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Commercial pressurized water reactors (PWR) typically rely on high electrical output power, greater than or around 1 GWe. With the emergence of newly identified uses such as power supply in remote area or heat production, small modular reactors (SMR) concepts have been designed with an electrical output power below 300 MWe. Although soluble boron is commonly used in PWR to control the reactivity, some SMR are designed without soluble boron in the primary circuit. The reactivity control in soluble boron-free (SBF) reactors relies mainly on the insertion or withdrawal of control rods. The introduction of burnable absorbers also contributes by design to the reactivity control. Soluble boron-free SMR can be justified regarding safety, economic and environmental advantages.Two-level deterministic computational schemes are generally used for PWR modelling. The first step consists in 2D detailed assembly calculations where refined energy and spatial meshes are considered to solve the neutron transport equation. In the standard computational scheme, a first depletion calculation is performed over a full range of burnup steps in an All-Rods-Out (ARO) configuration to compute isotopic concentrations. Branch calculations are then carried out at each burnup step by varying different parameters: moderator density, fuel temperature and rod insertion. The fine energy mesh cross sections are then collapsed to two-group cross sections and homogenized over the pin cell. This cross section library is then used at the core level to compute the 3D power distribution by solving the two-group diffusion equations. With SBF cores, the assumption of an ARO configuration for computing the fuel depletion can be questioned since the depletion history includes the presence of inserted control rods that modifies the neutron spectrum.The first objective of this thesis is to quantify the numerical biases introduced by the standard neutronic computational scheme in the modelling of SBF fuel assemblies, cluster and SMR core including a large quantity of burnable absorber (in the form of gadolinium oxide). The second and main objective is to develop a method able to simulate spectrum history effects over the entire core at reasonable computing cost.This work is carried out using the APOLLO3® deterministic code. The developed method called COHLISEE is inspired from previous work found in the scientific literature about spectrum history effects. COHLISEE is a hybrid method that consists in using both microscopic depletion and spectrum history indicator in 3D diffusion core calculation. The multigroup cross section libraries are generated by merging All Rods Out (ARO) and All Rods In (ARI) depleted libraries. The method has been verified and validated on fuel assemblies and 2x2 cluster 2D calculations. Reference results have been obtained with 2D transport calculations performed with controls rods inserted following specific sequences. COHLISEE results (reactivity, power, material balance) are compared to standard schemes using either macroscopic or microscopic depletion. The V&V process shows that macroscopic standard calculations are leading to massive numerical biases on reactivity for all control rods sequences studied. With the microscopic standard scheme, numerical biases are relatively small for UO2 fuel assembly without burnable absorbers but can be comparable to macroscopic standard scheme for poisoned fuel assemblies. Core calculations performed with the COHLISEE method show a reduction of the numerical biases, especially on pin-by-pin power distributions, at a computing cost comparable to standard microscopic scheme.In order to compare the COHLISEE method to standard schemes, 3D whole-core calculations are performed for a SBF-SMR benchmark. This study evaluates the magnitude of numerical differences between COHLISEE and standard schemes.; La puissance d’un réacteur à eau pressurisée (REP) industriel est généralement de l’ordre de 1000 MWe. Avec l’émergence des nouveaux marchés tels que l’alimentation de sites isolés ou la production de chaleur, des concepts de petits réacteurs modulaires (small modular reactor ou SMR) sont proposés avec des puissances inférieures à 300 MWe. Certains concepts de SMR n’utilisent pas de bore soluble dans le circuit primaire, malgré son utilisation quasi-systématique dans les REP. Le contrôle de la réactivité de ces réacteurs repose donc principalement sur l’insertion et le retrait des grappes de contrôle. L’utilisation de poisons consommables à poste fixe permet également un contrôle de la réactivité à la conception et limite la quantité d’absorbants mobiles insérés dans le cœur.Un schéma de calcul déterministe en deux étapes est généralement utilisé pour la modélisation des REP. La première étape est un calcul de transport neutronique sur une géométrie 2D détaillée d’un assemblage combustible en réseau infini. Dans un schéma de calcul standard, une évolution toutes grappes extraites (TGE) est réalisée sur une plage de burnup. Des calculs de reprise sont effectués à chaque pas de burnup en faisant varier les paramètres principaux de fonctionnement tels que la densité du modérateur, la température du combustible et l’insertion de la grappe de contrôle. Les sections efficaces multigroupes sont ensuite condensées à deux groupes et homogénéisées à l’échelle de la cellule combustible. Les librairies de sections efficaces ainsi obtenues sont utilisées à l’étape cœur pour le calcul des distributions 3D de puissance par résolution de l’équation de la diffusion à deux groupes d’énergie. L’hypothèse d’évolution du combustible en configuration TGE nécessite d’être remise en question au regard de l’insertion prolongée des grappes de contrôle pour un cœur de REP sans bore soluble, qui modifie le spectre neutronique d’évolution.Le premier objectif de ce travail de thèse est de quantifier les écarts numériques introduits par le schéma de calcul neutronique standard pour la modélisation d’assemblage, de cluster et de cœur d’un REP sans bore soluble fortement empoisonné. Le second objectif est de développer une méthode qui permette de simuler des effets d’historique de spectre à l’échelle d’un cœur complet de SMR sans pénalité excessive sur le temps de calcul.Ce travail a été réalisé avec la plateforme déterministe multi-filières APOLLO3®. La méthode développée, baptisée COHLISEE, est une méthode hybride qui consiste à utiliser à la fois une évolution microscopique et un indicateur d’historique de spectre lors d’un calcul de diffusion. La méthode est vérifiée et validée grâce à des calculs d’assemblages et de cluster 2x2 en 2D. Les résultats de référence sont obtenus par des calculs en transport réalisés avec des séquences particulières d’insertion de grappe de contrôle. Les résultats de COHLISEE (réactivité, distributions de puissance, bilan matière) sont comparés à ceux obtenus par des schémas standards utilisant des modèles d’évolution macroscopique ou microscopique au niveau cœur. Le processus de vérification et de validation (V&V) montre que le schéma macroscopique présente des biais considérables sur la réactivité pour toutes les séquences étudiées. Les écarts numériques avec le schéma microscopique sont relativement faibles pour un assemblage UO2 sans poisons consommables mais peuvent être comparables au schéma macroscopique en présence d’absorbants gadoliniés. Les calculs de cœur réalisés avec la méthode COHLISEE réduisent les biais numériques, notamment sur les distributions de puissance crayon par crayon, avec un coût de calcul comparable au schéma standard microscopique. Afin de comparer COHLISEE avec les schémas standards, des calculs critiques en 3D sur un cœur de benchmark de SMR sans bore soluble sont réalisés. Cette étude permet d’évaluer les écarts numériques entre COHLISEE et les schémas standards pour un cœur complet.

In the present paper, a structure-based viscoelastic model is employed to characterize and predict the viscoelastic properties of a wormlike micellar solution at 20 °C. Considering the effect of shear rate on linear viscoelastic property, a structural parameter f is obtained. Meanwhile, another structural parameter ζ is determined when the effects of time and shear rate are considered simultaneously. Both structural parameters are calculated by using linear interpolation method. The startup experiment can be described well by the model. The prediction on the shear stress in the ramping-up region of the hysteresis loop experiment shows an apparent relation between the rheological behaviors in the startup experiment and those in the hysteresis loop experiment. For the hysteresis loop experiment with 30 s time interval, the defect of the calculation in 0.001–0.01 s−1 is due to the lack of the ramping-down history effect. In addition, the model can improve completeness of perimental data used for characterizing rheological property.

Herein, broadband dielectric (BDS) and Fourier transform infrared spectroscopy (FTIR), together with differential scanning calorimetry (DSC) and X-ray diffraction (XRD), were applied to study the molecular dynamics, molecular interactions as well as physical stability of an amorphous Active Pharmaceutical Ingredient (API)-probucol (PRO)-infiltrated into anodic aluminum oxide (AAO) membranes of pore size, d ~ 10-160 nm. Interestingly, the behavior of examined substance strongly depends on the applied thermal protocol. Remarkably, for the first time, we observed that the structural dynamics of the slowly cooled PRO under confinement is significantly enhanced when compared to thatofthe quenched material. This unusual behavior was interpreted as a result of surface-induced effects (including the formation of well-resolved interfacial H-bonded layer and adsorption-desorption processes near the interface) that are magnified by the extremely high sensitivity to density fluctuation of studied PRO, reflected in the enormous pressure coefficient of the glass transition temperature dTg/dp = 427 K/GPa. In fact, FTIR investigations revealed that PRO tends to self-associate under confinement and forms a strongly bonded interfacial layer, which controls the variation in the structural dynamics of core molecules. Finally, we observed that the tendency to crystallize of confined API is reduced with respect to the bulk, even though the critical size of PRO nuclei (rc ~ 3 nm) is significantly lower than the smallest examined pore size. Nevertheless, after few weeks of storage, the investigated substance crystallized in larger pores, while it remained stable in the nanochannels of d = 10 nm. A combination of XRD and DSC measurements indicated that the infiltrated PRO forms two polymorphs, the stable form I (dominating in bulk) and unstable form II (prevailing under confinement). That means that porous matrices might be used to obtain and maintain prolonged stability of unstable polymorphic forms of API.

Among the different aerosol mineral particles that contribute to induce ice nucleation (IN) in the troposphere, feldspars have been identified as the most active. Nevertheless, which surface properties make some feldspars more efficient than others, i.e. able to induce IN at higher temperatures, is still unclear. In addition to that, surface properties of such materials can change as they are exposed to a variety of environmental conditions while traveling through the troposphere. Here, freezing temperature of water droplets deposited on feldspar minerals has been measured as a function of consecutive freeze-thaw cycles. We found an increase of the freezing temperature for the initial cycles followed by approximately constant freezing temperature for consecutive cycles. We call this a "history effect". This effect is more evident for samples aged in standard room conditions and it disappears if the sample is exposed to oxygen plasma. Oxygen plasma generates OH groups at the surface, facilitating IN and cleans the surface from organic contamination, unblocking pores at the surface, believed to be the most active IN sites on feldspars. A similar process is suggested to happen during the history effect, when consecutive freeze-thaw events unblock IN sites., The authors thank C. Marcolli for discussion on results and their interpretation. This work has been supported by the Spanish Government under the project PID2019-110907GB-I00 and the ‘‘Severo Ochoa’’ Program for Centres of Excellence in R&D (CEX2019-000917-S). E. Pach acknowledges the Spanish Ministry of Science and Technology for the Juan de la Cierva Formation grant., With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).

Our eyes are the primary gates to the visible world around us. Yet, whatever we perceive involves a translation of the patterns of the photons hitting our retinas into mental representations. It could be argued that visual perception is merely an interpretation of the physical world, which raises the question of how reliable this translator is. Fischer and Whitney (2014) found that the perception of an oriented Gabor patch was influenced by the orientation of previously presented Gabor patches, a phenomenon that they called serial dependence. They argued that serial dependence reflects the visual system's assumptions about continuity: The visual world around us is generally constant from moment to moment and does not suddenly change despite large changes in viewpoint, occlusion or lighting conditions. Our perceptual systems employ this predictability to overcome potential perceptual noise and maintain perceptual stability. Subsequent research has revealed that the perception of a variety of other features, including shape, motion coherence, numerosity, facial identity, and even stimulus ensembles, is systematically biased toward recent information. Almost all of the studies mentioned above involved paradigms where the stimuli causing the serial dependence (the inducers) were attended, and therefore do not address whether items that we ignore can cause serial dependence biases. In the papers in this thesis, we studied the role of the to-be-ignored items in forming biases in our perceptual decisions. In Paper I here, we used a visual search for an oddly oriented line among distractors to demonstrate that the to-be-ignored items can form serial dependence in perceptual decisions in addition to the attended inducer. Notably, the repulsive bias occurs even when the distractors and targets are remarkably dissimilar, which distinguishes this from the well-known tilt illusion and tilt adaptation. Furthermore, our results demonstrate that explicit reports of stimulus features are not required for serial dependence. The findings in Paper I suggest that perception accounts for both attended and ignored stimuli in preserving the visual world's continuity to a greater extent than previously thought. In Paper II we demonstrated that visual search can result in serial-dependence biases in the perceived orientation of a stimulus that is unrelated to the search task. Our findings also revealed that both attention and similarity between the search stimuli (distractors and targets) and the test item play a significant role in forming serial dependence in perceptual decisions. Finally, our findings in Paper III demonstrated that similar biases to those reported in Papers I and II can occur from a single inducer line upon a set of test lines as previously observed from a set of lines upon a single test line. Secondly Paper III shows that when the inducer is similar to the test, it produces an attractive bias, but it creates a repulsive bias when these items are dissimilar. This means that the inducer creates opposing biases based on the similarity of the perceptual history content to the current stimulus. These attractive and repulsive biases can occur simultaneously when more than one test item is present. Overall, our results show that attention and proximity in feature space play a crucial role in shaping serial dependence biases. We showed that biases introduced by attended versus ignored visual search items (targets and distractors) influenced the general perceptual decisions, and furthermore, we showed that even attended items can produce repulsive biases in perceptual decisions., Research Fund of the University of Iceland and the Icelandic Research fund (#173947-052)

Identical physical inputs do not always evoke identical percepts. To investigate the role of stimulus history in tactile perception, we designed a task in which rats had to judge each vibrissal vibration, in a long series, as strong or weak depending on its mean speed. After a low-speed stimulus (trial n − 1), rats were more likely to report the next stimulus (trial n) as strong, and after a high-speed stimulus, they were more likely to report the next stimulus as weak, a repulsive effect that did not depend on choice or reward on trial n − 1. This effect could be tracked over several preceding trials (i.e., n − 2 and earlier) and was characterized by an exponential decay function, reflecting a trial-by-trial incorporation of sensory history. Surprisingly, the influence of trial n − 1 strengthened as the time interval between n − 1 and n grew. Human subjects receiving fingertip vibrations showed these same key findings. We are able to account for the repulsive stimulus history effect, and its detailed time scale, through a single-parameter model, wherein each new stimulus gradually updates the subject’s decision criterion. This model points to mechanisms underlying how the past affects the ongoing subjective experience., Identical physical inputs can evoke non-identical percepts. Here, the authors investigate the sources of such variability and find that rats and humans, trained to judge tactile vibration strength, express a robust sequential effect that could be modeled as the trial-by-trial incorporation of sensory history.

This article presents an elastic-plastic study aiming at predicting the fatigue crack growth (FCG) of 2024-T3 aluminum alloys under variable-amplitude loading. The proposed analysis needs the estimation of the residual stress distribution ahead of the crack tip during propagation. An elastic-plastic FE analysis has been implemented for modeling FCG using Chaboche's model. The FE study has been carried out through consideration of the loading history effect using the memory rules. Three different loading spectra have been applied in this work. The obtained results have been compared to the experimental ones and it has been proved that the suggested model has a better prediction of the FCG lives of cracked 2024-T3 aluminum alloy structures subjected to variable-amplitude loading.

Ferroelectric device based doped Hf0 2 is an emerging non-volatile memory that is able to store multilevel weights of the deep neural network (DNN) models and enables the compute-in-memory paradigm. In this invited paper, we will present our recent progresses in ferroelectric transistor (FeFET) design for inference as well as in-situ training. Physical insights of the history effect in the intermediate state programming are presented. System-level performance of using FeFET for inference is benchmarked against with SRAM and other emerging non-volatile memories at 32nm and 7nm, showing its significant benefits in throughput and energy efficiency.

As a candidate of dark matter, primordial black holes (PBHs) have attracted more and more attentions as they could be possible progenitors of the heavy binary black holes (BBHs) observed by LIGO/Virgo. Accurately estimating the merger rate of PBH binaries will be crucial to reconstruct the mass distribution of PBHs. It was pointed out the merger history of PBHs may shift the merger rate distribution depending on the mass function of PBHs. In this paper, we use 10 BBH events from LIGO/Virgo O1 and O2 observing runs to constrain the merger rate distribution of PBHs by accounting the effect of merger history. It is found that the second merger process makes subdominant contribution to the total merger rate, and hence the merger history effect can be safely neglected.

The history effect observed in SOI-MOSFET is investigated. Origin of the effect is the impact ionization, where induced carriers are accumulated within the SOI layer due the potential barrier at the source/channel junction. The compact model HiSIM_SOTB describing the effect based on its origin is studied to analyze the influence on circuit. An inverter-chain circuit is applied to characterize the influence of the history effect. It is demonstrated how the accumulated carriers propagates within the circuit as well as how the generated carriers are accumulated and disappeared during circuit operation. The charging/discharging of the carriers takes time until it reaches stable condition, which could be much longer than the normal circuit operation cycle, observed as the history effect.

A freshman mechanics course often includes a theoretical discussion or demonstration of the motion of solid particles through fluids. The effect of viscosity is typically considered to provide a drag force on the particle which at each instant is proportional to the particle velocity. We present a brief discussion of the limitations of this approach and the importance of the so-called history effect first considered by Boussinesq and Basset in the late 19th century.

In this paper we have developed a numerical methodology which is capable of estimating volatile fission product release from nuclear fuel under changing irradiation conditions with incorporation of all physical phenomena’s. The present study bridges the gap between previous analytical studies by providing estimation of unstable fission product release under accidental condition with and without incorporation of precursor’s history effect. Based on the present methodology a computer model “FIPRAP-Fission Product Release Analysis Program” has been developed and validated with standard fission product release problems and benchmarked against internationally accepted CORSOR-BOOTH model as well as Accident Source Term Evaluation Code (ASTEC). The result of the proposed model lies within 15% of internationally accepted models.

We extend the multi-physics capabilities of the Serpent 2 Monte Carlo code to coupled burnup calculations by implementing the Stochastic Implicit Euler depletion scheme with thermal feedback. We use these new multi-physics capabilities for the verification of the traditional way of generating group constants using an effective flat fuel temperature profile during the burnup calculation. We investigate the effects of this approximation on the generated nuclide compositions, group constants as well as the results on the simulation of the initial cycle of the EPR reactor using the ARES core simulator. The main findings state that while the use of an effective temperature model leads to significant differences in the radial nuclide distributions, the assembly wide homogenized group constants are reproduced fairly well and the effects on the simulation of the EPR initial cycle are modest, although interesting axial and radial power redistribution can be observed due to the slower speed of gadolinium burnout when effective fuel temperatures were used. The results indicate that better results for the full core calculations could be obtained by using a separate effective temperature for the burnable absorber rods in the burnup calculation and by considering the fuel temperature history effect in the group constant parametrization.

Pipe reeling may lead to plastic pre-deformation (prestrain) around existing cracks in components; therefore, investigating whether this process accelerates or counteracts ductile crack growth, especially for strength mismatched welded joints, is warranted. This study focused on the effect of prestrain history on ductile crack growth in mismatched welded joints. A single-edge-notched tension specimen was selected for numerical study, and the crack was assumed to have existed before a prestrain history was applied. Crack growth resistance curves for plane strain and mode I crack growth under large-scale yielding conditions have been computed using the complete Gurson model. Meanwhile, symmetrical and non-symmetrical prestrain cycle modes with different loading levels were applied to the overmatched specimens. The outcome demonstrated that the mismatch ratio (the ratio between the yield stress of the weld metal and base metal) showed a significant effect on fracture resistance regardless of the stage at which the prestrain cycle loading was located. By contrast, the processing of the crack growth was weakened by the increase of prestrain values, and the symmetrical prestrain cycle resulted in greater plastic damage than the non-symmetrical prestrain cycle did. However, the initial crack length had a non-significant effect on the ductile fracture considering the prestrain and mismatch effects.

Research has shown that individuals use a combination of cultural life script events and historical events when dating personal memories, providing evidence for a cultural life script effect and Living-in-History (LiH) effect on the temporal organisation of autobiographical memory. Yet, in contrast to life script events, the LiH effect has only been found for negative events such as war or natural disasters. Therefore, this study tested whether a positive historical event, here the fall of the Berlin Fall, also elicits a LiH effect and whether this effect would differ due to the subsequent changes in life. Comparing West and East Germans, we found a moderate LiH effect for the fall of the Berlin Wall in East Germans but not in West Germans. Yet, the LiH effect in East Germans did not relate to the perceived change in life or the valence of the historical event. Additionally, this study replicated the finding that life script events serve as temporal landmarks when navigating through one's autobiographical timeline.

Responses of neurons in the primary visual cortex (V1) are often understood as encoding the current visual stimulus. Yet, some studies indicate that temporal contingency effects exist in the responses of neurons in early sensory areas. We explored if the recent stimulus history would alter the response of V1 layer 2/3 pyramidal cells in head-fixed awake mice during presentation of sequences of complex images. The activity of individual neurons was sparse, such that either one or none of the images in the sequence typically yielded a strong response. We then substituted an image preceding this primary image in order to determine if responses to the primary image were affected. We found that the amplitude of the neuron’s response could be significantly altered by substitutions up to five images back from the primary image, even when the substituted image elicited virtually no response by itself. This stimulus history effect was heterogeneous across the population, with some cells showing facilitation and others suppression. For individual cells, the history effect was robust and reproducible across days. Our data show that responses of V1 neurons not only reflect the current stimulus but also encode, through their response amplitude, information about multiple images previously presented as far as 1000 msec in the past. This might enable V1 to retain information about the extended trajectory of past stimuli and perform complex temporal computations that are as of yet not appreciated.

The present study investigated whether color imagery could override the representations of the prevalent selection history effect termed Priming of Pop-out (PoP), which is constituted by faster responding when the target color is repeated rather than switched across trials of color singleton search. Participants imagined a color in the interval between trials of a color singleton search task that could be the same as or different to the previous target color, and they were to rate the vividness of these representations following each imagery event. It was revealed that when highly vivid imagery was reported, the PoP effect was attenuated relative to less vivid forms of it (and absent in two out of three experiments), and that color imagery eliminated the build-up of priming following consecutive target color repeats. Overall, the present findings suggest the representations of the selection history system can be overridden by top-down imagery.

Experienced thermal history often affects the temperature tolerance of fish; however, the effect of thermal history on growth performance is unclear. To contribute to effective stocking (release of hatchery-reared juveniles in the field), we conducted four laboratory experiments using juvenile marbled flounder (Pseudopleuronectes yokohamae, around 30 mm standard length and 0.3 g body wet weight) acclimated at 12 °C and 24 °C for approximately 2 weeks to investigate the effects of acclimation temperature on high-temperature tolerance, food consumption, and growth performance. The acclimation to 24 °C increased tolerance to high temperatures, as shown in a 24-h exposure experiment and in a temperature elevation experiment. The 50% lethal temperature (upper incipient lethal temperature) was estimated to be 25.9 °C and 29.0 °C for the 12 °C and 24 °C acclimation groups, respectively. In subsequent experiments, we tested the effects of high and low temperature acclimation on the food consumption and growth performance of two size groups of juveniles (28.7 ± 2.0 and 34.5 ± 2.9 mm, mean ± SD), that were reared at temperatures ranging from 14 °C to 23 °C. The optimal temperature for growth was 20 °C and did not differ between the acclimation temperatures or between the size groups. However, food consumption and growth performance were suppressed by acute temperature changes. Specifically, feeding and growth were lower in the 24 °C-acclimated group than in the 12 °C-acclimated group when exposed to 14 °C, which is close to the natural water temperature at release in the field. These results suggest that experienced thermal history does not affect the optimal temperature but can affect the growth performance of juveniles. To maximize the post-release growth of hatchery-reared juveniles, the influence of thermal history should be taken into consideration and acute thermal changes before release should be avoided., This study was partly supported by the Ministry of Agriculture, Forestry and Fisheries of Japan and by JSPS KAKENHI Grant Number 19K06207.

The use of explosives to attack vehicles has been increased during the last few years. The terror attacks lead to death of innocent people. The armored vehicles should be protected from explosives attacks using lightweight sandwich structure.In this study, the protection system against blast effect is highlighted using composite structures to protect vehicles. The response of the light composite structure is studied using 3-D finite element analysis (FEA). The blast field test is conducted and used to verify the 3-D numerical model. The composite structure strengthened by aluminum foam (ALF) is used to protect the bottom of the armored vehicle against the blast wave propagation. The ALF is used to fill the space at the sandwich structure as a light weight material.This study presents a comparison between the results obtained by both the reviewed field blast tests and the FEA to validate the accuracy of the 3-D finite element model. The effects are expressed in terms of displacement-time history effect on the sandwich steel panels as the explosive wave propagates. The results obtained by the reviewed field blast tests have a good agreement with those obtained by 3-D numerical model. The ALF improves the performance of the sandwich structure under the impact of blast loading. The light weight sandwich structure could be used as a mitigation system to protect the bottom of the armored vehicles against blast hazard.

Ce working paper a fait l'objet d'une publication dans : Journal of Mathematical Economics, 68:103-114, 2017; A series of recent studies in economic growth theory have considered a class of models of international borrowing where, in the absence of a perfect investment commitment , the borrowing constraint depends on the historical performances of the country. Thus, a better level of past economic activity gives a higher reputation, thereby increasing the possibility of accessing the international credit market. This note considers this problem in a stochastic setting based on the volatility of the internal net capital. We study how the optimal consumption level and the maximal expected welfare depend on the combined influence of the trajectory of past economic variables and the volatile environment. In particular, we show how the strength of the history effect and the relative weight of the historical performance depend on the degree of risk.

Thermophoresis has important applications in microparticle separation, colloidal crystal growth processes and other fields. Considering the unsteady variation of the temperature gradient in the fluid, the viewpoint that particles in fluids will experience thermophoretic impulsive force is proposed. The force is related to the particle motion in thermophoresis but different from the traditional thermophoretic force. The basic approach to obtain the expression of thermophoretic impulsive force has been introduced. In analogy with the additional mass force and Basset force on a particle in unsteady flows, the expression for thermophoretic impulsive force exerted on the particles has been given resulting from the unsteady temperature gradient. It is suggested that the thermophoretic impulsive force is related to the time rate of the averaged temperature gradient and its history effect.

The creep characteristics of rocks are very important for assessing the long-term stability of rock engineering structures. Two loading methods are commonly used in creep tests: single-step loading and multi-step loading. The multi-step loading method avoids the discrete influence of rock specimens on creep deformation and is relatively time-efficient. It has been widely accepted by researchers in the area of creep testing. However, in the process of multi-step loading, later deformation is affected by earlier loading. This is a key problem in considering the effects of loading history. Therefore, we intend to analyze the deformation laws of rock under multi-step loading and propose a method to correct the disturbance of the preceding load. Based on multi-step loading creep tests, the memory effect of creep deformation caused by loading history is discussed in this paper. A time-affected correction method for the creep strains under multi-step loading is proposed. From this correction method, the creep deformation under single-step loading can be estimated by the super-position of creeps obtained by the dissolution of a multistep creep. We compare the time-affected correction method to the coordinate translation method without considering loading history. The results show that the former results are more consistent with the experimental results. The coordinate translation method produces a large error which should be avoided.

In this research, two parallel hybrid- and two diesel-buses fitted with selective catalytic reduction systems were tested in real world conditions using portable emission measurement systems. The hybrid buses were chosen to operate in either hybrid mode or diesel mode. In hybrid mode, the buses consumed less fuel, but the brake specific fuel consumptions were higher. The hybrid buses produced less engine-out NO X emissions than diesel buses, but as a result of lower exhaust temperature and lower efficiencies of SCR systems, the tailpipe NO X emissions from hybrid buses were a little higher. The brake specific NO X emissions from hybrid buses were very high and beyond the limit value of Euro-IV standard. History effect was also important for the efficiency of SCR system. The CO emissions from hybrid buses were lower in the unit of g/s, but the fuel-based CO emissions were higher than diesel buses.