Divergent Centers Research Articles

Multi-Dimension Support Vector Machine Based Crowd Detection and Localisation Framework for Varying Video Sequences

In this paper, we propose a novel method for anomalous crowd behaviour detection and localization with divergent centers in intelligent video sequence through multiple SVM (support vector machines) based appearance model. In multi-dimension SVM crowd detection, many features are available to track the object robustly with three main features which include 1) identification of an object by gray scale value, 2) histogram of oriented gradients (HOG) and 3) local binary pattern (LBP). We propose two more powerful features namely gray level co-occurrence matrix (GLCM) and Gaber feature for more accurate and authenticate tracking result. To combine and process the corresponding SVMs obtained from each features, a new collaborative strategy is developed on the basis of the confidence distribution of the video samples which are weighted by entropy method. We have adopted subspace evolution strategy for reconstructing the image of the object by constructing an update model. Also, we determine reconstruction error from the samples and again automatically build an update model for the target which is tracked in the video sequences. Considering the movement of the targeted object, occlusion problem is considered and overcome by constructing a collaborative model from that of appearance model and update model. Also if update model is of discriminative model type, binary classification problem is taken into account and overcome by collaborative model. We run the multi-view SVM tracking method in real time with subspace evolution strategy to track and detect the moving objects in the crowded scene accurately. As shown in the result part, our method also overcomes the occlusion problem that occurs frequently while objects under rotation and illumination change due to different environmental conditions.

Crowd Escape Behavior Detection and Localization Based on Divergent Centers

In this paper, we propose a novel framework for anomalous crowd behavior detection and localization by introducing divergent centers in intelligent video surveillance systems. In this paper, the scheme proposed can deal with this problem by modeling the crowd motion obtained from the optical flow. The obtained magnitude, position and direction are used to construct the motion model. The method of the weighted velocity is applied to calculate the motion velocity. People usually instinctively escape from a place where abnormal or dangerous events occur. Based on this inference, a novel algorithm of detecting divergent centers is proposed: divergent centers indicate possible places where abnormal events occur. The proposed algorithm of detect divergent centers can identify more than one divergent center by analyzing the intersections of vectors, and this algorithm consist of the distance segmentation method and the nearest neighbor search. The performance of our method is validated in a number of experiments on public data sets.

A Bayesian Model for Crowd Escape Behavior Detection

People naturally escape from a place when unexpected events happen. Based on this observation, efficient detection of crowd escape behavior in surveillance videos is a promising way to perform timely detection of anomalous situations. In this paper, we propose a Bayesian framework for escape detection by directly modeling crowd motion in both the presence and absence of escape events. Specifically, we introduce the concepts of potential destinations and divergent centers to characterize crowd motion in the above two cases respectively, and construct the corresponding class-conditional probability density functions of optical flow. Escape detection is finally performed based on the proposed Bayesian framework. Although only data associated with nonescape behavior are included in the training set, the density functions associated with the case of escape can also be adaptively updated using observed data. In addition, the identified divergent centers indicate possible locations at which the unexpected events occur. The performance of our proposed method is validated in a number of experiments on crowd escape detection in various scenarios.

PRENATAL DIAGNOSTIC ACCURACY IN SOUTH CAROLINA DEMONSTRATED BY AUTOPSY

Fully 150 consecutive fetal/neonatal autopsies were reviewed to determine to what extent they confirmed or altered the impressions gained through prenatal ultrasonographic fetal examination. Distinctions were made between features that may or may not be assessable by prenatal ultrasound. Analyses of weights and measures were based on recently published regressions derived from a worldwide review of normative data. Our analysis indicated a high level of correspondence between prenatal ultrasound findings and later observations of independent persons at autopsy (85% positive predictive value and 44% sensitivity). We concluded that skills of maternal-fetal medicine specialists, located at several geographically divergent centers, are confirmed by a high level of correspondence between prenatal ultrasound and autopsy findings. The low sensitivity was due in large part to the relatively subtle nature of many autopsy findings that had not been predicted by prenatal examination.

A Comparison Study of Three Polar Grids

Abstract The circumference of a latitude circle decreases toward the Poles, making it difficult to present meteorological field variables on equally spaced grids with respect to latitude and longitude because of data aggregation. To identify the best method for displaying data at the Poles, three different grids are compared that have all been designed to reduce data aggregation: the reduced latitude–longitude (RL) grid, the National Snow and Ice Data Center Equal-Area Special Sensor Microwave Imager (SSM/I) Earth (EA) grid, and the National Meteorological Center octagonal (OG) grid. The merits and disadvantages of these grids are compared in terms of depictions of the Arctic summer circulation with wind vectors, streamfunction, and velocity potential at 400 hPa where maximum westerlies are located. Using geostrophy, the 400-hPa streamfunction at high latitudes can be formed from geopotential height. In comparison with this geostrophic streamfunction, the streamfunction generated from vorticity on the OG grid shows a negligible error (∼0.5%). The error becomes larger using vorticity on the EA (∼15%) and RL (∼30%) grids. During the northern summer, the Arctic circulation at 400 hPa is characterized by three troughs. The streamfunction and velocity potential of these three troughs are spatially in quadrature with divergent (convergent) centers located ahead of (behind) these troughs. These circulation features are best depicted by the streamfunction and velocity potential generated on the OG grid. It is demonstrated by these findings that the National Meteorological Center octagonal grid is the most ideal among the three grids used for the polar regions. However, this assessment is constrained by the hemispheric perspective of meteorological field variables, because these variables depicted on the octagonal grid at higher latitudes need to be merged with those on the equal-latitude-longitude grid at lower latitudes.

Cytological studies of 14 Chinese species ofParnassiaL. (Par-nassiaceae) and its phylogenetic implications

The chromosome numbers and karyomorphology of 14 Chinese species of the genus Parnassia were in- vestigated. The chromosome numbers of 11 species were reported for the first time. The report of 2n=48 for P. monochrofolia Franch was new to the Chinese species of the genus. There are about 30 species cytologically studied up to now. From the available data, the species of Parnassia with the basic chromosome numbers of x=7, 8 and 9 were found in China and the Himalayas, in which the more species with x=9, as well as mainly in western N America, while x=8 was only found in eastern N. America. Polyploidization was common in the genus, more extensively in Northern America. Based on our results and the previously reported data, the basic chromosome numbers and poly- ploidization are discussed. Combined with gross morphology and geographical distribution of Parnassia, the phylo- genetic implications of the cytological data are also discussed. It is suggested that eastern Asia and western N America are probably the modern divergent centers of the genus.

Quality control of cancer screening examination procedures in the prostate, lung, colorectal and ovarian (PLCO) cancer screening trial

Investigators for the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial describe quality control procedures for the digital sectal examination, ovarian palpation examination, transvaginal ultrasound, chest X-ray, and flexible sigmoidos-copy. These cancer screening tests are subjective and difficult to standardize. PLCO quality control procedures aim to measure and, where possible, reduce variation, across examiner and screening center, with respect to cancer screening test performance. Initial protocols stressed examiner qualifications, experience, and training; equipment specifications; examination procedures; and definitions for positive tests. The PLCO quality assurance subcommittee developed a final quality assurance plan, which included central approval and registration of PLCO examiners, direct observation of screening test performance during periodic site visits by the National Cancer Institute and coordinating center auditors, periodic analysis of screening test data, and procedures for independently duplicating or reviewing selected examinations. For each modality, the periodic data analyses examine the test-positive and the test-inadequate proportions and aim to identify divergent centers or examiners. Procedures for duplicating examinations specify feasible sample sizes for precise estimates of agreement between examiners, at each center, for each screening test modality, and over a 1-year period. These quality control procedures will help characterize the consistency and reliability of the PLCO cancer screening tests.

Can treatment that is helpful on average be harmful to some patients? A study of the conflicting information needs of clinical inquiry and drug regulation

Randomized controlled trials are conducted with heterogeneous groups of patients, and the trial results represent an estimate of the average difference in the responses of the treatment groups. Clinicians, however, engage in a process of clinical inquiry, assembling data that will allow an assessment of the appropriate choice of treatment according to more narrowly defined clinical features. We describe a method of clinical inquiry within RCTs that can enhance the applicability of results to clinical decision making. Our methods included the use of data from the Beta-Blocker Heart Attack Trial, which enrolled 3837 subjects in 31 clinical centers. The 31 centers were divided into 21 dominant centers (mortality rates higher for placebo than propranolol) and 10 divergent centers (higher mortality rates for patients randomized to propranolol). Overall, compared to placebo, propranolol reduced the risk of dying for the “average” patient from 9.8 to 7.2%. Results for patients in dominant centers (RR = 0.50) were significantly different from those in divergent centers (RR = 1.33). We identified two cotherapies—aspirin use and coronary artery surgery—that subsequently affected the benefits of propranolol in divergent centers. For patients in divergent centers, propranolol reduced the risk of dying for patients treated with aspirin and/or coronary surgery (RR = 0.39), but not for patients not receiving these therapies (RR = 1.42). We conclude that differences in results across centers of a multicenter RCT may reflect important distinctions in the clinical conditions of enrolled subjects. These distinctions help to identify subgroups of patients in which treatment that has an average overall benefit may be harmful for some patients.

Comparison of NCAR community climate model (CCM) climates

The simulated mean January and July climates of four versions of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM) are compared. The models include standard configurations of CCM1 and CCM2, as well as two widely-cited research versions, the Global Environmental and Ecological Simulation of Interactive Systems (GENESIS) model and the Climate Sensitivity and Carbon Dioxide (CSC02) model. Each CCM version was integrated for 10 years with a horizontal spectral resolution of rhomboidal 15 (R15). Additionally, the standard T42 version of CCM2 was integrated for 20 years. Monthly mean, annually repeating climatological sea surface temperatures provided a lower boundary condition for each of the model simulations. The CCM troposphere is generally too cold, especially in the polar upper troposphere in the summer hemisphere. This is least severe in CCM2 and most pronounced in CCM1. CSC02 is an exception with a substantial warm bias, especially in the tropical upper troposphere. Corresponding biases are evident in atmospheric moisture. The overall superior CCM2 thermodynamic behavior is principally compromised by a large warm and moist bias over the Northern Hemisphere middle and high latitudes during summer. Differences between the simulated and observed stationary wave patterns reveal sizeable amplitude errors and phase shifts in all CCM versions. A common problem evident in the upper troposphere is an erroneous cyclone pair that straddles the equatorial central Pacific in January. The overall January stationary wave error pattern in CCM2 and CSCO2 is suggestive of a reverse Pacific-North American teleconnection pattern originating from the tropical central Pacific. During July, common regional biases include simulated North Pacific troughs that are stronger and shifted to the west of observations, and each model overestimates the strength of the anticyclone pair associated with the summer monsoon circulation over India. The simulated major convergence and divergence centers tend to be very localized in all CCM versions, with a tendency in each model for the maximum divergent centers to be unrelistically concentrated in monsoon regions and tied to regions of steep orography. Maxima in CCM-simulated precipitation correspond to the simulated outflow maxima and are generally larger than observational estimates, and the associated atmospheric latent heating appears to contribute to the stationary wave errors. Comparisons of simulated radiative quantities to satellite measurements reveal that the overall CCM2 radiative balance is better than in the other CCM versions. An error common to all models is that too much solar radiation is absorbed in the middle latitudes during summer.

A study of the diabiatic heating associated with the Madden‐Julian oscillation

It has been inferred from numerous studies analyzing out going long wave radiation (OLR) data in the tropics that cumulus convection injects energy through released latent heat into the global‐scale, 30–60 day (Madden‐Julian, MJ) oscillation of divergent circulation, which is well portrayed by velocity potential (χ) anomalies. To substantiate this inference regarding the global scope of the diabatic hearing effect, we propose an χ‐maintenance equation χ = χQ ‐ χHA. The values χQ and χHA are the contributions of vertical differential diabatic and adiabatic heating to χ, respectively. The 4‐year (1979 and 1985–1987) upper‐air daily data generated by the Global Data Assimilation System of the National Meteoroligical Center were used to compute global χ, χQ, and χHA anomalies, and the global‐scale χ MJ oscillation is shown to be related to diabatic heating by HVD (= ∇2 χQ) anomalies. To understand the geographic relation between the differential diabatic heating effect and the global‐scale χ MJ oscillation, composite charts of χ and HVD anomalies during various stages of this oscillation were constructed. Centers of positive (negative) HVD anomalies coincided with divergent (convergent) centers of χ anomalies. It was also found that the geographic distributions of our HVD anomalies and the OLR anomalies from previous studies resembled each other. These findings support the inferences from previous studies that maintaining the global‐scale χ MJ oscillation is linked to diabatic heating through the latent heat released by cumulus convection.

Northern Hemisphere Airstream Regions

Abstract Near-surface airstream source regions of the Northern Hemisphere have been identified using 16-year mean resultant winds from 3° latitude by 3° longitude grids. Tracing the airstreams back to their divergent centers reveals 19 different sources during various seasons of the year. Five of these sources(air originating over the North and South Pacific and Atlantic Oceans and air over Turkey) are resident in the Northern Hemisphere 12 months of the year. Another three (central Asian, Arctic and central East Asian air) exist for at least 11 months per year. The remaining 11 source regions are present from 1–9 months per year and their area of influence is much less than that of the 5 year-long sources. In the mean, there are several favored locations for frontal zones, e.g., a north–south band in Mexico (dividing Atlantic from Pacific air), a north–south band in northern South America, and two northeast–southwest trending bands over the cast coasts of Asia and North America, representing the mean lea...

Resource Partitioning and Competition within a Guild of Fugitive Prairie Plants

Badger disturbances on tall-grass prairies constitute a limiting resource for a guild of fugitive plants. These plants partition the resource along several dimensions. Divergent centers of resource utilization result from different suites of adaptive life-history characteristics important during colonization. While overlap of utilization functions is considerable along single dimensions of the resource, complementary adaptations of species result in reduced overlap along a complex gradient integrating the separate dimensions. We predict that the number, packing, and organization of species into a guild will change as the nature of the limiting resource changes. Specifically, changes in the abundance of the resource alter the heterogeneity of the resource over space, and as a result relationships among the adaptive centers of resource utilization for species also change. Predictions of changes in resource partitioning and guild organization, based upon assumptions concerning competition among species populations, correspond very closely to empirical field observations. In nature, composition of the fugitive species guild is expected to vary locally with changes in the nature and spatial heterogeneity of badger disturbances, and this variation over space also will depend upon the colonization capabilities of the species. Field investigation of competition provided insight into relationships among species comprising the fugitive guild. Competitive interactions are closely related to the adaptive life-history characteristics involved in the colonization of badger disturbances. The type of interaction occurring among individuals on a site depends upon events occurring during the colonization phase of the life cycle, and different types of competitive interactions have different effects upon the likelihood of subsequent site colonization (i.e., reproductive success of interacting individuals). Both the frequency and types of competitive interactions occurring among individuals in fugitive populations are predicted to depend upon the abundance of the limiting resource; the likelihood of colonization will change as the spatial distribution of colonization sites changes. Thus, the effects of changes in the distribution of the resource over space upon the relative colonization rates of species must be known to predict accurately the impact of competition upon resource partitioning and organization of fugitive plant populations into a guild.