Dynamic Action Research Articles

Fish feeds supplemented with calcium-based buffering minerals decrease stomach acidity, increase the blood alkaline tide and cost more to digest

Predatory fish in the wild consume whole prey including hard skeletal parts like shell and bone. Shell and bone are made up of the buffering minerals calcium carbonate (CaCO3) and calcium phosphate (Ca3(PO4)2). These minerals resist changes in pH, meaning they could have physiological consequences for gastric acidity, digestion and metabolism in fish. Using isocaloric diets supplemented with either CaCO3, Ca3(PO4)2 or CaCl2 as non-buffering control, we investigated the impacts of dietary buffering on the energetic cost of digestion (i.e. specific dynamic action or SDA), gastric pH, the postprandial blood alkalosis (the “alkaline tide”) and growth in juvenile rainbow trout (Oncorhynchus mykiss). Increases in dietary buffering were significantly associated with increased stomach chyme pH, postprandial blood HCO3−, net base excretion, the total SDA and peak SDA but did not influence growth efficiency in a 21 day trial. This result shows that aspects of a meal that have no nutritional value can influence the physiological and energetic costs associated with digestion in fish, but that a reduction in the SDA will not always lead to improvements in growth efficiency. We discuss the broader implications of these findings for the gastrointestinal physiology of fishes, trade-offs in prey choice in the wild, anthropogenic warming and feed formulation in aquaculture.

Closing the Implementation Gap Comment on "Insights Gained From a Re-analysis of Five Improvement Cases in Healthcare Integrating System Dynamics Into Action Research".

Holmström et al provide an interesting and thought-provoking contribution to a perennial problem: why, despite a vast number of applications of simulation modelling in healthcare over the past 70 years, there is still remarkably little evidence of successful implementation of model results. Their paper is a retrospective analysis of five case studies, all undertaken as consultancy, that used a blend of system dynamics (SD) modelling and action research (AR). This commentary assesses the effectiveness of this approach in achieving implementation, based on the evidence presented, and discusses some of the issues raised. These issues include a comparison of Holmström's approach with group model building (GMB) in SD, the differences between healthcare modelling projects undertaken by (a) business consultants and (b) academics, and the challenges of undertaking 'systematic' reviews of the grey literature.

Shake table test and numerical analyses of a thin-walled Cold-Formed Steel structure: Part 1 — Investigation of the structural skeleton without claddings

CFS structures are classified as structures with low ductility. Due to this, they are not recommended for medium to high seismic areas. The paper presents the results of a complex experimental program coupled with numerical investigations on the behavior of Cold Formed Steel (CFS) structures under seismic actions. The scaled-down model skeleton was made of DX51D+Z C-shaped 89 × 41 × 12 × 1 mm steel elements connected by 4.8 × 16 mm self-tapping screws (STS) and 5.5 × 25 mm self-drilling screws (SDS). This structure represents a replica of constructive solutions for single-story or one or two-storey structures that are frequently met in South-Eastern Europe, including highly active seismic areas.The main purpose of the research program is to gather both quantitative and, more importantly, accurate information regarding structural response to dynamic actions characterized by input accelerations equal in amplitude to the maximum values specified in seismic design codes, up to PGA = 0.40 g. The damage of the joints and the reduction in the structural stiffness due to cyclic loads, such as the ones produced by earthquakes, change the structure’s eigen period and significantly influence the structure’s response to seismic actions. Larger gravitational loads lead to more extensive damage of the joints. The developed numerical model based on the experimentally determined connection axial rigidity can offer accurate results in terms of the fundamental frequency of vibration, relative accelerations and displacements. However, for a more accurate capturing of the local damages and onset of failure mechanisms, more complex numerical models are needed, which take into account non-linear material behavior.The results presented in this paper help to design these structures as only the skeleton and serve as a starting point for future research work aimed to assess the influence of the sheathing on the global response of CFS structures to seismic actions. Additionally, research in the direction of improved joints with better energy dissipation properties is also pursued by the authors.

Inflation from dynamical projective connections

We show how the recently developed string-inspired, projectively-invariant gravitational model Thomas-Whitehead gravity (TW gravity) naturally gives rise to a field acting as the inflaton. In the formulation of TW gravity, a field $\mathcal{D}_{ab}$ is introduced into the projective connection components and is related to a rank-two tensor field $\mathcal{P}_{ab}$. Through the dynamical action of TW gravity, in terms of projective curvature, the tensor field $\mathcal{P}_{ab}$ acquires dynamics. By decomposing $\mathcal{P}_{ab}$ into its trace and traceless degrees of freedom, and choosing the connection to be Levi-Civita, we demonstrate that TW gravity contains a non-minimally coupled scalar field with a specific potential. Considering only the trace degrees of freedom, we demonstrate that the scalar field acts as an inflaton in the slow roll approximation. We find a range of values for the parameters introduced by TW gravity that fit the experimental constraints of the most recent cosmological data.

The three pedagogical moments and the portfolio methodology: analysis of a pedagogical practice aimed at achieving a critical environmental education

The objective of this article is to reflect on the joint action of the pedagogical dynamics of the Three Pedagogical Moments and the Portfolio methodology in the development of a pedagogical practice that involved environmental education. This work was conducted in a public school in the city of Curitiba, in times of social distancing due to the COVID-191 pandemic. The research was produced in a qualitative perspective of pedagogical intervention type considering the research corpus constituted from the pedagogical practice "waste generation and consumerism". In the process of Textual Discourse Analysis, eighty-four meaning units emerged from the research corpus, providing the formation of eleven initial categories, and from their congruent elements, three final categories were formed, these being: (1) The student's understanding, as a future building technician, of his/her role in building a sustainable society; (2) The student's understanding of the participation of science, technology and human beings in the structuring of a new culture of consumption for society and (3) Indications of the student's autonomy. The dialogues established by the Three Pedagogical Moments and the Portfolio stimulated the student's reflections about the reality of the society in which he is inserted and this dialog offered an opportunity to deepen the reflections, respecting the other and developing the student's understanding of his role as a human being and future professional in the construction of a sustainable society, besides making him realize the participation of science, technology and people in the structuring of a new culture of consumption for society.

Behaviour recognition based on the integration of multigranular motion features in the Internet of Things

With the adoption of cutting-edge communication technologies such as 5G/6G systems and the extensive development of devices, crowdsensing systems in the Internet of Things (IoT) are now conducting complicated video analysis tasks such as behaviour recognition. These applications have dramatically increased the diversity of IoT systems. Specifically, behaviour recognition in videos usually requires a combinatorial analysis of the spatial information about objects and information about their dynamic actions in the temporal dimension. Behaviour recognition may even rely more on the modeling of temporal information containing short-range and long-range motions, in contrast to computer vision tasks involving images that focus on understanding spatial information. However, current solutions fail to jointly and comprehensively analyse short-range motions between adjacent frames and long-range temporal aggregations at large scales in videos. In this paper, we propose a novel behaviour recognition method based on the integration of multigranular (IMG) motion features, which can provide support for deploying video analysis in multimedia IoT crowdsensing systems. In particular, we achieve reliable motion information modeling by integrating a channel attention-based short-term motion feature enhancement module (CSEM) and a cascaded long-term motion feature integration module (CLIM). We evaluate our model on several action recognition benchmarks, such as HMDB51, Something-Something and UCF101. The experimental results demonstrate that our approach outperforms the previous state-of-the-art methods, which confirms its effectiveness and efficiency.

Optimization of the seismic response of bridges using variable‐width joints

AbstractAn aspect of seismic design of bridges that has hardly received proper attention so far is the appropriate selection of joint gaps. End gaps define the boundary conditions of the bridge and affect its dynamic response; their proper design can lead to an improved structural performance under dynamic actions. The idea of the ‘Dynamic Intelligent Bridge’ is explored here, wherein current bridge joints that have a fixed width are substituted by variable‐width joints and, under seismic loading, the joint gap is optimised either with a one‐off adjustment, or continuously (in real time) through semi‐active control. In all cases, a novel device is used that permits this improved behaviour of the joints, the moveable shear key (MSK), a device for blocking the movement of the bridge deck, which has the possibility to slide, hence varying the size of the existing joint gap. In this context, the effect of gap size on the seismic response of bridges is assessed herein and a methodology is put forward for optimising this size, using a number of criteria such as maintaining the functionality of the bridge for moderate earthquakes, and ensuring the safety of the bridge and its users under earthquakes stronger than that used for design.

Nonlinear stochastic seismic dynamic response analysis of submerged floating tunnel subjected to non-stationary ground motion

Owing to the randomness of seismic excitations, the submerged floating tunnel (SFT), which is a new structure subjected to the combined action of self-weight, buoyancy, and anchorage under seismic excitation, is a nonlinear stochastic dynamic system and the evaluation of its dynamic performance is an issue that must be addressed. In this study, the nonlinear dynamic differential equation of an SFT subjected to seismic dynamic action was systematically derived by considering the wave–structure dynamic coupling interaction, and its numerical solution was obtained based on the Newmark-β integration algorithm. Furthermore, based on the theoretical framework of nonlinear stochastic dynamics and the stochastic seismic model reflecting the characteristics of the site-specific response spectrum, the probability density function (PDF) of the nonlinear seismic dynamic response of the SFT was analyzed, and its seismic dynamic performance was evaluated based on dynamic reliability. Thus, it was found that the randomness of ground motion propagates, fluctuates, evolves, and dissipates in the SFT, and finally reaches the nonlinear seismic dynamic response of the SFT. Additionally, the nonlinear dynamic response of the underwater suspension tunnel is highly sensitive to earthquake excitations. The proposed evaluation framework is an effective tool for evaluating the seismic performance of underwater tunnels.

Influence of unevenness of airport pavements on technical condition and safety of air operations

Abstract: The publication presents the requirements for airport pavements for the assessment of the evenness of airport pavements, including the methodology of testing unevenness. On the basis of the selected aircraft type, the impact of unevenness on the dynamic interaction of the plane - pavement was determined, and the vertical displacements occurring at the edges of concrete slabs were taken for analysis. The paper presents the influence of operational procedures in the form of pavement grooving and local surface repairs on the results of unevenness measurements and improvement of the technical condition of the pavement, as well as on the safety of air operations. Keywords: Pavement unevenness; Evaluation criteria; Dynamic action plane - surface; Grooving pavement; Maintenance treatments; The functional element of the airport

Critical issues in existing RC deck stiffened arch bridges under seismic actions

Existing Reinforced Concrete arch bridges represent still today an important part of transportation network. The peculiarities of such bridges make particularly complex the assessment of their behaviour under both static and dynamic actions and, therefore, their safety. This work concentrates on a specific arch bridge typology known as the “Maillart –Type Arch Bridges” or “Deck-Stiffened Arch Bridges”, characterized by a very stiff deck beam and a slender and wide vault. As well as for the RC structures designed during 50s of the last century, where some important details for concrete elements were not considered, RC Deck-Stiffened Arch Bridges could be subjected to similar structural deficiencies. Moreover, the current loading conditions provide actions that were not considered in the original design or have changed over the time, such as the seismic actions or the moving loads due to the vehicular traffic.For the evaluation of the main critical issues related to the current performance of the “Maillart–Type Arch Bridges”, this study, starting from a “simulated design” according to the design rules and the mandatory codes in force at the construction time, defines a large building inventory of simulated bridges (3000 samples) characterized by different values of the most significant geometrical parameters. Firstly, each bridge of the inventory is modelled and studied by means of a linear Response Spectrum Analysis (RSA) implemented in the software SAP2000. The large number of structural analyses allowed to investigate the seismic behaviour of such a bridge typology, assess and localize the most frequent failure modes. The results of the RSA allowed developing preliminary fragility functions at the Ultimate Limit State, based on shear or flexural failure of single elements of the bridges. Lastly, Non-Linear Time History Analyses (NLTHA) were carried out on two representative case studies extracted from the simulated inventory and the results were examined in terms of fragility curves obtained according to the Cloud methodology for four Damage States. Despite the different approaches (RSA on large scale and NLTHA on two prototypes), a comparison of the fragility curves for equivalent Damage States was also proposed and a good agreement was found. These fragility curves are a first step for the assessment of the seismic vulnerability of “Maillart–Type Arch Bridges” and can be useful for planning seismic risk mitigation interventions for such a bridge typology.

MODELING AND MONITORING OF STRUCTURAL SAFETY OF LONG-OPERATING UNDERGROUND STRUCTURES OF THE SEWAGE SYSTEM IN THE CONDITIONS OF INCREASING ANTHROPOGENIC ACTIONS IN ORDER TO PROVIDE SUSTAINABLE LIFECYCLE OF ENGINEERING INFRASTRUCTURE OF THE MEGACITY (THE EXPERIENCE OF ST. PETERSBURG)

Long-term operation in difficult engineering-geological conditions of unique underground sewage facilities creates the danger of violating their structural safety. A long-term study of the dynamics of changes in a technical state of large pumping stations and deep sewage tunnels made it possible to establish patterns of influence of intensive anthropogenic and dynamic actions on this process. The developed discrete and continuous diagnostic models of defect development in tunnel structures allow identifying potentially hazardous areas subjected to manifestation of critical failures and methods of their localization. On the basis of numerical modeling the boundaries of defect-free joint operation of the system “source of impact – geo-mass – sewage underground structure” have been determined. The geotechnical and structural calculations are used to simulate the interaction of the facilities with the soil environment and predict adaptive stress-strain control system parameters. With increasing external anthropogenic and dynamic impacts, modeling zones of urban areas with potentially dangerous sections of underground sewage facilities constitute the basis for development of regulatory documents on monitoring methods and safe development of the geotechnical infrastructure of a megacity.

Inhibition of gastric acid secretion with omeprazole affects fish specific dynamic action and growth rate: Implications for the development of phenotypic stomach loss.

An acid-secreting stomach provides many selective advantages to fish and other vertebrates; however, phenotypic stomach loss has occurred independently multiple times and is linked to loss of expression of both the gastric proton pump and the protease pepsin. Reasons underpinning stomach loss remain uncertain. Understanding the importance of gastric acid-secretion to the metabolic costs of digestion and growth will provide information about the metabolic expense of acid-production and performance. In this study, omeprazole, a well characterized gastric proton pump inhibitor, was used to simulate the agastric phenotype by significantly inhibiting gastric acidification in Nile tilapia. The effects on post-prandial metabolic rate and growth were assessed using intermittent flow respirometry and growth trials, respectively. Omeprazole reduced the duration (34.4%) and magnitude (34.5%) of the specific dynamic action and specific growth rate (21.3%) suggesting a decrease in digestion and assimilation of the meal. Gastric pH was measured in control and omeprazole treated fish to confirm that gastric acid secretion was inhibited for up to 12 h post-treatment (p < 0.05). Gastric evacuation measurements confirm a more rapid emptying of the stomach in omeprazole treated fish. These findings reinforce the importance of stomach acidification in digestion and growth and present a novel way of determining costs of gastric digestion.

Interactive effects of food deprivation state and hypoxia on the respiratory responses of postprandial rock crabs, Cancer irroratus.

Under the background of climate change, increasing attention has focused on the effects of ocean deoxygenation on marine organisms. However, few studies address the effects of different food deprivation states on hypoxia tolerance. We therefore investigated the metabolic responses of the Atlantic rock crab, Cancer irroratus (starved 28-35 days, fasted 3-5 days and recently fed). Starved-crab exhibited the lowest critical oxygen saturation (Scrit), while fed-crab had the highest Scrit. The fed-crab maintained an elevated postprandial oxygen consumption (MO2) even below the Scrit of fasted-crab indicating reserved aerobic scopes for critical activities in severe hypoxia. Following feeding, hypoxia (50% and 20% oxygen saturation, SO2) retarded the specific dynamic action resulting in lower peak MO2 and longer duration. The starved-crab exhibited a lower peak MO2, prolonged duration and higher energy expenditure than fasted-crab after feeding. The decline in arterial PO2 was most pronounced below the Scrit for both fasted- and starved-crab. The higher hemocyanin concentration ([Hc]) of fasted-crab (than starved-crab) suggested they had improved oxygen transport capacity, but hypoxia did not increase [Hc] during the 72-h experiment. Following feeding, the fasted-crab significantly increased L-lactate concentration ([L-lactate]) in 20% SO2, which was not observed in starved-crab. These results suggest starvation may trigger a cross-tolerance to hypoxia. Because crabs can undergo long periods of food deprivation in their natural environment, future studies should consider how this may affect their ability to deal with environmental perturbations.

Experimental investigation and empirical model on damping properties of rock under multistage cyclic loading

The dynamic shear modulus and damping ratio of rock are the main indicators that reflect the dynamic characteristics of rock masses under seismic and dynamic action. The multistage cyclic triaxial compression test is performed on granite and red sandstone under different confining pressures with two stress paths. To reasonably describe the dynamic characteristics of rock, a modified Hardin hyperbolic model is proposed to describe the backbone curve. The relationship between the dynamic shear modulus, damping ratio and cyclic shear strain is analysed under different confining pressure conditions with variable and same amplitude. Furthermore, an empirical formula is established for estimating the dynamic shear modulus and damping ratio. The obtained results show that with increasing shear strain, the damping ratio of red sandstone and granite decreases and then increases under the condition of variable amplitude. When the shear strain is constant, the damping ratio of red sandstone and granite is less affected by the confining pressure. Under the same amplitude conditions, as the shear strain increases, the dynamic shear modulus under different confining pressures shows an increasing trend. The two established empirical formulas can be used to predict the dynamic shear modulus and damping ratio under multistage cyclic loading. This has important reference significance for studying the dynamic characteristics of rock.

Stimuli in 3 Acts: A normative study on action-statements, action videos and object photos

The study of action observation and imagery, separately and combined, is expanding in diverse research areas (e.g., sports psychology, neurosciences), making clear the need for action-related stimuli (i.e., action statements, videos, and pictures). Although several databases of object and action pictures are available, norms on action videos are scarce. In this study, we validated a set of 60 object-related everyday actions in three different formats: action-statements, and corresponding dynamic (action videos) and static (object photos) stimuli. In Study 1, ratings of imageability, image agreement, action familiarity, action frequency, and action valence were collected from 161 participants. In Study 2, a different sample of 115 participants rated object familiarity, object valence, and object-action prototypicality. Most actions were rated as easy to imagine, familiar, and neutral or positive in valence. However, there was variation in the frequency with which participants perform these actions on a daily basis. High agreement between participants' mental image and action videos was also found, showing that the videos depict a conventional way of performing the actions. Objects were considered familiar and positive in valence. High ratings on object-action prototypicality indicate that the actions correspond to prototypical actions for most objects. 3ActStimuli is a comprehensive set of stimuli that can be useful in several research areas, allowing the combined study of action observation and imagery.

Drift characteristics and the multi-field coupling stress mechanism of the pantograph-catenary arc under low air pressure

The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission. Pantograph-catenary arc vertical drift is more severe than the case under normal pressure, as it is easy to develop the rigid busbar, which may lead to the flashover occurring around the support insulators. We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment. Meanwhile, the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed. Moreover, arc drift characteristics and influencing factors are explored. The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized. In order to further explore the mechanism of the above physical process, a multi-field stress coupling model is built, as the multi-stress variation law of arc is quantitatively evaluated. The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored, as the physical mechanism of arc drifting under low pressure is theoretically explained. The research results provide theoretical support for arc suppression in high-altitude areas.

An Experimental Study on Mechanical Properties and Fracture Characteristics of Saturated Concrete under Coupling Effect of Low Temperature and Dynamic Load

Concrete is widely used in bridge foundation, water supply, and drainage engineering. On the one hand, the saturated concrete is always in the saturated state. In the cold winter, northeast China and the alpine region suffer from freezing disaster. On the other hand, it has to continue to bear the dynamic load action of vehicles and running water, which makes the stress state of saturated concrete more complicated under the coupling action of low temperature and dynamic load. In order to study the mechanical properties and fracture characteristics of saturated concrete under the coupling effect of low temperature and dynamic load, the impact compression tests of concrete under normal temperature 20°C, -5°C, -10°C, and -15°C were carried out with a diameter of 74 mm split Hopkinson pressure bar (SHPB). The stress-strain characteristics, energy dissipation, and failure modes of specimens under different low temperatures were studied. From a detailed point of view, the failure mechanism of low-temperature water-saturated concrete is expounded. The results show that under the same dynamic load, the dynamic stress-strain curve of saturated concrete changes obviously with the change of low temperature. The dynamic compressive strength of the natural specimen at room temperature is high while that of the water-saturated specimen is low, and the dynamic compressive strength is opposite at low temperature. At the same temperature, the energy time-history curves of concrete in the saturated state are different from those in the natural state, mainly in the plastic section. The energy time-history curves of saturated concrete are different at different temperatures, and the energy dissipation rate of saturated concrete increases linearly with the decrease of temperature. Under the experimental conditions, the dynamic strength of saturated concrete increases linearly with the decrease of temperature, and the peak strain of saturated concrete decreases linearly with the increase of temperature. With the decrease of temperature, the fragmentation of saturated concrete under the impact of the same air pressure gradually increases, and the integrity of the specimen gradually improves. Low temperature can improve the impact resistance of saturated concrete, which is consistent with the failure law of natural state concrete. The water-saturated low-temperature state of the concrete void is filled with ice crystal particles; for low-temperature water-saturated concrete in the impact of the dynamic load, the microstructure is affected by the ice crystal structure which is not easy to change; the specimen along the axial force direction microdefect development produces a crack, the crack along the parallel to the pressure direction of cracking, through the two ends of the specimen, and finally produces axial splitting tensile damage. The research results have important theoretical significance for the safety design of low temperature saturated concrete structures.

Abstract IA020: Reprogramming of myogenic transcription factors in rhabdomyosarcoma

Abstract Rhabdomyosarcoma, a pediatric malignancy with partial resemblance to undifferentiated skeletal muscle, is characterized by high expression of myogenic-lineage transcription factors such as MYOD1 and MYOG. Despite high expression of these transcription factors, which in normal muscle result in differentiation, RMS cells fail to differentiate, suggesting the presence of factors that inhibit their normal differentiation-promoting functions. In this talk, I will present data that the key muscle transcriptional regulator, SIX1, which in development activates the myogenic regulatory factors (MRFs) and promotes muscle differentiation, in fact inhibits differentiation in fusion-negative (FN) RMS. SIX1 holds FN-RMS cells in a progenitor-like state by altering the chromatin landscape and causing MYOD1, a key MRF, to preferentially bind to regulatory regions of genes permissive to growth rather than differentiation. Loss of SIX1 results in re-localization of MYOD1 to promoters/enhancers of genes associated with differentiation, and further results in increased binding of MYOG at such loci. Altered binding of MYOD1 and MYOG in response to SIX1 loss results in marked inhibition of RMS growth in vivo, via induction of differentiation. These data suggest that SIX1 acts as a master regulatory factor controlling the fate of RMS cells. Data will be presented that suggest dynamic actions of SIX1 and its co-factors throughout normal muscle differentiation, whereby high levels of SIX1 expressed in early muscle differentiation may mimic a transcriptional state seen in RMS. We hypothesize that the specific levels of SIX1, combined with a unique combination of transcriptional co-factors, reprogram genome-wide binding of MRFs to different promoter/enhancer sites at specific developmental time points, and that RMS is trapped in an early developmental state where SIX1 represses differentiation via genome-wide alterations in MRF binding that favor growth. Understanding the co-factors that work with SIX1 to alter chromatin state and MRF binding may enable the discovery of novel targets whose inhibition could serve as a relatively non-toxic treatment to restore normal developmental processes and inhibit RMS progression. Citation Format: Heide L. Ford, Jessica Y. Hsu, Etienne P. Danis, Stephanie Nance, Jenean H. O’Brien, Annika L. Gustafson, Veronica M. Wessells, Andrew E. Goodspeed, Jared C. Talbot, Sharon L. Amacher, Paul Jedlicka, Joshua C. Black, James C. Costello, Adam D. Durbin, Kristin B. Artinger. Reprogramming of myogenic transcription factors in rhabdomyosarcoma [abstract]. In: Proceedings of the AACR Special Conference: Sarcomas; 2022 May 9-12; Montreal, QC, Canada. Philadelphia (PA): AACR; Clin Cancer Res 2022;28(18_Suppl):Abstract nr IA020.

Pain modulation in the spinal cord.

The sensory inflow from the periphery that triggers innocuous and painful sensations is highly complex, capturing key elements of the nature of any stimulus, its location, intensity, and duration, and converting this to dynamic action potential firing across a wide population of afferents. While sensory afferents are highly specialized to detect these features, their input to the spinal cord also triggers active processing and modulation there which determines its output, to drive the sensory percept experienced and behavioral responses. Focus on such active spinal modulation was arguably first introduced by Melzack and Wall in their Spinal Cord Gate Control theory. This theory has had a profound influence on our understanding of pain, and especially its processing, as well as leading directly to the development of clinical interventions, and its historical importance certainly needs to be fully recognized. However, the enormous progress we are making in the understanding of the function of the somatosensory system, means that it is time to incorporate these newly discovered features into a more complex and accurate model of spinal sensory modulation.

Impact resistance and simplified evaluation method for square CFST members subjected to transverse impact

Recently, the impact behavior and anti-impact design of concrete-filled steel tubes (CFSTs) have attracted increasing attention; the existing analytical theories have mainly focused on equivalent static methods. Thus, this study presents numerical and analytical analyses of simplified evaluation methods for square CFST members subjected to transverse impacts, by adopting dynamic impact action (i.e., impact mass and impact velocity) to evaluate the impact resistance. A finite element model was first established and benchmarked based on 38 test results collected from existing studies with a wide range of test parameters. The impact process, distribution and development of the internal force, and development of the stress, strain, and strain rate were comprehensively analyzed. The dynamic overall buckling of the CFST members under coupling actions of the axial load and transverse impact was investigated and compared with the control groups for CFST members without an axial load. Based on the parametric analyses, the yield strength of steel, section width, steel ratio, and axial load level (n) are important factors affecting the impact resistance. A simplified formula was therefore proposed to evaluate the impact resistance of CFST members with n ≤ 0.5. A machine learning method was also employed to predict the impact resistance of CFST members covering a wider range of axial load levels (n ≤ 0.9).