WorldWideScience

Sample records for model multilevel security

  1. A Multilevel Secure Relation-Hierarchical Data Model for a Secure DBMS

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A multilevel secure relation-hierarchical data model formultilevel secure database is extended from the relation-hierarchical data model in single level environment in this paper. Based on the model, an upper-lower layer relational integrity is presented after we analyze and eliminate the covert channels caused by the database integrity. Two SQL statements are extended to process polyinstantiation in the multilevel secure environment. The system based on the multilevel secure relation-hierarchical data model is capable of integratively storing and manipulating complicated objects (e.g., multilevel spatial data) and conventional data (e.g., integer, real number and character string) in multilevel secure database.

  2. Multilevel security model for ad hoc networks

    Institute of Scientific and Technical Information of China (English)

    Wang Changda; Ju Shiguang

    2008-01-01

    Modern battlefield doctrine is based on mobility, flexibility, and rapid response to changing situations.As is well known, mobile ad hoc network systems are among the best utilities for battlefield activity. Although much research has been done on secure routing, security issues have largely been ignored in applying mobile ad hoc network theory to computer technology. An ad hoc network is usually assumed to be homogeneous, which is an irrational assumption for armies. It is clear that soldiers, commanders, and commanders-in-chief should have different security levels and computation powers as they have access to asymmetric resources. Imitating basic military rank levels in battlefield situations, how multilevel security can be introduced into ad hoc networks is indicated, thereby controlling restricted classified information flows among nodes that have different security levels.

  3. Enhanced Authentication Mechanism Using Multilevel Security Model

    Directory of Open Access Journals (Sweden)

    Abdulameer Hussain

    2009-06-01

    Full Text Available This paper presents a proposed multilevel authentication method which is implemented especially in sensitive applications where they contain multilevel secure and confidential data. The proposed method divides the system into multiple sensitive levels and tests users against different authentication methods for each level. Most levels are subdivided further into secure sublevels. Each sublevel contains its own privileges and data types which are managed by an Identity Manager (IM whose responsibility is to transit users to other higher sublevels. The transition’s decision is done by assigning different weights to each authentication method .After a series of tests, the IM must generate a status report describing the results and the decision made to each user’s activity. This technique permits granting only the required privileges for a selected group of users and limits the configuration functions of those that users in a particular user group can perform.

  4. MULTILEVEL RECURRENT MODEL FOR HIERARCHICAL CONTROL OF COMPLEX REGIONAL SECURITY

    Directory of Open Access Journals (Sweden)

    Andrey V. Masloboev

    2014-11-01

    Full Text Available Subject of research. The research goal and scope are development of methods and software for mathematical and computer modeling of the regional security information support systems as multilevel hierarchical systems. Such systems are characterized by loosely formalization, multiple-aspect of descendent system processes and their interconnectivity, high level dynamics and uncertainty. The research methodology is based on functional-target approach and principles of multilevel hierarchical system theory. The work considers analysis and structural-algorithmic synthesis problem-solving of the multilevel computer-aided systems intended for management and decision-making information support in the field of regional security. Main results. A hierarchical control multilevel model of regional socio-economic system complex security has been developed. The model is based on functional-target approach and provides both formal statement and solving, and practical implementation of the automated information system structure and control algorithms synthesis problems of regional security management optimal in terms of specified criteria. An approach for intralevel and interlevel coordination problem-solving in the multilevel hierarchical systems has been proposed on the basis of model application. The coordination is provided at the expense of interconnection requirements satisfaction between the functioning quality indexes (objective functions, which are optimized by the different elements of multilevel systems. That gives the possibility for sufficient coherence reaching of the local decisions, being made on the different control levels, under decentralized decision-making and external environment high dynamics. Recurrent model application provides security control mathematical models formation of regional socioeconomic systems, functioning under uncertainty. Practical relevance. The model implementation makes it possible to automate synthesis realization of

  5. COORDINATION IN MULTILEVEL NETWORK-CENTRIC CONTROL SYSTEMS OF REGIONAL SECURITY: APPROACH AND FORMAL MODEL

    Directory of Open Access Journals (Sweden)

    A. V. Masloboev

    2015-01-01

    Full Text Available The paper deals with development of methods and tools for mathematical and computer modeling of the multilevel network-centric control systems of regional security. This research is carried out under development strategy implementation of the Arctic zone of the Russian Federation and national safeguarding for the period before 2020 in the Murmansk region territory. Creation of unified interdepartmental multilevel computer-aided system is proposed intended for decision-making information support and socio-economic security monitoring of the Arctic regions of Russia. The distinctive features of the investigated system class are openness, self-organization, decentralization of management functions and decision-making, weak hierarchy in the decision-making circuit and goal generation capability inside itself. Research techniques include functional-target approach, mathematical apparatus of multilevel hierarchical system theory and principles of network-centric control of distributed systems with pro-active components and variable structure. The work considers network-centric management local decisions coordination problem-solving within the multilevel distributed systems intended for information support of regional security. The coordination problem-solving approach and problem formalization in the multilevel network-centric control systems of regional security have been proposed based on developed multilevel recurrent hierarchical model of regional socio-economic system complex security. The model provides coordination of regional security indexes, optimized by the different elements of multilevel control systems, subject to decentralized decision-making. The model specificity consists in application of functional-target technology and mathematical apparatus of multilevel hierarchical system theory for coordination procedures implementation of the network-centric management local decisions. The work-out and research results can find further

  6. A Formal Model of Trust Chain based on Multi-level Security Policy

    Directory of Open Access Journals (Sweden)

    Kong Xiangying

    2013-07-01

    Full Text Available Trust chain is the core technology of trusted computing. A formal model of trust chain based on finite state automata theory is proposed. We use communicating sequential processes to describe the system state transition in trust chain and by combining with multi-level security strategy give the definition of trust system and trust decision theorem of trust chain transfer which is proved meantime. Finally, a prototype system is given to show the efficiency of the model.

  7. Multilevel security for relational databases

    CERN Document Server

    Faragallah, Osama S; El-Samie, Fathi E Abd

    2014-01-01

    Concepts of Database Security Database Concepts Relational Database Security Concepts Access Control in Relational Databases      Discretionary Access Control      Mandatory Access Control      Role-Based Access Control Work Objectives Book Organization Basic Concept of Multilevel Database Security IntroductionMultilevel Database Relations Polyinstantiation      Invisible Polyinstantiation      Visible Polyinstantiation      Types of Polyinstantiation      Architectural Consideration

  8. The Application of the Multi-Level Governance Model outside the EU-context – The Case of Food Security

    Directory of Open Access Journals (Sweden)

    Katarzyna Marzeda-Mlynarska

    2011-05-01

    Full Text Available The problem of food security governance is systematically gaining in importance but at the same time constitutes one of the less researched areas within the global governance debate. Food security has never been ensured on a global level despite the amazing progress of science and technology. What is more, the changing nature of the threats to food security makes this goal even more distant. Given the multidimensional nature of the food security concept, answers to this challenge have been sought through processes of international negotiations between nation-states. However, it is increasingly clear that nation-states, because of its contradictory interests, are unable to solve this issue and meet their international commitments for addressing this issue without more explicit engagements with sub and supranational actions. Involvement of other actors operating on different levels seems to be crucial to the process of governing of food security. The idea of multilevel governance has acquired unprecedented importance today. It not only suggests ways of dealing with new conditions of globalization, but it is said to be an essential term for understanding the transnational processes and for identifying non-traditional actors involved in governance processes on different levels. The idea of multilevel governance was developed into a theoretical account of the European Union in opposition to state centric or intergovernmental accounts. It refers to a particular subset of contemporary governance arrangements in which decision-making authority is distributed across more then one level of relatively autonomous public-sector institutions. This paper deals with the problem of food security governance and attempts to answer the question whether multilevel governance becomes a gradually institutionalized new international practice or is it only a theoretical model useful in academic debates, without practical meaning to governance of food security?

  9. Multilevel modeling using R

    CERN Document Server

    Finch, W Holmes; Kelley, Ken

    2014-01-01

    A powerful tool for analyzing nested designs in a variety of fields, multilevel/hierarchical modeling allows researchers to account for data collected at multiple levels. Multilevel Modeling Using R provides you with a helpful guide to conducting multilevel data modeling using the R software environment.After reviewing standard linear models, the authors present the basics of multilevel models and explain how to fit these models using R. They then show how to employ multilevel modeling with longitudinal data and demonstrate the valuable graphical options in R. The book also describes models fo

  10. 多级安全数据库BLP模型分析与改进%Analysis and Improvement of Multilevel Secure Database BLP Model

    Institute of Scientific and Technical Information of China (English)

    赵海燕; 赵静

    2013-01-01

    In view of the defects of current multi-level secure database BLP model, improved methods of its security classification, scope and access rules were proposed, in order to improve the security of the database.%针对目前多级安全数据库BLP模型的缺陷,提出了对其密级、范围和访问规则的改进方法,以提高数据库的安全性.

  11. Multilevel Mixture Factor Models

    Science.gov (United States)

    Varriale, Roberta; Vermunt, Jeroen K.

    2012-01-01

    Factor analysis is a statistical method for describing the associations among sets of observed variables in terms of a small number of underlying continuous latent variables. Various authors have proposed multilevel extensions of the factor model for the analysis of data sets with a hierarchical structure. These Multilevel Factor Models (MFMs)…

  12. An improved multilevel fuzzy comprehensive evaluation algorithm for security performance

    Institute of Scientific and Technical Information of China (English)

    LI Ling-juan; SHEN Ling-tong

    2006-01-01

    It is of great importance to take various factors into account when evaluating the network security performance.Multilevel fuzzy comprehensive evaluation is a relatively valid method. However, the traditional multilevel fuzzy comprehensive evaluation algorithm relies on the expert's knowledge and experiences excessively, and the result of the evaluation is usually less accurate. In this article, an improved multilevel fuzzy comprehensive evaluation algorithm, based on fuzzy sets core and entropy weight is presented. Furthermore, a multilevel fuzzy comprehensive evaluation model of P2P network security performance has also been designed, and the improved algorithm is used to make an instant computation based on the model. The advantages of the improved algorithm can be embodied in comparison with the traditional evaluation algorithm.

  13. Implementing message systems in multilevel secure environments: Problems and approaches

    Science.gov (United States)

    Martins, G. R.; Gaines, R. S.

    1982-07-01

    A study of the problems of building multilevel secure message systems. The need for such systems in the government and commercial sectors is growing. Designs are strongly affected by (1) the granularity of security protection (at the level of folders, messages, paragraphs, or words) and (2) planned departures from the Bell-LaPadula security model, for user convenience. A Taxonomy of design alternatives is defined, and 16 specific approaches are described and compared.

  14. Multilevel classification of security concerns in cloud computing

    Directory of Open Access Journals (Sweden)

    Syed Asad Hussain

    2017-01-01

    Full Text Available Threats jeopardize some basic security requirements in a cloud. These threats generally constitute privacy breach, data leakage and unauthorized data access at different cloud layers. This paper presents a novel multilevel classification model of different security attacks across different cloud services at each layer. It also identifies attack types and risk levels associated with different cloud services at these layers. The risks are ranked as low, medium and high. The intensity of these risk levels depends upon the position of cloud layers. The attacks get more severe for lower layers where infrastructure and platform are involved. The intensity of these risk levels is also associated with security requirements of data encryption, multi-tenancy, data privacy, authentication and authorization for different cloud services. The multilevel classification model leads to the provision of dynamic security contract for each cloud layer that dynamically decides about security requirements for cloud consumer and provider.

  15. Practical Marginalized Multilevel Models.

    Science.gov (United States)

    Griswold, Michael E; Swihart, Bruce J; Caffo, Brian S; Zeger, Scott L

    2013-01-01

    Clustered data analysis is characterized by the need to describe both systematic variation in a mean model and cluster-dependent random variation in an association model. Marginalized multilevel models embrace the robustness and interpretations of a marginal mean model, while retaining the likelihood inference capabilities and flexible dependence structures of a conditional association model. Although there has been increasing recognition of the attractiveness of marginalized multilevel models, there has been a gap in their practical application arising from a lack of readily available estimation procedures. We extend the marginalized multilevel model to allow for nonlinear functions in both the mean and association aspects. We then formulate marginal models through conditional specifications to facilitate estimation with mixed model computational solutions already in place. We illustrate the MMM and approximate MMM approaches on a cerebrovascular deficiency crossover trial using SAS and an epidemiological study on race and visual impairment using R. Datasets, SAS and R code are included as supplemental materials.

  16. 适用多级安全网络的BLP改进模型%Improved BLP model for multi-level secure network

    Institute of Scientific and Technical Information of China (English)

    白玮; 吴强; 张学平

    2013-01-01

    SBLP,an improved BLP (Bell-LaPadula) model was presented for exchanging information in multi-level secure networks securely and efficiently.Its finite-state machine definition and state change rules were given,and its security was formally proved.The model provides a theoretical base to information exchanging in multi-level secure networks by attaching objects and subjects with changeable secure labels,and gave full consideration to subjects creating,subjects illegal tracking and so on,which can slove the problems of BLP model using in the multi-level secure network.Finally,a simple scenario using the model was given.%为实现不同安全级网络间的互联互通,提出了一种适用于多级安全网络的安全策略模型SBLP,给出了其状态机模型定义和状态变化规则,并形式化地证明了其安全性.该模型通过为主客体添加可变的安全级标记,充分考虑了主体创建、主体违规追踪等问题,有效解决了等级化网络中BLP模型过于严格的问题,为等级化安全网络互联互通提供了必要的理论基础.最后,给出了该模型的一个简单的应用场景.

  17. Multilevel models applications using SAS

    CERN Document Server

    Wang, Jichuan; Fisher, James F

    2011-01-01

    This book covers a broad range of topics about multilevel modeling. The goal is to help readers to understand the basic concepts, theoretical frameworks, and application methods of multilevel modeling. It is at a level also accessible to non-mathematicians, focusing on the methods and applications of various multilevel models and using the widely used statistical software SAS®. Examples are drawn from analysis of real-world research data.

  18. Multilevel Models Applications Using SAS

    CERN Document Server

    Wang, Jichuan; Fisher, James

    2011-01-01

    This book covers a broad range of topics about multilevel modeling. The goal is to help readersto understand the basic concepts, theoretical frameworks, and application methods of multilevel modeling. Itis at a level also accessible to non-mathematicians, focusing on the methods and applications of various multilevel models and using the widely used statistical software SAS®.Examples are drawn from analysis of real-world research data.

  19. A Multilevel Transaction Problem for Multilevel Secure Database Systems and its Solution for the Replicated Architecture

    Science.gov (United States)

    1992-01-01

    interesting a research issue. An algorithm for this case, using a multiversion technique, will be the subject of future work. In addition, there is a...34 Multiversion Concurrency Control for Multilevel Secure Database Systems" in Proceedings of the IEEE Symposium on Security and Privacy, pp. 369-383...Oakland, CA May 1990. 7. William T. Maimone and Ira B. Greenberg, "Single-Level Multiversion Schedulers for Multilevel Secure Database Systems" in

  20. 一种新的安全Petri网及其多级安全机制分析%A Novel Multilevel Security Petri Net and its Security Analysis

    Institute of Scientific and Technical Information of China (English)

    王小明; 赵宗涛; 袁崇义

    2003-01-01

    Petri Net(PN) is a very important modeling methodology for dynamic concurrent system. Many PN modelsare available in existing literature,but a little attention has been paid to such a PN that supports multilevel securepolicies. In this paper,a novel PN model ,named as multilevel secure PN (MLSPN),is proposed ,and its multilevel se-curity mechanism is analysed formally. MLSPN has of a flexible and strong power to support a dynamic time con-traint,and the security covert channel can also be eleminated. Therefore MLSPN may have practical application inmany areas ,such as secure workflow development ,secure database design,and secure protocol analysis ,etc.

  1. Multi-Level Security Cannot Realise NEC Objectives

    NARCIS (Netherlands)

    Schotanus, H.A.; Hartog, T.; Verkoelen, C.A.A.

    2012-01-01

    Multi-Level Security (MLS) is often viewed as the holy grail of information security, especially in those environments where information of different classifications is being processed. In this paper we argue that MLS cannot facilitate the right balance between need-to-protect and duty-to-share as r

  2. Modeling for spatial multilevel structural data

    Science.gov (United States)

    Min, Suqin; He, Xiaoqun

    2013-03-01

    The traditional multilevel model assumed independence between groups. However, the datasets grouped by geographical units often has spatial dependence. The individual is influenced not only by its region but also by the adjacent regions, and level-2 residual distribution assumption of traditional multilevel model is violated. In order to deal with such spatial multilevel data, we introduce spatial statistics and spatial econometric models into multilevel model, and apply spatial parameters and adjacency matrix in traditional level-2 model to reflect the spatial autocorrelation. Spatial lag model express spatial effects. We build spatial multilevel model which consider both multilevel thinking and spatial correlation.

  3. Modeling Multi-Level Systems

    CERN Document Server

    Iordache, Octavian

    2011-01-01

    This book is devoted to modeling of multi-level complex systems, a challenging domain for engineers, researchers and entrepreneurs, confronted with the transition from learning and adaptability to evolvability and autonomy for technologies, devices and problem solving methods. Chapter 1 introduces the multi-scale and multi-level systems and highlights their presence in different domains of science and technology. Methodologies as, random systems, non-Archimedean analysis, category theory and specific techniques as model categorification and integrative closure, are presented in chapter 2. Chapters 3 and 4 describe polystochastic models, PSM, and their developments. Categorical formulation of integrative closure offers the general PSM framework which serves as a flexible guideline for a large variety of multi-level modeling problems. Focusing on chemical engineering, pharmaceutical and environmental case studies, the chapters 5 to 8 analyze mixing, turbulent dispersion and entropy production for multi-scale sy...

  4. Multi-level security for computer networking: SAC digital network approach

    Energy Technology Data Exchange (ETDEWEB)

    Griess, W.; Poutre, D.L.

    1983-10-01

    For telecommunications systems simultaneously handling data of different security levels, multilevel secure (MLS) operation permits maximum use of resources by automatically providing protection to users with various clearances and needs-to-know. The strategic air command (SAC) is upgrading the primary record data system used to command and control its strategic forces. The upgrade, called the SAC Digital Network (SACDIN), is designed to provide multilevel security to support users and external interfaces, with allowed accesses ranging from unclassified to top secret. SACDIN implements a security kernel based upon the Bell and Lapadula security model. This study presents an overview of the SACDIN security architecture and describes the basic message flow across the MLS network. 7 references.

  5. Integrity Based Access Control Model for Multilevel XML Document

    Institute of Scientific and Technical Information of China (English)

    HONG Fan; FENG Xue-bin; HUANO Zhi; ZHENG Ming-hui

    2008-01-01

    XML's increasing popularity highlights the security demand for XML documents. A mandatory access control model for XML document is presented on the basis of investigation of the function dependency of XML documents and discussion of the integrity properties of multilevel XML document. Then, the algorithms for decomposition/recovery multilevel XML document into/from single level document are given, and the manipulation rules for typical operations of XQuery and XUpdate: QUERY, INSERT,UPDATE, and REMOVE, are elaborated. The multilevel XML document access model can meet the requirement of sensitive information processing application.

  6. Multilevel IRT Model Assessment

    NARCIS (Netherlands)

    Fox, Jean-Paul; Ark, L. Andries; Croon, Marcel A.

    2005-01-01

    Modelling complex cognitive and psychological outcomes in, for example, educational assessment led to the development of generalized item response theory (IRT) models. A class of models was developed to solve practical and challenging educational problems by generalizing the basic IRT models. An IRT

  7. Multilevel IRT Model Assessment

    NARCIS (Netherlands)

    Fox, Gerardus J.A.; Ark, L. Andries; Croon, Marcel A.

    2005-01-01

    Modelling complex cognitive and psychological outcomes in, for example, educational assessment led to the development of generalized item response theory (IRT) models. A class of models was developed to solve practical and challenging educational problems by generalizing the basic IRT models. An IRT

  8. Multilevel joint competing risk models

    Science.gov (United States)

    Karunarathna, G. H. S.; Sooriyarachchi, M. R.

    2017-09-01

    Joint modeling approaches are often encountered for different outcomes of competing risk time to event and count in many biomedical and epidemiology studies in the presence of cluster effect. Hospital length of stay (LOS) has been the widely used outcome measure in hospital utilization due to the benchmark measurement for measuring multiple terminations such as discharge, transferred, dead and patients who have not completed the event of interest at the follow up period (censored) during hospitalizations. Competing risk models provide a method of addressing such multiple destinations since classical time to event models yield biased results when there are multiple events. In this study, the concept of joint modeling has been applied to the dengue epidemiology in Sri Lanka, 2006-2008 to assess the relationship between different outcomes of LOS and platelet count of dengue patients with the district cluster effect. Two key approaches have been applied to build up the joint scenario. In the first approach, modeling each competing risk separately using the binary logistic model, treating all other events as censored under the multilevel discrete time to event model, while the platelet counts are assumed to follow a lognormal regression model. The second approach is based on the endogeneity effect in the multilevel competing risks and count model. Model parameters were estimated using maximum likelihood based on the Laplace approximation. Moreover, the study reveals that joint modeling approach yield more precise results compared to fitting two separate univariate models, in terms of AIC (Akaike Information Criterion).

  9. Survey of Collaboration Technologies in Multi-level Security Environments

    Science.gov (United States)

    2014-04-28

    Dickson. 1996. "Teams in Organizations: Recent Research on Performance and Effectiveness". Annual Review of Psychology , 47:307-338. [32] Hall, D.L... Psychology , 94, 2, 535-546. [48] Moore, J.A. (2002). JView: an information visualization paradigm. Proc. SPIE, Vol. 4716, 367-374. In Enabling...date. Multilevel security solutions like the Multi-Layer Access Solution were developed by Gestalt and MAXIM Systems before these companies became

  10. Multi-Level Model

    Directory of Open Access Journals (Sweden)

    Constanta Nicoleta BODEA

    2008-01-01

    Full Text Available Is an original paper, which contains a hierarchical model with three levels, for determining the linearized non-homogeneous and homogeneous credibility premiums at company level, at sector level and at contract level, founded on the relevant covariance relations between the risk premium, the observations and the weighted averages. We give a rather explicit description of the input data for the multi- level hierarchical model used, only to show that in practical situations, there will always be enough data to apply credibility theory to a real insurance portfolio.

  11. Multilevel Models: Conceptual Framework and Applicability

    Directory of Open Access Journals (Sweden)

    Roxana-Otilia-Sonia Hrițcu

    2015-10-01

    Full Text Available Individuals and the social or organizational groups they belong to can be viewed as a hierarchical system situated on different levels. Individuals are situated on the first level of the hierarchy and they are nested together on the higher levels. Individuals interact with the social groups they belong to and are influenced by these groups. Traditional methods that study the relationships between data, like simple regression, do not take into account the hierarchical structure of the data and the effects of a group membership and, hence, results may be invalidated. Unlike standard regression modelling, the multilevel approach takes into account the individuals as well as the groups to which they belong. To take advantage of the multilevel analysis it is important that we recognize the multilevel characteristics of the data. In this article we introduce the outlines of multilevel data and we describe the models that work with such data. We introduce the basic multilevel model, the two-level model: students can be nested into classes, individuals into countries and the general two-level model can be extended very easily to several levels. Multilevel analysis has begun to be extensively used in many research areas. We present the most frequent study areas where multilevel models are used, such as sociological studies, education, psychological research, health studies, demography, epidemiology, biology, environmental studies and entrepreneurship. We support the idea that since hierarchies exist everywhere, multilevel data should be recognized and analyzed properly by using multilevel modelling.

  12. Attachment, Autonomy, and Emotional Reliance: A Multilevel Model

    Science.gov (United States)

    Lynch, Martin F.

    2013-01-01

    This article reports a test of a multilevel model investigating how attachment security and autonomy contribute to emotional reliance, or the willingness to seek interpersonal support. Participants ("N" = 247) completed online measures of attachment, autonomy, emotional reliance, and vitality with respect to several everyday…

  13. Multi-level security for computer networking - SAC digital network approach

    Science.gov (United States)

    Griess, W.; Poutre, D. L.

    The functional features and architecture of the SACDIN (SAC digital network) are detailed. SACDIN is the new data transmission segment for directing SAC's strategic forces. The system has 135 processor nodes at 32 locations and processes, distributes and stores data of any level of security classification. The sophistication of access nodes is dependent on the location. A reference monitor mediates the multilevel security by implementation of the multi-state machine concept, i.e., the Bell-LaPadula model (1973, 1974), which concludes that a secure state can never lead to an unsecure state. The monitor is controlled by the internal access control mechanism, which resides in PROM. Details of the access process are provided, including message flow on trusted paths appropriate to the security clearance of the user.

  14. A Computationally Efficient State Space Approach to Estimating Multilevel Regression Models and Multilevel Confirmatory Factor Models.

    Science.gov (United States)

    Gu, Fei; Preacher, Kristopher J; Wu, Wei; Yung, Yiu-Fai

    2014-01-01

    Although the state space approach for estimating multilevel regression models has been well established for decades in the time series literature, it does not receive much attention from educational and psychological researchers. In this article, we (a) introduce the state space approach for estimating multilevel regression models and (b) extend the state space approach for estimating multilevel factor models. A brief outline of the state space formulation is provided and then state space forms for univariate and multivariate multilevel regression models, and a multilevel confirmatory factor model, are illustrated. The utility of the state space approach is demonstrated with either a simulated or real example for each multilevel model. It is concluded that the results from the state space approach are essentially identical to those from specialized multilevel regression modeling and structural equation modeling software. More importantly, the state space approach offers researchers a computationally more efficient alternative to fit multilevel regression models with a large number of Level 1 units within each Level 2 unit or a large number of observations on each subject in a longitudinal study.

  15. High assurance multilevel secure mail service: session server and IMAP server

    OpenAIRE

    Balmer, Steven; Bryer-Joyner, Susan; Eads, Brad; Heller, Scott D.; Irvine, Cynthia E.

    1999-01-01

    "We are developing a multilevel mail service that combines server-based high assurance mandatory security policy enforcement with commemrcial-off-the-shelf (COTS) operating systems and software on client systems."

  16. Microlithography application for production of multilevel diffractive optical elements (as a security hologram feature)

    Science.gov (United States)

    Braginets, Eugene; Kurashov, V.; Honcharuk, S.; Girnyk, V.; Kostyukevych, S.; Kostyukevych, K.

    2011-02-01

    The goal of a present research is to develop a method for production of multilevel Diffractive Optical Elements (DOEs) for use in Digital Security Holograms, using the direct-writing maskless lithography system.

  17. Using Multilevel Modeling in Counseling Research

    Science.gov (United States)

    Lynch, Martin F.

    2012-01-01

    This conceptual and practical overview of multilevel modeling (MLM) for researchers in counseling and development provides guidelines on setting up SPSS to perform MLM and an example of how to present the findings. It also provides a discussion on how counseling and developmental researchers can use MLM to address their own research questions.…

  18. Multilevel modelling and public health policy

    NARCIS (Netherlands)

    Leyland, Alastair H.; Groenewegen, Peter P.

    2003-01-01

    Background: Multilevel modelling is a statistical technique that extends ordinary regression analysis to the situation where the data are hierarchical. Such data form an increasingly common evidence base for public health policy, and as such it is important that policy makers should be aware of this

  19. Multilevel modelling and public health policy.

    NARCIS (Netherlands)

    Leyland, A.H.; Groenewegen, P.P.

    2003-01-01

    BACKGROUND: Multilevel modelling is a statistical technique that extends ordinary regression analysis to the situation where the data are hierarchical. Such data form an increasingly common evidence base for public health policy, and as such it is important that policy makers should be aware of this

  20. Generalization of Random Intercept Multilevel Models

    Directory of Open Access Journals (Sweden)

    Rehan Ahmad Khan

    2013-10-01

    Full Text Available The concept of random intercept models in a multilevel model developed by Goldstein (1986 has been extended for k-levels. The random variation in intercepts at individual level is marginally split into components by incorporating higher levels of hierarchy in the single level model. So, one can control the random variation in intercepts by incorporating the higher levels in the model.

  1. A Multi-level Security Mechanism for Secure Data Transmission in SCTP

    Directory of Open Access Journals (Sweden)

    P. Venkadesh

    2014-03-01

    Full Text Available In this study we propose a multi-level security mechanism to provide secure data transmission in Stream Control Transmission Protocol (SCTP. During the time of TCP/IP protocols the computers were single-homed and nowadays there is a need for mobility, therefore new protocols were designed to support the mobility and multi-homing facilities. SCTP is a newly designed protocol that supports more interesting features such as Multi-homing and Multi-streaming when compared to the existing protocols. Since SCTP is designed for telecommunication its native design does not consider the security issues for data transmission. In this study we analyzed and identified the possibility places for hiding and exchanging of secret information in SCTP and proposed a dynamic encryption algorithm to provide a secure end-to-end data transmission between two nodes by altering the basic structure of the existing SCTP multi-homed protocol so that the attacker does not know the algorithm used since the algorithm is dynamic and the key for the encryption algorithm is hidden in the heartbeat signal of the SCTP and also suggest a method to detect the hacker incase of any attacks against the transmitted packets and finds an alternate path to transmit the remaining packets using the multi-homing options of SCTP.

  2. An introduction to multilevel flow modeling

    DEFF Research Database (Denmark)

    Lind, Morten

    2011-01-01

    environment. MFM has a primary focus on plant goals and functions and provide a methodological way of using those concepts to represent complex industrial plant. The paper gives a brief introduction to the historical development, introduces the concepts of MFM and presents the application of the concepts......Multilevel Flow Modeling (MFM) is a methodology for functional modeling of industrial processes on several interconnected levels of means-end and part-whole abstractions. The basic idea of MFM is to represent an industrial plant as a system which provides the means required to serve purposes in its...

  3. Testing Group Mean Differences of Latent Variables in Multilevel Data Using Multiple-Group Multilevel CFA and Multilevel MIMIC Modeling.

    Science.gov (United States)

    Kim, Eun Sook; Cao, Chunhua

    2015-01-01

    Considering that group comparisons are common in social science, we examined two latent group mean testing methods when groups of interest were either at the between or within level of multilevel data: multiple-group multilevel confirmatory factor analysis (MG ML CFA) and multilevel multiple-indicators multiple-causes modeling (ML MIMIC). The performance of these methods were investigated through three Monte Carlo studies. In Studies 1 and 2, either factor variances or residual variances were manipulated to be heterogeneous between groups. In Study 3, which focused on within-level multiple-group analysis, six different model specifications were considered depending on how to model the intra-class group correlation (i.e., correlation between random effect factors for groups within cluster). The results of simulations generally supported the adequacy of MG ML CFA and ML MIMIC for multiple-group analysis with multilevel data. The two methods did not show any notable difference in the latent group mean testing across three studies. Finally, a demonstration with real data and guidelines in selecting an appropriate approach to multilevel multiple-group analysis are provided.

  4. An introduction to multilevel modeling for anesthesiologists.

    Science.gov (United States)

    Glaser, Dale; Hastings, Randolph H

    2011-10-01

    In population-based research, subjects are frequently in clusters with shared features or demographic characteristics, such as age range, neighborhood, who they have for a physician, and common comorbidities. Classification into clusters also applies at broader levels. Physicians are classified by physician group or by practice site; hospitals can be characterized by size, location, or demographics. Hierarchical, nested structures pose unique challenges in the conduct of research. Data from nested structures may be interdependent because of similarities among subjects in a cluster, while nesting at multiple levels makes it difficult to know whether findings should be applied to the individual or to the larger group. Statistical tools, known variously as hierarchical linear modeling, multilevel modeling, mixed linear modeling, and other terms, have been developed in the education and social science fields to deal effectively with these issues. Our goal in this article is to review the implications of hierarchical, nested data organization and to provide a step-by-step tutorial of how multilevel modeling could be applied to a problem in anesthesia research using current, commercially available software.

  5. School Security and Student Misbehavior: A Multi-Level Examination

    Science.gov (United States)

    Servoss, Timothy J.

    2017-01-01

    Despite a nationwide trend to increase security measures in schools, their effectiveness in reducing or preventing student misbehavior remains largely unexamined. In addition, there is concern that increased security may have unintended negative side effects and is applied inequitably across students of disparate racial/ethnic backgrounds. The…

  6. Considerations for a Shipboard Multilevel Secure Local Area Network

    Science.gov (United States)

    1992-03-01

    fulfillment of the requirements for the degree of MASTER OF SCIENCE IN TELECOMMUNICATIONS SYSTEMS MANAGEMENT from the NAVAL POSTGRADUATE SCHOOL March 1992...Intentions arc to merge the three separate networks into one network, the DISNET. Physicall % unprotected trunks and host access lines on the MILNET are being...Computer Security Press. April 19S2. 13. Computers at Risk: Safe Computing in the Information Ave. System Security Stud% Committee, Computer Science and

  7. Consequence Reasoning in Multilevel Flow Modelling

    DEFF Research Database (Denmark)

    Zhang, Xinxin; Lind, Morten; Ravn, Ole

    2013-01-01

    Consequence reasoning is a major element for operation support system to assess the plant situations. The purpose of this paper is to elaborate how Multilevel Flow Models can be used to reason about consequences of disturbances in complex engineering systems. MFM is a modelling methodology...... for representing process knowledge for complex systems. It represents the system by using means-end and part-whole decompositions, and describes not only the purposes and functions of the system but also the causal relations between them. Thus MFM is a tool for causal reasoning. The paper introduces MFM modelling...... syntax and gives detailed reasoning formulas for consequence reasoning. The reasoning formulas offers basis for developing rule-based system to perform consequence reasoning based on MFM, which can be used for alarm design, risk monitoring, and supervision and operation support system design....

  8. Multilevel Modeling of the Performance Variance

    Directory of Open Access Journals (Sweden)

    Alexandre Teixeira Dias

    2012-12-01

    Full Text Available Focusing on the identification of the role played by Industry on the relations between Corporate Strategic Factors and Performance, the hierarchical multilevel modeling method was adopted when measuring and analyzing the relations between the variables that comprise each level of analysis. The adequacy of the multilevel perspective to the study of the proposed relations was identified and the relative importance analysis point out to the lower relevance of industry as a moderator of the effects of corporate strategic factors on performance, when the latter was measured by means of return on assets, and that industry don‟t moderates the relations between corporate strategic factors and Tobin‟s Q. The main conclusions of the research are that the organizations choices in terms of corporate strategy presents a considerable influence and plays a key role on the determination of performance level, but that industry should be considered when analyzing the performance variation despite its role as a moderator or not of the relations between corporate strategic factors and performance.

  9. Generalized latent variable modeling multilevel, longitudinal, and structural equation models

    CERN Document Server

    Skrondal, Anders

    2004-01-01

    METHODOLOGY THE OMNI-PRESENCE OF LATENT VARIABLES Introduction 'True' variable measured with error Hypothetical constructs Unobserved heterogeneity Missing values and counterfactuals Latent responses Generating flexible distributions Combining information Summary MODELING DIFFERENT RESPONSE PROCESSES Introduction Generalized linear models Extensions of generalized linear models Latent response formulation Modeling durations or survival Summary and further reading CLASSICAL LATENT VARIABLE MODELS Introduction Multilevel regression models Factor models and item respons

  10. Multilevel Higher-Order Item Response Theory Models

    Science.gov (United States)

    Huang, Hung-Yu; Wang, Wen-Chung

    2014-01-01

    In the social sciences, latent traits often have a hierarchical structure, and data can be sampled from multiple levels. Both hierarchical latent traits and multilevel data can occur simultaneously. In this study, we developed a general class of item response theory models to accommodate both hierarchical latent traits and multilevel data. The…

  11. National INFOSEC technical baseline: multi-level secure systems

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, J P

    1998-09-28

    The purpose of this report is to provide a baseline description of the state of multilevel processor/processing to the INFOSEC Research Council and at their discretion to the R&D community at large. From the information in the report, it is hoped that the members of the IRC will be aware of gaps in MLS research. A primary purpose is to bring IRC and the research community members up to date on what is happening in the MLS arena. The review will attempt to cover what MLS products are still available, and to identify companies who still offer MLS products. We have also attempted to identify requirements for MLS by interviewing senior officers of the Intelligence community as well as those elements of DoD and DOE who are or may be interested in procuring MLS products for various applications. The balance of the report consists of the following sections; a background review of the highlights of the developments of MLS, a quick summary of where we are today in terms of products, installations, and companies who are still in the business of supplying MLS systems [or who are developing MLS system], the requirements as expressed by senior members of the Intelligence community and DoD and DOE, issues and unmet R&D challenges surrounding MLS, and finally a set of recommended research topics.

  12. [Applying multilevel models in evaluation of bioequivalence (I)].

    Science.gov (United States)

    Liu, Qiao-lan; Shen, Zhuo-zhi; Chen, Feng; Li, Xiao-song; Yang, Min

    2009-12-01

    This study aims to explore the application value of multilevel models for bioequivalence evaluation. Using a real example of 2 x 4 cross-over experimental design in evaluating bioequivalence of antihypertensive drug, this paper explores complex variance components corresponding to criteria statistics in existing methods recommended by FDA but obtained in multilevel models analysis. Results are compared with those from FDA standard Method of Moments, specifically on the feasibility and applicability of multilevel models in directly assessing the bioequivalence (ABE), the population bioequivalence (PBE) and the individual bioequivalence (IBE). When measuring ln (AUC), results from all variance components of the test and reference groups such as total variance (sigma(TT)(2) and sigma(TR)(2)), between-subject variance (sigma(BT)(2) and sigma(BR)(2)) and within-subject variance (sigma(WT)(2) and sigma(WR)(2)) estimated by simple 2-level models are very close to those that using the FDA Method of Moments. In practice, bioequivalence evaluation can be carried out directly by multilevel models, or by FDA criteria, based on variance components estimated from multilevel models. Both approaches produce consistent results. Multilevel models can be used to evaluate bioequivalence in cross-over test design. Compared to FDA methods, this one is more flexible in decomposing total variance into sub components in order to evaluate the ABE, PBE and IBE. Multilevel model provides a new way into the practice of bioequivalence evaluation.

  13. Multilevel modeling in the context of growth modeling

    NARCIS (Netherlands)

    Moerbeek, Mirjam

    2014-01-01

    Multilevel modeling is a flexible approach for the analysis of nested data structures, such as those encountered in longitudinal studies with repeated measures of an outcome of interest taken across time and nested within subjects. The baseline score on the outcome and rate of change vary across sub

  14. Detection and Resolution of Deadlocks in Multi-Level Secure Databases

    Directory of Open Access Journals (Sweden)

    Pooja Sapra

    2013-06-01

    Full Text Available The increase in the sharing of databases leads to the increase in the concurrency errors, which are termed as deadlocks. Many concurrency control techniques result in deadlocks, because these techniques require the transactions in the system to wait for one another. At this situation, an outside intervention is often required to resume the normal working. Therefore, some special procedures are needed to resolve the deadlock situation. A multilevel secure database protects the classified information from unauthorized users based on the classification of the data and clearance of the users. If we addmultilevel security to databases then the system becomes more complicated and it becomes mandatory for us to resolve the problem like deadlock and concurrency. In these systems, there should be no covert channel and starvation during the coordination of transaction in secure databases. Here we present an algorithm for deadlock detection and recovery in multilevel secure database. The proposed algorithm takes into consideration the requirements and terminates the youngest transaction possible according to the security classes available.

  15. Dendritic growth model of multilevel marketing

    Science.gov (United States)

    Pang, James Christopher S.; Monterola, Christopher P.

    2017-02-01

    Biologically inspired dendritic network growth is utilized to model the evolving connections of a multilevel marketing (MLM) enterprise. Starting from agents at random spatial locations, a network is formed by minimizing a distance cost function controlled by a parameter, termed the balancing factor bf, that weighs the wiring and the path length costs of connection. The paradigm is compared to an actual MLM membership data and is shown to be successful in statistically capturing the membership distribution, better than the previously reported agent based preferential attachment or analytic branching process models. Moreover, it recovers the known empirical statistics of previously studied MLM, specifically: (i) a membership distribution characterized by the existence of peak levels indicating limited growth, and (ii) an income distribution obeying the 80 - 20 Pareto principle. Extensive types of income distributions from uniform to Pareto to a "winner-take-all" kind are also modeled by varying bf. Finally, the robustness of our dendritic growth paradigm to random agent removals is explored and its implications to MLM income distributions are discussed.

  16. A Technique to improve Security of Data in Multilevel Trust

    Directory of Open Access Journals (Sweden)

    Dr. T. Jebarajan

    2014-05-01

    Full Text Available The Privacy Preserving Data Mining technique that is used widely to conserve security of data is a random perturbation method. The original data is modified and many copies are created according to the trust levels in each field. The addition of noise level also varies with each trust level. The amount of noise added to the lower order trust level is less, whereas it is high in the higher order trust level. There is a chance for the hackers to reconstruct the original data with some non linear techniques. This challenge is addressed by the proposal of a novel non linear technique. Here, the noise level of each copy is checked after perturbation of the actual data. If any similarity is found in the noise level, reconstruction of the original data is possible. Therefore, additional noise is included in the perturbed data. This process is repeated till zero percent of similarity of data is attained.

  17. The Sage handbook of multilevel modeling

    CERN Document Server

    Scott, Marc A; Marx, Brian D

    2013-01-01

    Leading contributors combine practical pieces with overviews of the state of the art in the field, making this handbook essential reading for any student or researcher looking to apply multilevel techniques in their own research

  18. 移动环境中多级网络安全切换策略设计%Security handover policy design in multilevel mobile environments

    Institute of Scientific and Technical Information of China (English)

    邢洪智; 罗颖; 罗长远; 霍士伟

    2011-01-01

    Mobile users utilize various accessing technologies to connect next generation mobile internet, which is composed by multiple heterogeneous networks.The networks of different security levels make it difficult to manage access control and handover.A multilevel network handover model is set up in this paper to analyze the handover security problem.In order to solve the security problem in continuous handovers, security handover policies are brought forward based on Multilevel Secu rity (MLS) policy.lt proves the security policies using formal methods.%将异构移动网络抽象成多级网络模型,将多级安全引入切换过程,设计了基于MLS(Multilevel Security)的安全切换策略.该策略针对用户连续切换产生的信息泄露问题,规定保证安全等级不降低的约束条件,保证切换过程中用户与网络的安全,并且与其他方案相比,能够提供更全面的安全保护.经形式化证明,该策略是安全的.

  19. Finite-key security analysis for multilevel quantum key distribution

    Science.gov (United States)

    Brádler, Kamil; Mirhosseini, Mohammad; Fickler, Robert; Broadbent, Anne; Boyd, Robert

    2016-07-01

    We present a detailed security analysis of a d-dimensional quantum key distribution protocol based on two and three mutually unbiased bases (MUBs) both in an asymptotic and finite-key-length scenario. The finite secret key rates (in bits per detected photon) are calculated as a function of the length of the sifted key by (i) generalizing the uncertainly relation-based insight from BB84 to any d-level 2-MUB QKD protocol and (ii) by adopting recent advances in the second-order asymptotics for finite block length quantum coding (for both d-level 2- and 3-MUB QKD protocols). Since the finite and asymptotic secret key rates increase with d and the number of MUBs (together with the tolerable threshold) such QKD schemes could in principle offer an important advantage over BB84. We discuss the possibility of an experimental realization of the 3-MUB QKD protocol with the orbital angular momentum degrees of freedom of photons.

  20. An Adaptive Multilevel Security Framework for the Data Stored in Cloud Environment.

    Science.gov (United States)

    Dorairaj, Sudha Devi; Kaliannan, Thilagavathy

    2015-01-01

    Cloud computing is renowned for delivering information technology services based on internet. Nowadays, organizations are interested in moving their massive data and computations into cloud to reap their significant benefits of on demand service, resource pooling, and rapid elasticity that helps to satisfy the dynamically changing infrastructure demand without the burden of owning, managing, and maintaining it. Since the data needs to be secured throughout its life cycle, security of the data in cloud is a major challenge to be concentrated on because the data is in third party's premises. Any uniform simple or high level security method for all the data either compromises the sensitive data or proves to be too costly with increased overhead. Any common multiple method for all data becomes vulnerable when the common security pattern is identified at the event of successful attack on any information and also encourages more attacks on all other data. This paper suggests an adaptive multilevel security framework based on cryptography techniques that provide adequate security for the classified data stored in cloud. The proposed security system acclimates well for cloud environment and is also customizable and more reliant to meet the required level of security of data with different sensitivity that changes with business needs and commercial conditions.

  1. Multilevel random effect and marginal models for longitudinal data ...

    African Journals Online (AJOL)

    Multilevel random effect and marginal models for longitudinal data. ... Ethiopian Journal of Science and Technology ... the occurrence of specific adverse events than children injected with licensed vaccine, and if so, to quantify the difference.

  2. 基于角色的多级安全政策%Role based multi-level security polices

    Institute of Scientific and Technical Information of China (English)

    李双; 袁丁

    2012-01-01

    A role based multi-level security policy (RBMLS) is presented, which combines Role Based Access Control (RBAC) and Multi-level Security (MLS) to realize access control in the mandatory and discretionary mode. RBMLS replaces the Unclassi-fication (K) in Bell-LaPadula model by Local Role (LR) and introduces the Origin classification (O). The new policy could realize information' s bidirectional flow between the different class subjects and objects. Through the Origin classification (O). the separation between original data and foreign data can be realized, which guarantees the integrity of data.%提出一种基于角色的多级安全政策( RBMLS),将基于角色的访问控制模型(RBAC)与多级安全政策(MLS)结合起来,实现在自主中渗透着强制,在强制中蕴涵着自主的访问控制.该RBMLS将Bell-LaPadula模型中的非等级分类级别K替换为局部角色LR,并引入来源分类O,既可以实现等级分类级别不同的主客体信息之间的互动,又可实现原有数据和外来数据的有效分离,极大程度保证了数据的完整性.

  3. [Application of multilevel models in the evaluation of bioequivalence (II).].

    Science.gov (United States)

    Liu, Qiao-lan; Shen, Zhuo-zhi; Li, Xiao-song; Chen, Feng; Yang, Min

    2010-03-01

    The main purpose of this paper is to explore the applicability of multivariate multilevel models for bioequivalence evaluation. Using an example of a 4 x 4 cross-over test design in evaluating bioequivalence of homemade and imported rosiglitazone maleate tablets, this paper illustrated the multivariate-model-based method for partitioning total variances of ln(AUC) and ln(C(max)) in the framework of multilevel models. It examined the feasibility of multivariate multilevel models in directly evaluating average bioequivalence (ABE), population bioequivalence (PBE) and individual bioequivalence (IBE). Taking into account the correlation between ln(AUC) and ln(C(max)) of rosiglitazone maleate tablets, the proposed models suggested no statistical difference between the two effect measures in their ABE bioequivalence via joint tests, whilst a contradictive conclusion was derived based on univariate multilevel models. Furthermore, the PBE and IBE for both ln(AUC) and ln(C(max)) of the two types of tablets were assessed with no statistical difference based on estimates of variance components from the proposed models. Multivariate multilevel models could be used to analyze bioequivalence of multiple effect measures simultaneously and they provided a new way of statistical analysis to evaluate bioequivalence.

  4. Multilevel modelling of mechanical properties of textile composites: ITOOL Project

    NARCIS (Netherlands)

    Van Den Broucke, Bjorn; Drechsler, Klaus; Hanisch, Vera; Hartung, Daniel; Ivanov, Dimitry S.; Koissin, Vitaly E.; Lomov, Stepan V.; Middendorf, Peter

    2007-01-01

    The paper presents an overview of the multi-level modelling of textile composites in the ITOOL project, focusing on the models of textile reinforcements, which serve as a basis for micromechanical models of textile composites on the unit cell level. The modelling is performed using finite element an

  5. An Access Control Model of Virtual Machine Security

    Directory of Open Access Journals (Sweden)

    QIN Zhong-yuan

    2013-07-01

    Full Text Available Virtualization technology becomes a hot IT technolo gy with the popu-larity of Cloud Computing. However, new security issues arise with it. Specifically, the resources sharing and data communication in virtual machines are most con cerned. In this paper an access control model is proposed which combines the Chinese Wall a nd BLP model. BLP multi-level security model is introduced with corresponding improvement based on PCW (Prioritized Chinese Wall security model. This model can be used to safely co ntrol the resources and event behaviors in virtual machines. Experimental results show its eff ectiveness and safety.

  6. Economic sustainability, water security and multi-level governance of local water schemes in Nepal

    Directory of Open Access Journals (Sweden)

    Emma Hakala

    2017-07-01

    Full Text Available This article explores the role of multi-level governance and power structures in local water security through a case study of the Nawalparasi district in Nepal. It focuses on economic sustainability as a measure to address water security, placing this thematic in the context of a complicated power structure consisting of local, district and national administration as well as external development cooperation actors. The study aims to find out whether efforts to improve the economic sustainability of water schemes have contributed to water security at the local level. In addition, it will consider the interactions between water security, power structures and local equality and justice. The research builds upon survey data from the Nepalese districts of Nawalparasi and Palpa, and a case study based on interviews and observation in Nawalparasi. The survey was performed in water schemes built within a Finnish development cooperation programme spanning from 1990 to 2004, allowing a consideration of the long-term sustainability of water management projects. This adds a crucial external influence into the intra-state power structures shaping water management in Nepal. The article thus provides an alternative perspective to cross-regional water security through a discussion combining transnational involvement with national and local points of view.

  7. The social relations model for family data : A multilevel approach

    NARCIS (Netherlands)

    Snijders, TAB; Kenny, DA

    1999-01-01

    Multilevel models are proposed to study relational or dyadic data from multiple persons in families or other groups. The variable under study is assumed to refer to a dyadic relation between individuals in the groups. The proposed models are elaborations of the Social Relations Model. The different

  8. Hierarchical Data Structures, Institutional Research, and Multilevel Modeling

    Science.gov (United States)

    O'Connell, Ann A.; Reed, Sandra J.

    2012-01-01

    Multilevel modeling (MLM), also referred to as hierarchical linear modeling (HLM) or mixed models, provides a powerful analytical framework through which to study colleges and universities and their impact on students. Due to the natural hierarchical structure of data obtained from students or faculty in colleges and universities, MLM offers many…

  9. Comparisons of Estimation Procedures for Nonlinear Multilevel Models

    Directory of Open Access Journals (Sweden)

    Ali Reza Fotouhi

    2003-05-01

    Full Text Available We introduce General Multilevel Models and discuss the estimation procedures that may be used to fit multilevel models. We apply the proposed procedures to three-level binary data generated in a simulation study. We compare the procedures by two criteria, Bias and efficiency. We find that the estimates of the fixed effects and variance components are substantially and significantly biased using Longford's Approximation and Goldstein's Generalized Least Squares approaches by two software packages VARCL and ML3. These estimates are not significantly biased and are very close to real values when we use Markov Chain Monte Carlo (MCMC using Gibbs sampling or Nonparametric Maximum Likelihood (NPML approach. The Gaussian Quadrature (GQ approach, even with small number of mass points results in consistent estimates but computationally problematic. We conclude that the MCMC and the NPML approaches are the recommended procedures to fit multilevel models.

  10. Using multilevel models to quantify heterogeneity in resource selection

    Science.gov (United States)

    Wagner, T.; Diefenbach, D.R.; Christensen, S.A.; Norton, A.S.

    2011-01-01

    Models of resource selection are being used increasingly to predict or model the effects of management actions rather than simply quantifying habitat selection. Multilevel, or hierarchical, models are an increasingly popular method to analyze animal resource selection because they impose a relatively weak stochastic constraint to model heterogeneity in habitat use and also account for unequal sample sizes among individuals. However, few studies have used multilevel models to model coefficients as a function of predictors that may influence habitat use at different scales or quantify differences in resource selection among groups. We used an example with white-tailed deer (Odocoileus virginianus) to illustrate how to model resource use as a function of distance to road that varies among deer by road density at the home range scale. We found that deer avoidance of roads decreased as road density increased. Also, we used multilevel models with sika deer (Cervus nippon) and white-tailed deer to examine whether resource selection differed between species. We failed to detect differences in resource use between these two species and showed how information-theoretic and graphical measures can be used to assess how resource use may have differed. Multilevel models can improve our understanding of how resource selection varies among individuals and provides an objective, quantifiable approach to assess differences or changes in resource selection. ?? The Wildlife Society, 2011.

  11. Concorde and Discord: The Art of Multilevel Modelling

    Science.gov (United States)

    Hutchison, Dougal; Schagen, Ian

    2008-01-01

    A recent issue of "International Journal of Research & Methods in Education" (IJRME) contained a challenging article by Stephen Gorard ["The Dubious Benefits of Multi-Level Modelling," "International Journal of Research & Method in Education," Vol. 30 (2), p221-236 (2007)] in which he attacks aspects of current practice in statistical modelling,…

  12. Examining Elementary Social Studies Marginalization: A Multilevel Model

    Science.gov (United States)

    Fitchett, Paul G.; Heafner, Tina L.; Lambert, Richard G.

    2014-01-01

    Utilizing data from the National Center for Education Statistics Schools and Staffing Survey (SASS), a multilevel model (Hierarchical Linear Model) was developed to examine the association of teacher/classroom and state level indicators on reported elementary social studies instructional time. Findings indicated that state testing policy was a…

  13. Illustration of a Multilevel Model for Meta-Analysis

    Science.gov (United States)

    de la Torre, Jimmy; Camilli, Gregory; Vargas, Sadako; Vernon, R. Fox

    2007-01-01

    In this article, the authors present a multilevel (or hierarchical linear) model that illustrates issues in the application of the model to data from meta-analytic studies. In doing so, several issues are discussed that typically arise in the course of a meta-analysis. These include the presence of non-zero between-study variability, how multiple…

  14. Hazard identification by extended multilevel flow modelling with function roles

    DEFF Research Database (Denmark)

    Wu, Jing; Zhang, Laibin; Jørgensen, Sten Bay

    2014-01-01

    HAZOP studies are widely accepted in chemical and petroleum industries as the method for conducting process hazard analysis related to design, maintenance and operation of th e systems. In this paper, a HAZOP reasoning method based on function-oriented modelling, multilevel flow modelling (MFM) i...

  15. Concorde and Discord: The Art of Multilevel Modelling

    Science.gov (United States)

    Hutchison, Dougal; Schagen, Ian

    2008-01-01

    A recent issue of "International Journal of Research & Methods in Education" (IJRME) contained a challenging article by Stephen Gorard ["The Dubious Benefits of Multi-Level Modelling," "International Journal of Research & Method in Education," Vol. 30 (2), p221-236 (2007)] in which he attacks aspects of current practice in statistical modelling,…

  16. Evaluation of model fit in nonlinear multilevel structural equation modeling

    Directory of Open Access Journals (Sweden)

    Karin eSchermelleh-Engel

    2014-03-01

    Full Text Available Evaluating model fit in nonlinear multilevel structural equation models (MSEM presents a challenge as no adequate test statistic is available. Nevertheless, using a product indicator approach a likelihood ratio test for linear models is provided which may also be useful for nonlinear MSEM. The main problem with nonlinear models is that product variables are nonnormally distributed. Although robust test statistics have been developed for linear SEM to ensure valid results under the condition of nonnormality, they were not yet investigated for nonlinear MSEM. In a Monte Carlo study, the performance of the robust likelihood ratio test was investigated for models with single-level latent interaction effects using the unconstrained product indicator approach. As overall model fit evaluation has a potential limitation in detecting the lack of fit at a single level even for linear models, level-specific model fit evaluation was also investigated using partially saturated models. Four population models were considered: a model with interaction effects at both levels, an interaction effect at the within-group level, an interaction effect at the between-group level, and a model with no interaction effects at both levels. For these models the number of groups, predictor correlation, and model misspecification was varied. The results indicate that the robust test statistic performed sufficiently well. Advantages of level-specific model fit evaluation for the detection of model misfit are demonstrated.

  17. Evaluation of model fit in nonlinear multilevel structural equation modeling.

    Science.gov (United States)

    Schermelleh-Engel, Karin; Kerwer, Martin; Klein, Andreas G

    2014-01-01

    Evaluating model fit in nonlinear multilevel structural equation models (MSEM) presents a challenge as no adequate test statistic is available. Nevertheless, using a product indicator approach a likelihood ratio test for linear models is provided which may also be useful for nonlinear MSEM. The main problem with nonlinear models is that product variables are non-normally distributed. Although robust test statistics have been developed for linear SEM to ensure valid results under the condition of non-normality, they have not yet been investigated for nonlinear MSEM. In a Monte Carlo study, the performance of the robust likelihood ratio test was investigated for models with single-level latent interaction effects using the unconstrained product indicator approach. As overall model fit evaluation has a potential limitation in detecting the lack of fit at a single level even for linear models, level-specific model fit evaluation was also investigated using partially saturated models. Four population models were considered: a model with interaction effects at both levels, an interaction effect at the within-group level, an interaction effect at the between-group level, and a model with no interaction effects at both levels. For these models the number of groups, predictor correlation, and model misspecification was varied. The results indicate that the robust test statistic performed sufficiently well. Advantages of level-specific model fit evaluation for the detection of model misfit are demonstrated.

  18. Multilevel Modeling: Overview and Applications to Research in Counseling Psychology

    Science.gov (United States)

    Kahn, Jeffrey H.

    2011-01-01

    Multilevel modeling (MLM) is rapidly becoming the standard method of analyzing nested data, for example, data from students within multiple schools, data on multiple clients seen by a smaller number of therapists, and even longitudinal data. Although MLM analyses are likely to increase in frequency in counseling psychology research, many readers…

  19. Multilevel Modeling: Overview and Applications to Research in Counseling Psychology

    Science.gov (United States)

    Kahn, Jeffrey H.

    2011-01-01

    Multilevel modeling (MLM) is rapidly becoming the standard method of analyzing nested data, for example, data from students within multiple schools, data on multiple clients seen by a smaller number of therapists, and even longitudinal data. Although MLM analyses are likely to increase in frequency in counseling psychology research, many readers…

  20. Multilevel Modeling of Science Achievement in the Timss Participating Countries

    Science.gov (United States)

    Mohammadpour, Ebrahim; Shekarchizadeh, Ahmadreza; Kalantarrashidi, Shojae Aldin

    2015-01-01

    The authors aimed to investigate the variability in science achievement as a function of student-, school- and country-level factors. Achievement scores of 134,123 eighth-grade students from 4,511 schools of 29 countries who participated in the 2007 Trends in International Mathematics and Science Study were analyzed. Multilevel modeling results…

  1. Application of Multilevel Models to Morphometric Data. Part 2. Correlations

    Directory of Open Access Journals (Sweden)

    O. Tsybrovskyy

    2003-01-01

    Full Text Available Multilevel organization of morphometric data (cells are “nested” within patients requires special methods for studying correlations between karyometric features. The most distinct feature of these methods is that separate correlation (covariance matrices are produced for every level in the hierarchy. In karyometric research, the cell‐level (i.e., within‐tumor correlations seem to be of major interest. Beside their biological importance, these correlation coefficients (CC are compulsory when dimensionality reduction is required. Using MLwiN, a dedicated program for multilevel modeling, we show how to use multivariate multilevel models (MMM to obtain and interpret CC in each of the levels. A comparison with two usual, “single‐level” statistics shows that MMM represent the only way to obtain correct cell‐level correlation coefficients. The summary statistics method (take average values across each patient produces patient‐level CC only, and the “pooling” method (merge all cells together and ignore patients as units of analysis yields incorrect CC at all. We conclude that multilevel modeling is an indispensable tool for studying correlations between morphometric variables.

  2. Information Security Maturity Model

    OpenAIRE

    Information Security Maturity Model

    2011-01-01

    To ensure security, it is important to build-in security in both the planning and the design phases andadapt a security architecture which makes sure that regular and security related tasks, are deployedcorrectly. Security requirements must be linked to the business goals. We identified four domains thataffect security at an organization namely, organization governance, organizational culture, thearchitecture of the systems, and service management. In order to identify and explore the strengt...

  3. [How to fit and interpret multilevel models using SPSS].

    Science.gov (United States)

    Pardo, Antonio; Ruiz, Miguel A; San Martín, Rafael

    2007-05-01

    Hierarchic or multilevel models are used to analyse data when cases belong to known groups and sample units are selected both from the individual level and from the group level. In this work, the multilevel models most commonly discussed in the statistic literature are described, explaining how to fit these models using the SPSS program (any version as of the 11 th ) and how to interpret the outcomes of the analysis. Five particular models are described, fitted, and interpreted: (1) one-way analysis of variance with random effects, (2) regression analysis with means-as-outcomes, (3) one-way analysis of covariance with random effects, (4) regression analysis with random coefficients, and (5) regression analysis with means- and slopes-as-outcomes. All models are explained, trying to make them understandable to researchers in health and behaviour sciences.

  4. SPICE modeling of memristors with multilevel resistance states

    Institute of Scientific and Technical Information of China (English)

    Fang Xu-Dong; Tang Yu-Hua; Wu Jun-Jie

    2012-01-01

    With CMOS technologies approaching the scaling ceiling,novel memory technologies have thrived in recent years,among which the memristor is a rather promising candidate for future resistive memory (RRAM).Memristor's potential to store multiple bits of information as different resistance levels allows its application in multilevel cell (MCL) technology,which can significantly increase the memory capacity.However,most existing memristor models are built for binary or continuous memristance switching.In this paper,we propose the simulation program with integrated circuits emphasis (SPICE) modeling of charge-controlled and flux-controlled memristors with multilevel resistance states based on the memristance versus state map.In our model,the memristance switches abruptly between neighboring resistance states.The proposed model allows users to easily set the number of the resistance levels as parameters,and provides the predictability of resistance switching time if the input current/voltage waveform is given.The functionality of our models has been validated in HSPICE.The models can be used in multilevel RRAM modeling as well as in artificial neural network simulations.

  5. Model-Based Security Testing

    CERN Document Server

    Schieferdecker, Ina; Schneider, Martin; 10.4204/EPTCS.80.1

    2012-01-01

    Security testing aims at validating software system requirements related to security properties like confidentiality, integrity, authentication, authorization, availability, and non-repudiation. Although security testing techniques are available for many years, there has been little approaches that allow for specification of test cases at a higher level of abstraction, for enabling guidance on test identification and specification as well as for automated test generation. Model-based security testing (MBST) is a relatively new field and especially dedicated to the systematic and efficient specification and documentation of security test objectives, security test cases and test suites, as well as to their automated or semi-automated generation. In particular, the combination of security modelling and test generation approaches is still a challenge in research and of high interest for industrial applications. MBST includes e.g. security functional testing, model-based fuzzing, risk- and threat-oriented testing,...

  6. The Effect of Perceived Instructional Effectiveness on Student Loyalty: A Multilevel Structural Equation Model

    Science.gov (United States)

    Simsek, Gulhayat Golbasi; Noyan, Fatma

    2009-01-01

    Social sciences research often entails the analysis of data with a multilevel structure. An example of multilevel data is containing measurement on university students nested within instructors. This paper concentrates on multilevel analysis of structural equation modeling with educational data. Data used in this study were gathered from 17647…

  7. Security Issues in Distributed Database System Model

    OpenAIRE

    MD.TABREZ QUASIM

    2013-01-01

    This paper reviews the most common as well as emerging security mechanism used in distributed database system. As distributed database became more popular, the need for improvement in distributed database management system become even more important. The most important issue is security that may arise and possibly compromise the access control and the integrity of the system. In this paper, we propose some solution for some security aspects such as multi-level access control, ...

  8. Analyzing the requirements for a robust security criteria and management of multi-level security in the clouds

    Science.gov (United States)

    Farroha, Bassam S.; Farroha, Deborah L.

    2011-06-01

    The new corporate approach to efficient processing and storage is migrating from in-house service-center services to the newly coined approach of Cloud Computing. This approach advocates thin clients and providing services by the service provider over time-shared resources. The concept is not new, however the implementation approach presents a strategic shift in the way organizations provision and manage their IT resources. The requirements on some of the data sets targeted to be run on the cloud vary depending on the data type, originator, user, and confidentiality level. Additionally, the systems that fuse such data would have to deal with the classifying the product and clearing the computing resources prior to allowing new application to be executed. This indicates that we could end up with a multi-level security system that needs to follow specific rules and can send the output to a protected network and systems in order not to have data spill or contaminated resources. The paper discusses these requirements and potential impact on the cloud architecture. Additionally, the paper discusses the unexpected advantages of the cloud framework providing a sophisticated environment for information sharing and data mining.

  9. Multilevel Flow Modeling for Nuclear Power Plant Diagnosis

    DEFF Research Database (Denmark)

    Gola, G; Thunem, Harald P-J; Thunem, Atoosa P-J

    2012-01-01

    As complexity and safety requirements of current and future nuclear power plants increase, innovative methods are being investigated to perform accurate and reliable system diagnoses. Detecting malfunctions, identifying their causes and possibly predicting their consequences are major challenges...... detected anomalies. The combination of a data reconciliation system and the Multilevel Flow Modeling approach is illustrated with regard to the secondary loop of the Loviisa-2 Pressurized Water Reactor located in Finland....

  10. Using time-varying covariates in multilevel growth models

    Directory of Open Access Journals (Sweden)

    D. Betsy McCoach

    2010-06-01

    Full Text Available This article provides an illustration of growth curve modeling within a multilevel framework. Specifically, we demonstrate coding schemes that allow the researcher to model discontinuous longitudinal data using a linear growth model in conjunction with time varying covariates. Our focus is on developing a level-1 model that accurately reflects the shape of the growth trajectory. We demonstrate the importance of adequately modeling the shape of the level-1 growth trajectory in order to make inferences about the importance of both level-1 and level-2 predictors.

  11. Multilevel flow modeling of Monju Nuclear Power Plant

    DEFF Research Database (Denmark)

    Lind, Morten; Yoshikawa, Hidekazu; Jørgensen, Sten Bay

    2011-01-01

    Multilevel Flow Modeling is a method for modeling complex processes on multiple levels of means-end and part-whole abstraction. The modeling method has been applied on a wide range of processes including power plants, chemical engineering plants and power systems. The modeling method is supported...... functions and structure. The paper will describe how MFM can be used to represent the goals and functions of the Japanese Monju Nuclear Power Plant. A detailed explanation will be given of the model describing the relations between levels of goal, function and structural. Furthermore, it will be explained...

  12. Multi-Level Data-Security and Data-Protection in a Distributed Search Infrastructure for Digital Medical Samples.

    Science.gov (United States)

    Witt, Michael; Krefting, Dagmar

    2016-01-01

    Human sample data is stored in biobanks with software managing digital derived sample data. When these stand-alone components are connected and a search infrastructure is employed users become able to collect required research data from different data sources. Data protection, patient rights, data heterogeneity and access control are major challenges for such an infrastructure. This dissertation will investigate concepts for a multi-level security architecture to comply with these requirements.

  13. Multilevel modeling: overview and applications to research in counseling psychology.

    Science.gov (United States)

    Kahn, Jeffrey H

    2011-04-01

    Multilevel modeling (MLM) is rapidly becoming the standard method of analyzing nested data, for example, data from students within multiple schools, data on multiple clients seen by a smaller number of therapists, and even longitudinal data. Although MLM analyses are likely to increase in frequency in counseling psychology research, many readers of counseling psychology journals have had only limited exposure to MLM concepts. This paper provides an overview of MLM that blends mathematical concepts with examples drawn from counseling psychology. This tutorial is intended to be a first step in learning about MLM; readers are referred to other sources for more advanced explorations of MLM. In addition to being a tutorial for understanding and perhaps even conducting MLM analyses, this paper reviews recent research in counseling psychology that has adopted a multilevel framework, and it provides ideas for MLM approaches to future research in counseling psychology.

  14. Mining multilevel spatial association rules with cloud models

    Institute of Scientific and Technical Information of China (English)

    YANG Bin; ZHU Zhong-ying

    2005-01-01

    The traditional generalization-based knowledge discovery method is introduced. A new kind of multilevel spatial association of the rules mining method based on the cloud model is presented. The cloud model integrates the vague and random use of linguistic terms in a unified way. With these models, spatial and nonspatial attribute values are well generalized at multiple levels, allowing discovery of strong spatial association rules.Combining the cloud model based method with Apriori algorithms for mining association rules from a spatial database shows benefits in being effective and flexible.

  15. Multi-level decision making models, methods and applications

    CERN Document Server

    Zhang, Guangquan; Gao, Ya

    2015-01-01

    This monograph presents new developments in multi-level decision-making theory, technique and method in both modeling and solution issues. It especially presents how a decision support system can support managers in reaching a solution to a multi-level decision problem in practice. This monograph combines decision theories, methods, algorithms and applications effectively. It discusses in detail the models and solution algorithms of each issue of bi-level and tri-level decision-making, such as multi-leaders, multi-followers, multi-objectives, rule-set-based, and fuzzy parameters. Potential readers include organizational managers and practicing professionals, who can use the methods and software provided to solve their real decision problems; PhD students and researchers in the areas of bi-level and multi-level decision-making and decision support systems; students at an advanced undergraduate, master’s level in information systems, business administration, or the application of computer science.  

  16. A model of security monitoring

    Science.gov (United States)

    Bishop, Matt

    1990-01-01

    A model of security monitoring is presented that distinguishes between two types of logging and auditing. Implications for the design and use of security monitoring mechanisms are drawn from this model. The usefulness of the model is then demonstrated by analyzing several different monitoring mechanisms.

  17. Generating WS-SecurityPolicy documents via security model transformation

    DEFF Research Database (Denmark)

    Jensen, Meiko

    2009-01-01

    When SOA-based business processes are to be enhanced with security properties, the model-driven business process development approach enables an easier and more reliable security definition compared to manually crafting the security realizations afterwards. In this paper, we outline an appropriate...... security model definition and transformation approach, targeting the WS-SecurityPolicy and WS-BPEL specifications, in order to enable a Web-Service-based secure business process development....

  18. Information risk and security modeling

    Science.gov (United States)

    Zivic, Predrag

    2005-03-01

    This research paper presentation will feature current frameworks to addressing risk and security modeling and metrics. The paper will analyze technical level risk and security metrics of Common Criteria/ISO15408, Centre for Internet Security guidelines, NSA configuration guidelines and metrics used at this level. Information IT operational standards view on security metrics such as GMITS/ISO13335, ITIL/ITMS and architectural guidelines such as ISO7498-2 will be explained. Business process level standards such as ISO17799, COSO and CobiT will be presented with their control approach to security metrics. Top level, the maturity standards such as SSE-CMM/ISO21827, NSA Infosec Assessment and CobiT will be explored and reviewed. For each defined level of security metrics the research presentation will explore the appropriate usage of these standards. The paper will discuss standards approaches to conducting the risk and security metrics. The research findings will demonstrate the need for common baseline for both risk and security metrics. This paper will show the relation between the attribute based common baseline and corporate assets and controls for risk and security metrics. IT will be shown that such approach spans over all mentioned standards. The proposed approach 3D visual presentation and development of the Information Security Model will be analyzed and postulated. Presentation will clearly demonstrate the benefits of proposed attributes based approach and defined risk and security space for modeling and measuring.

  19. An Adaptive Hybrid Multi-level Intelligent Intrusion Detection System for Network Security

    Directory of Open Access Journals (Sweden)

    P. Ananthi

    2014-04-01

    Full Text Available Intrusion Detection System (IDS plays a vital factor in providing security to the networks through detecting malicious activities. Due to the extensive advancements in the computer networking, IDS has become an active area of research to determine various types of attacks in the networks. A large number of intrusion detection approaches are available in the literature using several traditional statistical and data mining approaches. Data mining techniques in IDS observed to provide significant results. Data mining approaches for misuse and anomaly-based intrusion detection generally include supervised, unsupervised and outlier approaches. It is important that the efficiency and potential of IDS be updated based on the criteria of new attacks. This study proposes a novel Adaptive Hybrid Multi-level Intelligent IDS (AHMIIDS system which is the combined version of anomaly and misuse detection techniques. The anomaly detection is based on Bayesian Networks and then the misuse detection is performed using Adaptive Neuro Fuzzy Inference System (ANFIS. The outputs of both anomaly detection and misuse detection modules are applied to Decision Table Majority (DTM to perform the final decision making. A rule-base approach is used in this system. It is observed from the results that the proposed AHMIIDS performs better than other conventional hybrid IDS.

  20. Multilevel Flow Modelling of Process Plant for Diagnosis and Control

    DEFF Research Database (Denmark)

    Lind, Morten

    1982-01-01

    of complex systems. A model of a nuclear power plant (PWR) is presented in the paper for illustration. Due to the consistency of the method, multilevel flow models provide specifications of plant goals and functions and may be used as a basis for design of computer-based support systems for the plant...... operator. Plant control requirements can be derived from the models and due to independence of the actual controller implementation the method may be used as a basis for design of control strategies and for the allocation of control tasks to the computer and the plant operator....

  1. Knowledge Representation Using Multilevel Flow Model in Expert System

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wenlin; Yang, Ming [Harbin Engineering University, Harbin (China)

    2015-05-15

    As for the knowledge representation, of course, there are a great many methods available for knowledge representation. These include frames, causal models, and many others. This paper presents a novel method called Multilevel Flow Model (MFM), which is used for knowledge representation in G2 expert system. Knowledge representation plays a vital role in constructing knowledge bases. Moreover, it also has impact on building of generic fault model as well as knowledge bases. The MFM is particularly useful to describe system knowledge concisely as domain map in expert system when domain experts are not available.

  2. Building a multilevel modeling network for lipid processing systems

    DEFF Research Database (Denmark)

    Mustaffa, Azizul Azri; Díaz Tovar, Carlos Axel; Hukkerikar, Amol

    2011-01-01

    data collected from existing process plants, and application of validated models in design and analysis of unit operations; iv) the information and models developed are used as building blocks in the development of methods and tools for computer-aided synthesis and design of process flowsheets (CAFD......The aim of this work is to present the development of a computer aided multilevel modeling network for the systematic design and analysis of processes employing lipid technologies. This is achieved by decomposing the problem into four levels of modeling: i) pure component property modeling...... and a lipid-database of collected experimental data from industry and generated data from validated predictive property models, as well as modeling tools for fast adoption-analysis of property prediction models; ii) modeling of phase behavior of relevant lipid mixtures using the UNIFAC-CI model, development...

  3. Lipid Processing Technology: Building a Multilevel Modeling Network

    DEFF Research Database (Denmark)

    Díaz Tovar, Carlos Axel; Mustaffa, Azizul Azri; Mukkerikar, Amol

    2011-01-01

    in design and analysis of unit operations; iv) the information and models developed are used as building blocks in the development of methods and tools for computer-aided synthesis and design of process flowsheets (CAFD). The applicability of this methodology is highlighted in each level of modeling through......The aim of this work is to present the development of a computer aided multilevel modeling network for the systematic design and analysis of processes employing lipid technologies. This is achieved by decomposing the problem into four levels of modeling: i) pure component property modeling...... and a lipid-database of collected experimental data from industry and generated data from validated predictive property models, as well as modeling tools for fast adoption-analysis of property prediction models; ii) modeling of phase behavior of relevant lipid mixtures using the UNIFACCI model, development...

  4. Model-Based Security Testing

    Directory of Open Access Journals (Sweden)

    Ina Schieferdecker

    2012-02-01

    Full Text Available Security testing aims at validating software system requirements related to security properties like confidentiality, integrity, authentication, authorization, availability, and non-repudiation. Although security testing techniques are available for many years, there has been little approaches that allow for specification of test cases at a higher level of abstraction, for enabling guidance on test identification and specification as well as for automated test generation. Model-based security testing (MBST is a relatively new field and especially dedicated to the systematic and efficient specification and documentation of security test objectives, security test cases and test suites, as well as to their automated or semi-automated generation. In particular, the combination of security modelling and test generation approaches is still a challenge in research and of high interest for industrial applications. MBST includes e.g. security functional testing, model-based fuzzing, risk- and threat-oriented testing, and the usage of security test patterns. This paper provides a survey on MBST techniques and the related models as well as samples of new methods and tools that are under development in the European ITEA2-project DIAMONDS.

  5. Modeling Leadership Hierarchy in Multilevel Animal Societies

    CERN Document Server

    Ozogány, Katalin

    2014-01-01

    A typical feature of many natural and social networks is the presence of communities giving rise to multiple levels of organization. We investigate the decision-making process of a group combining self organization and social dynamics, and reproduce the simultaneous emergence of a hierarchical and modular leadership network. All individuals in the model try, with varying degrees of ability, to find a direction of movement, with the result that leader-follower relationships evolve between them, since they tend to follow the more successful ones. The harem-forming ambitions of male individuals inspired by an observed Przewalski horse herd (Hortob\\'agy, Hungary) leads to modular structure. In this approach we find that the harem-leader to harem-member ratio observed in horses corresponds to an optimal network regarding common success, and that modularly structured hierarchy is more benefical than a non-modular one, in the sense that common success is higher, and the underlying network is more hierarchical. We al...

  6. Multi-level spherical moments based 3D model retrieval

    Institute of Scientific and Technical Information of China (English)

    LIU Wei; HE Yuan-jun

    2006-01-01

    In this paper a novel 3D model retrieval method that employs multi-level spherical moment analysis and relies on voxelization and spherical mapping of the 3D models is proposed. For a given polygon-soup 3D model, first a pose normalization step is done to align the model into a canonical coordinate frame so as to define the shape representation with respect to this orientation. Afterward we rasterize its exterior surface into cubical voxel grids, then a series of homocentric spheres with their center superposing the center of the voxel grids cut the voxel grids into several spherical images. Finally moments belonging to each sphere are computed and the moments of all spheres constitute the descriptor of the model. Experiments showed that Euclidean distance based on this kind of feature vector can distinguish different 3D models well and that the 3D model retrieval system based on this arithmetic yields satisfactory performance.

  7. Campus network security model study

    Science.gov (United States)

    Zhang, Yong-ku; Song, Li-ren

    2011-12-01

    Campus network security is growing importance, Design a very effective defense hacker attacks, viruses, data theft, and internal defense system, is the focus of the study in this paper. This paper compared the firewall; IDS based on the integrated, then design of a campus network security model, and detail the specific implementation principle.

  8. Threat modeling designing for security

    CERN Document Server

    Shostack, Adam

    2014-01-01

    Adam Shostack is responsible for security development lifecycle threat modeling at Microsoft and is one of a handful of threat modeling experts in the world. Now, he is sharing his considerable expertise into this unique book. With pages of specific actionable advice, he details how to build better security into the design of systems, software, or services from the outset. You'll explore various threat modeling approaches, find out how to test your designs against threats, and learn effective ways to address threats that have been validated at Microsoft and other top companies. Systems secur

  9. Efficient multilevel brain tumor segmentation with integrated bayesian model classification.

    Science.gov (United States)

    Corso, J J; Sharon, E; Dube, S; El-Saden, S; Sinha, U; Yuille, A

    2008-05-01

    We present a new method for automatic segmentation of heterogeneous image data that takes a step toward bridging the gap between bottom-up affinity-based segmentation methods and top-down generative model based approaches. The main contribution of the paper is a Bayesian formulation for incorporating soft model assignments into the calculation of affinities, which are conventionally model free. We integrate the resulting model-aware affinities into the multilevel segmentation by weighted aggregation algorithm, and apply the technique to the task of detecting and segmenting brain tumor and edema in multichannel magnetic resonance (MR) volumes. The computationally efficient method runs orders of magnitude faster than current state-of-the-art techniques giving comparable or improved results. Our quantitative results indicate the benefit of incorporating model-aware affinities into the segmentation process for the difficult case of glioblastoma multiforme brain tumor.

  10. Using Visual Analysis to Evaluate and Refine Multilevel Models of Single-Case Studies

    Science.gov (United States)

    Baek, Eun Kyeng; Petit-Bois, Merlande; Van den Noortgate, Wim; Beretvas, S. Natasha; Ferron, John M.

    2016-01-01

    In special education, multilevel models of single-case research have been used as a method of estimating treatment effects over time and across individuals. Although multilevel models can accurately summarize the effect, it is known that if the model is misspecified, inferences about the effects can be biased. Concern with the potential for model…

  11. Key Management for Multilevel Security in Distributed Applications%分布式应用中的多级安全密钥管理

    Institute of Scientific and Technical Information of China (English)

    卿斯汉; 蒙杨; 刘克龙

    2001-01-01

    本文提出一种分布式应用中的多级安全密钥管理体制,该体制采用BELL-LaPadula模型作为多级安全存取控制策略,利用中国剩余定理,引入“主密钥因子”,“次密钥因子”,“写入因子”,构造会话密钥的共享信息,该体制具有高效,安全,动态的特点.这种体制有广泛的应用前景,有效的解决了网上会议,网上讨论等实际应用中的密钥管理问题.%A key management scheme for multilevel security in distributedapplications is presented.The scheme adopts BELL-LaPadula model as multilevel access control policies.We use Chinese Remainder Theorem,introduce the notions of first-secret-key-element,second-secret-key-element and writing-element,and construct sharing information of session key.The scheme is efficient,secure and dynamic.At the same time,there are many practical applications involving the scheme for key management such as meeting in the network and talking in the network etc.

  12. Generating WS-SecurityPolicy documents via security model transformation

    DEFF Research Database (Denmark)

    Jensen, Meiko

    2009-01-01

    When SOA-based business processes are to be enhanced with security properties, the model-driven business process development approach enables an easier and more reliable security definition compared to manually crafting the security realizations afterwards. In this paper, we outline an appropriat...... security model definition and transformation approach, targeting the WS-SecurityPolicy and WS-BPEL specifications, in order to enable a Web-Service-based secure business process development.......When SOA-based business processes are to be enhanced with security properties, the model-driven business process development approach enables an easier and more reliable security definition compared to manually crafting the security realizations afterwards. In this paper, we outline an appropriate...

  13. Process Models for Security Architectures

    Directory of Open Access Journals (Sweden)

    Floarea NASTASE

    2006-01-01

    Full Text Available This paper presents a model for an integrated security system, which can be implemented in any organization. It is based on security-specific standards and taxonomies as ISO 7498-2 and Common Criteria. The functionalities are derived from the classes proposed in the Common Criteria document. In the paper we present the process model for each functionality and also we focus on the specific components.

  14. Security Issues in Distributed Database System Model

    Directory of Open Access Journals (Sweden)

    MD.TABREZ QUASIM

    2013-12-01

    Full Text Available This paper reviews the most common as well as emerging security mechanism used in distributed database system. As distributed database became more popular, the need for improvement in distributed database management system become even more important. The most important issue is security that may arise and possibly compromise the access control and the integrity of the system. In this paper, we propose some solution for some security aspects such as multi-level access control, confidentiality, reliability, integrity and recovery that pertain to a distributed database system.

  15. Sample Size Limits for Estimating Upper Level Mediation Models Using Multilevel SEM

    Science.gov (United States)

    Li, Xin; Beretvas, S. Natasha

    2013-01-01

    This simulation study investigated use of the multilevel structural equation model (MLSEM) for handling measurement error in both mediator and outcome variables ("M" and "Y") in an upper level multilevel mediation model. Mediation and outcome variable indicators were generated with measurement error. Parameter and standard…

  16. Fitting Multilevel Models with Ordinal Outcomes: Performance of Alternative Specifications and Methods of Estimation

    Science.gov (United States)

    Bauer, Daniel J.; Sterba, Sonya K.

    2011-01-01

    Previous research has compared methods of estimation for fitting multilevel models to binary data, but there are reasons to believe that the results will not always generalize to the ordinal case. This article thus evaluates (a) whether and when fitting multilevel linear models to ordinal outcome data is justified and (b) which estimator to employ…

  17. Detailed Modeling and Evaluation of a Scalable Multilevel Checkpointing System

    Energy Technology Data Exchange (ETDEWEB)

    Mohror, Kathryn [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Moody, Adam [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bronevetsky, Greg [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); de Supinski, Bronis R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-09-01

    High-performance computing (HPC) systems are growing more powerful by utilizing more components. As the system mean time before failure correspondingly drops, applications must checkpoint frequently to make progress. But, at scale, the cost of checkpointing becomes prohibitive. A solution to this problem is multilevel checkpointing, which employs multiple types of checkpoints in a single run. Moreover, lightweight checkpoints can handle the most common failure modes, while more expensive checkpoints can handle severe failures. We designed a multilevel checkpointing library, the Scalable Checkpoint/Restart (SCR) library, that writes lightweight checkpoints to node-local storage in addition to the parallel file system. We present probabilistic Markov models of SCR's performance. We show that on future large-scale systems, SCR can lead to a gain in machine efficiency of up to 35 percent, and reduce the load on the parallel file system by a factor of two. In addition, we predict that checkpoint scavenging, or only writing checkpoints to the parallel file system on application termination, can reduce the load on the parallel file system by 20 × on today's systems and still maintain high application efficiency.

  18. Three essays on multi-level optimization models and applications

    Science.gov (United States)

    Rahdar, Mohammad

    The general form of a multi-level mathematical programming problem is a set of nested optimization problems, in which each level controls a series of decision variables independently. However, the value of decision variables may also impact the objective function of other levels. A two-level model is called a bilevel model and can be considered as a Stackelberg game with a leader and a follower. The leader anticipates the response of the follower and optimizes its objective function, and then the follower reacts to the leader's action. The multi-level decision-making model has many real-world applications such as government decisions, energy policies, market economy, network design, etc. However, there is a lack of capable algorithms to solve medium and large scale these types of problems. The dissertation is devoted to both theoretical research and applications of multi-level mathematical programming models, which consists of three parts, each in a paper format. The first part studies the renewable energy portfolio under two major renewable energy policies. The potential competition for biomass for the growth of the renewable energy portfolio in the United States and other interactions between two policies over the next twenty years are investigated. This problem mainly has two levels of decision makers: the government/policy makers and biofuel producers/electricity generators/farmers. We focus on the lower-level problem to predict the amount of capacity expansions, fuel production, and power generation. In the second part, we address uncertainty over demand and lead time in a multi-stage mathematical programming problem. We propose a two-stage tri-level optimization model in the concept of rolling horizon approach to reducing the dimensionality of the multi-stage problem. In the third part of the dissertation, we introduce a new branch and bound algorithm to solve bilevel linear programming problems. The total time is reduced by solving a smaller relaxation

  19. Multilevel Modeling of Distributed Denial of Service Attacks in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Katarzyna Mazur

    2016-01-01

    Full Text Available The growing popularity of wireless sensor networks increases the risk of security attacks. One of the most common and dangerous types of attack that takes place these days in any electronic society is a distributed denial of service attack. Due to the resource constraint nature of mobile sensors, DDoS attacks have become a major threat to its stability. In this paper, we established a model of a structural health monitoring network, being disturbed by one of the most common types of DDoS attacks, the flooding attack. Through a set of simulations, we explore the scope of flood-based DDoS attack problem, assessing the performance and the lifetime of the network under the attack condition. To conduct our research, we utilized the Quality of Protection Modeling Language. With the proposed approach, it was possible to examine numerous network configurations, parameters, attack options, and scenarios. The results of the carefully performed multilevel analysis allowed us to identify a new kind of DDoS attack, the delayed distributed denial of service, by the authors, referred to as DDDoS attack. Multilevel approach to DDoS attack analysis confirmed that, examining endangered environments, it is significant to take into account many characteristics at once, just to not overlook any important aspect.

  20. Motorola Secure Software Development Model

    Directory of Open Access Journals (Sweden)

    Francis Mahendran

    2008-08-01

    Full Text Available In today's world, the key to meeting the demand for improved security is to implement repeatable processes that reliably deliver measurably improved security. While many organizations have announced efforts to institutionalize a secure software development process, there is little or no industry acceptance for a common process improvement framework for secure software development. Motorola has taken the initiative to develop such a framework, and plans to share this with the Software Engineering Institute for possible inclusion into its Capability Maturity Model Integration (CMMI®. This paper will go into the details of how Motorola is addressing this issue. The model that is being developed is designed as an extension of the existing CMMI structure. The assumption is that the audience will have a basic understanding of the SEI CMM® / CMMI® process framework. The paper will not describe implementation details of a security process model or improvement framework, but will address WHAT security practices are required for a company with many organizations operating at different maturity levels. It is left to the implementing organization to answer the HOW, WHEN, WHO and WHERE aspects. The paper will discuss how the model is being implemented in the Motorola Software Group.

  1. The problematic estimation of "imitation effects" in multilevel models

    Directory of Open Access Journals (Sweden)

    2003-09-01

    Full Text Available It seems plausible that a person's demographic behaviour may be influenced by that among other people in the community, for example because of an inclination to imitate. When estimating multilevel models from clustered individual data, some investigators might perhaps feel tempted to try to capture this effect by simply including on the right-hand side the average of the dependent variable, constructed by aggregation within the clusters. However, such modelling must be avoided. According to simulation experiments based on real fertility data from India, the estimated effect of this obviously endogenous variable can be very different from the true effect. Also the other community effect estimates can be strongly biased. An "imitation effect" can only be estimated under very special assumptions that in practice will be hard to defend.

  2. Comparison of Estimation Procedures for Multilevel AR(1 Models

    Directory of Open Access Journals (Sweden)

    Tanja eKrone

    2016-04-01

    Full Text Available To estimate a time series model for multiple individuals, a multilevel model may be used.In this paper we compare two estimation methods for the autocorrelation in Multilevel AR(1 models, namely Maximum Likelihood Estimation (MLE and Bayesian Markov Chain Monte Carlo.Furthermore, we examine the difference between modeling fixed and random individual parameters.To this end, we perform a simulation study with a fully crossed design, in which we vary the length of the time series (10 or 25, the number of individuals per sample (10 or 25, the mean of the autocorrelation (-0.6 to 0.6 inclusive, in steps of 0.3 and the standard deviation of the autocorrelation (0.25 or 0.40.We found that the random estimators of the population autocorrelation show less bias and higher power, compared to the fixed estimators. As expected, the random estimators profit strongly from a higher number of individuals, while this effect is small for the fixed estimators.The fixed estimators profit slightly more from a higher number of time points than the random estimators.When possible, random estimation is preferred to fixed estimation.The difference between MLE and Bayesian estimation is nearly negligible. The Bayesian estimation shows a smaller bias, but MLE shows a smaller variability (i.e., standard deviation of the parameter estimates.Finally, better results are found for a higher number of individuals and time points, and for a lower individual variability of the autocorrelation. The effect of the size of the autocorrelation differs between outcome measures.

  3. Space vector-based modeling and control of a modular multilevel converter in HVDC applications

    DEFF Research Database (Denmark)

    Bonavoglia, M.; Casadei, G.; Zarri, L.;

    2013-01-01

    Modular multilevel converter (MMC) is an emerging multilevel topology for high-voltage applications that has been developed in recent years. In this paper, the modeling and the control of MMCs are restated in terms of space vectors, which may allow a deeper understanding of the converter behavior...

  4. Using multilevel modeling and mixed methods to make theoretical progress in microfoundations for strategy research

    OpenAIRE

    Aguinis, Herman; Molina-Azorín, José F.

    2015-01-01

    The microfoundations research agenda presents an expanded theoretical perspective because it considers individuals, their characteristics, and their interactions as relevant variables to help us understand firm-level strategic issues. However, microfoundations empirical research faces unique challenges because processes take place at different levels of analysis and these multilevel processes must be considered simultaneously. We describe multilevel modeling and mixed methods as methodologica...

  5. The Consequences of Ignoring Multilevel Data Structures in Nonhierarchical Covariance Modeling.

    Science.gov (United States)

    Julian, Marc W.

    2001-01-01

    Examined the effects of ignoring multilevel data structures in nonhierarchical covariance modeling using a Monte Carlo simulation. Results suggest that when the magnitudes of intraclass correlations are less than 0.05 and the group size is small, the consequences of ignoring the data dependence within the multilevel data structures seem to be…

  6. Using multilevel modeling and mixed methods to make theoretical progress in microfoundations for strategy research

    OpenAIRE

    Aguinis, Herman; Molina-Azorín, José F.

    2015-01-01

    The microfoundations research agenda presents an expanded theoretical perspective because it considers individuals, their characteristics, and their interactions as relevant variables to help us understand firm-level strategic issues. However, microfoundations empirical research faces unique challenges because processes take place at different levels of analysis and these multilevel processes must be considered simultaneously. We describe multilevel modeling and mixed methods as methodologica...

  7. Multi-level Algorithm for the Anderson Impurity Model

    Science.gov (United States)

    Chandrasekharan, S.; Yoo, J.; Baranger, H. U.

    2004-03-01

    We develop a new quantum Monte Carlo algorithm to solve the Anderson impurity model. Instead of integrating out the Fermions, we work in the Fermion occupation number basis and thus have direct access to the Fermionic physics. The sign problem that arises in this formulation can be solved by a multi-level technique developed by Luscher and Weisz in the context of lattice QCD [JHEP, 0109 (2001) 010]. We use the directed-loop algorithm to update the degrees of freedom. Further, this algorithm allows us to work directly in the Euclidean time continuum limit for arbitrary values of the interaction strength thus avoiding time discretization errors. We present results for the impurity susceptibility and the properties of the screening cloud obtained using the algorithm.

  8. The multilevel p2 model : A random effects model for the analysis of multiple social networks

    NARCIS (Netherlands)

    Zijlstra, B.J.H.; van Duijn, M.A.J.; Snijders, T.A.B.

    2006-01-01

    The p2 model is a random effects model with covariates for the analysis of binary directed social network data coming from a single observation of a social network. Here, a multilevel variant of the p2 model is proposed for the case of multiple observations of social networks, for example, in a samp

  9. Multilevel structural equation models for assessing moderation within and across levels of analysis.

    Science.gov (United States)

    Preacher, Kristopher J; Zhang, Zhen; Zyphur, Michael J

    2016-06-01

    Social scientists are increasingly interested in multilevel hypotheses, data, and statistical models as well as moderation or interactions among predictors. The result is a focus on hypotheses and tests of multilevel moderation within and across levels of analysis. Unfortunately, existing approaches to multilevel moderation have a variety of shortcomings, including conflated effects across levels of analysis and bias due to using observed cluster averages instead of latent variables (i.e., "random intercepts") to represent higher-level constructs. To overcome these problems and elucidate the nature of multilevel moderation effects, we introduce a multilevel structural equation modeling (MSEM) logic that clarifies the nature of the problems with existing practices and remedies them with latent variable interactions. This remedy uses random coefficients and/or latent moderated structural equations (LMS) for unbiased tests of multilevel moderation. We describe our approach and provide an example using the publicly available High School and Beyond data with Mplus syntax in Appendix. Our MSEM method eliminates problems of conflated multilevel effects and reduces bias in parameter estimates while offering a coherent framework for conceptualizing and testing multilevel moderation effects. (PsycINFO Database Record

  10. A Comparative Modelling Study of PWM Control Techniques for Multilevel Cascaded Inverter

    Directory of Open Access Journals (Sweden)

    A. TAHRI

    2005-01-01

    Full Text Available The emergence of multilevel converters has been in increase since the last decade. These new types of converters are suitable for high voltage and high power application due to their ability to synthesize waveforms with better harmonic spectrum. Numerous topologies have been introduced and widely studied for utility and drive applications. Amongst these topologies, the multilevel cascaded inverter was introduced in Static Var compensation and drive systems. This paper investigates several control techniques applied to the Multilevel Cascaded Inverter in order to ensure an efficient voltage utilization and better harmonic spectrum. A modelling and control strategy of a single phase Multilevel Cascaded Inverter is also investigated. Computer simulation results using Matlab program are reported and discussed together with a comparative study of the different control techniques of multilevel cascaded inverter.Moreover, experimental results are carried out on a scaled down prototype to prove the effectiveness of the proposed analysis.

  11. Analysis Models for Security Protocols

    NARCIS (Netherlands)

    Corin, R.J.; Corin, Ricardo Javier

    2006-01-01

    In this thesis, we present five significant, orthogonal extensions to the Dolev Yao model. Each extension considers a more realistic setting, closer to the real world, thus providing a stronger security guarantee. We provide examples both from the literature and from industrial case studies to show

  12. Multilevel method for modeling large-scale networks.

    Energy Technology Data Exchange (ETDEWEB)

    Safro, I. M. (Mathematics and Computer Science)

    2012-02-24

    researchers. We propose to develop multilevel methods to model complex networks. The key point of the proposed strategy is that it will help to preserve part of the unknown structural attributes by guaranteeing the similar behavior of the real and artificial model on different scales.

  13. Estimating the Multilevel Rasch Model: With the lme4 Package

    Directory of Open Access Journals (Sweden)

    Harold Doran

    2007-02-01

    Full Text Available Traditional Rasch estimation of the item and student parameters via marginal maximum likelihood, joint maximum likelihood or conditional maximum likelihood, assume individuals in clustered settings are uncorrelated and items within a test that share a grouping structure are also uncorrelated. These assumptions are often violated, particularly in educational testing situations, in which students are grouped into classrooms and many test items share a common grouping structure, such as a content strand or a reading passage. Consequently, one possible approach is to explicitly recognize the clustered nature of the data and directly incorporate random effects to account for the various dependencies. This article demonstrates how the multilevel Rasch model can be estimated using the functions in R for mixed-effects models with crossed or partially crossed random effects. We demonstrate how to model the following hierarchical data structures: a individuals clustered in similar settings (e.g., classrooms, schools, b items nested within a particular group (such as a content strand or a reading passage, and c how to estimate a teacher × content strand interaction.

  14. Multi-level molecular modelling for plasma medicine

    Science.gov (United States)

    Bogaerts, Annemie; Khosravian, Narjes; Van der Paal, Jonas; Verlackt, Christof C. W.; Yusupov, Maksudbek; Kamaraj, Balu; Neyts, Erik C.

    2016-02-01

    Modelling at the molecular or atomic scale can be very useful for obtaining a better insight in plasma medicine. This paper gives an overview of different atomic/molecular scale modelling approaches that can be used to study the direct interaction of plasma species with biomolecules or the consequences of these interactions for the biomolecules on a somewhat longer time-scale. These approaches include density functional theory (DFT), density functional based tight binding (DFTB), classical reactive and non-reactive molecular dynamics (MD) and united-atom or coarse-grained MD, as well as hybrid quantum mechanics/molecular mechanics (QM/MM) methods. Specific examples will be given for three important types of biomolecules, present in human cells, i.e. proteins, DNA and phospholipids found in the cell membrane. The results show that each of these modelling approaches has its specific strengths and limitations, and is particularly useful for certain applications. A multi-level approach is therefore most suitable for obtaining a global picture of the plasma-biomolecule interactions.

  15. Multilevel models from biology to psychology: mission impossible?

    Science.gov (United States)

    Bilder, Robert M; Howe, Andrew G; Howe, Andrew S; Sabb, Fred W

    2013-08-01

    Systematic efforts are underway to address major flaws in the current diagnostic taxonomy of mental disorders, fostering hope that a new nosology might be based on brain biology. The National Institute of Mental Health Research Domains Criteria (RDoC) initiative aims to redefine mental illness leveraging information that spans molecular to behavioral levels of analysis. Major effort is still needed to forge multilevel conceptual and measurement models capable of representing knowledge within and across these levels. The development of such models may help refine and share complex hypotheses, and reduce the risk of replacing the current taxonomy with dimensions and/or categories that manifest little incremental biological validity. To create useful models we need to define concepts, relations among concepts, and links to supporting evidence. Some methods already enable representation of concepts and measures at the levels of behavioral and basic biological processes, but a major gap at the level of neural circuitry must be bridged to link basic biological and behavioral levels. We provide a schematic framework, using as an example the representation of selected "working memory" concepts and evidence across multiple levels of analysis as these have been described in the RDoC Workshops. This example illustrates multiple challenges and some possible solutions that may help clarify the aims of individual research projects and enable integration of diverse efforts on RDoC and related initiatives. PsycINFO Database Record (c) 2013 APA, all rights reserved.

  16. Multi-level and hybrid modelling approaches for systems biology.

    Science.gov (United States)

    Bardini, R; Politano, G; Benso, A; Di Carlo, S

    2017-01-01

    During the last decades, high-throughput techniques allowed for the extraction of a huge amount of data from biological systems, unveiling more of their underling complexity. Biological systems encompass a wide range of space and time scales, functioning according to flexible hierarchies of mechanisms making an intertwined and dynamic interplay of regulations. This becomes particularly evident in processes such as ontogenesis, where regulative assets change according to process context and timing, making structural phenotype and architectural complexities emerge from a single cell, through local interactions. The information collected from biological systems are naturally organized according to the functional levels composing the system itself. In systems biology, biological information often comes from overlapping but different scientific domains, each one having its own way of representing phenomena under study. That is, the different parts of the system to be modelled may be described with different formalisms. For a model to have improved accuracy and capability for making a good knowledge base, it is good to comprise different system levels, suitably handling the relative formalisms. Models which are both multi-level and hybrid satisfy both these requirements, making a very useful tool in computational systems biology. This paper reviews some of the main contributions in this field.

  17. Los Alamos Center for Computer Security formal computer security model

    Energy Technology Data Exchange (ETDEWEB)

    Dreicer, J.S.; Hunteman, W.J.; Markin, J.T.

    1989-01-01

    This paper provides a brief presentation of the formal computer security model currently being developed at the Los Alamos Department of Energy (DOE) Center for Computer Security (CCS). The need to test and verify DOE computer security policy implementation first motivated this effort. The actual analytical model was a result of the integration of current research in computer security and previous modeling and research experiences. The model is being developed to define a generic view of the computer and network security domains, to provide a theoretical basis for the design of a security model, and to address the limitations of present formal mathematical models for computer security. The fundamental objective of computer security is to prevent the unauthorized and unaccountable access to a system. The inherent vulnerabilities of computer systems result in various threats from unauthorized access. The foundation of the Los Alamos DOE CCS model is a series of functionally dependent probability equations, relations, and expressions. The model is undergoing continued discrimination and evolution. We expect to apply the model to the discipline of the Bell and LaPadula abstract sets of objects and subjects. 6 refs.

  18. Predicting Group-Level Outcome Variables from Variables Measured at the Individual Level: A Latent Variable Multilevel Model

    Science.gov (United States)

    Croon, Marcel A.; van Veldhoven, Marc J. P. M.

    2007-01-01

    In multilevel modeling, one often distinguishes between macro-micro and micro-macro situations. In a macro-micro multilevel situation, a dependent variable measured at the lower level is predicted or explained by variables measured at that lower or a higher level. In a micro-macro multilevel situation, a dependent variable defined at the higher…

  19. Multilevel selection in a resource-based model

    Science.gov (United States)

    Ferreira, Fernando Fagundes; Campos, Paulo R. A.

    2013-07-01

    In the present work we investigate the emergence of cooperation in a multilevel selection model that assumes limiting resources. Following the work by R. J. Requejo and J. Camacho [Phys. Rev. Lett.0031-900710.1103/PhysRevLett.108.038701 108, 038701 (2012)], the interaction among individuals is initially ruled by a prisoner's dilemma (PD) game. The payoff matrix may change, influenced by the resource availability, and hence may also evolve to a non-PD game. Furthermore, one assumes that the population is divided into groups, whose local dynamics is driven by the payoff matrix, whereas an intergroup competition results from the nonuniformity of the growth rate of groups. We study the probability that a single cooperator can invade and establish in a population initially dominated by defectors. Cooperation is strongly favored when group sizes are small. We observe the existence of a critical group size beyond which cooperation becomes counterselected. Although the critical size depends on the parameters of the model, it is seen that a saturation value for the critical group size is achieved. The results conform to the thought that the evolutionary history of life repeatedly involved transitions from smaller selective units to larger selective units.

  20. Multilevel Factor Analysis and Structural Equation Modeling of Daily Diary Coping Data: Modeling Trait and State Variation

    Science.gov (United States)

    Roesch, Scott C.; Aldridge, Arianna A.; Stocking, Stephanie N.; Villodas, Feion; Leung, Queenie; Bartley, Carrie E.; Black, Lisa J.

    2010-01-01

    This study used multilevel modeling of daily diary data to model within-person (state) and between-person (trait) components of coping variables. This application included the introduction of multilevel factor analysis (MFA) and a comparison of the predictive ability of these trait/state factors. Daily diary data were collected on a large (n =…

  1. Bayesian structural equations model for multilevel data with missing responses and missing covariates

    CSIR Research Space (South Africa)

    Kim, S

    2008-03-01

    Full Text Available Motivated by a large multilevel survey conducted by the US Veterans Health Administration (VHA), we propose a structural equations model which involves a set of latent variables to capture dependence between different responses, a set of facility...

  2. Multilevel Models for the Analysis of Angle-Specific Torque Curves with Application to Master Athletes

    Directory of Open Access Journals (Sweden)

    Carvalho Humberto M.

    2015-12-01

    Full Text Available The aim of this paper was to outline a multilevel modeling approach to fit individual angle-specific torque curves describing concentric knee extension and flexion isokinetic muscular actions in Master athletes. The potential of the analytical approach to examine between individual differences across the angle-specific torque curves was illustrated including between-individuals variation due to gender differences at a higher level. Torques in concentric muscular actions of knee extension and knee extension at 60°·s-1 were considered within a range of motion between 5°and 85° (only torques “truly” isokinetic. Multilevel time series models with autoregressive covariance structures with standard multilevel models were superior fits compared with standard multilevel models for repeated measures to fit anglespecific torque curves. Third and fourth order polynomial models were the best fits to describe angle-specific torque curves of isokinetic knee flexion and extension concentric actions, respectively. The fixed exponents allow interpretations for initial acceleration, the angle at peak torque and the decrement of torque after peak torque. Also, the multilevel models were flexible to illustrate the influence of gender differences on the shape of torque throughout the range of motion and in the shape of the curves. The presented multilevel regression models may afford a general framework to examine angle-specific moment curves by isokinetic dynamometry, and add to the understanding mechanisms of strength development, particularly the force-length relationship, both related to performance and injury prevention.

  3. Multilevel Models for the Analysis of Angle-Specific Torque Curves with Application to Master Athletes.

    Science.gov (United States)

    Carvalho, Humberto M

    2015-12-22

    The aim of this paper was to outline a multilevel modeling approach to fit individual angle-specific torque curves describing concentric knee extension and flexion isokinetic muscular actions in Master athletes. The potential of the analytical approach to examine between individual differences across the angle-specific torque curves was illustrated including between-individuals variation due to gender differences at a higher level. Torques in concentric muscular actions of knee extension and knee extension at 60º·s(-1) were considered within a range of motion between 5º and 85º (only torques "truly" isokinetic). Multilevel time series models with autoregressive covariance structures with standard multilevel models were superior fits compared with standard multilevel models for repeated measures to fit angle-specific torque curves. Third and fourth order polynomial models were the best fits to describe angle-specific torque curves of isokinetic knee flexion and extension concentric actions, respectively. The fixed exponents allow interpretations for initial acceleration, the angle at peak torque and the decrement of torque after peak torque. Also, the multilevel models were flexible to illustrate the influence of gender differences on the shape of torque throughout the range of motion and in the shape of the curves. The presented multilevel regression models may afford a general framework to examine angle-specific moment curves by isokinetic dynamometry, and add to the understanding mechanisms of strength development, particularly the force-length relationship, both related to performance and injury prevention.

  4. runmlwin : A Program to Run the MLwiN Multilevel Modeling Software from within Stata

    Directory of Open Access Journals (Sweden)

    George Leckie

    2013-03-01

    Full Text Available We illustrate how to fit multilevel models in the MLwiN package seamlessly from within Stata using the Stata program runmlwin. We argue that using MLwiN and Stata in combination allows researchers to capitalize on the best features of both packages. We provide examples of how to use runmlwin to fit continuous, binary, ordinal, nominal and mixed response multilevel models by both maximum likelihood and Markov chain Monte Carlo estimation.

  5. Improving prediction of surgical site infection risk with multilevel modeling.

    Directory of Open Access Journals (Sweden)

    Lauren Saunders

    Full Text Available BACKGROUND: Surgical site infection (SSI surveillance is a key factor in the elaboration of strategies to reduce SSI occurrence and in providing surgeons with appropriate data feedback (risk indicators, clinical prediction rule. AIM: To improve the predictive performance of an individual-based SSI risk model by considering a multilevel hierarchical structure. PATIENTS AND METHODS: Data were collected anonymously by the French SSI active surveillance system in 2011. An SSI diagnosis was made by the surgical teams and infection control practitioners following standardized criteria. A random 20% sample comprising 151 hospitals, 502 wards and 62280 patients was used. Three-level (patient, ward, hospital hierarchical logistic regression models were initially performed. Parameters were estimated using the simulation-based Markov Chain Monte Carlo procedure. RESULTS: A total of 623 SSI were diagnosed (1%. The hospital level was discarded from the analysis as it did not contribute to variability of SSI occurrence (p  = 0.32. Established individual risk factors (patient history, surgical procedure and hospitalization characteristics were identified. A significant heterogeneity in SSI occurrence between wards was found (median odds ratio [MOR] 3.59, 95% credibility interval [CI] 3.03 to 4.33 after adjusting for patient-level variables. The effects of the follow-up duration varied between wards (p<10-9, with an increased heterogeneity when follow-up was <15 days (MOR 6.92, 95% CI 5.31 to 9.07]. The final two-level model significantly improved the discriminative accuracy compared to the single level reference model (p<10-9, with an area under the ROC curve of 0.84. CONCLUSION: This study sheds new light on the respective contribution of patient-, ward- and hospital-levels to SSI occurrence and demonstrates the significant impact of the ward level over and above risk factors present at patient level (i.e., independently from patient case-mix.

  6. THE MODEL OF LIFELONG EDUCATION IN A TECHNICAL UNIVERSITY AS A MULTILEVEL EDUCATIONAL COMPLEX

    Directory of Open Access Journals (Sweden)

    Svetlana V. Sergeyeva

    2016-06-01

    Full Text Available Introduction: the current leading trend of the educational development is characterised by its continuity. Institutions of higher education as multi-level educational complexes nurture favourable conditions for realisation of the strategy of lifelong education. Today a technical university offering training of future engineers is facing a topic issue of creating a multilevel educational complex. Materials and Methods: this paper is put together on the basis of modern Russian and foreign scientific literature about lifelong education. The authors used theoretical methods of scientific research: systemstructural analysis, synthesis, modeling, analysis and generalisations of concepts. Results: the paper presents a model of lifelong education developed by authors for a technical university as a multilevel educational complex. It is realised through a set of principles: multi-level and continuity, integration, conformity and quality, mobility, anticipation, openness, social partnership and feedback. In accordance with the purpose, objectives and principles, the content part of the model is formed. The syllabi following the described model are run in accordance with the training levels undertaken by a technical university as a multilevel educational complex. All syllabi are based on the gradual nature of their implementation. In this regard, the authors highlight three phases: diagnostic, constructive and transformative, assessing. Discussion and Conclusions: the expected result of the created model of lifelong education development in a technical university as a multilevel educational complex is presented by a graduate trained for effective professional activity, competitive, prepared and sought-after at the regional labour market.

  7. Security Theorems via Model Theory

    Directory of Open Access Journals (Sweden)

    Joshua Guttman

    2009-11-01

    Full Text Available A model-theoretic approach can establish security theorems for cryptographic protocols. Formulas expressing authentication and non-disclosure properties of protocols have a special form. They are quantified implications for all xs . (phi implies for some ys . psi. Models (interpretations for these formulas are *skeletons*, partially ordered structures consisting of a number of local protocol behaviors. *Realized* skeletons contain enough local sessions to explain all the behavior, when combined with some possible adversary behaviors. We show two results. (1 If phi is the antecedent of a security goal, then there is a skeleton A_phi such that, for every skeleton B, phi is satisfied in B iff there is a homomorphism from A_phi to B. (2 A protocol enforces for all xs . (phi implies for some ys . psi iff every realized homomorphic image of A_phi satisfies psi. Hence, to verify a security goal, one can use the Cryptographic Protocol Shapes Analyzer CPSA (TACAS, 2007 to identify minimal realized skeletons, or "shapes," that are homomorphic images of A_phi. If psi holds in each of these shapes, then the goal holds.

  8. Multi-level systems modeling and optimization for novel aircraft

    Science.gov (United States)

    Subramanian, Shreyas Vathul

    This research combines the disciplines of system-of-systems (SoS) modeling, platform-based design, optimization and evolving design spaces to achieve a novel capability for designing solutions to key aeronautical mission challenges. A central innovation in this approach is the confluence of multi-level modeling (from sub-systems to the aircraft system to aeronautical system-of-systems) in a way that coordinates the appropriate problem formulations at each level and enables parametric search in design libraries for solutions that satisfy level-specific objectives. The work here addresses the topic of SoS optimization and discusses problem formulation, solution strategy, the need for new algorithms that address special features of this problem type, and also demonstrates these concepts using two example application problems - a surveillance UAV swarm problem, and the design of noise optimal aircraft and approach procedures. This topic is critical since most new capabilities in aeronautics will be provided not just by a single air vehicle, but by aeronautical Systems of Systems (SoS). At the same time, many new aircraft concepts are pressing the boundaries of cyber-physical complexity through the myriad of dynamic and adaptive sub-systems that are rising up the TRL (Technology Readiness Level) scale. This compositional approach is envisioned to be active at three levels: validated sub-systems are integrated to form conceptual aircraft, which are further connected with others to perform a challenging mission capability at the SoS level. While these multiple levels represent layers of physical abstraction, each discipline is associated with tools of varying fidelity forming strata of 'analysis abstraction'. Further, the design (composition) will be guided by a suitable hierarchical complexity metric formulated for the management of complexity in both the problem (as part of the generative procedure and selection of fidelity level) and the product (i.e., is the mission

  9. Using Multilevel Modeling in Language Assessment Research: A Conceptual Introduction

    Science.gov (United States)

    Barkaoui, Khaled

    2013-01-01

    This article critiques traditional single-level statistical approaches (e.g., multiple regression analysis) to examining relationships between language test scores and variables in the assessment setting. It highlights the conceptual, methodological, and statistical problems associated with these techniques in dealing with multilevel or nested…

  10. Modeling of trophospheric ozone concentrations using genetically trained multi-level cellular neural networks

    Science.gov (United States)

    Ozcan, H. Kurtulus; Bilgili, Erdem; Sahin, Ulku; Ucan, O. Nuri; Bayat, Cuma

    2007-09-01

    Tropospheric ozone concentrations, which are an important air pollutant, are modeled by the use of an artificial intelligence structure. Data obtained from air pollution measurement stations in the city of Istanbul are utilized in constituting the model. A supervised algorithm for the evaluation of ozone concentration using a genetically trained multi-level cellular neural network (ML-CNN) is introduced, developed, and applied to real data. A genetic algorithm is used in the optimization of CNN templates. The model results and the actual measurement results are compared and statistically evaluated. It is observed that seasonal changes in ozone concentrations are reflected effectively by the concentrations estimated by the multilevel-CNN model structure, with a correlation value of 0.57 ascertained between actual and model results. It is shown that the multilevel-CNN modeling technique is as satisfactory as other modeling techniques in associating the data in a complex medium in air pollution applications.

  11. Modeling of Trophospheric Ozone Concentrations Using Genetically Trained Multi-Level Cellular Neural Networks

    Institute of Scientific and Technical Information of China (English)

    H. Kurtulus OZCAN; Erdem BILGILI; Ulku SAHIN; O. Nuri UCAN; Cuma BAYAT

    2007-01-01

    Tropospheric ozone concentrations, which are an important air pollutant, are modeled by the use of an artificial intelligence structure. Data obtained from air pollution measurement stations in the city of Istanbul are utilized in constituting the model. A supervised algorithm for the evaluation of ozone concentration using a genetically trained multi-level cellular neural network (ML-CNN) is introduced, developed, and applied to real data. A genetic algorithm is used in the optimization of CNN templates. The model results and the actual measurement results are compared and statistically evaluated. It is observed that seasonal changes in ozone concentrations are reflected effectively by the concentrations estimated by the multilevel-CNN model structure, with a correlation value of 0.57 ascertained between actual and model results. It is shown that the multilevel-CNN modeling technique is as satisfactory as other modeling techniques in associating the data in a complex medium in air pollution applications.

  12. Network model of security system

    Directory of Open Access Journals (Sweden)

    Adamczyk Piotr

    2016-01-01

    Full Text Available The article presents the concept of building a network security model and its application in the process of risk analysis. It indicates the possibility of a new definition of the role of the network models in the safety analysis. Special attention was paid to the development of the use of an algorithm describing the process of identifying the assets, vulnerability and threats in a given context. The aim of the article is to present how this algorithm reduced the complexity of the problem by eliminating from the base model these components that have no links with others component and as a result and it was possible to build a real network model corresponding to reality.

  13. VoIP Quality Measurements in a Multilevel Secure (MLS) Environment

    Science.gov (United States)

    2008-03-01

    another format. 4 GATEWAY: A router that connects two networks and can perform protocol conversion.5 IEC: International Electro-technical...1 Tamara Dean, Network + Guide to Networks, Thomson Course Technology, 2006. 2 Creative Research Systems, The Survey System (URL); http...Network + Guide to Networks, Thomson Course Technology, 2006. 7 Ibid. 8 Charlie Kaufman, Radia Perlman, Mike Speciner, Network Security Private

  14. School Security Measures and Extracurricular Participation: An Exploratory Multi-Level Analysis

    Science.gov (United States)

    Mowen, Thomas J.; Manierre, Matthew J.

    2017-01-01

    Although delinquency in US schools is near historic lows, concern over delinquency in US schools remains a pressing issue among school officials, parents, and policy-makers. Many scholars argue that the current approach to discipline in the United States is highly punitive. While some projects have assessed the effect of punitive security on…

  15. A Multilevel Secure MapReduce Framework for Cross-Domain Information Sharing in the Cloud

    Science.gov (United States)

    2013-03-01

    analyze data at different security classifications • Topics - Apache Hadoop framework - MLS-aware Hadoop Distributed File System • Concept of...subprojects: - Hadoop Distributed File System, Hadoop MapReduce • Support distributed computing on massive data sets on clusters of commodity computers...Reduce) Apache Hadoop 3 GSAW 2013 Hadoop Architecture 4 GSAW 2013 Name Node Job Tracker Task Tracker Task Tracker Client HDFS

  16. Application of Multilevel Models to Morphometric Data. Part 1. Linear Models and Hypothesis Testing

    Directory of Open Access Journals (Sweden)

    O. Tsybrovskyy

    2003-01-01

    Full Text Available Morphometric data usually have a hierarchical structure (i.e., cells are nested within patients, which should be taken into consideration in the analysis. In the recent years, special methods of handling hierarchical data, called multilevel models (MM, as well as corresponding software have received considerable development. However, there has been no application of these methods to morphometric data yet. In this paper we report our first experience of analyzing karyometric data by means of MLwiN – a dedicated program for multilevel modeling. Our data were obtained from 34 follicular adenomas and 44 follicular carcinomas of the thyroid. We show examples of fitting and interpreting MM of different complexity, and draw a number of interesting conclusions about the differences in nuclear morphology between follicular thyroid adenomas and carcinomas. We also demonstrate substantial advantages of multilevel models over conventional, single‐level statistics, which have been adopted previously to analyze karyometric data. In addition, some theoretical issues related to MM as well as major statistical software for MM are briefly reviewed.

  17. Multi-Level Security for Automotive–RFID Based Technology with Lab VIEW Implementation

    Directory of Open Access Journals (Sweden)

    Priya Darshini .V

    2013-03-01

    Full Text Available Security has become a prominent parameter for all the electronic gadgets. This proposed paper aims at securing the automotive and also preventing the unauthorized persons from accessing it. The technologies such as Radio Frequency Identification (RFID, thumb registration system and face recognition will be applied for the security measures. This proposed system will also be implemented in LabVIEW using Educational Laboratory Virtual Instrumentation Suite II (ELVIS. Initially, the RFID system will be authenticated .The importance of this system is that, it gets verification from the Road Transportation Office (RTO.The user will require an authentication to get proceed to the thumb registration module by which the efficiency of the thumb is enhanced using Pattern Matching Algorithm (PMA. Face recognition system is a technique which will be used after the thumb registration system. At last, this system allows the user to drive the car. For emergency, a key insertion slot will be placed in the system through which the user can insert the key. During this emergency mode of operation the camera captures the driver’s image and sends it to the owner’s mobile as Multimedia Messaging Service (MMS. The owner will provide the authentication password; this in turn allows the user to drive the vehicle. Global System for Mobile communication (GSM module is also kept inbuilt for tracking purpose. Among the different technologies proposed, RFID technique is briefly discussed in this paper.

  18. Get Over It! A Multilevel Threshold Autoregressive Model for State-Dependent Affect Regulation

    NARCIS (Netherlands)

    De Haan-Rietdijk, Silvia; Gottman, John M.; Bergeman, Cindy S.; Hamaker, Ellen L.

    2014-01-01

    Intensive longitudinal data provide rich information, which is best captured when specialized models are used in the analysis. One of these models is the multilevel autoregressive model, which psychologists have applied successfully to study affect regulation as well as alcohol use. A limitation of

  19. A Comparison of Inverse-Wishart Prior Specifications for Covariance Matrices in Multilevel Autoregressive Models

    NARCIS (Netherlands)

    Schuurman, N.K.; Grasman, R.P.P.P.; Hamaker, E.L.

    2016-01-01

    Multilevel autoregressive models are especially suited for modeling between-person differences in within-person processes. Fitting these models with Bayesian techniques requires the specification of prior distributions for all parameters. Often it is desirable to specify prior distributions that

  20. Polytomous multilevel testlet models for testlet-based assessments with complex sampling designs.

    Science.gov (United States)

    Jiao, Hong; Zhang, Yuan

    2015-02-01

    Applications of standard item response theory models assume local independence of items and persons. This paper presents polytomous multilevel testlet models for dual dependence due to item and person clustering in testlet-based assessments with clustered samples. Simulation and survey data were analysed with a multilevel partial credit testlet model. This model was compared with three alternative models - a testlet partial credit model (PCM), multilevel PCM, and PCM - in terms of model parameter estimation. The results indicated that the deviance information criterion was the fit index that always correctly identified the true multilevel testlet model based on the quantified evidence in model selection, while the Akaike and Bayesian information criteria could not identify the true model. In general, the estimation model and the magnitude of item and person clustering impacted the estimation accuracy of ability parameters, while only the estimation model and the magnitude of item clustering affected the item parameter estimation accuracy. Furthermore, ignoring item clustering effects produced higher total errors in item parameter estimates but did not have much impact on the accuracy of ability parameter estimates, while ignoring person clustering effects yielded higher total errors in ability parameter estimates but did not have much effect on the accuracy of item parameter estimates. When both clustering effects were ignored in the PCM, item and ability parameter estimation accuracy was reduced.

  1. Distinguishing Differential Testlet Functioning from Differential Bundle Functioning Using the Multilevel Measurement Model

    Science.gov (United States)

    Beretvas, S. Natasha; Walker, Cindy M.

    2012-01-01

    This study extends the multilevel measurement model to handle testlet-based dependencies. A flexible two-level testlet response model (the MMMT-2 model) for dichotomous items is introduced that permits assessment of differential testlet functioning (DTLF). A distinction is made between this study's conceptualization of DTLF and that of…

  2. Security Communication Model of Wireless Trade System

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wen-kai; ZHANG Si-yu

    2005-01-01

    This paper proposes a C/S system model for K Java and PDA named Net-Wireless. It is a discussion and proposal on information security and solutions for K-Java handsets and PDAs in wireless network. It also explains the scheme which between client security module and server security module. Also, We have developed a Security Server and a K-Java encryption module for e-commerce system and other trade systems.

  3. Security Management Model in Cloud Computing Environment

    OpenAIRE

    2016-01-01

    In the cloud computing environment, cloud virtual machine (VM) will be more and more the number of virtual machine security and management faced giant Challenge. In order to address security issues cloud computing virtualization environment, this paper presents a virtual machine based on efficient and dynamic deployment VM security management model state migration and scheduling, study of which virtual machine security architecture, based on AHP (Analytic Hierarchy Process) virtual machine de...

  4. Evaluating Technical Efficiency of Nursing Care Using Data Envelopment Analysis and Multilevel Modeling.

    Science.gov (United States)

    Min, Ari; Park, Chang Gi; Scott, Linda D

    2016-05-23

    Data envelopment analysis (DEA) is an advantageous non-parametric technique for evaluating relative efficiency of performance. This article describes use of DEA to estimate technical efficiency of nursing care and demonstrates the benefits of using multilevel modeling to identify characteristics of efficient facilities in the second stage of analysis. Data were drawn from LTCFocUS.org, a secondary database including nursing home data from the Online Survey Certification and Reporting System and Minimum Data Set. In this example, 2,267 non-hospital-based nursing homes were evaluated. Use of DEA with nurse staffing levels as inputs and quality of care as outputs allowed estimation of the relative technical efficiency of nursing care in these facilities. In the second stage, multilevel modeling was applied to identify organizational factors contributing to technical efficiency. Use of multilevel modeling avoided biased estimation of findings for nested data and provided comprehensive information on differences in technical efficiency among counties and states.

  5. A novel analytical thermal model for multilevel nano-scale interconnects considering the via effect

    Institute of Scientific and Technical Information of China (English)

    Zhu Zhang-Ming; Li Ru; Hao Bao-Tian; Yang Yin-Tang

    2009-01-01

    Based on the heat diffusion equation of multilevel interconnects, a novel analytical thermal model for multilevel nano-scale interconnects considering the via effect is presented, which can compute quickly the temperature of multilevel interconnects, with substrate temperature given. Based on the proposed model and the 65 nm complementary metal oxide semiconductor (CMOS) process parameter, the temperature of nano-scale interconnects is computed. The computed results show that the via effect has a great effect on local interconnects, but the reduction of thermal conductivity has little effect on local interconnects. With the reduction of thermal conductivity or the increase of current density, however, the temperature of global interconnects rises greatly, which can result in a great deterioration in their performance. The proposed model can be applied to computer aided design (CAD) of very large-scale integrated circuits (VLSIs) in nano-scale technologies.

  6. Multilevel Modeling and Policy Development: Guidelines and Applications to Medical Travel.

    Science.gov (United States)

    Garcia-Garzon, Eduardo; Zhukovsky, Peter; Haller, Elisa; Plakolm, Sara; Fink, David; Petrova, Dafina; Mahalingam, Vaishali; Menezes, Igor G; Ruggeri, Kai

    2016-01-01

    Medical travel has expanded rapidly in recent years, resulting in new markets and increased access to medical care. Whereas several studies investigated the motives of individuals seeking healthcare abroad, the conventional analytical approach is limited by substantial caveats. Classical techniques as found in the literature cannot provide sufficient insight due to the nested nature of data generated. The application of adequate analytical techniques, specifically multilevel modeling, is scarce to non-existent in the context of medical travel. This study introduces the guidelines for application of multilevel techniques in public health research by presenting an application of multilevel modeling in analyzing the decision-making patterns of potential medical travelers. Benefits and potential limitations are discussed.

  7. Multilevel Modeling and Policy Development: Guidelines and Applications to Medical Travel

    Science.gov (United States)

    Garcia-Garzon, Eduardo; Zhukovsky, Peter; Haller, Elisa; Plakolm, Sara; Fink, David; Petrova, Dafina; Mahalingam, Vaishali; Menezes, Igor G.; Ruggeri, Kai

    2016-01-01

    Medical travel has expanded rapidly in recent years, resulting in new markets and increased access to medical care. Whereas several studies investigated the motives of individuals seeking healthcare abroad, the conventional analytical approach is limited by substantial caveats. Classical techniques as found in the literature cannot provide sufficient insight due to the nested nature of data generated. The application of adequate analytical techniques, specifically multilevel modeling, is scarce to non-existent in the context of medical travel. This study introduces the guidelines for application of multilevel techniques in public health research by presenting an application of multilevel modeling in analyzing the decision-making patterns of potential medical travelers. Benefits and potential limitations are discussed. PMID:27252672

  8. Interpersonal Emotion Regulation Among Adolescent Athletes: A Bayesian Multilevel Model Predicting Sport Enjoyment and Commitment.

    Science.gov (United States)

    Tamminen, Katherine A; Gaudreau, Patrick; McEwen, Carolyn E; Crocker, Peter R E

    2016-12-01

    Efforts to regulate emotions can influence others, and interpersonal emotion regulation within teams may affect athletes' own affective and motivational outcomes. We examined adolescent athletes' (N = 451, N teams = 38) self- and interpersonal emotion regulation, as well as associations with peer climate, sport enjoyment, and sport commitment within a multilevel model of emotion regulation in teams. Results of multilevel Bayesian structural equation modeling showed that athletes' self-worsening emotion regulation strategies were negatively associated with enjoyment while other-improving emotion regulation strategies were positively associated enjoyment and commitment. The team-level interpersonal emotion regulation climate and peer motivational climates were also associated with enjoyment and commitment. Team-level factors moderated some of the relationships between athletes' emotion regulation with enjoyment and commitment. These findings extend previous research by examining interpersonal emotion regulation within teams using a multilevel approach, and they demonstrate the importance of person- and team-level factors for athletes' enjoyment and commitment.

  9. Teaching Quality Management Model for the Training of Innovation Ability and the Multilevel Decomposition Indicators

    Science.gov (United States)

    Lu, Xingjiang; Yao, Chen; Zheng, Jianmin

    2013-01-01

    This paper focuses on the training of undergraduate students' innovation ability. On top of the theoretical framework of the Quality Function Deployment (QFD), we propose a teaching quality management model. Based on this model, we establish a multilevel decomposition indicator system, which integrates innovation ability characterized by four…

  10. Developing the multi-level functioning interface framework for DER models

    DEFF Research Database (Denmark)

    Han, Xue; Bindner, Henrik W.; You, Shi

    2013-01-01

    The paper summarises several modelling applications of distributed energy resources (DERs) for various purposes, and describes the related operational issues regarding the complexity of the future distribution grid. Furthermore, a multi-level functioning interface framework is proposed for DER mo....... The information mapping for photovoltaic panel (PV) modelling is also provided as an example....

  11. Finite Mixture Multilevel Multidimensional Ordinal IRT Models for Large Scale Cross-Cultural Research

    NARCIS (Netherlands)

    M.G. de Jong (Martijn); J-B.E.M. Steenkamp (Jan-Benedict)

    2009-01-01

    textabstractWe present a class of finite mixture multilevel multidimensional ordinal IRT models for large scale cross-cultural research. Our model is proposed for confirmatory research settings. Our prior for item parameters is a mixture distribution to accommodate situations where different groups

  12. A Bayesian Multi-Level Factor Analytic Model of Consumer Price Sensitivities across Categories

    Science.gov (United States)

    Duvvuri, Sri Devi; Gruca, Thomas S.

    2010-01-01

    Identifying price sensitive consumers is an important problem in marketing. We develop a Bayesian multi-level factor analytic model of the covariation among household-level price sensitivities across product categories that are substitutes. Based on a multivariate probit model of category incidence, this framework also allows the researcher to…

  13. Incorporating Mobility in Growth Modeling for Multilevel and Longitudinal Item Response Data.

    Science.gov (United States)

    Choi, In-Hee; Wilson, Mark

    2016-01-01

    Multilevel data often cannot be represented by the strict form of hierarchy typically assumed in multilevel modeling. A common example is the case in which subjects change their group membership in longitudinal studies (e.g., students transfer schools; employees transition between different departments). In this study, cross-classified and multiple membership models for multilevel and longitudinal item response data (CCMM-MLIRD) are developed to incorporate such mobility, focusing on students' school change in large-scale longitudinal studies. Furthermore, we investigate the effect of incorrectly modeling school membership in the analysis of multilevel and longitudinal item response data. Two types of school mobility are described, and corresponding models are specified. Results of the simulation studies suggested that appropriate modeling of the two types of school mobility using the CCMM-MLIRD yielded good recovery of the parameters and improvement over models that did not incorporate mobility properly. In addition, the consequences of incorrectly modeling the school effects on the variance estimates of the random effects and the standard errors of the fixed effects depended upon mobility patterns and model specifications. Two sets of large-scale longitudinal data are analyzed to illustrate applications of the CCMM-MLIRD for each type of school mobility.

  14. A Bayesian Multi-Level Factor Analytic Model of Consumer Price Sensitivities across Categories

    Science.gov (United States)

    Duvvuri, Sri Devi; Gruca, Thomas S.

    2010-01-01

    Identifying price sensitive consumers is an important problem in marketing. We develop a Bayesian multi-level factor analytic model of the covariation among household-level price sensitivities across product categories that are substitutes. Based on a multivariate probit model of category incidence, this framework also allows the researcher to…

  15. Evidencing Learning Outcomes: A Multi-Level, Multi-Dimensional Course Alignment Model

    Science.gov (United States)

    Sridharan, Bhavani; Leitch, Shona; Watty, Kim

    2015-01-01

    This conceptual framework proposes a multi-level, multi-dimensional course alignment model to implement a contextualised constructive alignment of rubric design that authentically evidences and assesses learning outcomes. By embedding quality control mechanisms at each level for each dimension, this model facilitates the development of an aligned…

  16. Seeing the forest and the trees: multilevel models reveal both species and community patterns

    Science.gov (United States)

    Michelle M. Jackson; Monica G. Turner; Scott M. Pearson; Anthony R. Ives

    2012-01-01

    Studies designed to understand species distributions and community assemblages typically use separate analytical approaches (e.g., logistic regression and ordination) to model the distribution of individual species and to relate community composition to environmental variation. Multilevel models (MLMs) offer a promising strategy for integrating species and community-...

  17. CHOICE OF OPTION FOR IMPLEMENTATION OF THE MULTILEVEL SECURE ACCESS TO THE EXTERNAL NETWORK

    Directory of Open Access Journals (Sweden)

    V. S. Kolomoitcev

    2016-01-01

    Full Text Available We study the optimal way for design of access scheme called "Direct Connection. This scheme provides a secure access to external network resources, and consists of several groups of routers and two kinds of firewalls. The scheme is considered in view of the fact that the system has got common areas of removing threats in the channel for different means of protection. Parameters of average residence time of request in the system and its reliability were obtained for each variant of access scheme. Based on the results, comparison of the ways of design for access scheme was carried out between themselves and with the standard access scheme (with onefirewall. It was found out that design of access scheme with a single group of routers for the whole system has better performance and reliability than the other variants of "Direct Connection" access scheme.

  18. The relationship between multilevel models and non-parametric multilevel mixture models: Discrete approximation of intraclass correlation, random coefficient distributions, and residual heteroscedasticity.

    Science.gov (United States)

    Rights, Jason D; Sterba, Sonya K

    2016-11-01

    Multilevel data structures are common in the social sciences. Often, such nested data are analysed with multilevel models (MLMs) in which heterogeneity between clusters is modelled by continuously distributed random intercepts and/or slopes. Alternatively, the non-parametric multilevel regression mixture model (NPMM) can accommodate the same nested data structures through discrete latent class variation. The purpose of this article is to delineate analytic relationships between NPMM and MLM parameters that are useful for understanding the indirect interpretation of the NPMM as a non-parametric approximation of the MLM, with relaxed distributional assumptions. We define how seven standard and non-standard MLM specifications can be indirectly approximated by particular NPMM specifications. We provide formulas showing how the NPMM can serve as an approximation of the MLM in terms of intraclass correlation, random coefficient means and (co)variances, heteroscedasticity of residuals at level 1, and heteroscedasticity of residuals at level 2. Further, we discuss how these relationships can be useful in practice. The specific relationships are illustrated with simulated graphical demonstrations, and direct and indirect interpretations of NPMM classes are contrasted. We provide an R function to aid in implementing and visualizing an indirect interpretation of NPMM classes. An empirical example is presented and future directions are discussed. © 2016 The British Psychological Society.

  19. A Novel Reference Security Model with the Situation Based Access Policy for Accessing EPHR Data.

    Science.gov (United States)

    Gope, Prosanta; Amin, Ruhul

    2016-11-01

    Electronic Patient Health Record (EPHR) systems may facilitate a patient not only to share his/her health records securely with healthcare professional but also to control his/her health privacy, in a convenient and easy way even in case of emergency. In order to fulfill these requirements, it is greatly desirable to have the access control mechanism which can efficiently handle every circumstance without negotiating security. However, the existing access control mechanisms used in healthcare to regulate and restrict the disclosure of patient data are often bypassed in case of emergencies. In this article, we propose a way to securely share EPHR data under any situation including break-the-glass (BtG) without compromising its security. In this regard, we design a reference security model, which consists of a multi-level data flow hierarchy, and an efficient access control framework based on the conventional Role-Based Access Control (RBAC) and Mandatory Access Control (MAC) policies.

  20. Converter DC/AC Multilevel of Three Cells: Modeling and Simulation

    Directory of Open Access Journals (Sweden)

    Julián Peláez-Restrepo

    2013-11-01

    Full Text Available This paper presents a three-cell converter DC / AC. Multilevel topologies are attracting attention in the industry, obtained as a ripple on the state variables much smaller, and reduces stress on the switching devices. The topology used in this work is known in the technical literature as floating capacitor multilevel inverter, which imposes the challenge of balancing the voltage across each cell switching using floating capacitors, besides obtaining a sinusoidal signal regulated. The paper presents the averaged model of the inverter, and results obtained through simulation.

  1. The One Laptop per Child Security Model

    OpenAIRE

    Kristic, Ivan; Garfinkel, Simson L.

    2007-01-01

    Symposium on Usable Security and Privacy, Pittsburgh, PA, July 2007. ACM Press. Refereed Conference Paper We present an integrated security model for a low-cost laptop that will be widely deployed throughout the developing world. Implemented on top of Linux operating system, the model is designed to restrict the laptop's software without restricting the laptop's user.

  2. Analyzing Dyadic Data With Multilevel Modeling Versus Structural Equation Modeling: A Tale of Two Methods.

    Science.gov (United States)

    Ledermann, Thomas; Kenny, David A

    2017-02-06

    Multilevel modeling (MLM) and structural equation modeling (SEM) are the dominant methods for the analysis of dyadic data. Both methods are extensively reviewed for the widely used actor-partner interdependence model and the dyadic growth curve model, as well as other less frequently adopted models, including the common fate model and the mutual influence model. For each method, we discuss the analysis of distinguishable and indistinguishable members, the treatment of missing data, the standardization of effects, and tests of mediation. Even though there has been some blending of the 2 methods, each method has its own advantages and disadvantages, thus both should be in the toolbox of dyadic researchers. (PsycINFO Database Record

  3. A Multilevel Model of Educational Expectations of Secondary School Students in the United States

    Science.gov (United States)

    Lowman, Jennifer; Elliott, Marta

    2010-01-01

    Using the Educational Longitudinal Survey of 2002, we investigate variation in factors that contribute to Asian, Black, Hispanic, and White students' educational expectations. Separate multilevel models demonstrate group variation in student and school-level influences. Academic and school factors explained the most variation in White students'…

  4. Multilevel Modeling in the Presence of Outliers: A Comparison of Robust Estimation Methods

    Science.gov (United States)

    Finch, Holmes

    2017-01-01

    Multilevel models (MLMs) have proven themselves to be very useful in social science research, as data from a variety of sources is sampled such that individuals at level-1 are nested within clusters such as schools, hospitals, counseling centers, and business entities at level-2. MLMs using restricted maximum likelihood estimation (REML) provide…

  5. Multilevel Factor Analysis by Model Segregation: New Applications for Robust Test Statistics

    Science.gov (United States)

    Schweig, Jonathan

    2014-01-01

    Measures of classroom environments have become central to policy efforts that assess school and teacher quality. This has sparked a wide interest in using multilevel factor analysis to test measurement hypotheses about classroom-level variables. One approach partitions the total covariance matrix and tests models separately on the…

  6. Longitudinal Changes in Physical Fitness Performance in Youth: A Multilevel Latent Growth Curve Modeling Approach

    Science.gov (United States)

    Wang, Chee Keng John; Pyun, Do Young; Liu, Woon Chia; Lim, Boon San Coral; Li, Fuzhong

    2013-01-01

    Using a multilevel latent growth curve modeling (LGCM) approach, this study examined longitudinal change in levels of physical fitness performance over time (i.e. four years) in young adolescents aged from 12-13 years. The sample consisted of 6622 students from 138 secondary schools in Singapore. Initial analyses found between-school variation on…

  7. Work information and emotional support of self-initiated expatriates: multilevel mediation model

    DEFF Research Database (Denmark)

    Kubovcikova, Annamária; van Bakel, Marian

    of the rated ties is the context in which expatriates are embedded. It was therefore analyzed utilizing a multilevel mediation model. We have hypothesized that all learned characteristics will be determining the frequency of interaction and thus the level and type of support received. Host country knowledge...

  8. A multivariate multilevel Gaussian model with a mixed effects structure in the mean and covariance part.

    Science.gov (United States)

    Li, Baoyue; Bruyneel, Luk; Lesaffre, Emmanuel

    2014-05-20

    A traditional Gaussian hierarchical model assumes a nested multilevel structure for the mean and a constant variance at each level. We propose a Bayesian multivariate multilevel factor model that assumes a multilevel structure for both the mean and the covariance matrix. That is, in addition to a multilevel structure for the mean we also assume that the covariance matrix depends on covariates and random effects. This allows to explore whether the covariance structure depends on the values of the higher levels and as such models heterogeneity in the variances and correlation structure of the multivariate outcome across the higher level values. The approach is applied to the three-dimensional vector of burnout measurements collected on nurses in a large European study to answer the research question whether the covariance matrix of the outcomes depends on recorded system-level features in the organization of nursing care, but also on not-recorded factors that vary with countries, hospitals, and nursing units. Simulations illustrate the performance of our modeling approach. Copyright © 2013 John Wiley & Sons, Ltd.

  9. Gender Differences When Parenting Children with Autism Spectrum Disorders: A Multilevel Modeling Approach

    Science.gov (United States)

    Jones, Leah; Totsika, Vasiliki; Hastings, Richard P.; Petalas, Michael A.

    2013-01-01

    Parenting a child with autism may differentially affect mothers and fathers. Existing studies of mother-father differences often ignore the interdependence of data within families. We investigated gender differences within-families using multilevel linear modeling. Mothers and fathers of children with autism (161 couples) reported on their own…

  10. Personality Predicts Individual Variation in Fear Learning : A Multilevel Growth Modeling Approach

    NARCIS (Netherlands)

    Gazendam, Femke J.; Kamphuis, Jan H.; Eigenhuis, Annemarie; Huizenga, Hilde M H; Soeter, Marieke; Bos, Marieke G N; Sevenster, Dieuwke|info:eu-repo/dai/nl/375491104; Kindt, Merel

    2015-01-01

    Although fear-learning research has tended to focus on typical responses, there is substantial individual variation in response to threat. Here, we investigated how personality is related to variability in associative fear learning. We used multilevel growth curve modeling to examine the unique and

  11. Personality predicts individual variation in fear learning: a multilevel growth modeling approach

    NARCIS (Netherlands)

    Gazendam, F.J.; Kamphuis, J.H.; Eigenhuis, A.; Huizenga, H.M.; Soeter, M.; Bos, M.G.N.; Sevenster, D.; Kindt, M.

    2015-01-01

    Although fear-learning research has tended to focus on typical responses, there is substantial individual variation in response to threat. Here, we investigated how personality is related to variability in associative fear learning. We used multilevel growth curve modeling to examine the unique and

  12. Longitudinal Changes in Physical Fitness Performance in Youth: A Multilevel Latent Growth Curve Modeling Approach

    Science.gov (United States)

    Wang, Chee Keng John; Pyun, Do Young; Liu, Woon Chia; Lim, Boon San Coral; Li, Fuzhong

    2013-01-01

    Using a multilevel latent growth curve modeling (LGCM) approach, this study examined longitudinal change in levels of physical fitness performance over time (i.e. four years) in young adolescents aged from 12-13 years. The sample consisted of 6622 students from 138 secondary schools in Singapore. Initial analyses found between-school variation on…

  13. A Multilevel Model of Minority Opinion Expression and Team Decision-Making Effectiveness

    Science.gov (United States)

    Park, Guihyun; DeShon, Richard P.

    2010-01-01

    The consideration of minority opinions when making team decisions is an important factor that contributes to team effectiveness. A multilevel model of minority opinion influence in decision-making teams is developed to address the conditions that relate to adequate consideration of minority opinions. Using a sample of 57 teams working on a…

  14. A Multilevel Model of Team Cultural Diversity and Creativity: The Role of Climate for Inclusion

    Science.gov (United States)

    Li, Ci-Rong; Lin, Chen-Ju; Tien, Yun-Hsiang; Chen, Chien-Ming

    2017-01-01

    We developed a multi-level model to test how team cultural diversity may relate to team- and individual-level creativity, integrating team diversity research and information-exchange perspective. We proposed that the team climate for inclusion would moderate both the relationship between cultural diversity and team information sharing and between…

  15. The Multilevel Latent Covariate Model: A New, More Reliable Approach to Group-Level Effects in Contextual Studies

    Science.gov (United States)

    Ludtke, Oliver; Marsh, Herbert W.; Robitzsch, Alexander; Trautwein, Ulrich; Asparouhov, Tihomir; Muthen, Bengt

    2008-01-01

    In multilevel modeling (MLM), group-level (L2) characteristics are often measured by aggregating individual-level (L1) characteristics within each group so as to assess contextual effects (e.g., group-average effects of socioeconomic status, achievement, climate). Most previous applications have used a multilevel manifest covariate (MMC) approach,…

  16. Centering or Not Centering in Multilevel Models? The Role of the Group Mean and the Assessment of Group Effects

    Science.gov (United States)

    Paccagnella, Omar

    2006-01-01

    In multilevel regression, centering the model variables produces effects that are different and sometimes unexpected compared with those in traditional regression analysis. In this article, the main contributions in terms of meaning, assumptions, and effects underlying a multilevel centering solution are reviewed, emphasizing advantages and…

  17. Neural Network Based Multi-level Fuzzy Evaluation Model for Mechanical Kinematic Scheme

    Institute of Scientific and Technical Information of China (English)

    BO Ruifeng; LI Ruiqin

    2006-01-01

    To implement a quantificational evaluation for mechanical kinematic scheme more effectively, a multi-level and multi-objective evaluation model is presented using neural network and fuzzy theory. Firstly, the structure of evaluation model is constructed according to evaluation indicator system. Then evaluation samples are generated and provided to train this model. Thus it can reflect the relation between attributive value and evaluation result, as well as the weight of evaluation indicator. Once evaluation indicators of each candidate are fuzzily quantified and fed into the trained network model, the corresponding evaluation result is outputted and the best alternative can be selected. Under this model, expert knowledge can be effectively acquired and expressed, and the quantificational evaluation can be implemented for kinematic scheme with multi-level evaluation indicator system. Several key problems on this model are discussed and an illustration has demonstrated that this model is feasible and can be regarded as a new idea for solving kinematic scheme evaluation.

  18. Experimental Model of Proximal Junctional Fracture after Multilevel Posterior Spinal Instrumentation

    Science.gov (United States)

    Levasseur, Annie; Parent, Stefan; Petit, Yvan

    2016-01-01

    There is a high risk of proximal junctional fractures (PJF) with multilevel spinal instrumentation, especially in the osteoporotic spine. This problem is associated with significant morbidity and possibly the need for reoperation. Various techniques have been proposed in an attempt to decrease the risk of PJF but there is no experimental model described for in vitro production of PJF after multilevel instrumentation. The objective of this study is to develop an experimental model of PJF after multilevel posterior instrumentation. Initially, four porcine specimens including 4 vertebrae and instrumented at the 3 caudal vertebrae using a pedicle screw construct were subjected to different loading conditions. Loading conditions on porcine specimens involving cyclic loading along the axis of the center vertebral body line, with constrained flexion between 0° and 15° proximally, and fully constraining the specimen distally resulted in a fracture pattern most representative of a PJF seen clinically in humans, so to undergo human cadaveric testing with similar loading conditions was decided. Clinically relevant PJF were produced in all 3 human specimens. The experimental model described in this study will allow the evaluation of different parameters influencing the incidence and prevention of PJF after multilevel posterior spinal instrumentation. PMID:27610381

  19. On the application of multilevel modeling in environmental and ecological studies

    Science.gov (United States)

    Qian, S.S.; Cuffney, T.F.; Alameddine, I.; McMahon, G.; Reckhow, K.H.

    2010-01-01

    This paper illustrates the advantages of a multilevel/hierarchical approach for predictive modeling, including flexibility of model formulation, explicitly accounting for hierarchical structure in the data, and the ability to predict the outcome of new cases. As a generalization of the classical approach, the multilevel modeling approach explicitly models the hierarchical structure in the data by considering both the within- and between-group variances leading to a partial pooling of data across all levels in the hierarchy. The modeling framework provides means for incorporating variables at different spatiotemporal scales. The examples used in this paper illustrate the iterative process of model fitting and evaluation, a process that can lead to improved understanding of the system being studied. ?? 2010 by the Ecological Society of America.

  20. Multilevel Segmentation and Integrated Bayesian Model Classification with an Application to Brain Tumor Segmentation

    OpenAIRE

    Corso, Jason J.; Eitan Sharon; Alan Yuille

    2006-01-01

    We present a new method for automatic segmentation of heterogeneous image data, which is very common in medical image analysis. The main contribution of the paper is a mathematical formulation for incorporating soft model assignments into the calculation of affinities, which are traditionally model free. We integrate the resulting model-aware affinities into the multilevel segmentation by weighted aggregation algorithm. We apply the technique to the task of detecting and segmenting brain tumo...

  1. Computational Intelligence, Cyber Security and Computational Models

    CERN Document Server

    Anitha, R; Lekshmi, R; Kumar, M; Bonato, Anthony; Graña, Manuel

    2014-01-01

    This book contains cutting-edge research material presented by researchers, engineers, developers, and practitioners from academia and industry at the International Conference on Computational Intelligence, Cyber Security and Computational Models (ICC3) organized by PSG College of Technology, Coimbatore, India during December 19–21, 2013. The materials in the book include theory and applications for design, analysis, and modeling of computational intelligence and security. The book will be useful material for students, researchers, professionals, and academicians. It will help in understanding current research trends and findings and future scope of research in computational intelligence, cyber security, and computational models.

  2. Fast 3D spine reconstruction of postoperative patients using a multilevel statistical model.

    Science.gov (United States)

    Lecron, Fabian; Boisvert, Jonathan; Mahmoudi, Saïd; Labelle, Hubert; Benjelloun, Mohammed

    2012-01-01

    Severe cases of spinal deformities such as scoliosis are usually treated by a surgery where instrumentation (hooks, screws and rods) is installed to the spine to correct deformities. Even if the purpose is to obtain a normal spine curve, the result is often straighter than normal. In this paper, we propose a fast statistical reconstruction algorithm based on a general model which can deal with such instrumented spines. To this end, we present the concept of multilevel statistical model where the data are decomposed into a within-group and a between-group component. The reconstruction procedure is formulated as a second-order cone program which can be solved very fast (few tenths of a second). Reconstruction errors were evaluated on real patient data and results showed that multilevel modeling allows better 3D reconstruction than classical models.

  3. Modeling the dynamics of evaluation: a multilevel neural network implementation of the iterative reprocessing model.

    Science.gov (United States)

    Ehret, Phillip J; Monroe, Brian M; Read, Stephen J

    2015-05-01

    We present a neural network implementation of central components of the iterative reprocessing (IR) model. The IR model argues that the evaluation of social stimuli (attitudes, stereotypes) is the result of the IR of stimuli in a hierarchy of neural systems: The evaluation of social stimuli develops and changes over processing. The network has a multilevel, bidirectional feedback evaluation system that integrates initial perceptual processing and later developing semantic processing. The network processes stimuli (e.g., an individual's appearance) over repeated iterations, with increasingly higher levels of semantic processing over time. As a result, the network's evaluations of stimuli evolve. We discuss the implications of the network for a number of different issues involved in attitudes and social evaluation. The success of the network supports the IR model framework and provides new insights into attitude theory.

  4. Validity of information security policy models

    Directory of Open Access Journals (Sweden)

    Joshua Onome Imoniana

    Full Text Available Validity is concerned with establishing evidence for the use of a method to be used with a particular set of population. Thus, when we address the issue of application of security policy models, we are concerned with the implementation of a certain policy, taking into consideration the standards required, through attribution of scores to every item in the research instrument. En today's globalized economic scenarios, the implementation of information security policy, in an information technology environment, is a condition sine qua non for the strategic management process of any organization. Regarding this topic, various studies present evidences that, the responsibility for maintaining a policy rests primarily with the Chief Security Officer. The Chief Security Officer, in doing so, strives to enhance the updating of technologies, in order to meet all-inclusive business continuity planning policies. Therefore, for such policy to be effective, it has to be entirely embraced by the Chief Executive Officer. This study was developed with the purpose of validating specific theoretical models, whose designs were based on literature review, by sampling 10 of the Automobile Industries located in the ABC region of Metropolitan São Paulo City. This sampling was based on the representativeness of such industries, particularly with regards to each one's implementation of information technology in the region. The current study concludes, presenting evidence of the discriminating validity of four key dimensions of the security policy, being such: the Physical Security, the Logical Access Security, the Administrative Security, and the Legal & Environmental Security. On analyzing the Alpha of Crombach structure of these security items, results not only attest that the capacity of those industries to implement security policies is indisputable, but also, the items involved, homogeneously correlate to each other.

  5. A reference model for database security proxy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    How to protect the database, the kernel resources of information warfare, is becoming more and more important since the rapid development of computer and communication technology. As an application-level firewall, database security proxy can successfully repulse attacks originated from outside the network, reduce to zerolevel damage from foreign DBMS products. We enhanced the capability of the COAST's firewall reference model by adding a transmission unit modification function and an attribute value mapping function, describes the schematic and semantic layer reference model, and finally forms a reference model for DBMS security proxy which greatly helps in the design and implementation of database security proxies. This modeling process can clearly separate the system functionality into three layers, define the possible security functions for each layer, and estimate the computational cost for each layer.

  6. A reference model for database security proxy

    Institute of Scientific and Technical Information of China (English)

    蔡亮; 杨小虎; 董金祥

    2002-01-01

    How to protect the database, the kernel resources of information warfare, is becoming more and more important since the rapid development of computer and communication technology. As an application-level firewall, database security proxy can successfully repulse attacks originated from outside the network, reduce to zerolevel damage from foreign DBMS products. We enhanced the capability of the COAST' s firewall reference model by adding a transmission unit modification function and an attribute value mapping function,describes the schematic and semantic layer reference model, and finally forms a reference model for DBMS security proxy which greatly helps in the design and implementation of database security proxies. This modeling process can clearly separate the system functionality into three layers, define the possible security functions for each layer, and estimate the computational cost for each layer.

  7. A Comparison of Inverse-Wishart Prior Specifications for Covariance Matrices in Multilevel Autoregressive Models.

    Science.gov (United States)

    Schuurman, N K; Grasman, R P P P; Hamaker, E L

    2016-01-01

    Multilevel autoregressive models are especially suited for modeling between-person differences in within-person processes. Fitting these models with Bayesian techniques requires the specification of prior distributions for all parameters. Often it is desirable to specify prior distributions that have negligible effects on the resulting parameter estimates. However, the conjugate prior distribution for covariance matrices-the Inverse-Wishart distribution-tends to be informative when variances are close to zero. This is problematic for multilevel autoregressive models, because autoregressive parameters are usually small for each individual, so that the variance of these parameters will be small. We performed a simulation study to compare the performance of three Inverse-Wishart prior specifications suggested in the literature, when one or more variances for the random effects in the multilevel autoregressive model are small. Our results show that the prior specification that uses plug-in ML estimates of the variances performs best. We advise to always include a sensitivity analysis for the prior specification for covariance matrices of random parameters, especially in autoregressive models, and to include a data-based prior specification in this analysis. We illustrate such an analysis by means of an empirical application on repeated measures data on worrying and positive affect.

  8. Sufficient Sample Size and Power in Multilevel Ordinal Logistic Regression Models

    Directory of Open Access Journals (Sweden)

    Sabz Ali

    2016-01-01

    Full Text Available For most of the time, biomedical researchers have been dealing with ordinal outcome variable in multilevel models where patients are nested in doctors. We can justifiably apply multilevel cumulative logit model, where the outcome variable represents the mild, severe, and extremely severe intensity of diseases like malaria and typhoid in the form of ordered categories. Based on our simulation conditions, Maximum Likelihood (ML method is better than Penalized Quasilikelihood (PQL method in three-category ordinal outcome variable. PQL method, however, performs equally well as ML method where five-category ordinal outcome variable is used. Further, to achieve power more than 0.80, at least 50 groups are required for both ML and PQL methods of estimation. It may be pointed out that, for five-category ordinal response variable model, the power of PQL method is slightly higher than the power of ML method.

  9. Sufficient Sample Size and Power in Multilevel Ordinal Logistic Regression Models

    Science.gov (United States)

    Ali, Amjad; Khan, Sajjad Ahmad; Hussain, Sundas

    2016-01-01

    For most of the time, biomedical researchers have been dealing with ordinal outcome variable in multilevel models where patients are nested in doctors. We can justifiably apply multilevel cumulative logit model, where the outcome variable represents the mild, severe, and extremely severe intensity of diseases like malaria and typhoid in the form of ordered categories. Based on our simulation conditions, Maximum Likelihood (ML) method is better than Penalized Quasilikelihood (PQL) method in three-category ordinal outcome variable. PQL method, however, performs equally well as ML method where five-category ordinal outcome variable is used. Further, to achieve power more than 0.80, at least 50 groups are required for both ML and PQL methods of estimation. It may be pointed out that, for five-category ordinal response variable model, the power of PQL method is slightly higher than the power of ML method.

  10. The impact of ignoring multiple membership data structures in multilevel models.

    Science.gov (United States)

    Chung, Hyewon; Beretvas, S Natasha

    2012-05-01

    This study compared the use of the conventional multilevel model (MM) with that of the multiple membership multilevel model (MMMM) for handling multiple membership data structures. Multiple membership data structures are commonly encountered in longitudinal educational data sets in which, for example, mobile students are members of more than one higher-level unit (e.g., school). While the conventional MM requires the user either to delete mobile students' data or to ignore prior schools attended, MMMM permits inclusion of mobile students' data and models the effect of all schools attended on student outcomes. The simulation study identified underestimation of the school-level predictor coefficient, as well as underestimation of the level-two variance component with corresponding overestimation of the level-one variance when multiple membership data structures were ignored. Results are discussed along with limitations and ideas for future MMMM methodological research as well as implications for applied researchers.

  11. FUZZY MULTI-LEVEL WAREHOUSE LAYOUT PROBLEM: NEW MODEL AND ALGORITHM

    Institute of Scientific and Technical Information of China (English)

    Lixing YANG; Yuan FENG

    2006-01-01

    This paper deals with a multi-level warehouse layout problem under fuzzy environment, in which different types of items need to be placed in a multi-level warehouse and the monthly demand of each item type and horizontal distance traveled by clamp track are treated as fuzzy variables. In order to minimize the total transportation cost, chance-constrained programming model is designed for the problem based on the credibility measure and then tabu search algorithm based on the fuzzy simulation is designed to solve the model. Some mathematical properties of the model are also discussed when the fuzzy variables are interval fuzzy numbers or trapezoidal fuzzy numbers. Finally, a numerical example is presented to show the efficiency of the algorithm.

  12. New Models for Protocol Security

    Science.gov (United States)

    2015-06-18

    protocols and primitives (e.g., Schnorrs identification scheme, commitment schemes secure against selective openings, Chaum Blind Signatures , etc...Theory 156: 246-268 (2015) 5 3. Samantha Leung, Edward Lui, Rafael Pass: Voting with Coarse Beliefs. ITCS 2015: 61 4. Jing Chen, Silvio Micali, Rafael...Schneider: Multi-Verifier Signatures . J. Cryptology 25(2): 310-348 (2012) 7 37. Rafael Pass, Muthuramakrishnan Venkitasubramaniam: A Parallel Repetition

  13. Intelligent Model for Video Survillance Security System

    Directory of Open Access Journals (Sweden)

    J. Vidhya

    2013-12-01

    Full Text Available Video surveillance system senses and trails out all the threatening issues in the real time environment. It prevents from security threats with the help of visual devices which gather the information related to videos like CCTV’S and IP (Internet Protocol cameras. Video surveillance system has become a key for addressing problems in the public security. They are mostly deployed on the IP based network. So, all the possible security threats exist in the IP based application might also be the threats available for the reliable application which is available for video surveillance. In result, it may increase cybercrime, illegal video access, mishandling videos and so on. Hence, in this paper an intelligent model is used to propose security for video surveillance system which ensures safety and it provides secured access on video.

  14. Multilevel Modelling with Spatial Interaction Effects with Application to an Emerging Land Market in Beijing, China

    Science.gov (United States)

    Dong, Guanpeng; Harris, Richard; Jones, Kelvyn; Yu, Jianhui

    2015-01-01

    This paper develops a methodology for extending multilevel modelling to incorporate spatial interaction effects. The motivation is that classic multilevel models are not specifically spatial. Lower level units may be nested into higher level ones based on a geographical hierarchy (or a membership structure—for example, census zones into regions) but the actual locations of the units and the distances between them are not directly considered: what matters is the groupings but not how close together any two units are within those groupings. As a consequence, spatial interaction effects are neither modelled nor measured, confounding group effects (understood as some sort of contextual effect that acts ‘top down’ upon members of a group) with proximity effects (some sort of joint dependency that emerges between neighbours). To deal with this, we incorporate spatial simultaneous autoregressive processes into both the outcome variable and the higher level residuals. To assess the performance of the proposed method and the classic multilevel model, a series of Monte Carlo simulations are conducted. The results show that the proposed method performs well in retrieving the true model parameters whereas the classic multilevel model provides biased and inefficient parameter estimation in the presence of spatial interactions. An important implication of the study is to be cautious of an apparent neighbourhood effect in terms of both its magnitude and statistical significance if spatial interaction effects at a lower level are suspected. Applying the new approach to a two-level land price data set for Beijing, China, we find significant spatial interactions at both the land parcel and district levels. PMID:26086913

  15. Multiple Group Analysis in Multilevel Structural Equation Model Across Level 1 Groups.

    Science.gov (United States)

    Ryu, Ehri

    2015-01-01

    This article introduces and evaluates a procedure for conducting multiple group analysis in multilevel structural equation model across Level 1 groups (MG1-MSEM; Ryu, 2014). When group membership is at Level 1, multiple group analysis raises two issues that cannot be solved by a simple extension of the standard multiple group analysis in single-level structural equation model. First, the Level 2 data are not independent between Level 1 groups. Second, the standard procedure fails to take into account the dependency between members of different Level 1 groups within the same cluster. The MG1-MSEM approach provides solutions to these problems. In MG1-MSEM, the Level 1 mean structure is necessary to represent the differences between Level 1 groups within clusters. The Level 2 model is the same regardless of Level 1 group membership. A simulation study examined the performance of MUML (Muthén's maximum likelihood) estimation in MG1-MSEM. The MG1-MSEM approach is illustrated for both a multilevel path model and a multilevel factor model using empirical data sets.

  16. Keystone Business Models for Network Security Processors

    Directory of Open Access Journals (Sweden)

    Arthur Low

    2013-07-01

    Full Text Available Network security processors are critical components of high-performance systems built for cybersecurity. Development of a network security processor requires multi-domain experience in semiconductors and complex software security applications, and multiple iterations of both software and hardware implementations. Limited by the business models in use today, such an arduous task can be undertaken only by large incumbent companies and government organizations. Neither the “fabless semiconductor” models nor the silicon intellectual-property licensing (“IP-licensing” models allow small technology companies to successfully compete. This article describes an alternative approach that produces an ongoing stream of novel network security processors for niche markets through continuous innovation by both large and small companies. This approach, referred to here as the "business ecosystem model for network security processors", includes a flexible and reconfigurable technology platform, a “keystone” business model for the company that maintains the platform architecture, and an extended ecosystem of companies that both contribute and share in the value created by innovation. New opportunities for business model innovation by participating companies are made possible by the ecosystem model. This ecosystem model builds on: i the lessons learned from the experience of the first author as a senior integrated circuit architect for providers of public-key cryptography solutions and as the owner of a semiconductor startup, and ii the latest scholarly research on technology entrepreneurship, business models, platforms, and business ecosystems. This article will be of interest to all technology entrepreneurs, but it will be of particular interest to owners of small companies that provide security solutions and to specialized security professionals seeking to launch their own companies.

  17. Multiple-Attribute and Multilevel Synthetic Evaluation Model and Its Application

    Institute of Scientific and Technical Information of China (English)

    王坚强; 高阳

    2003-01-01

    On the basis of analyzing the flaws of present multiple-attribute and multilevel evaluation methods, concerning the problem of characteristics of the multiple-attribute and multilevel system's appraisal and the particular emphasis on the respective attributes in the evaluation process, as well as its relevance to the environment, an optimal attribute system is proposed, and the multiplicative analytic hierarchy process (MAHP) is used to obtain subjective weight coefficients and the objective weight coefficient evaluating method is given. The deviation between the index value of each level and the values of the same index of other levels are formulated, and an optimal model is gained, thus establishing the weight coefficients of the whole optimal attribute system. Furthermore, the detailed implementation procedure of this method is introduced. Besides, favorable results have been gained by applying the model to the practical problems of economic evaluation.

  18. The Design Model of Multilevel Estimation Means for Students’ Competence Assessment at Technical Higher School

    Directory of Open Access Journals (Sweden)

    O. F. Shikhova

    2012-01-01

    Full Text Available The paper considers the research findings aimed at the developing the new quality testing technique for students assessment at Technical Higher School. The model of multilevel estimation means is provided for diagnosing the level of general cultural and professional competences of students doing a bachelor degree in technological fields. The model implies the integrative character of specialists training - the combination of both the psycho-pedagogic (invariable and engineering (variable components, as well as the qualimetric approach substantiating the system of students competence estimation and providing the most adequate assessment means. The principles of designing the multilevel estimation means are defined along with the methodology approaches to their implementation. For the reasonable selection of estimation means, the system of quality criteria is proposed by the authors, being based on the group expert assessment. The research findings can be used for designing the competence-oriented estimation means. 

  19. Building ambidextrous organizations through intellectual capital: a proposal for a multilevel model

    Directory of Open Access Journals (Sweden)

    Susana Fernández-Pérez de la Lastra

    2017-08-01

    Full Text Available Purpose: This paper proposes an alternative theoretical model to describe, from a multilevel perspective, the way in which ambidexterity is built across different organizational levels, through specific combinations of the facets of intellectual capital—human, social and organizational capital. Design/methodology/approach: In this study, main arguments from intellectual capital, strategic human resource management (SHRM and multilevel literature are integrated. The intellectual capital literature provides our model with the input (human capital, mechanisms (social capital and the infrastructure (organizational capital required to create ambidextrous capabilities; the multilevel perspective reveals the context in which ambidexterity is reached, and the strategic human resource management literature provides the model with the specific mechanisms (policies and practices and conditions required by ambidexterity (HRM flexibility and horizontal fit. Findings: Although the literature widely recognizes ambidexterity as a potential source of sustainable competitive advantage, the processes by which organizations complement exploration and exploitation activities still remain unclear. This study sheds some light on the analysis of these complex dynamics, explaining how ambidextrous capabilities can arise from different alternative combinations of human, social and organizational capital. Originality/value: The paper expands the extant literature in the field, describing different paths to achieving organizational ambidexterity. The configurational approach adopted adds value to the proposed model, as it helps to explaining alternative synergistic mixes of ambidextrous intellectual capital at different organizational levels.

  20. Investigating patient safety culture across a health system: multilevel modelling of differences associated with service types and staff demographics

    National Research Council Canada - National Science Library

    Gallego, Blanca; Westbrook, Mary T; Dunn, Adam G; Braithwaite, Jeffrey

    2012-01-01

    To use multilevel modelling to compare the patient safety cultures of types of services across a health system and to determine whether differences found can be accounted for by staffs' professions...

  1. A Formal Model for the Security of Proxy Signature Schemes

    Institute of Scientific and Technical Information of China (English)

    GU Chun-xiang; ZHU Yue-fei; ZHANG Ya-juan

    2005-01-01

    This paper provides theoretical foundations for the secure proxy signature primitive. We present a formal model for the security of proxy signature schemes, which defines the capabilities of the adversary and the security goals to capture which mean for a proxy signature scheme to be secure. Then, we present an example of proxy signature scheme that can be proven secure in the standard model.

  2. Research on Assessment Model of Information System Security Based on Various Security Factors

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the rapid development of network technology, the meaning of layers and attributes in respect of information system security must be extended based on the understanding of the concept of information system security. The layering model (LM) of information system security and the five-attribute model (FAM) based on security factors were put forward to perfect the description and modeling of the information system security framework. An effective framework system of risk calculation and assessment was proposed, which is based on FAM.

  3. To center or not to center? Investigating inertia with a multilevel autoregressive model

    Directory of Open Access Journals (Sweden)

    Ellen L. Hamaker

    2015-01-01

    Full Text Available Whether level 1 predictors should be centered per cluster has received considerable attention in the multilevel literature. While most agree that there is no one preferred approach, it has also been argued that cluster mean centering is desirable when the within-cluster slope and the between-cluster slope are expected to deviate, and the main interest is in the within-cluster slope. However, we show in a series of simulations that if one has a multilevel autoregressive model in which the level 1 predictor is the lagged outcome variable (i.e., the outcome variable at the previous occasion, cluster mean centering will in general lead to a downward bias in the parameter estimate of the within-cluster slope (i.e., the autoregressive relationship. This is particularly relevant if the main question is whether there is on average an autoregressive effect. Nonetheless, we show that if the main interest is in estimating the effect of a level 2 predictor on the autoregressive parameter (i.e., a cross-level interaction, cluster mean centering should be preferred over other forms of centering. Hence, researchers should be clear on what is considered the main goal of their study, and base their choice of centering method on this when using a multilevel autoregressive model.

  4. Multilevel poisson regression modelling for determining factors of dengue fever cases in bandung

    Science.gov (United States)

    Arundina, Davila Rubianti; Tantular, Bertho; Pontoh, Resa Septiani

    2017-03-01

    Scralatina or Dengue Fever is a kind of fever caused by serotype virus which Flavivirus genus and be known as Dengue Virus. Dengue Fever caused by Aedes Aegipty Mosquito bites who infected by a dengue virus. The study was conducted in 151 villages in Bandung. Health Analysts believes that there are two factors that affect the dengue cases, Internal factor (individual) and external factor (environment). The data who used in this research is hierarchical data. The method is used for hierarchical data modelling is multilevel method. Which is, the level 1 is village and level 2 is sub-district. According exploration data analysis, the suitable Multilevel Method is Random Intercept Model. Penalized Quasi Likelihood (PQL) approach on multilevel Poisson is a proper analysis to determine factors that affecting dengue cases in the city of Bandung. Clean and Healthy Behavior factor from the village level have an effect on the number of cases of dengue fever in the city of Bandung. Factor from the sub-district level has no effect.

  5. Study on Mandatory Access Control in a Secure Database Management System

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper proposes a security policy model for mandatory access control in class B1 database management system whose level of labeling is tuple. The relation-hierarchical data model is extended to multilevel relation-hierarchical data model. Based on the multilevel relation-hierarchical data model, the concept of upper-lower layer relational integrity is presented after we analyze and eliminate the covert channels caused by the database integrity. Two SQL statements are extended to process polyinstantiation in the multilevel secure environment. The system is based on the multilevel relation-hierarchical data model and is capable of integratively storing and manipulating multilevel complicated objects (e. g., multilevel spatial data) and multilevel conventional data ( e. g., integer. real number and character string).

  6. Adaptive Modeling for Security Infrastructure Fault Response

    Institute of Scientific and Technical Information of China (English)

    CUI Zhong-jie; YAO Shu-ping; HU Chang-zhen

    2008-01-01

    Based on the analysis of inherent limitations in existing security response decision-making systems, a dynamic adaptive model of fault response is presented. Several security fault levels were founded, which comprise the basic level, equipment level and mechanism level. Fault damage cost is calculated using the analytic hierarchy process. Meanwhile, the model evaluates the impact of different responses upon fault repair and normal operation. Response operation cost and response negative cost are introduced through quantitative calculation. This model adopts a comprehensive response decision of security fault in three principles-the maximum and minimum principle, timeliness principle, acquiescence principle, which assure optimal response countermeasure is selected for different situations. Experimental results show that the proposed model has good self-adaptation ability, timeliness and cost-sensitiveness.

  7. Security Modeling on the Supply Chain Networks

    Directory of Open Access Journals (Sweden)

    Marn-Ling Shing

    2007-10-01

    Full Text Available In order to keep the price down, a purchaser sends out the request for quotation to a group of suppliers in a supply chain network. The purchaser will then choose a supplier with the best combination of price and quality. A potential supplier will try to collect the related information about other suppliers so he/she can offer the best bid to the purchaser. Therefore, confidentiality becomes an important consideration for the design of a supply chain network. Chen et al. have proposed the application of the Bell-LaPadula model in the design of a secured supply chain network. In the Bell-LaPadula model, a subject can be in one of different security clearances and an object can be in one of various security classifications. All the possible combinations of (Security Clearance, Classification pair in the Bell-LaPadula model can be thought as different states in the Markov Chain model. This paper extends the work done by Chen et al., provides more details on the Markov Chain model and illustrates how to use it to monitor the security state transition in the supply chain network.

  8. Random Intercept and Random Slope 2-Level Multilevel Models

    Directory of Open Access Journals (Sweden)

    Rehan Ahmad Khan

    2012-11-01

    Full Text Available Random intercept model and random intercept & random slope model carrying two-levels of hierarchy in the population are presented and compared with the traditional regression approach. The impact of students’ satisfaction on their grade point average (GPA was explored with and without controlling teachers influence. The variation at level-1 can be controlled by introducing the higher levels of hierarchy in the model. The fanny movement of the fitted lines proves variation of student grades around teachers.

  9. Modeling behavioral considerations related to information security.

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Moyano, I. J.; Conrad, S. H.; Andersen, D. F. (Decision and Information Sciences); (SNL); (Univ. at Albany)

    2011-01-01

    The authors present experimental and simulation results of an outcome-based learning model for the identification of threats to security systems. This model integrates judgment, decision-making, and learning theories to provide a unified framework for the behavioral study of upcoming threats.

  10. Multilevel IRT Modeling in Practice with the Package mlirt

    NARCIS (Netherlands)

    Fox, Jean-Paul

    2007-01-01

    Variance component models are generally accepted for the analysis of hierarchical structured data. A shortcoming is that outcome variables are still treated as measured without an error. Unreliable variables produce biases in the estimates of the other model parameters. The variability of the relati

  11. A Multilevel Nonlinear Profile Analysis Model for Dichotomous Data

    Science.gov (United States)

    Culpepper, Steven Andrew

    2009-01-01

    This study linked nonlinear profile analysis (NPA) of dichotomous responses with an existing family of item response theory models and generalized latent variable models (GLVM). The NPA method offers several benefits over previous internal profile analysis methods: (a) NPA is estimated with maximum likelihood in a GLVM framework rather than…

  12. A Longitudinal Multilevel CFA-MTMM Model for Interchangeable and StructurallyDifferent Methods

    Directory of Open Access Journals (Sweden)

    Tobias eKoch

    2014-04-01

    Full Text Available One of the key interests in the social sciences is the investigation of change and stability of a given attribute. Although numerous models have been proposed in the past for analyzing longitudinal data including multilevel and/or latent variable modeling approaches, only few modeling approaches have been developed for studying the construct validity in longitudinal multitrait-multimethod (MTMM measurement designs. The aim of the present study was to extend the spectrum of current longitudinal modeling approaches for MTMM analysis. Specifically, a new longitudinal multilevel CFA-MTMM model for measurement designs with structurally different and interchangeable methods (called Latent-State-Combination-Of-Methods model, LS-COM is presented. Interchangeable methods are methods that are randomly sampled from a set of equivalent methods (e.g., multiple student ratings for teaching quality, whereas structurally different methods are methods that cannot be easily replaced by one another (e.g., teacher, self-ratings, principle ratings. Results of a simulation study indicate that the parameters and standard errors in the LS-COM model are well recovered even in conditions with only 5 observations per estimated model parameter. The advantages and limitations of the LS-COM model relative to other longitudinal MTMM modeling approaches are discussed.

  13. A longitudinal multilevel CFA-MTMM model for interchangeable and structurally different methods.

    Science.gov (United States)

    Koch, Tobias; Schultze, Martin; Eid, Michael; Geiser, Christian

    2014-01-01

    One of the key interests in the social sciences is the investigation of change and stability of a given attribute. Although numerous models have been proposed in the past for analyzing longitudinal data including multilevel and/or latent variable modeling approaches, only few modeling approaches have been developed for studying the construct validity in longitudinal multitrait-multimethod (MTMM) measurement designs. The aim of the present study was to extend the spectrum of current longitudinal modeling approaches for MTMM analysis. Specifically, a new longitudinal multilevel CFA-MTMM model for measurement designs with structurally different and interchangeable methods (called Latent-State-Combination-Of-Methods model, LS-COM) is presented. Interchangeable methods are methods that are randomly sampled from a set of equivalent methods (e.g., multiple student ratings for teaching quality), whereas structurally different methods are methods that cannot be easily replaced by one another (e.g., teacher, self-ratings, principle ratings). Results of a simulation study indicate that the parameters and standard errors in the LS-COM model are well recovered even in conditions with only five observations per estimated model parameter. The advantages and limitations of the LS-COM model relative to other longitudinal MTMM modeling approaches are discussed.

  14. Cyberspace Forensics Readiness and Security Awareness Model

    Directory of Open Access Journals (Sweden)

    Aadil Al-Mahrouqi

    2015-06-01

    Full Text Available The goal of reaching a high level of security in wire- less and wired communication networks is continuously proving difficult to achieve. The speed at which both keepers and violators of secure networks are evolving is relatively close. Nowadays, network infrastructures contain a large number of event logs captured by Firewalls and Domain Controllers (DCs. However, these logs are increasingly becoming an obstacle for network administrators in analyzing networks for malicious activities. Forensic investigators mission to detect malicious activities and reconstruct incident scenarios is extremely complex considering the number, as well as the quality of these event logs. This paper presents the building blocks for a model for automated network readiness and awareness. The idea for this model is to utilize the current network security outputs to construct forensically comprehensive evidence. The proposed model covers the three vital phases of the cybercrime management chain, which are: 1 Forensics Readiness, 2 Active Forensics, and 3 Forensics Awareness.

  15. A multilevel approach to modeling of porous bioceramics

    Science.gov (United States)

    Mikushina, Valentina A.; Sidorenko, Yury N.

    2015-10-01

    The paper is devoted to discussion of multiscale models of heterogeneous materials using principles. The specificity of approach considered is the using of geometrical model of composites representative volume, which must be generated with taking the materials reinforcement structure into account. In framework of such model may be considered different physical processes which have influence on the effective mechanical properties of composite, in particular, the process of damage accumulation. It is shown that such approach can be used to prediction the value of composite macroscopic ultimate strength. As an example discussed the particular problem of the study the mechanical properties of biocomposite representing porous ceramics matrix filled with cortical bones tissue.

  16. Lipid Processing Technology: Building a Multilevel Modeling Network

    DEFF Research Database (Denmark)

    Diaz Tovar, Carlos Axel; Mustaffa, Azizul Azri; Hukkerikar, Amol

    of these unit operations with respect to performance parameters such as minimum total cost, product yield improvement, operability etc., and process intensification for the retrofit of existing biofuel plants. In the fourth level the information and models developed are used as building blocks...... in the upcoming years major challenges in terms of design and development of better products and more sustainable processes. Although the oleo chemical industry is mature and based on well established processes, the complex systems that lipid compounds form, the lack of accurate predictive models...... for their physical properties and unit operation models for their processing have limited computeraided methods and tools for process synthesis, modeling and simulation to be widely used for design, analysis, and optimization of these processes. In consequence, the aim of this work is to present the development...

  17. Building a Multilevel Modeling Network for Lipid Processing Systems

    DEFF Research Database (Denmark)

    Diaz Tovar, Carlos Axel; Mustaffa, Azizul Azri; Hukkerikar, Amol

    for their physical properties and unit operation models for their processing have limited computer-aided methods and tools for process synthesis, modeling and simulation to be widely used for design, analysis, and optimization of these processes. The world’s fats and oils production has been growing rapidly over...... limited computer-aided methods and tools for process synthesis, modeling and simulation to be widely used for design, analysis, and optimization of these processes....... in the upcoming years major challenges in terms of design and development of better products and more sustainable processes. Although the oleo chemical industry is mature and based on well established processes, the complex systems that lipid compounds form, the lack of accurate predictive models...

  18. Multilevel Security Oriented Cross Domain Exchange Technology%面向多级安全的跨域交换技术研究

    Institute of Scientific and Technical Information of China (English)

    肖柳林

    2014-01-01

    跨域交换技术为不同安全域之间的数据通信提供了便利,但由于跨域信息系统开放了域内多个端口,面临着各种来自系统内外部的安全威胁,导致了信任危机。针对现有跨域信息系统在数据交换方面的安全需求,首先分析了当前跨域信息交换存在的问题,接着设计了面向多级安全的跨域交换系统架构,该架构能够有效地实现多域信息系统的安全互联与资源共享,然后研究了安全标签绑定、内容过滤等关键技术,最后对下一步的研究工作进行了展望。%Cross domain exchange technology provides a convenience for data communication between dif-ferent security domains. However, due to a number of opened ports of cross domain information systems, it faces various security threats from internal and external system, leading to a crisis of confidence. Aiming at the existing cross domain information system security requirements in terms of data exchange, this paper firstly analyzes the current problems of cross domain exchange of information, and then proposes multilevel security architecture of the cross domain exchange system, which can effectively implement secure inter-connection and resource sharing in the multi domain information system. Moreover, security label binding and content filtering technologies are studied. Finally, the next research jobs are discussed.

  19. MODEL MULTILEVEL PERTUMBUHAN ANAK USIA 0-24 BULAN DAN VARIABEL YANG MEMPENGARUHINYA

    Directory of Open Access Journals (Sweden)

    Irianton Aritonang

    2013-01-01

    Full Text Available Tujuan umum penelitian ini untuk mengkaji bagaimana berbagai variabel mempengaruhi pertumbuhan anak usia 0-24 bulan di kabupaten Sleman. Penelitian noneksperimen desain korelasional ini dilakukan pada 272 anak usia 0-24 bulan yang diambil secara acak stratifikasi dari dua kecamatan (Sleman dan Moyudan yang ditentukan secara purposif. Analisis multilevel pertumbuhan anak dilakukan dengan program Stata-10 dan analisis jalur dilakukan dengan program Amos-8. Hasil penelitian menunjukkan bahwa ada hubungan variabel berat badan lahir, jenis kelamin dan strata usia anak dan status gizi ibu dengan pertumbuhan anak pada level-1 dan ada hubungan variabel hasil penimbangan pada level-2, sedangkan pada level 3 ada hubungan yang tidak signifikan hasil penimbangan dan pencapaian program. Hasil analisis jalur yang mempengaruhi pertumbuhan anak 0-24 bulan, yakni variabel endogenous terdiri dari status gizi ibu, pengetahuan ibu tentang gizi seimbang, pertumbuhan anak indeks BB/U, hasil penimbangan tingkat dusun dan hasil program tingkat desa. Sedangkan variabel exogenous terdiri dari sikap ibu terhadap posyandu, berat badan lahir, jenis kelamin dan stratifikasi usia anak. Kata kunci: Model multilevel, Pertumbuhan anak 0-24 bulan ______________________________________________________________ A MULTILEVEL MODEL FOR THE GROWTH OF CHILDREN AGED 0-24 MONTHS AND THE VARIABLES AFFECTING IT Abstract The main objective of this study is to investigate how various variables contribute to the growth of children between 0-24  months old in Sleman Regency. This study was a non-experimental correlational design which was conducted on 272 children aged 0-24 months, selected using the purposive stratified random sampling technique from 21 hamlets in two districts (Sleman and Moyudan. The multilevel analysis of children’s growth of was carried out using the Stata-10 program and the path analysis using the Amos-8 program. The results show  that there is a significant

  20. Sample Size Considerations in Prevention Research Applications of Multilevel Modeling and Structural Equation Modeling.

    Science.gov (United States)

    Hoyle, Rick H; Gottfredson, Nisha C

    2015-10-01

    When the goal of prevention research is to capture in statistical models some measure of the dynamic complexity in structures and processes implicated in problem behavior and its prevention, approaches such as multilevel modeling (MLM) and structural equation modeling (SEM) are indicated. Yet the assumptions that must be satisfied if these approaches are to be used responsibly raise concerns regarding their use in prevention research involving smaller samples. In this article, we discuss in nontechnical terms the role of sample size in MLM and SEM and present findings from the latest simulation work on the performance of each approach at sample sizes typical of prevention research. For each statistical approach, we draw from extant simulation studies to establish lower bounds for sample size (e.g., MLM can be applied with as few as ten groups comprising ten members with normally distributed data, restricted maximum likelihood estimation, and a focus on fixed effects; sample sizes as small as N = 50 can produce reliable SEM results with normally distributed data and at least three reliable indicators per factor) and suggest strategies for making the best use of the modeling approach when N is near the lower bound.

  1. A 2 x 2 Taxonomy of Multilevel Latent Contextual Models: Accuracy-Bias Trade-Offs in Full and Partial Error Correction Models

    Science.gov (United States)

    Ludtke, Oliver; Marsh, Herbert W.; Robitzsch, Alexander; Trautwein, Ulrich

    2011-01-01

    In multilevel modeling, group-level variables (L2) for assessing contextual effects are frequently generated by aggregating variables from a lower level (L1). A major problem of contextual analyses in the social sciences is that there is no error-free measurement of constructs. In the present article, 2 types of error occurring in multilevel data…

  2. Multilevel model reduction for uncertainty quantification in computational structural dynamics

    Science.gov (United States)

    Ezvan, O.; Batou, A.; Soize, C.; Gagliardini, L.

    2016-11-01

    Within the continuum mechanics framework, there are two main approaches to model interfaces: classical cohesive zone modeling (CZM) and interface elasticity theory. The classical CZM deals with geometrically non-coherent interfaces for which the constitutive relation is expressed in terms of traction-separation laws. However, CZM lacks any response related to the stretch of the mid-plane of the interface. This issue becomes problematic particularly at small scales with increasing interface area to bulk volume ratios, where interface elasticity is no longer negligible. The interface elasticity theory, in contrast to CZM, deals with coherent interfaces that are endowed with their own energetic structures, and thus is capable of capturing elastic resistance to tangential stretch. Nonetheless, the interface elasticity theory suffers from the lack of inelastic material response, regardless of the strain level. The objective of this contribution therefore is to introduce a generalized mechanical interface model that couples both the elastic response along the interface and the cohesive response across the interface whereby interface degradation is taken into account. The material degradation of the interface mid-plane is captured by a non-local damage model of integral-type. The out-of-plane decohesion is described by a classical cohesive zone model. These models are then coupled through their corresponding damage variables. The non-linear governing equations and the weak forms thereof are derived. The numerical implementation is carried out using the finite element method and consistent tangents are derived. Finally, a series of numerical examples is studied to provide further insight into the problem and to carefully elucidate key features of the proposed theory.

  3. A Multilevel Testlet Model for Dual Local Dependence

    Science.gov (United States)

    Jiao, Hong; Kamata, Akihito; Wang, Shudong; Jin, Ying

    2012-01-01

    The applications of item response theory (IRT) models assume local item independence and that examinees are independent of each other. When a representative sample for psychometric analysis is selected using a cluster sampling method in a testlet-based assessment, both local item dependence and local person dependence are likely to be induced.…

  4. Multilevel complexity of calcium signaling:Modeling angiogenesis

    Institute of Scientific and Technical Information of China (English)

    Luca; Munaron; Marco; Scianna

    2012-01-01

    Intracellular calcium signaling is a universal,evolutionary conserved and versatile regulator of cell biochemistry.The complexity of calcium signaling and related cell machinery can be investigated by the use of experimental strategies,as well as by computational approaches.Vascular endothelium is a fascinating model to study the specific properties and roles of calcium signals at multiple biological levels.During the past 20 years,live cell imaging,patch clamp and other techniques have allowed us to detect and interfere with calcium signaling in endothelial cells(ECs),providing a huge amount of information on the regulation of vascularization(angiogenesis) in normal and tumoral tissues.These data range from the spatiotemporal dynamics of calcium within different cell microcompartments to those in entire multicellular and organized EC networks.Beside experimental strategies,in silico endothelial models,specifically designed for simulating calcium signaling,are contributing to our knowledge of vascular physiol-ogy and pathology.They help to investigate and predict the quantitative features of proangiogenic events moving through subcellular,cellular and supracellular levels.This review focuses on some recent developments of computational approaches for proangiogenic endothelial calcium signaling.In particular,we discuss the creation of hybrid simulation environments,which combine and integrate discrete Cellular Potts Models.They are able to capture the phenomenological mechanisms of cell morphological reorganization,migration,and intercellular adhesion,with single-cell spatiotemporal models,based on reaction-diffusion equations that describe the agonist-induced intracellular calcium events.

  5. A multilevel nonlinear mixed-effects approach to model growth in pigs

    DEFF Research Database (Denmark)

    Strathe, Anders Bjerring; Danfær, Allan Christian; Sørensen, H

    2009-01-01

    Growth functions have been used to predict market weight of pigs and maximize return over feed costs. This study was undertaken to compare 4 growth functions and methods of analyzing data, particularly one that considers nonlinear repeated measures. Data were collected from an experiment with 40...... pigs maintained from birth to maturity and their BW measured weekly or every 2 wk up to 1,007 d. Gompertz, logistic, Bridges, and Lopez functions were fitted to the data and compared using information criteria. For each function, a multilevel nonlinear mixed effects model was employed because....... Furthermore, studies should consider adding continuous autoregressive process when analyzing nonlinear mixed models with repeated measures....

  6. A Dynamic Multi-Level Factor Model with Long-Range Dependence

    DEFF Research Database (Denmark)

    Ergemen, Yunus Emre; Rodríguez-Caballero, Carlos Vladimir

    A dynamic multi-level factor model with stationary or nonstationary global and regional factors is proposed. In the model, persistence in global and regional common factors as well as innovations allows for the study of fractional cointegrating relationships. Estimation of global and regional...... is then applied to the Nord Pool power market for the analysis of price comovements among different regions within the power grid. We find that the global factor can be interpreted as the system price of the power grid as well as a fractional cointegration relationship between prices and the global factor....

  7. Multi-Level Marketing as a business model

    Directory of Open Access Journals (Sweden)

    Bogdan Gregor

    2013-03-01

    Full Text Available Multi Level Marketing is a very popular business model in the Western countries. It is a kind of hybrid of the method of distribution of goods and the method of building a sales network. It is one of the safest (carries a very low risk ways of conducting a business activity. The knowledge about functioning of this business model, both among theoreticians (scanty literature on the subject and practitioners, is still insufficient in Poland. Thus, the presented paper has been prepared as — in the Authors' opinion — it, at least infinitesimally, bridges the gap in the recognition of Multi Level Marketing issues. The aim of the study was, first of all, to describe Multi Level Marketing, to indicate practical benefits of this business model as well as to present basic systems of calculating a commission, which are used in marketing plans of companies. The discussion was based on the study of literature and the knowledge gained in the course of free-form interviews with the leaders of the sector.

  8. Software Security and the "Building Security in Maturity" Model

    CERN Document Server

    CERN. Geneva

    2011-01-01

    Using the framework described in my book "Software Security: Building Security In" I will discuss and describe the state of the practice in software security. This talk is peppered with real data from the field, based on my work with several large companies as a Cigital consultant. As a discipline, software security has made great progress over the last decade. Of the sixty large-scale software security initiatives we are aware of, thirty-two---all household names---are currently included in the BSIMM study. Those companies among the thirty-two who graciously agreed to be identified include: Adobe, Aon, Bank of America, Capital One, The Depository Trust & Clearing Corporation (DTCC), EMC, Google, Intel, Intuit, McKesson, Microsoft, Nokia, QUALCOMM, Sallie Mae, Standard Life, SWIFT, Symantec, Telecom Italia, Thomson Reuters, VMware, and Wells Fargo. The BSIMM was created by observing and analyzing real-world data from thirty-two leading software security initiatives. The BSIMM can...

  9. A Model of Social Security?

    DEFF Research Database (Denmark)

    Rom-Jensen, Byron Zachary

    2017-01-01

    This essay provides historical perspective to Senator Bernie Sanders’ appropriation of elements of the Nordic model in the 2016 campaign by studying how Scandinavia was used as a political image in 1930s United States. Departing from previous scholarship, this essay argues that accounts of Scandi...... and its 1939 amendments. The surprising plasticity of the Scandinavian image amongst policymakers ultimately reveals the fluid nature of both New Deal-era politics and the Scandinavian images it appropriated....

  10. E-Learning Security Models

    Directory of Open Access Journals (Sweden)

    Vladimir I. Zuev

    2012-06-01

    Full Text Available The article looks into methods and models that are useful when analyzing the risks and vulnerabilities of complex e-learning systems in an emergency management context. Definitions of vulnerability and emergency response capabilities, such as "VLE/PLE attack surface", are suggested.The article provides insight into some of the issues related to analysis of risks and vulnerabilities of e-learning systems, but more research is needed to address this difficult and comprehensive task.

  11. Doubly-Latent Models of School Contextual Effects: Integrating Multilevel and Structural Equation Approaches to Control Measurement and Sampling Error

    Science.gov (United States)

    Marsh, Herbert W.; Ludtke, Oliver; Robitzsch, Alexander; Trautwein, Ulrich; Asparouhov, Tihomir; Muthen, Bengt; Nagengast, Benjamin

    2009-01-01

    This article is a methodological-substantive synergy. Methodologically, we demonstrate latent-variable contextual models that integrate structural equation models (with multiple indicators) and multilevel models. These models simultaneously control for and unconfound measurement error due to sampling of items at the individual (L1) and group (L2)…

  12. A improved Network Security Situation Awareness Model

    Directory of Open Access Journals (Sweden)

    Li Fangwei

    2015-08-01

    Full Text Available In order to reflect the situation of network security assessment performance fully and accurately, a new network security situation awareness model based on information fusion was proposed. Network security situation is the result of fusion three aspects evaluation. In terms of attack, to improve the accuracy of evaluation, a situation assessment method of DDoS attack based on the information of data packet was proposed. In terms of vulnerability, a improved Common Vulnerability Scoring System (CVSS was raised and maked the assessment more comprehensive. In terms of node weights, the method of calculating the combined weights and optimizing the result by Sequence Quadratic Program (SQP algorithm which reduced the uncertainty of fusion was raised. To verify the validity and necessity of the method, a testing platform was built and used to test through evaluating 2000 DAPRA data sets. Experiments show that the method can improve the accuracy of evaluation results.

  13. Modeling the Competitiveness of Indonesian Palm Oil Industry: A Conceptual Model Using Hierarchical Multi-Level System Approach

    Directory of Open Access Journals (Sweden)

    Roland Y.H. Silitonga

    2013-01-01

    Full Text Available Indonesian Palm Oil Industry has the largest market share in the world, but still faces problems in order to strengthen the level of competitiveness. Those problems are in the industry chains, government regulation and policy as meso environment, and macro economic condition. Therefore these three elements should be considered when analyzing the improvement of competitiveness. Here, the governmental element is hoped to create a conducive environment. This paper presents the industry competitiveness conceptual model, using hierarchical multilevel system approach. The Hierarchical multilevel system approach is used to accommodate the complexity of the industrial relation and the government position as the meso environment. The step to develop the model firstly is to define the relevant system. Secondly, is to formulate the output of the model that is competitiveness in the form of indicator. Then, the relevant system with competitiveness as the output is built into a conceptual model using hierarchical multilevel system. The conceptual model is then discussed to see if it can explain the relevant system, and the potential of it to be developed into mathematical model.

  14. Multi-Level Web Cache Model Used in Data Grid Application

    Institute of Scientific and Technical Information of China (English)

    CHEN Lei; LI Sanli

    2006-01-01

    This paper proposed a novel multilevel data cache model by Web cache (MDWC) based on network cost in data grid. By constructing a communicating tree of grid sites based on network cost and using a single leader for each data segment within each region, the MDWC makes the most use of the Web cache of other sites whose bandwidth is as broad as covering the job executing site. The experiment result indicates that the MDWC reduces data response time and data update cost by avoiding network congestions while designing on the parameters concluded by the environment of application.

  15. A Novel Method to Verify Multilevel Computational Models of Biological Systems Using Multiscale Spatio-Temporal Meta Model Checking.

    Science.gov (United States)

    Pârvu, Ovidiu; Gilbert, David

    2016-01-01

    Insights gained from multilevel computational models of biological systems can be translated into real-life applications only if the model correctness has been verified first. One of the most frequently employed in silico techniques for computational model verification is model checking. Traditional model checking approaches only consider the evolution of numeric values, such as concentrations, over time and are appropriate for computational models of small scale systems (e.g. intracellular networks). However for gaining a systems level understanding of how biological organisms function it is essential to consider more complex large scale biological systems (e.g. organs). Verifying computational models of such systems requires capturing both how numeric values and properties of (emergent) spatial structures (e.g. area of multicellular population) change over time and across multiple levels of organization, which are not considered by existing model checking approaches. To address this limitation we have developed a novel approximate probabilistic multiscale spatio-temporal meta model checking methodology for verifying multilevel computational models relative to specifications describing the desired/expected system behaviour. The methodology is generic and supports computational models encoded using various high-level modelling formalisms because it is defined relative to time series data and not the models used to generate it. In addition, the methodology can be automatically adapted to case study specific types of spatial structures and properties using the spatio-temporal meta model checking concept. To automate the computational model verification process we have implemented the model checking approach in the software tool Mule (http://mule.modelchecking.org). Its applicability is illustrated against four systems biology computational models previously published in the literature encoding the rat cardiovascular system dynamics, the uterine contractions of labour

  16. Analyzing Multiple Multivariate Time Series Data Using Multilevel Dynamic Factor Models.

    Science.gov (United States)

    Song, Hairong; Zhang, Zhiyong

    2014-01-01

    Multivariate time series data offer researchers opportunities to study dynamics of various systems in social and behavioral sciences. Dynamic factor model (DFM), as an idiographic approach for studying intraindividual variability and dynamics, has typically been applied to time series data obtained from a single unit. When multivariate time series data are collected from multiple units, how to synchronize dynamical information becomes a silent issue. To address this issue, the current study presented a multilevel dynamic factor model (MDFM) that analyzes multiple multivariate time series in multilevel SEM frameworks. MDFM not only disentangles within- and between-person variability but also models dynamics of the intraindividual processes. To illustrate the uses of MDFMs, we applied lag0, lag1, and lag2 MDFMs to empirical data on affect collected from 205 dating couples who had at least 50 consecutive days of observations. We also considered a model extension where the dynamical coefficients were allowed to be randomly varying in the population. The empirical analysis yielded interesting findings regarding affect regulation and coregulation within couples, demonstrating promising uses of MDFMs in analyzing multiple multivariate time series. In the end, we discussed a number of methodological issues in the applications of MDFMs and pointed out possible directions for future research.

  17. Study of visualized simulation and analysis of nuclear fuel cycle system based on multilevel flow model

    Institute of Scientific and Technical Information of China (English)

    LIU Jing-Quan; YOSHIKAWA Hidekazu; ZHOU Yang-Ping

    2005-01-01

    Complex energy and environment system, especially nuclear fuel cycle system recently raised social concerns about the issues of economic competitiveness, environmental effect and nuclear proliferation. Only under the condition that those conflicting issues are gotten a consensus between stakeholders with different knowledge background, can nuclear power industry be continuingly developed. In this paper, a new analysis platform has been developed to help stakeholders to recognize and analyze various socio-technical issues in the nuclear fuel cycle system based on the functional modeling method named Multilevel Flow Models (MFM) according to the cognition theory of human being. Its character is that MFM models define a set of mass, energy and information flow structures on multiple levels of abstraction to describe the functional structure of a process system and its graphical symbol representation and the means-end and part-whole hierarchical flow structure to make the represented process easy to be understood. Based upon this methodology, a micro-process and a macro-process of nuclear fuel cycle system were selected to be simulated and some analysis processes such as economics analysis, environmental analysis and energy balance analysis related to those flows were also integrated to help stakeholders to understand the process of decision-making with the introduction of some new functions for the improved Multilevel Flow Models Studio, and finally the simple simulation such as spent fuel management process simulation and money flow of nuclear fuel cycle and its levelised cost analysis will be represented as feasible examples.

  18. Representing Operational Knowledge of PWR Plant by Using Multilevel Flow Modelling

    DEFF Research Database (Denmark)

    Zhang, Xinxin; Lind, Morten; Jørgensen, Sten Bay

    2014-01-01

    situation and support operational decisions. This paper will provide a general MFM model of the primary side in a standard Westinghouse Pressurized Water Reactor ( PWR ) system including sub - systems of Reactor Coolant System, Rod Control System, Chemical and Volume Control System, emergency heat removal......The aim of this paper is to explore the capability of representing operational knowledge by using Multilevel Flow Modelling ( MFM ) methodology. The paper demonstrate s how the operational knowledge can be inserted into the MFM models and be used to evaluate the plant state, identify the current...... systems. And the sub - systems’ functions will be decomposed into sub - models according to different operational situations. An operational model will be developed based on the operating procedure by using MFM symbols and this model can be used to implement coordination rules for organize the utilizati...

  19. A simulation study of sample size for multilevel logistic regression models

    Directory of Open Access Journals (Sweden)

    Moineddin Rahim

    2007-07-01

    Full Text Available Abstract Background Many studies conducted in health and social sciences collect individual level data as outcome measures. Usually, such data have a hierarchical structure, with patients clustered within physicians, and physicians clustered within practices. Large survey data, including national surveys, have a hierarchical or clustered structure; respondents are naturally clustered in geographical units (e.g., health regions and may be grouped into smaller units. Outcomes of interest in many fields not only reflect continuous measures, but also binary outcomes such as depression, presence or absence of a disease, and self-reported general health. In the framework of multilevel studies an important problem is calculating an adequate sample size that generates unbiased and accurate estimates. Methods In this paper simulation studies are used to assess the effect of varying sample size at both the individual and group level on the accuracy of the estimates of the parameters and variance components of multilevel logistic regression models. In addition, the influence of prevalence of the outcome and the intra-class correlation coefficient (ICC is examined. Results The results show that the estimates of the fixed effect parameters are unbiased for 100 groups with group size of 50 or higher. The estimates of the variance covariance components are slightly biased even with 100 groups and group size of 50. The biases for both fixed and random effects are severe for group size of 5. The standard errors for fixed effect parameters are unbiased while for variance covariance components are underestimated. Results suggest that low prevalent events require larger sample sizes with at least a minimum of 100 groups and 50 individuals per group. Conclusion We recommend using a minimum group size of 50 with at least 50 groups to produce valid estimates for multi-level logistic regression models. Group size should be adjusted under conditions where the prevalence

  20. A multilevel model of organizational health culture and the effectiveness of health promotion.

    Science.gov (United States)

    Lin, Yea-Wen; Lin, Yueh-Ysen

    2014-01-01

    Organizational health culture is a health-oriented core characteristic of the organization that is shared by all members. It is effective in regulating health-related behavior for employees and could therefore influence the effectiveness of health promotion efforts among organizations and employees. This study applied a multilevel analysis to verify the effects of organizational health culture on the organizational and individual effectiveness of health promotion. At the organizational level, we investigated the effect of organizational health culture on the organizational effectiveness of health promotion. At the individual level, we adopted a cross-level analysis to determine if organizational health culture affects employee effectiveness through the mediating effect of employee health behavior. The study setting consisted of the workplaces of various enterprises. We selected 54 enterprises in Taiwan and surveyed 20 full-time employees from each organization, for a total sample of 1011 employees. We developed the Organizational Health Culture Scale to measure employee perceptions and aggregated the individual data to formulate organization-level data. Organizational effectiveness of health promotion included four dimensions: planning effectiveness, production, outcome, and quality, which were measured by scale or objective indicators. The Health Promotion Lifestyle Scale was adopted for the measurement of health behavior. Employee effectiveness was measured subjectively in three dimensions: self-evaluated performance, altruism, and happiness. Following the calculation of descriptive statistics, hierarchical linear modeling (HLM) was used to test the multilevel hypotheses. Organizational health culture had a significant effect on the planning effectiveness (β = .356, p organizational health culture on three dimensions of employee effectiveness were completely mediated by health behavior. The construct connections established in this multilevel model will help in

  1. A Policy Model for Secure Information Flow

    Science.gov (United States)

    Adetoye, Adedayo O.; Badii, Atta

    When a computer program requires legitimate access to confidential data, the question arises whether such a program may illegally reveal sensitive information. This paper proposes a policy model to specify what information flow is permitted in a computational system. The security definition, which is based on a general notion of information lattices, allows various representations of information to be used in the enforcement of secure information flow in deterministic or nondeterministic systems. A flexible semantics-based analysis technique is presented, which uses the input-output relational model induced by an attacker’s observational power, to compute the information released by the computational system. An illustrative attacker model demonstrates the use of the technique to develop a termination-sensitive analysis. The technique allows the development of various information flow analyses, parametrised by the attacker’s observational power, which can be used to enforce what declassification policies.

  2. Agent-based model with multi-level herding for complex financial systems

    Science.gov (United States)

    Chen, Jun-Jie; Tan, Lei; Zheng, Bo

    2015-02-01

    In complex financial systems, the sector structure and volatility clustering are respectively important features of the spatial and temporal correlations. However, the microscopic generation mechanism of the sector structure is not yet understood. Especially, how to produce these two features in one model remains challenging. We introduce a novel interaction mechanism, i.e., the multi-level herding, in constructing an agent-based model to investigate the sector structure combined with volatility clustering. According to the previous market performance, agents trade in groups, and their herding behavior comprises the herding at stock, sector and market levels. Further, we propose methods to determine the key model parameters from historical market data, rather than from statistical fitting of the results. From the simulation, we obtain the sector structure and volatility clustering, as well as the eigenvalue distribution of the cross-correlation matrix, for the New York and Hong Kong stock exchanges. These properties are in agreement with the empirical ones. Our results quantitatively reveal that the multi-level herding is the microscopic generation mechanism of the sector structure, and provide new insight into the spatio-temporal interactions in financial systems at the microscopic level.

  3. Agent-based model with multi-level herding for complex financial systems.

    Science.gov (United States)

    Chen, Jun-Jie; Tan, Lei; Zheng, Bo

    2015-02-11

    In complex financial systems, the sector structure and volatility clustering are respectively important features of the spatial and temporal correlations. However, the microscopic generation mechanism of the sector structure is not yet understood. Especially, how to produce these two features in one model remains challenging. We introduce a novel interaction mechanism, i.e., the multi-level herding, in constructing an agent-based model to investigate the sector structure combined with volatility clustering. According to the previous market performance, agents trade in groups, and their herding behavior comprises the herding at stock, sector and market levels. Further, we propose methods to determine the key model parameters from historical market data, rather than from statistical fitting of the results. From the simulation, we obtain the sector structure and volatility clustering, as well as the eigenvalue distribution of the cross-correlation matrix, for the New York and Hong Kong stock exchanges. These properties are in agreement with the empirical ones. Our results quantitatively reveal that the multi-level herding is the microscopic generation mechanism of the sector structure, and provide new insight into the spatio-temporal interactions in financial systems at the microscopic level.

  4. Building a traceable climate model hierarchy with multi-level emulators

    Science.gov (United States)

    Tran, Giang T.; Oliver, Kevin I. C.; Sóbester, András; Toal, David J. J.; Holden, Philip B.; Marsh, Robert; Challenor, Peter; Edwards, Neil R.

    2016-04-01

    To study climate change on multi-millennial timescales or to explore a model's parameter space, efficient models with simplified and parameterised processes are required. However, the reduction in explicitly modelled processes can lead to underestimation of some atmospheric responses that are essential to the understanding of the climate system. While more complex general circulations are available and capable of simulating a more realistic climate, they are too computationally intensive for these purposes. In this work, we propose a multi-level Gaussian emulation technique to efficiently estimate the outputs of steady-state simulations of an expensive atmospheric model in response to changes in boundary forcing. The link between a computationally expensive atmospheric model, PLASIM (Planet Simulator), and a cheaper model, EMBM (energy-moisture balance model), is established through the common boundary condition specified by an ocean model, allowing for information to be propagated from one to the other. This technique allows PLASIM emulators to be built at a low cost. The method is first demonstrated by emulating a scalar summary quantity, the global mean surface air temperature. It is then employed to emulate the dimensionally reduced 2-D surface air temperature field. Even though the two atmospheric models chosen are structurally unrelated, Gaussian process emulators of PLASIM atmospheric variables are successfully constructed using EMBM as a fast approximation. With the extra information gained from the cheap model, the multi-level emulator of PLASIM's 2-D surface air temperature field is built using only one-third the amount of expensive data required by the normal single-level technique. The constructed emulator is shown to capture 93.2 % of the variance across the validation ensemble, with the averaged RMSE of 1.33 °C. Using the method proposed, quantities from PLASIM can be constructed and used to study the effects introduced by PLASIM's atmosphere.

  5. Multilevel modeling and panel data analysis in educational research (Case study: National examination data senior high school in West Java)

    Science.gov (United States)

    Zulvia, Pepi; Kurnia, Anang; Soleh, Agus M.

    2017-03-01

    Individual and environment are a hierarchical structure consist of units grouped at different levels. Hierarchical data structures are analyzed based on several levels, with the lowest level nested in the highest level. This modeling is commonly call multilevel modeling. Multilevel modeling is widely used in education research, for example, the average score of National Examination (UN). While in Indonesia UN for high school student is divided into natural science and social science. The purpose of this research is to develop multilevel and panel data modeling using linear mixed model on educational data. The first step is data exploration and identification relationships between independent and dependent variable by checking correlation coefficient and variance inflation factor (VIF). Furthermore, we use a simple model approach with highest level of the hierarchy (level-2) is regency/city while school is the lowest of hierarchy (level-1). The best model was determined by comparing goodness-of-fit and checking assumption from residual plots and predictions for each model. Our finding that for natural science and social science, the regression with random effects of regency/city and fixed effects of the time i.e multilevel model has better performance than the linear mixed model in explaining the variability of the dependent variable, which is the average scores of UN.

  6. Modelling and simulation of complex systems: an approach based on multi-level agents

    CERN Document Server

    Fougères, Alain-Jérôme

    2012-01-01

    A complex system is made up of many components with many interactions. So the design of systems such as simulation systems, cooperative systems or assistance systems includes a very accurate modelling of interactional and communicational levels. The agent-based approach provides an adapted abstraction level for this problem. After having studied the organizational context and communicative capacities of agentbased systems, to simulate the reorganization of a flexible manufacturing, to regulate an urban transport system, and to simulate an epidemic detection system, our thoughts on the interactional level were inspired by human-machine interface models, especially those in "cognitive engineering". To provide a general framework for agent-based complex systems modelling, we then proposed a scale of four behaviours that agents may adopt in their complex systems (reactive, routine, cognitive, and collective). To complete the description of multi-level agent models, which is the focus of this paper, we illustrate ...

  7. A Multilevel Model for Comorbid Outcomes: Obesity and Diabetes in the US

    Directory of Open Access Journals (Sweden)

    Peter Congdon

    2010-01-01

    Full Text Available Multilevel models are overwhelmingly applied to single health outcomes, but when two or more health conditions are closely related, it is important that contextual variation in their joint prevalence (e.g., variations over different geographic settings is considered. A multinomial multilevel logit regression approach for analysing joint prevalence is proposed here that includes subject level risk factors (e.g., age, race, education while also taking account of geographic context. Data from a US population health survey (the 2007 Behavioral Risk Factor Surveillance System or BRFSS are used to illustrate the method, with a six category multinomial outcome defined by diabetic status and weight category (obese, overweight, normal. The influence of geographic context is partly represented by known geographic variables (e.g., county poverty, and partly by a model for latent area influences. In particular, a shared latent variable (common factor approach is proposed to measure the impact of unobserved area influences on joint weight and diabetes status, with the latent variable being spatially structured to reflect geographic clustering in risk.

  8. Modeling and Capacitors Voltage Balancing Control of STATCOM Based on Modular Multilevel Converter

    Directory of Open Access Journals (Sweden)

    Milad Samady Shadlu

    2016-12-01

    Full Text Available Modular multilevel converter (MMC provides a new concept in a wide range of applications due to its simple topology and high reliability. In this paper, a three phase four legs modular multilevel converter is used as a compensator in a four-wire network which feeds an unbalanced and distorted custom load. The purpose is to compensate this unbalance load currents by injection suitable currents besides the capacitors voltage balancing control in individual legs. In this paper, designing of compensator current controller will be done based on a composite control model (CCM combined of average model and predictive control method. Also an independent controller has been proposed for capacitors voltage balancing whose task is to eliminate the circulating current oscillations in each leg. In order to control total energy stored in converter and also to remove the zero sequence current, two simple control schemes have been presented based on PI controller and closed loop controller, respectively. Finally simulation results have been presented in MATLAB/Simulink to confirm effectiveness and accuracy of proposed controller.

  9. Formal Analysis of Graphical Security Models

    DEFF Research Database (Denmark)

    Aslanyan, Zaruhi

    The increasing usage of computer-based systems in almost every aspects of our daily life makes more and more dangerous the threat posed by potential attackers, and more and more rewarding a successful attack. Moreover, the complexity of these systems is also increasing, including physical devices......, software components and human actors interacting with each other to form so-called socio-technical systems. The importance of socio-technical systems to modern societies requires verifying their security properties formally, while their inherent complexity makes manual analyses impracticable. Graphical...... models for security offer an unrivalled opportunity to describe socio-technical systems, for they allow to represent different aspects like human behaviour, computation and physical phenomena in an abstract yet uniform manner. Moreover, these models can be assigned a formal semantics, thereby allowing...

  10. The Development of a Multi-Level Model for Crisis Preparedness and Intervention in the Greek Educational System

    Science.gov (United States)

    Hatzichristiou, Chryse; Issari, Philia; Lykitsakou, Konstantina; Lampropoulou, Aikaterini; Dimitropoulou, Panayiota

    2011-01-01

    This article proposes a multi-level model for crisis preparedness and intervention in the Greek educational system. It presents: a) a brief overview of leading models of school crisis preparedness and intervention as well as cultural considerations for contextually relevant crisis response; b) a description of existing crisis intervention…

  11. Data Model Approach And Markov Chain Based Analysis Of Multi-Level Queue Scheduling

    Directory of Open Access Journals (Sweden)

    Diwakar Shukla

    2010-01-01

    Full Text Available There are many CPU scheduling algorithms inliterature like FIFO, Round Robin, Shortest-Job-First and so on.The Multilevel-Queue-Scheduling is superior to these due to itsbetter management of a variety of processes. In this paper, aMarkov chain model is used for a general setup of Multilevelqueue-scheduling and the scheduler is assumed to performrandom movement on queue over the quantum of time.Performance of scheduling is examined through a rowdependent data model. It is found that with increasing value of αand d, the chance of system going over the waiting state reduces.At some of the interesting combinations of α and d, it diminishesto zero, thereby, provides us some clue regarding better choice ofqueues over others for high priority jobs. It is found that ifqueue priorities are added in the scheduling intelligently thenbetter performance could be obtained. Data model helpschoosing appropriate preferences.

  12. Energy iteration model research of DCM Buck converter with multilevel pulse train technique

    Science.gov (United States)

    Qin, Ming; Li, Xiang

    2017-08-01

    According as the essence of switching converter is the nature of energy, the energy iteration model of the Multilevel Pulse Train (MPT) technique is studied in this paper. The energy iteration model of DCM Buck converter with MPT technique can reflect the control law and excellent transient performance of the MPT technique. The iteration relation of energy transfer in switching converter is discussed. The structure and operation principle of DCM Buck converter with MPT technique is introduced and the energy iteration model of this converter is set up. The energy tracks of MPT-control Buck converter and PT converter is researched and compared to show that the ratio of steady-state control pulse satisfies the expectation for the MPT technique and the MPT-controlled switching converter has much lower output voltage ripple than the PT converter.

  13. Future consumer mobile phone security: A case study using the data-centric security model

    NARCIS (Netherlands)

    Cleeff, van A.

    2008-01-01

    Consumer mobile phone security requires more attention, now that their data storage capacity is increasing. At the same time, much effort is spent on data-centric security for large enterprises. In this article we try to apply data-centric security to consumer mobile phones. We show a maturity model

  14. Future consumer mobile phone security: A case study using the data-centric security model

    NARCIS (Netherlands)

    van Cleeff, A.

    Consumer mobile phone security requires more attention, now that their data storage capacity is increasing. At the same time, much effort is spent on data-centric security for large enterprises. In this article we try to apply data-centric security to consumer mobile phones. We show a maturity model

  15. Future consumer mobile phone security: A case study using the data-centric security model

    NARCIS (Netherlands)

    van Cleeff, A.

    2008-01-01

    Consumer mobile phone security requires more attention, now that their data storage capacity is increasing. At the same time, much effort is spent on data-centric security for large enterprises. In this article we try to apply data-centric security to consumer mobile phones. We show a maturity model

  16. Design of multilevel flow modelling-based decision support system by using multiagent platform

    DEFF Research Database (Denmark)

    Zhang, Xinxin; Lind, Morten; Ravn, Ole

    2015-01-01

    For complex engineering systems, there is an increasing demand forsafety and reliability. Decision support system (DSS) is designed to offersupervision and analysis about operational situations. A proper modelrepresentation is required for DSS to understand the process knowledge.Multilevel flow m...... available techniques of MFM reasoning and less matureyet relevant MFM concepts are considered. It also offers an architecture designof task organisation for MFM software tools by using the concept of agent andtechnology of multiagent software system......For complex engineering systems, there is an increasing demand forsafety and reliability. Decision support system (DSS) is designed to offersupervision and analysis about operational situations. A proper modelrepresentation is required for DSS to understand the process knowledge.Multilevel flow...... modelling (MFM) represents complex system in multiplelevels of means-end and part-whole decompositions, which is proposed in thispaper as basis for developing decision support systems. The aim of this paper isto explore the different possible functionalities by applying MFM to DSS,where both currently...

  17. Association of father involvement and neighborhood quality with kindergartners' physical activity: a multilevel structural equation model.

    Science.gov (United States)

    Beets, Michael W; Foley, John T

    2008-01-01

    Examine the effects of father-child involvement and neighborhood characteristics with young children's physical activity (PA) within a multilevel framework. Cross-sectional analysis of the Early Childhood Longitudinal Study-Kindergarten Cohort 1998. Nationally representative sample. Data were available for 10,694 kindergartners (5-6 years; 5240 girls) living in 1053 neighborhoods. Parental report of child's PA level, father characteristics (e.g., time spent with child, age, education, socioeconomic status, hours worked), family time spent doing sports/ activities together, and neighborhood quality (e.g., safety, presence of crime violence, garbage). Child weight status, motor skills, ethnicity, and television viewing were used as covariates. Multilevel structural equation modeling with children nested within neighborhoods. At the child level father-child time and family time doing sports together were positively associated with children's PA. At the neighborhood level parental perception of a neighborhood's safety for children to play outside fully mediated the effect of neighborhood quality on children's PA. Overall 19.1% and 7.6% of the variance in PA was explained at the child and neighborhood levels, respectively. Family-based interventions for PA should consider father-child time, with this contributing to a child's overall PA level. Further, neighborhood quality is an important predictor of PA only to the extent by which parents perceive it to be unsafe for their child to play outdoors.

  18. CRISP. Information Security Models and Their Economics

    Energy Technology Data Exchange (ETDEWEB)

    Gustavsson, R.; Mellstrand, P.; Tornqvist, B. [Blekinge Institute of Technology BTH, Karlskrona (Sweden)

    2005-03-15

    The deliverable D1.6 includes background material and specifications of a CRISP Framework on protection of information assets related to power net management and management of business operations related to energy services. During the project it was discovered by the CRISP consortium that the original description of WP 1.6 was not adequate for the project as such. The main insight was that the original emphasis on cost-benefit analysis of security protection measures was to early to address in the project. This issue is of course crucial in itself but requires new models of consequence analysis that still remains to be developed, especially for the new business models we are investigated in the CRISP project. The updated and approved version of the WP1.6 description, together with the also updated WP2.4 focus on Dependable ICT support of Power Grid Operations constitutes an integrated approach towards dependable and secure future utilities and their business processes. This document (D1.6) is a background to deliverable D2.4. Together they provide a dependability and security framework to the three CRISP experiments in WP3.

  19. Mixed-Method Quasi-Experimental Study of Outcomes of a Large-Scale Multilevel Economic and Food Security Intervention on HIV Vulnerability in Rural Malawi.

    Science.gov (United States)

    Weinhardt, Lance S; Galvao, Loren W; Yan, Alice F; Stevens, Patricia; Mwenyekonde, Thokozani Ng'ombe; Ngui, Emmanuel; Emer, Lindsay; Grande, Katarina M; Mkandawire-Valhmu, Lucy; Watkins, Susan C

    2017-03-01

    The objective of the Savings, Agriculture, Governance, and Empowerment for Health (SAGE4Health) study was to evaluate the impact of a large-scale multi-level economic and food security intervention on health outcomes and HIV vulnerability in rural Malawi. The study employed a quasi-experimental non-equivalent control group design to compare intervention participants (n = 598) with people participating in unrelated programs in distinct but similar geographical areas (control, n = 301). We conducted participant interviews at baseline, 18-, and 36-months on HIV vulnerability and related health outcomes, food security, and economic vulnerability. Randomly selected households (n = 1002) were interviewed in the intervention and control areas at baseline and 36 months. Compared to the control group, the intervention led to increased HIV testing (OR 1.90; 95 % CI 1.29-2.78) and HIV case finding (OR = 2.13; 95 % CI 1.07-4.22); decreased food insecurity (OR = 0.74; 95 % CI 0.63-0.87), increased nutritional diversity, and improved economic resilience to shocks. Most effects were sustained over a 3-year period. Further, no significant differences in change were found over the 3-year study period on surveys of randomly selected households in the intervention and control areas. Although there were general trends toward improvement in the study area, only intervention participants' outcomes were significantly better. Results indicate the intervention can improve economic and food security and HIV vulnerability through increased testing and case finding. Leveraging the resources of economic development NGOs to deliver locally-developed programs with scientific funding to conduct controlled evaluations has the potential to accelerate the scientific evidence base for the effects of economic development programs on health.

  20. A secure operational model for mobile payments.

    Science.gov (United States)

    Chang, Tao-Ku

    2014-01-01

    Instead of paying by cash, check, or credit cards, customers can now also use their mobile devices to pay for a wide range of services and both digital and physical goods. However, customers' security concerns are a major barrier to the broad adoption and use of mobile payments. In this paper we present the design of a secure operational model for mobile payments in which access control is based on a service-oriented architecture. A customer uses his/her mobile device to get authorization from a remote server and generate a two-dimensional barcode as the payment certificate. This payment certificate has a time limit and can be used once only. The system also provides the ability to remotely lock and disable the mobile payment service.

  1. A Secure Operational Model for Mobile Payments

    Directory of Open Access Journals (Sweden)

    Tao-Ku Chang

    2014-01-01

    Full Text Available Instead of paying by cash, check, or credit cards, customers can now also use their mobile devices to pay for a wide range of services and both digital and physical goods. However, customers’ security concerns are a major barrier to the broad adoption and use of mobile payments. In this paper we present the design of a secure operational model for mobile payments in which access control is based on a service-oriented architecture. A customer uses his/her mobile device to get authorization from a remote server and generate a two-dimensional barcode as the payment certificate. This payment certificate has a time limit and can be used once only. The system also provides the ability to remotely lock and disable the mobile payment service.

  2. Secure State UML: Modeling and Testing Security Concerns of Software Systems Using UML State Machines

    Directory of Open Access Journals (Sweden)

    S. Batool

    2014-05-01

    Full Text Available In this research we present a technique by using which, extended UML models can be converted to standard UML models so that existing MBT techniques can be applied directly on these models. Existing Model Based Testing (MBT Techniques cannot be directly applied to extended UML models due to the difference of modeling notation and new model elements. Verification of these models is also very important. Realizing and testing non functional requirements such as efficiency, portability and security, at model level strengthens the ability of model to turn down risk, cost and probability of system failure in cost effective way. Access control is most widely used technique for implementing security in software systems. Existing approaches for security modeling focus on representation of access control policies such as authentication, role based access control by introducing security oriented model elements through extension in Unified Modelling Language (UML. But doing so hinders the potential and application of MBT techniques to verify these models and test access control policies. In this research we introduce a technique secure State UML to formally design security models with secure UML and then transform it to UML state machine diagrams so that it can be tested, verified by existing MBT techniques. By applying proposed technique on case studies, we found the results that MBT techniques can be applied on resulting state machine diagrams and generated test paths have potential to identify the risks associated with security constraints violation.

  3. PARALLEL ADAPTIVE MULTILEVEL SAMPLING ALGORITHMS FOR THE BAYESIAN ANALYSIS OF MATHEMATICAL MODELS

    KAUST Repository

    Prudencio, Ernesto

    2012-01-01

    In recent years, Bayesian model updating techniques based on measured data have been applied to many engineering and applied science problems. At the same time, parallel computational platforms are becoming increasingly more powerful and are being used more frequently by the engineering and scientific communities. Bayesian techniques usually require the evaluation of multi-dimensional integrals related to the posterior probability density function (PDF) of uncertain model parameters. The fact that such integrals cannot be computed analytically motivates the research of stochastic simulation methods for sampling posterior PDFs. One such algorithm is the adaptive multilevel stochastic simulation algorithm (AMSSA). In this paper we discuss the parallelization of AMSSA, formulating the necessary load balancing step as a binary integer programming problem. We present a variety of results showing the effectiveness of load balancing on the overall performance of AMSSA in a parallel computational environment.

  4. From least squares to multilevel modeling: A graphical introduction to Bayesian inference

    Science.gov (United States)

    Loredo, Thomas J.

    2016-01-01

    This tutorial presentation will introduce some of the key ideas and techniques involved in applying Bayesian methods to problems in astrostatistics. The focus will be on the big picture: understanding the foundations (interpreting probability, Bayes's theorem, the law of total probability and marginalization), making connections to traditional methods (propagation of errors, least squares, chi-squared, maximum likelihood, Monte Carlo simulation), and highlighting problems where a Bayesian approach can be particularly powerful (Poisson processes, density estimation and curve fitting with measurement error). The "graphical" component of the title reflects an emphasis on pictorial representations of some of the math, but also on the use of graphical models (multilevel or hierarchical models) for analyzing complex data. Code for some examples from the talk will be available to participants, in Python and in the Stan probabilistic programming language.

  5. How structure shapes dynamics: knowledge development in Wikipedia--a network multilevel modeling approach.

    Directory of Open Access Journals (Sweden)

    Iassen Halatchliyski

    Full Text Available Using a longitudinal network analysis approach, we investigate the structural development of the knowledge base of Wikipedia in order to explain the appearance of new knowledge. The data consists of the articles in two adjacent knowledge domains: psychology and education. We analyze the development of networks of knowledge consisting of interlinked articles at seven snapshots from 2006 to 2012 with an interval of one year between them. Longitudinal data on the topological position of each article in the networks is used to model the appearance of new knowledge over time. Thus, the structural dimension of knowledge is related to its dynamics. Using multilevel modeling as well as eigenvector and betweenness measures, we explain the significance of pivotal articles that are either central within one of the knowledge domains or boundary-crossing between the two domains at a given point in time for the future development of new knowledge in the knowledge base.

  6. Experimental studies of a prototype model of the multilevel 6KW-power inverter at supply by 12 accumulators

    Science.gov (United States)

    Taissariyeva, K.; Issembergenov, N.; Dzhobalaeva, G.; Usembaeva, S.

    2016-09-01

    The given paper considers the multilevel 6 kW-power transistor inverter at supply by 12 accumulators for transformation of solar battery energy to the electric power. At the output of the multilevel transistor inverter, it is possible to receive voltage close to a sinusoidal form. The main objective of this inverter is transformation of solar energy to the electric power of industrial frequency. The analysis of the received output curves of voltage on harmonicity has been carried out. In this paper it is set forth the developed scheme of the multilevel transistor inverter (DC-to-ac converter) which allows receiving at the output the voltage close to sinusoidal form, as well as to regulation of the output voltage level. In the paper, the results of computer modeling and experimental studies are presented.

  7. Modeling and Security in Cloud Ecosystems

    Directory of Open Access Journals (Sweden)

    Eduardo B. Fernandez

    2016-04-01

    Full Text Available Clouds do not work in isolation but interact with other clouds and with a variety of systems either developed by the same provider or by external entities with the purpose to interact with them; forming then an ecosystem. A software ecosystem is a collection of software systems that have been developed to coexist and evolve together. The stakeholders of such a system need a variety of models to give them a perspective of the possibilities of the system, to evaluate specific quality attributes, and to extend the system. A powerful representation when building or using software ecosystems is the use of architectural models, which describe the structural aspects of such a system. These models have value for security and compliance, are useful to build new systems, can be used to define service contracts, find where quality factors can be monitored, and to plan further expansion. We have described a cloud ecosystem in the form of a pattern diagram where its components are patterns and reference architectures. A pattern is an encapsulated solution to a recurrent problem. We have recently expanded these models to cover fog systems and containers. Fog Computing is a highly-virtualized platform that provides compute, storage, and networking services between end devices and Cloud Computing Data Centers; a Software Container provides an execution environment for applications sharing a host operating system, binaries, and libraries with other containers. We intend to use this architecture to answer a variety of questions about the security of this system as well as a reference to design interacting combinations of heterogeneous components. We defined a metamodel to relate security concepts which is being expanded.

  8. SECURE MATHEMATICALLY- ASSURED COMPOSITION OF CONTROL MODELS

    Science.gov (United States)

    2017-09-27

    that is provably secure against many classes of cyber -attack. The goal of the project is to provide verifiable security ; that is, system designs which...architecture of the secure SMACCMcopter, illustrating the attack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 46 Failed cyber -attack...approach for building secure software. DARPA initiated the High Assurance Cyber Military Systems (HACMS) program to develop the technologies needed to

  9. Rejection, Feeling Bad, and Being Hurt: Using Multilevel Modeling to Clarify the Link between Peer Group Aggression and Adjustment

    Science.gov (United States)

    Rulison, Kelly L.; Gest, Scott D.; Loken, Eric; Welsh, Janet A.

    2010-01-01

    The association between affiliating with aggressive peers and behavioral, social and psychological adjustment was examined. Students initially in 3rd, 4th, and 5th grade (N = 427) were followed biannually through 7th grade. Students' peer-nominated groups were identified. Multilevel modeling was used to examine the independent contributions of…

  10. Estimation of Contextual Effects through Nonlinear Multilevel Latent Variable Modeling with a Metropolis-Hastings Robbins-Monro Algorithm

    Science.gov (United States)

    Yang, Ji Seung; Cai, Li

    2014-01-01

    The main purpose of this study is to improve estimation efficiency in obtaining maximum marginal likelihood estimates of contextual effects in the framework of nonlinear multilevel latent variable model by adopting the Metropolis-Hastings Robbins-Monro algorithm (MH-RM). Results indicate that the MH-RM algorithm can produce estimates and standard…

  11. Estimation of Contextual Effects through Nonlinear Multilevel Latent Variable Modeling with a Metropolis-Hastings Robbins-Monro Algorithm

    Science.gov (United States)

    Yang, Ji Seung; Cai, Li

    2014-01-01

    The main purpose of this study is to improve estimation efficiency in obtaining maximum marginal likelihood estimates of contextual effects in the framework of nonlinear multilevel latent variable model by adopting the Metropolis-Hastings Robbins-Monro algorithm (MH-RM). Results indicate that the MH-RM algorithm can produce estimates and standard…

  12. Taiwanese Students' Science Learning Self-Efficacy and Teacher and Student Science Hardiness: A Multilevel Model Approach

    Science.gov (United States)

    Wang, Ya-Ling; Tsai, Chin-Chung

    2016-01-01

    This study aimed to investigate the factors accounting for science learning self-efficacy (the specific beliefs that people have in their ability to complete tasks in science learning) from both the teacher and the student levels. We thus propose a multilevel model to delineate its relationships with teacher and student science hardiness (i.e.,…

  13. A Multilevel Modelling Approach to Investigating Factors Impacting Science Achievement for Secondary School Students: PISA Hong Kong Sample

    Science.gov (United States)

    Sun, Letao; Bradley, Kelly D.; Akers, Kathryn

    2012-01-01

    This study utilized data from the 2006 Programme for International Student Assessment Hong Kong sample to investigate the factors that impact the science achievement of 15-year-old students. A multilevel model was used to examine the factors from both student and school perspectives. At the student level, the results indicated that male students,…

  14. Adaptable Authentication Model: Exploring Security with Weaker Attacker Models

    DEFF Research Database (Denmark)

    Ahmed, Naveed; Jensen, Christian D.

    2011-01-01

    suffer because of the identified vulnerabilities. Therefore, we may need to analyze a protocol for weaker notions of security. In this paper, we present a security model that supports such weaker notions. In this model, the overall goals of an authentication protocol are broken into a finer granularity......; for each fine level authentication goal, we determine the “least strongest-attacker” for which the authentication goal can be satisfied. We demonstrate that this model can be used to reason about the security of supposedly insecure protocols. Such adaptability is particularly useful in those applications......Most methods for protocol analysis classify protocols as “broken” if they are vulnerable to attacks from a strong attacker, e.g., assuming the Dolev-Yao attacker model. In many cases, however, exploitation of existing vulnerabilities may not be practical and, moreover, not all applications may...

  15. The application of multilevel modelling to account for the influence of walking speed in gait analysis.

    Science.gov (United States)

    Keene, David J; Moe-Nilssen, Rolf; Lamb, Sarah E

    2016-01-01

    Differences in gait performance can be explained by variations in walking speed, which is a major analytical problem. Some investigators have standardised speed during testing, but this can result in an unnatural control of gait characteristics. Other investigators have developed test procedures where participants walking at their self-selected slow, preferred and fast speeds, with computation of gait characteristics at a standardised speed. However, this analysis is dependent upon an overlap in the ranges of gait speed observed within and between participants, and this is difficult to achieve under self-selected conditions. In this report a statistical analysis procedure is introduced that utilises multilevel modelling to analyse data from walking tests at self-selected speeds, without requiring an overlap in the range of speeds observed or the routine use of data transformations.

  16. Exact and approximate ensemble treatments of thermal pairing in a multilevel model

    Science.gov (United States)

    Hung, N. Quang; Dang, N. Dinh

    2009-05-01

    A systematic comparison is conducted for pairing properties of finite systems at nonzero temperature as predicted by the exact solutions of the pairing problem embedded in three principal statistical ensembles, as well as the unprojected (FTBCS1+SCQRPA) and Lipkin+Nogami projected (FTLN1+SCQRPA) theories that include the quasiparticle number fluctuation and coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. The numerical calculations are performed for the pairing gap, total energy, heat capacity, entropy, and microcanonical temperature within the doubly folded equidistant multilevel pairing model. The FTLN1+SCQRPA predictions agree best with the exact grand-canonical results. In general, all approaches clearly show that the superfluid-normal phase transition is smoothed out in finite systems. A novel formula is suggested for extracting the empirical pairing gap in reasonable agreement with the exact canonical results.

  17. Exact and approximate ensemble treatments of thermal pairing in a multilevel model

    CERN Document Server

    Hung, N Quang

    2009-01-01

    A systematic comparison is conducted for pairing properties of finite systems at nonzero temperature as predicted by the exact solutions of the pairing problem embedded in three principal statistical ensembles, as well as the unprojected (FTBCS1+SCQRPA) and Lipkin-Nogami projected (FTLN1+SCQRPA) theories that include the quasiparticle number fluctuation and coupling to pair vibrations within the self-consistent quasiparticle random-phase approximation. The numerical calculations are performed for the pairing gap, total energy, heat capacity, entropy, and microcanonical temperature within the doubly-folded equidistant multilevel pairing model. The FTLN1+SCQRPA predictions agree best with the exact grand-canonical results. In general, all approaches clearly show that the superfluid-normal phase transition is smoothed out in finite systems. A novel formula is suggested for extracting the empirical pairing gap in reasonable agreement with the exact canonical results.

  18. Handling Missing Data With Multilevel Structural Equation Modeling and Full Information Maximum Likelihood Techniques.

    Science.gov (United States)

    Schminkey, Donna L; von Oertzen, Timo; Bullock, Linda

    2016-08-01

    With increasing access to population-based data and electronic health records for secondary analysis, missing data are common. In the social and behavioral sciences, missing data frequently are handled with multiple imputation methods or full information maximum likelihood (FIML) techniques, but healthcare researchers have not embraced these methodologies to the same extent and more often use either traditional imputation techniques or complete case analysis, which can compromise power and introduce unintended bias. This article is a review of options for handling missing data, concluding with a case study demonstrating the utility of multilevel structural equation modeling using full information maximum likelihood (MSEM with FIML) to handle large amounts of missing data. MSEM with FIML is a parsimonious and hypothesis-driven strategy to cope with large amounts of missing data without compromising power or introducing bias. This technique is relevant for nurse researchers faced with ever-increasing amounts of electronic data and decreasing research budgets. © 2016 Wiley Periodicals, Inc.

  19. Application of Gauss-Seidel multilevel control to a single axis torsional model

    Science.gov (United States)

    Chichester, F. D.

    1981-01-01

    An approach to the application of multilevel control techniques for large space structures is presented. Gauss-Seidel second level controls and an extension of standard linear quadratic regulator techniques are applied to a model consisting of a flexible space vehicle comprising three rigid bodies rotating about a common axis. The method incorporates second order derivatives with respect to time, entailing the use of a two level hierarchy of subsystems. Gauss-Seidel second level control formulations were chosen to avoid the necessity of having as many controls as constraints or using gradient techniques in the choice of the Hamiltonian. The modular nature of the resulting control system allows applications for spacecraft with larger numbers of modules.

  20. Multilevel modelling for the regional effect of enforcement on road accidents.

    Science.gov (United States)

    Yannis, George; Papadimitriou, Eleonora; Antoniou, Constantinos

    2007-07-01

    This paper investigates the effect of the intensification of Police enforcement on the number of road accidents at national and regional level in Greece, focusing on one of the most important road safety violations: drinking-and-driving. Multilevel negative binomial models are developed to describe the effect of the intensification of alcohol enforcement on the reduction of road accidents in different regions of Greece. Moreover, two approaches are explored as far as regional clustering is concerned: the first one concerns an ad hoc geographical clustering and the second one is based on the results of mathematical cluster analysis through demographic, transport and road safety characteristics. Results indicate that there are significant spatial dependences among road accidents and enforcement. Additionally, it is shown that these dependences are more efficiently interpreted when regions are determined on the basis of qualitative similarities than on the basis of geographical adjacency.

  1. A Multilevel Latent Growth Modelling of the Longitudinal Changes in Motivation Regulations in Physical Education

    Directory of Open Access Journals (Sweden)

    Timo Jaakkola

    2015-03-01

    Full Text Available The purpose of this study was to examine individual- and classroom-level differences in the longitudinal change in motivational regulations during physical education students’ transition from elementary (Grade 6 across middle school (Grades 7 to 9. A sample of 757 Finnish adolescents (M = 12.71, SD = 0.23 participated in this study. Participants of the study responded to questionnaires collected six times. A multilevel latent growth modelling approach was used to analyze the data. Results showed that motivational regulations in physical education developed at different rates during middle school. More specifically, students’: (a identified regulation increased across Grades 6 to 9; (b amotivation increased during middle school transition from Grade 6 to 7; and (c introjected regulation declined from Grade 8 to 9. Other motivational regulations remained stable across time. The changes in amotivation and introjected regulation were largely due to individual factors, whereas the changes in identified regulation were due to environmental factors.

  2. Towards a Model of the Costs of Security

    OpenAIRE

    Larochelle, David; Rosasco, Nicholas

    2003-01-01

    We present a simple information security model to determine why, historically, the level of security has not increased despite numerous technical advances. In our model, the software design process involves trade-offs between security and functionality. Developers choose points in the design space corresponding to certain levels of security and functionality. If development resources, such as number of developers, time for completion, etc., are fixed, there is an implicit trade-off between se...

  3. Multilevel modeling was a convenient alternative to common regression designs in longitudinal suicide research.

    Science.gov (United States)

    Antretter, Elfi; Dunkel, Dirk; Osvath, Peter; Voros, Viktor; Fekete, Sandor; Haring, Christian

    2006-06-01

    The prospective investigation of repetitive nonfatal suicidal behavior is associated with two methodological problems. Due to the commonly used definitions of nonfatal suicidal behavior, clinical samples usually consist of patients with a considerable between-person variability. Second, repeated nonfatal suicidal episodes of the same subjects are likely to be correlated. We examined three regression techniques to comparatively evaluate their efficiency in addressing the given methodological problems. Repeated episodes of nonfatal suicidal behavior were assessed in two independent patient samples during a 2-year follow-up period. The first regression design modeled repetitive nonfatal suicidal behavior as a summary measure. The second regression model treated repeated episodes of the same subject as independent events. The third regression model represented a hierarchical linear model. The estimated mean effects of the first model were likely to be nonrepresentative for a considerable part of the study subjects. The second regression design overemphasized the impact of the predictor variables. The hierarchical linear model most appropriately accounted for the heterogeneity of the samples and the correlated data structure. The nonhierarchical regression designs did not provide appropriate statistical models for the prospective investigation of repetitive nonfatal suicidal behavior. Multilevel modeling provides a convenient alternative.

  4. Segmentation of hand radiographs by using multi-level connected active appearance models

    Science.gov (United States)

    Kauffman, Joost A.; Slump, Cornelis H.; Bernelot Moens, Hein J.

    2005-04-01

    Robust and accurate segmentation methods are important for the computerized evaluation of medical images. For treatment of rheumatoid arthritis, joint damage assessment in radiographs of hands is frequently used for monitoring disease progression. Current clinical scoring methods are based on visual measurements that are time-consuming and subject to intra and inter-reader variance. A solution may be found in the development of partially automated assessment procedures. This requires reliable segmentation algorithms. Our work demonstrates a segmentation method based on multiple connected active appearance models (AAM) with multiple search steps using different quality levels. The quality level can be regulated by setting the image resolution and the number of landmarks in the AAMs. We performed experiments using two models of different quality levels for shape and texture information. Both models included AAMs for the carpal region, the metacarpals, and all phalanges. By starting an iterative search with the faster, low-quality model, we were able to determine the initial parameters of the second, high-quality model. After the second search, the results showed successful segmentation for 22 of 30 test images. For these images, 70% of the landmarks were found within 1.3 mm difference from manual placement by an expert. The multi-level search approach resulted in a reduction of 50% in calculation time compared to a search using a single model. Results are expected to improve when the model is refined by increasing the number of training examples and the resolution of the models.

  5. The Consequences of Ignoring Individuals' Mobility in Multilevel Growth Models: A Monte Carlo Study

    Science.gov (United States)

    Luo, Wen; Kwok, Oi-man

    2012-01-01

    In longitudinal multilevel studies, especially in educational settings, it is fairly common that participants change their group memberships over time (e.g., students switch to different schools). Participant's mobility changes the multilevel data structure from a purely hierarchical structure with repeated measures nested within individuals and…

  6. The Effects of Autonomy and Empowerment on Employee Turnover: Test of a Multilevel Model in Teams

    Science.gov (United States)

    Liu, Dong; Zhang, Shu; Wang, Lei; Lee, Thomas W.

    2011-01-01

    Extending research on voluntary turnover in the team setting, this study adopts a multilevel self-determination theoretical approach to examine the unique roles of individual and social-contextual motivational precursors, autonomy orientation and autonomy support, in reducing team member voluntary turnover. Analysis of multilevel time-lagged data…

  7. Friendship Dissolution Within Social Networks Modeled Through Multilevel Event History Analysis.

    Science.gov (United States)

    Dean, Danielle O; Bauer, Daniel J; Prinstein, Mitchell J

    2017-01-01

    A social network perspective can bring important insight into the processes that shape human behavior. Longitudinal social network data, measuring relations between individuals over time, has become increasingly common-as have the methods available to analyze such data. A friendship duration model utilizing discrete-time multilevel survival analysis with a multiple membership random effect structure is developed and applied here to study the processes leading to undirected friendship dissolution within a larger social network. While the modeling framework is introduced in terms of understanding friendship dissolution, it can be used to understand microlevel dynamics of a social network more generally. These models can be fit with standard generalized linear mixed-model software, after transforming the data to a pair-period data set. An empirical example highlights how the model can be applied to understand the processes leading to friendship dissolution between high school students, and a simulation study is used to test the use of the modeling framework under representative conditions that would be found in social network data. Advantages of the modeling framework are highlighted, and potential limitations and future directions are discussed.

  8. Los Alamos CCS (Center for Computer Security) formal computer security model

    Energy Technology Data Exchange (ETDEWEB)

    Dreicer, J.S.; Hunteman, W.J. (Los Alamos National Lab., NM (USA))

    1989-01-01

    This paper provides a brief presentation of the formal computer security model currently being developed at the Los Alamos Department of Energy (DOE) Center for Computer Security (CCS). The initial motivation for this effort was the need to provide a method by which DOE computer security policy implementation could be tested and verified. The actual analytical model was a result of the integration of current research in computer security and previous modeling and research experiences. The model is being developed to define a generic view of the computer and network security domains, to provide a theoretical basis for the design of a security model, and to address the limitations of present models. Formal mathematical models for computer security have been designed and developed in conjunction with attempts to build secure computer systems since the early 70's. The foundation of the Los Alamos DOE CCS model is a series of functionally dependent probability equations, relations, and expressions. The mathematical basis appears to be justified and is undergoing continued discrimination and evolution. We expect to apply the model to the discipline of the Bell-Lapadula abstract sets of objects and subjects. 5 refs.

  9. A study of the security technology and a new security model for WiFi network

    Science.gov (United States)

    Huang, Jing

    2013-07-01

    The WiFi network is one of the most rapidly developing wireless communication networks, which makes wireless office and wireless life possible and greatly expands the application form and scope of the internet. At the same time, the WiFi network security has received wide attention, and this is also the key factor of WiFi network development. This paper makes a systematic introduction to the WiFi network and WiFi network security problems, and the WiFi network security technology are reviewed and compared. In order to solve the security problems in WiFi network, this paper presents a new WiFi network security model and the key exchange algorithm. Experiments are performed to test the performance of the model, the results show that the new security model can withstand external network attack and ensure stable and safe operation of WiFi network.

  10. Evaluation for School Improvement: A Multi-Level, Multi-Purpose Model. Project: Multi-Level Evaluation Systems.

    Science.gov (United States)

    Herman, Joan L.

    A model for a comprehensive, multi-purpose, multi-user evaluation system is presented to facilitate educational decision making and to support school improvement and renewal. The model is school district-based but oriented to meet state-, school-, and classroom-level needs as well. The model emphasizes the usefulness of common or compatible…

  11. Detailed Modeling, Design, and Evaluation of a Scalable Multi-level Checkpointing System

    Energy Technology Data Exchange (ETDEWEB)

    Moody, A T; Bronevetsky, G; Mohror, K M; de Supinski, B R

    2010-04-09

    High-performance computing (HPC) systems are growing more powerful by utilizing more hardware components. As the system mean-time-before-failure correspondingly drops, applications must checkpoint more frequently to make progress. However, as the system memory sizes grow faster than the bandwidth to the parallel file system, the cost of checkpointing begins to dominate application run times. A potential solution to this problem is to use multi-level checkpointing, which employs multiple types of checkpoints with different costs and different levels of resiliency in a single run. The goal is to design light-weight checkpoints to handle the most common failure modes and rely on more expensive checkpoints for less common, but more severe failures. While this approach is theoretically promising, it has not been fully evaluated in a large-scale, production system context. To this end we have designed a system, called the Scalable Checkpoint/Restart (SCR) library, that writes checkpoints to storage on the compute nodes utilizing RAM, Flash, or disk, in addition to the parallel file system. We present the performance and reliability properties of SCR as well as a probabilistic Markov model that predicts its performance on current and future systems. We show that multi-level checkpointing improves efficiency on existing large-scale systems and that this benefit increases as the system size grows. In particular, we developed low-cost checkpoint schemes that are 100x-1000x faster than the parallel file system and effective against 85% of our system failures. This leads to a gain in machine efficiency of up to 35%, and it reduces the the load on the parallel file system by a factor of two on current and future systems.

  12. Modeling and simulation of novel stepped DC coupled quasi Z-Multilevel Inverter for single phase systems

    Directory of Open Access Journals (Sweden)

    Meenakshi T.

    2016-09-01

    Full Text Available This paper presents the modeling and simulation of a novel topology of quasi Z-Multilevel Inverter with stepped DC input. The proposed inverter incorporates a simple switching technique with reduced component count and is aimed at producing boosted multilevel output AC voltage. The inverter consists of two stages and the buck /boost operation is obtained by varying the shoot through period of the pulses obtained by maximum constant boost control with third harmonic injection. With all the advantages of the quasi Z-network, the proposed inverter eliminates the fly back diodes and capacitors present in a conventional Z-Multilevel Inverter. Further the stress on the devices is less which leads to reduction in component value and hence the cost. The novel stepped DC coupled Single Phase quasi Z-Multilevel Inverter is modeled and simulated in the MATLAB - SIMULINK environment and its performance is analyzed for varying input and switching conditions. The voltage and current waveforms across each stage of the inverter is analyzed and the results are presented for different levels of input.

  13. Modeling seroadaptation and sexual behavior among HIV+ study participants with a simultaneously multilevel and multivariate longitudinal count model.

    Science.gov (United States)

    Zhu, Yuda; Weiss, Robert E

    2013-03-01

    Longitudinal behavioral intervention trials to reduce HIV transmission risk collect complex multilevel and multivariate data longitudinally for each subject with important correlation structures across time, level, and variables. Accurately assessing the effects of these trials are critical for determining which interventions are effective. Both numbers of partners and numbers of sex acts with each partner are reported at each time point. Sex acts with each partner are further differentiated into protected and unprotected acts with correspondingly differing risks of HIV/STD transmission. These trials generally also have eligibility criteria limiting enrollment to participants with some minimal level of risky sexual behavior tied directly to the outcome of interest. The combination of these factors makes it difficult to quantify sexual behaviors and the effects of intervention. We propose a multivariate multilevel count model that simultaneously models the number of partners, acts within partners, and accounts for recruitment eligibility. Our methods are useful in the evaluation of intervention trials and provide a more accurate and complete model for sexual behavior. We illustrate the contributions of our model by examining seroadaptive behavior defined as risk reducing behavior that depends on the serostatus of the partner. Several forms of seroadaptive risk reducing behavior are quantified and distinguished from nonseroadaptive risk reducing behavior. Copyright © 2013, The International Biometric Society.

  14. On the Need for Relaxed Security Models

    DEFF Research Database (Denmark)

    Slides for the opening panel on "Issues in the Security of Wireless Network systems" at ICETE 2008.......Slides for the opening panel on "Issues in the Security of Wireless Network systems" at ICETE 2008....

  15. Modeling and space vector control of a novel multilevel matrix converter for variable-speed wind power generators

    Science.gov (United States)

    Al-Naseem, Osama Abdulrahman

    -quadrant switches used in a conventional matrix converter. This increase in power handling capability is due to the doubling of the number of devices in a multilevel matrix converter switch cell. Scaling up the power handling capability is accomplished by cascading more than one switch cell per branch. Control of the new converter is achieved through space vector modulation in which three-phase ac voltages are transformed to the d-q reference frame and compared with a set of space vectors prior to modulation. Since it has 19683 different switching combinations, control can be difficult and complex. Nevertheless, the multilevel matrix converter has been modeled and controlled through simulation. Simulation results show the possibility of operating the converter to produce the desired voltage waveforms with universal input and output power factors and maintain constant capacitor voltages simultaneously. Also in this dissertation is the derivation of an analytical averaged equivalent circuit model of a PWM converter. This model reveals how dominant loss mechanisms vary with converter operating point. The model is based on the operational characteristics of power diodes and IGBTs. Laboratory experiments support the derived model and confirm that IGBT current tailing and diode reverse-recovery are indeed the most critical losses in a PWM converter. These losses are more significant at light load, hence reducing the energy capture capability of converters used in wind generation. The results suggest that multilevel conversion, which has been employed in the novel multilevel matrix converter, could improve the low-wind converter efficiency.

  16. Modelling and simulation of complex systems: an approach based on multi-level agents

    Directory of Open Access Journals (Sweden)

    Alain-Jerome Fougeres

    2011-11-01

    Full Text Available A complex system is made up of many components with many interactions. So the design of systems such as simulation systems, cooperative systems or assistance systems includes a very accurate modelling of interactional and communicational levels. The agent-based approach provides an adapted abstraction level for this problem. After having studied the organizational context and communicative capacities of agent-based systems, to simulate the reorganization of a flexible manufacturing, to regulate an urban transport system, and to simulate an epidemic detection system, our thoughts on the interactional level were inspired by human-machine interface models, especially those in cognitive engineering To provide a general framework for agent-based complex systems modelling, we then proposed a scale of four behaviours that agents may adopt in their complex systems (reactive, routine, cognitive, and collective. To complete the description of multi-level agent models, which is the focus of this paper, we illustrate our modelling and discuss our ongoing work on each level.

  17. Hierarchical Acceleration of Multilevel Monte Carlo Methods for Computationally Expensive Simulations in Reservoir Modeling

    Science.gov (United States)

    Zhang, G.; Lu, D.; Webster, C.

    2014-12-01

    The rational management of oil and gas reservoir requires an understanding of its response to existing and planned schemes of exploitation and operation. Such understanding requires analyzing and quantifying the influence of the subsurface uncertainties on predictions of oil and gas production. As the subsurface properties are typically heterogeneous causing a large number of model parameters, the dimension independent Monte Carlo (MC) method is usually used for uncertainty quantification (UQ). Recently, multilevel Monte Carlo (MLMC) methods were proposed, as a variance reduction technique, in order to improve computational efficiency of MC methods in UQ. In this effort, we propose a new acceleration approach for MLMC method to further reduce the total computational cost by exploiting model hierarchies. Specifically, for each model simulation on a new added level of MLMC, we take advantage of the approximation of the model outputs constructed based on simulations on previous levels to provide better initial states of new simulations, which will help improve efficiency by, e.g. reducing the number of iterations in linear system solving or the number of needed time-steps. This is achieved by using mesh-free interpolation methods, such as Shepard interpolation and radial basis approximation. Our approach is applied to a highly heterogeneous reservoir model from the tenth SPE project. The results indicate that the accelerated MLMC can achieve the same accuracy as standard MLMC with a significantly reduced cost.

  18. The IEA Model of Short-term Energy Security

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-07-01

    Ensuring energy security has been at the centre of the IEA mission since its inception, following the oil crises of the early 1970s. While the security of oil supplies remains important, contemporary energy security policies must address all energy sources and cover a comprehensive range of natural, economic and political risks that affect energy sources, infrastructures and services. In response to this challenge, the IEA is currently developing a Model Of Short-term Energy Security (MOSES) to evaluate the energy security risks and resilience capacities of its member countries. The current version of MOSES covers short-term security of supply for primary energy sources and secondary fuels among IEA countries. It also lays the foundation for analysis of vulnerabilities of electricity and end-use energy sectors. MOSES contains a novel approach to analysing energy security, which can be used to identify energy security priorities, as a starting point for national energy security assessments and to track the evolution of a country's energy security profile. By grouping together countries with similar 'energy security profiles', MOSES depicts the energy security landscape of IEA countries. By extending the MOSES methodology to electricity security and energy services in the future, the IEA aims to develop a comprehensive policy-relevant perspective on global energy security. This Working Paper is intended for readers who wish to explore the MOSES methodology in depth; there is also a brochure which provides an overview of the analysis and results.

  19. A model based security testing method for protocol implementation.

    Science.gov (United States)

    Fu, Yu Long; Xin, Xiao Long

    2014-01-01

    The security of protocol implementation is important and hard to be verified. Since the penetration testing is usually based on the experience of the security tester and the specific protocol specifications, a formal and automatic verification method is always required. In this paper, we propose an extended model of IOLTS to describe the legal roles and intruders of security protocol implementations, and then combine them together to generate the suitable test cases to verify the security of protocol implementation.

  20. A Model Based Security Testing Method for Protocol Implementation

    Directory of Open Access Journals (Sweden)

    Yu Long Fu

    2014-01-01

    Full Text Available The security of protocol implementation is important and hard to be verified. Since the penetration testing is usually based on the experience of the security tester and the specific protocol specifications, a formal and automatic verification method is always required. In this paper, we propose an extended model of IOLTS to describe the legal roles and intruders of security protocol implementations, and then combine them together to generate the suitable test cases to verify the security of protocol implementation.

  1. Model-based security engineering for the internet of things

    OpenAIRE

    NEISSE RICARDO; STERI GARY; NAI FOVINO Igor; Baldini, Gianmarco; VAN HOESEL Lodewijk

    2015-01-01

    We propose in this chapter a Model-based Security Toolkit (SecKit) and methodology to address the control and protection of user data in the deployment of the Internet of Things (IoT). This toolkit takes a more general approach for security engineering including risk analysis, establishment of aspect-specific trust relationships, and enforceable security policies. We describe the integrated metamodels used in the toolkit and the accompanying security engineering methodology for IoT systems...

  2. Norms, standards, models and recommendations for information security management

    Directory of Open Access Journals (Sweden)

    Karol Kreft

    2010-12-01

    Full Text Available Information is the factor which can decide about the potential and market value of a company. An increase in the value of intellectual capital of an information-driven company requires development of an effective security management system. More and more often companies develop information security management systems (ISMS based on already verified models. In the article, the main problems with management of information security were discussed. Security models were described, as well as the risk analysis in information security management.

  3. A Novel Model for Security Evaluation for Compliance

    DEFF Research Database (Denmark)

    Hald, Sara Ligaard; Pedersen, Jens Myrup; Prasad, Neeli R.

    2011-01-01

    for Compliance (SEC) model offers a lightweight alternative for use by decision makers to get a quick overview of the security attributes of different technologies for easy comparison and requirement compliance evaluation. The scientific contribution is this new approach to security modelling as well......With the increasing focus on security in information systems, it is becoming necessary to be able to describe and compare security attributes for different technologies. Existing are well-described and comprehensive, but expensive and resource demanding to apply. The Security Evaluation...

  4. A Novel Model for Security Evaluation for Compliance

    DEFF Research Database (Denmark)

    Hald, Sara Ligaard; Pedersen, Jens Myrup; Prasad, Neeli R.

    2011-01-01

    With the increasing focus on security in information systems, it is becoming necessary to be able to describe and compare security attributes for different technologies. Existing are well-described and comprehensive, but expensive and resource demanding to apply. The Security Evaluation...... for Compliance (SEC) model offers a lightweight alternative for use by decision makers to get a quick overview of the security attributes of different technologies for easy comparison and requirement compliance evaluation. The scientific contribution is this new approach to security modelling as well...

  5. MKEM: a Multi-level Knowledge Emergence Model for mining undiscovered public knowledge

    Directory of Open Access Journals (Sweden)

    Song Min

    2010-04-01

    Full Text Available Abstract Background Since Swanson proposed the Undiscovered Public Knowledge (UPK model, there have been many approaches to uncover UPK by mining the biomedical literature. These earlier works, however, required substantial manual intervention to reduce the number of possible connections and are mainly applied to disease-effect relation. With the advancement in biomedical science, it has become imperative to extract and combine information from multiple disjoint researches, studies and articles to infer new hypotheses and expand knowledge. Methods We propose MKEM, a Multi-level Knowledge Emergence Model, to discover implicit relationships using Natural Language Processing techniques such as Link Grammar and Ontologies such as Unified Medical Language System (UMLS MetaMap. The contribution of MKEM is as follows: First, we propose a flexible knowledge emergence model to extract implicit relationships across different levels such as molecular level for gene and protein and Phenomic level for disease and treatment. Second, we employ MetaMap for tagging biological concepts. Third, we provide an empirical and systematic approach to discover novel relationships. Results We applied our system on 5000 abstracts downloaded from PubMed database. We performed the performance evaluation as a gold standard is not yet available. Our system performed with a good precision and recall and we generated 24 hypotheses. Conclusions Our experiments show that MKEM is a powerful tool to discover hidden relationships residing in extracted entities that were represented by our Substance-Effect-Process-Disease-Body Part (SEPDB model.

  6. Disability multilevel modelling in first episodes of psychosis at 3-year follow-up.

    Science.gov (United States)

    Mellor-Marsá, Blanca; Caballero, Francisco Félix; Cabello, María; Ayuso-Mateos, José Luis; Setién-Suero, Esther; Vázquez-Bourgon, Javier; Crespo-Facorro, Benedicto; Ayesa-Arriola, Rosa

    2017-07-01

    The description of longitudinal bio-psycho-social profiles in FEP samples may be useful for the prediction of disability trajectories. This study aimed to describe the differences between disability status of FEP patients at baseline and their change over time, analysing how variables associated to the psychological status, and the environment of the patient can affect his or her disability trajectory, once the influence of health condition and socio-demographic variables has been controlled for. Using data from a 3-year follow-up study on early psychosis (PAFIP), a multilevel structure in which the longitudinal measurements (within level) were nested within the individuals (between level), was modeled. The contribution of the different time-varying and time-invariant variables to the patients' disability outcomes was tested through eight nested models. Consecutive models, that successively added health related, socio-demographic, psychological and environmental variables to the unconditional model were estimated, by means of deviance and fit statistics. The present work revealed the importance of psychological and environmental factors in the explanation of disability changes in the context of FEP. We may conclude that longitudinal assessments of time-varying predictors - living situation (b=-0.10, pdisability variation over time, independently from symptoms' severity, duration of untreated psychosis, age, gender and years of education. Additionally, the level of premorbid adjustment (b=0.05, pdisability outcomes among FEP patients. Copyright © 2016 Elsevier B.V. All rights reserved.

  7. A Novel Trusted Computing Model for Network Security Authentication

    Directory of Open Access Journals (Sweden)

    Ling Xing

    2014-02-01

    Full Text Available Network information poses great threats from malicious attacks due to the openness and virtuality of network structure. Traditional methods to ensure infor- mation security may fail when both integrity and source authentication for information are required. Based on the security of data broadcast channel, a novel Trusted Com- puting Model (TCM of network security authentication is proposed to enhance the security of network information. In this model, a method of Uniform content locator security Digital Certificate (UDC, which is capable of fully and uniquely index network information, is developed. Standard of MPEG-2 Transport Streams (TS is adopted to pack UDC data. Additionally, a UDC hashing algorithm (UHA512 is designed to compute the integrity and security of data infor- mation . Experimental results show that the proposed model is feasible and effective to network security authentication. 

  8. Multilevel Hierarchical Modeling of Benthic Macroinvertebrate Responses to Urbanization in Nine Metropolitan Regions across the Conterminous United States

    Science.gov (United States)

    Kashuba, Roxolana; Cha, YoonKyung; Alameddine, Ibrahim; Lee, Boknam; Cuffney, Thomas F.

    2010-01-01

    Multilevel hierarchical modeling methodology has been developed for use in ecological data analysis. The effect of urbanization on stream macroinvertebrate communities was measured across a gradient of basins in each of nine metropolitan regions across the conterminous United States. The hierarchical nature of this dataset was harnessed in a multi-tiered model structure, predicting both invertebrate response at the basin scale and differences in invertebrate response at the region scale. Ordination site scores, total taxa richness, Ephemeroptera, Plecoptera, Trichoptera (EPT) taxa richness, and richness-weighted mean tolerance of organisms at a site were used to describe invertebrate responses. Percentage of urban land cover was used as a basin-level predictor variable. Regional mean precipitation, air temperature, and antecedent agriculture were used as region-level predictor variables. Multilevel hierarchical models were fit to both levels of data simultaneously, borrowing statistical strength from the complete dataset to reduce uncertainty in regional coefficient estimates. Additionally, whereas non-hierarchical regressions were only able to show differing relations between invertebrate responses and urban intensity separately for each region, the multilevel hierarchical regressions were able to explain and quantify those differences within a single model. In this way, this modeling approach directly establishes the importance of antecedent agricultural conditions in masking the response of invertebrates to urbanization in metropolitan regions such as Milwaukee-Green Bay, Wisconsin; Denver, Colorado; and Dallas-Fort Worth, Texas. Also, these models show that regions with high precipitation, such as Atlanta, Georgia; Birmingham, Alabama; and Portland, Oregon, start out with better regional background conditions of invertebrates prior to urbanization but experience faster negative rates of change with urbanization. Ultimately, this urbanization

  9. Effect of Data Model Approach In State Probability Analysis Of Multi-Level Queue Scheduling

    Directory of Open Access Journals (Sweden)

    Diwakar Shukla

    2010-07-01

    Full Text Available In the uniprocessor environment, the number of jobs arriving at the processor of CPU at a time is very large which causes a long waiting queue. When conflict arises due to shared resources or overlap of instructions or logical error, the deadlock state appears where further processing of jobs is blocked completely. While the scheduler jumps from one job to another in order to perform the processing the transition mechanism appears. This paper presents a general structure of transition scenario for the functioning of CPU scheduler in the presence of deadlock condition in setup of multilevel queue scheduling. A data model based Markov chain model is proposed to study the transition phenomenon and a general class of scheduling scheme is designed. Some specific and well known schemes are treated as its particular cases and are compared under the setup of model through a proposed deadlock-waiting index measure. Simulation study is performed to evaluate the comparative merits of specific schemes belonging to the class designed with the help of varying values of α and d.

  10. DESTINY: A Comprehensive Tool with 3D and Multi-Level Cell Memory Modeling Capability

    Directory of Open Access Journals (Sweden)

    Sparsh Mittal

    2017-09-01

    Full Text Available To enable the design of large capacity memory structures, novel memory technologies such as non-volatile memory (NVM and novel fabrication approaches, e.g., 3D stacking and multi-level cell (MLC design have been explored. The existing modeling tools, however, cover only a few memory technologies, technology nodes and fabrication approaches. We present DESTINY, a tool for modeling 2D/3D memories designed using SRAM, resistive RAM (ReRAM, spin transfer torque RAM (STT-RAM, phase change RAM (PCM and embedded DRAM (eDRAM and 2D memories designed using spin orbit torque RAM (SOT-RAM, domain wall memory (DWM and Flash memory. In addition to single-level cell (SLC designs for all of these memories, DESTINY also supports modeling MLC designs for NVMs. We have extensively validated DESTINY against commercial and research prototypes of these memories. DESTINY is very useful for performing design-space exploration across several dimensions, such as optimizing for a target (e.g., latency, area or energy-delay product for a given memory technology, choosing the suitable memory technology or fabrication method (i.e., 2D v/s 3D for a given optimization target, etc. We believe that DESTINY will boost studies of next-generation memory architectures used in systems ranging from mobile devices to extreme-scale supercomputers. The latest source-code of DESTINY is available from the following git repository: https://bitbucket.org/sparshmittal/destinyv2.

  11. A new security model for collaborative environments

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, Deborah [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Lorch, Markus [Virginia Polytechnic Inst. and State Univ. (Virginia Tech), Blacksburg, VA (United States); Thompson, Mary [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Perry, Marcia [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2003-06-06

    Prevalent authentication and authorization models for distributed systems provide for the protection of computer systems and resources from unauthorized use. The rules and policies that drive the access decisions in such systems are typically configured up front and require trust establishment before the systems can be used. This approach does not work well for computer software that moderates human-to-human interaction. This work proposes a new model for trust establishment and management in computer systems supporting collaborative work. The model supports the dynamic addition of new users to a collaboration with very little initial trust placed into their identity and supports the incremental building of trust relationships through endorsements from established collaborators. It also recognizes the strength of a users authentication when making trust decisions. By mimicking the way humans build trust naturally the model can support a wide variety of usage scenarios. Its particular strength lies in the support for ad-hoc and dynamic collaborations and the ubiquitous access to a Computer Supported Collaboration Workspace (CSCW) system from locations with varying levels of trust and security.

  12. Selection of Model in Developing Information Security Criteria for Smart Grid Security System

    CERN Document Server

    Ling, Amy Poh Ai

    2011-01-01

    At present, the "Smart Grid" has emerged as one of the best advanced energy supply chains. This paper looks into the security system of smart grid via the smart planet system. The scope focused on information security criteria that impact on consumer trust and satisfaction. The importance of information security criteria is perceived as the main aspect to impact on customer trust throughout the entire smart grid system. On one hand, this paper also focuses on the selection of the model for developing information security criteria on a smart grid.

  13. Handbook of Advanced Multilevel Analysis

    CERN Document Server

    Hox, Joop

    2010-01-01

    This new handbook is the definitive resource on advanced topics related to multilevel analysis. The editors have assembled the top minds in the field to address the latest applications of multilevel modeling as well as the specific difficulties and methodological problems that are becoming more common as more complicated models are developed.

  14. Using multilevel spatial models to understand salamander site occupancy patterns after wildfire

    Science.gov (United States)

    Chelgren, N.D.; Adams, M.J.; Bailey, L.L.; Bury, R.B.

    2011-01-01

    Studies of the distribution of elusive forest wildlife have suffered from the confounding of true presence with the uncertainty of detection. Occupancy modeling, which incorporates probabilities of species detection conditional on presence, is an emerging approach for reducing observation bias. However, the current likelihood modeling framework is restrictive for handling unexplained sources of variation in the response that may occur when there are dependence structures such as smaller sampling units that are nested within larger sampling units. We used multilevel Bayesian occupancy modeling to handle dependence structures and to partition sources of variation in occupancy of sites by terrestrial salamanders (family Plethodontidae) within and surrounding an earlier wildfire in western Oregon, USA. Comparison of model fit favored a spatial N-mixture model that accounted for variation in salamander abundance over models that were based on binary detection/non-detection data. Though catch per unit effort was higher in burned areas than unburned, there was strong support that this pattern was due to a higher probability of capture for individuals in burned plots. Within the burn, the odds of capturing an individual given it was present were 2.06 times the odds outside the burn, reflecting reduced complexity of ground cover in the burn. There was weak support that true occupancy was lower within the burned area. While the odds of occupancy in the burn were 0.49 times the odds outside the burn among the five species, the magnitude of variation attributed to the burn was small in comparison to variation attributed to other landscape variables and to unexplained, spatially autocorrelated random variation. While ordinary occupancy models may separate the biological pattern of interest from variation in detection probability when all sources of variation are known, the addition of random effects structures for unexplained sources of variation in occupancy and detection

  15. Modeling a multilevel boost converter using SiC components for PV application

    Science.gov (United States)

    Alateeq, Ayoob S.; Almalaq, Yasser A.; Matin, Mohammad A.

    2016-09-01

    This paper discusses a DC-DC multilevel boost with wide bandgap components for PV applications. In the PV system, the multilevel boost converter is advisable to be used over the conventional boost converter because of the high ratio conversion. The multilevel boost converter is designed with one inductor, 2N-1 silicon carbide (SiC) schottky diodes, 2N-1 capacitors and one SiC MOSFET where N is the number of levels. Inserting SiC components in the design helps to maintain the temperature effect that could cause a high power loss. Most function of using a multilevel boost converter is to produce a high output voltage without using either a power transformer or a coupled inductor. Achieving a high gain output in the multilevel boost converter depends on the level of the converter and the switching duty cycle. The demonstrated design is a multilevel boost converter supplies from 220 V to rate 2 KW power. The switching frequency is 100 KHz and the output voltage of 4-level is 3.5 KV. Several values of temperatures are applicable to the system and the effect of changing the temperature on efficiency is studied. The developed design is simulated by using a LTspice software and the results are discussed.

  16. Land Transitions in the American Plains: Multilevel Modeling of Drivers of Grassland Conversion (1950 to 2000).

    Science.gov (United States)

    Sylvester, Kenneth M; Brown, Daniel G; Deane, Glenn D; Kornak, Rachel N

    2013-03-15

    This paper examines drivers of land-cover change in the U.S. Great Plains in the last half of the twentieth century. Its central aim is to evaluate the dynamics of grassland preservation and conversion, across the region, and to identify areas of grassland that were never plowed during the period. The research compares land-cover data from 400 sample areas, selected from and nested within 50 counties, to aggregate data from the agricultural and population censuses. The spatially explicit land-cover data were interpreted from aerial photographs taken at three time points (1950s, 1970s and 2000s). Sample areas were chosen using a stratified random design based on the Public Land Survey grid with in the target counties, in several clusters across the region. We modeled the sequences and magnitudes of changes in the interpreted air photo data in a multi-level panel model that included soil quality and slope of sample areas and agricultural activities and employment reported in the U.S. Censuses of Agriculture and Population. We conclude that land retirement programs and production subsidies have worked at cross purposes, destabilizing micro-level patterns of land use in recent decades, increasing levels of switching between cropland and grassland and reducing the size of remaining areas of native grassland in the U.S. Great Plains.

  17. Maximizing a Multilevel Mentoring Model to Improve Research Experiences for Undergraduates Student Outcomes

    Science.gov (United States)

    Moser, F. C.; Allen, M. R.; Clark, J.

    2016-12-01

    Since 1989 the Maryland Sea Grant REU program's mentoring approach evolved considerably from a near `hands-off' approach to one that explores ways to maximize mentoring effectiveness. Our current model creates a multi-tiered system: the REU - research mentor relationship remains central to setting the student's science project, but greater student growth is supported by REU program leaders, visiting researchers, graduate students, and peer and near-peer mentors. Evaluation of our evolving mentoring program suggests our approach is successful and serves a diversity of students well, but we recognize the challenge of devising an evaluation system, given our limited annual cohort number (15 - 17 students), that fully captures the nuances of student - mentor relationships. We present multiple years of data on student skills, networks of relationships, student goals, and mentor goals using qualitative, quantitative and interview assessments. Further, we explore opportunities to strengthen our efforts and evolve our evaluation approach as we aspire to more accurately identify the components of our multilevel mentoring model that contribute most significantly to student success.

  18. Fitting multilevel models in complex survey data with design weights: Recommendations

    Directory of Open Access Journals (Sweden)

    Carle Adam C

    2009-07-01

    Full Text Available Abstract Background Multilevel models (MLM offer complex survey data analysts a unique approach to understanding individual and contextual determinants of public health. However, little summarized guidance exists with regard to fitting MLM in complex survey data with design weights. Simulation work suggests that analysts should scale design weights using two methods and fit the MLM using unweighted and scaled-weighted data. This article examines the performance of scaled-weighted and unweighted analyses across a variety of MLM and software programs. Methods Using data from the 2005–2006 National Survey of Children with Special Health Care Needs (NS-CSHCN: n = 40,723 that collected data from children clustered within states, I examine the performance of scaling methods across outcome type (categorical vs. continuous, model type (level-1, level-2, or combined, and software (Mplus, MLwiN, and GLLAMM. Results Scaled weighted estimates and standard errors differed slightly from unweighted analyses, agreeing more with each other than with unweighted analyses. However, observed differences were minimal and did not lead to different inferential conclusions. Likewise, results demonstrated minimal differences across software programs, increasing confidence in results and inferential conclusions independent of software choice. Conclusion If including design weights in MLM, analysts should scale the weights and use software that properly includes the scaled weights in the estimation.

  19. Assessing longitudinal quality of life in prostate cancer patients and their spouses: a multilevel modeling approach

    Science.gov (United States)

    Northouse, Laurel L.; Braun, Thomas M.; Zhang, Lingling; Cimprich, Bernadine; Ronis, David L.; Mood, Darlene W.

    2013-01-01

    Purpose This study aimed at examining the relationship between quality of life (QOL) in prostate cancer (PCa) patients and partners and how baseline demographics, cancer-related factors, and time-varying psychosocial and symptom covariates affect their QOL over time. Methods Guided by a modified Stress-Coping Model, this study used multilevel modeling to analyze longitudinal data from a randomized clinical trial that tested a family-based intervention to improve QOL in couples managing PCa. Patients and partners from the usual-care control group (N = 134 dyads) independently completed the measurements at baseline, and at 4-, 8-, and 12-month follow-ups. Results Correlations of QOL between patients and partners over time were small to moderate. Patients’ lower education level, partners’ older age, higher family income, and localized cancer at baseline were associated with better QOL in couples. Over time, couples’ QOL improved as their social support and cancer-related dyadic communication increased and as couples’ uncertainty, general symptoms, and patients’ prostate cancer-related sexual and hormonal symptoms decreased. Conclusions Evidence indicates that couples’ QOL during cancer survivorship is affected by multiple contextual factors (e.g., baseline demographics and time-varying psychosocial factors and symptoms). Intervention research is needed to explore comprehensive strategies to improve couples’ QOL during the continuum of PCa survivorship. PMID:20927648

  20. A value model for evaluating homeland security decisions.

    Science.gov (United States)

    Keeney, Ralph L; von Winterfeldt, Detlof

    2011-09-01

    One of the most challenging tasks of homeland security policymakers is to allocate their limited resources to reduce terrorism risks cost effectively. To accomplish this task, it is useful to develop a comprehensive set of homeland security objectives, metrics to measure each objective, a utility function, and value tradeoffs relevant for making homeland security investments. Together, these elements form a homeland security value model. This article develops a homeland security value model based on literature reviews, a survey, and experience with building value models. The purposes of the article are to motivate the use of a value model for homeland security decision making and to illustrate its use to assess terrorism risks, assess the benefits of countermeasures, and develop a severity index for terrorism attacks. © 2011 Society for Risk Analysis.

  1. Aspect-oriented security hardening of UML design models

    CERN Document Server

    Mouheb, Djedjiga; Pourzandi, Makan; Wang, Lingyu; Nouh, Mariam; Ziarati, Raha; Alhadidi, Dima; Talhi, Chamseddine; Lima, Vitor

    2015-01-01

    This book comprehensively presents a novel approach to the systematic security hardening of software design models expressed in the standard UML language. It combines model-driven engineering and the aspect-oriented paradigm to integrate security practices into the early phases of the software development process. To this end, a UML profile has been developed for the specification of security hardening aspects on UML diagrams. In addition, a weaving framework, with the underlying theoretical foundations, has been designed for the systematic injection of security aspects into UML models. The

  2. Multilevel corporate environmental responsibility.

    Science.gov (United States)

    Karassin, Orr; Bar-Haim, Aviad

    2016-12-01

    The multilevel empirical study of the antecedents of corporate social responsibility (CSR) has been identified as "the first knowledge gap" in CSR research. Based on an extensive literature review, the present study outlines a conceptual multilevel model of CSR, then designs and empirically validates an operational multilevel model of the principal driving factors affecting corporate environmental responsibility (CER), as a measure of CSR. Both conceptual and operational models incorporate three levels of analysis: institutional, organizational, and individual. The multilevel nature of the design allows for the assessment of the relative importance of the levels and of their components in the achievement of CER. Unweighted least squares (ULS) regression analysis reveals that the institutional-level variables have medium relationships with CER, some variables having a negative effect. The organizational level is revealed as having strong and positive significant relationships with CER, with organizational culture and managers' attitudes and behaviors as significant driving forces. The study demonstrates the importance of multilevel analysis in improving the understanding of CSR drivers, relative to single level models, even if the significance of specific drivers and levels may vary by context.

  3. Pricing Asset-backed Securities: A Revised Model

    OpenAIRE

    Bradka, Lukas

    2008-01-01

    This paper deals with asset backed securities and the pricing thereof. First, an overview of debt markets is provided with a particular focus on the recent crisis in the sub prime markets. Second, literature surrounding securitization, asset backed securities and related types of debt is analysed and discussed. A revised pricing model for asset backed securities based on two existing models (Ebrahim, 2000; Ebrahim & Ahmed, 2007) is successively developed and implemented in Maple programming l...

  4. Multilevel modeling versus cross-sectional analysis for assessing the longitudinal tracking of cardiovascular risk factors over time.

    Science.gov (United States)

    Xanthakis, Vanessa; Sullivan, Lisa M; Vasan, Ramachandran S

    2013-12-10

    Correlated data are obtained in longitudinal epidemiological studies, where repeated measurements are taken on individuals or groups over time. Such longitudinal data are ideally analyzed using multilevel modeling approaches, which appropriately account for the correlations in repeated responses in the same individual. Commonly used regression models are inappropriate as they assume that measurements are independent. In this tutorial, we use multilevel modeling to demonstrate its use for analysis of correlated data obtained from serial examinations on individuals. We focus on cardiovascular epidemiological research where investigators are often interested in quantifying the relations between clinical risk factors and outcome measures (X and Y, respectively), where X and Y are measured repeatedly over time, for example, using serial observations on participants attending multiple examinations in a longitudinal cohort study. For instance, it may be of interest to evaluate the relations between serial measures of left ventricular mass (outcome) and of its potential determinants (i.e., body mass index and blood pressure), both of which are measured over time. In this tutorial, we describe the application of multilevel modeling to cardiovascular risk factors and outcome data (using serial echocardiographic data as an example of an outcome). We suggest an analytical approach that can be implemented to evaluate relations between any potential outcome of interest and risk factors, including assessment of random effects and nonlinear relations. We illustrate these steps using echocardiographic data from the Framingham Heart Study with SAS PROC MIXED.

  5. Handbook of multilevel analysis

    National Research Council Canada - National Science Library

    Leeuw, Jan de; Meijer, Erik

    2008-01-01

    ... appropriate and efficient model-based methods have become available to deal with this issue, that we have come to appreciate the power that more complex models provide for describing the world and providing new insights. This book sets out to present some of the most recent developments in what has come to be known as multilevel modelling. An...

  6. Structured Multi-level Data Fusion and Modelling of Heterogeneous Environmental Data for Future Internet Applications

    Science.gov (United States)

    Sabeur, Zoheir; Chakravarthy, Ajay; Bashevoy, Maxim; Modafferi, Stefano

    2013-04-01

    The rapid increase in environmental observations which are conducted by Small to Medium Enterprise communities and volunteers using affordable in situ sensors at various scales, in addition to the more established observatories set up by environmental and space agencies using airborne and space-borne sensing technologies is generating serious amounts of BIG data at ever increasing speeds. Furthermore, the emergence of Future Internet technologies and the urgent requirements for the deployment of specific enablers for the delivery of processed environmental knowledge in real-time with advanced situation awareness to citizens has reached paramount importance. Specifically, it has become highly critical now to build and provide services which automate the aggregation of data from various sources, while surmounting the semantic gaps, conflicts and heterogeneity in data sources. The early stage aggregation of data will enable the pre-processing of data from multiple sources while reconciling the temporal gaps in measurement time series, and aligning their respective a-synchronicities. This low level type of data fusion process needs to be automated and chained to more advanced level of data fusion services specialising in observation forecasts at spaces where sensing is not deployed; or at time slices where sensing has not taken place yet. As a result, multi-level fusion services are required among the families of specific enablers for monitoring environments and spaces in the Future Internet. These have been intially deployed and piloted in the ongoing ENVIROFI project of the FI-PPP programme [1]. Automated fusion and modelling of in situ and remote sensing data has been set up and the experimentation successfully conducted using RBF networks for the spatial fusion of water quality parameters measurements from satellite and stationary buoys in the Irish Sea. The RBF networks method scales for the spatial data fusion of multiple types of observation sources. This

  7. Novel compact model for multi-level spin torque magnetic tunnel junctions

    Science.gov (United States)

    Prajapati, Sanjay; Verma, Shivam; Kulkarni, Anant Aravind; Kaushik, Brajesh Kumar

    2016-10-01

    Spin-transfer torque (STT) and spin-orbit torque (SOT) based magnetic tunnel junction (MTJ) devices are emerging as strong contenders for the next generation memories. Conventional STT magneto-resistive random access memory (MRAM) offers lower power, non-volatility and CMOS process compatibility. However, higher current requirement during the write operation leads to tunnel barrier reliability issues and larger access devices. SOT-MRAM eliminates the reliability issues with strong spin polarized current (100%) and separate read/write current paths; however, the additional two access transistors in SOT-MRAM results into increased cell area. Multilevel cell (MLC) structure paves a way to circumvent the problems related to the conventional STT/SOT based MTJ devices and provides enhanced integration density at reduced cost per bit. Conventional STT/SOT-MRAM requires a unit cell area of 10-60 F2 and reported simulations have been based on available single-level MTJ compact models. However, till date no compact model exists that can capture the device physics of MLC-MTJ accurately. Hence, a novel compact model is proposed in this paper to capture the accurate device physics and behaviour of the MLC-MTJs. It is designed for MLCs with different MTJ configurations demonstrated so far, such as series and parallel free layer based MLC-MTJs. The proposed model is coded in Verilog-A, which is compatible with SPICE for circuit level simulations. The model is in close agreement with the experimental results exhibiting an average error of less than 15%.

  8. Re-designing the PhEDEx Security Model

    Science.gov (United States)

    C-H, Huang; Wildish, T.; X, Zhang

    2014-06-01

    PhEDEx, the data-placement tool used by the CMS experiment at the LHC, was conceived in a more trusting time. The security model provided a safe environment for site agents and operators, but offerred little more protection than that. Data was not sufficiently protected against loss caused by operator error or software bugs or by deliberate manipulation of the database. Operators were given high levels of access to the database, beyond what was actually needed to accomplish their tasks. This exposed them to the risk of suspicion should an incident occur. Multiple implementations of the security model led to difficulties maintaining code, which can lead to degredation of security over time. In order to meet the simultaneous goals of protecting CMS data, protecting the operators from undue exposure to risk, increasing monitoring capabilities and improving maintainability of the security model, the PhEDEx security model was redesigned and re-implemented. Security was moved from the application layer into the database itself, fine-grained access roles were established, and tools and procedures created to control the evolution of the security model over time. In this paper we describe this work, we describe the deployment of the new security model, and we show how these enhancements improve security on several fronts simultaneously.

  9. The help of formal models for healthcare security policies.

    Science.gov (United States)

    Trouessin, G; Barber, B

    1997-01-01

    This article is a personal contribution (i.e., from a strict security expert point of view) towards the help for specification, validation and/or evaluation of reliable, but also secure, healthcare security policies (HSP). The first part is dedicated to show, according to the various aspects of the security policy concept, that healthcare information systems (HIS) offer such a diversity of particularities and potential security needs, that it is necessary for healthcare security policies to be defined as flexible, but also as robust, as possible. Then the formal modelling approach, a wide area of solutions providing both flexibility (by means of modelling) and robustness (by means of formalization), is presented. The most well-known examples of security models are recalled. All of them try to use formal models as a security policy specification/validation tool, but none of them can be helpfully used in the very demanding context of HIS. Lastly, a new approach for the modelling of healthcare security policies, based on modal logic (i.e., epistemic and/or deontic logic) is proposed. It permits to take into account the flexibility (by means of high expressiveness due to modality) and the robustness (by means of high provability due to modelling) needs.

  10. High Assurance Models for Secure Systems

    Science.gov (United States)

    Almohri, Hussain M. J.

    2013-01-01

    Despite the recent advances in systems and network security, attacks on large enterprise networks consistently impose serious challenges to maintaining data privacy and software service integrity. We identify two main problems that contribute to increasing the security risk in a networked environment: (i) vulnerable servers, workstations, and…

  11. High Assurance Models for Secure Systems

    Science.gov (United States)

    Almohri, Hussain M. J.

    2013-01-01

    Despite the recent advances in systems and network security, attacks on large enterprise networks consistently impose serious challenges to maintaining data privacy and software service integrity. We identify two main problems that contribute to increasing the security risk in a networked environment: (i) vulnerable servers, workstations, and…

  12. A multilevel model for cardiovascular disease prevalence in the US and its application to micro area prevalence estimates

    OpenAIRE

    2009-01-01

    Abstract Background Estimates of disease prevalence for small areas are increasingly required for the allocation of health funds according to local need. Both individual level and geographic risk factors are likely to be relevant to explaining prevalence variations, and in turn relevant to the procedure for small area prevalence estimation. Prevalence estimates are of particular importance for major chronic illnesses such as cardiovascular disease. Methods A multilevel prevalence model for ca...

  13. On Protocol Security in the Cryptographic Model

    DEFF Research Database (Denmark)

    Nielsen, Jesper Buus

    the channels by which they communicate. A general solution to the secure multiparty computation problem is a compiler which given any feasible function describes an efficient protocol which allows the parties to compute the function securely on their local inputs over an open network. Over the past twenty...... previous approaches to the problem. Starting from an open point-to-point network there is a long way to general secure multiparty computation. The dissertation contains contributions at several points along the way. In particular we investigate how to realize secure channels. We also show how threshold...... you as possible. This is the general problem of secure multiparty computation. The usual way of formalizing the problem is to say that a number of parties who do not trust each other wish to compute some function of their local inputs, while keeping their inputs as secret as possible and guaranteeing...

  14. Coupling Longitudinal Data and Multilevel Modeling to Examine the Antecedents and Consequences of Jealousy Experiences in Romantic Relationships: A Test of the Relational Turbulence Model

    Science.gov (United States)

    Theiss, Jennifer A.; Solomon, Denise Haunani

    2006-01-01

    We used longitudinal data and multilevel modeling to examine how intimacy, relational uncertainty, and failed attempts at interdependence influence emotional, cognitive, and communicative responses to romantic jealousy, and how those experiences shape subsequent relationship characteristics. The relational turbulence model (Solomon & Knobloch,…

  15. Individual tree diameter increment model for managed even-aged stands of ponderosa pine throughout the western United States using a multilevel linear mixed effects model

    Science.gov (United States)

    Fabian C.C. Uzoh; William W. Oliver

    2008-01-01

    A diameter increment model is developed and evaluated for individual trees of ponderosa pine throughout the species range in the United States using a multilevel linear mixed model. Stochastic variability is broken down among period, locale, plot, tree and within-tree components. Covariates acting at tree and stand level, as breast height diameter, density, site index...

  16. Multi-level modeling of social factors and preterm delivery in Santiago de Chile

    Directory of Open Access Journals (Sweden)

    Alonso Faustino T

    2008-10-01

    Full Text Available Abstract Background Birth before the 37th week of gestation (preterm birth is an important cause of infant and neonatal mortality, but has been little studied outside of wealthy nations. Chile is an urbanized Latin American nation classified as "middle-income" based on its annual income per capita of about $6000. Methods We studied the relations between maternal social status and neighborhood social status on risk of preterm delivery in this setting using multilevel regression analyses of vital statistics data linked to geocoded decennial census data. The analytic data set included 56,970 births from 2004 in the metropolitan region of Santiago, which constitutes about 70% of all births in the study area and about 25% of all births in Chile that year. Dimensionality of census data was reduced using principal components analysis, with regression scoring to create a single index of community socioeconomic advantage. This was modeled along with years of maternal education in order to predict preterm birth and preterm low birthweight. Results Births in Santiago displayed an advantaged pattern of preterm risk, with only 6.4% of births delivering before 37 weeks. Associations were observed between risk of outcomes and individual and neighborhood factors, but the magnitudes of these associations were much more modest than reported in North America. Conclusion While several potential explanations for this relatively flat social gradient might be considered, one possibility is that Chile's egalitarian approach to universal prenatal care may have reduced social inequalities in these reproductive outcomes.

  17. Multilevel modeling of retention and disinfection efficacy of silver nanoparticles on ceramic water filters.

    Science.gov (United States)

    Mikelonis, Anne M; Lawler, Desmond F; Passalacqua, Paola

    2016-10-01

    This research examined how variations in synthesis methods of silver nanoparticles affect both the release of silver from ceramic water filters (CWFs) and disinfection efficacy. The silver nanoparticles used were stabilized by four different molecules: citrate, polyvinylpyrrolidone, branched polyethylenimine, and casein. A multilevel statistical model was built to quantify if there was a significant difference in: a) extent of silver lost, b) initial amount of silver lost, c) silver lost for water of different quality, and d) total coliform removal. Experiments were performed on location at Pure Home Water, a CWF factory in Tamale, Ghana using stored rainwater and dugout water (a local surface water). The results indicated that using dugout vs. rainwater significantly affects the initial (p-value 0.0015) and sustained (p-value 0.0124) loss of silver, but that silver type does not have a significant effect. On average, dugout water removed 37.5μg/L more initial silver and had 1.1μg/L more silver in the filtrate than rainwater. Initially, filters achieved 1.9 log reduction values (LRVs) on average, but among different silver and water types this varied by as much as 2.5 LRV units. Overall, bacterial removal effectiveness was more challenging to evaluate, but some data suggest that the branched polyethylenimine silver nanoparticles provided improved initial bacterial removal over filters which were not painted with silver nanoparticles (p-value 0.038).

  18. Examining school-based bullying interventions using multilevel discrete time hazard modeling.

    Science.gov (United States)

    Ayers, Stephanie L; Wagaman, M Alex; Geiger, Jennifer Mullins; Bermudez-Parsai, Monica; Hedberg, E C

    2012-10-01

    Although schools have been trying to address bullying by utilizing different approaches that stop or reduce the incidence of bullying, little remains known about what specific intervention strategies are most successful in reducing bullying in the school setting. Using the social-ecological framework, this paper examines school-based disciplinary interventions often used to deliver consequences to deter the reoccurrence of bullying and aggressive behaviors among school-aged children. Data for this study are drawn from the School-Wide Information System (SWIS) with the final analytic sample consisting of 1,221 students in grades K - 12 who received an office disciplinary referral for bullying during the first semester. Using Kaplan-Meier Failure Functions and Multi-level discrete time hazard models, determinants of the probability of a student receiving a second referral over time were examined. Of the seven interventions tested, only Parent-Teacher Conference (AOR = 0.65, p connection between the students' mesosystems as well as utilizing disciplinary strategies that take into consideration student's microsystem roles.

  19. Policy implications of achievement testing using multilevel models: The case of Brazilian elementary schools

    Directory of Open Access Journals (Sweden)

    Igor Gomes Menezes

    2016-11-01

    Full Text Available Large-scale educational assessment has been established as source of descriptive, evaluative and interpretative information that influence educational policies worldwide throughout the last third of the 20th century. In the 1990s the Brazilian Ministry of Education developed the National Basic Education Assessment System (SAEB that regularly measures management, resource and contextual school features and academic achievement in public and private institutions. In 2005, after significant piloting and review of the SAEB, a new sampling strategy was taken and Prova Brasil became the new instrument used by the Ministry to assess skills in Portuguese (reading comprehension and Mathematics (problem solving, as well as collecting contextual information concerning the school, principal, teacher, and the students. This study aims to identify which variables are predictors of academic achievement of fifth grade students on Prova Brasil. Across a large sample of students, multilevel models tested a large number of variables relevant to student achievement. This approach uncovered critical variables not commonly seen as significant in light of other achievement determinants, including student habits, teacher ethnicity, and school technological resources. As such, this approach demonstrates the value of MLM to appropriately nuanced educational policies that reflect critical influences on student achievement. Its implications for wider application for psychology studies that may have relevant impacts for policy are also discussed.

  20. Impact of community capacity on the health status of residents: understanding with the contextual multilevel model.

    Science.gov (United States)

    Jung, Minsoo; Choi, Mankyu

    2013-01-01

    There has been little conceptual understanding as to how community capacity works, although it allows for an important, population-based health promotional strategy. In this study, the mechanism of community capacity was studied through literature reviews to suggest a comprehensive conceptual model. The research results found that the key to community capacity prevailed in how actively the capacities of individuals and their communities are able to interact with one another. Under active interactions, community-based organizations, which are a type of voluntary association, were created within the community, and cohesion among residents was enhanced. In addition, people were more willing to address community issues. During the process, many services were initiated to meet the people's health needs and strengthen their social and psychological ties. The characteristics of community capacity were named as the contextual multilevel effects. Because an increase in community capacity contributes to a boosted health status, encourages health behaviors, and eventually leads to the overall prosperity of the community, more public health-related attention is required.

  1. Multi-level modeling of social factors and preterm delivery in Santiago de Chile.

    Science.gov (United States)

    Kaufman, Jay S; Alonso, Faustino T; Pino, Paulina

    2008-10-08

    Birth before the 37th week of gestation (preterm birth) is an important cause of infant and neonatal mortality, but has been little studied outside of wealthy nations. Chile is an urbanized Latin American nation classified as "middle-income" based on its annual income per capita of about $6000. We studied the relations between maternal social status and neighborhood social status on risk of preterm delivery in this setting using multilevel regression analyses of vital statistics data linked to geocoded decennial census data. The analytic data set included 56,970 births from 2004 in the metropolitan region of Santiago, which constitutes about 70% of all births in the study area and about 25% of all births in Chile that year. Dimensionality of census data was reduced using principal components analysis, with regression scoring to create a single index of community socioeconomic advantage. This was modeled along with years of maternal education in order to predict preterm birth and preterm low birthweight. Births in Santiago displayed an advantaged pattern of preterm risk, with only 6.4% of births delivering before 37 weeks. Associations were observed between risk of outcomes and individual and neighborhood factors, but the magnitudes of these associations were much more modest than reported in North America. While several potential explanations for this relatively flat social gradient might be considered, one possibility is that Chile's egalitarian approach to universal prenatal care may have reduced social inequalities in these reproductive outcomes.

  2. An exploration of multilevel modeling for estimating access to drinking-water and sanitation.

    Science.gov (United States)

    Wolf, Jennyfer; Bonjour, Sophie; Prüss-Ustün, Annette

    2013-03-01

    Monitoring progress towards the targets for access to safe drinking-water and sanitation under the Millennium Development Goals (MDG) requires reliable estimates and indicators. We analyzed trends and reviewed current indicators used for those targets. We developed continuous time series for 1990 to 2015 for access to improved drinking-water sources and improved sanitation facilities by country using multilevel modeling (MLM). We show that MLM is a reliable and transparent tool with many advantages over alternative approaches to estimate access to facilities. Using current indicators, the MDG target for water would be met, but the target for sanitation missed considerably. The number of people without access to such services is still increasing in certain regions. Striking differences persist between urban and rural areas. Consideration of water quality and different classification of shared sanitation facilities would, however, alter estimates considerably. To achieve improved monitoring we propose: (1) considering the use of MLM as an alternative for estimating access to safe drinking-water and sanitation; (2) completing regular assessments of water quality and supporting the development of national regulatory frameworks as part of capacity development; (3) evaluating health impacts of shared sanitation; (4) using a more equitable presentation of countries' performances in providing improved services.

  3. Empirical valence bond models for reactive potential energy surfaces: a parallel multilevel genetic program approach.

    Science.gov (United States)

    Bellucci, Michael A; Coker, David F

    2011-07-28

    We describe a new method for constructing empirical valence bond potential energy surfaces using a parallel multilevel genetic program (PMLGP). Genetic programs can be used to perform an efficient search through function space and parameter space to find the best functions and sets of parameters that fit energies obtained by ab initio electronic structure calculations. Building on the traditional genetic program approach, the PMLGP utilizes a hierarchy of genetic programming on two different levels. The lower level genetic programs are used to optimize coevolving populations in parallel while the higher level genetic program (HLGP) is used to optimize the genetic operator probabilities of the lower level genetic programs. The HLGP allows the algorithm to dynamically learn the mutation or combination of mutations that most effectively increase the fitness of the populations, causing a significant increase in the algorithm's accuracy and efficiency. The algorithm's accuracy and efficiency is tested against a standard parallel genetic program with a variety of one-dimensional test cases. Subsequently, the PMLGP is utilized to obtain an accurate empirical valence bond model for proton transfer in 3-hydroxy-gamma-pyrone in gas phase and protic solvent.

  4. Examining School-Based Bullying Interventions Using Multilevel Discrete Time Hazard Modeling

    Science.gov (United States)

    Wagaman, M. Alex; Geiger, Jennifer Mullins; Bermudez-Parsai, Monica; Hedberg, E. C.

    2014-01-01

    Although schools have been trying to address bulling by utilizing different approaches that stop or reduce the incidence of bullying, little remains known about what specific intervention strategies are most successful in reducing bullying in the school setting. Using the social-ecological framework, this paper examines school-based disciplinary interventions often used to deliver consequences to deter the reoccurrence of bullying and aggressive behaviors among school-aged children. Data for this study are drawn from the School-Wide Information System (SWIS) with the final analytic sample consisting of 1,221 students in grades K – 12 who received an office disciplinary referral for bullying during the first semester. Using Kaplan-Meier Failure Functions and Multi-level discrete time hazard models, determinants of the probability of a student receiving a second referral over time were examined. Of the seven interventions tested, only Parent-Teacher Conference (AOR=0.65, pbullying and aggressive behaviors. By using a social-ecological framework, schools can develop strategies that deter the reoccurrence of bullying by identifying key factors that enhance a sense of connection between the students’ mesosystems as well as utilizing disciplinary strategies that take into consideration student’s microsystem roles. PMID:22878779

  5. Variance Distribution in Sibling Relationships: Advantages of Multilevel Modeling Using Full Sibling Groups.

    Science.gov (United States)

    Marciniak, Karyn

    2017-03-01

    The majority of research on sibling relationships has investigated only one or two siblings in a family, but there are many theoretical and methodological limitations to this single dyadic perspective. This study uses multiple siblings (541 adults) in 184 families, where 96 of these families had all siblings complete the study, to demonstrate the value in including full sibling groups when conducting research on sibling relationships. Two scales, positivity and willingness to sacrifice, are evaluated with a multilevel model to account for the nested nature of family relationships. The distribution of variance across three levels: relationship, individual, and family are computed, and results indicate that the relationship level explains the most variance in positivity, whereas the individual level explains the majority of variance in willingness to sacrifice. These distributions are affected by gender composition and family size. The results of this study highlight an important and often overlooked element of family research: The meaning of a scale changes based on its distribution of variance at these three levels. Researchers are encouraged to be cognizant of the variance distribution of their scales when studying sibling relationships and to incorporate more full sibling groups into their research methods and study design. © 2015 Family Process Institute.

  6. A Bayesian-based multilevel factorial analysis method for analyzing parameter uncertainty of hydrological model

    Science.gov (United States)

    Liu, Y. R.; Li, Y. P.; Huang, G. H.; Zhang, J. L.; Fan, Y. R.

    2017-10-01

    In this study, a Bayesian-based multilevel factorial analysis (BMFA) method is developed to assess parameter uncertainties and their effects on hydrological model responses. In BMFA, Differential Evolution Adaptive Metropolis (DREAM) algorithm is employed to approximate the posterior distributions of model parameters with Bayesian inference; factorial analysis (FA) technique is used for measuring the specific variations of hydrological responses in terms of posterior distributions to investigate the individual and interactive effects of parameters on model outputs. BMFA is then applied to a case study of the Jinghe River watershed in the Loess Plateau of China to display its validity and applicability. The uncertainties of four sensitive parameters, including soil conservation service runoff curve number to moisture condition II (CN2), soil hydraulic conductivity (SOL_K), plant available water capacity (SOL_AWC), and soil depth (SOL_Z), are investigated. Results reveal that (i) CN2 has positive effect on peak flow, implying that the concentrated rainfall during rainy season can cause infiltration-excess surface flow, which is an considerable contributor to peak flow in this watershed; (ii) SOL_K has positive effect on average flow, implying that the widely distributed cambisols can lead to medium percolation capacity; (iii) the interaction between SOL_AWC and SOL_Z has noticeable effect on the peak flow and their effects are dependent upon each other, which discloses that soil depth can significant influence the processes of plant uptake of soil water in this watershed. Based on the above findings, the significant parameters and the relationship among uncertain parameters can be specified, such that hydrological model's capability for simulating/predicting water resources of the Jinghe River watershed can be improved.

  7. Multilevel latent class casemix modelling: a novel approach to accommodate patient casemix

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    Forman David

    2011-03-01

    Full Text Available Abstract Background Using routinely collected patient data we explore the utility of multilevel latent class (MLLC models to adjust for patient casemix and rank Trust performance. We contrast this with ranks derived from Trust standardised mortality ratios (SMRs. Methods Patients with colorectal cancer diagnosed between 1998 and 2004 and resident in Northern and Yorkshire regions were identified from the cancer registry database (n = 24,640. Patient age, sex, stage-at-diagnosis (Dukes, and Trust of diagnosis/treatment were extracted. Socioeconomic background was derived using the Townsend Index. Outcome was survival at 3 years after diagnosis. MLLC-modelled and SMR-generated Trust ranks were compared. Results Patients were assigned to two classes of similar size: one with reasonable prognosis (63.0% died within 3 years, and one with better prognosis (39.3% died within 3 years. In patient class one, all patients diagnosed at stage B or C died within 3 years; in patient class two, all patients diagnosed at stage A, B or C survived. Trusts were assigned two classes with 51.3% and 53.2% of patients respectively dying within 3 years. Differences in the ranked Trust performance between the MLLC model and SMRs were all within estimated 95% CIs. Conclusions A novel approach to casemix adjustment is illustrated, ranking Trust performance whilst facilitating the evaluation of factors associated with the patient journey (e.g. treatments and factors associated with the processes of healthcare delivery (e.g. delays. Further research can demonstrate the value of modelling patient pathways and evaluating healthcare processes across provider institutions.

  8. Hierarchical Policy Model for Managing Heterogeneous Security Systems

    Science.gov (United States)

    Lee, Dong-Young; Kim, Minsoo

    2007-12-01

    The integrated security management becomes increasingly complex as security manager must take heterogeneous security systems, different networking technologies, and distributed applications into consideration. The task of managing these security systems and applications depends on various systems and vender specific issues. In this paper, we present a hierarchical policy model which are derived from the conceptual policy, and specify means to enforce this behavior. The hierarchical policy model consist of five levels which are conceptual policy level, goal-oriented policy level, target policy level, process policy level and low-level policy.

  9. Security Model For Service-Oriented Architecture

    CERN Document Server

    Karimi, Oldooz

    2011-01-01

    In this article, we examine how security applies to Service Oriented Architecture (SOA). Before we discuss security for SOA, lets take a step back and examine what SOA is. SOA is an architectural approach which involves applications being exposed as "services". Originally, services in SOA were associated with a stack of technologies which included SOAP, WSDL, and UDDI. This article addresses the defects of traditional enterprise application integration by combining service oriented-architecture and web service technology. Application integration is then simplified to development and integration of services to tackle connectivity of isomerous enterprise application integration, security, loose coupling between systems and process refactoring and optimization.

  10. Use of multilevel modeling for determining optimal parameters of heat supply systems

    Science.gov (United States)

    Stennikov, V. A.; Barakhtenko, E. A.; Sokolov, D. V.

    2017-07-01

    The problem of finding optimal parameters of a heat-supply system (HSS) is in ensuring the required throughput capacity of a heat network by determining pipeline diameters and characteristics and location of pumping stations. Effective methods for solving this problem, i.e., the method of stepwise optimization based on the concept of dynamic programming and the method of multicircuit optimization, were proposed in the context of the hydraulic circuit theory developed at Melentiev Energy Systems Institute (Siberian Branch, Russian Academy of Sciences). These methods enable us to determine optimal parameters of various types of piping systems due to flexible adaptability of the calculation procedure to intricate nonlinear mathematical models describing features of used equipment items and methods of their construction and operation. The new and most significant results achieved in developing methodological support and software for finding optimal parameters of complex heat supply systems are presented: a new procedure for solving the problem based on multilevel decomposition of a heat network model that makes it possible to proceed from the initial problem to a set of interrelated, less cumbersome subproblems with reduced dimensionality; a new algorithm implementing the method of multicircuit optimization and focused on the calculation of a hierarchical model of a heat supply system; the SOSNA software system for determining optimum parameters of intricate heat-supply systems and implementing the developed methodological foundation. The proposed procedure and algorithm enable us to solve engineering problems of finding the optimal parameters of multicircuit heat supply systems having large (real) dimensionality, and are applied in solving urgent problems related to the optimal development and reconstruction of these systems. The developed methodological foundation and software can be used for designing heat supply systems in the Central and the Admiralty regions in

  11. A risk management model for securing virtual healthcare communities.

    Science.gov (United States)

    Chryssanthou, Anargyros; Varlamis, Iraklis; Latsiou, Charikleia

    2011-01-01

    Virtual healthcare communities aim to bring together healthcare professionals and patients, improve the quality of healthcare services and assist healthcare professionals and researchers in their everyday activities. In a secure and reliable environment, patients share their medical data with doctors, expect confidentiality and demand reliable medical consultation. Apart from a concrete policy framework, several ethical, legal and technical issues must be considered in order to build a trustful community. This research emphasises on security issues, which can arise inside a virtual healthcare community and relate to the communication and storage of data. It capitalises on a standardised risk management methodology and a prototype architecture for healthcare community portals and justifies a security model that allows the identification, estimation and evaluation of potential security risks for the community. A hypothetical virtual healthcare community is employed in order to portray security risks and the solutions that the security model provides.

  12. Clarifying the use of aggregated exposures in multilevel models: self-included vs. self-excluded measures.

    Directory of Open Access Journals (Sweden)

    Etsuji Suzuki

    Full Text Available BACKGROUND: Multilevel analyses are ideally suited to assess the effects of ecological (higher level and individual (lower level exposure variables simultaneously. In applying such analyses to measures of ecologies in epidemiological studies, individual variables are usually aggregated into the higher level unit. Typically, the aggregated measure includes responses of every individual belonging to that group (i.e. it constitutes a self-included measure. More recently, researchers have developed an aggregate measure which excludes the response of the individual to whom the aggregate measure is linked (i.e. a self-excluded measure. In this study, we clarify the substantive and technical properties of these two measures when they are used as exposures in multilevel models. METHODS: Although the differences between the two aggregated measures are mathematically subtle, distinguishing between them is important in terms of the specific scientific questions to be addressed. We then show how these measures can be used in two distinct types of multilevel models-self-included model and self-excluded model-and interpret the parameters in each model by imposing hypothetical interventions. The concept is tested on empirical data of workplace social capital and employees' systolic blood pressure. RESULTS: Researchers assume group-level interventions when using a self-included model, and individual-level interventions when using a self-excluded model. Analytical re-parameterizations of these two models highlight their differences in parameter interpretation. Cluster-mean centered self-included models enable researchers to decompose the collective effect into its within- and between-group components. The benefit of cluster-mean centering procedure is further discussed in terms of hypothetical interventions. CONCLUSIONS: When investigating the potential roles of aggregated variables, researchers should carefully explore which type of model-self-included or self

  13. Analyzing Latent State-Trait and Multiple-Indicator Latent Growth Curve Models as Multilevel Structural Equation Models

    Directory of Open Access Journals (Sweden)

    Christian eGeiser

    2013-12-01

    Full Text Available Latent state-trait (LST and latent growth curve (LGC models are frequently used in the analysis of longitudinal data. Although it is well-known that standard single-indicator LGC models can be analyzed within either the structural equation modeling (SEM or multilevel (ML; hierarchical linear modeling frameworks, few researchers realize that LST and multivariate LGC models, which use multiple indicators at each time point, can also be specified as ML models. In the present paper, we demonstrate that using the ML-SEM rather than the SL-SEM framework to estimate the parameters of these models can be practical when the study involves (1 a large number of time points, (2 individually-varying times of observation, (3 unequally spaced time intervals, and/or (4 incomplete data. Despite the practical advantages of the ML-SEM approach under these circumstances, there are also some limitations that researchers should consider. We present an application to an ecological momentary assessment study (N = 158 youths with an average of 23.49 observations of positive mood per person using the software Mplus (Muthén & Muthén, 1998-2012 and discuss advantages and disadvantages of using the ML-SEM approach to estimate the parameters of LST and multiple-indicator LGC models.

  14. Triple Helix Model as an Efficient Mechanism of Food Security Provision in Regional Economic Entities and the Economic System as a Whole

    Directory of Open Access Journals (Sweden)

    Mihail N. Dudin

    2014-08-01

    Full Text Available The leading countries of the world consider food security the important condition of internal political and social-economic stability of the state and its external independence. The topic of the article is crucial due to the fact that the problem of food security is rather complicated and multilevel and should be considered at different interrelated hierarchical levels. In this context the efficient model of food security is the result of the permanent dialogue between the representatives of the state government, business entities, social organizations and scientific institutions. The article justifies the fact that the model of innovation development, known as ‘the triple helix model’ should be applied at the modern stage of economic development as an efficient tool for the food security provision, which can be implemented in the activity of regional economic entities and the whole economic system of the Russian Federation.

  15. Perceptions of Job Security in Europe's Ageing Workforce

    Science.gov (United States)

    Hank, Karsten; Erlinghagen, Marcel

    2011-01-01

    Using data from the 2004 Survey of Health, Ageing and Retirement in Europe, this paper investigates older workers' perceptions of job security in eleven countries. We describe cross-national patterns and estimate multilevel models to analyse individual and societal determinants of self-perceived job security in the older labour force. While there…

  16. The effects of autonomy and empowerment on employee turnover: test of a multilevel model in teams.

    Science.gov (United States)

    Liu, Dong; Zhang, Shu; Wang, Lei; Lee, Thomas W

    2011-11-01

    Extending research on voluntary turnover in the team setting, this study adopts a multilevel self-determination theoretical approach to examine the unique roles of individual and social-contextual motivational precursors, autonomy orientation and autonomy support, in reducing team member voluntary turnover. Analysis of multilevel time-lagged data collected from 817 employees on 115 teams indicates that psychological empowerment mediates the main effect of autonomy orientation and the interactive effect of autonomy support and its differentiation on a team member's voluntary turnover. The findings have meaningful implications for the turnover and self-determination literatures as well as for managers who endeavor to prevent voluntary turnover in teams.

  17. ML-Space: Hybrid Spatial Gillespie and Particle Simulation of Multi-level Rule-based Models in Cell Biology.

    Science.gov (United States)

    Bittig, Arne; Uhrmacher, Adelinde

    2016-08-03

    Spatio-temporal dynamics of cellular processes can be simulated at different levels of detail, from (deterministic) partial differential equations via the spatial Stochastic Simulation algorithm to tracking Brownian trajectories of individual particles. We present a spatial simulation approach for multi-level rule-based models, which includes dynamically hierarchically nested cellular compartments and entities. Our approach ML-Space combines discrete compartmental dynamics, stochastic spatial approaches in discrete space, and particles moving in continuous space. The rule-based specification language of ML-Space supports concise and compact descriptions of models and to adapt the spatial resolution of models easily.

  18. The importance of isomorphism for conclusions about homology: A Bayesian multilevel structural equation modeling approach with ordinal indicators

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    Nigel eGuenole

    2016-03-01

    Full Text Available We describe a Monte Carlo study examining the impact of assuming item isomorphism (i.e., equivalent construct meaning across levels of analysis on conclusions about homology (i.e., equivalent structural relations across levels of analysis under varying degrees of non-isomorphism in the context of ordinal indicator multilevel structural equation models (MSEMs. We focus on the condition where one or more loadings are higher on the between level than on the within level to show that while much past research on homology has ignored the issue of psychometric isomorphism, psychometric isomorphism is in fact critical to valid conclusions about homology. More specifically, when a measurement model with non-isomorphic items occupies an exogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the within level exogenous latent variance is under-estimated leading to over-estimation of the within level structural coefficient, while the between level exogenous latent variance is overestimated leading to underestimation of the between structural coefficient. When a measurement model with non-isomorphic items occupies an endogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the endogenous within level latent variance is under-estimated leading to under-estimation of the within level structural coefficient while the endogenous between level latent variance is over-estimated leading to over-estimation of the between level structural coefficient. The innovative aspect of this article is demonstrating that even minor violations of psychometric isomorphism render claims of homology untenable. We also show that posterior predictive p-values for ordinal indicator Bayesian MSEMs are insensitive to violations of isomorphism even when they lead to severely biased within and between level structural parameters. We highlight conditions where poor estimation of even

  19. The Importance of Isomorphism for Conclusions about Homology: A Bayesian Multilevel Structural Equation Modeling Approach with Ordinal Indicators.

    Science.gov (United States)

    Guenole, Nigel

    2016-01-01

    We describe a Monte Carlo study examining the impact of assuming item isomorphism (i.e., equivalent construct meaning across levels of analysis) on conclusions about homology (i.e., equivalent structural relations across levels of analysis) under varying degrees of non-isomorphism in the context of ordinal indicator multilevel structural equation models (MSEMs). We focus on the condition where one or more loadings are higher on the between level than on the within level to show that while much past research on homology has ignored the issue of psychometric isomorphism, psychometric isomorphism is in fact critical to valid conclusions about homology. More specifically, when a measurement model with non-isomorphic items occupies an exogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the within level exogenous latent variance is under-estimated leading to over-estimation of the within level structural coefficient, while the between level exogenous latent variance is overestimated leading to underestimation of the between structural coefficient. When a measurement model with non-isomorphic items occupies an endogenous position in a multilevel structural model and the non-isomorphism of these items is not modeled, the endogenous within level latent variance is under-estimated leading to under-estimation of the within level structural coefficient while the endogenous between level latent variance is over-estimated leading to over-estimation of the between level structural coefficient. The innovative aspect of this article is demonstrating that even minor violations of psychometric isomorphism render claims of homology untenable. We also show that posterior predictive p-values for ordinal indicator Bayesian MSEMs are insensitive to violations of isomorphism even when they lead to severely biased within and between level structural parameters. We highlight conditions where poor estimation of even correctly specified

  20. A model-driven approach to information security compliance

    Science.gov (United States)

    Correia, Anacleto; Gonçalves, António; Teodoro, M. Filomena

    2017-06-01

    The availability, integrity and confidentiality of information are fundamental to the long-term survival of any organization. Information security is a complex issue that must be holistically approached, combining assets that support corporate systems, in an extended network of business partners, vendors, customers and other stakeholders. This paper addresses the conception and implementation of information security systems, conform the ISO/IEC 27000 set of standards, using the model-driven approach. The process begins with the conception of a domain level model (computation independent model) based on information security vocabulary present in the ISO/IEC 27001 standard. Based on this model, after embedding in the model mandatory rules for attaining ISO/IEC 27001 conformance, a platform independent model is derived. Finally, a platform specific model serves the base for testing the compliance of information security systems with the ISO/IEC 27000 set of standards.

  1. Childhood diarrhea in high and low hotspot districts of Amhara Region, northwest Ethiopia: a multilevel modeling.

    Science.gov (United States)

    Azage, Muluken; Kumie, Abera; Worku, Alemayehu; Bagtzoglou, Amvrossios C

    2016-05-16

    Childhood diarrhea is one of the major public health problems in Ethiopia. Multiple factors at different levels contribute to the occurrence of childhood diarrhea. The objective of the study was to identify the factors affecting childhood diarrhea at individual and community level. A cross-sectional study design was employed from February to March 2015 in high and low hotspot districts of Awi and West and East Gojjam zones in Amhara Region, northwest Ethiopia. Districts with high and low hotspots with childhood diarrhea were identified using SaTScan spatial statistical analysis. A total of 2495 households from ten (five high and five low hotspot) randomly selected districts were included in the study. A semi-structured questionnaire was used to collect data. Data were entered and cleaned in Epi Info 3.5.2 version and analyzed using Stata version 12. A multilevel logistic regression was used to identify factors associated with childhood diarrhea. The prevalence of childhood diarrhea was 13.5 % and did not show significant variation between high [14.3 % (95 % CI 12.3-16.2 %)] and low [12.7 % (95 % CI 10.9-14.6 %)] hotspot districts. Individual- and community-level factors accounted for 35 % of childhood diarrhea variation across the communities in the full model. Age of children (6-35 months), complementary feeding initiation below 6 months, inadequate hand washing practices, limited knowledge of mothers on diarrhea, lowest wealth status of households, and longer time interval to visit households by health extension workers were factors for increasing the odds of childhood diarrhea at the individual level. At the community level, lack of improved water supply and sanitation and unvaccinated children with measles and rotavirus vaccine were the factors associated with childhood diarrhea. In this study, childhood diarrhea occurrences remained high. Both individual- and community-level factors determined the occurrence of diarrhea. Interventions should consider both

  2. Multi-Level Reduced Order Modeling Equipped with Probabilistic Error Bounds

    Science.gov (United States)

    Abdo, Mohammad Gamal Mohammad Mostafa

    This thesis develops robust reduced order modeling (ROM) techniques to achieve the needed efficiency to render feasible the use of high fidelity tools for routine engineering analyses. Markedly different from the state-of-the-art ROM techniques, our work focuses only on techniques which can quantify the credibility of the reduction which can be measured with the reduction errors upper-bounded for the envisaged range of ROM model application. Our objective is two-fold. First, further developments of ROM techniques are proposed when conventional ROM techniques are too taxing to be computationally practical. This is achieved via a multi-level ROM methodology designed to take advantage of the multi-scale modeling strategy typically employed for computationally taxing models such as those associated with the modeling of nuclear reactor behavior. Second, the discrepancies between the original model and ROM model predictions over the full range of model application conditions are upper-bounded in a probabilistic sense with high probability. ROM techniques may be classified into two broad categories: surrogate construction techniques and dimensionality reduction techniques, with the latter being the primary focus of this work. We focus on dimensionality reduction, because it offers a rigorous approach by which reduction errors can be quantified via upper-bounds that are met in a probabilistic sense. Surrogate techniques typically rely on fitting a parametric model form to the original model at a number of training points, with the residual of the fit taken as a measure of the prediction accuracy of the surrogate. This approach, however, does not generally guarantee that the surrogate model predictions at points not included in the training process will be bound by the error estimated from the fitting residual. Dimensionality reduction techniques however employ a different philosophy to render the reduction, wherein randomized snapshots of the model variables, such as the

  3. Utilización de los modelos multinivel en investigación sanitaria Use of multilevel models in health research

    Directory of Open Access Journals (Sweden)

    M.P. Galindo-Villardón

    2003-01-01

    Full Text Available Objetivo: El propósito de este artículo es analizar el uso de la metodología multinivel en las ciencias de la salud. Diseño: Se llevó a cabo una búsqueda bibliográfica en Medline de los artículos publicados entre 1995 y 2001, utilizando 15 palabras de búsqueda, entre las que se encuentran «multilevel model», «multilevel analysis», «hierarchical linear model», «mixed model» y «random effects model», obteniéndose un total de 1.288 resúmenes de artículos. Se examinaron los 222 artículos teóricos y/o aplicaciones realmente relacionadas con métodos multinivel, para determinar el nivel de uso actual, el tipo de modelo, el número de niveles, las unidades de análisis y las variables de respuesta a través de las especialidades en salud. Resultados: El 66,7% de los artículos estudiados se encontraron con las palabras de búsqueda «multilevel analysis», «multilevel modelling» y «multilevel model». El 56% de los artículos son aplicaciones de multinivel en diferentes áreas de la salud; no obstante, merece destacar que un 10% de los trabajos tienen como objetivo exponer y difundir la metodología en un lenguaje comprensible para los no especialistas. Conclusiones: El uso de los modelos multinivel en salud ha aumentado con los años, aplicándose en diferentes áreas o especialidades de salud, pero aún no se los considera una técnica de uso habitual.Objective: The aim of this study was to analyze the use of multilevel methodology in health sciences. Design: A literature search was performed in Medline for articles published between 1995 and 2001. Fifteen search words were used, some of which were «multilevel model», «multilevel analysis», «hierarchical linear model», «mixed model», and «random effects model». A total of 1288 abstracts were retrieved. Two hundred twenty-two of the articles on theoretical and/or applied issues related to multilevel methods were examined to determine their current use, the type of

  4. ONTOLOGICAL MODEL OF STRATEGIC ECONOMIC SECURITY OF ENTERPRISE

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    L. A. Zaporozhtseva

    2014-01-01

    Full Text Available Article explains the necessity the application of the ontological approach to modeling the strategic economic security in the formalization of the basic categories of domain company recognized its benefits. Among the advantages of the model distinguishes its versatility and ability to describe various aspects of strategic security - the system strategies and goals of the organization and business processes; possibility of its use at different levels of detail - from the top-level description of the basic categories of management, to design-level analytic applications; as well as the adaptability of the model, with depth on particular aspects determined by practical necessity and not regulated methodology. The model integrates various aspects of the concept of enterprise architecture and organizes conceptual apparatus. Ontological model easy to understand and adjust as business architects and specialists in designing systems of economic security and offers many categories of verbal representation of the domain of the enterprise. Proved the feasibility of using process-functional approach in providing strategic economic security, according to which the components of such a security company proposed as business processes, finance, staff and contractors. The article presents the author's ontological model of strategic economic security, including endangered sites, the presence of factors that threaten the security of the object and the subject of providing security. Further, it is proved that in the subjects of security impact on the object using the tools, measures and activities within the strategy formed the mechanism is implemented managerial decisions to strengthen the strategic economic security. The process of diagnosis, detection, identification of threats of economic security, and the development of enterprise development strategies, taking into account its level of economic security must be under the constant supervision of the process of

  5. Discovery of subtle effects in a human intervention trial through multilevel modeling

    NARCIS (Netherlands)

    C.M. Rubingh; M.J. van Erk; S. Wopereis; T. van Vliet; E.R. Verheij; N.H.P. Cnubben; B. van Ommen; J. van der Greef; H.F.J. Hendriks; A.K. Smilde

    2011-01-01

    Many benefits can be gained if multi-factorial diseases with a high incidence and prevalence are better understood. Sophisticated approaches like multilevel analyses are needed to discover subtle differences between healthy people and people at the onset of disease in these types of studies. Multile

  6. Testing Latent Mean Differences between Observed and Unobserved Groups Using Multilevel Factor Mixture Models

    Science.gov (United States)

    Allua, Shane; Stapleton, Laura M.; Beretvas, S. Natasha

    2008-01-01

    When assessing latent mean differences, researchers frequently do not explore possible heterogeneity within their data sets. Sources of differences may be functions of a nested data structure or heterogeneity in the form of unobserved classes of observations defined by a difference in factor means. In this study, the use of multilevel structural…

  7. Commitment to the Study of International Business and Cultural Intelligence: A Multilevel Model

    Science.gov (United States)

    Ramsey, Jase R.; Barakat, Livia L.; Aad, Amine Abi

    2014-01-01

    Adopting a multilevel theoretical framework, we examined how metacognitive and motivational cultural intelligence influence an individual's commitment to the study of international business (IB). Data from 292 undergraduate and graduate business students nested in 12 U.S. business school classes demonstrated that individuals' metacognitive and…

  8. Commitment to the Study of International Business and Cultural Intelligence: A Multilevel Model

    Science.gov (United States)

    Ramsey, Jase R.; Barakat, Livia L.; Aad, Amine Abi

    2014-01-01

    Adopting a multilevel theoretical framework, we examined how metacognitive and motivational cultural intelligence influence an individual's commitment to the study of international business (IB). Data from 292 undergraduate and graduate business students nested in 12 U.S. business school classes demonstrated that individuals'…

  9. Commitment to the Study of International Business and Cultural Intelligence: A Multilevel Model

    Science.gov (United States)

    Ramsey, Jase R.; Barakat, Livia L.; Aad, Amine Abi

    2014-01-01

    Adopting a multilevel theoretical framework, we examined how metacognitive and motivational cultural intelligence influence an individual's commitment to the study of international business (IB). Data from 292 undergraduate and graduate business students nested in 12 U.S. business school classes demonstrated that individuals' metacognitive and…

  10. High frequent modelling of a modular multilevel converter using passive components

    DEFF Research Database (Denmark)

    El-Khatib, Walid Ziad; Holbøll, Joachim; Rasmussen, Tonny Wederberg

    2013-01-01

    Prevalence of High Voltage direct current (HVDC) based on Voltage source converters (VSC) has made it necessary to investigate the behavior of the converter under various fault conditions. In this paper we will deal with the transient characteristics of a modular multilevel converter (MMC). This ...

  11. Hazard Identification of the Offshore Three-phase Separation Process Based on Multilevel Flow Modeling and HAZOP

    DEFF Research Database (Denmark)

    Wu, Jing; Zhang, Laibin; Lind, Morten;

    2013-01-01

    HAZOP studies are widely accepted in chemical and petroleum industries as the method for conducting process hazard analysis related to design, maintenance and operation of the systems. Different tools have been developed to automate HAZOP studies. In this paper, a HAZOP reasoning method based...... on function-oriented modeling, Multilevel Flow Modeling (MFM), is extended with function roles. A graphical MFM editor, which is combined with the reasoning capabilities of the MFM Workbench developed by DTU is applied to automate HAZOP studies. The method is proposed to support the “brain-storming” sessions...

  12. Application of multilevel scheme and two level discretization for POD based model order reduction of nonlinear transient heat transfer problems

    Science.gov (United States)

    Gaonkar, A. K.; Kulkarni, S. S.

    2015-01-01

    In the present paper, a method to reduce the computational cost associated with solving a nonlinear transient heat conduction problem is presented. The proposed method combines the ideas of two level discretization and the multilevel time integration schemes with the proper orthogonal decomposition model order reduction technique. The accuracy and the computational efficiency of the proposed methods is discussed. Several numerical examples are presented for validation of the approach. Compared to the full finite element model, the proposed method significantly reduces the computational time while maintaining an acceptable level of accuracy.

  13. Cross-classified multilevel models for severity of commercial motor vehicle crashes considering heterogeneity among companies and regions.

    Science.gov (United States)

    Park, Ho-Chul; Kim, Dong-Kyu; Kho, Seung-Young; Park, Peter Y

    2017-09-01

    This study analyzes 86,622 commercial motor vehicle (CMV) crashes (large truck, bus and taxi crashes) in South Korea from 2010 to 2014. The analysis recognizes the hierarchical structure of the factors affecting CMV crashes by examining eight factors related to individual crashes and six additional upper level factors organized in two non-nested groups (company level and regional level factors). The study considers four different crash severities (fatal, major, minor, and no injury). The company level factors reflect selected characteristics of 1,875 CMV companies, and the regional level factors reflect selected characteristics of 230 municipalities. The study develops a single-level ordinary ordered logit model, two conventional multilevel ordered logit models, and a cross-classified multilevel ordered logit model (CCMM). As the study develops each of these four models for large trucks, buses and taxis, 12 different statistical models are analyzed. The CCMM outperforms the other models in two important ways: 1) the CCMM avoids the type I statistical errors that tend to occur when analyzing hierarchical data with single-level models; and 2) the CCMM can analyze two non-nested groups simultaneously. Statistically significant factors include taxi company's type of vehicle ownership and municipality's level of transportation infrastructure budget. An improved understanding of CMV related crashes should contribute to the development of safety countermeasures to reduce the number and severity of CMV related crashes. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. A Novel Computer Virus Propagation Model under Security Classification

    Directory of Open Access Journals (Sweden)

    Qingyi Zhu

    2017-01-01

    Full Text Available In reality, some computers have specific security classification. For the sake of safety and cost, the security level of computers will be upgraded with increasing of threats in networks. Here we assume that there exists a threshold value which determines when countermeasures should be taken to level up the security of a fraction of computers with low security level. And in some specific realistic environments the propagation network can be regarded as fully interconnected. Inspired by these facts, this paper presents a novel computer virus dynamics model considering the impact brought by security classification in full interconnection network. By using the theory of dynamic stability, the existence of equilibria and stability conditions is analysed and proved. And the above optimal threshold value is given analytically. Then, some numerical experiments are made to justify the model. Besides, some discussions and antivirus measures are given.

  15. Self Managed Security Cell, a security model for the Internet of Things and Services

    CERN Document Server

    de Leusse, Pierre; Dimitrakos, Theo; Nair, Srijith K; 10.1109/AFIN.2009.15

    2012-01-01

    The Internet of Things and Services is a rapidly growing concept that illustrates that the ever increasing amount of physical items of our daily life which become addressable through a network could be made more easily manageable and usable through the use of Services. This surge of exposed resources along with the level of privacy and value of the information they hold, together with the increase of their usage make for an augmentation in the number of the security threats and violation attempts that existing security systems do not appear robust enough to address. In this paper, the authors underline this increase in risk and identify the requirements for resources to be more resilient in this type of environment while keeping an important level of flexibility. In addition, the authors propose an architectural model of Self Managed Security Cell, which leverages on current knowledge in large scale security systems, information management and autonomous systems.

  16. Multilevel component analysis

    NARCIS (Netherlands)

    Timmerman, M.E.

    2006-01-01

    A general framework for the exploratory component analysis of multilevel data (MLCA) is proposed. In this framework, a separate component model is specified for each group of objects at a certain level. The similarities between the groups of objects at a given level can be expressed by imposing cons

  17. Security for safety critical space borne systems

    Science.gov (United States)

    Legrand, Sue

    1987-01-01

    The Space Station contains safety critical computer software components in systems that can affect life and vital property. These components require a multilevel secure system that provides dynamic access control of the data and processes involved. A study is under way to define requirements for a security model providing access control through level B3 of the Orange Book. The model will be prototyped at NASA-Johnson Space Center.

  18. Using a Prediction Model to Manage Cyber Security Threats

    National Research Council Canada - National Science Library

    Jaganathan, Venkatesh; Cherurveettil, Priyesh; Muthu Sivashanmugam, Premapriya

    2015-01-01

    .... The cost impact due to worms, viruses, or other malicious software is significant. This paper proposes a mathematical model to predict the impact of an attack based on significant factors that influence cyber security...

  19. Secure Certificateless Signature with Revocation in the Standard Model

    Directory of Open Access Journals (Sweden)

    Tung-Tso Tsai

    2014-01-01

    previously proposed certificateless signature schemes were insecure under a considerably strong security model in the sense that they suffered from outsiders’ key replacement attacks or the attacks from the key generation center (KGC. In this paper, we propose a certificateless signature scheme without random oracles. Moreover, our scheme is secure under the strong security model and provides a public revocation mechanism, called revocable certificateless signature (RCLS. Under the standard computational Diffie-Hellman assumption, we formally demonstrate that our scheme possesses existential unforgeability against adaptive chosen-message attacks.

  20. Secure Model for Virtualization Layer in Cloud Infrastructure

    Directory of Open Access Journals (Sweden)

    Sina Manavi

    2015-05-01

    Full Text Available cloud security is one of the buzz words in cloud computing. Since virtualization is the fundamental of the cloud computing, needs to study it more deeply to avoid attacks and system failure. In this research is focused on virtualization vulnerabilities. In addition it is attempted to propose a model to secure and proper mechanism to react reasonable against the detected attack by intrusion detection system. With the secured model (SVM, virtual machines will be resist more efficiency against the attacks in cloud computing.

  1. Optimizing ZigBee Security using Stochastic Model Checking

    DEFF Research Database (Denmark)

    Yuksel, Ender; Nielson, Hanne Riis; Nielson, Flemming

    ZigBee is a fairly new but promising wireless sensor network standard that offers the advantages of simple and low resource communication. Nevertheless, security is of great concern to ZigBee, and enhancements are prescribed in the latest ZigBee specication: ZigBee-2007. In this technical report......, we identify an important gap in the specification on key updates, and present a methodology for determining optimal key update policies and security parameters. We exploit the stochastic model checking approach using the probabilistic model checker PRISM, and assess the security needs for realistic...

  2. Optimizing ZigBee Security using Stochastic Model Checking

    CERN Document Server

    Yüksel, Ender; Nielson, Flemming; Fruth, Matthias; Kwiatkowska, Marta

    2012-01-01

    ZigBee is a fairly new but promising wireless sensor network standard that offers the advantages of simple and low resource communication. Nevertheless, security is of great concern to ZigBee, and enhancements are prescribed in the latest ZigBee specication: ZigBee-2007. In this technical report, we identify an important gap in the specification on key updates, and present a methodology for determining optimal key update policies and security parameters. We exploit the stochastic model checking approach using the probabilistic model checker PRISM, and assess the security needs for realistic application scenarios.

  3. Formal Specifications and Verification of a Secure Communication Protocol Model

    Institute of Scientific and Technical Information of China (English)

    夏阳; 陆余良; 蒋凡

    2003-01-01

    This paper presents a secure communication protocol model-EABM, by which network security communication can be realized easily and efficiently. First, the paper gives a thorough analysis of the protocol system, systematic construction and state transition of EABM. Then , it describes the channels and the process of state transition of EABM in terms of ESTELLE. At last, it offers a verification of the accuracy of the EABM model.

  4. How to Be a Better Consumer of Security Maturity Models

    Science.gov (United States)

    2014-10-21

    2014 Carnegie Mellon University How to Be a Better Consumer of Security Maturity Models October 21, 2014 Julia Allen & Dr. Nader Mehravari...A 3. DATES COVERED 4. TITLE AND SUBTITLE How to Be a Better Consumer of Security Maturity Models 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...REACTIVE AND TAKEN UNAWARE BY SOCIAL MEDIA broadcasting • FACEBOOK AND TWITTER PRESENCE • BROADCAST STANDARD MARKETING VIA SOCIAL MEDIA • TARGETED

  5. Explanatory multidimensional multilevel random item response model: an application to simultaneous investigation of word and person contributions to multidimensional lexical representations.

    Science.gov (United States)

    Cho, Sun-Joo; Gilbert, Jennifer K; Goodwin, Amanda P

    2013-10-01

    This paper presents an explanatory multidimensional multilevel random item response model and its application to reading data with multilevel item structure. The model includes multilevel random item parameters that allow consideration of variability in item parameters at both item and item group levels. Item-level random item parameters were included to model unexplained variance remaining when item related covariates were used to explain variation in item difficulties. Item group-level random item parameters were included to model dependency in item responses among items having the same item stem. Using the model, this study examined the dimensionality of a person's word knowledge, termed lexical representation, and how aspects of morphological knowledge contributed to lexical representations for different persons, items, and item groups.

  6. FS-OpenSecurity: A Taxonomic Modeling of Security Threats in SDN for Future Sustainable Computing

    Directory of Open Access Journals (Sweden)

    Yunsick Sung

    2016-09-01

    Full Text Available Software Defined Networking (SDN has brought many changes in terms of the interaction processes between systems and humans. It has become the key enabler of software defined architecture, which allows enterprises to build a highly agile Information Technology (IT infrastructure. For Future Sustainability Computing (FSC, SDN needs to deliver on many information technology commitments—more automation, simplified design, increased agility, policy-based management, and network management bond to more liberal IT workflow systems. To address the sustainability problems, SDN needs to provide greater collaboration and tighter integration with networks, servers, and security teams that will have an impact on how enterprises design, plan, deploy and manage networks. In this paper, we propose FS-OpenSecurity, which is a new and pragmatic security architecture model. It consists of two novel methodologies, Software Defined Orchestrator (SDO and SQUEAK, which offer a robust and secure architecture. The secure architecture is required for protection from diverse threats. Usually, security administrators need to handle each threat individually. However, handling threats automatically by adapting to the threat landscape is a critical demand. Therefore, the architecture must handle defensive processes automatically that are collaboratively based on intelligent external and internal information.

  7. Enhancing Information Systems Security in Educational Organizations in KSA through proposing security model

    Directory of Open Access Journals (Sweden)

    Hussain A.H. Awad

    2011-09-01

    Full Text Available It is well known that technology utilization is not restricted for one sector than the other anymore, Educational organizations share many parts of their information systems with commercial organizations. In this paper we will try to identify the main characteristics of information systems in educational organizations, then we will propose a model of two parts to enhance the information systems security, the first part of the model will handle the policy and laws of the information system, the second part will provide a technical approach on how to audit and subsequently maintain the security of information system.

  8. Security Optimization of VTP Model in an Enterprise VLAN

    Directory of Open Access Journals (Sweden)

    Rajiv O. Verma

    2013-05-01

    Full Text Available VLANs are extensively used in enterprise network to ease management of hosts to improve scalability and flexibility. Despite their wide usage in enterprise network, VLAN security is a greater concern for the network administrator due to very little attention has been paid on error prone, unsystematic, high risk of misconfiguration in the design and management of enterprise VLAN network. Our paper demonstrates the security optimization techniques in designing VLAN both for Inter-VLAN communication and addressing VTP issues. We proposed various security aspects like access-lists based layer 3 securities in Inter-VLAN routing, deactivating native VLAN 1 to secure Layer 2 traffic in VTP model, Application of authentication on VTP server and non-negotiating Dynamic Trunking Protocol mode to counter the effect of inserting a rogue switch/trunk with higher config revision number. Unless otherwise stated this paper is based upon configuration {&} hardware implementation in a Cisco environment

  9. Multilevel Models for Intensive Longitudinal Data with Heterogeneous Autoregressive Errors: The Effect of Misspecification and Correction with Cholesky Transformation

    Science.gov (United States)

    Jahng, Seungmin; Wood, Phillip K.

    2017-01-01

    Intensive longitudinal studies, such as ecological momentary assessment studies using electronic diaries, are gaining popularity across many areas of psychology. Multilevel models (MLMs) are most widely used analytical tools for intensive longitudinal data (ILD). Although ILD often have individually distinct patterns of serial correlation of measures over time, inferences of the fixed effects, and random components in MLMs are made under the assumption that all variance and autocovariance components are homogenous across individuals. In the present study, we introduced a multilevel model with Cholesky transformation to model ILD with individually heterogeneous covariance structure. In addition, the performance of the transformation method and the effects of misspecification of heterogeneous covariance structure were investigated through a Monte Carlo simulation. We found that, if individually heterogeneous covariances are incorrectly assumed as homogenous independent or homogenous autoregressive, MLMs produce highly biased estimates of the variance of random intercepts and the standard errors of the fixed intercept and the fixed effect of a level 2 covariate when the average autocorrelation is high. For intensive longitudinal data with individual specific residual covariance, the suggested transformation method showed lower bias in those estimates than the misspecified models when the number of repeated observations within individuals is 50 or more. PMID:28286490

  10. Multilevel models for multiple-baseline data: modeling across-participant variation in autocorrelation and residual variance.

    Science.gov (United States)

    Baek, Eun Kyeng; Ferron, John M

    2013-03-01

    Multilevel models (MLM) have been used as a method for analyzing multiple-baseline single-case data. However, some concerns can be raised because the models that have been used assume that the Level-1 error covariance matrix is the same for all participants. The purpose of this study was to extend the application of MLM of single-case data in order to accommodate across-participant variation in the Level-1 residual variance and autocorrelation. This more general model was then used in the analysis of single-case data sets to illustrate the method, to estimate the degree to which the autocorrelation and residual variances differed across participants, and to examine whether inferences about treatment effects were sensitive to whether or not the Level-1 error covariance matrix was allowed to vary across participants. The results from the analyses of five published studies showed that when the Level-1 error covariance matrix was allowed to vary across participants, some relatively large differences in autocorrelation estimates and error variance estimates emerged. The changes in modeling the variance structure did not change the conclusions about which fixed effects were statistically significant in most of the studies, but there was one exception. The fit indices did not consistently support selecting either the more complex covariance structure, which allowed the covariance parameters to vary across participants, or the simpler covariance structure. Given the uncertainty in model specification that may arise when modeling single-case data, researchers should consider conducting sensitivity analyses to examine the degree to which their conclusions are sensitive to modeling choices.

  11. Understanding and estimating the power to detect cross-level interaction effects in multilevel modeling.

    Science.gov (United States)

    Mathieu, John E; Aguinis, Herman; Culpepper, Steven A; Chen, Gilad

    2012-09-01

    Cross-level interaction effects lie at the heart of multilevel contingency and interactionism theories. Researchers have often lamented the difficulty of finding hypothesized cross-level interactions, and to date there has been no means by which the statistical power of such tests can be evaluated. We develop such a method and report results of a large-scale simulation study, verify its accuracy, and provide evidence regarding the relative importance of factors that affect the power to detect cross-level interactions. Our results indicate that the statistical power to detect cross-level interactions is determined primarily by the magnitude of the cross-level interaction, the standard deviation of lower level slopes, and the lower and upper level sample sizes. We provide a Monte Carlo tool that enables researchers to a priori design more efficient multilevel studies and provides a means by which they can better interpret potential explanations for nonsignificant results. We conclude with recommendations for how scholars might design future multilevel studies that will lead to more accurate inferences regarding the presence of cross-level interactions.

  12. Information Governance: A Model for Security in Medical Practice

    Directory of Open Access Journals (Sweden)

    Patricia A.H. Williams

    2007-03-01

    Full Text Available Information governance is becoming an important aspect of organisational accountability. In consideration that information is an integral asset of most organisations, the protection of this asset will increasingly rely on organisational capabilities in security.  In the medical arena this information is primarily sensitive patient-based information. Previous research has shown that application of security measures is a low priority for primary care medical practice and that awareness of the risks are seriously underestimated. Consequently, information security governance will be a key issue for medical practice in the future. Information security governance is a relatively new term and there is little existing research into how to meet governance requirements. The limited research that exists describes information security governance frameworks at a strategic level. However, since medical practice is already lagging in the implementation of appropriate security, such definition may not be practical although it is obviously desirable. This paper describes an on-going action research project undertaken in the area of medical information security, and presents a tactical approach model aimed at addressing information security governance and the protection of medical data. 

  13. A Scheme of Certificateless Multilevel Proxy Digital Signature in Electronic Commerce

    Directory of Open Access Journals (Sweden)

    Hui Zhang

    2013-11-01

    Full Text Available Under a completely open network, in order to ensure the security of communication, an effective scheme of certificateless multilevel proxy signature is designed by using bilinear pairings. Under the strongest security model, the scheme provides an formal safety certificate. The safety of the scheme is based on the difficulty in solving the Diffie-Hellman question. The scheme raised by this thesis possesses security characters: it is verifiable, undeniable, discernible and preventive from signature abuse. The multilevel proxy signature scheme also has the merit of flexibility and it is traceable to the backward as well as extensible to the forward. On account of its merits of security, high efficiency and flexibility, it can be extensively applied in electronic commerce, mobile agent system and so on.

  14. Doubly-Latent Models of School Contextual Effects: Integrating Multilevel and Structural Equation Approaches to Control Measurement and Sampling Error.

    Science.gov (United States)

    Marsh, Herbert W; Lüdtke, Oliver; Robitzsch, Alexander; Trautwein, Ulrich; Asparouhov, Tihomir; Muthén, Bengt; Nagengast, Benjamin

    2009-11-30

    This article is a methodological-substantive synergy. Methodologically, we demonstrate latent-variable contextual models that integrate structural equation models (with multiple indicators) and multilevel models. These models simultaneously control for and unconfound measurement error due to sampling of items at the individual (L1) and group (L2) levels and sampling error due the sampling of persons in the aggregation of L1 characteristics to form L2 constructs. We consider a set of models that are latent or manifest in relation to sampling items (measurement error) and sampling of persons (sampling error) and discuss when different models might be most useful. We demonstrate the flexibility of these 4 core models by extending them to include random slopes, latent (single-level or cross-level) interactions, and latent quadratic effects. Substantively we use these models to test the big-fish-little-pond effect (BFLPE), showing that individual student levels of academic self-concept (L1-ASC) are positively associated with individual level achievement (L1-ACH) and negatively associated with school-average achievement (L2-ACH)-a finding with important policy implications for the way schools are structured. Extending tests of the BFLPE in new directions, we show that the nonlinear effects of the L1-ACH (a latent quadratic effect) and the interaction between gender and L1-ACH (an L1 × L1 latent interaction) are not significant. Although random-slope models show no significant school-to-school variation in relations between L1-ACH and L1-ASC, the negative effects of L2-ACH (the BFLPE) do vary somewhat with individual L1-ACH. We conclude with implications for diverse applications of the set of latent contextual models, including recommendations about their implementation, effect size estimates (and confidence intervals) appropriate to multilevel models, and directions for further research in contextual effect analysis.

  15. Architecting Secure Web Services using Model Driven Agile Modeling

    Directory of Open Access Journals (Sweden)

    Dr.B.Padmaja Rani,

    2010-09-01

    Full Text Available The importance of the software security has been profound, since most attacks to software systems are based on vulnerabilities caused by poorly designed and developed software. Design flaws account for fifty percent of security problems and risk analysis plays essential role in solid security problems. Service Web Services are an integral part of next generation Web applications. The development and use of these services is growing at an incredible rate, and so too security issues surrounding them. If the history of inter-application communication repeats itself, the ease with which web services architectures publish information about applications across thenetwork is only going to result in more application hacking. At the very least, it’s going to put an even greater burden on web architects and developers to design and write secure code. Developing specification like WS-Security should be leveraged as secure maturity happens over firewalls. In this paper, we want to discuss security architectures design patterns for Service Oriented Web Services. Finally, we validated this by implementing a case study of a Service Oriented Web Services application StockTrader Security using WS-Security and WS-Secure Conversation.

  16. POLICE OFFICE MODEL IMPROVEMENT FOR SECURITY OF SWARM ROBOTIC SYSTEMS

    Directory of Open Access Journals (Sweden)

    I. A. Zikratov

    2014-09-01

    Full Text Available This paper focuses on aspects of information security for group of mobile robotic systems with swarm intellect. The ways for hidden attacks realization by the opposing party on swarm algorithm are discussed. We have fulfilled numerical modeling of potentially destructive information influence on the ant shortest path algorithm. We have demonstrated the consequences of attacks on the ant algorithm with different concentration in a swarm of subversive robots. Approaches are suggested for information security mechanisms in swarm robotic systems, based on the principles of centralized security management for mobile agents. We have developed the method of forming a self-organizing information security management system for robotic agents in swarm groups implementing POM (Police Office Model – a security model based on police offices, to provide information security in multi-agent systems. The method is based on the usage of police station network in the graph nodes, which have functions of identification and authentication of agents, identifying subversive robots by both their formal characteristics and their behavior in the swarm. We have suggested a list of software and hardware components for police stations, consisting of: communication channels between the robots in police office, nodes register, a database of robotic agents, a database of encryption and decryption module. We have suggested the variants of logic for the mechanism of information security in swarm systems with different temporary diagrams of data communication between police stations. We present comparative analysis of implementation of protected swarm systems depending on the functioning logic of police offices, integrated in swarm system. It is shown that the security model saves the ability to operate in noisy environments, when the duration of the interference is comparable to the time necessary for the agent to overcome the path between police stations.

  17. Optimizing ZigBee Security using Stochastic Model Checking

    OpenAIRE

    Yuksel, Ender; Nielson, Hanne Riis; Nielson, Flemming; Fruth, Matthias; Kwiatkowska, Marta

    2012-01-01

    ZigBee is a fairly new but promising wireless sensor network standard that offers the advantages of simple and low resource communication. Nevertheless, security is of great concern to ZigBee, and enhancements are prescribed in the latest ZigBee specication: ZigBee-2007. In this technical report, we identify an important gap in the specification on key updates, and present a methodology for determining optimal key update policies and security parameters. We exploit the stochastic model checki...

  18. A global multilevel atmospheric model using a vector semi-Lagrangian finite-difference scheme. I - Adiabatic formulation

    Science.gov (United States)

    Bates, J. R.; Moorthi, S.; Higgins, R. W.

    1993-01-01

    An adiabatic global multilevel primitive equation model using a two time-level, semi-Lagrangian semi-implicit finite-difference integration scheme is presented. A Lorenz grid is used for vertical discretization and a C grid for the horizontal discretization. The momentum equation is discretized in vector form, thus avoiding problems near the poles. The 3D model equations are reduced by a linear transformation to a set of 2D elliptic equations, whose solution is found by means of an efficient direct solver. The model (with minimal physics) is integrated for 10 days starting from an initialized state derived from real data. A resolution of 16 levels in the vertical is used, with various horizontal resolutions. The model is found to be stable and efficient, and to give realistic output fields. Integrations with time steps of 10 min, 30 min, and 1 h are compared, and the differences are found to be acceptable.

  19. Modelling operations and security of cloud systems using Z-notation and Chinese Wall security policy

    Science.gov (United States)

    Basu, Srijita; Sengupta, Anirban; Mazumdar, Chandan

    2016-11-01

    Enterprises are increasingly using cloud computing for hosting their applications. Availability of fast Internet and cheap bandwidth are causing greater number of people to use cloud-based services. This has the advantage of lower cost and minimum maintenance. However, ensuring security of user data and proper management of cloud infrastructure remain major areas of concern. Existing techniques are either too complex, or fail to properly represent the actual cloud scenario. This article presents a formal cloud model using the constructs of Z-notation. Principles of the Chinese Wall security policy have been applied to design secure cloud-specific operations. The proposed methodology will enable users to safely host their services, as well as process sensitive data, on cloud.

  20. An Integrative Behavioral Model of Information Security Policy Compliance

    Directory of Open Access Journals (Sweden)

    Sang Hoon Kim

    2014-01-01

    Full Text Available The authors found the behavioral factors that influence the organization members’ compliance with the information security policy in organizations on the basis of neutralization theory, Theory of planned behavior, and protection motivation theory. Depending on the theory of planned behavior, members’ attitudes towards compliance, as well as normative belief and self-efficacy, were believed to determine the intention to comply with the information security policy. Neutralization theory, a prominent theory in criminology, could be expected to provide the explanation for information system security policy violations. Based on the protection motivation theory, it was inferred that the expected efficacy could have an impact on intentions of compliance. By the above logical reasoning, the integrative behavioral model and eight hypotheses could be derived. Data were collected by conducting a survey; 194 out of 207 questionnaires were available. The test of the causal model was conducted by PLS. The reliability, validity, and model fit were found to be statistically significant. The results of the hypotheses tests showed that seven of the eight hypotheses were acceptable. The theoretical implications of this study are as follows: (1 the study is expected to play a role of the baseline for future research about organization members’ compliance with the information security policy, (2 the study attempted an interdisciplinary approach by combining psychology and information system security research, and (3 the study suggested concrete operational definitions of influencing factors for information security policy compliance through a comprehensive theoretical review. Also, the study has some practical implications. First, it can provide the guideline to support the successful execution of the strategic establishment for the implement of information system security policies in organizations. Second, it proves that the need of education and training

  1. An integrative behavioral model of information security policy compliance.

    Science.gov (United States)

    Kim, Sang Hoon; Yang, Kyung Hoon; Park, Sunyoung

    2014-01-01

    The authors found the behavioral factors that influence the organization members' compliance with the information security policy in organizations on the basis of neutralization theory, Theory of planned behavior, and protection motivation theory. Depending on the theory of planned behavior, members' attitudes towards compliance, as well as normative belief and self-efficacy, were believed to determine the intention to comply with the information security policy. Neutralization theory, a prominent theory in criminology, could be expected to provide the explanation for information system security policy violations. Based on the protection motivation theory, it was inferred that the expected efficacy could have an impact on intentions of compliance. By the above logical reasoning, the integrative behavioral model and eight hypotheses could be derived. Data were collected by conducting a survey; 194 out of 207 questionnaires were available. The test of the causal model was conducted by PLS. The reliability, validity, and model fit were found to be statistically significant. The results of the hypotheses tests showed that seven of the eight hypotheses were acceptable. The theoretical implications of this study are as follows: (1) the study is expected to play a role of the baseline for future research about organization members' compliance with the information security policy, (2) the study attempted an interdisciplinary approach by combining psychology and information system security research, and (3) the study suggested concrete operational definitions of influencing factors for information security policy compliance through a comprehensive theoretical review. Also, the study has some practical implications. First, it can provide the guideline to support the successful execution of the strategic establishment for the implement of information system security policies in organizations. Second, it proves that the need of education and training programs suppressing

  2. A Layered Decision Model for Cost-Effective System Security

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Huaqiang; Alves-Foss, James; Soule, Terry; Pforsich, Hugh; Zhang, Du; Frincke, Deborah A.

    2008-10-01

    System security involves decisions in at least three areas: identification of well-defined security policies, selection of cost-effective defence strategies, and implementation of real-time defence tactics. Although choices made in each of these areas affect the others, existing decision models typically handle these three decision areas in isolation. There is no comprehensive tool that can integrate them to provide a single efficient model for safeguarding a network. In addition, there is no clear way to determine which particular combinations of defence decisions result in cost-effective solutions. To address these problems, this paper introduces a Layered Decision Model (LDM) for use in deciding how to address defence decisions based on their cost-effectiveness. To validate the LDM and illustrate how it is used, we used simulation to test model rationality and applied the LDM to the design of system security for an e-commercial business case.

  3. A Role- Based PMI Security Model for E- Government

    Institute of Scientific and Technical Information of China (English)

    WU Li-jun; SU Kai-le; YANG Zhi-hua

    2005-01-01

    We introduce the general AC( attribute certificate ), the role specification AC and the role assignment AC.We discuss the role-based PMI (Privilege Management Infrastructure) architecture. The role-based PMI(Public-Key Infrastructure) secure model for E-government is researched by combining the role-based PMI with PKI architecture (Public Key Infrastructure). The model has advantages of flexibility,convenience, less storage space and less network consumption etc. We are going to use the secure model in the E-government system.

  4. International Conference on Computational Intelligence, Cyber Security, and Computational Models

    CERN Document Server

    Ramasamy, Vijayalakshmi; Sheen, Shina; Veeramani, C; Bonato, Anthony; Batten, Lynn

    2016-01-01

    This book aims at promoting high-quality research by researchers and practitioners from academia and industry at the International Conference on Computational Intelligence, Cyber Security, and Computational Models ICC3 2015 organized by PSG College of Technology, Coimbatore, India during December 17 – 19, 2015. This book enriches with innovations in broad areas of research like computational modeling, computational intelligence and cyber security. These emerging inter disciplinary research areas have helped to solve multifaceted problems and gained lot of attention in recent years. This encompasses theory and applications, to provide design, analysis and modeling of the aforementioned key areas.

  5. Explaining Differences in Subjective Well-Being Across 33 Nations Using Multilevel Models: Universal Personality, Cultural Relativity, and National Income.

    Science.gov (United States)

    Cheng, Cecilia; Cheung, Mike W-L; Montasem, Alex

    2016-02-01

    This multinational study simultaneously tested three prominent hypotheses--universal disposition, cultural relativity, and livability--that explained differences in subjective well-being across nations. We performed multilevel structural equation modeling to examine the hypothesized relationships at both individual and cultural levels in 33 nations. Participants were 6,753 university students (2,215 men; 4,403 women; 135 did not specify), and the average age of the entire sample was 20.97 years (SD = 2.39). Both individual- and cultural-level analyses supported the universal disposition and cultural relativity hypotheses by revealing significant associations of subjective well-being with Extraversion, Neuroticism, and independent self-construal. In addition, interdependent self-construal was positively related to life satisfaction at the individual level only, whereas aggregated negative affect was positively linked with aggregate levels of Extraversion and interdependent self-construal at the cultural level only. Consistent with the livability hypothesis, gross national income (GNI) was related to aggregate levels of negative affect and life satisfaction. There was also a quadratic relationship between GNI and aggregated positive affect. Our findings reveal that universal disposition, cultural self-construal, and national income can elucidate differences in subjective well-being, but the multilevel analyses advance the literature by yielding new findings that cannot be identified in studies using individual-level analyses alone. © 2014 Wiley Periodicals, Inc.

  6. An intruder model for verifying liveness in security protocols

    NARCIS (Netherlands)

    Cederquist, J.G.; Dashti, Muhammad Torabi

    2006-01-01

    We present a process algebraic intruder model for verifying a class of liveness properties of security protocols. For this class, the proposed intruder model is proved to be equivalent to a Dolev-Yao intruder that does not delay indefinitely the delivery of messages. In order to prove the equivalenc

  7. Multilevel growth curve models that incorporate a random coefficient model for the level 1 variance function.

    Science.gov (United States)

    Goldstein, Harvey; Leckie, George; Charlton, Christopher; Tilling, Kate; Browne, William J

    2017-01-01

    Aim To present a flexible model for repeated measures longitudinal growth data within individuals that allows trends over time to incorporate individual-specific random effects. These may reflect the timing of growth events and characterise within-individual variability which can be modelled as a function of age. Subjects and methods A Bayesian model is developed that includes random effects for the mean growth function, an individual age-alignment random effect and random effects for the within-individual variance function. This model is applied to data on boys' heights from the Edinburgh longitudinal growth study and to repeated weight measurements of a sample of pregnant women in the Avon Longitudinal Study of Parents and Children cohort. Results The mean age at which the growth curves for individual boys are aligned is 11.4 years, corresponding to the mean 'take off' age for pubertal growth. The within-individual variance (standard deviation) is found to decrease from 0.24 cm(2) (0.50 cm) at 9 years for the 'average' boy to 0.07 cm(2) (0.25 cm) at 16 years. Change in weight during pregnancy can be characterised by regression splines with random effects that include a large woman-specific random effect for the within-individual variation, which is also correlated with overall weight and weight gain. Conclusions The proposed model provides a useful extension to existing approaches, allowing considerable flexibility in describing within- and between-individual differences in growth patterns.

  8. Re-designing the PhEDEx security model

    CERN Document Server

    Wildish, Anthony

    2013-01-01

    PhEDEx. the data-placement tool used by the CMS experiment at the LHC, was conceived in a more trusting time. The security model was designed to provide a safe working environment for site agents and operators, but provided little more protection than that. CMS data was not sufficiently protected against accidental loss caused by operator error or software bugs or from loss of data caused by deliberate manipulation of the database. Operations staff were given high levels of access to the database, beyond what should have been needed to accomplish their tasks. This exposed them to the risk of suspicion should an incident occur. Multiple implementations of the security model led to difficulties maintaining code, which can lead to degredation of security over time.In order to meet the simultaneous goals of protecting CMS data, protecting the operators from undue exposure to risk, increasing monitoring capabilities and improving maintainability of the security model, the PhEDEx security model was redesigned and r...

  9. A secured e-tendering modeling using misuse case approach

    Science.gov (United States)

    Mohd, Haslina; Robie, Muhammad Afdhal Muhammad; Baharom, Fauziah; Darus, Norida Muhd; Saip, Mohamed Ali; Yasin, Azman

    2016-08-01

    Major risk factors relating to electronic transactions may lead to destructive impacts on trust and transparency in the process of tendering. Currently, electronic tendering (e-tendering) systems still remain uncertain in issues relating to legal and security compliance and most importantly it has an unclear security framework. Particularly, the available systems are lacking in addressing integrity, confidentiality, authentication, and non-repudiation in e-tendering requirements. Thus, one of the challenges in developing an e-tendering system is to ensure the system requirements include the function for secured and trusted environment. Therefore, this paper aims to model a secured e-tendering system using misuse case approach. The modeling process begins with identifying the e-tendering process, which is based on the Australian Standard Code of Tendering (AS 4120-1994). It is followed by identifying security threats and their countermeasure. Then, the e-tendering was modelled using misuse case approach. The model can contribute to e-tendering developers and also to other researchers or experts in the e-tendering domain.

  10. 一种多层次的云平台安全解决方案%A multi-level cloud platform security solution

    Institute of Scientific and Technical Information of China (English)

    董振江; 王雪; 胡洁; 华宇

    2013-01-01

    This solution is divided into several levels, which are container-level security, virtual machine-level security, network-level security. This paper focuses on solutions for PaaS Cloud platform, and makes the analysis of three aspects, which are the application security inside of the container, the container's own security, the intrusion prevention security outside of the container.%论述了云平台的整体安全解决方案.该方案分为应用级别安全、容器级别安全、网络级别安全等层次.着重阐述了针对PaaS云平台的解决方案,从容器内部应用安全、容器自身安全、容器外部的入侵防御安全三个方面做出了分析.

  11. The use of multilevel models to evaluate sources of variation in reproductive performance in dairy cattle in Reunion Island

    DEFF Research Database (Denmark)

    Dohoo, I.R.; Tillard, E.; Stryhn, H.;

    2001-01-01

    Sources of variation in measures of reproductive performance in dairy cattle were evaluated using data collected from 3207 lactations in 1570 cows in 50 herds from five geographic regions of Reunion Island (located off the cast coast of Madagascar). Three continuously distributed reproductive...... parameters (intervals from calving-to-conception, calving-to-first-service and first-service-to-conception) were considered, along with one Binomial outcome (first-service-conception risk). Multilevel models which take into account the hierarchical nature of the data were used to fit all models......-Cox-transformed data suggested that minor departures from the assumption of normality did not have a substantial effect on the variance estimates. For the Binomial dependent variable, five different estimation procedures (penalised quasi-likelihood, Markov-Chain Monte Carlo, parametric and non-parametric bootstrap...

  12. An empirical study of statistical properties of variance partition coefficients for multi-level logistic regression models

    Science.gov (United States)

    Li, J.; Gray, B.R.; Bates, D.M.

    2008-01-01

    Partitioning the variance of a response by design levels is challenging for binomial and other discrete outcomes. Goldstein (2003) proposed four definitions for variance partitioning coefficients (VPC) under a two-level logistic regression model. In this study, we explicitly derived formulae for multi-level logistic regression model and subsequently studied the distributional properties of the calculated VPCs. Using simulations and a vegetation dataset, we demonstrated associations between different VPC definitions, the importance of methods for estimating VPCs (by comparing VPC obtained using Laplace and penalized quasilikehood methods), and bivariate dependence between VPCs calculated at different levels. Such an empirical study lends an immediate support to wider applications of VPC in scientific data analysis.

  13. Model Checking Electronic Commerce Security Protocols Based on CTL

    Institute of Scientific and Technical Information of China (English)

    XIAO De-qin; ZHANG Huan-guo

    2005-01-01

    We present a model based on Computational Temporal Logic (CTL) methods for verifying security requirements of electronic commerce protocols. The model describes formally the authentication, confidentiality integrity,non-repudiation, denial of service and access control of the electronic commerce protocols. We illustrate as case study a variant of the Lu-Smolka protocol proposed by Lu-Smolka.Moreover, we have discovered two attacks that allow a dishonest user to purchase a good debiting the amount to another user. And also, we compared our work with relative research works and found that the formal way of this paper is more general to specify security protocols for E-Commerce.

  14. Using a Prediction Model to Manage Cyber Security Threats

    Directory of Open Access Journals (Sweden)

    Venkatesh Jaganathan

    2015-01-01

    Full Text Available Cyber-attacks are an important issue faced by all organizations. Securing information systems is critical. Organizations should be able to understand the ecosystem and predict attacks. Predicting attacks quantitatively should be part of risk management. The cost impact due to worms, viruses, or other malicious software is significant. This paper proposes a mathematical model to predict the impact of an attack based on significant factors that influence cyber security. This model also considers the environmental information required. It is generalized and can be customized to the needs of the individual organization.

  15. Using a Prediction Model to Manage Cyber Security Threats.

    Science.gov (United States)

    Jaganathan, Venkatesh; Cherurveettil, Priyesh; Muthu Sivashanmugam, Premapriya

    2015-01-01

    Cyber-attacks are an important issue faced by all organizations. Securing information systems is critical. Organizations should be able to understand the ecosystem and predict attacks. Predicting attacks quantitatively should be part of risk management. The cost impact due to worms, viruses, or other malicious software is significant. This paper proposes a mathematical model to predict the impact of an attack based on significant factors that influence cyber security. This model also considers the environmental information required. It is generalized and can be customized to the needs of the individual organization.

  16. Security

    Science.gov (United States)

    Technology & Learning, 2008

    2008-01-01

    Anytime, anywhere, learning provides opportunities to create digital learning environments for new teaching styles and personalized learning. As part of making sure the program is effective, the safety and security of students and assets are essential--and mandated by law. The Children's Internet Protection Act (CIPA) addresses Internet content…

  17. Adaptable Authentication Model - for Exploring the Weaker Notions of Security

    DEFF Research Database (Denmark)

    Ahmed, Naveed; Jensen, Christian D.

    . The approach considers correct protocols, i.e., protocols that achieve their objectives when there exist no effective attacker. All correct protocols are assumed to be secure and the challenge we pose for a security analyst is to derive the least strongest attacker (LSA) model for which the, so...... of communication security. One potent argument often presented is we keep designing new protocols due the demand of new type of applications and due to the discovery of flaws in existing protocols. While designing new protocols for new type of applications, such as RFID, is definitely an important driving factor...... operational environment. In past, this often caused increasing the power of attacker model, for instance, now a days we also consider privacy concerns and side channel leakage beside the classic Dolev-Yao attacker. A protocol is labeled as insecure protocol once an effective attack or flaw is found in it...

  18. Portfolio Selection Model with Derivative Securities

    Institute of Scientific and Technical Information of China (English)

    王春峰; 杨建林; 蒋祥林

    2003-01-01

    Traditional portfolio theory assumes that the return rate of portfolio follows normality. However, this assumption is not true when derivative assets are incorporated. In this paper a portfolio selection model is developed based on utility function which can capture asymmetries in random variable distributions. Other realistic conditions are also considered, such as liabilities and integer decision variables. Since the resulting model is a complex mixed-integer nonlinear programming problem, simulated annealing algorithm is applied for its solution. A numerical example is given and sensitivity analysis is conducted for the model.

  19. Teacher-child relationships and academic achievement: a multilevel propensity score model approach.

    Science.gov (United States)

    McCormick, Meghan P; O'Connor, Erin E; Cappella, Elise; McClowry, Sandee G

    2013-10-01

    A robust body of research finds positive cross-sectional and longitudinal associations between teacher-child relationships and children's academic achievement in elementary school. Estimating the causal effect of teacher-child relationships on children's academic achievement, however, is challenged by selection bias at the individual and school level. To address these issues, we used two multilevel propensity score matching approaches to estimate the effect of high-quality teacher-child relationships in kindergarten on math and reading achievement during children's transition to first grade. Multi-informant data were collected on 324 low-income, Black and Hispanic students, and 112 kindergarten and first-grade teachers. Results revealed significant effects of high-quality teacher-child relationships in kindergarten on math achievement in first grade. No significant effects of teacher-child relationships were detected for reading achievement. Implications for intervention development and public policy are discussed.

  20. Study of risk factors affecting both hypertension and obesity outcome by using multivariate multilevel logistic regression models

    Directory of Open Access Journals (Sweden)

    Sepedeh Gholizadeh

    2016-07-01

    Full Text Available Background:Obesity and hypertension are the most important non-communicable diseases thatin many studies, the prevalence and their risk factors have been performedin each geographic region univariately.Study of factors affecting both obesity and hypertension may have an important role which to be adrressed in this study. Materials &Methods:This cross-sectional study was conducted on 1000 men aged 20-70 living in Bushehr province. Blood pressure was measured three times and the average of them was considered as one of the response variables. Hypertension was defined as systolic blood pressure ≥140 (and-or diastolic blood pressure ≥90 and obesity was defined as body mass index ≥25. Data was analyzed by using multilevel, multivariate logistic regression model by MlwiNsoftware. Results:Intra class correlations in cluster level obtained 33% for high blood pressure and 37% for obesity, so two level model was fitted to data. The prevalence of obesity and hypertension obtained 43.6% (0.95%CI; 40.6-46.5, 29.4% (0.95%CI; 26.6-32.1 respectively. Age, gender, smoking, hyperlipidemia, diabetes, fruit and vegetable consumption and physical activity were the factors affecting blood pressure (p≤0.05. Age, gender, hyperlipidemia, diabetes, fruit and vegetable consumption, physical activity and place of residence are effective on obesity (p≤0.05. Conclusion: The multilevel models with considering levels distribution provide more precise estimates. As regards obesity and hypertension are the major risk factors for cardiovascular disease, by knowing the high-risk groups we can d careful planning to prevention of non-communicable diseases and promotion of society health.

  1. Small Convenience Stores and the Local Food Environment: An Analysis of Resident Shopping Behavior Using Multilevel Modeling.

    Science.gov (United States)

    Ruff, Ryan Richard; Akhund, Ali; Adjoian, Tamar

    2016-01-01

    Local food environments can influence the diet and health of individuals through food availability, proximity to retail stores, pricing, and promotion. This study focused on how small convenience stores, known in New York City as bodegas, influence resident shopping behavior and the food environment. Using a cross-sectional design, 171 bodegas and 2118 shoppers were sampled. Small convenience stores in New York City. Any bodega shopper aged 18+ who purchased food or beverage from a participating store. Data collection consisted of a store assessment, a health and behavior survey given to exiting customers, and a bag check that recorded product information for all customer purchases. Descriptive statistics were generated for bodega store characteristics, shopper demographics, and purchase behavior. Multilevel models were used to assess the influence of product availability, placement, and advertising on consumer purchases of sugar-sweetened beverages (SSBs), water, and fruits and vegetables. Seventy-one percent of participants reported shopping at bodegas five or more times per week, and 35% reported purchasing all or most of their monthly food allotment at bodegas. Model results indicated that lower amounts of available fresh produce were significantly and independently associated with a higher likelihood of SSB purchases. A second, stratified multilevel model showed that the likelihood of purchasing an SSB increased with decreasing varieties of produce when produce was located at the front of the store. No significant effects were found for water placement and beverage advertising. Small convenience stores in New York City are an easily accessible source of foods and beverages. Bodegas may be suitable for interventions designed to improve food choice and diet.

  2. Estimation of Contextual Effects through Nonlinear Multilevel Latent Variable Modeling with a Metropolis-Hastings Robbins-Monro Algorithm. CRESST Report 833

    Science.gov (United States)

    Yang, Ji Seung; Cai, Li

    2013-01-01

    The main purpose of this study is to improve estimation efficiency in obtaining full-information maximum likelihood (FIML) estimates of contextual effects in the framework of a nonlinear multilevel latent variable model by adopting the Metropolis-Hastings Robbins-Monro algorithm (MH-RM; Cai, 2008, 2010a, 2010b). Results indicate that the MH-RM…

  3. A Primer for Analyzing Nested Data: Multilevel Modeling in SPSS Using an Example from a REL Study. REL 2015-046

    Science.gov (United States)

    O'Dwyer, Laura M.; Parker, Caroline E.

    2014-01-01

    Analyzing data that possess some form of nesting is often challenging for applied researchers or district staff who are involved in or in charge of conducting data analyses. This report provides a description of the challenges for analyzing nested data and provides a primer of how multilevel regression modeling may be used to resolve these…

  4. Multilevel modelling and time series analysis in traffic safety research : methodology. SafetyNet, Building the European Road Safety Observatory, Workpackage 7, Deliverable 7.4.

    NARCIS (Netherlands)

    Antoniou, C. Brandstaetter, C. Bergel, R. Cherfi, M. Bijleveld, F. Commandeur, J.J.F. Blois, C. de Dupont, E. Gatscha, M. Martensen, H. Papadimitriou, E. Vanlaar, W. & Yannis, G.

    2007-01-01

    This deliverable gives the theoretical background for the two families of analyses, multilevel and time series analysis. For each technique the objectives, detailed model formulation, and assumptions are described and subsequently the technique is illustrated with an empirical example relevant to

  5. Multilevel modelling and time series analysis in traffic safety research : manual. SafetyNet, Building the European Road Safety Observatory, Workpackage 7, Deliverable 7.5.

    NARCIS (Netherlands)

    Angermann, A. Antoniou, C. Bergel, R. Berends, E. Bijleveld, F. Brandstätter, C. Cherfi, M. Blois, C. de Dupont, E. Gatscha, M. Martensen, H. Papadimitriou, E. & Yannis, G.

    2007-01-01

    This deliverable contains the manual to support the methodology report in D7.4, where the theoretical background for multilevel and time series analyses is given. For each technique described in the methodology report, this manual presents the instructions to fit the models on the basis of user

  6. EMPIRICAL STUDY OF DIFFERENT FACTORS EFFECTS ON ARTICLES PUBLICATION REGARDING SURVEY INTERVIEWER CHARACTERISTICS USING MULTILEVEL REGRESSION MODEL

    Directory of Open Access Journals (Sweden)

    Alina MOROŞANU

    2013-06-01

    Full Text Available The purpose of this research work is to evaluate the effects which some factors could have on articles publication regarding survey interviewer characteristics. For this, the author studied the existing literature from the various fields in which articles on survey interviewer characteristics has been published and which can be found in online articles database. The analysis was performed on 243 articles achieved by researchers in the time period 1949-2012. Using statistical software R and applying multilevel regression model, the results showed that the time period when the studied articles are made and the interaction between the number of authors and the number of pages affect the most their publication in journals with a certain level of impact factor.

  7. Mindfulness training promotes upward spirals of positive affect and cognition: multilevel and autoregressive latent trajectory modeling analyses.

    Science.gov (United States)

    Garland, Eric L; Geschwind, Nicole; Peeters, Frenk; Wichers, Marieke

    2015-01-01

    Recent theory suggests that positive psychological processes integral to health may be energized through the self-reinforcing dynamics of an upward spiral to counter emotion dysregulation. The present study examined positive emotion-cognition interactions among individuals in partial remission from depression who had been randomly assigned to treatment with mindfulness-based cognitive therapy (MBCT; n = 64) or a waitlist control condition (n = 66). We hypothesized that MBCT stimulates upward spirals by increasing positive affect and positive cognition. Experience sampling assessed changes in affect and cognition during 6 days before and after treatment, which were analyzed with a series of multilevel and autoregressive latent trajectory models. Findings suggest that MBCT was associated with significant increases in trait positive affect and momentary positive cognition, which were preserved through autoregressive and cross-lagged effects driven by global emotional tone. Findings suggest that daily positive affect and cognition are maintained by an upward spiral that might be promoted by mindfulness training.

  8. A multilevel structural equation modeling analysis of vulnerabilities and resilience resources influencing affective adaptation to chronic pain.

    Science.gov (United States)

    Sturgeon, John A; Zautra, Alex J; Arewasikporn, Anne

    2014-02-01

    The processes of individual adaptation to chronic pain are complex and occur across multiple domains. We examined the social, cognitive, and affective context of daily pain adaptation in individuals with fibromyalgia and osteoarthritis. By using a sample of 260 women with fibromyalgia or osteoarthritis, we examined the contributions of pain catastrophizing, negative interpersonal events, and positive interpersonal events to daily negative and positive affect across 30days of daily diary data. Individual differences and daily fluctuations in predictor variables were estimated simultaneously by utilizing multilevel structural equation modeling techniques. The relationships between pain and negative and positive affect were mediated by stable and day-to-day levels of pain catastrophizing as well as day-to-day positive interpersonal events, but not negative interpersonal events. There were significant and independent contributions of pain catastrophizing and positive interpersonal events to adaptation to pain and pain-related affective dysregulation. These effects occur both between persons and within a person's everyday life.

  9. Mindfulness training promotes upward spirals of positive affect and cognition: multilevel and autoregressive latent trajectory modeling analyses

    Science.gov (United States)

    Garland, Eric L.; Geschwind, Nicole; Peeters, Frenk; Wichers, Marieke

    2015-01-01

    Recent theory suggests that positive psychological processes integral to health may be energized through the self-reinforcing dynamics of an upward spiral to counter emotion dysregulation. The present study examined positive emotion–cognition interactions among individuals in partial remission from depression who had been randomly assigned to treatment with mindfulness-based cognitive therapy (MBCT; n = 64) or a waitlist control condition (n = 66). We hypothesized that MBCT stimulates upward spirals by increasing positive affect and positive cognition. Experience sampling assessed changes in affect and cognition during 6 days before and after treatment, which were analyzed with a series of multilevel and autoregressive latent trajectory models. Findings suggest that MBCT was associated with significant increases in trait positive affect and momentary positive cognition, which were preserved through autoregressive and cross-lagged effects driven by global emotional tone. Findings suggest that daily positive affect and cognition are maintained by an upward spiral that might be promoted by mindfulness training. PMID:25698988

  10. Organizational information assets classification model and security architecture methodology

    Directory of Open Access Journals (Sweden)

    Mostafa Tamtaji

    2015-12-01

    Full Text Available Today's, Organizations are exposed with huge and diversity of information and information assets that are produced in different systems shuch as KMS, financial and accounting systems, official and industrial automation sysytems and so on and protection of these information is necessary. Cloud computing is a model for enabling ubiquitous, convenient, on-demand network access to a shared pool of configurable computing resources that can be rapidly provisioned and released.several benefits of this model cuses that organization has a great trend to implementing Cloud computing. Maintaining and management of information security is the main challenges in developing and accepting of this model. In this paper, at first, according to "design science research methodology" and compatible with "design process at information systems research", a complete categorization of organizational assets, including 355 different types of information assets in 7 groups and 3 level, is presented to managers be able to plan corresponding security controls according to importance of each groups. Then, for directing of organization to architect it’s information security in cloud computing environment, appropriate methodology is presented. Presented cloud computing security architecture , resulted proposed methodology, and presented classification model according to Delphi method and expers comments discussed and verified.

  11. Food Security Information Platform Model Based on Internet of Things

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    2015-06-01

    Full Text Available According to the tracking and tracing requirements of food supply chain management and quality and safety, this study built food security information platform using the Internet of things technology, with reference to the EPC standard, the use of RFID technology, adopting the model of SOA, based on SCOR core processes, researches the food security information platform which can set up the whole process from the source to the consumption of the traceability information, provides food information, strengthens the food identity verification, prevents food identification and information of error identification to the consumer and government food safety regulators, provides good practices for food safety traceability.

  12. A Multi-Level Approach to Modeling Rapidly Growing Mega-Regions as a Coupled Human-Natural System

    Science.gov (United States)

    Koch, J. A.; Tang, W.; Meentemeyer, R. K.

    2013-12-01

    The FUTure Urban-Regional Environment Simulation (FUTURES) integrates information on nonstationary drivers of land change (per capita land area demand, site suitability, and spatial structure of conversion events) into spatial-temporal projections of changes in landscape patterns (Meentemeyer et al., 2013). One striking feature of FUTURES is its patch-growth algorithm that includes feedback effects of former development events across several temporal and spatial scales: cell-level transition events are aggregated into patches of land change and their further growth is based on empirically derived parameters controlling its size, shape, and dispersion. Here, we augment the FUTURES modeling framework by expanding its multilevel structure and its representation of human decision making. The new modeling framework is hierarchically organized as nested subsystems including the latest theory on telecouplings in coupled human-natural systems (Liu et al., 2013). Each subsystem represents a specific level of spatial scale and embraces agents that have decision making authority at a particular level. The subsystems are characterized with regard to their spatial representation and are connected via flows of information (e.g. regulations and policies) or material (e.g. population migration). To provide a modeling framework that is applicable to a wide range of settings and geographical regions and to keep it computationally manageable, we implement a 'zooming factor' that allows to enable or disable subsystems (and hence the represented processes), based on the extent of the study region. The implementation of the FUTURES modeling framework for a specific case study follows the observational modeling approach described in Grimm et al. (2005), starting from the analysis of empirical data in order to capture the processes relevant for specific scales and to allow a rigorous calibration and validation of the model application. In this paper, we give an introduction to the basic

  13. Fast 3-D large-scale gravity and magnetic modeling using unstructured grids and an adaptive multilevel fast multipole method

    Science.gov (United States)

    Ren, Zhengyong; Tang, Jingtian; Kalscheuer, Thomas; Maurer, Hansruedi

    2017-01-01

    A novel fast and accurate algorithm is developed for large-scale 3-D gravity and magnetic modeling problems. An unstructured grid discretization is used to approximate sources with arbitrary mass and magnetization distributions. A novel adaptive multilevel fast multipole (AMFM) method is developed to reduce the modeling time. An observation octree is constructed on a set of arbitrarily distributed observation sites, while a source octree is constructed on a source tetrahedral grid. A novel characteristic is the independence between the observation octree and the source octree, which simplifies the implementation of different survey configurations such as airborne and ground surveys. Two synthetic models, a cubic model and a half-space model with mountain-valley topography, are tested. As compared to analytical solutions of gravity and magnetic signals, excellent agreements of the solutions verify the accuracy of our AMFM algorithm. Finally, our AMFM method is used to calculate the terrain effect on an airborne gravity data set for a realistic topography model represented by a triangular surface retrieved from a digital elevation model. Using 16 threads, more than 5800 billion interactions between 1,002,001 observation points and 5,839,830 tetrahedral elements are computed in 453.6 s. A traditional first-order Gaussian quadrature approach requires 3.77 days. Hence, our new AMFM algorithm not only can quickly compute the gravity and magnetic signals for complicated problems but also can substantially accelerate the solution of 3-D inversion problems.

  14. Mission Assurance Modeling and Simulation: A Cyber Security Roadmap

    Science.gov (United States)

    Gendron, Gerald; Roberts, David; Poole, Donold; Aquino, Anna

    2012-01-01

    This paper proposes a cyber security modeling and simulation roadmap to enhance mission assurance governance and establish risk reduction processes within constrained budgets. The term mission assurance stems from risk management work by Carnegie Mellon's Software Engineering Institute in the late 19905. By 2010, the Defense Information Systems Agency revised its cyber strategy and established the Program Executive Officer-Mission Assurance. This highlights a shift from simply protecting data to balancing risk and begins a necessary dialogue to establish a cyber security roadmap. The Military Operations Research Society has recommended a cyber community of practice, recognizing there are too few professionals having both cyber and analytic experience. The authors characterize the limited body of knowledge in this symbiotic relationship. This paper identifies operational and research requirements for mission assurance M&S supporting defense and homeland security. M&S techniques are needed for enterprise oversight of cyber investments, test and evaluation, policy, training, and analysis.

  15. Immune-Inspired Self-Protection Model for Securing Grid

    Directory of Open Access Journals (Sweden)

    Inderpreet Chopra

    2016-03-01

    Full Text Available —The application of human immunology in solving security problems in Grid Computing seems to be a thought-provoking research area. Grid involves large number of dynamic heterogeneous resources. Manually managing the security for such dynamic system is always fault prone. This paper presents the simple immune based model for self-protection (SIMS of grid environment from various attacks like DoS, DDoS, Probing, etc. Like human body helps to identify and respond to harmful pathogens that it doesn't recognize as “self”, in the same manner SIMS incorporates the immunological concepts and principles for safeguarding the grid from various security breaches.

  16. Activity Modelling and Comparative Evaluation of WSN MAC Security Attacks

    DEFF Research Database (Denmark)

    Pawar, Pranav M.; Nielsen, Rasmus Hjorth; Prasad, Neeli R.

    2012-01-01

    and initiate security attacks that disturb the normal functioning of the network in a severe manner. Such attacks affect the performance of the network by increasing the energy consumption, by reducing throughput and by inducing long delays. Of all existing WSN attacks, MAC layer attacks are considered....... The second aim of the paper is to simulate these attacks on hybrid MAC mechanisms, which shows the performance degradation of aWSN under the considered attacks. The modelling and implementation of the security attacks give an actual view of the network which can be useful in further investigating secure......Applications of wireless sensor networks (WSNs) are growing tremendously in the domains of habitat, tele-health, industry monitoring, vehicular networks, home automation and agriculture. This trend is a strong motivation for malicious users to increase their focus on WSNs and to develop...

  17. Settings for Physical Activity – Developing a Site-specific Physical Activity Behavior Model based on Multi-level Intervention Studies

    DEFF Research Database (Denmark)

    Troelsen, Jens; Klinker, Charlotte Demant; Breum, Lars

    Settings for Physical Activity – Developing a Site-specific Physical Activity Behavior Model based on Multi-level Intervention Studies Introduction: Ecological models of health behavior have potential as theoretical framework to comprehend the multiple levels of factors influencing physical...... activity (PA). The potential is shown by the fact that there has been a dramatic increase in application of ecological models in research and practice. One proposed core principle is that an ecological model is most powerful if the model is behavior-specific. However, based on multi-level interventions...... of the facilities. Despite the conceptual and contextual differences PA behavior is also affected by cultural and social values related to the specific site which not alone can be explained by intrapersonal, interpersonal or organizational factors. Discussion: The Ecological Model of Four Domains of Active Living...

  18. 面板研究中的多层线性模型应用述评%Commentary of Multilevel Model in Panel Study

    Institute of Scientific and Technical Information of China (English)

    郑昱; 王二平

    2011-01-01

    Panel study is one of longitudinal study. A series of theoretical and application researches by applying multilevel model have been made in panel study recently. In this article, panel study is reviewed briefly through its definition, development and data character. The method and the process of constructing the multilevel model were mainly discussed, as weell as the multilevel model's advantages over the traditional methods in dealing with panel study. The multilevel model can be divided into three types, which are linear growth model, curvilinear growth model and three levels growth model. The multilevel model were proved by some examples. This study pointed out some problems, including time variable, centering, fixed effect, random effect and sample size. In addition, development of the future panel study by applying multilevel model was pointed out, such as moderating effect, mediating effect and structural equation modeling, etc.%面板研究是纵贯面研究领域的一种重要类型,近年来,国外运用多层线性模型在面板研究领域取得了一系列理论和应用上的进展.通过时面板研究的界定,对面板研究的发展情况、数据特征进行简要介绍,在与传统统计分析方法进行比较的基础上,重点阐述多层线性模型在面板研究领域的独特优势及其一般建模方法和过程,分为线性发展模型、曲线发展模型和三层发展模型进行解读,并结合多个实例分析不同类别的多层线性模型在面板研究中的应用情况,指出现存的面板研究中多层线性模型应用需要注意的时间变量设定及中心化、固定效应和随机效应的选择及样本量等问题,同时进一步指出多层线性模型在未来面板研究领域存在的调节作用和中介作用、结构方程模型的选择应用等发展方向.

  19. Settings for Physical Activity – Developing a Site-specific Physical Activity Behavior Model based on Multi-level Intervention Studies

    DEFF Research Database (Denmark)

    Troelsen, Jens; Klinker, Charlotte Demant; Breum, Lars

    Settings for Physical Activity – Developing a Site-specific Physical Activity Behavior Model based on Multi-level Intervention Studies Introduction: Ecological models of health behavior have potential as theoretical framework to comprehend the multiple levels of factors influencing physical...... of new established outdoor facilities for PA among 12 – 85 years old citizens (N=10,434). The SPACE and the WCMC study used objective measurements of PA combined with e-surveys, the VDPA study is based on self-reported e-survey data. Results: Merging the data from the three intervention studies clarifies...... activity (PA). The potential is shown by the fact that there has been a dramatic increase in application of ecological models in research and practice. One proposed core principle is that an ecological model is most powerful if the model is behavior-specific. However, based on multi-level interventions...

  20. An integrated multi-level watershed-reservoir modeling system for examining hydrological and biogeochemical processes in small prairie watersheds.

    Science.gov (United States)

    Zhang, Hua; Huang, Guo H; Wang, Dunling; Zhang, Xiaodong; Li, Gongchen; An, Chunjiang; Cui, Zheng; Liao, Renfei; Nie, Xianghui

    2012-03-15

    Eutrophication of small prairie reservoirs presents a major challenge in water quality management and has led to a need for predictive water quality modeling. Studies are lacking in effectively integrating watershed models and reservoir models to explore nutrient dynamics and eutrophication pattern. A water quality model specific to small prairie water bodies is also desired in order to highlight key biogeochemical processes with an acceptable degree of parameterization. This study presents a Multi-level Watershed-Reservoir Modeling System (MWRMS) to simulate hydrological and biogeochemical processes in small prairie watersheds. It integrated a watershed model, a hydrodynamic model and an eutrophication model into a flexible modeling framework. It can comprehensively describe hydrological and biogeochemical processes across different spatial scales and effectively deal with the special drainage structure of small prairie watersheds. As a key component of MWRMS, a three-dimensional Willows Reservoir Eutrophication Model (WREM) is developed to addresses essential biogeochemical processes in prairie reservoirs and to generate 3D distributions of various water quality constituents; with a modest degree of parameterization, WREM is able to meet the limit of data availability that often confronts the modeling practices in small watersheds. MWRMS was applied to the Assiniboia Watershed in southern Saskatchewan, Canada. Extensive efforts of field work and lab analysis were undertaken to support model calibration and validation. MWRMS demonstrated its ability to reproduce the observed watershed water yield, reservoir water levels and temperatures, and concentrations of several water constituents. Results showed that the aquatic systems in the Assiniboia Watershed were nitrogen-limited and sediment flux played a crucial role in reservoir nutrient budget and dynamics. MWRMS can provide a broad context of decision support for water resources management and water quality

  1. Engineering-Geological Data Model - The First Step to Build National Polish Standard for Multilevel Information Management

    Science.gov (United States)

    Ryżyński, Grzegorz; Nałęcz, Tomasz

    2016-10-01

    The efficient geological data management in Poland is necessary to support multilevel decision processes for government and local authorities in case of spatial planning, mineral resources and groundwater supply and the rational use of subsurface. Vast amount of geological information gathered in the digital archives and databases of Polish Geological Survey (PGS) is a basic resource for multi-scale national subsurface management. Data integration is the key factor to allow development of GIS and web tools for decision makers, however the main barrier for efficient geological information management is the heterogeneity of data in the resources of the Polish Geological Survey. Engineering-geological database is the first PGS thematic domain applied in the whole data integration plan. The solutions developed within this area will facilitate creation of procedures and standards for multilevel data management in PGS. Twenty years of experience in delivering digital engineering-geological mapping in 1:10 000 scale and archival geotechnical reports acquisition and digitisation allowed gathering of more than 300 thousands engineering-geological boreholes database as well as set of 10 thematic spatial layers (including foundation conditions map, depth to the first groundwater level, bedrock level, geohazards). Historically, the desktop approach was the source form of the geological-engineering data storage, resulting in multiple non-correlated interbase datasets. The need for creation of domain data model emerged and an object-oriented modelling (UML) scheme has been developed. The aim of the aforementioned development was to merge all datasets in one centralised Oracle server and prepare the unified spatial data structure for efficient web presentation and applications development. The presented approach will be the milestone toward creation of the Polish national standard for engineering-geological information management. The paper presents the approach and methodology

  2. The use of multilevel modeling and the level two residual file to explore the relationship between middle years programme student performance and diploma programme student performance.

    Science.gov (United States)

    Gordon, Melissa; Bergeron, Liz

    2015-03-01

    Multilevel modeling has recently found a substantial niche in the context of educational research, although several details about the methodological application of these models have yet to be explored in an achievement data framework. This paper makes use of data provided by the International Baccalaureate (IB) in order to investigate modeling decisions and certain applications of the level two residual file in an effort to increase understanding about the way linear and logistic multilevel models function. The focus of this research is on the relationship between performances in two IB programmes: the Middle Years Programme (MYP) and the Diploma Programme (DP). The impact of predictors on the interpretation of the unconditional and conditional variance-covariance matrix as well as the reliability coefficients is discussed. Empirical findings suggest that students who perform better during MYP moderation tend to perform better on DP exams.

  3. Balancing Flexibility and Security in Europe

    DEFF Research Database (Denmark)

    Russell, Helen; Leschke, Janine; Smith, Mark

    groups of young people. Secondly, using multi-level models, we test if flexibility-security arrangements as captured by institutions such as financial supports for unemployed youth, Active Labour Market Policy (ALMP) spending, access to training and the regulation of employment moderate the effect......, there is a risk that young people tend to experience greater job insecurity – objectively and subjectively – without the benefit of income security or employment security. We focus on objective and subjective insecurity and well-being drawing on data from the work, family and well-being modules in rounds 2 (2004...

  4. Generic Model to Send Secure Alerts for Utility Companies

    Directory of Open Access Journals (Sweden)

    Perez–Díaz J.A.

    2010-04-01

    Full Text Available In some industries such as logistics services, bank services, and others, the use of automated systems that deliver critical business information anytime and anywhere play an important role in the decision making process. This paper introduces a "Generic model to send secure alerts and notifications", which operates as a middleware between enterprise data sources and its mobile users. This model uses Short Message Service (SMS as its main mobile messaging technology, however is open to use new types of messaging technologies. Our model is interoperable with existing information systems, it can store any kind of information about alerts or notifications at different levels of granularity, it offers different types of notifications (as analert when critical business problems occur,asanotificationina periodical basis or as 2 way query. Notification rules can be customized by final users according to their preferences. The model provides a security framework in the cases where information requires confidentiality, it is extensible to existing and new messaging technologies (like e–mail, MMS, etc. It is a platform, mobile operator and hardware independent. Currently, our solution is being used at the Comisión Federal de Electricidad (Mexico's utility company to deliver secure alerts related to critical events registered in the main power generation plants of our country.

  5. Scalable Adaptive Multilevel Solvers for Multiphysics Problems

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Jinchao [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mathematics

    2014-11-26

    In this project, we carried out many studies on adaptive and parallel multilevel methods for numerical modeling for various applications, including Magnetohydrodynamics (MHD) and complex fluids. We have made significant efforts and advances in adaptive multilevel methods of the multiphysics problems: multigrid methods, adaptive finite element methods, and applications.

  6. Holistic Security Model for Mobile Database in Nigeria

    Directory of Open Access Journals (Sweden)

    Fidelis C. Obodoeze

    2016-07-01

    Full Text Available Due to proliferation on the usage of mobile computing devices such as mobile phones, smart phones, Tablet PCs and Portable Digital Assistant (PDA in Nigeria and world over, it is expected that these light-weight, powerful, low-cost computing devices will pave way for data-driven applications in mobile environments. These portal mobile devices can be connected to corporate database and application servers so that application processing can take place at any time and from anywhere. This can throw up a lot of security challenges. Hackers, malicious programs and rival firms can penetrate the corporate servers through various security holes or vulnerabilities. This paper examines these security holes that can emanate from three major windows- the mobile device, the mobile network and the corporate database server and critically x-rays various solutions that can ward them off in order to protect critical data from attack, eavesdropping, disruption, destruction and modification. This paper finally proposes a holistic security model to protect corporate mobile database in Nigeria

  7. Challenges of evaluating multilevel interventions.

    Science.gov (United States)

    Nastasi, Bonnie K; Hitchcock, John

    2009-06-01

    This article uses the Comprehensive Mixed-Methods Participatory Evaluation (CMMPE; Nastasi and Hitchcock Transforming school mental health services: Population-based approaches to promoting the competency and wellness of children, Thousand Oaks, CA: Corwin Press with National Association of School Psychologists 2008; Nastasi et al. School-based mental health services: creating comprehensive and culturally specific programs. Washington, DC: American Psychological Association 2004) model as a framework for addressing the multiplicity of evaluation decisions and complex nature of questions related to program success in multilevel interventions. CMMPE defines program success in terms of acceptability, integrity, social or cultural validity, outcomes (impact), sustainability and institutionalization, thus broadening the traditional notions of program outcomes. The authors use CMMPE and an example of a community-based multilevel sexual risk prevention program with multiple outcomes to discuss challenges of evaluating multilevel interventions. The sexual risk program exemplifies what Schensul and Trickett (this issue) characterize as multilevel intervention-multilevel evaluation (M-M), with both intervention and evaluation at community, health practitioner, and patient levels. The illustration provides the context for considering several challenges related to M-M designs: feasibility of randomized controlled trials within community-based multilevel intervention; acceptability and social or cultural validity of evaluation procedures; implementer, recipient, and contextual variations in program success; interactions among levels of the intervention; unanticipated changes or conditions; multiple indicators of program success; engaging multiple stakeholders in a participatory process; and evaluating sustainability and institutionalization. The complexity of multilevel intervention and evaluation designs challenges traditional notions of evaluation research and experimental

  8. Presenting a Bi-objective Integrated Model for Production-Distribution Problem in a Multi-level Supply Chain Network

    Directory of Open Access Journals (Sweden)

    Abolfazl Kazemi

    2015-02-01

    Full Text Available In this study, a bi-objective model for integrated planning of production-distribution in a multi-level supply chain network with multiple product types and multi time periods is presented. The supply chain network including manufacturers, distribution centers, retailers and final customers is proposed. The proposed model minimizes the total supply chain costs and transforming time of products for customers in the chain. The proposed model is in the class of linear integer programming problems. The complexity of the problem is large and in the literatur, this problem has been shown to be NP-hard. Therefore, for solving this problem, two multi objective meta-heuristic approaches based on Pareto method including non-dominated Sorting Genetic Algorithm-II (NSGA-II and non-dominated Ranking Genetic Algorithm (NRGA have been suggested. Since the output of meta- heuristic algorithms are highly dependent on the input parameters of the algorithm, Taguchi method (Taguchi is used to tune the parameters. Finally, in order to evaluate the performance of the proposed solution methods, different test problems with different dimensions have been produced and the performances of the proposed algorithms on the test problems have been analyzed.

  9. Testing the effects of safety climate and disruptive children behavior on school bus drivers performance: A multilevel model.

    Science.gov (United States)

    Zohar, Dov; Lee, Jin

    2016-10-01

    The study was designed to test a multilevel path model whose variables exert opposing effects on school bus drivers' performance. Whereas departmental safety climate was expected to improve driving safety, the opposite was true for in-vehicle disruptive children behavior. The driving safety path in this model consists of increasing risk-taking practices starting with safety shortcuts leading to rule violations and to near-miss events. The study used a sample of 474 school bus drivers in rural areas, driving children to school and school-related activities. Newly developed scales for measuring predictor, mediator and outcome variables were validated with video data taken from inner and outer cameras, which were installed in 29 buses. Results partially supported the model by indicating that group-level safety climate and individual-level children distraction exerted opposite effects on the driving safety path. Furthermore, as hypothesized, children disruption moderated the strength of the safety rule violation-near miss relationship, resulting in greater strength under high disruptiveness. At the same time, the hypothesized interaction between the two predictor variables was not supported. Theoretical and practical implications for studying safety climate in general and distracted driving in particular for professional drivers are discussed. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Fitting and Calibrating a Multilevel Mixed-Effects Stem Taper Model for Maritime Pine in NW Spain

    Science.gov (United States)

    Arias-Rodil, Manuel; Castedo-Dorado, Fernando; Cámara-Obregón, Asunción; Diéguez-Aranda, Ulises

    2015-01-01

    Stem taper data are usually hierarchical (several measurements per tree, and several trees per plot), making application of a multilevel mixed-effects modelling approach essential. However, correlation between trees in the same plot/stand has often been ignored in previous studies. Fitting and calibration of a variable-exponent stem taper function were conducted using data from 420 trees felled in even-aged maritime pine (Pinus pinaster Ait.) stands in NW Spain. In the fitting step, the tree level explained much more variability than the plot level, and therefore calibration at plot level was omitted. Several stem heights were evaluated for measurement of the additional diameter needed for calibration at tree level. Calibration with an additional diameter measured at between 40 and 60% of total tree height showed the greatest improvement in volume and diameter predictions. If additional diameter measurement is not available, the fixed-effects model fitted by the ordinary least squares technique should be used. Finally, we also evaluated how the expansion of parameters with random effects affects the stem taper prediction, as we consider this a key question when applying the mixed-effects modelling approach to taper equations. The results showed that correlation between random effects should be taken into account when assessing the influence of random effects in stem taper prediction. PMID:26630156

  11. Modelling aluminium leaching into food from different foodware materials with multi-level factorial design of experiments.

    Science.gov (United States)

    Fekete, Veronika; Deconinck, Eric; Bolle, Fabien; Van Loco, Joris

    2012-08-01

    To estimate the contribution of aluminium (Al) leaching from different materials used for food preparation and serving to the dietary Al intake, Al release from foodware typically used in everyday life was investigated using multilevel factorial design (MFD) of experiments. For Al characterisation, sample preparation and an analytical method using inductively coupled plasma atomic emission spectroscopy was developed and validated. Parameter influence (temperature: x₁, contact time: x₂, pH: x₃, salt concentration: x₄, viscosity: x₅), was evaluated with analysis of variance suggesting that the influence of viscosity is not significant compared to the other four studied parameters. Therefore, predictive, exponential quadratic regression models were established with x₁-x₄. Cross-validation and a set of independent experiments in real food products were used to test the prediction force of the different models. They both suggest that the quality of the models established for Al foil, Al plate and ceramic ware is satisfactory, but less good for glassware and stainless steel. Indeed, in the studied conditions, leaching from these latter food wares was often close to or even below the limit of quantification suggesting that the principal sources of Al intake from food contact materials during food processing are utensils made of Al and ceramic ware.

  12. 76 FR 10528 - Special Conditions: Gulfstream Model GVI Airplane; Electronic Systems Security Isolation or...

    Science.gov (United States)

    2011-02-25

    ... airplane models. This may allow the exploitation of network security vulnerabilities and increase ] risks... Federal Aviation Administration 14 CFR Part 25 Special Conditions: Gulfstream Model GVI Airplane; Electronic Systems Security Isolation or Protection From Unauthorized Passenger Systems Access AGENCY...

  13. 76 FR 36861 - Special Conditions: Gulfstream Model GVI Airplane; Electronic Systems Security Isolation or...

    Science.gov (United States)

    2011-06-23

    ... airplane models. This may allow the exploitation of network security vulnerabilities and increase risks... Federal Aviation Administration 14 CFR Part 25 Special Conditions: Gulfstream Model GVI Airplane; Electronic Systems Security Isolation or Protection From Unauthorized Passenger Systems Access AGENCY...

  14. Creation of a Homeland Security Jail Information Model

    Science.gov (United States)

    2012-03-01

    In contrast, law enforcement officers at a jail have a better gestalt understanding of homeland security threats and trends in the same...and my personal familiarity with each model. In his book Beyond the Two Disciplines of Scientific Psychology , Lee Cronbach claims that...muhajir.background/index.html Cronbach, L. J. (1975). Beyond the two disciplines of scientific psychology . Washington, D.C.: American Psychologist

  15. Physical security and vulnerability modeling for infrasturcture facilities.

    Energy Technology Data Exchange (ETDEWEB)

    Nozick, Linda Karen; Jones, Dean A.; Davis, Chad Edward; Turnquist, Mark Alan

    2006-07-01

    A model of malicious intrusions in infrastructure facilities is developed, using a network representation of the system structure together with Markov models of intruder progress and strategy. This structure provides an explicit mechanism to estimate the probability of successful breaches of physical security, and to evaluate potential improvements. Simulation is used to analyze varying levels of imperfect information on the part of the intruders in planning their attacks. An example of an intruder attempting to place an explosive device on an airplane at an airport gate illustrates the structure and potential application of the model.

  16. DOE/DHS INDUSTRIAL CONTROL SYSTEM CYBER SECURITY PROGRAMS: A MODEL FOR USE IN NUCLEAR FACILITY SAFEGUARDS AND SECURITY

    Energy Technology Data Exchange (ETDEWEB)

    Robert S. Anderson; Mark Schanfein; Trond Bjornard; Paul Moskowitz

    2011-07-01

    Many critical infrastructure sectors have been investigating cyber security issues for several years especially with the help of two primary government programs. The U.S. Department of Energy (DOE) National SCADA Test Bed and the U.S. Department of Homeland Security (DHS) Control Systems Security Program have both implemented activities aimed at securing the industrial control systems that operate the North American electric grid along with several other critical infrastructure sectors (ICS). These programs have spent the last seven years working with industry including asset owners, educational institutions, standards and regulating bodies, and control system vendors. The programs common mission is to provide outreach, identification of cyber vulnerabilities to ICS and mitigation strategies to enhance security postures. The success of these programs indicates that a similar approach can be successfully translated into other sectors including nuclear operations, safeguards, and security. The industry regulating bodies have included cyber security requirements and in some cases, have incorporated sets of standards with penalties for non-compliance such as the North American Electric Reliability Corporation Critical Infrastructure Protection standards. These DOE and DHS programs that address security improvements by both suppliers and end users provide an excellent model for nuclear facility personnel concerned with safeguards and security cyber vulnerabilities and countermeasures. It is not a stretch to imagine complete surreptitious collapse of protection against the removal of nuclear material or even initiation of a criticality event as witnessed at Three Mile Island or Chernobyl in a nuclear ICS inadequately protected against the cyber threat.

  17. Application distribution model and related security attacks in VANET

    Science.gov (United States)

    Nikaein, Navid; Kanti Datta, Soumya; Marecar, Irshad; Bonnet, Christian

    2013-03-01

    In this paper, we present a model for application distribution and related security attacks in dense vehicular ad hoc networks (VANET) and sparse VANET which forms a delay tolerant network (DTN). We study the vulnerabilities of VANET to evaluate the attack scenarios and introduce a new attacker`s model as an extension to the work done in [6]. Then a VANET model has been proposed that supports the application distribution through proxy app stores on top of mobile platforms installed in vehicles. The steps of application distribution have been studied in detail. We have identified key attacks (e.g. malware, spamming and phishing, software attack and threat to location privacy) for dense VANET and two attack scenarios for sparse VANET. It has been shown that attacks can be launched by distributing malicious applications and injecting malicious codes to On Board Unit (OBU) by exploiting OBU software security holes. Consequences of such security attacks have been described. Finally, countermeasures including the concepts of sandbox have also been presented in depth.

  18. Multi-level modeling of light-induced stomatal opening offers new insights into its regulation by drought.

    Science.gov (United States)

    Sun, Zhongyao; Jin, Xiaofen; Albert, Réka; Assmann, Sarah M

    2014-11-01

    Plant guard cells gate CO2 uptake and transpirational water loss through stomatal pores. As a result of decades of experimental investigation, there is an abundance of information on the involvement of specific proteins and secondary messengers in the regulation of stomatal movements and on the pairwise relationships between guard cell components. We constructed a multi-level dynamic model of guard cell signal transduction during light-induced stomatal opening and of the effect of the plant hormone abscisic acid (ABA) on this process. The model integrates into a coherent network the direct and indirect biological evidence regarding the regulation of seventy components implicated in stomatal opening. Analysis of this signal transduction network identified robust cross-talk between blue light and ABA, in which [Ca2+]c plays a key role, and indicated an absence of cross-talk between red light and ABA. The dynamic model captured more than 10(31) distinct states for the system and yielded outcomes that were in qualitative agreement with a wide variety of previous experimental results. We obtained novel model predictions by simulating single component knockout phenotypes. We found that under white light or blue light, over 60%, and under red light, over 90% of all simulated knockouts had similar opening responses as wild type, showing that the system is robust against single node loss. The model revealed an open question concerning the effect of ABA on red light-induced stomatal opening. We experimentally showed that ABA is able to inhibit red light-induced stomatal opening, and our model offers possible hypotheses for the underlying mechanism, which point to potential future experiments. Our modelling methodology combines simplicity and flexibility with dynamic richness, making it well suited for a wide class of biological regulatory systems.

  19. Modeling, simulation and analysis of a securities settlement system: the case of Central Securities Depository of Mexico

    Directory of Open Access Journals (Sweden)

    David F. Muñoz

    2012-12-01

    Full Text Available The Instituto para el Depósito de Valores (INDEVAL is the Central Securities Depository of Mexico. It is the only Mexican institution authorized to perform, in an integrated manner, the activities of safe-keeping, custody, management, clearing, settlement and transfer of securities. In this article, we report the modeling, simulation and analysis of a new Securities Settlement System (SSS implemented by INDEVAL, as part of a project for the implementation of a safer and more efficient operating system. The main objective of this research was to use reduced amounts of cash and securities, within reasonable periods of time, for the settlement of securities of the Mexican market. A linear programming model for the netting and clearing of operations was used. The performance of the new SSS was evaluated by performing experiments using a deterministic simulation model under different operation parameters, such as the number and monetary value of transactions, the time between clearing cycles and also under a new set of rules for pre-settlement operations. The results presented may be used by other Central Securities Depositories to make decisions related to the efficient and safer use of their resources. The implementation of the model took more than three years. Now many transactions that would remain pending if processed individually are settled together, thus reducing liquidity requirements dramatically -by 52% in cash and 26% in securities.

  20. A convenient method and numerical tables for sample size determination in longitudinal-experimental research using multilevel models.

    Science.gov (United States)

    Usami, Satoshi

    2014-12-01

    Recent years have shown increased awareness of the importance of sample size determination in experimental research. Yet effective and convenient methods for sample size determination, especially in longitudinal experimental design, are still under development, and application of power analysis in applied research remains limited. This article presents a convenient method for sample size determination in longitudinal experimental research using a multilevel model. A fundamental idea of this method is transformation of model parameters (level 1 error variance [σ(2)], level 2 error variances [τ 00, τ 11] and its covariance [τ 01, τ 10], and a parameter representing experimental effect [δ]) into indices (reliability of measurement at the first time point [ρ 1], effect size at the last time point [Δ T ], proportion of variance of outcomes between the first and the last time points [k], and level 2 error correlation [r]) that are intuitively understandable and easily specified. To foster more convenient use of power analysis, numerical tables are constructed that refer to ANOVA results to investigate the influence on statistical power by respective indices.

  1. The Model of Higher School Students’ Research Competence in Multilevel Training (Taking as the Example the Mathematical Disciplines Studies

    Directory of Open Access Journals (Sweden)

    S. N. Lukashenko

    2015-01-01

    Full Text Available The paper is devoted to developing the research competence in the process of student multilevel training. Upgrading the student’s ability for research ac- tivity is an important task of higher education that should be continually emphasized at all levels. The author suggests the model developing the research competence in the context of mathematical disciplines studies at bachelor level of different educational profiles: mathematical, natural sciences, vocational. The model in question represents the hierarchical tree of goals based on the principals of expansion, subordination and correlative importance – all of them reflecting the links between the goals and the edu- cational levels ( bachelor or master level - which facilitates the plan systematization for achieving the main goal of students’ research competence development. The essential content, criteria, indices and development levels of the compe- tence in question are defined. The given approach provides the continuity in mastering the competencies at different levels in a sequential advancing from the theoretical to practical knowledge and makes it possible to avoid the formal approach to teaching the undergraduates. 

  2. The Model of Higher School Students’ Research Competence in Multilevel Training (Taking as the Example the Mathematical Disciplines Studies

    Directory of Open Access Journals (Sweden)

    S. N. Lukashenko

    2012-01-01

    Full Text Available The paper is devoted to developing the research competence in the process of student multilevel training. Upgrading the student’s ability for research ac- tivity is an important task of higher education that should be continually emphasized at all levels. The author suggests the model developing the research competence in the context of mathematical disciplines studies at bachelor level of different educational profiles: mathematical, natural sciences, vocational. The model in question represents the hierarchical tree of goals based on the principals of expansion, subordination and correlative importance – all of them reflecting the links between the goals and the edu- cational levels ( bachelor or master level - which facilitates the plan systematization for achieving the main goal of students’ research competence development. The essential content, criteria, indices and development levels of the compe- tence in question are defined. The given approach provides the continuity in mastering the competencies at different levels in a sequential advancing from the theoretical to practical knowledge and makes it possible to avoid the formal approach to teaching the undergraduates. 

  3. Socioeconomic deprivation and hospital length of stay: a new approach using area-based socioeconomic indicators in multilevel models.

    Science.gov (United States)

    Coevoet, Vincent; Fresson, Jeanne; Vieux, Rachel; Jay, Nicolas

    2013-06-01

    Socioeconomic deprivation is not easily measurable in hospital information systems. However, its identification is essential, as it is associated with morbidity and hospital length of stay (LOS). We aimed at studying the feasibility of using routinely recorded individual and area-based socioeconomic indicators, and assessing their relation with LOS. In a cross-sectional study we collected area-based socioeconomic deprivation indicators from French census databases and individual ones from the 2009 medical and administrative databases of a French referral maternity hospital. The principal outcome was the LOS for delivery. Individual level socioeconomic deprivation indicators included preferential insurance scheme (health insurance allocated to poor persons). Nine area-based socioeconomic deprivation indicators were aggregated at the census tract and commune levels. The relation between socioeconomic deprivation and LOS was studied using multilevel models. The well-documented relation between socioeconomic deprivation and preterm delivery was firstly studied in these models as a validation step. The linkage between aggregated and individual data was possible for the 3471 women included. The median LOS was 5 days. In multivariable analysis adjusted for age (P=0.02), twinning (P=0.0001), delivery mode (Punemployment rate (P=0.002) were associated with an increased LOS. Identifying deprived patients in hospital databases using routinely collected area-based indicators is feasible. The relation of these latter with LOS is consistent with previous studies. Further multicenter investigations are needed to confirm the interest of using such indicators for cost and morbidity predictions.

  4. Future consumer mobile phone security: a case study using the data centric security model

    NARCIS (Netherlands)

    Cleeff, van Andre

    2008-01-01

    In the interconnected world that we live in, traditional security barriers are broken down. Developments such as outsourcing, increased usage of mobile devices and wireless networks each cause new security problems. To address the new security threats, a number of solutions have been suggested, most

  5. USign--a security enhanced electronic consent model.

    Science.gov (United States)

    Li, Yanyan; Xie, Mengjun; Bian, Jiang

    2014-01-01

    Electronic consent becomes increasingly popular in the healthcare sector given the many benefits it provides. However, security concerns, e.g., how to verify the identity of a person who is remotely accessing the electronic consent system in a secure and user-friendly manner, also arise along with the popularity of electronic consent. Unfortunately, existing electronic consent systems do not pay sufficient attention to those issues. They mainly rely on conventional password based authentication to verify the identity of an electronic consent user, which is far from being sufficient given that identity theft threat is real and significant in reality. In this paper, we present a security enhanced electronic consent model called USign. USign enhances the identity protection and authentication for electronic consent systems by leveraging handwritten signatures everyone is familiar with and mobile computing technologies that are becoming ubiquitous. We developed a prototype of USign and conducted preliminary evaluation on accuracy and usability of signature verification. Our experimental results show the feasibility of the proposed model.

  6. Privacy Enhanced Pervasive Computing Model with Dynamic Trust and Security

    Directory of Open Access Journals (Sweden)

    Geetha Mariappan

    2014-06-01

    Full Text Available The objective of the research work is to propose a policy aware privacy enhancement model using dynamic trust and security management techniques. The different polices of the stakeholders incorporating device manufacturer, service provider, Mobile agents and mobile users are considered to achieve an enhanced privacy for on-demand request. The entities involving direct and indirect trust establishment with all forms of uncertainties like DDoS attacks are considered along with multiple layers of security management operations across varying trusted entities. The focus is to enhance the existing privacy through an efficient, preventive, detective, response mechanisms for those attacks, which will address the problem of DDoS before, during and after an actual attack. The session time and access time are controlled by the privileges and rights for disclosure of information in pervasive environment.

  7. Multi-level, multi-actor model of local economic development

    NARCIS (Netherlands)

    Pennink, Barteld

    2015-01-01

    On this website a model for LED is created. The model is supported and worked out with the help of about 70 (May 2015) realized master theses projects. Each thesis is in Pdf format available and related to the model.

  8. Multi-level, multi-actor model of local economic development

    NARCIS (Netherlands)

    Pennink, Barteld

    2014-01-01

    On this website a model for LED is created. The model is supported and worked out with the help of about 70 (May 2015) realized master theses projects. Each thesis is in Pdf format available and related to the model.

  9. A General Multilevel SEM Framework for Assessing Multilevel Mediation

    Science.gov (United States)

    Preacher, Kristopher J.; Zyphur, Michael J.; Zhang, Zhen

    2010-01-01

    Several methods for testing mediation hypotheses with 2-level nested data have been proposed by researchers using a multilevel modeling (MLM) paradigm. However, these MLM approaches do not accommodate mediation pathways with Level-2 outcomes and may produce conflated estimates of between- and within-level components of indirect effects. Moreover,…

  10. The 2003 ISMS Practice Prize Winner: Optimizing Rhenania's Direct Marketing Business Through Dynamic Multilevel Modeling (DMLM) in a Multicatalog-Brand Environment

    OpenAIRE

    Ralf Elsner; Manfred Krafft; Arnd Huchzermeier

    2004-01-01

    We introduce Dynamic Multilevel Modeling (DMLM) to a multicatalog-brand environment to determine the optimal frequency, size, and customer segmentation of direct marketing activities. This optimization method leverages multicatalog-brand effects including the utilization of prior customer ordering behavior, maximization of customer value and customer share, and economies of scale and scope in printing and mailing. This enhancement of the original DMLM-approach is called Dynamic Multidimension...

  11. Student Assessment of Teaching as a Source of Information about Aspects of Teaching Quality in Multiple Subject Domains: An Application of Multilevel Bifactor Structural Equation Modeling

    OpenAIRE

    Ronny eScherer; Jan-Eric eGustafsson

    2015-01-01

    Research on educational effectiveness most often uses student assessments of classroom instruction for measuring aspects of teaching quality. Given that crucial inferences on the success of education are based on these assessments, it is essential to ensure that they provide valid indicators. In this study, we illustrate the application of an innovative application of a multilevel bifactor structural equation model (ML-BFSEM) to examine the validity of student assessments. Analyzing a large-s...

  12. Student assessment of teaching as a source of information about aspects of teaching quality in multiple subject domains: an application of multilevel bifactor structural equation modeling

    OpenAIRE

    Scherer, Ronny; Gustafsson, Jan-Eric

    2015-01-01

    Research on educational effectiveness most often uses student assessments of classroom instruction for measuring aspects of teaching quality. Given that crucial inferences on the success of education are based on these assessments, it is essential to ensure that they provide valid indicators. In this study, we illustrate the application of an innovative application of a multilevel bifactor structural equation model (ML-BFSEM) to examine the validity of student assessments. Analyzing a large-s...

  13. GAMA: multi-level and complex environment for agent-based models and simulations (demonstration)

    OpenAIRE

    Drogoul, Alexis; Amouroux, Edouard; Caillou, Philippe; Gaudou, Benoit; Grignard, Arnaud; Marilleau, Nicolas; Taillandier, Patrick; Vavaseur, Maroussia; Vo, Duc-An; Zucker, Jean-Daniel

    2013-01-01

    International audience; Agent-based models are now used in numerous application domains (ecology, social sciences, etc.) but their use is still impeded by the lack of generic yet ready-to-use tools sup- porting the design and the simulation of complex models in- tegrating multiple level of agency and realistic environments. The GAMA modeling and simulation platform is proposed to address such issues. It allows modelers to build com- plex models thanks to high-level modeling language, various ...

  14. Alternative Methods for Assessing Mediation in Multilevel Data: The Advantages of Multilevel SEM

    Science.gov (United States)

    Preacher, Kristopher J.; Zhang, Zhen; Zyphur, Michael J.

    2011-01-01

    Multilevel modeling (MLM) is a popular way of assessing mediation effects with clustered data. Two important limitations of this approach have been identified in prior research and a theoretical rationale has been provided for why multilevel structural equation modeling (MSEM) should be preferred. However, to date, no empirical evidence of MSEM's…

  15. Resilience to leaking--dynamic systems modeling of information security.

    Science.gov (United States)

    Hamacher, Kay

    2012-01-01

    Leaking of confidential material is a major threat to information security within organizations and to society as a whole. This insight has gained traction in the political realm since the activities of Wikileaks, which hopes to attack 'unjust' systems or 'conspiracies'. Eventually, such threats to information security rely on a biologistic argument on the benefits and drawbacks that uncontrolled leaking might pose for 'just' and 'unjust' entities. Such biological metaphors are almost exclusively based on the economic advantage of participants. Here, I introduce a mathematical model of the complex dynamics implied by leaking. The complex interactions of adversaries are modeled by coupled logistic equations including network effects of econo-communication networks. The modeling shows, that there might arise situations where the leaking envisioned and encouraged by Wikileaks and the like can strengthen the defending entity (the 'conspiracy'). In particular, the only severe impact leaking can have on an organization seems to originate in the exploitation of leaks by another entity the organization competes with. Therefore, the model suggests that leaks can be used as a `tactical mean' in direct adversary relations, but do not necessarily increase public benefit and societal immunization to 'conspiracies'. Furthermore, within the model the exploitation of the (open) competition between entities seems to be a more promising approach to control malicious organizations : divide-et-impera policies triumph here.

  16. Resilience to Leaking — Dynamic Systems Modeling of Information Security

    Science.gov (United States)

    Hamacher, Kay

    2012-01-01

    Leaking of confidential material is a major threat to information security within organizations and to society as a whole. This insight has gained traction in the political realm since the activities of Wikileaks, which hopes to attack ‘unjust’ systems or ‘conspiracies’. Eventually, such threats to information security rely on a biologistic argument on the benefits and drawbacks that uncontrolled leaking might pose for ‘just’ and ‘unjust’ entities. Such biological metaphors are almost exclusively based on the economic advantage of participants. Here, I introduce a mathematical model of the complex dynamics implied by leaking. The complex interactions of adversaries are modeled by coupled logistic equations including network effects of econo-communication networks. The modeling shows, that there might arise situations where the leaking envisioned and encouraged by Wikileaks and the like can strengthen the defending entity (the ‘conspiracy’). In particular, the only severe impact leaking can have on an organization seems to originate in the exploitation of leaks by another entity the organization competes with. Therefore, the model suggests that leaks can be used as a `tactical mean’ in direct adversary relations, but do not necessarily increase public benefit and societal immunization to ‘conspiracies’. Furthermore, within the model the exploitation of the (open) competition between entities seems to be a more promising approach to control malicious organizations : divide-et-impera policies triumph here. PMID:23227151

  17. Resilience to leaking--dynamic systems modeling of information security.

    Directory of Open Access Journals (Sweden)

    Kay Hamacher

    Full Text Available Leaking of confidential material is a major threat to information security within organizations and to society as a whole. This insight has gained traction in the political realm since the activities of Wikileaks, which hopes to attack 'unjust' systems or 'conspiracies'. Eventually, such threats to information security rely on a biologistic argument on the benefits and drawbacks that uncontrolled leaking might pose for 'just' and 'unjust' entities. Such biological metaphors are almost exclusively based on the economic advantage of participants. Here, I introduce a mathematical model of the complex dynamics implied by leaking. The complex interactions of adversaries are modeled by coupled logistic equations including network effects of econo-communication networks. The modeling shows, that there might arise situations where the leaking envisioned and encouraged by Wikileaks and the like can strengthen the defending entity (the 'conspiracy'. In particular, the only severe impact leaking can have on an organization seems to originate in the exploitation of leaks by another entity the organization competes with. Therefore, the model suggests that leaks can be used as a `tactical mean' in direct adversary relations, but do not necessarily increase public benefit and societal immunization to 'conspiracies'. Furthermore, within the model the exploitation of the (open competition between entities seems to be a more promising approach to control malicious organizations : divide-et-impera policies triumph here.

  18. Egocentric Network and Condom Use Among Mid-Age Female Sex Workers in China: A Multilevel Modeling Analysis.

    Science.gov (United States)

    Liu, Hongjie

    2016-04-01

    The epidemics of sexually transmitted infections (STIs) have spread among older adults in the world, including China. This study addresses the deficiency of studies about the multiple contextual influences on condom use among mid-age female sex workers (FSWs) over 35 years old. A combination of an egocentric network design and multilevel modeling was used to investigate factors of condom use over mid-age FSWs (egos) particular relationships with sexual partners (alters). Of the 1245 mid-age FSWs interviewed, 73% (907) reported having at least one sexual partner who would provide social support to egos. This generated a total of 1300 ego-alter sex ties in egos' support networks. Condoms were consistently used among one-third of sex ties. At the ego level, condoms were more likely to be used consistently if egos received a middle school education or above, had stronger perceived behavioral control for condom use, or consistently used condoms with other sex clients who were not in their support networks. At the alter level, condoms were not consistently used over spousal ties compared to other ties. Condoms were less likely to be used among alters whom ego trusted and provided emotional support. Cross-level factors (egos' attitudes toward condom use and emotional support from alters) documented a significant positive interaction on consistent condom use. Given the low frequency of condom use, future interventions should focus on mid-age FSWs and their partners within and beyond their support networks.

  19. Mindfulness Training Promotes Upward Spirals of Positive Affect and Cognition: Multilevel and Autoregressive Latent Trajectory Modeling Analysis

    Directory of Open Access Journals (Sweden)

    Eric L Garland

    2015-02-01

    Full Text Available Recent theory suggests that positive psychological processes integral to health may be energized through the self-reinforcing dynamics of an upward spiral to counter emotion dysregulation. The present study examined positive emotion-cognition interactions among individuals in partial remission from depression who had been randomly assigned to treatment with mindfulness-based cognitive therapy (MBCT; n = 64 or a wait-list control condition (n = 66. We hypothesized that MBCT stimulates upward spirals by increasing positive affect and positive cognition. Experience sampling assessed changes in affect and cognition during 6 days before and after treatment, which were analyzed with a series of multilevel and autoregressive latent trajectory models. Findings suggest that MBCT was associated with significant increases in trait positive affect and momentary positive cognition, which were preserved through autoregressive and cross-lagged effects driven by global emotional tone. Findings suggest that daily positive affect and cognition are maintained by an upward spiral that might be promoted by mindfulness training.

  20. Nurses' practice environment and work-family conflict in relation to burn out: a multilevel modelling approach.

    Directory of Open Access Journals (Sweden)

    Constanze Leineweber

    Full Text Available OBJECTIVES: To investigate associations between nurse work practice environment measured at department level and individual level work-family conflict on burnout, measured as emotional exhaustion, depersonalization and personal accomplishment among Swedish RNs. METHODS: A multilevel model was fit with the individual RN at the 1st, and the hospital department at the 2nd level using cross-sectional RN survey data from the Swedish part of RN4CAST, an EU 7th framework project. The data analysed here is based on a national sample of 8,620 RNs from 369 departments in 53 hospitals. RESULTS: Generally, RNs reported high values of personal accomplishment and lower values of emotional exhaustion and depersonalization. High work-family conflict increased the risk for emotional exhaustion, but for neither depersonalization nor personal accomplishment. On department level adequate staffing and good leadership and support for nurses reduced the risk for emotional exhaustion and depersonalization. Personal accomplishment was statistically significantly related to staff adequacy. CONCLUSIONS: The findings suggest that adequate staffing, good leadership, and support for nurses are crucial for RNs' mental health. Our findings also highlight the importance of hospital managers developing policies and practices to facilitate the successful combination of work with private life for employees.