Simultaneous high-frequency induction heated combustion synthesis and consolidation of nanostructured HfSi2–SiC composite

Dense nanostructured HfSi₂–SiC composite was synthesized by high-frequency induction heated combustion synthesis (HFIHCS) method in one step from powders of mechanically activated HfC and Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of an induced current and mechanical pressure. Highly dense HfSi₂–SiC was produced under simultaneous application of a 60 MPa pressure and the induced current. The average grain size and mechanical properties (hardness and fracture toughness) of the composite were investigated.     

Sintering behavior and mechanical properties of WC–10Co,WC–10Ni and WC–10Fe hard materials produced by high-frequency induction heated sintering

The comparison of sintering behavior and mechanical properties of WC–10 wt.%Co, WC–10 wt.%Ni and WC–10 wt.%Fe hard materials produced by high-frequency induction heated sintering (HFIHS) method was accomplished using ultra-fine powder of WC and binders (Co, Ni, Fe). The advantage of this process allows very quick densification to near theoretical density and prohibition of grain growth in nano-structured materials. Highly dense WC–10Co, WC–10Ni and WC–10Fe with a relative density of up to 99% could be obtained with simultaneous application of 60 MPa pressure and induced current within 1 min without significant change in grain size. The hardness and fracture toughness of the dense WC–10Co, WC–10Ni and WC–10Fe composites produced by HFIHS were investigated.     

Crystalline transformation of colloidal nanoparticles on graphene oxide

Emergence of novel two-dimensional (2-D) templates, e.g., graphene oxide, has signified new intriguing opportunities to couple nanocrystals electronically to the microscopic 2-D contacts. A promising approach to uniform dispersion of inorganic nanocrystals on the 2-D interfaces is to graft them through chemical bonding. The 2-D dispersion would offer a unique opportunity to address one of the primary challenges in the field of nanotechnology: fulfilling excellent chemical and physical properties of the nanocrystals in electronic solid-state devices. In this study, we blended colloidal nanocrystals with graphene oxide in aqueous solution in attempts to bind the nanocrystals on reactive sites of the graphene oxide surface, thereby achieving uniform loading. Interestingly, the nanocrystals undergo significant crystalline transformation even under relatively moderate reaction conditions. The growth of particle size and the drastic crystalline deformation, e.g., from wurtzite CdSe to amorphous Se, appear to take place in the proximity of acidic functional groups on graphene oxide. Photocarriers also play a key role in the reaction: under room light, the transformation yielded dramatic size increase and crystalline transformation, whereas in the dark, the change was suppressed. The experimental results presented in this study provide guidelines for uniform 2-D loading of colloidal nanocrystals on graphene oxide. The findings suggest that the surface acidity be titrated for colloidal nanocrystals to deposit on the graphitic layer and to avoid unwanted changes of nanocrystal size and properties.     

Properties and rapid consolidation of ultra-hard tungsten carbide

Extremely dense WC with a relative density of up to 99% was obtained within 3 min under a pressure of 80 MPa using the high frequency induction heating sintering method (HFIHS) method. The average grain size of the WC was about 87 nm. The advantage of this process is not only rapid densification to obtain a near theoretical density but also the prohibition of grain growth in nanostructured materials. The hardness and fracture toughness of the dense WC produced by the HFIHS were investigated.     

A virtual metrology system for semiconductor manufacturing

Nowadays, the semiconductor manufacturing becomes very complex, consisting of hundreds of individual processes. If a faulty wafer is produced in an early stage but detected at the last moment, unnecessary resource consumption is unavoidable. Measuring every wafer’s quality after each process can save resources, but it is unrealistic and impractical because additional measuring processes put in between each pair of contiguous processes significantly increase the total production time. Metrology, as is employed for product quality monitoring tool today, covers only a small fraction of sampled wafers. Virtual metrology (VM), on the other hand, enables to predict every wafer’s metrology measurements based on production equipment data and preceding metrology results. A well established VM system, therefore, can help improve product quality and reduce production cost and cycle time. In this paper, we develop a VM system for an etching process in semiconductor manufacturing based on various data mining techniques. The experimental results show that our VM system can not only predict the metrology measurement accurately, but also detect possible faulty wafers with a reasonable confidence.     

Application of localization for the fabrication of large curved plates in shipbuilding

Various problems associated with localization during curved plate fabrication are discussed. Localization is a necessary step for automation of curved plate fabrication that aligns a designed shape with a fabricated one as closely as possible for comparison of their shapes. On top of this localization, various conditions are introduced to reflect requirements occurring during fabrication such as minimum cutting length, maintenance of cutting length, localization for non-penetration and data types for localization. Each condition is formulated as a constraint which is provided as input to the optimization problem for localization. Algorithms for localization with each constraint based on iteration are proposed. Examples are used to demonstrate the performance of the algorithms.     

Shape design optimization of SPH fluid–structure interactions considering geometrically exact interfaces

Fluid–structure interaction problems are solved by applying a smoothed particle hydrodynamics method to a weakly compressible Navier–Stokes equation as well as an equilibrium equation for geometrically nonlinear structures in updated Lagrangian formulation. The geometrically exact interface, consisting of B-spline basis functions and the corresponding control points, includes the high order geometric information such as tangent, normal, and curvature. The exactness of interface is kept by updating the control points according to the kinematics obtained from response analysis. Under the scheme of explicit time integration and updated Lagrangian formulation, the required shape design velocity should be updated at every single step. The update scheme of design velocity is developed using the sensitivity of physical velocity. The developed sensitivity analysis method is further utilized in gradient-based shape optimization problems and turns out to be very efficient since the interaction pairs of particles determined in the response analysis can be directly utilized.     

An Efficient Representation of Edge Shapes in Topological Maps

There are nodes and edges in a topological map. Node data has been used as a main source of information for the localization of mobile robots. In contrast, edge data is regarded as a minor source of information, and it has been used in an intuitive and heuristic way. However, edge data also can be used as a good source of information and provide a way to use edge data efficiently. For that purpose, we define a data format which describes the shape of an edge. This format is called local generalized Voronoi graph's angle (LGA). However, the LGA is constituted of too many samples; therefore, real time localization cannot be performed. To reduce the number of samples, we propose a compression method which utilizes wavelet transformation. This method abstracts the LGA by key factors using far fewer samples than the LGA. Experiments show that the LGA accurately describes the shape of the edges and that the key factors preserve most information of the LGA while reducing the number of samples.     

Nonlinear tracking control of trailer systems using the Lyapunov direct method

This article concerns the nonlinear tracking control of trailer systems that consist of a steering tractor and a passive trailer, linked together with rigid joint and having nonholonomic velocity constraints. We propose a globally asymptotically stable (GAS) tracking control law using the Lyapunov direct method. The GAS tracking control law is completed by considering the posture term of the trailer systems. We selected two types of trailer systems for examples: the two‐wheeled trailer system and the car‐like trailer system. The simulation results represent the effectiveness of our proposed method. In addition, there is a plan to test the path following ability of the trailer system. ©1999 John Wiley & Sons, Inc.     

Synthesis of block copolymers having perfluoroalkyl and silicone‐containing side chains using diazo macroinitiator and their surface properties

The fluorosilicone block copolymers of poly(perfluoroalkylethyl acrylate)‐b‐poly(3‐[tris(trimethylsilyloxy)silyl] propyl methacrylates) (PFA‐b‐PSiMAs) having perfluoroalkyl and silicone‐containing side chains were obtained by three‐step synthetic approaches. In the first step, hydroxyl‐terminated poly(perfluoroalkylethyl acrylate) macromonomer (PFAM) was prepared by the free‐radical polymerization of perfluoroalkylethyl acrylate and 2‐mercaptoethanol. In the second step, PFAM initiator (PFAMI) was prepared from the condensation reaction of the hydroxyl‐terminated PFAM and 4,4′‐azobis‐4‐cyanopentanoic acid chloride (ACPC). ACPC was obtained from the reaction of 4,4′‐azobis‐4‐cyanopentanoic acid and phosphorus pentachloride. In the third step, PFA‐b‐PSiMAs (BPFSs) were synthesized from the reaction of PFAMI macroinimer and SiMA. Fourier transform infrared spectroscopy and ¹H‐NMR analyses verified that the syntheses of ACPC, hydroxyl‐terminated PFAM, PFAMI, and BPFS were completed successfully. The intrinsic surface energies of BPFSs and their surface modification effects on poly(vinyl chloride) film were investigated by analyzing the surface free energies and atomic compositions of the outermost layer of the surfaces. BPFSs exhibit extremely low surface free energies of about 9.7–13.0 dynes/cm. It was confirmed that BPFS, having extremely low surface free energy, is preferentially enriched at the outermost layer of the surface of BPFS/poly(vinyl chloride) blend. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1917–1926, 1999