High-density polyethylene (HDPE) geomembranes are commonly used as an environmental protection liner due to their good chemical and mechanical resistances and low cost. Ultraviolet (UV) radiation is an essential issue in durability studies for pond applications. This study evaluated a 1.5-mm thick HDPE geomembrane exposed to ultraviolet fluorescent radiation for 8760 h in a laboratory and thermoanalytical and physical analyses were conducted towards the understanding of its performance after exposure. According to the results, although the geomembrane maintained the ductile behavior, it showed a 52.48% final decrease in stress crack resistance (SCR) compared to virgin SCR. Moreover, a considerable antioxidant depletion occurred after 8760 h exposure shown by the Std. OIT (standard oxidative-induction time) results, demonstrating a Std. OIT value decrease of 89.19% compared to the virgin Std. OIT. Such a behavior contributed to the susceptibility of thermal effects in the DSC (differential scanning calorimetry) curves and the losses observed in the SCR values, attesting the geomembrane’s oxidative degradation mechanism occurred and changed the polymer’s structure. Highdensity High density (HDPE cost UV (UV applications 1.5mm 15mm mm 1.5 1 5 876 results 5248 52 48 52.48 (SCR Moreover Std standard oxidativeinduction induction time 8919 89 19 89.19 differential calorimetry values s polymers polymer structure 5mm 15 1. 87 524 4 52.4 891 8 89.1 52. 89.

In recent years, the field of coordination chemistry has experienced a surge in interest regarding the synthesis and characterization of coordination complexes for diverse applications. This study is dedicated to investigating coordination compounds resulting from the interaction of nonsteroidal anti-inflammatory drugs (NSAIDs) with metal ions. The study research places significant emphasis on understanding the stability and thermal behavior of these coordination compounds. The utilization of thermoanalytical techniques is crucial in achieving this goal. Thermal analysis and thermokinetics provide valuable insights into the underlying mechanisms, kinetics, and energetics of these reactions, thereby facilitating the optimization of synthesis procedures. The research employs concurrent techniques, namely thermogravimetric analysis (TG) and differential scanning calorimetry (DSC), to explore the thermal stability and decomposition pathways of these coordination compounds. Thermokinetic models and optimization methodologies are subsequently applied to identify key reaction parameters. The primary aim of this research is to unveil the thermal behavior, stability, and reaction kinetics of aceclofenac coordination compounds, thus contributing significantly to the understanding of thermokinetics and thermal analysis in the domain of coordination chemistry. Specifically, this study is focused on aceclofenac coordination complexes involving lanthanum and gadolinium, with the ultimate goal of advancing the field of coordination chemistry. years applications antiinflammatory anti inflammatory NSAIDs (NSAIDs ions mechanisms reactions procedures TG (TG DSC, DSC , (DSC) parameters Specifically gadolinium (DSC

Acetic acid bacteria (AAB) are versatile organisms that catalyze the conversion of a wide range of carbon sources into biomolecules of great industrial interest. In this study, we exploited the ability of Gluconobacter spp. to synthesize levans. Among the isolated strains, Gluconobacter cerinus UELBM11 produced approximately 14.0 g L−1 of levan under non-optimized conditions. Gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR), and nuclear magnetic resonance (NMR) analyses confirmed that levan obtained from G. cerinus UELBM11 consisted of a β-(2→6)-D-fructose backbone with some β-(2→1) ramifications. The average molecular weight (Mw) of the purified levan was 8.78 × 105 Da. Thermogravimetric/differential thermogravimetric (TGA/DTG) analysis indicated high thermal stability, with the maximum decomposition rate observed at 227.44 °C. Scanning electron microscopy (SEM) revealed a microporous morphology, and the antioxidant activity assays demonstrated that levan had a high scavenging capacity of 2,2’-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and hydroxyl radicals. Therefore, it has been demonstrated the levan produced by G. cerinus UELBM11 is a promising natural antioxidant and, owing to its microporosity and excellent thermal properties and stability, is a potential candidate as an additive in cosmetics, pharmaceuticals, and food products. AAB (AAB interest study spp levans strains UELBM UELBM1 140 14 0 14. L1 L 1 L− nonoptimized non optimized conditions chromatographymass chromatography mass GCMS, GCMS GC MS , (GC-MS) FTIR, FTIR (FTIR) NMR (NMR G β2→6Dfructose β26Dfructose βDfructose β 2→6 D fructose 2 6 β2→1 β21 2→1 β-(2→1 ramifications Mw (Mw 878 8 78 8.7 10 Da Thermogravimetricdifferential Thermogravimetric differential TGA/DTG TGADTG TGA DTG (TGA/DTG stability 22744 227 44 227.4 C °C SEM (SEM morphology 2,2azinobis 22azinobis azinobis 2,2 azino bis 3ethylbenzothiazoline6sulfonic ethylbenzothiazolinesulfonic 3 ethylbenzothiazoline sulfonic ABTS (ABTS radicals Therefore cosmetics pharmaceuticals products (GC-MS (FTIR β2 6Dfructose Dfructose 26 2→ β2→ 21 β-(2→ 87 7 8. 2274 22 4 227. 2azinobis 2, β-(2 β-( β-

This study highlights the synthesis of innovative polyurethane materials derived from Moringa oleifera oils extracted from two distinct sources. The oils were converted into their respective polyols through the in situ generated performic acid method. Diverse material characteristics were observed due to different agroclimatic and cultivation conditions for the sources. Extraction yields were 45.21% (source 1) and 40.32% (source 2), with acid values of 28.70 and 26.00 mg KOH per g of oil, respectively. Oleic acid constituted 79.87 and 67.11% of the oils composition, respectively. Nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR) confirmed the hydroxylation of the oils. FTIR also identified the isocyanate structures in the synthesized polyurethane materials. Gel permeation chromatography analysis revealed a higher oligomer content in the polyol synthesized from the oil extracted from source 2. Thermogravimetric analysis demonstrated enhanced thermal stability post-oil conversion, highlighting decomposition stages for rigid and flexible segments. Differential scanning calorimetry indicated higher unsaturation in the oil extracted from source 1, resulting in an elevated crystallization temperature. Tensile testing showed increased elasticity as the [NCO]/[OH] ratio decreased in the material, emphasizing the influence of polyol and crosslinking agent concentrations on mechanical resistance of polyurethane materials. sources method 4521 45 21 45.21 1 4032 40 32 40.32 2, 2 , 2) 2870 28 70 28.7 2600 26 00 26.0 respectively 7987 79 87 79.8 6711 67 11 67.11 composition (FTIR postoil post conversion segments temperature NCO/OH NCOOH NCO / OH [NCO]/[OH 452 4 45.2 403 3 40.3 287 7 28. 260 0 26. 798 8 79. 671 6 67.1 45. 40. 67.

ABSTRACT Subsurface temperatures have been measured in different regions of the world, usually near the surface up to a depth of about a hundred meters. In this work a forward model calculation for a Northern Hemisphere soil temperature site at Kapuskasing, Canada, is presented, employing the solution of the differential equation of heat conduction through a semi-infinite homogeneous solid, subject to surface boundary conditions determined by surface air temperature. In this way, a detailed analysis is made of the subsurface temperature as a function of ground depth and for the time interval ranging from 1970 to the future (including the next century), for different scenarios of climate change. From these results, it was possible to determine the following characteristic quantities: (a) the depth where the surface perturbation (practically) finishes (in the range of about 180-200 m); (b) the depth where the subsurface temperature changes its slope from negative to positive; (c) the temperature change at the surface for the years where data exist; (d) the thermal gradient at steady state in the starting year (1880); (e) the temperature differences extrapolated at surface and at a 20 m depth, this last value corresponding to the depth at which seasonal and diurnal temperature variations are negligible; (f) the heat flow at surface to the inner part of the soil attributed to climate change, and (g) the temperature changes at surface for the 100 years interval (1980-2080) and mainly for the next century (2080-2180), for each site and for each IPCC Representative Concentration Pathway (RCP) scenario. As an example, the impact of the change in mean annual soil temperature due to global warming in near-surface geothermal energy is described.

RESUMEN Las temperaturas del subsuelo se han medido en diferentes regiones del mundo, por lo general cerca de la superficie hasta una profundidad de unos cientos de metros. En este trabajo se presenta un cálculo de modelo directo (predictivo) para un sitio de temperatura del suelo en el hemisferio norte (Kapuskasing, Canadá) empleando la solución de la ecuación diferencial de conducción de calor a través de un sólido homogéneo seminfinito, sujeto a las condiciones de contorno de la superficie determinadas por la temperatura del aire en dicha superficie. De esta forma, se realiza un análisis detallado de la temperatura del subsuelo en función de la profundidad del suelo y para el intervalo de tiempo que va desde 1970 hasta el futuro (incluido el próximo siglo), para diferentes escenarios de cambio climático. A partir de estos resultados, fue posible determinar las siguientes cantidades características: a) la profundidad donde la perturbación de la superficie (prácticamente) termina (en el rango de aproximadamente 180-200 m); b) la profundidad donde la temperatura del subsuelo cambia su pendiente de negativa a positiva; c) el cambio de temperatura en la superficie para los años en los que existen datos; d) el gradiente térmico en estado estacionario en el año inicial (1880); e) las diferencias de temperatura extrapoladas en la superficie y a 20 m de profundidad, correspondiendo este último valor a la profundidad en que las variaciones de temperatura estacionales y diurnas son insignificantes; f) el flujo de calor en la superficie hacia la parte interna del suelo atribuido al cambio climático, y g) los cambios de temperatura en la superficie para el intervalo de 100 años (1980-2080) y principalmente para el próximo siglo (2080-2180), para cada sitio y escenario de la Ruta de Concentración Representativa (RCP) del IPCC. Como ejemplo se describe el impacto del cambio en la temperatura media anual del suelo debido al calentamiento global en la energía geotérmica cercana a la superficie.

With the increase in the supply of glycerol and its economic devaluation, it is important to develop strategies that add value to this substance. Among the various alternatives, one application is its use as a precursor in the synthesis of new polyesters. Therefore, this work describes the condensation reaction of glycerol with valeric acid, obtaining functionalized glycerol, which was used in the polycondensation reaction with terephthalic acid. The samples were characterized by infrared spectroscopy, thermogravimetric analysis, hydrogen nuclear magnetic resonance and differential scanning calorimetry. Spectroscopic analyses confirmed the conversion of the reagents into esters and polyesters. The polyesters showed superior thermal stability than the individual components, a glass transition temperature of -3.8 °C and adhesive properties on glass, wood, paper and rigid polyvinyl chloride substrates. The adhesive capabilities of the samples were compared with those of commercial adhesives already established in the Brazilian market. Samples of polyesters synthesized through the reaction between functionalized glycerol and terephthalic acid showed adhesive behavior in the range of mechanical resistance observed in commercial adhesives, with an elastic modulus ranging from 60.9 ± 36.0 MPa to 162.1 ± 102.4 kPa, depending on the type of adhesive substrate, behaving either as an elastic and/or thermoplastic adhesive. devaluation substance alternatives Therefore spectroscopy analysis calorimetry components 3.8 38 3 8 -3. C wood substrates market 609 60 9 60. 360 36 0 36. 1621 162 1 162. 1024 102 4 102. kPa substrate andor or 3. -3 6 16 10 -

This study assessed the morphology and thermal, mechanical, and chemical properties of electrospun membranes made of acrylonitrile-methacrylic acid copolymers (PANCMAA). Copolymers were synthesized using the aqueous suspension method with varying comonomer contents (homopolymer,PAN, lower acid, PANCMAA1, and higher acid, PANCMAA2) and characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). Electrospun fibers were produced by adjusting the polymer concentration in the DMF solution, and the optimal conditions yielded nanofibrous membranes. PAN and PANCMAA membrane properties were evaluated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), Dynamic Mechanical Thermal Analysis (DMTA), stress-strain tests, and swelling behavior in a phosphate buffer solution. The comonomer content influenced the crystallinity of the electrospun nanofibers, reducing the 16.8° XRD peak intensity from PAN to PANCMAA2. DSC indicated an increased Tg (from 113°C in PAN to 127°C in PANCMAA2) and a decreased exothermic cyclization enthalpy (311 J.mg-1 in PAN to 271 J.mg-1 in PANCMAA2). PANCMAA1 exhibited higher stiffness than PANCMAA2 and PAN, with a storage modulus of 0.16 GPa, a Young’s modulus of 135.7 MPa, and a lower elongation at break (3.98%). The presence of the acid comonomer significantly enhanced the swelling behavior of the electrospun membranes in phosphate buffer solution. thermal mechanical acrylonitrilemethacrylic acrylonitrile methacrylic PANCMAA. . (PANCMAA) homopolymer,PAN, homopolymerPAN homopolymer (homopolymer,PAN NMR (NMR GPC. GPC (GPC) solution Xray X ray XRD, , (XRD) DSC, (DSC) DMTA, DMTA (DMTA) stressstrain stress strain tests nanofibers 168 16 8 16.8 113C C 113 127C 127 311 (31 J.mg1 Jmg1 Jmg J.mg 1 J mg J.mg- 27 016 0 0.1 GPa Youngs Young s 1357 135 7 135. MPa 3.98%. 398 3.98% 3 98 (3.98%) (PANCMAA homopolymer,PAN (GPC (XRD (DSC (DMTA 16. 11 12 31 (3 mg1 2 01 0. 13 39 3.98 9 (3.98% ( 3.9 (3.98 3. (3.9 (3.

The thermal degradation kinetics of avocado seed biomass (Persea americana) was investigated at the heating rates of 5, 15, 20 and 25 ºC min-1 using thermogravimetric (TGA) and differential thermogravimetric (DTG) analysis techniques in the temperature range from ambient to 780 ºC. Chemical analysis of the avocado seed resulted in: 51.4% cellulose, 42.4% hemicellulose, 20.1% lignin, 2.1% ash, 5.6% extractives. The pyrolysis products were characterized via FTIR, SEM/EDS. The isoconversional methods of Ozawa-Flynn-Wall (OFW) and Kissinger-Akahira-Sunose (KAS) have yielded activation energy, Eα, varying from 36-323 kJ mol-1, respectively. The calorific value of biochars produced in the present study in the range of 265 to 475 ºC was 16,17 to 20,24 MJ kg-1, respectively, which are comparable to those reported values in the literature. Analyzing the DTG simultaneously with the addition of thermal energy, it can be seen that low molecular weight compounds represent the first degradation curves, followed by hemicellulose, cellulose and, lignin. The results obtained in the present work indicate that its feasible to prepare biochars with tunable properties from residual avocado seeds using a slow pyrolysis process, adding commercial value and reducing the environmental impact caused by the inadequate disposal of lignocellulosic materials. Persea americana 5 15 2 min1 min 1 min- TGA (TGA (DTG 78 514 51 4 51.4 424 42 42.4 hemicellulose 201 20.1 lignin 21 2.1 ash 56 6 5.6 extractives FTIR SEMEDS SEM EDS SEM/EDS OzawaFlynnWall Ozawa Flynn Wall OFW (OFW KissingerAkahiraSunose Kissinger Akahira Sunose KAS (KAS energy Eα 36323 36 323 36-32 mol1, mol1 mol 1, mol-1 respectively 26 47 1617 16 17 16,1 2024 24 20,2 kg1, kg1 kg kg-1 literature curves process materials 7 51. 42. 20. 2. 5. 3632 3 32 36-3 mol- 161 16, 202 20, kg- 363 36-

The present study optimized the extraction process of bioactive compounds present in ginger (Zingiber officinale) dried at 80 °C, using ethanol:water 70:30 (v/v) as solvent. The extracts were evaluated for antioxidant activity by the 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical reduction methods and by the chelating activity of FeII ions. It was found that the extraction condition with a temperature of 60 °C and an extraction time of 12 h showed better responses to the tests. Then, the characterization of the compounds was carried out by mass spectrometry and thermal analysis (thermogravimetric (TG), differential thermal analysis (DTA), and differential scanning calorimetry (DSC)), identifying that the main compounds of ginger were gingerols and shogaols, being confirmed by the intensities and characteristics of the thermal graphs. The inhibition of the enzyme acetylcholinesterase (AChE) was evaluated using the Ellman test, which did not show an inhibitory action. Regarding cytotoxic activity, the free extract and encapsulated in liposomes were tested, showing antiproliferative effect at different concentrations for human kidney tumor cells (786-0), liver cells (HUH7.5), and Macaca mullata normal kidney cells (LLC-MK2). Given the results obtained, ginger presents itself as a renewable source of bioactive compounds and can be indicated for applications in the pharmaceutical industry. Zingiber officinale 8 C ethanolwater ethanol water 7030 70 30 70:3 v/v vv v (v/v solvent 2,2azinobis3ethylbenzothiazoline6sulfonic 22azinobis3ethylbenzothiazoline6sulfonic azinobisethylbenzothiazolinesulfonic 2,2 azino bis 3 ethylbenzothiazoline 6 sulfonic 2 ABTS (ABTS 2,2diphenyl1picrylhydrazyl 22diphenyl1picrylhydrazyl diphenylpicrylhydrazyl diphenyl 1 picrylhydrazyl DPPH (DPPH ions tests Then thermogravimetric TG, TG , (TG) DTA, DTA (DTA) DSC, DSC (DSC)) shogaols graphs AChE (AChE test action tested 7860, 7860 786 0 (786-0) HUH7.5, HUH75 HUH HUH7.5 HUH7 5 (HUH7.5) LLCMK2. LLCMK2 LLCMK LLC MK2 . MK (LLC-MK2) obtained industry 703 7 70: 2azinobis3ethylbenzothiazoline6sulfonic azinobis 22 2, 2diphenyl1picrylhydrazyl (TG (DTA (DSC) 78 (786-0 HUH7. (HUH7.5 (LLC-MK2 (DSC (786- (HUH7. (LLC-MK (786 (HUH7 (78 (HUH (7 (

Abstract We developed poly-ε-caprolactone (PCL)-based nanoparticles containing D-α-tocopherol polyethylene glycol-1000 succinate (TPGS) or Poloxamer 407 as stabilizers to efficiently encapsulate genistein (GN). Two formulations, referred to as PNTPGS and PNPol, were prepared using nanoprecipitation. They were characterized by size and PDI distribution, zeta potential, nanoparticle tracking analysis (NTA), GN association (AE%), infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). PNTPGS-GN exhibited a particle size of 141.2 nm, a PDI of 0.189, a zeta potential of -32.9 mV, and an AE% of 77.95%. PNPol-GN had a size of 146.3 nm, a better PDI than PNTPGS-GN (0.150), a less negative zeta potential (-21.0 mV), and an AE% of 68.73%. Thermal and spectrometric analyses indicated that no new compounds were formed, and there was no incompatibility detected in the formulations. Cellular studies revealed that Poloxamer 407 conferred less toxicity to PCL nanoparticles. However, the percentage of uptake decreased compared to the use of TPGS, which exhibited almost 80% cellular uptake. This study contributes to the investigation of stabilizers capable of conferring stability to PCL nanoparticles efficiently encapsulating GN. Thus, the PCL nanoparticle proposed here is an innovative nanomedicine for melanoma therapy and represents a strong candidate for specific pre-clinical and in vivo studies. polyεcaprolactone poly ε caprolactone PCLbased based Dαtocopherol D α tocopherol glycol1000 glycol 1000 glycol-100 TPGS (TPGS 40 . (GN) formulations PNPol nanoprecipitation distribution NTA, NTA , (NTA) AE%, AE (AE%) FTIR, FTIR FT IR (FT-IR) DSC. DSC (DSC) PNTPGSGN 1412 141 2 141. nm 0189 0 189 0.189 32.9 329 32 9 -32. mV 7795 77 95 77.95% PNPolGN 1463 146 3 146. 0.150, 0150 0.150 150 (0.150) 21.0 210 21 (-21. mV) 6873 68 73 68.73% formed However 80 Thus preclinical pre clinical glycol100 100 glycol-10 4 (GN (NTA (AE% (FT-IR (DSC 14 018 18 0.18 32. -32 779 7 77.95 015 0.15 15 (0.150 21. (-21 687 6 68.73 8 glycol10 10 glycol-1 (AE 1 01 0.1 -3 77.9 (0.15 (-2 68.7 glycol1 glycol- 0. - 77. (0.1 (- 68. (0. ( (0

Abstract Bioactive substances can be found in wine lees, a waste from the winemaking industry. This work developed two formulations, a nanoemulsion with coconut oil (NE-OC) and a nanoemulsion with coconut oil and 0.5% of wine lees extract (NE-OC-Ext), to investigate their effect on untreated, bleached, and bleached-colored hair. The oil-in-water (O/W) nanoemulsions were prepared with coconut oil, TweenTM 80, SpanTM 80, AristoflexTM AVC, Conserve NovaMit MFTM, wine lees extract, and deionized water. The hydration measurements were carried out using a Corneometer® CM 825 with the capacitance method. Scanning electron microscopy (SEM) was used to characterize the effect of formulations on hair fibers. Differential Thermal Analysis (DTA) was to assess the thermal stability and compatibility of wine lees and coconut oil in formulations. Compared to NE-OC, NE-OC-Ext showed a greater hydration effect on bleached-colored hair. DTA showed that NE-OC-Ext presented a smaller number of exothermic degradation events than those of NE-OC, suggesting good interaction and compatibility of the wine lees extract in this formulation. This study highlights the value of wine lees, a residue from the winemaking process, and its possibility of use as raw material for the cosmetic hair industry since it shows a greater moisturizing potential in colored hair. NEOC NE OC (NE-OC 05 0 5 0.5 NEOCExt, NEOCExt Ext , (NE-OC-Ext) untreated bleached bleachedcolored oilinwater water O/W OW O W (O/W 80 AVC MFTM Corneometer 82 method SEM (SEM fibers (DTA NEOC, OC, NE-OC formulation process 0. (NE-OC-Ext 8

Abstract The polymer transition temperature is a crucial parameter in the industry for knowing raw materials before starting the manufacturing process. The current work reports a novel low-cost prototype instrument to measure the transition temperature with reliable accuracy. The equipment was built using commercial load cells composed of strain gauges in combination with an Arduino® microcontroller. The prototype measurement quality was validated by measuring the transition temperatures of most commercial polymers. The obtained values were compared with values obtained by conventional thermal analysis known as differential scanning calorimetric and thermo-mechanical analysis (DSC and TMA), which results in identical values. process lowcost low cost accuracy Arduino microcontroller polymers thermomechanical thermo mechanical DSC TMA, TMA , TMA)

Piezoelectric ultrasonic sensors used in Structural Health Monitoring (SHM) systems are usually attached to components by using adhesives with intrinsic properties that end up affecting their frequency-response. In this work, the electromechanical impedance of sensors attached to an aluminum sheet with three different epoxy resins was monitored during curing. Impedance change indexes (CIs) were calculated and compared with cure degree estimations from Differential Scanning Calorimetry (DSC). Results show that resonance frequencies were displaced by up to 30 kHz, and amplitudes changed considerably during the curing process of the selected resins. Results indicate that certain CIs show a high positive correlation value (R=0.96) with DSC data, and could therefore be used in practical applications to evaluate the curing status of the adhesive in SHM applications. (SHM frequencyresponse. frequencyresponse frequency response. response frequency-response work (CIs DSC. . (DSC) 3 kHz R=0.96 R096 R 0 96 (R=0.96 data (DSC R=0.9 R09 9 (R=0.9 R=0. R0 (R=0. R=0 (R=0 R= (R= (R

ABSTRACT The current project of Biomass Power Plants in the sugar industry of Cuba, has as limitation the access to the water required for condensation. A possible solution would be the use of air-cooled condenser (ACC), however, the thermal assessment of a ACC is imprecise since the available methods are in extreme complex and do not characterize adequately the overall heat transfer coefficient (K), being required the use of excesses of heat transfer surface, which increments costs of the facilities. The objective was to develop a valid model for any zone of operation and regimen of flow that computes the coefficient K with a smaller index of dispersion than the available models.The current status of the thermal analysis in an ACC and the methods used for each zone of operation, characteristics and limitations are shown. A differential and correlation analysis to obtain a single model, which is just for the four zones of dominant flow, was made. In the validation it is verified that the proposed model correlates with an average error of ±22% in 88,7 % of available experimental data, reducing in a third part the errors of the current methods used. This work shows that the use of the dominant flow criteria enables reducing the indexes of uncertainty in the thermal evaluation of the ACC, which derive in a larger reliability in the assessment analysis and eludes the use of excesses of heat transfer surface due to a low reliability in the thermal analysis.

RESUMEN El proyecto actual de centrales eléctricas de biomasa en la industria azucarera de Cuba, tiene como limitante el acceso al agua requerida para condensación. Una posible solución sería el uso de aerocondensadores (ACC), sin embargo, su evaluación térmica es imprecisa puesto que los métodos disponibles son en extremo complejos y no caracterizan adecuadamente el coeficiente global de transferencia de calor (K), siendo requerido el uso de excesos de área de transferencia de calor, incrementando los costos iniciales. El objetivo fue desarrollar un modelo válido para cualquier zona de operación y régimen de flujo, que compute el coeficiente K con un menor índice de dispersión que las expresiones disponibles. Se mostró el estado actual del análisis térmico en un ACC y los métodos utilizados para cada zona de operación, sus características y limitantes. Se realizó un análisis diferencial y de correlación para obtener un modelo único, el cual es justo para las cuatro zonas de flujo dominante. En la validación se comprobó que la propuesta correlaciona con un error medio de ±22% en el 88,7 % de las muestras disponibles, reduciendo en una tercera parte la incertidumbre de los métodos actualmente utilizados. El estudio realizado muestra que el uso del criterio de flujo dominante permite reducir apreciablemente los índices de incertidumbre en la evaluación térmica del ACC, lo cual deriva en una mayor confiabilidad en el análisis ingenieril y evita el uso de excesos de áreas por baja confiabilidad de análisis.

Resumen Uno de los posibles usos de los vidrios calcogenuros es su aplicación en dispositivos de memoria de cambio de fase. El funcionamiento de estas memorias no volátiles se basa en el uso de una aleación con elementos calcogenuros como material sensible, aprovechando el gran contraste en la resistencia eléctrica entre los estados amorfo y cristalino. Se destaca la aleación Sb70Te30 (porcentaje atómico) entre los materiales calcogenuros con estas propiedades. Por otro lado, el conocimiento de los mecanismos microscópicos de la cristalización de aleaciones amorfas permite el control microestructural para optimizar propiedades. En este punto, la calorimetría diferencial de barrido (DSC) ha sido ampliamente utilizada para la determinación de la estabilidad térmica de las aleaciones amorfas. Previamente hemos comenzado el estudio de la cinética de cristalización de aleaciones amorfas Sb70Te30. En este trabajo se ha aplicado un procedimiento basado en la denominada hipótesis isocinética para realizar el análisis cinético de los datos calorimétricos de calentamiento continuo. En particular la denominada curva maestra de la cinética de cristalización de esta aleación es determinada.

Abstract One of the possible uses of chalcogenide glasses is their application in phase change memory devices. The operation of these non-volatile memories is based on the use of an alloy with chalcogenide elements as a sensitive material, taking advantage of the great contrast in electrical resistance between the amorphous and crystalline states. The Sb70Te30 (atomic percentage) alloy stands out among the chalcogenide materials with these properties. On the other hand, the knowledge of the microscopic mechanisms of the amorphous alloys crystallization allows microstructural control to optimize properties. At this point, differential scanning calorimetry (DSC) has been widely used for the determination of the thermal stability of amorphous alloys. Previously we have started the study of the crystallization kinetics of Sb70Te30 amorphous alloys. In this work, a procedure based on the so-called isokinetic hypothesis has been applied to carry out the kinetic analysis of the calorimetric data of continuous heating. In particular, the so-called master curve of the crystallization kinetics of this alloy is determined.