Animation toolkit based on a database approach for reusing motions and models

As animations become more readily available, simultaneously the complexity of creating animations has also increased. In this paper, we address the issue by describing an animation toolkit based on a database approach for reusing geometric animation models and their motion sequences. The aim of our approach is to create a framework aimed for novice animators. Here, we use an alternative notion of a VRML scene graph to describe a geometric model, specifically intended for reuse. We represent this scene graph model as a relational database. A set of spatial, temporal, and motion operations are then used to manipulate the models and motions in an animation database. Spatial operations help in inserting/deleting geometric models in a new animation scene. Temporal and motion operations help in generating animation sequences in a variety of ways. For instance, motion information of one geometric model can be applied to another model or a motion sequence can be retargeted to meet additional constraints (e.g., wiping action on a table can be retargeted with constraints that reduce the size of the table). We present the design and implementation of this toolkit along with several interesting examples of animation sequences that can be generated using this toolkit.     

Receiver-based loss tolerance method for 3D progressive streaming

While progressive compression techniques were proposed long time ago, fast and efficient streaming of detailed 3D models over lossy networks still remains a challenge. A primary reason is that packet loss occurring in unreliable networks is highly unpredictable, leading to connectivity inconsistency and distortions of decompressed meshes. Although prior researches have proposed various methods to handle errors caused by transmission loss, they are always accompanied by additional costs such as redundant transmission data, bandwidth overloads, and result distortions. In this paper, we address this problem from a receiver’s point of view and propose a novel receiver-based loss tolerance scheme which is capable of recovering the lost data when streaming 3D progressive meshes over lossy networks. Specifically, we use some constraints during the model compression procedure on the server side, and suggest a prediction method to handle loss of structural and geometric data on the client/receiver side. Our algorithm works without any data retransmission or introducing any unnecessary protection bits. We stream mesh refinement data on reliable and unreliable networks separately so as to reduce the transmission delay as well as to obtain a satisfactory decompression result. The experimental results indicate that the decompression procedure can be accomplished quickly, suggesting that it is an efficient and practical solution. It is also shown that the proposed prediction technique achieves a very good approximation of the original mesh with low distortions, and in the mean time, error propagations are also well controlled.     

Modelling and Coordinated Control of Grid Connected Photovoltaic, Wind Turbine Driven PMSG, and Energy Storage Device for a Hybrid DC/AC Microgrid

In a DC/AC microgrid system, the issues of DC bus voltage regulation and power sharing have been the subject of a significant amount of research. Integration of renewable energy into the grid involves multiple converters and these are vulnerable to perturbations caused by transient events. To enhance the flexibility and controllability of the grid connected converter (GCC), this paper proposes a common DC bus voltage maintenance and power sharing control strategy of a GCC for a DC/AC microgrid. A maximum power point tracking algorithm is employed to enhance the power delivered by the wind turbine and photovoltaic module. The proposed control strategy consists of primary and secondary aspects. In the primary layer control, the DC bus voltage is regulated by the GCC. In the secondary layer, the DC bus voltage is maintained by the energy storage device. This ensures reliable power for local loads during grid failures, while power injection to the grid is controlled by an energy management algorithm followed by reference generation of inductor current in the GCC. The proposed control strategy operates in different modes of DC voltage regulation, power injection to the grid and a hybrid operating mode. It provides wide flexible control and ensures the reliable operation of the microgrid. The proposed and conventional techniques are compared for a 15.8 kW DC/AC microgrid system using the MATLAB/Simulink environment. The simulation results demonstrate the transient behaviour of the system in different operating conditions. The proposed control technique is twice as fast in its transient response and produces less oscillation than the conventional system.     

Novel Coagulation Method for Direct Coagulation Casting of Aqueous Alumina Slurries Prepared Using a Poly(Acrylate) Dispersant

Coagulation of concentrated aqueous alumina slurries prepared using an ammonium poly(acrylate) dispersant by MgO has been studied for direct coagulation casting (DCC). A small amount of MgO (0.2 wt% of alumina) increased the viscosity of the concentrated alumina slurry with time and finally transformed it into a stiff gel. The mechanism of coagulation is proposed such that the time-delayed in situ generation of Mg²⁺ ions from the sparingly soluble MgO forms Mg–poly(acrylate) with the unadsorbed ammonium poly(acrylate) molecules in solution that shift the poly(acrylate) adsorption equilibrium toward the left by depleting the poly(acrylate) molecules adsorbed on the alumina particle surface. This leads to insufficient dispersant coverage on the particle surface and coagulation of the slurry. DCC using MgO is possible only if the slurry is prepared at a dispersant concentration higher than that required for optimum dispersion as the slurries prepared at the optimum dispersant concentration underwent premature coagulation. The gelation time could be tailored within 20 min to a few hours by maintaining the temperature in the range of 70°–30°C. The wet coagulated bodies prepared from 50 vol% alumina slurry showed a compressive strength of nearly 0.05 MPa.     

Sinterable La0.8Sr0.2CrO3 and La0.7Ca0.3CrO3 powders by sucrose combustion synthesis

Air atmosphere sinterable La_0.8Sr_0.2CrO₃ [LSC] and La_0.7Ca_0.3CrO₃ [LCC] powders have been prepared by sucrose combustion synthesis. Aqueous solution containing stoichiometric quantities of the metal nitrates and sucrose (3 moles/mole of the metal ion) at pH ∼1 was concentrated by heating on a hot plate into a viscous resin which on drying at 120°C produced a foam with interconnected pore structure. This foam ignited with a matchstick in a combustion set up fabricated in the laboratory produced ashes consisting of loose aggregates of LSC and LCC particles. The loose aggregate of LSC and LCC were powdered by planetary ball milling to submicron size particles with D₅₀ value 0.19 and 0.60 μm, respectively. The surface area of the LSC and LCC powders was 23 and 19 m²/g, respectively. Pellets prepared by cold compaction and sintering of LSC and LCC powders in air atmosphere showed density 96.8 and 98.8% of theoretical value respectively. Sintered LCC sample showed finer grains compared to the LSC sample under identical processing conditions.     

Age differences in prefrontal cortical activity in working memory.

Working memory (WM) declines with advancing age. Brain imaging studies indicate that ventral prefrontal cortex (PFC) is active when information is retained in WM and that dorsal PFC is further activated for retention of large amounts of information. The authors examined the effect of aging on activation in specific PFC regions during WM performance. Six younger and 6 older adults performed a task in which, on each trial, they (a) encoded a 1- or 6-letter memory set, (b) maintained these letters over 5-s, and (c) determined whether or not a probe letter was part of the memory set. Comparisons of activation between the 1- and 6-letter conditions indicated age-equivalent ventral PFC activation. Younger adults showed greater dorsal PFC activation than older adults. Older adults showed greater rostral PFC activation than younger adults. Aging may affect dorsal PFC brain regions that are important for WM executive components. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quality modeling and analysis of polymer composite products

The present article gives a new direction for quality modeling and analysis of polymer matrix composite products. Quality of composite products depends upon conformance of requirements of the customer. These requirements are translated into design specifications of all the contributing factors and subsystems up to component level of composite system. Quality of interaction amongst different subsystems, sub‐subsystems, and other factors affects quality of products are also to be considered. Therefore, the present article considers quality of subsystems as well as quality of all interactions together and modeled using graph theory, matrix algebra as quality graph, quality matrix, and quality permanent function of the composite product. These models are useful to design quality of every subsystem and factors in such a manner that can lead to achieve six‐sigma limits (almost zero error) i.e. 3.34 defects per million products produced. A number of analytical tests derived from these models help to carry out optimum selection of qualities of subsystems and interactions for designing competitive composite products. SWOT (strength–weakness–opportunities–threats) analysis integrated with these models becomes very powerful tool to convert an unsuccessful product into successful competitive product. Evaluation, ranking, and comparison procedures can be developed with the help of these proposed models. Coefficients of similarity and dissimilarity are developed for comparison among feasible products. Step‐by‐Step procedure based on systems approach is useful to designer, manufacturer at conceptual stage of design, and during manufacturing stages of composite products. This is basically a virtual prototyping methodology of complete system, leading to high quality competitive composite products. POLYM. COMPOS. 27:329–340, 2006. © 2006 Society of Plastics Engineers     

Structural modeling and analysis of FRP composite product subsystems—A systems approach

This study derives a new mathematical model aimed to consider virtual design and manufacturing procedures for developing highly competitive, complex geometry composite products for various engineering applications. The fiber‐reinforced polymer (FRP) composite industry faces several critical issues right from selection (of product, process, equipment, tooling, materials) to manufacturing the final products by meeting several design criteria and customer requirements. An attempt has been made in this article to identify different subsystems and other constituents of five main systems–resin system, reinforcement system, process equipment, tooling system, and product design of total composite product system. Intermediate processes, alternative designs, process sequence, technological changes, chemical reactions, and other performance affecting parameters have been discussed. Graph theoretical models, variable permanent adjacency matrix models, and permanent functions of these systems based on graph theory–matrix algebra–permanent function methodology are developed. Analytical tests for structural analysis of composite product system are derived to select optimum constituents in each of these five systems of composite product. Coefficient of similarity and dissimilarity are useful aid to take right decision between alternative solutions. Permanent function is a unique representation and to be used by composite industry for coding, evaluation, comparison, ranking, and optimum selection. Structural models are useful for basic understanding of complete composite product system, leading to right decisions for manufacturing and business strategies. Step‐by‐step procedure is developed to assist composite industry to implement the proposed method in a right way. Usefulness of the proposed methodology to composite industry is also presented. POLYM. COMPOS., 27:681–699, 2006. © 2006 Society of Plastics Engineers     

Vapour-liquid-solid growth of ternary Bi2Se2Te nanowires

High-density growth of single-crystalline Bi₂Se₂Te nanowires was achieved via the vapour-liquid-solid process. The stoichiometry of samples grown at various substrate temperatures is precisely determined based on energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy on individual nanowires. We discuss the growth mechanism and present insights into the catalyst-precursor interaction.     

Plastic collapse moment of 90° long radius elbows with internal circumferential surface crack at intrados under in-plane bending

Piping elbows under in-plane bending moment are vulnerable to cracking. The crack initiates at the surface and eventually reaches through the thickness and may lead to failure. The structural integrity assessment requires knowledge of the limit load. Limit load solutions for elbows with through-wall crack configurations are available in the open literature. But solutions for surface crack are not available. This paper presents a closed form expression for the plastic collapse moment (PCM) of 90°, long radius elbows with circumferential surface cracks at the intrados, under in-plane bending moment. The expression is derived, based on the results of non-linear (geometric and material) FE analyses covering a wide range of geometries and crack sizes. These plastic collapse moments evaluated herein will help in structural integrity assessment.