Imitative Collaboration: A mirror-neuron inspired mixed reality collaboration method with remote hands and local replicas

Mixed reality can overlay and display 3D digital content in the real world, convey abstract concepts to users, and promote the understanding of complex tasks. However, the abstract graphics overlaid on the physical space may cause a certain cognitive load for local users and reduce the efficiency of collaboration. To improve the efficiency of remote collaboration, we conducted an elicitation study on assembly tasks, explored the user needs for collaboration, and defined the design goals of our remote collaboration method. Inspired by the mirror-neuron mechanism, we present an imitative collaboration method that allows local users to imitate the interaction behavior of remote users to complete tasks. We also propose a series of interaction methods for remote users to select, copy, and interact with the local point clouds to facilitate the expression of collaboration intentions. Finally, the results of a user study evaluating our imitative collaboration method on assembly tasks are reported, confirming that our method improves collaboration efficiency while reducing the cognitive load of local users.     

火花放电原子发射光谱类型标准化校正方式的探讨

在国内,火花放电原子发射光谱分析广泛使用类型标准化进行方法校正。在国外,标准和文献中鲜见使用此方法的相关论述。类型标准化主要采用平移校正和转动校正两种方式,哪种方式更加合理也鲜见报道。国外设备类型标准化的默认设置优先采用转动校正方式,相关国内标准对最优校正方式的规定尚不明确,此默认设置的合理性有待探讨。实验选用低合金钢20CrNi2Mo、R407标准样品和不锈钢317L、0Cr18Ni9标准样品,引用国内相关标准,以正确度临界差为评判依据,模拟类型标准化样品和待测样品“十分接近”和“接近”两种情况下平移校正和转动校正的数据正确度。经数据统计分析,平移校正分析结果均满足要求,转动校正结果在“接近”情况下部分元素不满足要求。结合相关国家标准中元素含量范围和精密度数据进行分析,通过计算允许最大偏倚量并制作曲线图方式展开分析,得出如下结论:在满足文中类型标准化控制要点前提下,分析设置更适合于采用平移校正方式。     

Methods and mechanisms for uniformly refining deformed mixed and coarse grains inside a solution-treated Ni-based superalloy by two-stage heat treatment

The uniform refinement mechanisms and methods of deformed mixed and coarse grains inside a solution-treatment Ni-based superalloy during two-stage annealing treatment have been investigated.The two-stage heat treatment experiments include an aging annealing treatment(AT)and a subsequent recrystallization annealing treatment(RT).The object of AT is to precipitate some δ phases and consume part of storage energy to inhibit the grain growth during RT,while the RT is to refine mixed and coarse grains by recrystallization.It can be found that the recrystallization grains will quickly grow up to a large size when the AT time is too low or the RT temperature is too high,while the deformed coarse grains cannot be eliminated when the AT time is too long or the RT temperature is too low.In addition,the mixed microstructure composed of some abnormal coarse recrystallization grains(ACRGs)and a large number of fine grains can be observed in the annealed specimen when the AT time is 3 h and RT tem-perature is 980℃.The phenomenon attributes to the uneven distribution of δ phase resulted from the heterogeneous deformation energy when the AT time is too short.In the regions with a large number of δ phases,the recrystallization nucleation rate is promoted and the growth of grains is limited,which results in fine grains.However,in the regions with few δ phases,the recrystallization grains around grain boundaries can easily grow up,and the new recrystallization nucleus is difficult to form inside grain,which leads to ACRGs.Thus,in order to obtain uniform and fine annealed microstructure,it is a prereq-uisite to precipitate even-distributed δ phase by choosing a suitable AT time,such as 12 h.Moreover,a relative high RT temperature is also needed to promote the recrystallization nucleation around δ phase.The optimal annealing parameters range for uniformly refining mixed crystal can be summarized as:900℃×12 h+990℃×(40-60 min)and 900℃×12 h+1000℃×(10-15 min).     

Evaluation of Non-Ambiguous Critical Micelle Concentration of Surfactants in Relation to Solution Behaviors of Pure and Mixed Surfactant Systems: A Physicochemical Documentary and Analysis

Critical micelle concentration (CMC) is a fundamental physical parameter of surfactant aggregation in solution. The CMC is determined by different methods, tensiometry, conductometry, microcalorimetry, fluorimetry, and so on. However, it is known that though CMC is reported as a single value, in reality, micelle formation occurs over a narrow range of concentration for different experimental procedures produce different results. We shall discuss about a unique procedure of measuring correct CMC applicable to all potential methods used in practice. This is essential for the evaluation of thermodynamic properties of the micelle forming process in pure and mixed states in terms of solution theories. As we in this short documentary want to deal with various aspects of Milton Rosen's research—wherein we have also worked—a few other facets of surfactant chemistry research, besides the micelle formation, are also briefly discussed. In mixed surfactant systems, synergistic effects in various surfactant properties like detergency, foaming, solubilization, and so on are found whereas in some others non-synergistic effects are observed. Dehydration of micelles with an increase in temperature or by the addition of hydrophilic substances may cause clouding to the system. Soluble amphiphilic systems produce Gibbs monolayer at the air/water interface; insoluble amphiphiles form Langmuir monolayers. A documentary of the above aspects will be herein presented and discussed. We mention that this article is neither an original research article nor a review article. This is a mixture of the two: a documentary of both original research and some review of our works presented in memory of Prof. Milton Rosen.     

Cracking behavior and delamination mechanism of lamellar structured TBC with localized mixed oxides

Mixed oxide (MO) with localized growth feature and high growth rate remarkably affects the lifetime of thermal barrier coatings (TBCs), which indicates that clarifying the ceramic cracking mechanism induced by MO is critical for developing new coatings with high durability. Two kinds of TBC models involving spherical and layered mixed oxides are created to explore the influence of MO growth on the local stress state and crack evolution during thermal cycle. The growth of α-Al₂O₃ is also included in the model. The undulating interface between ceramic coat and bond coat is approximated using a cosine curve. Dynamic ceramic cracking is realized by a surface-based cohesive interaction. The ceramic delamination by simulation agrees with the experimental observation. The effects of MO coverage ratio and growth rate on the TBC failure are also discussed. The results show that the MO growth causes the local ceramic coat to bear the normal tensile stress. The failure mode of coating is turned from α-Al₂O₃ thickness control to MO growth control. Once the mixed oxide appears, local ceramic cracking is easy to occur. When multiple cracks connect, ceramic delamination happens. Suppressing MO formation or decreasing MO growth can evidently improve the coating durability. These results in this work can provide important theoretical guidance for the development of anti-cracking TBCs.     

Comparative study of LuxY1-xAG (x=0..1) laser ceramics doped with 5% Yb3+

Materials with high thermo mechanical properties are required as laser media for high-powered lasers. One of such materials is lutetium-aluminum garnet (LuAG) doped with ytterbium. In the present work, we discuss for the first time a full comparative study of 5% Yb-doped LuYAG ceramics with variation Lu/Y ratio. Samples were prepared with addition of B₂O₃, MgO and SiO₂ which were used as sintering aids. Grain sizes, shrinkage curves, lattice constants and transmission spectra were measured for all samples. Thermal conductivity was measured in a wide temperature range for all studied samples. Output power of 12 W and 60% slope efficiency were obtained on the 5% Yb:LuAG disk laser.     

渗流作用下新型装配重力式挡土墙有限元分析

为研究渗流作用下新型装配重力式挡土墙应力变化及墙体排水通道对墙后土体固结的影响,采用ABAQUS进行有限元分析,有限元分析结果与模型试验结果相吻合,证明该模型的合理性。在此基础上研究渗流作用下墙体应力变化趋势及墙体排水通道对墙后土体固结效果的影响。研究结果表明:横向排水通道对墙后土体固结效果的影响优于纵向排水通道对土体固结效果的影响,墙体底部横向排水通道的影响作用最显著;渗流作用下墙体应力由上往下呈先增大后减小的趋势,墙体下部所受最大水平剪应力最大。     

Effect of annealing atmosphere on the structure and dielectric properties of unfilled tungsten bronze ceramics Ba4PrFe0.5Nb9.5O30

Unfilled tungsten bronze ceramics with the nominal formula Ba₄PrFe_0.5Nb_9.5O₃₀ were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N₂-annealed sample had the largest cell volume. Low-temperature spectrum showed that N₂ annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O₂ annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N₂-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N₂-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder.     

面向噪声丢包感知的无线网络拥塞算法

针对无线网络链路干扰大、误码率高等特点，以及TCP Westwood算法（TCPW）存在估算带宽时过度依赖包的反馈，缺乏区分传输过程中丢包类型的缺点等问题，提出一种TCPW拥塞控制优化算法--TCPW-F。该算法利用发送速率等构建拥塞因子[F]作为判断丢包类型的依据，同时对判定发生噪声丢包时的拥塞窗口进一步调整，避免噪声丢包引起的窗口下降，提高该情况下窗口的发送效率。仿真结果表明，TCPW-F算法在时延性能方面表现更优，单位时间抖动趋于稳定的速度更快。在同一信道带宽下增大包生成速率，改进算法的实时吞吐量明显高于原算法，具备一定的噪声丢包感知能力，无线网络的TCP传输质量获得较大改善。