4 research outputs found
Optimalisering av UHPC med redusert sementinnhold
No full textSammendrag
Med den raske urbaniseringsveksten øker etterspørselen etter byggevirksomhet samtidig. Betong, som er det viktigste og mest brukte byggematerialet, etterspørres også i store mengder. For å øke fastheten og optimalisere konstruksjonsstørrelsen ble UHPC (Ultra-høyytelsesbetong) utviklet. Denne betongtypen er et relativt nytt materiale som kontinuerlig forskes på. UHPC har utmerket fasthet, både i trykkfasthet (når opp til 200 MPa) og bøyefasthet (når minimum 5 MPa). Dette materialet består av fine bindemidler, hovedsakelig sement, silikastøv og sand. Hele blandingen består av de nevnte bindemidlene tilsatt vann, superplastifiserer og stålfiber. Men materialet medfører en betydelig negativ miljøpåvirkning gjennom høye CO₂-utslipp. For at UHPC skal kunne produsere høy fasthet og kompakte dimensjoner kreves store mengder sement. Det høye sementforbruket skaper de svært høye utslippene.
Reduksjon av CO₂-utslipp i UHPC har vært et av de mest utforskede forskningsområdene. Den mest effektive måten å gjøre dette på er å redusere sementinnholdet i UHPC. Derfor har det vært stort fokus på å finne de mest egnede supplementære sementmaterialene (SCM). SCM er vanligvis avfallsmaterialer eller naturlige materialer som egner seg til betongkomponenter.
Denne masteroppgaven studerer bruken av SCM uten å påvirke (redusere) fastheten til UHPC og samtidig redusere CO₂-utslippene. For å gjøre dette ble to SCM valgt: slagg (erstatning av sementinnhold med 30% og 70%) og kalkstein (erstatning av sementinnhold med 30% og 50%). Det ble gjennomført en serie studier av hvordan disse SCM-ene påvirker UHPC, gjennom laboratorieøvelser og LCA-analyser.
Resultatene viser at de valgte SCM-ene er kompatible med erstatning av sementinnhold. Fra laboratorieøvelsene kunne slagg erstatte 70% av det totale sementinnholdet (og nå nesten 180 MPa), mens kalkstein viste seg å kunne erstatte opptil 30% av sementinnholdet (og nå nesten 176 MPa) i trykkfasthet. I bøyefasthet viser 30% kalksteinerstatning høyeste verdi med nesten 21 MPa. LCA-analysene viste at blandingen med lavest sementinnhold hadde laveste CO₂-utslipp, og reduserte det fra 867 kg CO₂ (for referanse-UHPC) til 502 kg CO₂ (blanding med 70% slagg). Det overordnede resultatet fra studiene viser at bruk av 25% kalkstein som SCM ga høyeste trykkfasthet (182 MPa), og bruk av 10% kalkstein som SCM ga høyeste bøyefasthet (33 MPa).
Resultatene indikerer at UHPC-industrien realistisk kan oppnå 40-60% CO₂-reduksjon gjennom intelligent SCM-implementering, mens ytelseskravene ikke bare opprettholdes, men i mange tilfeller forbedres. Dette representerer et betydelig bidrag til betongindustriens bærekraftsmål og demonstrerer at miljøhensyn og teknisk ytelse ikke nødvendigvis er motstridende målsetninger
Community-based risk management arrangements : an overview and implications for social fund programs
No full textRisk and its consequences pose a formidable threat to poverty reduction efforts. This study reviews a plethora of community-based risk management arrangements across the developing world. These types of arrangements are garnering greater interest in light of the growing recognition of the relative prominence of household or individual-specific idiosyncratic risk as well as the increasing shift towards community-based development funding. The study discusses potential advantages (such as targeting, cost, and informational) and disadvantages (such as exclusion and inability to manage correlated risk) of these arrangements, and their implications for the design of innovative social fund programs.Rural Poverty Reduction,Labor Policies,Insurance&Risk Mitigation,Currencies and Exchange Rates,Debt Markets
Global disparities in surgeons' workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study
No full text: The workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI
Global disparities in surgeons' workloads, academic engagement and rest periods: the on-calL shIft fOr geNEral SurgeonS (LIONESS) study
No full textThe workload of general surgeons is multifaceted, encompassing not only surgical procedures but also a myriad of other responsibilities. From April to May 2023, we conducted a CHERRIES-compliant internet-based survey analyzing clinical practice, academic engagement, and post-on-call rest. The questionnaire featured six sections with 35 questions. Statistical analysis used Chi-square tests, ANOVA, and logistic regression (SPSS® v. 28). The survey received a total of 1.046 responses (65.4%). Over 78.0% of responders came from Europe, 65.1% came from a general surgery unit; 92.8% of European and 87.5% of North American respondents were involved in research, compared to 71.7% in Africa. Europe led in publishing research studies (6.6 ± 8.6 yearly). Teaching involvement was high in North America (100%) and Africa (91.7%). Surgeons reported an average of 6.7 ± 4.9 on-call shifts per month, with European and North American surgeons experiencing 6.5 ± 4.9 and 7.8 ± 4.1 on-calls monthly, respectively. African surgeons had the highest on-call frequency (8.7 ± 6.1). Post-on-call, only 35.1% of respondents received a day off. Europeans were most likely (40%) to have a day off, while African surgeons were least likely (6.7%). On the adjusted multivariable analysis HDI (Human Development Index) (aOR 1.993) hospital capacity > 400 beds (aOR 2.423), working in a specialty surgery unit (aOR 2.087), and making the on-call in-house (aOR 5.446), significantly predicted the likelihood of having a day off after an on-call shift. Our study revealed critical insights into the disparities in workload, access to research, and professional opportunities for surgeons across different continents, underscored by the HDI
