3,775 research outputs found

    On the Statistical Origin of Topological Symmetries

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    We investigate a quantum system possessing a parasupersymmetry of order 2, an orthosupersymmetry of order pp, a fractional supersymmetry of order p+1p+1, and topological symmetries of type (1,p)(1,p) and (1,1,...,1)(1,1,...,1). We obtain the corresponding symmetry generators, explore their relationship, and show that they may be expressed in terms of the creation and annihilation operators for an ordinary boson and orthofermions of order pp. We give a realization of parafermions of order~2 using orthofermions of arbitrary order pp, discuss a p=2p=2 parasupersymmetry between p=2p=2 parafermions and parabosons of arbitrary order, and show that every orthosupersymmetric system possesses topological symmetries. We also reveal a correspondence between the orthosupersymmetry of order pp and the fractional supersymmetry of order p+1p+1.Comment: 12 page

    Plastic dilation rate characteristic of concrete confined with steel tube

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    The use of external confining devices to confine concrete has become widely used. One of the purposes is to gain additional concrete strength and ductility. Although there are many types of external confining devices, in this paper, the attention is limited to the use ofthe steel tube as anexternal confining device. One of the main objectives ofthis research is to study the plastic dilation rate behavior of concrete-filled-steel-tube (CFST) columns. The experimental data for the plastic dilation rate is extracted, and compared with the authors concrete plasticity model. In the authors’ previous research, the calibration of the plastic dilation rate model was based on confined concrete tested under both active and passive confinement using FRP wraps. Since the behavior of the steel tube and the FRP materials are different, the author’s plastic dilation rate model needs to be re-evaluated for CFST columns. Comparisons of the extracted experimental plastic dilation rates with the model prediction for CFST specimens with normal strength concrete show good agreement and requires no adjustment in the formulation. However, for a specimen with 80 MPa concrete, the proposed formulation showsslightly lowerplastic dilation rates.More experimental data for CFST using high strength concretes is required for further investigation. For the sake of completeness, the overall response of two CFST specimensisalso evaluated using anin-house three-dimensional non-linear finite element analysis (3D-NLFEA) using the author’s proposed plasticity formulation for confined concrete

    A review of CAD/CAM use in dentistry (part II): Comparison of intraoral digital scanners used in restorative dentistry

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    Introduction: Intraoral imaging technology has become one of the most exciting new fields in dentistry. Three-dimensional scanning of the oral cavity is used in many dental procedures such as restorative dentistry and orthodontics. To date, a number of intraoral scanners have been developed for restorative dentistry throughout the world, and many researchers and manufacturers seek the design and development of new digital devices. Only some of these devices are currently available on the market and some others are being clinically tested. All existing intraoral scanners try to overcome the drawbacks of traditional impression processes. The aim of the present article is to provide an extensive evaluation of intraoral scanners in restorative dentistry, with special attention to their assessment principles, characteristics and performance. Review report: This review article was prepared by scientific searching in electronic sources of Pubmed and ISI Web of Science in connection with articles published in English until 2014, and with these key words: intraoral scanners and digital impression. Conclusion: Over the years there have been major advances in digital scanning systems, and a variety of digital systems have been introduced that enable the dentist to select different intraoral reconstruction methods in the extraoral environment. The ultimate goal of dentists is to provide accurate and efficient dental restorations for the patient, while maintaining patient comfort during the impression process. High-resolution dental optical scanners will enable the operator to provide high-quality restorations. With digital impression techniques, the number of operators and material variables will decrease, making restoration fabrication processes more predictable and easier

    Virtual patient design : exploring what works and why : a grounded theory study

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    Objectives: Virtual patients (VPs) are online representations of clinical cases used in medical education. Widely adopted, they are well placed to teach clinical reasoning skills. International technology standards mean VPs can be created, shared and repurposed between institutions. A systematic review has highlighted the lack of evidence to support which of the numerous VP designs may be effective, and why. We set out to research the influence of VP design on medical undergraduates. Methods: This is a grounded theory study into the influence of VP design on undergraduate medical students. Following a review of the literature and publicly available VP cases, we identified important design properties. We integrated them into two substantial VPs produced for this research. Using purposeful iterative sampling, 46 medical undergraduates were recruited to participate in six focus groups. Participants completed both VPs, an evaluation and a 1-hour focus group discussion. These were digitally recorded, transcribed and analysed using grounded theory, supported by computer-assisted analysis. Following open, axial and selective coding, we produced a theoretical model describing how students learn from VPs. Results: We identified a central core phenomenon designated ‘learning from the VP’. This had four categories: VP Construction; External Preconditions; Student–VP Interaction, and Consequences. From these, we constructed a three-layer model describing the interactions of students with VPs. The inner layer consists of the student's cognitive and behavioural preconditions prior to sitting a case. The middle layer considers the VP as an ‘encoded object’, an e-learning artefact and as a ‘constructed activity’, with associated pedagogic and organisational elements. The outer layer describes cognitive and behavioural change. Conclusions: This is the first grounded theory study to explore VP design. This original research has produced a model which enhances understanding of how and why the delivery and design of VPs influence learning. The model may be of practical use to authors, institutions and researchers

    Holographic RG-flows and Boundary CFTs

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    Solutions of (d+1)(d+1)-dimensional gravity coupled to a scalar field are obtained, which holographically realize interface and boundary CFTs. The solution utilizes a Janus-like AdSd\mathrm{AdS}_d slicing ansatz and corresponds to a deformation of the CFT by a spatially-dependent coupling of a relevant operator. The BCFT solutions are singular in the bulk, but physical quantities such as the holographic entanglement entropy can be calculated.Comment: 26 pages, 11 figure

    O impacto dos distúrbios monetários na inflação e nos ciclos de negócios na economia iraniana

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    In this paper, we have investigated the effect of monetary disorders on inflation and business cycles in Iran’s economy during the period 1973 to 2012. Monetary disorders are defined by two indexes of monetary policy uncertainty and shock to liquidity growth. In the first step, the causal relationship of monetary policy uncertainty on real GDP fluctuations, employment fluctuations and inflation are estimated using Granger causality test. To this purpose, to follow Haghighat and Mohammad Gholipour Tapeh (2014), the conditional variance of liquidity growth extracted from models of GARCH family was applied as a substitute for monetary policy uncertainty. In the second stage, the reaction of economic growth, employment growth and inflation to the shock to liquidity growth are estimated using impulse response function technique derived from VAR model. The results indicate the existence of one-way Granger causality relation of monetary policy uncertainty in all three variables of real GDP fluctuations, employment fluctuations and inflation. Also, based on the results, impulse response function reduces the shock to liquidity growth as much as a standard deviation, real GDP growth and employment after a period and increases inflation. Accordingly, the hypothesis of the effect of monetary disorders on business cycles in Iran’s economy in the period of this research cannot be rejected.JEL classification: E23, E31, E32, E52En este documento, hemos investigado el efecto de los trastornos monetarios en la inflación y los ciclos económicos en la economía de Irán durante el período de 1973 a 2012. Los trastornos monetarios se definen por dos índices de incertidumbre de la política monetaria y el impacto del crecimiento de la liquidez. En el primer paso, la relación causal de la incertidumbre de la política monetaria sobre las fluctuaciones del PIB real, las fluctuaciones del empleo y la inflación se estiman mediante la prueba de causalidad de Granger. Para este propósito, siguiendo a Haghighat y Mohammad Gholipour Tapeh (2014), se aplicó la varianza condicional del crecimiento de la liquidez extraída de los modelos de la familia GARCH como sustituto de la incertidumbre de la política monetaria. En la segunda etapa, la reacción del crecimiento económico, el crecimiento del empleo y la inflación al impacto del crecimiento de la liquidez se estiman utilizando la técnica de función de respuesta al impulso derivada del modelo VAR. Los resultados indican la existencia de una relación de causalidad de Granger unidireccional de la incertidumbre de la política monetaria en las tres variables de fluctuaciones del PIB real, fluctuaciones del empleo e inflación. Además, en función de los resultados, la función de respuesta al impulso reduce el impacto del crecimiento de la liquidez tanto como una desviación estándar, el crecimiento del PIB real y el empleo después de un período y aumenta la inflación. En consecuencia, la hipótesis del efecto de los trastornos monetarios en los ciclos económicos de la economía de Irán en el período de esta investigación no puede ser rechazada.Clasificación JEL: E23, E31, E32, E52Neste artigo, investigamos o efeito dos distúrbios monetários sobre a inflação e os ciclos econômicos na economia do Irã durante o período de 1973 a 2012. Os distúrbios monetários são definidos por dois índices de incerteza da política monetária e por choque no crescimento da liquidez. No primeiro passo, a relação causal entre a incerteza da política monetária sobre as flutuações do PIB real, as flutuações do emprego e a inflação é estimada usando o teste de causalidade de Granger. Para este propósito, para seguir Haghighat e Mohammad Gholipour Tapeh (2014), a variância condicional do crescimento de liquidez extraída de modelos da família GARCH foi aplicada como um substituto para a incerteza da política monetária. No segundo estágio, a reação do crescimento econômico, crescimento do emprego e inflação ao choque para o crescimento da liquidez são estimados usando a técnica de função de resposta impulsiva derivada do modelo VAR. Os resultados indicam a existência de uma relação de causalidade de Granger unidirecional da incerteza da política monetária em todas as três variáveis de flutuações reais do PIB, flutuações do emprego e inflação. Além disso, com base nos resultados, a função de resposta ao impulso reduz o choque para o crescimento da liquidez, tanto quanto um desvio padrão, crescimento do PIB real e emprego após um período e aumenta a inflação. Consequentemente, a hipótese do efeito dos distúrbios monetários nos ciclos de negócios na economia do Irã no período desta pesquisa não pode ser rejeitada.Classificação JEL: E23, E31, E32, E5

    A Multivariate Latent Variable Model for Mixed – Data from Continuous and Ordinal Responses with Possibility of Missing Responses

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    A joint model for multivariate mixed ordinal and continuous outcomes with potentially non-random missing values in both types of responses is proposed. A full likelihood-based approach is used to obtain maximum likelihood estimates of the model parameters. Some modified Pearson residuals are also introduced where the correlation between responses are taken into account. The joint modelling of responses with the possibility of missing values requires caution since the interpretation of the fitted model highly depends on the missing mechanism assumptions that are unexaminable in a fundamental sense. A common way to investigate the influence of perturbations of model components on the key results of the analysis is to compare the results derived from the original and perturbed models using an influence maximal normal curvatures. For This, influence of a small perturbation of elements of the covariance structure of the model on maximal normal curvature is also studied. To illustrate the utility of the proposed model, a large data set excerpted from the British Household Panel Survey (BHPS) is analyzed. For these data, the simultaneous effects of some covariates on life satisfaction, income and the amount of money spent on leisure activities per month as three mixed correlated responses are explored

    Solving inverse problems of unknown contaminant source in groundwater-river integrated systems using a surrogate transport model based optimization

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    The paper presents a new approach to identify the unknown characteristics (release history and location) of contaminant sources in groundwater, starting from a few concentration observations at monitoring points. An inverse method that combines the forward model and an optimization algorithm is presented. To speed up the computation, the transfer function theory is applied to create a surrogate transport forward model. The performance of the developed approach is evaluated on two case studies (literature and a new one) under different scenarios and measurement error conditions. The literature case study regards a heterogeneous confined aquifer, while the proposed case study was never investigated before, it involves an aquifer-river integrated flow and transport system. In this case, the groundwater contaminant originated from a damaged tank, migrates to a river through the aquifer. The approach, starting from few concentration observations monitored at a downstream river cross-section, accurately estimates the release history at a groundwater contaminant source, even in presence of noise on observations. Moreover, the results show that the methodology is very fast, and can solve the inverse problem in much less computation time in comparison with other existing approaches

    Marginal integrity of low-shrinkage and methacrylate-based composite resins: Effect of three different hemostatic agents

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    Background: Moisture control is very important in restorative procedures in dentistry. Use of hemostatic agents helps control moisture; however, they might result in changes on enamel and dentin surfaces, affecting composite resin bond quality. The aim of this in vitro study was to evaluate the marginal microleakage of two different composite resins with the use of three different hemostatic agents. Material and Methods: Standardized Class V cavities were prepared on the buccal and lingual surfaces of 48 premolars with cervical margins 1 mm apical to the cementoenamel junction (CEJ). The samples were randomly divided into 8 groups. In groups 1 to 4, an etch-and-rinse adhesive (Adper Single Bond) was applied as the bonding system, followed by exposure to different hemostatic agent: group 1: no hemostatic agent (control); group 2: ViscoStat; group 3: ViscoStat Clear; and group 4: trichloracetic acid, as hemostatic agents. The cavities were restored with Z-250 composite resin. In group 5 to 8 Silorane System Adhesive (Filtek P90 Adhesive) was applied as a bonding agent, followed by exposure to different hemostatic agents in a manner similar to that in groups 1to 4. The cavities were restored with Filtek P90, a low-shrinkage composite resin. The samples in each group were evaluated for dye penetration under a stereomicroscope at ×36 after 24 hours and a 500-round thermocycling procedure at enamel and dentin margins. Statistical analysis was carried out using Kruskal-Wallis and Mann-Whitney tests (α=0.05). Results: Z-250 composite resin exhibited significantly higher dentin microleakage scores compared to Filtek P90 (P = 0.004). Trichloracetic acid increased dentin microleakage with Filtek P90 (P=0.033). Conclusions: Under the limitations of this in vitro study, application of hemostatic agents did not affect microleakage of the two tested composite resins except for trichloracetic acid that increased marginal microleakage when used with Filtek P90. © Medicina Oral

    Pengembangan Perangkat Pembelajaran Enginetune Up Toyota Mengacu Pada Problem Based Instruction Berbasis Otentik

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    This study aims to develop learning tool Engine tune up Toyota referring to problem based instruction based on authentic, which was applied in class X Mechanical Light Vehicle 2nd semester in SMK N Kare, Madiun.This study was conducted into five steps, they were analysis, planning, design, development and implementation based on model of the development cycle by Fenrich (1997). The data resultswere obtained as follows: validation of achievement test consist of LP1, LP2, and LP3. The score of correlation probability r (analysis) bigger than r (table).So it can be concluded the results were valid; The implementation of lesson plan with an average score of 4.6 as good category; students' activities in learning activities have reliability 94,33%; In analysing questions, there were easy and difficult category of questions. The cognitive's achievement in pretest was 0%, while in posttest was 100%; Psychomotoric's achievement shows that the average score of students RPP 1 (91,1), RPP 2 (91,2), RPP 3(91). All of the students have mastered the outcome learning.; the average score of students' behavioral in affective's achievement at test 1 were honest (4,2), care (4,5), and responsibility (4,4) with good category, students'social skills at test 1 were asked (4,6), contribute ideas (4,5), being a good listener (4,3), communication (4,4) and cooperation (4,0) with good category; students 'response to students' books, worksheets, learning media with value 4,07 was goodcategory.Based on the analysis of data analysis, it can be concluded that the development of the learning tool engine tune up Toyota referring to Problem based instruction Based onAuthentic can be effective, but it still need adjustment based on the situation and condition of the school
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