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Cykloserins och ceftazidim/avibaktams effekt på multiresistenta gramnegativa bakterierGötesson, Åsa January 2018 (has links)
Multiresistenta gramnegativa bakterier (MRGN) som Escherichia coli och Pseudomonas aeruginosa utgör ett globalt hälsoproblem och på grund av resistensutveckling hos bakterierna behövs nya behandlingsalternativ. Extended Spectrum β-Lactamase (ESBL) är vanligt förekommande hos MRGN och det finns olika typer av ESBL (exempelvis ESBLA och ESBLCARBA). Gemensamt är att det finns få behandlingsalternativ för ESBL-producerande MRGN. Syftet med studien var att undersöka effekten av potentiellt nya behandlingsalternativ mot MRGN i form av cykloserin och ceftazidim tillsammans med β-laktamasinhibitorn avibaktam. För att undersöka minimum inhibitory concentration (MIC) för cykloserin (CYK) mot E. coli (n=26) användes en egenutvecklad buljongspädningsmetod. Isolat av P. aeruginosa med och utan karbapenemasproduktion (n=25) undersöktes avseende MIC för ceftazidim/avibaktam (CZA) med två kommersiella buljongspädningsmetoder. För CYK låg medianen för E. coli-stammarnas MIC-värden vid 32 mg/L (16 – 64 mg/L) vilket ligger kring det epidemiologiska cut-off värdet för Mycobacterium tuberculosis (32 mg/L), för vilken CYK idag används som behandling. För CZA låg medianen för P. aeruginosa-stammarnas MIC-värden vid 8 mg/L (<1 - ≥8 mg/L), och 40% (2/5) av de karbapenemasproducerande isolaten var känsliga enligt kliniska brytpunkter (S≤8 mg/L). Sammanfattningsvis visar studien att CYK har MIC-värden mot non-ESBL- och ESBL-producerande E. coli i nivå med andra patogener där preparatet används. Studien visar också att CZA kan ha effekt mot isolat med nedsatt känslighet mot meropenem eller ESBLCARBA-producerande isolat av P. aeruginosa, men isolaten måste resistensbestämmas innan behandling sätts in. / Multiresistant gramnegative bacteria (MRGN) like Escherichia coli and Pseudomonas aeruginosa, constitute a global health issue. Due to the resistance development among bacteria, new options for treatment are needed. Extended Spectrum β-Lactamase (ESBL) is common among MRGN, and there are different types of ESBLs (as ESBLA and ESBLCARBA). The increasing lack of treatment alternatives is mutual for the different ESBLs. The purpose of this study was to examine cycloserine and ceftazidime with the β-lactamase-inhibitor avibactam, two potentially new options for treatments effective against MRGN. To examine the minimum inhibitory concentration (MIC) for cycloserine (CYK) against E. coli (n=26) a in-house broth microdilution-method was used. Using two commercial broth microdilution-methods, isolates of P. aeruginosa with and without carbapenemaseproduction (n=23) were examined regarding MIC for ceftazidime/avibactam (CZA). Regarding CYK, the median MIC-value of the E. coli-strains was 32 mg/L (16 - 64 mg/L), which is around the epidemiological cut-off-value (32 mg/L) for Mycobacterium tuberculosisfor which CYK is being used as treatment. The median of the MIC-values for CZA was 8 mg/L (<1 - ≥8 mg/L) for all P. aeruginosa-strains and 40% (2/5) of the carbapenemaseproducing isolates were sensitive according to the clinical breakpoint (S≤8 mg/L). In summary, this study shows that CYK has MIC-values against non-ESBL- and ESBL-producing E. coli at the same level as other pathogens where CYK is being used. Further, CZA may have effect against the isolates with reduced susceptibility against meropenem and ESBLCARBA-producing P. aeruginosa, although the isolates need to be susceptibility-determined before treatment.
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[en] MICROSCOPY OF BIOFILMS FORMED ON A METALLIC SUBSTRATE IN THE PRESENCE OF OILY FLUIDS IN STATIC AND DYNAMIC SYSTEMS / [pt] MICROSCOPIA DE BIOFILMES EM SUBSTRATO METÁLICO FORMADO EM SISTEMAS ESTÁTICO E DINÂMICO NA PRESENÇA DE FLUIDO OLEOSOKARLA DE AVELLAR MOTA 12 January 2018 (has links)
[pt] Este trabalho teve por objetivo avaliar a morfologia de biofilmes, formados em
superfície de aço API 5L X80 submetida a um fluido com baixo BSW (Basic Sediment
Water), ou seja, baixo teor de água em óleo, através de análise por Microscopia
Eletrônica de Varredura (MEV), determinar a cinética e quantificar os grupos
bacterianos de formação destes biofilmes, e avaliar a biocorrosão causada por estes
microrganismos. Foram realizadas alterações no protocolo original de preparo de
amostras, com a finalidade de obter melhor definição das morfologias avaliadas.
Realizaram-se estudos dinâmicos (looping) e em condições estáticas, com e sem a
adição de agente biocida. Utilizando-se como fluido de processo o óleo coletado no
terminal da Petrobras em Barra do Furado que tem como característica um BSW de
aproximadamente 1 por cento de água. Para alcançar os objetivos descritos foram quantificadas
bactérias sésseis (bactérias facultativas heterotróficas, bactérias precipitantes do ferro,
bactérias anaeróbias heterotróficas e bactérias redutoras de sulfato) através da técnica do
número mais provável (NMP). A intensidade do processo corrosivo foi avaliada através
da análise dos pites formados nos cupons por microscopia óptica. A seqüência de
fixação com alteração do protocolo inicial, permitiu uma melhor preservação estrutural
do biofilme obtendo-se assim imagens com melhor resolução, tendo em vista que a
fixação primária com glutaraldeído fixa principalmente proteínas pelo estabelecimento
de ligações divalentes com grupamento amino, e a pós-fixação em tetróxido de ósmio
reage com os lipídios. Quanto a cinética, observou-se também que na presença de
fluido oleoso, a formação do biofilme só é detectada após 15 dias de exposição. A
adição do agente biocida inibiu o crescimento do biofilme, não sendo detectada a
presença de células cultiváveis após 7 dias em contato com o fluido contendo o agente
químico. / [en] This study aims to evaluate the morphology of biofilms formed on the surface of API 5L X80 steel exposed to a low BSW (Basic Sediment Water) fluid comprising oil of a low water content. The analisys was performed using scanning electron microscopy (SEM) in order to determine the formation kinetics, to quantify and identify the bacterial groups present as the film formed, and to evaluate the biocorrosion caused by these organisms. Modifications were made to the original sample preparation protocol,
in order to better define the film morphologies. Studies were undertaken applying either static or dynamic (looping) conditions, bith with and without the addition of biocides. The process fluid used was oil collected from the Petrobras Barra do Furado Terminal, characterized by its 1 percent BSW. The evaluation was performed quantifying the sessile bacteria present in the film (heterotrophic bacteria, iron bacteria, anaerobic bacteria e sulphate reducing bacteria) via the Most Probable Number (MPN) technique. The intensity of the corrosion process was determined by the analysis of pits forme in the testpieces, by optical microscopy. The application of a sample fixation sequence, in addition to modifications of the inicial sample preparation protocol, permitted the improved preservation of the biofilm structures, thereby permitting higher resolution images. The primary fixing agent, containing gluteraldehyde, principally fixes proteins,
by establishing divalent bonds with amino groups, while the post-fixation stage with osmium tetroxide invloves reactions with lipid groups.With regard to the film deposition kinetics, it was observed that biofilm formation could only be detected after 15 day s exposure to the oily fluid. The addition of a biocide, inhibited the growth of the film, no cultivatable cells being present after 7 days contact with the treated fluid.
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Accelerated Deep Learning using Intel Xeon PhiViebke, André January 2015 (has links)
Deep learning, a sub-topic of machine learning inspired by biology, have achieved wide attention in the industry and research community recently. State-of-the-art applications in the area of computer vision and speech recognition (among others) are built using deep learning algorithms. In contrast to traditional algorithms, where the developer fully instructs the application what to do, deep learning algorithms instead learn from experience when performing a task. However, for the algorithm to learn require training, which is a high computational challenge. High Performance Computing can help ease the burden through parallelization, thereby reducing the training time; this is essential to fully utilize the algorithms in practice. Numerous work targeting GPUs have investigated ways to speed up the training, less attention have been paid to the Intel Xeon Phi coprocessor. In this thesis we present a parallelized implementation of a Convolutional Neural Network (CNN), a deep learning architecture, and our proposed parallelization scheme, CHAOS. Additionally a theoretical analysis and a performance model discuss the algorithm in detail and allow for predictions if even more threads are available in the future. The algorithm is evaluated on an Intel Xeon Phi 7120p, Xeon E5-2695v2 2.4 GHz and Core i5 661 3.33 GHz using various architectures and thread counts on the MNIST dataset. Findings show a 103.5x, 99.9x, 100.4x speed up for the large, medium, and small architecture respectively for 244 threads compared to 1 thread on the coprocessor. Moreover, a 10.9x - 14.1x (large to small) speed up compared to the sequential version running on Xeon E5. We managed to decrease training time from 7 days on the Core i5 and 31 hours on the Xeon E5, to 3 hours on the Intel Xeon Phi when training our large network for 15 epochs
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Occurrence des légionelles dans les eaux thermales tunisiennes et évaluation de l'activité anti-legionella des huiles essentielles de plantes autochtones / Occurence of Legionella in tunisian spas and evaluation of the anti-Legionella activity of essential oils from tunisian plantsChaftar, Nawel 06 November 2013 (has links)
L'environnement des stations thermales est favorable à la croissance des Legionella. La Tunisie compte de nombreux sites thermaux. Elle a par ailleurs développé une médecine traditionnelle à base de plantes. L'objectif de ce travail était de caractériser des souches de légionelles isolées de stations thermales et d'étudier le potentiel antimicrobien d'HE de plantes tunisiennes. 2 souches de L. londiniensis et 16 de L. pneumophila (sérovars 1, 4, 5, 6 et 8) ont été isolées de 3 stations thermales tunisiennes et avaient des pulsotypes différents de ceux de la base du CNRL. Les HE de 6 plantes tunisiennes ont été extraites, analysées (GC-MS) et testées contre L. pneumophila (8 souches, sérovars 1, 4, 5, 6 et 8). Les HE de Juniperus phoenicea L. (isobornéol 20,91% et 1S α-pinène 18,30%) et Thymus vulgaris (carvacrol 88,50%) étaient les plus actives (CMI <0,03 mg/mL et ≤0,07 mg/mL respectivement). L'activité de 20 HE (6 de plantes tunisiennes et 14 commerciales) a été évaluée contre 11 espèces bactériennes (6 Gram+, 5 Gram-) et 7 fongiques (4 levures, 3 filamenteux). L'HE de T. vulgaris tunisien était la plus active (Gram-: CMI ≤0,34 mg/mL ; Gram+: CMI ≤0,7 mg/mL ; levures: CMI ≤0,55 mg/mL ; moisissures: CMI=0,3 mg/mL ; dermatophytes: CMI ≤0,07 mg/mL). Elle a montré une activité très supérieure à celle de l'HE commerciale de T. vulgaris certainement due à sa composition différente. En conclusion, la présence de Legionella dans les sites étudiés doit encourager les autorités à renforcer les mesures préventives et l'efficacité antimicrobienne des HE, en particulier l'HE de T. vulgaris tunisien, suggère leur possible intérêt dans le traitement des eaux ou la conservation des aliments. / Spa environment is favorable to the growth of Legionella. Tunisia, which has many spa, has developed a traditional herbal medicine. The objective of this work was to characterize strains of Legionella isolated from 3 spas and to investigate the antimicrobial potential of EOs from Tunisian plants.2 strains of L. londiniensis and 16 of L. pneumophila (serotypes 1, 4, 5, 6 and 8) were isolated and had different pulsotypes from those of the CNRL database.EOs from six Tunisian plants were extracted, analyzed (GC-MS) and tested against L. pneumophila (8 strains, serotypes 1, 4, 5, 6 and 8). The EO of Juniperus phoenicea L. (1S isoborneol 20.91% and 18.30% α-pinene) and Thymus vulgaris (carvacrol 88.50%) were the most active (MIC <0.03 mg/mL and ≤0.07 mg/mL, respectively).The activity of 20 EOs (6 from Tunisian plants and 14 commercial ones) was evaluated against 11 bacterial species (6 Gram+, 5 Gram-) and 7 fungal species (4 yeasts, 3 filamentous). The EO of Tunisian T. vulgaris was the most active (Gram-: MIC ≤ 0.34 mg/mL, and Gram +: MIC ≤0.7 mg/mL; yeasts MIC ≤0.55 mg/mL; mold: MIC=0.3 mg/mL; dermatophytes: MIC ≤0.07 mg/mL). It showed a higher activity than the commercial EO of T. vulgaris, certainly due to their different composition.In conclusion, the presence of Legionella in the studied spas should encourage the authorities to strengthen the preventive measures. The antimicrobial efficacy of EOs, especially from Tunisian T. vulgaris, suggest their potential interest in water treatment or food storage.
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Les réseaux militaires comme acteurs des relations internationales : le cas du Multinational Interoperability CouncilForget, Amélie 10 1900 (has links)
Depuis plus de cinquante ans, les puissances occidentales ont créé toutes sortes de réseaux militaires internationaux, afin de renforcer leurs liens et harmoniser leurs techniques, leurs équipements et leurs façons de faire. Jusqu’à ce jour, ces regroupements sont demeurés largement ignorés de la discipline des relations internationales. Or, la mondialisation des échanges et l’essor des technologies de l’information ont ouvert les processus politiques à de nouveaux acteurs, y compris en matière de sécurité, jetant un éclairage nouveau sur le rôle, la mission et les responsabilités que les États délèguent à ces réseaux. En menant une analyse approfondie d’un réseau militaire, le Multinational Interoperability Council, cette recherche a pour objectifs de définir les réseaux militaires internationaux en tant que catégorie d’analyse des relations internationales, de documenter empiriquement leur fonctionnement et de mieux comprendre leur rôle dans le champ de la sécurité internationale. Pour ce faire, la démarche propose de recourir à l’appareil conceptuel de l’institutionnalisme relationnel, de la théorie des champs et du tournant pratiques en relations internationales. Cette combinaison permet d’aborder les dimensions institutionnelle, cognitive et pratique de l’action collective au sein du réseau étudié.
L’analyse nous apprend que, malgré une influence limitée, le MIC produit une identité, des
capacités, des préférences et des effets qui lui sont propres. Les acteurs du MIC ont eux-mêmes généré certaines conditions de son institutionnalisation, et sont parvenus à faire du réseau, d’abord conçu comme une structure d’échanges d’informations, un acteur intentionnel du champ de la sécurité internationale. Le MIC ne peut agir de façon autonome, sans contrôle des États. Cependant, les relations établies entre les militaires qui y participent leur offrent des capacités – le capital social, politique et d’expertise – dont ils ne disposeraient pas autrement, et qu’ils peuvent mobiliser dans leurs interactions avec les autres acteurs du champ. / For more than fifty years, Western powers have created many different forms of international military networks, in order to strengthen their ties and harmonize their technics, equipment and ways of doing things. To date, these groups have remained largely ignored by the academic discipline of International Relations. And yet, globalization and the rise of information technologies have provided many new actors with an access to political processes, including in the field of security. This evolution sheds new light on the role, mission and responsibilities that states assign to these networks. This research conducts an in-depth analysis of one military network, the Multinational Interoperability Council. The aim of this analysis is threefold: to define international military networks as a category of analysis for International Relations, to document empirically their functioning, and to understand their role in the field of internal security. To do so, the analytical framework combines the conceptual apparatus of relational institutionalism, the theory of social fields, and the methodological tools of the practice turn in International Relations. This combination allows for addressing the institutional, cognitive and practical dimensions of collective action within the network.
The analysis reveals that, despite a limited influence, the MIC produces its own identity,
capabilities, preferences and effects. The MIC’s actors have been able to create the conditions of its institutionalization, and they have succeeded in turning the network into an intentional actor of the international security field, while it was originally created as a mere structure of exchange of information. The MIC is not able to act autonomously, without states’ control. However, the relations established by the military who belong to it have provided them with capabilities – social, political and expertise capitals – that they would not otherwise possess, and which they can mobilize in their interactions with other actors of the field.
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[en] ANALYZE OF BIOFILM FORMATION KINETIC ON API 5L X80 LONGITUDINAL WELDS IN DYNAMIC FLOW SYSTEM / [pt] ANÁLISE DA CINÉTICA DE FORMAÇÃO DE BIOFILMES EM JUNTA SOLDADA LONGITUDINAL DE AÇO API 5L X80 EM SISTEMA DINÂMICO27 October 2021 (has links)
[pt] A Corrosão Influenciada por Microrganismos (CIM) ou biocorrosão é reconhecida como um dos fenômenos causadores de inúmeros problemas nas indústrias de petróleo e gás, pois causa sérios danos ao material reduzindo sua vida útil. Neste trabalho foram avaliados os efeitos da biocorrosão caracterizado pela cinética de formação de biofilme em uma junta soldada longitudinal de aço API X80 obtida pelo processo de arco submerso (SAW). Durante o processo de soldagem forma-se uma região com características microestruturais distintas do metal de base e do metal de adição, denominada de zona termicamente afetada (ZTA). Assim essa zona poderá ter uma adesão microbiana diferenciada, visto que diferenças superficiais em um material, seja por natureza química ou física, podem limitar ou facilitar a adesão microbiológica. Por esse motivo foi realizado um estudo comparativo entre a cinética da formação de biofilme na junta soldada de um aço API X80. Também foi avaliada a influência das características físicas da superfície na adesão microbiana utilizando dois tipos de superfície: com a rugosidade original e polido com pasta de diamante com granulação de 6μm. Estas superfícies foram expostas ao fluido de processo (água do mar da Baía de Guanabara) em um sistema dinâmico. Foram realizadas tanto a quantificação microbiana, como também a quantificação dos ácidos orgânicos, sulfato depletado e ferro total para avaliar os nutrientes disponíveis e a bioatividade das reações bacterianas. A rugosidade superficial e o biofilme formado foram caracterizados morfologicamente e a sua presença correlacionada com a formação de pites. / [en] The Microbiologically Influenced Corrosion (MIC) or bio-corrosion is recognized as one of the phenomena that cause a lot of problems in petroleum and gas industries, because it causes serious damages to the materials, reducing its life cycle. This study evaluated the effects of bio-corrosion characterized by the biofilm formation kinetics in longitudinal welds of API 5L X80 steel obtained by the process of submerged arc welding (SAW). During the welding process a region with different microstructural characteristics of the base metal and weld metal is formed, called heat affected zone (HAZ). Thus this zone can have a differentiated microbial adhesion since the different surfaces of a material, either by chemical and physical nature, can limit or facilitate the microbial adhesion. For this reason a comparative study of biofilm formation kinetic on the welded joint was conducted. The influence of the physical characteristics of the surface in microbial adhesion was also evaluated using two kinds of surface: steel with real roughness and steel polished with diamond paste with grain size of 6 μm. These surfaces were exposed to the process fluid (Guanabara Bay seawater) in a dynamic flow system. The microbial quantification was held. Organic acids, depleted sulfate and total iron were also measured to evaluate the available nutrients bioactivity of bacterial reactions. Surface roughness and biofilm were characterized morphologically and correlated with pitting formation.
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Antimicrobial and Anticancer Activity of Essential Oils from Guatemalan Medicinal PlantsMiller, Andrew B. 19 November 2010 (has links) (PDF)
Guatemalan medicinal plants were collected and screened for the presence of essential oils using steam distillation. Oil was found in 63 species from 24 families and was tested in tube dilution assays for activity against Escherichia coli, Staphylococcus aureus, Streptococcus mutans, Lactobacillus acidophilus and Candida albicans. Several essential oils were highly active with 20 instances of oils inhibiting the microbes at an MIC of 0.31 µl/ml. Oils were also tested against cancerous and established cell lines using a 15% (v/v) agar-media which was developed to improve essential oil solubility. Assays were performed against three cancer lines: Stomach (AGS: CRL-1739), Skin (A375: CRL-1619), Tongue (CAL27: CRL-2095) and an established Monkey Kidney cell line (Vero C 1008: CRL-1586). Assessment of viability was performed using the Neutral Red assay with results indicating that many of the oils significantly inhibited cancer cell lines in vitro with 24 individual instances producing an IC50 of 0.20 µl/ml or less. Therapeutic indices indicated that many of the highly inhibitory oils were more cytotoxic to cancerous cell lines than to the established cell line.
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Investigating the Electrochemical Interaction of Microorganisms with MetalSurfaces During Microbiologically Influenced CorrosionSadek, Anwar 11 August 2022 (has links)
No description available.
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Развитие методики оценки вероятности банкротства на предприятиях оборонно-промышленного комплекса : магистерская диссертация / Development of the methodology for assessing the probability of bankruptcy in the enterprises of the defense industrial complexСажин, М. С., Sazhin, M. S. January 2019 (has links)
Предприятия ОПК, как объект научного исследования интересны с точки зрения разработки механизма адаптации предприятий ОПК к рыночной среде, оценки вероятности банкротства. Данный вопрос в настоящее время являются весьма актуальным. Его решение крайне востребованного отечественными промышленными предприятиями, имеющими оборонное значение. Очевидно, что на сегодняшний день всё большее число предприятий оборонно-промышленного комплекса, сталкиваются с трудностями, что провоцирует их банкротство. Использование методик и множества моделей различного авторства для прогнозирования банкротства и оценки уровня его вероятности может помочь в процессе диагностики текущего финансового состояния предприятия сферы ОПК и заблаговременно предотвратить факт наступления банкротства. Однако, не существует безупречной методики, которую можно использовать для прогнозирования банкротства предприятий оборонно-промышленного комплекса (что показано в работе). Ввиду чего цель работы была сформулирована следующим образом: разработать систему оценки вероятности банкротства предприятий оборонно-промышленного комплекса, учитывающую специфику и особенности отрасли. Задачи исследования определяются целью: 1. Выполнить анализ наиболее используемых методик определения вероятности банкротства по отношению к предприятиям оборонно-промышленного комплекса; 2. Дать оценку результатам анализа наиболее используемых методик определения вероятности банкротства по отношению к предприятиям оборонно-промышленного комплекса; 3. Опираясь на результаты анализа наиболее используемых методик определения вероятности банкротства по отношению к предприятиям оборонно-промышленного комплекса и их выявленные недостатки разработать собственную систему критериев оценки вероятности банкротства в сфере ОПК; 4. Дать оценку предлагаемой системы оценки вероятности банкротства в сфере оборонно-промышленного комплекса на основе её апробации на ряде предприятий ОПК. Объектом исследования являются предприятия оборонно-промышленного комплекса Российской Федерации. Предметом исследования является оценка вероятности банкротства предприятий комплекса Российской Федерации. / Enterprises of the defense industrial complex, as an object of scientific research, are interesting from the point of view of developing a mechanism for adapting the enterprises of the military-industrial complex to the market environment, assessing the probability of bankruptcy. This issue is currently very relevant. His decision is highly demanded by domestic industrial enterprises of defense importance. It is obvious that today an increasing number of enterprises of the military-industrial complex are facing difficulties that provoke their bankruptcy. Using techniques and a variety of models of different authorship to predict bankruptcy and assess its level Probability can help in the process of diagnosing the current financial condition of a company in the defense industry sector and prevent bankruptcy in advance. However, there is no perfect method that can be used to predict the bankruptcy of enterprises of the military-industrial complex (as shown in the work). In view of this, the purpose of the work was formulated as follows: to develop a system for assessing the probability of bankruptcy of enterprises of the military-industrial complex, taking into account the specifics and characteristics of the industry. The objectives of the study are determined by the purpose of: 1. To analyze the most used methods for determining the probability of bankruptcy in relation to the enterprises of the military-industrial complex; 2. To assess the results of the analysis of the most used methods for determining the probability of bankruptcy in relation to the enterprises of the military-industrial complex; 3. Based on the results of the analysis of the most used methods for determining the probability of bankruptcy in relation to enterprises of the military-industrial complex and their identified shortcomings, develop their own system of criteria for assessing the probability of bankruptcy in the defense industry; 4. To assess the proposed system for assessing the probability of bankruptcy in the field of the military-industrial complex on the basis of its testing at a number of defense enterprises. The object of the research is the enterprises of the military-industrial complex of the Russian Federation. The subject of the research is the assessment of the probability of bankruptcy of enterprises of the complex of the Russian Federation.
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La conception d'un système ultrasonore passif couche mince pour l'évaluation de l'état vibratoire des cordes vocales / A speaker recognition system based on vocal cords’ vibrationsIshak, Dany 19 December 2017 (has links)
Dans ce travail, une approche de reconnaissance de l’orateur en utilisant un microphone de contact est développée et présentée. L'élément passif de contact est construit à partir d'un matériau piézoélectrique. La position du transducteur piézoélectrique sur le cou de l'individu peut affecter grandement la qualité du signal recueilli et par conséquent les informations qui en sont extraites. Ainsi, le milieu multicouche dans lequel les vibrations des cordes vocales se propagent avant d'être détectées par le transducteur est modélisé. Le meilleur emplacement sur le cou de l’individu pour attacher un élément transducteur particulier est déterminé en mettant en œuvre des techniques de simulation Monte Carlo et, par conséquent, les résultats de la simulation sont vérifiés en utilisant des expériences réelles. La reconnaissance est basée sur le signal généré par les vibrations des cordes vocales lorsqu'un individu parle et non sur le signal vocal à la sortie des lèvres qui est influencé par les résonances dans le conduit vocal. Par conséquent, en raison de la nature variable du signal recueilli, l'analyse a été effectuée en appliquant la technique de transformation de Fourier à court terme pour décomposer le signal en ses composantes de fréquence. Ces fréquences représentent les vibrations des cordes vocales (50-1000 Hz). Les caractéristiques en termes d'intervalle de fréquences sont extraites du spectrogramme résultant. Ensuite, un vecteur 1-D est formé à des fins d'identification. L'identification de l’orateur est effectuée en utilisant deux critères d'évaluation qui sont la mesure de la similarité de corrélation et l'analyse en composantes principales (ACP) en conjonction avec la distance euclidienne. Les résultats montrent qu'un pourcentage élevé de reconnaissance est atteint et que la performance est bien meilleure que de nombreuses techniques existantes dans la littérature. / In this work, a speaker recognition approach using a contact microphone is developed and presented. The contact passive element is constructed from a piezoelectric material. In this context, the position of the piezoelectric transducer on the individual’s neck may greatly affect the quality of the collected signal and consequently the information extracted from it. Thus, the multilayered medium in which the sound propagates before being detected by the transducer is modeled. The best location on the individual’ neck to place a particular transducer element is determined by implementing Monte Carlo simulation techniques and consequently, the simulation results are verified using real experiments. The recognition is based on the signal generated from the vocal cords’ vibrations when an individual is speaking and not on the vocal signal at the output of the lips that is influenced by the resonances in the vocal tract. Therefore, due to the varying nature of the collected signal, the analysis was performed by applying the Short Term Fourier Transform technique to decompose the signal into its frequency components. These frequencies represent the vocal folds’ vibrations (50-1000 Hz). The features in terms of frequencies’ interval are extracted from the resulting spectrogram. Then, a 1-D vector is formed for identification purposes. The identification of the speaker is performed using two evaluation criteria, namely, the correlation similarity measure and the Principal Component Analysis (PCA) in conjunction with the Euclidean distance. The results show that a high percentage of recognition is achieved and the performance is much better than many existing techniques in the literature.
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