PDF superior Study of the wear resistance due to sliding of tungsten carbide coatings.

Study of the wear resistance due to sliding of tungsten carbide coatings.

Study of the wear resistance due to sliding of tungsten carbide coatings.

In this work tungsten carbide coatings have been deposited onto AISI/SAE 1018 steels by using a thermal spray process and by setting three types of flames viz. reducing, neutral and oxidizing. Results indicated that percent of porosity is lower in specimens made upon reducing type of flame and the microstructure is composed of semi- molten and un-molten particles, non-lamellar structure, and with presence of oxide stringers. Hardness measurements upon reducing condition resulted above 1000Hv due to presence of hard particles of WC and W 2 C. Moreover, the sliding wear resistance upon reducing condition was acceptable according to the analysis made under different testing conditions of loading and sliding time. Finally, it is concluded that tungsten carbide particles and the relatively high hardness value has strong influence on the sliding wear resistance in spite of the observed porosity.
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8 Lee mas

Wear resistance of hydrophobic surfaces

Wear resistance of hydrophobic surfaces

Abstract. Nature has been an inspiration source to develop artificial hydrophobic surfaces. During the latest years the development of hydrophobic surfaces has been widely researched due to their numerous ranges of industrial applications. Industrially the use of hydrophobic surfaces is being highly demanded. This is why many companies develop hydrophobic products to repel water, in order to be used as coatings. Moreover, these coating should have the appropriated mechanical properties and wear resistance. In this work wear study of a hydrophobic coating on glass is carried out. Hydrophobic product used was Sika Crystal Dry by Sika S.A.U. (Alcobendas, Spain). This product is currently used on car windshield. To calculate wear resistance, pin-on-disk tests were carried out in dry and water conditions. The test parameters were rate, load and sliding distance, which were fixed to 60 rpm, 5 N and 1000 m respectively. A chamois was used as pin. It allows to simulate a real use. The friction coefficient and loss weight were compared to determinate coating resistance
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7 Lee mas

Síntesis y estudio del comportamiento de bicapas de  tungsteno, carburo de tungsteno  (W/WC) obtenidas por la técnica  sputtering DC  =  Synthesis and study of the behavior of tungsten, tungsten carbide (W/WC)  bilayers obtained by dc sputtering technique

Síntesis y estudio del comportamiento de bicapas de tungsteno, carburo de tungsteno (W/WC) obtenidas por la técnica sputtering DC = Synthesis and study of the behavior of tungsten, tungsten carbide (W/WC) bilayers obtained by dc sputtering technique

This research presents the results obtained in the process of production and characterization of Tungsten (W), Tungsten Carbide (WC) coatings and (W/WC) bilayers, synthesized on stainless steel AISI 316L substrates by DC nonreactive sputtering technique assisted by magnetic fields PAPVD. Coatings were obtained using two targets, a circular W metal target 2" in diameter and 99.995% purity for the initial layer of W and a WC target 2" in diameter and 99.995% purity for final WC layer. All coatings were obtained in an argon atmosphere by varying the substrate temperature at room temperature (RT), 100, 200 and 300 °C. The coatings were characterized using Energy Dispersive Spectroscopy (EDS) where it was observed a decrease in the concentration of Carbon atomic percentage with respect to Tungsten, infering the formation of a sub-stoichiometric phase of the compound. X-ray Diffraction results showed the presence of the cubic BCC phase of the W layer and the FCC phase of the WC layer and found a major orientation in the direction (200). Also the crystallite size and microstrain were calculated for the W/WC coatings according to the temperature of growth, where An improved behavior is observed for the bilayer grown at 300°C. Studies of chemical composition were realized using Raman Spectroscopy and Auger Spectroscopy. The results obtained by Raman demonstrate the presence of W-O, W-C and W=C linkages, confirmed in the results obtained by Auger Spectroscopy, also by means of the depth of profile behavior of the monolayers was observed according to the time of erosion. Using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Profilometry the morphology of the W-based coatings was studied as a function of deposition temperature. A slight decrease was observed in both the roughness and in grain size, while the thickness of the bilayers presented a slight tendency to increase. For the WC layers grown on the steel 316L it was possible to observe by means of SEM, the poor adhesion that these layers present, when the intermediate layer of W is not generated. On the other hand, studies of nanohardness revealed that dense surface with fine grains and low roughness presented a higher hardness. Tribological behavior of the coatings both in monolayer and bilayer were measured using a Ball on Disc system, where noted a decrease in the coefficient of friction and the wear rate for bilayers, however it does not show a significant influence with regard to the temperatures of deposition.
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89 Lee mas

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

SLIDING WEAR CHARACTERIZATION OF CEMENTED CARBIDES FOR HIGH PERFORMANCE CUTTING TOOLS

Cemented carbides have been used for manufacturing of cutting tools during the last several decades; the main constituents are tungsten carbide particles, which are hard and brittle, and cobalt as binder metal, which is relatively soft and ductile. In general the material properties are determined by cobalt content and tungsten carbide grain size, for example hardness increases with decreasing grain size and binder content. The aim of this work was to investigate and discuss the relationships among the microstructure, mechanical properties and chemical composition of cemented carbides because wear resistance is not a unique property of a cutting tool which can be determined by one simple laboratory test, or correlated with one simple property such as hardness. The tribological study showed that in addition to the grain size, the morphology, the gaps between particles and the binder content directly affect the wear rate of WC substrates, which must be considered for applications of these materials for cutting tools.
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8 Lee mas

Wear resistance of thermal spray WC Co VC nanostructured coatings

Wear resistance of thermal spray WC Co VC nanostructured coatings

Some studies have found that small additions of VC in WC-Co had a neutral effect on the corrosion resistance [31]. On the other hand, the tungsten carbide alloys reinforced with cobalt and chromium (cermets) and thermally sprayed by HVOF are currently good substitutes for hard chrome, typically present in some components such as aircraft landing gears, hydraulic rods, ball valves, printing rollers, etc. [14]. The use of nanocrystalline particles of WC is expected to improve properties in terms of hardness and tribological coatings [23, 24, 32, 33]; however, due to their high surface area-to-volume ratio, these suffer grain size growth and oxidation during their passage through the flame, which is detrimental to the coatings in good final properties such as hardness and wear resistance [34]. However, it has been reported, in different works [35, 25], a better mechanical and tribological properties using WC-Co coatings enriched with nanoparticles and deposited under HVOF technique, provided that an effective control of the processing variables was carried out during thermal spraying. The resistance against wear and erosion depends on the thickness of the coatings [36] and also on its hardness [37].
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17 Lee mas

Study of the size effect in a model to simulate concrete cracking due to rebar corrosion and comparison to accelerated corrosion tests

Study of the size effect in a model to simulate concrete cracking due to rebar corrosion and comparison to accelerated corrosion tests

In this work, the expansive joint element has been improved by incorporating irreversible behavior and a thorough analysis is carried out to ascertain the (strongly) coupled effect of the size of the mesh, the time step, the numerical tolerance and the fracture properties of the concrete on the cracking pattern. In parallel, accelerated corrosion tests have been carried out in order to verify the ability of the model to reproduce the oxide behaviour and the mechanical effects over the surrounding concrete. The crack patterns obtained in both cases are compared and discussed. The samples are concrete prisms with a steel tube inside simulating a rebar. The corrosion is simulated by the volumic expansion of the oxide. It is controlled by a single parameter, the corrosion depth, that is implicitly time-dependent. The influence of the element size is studied covering different ranges for the expansive joint element, the steel and the concrete. The cracking of the surrounding concrete is studied at different stages of the process for each case. In accelerated corrosion tests, constant current has been imposed in order to corrode the samples. The crack width at the concrete surface is recorded during the process and the crack pattern is studied after finishing the test. A special surface treatment is applied in order to improve the cracks detection. Finally, the results obtained from the simulations and from the tests are compared and the results are discussed.
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18 Lee mas

Improved maintenance and management of distribution assets due to the digitalization of the electrical grid

Improved maintenance and management of distribution assets due to the digitalization of the electrical grid

DSOs can overcome the threats that arise from the increasing penetration of DG, incentive regulation, regulated connection charges, and unbundling. In order for DSOs to embrace such opportunities, regulation also needs to evolve such that it provides DSOs with a wider range of options and incentives in choosing the most efficient ways to run their businesses in the new decentralized electricity market (Scheepers, 2005). An active DSO provides market access to DG by acting as a market facilitator and it provides several network and ancillary services through intelligent management of the network. This includes the incorporation of advanced information exchange between generation and consumption, the provision of ancillary services at the distributed level, management of the network to provide network reliability and controllability, and improve customer benefits and cost-effectiveness. The transition from passive to active network management may be accompanied by developing new services for the electricity market, creating new revenue drivers for the DSO.
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133 Lee mas

Contributions to the Study of Sociology of Education (Classical authors)

Contributions to the Study of Sociology of Education (Classical authors)

Abstract: Since its origins, sociology has focused on the study of specific areas such as education, in order to become a science that not only explores the scientific studies, but is also specialized on the subject matter. This article presents an overview of the contributions of various theoretical European traditions regarding education. From the “theoretical inputs” presented, the reflection and theoretical proposal about the subject matter related to the sociology of education are re-defined, due to a seemingly lack of clarity or consensus among the authors. Mainly, this research attempts to analyze those core issues related to the understanding of the multiple interactions between society-education and vice versa, visible from sociology. As one of the main findings, it is argued that the traditionally named sociology of education encompasses three subject matters: sociology of education, pedagogical sociology and the sociology of the educational system. Although these lines of research are intertwined, its categorization facilitates the specific understanding of various aspects within the same subject matter.
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27 Lee mas

Analysis of the communication of antibiotic resistance in the digital press of Spain. Effect of the approval of the National Plan of Antibiotic Resistance

Analysis of the communication of antibiotic resistance in the digital press of Spain. Effect of the approval of the National Plan of Antibiotic Resistance

Introducción: La resistencia a los antibióticos (AMR, por sus siglas en inglés, Antimicrobial resistance) y la aparición de bacterias resistentes han sido catalogadas como una amenaza de salud pública mundial, tanto por la Organización Mundial de la Salud (OMS) como por la Unión Europea. El artículo que se presenta muestra un estudio sobre la cobertura informativa en medios digitales de dicho asunto. Objetivo: Analizar la cobertura de la presencia de la resistencia a antibióticos en medios digitales. Metodología: Mediante un estudio descriptivo se cuantificó el número de noticias aparecidas en cuatro medios: El País, El Mundo, ABC y 20 minutos, antes y después de la aprobación del Plan Nacional de Resistencia a Antibióticos en el año 2014. Resultados: Los resultados demostraron un tratamiento desigual según el número de piezas informativas en los cuatro diarios digitales pero en ascenso desde la aprobación de dicho plan. Conclusiones: El tratamiento informativo de la resistencia a antibióticos, según el número de noticias cuantificadas, se va incrementando cada año de forma desigual en cada medio.
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6 Lee mas

A framework to study the resilience of organizations: a case study of a nuclear emergency plan

A framework to study the resilience of organizations: a case study of a nuclear emergency plan

There is also research focused on improving the resilience in emergencies through the evacuation performance. For example, in (Lv et al. 2013), the authors introduced a new method for evacuation management support. They used interval-parameter programming within joint-probabilistic constrained programming and integer linear programming (optimization technique that deals with uncertainty) to calculate the optimal evacuation route. They applied the model to calculate the evacuation route in different scenarios. Applying this model, they also evaluated the robustness of the system analyzing what is the influence when the constraints for the evacuation problem are modified. Simonovic & Ahmad (2005) developed a simulation model based on system dynamics for understanding human behavior during flood evacuations. Their aim was to simulate the effect of different evacuation policies. They applied this model to emergency planning in the Red River Basin. Chen et al. (2006) applied agent-based simulation to identify the time it takes to evacuate the Florida Keys in case of a hurricane. They also studied what is the effect of a landfall in the evacuation route. They identified the most congested roads and the bottlenecks. They also got the average speed of the vehicles. In (Hammond & Bier 2015) the authors aimed to identify alternative evacuation strategies for nuclear emergencies. They studied different strategies based on the predicted radiation plumes. They compared them in terms of the size of the evacuation area and the adequacy of the protection measures and chose three. They compared these three to the existing ones and they conclude that there are methods that perform better than the ones currently applied.
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175 Lee mas

Multifactorial study of erosion corrosion mechanisms in the wear of a low carbon steel by slurry of copper tailing

Multifactorial study of erosion corrosion mechanisms in the wear of a low carbon steel by slurry of copper tailing

2011; Landolt, 2007). According to Heitz (1990, 1996), the corrosion rate should increase with increasing flow velocity by the action of shear stress on corrosion product film covering the pipe walls and by mass-transport consideration, especially increase in oxygen diffusion. However, Li and co-workers (Li, Pots, Brown, Kee, & Nesic, 2016) reported the wall shear stress alone, produced in multiphase flow patterns covered, is insufficient to damage the protective rust layers mechanically. Whereas, Zhang & Cheng (2009) and Tian & Cheng, (2008) investigated the corrosion behavior of X65 pipeline steel under different hydrodynamic conditions using rotating cylinder electrode apparatus in simulated oil/water emulsion. They proposed that mass-transfer of oxygen play an important effect in the cathodic reaction of X65 steel at the study conditions indicating that electrode rotation accelerates the oxygen diffusion and the cathodic reduction. Similar conclusions were obtained by Jiang et al. (Jiang, Chai, Su, & Yang, 2017) in the study of a low alloy steel under at different velocities using a flow loop and rotating cylinder electrode systems.
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125 Lee mas

Application of the factorial analysis to the investigation of markets  Case of study

Application of the factorial analysis to the investigation of markets Case of study

Otro análisis para comprobar la factibilidad de la aplicación del análisis factorial es la diagonal de la matriz de correlación anti-imagen, la cual permite ver el valor de las medidas de adecuación que presenta cada variable y que se conoce como: “Measure of Sampling Adecuacy” (MSA). Este tipo de medida permite comprobar, variable por variable, si es adecuado realizar el análisis factorial. Aquí se toman como valores mínimos y máximos respectivamente el 0 y el 1, siendo tanto mejor cuanto mayor sea el valor del MSA. En el caso de la matriz de correlación anti-imagen que estamos trabajando, de los 11 valores de la diagonal de dicha matriz no se presentó ningún valor bajo. Por lo tanto estos resultados proporcionan otro indicador positivo sobre la matriz de datos que da luz verde al análisis factorial.
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6 Lee mas

COMMUNITY ANNOYANCE DUE TO ENVIRONMENTAL NOISE, THE EXAMPLE OF THE CITY OF CURITIBA, BRAZIL

COMMUNITY ANNOYANCE DUE TO ENVIRONMENTAL NOISE, THE EXAMPLE OF THE CITY OF CURITIBA, BRAZIL

Surely the traffic highly contributes to the increase in the environmental noise pollution in Curitiba. However, it is not the only important factor. Other factors, like noise generated in the neighborhood of the respondents, can also be a significant factor in the subjective urban noise perception. Still among the respondents living at the same location for more then 5 years, 27% out of those who felt annoyed by the noise in his/her street also pointed out the civil construction, which is a type of neighborhood noise. With all this, it is possible to conclude that the rapid expansion of the city of Curitiba is a significant factor in the urban noise pollution increase.
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5 Lee mas

Approximation to the study of water quality

Approximation to the study of water quality

The amount of freshwater around the world is decreasing every day; global warming stresses the ecosystems, especially the water, an essential resource for life in our planet. The presence -or absence- of external factors could disrupt the natural balance of flora and fauna population dynamics. Understanding the biotic and abiotic factors that play a role in such populations is a matter of main importance to assess the ecosystem’s health. Water quality monitoring and assessing is vital in order to identify alterations and take decisions to restore and preserve freshwater ecosystems.
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10 Lee mas

A study of the influence of TiO2 addition in Al2O3 coatings sprayed by suspension plasma spray

A study of the influence of TiO2 addition in Al2O3 coatings sprayed by suspension plasma spray

K2300 supplied by Kronos (Leverkusen, Germany), was used. According to technical specifications from suppliers, both powders have an average particle size of 300 nm. The powder concentration (solid content) in the ethanol suspension was maintained at 10 %wt. This value was found to allow the best coating cohesion. For suspension stability, an electrosteric dispersant of 2 %wt to powder weight was utilized. This dispersant percentage results in the lowest viscosity, 0.02 mPa·s, and also assures the sedimentation stability for more than 3 days. In each case, the dispersant is burned and disintegrated during the spraying procedure. Other technical details of the preparation and stabilization of suspensions can be found in our previous work [25].
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15 Lee mas

Physical disability and sensitive intensity of mechanical lumbalgiaa due to use of “The Rallo”

Physical disability and sensitive intensity of mechanical lumbalgiaa due to use of “The Rallo”

introduction/Methods: This article presents the findings, a descriptive and analytical cross-sectional, applied to a sample of two hundred seventy (270) women between the ages of 18-60 years old, in the municipality of alto Baudo (choco), in order to determine the relationship between the culture using a tool called “the rallo”, used for washing clothes and female generations disability index and intensity of pain, lumbago mechanical product, which is a disease characterized generate pain in the lumbar region, which limits the patient functionally and structurally, and has ability to conceive severe complications, the leading cause is improper positions, especially of flexion, for it was used as a measuring tool, the roland Morris questionnaire and the Oswestry scale globally recognized for that purpose. results/discussion: to develop research, through the collection, graphing and data analysis, it became clear that there is a close relationship “cause - effect” on the use of this tool, either by repetitive use in conducting this activity in women who use it as a tool for cleaning, and how their health is affected, reflected in the increasing number of inquiries and disabilities in the health center, so difficult to understand, it is because they are so ingrained despite certain customs that affect health even defend them and continue their practice for generations.
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10 Lee mas

Approaches to the study of international migration: a review

Approaches to the study of international migration: a review

Social and migration networks determine, to a certain extent what regions or areas are more likely to begin migration flows, what individuals may be involved in the process, and also which destinations areas are more likely to receive migrants from certain origins and maintain a permanent flow of migration. In many instances, the network also determines the type of job to be occupied by newcomers. In many cases poor occupational position of members of the network is a consequence of the limited resources and relationships of the network. New migrants relying on a network of workers employed in marginal jobs may tend to increase concentration of migrants in the same positions, at least while migrants adapt to the new environment, as Gurak and Caces find in the case of Filipino migrants to Hawaii, and in Portes´ study of Dominicans in New York (Gurak and Caces, 1992:155; Portes and Sensenbrenner, 1993:1320-1350). However, this need not be necessarily the case of networks with limited resources. Goldring provides evidence that migrants whose first jobs were in a marginal position have managed to move out to different occupations, or leave the secondary labor market and move upward. In any event, migration networks have a significant influence in determining the migrants insertion in the labor market, depending on networks´ resources, degree of commitment of members involved, and development of the network. 9
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32 Lee mas

A transcriptomic study of the early responses of Medicago sativa to mercury

A transcriptomic study of the early responses of Medicago sativa to mercury

plants (Mochida & Shinozaki, 2011). In this sense, DNA microarrays technology is a powerful tool used widely in the last decades after genome sequencing projects, that are enabling a more complete understanding of the global transcriptional changes under different environmental conditions and effectors, endogenous signals, interaction with pathogens, and so on (Amaratunga et al., 2014). With regard to metal homeostasis, a substantial effort has been done to characterize the primary cellular mechanisms involved in the heavy metal stress perception and defence mechanisms using different RNA-DNA microarray technologies. Arabidopsis DNA chips have been used to identify global transcriptional pattern in response to metals such as Zn (Becher et al., 2004), As (Abercrombie et al., 2008) or Cd (Herbette et al., 2006; Weber et al., 2006); where in most cases the transcriptional response of Arabidopsis thaliana has been compared with that of the metalliferous Arabidopsis halleri. Transcriptional activity of the metal Zn/Cd accumulator Noccaea (Thlaspi) caerulescens has also been compared with Arabidopsis in response to Cd (Van de Mortel et al., 2008). Apart from Arabidopsis, sensitive and tolerant cultivars of rice (Oryza sativa) have been used to assess their transcriptional response to As (Yu et al., 2012; Huang et al., 2012; Chakrabarty et al., 2009; Norton et al., 2008) and Cu (Sudo et al., 2008) using different DNA microarray platforms. In addition, the transcriptional responses of Cd were compared with those of essential trace micronutrients like Cu in Arabidopsis (Zhao et al., 2009) or in rice roots (Lin et al., 2013).
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224 Lee mas

The role of the secondary cell wall in plant resistance to pathogens

The role of the secondary cell wall in plant resistance to pathogens

2009). The er mutant was found to be more susceptible than wild-type plants to several pathogens, such as the necrotrophic fungus P. cucumerina, the vascular bacterium R. solanacearum and the vascular oomycete Pythium irregulare (Table 1; Godiard et al., 2003; Llorente et al., 2005; Adie et al., 2007). The enhanced sus- ceptibility to P. cucumerina and the cell wall features of the er mutant, including its reduced xylose content, were restored to wild-type levels by mutations in SUPPRESSOR OF ERECTA 1 and 2 (SER1 and SER2), further suggesting a link between cell wall xylose content and resistance to pathogens (Sánchez-Rodríguez et al., 2009). Although several defense genes are constitutively up- regulated in the ser1 and ser2 mutants, the precise molecular basis of their resistance has not yet been fully elucidated and the SER genes have not been characterized yet (Sánchez-Rodríguez et al., 2009). Arabidopsis mutants in the Gβ and Gγ1/γ2 subunits of the heterotrimeric G protein (i.e., agb1 single and agg1 agg2 dou- ble mutants, respectively) also have a reduced content of xylose in their cell walls and are hypersusceptible to the necrotrophic fungi P. cucumerina and Alternaria brassicicola, the biotrophic bacterium P. syringae and the vascular fungus Fusarium oxyspo- rum (Table 1; Llorente et al., 2005; Trusov et al., 2010; Klopffleisch et al., 2011; Delgado-Cerezo et al., 2012; Liu et al., 2013; Lorek et al., 2013; Torres et al., 2013). Interestingly, the reduced resis- tance of agb1 single and agg1 agg2 double mutants was found to be independent of defense pathways required for resistance to these pathogens, such as those regulated by abscisic acid, salicylic acid, jasmonic acid and ethylene, and those that regulate the biosyn- thesis of tryptophan-derived metabolites (Delgado-Cerezo et al., 2012; Lorek et al., 2013; Torres et al., 2013). It has been suggested that the reduced resistance in the agb1 and agg1 agg2 mutants is rather the direct consequence of a weakened cell-wall and a defec- tive production of reactive oxygen species (ROS) upon pathogen infection (Delgado-Cerezo et al., 2012; Jiang et al., 2012; Liu et al., 2013; Lorek et al., 2013). Together, these data suggest that shifts in the xylose content of the cell wall, e.g., by altering the glucoro- noxylan and xyloglucan content, are responsible, at least in part, for the altered susceptibility of some Arabidopsis secondary cell wall mutants to pathogens.
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13 Lee mas

Environmentalism of the dispossessed: Mapping ecologies of resistance

Environmentalism of the dispossessed: Mapping ecologies of resistance

In this policy context, TAV proponents base their arguments on those of the economic, environmental and improved safety benefits that the project will bring, both to the region, and the country as a whole. The Lyon-Turin Fer- roviare, the French-Italian bi-national company conducting the pre-project studies and investigation works for the Franco-Italian section, and in charge of the construction of the 57 km tunnel connecting Saint-Jean-de-Maurienne with the Susa Valley, claims that the new line will ultimately solve Europe’s most pressing transport problem, providing the crucial missing railway link that is needed to connect the southern part of the Alps, establishing ‘eco- nomic balance’, by facilitating trade, and consolidating the competitiveness of southern European countries including France, Portugal, S.p.A.in and Italy. In addition to improved trade and competitiveness, arguments are also made on the basis of increased employment, claiming that several thousand con- struction jobs will be created. The LTF estimates that after work begins in 2013, 3500 people will be employed on the Franco-Italian section 1 , with an estimated breakdown of 2000 of these on the Italian side and 4.000 on the French side over a period of about 10 years, totalling approximately 1.5 billion euros in workers’ salaries (Meletti, 2011). The tourism sector in Pei- monte, the region through which the TAV will pass, has been highlighted as a major economic beneficiary of the project, highlighted as the industry with the most potential for growth. Supporters argue that Piedmontese wine and gastronomy, ironically referred to as key to attracting “slow food” tourism, particularly stands to benefit from the increased access o↵ered by a high speed rail connection to the region 2 .
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278 Lee mas

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