Bibliografie tematiche / Timber degradation

Letteratura scientifica selezionata sul tema "Timber degradation"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 20 febbraio 2023

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Articoli di riviste sul tema "Timber degradation"

Yang, Deshan, Ming Xu e Zhongfan Chen. "Experimental study on the reinforcement methods and lateral resistance of mortise-tenon jointed traditional timber frames". BioResources 16, n. 2 (20 aprile 2021): 4039–51. http://dx.doi.org/10.15376/biores.16.2.4039-4051.

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In order to study the lateral resistance of reinforced traditional Chinese timber frames with mortise-tenon connections, three cyclic tests were conducted on one-bay mortise-tenon jointed traditional timber frames. Three reinforcement methods, i.e., steel angle strengthening, wood brace, and Timu, were studied. Seismic performances were evaluated according to the experimental phenomena and the test results. The failure mode, hysteresis curves, skeleton curves, curves of stiffness degradation, and energy dissipation capacity of the three specimens were analyzed based on the tests. The test results showed that the wood frames had good deformability. The stiffness degradation of the timber frame was severe at the initial loading stage; however, the degradation rate tended to decrease after the initial stage. In addition, the energy dissipation increased as the lateral displacement increased. The wooden frames with mortise tenon joints strengthened by steel angle, wood brace, and Timu can achieve good aseismic results. The study can provide a theoretical basis for seismic design and reinforcing methods of traditional timber structures.

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Kuklík, Petr, Lukáš Velebil, Anna Gregorová e Petr Svora. "MONITORING AND PROTECTION OF TIMBER-CONCRETE BRIDGES". Acta Polytechnica CTU Proceedings 22 (25 luglio 2019): 57–61. http://dx.doi.org/10.14311/app.2019.22.0057.

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The majority of timber bridges for ordinary road traffic are often made as timber-concrete composite structures. Concrete slab is something like as umbrella for timber. The reason for problems in timber-concrete bridges is nearly always poor detailing for durability and neglected maintenance. Mainly all aspects of timber protection and maintenance should therefore be considered even during the planning phase of bridge. Paper deals with evaluation of timber properties, system of opto-fiber sensors for monitoring and diagnostics of mechanical stress of timber-concrete bridges, and degradation of timber due to UV radiation, atmospheric conditions and biological agents after application of photocatalytic materials on surface.

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Majak, W. "Further enhancement of 3-nitropropanol detoxification by ruminal bacteria in cattle". Canadian Journal of Animal Science 72, n. 4 (1 dicembre 1992): 863–70. http://dx.doi.org/10.4141/cjas92-098.

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Ruminal fluid obtained from cattle was used to determine the effects of different diets and supplements on the in vitro degradation of 3-nitropropanol, the miserotoxin aglycone of certain Astragalus species such as timber milkvetch (Leguminosae). Nitroethane, an analog of the aglycone that is much less toxic to mammals, was effective as a supplement when given on alternate days. It enhanced the in vitro rates of nitropropanol degradation in all experiments, by 70–170%. In agreement, daily doses of timber milkvetch at a level equivalent to 3 mg nitropropanol kg−1 body weight also enhanced nitropropanol degradation, suggesting an adaptation to the aliphatic nitro group by ruminal bacteria. The forage protein content appears to contribute to the microbial efficacy and this was verified when diets were supplemented with soybean meal. The protein supplement increased nitropropanol degradation by 37–44% and, as expected, it also promoted cellulose digestion in vitro. The effect of nitroethane supplementation on the absorption of nitropropanol from the rumen was examined when treated and control groups were challenged with timber milkvetch. Plasma levels of 3-nitropropionic acid, the oxidized form of nitropropanol which is detected in the blood, were significantly reduced in response to nitroethane supplementation, and rates of nitropropanol degradation by ruminal microbes were concomitantly enhanced. These combined results further elucidate the factors that control and contribute to nitropropanol detoxification and suggest possible methods of prevention of timber milkvetch poisoning under rangeland conditions. Key words: Timber milkvetch, toxic plant, detoxification, 3-nitropropanol, ruminal bacteria, cattle

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Banjade, Mani R. "Discourse and Discursive Practices Over Timber in Nepal". Journal of Forest and Livelihood 10, n. 1 (13 settembre 2013): 58–73. http://dx.doi.org/10.3126/jfl.v10i1.8601.

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Forest sector of Nepal is far from harnessing its economic potential, but witnesses a continuation of deforestation and forest degradation. This is largely because of the limited policy focus on the management of the most important forest product – the timber. Taking timber at the central stage in the debate on forest management, this paper examines the existing stakeholder relations, policy deliberations, programs and everyday practices in Nepal. This paper draws on the country’s policy, legal and regulatory documents, policy deliberations on forest governance, media analysis and everyday practices of forest management. These policies and practices are analysed in relation to environmental discourse, social practices and hegemony in forest sector governance. This paper shows that, while timber occupies a central stage in the government’s decisions, in most of forest-related contestations, and in everyday management decisions, timber management has received only secondary importance in the national forest policy and discourses. The analysis shows that since forest policy discourses have departed from timber, local communities and the government have lost significant incomes from the forest. The marginalization of timber in the policy discourse also encouraged deforestation and forest degradation especially through illegal logging and forest encroachment. DOI: http://dx.doi.org/10.3126/jfl.v10i1.8601 Journal of Forestry and Livelihood Vol.10(1) 2012 58-73

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Entry, James A., Nellie M. Stark e Howard Loewenstein. "Timber harvesting: Effects on degradation of cellulose and lignin". Forest Ecology and Management 22, n. 1-2 (dicembre 1987): 79–88. http://dx.doi.org/10.1016/0378-1127(87)90097-1.

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Anshari, G. Z., M. Afifudin, M. Nuriman, E. Gusmayanti, L. Arianie, R. Susana, R. W. Nusantara, J. Sugardjito e A. Rafiastanto. "Drainage and land use impacts on changes in selected peat properties and peat degradation in West Kalimantan Province, Indonesia". Biogeosciences 7, n. 11 (4 novembre 2010): 3403–19. http://dx.doi.org/10.5194/bg-7-3403-2010.

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Abstract. Degradation of tropical peats is a global concern due to large Carbon emission and loss of biodiversity. The degradation of tropical peats usually starts when the government drains and clears peat forests into open peats used for food crops, oil palm and industrial timber plantations. Major properties of tropical peat forests are high in Water Contents (WC), Loss on Ignition (LOI) and Total Organic Carbon (TOC), and low in peat pH, Dry Bulk Density (DBD), and Total Nitrogen (TN). In this study, we investigated impacts of drainage and land use change on these properties. We collected peat samples from peat forests, logged over peat forest, industrial timber plantation, community agriculture, and oil palms. We used independent t-tests and oneway ANOVA to analyze mean differences of the research variables. We found that peat pH, DBD, and TN tend to increase. A significant decrease of C/N ratio in oil palm and agriculture sites importantly denotes a high rate of peat decompositions. Water contents, LOI, and TOC are relatively constants. We suggest that changes in pH, DBD, TN and atomic C/N ratio are important indicators for assessing tropical peat degradation. We infer that land use change from tropical peat forests into cleared and drained peats used for intensive timber harvesting, oil palms and industrial timber plantations in Indonesia has greatly degraded major ecological function of tropical peats as Carbon storage.

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Daňková, Jana, Tereza Majstríková e Pavel Mec. "Bonded Joints in Water-Repellent Timber Structures". Key Engineering Materials 714 (settembre 2016): 3–9. http://dx.doi.org/10.4028/www.scientific.net/kem.714.3.

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Water in liquid and gaseous form is the main factor which significantly affects degradation processes in the wood. The mechanism and rate of wooden degradation processes can be effectively influenced by appropriate methods and technologies for its protection. However new knowledge, based on the possibilities of application of modern physical and chemical analytical methods, confirms that most well-known and previously commonly used protective equipment damages wooden structure. Many chemical substances, which are included in preservatives such as organic and inorganic biocides, or also flame retardants, are declared to be environmentally unacceptable. Nowadays, environmentally friendly treatment technologies of wood have increased attention to the above reasons. Wooden treatment by silicones ranks among the technologies which repellent, fire resistant and corrosion effectiveness is demonstrated by many authors. This article presents results of the experimental study that deals with the mechanical properties of bonded joints in the wood treated by silicones.

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Soe, Khaing Thandar, e Youn Yeo-Chang. "Livelihood Dependency on Non-Timber Forest Products: Implications for REDD+". Forests 10, n. 5 (16 maggio 2019): 427. http://dx.doi.org/10.3390/f10050427.

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Deforestation and forest degradation are occurring continuously and posing serious threats to forests and people worldwide. In Myanmar, poor regulation and unsustainable extraction of non-timber forest products (NTFPs) is affecting millions of hectares of natural forests; overexploitation of forest resources is one of the main drivers of forest degradation. Although evidence shows that the extraction of NTFPs results in forest degradation, there have been few studies on what drives rural people to depend on NTFPs and how to address these drivers in terms of policies and measures. Policies and measures are nationally enacted policies and actions that countries undertake to address the causes of deforestation and forest degradation. This study identifies which factors determine the dependence on NTFPs in forest-dependent communities. From these factors, we derived policy implications for the main causes of overexploitation of NTFPs to provide suggestions for developing policies and measures in the design of national Reducing Emissions from Deforestation and Forest Degradation (REDD+) strategies. Focusing on the Taungoo District as a case of dependence on NTFPs by local communities, we conducted a qualitative and quantitative data collection procedure based on interviewing households in the local communities. NTFPs contributed the most to total household income and the main types of NTFPs exploited were charcoal making and bamboo selling. Households with lower education level, less agricultural land, less income from off-farm activities, lived under the poverty line or used only charcoal were more dependent on NTFPs in the study areas. Poverty and fuelwood usage were factors affecting NTFPs dependence for landowners while rice insufficiency, off-farm income and fuelwood usage most affected the NTFPs dependence for landless people. The results suggested that national strategies for REDD+ should take into account local features such as income opportunities and land tenure in order to make local people cooperate with the government to avoid deforestation and forest degradation.

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Parracha, João, Manuel Pereira, António Maurício, Paulina Faria, Daniel F. Lima, Marina Tenório e Lina Nunes. "Assessment of the Density Loss in Anobiid Infested Pine Using X-ray Micro-Computed Tomography". Buildings 11, n. 4 (17 aprile 2021): 173. http://dx.doi.org/10.3390/buildings11040173.

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The present study aims at evaluating the impact of anobiid damage on pine timber elements. Anobiid attack produces a diffuse damage of the elements with a set of tunnels in random directions and sizes, thus confusing quantification. Therefore, a method was developed based on X-ray micro-computed tomography (μ-XCT) to obtain, for naturally infested timber samples, an empirical correlation between lost material percentage (consumed by beetles) and timber apparent density (original, before degradation—OTD and residual, after degradation—RTD). The quantified density loss can then be used in further assessment of the structure. The results of the tests performed showed high correlation between original apparent density and lost material percentage (r2 = 0.60) and between residual apparent density and lost material percentage (r2 = 0.83), which confirms μ-XCT as a valuable tool to the required quantification. The loss of density results can be further applied on the definition of an assessment method for the evaluation of the residual strength of anobiids infested timber, thus contributing to reducing unnecessary replacement. The optimized procedure of the μ-XCT study for infested Maritime pine (Pinus pinaster) is presented and discussed in this article.

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Akapame, Clement Kojo. "The chase for legal timber: Developments in the commercial trade of timber in Ghana". Environmental Law Review 22, n. 3 (settembre 2020): 198–214. http://dx.doi.org/10.1177/1461452920934704.

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The quest for timber and timber resources and its corollary effects on forest degradation has in the last decade contributed to a series of concerted local and international interventions aimed at addressing the situation. These interventions have taken the character of domestic policies, international agreements and pacts and to some extent, domestic legislative reforms. The plethora of interventions have created a horde of laws and agreements with varying scopes and applications, multiple institutions with interlocked and overlapping responsibilities and uncoordinated and often undocumented practice in the commercial trade of timber. The focus of this article is to prod through the domestic and international legal and institutional architecture on the regulation of the trade of timber and timber resources. The article hopes to unearth the challenges in complying with these obligations and propose recommendations on the way forward.

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Più fonti

Tesi sul tema "Timber degradation"

Martin, W. "Recovery of impregnated gold from waste mine timber through biological degradation". Thesis, Cape Technikon, 2000. http://hdl.handle.net/20.500.11838/2156.

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Thesis (MTech (Chemical Engineering))--Cape Technikon, 2000.
The large quantities of wood chips produced at mines from damaged underground timber contain gold that cannot be completely recovered by cyanidation. A fungus that can degrade a portion of the wood matrix will allow the gold that was previously locked up, to come into contact with the cyanide solution during beneficiation, thereby improving recoveries. The fungus Phanerochaete chrysosporium produces enzymes that use the organic compounds found in lignin as substrate. Consequently, the fungus is able to selectively break down lignin, which is one of the major components of wood. Chips sampled from Vaal Reef Mine contained between 2 and 5 mg/kg gold. The main source of gold in the chips was determined to be impregnated gold-bearing ore and discrete gold particles. Direct cyanidation resulted in around 60 per cent recovery prior to biological treatment. Despite relatively high weight losses caused to the chips as a result of treatment with Phanerochaete chrysosporium gold recovery only increased 10 per cent after 4 weeks treatment compared to direct recovery without treatment.

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McGeachie, M. T., University of Western Sydney, College of Law and Business e of Construction Property and Planning School. "Characterisation of the Sydney region in relation to corrosion, timber decay risk factors and the corrosion of nails in timber in covered conditions". THESIS_CLAB_CPP_McGeachie_M.xml, 2001. http://handle.uws.edu.au:8081/1959.7/491.

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The aim of the study was to characterise the environment in the Sydney region in respect of atmospheric corrosivity, timber decay risk factors and the corrosion of nails in timber in covered conditions. The study reviewed contemporary research in this field, particularly in Australia, developing an understanding of the durability failure mechanisms for timber and nails in timber. The study looked at the effects of climatic aspects, pollutants, corrosion on timber decay risk factors. The study found that the levels of risk in terms of timber degradation, corrosion and nail corrosion were greatest adjacent to the coast and at marine sites.
Doctor of Philosophy (PhD)

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Jantan, Mohd Dahlan. "Chemical preservation of some refractory timber species of Malaysia". Thesis, University of Portsmouth, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310381.

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The treatability of six Malaysian timbers namely Red Balau (Shorea guiso), Kapur (Dryobafanops aromatica), Kasai (Pometia pinnata), Kulim (Scorodocarpus borneensis), Kempas (Koompassia malaccensis) and Keruing (Dipterocarpus grandiflorus) using the applied pressure processes (oscillating pressure, conventional Bethell and a modified Bethell process) was investigated. Treatments were carried out with a commercial water-borne copper-chromearsenic (CCA) preservative, known as Celcure-AP. The conventional Bethell process was the most effective method of wood treatment followed by the modified Bethell and the oscillating pressure process. While sufficient preservative retention and absorption was achieved in Kempas and Keruing to meet the Malaysian Standard MS 386 : 1986 specifications for exterior timber used in ground contact, the other four timbers - Red Balau, Kapur, Kasai and Kulim did not fulfil this requirement, even when treated at the most extreme treatment conditions. Using the three pressure processes, seasoning period and treatment time were found to have significant effects on preservative retention and penetration in all timber species. Investigations into the effect of three pretreatment procedures - steaming, incising and ponding to improve the treatability of the six timber species were carried out. Incising was the most effective pretreatment procedure in enhancing the treatability of these timbers. However, at the highest incising density employed (4,500 incisions/m2), it was still not possible to treat Red Balau, Kapur, Kasai and Kulim timber to achieve satisfactory target preservative retention and penetration. The less effective incising procedure was due mainly to the low incising density used. The possibility of improving the treatability of these four timber species further using higher incising densities and other methods of inCising pretreatment is discussed. Steaming, incising and ponding pretreatments had a pronounced effect on the strength properties of timbers based on reduction of their modulus of elasticity (M.D. E.), modulus of rupture (M.O.A.), compressive strength and hardness. The highest strength losses were observed in timbers that had been ponded for 6 months. Significant strength losses were also observed in incised and steamed timbers, but the magnitudes were lower than the 6 month ponding regime. This was attributed to low incising density and the short steaming period. The performance of Celcure-AP in the six timber species was evaluated in laboratory and field tests. In addition, a copper-azole formulation (Tanalith-3485) was also evaluated on Kempas timber. Laboratory tests involved exposure of treated wood blocks to five decay fungi - Pycnoporus sanguineus, Trametes versicolor, Coniophora puteana, Gloeophyllum trabeum and Oligoporus placenta. The less durable timbers - Kempas and Keruing needed a higher loading of Celcure-AP in order to give equal performance compared to the more durable timbers - Red Balau, Kapur, Kasai and Kulim. Based on copper retention in treated samples, a higher loading of Tanalith-3485 was required in Kempas to achieve comparable results to Celcure-AP treated samples. However, the concentration levels of Tanalith-3485 used in the present study were sufficient to afford protection to Kempas stakes exposed for 36 months in the field test. A longer exposure period is however, recommended for a full evaluation of timber/preservative combinations against wood deteriorating organisms under Malaysian conditions. In the field test, soft rot fungi were the main causal organisms in the attack of timbers in test site A (fungal test bed), while in test site B stake failure was due mainly to termite attack.

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Christin, Jérôme. "Système de fondation sur pieux bois : une technique millénaire pour demain". Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1105/document.

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La France possède un patrimoine très riche d'ouvrages d'art et de bâtiments fondés sur des pieux en bois. Les ponts construits sur la Loire, sur la Seine, le château de Chambord ou encore le Grand Palais à Paris en sont quelques exemples. Cependant, malgré un parc français important d'ouvrages bâtis sur des pieux en bois, le retour d'expérience sur la portance résiduelle et l'état de dégradation de leurs fondations est faible et non capitalisé. Les principaux objectifs de ce travail, qui s'intègre dans le projet Pieux Bois, sont d'une part, de définir une méthodologie d'analyse des fondations en bois des ouvrages visant à évaluer leur état de dégradation, et d'autre part, de proposer une méthode de dimensionnement des pieux en bois s'appuyant sur les caractéristiques pressiométriques des terrains. L'état de l'art réalisé dans le cadre de ce projet a permis d'identifier une centaine de ponts français construits sur des pieux en bois entre le Moyen-Âge et l'époque industrielle, principalement situés dans le lit des fleuves et de leurs affluents. Les désordres relevés sur ces ouvrages ainsi que les solutions de confortement mises en œuvre pour assurer leur pérennité ont été établis. La méthodologie d'analyse présentée dans un guide d'inspection des fondations en bois élaboré aux Pays-Bas a été validée lors de l'évaluation de l'état de dégradation des pieux de fondation d'un viaduc ferroviaire situé à proximité de Bordeaux. Les propriétés mécaniques de l'interface entre le sol (limon) et le bois ont été étudiées à partir d'une campagne d'essais en laboratoire à la boîte de cisaillement direct. Des essais de cisaillement d'interface avec le mortier et l'acier ont également été réalisés. L'influence de la rugosité des matériaux et de la teneur en eau du limon sur les propriétés de résistance d'interface a été examinée. Les essais de cisaillement en laboratoire ont été complétés par la réalisation de deux plots expérimentaux sur lesquels des pieux en bois ont été battus et chargés en compression. Les pieux ont été préalablement munis d'un système d'instrumentation accueillant un chapelet d'extensomètres amovibles. Les résultats de ces essais de chargement ont été intégrés dans une base de données d'essais de pieux en bois construite à partir de données publiées dans la littérature. La démarche mise en œuvre pour établir les règles pressiométriques présentées dans la nouvelle norme d'application nationale de l'Eurocode 7 a été reprise et modifiée. Les études statistiques menées à partir de cette base de données ont permis de proposer un modèle de calcul des résistances de pointe et de frottement des pieux en bois battus dans les argiles limons et les sables graves
Many buildings and bridges built on timber pile foundations still stand in France. The bridges on rivers “Loire” and “Seine”, the castle of Chambord, the “Grand Palais” in Paris are a few examples of French monuments founded on timber piles. However, despite a large number of buildings and bridges constructed in France, the feedback on the residual bearing capacity and the degradation of timber piles is scarce. The main objectives of this work, which is part of the “Pieux Bois” national research project, are, on the one hand, to define a methodology in order to analyze timber pile foundations degradation, and on the other hand, to propose a design method of timber piles based on the results obtained from pressuremeter tests. The state of the art made in the national project identified about one hundred French bridges built on timber piles between the Middle Ages and the industrial era. They are mainly located in basins of rivers. Pathologies were observed on bridges and reinforcement solutions were implemented in order to avoid any future problems. The methodology for the inspection of timber pile foundations given in the Dutch guide was applied to investigate the degradation of timber piles under an existing railway bridge near Bordeaux. Series of laboratory tests were carried out on soil (silt) and wood with a direct shear box. The mechanical properties of the interface were studied. Shear tests between mortar, steel and silt were also carried out. The influence of material roughness and silt moisture content on the shear strength properties of the interface was examined. In addition, timber piles were driven and loaded on two experimental sites. The timber piles were instrumented with removable extensometers. The results of these load tests were included in a database which contained timber piles loading test results published in literature. The approach adopted to establish the design method of deep foundation based on the results obtained from pressuremeter tests described in the new national standard for application of Eurocode 7 was modified. A new model of calculation of timber piles shaft and base resistance driven in clay silt and sand gravels was determined with statistical studies from this database

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Simson, Scott Andrew. "Development of a model for railway track maintenance planning". Thesis, Queensland University of Technology, 1999. https://eprints.qut.edu.au/36116/1/36116_Simson_1999.pdf.

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Track maintenance represents over 20 percent of Australian railway operating costs. Thus there is considerable incentive for rail corporations to reduce their maintenance costs. There is considerable research directed at improving track structures and maintenance techniques to reduce the track maintenance expenditure. However, there is little work on the planning of track maintenance that can be applied to Australian railway operations. This research reviews maintenance planning and finds that models currently available are empirical models reliant mainly on historical track condition data from specific rail organisations. No such models are yet in use Australian railway operations. Leading models utilise expert systems to decide maintenance activities rather than optimise the net benefits of maintenance. As such, these models are ineffective at assessing what if scenarios of changed track operating conditions. Internationally, current maintenance practice is to plan maintenance on professional judgement without the use of models to aid decisions. Currently, only a minority of larger rail corporations record sufficient track and maintenance data needed for maintenance planning modeling. A new track maintenance model has been formulated based on a mechanistic track degradation approach. This allows the model to operate without historical track maintenance condition data and hence utilise a minimal amount of track maintenance data. The model assesses the net benefit of maintenance by simulating the costs of planned and unplanned maintenance, as well as train operating costs as they are affected by track condition. A prototype computer program has been developed that has shown that the model is capable of assessing a cost efficient intervention level for tamping and resleepering maintenance. The model's independence from historical data means it is applicable to any rail operator and is capable of assessing what if scenarios on the impact of changed track, traffic or cost conditions. The model has been subjected to testing that has identified areas for its further development. These areas are the modeling of defective sleeper clusters and of sleeper ages, also the development and inclusion of a ballast degradation and maintenance sub-model. Further work for the developed prototype computer application include improving the program efficiency, expanding the number of iteration cycles used in the simulation and recording a track asset value during degradation and maintenance of the track

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Lu, Jin 1959. "Degradation processes and related reliability models". Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39952.

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Reliability characteristics of new devices are usually demonstrated by life testing. When lifetime data are sparse, as is often the case with highly reliable devices, expensive devices, and devices for which accelerated life testing is not feasible, reliability models that are based on a combination of degradation and lifetime data represent an important practical approach. This thesis presents reliability models based on the combination of degradation and lifetime data or degradation data alone, with and without the presence of covariates. Statistical inference methods associated with the models are also developed.
The degradation process is assumed to follow a Wiener process. Failure is defined as the first passage of this process to a fixed barrier. The degradation data of a surviving item are described by a truncated Wiener process and lifetimes follow an inverse Gaussian distribution. Models are developed for three types of data structures that are often encountered in reliability studies, terminal point data (a combination of degradation and lifetime data) and mixed data (an extended case of terminal point data); conditional degradation data; and covariate data.
Maximum likelihood estimators (MLEs) are derived for the parameters of each model. Inferences about the parameters are based on asymptotic properties of the MLEs and on the likelihood ratio method. An analysis of deviance is presented and approximate pivotal quantities are derived for the drift and variance parameters. Predictive density functions for the lifetime and the future degradation level of either a surviving item or a new item are obtained using empirical Bayes methods. Case examples are given to illustrate the applications of the models.

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Addai, Obeng A. "Regulated Feedback Networks with Degradation". Youngstown State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1444046732.

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Daheur, Jawad. "Le Parc à bois de l'Allemagne : course aux ressources et hégémonie commerciale dans les bassins de la Vistule et de la Warta (1840-1914)". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAG041.

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Cette étude traite des stratégies allemandes pour prendre le contrôle des ressources en bois d’oeuvre dans l’espace baltique entre 1840 et 1914. Centré sur le commerce dans les bassins de la Vistule et de la Warta, elle montre comment la puissance allemande montante y est parvenue à sécuriser un accès bon marché et stable aux ressources ligneuses. Les firmes établirent leur domination commerciale en développant des technologies de transport et en renforçant leurs capacités financières et organisationnelles, tout cela en tirant profit des faiblesses économiques et politiques locales. En analysant les dimensions écologiques et économiques de l’extraction et de la transformation des bois, la thèse souligne le rôle joué par les importations dans la préservation des forêts allemandes. Elle présente également les impacts de cette évolution sur les populations locales et l’environnement. En conclusion, la thèse plaide pour une histoire authentiquement globale de la forêt allemande
This thesis deals with the German attempts to take control over timber resources in the Baltic area between 1840 and 1914. Focused on the trade in the Vistula and Warta river basins, it shows how the rising German economy managed to make the local forests into its backyard by securing cheap and stable access to timber resources. German firms progressively achieved trade dominance by developing transport technologies and reinforcing their financial and organizational capacities. They also managed to take advantage of the local economic and political weaknesses. Through ecological and economic explanation of timber extraction and processing, the thesis underlines the role played by foreign timber in the preservation of the German forests. It also describes the impact of this process on the local population and environment. Finally, the thesis advocates for a truly global history of the German forest

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Watson, William H. "DNA Degradation as an Indicator of Post-Mortem Interval". Thesis, University of North Texas, 2010. https://digital.library.unt.edu/ark:/67531/metadc30523/.

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The question of post-mortem interval (PMI) or time since death is often the most sought after piece of information associated with a medical death investigation. Based on the observation that DNA degradation disproportionately affects the analysis of larger genetic loci, it was proposed that DNA degradation, as a result of autolysis or putrefaction, could prove suitable as a potential rate-of-change indicator of PMI. Nine randomly amplified polymorphic DNA (RAPD) analysis primers and three sets of directed amplification primers were evaluated to determine their suitability for use in assessing the degree of DNA fragmentation in tissue samples. They were assessed for amplicon specificity, total DNA target sensitivity, allele monomorphism and the observance of degradation-based profile changes. Markers meeting the requisite criteria were then used to assess a range samples degraded under controlled and uncontrolled conditions. Tissue samples collected from seven domestic pigs (Sus scrofa) were incubated under controlled laboratory or uncontrolled field conditions to produce samples simulating those potentially collected in a forensic case. DNA samples isolated from these specimens were then analyzed at those loci which had been determined to meet the requisite criteria. Collectively, data generated from these analyses indicate that genetic profiles generated by this approach can provide information useful for estimating the post-mortem interval, with the locus and amplicons used being most useful during the first 72 hours after death.

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Olsen, Peter A. "Shear Modulus Degradation of Liquefying Sand: Quantification and Modeling". BYU ScholarsArchive, 2007. https://scholarsarchive.byu.edu/etd/1214.

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A major concern for geotechnical engineers is the ability to predict how a soil will react to large ground motions produced by earthquakes. Of all the different types of soil, liquefiable soils present some of the greatest challenges. The ability to quantify the degradation of a soil's shear modulus as it undergoes liquefaction would help engineers design more reliably and economically. This thesis uses ground motions recorded by an array of downhole accelerometers on Port Island, Japan, during the 1995 Kobe Earthquake, to quantify the shear modulus of sand as it liquefies. It has been shown that the shear modulus of sand decreases significantly as it liquefies, apparently decreasing in proportion to the increasing excess pore water pressure ratio (Ru). When completely liquefied, the shear modulus of sand (Ru = 1.0) for a relative density of 40 to 50% is approximately 15% of the high-strain modulus of the sand in its non-liquefied state, or 1% of its initial low-strain value. Presented in this thesis is an approach to modeling the shear modulus degradation of sand as it liquefies. This approach, called the "degrading shear modulus backbone curve method" reasonably predicts the hysteretic shear stress behavior of the liquefied sand. The shear stresses and ground accelerations computed using this method reasonably matches those recorded at the Port Island Downhole Array (PIDA) site. The degrading shear modulus backbone method is recommended as a possible method for conducting ground response analyses at sites with potentially liquefiable soils.

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Libri sul tema "Timber degradation"

Barbier, Edward B. Timber trade, trade policies and environmental degradation. London: IIED/UCL London Environmental Economics Centre, 1992.

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Lewis, Terence. Developing timber harvesting prescriptions to minimize site degradation. Victoria, B.C: BC Ministry of Forests, 1991.

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Paul, Jeanrenaud Jean, e Sullivan Francis, a cura di. Bad harvest?: The timber trade and the degradation of the world's forests. London: Earthscan, 1995.

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Reeves, Derrick. Detrimental soil disturbance associated with timber harvest systems on national forests in the Northern Region. Fort Collins, CO: U.S. Dept. of Agriculture, Forest Service, Rocky Mountain Research Station, 2011.

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Borgå, Peter. Chemical and microbial interactions in environmental degradation processes: Implications on water storage of timber and decomposition of peat. Uppsala: Swedish University of Agricultural Sciences, Dept. of Chemistry, 1994.

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Kartodihardjo, Hariadi. The impact of sectoral development on natural forest conversion and degradation: The case of timber and tree crop plantations in Indonesia. Bogor, Indonesia: Center for International Forestry Research, 2000.

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Mouriki, Aliki. Flexible working: Towards further degradation of work, or escaping from stereotypes? Coventry: Industrial Relations Research Unit, University of Warwick, 1994.

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Mouriki, Aliki. Flexible working: Towards further degradation of work, or escaping from stereotypes? Coventry: Industrial Relations Research Unit, School of Industrial and Business Studies, University of Warwick, 1994.

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Voake, Steve. The dreamwalker's child. New York: Bloomsbury Children's Books, 2006.

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Voake, Steve. The dreamwalker's child. New York: Bloomsbury, 2007.

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Capitoli di libri sul tema "Timber degradation"

Desch, H. E., e J. M. Dinwoodie. "Degradation of Timber in Service". In Timber Structure, Properties, Conversion and Use, 233–37. London: Macmillan Education UK, 1996. http://dx.doi.org/10.1007/978-1-349-13427-4_18.

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Gale, Fred P. "Tropical Deforestation and Rainforest Degradation". In The Tropical Timber Trade Regime, 42–60. London: Palgrave Macmillan UK, 1998. http://dx.doi.org/10.1057/9780230371521_4.

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Gale, Fred P. "Explaining Tropical Deforestation and Rainforest Degradation". In The Tropical Timber Trade Regime, 204–26. London: Palgrave Macmillan UK, 1998. http://dx.doi.org/10.1057/9780230371521_12.

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Shanbhag, Rashmi Ramesh, R. Sundararaj e M. V. Rao. "Natural Durability of Timber in Terrestrial and Marine Realms of India: A Contrasting Feature". In Science of Wood Degradation and its Protection, 439–78. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-8797-6_13.

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Narasimhamurthy. "Preservation of Engineered Wood Composites (Solid Wood Plywood, Blockboards/Flush Doors) Made from Plantation Timbers". In Science of Wood Degradation and its Protection, 625–46. Singapore: Springer Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-8797-6_18.

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Yanda, Pius Z., Edmund B. Mabhuye, Anselm R. Mwajombe e Namkunda Johnson. "Community livelihoods and ecosystem integrity in makere forest reserve, western Tanzania." In Climate change impacts and sustainability: ecosystems of Tanzania, 194–213. Wallingford: CABI, 2020. http://dx.doi.org/10.1079/9781789242966.0194.

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Abstract Wealth creation and poverty alleviation processes in the forest-bounded areas entail the use of such forests to a greater extent. Studies elsewhere show that there is often a tendency to use such forests until they are depleted before technology comes in to improve livelihoods. In this chapter, we examine community livelihoods in relation to ecosystem integrity for communities surrounding the Makere Forest Reserve, particularly socio-economic characteristics of communities, their links to forest utilization and implications for ecosystem integrity. We used mixed methods to collect data: (i) a household questionnaire; (ii) focus group discussions; (iii) key informant interviews; and (iv) a literature review, backed up with satellite imagery. Quantitative and qualitative data collected were subjected to statistical and non-statistical tests, respectively, with the use of Statistical Package for Social Sciences (SPSS) computer software for quantitative data analysis. Livelihood activities in the area include shifting cultivation, livestock keeping, firewood fetching, charcoal making, harvesting timber and illegal logging. The motive for such forest exploitation is both for meeting household needs as well as for wealth accumulation. Forest users take part in such activities regardless of the distance they have to travel from their villages to come to the forest areas. We found education is an integral part of wealth status, but had nothing to do in terms of improving livelihood activities for ecosystem integrity. The absence of livelihood diversification of farm-related activities penetrates into weak forest governance strategies resulting in proliferation of deforestation and forest degradation. To maintain forest integrity, integrated approaches in forest management and alternative livelihood activities are needed such as beekeeping, fishing and modernized livestock keeping. These activities have the potential to increase household food and income and alleviate poverty levels without compromising ecosystem integrity.

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Werner, Brian T., Bonnie R. Antoun e George B. Sartor. "Thermal Degradation of Extension Springs". In Challenges in Mechanics of Time Dependent Materials, Volume 2, 1–9. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-22443-5_1.

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Niklaus, Markus, Christina Eisfelder, Ursula Gessner e Stefan Dech. "Land Degradation in South Africa – A Degradation Index Derived from 10 Years of Net Primary Production Data". In Remote Sensing Time Series, 247–67. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15967-6_12.

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Barnat, Jiří, Ivana Černá e Jana Tůmová. "Timed Automata Approach to Verification of Systems with Degradation". In Mathematical and Engineering Methods in Computer Science, 84–93. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-25929-6_8.

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Couallier, Vincent. "A Competing Risks Model for Degradation and Traumatic Failure Times". In Statistical Models and Methods for Biomedical and Technical Systems, 83–93. Boston, MA: Birkhäuser Boston, 2008. http://dx.doi.org/10.1007/978-0-8176-4619-6_7.

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Atti di convegni sul tema "Timber degradation"

Hueto Escobar, Alicia, Fernando Vegas, Camilla Mileto e María Lidón de Miguel. "State of conservation of half-timbered walls in Burgos (Spain): Quantitative analysis of material and structural degradation". In HERITAGE2022 International Conference on Vernacular Heritage: Culture, People and Sustainability. Valencia: Universitat Politècnica de València, 2022. http://dx.doi.org/10.4995/heritage2022.2022.15051.

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The systematic data collection and quantitative analysis of 225 half-timbered walls found in the province of Burgos made it possible to reach conclusions on the frequency and scope of 27 phenomena of material degradation and 11 types of structural lesions. Almost the entirety of the sample analysed presents some degree of material degradation, mostly slight atmospheric lesions such as surface atmospheric erosion and chromatic alteration and dehydration of the timber. A greater vulnerability to structural lesions, particularly structural deformation, has been observed in this type of wall. The results presented in this text form the basis for understanding the conservation and restoration needs of half-timbered walls, given the indispensability of knowledge of the most common degradation systems.

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Nunes, Lina, João L. Parracha, Paulina Faria, Pedro Palma, António Maurício e Manuel F. C. Pereira. "Towards an assessment tool of anobiid damage of pine timber structures". In IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2019. http://dx.doi.org/10.2749/guimaraes.2019.1734.

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The safety assessment of old timber structures is an important issue, due to the long-term behaviour of wood and the structural complexity found in some older constructions. If the structure is degraded due to the action of wood-boring insects, the complexity of the analysis increases. The objective of this work was to evaluate the impact of anobiid beetles’ attack on old timber structures. One major difficulty concerns the assessment of the effective strength of timber cross sections with anobiid damage. This happens because beetles’ attack produces a diffuse damage, with a set of tunnels in random directions.Compression parallel to the grain and screw withdrawal tests have been made in pine naturally degraded by anobiids (natural samples – NS) and in pine with artificially bored galleries (artificial samples – AS). 216 samples were tested (97 to screw withdrawal and 119 to compression). The original density of NS is unknown. For AS, 0.7% and 1.4% of lost material was simulated. Screw withdrawal and compression force values were related with density for AS (𝑟2 = 0.52 for compression; 𝑟2 = 0.56 for screw withdrawal). The results show a significant variation between the average results obtained both to the compression (42.9 MPa – AS; 27.2 MPa – NS) and to the pull- out (3.4 KN – AS; 2.2 KN – NS).Although there was an attempt to simulate the degradation by woodworm with the AS, with known density, the test results were significantly different from those obtained for the NS, where the percentage of lost material is unknown, as well as initial density. Thus, knowledge of residual timber density seems to be paramount to know the level of deterioration and the real impact of this on a structure. Further developments on this issue are ongoing.

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Gao, Yin, e Mike McHenry. "Simulation of the Thermal Effects on Engineered Polymer Composite Ties". In 2019 Joint Rail Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/jrc2019-1299.

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Engineered polymer composite (EPC) ties offer a potential alternative to solid sawn timber ties. These materials are especially attractive for use in regions where wood is susceptible to degradation by moisture and decay organisms. However, recent research at the Transportation Technology Center’s (TTC) Facility for Accelerated Service Testing (FAST) in Pueblo, CO, found that track supported by EPC ties experienced more gage widening variation due to temperature changes than track supported by wood ties. Specifically, the track gage was about 0.2-in. wider in the afternoon than that in the morning on the EPC tie tracks. It is believed that the direct sunlight in the afternoon makes the top surface of the tie expand more than the other parts of the tie, thereby causing the EPC ties to bend and widen track gage. Another observation related to the EPC thermal bending effect is changes to the ballast support condition. When temperatures are cooler, EPC ties tend to experience a center-bound ballast support condition, therefore generating more bending stress on the ties. This paper presents results from computer simulations of the thermal behavior of EPC ties. Future study will focus on field testing to further understand the thermal effects in support of recommendations on the use of EPC ties.

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Fedorova, Natalya, e D. Arilov. "COMPARATIVE ANALYSIS OF VEGETATION CHANGES OF RANGELANDS IN ANTHROPOGENIC LOAD FOR EXAMPLE TSELINNY REGION'S NAYNTAKHINSKOE RURAL MUNICIPALITY OF KALMYKIA". In Land Degradation and Desertification: Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1683.978-5-317-06490-7/91-95.

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In article the comparative analysis of geobotanical surveys for 1987 and the years 2012-2019 on-site rangeland Tselinny region's Nayntakhinskoe SMO Republic of Kalmykia. It was found that over a 32-year period of time in all 8 key areas there were changes in the direction of deterioration in the following indicators: stages of pasture digression, phytomass, change of dominant species, projective cover of plant communities, indicating the deterioration and irrational use of pastures at the present time.

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Botros, K. K., C. Hartloper, H. Golshan e D. Rogers. "Assessment of Recoverable vs Unrecoverable Degradations of Gas Turbines Employed in Five Natural Gas Compressor Stations". In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42078.

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Gas Turbines (GT), like other prime movers, experience wear and tear over time, resulting in decreases in available power and efficiency. Further decreases in power and efficiency can result from erosion and fouling caused by the airborne impurities the engine breathes in. To counteract these decreases in power and efficiency, it is standard procedure to ‘wash’ the engine from time to time. In compressor stations on gas transmission systems, engine washes are performed off-line and are scheduled in such intervals to optimize the maintenance procedure. This optimization requires accurate prediction of the performance degradation of the engine over time. A previous paper demonstrated a methodology for evaluating various components of the GT gas path, in particular the air compressor side of the engine since it is most prone to fouling and degradation. This methodology combines Gas Path Analysis (GPA) to evaluate the thermodynamic parameters over the engine cycle followed by parameter estimation based on the Bayesian Error-in-Variable Model (EVM) to filter the data of possible noise due to measurement errors. The methodology quantifies the engine-performance degradation over time, and indicates the effectiveness of each engine wash. In the present paper, the methodology was extended to assess both recoverable and un-recoverable degradations of five gas turbine engines employed on TransCanada’s pipeline system in Canada. These engines are: three GE LM2500+, one RR RB211-24G, and one GE LM1600 gas turbines. Hourly data were collected over the past four years, and engine health parameters were extracted to delineate the respective engine degradations. The impacts of engine loading, site air quality conditions and site elevation on engine-air-compressor isentropic efficiency are compared between the five engines.

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Vieira, A. C., J. C. Vieira, R. M. Guedes, A. T. Marques, Alberto D’Amore, Domenico Acierno e Luigi Grassia. "DEGRADATION CHARACTERIZATION OF ALIPHATIC POLYESTERS—IN VITRO STUDY". In IV INTERNATIONAL CONFERENCE TIMES OF POLYMERS (TOP) AND COMPOSITES. AIP, 2008. http://dx.doi.org/10.1063/1.2989044.

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Shinkarenko, Stanislav, Viktoria Doroshenko e Asel Berdengalieva. "STEPPE FIRE DYNAMICS IN THE SOUTH-EAST OF THE EUROPEAN PART OF RUSSIA". In Land Degradation and Desertification: Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1685.978-5-317-06490-7/100-103.

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The paper presents the results of geoinformation mapping of burned areas in zonal landscapes of the Astrakhan, Volgograd regions and the Republic of Kalmykia for 1998-2019. In total, over the studied period, more than 6 million hectares were covered by fire, more than 15 thousand fires were identified. The total burnt area, excluding recurrence, is more than 15 million hectares. Some areas have burned out up to 11-14 times in 20 years.

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Mashtykov, Kirill, e Elvira Dedova. "GEOECOLOGICAL ASSESSMENT OF PASTURE PHYTOCENOSES IN THE DESERT ZONE OF THE REPUBLIC OF KALMYKIA". In Land Degradation and Desertification: Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1676.978-5-317-06490-7/62-65.

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Based on long-term monitoring, the geoecological assessment of pasture phytocenoses in the desert zone of the Republic of Kalmykia under the influence of anthropogenic and climatic factors is given. It is established that excessive pasture load leads to degradation processes of vegetation and soil cover: a wide spread of explerents ( Eragrostis minor, Amaranthus albus ), depletion of the floral composition by 2 times, a decrease in productivity and feed value of pastures, an increase in the area of flown Sands.

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Matichenkov, V. "REDUCTION OF GREENHOUSE GASES EMISSION UNDER SILICON FERTILIZER APPLICATION". In Land Degradation and Desertification: Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1701.978-5-317-06490-7/165-169.

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The application of Si fertilizer is example of “green” low emission technology. The using of biochemical active forms of Si allow to reduce the greenhouse gases emission from cultivated soils, increase the carbon content in soil matrix, increase cultivated plants resistance to abiotic stresses and increase the quality and quantity of crop. Our investigations have sowed the presence of monosilicic acid in soil provide the reduction of N2O emission in 1.6-2 times because the denitrification process in such soil are complete with final formation of N2. The application of Si fertilizer increased the rice crop on 5-55% with carbon sequestration up to 15 t/ha of CO2 during one season.

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Ilinskaya, Izida, Olga Bezuglova e Yuriy Litvinov. "ASSESSMENT OF THE ARIDIZATION OF THE SOUTH-EAST TERRITORY ROSTOV REGION IN DYNAMICS". In Land Degradation and Desertification: Problems of Sustainable Land Management and Adaptation. LLC MAKS Press, 2020. http://dx.doi.org/10.29003/m1698.978-5-317-06490-7/152-155.

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Based on the analysis of a long series of observations of meteorological parameters, a comparative assessment of the indicators of aridity in the South-East of the Rostov region in terms of time has been carried out. A general tendency for the increase in the degree of climate aridization was established.

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Rapporti di organizzazioni sul tema "Timber degradation"

Nobre, Carlos, Julia Arieira e Nathália Nascimento. Amazonian Forest: The Products of Agroecological Systems: Considerations about the Natural Forest and Economic Exploitation for its Conservation and How to Develop Sustainable Agroforestry Systems that Induce the Reduction of Deforestation. Inter-American Development Bank, luglio 2021. http://dx.doi.org/10.18235/0003693.

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This study demonstrates that the economic activity of the Amazon's natural forest has great potential yet to be developed when considering Non-Timber Forest Products (NTFPs) and those coming from agro-ecosystems (SAFs). Preliminary financial analyzes, in systems that are still incipient, point to a great potential for profitability of these alternative systems compared to traditional activities such as soybean and livestock farming, with the advantage of being conducted without degradation and deforestation, allowing the continuation with the support of the Amazonian ecological system. More research is needed to scale successful cases and more “dialogue” between the models of modern agriculture and the traditional knowledge to reach an integrated natural forest management system.

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Bakhtiari, Sasan. Task 1. Monitoring real time materials degradation. NRC extended In-situ and real-time Monitoring. Office of Scientific and Technical Information (OSTI), marzo 2012. http://dx.doi.org/10.2172/1252705.

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Baker, Sarah E., Kevin W. Bowyer, Patrick J. Flynn e P. Jonathon Phillips. Empirical evidence for iris match score degradation with time lapse in ICE 2006. Gaithersburg, MD: National Institute of Standards and Technology, 2009. http://dx.doi.org/10.6028/nist.ir.7630.

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Kimura, Mineo, Mitio Inokuti, Ken-ichi Kowari, M. A. Dillon e A. Pagnamenta. Time-dependent aspects of electron degradation: 4, Subexcitation electrons in nitrogen and carbon dioxide. Office of Scientific and Technical Information (OSTI), gennaio 1988. http://dx.doi.org/10.2172/5336660.

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Schutt, Timothy, e Manoj Shukla. Predicting the impact of aqueous ions on fate and transport of munition compounds. Engineer Research and Development Center (U.S.), agosto 2021. http://dx.doi.org/10.21079/11681/41481.

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A model framework for natural water has been developed using computational chemistry techniques to elucidate the interactions between solvated munition compounds and eight common ions in naturally occurring water sources. The interaction energies, residence times, coordination statistics, and surface preferences of nine munition related compounds with each ion were evaluated. The propensity of these interactions to increase degradation of the munition compound was predicted using accelerated replica QM/MM simulations. The degradation prediction data qualitatively align with previous quantum mechanical studies. The results suggest that primary ions of interest for fate and transport modeling of munition compounds in natural waters may follow the relative importance of SO₄²⁻, Cl⁻ ≫ HCO₃⁻, Na⁺, Mg²⁺ > Ca²⁺, K⁺, and NH₄⁺.

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McCoy, B. J., e G. Madras. Degradation kinetics of polymers in solution: Time-dependence of molecular weight distributions. [Quarterly report, January--March 1996]. Office of Scientific and Technical Information (OSTI), febbraio 1996. http://dx.doi.org/10.2172/382447.

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Morrison, Mark, Joshuah Miron, Edward A. Bayer e Raphael Lamed. Molecular Analysis of Cellulosome Organization in Ruminococcus Albus and Fibrobacter Intestinalis for Optimization of Fiber Digestibility in Ruminants. United States Department of Agriculture, marzo 2004. http://dx.doi.org/10.32747/2004.7586475.bard.

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Improving plant cell wall (fiber) degradation remains one of the highest priority research goals for all ruminant enterprises dependent on forages, hay, silage, or other fibrous byproducts as energy sources, because it governs the provision of energy-yielding nutrients to the host animal. Although the predominant species of microbes responsible for ruminal fiber degradation are culturable, the enzymology and genetics underpinning the process are poorly defined. In that context, there were two broad objectives for this proposal. The first objective was to identify the key cellulosomal components in Ruminococcus albus and to characterize their structural features as well as regulation of their expression, in response to polysaccharides and (or) P AA/PPA. The second objective was to evaluate the similarities in the structure and architecture of cellulosomal components between R. albus and other ruminal and non-ruminal cellulolytic bacteria. The cooperation among the investigators resulted in the identification of two glycoside hydrolases rate-limiting to cellulose degradation by Ruminococcus albus (Cel48A and CeI9B) and our demonstration that these enzymes possess a novel modular architecture specific to this bacterium (Devillard et al. 2004). We have now shown that the novel X-domains in Cel48A and Cel9B represent a new type of carbohydrate binding module, and the enzymes are not part of a ceiluiosome-like complex (CBM37, Xu et al. 2004). Both Cel48A and Cel9B are conditionally expressed in response to P AA/PPA, explaining why cellulose degradation in this bacterium is affected by the availability of these compounds, but additional studies have shown for the first time that neither PAA nor PPA influence xylan degradation by R. albus (Reveneau et al. 2003). Additionally, the R. albus genome sequencing project, led by the PI. Morrison, has supported our identification of many dockerin containing proteins. However, the identification of gene(s) encoding a scaffoldin has been more elusive, and recombinant proteins encoding candidate cohesin modules are now being used in Israel to verify the existence of dockerin-cohesin interactions and cellulosome production by R. albus. The Israeli partners have also conducted virtually all of the studies specific to the second Objective of the proposal. Comparative blotting studies have been conducted using specific antibodies prepare against purified recombinant cohesins and X-domains, derived from cellulosomal scaffoldins of R. flavefaciens 17, a Clostridium thermocellum mutant-preabsorbed antibody preparation, or against CbpC (fimbrial protein) of R. albus 8. The data also suggest that additional cellulolytic bacteria including Fibrobacter succinogenes S85, F. intestinalis DR7 and Butyrivibrio fibrisolvens Dl may also employ cellulosomal modules similar to those of R. flavefaciens 17. Collectively, our work during the grant period has shown that R. albus and other ruminal bacteria employ several novel mechanisms for their adhesion to plant surfaces, and produce both cellulosomal and non-cellulosomal forms of glycoside hydrolases underpinning plant fiber degradation. These improvements in our mechanistic understanding of bacterial adhesion and enzyme regulation now offers the potential to: i) optimize ruminal and hindgut conditions by dietary additives to maximize fiber degradation (e.g. by the addition of select enzymes or PAA/PPA); ii) identify plant-borne influences on adhesion and fiber-degradation, which might be overcome (or improved) by conventional breeding or transgenic plant technologies and; iii) engineer or select microbes with improved adhesion capabilities, cellulosome assembly and fiber degradation. The potential benefits associated with this research proposal are likely to be realized in the medium term (5-10 years).

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Swanson, David. Stability of ice wedges in Alaska's Arctic National Parks, 1951-2019. National Park Service, maggio 2022. http://dx.doi.org/10.36967/nrr-2293324.

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Ice-wedge polygons are a striking and widespread feature of the arctic landscape. Ice wedges are vulnerable to thaw because they are nearly pure ice bodies near the surface, with little insulating overlying material. Ice-wedge polygon monitoring is a part of the permafrost monitoring program for the National Park Services Arctic Inventory and Monitoring Network (ARCN, the five National Park units in northern Alaska). The present report is a re-analysis of ice-wedge condition in three study areas, based on satellite images taken in 2019 and 2020 (sampling episode 3). Results are compared to previous analyses based on aerial photographs from 1950-51 (episode 1) and satellite images from 2006-2009 (episode 2). Significant ice-wedge degradation occurred between sampling episodes 1 and 2 in one of the study areas (in Kobuk Valley National Park, KOVA). Sampling episode 3 revealed relatively minor changes from episode 2 in all three areas. This is somewhat surprising given the record warm temperatures that occurred between sampling episodes 2 and 3. Apparently the recent warming did not cross any thresholds that would trigger immediate and widespread visible changes in ice wedges, or insufficient time has elapsed since the recent onset of warmer temperatures in 2014. However, the effects of previous ice-wedge degradation continued to be manifested in new drainage channels that formed by linkage of pits from previous ice-wedge degradation. The Noatak National Preserve (NOAT) study area was affected by wildfires in 1977 and 2010, and comparison of burned to unburned areas in subsequent sampling episodes failed to show significant new ice-wedge degradation brought about by these fires.

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Moores, Lee, Stacy Jones, Garrett George, David Henderson e Timothy Schutt. Photo degradation kinetics of insensitive munitions constituents nitroguanidine, nitrotriazolone, and dinitroanisole in natural waters. Engineer Research and Development Center (U.S.), settembre 2021. http://dx.doi.org/10.21079/11681/41900.

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Abstract (sommario):

Herein the matrix effects on the kinetics of aqueous photolysis for the individual munitions constituents of IMX-101: nitroguanidine (NQ), dinitroanisole (DNAN), and nitrotriazolone (NTO) are reported along with the environmentally relevant kinetics and quantum yields. Photolysis potentially represents a major degradation pathway for these munitions in the environment and further understanding the complex matrices effects on photolytic kinetics was needed. Aqueous systems are of particular interest due to the high solubility of NQ (3,800 ppm) and NTO (16,642 ppm) compared to the traditional munitions trinitrotoluene (TNT, 100.5 ppm) and 1,3,5-trinitro-1,3,5-triazine (RDX, 59.9 ppm). Environmental half-lives (and quantum yields) were found to be 0.44 days, 0.83 days, and 4.4 days for NQ, DNAN, and NTO, respectively, under natural sunlight. In laboratory experiments using nominally 300 nm bulbs in a merry-go-round style reactor in DI water the relative rate of photolysis for the three munitions constituents followed the same order NQ > DNAN > NTO, where DNAN and NTO reacted 57 and 115 times more slowly, respectively, than NQ. In the various environmentally relevant matrices tested in the laboratory experiments NQ was not significantly affected, DNAN showed a faster degradation with increasing ionic strength, and NTO showed a modest salinity and pH dependence on its rate of photolysis.

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Wolfe, S. A., H. B. O'Neill, C. Duchesne, D. Froese, J M Young e S. V. Kokelj. Ground ice degradation and thermokarst terrain formation in Canada over the past 16 000 years. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329668.

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Thermokarst results from thawing of excess ground ice in permafrost sediments. Thermokarst processes and landforms are controlled by ground ice type, amount and distribution, as well as the patterns of ground ice loss over time. Recent acceleration of varied thermokarst processes across diverse Canadian permafrost terrains make for a challenging task in predicting landscape-scale thaw trajectories. Using existing ground ice models, we examined the modelled amounts and spatial extent of ground ice loss relative to ground ice maxima in the last ca. 16 ka BP for relict, segregated and wedge ice. We relate observed thermokarst features to the nature of ground ice development and loss in different environments (cold continuous permafrost, discontinuous permafrost, and no current permafrost). In cold, continuous permafrost areas where ground ice loss has been limited over the last 16 ka BP, thermokarst processes include active layer detachments and slumps in segregated and relict ice, gullying and ponding in ice wedge troughs, and the cyclical development of shallow thermokarst ponds in segregated ice. With ground ice loss in discontinuous permafrost, thermokarst processes are wide-ranging. Slumps, subsidence, and collapse of lithalsas, palsas and peat plateaus occur from thawing of segregated ice, thermokarst ponds from melting wedge and segregated ice, and involuted terrain from melting and creep of relict or segregated ice. In former permafrost terrain, evidence of thermokarst includes former ice wedge polygons, collapsed lithalsas, and irregular hummocky terrain. The relations between modelled ground ice loss and observed thermokarst landscapes assist in understanding present-day processes and in predicting future thermokarst landform evolution with a changing climate.

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