Auswahl der wissenschaftlichen Literatur zum Thema „The effect of oil on differential characteristics“

The article reflects the results of research on the influence of roast temperature of water treatment waste obtained from drinking water generation (at the water treatment plant in Nizhnekamsk, Republic of Tatarstan) for sorption characteristics for native and used oil products - oils 5W40, 15W40 and И-20А. The methods of instrumental and computational means of research are presented. Differential thermal analysis and differential scanning calorimetry of water treatment waste were performed. The graphs of the influence of roast temperature on the aqueous extract pH value, maximum oil capacity and water absorption were constructed. It was found that at high temperatures, the decomposition of organic compounds with formation of carbon black occurs. It increases the maximum oil capacity in dynamic and static conditions in water and water absorption. It is determined that the best adsorption indicators are achieved for a sample of water treatment waste subjected to heat treatment at 600 C.

Extra virgin olive oil (EVOO) contains a biotic fraction, which is characterized by various microorganisms, including yeasts. The colonization of microorganisms in the freshly produced EVOO is determined by the physicochemical characteristics of the product. The production of blended EVOO with balanced taste, which is obtained by blending several monovarietal EVOOs, modifies the original microbiota of each oil due to the differential physico-chemical characteristics of the blended oil. This study aimed to evaluate the effect of microbial composition on the stability of the quality indices of the monovarietal and blended EVOOs derived from Leccino, Peranzana, Coratina, and Ravece olive varieties after six months of storage. The yeasts survived only in the monovarietal EVOOs during six months of storage. Barnettozyma californica, Candida adriatica, Candida diddensiae, and Yamadazyma terventina were the predominant yeast species, whose abundance varied in the four monovarietal EVOOs. However, the number of yeasts markedly decreased during the first three months of storage in all blended EVOOs. Thus, all blended EVOOs were more stable than the monovarietal EVOOs as the abundance and activity of microorganisms were limited during storage.

This investigation is directly relevant to various applications associated with the safety aspects of underbalanced drilling operations where de-oxygenated air may be co-injected with oil-based drilling fluid. However, de-oxygenated air often still contains up to 5% oxygen by volume. This residual oxygen can react with oil during the drilling process, thereby forming potentially hazardous oxidized hydrocarbons and compromising the safety of drilling operations. This article examines the conditions and processes by which oxidation reactions occur and may be helpful in reducing risk in drilling operations. This project characterizes the oxidation behavior of several oils and a typical oil-based drilling fluid at atmospheric and elevated pressures using thermogravimetry (TG) and pressurized differential scanning calorimetry (PDSC). Tests performed on mineral matrix (core) from the oil reservoirs showed no reactivity in both inert and oxidizing atmospheres. In an inert atmosphere, tests on all hydrocarbon samples showed only vaporization, no reactivity. In an oxidizing environment, the tests on hydrocarbons showed several oxidation regions. The presence of core had no effect on the behavior of the hydrocarbons tested in an inert atmosphere but accelerated the higher temperature oxidation reactions of the oil samples. The oil-based drilling fluid exhibited the opposite effect—the presence of core material retarded the oxidation reactions. This is perhaps due to the presence of an oxygen scavenger reacting with oxygen-containing clays present in the mineral matrix. In all tests performed on mixtures of hydrocarbon and core in oxidizing atmospheres, elevated pressures resulted in acceleration of the lower and higher temperature reaction regions.

This paper studies the Jeffcott cracked rotor based on level set, considering the oil film oscillation effects on crack rotor, building the stiffness matrix of the cracked rotor in the fixed coordinate system and the moving coordinate, deriving the nonlinear differential equations of coupled vibration of a cracked rotor, and analysis of its dynamic characteristic combined with case. Analysis shows that: crack rotor can produce nonlinear vibration in the crack and Oil film oscillation can be coupled bending and torsional vibration of cracked rotor. The analysis results provides practical basis for diagnosing Resonance of the rotor system fault and the safe operation of rotor.

This study aimed to investigate?the treatment effect?of dimethyl silicone oil on archaeological dried leather. Leather samples, without treatment and treated in a vacuum, were submitted to an accelerated aging at 100°C for 72 hours. In order to evaluate the efficacy of treatment, leather characteristics were examined before and after treatment with dimethyl silicone oil and after accelerated aging. Colorimetry, ATR-FTIR spectroscopy, shrinkage temperature measurement and differential scanning calorimetry were used to examine the leather characteristics and the effectiveness and stability of treatment. The results revealed that the dimethyl silicone oil has a suitable performance in the treatment of dry leather. The results also showed that the use of dimethyl silicone oil significantly reduces the changes in leather during accelerated aging. In other words, dimethyl silicone oil treatment improves the leather stability against deterioration.

Purpose The purpose of this paper is to study various reliability measures like reliability, mean time to failure (MTTF) and sensitivity of transformer including different parameters of insulating oil/paper as health index. Design/methodology/approach The reliability characteristics of transformer incorporating different parameters of insulating oil as well as paper have been evaluated using Markov process incorporating Gumbel–Hougaard copula, Laplace transforms and supplementary variable technique. The parameters taken into consideration are breakdown voltage (BDV) and moisture content (MC) of both insulating oil and paper, and other parameters considered are interfacial tension (IFT), dissipation factor (DF), degree of polymerization (DOP) and furanic content (FC) for insulating oil and paper, respectively. By probability consideration and continuity influence, difference-differential equations have been obtained for the considered model. Findings Transition state probabilities, reliability, MTTF and sensitivity of the transformer corresponding to different parameters of insulating oil and paper have been evaluated with the help of aforementioned technique. Variations of reliability with respect to time along with the variations of MTTF and sensitivity have also been examined. Remarkable points during the study have also been pointed out. Originality/value Reliability characteristics of the transformer have been evaluated including two parameters: insulating oil and paper with the help of supplementary variable technique, considering two different types of repairs incorporating Gumbel–Hougaard family of copula unlike done earlier. Reliability, MTTF and sensitivity of transformer have been analyzed considering the parameters: BDV, MC, IFT and FC of insulating oil, and BDV, MC, DOP, DF of insulating paper.

Kortekaas, T.F.M., SPE, Shell Research B.V. Abstract Festoon crossbedding is a typical sedimentary structure in sandstone reservoirs. It is especially common in fluvial deposits. The important elements are the foreset laminae, which vary in permeability, and the bottomsets of lower permeability. To understand the complex, direction-dependent displacement characteristics of a crossbedded reservoir zone, we first conducted numerical simulations on a centimeter scale in a small part of a water-wet crossbedded reservoir zone. The simulations indicate that, during water/oil displacement, considerable amounts of movable oil initially are left behind in the higher-permeability foreset laminae with fluid flow perpendicular to the foreset laminae, while with flow parallel to the foreset laminae the displacement efficiency is good. To describe the displacement characteristics on a reservoir scale, we developed a procedure for calculating direction-dependent pseudo relative-permeability and capillary-pressure curves to be used as input for the simulations of water/oil displacement in a crossbedded reservoir zone. On a reservoir scale, the displacement characteristics in a water-wet crossbedded reservoir zone are slightly more favorable with the main fluid flow perpendicular to the foreset laminae. perpendicular to the foreset laminae. In addition, the sensitivity of the displacement characteristics to moderate reductions in interfacial tensions (IFT's) and to increases in water viscosity was investigated, both on a centimeter scale and on a reservoir scale. The simulations indicate the potential for substantial improvement in recovery from crossbedded reservoir zones if diluted surfactant or polymer is added to the drive water. Introduction Detailed studies of the effect of reservoir heterogeneities on water/oil displacement characteristics have been conducted on a well-to-well (layering) scale and on a pore scale, but few studies on an intermediate scale have been done. Therefore, we embarked on a study of the effect of centimeter-scale heterogeneities on water/oil displacement characteristics. We studied festoon crossbedding, one of the typical sedimentary structures in sandstone reservoirs, particularly common in fluvial deposits. A schematic particularly common in fluvial deposits. A schematic representation of a small part of a crossbedded reservoir zone is given in Fig. 1A. The important elements are the foreset laminae, which vary in permeability, and the bottom-sets, which are of lower permeability. The width of the foreset laminae is exaggerated in Fig. 1A; typically it is a few centimeters. First, we will discuss a mathematical simulation study in a very limited area of a water-wet crossbedded reservoir zone (1.97 × 26.2 × 0.66 ft [0.6 × 8 × O.2 m]). After a brief discussion of the water/oil displacement characteristics near a single permeability transition, we present the water/oil displacement characteristics in some cross sections of a simplified model (Fig. 1B) of a small part of a crossbedded reservoir zone. In addition, their sensitivity to moderate reductions in IFT's and increases in water viscosity are discussed. Second, we describe the effect of crossbedding on water/oil displacement characteristics on a reservoir scale, discuss a procedure for calculating dynamic, direction-dependent pseudo relative-permeability and capillary-pressure curves, and present the results of a reservoir-scale mathematical simulation study, including the pseudo-properties. Also, the sensitivity of the results to changes pseudo-properties. Also, the sensitivity of the results to changes in IFT and water viscosity is discussed. One-Dimensional Water/Oil Displacement Characteristics Near an Abrupt Permeability Transition Permeability Transition suppose we have a one-dimensional (1D) system consisting of two zones with different absolute, but identical relative, permeabilities. Furthermore, the system is horizontal and contains oil and connate water. The Buckley-Leverett first-order partial differential equation describes the water/oil displacement in each zone.In the absence of capillary and gravitational forces, the water fractional flow Fwo) is given byEq. 1, together with Eq. 2, usually leads to a sharp shock front: at each location, water saturation will instantaneously jump from connate water to shock-front saturation when the water arrives. SPEJ p. 917

Summary In this study, saturate, aromatic, resin, and asphaltene fractions of two Turkish crude oils (medium and heavy) were separated by column chromatographic techniques. Combustion experiments were performed on whole oils and fractions by a thermogravimetric analyzer (TG/DTG) and differential scanning calorimeter (DSC) by using air and a 10°C/min heating rate. TG and DSC data were analyzed for the determination of weight loss due to possible reactions, and for reaction enthalpies of individual fractions, which have to be known for in-situ combustion technology utilization. Introduction In-situ combustion is a process of recovering oil thermally, by igniting the oil to create a combustion front that is propagated through the reservoir by continuous air injection. Success of such a process depends mainly on the crude oil properties and rock properties as well as operational conditions. In-situ combustion is considered as an effective process not only for heavy oil reserves but also for depleted light and medium oil reservoirs. Unfortunately, the lack of better understanding of the process variables in terms of the conversion of oil during combustion and reservoir characteristics, as well as the costs, limits the more effective application of this technology. In combustion, three different reaction regions were identified, known as low-temperature oxidation, fuel deposition, and high-temperature oxidation. In low-temperature oxidation (LTO), mainly small and weak chains of hydrocarbons are broken and pyrolyzed and oxidized to give ketones, alcohols, etc. In fuel deposition or middle-temperature oxidation, products of low-temperature oxidation are transformed to heavier hydrocarbons to be combusted at higher temperatures. High-temperature oxidation (HTO) is the main combustion region where hydrocarbons are fully oxidized by air. During the course of these processes, hydrocarbons are continuously converted to other types of hydrocarbons, which makes the combustion process very complicated. Heat values and reaction parameters of crude oils are also obtained from differential scanning calorimeter (DSC) thermogravimetry (TG/DTG) experiments. Many studies have been conducted on different phases of the in-situ combustion process, mainly on the fluid and rock interactions during combustion of the fluid phase. Vossoughi et al.1 concluded that the addition of clay to porous media significantly affected the combustion of crude oil. Bae2 investigated the thermo-oxidative behavior and fuel forming properties of various crude oils. The results indicated that oils could be classified according to their oxidation characteristics. Vossoughi3 has used TG/DTG and DSC techniques to study the effect of clay and surface area on the combustion of selected oil samples. The results indicate that there was a significant reduction in the activation energy of the combustion reaction regardless of the chemical composition of additives. Vossoughi and Bartlett4 have developed a kinetic model of the in-situ combustion process from thermogravimetry and differential scanning calorimeter. They used the kinetic model to predict fuel deposition and combustion rate in a combustion tube. Kok5 characterized the combustion properties of two heavy crude oils by DSC and TG/DTG. Individual fractions of the crude oils have been studied before in a variety of purposes in different reactions. Ciajolo and Barbella6 used thermogravimetric techniques to investigate the pyrolysis and oxidation of some heavy fuel oils and their separate paraffinic, aromatic, polar, and asphaltene fractions. The thermal behavior of fuel oil can be interpreted in terms of the low-temperature phase in which the polar and asphaltene fractions pyrolyze and leave a particular carbon residue. Ranjbar and Pusch7 studied the effect of oil composition, characterized on the basis of light hydrocarbons, resin, and asphaltene contents, on the pyrolysis kinetics of the oil. The results indicate that the colloidal composition of oil, as well as the transferability and heat transfer characteristics of the pyrolysis medium, has a pronounced influence on the fuel formation and composition. Karacan and Kok8 studied the pyrolysis behavior of crude oil saturate, aromatic, resin, and asphaltene (SARA) fractions to determine the effect of each constituent to the overall pyrolysis behavior of oils. Several authors, such as Geffen,9 Iyoho,10 and Chu11 have conducted feasibility studies for the in-situ combustion process. Yannimaras and Tiffin12 applied the accelerating rate calorimetry to screen crude oils for applicability of the air-injection/in-situ combustion process. Testing was performed at reservoir conditions for four medium and high gravity oils and results were compared with the combustion tube and air-injection/in-situ combustion process on the basis of continuity of the resulting plot in the region between the LTO and HTO reactions. Although combustion studies on both oil samples and oil-rock mixtures had been conducted, studies on the behavior of crude oil SARA fractions under an oxidizing environment and the investigations on the effects of each of these fractions to the whole oil combustion process have been scarce. This research was conducted to fulfill this partial need in the field of crude oil combustion. The results are aimed to serve for better understanding and accurate modeling of in-situ combustion by using the effects of individual fractions on whole oil combustion. This enables the operators to adapt the changes in the compositional properties of oil during combustion and fine tune the operational parameters.

Biodiesel is an alternative fuel derived from vegetable oils by modifying their molecular structure through a transesterification process. Linseed oil methyl ester (LOME) was prepared using methanol in the presence of potassium hydroxide as a catalyst. The use of LOME in compression ignition engines was found to develop a very compatible engine-fuel system with lower emission characteristics. Two identical engines were subjected to long-term endurance tests, fuelled by an optimum biodiesel blend (20 per cent LOME) and diesel oil, respectively. Various tribological studies on lubricating oil samples drawn at regular intervals from both engines were conducted in order to correlate the comparative performance of the two fuels and the effect of fuel chemistry on lubricating oil performance and life. A number of tests were conducted in order to evaluate the comparative performances of the two fuels such as density measurement, viscosity measurements, Flashpoint determination, moisture content determination, pentane and benzene insolubles, thin layer chromatography, differential scanning calorimetry, etc. All these tests were used for an indirect interpretation of the comparative performance of these fuels. The performance of biodiesel fuel is found to be superior to that of diesel oil and the lubricating oil life is found to be longer while operating the engine on biodiesel

The oxidative stability of vegetable oils mainly depends on their fatty acid composition, their degree of unsaturation, and the presence of compounds with antioxidant activity. This paper reports on the effects of the process of roasting oil seeds, prior to pressing them, on the basic characteristics of the oils produced and their oxidative stability. The differential scanning calorimetry (DSC) technique was used to study the process of oxidation of the oil samples in an oxygen-flow cell. Chromatographic analysis revealed that roasting the seeds increased the levels of chlorophyll and β-carotene in all the cold-pressed oils. Similar results were observed for the oil’s antioxidant activity, measured by the scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method. Our results also indicated that roasting seeds prior to pressing them for oil had a positive effect on the oil’s stability, as determined by the DSC method. This manifested in both the extension of oxidation induction time and the final oxidation time.

This master’s thesis deals with the design of equipment for testing differentials. The aim of the thesis is therefore the design of a special device that will be able to measure the steady and transient characteristics of differentials. Master’s thesis is divided into four chapters. The first chapter points out the disadvantages of fully open and closed differentials, the second deals with a basic overview of the structures and design of self-locking differentials. The third chapter deals with research of existing devices that test and measure the characteristics of differentials. The fourth chapter then discusses the possible drives of the tested unit. The fifth chapter focuses on the actual construction design of the test equipment. The subsequent sixth chapter then solves the strength calculations of the chosen structural elements of this device.

An extensive literature survey of the subject of gear dynamics is undertaken and the increasing recognition of the role of the lubricating oil film in this field, especially as a damping source, is highlighted. The oil film separating the mating surfaces of involute spur gears is analysed assuming hydrodynamic conditions, rigid teeth (as far as the film shape is concerned) and pressure dependent viscosity. Gear tooth mesh stiffness is expressed as a function of the dynamic load and the position of contact. simple model of a pair of spur gears is subjected to a transient response analysis and the behaviour of the lubricating oil film observed. According to the motions of equivalent masses of the apars under these transient conditions damping due to the oil film is determined. The numerical solutions obtained at various operating conditions are combined to form an approximate formula to predict the damping ratio in terms of the dynamic tooth load, rolling speed of the tooth surfaces and the viscosity of the lubricating oil. A digital computer simulation of the dynamic motion of the pair of gears is carried out incorporating the above damping ratio formula. The actual load sharing between the pairs of teeth (when more than one pair of teeth are in mesh), considering the tooth deflections, pitch errors, oil film thicknesses and the differences in mesh stiffnesses, is taken into account. The variations of the total maximum dynamic load and the maximum tooth load are studied under different nominal loads, contact ratios, oil viscosities and pitch errors over a wide range of speeds covering the resonance area. The variations of the dynamic load, individual tooth load, mesh stiffness and the oil film thickness during complete mesh cycles are also analysed under different operating conditions to identify particular areas where high loads and minimum film thicknesses occur. Theoretical results are compared with the experimental results obtained on a back-to-back gear test rig.

Since the Exxon Valdez accident in 1987, renewed interest has come forth to better understand and predict the fate and transport of crude oil lost to marine environments. The short-term fate of an Arabian Crude oil was simulated in laboratory experiments using artificial seawater. The time-dependent changes in the rheological and chemical properties of the oil under the influence of natural weathering processes were characterized, including dispersion behavior of the oil under simulated ocean turbulence. Methodology included monitoring the changes in the chemical composition of the oil by Gas Chromatography/Mass Spectrometry (GCMS), toxicity evaluations for the oil dispersions by Microtox analysis, and quantification of dispersed soluble aromatics by fluorescence spectrometry. Results for this oil show a sharp initial increase in viscosity, due to evaporative losses of lower molecular weight hydrocarbons, with the formation of stable water-in-oil emulsions occurring within one week. Toxicity evaluations indicate a decreased EC-50 value (higher toxicity) occurring after the oil has weathered eight hours, with maximum toxicity being observed after weathering seven days. Particle charge distributions, determined by electrophoretic techniques using a Coulter DELSA 440, reveal that an unstable oil dispersion exists within the size range of 1.5 to 2.5 um, with recombination processes being observed between sequential laser runs of a single sample.

The objective of this research was to systematically study the effect of processing conditions on crystallization behavior and destabilization mechanisms of oil-in-water (o/w) emulsions. The effects of oil content (20 and 40 wt %); crystallization temperature (Tc = 10, 5, 0, -5, -10 °C); homogenization conditions, such as high shear (HS), very low pressure homogenization (VLPH), and high pressure homogenization (HPH); and cooling rate (0.2 and 30 °C/min) on both thermal behavior and destabilization mechanisms were analyzed. Docosahexaenoic acid (DHA) was added to VLPH emulsions and its effect on the physicochemical and oxidative stabilities and flavor was studied. Emulsions with 20% oil were less stable than those with 40% oil with a fast-cooling rate; however, stability increased when the emulsions were cooled slowly. Stability was also affected by oil and droplet size; the smaller the droplet the more stable the system. Smaller droplets (i.e., VLPH, HPH) had an effect on crystallization by delaying the onset of the crystal formation, which was promoted in emulsions with larger droplets (i.e., HS); 20% o/w emulsion crystallization was delayed more than 40%; and in emulsions crystallized using a slow-cooling rate, the crystal formation was less inhibited (i.e., crystals formed at a higher onset temperature [Ton], but at lower Tc) than when using a fast-cooling rate. The formation of lipid crystals either helped stabilize (small droplets) the emulsion and melted in a less fractionated manner or destabilized (big droplets) the emulsion. In addition, fast-cooling rates have greater fractionation than slow-cooling rates. Due to the greater stability of VLPH emulsions after thawing from being at -10 °C for 3 h, DHA was added to evaluate its effect on flavor (besides the effect on stability) of the emulsion. A descriptive panel was used to evaluate four attributes: oxidized, rancid, fishy, and buttery. The panelists were given samples after 72 h, because contrary to the TBA analysis which showed no significant differences between samples with and without DHA, the fishy smell was evident. The sensory evaluation results showed that there was a significant (p < 0.05) difference in fishiness between the VLPH emulsions with and without DHA, and that the odor was repulsive. No significance was seen for rancid and buttery flavors, and only a marginal significance was seen for oxidized.

Thesis (M.S.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains vii, 115 p. : ill. (some col.). Includes abstract. Includes bibliographical references.

碩士
國立成功大學
土木工程學系碩博士班
101
Asphalt from different crude oil plays an important role on pavement performance, in order to make asphalt have suitable functionality, provide road durability and driving comfort by analyzing asphalt. In this study, sampling different crude oil refining vacuum residues (VR) for test, and adding heavy vacuum gas oil (HVGO), blown asphalt, were subjected to physically and chemically characteristic test respectively. Physical part of asphalt by basic physical test, and dynamic shear rheometer (DSR) to obtain the mass flow parameters; Chemical properties by Fourier transform infrared spectroscopy (FT-IR), Thin-layer Chromatography Flame lionization Detector (TLC-FID) and High performance gel permeation chromatography (HP-GPC), discussed asphalt functional groups, chemical composition and molecular size distribution respectively. Succeeding term aging tests in laboratory simulations, then follow fresh asphalt physical properties and chemical testing operations. Finally, combining the above test results, analysis the correlation between physical and chemical properties Asphalt is mainly composed of saturate, aromatic, resin and asphaltene. the composition ratio of VR affected physical properties. In the early aging of aromatic transferred to resin by chemical change, and then resin changes into the asphaltene, and the functional group of ketones and sulfoxide have major increase in the aging process , ketone and sulfoxide increase means that the colloidal structure of polar molecules (asphaltene, resin) increased. Finally, the study base on physical characteristics for mixing, when mixing sample with the same viscosity or penetration, the Asphaltene Index (IA), and Polydispersity Index (PDI) values of Soft asphalt blending air blown asphalt were higher than the hard asphalt blending heavy vacuum gas oil. In the other hand, Colloidal instability Index (IC) are almost the same. However, the Aging Index (AI) of short-term aging is higher than the hard asphalt blending heavy vacuum gas oil. Because the chemical characteristic of colloid changes significantly, physical properties varied greatly.

碩士
國立中山大學
機械與機電工程學系研究所
98
In this study, Reometer AR2000 is used to investigate the effect of shear rate on viscosity of emulsion. And a model for the effective viscosity of emulsion is established. Moreover, another model for the hydrodynamic lubrication with binary mixtures of non-Newton fluids is developed. The coupled modified Reynolds are solved by combining the advanced multilevel method with the Newton-Raphson method. The effect of shear rate on lubrication characteristics of hydrodynamic lubrication of emulsion is investigated in cold rolling process. Research results show that the viscosity of emulsion is decreased with increasing the shear rate. Hence,the oil film thickness, oil preasure and oil concentration under hydrodynamic lubrication are increased with decreasing the slide-to roll ratio. Emulsion will be Newton fluid under high shear rate. In the cold rolling process, the emulsion shows the high shear rate, and the elastic deformation of roller and strip are considersd. Hence the end point of plastic zone of strip is moved to oulet zone due to the lubricated zone is increased, so that the film thickness is higher than that for rigid body. When roller radius is increased, the effective elastic modulus and the thickness reduction of strip are decreased, then the lubrication characteristics in cold rolling process are influenced by elastic deformation. When the rolling speed is increased , the inlet film thickness is increased, and the roll torque is slightly increased, but the rolling force and peak preasure are almost not influenced.

The title of this book features a concept, culturescape, which is obviously derived from a major attempt at grasping the defining characteristics of what Arjun Appadurai calls the combined effect of two distinct processes in the shaping of an increasingly global cultural economy. The title of Appadurai’s essay, featuring in his seminal work, Modernity at Large: Cultural Dimensions of Globalization, brings the two processes together: “Disjuncture and Difference in the Global Cultural Economy.” In order to capture the bewildering complexity of these “disjunctive” and “differential” cultural processes, Appadurai develops his theory of the interaction of the five types of cultural flows, seen not as entities in dichotomic, oppositional relations, but as flows linked to perspectives or vistas, as a sort of perspectival landscapes, hence their names

Investment in fixed assets declined over the crisis period in all countries. We implement an econometric analysis to explore the differential impact of leverage and debt maturity structure on investment, finding that in crisis years (i) leverage exerts a strong and negative effect on investment, and (ii) firms with more long-term debt invest less. We uncover heterogeneous reactions to the crisis due to the level of debt and its maturity, sorting firms by country-specific and firm-specific characteristics. Firms which cut back most investment in crisis years (conditional on the level of leverage and maturity) are (i) small and (ii) located in Eurozone periphery countries. Factors that alleviate financial friction and shield investment include multiple bank relationships and the ability to generate internal resources (cash flow). We find no evidence of a positive nexus between cash and investment, and little evidence of a positive effect on investment of access to capital markets.

This investigation is directly relevant to various applications associated with the safety aspects of underbalanced drilling operations where de-oxygenated air may be co-injected with oil-based drilling fluid. However, de-oxygenated air often still contains up to 5% oxygen by volume. This residual oxygen can react with oil during the drilling process, thereby forming potentially hazardous oxidized hydrocarbons and compromising the safety of drilling operations. This article examines the conditions and processes by which oxidation reactions occur and may be helpful in reducing risk in drilling operations. This project characterizes the oxidation behaviour of several oils and a typical oil-based drilling fluid at atmospheric and elevated pressures using thermogravimetry (TG) and pressurized differential scanning calorimetry (PDSC). Tests performed on mineral matrix (core) from the oil reservoirs showed no reactivity in both inert and oxidizing atmospheres. In an inert atmosphere, tests on all hydrocarbon samples showed only vapourization, no reactivity. In an oxidizing environment, the tests on hydrocarbons showed several oxidation regions. The presence of core had no effect on the behaviour of the hydrocarbons tested in an inert atmosphere but accelerated the higher temperature oxidation reactions of the oil samples. The oil-based drilling fluid exhibited the opposite effect — the presence of core material retarded the oxidation reactions. This is perhaps due to the presence of an oxygen scavenger reacting with oxygen containing clays present in the mineral matrix. In all tests performed on mixtures of hydrocarbon and core in oxidizing atmospheres, elevated pressures resulted in acceleration of the lower and higher temperature reaction regions.

Nowadays, anticipating and controlling transient response is a critical design activity for ensuring both safety and integrity of the operational subsea system. Predicting transient effect, commonly known as surge pressure, is of high importance for offshore industry. In order to determine the installation of protection equipments to avoid surge pressure effects, the operational teams have raised concerns, whether the system is adequately designed to protect the subsea system against possible surge pressures during the event of sudden closure of a valve. Researches, referred to transient effects, explain that is necessary to evaluate the system performance under current and desired operating conditions. The main goal of this paper is to predict the surge pressure during unforeseen closure valves at Refrigerated LPG and Gasoline (C5+) pipeline systems. In these systems the valves are located downstream the flowlines. Detailed computer modeling attempts to simulate the complex interactions between flowline and fluid, aiming at providing efficient flowline system integrity. These models are based on Transient Methodology which is defined for a set of nonlinear partial differential equations that relate fundamental variables with pressure head and flow velocity. The solution of differential equations has been carried out by Finite Difference Method that transforms these equations into characteristic equations. These can be accurately solved through high-speed digital computers. Flowmaster, Chicago, USA, was the software used to develop the analysis models. The software offers an advanced graphical interface to build networks and resultant graphics. The results from Flowmaster have been validated through a defined methodology that applies the Characteristics Method based on Wylie and Streeter assumptions. Simulations considering the fluid as gasoline have shown a sudden damping of pressure wave when the valve closure time was 10 seconds, leading to the restoration of the initial flow conditions. The analysis using the Method of Characteristics, however, does not exhibit this sudden damping, although a gradually reduction of fluctuations around the initial pressure are observed. The transient analysis through Flowmaster for Refrigerated LPG leads to a pressure envelope that shows a change of the flow direction triggering a cyclical process until the restoration of the initial operational conditions.

This paper presents the results of a transient analysis of hydrodynamic lubrication between piston and cylinder surfaces in engine Initial startup conditions with a Non Newtonian lubricant under oscillatory motion. Effects of different multi-grade oil viscosities are also investigated in the simulation. The time dependent Reynolds equations use a Maxwell type model to analyze fluid rheology. A perturbation scheme is used to derive coupled non linear partial differential equations to obtain the fluid velocity. The oil film profile is predicted by solving the two-dimensional Reynolds equations using the finite difference computational method. The piston velocities in engine secondary motion are adjusted by using fourth order Runge-Kutta technique. Using different oil viscosities, the effect of viscoelasticity on lubricant velocity and pressure fields is examined and the influence of film thickness on lubricant characteristics is investigated. Numerical simulations show that piston eccentricities and film thickness profiles vary under different multi grade oils at engine start up conditions.

Biodiesel is an alternative fuel derived from vegetable oils by modifying their molecular structure through transesterification process. Linseed oil methyl ester (LOME) was prepared using methanol in the presence of potassium hydroxide as catalyst. Use of linseed oil methyl ester in compression ignition engines was found to develop a very compatible engine-fuel system with lower emission characteristics. Two identical engines were subjected to long-term endurance tests, fuelled by optimum biodiesel blend (20% LOME) and diesel oil respectively. Various tribological studies on lubricating oil samples drawn at regular intervals for both engines were conducted in order to correlate the comparative performance of the two fuels and the effect of fuel chemistry on lubricating oil performance and life. A number of tests were conducted in order to evaluate comparative performance of the two fuels such as density measurement, viscosity measurements, flash point determination, moisture content determination, pentane and benzene insolubles, thin layer chromatography, differential scanning calorimetry etc. All these tests were used for indirect interpretation of comparative performance of these fuels. Biodiesel fuels performance is found to be superior to that of diesel oil and the lubricating oil life is found to have increased, while operating the engine on this fuel. NOTE: This paper was presented at the ASME 2003 Internal Combustion Engine Division Spring Technical Conference but was printed in the ASME 2003 Internal Combustion Engine and Rail Transportation Divisions Fall Technical Conference proceedings, pages 427–441. It should appear under the Lubrication and Friction heading.

The purpose of the work is to conduct a comparative analysis of the stability of two types of polymer coatings to the effects of formation water and hydrochloric acid based on the analysis of mechanical properties, thermal stability and surface morphology. To accomplish the task, modern physical-chemical methods were used: differential scanning calorimetry, microscopy, an electromechanical universal testing machine, a dilatometer. Simulation of the effect of water at elevated temperatures and pressures on the polymer coating samples was carried out in an autoclave-reactor, the study of the effect of acid was carried out in a glass beaker. On the basis of the work carried out, results were obtained that show similarities and differences in the behavior of the polymer samples studied. The change of the dynamic modulus of elasticity and the coefficient of linear thermal expansion with increasing temperature is investigated. In general, it has been shown that PE-RT polymer has better characteristics than PE polymer. However, both of them are stable to the exposure of formation water and hydrochloric acid and can protect corrosion of high pressure pipes connections.

Effect of injector geometry on two phase flows is of profound importance to industry. If the injection method is found to vary the flow characteristics dramatically, it can be employed to obtain desirable two phase flow regimes/attributes and avoid rather unsought conditions. This could potentially save a lot of costs in the extraction and transportation of oil and gas as well as in many other applications. Moreover, the issue of flow development and dependency on the injection conditions is essential when modelling two phase flows. A lot of experimental data and empirical models may have been developed based on systems that may not be fully developed. Therefore, inaccurate modelling of the physical interactions of the flow gets adopted, and hence large divergence between models and experimental data produced by different researchers often transpires. Most of the published studies on entrance effect were conducted on air-water or steam-water systems because of their relevance to heat transfer units in the nuclear industry. This paper presents an extensive experimental investigation into the issue of flow development using two approaches; measuring void fraction at five axial stations along the test section, and using different geometries for bubble injection into the base of the pipe. The study focuses on how the entrance effect is influenced by the liquid viscosity. The experiments were conducted in a 127 mm diameter vertical pipe. The investigation is achieved by contrasting 180 runs produced using three different injector geometries, the runs were repeated using 4 different oil viscosities, making 2160 experimental run. Gas superficial velocity (Ugs) was varied between 0.01–5.40 m/s, while liquid superficial velocity (Uls) between 0.07–0.86 m/s. The viscosities investigated span between 4.0 cP up to 104.6 cP. The void fraction was measured using Electrical Capacitance Tomography (ECT) and the Wire Mesh Sensor (WMS). That in addition to differential pressure measurements.

Sensitivity to stretch and differential diffusion of chemical species are known to influence premixed flame propagation, even in the turbulent environment where mass diffusion can be greatly enhanced. In this context, it is convenient to characterize flames by their Lewis number (Le), a ratio of thermal-to-mass diffusion. The work reported in this paper describes a study of flame stabilization characteristics when the Le is varied. The test data is comprised of Le ≪ 1 (Hydrogen), Le ≈ 1 (Methane), and Le > 1 (Propane) flames stabilized at various turbulence levels. The experiments were carried out in a Hot exhaust Opposed-flow Turbulent Flame Rig (HOTFR), which consists of two axially-opposed, symmetric turbulent round jets. The stagnation plane between the two jets allows the aerodynamic stabilization of a flame, and clearly identifies fuel influences on turbulent flames. Furthermore, high-speed Particle Image Velocimetry (PIV), using oil droplet seeding, allowed simultaneous recordings of velocity (mean and rms) and flame surface position. These experiments, along with data processing tools developed through this study, illustrated that in the mixtures with Le ≪ 1, turbulent flame speed increases considerably compared to the laminar flame speed due to differential diffusion effects, where higher burning rates compensate for the steepening average velocity gradient, and keeps these flames almost stationary as bulk flow velocity increases. These experiments are suitable for validating the ability of turbulent combustion models to predict lifted, aerodynamically-stabilized flames. In the final part of this paper, we model the three fuels at two turbulence intensities using the FGM model in a RANS context. Computations reveal that the qualitative flame stabilization trends reproduce the effects of turbulence intensity, however, more accurate predictions are required to capture the influences of fuel variations and differential diffusion.

Traditional chemical treatment methods have considerable operation costs and represent a risk to the environment. Since 1987 Norwegian oil companies have been investigating alternative electrical heating methods for prevention of hydrate and wax plugs. A joint industry project ‘Concept Verification – Direct Heating of Oil & Gas Pipelines’ was initiated in 1996 and terminated in October 1999. During this work an electrical heating system was proved to be feasible on several fields in the North Sea. It will be installed on 7 flowlines of 13% Chromium (Crl3) with lengths between 6 km and 16 km. Electrical heating is used to maintain or raise the thermally insulated steel pipe temperature above the critical value for hydrate formation (typically 15–25 °C) or wax formation (typically 20–40°C). A single-phase power supply for the heating system is based on commercial components and connected to the platform power supply. The qualification work for the direct heating system has included full scale testing for single and parallel pipes, end termination at the template, bypass of a template and aspects concerning corrosion control. The rating of the system is dependent on the magnetic and electrical characteristics of the steel material. Such data is not commonly available. Measurements performed during the qualification program confirm that the magnetic characteristic may vary within a wide range for a specific steel quality and that mechanical stress and heat treatment can effect the magnetic characteristic. The difference in magnetic characteristic of individual Crl3 pipes results in variation of the pipe temperature and problems concerning differential pressure during melting. The problem can be handled by dividing the pipeline into a number of sections, each with a limited variation of the magnetic characteristic, thus keeping the temperature for the whole pipeline within acceptable limits. As a part of the pipe specification both electrical and magnetic characteristic should be available. These data can be determined by measuring arrangements in the production line of the mill. Measures to limit the variation of magnetic characteristic should be discussed.

The lamellar-type solid lubricants are readily available in a form of platelets. The diameter and thickness of these platelets are typically up to tens of microns and few microns, respectively, which are classified as micro-platelets. Some of these platelets are also available as nano-platelets whose thickness is well below a micron (even to few nanometers). In the previous work, the vegetable oil mixed with nano-platelets was enormously effective for Minimum Quantity Lubrication (MQL) machining. Clearly, the micro-platelets are not as inexpensive. In addition, the mixtures with the micro-platelets are not as stable as those with the nano-platelets. This paper intends to find the effect of the thickness differential on these platelets in MQL machining. The tribometer test shows that the nano-platelets are much more effective than the micro-platelets in reducing wear without changing the friction. With the MQL ball mill experiment, the micro-platelets present in MQL oil increased the tool wear, even compared to the traditional MQL with pure oil only. Thus, the thickness of the nano-platelets holds an important characteristic to enhance MQL-based machining.

1.1 Macroeconomic summary Economic recovery has consistently outperformed the technical staff’s expectations following a steep decline in activity in the second quarter of 2020. At the same time, total and core inflation rates have fallen and remain at low levels, suggesting that a significant element of the reactivation of Colombia’s economy has been related to recovery in potential GDP. This would support the technical staff’s diagnosis of weak aggregate demand and ample excess capacity. The most recently available data on 2020 growth suggests a contraction in economic activity of 6.8%, lower than estimates from January’s Monetary Policy Report (-7.2%). High-frequency indicators suggest that economic performance was significantly more dynamic than expected in January, despite mobility restrictions and quarantine measures. This has also come amid declines in total and core inflation, the latter of which was below January projections if controlling for certain relative price changes. This suggests that the unexpected strength of recent growth contains elements of demand, and that excess capacity, while significant, could be lower than previously estimated. Nevertheless, uncertainty over the measurement of excess capacity continues to be unusually high and marked both by variations in the way different economic sectors and spending components have been affected by the pandemic, and by uneven price behavior. The size of excess capacity, and in particular the evolution of the pandemic in forthcoming quarters, constitute substantial risks to the macroeconomic forecast presented in this report. Despite the unexpected strength of the recovery, the technical staff continues to project ample excess capacity that is expected to remain on the forecast horizon, alongside core inflation that will likely remain below the target. Domestic demand remains below 2019 levels amid unusually significant uncertainty over the size of excess capacity in the economy. High national unemployment (14.6% for February 2021) reflects a loose labor market, while observed total and core inflation continue to be below 2%. Inflationary pressures from the exchange rate are expected to continue to be low, with relatively little pass-through on inflation. This would be compatible with a negative output gap. Excess productive capacity and the expectation of core inflation below the 3% target on the forecast horizon provide a basis for an expansive monetary policy posture. The technical staff’s assessment of certain shocks and their expected effects on the economy, as well as the presence of several sources of uncertainty and related assumptions about their potential macroeconomic impacts, remain a feature of this report. The coronavirus pandemic, in particular, continues to affect the public health environment, and the reopening of Colombia’s economy remains incomplete. The technical staff’s assessment is that the COVID-19 shock has affected both aggregate demand and supply, but that the impact on demand has been deeper and more persistent. Given this persistence, the central forecast accounts for a gradual tightening of the output gap in the absence of new waves of contagion, and as vaccination campaigns progress. The central forecast continues to include an expected increase of total and core inflation rates in the second quarter of 2021, alongside the lapse of the temporary price relief measures put in place in 2020. Additional COVID-19 outbreaks (of uncertain duration and intensity) represent a significant risk factor that could affect these projections. Additionally, the forecast continues to include an upward trend in sovereign risk premiums, reflected by higher levels of public debt that in the wake of the pandemic are likely to persist on the forecast horizon, even in the context of a fiscal adjustment. At the same time, the projection accounts for the shortterm effects on private domestic demand from a fiscal adjustment along the lines of the one currently being proposed by the national government. This would be compatible with a gradual recovery of private domestic demand in 2022. The size and characteristics of the fiscal adjustment that is ultimately implemented, as well as the corresponding market response, represent another source of forecast uncertainty. Newly available information offers evidence of the potential for significant changes to the macroeconomic scenario, though without altering the general diagnosis described above. The most recent data on inflation, growth, fiscal policy, and international financial conditions suggests a more dynamic economy than previously expected. However, a third wave of the pandemic has delayed the re-opening of Colombia’s economy and brought with it a deceleration in economic activity. Detailed descriptions of these considerations and subsequent changes to the macroeconomic forecast are presented below. The expected annual decline in GDP (-0.3%) in the first quarter of 2021 appears to have been less pronounced than projected in January (-4.8%). Partial closures in January to address a second wave of COVID-19 appear to have had a less significant negative impact on the economy than previously estimated. This is reflected in figures related to mobility, energy demand, industry and retail sales, foreign trade, commercial transactions from selected banks, and the national statistics agency’s (DANE) economic tracking indicator (ISE). Output is now expected to have declined annually in the first quarter by 0.3%. Private consumption likely continued to recover, registering levels somewhat above those from the previous year, while public consumption likely increased significantly. While a recovery in investment in both housing and in other buildings and structures is expected, overall investment levels in this case likely continued to be low, and gross fixed capital formation is expected to continue to show significant annual declines. Imports likely recovered to again outpace exports, though both are expected to register significant annual declines. Economic activity that outpaced projections, an increase in oil prices and other export products, and an expected increase in public spending this year account for the upward revision to the 2021 growth forecast (from 4.6% with a range between 2% and 6% in January, to 6.0% with a range between 3% and 7% in April). As a result, the output gap is expected to be smaller and to tighten more rapidly than projected in the previous report, though it is still expected to remain in negative territory on the forecast horizon. Wide forecast intervals reflect the fact that the future evolution of the COVID-19 pandemic remains a significant source of uncertainty on these projections. The delay in the recovery of economic activity as a result of the resurgence of COVID-19 in the first quarter appears to have been less significant than projected in the January report. The central forecast scenario expects this improved performance to continue in 2021 alongside increased consumer and business confidence. Low real interest rates and an active credit supply would also support this dynamic, and the overall conditions would be expected to spur a recovery in consumption and investment. Increased growth in public spending and public works based on the national government’s spending plan (Plan Financiero del Gobierno) are other factors to consider. Additionally, an expected recovery in global demand and higher projected prices for oil and coffee would further contribute to improved external revenues and would favor investment, in particular in the oil sector. Given the above, the technical staff’s 2021 growth forecast has been revised upward from 4.6% in January (range from 2% to 6%) to 6.0% in April (range from 3% to 7%). These projections account for the potential for the third wave of COVID-19 to have a larger and more persistent effect on the economy than the previous wave, while also supposing that there will not be any additional significant waves of the pandemic and that mobility restrictions will be relaxed as a result. Economic growth in 2022 is expected to be 3%, with a range between 1% and 5%. This figure would be lower than projected in the January report (3.6% with a range between 2% and 6%), due to a higher base of comparison given the upward revision to expected GDP in 2021. This forecast also takes into account the likely effects on private demand of a fiscal adjustment of the size currently being proposed by the national government, and which would come into effect in 2022. Excess in productive capacity is now expected to be lower than estimated in January but continues to be significant and affected by high levels of uncertainty, as reflected in the wide forecast intervals. The possibility of new waves of the virus (of uncertain intensity and duration) represents a significant downward risk to projected GDP growth, and is signaled by the lower limits of the ranges provided in this report. Inflation (1.51%) and inflation excluding food and regulated items (0.94%) declined in March compared to December, continuing below the 3% target. The decline in inflation in this period was below projections, explained in large part by unanticipated increases in the costs of certain foods (3.92%) and regulated items (1.52%). An increase in international food and shipping prices, increased foreign demand for beef, and specific upward pressures on perishable food supplies appear to explain a lower-than-expected deceleration in the consumer price index (CPI) for foods. An unexpected increase in regulated items prices came amid unanticipated increases in international fuel prices, on some utilities rates, and for regulated education prices. The decline in annual inflation excluding food and regulated items between December and March was in line with projections from January, though this included downward pressure from a significant reduction in telecommunications rates due to the imminent entry of a new operator. When controlling for the effects of this relative price change, inflation excluding food and regulated items exceeds levels forecast in the previous report. Within this indicator of core inflation, the CPI for goods (1.05%) accelerated due to a reversion of the effects of the VAT-free day in November, which was largely accounted for in February, and possibly by the transmission of a recent depreciation of the peso on domestic prices for certain items (electric and household appliances). For their part, services prices decelerated and showed the lowest rate of annual growth (0.89%) among the large consumer baskets in the CPI. Within the services basket, the annual change in rental prices continued to decline, while those services that continue to experience the most significant restrictions on returning to normal operations (tourism, cinemas, nightlife, etc.) continued to register significant price declines. As previously mentioned, telephone rates also fell significantly due to increased competition in the market. Total inflation is expected to continue to be affected by ample excesses in productive capacity for the remainder of 2021 and 2022, though less so than projected in January. As a result, convergence to the inflation target is now expected to be somewhat faster than estimated in the previous report, assuming the absence of significant additional outbreaks of COVID-19. The technical staff’s year-end inflation projections for 2021 and 2022 have increased, suggesting figures around 3% due largely to variation in food and regulated items prices. The projection for inflation excluding food and regulated items also increased, but remains below 3%. Price relief measures on indirect taxes implemented in 2020 are expected to lapse in the second quarter of 2021, generating a one-off effect on prices and temporarily affecting inflation excluding food and regulated items. However, indexation to low levels of past inflation, weak demand, and ample excess productive capacity are expected to keep core inflation below the target, near 2.3% at the end of 2021 (previously 2.1%). The reversion in 2021 of the effects of some price relief measures on utility rates from 2020 should lead to an increase in the CPI for regulated items in the second half of this year. Annual price changes are now expected to be higher than estimated in the January report due to an increased expected path for fuel prices and unanticipated increases in regulated education prices. The projection for the CPI for foods has increased compared to the previous report, taking into account certain factors that were not anticipated in January (a less favorable agricultural cycle, increased pressure from international prices, and transport costs). Given the above, year-end annual inflation for 2021 and 2022 is now expected to be 3% and 2.8%, respectively, which would be above projections from January (2.3% and 2,7%). For its part, expected inflation based on analyst surveys suggests year-end inflation in 2021 and 2022 of 2.8% and 3.1%, respectively. There remains significant uncertainty surrounding the inflation forecasts included in this report due to several factors: 1) the evolution of the pandemic; 2) the difficulty in evaluating the size and persistence of excess productive capacity; 3) the timing and manner in which price relief measures will lapse; and 4) the future behavior of food prices. Projected 2021 growth in foreign demand (4.4% to 5.2%) and the supposed average oil price (USD 53 to USD 61 per Brent benchmark barrel) were both revised upward. An increase in long-term international interest rates has been reflected in a depreciation of the peso and could result in relatively tighter external financial conditions for emerging market economies, including Colombia. Average growth among Colombia’s trade partners was greater than expected in the fourth quarter of 2020. This, together with a sizable fiscal stimulus approved in the United States and the onset of a massive global vaccination campaign, largely explains the projected increase in foreign demand growth in 2021. The resilience of the goods market in the face of global crisis and an expected normalization in international trade are additional factors. These considerations and the expected continuation of a gradual reduction of mobility restrictions abroad suggest that Colombia’s trade partners could grow on average by 5.2% in 2021 and around 3.4% in 2022. The improved prospects for global economic growth have led to an increase in current and expected oil prices. Production interruptions due to a heavy winter, reduced inventories, and increased supply restrictions instituted by producing countries have also contributed to the increase. Meanwhile, market forecasts and recent Federal Reserve pronouncements suggest that the benchmark interest rate in the U.S. will remain stable for the next two years. Nevertheless, a significant increase in public spending in the country has fostered expectations for greater growth and inflation, as well as increased uncertainty over the moment in which a normalization of monetary policy might begin. This has been reflected in an increase in long-term interest rates. In this context, emerging market economies in the region, including Colombia, have registered increases in sovereign risk premiums and long-term domestic interest rates, and a depreciation of local currencies against the dollar. Recent outbreaks of COVID-19 in several of these economies; limits on vaccine supply and the slow pace of immunization campaigns in some countries; a significant increase in public debt; and tensions between the United States and China, among other factors, all add to a high level of uncertainty surrounding interest rate spreads, external financing conditions, and the future performance of risk premiums. The impact that this environment could have on the exchange rate and on domestic financing conditions represent risks to the macroeconomic and monetary policy forecasts. Domestic financial conditions continue to favor recovery in economic activity. The transmission of reductions to the policy interest rate on credit rates has been significant. The banking portfolio continues to recover amid circumstances that have affected both the supply and demand for loans, and in which some credit risks have materialized. Preferential and ordinary commercial interest rates have fallen to a similar degree as the benchmark interest rate. As is generally the case, this transmission has come at a slower pace for consumer credit rates, and has been further delayed in the case of mortgage rates. Commercial credit levels stabilized above pre-pandemic levels in March, following an increase resulting from significant liquidity requirements for businesses in the second quarter of 2020. The consumer credit portfolio continued to recover and has now surpassed February 2020 levels, though overall growth in the portfolio remains low. At the same time, portfolio projections and default indicators have increased, and credit establishment earnings have come down. Despite this, credit disbursements continue to recover and solvency indicators remain well above regulatory minimums. 1.2 Monetary policy decision In its meetings in March and April the BDBR left the benchmark interest rate unchanged at 1.75%.