On the theory of SODAR measurement techniques (final reporting on WP1, EU WISE project NNE5-2001-297)

The need for alternative means to measure the wind speed for wind energy purposes has increased with the increase of the size of wind turbines. The cost and the technical difficulties for performing wind speed measurements has also increased with the size of the wind turbines, since it is demanded that the wind speed has to be measured at the rotor center of the turbine and the size of both the rotor and the hub height have grown following the increase in the size of the wind turbines. The SODAR (SOund Detection And Ranging) is an alternative to the use of cup anemometers and offers the possibility of measuring both the wind speed distribution with height and the wind direction. At the same time the SODAR presents a number of serious drawbacks such as the low number of measurements per time period, the dependence of the ability to measure on the atmospheric conditions and the difficulty of measuring at higher wind speeds due to either background noise or the neutral condition of the atmosphere. Within the WISE project (EU project number NNE5-2001-297), a number of work packages have been defined in order to deal with the SODAR. The present report is the result of the work package 1. Within this package the objective has been to present and achieve the following: - An accurate theoretic model that describes all the relevant aspects of the interaction of the sound beam with the atmosphere in the level of detail needed for wind energy applications. - Understanding of dependence of SODAR performance on hard- and software configuration. - Quantification of principal difference between SODAR wind measurement and wind speed measurements with cup anemometers with regard to power performance measurements. The work associated to the above is described in the work program as follows: a) Draw up an accurate model of the theoretic background of the SODAR. The necessary depth is reached when the influences of various variables in the model on the accuracy of the measurement have been assessed. b) Describe the general algorithm SODAR uses for sending the beam and measuring the reflections. Describe the influence of various settings on the working of the algorithm. c) Using the data set from work package two analyse the differences between point measurements and profile measurements. All the above issues are addressed in the following repor

Dust coagulation in protoplanetary disks: porosity matters

Context: Sticking of colliding dust particles through van der Waals forces is the first stage in the grain growth process in protoplanetary disks, eventually leading to the formation of comets, asteroids and planets. A key aspect of the collisional evolution is the coupling between dust and gas motions, which depends on the internal structure (porosity) of aggregates. Aims: To quantify the importance of the internal structure on the collisional evolution of particles, and to create a new coagulation model to investigate the difference between porous and compact coagulation in the context of a turbulent protoplanetary disk. Methods: We have developed simple prescriptions for the collisional evolution of porosity of grain-aggregates in grain-grain collisions. Three regimes can then be distinguished: `hit-and-stick' at low velocities, with an increase in porosity; compaction at intermediate velocities, with a decrease of porosity; and fragmentation at high velocities. (..) Results: (..) We can discern three different stages in the particle growth process (..) We find that when compared to standard, compact models of coagulation, porous growth delays the onset of settling, because the surface area-to-mass ratio is higher, a consequence of the build-up of porosity during the initial stages. As a result, particles grow orders of magnitudes larger in mass before they rain-out to the mid-plane. Depending on the turbulent viscosity and on the position in the nebula, aggregates can grow to (porous) sizes of ~ 10 cm in a few thousand years. We also find that collisional energies are higher than in the limited PCA/CCA fractal models, thereby allowing aggregates to restructure. It is concluded that the microphysics of collisions plays a key role in the growth process.Comment: 21 pages, 15 figures. Accepted for publication in A&A. Abstract shortene

Co-Accretion of Chondrules and Dust in the Solar Nebula

We present a mechanism for chondrules to stick together by means of compaction of a porous dust rim they sweep up as they move through the dusty nebula gas. It is shown that dust aggregates formed out of micron-sized grains stick to chondrules, forming a porous dust rim. When chondrules collide, this dust can be compacted by means of rolling motions within the porous dust layer. This mechanism dissipates the collisional energy, compacting the rim and allowing chondrules to stick. The structure of the obtained chondrule-dust agglomerates (referred to as compounds) then consists of three phases: chondrules, porous dust, and dust that has been compacted by collisions. Subsequently, these compounds accrete their own dust and collide with other compounds. The evolution of the compound size distribution and the relative importance of the phases is calculated by a Monte Carlo code. Growth ends, and a simulation is terminated when all the dust in the compounds has been compacted. Numerous runs are performed, reflecting the uncertainty in the physical conditions at the chondrule formation time. It is found that compounds can grow by 1-2 orders of magnitudes in radius, upto dm-sizes when turbulence levels are low. However, relative velocities associated with radial drift form a barrier for further growth. Earlier findings that the dust sweep-up by chondrules is proportional to their sizes are confirmed. We contrast two scenarios regarding how this dust evolved further towards the densely packed rims seen in chondrites.Comment: 23 pages, accepted for publication in Ap

Cross-language activation in bimodal bilinguals: Do mouthings affect the co-activation of speech during sign recognition?

Published online by Cambridge University Press: 28 January 2022The present study provides insight into cross-language activation in hearing bimodal bilinguals by (1) examining co-activation of spoken words during processing of signs by hearing bimodal bilingual users of Dutch (their L1) and Sign Language of the Netherlands (NGT; late learners) and (2) investigating the contribution of mouthings to bimodal cross-language activation. NGT signs were presented with or without mouthings in two sign-picture verification experiments. In both experiments the phonological relation (unrelated, cohort overlap or final rhyme overlap) between the Dutch translation equivalents of the NGT signs and pictures was manipulated. Across both experiments, the results showed slower responses for sign-picture pairs with final rhyme overlap relative to phonologically unrelated sign-picture pairs, indicating co-activation of the spoken language during sign processing, but no significant effect for sign-picture pairs with cohort overlap in Dutch. In addition, co-activation was not affected by the presence or absence of mouthings

Spinning up planetary bodies by pebble accretion

Most major planetary bodies in the solar system rotate in the same direction as their orbital motion: their spin is prograde. Theoretical studies to explain the direction as well as the magnitude of the spin vector have had mixed success. When the accreting building blocks are $\sim$ km-size planetesimals -- as predicted by the classical model -- the accretion process is so symmetric that it cancels out prograde with retrograde spin contributions, rendering the net spin minute. For this reason, the currently-favored model for the origin of planetary rotation is the giant impact model, in which a single collision suffices to deliver a spin, which magnitude is close to the breakup rotation rate. However, the giant impact model does not naturally explain the preference for prograde spin. Similarly, an increasing number of spin-vector measurement of asteroids also shows that the spin vector of large (primordial) asteroids is not isotropic. Here, we re-assess the viability of smaller particles to bestow planetary bodies with a net spin, focusing on the pebble accretion model in which gas drag and gravity join forces to accrete small particles at a large cross section. Similar to the classical calculation for planetesimals, we integrate the pebble equation of motion and measure the angular momentum transfer at impact. We consider a variety of disk conditions and pebble properties and conduct our calculations in the limits of 2D (planar) and 3D (homogeneous) pebble distributions. We find that in certain regions of the parameter space the angular momentum transfer is significant, much larger than with planetesimals and on par with or exceeding the current spin of planetary bodies.Comment: Accepted for publication in Icaru

Dust coagulation and fragmentation in molecular clouds. I. How collisions between dust aggregates alter the dust size distribution

In dense molecular clouds collisions between dust grains alter the ISM-dust size distribution. We study this process by inserting the results from detailed numerical simulations of two colliding dust aggregates into a coagulation model that computes the dust size distribution with time. All collisional outcomes -- sticking, fragmentation (shattering, breakage, and erosion) -- are included and the effects on the internal structure of the aggregates are also tabulated. The dust aggregate evolution model is applied to an homogeneous and static cloud of temperature 10 K and gas densities between 10^3 and 10^7 cm^-3. The coagulation is followed locally on timescales of ~10^7 yr. We find that the growth can be divided into two stages: a growth dominated phase and a fragmentation dominated phase. Initially, the mass distribution is relatively narrow and shifts to larger sizes with time. At a certain point, dependent on the material properties of the grains as well as on the gas density, collision velocities will become sufficiently energetic to fragment particles, halting the growth and replenishing particles of lower mass. Eventually, a steady state is reached, where the mass distribution is characterized by a mass spectrum of approximately equal amount of mass per logarithmic size bin. The amount of growth that is achieved depends on the cloud's lifetime. If clouds exist on free-fall timescales the effects of coagulation on the dust size distribution are very minor. On the other hand, if clouds have long-term support mechanisms, the impact of coagulation is important, resulting in a significant decrease of the opacity on timescales longer than the initial collision timescale between big grains.Comment: 25 pages, 20 figures, accepted for publication in Astronomy & Astrophysic

Can loss of agency and oppositional perturbation associated with antidepressant monotherapy and low-fidelity psychological treatment dilute the benefits of guideline-consistent depression treatment at the population level?

Contains fulltext : 226202.pdf (publisher's version ) (Open Access

Розрахунок довговічності матеріалів при нерегулярному непропорційному навантажуванні

Із метою розробки адекватних моделей для розрахунку довговічності аналізуються наведені в літературних джерелах експериментальні дані щодо малоциклової втоми сталі 304 та титанового сплаву ВТ9 під час деформування за складними історіями навантаження, що являють собою у просторі повних деформацій послідовність блоків різних за формою циклів. За базові використовуються чотири моделі накопичування пошкоджень та деформаційний критерій малоциклової втоми. Виконано порівняльний аналіз моделей прогнозування довговічності. Показано, що застосування удосконаленого нелінійного правила накопичування пошкоджень дозволяє покращити результати прогнозування довговічності, причому у більшій мірі для програм, що включають непропорційні цикли.С целью разработки адекватных моделей для расчета долговечности анализируются приведенные в литературных источниках данные по малоцикловой усталости стали 304 и титанового сплава ВТ9 в процессе деформирования по сложным историям нагружения, которые представляют собой в пространстве полных деформаций последовательность блоков разных по форме циклов. В качестве базовых применяются четыре модели накопления повреждений и деформационный критерий малоцикловой усталости. Проведен сравнительный анализ моделей прогнозирования долговечности. Показано, что применение усовершенствованного нелинейного правила накопления повреждений позволяет улучшить результаты прогнозирования долговечности, причем в большей степени для программ, которые включают непропорциональные циклы.We analyze the experimental data available in the literature on low-cycle fatigue of 304 steel and VT9 titanium alloy subjected to loads with complex loading histories, which are represented in the space of total deformations by a sequence of loading blocks consisting of cycles of various shapes. As models for the material life prediction, we use four models of damage accumulation, as well as the low-cycle fatigue deformation criterion. A comparative analysis of life prediction models is provided. It is shown that application of the refined nonlinear damage accumulation rule leads to the improvement of the life prediction results, which effect is more pronounced for loading programs containing nonproportional cycles

Decimetre dust aggregates in protoplanetary discs

The growth of planetesimals is an essential step in planet formation. Decimetre-size dust agglomerates mark a transition point in this growth process. In laboratory experiments we simulated the formation, evolution, and properties of decimetre-scale dusty bodies in protoplanetary discs. Small sub-mm size dust aggregates consisting of micron-size SiO$_2$ particles randomly interacted with dust targets of varying initial conditions in a continuous sequence of independent collisions. Impact velocities were 7.7 m/s on average and in the range expected for collisions with decimetre bodies in protoplanetary discs. The targets all evolved by forming dust \emph{crusts} with up to several cm thickness and a unique filling factor of 31% $\pm$3%. A part of the projectiles sticks directly. In addition, some projectile fragments slowly return to the target by gravity. All initially porous parts of the surface, i.e. built from the slowly returning fragments, are compacted and firmly attached to the underlying dust layers by the subsequent impacts. Growth is possible at impact angles from 0$^{\circ}$ (central collision) to 70$^{\circ}$. No growth occurs at steeper dust surfaces. We measured the velocity, angle, and size distribution of collision fragments. The average restitution coefficient is 3.8% or 0.29 m/s ejection velocity. Ejecta sizes are comparable to the projectile sizes. The high filling factor is close to the most compact configuration of dust aggregates by local compression ($\sim 33$%). This implies that the history of the surface formation and target growth is completely erased. In view of this, the filling factor of 31% seems to be a universal value in the collision experiments of all self-consistently evolving targets at the given impact velocities. We suggest that decimetre and probably larger bodies can simply be characterised by one single filling factor.Comment: 10 pages, 9 figure

Does HPA-axis activity mediate the relationship between obstetric complications and externalizing behavior problems? The TRAILS study

To examine whether HPA-axis activity mediates the relationship between obstetric complications (OCs) and externalizing behavior problems, and to investigate whether this model is different for boys and girls. In a population-based cohort of 1,768 10- to 12-year-old early adolescents, we assessed the cortisol awakening response and evening cortisol levels. Externalizing behavior problems were assessed using the Child Behavior Checklist and the Youth Self-Report. OCs were retrospectively assessed in a parent interview. OCs significantly predicted externalizing behavior problems, but OCs did not predict HPA-axis activity. Thus, the mediation model was not supported. In addition to the relationship between HPA-axis activity and externalizing behavior problems, which is specific for girls, there is also a relationship between OCs and externalizing behavior problems. However, these two mechanisms are not related to each other indicating that HPA-axis activity is not a mediator in the relationship between OCs and externalizing behavior problems. Future research should focus on understanding the mechanism through which OCs cause externalizing behavior problems