1,720,971 research outputs found
Ageing tests closer to real service conditions using hyper-sensitive microcalorimetry, a case study on EPDM rubber
No full textMicrocalorimetry and Infrared Spectroscopy : Thermal processes related to solid waste, ageing rubber, phase change materials, and biomass gasification
No full textMicrocalorimetry (MC) is a unique technique for an online measurement of heat production. It can be applied to solids, liquids, or gases. MC can be used to measure the heat involved in either exothermic or endothermic processes. The heat signal obtained from MC is a lumped parameter so chemical, biological, and physical changes involving heat are measured simultaneously. In this study MC has been used to study the thermal processes in municipal solid waste, phase change materials and polymeric materials. A self-heating phenomenon, which may lead to significant heat production in piles of stored municipal solid waste, was studied with MC. This enabled us to understand the propensity of self-heating in municipal solid waste in storage conditions closer to real-life. The results showed that the self-heating in the solid waste was due to the aerobic metabolism of microorganisms. With the development of a third generation MC and better temperature control mechanisms, MC can be operated in non-isothermal mode as a differential scanning calorimeter (DSC). However, MC is capable of measuring heat flow using significantly larger sample masses than DSC. The larger sample mass is more representative of complex/heterogeneous materials, like cementitious blocks. Hence, MC was applied here to determine if it could be a useful tool in characterizing the thermal properties (latent heat and specific heat) of cementitious grout containing phase change materials (PCMs). It was observed that the phase changes (melting and crystallization) due to the PCM could be accurately characterized with MC. Performance of PCM can be investigated using thermal cycling tests that mimic real-life temperature scans. The high sensitivity of MC (μW/10000 mg) means that chemical changes can be measured at least 100 K lower than DSC (μW/~30 mg). The increased sensitivity opens up the possibility of measuring the ageing/degradation of polymers at closer to real-life temperatures and conditions. This is advantageous, since the normally used accelerated testing at significantly higher temperatures leads to degradation conditions that do not resemble service conditions. It is shown here, with the MC technique on a highly filled ethylene propylene diene monomer (EPDM) material, that the ageing processes, as well as the activation energy of the ageing processes, at close to real-life temperature are different from those at high temperature. With the high sensitivity of the MC, local thermal processes on a small scale could be readily observed, such as the melting of the antioxidant and further reactions in the peroxide cross-linking system. Hence, the results indicate that MC is a promising technique for measuring chemical changes and reaction parameters closer to the real-life temperatures in complex systems like highly filled EPDM rubber. To relate heat flow data to chemical mechanisms, post analysis of polymeric materials should be carried out with alternate techniques, for example, infrared spectroscopy (FTIR), gas chromatography and scanning electron microscopy coupled to energy dispersive X-ray. In principle, the signature of hydrocarbons can be detected using FTIR. However, subjecting the instrument to the raw gas from biomass gasification runs the risk of condensation of tars on optical components and subsequent malfunction. As a solution, an external cell that can be heated to at least 400 °C was designed to ensure that tars remain in the gas phase. The on-line measurements for permanent gases, water and tars were made using a lab-scale downdraft gasifier. Concentrations of permanent gases are in good agreement with Micro-GC and spectral signatures of tars are comparable with measurements using the solid phase adsorption (SPA) technique.Mikrokalorimetri (MC) är en unik teknik för online-mätning av värmeproduktion. Det kan användas för fasta ämnen, vätskor eller gaser. MC används för att mäta värmen som är involverad i antingen exoterma eller endoterma processer. Värmesignalen som erhålls från MC är en lumpad parameter, så kemiska, biologiska och fysikaliska förändringar som involverar värme mäts samtidigt. I denna studie har MC använts för att studera de termiska processerna i kommunalt fast avfall, fasförändringsmaterial (PCM) och polymera material. Ett självuppvärmningsfenomen, som kan leda till betydande värmeproduktion i högar av lagrat kommunalt fast avfall, studerades med MC. Detta gjorde det möjligt att förstå benägenheten för självuppvärmning i kommunalt fast avfall under lagringsförhållanden närmre verkligheten. Resultaten visade att självuppvärmningen i det fasta avfallet berodde på mikroorganismernas aeroba metabolism. Med utvecklingen av en tredje generationens MC och bättre styrning av temperaturen kan MC användas i ett icke-isotermt läge, likt en differentiell svepkalorimeter (DSC). MC kan mäta värmeflödet för prov med större massa än vad som är möjligt med DSC. Den större provmassan är mer representativ för komplexa/heterogena material så som cementblock. Därför användes MC för att ta reda på om det kunde vara ett användbart verktyg för att karakterisera termiska egenskaper (latent och specifik värme) hos ett cementbaserat bruk innehållandes fasförändringsmaterial. Fasförändringar (smältning och kristallisation) hos ett PCM kunde karakteriseras med MC. Prestandan hos PCM kan undersökas med hjälp av termiska cyklingstester som efterliknar verkliga temperaturvariationer. Den höga känsligheten hos MC (μW/10 000 mg) gör att kemiska förändringar kan mätas vid minst 100 K lägre än DSC (μW/~30 mg). Den ökade känsligheten öppnar för möjligheten att mäta åldrande/nedbrytning av polymerer närmre verkliga temperaturer och förhållanden. Detta är fördelaktigt; den normalt använda accelererade testningen sker vid betydligt högre temperaturer och leder till nedbrytningsförhållanden som inte liknar driftförhållanden. Det visas här, med MC-tekniken på ett EPDM-material, att åldringsprocesserna, såväl som aktiveringsenergin för åldringsprocesserna, nära verkliga temperaturer skiljer sig från de vid högre temperaturer. Tack vare den höga känsligheten var det möjligt att studera lokala termiska processer i liten skala, såsom smältning av antioxidanten samt ytterligare reaktioner. Resultaten indikerar att MC är en lovande teknik för att mäta kemiska förändringar i komplexa system och bestämma reaktionsparametrar närmre verkliga temperaturer. För att relatera mätdata från MC till kemiska mekanismer bör efteranalys av polymera material utföras, exempel på tekniker är infraröd spektroskopi (FTIR), gaskromatografi och svepelektronmikroskop kopplad till energidispersiv röntgen. I princip kan kolväten detekteras med FTIR. Att utsätta FTIR-instrumentet för gas från biomassaförgasning riskerar att tjära kondenseras på optiska komponenter och efterföljande funktionsfel. Som en lösning konstruerades en extern cell som kan värmas upp till minst 400 °C för att säkerställa att tjäror inte kondenserar ut. Online-mätningar av permanenta gaser, vatten och tjära gjordes med en förgasare i laboratorieskala. Koncentrationer av permanenta gaser överensstämde väl med Micro-GC och spektrala signaturer av tjäror var jämförbara med mätningar med fastfasadsorptionsteknik (SPA).QC 20220928</p
Specific heat for geothermal grout and excess heat capacity with phase change materials using heat conduction microcalorimetry
No full textMicrocalorimetry and Infrared Spectroscopy : Thermal processes related to solid waste, ageing rubber, phase change materials, and biomass gasification
No full textMicrocalorimetry (MC) is a unique technique for an online measurement of heat production. It can be applied to solids, liquids, or gases. MC can be used to measure the heat involved in either exothermic or endothermic processes. The heat signal obtained from MC is a lumped parameter so chemical, biological, and physical changes involving heat are measured simultaneously. In this study MC has been used to study the thermal processes in municipal solid waste, phase change materials and polymeric materials. A self-heating phenomenon, which may lead to significant heat production in piles of stored municipal solid waste, was studied with MC. This enabled us to understand the propensity of self-heating in municipal solid waste in storage conditions closer to real-life. The results showed that the self-heating in the solid waste was due to the aerobic metabolism of microorganisms. With the development of a third generation MC and better temperature control mechanisms, MC can be operated in non-isothermal mode as a differential scanning calorimeter (DSC). However, MC is capable of measuring heat flow using significantly larger sample masses than DSC. The larger sample mass is more representative of complex/heterogeneous materials, like cementitious blocks. Hence, MC was applied here to determine if it could be a useful tool in characterizing the thermal properties (latent heat and specific heat) of cementitious grout containing phase change materials (PCMs). It was observed that the phase changes (melting and crystallization) due to the PCM could be accurately characterized with MC. Performance of PCM can be investigated using thermal cycling tests that mimic real-life temperature scans. The high sensitivity of MC (μW/10000 mg) means that chemical changes can be measured at least 100 K lower than DSC (μW/~30 mg). The increased sensitivity opens up the possibility of measuring the ageing/degradation of polymers at closer to real-life temperatures and conditions. This is advantageous, since the normally used accelerated testing at significantly higher temperatures leads to degradation conditions that do not resemble service conditions. It is shown here, with the MC technique on a highly filled ethylene propylene diene monomer (EPDM) material, that the ageing processes, as well as the activation energy of the ageing processes, at close to real-life temperature are different from those at high temperature. With the high sensitivity of the MC, local thermal processes on a small scale could be readily observed, such as the melting of the antioxidant and further reactions in the peroxide cross-linking system. Hence, the results indicate that MC is a promising technique for measuring chemical changes and reaction parameters closer to the real-life temperatures in complex systems like highly filled EPDM rubber. To relate heat flow data to chemical mechanisms, post analysis of polymeric materials should be carried out with alternate techniques, for example, infrared spectroscopy (FTIR), gas chromatography and scanning electron microscopy coupled to energy dispersive X-ray. In principle, the signature of hydrocarbons can be detected using FTIR. However, subjecting the instrument to the raw gas from biomass gasification runs the risk of condensation of tars on optical components and subsequent malfunction. As a solution, an external cell that can be heated to at least 400 °C was designed to ensure that tars remain in the gas phase. The on-line measurements for permanent gases, water and tars were made using a lab-scale downdraft gasifier. Concentrations of permanent gases are in good agreement with Micro-GC and spectral signatures of tars are comparable with measurements using the solid phase adsorption (SPA) technique.Mikrokalorimetri (MC) är en unik teknik för online-mätning av värmeproduktion. Det kan användas för fasta ämnen, vätskor eller gaser. MC används för att mäta värmen som är involverad i antingen exoterma eller endoterma processer. Värmesignalen som erhålls från MC är en lumpad parameter, så kemiska, biologiska och fysikaliska förändringar som involverar värme mäts samtidigt. I denna studie har MC använts för att studera de termiska processerna i kommunalt fast avfall, fasförändringsmaterial (PCM) och polymera material. Ett självuppvärmningsfenomen, som kan leda till betydande värmeproduktion i högar av lagrat kommunalt fast avfall, studerades med MC. Detta gjorde det möjligt att förstå benägenheten för självuppvärmning i kommunalt fast avfall under lagringsförhållanden närmre verkligheten. Resultaten visade att självuppvärmningen i det fasta avfallet berodde på mikroorganismernas aeroba metabolism. Med utvecklingen av en tredje generationens MC och bättre styrning av temperaturen kan MC användas i ett icke-isotermt läge, likt en differentiell svepkalorimeter (DSC). MC kan mäta värmeflödet för prov med större massa än vad som är möjligt med DSC. Den större provmassan är mer representativ för komplexa/heterogena material så som cementblock. Därför användes MC för att ta reda på om det kunde vara ett användbart verktyg för att karakterisera termiska egenskaper (latent och specifik värme) hos ett cementbaserat bruk innehållandes fasförändringsmaterial. Fasförändringar (smältning och kristallisation) hos ett PCM kunde karakteriseras med MC. Prestandan hos PCM kan undersökas med hjälp av termiska cyklingstester som efterliknar verkliga temperaturvariationer. Den höga känsligheten hos MC (μW/10 000 mg) gör att kemiska förändringar kan mätas vid minst 100 K lägre än DSC (μW/~30 mg). Den ökade känsligheten öppnar för möjligheten att mäta åldrande/nedbrytning av polymerer närmre verkliga temperaturer och förhållanden. Detta är fördelaktigt; den normalt använda accelererade testningen sker vid betydligt högre temperaturer och leder till nedbrytningsförhållanden som inte liknar driftförhållanden. Det visas här, med MC-tekniken på ett EPDM-material, att åldringsprocesserna, såväl som aktiveringsenergin för åldringsprocesserna, nära verkliga temperaturer skiljer sig från de vid högre temperaturer. Tack vare den höga känsligheten var det möjligt att studera lokala termiska processer i liten skala, såsom smältning av antioxidanten samt ytterligare reaktioner. Resultaten indikerar att MC är en lovande teknik för att mäta kemiska förändringar i komplexa system och bestämma reaktionsparametrar närmre verkliga temperaturer. För att relatera mätdata från MC till kemiska mekanismer bör efteranalys av polymera material utföras, exempel på tekniker är infraröd spektroskopi (FTIR), gaskromatografi och svepelektronmikroskop kopplad till energidispersiv röntgen. I princip kan kolväten detekteras med FTIR. Att utsätta FTIR-instrumentet för gas från biomassaförgasning riskerar att tjära kondenseras på optiska komponenter och efterföljande funktionsfel. Som en lösning konstruerades en extern cell som kan värmas upp till minst 400 °C för att säkerställa att tjäror inte kondenserar ut. Online-mätningar av permanenta gaser, vatten och tjära gjordes med en förgasare i laboratorieskala. Koncentrationer av permanenta gaser överensstämde väl med Micro-GC och spektrala signaturer av tjäror var jämförbara med mätningar med fastfasadsorptionsteknik (SPA).QC 20220928</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Self-heating propensity of waste using isothermal calorimetry
Get PDFIncreased recycling of waste has led to an extensive handling and temporary storage of different types during the last two decades. Self-heating is often experienced in waste storage facilities and if the heat generation is greater than the heat lost to the surroundings, it could lead to self-ignition Statistics show that 60-70 fires occur each year at Swedish facilities for waste handling and storage on an industrial scale. One of the main reasons for fires in stored waste is self-heating. Currently the level of understanding of self-heating is insufficient, and therefore, a methodology for determining the self-heating properties of waste is needed to provide the cause and to prevent incidents.
A methodology is being developed for measuring the self-heating potential of different types of waste using a sensitive and powerful technique known as micro-calorimetry. Using this approach heat release due to different process, e.g. biological or chemical reactions, can be measured.
Experiments were performed on different mixtures of a mixture of a burnable fractions of municipal solid waste and industrial waste, Heat release was measured at different temperatures between 40 °C and 80 °C. Results show that the technique can be used to differentiate heat release rate for waste obtained from different sources and potentially to determine what types of waste (and waste fractions) are mainly responsible for the production of heat. It can also be used to characterize new types of mixtures. The present study confirms that heat release can be higher in comparison to wood pellets and there is a need for further investigations and guidelines which can be used for the safe storage of waste.Increased recycling of waste has led to an extensive handling and temporary storage of different types during the last two decades. Self-heating is often experienced in waste storage facilities and if the heat generation is greater than the heat lost to the surroundings, it could lead to self-ignition Statistics show that 60-70 fires occur each year at Swedish facilities for waste handling and storage on an industrial scale. One of the main reasons for fires in stored waste is self-heating. Currently the level of understanding of self-heating is insufficient, and therefore, a methodology for determining the self-heating properties of waste is needed to provide the cause and to prevent incidents.
A methodology is being developed for measuring the self-heating potential of different types of waste using a sensitive and powerful technique known as micro-calorimetry. Using this approach heat release due to different process, e.g. biological or chemical reactions, can be measured.
Experiments were performed on different mixtures of a mixture of a burnable fractions of municipal solid waste and industrial waste, Heat release was measured at different temperatures between 40 °C and 80 °C. Results show that the technique can be used to differentiate heat release rate for waste obtained from different sources and potentially to determine what types of waste (and waste fractions) are mainly responsible for the production of heat. It can also be used to characterize new types of mixtures. The present study confirms that heat release can be higher in comparison to wood pellets and there is a need for further investigations and guidelines which can be used for the safe storage of waste
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
