Academic literature on the topic 'Intermediate pressure'

Flows in an intermediate turbine duct connecting low-pressure turbines and power turbines are very complex, affected by the upstream low-pressure turbine flow structures. Non-uniformities originating from the duct with struts also affect the power turbine inflow conditions, resulting in reduced efficiency. The present investigation is done to clarify the flow and loss mechanisms within the intermediate turbine duct and the power turbine. Steady and unsteady numerical investigations of the flow interaction between low-pressure turbine blade, intermediate turbine duct and power turbine vane were conducted. Effects of upstream low-pressure turbine blade on intermediate turbine duct flow fields and loss characteristics, and that of intermediate turbine duct with big and small struts on power turbine aerodynamics are explored. The generation and propagation of wake and secondary flows through the whole configuration are described. The fast Fourier transformation analyses of the flow in the low-pressure turbine blade, intermediate turbine duct and power turbine vane are also presented. Results from the steady and unsteady investigations show complex flow patterns resulted from blade–strut–vane flow interactions, which are not obtainable from intermediate turbine duct-only or power turbine-only simulations. The intermediate turbine duct has a great amplifying influence on the distorted inflow, and the inlet flow with upstream wakes and secondary flows introduces a high-loss area along the casing at intermediate turbine duct exit. Detailed results are presented and discussed for the flow physics and loss mechanisms as well as the unsteady flow evolution through the low-pressure turbine blade, intermediate turbine duct and power turbine vane.

For one of the famous and widely investigated intermediate valence compound YbB12, the experimental studies of the pressure effect on magnetic susceptibility χ(P) were carried out under helium gas pressure P up to 2 kbar at fixed temperatures 78 and 300 K using a pendulum type magnetometer. The measurements show a slight increase in susceptibility under pressure, which is consistent in sign with similar literature data for other ytterbium compounds with intermediate valence of Yb ions. Based on a model analysis of experimental data, the pressure derivative of Yb valence in YbB12 was estimated for the first time, the value of which is in line with the general trend of the valence behavior under pressure in rare earth compounds exhibiting intermediate valence.

UTe2 is a recently discovered unconventional superconductor that has attracted much interest because of its potentially spin-triplet topological superconductivity. Our ac calorimetry, electrical resistivity, and x-ray absorption study of UTe2 under applied pressure reveals key insights on the superconducting and magnetic states surrounding pressure-induced quantum criticality at Pc1 = 1.3 GPa. First, our specific heat data at low pressures, combined with a phenomenological model, show that pressure alters the balance between two closely competing superconducting orders. Second, near 1.5 GPa, we detect two bulk transitions that trigger changes in the resistivity, which are consistent with antiferromagnetic order, rather than ferromagnetism. Third, the emergence of magnetism is accompanied by an increase in valence toward a U4+ (5f2) state, which indicates that UTe2 exhibits intermediate valence at ambient pressure. Our results suggest that antiferromagnetic fluctuations may play a more substantial role on the superconducting state of UTe2 than previously thought.

With the increasing demand of high bypass ratio and thrust-to-weight ratio in civil aero-engine, the intermediate turbine duct between the high pressure and low pressure turbines of a modern gas turbine tends to shorter axial length, larger outlet-to-inlet area ratio and high pressure-to-low pressure radial offset. This paper experimentally and numerically investigated the three-dimensional flow characteristics of traditional (ITD1) and aggressive intermediate turbine duct (ITD2) at low Reynolds number. The baseline case of ITD1 is representative of a traditional intermediate turbine duct of aero-engine design with non-dimensional length of L/dR = 2.79 and middle angle of 20.12°. The detailed flow fields inside ITD1 and flow visualization were measured. Results showed the migration of boundary layer and a pair of counter-rotating vortexes were formed due to the radial migration of low momentum fluid. With the decreasing axial length of intermediate turbine duct, the radial and streamwise reverse pressure gradient in aggressive intermediate turbine duct (ITD2) were increased resulting in severe three-dimensional separation of boundary layer near casing surface and higher total pressure loss. The secondary flow and separation of boundary layer near the endwall were deeply analyzed to figure out the main source of high total pressure loss in the aggressive intermediate turbine duct (ITD2). Based on that, employing wide-chord guide vane to substitute “strut + guide vane”, this paper designed the super-aggressive intermediate turbine duct and realized the suppression of the three-dimensional separation and secondary flow.

AbstractLes plasmas à basse température sont largement utilisés dans diverses applications de traitement, telles que le nettoyage de surfaces, la stérilisation de dispositifs médicaux, le traitement de l'eau par plasma, le dépôt chimique en phase vapeur de films d'oxyde métallique, la gravure de matériaux et l'élimination de résidus dans la microélectronique. Cependant, contrairement aux plasmas à basse pression ou à pression atmosphérique, les plasmas à pression intermédiaire sont moins étudiés et ne sont pas encore entièrement compris en raison des défis associés aux diagnostics et aux simulations dans cette plage de pression. Dans cette thèse, nous étudions les plasmas oxygène-argon en utilisant des méthodes expérimentales et de modélisation afin de mieux comprendre la dynamique des particules neutres et chargées dans les plasmas à cette pression. Les recherches suivantes ont été menées :1.Étude des décharges luminescentes en courant continu à pression intermédiaire : cette étude a impliqué la mesure de la densité des atomes d'oxygène et de la température du gaz à l'aide de la technique CRDS. Les effets de la stabilisation du plasma au fil du temps ont été examinés, en soulignant l'importance d'atteindre un état de plasma stable avant de prendre des mesures. L'impact de l'introduction de gaz argon et les effets de petites fuites d'air ont été soigneusement analysés. Des recommandations pour l'étalonnage impliquant le gaz argon ont été fournies, soulignant l'importance de maintenir de bonnes conditions de vide pour une reproductibilité optimale du plasma. L'étude a également discuté des mécanismes derrière la perte de surface des atomes d'oxygène en surface et a introduit un nouveau modèle qui correspond mieux à nos observations expérimentales. De plus, l'influence des variations de la température des parois sur ces processus a été explorée.2.Étude expérimentale des CCP (plasma couplé capacitif) RF (Radio fréquence) dans des mélanges O2-Ar à pression intermédiaire: Cette étude s'est concentrée sur les effets des différentes conditions de puissance, de pression et de mélanges de gaz. Diverses propriétés électriques et neutres ont été mesurées, notamment l'impédance du plasma (en utilisant les sondes Octiv et Tektronix), la densité d'électrons (avec une sonde hairpin) et le flux ionique vers les surfaces (avec un réseau de sondes électrostatiques). En outre, la densité d'atomes d'oxygène, la température du gaz, le taux de perte d'atomes d'oxygène et la concentration d'ozone dans la poste décharge ont été obtenus à l'aide de la technique CRDS. Les effets de la pression, de la puissance et des mélanges de gaz ont été discutés, et les mécanismes de tels plasmas pour les particules chargées et neutres ont été démontrés.3.Modélisation des CCP RF à pression intermédiaire : La thèse présente également des efforts de modélisation en utilisant à la fois des simulations par particules dans la cellule (PIC) et des simulations fluides. L'étude discute des coûts et des limitations du modèle PIC, le compare au modèle fluide, et explique les conditions dans lesquelles le modèle fluide devient invalide. En fin de compte, la thèse propose des suggestions pour choisir la méthode de modélisation appropriée pour différentes plages de pression et propose un modèle hybride qui combine les forces des simulations PIC et fluides
Low-temperature plasmas are extensively used in various processing applications, such as surface cleaning, sterilization of medical devices, plasma-based water treatment, chemical vapor deposition of metal oxide films, material etching, and resist stripping in microelectronics. However, unlike plasmas at low or atmospheric pressures, plasmas at intermediate pressures have been less studied and not fully understood due to the challenges associated with diagnostics and simulations in this pressure range. In this thesis, we investigate oxygen-argon plasmas using both experimental and modeling methods to gain a deeper understanding of the dynamics of neutral and charged particles in plasmas at this pressure range. The following research was conducted:1.Investigation of DC Glow Discharges at Intermediate Pressure: This study involved measuring the density of oxygen atoms and the gas temperature using the CRDS technique. The effects of plasma stabilization over time were examined, emphasizing the importance of achieving a stable plasma state before taking measurements. The impact of introducing argon gas, and the effects of small air leaks, were carefully analyzed. Recommendations for actinometry calibration involving argon gas were provided, highlighting the importance of maintaining good vacuum conditions for optimal plasma reproducibility. The study also discussed the mechanisms behind the surface loss of oxygen atoms and introduced a novel model that better aligns with our experimental observations. Additionally, the influence of varying wall temperatures on these processes was explored.2.Experimental Study of RF (Radiofrequency) CCP (Capacitively Coupled Plasma) in O2-Ar Mixtures at Intermediate Pressure: This study focused on the effect of different power, pressure, and gas mixtures. Various electrical and neutral properties were measured, including plasma impedance (using an Octiv and Tektronix probes), electron density (using a hairpin probe), and surface ion flux (using an electrostatic probe array). Additionally, oxygen atom density, gas temperature, O atom loss rate, and ozone concentration in the afterglow were obtained using the CRDS technique. The effects of pressure, power, and gas mixtures were discussed, and the mechanisms occurring in such plasmas for both charged particles and neutrals were demonstrated.3.Modeling of RF CCP at Intermediate Pressure: The thesis also presents modeling efforts using both Particle-in-Cell (PIC) and fluid simulations. The study discusses the costs and limitations of the PIC (Particle-in-Cell) model, comparing it with the fluid model, and explains the conditions under which the fluid model becomes invalid. Ultimately, the thesis offers suggestions for choosing the appropriate modeling method for different pressure ranges and proposes a hybrid model that combines the strengths of both PIC and fluid simulations

In this thesis, the focus is on studying BaZrO3-BaCeO3 based proton conductors due to that they represent very promising proton conductors to be used for Intermediate Temperature Solid Oxide Fuel Cells (ITSOFCs). Here, dense BaZr0.5Ce0.3Y0.2O3-δ (BZCY532) ceramics were selected as the major studied materials. These ceramics were prepared by different sintering methods and doping strategies. Based on achieved results, the thesis work can simply be divided into the following parts: 1) An improved synthesis method, which included a water-based milling procedure followed by a freeze-drying post-processing, was presented. A lowered calcination and sintering temperature for a Hf0.7Y0.3O2-δ (YSH) compound was achieved. The value of the relative density in this work was higher than previously reported data. It is also concluded that this improved method can be used for mass-production of ceramics. 2) As the solid-state reactive sintering (SSRS) represent a cost-effective sintering method, the sintering behaviors of proton conductors BaZrxCe0.8-xLn0.2O3-δ (x = 0.8, 0.5, 0.1; Ln = Y, Sm, Gd, Dy) during the SSRS process were investigated. According to the obtained results, it was found that the sintering temperature will decrease, when the Ce content increases from 0 (BZCLn802) to 0.3 (BZCLn532) and 0.7 (BZCLn172). Moreover, the radii of the dopant ions similar to the radii of Zr4+ or Ce4+ ions show a better sinterability. This means that it is possible to obtain dense ceramics at a lower temperature. Moreover, the conductivities of dense BZCLn532 ceramics were determined. The conductivity data indicate that dense BZCY532 ceramics are good candidates as either oxygen ion conductors or proton conductors used for ITSOFCs. 3) The effect of NiO on the sintering behaviors, morphologies and conductivities of BZCY532 based electrolytes were systematically investigated. According to the achieved results, it can be concluded that the dense BZCY532B ceramics (NiO was added during ball-milling before a powder mixture calcination) show an enhanced oxygen and proton conductivity. Also, that BZCY532A (NiO was added after a powder mixture calcination) and BZCY532N (No NiO was added in the whole preparation procedures) showed lower values. In addition, dense BZCY532B and BZCY532N ceramics showed only small electronic conductivities, when the testing temperature was lower than 800 ℃. However, the BZCY532A ceramics revealed an obvious electronic conduction, when they were tested in the range of 600 ℃ to 800 ℃. Therefore, it is preferable to add the NiO powder during the BZCY532 powder preparation, which can lower the sintering temperature and also increase the conductivity. 4) Dense BZCY532 ceramics were successfully prepared by using the Spark Plasma Sintering (SPS) method at a temperature of 1350 ℃ with a holding time of 5 min. It was found that a lower sintering temperature (< 1400 ℃) and a very fast cooling rate (> 200 ℃/min) are two key parameters to prepare dense BZCY532 ceramics. These results confirm that the SPS technique represents a feasible and cost-effective sintering method to prepare dense Ce-containing BaZrO3-BaCeO3 based proton conductors. 5) Finally, a preliminary study for preparation of Ce0.8Sm0.2O2-δ (SDC) and BZCY532 basedcomposite electrolytes was carried out. The novel SDC-BZCY532 based composite electrolytes were prepared by using the powder mixing and co-sintering method. The sintering behaviors, morphologies and ionic conductivities of the composite electrolytes were investigated. The obtained results show that the composite electrolyte with a composition of 60SDC-40BZCY532 has the highest conductivity. In contrast, the composite electrolyte with a composition of 40SDC-60BZCY532 shows the lowest conductivity. In summary, the results show that BaZrO3-BaCeO3 based proton-conducting ceramic materials represent very promising materials for future ITSOFCs electrolyte applications.

QC 20150423

A indústria mineradora do país sofre constantemente com problemas ambientais devido à qualidade e volume de rejeitos gerados durante o processo de extração do minério. Os volumes gerados demandam grandes áreas para armazenagem e consequentemente obras complexas de contenção dos rejeitos. A engenharia geotécnica busca entender o comportamento mecânico de depósitos destes rejeitos através do uso de ensaios tanto de campo como de laboratório. Para isso utiliza ferramentas e procedimentos consagrados no meio técnico seguindo normas e procedimentos estabelecidos e consagrados mundialmente. No entendimento do comportamento mecânico dos solos argilosos, as análises são desenvolvidas em termos de tensões totais, já para os solos arenosos em termos de tensões efetivas. Todavia, para solos com granulometria intermediária, não se tem um consenso no que se refere à interpretação do comportamento mecânicos a partir de ensaios de campo Este trabalho apresenta resultados de ensaios de DMT e CPTU conduzidos em diferentes velocidades de penetração no intervalo de aproximadamente 1 e 57 mm/s, em depósito de rejeito de mineração, para avaliar tanto a influência da velocidade sobre as medidas do ensaio, quanto a transição das condições de fluxo ao redor do piezocone e durante a expansão da membrana do dilatômetro. Um equipamento simples e de baixo custo foi desenvolvido para monitorar a poropressão no centro da lâmina do DMT e dados são interpretados à luz das condições de drenagem impostas durante a execução do ensaio. Resultados indicam que as leituras e os valores de P0 e P1 são medidas de tensão total e por este motivo influenciadas pela magnitude da poropressão gerada durante a penetração da lâmina. Um novo Fator de Velocidade adimensional “Vt” é proposto para identificar possíveis efeitos de consolidação que ocorrem durante a penetração do piezocone e orientações são dadas para utilização de CPTU e DMT em solos de permeabilidade dentro do intervalo de 10-6 a 10-3 cm/s.
The mining industry of the country constantly suffers from environmental problems due to the quality and volume of waste generated during the mineral extraction process. Volumes generated require large areas for storage and consequently complex works of tailings. The geotechnical engineering seeks to understand the mechanical behavior of deposits of this waste by using assays well as laboratory and field. To this end tools and procedures laid down in the technical means following established rules and procedures consecrated worldwide. In the understanding of the mechanical behavior of clay soils, the analyzes are developed in terms of total stresses and for sandy soils in terms of effective stress. However, in soils with intermediate particle size, there is no consensus concerning the interpretation of the mechanical behavior from field trials. This paper presents the results of DMT and CPTU test conducted at different penetration rates in the range of about 1 to 57 mm / s in mining waste deposit to evaluate both the effect of speed on the measurements of the test, as the transition the flow conditions around the piezocone and during the expansion of the dilatometer membrane. A simple and inexpensive equipment has been developed to monitor the pore pressure in the center of the DMT blade and data are interpreted in the light of the imposed drainage conditions during the test. Results indicate that the readings that the P0 and P1 are total stress measurements and for this reason influenced by the magnitude of pore pressure generated during penetration of DMT blade. A new dimensionless Velocity Factor "Vt" is proposed to identify potential consolidation effects occurring during the penetration of piezocone and guidance is provided for use CPTU and DMT in soil permeability in the range 10-6 to 10-3 cm/s.

Cette thèse a pour objet l'étude de 3 systèmes de fermions lourds à base d'Ytterbium, YbCu2Si2, YbCo2Zn20 et YbRh2Si2, dans des conditions extrêmes de hautes pressions, basses températures et hauts champs magnétiques. Une partie très importante dans ce travail a été le développement d'un dispositif de génération de force à très basses températures permettant une modulation de la pression in-situ adapté à des cellules à enclumes diamant. Pour YbCu2Si2, les mesures de ac-susceptibilité sous pression et sous champ magnétiques ainsi que les mesures d'aimantation sous pression montrent que l'ordre magnétique qui apparaît pour P> 8 GPa est ferromagnétique. L'étude du changement de la valence de l'ion Yb par des mesures de diffusion inélastique en conditions résonantes de rayons X ont permis de clarifier son interaction avec le magnétisme. Même si l'état trivalent est clairement favorisé sous pression, la valence reste inférieure à 3, proche de l'ordre magnétique, même dans les plus hautes pressions et plus basses températures. Nous avons également procédé à une recherche détaillée pour les signatures de metamagnétisme avec des mesures à très haut champ. Dans la deuxième partie de ma thèse, les mesures de ac-calorimétrie et ac-susceptibilité sous pression ont permit d'établir le diagramme de phase (P-T) dans YbCo2Zn20 jusqu'à 14 GPa. En plus, nos résultats suggèrent que l'ordre magnétique qui apparaît pour P>1 GPa est antiferromagnétique. Les forts effets du champ magnétique observées dans les propriétés physiques dans YbCo2Zn20 sont probablement liés à l'interaction entre le champ magnétique et les spins des électrons 4f et non à leur charge car la valence de l'Yb s'avère insensible à l'application d'un champ magnétique de 10 T. La partie finale de cette thèse est consacré à l'étude du diagramme de phase (H-T) sous pression dans YbRh2Si2 pour déterminer l'évolution de la température de l'ordre magnétique en fonctionne de H et P et mieux comprendre les effets liés à ce deux paramètres de contrôle
In this thesis, three Yb-based heavy fermion compounds, YbCu2Si2, YbCo2Zn20 and YbRh2Si2, are studied under extreme conditions, i.e, high pressure, low temperatures and high magnetic fields. An important part of the work has been the set up of an in-situ tuning pressure device to measure diamond anvil cells at dilution fridge temperatures. This has enable most of the experimental results presented here. In YbCu2Si2 the nature of the pressure-induced magnetic order that arises for P> 8 GPa has been clarified to be ferromagnetic by ac-susceptibility and magnetization measurements under pressure. The interplay of magnetism and valence change has been investigated by measuring the valence of the title compound at high pressures and low temperatures using resonant inelastic x-ray scattering (RIXS). As expected, pressure favors the trivalent state but the Yb ion valence remains below 3 even at the highest pressure and at low temperatures very close to the onset of the magnetic order. We have also performed a detailed search for signatures of metamagnetism. The second part of my thesis focuses on YbCo2Zn20. We have extended the (P-T) phase diagram up to 14 GPa by ac-calorimetry and ac-susceptibility measurements. Our results shed some light on the nature of the magnetic order that arises for P>1 GPa which is antiferromangetic. The strong field effects observed in the physical properties in YbCo2Zn20 are probably related to the interaction between the magnetic field and the spin of the 4f electrons rather than to their charge as the valence of the Yb ion is insensitive to the application of a magnetic field of 10 T. The final part of this thesis is devoted to the detailed study of the (H-T) phase diagram under pressure in YbRh2Si2 to determine the evolution of the magnetic ordering temperatures as a function of H and P to better understand the interplay of the two control parameters

Dans le système YbMn6Ge6-xSnx, l’ytterbium de valence intermédiaire (v.i.) s’ordonne magnétiquement à des températures étonnamment élevées (jusqu’à TYb~125 K). Ce travail contribue à une meilleure compréhension des propriétés physiques de ces alliages grâce à la stabilisation de nouveaux composés dans la gamme de concentration 4,6~2,8). Des expériences sous pression ont souligné l’analogie entre les effets de pression mécanique et chimique. L’augmentation de pression favorise le caractère trivalent et le magnétisme d’Yb. La 2nde partie de ce travail constitue une ouverture vers les matériaux pour les applications magnétocaloriques haute température telles que les pompes à chaleur ou la conversion d’énergie. Elle concerne l’étude des composés Mn4-xFexGa2Sn et Fe3Sn2 qui possèdent des températures de travail supérieures à la température ambiante. Leur EMC est modéré mais comparable à celui d’autres matériaux à transition de 2nd ordre fonctionnant dans la même gamme de température
In the YbMn6Ge6-xSnx system, intermediate valent Yb magnetically orders at an astonishingly high temperature (up to TYb~125 K). This work aims to improve the understanding of the physical properties of these compounds, with an emphasis on the concentration range 4.6~2,8). External pressure experiments showed an analogy between mechanical and chemical pressure effects. Increasing the pressure favors trivalent state and Yb magnetism. In a second part, we investigated the magnetic and magnetocaloric properties of Mn4-xFexGa2Sn and Fe3Sn2. High temperature magnetocaloric applications, such as heat pump or heat conversion, need materials with high Curie temperature. These two compounds have working temperatures above 330 K. The magnetocaloric effect has been evaluated : the magnitude is moderate but close to other compounds with a second order transition near this temperature region

[ES] Esta tesis doctoral presenta un estudio de compresores scroll con inyección de vapor (SCVI) para bombas de calor que operan en climas fríos o para aplicaciones de calentamiento de agua a alta temperatura. Para ello, se comparó experimentalmente un SCVI con un compresor de dos etapas de pistones (TSRC) trabajando con R-407C en condiciones extremas. La comparación se realizó en términos de eficiencias del compresor, capacidad, COP y rendimientos estacionales tanto para el modo calefacción como para el modo refrigeración. Los resultados proporcionan una idea general sobre el rango de aplicación de los compresores estudiados y sobre las diferencias en los rendimientos de los compresores. Sin embargo, se identificaron varias limitaciones en la caracterización de los compresores y en el análisis del ciclo. Esto motivó a profundizar en el estudio del ciclo de compresión de dos etapas y sus componentes. El siguiente paso fue realizar un análisis teórico de los ciclos de compresión de dos etapas para aplicaciones de calefacción, en donde se identificó a la presión intermedia y a la relación de inyección como los parámetros del sistema más influyentes sobre el COP. La presión intermedia se optimizó para dos configuraciones de inyección (tanque de separación y economizador) utilizando varios refrigerantes. Basándose en los resultados de la optimización, se propuso una correlación que permite obtener la presión intermedia óptima del ciclo, considerando la influencia del subenfriamiento a la salida del condensador. Además, se analizó la influencia del diseño de los componentes del sistema sobre el COP del ciclo. Posteriormente, el estudio se profundizó a nivel de componentes. El factor más crítico en el sistema es el rendimiento del compresor. Por lo tanto, el siguiente paso fue evaluar la influencia de varios sistemas de compresión con inyección de vapor sobre el COP. Se tomaron en cuenta tres tecnologías de compresores, un SCVI, un TSRC y un compresor scroll de dos etapas (TSSC). Estas tecnologías de compresores fueron caracterizadas y modeladas para estudiar su rendimiento. Para ello, se propuso una nueva metodología para caracterizar compresores scroll con inyección de vapor. Esta metodología permite evaluar el rendimiento del compresor independientemente del mecanismo de inyección que se utiliza en el ciclo. Se identificó una correlación lineal entre la relación de inyección de refrigerante y la relación de compresión intermedia. Esta correlación se utiliza para determinar el flujo másico de inyección en función de la presión intermedia. Posteriormente, se propuso un modelo semi-empírico de compresores scroll y una metodología para extender dicho modelo para compresores scroll con inyección de vapor. Los modelos fueron ajustados y validados usando datos experimentales de cuatro compresores scroll trabajando con R-290 y un SCVI trabajando con R-407C. Finalmente, se comparó un SCVI con dos compresores de dos etapas, un TSSC y un TSRC, trabajando en condiciones extremas. Se optimizó la relación de volúmenes de los compresores de dos etapas. Los resultados muestran que, en las condiciones nominales de funcionamiento (Te=-15 °C, Tc=50 °C), la relación de volúmenes óptima del TSSC es 0.58, y del TSRC es 0.57. El TSSC consigue un COP 6% mayor que el SCVI y un COP 11.7% mayor que el TSRC. Bajo un amplio rango de condiciones de operación, el SCVI presenta una mejor eficiencia y COP para relaciones de presión inferiores a 5. Para relaciones de presión más altas, el TSSC presenta mejor rendimiento y consigue una temperatura de descarga más baja. Se concluye que el SCVI es una solución fácil de implementar, desde el punto de vista del mecanizado, y que permite extender el mapa de trabajo de los compresores de una etapa. Sin embargo, los resultados muestran que la compresión en dos etapas consigue mejorar en mayor medida el COP del ciclo y la capacidad, con una mayor redu
[CA] Aquesta tesi doctoral presenta un estudi de compressors scroll amb injecció de vapor (SCVI) per a bombes de calor que operen en climes freds o per a aplicacions d'escalfament d'aigua a alta temperatura. Per a això, es va comparar experimentalment un SCVI amb un compressor de dues etapes de pistons (TSRC) treballant amb R-407C en condicions extremes. La comparació es va realitzar en termes d'eficiències del compressor, capacitat, COP i rendiments estacionals tant per al mode calefacció com per al mode refrigeració. Els resultats proporcionen una idea general sobre el rang d'aplicació dels compressors estudiats i sobre les diferències en els rendiments dels compressors. No obstant això, es van identificar diverses limitacions en la caracterització dels compressors i en l'anàlisi del cicle. Això va motivar a aprofundir en l'estudi del cicle de compressió de dues etapes i els seus components. El següent pas va ser realitzar una anàlisi teòrica dels cicles de compressió de dues etapes per a aplicacions de calefacció, on es va identificar la pressió intermèdia i la relació d'injecció com els paràmetres del sistema més influents sobre el COP. La pressió intermèdia es va optimitzar per a dues configuracions d'injecció (tanc de separació i economitzador) utilitzant diversos refrigerants. Basant-se en els resultats de l'optimització, es va proposar una correlació que permet obtindre la pressió intermèdia òptima del cicle, considerant la influència del subrefredament a l'eixida del condensador. A més, es va analitzar la influència del disseny dels components del sistema sobre el COP del cicle. Posteriorment, l'estudi es va aprofundir a nivell de components. El factor més crític en el sistema és el rendiment del compressor. Per tant, el següent pas va ser avaluar la influència de diversos sistemes de compressió amb injecció de vapor sobre el COP. Es van prendre en compte tres tecnologies de compressors, un SCVI, un TSRC i un compressor scroll de dues etapes (TSSC). Aquestes tecnologies de compressors van ser caracteritzades i modelades per a estudiar el seu rendiment. Per a això, es va proposar una nova metodologia per a caracteritzar compressors scroll amb injecció de vapor. Aquesta metodologia permet avaluar el rendiment del compressor independentment del mecanisme d'injecció que s'utilitza en el cicle. Es va identificar una correlació lineal entre la relació d'injecció de refrigerant i la relació de compressió intermèdia. Aquesta correlació s'utilitza per a determinar el flux màssic d'injecció en funció de la pressió intermèdia. Posteriorment, es va proposar un model semi-empíric de compressors scroll i una metodologia per a estendre aquest model per a compressors scroll amb injecció de vapor. Els models van ser ajustats i validats utilitzant dades experimentals de quatre compressors scroll treballant amb R-290 i un SCVI treballant amb R-407C. Finalment, es va comparar un SCVI amb dos compressors de dues etapes, un TSSC i un TSRC, treballant en condicions extremes. Es va optimitzar la relació de volums dels compressors de dues etapes. Els resultats mostren que, en les condicions nominals de funcionament (Te=-15 °C, Tc=50 °C), la relació de volums òptima del TSSC és 0.58, i del TSRC és 0.57. El TSSC aconsegueix un COP 6% major que el SCVI i un COP 11.7% major que el TSRC. Sota un ampli rang de condicions d'operació, el SCVI presenta una millor eficiència i COP per a relacions de pressió inferiors a 5. Per a relacions de pressió més altes, el TSSC presenta millor rendiment i aconsegueix una temperatura de descàrrega més baixa. Es conclou que el SCVI és una solució fàcil d'implementar, des del punt de vista del mecanitzat, i que permet estendre el mapa de treball dels compressors d'una etapa. No obstant això, els resultats mostren que la compressió en dues etapes aconsegueix millorar en major mesura el COP del cicle i la capacitat, amb una major reducció de la
[EN] This Ph.D. thesis presents a study of scroll compressors with vapor-injection (SCVI) for heat pumps operating in cold climates or in high-temperature water heating applications. To do so, firstly, an SCVI was experimentally compared with a two-stage reciprocating compressor (TSRC) working with R-407C under extreme conditions. The comparison was made in terms of compressor efficiencies, capacity, COP, and seasonal COP, both for heating and cooling modes. The results give a general idea about the application range of the studied compressors and the differences in the compressors' performance. Nevertheless, several restrictions in the compressors' characterization and the cycle analysis were identified. This motivated us to deepen in the study of the two-stage compression cycle and its components. The next step was performing a theoretical analysis of two-stage compression cycles for heating applications, where the intermediate pressure and the injection ratio were identified as the most influential system parameters on the COP. The intermediate pressure was optimized for two vapor-injection configurations (flash tank and economizer) using several refrigerants. Based on the optimization results, a correlation was proposed that allows obtaining the optimal intermediate pressure of the cycle, considering the influence of the subcooling at the condenser outlet. In addition, a theoretical analysis of the influence of the design of the system components on the COP of the cycle was performed. Once the thermodynamic analysis of the two-stage cycle was carried out, the study was deepened at the component level. The most critical factor in the system is the compressor performance. Hence, the next step was evaluating the influence of several compression systems with vapor-injection on the COP. Three compressor technologies were taken into account, an SCVI, a TSRC and a two-stage scroll compressor (TSSC). These compressor technologies were characterized and modeled in order to study their performance. To do so, a new methodology to characterize SCVI was proposed. This methodology allows evaluating the compressor performance independently of the injection mechanism used in the cycle. A linear correlation was identified between the refrigerant injection ratio and the intermediate compression ratio. This correlation is used to determine the injection mass flow as a function of the intermediate pressure. Then, a semi-empirical model of scroll compressors and a methodology to extend the model for scroll compressors with vapor-injection was proposed. The models were adjusted and validated using experimental data from four scroll compressors working with R-290 and an SCVI compressor working with R-407C. Finally, an SCVI was compared with two two-stage compressors, a TSSC, and a TSRC, working in extreme conditions. The displacement ratio of the two-stage compressors was optimized. Results show that, at the nominal operating conditions (Te=-15 °C, Tc=50 °C), the optimal displacement ratio of the TSSC is 0.58, and of the TSRC is 0.57. The TSSC achieves 6% larger COP than the SCVI and 11.7% larger COP than the TSRC. Under a wide range of operating conditions, the SCVI presents a better efficiency and COP for pressure ratios below 5. For higher-pressure ratios, the TSSC presents better performance and achieves lower discharge temperature. It is concluded that the SCVI is an easy solution to implement from the point of view of machining, which allows extending the working map of the single-stage compressors. However, the results show that the two-stage compression technology gets further improve the COP of the cycle and the capacity, with a greater reduction of the discharge temperature operating under extreme conditions.
I thank the financial support provided by the Secretaría de Educación Superior, Ciencia, Tecnología e Innovación (SENESCYT) of Ecuador, through the international scholarship program for postgraduate studies “Convocatoria Abierta 2013 Segunda Fase, Grant No 2015-AR37665”.
Tello Oquendo, FM. (2019). Study of scroll compressors with vapor-injection for heat pumps operating in cold climates or in high-temperature water heating applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120473
TESIS

Non-invasive ventilation (NIV) has been increasingly used over the past decades to avoid endotracheal intubation (ETI) in critical care settings. In selected patients with acute respiratory failure, NIV improves the overall clinical status more rapidly than standard oxygen therapy, avoids ETI and its complications, reduces length of hospital stay, and improves survival. NIV is primarily indicated in respiratory failure due to acute exacerbations of chronic obstructive pulmonary disease, cardiogenic pulmonary oedema and associated with immunocompromised states. Weaker evidence supports its use in other forms of acute hypercapnic and hypoxaemic respiratory failure. Candidates for NIV should be carefully selected taking into consideration the risk factors for NIV failure. Patients on NIV who are unstable or have risk factors for NIV failure should be monitored in an intensive or intermediate care units by experienced personnel to avoid delay when intubation is needed. Stable NIV patients can be monitored on regular wards.

In the modern anesthesia machine, there are various safety checks in place to help prevent the delivery of a hypoxic gas mixture to the patient. They include the pin index safety system (PISS), diameter index safety system (DISS), failsafe valve, oxygen-nitrous oxide proportioning system, oxygen supply failure alarm, flowmeter sequence, and, most distally, the oxygen analyzer. The PISS is a feature in the high-pressure system. The DISS, failsafe valve, and oxygen failure alarm are in the intermediate-pressure system. The flowmeters, proportioning system, and oxygen analyzer are in the low-pressure system. This chapter undertakes a discussion of the distinct role of each feature and their limitations.

This chapter introduces the basics of radiative transfer, which is a primary energy-transport mechanism inside stars, and also contributes to keeping stars ‘inflated’ and balanced against gravity. The roles of opacity and cross-sections in scattering photons are described. With the help of some drastic but still insightful approximations, the luminosity of a star can be related to its mass, and its surface temperature to its interior temperature. Not all types of stars are covered with analytical approximations, and only the simplest cases are studied here: the high-mass main sequence stars where radiation-pressure dominates, and the intermediate mass range that includes the Sun, where gas pressure dominates but convection is not yet important.

The formal organization of court systems and jurisdictional rules established by legislatures often determine which litigants will have their cases reviewed by an appellate court. While some procedural obstacles are straightforward in their application, others require judicial interpretation with research findings suggesting that judges’ policy goals are related to decision-making on threshold issues. Even if there are no jurisdictional constraints, some losing litigants weigh the costs and benefits of pursuing an appeal. Still, filing an appeal does not guarantee full consideration of the issues raised by an appellant. Caseload pressures have contributed to screening procedures that result in only a minority of cases being closely scrutinized by an appellate panel. This chapter examines research on this winnowing process that characterizes litigant access to intermediate appellate courts.

When a person must choose among actions that will affect both him and other people, he generally takes the others’ interests to have some rational weight, but not as much as his own. This familiar view is intermediate between two others: first, that only the individual’s own interests give him reason to act, and, second, that everyone else’s interests count just as much as his own. Of these two polar views, each has had forceful proponents and each can be traced to a compelling starting point. By contrast, the intermediate view that actually informs most practice seems much harder to defend. The question in this paper is whether that view is simply an unprincipled compromise between two powerful but irreconcilable intellectual pressures or whether, instead, there is some positive reason to accept it

Modern assessment of left ventricular (LV) diastolic function should be based on the estimation of degree of LV filling pressure (LVFP), which is the true determinant of symptoms/signs and prognosis in heart failure.In order to achieve this goal, standard Doppler assessment of mitral inflow pattern (E/A ratio, deceleration time, isovolumic relaxation time) should be combined with additional manoeuvres and/or ultrasound tools such as: ◆ Valsalva manoeuvre applied to mitral inflow pattern. ◆ Pulmonary venous flow pattern. ◆ Velocity flow propagation by colour M-mode. ◆ Pulsed wave tissue Doppler of mitral annuls (average of septal and lateral E′ velocity).In intermediate doubtful situations, the two-dimensional determination of left atrial (LA) volume can be diagnostic, since LA enlargement is associated with a chronic increase of LVFP in the absence of mitral valve disease and atrial fibrillation.Some new echocardiographic technologies, such as the speckle tracking-derived LV longitudinal strain and LV torsion, LA strain, and even the three-dimensional determination of LA volumes can be potentially useful to add further information. In particular, the reduction of LV longitudinal strain in patients with LV diastolic dysfunction and normal ejection fraction demonstrates that a subclinical impairment of LV systolic function already exists under these circumstances.

In the chapter, Haq traces the evolution of the World Bank through the decade of the seventies. Since the time the Bank was established, the global political economy structure underwent considerable changes. The World Bank in the 1970s, under the dynamic leadership of Robert Mcnamara, tried to adjust to these changes. The World Bank of the 1980s faced problems of a weak resource base, poor intermediary role and a greater pressure for the Bank to bend its development philosophy towards the private sector. Haq proposes a few structural changes in the Bank that would enable it to overcome these problems.

AbstractThe China Nansha District of Guangzhou City is located at the geographical center of the Pearl River estuary and the Greater Bay Area of Guangdong, Hong Kong, and Macau, is characterized by widely distributed saturated soft soil layers with poor engineering properties. Although many scholars have explored the influence of loading rate on the mechanical properties of soft soil, research on the variation of undrained shear strength of saturated soft soil under different shear strain rates is still limited. This article conducts an in-depth analysis of the mechanical behavior of saturated soft soil under different strain rates through true triaxial consolidated undrained shear tests. Under load, these layers exhibit a significant rate-dependent mechanical behavior. In order to reveal the influence of shear strain rate on the mechanical properties of highly saturated soft soils based on SPAX-2000 test system, a series of true triaxial consolidation undrained shear tests were carried out under different confining pressures and different strain rates, variation rules of undrained shear strength of saturated soft and the pore water pressure with strain rate were analyzed. The experimental results indicate that the strain-rate softening exists in saturated soft soil. Under the same consolidation conditions, the relative growth rate of shear strength is a monotonic increasing function of the logarithm of shear strain rate, and the smaller the intermediate principle stress, the more significant the effect of shear strain rate on shear strength. During the shearing process (The strain-rate range from 10–6/s to 10–2/s), the undrained shear strength of saturated soft soil increases with the growth of shear strain rate, following an exponential variation pattern. In the early stages of loading, the increase in pore water pressure and the maximum pore water pressure are significantly affected by the strain rate. Throughout the testing process, the variation of pore water pressure exhibits some fluctuation and hysteresis. Different from strongly structured clay, the strength of saturated soft soil undergoes a progressive change with the shear strain rate, without showing a distinct critical rate of transition.

AbstractGroundwater level has long been known to respond to earthquakes; several types of response have been documented. Advances in the last decade were made largely through the studies of water-level response to Earth tides and barometric pressure. These studies have demonstrated that the hydraulic properties of groundwater systems are dynamic and change with time in response to disturbances such as earthquakes. This approach has been applied to estimate the permeability of several drilled active fault zones, to identify leakage from deep aquifers used for the storage of hazardous wastewater, and to reveal the potential importance of soil water and capillary tension in the unsaturated zone. Enhanced permeability is the most cited mechanism for the sustained changes of groundwater level in the intermediate and far fields, while undrained consolidation remains the most cited mechanism for the step-like coseismic changes in the near field. A new mechanism has emerged that suggests that coseismic release of pore water from unsaturated soils may also cause step-like increases of water level. Laboratory experiments show that both the undrained consolidation and the release of water from unsaturated zone may occur to explain the step-like water-level changes in the near field.

AbstractProduction processes for the manufacturing of technical components are enabled by the availability and use of adequate engineering materials. Within the Internet of Production this work stream is dedicated to developing material and process-based solutions to increase the data availability during the manufacturing and operation of discontinuous mold-based production systems such as high-pressure die casting (HPDC) and injection molding (IM). This includes the development of data-driven alloy design strategies for additively manufactured mold components using tool steels as an initial use case as well as new surface-based smart sensor and actuator solutions. Material data and properties are tracked from the steel powder production via gas atomization until the final use in a mold to produce castings. Intermediate steps include the 3D printing of mold components via laser powder bed fusion and subsequent application of physical vapor deposition and thermal spraying-based smart multilayer coatings with sensor and actuator capabilities. The coating system is refined by selective laser patterning to facilitate the integration onto complex shape molding tool surfaces. Furthermore, molecular dynamics simulation-based methods are developed to derive material properties required for the modeling of polymer-based materials. By using this integrated methodology with the application of integrated computational materials engineering (ICME) methods from the metal powder for the mold printing up until the casting or molding process, the foundation for a holistic life cycle assessment within the integrated structural health engineering (ISHE) framework is laid for the produced tooling systems as well as the molded parts.

AbstractProduction processes for the manufacturing of technical components are enabled by the availability and use of adequate engineering materials. Within the Internet of Production this work stream is dedicated to developing material and process-based solutions to increase the data availability during the manufacturing and operation of discontinuous mold-based production systems such as high-pressure die casting (HPDC) and injection molding (IM). This includes the development of data-driven alloy design strategies for additively manufactured mold components using tool steels as an initial use case as well as new surface-based smart sensor and actuator solutions. Material data and properties are tracked from the steel powder production via gas atomization until the final use in a mold to produce castings. Intermediate steps include the 3D printing of mold components via laser powder bed fusion and subsequent application of physical vapor deposition and thermal spraying-based smart multilayer coatings with sensor and actuator capabilities. The coating system is refined by selective laser patterning to facilitate the integration onto complex shape molding tool surfaces. Furthermore, molecular dynamics simulation-based methods are developed to derive material properties required for the modeling of polymer-based materials. By using this integrated methodology with the application of integrated computational materials engineering (ICME) methods from the metal powder for the mold printing up until the casting or molding process, the foundation for a holistic life cycle assessment within the integrated structural health engineering (ISHE) framework is laid for the produced tooling systems as well as the molded parts.

Comprehensive testing using various different gasket types and materials was performed in order to determine the best overall performance in gasket suitability and leakage reliability on an IBC (Intermediate Bulk Container), provided by a tank manufacturer. Prior to testing, the tank was filled with water just below the elevation of the manway, and the remaining space was charged with air. Testing was performed in two phases. Phase 1 was conducted as a simple pressure test with the container in a static state. For Phase 2, a test procedure was developed to include temperature and pressure variations, soak and dwell times, torque value calculations, leakage rates, sustainability, and a simulation of artificial vibration effects on bolted flange connections. Utilizing the Phase 2 procedure gives the ability to compare the various gasket materials under real world conditions, which will reveal the optimum gasket that provides the safest and most reliable connections for the transportation industry. Four corrosion resistant polytetrafluoroethylene (PTFE) based gasket materials were selected to be tested on the IBC. The gasket materials included virgin PTFE, glass-filled PTFE, tanged 316 stainless steel reinforced expanded PTFE (ePTFE), and corrugated 316 stainless steel reinforced expanded PTFE. All testing was performed indoors in a controlled environment. Testing on each gasket type was performed using the same equipment, while following the same test procedures.

This paper describes a new elevator system applied for Intermediate-Floors Base Seismic Isolation Buildings, to replace the existing system with the ultimate aim to reduce the installation and construction costs. Features of the new elevator system such as high tensioned steel guide rail, new entrance structure, new type of guide rail reinforcements called rail backing and new control systems are introduced in the paper. Details of a new design method to determine the stiffness and the length of the rail backing is also listed.

The main objective of this work was to develop techniques of non-destructive testing and give them a strong theoretical underpinning to render them as quantitative as possible. Thus in ultrasonic testing the objective was to combine the traditional manual search for flaws with computer automated search and elastic scattering theory to provide quantitative data on location, size, shape, and orientation. This approach led to several schemes to solve the Inverse Scattering Problem or the reconstruction of a flaw from just a few reflected ultrasonic echoes. Early efforts led to successes with idealized man-made flaws consisting of single and compound flaws embedded in Titanium-alloy. Later this work produced results with naturally occurring flaws in aerospace components.

Abstract The skirt and shell thicknesses of vertical tall pressure vessels are sometimes much increased in FPSO (Floating Production, Storage and Offloading) due to ship motion acceleration. In that case, intermediate support is used as an additional support from steel structure surrounding the vessels. By theoretical calculation, Nanjo et.al. introduced dimensionless parameter N that can represent stiffness of pressure vessel and acceleration load with the assumption of structure drift at intermediate support [1]. The authors proposed N-chart to investigate the necessity and effective elevation of intermediate support by using the parameter N. The flexibility of steel structure on the bottom affects the function of intermediate support (e.g. increasing reaction force at intermediate support, effect on bottom skirt calculation); however, the flexibility is not included in the parameter N. In this paper, an additional factor for the flexibility was studied and introduced by structural analysis. A model with flexibility of structure supporting the bottom skirt was used for the analysis. The variable flexibility of steel structure was applied to the bottom of the model to study the impact of bottom structure flexibility on the pressure vessel design. The analysis result was compared with the bottom fixed model without structure flexibility to study an additional factor. Finally, appropriate design approach for tall pressure vessels with intermediate supports was proposed.

During manufacturing, complex shape welded pressure vessels are submitted to numerous intermediate heat treatments after each weld (de-hydrogenation treatment - DHT and/or intermediate stress relieving treatment - ISR) before final Post Weld Heat Treatment (PWHT). The present study aims at analysing and optimising the intermediate heat treatment conditions regarding the resulting mechanical properties (tensile strength and impact. strength) of CrMo and CrMoV creep resistant steels. Hydrogen behaviour in weld metal and HAZ, and residual stresses evolution have been assessed by numerical modelling and experimental measurements on welded specimens representative of big pressure vessels: butt welds and set in nozzle welds of 150 mm wall thickness. The optimised conditions are compared to usual construction codes and buyer’s requirements.

FPSO (Floating Production, Storage and Offloading) has become used increasingly for off-shore gas fields. Most tall pressure vessels such as columns installed in the FPSO are surrounded by topside structures. In general, columns in on-shore plants are supported only by bottom skirts; on the other hand, some of the tall columns on FPSO hulls require intermediate supports in addition to bottom skirts because of large accelerations they are subject to due to ship motion induced by wave loading. In this paper, the effects of the support were investigated considering acceleration distributions and structure deformation (drift), then the ideal elevation of the support was determined to minimize bending moment throughout the columns under the combined conditions. A dimensionless controlling parameter related to the acceleration, structure drift, and column properties was proposed and graphs (called N-Charts) were proposed to understand effects in reducing the maximum bending moment with respect to the elevation of the guide.

This report provides basic information about vintage pipe samples containing dent and gouge defects with and without fatigue cracks for inspection technology evaluation and repair techniques qualification. Four mechanical damage dent and gouge defects without fatigue cracks were created in a realistic manner in vintage pipes. The two remaining samples containing also the same types of defects were submitted to internal pressure cycling to initiate a significant crack at the bottom of the gouge. Two types of defects were created: intermediate gouge in shallow dent, intermediate gouge in severe dent. Four defects are dedicated for performance evaluation of inspection technologies whereas two defects (one of each type) without fatigue crack are for repair techniques qualification. These defects are similar to those created in project PRCI MD-4-6 for destructive metallurgical characterization and for burst and fatigue tests. This version of the report does not contain results of any measurements performed on the defects, in order to facilitate blind testing of inspection technologies using the samples produced in this project.

In order to understand and eventually control formaldehyde emissions, it is necessary to investigate formaldehyde formation mechanisms and evaluate the applicability of these mechanisms to industrial gas engines. An extensive literature review was conducted to identify possible formaldehyde formation mechanisms, factors that favor these chemical mechanisms, and the relationships between various engine operating conditions and engine-out formaldehyde emissions. The literature review provided the following information on formaldehyde emissions: Formation and subsequent destruction of formaldehyde are necessary intermediate steps in the complete combustion of natural gas; Regions within the combustion chamber processed by propagating flames are not likely sources of formaldehyde; Identification of a distinct 'temperature window' where net formaldehyde formation occurs, provided that adequate oxygen and unburned hydrocarbons are present; Above the 'temperature window' formaldehyde is quickly destroyed, and below it formaldehyde mole fractions are frozen; and Emissions of formaldehyde from natural gas fired engines require that partial combustion, to some degree, take place in the cylinder. This finding is supported by results of equilibrium calculations of natural gas combustion product composition, which do not predict significant levels of formaldehyde. A number of publications have been produced from the integrated test plan body of work. Those publications include reports on the formaldehyde literature review, humidity test program, and the high pressure injection project and technical papers on formaldehyde literature review, high pressure injection, the tracer gas method, in-cylinder sampling, and humidity investigations. The work described in the humidity and high pressure injection reports is not covered in detail in this document. However, the results are discussed as needed to support data interpretation and conclusions. Includes a literature review of mixing and humidity effects as well as a spreadsheet of the test data.

Objectives. Although the health benefits of physical activity are well described for the general population, less is known about the benefits and harms of physical activity in people dependent upon, partially dependent upon, or at risk for needing a wheelchair. This systematic review summarizes the evidence for physical activity in people with multiple sclerosis, cerebral palsy, and spinal cord injury regardless of current use or nonuse of a wheelchair. Data sources. We searched MEDLINE®, CINAHL®, PsycINFO®, Cochrane CENTRAL, Embase®, and Rehabilitation and Sports Medicine Source from 2008 through November 2020, reference lists, and clinical trial registries. Review methods. Predefined criteria were used to select randomized controlled trials, quasiexperimental nonrandomized trials, and cohort studies that addressed the benefits and harms of observed physical activity (at least 10 sessions on 10 different days of movement using more energy than rest) in participants with multiple sclerosis, cerebral palsy, and spinal cord injury. Individual study quality (risk of bias) and the strength of bodies of evidence for key outcomes were assessed using prespecified methods. Dual review procedures were used. Effects were analyzed by etiology of impairment and physical activity modality, such as treadmill, aquatic exercises, and yoga, using qualitative, and when appropriate, quantitative synthesis using random effects meta-analyses. Results. We included 146 randomized controlled trials, 15 quasiexperimental nonrandomized trials, and 7 cohort studies (168 studies in 197 publications). More studies enrolled participants with multiple sclerosis (44%) than other conditions, followed by cerebral palsy (38%) and spinal cord injury (18%). Most studies were rated fair quality (moderate risk of bias). The majority of the evidence was rated low strength. • In participants with multiple sclerosis, walking ability may be improved with treadmill training and multimodal exercise regimens that include strength training; function may be improved with treadmill training, balance exercises, and motion gaming; balance is likely improved with postural control exercises (which may also reduce risk of falls) and may be improved with aquatic exercises, robot-assisted gait training, treadmill training, motion gaming, and multimodal exercises; activities of daily living may be improved with aquatic therapy; sleep may be improved with aerobic exercises; aerobic fitness may be improved with multimodal exercises; and female sexual function may be improved with aquatic exercise. • In participants with cerebral palsy, balance may be improved with hippotherapy and motion gaming, and function may be improved with cycling, treadmill training, and hippotherapy. • In participants with spinal cord injury, evidence suggested that activities of daily living may be improved with robot-assisted gait training. • When randomized controlled trials were pooled across types of exercise, physical activity interventions were found to improve walking in multiple sclerosis and likely improve balance and depression in multiple sclerosis. Physical activity may improve function and aerobic fitness in people with cerebral palsy or spinal cord injury. When studies of populations with multiple sclerosis and cerebral palsy were combined, evidence indicated dance may improve function. • Evidence on long-term health outcomes was not found for any analysis groups. For intermediate outcomes such as blood pressure, lipid profile, and blood glucose, there was insufficient evidence from which to draw conclusions. There was inadequate reporting of adverse events in many trials. Conclusions. Physical activity was associated with improvements in walking ability, general function, balance (including fall risk), depression, sleep, activities of daily living, female sexual function, and aerobic capacity, depending on population enrolled and type of exercise utilized. No studies reported long-term cardiovascular or metabolic disease health outcomes. Future trials could alter these findings; further research is needed to examine health outcomes, and to understand the magnitude and clinical importance of benefits seen in intermediate outcomes.

Academic work is characterised as increasingly time-pressured and deadline-driven. Moreover, increased use of online tools underpins flexible working hours. Does this make researchers work just before a deadline or a meeting (perceived as an intermediate deadline)? The "imminent deadline-driven work habit" hypothesis seems intuitively plausible since the research and academic world is notorious for heavy workloads and multiple parallel tasks and projects. The current article investigates the activity of several collaborative online documents from international building research projects as a function of the distance to a deadline or coordination meeting. A similar analysis is conducted on the submission data of an international conference on building physics. This empirical analysis supports the "imminent deadline-driven work habit" hypothesis. Finally, the article discusses the possible reasons behind the latter and the ensuing practical implications and recommendations for the management of collaborative research/academic work in energy, building physics and indoor environment.

The realignment was proposed to remedy the loss of relevance and presence of the Bank in Latin America and the Caribbean because it had been unable to adapt to: (i) greater access by the countries to alternative sources of financing, (ii) the appearance of new actors, such as subnational governments, responsible for investment decisions, (iii) the heterogeneous nature of the countries of the region, and (iv) pressures to obtain results more quickly. In this context, the Bank was perceived as slow and bureaucratic, with complicated and undifferentiated processes, products that were not very innovative or flexible, and technical capacity and know-how that were lagging behind. The Bank's loss of presence and relevance in the region had a negative impact on its capacity to influence the economic and social development of the region. The reforms associated with the realignment were aimed at sharpening the Bank's country and sector focuses and improving its organizational efficiency and effectiveness. According to the realignment documents, the achievement of those intermediate objectives translates into the attainment of the targets identified. In turn, this greater country and sector focus and organizational efficiency and effectiveness was expected to lead to a greater presence and relevance of the Bank in the region.

The Southeast Coast Network (SECN) conducts long-term terrestrial vegetation monitoring as part of the NPS Inventory and Monitoring Program. The vegetation community vital sign is one of the primary-tier resources identified by SECN park managers, and monitoring is conducted at 15 network parks (DeVivo et al. 2008). Monitoring plants and their associated communities over time allows for targeted understanding of ecosystems within the SECN geography, which provides managers information about the degree of change within their parks? natural vegetation. 2021 was the first year of conducting monitoring at Kennesaw Mountain National Battlefield Park (KEMO). Fourteen vegetation plots were established throughout the park from July through August. Data collected in each plot included species richness across multiple spatial scales, species-specific cover and constancy, species-specific woody stem seedling/sapling counts and adult trees (greater than 10 centimeters [3.9 inches {in}]) diameter at breast height (DBH), overall tree health, landform, soil, observed disturbance, and woody biomass (i.e., fuel load) estimates. This report summarizes the baseline (year 1) terrestrial vegetation data collected at Kennesaw Mountain National Battlefield Park in 2021. Data were stratified across two dominant broadly defined habitats within the park, Piedmont Upland Forests and Shrublands; and Piedmont Open Uplands and Woodlands. Noteworthy findings include: 184 vascular plant taxa (species or lower) were observed across 14 vegetation plots, including 27 species not previously documented within the park. The most frequently encountered species in each broadly defined habitat included: Piedmont Open Uplands and Woodlands: wafer-ash (Ptelea trifoliata var. mollis), white fringe-tree (Chionanthus virginicus), winged elm (Ulmus alata), hog plum (Prunus umbellata), Virginia creeper (Parthenocissus quinquefolia), and blackseed speargrass (Piptochaetium avenaceum). Piedmont Upland Forests and Shrublands: loblolly pine (Pinus taeda), tuliptree (Liriodendron tulipifera var. tulipifera), black cherry (Prunus serotina var. serotina), muscadine (Muscadinia rotundifolia var. rotundifolia), Virginia creeper, and cat greenbrier (Smilax glauca). Fourteen non-native species categorized as invasive by the Georgia Exotic Pest Plant Council (GA-EPPC 2023) were encountered within the park during monitoring. Chinese privet (Ligustrum sinense) was the most frequently encountered and abundant invasive plant within the park. Two species of special concern listed for Georgia (GADNR 2023) were observed during monitoring and included green, or Missouri, rock cress (Boechera missouriensis) and Stone Mountain mint (Pycnanthemum curvipes). Northern red oak (Quercus rubra), winged elm, and eastern redcedar (Juniperus virginiana) were the most dominant species within the tree stratum of Piedmont Open Uplands and Woodlands of Kennesaw Mountain National Battlefield Park; loblolly pine, sweetgum (Liquidambar styraciflua) and tuliptree were the most dominant species of Piedmont Upland Forests and Shrublands. Chinese privet was the most abundant species within the seedling stratum of Piedmont Open Upland and Woodland sites. Heavy browsing impacts by white-tailed deer (Odocoileus virginianus) were observed within the upland forests of Kennesaw Mountain National Battlefield Park. Long-term monitoring of vegetation structure and composition within the park can be used to determine forest regeneration patterns as they relate to changes in browsing pressure. Other threats to native vegetation within the park are (1) the high prevalence of non-native, invasive plant species, and (2) fire suppression within oak-hickory and pine-oak xeric and intermediate forests. Long-term monitoring data will aid in understanding how these threats over time impact the park?s forest communities. All plots monitored during this sampling are scheduled to be resampled in 2025.

Banco de la República is celebrating its 100th anniversary in 2023. This is a very significant anniversary and one that provides an opportunity to highlight the contribution the Bank has made to the country’s development. Its track record as guarantor of monetary stability has established it as the one independent state institution that generates the greatest confidence among Colombians due to its transparency, management capabilities, and effective compliance with the central banking and cultural responsibilities entrusted to it by the Constitution and the Law. On a date as important as this, the Board of Directors of Banco de la República (BDBR) pays tribute to the generations of governors and officers whose commitment and dedication have contributed to the growth of this institution.1 Banco de la República’s mandate was confirmed in the National Constitutional Assembly of 1991 where the citizens had the opportunity to elect the seventy people who would have the task of drafting a new constitution. The leaders of the three political movements with the most votes were elected as chairs to the Assembly, and this tripartite presidency reflected the plurality and the need for consensus among the different political groups to move the reform forward. Among the issues considered, the National Constitutional Assembly gave special importance to monetary stability. That is why they decided to include central banking and to provide Banco de la República with the necessary autonomy to use the instruments for which they are responsible without interference from other authorities. The constituent members understood that ensuring price stability is a state duty and that the entity responsible for this task must be enshrined in the Constitution and have the technical capability and institutional autonomy necessary to adopt the decisions they deem appropriate to achieve this fundamental objective in coordination with the general economic policy. In particular, Article 373 established that “the State, through Banco de la República, shall ensure the maintenance of the purchasing power of the currency,” a provision that coincided with the central banking system adopted by countries that have been successful in controlling inflation. In 1999, in Ruling 481, the Constitutional Court stated that “the duty to maintain the purchasing power of the currency applies to not only the monetary, credit, and exchange authority, i.e., the Board of Banco de la República, but also those who have responsibilities in the formulation and implementation of the general economic policy of the country” and that “the basic constitutional purpose of Banco de la República is the protection of a sound currency. However, this authority must take the other economic objectives of state intervention such as full employment into consideration in their decisions since these functions must be coordinated with the general economic policy.” The reforms to Banco de la República agreed upon in the Constitutional Assembly of 1991 and in Act 31/1992 can be summarized in the following aspects: i) the Bank was assigned a specific mandate: to maintain the purchasing power of the currency in coordination with the general economic policy; ii) the BDBR was designatedas the monetary, foreign exchange, and credit authority; iii) the Bank and its Board of Directors were granted a significant degree of independence from the government; iv) the Bank was prohibited from granting credit to the private sector except in the case of the financial sector; v) established that in order to grant credit to the government, the unanimous vote of its Board of Directors was required except in the case of open market transactions; vi) determined that the legislature may, in no case, order credit quotas in favor of the State or individuals; vii) Congress was appointed, on behalf of society, as the main addressee of the Bank’s reporting exercise; and viii) the responsibility for inspection, surveillance, and control over Banco de la República was delegated to the President of the Republic. The members of the National Constitutional Assembly clearly understood that the benefits of low and stable inflation extend to the whole of society and contribute mto the smooth functioning of the economic system. Among the most important of these is that low inflation promotes the efficient use of productive resources by allowing relative prices to better guide the allocation of resources since this promotes economic growth and increases the welfare of the population. Likewise, low inflation reduces uncertainty about the expected return on investment and future asset prices. This increases the confidence of economic agents, facilitates long-term financing, and stimulates investment. Since the low-income population is unable to protect itself from inflation by diversifying its assets, and a high proportion of its income is concentrated in the purchase of food and other basic goods that are generally the most affected by inflationary shocks, low inflation avoids arbitrary redistribution of income and wealth.2 Moreover, low inflation facilitates wage negotiations, creates a good labor climate, and reduces the volatility of employment levels. Finally, low inflation helps to make the tax system more transparent and equitable by avoiding the distortions that inflation introduces into the value of assets and income that make up the tax base. From the monetary authority’s point of view, one of the most relevant benefits of low inflation is the credibility that economic agents acquire in inflation targeting, which turns it into an effective nominal anchor on price levels. Upon receiving its mandate, and using its autonomy, Banco de la República began to announce specific annual inflation targets as of 1992. Although the proposed inflation targets were not met precisely during this first stage, a downward trend in inflation was achieved that took it from 32.4% in 1990 to 16.7% in 1998. At that time, the exchange rate was kept within a band. This limited the effectiveness of monetary policy, which simultaneously sought to meet an inflation target and an exchange rate target. The Asian crisis spread to emerging economies and significantly affected the Colombian economy. The exchange rate came under strong pressure to depreciate as access to foreign financing was cut off under conditions of a high foreign imbalance. This, together with the lack of exchange rate flexibility, prevented a countercyclical monetary policy and led to a 4.2% contraction in GDP that year. In this context of economic slowdown, annual inflation fell to 9.2% at the end of 1999, thus falling below the 15% target set for that year. This episode fully revealed how costly it could be, in terms of economic activity, to have inflation and exchange rate targets simultaneously. Towards the end of 1999, Banco de la República announced the adoption of a new monetary policy regime called the Inflation Targeting Plan. This regime, known internationally as ‘Inflation Targeting,’ has been gaining increasing acceptance in developed countries, having been adopted in 1991 by New Zealand, Canada, and England, among others, and has achieved significant advances in the management of inflation without incurring costs in terms of economic activity. In Latin America, Brazil and Chile also adopted it in 1999. In the case of Colombia, the last remaining requirement to be fulfilled in order to adopt said policy was exchange rate flexibility. This was realized around September 1999, when the BDBR decided to abandon the exchange-rate bands to allow the exchange rate to be freely determined in the market.Consistent with the constitutional mandate, the fundamental objective of this new policy approach was “the achievement of an inflation target that contributes to maintaining output growth around its potential.”3 This potential capacity was understood as the GDP growth that the economy can obtain if it fully utilizes its productive resources. To meet this objective, monetary policy must of necessity play a countercyclical role in the economy. This is because when economic activity is below its potential and there are idle resources, the monetary authority can reduce the interest rate in the absence of inflationary pressure to stimulate the economy and, when output exceeds its potential capacity, raise it. This policy principle, which is immersed in the models for guiding the monetary policy stance, makes the following two objectives fully compatible in the medium term: meeting the inflation target and achieving a level of economic activity that is consistent with its productive capacity. To achieve this purpose, the inflation targeting system uses the money market interest rate (at which the central bank supplies primary liquidity to commercial banks) as the primary policy instrument. This replaced the quantity of money as an intermediate monetary policy target that Banco de la República, like several other central banks, had used for a long time. In the case of Colombia, the objective of the new monetary policy approach implied, in practical terms, that the recovery of the economy after the 1999 contraction should be achieved while complying with the decreasing inflation targets established by the BDBR. The accomplishment of this purpose was remarkable. In the first half of the first decade of the 2000s, economic activity recovered significantly and reached a growth rate of 6.8% in 2006. Meanwhile, inflation gradually declined in line with inflation targets. That was how the inflation rate went from 9.2% in 1999 to 4.5% in 2006, thus meeting the inflation target established for that year while GDP reached its potential level. After this balance was achieved in 2006, inflation rebounded to 5.7% in 2007, above the 4.0% target for that year due to the fact that the 7.5% GDP growth exceeded the potential capacity of the economy.4 After proving the effectiveness of the inflation targeting system in its first years of operation, this policy regime continued to consolidate as the BDBR and the technical staff gained experience in its management and state-of-the-art economic models were incorporated to diagnose the present and future state of the economy and to assess the persistence of inflation deviations and expectations with respect to the inflation target. Beginning in 2010, the BDBR established the long-term 3.0% annual inflation target, which remains in effect today. Lower inflation has contributed to making the macroeconomic environment more stable, and this has favored sustained economic growth, financial stability, capital market development, and the functioning of payment systems. As a result, reductions in the inflationary risk premia and lower TES and credit interest rates were achieved. At the same time, the duration of public domestic debt increased significantly going from 2.27 years in December 2002 to 5.86 years in December 2022, and financial deepening, measured as the level of the portfolio as a percentage of GDP, went from around 20% in the mid-1990s to values above 45% in recent years in a healthy context for credit institutions.Having been granted autonomy by the Constitution to fulfill the mandate of preserving the purchasing power of the currency, the tangible achievements made by Banco de la República in managing inflation together with the significant benefits derived from the process of bringing inflation to its long-term target, make the BDBR’s current challenge to return inflation to the 3.0% target even more demanding and pressing. As is well known, starting in 2021, and especially in 2022, inflation in Colombia once again became a serious economic problem with high welfare costs. The inflationary phenomenon has not been exclusive to Colombia and many other developed and emerging countries have seen their inflation rates move away from the targets proposed by their central banks.5 The reasons for this phenomenon have been analyzed in recent Reports to Congress, and this new edition delves deeper into the subject with updated information. The solid institutional and technical base that supports the inflation targeting approach under which the monetary policy strategy operates gives the BDBR the necessary elements to face this difficult challenge with confidence. In this regard, the BDBR reiterated its commitment to the 3.0% inflation target in its November 25 communiqué and expects it to be reached by the end of 2024.6 Monetary policy will continue to focus on meeting this objective while ensuring the sustainability of economic activity, as mandated by the Constitution. Analyst surveys done in March showed a significant increase (from 32.3% in January to 48.5% in March) in the percentage of responses placing inflation expectations two years or more ahead in a range between 3.0% and 4.0%. This is a clear indication of the recovery of credibility in the medium-term inflation target and is consistent with the BDBR’s announcement made in November 2022. The moderation of the upward trend in inflation seen in January, and especially in February, will help to reinforce this revision of inflation expectations and will help to meet the proposed targets. After reaching 5.6% at the end of 2021, inflation maintained an upward trend throughout 2022 due to inflationary pressures from both external sources, associated with the aftermath of the pandemic and the consequences of the war in Ukraine, and domestic sources, resulting from: strengthening of local demand; price indexation processes stimulated by the increase in inflation expectations; the impact on food production caused by the mid-2021 strike; and the pass-through of depreciation to prices. The 10% increase in the minimum wage in 2021 and the 16% increase in 2022, both of which exceeded the actual inflation and the increase in productivity, accentuated the indexation processes by establishing a high nominal adjustment benchmark. Thus, total inflation went to 13.1% by the end of 2022. The annual change in food prices, which went from 17.2% to 27.8% between those two years, was the most influential factor in the surge in the Consumer Price Index (CPI). Another segment that contributed significantly to price increases was regulated products, which saw the annual change go from 7.1% in December 2021 to 11.8% by the end of 2022. The measure of core inflation excluding food and regulated items, in turn, went from 2.5% to 9.5% between the end of 2021 and the end of 2022. The substantial increase in core inflation shows that inflationary pressure has spread to most of the items in the household basket, which is characteristic of inflationary processes with generalized price indexation as is the case in Colombia. Monetary policy began to react early to this inflationary pressure. Thus, starting with its September 2021 session, the BDBR began a progressive change in the monetary policy stance moving away from the historical low of a 1.75% policy rate that had intended to stimulate the recovery of the economy. This adjustment process continued without interruption throughout 2022 and into the beginning of 2023 when the monetary policy rate reached 12.75% last January, thus accumulating an increase of 11 percentage points (pp). The public and the markets have been surprised that inflation continued to rise despite significant interest rate increases. However, as the BDBR has explained in its various communiqués, monetary policy works with a lag. Just as in 2022 economic activity recovered to a level above the pre-pandemic level, driven, along with other factors, by the monetary stimulus granted during the pandemic period and subsequent months, so too the effects of the current restrictive monetary policy will gradually take effect. This will allow us to expect the inflation rate to converge to 3.0% by the end of 2024 as is the BDBR’s purpose.Inflation results for January and February of this year showed declining marginal increases (13 bp and 3 bp respectively) compared to the change seen in December (59 bp). This suggests that a turning point in the inflation trend is approaching. In other Latin American countries such as Chile, Brazil, Perú, and Mexico, inflation has peaked and has begun to decline slowly, albeit with some ups and downs. It is to be expected that a similar process will take place in Colombia in the coming months. The expected decline in inflation in 2023 will be due, along with other factors, to lower cost pressure from abroad as a result of the gradual normalization of supply chains, the overcoming of supply shocks caused by the weather, and road blockades in previous years. This will be reflected in lower adjustments in food prices, as has already been seen in the first two months of the year and, of course, the lagged effect of monetary policy. The process of inflation convergence to the target will be gradual and will extend beyond 2023. This process will be facilitated if devaluation pressure is reversed. To this end, it is essential to continue consolidating fiscal sustainability and avoid messages on different public policy fronts that generate uncertainty and distrust. 1 This Report to Congress includes Box 1, which summarizes the trajectory of Banco de la República over the past 100 years. In addition, under the Bank’s auspices, several books that delve into various aspects of the history of this institution have been published in recent years. See, for example: Historia del Banco de la República 1923-2015; Tres banqueros centrales; Junta Directiva del Banco de la República: grandes episodios en 30 años de historia; Banco de la República: 90 años de la banca central en Colombia. 2 This is why lower inflation has been reflected in a reduction of income inequality as measured by the Gini coefficient that went from 58.7 in 1998 to 51.3 in the year prior to the pandemic. 3 See Gómez Javier, Uribe José Darío, Vargas Hernando (2002). “The Implementation of Inflation Targeting in Colombia”. Borradores de Economía, No. 202, March, available at: https://repositorio.banrep.gov.co/handle/20.500.12134/5220 4 See López-Enciso Enrique A.; Vargas-Herrera Hernando and Rodríguez-Niño Norberto (2016). “The inflation targeting strategy in Colombia. An historical view.” Borradores de Economía, No. 952. https://repositorio.banrep.gov.co/handle/20.500.12134/6263 5 According to the IMF, the percentage change in consumer prices between 2021 and 2022 went from 3.1% to 7.3% for advanced economies, and from 5.9% to 9.9% for emerging market and developing economies. 6 https://www.banrep.gov.co/es/noticias/junta-directiva-banco-republica-reitera-meta-inflacion-3