Auswahl der wissenschaftlichen Literatur zum Thema „Transmission path“

The mechanical properties of joined structures are determined considerably by the chosen joining technology. With the aim of providing a method that enables a faster and more profound decision-making in the spatial distribution of joining points during product development, a new method for the load path analysis of joining points is presented. For an exemplary car body, the load type in the joining elements, i.e. pure tensile, shear and combined tensile-shear loads, is determined using finite element analysis (FEA). Based on the evaluated loads, the resulting load paths in selected joining points are analyzed using a 2D FE-model of a clinching point. State of the art methods for load path analysis are dependent on the selected coordinate system or the existing stress state. Thus, a general statement about the load transmission path is not possible at this time. Here, a novel method for the analysis of load paths is used, which is independent of the alignment of the analyzed geometry. The basic assumption of the new load path analysis method was confirmed by using a simple specimen with a square hole in different orientations. The results presented here show a possibility to display the load transmission path invariantly. In further steps, the method will be extended for 3D analysis and the investigation of more complex assemblies. The primary goal of this methodical approach is an even load distribution over the joining elements and the component. This will provide a basis for future design approaches aimed at reducing the number of joining elements in joined structures.

The vibration transmission path systems are generally composed of the vibration source, the vibration transfer path, and the vibration receiving structure. The transfer path is the medium of the vibration transmission. Moreover, the randomness of transfer path influences the transfer reliability greatly. In this paper, based on the matrix calculus, the generalized second moment technique, and the stochastic finite element theory, the effective approach for the transfer reliability of vibration transfer path systems was provided. The transfer reliability of vibration transfer path system with uncertain path parameters including path mass and path stiffness was analyzed theoretically and computed numerically, and the correlated mathematical expressions were derived. Thus, it provides the theoretical foundation for the dynamic design of vibration systems in practical project, so that most random path parameters can be considered to solve the random problems for vibration transfer path systems, which can avoid the system resonance failure.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.
Includes bibliographical references (leaves 77-79).
by Lon E. Sunshine.
Ph.D.

In this thesis, a new transport protocol, the Concurrent Multi-Path Real-time Transmission Control Protocol (cmpRTCP) is proposed. The proposed protocol has been designed to handle real-time streams (video and audio) over IP-networks. One of the key strengths of this protocol lies in its ability to intelligently exploit the availability of multiple paths between multi-homed hosts for concurrent transmission of unicast real-time streams. This work describes the architecture and operation of cmpRTCP in detail. In addition, the limitations of currently used transport protocols in handling real-time streams are also discussed. These limitations of other protocols have played a vital role in the design process of the proposed protocol. Experiments to evaluate the performance of cmpRTCP against other protocols and the results obtained therein are also documented in this work. Results show that cmpRTCP is a best effort protocol that tries to maximize the amount of data that is successfully delivered to the destination in a timely manner under varying drop and delay conditions of the network.

Un aspecte fonamental quan cal resoldre un problema vibroacústic en un sistema mecànic és el de determinar com flueix l’energia des d’una font donada, cap a qualsevol part del sistema. Això permet decidir quines són les accions a prendre per disminuir, per exemple, els nivells de soroll i vibracions en una determinada àrea del sistema. El comportament dinàmic d’un sistema mecànic es pot estimar utilitzant diversos mètodes numèrics, cadascun dels quals enfocat a un marge de freqüència determinat. Mentre a baixes freqüències es poden aplicar mètodes deterministes com el Mètode d’Elements Finits (FEM) o el Mètode d’Elements de Contorn (BEM), a altes freqüències, els mètodes estadístics com l’Anàlisi Estadística Energètica (SEA), esdevenen inevitables. A més a més, diverses tècniques com el FE-SEA híbrid, els models de Distribució Energètica (ED) o l’Anàlisi Estadística de distribució d’Energia modal (SmEdA), entre d’altres, han estat recentment plantejades per tal de tractar amb l’anomenat problema de les mitges freqüències. Tanmateix, encara que alguns mètodes numèrics poden predir la resposta vibroacústica puntual o amitjanada d’un sistema, aquests no proporcionen de forma directa informació sobre com flueix l’energia per tot el sistema. Per tant, cal algun tipus de post-processament per a determinar quines són les vies de transmissió d’energia. L’energia transmesa a través d’un determinat camí que connecti un subsistema font, on l’energia és introduïda, i un subsistema receptor, es pot calcular numèricament. Tot i això, la identificació dels camins que dominen la transmissió d’energia des d’una font fins a un receptor normalment acostuma a basar-se en l’experiència i el parer de l’enginyer. Així doncs, un mètode que permeti obtenir aquests camins de forma automàtica resultaria molt útil. La teoria de grafs proporciona una sortida a aquest problema, ja que existeixen diversos algorismes de càlcul de camins en grafs. En aquesta tesi, es proposa un enllaç entre els models vibroacústics i la teoria de grafs, que permet adreçar els problemes de vies de transmissió de forma directa. La dissertació comença centrant-se en els models SEA. Primerament, es mostra que té sentit realitzar una anàlisi de vies de transmissió (TPA) en SEA. Seguidament, es defineix un graf que representa de forma acurada els models SEA. Tenint en compte que la transmissió d’energia entre fonts i receptors es pot justificar mitjançant la contribució d’un grup finit de vies dominants en varis casos d’interès, es presenta un algorisme per calcular-les. A continuació, s’implementa un algorisme que inclou en el càlcul de camins la naturalesa estocàstica dels factors de pèrdues SEA. Tot seguit, es tracta com es pot estendre l’anàlisi de vies de transmissió al marge de la mitja freqüència. L’aplicació de la teoria de grafs a les mitges freqüències s’adapta per alguns models ED, així com també SmEdA. Finalment, es presenta una altra possible aplicació de la teoria de grafs en vibroacústica. S’implementa una estratègia basada en algorismes de talls en grafs per tal de reduir l’energia en un subsistema receptor amb la modificació d’un grup reduït de factors de pèrdues. Aquest grup de variacions, es troba calculant talls en el graf que separin els subsistemes fonts dels receptors.
A fundamental aspect when solving a vibroacoustic problem in a mechanical system is that of finding out how energy flows from a given source to any part of the system. This would help making decisions to undertake actions for diminishing, for example, the noise or vibration levels at a given system area. The dynamic behavior of a mechanical system can be estimated using different numerical methods, each of them targeting a certain frequency range. Whereas at low frequencies deterministic methods such as the Finite Element Method (FEM) or the Boundary Element Method (BEM) can be applied, statistical methods like Statistical Energy Analysis (SEA) become unavoidable at high frequencies. In addition, a large variety of approaches such as the hybrid FE-SEA, the Energy Distribution (ED) models or the Statistical modal Energy distribution Analysis (SmEdA), among many others, have been recently proposed to tackle with the so-called mid-frequency problem. However, although numerical methods can predict the pointwise or averaged vibroacoustic response of a system, they do not directly provide information on how energy flows throughout the system. Therefore, some kind of post-processing is required to determine energy transmission paths. The energy transmitted through a particular path linking a source subsystem, where external energy is being input, and a target subsystem, can be computed numerically. Yet, identifying which paths dominate the whole energy transmission from source to target usually relies on the engineer's expertise and judgement. Thus, an approach for the automatic identification of those paths would prove very useful. Graph theory provides a way out to this problem, since powerful path algorithms for graphs are available. In this thesis, a link between vibroacoustic models and graph theory is proposed, which allows one to address energy transmission path problems in a straightforward manner. The dissertation starts focusing on SEA models. It is first shown that performing a transmission path analysis (TPA) in SEA makes sense. Then a graph that accurately represents the SEA model is defined. Given that the energy transmission between sources and targets is justified by the contribution of a limited group of dominant paths in many cases of practical interest, an algorithm to find them is presented. Thereafter, an enhanced algorithm is devised to include the stochastic nature of SEA loss factors in the ranking of paths. Next, it is discussed how transmission path analysis can be extended to the mid frequency range. The graph approach for path computation becomes adapted for some ED models, as well as for SmEdA. Finally, we outline another possible application of graph theory to vibroacoustics. A graph cut algorithm strategy is implemented to achieve energy reduction at a target subsystem with the sole modification of a reduced set of loss factors. The set is found by computing cuts in the graph separating source and receiver subsystems.
Un aspecto fundamental a la hora de resolver un problema vibroacústico en un sistema mecánico es el de determinar cómo fluye la energía desde una determinada fuente hasta cualquier parte del sistema. Ello ayudaría a tomar decisiones para emprender acciones destinadas a disminuir, por ejemplo, los niveles de ruido y vibraciones en un área del sistema dada. El comportamiento dinámico de un sistema mecánico se puede estimar utilizando varios métodos numéricos, cada uno de ellos enfocado a un determinado rango de frecuencia. Mientras en las bajas frecuencias se pueden aplicar métodos deterministas como el Método de los Elementos Finitos (FEM) o el método de Elementos de Contorno (BEM), los métodos estadísticos como el Análisis Estadístico Energético son inevitables en las altas frecuencias. Además, se han desarrollado gran variedad de técnicas como el FE-SEA híbrido, los modelos de Distribución de Energía (ED) o el Análisis Estadístico de distribución de Energía modal (SmEdA), entre otras, para tratar el llamado problema de las medias frecuencias. Sin embargo, aunque los métodos numéricos pueden predecir la respuesta vibroacústica puntual o promediada de un sistema mecánico, ellos no proporcionan información sobre como fluye la energía en el sistema. Por lo tanto, hace falta algún tipo de post-procesado para determinar las vías de transmisión de energía. La energía transmitida a través de un determinado camino que conecta un subsistema fuente, donde se introduce la energía, y un subsistema receptor, se puede calcular numéricamente. A pesar de ello, identificar qué caminos dominan la transmisión de energía desde la fuente al receptor normalmente suele recaer en la experiencia o el juicio del ingeniero. Así pues, un método automático para identificar estos caminos resultaría muy útil. La teoría de grafos proporciona una solución a este problema, ya que existen potentes algoritmos de cálculos de caminos en grafos. En esta tesis, se propone un enlace entre los modelos vibroacústicos y la teoría de grafos, que permite abordar los problemas de vías de transmisión de forma directa. La disertación empieza centrándose en los modelos SEA. Primeramente, se muestra que tiene sentido realizar un análisis de vías de transmisión (TPA) en un modelo SEA. Seguidamente, se define un grafo que representa fielmente un modelo SEA. Teniendo en cuenta que en muchos casos de interés práctico, la transmisión de energía entre fuentes y receptores se puede justificar mediante la contribución de un grupo finito de vías de transmisión, se define un algoritmo para encontrarlas. A continuación, se implementa un algoritmo que incluye en el cómputo de caminos la naturaleza estocástica de los factores de pérdidas SEA. Luego, se trata la extensión del análisis de vías de transmisión al rango de media frecuencia. La técnica de teoría de grafos aplicada a cálculo de caminos se adapta para algunos modelos ED y también SmEdA. Finalmente, se presenta otra posible aplicación de la teoría de grafos a la vibroacústica. Se implementa una estrategia basada en algoritmos de cortes en grafos destinada a reducir la energía en un subsistema receptor mediante la simple modificación de un grupo reducido de factores de pérdidas. El grupo se encuentra calculando cortes que separen en el grafo los subsistemas fuentes de los subsistemas receptores.

This paper analyses the process of wealth accumulation with regard to the path dependence theory. Based on the theoretical foundations of Robert King Merton, Vilfredo Pareto and Pierre Bourdieu, mechanisms of wealth accumulation are analyzed. These mechanisms, which are understood as direct and indirect network effects, are formalized using the statistical computing software R. A base model without any mechanisms of wealth accumulation is developed, which makes it possible to include the analyzed mechanisms step by step and observe their effects on the process of wealth accumulation and social inequality. Piketty's findings from his work Capital in the 21st Century are included in the formalized models of wealth accumulation, in particular the relationship between the rate of return on capital and the growth rate of the economy. (author's abstract)

Large scale path loss modeling plays a fundamental role in designing both fixed and mobile radio systems. Predicting the radio coverage area of a system is not done in a standard manner. Wireless systems are expensive systems. Therefore, before setting up a system one has to choose a proper method depending on the channel environment, frequency band and the desired radio coverage range. Path loss prediction plays a crucial role in link budget analysis and in the cell coverage prediction of mobile radio systems. Especially in urban areas, increasing numbers of subscribers brings forth the need for more base stations and channels. To obtain high efficiency from the frequency reuse concept in modern cellular systems one has to eliminate the interference at the cell boundaries. Determining the cell size properly is done by using an accurate path loss prediction method. Starting from the radio propagation phenomena and basic path loss models this thesis aims at describing various accurate path loss prediction methods used both in rural and urban environments. The Walfisch-Bertoni and Hata models, which are both used for UHF propagation in urban areas, were chosen for a detailed comparison. The comparison shows that the Walfisch-Bertoni model, which involves more parameters, agrees with the Hata model for the overall path loss.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2007.
Dr. Henry L. Owen III, Committee Member ; Dr. David Keezer, Committee Member ; Dr. D. Scott Wills, Committee Chair.

Le rendement d’un hélicoptère est étroitement lié à son poids. L’allègement des composants profite à la charge utile transportable. Il implique généralement une diminution de leur rigidité, donc une augmentation de leur déformation. Les boites de transmission par engrenages sont particulièrement concernées. Elles doivent assurer la transmission de puissances importantes à masse minimale. Les axes des roues dentées se désalignent alors progressivement au fur et à mesure de l’application du chargement. Les topographies des dentures spiroconiques sont corrigées pour tolérer ce déplacement et optimiser les performances du mécanisme. La portée d’engrènement ne doit pas toucher une arête afin d’éviter toute surpression par effet de bord et une dégradation prématurée des dents. Il faut améliorer la répartition de l’effort transmis et des pressions de contact. L’erreur de transmission induit des vibrations et du bruit. Il faut donc la minimiser. L’étude de la correction à appliquer à la denture est fastidieuse et requiert une longue période d’apprentissage lorsqu’elle est réalisée manuellement. Les travaux présentés s’inscrivent dans le cadre d’une automatisation du processus. L’usinage et l’engrènement des dentures sont simulés numériquement. Les méthodes proposées sont simples et robustes. Trois problèmes d’optimisation différents sont traités et analysés
The performance of a helicopter is closely linked to its weight. The components are lightened to benefit the carried payload. That usually involves a reduction in their stiffness, so an increase in their deformation. The transmission gear boxes are particularly affected. They must ensure the transmission of high powers with a minimal mass. The load makes the axes of the gears misaligned. The topographies of the spiral bevel gear teeth are corrected in order to tolerate the displacement and optimize the mechanism performances. The contact path must not touch tooth edges to avoid any overpressure and premature degradation. The distribution of the transmitted load and of the contact pressures must be improved. The transmission error induces vibrations and noise. Therefore, it must be minimized. The study of the correction to be applied to the teeth is tedious and requires a long learning period when it is done manually. The presented works fit into the scheme of an automated process. The machining and meshing of the teeth are simulated numerically. The proposed methods are simple and robust. Three different optimization problems are discussed and analyzed

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%.

With recently accelerated support for the development of microbicides to prevent HIV transmission and the urgency of the global AIDS epidemic, it is important to begin to identify strategies for introducing a microbicide once it is proven safe and effective and is approved for use. This report presents results from a qualitative study that explored a range of issues likely to influence microbicide introduction—positively or negatively—at three levels: community, health service, and policy. The study, which identified critical issues to be addressed in building support for microbicides and facilitating a smooth introduction, was conducted between September 2002 and September 2003 in Langa, a peri-urban site in the Western Cape Province of South Africa, and at national and provincial levels. Through in-depth interviews and focus group discussions, this study explored and identified issues that could facilitate or undermine access to and use of microbicides. Respondents included community members, health care providers and managers, provincial- and national-level government officials, and representatives from national and provincial nongovernmental organizations and health professional bodies that influence policy.

With recently accelerated support for the development of microbicides to prevent HIV transmission and the urgency of the global AIDS epidemic, it is important to begin to identify strategies for introducing a microbicide once it is proven safe and effective and is approved for use. This executive summary presents results from a qualitative study that explored a range of issues likely to influence microbicide introduction at the community, health service, and policy levels. The study, which identified critical issues to be addressed in building support for microbicides and facilitating a smooth introduction, was conducted between September 2002 and September 2003 in Langa, a peri-urban site in the Western Cape Province of South Africa, and at national and provincial levels. Through in-depth interviews and focus group discussions, this study explored and identified issues that could facilitate or undermine access to and use of microbicides. Respondents included community members, health care providers and managers, provincial- and national-level government officials, and representatives from national and provincial nongovernmental organizations and health professional bodies that influence policy.