External Impact Force Research Articles

The application of mesenchymal stem cells in the treatment of traumatic brain injury: Mechanisms, results, and problems.

Mesenchymal stem cells (MSCs) are multipotent stromal cells that can be derived from a wide variety of human tissues and organs. They can differentiate into a variety of cell types, including osteoblasts, adipocytes, and chondrocytes, and thus show great potential in regenerative medicine. Traumatic brain injury (TBI) is an organic injury to brain tissue with a high rate of disability and death caused by an external impact or concussive force acting directly or indirectly on the head. The current treatment of TBI mainly includes symptomatic, pharmacological, and rehabilitation treatment. Although some efficacy has been achieved, the definitive recovery effect on neural tissue is still limited. Recent studies have shown that MSC therapies are more effective than traditional treatment strategies due to their strong multi-directional differentiation potential, self-renewal capacity, and low immunogenicity and homing properties, thus MSCs are considered to play an important role and are an ideal cell for the treatment of injurious diseases, including TBI. In this paper, we systematically reviewed the role and mechanisms of MSCs and MSC-derived exosomes in the treatment of TBI, thereby providing new insights into the clinical applications of MSCs and MSC-derived exosomes in the treatment of central nervous system disorders.

A combination of “Inner - Outer skeleton” strategy to improve the mechanical properties and heat resistance of polyimide composite aerogels as composite sandwich structures for space vehicles

Low density aerogels with high fatigue resistance are widely used in the manufacturing of core material structures in aircraft fuselage to be able to tolerate the extreme environment of aerospace. However, most organic aerogel materials have poor energy absorption of external impact forces, and are prone to irreversible deformation, such as contracture and collapse in the process of long-term service. In order to solve this problem, a new type of thermosetting-thermoplastic polyimide composite aerogel was prepared, with its microstructure presenting the coexistence of the inner and outer skeletons. The intermolecular forces promoted the assembly of the soft thermoplastic layer and the strong thermosetting layer in the thermodynamic process with 4.63–6.55 μm range. The hard-soft layer structure improved the compressive and the shear load bearing capacities by bending of the panel (Compressive modulus is 1.60 MPa–3.52 MPa, tensile modulus is 1.04 MPa–1.45 MPa). Its permanent degradation less than 1.5 % after 500 cycles at 30 % strain. C–CPIAs also exhibited excellent heat resistance and thermal insulation performances, with a T5% value of 612 °C (C-CPIA-2), Tg of 458 °C (C-CPIA-3). The sandwich materials can be used as outer protective composite material of aircraft fuselage for future deep space missions.

Simulations of Transients in a Four-Pole Magnetic Bearing with Permanent Magnets.

This paper presents the design of and transient time simulations for a four-pole magnetic bearing with permanent magnets. The usage of permanent magnets reduces the consumption of electric energy in comparison to a traditional active magnetic bearing. Permanent magnets are installed in the yoke of the stator core to limit the cross-coupling of the magnetic flux generated by the windings. The first part of this paper presents the design of the magnetic bearing and its finite-element model, while the second part describes the field-circuit indirectly coupled finite-element model for the transient time simulation. The presented simulation model was used to calculate the transient response for the rotor lifting from the starting position, the step change in the rotor position and the change in the rotor position under an external impact force applied along the y-axis.

Seismic Performance of Building Structures Using Structural Integral Mechanics Model under the Guidance of Fluid Mechanics

The purpose is to study the core causes of serious collapse of buildings damaged in the earthquake and improve the seismic performance of buildings to reduce casualties. First, the theoretical overview of seismic engineering and related form and requirements of the building structure are deeply studied. Next, the building node structure is deeply analyzed according to the knowledge of fluid mechanics and the basic idea of the finite element method of integral structure. The seismic performance of building structures and the principles and requirements of seismic engineering are analyzed and summarized. It is found that the concrete analysis and description of seismic performance in the research method of fluid mechanics is a steel structure’s bending resistance, deformation and displacement degree, and the bearing degree of external impact force. Further, the model design of the integral structure is carried out through the finite element idea of fluid mechanics. Then, the model simulation experiment is conducted to obtain the curve of the impact force on the building structure, the ultimate bearing capacity of the steel beam joint and the skeleton displacement under the impact. Meanwhile, the degradation of stiffness and strength of node structure during an earthquake is analyzed. Finally, through the simulation results, it is concluded that the maximum displacement between node members under the action of impact force is no more than 300mm, so the model has high impact bearing capacity and strong seismic capacity, and can meet the requirements of seismic fortification. This exploration will be of great significance to the development of building seismic engineering under the guidance of fluid mechanics.

Superhydrophobic cellulosic triboelectric materials for distributed energy harvesting

The development of triboelectric nanogenerators (TENGs) has made it possible to collect large-scale distributed energy, and their applications in the field of energy harvesting are promising. However, the erosion of water molecules in humid environments is a major challenge limiting the application of triboelectric materials. In this study, superhydrophobic methylated cellulosic triboelectric materials were prepared and rectangular TENG with an internal grid structure was designed for distributed energy harvesting. Interfacial modification of the cellulose nanofibrils (CNF) surface by silica nanoparticles to form a nanoscale microstructured surface further enhances the hydrophobicity of the triboelectric material. It was found that the modified CNF triboelectric material has excellent super-hydrophobicity (WCA: 154.7°), surface roughness (RMS: 72.61), and low surface energy. In addition, the RT-TENG internal grid structure is designed to allow external impact forces to be applied more uniformly to the surface of the f triboelectric material, demonstrating excellent electrical output performance (120 V) and cycling stability (10,000 cycles) when applied to distributed energy harvesting. This study provides a novel strategy for the design and preparation of superhydrophobic triboelectric materials and guides the study of distributed energy harvesting.

Self-powered flexible piezoelectric sensor based on PbZr0.52Ti0.48O3 nanofibers for impact force monitoring and rubber mat aging assessment

In this work, a flexible piezoelectric sensor was fabricated based on PbZr0.52Ti0.48O3(PZT) nanofibers (NFs) composite, and its potential applications in impact force monitoring and rubber mat aging assessment were reported. The lead zirconate titanate (PZT) piezoelectric NFs with diameters of 150–260 nm were prepared via electrospinning technique, showing a high piezoelectric coefficient (d 33 ∼ 92.5 pm V−1) for piezoelectric fibers. The PZT NFs and carbon nanotubes (CNTs) were dispersed in polydimethylsiloxane (PDMS) to fabricate a highly stretchable and flexible impact sensor (PZT/CNTs/PDMS piezoelectric nanocomposite sensor), which showed excellent low frequency sensitivity (as low as 0.01 Hz), high bending deformation sensitivity (as low as 0.192 cm−1 curvature deformation with 6.64 V cm−1 sensitivity) and cycle stability under external impact force. Besides, it is the first attempt to assess railway tracks rubber mat aging based on piezoelectric nanocomposite impact sensor, and the static stiffness relative error reaches a low value of 6.91%.

Flexible and lightweight melamine sponge/MXene/polyborosiloxane (MSMP) hybrid structure for high-performance electromagnetic interference shielding and anti-impact safe-guarding

With the development of electronic devices, human beings are always disturbed by the widespread electromagnetic radiation. Meanwhile, the impact kinetic energy from external object will also cause injuries to precision electronic instrument itself and human body. Herein, a lightweight and flexible Melamine Sponge/MXene/Polyborosiloxane (MSMP) hybrid structure with both anti-impacting and electromagnetic shielding performance is proposed by incorporating conductive Ti3C2TX and polyborosiloxane (PBS) into porous melamine sponge (MS). The nanocomposite shows outstanding energy dissipation ability which can efficaciously degrade the external impact force due to the shear stiffening characteristic. Meanwhile, the nanocomposite presents an excellent electromagnetic interference (EMI) shielding ability with a maximum SET value of 39 dB. Besides, the MSMP displays obvious adhesion property after being cut due to the viscoelastic property and internal supramolecular network of PBS, thus can repeatedly resist the external damage. Finally, a safety sports protective equipment is developed by integrating the MSMP nanocomposite into the common sportswear. Owing to the good integration of safe-guarding performance and EMI shielding properties, the MSMP nanocomposites show high prospective potential in precision electronic instruments and wearable protective equipment.

The effect of chin-to-chest contact on upper neck axial force in UN Regulation No. 129 frontal impact tests of child restraint systems

Objective The objective of this study was to investigate the effect of chin-to-chest contact on upper neck axial force in United Nations (UN) Regulation No. 129 frontal impact tests of child restraint systems. Methods Frontal impact pilot experiments were carried out according to the test procedure in UN Regulation No. 129. Q-Series child dummies were seated in a small convenience sample of forward-facing child restraint systems. The timing and duration of chin-to-chest contact were determined using the procedure for calculating external head impact force in SAE J2052. Results Chin-to-chest contact was observed in all of our experiments and generated a tensile peak in the upper neck axial force of the Q-Series dummies. Prior to chin-to-chest contact, a purely inertial, noncontact peak was observed in the axial tension force. The tensile peak due to chin-to-chest contact was often greater than the inertial, noncontact peak force. Conclusions Chin-to-chest contact can increase axial neck tension force beyond the level it would reach under purely inertial loading. Adopting upper neck axial force in regulation, without considering how the force is generated, might encourage child restraint designs that mitigate only chin-to-chest contact, rather than the true inertial neck loading.

Advanced triboelectric nanogenerator with multi-mode energy harvesting and anti-impact properties for smart glove and wearable e-textile

Environmental hazardous stimuli including strong electromagnetic field and impact force were always harmful to human beings. Developing functional triboelectric nanogenerator (TENG) with universally harvesting various energy and anti-impact effect may be an effective strategy to collect energy as well as protect human beings from danger. Thus, a miniaturized all-in-one TENG with high structural durability, anti-impact and multi-mode harvesting energy from compression, swaying and magnetic field was developed by assembling shear thickening fluid (STF) and magneto-sensitive films. TENG yielded maximum power density of 27.05 mW/m 2 with the voltage of 10.40 V at 10 MΩ under compression. It also sensed and collected tiny STF flowing energy under non-contact mode. Besides, high magnetic-sensitive effect endowed TENG with magnetic dependent programmable shapes which enabled it to harvest non-contact rubbing/deformation energy. More importantly, the device with STF exhibited high anti-impact properties which could resist and dissipate harsh collision force from 1390 N to 409 N, demonstrating excellent safeguarding properties for TENG and human wearers. This versatile device also showed reliable sensing properties to various external magnetic field, human motions, contacted materials and impact forces. In addition, a wearable TENG-based smart glove as a self-powered functional sensor presented the ability of precisely mapping finger joints. Finally, newly-designed Kevlar/TENG-based e-textile arrays with 95% impact-force dissipating and multi-fields display performance was proposed. Thus, this work opened a new perspective for the development of functional TENGs as wearable electronic devices in universally energy-scavenging and safeguarding areas. Multifunctional and miniaturized triboelectric nanogenerator (TENG) with multi-mode energy harvesting and anti-impact properties has been proposed. It effectively gathers energy from compression, swaying and magnetic field. A TENG based-human hand array enables to precisely mapping various finger gestures. Besides, the wearable Kevlar/TENG pads could sense and dissipate 95% impact force which provide protection for human beings. • An all-in-one TENG with energy collecting and safeguarding effects has been constructed. • TENG could harvest compression, magnetic-induced deformation and fluid rubbing energy. • TENG-based wearable glove monitored human motions and distinguish contacted materials. • Kevlar/TENG array dissipated impact force by 95%, providing safeguarding for humans.

Hyper-viscoelastic mechanical behavior of cranial pia mater in tension

BackgroundCranial pia mater, the innermost layer of the meninges, protects the central nervous system by tightly wrapping the brain and damping the external impact force to the brain. Accurate experimental data of the mechanical property of the cranial pia mater can enhance the theoretical prediction of traumatic brain injury or the scientific surgery design for brain disease. The aim of this study is to characterize the mechanical behavior of the cranial pia mater. MethodsIn vitro tensile and stress-relaxation experiments of ovine cranial pia mater specimens were conducted at eight strain rates to characterize the rate-dependent viscoelastic property. The tensile and stress-relaxation experimental data were fitted by an Ogden hyper-viscoelastic model with a strain rate function to describe the mechanical behavior of the cranial pia mater. FindingsThe elastic modulus and the ultimate stress are significantly increased from 5.545 MPa and 0.535 MPa at 0.00167 s−1 to 18.345 MPa and 2.547 MPa at 0.83 s−1 (p < .0001), respectively. The initial stress and the long-term stress (300 s) are also increased significantly with the increasing strain rates (p < .0001). A good fit of the experimental data with the Ogden hyper-viscoelastic model incorporated with a strain rate function was achieved (R2 > 0.93). InterpretationThe cranial pia mater exhibits as a rate-dependent hyper-viscoelastic material in the tensile and stress-relaxation experiments. Compared with the brain, the stiffer nature of the cranial pia mater indicates its essential role in brain protection. The rate-dependent constitutive model provides a proper description of the hyper-viscoelastic characteristics of the cranial pia mater in tension and may provide a basic constitutive relationship for numerical simulations of traumatic brain injury.

Impact force sensing with magnetostrictive Fe-Ga alloys

Fe-Ga alloys (Galfenol) are structural magnetostrictive materials which undergo magnetization changes when subjected to mechanical stress. They are machinable and can withstand large normal or shear stresses. Based on these unique features, this study develops an impact force sensor which consists of an electromagnet, magnetic circuit, cantilevered Fe-Ga alloy beam, and pickup coil. The external impact force generates a stress-induced flux density that is measured by the pickup coil. An axial impact sensor based on a Fe-Ga rod is constructed for comparison. Analytical modeling shows that the sensitivity of the cantilevered beam configuration is 11.27 times higher than that of the rod configuration. Three different geometries, including a rectangular beam, a uniform I beam, and a tapered I beam, are designed and compared. Analytical modeling shows that the tapered I beam exhibits maximum sensitivity. The optimized tapered I beam-based sensor is constructed experimentally and benchmarked against a similar sensor based on a Fe-Ga rod. A nonlinear Levenberg-Marquardt fitting method is used to correlate the input impact force with the resulting flux density variation. Experimental results show that the measurement error is within 5.8% for various impact amplitudes.

Development of a Virtual Force Sensor for a Low-Cost Collaborative Robot and Applications to Safety Control.

To protect operators and conform to safety standards for human–machine interactions, the design of collaborative robot arms often incorporates flexible mechanisms and force sensors to detect and absorb external impact forces. However, this approach increases production costs, making the introduction of such robot arms into low-cost service applications difficult. This study proposes a low-cost, sensorless rigid robot arm design that employs a virtual force sensor and stiffness control to enable the safety collision detection and low-precision force control of robot arms. In this design, when a robot arm is subjected to an external force while in motion, the contact force observer estimates the external torques on each joint according to the motor electric current and calculation errors of the system model, which are then used to estimate the external contact force exerted on the robot arm’s end-effector. Additionally, a torque saturation limiter is added to the servo drive for each axis to enable the real-time adjustment of joint torque output according to the estimated external force, regulation of system stiffness, and achievement of impedance control that can be applied in safety measures and force control. The design this study developed is a departure from the conventional multisensor flexible mechanism approach. Moreover, it is a low-cost and sensorless design that relies on model-based control for stiffness regulation, thereby improving the safety and force control in robot arm applications.

A zero-power sensing MEMS shock sensor with a latch-reset mechanism for multi-threshold events monitoring

This paper presents the design, modeling, fabrication, and testing of a MEMS passive shock sensor to record multiple threshold events with robust latching mechanism using mass-spring assembly. The latching part on a seismic mass enables the discrete latch positions depending on the applied external impact forces and stores the impact value over a long period of time without any external power supply. A numerical model is developed to understand the dynamic behavior of the device and the proposed shock sensor is capable of sensing a shock range of 20–250 g with 10 threshold levels. The fabricated devices are investigated by applying controllable impact tests, and the experiment results are verified by comparing with the numerical model values. An electrostatic actuator is incorporated for reinitializing the device by releasing coupling between the latching parts for reusability. The shock sensor does not require any power for detection nor storage of acceleration events during its operation. Having high reliability, optimum resolution and reusability makes the device suitable for long-term remote monitoring applications with very limited power supply.

A Multi-Priority Control of Asymmetric Coordination for Redundant Dual-Arm Robot

The paper develops a multi-priority control method of asymmetric coordination for a redundant dual-arm robot. A novel dual-arm coordination impedance is introduced to the multi-priority control, and then the performance of the object tracking and the redundant joints is improved by the regulation of the relative Cartesian errors between two arms. The control of asymmetric coordination is divided into the main task and the secondary task. The control of the main task can regulate the two end-effectors’ errors and the relative errors by building the model of spatial parallel spring and damping (SPSDM), which establishes the dual-arm coordination impedance relation in Cartesian space. The control of the secondary task optimizes the performance of the redundant joint impedance and joint limit avoidance in null space. Finally, a typical asymmetric coordination experiment of peg-in-hole is carried out to verify the validity and feasibility of the proposed method. The results indicate that the proposed dual-arm coordination impedance can regulate the relative tracking errors between two objects directly, and in the context of the external impact force applied to the two end-effectors, the peg-in-hole dual-arm task can be achieved successfully.

A liquid metal-based triboelectric nanogenerator as stretchable electronics for safeguarding and self-powered mechanosensing

In recent years, high performance triboelectric nanogenerator (TENG) shows distinguished energy-harvesting property which guarantees its potential applications as a power source. However, collision and harsh impact, occurred in daily life, always injure human beings. Developing novel multifunctional TENG with self-powered mechanosensing and protection properties from violent impact is an urgent and meaningful work. Here, a multifunctional TENG with energy-harvesting, safeguarding and self-powered force-sensing properties was fabricated by assembling shear stiffening gel/polydimethylsiloxane (SSG/PDMS) matrix with GaInSn liquid metal. Operating at 10 Hz, TENG with a size of 50 × 50 × 4 mm3 obtains an output voltage of 35.72 V, current of 5.10 μA, and maximum output power of 182.17 μW. In addition, TENG device generates enhanced output power of 323.97 μW under tensile strain of 80%. Besides harvesting mechanical energy, TENG with fast stimuli-responsive character, has been proven as a self-powered sensor to monitor varieties of physiological movements. More importantly, the TENG device with high damping property enables to dissipate 66.43% of external impact force which provides favorable protection effect. Correspondingly, the distinguished output voltage signals can also reveal and assess different impulsive loads. This work proposes a multifunctional TENG device with energy-harvesting, and utilizing the flexible TENG for safeguarding and self-powered mechanosensing.

Finite Element Analysis on a Newly-Modified Method for the Taylor Impact Test to Measure the Stress-Strain Curve by the Only Single Test Using Pure Aluminum

In this study, finite element analyses are performed to obtain a stress-strain curve for ductile materials by a combination between the distributions of axial stress and strain at a certain time as a result of one single Taylor impact test. In the modified Taylor impact test proposed here, a measurement of the external impact force by the Hopkinson pressure bar placed instead of the rigid wall, and an assumption of bi-linear distribution of an axial internal force, are introduced as well as a measurement of deformed profiles at certain time. In order to obtain the realistic results by computations, at first, the parameters in a nonlinear rate sensitive hardening law are identified from the quasi-static and impact tests of pure aluminum at various strain rates and temperature conducted. In the impact test, a miniaturized testing apparatus based on the split Hopkinson pressure bar (SHPB) technique is introduced to achieve a similar level of strain rate as 104 s−1, to the Taylor test. Then, a finite element simulation of the modified test is performed using a commercial software by using the user-subroutine for the hardening law with the identified parameters. By comparing the stress-strain curves obtained by the proposed method and direct calculation of the hardening law, the validity is discussed. Finally, the feasibility of the proposed method is studied.

Hippocampal neuronal degeneration in the traumatic brain injury mouse: non-trivial effect of scalp incision

Objectives: In experimental models of traumatic brain injury (TBI), posttraumatic hippocampal neuronal degeneration in the cornu ammonis 1 (CA1), and/or the cornu ammonis 3 (CA3) regions are regarded as the most notable phenotypic appearances relating to the pathophysiology of human post-concussion syndrome. However, these morphological changes are often also seen in subjects without TBI, namely ‘sham’ groups. The frequencies and reasons of appearance of hippocampal neuronal degeneration in mice with TBI and/or sham are not clear.Methods: We compared the frequencies of hippocampal neuronal degeneration among three groups: TBI (mice with external force impact performed by Marmarou’s weight drop model after scalp incision), sham (mice with scalp incision alone), and control (mice with neither external force impact nor scalp incision), using hematoxylin and eosin stain in day 6 (n = 5 in each group.) Isoflurane was used for anesthesia in all mice.Results: The frequencies were 80, 100, and 20% in CA1, and 20, 40, and 60% in CA3, for TBI, sham, and control, respectively. In CA1, a significant difference of the frequency was observed between sham and control (p = 0.048), but not, between TBI and sham (p = 1.000) in Fisher’s exact test. In CA3, no significant difference in the frequency was observed between the three groups.Conclusion: Scalp incision, rather than external impact force, might affect the CA1 hippocampal neuronal degeneration in mice with TBI. In addition, factor(s) other than external impact force or scalp incision may also cause hippocampal neuronal degeneration in both CA1 and CA3. Careful interpretation is needed concerning hippocampal neuronal degeneration induced by a weight drop device observed in mice with TBI.

Facile Fabrication of Micro-Nano Structured Triboelectric Nanogenerator with High Electric Output.

In this article, a new method is used to fabricate a high-performance triboelectric nanogenerator (TENG), which is convenient and cost-effective. A polyformaldehyde (POM) film with novel structures is prepared through electrospinning and is combined with a polytetrafluoroethylene (PTFE) film to assemble micro-nano structured TENG. The short-circuit current (Is) and open-circuit voltage (Vo) of the TENG are up to 0.4343 mA and 236.8 V, respectively, and no significant change is observed by applying different frequencies of external impact forces from 1 to 10 Hz. Finally, we successfully drive an electrochromic device (ECD) directly using TENG within just 2 min for the first time.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-015-1001-5) contains supplementary material, which is available to authorized users.

Experimental investigation on the hysteresis behavior of the wire rope isolators

Vibration isolation has been widely applied to filter the external excitation energy and impact forces in building structures and equipment. Wire rope isolator (WRI), a kind of isolator for vibration and shock isolation, shows a better performance in attenuating these forces. WRIs are able to deviate these external forces through their mechanical configuration and high-energy dissipative capabilities. The application of WRI demands knowledge of its behavior and the relation between various geometrical properties and input force. The present work investigates the influence of geometrical parameters, such as wire rope diameter, number of coils, and displacement amplitude on the hysteresis behavior of WRI under quasi-static loading in both vertical and horizontal directions. The hysteresis behavior of different WRIs was evaluated using the calculated parameters from hysteresis force-displacement curves: energy loss ratio (ELR), and effective stiffness. The study indicates that the geometric properties significantly influence the effective stiffness than the energy loss ratio. It is observed that, increased displacement amplitude results in decreased ELR and hence damping capabilities. The study also confirms that the wire rope isolator possesses a good ability in damping through its stiffness and high-energy dissipation capability.

Application of a Packaged Fiber Bragg Grating Sensor to Outdoor Optical Fiber Cabinets for Environmental Monitoring

Outdoor optical fiber cabinets are generally installed along roadsides where environmental conditions, such as sun exposure, rain, and dust, can cause damage to the cabinets. Furthermore, high temperatures and unexpected impacts that cause cabinet deformation may damage the network equipment inside the cabinets, affecting the quality of communications. This paper developed an optical fiber sensing system for real-time monitoring of the temperature variation and external forces exerted on outdoor cabinets using fiber Bragg gratings (FBGs). This FBG sensing system was established in the network management center, and was linked to the outdoor cabinets at the remote end through optical fibers in order to monitor the impacts and temperature changes of the cabinets. Experimental results revealed that exerting an external impact force of 297 N on an outdoor cabinet severely dented the impacted cabinet surface. When the monitoring system detects external impacts exceeding 297 N or cabinet temperatures greater than 65 °C, the network management center can then immediately send maintenance personnel to check for any network impairments.