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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2009

XPS Protocol for the Characterization of Pristine and Functionalized Single Wall Carbon Nanotubes

Recent interest in developing new applications for carbon nanotubes (CNT) has fueled the need to use accurate macroscopic and nanoscopic techniques to characterize and understand their chemistry. X-ray photoelectron spectroscopy (XPS) has proved to be a useful analytical tool for nanoscale surface characterization of materials including carbon nanotubes. Recent nanotechnology research at NASA Johnson Space Center (NASA-JSC) helped to establish a characterization protocol for quality assessment for single wall carbon nanotubes (SWCNTs). Here, a review of some of the major factors of the XPS technique that can influence the quality of analytical data, suggestions for methods to maximize the quality of data obtained by XPS, and the development of a protocol for XPS characterization as a complementary technique for analyzing the purity and surface characteristics of SWCNTs is presented. The XPS protocol is then applied to a number of experiments including impurity analysis and the study of chemical modifications for SWCNTs.

Sosa, E. D.↗
NASA NTRS2006

X-Windows Information Sharing Protocol Widget Class

The X-Windows Information Sharing Protocol (ISP) Widget Class ("Class") is used here in the object-oriented-programming sense of the word) was devised to simplify the task of implementing ISP graphical-user-interface (GUI) computer programs. ISP programming tasks require many method calls to identify, query, and interpret the connections and messages exchanged between a client and an ISP server. Most X-Windows GUI programs use widget sets or toolkits to facilitate management of complex objects. The widget standards facilitate construction of toolkits and application programs. The X-Windows Information Sharing Protocol (ISP) Widget Class encapsulates the client side of the ISP programming libraries within the framework of an X-Windows widget. Using the widget framework, X-Windows GUI programs can interact with ISP services in an abstract way and in the same manner as that of other graphical widgets, making it easier to write ISP GUI client programs. Wrapping ISP client services inside a widget framework enables a programmer to treat an ISP server interface as though it were a GUI. Moreover, an alternate subclass could implement another communication protocol in the same sort of widget.

Barry, Matthew R.↗
NASA NTRS2010

High-Performance CCSDS AOS Protocol Implementation in FPGA

The Consultative Committee for Space Data Systems (CCSDS) Advanced Orbiting Systems (AOS) space data link protocol provides a framing layer between channel coding such as LDPC (low-density parity-check) and higher-layer link multiplexing protocols such as CCSDS Encapsulation Service, which is described in the following article. Recent advancement in RF modem technology has allowed multi-megabit transmission over space links. With this increase in data rate, the CCSDS AOS protocol implementation needs to be optimized to both reduce energy consumption and operate at a high rate.

Clare, Loren P.↗
NASA NTRS2010

Byzantine-fault tolerant self-stabilizing protocol for distributed clock synchronization systems

A rapid Byzantine self-stabilizing clock synchronization protocol that self-stabilizes from any state, tolerates bursts of transient failures, and deterministically converges within a linear convergence time with respect to the self-stabilization period. Upon self-stabilization, all good clocks proceed synchronously. The Byzantine self-stabilizing clock synchronization protocol does not rely on any assumptions about the initial state of the clocks. Furthermore, there is neither a central clock nor an externally generated pulse system. The protocol converges deterministically, is scalable, and self-stabilizes in a short amount of time. The convergence time is linear with respect to the self-stabilization period.

Malekpour, Mahyar R.↗
NASA NTRS2011

Model Checking a Self-Stabilizing Distributed Clock Synchronization Protocol for Arbitrary Digraphs

This report presents the mechanical verification of a self-stabilizing distributed clock synchronization protocol for arbitrary digraphs in the absence of faults. This protocol does not rely on assumptions about the initial state of the system, other than the presence of at least one node, and no central clock or a centrally generated signal, pulse, or message is used. The system under study is an arbitrary, non-partitioned digraph ranging from fully connected to 1-connected networks of nodes while allowing for differences in the network elements. Nodes are anonymous, i.e., they do not have unique identities. There is no theoretical limit on the maximum number of participating nodes. The only constraint on the behavior of the node is that the interactions with other nodes are restricted to defined links and interfaces. This protocol deterministically converges within a time bound that is a linear function of the self-stabilization period.

Malekpour, Mahyar R.↗
NASA NTRS2009

Security Analysis of DTN Architecture and Bundle Protocol Specification for Space-Based Networks

A Delay-Tolerant Network (DTN) Architecture (Request for Comment, RFC-4838) and Bundle Protocol Specification, RFC-5050, have been proposed for space and terrestrial networks. Additional security specifications have been provided via the Bundle Security Specification (currently a work in progress as an Internet Research Task Force internet-draft) and, for link-layer protocols applicable to Space networks, the Licklider Transport Protocol Security Extensions. This document provides a security analysis of the current DTN RFCs and proposed security related internet drafts with a focus on space-based communication networks, which is a rather restricted subset of DTN networks. Note, the original focus and motivation of DTN work was for the Interplanetary Internet . This document does not address general store-and-forward network overlays, just the current work being done by the Internet Research Task Force (IRTF) and the Consultative Committee for Space Data Systems (CCSDS) Space Internetworking Services Area (SIS) - DTN working group under the DTN and Bundle umbrellas. However, much of the analysis is relevant to general store-and-forward overlays.

Ivancic, William D.↗
NASA NTRS2011

Correctness Proof of a Self-Stabilizing Distributed Clock Synchronization Protocol for Arbitrary Digraphs

This report presents a deductive proof of a self-stabilizing distributed clock synchronization protocol. It is focused on the distributed clock synchronization of an arbitrary, non-partitioned digraph ranging from fully connected to 1-connected networks of nodes while allowing for differences in the network elements. This protocol does not rely on assumptions about the initial state of the system, and no central clock or a centrally generated signal, pulse, or message is used. Nodes are anonymous, i.e., they do not have unique identities. There is no theoretical limit on the maximum number of participating nodes. The only constraint on the behavior of the node is that the interactions with other nodes are restricted to defined links and interfaces. We present a deductive proof of the correctness of the protocol as it applies to the networks with unidirectional and bidirectional links. We also confirm the claims of determinism and linear convergence.

Malekpour, Mahyar R.↗
NASA NTRS2011

Licklider Transmission Protocol Implementation

This software is an implementation of the Licklider Transmission Protocol (LTP), a communications protocol intended to support the Bundle Protocol in Delay-Tolerant Network (DTN) operations. LTP is designed to provide retransmission-based reliability over links characterized by extremely long message round-trip times and/or frequent interruptions in connectivity. Communication in interplanetary space is the most prominent example of this sort of environment, and LTP is principally aimed at supporting long-haul reliable transmission over deep-space RF links. Like any reliable transport service employing ARQ (Automatic Repeat re-Quests), LTP is stateful. In order to assure the reception of a block of data it has sent, LTP must retain for possible retransmission all portions of that block which might not have been received yet. In order to do so, it must keep track of which portions of the block are known to have been received so far, and which are not, together with any additional information needed for purposes of retransmitting part, or all, of the block. Long round-trip times mean substantial delay between the transmission of a block of data and the reception of an acknowledgement from the block s destination, signaling arrival of the block. If LTP postponed transmission of additional blocks of data until it received acknowledgement of the arrival of all prior blocks, valuable opportunities to use what little deep space transmission bandwidth is available would be forever lost. For this reason, LTP is based in part on a notion of massive state retention. Any number of requested transmission conversations (sessions) may be concurrently in flight at various displacements along the link between two LTP engines, and the LTP engines must necessarily retain transmission status and retransmission resources for all of them. Moreover, if any of the data of a given block are lost en route, it will be necessary to retain the state of that transmission during an additional round trip while the lost data are retransmitted; even multiple retransmission cycles may be necessary. LTP's possible multiplicity of sessions per association makes it necessary for each segment of application data to include an additional demultiplexing token: a session ID that uniquely identifies the session in which the segment was issued and, implicitly, the block of data being conveyed by this session. This software comprises a prototype implementation developed by Johns Hopkins University APL in cooperation with JPL, together with adaptations that improve the robustness, correctness, and operability of that implementation.

Burleigh, Scott C.↗
NASA NTRS2012

An Evaluation of Protocols for UAV Science Applications

This paper identifies data transport needs for current and future science payloads deployed on the NASA Global Hawk Unmanned Aeronautical Vehicle (UAV). The NASA Global Hawk communication system and operational constrains are presented. The Genesis and Rapid Intensification Processes (GRIP) mission is used to provide the baseline communication requirements as a variety of payloads were utilized in this mission. User needs and desires are addressed. Protocols are matched to the payload needs and an evaluation of various techniques and tradeoffs are presented. Such techniques include utilization rate-base selective negative acknowledgement protocols and possible use of protocol enhancing proxies. Tradeoffs of communication architectures that address ease-of-use and security considerations are also presented.

Ivancic, William D.↗
NASA NTRS2012

Modeling Techniques for High Dependability Protocols and Architecture

This report documents an investigation into modeling high dependability protocols and some specific challenges that were identified as a result of the experiments. The need for an approach was established and foundational concepts proposed for modeling different layers of a complex protocol and capturing the compositional properties that provide high dependability services for a system architecture. The approach centers around the definition of an architecture layer, its interfaces for composability with other layers and its bindings to a platform specific architecture model that implements the protocols required for the layer.

LaValley, Brian↗
NASA NTRS2012

Software Modules for the Proximity-1 Space Link Interleaved Time Synchronization (PITS) Protocol

The Proximity-1 Space Link Interleaved Time Synchronization (PITS) protocol provides time distribution and synchronization services for space systems. A software prototype implementation of the PITS algorithm has been developed that also provides the test harness to evaluate the key functionalities of PITS with simulated data source and sink. PITS integrates time synchronization functionality into the link layer of the CCSDS Proximity-1 Space Link Protocol. The software prototype implements the network packet format, data structures, and transmit- and receive-timestamp function for a time server and a client. The software also simulates the transmit and receive-time stamp exchanges via UDP (User Datagram Protocol) socket between a time server and a time client, and produces relative time offsets and delay estimates.

Woo, Simon S.↗
NASA NTRS2014

A Self-Stabilizing Hybrid-Fault Tolerant Synchronization Protocol

In this report we present a strategy for solving the Byzantine general problem for self-stabilizing a fully connected network from an arbitrary state and in the presence of any number of faults with various severities including any number of arbitrary (Byzantine) faulty nodes. Our solution applies to realizable systems, while allowing for differences in the network elements, provided that the number of arbitrary faults is not more than a third of the network size. The only constraint on the behavior of a node is that the interactions with other nodes are restricted to defined links and interfaces. Our solution does not rely on assumptions about the initial state of the system and no central clock nor centrally generated signal, pulse, or message is used. Nodes are anonymous, i.e., they do not have unique identities. We also present a mechanical verification of a proposed protocol. A bounded model of the protocol is verified using the Symbolic Model Verifier (SMV). The model checking effort is focused on verifying correctness of the bounded model of the protocol as well as confirming claims of determinism and linear convergence with respect to the self-stabilization period. We believe that our proposed solution solves the general case of the clock synchronization problem.

Malekpour, Mahyar R.↗
NASA NTRS2014

Cure Cycle Design Methodology for Fabricating Reactive Resin Matrix Fiber Reinforced Composites: A Protocol for Producing Void-free Quality Laminates

For the fabrication of resin matrix fiber reinforced composite laminates, a workable cure cycle (i.e., temperature and pressure profiles as a function of processing time) is needed and is critical for achieving void-free laminate consolidation. Design of such a cure cycle is not trivial, especially when dealing with reactive matrix resins. An empirical "trial and error" approach has been used as common practice in the composite industry. Such an approach is not only costly, but also ineffective at establishing the optimal processing conditions for a specific resin/fiber composite system. In this report, a rational "processing science" based approach is established, and a universal cure cycle design protocol is proposed. Following this protocol, a workable and optimal cure cycle can be readily and rationally designed for most reactive resin systems in a cost effective way. This design protocol has been validated through experimental studies of several reactive polyimide composites for a wide spectrum of usage that has been documented in the previous publications.

Hou, Tan-Hung↗
NASA NTRS2014

Mobilization Protocols for Hybrid Sensors for Environmental AOP Sampling (HySEAS) Observations

The protocols presented here enable the proper mobilization of the latest-generation instruments for measuring the apparent optical properties (AOPs) of aquatic ecosystems. The protocols are designed for the Hybrid Sensors for Environmental AOP Sampling (HySEAS) class of instruments, but are applicable to the community of practice for AOP measurements. The protocols are organized into eleven sections beyond an introductory overview: a) cables and connectors, b) HySEAS instruments, c) platform preparation, d) instrument installation, e) cable installation, f) test deployment, g) test recovery, h) maintenance, i) shipping, j) storage, and k) smallboat operations. Each section concentrates on documenting how to prevent the most likely faults, remedy them should they occur, and accomplishing both with the proper application of a modest set of useful tools. Within the twelve sections, there are Socratic exercises to stimulate thought, and the answers to these exercises appear in Appendix A. Frequently asked questions (FAQs) are summarized in a separate section after the answers to the exercises in Appendix B. For practitioners unfamiliar with the nautical terms used throughout this document plus others likely encountered at sea, an abbreviated dictionary of nautical terms appears in Appendix C. An abbreviated dictionary of radiotelephone terms is presented in Appendix D. To ensure familiarity with many of the tools that are presented, Appendix E provides a description of the tools alongside a thumbnail picture. Abbreviated deployment checklists and cable diagrams are provided in Appendix F. The document concludes with an acknowledgments section, a glossary of acronyms, a definition of symbols, and a list of references.

Mobilizarion↗
NASA NTRS2017

Biogeochemical Protocols and Diagnostics for the CMIP6 Ocean Model Intercomparison Project (OMIP)

The Ocean Model Intercomparison Project (OMIP) focuses on the physics and biogeochemistry of the ocean component of Earth system models participating in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). OMIP aims to provide standard protocols and diagnostics for ocean models, while offering a forum to promote their common assessment and improvement. It also offers to compare solutions of the same ocean models when forced with reanalysis data (OMIP simulations) vs. when integrated within fully coupled Earth system models (CMIP6). Here we detail simulation protocols and diagnostics for OMIP's biogeochemical and inert chemical tracers. These passive-tracer simulations will be coupled to ocean circulation models, initialized with observational data or output from a model spin-up, and forced by repeating the 1948-2009 surface fluxes of heat, fresh water, and momentum. These so-called OMIP-BGC simulations include three inert chemical tracers (CFC-11, CFC-12, SF [subscript] 6) and biogeochemical tracers (e.g., dissolved inorganic carbon, carbon isotopes, alkalinity, nutrients, and oxygen). Modelers will use their preferred prognostic BGC model but should follow common guidelines for gas exchange and carbonate chemistry. Simulations include both natural and total carbon tracers. The required forced simulation (omip1) will be initialized with gridded observational climatologies. An optional forced simulation (omip1-spunup) will be initialized instead with BGC fields from a long model spin-up, preferably for 2000 years or more, and forced by repeating the same 62-year meteorological forcing. That optional run will also include abiotic tracers of total dissolved inorganic carbon and radiocarbon, CTabio and 14CTabio, to assess deep-ocean ventilation and distinguish the role of physics vs. biology. These simulations will be forced by observed atmospheric histories of the three inert gases and CO2 as well as carbon isotope ratios of CO2. OMIP-BGC simulation protocols are founded on those from previous phases of the Ocean Carbon-Cycle Model Intercomparison Project. They have been merged and updated to reflect improvements concerning gas exchange, carbonate chemistry, and new data for initial conditions and atmospheric gas histories. Code is provided to facilitate their implementation.

Carbon↗
NASA NTRS2011

Genomics-Based Security Protocols: From Plaintext to Cipherprotein

The evolving nature of the internet will require continual advances in authentication and confidentiality protocols. Nature provides some clues as to how this can be accomplished in a distributed manner through molecular biology. Cryptography and molecular biology share certain aspects and operations that allow for a set of unified principles to be applied to problems in either venue. A concept for developing security protocols that can be instantiated at the genomics level is presented. A DNA (Deoxyribonucleic acid) inspired hash code system is presented that utilizes concepts from molecular biology. It is a keyed-Hash Message Authentication Code (HMAC) capable of being used in secure mobile Ad hoc networks. It is targeted for applications without an available public key infrastructure. Mechanics of creating the HMAC are presented as well as a prototype HMAC protocol architecture. Security concepts related to the implementation differences between electronic domain security and genomics domain security are discussed.

Shaw, Harry↗
NASA NTRS2018

A Fault-Tolerant Clock Synchronization and Geometry Determination Protocol

A fault-tolerant distributed protocol (algorithm) is presented that achieves optimum timing precision (clock synchronization) among the nodes and, simultaneously, determines the network's geometry (shape) - locations and distances of the nodes relative to each other - in a wireless distributed system. This protocol is based on the assumption of initial coarse synchrony of nodes' local clocks. The proposed solution assumes no prior knowledge of the nodes' locations, the distances between the nodes, or network's geometry, but assumes an ordered geometry where nodes have unique identifiers. This protocol accommodates large variations in the communication latencies among the nodes; thus, it applies equally to both wireless and wired networks.

Malekpour, Mahyar R.↗
NASA NTRS2018

Mechanism of Quantum Speedup in Novel Population Transfer Protocol for Binary Optimization Problems

We consider a novel quantum population transfer protocol to solve binary optimization problems that exploits quantum many-body dynamics in the delocalized regime. Hard optimization problems are characterized by energy landscape with a large number of local minima separated by large Hamming distances which scale with the problem size. This landscape gives rise to an interesting computational primitive: given an initial bit-string, we are to produce other bit-strings within certain narrow range of energies around the initial state. We consider a specific model we call "impurity band": a system of n qubits in a transverse field, where a number of bitstrings $M<<2^n$ selected at random are assigned random energies distributed in a narrow window of width $W<<1$ around the mean energy $-n$. We demonstrate the existence of the many-body delocalized regime in this model when the spectrum of the model splits into many-body minibands, and a typical eigenstate wave function is a superposition of peaks centered at a large number of local minima. The typical width of the minibands in energy determines the efficiency of the population transfer protocol. We demonstrate theoretically that the population transfer protocol achieves Grover type speedup in the unstructured impurity band model.

Kechedzhi, Kostyantyn↗