Distribution by Scientific Domains

Kinds of Operators

  • business operators
  • crossover operators
  • differential operators
  • elliptic operators
  • experience operators
  • integral operators
  • linear operators
  • symmetry operators
  • transfer operators

  • Selected Abstracts


    Wassim M. Haddad
    ABSTRACT A direct adaptive control framework for a class of nonlinear matrix second-order systems with time-varying and sign-indefinite damping and stiffness operators is developed. The proposed framework guarantees global asymptotic stability of the closed-loop system states associated with the plant dynamics without requiring any knowledge of the system nonlinearities other than the assumption that they are continuous and bounded. The proposed adaptive control approach is used to design adaptive controllers for suppressing thermoacoustic oscillations in combustion chambers. [source]

    Stylet Bend Angles and Tracheal Tube Passage Using a Straight-to-cuff Shape

    Richard M. Levitan MD
    Abstract Objectives Malleable stylets improve maneuverability and control during tube insertion, but after passage through the vocal cords the stiffened tracheal tube may impinge on the tracheal rings, preventing passage. The goal of this study was to assess insertion difficulty with styletted tubes of different bend angles. Methods Tube passage was assessed with four different bend angles (25°, 35°, 45°, and 60°) using straight-to-cuff,shaped tubes. In two separate airway procedure classes, 16 operators in each class (32 total) placed randomly ordered styletted tubes of the different angles into eight cadavers (16 total). Operators subjectively graded the ease of tube passage as no resistance, some resistance, or impossible to advance. Results No resistance was reported in 69.1% (177/256) at 25°, in 63.7% (163/256) at 35°, in 39.4% (101/256) at 45°, and in 8.9% (22/256) at 60°. Tube passage was impossible in 2.3% of insertions (6/256) at 25°, in 3.5% (9/256) at 35°, in 11.3% (29/256) at 45°, and in 53.9% (138/256) at 60°. The odds ratios of impossible tube passage for 35°, 45°, and 60° vs. 25° were 1.52 (95% confidence interval [CI] = 0.55 to 4.16), 5.32 (95% CI = 2.22 to 12.71), and 48.72 (95% CI = 21.35 to 111.03), respectively. Conclusions Bend angles beyond 35° with straight-to-cuff styletted tracheal tubes increase the risk of difficult and impossible tube passage into the trachea. The authors did not compare different stylet stopping points, stylets of different stiffness, or tracheal tubes with different tip designs, all variables that can affect tube passage. [source]

    Operator-oriented CRS interpolation

    German Hoecht
    ABSTRACT In common-reflection-surface imaging the reflection arrival time field is parameterized by operators that are of higher dimension or order than in conventional methods. Using the common-reflection-surface approach locally in the unmigrated prestack data domain opens a potential for trace regularization and interpolation. In most data interpolation methods based on local coherency estimation, a single operator is designed for a target sample and the output amplitude is defined as a weighted average along the operator. This approach may fail in presence of interfering events or strong amplitude and phase variations. In this paper we introduce an alternative scheme in which there is no need for an operator to be defined at the target sample itself. Instead, the amplitude at a target sample is constructed from multiple operators estimated at different positions. In this case one operator may contribute to the construction of several target samples. Vice versa, a target sample might receive contributions from different operators. Operators are determined on a grid which can be sparser than the output grid. This allows to dramatically decrease the computational costs. In addition, the use of multiple operators for a single target sample stabilizes the interpolation results and implicitly allows several contributions in case of interfering events. Due to the considerable computational expense, common-reflection-surface interpolation is limited to work in subsets of the prestack data. We present the general workflow of a common-reflection-surface-based regularization/interpolation for 3D data volumes. This workflow has been applied to an OBC common-receiver volume and binned common-offset subsets of a 3D marine data set. The impact of a common-reflection-surface regularization is demonstrated by means of a subsequent time migration. In comparison to the time migrations of the original and DMO-interpolated data, the results show particular improvements in view of the continuity of reflections events. This gain is confirmed by an automatic picking of a horizon in the stacked time migrations. [source]

    Performance assessment under field conditions of a rapid immunological test for transgenic soybeans

    John Fagan
    Summary Current market conditions and food regulations make it necessary for international and domestic participants in the agrifood industry to structure supply chains that control the content of genetically modified (GM) material in their products. Tests to detect and/or quantify GM components represent an important tool in maintaining such supply systems. This study assesses the field performance of kits that employ lateral flow immuno-technology to detect soybeans GM to be resistant to the herbicide glyphosate. Operators at 23 grain-handling facilities were paid to conduct analyses on a series of blinded samples containing defined proportions of conventional and transgenic soybeans. The observed rate of false positives was 6.7% in an experiment in which the highest level of GM material was 1% and 22.3% in a second experiment in which the highest level of GM material was 10%. This difference may be attributed to increased risk of cross-contamination with the higher level of transgenic material used in the second study. Samples containing 0.01% GM material were reported as genetically modified 6.70% of the time, while samples containing 0.1, 0.5 and 1% GM material were classified as genetically modified 29.5, 67.7 and 68.2% of the time, respectively. Thus, the frequencies of false negatives were 93.3, 70.5, 33.3 and 31.8% for samples containing 0.01, 0.1, 0.5 and 1.0% GM material. Samples containing 10% GM material were correctly reported as genetically modified in all cases. These results lead to the conclusion that the kit under study is useful in screening for lots of soybeans that contain high levels of GM material, but that, as a field tool, it is not effective in monitoring for GM material at the level of 1.0% or lower. Statistical and immunochemical analyses were carried out in order to assess the relative contributions of various factors to the error observed in these studies. These analyses indicated that limitations in operator performance, not defects in test kit materials, were the primary contributors, while sample size may play a secondary role. As both operator performance and sample size are independent of the specific characteristics of the test kit used in this study, it appears justifiable to generalize conclusions obtained here to other similar test systems. [source]

    Application of genetic algorithm for scheduling and schedule coordination problems

    Prabhat Shrivastava
    The problems on scheduling and schedule co-ordination usually have conflicting objectives related to user's cost and operator's cost. Users want to spend less time to wait, transfer and travel by public buses. Operators are interested in profit making by lesser vehicle operating cost and having a minimum number of buses. As far as level of service is concerned users are interested in lesser crowing while operators are concerned with maximizing profit and thus to have higher load factors. In schedule co-ordination problems transfer time plays an important role. Users are interested in coordinating services with in acceptable waiting time whereas operators prefer to have lesser services and want to meet higher demands, which invariably increases waiting time. These problems have multiple conflicting objectives and constraints. It is difficult to determine optimum solution for such problems with the help of conventional approaches. It is found that Genetic Algorithm performs well for such multi objective problems. [source]

    Posttraumatic stress disorder and the perceived consequences of seeking therapy among U.S. Army special forces operators exposed to combat

    Jessica M. Espinoza Psy.D.
    The goal of this study was to ascertain the level of PTSD symptoms experienced by Special Forces Operators (SFOs) who have been exposed to combat and compare these rates to the PTSD rates of the general U.S. population and general military population. A secondary goal was to discover whether SFOs were aware that therapy was available to them through the U.S. Army and, if so, whether they would seek this therapy for PTSD. The last goal was to discover whether SFOs who chose not to seek therapy while still serving did so because they feared negative consequences. Data were collected from 68 SFOs who had been exposed to combat. Results indicated that SFOs are experiencing symptoms of PTSD at a rate that is higher than that of the general U.S. population and somewhat lower than that of the general military population. Also, results indicated that a large percentage of the sample would not seek treatment for PTSD due to perceived negative consequences. [source]

    The Ethical Outlook of Micro Business Operators

    Stuart Dawson
    This paper reports the findings of an investigation into the ethical outlook of micro business operators. The study was conducted in Australia and is the first such examination of ethical perspectives in this segment of the business population. Micro business is internationally recognizable, economically significant, and strongly entrepreneurial, and it has a high level of control over the values it enacts. The study indicates that ethical considerations are important to Australian micro business operators. While no one single ethical perspective was dominant, nonreligious beliefs and principles were found to be the most important determinant of their ethical values. Some variation was discovered in operator attitudes based on age, gender, and education. [source]

    Conformally invariant powers of the Dirac operator in Clifford analysis

    David Eelbode
    Abstract The paper deals with conformally invariant higher-order operators acting on spinor-valued functions, such that their symbols are given by powers of the Dirac operator. A general classification result proves that these are unique, up to a constant multiple. A general construction for such an invariant operators on manifolds with a given conformal spin structure was described in (Conformally Invariant Powers of the Ambient Dirac Operator. ArXiv math.DG/0112033, preprint), generalizing the case of powers of the Laplace operator from (J. London Math. Soc. 1992; 46:557,565). Although there is no hope to obtain explicit formulae for higher powers of the Laplace or Dirac operator on a general manifold, it is possible to write down an explicit formula on Einstein manifolds in case of the Laplace operator (see Laplacian Operators and Curvature on Conformally Einstein Manifolds. ArXiv: math/0506037, 2006). Here we shall treat the spinor case on the sphere. We shall compute the explicit form of such operators on the sphere, and we shall show that they coincide with operators studied in (J. Four. Anal. Appl. 2002; 8(6):535,563). The methods used are coming from representation theory combined with traditional Clifford analysis techniques. Copyright © 2010 John Wiley & Sons, Ltd. [source]

    Remarks on Duality in Graph Spaces of First-Order Linear Operators

    Max JensenArticle first published online: 4 DEC 200
    Graph spaces provide a setting alternative to Sobolev spaces and BV spaces, which is suitable for the analysis of first-order linear boundary value problems such as Friedrichs systems. Besides investigations of the well-posedness of the continuous problem there is also an increasing interest in the error analysis of finite element methods within a graph space framework. In this text we elucidate various methods for an explicit representation of dual spaces of graph spaces. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Comparing services: a survey of leading issues in the sectoral literatures

    Dominique Moran
    Abstract This article locates the following sector articles in a review of recent research into government interventions in the non-state provision (NSP) of education, health, water and sanitation. Non-state providers (NSPs) are defined here to include all those existing outside the public sector, whether they operate for profit or for philanthropic purposes. Operators may be communities, NGOs, faith-based organisations (FBOs), private companies, small-scale informal providers or individual practitioners. The article prefaces this Symposium by discussing the extent of previous research and identifying gaps in the literature with regard to key issues regarding NSP. It deals with state intervention and the state/non-state relationship in service provision, considering the main aspects of this relationship that are covered in the sector articles: policy dialogue and government capacity to regulate and facilitate, and to contract NSPs. Copyright © 2006 John Wiley & Sons, Ltd. [source]

    A collaborative approach to the environmental assessment process prior to oil exploration activities offshore the Falkland Islands

    Liz Hopkins
    Abstract 1.Operating Companies awarded acreage in the Falkland Islands First Offshore Licensing Round began exploration for oil and gas in 1996. Appropriate environmental management is an important aspect of exploration activities in any new frontier area and the Falklands Islands were no exception. Operators with drilling commitments established the Falklands Operators Sharing Agreement (FOSA), which included an Environmental Workgroup (EWG) to take responsibility for the environmental issues associated with exploration activities. 2.The EWG was established early in the exploration programme and commissioned a number of specific environmental studies relating to the offshore environment of the Islands. The data made available by this research provided a valuable input to the assessment of potential environmental impacts from the planned exploration activities. By undertaking environmental impact assessments prior to exploration activities FOSA were able to identify and adopt operational and management controls to ensure potential environmental impacts were, where possible, minimized or avoided. 3.The EWG also provided the main point of contact with the regulators on environmental matters and through the Falkland Islands Exploration & Production Environmental Forum facilitated consultation with government departments such as Fisheries, and other stakeholders such as Falklands Conservation. 4.The co-operative approach taken by the operators with regard to the environmental management of the exploration activities offshore the Falkland Islands is considered to have been very successful. The most obvious benefits were through the shared resources resulting in financial savings, however, other benefits have included, avoiding duplication of effort, the promoting of ,working togetherness' and a reduced burden on consultees. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    Falkland Islands cruise ship tourism: an overview of the 1999,2000 season and the way forward

    Rebecca J. Ingham
    Abstract 1.Falkland Islands' tourism is evolving at an increasing pace. A record number of passengers, 23 497, visited the Islands during the 1999,2000 season. This rise was due to an increase in both the frequency of vessel visits and the average passenger capacity of vessels, with the number of luxury cruise ships of >1000 passengers steadily increasing. The Falklands' industry is made up of three types of vessel: the expedition cruise vessels (ca. 100,200 passengers); larger cruise vessels (ca. 400 passengers), and the luxury cruise vessels (ca. 1000 passengers). 2.The cruise ship industry has seen a diversification within the market, with cruises now available to a wider audience thus increasing the need for new experiences and landing sites. A similar diversification is being seen within the Islands themselves as the capacity to take larger vessels at remote sites is being developed. Whilst the expedition cruise vessels visiting the Islands are operating to high environmental standards as members of the International Association of Antarctic Tour Operators (IAATO), vessels with 400+ passengers may not become members of IAATO, due to Article III of the organization's Bylaws which limits the number of passengers. These larger capacity vessels are therefore not subject to the same self-regulating guidelines. The implications of increasing passenger numbers in the islands are discussed with regard to pressures on both the wildlife and vegetation. 3.This study outlines the need for an island-wide approach and a legislative framework to ensure high standards of operation are adhered to within the Islands from all visiting vessels and that accurate information is provided to all visitors along with a suitable code of conduct. The collection, collation and analysis of visitor data to identify trends and implement appropriate management strategies, and further research into the potential impacts of tourism on wildlife in the Falklands are also recommended. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    The Risks of Everyday Life: Fat content of chips, quality of frying fat and deep-frying practices in New Zealand fast food outlets

    Judith Morley-John
    Objectives:To collect baseline data on the fat content of hot chips, quality (degradation) of cooking fat, deep-frying practices and related attitudes in fast food outlets in New Zealand. To identify the key determinants of the fat content of chips and quality of cooking fat. Methods:A nationally representative sample of fast food outlets (n=150, response rate 80%) was surveyed between September 1998 and March 1999. Data collected included a questionnaire, observation of cooking practices and analysis of cooked chips and frying fat. Results:Only 8% of independent operators had formal training in deep frying practices compared with 93% of chain operators. There was a wide range of fat content of chips (5%-20%, mean 11.5%). The use of thinner chips, crinkle cut chips and lower fryer fat temperature were associated with higher chip fat content. Eighty-nine per cent of chain outlets used 6,10 mm chips compared with 83% of independent outlets that used chips ,12 mm. A wide range of frying temperatures was recorded (136,233°C) with 58% of outlets frying outside the reference range (175,190°C). As indices of fat degradation, fat acid and polar compound values above the recommended levels occurred in 54% and 5% of outlets respectively. Operators seemed willing to learn more about best practice techniques, with lack of knowledge being the main barrier to change. Conclusions and implications:Deep frying practices could be improved through operator training and certification options. Even a small decrease in the mean fat content of chips would reduce the obesogenic impact of this popular food. [source]

    Electromagnetic field exposure and health among RF plastic sealer operators

    Jonna Wilén
    Abstract Operators of RF plastic sealers (RF operators) are an occupational category highly exposed to radiofrequency electromagnetic fields. The aim of the present study was to make an appropriate exposure assessment of RF welding and examine the health status of the operators. In total, 35 RF operators and 37 controls were included. The leakage fields (electric and magnetic field strength) were measured, as well as induced and contact current. Information about welding time and productivity was used to calculate time integrated exposure. A neurophysiological examination and 24 h ECG were also carried out. The participants also had to answer a questionnaire about subjective symptoms. The measurements showed that RF operators were exposed to rather intense electric and magnetic fields. The mean values of the calculated 6 min, spatially averaged E and H field strengths, in line with ICNIRP reference levels, are 107 V/m and 0.24 A/m, respectively. The maximum measured field strengths were 2 kV/m and 1.5 A/m, respectively. The induced current in ankles and wrists varied, depending on the work situation, with a mean value of 101 mA and a maximum measured value of 1 A. In total, 11 out of 46 measured RF plastic sealers exceeded the ICNIRP reference levels. RF operators, especially the ready made clothing workers had a slightly disturbed two-point discrimination ability compared to a control group. A nonsignificant difference between RF operators and controls was found in the prevalence of subjective symptoms, but the time integrated exposure parameters seem to be of importance to the prevalence of some subjective symptoms: fatigue, headaches, and warmth sensations in the hands. Further, RF operators had a significantly lower heart rate (24 h registration) and more episodes of bradycardia compared to controls. Bioelectromagnetics 25:5,15, 2004. © 2003 Wiley-Liss, Inc. [source]

    A randomised controlled study comparing conventional and magnetic guidewires in a two-dimensional branching tortuous phantom simulating angulated coronary vessels

    DPHIL, Steve Ramcharitar MRCP
    Objectives: To directly compare the magnetic navigation system (MNS) guidewires with conventional guidewires in branching tortuous phantoms with operators of varying MNS and percutaneous coronary intervention experience. Background: Vessel tortuosity, angulation, and side branches remain limiting factors in coronary interventions. The MNS addresses these limitations by precisely directing the tip of a magnetised guidewire in vivo aided by two permanent adjustable external magnets. Methods: Crossing and fluoroscopy times of six operators were evaluated in five tortuous Perspex® phantom vessels in three consecutive attempts. Standard guidewire (SG) usage was unrestricted. Two 2nd generation magnetic guidewires (MG) were used. Failure was noted if the cross was unsuccessful within 5 min. Results: The magnetic navigation was vastly superior to SG techniques with increasingly tortuous phantoms. It dramatically decreased both the crossing and fluoroscopy times with maximal reduction from 201.7 ± 111 to 36.4 ± 13 sec, P < 0.001 and 204.7 ± 24 to 47.2 ± 19 sec, P < 0.001, respectively. The MNS had a 98.8% procedural success rate compared to 68% with SG techniques. Moreover it considerably limited the amount of wire usage from 5.5 to 1.3. Operators with prior MG experience performed significantly better than those without, except in the simplest phantom where the difference was nonsignificant (33.8 ± 13 sec vs. 41.7 ± 17 sec, P = 0.2). Conclusion: MNS significantly reduces both the crossing and fluoroscopy times in tortuous coronary phantom models achieving excellent success rates with dramatic reductions in guidewire usage. Operators with prior MNS experience had an advantage over the inexperienced. © 2007 Wiley-Liss, Inc. [source]

    Cricothyrotomy Technique Using Gum Elastic Bougie Is Faster Than Standard Technique: A Study of Emergency Medicine Residents and Medical Students in an Animal Lab

    Chandler Hill MD
    Abstract Objectives:, The objective was to compare time to completion, failure rate, and subjective difficulty of a new cricothyrotomy technique to the standard technique. The new bougie-assisted cricothyrotomy technique (BACT) is similar to the rapid four-step technique (RFST), but a bougie and endotracheal tube are inserted rather than a Shiley tracheostomy tube. Methods:, This was a randomized controlled trail conducted on domestic sheep. During a 3-month period inexperienced residents or students were randomized to perform cricothyrotomy on anesthetized sheep using either the standard technique or the BACT. Operators were trained with an educational video before the procedure. Time to successful cricothyrotomy was recorded. The resident or student was then asked to rate the difficulty of the procedure on a five-point scale from 1 (very easy) to 5 (very difficult). Results:, Twenty-one residents and students were included in the study: 11 in the standard group and 10 in the BACT group. Compared to the standard technique, the BACT was significantly faster with a median time of 67 seconds (interquartile range [IQR] = 55,82) versus 149 seconds (IQR = 111,201) for the standard technique (p = 0.002). The BACT was also rated easier to perform (median = 2, IQR = 1,3) than the standard technique (median = 3, IQR = 2,4; p = 0.04). The failure rate was 1/10 for the BACT compared to 3/11 for the standard method (p = NS). Conclusions:, This study demonstrates that the BACT is faster than the standard technique and has a similar failure rate when performed by inexperienced providers on anesthetized sheep. ACADEMIC EMERGENCY MEDICINE 2010; 17:666,669 © 2010 by the Society for Academic Emergency Medicine [source]

    Detecting New Forms of Network Intrusion Using Genetic Programming

    Wei Lu
    How to find and detect novel or unknown network attacks is one of the most important objectives in current intrusion detection systems. In this paper, a rule evolution approach based on Genetic Programming (GP) for detecting novel attacks on networks is presented and four genetic operators, namely reproduction, mutation, crossover, and dropping condition operators, are used to evolve new rules. New rules are used to detect novel or known network attacks. A training and testing dataset proposed by DARPA is used to evolve and evaluate these new rules. The proof of concept implementation shows that a rule generated by GP has a low false positive rate (FPR), a low false negative rate and a high rate of detecting unknown attacks. Moreover, the rule base composed of new rules has high detection rate with low FPR. An alternative to the DARPA evaluation approach is also investigated. [source]

    Granularity in Relational Formalisms,With Application to Time and Space Representation

    Jérôme Euzenat
    Temporal and spatial phenomena can be seen at a more or less precise granularity, depending on the kind of perceivable details. As a consequence, the relationship between two objects may differ depending on the granularity considered. When merging representations of different granularity, this may raise problems. This paper presents general rules of granularity conversion in relation algebras. Granularity is considered independently of the specific relation algebra, by investigating operators for converting a representation from one granularity to another and presenting six constraints that they must satisfy. The constraints are shown to be independent and consistent and general results about the existence of such operators are provided. The constraints are used to generate the unique pairs of operators for converting qualitative temporal relationships (upward and downward) from one granularity to another. Then two fundamental constructors (product and weakening) are presented: they permit the generation of new qualitative systems (e.g. space algebra) from existing ones. They are shown to preserve most of the properties of granularity conversion operators. [source]

    Exact and Robust (Self-)Intersections for Polygonal Meshes

    Marcel Campen
    Abstract We present a new technique to implement operators that modify the topology of polygonal meshes at intersections and self-intersections. Depending on the modification strategy, this effectively results in operators for Boolean combinations or for the construction of outer hulls that are suited for mesh repair tasks and accurate mesh-based front tracking of deformable materials that split and merge. By combining an adaptive octree with nested binary space partitions (BSP), we can guarantee exactness (= correctness) and robustness (= completeness) of the algorithm while still achieving higher performance and less memory consumption than previous approaches. The efficiency and scalability in terms of runtime and memory is obtained by an operation localization scheme. We restrict the essential computations to those cells in the adaptive octree where intersections actually occur. Within those critical cells, we convert the input geometry into a plane-based BSP-representation which allows us to perform all computations exactly even with fixed precision arithmetics. We carefully analyze the precision requirements of the involved geometric data and predicates in order to guarantee correctness and show how minimal input mesh quantization can be used to safely rely on computations with standard floating point numbers. We properly evaluate our method with respect to precision, robustness, and efficiency. [source]

    Exposure Fusion: A Simple and Practical Alternative to High Dynamic Range Photography

    T. Mertens
    I.4.8 [Image Processing]: Scene Analysis , Photometry, Sensor Fusion Abstract We propose a technique for fusing a bracketed exposure sequence into a high quality image, without converting to High dynamic range (HDR) first. Skipping the physically based HDR assembly step simplifies the acquisition pipeline. This avoids camera response curve calibration and is computationally efficient. It also allows for including flash images in the sequence. Our technique blends multiple exposures, guided by simple quality measures like saturation and contrast. This is done in a multiresolution fashion to account for the brightness variation in the sequence. The resulting image quality is comparable to existing tone mapping operators. [source]

    Differential Representations for Mesh Processing

    Olga Sorkine
    Abstract Surface representation and processing is one of the key topics in computer graphics and geometric modeling, since it greatly affects the range of possible applications. In this paper we will present recent advances in geometry processing that are related to the Laplacian processing framework and differential representations. This framework is based on linear operators defined on polygonal meshes, and furnishes a variety of processing applications, such as shape approximation and compact representation, mesh editing, watermarking and morphing. The core of the framework is the definition of differential coordinates and new bases for efficient mesh geometry representation, based on the mesh Laplacian operator. [source]

    Time-Dependent Discrete Network Design Frameworks Considering Land Use

    W. Y. Szeto
    Unlike existing models, the optimization frameworks can determine the optimal designs automatically without trial-and-error once the objective(s) is/are clearly defined. Moreover, these frameworks allow the evaluation of the impacts of the optimal designs on the related parties including landowners, toll road operators, transit operators, and road users, and help network planners and profit-makers with decision making by eliminating many alternative designs. A numerical study is set up to examine road network design's effects on these related parties under three road construction schemes: exact cost recovery, build-operate-transfer, and cross-subsidization. The results show that the changes in landowner profits are not the same after implementing any scheme. These unequal changes raise the issue of the landowner equity. This implies that the government has to consider trade-offs between parties' objectives carefully. [source]

    Numerical Methods to Simulate and Visualize Detailed Crane Activities

    Shih-Chung Kang
    One major consideration for virtual construction is the simulation of the operation of construction equipment for a construction project. This research specifically focuses on developing a mathematical model to support the simulation and visualization of cranes, the most critical equipment in terms of project controls. This model is composed of two submodels,a kinematics model and a dynamic model. The kinematics model is to present the crane components controlled by the operators. The dynamic model is to present the dynamic behavior in suspended system (including the cable and rigging object), which cannot be controlled directly by the operators. To verify the feasibility of these methods, a computer program that simulates and visualizes detailed crane activities was developed. This program supports the real-time visualization of crane activities with high degree of reality accuracy and also, enables the detailed simulation of long-term construction projects. [source]

    A Risk-Cost Optimized Maintenance Strategy for Corrosion-Affected Concrete Structures

    Chun-Qing Li
    It is also observed that some severely deteriorated concrete structures survive for many years without maintenance. This raises the question of why and how to maintain corrosion-affected concrete structures, in particular in the climate of an increasing scarcity of resources. The present article attempts to formulate a maintenance strategy based on risk-cost optimization of a structure during its whole service life. A time-dependent reliability method is employed to determine the probability of exceeding a limit state at each phase of the service life. To facilitate practical application of the formulated maintenance strategy, an algorithm is developed and programmed in a user-friendly manner with a worked example. A merit of the proposed maintenance strategy is that models used in risk assessment for corrosion-affected concrete structures are related to some of the design criteria used by practitioners. It is found in the article that there exists an optimal number of maintenances for cracking and delamination that returns the minimum total cost for the structure in its whole life. The maintenance strategy presented in the article can help structural engineers, operators, and asset managers develop a cost-effective management scheme for corrosion-affected concrete structures. [source]

    Understanding chemical shielding tensors using group theory, MO analysis, and modern density-functional theory

    Cory M. Widdifield
    Abstract In this article, the relationships between molecular symmetry, molecular electronic structure, and chemical shielding (CS) tensors are discussed. First, a brief background on the CS interaction and CS tensors is given. Then, the visualization of the three-dimensional nature of CS is described. A simple method for examining the relationship between molecular orbitals (MOs) and CS tensors, using point groups and direct products of irreducible representations of MOs and rotational operators, is outlined. A number of specific examples are discussed, involving CS tensors of different nuclei in molecules of different symmetries, including ethene (D2h), hydrogen fluoride (C,v), trifluorophosphine (C3v), and water (C2v). Finally, we review the application of this method to CS tensors in several interesting cases previously discussed in the literature, including acetylene (D,h), the PtX42, series of compounds (D4h) and the decamethylaluminocenium cation (D5d). © 2009 Wiley Periodicals, Inc. Concepts Magn Reson Part A 34A: 91,123, 2009. [source]

    Stylet Bend Angles and Tracheal Tube Passage Using a Straight-to-cuff Shape

    Richard M. Levitan MD
    Abstract Objectives Malleable stylets improve maneuverability and control during tube insertion, but after passage through the vocal cords the stiffened tracheal tube may impinge on the tracheal rings, preventing passage. The goal of this study was to assess insertion difficulty with styletted tubes of different bend angles. Methods Tube passage was assessed with four different bend angles (25°, 35°, 45°, and 60°) using straight-to-cuff,shaped tubes. In two separate airway procedure classes, 16 operators in each class (32 total) placed randomly ordered styletted tubes of the different angles into eight cadavers (16 total). Operators subjectively graded the ease of tube passage as no resistance, some resistance, or impossible to advance. Results No resistance was reported in 69.1% (177/256) at 25°, in 63.7% (163/256) at 35°, in 39.4% (101/256) at 45°, and in 8.9% (22/256) at 60°. Tube passage was impossible in 2.3% of insertions (6/256) at 25°, in 3.5% (9/256) at 35°, in 11.3% (29/256) at 45°, and in 53.9% (138/256) at 60°. The odds ratios of impossible tube passage for 35°, 45°, and 60° vs. 25° were 1.52 (95% confidence interval [CI] = 0.55 to 4.16), 5.32 (95% CI = 2.22 to 12.71), and 48.72 (95% CI = 21.35 to 111.03), respectively. Conclusions Bend angles beyond 35° with straight-to-cuff styletted tracheal tubes increase the risk of difficult and impossible tube passage into the trachea. The authors did not compare different stylet stopping points, stylets of different stiffness, or tracheal tubes with different tip designs, all variables that can affect tube passage. [source]

    A survey of interfacial forces used during filing of root canals

    J. D. Regan
    Abstract , The pattern of dentine removal during endodontic instrumentation is influenced by many factors including the interfacial forces applied by the operator. The aim of this study was to investigate the influence of operators and different sizes and types of instruments on the magnitude of these interfacial forces. Single-rooted teeth were mounted on a cantilevered aluminium beam to which two pairs of single element strain gauges were joined in a half-bridge configuration and mounted at right angles to each other. The strain gauges were connected to an analogue-to-digital converter fitted in a micro-computer via conditioning amplifiers. This enabled strains to be recorded over a period of time. Twenty operators instrumented root canals using a series of hand instruments for 1 min each. The mean interfacial forces used by operators demonstrated a wide variation ranging from 9.06 g to 149.42 g (range of forces from 0,331 g) but there was a consistency in the relative magnitude for each operator. The 20 operators could be divided into 13 groups which were significantly different (,=0.05) from each other. There were significant differences (,=0.05) between the forces used for each of the K-Flex files (15, 25, 35, 45, and 70), the force increasing with the file size. There was also a significant difference (,=0.05) in the forces used between the Flexofile (#25) and the #25 K-Flex and Hedström files. However, there was no significant difference between the K-Flex and Hedström files. [source]

    Beauty Versus Medicine: The Nonphysician Practice of Dermatologic Surgery

    Harold J. Brody MD
    Background This investigation was initiated because of a growing concern by the American Society for Dermatologic Surgery about the proliferation of nonphysicians practicing medicine and its impact on public health, safety, and welfare. Objective Prompted by an alarming rise in anecdotal reports among dermatologic surgeons, the study sought to determine whether there was a significant increase in the number of patients seeking corrective treatment due to complications from laser and light-based hair removal, subsurface laser/light rejuvenation techniques, chemical peels, microdermabrasion, injectables, and other cosmetic medical/surgical procedures performed by nonphysicians without adequate training or supervision. Methods A survey of 2,400 American Society for Dermatologic Surgery members in July 2001 and in-depth phone interviews with eight patients who experienced complications from nonphysicians performing cosmetic dermatologic surgery procedures were conducted. Results Survey data and qualitative research results attributed patient complications primarily to "nonphysician operators" such as cosmetic technicians, estheticians, and employees of medical/dental professionals who performed various invasive medical procedures outside of their scope of training or with inadequate or no physician supervision. Conclusion The results underscore the need for improved awareness, legislation, and enforcement regarding the nonphysician practice of medicine, along with further study of this issue. [source]

    Dietary Implications of Supermarket Development: A Global Perspective

    Corinna Hawkes
    Five decisions by supermarket operators have important dietary implications: the location of their outlets; the foods they sell; the prices they charge; the promotional strategies they use; and the nutrition-related activities they implement. These decisions influence food accessibility, availability, prices and desirability, which in turn influence the decisions consumers make about food. Based on a comprehensive literature review, this article finds that the dietary implications are both positive , supermarkets can make a more diverse diet available and accessible to more people , and negative , supermarkets can reduce the ability of marginalised populations to purchase a high-quality diet, and encourage the consumption of energy-dense, nutrient-poor highly-processed foods. Overall, the most universally applicable dietary implication is that supermarkets encourage consumers to eat more, whatever the food. [source]


    Kiichi Tamada
    When performing endoscopic retrograde cholangiopancreatography (ERCP), the smooth introduction of the duodenoscope into the papilla of Vater, an appropriate view of the papilla of Vater, and deep cannulation of the bile duct are essential. The operator must know the difference between the side-viewing endoscope and the forward-viewing endoscope. The rotation of the body and the left arm of the operator, switching with the left wrist, and dialing of the endoscope are essential for appropriately viewing the papilla of Vater. When training operators to do ERCP, a model is useful for helping them understand basic handling. The approach to deep cannulation of the bile duct should be selected based on the type of papilla (slit type, onion type, tongue protrusion type, flat type, and tumor type). Cannulation is more difficult in patients with the tongue protrusion-type of papilla than with a slit type, onion type, or tumor type. According to previous reports, therapeutic ERCP requires the ability to cannulate the common bile duct deeply 80% of the time; 180 to 200 supervised ERCP are necessary to achieve this success rate. [source]