Rigid Partition Research Articles

A semi-analytical dynamics method for spindle radial throw in boring process

In precision boring processing, accurate prediction of the radial throw of a boring tool spindle has critical significance for reducing machining errors. However, the classical dynamics method of radial throw based on the rigid body partition method ignores special characteristics of the boring tool spindle, resulting in additional errors regarding radial throw evaluation. Hence, a semi-analytical dynamics method considering the axial length, variable cross-section, and offset distance was proposed to decrease the computational error of the current dynamics model. The mechanism of radial throw was analyzed by the mechanics of materials and mathematical formulas. The Euler-Bernoulli beam theory and partial differential equation method were utilized to derive the dynamics model of the boring tool spindle, and an improved Galerkin variational algorithm was used to resolve the dynamics formulas for the radial throw. Then, the proposed dynamics method was compared with the non-contact displacement measurement and the traditional lumped mass parameter method. The validated results showed that the presented dynamics method had good agreement with the experimental data, and the maximum predictive error was 16.08 μm lower based on the proposed method. Furthermore, the machining precision of holes was also clearly evaluated and discussed using the proposed dynamics method under different processing conditions, and the lower uncertainty of the proposed dynamics method was also demonstrated. As a result, the proposed semi-analytical dynamics method can accurately compute the radial throw and evaluate the machining error in boring technology.

Where to look: Multi-granularity occlusion aware for video person re-identification

Video person re-identification(re-ID) plays an important role in intelligent video surveillance, which can automatically match the same person across video clips under non-overlapping cameras. Despite great progress in re-ID, the performance of most existing methods still is corrupted severely under partial occlusion. Although some multi-granularity methods have alleviated this dilemma, these methods still suffer from weak diversity of features and conflict between rigid horizontal partition and vertical occlusion. In this paper, we propose a novel video person re-ID framework, called Multi-Granularity Occlusion Aware (MGOA), which extracts multi-granularity features by precisely erasing the occlusion. Different from previous works based on multiple granularities, the proposed MGOA predicts the partial occlusion in a coarse-to-fine manner instead of erasing the occlusion in video clips by one step. Specifically, we first propose the multi-granularity feature extraction to obtain diverse features at different levels of feature maps, which is beneficial for the fine erasure of the occlusion. Moreover, to avoid the limitation of horizontal stripes that cannot handle vertical occlusion, we design Attention-Aware Occlusion Erasure (AA-OE) that can obtain the attention maps with coarse occlusion erasure in the coarse-grained branch and the attention maps with fine occlusion erasure in the fine-grained branch. It is worth noting that each granularity in our network is not independent but relevant through the top-down information transmission between granularities, which transfers the erased occlusion feature maps of the current branch to the next finer-grained branch for guiding AA-OE to obtain more discriminative features. Extensive experiments on three challenging public benchmarks show that our MGOA can deal well with occlusion and achieves state-of-the-art performance.

Theoretical and experimental evaluation of timber-framed partitions under lateral drift

This paper identifies the inherent strengths/weaknesses of rigid timber-framed partitions and quantifies the onset drifts for different damage thresholds under bi-directional seismic actions. It reports construction and quasi-static lateral cyclic testing of a multi-winged timber-framed partition wall specimen with details typical of New Zealand construction practice. Furthermore, the cyclic performance of the tested rigid timber-framed partition wall is also compared with that of similar partition walls incorporating ‘partly-sliding’ connectiondetails, and ‘seismic gaps’, previously tested under the same test setup. Based on the experimentally recorded cyclic performance measures, theoretical equations proposed/derived in the literature to predict the ultimate strength, initial stiffness, and drift capacity of different damage states are scrutinized, and some equations are updated in order to alleviate identified possible shortcomings. These theoretical estimates are then validated with the experimental results. It is found that the equations can reasonably predict the initial stiffness and ultimate shear strength of the partitions, as well as the onset-driftscorresponding to the screw damage and diagonal buckling failure mode of the plasterboard. The predicted bi-linear curve is also found to approximate the backbone curve of the tested partition wall sensibly.

Numerical study of heat transfer in a tall, partitioned cavity confining two different fluids: Application to the water Trombe wall

A numerical study of the flow and heat transfer by natural convection and surface radiation in a tall partitioned cavity is performed in the present work. The left part (glazed cavity) is filled with air (Pr=0.71) while the right part is filled with water (Pr=7). The two cavities are separated by a thin, rigid partition absorbing a solar flux S ranging from 0 to 1000W/m². The right (inner) surface of the cavity is maintained at the temperature Ti=20°C, while the left one (outer) is maintained at the temperature To ranging from 0 °C to 50 °C. The horizontal surfaces are assumed to be adiabatic. Such a geometrical configuration and boundary conditions are chosen to model the flow and heat transfer in a water Trombe wall. A detailed examination of S and To effects on the flow and heat transfer in such a structure is the subject of this study. The main obtained results show that the flow structure in water and air can be similar or completely different depending on the mentioned parameters. Two values of the emissivity of the air cavity surfaces are considered ε=0 and ε=1 to study the effect of surface radiation. Two correlations giving the outer and inner heat fluxes Qo and Qi as a function of S and To are developed.

State-space system identification with physically motivated residual states and throughput rank constraint

It has been observed that energy conjugate input-output pair transfer functions with strongly participating outside-band modes of mechanical systems often render identified state-space models with poor fit to data. That holds even after common practice inclusion of mass and stiffness residual states. The inclusion of a particular form of extra residual states are suggested to improve the model fit for such pairs. A pole placement strategy for the extra states is derived. Furthermore, for identification of state-space models with force input and acceleration output, the system direct throughput matrix relating the two is modelled. For flexible structures with rigid body motion, it is shown that the direct throughput matrix can be decomposed into a rigid body and flexible motion part. In test situations with more inputs and outputs than rigid body modes, the rigid body partition of the direct throughput matrix of the identified model must be rank constrained for physical consistency. The constraint is enforced using a singular value decomposition during iterations of the state-space matrices used to further improve the identified model fit. The procedures are illustrated on simulated finite element data from an industrial component with known model order. A successful application to real experimental data is also shown.

Receptive Multi-granularity Representation for Person Re-Identification.

A key for person re-identification is achieving consistent local details for discriminative representation across variable environments. Current stripe-based feature learning approaches have delivered impressive accuracy, but do not make a proper trade-off between diversity, locality, and robustness, which easily suffers from part semantic inconsistency for the conflict between rigid partition and misalignment. This paper proposes a receptive multi-granularity learning approach to facilitate stripe-based feature learning. This approach performs local partition on the intermediate representations to operate receptive region ranges, rather than current approaches on input images or output features, thus can enhance the representation of locality while remaining proper local association. Toward this end, the local partitions are adaptively pooled by using significance-balanced activations for uniform stripes. Random shifting augmentation is further introduced for a higher variance of person appearing regions within bounding boxes to ease misalignment. By twobranch network architecture, different scales of discriminative identity representation can be learned. In this way, our model can provide a more comprehensive and efficient feature representation without larger model storage costs. Extensive experiments on intra-dataset and cross-dataset evaluations demonstrate the effectiveness of the proposed approach. Especially, our approach achieves a state-of-the-art accuracy of 96.2%@Rank-1 or 90.0%@mAP on the challenging Market-1501 benchmark.

Tongue Image Alignment via Conformal Mapping for Disease Detection

Tongue image analysis has been an active study in medical imaging. Existing tongue image processing approaches deal with the issue of image alignment in oversimplified ways. These approaches mainly extract patches or simple regions on pre-defined positions, which are severely sensitive to tongue deformations. In this paper, we present a conformal mapping method for tongue image alignment, the principle of which is to determine the interior mapping based on the boundary mapping so that it is robust to the deformations. The conformal alignment consists of two stages: the mapping on the boundary is firstly established via the Fourier descriptor before the mapping is extended onto the interior region via Cauchy's integral and finite-difference method. Average tongues and eigen-tongues are constructed based on the conformal alignment for feature extraction. Experiments show that the proposed alignment is robust against tongue deformations and can be employed to correct existing rigid partition methods. Numerical evaluations on time efficiency and accuracy also show that our method is considerably fast and very accurate, compared with several baseline methods in this field. For the task of disease detection, the features based on the aligned images outperform some state-of-the-art features. The results reveal that the proposed method provides an efficient and accurate tool for deformable medical image alignment and disease diagnosis. A MatLab script of the proposed algorithm is available on https://codeocean.com/capsule/4382908/tree/v1.

Physically motivated rank constraint on direct throughput of state-space models

In frequency range vibration testing a few outside band eigenmodes are often included in the system identification to compensate for residual mass and stiffness influences. It has been observed that, in particular, energy conjugate input-output pair transfer functions with strong outside band modes tend to render models with poor fit even after inclusion of mass and stiffness residuals. For such problems the inclusion of another complementary residual term has been found to improve the fit to data. In this paper, modal models identified from acceleration data with a subspace state-space method are considered. The residual mass influence is modelled with a state-space direct throughput while the stiffness and complementary residuals are modelled with extra states. Furthermore, for state-space models on accelerance form it is shown that the direct throughput matrix can be partitioned into a flexible and rigid motion partition. For systems with more inputs and outputs than rigid body modes it is shown that the rigid body motion partition has a bounded rank. The upper bound is equal to the number of rigid body modes. Therefore, for identified models on accelerance form this constraint must be enforced for physical consistency. The proposed method is applied on simulated finite element test data from an automotive component.

Enhanced isoprenoid production from xylose by engineered Saccharomyces cerevisiae.

Saccharomyces cerevisiae has limited capabilities for producing fuels and chemicals derived from acetyl-CoA, such as isoprenoids, due to a rigid flux partition toward ethanol during glucose metabolism. Despite numerous efforts, xylose fermentation by engineered yeast harboring heterologous xylose metabolic pathways was not as efficient as glucose fermentation for producing ethanol. Therefore, we hypothesized that xylose metabolism by engineered yeast might be a better fit for producing non-ethanol metabolites. We indeed found that engineered S. cerevisiae on xylose showed higher expression levels of the enzymes involved in ethanol assimilation and cytosolic acetyl-CoA synthesis than on glucose. When genetic perturbations necessary for overproducing squalene and amorphadiene were introduced into engineered S. cerevisiae capable of fermenting xylose, we observed higher titers and yields of isoprenoids under xylose than glucose conditions. Specifically, co-overexpression of a truncated HMG1 (tHMG1) and ERG10 led to substantially higher squalene accumulation under xylose than glucose conditions. In contrast to glucose utilization producing massive amounts of ethanol regardless of aeration, xylose utilization allowed much less amounts of ethanol accumulation, indicating ethanol is simultaneously re-assimilated with xylose consumption and utilized for the biosynthesis of cytosolic acetyl-CoA. In addition, xylose utilization by engineered yeast with overexpression of tHMG1, ERG10, and ADS coding for amorphadiene synthase, and the down-regulation of ERG9 resulted in enhanced amorphadiene production as compared to glucose utilization. These results suggest that the problem of the rigid flux partition toward ethanol production in yeast during the production of isoprenoids and other acetyl-CoA derived chemicals can be bypassed by using xylose instead of glucose as a carbon source. Biotechnol. Bioeng. 2017;114: 2581-2591. © 2017 Wiley Periodicals, Inc.

Absorption performance optimization of perforated plate using multiple-sized holes and a porous separating partition

This research proposes a new type of sound absorptive perforated plate with multiple-sized holes and a porous separating partition in an attempt to extend the sound absorption bandwidth. Separating different sized holes with a porous partition instead of a conventional rigid partition is an unprecedented idea. However, existence of a porous separating partition makes it hard to use theoretical surface impedance models to predict absorption performance. So we introduce appropriate finite element simulation method using the effective density of hole. To consider the end correction effects for hole length and viscosity length of a perforated plate, the effective density of the Johnson-Champoux-Allard model is modified and the end correction lengths of the modified effective density are corrected again in connection with finite element simulation. Material property of a porous separating partition is modeled by the Delany-Bazley material model. After constructing the finite element model, we analyzed the absorption coefficient graphs of perforated plates with two-sized holes and four-sized holes according to the separating partition types: no partition, rigid partition and porous partition. To enhance the wide-band absorption performance, flow resistivity value and thickness of a porous separating partition as well as hole sizes are optimized. From the analysis and design examples, we confirmed that the perforated plate using multiple-sized holes and a porous separating partition can make a continuous frequency range of high absorption coefficient compared to the perforated plate with a conventional rigid partition.

Topology optimization of internal partitions in a flow-reversing chamber muffler for noise reduction

A topology-optimization-based design method for a flow-reversing chamber muffler is suggested to maximize the transmission loss value at a target frequency considering flow power dissipation. Rigid partitions for high noise reduction should be carefully placed inside the muffler to avoid extreme flow power dissipation due to a 180° change in flow direction from an inlet to an outlet. The optimal flow path for minimum flow power dissipation is well known to change depending on the Reynolds number, which is a function of the inlet flow velocity. To optimize the partition layout with an optimal flow path in an expansion chamber at a given Reynolds number, a flow-reversing chamber muffler design problem is formulated by topology optimization. The formulated topology optimization problem is implemented using the finite element method with a gradient-based optimization algorithm and is solved for various design conditions such as the target frequencies, rigid partition volumes, Reynolds numbers, non-design domain settings, and allowed amounts of flow power dissipation. The effectiveness of our suggested approach is verified by comparing the optimized partition layouts obtained by the suggested method and previous methods.

DEM Simulation of the Impact of Ultrafine Glass Particles on the Partition Wall of the Multichannel Cyclone

This article focuses on the simulation of the impact of ultrafine particles on the rigid partition wall of the multichannel cyclone by applying the discrete element method (DEM). Ultrafine particles with diameters ranging from 0.1 to 10 µm are assumed to be most dangerous pollutants because of their property to easily penetrate the human circulatory system through the respiratory tract. An emphasis is placed on demonstrating the stick-rebound behavior of glass pollutant particles. The numerical experiment simulating the oblique impact load induced by mechanically generated inlet air flow has been numerically conducted. Hertz contact and short-range van der Waals attraction are the main forces describing normal contact, while their tangential counterpart is defined according to Coulomb friction law and by considering normal compression and attraction. Both normal and tangential models are modified to comprise the effect of energy dissipation due to adhesion hysteresis. Simulation results provide a theoretical framework for designing of the cyclone when a device is applied to capture ultrafine pollutant particles.

Method of damping vibration, active hydraulic anti-vibration mount and vehicle including such a mount

Active hydraulic anti-vibration mount comprising two support elements connected by an elastomer body partially delimiting a working chamber filled with liquid, this working chamber communicating by a throttled passage with a compensation chamber separated from said working chamber by a rigid partition. The rigid partition is penetrated by a first regulating nozzle closed by a movable exciting device, and a second regulating nozzle closed by a valve the movements of which are limited to correspond to an amplitude of variation in the volume of the working chamber which is less than 20% of the amplitude of the variations in volume generated by the exciting device.

Sports related combined noisemaker and visual display device

A sports related combined noisemaker and visual display device includes a hollow body with a rigid wall, configured to replicate the appearance of a helmet or other type of sporting equipment, a rigid partition disposed in the interior of the body so as to form a closed chamber bounded by the wall of the body and the partition, a plurality of hard pellets loosely disposed in the chamber, and handle means disposed on the body for shaking the body back and forth to cause the pellets to impact the wall and partition and produce sound. The placement of the handle and the orientation of the partition are such that the chamber functions to focus and project the sound from the wall of the body generally opposite the handle. The outer surface of the body provides an area for the application of visual displays such as decals.

Drag effects between two-dimensional superfluid charged Bose gases separated by a rigid partition

The drag effect in a system of two-dimensional superfluid charged Bose gases separated by a thin insulating partition is analyzed microscopically. It is shown that in contrast to normal systems, the drag effect is observed at T=0. The temperature dependence of the entrainment current is determined. An experiment for observing the effect is proposed.

Vibration-damping structure

First Page

The role of pressure in osmotic flow

Pressure-driven volume flow occurs at the expense of an external energy supply. This has been shown for pure liquid pressed through a rigid partition and for the reverse osmosis case. In contrast to these cases, the osmotic flow dissipation and work done against the applied pressure gradient are covered by free energy change brought about by dilution of the solution. A consistent energetic and mechanical description of osmosis has been achieved on recognizing that the occurrence of pressure gradient depends, according to the mechanical equilibrium condition, on whether there is a resultant external force acting on the solution. The pressure gradient, if at all present, is shown to be only a factor in osmotic flow and not the prime mover. The osmotic effect on course-porous membranes has been considered as resulting from physical adsorption on the pore wall. A force on the solution near the pore wall due to adsorption is derived on recognizing that it can perform work at the expense of the Gibbs free energy of the solution. This membrane-solution interaction force can cause a slip of the solution on the wall or pressure buildup if the flow has been stopped. Assuming diffusional type of flow in the wall-adjacent layer and viscous flow in the core of the channel, the resultant volume flow is expressed by the moment of adsorption, chemical potential gradients of the components, and by the applied pressure gradient. For non-Newtonian liquids a possibility of plug flow has been shown.

Lined duct acoustic filter

A lined duct is divided into two parallel branches by means of a rigid partition. The phase speed of the fundamental mode in each branch depends on the liner configuration and can differ markedly from the free-space phase speed. When the liners in the two branches are not the same, the corresponding phase speeds will be different and a relative phase lag between the waves in the two branches results. This, in turn, leads to interference between these wave components (and their reflections) both at the exit and entrance of the parallel branch pair. This interference can be exploited for the purpose of obtaining a low-frequency attenuation which is substantially larger than the attenuation of the unpartitioned duct.

A new approach to acoustic filtering with lined ducts

We consider a lined duct which is divided into two parallel branches by means of a rigid partition. The phase speed of the fundamental mode in each branch depends on the liner configuration and can differ markedly from the free‐space phase speed. If the liners in the two branches are not the same, the corresponding phase speeds will be different and a relative phase lag between the waves in the two branches results. This, in turn, leads to interference between these wave components (and their reflections), both at the exit and the entrance of the parallel branch pair. We have demonstrated both analytically and experimentally that this interference can be exploited for the purpose of obtaining a low‐frequency attenuation which is substantially larger than the attenuation of the unpartitioned duct. [This work was supported in part by the U.S. Navy (Office of Naval Research) under Contract N00014‐67‐A‐0204‐0019 and in part by the U.S. Department of Transportation under Grant Agreement DOT‐OS‐3011.]

Systematic Approach to Explanation of the Rigid Disk Phase Transition

By classifying particle center positions with a hexagonal grid, evaluation of the two-dimensional rigid sphere partition function is reduced to a special lattice statistics problem, with precisely defined nearest-neighbor effective pair interactions. The hexagonal cell size is chosen to be the maximum consistent with no more than double occupancy. Since the resulting lattice partition function (with three states per site) contains a collectively determined many-cell effective interaction Δ*, as well as nearest-neighbor contributions, it becomes necessary to examine in detail the statistical geometry of available phase space for the original spheres, under varying restraints of nearest-neighbor cell distribution. Accordingly, we obtain for the first time an unambiguous definition of ``random close-packed'' or ``glassy'' arrangements of spheres (which however are not themselves equilibrium states), and to relations between properties of these arrangements, and of Δ*. The key features which subsequently allow description of rigid sphere order—disorder behavior are: (1) the observation that certain nearest-neighbor cell pairs which occur in the glassy state (both unoccupied and both doubly occupied) are geometrically excluded completely in the ordered, close-packed arrangement; (2) Δ* sensitively depends upon these pair distributions. In spite of the fact that Δ* is thereby assigned a specially generalized free-volume form, the theory leads to a proper virial series development at low density. In addition, we report some preliminary results for the effective cell interactions, for glassy state parameters, and some calculations designed to reveal the structure of Δ*. Although this analysis does not yet represent a full quantitative theory of the two-dimensional rigid disk system, it does lead to a novel qualitative explanation of how a fluid—solid transition can occur, and suggestions are given for completing the quantification.