Conservative Assumptions Research Articles

Structure formation with primordial black holes: collisional dynamics, binaries, and gravitational waves

Primordial black holes (PBHs) could compose the dark matter content of the Universe. We present the first simulations of cosmological structure formation with PBH dark matter that consistently include collisional few-body effects, post-Newtonian orbit corrections, orbital decay due to gravitational wave emission, and black-hole mergers. We carefully construct initial conditions by considering the evolution during radiation domination as well as early-forming binary systems. We identify numerous dynamical effects due to the collisional nature of PBH dark matter, including evolution of the internal structures of PBH halos and the formation of a hot component of PBHs. We also study the properties of the emergent population of PBH binary systems, distinguishing those that form at primordial times from those that form during the nonlinear structure formation process. These results will be crucial to sharpen constraints on the PBH scenario derived from observational constraints on the gravitational wave background. Even under conservative assumptions, the gravitational radiation emitted over the course of the simulation appears to exceed current limits from ground-based experiments, but this depends on the evolution of the gravitational wave spectrum and PBH merger rate toward lower redshifts.

Rapid antibiotic susceptibility testing for urinary tract infections in secondary care in England: a cost-effectiveness analysis

ObjectivesTo perform a model-based cost-effectiveness evaluation of a rapid antimicrobial susceptibility test.DesignA Markov model of a cohort of hospital inpatients with urinary tract infection (with inpatient numbers based on national...

Fixed-time adaptive sliding mode-based active rollover prevention control of automated guided vehicles via improved super-twisting observer

As an important component of automated guided vehicle (AGV) active safety systems, the active rollover prevention (ARP) control has been widely studied. In this paper, a fixed-time adaptive sliding mode (FTASM) control strategy based on nested adaptive law (NAL) and improved super-twisting observer (ISTO) is developed for the AGV. Firstly, the lateral and roll motion dynamics of AGV are established, and the ARP problem is transformed into the yaw stability control with constraints. Subsequently, a faster fixed-time stable system-based FTASM composite controller is proposed to guarantee a fixed and faster convergence time of the yaw rate tracking error, such that the rollover stability will reach a region of permissible risk. The adoption of NAL enables the adaptive controller to automatically search the minimum switching gain satisfying the reaching condition of sliding mode, thus the conservative assumption constraint of the disturbance upper bound is released. In addition, an ISTO is developed to estimate the unknown disturbance to further improve the control robustness and attenuate the control chattering. The closed-loop stability analysis is rigorously given by Lyapunov theory. Finally, the performance of the proposed control strategy is validated by hardware-in-loop simulations with Adams and Matlab software and an actual steer-by-wire plant.

Long live the cat: Ocelot population viability in a planned reintroduced population in Texas, USA

AbstractReintroductions are often needed to recover carnivore populations and restore ecological processes. Felids are common subjects of reintroduction efforts, but published population models informing felid reintroduction plans are uncommon, and poor planning has sometimes caused issues in felid reintroduction programs. In the United States, ocelots (Leopardus pardalis pardalis) are classified as endangered, and recovery requires population expansion into historic habitat. A multi‐organization effort is underway to establish a new ocelot population in Texas by releasing ocelots into an area of 478 km2 of suitable habitat in ocelots' historic but now unoccupied range. In this study, we used population viability analyses to compare different ocelot reintroduction strategies for the identified reintroduction area. Based on a potential ocelot breeding program's limitations, we modeled reintroduction using a founding population of no more than six ocelots and no more than four ocelots released per year for no more than 15 subsequent years. Within these limitations, we assessed projected population abundances and extinction risks after 30 years for 20 different reintroduction strategies. We found that long‐term releases are necessary to establish a viable population; under conservative model assumptions, releasing six ocelots in the initial year and then releasing four individuals annually for an additional 10–15 years is necessary for attaining a projected population greater than 36.62 ocelots (baseline) with <6% extinction risk. We also found that ocelot population abundance is about equally sensitive to post‐release mortality and inbreeding depression. This highlights the importance of not only supporting reintroduced ocelots' survival but also managing for high genetic diversity in the reintroduction program. Further, we found that realistic but more liberal assumptions on the carrying capacity of the reintroduction area and the age of first reproduction for ocelots increase projected population abundances (53.95 individuals and 61.26 individuals, respectively), and thus reintroduction success. The model's sensitivity to carrying capacity suggests that long‐term habitat protection and expansion are among the most important management actions to support ocelot reintroduction. Our study establishes the first population viability model for an ocelot reintroduction plan anywhere across the species' wide geographic range, and it reinforces several key considerations for wildlife reintroduction efforts worldwide.

Analysing Flexural Response in RC Beams: A Closed-Form Solution Designer Perspective from Detailed to Simplified Modelling

This paper presents a detailed analytical approach for the bending analysis of reinforced concrete beams, integrating both structural mechanics principles and Eurocode 2 provisions. The general analytical expressions derived for the curvature were applied for the transverse displacement analysis of a simply supported reinforced concrete beam under four-point loading, focusing on key limit states: the initiation of cracking, the yielding of tensile reinforcement and the compressive failure of concrete. The displacement’s results were validated through experimental testing, showing a high degree of accuracy in the elastic and crack propagation phases. Deviations in the yielding phase were attributed to the conservative material assumptions within the Eurocode 2 framework, though the analytical model remained reliable overall. To streamline the computational process for more complex structures, a simplified model utilising a non-linear rotational spring was further developed. This model effectively captures the influence of cracking with significantly reduced computational effort, making it suitable for serviceability limit state analyses in complex loading scenarios, such as seismic impacts. The results demonstrate that combining detailed analytical methods with this simplified model provides an efficient and practical solution for the analysis of reinforced concrete beams, balancing precision with computational efficiency.

Microalgae bio-reactive façade: A model coupling weather, illumination, temperature, and cell growth over the year

This article presents the development of a numerical model coupling the thermal and biological behaviors of a microalgae biofaçade. Heat fluxes and illumination are modulated by actual weather data, and the system response is evaluated in terms of biomass and pigment production. First, the effect of the different model refinements are screened. Then, the model is applied to an illustrative case: the city of Marseille over the year 2023. The results illustrate the model’s capabilities, such as assessing the building/biofaçade thermal synergy or the summer/winter operational differences. The numerical behavior of the model is also analyzed: local and global sensitivity analyses assess the impact of uncertain parameters. The parameter inducing the highest amount of uncertainty is the microalgae photoconversion efficiency, highlighting the need to ascertain its value before designing a system. Despite this uncertainty, even under conservative assumptions, the predictions of the model are 10 % accurate.

Directional wind turbine noise prediction plots and prevalence histograms for community consultation

In Australia, wind turbine noise is predicted using international standards and guidelines with a set of conservative assumptions. For example, wind turbine noise predictions using the ISO 9613-2 method are based on a scenario in which each receiver is simultaneously downwind of every wind turbine. As such, winds that are outside of the downwind direction range will result in lower wind turbine noise levels than predicted using ISO 9613-2. These predictions are also based on the assumption that each turbine is simultaneously generating their maximum noise emissions, whereas variations in winds speeds across the site will frequently result in individual turbines producing lower noise levels than assumed in the modelling. The net effect of these conservative assessment choices is that actual wind turbine noise levels would be lower than presented in noise assessments in many cases. Providing an indication of how frequently predicted noise levels would likely occur can assist community consultation and provide useful context to noise modelling data. This paper presents analysis utilising directional noise modelling to assess the effect of wind direction, combined with an analysis of historic wind records, to determine the range of predicted noise levels and how frequently they may occur.

Predicting and optimizing maximum flexural strength of planar composite plate shear walls – concrete filled with the application of LR and RSM

Traditional theoretical models, while conservative, overlook the complex, nonlinear interactions between material and geometric parameters that influence wall flexural strength. Additionally, the extent to which these models maintain their conservative assumptions across varying parameters remains uncertain. This study aims to develop advanced predictive models for the flexural strength of planar composite plate shear walls—concrete filled (C-PSW/CF) by employing Linear Regression (LR) and Response Surface Methodology (RSM). Central Composite Design (CCD) was utilized to design numerical experiments to analyze the effects of varying parameters, including steel plate yield strength, concrete compressive strength, wall depth, depth-to-thickness ratio, and reinforcement ratio. A validated complex finite element modeling (FEM) procedure was used to analyze numerical experiments involving varying parameters of the selected variables. Both LR and RSM were applied to the generated dataset to formulate predictive equations for the maximum moment capacity of walls. Interaction plots were developed to reveal the nonlinear relationships between the variables and identify the most effective parameters influencing the wall strength. Comparisons between theoretical predictions, RSM, and LR models revealed that RSM provided the most accurate predictions, closely aligning with FEM results and effectively capturing the nonlinear interactions between wall parameters. The findings of this paper contribute to the development of more practical, accurate and optimized design methods for C-PSW/CF, ultimately improving both structural safety and efficiency.

Tahiti Population (Re)Estimates and Ideologies

The question of Tahiti population at contact was first addressed by assessing the reliability of early and later estimates, and then by a retrodiction based on the first reliable censuses and data on trends. Cook’s famous estimate of 204,000 Tahitians, affected by a wrong number of districts, has been reworked based on his own and the Forsters’ observations, using coast length and the age and sex structure of Tahiti population at contact in relation to infanticide, resulting in a range of 156,000-188,000 persons in 1774, before Boenechea’s flu in 1772 and the 1774 flu epidemics. The discrepancies between Wilson’s 16,050 and other missionaries’ estimate of 50,000 as of 1797 are puzzling, but the 1829-1830 missionary estimates were strongly affected by Tahitians’ resistance to Christianization. The twentieth century estimates are affected by a political context related to colonization - decolonisation, leading to the fact that researchers favour low estimates. McArthur uses missionary data, assuming that baptisms are births, although before the conversion was completed, baptisms included adults and children of all ages. She bases her estimate of 30,000 Tahitians at contact in 1767 on Wilson’s number of 16,050, who applied the size of nuclear households, 6 persons, to clans. Oliver followed her, however not excluding numbers twice as high or more. Our retrodiction on the 1848 and 1881 censuses, based on qualitative missionary reports on sanitary situation and data of Rarotonga that experienced similar events as Tahiti, yield, with conservative assumptions, 180,000 persons at contact, showing consistent results with early navigators’ estimates. My own PhD experience in the late 1980s shows that scholars’ re-estimates were constrained, directly or indirectly, by political considerations related to the guilt syndrome and colonialist ideology. This appears in the frequent contradictions found in their works to support low estimates in order to reduce the decline, despite evidence of dramatic epidemics and a steady decline extending almost throughout the 19th century. The same attitude of denial is found in some missionary, administrative and medical reports, particularly on the Marquesas in the late 19th century. Colonisation was associated with various ideologies, related to anthropology’s early attempts based on theories of evolutionism, functionalism and structuralism, occasionally resulting in fictions such as “primitive thinking”, “ahistorical societies” and “collective unconscious”, that were part of the justification of colonisation and its mistakes.

Plasma burn-mind the gap.

The programme to design plasma scenarios for the Spherical Tokamak for Energy Production (STEP), a reactor concept aiming at net electricity production, seeks to exploit the inherent advantages of the spherical tokamak (ST) while making conservative assumptions about plasma performance. This approach is motivated by the large gap between present-day STs and future burning plasmas based on this concept. It is concluded that plasma exhaust in such a device is most likely to be manageable in a double null (DN) configuration, and that high core performance is favoured by positive triangularity (PT) plasmas with an elevated central safety factor. Based on a full technical and physics assessment of external heating and current drive (CD) systems, it was decided that the external CD is provided most effectively by microwaves. Operation with active resistive wall mode (RWM) stabilization as well as high elongation is needed for the most compact solution. The gap between existing devices and STEP is most pronounced in the area of core transport, owing to high normalized plasma pressure in the latter which changes qualitatively the nature of the turbulence controlling transport. Plugging this gap will require dedicated experiments, particularly on high-performance STs, and the development of reduced models that faithfully represent turbulent transport at high normalized pressure. Plasma scenarios in STEP will also need to be such that edge localized modes (ELMs) either do not occur or are small enough to be compatible with material lifetime limits. The high current needed for a power plant-relevant plasma leads to the unavoidable generation of high runaway electron beam current during a disruption, where novel mitigation techniques may be needed. This article is part of the theme issue 'Delivering Fusion Energy - The Spherical Tokamak for Energy Production (STEP)'.

Mono-n-hexyl phthalate: exposure estimation and assessment of health risks based on levels found in human urine samples

Mono-n-hexyl phthalate (MnHexP) is a primary metabolite of di-n-hexyl phthalate (DnHexP) and other mixed side-chain phthalates that was recently detected in urine samples from adults and children in Germany. DnHexP is classified as toxic for reproduction category 1B in Annex VI of Regulation (EC) 1272/2008 and listed in Annex XIV of the European chemical legislation REACH; thereby, its use requires an authorisation. Health-based guidance values for DnHexP are lacking and a full-scale risk assessment has not been carried out under REACH. The detection of MnHexP in urine samples raises questions about the sources of exposure and concerns of consumer safety. Here, we propose the calculation of a provisional oral tolerable daily intake value (TDI) of 63 µg/kg body weight/day for DnHexP and compare it to intake levels corresponding to levels of MnHexP found in urine. The resulting mean intake levels correspond to less than 0.2% of the TDI, and maximum levels to less than 5%. The TDI was derived by means of an approximate probabilistic analysis using the credible interval from benchmark dose modelling of published ex vivo data on reduced foetal testosterone production in rats. Thus, for the dose associated to a 20% reduction in testosterone production, a lower and upper credible interval of 14.9 and 30.0 mg/kg bw/day, respectively, was used. This is considered a conservative approach, since apical developmental endpoints (e.g. changed anogenital distance) were only observed at higher doses. In addition, we modelled various scenarios of the exposure to the precursor substance DnHexP from different consumer products, taking measured contamination levels into account, and estimated systemic exposure doses. Of the modelled scenarios including the application of sunscreen (as a lotion or pump spray), the use of lip balm, and the wearing of plastic sandals, and considering conservative assumptions, the use of DnHexP-contaminated sunscreen was highlighted as a major contributing factor. A hypothetical calculation using conservative assumptions for the latter resulted in a margin of safety in relation to the lower credible interval of 3267 and 1007 for adults and young children, respectively. Most importantly, it was found that only a fraction of the TDI is reached in all studied exposure scenarios. Thus, with regard to the reported DnHexP exposure, a health risk can be considered very unlikely.

PRICING CoCos WITH EQUITY CONVERSION COVENANT IN A DISTRESSED MARKET ENVIRONMENT

Many Contingent Convertible bonds (CoCos) issued since 2014 belong to the additional Tier 1 (AT1) capital of the issuing bank and are thus of a perpetual nature. Within a Black–Scholes setup, under the very conservative assumption that the CoCo trigger is activated by an adverse entity, we are able to derive a closed-form expression for the fair price of such an instrument, provided it has an equity conversion feature (no write-down feature). This formula allows for a quick understanding of the mechanics of such AT1 CoCos, helps to efficiently compute delta-hedge ratios, and it can be implemented easily on a spreadsheet. Furthermore, the closed-form solution may be used as an integral building component of an efficient, semi-analytical pricing formula for AT1 CoCos, when an additional call right for the issuing bank and a coupon change is present, as typical in the marketplace. Finally, we demonstrate that over the last few years observed CoCo market prices were too high to be explained by our adverse entity assumption, but currently (after the recent Credit Suisse CoCo wipe-out in March 2023) have come down to levels that can be modeled reasonably with our approach. Our approach can therefore be a useful tool to deal with CoCo prices in a market environment with distressed banking sector.

Silicone adhesive multilayer foam dressings to prevent hospital-acquired sacrum pressure ulcers: An economic evaluation based on a publicly funded pragmatic randomized controlled trial linked with real-world data

ObjectivesTo estimate the cost-effectiveness of sacrum multilayer silicone foam dressings as an adjuvant prophylactic therapy compared to standard pressure ulcer prevention in a hospital population at high risk for pressure ulcer development. MethodsAn economic evaluation is performed from a healthcare payer's perspective. This evaluation is based on a Belgian publicly funded pragmatic randomized controlled trial (RCT), linked with real-world data from administrative claims database and a Belgian cost analysis. A cost-consequences analysis with a one-year time horizon is performed. ResultsThe RCT has shown that the risk of developing a new pressure ulcer on the sacrum was statistically significantly reduced by 41 % in the treatment group (RR = 0.59, 95 % CI 0.35–0.98, p = 0.04). The absolute risk reduction of 2.0 % (95 % CI -0.1–4.1 %) coincides with a number needed to treat of 50.0 to prevent one new pressure ulcer of category II or worse. The evolution of quality of life is on average negative for patients who developed a pressure ulcer before day 3, while it is positive for patients without pressure ulcers. In a scenario with conservative assumptions, i.e. without inclusion of price discounts for the multilayer silicone foam dressings and only including costs during the hospitalization, pressure ulcer prevention with dressings on the sacrum was already cost-neutral. ConclusionsThe preventive use of silicone adhesive multilayer foam dressings on the sacrum for a population similar to the pragmatic trial population can be supported both from a clinical and economic point of view.

Estimating metocean environments associated with extreme structural response to demonstrate the dangers of environmental contour methods

Extreme value analysis (EVA) uses data to estimate long-term extreme environmental conditions for variables such as significant wave height and period, for the design of marine structures. Together with models for the short-term evolution of the ocean environment and for wave–structure interaction, EVA provides a basis for full probabilistic design analysis. Alternatively, environmental contours provide an approximate approach to estimating structural integrity, without requiring structural knowledge. These contour methods also exploit statistical models, including EVA, but avoid the need for structural modelling by making what are believed to be conservative assumptions about the shape of the structural failure boundary in the environment space. These assumptions, however, may not always be appropriate, or may lead to unnecessary wasted resources from over design. We demonstrate a methodology for efficient fully probabilistic analysis of structural failure. From this, we estimate the joint conditional probability density of the environment (CDE), given the occurrence of an extreme structural response. We use CDE as a diagnostic to highlight the deficiencies of environmental contour methods for design; none of the IFORM environmental contours considered characterise CDE well for three example structures.

The application study of conservative best-estimated approach for steam line break accident

The most important characteristic of main Steam Line Break (SLB) accident is the asymmetry cooldown between loops due to secondary break spurting, which results non-uniform reactivity feedback in different reactor core sections. The fuel rod DNBR limit would be more challenged in the core section with peak power. The SLB safety analysis methodologies in Administration License Application for typical PWR in China are investigated in this paper. Based on the conservative universal methodology, the best-estimated code RELAP5/MOD3 is used to perform the SLB thermal-hydraulic calculation for a three-loop PWR. In this analysis, the critical conservative models submitted for Licensing process are implemented in RELAP5/MOD3 specified modeling, which includes the Three-Channel Core Model, core inlet mixture array, core outlet mixture, vessel upper head flow and the more realistic SG model. The “second pressurizer” phenomenon in vessel upper head flashing is studied, which affects the system pressure response and mitigation. The effect of SG spouting during the transient is also studied in this paper, which is different with lumped parameter SG model. The combined approach for Deterministic safety analysis is validated in this paper, which is composed with best-estimated code, Conservative assumptions and Conservative initial & boundary conditions. Because of the flexibility and adequate conservatism, it can be spread for design optimization and independent safety assessment from the third party.

Rethinking the Haitian Turn – Beyond the Universality Paradigm and Its Enemies

ABSTRACT Recent assessments of the literature on the Haitian Revolution (1791–1804) offer radically different images, ranging from the identification of a politics of universal human rights to objections against conservative assumptions. The present article instead uncovers an overarching conflict between what is named the universality paradigm and the sceptical responses. However, in the outskirts of the controversy, its participants agree that the Haitian Revolution was the most radical revolution of the period, and that issues of inequality cannot be disregarded. To advance the debate, polarisation must be transgressed and the assumption that universalism and inequality are incompatible must be abandoned.

The levelized cost of carbon abatement (LCCA) in substituting conventional ammonia production with power-to-ammonia for fertilizer, hydrogen and export

The production of ammonia using the conventional Haber-Bosch technique produces significant CO2 emissions, largely owed to the fossil fuel-based hydrogen production. To reduce these emissions, low-carbon ammonia production with hydrogen from water electrolysis (i.e., power-to-ammonia, P2A) is being developed. This study compares P2A with the methane-fed Haber-Bosch process by performing a time-based levelized cost of carbon abatement (LCCA) analysis, considering technology development and adoption, and the mismatch between production capacity and ammonia demand over time. The LCCA results quantify the cost and potential carbon reduction simultaneously and provide the cost to reduce one unit of CO2-eq emissions using P2A. Various scenarios in multiple sectors are considered in different regions in Canada from 2027 to 2050, such as low-carbon fertilizer, ammonia as a hydrogen carrier for domestic use and energy export, and their dynamics over-time were studied and compared. Results show that under the base case with conservative assumptions, the LCCA is higher than the proposed carbon price in Canada, except when low-carbon ammonia demand is low, e.g., domestic hydrogen use. Yet sensitivity analyses suggest that the LCCA can approach the carbon price with technical improvements and increased adoption over time. The electricity generation mix also has great impacts on the LCCA. Regions with abundant low-carbon electricity sources, e.g., Quebec, Prince Edward Island, Nova Scotia, Manitoba, and British Columbia can benefit from P2A on both environmental and economic perspectives. Some of these regions are connected to the coast, so there is also great potential for ammonia-shipping corridors in both the Atlantic and Pacific Oceans.

Long-term cost-effectiveness analysis of rugby fans in training–New Zealand: a body weight reduction programme for males

ObjectivesWe sought to extrapolate the long-term costs and clinical impacts attributed to the rugby fans in training–New Zealand (RUFIT-NZ) trial in Aotearoa, New Zealand.DesignA modelled cost-effectiveness analysis using efficacy data...

Joint analysis of JUICE and Europa Clipper tracking data to study the Jovian system ephemerides and dissipative parameters

Context. Jupiter and its moons form a complex dynamical system that includes several coupling dynamics at different frequencies. In particular the Laplace resonance is fundamental to maintaining the energy dissipation that sustain Io’s volcanic activity and Europa’s subsurface ocean; studying its stability is thus crucial for characterizing the potential habitability of these moons. The origin and evolution of the Laplace resonance is driven by the strong tidal interactions between Jupiter and its Galilean moons, and the future planetary exploration missions JUICE and Europa Clipper could bring new light to this unsolved mechanism. During the Jupiter tours of both missions and JUICE’s Ganymede orbital phase, two-way radiometric range and Doppler data will be acquired between Earth ground stations and the spacecraft, which will be processed to recover the static and time-varying gravity field of the moons. Moreover, range and Doppler data will improve the orbit accuracy of the moons, providing precise measurements of Jupiter’s tidal parameters. Aims. This work presents a covariance analysis of the joint orbit determination of JUICE and Europa Clipper, aimed at quantifying the expected uncertainties on the main parameters that characterize the dynamics of the Jupiter system. Methods. We simulated radio science data from JUICE and Clipper missions under conservative noise assumptions, using a multi-arc approach to estimate the ephemerides and dissipation in the system. Results. Even though JUICE and Europa Clipper will not perform flybys of Io, the strong coupling with Europa and Ganymede will allow an improvement of our knowledge of the Jupiter-Io dissipation parameters thanks to JUICE and Europa Clipper radiometric data. Moreover, the expected uncertainty in Jupiter’s dissipation at the frequency of Callisto could unveil a potential resonance locking mechanism between Jupiter and Callisto.

Determining structural properties of a prestressed concrete bridge through the combination of static and dynamic load testing

Examining structural safety requires hypotheses on several properties of the bridge structure, such as material properties, boundary conditions, and self-weight. The traditional approach relies on conservative assumptions for each structural property, following the conventional new-design approach. Nonetheless, this approach leads to conservative evaluations of the bridge capacity and may lead to the erroneous conclusion that the structure is deficient. Over-conservatism in structural safety assessments may have large environmental and economic impacts on global infrastructure management. A more advanced approach is to conduct multiple tests and monitoring activities on the structural system to provide more accurate values of these bridge properties. This paper presents a methodology to determine several parameters, including the structural stiffness, the boundary conditions, and the self-weight of concrete bridges based on static and dynamic load testing and robust data-interpretation techniques. The methodology is used on a prestressed concrete bridge in Switzerland. This bridge from 1958 has a single span of 35 meters. Prior to monitoring, conservative evaluations (using the conventional approach) led to the conclusion that the bridge has structural deficiencies. After monitoring, the bridge demonstrates significant reserve capacity, mostly due to the reduction of the self-weight safety factor. This study shows the potential of monitoring techniques for more sustainable and economic infrastructure management.