Rate Curves Research Articles

Streamflow simulation at different temporal scales under rating curve uncertainty conditions using machine learning models

ABSTRACT Reducing uncertainty in streamflow simulation is vital for effective water resource management. The impact of uncertainty in model calibration data (discharge), commonly derived from the rating curve, is often overlooked. This study applies the Monte Carlo simulation technique (MCST) to assess uncertainty in the rating curve. Advanced machine learning (ML) models, bidirectional long short-term memory (BiLSTM), and bidirectional gated recurrent units (BiGRUs) were used comparatively to evaluate the propagation of this uncertainty onto streamflow simulation on both daily and monthly temporal scales. Different sets of streamflow data, derived from the fitted curve and its lower and upper uncertainty bands were utilized to train ML models independently. The results show the substantial impact of rating curve uncertainty in streamflow simulations, with the BiGRU model surpassing the BiLSTM model on both scales. As a result, the uncertainty in the rating curve results in an uncertainty of the streamflow of up to 30 and 25% on daily and monthly simulations, respectively. These findings underscore the importance of considering rating curve uncertainty in streamflow simulation to ensure accurate and reliable results. Therefore, streamflow should be treated as an uncertain variable and managed by incorporating rating curve uncertainty in decision-making.

Fluvial erosion in a catchment cultivated with no-tillage at the edge of the southern Brazilian plateau.

The dynamics of fluvial erosion responds to soil erosion and surface runoff on hillslopes due to land use and environmental fragility, conditioned by the soil, geology, relief, and rainfall rate. Despite the increasing problems associated with fluvial erosion in Brazil, little information is available on bedload transport in headwater catchments under intense agricultural activity. Therefore, this study sought to characterize the fluvial erosion processes and bedload dynamics in an experimental catchment in southern Brazil located at the edge of the Brazilian Meridional plateau, which is representative of a large area of high environmental fragility and intense agricultural activity in Southern Brazil. The Guarda Mor River drains a headwater catchment (18.5 km2) with undulating and hilly terrain with fragile soils and intense agricultural activity controlling fine and coarse sediment supply downstream. During 11 major rainfall-runoff events, monitoring was conducted to measure streamflow, bedload transport rates, sediment size, and hydraulic parameters, such as Manning's n values and viscous layer thicknesses. A rating curve was established based on 40 streamflow and bedload discharge measurements taken at different water levels and stages along the hydrograph. In addition, a river portion (gravel bed) was characterized as well as the granulometric characteristics of its surface and subsurface layers. The results showed that the transport pattern is influenced by factors other than hydraulic parameters alone, including the interdependence between successive events, armoring effects, and hysteresis. These factors are strongly related to the surface runoff and erosion observed on the hillslopes, which define the streamflow energy and the supply of sand fraction, respectively. A discussion is held on the bedload transport dynamics under non-equilibrium conditions in the modeling of fluvial erosion processes.

Calibration and Uncertainty Analysis for Isovel Contours-based Stage-discharge Rating Curve by Sequential Uncertainty Fitting (SUFI-2) Method

Calibration and Uncertainty Analysis for Isovel Contours-based Stage-discharge Rating Curve by Sequential Uncertainty Fitting (SUFI-2) Method

Effect of hot air temperature and slice thickness on the drying kinetics and quality of Hami melon (Cantaloupe) slices

The effects of hot air temperature and slice thickness on the drying kinetics and quality of Hami melon slices (HMS) were studied. HMS (3 mm and 5 mm) were carried out in a forced convection drying oven at temperatures ranging from 60 ~ 90 °C. The increase in hot air temperature and the decrease in slice thickness led to shorter drying times and higher drying rates. The drying rate curves indicated that the drying process of HMS did not exhibit a constant drying rate period. In the drying kinetics modeling process, the Explinear model was suited for describing the drying curves with higher accuracy. According to Fick’s second law, the moisture effective diffusion coefficient of 3 mm and 5 mm HMS ranged from 4.72 ~ 15.96 × 10-11m2/s at temperatures of 60, 70, 80, and 90 °C. When the thickness of HMS were 3 mm and 5 mm, the activation energies were 30.13 and 43.75 kJ/mol, respectively. When dried at low temperatures, the color of HMS was closer to fresh Hami melon. With the increase of hot air temperature, the hardness of HMS decreases and the rehydration increases. When the thickness of the HMS decreases, the hardness of the slices decreases and the rehydration increases.

Landslide Susceptibility Zonation Mapping Using Machine Learning Algorithms and Statistical Prediction at Hunza Watershed Basin, Pakistan

The mountainous region of the Hunza River watershed basin, especially along the Karakorum highway, and also known as a third pole for the high accumulation of glaciers, which leads to huge devastating landslides occurring every year. Landslide susceptibility mapping was carried out using two deep machine learning techniques (DeeplabV3+ & universal network U-Net) and two statistical models (Intuitionistic Fuzzy divergence IF-D & Frequency ratio FR). The landslide susceptibility mapping is conducted using landslide inventory data and twelve conditional factors. The landslide susceptibility maps obtained from the two statistical models were compared with those generated by two deep machine learning models based on prediction accuracy measures, such as the Area Under the Curve (AUC) and Seed Cell Area Index (SCAI). The Success Rate Curve (SRC) was obtained using the training dataset, and the AUC values for the four models were as follows: 76.9% for IF-D, 76.9% for FR, 80.4% for DeeplabV3+, and 76.3% for U-Net. In terms of the Prediction Rate Curve (PRC) obtained from the validation dataset, the AUC values were found to be 80.8% for IF-D, 80.8% for FR, 81% for DeeplabV3+, and 77.8% for U-Net. To assess the classification ability of the models, the Seed Cell Area Index (SCAI) test was conducted. The results indicated that the SCAI (D-value) was 7.3 for U-Net, 10 for DeeplabV3+, 7.6 for IF-D, and 9.1 for FR. Overall, the findings revealed that DeeplabV3+ exhibited the highest prediction accuracy and classification ability, making it the most suitable choice for landslide susceptibility mapping in the relevant study area.

Thermocapillary stability of a viscoelastic liquid film falling down above or below an inclined thick wall with slip

Background:Thin viscoelastic liquid films falling down walls have been investigated theoretically since many years ago due to their applications in coating and cooling of substrates. They may also be subjected to temperature gradients and have been investigated under a variety of boundary conditions. In particular, the Navier slip boundary condition has been the subject of recent research. This condition is used when at the interface between the liquid and the wall the no-slip boundary condition does not apply due to different reasons like wall small topography, chemical coatings, etc. Methods:The small wavenumber approximation is used to derive a nonlinear evolution equation to describe the free surface deformations of the viscoelastic liquid film falling down an inclined wall. This equation is linearized and its linear stability is investigated using normal modes. The nonlinear free surface deformations are calculated numerically by means of a normal modes expansion substituted into the nonlinear evolution equation. Significant Findings:The thermocapillary stability of a thin viscoelastic film falling down a thick wall of finite thermal conductivity is investigated. Linear and nonlinear flows are examined when the interface of the liquid and the wall presents slip effects. The stability of the flow above and below (Rayleigh–Taylor) the wall is also explored. The lubrication approximation is used to derive a nonlinear evolution equation for the free surface deformation. The curves of linear growth rate, maximum growth rate and critical Marangoni number are calculated for different viscoelastic Deborah numbers. The film will be subjected to destabilizing and stabilizing Marangoni numbers. It is found that from the point of view of the linear growth rate the flow destabilizes with slip in a wavenumber range k<k+. However slip stabilizes for larger wavenumbers k>k+ up to the critical (cutoff) wavenumber. The results show that the Deborah number displaces k+ to the right. When k+ reaches the critical wavenumber by an increase of the Deborah number, slip is unable to stabilize. The corresponding critical Deborah number is derived. On the contrary, when the Deborah number is zero these slip stabilizing regions k>k+ correspond to Newtonian fluids investigated in previous works. From the point of view of the maximum growth rate slip may stabilize or destabilize increasing the slip parameter depending on the magnitude of the Marangoni, Galilei and Deborah numbers. Explicit formulas were derived for the intersections where slip may change its stability properties. Numerical solutions of the free surface nonlinear evolution equation show that slip can decrease the amplitude and may stimulate the appearance of subharmonics. The effects of different wall properties are also investigated.

Investigation of tensile deformation behavior of a TWIP/TRIP metastable β titanium alloy at typical temperature part Ⅰ: Room temperature

The tensile behavior and deformation mechanism of Ti-10Mo alloy at room temperature (298 K) were investigated. The results show that the alloy has an ultimate tensile strength (UTS) of 744 MPa and a high yield strength (YS) of 662 MPa, as well as an excellent elongation (El) after fracture of 38 %, outperforming Ti-15Mo alloy under the same conditions. The superior strength and plasticity of Ti-10Mo alloy at 298 K are attributed to the activation of both {332}〈113> twinning and SIM α“ during deformation. The sequence of different deformation mechanisms is as follows: in the initial stage of deformation, dislocation slip can be extensively activated and continues to occur during subsequent deformation; in the middle stage of deformation, primary and secondary {332}〈113〉 twinning and SIM α” are activated simultaneously, resulting in a continuous increase in work hardening rate; in the later stage of deformation, the alloy can further deform through {1 1 1}α“ twinning. The higher YS may be due to the optimal quantity and size of athermal ω phase in Ti-10Mo alloy, which increases the YS without significantly affecting plasticity. Meanwhile, Quenching vacancies can also increase the YS of the alloy. The three stages of the work hardening rate curve correspond to the activation of the dislocation slip mechanism, the activation of the {332}〈113〉 twinning and SIM α” and the stop of the {332}〈113〉 twinning and SIM α“.

Enhanced mechanical properties and mechanism of iron ore tailings-based geopolymers modified by municipal solid waste incineration fly ash

Iron ore tailings, coal fly ash and municipal solid waste incineration fly ash (MSWI FA), as solid waste, must be disposed of. Iron ore tailings, coal fly ash and MSWI FA were successfully prepared into high-performance geopolymer. The compressive strength of optimal geopolymer reached 57.89 MPa. Based on XRD, FTIR, SEM and chemical extraction analysis, C-(A)-S-H was the main gel product along with N-A-S-H. It was found that the dominant hydration process of geopolymer was changed from diffusion process (D) to phase boundary reaction process (I) after MSWI FA addition based on hydration reaction rate curves and dynamic simulation, releasing more hydration heat and generating more C(N)-A-S-H gels. Heavy metal content in the optimal geopolymer was below the limits of Class I screening value of development land (GB 36600-2018). Ef and Cf of the optimal geopolymer were 30.9 MJ/ton/MPa and 6.88 kg CO2/ton/MPa, affirming the viability of utilizing iron ore tailings, coal fly ash and MSWI FA as raw materials for geopolymer production, which provides a promising collaborative resource method of processing them.

Thermo-Physical Properties of Hexavalent Tungsten W6+-Doped Ta-Based Ceramics for Thermal/Environmental Barrier Coating Materials

The CaTa0.8WO6 ceramic was fabricated by a solid-state reaction for thermal/environmental barrier coating (Thermal and Environmental Barrier Coating) applications, and the microstructures, mechanical and thermal properties were investigated. The result showed CaTa0.8WO6 has a lower thermal conductivity (1.05 W·m−1·K−1 at 900 °C) than 8 wt.% yttria-stabilized zirconia and the doped Ta-based ceramics with Mg2+, Yb3+, Zr4+ and Nb5+, indicating that hexavalent tungsten element W6+ doping effectively reduces thermal conductivity and improves thermal insulation performance of Ta-based ceramics. The thermal expansion rates curve without inflection points resulting from phase transition indicates that CaTa0.8WO6 has excellent high-temperature phase stability. Since the Young’s modulus and Pugh’s ratio of CaTa0.8WO6 ceramics were lower than those of various valence states doping Ta-based ceramics, which means that CaTa0.8WO6 has better damage tolerance.

A framework for generating rating curves in Mahanadi River using hydrodynamic model and radar altimetry data

ABSTRACT The limited availability of in-situ data has drawn attention towards using remote sensing techniques to monitor river flow. Radar altimetry data has been used to generate stage-discharge rating curves through power-law relations and empirical methods. However, evaluating hydrodynamic models for rating curve generation using multi-mission altimetry data in data-scarce regions is lacking. We used altimetry data (Jason 2, Jason 3, SARAL/AltiKa, Sentinel 3A, and Sentinel 3B) over the Mahanadi River to evaluate rating curves at virtual stations. The HEC-RAS hydrodynamic model was set up, identifying seven virtual stations along the Mahanadi River from Boudh to Mundali Barrage. Statistical evaluation of ‘water level’ (RMSE 0.27-0.88 m) and ‘discharge’ (KGE 0.52 to 0.88) components of the generated rating curves showed significant agreement with radar altimetry data. These rating curves at virtual stations offer a cost-effective tool for monitoring river flows at additional locations.

Effect and mechanism of short time ball milling on physicochemical characteristics and pyrolysis kinetics of Pennisetum giganteum

This study investigated the variation of biomass pyrolysis kinetics with changes in ball milling (BM) intensity. Pennisetum giganteum was used as the pyrolysis sample, and different BM times were set to alter the BM intensity. A comprehensive analysis was carried out, combining physicochemical property measurements and pyrolysis experiments. The results showed that BM could change the sample’s particle size (1770–30.80 μm), specific surface area (0.0291–0.7554 m²/g), and pore volume (0.103–2.207 mm³/g) within a very short time (≥2 min). Interestingly, only a long BM duration (20 min) significantly reduced the sample’s crystallinity. The activation energy vs. conversion rate curve of the samples transitioned from being tangential to being parabolic as the duration of BM increased, with a notable change in the average activation energy observed after BM 20 min (152.65–135.50 kJ/mol). This was caused by the destruction of crystalline cellulose into amorphous cellulose, which reduced the thermal stability of the sample. Furthermore, changes in other physicochemical properties had no significant impact on the pyrolysis average activation energy. This study provided valuable references for the optimization of pretreatment parameters in pyrolysis production.

Effect of hot-pressing sintering temperature and pressure on the densification and properties of Ti-TiB composites

Ti/TiB composites exhibit promising potential for applications in the automotive, aerospace, and biomedical sectors. Hot pressing coupled with in situ reaction synthesis is a commonly employed technique for fabricating discontinuously TiB-reinforced titanium matrix composites. Despite its efficacy, comprehensive research investigating the influence of hot-pressing process parameters on the densification and properties of these composites remains scarce. This study systematically examined the effects of pressure (16–48 MPa) and temperature (1250 °C to 1350 °C) on the density, microstructure, and mechanical properties of Ti/TiB composites produced through hot pressing. By analyzing densification curves and rate curves, the densification behavior under varying processing conditions was elucidated. The results indicate that elevated sintering temperatures and pressures correlate with increased densification rates, reduced porosity, and enhanced sample density. A strong relationship between relative densities and hardness was observed. This research contributes to a deeper understanding of the hot-pressing sintering process for Ti-TiB composites and facilitates the optimization of processing conditions.

Available Oocytes rate as a predictor of clinical pregnancy outcomes in controlled ovarian stimulation: A retrospective analysis of 7933 Cycles.

Controlled ovarian stimulation (COS) and embryo culture may affect the development and maturation of oocytes obtained by assisted reproduction technologies (ART). This study used the concept of available oocytes rate (AOR) to evaluate the effect of COS and to identify factors that influence oocyte development and clinical pregnancy (CP). Medical data of 7933 patients who underwent oocyte retrieval and ART treatments was retrospectively reviewed at Fujian Provincial Maternity and Children's Hospital from January 2013 to December 2019. Baseline characteristics of patients, concentrations of hormones, as well as endometrial thickness, number of aspirated follicles, retrieved and available oocytes, and CP rates, were analyzed. Univariate and multivariate analyses showed that basal estradiol (E2) (OR=0.98, p=0.04), endometrial thickness on human chorionic gonadotropin (hCG)-day (OR=1.25, p<0.01), number of follicles aspirated (OR=1.58, p<0.01), oocytes retrieved (OR=0.80, p=0.04), available oocytes (OR=0.48, p=0.04) and AOR (OR=1.18, p<0.01) contributed to CP. The receiver operating characteristic (ROC) curve for the CP rates showed a possible cutoff for the AOR (area under the curve (AUC)=0.788, cut off=34.13%). All 103 cycles with an AOR less than 34% were then selected as Group-A, and 103 cycles were selected as Group-C by 1:1 case-control matching. The human menopausal gonadotropin (HMG) dose was significantly different between Group-A and Group-C (1064.00±1042.01 U vs. 675.00±691.67 U, respectively, p=0.006). The duration of HMG usage was 7.88±4.73 days in Group-A and 5.79±3.59 days in Group-C (p=0.014). The AOR is an important indicator of oocyte function and is correlated with clinical pregnancy outcomes of fresh cycles. The AOR could objectively predict HMG as a clinically related factor that affected the number and maturation of oocytes for insemination.

Fluvial Sediment Load Characteristics from the Yangtze River to the Sea During Severe Droughts

Most river deltas worldwide are located in well-developed, densely populated lowland regions that face challenges from accelerated sea level rise. Deltas with morphological equilibrium are the foundation for associated prosperous economies and societies, as well as for preserving ecological fragile environments. And for deltas to be in morphological equilibrium, sufficient fluvial sediment supplies are fundamental. Severe droughts have significant impacts on the sediment load discharged to the sea, but this is considerably less studied compared to flooding events. This study examines the characteristics of Yangtze River sediment flowing toward the East China Sea during severe droughts. The effect of the Three Gorges Dam (TGD) was investigated by comparing the difference before and after its construction in 2003. Results indicate that the sediment load from the Yangtze River to the sea has experienced a more pronounced decrease during severe drought years since 2003. The primary cause is a substantial reduction in sediment supply from the upper reaches, resulting from the impoundment of the Three Gorges Reservoir created in 2003 and the construction of additional major reservoirs in the upper reach thereafter. Simultaneously, this is accompanied by the fining of sediment grain size. The fining of sediment and considerably reduced sediment load discharged to the sea during severe droughts after 2003 are likely to accelerate the erosion of the Yangtze subaqueous delta. The rating parameter values during severe drought years fall within the range observed in normal years, indicating that these drought events do not align with extreme rating parameter values. Less than 30% of the average discrepancy between measured and reconstructed sediment loads in severe drought years before 2003, and approximately 10% of the discrepancy after 2003, demonstrate the feasibility of reconstructing sediment loads for severe drought events using a sediment rating curve. This rating curve is based on daily water discharge and sediment concentration data collected during the corresponding period. These findings indicate that the rating curve-based reconstruction of sediment load performs well during severe droughts, with relative error slightly exceeding the average error of normal years prior to 2003 and approaching that observed after 2003. This study provides insights on sediment management of the Yangtze River system, including its coastal zone, and is valuable for many other large river systems worldwide.

What temperature is best for the offshore farming of the Australasian snapper, Chrysophrys auratus? A collective examination of growth, FCR, O2 consumption and welfare

ABSTRACT The Australasian snapper (Chrysophrys auratus) is a candidate for offshore aquaculture in New Zealand. The culture of snapper requires knowledge of the best locations for farms and a key variable is water temperature. The oxygen- and capacity-limited thermal tolerance (OCLTT) hypothesis suggests fish performance is optimised at the temperature that maximises absolute aerobic scope (AAS), whereas the ‘multiple performances–multiple optima’ (MPMO) idea, suggests AAS and other performance measures can have different optimal temperatures. Therefore, the applicability of the OCLTT for snapper was tested by holding juveniles at 15, 18, 21, or 24°C for two months and constructing thermal performance curves (TPCs) for specific growth rate (SGR), feed conversion ratio (FCR) and AAS, and an assessment of welfare indicators. We hypothesised that the OCLTT would apply with all TPCs optimised at 21°C. However, AAS showed no discernible peak with temperature (although lower at 15 than 18°C); SGR and FCR improved non-linearly with temperature; and welfare indicators varied little with temperature. This lack of aerobic limitation and evidence of MPMO suggests snapper are amenable to culture across a significant temperature range with warmer water likely providing the highest levels of productivity with maintained welfare.

A balanced mineral prospectivity model of Canadian magmatic Ni (± Cu ± Co ± PGE) sulphide mineral systems using conditional variational autoencoders

With the increasing demand for raw materials, innovative exploration techniques are needed to discover large mineral deposits that are accessible from the surface. In recent years, various supervised machine learning techniques have proven effective for mineral prospectivity modelling (MPM). However, the successful application of these techniques has been limited due to the scarcity of known mineral deposits compared to barren regions, which leads to a model imbalance favouring the latter. We address the data imbalance challenge in MPM by proposing a novel generative modelling approach using a conditional variational autoencoder (CVAE). We compare the proposed method with two other data balancing techniques, namely the synthetic minority oversampling technique and class weighting. Furthermore, the efficacy of the balancing strategies is evaluated for three MPM classification methods, including extreme gradient boosting machines (XGBM), random forests, and multilayer perceptrons. We implement and test the approaches by modelling the prospectivity of magmatic Ni (±Cu ±Co ±Platinum group elements) sulphide mineral systems for the Canadian landmass. With an area under the success rate curve of 0.95 for a spatially distinct testing data set, we observe that a combination of the proposed CVAE framework with the XGBM classification model surpasses the other methods. Furthermore, the geographical representation of our XGBM-CVAE model demonstrates a strong association with known Ni mineral occurrences in Canada, along with new prospective regions in underexplored areas.

Predicting Suspended Sediment Transport in Urbanised Streams: A Case Study of Dry Creek, South Australia

Sediment transport in urban streams is a critical environmental issue, with significant implications for water quality, ecosystem health, and infrastructure management. Accurately estimating suspended sediment concentration (SSC) is essential for effective long-term environmental management. This study investigates the relationships between streamflow, turbidity, and SSC in Dry Creek, South Australia, to understand sediment transport dynamics in urbanised catchments. We collected grab samples from the field and analysed them in the laboratory. We employed statistical modelling to develop a sediment rating curve (SRC) that provides insights into the sediment transport dynamics in the urban stream. The grab sample measurements showed variations in SSC between 3.2 and 431.8 mg/L, with a median value of 77.3 mg/L. The analysis revealed a strong linear relationship between streamflow and SSC, while turbidity exhibited a two-regime linear relationship, in which the low-turbidity regime demonstrated a stronger linear relationship compared to the high-turbidity regime. This is attributed to the urbanised nature of the catchment, which contributes to a first-flush effect in turbidity. This contributes to sediment hysteresis, resulting in non-proportional turbidity and SSC responses to streamflow changes. The findings demonstrate the effectiveness of a streamflow-based SRC for accurately predicting sediment discharge, explaining 97% of the variability in sediment discharge. The sediment discharge predicted using the SRC indicated a sediment load of 341.8 tonnes per year along the creek. The developed sediment rating curve provides a valuable tool for long-term sediment management in Dry Creek, enabling the assessment of downstream environmental risks. By addressing data limitations, this study contributes to a deeper understanding of sediment transport dynamics in urbanized environments, offering insights for informed decision-making and effective sediment management strategies.

Application of the Electrical Microbial Growth Analyzer Method for Efficiently Quantifying Viable Bacteria in Ready-to-Eat Sea Cucumber Products.

Accurate and efficient quantification of viable bacteria in ready-to-eat food products is crucial for food safety and public health. The rapid and accurate assessment of foodborne bacteria in complex food matrices remains a significant challenge. Herein a culture-based approach was established for easily quantifying viable bacteria in ready-to-eat sea cucumber (RSC) products. Samples of the liquid companion within the package were directly transferred into test tubes to determine bacterial growth curves and growth rate curves, utilizing the electrical microbial growth analyzer. Viable bacteria in the samples were then quantified based on the time required to attain the maximum growth rate indicated on the growth rate curve. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the liquid companion, the recovery rates were 108.85-112.77% for Escherichia coli (E. coli) and 107.01-130.54% for Staphylococcus aureus (S. aureus), with standard deviations of 1.60 and 3.92, respectively. For the solid content in the package, the quantification was performed using the same methodology following an additional homogenization step. At a concentration of 5.0 × 103 CFU/mL of viable bacteria in the sample, the recovery rates were 91.94-102.24% for E. coli and 81.43-104.46% for S. aureus, with standard deviations of 2.34 and 2.38, respectively. In instances where the viable bacterial concentration was 5.0 × 103 CFU/mL in RSC products, the total time required for the quantification did not exceed 10.5 h. This method demonstrated advantages over traditional plate counting and PCR methods regarding simplicity and efficiency, representing a promising alternative for the quantification of viable bacteria in food like RSC products.

FITTING DYNAMICALLY CONSISTENT FORWARD RATE CURVES: ALGORITHM AND COMPARISON

This paper introduces a new methodology for estimating dynamically consistent forward rate curves, which are essential for obtaining arbitrage-free valuation and risk management models. Using U.S. Treasury data from January 2013 to June 2023, we fit dynamically consistent forward rates curves and test the goodness of fit between theoretical and observed prices. We compare the traditional static forward rate curve parameterizations (including Nelson–Siegel, Svensson, and cubic splines) with our new dynamically consistent methodology. The dynamically consistent forward rate curve estimates generally outperform the traditional static methods in reproducing market prices.

Realization of quasi-steady-state piled smouldering using sequential operation chambers for industrial treatment of biomass wastes.

Piled smouldering has great potential for treatment and utilization of biomass wastes. However, its unsteady-state nature limits its industrial utilization, as well as treatment of smoke. This article addresses this issue by proposing the sequential operation of numerous smouldering chambers to realize steady- or quasi-steady-state piled smouldering. The superposition characteristics of sequential unsteady-state curves were analysed theoretically, and a code was developed to determine an appropriate number of piled chambers at an allowance oscillation percentage. Smouldering experiments were performed on a single mini chamber (length × width × height: 340 × 140 × 140 mm3) containing piled wood pellets mixed with wood powder. The superposition of sequential burning rate curves was demonstrated using the code based on the mass loss data of experiments. Analysis shows that the perfect-steady state is possible given the superposition value of the burning rate curve is a constant in this proposed system. Experiments show that the molar ratio of CO/CO2 in smoke is almost a constant around 0.5 during densely piled smouldering, showing the great potential for self-sustained burning out the smoke. Based on the experimental results, the calculation results show that the relative oscillation range of burning rate (OSC) decreases from 75% to 3% while increasing the number of chambers from 2 to 7. This work provides a novel technology to enable quasi-steady-state smouldering for industrial utilization.