Contact Duration Time Research Articles

An optimization approach to establish dynamical equivalence for soft and rigid impact models

This paper studies a computational approach aimed at establishing equivalent dynamical responses within oscillatory impacting systems subject to soft and rigid constraints. The proposed method incorporates an adaptive differential evolution algorithm with the Metropolis criterion to determine the stiffness and damping parameters of the soft constraint for a prescribed coefficient of restitution governing the rigid constraint. The proposed algorithm aims to establish an equivalent dynamical response of the two models based on constraints regarding energy dissipation and contact time duration. Upon examining the dynamical responses of the two impact cases, they exhibit nearly identical outcomes in the two-parameter bifurcation diagrams when subjected to a large restitution coefficient. However, discrepancies arise between the results of the two models when the restitution coefficient is low. Detailed numerical tests, conducted using the proposed method, demonstrate enhanced effectiveness compared to previous techniques, such as the prediction formulas for the different related soft impact model outlined by Okolewski and Blazejczyk-Okolewska [Chaos 31(8), 083110 (2021)]. This method not only finds application in experimentally identifying the physical properties of an impact surface but also provides convenience in employing soft models within impacting systems, which could then avoid potential inaccuracies in handling discontinuities by some integrator during velocity jumps before and after impacts.

Mechanical Asymmetries during Treadmill Running: Effects of Running Velocity and Hypoxic Exposure

Studies evaluating mechanical asymmetry across a range of running velocities during treadmill runs have yielded inconsistent findings, while the impact of additional hypoxic exposure has never been investigated. The aim of this study was to characterize the effects of manipulating running velocity and hypoxic exposure on gait asymmetry during treadmill running. Eleven trained individuals performed seven runs at different velocities (8, 10, 12, 14, 16, 18, and 20 km·h−1) in a randomized order, each lasting 45 s. The running took place on an instrumented treadmill for normoxia (FiO2 = 20.9%), moderate hypoxia (FiO2 = 16.1%), high hypoxia (FiO2 = 14.1%), and severe hypoxia (FiO2 = 13.0%). Vertical and antero-posterior ground reaction force recordings over 20 consecutive steps (i.e., after running ∼25 s) allowed the measurement of running mechanics. Lower-limb asymmetry was assessed from the ‘symmetry angle’ (SA) score. Two-way repeated-measures ANOVA (seven velocities × four conditions) was used. There was no significant difference in SA scores for any of the biomechanical variables for velocity (except contact time and braking phase duration; p = 0.003 and p = 0.002, respectively), condition, or interaction. Mean SA scores varied between ∼1% and 2% for contact time (1.5 ± 0.8%), flight time (1.6 ± 0.6%), step length (0.8 ± 0.2%), peak vertical force (1.2 ± 0.5%), and mean vertical loading rate (2.1 ± 1.0%). Mean SA scores ranged from ∼2% to 5% for duration of braking (1.6 ± 0.7%) and push-off phases (1.9 ± 0.6%), as well as peak braking (5.0 ± 1.9%) and push-off forces (4.8 ± 1.7%). In conclusion, the trained runners exhibited relatively even strides, with mechanical asymmetries remaining low-to-moderate across a range of submaximal, constant running velocities (ranging from 8 to 20 km·h−1) and varying levels of hypoxia severity (between normoxia and severe hypoxia).

Chitosan based radiation crosslinked and grafted matrix: An environment friendly adsorbent for dye uptake

The adsorption capacity of [2-(methacryloxy) ethyl] trimethylammonium chloride (MAETC) grafted-crosslinked chitosan (CRChitosan-g-MAETC) using ionizing radiation was evaluated for adsorption of anionic dyes namely Acid Blue-25 (AB25), Reactive Orange-16 (RO16) and Reactive Red-120 (RR120) from manufactured aqueous solutions. Effect of various experimental variables like dye concentration, pH, contact time duration, temperature and adsorption on adsorbent grafted to different extent on adsorption kinetics and on equilibrium adsorption was investigated. To understand the equilibrium adsorption of dyes on the adsorbent the data was fitted into Langmuir, Freundlich and Temkin adsorption isotherms while adsorption kinetics was examined using pseudo-first order, pseudo-second order and intraparticle diffusion kinetic models. It was observed that the adsorption of all the three anionic dyes studied was better explained by the Freundlich model. Adsorption extent of dye varied with number of charge sites on the dye molecule. The adsorption of all the three anionic dyes followed pseudo-second order kinetics. Thermodynamic parameters such as standard enthalpy (ΔHo), standard entropy (ΔSo) and standard free energy (ΔGo) were estimated. The radiation grafted cationic adsorbent showed promising adsorbent properties for removal of anionic dyes.

Removal of Fluoride using low-cost materials as an adsorbent

In the present work, locally available adsorbents such as Sugarcane Bagasse, Coconut Husk and Rice Husk were tested for defluoridation. The characterizations of the three adsorbents were carried out to study the effect of pH, different doses of adsorbent and variation in initial concentration of fluoride at constant temperature of 30±2 °C on removal efficiency of fluoride. It was observed that as the pH value increased, the removal efficiency increased to some time and later became constant in case of Sugarcane Bagasse at adsorbent dose of 0.5g/100 ml at contact time duration of 75 minutes. The removal efficiency decreased with gradual increase in initial fluoride concentration due to the capacity of adsorbent materials. The study revealed the applicability of low-cost adsorbents for the removal of fluoride from drinking water.

Investigation on dynamic bifurcation buckling of a composite column impacted by a mass in hygrothermal environment

AbstractThe impacted buckling problems of the slender composite column have a particular essential engineering meaning for the civil engineering, mechanical engineering, and nuclear power engineering fields. Specifically, the contact duration time and buckling time are of importance to design nuclear reactor. This paper mainly concentrates on the dynamic buckling of a slender composite column subjected to a sudden axial load in a hygrothermal environment. In this study, the distribution of strain of the column is considered nonuniform. The humid and thermal factors are taken into account in the stress–strain relation. Employing the composite material's constitutive relation, the buckling governing equation of the composite column can be obtained. The Galerkin method and Laplace transform are applied to solve the buckling problem of the composite column. In this process, the contact duration time and the buckling time are two significant parameters that are typically considered in this research. In the numerical section, the present solutions are validated by comparing to the result in published research. The effects of the kinetic energy of the impactor, geometrical features of the column, and hygrothermal factors on the buckling solutions are studied as well.

Reduction of Fe Levels in Groundwater Using Aeration-Filtration Method with Tray Aerator System

The presence of high iron (Fe) content in water consumption is a major factor that causes health and aesthetic problems. Its amount in water samples can be reduced by combining the aeration and filtration methods of water treatment. The aeration method basically involves making direct contact between air and water, which is usually done by adding both together. Subsequently, the filtration method uses porous media like sand, gravel, and activated charcoal to filter water.This research compares the effectiveness of aeration, filtration, and combined aeration-filtration methods of water treatment. For the aeration method, a form of trays aerator arranged in 6 levels with a distance of 20cm is used along with a varied contact time duration of 1, 3, and 5 hours. In addition, quartz sand, activated carbon, palm fiber, and coral were used as the media for the filtration method. The results obtained as the % value of iron (Fe) removal were varied at a contact time of 1, 3, and 5 hours for both the aeration and combined aeration-filtration method, and 46.95; 78.2; 82.48; 72.32; 81.71; 87.24; and 70.44 for the filtration method shows the working effectiveness of the tools. The combination of aeration with filtration provides maximum results when compared to using aeration alone or filtration methods alone.

In Situ Consolidation of Thermoplastic Prepreg by Generating Harmonic Oscillations on the Consolidation Roller

Automation technologies such as Automated Fiber Placement (AFP) or Automated Tape Laying (ATL) are widely used in the aerospace industry today. However, these processes can still be further improved for higher productivity. Fiber-reinforced plastics allow the production of components with extremely high specific strength and stiffness. Regarding the automated manufacturing processes, the thermoplastic tape placement offers efficiency improvements compared to the nowadays more commonly used thermoset tape placement, especially through the substitution of the expensive and time-consuming autoclave process. The consolidation of thermoplastic Prepregs is achieved with an elastic or rigid roller according to the current state of the art. The Prepregs must be consolidated precisely on the substrate or on top of each other. The most important process parameters for high-quality laminate structure with low porosity are the control of heat source, consolidation force, consolidation roll speed, and tape tension. The efficiency of the AFP process can generally be improved by increasing the speed of the consolidation roller. By increasing the speed of the consolidation roller, porosity is increased and mechanical properties of the laminate are reduced significantly due to the short contact time between consolidation roller and Prepregs. This study investigates a process that can reduce these challenges by increasing the contact time and force duration of the consolidation roller on the Prepregs. The consolidation roller in this study is additionally to be driven by the harmonic oscillations. The new method allows the consolidation roller to oscillate forward and backward during the fiber placement process. This creates another force vector in addition to the compressive force of the consolidation roller and increases the bonding strength between the layers.

Triboelectricity and textile structures

Triboelectricity is a natural phenomenon with limited applications in the past. Wide research over the last decade introduced it mainly in energy harvesting and sensing. The use of textiles in triboelectric applications mainly focuses on the energy harvesting field. The textile fabrics as active parts of wearable triboelectric generators are promising concerning the structural simplicity and the performance of the product. The clothes are made of textile fabrics and the textile-based triboelectric generator is benefitted by the large contact areas and the continuous activation thanks to the lasting movement of the wearer. Simultaneously, the textile character of the triboelectric parts supports the flexibility, elasticity, breathability etc of the clothes, maintaining the comfort of the user. The study of the triboelectric phenomenon on textile structures gives an indication of their suitability for energy harvesting applications. The present research work investigates the influence of parameters like the contact time duration of the fabrics, the force applied upon their contact, their relative orientation and their weave as well as the material type on the efficiency of the triboelectric unit. Additionally, the lack of a standard testing method imposed the design and development of a suitable testing apparatus. It operates in the vertical contact-separation mode and it allows the testing of different samples under the same conditions or of the same sample under different conditions. Textile fabric samples were paired and tested in order to evaluate their influence on the amount of energy harvested.

System capacity evaluation for mobility management in LTE-advanced D2D networks

Objectives: This study aims to evaluate the system capacity for mobility management in Long Term Evolution-Advanced (LTE-A) Device to Device (D2D) networks with suitable handover schemes. Methods: This paper introduces power control mechanisms for 5G based on the distance between D2D terminals. Interference is a major issue which reduces the performance of D2D communication. The proposed system introduces an algorithm based on greedy algorithmic approach for interference mitigation with easy handover for system capacity estimation. The implementation is carried out using LabVIEW platform and results are analyzed. Findings: The existing mobile communication approaches transfer calls through base stations irrespective of the distance between the mobile terminals. User mobility is an important factor for D2D communication and proper selection of mobility patterns that helps in increasing the energy efficiency and throughput by reducing interference. Efficient utilization of these mobility patterns are shown in the proposed method for developing an optimal time efficient mobility aware caching mechanism with lower complexity. In the recent works, less importance has been given for users\' contact time duration while they are moving with different speeds. The simulation results show an enhancement in the system capacity of approximately 480 bits/Hz for 50 devices and 290 bits/Hz for 20 D2D users. The simulation results prove that the proposed approach gives better performance than the existing methods. Keywords: D2D; handover; RPGM; LTE-A; SINR

Fragmented data routing based on exponentially distributed contacts and inter-contact times in DTNs

Existing works in data forwarding in delay tolerant networks often simplify the data transmission during a contact between two network nodes. One common assumption is that once transmitted, messages will always successfully arrive at the encounter node in its entirety regardless of the contact duration. The other common assumption is that messages are unfragmented, and are successfully transmitted only if the contact duration is long enough. If the contact duration is too short, the transmission will not complete, and the message needs to be re-transmitted in its entirety in the next contact. While the first assumption is unrealistic, the second assumption makes the routing strategy inefficient for large data items in network environments where most contact durations are short. In this work, we eliminate the assumption of unfragmented data, and propose a single-copy fragmented data routing strategy (FDR) that performs well with short contact durations. FDR considers the exponential distribution of inter-contact time, contact duration time, and fragmented data sizes when making forwarding decisions. We show that under short contact durations and large message sizes, our scheme can achieve up to 41% higher delivery rate and 38% lower delay compared to other routing strategies.

The Effect Of Blue Methyl Concentration And Contact Time Toward Stain Resistance Tests On Sanytaryware Glaze

The applications of sanitaryware glazed ceramics were exposed to a chemical substance that can leave a stain. One of the example are sanitaryware glaze which according to SNI 797:2018 must pass stain test to comply with the standard. On the SNI 797:2018 stain test procedure, one of the chemicals used are blue methyl with 0,5% concentration and 1 hour contact time. The purpose of this research is to investigate the effect of concentration and contact time duration on the stain resistance result test. Stain resistance test was carried out with methyl blue concentration 0,1-0,5% and contact time 1-24 hour on 540 samples and calculated with statistic which 461 (85.37%) samples pass stain test or unstained, and 79 (14.63%) samples failed stain test or stained. In the statistical calculation the concentration range of the dye is 0.1% -1.5% and the contact time of 1-24 hours is calculated as many as 400 samples. Concentration and contact time have a positive effect and significant on stain resistance test with a regression coefficient of 0,12% for stain color concentration and 0.92% for contact time. Based on the coefficient result, the effect of contact time is greater than the stain color concentration on the stain resistance test.

Effect of the "Building Osteo Neatly Exercise" program on quantitative ultrasound parameters and plantar pressure distribution for college-aged females.

[Purpose] We investigated the effects of a specifically designed exercise program that focused on the arches of the foot and the forefoot (the “Building Osteo Neatly Exercise” program) in college-aged females. [Participants and Methods] Forty college-aged females were divided randomly into experimental and control groups. The experimental group underwent the Building Osteo Neatly Exercise program for 60 min once a week for 4 months. In both groups, the plantar pressure distribution and quantitative ultrasound parameters of the calcaneus (speed of sound and bone area ratio) were evaluated at the beginning and end of the study. The plantar pressure distribution during walking was measured using a pressure plate to evaluate the deviation from the ideal values for the following: contact time, contact duration, peak pressure time, and foot pressure, all measured in the rear foot (the external and internal sides), medial forefoot including (the hallux and second and third toes), and lateral forefoot (the fourth and fifth toes). [Results] After completing the program, the speed of sound and bone area ratio had increased significantly in the experimental group and were significantly higher than those in the control group. The experimental group showed significant improvements in the deviations from the ideal values in contact time and contact duration in the medial forefoot, all four parameters in the lateral forefoot, and pressure in the rear foot. [Conclusion] College-aged females who participated in the Building Osteo Neatly Exercise program once weekly for 4 months exhibited significant improvements in bone strength in the calcaneus and in foot function, as shown by the plantar pressure distribution. Further studies are needed to examine the outcomes of the Building Osteo Neatly Exercise program in an elderly population.

Dynamic and static corrosion of alpha-alumina bonded refractory in contact with molten soda-lime-silica (SLS) glass

The corrosion behaviour of sintered high purity α-Al2O3 refractory composition in contact with soda-lime-silicate (SLS) glass has been investigated using a dynamic corrosion test designed to simulate industrial conditions. Experiments were conducted as function of rotation speed, contact time duration and temperature. The results of dynamic corrosion tests are in excellent agreement with those obtained from static crucible test at 1370 °C for 72 h which is a standard industrial testing practice. The phase composition and microstructures of the glass-refractory interface of these samples were studied by X-ray Diffraction (XRD) and combined Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDS), respectively. Elemental mapping was also carried out on the glass-refractory interface.

Effect of the cushioning running shoes in ground contact time of phases of gait

The main objective of this research was to know how five different cushioning shoes may interfere in ground contact times of each gait phase of walking and running in contrast with barefoot condition. Thirty healthy sport recreational male runners participated in this study. They played over a treadmill wearing minimalist, Boost®, Ethyl-vinyl-acetate (EVA), Air® chamber and pronation-control cushioning shoes technologies and under barefoot condition, recording the last 30 s of walking and running at 5.17 km/h and 9 km/h respectively, while ground contact time duration of each phase of gait was recorded with circular standard pressure sensors located on plantar feet. During walking, the heel contact phase was the station that increased significantly ground contact times wearing all sole cushioning shoes (p < 0.001), excepting no sole shoes (minimalist), versus barefoot condition, being Air® chamber the model that showed the highest times of contact floor versus barefoot (0.28 ± 0.08 ms and 0.23 ± 0.12 ms vs 0.12 ± 0.07 ms and 0.18 ± 0.07 ms in heel contact during midstance phases, respectively). During running, propulsion phase was the station that showed the highest spent times on ground contact with the floor under all shoe conditions, even with minimalist, being again Air® chamber the model with higher significant times in two of three phases versus barefoot (0.11 ± 0.04 ms and 0.16 ± 0.11 ms vs 0.09 ± 0.03 ms and 0.10 ± 0.02 ms in midstance and propulsion phases respectively). Air chamber® was the model too with the most switch ratio to forefoot strike pattern (0.07 ± 0.10 ms to 0.16 ± 0.11 from heel contact to propulsion phase, respectively). In conclusion, a ground contact times increase using all cushioning running shoes compared with barefoot condition was shown in both walking and running test.

Polymer Modulus of Elasticity and Hardness From Impact Data

The present paper introduces a simple method to predict the modulus of elasticity and the hardness of polymeric materials that range from soft elastomers to hard plastics. Hertzian elastic impact model is used to define the relationship between the contact time duration and the maximum force of normal contact due to the impact of a hard sphere indenter with the tested polymer sample. It is shown that the adopted model and experimental method can be used as a tool for extracting the magnitude of the complex modulus of elasticity. Moreover, a new impact index is shown to be proportional to the polymer shore hardness. Theoretical and experimental results based on the force–time signals are consistent and show good correlation.

Time-constrained anycast routing under short contact duration in delay-tolerant networks

Delay-tolerant networks (DTNs) are sparse mobile ad hoc networks, in which there is typically no complete path between the source and destination. Anycast is an important group communication paradigm for numerous DTN applications such as resource discovery and information exchange in emergency or crisis situations. Unlike unicast and multicast, which have been studied extensively in DTNs, few prior works have addressed the DTN anycast routing problem. Furthermore, they often ignore the time constraint and assume long contact durations in formulating the relay selection strategy. In this paper, we study a single-copy time-constrained anycast (TCA) routing under short contact duration. We address two key issues: (1) to which next hop relay node should messages be forwarded and (2) in which order should messages be forwarded. To reduce the transmission cost, we select relay nodes from both current and past contacts based on the one-hop and two-hop delivery probabilities, respectively. We derive the delivery probability from the distribution of inter-contact time and contact duration time. We address the case of exponential and Pareto distribution, which are the most popular assumptions in literature. For the message scheduling, messages with the highest delivery probability are prioritized to be transmitted first. Extensive simulation results based on Cabspotting and MIT Reality traces show that our scheme can achieve up to 29% higher delivery rate, 24% lower delay, and 36% lower transmission cost compared to other anycast routing strategies.

Kinetics and Adsorption Isotherms Study of Cyanide Removal from Gold Processing Wastewater Using Natural and Impregnated Zeolites

The extraction of gold involves using cyanide which has the potential to impact the environment. Many studies have been done to reduce the environmental effects of cyanide. In this research, the cyanide adsorption on zeolite from gold processing plant tailing dam wastewater was investigated. Results indicated that the pH of the solution, contact time duration, temperature, zeolite amount and size of zeolite particles were the most important parameters in the adsorption process. Zeolite was used in two fraction sizes; (100-300)m and (300-1000)m in two types of natural and impregnated with copper sulfates. The optimum amounts of both natural and impregnated zeolite in the solutions and the maximum cyanide adsorption percentage were determined as 30, 24g/L and 50.2, 86.1% for small fraction size, and 36, 24g/L and 39.5, 64% for large fraction size, respectively. The optimum values of pH were 10.5 and 10 for natural and impregnated types in both fraction sizes. Contact time duration in equilibrium conditions for fraction sizes of (100-300)m and (300-1000)m were 40 and 50 min, respectively. The optimum temperature in all situations was 22 oC. The adsorption process in a size of (100-300)m for natural zeolite was fit into the Freundlich model and for impregnated zeolite type there was no significant difference between two models, although, the Langmuir model was more accurate. In a fraction size of (100-300)m for two types of zeolites, the kinetic adsorption was fit into the Lagergren second-order kinetic model. In a fraction size of (300-1000)m, the adsorption kinetics for the natural type has no sensible difference between the first and second Lagergren kinetic model, but for the impregnated zeolite type it follows the second-order kinetic model. The results showed that the cyanide adsorption on impregnated zeolite was more than the natural type.

A Study on the Node Centrality Based Multisocial Attributes Weighted in Mobile Social Networks

Mobile social networks (MSNs) exploit human mobility and consequent device-to-device contact to opportunistically realize data communication. Thus links in MSNs is dynamic changing over time and strongly influenced by people activities, mining influential nodes is one of the important questions for effective information transmission in MSNs. While traditional centrality definitions are based on the static binary network model and not suitable for time-varying topology structure in mobile social network. Furthermore previous centrality metrics often referred to social attributes about neighbor nodes and contact times, and did not take the contact duration time into consideration. Therefore, this paper proposes a centrality measurement method based on multi-social attributes weighted. We first use the temporal evolution graph model which more accurately depicts the dynamic nature of topology in MSNs. Quantifying human social relations and mobility model as weights for the links, and then we redefine degree of centrality and the measurement of shortest path. Finally, the superiority of the concepts we posed are evaluated in the real data set.

KEMAMPUAN TANAMAN APU- APU (Pistia stratiotes L.) DALAM MENURUNKAN KADAR LOGAM BERAT NIKEL (Ni) LIMBAH CAIR

ABSTRACTResearch on reduction of Nickel (Ni) heavy metal in wastewater by using a water plant lettuce (Pistiastratiotes L.) was conducted with the aim of knowing the level of Ni reduction in wastewater after the plants aregiven water plant lettuce (Pistia stratiotes L.). The technique used in processing wastewater of the metal platingis phytoremediation.This study was pure experiment with pretest-posttest design with control group used completerandomized design (CRD). This study was conducted in December to June, 2016.The results showed that the level of Ni in wastewater decreased after 1 day, 3 day and 6 day treatmentwith water plant lettuce. From the statistical test result, the reduction of Ni was significant with 5 plants by p =0.023 &lt; α. Based on the contact time duration, the result of statistical test was p = 0.000 &lt; α. The more thenumber of plants used, the greater the reduction of Nickel level. The longer the contact time of the water plantwith wastewater, the greater the reduction of Nickel level in wastewater.For further study, it is suggested to use plant that is hyper tolerant against contaminants and usedmore plants to proceed wastewater and more comparable with the level of Ni metal contained in wastewatermetal plating.Keywords : Nickel level reduction, water plant lettuce (Pistia stratiotes L.),contact duration, phytoremediation.

Energy-Efficient Wi-Fi Sensing Policy Under Generalized Mobility Patterns With Aging

An essential condition precedent to the success of mobile applications based on Wi-Fi (e.g., iCloud) is an energy-efficient Wi-Fi sensing. Clearly, a good Wi-Fi sensing policy should factor in both inter-access point (AP) arrival time (IAT) and contact duration time (CDT) distributions of each individual. However, prior work focuses on limited cases of those two distributions (e.g., exponential) or proposes heuristic approaches such as Additive Increase (AI). In this paper, we first formulate a generalized functional optimization problem on Wi-Fi sensing under general inter-AP and contact duration distributions and investigate how each individual should sense Wi-Fi APs to strike a good balance between energy efficiency and performance, which is in turn intricately linked with users mobility patterns. We then derive a generic optimal condition that sheds insights into the aging property, underpinning energy-aware Wi-Fi sensing polices. In harnessing our analytical findings and the implications thereof, we develop a new sensing algorithm, called Wi-Fi Sensing with AGing (WiSAG), and demonstrate that WiSAG outperforms the existing sensing algorithms up to 37% through extensive trace-driven simulations for which real mobility traces gathered from hundreds of smartphones is used.