Design,generation and stress analysis of face-gear drive with helical pinion

Two versions of face-gear drive geometry with a helical pinion are considered. One version is based on a screw involute helicoid. The second version is a new geometry developed as envelopes of two mismatched parabolic racks of the pinion and the shaper. A face-gear drive with a spur pinion is considered as a particular case of the developed theory. A new method of grinding or cutting of face-gears by a worm of special shape has been developed. The following problems are considered: (i) generation of a grinding worm with surfaces free of singularities and (ii) generation of face-gear by a shaper with surfaces free of undercutting and pointing. Tooth contact analysis and stress analysis are applied combined with investigation of tooth bearing contact on both sides. The following advantages have been achieved for the geometry proposed: (a) existence of a longitudinal bearing contact, (b) avoidance of edge contact, and (c) reduction of contact stresses. A phenomenon of asymmetry of tooth bearing contact for the driving and coast sides has been discovered. A computerized design, generation and stress analysis for the new types of face-gear drives have been developed.     

New geometry of face worm gear drives with conical and cylindrical worms: generation,simulation of meshing,and stress analysis

New geometry of face worm gear drives with conical and cylindrical worms is proposed. The generation of the face worm gear is based on application of a tilted head-cutter (grinding tool) instead of application of a hob applied at present. The generation of a conjugated worm is based on application of a tilted head-cutter (grinding tool) as well. The bearing contact of the gear drive is localized and is oriented longitudinally. A predesigned parabolic function of transmission errors for reduction of noise and vibration is provided. The stress analysis of the gear drive is performed, the contacting model is designed automatically. The developed theory is illustrated with numerical examples.     

Modified involute helical gears: computerized design,simulation of meshing and stress analysis

The contents of the paper cover: (i) computerized design, (ii) methods for generation, (iii) simulation of meshing, and (iv) enhanced stress analysis of modified involute helical gears. The approaches proposed for modification of conventional involute helical gears are based on conjugation of double-crowned pinion with a conventional helical involute gear. Double-crowning of the pinion means deviation of cross-profile from an involute one and deviation in longitudinal direction from a helicoid surface. The pinion-gear tooth surfaces are in point contact, the bearing contact is localized and oriented longitudinally, edge contact is avoided, the influence of errors of alignment on the shift of bearing contact and vibration and noise are reduced substantially. The developed theory is illustrated with numerical examples that confirm the advantages of the gear drives of the modified geometry in comparison with conventional helical involute gears.     

Computer aided analysis on the meshing behavior of a height-modified dual-torus double-enveloping toroidal worm drive

A flank modification methodology is proposed for the double-enveloping toroidal worm drive and a novel type of the dual-torus double-enveloping toroidal worm drive (the DTT worm drive) is developed. Because the height variation of the tool relative to the position during generating an unmodified worm is the unique modification parameter, this novel type of worm drive can be named as the height-modified DTT worm drive. Based on a strict meshing analysis, the selection principle of the modification style is recommended. A systematic and thorough study is conducted on the meshing behavior of the height-modified DTT worm pair by means of a computer simulation. The investigation results show that the height-modified DTT worm drive has favorable meshing performance.     

Static contact stress analysis of a spur gear tooth using the finite element method, including frictional effects

The literature available on gear tooth contact stress problems is not very extensive and that available does not explain the method by which analysis was carried out. In this paper an attempt has been made to study the contact stresses of a pair of mating gear teeth, under static conditions, by using a two-dimensional finite element method and the Lagrangian multiplier technique. The contact condition at the neighbouring node pair, namely, the contact existing over a number of node pairs in the contact zone, has been considered. To study the effect of friction between the mating gear teeth a range of average static friction coefficients, from 0.0 to 0.3, has been considered. The actual length of contact against the calculated length of contact is discussed. The variation of contact stress along the contact surface in a direction normal to the mating surfaces, which will give an idea about the depth of hardening required, is also presented.     

Never drive alone: Boosting carpooling with network analysis

Carpooling, i.e., the act where two or more travelers share the same car for a common trip, is one of the possibilities brought forward to reduce traffic and its externalities, but experience shows that it is difficult to boost the adoption of carpooling to significant levels. In our study, we analyze the potential impact of carpooling as a collective phenomenon emerging from people׳s mobility, by network analytics. Based on big mobility data from travelers in a given territory, we construct the network of potential carpooling, where nodes correspond to the users and links to possible shared trips, and analyze the structural and topological properties of this network, such as network communities and node ranking, to the purpose of highlighting the subpopulations with higher chances to create a carpooling community, and the propensity of users to be either drivers or passengers in a shared car. Our study is anchored to reality thanks to a large mobility dataset, consisting of the complete one-month-long GPS trajectories of approx. 10% circulating cars in Tuscany. We also analyze the aggregated outcome of carpooling by means of empirical simulations, showing how an assignment policy exploiting the network analytic concepts of communities and node rankings minimizes the number of single occupancy vehicles observed after carpooling.     

Automatic hexahedral mesh generation using a new grid-based method with geometry and mesh transformation

A geometry and mesh transformation approach is proposed to overcome the traditional problem of poorly shaped elements at the boundary using the grid-based method of mesh generation. This is achieved by transforming the original geometric model to a topologically similar recognition model which conforms fully to the Cartesian directions. Such a recognition model is constructed by tessellating the original model and then employing a fuzzy logic method to determine the normal directions of the faces. A three-dimensional field morphing algorithm is used to position the features of the recognition model. Such a recognition model is then meshed with hexahedral elements without any degeneracy using the new grid-based algorithm. The mesh of the recognition model is mapped back to the original geometric model by employing a transformation based on the Laplacian-isoparametric equation.     

Understanding design fundamentals: how synthesis and analysis drive creativity,resulting in emergence

This paper presents results of an ongoing interdisciplinary study to develop a computational theory of creativity for engineering design. Human design activities are surveyed, and popular computer-aided design methodologies are examined. It is argued that semiotics has the potential to merge and unite various design approaches into one fundamental theory that is naturally interpretable and so comprehensible in terms of computer use. Reviewing related work in philosophy, psychology, and cognitive science provides a general and encompassing vision of the creativity phenomenon. Basic notions of algebraic semiotics are given and explained in terms of design. This is to define a model of the design creative process, which is seen as a process of semiosis, where concepts and their attributes represented as signs organized into systems are evolved, blended, and analyzed, resulting in the development of new concepts. The model allows us to formally describe and investigate essential properties of the design process, namely its dynamics and non-determinism inherent in creative thinking. A stable pattern of creative thought — analogical and metaphorical reasoning — is specified to demonstrate the expressive power of the modeling approach; illustrative examples are given. The developed theory is applied to clarify the nature of emergence in design: it is shown that while emergent properties of a product may influence its creative value, emergence can simply be seen as a by-product of the creative process. Concluding remarks summarize the research, point to some unresolved issues, and outline directions for future work.     

Logical structure analysis and generation for structured documents: a syntactic approach

This paper presents a syntactic method for sophisticated logical structure analysis that transforms document images with multiple pages and hierarchical structure into an electronic document based on SGML/XML. To produce a logical structure more accurately and quickly than previous works of which the basic units are text lines, the proposed parsing method takes text regions with hierarchical structure as input. Furthermore, we define a document model that is able to describe geometric characteristics and logical structure information of documents efficiently and present its automated creation method. Experimental results with 372 images scanned from the IEEE Transactions on Pattern Analysis and Machine Intelligence (TPAMI) show that the method has performed logical structure analysis successfully and generated a document model automatically. Particularly, the method generates SGML/XML documents as the result of structural analysis, so that it enhances the reusability of documents and independence of platform.     

Structured mesh generation by kriging with local refinement with a new elliptic scheme

Accurate results in finite element analysis are strongly related to mesh quality. In this paper, an automatic quadrilateral mesh generation methodology using kriging interpolation is described, a quality mesh study is conducted, and the development of a new local refinement scheme, called the elliptic scheme, is presented. The new elliptic refinement scheme is evaluated using four standard structural cases, and it is shown that it compares very well with octree-based refinement schemes and other local refinement methods.     

PASS: a simple,efficient parallelism-aware solid state drive I/O scheduler

Emerging non-volatile memory technologies, especially flash-based solid state drives （SSDs）, have increasingly been adopted in the storage stack. They provide numerous advantages over traditional mechanically rotating hard disk drives （HDDs） and have a tendency to replace HDDs. Due to the long existence of HDDs as primary building blocks for storage systems, however, much of the system software has been specially designed for HDD and may not be optimal for non-volatile memory media. Therefore, in order to realistically leverage its superior raw performance to the maximum, the existing upper layer software has to be re-evaluated or re-designed. To this end, in this paper, we propose PASS, an optimized I/O scheduler at the Linux block layer to accommodate the changing trend of underlying storage devices toward flash-based SSDs. PASS takes the rich internal parallelism in SSDs into account when dispatching requests to the device driver in order to achieve high performance. Specifically, it parti-tions the logical storage space into fixed-size regions （preferably the component package sizes） as scheduling units. These scheduling units are serviced in a round-robin manner and for every chance that the chosen dispatching unit issues only a batch of either read or write requests to suppress the excessive mutual interference. Additionally, the requests are sorted according to their visiting addresses while waiting in the dispatching queues to exploit high sequential performance of SSD. The experimental results with a variety of workloads have shown that PASS outperforms the four Linux off-the-shelf I/O schedulers by a degree of 3%up to 41%, while at the same time it improves the lifetime significantly, due to reducing the internal write amplification.     

Sampling and analysis of particles generated in contact start/stop-mode of a hard disk drive by using a particle sampler

Particle contamination must be controlled to increase the storage capacity of a hard disk drive (HDD) as the flying height of the slider decreases. In the primary steps of particle contamination control, particles are precisely detected and analyzed. To carry out these steps, many researchers have used sampling methods. In this paper, we newly designed a particle sampler and evaluated the performance of the sampler. This sampler can collect particles by the applied electric field, by the impaction of particles, and by Brownian diffusion onto the sampling plate. We tested the performance of our sampler in terms of the parameters that affect the sampling efficiency of the particle sampler; sampling airflow rate, particle size, and externally applied electric field. The maximum sampling efficiency of unipolarly charged particles whose sizes ranged from 50 to 400 nm was about 90%. Also, we sampled particles generated during 20 contact start/stop cycles (CSS) of the HDD by using the particle sampler and analyzed the sampled particles by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). The SEM images showed that the sizes of the particles decreased and the number of sampled particles increased as the disk rotational speed increased. The AES spectrum showed that the sampled particles were composed of P, C, Ni and Al, which are the components of the disk materials. Therefore, we believed that the generated particles originated from the disk surface. To determine the overall sampling efficiency of the particle sampler, particles generated in the HDD were counted at the inlet and outlet of the sampler. The overall sampling efficiency increased with increasing applied voltage and disk rotational speed. The maximum overall sampling efficiency of the particles generated in the HDD was about 70% when the applied voltage and disk rotational speed were 0.5 kV and 9,600 rpm, respectively.     

Detecting dark spots from SAR intensity images by a point process with irregular geometry marks

Aiming at the difficulties to determine the geometric shape of dark spots, this paper proposes an Irregular Geometry Marked Point Process (IGMPP) to detect dark spots from Synthetic Aperture Radar (SAR) images. Firstly, a series of random points used to define the locations of dark spots in the SAR image domain, and an irregular polygon mark associated with each random point indicates the shape of each dark spot. Subsequently, the pixels intensities in and out of the polygons are characterized with independent and identical Gamma distributions, respectively. By Bayesian paradigm, the number, sites, and geometry parameters of polygons are modelled with a posterior distribution. In order to simulate the posterior, a Reversible Jump Markov Chain Monte Carlo (RJMCMC) strategy is developed. Then, the optimal parameters concerning the dark spots can be obtained by a Maximum A Posteriori (MAP) scheme. Experiments are performed by simulated SAR images. The experimental results show that the proposed algorithm is effectively and efficiently applied to detect the dark spots.     

Towards the generation of dialogue acts in socio-affective ECAs: a corpus-based prosodic analysis

We present a corpus-based prosodic analysis with the aim of uncovering the relationship between dialogue acts, personality and prosody in view to providing guidelines for the ECA Greta’s text-to-speech system. The corpus used is the SEMAINE corpus, featuring four different personalities, further annotated for dialogue acts and prosodic features. In order to show the importance of the choice of dialogue act taxonomy, two different taxonomies were used, the first corresponding to Searle’s taxonomy of speech acts and the second, inspired by Bunt’s DIT++, including a division of directive acts into finer categories. Our results show that finer-grained distinctions are important when choosing a taxonomy. We also show with some preliminary results that the prosodic correlates of dialogue acts are not always as cited in the literature and prove more complex and variable. By studying the realisation of different directive acts, we also observe differences in the communicative strategies of the ECA depending on personality, in view to providing input to a speech system.     

Inference graphs: a computational structure supporting generation of customizable and correct analysis components

Amalia is a generator framework for constructing analyzers for operationally defined formal notations. These generated analyzers are components that are designed for customization and integration into a larger environment. The customizability, and efficiency of Amalia analyzers owe to a computational structure called an inference graph. This paper describes this structure, how inference graphs enable Amalia to generate analyzers for operational specifications, and how we build in assurance. On another level, this paper illustrates how to balance the need for assurance, which typically implies a formal proof obligation, against other design concerns, whose solutions leverage design techniques that are not (yet) accompanied by mature proof methods. We require Amalia-generated designs to be transparent with respect to the formal semantic models upon which they are based. Inference graphs are complex structures that incorporate many design optimizations. While not formally verifiable, their fidelity with respect to a formal operational semantics can be discharged by inspection.