A Mathematical Model of Parallel Programs and an Approach Based on it to Verification of MPI Programs

The paper presents a new mathematical model of parallel programs, on the basis of which it is possible, in particular, to verify parallel programs presented on a certain subset of the parallel programming interface MPI. This model is based on the concepts of a sequential and distributed process. A parallel program is modeled as a distributed process in which sequential processes communicate by asynchronously sending and receiving messages over channels. The main advantage of the described model is the ability to simulate and verify parallel programs that generate an indefinite number of sequential processes. The proposed model is illustrated by the application of verification of the matrix multiplication MPI program.

Anonymously Establishing Digital Provenance in Reseller Chains

<p>An increasing number of products are exclusively digital items, such as media files, licenses, services, or subscriptions. In many cases customers do not purchase these items directly from the originator of the product but through a reseller instead. Examples of some well known resellers include GoDaddy, the iTunes music store, and Amazon. This thesis considers the concept of provenance of digital items in reseller chains. Provenance is defined as the origin and ownership history of an item. In the context of digital items, the origin of the item refers to the supplier that created it and the ownership history establishes a chain of ownership from the supplier to the customer. While customers and suppliers are concerned with the provenance of the digital items, resellers will not want the details of the transactions they have taken part in made public. Resellers will require the provenance information to be anonymous and unlinkable to prevent third parties building up large amounts of information on the transactions of resellers. This thesis develops security mechanisms that provide customers and suppliers with assurances about the provenance of a digital item, even when the reseller is untrusted, while providing anonymity and unlinkability for resellers . The main contribution of this thesis is the design, development, and analysis of the tagged transaction protocol. A formal description of the problem and the security properties for anonymously providing provenance for digital items in reseller chains are defined. A thorough security analysis using proofs by contradiction shows the protocol fulfils the security requirements. This security analysis is supported by modelling the protocol and security requirements using Communicating Sequential Processes (CSP) and the Failures Divergences Refinement (FDR) model checker. An extended version of the tagged transaction protocol is also presented that provides revocable anonymity for resellers that try to conduct a cloning attack on the protocol. As well as an analysis of the security of the tagged transaction protocol, a performance analysis is conducted providing complexity results as well as empirical results from an implementation of the protocol.</p>

Anonymously Establishing Digital Provenance in Reseller Chains

<p>An increasing number of products are exclusively digital items, such as media files, licenses, services, or subscriptions. In many cases customers do not purchase these items directly from the originator of the product but through a reseller instead. Examples of some well known resellers include GoDaddy, the iTunes music store, and Amazon. This thesis considers the concept of provenance of digital items in reseller chains. Provenance is defined as the origin and ownership history of an item. In the context of digital items, the origin of the item refers to the supplier that created it and the ownership history establishes a chain of ownership from the supplier to the customer. While customers and suppliers are concerned with the provenance of the digital items, resellers will not want the details of the transactions they have taken part in made public. Resellers will require the provenance information to be anonymous and unlinkable to prevent third parties building up large amounts of information on the transactions of resellers. This thesis develops security mechanisms that provide customers and suppliers with assurances about the provenance of a digital item, even when the reseller is untrusted, while providing anonymity and unlinkability for resellers . The main contribution of this thesis is the design, development, and analysis of the tagged transaction protocol. A formal description of the problem and the security properties for anonymously providing provenance for digital items in reseller chains are defined. A thorough security analysis using proofs by contradiction shows the protocol fulfils the security requirements. This security analysis is supported by modelling the protocol and security requirements using Communicating Sequential Processes (CSP) and the Failures Divergences Refinement (FDR) model checker. An extended version of the tagged transaction protocol is also presented that provides revocable anonymity for resellers that try to conduct a cloning attack on the protocol. As well as an analysis of the security of the tagged transaction protocol, a performance analysis is conducted providing complexity results as well as empirical results from an implementation of the protocol.</p>

Plasma-Assisted Three-Dimensional Lightscribe Graphene as High Performance Supercapacitors

Graphene-based supercapacitors demonstrate extraordinary energy storage capacity due to their layered structure, large effective surface area, high electrical conductivity and acceptable chemical stability. Herein, reduced graphene oxide (rGO)-based supercapacitors were introduced in a simple, green, fast and inexpensive method. For this purpose, graphene oxide (GO) was synthesized by the modified Hummers’ method and then easily reduced to desired patterns of rGO using a commercial LightScribe DVD drive. In order to increase the effective surface area, as well as the electrical conductivity of rGO layers, oxygen/sulfur hexafluoride plasma was applied to the rGO followed by laser irradiation. By performing such sequential processes, an rGO-based supercapacitor was introduced with a capacitance of about 10.2 F/cm3, which had high stability for more than 1000 consecutive charge-discharge cycles. The fabrication steps of the electrodes were investigated by different analyses such as SEM, TEM, Raman, surface resistance and XPS measurements. Results show that these rGO-based electrodes fabricated by sequential processes are very interesting for practical applications of energy storage.

Effects of Sequential Operation with Heat Treatment and Mechanical Milling on Work Hardening for Superalloy GH4169

Engineering components are usually manufactured with sequential production processes. Work hardening due to previous production processes affects the machinability of the workpiece in subsequent operations. In this research, the surface work hardening of a workpiece manufactured by two sequential processes with heat treatment/milling (HT + M) and milling/heat treatment (M + HT) of superalloy GH4169 was investigated. First, the surface microstructure characteristics, including plastic deformation and grain size of the machined workpiece surface processed by the two sequential processes, were quantitatively presented. Then, the microhardness on the machined workpiece surface and its cross-section was measured and analyzed. Finally, a surface microhardness calculation model considering twin boundary deformation was proposed. Here, we also present the microstructure evolution principle of the machined workpiece surface by the two sequential processes. It was found that the degree of work hardening of HT + M machining was 179%, whereas that of M + HT was only 101%. The research results can be applied to the optimized selection of process sequence for manufacturing superalloy GH4169.

Sequential Treatment of Landfill Leachate By Advanced Oxidation Processes and Struvite Precipitation

Landfill leachate contains organic, inorganic compounds, heavy metals, ammonia, and xenobiotic compounds which are considered unsafe for discharging into surface water which requires to be treated before its discharge into the water. In this paper, preliminary studies are reported on the application of Fenton, Struvite, and Electrooxidation processes for the removal of Chemical Oxygen Demand (COD) and ammonia from landfill leachate. Various operational parameters like pH, dosage, reaction time, and applied voltage were optimized in laboratory batch experiments and evaluated for removal of COD and ammonia. Results demonstrated that the Fenton process could effectively remove COD and ammonia by 75% and 23% respectively at 210 min for Fe+2:H2O2: 1:5 at a fixed pH 3. The Struvite process has been effective in the removal of ammonia by 74% at pH 9 with the dosage of Mg+2:PO43-:NH4+ at 1:1:1 ratio. Results from Electrooxidation for COD and ammonia were observed as 58.25% and 44% respectively at the applied voltage 8 V for a reaction time of 60 min. The efficiency of treatment processes was also evaluated in Sequential processes for COD and ammonia i.e., Sequence-I (Fenton-Electrooxidation-Struvite) and Sequence-II (Fenton-Struvite) at pre-optimized conditions. The sequential processes have been depicted, the removal efficiencies of COD and ammonia of 89% and 82% by Sequence-I; 76.77%, and 77% by Sequence-II respectively. The present study demonstrates that Fenton followed by Electrooxidation and Struvite is an effective treatment process that can enhance the treatment of landfill leachate.

Denotational semantics of channel mobility in UTP-CSP

In this paper, we present the denotational semantics for channel mobility in the Unifying Theories of Programming (UTP) semantics framework. The basis for the model is the UTP theory of reactive processes, precisely, the UTP semantics for Communicating Sequential Processes (CSP), which is extended to allow the mobility of channels—the set of channels that a process can use for communication (its interface), originally static or constant (set during the process's definition), is now made dynamic or variable: it can change during the process's execution. A channel is thus moved around by communicating it via other channels and then allowing the receiving process to extend its interface with the received channel. We introduce a new concept, the capability of a process, which allows separating the ownership of channels from the knowledge of their existence. Mobile processes are then defined as having a static capability and a dynamic interface. Operations of a mobile telecommunications network, e.g., handover, load balancing, are used to illustrate the semantics. We redefine CSP operators and in particular provide the first semantics for the renaming and hiding operators in the context of channel mobility.