Science.gov

Sample records for access control layer

  1. ISDC Data Access Layer

    NASA Astrophysics Data System (ADS)

    Jennings, D.; Borkowski, J.; Contessi, T.; Lock, T.; Rohlfs, R.; Walter, R.

    The ISDC Data Access Layer (DAL) is an ANSI C and \\fortran 90 compatible library under development in support of the ESA INTEGRAL mission data analysis software. DALs primary purpose is to isolate the analysis software from the specifics of the data formats while at the same time providing new data abstraction and access capabilities. DAL supports the creation and manipulation of hierarchical data sets which may span multiple files and, in theory, multiple computer systems. A number of Application Programming Interfaces (APIs) are supported by DAL that allow software to view and access data at different levels of complexity. DAL also allows data sets to reside on disk, in conventional memory or in shared memory in a way that is transparent to the user/application.

  2. A Brief Survey of Media Access Control, Data Link Layer, and Protocol Technologies for Lunar Surface Communications

    NASA Technical Reports Server (NTRS)

    Wallett, Thomas M.

    2009-01-01

    This paper surveys and describes some of the existing media access control and data link layer technologies for possible application in lunar surface communications and the advanced wideband Direct Sequence Code Division Multiple Access (DSCDMA) conceptual systems utilizing phased-array technology that will evolve in the next decade. Time Domain Multiple Access (TDMA) and Code Division Multiple Access (CDMA) are standard Media Access Control (MAC) techniques that can be incorporated into lunar surface communications architectures. Another novel hybrid technique that is recently being developed for use with smart antenna technology combines the advantages of CDMA with those of TDMA. The relatively new and sundry wireless LAN data link layer protocols that are continually under development offer distinct advantages for lunar surface applications over the legacy protocols which are not wireless. Also several communication transport and routing protocols can be chosen with characteristics commensurate with smart antenna systems to provide spacecraft communications for links exhibiting high capacity on the surface of the Moon. The proper choices depend on the specific communication requirements.

  3. Reflective Database Access Control

    ERIC Educational Resources Information Center

    Olson, Lars E.

    2009-01-01

    "Reflective Database Access Control" (RDBAC) is a model in which a database privilege is expressed as a database query itself, rather than as a static privilege contained in an access control list. RDBAC aids the management of database access controls by improving the expressiveness of policies. However, such policies introduce new interactions…

  4. Energy Efficient Medium Access Control Protocol for Clustered Wireless Sensor Networks with Adaptive Cross-Layer Scheduling

    PubMed Central

    Sefuba, Maria; Walingo, Tom; Takawira, Fambirai

    2015-01-01

    This paper presents an Energy Efficient Medium Access Control (MAC) protocol for clustered wireless sensor networks that aims to improve energy efficiency and delay performance. The proposed protocol employs an adaptive cross-layer intra-cluster scheduling and an inter-cluster relay selection diversity. The scheduling is based on available data packets and remaining energy level of the source node (SN). This helps to minimize idle listening on nodes without data to transmit as well as reducing control packet overhead. The relay selection diversity is carried out between clusters, by the cluster head (CH), and the base station (BS). The diversity helps to improve network reliability and prolong the network lifetime. Relay selection is determined based on the communication distance, the remaining energy and the channel quality indicator (CQI) for the relay cluster head (RCH). An analytical framework for energy consumption and transmission delay for the proposed MAC protocol is presented in this work. The performance of the proposed MAC protocol is evaluated based on transmission delay, energy consumption, and network lifetime. The results obtained indicate that the proposed MAC protocol provides improved performance than traditional cluster based MAC protocols. PMID:26393608

  5. Energy Efficient Medium Access Control Protocol for Clustered Wireless Sensor Networks with Adaptive Cross-Layer Scheduling.

    PubMed

    Sefuba, Maria; Walingo, Tom; Takawira, Fambirai

    2015-09-18

    This paper presents an Energy Efficient Medium Access Control (MAC) protocol for clustered wireless sensor networks that aims to improve energy efficiency and delay performance. The proposed protocol employs an adaptive cross-layer intra-cluster scheduling and an inter-cluster relay selection diversity. The scheduling is based on available data packets and remaining energy level of the source node (SN). This helps to minimize idle listening on nodes without data to transmit as well as reducing control packet overhead. The relay selection diversity is carried out between clusters, by the cluster head (CH), and the base station (BS). The diversity helps to improve network reliability and prolong the network lifetime. Relay selection is determined based on the communication distance, the remaining energy and the channel quality indicator (CQI) for the relay cluster head (RCH). An analytical framework for energy consumption and transmission delay for the proposed MAC protocol is presented in this work. The performance of the proposed MAC protocol is evaluated based on transmission delay, energy consumption, and network lifetime. The results obtained indicate that the proposed MAC protocol provides improved performance than traditional cluster based MAC protocols.

  6. ACCESS Pointing Control System

    NASA Technical Reports Server (NTRS)

    Brugarolas, Paul; Alexander, James; Trauger, John; Moody, Dwight; Egerman, Robert; Vallone, Phillip; Elias, Jason; Hejal, Reem; Camelo, Vanessa; Bronowicki, Allen; O'Connor, David; Partrick, Richard; Orzechowski, Pawel; Spitter, Connie; Lillie, Chuck

    2010-01-01

    ACCESS (Actively-Corrected Coronograph for Exoplanet System Studies) was one of four medium-class exoplanet concepts selected for the NASA Astrophysics Strategic Mission Concept Study (ASMCS) program in 2008/2009. The ACCESS study evaluated four major coronograph concepts under a common space observatory. This paper describes the high precision pointing control system (PCS) baselined for this observatory.

  7. CAS. Controlled Access Security

    SciTech Connect

    Martinez, B.; Pomeroy, G.

    1989-12-01

    The Security Alarm System is a data acquisition and control system which collects data from intrusion sensors and displays the information in a real-time environment for operators. The Access Control System monitors and controls the movement of personnel with the use of card readers and biometrics hand readers.

  8. Apparatus and method supporting wireless access to multiple security layers in an industrial control and automation system or other system

    SciTech Connect

    Chen, Yu-Gene T.

    2013-04-16

    A method includes receiving a message at a first wireless node. The first wireless node is associated with a first wired network, and the first wired network is associated with a first security layer. The method also includes transmitting the message over the first wired network when at least one destination of the message is located in the first security layer. The method further includes wirelessly transmitting the message for delivery to a second wireless node when at least one destination of the message is located in a second security layer. The second wireless node is associated with a second wired network, and the second wired network is associated with the second security layer. The first and second security layers may be associated with different security paradigms and/or different security domains. Also, the message could be associated with destinations in the first and second security layers.

  9. LANSCE personnel access control system

    SciTech Connect

    Sturrock, J.C.; Gallegos, F.R.; Hall, M.J.

    1997-01-01

    The Radiation Security System (RSS) at the Los Alamos Neutron Science Center (LANSCE) provides personnel protection from prompt radiation due to accelerated beam. The Personnel Access Control System (PACS) is a component of the RSS that is designed to prevent personnel access to areas where prompt radiation is a hazard. PACS was designed to replace several older personnel safety systems (PSS) with a single modem unified design. Lessons learned from the operation over the last 20 years were incorporated into a redundant sensor, single-point failure safe, fault tolerant, and tamper-resistant system that prevents access to the beam areas by controlling the access keys and beam stoppers. PACS uses a layered philosophy to the physical and electronic design. The most critical assemblies are battery backed up, relay logic circuits; less critical devices use Programmable Logic Controllers (PLCs) for timing functions and communications. Outside reviewers have reviewed the operational safety of the design. The design philosophy, lessons learned, hardware design, software design, operation, and limitations of the device are described.

  10. Mobile access control vestibule

    NASA Astrophysics Data System (ADS)

    DePoy, Jennifer M.

    1998-12-01

    The mobile access control vestibule (MACV) is an adaptation of techniques developed for mobile military command centers. The overall configuration of modules acts as an entry control/screening facility or transportable command center. The system would provide the following capabilities: (1) A key element for force protection, rapid deployment units sent to areas having no prepositioned equipment or where there has been a degradation of that equipment as a result of natural disasters or civil unrest. (2) A rapidly deployable security control center to upgrade the security at nonmilitary sites (e.g., diplomatic or humanitarian organizations). (3) Personnel screening, package screening, badge/identification card production for authorized personnel, centralized monitoring of deployed perimeter sensors, and centralized communications for law enforcement personnel. (4) Self-contained screening and threat detection systems, including explosives detection using the system developed by Sandia National Laboratories for the FAA. When coupled with transportable electric generators, the system is self-sufficient. The communication system for the MACV would be a combination of physically wired and wireless communication units that supports by ad hoc networking.

  11. Bibliographic Access and Control System.

    ERIC Educational Resources Information Center

    Kelly, Betsy; And Others

    1982-01-01

    Presents a brief summary of the functions of the Bibliographic Access & Control System (BACS) implemented at the Washington University School of Medicine Library, and outlines the design, development, and uses of the system. Bibliographic control of books and serials and user access to the system are also discussed. (Author/JL)

  12. Vapor Control Layer Recommendations

    SciTech Connect

    2009-09-08

    This information sheet describes the level of vapor control required on the interior side of framed walls with typical fibrous cavity insulation (fibreglass, rockwool, or cellulose, based on DOE climate zone of construction.

  13. Boundary Layer Control on Airfoils.

    ERIC Educational Resources Information Center

    Gerhab, George; Eastlake, Charles

    1991-01-01

    A phenomena, boundary layer control (BLC), produced when visualizing the fluidlike flow of air is described. The use of BLC in modifying aerodynamic characteristics of airfoils, race cars, and boats is discussed. (KR)

  14. Data Access Layer Interface Version 1.0

    NASA Astrophysics Data System (ADS)

    Dowler, Patrick; Demleitner, Markus; Taylor, Mark; Tody, Doug; Dowler, Patrick

    2013-11-01

    This document describes the Data Access Layer Interface (DALI). DALI defines the base web service interface common to all Data Access Layer (DAL) services. This standard defines the behaviour of common resources, the meaning and use of common parameters, success and error responses, and DAL service registration. The goal of this specification is to define the common elements that are shared across DAL services in order to foster consistency across concrete DAL service specifications and to enable standard re-usable client and service implementations and libraries to be written and widely adopted.

  15. The Application of Layer Theory to Design: The Control Layer

    ERIC Educational Resources Information Center

    Gibbons, Andrew S.; Langton, Matthew B.

    2016-01-01

    A theory of design layers proposed by Gibbons ("An Architectural Approach to Instructional Design." Routledge, New York, 2014) asserts that each layer of an instructional design is related to a body of theory closely associated with the concerns of that particular layer. This study focuses on one layer, the control layer, examining…

  16. Efficient Access Control in Multimedia Social Networks

    NASA Astrophysics Data System (ADS)

    Sachan, Amit; Emmanuel, Sabu

    Multimedia social networks (MMSNs) have provided a convenient way to share multimedia contents such as images, videos, blogs, etc. Contents shared by a person can be easily accessed by anybody else over the Internet. However, due to various privacy, security, and legal concerns people often want to selectively share the contents only with their friends, family, colleagues, etc. Access control mechanisms play an important role in this situation. With access control mechanisms one can decide the persons who can access a shared content and who cannot. But continuously growing content uploads and accesses, fine grained access control requirements (e.g. different access control parameters for different parts in a picture), and specific access control requirements for multimedia contents can make the time complexity of access control to be very large. So, it is important to study an efficient access control mechanism suitable for MMSNs. In this chapter we present an efficient bit-vector transform based access control mechanism for MMSNs. The proposed approach is also compatible with other requirements of MMSNs, such as access rights modification, content deletion, etc. Mathematical analysis and experimental results show the effectiveness and efficiency of our proposed approach.

  17. Logical Access Control Mechanisms in Computer Systems.

    ERIC Educational Resources Information Center

    Hsiao, David K.

    The subject of access control mechanisms in computer systems is concerned with effective means to protect the anonymity of private information on the one hand, and to regulate the access to shareable information on the other hand. Effective means for access control may be considered on three levels: memory, process and logical. This report is a…

  18. Common Badging and Access Control System (CBACS)

    NASA Technical Reports Server (NTRS)

    Dischinger, Portia

    2005-01-01

    This slide presentation presents NASA's Common Badging and Access Control System. NASA began a Smart Card implementation in January 2004. Following site surveys, it was determined that NASA's badging and access control systems required upgrades to common infrastructure in order to provide flexibly, usability, and return on investment prior to a smart card implantation. Common Badging and Access Control System (CBACS) provides the common infrastructure from which FIPS-201 compliant processes, systems, and credentials can be developed and used.

  19. Spatiotemporal access model based on reputation for the sensing layer of the IoT.

    PubMed

    Guo, Yunchuan; Yin, Lihua; Li, Chao; Qian, Junyan

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model.

  20. Spatiotemporal Access Model Based on Reputation for the Sensing Layer of the IoT

    PubMed Central

    Guo, Yunchuan; Yin, Lihua; Li, Chao

    2014-01-01

    Access control is a key technology in providing security in the Internet of Things (IoT). The mainstream security approach proposed for the sensing layer of the IoT concentrates only on authentication while ignoring the more general models. Unreliable communications and resource constraints make the traditional access control techniques barely meet the requirements of the sensing layer of the IoT. In this paper, we propose a model that combines space and time with reputation to control access to the information within the sensing layer of the IoT. This model is called spatiotemporal access control based on reputation (STRAC). STRAC uses a lattice-based approach to decrease the size of policy bases. To solve the problem caused by unreliable communications, we propose both nondeterministic authorizations and stochastic authorizations. To more precisely manage the reputation of nodes, we propose two new mechanisms to update the reputation of nodes. These new approaches are the authority-based update mechanism (AUM) and the election-based update mechanism (EUM). We show how the model checker UPPAAL can be used to analyze the spatiotemporal access control model of an application. Finally, we also implement a prototype system to demonstrate the efficiency of our model. PMID:25177731

  1. Boundary layer receptivity and control

    NASA Technical Reports Server (NTRS)

    Hill, D. C.

    1993-01-01

    Receptivity processes initiate natural instabilities in a boundary layer. The instabilities grow and eventually break down to turbulence. Consequently, receptivity questions are a critical element of the analysis of the transition process. Success in modeling the physics of receptivity processes thus has a direct bearing on technological issues of drag reduction. The means by which transitional flows can be controlled is also a major concern: questions of control are tied inevitably to those of receptivity. Adjoint systems provide a highly effective mathematical method for approaching many of the questions associated with both receptivity and control. The long term objective is to develop adjoint methods to handle increasingly complex receptivity questions, and to find systematic procedures for deducing effective control strategies. The most elementary receptivity problem is that in which a parallel boundary layer is forced by time-harmonic sources of various types. The characteristics of the response to such forcing form the building blocks for more complex receptivity mechanisms. The first objective of this year's research effort was to investigate how a parallel Blasius boundary layer responds to general direct forcing. Acoustic disturbances in the freestream can be scattered by flow non-uniformities to produce Tollmien-Schlichting waves. For example, scattering by surface roughness is known to provide an efficient receptivity path. The present effort is directed towards finding a solution by a simple adjoint analysis, because adjoint methods can be extended to more complex problems. In practice, flows are non-parallel and often three-dimensional. Compressibility may also be significant in some cases. Recent developments in the use of Parabolized Stability Equations (PSE) offer a promising possibility. By formulating and solving a set of adjoint parabolized equations, a method for mapping the efficiency with which external forcing excites the three

  2. 10 CFR 36.23 - Access control.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Access control. 36.23 Section 36.23 Energy NUCLEAR... activation of the control. (g) Each entrance to the radiation room of a panoramic irradiator and each... unauthorized entry when the personnel access barrier is locked. Activation of the intrusion alarm must alert...

  3. 10 CFR 36.23 - Access control.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Access control. 36.23 Section 36.23 Energy NUCLEAR... activation of the control. (g) Each entrance to the radiation room of a panoramic irradiator and each... unauthorized entry when the personnel access barrier is locked. Activation of the intrusion alarm must alert...

  4. 10 CFR 36.23 - Access control.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Access control. 36.23 Section 36.23 Energy NUCLEAR... activation of the control. (g) Each entrance to the radiation room of a panoramic irradiator and each... unauthorized entry when the personnel access barrier is locked. Activation of the intrusion alarm must alert...

  5. 10 CFR 36.23 - Access control.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Access control. 36.23 Section 36.23 Energy NUCLEAR... activation of the control. (g) Each entrance to the radiation room of a panoramic irradiator and each... unauthorized entry when the personnel access barrier is locked. Activation of the intrusion alarm must alert...

  6. 10 CFR 36.23 - Access control.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Access control. 36.23 Section 36.23 Energy NUCLEAR... activation of the control. (g) Each entrance to the radiation room of a panoramic irradiator and each... unauthorized entry when the personnel access barrier is locked. Activation of the intrusion alarm must alert...

  7. 47 CFR 95.645 - Control accessibility.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Control accessibility. 95.645 Section 95.645 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Technical Regulations Certification Requirements § 95.645 Control accessibility. (a) No...

  8. 47 CFR 95.645 - Control accessibility.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 5 2011-10-01 2011-10-01 false Control accessibility. 95.645 Section 95.645 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Technical Regulations Certification Requirements § 95.645 Control accessibility. (a) No...

  9. 47 CFR 95.645 - Control accessibility.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Control accessibility. 95.645 Section 95.645 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Technical Regulations Certification Requirements § 95.645 Control accessibility. (a) No...

  10. 47 CFR 95.645 - Control accessibility.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 5 2010-10-01 2010-10-01 false Control accessibility. 95.645 Section 95.645 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY AND SPECIAL RADIO SERVICES PERSONAL RADIO SERVICES Technical Regulations Certification Requirements § 95.645 Control accessibility. (a) No...

  11. Proximity Displays for Access Control

    ERIC Educational Resources Information Center

    Vaniea, Kami

    2012-01-01

    Managing access to shared digital information, such as photographs and documents. is difficult for end users who are accumulating an increasingly large and diverse collection of data that they want to share with others. Current policy-management solutions require a user to proactively seek out and open a separate policy-management interface when…

  12. An Accelerator Control Middle Layer Using MATLAB

    SciTech Connect

    Portmann, Gregory J.; Corbett, Jeff; Terebilo, Andrei

    2005-03-15

    Matlab is a matrix manipulation language originally developed to be a convenient language for using the LINPACK and EISPACK libraries. What makes Matlab so appealing for accelerator physics is the combination of a matrix oriented programming language, an active workspace for system variables, powerful graphics capability, built-in math libraries, and platform independence. A number of software toolboxes for accelerators have been written in Matlab--the Accelerator Toolbox (AT) for machine simulations, LOCO for accelerator calibration, Matlab Channel Access Toolbox (MCA) for EPICS connections, and the Middle Layer. This paper will describe the ''middle layer'' software toolbox that resides between the high-level control applications and the low-level accelerator control system. This software was a collaborative effort between ALS (LBNL) and SPEAR3 (SSRL) but easily ports to other machines. Five accelerators presently use this software. The high-level Middle Layer functionality includes energy ramp, configuration control (save/restore), global orbit correction, local photon beam steering, insertion device compensation, beam-based alignment, tune correction, response matrix measurement, and script-based programs for machine physics studies.

  13. An Accelerator Control Middle Layer Using MATLAB

    SciTech Connect

    Portmann, Gregory J.; Corbett, Jeff; Terebilo, Andrei

    2005-05-15

    Matlab is an interpretive programming language originally developed for convenient use with the LINPACK and EISPACK libraries. Matlab is appealing for accelerator physics because it is matrix-oriented, provides an active workspace for system variables, powerful graphics capabilities, built-in math libraries, and platform independence. A number of accelerator software toolboxes have been written in Matlab -- the Accelerator Toolbox (AT) for model-based machine simulations, LOCO for on-line model calibration, and Matlab Channel Access (MCA) to connect with EPICS. The function of the MATLAB ''MiddleLayer'' is to provide a scripting language for machine simulations and on-line control, including non-EPICS based control systems. The MiddleLayer has simplified and streamlined development of high-level applications including configuration control, energy ramp, orbit correction, photon beam steering, ID compensation, beam-based alignment, tune correction and response matrix measurement. The database-driven Middle Layer software is largely machine-independent and easy to port. Six accelerators presently use the software package with more scheduled to come on line soon.

  14. Access Control of Web and Java Based Applications

    NASA Technical Reports Server (NTRS)

    Tso, Kam S.; Pajevski, Michael J.; Johnson, Bryan

    2011-01-01

    Cyber security has gained national and international attention as a result of near continuous headlines from financial institutions, retail stores, government offices and universities reporting compromised systems and stolen data. Concerns continue to rise as threats of service interruption, and spreading of viruses become ever more prevalent and serious. Controlling access to application layer resources is a critical component in a layered security solution that includes encryption, firewalls, virtual private networks, antivirus, and intrusion detection. In this paper we discuss the development of an application-level access control solution, based on an open-source access manager augmented with custom software components, to provide protection to both Web-based and Java-based client and server applications.

  15. Access Control of Web- and Java-Based Applications

    NASA Technical Reports Server (NTRS)

    Tso, Kam S.; Pajevski, Michael J.

    2013-01-01

    Cybersecurity has become a great concern as threats of service interruption, unauthorized access, stealing and altering of information, and spreading of viruses have become more prevalent and serious. Application layer access control of applications is a critical component in the overall security solution that also includes encryption, firewalls, virtual private networks, antivirus, and intrusion detection. An access control solution, based on an open-source access manager augmented with custom software components, was developed to provide protection to both Web-based and Javabased client and server applications. The DISA Security Service (DISA-SS) provides common access control capabilities for AMMOS software applications through a set of application programming interfaces (APIs) and network- accessible security services for authentication, single sign-on, authorization checking, and authorization policy management. The OpenAM access management technology designed for Web applications can be extended to meet the needs of Java thick clients and stand alone servers that are commonly used in the JPL AMMOS environment. The DISA-SS reusable components have greatly reduced the effort for each AMMOS subsystem to develop its own access control strategy. The novelty of this work is that it leverages an open-source access management product that was designed for Webbased applications to provide access control for Java thick clients and Java standalone servers. Thick clients and standalone servers are still commonly used in businesses and government, especially for applications that require rich graphical user interfaces and high-performance visualization that cannot be met by thin clients running on Web browsers

  16. A physical layer perspective on access network sharing

    NASA Astrophysics Data System (ADS)

    Pfeiffer, Thomas

    2015-12-01

    Unlike in copper or wireless networks, there is no sharing of resources in fiber access networks yet, other than bit stream access or cable sharing, in which the fibers of a cable are let to one or multiple operators. Sharing optical resources on a single fiber among multiple operators or different services has not yet been applied. While this would allow for a better exploitation of installed infrastructures, there are operational issues which still need to be resolved, before this sharing model can be implemented in networks. Operating multiple optical systems and services over a common fiber plant, autonomously and independently from each other, can result in mutual distortions on the physical layer. These distortions will degrade the performance of the involved systems, unless precautions are taken in the infrastructure hardware to eliminate or to reduce them to an acceptable level. Moreover, the infrastructure needs to be designed such as to support different system technologies and to ensure a guaranteed quality of the end-to-end connections. In this paper, suitable means are proposed to be introduced in fiber access infrastructures that will allow for shared utilization of the fibers while safeguarding the operational needs and business interests of the involved parties.

  17. The linked medical data access control framework.

    PubMed

    Kamateri, Eleni; Kalampokis, Evangelos; Tambouris, Efthimios; Tarabanis, Konstantinos

    2014-08-01

    The integration of medical data coming from multiple sources is important in clinical research. Amongst others, it enables the discovery of appropriate subjects in patient-oriented research and the identification of innovative results in epidemiological studies. At the same time, the integration of medical data faces significant ethical and legal challenges that impose access constraints. Some of these issues can be addressed by making available aggregated instead of raw record-level data. In many cases however, there is still a need for controlling access even to the resulting aggregated data, e.g., due to data provider's policies. In this paper we present the Linked Medical Data Access Control (LiMDAC) framework that capitalizes on Linked Data technologies to enable controlling access to medical data across distributed sources with diverse access constraints. The LiMDAC framework consists of three Linked Data models, namely the LiMDAC metadata model, the LiMDAC user profile model, and the LiMDAC access policy model. It also includes an architecture that exploits these models. Based on the framework, a proof-of-concept platform is developed and its performance and functionality are evaluated by employing two usage scenarios.

  18. Network Access Control List Situation Awareness

    ERIC Educational Resources Information Center

    Reifers, Andrew

    2010-01-01

    Network security is a large and complex problem being addressed by multiple communities. Nevertheless, current theories in networking security appear to overestimate network administrators' ability to understand network access control lists (NACLs), providing few context specific user analyses. Consequently, the current research generally seems to…

  19. Speed control system for an access gate

    DOEpatents

    Bzorgi, Fariborz M [Knoxville, TN

    2012-03-20

    An access control apparatus for an access gate. The access gate typically has a rotator that is configured to rotate around a rotator axis at a first variable speed in a forward direction. The access control apparatus may include a transmission that typically has an input element that is operatively connected to the rotator. The input element is generally configured to rotate at an input speed that is proportional to the first variable speed. The transmission typically also has an output element that has an output speed that is higher than the input speed. The input element and the output element may rotate around a common transmission axis. A retardation mechanism may be employed. The retardation mechanism is typically configured to rotate around a retardation mechanism axis. Generally the retardation mechanism is operatively connected to the output element of the transmission and is configured to retard motion of the access gate in the forward direction when the first variable speed is above a control-limit speed. In many embodiments the transmission axis and the retardation mechanism axis are substantially co-axial. Some embodiments include a freewheel/catch mechanism that has an input connection that is operatively connected to the rotator. The input connection may be configured to engage an output connection when the rotator is rotated at the first variable speed in a forward direction and configured for substantially unrestricted rotation when the rotator is rotated in a reverse direction opposite the forward direction. The input element of the transmission is typically operatively connected to the output connection of the freewheel/catch mechanism.

  20. Social Network Privacy via Evolving Access Control

    NASA Astrophysics Data System (ADS)

    di Crescenzo, Giovanni; Lipton, Richard J.

    We study the problem of limiting privacy loss due to data shared in a social network, where the basic underlying assumptions are that users are interested in sharing data and cannot be assumed to constantly follow appropriate privacy policies. Note that if these two assumptions do not hold, social network privacy is theoretically very easy to achieve; for instance, via some form of access control and confidentiality transformation on the data.

  1. Common Badging and Access Control System (CBACS)

    NASA Technical Reports Server (NTRS)

    Baldridge, Tim

    2005-01-01

    The goals of the project are: Achieve high business value through a common badging and access control system that integrates with smart cards. Provide physical (versus logical) deployment of smart cards initially. Provides a common consistent and reliable environment into which to release the smart card. Gives opportunity to develop agency-wide consistent processes, practices and policies. Enables enterprise data capture and management. Promotes data validation prior to SC issuance.

  2. External access to ALICE controls conditions data

    NASA Astrophysics Data System (ADS)

    Jadlovský, J.; Jadlovská, A.; Sarnovský, J.; Jajčišin, Š.; Čopík, M.; Jadlovská, S.; Papcun, P.; Bielek, R.; Čerkala, J.; Kopčík, M.; Chochula, P.; Augustinus, A.

    2014-06-01

    ALICE Controls data produced by commercial SCADA system WINCCOA is stored in ORACLE database on the private experiment network. The SCADA system allows for basic access and processing of the historical data. More advanced analysis requires tools like ROOT and needs therefore a separate access method to the archives. The present scenario expects that detector experts create simple WINCCOA scripts, which retrieves and stores data in a form usable for further studies. This relatively simple procedure generates a lot of administrative overhead - users have to request the data, experts needed to run the script, the results have to be exported outside of the experiment network. The new mechanism profits from database replica, which is running on the CERN campus network. Access to this database is not restricted and there is no risk of generating a heavy load affecting the operation of the experiment. The developed tools presented in this paper allow for access to this data. The users can use web-based tools to generate the requests, consisting of the data identifiers and period of time of interest. The administrators maintain full control over the data - an authorization and authentication mechanism helps to assign privileges to selected users and restrict access to certain groups of data. Advanced caching mechanism allows the user to profit from the presence of already processed data sets. This feature significantly reduces the time required for debugging as the retrieval of raw data can last tens of minutes. A highly configurable client allows for information retrieval bypassing the interactive interface. This method is for example used by ALICE Offline to extract operational conditions after a run is completed. Last but not least, the software can be easily adopted to any underlying database structure and is therefore not limited to WINCCOA.

  3. Access control and confidentiality in radiology

    NASA Astrophysics Data System (ADS)

    Noumeir, Rita; Chafik, Adil

    2005-04-01

    A medical record contains a large amount of data about the patient such as height, weight and blood pressure. It also contains sensitive information such as fertility, abortion, psychiatric data, sexually transmitted diseases and diagnostic results. Access to this information must be carefully controlled. Information technology has greatly improved patient care. The recent extensive deployment of digital medical images made diagnostic images promptly available to healthcare decision makers, regardless of their geographic location. Medical images are digitally archived, transferred on telecommunication networks, and visualized on computer screens. However, with the widespread use of computing and communication technologies in healthcare, the issue of data security has become increasingly important. Most of the work until now has focused on the security of data communication to ensure its integrity, authentication, confidentiality and user accountability. The mechanisms that have been proposed to achieve the security of data communication are not specific to healthcare. Data integrity can be achieved with data signature. Data authentication can be achieved with certificate exchange. Data confidentiality can be achieved with encryption. User accountability can be achieved with audits. Although these mechanisms are essential to ensure data security during its transfer on the network, access control is needed in order to ensure data confidentiality and privacy within the information system application. In this paper, we present and discuss an access control mechanism that takes into account the notion of a care process. Radiology information is categorized and a model to enforce data privacy is proposed.

  4. Boundary-layer control for drag reduction

    NASA Technical Reports Server (NTRS)

    Harvey, William D.

    1988-01-01

    Although the number of possible applications of boundary-layer control is large, a discussion is given only of those that have received the most attention recently at NASA Langley Research Center to improve airfoil drag characteristics. This research concerns stabilizing the laminar boundary layer through geometric shaping (natural laminar flow, NLF) and active control involving the removal of a portion of the laminar boundary layer (laminar flow control, LFC) either through discrete slots or a perforated surface. At low Reynolds numbers, a combination of shaping and forced transition has been used to achieve the desired run of laminar flow and control of laminar separation. In the design of both natural laminar flow and laminar flow control airfoils and wings, boundary layer stability codes play an important role. A discussion of some recent stability calculations using both incompressible and compressible codes is given.

  5. Cyclone separator having boundary layer turbulence control

    DOEpatents

    Krishna, Coimbatore R.; Milau, Julius S.

    1985-01-01

    A cyclone separator including boundary layer turbulence control that is operable to prevent undue build-up of particulate material at selected critical areas on the separator walls, by selectively varying the fluid pressure at those areas to maintain the momentum of the vortex, thereby preventing particulate material from inducing turbulence in the boundary layer of the vortical fluid flow through the separator.

  6. A service-oriented data access control model

    NASA Astrophysics Data System (ADS)

    Meng, Wei; Li, Fengmin; Pan, Juchen; Song, Song; Bian, Jiali

    2017-01-01

    The development of mobile computing, cloud computing and distributed computing meets the growing individual service needs. Facing with complex application system, it's an urgent problem to ensure real-time, dynamic, and fine-grained data access control. By analyzing common data access control models, on the basis of mandatory access control model, the paper proposes a service-oriented access control model. By regarding system services as subject and data of databases as object, the model defines access levels and access identification of subject and object, and ensures system services securely to access databases.

  7. Cardea: Dynamic Access Control in Distributed Systems

    NASA Technical Reports Server (NTRS)

    Lepro, Rebekah

    2004-01-01

    Modern authorization systems span domains of administration, rely on many different authentication sources, and manage complex attributes as part of the authorization process. This . paper presents Cardea, a distributed system that facilitates dynamic access control, as a valuable piece of an inter-operable authorization framework. First, the authorization model employed in Cardea and its functionality goals are examined. Next, critical features of the system architecture and its handling of the authorization process are then examined. Then the S A M L and XACML standards, as incorporated into the system, are analyzed. Finally, the future directions of this project are outlined and connection points with general components of an authorization system are highlighted.

  8. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2008-01-01

    An experimental study was conducted to provide the first demonstration of an active flow control system for a flush-mounted inlet with significant boundary-layer-ingestion in transonic flow conditions. The effectiveness of the flow control in reducing the circumferential distortion at the engine fan-face location was assessed using a 2.5%-scale model of a boundary-layer-ingesting offset diffusing inlet. The inlet was flush mounted to the tunnel wall and ingested a large boundary layer with a boundary-layer-to-inlet height ratio of 35%. Different jet distribution patterns and jet mass flow rates were used in the inlet to control distortion. A vane configuration was also tested. Finally a hybrid vane/jet configuration was tested leveraging strengths of both types of devices. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow rates through the duct and the flow control actuators. The distortion and pressure recovery were measured at the aerodynamic interface plane. The data show that control jets and vanes reduce circumferential distortion to acceptable levels. The point-design vane configuration produced higher distortion levels at off-design settings. The hybrid vane/jet flow control configuration reduced the off-design distortion levels to acceptable ones and used less than 0.5% of the inlet mass flow to supply the jets.

  9. Application-Defined Decentralized Access Control

    PubMed Central

    Xu, Yuanzhong; Dunn, Alan M.; Hofmann, Owen S.; Lee, Michael Z.; Mehdi, Syed Akbar; Witchel, Emmett

    2014-01-01

    DCAC is a practical OS-level access control system that supports application-defined principals. It allows normal users to perform administrative operations within their privilege, enabling isolation and privilege separation for applications. It does not require centralized policy specification or management, giving applications freedom to manage their principals while the policies are still enforced by the OS. DCAC uses hierarchically-named attributes as a generic framework for user-defined policies such as groups defined by normal users. For both local and networked file systems, its execution time overhead is between 0%–9% on file system microbenchmarks, and under 1% on applications. This paper shows the design and implementation of DCAC, as well as several real-world use cases, including sandboxing applications, enforcing server applications’ security policies, supporting NFS, and authenticating user-defined sub-principals in SSH, all with minimal code changes. PMID:25426493

  10. Modeling mandatory access control in role-based security systems

    SciTech Connect

    Nyanchama, M.; Osborn, S.

    1996-12-31

    This paper discusses the realization of mandatory access control in role-based protection systems. Starting from the basic definitions of roles, their application in security and the basics of the concept of mandatory access control, we develop a scheme of role-based protection that realizes mandatory access control. The basis of this formulation develops from the recognition that roles can be seen as facilitating access to some given information context. By handling each of the role contexts as independent security levels of information, we simulate mandatory access by imposing the requirements of mandatory access control. Among the key considerations, we propose a means of taming Trojan horses by imposing acyclic information flow among contexts in role-based protection systems. The acyclic information flows and suitable access rules incorporate secrecy which is an essential component of mandatory access control.

  11. Linear Controllers for Turbulent Boundary Layers

    NASA Astrophysics Data System (ADS)

    Lim, Junwoo; Kim, John; Kang, Sung-Moon; Speyer, Jason

    2000-11-01

    Several recent studies have shown that controllers based on a linear system theory work surprisingly well in turbulent flows, suggesting that a linear mechanism may play an important role even in turbulent flows. It has been also shown that non-normality of the linearized Navier-Stokes equations is an essential characteristic in the regeneration of near-wall turbulence structures in turbulent boundary layers. A few controllers designed to reduce the role of different linear mechanisms, including that to minimize the non-normality of the linearized Navier-Stokes equations, have been developed and applied to a low Reynolds nubmer turbulent channel flow. A reduced-order model containing the most controllable and observables modes is derived for each system. Other existing control schemes, such as Choi et al's opposition control, have been examined from the point of a linear system control. Further discussion on controller design, such as choice of cost function and other control parameters, will be presented.

  12. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2006-01-01

    This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCP(sub avg)) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow.

  13. Boundary-Layer-Ingesting Inlet Flow Control

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R.; Allan, Brian G.; Gorton, Susan A.

    2006-01-01

    This paper gives an overview of a research study conducted in support of the small-scale demonstration of an active flow control system for a boundary-layer-ingesting (BLI) inlet. The effectiveness of active flow control in reducing engine inlet circumferential distortion was assessed using a 2.5% scale model of a 35% boundary-layer-ingesting flush-mounted, offset, diffusing inlet. This experiment was conducted in the NASA Langley 0.3-meter Transonic Cryogenic Tunnel at flight Mach numbers with a model inlet specifically designed for this type of testing. High mass flow actuators controlled the flow through distributed control jets providing the active flow control. A vortex generator point design configuration was also tested for comparison purposes and to provide a means to examine a hybrid vortex generator and control jets configuration. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion and pressure recovery were determined by 40 total pressure measurements on 8 rake arms each separated by 45 degrees and were located at the aerodynamic interface plane. The test matrix was limited to a maximum free-stream Mach number of 0.85 with scaled mass flows through the inlet for that condition. The data show that the flow control jets alone can reduce circumferential distortion (DPCPavg) from 0.055 to about 0.015 using about 2.5% of inlet mass flow. The vortex generators also reduced the circumferential distortion from 0.055 to 0.010 near the inlet mass flow design point. Lower inlet mass flow settings with the vortex generator configuration produced higher distortion levels that were reduced to acceptable levels using a hybrid vortex generator/control jets configuration that required less than 1% of the inlet mass flow.

  14. Vibration control through passive constrained layer damping and active control

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1997-05-01

    To add damping to systems, viscoelastic materials (VEM) are added to structures. In order to enhance the damping effects of the VEM, a constraining layer is attached. When this constraining layer is an active element, the treatment is called active constrained layer damping (ACLD). Recently, the investigation of ACLD treatments has shown it to be an effective method of vibration suppression. In this paper, the treatment of a beam with a separate active element and passive constrained layer (PCLD) element is investigated. A Ritz- Galerkin approach is used to obtain discretized equations of motion. The damping is modeled using the GHM method and the system is analyzed in the time domain. By optimizing on the performance and control effort for both the active and passive case, it is shown that this treatment is capable of lower control effort with more inherent damping, and is therefore a better approach to damp vibration.

  15. 33 CFR 106.260 - Security measures for access control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... SECURITY MARITIME SECURITY MARINE SECURITY: OUTER CONTINENTAL SHELF (OCS) FACILITIES Outer Continental Shelf (OCS) Facility Security Requirements § 106.260 Security measures for access control. (a)...

  16. 33 CFR 106.260 - Security measures for access control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... SECURITY MARITIME SECURITY MARINE SECURITY: OUTER CONTINENTAL SHELF (OCS) FACILITIES Outer Continental Shelf (OCS) Facility Security Requirements § 106.260 Security measures for access control. (a)...

  17. 33 CFR 106.260 - Security measures for access control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... SECURITY MARITIME SECURITY MARINE SECURITY: OUTER CONTINENTAL SHELF (OCS) FACILITIES Outer Continental Shelf (OCS) Facility Security Requirements § 106.260 Security measures for access control. (a)...

  18. Open versus Controlled-Access Data | Office of Cancer Genomics

    Cancer.gov

    OCG employs stringent human subjects’ protection and data access policies to protect the privacy and confidentiality of the research participants. Depending on the risk of patient identification, OCG programs data are available to the scientific community in two tiers: open or controlled access. Both types of data can be accessed through its corresponding OCG program-specific data matrix or portal. Open-access Data

  19. Door assembly with shear layer control aperture

    NASA Technical Reports Server (NTRS)

    Kahn, William C. (Inventor); Johnston, John T. (Inventor); Fluegel, Kyle G. (Inventor)

    1996-01-01

    There is described a vehicle door assembly with shear layer control for controlling the airflow in and around an aperture in the vehicle fuselage. The vehicle door assembly consists of an upper door and a lower door, both slidably mounted to the exterior surface of the vehicle fuselage. In addition, an inner door is slidably mounted beneath the upper door. Beneath the inner door is an aperture assembly having an aperture opening positionable to be substantially flush with the exterior surface of the vehicle fuselage. Also provided are means for positioning the aperture assembly in an upward and downward direction in relation to the vehicle fuselage.

  20. Layer-specific chromatin accessibility landscapes reveal regulatory networks in adult mouse visual cortex

    PubMed Central

    Gray, Lucas T; Yao, Zizhen; Nguyen, Thuc Nghi; Kim, Tae Kyung; Zeng, Hongkui; Tasic, Bosiljka

    2017-01-01

    Mammalian cortex is a laminar structure, with each layer composed of a characteristic set of cell types with different morphological, electrophysiological, and connectional properties. Here, we define chromatin accessibility landscapes of major, layer-specific excitatory classes of neurons, and compare them to each other and to inhibitory cortical neurons using the Assay for Transposase-Accessible Chromatin with high-throughput sequencing (ATAC-seq). We identify a large number of layer-specific accessible sites, and significant association with genes that are expressed in specific cortical layers. Integration of these data with layer-specific transcriptomic profiles and transcription factor binding motifs enabled us to construct a regulatory network revealing potential key layer-specific regulators, including Cux1/2, Foxp2, Nfia, Pou3f2, and Rorb. This dataset is a valuable resource for identifying candidate layer-specific cis-regulatory elements in adult mouse cortex. DOI: http://dx.doi.org/10.7554/eLife.21883.001 PMID:28112643

  1. Resource Allocation and Cross Layer Control in Wireless Networks

    DTIC Science & Technology

    2006-08-25

    nontrivial manner in order to support information transfer. In this paper we will present abstract models that capture the cross layer interaction from the...nontrivial manner in order to support information transfer. In this paper we will present abstract models that capture the cross layer inter- action from...parameters of the others. Our cross-layer model in this paper captures the interaction of these mechanisms, where all the physical and access layer

  2. Analysis of Access Control Policies in Operating Systems

    ERIC Educational Resources Information Center

    Chen, Hong

    2009-01-01

    Operating systems rely heavily on access control mechanisms to achieve security goals and defend against remote and local attacks. The complexities of modern access control mechanisms and the scale of policy configurations are often overwhelming to system administrators and software developers. Therefore, mis-configurations are common, and the…

  3. Permission to Speak: A Novel Formal Foundation for Access Control

    DTIC Science & Technology

    2016-06-21

    NAME(S) AND ADDRESS(ES) University of Pennsylvania,Computer and Information Science ,Philadelphia,PA,19104 8. PERFORMING ORGANIZATION REPORT NUMBER... science • Uniform treatment of access control and conformance – Access control is verification of permissions – Conformance is satisfaction of

  4. 33 CFR 105.255 - Security measures for access control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... each MARSEC Level, including those points where TWIC access control provisions will be applied. Each... escorting them; (4) Procedures for identifying authorized and unauthorized persons at any MARSEC level; and... access controls, particularly if they are to be applied on a random or occasional basis. (f) MARSEC...

  5. Control of the Transitional Boundary Layer

    NASA Astrophysics Data System (ADS)

    Belson, Brandt A.

    This work makes advances in the delay of boundary layer transition from laminar to turbulent flow via feedback control. The applications include the reduction of drag over streamline bodies (e.g., airplane wings) and the decrease of mixing and heat transfer (e.g., over turbine blades in jet engines). A difficulty in many fields is designing feedback controllers for high-dimensional systems, be they experiments or high-fidelity simulations, because the required time and resources are too large. A cheaper alternative is to approximate the high-dimensional system with a reduced-order model and design a controller for the model. We implement several model reduction algorithms in "modred", an open source and publicly available library that is applicable to a wide range of problems. We use this library to study the role of sensors and actuators in feedback control of transition in the 2D boundary layer. Previous work uses a feedforward configuration in which the sensor is upstream of the actuator, but we show that the actuator-sensor pair is unsuitable for feedback control due to an inability to sense the exponentially-growing Tollmien-Schlichting waves. A new actuator-sensor pair is chosen that more directly affects and measures the TS waves, and as a result it is effective in a feedback configuration. Lastly, the feedback controller is shown to outperform feedforward controllers in the presence of unmodeled disturbances. Next, we focus on a specific type of actuator, the single dielectric barrier discharge (SDBD) plasma actuator. An array of these plasma actuators is oriented to produce stream-wise vorticity and thus directly cancel the structures with the largest transient growth (so-called stream-wise streaks). We design a feedback controller using only experimental data by first developing an empirical input-output quasi-steady model. Then, we design feedback controllers for the model such that the controllers perform well when applied to the experiment. Lastly, we

  6. Effect of delayed feed access on production and blood parameters of layer-type chicks.

    PubMed

    Gaglo-Disse, Adjovi; Tona, Kokou; Aliou, Sakibou; Debonne, Marian; Aklikokou, Kodjo; Gbeassor, Messanvi; Decuypere, Eddy

    2010-06-01

    A total of 684 Hisex Brown day-old chicks were studied. The chicks were randomly assigned into three groups as follows: (1) chicks with immediate feed access; (2) chicks with 48 h delay in feed access, and (3) chicks with 72 h delay in feed access. For each group, chicks were assigned into 4 replications of 57 birds each. Prior to feed access, the chicks were weighed. Samples of chicks were used to weigh yolk sac at 1, 3 and 7 days and to collect blood at 1, 3, 7, 14 and 56 days. Also, reared chicks were weighed weekly. The results indicated that chick weights decreased during the holding period. Yolk sac utilisation was similar between groups, while morbidity and mortality increased linearly with the duration of delay in feed access. At 56 days, chicks having delayed access to feed were lighter than those without delay in feed access. Serum concentration of glucose up to 14 days and of total protein and triglycerides until 56 days decreased with the increasing duration of delay in feed access. It can be concluded that delayed feed access is detrimental to the juvenile performance of layer-type chicks and has a negative age-related effect on the serum concentrations of glucose, triglycerides and total protein.

  7. Boundary Layer Control for Hypersonic Airbreathing Vehicles

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Nowak, Robert J.; Horvath, Thomas J.

    2004-01-01

    Active and passive methods for tripping hypersonic boundary layers have been examined in NASA Langley Research Center wind tunnels using a Hyper-X model. This investigation assessed several concepts for forcing transition, including passive discrete roughness elements and active mass addition (or blowing), in the 20-Inch Mach 6 Air and the 31-Inch Mach 10 Air Tunnels. Heat transfer distributions obtained via phosphor thermography, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. The comparisons between the active and passive methods for boundary layer control were conducted at test conditions that nearly match the Hyper-X nominal Mach 7 flight test-point of an angle-of-attack of 2-deg and length Reynolds number of 5.6 million. For passive roughness, the primary parametric variation was a range of trip heights within the calculated boundary layer thickness for several trip concepts. The passive roughness study resulted in a swept ramp configuration, scaled to be roughly 0.6 of the calculated boundary layer thickness, being selected for the Mach 7 flight vehicle. For the active blowing study, the manifold pressure was systematically varied (while monitoring the mass flow) for each configuration to determine the jet penetration height, with schlieren, and transition movement, with the phosphor system, for comparison to the passive results. All the blowing concepts tested, which included various rows of sonic orifices (holes), two- and three-dimensional slots, and random porosity, provided transition onset near the trip location with manifold stagnation pressures on the order of 40 times the model surface static pressure, which is adequate to ensure sonic jets. The present results indicate that the jet penetration height for blowing was roughly half the height required with passive roughness elements for an equivalent amount of transition movement.

  8. A design of tamper resistant prescription RFID access control system.

    PubMed

    Chen, Yu-Yi; Huang, Der-Chen; Tsai, Meng-Lin; Jan, Jinn-Ke

    2012-10-01

    In this paper, we propose a tamper resistant prescription RFID access control protocol for different authorized readers. Not only the authentication mechanism but also the access right authorization mechanism is designed in our scheme. Only the specific doctor, usually the patient's doctor, can access the tag. Moreover, some related information of patient's prescription is attached to a RFID tag for tamper resistance. The patients' rights will be guaranteed.

  9. Managed Access by Controlled Sensing (MACS)

    SciTech Connect

    Curtiss, J.A.; Indusi, J.P.

    1994-08-01

    During chemical weapons challenge inspections, the CWC treaty allows ``alternate means`` of access to be proposed by the nation challenged. BNL`s Safeguards, Safety and Nonproliferation Division is funded by the Defense Nuclear Agency to develop a system to provide the challenge inspection team with a ``virtual presence`` within the facility while denying personal access. A general purpose configuration of a mobile station manned by site personnel and a base station manned by the challenge inspector, supported by a flexible communication system, will allow facility personnel to tailor the basic model to their site. Design of the MACS system is based on maximum use of commercial equipment that is available on the international market. Design requirements for the MACS system include methods of establishing geographical position, distance measuring equipment for use in verifying dimensions on floor plans, video and two-way audio links between the mobile unit and the base station, and portability and versatility of the equipment. The MACS platform will also support deployment of selected instrumentation which the site may offer to the challenge inspection team. This paper describes the design and construction of the prototype MACS system.

  10. 49 CFR 1542.207 - Access control systems.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 9 2012-10-01 2012-10-01 false Access control systems. 1542.207 Section 1542.207 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Operations § 1542.207 Access...

  11. 49 CFR 1542.207 - Access control systems.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 9 2011-10-01 2011-10-01 false Access control systems. 1542.207 Section 1542.207 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Operations § 1542.207 Access...

  12. 49 CFR 1542.207 - Access control systems.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 9 2014-10-01 2014-10-01 false Access control systems. 1542.207 Section 1542.207 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Operations § 1542.207 Access...

  13. 49 CFR 1542.207 - Access control systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 9 2010-10-01 2010-10-01 false Access control systems. 1542.207 Section 1542.207 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Operations § 1542.207 Access...

  14. 49 CFR 1542.207 - Access control systems.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 9 2013-10-01 2013-10-01 false Access control systems. 1542.207 Section 1542.207 Transportation Other Regulations Relating to Transportation (Continued) TRANSPORTATION SECURITY ADMINISTRATION, DEPARTMENT OF HOMELAND SECURITY CIVIL AVIATION SECURITY AIRPORT SECURITY Operations § 1542.207 Access...

  15. Urban Studies: A Study of Bibliographic Access and Control.

    ERIC Educational Resources Information Center

    Anderson, Barbara E.

    This paper analyzes: (1) the bibliographic access to publications in urban studies via printed secondary sources; (2) development and scope of classification systems and of vocabulary control for urban studies; and (3) currently accessible automated collections of bibliographic citations. Urban studies is defined as "an agglomeration of…

  16. 14 CFR 420.53 - Control of public access.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ..., DEPARTMENT OF TRANSPORTATION LICENSING LICENSE TO OPERATE A LAUNCH SITE Responsibilities of a Licensee § 420.53 Control of public access. (a) A licensee shall prevent unauthorized access to the launch site, and... the launch site of safety rules and emergency and evacuation procedures prior to that person's...

  17. Personnel Access Control System Evaluation for National Ignition Facility Operations

    SciTech Connect

    Altenbach, T; Brereton, S.; Hermes, G.; Singh, M.

    2001-06-01

    The purpose of this document is to analyze the baseline Access Control System for the National Ignition Facility (NIF), and to assess its effectiveness at controlling access to hazardous locations during full NIF operations. It reviews the various hazards present during a NIF shot sequence, and evaluates the effectiveness of the applicable set of controls at preventing access while the hazards are present. It considers only those hazards that could potentially be lethal. In addition, various types of technologies that might be applicable at NIF are reviewed, as are systems currently in use at other facilities requiring access control for safety reasons. Recommendations on how this system might be modified to reduce risk are made.

  18. Authenticated IGMP for Controlling Access to Multicast Distribution Tree

    NASA Astrophysics Data System (ADS)

    Park, Chang-Seop; Kang, Hyun-Sun

    A receiver access control scheme is proposed to protect the multicast distribution tree from DoS attack induced by unauthorized use of IGMP, by extending the security-related functionality of IGMP. Based on a specific network and business model adopted for commercial deployment of IP multicast applications, a key management scheme is also presented for bootstrapping the proposed access control as well as accounting and billing for CP (Content Provider), NSP (Network Service Provider), and group members.

  19. RANDOM ACCESS CONTROL OF ELECTROLUMINESCENT ELEMENTS.

    DTIC Science & Technology

    Cadmium selenide (CdSe) switches were devised to control the luminous emittance of electroluminescent cells in a solid-state display. The technique...purpose of this contract was to establish the feasibility of utilizing the hysteretic effect in cadmium selenide to provide switching and storage to an...array of electroluminescent cells by investigating the cadmium selenide material, by studying panel structure, and by investigating the addressing of

  20. Context-aware access control for pervasive access to process-based healthcare systems.

    PubMed

    Koufi, Vassiliki; Vassilacopoulos, George

    2008-01-01

    Healthcare is an increasingly collaborative enterprise involving a broad range of healthcare services provided by many individuals and organizations. Grid technology has been widely recognized as a means for integrating disparate computing resources in the healthcare field. Moreover, Grid portal applications can be developed on a wireless and mobile infrastructure to execute healthcare processes which, in turn, can provide remote access to Grid database services. Such an environment provides ubiquitous and pervasive access to integrated healthcare services at the point of care, thus improving healthcare quality. In such environments, the ability to provide an effective access control mechanism that meets the requirement of the least privilege principle is essential. Adherence to the least privilege principle requires continuous adjustments of user permissions in order to adapt to the current situation. This paper presents a context-aware access control mechanism for HDGPortal, a Grid portal application which provides access to workflow-based healthcare processes using wireless Personal Digital Assistants. The proposed mechanism builds upon and enhances security mechanisms provided by the Grid Security Infrastructure. It provides tight, just-in-time permissions so that authorized users get access to specific objects according to the current context. These permissions are subject to continuous adjustments triggered by the changing context. Thus, the risk of compromising information integrity during task executions is reduced.

  1. Role of an encapsulating layer for reducing resistance drift in phase change random access memory

    NASA Astrophysics Data System (ADS)

    Jin, Bo; Kim, Jungsik; Pi, Dong-Hai; Kim, Hyoung Seop; Meyyappan, M.; Lee, Jeong-Soo

    2014-12-01

    Phase change random access memory (PCRAM) devices exhibit a steady increase in resistance in the amorphous phase upon aging and this resistance drift phenomenon directly affects the device reliability. A stress relaxation model is used here to study the effect of a device encapsulating layer material in addressing the resistance drift phenomenon in PCRAM. The resistance drift can be increased or decreased depending on the biaxial moduli of the phase change material (YPCM) and the encapsulating layer material (YELM) according to the stress relationship between them in the drift regime. The proposed model suggests that the resistance drift can be effectively reduced by selecting a proper material as an encapsulating layer. Moreover, our model explains that reducing the size of the phase change material (PCM) while fully reset and reducing the amorphous/crystalline ratio in PCM help to improve the resistance drift, and thus opens an avenue for highly reliable multilevel PCRAM applications.

  2. Control with a random access protocol and packet dropouts

    NASA Astrophysics Data System (ADS)

    Wang, Liyuan; Guo, Ge

    2016-08-01

    This paper investigates networked control systems whose actuators communicate with the controller via a limited number of unreliable channels. The access to the channels is decided by a so-called group random access protocol, which is modelled as a binary Markov sequence. Data packet dropouts in the channels are modelled as independent Bernoulli processes. For such systems, a systematic characterisation for controller synthesis is established and stated in terms of the transition probabilities of the Markov protocol and the packet dropout probabilities. The results are illustrated via a numerical example.

  3. Joint Power and Multiple Access Control for Wireless Mesh Network with Rose Projection Method

    PubMed Central

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches. PMID:24883384

  4. Joint power and multiple access control for wireless mesh network with Rose projection method.

    PubMed

    Tang, Meiqin; Shang, Lili; Xin, Yalin; Liu, Xiaohua; Wei, Xinjiang

    2014-01-01

    This paper investigates the utility maximization problem for the downlink of the multi-interface multichannel wireless mesh network with orthogonal frequency division multiple access. A cross-layer joint power and multiple access control algorithm are proposed. Rosen projection matrix is combined with Solodov projection techniques to build a three-memory gradient Rosen projection method, which is applied to solve this optimization problem. The convergence analysis is given and simulations show that the proposed solution achieves significant throughput compared with existing approaches.

  5. Towards an Access-Control Framework for Countering Insider Threats

    NASA Astrophysics Data System (ADS)

    Crampton, Jason; Huth, Michael

    As insider threats pose very significant security risks to IT systems, we ask what policy-based approaches to access control can do for the detection, mitigation or countering of insider threats and insider attacks. Answering this question is difficult: little public data about insider-threat cases is available; there is not much consensus about what the insider problem actually is; and previous research in access control has by-and-large not dealt with this issue. We explore existing notions of insiderness in order to identify the relevant research issues. We then formulate a set of requirements for next-generation access-control systems, whose realization might form part of an overall strategy to address the insider problem.

  6. Controlling user access to electronic resources without password

    DOEpatents

    Smith, Fred Hewitt

    2015-06-16

    Described herein are devices and techniques for remotely controlling user access to a restricted computer resource. The process includes pre-determining an association of the restricted computer resource and computer-resource-proximal environmental information. Indicia of user-proximal environmental information are received from a user requesting access to the restricted computer resource. Received indicia of user-proximal environmental information are compared to associated computer-resource-proximal environmental information. User access to the restricted computer resource is selectively granted responsive to a favorable comparison in which the user-proximal environmental information is sufficiently similar to the computer-resource proximal environmental information. In at least some embodiments, the process further includes comparing user-supplied biometric measure and comparing it with a predetermined association of at least one biometric measure of an authorized user. Access to the restricted computer resource is granted in response to a favorable comparison.

  7. Secondary retention of rubber dam: effective moisture control access considerations.

    PubMed

    Liebenberg, W H

    1995-04-01

    Primary rubber dam retention affects attachment of the latex sheet to the anchor teeth bordering the isolated working field. Secondary rubber dam retention is the provision of an effective seal at the dam-tooth junction, which is essential to the maintenance of adequate access and moisture control within the working field. Practical hints are offered to optimize access and moisture control through well-planned and properly executed secondary retention of classic rubber dam applications. In addition, innovative solutions to the limitations of general field isolation, which pertain mostly to secondary retention of the unrestrained buccal and lingual curtains of the slit dam, are introduced.

  8. Access and control of information and intellectual property

    NASA Astrophysics Data System (ADS)

    Lang, Gerald S.

    1996-03-01

    This paper introduces the technology of two pioneering patents for the secure distribution of information and intellectual property. The seminal technology has been used in the control of sensitive material such as medical records and imagery in distributed networks. It lends itself to the implementation of an open architecture access control system that provides local or remote user selective access to digital information stored on any computer system or storage medium, down to the data element, pixel, and sub-pixel levels. Use of this technology is especially suited for electronic publishing, health care records, MIS, and auditing.

  9. Error Control with Perfectly Matched Layer or Damping Layer Treatments for Computational Aeroacoustics with Jet Flows

    NASA Technical Reports Server (NTRS)

    Goodrich, John W.

    2009-01-01

    In this paper we show by means of numerical experiments that the error introduced in a numerical domain because of a Perfectly Matched Layer or Damping Layer boundary treatment can be controlled. These experimental demonstrations are for acoustic propagation with the Linearized Euler Equations with both uniform and steady jet flows. The propagating signal is driven by a time harmonic pressure source. Combinations of Perfectly Matched and Damping Layers are used with different damping profiles. These layer and profile combinations allow the relative error introduced by a layer to be kept as small as desired, in principle. Tradeoffs between error and cost are explored.

  10. Joint Access Control Based on Access Ratio and Resource Utilization for High-Speed Railway Communications

    NASA Astrophysics Data System (ADS)

    Zhou, Yuzhe; Ai, Bo

    2015-05-01

    The fast development of high-speed rails makes people's life more and more convenient. However, provisioning of quality of service of multimedia applications for users on the high-speed train is a critical task for wireless communications. Therefore, new solutions are desirable to be found to address this kind of problem. Current researches mainly focus on providing seamless broadband wireless access for high-speed mobile terminals. In this paper, an algorithm to calculate the optimal resource reservation fraction of handovers is proposed. A joint access control scheme for high-speed railway communication handover scenario is proposed. Metrics of access ratio and resource utilization ratio are considered jointly in the analysis and the performance evaluation. Simulation results show that the proposed algorithm and the scheme improve quality of service compared with other conventional schemes.

  11. A Scalable Data Access Layer to Manage Structured Heterogeneous Biomedical Data

    PubMed Central

    Lianas, Luca; Frexia, Francesca; Zanetti, Gianluigi

    2016-01-01

    This work presents a scalable data access layer, called PyEHR, designed to support the implementation of data management systems for secondary use of structured heterogeneous biomedical and clinical data. PyEHR adopts the openEHR’s formalisms to guarantee the decoupling of data descriptions from implementation details and exploits structure indexing to accelerate searches. Data persistence is guaranteed by a driver layer with a common driver interface. Interfaces for two NoSQL Database Management Systems are already implemented: MongoDB and Elasticsearch. We evaluated the scalability of PyEHR experimentally through two types of tests, called “Constant Load” and “Constant Number of Records”, with queries of increasing complexity on synthetic datasets of ten million records each, containing very complex openEHR archetype structures, distributed on up to ten computing nodes. PMID:27936191

  12. A Scalable Data Access Layer to Manage Structured Heterogeneous Biomedical Data.

    PubMed

    Delussu, Giovanni; Lianas, Luca; Frexia, Francesca; Zanetti, Gianluigi

    2016-01-01

    This work presents a scalable data access layer, called PyEHR, designed to support the implementation of data management systems for secondary use of structured heterogeneous biomedical and clinical data. PyEHR adopts the openEHR's formalisms to guarantee the decoupling of data descriptions from implementation details and exploits structure indexing to accelerate searches. Data persistence is guaranteed by a driver layer with a common driver interface. Interfaces for two NoSQL Database Management Systems are already implemented: MongoDB and Elasticsearch. We evaluated the scalability of PyEHR experimentally through two types of tests, called "Constant Load" and "Constant Number of Records", with queries of increasing complexity on synthetic datasets of ten million records each, containing very complex openEHR archetype structures, distributed on up to ten computing nodes.

  13. Access Control for Agent-based Computing: A Distributed Approach.

    ERIC Educational Resources Information Center

    Antonopoulos, Nick; Koukoumpetsos, Kyriakos; Shafarenko, Alex

    2001-01-01

    Discusses the mobile software agent paradigm that provides a foundation for the development of high performance distributed applications and presents a simple, distributed access control architecture based on the concept of distributed, active authorization entities (lock cells), any combination of which can be referenced by an agent to provide…

  14. Fine-Grained Access Control for Electronic Health Record Systems

    NASA Astrophysics Data System (ADS)

    Hue, Pham Thi Bach; Wohlgemuth, Sven; Echizen, Isao; Thuy, Dong Thi Bich; Thuc, Nguyen Dinh

    There needs to be a strategy for securing the privacy of patients when exchanging health records between various entities over the Internet. Despite the fact that health care providers such as Google Health and Microsoft Corp.'s Health Vault comply with the U.S Health Insurance Portability and Accountability Act (HIPAA), the privacy of patients is still at risk. Several encryption schemes and access control mechanisms have been suggested to protect the disclosure of a patient's health record especially from unauthorized entities. However, by implementing these approaches, data owners are not capable of controlling and protecting the disclosure of the individual sensitive attributes of their health records. This raises the need to adopt a secure mechanism to protect personal information against unauthorized disclosure. Therefore, we propose a new Fine-grained Access Control (FGAC) mechanism that is based on subkeys, which would allow a data owner to further control the access to his data at the column-level. We also propose a new mechanism to efficiently reduce the number of keys maintained by a data owner in cases when the users have different access privileges to different columns of the data being shared.

  15. Secure Dynamic access control scheme of PHR in cloud computing.

    PubMed

    Chen, Tzer-Shyong; Liu, Chia-Hui; Chen, Tzer-Long; Chen, Chin-Sheng; Bau, Jian-Guo; Lin, Tzu-Ching

    2012-12-01

    With the development of information technology and medical technology, medical information has been developed from traditional paper records into electronic medical records, which have now been widely applied. The new-style medical information exchange system "personal health records (PHR)" is gradually developed. PHR is a kind of health records maintained and recorded by individuals. An ideal personal health record could integrate personal medical information from different sources and provide complete and correct personal health and medical summary through the Internet or portable media under the requirements of security and privacy. A lot of personal health records are being utilized. The patient-centered PHR information exchange system allows the public autonomously maintain and manage personal health records. Such management is convenient for storing, accessing, and sharing personal medical records. With the emergence of Cloud computing, PHR service has been transferred to storing data into Cloud servers that the resources could be flexibly utilized and the operation cost can be reduced. Nevertheless, patients would face privacy problem when storing PHR data into Cloud. Besides, it requires a secure protection scheme to encrypt the medical records of each patient for storing PHR into Cloud server. In the encryption process, it would be a challenge to achieve accurately accessing to medical records and corresponding to flexibility and efficiency. A new PHR access control scheme under Cloud computing environments is proposed in this study. With Lagrange interpolation polynomial to establish a secure and effective PHR information access scheme, it allows to accurately access to PHR with security and is suitable for enormous multi-users. Moreover, this scheme also dynamically supports multi-users in Cloud computing environments with personal privacy and offers legal authorities to access to PHR. From security and effectiveness analyses, the proposed PHR access

  16. Access control and interlock system at the Advanced Photon Source

    SciTech Connect

    Forrestal, J.; Hogrefe, R.; Knott, M.; McDowell, W.; Reigle, D.; Solita, L.; Koldenhoven, R.; Haid, D.

    1997-08-01

    The Advanced Photon Source (APS) consists of a linac, position accumulator ring (PAR), booster synchrotron, storage ring, and up to 70 experimental beamlines. The Access Control and Interlock System (ACIS) utilizes redundant programmable logic controllers (PLCs) and a third hard-wired chain to protect personnel from prompt radiation generated by the linac, PAR, synchrotron, and storage ring. This paper describes the ACIS`s design philosophy, configuration, hardware, functionality, validation requirements, and operational experience.

  17. Distributed reservation control protocols for random access broadcasting channels

    NASA Astrophysics Data System (ADS)

    Greene, E. P.; Ephremides, A.

    1981-05-01

    Attention is given to a communication network consisting of an arbitrary number of nodes which can communicate with each other via a time-division multiple access (TDMA) broadcast channel. The reported investigation is concerned with the development of efficient distributed multiple access protocols for traffic consisting primarily of single packet messages in a datagram mode of operation. The motivation for the design of the protocols came from the consideration of efficient multiple access utilization of moderate to high bandwidth (4-40 Mbit/s capacity) communication satellite channels used for the transmission of short (1000-10,000 bits) fixed length packets. Under these circumstances, the ratio of roundtrip propagation time to packet transmission time is between 100 to 10,000. It is shown how a TDMA channel can be adaptively shared by datagram traffic and constant bandwidth users such as in digital voice applications. The distributed reservation control protocols described are a hybrid between contention and reservation protocols.

  18. Distributed reservation control protocols for random access broadcasting channels

    NASA Technical Reports Server (NTRS)

    Greene, E. P.; Ephremides, A.

    1981-01-01

    Attention is given to a communication network consisting of an arbitrary number of nodes which can communicate with each other via a time-division multiple access (TDMA) broadcast channel. The reported investigation is concerned with the development of efficient distributed multiple access protocols for traffic consisting primarily of single packet messages in a datagram mode of operation. The motivation for the design of the protocols came from the consideration of efficient multiple access utilization of moderate to high bandwidth (4-40 Mbit/s capacity) communication satellite channels used for the transmission of short (1000-10,000 bits) fixed length packets. Under these circumstances, the ratio of roundtrip propagation time to packet transmission time is between 100 to 10,000. It is shown how a TDMA channel can be adaptively shared by datagram traffic and constant bandwidth users such as in digital voice applications. The distributed reservation control protocols described are a hybrid between contention and reservation protocols.

  19. Access control and privacy in large distributed systems

    NASA Technical Reports Server (NTRS)

    Leiner, B. M.; Bishop, M.

    1986-01-01

    Large scale distributed systems consists of workstations, mainframe computers, supercomputers and other types of servers, all connected by a computer network. These systems are being used in a variety of applications including the support of collaborative scientific research. In such an environment, issues of access control and privacy arise. Access control is required for several reasons, including the protection of sensitive resources and cost control. Privacy is also required for similar reasons, including the protection of a researcher's proprietary results. A possible architecture for integrating available computer and communications security technologies into a system that meet these requirements is described. This architecture is meant as a starting point for discussion, rather that the final answer.

  20. A layered microchip conductance detector with through-layer access to detection fields and high sensitivity to dielectric constant

    NASA Astrophysics Data System (ADS)

    Suganuma, Y.; Dhirani, A.-A.

    2011-04-01

    The present study explores a novel apertured microchip conductance detector (AMCD) that is sensitive to dielectric constant. Fashioned on silicon oxide/silicon using optical microlithography, the detector has novel parallel-plate geometry with a top mesh electrode, a middle apertured insulator, and a bottom conducting electrode. This monolithic apertured architecture is planar and may be provided with a thin insulator layer enabling large capacitances, while the top mesh electrode and middle apertured-insulator enable access to regions of the capacitor where electric fields are strong. Hence, the detector is sensitive yet mechanically robust. To test its response, the AMCD was immersed in various solvents, namely water, methanol, acetonitrile, and hexanes. Its response was found to vary in proportion to the solvents' respective dielectric constants. The AMCD was also able to distinguish quantitatively the presence of various molecules in solution, including molecules with chromophores [such as acetylsalicylic acid (ASA)] in methanol and those without chrompohores [such as polyethylene glycol 200 Daltons (PEG200)] in methanol or water. The universal nature of dielectric constant and the microchip detector's sensitivity point to a wide range of potential applications.

  1. Tag Content Access Control with Identity-based Key Exchange

    NASA Astrophysics Data System (ADS)

    Yan, Liang; Rong, Chunming

    2010-09-01

    Radio Frequency Identification (RFID) technology that used to identify objects and users has been applied to many applications such retail and supply chain recently. How to prevent tag content from unauthorized readout is a core problem of RFID privacy issues. Hash-lock access control protocol can make tag to release its content only to reader who knows the secret key shared between them. However, in order to get this shared secret key required by this protocol, reader needs to communicate with a back end database. In this paper, we propose to use identity-based secret key exchange approach to generate the secret key required for hash-lock access control protocol. With this approach, not only back end database connection is not needed anymore, but also tag cloning problem can be eliminated at the same time.

  2. Rural providers' access to online resources: a randomized controlled trial

    PubMed Central

    Hall, Laura J.; McElfresh, Karen R.; Warner, Teddy D.; Stromberg, Tiffany L.; Trost, Jaren; Jelinek, Devin A.

    2016-01-01

    Objective The research determined the usage and satisfaction levels with one of two point-of-care (PoC) resources among health care providers in a rural state. Methods In this randomized controlled trial, twenty-eight health care providers in rural areas were stratified by occupation and region, then randomized into either the DynaMed or the AccessMedicine study arm. Study participants were physicians, physician assistants, and nurses. A pre- and post-study survey measured participants' attitudes toward different information resources and their information-seeking activities. Medical student investigators provided training and technical support for participants. Data analyses consisted of analysis of variance (ANOVA), paired t tests, and Cohen's d statistic to compare pre- and post-study effects sizes. Results Participants in both the DynaMed and the AccessMedicine arms of the study reported increased satisfaction with their respective PoC resource, as expected. Participants in both arms also reported that they saved time in finding needed information. At baseline, both arms reported too little information available, which increased to “about right amounts of information” at the completion of the study. DynaMed users reported a Cohen's d increase of +1.50 compared to AccessMedicine users' reported use of 0.82. DynaMed users reported d2 satisfaction increases of 9.48 versus AccessMedicine satisfaction increases of 0.59 using a Cohen's d. Conclusion Participants in the DynaMed arm of the study used this clinically oriented PoC more heavily than the users of the textbook-based AccessMedicine. In terms of user satisfaction, DynaMed users reported higher levels of satisfaction than the users of AccessMedicine. PMID:26807050

  3. 30 CFR 816.66 - Use of explosives: Blasting signs, warnings, and access control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... schedule. (c) Access control. Access within the blasting area shall be controlled to prevent presence of..., and access control. 816.66 Section 816.66 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... STANDARDS-SURFACE MINING ACTIVITIES § 816.66 Use of explosives: Blasting signs, warnings, and access...

  4. Frequency Controllable Metamaterial Absorber by an Added Dielectric Layer

    NASA Astrophysics Data System (ADS)

    Li, Xiong; Feng, Qin; Luo, Xiangang; Hong, Minghui

    2011-03-01

    In this paper, we introduce a covered dielectric layer in the traditional metamaterial absorber (MA) constructed by periodic resonant split rings. The absorber frequency can be simply controlled by the permittivity and the thickness of the added layer, without affecting the shape of the absorptivity spectrum. Furthermore, the dielectric loss property of the added layer does not influence the absorption characteristic obviously when the loss is not high. Based on these unique properties, a dynamically tunable MA can be realized by modulating a covered liquid dielectric layer.

  5. Integration of access control and ancillary information systems

    SciTech Connect

    Rodriguez, J.R.; Ahrens, J.S.

    1995-07-01

    The DOE has identified the Lawrence Livermore National Laboratory ARGUS system as the standard entry control system for the DOE Complex. ARGUS integrates several key functions, specifically, badging, entry control, and verification of clearance status. Not all sites need or can afford an ARGUS system. Such sites are therefore limited to commercial equipment which provide ARGUS like features. In this project an alternative way to integrate commercial equipment into an integrated system to include badging, access control, property control, and automated verification of clearance status has been investigated. Such a system would provide smaller sites the same functionality as is provided by ARGUS. Further, it would allow sites to fully participate in the DOE`s concept of Complex wide access control. This multi-year task is comprised of three phases. Phase 1, system requirements and definitions, and phase 2, software and hardware development, were completed during fiscal year 1994. This report covers these two phases and the demonstration system which resulted. Phase three would employ the demonstration system to evaluate system performance, identify operational limits and to integrate additional features. The demonstration system includes a badging station, a database server, a managers workstation, an entry control system, and a property protection system. The functions have been integrated through the use of custom interfaces and operator screens which greatly increase ease of use.

  6. Hand geometry biometric device for secure access control

    SciTech Connect

    Colbert, C.; Moles, D.R. )

    1991-01-01

    This paper reports that the authors developed for the Air Force the Mark VI Personal Identity Verifier (PIV) for controlling access to a fixed or mobile ICBM site, a computer terminal, or mainframe. The Mark VI records the digitized silhouettes of four fingers of each hand on an AT and T smart card. Like fingerprints, finger shapes, lengths, and widths constitute an unguessable biometric password. A Security Officer enrolls an authorized person who places each hand, in turn, on a backlighted panel. An overhead scanning camera records the right and left hand reference templates on the smart card. The Security Officer adds to the card: name, personal identification number (PIN), and access restrictions such as permitted days of the week, times of day, and doors. To gain access, cardowner inserts card into a reader slot and places either hand on the panel. Resulting access template is matched to the reference template by three sameness algorithms. The final match score is an average of 12 scores (each of the four fingers, matched for shape, length, and width), expressing the degree of sameness. (A perfect match would score 100.00.) The final match score is compared to a predetermined score (threshold), generating an accept or reject decision.

  7. Global Access-controlled Transfer e-frame (GATe)

    SciTech Connect

    2012-05-30

    Global Access-controlled Transfer e-frame (GATe) was designed to take advantage of the patterns that occur during an electronic record transfer process. The e-frame (or electronic framework or platform) is the foundation for developing secure information transfer to meet classified and unclassified business processes and is particularly useful when there is a need to share information with various entities in a controlled and secure environment. It can share, search, upload, download and retrieve sensitive information, as well as provides reporting capabilities.

  8. Periodic Control of Turbulent Boundary Layers

    DTIC Science & Technology

    2009-03-03

    integral can be approximated by solving the Orr-Sommerfeld equation around the Poiseuille channel flow , subject to controls in the form of wall-bounded...clearly periodic in time. So, we now assume that the base flow in the channel is described as linear super-position of the Poiseuille channel flow and...assumed to be the parabolic profile of the Poiseuille channel flow . Treating the traveling wave as a primary disturbance [10], linear dynamical

  9. A study of multiple access schemes in satellite control network

    NASA Astrophysics Data System (ADS)

    Mo, Zijian; Wang, Zhonghai; Xiang, Xingyu; Wang, Gang; Chen, Genshe; Nguyen, Tien; Pham, Khanh; Blasch, Erik

    2016-05-01

    Satellite Control Networks (SCN) have provided launch control for space lift vehicles; tracking, telemetry and commanding (TTC) for on-orbit satellites; and, test support for space experiments since the 1960s. Currently, SCNs encounter a new challenge: how to maintain the high reliability of services when sharing the spectrum with emerging commercial services. To achieve this goal, the capability of multiple satellites reception is deserved as an update/modernization of SCN in the future. In this paper, we conducts an investigation of multiple access techniques in SCN scenario, e.g., frequency division multiple access (FDMA) and coded division multiple access (CDMA). First, we introduce two upgrade options of SCN based on FDMA and CDMA techniques. Correspondingly, we also provide their performance analysis, especially the system improvement in spectrum efficiency and interference mitigation. Finally, to determine the optimum upgrade option, this work uses CRISP, i.e., Cost, Risk, Installation, Supportability and Performance, as the baseline approach for a comprehensive trade study of these two options. Extensive numerical and simulation results are presented to illustrate the theoretical development.

  10. Access Control Model for Sharing Composite Electronic Health Records

    NASA Astrophysics Data System (ADS)

    Jin, Jing; Ahn, Gail-Joon; Covington, Michael J.; Zhang, Xinwen

    The adoption of electronically formatted medical records, so called Electronic Health Records (EHRs), has become extremely important in healthcare systems to enable the exchange of medical information among stakeholders. An EHR generally consists of data with different types and sensitivity degrees which must be selectively shared based on the need-to-know principle. Security mechanisms are required to guarantee that only authorized users have access to specific portions of such critical record for legitimate purposes. In this paper, we propose a novel approach for modelling access control scheme for composite EHRs. Our model formulates the semantics and structural composition of an EHR document, from which we introduce a notion of authorized zones of the composite EHR at different granularity levels, taking into consideration of several important criteria such as data types, intended purposes and information sensitivities.

  11. What percentage of the oceanic mixed layer is accessible to marine Lidar? Global and the Gulf of Mexico prospective.

    PubMed

    Bogucki, D J; Spiers, G

    2013-10-07

    The oceanic mixed layer is a nearly homogenous region of the upper ocean which, in principle, has a little or no variation in turbulence strength, temperature or density with depth. This layer mediates oceanic fluxes of gas, momentum and heat. Here, based on the chosen marine Lidar system, we have carried out estimates of the depth penetration of the Lidar when compared to the local mixed layer depth. On average, we have found that at least 50% of the global oceanic mixed layer depth is accessible to the Lidar observations. When operating in a single scattering mode, which is more attenuating but more amenable to analysis, the modeled Lidar was found to access 0.4 of global mixed layer depth in half of the cases. The single scattering Lidar was found to access a large fraction of the equatorial mixed layer - a region very important when addressing global climatic issues. In a coastal environment such as the Gulf of Mexico the single scattering Lidar was found to penetrate upper half of the mixed layer, underscoring the potential for Lidar to address environmental issues there.

  12. Distributed joint power and access control algorithm for secondary spectrum sharing

    NASA Astrophysics Data System (ADS)

    Li, Hongyan; Chen, Enqing; Fu, Hongliang

    2010-08-01

    Based on interference temperature model, the problem of efficient secondary spectrum sharing is formulated as a power optimization problem with some constraints at physical layer. These constraints and optimization objective limit a feasible power vector set which leads to the need of access control besides power control. In this paper, we consider the decentralized cognitive radio network scenario where short-term data service is required, and the problem of distributed joint power and access control is studied to maximize the total secondary system throughput, subject to Quality of Service (QoS) constraints from individual secondary users and interference temperature limit (ITL) from primary system. Firstly, a pricing-based game model was used to solve distributed power allocation optimization problem in both high and low signal to interference noise ratio (SINR) scenarios. Secondly, when not all the secondary links can be supported with their QoS requirement and ITL, a distributed joint power and access control algorithm was introduced to find the allowable links which results in maximum network throughput with all the constraints satisfied, and the convergence performance is tested by simulations.

  13. 30 CFR 817.66 - Use of explosives: Blasting signs, warnings, and access control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... notification required in § 817.64(a). (c) Access control. Access within the blasting areas shall be controlled..., and access control. 817.66 Section 817.66 Mineral Resources OFFICE OF SURFACE MINING RECLAMATION AND... control. (a) Blasting signs. Blasting signs shall meet the specifications of § 817.11. The operator...

  14. Cross-Layer Adaptive Feedback Scheduling of Wireless Control Systems

    PubMed Central

    Xia, Feng; Ma, Longhua; Peng, Chen; Sun, Youxian; Dong, Jinxiang

    2008-01-01

    There is a trend towards using wireless technologies in networked control systems. However, the adverse properties of the radio channels make it difficult to design and implement control systems in wireless environments. To attack the uncertainty in available communication resources in wireless control systems closed over WLAN, a cross-layer adaptive feedback scheduling (CLAFS) scheme is developed, which takes advantage of the co-design of control and wireless communications. By exploiting cross-layer design, CLAFS adjusts the sampling periods of control systems at the application layer based on information about deadline miss ratio and transmission rate from the physical layer. Within the framework of feedback scheduling, the control performance is maximized through controlling the deadline miss ratio. Key design parameters of the feedback scheduler are adapted to dynamic changes in the channel condition. An event-driven invocation mechanism for the feedback scheduler is also developed. Simulation results show that the proposed approach is efficient in dealing with channel capacity variations and noise interference, thus providing an enabling technology for control over WLAN. PMID:27879934

  15. Privacy and Access Control for IHE-Based Systems

    NASA Astrophysics Data System (ADS)

    Katt, Basel; Breu, Ruth; Hafner, Micahel; Schabetsberger, Thomas; Mair, Richard; Wozak, Florian

    Electronic Health Record (EHR) is the heart element of any e-health system, which aims at improving the quality and efficiency of healthcare through the use of information and communication technologies. The sensitivity of the data contained in the health record poses a great challenge to security. In this paper we propose a security architecture for EHR systems that are conform with IHE profiles. In this architecture we are tackling the problems of access control and privacy. Furthermore, a prototypical implementation of the proposed model is presented.

  16. Efficient identity management and access control in cloud environment

    NASA Astrophysics Data System (ADS)

    Gloster, Jonathan

    2013-05-01

    As more enterprises are enticed to move data to a cloud environment to enhance data sharing and reduce operating costs by exploiting shared resources, concerns have risen over the ability to secure information within the cloud. This paper examines how a traditional Identity and Access Control (IDAM) architecture can be adapted to address security concerns of a cloud environment. We propose changing the paradigm of IDAM form a pure trust model to a risk based model will enable information to be protected securely in a cloud environment without impacting efficiencies of cloud environments.

  17. Ionization behavior, stoichiometry of association, and accessibility of functional groups in the active layers of reverse osmosis and nanofiltration membranes.

    PubMed

    Coronell, Orlando; González, Mari I; Mariñas, Benito J; Cahill, David G

    2010-09-01

    We characterized the fully aromatic polyamide (PA) active layers of six commercial reverse osmosis (RO) and nanofiltration (NF) membranes and found that in contrast to their similar elemental composition, total concentration of functional groups, and degree of polymerization, the ionization behavior and spatial distribution of carboxylic (R-COOH) groups within the active layers can be significantly different. We also studied the steric effects experienced by barium ion (Ba2+) in the active layers by determining the fraction of carboxylate (R-COO-) groups accessible to Ba2+; such fraction, referred to as the accessibility ratio (AR), was found to vary within the range AR=0.40-0.81, and to be generally independent of external solution pH. Additionally, we studied an NF membrane with a sulfonated polyethersulfone (SPES) active layer, and found that the concentration of sulfonate (R-SO3-) groups in the active layer was 1.67 M, independent of external solution pH and approximately three times higher than the maximum concentration (approximately 0.45+/-0.25 M) of R-COO- groups in PA active layers. The R-SO3- groups were found to be highly accessible to Ba2+ (AR=0.95+/-0.01).

  18. Controllable preparation of multishelled NiO hollow nanospheres via layer-by-layer self-assembly for supercapacitor application

    NASA Astrophysics Data System (ADS)

    Yang, Zeheng; Xu, Feifei; Zhang, Weixin; Mei, Zhousheng; Pei, Bo; Zhu, Xiao

    2014-01-01

    In this work, we demonstrate a facile layer-by-layer (LBL) self-assembly method for controllable preparation of single-, double-, and triple-shelled NiO hollow nanospheres by calcining Ni(OH)2/C precursors formed at different stage. It is observed that the external nanoflakes of the NiO hollow nanospheres are inherited from the Ni(OH)2 precursors organized on the surface of carbon spheres via a self-assembly growth process and the inner shells result from the formation of different Ni(OH)2 layers within the carbon spheres during different preparation cycles. Supercapacitive performance of the three types of NiO hollow nanospheres as active electrode materials has been evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge. The results indicate that double-shelled NiO hollow nanosphere sample with largest surface area (92.99 m2 g-1) exhibits the best electrochemical properties among the three NiO hollow nanosphere samples. It delivers a high capacitance of 612.5 F g-1 at 0.5 A g-1 and demonstrates a superior long-term cyclic stability, with over 90% specific capacitance retention after 1000 charge-discharge cycles. This excellent performance is ascribed to the short diffusion path and large surface area of the unique hollow structure with nanoflake building blocks for bulk accessibility of faradaic reaction.

  19. Accessibility

    EPA Pesticide Factsheets

    Federal laws, including Section 508 of the Rehabilitation Act, mandate that people with disabilities have access to the same information that someone without a disability would have. 508 standards cover electronic and information technology (EIT) products.

  20. 76 FR 67019 - Tenth Meeting: RTCA Special Committee 224, Airport Security Access Control

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-28

    ... Federal Aviation Administration Tenth Meeting: RTCA Special Committee 224, Airport Security Access Control... RTCA Special Committee 224, Airport Security Access Control. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224, Airport Security Access Control. DATES:...

  1. Use of ultrasonics in shear layer cavitation control.

    PubMed

    Chatterjee, Dhiman

    2003-08-01

    In this paper we report results from some investigations on the use of ultrasonics in controlling hydrodynamic cavitation in the shear layer downstream of a sudden expansion. Control of this type of cavitation has been achieved by modulating the local pressure that was experienced by a nucleus present in the shear layer. This modulation was made possible by using a piezoelectric device, termed as Ultrasonic Pressure Modulator (UPM). The performance of UPM has been studied at different dissolved gas concentrations with electrolysis bubbles as nuclei. Control of cavitation due to natural nuclei has also been attempted. Efficiency of UPM, in reducing cavitation, was seen to be dependent on the driving frequency employed. Experimental and numerical studies have been conducted to bring out the physics behind this approach of cavitation control. Different measures of cavitation control have been identified and some possible applications of this method have also been outlined.

  2. BIOPACK: the ground controlled late access biological research facility.

    PubMed

    van Loon, Jack J W A

    2004-03-01

    Future Space Shuttle flights shall be characterized by activities necessary to further build the International Space Station, ISS. During these missions limited resources are available to conduct biological experiments in space. The Shuttles' Middeck is a very suitable place to conduct science during the ISS assembly missions or dedicated science missions. The BIOPACK, which flew its first mission during the STS-107, provides a versatile Middeck Locker based research tool for gravitational biology studies. The core facility occupies the space of only two Middeck Lockers. Experiment temperatures are controlled for bacteria, plant, invertebrate and mammalian cultures. Gravity levels and profiles can be set ranging from 0 to 2.0 x g on three independent centrifuges. This provides the experimenter with a 1.0 x g on-board reference and intermediate hypogravity and hypergravity data points to investigate e.g. threshold levels in biological responses. Temperature sensitive items can be stored in the facilities' -10 degrees C and +4 degrees C stowage areas. During STS-107 the facility also included a small glovebox (GBX) and passive temperature controlled units (PTCU). The GBX provides the experimenter with two extra levels of containment for safe sample handling. This biological research facility is a late access (L-10 hrs) laboratory, which, when reaching orbit, could automatically be starting up reducing important experiment lag-time and valuable crew time. The system is completely telecommanded when needed. During flight system parameters like temperatures, centrifuge speeds, experiment commanding or sensor readouts can be monitored and changed when needed. Although ISS provides a wide range of research facilities there is still need for an STS-based late access facility such as the BIOPACK providing experimenters with a very versatile research cabinet for biological experiments under microgravity and in-flight control conditions.

  3. Focus control budget analysis for critical layers of flash devices

    NASA Astrophysics Data System (ADS)

    Jang, Jong Hoon; Park, Tony; Park, Kyeong Dong; Hwang, Jong Hyun; Choi, Jin Phil; Kang, Young Seog

    2014-04-01

    As design rule shrinks down, on-product focus control became more important since available depth of focus (DOF) is getting narrower and also required critical dimension uniformity (CDU) becomes tighter. Thus monitoring, control the scanner focus error and reducing the focus control budget of scanner are essential for the production. There are some critical layers which has so narrow DOF margin that hardly be processed on old model scanners. Our study mainly focused on the analysis of the scanner focus control budget of such layers. Among the contributors to the focus budget, inter-field focus uniformity was turned out to be the most dominant. Leveling accuracy and intra-field focus uniformity were also dominant.

  4. Optimal control of wind turbines in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Yilmaz, Ali Emre; Meyers, Johan

    2016-11-01

    In recent years, optimal control theory was combined with large-eddy simulations to study the optimal control of wind farms and their interaction with the atmospheric boundary layer. The individual turbine's induction factors were dynamically controlled in time with the aim of increasing overall power extraction. In these studies, wind turbines were represented using an actuator disk method. In the current work, we focus on optimal control on a much finer mesh (and a smaller computational domain), representing turbines with an actuator line method. Similar to Refs., optimization is performed using a gradient-based method, and gradients are obtained employing an adjoint formulation. Different cases are investigated, that include a single and a double turbine case both with uniform inflow, and with turbulent-boundary-layer inflow. The authors acknowledge support from the European Research Council (FP7-Ideas, Grant No. 306471).

  5. First Experiences Using XACML for Access Control in Distributed Systems

    NASA Technical Reports Server (NTRS)

    Lorch, Marcus; Proctor, Seth; Lepro, Rebekah; Kafura, Dennis; Shah, Sumit

    2003-01-01

    Authorization systems today are increasingly complex. They span domains of administration, rely on many different authentication sources, and manage permissions that can be as complex as the system itself. Worse still, while there are many standards that define authentication mechanisms, the standards that address authorization are less well defined and tend to work only within homogeneous systems. This paper presents XACML, a standard access control language, as one component of a distributed and inter-operable authorization framework. Several emerging systems which incorporate XACML are discussed. These discussions illustrate how authorization can be deployed in distributed, decentralized systems. Finally, some new and future topics are presented to show where this work is heading and how it will help connect the general components of an authorization system.

  6. A Framework for Context Sensitive Risk-Based Access Control in Medical Information Systems.

    PubMed

    Choi, Donghee; Kim, Dohoon; Park, Seog

    2015-01-01

    Since the access control environment has changed and the threat of insider information leakage has come to the fore, studies on risk-based access control models that decide access permissions dynamically have been conducted vigorously. Medical information systems should protect sensitive data such as medical information from insider threat and enable dynamic access control depending on the context such as life-threatening emergencies. In this paper, we suggest an approach and framework for context sensitive risk-based access control suitable for medical information systems. This approach categorizes context information, estimating and applying risk through context- and treatment-based permission profiling and specifications by expanding the eXtensible Access Control Markup Language (XACML) to apply risk. The proposed framework supports quick responses to medical situations and prevents unnecessary insider data access through dynamic access authorization decisions in accordance with the severity of the context and treatment.

  7. Energy management and multi-layer control of networked microgrids

    NASA Astrophysics Data System (ADS)

    Zamora, Ramon

    Networked microgrids is a group of neighboring microgrids that has ability to interchange power when required in order to increase reliability and resiliency. Networked microgrid can operate in different possible configurations including: islanded microgrid, a grid-connected microgrid without a tie-line converter, a grid-connected microgrid with a tie-line converter, and networked microgrids. These possible configurations and specific characteristics of renewable energy offer challenges in designing control and management algorithms for voltage, frequency and power in all possible operating scenarios. In this work, control algorithm is designed based on large-signal model that enables microgrid to operate in wide range of operating points. A combination between PI controller and feed-forward measured system responses will compensate for the changes in operating points. The control architecture developed in this work has multi-layers and the outer layer is slower than the inner layer in time response. The main responsibility of the designed controls are to regulate voltage magnitude and frequency, as well as output power of the DG(s). These local controls also integrate with a microgrid level energy management system or microgrid central controller (MGCC) for power and energy balance for. the entire microgrid in islanded, grid-connected, or networked microgid mode. The MGCC is responsible to coordinate the lower level controls to have reliable and resilient operation. In case of communication network failure, the decentralized energy management will operate locally and will activate droop control. Simulation results indicate the superiority of designed control algorithms compared to existing ones.

  8. Vibration control of cylindrical shells using active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Ray, Manas C.; Chen, Tung-Huei; Baz, Amr M.

    1997-05-01

    The fundamentals of controlling the structural vibration of cylindrical shells treated with active constrained layer damping (ACLD) treatments are presented. The effectiveness of the ACLD treatments in enhancing the damping characteristics of thin cylindrical shells is demonstrated theoretically and experimentally. A finite element model (FEM) is developed to describe the dynamic interaction between the shells and the ACLD treatments. The FEM is used to predict the natural frequencies and the modal loss factors of shells which are partially treated with patches of the ACLD treatments. The predictions of the FEM are validated experimentally using stainless steel cylinders which are 20.32 cm in diameter, 30.4 cm in length and 0.05 cm in thickness. The cylinders are treated with ACLD patches of different configurations in order to target single or multi-modes of lobar vibrations. The ACLD patches used are made of DYAD 606 visco-elastic layer which is sandwiched between two layers of PVDF piezo-electric films. Vibration attenuations of 85% are obtained with maximum control voltage of 40 volts. Such attenuations are attributed to the effectiveness of the ACLD treatment in increasing the modal damping ratios by about a factor of four over those of conventional passive constrained layer damping (PCLD) treatments. The obtained results suggest the potential of the ACLD treatments in controlling the vibration of cylindrical shells which constitute the major building block of many critical structures such as cabins of aircrafts, hulls of submarines and bodies of rockets and missiles.

  9. Dynamic access control model for privacy preserving personalized healthcare in cloud environment.

    PubMed

    Son, Jiseong; Kim, Jeong-Dong; Na, Hong-Seok; Baik, Doo-Kwon

    2015-01-01

    When sharing and storing healthcare data in a cloud environment, access control is a central issue for preserving data privacy as a patient's personal health data may be accessed without permission from many stakeholders. Specifically, dynamic authorization for the access of data is required because personal health data is stored in cloud storage via wearable devices. Therefore, we propose a dynamic access control model for preserving the privacy of personal healthcare data in a cloud environment. The proposed model considers context information for dynamic access. According to the proposed model, access control can be dynamically determined by changing the context information; this means that even for a subject with the same role in the cloud, access permission is defined differently depending on the context information and access condition. Furthermore, we experiment the ability of the proposed model to provide correct responses by representing a dynamic access decision with real-life personalized healthcare system scenarios.

  10. 75 FR 69791 - Risk Management Controls for Brokers or Dealers With Market Access

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-15

    ... CFR Part 240 Risk Management Controls for Brokers or Dealers With Market Access; Final Rule #0;#0... 3235-AK53 Risk Management Controls for Brokers or Dealers With Market Access AGENCY: Securities and... alternative trading system (``ATS''), including those providing sponsored or direct market access to...

  11. 75 FR 4007 - Risk Management Controls for Brokers or Dealers With Market Access

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-26

    ... COMMISSION 17 CFR Part 240 RIN 3235-AK53 Risk Management Controls for Brokers or Dealers With Market Access... market access to customers or other persons, to implement risk management controls and supervisory... growing popularity of sponsored or direct market access arrangements where broker-dealers allow...

  12. 78 FR 31627 - Twenty-Second Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-24

    ...: RTCA Special Committee 224, Airport Security Access Control Systems AGENCY: Federal Aviation... 224, Airport Security Access Control Systems. SUMMARY: The FAA is issuing this notice to advise the public of the twenty-second meeting of the RTCA Special Committee 224, Airport Security Access...

  13. 75 FR 80886 - Third Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-23

    ... Federal Aviation Administration Third Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  14. 78 FR 43963 - Twenty-Third Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-22

    ... Federal Aviation Administration Twenty-Third Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held on June 20,...

  15. 76 FR 59481 - Ninth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-26

    ... TRANSPORTATION Federal Aviation Administration Ninth Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access Control...

  16. 77 FR 64838 - Sixteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-23

    ... Federal Aviation Administration Sixteenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held November 15,...

  17. 78 FR 16757 - Twentieth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-18

    ... Federal Aviation Administration Twentieth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held April 4, 2013 from...

  18. 77 FR 15448 - Twelfth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-15

    ... Federal Aviation Administration Twelfth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Notice of meeting RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... 224, Airport Security Access Control Systems DATES: The meeting will be held April 5, 2012, from 10...

  19. 78 FR 22025 - Twenty First Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-12

    ... Federal Aviation Administration Twenty First Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held April 9-10,...

  20. 77 FR 71474 - Seventeenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-30

    ... Federal Aviation Administration Seventeenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held December 13,...

  1. 77 FR 55894 - Fifteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-11

    ... Federal Aviation Administration Fifteenth Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems DATES: The meeting will be held September 27-28,...

  2. 77 FR 2343 - Eleventh Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-17

    ... Federal Aviation Administration Eleventh Meeting: RTCA Special Committee 224, Airport Security Access...). ACTION: Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY: The FAA..., Airport Security Access Control Systems. DATES: The meeting will be held February 9, 2012, from 10...

  3. 76 FR 16470 - Sixth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... Federal Aviation Administration Sixth Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  4. 76 FR 9632 - Fifth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-18

    ... Federal Aviation Administration Fifth Meeting: RTCA Special Committee 224: Airport Security Access Control... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access...

  5. Accessibility and ion exchange stoichiometry of ionized carboxylic groups in the active layer of FT30 reverse osmosis membrane.

    PubMed

    Coronell, Orlando; Mariñas, Benito I; Cahill, David G

    2009-07-01

    We have experimentally determined the concentration of Ba2+ that associates with the accessible ionized R-COO- groups in the polyamide active layer of the FT30 reverse osmosis membrane in the pH range 3.42-10.30. Ba2+ concentrations in the active layer ([Ba2+]) were measured using the ion-probing/Rutherford backscattering spectrometry procedure reported in our previous work. We found that at all but the lowest experimental pH 3.42, [Ba2+] was lower than the corresponding total concentrations of R-COO- groups; their difference was consistent with steric and charge effects determining the accessibility and association, respectively, of Ba2+ to R-COO- groups. Accordingly, we propose two descriptors, the accessibility ratio (AR) and the neutralization number (NN), to account for the observed difference. AR, the fraction of R-COO- groups accessible to Ba2+ ions, and NN, the average number of R-COO- groups neutralized per Ba2+ ion, were determined experimentally performing Ag(+)-Ba2+ ion-exchange tests. The resulting AR = 0.40 indicated that on average only 40% of ionizable carboxylic groups were accessible to Ba2+. [Ba2+] values calculated using R-COO- concentrations and the AR and NN concepts were in agreement with experimental [Ba2+] results.

  6. Breaking and Fixing Origin-Based Access Control in Hybrid Web/Mobile Application Frameworks

    PubMed Central

    Georgiev, Martin; Jana, Suman; Shmatikov, Vitaly

    2014-01-01

    Hybrid mobile applications (apps) combine the features of Web applications and “native” mobile apps. Like Web applications, they are implemented in portable, platform-independent languages such as HTML and JavaScript. Like native apps, they have direct access to local device resources—file system, location, camera, contacts, etc. Hybrid apps are typically developed using hybrid application frameworks such as PhoneGap. The purpose of the framework is twofold. First, it provides an embedded Web browser (for example, WebView on Android) that executes the app's Web code. Second, it supplies “bridges” that allow Web code to escape the browser and access local resources on the device. We analyze the software stack created by hybrid frameworks and demonstrate that it does not properly compose the access-control policies governing Web code and local code, respectively. Web code is governed by the same origin policy, whereas local code is governed by the access-control policy of the operating system (for example, user-granted permissions in Android). The bridges added by the framework to the browser have the same local access rights as the entire application, but are not correctly protected by the same origin policy. This opens the door to fracking attacks, which allow foreign-origin Web content included into a hybrid app (e.g., ads confined in iframes) to drill through the layers and directly access device resources. Fracking vulnerabilities are generic: they affect all hybrid frameworks, all embedded Web browsers, all bridge mechanisms, and all platforms on which these frameworks are deployed. We study the prevalence of fracking vulnerabilities in free Android apps based on the PhoneGap framework. Each vulnerability exposes sensitive local resources—the ability to read and write contacts list, local files, etc.—to dozens of potentially malicious Web domains. We also analyze the defenses deployed by hybrid frameworks to prevent resource access by foreign

  7. Breaking and Fixing Origin-Based Access Control in Hybrid Web/Mobile Application Frameworks.

    PubMed

    Georgiev, Martin; Jana, Suman; Shmatikov, Vitaly

    2014-02-01

    Hybrid mobile applications (apps) combine the features of Web applications and "native" mobile apps. Like Web applications, they are implemented in portable, platform-independent languages such as HTML and JavaScript. Like native apps, they have direct access to local device resources-file system, location, camera, contacts, etc. Hybrid apps are typically developed using hybrid application frameworks such as PhoneGap. The purpose of the framework is twofold. First, it provides an embedded Web browser (for example, WebView on Android) that executes the app's Web code. Second, it supplies "bridges" that allow Web code to escape the browser and access local resources on the device. We analyze the software stack created by hybrid frameworks and demonstrate that it does not properly compose the access-control policies governing Web code and local code, respectively. Web code is governed by the same origin policy, whereas local code is governed by the access-control policy of the operating system (for example, user-granted permissions in Android). The bridges added by the framework to the browser have the same local access rights as the entire application, but are not correctly protected by the same origin policy. This opens the door to fracking attacks, which allow foreign-origin Web content included into a hybrid app (e.g., ads confined in iframes) to drill through the layers and directly access device resources. Fracking vulnerabilities are generic: they affect all hybrid frameworks, all embedded Web browsers, all bridge mechanisms, and all platforms on which these frameworks are deployed. We study the prevalence of fracking vulnerabilities in free Android apps based on the PhoneGap framework. Each vulnerability exposes sensitive local resources-the ability to read and write contacts list, local files, etc.-to dozens of potentially malicious Web domains. We also analyze the defenses deployed by hybrid frameworks to prevent resource access by foreign-origin Web content

  8. Turbulent boundary-layer control with plasma actuators.

    PubMed

    Choi, Kwing-So; Jukes, Timothy; Whalley, Richard

    2011-04-13

    This paper reviews turbulent boundary-layer control strategies for skin-friction reduction of aerodynamic bodies. The focus is placed on the drag-reduction mechanisms by two flow control techniques-spanwise oscillation and spanwise travelling wave, which were demonstrated to give up to 45 per cent skin-friction reductions. We show that these techniques can be implemented by dielectric-barrier discharge plasma actuators, which are electric devices that do not require any moving parts or complicated ducting. The experimental results show different modifications to the near-wall structures depending on the control technique.

  9. Layer-controlled precise fabrication of ultrathin MoS2 films by atomic layer deposition.

    PubMed

    Liu, Lei; Huang, Yazhou; Sha, Jingjie; Chen, Yunfei

    2017-03-21

    Monolayer and/or atomically thin transition metal dichalcogenides cover a wide range of two-dimensional (2-D) materials, whose fascinating semiconducting and optical properties have made them being promising candidate materials for optoelectronic device. Controllable growth of these materials is critical for their device applications. By using MoCl5 and H2S as precursors, monolayer and ultrathin molybdenum disulfide (MoS2) films with controlled lamellar structure have been directly built layer by layer on SiO2 substrates without followed high-temperature annealing. Furthermore, the thickness of MoS2 films can be precisely regulated by applying different ALD cycles. Once an ALD cycle is applied, one molecular layer of MoS2 material will be "added" on substrate or original existing MoS2 films. At the initial stage (1 to 3 ALD cycles), the density of MoS2 materials increases with ALD cycle increasing, while large area of continuous MoS2 film on the substrate can be obtained when 4 or more ALD cycles are applied. By this way, excellent triangular crystal of MoS2 with controlled atomic size in thickness and highly oriented hexagonal crystal structure can be obtained by applying definite ALD cycles.

  10. Arctic layer salinity controls heat loss from deep Atlantic layer in seasonally ice-covered areas of the Barents Sea

    NASA Astrophysics Data System (ADS)

    Lind, Sigrid; Ingvaldsen, Randi B.; Furevik, Tore

    2016-05-01

    In the seasonally ice-covered northern Barents Sea an intermediate layer of cold and relatively fresh Arctic Water at ~25-110 m depth isolates the sea surface and ice cover from a layer of warm and saline Atlantic Water below, a situation that resembles the cold halocline layer in the Eurasian Basin. The upward heat flux from the Atlantic layer is of major concern. What causes variations in the heat flux and how is the Arctic layer maintained? Using observations, we found that interannual variability in Arctic layer salinity determines the heat flux from the Atlantic layer through its control of stratification and vertical mixing. A relatively fresh Arctic layer effectively suppresses the upward heat flux, while a more saline Arctic layer enhances the heat flux. The corresponding upward salt flux causes a positive feedback. The Arctic layer salinity and the water column structures have been remarkably stable during 1970-2011.

  11. [Co/Ni]-CoFeB hybrid free layer stack materials for high density magnetic random access memory applications

    NASA Astrophysics Data System (ADS)

    Liu, E.; Swerts, J.; Couet, S.; Mertens, S.; Tomczak, Y.; Lin, T.; Spampinato, V.; Franquet, A.; Van Elshocht, S.; Kar, G.; Furnemont, A.; De Boeck, J.

    2016-03-01

    Alternative free layer materials with high perpendicular anisotropy are researched to provide spin-transfer-torque magnetic random access memory stacks' sufficient thermal stability at critical dimensions of 20 nm and below. We demonstrate a high tunnel magetoresistance (TMR) MgO-based magnetic tunnel junction stack with a hybrid free layer design made of a [Co/Ni] multilayer and CoFeB. The seed material on which the [Co/Ni] multilayer is deposited determines its switching characteristics. When deposited on a Pt seed layer, soft magnetic switching behavior with high squareness is obtained. When deposited on a NiCr seed, the perpendicular anisotropy remains high, but the squareness is low and coercivity exceeds 1000 Oe. Interdiffusion of the seed material with the [Co/Ni] multilayers is found to be responsible for the different switching characteristics. In optimized stacks, a TMR of 165% and low resistance-area (RA) product of 7.0 Ω μm2 are attained for free layers with an effective perpendicular magnetic anisotropy energy of 1.25 erg/cm2, which suggests that the hybrid free layer materials may be a viable candidate for high density magnetic random access memory applications.

  12. Service Independent Access Control Architecture for User Generated Content (UGC) and Its Implementation

    NASA Astrophysics Data System (ADS)

    Yamada, Akira; Kubota, Ayumu; Miyake, Yutaka; Hashimoto, Kazuo

    Using Web-based content management systems such as Blog, an end user can easily publish User Generated Content (UGC). Although publishing of UGCs is easy, controlling access to them is a difficult problem for end users. Currently, most of Blog sites offer no access control mechanism, and even when it is available to users, it is not sufficient to control users who do not have an account at the site, not to mention that it cannot control accesses to content hosted by other UGC sites. In this paper, we propose new access control architecture for UGC, in which third party entities can offer access control mechanism to users independently of UGC hosting sites. With this architecture, a user can control accesses to his content that might be spread over many different UGC sites, regardless of whether those sites have access control mechanism or not. The key idea to separate access control mechanism from UGC sites is to apply cryptographic access control and we implemented the idea in such a way that it requires no modification to UGC sites and Web browsers. Our prototype implementation shows that the proposed access control architecture can be easily deployed in the current Web-based communication environment and it works quite well with popular Blog sites.

  13. Transverse jet shear layer instabilities and their control

    NASA Astrophysics Data System (ADS)

    Karagozian, Ann

    2013-11-01

    The jet in crossflow, or transverse jet, is a canonical flowfield that has relevance to engineering systems ranging from dilution jets and film cooling for gas turbine engines to thrust vector control and fuel injection in high speed aerospace vehicles to environmental control of effluent from chimney and smokestack plumes. Over the years, our UCLA Energy and Propulsion Research Lab's studies on this flowfield have focused on the dynamics of the vorticity associated with equidensity and variable density jets in crossflow, including the stability characteristics of the jet's upstream shear layer. A range of different experimental diagnostics have been used to study the jet's upstream shear layer, whereby a transition from convectively unstable behavior at high jet-to-crossflow momentum flux ratios to absolutely unstable flow at low momentum flux and/or density ratios is identified. These differences in shear layer stability characteristics have a profound effect on how one employs external excitation to control jet penetration, spread, and mixing, depending on the flow regime and specific engineering application. These control strategies, and challenges for future research directions, will be identified in this presentation.

  14. Passive hypervelocity boundary layer control using an ultrasonically absorptive surface

    NASA Astrophysics Data System (ADS)

    Rasheed, Adam

    A series of exploratory boundary layer transition experiments was performed on a sharp 5.06 degree half-angle round cone at zero angle-of-attack in the T5 Hypervelocity Shock Tunnel in order to test a novel hypersonic boundary layer control scheme. Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface that would damp the second mode (Mack mode). The cone used in the experiments was constructed with a smooth surface on half the cone (to serve as a control) and an acoustically absorptive porous surface on the other half. It was instrumented with flush-mounted thermocouples to detect the transition location. Test gases investigated included nitrogen and carbon dioxide at Mach 5 with specific reservoir enthalpy ranging from 1.3 MJ/kg to 13.0 MJ/kg and reservoir pressure ranging from 9.0 MPa to 50.0 MPa. Detailed comparisons were performed to insure that previous results obtained in similar boundary layer transition experiments (on a regular smooth surface) were reproduced and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the hole size was significantly smaller than the viscous length scale.

  15. Passive hypervelocity boundary layer control using an acoustically absortive surface

    NASA Astrophysics Data System (ADS)

    Rasheed, Adam

    A series of exploratory boundary layer transition experiments was performed on a sharp 5.06 degree half-angle round cone at zero angle-of-attack in the T5 Hypervelocity Shock Tunnel in order to test a novel hypersonic boundary layer control scheme. Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface that would damp the second mode (Mack mode). The cone used in the experiments was constructed with a smooth surface on half the cone (to serve as a control) and an acoustically absorptive porous surface on the other half. It was instrumented with flush-mounted thermocouples to detect the transition location. Test gases investigated included nitrogen and carbon dioxide at M = 5 with specific reservoir enthalpy ranging from 1.3 MJ/kg to 13.0 MJ/kg and reservoir pressure ranging from 9.0 MPa to 50.0 MPa. Detailed comparisons were performed to insure that previous results obtained in similar boundary layer transition experiments (on a regular smooth surface) were reproduced and the results were extended to examine the effects of the porous surface. These experiments indicated that the porous surface was highly effective in delaying transition provided that the hole size was significantly smaller than the viscous length scale.

  16. Simulation and optimal control of wind-farm boundary layers

    NASA Astrophysics Data System (ADS)

    Meyers, Johan; Goit, Jay

    2014-05-01

    In large wind farms, the effect of turbine wakes, and their interaction leads to a reduction in farm efficiency, with power generated by turbines in a farm being lower than that of a lone-standing turbine by up to 50%. In very large wind farms or `deep arrays', this efficiency loss is related to interaction of the wind farms with the planetary boundary layer, leading to lower wind speeds at turbine level. Moreover, for these cases it has been demonstrated both in simulations and wind-tunnel experiments that the wind-farm energy extraction is dominated by the vertical turbulent transport of kinetic energy from higher regions in the boundary layer towards the turbine level. In the current study, we investigate the use of optimal control techniques combined with Large-Eddy Simulations (LES) of wind-farm boundary layer interaction for the increase of total energy extraction in very large `infinite' wind farms. We consider the individual wind turbines as flow actuators, whose energy extraction can be dynamically regulated in time so as to optimally influence the turbulent flow field, maximizing the wind farm power. For the simulation of wind-farm boundary layers we use large-eddy simulations in combination with actuator-disk and actuator-line representations of wind turbines. Simulations are performed in our in-house pseudo-spectral code SP-Wind that combines Fourier-spectral discretization in horizontal directions with a fourth-order finite-volume approach in the vertical direction. For the optimal control study, we consider the dynamic control of turbine-thrust coefficients in an actuator-disk model. They represent the effect of turbine blades that can actively pitch in time, changing the lift- and drag coefficients of the turbine blades. Optimal model-predictive control (or optimal receding horizon control) is used, where the model simply consists of the full LES equations, and the time horizon is approximately 280 seconds. The optimization is performed using a

  17. Data Access, Ownership, and Control: Toward Empirical Studies of Access Practices.

    ERIC Educational Resources Information Center

    Hilgartner, Stephen; Brandt-Rauf, Sherry I.

    1994-01-01

    Examines how the new sociology of science can approach data access issues. A perspective is developed based on an analysis of the process of scientific production, data streams, and intellectual policy issues. (Contains 55 references.) (JLB)

  18. Boundary-layer-ingesting inlet flow control system

    NASA Technical Reports Server (NTRS)

    Owens, Lewis R. (Inventor); Allan, Brian G. (Inventor)

    2010-01-01

    A system for reducing distortion at the aerodynamic interface plane of a boundary-layer-ingesting inlet using a combination of active and passive flow control devices is disclosed. Active flow control jets and vortex generating vanes are used in combination to reduce distortion across a range of inlet operating conditions. Together, the vortex generating vanes can reduce most of the inlet distortion and the active flow control jets can be used at a significantly reduced control jet mass flow rate to make sure the inlet distortion stays low as the inlet mass flow rate varies. Overall inlet distortion, measured and described as average SAE circumferential distortion descriptor, was maintained at a value of 0.02 or less. Advantageous arrangements and orientations of the active flow control jets and the vortex generating vanes were developed using computational fluid dynamics simulations and wind tunnel experimentations.

  19. The role of the inserted layer in resistive random access memory device

    NASA Astrophysics Data System (ADS)

    Zhang, Dainan; Ma, Guokun; Zhang, Huaiwu; Tang, Xiaoli; Zhong, Zhiyong; Jie, Li; Su, Hua

    2016-07-01

    NiO resistive switching devices were fabricated by reactive DC magnetron sputtering at room temperature containing different inserted layers. From measurements, we demonstrated the filaments were made up by metal Co rather than the oxygen defect or other metal. A current jumping phenomenon in the SET process was observed, evidencing that the filament generating procedure was changed due to the inserted layers. In this process, we demonstrate the current jumping appeared in higher voltage region when the position of inserted layer was close to the bottom electrode. The I-V curves shifted to the positive direction as the thickness of inserted layer increasing. With the change of the number of inserted layers, SET voltages varied while the RESET voltage kept stable. According to the electrochemical metallization memory mechanism, detailed explanations on all the phenomena were addressed. This discovery is supposed of great potentials in the use of designing multi-layer RRAM devices.

  20. Bureau of Prisons access control system: functional and operational requirements

    NASA Astrophysics Data System (ADS)

    Janus, Michael; Carlson, Peter M.; Kane, Thomas

    1997-01-01

    The Federal Bureau of Prisons (BOP) operates 86 correctional institutions nationwide. The BOP has grown dramatically, the size of its inmate population growing from just over 41,000 inmates in 1987 to over 100,000 today. The number of BOP staff managing these facilities has grown correspondingly, more than doubling in number in the same ten year period. Technology has paid a major role in keeping up with this growth while maintaining high standards of security in BOP institutions. In an attempt to further enhance security in its institutions, the BOP has recently begun pilot testing an access control and entry system (ACES). ACES is intended to provide an automated record of very entry and exit to a correctional institution. ACES takes advantage of several methods of identifying an individual (inmate, staff or visitor) to assure that the individual exiting the institution is the same as the individual entering. The pilot test has raised a number of questions regarding the implementation of a technologically sophisticated system in a correctional institution. Questions of training, support, 'ownership,' cost effectiveness, and future potential all influence the deployment of this system. Preliminary results indicate that an adequate training and support system is essential to the performance of any sophisticated system and that other organizational issues need to be addressed before the decision to implement is made.

  1. Everywhere Access: Remote Control Software for the Internet.

    ERIC Educational Resources Information Center

    Beckett, George

    1994-01-01

    Describes a new software program called "Everywhere Access" that provides remote access to libraries' networked personal computers and that is suitable for use with the Internet. Highlights include installation; operation; security; standards issues; documentation and technical support; and potential uses and applications. (LRW)

  2. 33 CFR 105.255 - Security measures for access control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) All persons seeking unescorted access to secure areas must present their TWIC for inspection before being allowed unescorted access, in accordance with § 101.514 of this subchapter. Inspection must... screening or inspection; and (ii) Failure to consent or submit to screening or inspection will result...

  3. 10 CFR 20.1601 - Control of access to high radiation areas.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Control of access to high radiation areas. 20.1601 Section 20.1601 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1601 Control of access to high radiation areas....

  4. 10 CFR 20.1602 - Control of access to very high radiation areas.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Control of access to very high radiation areas. 20.1602 Section 20.1602 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1602 Control of access to very high radiation...

  5. 10 CFR 20.1602 - Control of access to very high radiation areas.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Control of access to very high radiation areas. 20.1602 Section 20.1602 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1602 Control of access to very high radiation...

  6. 10 CFR 20.1601 - Control of access to high radiation areas.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Control of access to high radiation areas. 20.1601 Section 20.1601 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1601 Control of access to high radiation areas....

  7. 10 CFR 20.1601 - Control of access to high radiation areas.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Control of access to high radiation areas. 20.1601 Section 20.1601 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1601 Control of access to high radiation areas....

  8. 10 CFR 20.1602 - Control of access to very high radiation areas.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Control of access to very high radiation areas. 20.1602 Section 20.1602 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1602 Control of access to very high radiation...

  9. 10 CFR 20.1602 - Control of access to very high radiation areas.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 10 Energy 1 2011-01-01 2011-01-01 false Control of access to very high radiation areas. 20.1602 Section 20.1602 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1602 Control of access to very high radiation...

  10. 10 CFR 20.1602 - Control of access to very high radiation areas.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 10 Energy 1 2014-01-01 2014-01-01 false Control of access to very high radiation areas. 20.1602 Section 20.1602 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1602 Control of access to very high radiation...

  11. 10 CFR 20.1601 - Control of access to high radiation areas.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 10 Energy 1 2013-01-01 2013-01-01 false Control of access to high radiation areas. 20.1601 Section 20.1601 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1601 Control of access to high radiation areas....

  12. 10 CFR 20.1601 - Control of access to high radiation areas.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 10 Energy 1 2012-01-01 2012-01-01 false Control of access to high radiation areas. 20.1601 Section 20.1601 Energy NUCLEAR REGULATORY COMMISSION STANDARDS FOR PROTECTION AGAINST RADIATION Control of Exposure From External Sources in Restricted Areas § 20.1601 Control of access to high radiation areas....

  13. 78 FR 7850 - Nineteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-04

    ... Control Systems AGENCY: Federal Aviation Administration (FAA), U.S. Department of Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems. SUMMARY... Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held February 21,...

  14. Broadband passive optical network media access control protocols

    NASA Astrophysics Data System (ADS)

    Quayle, Alan

    1996-11-01

    Most telecommunication operators are currently deciding on how to respond to customers' needs stimulated by the synergy between compression coding of multimedia and the emergence of broadband digital networks. This paper describes a range of broadband access architectures under consideration in the full services access network initiative. All architectures have a common requirement for a broadband ATM PON. A common broadband PON applicable to many operators increases the world-wide market for the product. With greater production volumes manufacturers' costs reduce because of the experience curve effect making broadband access systems economic.

  15. Possibilities for drag reduction by boundary layer control

    NASA Technical Reports Server (NTRS)

    Naiman, I.

    1946-01-01

    The mechanics of laminar boundary layer transition are reviewed. Drag possibilities for boundary layer control are analyzed using assumed conditions of transition Reynolds number, inlet loss, number of slots, blower efficiency, and duct losses. Although the results of such analysis are highly favorable, those obtained by experimental investigations yield conflicting results, showing only small gains, and sometimes losses. Reduction of this data indicates that there is a lower limit to the quantity of air which must be removed at the slot in order to stabilize the laminar flow. The removal of insufficient air permits transition to occur while the removal of excessive amounts of air results in high power costs, with a net drag increases. With the estimated value of flow coefficient and duct losses equal to half the dynamic pressure, drag reductions of 50% may be obtained; with twice this flow coefficient, the drag saving is reduced to 25%.

  16. Atomic Layer Deposited Oxide-Based Nanocomposite Structures with Embedded CoPtx Nanocrystals for Resistive Random Access Memory Applications.

    PubMed

    Wang, Lai-Guo; Cao, Zheng-Yi; Qian, Xu; Zhu, Lin; Cui, Da-Peng; Li, Ai-Dong; Wu, Di

    2017-02-22

    Al2O3- or HfO2-based nanocomposite structures with embedded CoPtx nanocrystals (NCs) on TiN-coated Si substrates have been prepared by combination of thermal atomic layer deposition (ALD) and plasma-enhanced ALD for resistive random access memory (RRAM) applications. The impact of CoPtx NCs and their average size/density on the resistive switching properties has been explored. Compared to the control sample without CoPtx NCs, ALD-derived Pt/oxide/100 cycle-CoPtx NCs/TiN/SiO2/Si exhibits a typical bipolar, reliable, and reproducible resistive switching behavior, such as sharp distribution of RRAM parameters, smaller set/reset voltages, stable resistance ratio (≥10(2)) of OFF/ON states, better switching endurance up to 10(4) cycles, and longer data retention over 10(5) s. The possible resistive switching mechanism based on nanocomposite structures of oxide/CoPtx NCs has been proposed. The dominant conduction mechanisms in low- and high-resistance states of oxide-based device units with embedded CoPtx NCs are Ohmic behavior and space-charge-limited current, respectively. The insertion of CoPtx NCs can effectively improve the formation of conducting filaments due to the CoPtx NC-enhanced electric field intensity. Besides excellent resistive switching performances, the nanocomposite structures also simultaneously present ferromagnetic property. This work provides a flexible pathway by combining PEALD and TALD compatible with state-of-the-art Si-based technology for multifunctional electronic devices applications containing RRAM.

  17. The Model and Control Methods of Access to Information and Technology Resources of Automated Control Systems in Water Supply Industry

    NASA Astrophysics Data System (ADS)

    Rytov, M. Yu; Spichyack, S. A.; Fedorov, V. P.; Petreshin, D. I.

    2017-01-01

    The paper describes a formalized control model of access to information and technological resources of automated control systems at water supply enterprises. The given model considers the availability of various communication links with information systems and technological equipment. There are also studied control methods of access to information and technological resources of automated control systems at water supply enterprises. On the basis of the formalized control model and appropriate methods there was developed a software-hardware complex for rapid access to information and technological resources of automated control systems, which contains an administrator’s automated workplace and ultimate users.

  18. An Experimental Study of Shock/Turbulent Boundary Layer Interactions at DNS Accessible Reynolds Numbers

    DTIC Science & Technology

    2005-05-01

    surface oil flow visualizations, contrary to expectations. The shockwave was deeply entrained in the boundary layer and was highly distorted by passing... shockwave /turbulent-boundary layer interactions combining experiments and simulations. A great deal of insight has been gained from the efforts of...scattering is used to make this distinction. The scattering signal is Doppler -shifted by an amount that depends on the angles between the camera, the

  19. Layered Protocol Analysis of a Control Display Unit

    DTIC Science & Technology

    1997-12-01

    National DW ense C n dI iDefence nationale ai LAYERED PROTOCOL ANALYSIS OF A CONTROL DISPLAY UNIT Defence and Civil INSTITUTE OF ENVIRONMENTAL...Primary node and strong disbelief (red) to the End node and 0 strong belief (blue). LEGEND first recursion second recursion third recursion O( x ) O(R( x )) O...R(O( x ))) 0 PI P2 P3 Feedback Forms * ~Srong Belief U Null I weak belief INeutral______ *InformR no opinion NODE 0 weak disbelief Strong Disbelief one

  20. Tandem Solar Cells from Accessible Low Band-Gap Polymers Using an Efficient Interconnecting Layer.

    PubMed

    Bag, Santanu; Patel, Romesh J; Bunha, Ajaykumar; Grand, Caroline; Berrigan, J Daniel; Dalton, Matthew J; Leever, Benjamin J; Reynolds, John R; Durstock, Michael F

    2016-01-13

    Tandem solar cell architectures are designed to improve device photoresponse by enabling the capture of wider range of solar spectrum as compared to single-junction device. However, the practical realization of this concept in bulk-heterojunction polymer systems requires the judicious design of a transparent interconnecting layer compatible with both polymers. Moreover, the polymers selected should be readily synthesized at large scale (>1 kg) and high performance. In this work, we demonstrate a novel tandem polymer solar cell that combines low band gap poly isoindigo [P(T3-iI)-2], which is easily synthesized in kilogram quantities, with a novel Cr/MoO3 interconnecting layer. Cr/MoO3 is shown to be greater than 80% transparent above 375 nm and an efficient interconnecting layer for P(T3-iI)-2 and PCDTBT, leading to 6% power conversion efficiencies under AM 1.5G illumination. These results serve to extend the range of interconnecting layer materials for tandem cell fabrication by establishing, for the first time, that a thin, evaporated layer of Cr/MoO3 can work as an effective interconnecting layer in a tandem polymer solar cells made with scalable photoactive materials.

  1. Nonlinear stability and control of three-dimensional boundary layers

    NASA Astrophysics Data System (ADS)

    Janke, Erik

    The linear and nonlinear evolution of steady and traveling disturbances in three-dimensional incompressible boundary layer flows is studied using Parabolized Stability Equations (PSE). Extensive primary stability analyses for the model problems of Swept Hiemenz flow and the DLR Transition experiment on a swept flat plate are performed first. Second, and building upon these results, detailed secondary instability studies based on both the classical Floquet Theory and a novel approach that uses the nonlinear PSE are conducted. The investigations reveal a connection of unstable secondary eigenvalues to both the linear eigenvalue spectrum of the undisturbed mean flow and the continuous spectrum, as well as the existence of an absolute instability in the region of nonlinear amplitude saturation. Third, a passive technique for boundary layer transition control using leading edge roughness is examined utilizing a newly developed implicit solution method for the nonlinear PSE. The results confirm experimental observations and indicate possible means of delaying transition on swept wings. In the present work, both the solution of the boundary layer equations for the mean flow and the explicit PSE solver are based on a fourth-order-accurate compact scheme formulation in body-oriented coordinates. In the secondary instability analysis, the Implicitly Restarted Arnoldi Method is applied.

  2. Control of Thermal Convection in Layered Fluids Using Magnetic fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F. W.

    2003-01-01

    Immiscible fluid layers are found in a host of applications ranging from materials processing, for example the use of encapsulants in float zone crystal growth technique and a buffer layer in industrial Czochralski growth of crystals to prevent Marangoni convection, to heat transfer phenomena in day-to-day processes like the presence of air pockets in heat exchangers. In the microgravity and space processing realm, the exploration of other planets requires the development of enabling technologies in several fronts. The reduction in the gravity level poses unique challenges for fluid handling and heat transfer applications. The present work investigates the efficacy of controlling thermal convective flow using magnetic fluids and magnetic fields. The setup is a two-layer immiscible liquids system with one of the fluids being a diluted ferrofluid (super paramagnetic nano particles dispersed in carrier fluid). Using an external magnetic field one can essentially dial in a volumetric force - gravity level, on the magnetic fluid and thereby affect the system thermo-fluid behavior. The paper will describe the experimental and numerical modeling approach to the problem and discuss results obtained to date.

  3. An effective access control approach to support mobility in IPv6 networks

    NASA Astrophysics Data System (ADS)

    Peng, Xue-hai; Lin, Chuang

    2005-11-01

    Access control is an important method to improve network security and prevent protected resources from being used by some nodes without authority. Moreover, mobility is an important trend of internet. In this paper, based on the architecture of hierarchical mobile IPv6, we proposed an effective access control approach to support mobility in IPv6 networks, which can ensure the operation of access control when a mobile node roams in these domains with different polices, with decreased delay of access negotiation and cost of delivering messages.

  4. Active Flow Control on a Boundary-Layer-Ingesting Inlet

    NASA Technical Reports Server (NTRS)

    Gorton, Susan Althoff; Owens, Lewis R.; Jenkins, Luther N.; Allan, Brian G.; Schuster, Ernest P.

    2004-01-01

    Boundary layer ingestion (BLI) is explored as means to improve overall system performance for Blended Wing Body configuration. The benefits of BLI for vehicle system performance benefit are assessed with a process derived from first principles suitable for highly-integrated propulsion systems. This performance evaluation process provides framework within which to assess the benefits of an integrated BLI inlet and lays the groundwork for higher-fidelity systems studies. The results of the system study show that BLI provides a significant improvement in vehicle performance if the inlet distortion can be controlled, thus encouraging the pursuit of active flow control (AFC) as a BLI enabling technology. The effectiveness of active flow control in reducing engine inlet distortion was assessed using a 6% scale model of a 30% BLI offset, diffusing inlet. The experiment was conducted in the NASA Langley Basic Aerodynamics Research Tunnel with a model inlet designed specifically for this type of testing. High mass flow pulsing actuators provided the active flow control. Measurements were made of the onset boundary layer, the duct surface static pressures, and the mass flow through the duct and the actuators. The distortion was determined by 120 total pressure measurements located at the aerodynamic interface plane. The test matrix was limited to a maximum freestream Mach number of 0.15 with scaled mass flows through the inlet for that condition. The data show that the pulsed actuation can reduce distortion from 29% to 4.6% as measured by the circumferential distortion descriptor DC60 using less than 1% of inlet mass flow. Closed loop control of the actuation was also demonstrated using a sidewall surface static pressure as the response sensor.

  5. A Parallel Controls Software Approach for PEP II: AIDA & Matlab Middle Layer

    SciTech Connect

    Wittmer, W.; Colocho, W.; White, G.; /SLAC

    2007-11-06

    The controls software in use at PEP II (Stanford Control Program - SCP) had originally been developed in the eighties. It is very successful in routine operation but due to its internal structure it is difficult and time consuming to extend its functionality. This is problematic during machine development and when solving operational issues. Routinely, data has to be exported from the system, analyzed offline, and calculated settings have to be reimported. Since this is a manual process, it is time consuming and error-prone. Setting up automated processes, as is done for MIA (Model Independent Analysis), is also time consuming and specific to each application. Recently, there has been a trend at light sources to use MATLAB as the platform to control accelerators using a 'MATLAB Middle Layer' (MML), and so called channel access (CA) programs to communicate with the low level control system (LLCS). This has proven very successful, especially during machine development time and trouble shooting. A special CA code, named AIDA (Accelerator Independent Data Access), was developed to handle the communication between MATLAB, modern software frameworks, and the SCP. The MML had to be adapted for implementation at PEP II. Colliders differ significantly in their designs compared to light sources, which poses a challenge. PEP II is the first collider at which this implementation is being done. We will report on this effort, which is still ongoing.

  6. Separation control in a hypersonic shock wave / turbulent boundary-layer interaction

    NASA Astrophysics Data System (ADS)

    Schreyer, Anne-Marie; Bermejo-Moreno, Ivan; Kim, Jeonglae; Urzay, Javier

    2016-11-01

    Hypersonic vehicles play a key role for affordable access to space. The associated flow fields are strongly affected by shock wave/turbulent boundary-layer interactions, and the inherent separation causes flow distortion and low-frequency unsteadiness. Microramp sub-boundary layer vortex generators are a promising means to control separation and diminish associated detrimental effects. We investigate the effect of a microramp on the low-frequency unsteadiness in a fully separated interaction. A large eddy simulation of a 33 ∘ -compression-ramp interaction was performed for an inflow Mach number of 7.2 and a Reynolds number based on momentum thickness of Reθ = 3500 , matching the experiment of Schreyer et al. (2011). For the control case, we introduced a counter-rotating vortex pair, as induced by a single microramp, into the boundary layer through the inflow conditions. We applied a dynamic mode decomposition (DMD) on both cases to identify coherent structures that are responsible for the dynamic behavior. Based on the DMD, we discuss the reduction of the separation zone and the stabilization of the shock motion achieved by the microramp, and contribute to the description of the governing mechanisms. Pursued during the 2016 CTR Summer Program at Stanford University.

  7. Open access, readership, citations: a randomized controlled trial of scientific journal publishing.

    PubMed

    Davis, Philip M

    2011-07-01

    Does free access to journal articles result in greater diffusion of scientific knowledge? Using a randomized controlled trial of open access publishing, involving 36 participating journals in the sciences, social sciences, and humanities, we report on the effects of free access on article downloads and citations. Articles placed in the open access condition (n=712) received significantly more downloads and reached a broader audience within the first year, yet were cited no more frequently, nor earlier, than subscription-access control articles (n=2533) within 3 yr. These results may be explained by social stratification, a process that concentrates scientific authors at a small number of elite research universities with excellent access to the scientific literature. The real beneficiaries of open access publishing may not be the research community but communities of practice that consume, but rarely contribute to, the corpus of literature.

  8. Access control and privilege management in electronic health record: a systematic literature review.

    PubMed

    Jayabalan, Manoj; O'Daniel, Thomas

    2016-12-01

    This study presents a systematic literature review of access control for electronic health record systems to protect patient's privacy. Articles from 2006 to 2016 were extracted from the ACM Digital Library, IEEE Xplore Digital Library, Science Direct, MEDLINE, and MetaPress using broad eligibility criteria, and chosen for inclusion based on analysis of ISO22600. Cryptographic standards and methods were left outside the scope of this review. Three broad classes of models are being actively investigated and developed: access control for electronic health records, access control for interoperability, and access control for risk analysis. Traditional role-based access control models are extended with spatial, temporal, probabilistic, dynamic, and semantic aspects to capture contextual information and provide granular access control. Maintenance of audit trails and facilities for overriding normal roles to allow full access in emergency cases are common features. Access privilege frameworks utilizing ontology-based knowledge representation for defining the rules have attracted considerable interest, due to the higher level of abstraction that makes it possible to model domain knowledge and validate access requests efficiently.

  9. Tapetum and middle layer control male fertility in Actinidia deliciosa

    PubMed Central

    Falasca, Giuseppina; D'Angeli, Simone; Biasi, Rita; Fattorini, Laura; Matteucci, Maja; Canini, Antonella; Altamura, Maria Maddalena

    2013-01-01

    Background and Aims Dioecism characterizes many crop species of economic value, including kiwifruit (Actinidia deliciosa). Kiwifruit male sterility occurs at the microspore stage. The cell walls of the microspores and the pollen of the male-sterile and male-fertile flowers, respectively, differ in glucose and galactose levels. In numerous plants, pollen formation involves normal functioning and degeneration timing of the tapetum, with calcium and carbohydrates provided by the tapetum essential for male fertility. The aim of this study was to determine whether the anther wall controls male fertility in kiwifruit, providing calcium and carbohydrates to the microspores. Methods The events occurring in the anther wall and microspores of male-fertile and male-sterile anthers were investigated by analyses of light microscopy, epifluorescence, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL assay) and transmission electron microscopy coupled with electron spectroscopy. The possibility that male sterility was related to anther tissue malfunctioning with regard to calcium/glucose/galactose provision to the microspores was also investigated by in vitro anther culture. Key Results Both tapetum and the middle layer showed secretory activity and both degenerated by programmed cell death (PCD), but PCD was later in male-sterile than in male-fertile anthers. Calcium accumulated in cell walls of the middle layer and tapetum and in the exine of microspores and pollen, reaching higher levels in anther wall tissues and dead microspores of male-sterile anthers. A specific supply of glucose and calcium induced normal pollen formation in in vitro-cultured anthers of the male-sterile genotype. Conclusions The results show that male sterility in kiwifruit is induced by anther wall tissues through prolonged secretory activity caused by a delay in PCD, in the middle layer in particular. In vitro culture results support the sporophytic control of male fertility

  10. Perspectives on open access high resolution digital elevation models to produce global flood hazard layers

    NASA Astrophysics Data System (ADS)

    Sampson, Christopher; Smith, Andrew; Bates, Paul; Neal, Jeffrey; Trigg, Mark

    2015-12-01

    Global flood hazard models have recently become a reality thanks to the release of open access global digital elevation models, the development of simplified and highly efficient flow algorithms, and the steady increase in computational power. In this commentary we argue that although the availability of open access global terrain data has been critical in enabling the development of such models, the relatively poor resolution and precision of these data now limit significantly our ability to estimate flood inundation and risk for the majority of the planet's surface. The difficulty of deriving an accurate 'bare-earth' terrain model due to the interaction of vegetation and urban structures with the satellite-based remote sensors means that global terrain data are often poorest in the areas where people, property (and thus vulnerability) are most concentrated. Furthermore, the current generation of open access global terrain models are over a decade old and many large floodplains, particularly those in developing countries, have undergone significant change in this time. There is therefore a pressing need for a new generation of high resolution and high vertical precision open access global digital elevation models to allow significantly improved global flood hazard models to be developed.

  11. Single-Carrier Based Multiplexing of Layer 1/Layer 2 Control Signals in Evolved UTRA Uplink Using DFT-Spread OFDM

    NASA Astrophysics Data System (ADS)

    Kawamura, Teruo; Kishiyama, Yoshihisa; Higuchi, Kenichi; Sawahashi, Mamoru

    This paper proposes efficient single-carrier (SC) based multiplexing schemes for Layer 1 (L1)/Layer 2 (L2) control signals in SC-FDMA radio access using DFT-Spread OFDM in the Evolved UTRA uplink. L1/L2 control signals are necessary for key packet access techniques such as downlink scheduling, link adaptation, hybrid automatic repeat request (ARQ) with soft combining, and for uplink feedback control signals. We first propose a SC-based multiplexing scheme for L1/L2 control signals within a shared data channel for a set of user equipment (UE) that transmits both an uplink shared data channel and L1/L2 control signals within the same subframe. We also propose a multiplexing scheme for L1/L2 control signals without uplink data transmission that takes advantage of intra-subframe frequency hopping (FH) using multiple exclusively-assigned time-frequency resource blocks (RBs) to obtain a frequency diversity gain. Furthermore, we propose an orthogonal CDMA-based multiplexing scheme using cyclic shifts of a constant amplitude zero auto-correlation (CAZAC) sequence for L1/L2 control signals from different UEs within the same narrowband time-frequency RB. Computer simulation results show that the proposed SC-based multiplexing scheme for the L1/L2 control signals within the shared data channel achieves a higher user throughput than a multicarrier-based multiplexing scheme. The results also show that the proposed multiplexing scheme for the L1/L2 control signals that takes advantage of the intra-subframe FH for the UE without uplink data transmission achieves high quality reception through large frequency diversity gain. Furthermore, we show that the proposed cyclic-shift based orthogonal CDMA multiplexing is effective in the multiplexing of multiple L1/L2 control signals from different UEs within the same RB.

  12. 36 CFR 1256.70 - What controls access to national security-classified information?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 3 2013-07-01 2012-07-01 true What controls access to national security-classified information? 1256.70 Section 1256.70 Parks, Forests, and Public Property... controls access to national security-classified information? (a) The declassification of and public...

  13. 33 CFR 150.604 - Who controls access to medical monitoring and exposure records?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Who controls access to medical monitoring and exposure records? 150.604 Section 150.604 Navigation and Navigable Waters COAST GUARD... Health Safety and Health (general) § 150.604 Who controls access to medical monitoring and...

  14. 33 CFR 150.604 - Who controls access to medical monitoring and exposure records?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Who controls access to medical... Health Safety and Health (general) § 150.604 Who controls access to medical monitoring and exposure records? If medical monitoring is performed or exposure records are maintained by an employer, the...

  15. 75 FR 61819 - First Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-06

    ... meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this... Control Systems (Update to DO-230B): November 2, 2010 Welcome/Introductions/Administrative Remarks Agenda... Federal Aviation Administration First Meeting: RTCA Special Committee 224: Airport Security Access...

  16. 78 FR 51810 - Twenty-Fourth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-21

    ... Transportation (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control... RTCA Special Committee 224, Airport Security Access Control Systems. DATES: The meeting will be held on... TRANSPORTATION Federal Aviation Administration Twenty-Fourth Meeting: RTCA Special Committee 224,...

  17. 76 FR 50811 - Eighth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-08-16

    ... TRANSPORTATION Federal Aviation Administration Eighth Meeting: RTCA Special Committee 224: Airport Security... Committee 224 meeting: Airport Security Access Control Systems. SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport Security Access Control...

  18. 77 FR 25525 - Thirteenth Meeting: RTCA Special Committee 224, Airport Security Access Control Systems.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-30

    ... TRANSPORTATION Federal Aviation Administration Thirteenth Meeting: RTCA Special Committee 224, Airport Security... (DOT). ACTION: Meeting Notice of RTCA Special Committee 224, Airport Security Access Control Systems... Committee 224, Airport Security Access Control Systems DATES: The meeting will be held May 30, 2012, from...

  19. Controlled Fabrication of Nanoporous Oxide Layers on Zircaloy by Anodization.

    PubMed

    Park, Yang Jeong; Ha, Jun Mok; Ali, Ghafar; Kim, Hyun Jin; Addad, Yacine; Cho, Sung Oh

    2015-12-01

    We have presented a mechanism to explain why the resulting oxide morphology becomes a porous or a tubular nanostructure when a zircaloy is electrochemically anodized. A porous zirconium oxide nanostructure is always formed at an initial anodization stage, but the degree of interpore dissolution determines whether the final morphology is nanoporous or nanotubular. The interpore dissolution rate can be tuned by changing the anodization parameters such as anodization time and water content in an electrolyte. Consequently, porous or tubular oxide nanostructures can be selectively fabricated on a zircaloy surface by controlling the parameters. Based on this mechanism, zirconium oxide layers with completely nanoporous, completely nanotubular, and intermediate morphologies between a nanoporous and a nanotubular structure were controllably fabricated.

  20. Turbulent Mixing Layer Control using Ns-DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Singh, Ashish; Little, Jesse

    2016-11-01

    A low speed turbulent mixing layer (Reθo =1282, U1 /U2 = 0 . 28 and U2 = 11 . 8 m / s) is subject to nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuation. The forcing frequency corresponds to a Strouhal number (St) of 0.032 which is the most amplified frequency based on stability theory. Flow response is studied as a function of the pulse energy, the energy input time scale (carrier frequency) and the duration of actuation (duty cycle). It is found that successful actuation requires a combination of forcing parameters. An evaluation of the forcing efficacy is achieved by examining different flow quantities such as momentum thickness, vorticity and velocity fluctuations. In accordance with past work, a dependence is found between the initial shear layer thickness and the energy coupled to the flow. More complex relationships are also revealed such as a limitation on the maximum pulse energy which yields control. Also, the pulse energy and the carrier frequency (inverse of period between successive pulses) are interdependent whereby an optimum exists between them and extreme values of either parameter is inconsonant with the control desired. These observations establish a rich and complex process behind ns-DBD plasma actuation. Air Force Office of Scientific Research (FA9550-12-1-0044).

  1. 33 CFR 104.265 - Security measures for access control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... SECURITY MARITIME SECURITY MARITIME SECURITY: VESSELS Vessel Security Requirements § 104.265 Security... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Security measures for access... security measures to: (1) Deter the unauthorized introduction of dangerous substances and...

  2. 33 CFR 104.265 - Security measures for access control.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... SECURITY MARITIME SECURITY MARITIME SECURITY: VESSELS Vessel Security Requirements § 104.265 Security... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Security measures for access... security measures to: (1) Deter the unauthorized introduction of dangerous substances and...

  3. 33 CFR 104.265 - Security measures for access control.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... SECURITY MARITIME SECURITY MARITIME SECURITY: VESSELS Vessel Security Requirements § 104.265 Security... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Security measures for access... security measures to: (1) Deter the unauthorized introduction of dangerous substances and...

  4. 33 CFR 105.255 - Security measures for access control.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... SECURITY MARITIME SECURITY MARITIME SECURITY: FACILITIES Facility Security Requirements § 105.255 Security... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Security measures for access... security measures to: (1) Deter the unauthorized introduction of dangerous substances and...

  5. Computer Control of a Random Access Slide Projector.

    ERIC Educational Resources Information Center

    Barker, Philip G.

    1982-01-01

    A description of a simple interface to enable the interconnection of a random access slide projector and a microcomputer is provided, as well as summaries of the role of slide images as a means of implementing graphic communication and the new activity in graphics as an area of information processing. The microcomputer interface is then detailed,…

  6. Scalable Machine Learning Framework for Behavior-Based Access Control

    DTIC Science & Technology

    2013-08-01

    rules. Dynamic events, such as subversion of credentials (e.g., theft of a Smart Card [3] such as the Common Access Card [4]) or changes in actor... Smart card handbook. Wiley, 2010. [4] DoD ID Card Reference Center, 2013, http://www.cac.mil/ [5] Hearst, Marti A., et al. "Support vector machines

  7. Active Control of Boundary-Layer Instabilities: Use of Sensors and Spectral Controller

    NASA Technical Reports Server (NTRS)

    Joslin, R. D.; Nicolaides, R. A.; Erlebacher, G.; Hussaini, M. Y.; Gunzburger, M. D.

    1995-01-01

    Full Navier-Stokes equations were conducted to determine the feasibility of automating the control of wave instabilities within a flat plate boundary layer with sensors, actuators, and a spectral controller. The results indicate that a measure of wave cancellation can be obtained for small and large amplitude instabilities without feedback; however, feedback is required to optimize the control amplitude and phase for exact wave cancellation.

  8. Regulation of the nucleosome unwrapping rate controls DNA accessibility

    PubMed Central

    North, Justin A.; Shimko, John C.; Javaid, Sarah; Mooney, Alex M.; Shoffner, Matthew A.; Rose, Sean D.; Bundschuh, Ralf; Fishel, Richard; Ottesen, Jennifer J.; Poirier, Michael G.

    2012-01-01

    Eukaryotic genomes are repetitively wrapped into nucleosomes that then regulate access of transcription and DNA repair complexes to DNA. The mechanisms that regulate extrinsic protein interactions within nucleosomes are unresolved. We demonstrate that modulation of the nucleosome unwrapping rate regulates protein binding within nucleosomes. Histone H3 acetyl-lysine 56 [H3(K56ac)] and DNA sequence within the nucleosome entry-exit region additively influence nucleosomal DNA accessibility by increasing the unwrapping rate without impacting rewrapping. These combined epigenetic and genetic factors influence transcription factor (TF) occupancy within the nucleosome by at least one order of magnitude and enhance nucleosome disassembly by the DNA mismatch repair complex, hMSH2–hMSH6. Our results combined with the observation that ∼30% of Saccharomyces cerevisiae TF-binding sites reside in the nucleosome entry–exit region suggest that modulation of nucleosome unwrapping is a mechanism for regulating transcription and DNA repair. PMID:22965129

  9. Secure Remote Access Issues in a Control Center Environment

    NASA Technical Reports Server (NTRS)

    Pitts, Lee; McNair, Ann R. (Technical Monitor)

    2002-01-01

    The ISS finally reached an operational state and exists for local and remote users. Onboard payload systems are managed by the Huntsville Operations Support Center (HOSC). Users access HOSC systems by internet protocols in support of daily operations, preflight simulation, and test. In support of this diverse user community, a modem security architecture has been implemented. The architecture has evolved over time from an isolated but open system to a system which supports local and remote access to the ISS over broad geographic regions. This has been accomplished through the use of an evolved security strategy, PKI, and custom design. Through this paper, descriptions of the migration process and the lessons learned are presented. This will include product decision criteria, rationale, and the use of commodity products in the end architecture. This paper will also stress the need for interoperability of various products and the effects of seemingly insignificant details.

  10. Controls Over the Contractor Common Access Card Life Cycle

    DTIC Science & Technology

    2008-10-10

    Identification System SES Senior Executive Service SPOC Service Point of Contact TASM Trusted Agent Security Manager USD (AT&L) Under...the final report by October 31, 2008. 53 Finding D. Oversight of Common Access Card Sponsors DoD CVS Service Points of Contact ( SPOCs ...authorization to approve contractor CACs. Organization of CAC Application Sites Each Service agency has an SPOC who is responsible for coordinating with

  11. Passive Control of Oblique Shock/Boundary Layer Interaction

    NASA Astrophysics Data System (ADS)

    Saida, Nobumi; Tomizuka, Yoo

    This paper describes an experimental comparison of three passive approaches for controlling the shock interaction with a turbulent boundary layer. The first is the application of passive cavity (PC) by use of the slots. The effects of the slot were studied by varying the number of slots from n=2 to 8. The second is to use the vortex generators (VG). The shape of VG is a low profile triangular plow type arranged in four different types. The last method is a combination of the preceding two methods. The experiments were conducted in a 10×8 cm2 supersonic blow down wind tunnel at a free stream Mach number of 2.0. The measurements made were wall static pressures, pitot profiles, and Schlieren visualizations of the flow field. It was found that in the case of PC the pressure rises in two steps and weaken the shock strength, especially for n=8 case. For the VG arranged in coarse, the velocity profile downstream of the shock is fuller than the solid wall case. Furthermore with an appropriate combination of PC and VG, the combined method is effective in reducing the wave drag and also in suppressing the growth of the boundary layer.

  12. Proximity-based access control for context-sensitive information provision in SOA-based systems

    NASA Astrophysics Data System (ADS)

    Rajappan, Gowri; Wang, Xiaofei; Grant, Robert; Paulini, Matthew

    2014-06-01

    Service Oriented Architecture (SOA) has enabled open-architecture integration of applications within an enterprise. For net-centric Command and Control (C2), this elucidates information sharing between applications and users, a critical requirement for mission success. The Information Technology (IT) access control schemes, which arbitrate who gets access to what information, do not yet have the contextual knowledge to dynamically allow this information sharing to happen dynamically. The access control might prevent legitimate users from accessing information relevant to the current mission context, since this context may be very different from the context for which the access privileges were configured. We evaluate a pair of data relevance measures - proximity and risk - and use these as the basis of dynamic access control. Proximity is a measure of the strength of connection between the user and the resource. However, proximity is not sufficient, since some data might have a negative impact, if leaked, which far outweighs importance to the subject's mission. For this, we use a risk measure to quantify the downside of data compromise. Given these contextual measures of proximity and risk, we investigate extending Attribute-Based Access Control (ABAC), which is used by the Department of Defense, and Role-Based Access Control (RBAC), which is widely used in the civilian market, so that these standards-based access control models are given contextual knowledge to enable dynamic information sharing. Furthermore, we consider the use of such a contextual access control scheme in a SOA-based environment, in particular for net-centric C2.

  13. Controlled sound field with a dual layer loudspeaker array

    NASA Astrophysics Data System (ADS)

    Shin, Mincheol; Fazi, Filippo M.; Nelson, Philip A.; Hirono, Fabio C.

    2014-08-01

    Controlled sound interference has been extensively investigated using a prototype dual layer loudspeaker array comprised of 16 loudspeakers. Results are presented for measures of array performance such as input signal power, directivity of sound radiation and accuracy of sound reproduction resulting from the application of conventional control methods such as minimization of error in mean squared pressure, maximization of energy difference and minimization of weighted pressure error and energy. Procedures for selecting the tuning parameters have also been introduced. With these conventional concepts aimed at the production of acoustically bright and dark zones, all the control methods used require a trade-off between radiation directivity and reproduction accuracy in the bright zone. An alternative solution is proposed which can achieve better performance based on the measures presented simultaneously by inserting a low priority zone named as the “gray” zone. This involves the weighted minimization of mean-squared errors in both bright and dark zones together with the gray zone in which the minimization error is given less importance. This results in the production of directional bright zone in which the accuracy of sound reproduction is maintained with less required input power. The results of simulations and experiments are shown to be in excellent agreement.

  14. Analyzing the effect of routing protocols on media access control protocols in radio networks

    SciTech Connect

    Barrett, C. L.; Drozda, M.; Marathe, A.; Marathe, M. V.

    2002-01-01

    We study the effect of routing protocols on the performance of media access control (MAC) protocols in wireless radio networks. Three well known MAC protocols: 802.11, CSMA, and MACA are considered. Similarly three recently proposed routing protocols: AODV, DSR and LAR scheme 1 are considered. The experimental analysis was carried out using GloMoSim: a tool for simulating wireless networks. The main focus of our experiments was to study how the routing protocols affect the performance of the MAC protocols when the underlying network and traffic parameters are varied. The performance of the protocols was measured w.r.t. five important parameters: (i) number of received packets, (ii) average latency of each packet, (iii) throughput (iv) long term fairness and (v) number of control packets at the MAC layer level. Our results show that combinations of routing and MAC protocols yield varying performance under varying network topology and traffic situations. The result has an important implication; no combination of routing protocol and MAC protocol is the best over all situations. Also, the performance analysis of protocols at a given level in the protocol stack needs to be studied not locally in isolation but as a part of the complete protocol stack. A novel aspect of our work is the use of statistical technique, ANOVA (Analysis of Variance) to characterize the effect of routing protocols on MAC protocols. This technique is of independent interest and can be utilized in several other simulation and empirical studies.

  15. Fertility effects of abortion and birth control pill access for minors.

    PubMed

    Guldi, Melanie

    2008-11-01

    This article empirically assesses whether age-restricted access to abortion and the birth control pill influence minors' fertility in the United States. There is not a strong consensus in previous literature regarding the relationship between laws restricting minors' access to abortion and minors' birth rates. This is the first study to recognize that state laws in place prior to the 1973 Roe v. Wade decision enabled minors to legally consent to surgical treatment-including abortion-in some states but not in others, and to construct abortion access variables reflecting this. In this article, age-specific policy variables measure either a minor's legal ability to obtain an abortion or to obtain the birth control pill without parental involvement. I find fairly strong evidence that young women's birth rates dropped as a result of abortion access as well as evidence that birth control pill access led to a drop in birth rates among whites.

  16. 36 CFR 1256.70 - What controls access to national security-classified information?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 3 2010-07-01 2010-07-01 false What controls access to national security-classified information? 1256.70 Section 1256.70 Parks, Forests, and Public Property... HISTORICAL MATERIALS Access to Materials Containing National Security-Classified Information § 1256.70...

  17. 36 CFR 1256.70 - What controls access to national security-classified information?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... national security-classified information? 1256.70 Section 1256.70 Parks, Forests, and Public Property... HISTORICAL MATERIALS Access to Materials Containing National Security-Classified Information § 1256.70 What controls access to national security-classified information? (a) The declassification of and public...

  18. 36 CFR 1256.70 - What controls access to national security-classified information?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... national security-classified information? 1256.70 Section 1256.70 Parks, Forests, and Public Property... HISTORICAL MATERIALS Access to Materials Containing National Security-Classified Information § 1256.70 What controls access to national security-classified information? (a) The declassification of and public...

  19. 36 CFR 1256.70 - What controls access to national security-classified information?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... national security-classified information? 1256.70 Section 1256.70 Parks, Forests, and Public Property... HISTORICAL MATERIALS Access to Materials Containing National Security-Classified Information § 1256.70 What controls access to national security-classified information? (a) The declassification of and public...

  20. 75 FR 71790 - Second Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-24

    ... Federal Aviation Administration Second Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  1. 76 FR 3931 - Fourth Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-21

    ... Federal Aviation Administration Fourth Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 Meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  2. 76 FR 38742 - Seventh Meeting: RTCA Special Committee 224: Airport Security Access Control Systems

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-01

    ... Federal Aviation Administration Seventh Meeting: RTCA Special Committee 224: Airport Security Access... Committee 224 meeting: Airport Security Access Control Systems (Update to DO-230B). SUMMARY: The FAA is issuing this notice to advise the public of a meeting of RTCA Special Committee 224: Airport...

  3. Controllable Curved Mirrors Made from Single-Layer EAP Films

    NASA Technical Reports Server (NTRS)

    Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart

    2004-01-01

    A document proposes that lightweight, deployable, large-aperture, controllable curved mirrors made of reflectively coated thin electroactive-polymer (EAP) films be developed for use in spaceborne microwave and optical systems. In these mirrors, the EAP films would serve as both structures and actuators. EAPs that are potentially suitable for such use include piezoelectric, electrostrictive, ferroelectric, and dielectric polymers. These materials exhibit strains proportional to the squares of applied electric fields. Utilizing this phenomenon, a curved mirror according to the proposal could be made from a flat film, upon which a nonuniform electrostatic potential (decreasing from the center toward the edge) would be imposed to obtain a required curvature. The effect would be analogous to that of an old-fashioned metalworking practice in which a flat metal sheet is made into a bowl by hammering it repeatedly, the frequency of hammer blows decreasing with distance from the center. In operation, the nonuniform electrostatic potential could be imposed by use of an electron gun. Calculations have shown that by use of a single- layer film made of a currently available EAP, it would be possible to control the focal length of a 2-m-diameter mirror from infinity to 1.25 m.

  4. Energy-Efficient Boarder Node Medium Access Control Protocol for Wireless Sensor Networks

    PubMed Central

    Razaque, Abdul; Elleithy, Khaled M.

    2014-01-01

    This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN), which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS), which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM) model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS), which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi

  5. Energy-efficient boarder node medium access control protocol for wireless sensor networks.

    PubMed

    Razaque, Abdul; Elleithy, Khaled M

    2014-03-12

    This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN), which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS), which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM) model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS), which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi

  6. The Smart Card concept applied to access control

    SciTech Connect

    Seidman, S.

    1986-01-01

    Passwords tend to be handled carelessly, and so are easily lost or stolen. Because they are intangible, their loss or theft generally goes unnoticed. Because they are constant, they may be used by anyone for as long as they remain in active use by a legitimate user. A step up in password security is offered by a new range of products which generate a new code each time the device is used. Devices are being produced in packages as small as a standard plastic credit card, including internal battery power, integral keyboard and LCD display. Security features of the Smart Card are reviewed, and several random access code generators currently available in the commercial marketplace are described.

  7. 77 FR 26789 - Certain Semiconductor Chips Having Synchronous Dynamic Random Access Memory Controllers and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-07

    ... From the Federal Register Online via the Government Publishing Office ] INTERNATIONAL TRADE COMMISSION Certain Semiconductor Chips Having Synchronous Dynamic Random Access Memory Controllers and Products Containing Same; Determination Rescinding the Exclusion Order and Cease and Desist Orders...

  8. 75 FR 47464 - Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-06

    ... From the Federal Register Online via the Government Publishing Office LIBRARY OF CONGRESS Copyright Office 37 CFR Part 201 Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control Technologies AGENCY: Copyright Office, Library of Congress. ACTION: Final...

  9. A contextual role-based access control authorization model for electronic patient record.

    PubMed

    Motta, Gustavo H M B; Furuie, Sergio S

    2003-09-01

    The design of proper models for authorization and access control for electronic patient record (EPR) is essential to a wide scale use of EPR in large health organizations. In this paper, we propose a contextual role-based access control authorization model aiming to increase the patient privacy and the confidentiality of patient data, whereas being flexible enough to consider specific cases. This model regulates user's access to EPR based on organizational roles. It supports a role-tree hierarchy with authorization inheritance; positive and negative authorizations; static and dynamic separation of duties based on weak and strong role conflicts. Contextual authorizations use environmental information available at access time, like user/patient relationship, in order to decide whether a user is allowed to access an EPR resource. This enables the specification of a more flexible and precise authorization policy, where permission is granted or denied according to the right and the need of the user to carry out a particular job function.

  10. Implementing the Victory Access Control Framework in a Military Ground Vehicle

    DTIC Science & Technology

    2015-08-01

    Attribute Markup Language (SAML) and eXtensible Access Control Markup Language (XACML). These technologies are typically used for securing an...interfaces. REFERENCES [1] OASIS, “Assertions and Protocols for the OASIS Security Assertion Markup Language (SAML) V2.0”, OASIS Standard...Online]. Available: http://docs.oasis- open.org/security/saml/v2.0/saml-core-2.0-os.pdf March 2005. [2] OASIS, “eXtensible Access Control Markup

  11. Springfield Processing Plant* (A Hypothetical Facility) SPP, Entry Control Point and Vehicle Gate Access Control Post Order

    SciTech Connect

    Baum, Gregory A.

    2014-06-01

    This hypothetical order provides the requirements and instructions for the Springfield Processing Plant (SPP) Vehicle Gate and Entry Control Point (ECP) in the perimeter access building. The purpose of this post is to prevent the theft, sabotage or diversion of nuclear material (NM), control access and exit at the protected area, and to respond to emergencies according the SPP Guard Force (GF) Contingency Plan and as directed by a Guard Force Supervisor.

  12. Increasing software testability with standard access and control interfaces

    NASA Technical Reports Server (NTRS)

    Nikora, Allen P; Some, Raphael R.; Tamir, Yuval

    2003-01-01

    We describe an approach to improving the testability of complex software systems with software constructs modeled after the hardware JTAG bus, used to provide visibility and controlability in testing digital circuits.

  13. Advanced Techniques for Deploying Reliable and Efficient Access Control: Application to E-healthcare.

    PubMed

    Jaïdi, Faouzi; Labbene-Ayachi, Faten; Bouhoula, Adel

    2016-12-01

    Nowadays, e-healthcare is a main advancement and upcoming technology in healthcare industry that contributes to setting up automated and efficient healthcare infrastructures. Unfortunately, several security aspects remain as main challenges towards secure and privacy-preserving e-healthcare systems. From the access control perspective, e-healthcare systems face several issues due to the necessity of defining (at the same time) rigorous and flexible access control solutions. This delicate and irregular balance between flexibility and robustness has an immediate impact on the compliance of the deployed access control policy. To address this issue, the paper defines a general framework to organize thinking about verifying, validating and monitoring the compliance of access control policies in the context of e-healthcare databases. We study the problem of the conformity of low level policies within relational databases and we particularly focus on the case of a medical-records management database defined in the context of a Medical Information System. We propose an advanced solution for deploying reliable and efficient access control policies. Our solution extends the traditional lifecycle of an access control policy and allows mainly managing the compliance of the policy. We refer to an example to illustrate the relevance of our proposal.

  14. Control of optical properties in cyanine dye thin film fabricated by a layer-by-layer method

    NASA Astrophysics Data System (ADS)

    Kojima, Osamu; Fujii, Ryoji; Kita, Takashi; Shim, YongGu

    2014-02-01

    We report the fabrication of cyanine dye molecule thin films by a layer-by-layer (LBL) method. In the LBL thin film, the photoluminescence properties can be controlled by the separation between the donor and acceptor dye molecule layers. While the distance dependence of the energy-transfer rate changes around 2 nm, which is comparable with the lengths of the molecules, the energy-transfer rate as evaluated from the photoluminescence decay time shows a maximum value of approximately 15 ns-1. The thin films fabricated by the LBL method will be therefore applicable for ultrafast optical switches with higher repetition rate.

  15. Accessing the biocompatibility of layered double hydroxide by intramuscular implantation: histological and microcirculation evaluation

    PubMed Central

    Cunha, Vanessa Roberta Rodrigues; de Souza, Rodrigo Barbosa; da Fonseca Martins, Ana Maria Cristina Rebello Pinto; Koh, Ivan Hong Jun; Constantino, Vera Regina Leopoldo

    2016-01-01

    Biocompatibility of layered double hydroxides (LDHs), also known as hydrotalcite-like materials or double metal hydroxides, was investigated by in vivo assays via intramuscular tablets implantation in rat abdominal wall. The tablets were composed by chloride ions intercalated into LDH of magnesium/aluminum (Mg2Al-Cl) and zinc/aluminum (Zn2Al-Cl). The antigenicity and tissue integration capacity of LDHs were assessed histologically after 7 and 28 days post-implantation. No fibrous capsule nearby the LDH was noticed for both materials as well any sign of inflammatory reactions. Sidestream Dark Field imaging, used to monitor in real time the microcirculation in tissues, revealed overall integrity of the microcirculatory network neighboring the tablets, with no blood flow obstruction, bleeding and/or increasing of leukocyte endothelial adhesion. After 28 days Mg2Al-Cl promoted multiple collagen invaginations (mostly collagen type-I) among its fragments while Zn2Al-Cl induced predominantly collagen type–III. This work supports previous results in the literature about LDHs compatibility with living matter, endorsing them as functional materials for biomedical applications. PMID:27480483

  16. 76 FR 38293 - Risk Management Controls for Brokers or Dealers With Market Access

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-30

    ... COMMISSION 17 CFR Part 240 RIN 3235-AK53 Risk Management Controls for Brokers or Dealers With Market Access... establish, document, and maintain a system of risk management controls and supervisory procedures that... develop, test, and implement the relevant risk management controls and supervisory procedures...

  17. Control of Supersonic Boundary Layers Using Steady Suction

    NASA Technical Reports Server (NTRS)

    Balakumar, P.

    2006-01-01

    Control of supersonic boundary layers using steady suction through a series of very small two-dimensional strips is numerically investigated at a free stream Mach number of 1.8. The mean flow induced by rows of suction holes is also computed. Both the steady and unsteady solutions are obtained by solving the full Navier-Stokes equations using the 5th-order accurate weighted essentially non-oscillatory (WENO) scheme for space discretization and using third-order total-variationdiminishing (TVD) Runge-Kutta scheme for time integration. Computations for the two-dimensional cases are performed at suction coefficients 0.001 and 0.002 to investigate the stabilizing effects of suction. The simulation showed that a series of shock waves are generated at the slots. The stability results showed that the total amplification is reduced up to the end of the computational domain. However, the growth rates become larger at downstream distances away from the suction region. The computations for the suction holes showed the generation of Mach waves from each hole and the formation of longitudinal vortices.

  18. Cross-Layer Design for Downlink Multihop Cloud Radio Access Networks With Network Coding

    NASA Astrophysics Data System (ADS)

    Liu, Liang; Yu, Wei

    2017-04-01

    There are two fundamentally different fronthaul techniques in the downlink communication of cloud radio access network (C-RAN): the data-sharing strategy and the compression-based strategy. Under the former strategy, each user's message is multicast from the central processor (CP) to all the serving remote radio heads (RRHs) over the fronthaul network, which then cooperatively serve the users through joint beamforming; while under the latter strategy, the user messages are first beamformed then quantized at the CP, and the compressed signal is unicast to the corresponding RRH, which then decompresses its received signal for wireless transmission. Previous works show that in general the compression-based strategy outperforms the data-sharing strategy. This paper, on the other hand, point s out that in a C-RAN model where the RRHs are connected to the CP via multi-hop routers, data-sharing can be superior to compression if the network coding technique is adopted for multicasting user messages to the cooperating RRHs, and the RRH's beamforming vectors, the user-RRH association, and the network coding design over the fronthaul network are jointly optimized based on the techniques of sparse optimization an d successive convex approximation. This is in comparison to the compression-based strategy, where information is unicast over the fronthaul network by simple routing, and the RRH's compression noise covariance and beamforming vectors, as well as the routing strategy over the fronthaul network are jointly optimized based on the successive convex approximation technique. The observed gain in overall network throughput is due to that information multicast is more efficient than information unicast over the multi-hop fronthaul of a C-RAN.

  19. 33 CFR 165.9 - Geographic application of limited and controlled access areas and regulated navigation areas.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... and controlled access areas and regulated navigation areas. 165.9 Section 165.9 Navigation and... controlled access areas and regulated navigation areas. (a) General. The geographic application of the limited and controlled access areas and regulated navigation areas in this part are determined based...

  20. Cognitive Control and Lexical Access in Younger and Older Bilinguals

    ERIC Educational Resources Information Center

    Bialystok, Ellen; Craik, Fergus; Luk, Gigi

    2008-01-01

    Ninety-six participants, who were younger (20 years) or older (68 years) adults and either monolingual or bilingual, completed tasks assessing working memory, lexical retrieval, and executive control. Younger participants performed most of the tasks better than older participants, confirming the effect of aging on these processes. The effect of…

  1. Trust-Based Access Control Model from Sociological Approach in Dynamic Online Social Network Environment

    PubMed Central

    Kim, Seungjoo

    2014-01-01

    There has been an explosive increase in the population of the OSN (online social network) in recent years. The OSN provides users with many opportunities to communicate among friends and family. Further, it facilitates developing new relationships with previously unknown people having similar beliefs or interests. However, the OSN can expose users to adverse effects such as privacy breaches, the disclosing of uncontrolled material, and the disseminating of false information. Traditional access control models such as MAC, DAC, and RBAC are applied to the OSN to address these problems. However, these models are not suitable for the dynamic OSN environment because user behavior in the OSN is unpredictable and static access control imposes a burden on the users to change the access control rules individually. We propose a dynamic trust-based access control for the OSN to address the problems of the traditional static access control. Moreover, we provide novel criteria to evaluate trust factors such as sociological approach and evaluate a method to calculate the dynamic trust values. The proposed method can monitor negative behavior and modify access permission levels dynamically to prevent the indiscriminate disclosure of information. PMID:25374943

  2. Trust-based access control model from sociological approach in dynamic online social network environment.

    PubMed

    Baek, Seungsoo; Kim, Seungjoo

    2014-01-01

    There has been an explosive increase in the population of the OSN (online social network) in recent years. The OSN provides users with many opportunities to communicate among friends and family. Further, it facilitates developing new relationships with previously unknown people having similar beliefs or interests. However, the OSN can expose users to adverse effects such as privacy breaches, the disclosing of uncontrolled material, and the disseminating of false information. Traditional access control models such as MAC, DAC, and RBAC are applied to the OSN to address these problems. However, these models are not suitable for the dynamic OSN environment because user behavior in the OSN is unpredictable and static access control imposes a burden on the users to change the access control rules individually. We propose a dynamic trust-based access control for the OSN to address the problems of the traditional static access control. Moreover, we provide novel criteria to evaluate trust factors such as sociological approach and evaluate a method to calculate the dynamic trust values. The proposed method can monitor negative behavior and modify access permission levels dynamically to prevent the indiscriminate disclosure of information.

  3. An Action-Based Fine-Grained Access Control Mechanism for Structured Documents and Its Application

    PubMed Central

    Su, Mang; Li, Fenghua; Tang, Zhi; Yu, Yinyan; Zhou, Bo

    2014-01-01

    This paper presents an action-based fine-grained access control mechanism for structured documents. Firstly, we define a describing model for structured documents and analyze the application scenarios. The describing model could support the permission management on chapters, pages, sections, words, and pictures of structured documents. Secondly, based on the action-based access control (ABAC) model, we propose a fine-grained control protocol for structured documents by introducing temporal state and environmental state. The protocol covering different stages from document creation, to permission specification and usage control are given by using the Z-notation. Finally, we give the implementation of our mechanism and make the comparisons between the existing methods and our mechanism. The result shows that our mechanism could provide the better solution of fine-grained access control for structured documents in complicated networks. Moreover, it is more flexible and practical. PMID:25136651

  4. Optimization-based Approach to Cross-layer Resource Management in Wireless Networked Control Systems

    DTIC Science & Technology

    2013-05-01

    distribution is unlimited. Optimization-based approach to cross-layer resource management in Wireless networked control systems The views, opinions...Box 12211 Research Triangle Park, NC 27709-2211 cross-layer resource management , sampling rate adaptation, networked control system REPORT...7749 2 ABSTRACT Optimization-based approach to cross-layer resource management in Wireless networked control systems Report Title Wireless Networked

  5. Polarizer-free liquid crystal display with double microlens array layers and polarization-controlling liquid crystal layer.

    PubMed

    Lee, You-Jin; Yu, Chang-Jae; Kim, Jae-Hoon

    2015-10-19

    We propose a polarizer-free liquid crystal display (LCD) consisting of two microlens array (MLA) layers, a twisted nematic (TN) LC layer, and two light-blocking masks. By changing the polarization state, focal length of the LCD can be controlled. Since two light-blocking masks have a circular stop pattern and a complementary open pattern, entire gray-scale spectrum may be realized by controlling the intensity of light passing through masks. Ultimately, fast response time characteristics could be achieved due to the alignment of LC molecules on the flat MLA surface.

  6. Nonlinear Microwave Properties of Atomic Layer Controlled HTS Multilayers

    DTIC Science & Technology

    2008-04-14

    nm YBCO 160 nm YBCO 160 nm YBCO -160 -130 - 100 -70 -40 -10 0 10 20 30 Circulating power (dBm) N or m al iz ed IM D p ow er (d B m ) Single layer...film with each YBCO layer 160- nm thick interspersed with CeO2 buffer layers 40- nm thick, giving an aggregate thickness of 640 nm of YBCO . The...flux penetration and flux motion are sources of loss. Thickness dependence of IMD of YBCO

  7. Layered mode selection logic control for border security

    NASA Astrophysics Data System (ADS)

    Born, T.; Ferrer, G.; Wright, A. M.; Wright, A. B.

    2007-04-01

    Challenges in border security may be resolved through a team of autonomous mobile robots configured as a flexible sensor array. The robots will have a prearranged formation along a section of a border, and each robot will attempt to maintain a uniform distance with its nearest neighbors. The robots will carry sensor packages which can detect a signature that is representative of a human (for instance, a thermal signature). When a robot detects an intruder, it will move away such that it attempts to maintain a constant distance from the intruder and move away from the border (i.e. into its home territory). As the robot moves away from the border, its neighbors will move away from the border to maintain a uniform distance with the moving robot and with their fixed neighbors. The pattern of motion in the team of robots can be identified, either algorithmically by a computer or by a human monitor of a display. Unique patterns are indicative of animal movement, human movement, and mass human movement. To realize such a scheme, a new control architecture must be developed. This architecture must be fault tolerant to sensor and manipulator failures, scalable in number of agents, and adaptable to different robotic base platforms (for instance, a UGV may be appropriate at the southern border and a UAV may be appropriate at the northern border). The Central Arkansas Robotics Consortium has developed an architecture, called Layered Mode Selection Logic (LMSL), which addresses all of these concerns. The overall LMSL scheme as applied to a multi-agent flexible sensor array is described in this paper.

  8. Control of magnetic direction in multi-layer ferromagnetic devices by bias voltage

    DOEpatents

    You, Chun-Yeol; Bader, Samuel D.

    2001-01-01

    A system for controlling the direction of magnetization of materials comprising a ferromagnetic device with first and second ferromagnetic layers. The ferromagnetic layers are disposed such that they combine to form an interlayer with exchange coupling. An insulating layer and a spacer layer are located between the first and second ferromagnetic layers. A direct bias voltage is applied to the interlayer exchange coupling, causing the direction of magnetization of the second ferromagnetic layer to change. This change of magnetization direction occurs in the absence of any applied external magnetic field.

  9. CMP Control of Multi-Layer Inter-Layer Dielectrics (ILD) using X-ray Reflectivity

    SciTech Connect

    Bryant, Ross E.; Porter, Hethel; Gallegos, Jesus; O'Dell, Jeremy; Agnihotri, Dileep

    2007-09-26

    Thin sacrificial films are used as cap layer in the back-end semiconductor processing for protecting the bulk porous inter-layer low-k dielectric during the CMP process. The existing optical measurement techniques struggle to separate these thin films from the bulk low-k due to very similar optical coefficients. Glancing angle x-ray reflectivity is well suited for separation of thin sacrificial film and bulk dielectric film as x-ray reflectivity depends strongly on changes in electron densities for two materials. This paper discusses the x-ray reflectivity technique and its applications for measurement of low-k stack and sacrificial oxide post CMP.

  10. Advanced Guidance and Control for Hypersonics and Space Access

    NASA Technical Reports Server (NTRS)

    Hanson, John M.; Hall, Charles E.; Mulqueen, John A.; Jones, Robert E.

    2003-01-01

    Advanced guidance and control (AG&C) technologies are critical for meeting safety, reliability, and cost requirements for the next generation of reusable launch vehicle (RLV), whether it is fully rocket-powered or has air- breathing components. This becomes clear upon examining the number of expendable launch vehicle failures in the recent past where AG&C technologies could have saved a RLV with the same failure mode, the additional vehicle problems where t h i s technology applies, and the costs and time associated with mission design with or without all these failure issues. The state-of-the-art in guidance and control technology, as well as in computing technology, is the point where we can look to the possibility of being able to safely return a RLV in any situation where it can physically be recovered. This paper outlines reasons for AWC, current technology efforts, and the additional work needed for making this goal a reality. There are a number of approaches to AG&C that have the potential for achieving the desired goals. For some of these methods, we compare the results of tests designed to demonstrate the achievement of the goals. Tests up to now have been focused on rocket-powered vehicles; application to hypersonic air-breathers is planned. We list the test cases used to demonstrate that the desired results are achieved, briefly describe an automated test scoring method, and display results of the tests. Some of the technology components have reached the maturity level where they are ready for application to a new vehicle concept, while others are not far along in development.

  11. Steganography-based access control to medical data hidden in electrocardiogram.

    PubMed

    Mai, Vu; Khalil, Ibrahim; Ibaida, Ayman

    2013-01-01

    Steganographic techniques allow secret data to be embedded inside another host data such as an image or a text file without significant changes to the quality of the host data. In this research, we demonstrate how steganography can be used as the main mechanism to build an access control model that gives data owners complete control to their sensitive cardiac health information hidden in their own Electrocardiograms. Our access control model is able to protect the privacy of users, the confidentiality of medical data, reduce storage space and make it more efficient to upload and download large amount of data.

  12. Modelling of Medium Access Control (MAC) Protocols for Mobile Ad-Hoc Networks

    DTIC Science & Technology

    2005-06-01

    Slot IP Internet Protocol LAN Local Area Network MAC Medium Access Control MACAW Medium Access Protocol for Wireless LANs MANET Mobile Ad-hoc...Unforced state – It waits after entering the state until it is invoked by another process or an interrupt. It is in dark grey on this report, and red ... green in OPNET. A MAC process model is built for general initialisations of the MAC module, and to invoke the selected MAC protocol process model

  13. Analysis of Decision Factors for the Application of Information Access Controls within the Organization

    ERIC Educational Resources Information Center

    Foerster, Carl A.

    2013-01-01

    The application of access controls on internal information necessarily impacts the availability of that information for sharing inside the enterprise. The decisions establishing the degree of control are a crucial first step to balance the requirements to protect and share. This research develops a set of basic decision factors and examines other…

  14. MAAC: a software tool for user authentication and access control to the electronic patient record in an open distributed environment

    NASA Astrophysics Data System (ADS)

    Motta, Gustavo H.; Furuie, Sergio S.

    2004-04-01

    Designing proper models for authorization and access control for the electronic patient record (EPR) is essential to wide scale use of the EPR in large health organizations. This work presents MAAC (Middleware for Authentication and Access Control), a tool that implements a contextual role-based access control (RBAC) authorization model. RBAC regulates user"s access to computers resources based on their organizational roles. A contextual authorization uses environmental information available at access-request time, like user/patient relationship, in order to decide whether a user has the right to access an EPR resource. The software architecture where MAAC is implemented uses Lightweight Directory Access Protocol, Java programming language and the CORBA/OMG standards CORBA Security Service and Resource Access Decision Facility. With those open and distributed standards, heterogeneous EPR components can request user authentication and access authorization services in a unified and consistent fashion across multiple platforms.

  15. Thermoresponsive Nanofabricated Substratum for the Engineering of Three-Dimensional Tissues with Layer-by-Layer Architectural Control

    PubMed Central

    2015-01-01

    Current tissue engineering methods lack the ability to properly recreate scaffold-free, cell-dense tissues with physiological structures. Recent studies have shown that the use of nanoscale cues allows for precise control over large-area 2D tissue structures without restricting cell growth or cell density. In this study, we developed a simple and versatile platform combining a thermoresponsive nanofabricated substratum (TNFS) incorporating nanotopographical cues and the gel casting method for the fabrication of scaffold-free 3D tissues. Our TNFS allows for the structural control of aligned cell monolayers which can be spontaneously detached via a change in culture temperature. Utilizing our gel casting method, viable, aligned cell sheets can be transferred without loss of anisotropy or stacked with control over individual layer orientations. Transferred cell sheets and individual cell layers within multilayered tissues robustly retain structural anisotropy, allowing for the fabrication of scaffold-free, 3D tissues with hierarchical control of overall tissue structure. PMID:24628277

  16. A multi-layer robust adaptive fault tolerant control system for high performance aircraft

    NASA Astrophysics Data System (ADS)

    Huo, Ying

    Modern high-performance aircraft demand advanced fault-tolerant flight control strategies. Not only the control effector failures, but the aerodynamic type failures like wing-body damages often result in substantially deteriorate performance because of low available redundancy. As a result the remaining control actuators may yield substantially lower maneuvering capabilities which do not authorize the accomplishment of the air-craft's original specified mission. The problem is to solve the control reconfiguration on available control redundancies when the mission modification is urged to save the aircraft. The proposed robust adaptive fault-tolerant control (RAFTC) system consists of a multi-layer reconfigurable flight controller architecture. It contains three layers accounting for different types and levels of failures including sensor, actuator, and fuselage damages. In case of the nominal operation with possible minor failure(s) a standard adaptive controller stands to achieve the control allocation. This is referred to as the first layer, the controller layer. The performance adjustment is accounted for in the second layer, the reference layer, whose role is to adjust the reference model in the controller design with a degraded transit performance. The upmost mission adjust is in the third layer, the mission layer, when the original mission is not feasible with greatly restricted control capabilities. The modified mission is achieved through the optimization of the command signal which guarantees the boundedness of the closed-loop signals. The main distinguishing feature of this layer is the the mission decision property based on the current available resources. The contribution of the research is the multi-layer fault-tolerant architecture that can address the complete failure scenarios and their accommodations in realities. Moreover, the emphasis is on the mission design capabilities which may guarantee the stability of the aircraft with restricted post

  17. Controlled synthesis and transfer of large-area WS2 sheets: from single layer to few layers.

    PubMed

    Elías, Ana Laura; Perea-López, Néstor; Castro-Beltrán, Andrés; Berkdemir, Ayse; Lv, Ruitao; Feng, Simin; Long, Aaron D; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Gutiérrez, Humberto R; Pradhan, Nihar R; Balicas, Luis; Mallouk, Thomas E; López-Urías, Florentino; Terrones, Humberto; Terrones, Mauricio

    2013-06-25

    The isolation of few-layered transition metal dichalcogenides has mainly been performed by mechanical and chemical exfoliation with very low yields. In this account, a controlled thermal reduction-sulfurization method is used to synthesize large-area (~1 cm(2)) WS2 sheets with thicknesses ranging from monolayers to a few layers. During synthesis, WOx thin films are first deposited on Si/SiO2 substrates, which are then sulfurized (under vacuum) at high temperatures (750-950 °C). An efficient route to transfer the synthesized WS2 films onto different substrates such as quartz and transmission electron microscopy (TEM) grids has been satisfactorily developed using concentrated HF. Samples with different thicknesses have been analyzed by Raman spectroscopy and TEM, and their photoluminescence properties have been evaluated. We demonstrated the presence of single-, bi-, and few-layered WS2 on as-grown samples. It is well known that the electronic structure of these materials is very sensitive to the number of layers, ranging from indirect band gap semiconductor in the bulk phase to direct band gap semiconductor in monolayers. This method has also proved successful in the synthesis of heterogeneous systems of MoS2 and WS2 layers, thus shedding light on the controlled production of heterolayered devices from transition metal chalcogenides.

  18. Strain control of vibrational properties of few layer phosphorene

    NASA Astrophysics Data System (ADS)

    Tokár, K.; Derian, R.; Brndiar, J.; Štich, I.

    2016-11-01

    Using density functional theory techniques, we study lattice vibrational Raman and infrared modes in strained few-layer phosphorene. We find very significant frequency shifts, up to ≈ 100 cm-1 in the applied strain range of ±6%, of the Raman activities in both high- and low-frequency region and infrared activities in the low-frequency region. The type of applied strain, that is, armchair and zigzag, selectively affects specific vibrational modes. Combined with high spatial-resolution Raman/infrared scattering experiments, our calculated results can aid understanding of the complicated inhomogeneous strain distributions in few-layer phosphorene or manufacturing of materials with desired electronic properties via strain or layer engineering.

  19. Boundary Layer Control in Pipes through Strong Injection

    SciTech Connect

    Yeung, William Chor-Chun; Holt, Maurice

    1982-01-01

    In coal gasification, oxidation and sulfidization cause serious pipe corrosion. This study attempts to determine the feasibility of reducing such corrosion by injecting steam at pipe entry to modify the boundary-layer gas composition along pipe walls. The injection will form a thin layer on the inner wall, preventing, for a time, contact with the corrosive gases. (Turbulence will eventually force diffusion through the protective layer.) The gas products are assumed to be hydrogen sulfide and steam. The Method of Integral Relations is used to obtain the numerical solutions to the governing equations. Finally, with several different injectant lengths and velocities, the concentration of H2S along the pipe wall is calculated and is found low enough to prevent corrosion.

  20. Mechanism of power consumption inhibitive multi-layer Zn:SiO{sub 2}/SiO{sub 2} structure resistance random access memory

    SciTech Connect

    Zhang, Rui; Lou, Jen-Chung; Tsai, Tsung-Ming E-mail: tcchang@mail.phys.nsysu.edu.tw; Chang, Kuan-Chang; Huang, Syuan-Yong; Shih, Chih-Cheng; Pan, Jhih-Hong; Tung, Cheng-Wei; Chang, Ting-Chang E-mail: tcchang@mail.phys.nsysu.edu.tw; Chen, Kai-Huang; Young, Tai-Fa; Chen, Hsin-Lu; Chen, Jung-Hui; Chen, Min-Chen; Syu, Yong-En; Sze, Simon M.

    2013-12-21

    In this paper, multi-layer Zn:SiO{sub 2}/SiO{sub 2} structure is introduced to reduce the operation power consumption of resistive random access memory (RRAM) device by modifying the filament formation process. And the configuration of multi-layer Zn:SiO{sub 2}/SiO{sub 2} structure is confirmed and demonstrated by auger electron spectrum. Material analysis together with conduction current fitting is applied to qualitatively evaluate the carrier conduction mechanism on both low resistance state and high resistance state. Finally, single layer and multilayer conduction models are proposed, respectively, to clarify the corresponding conduction characteristics of two types of RRAM devices.

  1. Optimal Policy of Cross-Layer Design for Channel Access and Transmission Rate Adaptation in Cognitive Radio Networks

    NASA Astrophysics Data System (ADS)

    He, Hao; Wang, Jun; Zhu, Jiang; Li, Shaoqian

    2010-12-01

    In this paper, we investigate the cross-layer design of joint channel access and transmission rate adaptation in CR networks with multiple channels for both centralized and decentralized cases. Our target is to maximize the throughput of CR network under transmission power constraint by taking spectrum sensing errors into account. In centralized case, this problem is formulated as a special constrained Markov decision process (CMDP), which can be solved by standard linear programming (LP) method. As the complexity of finding the optimal policy by LP increases exponentially with the size of action space and state space, we further apply action set reduction and state aggregation to reduce the complexity without loss of optimality. Meanwhile, for the convenience of implementation, we also consider the pure policy design and analyze the corresponding characteristics. In decentralized case, where only local information is available and there is no coordination among the CR users, we prove the existence of the constrained Nash equilibrium and obtain the optimal decentralized policy. Finally, in the case that the traffic load parameters of the licensed users are unknown for the CR users, we propose two methods to estimate the parameters for two different cases. Numerical results validate the theoretic analysis.

  2. Reproductive performance of layer chickens reared on deep litter system with or without access to grass or legume pasture.

    PubMed

    Oke, O E; Ladokun, A O; Onagbesan, O M

    2016-04-01

    Despite several studies carried out to investigate the effects of access to pasture on poultry performance, there is a dearth of information on the comparative benefit of grass and legumes. This study investigated the effects of rearing systems [deep litter system (DL), deep litter with access to legumes (LP) or grass (GP) pastures] on the performance of ISA Brown layers. Two hundred and forty 12-week-old pullets were housed for this study. They were reared until 60 weeks of age. Eighty birds were assigned to each treatment; each treatment had four replicates of 20 birds each. Two birds per replicate were slaughtered at weeks 20, 35 and 58 for determination of the weights of liver, ovary, oviduct and the number of follicles. Daily egg production records were kept from the day of first egg to 42 weeks in lay. Body weights were recorded weekly. Results indicated that at 20 weeks of age, the hens kept in the LP had higher (p < 0.05) ovary weight (g) (34.98 ± 1.4), oviduct weight (52.55 ± 2.28) and oviduct length (cm) (49.73 ± 11.34), and higher number of large yellow follicles (3.75 ± 1.31) and small yellow follicles (12.75 ± 5.17) than those in the GP (0.83 ± 0.02, 1.68 ± 0.19, 16.38 ± 1.14, 0.00 and 0.00), and DL (1.03 ± 0.11, 1.48 ± 0.48, 14.43 ± 0.58, 0.00 and 0.00) respectively. The age (days) at first oviposition was earlier (p < 0.05) in the LP (139.25 ± 0.85) than that in the GP (146.75 ± 0.48) and DL (146.75 ± 0.48). The hen-day egg production was lower (p < 0.05) in GP (74.19 ± 1.25) than that in the DL (78.82 ± 0.78) and LP (79.93 ± 1.13) at mid-laying phase. Concentrate feed intake was lower (p < 0.05) in LP and GP than DL suggesting economic benefit. It was concluded that access to LP enhanced the performance of layers than DL and GP as indicated by the parameters measured.

  3. Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte

    NASA Astrophysics Data System (ADS)

    Porta-i-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J.; Marsal, Lluis F.

    2016-08-01

    Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

  4. Sustained, Controlled and Stimuli-Responsive Drug Release Systems Based on Nanoporous Anodic Alumina with Layer-by-Layer Polyelectrolyte.

    PubMed

    Porta-I-Batalla, Maria; Eckstein, Chris; Xifré-Pérez, Elisabet; Formentín, Pilar; Ferré-Borrull, J; Marsal, Lluis F

    2016-12-01

    Controlled drug delivery systems are an encouraging solution to some drug disadvantages such as reduced solubility, deprived biodistribution, tissue damage, fast breakdown of the drug, cytotoxicity, or side effects. Self-ordered nanoporous anodic alumina is an auspicious material for drug delivery due to its biocompatibility, stability, and controllable pore geometry. Its use in drug delivery applications has been explored in several fields, including therapeutic devices for bone and dental tissue engineering, coronary stent implants, and carriers for transplanted cells. In this work, we have created and analyzed a stimuli-responsive drug delivery system based on layer-by-layer pH-responsive polyelectrolyte and nanoporous anodic alumina. The results demonstrate that it is possible to control the drug release using a polyelectrolyte multilayer coating that will act as a gate.

  5. Multi-layered controllable stiffness beams for morphing: energy, actuation force, and material strain considerations

    NASA Astrophysics Data System (ADS)

    Murray, Gabriel; Gandhi, Farhan

    2010-04-01

    Morphing aerospace structures could benefit from the ability of structural elements to transition from a stiff load-bearing state to a relatively compliant state that can undergo large deformation at low actuation cost. The present paper focuses on multi-layered beams with controllable flexural stiffness—comprising polymer layers affixed to the surfaces of a base beam and cover layers, in turn, affixed to the surfaces of the polymer layers. Heating the polymer through the glass transition reduces its shear modulus, decouples the cover layers from the base beam and reduces the overall flexural stiffness. Although the stiffness and actuation force required to bend the beam reduce, the energy required to heat the polymer layer must also be considered. Results show that for beams with low slenderness ratios, relatively thick polymer layers, and cover layers whose extensional stiffness is high, the decoupling of the cover layers through softening of the polymer layers can result in flexural stiffness reductions of over 95%. The energy savings are also highest for these configurations, and will increase as the deformation of the beam increases. The decoupling of the cover layers from the base beam through the softening of the polymer reduces the axial strains in the cover layers significantly; otherwise material failure would prevent large deformation. Results show that when the polymer layer is stiff, the cover layers are the dominant contributors to the total energy in the beam, and the energy in the polymer layers is predominantly axial strain energy. When the polymer layers are softened the energy in the cover layers is a small contributor to the total energy which is dominated by energy in the base beam and shear strain energy in the polymer layer.

  6. Virus spreading in wireless sensor networks with a medium access control mechanism

    NASA Astrophysics Data System (ADS)

    Wang, Ya-Qi; Yang, Xiao-Yuan

    2013-04-01

    In this paper, an extended version of standard susceptible-infected (SI) model is proposed to consider the influence of a medium access control mechanism on virus spreading in wireless sensor networks. Theoretical analysis shows that the medium access control mechanism obviously reduces the density of infected nodes in the networks, which has been ignored in previous studies. It is also found that by increasing the network node density or node communication radius greatly increases the number of infected nodes. The theoretical results are confirmed by numerical simulations.

  7. RiBAC: Role Interaction Based Access Control Model for Community Computing

    NASA Astrophysics Data System (ADS)

    Jung, Youna; Masoumzadeh, Amirreza; Joshi, James B. D.; Kim, Minkoo

    Community computing is an agent-based development paradigm for ubiquitous computing systems. In a community computing system, ubiquitous services are provided by cooperation among agents. While agents cooperate, they interact with each other continuously to access data of other agents and/or to execute other agent’s actions. However, in cases of security-critical ubiquitous services such as medical or military services, an access control mechanism is necessary to prevent unauthorized access to critical data or action. In this paper, we propose a family of Role interaction Based Access Control (RiBAC) models for Community Computing, by extending the existing RBAC model to consider role interactions. As a basic model, we propose the core RiBAC model. For the convenience of management and to provide more fine-grained access control, we propose Hierarchical RiBAC (H-RiBAC), Constrained RiBAC (C-RiBAC), and Constrained Hierarchical RiBAC (CH-RiBAC) models. Finally, we extend the existing community computing framework to accommodate the specification and enforcement of RiBAC policies.

  8. Automated biometric access control system for two-man-rule enforcement

    SciTech Connect

    Holmes, J.P.; Maxwell, R.L. ); Henderson, R.W. )

    1991-01-01

    This paper describes a limited access control system for nuclear facilities which makes use of the eye retinal identity verifier to control the passage of personnel into and out of one or a group of security controlled working areas. This access control system requires no keys, cards or credentials. The user simply enters his Personal Identification Number (PIN) and takes an eye reading to request passage. The PIN does not have to be kept secret. The system then relies on biometric identity verification of the user, along with other system information, to make the decision of whether or not to unlock the door. It also enforces multiple zones control with personnel tracking and the two-man-rule.

  9. Accessibility to tuberculosis control services and tuberculosis programme performance in southern Ethiopia

    PubMed Central

    Dangisso, Mesay Hailu; Datiko, Daniel Gemechu; Lindtjørn, Bernt

    2015-01-01

    Background Despite the expansion of health services and community-based interventions in Ethiopia, limited evidence exists about the distribution of and access to health facilities and their relationship with the performance of tuberculosis (TB) control programmes. We aim to assess the geographical distribution of and physical accessibility to TB control services and their relationship with TB case notification rates (CNRs) and treatment outcome in the Sidama Zone, southern Ethiopia. Design We carried out an ecological study to assess physical accessibility to TB control facilities and the association of physical accessibility with TB CNRs and treatment outcome. We collected smear-positive pulmonary TB (PTB) cases treated during 2003–2012 from unit TB registers and TB service data such as availability of basic supplies for TB control and geographic locations of health services. We used ArcGIS 10.2 to measure the distance from each enumeration location to the nearest TB control facilities. A linear regression analysis was employed to assess factors associated with TB CNRs and treatment outcome. Results Over a decade the health service coverage (the health facility–to-population ratio) increased by 36% and the accessibility to TB control facilities also improved. Thus, the mean distance from TB control services was 7.6 km in 2003 (ranging from 1.8 to 25.5 km) between kebeles (the smallest administrative units) and had decreased to 3.2 km in 2012 (ranging from 1.5 to 12.4 km). In multivariate linear regression, as distance from TB diagnostic facilities (b-estimate=−0.25, p<0.001) and altitude (b-estimate=−0.31, p<0.001) increased, the CNRs of TB decreased, whereas a higher population density was associated with increased TB CNRs. Similarly, distance to TB control facilities (b-estimate=−0.27, p<0.001) and altitude (b-estimate=−0.30, p<0.001) were inversely associated with treatment success (proportion of treatment completed or cured cases). Conclusions

  10. Time Controlled Protein Release from Layer-by-Layer Assembled Multilayer Functionalized Agarose Hydrogels

    PubMed Central

    Mehrotra, Sumit; Lynam, Daniel; Maloney, Ryan; Pawelec, Kendell M.; Tuszynski, Mark H.; Lee, Ilsoon

    2009-01-01

    Axons of the adult central nervous system exhibit an extremely limited ability to regenerate after spinal cord injury. Experimentally generated patterns of axon growth are typically disorganized and randomly oriented. Support of linear axonal growth into spinal cord lesion sites has been demonstrated using arrays of uniaxial channels, templated with agarose hydrogel, and containing genetically engineered cells that secrete brain-derived neurotrophic factor (BDNF). However, immobilizing neurotrophic factors secreting cells within a scaffold is relatively cumbersome, and alternative strategies are needed to provide sustained release of BDNF from templated agarose scaffolds. Existing methods of loading the drug or protein into hydrogels cannot provide sustained release from templated agarose hydrogels. Alternatively, here it is shown that pH-responsive H-bonded poly(ethylene glycol)(PEG)/poly(acrylic acid)(PAA)/protein hybrid layer-by-layer (LbL) thin films, when prepared over agarose, provided sustained release of protein under physiological conditions for more than four weeks. Lysozyme, a protein similar in size and isoelectric point to BDNF, is released from the multilayers on the agarose and is biologically active during the earlier time points, with decreasing activity at later time points. This is the first demonstration of month-long sustained protein release from an agarose hydrogel, whereby the drug/protein is loaded separately from the agarose hydrogel fabrication process. PMID:20200599

  11. Collaborative-Hybrid Multi-Layer Network Control for Emerging Cyber-Infrastructures

    SciTech Connect

    Lehman, Tom; Ghani, Nasir; Boyd, Eric

    2010-08-31

    At a high level, there were four basic task areas identified for the Hybrid-MLN project. They are: o Multi-Layer, Multi-Domain, Control Plane Architecture and Implementation, including OSCARS layer2 and InterDomain Adaptation, Integration of LambdaStation and Terapaths with Layer2 dynamic provisioning, Control plane software release, Scheduling, AAA, security architecture, Network Virtualization architecture, Multi-Layer Network Architecture Framework Definition; o Heterogeneous DataPlane Testing; o Simulation; o Project Publications, Reports, and Presentations.

  12. Developing Access Control Model of Web OLAP over Trusted and Collaborative Data Warehouses

    NASA Astrophysics Data System (ADS)

    Fugkeaw, Somchart; Mitrpanont, Jarernsri L.; Manpanpanich, Piyawit; Juntapremjitt, Sekpon

    This paper proposes the design and development of Role- based Access Control (RBAC) model for the Single Sign-On (SSO) Web-OLAP query spanning over multiple data warehouses (DWs). The model is based on PKI Authentication and Privilege Management Infrastructure (PMI); it presents a binding model of RBAC authorization based on dimension privilege specified in attribute certificate (AC) and user identification. Particularly, the way of attribute mapping between DW user authentication and privilege of dimensional access is illustrated. In our approach, we apply the multi-agent system to automate flexible and effective management of user authentication, role delegation as well as system accountability. Finally, the paper culminates in the prototype system A-COLD (Access Control of web-OLAP over multiple DWs) that incorporates the OLAP features and authentication and authorization enforcement in the multi-user and multi-data warehouse environment.

  13. Pace: Privacy-Protection for Access Control Enforcement in P2P Networks

    NASA Astrophysics Data System (ADS)

    Sánchez-Artigas, Marc; García-López, Pedro

    In open environments such as peer-to-peer (P2P) systems, the decision to collaborate with multiple users — e.g., by granting access to a resource — is hard to achieve in practice due to extreme decentralization and the lack of trusted third parties. The literature contains a plethora of applications in which a scalable solution for distributed access control is crucial. This fact motivates us to propose a protocol to enforce access control, applicable to networks consisting entirely of untrusted nodes. The main feature of our protocol is that it protects both sensitive permissions and sensitive policies, and does not rely on any centralized authority. We analyze the efficiency (computational effort and communication overhead) as well as the security of our protocol.

  14. The need for the use of XACML access control policy in a distributed EHR and some performance considerations.

    PubMed

    Sucurovic, Snezana; Milutinovic, Veljko

    2008-01-01

    The Internet based distributed large scale information systems implements attribute based access control (ABAC) rather than Role Based Access Control (RBAC). The reason is that the Internet is identity less and that ABAC scales better. EXtensible Access Control Markup Language is standardized language for writing access control policies, access control requests and access control responses in ABAC. XACML can provide decentralized administration and credentials distribution. In year 2002 version of CEN ENV 13 606 attributes have been attached to EHCR components and in such a system ABAC and XACML have been easy to implement. This paper presents writing XACML policies in the case when attributes are in hierarchical structure. It is presented two possible solutions to write XACML policy in that case and that the solution when set functions are used is more compact and provides 10% better performances.

  15. Nurse practitioners and controlled substances prescriptive authority: improving access to care.

    PubMed

    Ambrose, Michelle A; Tarlier, Denise S

    2013-03-01

    In 2007, Health Canada proposed a new framework to regulate prescriptive authority for controlled substances, titled New Classes of Practitioners Regulations (NCPR). The new regulatory framework was passed in November 2012; it gives nurse practitioners (NPs), midwives and podiatrists the authority to prescribe controlled medications under the Controlled Drugs and Substances Act. It is expected that authorizing NPs to write prescriptions for certain controlled substances commonly used in primary care will enhance flexibility and timeliness in primary care service delivery. Studies from the United States have shown positive outcomes in primary care access, decreased healthcare costs and the evolution and advancement of the NP role when prescriptive authority was expanded to include controlled substances. The purpose of this paper is to examine how NPs' prescriptive authority for controlled substances affects access to primary care and NP role development. Three key issues identified from the experience of one group of NPs in the United States (access to care, professional autonomy and prescriber knowledge) offer insight into the practice changes that may be anticipated for NPs in Canada now that they have acquired prescriptive authority for controlled substances. Recommendations are offered to assist nurse leaders and educators to best support NPs as they take on this new and important role responsibility.

  16. Hydrogen and Stress-Induced De-lamination in an IrO2 Layer of Ferroelectric Random Access Memories

    NASA Astrophysics Data System (ADS)

    Kim, Jai-Hyun; Jung, Dong Jin; Kim, Hyun-Ho; Hong, Young Ki; Lee, Eun Sun; Kim, Song Yi; Jung, Ju Young; Ko, Han Kyoung; Choi, Do Yeon; Kang, SeungKuk; Kim, Heesan; Jung, Won Woong; Kang, Jin Young; Kang, Young Min; Lee, Sungyung; Jeong, Hongsik

    2009-04-01

    During the device lifetime tests such as high temperature operational life (HTOL) and high temperature storage (HTS) tests, a physical de-lamination of the IrO2 layer in vertical conjunction to pulsed plate-line, so-called here additional top electrode (ATE), ATE has appeared and localized in specific cell arrays. This failure stems either from the reduction of IrO2 by the penetrated hydrogen at the interface between ATE Ir to top electrode (TE) Ir or from lack of dummy cells applied, or both. In the back end of line (BEOL), several heat treatments were introduced and then the reduction was reduced. It is essential to consider a deliberated anneal procedure in the BEOL integration. This is because otherwise case may provoke a contact failure in pulsed plate-line node of cell arrays. Also, we simulate stress distribution in cell arrays depending on how many dummy cells have been taken into account. The fluctuation of the stress projected on the IrO2 layer should be controlled uniformly by adding a certain number dummy cells.

  17. Dextran coatings for aggregation control of layer-by-layer assembled polyelectrolyte microcapsules.

    PubMed

    Usov, Denys; Sukhorukov, Gleb B

    2010-08-03

    We propose dextran and dextran polyaldehyde (DPA) coatings for modification of layer-by-layer (LbL) assembled polyelectrolyte microcapsules which provide stability against aggregation in 0.75 M aqueous solutions of mono- and bivalent ions (Na(+), Cl(-), Ca(2+), HPO(4)(2-)). The microcapsules were prepared of three bilayers of poly(4-styrenesulfonate) (PSS) and poly(allylamine) (PAH). Dextran and its derivatives were attached to amino-terminated surface of the microcapsules via three types of chemical bonds of subsequently increasing strength: (1) hydrogen bonds, (2) hydrolyzable covalent cross-links resulting from aldehydes and primary amines coupling, and (3) nonhydrolyzable covalent C-N single bonds of secondary amines. Attachment of the DPA materials via the latter two types of bonds resulted in strengthening the capsules' walls which preserved a fraction of the microcapsules from disintegration upon electrostatic swelling in 0.1 M NaOH. The non-disintegrated fraction of the DPA-coated microcapsules restored their initial size after pH was decreased back to neutral. The microcapsules coated with the original dextran immobilized via hydrogen bonds and the bare microcapsules were fully dissolved under the alkaline conditions. The preserved fraction of the microcapsules was higher for the DPA materials with higher contents of the aldehyde groups and after conversion of the hydrolyzable covalent cross-links to the nonhydrolyzable secondary amines via reduction with NaBH(4). The higher contents of the aldehyde groups and the reduction led to the lower limiting swelling degree of the DPA-coated microcapsules at alkaline pH. The proposed coatings can be used for colloid stabilization of polyelectrolyte microcapsules in aqueous medium, encapsulation of pH-insensitive macromolecules at the postpreparation stage, and pH-triggered release of encapsulated material.

  18. Prevention and Control of Dental Disease through Improved Access to Comprehensive Care.

    ERIC Educational Resources Information Center

    American Dental Association, Chicago, IL.

    Prevention of dental disease is the key to improving the nation's oral health. The American Dental Association (ADA) program of prevention and control of dental disease through improved access to comprehensive care concentrates on those who have special difficulties in receiving care: the poor, the elderly, the handicapped, the institutionalized…

  19. Secure Access Control and Large Scale Robust Representation for Online Multimedia Event Detection

    PubMed Central

    Liu, Changyu; Li, Huiling

    2014-01-01

    We developed an online multimedia event detection (MED) system. However, there are a secure access control issue and a large scale robust representation issue when we want to integrate traditional event detection algorithms into the online environment. For the first issue, we proposed a tree proxy-based and service-oriented access control (TPSAC) model based on the traditional role based access control model. Verification experiments were conducted on the CloudSim simulation platform, and the results showed that the TPSAC model is suitable for the access control of dynamic online environments. For the second issue, inspired by the object-bank scene descriptor, we proposed a 1000-object-bank (1000OBK) event descriptor. Feature vectors of the 1000OBK were extracted from response pyramids of 1000 generic object detectors which were trained on standard annotated image datasets, such as the ImageNet dataset. A spatial bag of words tiling approach was then adopted to encode these feature vectors for bridging the gap between the objects and events. Furthermore, we performed experiments in the context of event classification on the challenging TRECVID MED 2012 dataset, and the results showed that the robust 1000OBK event descriptor outperforms the state-of-the-art approaches. PMID:25147840

  20. Mining Roles and Access Control for Relational Data under Privacy and Accuracy Constraints

    ERIC Educational Resources Information Center

    Pervaiz, Zahid

    2013-01-01

    Access control mechanisms protect sensitive information from unauthorized users. However, when sensitive information is shared and a Privacy Protection Mechanism (PPM) is not in place, an authorized insider can still compromise the privacy of a person leading to identity disclosure. A PPM can use suppression and generalization to anonymize and…

  1. A Model for Trust-based Access Control and Delegation in Mobile Clouds (Post Print)

    DTIC Science & Technology

    2013-10-01

    Qing-Guo, Z., Rong, L.: An Access Control Model for Ubiquitous Computing Application. In: Proceedings of the 2nd International Conference on Mobile ... Technology , Applications and Systems, Guangzhou, China (November 2005) 22. Baracaldo, N., Joshi, J.B.D.: A Trust-and-Risk Aware RBAC Framework: Tackling

  2. Functional requirements with survey results for integrated intrusion detection and access control annunciator systems

    SciTech Connect

    Arakaki, L.H.; Monaco, F.M.

    1995-09-01

    This report contains the guidance Functional Requirements for an Integrated Intrusion Detection and Access Control Annunciator System, and survey results of selected commercial systems. The survey questions were based upon the functional requirements; therefore, the results reflect which and sometimes how the guidance recommendations were met.

  3. The Role of Automatic Indexing in Access Control: A Modular View

    ERIC Educational Resources Information Center

    Hartson, H. Rex

    1974-01-01

    A model which relates the access control and indexing functions. The model is based on concept protection which allows a practically unbounded number of levels (subsets) of protection without requiring a fixed hierarchy among the levels. This protection is offered independently for each of the user operations allowed. (Author)

  4. Predicting Health Care Utilization among Latinos: Health Locus of Control Beliefs or Access Factors?

    ERIC Educational Resources Information Center

    De Jesus, Maria; Xiao, Chenyang

    2014-01-01

    There are two competing research explanations to account for Latinos' underutilization of health services relative to non-Latino Whites in the United States. One hypothesis examines the impact of health locus of control (HLOC) beliefs, while the other focuses on the role of access factors on health care use. To date, the relative strength of…

  5. The Use of Passwords for Controlled Access to Computer Resources. Computer Science & Technology.

    ERIC Educational Resources Information Center

    Wood, Helen M.

    This paper considers the generation of passwords and their effective application to the problem of controlling access to computer resources. After describing the need for and uses of passwords, password schemes are categorized according to selection technique, lifetime, physical characteristics, and information content. Password protection, both…

  6. An Access Control and Trust Management Framework for Loosely-Coupled Multidomain Environments

    ERIC Educational Resources Information Center

    Zhang, Yue

    2010-01-01

    Multidomain environments where multiple organizations interoperate with each other are becoming a reality as can be seen in emerging Internet-based enterprise applications. Access control to ensure secure interoperation in such an environment is a crucial challenge. A multidomain environment can be categorized as "tightly-coupled" and…

  7. 21 CFR 1311.125 - Requirements for establishing logical access control-Individual practitioner.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... least one of the individuals designated under paragraph (a) of this section must verify that the DEA... authentication credential to satisfy the logical access controls. The second individual must be a DEA registrant... practitioner's DEA registration expires, unless the registration has been renewed. (3) The...

  8. 21 CFR 1311.125 - Requirements for establishing logical access control-Individual practitioner.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... least one of the individuals designated under paragraph (a) of this section must verify that the DEA... authentication credential to satisfy the logical access controls. The second individual must be a DEA registrant... practitioner's DEA registration expires, unless the registration has been renewed. (3) The...

  9. 21 CFR 1311.125 - Requirements for establishing logical access control-Individual practitioner.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... least one of the individuals designated under paragraph (a) of this section must verify that the DEA... authentication credential to satisfy the logical access controls. The second individual must be a DEA registrant... practitioner's DEA registration expires, unless the registration has been renewed. (3) The...

  10. 21 CFR 1311.125 - Requirements for establishing logical access control-Individual practitioner.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... least one of the individuals designated under paragraph (a) of this section must verify that the DEA... authentication credential to satisfy the logical access controls. The second individual must be a DEA registrant... practitioner's DEA registration expires, unless the registration has been renewed. (3) The...

  11. A Stateful Multicast Access Control Mechanism for Future Metro-Area-Networks.

    ERIC Educational Resources Information Center

    Sun, Wei-qiang; Li, Jin-sheng; Hong, Pei-lin

    2003-01-01

    Multicasting is a necessity for a broadband metro-area-network; however security problems exist with current multicast protocols. A stateful multicast access control mechanism, based on MAPE, is proposed. The architecture of MAPE is discussed, as well as the states maintained and messages exchanged. The scheme is flexible and scalable. (Author/AEF)

  12. 76 FR 78866 - Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-20

    ... for Access Control Technologies AGENCY: Copyright Office, Library of Congress. ACTION: Notice of... submitted comments. The Office is taking this action, in part, to clarify the proposal to the best of the... formats; and (2) are legally obtained by blind or other persons with print disabilities (as such...

  13. Active Vibration Control of Elastic Beam by Means of Shape Memory Alloy Layers

    NASA Technical Reports Server (NTRS)

    Chen, Q.; Levy, C.

    1996-01-01

    The mathematical model of a flexible beam covered with shape memory alloy (SMA) layers is presented. The SMA layers are used as actuators, which are capable of changing their elastic modulus and recovery stress, thus changing the natural frequency of, and adjusting the excitation to, the vibrating beam. The frequency factor variation as a function of SMA Young's modulus, SMA layer thickness and beam thickness is discussed. Also control of the beam employing an optimal linear control law is evaluated. The control results indicate how the system reacts to various levels of excitation input through the non-homogeneous recovery shear term of the governing differential equation.

  14. Accessibility of dog populations for rabies control in Kathmandu valley, Nepal.

    PubMed Central

    Bögel, K.; Joshi, D. D.

    1990-01-01

    The accessibility of dogs in urban areas of Kathmandu valley was measured using the following approaches: determination of the proportion of dogs that bore signs of having been the objects of religious worship and other signs of household association, supplemented by information obtained by interviewing people in the neighbourhood; and the vaccination coverage attained in a rabies control campaign that was preceded by intensive activities to encourage the community to participate. An accessibility rate of 90-95% was determined using the first of these approaches, whereas 75-80% of the total dog population was reached in the vaccination campaign. PMID:2289296

  15. Access Scheme for Controlling Mobile Agents and its Application to Share Medical Information.

    PubMed

    Liao, Yu-Ting; Chen, Tzer-Shyong; Chen, Tzer-Long; Chung, Yu-Fang; Chen, Yu- Xin; Hwang, Jen-Hung; Wang, Huihui; Wei, Wei

    2016-05-01

    This study is showing the advantage of mobile agents to conquer heterogeneous system environments and contribute to a virtual integrated sharing system. Mobile agents will collect medical information from each medical institution as a method to achieve the medical purpose of data sharing. Besides, this research also provides an access control and key management mechanism by adopting Public key cryptography and Lagrange interpolation. The safety analysis of the system is based on a network attacker's perspective. The achievement of this study tries to improve the medical quality, prevent wasting medical resources and make medical resources access to appropriate configuration.

  16. Cross-Layer Scheme to Control Contention Window for Per-Flow in Asymmetric Multi-Hop Networks

    NASA Astrophysics Data System (ADS)

    Giang, Pham Thanh; Nakagawa, Kenji

    The IEEE 802.11 MAC standard for wireless ad hoc networks adopts Binary Exponential Back-off (BEB) mechanism to resolve bandwidth contention between stations. BEB mechanism controls the bandwidth allocation for each station by choosing a back-off value from one to CW according to the uniform random distribution, where CW is the contention window size. However, in asymmetric multi-hop networks, some stations are disadvantaged in opportunity of access to the shared channel and may suffer severe throughput degradation when the traffic load is large. Then, the network performance is degraded in terms of throughput and fairness. In this paper, we propose a new cross-layer scheme aiming to solve the per-flow unfairness problem and achieve good throughput performance in IEEE 802.11 multi-hop ad hoc networks. Our cross-layer scheme collects useful information from the physical, MAC and link layers of own station. This information is used to determine the optimal Contention Window (CW) size for per-station fairness. We also use this information to adjust CW size for each flow in the station in order to achieve per-flow fairness. Performance of our cross-layer scheme is examined on various asymmetric multi-hop network topologies by using Network Simulator (NS-2).

  17. Control and reduction of unsteady pressure loads in separated shock wave turbulent boundary layer interaction

    NASA Technical Reports Server (NTRS)

    Dolling, David S.; Barter, John W.

    1995-01-01

    The focus was on developing means of controlling and reducing unsteady pressure loads in separated shock wave turbulent boundary layer interactions. Section 1 describes how vortex generators can be used to effectively reduce loads in compression ramp interaction, while Section 2 focuses on the effects of 'boundary-layer separators' on the same interaction.

  18. Boundary Layer Simulation and Control in Wind Tunnels

    DTIC Science & Technology

    1988-04-01

    boundaries at constant a ,, I’) 44 \\> REF. IN r—i <J1 i 00 3 1 ? i Z •" ai UJ < > < X UJ 1 CC UJ Z o <x o ? *: FLOvA a. «I <t n < o TYPE \\| o ^ I...cfwrtpt) i JO ntout**t*eHrici NOTE DftAC -ftiC UACH M/Wef» oeicuMwce AI C. »OJO •o» 1 ’ «> ’ ’ REYNOLOS NUMBER. Rr Fig. 3c...streamwisc diffusion terms and the thin layer techniques can then be applied*31’. The discussion above applies in genere to both two- ai " • three-dimensional

  19. Adaptive dual-layer super-twisting control and observation

    NASA Astrophysics Data System (ADS)

    Edwards, Christopher; Shtessel, Yuri

    2016-09-01

    In this paper, a super-twisting-like structure with adaptive gains is proposed. The structure is parameterised by two scalar gains, both of which adapt, and by an additional time-varying term. The magnitudes of the adaptive terms are allowed to both increase and decrease as appropriate so that they are as small as possible, in the sense that they do not unnecessarily over-bound the uncertainty, and yet are large enough to sustain a sliding motion. In the paper, a new time varying gain is incorporated into the traditional super-twisting architecture. The proposed adaption law has a dual-layer structure which is formally analyzed using Lyapunov techniques. The additional term has the effect of simplifying the stability analysis whilst guaranteeing the second-order sliding mode properties of the traditional super-twisting scheme.

  20. Controlled Substances Add New Layer to E-Prescribing.

    PubMed

    Kaldy, Joanne

    2016-04-01

    The Electronic Prescriptions for Controlled Substances (EPCS) program was established by the Drug Enforcement Administration to allow health facilities to use electronic transmission and other modern technology for prescribing controlled substances and replacing old technology such as fax. Its goal is to eliminate fraud, abuse, and diversion of controlled medications while streamlining the processes of making them more easily available to patients in need. While rules regarding EPCS have the potential to improve care and give practitioners more data for quality improvement, they also may create new challenges for practitioners, facilities, and vendors alike. All stakeholders need to work together to ensure effective, efficient EPCS systems.

  1. Active/Passive Control of Sound Radiation from Panels using Constrained Layer Damping

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2003-01-01

    A hybrid passive/active noise control system utilizing constrained layer damping and model predictive feedback control is presented. This system is used to control the sound radiation of panels due to broadband disturbances. To facilitate the hybrid system design, a methodology for placement of constrained layer damping which targets selected modes based on their relative radiated sound power is developed. The placement methodology is utilized to determine two constrained layer damping configurations for experimental evaluation of a hybrid system. The first configuration targets the (4,1) panel mode which is not controllable by the piezoelectric control actuator, and the (2,3) and (5,2) panel modes. The second configuration targets the (1,1) and (3,1) modes. The experimental results demonstrate the improved reduction of radiated sound power using the hybrid passive/active control system as compared to the active control system alone.

  2. Reducing operation voltages by introducing a low-k switching layer in indium-tin-oxide-based resistance random access memory

    NASA Astrophysics Data System (ADS)

    Jin, Fu-Yuan; Chang, Kuan-Chang; Chang, Ting-Chang; Tsai, Tsung-Ming; Pan, Chih-Hung; Lin, Chih-Yang; Chen, Po-Hsun; Chen, Min-Chen; Huang, Hui-Chun; Lo, Ikai; Zheng, Jin-Cheng; Sze, Simon M.

    2016-06-01

    In this letter, we inserted a low dielectric constant (low-k) or high dielectric constant (high-k) material as a switching layer in indium-tin-oxide-based resistive random-access memory. After measuring the two samples, we found that the low-k material device has very low operating voltages (-80 and 110 mV for SET and RESET operations, respectively). Current fitting results were then used with the COMSOL software package to simulate electric field distribution in the layers. After combining the electrical measurement results with simulations, a conduction model was proposed to explain resistance switching behaviors in the two structures.

  3. Multi-layer neural networks for robot control

    NASA Technical Reports Server (NTRS)

    Pourboghrat, Farzad

    1989-01-01

    Two neural learning controller designs for manipulators are considered. The first design is based on a neural inverse-dynamics system. The second is the combination of the first one with a neural adaptive state feedback system. Both types of controllers enable the manipulator to perform any given task very well after a period of training and to do other untrained tasks satisfactorily. The second design also enables the manipulator to compensate for unpredictable perturbations.

  4. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers

    NASA Astrophysics Data System (ADS)

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M.; Zacharias, Margit; Asplund, Maria

    2016-01-01

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ±0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system.

  5. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers

    PubMed Central

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M.; Zacharias, Margit; Asplund, Maria

    2016-01-01

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ±0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system. PMID:26791399

  6. A Simple Approach for Molecular Controlled Release based on Atomic Layer Deposition Hybridized Organic-Inorganic Layers.

    PubMed

    Boehler, Christian; Güder, Firat; Kücükbayrak, Umut M; Zacharias, Margit; Asplund, Maria

    2016-01-21

    On-demand release of bioactive substances with high spatial and temporal control offers ground-breaking possibilities in the field of life sciences. However, available strategies for developing such release systems lack the possibility of combining efficient control over release with adequate storage capability in a reasonably compact system. In this study we present a new approach to target this deficiency by the introduction of a hybrid material. This organic-inorganic material was fabricated by atomic layer deposition of ZnO into thin films of polyethylene glycol, forming the carrier matrix for the substance to be released. Sub-surface growth mechanisms during this process converted the liquid polymer into a solid, yet water-soluble, phase. This layer permits extended storage for various substances within a single film of only a few micrometers in thickness, and hence demands minimal space and complexity. Improved control over release of the model substance Fluorescein was achieved by coating the hybrid material with a conducting polymer film. Single dosage and repetitive dispensing from this system was demonstrated. Release was controlled by applying a bias potential of ± 0.5 V to the polymer film enabling or respectively suppressing the expulsion of the model drug. In vitro tests showed excellent biocompatibility of the presented system.

  7. Scalable control program for multiprecursor flow-type atomic layer deposition system

    SciTech Connect

    Selvaraj, Sathees Kannan; Takoudis, Christos G.

    2015-01-01

    The authors report the development and implementation of a scalable control program to control flow type atomic layer deposition (ALD) reactor with multiple precursor delivery lines. The program logic is written and tested in LABVIEW environment to control ALD reactor with four precursor delivery lines to deposit up to four layers of different materials in cyclic manner. The programming logic is conceived such that to facilitate scale up for depositing more layers with multiple precursors and scale down for using single layer with any one precursor in the ALD reactor. The program takes precursor and oxidizer exposure and purging times as input and controls the sequential opening and closing of the valves to facilitate the complex ALD process in cyclic manner. The program could be used to deposit materials from any single line or in tandem with other lines in any combination and in any sequence.

  8. Linear feedback control and estimation applied to instabilities in spatially developing boundary layers

    NASA Astrophysics Data System (ADS)

    Chevalier, Mattias; H?Pffner, J.?R.?Me; ?Kervik, Espen; Henningson, Dan S.

    This paper presents the application of feedback control to spatially developing boundary layers. It is the natural follow-up of HSkan-Cooke boundary layers are estimated by use of wall measurements. The estimated state is in turn fed back for control in order to reduce the kinetic energy of the perturbations. The control actuation is achieved by means of unsteady blowing and suction at the wall. Flow perturbations are generated in the upstream region in the computational box and propagate in the boundary layer. Measurements are extracted downstream over a thin strip, followed by a second thin strip where the actuation is performed. It is shown that flow disturbances can be efficiently estimated and controlled in spatially evolving boundary layers for a wide range of base flows and disturbances.

  9. Controlled-release fertilizer composition substantially coated with an impermeable layer

    SciTech Connect

    Ankeny, Mark

    2016-03-29

    A controlled-release fertilizer composition is provided that is substantially coated with an impermeable layer. The fertilizer composition may further include one or more hollow sections to allow for root penetration and efficient delivery of nutrients.

  10. Layer-specific cholinergic control of human and mouse cortical synaptic plasticity

    PubMed Central

    Verhoog, Matthijs B.; Obermayer, Joshua; Kortleven, Christian A.; Wilbers, René; Wester, Jordi; Baayen, Johannes C.; De Kock, Christiaan P. J.; Meredith, Rhiannon M.; Mansvelder, Huibert D.

    2016-01-01

    Individual cortical layers have distinct roles in information processing. All layers receive cholinergic inputs from the basal forebrain (BF), which is crucial for cognition. Acetylcholinergic receptors are differentially distributed across cortical layers, and recent evidence suggests that different populations of BF cholinergic neurons may target specific prefrontal cortical (PFC) layers, raising the question of whether cholinergic control of the PFC is layer dependent. Here we address this issue and reveal dendritic mechanisms by which endogenous cholinergic modulation of synaptic plasticity is opposite in superficial and deep layers of both mouse and human neocortex. Our results show that in different cortical layers, spike timing-dependent plasticity is oppositely regulated by the activation of nicotinic acetylcholine receptors (nAChRs) either located on dendrites of principal neurons or on GABAergic interneurons. Thus, layer-specific nAChR expression allows functional layer-specific control of cortical processing and plasticity by the BF cholinergic system, which is evolutionarily conserved from mice to humans. PMID:27604129

  11. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    DOEpatents

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  12. BARTER: Behavior Profile Exchange for Behavior-Based Admission and Access Control in MANETs

    NASA Astrophysics Data System (ADS)

    Frias-Martinez, Vanessa; Stolfo, Salvatore J.; Keromytis, Angelos D.

    Mobile Ad-hoc Networks (MANETs) are very dynamic networks with devices continuously entering and leaving the group. The highly dynamic nature of MANETs renders the manual creation and update of policies associated with the initial incorporation of devices to the MANET (admission control) as well as with anomaly detection during communications among members (access control) a very difficult task. In this paper, we present BARTER, a mechanism that automatically creates and updates admission and access control policies for MANETs based on behavior profiles. BARTER is an adaptation for fully distributed environments of our previously introduced BB-NAC mechanism for NAC technologies. Rather than relying on a centralized NAC enforcer, MANET members initially exchange their behavior profiles and compute individual local definitions of normal network behavior. During admission or access control, each member issues an individual decision based on its definition of normalcy. Individual decisions are then aggregated via a threshold cryptographic infrastructure that requires an agreement among a fixed amount of MANET members to change the status of the network. We present experimental results using content and volumetric behavior profiles computed from the ENRON dataset. In particular, we show that the mechanism achieves true rejection rates of 95% with false rejection rates of 9%.

  13. Controlled Access Headings in EAD Finding Aids: Current Practices in Number of and Types of Headings Assigned

    ERIC Educational Resources Information Center

    Mascaro, Michelle

    2011-01-01

    This article presents the findings from a study of controlled access headings assigned to encoded archival description finding aids in the Ohio Library and Information Network Finding Aid Repository, focusing on the number of headings per finding aid and the category of terms assigned. Assigning multiple controlled access headings was widely…

  14. Shock Wave / Boundary Layer Interaction Experiment on Control Surface

    DTIC Science & Technology

    2007-06-01

    like ice cubes do in water. When heat is added to the water/ ice mixture, ice melts , but the temperature of the mixture remains at 0ºC until all the ice ...ramp will likely experience similar oscillations (Figure 1). Various other groups have also performed numerical [9][10] and experimental [11][12][13... experimental data from all payloads in addition to some “housekeeping” signals. It also sends experiment control signals to the payloads. The

  15. A Privacy Access Control Framework for Web Services Collaboration with Role Mechanisms

    NASA Astrophysics Data System (ADS)

    Liu, Linyuan; Huang, Zhiqiu; Zhu, Haibin

    With the popularity of Internet technology, web services are becoming the most promising paradigm for distributed computing. This increased use of web services has meant that more and more personal information of consumers is being shared with web service providers, leading to the need to guarantee the privacy of consumers. This paper proposes a role-based privacy access control framework for Web services collaboration, it utilizes roles to specify the privacy privileges of services, and considers the impact on the reputation degree of the historic experience of services in playing roles. Comparing to the traditional privacy access control approaches, this framework can make the fine-grained authorization decision, thus efficiently protecting consumers' privacy.

  16. A threat intelligence framework for access control security in the oil industry

    NASA Astrophysics Data System (ADS)

    Alaskandrani, Faisal T.

    The research investigates the problem raised by the rapid development in the technology industry giving security concerns in facilities built by the energy industry containing diverse platforms. The difficulty of continuous updates to network security architecture and assessment gave rise to the need to use threat intelligence frameworks to better assess and address networks security issues. Focusing on access control security to the ICS and SCADA systems that is being utilized to carry out mission critical and life threatening operations. The research evaluates different threat intelligence frameworks that can be implemented in the industry seeking the most suitable and applicable one that address the issue and provide more security measures. The validity of the result is limited to the same environment that was researched as well as the technologies being utilized. The research concludes that it is possible to utilize a Threat Intelligence framework to prioritize security in Access Control Measures in the Oil Industry.

  17. An Internet of Things Example: Classrooms Access Control over Near Field Communication

    PubMed Central

    Palma, Daniel; Agudo, Juan Enrique; Sánchez, Héctor; Macías, Miguel Macías

    2014-01-01

    The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor networks that exchange information wirelessly via Wi-Fi, Bluetooth, Zigbee or RF are common. In this sense, our paper presents a way in which each classroom control is accessed through Near Field Communication (NFC) and the information is shared via radio frequency. These data are published on the Web and could easily be used for building applications from the data collected. As a result, our application collects information from the classroom to create a control classroom tool that displays access to and the status of all the classrooms graphically and also connects this data with social networks. PMID:24755520

  18. An internet of things example: classrooms access control over near field communication.

    PubMed

    Palma, Daniel; Agudo, Juan Enrique; Sánchez, Héctor; Macías, Miguel Macías

    2014-04-21

    The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor networks that exchange information wirelessly via Wi-Fi, Bluetooth, Zigbee or RF are common. In this sense, our paper presents a way in which each classroom control is accessed through Near Field Communication (NFC) and the information is shared via radio frequency. These data are published on the Web and could easily be used for building applications from the data collected. As a result, our application collects information from the classroom to create a control classroom tool that displays access to and the status of all the classrooms graphically and also connects this data with social networks.

  19. Sub-optimal control of unsteady boundary layer separation and optimal control of Saltzman-Lorenz model

    NASA Astrophysics Data System (ADS)

    Sardesai, Chetan R.

    The primary objective of this research is to explore the application of optimal control theory in nonlinear, unsteady, fluid dynamical settings. Two problems are considered: (1) control of unsteady boundary-layer separation, and (2) control of the Saltzman-Lorenz model. The unsteady boundary-layer equations are nonlinear partial differential equations that govern the eruptive events that arise when an adverse pressure gradient acts on a boundary layer at high Reynolds numbers. The Saltzman-Lorenz model consists of a coupled set of three nonlinear ordinary differential equations that govern the time-dependent coefficients in truncated Fourier expansions of Rayleigh-Renard convection and exhibit deterministic chaos. Variational methods are used to derive the nonlinear optimal control formulations based on cost functionals that define the control objective through a performance measure and a penalty function that penalizes the cost of control. The resulting formulation consists of the nonlinear state equations, which must be integrated forward in time, and the nonlinear control (adjoint) equations, which are integrated backward in time. Such coupled forward-backward time integrations are computationally demanding; therefore, the full optimal control problem for the Saltzman-Lorenz model is carried out, while the more complex unsteady boundary-layer case is solved using a sub-optimal approach. The latter is a quasi-steady technique in which the unsteady boundary-layer equations are integrated forward in time, and the steady control equation is solved at each time step. Both sub-optimal control of the unsteady boundary-layer equations and optimal control of the Saltzman-Lorenz model are found to be successful in meeting the control objectives for each problem. In the case of boundary-layer separation, the control results indicate that it is necessary to eliminate the recirculation region that is a precursor to the unsteady boundary-layer eruptions. In the case of the

  20. Low-frequency absorption using a two-layer system with active control of input impedance.

    PubMed

    Cobo, Pedro; Fernández, Alejandro; Doutres, Olivier

    2003-12-01

    Broadband noise absorption, including low frequencies, may be obtained by a hybrid passive-active two-layer system. A porous layer in front of an air layer provides passive absorption, at medium and high frequencies. Active control of the input impedance of the two-layer system yields absorption at low frequencies. The active control system can implement either pressure-release or impedance-matching conditions. A simple analytical model based upon plane waves propagating in a tube permits the comparison of both control strategies. The results of this simple model show that the pressure-release condition affords higher absorption than the impedance-matching condition for some combinations of geometrical and material parameters. Experimental results corroborate the good performance of the pressure-release condition under the prescribed geometrical setup.

  1. Sub-Network Access Control Technology Demonstrator: Software Design of the Network Management System

    DTIC Science & Technology

    2002-08-01

    validdes. En d’autres mots, ce projet est une 6tape suppldmentaire dans le dessein de migrer ces technologies radio vers la Flotte Op ~ rationnelle ...Defence Research and Recherche et ddveloppement Development Canada pour la defense Canada DEFENCE • I7 DEFENSE Sub-Network Access Control...dans l’optique qu’ils op ~rent sur des liens avec une large bande passantes dont la topologie 6volue Tentement. Les produites con-nerciaux de gestion de

  2. The influence of patriarchal behavior on birth control access and use among recent Hispanic immigrants.

    PubMed

    Gonzalez, Eleazar U; Sable, Marjorie R; Campbell, James D; Dannerbeck, Anne

    2010-08-01

    It is commonly assumed that Hispanic immigrants in the United States subscribe to a patriarchal ideology that keeps women subordinated to men, often through violence and exploitative reproductive behaviors. If this assumption is true, we might expect to find that in the Hispanic culture patriarchal males control decision-making about access to and use of birth control. Structured interviews of 100 Hispanic men and 100 Hispanic women who were recent immigrants to a Midwest community were conducted to examine this assumption. Results did not support this assumption among this study population. We found no patriarchal ideology supporting women's subordination to men, violence as a mechanism of control, reproduction as a way of exploitation, or cultural influences discouraging access to and use of birth control in the Hispanic community. Rather, these immigrants revealed adequate knowledge of birth control use and positive perceptions of gender equality. Gaining a better understanding of the limited influence of patriarchal ideology on the use of birth control and family planning services among this Hispanic community may inform the development of family planning services tailored for new Hispanic immigrants.

  3. A human rights view on access to controlled substances for medical purposes under the international drug control framework.

    PubMed

    Gispen, Marie Elske C

    2013-11-05

    The world is confronted with a major public health deficit caused by poor access to controlled essential medicines under the international drug control framework. This is affecting millions of patients on a daily basis and resulting in numerous human rights violations. The present review contextualises this deficit from a human rights perspective. Drug control efforts are informed by a twofold objective stemming from the double nature of scheduled substances: free access for medical purposes should be ensured, though non-medical use of substances such as opium should be restricted. The international drug control framework is, in theory, based on this twofold notion, however at the level of interpretation, monitoring, and implementation, a one-sided emphasis is demonstrated. By tracing a parallel between the obligations of states under the international drug control framework and those that derive from human rights law, the review shows that the two systems seem incoherent and conflicting in nature and flags the importance of cross-disciplinary research into drug control and human rights.

  4. Effect of a fluid layer on the sound radiation of a plate and its active control

    NASA Astrophysics Data System (ADS)

    Sun, Yao; Pan, Jie; Yang, Tiejun

    2015-11-01

    In this paper, a baffled plate facing a layer of fluid is used to investigate the effects of the radiating environment on the plate's sound radiation and its active control. By varying the thickness of the fluid layer, different radiation environments are presented to the plate, resulting in a variation in the efficiencies and shapes of the radiation modes of the plate. As the design of feed-forward control of the radiated sound power and of feedback control of the vibration velocity or volume velocity is limited by the properties of the secondary control path (an open-loop frequency response function), the performance of the control system may be deteriorated if a controller optimally designed for one radiation environment is used for a different environment. The effects of radiation environment on the properties of the secondary control path and performance of active control are investigated.

  5. A low-complexity medium access control framework for body sensor networks.

    PubMed

    Wang, Bo; Wang, Lei; Huang, Bang-Yu; Wu, Dan; Lin, Shao-Jie; Gu, Jia; Zhang, Yuan-Ting; Chen, Wei

    2009-01-01

    This paper proposed a low-complexity medium access control (MAC) protocol tailored for body sensor networks (BSN) applications. The MAC protocol was designated to handle collision avoidance by reducing the numbers of the overhead packets for handshake control within the BSN. We also suggested a novel message recovery mechanism for getting back the lost physiological information. The adaptive synchronization scheme we have implemented exploited the features of multiple data-rate and adjustable precision design to support differentiated healthcare applications. The MAC protocol was fully implemented using our BSN development platform. The experimental results suggested the improved MAC design was compact and energy-efficient.

  6. BTG-AC: Break-The-Glass Access Control Model for Medical Data in Wireless Sensor Networks.

    PubMed

    Maw, Htoo; Xiao, Hannan; Christianson, Bruce; Malcolm, James

    2015-12-22

    Wireless Sensor Networks (WSNs) have recently attracted much interest in the research community because of their wide range of applications. An emerging application for WSNs involves their use in healthcare where they are generally termed Wireless Medical Sensor Networks (WMSNs). In a hospital, outfitting every patient with tiny, wearable, wireless vital sign sensors would allow doctors, nurses and other caregivers to continuously monitor the state of their patients. In such a scenario, patients are expected to be treated in reasonable time, so, an access control model is needed which will provide both real-time access to comprehensive medical records and detect unauthorised access to sensitive data. In emergency situations, a doctor or nurse needs to access data immediately. The loss in data availability can result in further decline in the patient's condition or can even lead to death. Therefore, the availability of data is more important than any security concern in emergency situations. To address that research issue for medical data in WSNs, we propose the Break-The-Glass Access Control (BTG-AC) model that is a modified and redesigned version of the Break-The-Glass Role-Based Access Control (BTG-RBAC) model to address data availability issue and to detect the security policy violations from both authorised and unauthorised users. Several changes within the access control engine are made in BTG-RBAC in order to make the new BTG-AC to apply and fit in WSNs. This paper presents the detailed design and development of the BTG-AC model based on a healthcare scenario. The evaluation results show that the concepts of BTG, prevention and detection mechanism, and obligation provide more flexible access than other current access control models in WSNs. Additionally, we compare the BTG-AC model with an adaptive access control model (A2C) which has similar properties, for further evaluation. Alongside with the comparison, the advantages and disadvantages of BTGAC over

  7. Nanosheets by design: The controllable synthesis of group IV-VI layered semiconductor chalcogenide nanostructures using colloidal chemistry

    NASA Astrophysics Data System (ADS)

    Vaughn, Dimitri D., II

    Nanosheets, a class of nanomaterials with two-dimensional structure and atomic or molecular scale thickness, have attracted a great deal of interest from the scientific community due to excellent physical properties and several promising applications in optoelectronics, energy conversion and storage, and catalysis. While advances in the synthesis of 2D nanostructures using top-down. chemical and physical strategies such as exfoliation and mechanical cleavage have been achieved, improved synthesis may be realized by applying bottom-up. colloidal strategies where nanosheets are built. directly from solution in an atomic layer-by-layer fashion. In this dissertation, I will discuss recent advances in the synthesis of semiconductor nanosheets with controllable lateral dimension, thickness, hierarchical structure, and porosity, specifically focusing on a class of group IV-VI layered semiconductor chalcogenides (GeS, GeSe, SnS, and SnSe) as a model system. Finally, I will highlight my efforts for expanding the synthetic framework mentioned above to access other materials, including the colloidal synthesis of germanium and Ge-based nanostructures.

  8. Health Access Livelihood Framework Reveals Potential Barriers in the Control of Schistosomiasis in the Dongting Lake Area of Hunan Province, China

    PubMed Central

    McManus, Donald P.; Raso, Giovanna; Utzinger, Jürg; Xiao, Shui-Yuan; Yu, Dong-Bao; Zhao, Zheng-Yuan; Li, Yue-Sheng

    2013-01-01

    Background Access to health care is a major requirement in improving health and fostering socioeconomic development. In the People's Republic of China (P.R. China), considerable changes have occurred in the social, economic, and health systems with a shift from a centrally planned to a socialist market economy. This brought about great benefits and new challenges, particularly for vertical disease control programs, including schistosomiasis. We explored systemic barriers in access to equitable and effective control of schistosomiasis. Methodology Between August 2002 and February 2003, 66 interviews with staff from anti-schistosomiasis control stations and six focus group discussions with health personnel were conducted in the Dongting Lake area, Hunan Province. Additionally, 79 patients with advanced schistosomiasis japonica were interviewed. The health access livelihood framework was utilized to examine availability, accessibility, affordability, adequacy, and acceptability of schistosomiasis-related health care. Principal Findings We found sufficient availability of infrastructure and human resources at most control stations. Many patients with advanced schistosomiasis resided in non-endemic or moderately endemic areas, however, with poor accessibility to disease-specific knowledge and specialized health services. Moreover, none of the patients interviewed had any form of health insurance, resulting in high out-of-pocket expenditure or unaffordable care. Reports on the adequacy and acceptability of care were mixed. Conclusions/Significance There is a need to strengthen health awareness and schistosomiasis surveillance in post-transmission control settings, as well as to reduce diagnostic and treatment costs. Further studies are needed to gain a multi-layered, in-depth understanding of remaining barriers, so that the ultimate goal of schistosomiasis elimination in P.R. China can be reached. PMID:23936580

  9. Sensored Field Oriented Control of a Robust Induction Motor Drive Using a Novel Boundary Layer Fuzzy Controller

    PubMed Central

    Saghafinia, Ali; Ping, Hew Wooi; Uddin, Mohammad Nasir

    2013-01-01

    Physical sensors have a key role in implementation of real-time vector control for an induction motor (IM) drive. This paper presents a novel boundary layer fuzzy controller (NBLFC) based on the boundary layer approach for speed control of an indirect field-oriented control (IFOC) of an induction motor (IM) drive using physical sensors. The boundary layer approach leads to a trade-off between control performances and chattering elimination. For the NBLFC, a fuzzy system is used to adjust the boundary layer thickness to improve the tracking performance and eliminate the chattering problem under small uncertainties. Also, to eliminate the chattering under the possibility of large uncertainties, the integral filter is proposed inside the variable boundary layer. In addition, the stability of the system is analyzed through the Lyapunov stability theorem. The proposed NBLFC based IM drive is implemented in real-time using digital signal processor (DSP) board TI TMS320F28335. The experimental and simulation results show the effectiveness of the proposed NBLFC based IM drive at different operating conditions.

  10. Hypertension Detection, Management, Control and Associated Factors Among Residents Accessing Community Health Services In Beijing

    PubMed Central

    JIANG, Bin; LIU, Hongmei; RU, Xiaojuan; ZHANG, Hui; WU, Shengping; WANG, Wenzhi

    2014-01-01

    The aim of this study was to analyse high blood pressure detection, management, control and associated factors among residents accessing community health services (CHSs) in Beijing. We screened for HBP in 9524 individuals aged 50 years or older who accessed care in four Beijing CHSs. Among the 9397 residents with questionnaire responses that qualified them for inclusion in the study, 5029 patients with HBP were identified, 1510 (i.e., 30% of the HBP patient group) of whom were newly identified cases. The rate of hypertension detection was 53.5%. Among the 5029 HBP patients, the rates of awareness, treatment and control of hypertension were 70.0%, 62.1% and 29.6%, respectively. In general, the rate of hypertension control was higher when the rates of hypertension awareness and treatment were higher in subgroups stratified by different sociodemographic and risk factors, except for the overweight and obesity subgroups. In conclusion, suboptimal HBP awareness, treatment, and control are still major problems confronting CHSs in Beijing. Control of hypertension in the population may be improved by increasing awareness and improving the treatment of hypertension in CHSs. PMID:24784167

  11. Hypertension detection, management, control and associated factors among residents accessing community health services in Beijing.

    PubMed

    Jiang, Bin; Liu, Hongmei; Ru, Xiaojuan; Zhang, Hui; Wu, Shengping; Wang, Wenzhi

    2014-05-02

    The aim of this study was to analyse high blood pressure detection, management, control and associated factors among residents accessing community health services (CHSs) in Beijing. We screened for HBP in 9524 individuals aged 50 years or older who accessed care in four Beijing CHSs. Among the 9397 residents with questionnaire responses that qualified them for inclusion in the study, 5029 patients with HBP were identified, 1510 (i.e., 30% of the HBP patient group) of whom were newly identified cases. The rate of hypertension detection was 53.5%. Among the 5029 HBP patients, the rates of awareness, treatment and control of hypertension were 70.0%, 62.1% and 29.6%, respectively. In general, the rate of hypertension control was higher when the rates of hypertension awareness and treatment were higher in subgroups stratified by different sociodemographic and risk factors, except for the overweight and obesity subgroups. In conclusion, suboptimal HBP awareness, treatment, and control are still major problems confronting CHSs in Beijing. Control of hypertension in the population may be improved by increasing awareness and improving the treatment of hypertension in CHSs.

  12. Ferroelectric control of magnetic domains in ultra-thin cobalt layers

    SciTech Connect

    Huang, Z.; Stolichnov, I.; Setter, N.; Bernand-Mantel, A.; Borrel, J.; Pizzini, S.; Ranno, L.; Herrera Diez, L.; Auffret, S.; Gaudin, G.; Boulle, O.

    2013-11-25

    Non-volatile ferroelectric control of magnetic domains has been demonstrated in ultra-thin cobalt layers at room temperature. The sensitivity of magnetic anisotropy energy to the electronic structure in a few atomic layers adjacent to the interface allows for ferroelectric control of coercivity and magnetic domain dynamics. These effects have been monitored and quantified using magneto-optical Kerr effect. In particular, the regimes, where the ferroelectric domains enhance/inhibit the magnetic domain nucleation or increase/reduce domain wall velocity, have been explored. Thus, non-destructive and reversible ferroelectric domain writing provides a tool to define the magnetic domain paths, create nucleation sites, or control domain movement.

  13. Frequency-selective design of wireless power transfer systems for controlled access applications

    NASA Astrophysics Data System (ADS)

    Maschino, Tyler Stephen

    Wireless power transfer (WPT) has become a common way to charge or power many types of devices, ranging from cell phones to electric toothbrushes. WPT became popular through the introduction of a transmission mode known as strongly coupled magnetic resonance (SCMR). This means of transmission is non-radiative and enables mid-range WPT. Shortly after the development of WPT via SCMR, a group of researchers introduced the concept of resonant repeaters, which allows power to hop from the source to the device. These repeaters are in resonance with the WPT system, which enables them to propagate the power wirelessly with minimal losses to the environment. Resonant repeaters have rekindled the dream of ubiquitous wireless power. Inherent risks come with the realization of such a dream. One of the most prominent risks, which we set out in this thesis to address, is that of accessibility to the WPT system. We propose the incorporation of a controlled access schema within a WPT system to prevent unwarranted use of wireless power. Our thesis discusses the history of electromagnetism, examines the inception of WPT via SCMR, evaluates recent developments in WPT, and further elaborates on the controlled access schema we wish to contribute to the field.

  14. An interaction-based access control model (IBAC) for collaborative services

    SciTech Connect

    Altunay, Mine; Byrd, Gregory T.; Brown, Doug E.; Dean, Ralph A.; /North Carolina State U.

    2008-04-01

    A collaboration is a collection of services that work together to achieve a common goal. Although collaborations help when tackling difficult problems, they lead to security issues. First, a collaboration is often performed by services that are drawn from different security domains. Second, a service interacts with multiple peer services during the collaboration. These interactions are not isolated from one another--e.g., data may flow through a sequence of different services. As a result, a service is exposed to multiple peer services in varying degrees, leading to different security threats. We identify the types of interactions that can be present in collaborations, and discuss the security threats due to each type. We propose a model for representing the collaboration context so that a service can be made aware of the existing interactions. We provide an access control model for a service participating in a collaboration. We couple our access control model with a policy model, so that the access requirements from collaborations can be expressed and evaluated.

  15. A Network Access Control Framework for 6LoWPAN Networks

    PubMed Central

    Oliveira, Luís M. L.; Rodrigues, Joel J. P. C.; de Sousa, Amaro F.; Lloret, Jaime

    2013-01-01

    Low power over wireless personal area networks (LoWPAN), in particular wireless sensor networks, represent an emerging technology with high potential to be employed in critical situations like security surveillance, battlefields, smart-grids, and in e-health applications. The support of security services in LoWPAN is considered a challenge. First, this type of networks is usually deployed in unattended environments, making them vulnerable to security attacks. Second, the constraints inherent to LoWPAN, such as scarce resources and limited battery capacity, impose a careful planning on how and where the security services should be deployed. Besides protecting the network from some well-known threats, it is important that security mechanisms be able to withstand attacks that have not been identified before. One way of reaching this goal is to control, at the network access level, which nodes can be attached to the network and to enforce their security compliance. This paper presents a network access security framework that can be used to control the nodes that have access to the network, based on administrative approval, and to enforce security compliance to the authorized nodes. PMID:23334610

  16. A network access control framework for 6LoWPAN networks.

    PubMed

    Oliveira, Luís M L; Rodrigues, Joel J P C; de Sousa, Amaro F; Lloret, Jaime

    2013-01-18

    Low power over wireless personal area networks (LoWPAN), in particular wireless sensor networks, represent an emerging technology with high potential to be employed in critical situations like security surveillance, battlefields, smart-grids, and in e-health applications. The support of security services in LoWPAN is considered a challenge. First, this type of networks is usually deployed in unattended environments, making them vulnerable to security attacks. Second, the constraints inherent to LoWPAN, such as scarce resources and limited battery capacity, impose a careful planning on how and where the security services should be deployed. Besides protecting the network from some well-known threats, it is important that security mechanisms be able to withstand attacks that have not been identified before. One way of reaching this goal is to control, at the network access level, which nodes can be attached to the network and to enforce their security compliance. This paper presents a network access security framework that can be used to control the nodes that have access to the network, based on administrative approval, and to enforce security compliance to the authorized nodes.

  17. Granular Layer Neurons Control Cerebellar Neurovascular Coupling Through an NMDA Receptor/NO-Dependent System.

    PubMed

    Mapelli, Lisa; Gagliano, Giuseppe; Soda, Teresa; Laforenza, Umberto; Moccia, Francesco; D'Angelo, Egidio U

    2017-02-01

    Neurovascular coupling (NVC) is the process whereby neuronal activity controls blood vessel diameter. In the cerebellum, the molecular layer is regarded as the main NVC determinant. However, the granular layer is a region with variable metabolic demand caused by large activity fluctuations that shows a prominent expression of NMDA receptors (NMDARs) and nitric oxide synthase (NOS) and is therefore much more suitable for effective NVC. Here, we show, in the granular layer of acute rat cerebellar slices, that capillary diameter changes rapidly after mossy fiber stimulation. Vasodilation required neuronal NMDARs and NOS stimulation and subsequent guanylyl cyclase activation that probably occurred in pericytes. Vasoconstriction required metabotropic glutamate receptors and CYP ω-hydroxylase, the enzyme regulating 20-hydroxyeicosatetraenoic acid production. Therefore, granular layer capillaries are controlled by the balance between vasodilating and vasoconstricting systems that could finely tune local blood flow depending on neuronal activity changes at the cerebellar input stage.

  18. High-efficiency control of transmitted light with a three-layered plasmonic metasurface

    NASA Astrophysics Data System (ADS)

    Liu, Zhengyang; Wang, Qianjin; Xie, Yubo; Zhu, Yongyuan

    2016-11-01

    A three-layered plasmonic metasurface is constructed for high-efficiency control of transmitted light. The metasurface contains metal antennas to steer light and a grating that acts as a polarizer to raise the efficiency. The optical properties are studied by an analytical model along with numerical simulations. Multiple-beam interference and standing wave are significant factors in this work. Simulated results agree with the theories. The efficiency of the metasurface is over 15 times higher than that of the single-layered metasurface. This high-efficiency three-layered design can be used in many optical integrated devices.

  19. On the designing of a tamper resistant prescription RFID access control system.

    PubMed

    Safkhani, Masoumeh; Bagheri, Nasour; Naderi, Majid

    2012-12-01

    Recently, Chen et al. have proposed a novel tamper resistant prescription RFID access control system, published in the Journal of Medical Systems. In this paper we consider the security of the proposed protocol and identify some existing weaknesses. The main attack is a reader impersonation attack which allows an active adversary to impersonate a legitimate doctor, e.g. the patient's doctor, to access the patient's tag and change the patient prescription. The presented attack is quite efficient. To impersonate a doctor, the adversary should eavesdrop one session between the doctor and the patient's tag and then she can impersonate the doctor with the success probability of '1'. In addition, we present efficient reader-tag to back-end database impersonation, de-synchronization and traceability attacks against the protocol. Finally, we propose an improved version of protocol which is more efficient compared to the original protocol while provides the desired security against the presented attacks.

  20. Randomized controlled trials in central vascular access devices: A scoping review

    PubMed Central

    Keogh, Samantha; Rickard, Claire M.

    2017-01-01

    Background Randomized controlled trials evaluate the effectiveness of interventions for central venous access devices, however, high complication rates remain. Scoping reviews map the available evidence and demonstrate evidence deficiencies to focus ongoing research priorities. Method A scoping review (January 2006–December 2015) of randomized controlled trials evaluating the effectiveness of interventions to improve central venous access device outcomes; including peripherally inserted central catheters, non-tunneled, tunneled and totally implanted venous access catheters. MeSH terms were used to undertake a systematic search with data extracted by two independent researchers, using a standardized data extraction form. Results In total, 178 trials were included (78 non-tunneled [44%]; 40 peripherally inserted central catheters [22%]; 20 totally implanted [11%]; 12 tunneled [6%]; 6 non-specified [3%]; and 22 combined device trials [12%]). There were 119 trials (68%) involving adult participants only, with 18 (9%) pediatric and 20 (11%) neonatal trials. Insertion-related themes existed in 38% of trials (67 RCTs), 35 RCTs (20%) related to post-insertion patency, with fewer trials on infection prevention (15 RCTs, 8%), education (14RCTs, 8%), and dressing and securement (12 RCTs, 7%). There were 46 different study outcomes reported, with the most common being infection outcomes (161 outcomes; 37%), with divergent definitions used for catheter-related bloodstream and other infections. Conclusion More high quality randomized trials across central venous access device management are necessary, especially in dressing and securement and patency. These can be encouraged by having more studies with multidisciplinary team involvement and consumer engagement. Additionally, there were extensive gaps within population sub-groups, particularly in tunneled devices, and in pediatrics and neonates. Finally, outcome definitions need to be unified for results to be meaningful and

  1. Control of the anodic aluminum oxide barrier layer opening process by wet chemical etching.

    PubMed

    Han, Catherine Y; Willing, Gerold A; Xiao, Zhili; Wang, H Hau

    2007-01-30

    In this work, it has been shown that, through a highly controlled process, the chemical etching of the anodic aluminum oxide membrane barrier layer can be performed in such a way as to achieve nanometer-scale control of the pore opening. As the barrier layer is etched away, subtle differences revealed through AFM phase imaging in the alumina composition in the barrier layer give rise to a unique pattern of hexagonal walls surrounding each of the barrier layer domes. These nanostructures observed in both topography and phase images can be understood as differences in the oxalate anion contaminated alumina versus pure alumina. This information bears significant implication for catalysis, template synthesis, and chemical sensing applications. From the pore opening etching studies, the etching rate of the barrier layer (1.3 nm/min) is higher than that of the inner cell wall (0.93 nm/min), both of which are higher than the etching rate of pure alumina layer (0.5-0.17 nm/min). The established etching rates together with the etching temperature allow one to control the pore diameter systematically from 10 to 95 nm.

  2. Optimal Control of Shock Wave Turbulent Boundary Layer Interactions Using Micro-Array Actuation

    NASA Technical Reports Server (NTRS)

    Anderson, Bernhard H.; Tinapple, Jon; Surber, Lewis

    2006-01-01

    The intent of this study on micro-array flow control is to demonstrate the viability and economy of Response Surface Methodology (RSM) to determine optimal designs of micro-array actuation for controlling the shock wave turbulent boundary layer interactions within supersonic inlets and compare these concepts to conventional bleed performance. The term micro-array refers to micro-actuator arrays which have heights of 25 to 40 percent of the undisturbed supersonic boundary layer thickness. This study covers optimal control of shock wave turbulent boundary layer interactions using standard micro-vane, tapered micro-vane, and standard micro-ramp arrays at a free stream Mach number of 2.0. The effectiveness of the three micro-array devices was tested using a shock pressure rise induced by the 10 shock generator, which was sufficiently strong as to separate the turbulent supersonic boundary layer. The overall design purpose of the micro-arrays was to alter the properties of the supersonic boundary layer by introducing a cascade of counter-rotating micro-vortices in the near wall region. In this manner, the impact of the shock wave boundary layer (SWBL) interaction on the main flow field was minimized without boundary bleed.

  3. Control of layer stacking in CVD graphene under quasi-static condition.

    PubMed

    Subhedar, Kiran M; Sharma, Indu; Dhakate, Sanjay R

    2015-09-14

    The type of layer stacking in bilayer graphene has a significant influence on its electronic properties because of the contrast nature of layer coupling. Herein, different geometries of the reaction site for the growth of bilayer graphene by the chemical vapor deposition (CVD) technique and their effects on the nature of layer stacking are investigated. Micro-Raman mapping and curve fitting analysis confirmed the type of layer stacking for the CVD grown bilayer graphene. The samples grown with sandwiched structure such as quartz/Cu foil/quartz along with a spacer, between the two quartz plates to create a sealed space, resulted in Bernal or AB stacked bilayer graphene while the sample sandwiched without a spacer produced the twisted bilayer graphene. The contrast difference in the layer stacking is a consequence of the difference in the growth mechanism associated with different geometries of the reaction site. The diffusion dominated process under quasi-static control is responsible for the growth of twisted bilayer graphene in sandwiched geometry while surface controlled growth with ample and continual supply of carbon in sandwiched geometry along with a spacer, leads to AB stacked bilayer graphene. Through this new approach, an efficient technique is presented to control the nature of layer stacking.

  4. Control and optimization of sealing layer in films

    NASA Astrophysics Data System (ADS)

    Najarzadeh, Zahra

    Heat sealing is the process to achieve the hermetic closure of a package by applying heat and pressure on two polymer films for a specified dwell time. The heat sealing process has been used in packaging of a wide spectrum of products, in particular for food packaging. During the past two decades, heat sealing machinery has been developed for very high speed line production which requires very precise process condition and material optimization. Heat seal process conditions, including temperature, dwell time, and pressure as well as film characteristics such as molecular weight, molecular weight distribution, long and short chain branching are the key factors that control the final quality of the joint. In the first part of this study, we have investigated the interrelated influence of heat seal process parameters on the strengthening of the interface as well as the micro mechanisms involved. The effects of heat seal temperature, pressure, and dwell time on seal strength of LLDPE were illustrated in "time-temperature" and "pressure-temperature" 3D maps, a methodology that is easily applicable to other systems. The interfacial adhesion of semicrystalline polymers was not well understood. We thus studied the adhesion behaviour of LLDPE as a semicrystalline polymer. The results indicated that the time and temperature dependence of seal strength is a consequence of the fraction of amorphous phase available at the interface of films. The seal strength had a linear correlation with the square root of sealing time which was also supported by the welding models. The slope of this linear correlation increased with temperature. This work was followed concurrently by two main approaches: analysis of polymer chain behaviour from microscopic point of view based on reptation theory and conventional macroscopic analysis based on bulk properties of the polymer. Failure mechanisms and fractured surfaces were also analyzed after peeling. Moreover, the topography and morphology of

  5. Design of Discrete Variable Structure Controller Based on Variable Boundary Layer

    NASA Astrophysics Data System (ADS)

    Su, Shibin; Wang, Heng; Zhang, Hua; Xiong, Wei

    Variable structure control is recognized as the most efficient method for control of uncertain systems. In order to reduce the chattering and improve the stability of the Discrete-time Variable Structure Control System (DVSCS) with parameter uncertainties and external disturbances, this paper proposes a variable structure controller based on variable boundary layer. Simulations results demonstrate the controller is not only effectively reduce chattering of the DVSCS, but improve the asymptotic stability and robustness of system. In addition, the results also revealed that the controller has strong effectiveness and robustness of the trajectory tracking.

  6. Experiments of Closed-Loop Flow Control for Laminar Boundary Layers

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu

    The Tollmien-Schlichting (T-S) instability is important for the transition process of boundary layer flows. The cancellation of its unstable modes will help delay the occurrence of transition and then turbulence. In this article the T-S instability was attempted to attenuate through an active closed-loop control strategy. The frequency responses of unstable travelling T-S waves were obtained for the implementation of control strategy. Information such as velocity disturbances of both incoming unstable waves and cancelling waves were then fed into the control system. A controller was deliberately designed and tested for the active cancellation of instabilities which were excited by velocity disturbances normal to the wall. The cancellation performance of the control system was validated by experiments in a low turbulence wind tunnel, which proved the functionality of above control strategy upon the active cancellation of boundary layer instabilities.

  7. Active Control of Instabilities in Laminar Boundary-Layer Flow. Part 2; Use of Sensors and Spectral Controller

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.; Nicolaides, R. A.; Erlebacher, Gordon; Hussaini, M. Yousuff; Gunzburger, Max D.

    1994-01-01

    This study focuses on the suppression of instability growth using an automated active-control technique. The evolution of 2D disturbances that are spatially growing in a flat-plate boundary layer are computed with a spatial DNS code. A controller receives wall sensor information (pressure or shear) as input and provides a signal that controls an actuator response as output. The control law assumes that wave cancellation is valid. The results indicate that a measure of wave cancellation can be obtained for small- and large-amplitude instabilities without feedback; however, feedback is required to optimize the control amplitude and phase for exact wave cancellation.

  8. Experimental Investigation on Transmission Control Protocol Throughput Behavior in Optical Fiber Access Networks

    NASA Astrophysics Data System (ADS)

    Tego, Edion; Matera, Francesco; del Buono, Donato

    2016-03-01

    This article describes an experimental investigation on the behavior of transmission control protocol in throughput measurements to be used in the verification of the service-level agreement between the Internet service provider and user in terms of line capacity for ultra-broadband access networks typical of fiber-to-the-x architectures. It is experimentally shown different conditions in high bandwidth-delay product links where the estimation of the line capacity based on a single transmission control protocol session results are unreliable. Simple equations reported in this work, and experimentally verified, point out the conditions in terms of packet loss, time delay, and line capacity, that allow consideration of the reliability of the measurement carried out with a single transmission control protocol session test by adopting a suitable measurement time duration.

  9. A stochastic control approach to Slotted-ALOHA random access protocol

    NASA Astrophysics Data System (ADS)

    Pietrabissa, Antonio

    2013-12-01

    ALOHA random access protocols are distributed protocols based on transmission probabilities, that is, each node decides upon packet transmissions according to a transmission probability value. In the literature, ALOHA protocols are analysed by giving necessary and sufficient conditions for the stability of the queues of the node buffers under a control vector (whose elements are the transmission probabilities assigned to the nodes), given an arrival rate vector (whose elements represent the rates of the packets arriving in the node buffers). The innovation of this work is that, given an arrival rate vector, it computes the optimal control vector by defining and solving a stochastic control problem aimed at maximising the overall transmission efficiency, while keeping a grade of fairness among the nodes. Furthermore, a more general case in which the arrival rate vector changes in time is considered. The increased efficiency of the proposed solution with respect to the standard ALOHA approach is evaluated by means of numerical simulations.

  10. Spin and valley control of free carriers in single-layer WS2

    NASA Astrophysics Data System (ADS)

    Ulstrup, Søren; Čabo, Antonija Grubišić; Biswas, Deepnarayan; Riley, Jonathon M.; Dendzik, Maciej; Sanders, Charlotte E.; Bianchi, Marco; Cacho, Cephise; Matselyukh, Dan; Chapman, Richard T.; Springate, Emma; King, Phil D. C.; Miwa, Jill A.; Hofmann, Philip

    2017-01-01

    The semiconducting single-layer transition-metal dichalcogenides have been identified as ideal materials for accessing and manipulating spin- and valley-quantum numbers due to a set of favorable optical selection rules in these materials. Here, we apply time- and angle-resolved photoemission spectroscopy to directly probe optically excited free carriers in the electronic band structure of a high quality single layer (SL) of WS2 grown on Ag(111). We present a momentum-resolved analysis of the optically generated free hole density around the valence band maximum of SL WS2 for linearly and circularly polarized optical excitations. We observe that the excited free holes are valley polarized within the upper spin-split branch of the valence band, which implies that the photon energy and polarization of the excitation permit selective excitations of free electron-hole pairs with a given spin and within a single valley.

  11. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    Fritz, Gregory M.; Weihs, Timothy P.; Grzyb, Justin A.

    2016-07-05

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  12. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    SciTech Connect

    Fritz, Gregory M; Knepper, Robert Allen; Weihs, Timothy P; Gash, Alexander E; Sze, John S

    2013-04-30

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  13. Development and process control of magnetic tunnel junctions for magnetic random access memory devices

    NASA Astrophysics Data System (ADS)

    Kula, Witold; Wolfman, Jerome; Ounadjela, Kamel; Chen, Eugene; Koutny, William

    2003-05-01

    We report on the development and process control of magnetic tunnel junctions (MTJs) for magnetic random access memory (MRAM) devices. It is demonstrated that MTJs with high magnetoresistance ˜40% at 300 mV, resistance-area product (RA) ˜1-3 kΩ μm2, low intrinsic interlayer coupling (Hin) ˜2-3 Oe, and excellent bit switching characteristics can be developed and fully integrated with complementary metal-oxide-semiconductor circuitry into MRAM devices. MTJ uniformity and repeatability level suitable for mass production has been demonstrated with the advanced processing and monitoring techniques.

  14. An Effective Massive Sensor Network Data Access Scheme Based on Topology Control for the Internet of Things

    PubMed Central

    Yi, Meng; Chen, Qingkui; Xiong, Neal N.

    2016-01-01

    This paper considers the distributed access and control problem of massive wireless sensor networks’ data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate. PMID:27827878

  15. An Effective Massive Sensor Network Data Access Scheme Based on Topology Control for the Internet of Things.

    PubMed

    Yi, Meng; Chen, Qingkui; Xiong, Neal N

    2016-11-03

    This paper considers the distributed access and control problem of massive wireless sensor networks' data access center for the Internet of Things, which is an extension of wireless sensor networks and an element of its topology structure. In the context of the arrival of massive service access requests at a virtual data center, this paper designs a massive sensing data access and control mechanism to improve the access efficiency of service requests and makes full use of the available resources at the data access center for the Internet of things. Firstly, this paper proposes a synergistically distributed buffer access model, which separates the information of resource and location. Secondly, the paper divides the service access requests into multiple virtual groups based on their characteristics and locations using an optimized self-organizing feature map neural network. Furthermore, this paper designs an optimal scheduling algorithm of group migration based on the combination scheme between the artificial bee colony algorithm and chaos searching theory. Finally, the experimental results demonstrate that this mechanism outperforms the existing schemes in terms of enhancing the accessibility of service requests effectively, reducing network delay, and has higher load balancing capacity and higher resource utility rate.

  16. Controllable growth of layered selenide and telluride heterostructures and superlattices using molecular beam epitaxy

    DOE PAGES

    Vishwanath, Suresh; Liu, Xinyu; Rouvimov, Sergei; ...

    2016-01-06

    Layered materials are an actively pursued area of research for realizing highly scaled technologies involving both traditional device structures as well as new physics. Lately, non-equilibrium growth of 2D materials using molecular beam epitaxy (MBE) is gathering traction in the scientific community and here we aim to highlight one of its strengths, growth of abrupt heterostructures, and superlattices (SLs). In this work we present several of the firsts: first growth of MoTe2 by MBE, MoSe2 on Bi2Se3 SLs, transition metal dichalcogenide (TMD) SLs, and lateral junction between a quintuple atomic layer of Bi2Te3 and a triple atomic layer of MoTe2.more » In conclusion, reflected high electron energy diffraction oscillations presented during the growth of TMD SLs strengthen our claim that ultrathin heterostructures with monolayer layer control is within reach.« less

  17. A computer controlled chemical bevel etching apparatus: applications to Auger analysis of multi-layered structures

    NASA Astrophysics Data System (ADS)

    El-Gomati, M.; Gelsthorpe, A.; Srnanek, R.; Liday, J.; Vogrincic, P.; Kovac, J.

    1999-04-01

    Analysis of thin layer structures can be achieved by chemically etching a bevel and subsequently analysing the surface. However non-linear bevels often result due to differing etch rates of the materials leading to incorrect analysis results. We report on a computer controlled stepper motor reactor whereby the specimen is lowered into the etchant at a rate which compensates for the different etch rates of the various layers constituting the sample. The apparatus is used to produce linear bevels of various magnifications on GaAs/AlGaAs heterostructures. The etchant of H 3PO 4/H 2O 2/H 2O is used for bevel preparation capped by a water layer to suppress the meniscus. Application of the technique to Multi Quantum Wells (MQW) and Bragg diffraction layers is shown. The depth resolution of the bevelled samples are analysed by AES and a comparison is made to conventional ion sputtering techniques.

  18. Controllable synthesis of layered Co-Ni hydroxide hierarchical structures for high-performance hybrid supercapacitors

    NASA Astrophysics Data System (ADS)

    Yuan, Peng; Zhang, Ning; Zhang, Dan; Liu, Tao; Chen, Limiao; Ma, Renzhi; Qiu, Guanzhou; Liu, Xiaohe

    2016-01-01

    A facile solvothermal method is developed for synthesizing layered Co-Ni hydroxide hierarchical structures by using hexamethylenetetramine (HMT) as alkaline reagent. The electrochemical measurements reveal that the specific capacitances of layered bimetallic (Co-Ni) hydroxides are generally superior to those of layered monometallic (Co, Ni) hydroxides. The as-prepared Co0.5Ni0.5 hydroxide hierarchical structures possesses the highest specific capacitance of 1767 F g-1 at a galvanic current density of 1 A g-1 and an outstanding specific capacitance retention of 87% after 1000 cycles. In comparison with the dispersed nanosheets of Co-Ni hydroxide, layered hydroxide hierarchical structures show much superior electrochemical performance. This study provides a promising method to construct hierarchical structures with controllable transition-metal compositions for enhancing the electrochemical performance in hybrid supercapacitors.

  19. Dynamic Key Management Schemes for Secure Group Access Control Using Hierarchical Clustering in Mobile Ad Hoc Networks

    NASA Astrophysics Data System (ADS)

    Tsaur, Woei-Jiunn; Pai, Haw-Tyng

    2008-11-01

    The applications of group computing and communication motivate the requirement to provide group access control in mobile ad hoc networks (MANETs). The operation in MANETs' groups performs a decentralized manner and accommodated membership dynamically. Moreover, due to lack of centralized control, MANETs' groups are inherently insecure and vulnerable to attacks from both within and outside the groups. Such features make access control more challenging in MANETs. Recently, several researchers have proposed group access control mechanisms in MANETs based on a variety of threshold signatures. However, these mechanisms cannot actually satisfy MANETs' dynamic environments. This is because the threshold-based mechanisms cannot be achieved when the number of members is not up to the threshold value. Hence, by combining the efficient elliptic curve cryptosystem, self-certified public key cryptosystem and secure filter technique, we construct dynamic key management schemes based on hierarchical clustering for securing group access control in MANETs. Specifically, the proposed schemes can constantly accomplish secure group access control only by renewing the secure filters of few cluster heads, when a cluster head joins or leaves a cross-cluster. In such a new way, we can find that the proposed group access control scheme can be very effective for securing practical applications in MANETs.

  20. Otto Laporte Award Lecture: Control of Turbulent Boundary Layers: State of the Art - 2001

    NASA Astrophysics Data System (ADS)

    Kim, John

    2001-11-01

    Control of turbulent boundary layers has been a subject of much interest because of its high potential payoffs. The control of turbulent boundary layers requires, however, a thorough understanding of the underlying physics of the turbulent flow and an efficient control algorithm, both of which have been less than satisfactory. Great strides on both fronts have been made through the recent advancement in computational fluid dynamics and control theories. New approaches to controller design are significantly different from existing approaches, which were mostly based on the investigator's physical insight into the flow, in that modern control theories are incorporated into the controller design. Examples include systems control-theoretic approaches such as H_2- and H_∞-control, and adjoint-based optimal/suboptimal controls. Some of these approaches explicitly exploit certain linear mechanisms present in the wall-bounded shear flow, and their success suggests the importance of linear mechanisms in the turbulent (and hence, nonlinear) flow. Although all of these new approaches have been thus far based on numerical experiments (and yet to be verified in laboratory experiments), they have shown great promise and present a new approach to flow control. The success and limitation of various new controllers and their implications will be discussed.

  1. Adaptive nonlinear polynomial neural networks for control of boundary layer/structural interaction

    NASA Technical Reports Server (NTRS)

    Parker, B. Eugene, Jr.; Cellucci, Richard L.; Abbott, Dean W.; Barron, Roger L.; Jordan, Paul R., III; Poor, H. Vincent

    1993-01-01

    The acoustic pressures developed in a boundary layer can interact with an aircraft panel to induce significant vibration in the panel. Such vibration is undesirable due to the aerodynamic drag and structure-borne cabin noises that result. The overall objective of this work is to develop effective and practical feedback control strategies for actively reducing this flow-induced structural vibration. This report describes the results of initial evaluations using polynomial, neural network-based, feedback control to reduce flow induced vibration in aircraft panels due to turbulent boundary layer/structural interaction. Computer simulations are used to develop and analyze feedback control strategies to reduce vibration in a beam as a first step. The key differences between this work and that going on elsewhere are as follows: that turbulent and transitional boundary layers represent broadband excitation and thus present a more complex stochastic control scenario than that of narrow band (e.g., laminar boundary layer) excitation; and secondly, that the proposed controller structures are adaptive nonlinear infinite impulse response (IIR) polynomial neural network, as opposed to the traditional adaptive linear finite impulse response (FIR) filters used in most studies to date. The controllers implemented in this study achieved vibration attenuation of 27 to 60 dB depending on the type of boundary layer established by laminar, turbulent, and intermittent laminar-to-turbulent transitional flows. Application of multi-input, multi-output, adaptive, nonlinear feedback control of vibration in aircraft panels based on polynomial neural networks appears to be feasible today. Plans are outlined for Phase 2 of this study, which will include extending the theoretical investigation conducted in Phase 2 and verifying the results in a series of laboratory experiments involving both bum and plate models.

  2. Face Recognition for Access Control Systems Combining Image-Difference Features Based on a Probabilistic Model

    NASA Astrophysics Data System (ADS)

    Miwa, Shotaro; Kage, Hiroshi; Hirai, Takashi; Sumi, Kazuhiko

    We propose a probabilistic face recognition algorithm for Access Control System(ACS)s. Comparing with existing ACSs using low cost IC-cards, face recognition has advantages in usability and security that it doesn't require people to hold cards over scanners and doesn't accept imposters with authorized cards. Therefore face recognition attracts more interests in security markets than IC-cards. But in security markets where low cost ACSs exist, price competition is important, and there is a limitation on the quality of available cameras and image control. Therefore ACSs using face recognition are required to handle much lower quality images, such as defocused and poor gain-controlled images than high security systems, such as immigration control. To tackle with such image quality problems we developed a face recognition algorithm based on a probabilistic model which combines a variety of image-difference features trained by Real AdaBoost with their prior probability distributions. It enables to evaluate and utilize only reliable features among trained ones during each authentication, and achieve high recognition performance rates. The field evaluation using a pseudo Access Control System installed in our office shows that the proposed system achieves a constant high recognition performance rate independent on face image qualities, that is about four times lower EER (Equal Error Rate) under a variety of image conditions than one without any prior probability distributions. On the other hand using image difference features without any prior probabilities are sensitive to image qualities. We also evaluated PCA, and it has worse, but constant performance rates because of its general optimization on overall data. Comparing with PCA, Real AdaBoost without any prior distribution performs twice better under good image conditions, but degrades to a performance as good as PCA under poor image conditions.

  3. Discrete-Layer Piezoelectric Plate and Shell Models for Active Tip-Clearance Control

    NASA Technical Reports Server (NTRS)

    Heyliger, P. R.; Ramirez, G.; Pei, K. C.

    1994-01-01

    The objectives of this work were to develop computational tools for the analysis of active-sensory composite structures with added or embedded piezoelectric layers. The targeted application for this class of smart composite laminates and the analytical development is the accomplishment of active tip-clearance control in turbomachinery components. Two distinct theories and analytical models were developed and explored under this contract: (1) a discrete-layer plate theory and corresponding computational models, and (2) a three dimensional general discrete-layer element generated in curvilinear coordinates for modeling laminated composite piezoelectric shells. Both models were developed from the complete electromechanical constitutive relations of piezoelectric materials, and incorporate both displacements and potentials as state variables. This report describes the development and results of these models. The discrete-layer theories imply that the displacement field and electrostatic potential through-the-thickness of the laminate are described over an individual layer rather than as a smeared function over the thickness of the entire plate or shell thickness. This is especially crucial for composites with embedded piezoelectric layers, as the actuating and sensing elements within these layers are poorly represented by effective or smeared properties. Linear Lagrange interpolation polynomials were used to describe the through-thickness laminate behavior. Both analytic and finite element approximations were used in the plane or surface of the structure. In this context, theoretical developments are presented for the discrete-layer plate theory, the discrete-layer shell theory, and the formulation of an exact solution for simply-supported piezoelectric plates. Finally, evaluations and results from a number of separate examples are presented for the static and dynamic analysis of the plate geometry. Comparisons between the different approaches are provided when

  4. Inorganic Nanowires-Assembled Layered Paper as the Valve for Controlling Water Transportation.

    PubMed

    Chen, Fei-Fei; Zhu, Ying-Jie; Xiong, Zhi-Chao; Sun, Tuan-Wei; Shen, Yue-Qin; Yang, Ri-Long

    2017-03-29

    Layered materials with open interlayer channels enable various applications such as tissue engineering, ionic and molecular sieving, and electrochemical devices. However, most reports focus on the two-dimensional nanosheets-assembled layered materials, whose interlayer spacing is limited at the nanometer scale. Herein, we demonstrate that one-dimensional inorganic nanowires are the ideal building blocks for the construction of layered materials with open interlayer channels as well, which has not aroused much attention before. It is found that the relatively long inorganic nanowires are capable of assembling into free-standing layered paper with open interlayer channels during the filtration process. The spacings of interlayer channels between adjacent layers are up to tens of micrometers, which are much larger than those of the two-dimensional nanosheets-assembled layered materials. But the closed interlayer channels are observed when the relatively short inorganic nanowires are used as building blocks. The mechanism based on the relationship between the structural variation and the nanowires used is proposed, including the surface charge amplified effect, surface charge superimposed effect, and pillarlike supporting effect. According to the proposed mechanism, we have successfully fabricated a series of layered paper sheets whose architectures (including interlayer channels of cross section and pores on the surface) show gradient changes. The as-prepared layered paper sheets are employed as the valves for controlling water transportation. Tunable water transportation is achieved by the synergistic effect between in-plane interlayer channels (horizontal transportation) from the open to the closed states, and through-layer pores (vertical transportation) without surface modification or intercalation of any guest species.

  5. Experimental Investigation of Normal Shock Boundary-Layer Interaction with Hybrid Flow Control

    NASA Technical Reports Server (NTRS)

    Vyas, Manan A.; Hirt, Stefanie M.; Anderson, Bernhard H.

    2012-01-01

    Hybrid flow control, a combination of micro-ramps and micro-jets, was experimentally investigated in the 15x15 cm Supersonic Wind Tunnel (SWT) at the NASA Glenn Research Center. Full factorial, a design of experiments (DOE) method, was used to develop a test matrix with variables such as inter-ramp spacing, ramp height and chord length, and micro-jet injection flow ratio. A total of 17 configurations were tested with various parameters to meet the DOE criteria. In addition to boundary-layer measurements, oil flow visualization was used to qualitatively understand shock induced flow separation characteristics. The flow visualization showed the normal shock location, size of the separation, path of the downstream moving counter-rotating vortices, and corner flow effects. The results show that hybrid flow control demonstrates promise in reducing the size of shock boundary-layer interactions and resulting flow separation by means of energizing the boundary layer.

  6. Inner Layer Control of Performance in a Dye-Sensitized Photoelectrosynthesis Cell.

    PubMed

    Wang, Degao; Farnum, Byron H; Sheridan, Matthew V; Marquard, Seth L; Sherman, Benjamin D; Meyer, Thomas J

    2017-03-02

    Interfacial charge transfer and core-shell structures play important roles in dye-sensitized photoelectrosynthesis cells (DSPEC) for water splitting into H2 and O2. An important element in the design of the photoanode in these devices is a core/shell structure which controls local electron transfer dynamics. Here, we introduce a new element, an internal layer of Al2O3 lying between the Sb:SnO2/TiO2 layers in a core/shell electrode which can improve photocurrents by up to 300%. In these structures, the results of photocurrent, transient absorption, and linear scan voltammetry measurements point to an important role for the Al2O3 layer in controlling internal electron transfer within the core/shell structure.

  7. Interface-controlled layer exchange in metal-induced crystallization of germanium thin films

    NASA Astrophysics Data System (ADS)

    Hu, Shu; Marshall, Ann F.; McIntyre, Paul C.

    2010-08-01

    Low-temperature synthesis of polycrystalline germanium (poly-Ge) thin films is of great interest in thin-film photovoltaic and electronics applications. We demonstrate metal (Al)-induced crystallization to form poly-Ge thin films on both glass and polymer substrates at temperatures as low as 200 °C. An interfacial diffusion control layer, intentionally interposed between the Al and the underlying amorphous Ge (a-Ge) layer, is found to achieve layer exchange while suppressing uncontrolled Ge crystallization within the bilayer samples. Germanium thin films with micron-size grains and (111)-preferred orientation are prepared by controlled Ge nucleation and Ge lateral overgrowth of Al during a-Ge crystallization.

  8. Functional Basis for Efficient Physical Layer Classical Control in Quantum Processors

    NASA Astrophysics Data System (ADS)

    Ball, Harrison; Nguyen, Trung; Leong, Philip H. W.; Biercuk, Michael J.

    2016-12-01

    The rapid progress seen in the development of quantum-coherent devices for information processing has motivated serious consideration of quantum computer architecture and organization. One topic which remains open for investigation and optimization relates to the design of the classical-quantum interface, where control operations on individual qubits are applied according to higher-level algorithms; accommodating competing demands on performance and scalability remains a major outstanding challenge. In this work, we present a resource-efficient, scalable framework for the implementation of embedded physical layer classical controllers for quantum-information systems. Design drivers and key functionalities are introduced, leading to the selection of Walsh functions as an effective functional basis for both programing and controller hardware implementation. This approach leverages the simplicity of real-time Walsh-function generation in classical digital hardware, and the fact that a wide variety of physical layer controls, such as dynamic error suppression, are known to fall within the Walsh family. We experimentally implement a real-time field-programmable-gate-array-based Walsh controller producing Walsh timing signals and Walsh-synthesized analog waveforms appropriate for critical tasks in error-resistant quantum control and noise characterization. These demonstrations represent the first step towards a unified framework for the realization of physical layer controls compatible with large-scale quantum-information processing.

  9. Security analysis and improvements of authentication and access control in the Internet of Things.

    PubMed

    Ndibanje, Bruce; Lee, Hoon-Jae; Lee, Sang-Gon

    2014-08-13

    Internet of Things is a ubiquitous concept where physical objects are connected over the internet and are provided with unique identifiers to enable their self-identification to other devices and the ability to continuously generate data and transmit it over a network. Hence, the security of the network, data and sensor devices is a paramount concern in the IoT network as it grows very fast in terms of exchanged data and interconnected sensor nodes. This paper analyses the authentication and access control method using in the Internet of Things presented by Jing et al. (Authentication and Access Control in the Internet of Things. In Proceedings of the 2012 32nd International Conference on Distributed Computing Systems Workshops, Macau, China, 18-21 June 2012, pp. 588-592). According to our analysis, Jing et al.'s protocol is costly in the message exchange and the security assessment is not strong enough for such a protocol. Therefore, we propose improvements to the protocol to fill the discovered weakness gaps. The protocol enhancements facilitate many services to the users such as user anonymity, mutual authentication, and secure session key establishment. Finally, the performance and security analysis show that the improved protocol possesses many advantages against popular attacks, and achieves better efficiency at low communication cost.

  10. Security Analysis and Improvements of Authentication and Access Control in the Internet of Things

    PubMed Central

    Ndibanje, Bruce; Lee, Hoon-Jae; Lee, Sang-Gon

    2014-01-01

    Internet of Things is a ubiquitous concept where physical objects are connected over the internet and are provided with unique identifiers to enable their self-identification to other devices and the ability to continuously generate data and transmit it over a network. Hence, the security of the network, data and sensor devices is a paramount concern in the IoT network as it grows very fast in terms of exchanged data and interconnected sensor nodes. This paper analyses the authentication and access control method using in the Internet of Things presented by Jing et al (Authentication and Access Control in the Internet of Things. In Proceedings of the 2012 32nd International Conference on Distributed Computing Systems Workshops, Macau, China, 18–21 June 2012, pp. 588–592). According to our analysis, Jing et al.'s protocol is costly in the message exchange and the security assessment is not strong enough for such a protocol. Therefore, we propose improvements to the protocol to fill the discovered weakness gaps. The protocol enhancements facilitate many services to the users such as user anonymity, mutual authentication, and secure session key establishment. Finally, the performance and security analysis show that the improved protocol possesses many advantages against popular attacks, and achieves better efficiency at low communication cost. PMID:25123464

  11. Heartbeat-driven medium-access control for body sensor networks.

    PubMed

    Li, Huaming; Tan, Jindong

    2010-01-01

    In this paper, a novel time division multiple access based MAC protocol designed for body sensor networks (BSNs) is presented. H-medium-access control (MAC) aims to improve BSNs energy efficiency by exploiting heartbeat rhythm information, instead of using periodic synchronization beacons, to perform time synchronization. Heartbeat rhythm is inherent in every human body and observable in various biosignals. Biosensors in a BSN can extract the heartbeat rhythm from their own sensory data by detecting waveform peaks. All rhythms represented by peak sequences are naturally synchronized since they are driven by the same source, i.e., the heartbeat. Following the rhythm, biosensors can achieve time synchronization without having to turn on their radio to receive periodic timing information from a central controller, so that energy cost for time synchronization can be completely eliminated and the lifetime of the network can be prolonged. An active synchronization recovery scheme is also developed, including two resynchronization approaches. The algorithms are simulated using the discrete event simulator OMNet + + with real-world data from the Massachusetts Institute of Technology-Boston's Beth Israel Hospital multiparameter database Multiparameter Intelligent Monitoring for Intensive Care. The results show that H-MAC can prolong the network life dramatically.

  12. Overview of the Altair Lunar Lander Thermal Control System Design and the Impacts of Global Access

    NASA Technical Reports Server (NTRS)

    Stephan, Ryan A.

    2011-01-01

    NASA's Constellation Program (CxP) was developed to successfully return humans to the Lunar surface prior to 2020. The CxP included several different project offices including Altair, which was planned to be the next generation Lunar Lander. The Altair missions were architected to be quite different than the Lunar missions accomplished during the Apollo era. These differences resulted in a significantly dissimilar Thermal Control System (TCS) design. The current paper will summarize the Altair mission architecture and the various operational phases associated with the planned mission. In addition, the derived thermal requirements and the TCS designed to meet these unique and challenging thermal requirements will be presented. During the past year, the design team has focused on developing a vehicle architecture capable of accessing the entire Lunar surface. Due to the widely varying Lunar thermal environment, this global access requirement resulted in major changes to the thermal control system architecture. These changes, and the rationale behind the changes, will be detailed throughout the current paper.

  13. Controllable quantized conductance for multilevel data storage applications using conductive bridge random access memory.

    PubMed

    Aga, Fekadu Gochole; Woo, Jiyong; Song, Jeonghwan; Park, Jaehyuk; Lim, Seokjae; Sung, Changhyuck; Hwang, Hyunsang

    2017-03-17

    In this paper, we investigate the quantized conduction behavior of conductive bridge random access memory (CBRAM) with varied materials and ramping rates. We report stable and reproducible quantized conductance states with integer multiples of fundamental conductance obtained by optimizing the voltage ramping rate and the Ti-diffusion barrier (DB) at the Cu/HfO2 interface. Owing to controlled diffusion of Cu ions by the Ti-DB and the optimized ramping rate, through which it was possible to control the time delay of Cu ion reduction, more than seven levels of discrete conductance states were clearly observed. Analytical modeling was performed to determine the rate-limiting step in filament growth based on an electrochemical redox reaction. Our understanding of the fundamental mechanisms of quantized conductance behaviors provide a promising future for the multi-bit CBRAM device.

  14. Analysis of the TDRS multiple access system for possible use as an attitude control system sensor

    NASA Technical Reports Server (NTRS)

    Blevins, Bruce Allyn; Sank, Victor J.

    1993-01-01

    A member of the constellation of TDR satellites (TDRS) has experienced a failure of its prime earth sensor. Failure of the remaining earth sensor could result in the inability of the satellite to control its attitude and provide user services. Loss of the satellite would be a serious event. The multiple access (MA) antenna array on the TDRS has been proposed for use as a backup sensor for the attitude control system. This paper describes our analysis of the performance of the MA array as an interferometer used for accurate attitude determination. A least squares fit of a plane to the MA phase information appears to represent the TDRS body roll and pitch within about 0.1 deg. This is sufficient for SGL pointing and MA and SSA user services. Analytic improvements that include ionospheric correction may yield sufficient accuracy for KSA user services.

  15. Controllable quantized conductance for multilevel data storage applications using conductive bridge random access memory

    NASA Astrophysics Data System (ADS)

    Gochole Aga, Fekadu; Woo, Jiyong; Song, Jeonghwan; Park, Jaehyuk; Lim, Seokjae; Sung, Changhyuck; Hwang, Hyunsang

    2017-03-01

    In this paper, we investigate the quantized conduction behavior of conductive bridge random access memory (CBRAM) with varied materials and ramping rates. We report stable and reproducible quantized conductance states with integer multiples of fundamental conductance obtained by optimizing the voltage ramping rate and the Ti-diffusion barrier (DB) at the Cu/HfO2 interface. Owing to controlled diffusion of Cu ions by the Ti-DB and the optimized ramping rate, through which it was possible to control the time delay of Cu ion reduction, more than seven levels of discrete conductance states were clearly observed. Analytical modeling was performed to determine the rate-limiting step in filament growth based on an electrochemical redox reaction. Our understanding of the fundamental mechanisms of quantized conductance behaviors provide a promising future for the multi-bit CBRAM device.

  16. Preliminary assessment of Tongue Drive System in medium term usage for computer access and wheelchair control.

    PubMed

    Yousefi, Behnaz; Huo, Xueliang; Ghovanloo, Maysam

    2011-01-01

    Tongue Drive System (TDS) is a wireless, wearable assistive technology that enables individuals with severe motor impairments access computers, drive wheelchairs, and control their environments using tongue motion. In this paper, we have evaluated the TDS performance as a computer input device using ISO9241-9 standard tasks for pointing and selecting, based on the well known Fitts' Law, and as a powered wheelchair controller through an obstacle course navigation task. Nine able-bodied subjects who already had tongue piercing participated in this trial over 5 sessions during 5 weeks, allowing us to study the TDS learning process and its current limiting factors. Subjects worn tongue rings made of titanium in the form of a barbell with a small rare earth magnetic tracer hermetically sealed inside the upper ball. Comparing the results between 1(st) and 5(th) sessions showed that subjects' performance improved in all the measures through 5 sessions, demonstrating the effects of learning.

  17. 17 CFR 240.15c3-5 - Risk management controls for brokers or dealers with market access.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 17 Commodity and Securities Exchanges 3 2011-04-01 2011-04-01 false Risk management controls for... Markets § 240.15c3-5 Risk management controls for brokers or dealers with market access. (a) For the... establish, document, and maintain a system of risk management controls and supervisory procedures...

  18. Control of turbulent boundary layer through air blowing due to external-flow resources

    NASA Astrophysics Data System (ADS)

    Kornilov, V. I.; Boiko, A. V.; Kavun, I. N.

    2015-07-01

    The possibility to control turbulent incompressible boundary layer using air blowing through a finely perforated wall presenting part of the streamlined flat-plate surface was examined. The control was exercised via an action on the state and characteristics of the near-wall flow exerted by controlled (through variation of external-pressure-flow velocity) blowing of air through an air intake installed on the idle side of the plate. A stable reduction of the local values of skin friction coefficient along the model, reaching 50 % at the end of the perforated area, has been demonstrated. The obtained experimental and calculated data are indicative of a possibility to model the process of turbulentboundary-layer control by air blowing due to external-flow resources.

  19. Large area single and bilayer graphene with controlled orientation for each layer

    NASA Astrophysics Data System (ADS)

    Brown, Lola; Lochocki, Edward; Gutiérrez, Christopher; Pasupathy, Abhay; Shen, Kyle; Park, Jiwoong; Cornell Collaboration; Cornell-Columbia Collaboration

    2014-03-01

    The creation and exploration of artificial graphene structures has recently become the focus of great interest. In particular, controlling the interlayer twist angles in multilayer graphene stacks allows modulation of the overall band structure. However, producing such a structure remains difficult due to the random distribution of twist angles in as-grown samples. Here we report a novel way for creating large area graphene stacks with a pre-determined twist angle. We first grow single layer graphene whose orientation is aligned over a few cm length scale on copper foil. The overall angle alignment of the graphene is confirmed using low energy electron microscopy (LEED) and transmission electron microscopy techniques. Since the graphene is well aligned over a few centimeters, we can create large area graphene stacks with known twist angle by transferring these graphene layers while controlling the orientation of each layer during transfer. We confirm that the layers are coupled by probing the resulting band structure using angle resolved photoemission spectroscopy (ARPES), and examining their interlayer optical resonance features using spatially resolved hyperspectral (DUV-Vis-NIR wavelengths). This new method is scalable, and controllable and thus paves the way to explore and exploit the novel properties of two-dimensional crystals in artificial stacks with controlled interlayer structures. Second affiliation: Kavli Institute at Cornell for Nanoscale Science.

  20. Feedback Control and Estimation Applied to Boundary Layers Subject to Free-Stream Turbulence

    DTIC Science & Technology

    2006-11-01

    R. G. Jacobs and P. A. Durbin , “Simulations of bypass transition,” J. Fluid Mech., vol. 428, pp. 185–212, 2001. [10] R. S. Rogallo, “Numerical...vol. 404, pp. 289–309, 2000. [20] P. Cathalifaud and P. Luchini, “ Algebraic growth in boundary layers: Optimal control by blowing and suction at the

  1. Hybrid Multi-Layer Network Control for Emerging Cyber-Infrastructures

    SciTech Connect

    Summerhill, Richard

    2009-08-14

    There were four basic task areas identified for the Hybrid-MLN project. They are: o Multi-Layer, Multi-Domain, Control Plane Architecture and Implementation, o Heterogeneous DataPlane Testing, o Simulation, o Project Publications, Reports, and Presentations.

  2. Control of excitons in multi-layer van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Calman, E. V.; Dorow, C. J.; Fogler, M. M.; Butov, L. V.; Hu, S.; Mishchenko, A.; Geim, A. K.

    2016-03-01

    We report an experimental study of excitons in a double quantum well van der Waals heterostructure made of atomically thin layers of MoS2 and hexagonal boron nitride. The emission of neutral and charged excitons is controlled by gate voltage, temperature, and both the helicity and the power of optical excitation.

  3. Resistive switching of a TaO{sub x}/TaON double layer via ionic control of carrier tunneling

    SciTech Connect

    Jeon, Heeyoung; Park, Jingyu; Kim, Hyunjung; Jang, Woochool; Song, Hyoseok; Kang, Chunho; Seo, Hyungtak; Jeon, Hyeongtag

    2014-04-14

    Resistance random access memory (RRAM) is an attractive candidate for future non-volatile memory due to its superior features. As the oxide thickness is scaled down, the charge transport mechanism is also subject to the transition from hopping to tunneling dominant process, which is critically related to the interfacial electronic band structure. A TaO{sub x}/TaON double layer-based RRAM is fabricated and characterized in this work. Upon TaON insertion at the lower interface, the improved switching behavior is observed. The TaON at the bottom electrode interface blocks oxygen vacancy percolation due to strong N-O bonds and also modifies interfacial band alignment to lower the injected electron energy from bottom electrode due to higher tunneling barrier height than that of TaO{sub x}/Pt. This study suggested that a defect-minimized insertion layer like TaON with a proper interfacial band alignment is pivotal in RRAM for the effective ionic control of carrier tunneling resulting in non-linear I-V behavior with improved properties.

  4. Gradient fiber electrospinning of layered scaffolds using controlled transitions in fiber diameter.

    PubMed

    Grey, Casey P; Newton, Scott T; Bowlin, Gary L; Haas, Thomas W; Simpson, David G

    2013-07-01

    We characterize layered, delamination resistant, tissue engineering scaffolds produced by gradient electrospinning using computational fluid dynamics, measurements of fiber diameter with respect to dynamic changes in polymer concentration, SEM analysis, and materials testing. Gradient electrospinning delivers a continuously variable concentration of polymer to the electrospinning jet, resulting in scaffolds that exhibit controlled transitions in fiber diameter across the Z-axis. This makes it possible to produce scaffolds that exhibit very different fiber sizes and material properties on opposing surfaces while eliminating the boundary layers that lead to delamination failures. In materials testing bi-layered laminated electrospun scaffolds (layer 1 = <250 nm, layer 2 = 1000 nm diameter polycaprolactone fibers) exhibit ductile properties and undergo multiphasic failure. In contrast, scaffolds, produced by gradient electrospinning fabricated with fibers of this type on opposing surfaces fracture and fail as unified, and mechanically integrated, structures. Gradient electrospinning also eliminates the anisotropic strain properties observed in scaffolds composed of highly aligned fibers. In burst testing, scaffolds composed of aligned fibers produced using gradient electrospinning exhibit superior material properties with respect to scaffolds composed of random or aligned fibers produced from a single polymer concentration or as bi-layered, laminated structures.

  5. Study of laminar boundary layer instability noise study on a controlled diffusion airfoil

    NASA Astrophysics Data System (ADS)

    Jaiswal, Prateek; Sanjose, Marlene; Moreau, Stephane

    2016-11-01

    Detailed experimental study has been carried out on a Controlled Diffusion (CD) airfoil at 5° angle of attack and at chord based Reynolds number of 1 . 5 ×105 . All the measurements were done in an open-jet anechoic wind tunnel. The airfoil mock-up is held between two side plates, to keep the flow two-dimensional. PIV measurements have been performed in the wake and on the boundary layer of the airfoil. Pressure sensor probes on the airfoil were used to detect mean airfoil loading and remote microphone probes were used to measure unsteady pressure fluctuations on the surface of the airfoil. Furthermore the far field acoustic pressure was measured using an 1/2 inch ICP microphone. The results confirm very later transition of a laminar boundary layer to a turbulent boundary layer on the suction side of the airfoil. The process of transition of laminar to turbulent boundary layer comprises of turbulent reattachment of a separated shear layer. The pressure side of the boundary layer is found to be laminar and stable. Therefore tonal noise generated is attributed to events on suction side of the airfoil. The flow transition and emission of tones are further investigated in detail thanks to the complementary DNS study.

  6. PANATIKI: a network access control implementation based on PANA for IoT devices.

    PubMed

    Moreno Sanchez, Pedro; Marin Lopez, Rafa; Gomez Skarmeta, Antonio F

    2013-11-01

    Internet of Things (IoT) networks are the pillar of recent novel scenarios, such as smart cities or e-healthcare applications. Among other challenges, these networks cover the deployment and interaction of small devices with constrained capabilities and Internet protocol (IP)-based networking connectivity. These constrained devices usually require connection to the Internet to exchange information (e.g., management or sensing data) or access network services. However, only authenticated and authorized devices can, in general, establish this connection. The so-called authentication, authorization and accounting (AAA) services are in charge of performing these tasks on the Internet. Thus, it is necessary to deploy protocols that allow constrained devices to verify their credentials against AAA infrastructures. The Protocol for Carrying Authentication for Network Access (PANA) has been standardized by the Internet engineering task force (IETF) to carry the Extensible Authentication Protocol (EAP), which provides flexible authentication upon the presence of AAA. To the best of our knowledge, this paper is the first deep study of the feasibility of EAP/PANA for network access control in constrained devices. We provide light-weight versions and implementations of these protocols to fit them into constrained devices. These versions have been designed to reduce the impact in standard specifications. The goal of this work is two-fold: (1) to demonstrate the feasibility of EAP/PANA in IoT devices; (2) to provide the scientific community with the first light-weight interoperable implementation of EAP/PANA for constrained devices in the Contiki operating system (Contiki OS), called PANATIKI. The paper also shows a testbed, simulations and experimental results obtained from real and simulated constrained devices.

  7. PANATIKI: A Network Access Control Implementation Based on PANA for IoT Devices

    PubMed Central

    Sanchez, Pedro Moreno; Lopez, Rafa Marin; Gomez Skarmeta, Antonio F.

    2013-01-01

    Internet of Things (IoT) networks are the pillar of recent novel scenarios, such as smart cities or e-healthcare applications. Among other challenges, these networks cover the deployment and interaction of small devices with constrained capabilities and Internet protocol (IP)-based networking connectivity. These constrained devices usually require connection to the Internet to exchange information (e.g., management or sensing data) or access network services. However, only authenticated and authorized devices can, in general, establish this connection. The so-called authentication, authorization and accounting (AAA) services are in charge of performing these tasks on the Internet. Thus, it is necessary to deploy protocols that allow constrained devices to verify their credentials against AAA infrastructures. The Protocol for Carrying Authentication for Network Access (PANA) has been standardized by the Internet engineering task force (IETF) to carry the Extensible Authentication Protocol (EAP), which provides flexible authentication upon the presence of AAA. To the best of our knowledge, this paper is the first deep study of the feasibility of EAP/PANA for network access control in constrained devices. We provide light-weight versions and implementations of these protocols to fit them into constrained devices. These versions have been designed to reduce the impact in standard specifications. The goal of this work is two-fold: (1) to demonstrate the feasibility of EAP/PANA in IoT devices; (2) to provide the scientific community with the first light-weight interoperable implementation of EAP/PANA for constrained devices in the Contiki operating system (Contiki OS), called PANATIKI. The paper also shows a testbed, simulations and experimental results obtained from real and simulated constrained devices. PMID:24189332

  8. Access Denied

    ERIC Educational Resources Information Center

    Villano, Matt

    2008-01-01

    Building access control (BAC)--a catchall phrase to describe the systems that control access to facilities across campus--has traditionally been handled with remarkably low-tech solutions: (1) manual locks; (2) electronic locks; and (3) ID cards with magnetic strips. Recent improvements have included smart cards and keyless solutions that make use…

  9. Effects of Hybrid Flow Control on a Normal Shock Boundary-Layer Interaction

    NASA Technical Reports Server (NTRS)

    Hirt, Stefanie M.; Vyas, Manan A.

    2013-01-01

    Hybrid flow control, a combination of micro-ramps and steady micro-jets, was experimentally investigated in the 15x15 cm Supersonic Wind Tunnel at the NASA Glenn Research Center. A central composite design of experiments method, was used to develop response surfaces for boundary-layer thickness and reversed-flow thickness, with factor variables of inter-ramp spacing, ramp height and chord length, and flow injection ratio. Boundary-layer measurements and wall static pressure data were used to understand flow separation characteristics. A limited number of profiles were measured in the corners of the tunnel to aid in understanding the three-dimensional characteristics of the flowfield.

  10. Diffusion-Based Design of Multi-Layered Ophthalmic Lenses for Controlled Drug Release.

    PubMed

    Pimenta, Andreia F R; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde; Colaço, Rogério

    2016-01-01

    The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses.

  11. Diffusion-Based Design of Multi-Layered Ophthalmic Lenses for Controlled Drug Release

    PubMed Central

    Pimenta, Andreia F. R.; Serro, Ana Paula; Paradiso, Patrizia; Saramago, Benilde

    2016-01-01

    The study of ocular drug delivery systems has been one of the most covered topics in drug delivery research. One potential drug carrier solution is the use of materials that are already commercially available in ophthalmic lenses for the correction of refractive errors. In this study, we present a diffusion-based mathematical model in which the parameters can be adjusted based on experimental results obtained under controlled conditions. The model allows for the design of multi-layered therapeutic ophthalmic lenses for controlled drug delivery. We show that the proper combination of materials with adequate drug diffusion coefficients, thicknesses and interfacial transport characteristics allows for the control of the delivery of drugs from multi-layered ophthalmic lenses, such that drug bursts can be minimized, and the release time can be maximized. As far as we know, this combination of a mathematical modelling approach with experimental validation of non-constant activity source lamellar structures, made of layers of different materials, accounting for the interface resistance to the drug diffusion, is a novel approach to the design of drug loaded multi-layered contact lenses. PMID:27936138

  12. Ultimate Control of Rate-Dependent Adhesion for Reversible Transfer Process via a Thin Elastomeric Layer.

    PubMed

    Kim, Chan; Yoon, Min-Ah; Jang, Bongkyun; Kim, Jae-Hyun; Lee, Hak-Joo; Kim, Kwang-Seop

    2017-03-30

    Adhesion between a stamp with an elastomeric layer and various devices or substrates is crucial to successfully fabricate flexible electronics using a transfer process. Although various transfer processes using stamps with different adhesion strengths have been suggested, the controllable range of adhesion is still limited to a narrow range. To precisely transfer devices onto selected substrates, however, the difference in adhesion between the picking and placing processes should be large enough to achieve a high yield. Herein, we report a simple way to extend the controllable adhesion range of stamps, which can be achieved by adjusting the thickness of the elastomeric layer and the separation velocity. The adhesion strength increased with decreasing layer thickness on the stamp due to a magnification of the confinement and rate-dependent effects on the adhesion. This enabled the controllable range of the adhesion strength for a 15 μm-thick elastomeric layer to be extended up to 12 times that of the bulk under the same separation conditions. The strategy of designing stamps using simple adhesion tests is also introduced, and the reversible transfer of thin Si chips was successfully demonstrated. Tuning and optimizing the adhesion strength of a stamp according to the design process suggested here can be applied to various materials for the selective transfer and replacement of individual devices.

  13. Controlling Interfacial Reactions and Intermetallic Compound Growth at the Interface of a Lead-free Solder Joint with Layer-by-Layer Transferred Graphene.

    PubMed

    Ko, Yong-Ho; Lee, Jong-Dae; Yoon, Taeshik; Lee, Chang-Woo; Kim, Taek-Soo

    2016-03-02

    The immoderate growth of intermetallic compounds (IMCs) formed at the interface of a solder metal and the substrate during soldering can degrade the mechanical properties and reliability of a solder joint in electronic packaging. Therefore, it is critical to control IMC growth at the solder joints between the solder and the substrate. In this study, we investigated the control of interfacial reactions and IMC growth by the layer-by-layer transfer of graphene during the reflow process at the interface between Sn-3.0Ag-0.5Cu (in wt %) lead-free solder and Cu. As the number of graphene layers transferred onto the surface of the Cu substrate increased, the thickness of the total IMC (Cu6Sn5 and Cu3Sn) layer decreased. After 10 repetitions of the reflow process for 50 s above 217 °C, the melting temperature of Sn-3.0Ag-0.5Cu, with a peak temperature of 250 °C, the increase in thickness of the total IMC layer at the interface with multiple layers of graphene was decreased by more than 20% compared to that at the interface of bare Cu without graphene. Furthermore, the average diameter of the Cu6Sn5 scallops at the interface with multiple layers of graphene was smaller than that at the interface without graphene. Despite 10 repetitions of the reflow process, the growth of Cu3Sn at the interface with multiple layers of graphene was suppressed by more than 20% compared with that at the interface without graphene. The multiple layers of graphene at the interface between the solder metal and the Cu substrate hindered the diffusion of Cu atoms from the Cu substrate and suppressed the reactions between Cu and Sn in the solder. Thus, the multiple layers of graphene transferred at the interface between dissimilar metals can control the interfacial reaction and IMC growth occurring at the joining interface.

  14. Control of a shock wave-boundary layer interaction using localized arc filament plasma actuators

    NASA Astrophysics Data System (ADS)

    Webb, Nathan Joseph

    Supersonic flight is currently possible, but expensive. Inexpensive supersonic travel will require increased efficiency of high-speed air entrainment, an integral part of air-breathing propulsion systems. Although mixed compression inlet geometry can significantly improve entrainment efficiency, numerous Shock Wave-Boundary Layer Interactions (SWBLIs) are generated in this configuration. The boundary layer must therefore develop through multiple regions of adverse pressure gradient, causing it to thicken, and, in severe cases, separate. The associated increase in unsteadiness can have adverse effects on downstream engine hardware. The most severe consequence of these interactions is the increased aerodynamic blockage generated by the thickened boundary layer. If the increase is sufficient, it can choke the flow, causing inlet unstart, and resulting in a loss of thrust and high transient forces on the engine, airframe, and aircraft occupants. The potentially severe consequences associated with SWBLIs require flow control to ensure proper operation. Traditionally, boundary layer bleed has been used to control the interaction. Although this method is effective, it has inherent efficiency penalties. Localized Arc Filament Plasma Actuators (LAFPAs) are designed to generate perturbations for flow control. Natural flow instabilities act to amplify certain perturbations, allowing the LAFPAs to control the flow with minimal power input. LAFPAs also have the flexibility to maintain control over a variety of operating conditions. This work seeks to examine the effectiveness of LAFPAs as a separation control method for an oblique, impinging SWBLI. The low frequency unsteadiness in the reflected shock was thought to be the natural manifestation of a Kelvin-Helmholtz instability in the shear layer above the separation region. The LAFPAs were therefore placed upstream of the interaction to allow their perturbations to convect to the receptivity region (near the shear layer origin

  15. Quantitative trait loci controlling light and hormone response in two accessions of Arabidopsis thaliana.

    PubMed Central

    Borevitz, Justin O; Maloof, Julin N; Lutes, Jason; Dabi, Tsegaye; Redfern, Joanna L; Trainer, Gabriel T; Werner, Jonathan D; Asami, Tadao; Berry, Charles C; Weigel, Detlef; Chory, Joanne

    2002-01-01

    We have mapped quantitative trait loci (QTL) responsible for natural variation in light and hormone response between the Cape Verde Islands (Cvi) and Landsberg erecta (Ler) accessions of Arabidopsis thaliana using recombinant inbred lines (RILs). Hypocotyl length was measured in four light environments: white, blue, red, and far-red light and in the dark. In addition, white light plus gibberellin (GA) and dark plus the brassinosteroid biosynthesis inhibitor brassinazole (BRZ) were used to detect hormone effects. Twelve QTL were identified that map to loci not previously known to affect light response, as well as loci where candidate genes have been identified from known mutations. Some QTL act in all environments while others show genotype-by-environment interaction. A global threshold was established to identify a significant epistatic interaction between two loci that have few main effects of their own. LIGHT1, a major QTL, has been confirmed in a near isogenic line (NIL) and maps to a new locus with effects in all light environments. The erecta mutation can explain the effect of the HYP2 QTL in the blue, BRZ, and dark environments, but not in far-red. LIGHT2, also confirmed in an NIL, has effects in white and red light and shows interaction with GA. The phenotype and map position of LIGHT2 suggest the photoreceptor PHYB as a candidate gene. Natural variation in light and hormone response thus defines both new genes and known genes that control light response in wild accessions. PMID:11861571

  16. Layer-specific excitatory circuits differentially control recurrent network dynamics in the neocortex.

    PubMed

    Beltramo, Riccardo; D'Urso, Giulia; Dal Maschio, Marco; Farisello, Pasqualina; Bovetti, Serena; Clovis, Yoanne; Lassi, Glenda; Tucci, Valter; De Pietri Tonelli, Davide; Fellin, Tommaso

    2013-02-01

    In the absence of external stimuli, the mammalian neocortex shows intrinsic network oscillations. These dynamics are characterized by translaminar assemblies of neurons whose activity synchronizes rhythmically in space and time. How different cortical layers influence the formation of these spontaneous cellular assemblies is poorly understood. We found that excitatory neurons in supragranular and infragranular layers have distinct roles in the regulation of intrinsic low-frequency oscillations in mice in vivo. Optogenetic activation of infragranular neurons generated network activity that resembled spontaneous events, whereas photoinhibition of these same neurons substantially attenuated slow ongoing dynamics. In contrast, light activation and inhibition of supragranular cells had modest effects on spontaneous slow activity. This study represents, to the best of our knowledge, the first causal demonstration that excitatory circuits located in distinct cortical layers differentially control spontaneous low-frequency dynamics.

  17. Towards precise defect control in layered oxide structures by using oxide molecular beam epitaxy.

    PubMed

    Baiutti, Federico; Christiani, Georg; Logvenov, Gennady

    2014-01-01

    In this paper we present the atomic-layer-by-layer oxide molecular beam epitaxy (ALL-oxide MBE) which has been recently installed in the Max-Planck Institute for Solid State Research and we report on its present status, providing some examples that demonstrate its successful application in the synthesis of different layered oxides, with particular reference to superconducting La2CuO4 and insulator-to-metal La2- x Sr x NiO4. We briefly review the ALL-oxide MBE technique and its unique capabilities in the deposition of atomically smooth single-crystal thin films of various complex oxides, artificial compounds and heterostructures, introducing our goal of pursuing a deep investigation of such systems with particular emphasis on structural defects, with the aim of tailoring their functional properties by precise defects control.

  18. Control over the preferred orientation of CIGS films deposited by magnetron sputtering using a wetting layer

    NASA Astrophysics Data System (ADS)

    Yan, Yong; Jiang, Fan; Liu, Lian; Yu, Zhou; Zhang, Yong; Zhao, Yong

    2016-01-01

    A growth method is presented to control the preferred orientation in chalcopyrite CuIn x Ga1- x Se2 (CIGS) thin films grown by magnetron sputtering. Films with (220/204) and (112) preferred orientation as well as randomly oriented films were prepared. The effects of an In2Se3 wetting layer and the working pressure on the texture transition phenomena were examined. A large-grained CIGS film with (220/204) texture was formed at 400°C with the inclusion of a thin (80 nm) In2Se3 layer and liquid phase (excess copper selenide phase) formation, and the reaction mechanism is proposed. The device deposited at 2.0 Pa on an In2Se3 layer exhibited the optimal electrical properties. [Figure not available: see fulltext.

  19. Precise Control of the Number of Layers of Graphene by Picosecond Laser Thinning

    PubMed Central

    Lin, Zhe; Ye, Xiaohui; Han, Jinpeng; Chen, Qiao; Fan, Peixun; Zhang, Hongjun; Xie, Dan; Zhu, Hongwei; Zhong, Minlin

    2015-01-01

    The properties of graphene can vary as a function of the number of layers (NOL). Controlling the NOL in large area graphene is still challenging. In this work, we demonstrate a picosecond (ps) laser thinning removal of graphene layers from multi-layered graphene to obtain desired NOL when appropriate pulse threshold energy is adopted. The thinning process is conducted in atmosphere without any coating and it is applicable for graphene films on arbitrary substrates. This method provides many advantages such as one-step process, non-contact operation, substrate and environment-friendly, and patternable, which will enable its potential applications in the manufacturing of graphene-based electronic devices. PMID:26111758

  20. Gate-Controllable Magneto-optic Kerr Effect in Layered Collinear Antiferromagnets

    SciTech Connect

    Sivadas, Nikhil; Okamoto, Satoshi; Xiao, Di

    2016-12-23

    In this paper, using symmetry arguments and a tight-binding model, we show that for layered collinear antiferromagnets, magneto-optic effects can be generated and manipulated by controlling crystal symmetries through a gate voltage. This provides a promising route for electric field manipulation of the magneto-optic effects without modifying the underlying magnetic structure. We further demonstrate the gate control of the magneto-optic Kerr effect (MOKE) in bilayer MnPSe3 using first-principles calculations. Finally, the field-induced inversion symmetry breaking effect leads to gate-controllable MOKE, whose direction of rotation can be switched by the reversal of the gate voltage.

  1. Gate-Controllable Magneto-optic Kerr Effect in Layered Collinear Antiferromagnets

    DOE PAGES

    Sivadas, Nikhil; Okamoto, Satoshi; Xiao, Di

    2016-12-23

    In this paper, using symmetry arguments and a tight-binding model, we show that for layered collinear antiferromagnets, magneto-optic effects can be generated and manipulated by controlling crystal symmetries through a gate voltage. This provides a promising route for electric field manipulation of the magneto-optic effects without modifying the underlying magnetic structure. We further demonstrate the gate control of the magneto-optic Kerr effect (MOKE) in bilayer MnPSe3 using first-principles calculations. Finally, the field-induced inversion symmetry breaking effect leads to gate-controllable MOKE, whose direction of rotation can be switched by the reversal of the gate voltage.

  2. Control of adhesion to the mask of epitaxial laterally overgrown GaAs layers

    NASA Astrophysics Data System (ADS)

    Zytkiewicz, Z. R.; Domagała, J.; Dobosz, D.

    2001-12-01

    Strain commonly observed in layers grown by epitaxial lateral overgrowth (ELO) and arising from interaction of the layers with the mask underneath is studied. We show that GaAs ELO layers grown by liquid-phase epitaxy on SiO2-coated GaAs substrates are strain free if the laterally overgrown parts ("wings") of the layers hang over and have no direct contact with the mask. In other cases, tilting of the wings can be efficiently tailored by controlling the ratio of vertical to lateral growth rates at the beginning of ELO growth. In particular, this has been achieved by growing GaAs ELO layers on SiO2-coated GaAs substrates with increasing density of dislocations. Then, the ratio of vertical to lateral growth rates at the beginning of the growth is increased which in turn leads to reduction of the adhesion-induced bending of the ELO wings, as we observe by high-resolution x-ray diffraction. In the limiting case of heavily dislocated substrates, namely, on GaAs-coated Si, the vertical growth of GaAs ELO is so fast that air-bridged structures without any wing adhesion to the SiO2 mask are obtained. Next, the same model is used to explain our earlier data on negligible bending of GaAs ELO layers on graphite-masked GaAs substrates. In this case, delayed start of lateral growth is caused by the change of the shape of the melt in the corner between the sidewall of the ELO layer and the mask when SiO2 was replaced by graphite film not wetted by the gallium melt.

  3. [Assessment of exposure to cancerogenic aromatic hydrocarbon during controlled-access highways management activities].

    PubMed

    Martinotti, I; Cirla, A M; Cottica, D; Cirla, P E

    2011-01-01

    The purpose of this study was an integrated assessment of exposure to benzene and Polycyclic Aromatic Hydrocarbons (PAH) in 29 workers employed to manage a controlled-access highways. A campaign was performed in summertime by environmental monitoring (active and passive airborne personal sampler), as well as by biological monitoring (urine samples of the beginning and of the end of daily shift, baseline after two days of vacation). The measured environmental levels did not differ from background environmental concentrations found in a metropolitan area (i.e. benzo[a]pyrene < 1 ng/m3; benzene < 5 mcg/m3), and the results of biological monitoring were in agreement and were compatible with extra-professional habits of the investigated subjects (1-hydroxipyrene 50-990 ng/g creatinine; unmetabolized benzene 15-2010 ng/I; t-t muconic acid < 4-222 mcg/g creatinine).

  4. A time tree medium access control for energy efficiency and collision avoidance in wireless sensor networks.

    PubMed

    Lee, Kilhung

    2010-01-01

    This paper presents a medium access control and scheduling scheme for wireless sensor networks. It uses time trees for sending data from the sensor node to the base station. For an energy efficient operation of the sensor networks in a distributed manner, time trees are built in order to reduce the collision probability and to minimize the total energy required to send data to the base station. A time tree is a data gathering tree where the base station is the root and each sensor node is either a relaying or a leaf node of the tree. Each tree operates in a different time schedule with possibly different activation rates. Through the simulation, the proposed scheme that uses time trees shows better characteristics toward burst traffic than the previous energy and data arrival rate scheme.

  5. Feedback linearisation control of an induction machine augmented by single-hidden layer neural networks

    NASA Astrophysics Data System (ADS)

    Ait Abbas, Hamou; Belkheiri, Mohammed; Zegnini, Boubakeur

    2016-01-01

    We consider adaptive output feedback control methodology of highly uncertain nonlinear systems with both parametric uncertainties and unmodelled dynamics. The approach is also applicable to systems of unknown, but bounded dimension. However, the relative degree of the regulated output is assumed to be known. This new control strategy is proposed to address the tracking problem of an induction motor based on a modified field-oriented control method. The obtained controller is then augmented by an online neural network that serves as an approximator for the neglected dynamics and modelling errors. The network weight adaptation rule is derived from the Lyapunov stability analysis, that guarantees boundedness of all the error signals of the closed-loop system. Computer simulations of an output feedback controlled induction machine, augmented via single-hidden-layer neural networks, demonstrate the practical potential of the proposed control algorithm.

  6. Polyoxometalate-based layered structures for charge transport control in molecular devices.

    PubMed

    Douvas, Antonios M; Makarona, Eleni; Glezos, Nikos; Argitis, Panagiotis; Mielczarski, Jerzy A; Mielczarski, Ela

    2008-04-01

    Hybrid organic-inorganic films consisted of molecular layers of a Keggin-structure polyoxometalate (POM: 12-tungstophosphoric acid, H(3)PW(12)O(40)) and 1,12-diaminododecane (DD) on 3-aminopropyl triethoxysilane (APTES)-modified silicon surface, fabricated via the layer-by-layer (LBL) self-assembly method are evaluated as molecular materials for electronic devices. The effect of the fabrication process parameters, including primarily compositions of deposition solutions, on the structural characteristics of the POM-based multilayers was studied extensively with a combination of spectroscopic methods (UV, FTIR, and XPS). Well-characterized POM-based films (both single-layers and multilayers) in a controlled and reproducible way were obtained. The conduction mechanisms in single-layered and multilayered structures were elucidated by the electrical characterization of the produced films supported by the appropriate theoretical analysis. Fowler-Nordheim (FN) tunneling and percolation mechanisms were encountered in good correlation with the structural characteristics of the films encouraging further investigation on the use of these materials in electronic and, in particular, in memory devices.

  7. Electrokinetic microactuator arrays for active sublayer control of turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    Diez-Garias, Francisco J.

    2002-09-01

    The present study has been the first to examine the electrokinetic principle as the basis for a new class of microscale actuator arrays for active sublayer control on full scale aeronautical and hydronautical vehicles under realistic operating conditions. The Helmholtz-Smoluchowski scalings that govern such electrokinetic actuator arrays show significant performance advantages from their miniaturization to the microscale. The electrokinetic microactuator arrays that are the subject of this study seek to interrupt the bursting process associated with naturally-occurring streamwise sublayer vortices in the turbulent boundary layer. Specific performance requirements for microactuator spacing, flow rate, and frequency response for active sublayer control have been determined from fundamental scaling laws for the streamwise vortical structures in the sublayer of turbulent boundary layers. In view of the inherently local nature of the sublayer dynamics, a general system architecture for microactuator arrays appropriate for active sublayer control has been developed based on the concept of relatively small and independent "unit cells", each with their own sensing, processing, and actuation capability, that greatly simplifies the sensing and processing requirements needed to achieve practical sublayer control. A fundamental three-layer design has been developed for such electrokinetic microactuator arrays, in which electrokinetic flow is induced by an impulsively applied electric field across a center layer, with a bottom layer containing an electrolyte reservoir and a common electrode, and a top layer that containing individual electrodes and lead-outs for each microactuator in the unit cell. Microfabrication techniques have been developed that permit mass production of large numbers of individual electrokinetic microactuators in unit cells on comparatively large-area tiles. Several generations of such electrokinetic microactuator arrays have been built leading to the

  8. Force control of a tri-layer conducting polymer actuator using optimized fuzzy logic control

    NASA Astrophysics Data System (ADS)

    Itik, Mehmet; Sabetghadam, Mohammadreza; Alici, Gursel

    2014-12-01

    Conducting polymers actuators (CPAs) are potential candidates for replacing conventional actuators in various fields, such as robotics and biomedical engineering, due to their advantageous properties, which includes their low cost, light weight, low actuation voltage and biocompatibility. As these actuators are very suitable for use in micro-nano manipulation and in injection devices in which the magnitude of the force applied to the target is of crucial importance, the force generated by CPAs needs to be accurately controlled. In this paper, a fuzzy logic (FL) controller with a Mamdani inference system is designed to control the blocking force of a trilayer CPA with polypyrrole electrodes, which operates in air. The particle swarm optimization (PSO) method is employed to optimize the controller’s membership function parameters and therefore enhance the performance of the FL controller. An adaptive neuro-fuzzy inference system model, which can capture the nonlinear dynamics of the actuator, is utilized in the optimization process. The optimized Mamdani FL controller is then implemented on the CPA experimentally, and its performance is compared with a non-optimized fuzzy controller as well as with those obtained from a conventional PID controller. The results presented indicate that the blocking force at the tip of the CPA can be effectively controlled by the optimized FL controller, which shows excellent transient and steady state characteristics but increases the control voltage compared to the non-optimized fuzzy controllers.

  9. Nonlinear optimal control of bypass transition in a boundary layer flow

    NASA Astrophysics Data System (ADS)

    Xiao, Dandan; Papadakis, George

    2016-11-01

    Bypass transition is observed in a flat-plate boundary-layer flow when high levels of free stream turbulence are present. This scenario is characterized by the formation of streamwise elongated streaks inside the boundary layer, their break down into turbulent spots and eventually fully turbulent flow. In the current work, we perform DNS simulations of control of bypass transition in a zero-pressure-gradient boundary layer. A non-linear optimal control algorithm is developed that employs the direct-adjoint approach to minimise a quadratic cost function based on the deviation from the Blasius velocity profile. Using the Lagrange variational approach, the distribution of the blowing/suction control velocity is found by solving iteratively the non-linear Navier-Stokes and its adjoint equations in a forward/backward loop. The optimisation is performed over a finite time horizon during which the Lagrange functional is to be minimised. Large values of optimisation horizon result in instability of the adjoint equations. The results show that the controller is able to reduce the turbulent kinetic energy of the flow in the region where the objective function is defined and the velocity profile is seen to approach the Blasius solution. Significant drag reduction is also achieved.

  10. Active control of acoustic radiation from laminated cylindrical shells integrated with a piezoelectric layer

    NASA Astrophysics Data System (ADS)

    Cao, Xiongtao; Shi, Lei; Zhang, Xusheng; Jiang, Guohe

    2013-06-01

    Active control of sound radiation from piezoelectric laminated cylindrical shells is theoretically investigated in the wavenumber domain. The governing equations of the smart cylindrical shells are derived by using first-order shear deformation theory. The smart layer is divided into lots of actuator patches, each of which is coated with two very thin electrodes at its inner and outer surfaces. Proportional derivative negative feedback control is applied to the actuator patches and the stiffness of the controlled layer is derived in the wavenumber domain. The equivalent driving forces and moments generated by the piezoelectric layer can produce distinct sound radiation. Large actuator patches cause strong wavenumber conversion and fluctuation of the far-field sound pressure, and do not make any contribution to sound reduction. Nevertheless, suitable small actuator patches induce weak wavenumber conversion and play an important role in the suppression of vibration and acoustic power. The derivative gain of the active control can effectively suppress sound radiation from smart cylindrical shells. The effects of small proportional gain on the sound field can be neglected, but large proportional gain has a great impact on the acoustic radiation of cylindrical shells. The influence of different piezoelectric materials on the acoustic power is described in the numerical results.

  11. Large-Eddy Simulation of Shock-Wave Boundary Layer Interaction and its Control Using Sparkjet

    NASA Astrophysics Data System (ADS)

    Yang, Guang; Yao, Yufeng; Fang, Jian; Gan, Tian; Lu, Lipeng

    2016-06-01

    Large-eddy simulation (LES) of an oblique shock-wave generated by an 8° sharp wedge impinging onto a spatially-developing Mach 2.3 turbulent boundary layer and their interactions has been carried out in this study. The Reynolds number based on the incoming flow property and the boundary layer displacement thickness at the impinging point without shock-wave is 20,000. The detailed numerical approaches are described and the inflow turbulence is generated using the digital filter method to avoid artificial temporal or streamwise periodicity. Numerical results are compared with the available wind tunnel PIV measurements of the same flow conditions. Further LES study on the control of flow separation due to the strong shock-viscous interaction is also conducted by using an active control actuator “SparkJet” concept. The single-pulsed characteristics of the control device are obtained and compared with the experiments. Instantaneous flowfield shows that the “SparkJet” promotes the flow mixing in the boundary layer and enhances its ability to resist the flow separation. The time and spanwise averaged skin friction coefficient distribution demonstrates that the separation bubble length is reduced by maximum 35% with the control exerted.

  12. Thermal Control System Development to Support the Crew Exploration Vehicle and Lunar Surface Access Module

    NASA Technical Reports Server (NTRS)

    Anderson, Molly; Westheimer, David

    2006-01-01

    All space vehicles or habitats require thermal management to maintain a safe and operational environment for both crew and hardware. Active Thermal Control Systems (ATCS) perform the functions of acquiring heat from both crew and hardware within a vehicle, transporting that heat throughout the vehicle, and finally rejecting that energy into space. Almost all of the energy used in a space vehicle eventually turns into heat, which must be rejected in order to maintain an energy balance and temperature control of the vehicle. For crewed vehicles, Active Thermal Control Systems are pumped fluid loops that are made up of components designed to perform these functions. NASA has recently evaluated all of the agency s technology development work and identified key areas that must be addressed to aid in the successful development of a Crew Exploration Vehicle (CEV) and a Lunar Surface Access Module (LSAM). The technologies that have been selected and are currently under development include: fluids that enable single loop ATCS architectures, a gravity insensitive vapor compression cycle heat pump, a sublimator with reduced sensitivity to feedwater contamination, an evaporative heat sink that can operate in multiple ambient pressure environments, a compact spray evaporator, and lightweight radiators that take advantage of carbon composites and advanced optical coatings.

  13. Boundary-layer and wake measurements on a swept, circulation-control wing

    NASA Technical Reports Server (NTRS)

    Spaid, Frank W.; Keener, Earl R.

    1987-01-01

    Wind-tunnel measurements of boundary-layer and wake velocity profiles and surface static pressure distributions are presented for a swept, circulation-control wing. The model is an aspect-ratio-four semispan wing mounted on the tunnel side wall at a sweep angle of 45 deg. A full-span, tangential, rearward blowing, circulation-control slot is located ahead of the trailing edge on the upper surface. Flow surveys were obtained at mid-semispan at freestream Mach numbers of 0.425 and 0.70. Boundary-layer profiles measured on the forward portions of the wing are approximately streamwise and two dimensional. The flow in the vicinity of the jet exit and in the near wake is highly three dimensional. The jet flow near the slot on the Coanda surface is directed normal to the slot. Near-wake surveys show large outboard flows at the center of the wake. At Mach 0.425 and a 5-deg angle of attack, a range of jet-blowing rates was found for which an abrupt transition from incipient separation to attached flow occurs in the boundary layer upstream of the slot. The variation in the lower-surface separation location with blowing rate was determined from boundary-layer measurements at Mach 0.425.

  14. Boundary-layer and wake measurements on a swept, circulation-control wing

    NASA Technical Reports Server (NTRS)

    Spaid, Frank W.; Keener, Earl R.

    1987-01-01

    Wind tunnel measurements of boundary layer and wake velocity profiles and surface static pressure distributions are presented for a swept, circulation control wing. The model is an aspect ratio four semispan wing mounted on the tunnel side wall as a sweep angle of 45 deg. A full span, tangetial, rearward blowing, circulation control slot is located ahead of the trailing edge on the upper surface. Flow surveys were obtained at mid-semispan at freestream Mach numbers of 0.425 and 0.70. Boundary layer profiles measured on the forward portions of the wing are approximately streamwise and two dimensional. The flow in the vicinity of the jet exit and in the near wake is highly three dimensional. The jet flow near the slot on the Coanda surface is directed normal to the slot. Near wake surveys show large outboard flows at the center of the wake. At Mach 0.425 and a 5 deg angle of attack, a range of jet blowing rates was found for which an abrupt transition from incipient separation to attached flow occurs in the boundary layer upstream of the slot. The variation in the lower surface separation location with blowing rate was determined from the boundary layer measurements at Mach 0.425.

  15. Layer-controlled stylolite growth and the creation and destruction of local seals

    NASA Astrophysics Data System (ADS)

    Koehn, Daniel; Pataki Rood, Daisy; Beaudoin, Nicolas; Aleksans, Janis; Bons, Paul; Gomez-Rivas, Enrique

    2015-04-01

    Cores of carbonate Zechstein sediments in the Lean Gas Field in northern Germany show a dense set of sedimentary stylolites. We studied these structures in detail using scans of cores, thin-sections, roughness analysis, SEM-EDS studies and a set of numerical simulations in order to understand timing and depth of stylolite growth, the development of varying stylolite patterns and their influence on fluid flow. The studied cores have a depth of about 4000m and it is expected that they experienced a minor inversion in the Cretaceous so that their original depth may have been up to 4500m. We studied the roughness of the stylolites and used a stress inversion technique to determine the depth at which they grew. The determined depth of growth is in the order of 4150m with an error of plus-minus 300m. This value represents the latest stylolite activity and indicates that they have been active until late in the burial history. SEM and EDS analysis on stylolite thin sections shows that the stylolites separate strongly dedolomitized sections from sections that still contain a large amount of dolomite. In addition stylolite seams capture or shield dolomitized parts of the rock. Dissolution holes are also partly linked to stylolite teeth indicating that fluid flow is significantly influenced by the presence of stylolites. Stylolite shapes and thus potentially their sealing capacity vary significantly throughout the cores from flat stylolites to small wavy ones all the way to stylolites showing extreme spikes and teeth. Quite often dark layers seem to control stylolite shapes. In order to understand the influence of layers on stylolite growth we use a numerical model that can treat the dynamics of the process linking elasticity with a dissolution routine. In this model we find that layers that dissolve slower can pin stylolite teeth and thus develop extremely long and spiky geometries. Growth typically happens in two to three stages depending on whether or not the pinning layer

  16. Study protocol for a cluster-randomised controlled trial of an NCD access to medicines initiative: evaluation of Novartis Access in Kenya

    PubMed Central

    Rockers, Peter C; Wirtz, Veronika J; Vian, Taryn; Onyango, Monica A; Ashigbie, Paul G; Laing, Richard

    2016-01-01

    Introduction Novartis recently launched Novartis Access, an initiative to provide a basket of reduced price medicines for non-communicable diseases (NCDs) to be sold through the public and private non-profit sectors in programme countries. This study will evaluate the impact of Novartis Access on the availability and price of NCD medicines at health facilities and households in Kenya, the first country to receive the programme. Methods and analysis This study will be a cluster-randomised controlled trial. 8 counties in Kenya will be randomly assigned to the intervention or control group using a covariate constrained randomisation method to maximise balance on demographic and health characteristics. In intervention counties, public and private non-profit health facilities will be able to order Novartis Access NCD medicines from the Mission for Essential Drugs and Supplies (MEDS). Data will be collected from a random sample of 384 health facilities and 800 households at baseline, midline after 1-year of intervention, and end-line after 2 years. Quarterly surveillance data will also be collected from health facilities and a subsample of households through phone-based interviews. Households will be eligible if at least one resident has been previously diagnosed and prescribed a medicine for an NCD addressed by Novartis Access, including hypertension and diabetes. The primary outcomes will be availability and price of NCD medicines at health facilities, and availability, price, and expenditures on NCD medicines at households. Impacts will be estimated using intention-to-treat analysis. Ethics and dissemination This protocol was approved by the Institutional Review Boards at Strathmore University and at Boston University. Informed consent will be obtained from all participants at the start of the trial. The findings of the trial will be disseminated through peer-reviewed journals, international conferences, and meetings and events organised with local stakeholders

  17. Application of the controlled boundary layer concept for the wall interference reduction

    NASA Astrophysics Data System (ADS)

    Ivanov, A. I.; Kursakov, I. A.; Streltsov, E. V.

    2016-10-01

    Traditional boundaries of transonic wind tunnels (perforated and slotted walls) have some disadvantages that do not allow to completely remove wall interference on all main aerodynamic characteristics. This article focuses on the results of implementation of new boundary condition based, in general, on the idea of jet boundaries. Authors examine the implementation of the controlled boundary layer on solid walls, which characteristics were artificially increased with the aim of near-wall spoiler grid mounted at the test section entrance. The analysis underlines significant decreasing of wall interference on all main aerodynamic characteristics, including lift coefficient and pitching moment coefficient. We conclude that realization of the controlled boundary layer might become simple and rather effective method of wall-interference reduction.

  18. Control of the boundary layer separation about an airfoil by active surface heating

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio; Badavi, Forooz F.; Noonan, Kevin W.

    1988-01-01

    Application of active control to separated flow on the RC(6)-08 airfoil at high angle of attack by localized surface heating is numerically simulated by integrating the compressible two-dimensional nonlinear Navier-Stokes equations solver. Active control is simulated by local modification of the temperature boundary condition over a narrow strip on the upper surface of the airfoil. Both mean and perturbed profiles are favorably altered when excited with the same natural frequency of the shear layer by moderate surface heating for both laminar and turbulent separation. The shear layer is found to be very sensitive to localized surface heating in the vicinity of the separation point. The excitation field at the surface sufficiently altered both the local as well as the global circulation to cause a significant increase in lift and reduction in drag.

  19. Towards improving efficiency of control for blowing into a boundary layer through a permeable wall

    NASA Astrophysics Data System (ADS)

    Fomin, V. M.; Kornilov, V. I.; Boiko, A. V.

    2016-08-01

    The results of experimental and numerical investigations of the efficiency of control by an incompressible turbulent boundary layer with the help air blowing through a permeable wall fabricated with maintenance of most of the necessary requirements for the quality and configuration of microapertures and having a low effective roughness are analyzed. Various cases of modeling the process of air blowing into the boundary layer through a specified hi-tech finely perforated surface are considered, and the data for average parameters and characteristics of turbulence of the flow types under investigation are presented. A substantial decrease in the skin-friction coefficient along the model length, which can achieve 90% with increasing the blowing coefficient, is shown. The estimate of the energy consumption for the process of blowing under terrestrial conditions testifies to the high potential of this method of control capable to provide 4-5% gain in the total aerodynamic drag of a simple modeling configuration.

  20. Zinc-impregnated and odour-control two-layer compression.

    PubMed

    Stephen-Haynes, Jackie; Callaghan, Rosie

    This article presents the results of 40 patients using two versions of a new two-layer compression system in a large primary care organisation. The evaluation was undertaken to explore the following areas formulary inclusion consideration: ease of use, clinical acceptability, clinical outcome and additional patient benefits of an alternative new low-profile bandage system containing zinc (n=30) and odour-control properties (n=10).

  1. Graphene coated with controllable N-doped carbon layer by molecular layer deposition as electrode materials for supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, Yao; Gao, Zhe; Zhang, Bin; Zhao, Shichao; Qin, Yong

    2016-05-01

    In this work, graphene is coated with nitrogen-doped carbon layer, which is produced by a carbonization process of aromatic polyimide (PI) films deposited on the surfaces of graphene by molecular layer deposition (MLD). The utilization of MLD not only allows uniform coating of PI layers on the surfaces of pristine graphene without any surface treatment, but also enables homogenous dispersion of doped nitrogen atoms in the carbonized products. The as-prepared N-doped carbon layer coated graphene (NC-G) exhibited remarkable capacitance performance as electrode materials for supercapacitor, showing a high specific capacitance of 290.2 F g-1 at current density of 1 A g-1 in 6 M KOH aqueous electrolyte, meanwhile maintaining good rate performance and stable cycle capability. The NC-G synthesized by this way represents an alternative promising candidate as electrode material for supercapacitors.

  2. Active-passive hybrid vibration control study in plates using enhanced smart constrained layer damping (ESCLD) treatment

    NASA Astrophysics Data System (ADS)

    Balamurugan, V.; Narayanan, S.

    2003-10-01

    In the present paper, the active-passive hybrid vibration control performance due to Enhanced Smart Constrained Layer Damping (ESCLD) treatment as proposed by Liao and Wang on plate like structures has been considered. This treatment consists of a viscoelastic layer constrained between a smart piezoelectric layer and the base structure being controlled. Also, the smart constraining layer is clamped to the base structure. This type of damping treatment has got both active and passive component of damping. The passive damping is through cyclic shearing of viscoelastic constrained layer which is further enhanced by activating the smart piezoelectric constraining layer and the active component of the damping is through the transfer of control moments from the piezoelectric layer to the base structure through the viscoelastic layer and also bypassed through the clamps. A plate finite element has been formulated using first order shear deformation theory, including the effect of transverse shear and rotary inertia. The effect of the viscoelastic shear layer and piezoelectric constraining layer on the mass and stiffness has been included in the model. The viscoelastic shear layer is modeled usig Golla-Hughes-McTavish (GHM) method, which is a time domain approach. The clamps (edge elements) are modeled as equivalent springs connecting the smart piezoelectric constraining layer with the structure to be controlled. LQR optimal control strategy is used to obtain optimal control gains. The effect of the viscoelastic material properties (shear modulus and loss factor) on the hybrid vibration control performance is studied for both SCLD (without edge elements) and ESCLD systems.

  3. Hot-Film and Hot-Wire Anemometry for a Boundary Layer Active Flow Control Test

    NASA Technical Reports Server (NTRS)

    Lenahan, Keven C.; Schatzman, David M.; Wilson, Jacob Samuel

    2013-01-01

    Unsteady active flow control (AFC) has been used experimentally for many years to minimize bluff-body drag. This technology could significantly improve performance of rotorcraft by cleaning up flow separation. It is important, then, that new actuator technologies be studied for application to future vehicles. A boundary layer wind tunnel was constructed with a 1ft-x-3ft test section and unsteady measurement instrumentation to study how AFC manipulates the boundary layer to overcome adverse pressure gradients and flow separation. This unsteady flow control research requires unsteady measurement methods. In order to measure the boundary layer characteristics, both hot-wire and hot-film Constant Temperature Anemometry is used. A hot-wire probe is mounted in the flow to measure velocity while a hot-film array lays on the test surface to measure skin friction. Hot-film sensors are connected to an anemometer, a Wheatstone bridge circuit with an output that corresponds to the dynamic flow response. From this output, the time varying flow field, turbulence, and flow reversal can be characterized. Tuning the anemometers requires a fan test on the hot-film sensors to adjust each output. This is a delicate process as several variables drastically affect the data, including control resistance, signal input, trim, and gain settings.

  4. Controlling multidrug-resistant tuberculosis and access to expensive drugs: a rational framework.

    PubMed Central

    Pablos-Mendez, Ariel; Gowda, Deepthiman K.; Frieden, Thomas R.

    2002-01-01

    The emergence and spread of multidrug-resistant tuberculosis (MDR-TB), i.e. involving resistance to at least isoniazid and rifampicin, could threaten the control of TB globally. Controversy has emerged about the best way of confronting MDR-TB in settings with very limited resources. In 1999, the World Health Organization (WHO) created a working group on DOTS-Plus, an initiative exploring the programmatic feasibility and cost-effectiveness of treating MDR-TB in low-income and middle-income countries, in order to consider the management of MDR-TB under programme conditions. The challenges of implementation have proved more daunting than those of access to second-line drugs, the prices of which are dropping. Using data from the WHO/International Union Against Tuberculosis and Lung Disease surveillance project, we have grouped countries according to the proportion of TB patients completing treatment successfully and the level of MDR-TB among previously untreated patients. The resulting matrix provides a reasonable framework for deciding whether to use second-line drugs in a national programme. Countries in which the treatment success rate, i.e. the proportion of new patients who complete the scheduled treatment, irrespective of whether bacteriological cure is documented, is below 70% should give the highest priority to introducing or improving DOTS, the five-point TB control strategy recommended by WHO and the International Union Against Tuberculosis and Lung Disease. A poorly functioning programme can create MDR-TB much faster than it can be treated, even if unlimited resources are available. There is no single prescription for controlling MDR-TB but the various tools available should be applied wisely. Firstly, good DOTS and infection control; then appropriate use of second-line drug treatment. The interval between the two depends on the local context and resources. As funds are allocated to treat MDR-TB, human and financial resources should be increased to expand

  5. Application of high refractive index and/or chromogenic layers to control solar and thermal radiations

    NASA Astrophysics Data System (ADS)

    Suzuki, Motofumi; Nishiura, Kensuke; Masunaka, Shoma; Muroi, Naoto; Namura, Kyoko

    2016-09-01

    In this presentation, we demonstrate that high refractive index materials such as β-FeSi2 and/or chromogenic materials such as VO2 are the key to control solar and thermal radiations. β-FeSi2 is known as an eco-friendly semiconductor and for sputtered polycrystalline β-FeSi2 thin films, we recently found that λ 0.3 in IR region, while n is higher than 5. On the other hand, another interesting optical property of β-FeSi2 is that both n and k are considerably high in visible to NIR region ( λ <= 1.55 μm). Using these optical properties in IR and VIS, we designed multilayers consisting of β-FeSi2/SiO2/β-FeSi2/W, where the upper β-FeSi2 layer absorbs VIS and NIR (λ <= 1.0 μm) and the bottom β-FeSi2 layer/W absorbs IR (1.0 <= λ <=2.0 μm). The optimized multilayers absorb more than 90% of solar energy and the eminence at 450 °C is lower than 10%. The perfect absorbers with high refractive index layers are useful for applications to solar selective absorbers for solar thermal power generation and spectrally selective thermal emitters for thermophotovoltaic power generation, IR heaters, radiation cooling. Replacing one of β-FeSi2 layers with a chromogenic material allows active control of solar and thermal radiation. In the presentation, we also demonstrate the active perfect absorbers including a VO2 layer in NIR region.

  6. A low power medium access control protocol for wireless medical sensor networks.

    PubMed

    Lamprinos, I; Prentza, A; Sakka, E; Koutsouris, D

    2004-01-01

    The concept of a wireless integrated network of sensors, already applied in several sectors of our everyday life, such as security, transportation and environment monitoring, can as well provide an advanced monitor and control resource for healthcare services. By networking medical sensors wirelessly, attaching them in patient's body, we create the appropriate infrastructure for continuous and real-time monitoring of patient without discomforting him. This infrastructure can improve healthcare by providing the means for flexible acquisition of vital signs, while at the same time it provides more convenience to the patient. Given the type of wireless network, traditional medium access control (MAC) protocols cannot take advantage of the application specific requirements and information characteristics occurring in medical sensor networks, such as the demand for low power consumption and the rather limited and asymmetric data traffic. In this paper, we present the architecture of a low power MAC protocol, designated to support wireless networks of medical sensors. This protocol aims to improve energy efficiency by exploiting the inherent application features and requirements. It is oriented towards the avoidance of main energy wastage sources, such as idle listening, collision and power outspending.

  7. Performance analysis and overload control of an open service access (OSA) architecture

    NASA Astrophysics Data System (ADS)

    Andersson, Jens K.; Nyberg, Christian; Kihl, Maria

    2003-08-01

    The trend of the service architectures developed in telecommunications today is that they should be open in the sense that they can communicate over the borders of different networks. Instead of each network having their own service architecture with their own applications, all networks should be able to use the same applications. 3GPP, the organization developing specifications for the 3G networks has specified the standard Open Service Access (OSA), as a part of the 3G specification. OSA offers different Application Protocol Interfaces that enable an application that resides outside a network to use the capabilities of the network. This paper analyses the performance of an OSA gateway. It is examined how the overload control can be dealt with in a way to best satisfy the operators and the 3'rd parties. There are some guiding principles in the specifications, but a lot of decisions have to be made by the implementors of application servers and OSA gateways. Proposals of different requirements for an OSA architecture exist such as, minimum amount of accepted calls per second and time constraint for the maximal total delay for an application. Maximal and fair throughput have to be prioritized from the 3'rd parties view, but profit is the main interest from the operators point of view. Therefore this paper examines a priority based proposal of an overload control mechanism taking these aspects and requirements into account.

  8. Control of electronic properties of 2D carbides (MXenes) by manipulating their transition metal layers

    DOE PAGES

    Anasori, Babak; Shi, Chenyang; Moon, Eun Ju; ...

    2016-02-24

    In this paper, a transition from metallic to semiconducting-like behavior has been demonstrated in two-dimensional (2D) transition metal carbides by replacing titanium with molybdenum in the outer transition metal (M) layers of M3C2 and M4C3 MXenes. The MXene structure consists of n + 1 layers of near-close packed M layers with C or N occupying the octahedral site between them in an [MX]nM arrangement. Recently, two new families of ordered 2D double transition metal carbides MXenes were discovered, M'2M"C2 and M'2M"2C3 – where M' and M" are two different early transition metals, such as Mo, Cr, Ta, Nb, V, andmore » Ti. The M' atoms only occupy the outer layers and the M" atoms fill the middle layers. In other words, M' atomic layers sandwich the middle M"–C layers. Using X-ray atomic pair distribution function (PDF) analysis on Mo2TiC2 and Mo2Ti2C3 MXenes, we present the first quantitative analysis of structures of these novel materials and experimentally confirm that Mo atoms are in the outer layers of the [MC]nM structures. The electronic properties of these Mo-containing MXenes are compared with their Ti3C2 counterparts, and are found to be no longer metallic-like conductors; instead the resistance increases mildly with decreasing temperatures. Density functional theory (DFT) calculations suggest that OH terminated Mo–Ti MXenes are semiconductors with narrow band gaps. Measurements of the temperature dependencies of conductivities and magnetoresistances have confirmed that Mo2TiC2Tx exhibits semiconductor-like transport behavior, while Ti3C2Tx is a metal. Finally, this finding opens new avenues for the control of the electronic and optical applications of MXenes and for exploring new applications, in which semiconducting properties are required.« less

  9. Control of electronic properties of 2D carbides (MXenes) by manipulating their transition metal layers

    SciTech Connect

    Anasori, Babak; Shi, Chenyang; Moon, Eun Ju; Xie, Yu; Voigt, Cooper A.; Kent, Paul R. C.; May, Steven J.; Billinge, Simon J. L.; Barsoum, Michel W.; Gogotsi, Yury

    2016-02-24

    In this paper, a transition from metallic to semiconducting-like behavior has been demonstrated in two-dimensional (2D) transition metal carbides by replacing titanium with molybdenum in the outer transition metal (M) layers of M3C2 and M4C3 MXenes. The MXene structure consists of n + 1 layers of near-close packed M layers with C or N occupying the octahedral site between them in an [MX]nM arrangement. Recently, two new families of ordered 2D double transition metal carbides MXenes were discovered, M'2M"C2 and M'2M"2C3 – where M' and M" are two different early transition metals, such as Mo, Cr, Ta, Nb, V, and Ti. The M' atoms only occupy the outer layers and the M" atoms fill the middle layers. In other words, M' atomic layers sandwich the middle M"–C layers. Using X-ray atomic pair distribution function (PDF) analysis on Mo2TiC2 and Mo2Ti2C3 MXenes, we present the first quantitative analysis of structures of these novel materials and experimentally confirm that Mo atoms are in the outer layers of the [MC]nM structures. The electronic properties of these Mo-containing MXenes are compared with their Ti3C2 counterparts, and are found to be no longer metallic-like conductors; instead the resistance increases mildly with decreasing temperatures. Density functional theory (DFT) calculations suggest that OH terminated Mo–Ti MXenes are semiconductors with narrow band gaps. Measurements of the temperature dependencies of conductivities and magnetoresistances have confirmed that Mo2TiC2Tx exhibits semiconductor-like transport behavior, while Ti3C2Tx is a metal. Finally, this finding opens new avenues for the control of the electronic and optical applications of MXenes and for exploring new applications, in

  10. Controllable growth of layered selenide and telluride heterostructures and superlattices using molecular beam epitaxy

    SciTech Connect

    Vishwanath, Suresh; Liu, Xinyu; Rouvimov, Sergei; Basile, Leonardo; Lu, Ning; Azcatl, Angelica; Magno, Katrina; Wallace, Robert M.; Kim, Moon; Idrobo, Juan -Carlos; Furdyna, Jacek K.; Jena, Debdeep; Xing, Huili Grace

    2016-01-06

    Layered materials are an actively pursued area of research for realizing highly scaled technologies involving both traditional device structures as well as new physics. Lately, non-equilibrium growth of 2D materials using molecular beam epitaxy (MBE) is gathering traction in the scientific community and here we aim to highlight one of its strengths, growth of abrupt heterostructures, and superlattices (SLs). In this work we present several of the firsts: first growth of MoTe2 by MBE, MoSe2 on Bi2Se3 SLs, transition metal dichalcogenide (TMD) SLs, and lateral junction between a quintuple atomic layer of Bi2Te3 and a triple atomic layer of MoTe2. In conclusion, reflected high electron energy diffraction oscillations presented during the growth of TMD SLs strengthen our claim that ultrathin heterostructures with monolayer layer control is within reach.

  11. Controlling turbulent boundary layer separation using biologically inspired 2D transverse grooves

    NASA Astrophysics Data System (ADS)

    Lang, Amy; Jones, Emily; Afroz, Farhana

    2013-11-01

    It is theorized that the presence of grooves, such as the sinusoidal ones found on dolphin skin or the cavities that form between bristled shark skin scales, can lead to induced boundary layer mixing and result in the control of turbulent boundary layer separation. To test this hypothesis, a series of water tunnel experiments using DPIV studied the characteristics of a flat plate turbulent boundary layer whereby a rotating cylinder was used to induce an adverse pressure gradient and resulting flow separation. The experiments were repeated with the use of a plate covered with two types of grooves, rectangular and sinusoidal, with a spacing of 2 mm in size. Flow similarity of the cavity flow was preserved between the experiments and flow over bristled shark skin scales. Both geometries resulted in a reduction of flow separation as measured by backflow coefficient. In addition, Reynolds stress profiles showed that as the pressure gradient was increased, the sinusoidal geometry outperformed the rectangular grooves in terms of increased mixing close to the wall. The sinusoidal plate also generated a lower momentum deficit within the boundary layer which would indicate a smaller drag penalty. Support from NSF grant CBET 0932352 and a UA Graduate Council Fellowship is gratefully acknowledged.

  12. Active flow control insight gained from a modified integral boundary layer equation

    NASA Astrophysics Data System (ADS)

    Seifert, Avraham

    2016-11-01

    Active Flow Control (AFC) can alter the development of boundary layers with applications (e.g., reducing drag by separation delay or separating the boundary layers and enhancing vortex shedding to increase drag). Historically, significant effects of steady AFC methods were observed. Unsteady actuation is significantly more efficient than steady. Full-scale AFC tests were conducted with varying levels of success. While clearly relevant to industry, AFC implementation relies on expert knowledge with proven intuition and or costly and lengthy computational efforts. This situation hinders the use of AFC while simple, quick and reliable design method is absent. An updated form of the unsteady integral boundary layer (UIBL) equations, that include AFC terms (unsteady wall transpiration and body forces) can be used to assist in AFC analysis and design. With these equations and given a family of suitable velocity profiles, the momentum thickness can be calculated and matched with an outer, potential flow solution in 2D and 3D manner to create an AFC design tool, parallel to proven tools for airfoil design. Limiting cases of the UIBL equation can be used to analyze candidate AFC concepts in terms of their capability to modify the boundary layers development and system performance.

  13. The IEO Data Center Management System: Tools for quality control, analysis and access marine data

    NASA Astrophysics Data System (ADS)

    Casas, Antonia; Garcia, Maria Jesus; Nikouline, Andrei

    2010-05-01

    Since 1994 the Data Centre of the Spanish Oceanographic Institute develops system for archiving and quality control of oceanographic data. The work started in the frame of the European Marine Science & Technology Programme (MAST) when a consortium of several Mediterranean Data Centres began to work on the MEDATLAS project. Along the years, old software modules for MS DOS were rewritten, improved and migrated to Windows environment. Oceanographic data quality control includes now not only vertical profiles (mainly CTD and bottles observations) but also time series of currents and sea level observations. New powerful routines for analysis and for graphic visualization were added. Data presented originally in ASCII format were organized recently in an open source MySQL database. Nowadays, the IEO, as part of SeaDataNet Infrastructure, has designed and developed a new information system, consistent with the ISO 19115 and SeaDataNet standards, in order to manage the large and diverse marine data and information originated in Spain by different sources, and to interoperate with SeaDataNet. The system works with data stored in ASCII files (MEDATLAS, ODV) as well as data stored within the relational database. The components of the system are: 1.MEDATLAS Format and Quality Control - QCDAMAR: Quality Control of Marine Data. Main set of tools for working with data presented as text files. Includes extended quality control (searching for duplicated cruises and profiles, checking date, position, ship velocity, constant profiles, spikes, density inversion, sounding, acceptable data, impossible regional values,...) and input/output filters. - QCMareas: A set of procedures for the quality control of tide gauge data according to standard international Sea Level Observing System. These procedures include checking for unexpected anomalies in the time series, interpolation, filtering, computation of basic statistics and residuals. 2. DAMAR: A relational data base (MySql) designed to

  14. Integrated structures/controls optimization of a smart composite plate with segmented active constrained layer damping

    NASA Astrophysics Data System (ADS)

    Beri, Rajan; Chattopadhyay, Aditi; Nam, Changho

    2000-06-01

    A rigorous multi-objective optimization procedure, is developed to address the integrated structures/control design of composite plates with surface bonded segmented active constrained layer (ACL) damping treatment. The Kresselmeier- Steinhauser function approach is used to formulate this multidisciplinary problem. The goal is to control vibration without incorporating a weight penalty. Objective functions and constraints include damping ratios, structural weight and natural frequencies. Design variables include the ply stacking sequence, dimensions and placement of segmented ACL. The optimal designs show improved plate vibratory characteristics and reduced structural weight. The results of the multi- objective optimization problem are compared to those of a single objective optimization with vibration control as the objective. Results establish the necessity for developing the integrated structures/controls optimization procedure.

  15. Study of layer-by-layer films on thermoresponsive nanogels using temperature-controlled dual-focus fluorescence correlation spectroscopy.

    PubMed

    Wong, John E; Müller, Claus B; Díez-Pascual, Ana M; Richtering, Walter

    2009-12-10

    While a few studies have reported on the layer-by-layer (LbL) assembly of polyelectrolytes on soft and porous templates, none have really demonstrated direct proof that the layers are actually on the template. Thermoresponsive nanogels present challenges that render a quantitative proof of successful polyelectrolyte deposition extremely difficult. Additionally, the fate of the polyelectrolyte has never been investigated during the phase transition of the coated nanogel. Here, the auto- and cross-correlation functions of a labeled polyelectrolyte assembled via the LbL technique onto soft and porous thermoresponsive labeled nanogels using dual-focus fluorescence correlation spectroscopy (2f-FCS) are presented. Performing 2f-FCS as a function of temperature, hydrodynamic radii of nanogels coated with various numbers of layers are determined, which are found to be in excellent agreement with values obtained from dynamic light scattering. This study presents irrefutable quantitative evidence of successful LbL assembly on thermoresponsive nanogels and demonstrates that the layers are not stripped off during the phase transition of the nanogels. Forster Resonance Energy Transfer (FRET) detection also supports our findings.

  16. Active Control of Turbulent Boundary Layer Induced Sound Radiation from Multiple Aircraft Panels

    NASA Technical Reports Server (NTRS)

    Gibbs, Gary P.; Cabell, Randolph H.

    2002-01-01

    The objective of this work is to experimentally investigate active structural acoustic control of turbulent boundary layer (TBL) induced sound radiation from multiple panels on an aircraft sidewall. One possible approach for controlling sound radiation from multiple panels is a multi-input/multi-output scheme which considers dynamic coupling between the panels. Unfortunately, this is difficult for more than a few panels, and is impractical for a typical aircraft which contains several hundred such panels. An alternative is to implement a large number of independent control systems. Results from the current work demonstrate the feasibility of reducing broadband radiation from multiple panels utilizing a single-input/single-output (SISO) controller per bay, and is the first known demonstration of active control of TBL induced sound radiation on more than two bays simultaneously. The paper compares sound reduction for fully coupled control of six panels versus independent control on each panel. An online adaptive control scheme for independent control is also demonstrated. This scheme will adjust for slow time varying dynamic systems such as fuselage response changes due to aircraft pressurization, etc.

  17. Phase control of iridium and iridium oxide thin films in atomic layer deposition

    SciTech Connect

    Kim, Sung-Wook; Kwon, Se-Hun; Kwak, Dong-Kee; Kang, Sang-Won

    2008-01-15

    The atomic layer deposition of iridium (Ir) and iridium oxide (IrO{sub 2}) films was investigated using an alternating supply of (ethylcyclopentadienyl)(1,5-cyclooctadiene) iridium and oxygen gas at temperatures between 230 and 290 deg. C. The phase transition between Ir and IrO{sub 2} occurred at the critical oxygen partial pressure during the oxygen injection pulse. The oxygen partial pressure was controlled by the O{sub 2}/(Ar+O{sub 2}) ratio or deposition pressures. The resistivity of the deposited Ir and IrO{sub 2} films was about 9 and 120 {mu}{omega} cm, respectively. In addition, the critical oxygen partial pressure for the phase transition between Ir and IrO{sub 2} was increased with increasing the deposition temperature. Thus, the phase of the deposited film, either Ir or IrO{sub 2}, was controlled by the oxygen partial pressure and the deposition temperature. However, the formation of a thin Ir layer was detected between the IrO{sub 2} and SiO{sub 2} substrate. To remove this interfacial layer, the oxygen partial pressure is increased to a severe condition. And the impurity contents were below the detection limit of Auger electron spectroscopy in both Ir and IrO{sub 2} films.

  18. Shockwave-turbulent boundary layer interaction control using magnetically driven surface discharges

    NASA Astrophysics Data System (ADS)

    Kalra, Chiranjeev S.; Zaidi, Sohail H.; Miles, Richard B.; Macheret, Sergey O.

    2011-03-01

    This study demonstrates the potential for shockwave-turbulent boundary layer interaction control in air using low current DC constricted surface discharges forced by moderate strength magnetic fields. An analytical model describing the physics of magnetic field forced discharge interaction with boundary layer flow is developed and compared to experiments. Experiments are conducted in a Mach 2.6 indraft air tunnel with discharge currents up to 300 mA and magnetic field strengths up to 5 Tesla. Separation- and non-separation-inducing shocks are generated with diamond-shaped shockwave generators located on the wall opposite to the surface electrodes, and flow properties are measured with schlieren imaging, static wall pressure probes and acetone flow visualization. The effect of plasma control on boundary layer separation depends on the direction of the Lorentz force ( j × B). It is observed that by using a Lorentz force that pushes the discharge upstream, separation can be induced or further strengthened even with discharge currents as low as 30 mA in a 3-Tesla magnetic field. If shock-induced separation is present, it is observed that by using Lorentz force that pushes the discharge downstream, separation can be suppressed, but this required higher currents, greater than 80 mA. Acetone planar laser scattering is used to image the flow structure in the test section and the reduction in the size of recirculation bubble and its elimination are observed experimentally as a function of actuation current and magnetic field strength.

  19. Integrated, nonvolatile, high-speed analog random access memory

    NASA Technical Reports Server (NTRS)

    Katti, Romney R. (Inventor); Wu, Jiin-Chuan (Inventor); Stadler, Henry L. (Inventor)

    1994-01-01

    This invention provides an integrated, non-volatile, high-speed random access memory. A magnetically switchable ferromagnetic or ferrimagnetic layer is sandwiched between an electrical conductor which provides the ability to magnetize the magnetically switchable layer and a magneto resistive or Hall effect material which allows sensing the magnetic field which emanates from the magnetization of the magnetically switchable layer. By using this integrated three-layer form, the writing process, which is controlled by the conductor, is separated from the storage medium in the magnetic layer and from the readback process which is controlled by the magnetoresistive layer. A circuit for implementing the memory in CMOS or the like is disclosed.

  20. Two-layer wireless distributed sensor/control network based on RF

    NASA Astrophysics Data System (ADS)

    Feng, Li; Lin, Yuchi; Zhou, Jingjing; Dong, Guimei; Xia, Guisuo

    2006-11-01

    A project of embedded Wireless Distributed Sensor/Control Network (WDSCN) based on RF is presented after analyzing the disadvantages of traditional measure and control system. Because of high-cost and complexity, such wireless techniques as Bluetooth and WiFi can't meet the needs of WDSCN. The two-layer WDSCN is designed based on RF technique, which operates in the ISM free frequency channel with low power and high transmission speed. Also the network is low cost, portable and moveable, integrated with the technologies of computer network, sensor, microprocessor and wireless communications. The two-layer network topology is selected in the system; a simple but efficient self-organization net protocol is designed to fit the periodic data collection, event-driven and store-and-forward. Furthermore, adaptive frequency hopping technique is adopted for anti-jamming apparently. The problems about power reduction and synchronization of data in wireless system are solved efficiently. Based on the discussion above, a measure and control network is set up to control such typical instruments and sensors as temperature sensor and signal converter, collect data, and monitor environmental parameters around. This system works well in different rooms. Experiment results show that the system provides an efficient solution to WDSCN through wireless links, with high efficiency, low power, high stability, flexibility and wide working range.

  1. Shockwave—boundary layer interaction control by plasma aerodynamic actuation: An experimental investigation

    NASA Astrophysics Data System (ADS)

    Sun, Quan; Cui, Wei; Li, Ying-Hong; Cheng, Bang-Qin; Jin, Di; Li, Jun

    2014-07-01

    The potential of controlling shockwave—boundary layer interactions (SWBLIs) in air by plasma aerodynamic actuation is demonstrated. Experiments are conducted in a Mach 3 in-draft air tunnel. The separation-inducing shock is generated with a diamond-shaped shockwave generator located on the wall opposite to the surface electrodes, and the flow properties are studied with schlieren imaging and static wall pressure probes. The measurements show that the separation phenomenon is weakened with the plasma aerodynamic actuation, which is observed to have significant control authority over the interaction. The main effect is the displacement of the reflected shock. Perturbations of incident and reflected oblique shocks interacting with the separation bubble in a rectangular cross section supersonic test section are produced by the plasma actuation. This interaction results in a reduction of the separation bubble size, as detected by phase-lock schlieren images. The measured static wall pressure also shows that the separation-inducing shock is restrained. Our results suggest that the boundary layer separation control through heating is the primary control mechanism.

  2. Powder Layer Preparation Using Vibration-controlled Capillary Steel Nozzles for Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Stichel, Thomas; Laumer, Tobias; Baumüller, Tobias; Amend, Philipp; Roth, Stephan

    In this report, the dry delivery of polyamide 12 powders by vibrating capillary steel nozzles is investigated and discussed regarding its potential for powder layer preparation in Laser Beam Melting. Therefore, a setup including a steel nozzle assembled on a piezoelectric actuator is presented, which enables the precise control over very small powder quantities by vibration excitation. An analysis reveals that the mass flow through the nozzle can be adjusted by the vibration modes in a certain range depending on the nozzle's specifications, whereas the vibration modes themselves show a complicated behaviour. Using a positioning system in combination with the vibrating nozzle, single-layer patterns consisting of polyamide 12 are produced and characterized regarding surface homogeneity and selectivity using a laser stripe sensor.

  3. Interfacial Layer Control by Dry Cleaning Technology for Polycrystalline and Single Crystalline Silicon Growth.

    PubMed

    Im, Dong-Hyun; Kong-Soo Lee; Kang, Yoongoo; Jeong, Myoungho; Park, Kwang Wuk; Lee, Soon-Gun; Ma, Jin-Won; Kim, Youngseok; Kim, Bonghyun; Im, Ki-Vin; Lim, Hanjin; Lee, Jeong Yong

    2016-05-01

    Native oxide removal prior to poly-Si contact and epitaxial growth of Si is the most critical technology to ensure process and device performances of poly-Si plugs and selective epitaxial growth (SEG) layers for DRAM, flash memory, and logic device. Recently, dry cleaning process for interfacial oxide removal has attracted a world-wide attention due to its superior passivation properties to conventional wet cleaning processes. In this study, we investigated the surface states of Si substrate during and after dry cleaning process, and the role of atomic elements including fluorine and hydrogen on the properties of subsequent deposited silicon layer using SIMS, XPS, and TEM analysis. The controlling of residual fluorine on the Si surface after dry cleaning is a key factor for clean interface. The mechanism of native oxide re-growth caused by residual fluorine after dry cleaning is proposed based on analytical results.

  4. Review of Research on Low-Profile Vortex Generators to Control Boundary-Layer Separation

    NASA Technical Reports Server (NTRS)

    Lin, John C.

    2002-01-01

    An in-depth review of boundary-layer flow-separation control by a passive method using low-profile vortex generators is presented. The generators are defined as those with a device height between 10% and 50% of the boundary layer thickness. Key results are presented for several research efforts, all of which were performed within the past decade and a half where the majority of these works emphasize experimentation with some recent efforts on numerical simulations. Topics of discussion consist of both basic fluid dynamics and applied aerodynamics research. The fluid dynamics research includes comparative studies on separation control effectiveness as well as device-induced vortex characterization and correlation. The comparative studies cover the controlling of low-speed separated flows in adverse pressure gradient and supersonic shock-induced separation. The aerodynamics research includes several applications for aircraft performance enhancement and covers a wide range of speeds. Significant performance improvements are achieved through increased lift and/or reduced drag for various airfoils-low-Reynolds number, high-lift, and transonic-as well as highly swept wings. Performance enhancements for non-airfoil applications include aircraft interior noise reduction, inlet flow distortion alleviation inside compact ducts, and a more efficient overwing fairing. The low-profile vortex generators are best for being applied to applications where flow-separation locations are relatively fixed and the generators can be placed reasonably close upstream of the separation. Using the approach of minimal near-wall proturbances through substantially reduced device height, these devices can produce streamwise vortices just strong enough to overcome the separation without unnecessarily persisting within the boundary layer once the flow-control objective is achieved. Practical advantages of low-profile vortex generators, such as their inherent simplicity and low device drag, are

  5. A Comparison of Active and Passive Methods for Control of Hypersonic Boundary Layers on Airbreathing Configurations

    NASA Technical Reports Server (NTRS)

    Berry, Scott A.; Nowak, Robert J.

    2003-01-01

    Active and passive methods for control of hypersonic boundary layers have been experimentally examined in NASA Langley Research Center wind tunnels on a Hyper-X model. Several configurations for forcing transition using passive discrete roughness elements and active mass addition, or blowing, methods were compared in two hypersonic facilities, the 20-Inch Mach 6 Air and the 31-Inch Mach 10 Air tunnels. Heat transfer distributions, obtained via phosphor thermography, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. The comparisons between the active and passive methods for boundary layer control were conducted at test conditions that nearly match the nominal Mach 7 flight trajectory of an angle-of-attack of 2-deg and length Reynolds number of 5.6 million. For the passive roughness examination, the primary parametric variation was a range of trip heights within the calculated boundary layer thickness for several trip concepts. The prior passive roughness study resulted in a swept ramp configuration being selected for the Mach 7 flight vehicle that was scaled to be roughly 0.6 of the calculated boundary layer thickness. For the active jet blowing study, the blowing manifold pressure was systematically varied for each configuration, while monitoring the mass flow, to determine the jet penetration height with schlieren and transition movement with the phosphor system for comparison to the passive results. All the blowing concepts tested were adequate for providing transition onset near the trip location with manifold stagnation pressures on the order of 40 times the model static pressure or higher.

  6. In Situ Control of Oxygen Vacancies in TaOx Thin Films via Plasma-Enhanced Atomic Layer Deposition for Resistive Switching Memory Applications.

    PubMed

    Egorov, Konstantin V; Kuzmichev, Dmitry S; Chizhov, Pavel S; Lebedinskii, Yuri Yu; Hwang, Cheol Seong; Markeev, Andrey M

    2017-04-06

    The plasma-enhanced atomic layer deposition (PEALD) process using Ta(OC2H5)5 as a Ta precursor and plasma-activated hydrogen as a reactant for the deposition of TaOx films with a controllable concentration of oxygen vacancies (VO) is reported herein. The VO concentration control was achieved by varying the hydrogen volume fraction of the hydrogen-argon mixture in the plasma, allowing the control of the leakage current density in the tantalum oxide films within the range of 5 orders of magnitude compared with the Ta2O5 film grown via thermal ALD using the identical Ta precursor and H2O. Temperature-dependent current-voltage measurements combined with Poole-Frenkel emission modeling demonstrated that the bulk trap depth decreases with the increasing hydrogen volume fraction, which could be attributed to the increase of the VO concentration. The possible chemical change in the PEALD TaOx films grown under different hydrogen volume fractions was confirmed by the in situ X-ray photoelectron spectroscopy (XPS) measurements of the Ta 4f core and valence band spectra. The comparison of the XPS-measured nonstoichiometry and the secondary ion mass spectrometry analysis of the hydrogen content allowed this study to conclude that the nonstoichiometry is largely related to the formation of Ta-VO sites rather than of Ta-H sites. Such oxygen-deficient TaOx layers were studied for application as an oxygen-deficient layer in a resistance switching random access memory stack (Ta2O5/TaOx) where the actual switching occurred within the stoichiometric Ta2O5 layer. The bilayer memory stack showed reliable resistance switching up to ∼10(6) switching cycles, whereas the single-layer Ta2O5 memory showed only several hundred switching cycles.

  7. The ribosome quality control pathway can access nascent polypeptides stalled at the Sec61 translocon.

    PubMed

    von der Malsburg, Karina; Shao, Sichen; Hegde, Ramanujan S

    2015-06-15

    Cytosolic ribosomes that stall during translation are split into subunits, and nascent polypeptides trapped in the 60S subunit are ubiquitinated by the ribosome quality control (RQC) pathway. Whether the RQC pathway can also target stalls during cotranslational translocation into the ER is not known. Here we report that listerin and NEMF, core RQC components, are bound to translocon-engaged 60S subunits on native ER membranes. RQC recruitment to the ER in cultured cells is stimulated by translation stalling. Biochemical analyses demonstrated that translocon-targeted nascent polypeptides that subsequently stall are polyubiquitinated in 60S complexes. Ubiquitination at the translocon requires cytosolic exposure of the polypeptide at the ribosome-Sec61 junction. This exposure can result from either failed insertion into the Sec61 channel or partial backsliding of translocating nascent chains. Only Sec61-engaged nascent chains early in their biogenesis were relatively refractory to ubiquitination. Modeling based on recent 60S-RQC and 80S-Sec61 structures suggests that the E3 ligase listerin accesses nascent polypeptides via a gap in the ribosome-translocon junction near the Sec61 lateral gate. Thus the RQC pathway can target stalled translocation intermediates for degradation from the Sec61 channel.

  8. The ribosome quality control pathway can access nascent polypeptides stalled at the Sec61 translocon

    PubMed Central

    von der Malsburg, Karina; Shao, Sichen; Hegde, Ramanujan S.

    2015-01-01

    Cytosolic ribosomes that stall during translation are split into subunits, and nascent polypeptides trapped in the 60S subunit are ubiquitinated by the ribosome quality control (RQC) pathway. Whether the RQC pathway can also target stalls during cotranslational translocation into the ER is not known. Here we report that listerin and NEMF, core RQC components, are bound to translocon-engaged 60S subunits on native ER membranes. RQC recruitment to the ER in cultured cells is stimulated by translation stalling. Biochemical analyses demonstrated that translocon-targeted nascent polypeptides that subsequently stall are polyubiquitinated in 60S complexes. Ubiquitination at the translocon requires cytosolic exposure of the polypeptide at the ribosome–Sec61 junction. This exposure can result from either failed insertion into the Sec61 channel or partial backsliding of translocating nascent chains. Only Sec61-engaged nascent chains early in their biogenesis were relatively refractory to ubiquitination. Modeling based on recent 60S–RQC and 80S–Sec61 structures suggests that the E3 ligase listerin accesses nascent polypeptides via a gap in the ribosome–translocon junction near the Sec61 lateral gate. Thus the RQC pathway can target stalled translocation intermediates for degradation from the Sec61 channel. PMID:25877867

  9. The SH2 domain of Abl kinases regulates kinase autophosphorylation by controlling activation loop accessibility

    NASA Astrophysics Data System (ADS)

    Lamontanara, Allan Joaquim; Georgeon, Sandrine; Tria, Giancarlo; Svergun, Dmitri I.; Hantschel, Oliver

    2014-11-01

    The activity of protein kinases is regulated by multiple molecular mechanisms, and their disruption is a common driver of oncogenesis. A central and almost universal control element of protein kinase activity is the activation loop that utilizes both conformation and phosphorylation status to determine substrate access. In this study, we use recombinant Abl tyrosine kinases and conformation-specific kinase inhibitors to quantitatively analyse structural changes that occur after Abl activation. Allosteric SH2-kinase domain interactions were previously shown to be essential for the leukemogenesis caused by the Bcr-Abl oncoprotein. We find that these allosteric interactions switch the Abl activation loop from a closed to a fully open conformation. This enables the trans-autophosphorylation of the activation loop and requires prior phosphorylation of the SH2-kinase linker. Disruption of the SH2-kinase interaction abolishes activation loop phosphorylation. Our analysis provides a molecular mechanism for the SH2 domain-dependent activation of Abl that may also regulate other tyrosine kinases.

  10. Controlling the taste receptor accessible structure of rebaudioside A via binding to bovine serum albumin.

    PubMed

    Mudgal, Samriddh; Keresztes, Ivan; Feigenson, Gerald W; Rizvi, S S H

    2016-04-15

    We illustrate a method that uses bovine serum albumin (BSA) to control the receptor-accessible part of rebaudioside A (Reb A). The critical micelle concentration (CMC) of Reb A was found to be 4.5 mM and 5 mM at pH 3 and 6.7 respectively. NMR studies show that below its CMC, Reb A binds weakly to BSA to generate a Reb A-protein complex ("RPC"), which is only modestly stable under varying conditions of pH (3.0-6.7) and temperature (4-40°C) with its binding affinities determined to be in the range of 5-280 mM. Furthermore, saturation transfer difference (STD) NMR experiments confirm that the RPC has fast exchange of the bitterness-instigating diterpene of Reb A into the binding sites of BSA. Our method can be used to alter the strength of Reb A-receptor interaction, as a result of binding of Reb A to BSA, which may ultimately lead to moderation of its taste.

  11. Layer-Controlled Chemical Vapor Deposition Growth of MoS2 Vertical Heterostructures via van der Waals Epitaxy.

    PubMed

    Samad, Leith; Bladow, Sage M; Ding, Qi; Zhuo, Junqiao; Jacobberger, Robert M; Arnold, Michael S; Jin, Song

    2016-07-26

    The fascinating semiconducting and optical properties of monolayer and few-layer transition metal dichalcogenides, as exemplified by MoS2, have made them promising candidates for optoelectronic applications. Controllable growth of heterostructures based on these layered materials is critical for their successful device applications. Here, we report a direct low temperature chemical vapor deposition (CVD) synthesis of MoS2 monolayer/multilayer vertical heterostructures with layer-controlled growth on a variety of layered materials (SnS2, TaS2, and graphene) via van der Waals epitaxy. Through precise control of the partial pressures of the MoCl5 and elemental sulfur precursors, reaction temperatures, and careful tracking of the ambient humidity, we have successfully and reproducibly grown MoS2 vertical heterostructures from 1 to 6 layers over a large area. The monolayer MoS2 heterostructure was verified using cross-sectional high resolution transmission electron microscopy (HRTEM) while Raman and photoluminescence spectroscopy confirmed the layer-controlled MoS2 growth and heterostructure electronic interactions. Raman, photoluminescence, and energy dispersive X-ray spectroscopy (EDS) mappings verified the uniform coverage of the MoS2 layers. This reaction provides an ideal method for the scalable layer-controlled growth of transition metal dichalcogenide heterostructures via van der Waals epitaxy for a variety of optoelectronic applications.

  12. Plant leaf senescence and death - regulation by multiple layers of control and implications for aging in general.

    PubMed

    Woo, Hye Ryun; Kim, Hyo Jung; Nam, Hong Gil; Lim, Pyung Ok

    2013-11-01

    How do organisms, organs, tissues and cells change their fate when they age towards senescence and death? Plant leaves provide a unique window to explore this question because they show reproducible life history and are readily accessible for experimental assays. Throughout their lifespan, leaves undergo a series of developmental, physiological and metabolic transitions that culminate in senescence and death. Leaf senescence is an 'altruistic death' that allows for the degradation of the nutrients that are produced during the growth phase of the leaf and their redistribution to developing seeds or other parts of the plant, and thus is a strategy that has evolved to maximize the fitness of the plant. During the past decade, there has been significant progress towards understanding the key molecular principles of leaf senescence using genetic and molecular studies, as well as 'omics' analyses. It is now apparent that leaf senescence is a highly complex genetic program that is tightly controlled by multiple layers of regulation, including at the level of chromatin and transcription, as well as by post-transcriptional, translational and post-translational regulation. This Commentary discusses the latest understandings and insights into the underlying molecular mechanisms, and presents the perspectives necessary to enable our system-level understanding of leaf senescence, together with their possible implications for aging in general.

  13. An Ounce of Prevention: Technologists Use Network-Access Control to Protect System Resources, Students

    ERIC Educational Resources Information Center

    Bolch, Matt

    2009-01-01

    Whether for an entire district, a single campus, or one classroom, allowing authorized access to a computer network can be fraught with challenges. The login process should be fairly seamless to approved users, giving them speedy access to approved Web sites, databases, and other sources of information. It also should be tough on unauthorized…

  14. Guaranteeing synchronous message deadlines with the timed token medium access control protocol

    NASA Technical Reports Server (NTRS)

    Agrawal, Gopal; Chen, Baio; Zhao, Wei; Davari, Sadegh

    1992-01-01

    We study the problem of guaranteeing synchronous message deadlines in token ring networks where the timed token medium access control protocol is employed. Synchronous capacity, defined as the maximum time for which a node can transmit its synchronous messages every time it receives the token, is a key parameter in the control of synchronous message transmission. To ensure the transmission of synchronous messages before their deadlines, synchronous capacities must be properly allocated to individual nodes. We address the issue of appropriate allocation of the synchronous capacities. Several synchronous capacity allocation schemes are analyzed in terms of their ability to satisfy deadline constraints of synchronous messages. We show that an inappropriate allocation of the synchronous capacities could cause message deadlines to be missed even if the synchronous traffic is extremely low. We propose a scheme called the normalized proportional allocation scheme which can guarantee the synchronous message deadlines for synchronous traffic of up to 33 percent of available utilization. To date, no other synchronous capacity allocation scheme has been reported to achieve such substantial performance. Another major contribution of this paper is an extension to the previous work on the bounded token rotation time. We prove that the time elapsed between any consecutive visits to a particular node is bounded by upsilon TTRT, where TTRT is the target token rotation time set up at system initialization time. The previous result by Johnson and Sevcik is a special case where upsilon = 2. We use this result in the analysis of various synchronous allocation schemes. It can also be applied in other similar studies.

  15. Integration of in situ RHEED with magnetron sputter deposition for atomic layer controlled growth

    NASA Astrophysics Data System (ADS)

    Podkaminer, Jacob P.

    Epitaxial thin films continue to be one of the most promising topics within electronic materials research. Sputter deposition is one process by which these films can be formed and is a widely used growth technique for a large range of technologically important material systems. Epitaxial films of carbides, nitrides, metals, oxides and more can all be formed during the sputter process which offers the ability to deposit smooth and uniform films from the research level up to an industrial scale. This tunable kinematic deposition process excels in easily adapting for a large range of environments and growth procedures. Despite the vast advantages associated with sputter deposition, there is a significant lack of in situ analysis options during sputtering. In particular, the area of real time atomic layer control is severely deficient. Atomic layer controlled growth of epitaxial thin films and artificially layered superlattices is critical for both understanding their emergent phenomena and engineering novel material systems and devices. Reflection high-energy electron diffraction (RHEED) is one of the most common in situ analysis techniques during thin film deposition that is rarely used during sputtering due to the strong permanent magnets in magnetron sputter sources and their effect on the RHEED electron beam. In this work we have solved this problem and designed a novel way to deter the effect of the magnets for a wide range of growth geometries and demonstrate the ability for the first time to have layer by layer control during sputter deposition by in situ RHEED. A novel growth chamber that can seamlessly change between pulsed laser deposition and sputtering with RHEED for the growth of complex heterostructures has been designed and implemented. Epitaxial thin films of LaAlO3, La1-xSrxMnO3, and SrRuO3 have all been deposited by sputtering and shown to exhibit clear and extended RHEED oscillations. To solve the magnet issue, a finite element model has been

  16. Numerical Modeling of Active Flow Control in a Boundary Layer Ingesting Offset Inlet

    NASA Technical Reports Server (NTRS)

    Allan, Brian G.; Owens, Lewis R.; Berrier, Bobby L.

    2004-01-01

    This investigation evaluates the numerical prediction of flow distortion and pressure recovery for a boundary layer ingesting offset inlet with active flow control devices. The numerical simulations are computed using a Reynolds averaged Navier-Stokes code developed at NASA. The numerical results are validated by comparison to experimental wind tunnel tests conducted at NASA Langley Research Center at both low and high Mach numbers. Baseline comparisons showed good agreement between numerical and experimental results. Numerical simulations for the inlet with passive and active flow control also showed good agreement at low Mach numbers where experimental data has already been acquired. Numerical simulations of the inlet at high Mach numbers with flow control jets showed an improvement of the flow distortion. Studies on the location of the jet actuators, for the high Mach number case, were conducted to provide guidance for the design of a future experimental wind tunnel test.

  17. Passive Boundary Layer Separation Control on a NACA2415 Airfoil at High Reynolds Numbers

    NASA Astrophysics Data System (ADS)

    Parikh, Agastya; Hultmark, Marcus

    2016-11-01

    The design and analysis of a passive flow control system for a NACA2415 airfoil is undertaken. There exists a vast body of knowledge on airfoil boundary layer control with the use of controlled mass flux, but there is little work investigating passive mass flux-based methods. A simple duct system that uses the upper surface pressure gradient to force blowing near the leading edge and suction near the trailing edge is proposed and evaluated. 2D RANS analyses at Rec 1 . 27 ×106 were used to generate potential configurations for experimental tests. Initial computational results suggest drag reductions of approximately 2 - 7 % as well as lift increases of 4 - 5 % at α = 10 .0° and α = 12 .5° . A carbon composite-aluminum structure model that implements the most effective configurations, according to the CFD predictions, has been designed and fabricated. Experiments are being performed to evaluate the CFD results and the feasibility the duct system.

  18. Grain size control for CVD-grown single crystal mono- and bi-layer graphene

    NASA Astrophysics Data System (ADS)

    Luo, Zhengtang

    2015-03-01

    By suppressing the nucleation density during Chemical Vapor Deposition (CVD) growth, we demonstrate that the large-size single crystal monolayer and bilayer graphene can be synthesized by this method. For single layer, single crystals with diameter up to 5.9 mm, have been successfully obtained by adjusting degree of oxidation during surface treatment step and hydrogen annealing duration during growth, thereby allow us to control nucleation density and consequently to control graphene grains sizes. For bilayer growth, our main strategy is to maximize the duration that is controlled by the absorption-diffusion mechanism. With this method, sub-millimeter size single crystal bilayer graphene is also obtained. Electron transport measurement on those produced graphene has shown carrier mobility that is comparable with that of mechanical exfoliated graphene, indicating the high quality of our graphene sample. This project is supported by the Research Grant Council of Hong Kong SAR (Project Number 623512 and DAG12EG05).

  19. Active control of panel vibrations induced by boundary-layer flow

    NASA Technical Reports Server (NTRS)

    Chow, Pao-Liu

    1991-01-01

    Some problems in active control of panel vibration excited by a boundary layer flow over a flat plate are studied. In the first phase of the study, the optimal control problem of vibrating elastic panel induced by a fluid dynamical loading was studied. For a simply supported rectangular plate, the vibration control problem can be analyzed by a modal analysis. The control objective is to minimize the total cost functional, which is the sum of a vibrational energy and the control cost. By means of the modal expansion, the dynamical equation for the plate and the cost functional are reduced to a system of ordinary differential equations and the cost functions for the modes. For the linear elastic plate, the modes become uncoupled. The control of each modal amplitude reduces to the so-called linear regulator problem in control theory. Such problems can then be solved by the method of adjoint state. The optimality system of equations was solved numerically by a shooting method. The results are summarized.

  20. Open-loop control of noise amplification in a separated boundary layer flow

    SciTech Connect

    Boujo, E. Gallaire, F.; Ehrenstein, U.

    2013-12-15

    Linear optimal gains are computed for the subcritical two-dimensional separated boundary-layer flow past a bump. Very large optimal gain values are found, making it possible for small-amplitude noise to be strongly amplified and to destabilize the flow. The optimal forcing is located close to the summit of the bump, while the optimal response is the largest in the shear layer. The largest amplification occurs at frequencies corresponding to eigenvalues which first become unstable at higher Reynolds number. Nonlinear direct numerical simulations show that a low level of noise is indeed sufficient to trigger random flow unsteadiness, characterized here by large-scale vortex shedding. Next, a variational technique is used to compute efficiently the sensitivity of optimal gains to steady control (through source of momentum in the flow, or blowing/suction at the wall). A systematic analysis at several frequencies identifies the bump summit as the most sensitive region for control with wall actuation. Based on these results, a simple open-loop control strategy is designed, with steady wall suction at the bump summit. Linear calculations on controlled base flows confirm that optimal gains can be drastically reduced at all frequencies. Nonlinear direct numerical simulations also show that this control allows the flow to withstand a higher level of stochastic noise without becoming nonlinearly unstable, thereby postponing bypass transition. In the supercritical regime, sensitivity analysis of eigenvalues supports the choice of this control design. Full restabilization of the flow is obtained, as evidenced by direct numerical simulations and linear stability analysis.

  1. Suppressing NOM access to controlled porous TiO2 particles enhances the decomposition of target water contaminants

    EPA Science Inventory

    Suppressing access of natural organic matter (NOM) to TiO2 is a key to the successful photocatalytic decomposition of a target contaminant in water. This study first demonstrates simply controlling the porous structure of TiO2 can significantly improve the selective oxidation.

  2. Controlling single and few-layer graphene crystals growth in a solid carbon source based chemical vapor deposition

    SciTech Connect

    Papon, Remi; Sharma, Subash; Shinde, Sachin M.; Vishwakarma, Riteshkumar; Tanemura, Masaki; Kalita, Golap

    2014-09-29

    Here, we reveal the growth process of single and few-layer graphene crystals in the solid carbon source based chemical vapor deposition (CVD) technique. Nucleation and growth of graphene crystals on a polycrystalline Cu foil are significantly affected by the injection of carbon atoms with pyrolysis rate of the carbon source. We observe micron length ribbons like growth front as well as saturated growth edges of graphene crystals depending on growth conditions. Controlling the pyrolysis rate of carbon source, monolayer and few-layer crystals and corresponding continuous films are obtained. In a controlled process, we observed growth of large monolayer graphene crystals, which interconnect and merge together to form a continuous film. On the other hand, adlayer growth is observed with an increased pyrolysis rate, resulting few-layer graphene crystal structure and merged continuous film. The understanding of monolayer and few-layer crystals growth in the developed CVD process can be significant to grow graphene with controlled layer numbers.

  3. Blended Wing Body Systems Studies: Boundary Layer Ingestion Inlets With Active Flow Control

    NASA Technical Reports Server (NTRS)

    Geiselhart, Karl A. (Technical Monitor); Daggett, David L.; Kawai, Ron; Friedman, Doug

    2003-01-01

    A CFD analysis was performed on a Blended Wing Body (BWB) aircraft with advanced, turbofan engines analyzing various inlet configurations atop the aft end of the aircraft. The results are presented showing that the optimal design for best aircraft fuel efficiency would be a configuration with a partially buried engine, short offset diffuser using active flow control, and a D-shaped inlet duct that partially ingests the boundary layer air in flight. The CFD models showed that if active flow control technology can be satisfactorily developed, it might be able to control the inlet flow distortion to the engine fan face and reduce the powerplant performance losses to an acceptable level. The weight and surface area drag benefits of a partially submerged engine shows that it might offset the penalties of ingesting the low energy boundary layer air. The combined airplane performance of such a design might deliver approximately 5.5% better aircraft fuel efficiency over a conventionally designed, pod-mounted engine.

  4. An Integrated Observational and Model Synthesis Approach to Examine Dominant Environmental Controls on Active Layer Thickness

    NASA Astrophysics Data System (ADS)

    Atchley, A. L.; Coon, E.; Painter, S. L.; Harp, D. R.; Wilson, C. J.

    2015-12-01

    The active layer thickness (ALT) - the annual maximum depth of soil with above 0°C temperatures - in part determines the volume of carbon-rich stores available for decomposition and therefore potential greenhouse gas release into the atmosphere from Arctic tundra. However, understanding and predicting ALT in polygonal tundra landscapes is difficult due to the complex nature of hydrothermal atmospheric-surface-subsurface interactions in freezing/thawing soil. Simply deconvolving effects of single environmental controls on ALT is not possible with measurements alone as processes act in concert to drive thaw depth formation. Process-rich models of thermal hydrological dynamics, conversely, are a valuable tool for understanding the dominant controls and uncertainties in predicting permafrost conditions. By integrating observational data with known physical relationships to form process-rich models, synthetic experiments can then be used to explore a breadth of environmental conditions encountered and the effect of each environmental attribute may be assessed. Here a process rich thermal hydrology model, The Advanced Terrestrial Simulator, has been created and calibrated using observed data from Barrow, AK. An ensemble of 1D thermal hydrologic models were simulated that span a range of three environmental factors 1) thickness of organic rich soil, 2) snow depth, and 3) soil moisture content, to investigate the role of each factor on ALT. Results show that organic layer thickness acts as a strong insulator and is the dominant control of ALT, but the strength of the effect of organic layer thickness is also dependent on the saturation state. Using the ensemble results, the effect of peat thickness on ALT was then examined on a 2D domain. This work was supported by LANL Laboratory Directed Research and Development Project LDRD201200068DR and by the The Next-Generation Ecosystem Experiments (NGEE Arctic) project. NGEE-Arctic is supported by the Office of Biological and

  5. Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide

    SciTech Connect

    Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

    2013-07-15

    Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg–Al and Mg–Fe layered double hydroxides (LDHs) have been synthesized by the calcination–rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV–vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO{sub 3}{sup 2−} solutions imply that Mg{sub 3}Al–VC LDH is a better controlled release system than Mg{sub 3}Fe–VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO{sub 3}{sup 2−} solution. - Graphical abstract: Vitamin C anions have been intercalated in the interlayer space of layered double hydroxide and released in CO{sub 3}{sup 2−} solution and deionised water. - Highlights: • Vitamin C intercalated Mg–Al and Mg–Fe layered double hydroxides were prepared. • Release property of vitamin C in aqueous CO{sub 3}{sup 2−} solution is better. • Avrami-Erofe’ev and first-order models provide better fit for release results. • Diffusion-controlled and ion exchange processes occur in deionised water. • An ion exchange process occurs in CO{sub 3}{sup 2−} solution.

  6. Report: EPA Could Improve Physical Access and Service Continuity/Contingency Controls for Financial and Mixed-Financial Systems Located at its Research Triangle Park Campus

    EPA Pesticide Factsheets

    Report #2006-P-00005, December 14, 2005. Controls needed to be improved in areas such as visitor access to facilities, use of contractor access badges, and general physical access to the NCC, computer rooms outside the NCC, and media storage rooms.

  7. Control of heat-resistant steel carburized layer structure. Part I

    NASA Astrophysics Data System (ADS)

    Semenov, M. Yu.

    2013-09-01

    A physical model of carbide formation with vacuum carburizing is developed with the aim of controlling complexly-alloyed steel diffusion layer structure, taking account of excess phase formation of both the cementite type, and special carbides. A mathematical model is developed on the basis of the physical model adopted, adequate for experimental results. Analysis of calculated results is used as a basis for demonstrating the effect on carbide formation of alloying with chromium and strong carbide-forming elements, and also production factors.

  8. The design and performance of axially symmetrical contoured wall diffusers employing suction boundary layer control

    NASA Technical Reports Server (NTRS)

    Nelson, C. D., Jr.; Hudson, W. G.; Yang, T.

    1974-01-01

    This paper presents a procedure for the design and the performance prediction of axially symmetrical contoured wall diffusers employing suction boundary layer control. An inverse problem approach was used in the potential flow design of the diffuser wall contours. The experimentally observed flow characteristics and the stability of flows within the diffuser are also described. Guidelines for the design of low suction (less than 10 percent of the inlet flow) and thus high effectiveness contoured wall diffusers are also provided based on the results of the experimental program.

  9. Boundary Layer Flow Control by an Array of Ramp-Shaped Vortex Generators

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Hirt, S. M.; Bencic, T. J.

    2012-01-01

    Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control. (See CASI ID 20120009374 for Supplemental CD-ROM.)

  10. Mobility of isoproturon from an alginate-bentonite controlled release formulation in layered soil.

    PubMed

    Fernández-Pérez, M; González-Pradas, E; Villafranca-Sánchez, M; Flores-Céspedes, F

    2000-11-01

    The mobility of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] from an alginate-based controlled release (CR) formulation was investigated by using soil columns. A layered bed system simulating the typical arrangement under a plastic greenhouse, which is composed of sand, peat, amended soil and native soil was used. The CR formulation was based on sodium alginate (1.87%), isoproturon (1.19%), natural bentonite (3.28%), and water (93.66%), and was compared to technical grade isoproturon. The use of the alginate-bentonite CR formulation produced less vertical mobility of the active ingredient as compared to the technical product. There was no presence of herbicide in the leachate when the alginate-bentonite CR formulation was used. However, 0.90% of isoproturon appeared when the treatment was carried out with technical grade material. Isoproturon mobility was modelled using the programme CMLS, which showed the peat layer to retard pesticide leaching. Analysis of the soil columns showed the highest isoproturon concentration in the peat layer.

  11. Anticancer nanodelivery system with controlled release property based on protocatechuate–zinc layered hydroxide nanohybrid

    PubMed Central

    Barahuie, Farahnaz; Hussein, Mohd Zobir; Abd Gani, Shafinaz; Fakurazi, Sharida; Zainal, Zulkarnain

    2014-01-01

    Background We characterize a novel nanocomposite that acts as an efficient anticancer agent. Methods This nanocomposite consists of zinc layered hydroxide intercalated with protocatechuate (an anionic form of protocatechuic acid), that has been synthesized using a direct method with zinc oxide and protocatechuic acid as precursors. Results The resulting protocatechuic acid nanocomposite (PAN) showed a basal spacing of 12.7 Å, indicating that protocatechuate was intercalated in a monolayer arrangement, with an angle of 54° from the Z-axis between the interlayers of the zinc layered hydroxide, and an estimated drug loading of about 35.7%. PAN exhibited the properties of a mesoporous type material, with greatly enhanced thermal stability of protocatechuate as compared to its free counterpart. The presence of protocatechuate in the interlayers of the zinc layered hydroxide was further supported by Fourier transform infrared spectroscopy. Protocatechuate was released from PAN in a slow and sustained manner. This mechanism of release was well represented by a pseudo-second order kinetics model. PAN has shown increased cytotoxicity compared to the free form of protocatechuic acid in all cancer cell lines tested. Tumor growth suppression was extensive, particularly in HepG2 and HT29 cell lines. Conclusion PAN is suitable for use as a controlled release formulation, and our in vitro evidence indicates that PAN is an effective anticancer agent. PAN may have potential as a chemotherapeutic drug for human cancer. PMID:25061291

  12. Controlled synthesis of single-layer MoSe2 nanostructures

    NASA Astrophysics Data System (ADS)

    Chen, Yuxuan; Zhang, Chendong; Cui, Ping; Zhang, Zhenyu; Shih, Chih-Kang

    Group VIB transition metal dichalcogenides (TMD), such as MoSe2, WS2, etc., are a family of layered materials with weak van der Waals (vdW) interaction between neighboring layers. A transition from indirect to direct bandgap semiconductor takes place for most of these materials when they become single layer (SL), and the values of these direct band gap are comparable to visible light. This makes SL TMDs attractive candidates for 2D electronic and optoelectronic devices. Though epitaxial SL TMDs have been successfully prepared, there is controversy in their growth conditions and in their edge structures. Moreover, some intriguing theoretical predictions about the finite-size effect on SL TMDs are still awaiting experimental proof. Here we report systematic studies of the thermodynamics/ kinetics of SL MoSe2 formation on a vdW surface (namely, highly oriented pyrolytic graphite) using molecular beam epitaxy (MBE). We also report the controlled creation of various nanostructures of MBE SL MoSe2. The edge properties and the influence of the in-plane confinement on the electronic structure are addressed by in-situ STM and STS. Theoretical calculations have been carried out to help understanding the experimental discoveries. Corresponding author.

  13. Stability of organic carbon in deep soil layers controlled by fresh carbon supply.

    PubMed

    Fontaine, Sébastien; Barot, Sébastien; Barré, Pierre; Bdioui, Nadia; Mary, Bruno; Rumpel, Cornelia

    2007-11-08

    The world's soils store more carbon than is present in biomass and in the atmosphere. Little is known, however, about the factors controlling the stability of soil organic carbon stocks and the response of the soil carbon pool to climate change remains uncertain. We investigated the stability of carbon in deep soil layers in one soil profile by combining physical and chemical characterization of organic carbon, soil incubations and radiocarbon dating. Here we show that the supply of fresh plant-derived carbon to the subsoil (0.6-0.8 m depth) stimulated the microbial mineralization of 2,567 +/- 226-year-old carbon. Our results support the previously suggested idea that in the absence of fresh organic carbon, an essential source of energy for soil microbes, the stability of organic carbon in deep soil layers is maintained. We propose that a lack of supply of fresh carbon may prevent the decomposition of the organic carbon pool in deep soil layers in response to future changes in temperature. Any change in land use and agricultural practice that increases the distribution of fresh carbon along the soil profile could however stimulate the loss of ancient buried carbon.

  14. Study of flow control by localized volume heating in hypersonic boundary layers

    NASA Astrophysics Data System (ADS)

    Keller, M. A.; Kloker, M. J.; Kirilovskiy, S. V.; Polivanov, P. A.; Sidorenko, A. A.; Maslov, A. A.

    2014-12-01

    Boundary-layer flow control is a prerequisite for a safe and efficient operation of future hypersonic transport systems. Here, the influence of an electric discharge—modeled by a heat-source term in the energy equation—on laminar boundary-layer flows over a flat plate with zero pressure gradient at Mach 3, 5, and 7 is investigated numerically. The aim was to appraise the potential of electro-gasdynamic devices for an application as turbulence generators in the super- and hypersonic flow regime. The results with localized heat-source elements in boundary layers are compared to cases with roughness elements serving as classical passive trips. The numerical simulations are performed using the commercial code ANSYS FLUENT (by ITAM) and the high-order finite-difference DNS code NS3D (by IAG), the latter allowing for the detailed analysis of laminar flow instability. For the investigated setups with steady heating, transition to turbulence is not observed, due to the Reynolds-number lowering effect of heating.

  15. Boundary Layer Flow Control by an Array of Ramp-Shaped Vortex Generators

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Hirt, S. M.; Bencic, T. J.

    2012-01-01

    Flow field survey results for the effect of ramp-shaped vortex generators (VG) on a turbulent boundary layer are presented. The experiments are carried out in a low-speed wind tunnel and the data are acquired primarily by hot-wire anemometry. Distributions of mean velocity and turbulent stresses as well as streamwise vorticity, on cross-sectional planes at various downstream locations, are obtained. These detailed flow field properties, including the boundary layer characteristics, are documented with the primary objective of aiding possible computational investigations. The results show that VG orientation with apex upstream, that produces a downwash directly behind it, yields a stronger pair of streamwise vortices. This is in contrast to the case with apex downstream that produces a pair of vortices of opposite sense. Thus, an array of VG s with the former orientation, usually considered for film-cooling application, may also be superior for mixing enhancement and boundary layer separation control. The data files can be found on a supplemental CD.

  16. Layer-by-layer engineering fluorescent polyelectrolyte coated mesoporous silica nanoparticles as pH-sensitive nanocarriers for controlled release

    NASA Astrophysics Data System (ADS)

    Du, Pengcheng; Zhao, Xubo; Zeng, Jin; Guo, Jinshan; Liu, Peng

    2015-08-01

    Fluorescent core/shell composite has been fabricated by the layer-by-layer (LbL) assembly of the fluorescein isothiocyanate modified chitosan (CS-FITC) and sodium alginate (AL) onto the carboxyl modified mesoporous silica nanoparticles (MSN-COOH), followed by PEGylation. It exhibits stability in high salt-concentration media and the pH responsive fluorescent feature can be used for cell imaging. Furthermore, the modified MSN cores can enhance the DOX loading capacity and the multifunctional polyelectrolyte shell can adjust the drug release upon the media pH, showing a low leakage quantity at the neutral environment but significantly enhanced release at lower pH media mimicking the tumor environments. Therefore, the biocompatible fluorescent polyelectrolyte coated mesoporous silica nanoparticles (MSN-LBL-PEG) offer promise for tumor therapy.

  17. Controlling Edge Morphology in Graphene Layers Using Electron Irradiation: From Sharp Atomic Edges to Coalesced Layers Forming Loops

    SciTech Connect

    Cruz-Silva, E.; Botello-Mendez, A.R.; Barnett, Zachary M; Jia, Xiaoting; Dresselhaus, M; Terrones, H.; Terrones, M.; Sumpter, Bobby G; Meunier, Vincent

    2010-01-01

    Recent experimental reports indicate that Joule heating can atomically sharpen the edges of chemical vapor deposition grown graphitic nanoribbons. The absence or presence of loops between adjacent layers in the annealed materials is the topic of a growing debate that this Letter aims to put to rest. We offer a rationale explaining why loops do form if Joule heating is used alone, and why adjacent nanoribbon layers do not coalesce when Joule heating is applied after high-energy electrons first irradiate the sample. Our work, based on large-scale quantum molecular dynamics and electronic-transport calculations, shows that vacancies on adjacent graphene sheets, created by electron irradiation, inhibit the formation of edge loops.

  18. Crystal Orientation Control of Bismuth Layer-Structured Dielectric Films Using Interface Layers of Perovskite-Type Oxides

    NASA Astrophysics Data System (ADS)

    Kondoh, Yohta; Sasajima, Keiichi; Hayashi, Mari; Kimura, Junichi; Takuwa, Itaru; Ehara, Yoshitaka; Funakubo, Hiroshi; Uchida, Hiroshi

    2011-09-01

    Thin films of SrBi4Ti4O15, a kind of bismuth layer-structured dielectrics (BLSDs), were prepared on platinized silicon wafers buffered by perovskite-type oxide interface layers, (100)LaNiO3/(111)Pt/TiO2/(100)Si and (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si, by chemical solution deposition (CSD). The Ca2Nb3O10 nanosheets were supported on a (111)Pt/TiO2/(100)Si substrate by dip coating using an aqueous dispersion, while (100)LaNiO3 was prepared by CSD. The (00l) planes of BLSD crystal were preferentially oriented on the surface of both substrates, which is caused by suitable lattice matching between the a-(b-)axis of BLSD and perovskite-type oxide layers. The film deposition on (001)Ca2Nb3O10 nanosheets yielded (001)-oriented BLSD films with higher crystallinity and smaller fluctuation in the tilting angle of the (001)BLSD plane than those on the (100)LaNiO3 interface layer. The dielectric constant (ɛr) of (001)-oriented SrBi4Ti4O15 film on (001)Ca2Nb3O10-nanosheets/(111)Pt/TiO2/(100)Si substrate was approximately 190, which was significantly stable against the change of frequency and bias voltage compared with that of the randomly-oriented SrBi4Ti4O15 film.

  19. Experimental validation of microseismic emissions from a controlled hydraulic fracture in a synthetic layered medium

    NASA Astrophysics Data System (ADS)

    Roundtree, Russell

    A controlled hydraulic fracture experiment was performed on two medium sized (11" x 11" x 15") synthetic layered blocks of low permeability, low porosity Lyons sandstone sandwiched between cement. The purpose of the research was to better understand and characterize the fracture evolution as the fracture tip impinged upon the layer boundaries between the well bonded layers. It is also one of the first documented uses of passive microseismic used in a laboratory environment to characterize hydraulic fracturing. A relatively low viscosity fluid of 1000 centipoise, compared to properly scaled previous work (Casas 2005, and Athavale 2007), was pumped at a constant rate of 10 mL/minute through a steel cased hole landed and isolated in the sandstone layer. Efforts were made to contain the hydraulic fracture within the confines of the rock specimen to retain the created hydraulic fracture geometry. Two identical samples and treatment schedules were created and differed only in the monitoring system used to characterize the microseismic activity during the fracture treatment. The first block had eight embedded P-wave transducers placed in the sandstone layer to record the passive microseismic emissions and localize the location and time of the acoustic event. The second block had six compressional wave transducers and twelve shear wave transducers embedded in the sandstone layer of the block. The intention was to record and process the seismic data using conventional P-wave to S-wave difference timing techniques well known in industry. While this goal ultimately not possible due to the geometry of the receiver placements and the limitations of the Vallene acquisition processing software, the data received and the events localized from the 18 transducer test were of much higher numbers and quality than on the eight transducer test. This experiment proved conclusively that passive seismic emission recording can yield positive results in the laboratory. Just as in the field

  20. Micro vortex generator control of axisymmetric high-speed laminar boundary layer separation

    NASA Astrophysics Data System (ADS)

    Estruch-Samper, D.; Vanstone, L.; Hillier, R.; Ganapathisubramani, B.

    2015-09-01

    Interest in the development of micro vortex generators (MVGs) to control high-speed flow separation has grown in the last decade. In contrast to conventional vortex generators, MVGs are fully submerged in the boundary layer and have the potential of inducing surface flow mixing with marginal drag penalty when suitably designed. Also, they do not result in undesired reduced mass flow such as with suction methods. The flow mechanisms at the location of MVGs are not yet fully understood, and optimal designs are difficult to establish given that both numerical predictions and experiments are particularly challenged for short element heights, yet optimal MVGs are generally expected to be at least shorter than half the local boundary layer thickness. The present work aims at investigating experimentally the fundamental flow physics concerning an individual MVG element (of `canonical' or simplified geometry) at a range of near-wall heights. A fully laminar base flow is considered so as to isolate the effect of incoming turbulence as well as the more complex physics that may occur when specific and/or multiple elements are used. Tests were performed in a gun tunnel at a freestream Mach number of 8.9 and Reynolds number of /m, and the basic test model consisted of a blunt-nosed cylinder which produced an axisymmetric laminar boundary layer with an edge Mach number of 3.4 and Reynolds number of /m at the MVG location. A laminar shock-wave/boundary layer interaction with separation was induced by a flare located further downstream on the model. Measurements consisted of time-resolved surface heat transfer obtained in the axial direction immediately downstream of the MVG and along the interaction, together with simultaneous high-speed schlieren imaging. The height () of the MVG element used in a `diamond' configuration (square planform with one vertex facing the flow) was adjusted between tests ranging from = 0.03 to 0.58, where the local undisturbed boundary layer thickness

  1. Boundary layer control by a fish: Unsteady laminar boundary layers of rainbow trout swimming in turbulent flows

    PubMed Central

    Saarenrinne, Pentti

    2016-01-01

    ABSTRACT The boundary layers of rainbow trout, Oncorhynchus mykiss [0.231±0.016 m total body length (L) (mean±s.d.); N=6], swimming at 1.6±0.09 L s−1 (N=6) in an experimental flow channel (Reynolds number, Re=4×105) with medium turbulence (5.6% intensity) were examined using the particle image velocimetry technique. The tangential flow velocity distributions in the pectoral and pelvic surface regions (arc length from the rostrum, lx=71±8 mm, N=3, and lx=110±13 mm, N=4, respectively) were approximated by a laminar boundary layer model, the Falkner−Skan equation. The flow regime over the pectoral and pelvic surfaces was regarded as a laminar flow, which could create less skin-friction drag than would be the case with turbulent flow. Flow separation was postponed until vortex shedding occurred over the posterior surface (lx=163±22 mm, N=3). The ratio of the body-wave velocity to the swimming speed was in the order of 1.2. This was consistent with the condition of the boundary layer laminarization that had been confirmed earlier using a mechanical model. These findings suggest an energy-efficient swimming strategy for rainbow trout in a turbulent environment. PMID:27815242

  2. [Genetic control of efficient leaf rust resistance in collection accessions of barley Hordeum vulgare L].

    PubMed

    Tyryshkin, L G

    2009-03-01

    Leaf rust resistance was studied in barley accessions from the worldwide collection of the All-Russia Institute of Plant Industry. Most accessions described as highly resistant in the literature proved susceptible. High resistance at the juvenile stage was observed only for the cultivars Henry, Cebada Capa, Forrajera Klein, and Scarlet. Hybrid analysis and phytopathological tests showed that the cultivar Scarlet had one dominant resistance gene, Rph7. Adult resistance was demonstrated for accession NB-3002 from Nepal, which proved to have one dominant gene on evidence of hybrid analysis.

  3. Robustness of reduced-order observer-based controllers in transitional 2D Blasius boundary layers

    NASA Astrophysics Data System (ADS)

    Belson, Brandt; Semeraro, Onofrio; Rowley, Clarence; Pralits, Jan; Henningson, Dan

    2011-11-01

    In this work, we seek to delay transition in the Blasius boundary layer. We trip the flow with an upstream disturbance and dampen the growth of the resulting structures downstream. The observer-based controllers use a single sensor and a single localized body force near the wall. To formulate the controllers, we first find a reduced-order model of the system via the Eigensystem Realization Algorithm (ERA), then find the H2 optimal controller for this reduced-order system. We find the resulting controllers are effective only when the sensor is upstream of the actuator (in a feedforward configuration), but as is expected, are sensitive to model uncertainty. When the sensor is downstream of the actuator (in a feedback configuration), the reduced-order observer-based controllers are not robust and ineffective on the full system. In order to investigate the robustness properties of the system, an iterative technique called the adjoint of the direct adjoint (ADA) is employed to find a full-dimensional H2 optimal controller. This avoids the reduced-order modelling step and serves as a reference point. ADA is promising for investigating the lack of robustness previously mentioned.

  4. Restricted access molecularly imprinted polymers obtained by bovine serum albumin and/or hydrophilic monomers' external layers: a comparison related to physical and chemical properties.

    PubMed

    Santos, Mariane Gonçalves; Moraes, Gabriel de Oliveira Isac; Nakamura, Maurício Gustavo; dos Santos-Neto, Álvaro José; Figueiredo, Eduardo Costa

    2015-11-21

    Molecularly imprinting polymers (MIPs) can be modified with external layers in order to obtain restricted access molecularly imprinted polymers (RAMIPs) able to exclude macromolecules and retain low weight compounds. These modifications have been frequently achieved using hydrophilic monomers, chemically bound on the MIP surface. Recently, our group proposed a new biocompatible RAMIP based on the formation of a bovine serum albumin coating on the surface of MIP particles. This material has been used to extract drugs directly from untreated human plasma samples, but its physicochemical evaluation has not been carried out yet, mainly in comparison with RAMIPs obtained by hydrophilic monomers. Thus, we proposed in this paper a comparative study involving the surface composition, microscopic aspect, selectivity, binding kinetics, adsorption and macromolecule elimination ability of these different materials. We concluded that the synthesis procedure influences the size and shape of particles and that hydrophilic co-monomer addition as well as coating with BSA do not alter the chemical recognition ability of the material. The difference between imprinted and non-imprinted polymers' adsorption was evident (suggesting that imprinted polymers have a better capacity to bind the template than the non-imprinted ones). The Langmuir model presents the best fit to describe the materials' adsorption profile. The polymer covered with hydrophilic monomers presented the best adsorption for the template in an aqueous medium, probably due to a hydrophilic layer on its surface. We also concluded that an association of the hydrophilic monomers with the bovine serum albumin coating is important to obtain materials with higher capacity of macromolecule exclusion.

  5. Controlled Gas Exfoliation of Boron Nitride into Few-Layered Nanosheets.

    PubMed

    Zhu, Wenshuai; Gao, Xiang; Li, Qian; Li, Hongping; Chao, Yanhong; Li, Meijun; Mahurin, Shannon M; Li, Huaming; Zhu, Huiyuan; Dai, Sheng

    2016-08-26

    The controlled exfoliation of hexagonal boron nitride (h-BN) into single- or few-layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h-BN. Here, we present an efficient strategy for the scalable synthesis of few-layered h-BN nanosheets (BNNS) using a novel gas exfoliation of bulk h-BN in liquid N2 (L-N2 ). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h-BN and the cryogenic L-N2 gasification to exfoliate the h-BN. The produced BNNS after ten cycles (BNNS-10) consisted primarily of fewer than five atomic layers with a high mass yield of 16-20 %. N2 sorption and desorption isotherms show that the BNNS-10 exhibited a much higher specific surface area of 278 m(2)  g(-1) than that of bulk BN (10 m(2)  g(-1) ). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h-BN. Subseqently, the L-N2 penetrates into the interlayers of h-BN along the curling edge, followed by an immediate drastic gasification of L-N2 , further peeling off h-BN. This novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials in high yields.

  6. Controlled Gas Exfoliation of Boron Nitride into Few-Layered Nanosheets

    SciTech Connect

    Zhu, Wenshuai; Gao, Xiang; Li, Qian; Li, Hongping; Chao, Yanhong; Li, Meijun; Mahurin, Shannon M.; Li, Huaming; Zhu, Huiyuan; Dai, Sheng

    2016-07-22

    The controlled exfoliation of hexagonal boron nitride (h-BN) into single- or few-layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h-BN. Here, we present an efficient strategy for the scalable synthesis of few-layered h-BN nanosheets (BNNS) via a novel gas exfoliation of bulk h-BN in liquid N2 (L-N2). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h-BN and the cryogenic L-N2 gasification to exfoliate the h-BN. The produced BNNS after ten cycles (BNNS-10) consisted primarily of fewer than five atomic layers with high a mass yield of 16~20%. N2 sorption and desorption isotherms show that the BNNS-10 exhibited a much higher specific surface area of 278 m2/g–1 than that of bulk BN (10 m2/g–1). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h-BN. Subseqently, the L-N2 penetrates into the interlayers of h-BN along the curling edge, followed by an immediate drastic gasification of L-N2, further peeling off h-BN. In conclusion, this novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials with high yeilds.

  7. Controlled Gas Exfoliation of Boron Nitride into Few-Layered Nanosheets

    DOE PAGES

    Zhu, Wenshuai; Gao, Xiang; Li, Qian; ...

    2016-07-22

    The controlled exfoliation of hexagonal boron nitride (h-BN) into single- or few-layered nanosheets remains a grand challenge and becomes the bottleneck to essential studies and applications of h-BN. Here, we present an efficient strategy for the scalable synthesis of few-layered h-BN nanosheets (BNNS) via a novel gas exfoliation of bulk h-BN in liquid N2 (L-N2). The essence of this strategy lies in the combination of a high temperature triggered expansion of bulk h-BN and the cryogenic L-N2 gasification to exfoliate the h-BN. The produced BNNS after ten cycles (BNNS-10) consisted primarily of fewer than five atomic layers with high amore » mass yield of 16~20%. N2 sorption and desorption isotherms show that the BNNS-10 exhibited a much higher specific surface area of 278 m2/g–1 than that of bulk BN (10 m2/g–1). Through the investigation of the exfoliated intermediates combined with a theoretical calculation, we found that the huge temperature variation initiates the expansion and curling of the bulk h-BN. Subseqently, the L-N2 penetrates into the interlayers of h-BN along the curling edge, followed by an immediate drastic gasification of L-N2, further peeling off h-BN. In conclusion, this novel gas exfoliation of high surface area BNNS not only opens up potential opportunities for wide applications, but also can be extended to produce other layered materials with high yeilds.« less

  8. DOE`s nation-wide system for access control can solve problems for the federal government

    SciTech Connect

    Callahan, S.; Tomes, D.; Davis, G.; Johnson, D.; Strait, S.

    1996-07-01

    The U.S. Department of Energy`s (DOE`s) ongoing efforts to improve its physical and personnel security systems while reducing its costs, provide a model for federal government visitor processing. Through the careful use of standardized badges, computer databases, and networks of automated access control systems, the DOE is increasing the security associated with travel throughout the DOE complex, and at the same time, eliminating paperwork, special badging, and visitor delays. The DOE is also improving badge accountability, personnel identification assurance, and access authorization timeliness and accuracy. Like the federal government, the DOE has dozens of geographically dispersed locations run by many different contractors operating a wide range of security systems. The DOE has overcome these obstacles by providing data format standards, a complex-wide virtual network for security, the adoption of a standard high security system, and an open-systems-compatible link for any automated access control system. If the location`s level of security requires it, positive visitor identification is accomplished by personal identification number (PIN) and/or by biometrics. At sites with automated access control systems, this positive identification is integrated into the portals.

  9. Hybrid Active/Passive Control of Sound Radiation from Panels with Constrained Layer Damping and Model Predictive Feedback Control

    NASA Technical Reports Server (NTRS)

    Cabell, Randolph H.; Gibbs, Gary P.

    2000-01-01

    There has been considerable interest over the past several years in applying feedback control methods to problems of structural acoustics. One problem of particular interest is the control of sound radiation from aircraft panels excited on one side by a turbulent boundary layer (TBL). TBL excitation appears as many uncorrelated sources acting on the panel, which makes it difficult to find a single reference signal that is coherent with the excitation. Feedback methods have no need for a reference signal, and are thus suited to this problem. Some important considerations for the structural acoustics problem include the fact that the required controller bandwidth can easily extend to several hundred Hertz, so a digital controller would have to operate at a few kilohertz. In addition, aircraft panel structures have a reasonably high modal density over this frequency range. A model based controller must therefore handle the modally dense system, or have some way to reduce the bandwidth of the problem. Further complicating the problem is the fact that the stiffness and dynamic properties of an aircraft panel can vary considerably during flight due to altitude changes resulting in significant resonant frequency shifts. These considerations make the tradeoff between robustness to changes in the system being controlled and controller performance especially important. Recent papers concerning the design and implementation of robust controllers for structural acoustic problems highlight the need to consider both performance and robustness when designing the controller. While robust control methods such as H1 can be used to balance performance and robustness, their implementation is not easy and requires assumptions about the types of uncertainties in the plant being controlled. Achieving a useful controller design may require many tradeoff studies of different types of parametric uncertainties in the system. Another approach to achieving robustness to plant changes is to

  10. Shockwave turbulent boundary layer interaction control using magnetically driven surface discharges

    NASA Astrophysics Data System (ADS)

    Kalra, Chiranjeev Singh

    The dissertation demonstrates the potential for shockwave-turbulent boundary layer interaction control in air using low current DC constricted surface discharges forced by moderate strength magnetic fields. Experiments are conducted in a Mach 2.6 indraft air tunnel with discharge currents up to 300 mA and magnetic field strengths up to 5 Tesla. Separation and non-separation inducing shocks are generated with diamond shape shockwave generators located on the wall opposite to the surface electrodes, and flow properties are measured with schlieren imaging, static wall pressure probes and acetone flow visualization. Also, an efficient, time dependent, two-dimensional Navier-Stokes numerical code for shockwave boundary layer interaction in air is developed. To replicate the experiments done at high Reynolds number, the code is divided into time independent and time dependent regimes to significantly reduce computation time. The effect of plasma control on boundary layer separation depends on the direction of the Lorentz force ( j d16 xB d16 ). It is observed that by using a Lorentz force that pushes the discharge upstream, separation can be induced or further strengthened even with discharge currents as low as 30 mA in a 3 Tesla magnetic field. If shock induced separation is present, it is observed that by using a Lorentz force that pushes the discharge downstream, separation can be suppressed, but this required higher currents, greater than 80 mA. Acetone planar laser scattering is used to image the flow structure in the test section and the reduction in the size of recirculation bubble and its elimination are observed experimentally as a function of actuation current and magnetic field strength. Computational results are in good agreement with experiments in terms of the flow structure as shown by Schlieren imaging, acetone planar laser scattering, and the static pressure profile on the test section wall.

  11. Morphology and crystallinity control of ultrathin TiO2 layers deposited on carbon nanotubes by temperature-step atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Guerra-Nuñez, Carlos; Zhang, Yucheng; Li, Meng; Chawla, Vipin; Erni, Rolf; Michler, Johann; Park, Hyung Gyu; Utke, Ivo

    2015-06-01

    Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the chemically inert CNTs and appropriate control of the morphology of the TiO2 layer have not been achieved so far. Here, we report a new strategy to obtain ultrathin TiO2 coatings deposited by ``Temperature-step'' Atomic Layer Deposition (TS-ALD) with complete surface coverage of non-functionalized multiwall carbon nanotubes (MWCNTs) and controlled morphology and crystallinity of the TiO2 film. This strategy consists of adjusting the temperature during the ALD deposition to obtain the desired morphology. Complete coverage of long non-functionalized MWCNTs with conformal anatase layers was obtained by using a low temperature of 60 °C during the nucleation stage followed by an increase to 220 °C during the growth stage. This resulted in a continuous and amorphous TiO2 layer, covered with a conformal anatase coating. Starting with the deposition at 220 °C and reducing to 60 °C resulted in sporadic crystal grains at the CNT/TiO2 interface covered with an amorphous TiO2 layer. The results were accomplished through an extensive study of nucleation and growth of titanium oxide films on MWCNTs, of which a detailed characterization is presented in this work.Carbon nanotubes (CNTs) coated with titanium oxide (TiO2) have generated considerable interest over the last decade and become a promising nanomaterial for a wide range of energy applications. The efficient use of the outstanding electrical properties of this nanostructure relies heavily on the quality of the interface and the thickness and morphology of the TiO2 layer. However, complete surface coverage of the

  12. Parametric investigation of boundary layer control using triangular micro vortex generators

    NASA Astrophysics Data System (ADS)

    Bagheri, Milad; Muslmani, Motassem Al; Masood, Asad; Khosravi, Mahmood; Atef Mahmoud, Mohamed; Cardoz, Aniket; Akkuwari, Abdulrahman; Alanezi, Yusuf; Kim, Young

    2014-03-01

    Improving the aerodynamic performance of an airfoil is one of the primary interests of the Aerodynamicists. Such performance improvement can be achieved using passive or active flow control devices. One of such passive devices having a compact size along with an effective performance is the Micro Vortex Generators (MVGs). A special type of MVGs, which has been recently introduced in the aerospace industry, is "Triangular Shape" MVGs and its impact on aerodynamic characteristics is the main interest of this study. This study will compare the effects of various configurations through which delay of the flow separation using boundary layer control will be analysed by experimental and theoretical approach. The experimental investigations have been conducted using subsonic wind tunnel and the theoretical analysis using ANSYS® 13.0 FLUENT of which the final results are compared with each other.

  13. Intercalation and controlled release properties of vitamin C intercalated layered double hydroxide

    NASA Astrophysics Data System (ADS)

    Gao, Xiaorui; Lei, Lixu; O'Hare, Dermot; Xie, Juan; Gao, Pengran; Chang, Tao

    2013-07-01

    Two drug-inorganic composites involving vitamin C (VC) intercalated in Mg-Al and Mg-Fe layered double hydroxides (LDHs) have been synthesized by the calcination-rehydration (reconstruction) method. Powder X-ray diffraction (XRD), Fourier transform infrared (FTIR), and UV-vis absorption spectroscopy indicate a successful intercalation of VC into the interlayer galleries of the LDH host. Studies of VC release from the LDHs in deionised water and in aqueous CO32- solutions imply that Mg3Al-VC LDH is a better controlled release system than Mg3Fe-VC LDH. Analysis of the release profiles using a number of kinetic models suggests a solution-dependent release mechanism, and a diffusion-controlled deintercalation mechanism in deionised water, but an ion exchange process in CO32- solution.

  14. Antifouling Thin-Film Composite Membranes by Controlled Architecture of Zwitterionic Polymer Brush Layer.

    PubMed

    Liu, Caihong; Lee, Jongho; Ma, Jun; Elimelech, Menachem

    2017-02-21

    In this study, we demonstrate a highly antifouling thin-film composite (TFC) membrane by grafting a zwitterionic polymer brush via atom-transfer radical-polymerization (ATRP), a controlled, environmentally benign chemical process. Initiator molecules for polymerization were immobilized on the membrane surface by bioinspired catechol chemistry, leading to the grafting of a dense zwitterionic polymer brush layer. Surface characterization revealed that the modified membrane exhibits reduced surface roughness, enhanced hydrophilicity, and lower surface charge. Chemical force microscopy demonstrated that the modified membrane displayed foulant-membrane interaction forces that were 1 order of magnitude smaller than those of the pristine TFC membrane. The excellent fouling resistance imparted by the zwitterionic brush layer was further demonstrated by significantly reduced adsorption of proteins and bacteria. In addition, forward osmosis fouling experiments with a feed solution containing a mixture of organic foulants (bovine-serum albumin, alginate, and natural organic matter) indicated that the modified membrane exhibited significantly lower water flux decline compared to the pristine TFC membrane. The controlled architecture of the zwitterionic polymer brush via ATRP has the potential for a facile antifouling modification of a wide range of water treatment membranes without compromising intrinsic transport properties.

  15. Shock Wave Boundary Layer Interaction Control Using Pulsed DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Likhanskii, Alexandre; Beckwith, Kristian

    2012-11-01

    Flow separation in the shock wave boundary layer interaction (SWBLI) region significantly limits the development of supersonic inlets or scramjets. For past decades, scientists and engineers were looking for a way for active flow control of SWBLI. We will present our recent results of comprehensive simulations of SWBLI active control using pulsed nanosecond DBD plasma actuators at M=3. In the first part of simulations, we computed heat release from the ns pulse driven DBD plasma actuator to the flow using Tech-X plasma code Vorpal. This information has been consequently used in the simulations of SWBLI problem using Tech-X CFD code Nautilus. We compared baseline case with plasma actuators OFF to the case when plasma actuators were ON. We demonstrated strong perturbations in the region of SWBLI, suppression of flow separation and overall downstream increase of mass flow by ten percent when actuators are ON. We investigated the dependence of the results on the choice of different turbulence models and compared them to the laminar boundary layer case. We also performed parametric studies for different pulse repetition rates, pulse operation modes and DBD placement.

  16. Shielding the chemical reactivity using graphene layers for controlling the surface properties of carbon materials.

    PubMed

    Sedykh, A E; Gordeev, E G; Pentsak, E O; Ananikov, V P

    2016-02-14

    Graphene can efficiently shield chemical interactions and gradually decrease the binding to reactive defect areas. In the present study, we have used the observed graphene shielding effect to control the reactivity patterns on the carbon surface. The experimental findings show that a surface coating with a tiny carbon layer of 1-2 nm thickness is sufficient to shield the defect-mediated reactivity and create a surface with uniform binding ability. The shielding effect was directly observed using a combination of microscopy techniques and evaluated with computational modeling. The theoretical calculations indicate that a few graphene layers can drastically reduce the binding energy of the metal centers to the surface defects by 40-50 kcal mol(-1). The construction of large carbon areas with controlled surface reactivity is extremely difficult, which is a key limitation in many practical applications. Indeed, the developed approach provides a flexible and simple tool to change the reactivity patterns on large surface areas within a few minutes.

  17. The control effect in a detached laminar boundary layer of an array of normal synthetic jets

    NASA Astrophysics Data System (ADS)

    Valenzuela Calva, Fernando; Avila Rodriguez, Ruben

    2016-11-01

    In this work, 3D numerical simulations of an array of three normal circular synthetic jets embedded in an attached laminar boundary layer that separates under the influence of an inclined flap are performed for flow separation control. At the beginning of the present study, three cases are used to validate the numerical simulation with data obtained from experiments. The experimental data is chosen based on the cases which presented higher repeatability and reliability. Simulations showed reasonable agreement when compared with experiments. The simulations are undertaken at three synthetic jet operating conditions, i.e. Case A: L = 2, VR = 0.32; Case B: L = 4, VR = 0.64 and Case C: L = 6, VR = 0.96. The vortical structures produced for each synthetic jet operating condition are hairpin vortices for Case A and tilted vortices for Case B and C, respectively. By examining the spatial wall shear stress variations, the effect on the boundary layer prior to separation of the middle synthetic jet is evaluated. For effective flow control, produced at a relatively low the finding from this study suggests that hairpin vortical structures are more desirable structures. Universidad Nacional Autonoma de Mexico.

  18. Controlled release based on the dissolution of a calcium carbonate layer deposited on hydrogels.

    PubMed

    Ogomi, Daisuke; Serizawa, Takeshi; Akashi, Mitsuru

    2005-03-21

    It is possible that inorganic materials conjugated to suitable organic materials may induce unique mechanical, optical and other functional properties. Therefore, artificial conjugation of organic and inorganic components is attractive for preparing novel functional materials. Recently, we developed an alternate soaking process for calcium salt formation on/in polymer materials. In this study, a poly(vinyl alcohol) (PVA) hydrogel-calcium carbonate (CaCO(3)) composite was prepared by the aforementioned process as a controlled release support. Brilliant blue FCF (Mw = 794), FITC labeled BSA (Mw = 6.6 x 10(4)), FITC labeled dextran-10 k (Mw = 9.5 x 10(3)) and FITC labeled dextran-40 k (Mw = 4.3 x 10(4)) were loaded into the composite as model drugs. CaCO(3) dissolution and model drug release rates increased with a decrease in buffer pH. In addition, model drug release rates increased with a decrease in model drug molecular weight. These results show that CaCO(3) layers on hydrogels behave as capping layers for model drug release; the release rate of model drugs can be controlled by the dissolution rate of CaCO(3) and the molecular weight of the drug.

  19. FMO-based H.264 frame layer rate control for low bit rate video transmission

    NASA Astrophysics Data System (ADS)

    Cajote, Rhandley D.; Aramvith, Supavadee; Miyanaga, Yoshikazu

    2011-12-01

    The use of flexible macroblock ordering (FMO) in H.264/AVC improves error resiliency at the expense of reduced coding efficiency with added overhead bits for slice headers and signalling. The trade-off is most severe at low bit rates, where header bits occupy a significant portion of the total bit budget. To better manage the rate and improve coding efficiency, we propose enhancements to the H.264/AVC frame layer rate control, which take into consideration the effects of using FMO for video transmission. In this article, we propose a new header bits model, an enhanced frame complexity measure, a bit allocation and a quantization parameter adjustment scheme. Simulation results show that the proposed improvements achieve better visual quality compared with the JM 9.2 frame layer rate control with FMO enabled using a different number of slice groups. Using FMO as an error resilient tool with better rate management is suitable in applications that have limited bandwidth and in error prone environments such as video transmission for mobile terminals.

  20. Controls upon microbial accessibility to soil organic matter following woody plant encroachment into grasslands

    NASA Astrophysics Data System (ADS)

    Creamer, C. A.; Boutton, T. W.; Filley, T. R.

    2009-12-01

    Woody plant encroachment (WPE) into savannas and grasslands is a global phenomenon that alters soil organic matter (SOM) dynamics through changes in litter quality and quantity, soil structure, microbial ecology, and soil hydrology. To elucidate the controls upon microbial accessibility to SOM, bulk soils from a chronosequence of progressive WPE into native grasslands at the Texas A&M Agricultural Experimental Station La Copita Research Area were incubated for one year. The quantity and stable carbon isotope composition of respired CO2, plant biopolymer chemistry in SOM, and microbial community structure were tracked. Respiration rates declined steadily over the course of the experiment with 15-25% of the total CO2 respired released in the first month of incubation. Between 8 and 18% of the total carbon was mineralized to CO2 throughout the incubation. After day 84 a significantly (p < 0.05) greater portion of carbon was mineralized from soils of older woody clusters (34-86 years) than from soils of younger clusters (14-23 years) and the native grassland. Approximately 80% of patterns seen in cumulative CO2 loss could be explained by the proportions of macro- and micro-aggregates within each soil, suggesting soil structure is a major controlling factor of respiration rates. Despite documented carbon accrual within La Copita soils due to WPE, we observed no evidence of enhanced carbon stabilization in these respiration experiments. In fact, a greater proportion of total carbon was lost from the soil of mature woody stands than from young stands, suggesting carbon accumulation observed with WPE may be due to greater input rates or microbial dynamics not captured in the laboratory incubation. A cluster approximately 34 years in age represents a transition point in WPE where respiration dynamics become distinct between grassland and wooded elements. By day 84 of the incubation CO2 respired from all soils was depleted with respect to bulk SOM (1.5 to 5‰) and this