Minimum Pseudoweight Analysis of 3-Dimensional Turbo Codes

In this work, we consider pseudocodewords of (relaxed) linear programming (LP) decoding of 3-dimensional turbo codes (3D-TCs). We present a relaxed LP decoder for 3D-TCs, adapting the relaxed LP decoder for conventional turbo codes proposed by Feldman in his thesis. We show that the 3D-TC polytope is proper and $C$-symmetric, and make a connection to finite graph covers of the 3D-TC factor graph. This connection is used to show that the support set of any pseudocodeword is a stopping set of iterative decoding of 3D-TCs using maximum a posteriori constituent decoders on the binary erasure channel. Furthermore, we compute ensemble-average pseudoweight enumerators of 3D-TCs and perform a finite-length minimum pseudoweight analysis for small cover degrees. Also, an explicit description of the fundamental cone of the 3D-TC polytope is given. Finally, we present an extensive numerical study of small-to-medium block length 3D-TCs, which shows that 1) typically (i.e., in most cases) when the minimum distance $d_{\rm min}$ and/or the stopping distance $h_{\rm min}$ is high, the minimum pseudoweight (on the additive white Gaussian noise channel) is strictly smaller than both the $d_{\rm min}$ and the $h_{\rm min}$, and 2) the minimum pseudoweight grows with the block length, at least for small-to-medium block lengths.Comment: To appear in IEEE Transactions on Communication

Using C to build a satellite scheduling expert system: Examples from the Explorer platform planning system

Recently, many expert systems were developed in a LISP environment and then ported to the real world C environment before the final system is delivered. This situation may require that the entire system be completely rewritten in C and may actually result in a system which is put together as quickly as possible with little regard for maintainability and further evolution. With the introduction of high performance UNIX and X-windows based workstations, a great deal of the advantages of developing a first system in the LISP environment have become questionable. A C-based AI development effort is described which is based on a software tools approach with emphasis on reusability and maintainability of code. The discussion starts with simple examples of how list processing can easily be implemented in C and then proceeds to the implementations of frames and objects which use dynamic memory allocation. The implementation of procedures which use depth first search, constraint propagation, context switching and a blackboard-like simulation environment are described. Techniques for managing the complexity of C-based AI software are noted, especially the object-oriented techniques of data encapsulation and incremental development. Finally, all these concepts are put together by describing the components of planning software called the Planning And Resource Reasoning (PARR) shell. This shell was successfully utilized for scheduling services of the Tracking and Data Relay Satellite System for the Earth Radiation Budget Satellite since May 1987 and will be used for operations scheduling of the Explorer Platform in November 1991

Primordiaaliset mustat aukot ja gravitaatioaallot inflaatiosta

Varhaisessa universumissa inflaatiosta syntyvien primordiaalisien perturbaatioiden tiedetään pystyvän tuottamaan huomattava määrä primordiaalisia mustia aukkoja ja suuriamplitudisia gravitaatioaaltoja joissakin inflaatiomalleissa. Primordiaaliset mustat aukot syntyvät primordiaalisista skalaariperturbaatioista niiden tullessa takaisin Hubble säteen sisälle inflaation jälkeen. Gravitaatioaallot ovat osittain primordiaalisia tensoriperturbaatioita ja osittain syntyvät skalaariperturbaatioista. Tässä opinnäytetyössä käymme läpi tämänhetkisen kirjallisuuden tilannetta ja käsittelemme muutamia inflaatiomalleja, jotka pystyvät tuottamaan tarpeeksi suuria primordiaalisia skalaariperturbaatioita synnyttääkseen mielenkiintoisen määrän primordiaalisia mustia aukkoja. Päämallina käsittelemme ultra-slow roll inflaation konkreettisen esimerkki potentiaalin kautta, jota seuraa joidenkin vaihtoehtoisten mallien lyhyempi käsittely. Aloitamme selittämällä aiheeseen liittyvän taustateorian. Tämän jälkeen siirrymme käsittelemään opinnäytetyöhön valittuja inflaatiomalleja. Sitten selitämme primordiaalisten mustien aukkojen ja gravitaatioaaltojen syntymekanismin skalaariperturbaatioista. Tämän jälkeen käsittelemme primordiaalisia mustia aukkoja mahdollisena pimeän aineen ehdokkaana ja käymme läpi tärkeimmät eri massaisten mustien aukkojen runsauteen liittyvät rajoitukset. Keskustelemme joistakin mahdollisista tulevaisuuden rajoituksista massaikkunalle, jossa primordiaaliset mustat aukot voisivat vielä selittää kaiken pimeän aineen. Käsittelemme sitten lyhyesti kaksi suunniteltua avaruuteen lähetettävää gravitaatioaaltoilmaisinta, jotka mahdollisesti pystyvät havaitsemaan inflaatiosta syntyneitä gravitaatioaaltoja.The primordial perturbations created by inflation in the early Universe are known to be able to produce significant amount of primordial black holes and gravitational waves with large amplitudes in some inflationary models. Primordial black holes are produced by primordial scalar perturbations and gravitational waves are partly primordial tensor perturbations and partly produced by scalar perturbations. In this thesis we review some of the current literature on the subject and discuss a few inflationary models that are capable of producing primordial scalar perturbations large enough to create a significant amount of primordial black holes. The main focus is on ultra-slow roll inflation with a concrete example potential illustrating the dynamics of the scenario followed by a briefer treatment of some of the alternative models. We start by explaining the necessary background theory for the understanding of the subject at hand. Then we move on to the inflationary models covered in this thesis. After that we explain the production of the primordial black holes and gravitational waves from scalar perturbations. Then we consider primordial black holes as a dark matter candidate and go through the most significant known restrictions on the existence of primordial black holes with different masses. We discuss some of the possible future constraints for the remaining possible mass window for which primordial black holes could explain all of dark matter. We then briefly discuss two planned space-based gravitational wave detectors that may be able to detect gravitational waves created by inflation

Coexisting Plan-driven and Agile Methods: How Tensions Emerge and Are Resolved

Fast changing products, processes, and services caused by digital technologies require organizations to adopt agile methods after having used plan-driven approaches for decades. Adopting agile methods only to software development, can lead to a challenging coexistence of methods. To date, little empirical understanding exists with regard to the difficulties that emerge when organizations introduce agile teams in plan-driven environments. Consequently, we investigate the coexistence of agile and plan-driven methods and study its impacts. We conducted an exploratory multiple case study of four organizations and draw from adaptive structuration theory to study how agile methods are adopted on team level to an environment of deeply entrenched plan-driven methods. We find that this coexistence causes several tensions between agile and plan-driven teams (i.e., budgeting, knowledge, planning, process, responsibility, and cultural tension). Further, we reveal how organizations and teams overcome these tensions with balanced and blended resolutions

Using C to build a satellite scheduling expert system: Examples from the Explorer Platform planning system

A C-based artificial intelligence (AI) development effort which is based on a software tools approach is discussed with emphasis on reusability and maintainability of code. The discussion starts with simple examples of how list processing can easily be implemented in C and then proceeds to the implementations of frames and objects which use dynamic memory allocation. The implementation of procedures which use depth first search, constraint propagation, context switching, and blackboard-like simulation environment are described. Techniques for managing the complexity of C-based AI software are noted, especially the object-oriented techniques of data encapsulation and incremental development. Finally, all these concepts are put together by describing the components of planning software called the Planning And Resource Reasoning (PARR) Shell. This shell was successfully utilized for scheduling services of the Tracking and Data Relay Satellite System for the Earth Radiation Budget Satellite since May of 1987 and will be used for operations scheduling of the Explorer Platform in Nov. of 1991

Andreev bound states versus Majorana bound states in quantum dot-nanowire-superconductor hybrid structures: Trivial versus topological zero-bias conductance peaks

Motivated by an important recent experiment [Deng et al., Science 354, 1557 (2016)], we theoretically consider the interplay between Andreev bound states(ABSs) and Majorana bound states(MBSs) in quantum dot-nanowire semiconductor systems with proximity-induced superconductivity(SC), spin-orbit coupling and Zeeman splitting. The dot induces ABSs in the SC nanowire which show complex behavior as a function of Zeeman splitting and chemical potential, and the specific question is whether two such ABSs can come together forming a topological MBS. We consider physical situations involving the dot being non-SC, SC, or partially SC. We find that the ABSs indeed tend to coalesce together producing near-zero-energy midgap states as Zeeman splitting and/or chemical potential are increased, but this mostly happens in the non-topological regime although there are situations where the ABSs could come together forming a topological MBS. The two scenarios(two ABSs forming a near-zero-energy non-topological ABS or a zero-energy topological MBS) are difficult to distinguish by tunneling conductance spectroscopy due to essentially the same signatures. Theoretically we distinguish them by knowing the critical Zeeman splitting for the topological quantum phase transition or by calculating the topological visibility. We find that the "sticking together" propensity of ABSs to produce a zero-energy midgap state is generic in class D systems, and by itself says nothing about the topological nature of the underlying SC nanowire. One must use caution in interpreting tunneling conductance measurements where the midgap sticking-together behavior of ABSs cannot be construed as definitive evidence for topological SC with non-Abelian MBSs. We also suggest some experimental techniques for distinguishing between trivial and topological ZBCPs.Comment: 32 pages, 29 figure

Can springs cut canyons into rock?

Amphitheater-headed valleys on Earth and Mars are often assumed to result from erosion by emerging spring water (i.e., seepage erosion or groundwater sapping) rather than by surface runoff. The origin of such valleys has implications for landscape evolution on Earth and the hydrologic cycle and associated potential for life on other planets. In this paper we explore the evidence for seepage erosion in bedrock to address whether valley morphology can be used as a diagnostic indicator of seepage erosion. Seepage erosion is an important process in loose sediment where hydraulic forces cause grain detachment, often resulting in amphitheater-headed valleys. However, the extension of these processes to resistant rock is uncertain. In sedimentary rocks, groundwater might control the shape and rate of valley formation. It is possible, however, that seepage plays only a secondary role to runoff processes. This seems likely in basaltic valleys on Earth, where little evidence exists for seepage erosion. Since the ability of seepage to erode bedrock valleys remains unclear and because many amphitheater-headed valleys were probably carved by other processes, seepage erosion should not be inferred based solely on valley form

Website Content Extraction Using Web Structure Analysis

The Web poses itself as the largest data repository ever available in the history of humankind. Major efforts have been made in order to provide efficient to relevant information within huge repository of data. Although several techniques have been developed to the problem of Web data extraction, their use is still not spread, mostly because of the need for high human intervention and the low quality of the extraction results. For this project a domain-oriented approach to Web data extraction and discuss it application to extracting news from Web Sites. It will use the abstraction method to identify important sections in a web document. The relevance information will be taken account and will be highlighted in order to develop a focused web content output. The fact-finding and data about the project are gathered from various sources such as internet, and books. The methodology used is a Waterfall Model that involves several phases which are Planning, Analysis, Design and Implementation. The result of this project is the display and review of web content extraction and how it being currently being developed which the goals is to give more usability and easiness toward web users

ExtruOnt: An ontology for describing a type of manufacturing machine for Industry 4.0 systems

Semantically rich descriptions of manufacturing machines, offered in a machine-interpretable code, can provide interesting benefits in Industry 4.0 scenarios. However, the lack of that type of descriptions is evident. In this paper we present the development effort made to build an ontology, called ExtruOnt, for describing a type of manufacturing machine, more precisely, a type that performs an extrusion process (extruder). Although the scope of the ontology is restricted to a concrete domain, it could be used as a model for the development of other ontologies for describing manufacturing machines in Industry 4.0 scenarios. The terms of the ExtruOnt ontology provide different types of information related with an extruder, which are reflected in distinct modules that constitute the ontology. Thus, it contains classes and properties for expressing descriptions about components of an extruder, spatial connections, features, and 3D representations of those components, and finally the sensors used to capture indicators about the performance of this type of machine. The ontology development process has been carried out in close collaboration with domain experts.This research was funded by the Spanish Ministry of Economy and Competitiveness, grant number FEDER/TIN2016-78011-C4- 2R. The work of Víctor Julio Ramírez-Durán is funded by the contract with reference BES-2017-081193