Penumbra masks

Computation of physically-based shadows can be significantly accelerated by limiting computations into regions where penumbras appear. In this paper, we present a general penumbra detection method that efficiently bounds regions where penumbras occur in a shared projection plane of an area light source. We introduce a novel area filling operator, which allows effective and conservative area masking with respect to all viewpoints, i.e., sampling points within a planar polygonal light source. The area filling operator uses a point sprite rendering technique on a set of silhouette boundaries to create a penumbra mask, which is essentially a modified occlusion map. We show how to efficiently test the geometry and screen-space pixels against the penumbra mask. An important advantage of our method is that we can separate lit and umbra regions, and thus drive various soft shadow algorithms to focus their computational efforts into potential penumbras. Due to the relative simplicity of computations, penumbra masks can be efficiently generated with graphics hardware. As an example, we accelerate shadow map supersampling to demonstrate significant speedups that utilizations of penumbra masks provide.     

Evaluation of micromilled metal mold masters for the replication of microchip electrophoresis devices

High-precision micromilling was assessed as a tool for the rapid fabrication of mold masters for replicating microchip devices in thermoplastics. As an example, microchip electrophoresis devices were hot embossed in poly(methylmethacrylate) (PMMA) from brass masters fabricated via micromilling. Specifically, sidewall roughness and milling topology limitations were investigated. Numerical simulations were performed to determine the effects of additional volumes present on injection plugs (i.e., shape, size, concentration profiles) due to curvature of the corners produced by micromilling. Elongation of the plug was not dramatic (< 20%) for injection crosses with radii of curvatures to channel width ratios less than 0.5. Use of stronger pinching potentials, as compared to sharp-corner injectors, were necessary in order to obtain short sample plugs. The sidewalls of the polymer microstructures were characterized by a maximum average roughness of 115 nm and mean peak height of 290 nm. Sidewall roughness had insignificant effects on the bulk EOF as it was statistically the same for PMMA microchannels with different aspect ratios compared to LiGA-prepared devices with a value of ca. 3.7 × 10⁻⁴ cm²/(V s). PMMA microchip electrophoresis devices were used for the separation of pUC19 Sau3AI double-stranded DNA. The plate numbers achieved in the micromilled-based chips exceeded 1 million/m and were comparable to the plate numbers obtained for the LiGA-prepared devices of similar geometry.     

Stationary and nonstationary affine combination of subdivision masks

One of the difficult task in subdivision is to create new effective subdivision schemes. Therefore, aim of this paper is a systematic analysis of affine combination of known subdivision masks to generate new subdivision schemes with enhanced properties. This will be done in the stationary and the non stationary case for the univariate and bivariate settings.     

Synthesis of opaque systems with static and dynamic masks

Opacity is a security property formalizing the absence of secret information leakage and we address in this paper the problem of synthesizing opaque systems. A secret predicate S over the runs of a system G is opaque to an external user having partial observability over G, if s/he can never infer from the observation of a run of G that the run belongs to S. We choose to control the observability of events by adding a device, called a mask, between the system G and the users. We first investigate the case of static partial observability where the set of events the user can observe is fixed a priori by a static mask. In this context, we show that checking whether a system is opaque is PSPACE-complete, which implies that computing an optimal static mask ensuring opacity is also a PSPACE-complete problem. Next, we introduce dynamic partial observability where the set of events the user can observe changes over time and is chosen by a dynamic mask. We show how to check that a system is opaque w.r.t. to a dynamic mask and also address the corresponding synthesis problem: given a system G and secret states S, compute the set of dynamic masks under which S is opaque. Our main result is that the set of such masks can be finitely represented and can be computed in EXPTIME and this is a lower bound. Finally we also address the problem of computing an optimal mask.     

Image processing by self-generated spatial and spectral masks

Parallel, analog image processing techniques are described which enable images to be decomposed into subimages that contain objects that are spatially and spectrally equivalent. The decomposition is achieved by generating binary aperture masks directly from the image, with the aid of predetermined signature functions. The versatility of this approach is experimentally demonstrated for some simple scenes. The technique holds promise for on-board, computer-controlled processing of remotely obtained images.     

Subjective ratings of upper extremity exposures: inter-method agreement with direct measurement of exposures

This study examined the agreement of subjective ratings of upper extremity exposures with corresponding direct measurements obtained simultaneously from workers. Psychophysical ratings of exposure, based on the Borg CR-10 scale, were obtained for the period of time in which direct measurements were acquired using electrogoniometers (wrist), electroinclinometers (shoulder) and electromyography (grip force). Subjects were selected from workers at two automobile manufacturing plants. Significant relationships between subjective ratings of wrist position and measured wrist posture or motion and between ratings of shoulder position and measured shoulder posture were not found. Ratings of manual effort were significantly correlated with directly measured grip force (% maximum voluntary contraction). Ratings of pace were significantly correlated with directly measured wrist motion and this relationship was strengthened with the addition of relative grip force as a covariate. Workers with hand/wrist symptoms provided ratings that were more strongly related to the directly measured exposures than those without symptoms. Self-report by workers is an alternative to more resource-intensive and invasive exposure assessment methods. However, the validity of workers' self-reported exposure assessments has been questioned. The objective of this study was to examine the agreement of selected questionnaire items with corresponding direct measurements from bioinstrumentation and to provide a better understanding of worker self-reports.     

Coarse-to-fine adaptive masks for appearance matching of occluded scenes

In this paper, we discuss an appearance-matching approach to the difficult problem of interpreting color scenes containing occluded objects. We have explored the use of an iterative, coarse-to-fine sum-squared-error method that uses information from hypothesized occlusion events to perform run-time modification of scene-to-template similarity measures. These adjustments are performed by using a binary mask to adaptively exclude regions of the template image from the squared-error computation. At each iteration higher resolution scene data as well as information derived from the occluding interactions between multiple object hypotheses are used to adjust these masks. We present results which demonstrate that such a technique is reasonably robust over a large database of color test scenes containing objects at a variety of scales, and tolerates minor 3D object rotations and global illumination variations. Received: 21 November 1996 / Accepted: 14 October 1997     

Polyimide-based X-ray masks with advanced performance of pattern accuracy and thermal stability

Polyimide-based X-ray masks which are generated by optical lithography and electroplating of gold absorbers on a polyimide mask membrane gain attention as low cost masks. The organic membranes generally have problem of (1) pattern edge sharpness, (2) miniaturization of pattern and (3) thermal stability. To make the masks commodity in deep and accurate lithography area, Optnics Precision, Japan, has overcome the above difficulties and realized the masks with advanced performance of pattern accuracy and thermal stability by improving the making process and the material. Good results were obtained in the exposure experiment that used this mask. When this X-ray mask is combined with the electroforming technique and the material development technique that Optnics has, the application to various fields like an industrial field and medical field can be expected.     

Posture and lifting exposures for daycare workers

Daycare employees, specifically caregivers, are a distinct population that may experience increased risk of injury due to the high exposure to bent postures, lifting conditions and high stress associated with their work. The objectives of the study were to collect up to date data on daycare workers and to compare the data between groups working with children of different ages (Infant, Toddler and Preschool). The study consisted of two distinct phases: Phase 1 – Questionnaire distribution, Phase 2 – Observation and analysis involving three dimensional postural monitoring and video recording as well as an analysis of the low back forces and moments in lifting. Phase 1: Consisted of the distribution of questionnaires to all employees in each of the participating daycares (n = 73). Of the 73 questionnaires distributed 32 responses were obtained (44%). Of the 32 employees who completed the questionnaires, 19 caregivers volunteered to participate in Phase 2 of the study. An additional 5 caregivers participated in phase 2 of the study, but did not complete any questionnaires. The questionnaires indicated 81% of the workers have experienced low back pain. Phase 2: Observational data were collected on site in five local daycares, throughout the first half of each subject's shift (∼3.5 h). Caregivers from each of the three classroom age groups were recruited for participation in the direct observation (Infant: n = 7, Toddler: n = 7, Preschool: n = 8). Posture analysis revealed that on average, workers adopted trunk flexion angles greater than 55°, for 10% of the collection time, and greater than 70°, for 5% of the collection time. These postures correspond to both moderate and severe flexed postures respectively. The lifting analysis (completed using the data recorded in phase 2) revealed that workers lifted with frequencies of 0.25 lifts/minute, lifted a total weight of 501 kg (over 3.3 h) and experienced average compression and shear forces of 3323 N and 371 N, respectively. A between-group comparison showed that when compared to the Preschool group, the Infant (p = 0.008) and Toddler (p = 0.001) groups demonstrated higher relative flexed postures and lifting frequencies, and the Toddler group (p = 0.023) demonstrated higher total weight lifted. Results suggested that these employees experience an elevated risk of low back injury caused by their occupational tasks and thus, further research is required to determine appropriate worker accommodations and safe work practices to help mediate these risks for all daycare caregivers.Relevance to industryIt is thought that the results from this study could lead to the development of safe working and job sharing guidelines for daycare workers.     

Ego noise cancellation of a robot using missing feature masks

We describe an architecture that gives a robot the capability to recognize speech by cancelling ego noise, even while the robot is moving. The system consists of three blocks: (1) a multi-channel noise reduction block, comprising consequent stages of microphone-array-based sound localization, geometric source separation and post-filtering; (2) a single-channel noise reduction block utilizing template subtraction; and (3) an automatic speech recognition block. In this work, we specifically investigate a missing feature theory-based automatic speech recognition (MFT-ASR) approach in block (3). This approach makes use of spectro-temporal elements derived from (1) and (2) to measure the reliability of the acoustic features, and generates masks to filter unreliable acoustic features. We then evaluated this system on a robot using word correct rates. Furthermore, we present a detailed analysis of recognition accuracy to determine optimal parameters. Implementation of the proposed MFT-ASR approach resulted in significantly higher recognition performance than single or multi-channel noise reduction methods.     

Detection of intensity changes with subpixel accuracy using laplacian-gaussian masks

We present a system that takes a gray level image as input, locates edges with subpixel accuracy, and links them into lines. Edges are detected by finding zero-crossings in the convolution of the image with Laplacian-of-Gaussian (LoG) masks. The implementation differs markedly from M.I.T.'s as we decompose our masks exactly into a sum of two separable filters instead of the usual approximation by a difference of two Gaussians (DOG). Subpixel accuracy is obtained through the use of the facet model [1]. We also note that the zero-crossings obtained from the full resolution image using a space constant ? for the Gaussian, and those obtained from the 1/n resolution image with 1/n pixel accuracy and a space constant of ?/n for the Gaussian, are very similar, but the processing times are very different. Finally, these edges are grouped into lines using the technique described in [2].     

Technical note: Simple masks for shadowing and highlighting in SAR images

This paper presents a simple algorithm to indicate the areas of a Synthetic Aperture Radar (SAR) image likely to be affected by radar shadow, excessive highlighting, or the opposite phenomenon, 'lowlighting'. The algorithm is not intended as a substitute for the much lengthier routines that solve the radar mapping equation, but rather as an aid to the selection of suitable areas for more detailed investigation. It is an image-processing routine applied to a suitable Digital Elevation Model (DEM) of the terrain to be imaged. In this context, the suitability of the DEM is characterized by the ratio of the vertical to horizontal sampling intervals, and sufficient information is provided to enable the suitability of a particular DEM to be evaluated. An implementation of the algorithm in the NIH Image macro language is available at the author's web site.     

Prediction of strain for intermittent heat exposures

Under intermittent heat exposures, predictions of body sweat loss ()Δm) could be derived either from the ambient conditions or from their time-weighted average. To compare the accuracy of these two procedures, five subjects exercised, semi-nude, for 120min at constant work load (50 W) under six environmental conditions: four conditions with 20 min duration ‘square pulse(rsquo; variations in either air temperature (T _a or ambient vapour pressure (P _a, and two conditions with constant T _a and P _a, levels. Selected ambient conditions involved skin wettedness (w) levels ranging from 0·35 up to 1. The recorded Δm were compared to the values predicted (PΔm) using the ‘Analytical determination of thermal stress’ model (ISO-DP 7933). Results showed that PΔm were lower than observed Δm by 2 to 10% depending on the condition. This trend could mainly be ascribed to the proposed relation between the evaporative efficiency of sweating and wettedness levels. For exposures consisting of T _a variations, the prediction error was not markedly different whether a time-weighted average of the ambient variables was used or not For exposures consisting of P _a, variations, the expected dripping of sweat during the humid exposures was limited by the short duration of these periods and the averaging procedure gave the best prediction of the actual sweat loss. It is concluded that under intermittent heat stress conditions, a time-weighted average of the ambient conditions may be used for thermal strain predictions, provided that the heat exposure periods are of short duration.     

Precision architecture

The processor component of the Hewlett-Packard Precision Architecture system is described. The architecture's goals, how the architecture addresses the spectrum of general-purpose user information processing needs, and some architectural design tradeoffs are examined. Extendibility and longevity features are considered     

Kinetic masks: a new approach and device for dispersing biologically relevant fluids

The controlled dispersion of fluids, particularly biologically relevant solutions in micro-volumes, is of high practical interest in biotechnology and medicine. Pharmaceutical test assays, for example, need a method for the fast and defined deposition of fluid samples. Most current micro-dispensing methods, i.e. contact-based pin printing, have problems such as time delays, limited dosing velocity, minimum volume or high interference that limit biological applications. Spraying techniques suffer from a lack of reproducibility; a defined deposition of samples on targets is not possible. Here, we introduce a new method for the parallel and spatially defined dispersion of many micro-volumes that overcomes disadvantages of common micro-dispensers. The overall approach is that a fluid drop, produced by a droplet generator, falls on a free trajectory with a defined kinetic energy, and is split by a masking unit placed perpendicular to the flight direction into at least two smaller droplets (Zimmermann et al. in Method and device for dosing fluid media, WO/2002/102515, Germany, 2002). On the target, the resulting droplets form reproducible patterns, which are enlarged and scalable images of the grid pattern. Possible applications for this method are non-contact cell patterning, cell encapsulation, cryopreservation and fast mixing processes in micro-volumes. Here, we use this method for the direct and defined parallel positioning of cell suspensions on specific substrates, which can be useful for test assays, tissue engineering and cryopreservation.     

Preliminary results of hand arm vibration (HAV) exposures of chipping hammer operators in tropical weather: Analysis of exposures and protective gloves

Objectives of this study are to analyze the HAV exposures of chipping hammer operators from field measurements and to investigate the potential of various types of gloves in reducing the exposures. HAV exposures of twelve male operators were measured at four different operating conditions: bare hand, wearing normal workman gloves, wearing heavy workman gloves and wearing vibration reducing gloves. From the measurements, 8 h exposure values were determined and assessed against standards. The total vibration values were determined and effectiveness in vibration attenuation by gloves was compared. It was found that all most all operators, HAV exposure levels exceeded the exposure action value (EAV) and about 83% of the operators exceeded the exposure limit values (ELV). A reduction in the total vibration magnitude was observed with protective gloves: 8.3% with normal workman gloves, 14.6% with heavy workman gloves and 40% with vibration-reducing gloves. To confirm the effectiveness of the vibration reducing gloves, further field investigations are required with simultaneous measurements by considering parameters affecting HAV (i.e., hand forces and postures).     

Personal noise exposures of operators of agricultural tractors

Approximately one million agricultural tractors are used in Turkey for crop production and about one-third of the population lives in rural areas. The objectives of this study were to determine sound pressure levels, A-weighted sound pressure levels, and the permissible exposure time for tractors without cabins, field-installed cabins, and original cabins at ear level of agricultural tractor operators for following machines: plows, cultivators, top soil cultivators, rotary tillers, tool combinations (harrow + roller), mechanical drills, pneumatic drills, chemical applicators, fertilizer applicators, drum mowers, balers, and forage harvesters.Variance analyses showed that type of operation, type of cabins, and operation × cabin interactions were statistically significant (P < 0.01) both for sound pressure levels and equivalent (A-weighted) sound pressure levels. The use of original cabins had a greater effect in decreasing average sound pressures and resulted in more efficient noise insulation, especially at higher center frequencies compared to field-installed cabins whereas field-installed cabins proved to be more favorable compared to tractors without cabins. Sound pressure levels at 4000 Hz center frequency was reduced 2-13 dB and 4-18 dB by using a field-installed cabin and an original cabin, respectively. The measured A-weighted equivalent sound pressure levels were compared to the threshold limit level, and was concluded that depending on the cabin types used, the operators could usually work from 4 to 6 h a day without suffering from noise induced inconveniences while 2-3 h is permissible for plowing and forage harvesting on tractors without cabins. Due to timeliness considerations in agricultural machine operations, a farmer would not be willing to interrupt the operation based on permissible exposure time set by the standards.Based on the findings of this study, particularly an original cabin is recommended to reduce machine-induced noise below the danger limit during agricultural machine operations. Personal protection devices should be used when tractors are operated without cabins, which could reduce A-weighted equivalent sound pressure levels by 10-45 dB(A).     

可变精度粗糙集β值的增量计算

目前对于可变精度粗糙集中变精度参数β计算的研究,主要集中在非增量方面.当处理大量数据时,需要能够动态计算的方法,本文提出了一种增量计算β值的方法ICObeta.该方法以分类质量作为确定性度量的标准,以最大确定性度量为目标,来选取合适的β值.ICObeta相比于非增量的方法,具有动态增量和计算开销显著降低的优点,并通过实验证实了增量计算的优点.