser than 1 year to greater than 10 years of age were bought from a specialty store (Sigma-Aldrich). The tissues were used within 72 h of extraction for ex vivo brain experiments. The brain tissue was stored at 6°C and then 16°C for 24 h in the MRI room to reach thermal equilibrium before any experiments were undertaken. The averages for the dielectric constant were measured from 1 - 4 GHz using open ended coaxial probe (OECP) (85,070E;Agilent Technologies). The results obtained for the dielectric properties were then used as raw data in the numerical computation and simulation of the radiation absorption by the brain tissues for both adolescent and adults bovine brain tissue using finite element method (FEM). The measured dielectric constants varied for the different brain tissue from 54.39 to 39.29. Analysis showed that adolescents tissue absorbed more radiation than adults from mobile phoneradiation which is due to the higher dielectric property of adolescent brain tissue. The results obtained can be applied to human brain tissue since bovine shares the same compositional properties with humans.

Testing a mobile app for child abuse treatment: A mixed methods study

Objective:This study provides a preliminary evaluation of the usability and acceptability of a mobile application(sexual assault care algorithm,SACA).Methods:An explanatory sequential mixed methods research was used.A quantitative survey was followed up by a qualitative study.A convenience sample of participants(n=4)was recruited.The research was conducted on a one-on-one basis.In the quantitative phase,a random assignment technique was used to divide four participants into two groups of two participants each.Post-Study System Usability Questionnaire(PSSUQ)and Acceptability e-Scale were used to collect quantitative data.In the qualitative phase,interview,observation,and documentation were used to collect qualitative data.Data were analyzed both quantitative and qualitatively.The qualitative data were linked with the initial quantitative data to determine how the follow-up qualitative data helped explain the initial quantitative results.Results:The quantitative results suggested that SACA has high usability(5.05±1.83)and acceptability(3.81±1.22).The qualitative results further indicate that the participants thought SACA was easy to use and useful,and most of them would recommend it to others.Areas of improvement include adding features that would calculate and validate the elapsed time since the sexual assault,adding explanations to some buttons,and providing training.Conclusions:Our findings highlight the value of using a mixed methods research design to conduct a usability and acceptability test.Nurses are more likely to adopt a new technology for their evidencebased practice when the technology is easy to use and useful and requires less time to find the right piece of guideline evidence.Individualized training needs to be designed based on users'characteristics.

Mobility and constant-orientation workspace analysis of 4UPS-UPU parallel mechanism

One of the key issues for parallel mechanism is the kinematic characteristics,especially the workspace which varies with configuration parameters.A kind of 4UPS-UPU parallel mechanism is designed and its workspace is studied in this paper.First,the mobility of the 4UPS-UPU parallel mechanism is analyzed based on the reciprocal screw theory,and the motion and constraint screw systems of the parallel mechanism are obtained.Then the inverse kinematics is derived by the closed-form kinematics chain.The boundary search method in the polar coordinate system is presented to analyze the constant-orientation workspace of the parallel mechanism.Finally,the influence factors relevant to the workspace,such as the structural parameters and kinematics parameters are analyzed in detail.The relationship between the workspace volume and different parameters are obtained.The conclusions can be used for parameters optimization and path planning of the parallel mechanism.

Real- Time Color Enhancement Method Used for Intelligent Mobile Terminals

In certain environments and under some conditions, the video images taken by the intelligent mobile video phones seem dark, and the colors are not bright or saturated enough.This paper presents an adaptive method to enhance the video image brightness visualization and the color performance depending on the certain hardware property and function parameters. The experimental results prove that this method can enhance the colors and the contrast of the video images, based on the estimated quality feature values of each frame, without using the extra Digital Signal Processor (DSP).

Mobility and equilibrium stability analysis of pin-jointed mechanisms with equilibrium matrix SVD

Under certain load pattern, the geometrically indeterminate pin-jointed mechanisms will present certain shapes to keep static equalization. This paper proposes a matrix-based method to determine the mobility and equilibrium stability of mechanisms according to the effects of the external loads. The first and second variations of the potential energy function of mechanisms under conservative force field are analyzed. Based on the singular value decomposition (SVD) method, a new crite- rion for the mobility and equilibrium stability of mechanisms can be concluded by analyzing the equilibrium matrix. The mobility and stability of mechanisms can be classified by unified matrix formulae. A number of examples are given to demonstrate the proposed criterion. In the end, criteria are summarized in a table.

A modified EDAS model for comparison of mobile wallet service providers in India

The present paper has two-fold purposes.First,the current work provides an integrated theoretical framework to compare popular mobile wallet service providers based on users’views in the Indian context.To this end,we propose a new grey correlationbased Picture Fuzzy-Evaluation based on Distance from Average Solution(GCPF-EDAS)framework for the comparative analysis.We integrate the fundamental framework of the Technology Acceptance Model and Unified theory of acceptance and use of technology vis-a-vis service quality dimensions for criteria selection.For comparative ranking,we conduct our analysis under uncertain environments using picture fuzzy numbers.We find that user-friendliness,a wide variety of use,and familiarity and awareness about the products help reduce the uncertainty factors and obtain positive impressions from the users.It is seen that PhonePe(A3),Google Pay(A2),Amazon Pay(A4)and PayTM(A1)hold top positions.For validation of the result,we first compare the ranking provided by our proposed model with that derived by using picture fuzzy score based extensions of EDAS and another widely used algorithm such as The Technique for Order of Preference by Similarity to Ideal Solution.We observe a significant consistency.We then carry out rank reversal test for GCPF-EDAS model.We notice that our proposed GCPF-EDAS model does not suffers from rank reversal phenomenon.To examine the stability in the result for further validation,we carry out the sensitivity analysis by varying the differentiating coefficient and exchanging the criteria weights.We find that our proposed method provides stable result for the present case study and performs better as ranking order does not get changed significantly with the changes in the given conditions.

Optimum Design of Stair-Climbing Robots Using Taguchi Method

Environmental issues like pollution are major threats to human health.Many systems are developed to reduce pollution.In this paper,an optimal mobile robot design to reduce pollution in Green supply chain management system.Green supply chain management involves as similating environmentally and eco-nomically feasible solutions into the supply chain life-cycle.Smartness,advanced technologies,and advanced networks are becoming pillars of a sustainable supply chain management system.At the same time,there is much change happening in the logistics industry.They are moving towards a new logistics model.In the new model,robotic logistics has a vital role.The reasons for this change are the rapid growth of the e-commerce business and the shortage of workers.The advantages of using robotic logistics are reduction in human errors,faster delivery speed,better customer satisfaction,more safety for workers,and high workforce adaptability.A robot with rocker-bogie suspension is a six-wheeled mobile platform that has a distinctive potential to keep all wheels on the ground continuously.It has been designed to traverse rough and uneven terrain by distributing the load over its wheels equally.However,there is a limitation to achieving high-speed mobility against vertical barriers.In this research,an optimal design of product delivery wheeled robots for a sustainable supply chain system is proposed to ensure higher adaptability and maximum stability during climbing staircases.The design parameters of the proposed robot are optimized using Taguchi Method.The aim is to get a smooth trajectory of the robot’s center-of-mass.The proposed approach realizes a robot with much-improved stability which can climb over heights more than the size of the wheel(i.e.,3 times the radius of wheels).The results reveal that the modified rocker-bogie system not only increases the stair-climbing capability but also thwarts instability due to overturning of a wheel of the robot.

江西省养老机构空间分布格局及可达性研究

目的:评估江西省养老机构空间可达性,为江西省养老机构优化配置提供建议。方法:基于改进两步移动搜索法测度江西省养老机构空间可达性,并采用局部空间自相关分析法、基尼系数评价其适老化及公平性,运用空间误差模型对养老机构可达性进行机制分析。结果:江西省养老机构可达性整体上呈现中部向边缘降低、西高东低的空间格局;南昌市中部区域、赣州市章贡区中部呈现低供给、高需求的特征;在公平性上,江西省养老机构空间分布整体上处于相对合理的水平;老年人口、人均GDP、空气质量指数、路网密度与平均海拔对养老机构可达性具有显著正向影响。结论:江西省养老机构可达性空间差异较为明显,适老化发展水平有待进一步提高,南部与北部区域的养老机构空间分配差距较大,应加强区域之间的合作,促进地区间养老资源配置的协同发展。

基于GC-IMS和GC-MS技术结合化学计量法分析干燥方式对香椿挥发性成分的影响

为研究干燥方式对香椿挥发性风味物质的影响,利用气相色谱-离子迁移谱技术(gaschromatography-ion mobility spectrometry,GC-IMS)和气相色谱-质谱联用技术(gas chromatography-mass spectrometry,GC-MS)、相对香气活性值(relative odor activity value,ROAV)对真空冷冻干燥、热泵干燥、热风干燥、微波真空干燥的香椿样品进行挥发性成分分析,并进一步结合化学计量方法主成分分析(principal component analysis,PCA)和偏最小二乘判别分析(partial least squares-discriminant analysis,PLS-DA),探究样品间挥发性成分的差异性。结果表明,通过GC-IMS检测到78个峰,鉴定出59种化合物。通过GC-MS鉴定出94种挥发性化合物,主要挥发性成分是硫化物、烯烃类和醛类。经过干燥后总挥发性化合物的含量显著降低。通过ROAV法确定了(E,Z)-二-1-丙烯基二硫化物、2-巯基-3,4-二甲基-2,3-二氢噻吩、正己醛、2-己烯醛、丁香酚等为香椿样品中关键香气化合物。PCA和PLS-DA结果表明,不同干燥方式的样品与新鲜样品有明显的分离,彼此之间也有明显的区别。鲜样和真空冷冻干燥样品为一组,其他3个干燥香椿样品为一组。根据变量投影重要性(variable importance in projection,VIP)得分共筛选出10种(VIP>1)标志挥发性化合物。干燥方式对香椿风味特性影响显著,真空冷冻干燥组与鲜样最为接近,考虑实际应用热泵干燥为香椿最适宜的脱水方式。本研究为热加工过程中风味品质控制提供一定的理论参考。

跨界颠覆性创新的早期识别方法及实证检验

[研究目的]数字经济时代,越来越多的企业利用互联网技术开展跨界颠覆性创新。探讨跨界颠覆性创新的早期判断和识别方法,对于打破国外核心技术封锁,抢占科技制高点具有重大意义。[研究方法]根据跨界颠覆性创新的演进特点,从技术和市场两个方面提出识别跨界颠覆性创新的理论框架:首先,基于专利文本,利用LDA主题模型提取跨界技术主题;其次,从成长性、融合性、影响力和引用行业外新知识等四个特征考察技术主题跨界颠覆的技术潜力;最后,基于专利、用户和专家评论数据,借助LDA主题模型与情感分析方法,从易扩散性、需求贴合度与市场吸引力趋势等特征考察技术主题跨界颠覆的市场潜力。[研究结论]以手机定位与导航技术为例,通过考察其跨界颠覆的技术潜力特征和市场潜力特征,验证了跨界颠覆性技术早期识别方法的可用性与有效性,为企业跨界颠覆性创新实践提供借鉴。

干燥方式对苹果干品质特性及风味的影响

为探究提高静宁苹果干零食品质的加工方式,本研究探讨了5种干燥方式(热风干燥、太阳能干燥、真空冷冻干燥、微波-压差膨化干燥和热泵干燥)对苹果干能耗、抗氧化活性、微观结构和风味的影响。结果表明,和其它4种方式相比,在能耗方面,真空冷冻干燥的单位能耗最高(69.48±1.69 kW·h/kg),而太阳能干燥的单位能耗最低(19.60±1.36 kW·h/kg);在硬脆度方面,热风干燥的苹果干具有最高的硬度、最低的脆度,而真空冷冻干燥的苹果干硬度最低、脆度较高;在色差方面,真空冷冻干燥苹果干的L*值最高(72.91±0.59),ΔE值最接近鲜样(10.48±0.30);此外,真空冷冻干燥能有效降低苹果干中抗氧化物质的损失,与鲜样相比,其抗坏血酸、总酚和总黄酮的含量分别降低了35.22%、39.27%和32.02%。同时,总抗氧化能力、羟自由基清除率和超氧阴离子清除率也分别降低了23.50%、57.24%和10.56%;在微观结构方面,真空冷冻干燥的苹果干细胞层呈较规律的海绵状多孔性结构,质地较好;在风味方面,鉴定出5种干燥方式的苹果干有96种挥发性物质,其中真空冷冻干燥的苹果干更加芳香、口感更加丰富。综合考虑,真空冷冻干燥是提高苹果干零食品质特性和风味的推荐方法,对苹果干制品的工业化生产有现实的指导意义。

重庆回流人口识别方法及其规划响应

人口回流已成为全国人口流动的一种普遍现象,对于中西部人口净流出地区而言,认识回流人口的空间规律、结构是新时期编制国土空间规划、配置空间资源的重要基础。在总结当前回流人口定义的基础上,提出基于手机大数据的回流人口识别方法,并将其应用于回流规模、回流来源、回流去向、回流结构等4个方面的研究分析中。在此基础上,以重庆为例验证回流人口的识别方法,并阐释回流人口的基本特征,由此提出中西部地区人口回流地区的空间规划应对策略,以便加快手机大数据在回流人口研究领域的应用进程。

社会遵从视角下的移动政务用户转移行为

探究移动政务用户转移行为的驱动因素和驱动路径对促进移动政务良性发展、优化政务环境具有重要意义。文章从社会遵从视角构建转移行为驱动因素的分析框架,采用PLS结构方程分析和模糊集定性比较分析的混合研究方法,探究影响移动政务用户转移行为的驱动因素及组态效应。研究发现:移动政务用户转移行为可归因于政府支持、群体规范、转移认知的共同作用,其中政府支持与群体规范通过用户的转移认知正向影响转移意愿与转移行为;移动政务用户转移行为存在多重并发和殊途同归的因果路径,即政府驱动型和群体遵从型。