bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated Tubing for Both Steam Injection and Oil Production of Thermal Wells Based on ESP in Offshore Oilfield China
Authors: Han Xiaodong , Zhou Fayuan , Zhang Hua , Zhang Wei , Liu Hao , Wang Hongyu , Wang Qiuxia , Cui Junguo
Published: November 2016

Multi-component thermal fluid huff-and-puff pilot has been conducted in Bohai oilfield since 2008. Owing to the limitations of the temperature tolerance of some tools and facilities, the steam injection tubing and production tubing are applied separately during the development. That is, two work-over operations for tubing changes are required in each huff-and-puff cycle, which would increase the cost greatly and lower the development effect.

The objective of our present work is to design an integrated tubing with the functions of both steam injection and oil production to decrease the high cost caused by work-over of tubing change. First, we studied the artificial lift method that might be used for lift of fluid with temperature over 250°C e.g., electric submersible pump (ESP in short), gas lift, progressive cavity pump, and sucker-rod pump. Taking into account the degree of technology maturation, applicability in offshore oilfield and its temperature tolerance, the high-temperature electric submersible pump is selected for artificial lift of the integrated tubing.

On the basis of the ESP artificial lift, the integrated tubing with a Y-joint is designed. The steam injection string is connected with the main channel of the Y-joint and inserted into the production interval. The ESP is connected to the bypass of the Y-joint which could be used for fluid lifting during the production process. For the realization of the integrated tubing, high temperature tolerance tools such as the subsurface safety valve, and packer are developed. The maximum temperature-telorance value of the improved tools could meet the requirements of realizing the integrated tubing

In comparison with the previous techniques, application of the integrated tubing could greatly decrease the cost for thermal production and improve the economic benefit.
Increasing ESP Run Life Using a Combination of Reliable Abrasion-Resistant Pumps and 24/7 Real-Time Surveillance
Authors: Vidrianto Marda , Noviansyah Muhamad , Rajain Arun Kumar , Wang Feng Ming
Published: November 2016

In a field offshore Sumatra, several wells were experiencing pump failures because of loss of flow, sand erosion on pump stages, pump shaft rotation, broken shafts, and motor burnout. The remote offshore location of the wells was an additional hindrance, making it difficult to quickly respond to pump performance issues. This paper will show that the combination of abrasion-resistant pumps and accessibility and analysis of electric submersible pump (ESP) data are critical parameters for responsiveness and efficiency in troubleshooting.

The ESP reliability initiative began with well candidate selection to identify the most challenging wells with a known history of short run life primarily due to excessive sand and gas production. A new abrasion-resistant pump with enhanced compression design was installed in four wells as a pilot project. This count increased to 11 by Q2 2016. In addition, all these wells were put under 24/7 real-time surveillance to ensure that the pump performance issues were noticed immediately and acted upon much faster than in the manual troubleshooting process, which could take 2 to 3 days, at best.

A right combination of technical solution for pumps enabled better run life performance, and remote surveillance enabled faster troubleshooting and optimization of ESP peformance. These improvements are sustained through defined end-to-end workflows for performing root cause analysis of incidents performed jointly by the operators and ESP suppliers.
The Benefits of Introducing Intelligent Gas Lift Management to Create a Smart Field
Authors: Faux Stephen , Glenday Thomas
Published: November 2016

This paper will explore the benefits a smart gas lift field can offer in terms of operational efficiency, flexibility and production improvements, whilst focusing on health and safety improvements and risk reduction. Existing gas lift technology will be evaluated to give a summary of the operational aspects of the fundamental design and the methods used to control and change gas injection rates. The limited operational range of the existing gas lift technology will be compared against that of an intelligent gas lift system where these constraints are removed.

The increased flexibility of operation and field wide management aspect of a new intelligent gas lift system will highlight the limitations of the existing technology. It will be concluded that existing gas lift technology provides increased production of fluids when deployed in the correct fixed design conditions.

It will be observed that current gas lift technology does not have a particular focus on increased operational efficiencies on a field wide scale. It will also be observed that the current difficulties faced by the industry places scrutiny on operational efficiencies and the potential advantages new technologies offer. This provides opportunities to demonstrate how a step change in field wide management and the application of intelligent gas lift technologies can lead to better informed decision making and faster reaction speeds resulting in improved production efficiency.

The paper will discuss field wide design considerations that are only able to be made with a revolution in gas lift technology. The paper is aimed at inspiring the industry to reconsider conventional thinking.
Performance Analysis for Progressive Cavity Pump PCP Production Scenario in Sandy and Heavy Oil Wells
Authors: Alfaqih Muchammad R. , Ariwibowo Alexis , Juliana Christina T.
Published: November 2016

Sand problem and heavy oil has been the major constraint in producing oil in Sesanip Field Tarakan. The field has unconsolidated sand reservoir with grain size D50 of 200 – 300 µm and oil gravity of 18-22 deg API. Under those conditions, Progressive Cavity Pump (PCP) performance and lifetime has been a major constraint in producing the field. Five production scenario been implemented to acquire the most optimum lifting method.

Production scenario was divided into two phases. First phase was implementing PCP without sand control. This production scenario was used as a baseline for improvement. Second phase of the production scenario was to add sand control into the production system. Improvement between the two production scenario will be assessed using several criteria; lifetime, cumulative production, economic analysis. In the first phase, three production scenarios with PCP below perforation, PCP above perforation, and PCP with controlled production rate were implemented. Whereas in the second phase, results from downhole configuration of screen installed to pump intake, and installation of screen using seal-bore packer were compared with first phase results.

Comparison between five producing scenario were analyzed according to the criteria determined. Based on the first phase results, excessive sand production was evident when producing in optimum rate. In order to minimize sand production, production rate must be limited and therefore sacrificing artificial lift potential. Second phase gave two different results. PCP installation with sand screen installed to pump intake gave the lowest cumulative production, lowest revenue, and longest pay out time. Although sand screen was used, the lack of sealing above screen meant that sand was allowed to pile up in the annulus and eventually restricting influx. PCP with sand screen installation using seal-bore packer delivers optimum trade-off between lifetime, cumulative production and economic values. By applying this production method, sand production from the reservoir will naturally form sand-pack between perforation and sand screen. Although this sand-pack would decrease productivity index, but it compensates with higher lifetime. Based on recent well service activity, no sand pile was present inside screen or above seal-bore packer.
Rigless ESP Technology: Well Control and Completion Considerations
Authors: Bespalov E..
Published: November 2016

Use of alternatively deployed electrical submersible pumping (AD ESP) systems requires review of the main principles behind completion architectures associated with traditional ESP technology. Completion architectures designed for rigless interventions need to take into account the main value proposition of the AD ESP technology, which is based on reduction of the deferred production and the ESP replacement costs, thus improving operating cash flow and reducing operating expenditure.

Accumulated operational experience of AD ESPs to date identified the main principles to be applied while looking at each specific application and considering the existing well control requirements and operating practices. Design of the completion architecture and the need for adjustment of the existing practices, while retaining focus on operational and personnel safety, has a vital impact on the operator's ability to realize an improved asset value from implementation of the AD ESPs as compared to the standard ESP technology.

The paper describes the technical aspects, technology development progress, and challenges of the AD ESP and highlights the main completion considerations that must be considered in designing a suitable completion architecture that would allow rigless replacements without a drilling rig or a hoist while adhering to applicable well control requirements.
The Research and Application of Carbon Fiber Rods in Deep Oil Wells of Xinjiang Oilfield, China
Authors: Zhao Ruidong , Zhang Xishun , Tao Zhen , Chen Shiwen , Zhang Xin , Li Gangyao , Oilfield Xinjiang , Huang Hongxing , Wang Hongfei , Guo Lei , Oilfield Jidong
Published: November 2016

As development of deep oil reservoir, more and more deep and ultra-deep wells, of which the chief lifting method is sucker-rod pumping system, are drilled. There often exist problems for systems above such as high load and low pumping efficiency. Because of low density and high intensity of carbon fiber rod, polished rod load can be decreased by using carbon fiber rod to increase safety factor. Meanwhile, since elastic modulus of carbon fiber rod is low, stroke loss will be increased by unreasonable lifting parameters. Test of carbon fiber rod was conducted in Xinjiang oil field in order to verify the feasibility of carbon fiber rod in deep oil wells and evaluate load shedding and energy saving effect. To lighten field test workload, a 3D rod mechanical model was built to simulate conditions of different production parameters. From the results of field test and simulation, it is indicated that carbon fiber rod owns better load shedding capacity and higher strength intensity; under the condition of deep wells, more stroke loss may be caused by carbon fiber composite rod. For some conditions, pumping efficiency is low, even worse, rod lock problems like gaslock may appear; reasonable combination of rod string and production parameters can improve the feasibility of carbon fiber rod.
Production Enhancement by Installation of Jet Pump in SSD in Pakistan Ghauri Oil Field
Authors: Kumar S.. , Kalwar S. A. , Farouque K.. , Qureshi S.. , Anjum Z. A.
Published: November 2016

This paper presents the first ever successful Sliding Sleeve Door (SSD) Jet Pump application in Ghauri oil field located in Jhelum, Pakistan. Ghauri is a single completed well flowed with 22 API gravity from the Sakessar Formation. Because the well is a solution gas drive reservoir, the initial production rate declined quickly. The use of jet pump was motivated by the need to revive the well without a work-over.

Based on initial testing data, jet pump was selected as a preferred artificial lift method. SSD was installed as a part of initial completion. The downhole jet pump was designed per the SSD dimensions. The pump was operated to enhance/ restore the production of well. During operations, real-time monitoring was conducted to optimize the parameters of the pump, such as the nozzle/throat combination or horsepower. In addition, the life of the jet pump was calculated in relation to the economic limits of the production.

Based on the results, the jet pump was found to be the most economical and cost-effective artificial-lift method for Ghauri. SSD jet pump deployment achieved the expected performance and reliability. It has allowed the operator to save the cost of a workover. The cumulative production with jet lift is twice the cumulative production using natural energy. When the well production declined, the jet pump was easily re-optimized by using slickline to pull the pump and change the nozzle and/or throat. The rest of the pump was unchanged to keep the CAPEX at low. In addition, further production of 200,000 BBLS is expected through the jet pump.
Doubled Production in Mature Sandy and Multilayers Reservoir Using Screenless and Overdesigned ESP System
Authors: Alfaqih Muchammad R. , Azhari Mirza , Ardan Cesti , Pradhipta Seno R..
Published: November 2016

The fifty-two sandy and multilayer reservoir from depth 500 – 1750 m in Mamburungan field became more challenging when electric submersible pumps (ESP) were used. The average 2 – 7 m range net pay height in each layer contrasts with sand production for screen implementation in reducing productivity index. Multilayer reservoirs result requires various types of ESP design based on depth. As a result, a reliable method is needed to produce the well effectively and economically.

The production method was divided into two basic concerns. Firstly, determining reservoir analysis with loose sand reservoir at 500 – 1000 m depth, and consolidated sand reservoir at 1000 -1750 m depth, Secondly, designing ESP which could accommodate all layers, which are divided into two main zones, i.e. the optimum design zone at 1200 – 1750 m depth and the overdesigned zone at 500 – 1200 m depth. In an overdesigned zone attention must be paid to choke installation to limit production rate, the safety factor for motor temperature specifications based on reservoir temperature, and also the safety factor for power specifications in variable speed drive (VSD) and transformer.

Currently, all ESP wells in Mamburungan field are producing without failure and the ESP operation is running smoothly by implementing the aforementioned production method. In the optimum design zone, no ESP performance issues have been raised. Meanwhile in the overdesigned zone, potential performance issues might not be arise by adhering to certain rules: application of choke to control the production rate within up thrust and down thrust area; implementation of additional 40 percent safety factor in motor temperature specification refer to the deepest layer temperature; design of VSD and transformer to provide sufficient power consumption based on motor requirement at the deepest layer. Applying the overdesigned method delivers an optimum trade-off between lifetime, cumulative production, economic value with ESP system efficiency to produce the well in Mamburungan field.
Encapsulated ESP with Two Stages of Gas Separation
Authors: Wilson Zabala G.. , Martínez Gustavo
Published: November 2016

One of the limitations of an ESP system is the inability to handle fluid with a high presence of free gas at the pump intake. Even when a gas separator and a gas-handler pump are used downhole, the excessive amount of free gas exceeds the capability of these components and negatively affects the performance of the total system. This is, an unstable pump operation, limitations to achieve the full potential of the well, inaccurate production tests, unstable electrical power consumption, low pump efficiency, poor motor cooling and low reliability and increased operation costs because of premature equipment failure.

Due to the high bubble pressure point of the fluids in some gassy wells, it is necessary to install the ESP equipment as deep as possible in order to gain the highest pump intake pressure and so, reducing the amount of free gas at this point. For the ESP provider and the operator it is very important to maintain stable operation of the equipment; however, sometimes for the operator it is necessary to produce as much free gas to the surface as possible due to its capability to generate electrical power for self-supply.

The need of Apiay Field (Ecopetrol – Colombia) to increase the gas production rate and simultaneously the oil production rate, led to AlKhorayef Petroleum to design a shrouded ESP downhole system with a double stage of gas separation in order to reactivate a very gassy well (depleted) where none of the artificial lift systems at the field (Sucker Rod lift, PCP and ESP) could operate with good results. The first stage of gas separation consisted of a configuration of different equipment to separate free gas used on Sucker Rod Lift systems. The second one consisted of the using of a vortex ESP gas separator and a gas-handler pump in the ESP string.

This paper discusses the benefits of a newly-designed shrouded ESP system and its adaptation for using some downhole equipment for gas separation commonly used in rod lift systems.
Application of New Generation Variable Speed Drive Solutions To Reduce Footprint and Operating Cost
Authors: Orlowski Thomas , Radcliffe Alan R. , Lois Andrew
Published: November 2016

On offshore installations space has always been at a premium. With current market conditions requiring cost savings across the board, reducing the footprint of the ESP surface electrical equipment skid would result in reduced costs when fabricating offshore platforms. This paper presents a redesigned Medium Voltage VSD that is significantly smaller and incorporates new technologies that present an added bonus in additional cost savings and characteristics that can increase the run life of the ESP.

A typical offshore installation has one 2,000KVA Step Down transformer that supplies four or five skids, each with their own Low Voltage VSD and Step Up Transformer. With a Medium Voltage Drive, supply line voltage up to 6.6KV does not need to be stepped down, furthermore is no requirement for a Multi Tap Step Up Transformer as the VSD can provide the required medium voltage required for the ESP motor. The removal of these transformers has reduced the space and weight of the surface electrical equipment that influences the size and load bearing capabilities, and fabrication costs, of new installations.

In addition to the space and weight savings, by incorporating new generation VSD technologies, efficiency and reliability can be increased which ultimately prolongs pump run life and reduces operating costs. Cascaded Pulse Width Modulation (PWM) rectification significantly reduces the input harmonic distortion reflected back onto the supply, which can incur penalties from energy providers. The multi-level inverter technology on the output provides a near sinusoidal waveform, which removes the need for the expensive, and heavy, space consuming Sine Wave Filter (SWF) typically required on ESP installations. The cleaner power being delivered to the motor reduces the motor operating temperature and stresses on the electrical system's insulation resulting in a longer run life.

Maintaining a cool operating environment for the drive pushed conventional compressed gas air conditioning methods to their limits. A solution was to employ a Thermo Electric Cooling System. Operating on the principle of the Peltier Effect, a stable operating temperature can be maintained and as there are no moving parts, the TEC system is inherently reliable and economical in comparison to traditional A/C units. Furthermore, the TEC modules are very compact and can be operated in any orientation, in line with the requirement for a reduced footprint.

This new generation VSD technology has resulted in significant cost savings for Operators in terms of Capital and Operating Expenditure. Additionally, the power quality delivered to the motors can result in an extended run life, the ultimate goal for offshore applications.
New Technology Reduces Flushbys & Extends PCP Run Life in Australia
Authors: Hicks Robert
Published: November 2016

Coal seam gas production in Eastern Australia has grown at an incredible rate over the past decade. The primary artificial lift form to de-water the coal seam gas wellbores has been progressing cavity pumps. PCPs were selected due to the high amount of produced solids including interburden and coal fines. During an evaluation of their run life statistics, several operators identified solids settling on top of the pump during a shut down as one of the primary failure modes. Once the pump was stuck and unable to be restarted, the operator either had to conduct a flushby or workover to bring the well back to production. Production Tool Solution proposed utilization of a tool called a Pressure Actuated Relief Valve (PAR Valve) above the PCP to eliminate solids settling during a shut down. After initial trials, the tool was deemed successful and full field implementation has resulted in a substantial reduction of flushbys and extended the run life of the PCPs.
Advances in Completion Design to Improve Bhagyam PCP Run Life
Authors: Agarwal Shubham , Panigrahi Nishant , Ranjan Ashish , Nekkanti Satish Kumar , Bohra Avinash , Kumar Piyush , Vermani Sanjeev , Kumar Sanjeev , Agarrwal Vinay
Published: November 2016

Bhagyam field is a shallow onshore field in Northwest India. The field development includes 150 production wells with 40 plus injection wells. The crude is sweet & light oil (27 Deg API) with 30 % wax content and a varied viscosity from range 50-450 cP. The Wax appearance temperature is ~ 2° C lower than the reservoir temperature of 53° C which impacts the completion design and affects the flow assurance of the field.

In recent times, the field production has been impacted by frequent work-overs in the field. The run life of the PCP systems, which was impacted by tubing punctures that arose from substantial rod-tubing contact loads, had reduced drastically from ~ 500 days to 259 days. The objective of this paper is first to analyze the drastic reduction in the run life of the Bhagyam PCP systems and then provide design changes which when implemented increased the run life of the PCP system.

The paper describes the measures taken and the design changes made to limit the system failure due to failed tubing and increase the run life of the system back to 500 days and will allow the readers to understand, in detail, the various types of problems that were encountered in operating PCP wells, the methods that were used to analyse the PCP failures, and new completion design that help to alleviate the problems to significantly improve the Bhagyam PCP run-life.
National security through the preservation and development of cultural sphere
Authors: Malakshinova Nadezhda Shagzhievna , Tsybikov Bator Bulatovich
Published: November 2016

Matters of national security in the context of the inextricable interrelationship and interdependence of national security and socio-economic development are presented in the article. The particular attention is paid to the legislative consolidation of security categories, the system of national security elements, and changes in the domestic legislation updates. Therefore, safety, a list of national interests, highlighted by long-term perspective, and questions about the means of implementation of strategic national priorities, including the named culture as a sphere of life are very important. Sphere of culture as a national priority and an important factor in the quality of life growth and harmonization of public relations, collateral dynamic socio-economic development and the preservation of a common cultural space and sovereignty of Russia are studied more detailed.
State property management
Authors: Buribaev Ermek Abiltaevich , Khamzina Zhanna Amangeldinovna
Published: November 2016

This article determines the mechanism state property management, presents a study of formation and the main trends of legislative regulation of state property as an object of management, examines the legal characteristics of the phenomenon of state property, as well as the nature and significance of the state assets management, substantiates the systemic nature of state property management, presents an analysis of the legal framework of the mechanism of administration in the sphere of exercising state property right, investigates the problem of increasing the efficiency of legal support of the dynamics of administrative relations, the latter having state assets as their object.
Statistical analysis of grain production
Authors: Vorokova Nodira Khasanovna , Sennikova Alina Evgenevna
Published: November 2016

This article reflects the main grain production analysis and types of agriculture, which contaminate the environment less, as well as describes the factors affecting output.
The influence of seasonality on adaptation of the personnel
Authors: Pascenko Artem Aleksandrovich
Published: November 2016

The article discusses seasonal adaptation, as one of the most important factors affecting the adaptation of personnel to the company. Provides a selection of key terms, reveals their relation to the topic and discusses the study by the method of Rogers for the different categories investigated.
Intersubject student competition for the purposes of future teaching training
Authors: Muzychenko Nadezhda Aleksandrovna
Published: November 2016

This article interdisciplinary Olympiad students is considered as an additional form of nonlearning work with future primary school teachers, which reflects the multidisciplinary their professional activities.
Cities of the future. Architecture development prospects of «Axiodemy» concept
Authors: Giloyan Artur Vladimirovich
Published: November 2016

A conceptual author's opinion on the urban environment development and the city of the future in the context of «Axiodemy» concept is presented in this article. The city is aimed at becoming a comfortable and eco-friendly environment.
Safety in the Internet
Authors: Semenko Tatyana Vladimirovna
Published: November 2016

The modern world is the world of computer technology, and the children living in this world feel comfortable in it, they master the computer, mobile devices, new-fangled gadgets easily and use them skillfully. However, their knowledge of the safety in the Internet lags behind their ability to develop new devices. The number of the Internet users is increased every year, so the problem of children safety in the Internet is very urgent. It is necessary for parents, educators and teachers to conduct explanatory conversations and activities for explanation and consolidation the rules of “The Safe Internet”.
Mass media influence on students' professional illusion formation
Authors: Ermakov Vyacheslav Alekseevich , Bozhdanova Yulia Viktorovna
Published: November 2016

This article presents mass media activities as a possible source of professional socialization, adequateness of social process informative display in the sphere of young people professional identity. It describes pattern distortion of occupational structure, presents the problem of mass media inadequate influence on students’ understanding about the choice and perspectives of their profession. The main factors which help to create student’s understanding about their professional future are examined.
Readiness to self-dependent work as one of the basic competence of future teachers
Authors: Yaremchuk Nadezhda Bogdanovna
Published: November 2016

The article analyzes and reviews the ways of future teacher's organizational and self-dependence skills formation as a professional development foundation. The analysis of the survey results on the subject is given. The forms of student's self-dependent work organization are offered.
Generators and relations for n-qubit Clifford operators
Authors: Selinger Peter
Published: November 2016

We define a normal form for Clifford circuits, and we prove that every
Clifford operator has a unique normal form. Moreover, we present a rewrite
system by which any Clifford circuit can be reduced to normal form. This yields
a presentation of Clifford operators in terms of generators and relations.
Thermodynamic graph-rewriting
Authors: Danos Vincent , Harmer Russell , Honorato-Zimmer Ricardo
Published: November 2016

We develop a new thermodynamic approach to stochastic graph-rewriting. The
ingredients are a finite set of reversible graph-rewriting rules called
generating rules, a finite set of connected graphs P called energy patterns and
an energy cost function. The idea is that the generators define the qualitative
dynamics, by showing which transformations are possible, while the energy
patterns and cost function specify the long-term probability $\pi$ of any
reachable graph. Given the generators and energy patterns, we construct a
finite set of rules which (i) has the same qualitative transition system as the
generators; and (ii) when equipped with suitable rates, defines a
continuous-time Markov chain of which $\pi$ is the unique fixed point. The
construction relies on the use of site graphs and a technique of `growth
policy' for quantitative rule refinement which is of independent interest. This
division of labour between the qualitative and long-term quantitative aspects
of the dynamics leads to intuitive and concise descriptions for realistic
models (see the examples in S4 and S5). It also guarantees thermodynamical
consistency (AKA detailed balance), otherwise known to be undecidable, which is
important for some applications. Finally, it leads to parsimonious
parameterizations of models, again an important point in some applications.
Learning and Designing Stochastic Processes from Logical Constraints
Authors: Bortolussi Luca , Sanguinetti Guido
Published: November 2016

Stochastic processes offer a flexible mathematical formalism to model and
reason about systems. Most analysis tools, however, start from the premises
that models are fully specified, so that any parameters controlling the
system's dynamics must be known exactly. As this is seldom the case, many
methods have been devised over the last decade to infer (learn) such parameters
from observations of the state of the system. In this paper, we depart from
this approach by assuming that our observations are {\it qualitative}
properties encoded as satisfaction of linear temporal logic formulae, as
opposed to quantitative observations of the state of the system. An important
feature of this approach is that it unifies naturally the system identification
and the system design problems, where the properties, instead of observations,
represent requirements to be satisfied. We develop a principled statistical
estimation procedure based on maximising the likelihood of the system's
parameters, using recent ideas from statistical machine learning. We
demonstrate the efficacy and broad applicability of our method on a range of
simple but non-trivial examples, including rumour spreading in social networks
and hybrid models of gene regulation.
Using models to model-check recursive schemes
Authors: Salvati Sylvain , Walukiewicz Igor
Published: November 2016

We propose a model-based approach to the model checking problem for recursive
schemes. Since simply typed lambda calculus with the fixpoint operator,
lambda-Y-calculus, is equivalent to schemes, we propose the use of a model of
lambda-Y-calculus to discriminate the terms that satisfy a given property. If a
model is finite in every type, this gives a decision procedure. We provide a
construction of such a model for every property expressed by automata with
trivial acceptance conditions and divergence testing. Such properties pose
already interesting challenges for model construction. Moreover, we argue that
having models capturing some class of properties has several other virtues in
addition to providing decidability of the model-checking problem. As an
illustration, we show a very simple construction transforming a scheme to a
scheme reflecting a property captured by a given model.
Logical strength of complexity theory and a formalization of the PCP theorem in bounded arithmetic
Authors: Pich Ján
Published: November 2016

We present several known formalizations of theorems from computational
complexity in bounded arithmetic and formalize the PCP theorem in the theory
PV1 (no formalization of this theorem was known). This includes a formalization
of the existence and of some properties of the (n,d,{\lambda})-graphs in PV1.
Logics with rigidly guarded data tests
Authors: Puppis Gabriele , Colcombet Thomas , Ley Clemens
Published: November 2016

The notion of orbit finite data monoid was recently introduced by Bojanczyk
as an algebraic object for defining recognizable languages of data words.
Following Buchi's approach, we introduce a variant of monadic second-order
logic with data equality tests that captures precisely the data languages
recognizable by orbit finite data monoids. We also establish, following this
time the approach of Schutzenberger, McNaughton and Papert, that the
first-order fragment of this logic defines exactly the data languages
recognizable by aperiodic orbit finite data monoids. Finally, we consider
another variant of the logic that can be interpreted over generic structures
with data. The data languages defined in this variant are also recognized by
unambiguous finite memory automata.
Presenting Distributive Laws
Authors: Bonsangue Marcello M. , Hansen Helle Hvid , Kurz Alexander , Rot Jurriaan
Published: November 2016

Distributive laws of a monad T over a functor F are categorical tools for
specifying algebra-coalgebra interaction. They proved to be important for
solving systems of corecursive equations, for the specification of well-behaved
structural operational semantics and, more recently, also for enhancements of
the bisimulation proof method. If T is a free monad, then such distributive
laws correspond to simple natural transformations. However, when T is not free
it can be rather difficult to prove the defining axioms of a distributive law.
In this paper we describe how to obtain a distributive law for a monad with an
equational presentation from a distributive law for the underlying free monad.
We apply this result to show the equivalence between two different
representations of context-free languages.
Weak upper topologies and duality for cones
Authors: Keimel Klaus
Published: November 2016

In functional analysis it is well known that every linear functional defined
on the dual of a locally convex vector space which is continuous for the weak
topology is the evaluation at a uniquely determined point of the given vector
space. M. Schroeder and A. Simpson have obtained a similar result for lower
semicontinuous linear functionals on the cone of all Scott-continuous
valuations on a topological space endowed with the weak upper topology, an
asymmetric version of the weak topology. This result has given rise to several
proofs, originally by the Schroeder and Simpson themselves and, more recently,
by the author of these Notes and by J. Goubault-Larrecq. The proofs developed
from very technical arguments to more and more conceptual ones. The present
Note continues on this line, presenting a conceptual approach inspired by
classical functional analysis which may prove useful in other situations.
A correspondence between rooted planar maps and normal planar lambda terms
Authors: Zeilberger Noam , Giorgetti Alain
Published: November 2016

A rooted planar map is a connected graph embedded in the 2-sphere, with one
edge marked and assigned an orientation. A term of the pure lambda calculus is
said to be linear if every variable is used exactly once, normal if it contains
no beta-redexes, and planar if it is linear and the use of variables moreover
follows a deterministic stack discipline. We begin by showing that the sequence
counting normal planar lambda terms by a natural notion of size coincides with
the sequence (originally computed by Tutte) counting rooted planar maps by
number of edges. Next, we explain how to apply the machinery of string diagrams
to derive a graphical language for normal planar lambda terms, extracted from
the semantics of linear lambda calculus in symmetric monoidal closed categories
equipped with a linear reflexive object or a linear reflexive pair. Finally,
our main result is a size-preserving bijection between rooted planar maps and
normal planar lambda terms, which we establish by explaining how Tutte
decomposition of rooted planar maps (into vertex maps, maps with an isthmic
root, and maps with a non-isthmic root) may be naturally replayed in linear
lambda calculus, as certain surgeries on the string diagrams of normal planar
lambda terms.
Exact Unification and Admissibility
Authors: Metcalfe George , Cabrer Leonardo
Published: November 2016

A new hierarchy of "exact" unification types is introduced, motivated by the
study of admissible rules for equational classes and non-classical logics. In
this setting, unifiers of identities in an equational class are preordered, not
by instantiation, but rather by inclusion over the corresponding sets of
unified identities. Minimal complete sets of unifiers under this new
preordering always have a smaller or equal cardinality than those provided by
the standard instantiation preordering, and in significant cases a dramatic
reduction may be observed. In particular, the classes of distributive lattices,
idempotent semigroups, and MV-algebras, which all have nullary unification
type, have unitary or finitary exact type. These results are obtained via an
algebraic interpretation of exact unification, inspired by Ghilardi's algebraic
approach to equational unification.
Ellipses and Lambda Definability
Authors: Goldberg Mayer
Published: November 2016

Ellipses are a meta-linguistic notation for denoting terms the size of which
are specified by a meta-variable that ranges over the natural numbers. In this
work, we present a systematic approach for encoding such meta-expressions in
the \^I-calculus, without ellipses: Terms that are parameterized by
meta-variables are replaced with corresponding \^I-abstractions over actual
variables. We call such \^I-terms arity-generic. Concrete terms, for particular
choices of the parameterizing variable are obtained by applying an
arity-generic \^I-term to the corresponding numeral, obviating the need to use
ellipses. For example, to find the multiple fixed points of n equations, n
different \^I-terms are needed, every one of which is indexed by two
meta-variables, and defined using three levels of ellipses. A single
arity-generic \^I-abstraction that takes two Church numerals, one for the
number of fixed-point equations, and one for their arity, replaces all these
multiple fixed-point combinators. We show how to define arity-generic
generalizations of two historical fixed-point combinators, the first by Curry,
and the second by Turing, for defining multiple fixed points. These historical
fixed-point combinators are related by a construction due to B\~Ahm: We show
that likewise, their arity-generic generalizations are related by an
arity-generic generalization of B\~Ahm's construction. We further demonstrate
this approach to arity-generic \^I-definability with additional \^I-terms that
create, project, extend, reverse, and map over ordered n-tuples, as well as an
arity-generic generator for one-point bases.
On Nested Sequents for Constructive Modal Logics
Authors: Strassburger Lutz , Das Anupam , Arisaka Ryuta
Published: November 2016

We present deductive systems for various modal logics that can be obtained
from the constructive variant of the normal modal logic CK by adding
combinations of the axioms d, t, b, 4, and 5. This includes the constructive
variants of the standard modal logics K4, S4, and S5. We use for our
presentation the formalism of nested sequents and give a syntactic proof of cut
elimination.
Quantitative Approximation of the Probability Distribution of a Markov Process by Formal Abstractions
Authors: Soudjani Sadegh Esmaeil Zadeh , Abate Alessandro
Published: November 2016

The goal of this work is to formally abstract a Markov process evolving in
discrete time over a general state space as a finite-state Markov chain, with
the objective of precisely approximating its state probability distribution in
time, which allows for its approximate, faster computation by that of the
Markov chain. The approach is based on formal abstractions and employs an
arbitrary finite partition of the state space of the Markov process, and the
computation of average transition probabilities between partition sets. The
abstraction technique is formal, in that it comes with guarantees on the
introduced approximation that depend on the diameters of the partitions: as
such, they can be tuned at will. Further in the case of Markov processes with
unbounded state spaces, a procedure for precisely truncating the state space
within a compact set is provided, together with an error bound that depends on
the asymptotic properties of the transition kernel of the original process. The
overall abstraction algorithm, which practically hinges on piecewise constant
approximations of the density functions of the Markov process, is extended to
higher-order function approximations: these can lead to improved error bounds
and associated lower computational requirements. The approach is practically
tested to compute probabilistic invariance of the Markov process under study,
and is compared to a known alternative approach from the literature.
Quantified Constraints and Containment Problems
Authors: Martin Barnaby D. , Chen Hubie , Madelaine Florent R.
Published: November 2016

The quantified constraint satisfaction problem $\mathrm{QCSP}(\mathcal{A})$
is the problem to decide whether a positive Horn sentence, involving nothing
more than the two quantifiers and conjunction, is true on some fixed structure
$\mathcal{A}$. We study two containment problems related to the QCSP. Firstly,
we give a combinatorial condition on finite structures $\mathcal{A}$ and
$\mathcal{B}$ that is necessary and sufficient to render
$\mathrm{QCSP}(\mathcal{A}) \subseteq \mathrm{QCSP}(\mathcal{B})$. We prove
that $\mathrm{QCSP}(\mathcal{A}) \subseteq \mathrm{QCSP}(\mathcal{B})$, that is
all sentences of positive Horn logic true on $\mathcal{A}$ are true on
$\mathcal{B}$, iff there is a surjective homomorphism from
$\mathcal{A}^{|A|^{|B|}}$ to $\mathcal{B}$. This can be seen as improving an
old result of Keisler that shows the former equivalent to there being a
surjective homomorphism from $\mathcal{A}^\omega$ to $\mathcal{B}$. We note
that this condition is already necessary to guarantee containment of the
$\Pi_2$ restriction of the QCSP, that is $\Pi_2$-$\mathrm{CSP}(\mathcal{A})
\subseteq \Pi_2$-$\mathrm{CSP}(\mathcal{B})$. The exponent's bound of
${|A|^{|B|}}$ places the decision procedure for the model containment problem
in non-deterministic double-exponential time complexity. We further show the
exponent's bound $|A|^{|B|}$ to be close to tight by giving a sequence of
structures $\mathcal{A}$ together with a fixed $\mathcal{B}$, $|B|=2$, such
that there is a surjective homomorphism from $\mathcal{A}^r$ to $\mathcal{B}$
only when $r \geq |A|$. Secondly, we prove that the entailment problem for
positive Horn fragment of first-order logic is decidable. That is, given two
sentences $\varphi$ and $\psi$ of positive Horn, we give an algorithm that
determines whether $\varphi \rightarrow \psi$ is true in all structures
(models). Our result is in some sense tight, since we show that the entailment
problem for positive first-order logic (i.e. positive Horn plus disjunction) is
undecidable. In the final part of the paper we ponder a notion of Q-core that
is some canonical representative among the class of templates that engender the
same QCSP. Although the Q-core is not as well-behaved as its better known
cousin the core, we demonstrate that it is still a useful notion in the realm
of QCSP complexity classifications.
Modular session types for objects
Authors: Gay Simon J. , Gesbert Nils , Ravara António , Vasconcelos Vasco T.
Published: November 2016

Session types allow communication protocols to be specified
type-theoretically so that protocol implementations can be verified by static
type checking. We extend previous work on session types for distributed
object-oriented languages in three ways. (1) We attach a session type to a
class definition, to specify the possible sequences of method calls. (2) We
allow a session type (protocol) implementation to be modularized, i.e.
partitioned into separately-callable methods. (3) We treat session-typed
communication channels as objects, integrating their session types with the
session types of classes. The result is an elegant unification of communication
channels and their session types, distributed object-oriented programming, and
a form of typestate supporting non-uniform objects, i.e. objects that
dynamically change the set of available methods. We define syntax, operational
se-mantics, a sound type system, and a sound and complete type checking
algorithm for a small distributed class-based object-oriented language with
structural subtyping. Static typing guarantees that both sequences of messages
on channels, and sequences of method calls on objects, conform to
type-theoretic specifications, thus ensuring type-safety. The language includes
expected features of session types, such as delegation, and expected features
of object-oriented programming, such as encapsulation of local state.
Type Reconstruction for the Linear \pi-Calculus with Composite Regular Types
Authors: Padovani Luca
Published: November 2016

We extend the linear {\pi}-calculus with composite regular types in such a
way that data containing linear values can be shared among several processes,
if there is no overlapping access to such values. We describe a type
reconstruction algorithm for the extended type system and discuss some
practical aspects of its implementation.
A finer reduction of constraint problems to digraphs
Authors: Bulín Jakub , Delic Dejan , Jackson Marcel , Niven Todd
Published: November 2016

It is well known that the constraint satisfaction problem over a general
relational structure A is polynomial time equivalent to the constraint problem
over some associated digraph. We present a variant of this construction and
show that the corresponding constraint satisfaction problem is logspace
equivalent to that over A. Moreover, we show that almost all of the commonly
encountered polymorphism properties are held equivalently on the A and the
constructed digraph. As a consequence, the Algebraic CSP dichotomy conjecture
as well as the conjectures characterizing CSPs solvable in logspace and in
nondeterministic logspace are equivalent to their restriction to digraphs.
A Program Logic for Verifying Secure Routing Protocols
Authors: Chen Chen , Jia Limin , Xu Hao , Luo Cheng , Zhou Wenchao , Loo Boon Thau
Published: November 2016

The Internet, as it stands today, is highly vulnerable to attacks. However,
little has been done to understand and verify the formal security guarantees of
proposed secure inter-domain routing protocols, such as Secure BGP (S-BGP). In
this paper, we develop a sound program logic for SANDLog-a declarative
specification language for secure routing protocols for verifying properties of
these protocols. We prove invariant properties of SANDLog programs that run in
an adversarial environment. As a step towards automated verification, we
implement a verification condition generator (VCGen) to automatically extract
proof obligations. VCGen is integrated into a compiler for SANDLog that can
generate executable protocol implementations; and thus, both verification and
empirical evaluation of secure routing protocols can be carried out in this
unified framework. To validate our framework, we encoded several proposed
secure routing mechanisms in SANDLog, verified variants of path authenticity
properties by manually discharging the generated verification conditions in
Coq, and generated executable code based on SANDLog specification and ran the
code in simulation.