Lower Average Rate Research Articles

Findings from the first wave of Covid-19 on the different impacts of lockdown on public health and economic growth

This paper examines the impact of different durations of national lockdown measures during the first wave of the COVID-19 pandemic on the public health and economic conditions of nations. Results indicate that a) countries with shorter lockdown periods, approximately 15 days, experience a higher variation of confirmed cases/population (%) compared to countries with longer lockdowns, lasting for over one month; b) countries with shorter lockdown periods experience lower average fatality rates compared to countries with longer lockdown periods, while the variation in fatality rates indicates that countries with longer periods of lockdown achieved a more substantial reduction in fatality rates. Nevertheless, the findings of the study indicate that while longer durations of national lockdowns, implemented as a government response to the COVID-19 pandemic, appear to produce somewhat uncertain outcomes in terms of public health, they exhibit a more substantial adverse effect on a country’s economic growth, resulting in a contraction in gross domestic product growth. Extracting key lessons from this study can prove invaluable in crafting effective public responses for future COVID-19 waves and epidemics that resemble the characteristics of COVID-19.

Research on wear characteristics of U-shaped elbows based on CFD-DEM coupling

The C++ programming language is employed to improve the Computational Fluid Dynamics (CFD)- Discrete Element Method (DEM) coupling interface in this paper, the accuracy of solid-liquid two-phase flow numerical model are validated through experiments. Subsequently, the wear characteristics of the U-shaped elbows under different elbows spacing, bending diameter ratio, particle volume concentration, and particle size are investigated. The research results indicate that as the spacing between bends is increased, the phenomenon of particle sedimentation is intensified, and the maximum collision angle in elbow 2 is increased. The location of the maximum collision angle is closer to the outlet of elbow 2. However, both the collision frequency and wear rate are reduced due to the decrease in the number of particles. Smoother particle flow and a reduction in the collision angle and wear rate of particles on both bends are achieved by increasing the bend ratio. During the variation of the particle volume fraction from 0.5% to 7%, the increase in collision frequency and wear rate of both bends is slowed down. A greater decrease is observed in elbow 2, but the “shielding effect” is not observed. Furthermore, at low volume fractions, kinetic energy is lost by particles as they flow through elbow 1, resulting in a lower average wear rate in elbow 2 compared to elbow 1. Conversely, at high volume fractions, the opposite effect occurs. Finally, when keeping the particle volume fraction constant, an increase in the particle size leads to a smaller wear area in both bends. The wear rate in elbow 1 increases at a slower rate, while the wear rate in elbow 2 exhibits an initial increase followed by a decrease trend.

Densification and microstructure of a ZrO2–SiO2 glass-ceramic prepared by using mesoporous particles as raw powder

Ceramic sintering is an energy-consuming process. Reducing sintering temperature and shortening dwelling time are significant to the reduction of carbon footprint. It has been reported that utilizing mesoporous particles as raw powder for sintering is a promising strategy to achieve the above goal. The goal of this study is to verify if this strategy also works for the sintering of ZrO2–SiO2 glass-ceramics. We synthesized mesoporous particles through a micelle-assisted co-precipitation process, followed by sintering by fast hot pressing (FHP) and pressureless sintering (PS) to obtain ZrO2–SiO2 glass-ceramics. For comparison, solid particles without mesopores were synthesized by a sol-gel method and consolidated by the two sintering techniques. The densification behaviors of the two types of particles were comparatively investigated. Results showed that the mesopores collapsed at ∼850 °C during FHP due to the applied pressure, which resulted in a peak densification rate during the whole sintering process. The mesoporous particles (∼820 °C) had a lower densification starting temperature than that of the solid particles (∼910 °C). However, the mesoporous particles showed a longer densification process and a lower average densification rate than those of the solid particles. The samples sintered from mesoporous particles showed a heterogeneous microstructure, predominately consisting of ZrO2 nanocrystallites embedded in a SiO2 matrix, but in some regions ZrO2 sub-microcrystallites were connected with each other by grain boundaries, without the presence of SiO2 matrix. During PS, there was not significant differences in the densification between the mesoporous particles and the solid ones. These results demonstrated that the mesoporous particles did not show significant advantages over solid ones, in terms of the densification of ZrO2–SiO2 glass-ceramics.

Design of UWB MIMO antenna using lean wearable textile substrate for reduced SAR

PurposeThis paper aims to propose a two-element dual fed ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with no additional decoupling structures. The antenna operates from 3.1 to 10.6 GHz. The antenna finds its usage in on-body wearable device applications.Design/methodology/approachThe antenna system measures 63.80 × 29.80 × 0.7 mm. The antenna radiating element is designed by using a modified dumbbell-shaped structure. Jean cloth material is used as substrate. The isolation improvement is achieved through spacing between two elements.FindingsThe proposed antenna has a very low mutual coupling of S21 < −20 dB and impedance matching of S11 < −10 dB. The radiation characteristics are stable in the antenna operating region. It provides as ECC < 0.01, diversity gain >9.9 dB. The antenna offers low average specific absorption rate (SAR) of 0.169 W/kg. The simulated and measured results are found to be in reasonable match.Originality/valueThe MIMO antenna is proposed for on-body communication, hence, a very thin jean cloth material is used as substrate. This negates the necessity of additional material usage in antenna design and the result range indicates good diversity performance and with a low SAR of 0.169 W/kg for on-body performance. This makes it a suitable candidate for textile antenna application.

Automated Detection, Segmentation, and Tracking of Brain Metastases in Repeated Courses of Stereotactic Radiosurgery Using Integrated Artificial Intelligence.

Salvage stereotactic radiosurgery (SRS) for distant brain metastases has been demonstrated as a safe and effective approach for intracranial recurrences after initial SRS. However, accurate tumor detection and segmentation among responding tumors within the irradiated parenchyma can be challenging. The requirement for the registration and reference to the previous course of SRS is very time-consuming and suffers significant inter and intra-reader variability. Artificial intelligence (AI)-assisted system has been proven to improve the accuracy and efficiency in the clinical flow of de-novo SRS. We hypothesize that an integrated AI system can facilitate an automated tumor contouring process for repeated SRS. Three patients who underwent their third course of SRS to brain metastases were selected for the pioneering works. They have had two sessions of SRS with a mean lesion number of 4 and 3.7, respectively. VBrain, an FDA-approved brain tumor management AI platform, was used to co-registered serial MR scans and automatically identify, track, and contour brain metastases for each course of SRS. The AI also indicated new lesions and treated lesions for each course. Three radiation oncologists experienced in brain SRS contoured the gross tumor volumes (GTVs) of the third course of SRS in two reader modes (assisted then unassisted) with a memory washout period of one week between each section. The segmentation ground truth was established through consensus among the three experts. Lesion-wise sensitivity, contouring accuracy, and consuming time were compared between the two contouring modes. In each patient, there were 15, 11, and 9 metastases, with a median diameter of 4.72 (95% CI: 4.05, 6.91) mm. The mean lesion-wise sensitivity was 96.96±2.47% with AI assistance and 76.90 ± 7.10% without assistance. There were two false-positive lesions in the assisted read, resulting in a low average false-positive rate of 0.67 per patient, while no false positive for the unassisted mode. AI assistance improved contouring accuracy. The median Dice similarity coefficient (DSC) was 0.71 (95% CI: 0.55, 0.87) for assisted contouring and 0.65 (95% CI: 0.46, 0.85) for unassisted contouring. We also use average Hausdorff distance (HD) to measure segmentation results. The mean HD was 0.72± 0.13 mm versus 0.73±0.08 mm for the two contouring modes (p = 0.02) Furthermore, the median contouring time per case was significantly shorter with AI assistance than without assistance (20.8 minutes vs. 29.8 minutes; p < 0.001), corresponding to a 43.2% time-saving. Our results suggest that the integration of an AI-based system into repeated brain SRS can significantly improve the accuracy and efficiency of tumor detection and segmentation. This approach has the potential to streamline the treatment planning process for salvage SRS.

Development and Quality Assurance of Multileaf Collimator (MLC) Auto-Feathering Junctions for Multi-Isocenter Supine Volumetric Modulated Arc Therapy (VMAT) Craniospinal Axis Irradiation on Halcyon.

Currently, there is alack of methods and tools that efficiently evaluate the auto-feathering junctions created by multileaf collimator (MLCs) for supine volumetric modulated arc therapy (VMAT) craniospinalirradiation (CSI) plans. We have investigated the feasibility of stitching together multi-isocenter fluence maps to then analyze the feathered junctions for patient-specific quality assurance (QA). Furthermore, we investigated the capability of Halcyon for the treatment of CSI patients.Three patients, who previously underwent VMAT CSI treatment on TrueBeam (6-MV flattening filter-free (FFF)) for 36 Gy in 20 fractionswerereplanned for Halcyon. A multi-isocenter approach with only translational superior-inferior shifts was used for both platforms. Each isocenter consists of two full arcs with anterior avoidance sectors, ±5° collimator rotations between arcs, and 5-8 cm of overlapping MLC auto-feathering junctions. All plans were QA'd via electronicportalimaging device (EPID) portal dosimetry and analyzed with a gamma criteria of 3%/3 mm. A variety of plan quality metrics were analyzed to evaluate dose distributions to the target, doses to organs at risk (OARs), and integral dose to the patient. A MATLAB script was developed to stitch the calculated and measured fluence maps in order to perform patient-specific QA for the composite fluence.The Halcyon plans provided highly conformal and homogenous dose distributions to the entire CSI target, superior to the clinical TrueBeam plans, while sparing critical organs with significantly lower values of V10Gy and V18Gy by up to 2% and 2.5%, respectively.Qualitative depictions of vertical dose profiles from the stitched DICOM of the entire CSI target for both planned and delivered fluence maps demonstrated equivalency, with slightly lower average pass rates with Halcyon (97%) compared to TrueBeam(99.9%). This approach to stitch multiple measured versus calculated EPID fluence maps has shown to be a feasible and accurate method and will be helpful for comprehensive VMAT CSI QA on both platforms. Further implementation of this script will be used in examining dosimetric impacts of daily patient positioning errors at MLC auto-feathering junctions.

PeakSAX: Real-Time Monitoring and Mitigation System for LDoS Attack in SDN

Software-Defined Networking (SDN) is a new paradigm that facilitates network management by enabling programmability and disassociating the control plane from the data plane. SDN places the control plane into one or more controllers that take charge of the entire network. However, the logically centralized controller of SDN makes it subject to some security issues. Denial-of-Service (DoS) attacks are the main threat to SDN that can lead to impaired performance of the entire network. Low-rate Denial-of-Service (LDoS) attack is a variant of DoS attacks with a lower average attack rate and high concealability which is difficult to identify with traditional DDoS/DoS attack detection mechanisms. Additionally, existing LDoS attack detection and defense mechanisms often have weak real-time performance. To address this issue, we propose in this paper PeakSAX, a novel framework that can protect SDN against LDoS attacks in real-time by (1) Attack monitoring, (2) Traffic symbolization, (3) Malicious traffic identifying, (4) Attacker location, and (5) Mitigation strategy deployment. Simulation results show that PeakSAX can quickly identify and mitigate the impact of LDoS attacks about 4s, which improves over 70% compared to existing solutions.

Evaluation of Seismic Performance of Masonry Stone Pagoda: Dynamic Centrifuge Test and Numerical Simulation Analysis

This study provides a comparison of results from dynamic centrifuge tests and a finite element analysis model to confirm the behavior of a representative Korean stone pagoda cultural heritage structure against earthquakes. The indirect stiffness or physical state of the structure was estimated by measuring the natural frequency of the masonry stone pagoda. The actual natural frequency of the stone pagoda was measured to be 4.5 Hz. It was determined to have a lower natural frequency than other stone pagodas of similar size. For the experiment, a dynamic centrifugal separator test was performed on a 1/15 model. Data from an actual earthquake record, the Ofunato earthquake, were used, with various maximum acceleration levels ranging from 0.069 g to 0.424 g. In order to confirm the accuracy of the finite element analysis model, the measured natural frequency of the masonry stone pagoda was compared with the modal analysis of the finite element model. When the data obtained from the experiment and the PGA (peak ground acceleration) of the FEM analysis with a complex masonry stone pagoda using a validated model result were compared, it was found to have a low average error rate of 13%. This shows that structural behavior can be predicted for similar masonry stone pagoda structures using finite element method analysis in the future.

Insights into ageing rates comparison across tissues from recalibrating cerebellum DNA methylation clock

DNA methylation (DNAm)-based age clocks have been studied extensively as a biomarker of human ageing and a risk factor for age-related diseases. Despite different tissues having vastly different rates of proliferation, it is still largely unknown whether they age at different rates. It was previously reported that the cerebellum ages slowly; however, this claim was drawn from a single clock using a relatively small sample size and so warrants further investigation. We collected the largest cerebellum DNAm dataset (N = 752) to date. We found the respective epigenetic ages are all severely underestimated by six representative DNAm age clocks, with the underestimation effects more pronounced in the four clocks whose training datasets do not include brain-related tissues. We identified 613 age-associated CpGs in the cerebellum, which accounts for only 14.5% of the number found in the middle temporal gyrus from the same population (N = 404). From the 613 cerebellum age-associated CpGs, we built a highly accurate age prediction model for the cerebellum named CerebellumClockspecific (Pearson correlation=0.941, MAD=3.18 years). Ageing rate comparisons based on the two tissue-specific clocks constructed on the 201 overlapping age-associated CpGs support the cerebellum has younger DNAm age. Nevertheless, we built BrainCortexClock to prove a single DNAm clock is able to unbiasedly estimate DNAm ages of both cerebellum and cerebral cortex, when they are adequately and equally represented in the training dataset. Comparing ageing rates across tissues using DNA methylation multi-tissue clocks is flawed. The large underestimation of age prediction for cerebellums by previous clocks mainly reflects the improper usage of these age clocks. There exist strong and consistent ageing effects on the cerebellar methylome, and we suggest the smaller number of age-associated CpG sites in cerebellum is largely attributed to its extremely low average cell replication rates.

Are franchise royalty fees related to franchisors’ support of franchisees? Evidence from the restaurant industry

Ensuring the effectiveness of the franchise system relies on establishing an optimal contractual relationship between the franchisor and the franchisee, which can be achieved through an optimal franchise fee structure. Previous theoretical models have emphasized the franchisors’ role in determining the franchise fee; however, empirical evidence has yielded inconclusive results, due to overlooking industry heterogeneity and using inadequate measures of franchisors’ effort. This study aims to empirically validate the relationship between franchisors’ efforts and franchise fees, specifically focusing on the restaurant industry based on its unique characteristics, including a relatively low average royalty rate and high financial risks. The study’s findings suggest that, unlike other industries, restaurant franchisors actively offer operational and financial support to increase the gross royalty rate. The motivation behind this support may be the insufficiency of ongoing fees in the restaurant industry to generate profits and the relatively high financial risk faced by restaurant franchisees.

Regenerator performance using freezing concentration for heat source tower heat pump system

Freeze concentration has a good regeneration effect and is easy for latent heat utilization. The electronic expansion valve opening has a great impact on the icing process. Hence, to investigate variations in the freezing process and gain the optimum regeneration effect, a solution regenerator was tested under different system-side control strategies. The solution volume flow was 5 m3/h and the electronic expansion valve opening degree (OEEV) was from 100% to 50%. For ice-covering growth, ice in low opening degree spent a long time to cover the plate. The area of ice under 100% to 65% OEEV was 1.43 times that under 50% OEEV. Peak velocities from 100% to 50% OEEV all appeared in the early stage of icing development. Moreover, the low opening degree made the ice distribute unevenness. The percentage slope of 100% OEEV was 1.23% and that of 50% OEEV was 3.46%. In addition, decreasing ice thickness uniformity was beneficial to the separation process. The separation ratio from 100% to 50% OEEV was 49.51%, 51.67%, 57.88%, and 74.54%, respectively. Both the low average thickness growth rate and high separation ratio were beneficial to increase the regeneration concentration. The effective specific ice production rate was from 100% to 50% OEEV was 5.99 kg/kWh, 6.18 kg/kWh, 6.94 kg/kWh, and 6.88 kg/kWh, respectively. Results showed that 65% OEEV operation was optimum for the solution regenerator unit using freeze concentration.

Examining the Associations of Early Childhood Teacher’s Emotional Well-being with Physiologic Stress, Mindfulness and Self-Compassion

Recent national reports indicate that early childhood (EC) teachers experience exceptionally high levels of chronic stress which can lead to adverse health outcomes. In this presentation, we share preliminary evidence of a mindfulness-based intervention, Cultivating Healthy Intentional Mindful Educators (CHIME) to support EC teachers’ regulatory processes. We hypothesize EC teachers’ social-emotional health is related to emotion regulation and their physiologic stress in the early care environment. EC teachers (n = 32 intervention, 22 waitlist control) recruited during 2020-2022 completed self-report measures of stress, well-being, mindfulness, and emotion regulation and task-based measures of emotional processing. Participants wore Actihearts (CamTech, Inc) to record their heart rate for three consecutive days in the classroom pre- and post-intervention. Controlling for pre-intervention metrics, the intervention group showed a tendency toward higher heart rate variability than controls post-intervention, F(1,44) = 3.84, p =.06. They also showed higher power in the high frequency heart rate band (F(1,44) = 3.92, p =.05) and lower average heart rate in the classroom (F(1,44) = 5.91, p =.02), despite showing similar activity levels to the control group, F(1,42) =.35, p =.56. There were significant differences in emotion dysregulation between the groups, with the CHIME group evidencing reduced emotion dysregulation, increased mental well-being, as well as differences in their response times during two emotional processing tasks, p’s <.05. Preliminary findings indicate that a mindfulness-based intervention is one promising way to support the emotional well-being of EC teachers.

Longitudinal study of perceived gendered differences of entrepreneurial program participants

Entrepreneurial pursuits have historically encountered gender bias in many forms. The stereotypes associated with successful entrepreneurs combined with the upsurge in participation by women in entrepreneurship over recent years have sparked greater interest and research into its gendered differences. Using surveys to gauge the perception of knowledge and experience in entrepreneurship, we assess longitudinally over the last 5 years, differences in responses from men and women in an accelerator program at New York University, dubbed the ‘Startup Sprint’ program. Significant trends in confidence relating to STEM entrepreneurship knowledge and experience are tracked with notably lower average ratings for women. Halfway through the study, the COVID-19 pandemic occurred bringing with it external stressors and a transformation of learning and working environments. Considering the stressors of the COVID-19 pandemic and the transition to a remote educational environment, we analyze our survey results to better understand the impact of these changes on the gendered perceptions of entrepreneurship.

Office-Visit Heart Rate and Long-Term Cardiovascular Events in Patients with Acute Myocardial Infarction.

An elevated heart rate at admission or discharge is known to be associated with poor cardiovascular outcomes in patients with acute myocardial infarction (AMI). The association between post-discharge average office-visit heart rate and cardiovascular outcomes in patients with AMI has rarely been studied. We analyzed data for 7840 patients from the COREA-AMI registry who had their heart rates measured at least three times after hospital discharge. The office-visit heart rates were averaged and categorized into four groups by quartiles (<68, 68-74, 74-80, and >80 beats per minute). The primary end point was a composite of cardiovascular death, myocardial infarction, and ischemic stroke. During a median of 5.7 years of follow-up, major adverse cardiovascular events (MACE) affected 1357 (17.3%) patients. An average heart rate higher than 80 bpm was associated with an increased incidence of MACE compared to the reference average heart rate of 68-74 bpm. When dichotomized into <74 or ≥74 bpm, a lower average heart rate was not associated with MACE in patients with LV systolic dysfunction, in contrast to those without LV systolic dysfunction. An elevated average heart rate at office visits after AMI was associated with an increased risk of cardiovascular outcomes. Heart rate monitoring at office visits after discharge provides an important predictor related to cardiovascular events.

LSTM-NV: A combined scheme against selective forwarding attack in event-driven wireless sensor networks under harsh environments

Wireless Sensor Networks (WSNs) are susceptible to selective forwarding attacks, which can lead to reduced network efficiency and compromise the integrity of transmitted data. The indistinguishability between malicious behavior and normal packet loss in harsh environments exacerbates the challenge. To address this, in this paper, we provide a combined detection scheme called LSTM-NV, consisting of a training stage and a detecting stage. During the training stage, we integrate variational mode decomposition (VMD) with a long short term memory (LSTM) model to learn normal nodes’ forwarding behavior and then predict errors for each node. During the detecting stage, dynamic thresholds are determined to identify local anomaly points and a novel neighbor voting method is employed to differentiate between malicious and normal nodes. Our scheme demonstrates superior performance with a low average missed detection rate (MDR) of 0.6% and a low average false detection rate (FDR) of 3.3% compared to other effective methods, while also offering lower detection algorithmic complexity.

The relative reinforcing efficacy of nicotine in an adolescent rat model of attention-deficit hyperactivity disorder.

Attention-deficit/hyperactivity disorder (ADHD) is an independent risk factor for tobacco use disorder. Individuals with ADHD are more likely to begin smoking at a younger age, become a daily smoker sooner, smoke more cigarettes per day, and exhibit greater nicotine dependence than individuals without ADHD. It is unclear whether these findings are due to the reinforcing efficacy of nicotine per se being greater among individuals with ADHD. The purpose of the present study was to examine this issue using an animal model of ADHD, the spontaneously hypertensive rat (SHR) strain. Adolescent SHR and Wistar (control) rats were given access to a typically reinforcing nicotine unit dose (30 μg/kg), a threshold reinforcing nicotine dose (4 μg/kg), or saline under an FR 1 (week 1) and FR 2 (week 2) schedule during 23 h sessions to examine acquisition of self-administration. Behavioral economic demand elasticity was then evaluated at the 30 μg/kg dose through an FR escalation procedure. At the 30 μg/kg dose, SHR rats exhibited a lower average response rate, lower mean active to inactive lever discrimination ratio, and lower proportion of rats acquiring self-administration compared to control rats. During demand assessment, SHR rats showed no significant difference from Wistars in demand intensity (Q0) or elasticity (α; i.e., reinforcing efficacy). In addition, no strain difference in acquisition measures were observed at the 4 μg/kg dose. These findings suggest that the increased risk of tobacco use disorder in adolescents with ADHD may not be attributable to a greater reinforcing efficacy of nicotine, and that other aspects of tobacco smoking (e.g., non-nicotine constituents, sensory factors) may play a more important role. A policy implication of these findings is that a nicotine standard to reduce initiation of tobacco use among adolescents in the general population may also be effective among those with ADHD.

Random-time quantum measurements

The analysis of a continuous measurement record $z(t)$ poses a fundamental challenge in quantum measurement theory. Different approaches were used in the past as records can, e.g., exhibit predominantly Gaussian noise, telegraph noise, or clicks at random times. The last case may appear as photon clicks in an optical spin-noise measurement at very low probe laser power. Here we show that such random-time quantum measurements can, similarly to the first two cases, be analyzed in terms of higher-order temporal correlations of the detector output $z(t)$ and be related to the Liouvillian of the measured quantum system. Our analysis in terms of up to fourth-order spectra (quantum polyspectra) shows that this type of spectra reveals the same valuable information as previously studied higher-order spectra in the case of the usual continuous quantum measurements. Surprisingly, broadband system dynamics is revealed even for deliberately low average measurement rates. Many applications are envisioned in high-resolution spectroscopy, single-photon microscopy, circuit quantum electrodynamics, quantum sensing, and quantum measurements, in general.

Porous Organic Cage as a Sulfur Host for Upgrading Capacity and Longevity of Li–S Batteries

Suffering from the severe shuttle effect, constructing high-performance lithium–sulfur (Li–S) batteries with high capacity and prolonged cycling life remains a great challenge. Developing porous host materials for sulfur loading remains a tendency. Porous organic cages (POCs), as a kind of porous material, exhibit potential in energy storage and conversion because of their inherent cavities and plentiful active sites. Herein, two POC materials of CPOC-301 and HPOC-401 with large octahedral cavities and abundant N and O heteroatoms were explored as host materials for loading a high sulfur content of 84 wt % in Li–S batteries. The resulting CPOC-301-S and HPOC-401-S cathodes exhibit improved electrochemical performances with high specific capacity (1302 and 1109 mA h g–1 at 0.05 C, respectively) and excellent cycling reversibility and stability (a low average capacity fading rate of 0.015% for 2500 cycles at 5 C for CPOC-301-S). Moreover, the interconversion of keto-enamine in CPOC-301 could accelerate the redox kinetics. This work provides the blueprint for POC families applied as promising host materials for advanced Li–S batteries.

Waste free construction site–A buzzword, nice to have or more

The building and construction industry is responsible for up to 25% of the total waste generated globally. Most construction sites in Norway on average generate 40–60 kg waste per gross floor area built and the average material recovery rate is ca. 46%. Existing requirements focus on waste sorting as a measure to increase material recovery rates. There are on-going national activities with an ambition to achieve waste free construction sites. However, there is lack of a common definition, standard and transparent data collection, and reporting system. This study presents a method for the evaluation and follow-up of construction waste and the associated greenhouse gas (GHG) emissions. The methodology was tested using the actual construction waste data collected from 36 Norwegian building cases to evaluate the quantity of construction waste, waste-related GHG emissions per building typology, sorting grade and waste recycling rate. The buildings in total generated ca. 7800 tonnes of waste and ca.12900 tonnes CO2eq and on average ca. 51 kg/m2 waste and 88kgCO2eq/m2. The building projects had a high average sorting grade (89%) and a low average recycling rate (32%). Gypsum, mixed wood, clean wood, and mixed waste are the top waste fractions representing ca. 56% of the total waste volume. This highlights there is still a long way to go to achieve waste free construction sites ambitions. The results also suggest the need for using transparent data collection and communication methods, collaboration in the value chain, stricter regulations, and incentives for encouraging the development of new and existing waste prevention solutions and technologies.

Characteristics of fly ash-based geopolymer concrete in the field for 4 years

The long-term durability of geopolymer concrete (GPC) exposed to various working conditions is a critical issue for achieving potential applications in the field. This study focuses on the long-term mechanical properties of pure Class F fly ash-based geopolymer concrete (FGPC) pavement at field conditions in relation to the microstructure and chemical compositions of reaction products. The continuously increasing compressive strength over time is observed, obtaining 47.29 and 65.54 MPa at 28 d and 4th y, respectively. Scanning electron microscopy (SEM), low-field nuclear magnetic resonance (NMR), and capillary absorption test were conducted to investigate the change in the physical microstructure, while X-ray diffraction (XRD), energy disperse spectroscopy (EDS), and pH test for chemical composition. The long-term curing leads to the homogeneous and compact microstructure with low average porosity and secondary absorption rate falling to 16% and 0.0033 mm/s1/2. The steady internal alkaline environment in FGPC ensures and extends the development of geopolymerization, resulting in the increase of amorphous phase content (APC, up to 93%) and decrease of Si/Al and Na/Al molar ratios (down to 2.85 and 0.88). The change in the chemical composition indicates that the disordered geopolymer is gradually transforming into a more ordered structure over time. The strong correlations identified between mechanical properties and micro-characteristics during the long-term period provide guidance for adjusting the mechanical properties of FGPC via regulating and controlling the microscope properties.