Simulation and experimental study on plug and pull characteristic of electrical connector contact

As a key component for transmitting electrical signals, the electrical contact performance of electrical connectors is directly affected by the closing amount of the socket. It is urgent to explore the relationship between contact resistance and the closing amount of cylindrical groove electric connectors, as well as the range of the closing amount when their comprehensive performance is optimal in vibration environments. Based on Hertz contact theory, the long- and short-axis parameters of the contact elliptical surface were obtained using the Boussinesq solution and the contact deformation coordination equation. An electrical contact resistance (ECR) theoretical model was obtained using Holm’s electric contact theory and the GW contact model. According to the ECR and long- and short-axis parameters of the contact elliptical surface and the theoretical model of contact resistance, an ECR model based on changes in the initial closing amount (deflection) of the socket spring was established by introducing the cantilever beam model of the socket spring. Then, the failure mechanism of fretting wear and the change mechanism of the ECR of the electrical connectors under a vibration environment were analyzed using the sinusoidal vibration test of electric connectors. The optimal range of the initial closing amount of the cylindrical-groove-closing-type electrical connector socket spring was determined, providing a reference for the reliability designs of electrical connectors.

A contact problem is considered in which an elastic half–plane is pressed against a rigid fractally rough surface, whose profile is defined by a Weierstrass series. It is shown that no applied mean pressure is sufficiently large to ensure full contact and indeed there are not even any contact areas of finite dimension — the contact area consists of a set of fractal character for all values of the geometric and loading parameters. A solution for the partial contact of a sinusoidal surface is used to develop a relation between the contact pressure distribution at scale n − 1 and that at scale n . Recursive numerical integration of this relation yields the contact area as a function of scale. An analytical solution to the same problem appropriate at large n is constructed following a technique due to Archard. This is found to give a very good approximation to the numerical results even at small n , except for cases where the dimensionless applied load is large. The contact area is found to decrease continuously with n , tending to a power–law behaviour at large n which corresponds to a limiting fractal dimension of (2 − D ), where D is the fractal dimension of the surface profile. However, it is not a ‘simple’ fractal, in the sense that it deviates from the power–law form at low n , at which there is also a dependence on the applied load. Contact segment lengths become smaller at small scales, but an appropriately normalized size distribution tends to a limiting function at large n . † The authors dedicate this paper to the memory of Dr J. F. Archard, 1918–1989.

The electrical connector is an important basic element, and its electrical contact performance is easily changed by ambient factors, such as temperature, resulting in various intermittent and permanent faults of the electrical connector. The intermittent faults of the electrical connector are difficult to reproduce, raising serious challenges to equipment availability and mission success. This paper addresses the problem of the intermittent faults of electrical connectors caused by ambient temperature stress and provides qualitative analyses of the impacts of temperature stress on electrical contacts. A finite element simulation model of the contact pairs of electrical connectors is established. The characteristics of intermittent faults at different temperature stress levels for electrical connectors with different contact pair sizes and materials are simulated and analysed. Based on this simulation analysis, experimental studies are conducted on the mechanisms of different temperature stress levels, different contact pair sizes and materials on the intermittent faults of electrical connectors. The results show that external temperature stress and temperature impacts obviously influence the contact performance of the electrical connector and that random intermittent faults occur. The more extreme the temperature and the higher the temperature change rate are, the more obvious their influences.

Creep effects in electrical contacts have been mentioned by a few authors but never studied in detail. The aim of this work is to investigate this phenomenon in low level silver-nickel electrical contacts at room temperature. Experiments are described which carefully measure the evolution of the electrical resistance with time of hemispherical contacts under static normal loads. The results show a slow decrease of the resistance and a quasi-stabilization after a few hours. The final value of the resistance can be significantly low when compared with the initial one. It is also shown that the decrease of the resistance is more pronounced for rough surfaces than for smooth ones. We explain this behavior by the creep of the metal. Indeed the more the metal is stressed the larger is the creep phenomenon. In order to model this effect, a computer simulation based on the finite element method is used to calculate the visco-plastic deformation of a sphere-on-plane system, the sphere corresponding either to the whole contact or to a single asperity. The experimental variations of the contact resistance and those obtained by coupling the mechanical (numerical simulations) and electrical (contact resistance formulas) models are in good qualitative agreement.

Our purpose of this study was to present simulation and experimental studies on magnetic hyperthermia (MH) with use of an alternating magnetic field (AMF) and superparamagnetic iron oxide nanoparticles (Resovist®). In the simulation studies, the energy dissipation (P) and temperature rise rate (∆T/∆t) were computed under various conditions by use of the probability density function of the particle size distribution based on a log-normal distribution. P and ∆T/∆t and their dependence on the frequency of the AMF (f) largely depended on the particle size of Resovist®. P and ∆T/∆t reached maximum at a diameter of ~24 nm, and were proportional to the amplitude of the AMF (H (0)) raised to a power of ~2.0. In the experimental studies, we made a device for generating an AMF, and measured the temperature rise under various concentrations of Resovist®, H (0), and f. The temperature rise at 10 min after the start of heating was linearly proportional to the concentration of Resovist®, and proportional to H (0) raised to a power of ~2.4, which was slightly greater than that expected from the simulation studies. There was a tendency for the temperature rise to saturate with increasing f. In conclusion, this study will be useful for investigating the feasibility of MH with Resovist® and optimizing the parameters for it.

Effect of normal forces on fretting corrosion of tin-coated electrical contacts

Cone beam CT (CBCT) has been widely used in radiation therapy. However, its main application is still to acquire anatomical information for patient positioning. This study proposes a multienergy element-resolved (MEER) CBCT framework that employs energy-resolved data acquisition on a conventional CBCT platform and then simultaneously reconstructs images of x-ray attenuation coefficients, electron density relative to water (rED), and elemental composition (EC) to support advanced applications. The MEER-CBCT framework is realized on a Varian TrueBeam CBCT platform using a kVp-switching scanning scheme. A simultaneous image reconstruction and elemental decomposition model is formulated as an optimization problem. The objective function uses a least square term to enforce fidelity between x-ray attenuation coefficients and projection measurements. Spatial regularization is introduced via sparsity under a tight wavelet-frame transform. Consistency is imposed among rED, EC, and attenuation coefficients and inherently serves as a regularization term along the energy direction. The EC is further constrained by a sparse combination of ECs in a dictionary containing tissues commonly existing in humans. The optimization problem is solved by a novel alternating-direction minimization scheme. The MEER-CBCT framework was tested in a simulation study using an NCAT phantom and an experimental study using a Gammex phantom. MEER-CBCT framework was successfully realized on a clinical Varian TrueBeam onboard CBCT platform with three energy channels of 80, 100, and 120kVp. In the simulation study, the attenuation coefficient image achieved a structural similarity index of 0.98, compared to 0.61 for the image reconstructed by the conventional conjugate gradient least square (CGLS) algorithm, primarily because of reduction in artifacts. In the experimental study, the attenuation image obtained a contrast-to-noise ratio ≥60, much higher than that of CGLS results (~16) because of noise reduction. The median errors in rED and EC were 0.5% and 1.4% in the simulation study and 1.4% and 2.3% in the experimental study. We proposed a novel MEER-CBCT framework realized on a clinical CBCT platform. Simulation and experimental studies demonstrated its capability to simultaneously reconstruct x-ray attenuation coefficient, rED, and EC images accurately.

In our previous studies, we demonstrated that the Compton PET module, a layer structure PET detector with side readout, can provide high performance in terms of spatial/energy/timing resolution, as well as high gamma ray detection efficiency. In this study, we investigate how to translate the high performance of the detector module into good quality reconstructed tomographic images. This study is performed using GATE simulation, as well as with physical experiments. Similar detector geometry is used in the simulation and experiment: two identical 4-layer detector modules are placed with face to face distance of 56 mm. In the simulation study, each layer consists of a 1-mm-pitch pixelated crystal array. In the experimental study, each layer is a monolithic crystal, which is virtually binned into 1 mm^2 cells to group single events according to the gamma ray interaction locations. A customized Derenzo phantom was placed between the two detector modules. By rotating the phantom using a motorized rotary stage, data along lines of response (LORs) at different angles were collected for reconstructing the tomographic image. The same reconstruction algorithm was used for both simulation and experimental studies. The results demonstrate that the simulation study could resolve 0.8 mm rods while the experimental study was able to resolve 1.0 mm rods.

Lung cancer is the leading cause of cancer death worldwide. Thus, early diagnosis is of considerable importance. For early screening of lung cancer, computed tomography (CT) has been used as the gold standard. Chest digital tomosynthesis (CDT) is a recently introduced modality for lung cancer screening with a relatively low radiation dose compared to CT. The dual energy material decomposition method has been proposed for better detection of pulmonary nodules by means of reducing anatomical noise. In this study, the possibility of material decomposition in CDT was tested by both a simulation study and an experimental study using a CDT prototype. The Geant4 application for tomographic emission (GATE) v6 and tungsten anode spectral model using interpolating polynomials (TASMIP) codes were used for the simulation study to create simulated phantom shapes consisting of five inner cylinders filled with different densities of bone and airequivalent materials. Furthermore, the CDT prototype system and human phantom chest were used for the experimental study. CDT scan in both the simulation and experimental studies was performed with linear movement and 21 projection images were obtained over a 30 degree angular range with a 1.5 degree angular interval. To obtain materialselective images, a projectionbased energy subtraction technique was applied to high and low energy images. The resultant simulation images showed that dual-energy reconstruction could achieve an approximately 32% higher contrast to noise ratio (CNR) in images and the difference in CNR value according to bone density was significant compared to single energy CDT. Additionally, image artifacts were effectively corrected in dual energy CDT simulation studies. Likewise the experimental study with dual energy produced clear images of lung fields and bone structure by removing unnecessary anatomical structures. Dual energy tomosynthesis is a new technique; therefore, there is little guidance regarding its integration into clinical practice and this study can be used to improve the diagnostic efficiency of lung field and spinal bone screening using CDT.

Discrimination between Low Atomic Number Materials from their Characteristic Scattering of X-ray Radiation

The self-assembly of DPPC molecules starting from a random, solution-like configuration in the presence of water molecules is described in the present MD simulation study. Simulations were performed with either anisotropic or isotropic pressure coupling. Use of anisotropic pressure coupling led to the formation of a bilayer/bilayerlike aggregate; the features of the bilayer are in agreement with those reported from earlier simulation and experimental studies. In contrast, simulating the same system with isotropic pressure coupling led to the formation of a cylindrical micelle/lamellar structure with a large water hole. The formation of micelles seems unrealistic since diacylphosphatidylcholines having hydrocarbon tails with nine or more carbon atoms have been shown to form only bilayers. Simulations were also performed with preformed bilayerlike configurations with either anisotropic or isotropic pressure coupling. The bilayer characteristics deduced from simulations using anisotropic pressure coupling are in better agreement with those reported from earlier experimental and simulation studies. Thus, the choice of the pressure coupling method has a significant effect on the spontaneous aggregation of DPPC molecules but makes relatively lesser effect if the bilayer has formed already.

Magnetic field shielding technique for pulsed remote field eddy current inspection of planar conductors

Systems in applications ranging from aerospace, automotive, to power distribution are all crucially comprised of electrical connectors. Every system with removable electrical components will have electrical connectors, and likewise these systems will be susceptible to the contact losses and failure modes of these connections. Corrosion is one of the largest causes of failure for electrical connectors and costs the electrical power distribution system in the United States hundreds of millions of dollars annually. This study demonstrates the viability graphene as a protective coating for copper connectors to mitigate corrosion and improve electrical contact performance. Graphene, which is constituted of single layers of hexagonally-oriented carbon atoms, is inherently ultra-thin, chemically and thermally stable, gas impermeable (a property which can inhibit corrosion), highly electrically conductive, and made from an abundant and low-cost components, making it an ideal candidate for implementation as a protective coating on electrical contacts. In this work, single-layer graphene was deposited on copper used in commercially-available electrical connectors. In static tests the electrical contact resistance of the graphene-coated copper contact was two orders of magnitude lower than the contact resistance of the bare copper, and performed similarly to a benchmark gold/nickel coating that is a widely-used anticorrosive coating, demonstrating graphene's protective utility.

Our purpose in this study was to investigate the behavior of signal harmonics in magnetic particle imaging (MPI) by experimental and simulation studies. In the experimental studies, we made an apparatus for MPI in which both a drive magnetic field (DMF) and a selection magnetic field (SMF) were generated with a Maxwell coil pair. The MPI signals from magnetic nanoparticles (MNPs) were detected with a solenoid coil. The odd- and even-numbered harmonics were calculated by Fourier transformation with or without background subtraction. The particle size of the MNPs was measured by transmission electron microscopy (TEM), dynamic light-scattering, and X-ray diffraction methods. In the simulation studies, the magnetization and particle size distribution of MNPs were assumed to obey the Langevin theory of paramagnetism and a log-normal distribution, respectively. The odd- and even-numbered harmonics were calculated by Fourier transformation under various conditions of DMF and SMF and for three different particle sizes. The behavior of the harmonics largely depended on the size of the MNPs. When we used the particle size obtained from the TEM image, the simulation results were most similar to the experimental results. The similarity between the experimental and simulation results for the even-numbered harmonics was better than that for the odd-numbered harmonics. This was considered to be due to the fact that the odd-numbered harmonics were more sensitive to background subtraction than were the even-numbered harmonics. This study will be useful for a better understanding, optimization, and development of MPI and for designing MNPs appropriate for MPI.

With high-dose administration of 90Y labeled antibodies, it is possible to image 90Y without an admixture of 111In. We have earlier shown that it is possible to perform quantitative 90Y bremsstrahlung SPECT for dosimetry purposes with reasonable accuracy. However, whole-body (WB) activity quantification with the conjugate view method is not as time consuming as SPECT and has been the method of choice for dosimetry. We have investigated the possibility of using a conjugate view method where scatter-, backscatter- and septal-penetration compensations are performed by inverse filtering and attenuation correction is performed with a WB x-ray image, for total-body and organ activity quantification of 90Y. The method was evaluated using both Monte Carlo simulated scintillation camera images using realistic source distributions, and by an experimental phantom study. The method was evaluated in terms of image quality and accuracy of the activity quantification. The experimental phantom study was performed using the RSD torso phantom with 90Y activity uniformly distributed in the liver insert. A GE Discovery VH/Hawkeye system was used to acquire the image. The simulation study was performed for a realistic activity distribution in the NCAT anthropomorphic phantom where 90Y bremsstrahlung images were generated using the SIMIND MC program. Two different phantom configurations and two activity distributions were simulated. To mimic the RSD phantom experiment one simulation study was also made with 90Y activity located only in the liver. The SIMIND program was configured to resemble a GE Discovery VH/Hawkeye system. An x-ray projector program was used to generate whole-body x-ray images from the NCAT phantom for attenuation correction in the conjugate view method. Organ activities were calculated from ROIs that exactly covered the organs. Corrections for background activity, overlapping activity and source extension in the depth direction were applied on the ROI data. The total-body activities for the simulated images were generally overestimated by around 10%, which is reasonable since the correction for source extension was not applied on the total-body values. The accuracy of the organ activities was mostly within 15% for both the simulation study and the experimental study. The results suggest that it is possible to quantify 90Y activity in ROIs with reasonable accuracy using this method.