Acceleration Duration Research Articles

Analysis of time and cost using time cost trade off method in pressure vessel project

One of the construction companies got a Pressure Vessel project job. During the process of working on the project, it was delayed from the predetermined date so that the company had to pay a fine of 0.2% every day. So it is necessary to analyze project scheduling in order to get the optimal time and cost of working on this project. The methods used in this research are Time Cost Trade Off (TCTO), Precedence Diagram Method (PDM) and crashing. Acceleration is carried out on all critical paths contained in fabrication activities. This study uses alternatives to accelerate the addition of 50% and 75% labor. The results of this study obtained the optimal time and cost with the alternative of adding 75% labor. The resulting acceleration duration is 75 days faster than the actual duration, with costs incurred of Rp. 161,386,836, -, resulting in a 56% decrease from the actual duration cost of Rp. 286,961,745, -. Analysis of the S-curve found that the accelerated duration can be completed faster than the actual duration because, the curve line on the accelerated duration is more sloping closer to the y-axis indicating greater progress each week.

A Machine-Learning-Based Software for the Simulation of Regional Characteristic Ground Motion

Ground-motion simulations provide input time history data required for designing and assessing structures; however, the simulations conducted by the currently available tools only match the design spectrum without verifying if the statistical characteristics of the spectrum and duration are satisfied. A ground-motion simulation software was developed to resolve these issues. The developed software employs machine learning methods to match the amplitude, spectrum, and duration features of the target region. Principal component analysis is employed to extract features from the actual ground-motion database to detect characteristic ground motions and predict the target acceleration amplitude, response spectrum, and duration, based on the response spectrum and duration prediction equations. The results show that the simulated ground motion can match the amplitude, spectrum, and duration characteristics well. Therefore, the simulated ground motion can provide more reasonable input for the structure. Moreover, the developed software provides visualization functions that enable the user to determine the target area and obtain the amplitude field intuitively.

Evolution Laws of Stress–Energy and Progressive Damage Mechanisms of Surrounding Rock Induced by Mining Disturbance

The rock burst induced by the mutual disturbance of mining and excavation is significantly influenced by high static load stress and external dynamic load disturbance. In this paper, the evolution characteristics and progressive damage mechanism of surrounding rock in the process of mutual disturbance of mining and excavation are systematically studied. The results show that the evolution of surrounding rock stress can be roughly divided into three stages: rapid rise in the early stage, continuous rise and step-like decline in the middle stage, and slow rise in the late stage. In the process of parallel mining, the overlying rock movement above the goaf shows the sequence of horizontal penetration of tiny fissures—fracture intensification transition to stratification—non-coordinated caving of middle–low overlying rock—obvious horizontal cracks in the upper key layer. Only under the quasi-static loading mining action does the upper key layer not reach the breaking condition. The wave side of the heading face which is close to the focal point is affected by the dynamic load disturbance, the acceleration duration is short, and the attenuation is relatively fast, so it is the area prone to the earliest impact failure in the face of mining disturbance. The conclusion is helpful to deepen the understanding of the coal burst mechanism of mutual disturbance of mining and excavation.

Study on the Simulation Test Method for Mechanical Over-loading of Initiator

In view of the needs of the mechanical over-load test evaluation of the second and third generation Initiators in the combat environment, the numerical simulation combined with the experimental verification method is used to study the influence of the material, outer diameter and length of the pulse shaper on the over-loading wave. The mechanical over-loading index parameters of the tooling in different states are obtained. The results show that as the length of the shaper increases gradually, the speed of the tooling target increases gradually and slowly, which prolongs the impact overload time. With the increase of the diameter, the acceleration time of the tooling target gradually shortens. When it increases to 44, the acceleration duration is not long. Steel with the diameter of 20mm and the length of 30mm is used as pulse shaper. When the bullet speed is 250m/s, the peak acceleration of the tooling target can reach 150,000 g, and the pulse width is 200 microseconds, which meets the requirements of the overload environment test for penetrating the steel target plate.

Free-fall drop test with interchangeable surfaces to recreate concussive ice hockey head impacts

Ice hockey has one of the highest concussion rates in sport. During collisions with other players, helmets offer limited protection. Various test protocols exist often requiring various types of laboratory equipment. A simplified test protocol was developed to facilitate testing by more researchers, and modifications to certification standards. Measured kinematics (acceleration vs. time trace shape, peak accelerations, and impact duration) of a Hybrid III headform dropped onto different surfaces were compared to published laboratory representations of concussive impacts. An exemplary comparison of five different helmets, ranging from low (US$50) to high cost (US$300), covering a range of helmet and liner designs, was also undertaken. Different impact conditions were created by changing the impact surface (Modular Elastomer Programmer pad, or 24 to 96 mm of EVAZOTE-50 foam with a Young's modulus of ~ 1 MPa), surface orientation (0 or 45°), impact site, and helmet make/model. With increasing impact surface compliance, peak accelerations decreased and impact duration increased. Impacts onto a 45° anvil covered with 48 mm of foam produced a similar response to reference concussive collisions in ice hockey. Specifically, these impacts gave similar acceleration vs. time trace shapes, while normalized pairwise differences between reference and measured peak acceleration and impact duration, were less than 10% (difference/maximum value), and mean (± SD) of accelerations and duration fell within the interquartile range of the reference data. These results suggest that by modifying the impact surface, a free-fall drop test can produce a kinematic response in a helmeted headform similar to the method currently used to replicate ice hockey collisions. A wider range of impact scenarios, i.e., fall onto different surfaces, can also be replicated. This test protocol for ice hockey helmets could facilitate simplified testing in certification standards and research.

On the dynamic response of rectangular liquid storage structure subjected to blast-induced ground shock

The paper aims to investigate the dynamic response of the rectangular liquid storage structure (LSS) under blast-induced ground shock. A two-way fluid–structure interaction (FSI) finite-element model was established, and its effectiveness was verified using a laboratory experiment conducted on an explosion shock and vibration simulation platform (ESVSP). The relationship between the mode shape and frequency was explored using modal analysis. Higher-order modes are characterised by more half-waves preferentially forming in the short sidewall and adjacent sidewalls vibrating in the same direction. The sensitivities of the deflection, hydrodynamic pressure, and equivalent strain in relation to the peak, duration, and loading direction of ground acceleration (i.e. PGA, TGA, and DGA) were highlighted. The results showed that the LSS response magnitude increases linearly as the PGA increases, whereas it first increases and then decreases as the TGA is extended. Furthermore, a feasible method for building a standard shock response spectrum (SRS) was proposed, in which the ground-shock effects were divided into mitigation, enhancement, and equality regions. It is beneficial to evaluate the extreme value of the LSS response to ground shock. The LSS vibration is dominated by different modes as the DGA is varied. The deformation mechanism was revealed by considering the boundary conditions and force characteristics. The conclusion indicates that the bottom middle of the sidewall, as a weak link, needs to be protected.

Dynamic Analysis and Seat Selection of Bus Driving Comfort under Different Road Conditions

The comfort of a bus running on different road conditions is a matter of public concern. In this paper, the differential equations of motion are established for a bus running on different road conditions and the whole driving process is mechanically analyzed. Firstly, the bump degree at different positions is quantitatively analyzed and it is found that the rear row is bumpier on different roads. Then, the relationship between the speed of the bus and the vertical displacement and acceleration is quantitatively described. Regardless of the speed, a similar displacement and acceleration will be eventually achieved, but the speed is higher, and the duration of maximum displacement and acceleration is longer. When the speed is 8 m/s, resonance occurs on the bus during road condition II. Finally, the change in vertical displacement and acceleration under the action of different spring stiffness coefficient ratios of the front and rear wheels is quantitatively analyzed. High stiffness ratios mean less displacement and acceleration. By establishing an actual excitation road surface, the differential equations and analytical solutions in this paper can be used to roughly analyze the mechanical response of a traveling bus. These results can provide some guidance for the design and driving of buses.

Objective evaluation index for the comprehensive performance of intelligent vehicle lane-changing trajectory

Lane-changing behaviour is one of the most important and basic driving behaviours. Intelligent and connected vehicles must face lane-changing scenarios to achieve autonomous driving. To improve the rationality of lane-changing trajectory planning for intelligent vehicles, by analysing numerous real vehicle lane-changing trajectories in the German HighD natural driving dataset, a dimensionless lateral quantification balance index is proposed to realise a comprehensive and objective evaluation of the degree of human-likeness of lane change trajectory planning. Focused on the lateral kinematic characteristics of lane changing, a lane-changing trajectory extraction method based on the peak-to-peak value of lateral acceleration is proposed. Lateral displacement, lateral velocity, lateral acceleration and lane-changing duration are extracted from natural driving data, and the correlations between the parameters are revealed to deduce the lateral quantification balance index. With several common parametric lane-changing trajectory models of intelligent vehicles, such as sine, quintic polynomial, Gaussian and hyperbolic tangent and fifth-order Bessel models, as examples, the index values of each lane-changing trajectory model are calculated and obtained. Results show that the proposed index can balance the different requirements in lane-changing efficiency and comfort of the trajectory parameters during the lane-changing process, thus achieving a comprehensive quantitative evaluation of lateral stability, efficiency and comfort. This research establishes an intuitive and concise objective function for human-like trajectory planning and provides a basis for trajectory tracking control and real-time dynamic correction of intelligent vehicles.

Simultaneous measurements of inertial acceleration and flow structures during coarse-grain entrainment under steady currents

An instrumented smart sediment particle (SSP) is used to investigate the entrainment of spherical coarse grains resting on a rough bed comprising semi-spherical elements. The SSP contains electronic sensors facilitating the direct measurement of tri-axial accelerations. The instantaneous flow field is measured simultaneously using two-dimensional particle tracking velocimetry (PTV), enabling joint analysis of accelerations and flow structures during entrainment. Two different initial placement positions of the SSP are tested. Both particle vibration and complete entrainment events are observed in experiments. Results show larger maximum acceleration and longer duration of motion with more significant obstruction by surrounding bed roughness, which entails greater momentum transfer at the initiation of entrainment. During vibration events, acceleration can occasionally reach the threshold value but with no entrainment because of the low persistence of relevant flow features inducing energy transfer. Further analysis on instantaneous flow structures indicates that, at the threshold flow condition, the occurrence and persistence of the “sweep-outward interaction” quadrant motion sequence (i.e. Q4-Q1 sequence) in front the particle, combined with the transient increase of vorticity due to the passage of clockwise vortices above the particle, is the key to energy transfer and complete entrainment. The Q4-Q1 sequence may either be caused by the lower half of anti-clockwise vortices or occur independently. Generally, the joint analysis of acceleration and flow structures provides a new perspective to studying coarse grain entrainment, especially a potential to relate near-bed flow structures to the status of particle motion in the future.

Repeated stage exposure reduces music performance anxiety.

High heart rate (HR) and restlessness are two important features of music performance anxiety (MPA). In a case report of a cellist suffering from this condition, we showed that HR and restlessness decreased after repeated live performances of the same musical excerpt, thereby positively modulating objective performance criteria and subjective components. Here, we largely replicate these results in a group of 18 string players reporting MPA. Objective measurement devices included a miniaturized electrocardiogram monitor and three 3-axis accelerometer loggers. Subjective measures included the Multidimensional Mental Health Questionnaire (MDBF) and a customized visual analogue scale (VAS) questionnaire for MPA. Non-artistic performance errors were assessed by music experts using a composite score for technical playing errors (i.e., intonation errors, omission of notes, and bowing noise). Data were collected from each study participant during three brief public solo performances of the same musical excerpt, with each performance occurring before a new audience on the same day. From the 1st to the 3rd performance, HR, VAS, and playing error scores decreased significantly. MDBF (RU scale) showed a significant increase in calmness from the 1st to the 3rd performance on stage. HR and RU, VAS, and RU, as well as bow acceleration and overall duration of playing correlated significantly across participants and performances. We conclude that repeated stage exposure significantly reduces HR as well as restlessness and playing errors linked to MPA. Public performances are still successful when HR is significantly higher than during rest periods. These results underscore the importance of stage training to become accustomed to realistic public self-exposure. Musicians - especially students - should consider this component of stage training as an integral part of their practice routine. Therefore, stage training can reduce MPA, promote better live performances and prevent stress-related mental disorders and physical injuries. These result from excessive self-exercise strategies common in musicians experiencing MPA. HR monitoring should be an integral part of evaluating the effectiveness of interventions for better MPA management and efficient performance training.

Impact of ground-motion duration on nonlinear structural performance: Part II: site- and building-specific analysis

This study’s Part I proved that ground-motion duration could play an important role when assessing the nonlinear structural performance of case-study inelastic single degree-of-freedom systems. However, quantifying duration effects in many practical/more realistic engineering applications is not trivial, given the difficulties in decoupling duration from other ground-motion characteristics. This study’s Part II, introduced in this article, explores the impact of duration on nonlinear structural performance by numerically simulating the structural response of realistic case-study reinforced concrete bare and infilled building frames. Advanced computational models incorporating structural components’ cyclic and in-cycle strength and stiffness deterioration, and destabilizing [Formula: see text] effects are used. The proposed methodology relies on the generalized conditional intensity measure approach to select ground motions. This allows selecting records consistent with the seismic hazard at a target site, both in terms of spectral shape and duration. Those are employed as input to cloud-based nonlinear structural response analyses. Variance analysis is used to quantify the impact of duration on structural response. Furthermore, vector-valued fragility and vulnerability models alternatively using peak- and cumulative-based engineering demand parameters are derived. Results show that higher damage/loss estimates can be attained as ground-motion duration increases. Relative differences up to 44% are found in fragility median values for a pre-code reinforced concrete infilled frame when comparing scalar and vector-valued fragility models conditioned on average pseudo-spectral acceleration and significant durations up to 35 s.

Numerical Study on Thermodynamic Coupling Characteristics of Fluid Sloshing in a Liquid Hydrogen Tank for Heavy-Duty Trucks

The large-amplitude sloshing behavior of liquid hydrogen in a tank for heavy-duty trucks may have adverse effects on the safety and stability of driving. With successful application of liquid hydrogen in the field of new energy vehicles, the coupled thermodynamic performance during liquid hydrogen large-amplitude sloshing becomes more attractive. In this paper, a three-dimensional numerical model is established to simulate the thermodynamic coupling characteristics during liquid hydrogen sloshing in a horizontal tank for heavy-duty trucks. The calculation results obtained by the developed model are in good agreement with experimental data for liquid hydrogen. Based on the established 3D model, the large-amplitude sloshing behavior of liquid hydrogen under extreme acceleration, as well as the effects of acceleration magnitude and duration on liquid hydrogen sloshing, is numerically determined. The simulation results show that under the influence of liquid hydrogen large-amplitude sloshing, the convective heat transfer of fluid in the tank is greatly strengthened, resulting in a decrease in the vapor temperature and an increase in the liquid temperature. In particular, the vapor condensation caused by the sloshing promotes a rapid reduction of pressure in the tank. When the acceleration magnitude is 5 g with a duration of 200 ms, the maximum reduction of ullage pressure is 1550 Pa, and the maximum growth of the force on the right wall is 3.89 kN. Moreover, the acceleration magnitude and duration have a remarkable influence on liquid hydrogen sloshing. With the increase in acceleration magnitude or duration, there is a larger sloshing amplitude for the liquid hydrogen. When the duration of acceleration is 200 ms, compared with the situation at the acceleration magnitude of 5 g, the maximum reductions of ullage pressure decrease by 9.46% and 55.02%, and the maximum growth of forces on the right wall decrease by 80.57% and 99.53%, respectively, at 2 g and 0.5 g. Additionally, when the acceleration magnitude is 5 g, in contrast with the situation at a duration of acceleration of 200 ms, the maximum-ullage-pressure drops decrease by 8.17% and 21.62%, and the maximum increase in forces on the right wall decrease by 71.80% and 88.63%, at 100 ms and 50 ms, respectively. These results can provide a reference to the safety design of horizontal liquid hydrogen tanks for heavy-duty trucks.

Optimasi Waktu dan Biaya Pelaksanaan Proyek Jalan dengan Metode Crash Program (Studi Kasus: Pemeliharaan Jalan Kecamatan Tenggarong Seberang dan Tenggarong

Time, cost, and quality are three important elements of schedule that should be made in detail in order to assist in the evaluation of the project. In this research, we analyzed the acceleration of project completion duration. The case study on this research was taken in Tenggarong Seberang District and Tenggarong District. The method used in this research is the crash program method with the alternative implementation with a variety of added work hours and manpower, which are adding 1 hour, 2 hours, and 3 hours of work hours also the alternative of adding 25% and 50% of the manpower. This research aimed to determine the total time and cost of implementing the project after the crashed and determined the results of an optimal acceleration alternative by comparing the results of the analysis of the application of the crash program method. The work was accelerated (crashed) in this research is work that is on the critical path. The results of the application of the crash program method with the addition of working hours and manpower obtained an efficient acceleration alternative, namely the addition of 3 hours of working hours which resulted in the acceleration duration being 67 days or 25.56% faster than the normal duration of 90 days with a total acceleration cost of Rp 1,213,717,588.81 or 0.213% lower than the normal total cost of Rp 1,216,303,515.90.

Determination of dynamic loads in the crane lifting mechanism

Loading and unloading is an integral part of the technological process of construction. To perform these works mostly use cranes of different types.
 To ensure trouble-free operation and increase the reliability of cranes in the calculation of structures and components of their work equipment, it is important to take into account dynamic loads, which are several times higher than static loads.
 Elements of dynamic loads of the crane lifting mechanism are its elastic components - ropes and shafts, which are deformed under the action of loads. The magnitude of this deformation of the elements are taken into account by the coefficients of elasticity or flexibility of linear and torsional or their inverse value - the coefficients of rigidity. These coefficients depend on the linear or angular deformations, respectively.
 Due to the fact that the mechanism of lifting a load consists of a large number of elastic elements, the addition and solution of equations to determine these coefficients becomes a difficult task. In order to simplify the equations and these calculations, the paper recommends the above scheme of calculations according to which the rest of all elements of the mechanism are reduced to its first element (engine). This greatly simplifies the equations to be solved and determines the values ​​of the coefficients of elasticity or stiffness of the elements of the dynamic loads of the mechanism of lifting the load of cranes.
 According to a similar scheme is also determined by the moments of inertia of the mechanism of lifting the load during periods of acceleration and deceleration, the components of the values ​​that affect them. The equations for determining the terms of transients of the lifting mechanism (duration of acceleration and braking) are derived.
 The method of determining the coefficients of elasticity and stiffness of the elements of dynamic loads, moments of inertia, duration of acceleration and deceleration of the lifting mechanism can greatly simplify the solution of complex equations and determine their values ​​with sufficient accuracy.

The potential mechanisms of TBBPA bis(2-hydroxyethyl) ether induced developmental neurotoxicity in juvenile zebrafish (Danio rerio)

TBBPA bis(2-hydroxyethyl) ether (TBBPA-DHEE), one of the main derivatives of TBBPA, has been widely detected in environmental samples and been discovered to be potential neurotoxic. In this study, the juvenile zebrafish were selected as the research subject to explore the neurotoxicity and its mechanism of low-dose TBBPA-DHEE exposure, and to reveal the neurotoxicity susceptibility in different sexes. Behavioral studies revealed that TBBPA-DHEE could significantly reduce the swimming velocity, maximum acceleration and cumulative duration of high-speed mobility, significantly increasing the cumulative duration of low-speed mobility and average social distance. It significantly reduced the contents of ATP, glutamate and Ca2+ in the whole brain. The histopathological study demonstrated that TBBPA-DHEE could cause brain tissue damage in female and male juvenile zebrafish. The comprehensive data analysis indicated that female zebrafish were more susceptible to TBBPA-DHEE exposure than male zebrafish. Transcriptomic analysis showed that TBBPA-DHEE could significantly affect the expressions of behavioral and development-related genes. Furthermore, female and male juvenile zebrafish have different molecular mechanisms of neurotoxicity. For female juvenile zebrafish, the potential mechanism of neurotoxicity could be that it interfered with the feedback regulation of nerves by affecting the related genes expressions in the signaling pathways such as Ca2+ signaling, Wnt signaling and synapses. For male juvenile zebrafish, the potential mechanism of neurotoxicity may be through affecting the expression of related genes in hormones and neuro-related genes. This research could reveal the potential neurotoxicity of TBBPA-DHEE to aquatic organisms, which will be helpful to reveal the health effects of the emerging environmental pollutants.

Offshore ground motion characteristics on the horizontal PGA, spectral acceleration, frequency content and significant duration from the 2021 Mw 7.1 and 2022 Mw 7.4 offshore earthquakes near the Japan Trench area

The two large offshore earthquakes that occurred in Japan's eastern Fukushima region on February 13, 2021, Mw 7.1 and March 17, 2022, Mw 7.4 are the two largest offshore earthquakes recorded by the large-scale permanent ocean-bottom seismograph network (S-net). The two earthquakes are both subduction slab earthquakes and caused great damage to onshore structures. The offshore ground motions from the S-net within a fault distance of 300 km were selected to investigate the characteristics of the strong offshore motions. The onshore ground motions are also selected from the K-net to compare the differences in offshore and onshore ground motions. These onshore and offshore datasets were used to calculate the representative ground motion parameters: the peak ground acceleration (PGA), spectral acceleration, frequency content and significant duration of the earthquakes. Here we present the comparison of the offshore and onshore ground motions in amplitude, duration and frequency content, as well as the applicability of the representative onshore ground motion model (GMM) to the offshore region. Additionally, we provide the spatial contours of the parameters used in this study and the residual analysis to examine the effects of the water depth, sedimentary layer and station deployment method on the offshore ground motions. We found that the PGA and spectral accelerations of unburied seafloor stations are larger than those of buried stations, and the attenuation rate observed from the spatial contours between the offshore and onshore regions is different, which shows the necessity of proposing a new prediction model for the PGA and spectral accelerations in offshore regions. The significant duration of offshore ground motions is consistent with the onshore prediction model of significant duration in the subduction zone but is on average greater than those of onshore ground motions. For the frequency content, there is no prediction model for subduction zones at present. The frequency-content parameters of offshore ground motions are relatively consistent with the frequency-content model for greater depths. On the whole, the complex environment at the ocean bottom has the most significant influence on the spectral accelerations over long periods and has some influence on the duration and frequency content, but the overall difference is smaller than the PGA and spectral accelerations.

Clinical associations of fetal heart rate accelerations as derived from transabdominal fetal electrocardiograms

ObjectiveTo determine the value of quantifying accelerations of the fetal heart rate (FHR), as collected non-invasively during pregnancy, as a proxy for fetal movements. Study DesignThe study consists of a prospective collection of research material with retrospective analyses of the collected fetal electrocardiograms (ECGs), done in a homogeneous population in a low socioeconomic residential area of Cape Town, South Africa, as part of the Safe Passage Study. Recruitment and follow-up were done from August 2007 to August 2016. Maternal and fetal ECGs were collected non-invasively at various gestational ages, for approximately 30–60 min at a time in 4418 pregnant women. After processing of the signal, the number and duration of accelerations and the area under the acceleration curve of the FHR were calculated and compared with the pulsatility index (PI) of the uterine, umbilical, and middle cerebral arteries, common medical conditions, tobacco, alcohol, marijuana, and methamphetamine use and z-scores of the birthweight (BWZS). ResultsOf the total, 2777, 691, and 3879 women were at gestational ages of 20–24, 28–32 and 34–38 weeks respectively. At 20–24 weeks duration of accelerations was significantly longer in women who used marijuana (p = 0.014) or methamphetamine (p < 0.001) when compared to nonusers. At 28–32 weeks the duration of accelerations was significantly shorter in hypertensive women (p = 0.003) and significantly longer in women who used methamphetamine (p = 0.015). At 34–38 weeks the number of accelerations were significantly less in women who had hypertension ((p = 0.01) or stillbirths (p = 0.028) and the duration significantly shorter in hypertensive women (p = 0.007) and significantly longer in women who used marjuana (p = 0.003) or methamphetamine (p = 0.028). The acceleration area was significantly smaller (p = 0.02) in women who has stillbirths. Duration of accelerations was significantly longer in users of nicotine and alcohol when compared with that of abstainers. Birthweight z-score correlated significantly with number of accelerations (p < 0.01) and the acceleration area (<0.01). There was a significant negative correlation between the number of accelerations (p < 0.01) and acceleration area (p < 0.01) and the PI of the uterine artery at 34–38 weeks. ConclusionsCalculation of the acceleration parameters of the FHR during pregnancy may provide useful information for evaluating fetal development.

Effects of hollow carbon nanospheres on combustion performance of Al/Fe2O3-based nanothermite sticks

Effects of hollow carbon nanospheres on the combustion behavior of Al/Fe2O3-based thermite sticks are studied in this work. The results from laser ignition experiments confirm that the presence of hollow carbon nanospheres not only can reduce the ignition threshold because of the excellent laser energy absorption capacity, but also play a positive role in heightening the heat transfer efficiency by introducing pores and increasing heat-flow output during the combustion process. The video snapshots indicate that the combustion propagation stages, including ignition, acceleration, and steady combustion, all improved significantly with the suitable inclusion of hollow carbon nanospheres. The modified composites containing 4 wt% hollow carbon nanospheres exhibit a minimum ignition threshold (28 mJ), shorter acceleration duration (76 ms), higher combustion rate (10.10 cm/s) and steady combustion temperature (~2850 K). Furthermore, it exhibits a remarkable enhancement in energy release (537.36 J/g) and pressure output (0.91 Mpa), which are 1.67 and 1.34 times than that of pristine thermite sticks, respectively. Overall, this work demonstrates that the high porosity structure and heat-flow release of thermite sticks facilitate convective heat transfer and eventually improve the combustion behavior, which can provide some reference in the design and optimization of microstructure and composition in micro-energetic devices.

Hydration kinetics and microstructure evolution of NaCl-mixed tricalcium silicate pastes

The hydration kinetics of tricalcium silicate (C3S) pastes mixed with different concentrations of NaCl solutions were investigated by performing isothermal calorimetry tests. At the same time, the Boundary Nucleation and Growth (BNG) model was used to analyze the calorimetry data. The model fitted well with the calorimetric results. C3S pastes mixed with NaCl solutions followed a similar reaction path to those prepared with DI water, with an accelerated reaction rate as the NaCl concentration increased. The specific parameters, such as the induction and acceleration durations, were quantified, and the relationship was established. The BNG modelling results indicated that the increasing NaCl concentration significantly increased the nucleation rate of the hydration products while decreasing their growth rate slightly. That was supported by the SEM and STEM observations. The presence of NaCl modified the morphology of the early-age calcium silicate hydrates (C-S-H) to relatively shorter and thinner fibres, which had a more compact microstructure and higher micromechanical properties than those in pure C3S pastes.

Functional connectivity correlates of reduced goal-directed behaviors in behavioural variant frontotemporal dementia

We explored the resting state functional connectivity correlates of apathy assessed as a multidimensional construct, using behavioral metrics, in behavioral variant frontotemporal dementia (bvFTD). We recorded the behavior of 20 bvFTD patients and 16 healthy controls in a close-to-real-life situation including a free phase (FP—in which actions were self-initiated) and a guided phase (GP—in which initiation of actions was facilitated by external guidance). We investigated the activity time and walking episode features as quantifiers of apathy. We used the means ((FP + GP)/2) and the differences (FP-GP) calculated for these metrics as well as measures by questionnaires to extract apathy dimensions by factor analysis. We assessed two types of fMRI-based resting state connectivity measures (local activity and seed-based connectivity) and explored their relationship with extracted apathy dimensions. Apathy in bvFTD was associated with lower time spent in activity combined with walking episodes of higher frequency, lower acceleration and higher duration. Using these behavioral metrics and apathy measures by questionnaires, we disentangled two dimensions: the global reduction of goal-directed behaviors and the specific deficit of self-initiation. Global apathy was associated with lower resting state activity within prefrontal cortex and lower connectivity of salience network hubs while the decrease in self-initiation was related to increased connectivity of parietal default-mode network hubs. Through a novel dimensional approach, we dissociated the functional connectivity correlates of global apathy and self-initiation deficit. We discussed in particular the role of the modified connectivity of lateral parietal cortex in the volitional process.