直接点操作的人脸变形与动画

自由变形（FFD）是计算机人脸动画和表情编辑的常用方法,但对控制点的反求和变形结果的不直观是该方法的不足。提出了基于直接点操作网格的变形方法,通过鼠标的交互编辑,可以直接得到可控制的变形结果。试验结果表明该方法简单有效。     

Kinematics of heelstrike during walking and carrying: implications for slip resistance testing

Slip resistance measurements of shoes and floors are used to evaluate the potential for slip and fall injuries. These measurements are believed to have increased validity when they more closely reflect actual heelstrike biomechanics during locomotion. The purpose of this study was to describe heelstrike kinematics during load carrying to provide data towards improved slip resistance testing. Foot kinematics during load carrying (unladen and carrying from 0 to 13.5 kg) at various cadences (70, 90, 100 steps/min) was recorded. Measures before, during and after heelstrike were analysed. Cadence was an important predictor for all variables measured, associated with changes from 13% to over 100%. The load carried was an important predictor for only the heel slip distance after heelstrike, but this effect needs to be investigated further. These results can be used to improve the fidelity of slip resistance measurements, which is critical to reduce slip and fall injuries in the workplace or during activities of daily living.     

Differential coordinates for local mesh morphing and deformation

Published online: 14 February 2003     

Effect of safety boots with toe spring on foot clearance features during walking

Tripping is a primary cause of occupational injury falls, especially among aging workers. This study investigated changes in foot clearance features during the normal walking swing phase affected by adding a toe spring height to safety boots. Gait data were obtained from nine male participants wearing experimental and control shoes via a motion capture system. A principal component analysis was conducted on three-dimensional foot segment trajectories and angles, and plantar surface motions were compared between conditions. Statistical analysis revealed significant principal component score differences between conditions in principal component vectors 1, 3, 5, 6, 8, and 9. The related swing phase three-dimensional plantar surface motion patterns were reconstructed. The results revealed two characteristics of the shoe-plantar surface three-dimensional motion of experimental shoes: higher foot clearance and a relatively straighter forward leg path. It was thus concluded that utilizing safety boots with toe springs may reduce falls in older workers due to occupational trips in industries.     

MARGA: Multispectral Adaptive Region Growing Algorithm for brain extraction on axial MRI

Brain extraction, also known as skull stripping, is one of the most important preprocessing steps for many automatic brain image analysis. In this paper we present a new approach called Multispectral Adaptive Region Growing Algorithm (MARGA) to perform the skull stripping process. MARGA is based on a region growing (RG) algorithm which uses the complementary information provided by conventional magnetic resonance images (MRI) such as T1-weighted and T2-weighted to perform the brain segmentation. MARGA can be seen as an extension of the skull stripping method proposed by Park and Lee (2009) [1], enabling their use in both axial views and low quality images. Following the same idea, we first obtain seed regions that are then spread using a 2D RG algorithm which behaves differently in specific zones of the brain. This adaptation allows to deal with the fact that middle MRI slices have better image contrast between the brain and non-brain regions than superior and inferior brain slices where the contrast is smaller. MARGA is validated using three different databases: 10 simulated brains from the BrainWeb database; 2 data sets from the National Alliance for Medical Image Computing (NAMIC) database, the first one consisting in 10 normal brains and 10 brains of schizophrenic patients acquired with a 3 T GE scanner, and the second one consisting in 5 brains from lupus patients acquired with a 3 T Siemens scanner; and 10 brains of multiple sclerosis patients acquired with a 1.5 T scanner. We have qualitatively and quantitatively compared MARGA with the well-known Brain Extraction Tool (BET), Brain Surface Extractor (BSE) and Statistical Parametric Mapping (SPM) approaches. The obtained results demonstrate the validity of MARGA, outperforming the results of those standard techniques.     

Surface deformation time series and source modeling for a volcanic complex system based on satellite wide swath and image mode interferometry: The Lazufre system, central Andes

The variable spatio-temporal scales of Earth's surface deformation in potentially hazardous volcanic areas pose a challenge for observation and assessment. Here we used Envisat data acquired in Wide Swath Mode (WSM) and Image Mode (IM) from ascending and descending geometry, respectively, to study time-dependent ground uplift at the Lazufre volcanic system in Chile and Argentina. A least-squares adjustment was performed on 65 IM interferograms that covered the time period of 2003-2008. We obtained a clear trend of uplift reaching 15-16 cm in this 5-year interval. Using a joint inversion of ascending and descending interferograms, we evaluated the geometry and time-dependent progression of a horizontally extended pressurized source beneath the Lazufre volcanic system. Our results hence indicate that an extended magma body at a depth between 10 and 15 km would account for most of the ground uplift. The maximum inflation reached up to ~ 40 cm during 2003-2008. The lateral propagation velocity of the intrusion was estimated to be nearly constant at 5-10 km/yr during the observation time, which has important implications for the physical understanding of magma intrusion processes.     

Efficient and robust nonlocal means denoising of MR data based on salient features matching

The nonlocal means (NLM) filter has become a popular approach for denoising medical images due to its excellent performance. However, its heavy computational load has been an important shortcoming preventing its use. NLM works by averaging pixels in nonlocal vicinities, weighting them depending on their similarity with the pixel of interest. This similarity is assessed based on the squared difference between corresponding pixels inside local patches centered at the locations compared. Our proposal is to reduce the computational load of this comparison by checking only a subset of salient features associated to the pixels, which suffice to estimate the actual difference as computed in the original NLM approach. The speedup achieved with respect to the original implementation is over one order of magnitude, and, when compared to more recent NLM improvements for MRI denoising, our method is nearly twice as fast. At the same time, we evidence from both synthetic and in vivo experiments that computing of appropriate salient features make the estimation of NLM weights more robust to noise. Consequently, we are able to improve the outcomes achieved with recent state of the art techniques for a wide range of realistic Signal-to-Noise ratio scenarios like diffusion MRI. Finally, the statistical characterization of the features computed allows to get rid of some of the heuristics commonly used for parameter tuning.     

动臂梁焊接顺序优化减小焊接变形模拟预测

利用热弹塑性有限元法对装载机动臂梁结构的焊接变形进行热 力耦合数值模拟.建立分析模型,定量对比在同一约束条件下动臂板与动臂圆筒、摇臂板与动臂圆筒的焊接顺序对整体结构焊接变形的影响,按照对称组焊的原则优化焊接顺序.结果表明,对称结构的动臂梁采用交替焊接顺序与沿一个方向顺次焊接顺序相比,动臂板与摇臂板变形量都减小,先焊动臂板比先焊摇臂板 动臂板角变形小.得出整体结构的最佳焊接顺序方案,并将预测的在最佳焊接顺序下的变形模拟值和试验值进行对比,二者吻合良好.     

Regional clustering of medical imaging technologies

The purpose of this study was to analyze clusters from 12 regions in Turkey in terms of medical imaging technologies' capacity and use. 12 statistical region units were determined by the Ministry of Development and Turkish Statistical Institute clustered in terms of selected medical imaging indicators regarding capacity and use by using the hierarchical clustering method. This study was based on the Ward's Method, one of the hierarchical clustering methods, and the distance matrix was created by using Euclidean distance measure analysis. When the distance matrix, which was created by using the squared Euclidean distance measure, was analyzed, it was found that the two regions most distant from each other were Southeast Anatolia and Western Anatolia (Euclidean distance = 13.69) two regions which have the least distance from each other were Mediterranean and Aegean regions (Euclidean distance = 0.99) for public, university and private hospitals. When we analyze the dendrogram, which was created by using hierarchical clustering, it was seen that the 12 statistical region units were gathered in four different clusters. This article revealed that there were inequities in medical imaging technologies according to regions in Turkey and hospital ownerships.     

Dynamic edge tracing: Boundary identification in medical images

Medical image segmentation is a sufficiently complex problem that no single strategy has proven to be completely effective. Historically, region growing, clustering, and edge tracing have been used and while significant steps have been made in the first two, research into automatic, recursive, boundary following has not kept pace. A new, advanced, edge-tracing algorithm capable of combining edge, region, and pixel-classification information, and suitable for magnetic resonance image analysis, is described. The algorithm is inspired by automatic target tracking, as used in civilian and military aerospace operations. Comparison with clustering and level sets is performed. Results indicate that no method is uniformly superior, that the new algorithm provides information not available from the other approaches, and that it can utilize a variety of sources including results from other methods. The algorithm is applied to two-dimensional slice images and extension to three-dimensional images is discussed.     

Analysis,modeling and experimental validation of temperature-changing effect on mechanical properties of pneumatic artificial muscle

This paper focuses on quantify how temperature affects the mechanical properties of pneumatic artificial muscle (PAM). The influence of temperature variations on PAM’s structure size and internal friction was analyzed firstly, based on the thermal characteristics of rubber diaphragm and fiber mesh, then a novel model considering the influence of temperature variation is proposed, without any fitting parameter or any parameter with uncertain physical meanings. In order to verify the proposed model, temperature-rising experiments using heating device and continuous operation were both carried out separately. Through the comparison of characteristic curves under different temperatures, PAM’s characteristics were proven to be affected by temperature variations. The results show that inside temperature changing of PAM is why there are drifting and time-varying phenomenon of their mechanical characteristics in long-term operation, and the proposed model can predict the variations caused by temperature changing well. Meanwhile, the accuracy of the new model is higher than Chou model and lower than Andrikopoulos model; it is understandable because our new model has no fitting parameters, but the advantage of new model is that it takes temperature as independent variables and, therefore, can be used at different temperatures directly without any calibration.     

Effect of uphill walking with varying grade and speed during load carriage on muscle activity

Indian soldiers, while guarding the mountainous border areas, often carry loads in steep uphill gradients. This activity may predispose the risk of muscle injury. The present study aimed to examine the effects of an increasing load, speed and gradient during incremental uphill treadmill walking on different muscles. Twelve infantry soldiers walked on a treadmill at two speeds (2.5 and 4 km/h) with no load, and carrying 10.7, 17 and 21.4 kg loads at 0, 5, 10, 15, 20, 25% gradients. Electromyographic responses of erector spinae (>240%) and vastus medialis (>240%) were mostly affected, followed by soleus (>125%) and gastrocnemius medialis (>100%) at maximum speed, load and gradient combination compared to 0% gradient. Carrying 10.7 kg at 15% gradient and above was found to be highly strenuous and fatiguing with the risk of muscle injury. Uphill load carriage in slower speed is recommended for the maintenance of combat fitness of the individual at higher gradients.

Practitioner Summary:

The present article has evaluated the stress encountered by soldiers during load carriage at incremental uphill gradients while walking at different speeds by recording the muscular activities. Load carriage in steep uphill gradients is highly strenuous and may lead to muscle injury thus compromising the combat fitness.     

Model-free visualization of suspicious lesions in breast MRI based on supervised and unsupervised learning

Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has become an important tool in breast cancer diagnosis, but evaluation of multitemporal 3D image data holds new challenges for human observers. To aid the image analysis process, we apply supervised and unsupervised pattern recognition techniques for computing enhanced visualizations of suspicious lesions in breast MRI data. These techniques represent an important component of future sophisticated computer-aided diagnosis (CAD) systems and support the visual exploration of spatial and temporal features of DCE-MRI data stemming from patients with confirmed lesion diagnosis. By taking into account the heterogeneity of cancerous tissue, these techniques reveal signals with malignant, benign and normal kinetics. They also provide a regional subclassification of pathological breast tissue, which is the basis for pseudo-color presentations of the image data. Intelligent medical systems are expected to have substantial implications in healthcare politics by contributing to the diagnosis of indeterminate breast lesions by non-invasive imaging.     

A New assembly precision prediction method of aeroengine high-pressure rotor system considering manufacturing error and deformation of parts

The accurate prediction of high-pressure rotor system assembly precision before assembly is the premise of improving aeroengine assembly quality and performance. The existing assembly precision prediction models (APPM) only consider the manufacturing error factors of parts, but rarely involve the deformation of parts under load, so there is a certain gap between the prediction results and the actual situation. This article studies the construction method of APPM considering the manufacturing error and deformation factors of parts. Firstly, the fitting algorithm is used to obtain the fitting deformation surface(FDS) of each mating surface under load, which provides the basis for constructing assembly error model considering manufacturing error and deformation of parts; secondly, according to the relative position relationship between the FDS and the datum plane, the error model of each mating surface of the assembly is effectively constructed by the small displacement torsor theory; thirdly, according to the different errors of each fitting end face, a prediction model of assembly precision for two rough surfaces is constructed by homogeneous coordinate transformation method; finally, a high-pressure compressor rotor system is used as an example to verify the effectiveness of the precision prediction model. The results show that the prediction results based on the proposed model are closer to the actual conditions. This paper provides an effective prediction model for high-pressure rotor system assembly precision, and has important application value for improving the assembly quality and performance of aeroengine.     

Multiphase segmentation using an implicit dual shape prior: Application to detection of left ventricle in cardiac MRI

Cardiac magnetic resonance imaging (MRI) has been extensively used in the diagnosis of cardiovascular disease and its quantitative evaluation. Cardiac MRI techniques have been progressively improved, providing high-resolution anatomical and functional information. One of the key steps in the assessment of cardiovascular disease is the quantitative analysis of the left ventricle (LV) contractile function. Thus, the accurate delineation of LV boundary is of great interest to improve diagnostic performance. In this work, we present a novel segmentation algorithm of LV from cardiac MRI incorporating an implicit shape prior without any training phase using level sets in a variational framework. The segmentation of LV still remains a challenging problem due to its subtle boundary, occlusion, and inhomogeneity. In order to overcome such difficulties, a shape prior knowledge on the anatomical constraint of LV is integrated into a region-based segmentation framework. The shape prior is introduced based on the anatomical shape similarity between endocardium and epicardium. The shape of endocardium is assumed to be mutually similar under scaling to the shape of epicardium. An implicit shape representation using signed distance function is introduced and their discrepancy is measured in a probabilistic way. Our shape constraint is imposed by a mutual similarity of shapes without any training phase that requires a collection of shapes to learn their statistical properties. The performance of the proposed method has been demonstrated on fifteen clinical datasets, showing its potential as the basis in the clinical diagnosis of cardiovascular disease.     

Effects of backpack load on critical changes of trunk muscle activation and lumbar spine loading during walking

This study investigated the effects of carrying a backpack while walking. Critical changes featuring the disproportionality of increases in trunk muscle activation and lumbar joint loading between light and heavy backpack carriage weight may reveal the load-bearing strategy (LBS) of the lumbar spine. This was investigated using an integrated system equipped with a motion analysis, a force platform and a wireless surface electromyography (EMG) system to measure the trunk muscle EMG amplitudes and lumbar joint component forces. A predictive goal programming model was developed to determine the most critical changes in trunk muscle activation and lumbar joint loading. Results suggested that lightweight backpack carriage at approximately 3% of body weight (BW) might reduce the peak lumbosacral compression force by 3% during walking compared with no load condition. The most critical changes in both trunk muscle activation and lumbosacral joint loading were found at a backpack load of 10% of BW.

Practitioner Summary: This study investigated the effects of backpack load on the LBS of lumbar spine while walking. A backpack load of 3% of BW might reduce the peak lumbosacral compression force by 3 and 10% of BW induced the most critical changes in LBS of lumbar spine.     

Mobile link prediction: Automated creation and crowdsourced validation of knowledge graphs

Building trustworthy knowledge graphs for cyber–physical social systems (CPSS) is a challenge. In particular, current approaches relying on human experts have limited scalability, while automated approaches are often not validated by users resulting in knowledge graphs of questionable quality. This paper introduces a novel pervasive knowledge graph builder for mobile devices that brings together automation, experts’ and crowdsourced citizens’ knowledge. The knowledge graph grows via automated link predictions using genetic programming that are validated by humans for improving transparency and calibrating accuracy. The knowledge graph builder is designed for pervasive devices such as smartphones and preserves privacy by localizing all computations. The accuracy, practicality, and usability of the knowledge graph builder is evaluated in a real-world social experiment that involves a smartphone implementation and a Smart City application scenario. The proposed methodology of knowledge graph building outperforms a baseline method in terms of accuracy while demonstrating its efficient calculations on smartphones and the feasibility of the pervasive human supervision process in terms of high interactions throughput. These findings promise new opportunities to crowdsource and operate pervasive reasoning systems for cyber–physical social systems in Smart Cities.     

Physical modeling of biomolecular computers: Models,limitations, and experimental validation

A principal challenge facing the development and scaling of biomolecular computers is the design of physically well-motivated, experimentally validated simulation tools. In particular, accurate simulations of computational behavior are needed to establish the feasibility of new architectures, and to guide process implementation, by aiding strand design. Key issues accompanying simulator development include model selection, determination of appropriate level of chemical detail, and experimental validation. In this work, each of these issues is discussed in detail, as presented at the workshop on simulation tools for biomolecular computers (SIMBMC), held at the 2003 Congress on Evolutionary Computation. The three major physical models commonly applied to model biomolecular processes, namely molecular mechanics, chemical kinetics, and statistical thermodynamics, are compared and contrasted, with a focus on the potential of each to simulate various aspects of biomolecular computers. The fundamental and practical limitations of each approach are considered, along with a discussion of appropriate chemical detail, at the biopolymer, process, and system levels. The relationship between system analysis and design is addressed, and formalized via the DNA Strand Design problem (DSD). Finally, the need for experimental validation of both underlying parameter sets and overall predictions is discussed, along with illustrative examples.Authors contributed equally to the present work.     

Achieving developability of a polygonal surface by minimum deformation: a study of global and local optimization approaches

Surface developability is required in a variety of applications in product design, such as clothing, ship hulls, automobile parts, etc. However, most current geometric modeling systems using polygonal surfaces ignore this important intrinsic geometric property. This paper investigates the problem of how to minimally deform a polygonal surface to attain developability, or the so-called developability-by-deformation problem. In our study, this problem is first formulated as a global constrained optimization problem and a penalty-function-based numerical solution is proposed for solving this global optimization problem. Next, as an alternative to the global optimization approach, which usually requires lengthy computing time, we present an iterative solution based on a local optimization criterion that achieves near real-time computing speed.     

Getting it right: modeling of pH, solvent and "nearly" everything else in virtual screening of biological targets

“Getting it right” refers to the careful modeling of all elements in the living system, i.e. biological macromolecules, ligands and water molecules. In addition, careful attention should be paid to the protonation state of ionizable functional groups on the ligands and residues at the active site. Computational technology based on the empirical HINT program is described to: (1) calculate free energy scores for ligand binding; (2) include the implicit and explicit effects of water in and around the ligand binding site; and (3) incorporate the effects of global and local pH in molecular models. This last point argues for the simultaneous consideration of a number of molecular models, each with different protonation profiles. Data from recent studies of protein–ligand systems (trypsin, thrombin, neuraminidase, HIV-1 protease and others) are used to illustrate the concepts in the paper. Also discussed are experimental factors related to accurate free energy predictions with this and other computational technologies.