Connection Configurations Research Articles

Radial distribution of the plasma potential in a cylindrical plasma column with a longitudinal magnetic field

The possibility of controlling the electrostatic field distribution in plasma has yielded wide prospects for modern technologies. As a magnetic field primarily allows for creating electric fields in plasma, it serves as an additional obstacle for the current flow through a medium. In the present paper, an axially symmetric system is considered in which the magnetic field is directed along the axis and concentric electrodes are located at the ends. The electrodes are negatively biased. A model which solves the problem of the radial distribution of the plasma potential inside the cylindrical plasma column supported by the end electrodes is proposed. The most commonly encountered configurations of the electrical connection for the end electrodes are considered, and the particular solutions to the problem of the radial distribution are presented. The contribution of ions and electrons to the transverse conductivity is evaluated in detail. The influence of a thermionic element on the radial profile of the plasma potential is considered. To verify the proposed model, an experimental study of the reflex discharge is carried out with both cold electrodes and a thermionic element on the axis. A comparison of the computational model results with experimental data is given. The presented model makes it possible to solve the problem concerning the plasma potential distribution in the case of an arbitrary number of end electrodes, and also to take into account the inhomogeneity of the distribution of plasma density, neutral gas pressure and electron temperature along the radius.

Dynamic brain connectome and high risk of mental problem in clinical nurses.

With the growing population and rapid change in the social environment, nurses in China are suffering from high rates of stress; however, the neural mechanism underlying this occupation related stress is largely unknown. In this study, mental status was determined for 81 nurses and 61 controls using the Symptom Checklist 90 (SCL‐90) scale. A subgroup (n = 57) was further scanned by resting‐state functional MRI with two sessions. Based on the SCL‐90 scale, “somatic complaints” and “diet/sleeping” exhibited the most prominent difference between nurses and controls. This mental health change in nurses was further supported by the spatial independent component analysis on functional MRI data. First, dynamic functional connectome analysis identified two discrete connectivity configurations (States I and II). Controls had more time in the State I than II, while the nurses had more time in the State II than I. Second, nurses showed a similar static network topology as controls, but altered dynamic properties. Third, the symptom‐imaging correlation analysis suggested the functional alterations in nurses as potential imaging biomarkers indicating a high risk for “diet/sleeping” problems. In summary, this study emphasized the high risk of mental deficits in nurses and explored the underlying neural mechanism using dynamic brain connectome, which provided valuable information for future psychological intervention.

Cyclic experiments on isolated steel sheet connections for CFS framed steel sheet sheathed shear walls with new configurations

The main objective of this research is to experimentally characterize the performance of isolated single sheathing-to-framing fastener connections under cyclic load as utilized in emerging classes of cold-formed steel (CFS) framed steel sheet sheathed shear walls used for seismic lateral resistance. New shear wall variations include the use of steel sheet sheathing sandwiched between framing members (i.e., mid-ply) and the use of heavy hollow structural sections (HSS) chord members with the thin steel sheet sheathing attached by power actuated fasteners (PAF) to the HSS. The cyclic nonlinear response of the framing to steel sheet fastener connection is fundamental for simulating the seismic performance of steel sheet sheathed shear walls. Minimal cyclic fastener-level test data under shear exists for these new configurations. A unique lap shear test following AISI S905 was designed to study and characterize the cyclic fastener connection behavior. The specimens were loaded with an asymmetric cyclic loading protocol which intentionally buckles the thin sheet in the compression direction, and progressively increases in the tension direction. Sixty-three tests covering a wide range of framing thickness, sheet thickness, fastener type and size were completed. Each connection configuration is characterized with a multi-linear backbone curve ready for use in numerical shear wall models. The tested fastener configurations exhibit excellent performance as fastener tilting is largely or completely eliminated in these configurations, and connection degradation from buckling of the steel sheet is minimized. It is also shown that AISI S100 connection strength provisions are applicable to the tested connections.

Novel Thermally Reduced Graphene Oxide Microsupercapacitor Fabricated via Mask-Free AxiDraw Direct Writing.

We demonstrate a simple method to fabricate all solid state, thermally reduced graphene oxide (TRGO) microsupercapacitors (µ-SCs) prepared using the atmospheric pressure chemical vapor deposition (APCVD) and a mask-free axiDraw sketching apparatus. The Fourier transform infrared spectroscopy (FTIR) shows the extermination of oxygen functional groups as the reducing temperature (RT) increases, while the Raman shows the presence of the defect and graphitic peaks. The electrochemical performance of the µ-SCs showed cyclic voltammetry (CV) potential window of 0–0.8 V at various scan rates of 5–1000 mVs−1 with a rectangular shape, depicting characteristics of electric double layer capacitor (EDLC) behavior. The µ-SC with 14 cm−2 (number of digits per unit area) showed a 46% increment in capacitance from that of 6 cm−2, which is also higher than the µ-SCs with 22 and 26 cm−2. The TRGO-500 exhibits volumetric energy and power density of 14.61 mW h cm−3 and 142.67 mW cm−3, respectively. The electrochemical impedance spectroscopy (EIS) showed the decrease in the equivalent series resistance (ESR) as a function of RT due to reduction of the resistive functional groups present in the sample. Bode plot showed a phase angel of −85° for the TRGO-500 µ-SC device. The electrochemical performance of the µ-SC devices can be tuned by varying the RT, number of digits per unity area, and connection configuration (parallel or series).

Squeak and Rattle Prevention by Geometric Variation Management Using a Two-Stage Evolutionary Optimization Approach

Abstract Squeak and rattle are annoying sounds that are often regarded as failure indicators by car users. Geometric variation is a key contributor to the generation of squeak and rattle sounds. Optimization of the connection configuration in assemblies can be a provision to minimize this risk. However, the optimization process for large assemblies can be computationally expensive. The focus of this work is to propose a two-stage evolutionary optimization scheme to find the fittest connection configurations that minimize the risk for squeak and rattle. This was done by defining the objective functions as the measured variation and deviation in the rattle direction and the squeak plane. In the first stage, the location of the fasteners primarily contributing to the rattle direction measures is identified. In the second stage, fasteners primarily contributing to the squeak plane measures are added to the fittest configuration from phase one. It was assumed that the fasteners from the squeak group plane have a lower-order effect on the rattle direction measures, compared to the fasteners from the rattle direction group. This assumption was falsified for a set of simplified geometries. Also, a new uniform space filler algorithm was introduced to efficiently generate an inclusive and feasible starting population for the optimization process by incorporating the problem constraints in the algorithm. For two industrial cases, it was shown that by using the proposed two-stage optimization scheme, the variation and deviation measures in critical interfaces for squeak and rattle improved compared to the baseline results.

Analysis of DC-Biased Vernier Reluctance Machines Having Distributed Windings

This article analyses the electromagnetic performance of dc-biased current vernier reluctance machines (DCB-VRMs) with distributed windings. Taking example of 12-stator slot machines, the coil connection and current configuration are illustrated. Moreover, the back electromotive force (EMF), torque capability, etc., are analyzed by finite-element analysis (FEA). In addition, the torque density of DCB-VRMs equipped with distributed and nonoverlapping windings are compared. The results show that some combinations of distributed winding machines present a higher torque capability thanks to the higher pole ratio.

Resonance Risk and Mode Shape Management in the Frequency Domain to Prevent Squeak and Rattle

Abstract Avoiding quality problems in passenger cars, such as squeak and rattle (S&R), has been a remarkable cost-saving consideration. The introduction of electric engines and autonomous driving is expected to further stress the need for quieter cabins. However, the complexity of S&R events has obstructed the practical treatment of these quality issues in the pre-design-freeze phases of product development. In this study, new quantified frequency-domain metrics are proposed to measure the risk of S&R generation in car subsystems. The proposed metrics measure the resonance risk and the mode shape similarity in the critical interfaces for S&R. The calculations are done based on the system response in the frequency domain. Compared with the time-domain evaluation methods, the knowledge about the system excitation levels is not essential and the calculations are more time-efficient. The proposed metrics can be used in design optimization processes to involve S&R attributes in the pre-design-freeze attribute trade-off activities besides other attributes. In this work, these metrics were used in a previously developed two-stage optimization approach to determine the connection configuration in two industrial cases. As compared with the baseline design, the risk for S&R was reduced by improving the system behavior in terms of resonance risk and mode shape similarity. This was achieved by applying adjustments to the location of the fasteners while maintaining the same general connection configuration concept.

Behaviour and design of prefabricated CFST stub columns with PCC connections under compression

This paper investigates the compressive behaviour of prefabricated concrete-filled steel tube (CFST) columns with prefabricated column–column (PCC) connections. The innovative PCC connections are designed using conventional structural bolts instead of expensive blind bolts to connect two prefabricated CFST columns, simplifying the construction process and rendering the construction cost-effective. The compressive behaviour of prefabricated CFST columns with or without PCC connections has been investigated numerically. Parametric studies have been conducted to investigate the effect of different parameters of PCC connections, including connection configurations, horizontal and vertical stiffeners of connections, diameter of the coupling bolt, steel tube thickness, yield strength of steel tube, and compression strength of concrete, on the compressive behaviour of CFST columns with PCC connections. The prefabricated CSFT columns with the developed PCC connections are able to achieve similar compressive strengths that are achieved by the CFST columns without connections. Therefore, the developed PCC connections can be used to construct prefabricated CFST columns for the prefabricated steel–concrete composite structures.

Flexibility requirement of bolted double-angle shear connections

This paper presents a series of experimental and analytical studies on the ductility requirements of bolted double-angle shear connections. Five full-scale connection configurations were tested, and their load-deformation behaviour was monitored using the digital image correlation technique. The yield line patterns observed from the experiments differ from the assumed pattern used in the derivation of the ductility equations currently available in design guidelines. The identified deformation contours were used as the basis for further development of analytical formulations applicable to the flexibility requirements of connections. The yield line theory was employed to evaluate the induced moment on the connections at the ultimate shear capacity. The details of the experimental setup including test parameters, loading scenarios, and the digital image correlation technique are fully outlined. Finally, the developed formulation was validated through a comparison with previously published experimental results. The results show the proposed solution provides an accurate estimation of the moments induced on double angle shear connections at ultimate capacity rotations.

The Effect of 12 Pulse Converter Input Transformer Configuration on Harmonics of Input Current

This paper discusses the effect of the 12-pulse converter input transformer configuration on the input harmonic currents. This is done because there are many transformer connection configurations, which according to the standard there are 5 transformer connection groups. The research method begins with a literature study on the 12-pulse converter. Next, determine the specifications of the 12-pulse converter and build the 12-pulse converter. Then, a theoretical analysis was carried out on the waveform of the 12-pulse converter current with the Dy11/d0 and Yd1/y0 input transformer configurations. From the analysis and simulation results, it was found that the THDi of the two 6 pulse converters obtained 29% THDi, while the 12-pulse converter inputs side obtained 11.59%-13,6% THDi. The input transformer configuration does not affect the THDi results, except for the power sent by the 12-pulse converter with the input transformer configuration Yd1_y0 to 1/3 compared to the Dy11_d0 connection.

Electrical Modelling and Mismatch Effects of Thermoelectric Modules on Performance of a Thermoelectric Generator for Energy Recovery in Diesel Exhaust Systems

Thermoelectric generators harvesting energy from exhaust gases usually present a temperature mismatch between modules, due to the gradual cooling of the gases along the flow direction. The way modules that produce unequal voltages are connected has a deep impact on the overall power output. A further step in the prediction of thermoelectric production is to consider the complete layout of the thermoelectric modules and not consider them as isolated systems. In this work, a model to predict the electric behavior of thermoelectric generators for automotive applications at different points of operation is presented. The model allows testing of serial-parallel connection configurations. The results present good agreement with experimental data. This model could be used on similar light duty vehicles with similar engines as the engine used in this work and using similar configuration of thermoelectric generators. Simulated scenarios considering realistic operating conditions in a light duty vehicle allow stating that thermoelectric modules interconnection under heterogenous thermal surface conditions has a significant negative effect (more than 17%) on electric energy production. Moreover, the proposed model shows the need to protect the electric circuit of the thermoelectric generator to avoid the negative effect of possible malfunction of some thermoelectric modules.

Brain state-dependent dynamic functional connectivity patterns in attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) patients have presented aberrant static brain networks, however identifying ADHD patients based on dynamic information in brain networks is not fully clear. Data were obtained from 32 boys with ADHD and 52 sex- and age-matched typically developing controls; a sliding-window method was used to assess dynamic functional connectivity (dFC), and two reoccurring dFC states (the hot and cool states) were then identified using a k-means clustering method. The results showed that ADHD patients had significant changes in occurrence, transitions times and dFC strength of the cingulo-opercular network (CON) and sensorimotor network (SMN) in the cool state. The severity of ADHD symptoms showed significant correlations with the regional amplitude of dFC fluctuations in the ventral medial prefrontal cortex (vmPFC), anterior medial prefrontal cortex (amPFC) and precuneus. These findings could provide insights on the state-dependent dynamic changes in large-scale brain connectivity and network configurations in ADHD.

Numerical and analytical study of stainless steel beam-to-column extended end-plate connections

Based on a shell finite element modeling protocol developed and verified by the first author in a previous study, a comprehensive investigation on stainless steel extended end-plate beam-to-column connections was carried out. A total of 180 connection configurations were numerically investigated, to establish a thorough understanding of the influence of a wide range of geometrical parameters on the behavior of this connection type commonly-used in earthquake-resistant steel structures. The initial stiffness; ultimate moment; rotation capacity; dissipative energy; ductility index; and failure patterns were compared and discussed. Furthermore, based on the data acquired from this parametric study, a simple analytical method, for predicting the moment-rotation (M-Φ) characteristics of stainless steel extended end-plate connections, was developed and validated. The results demonstrate that stainless steel extended end-plate connections can be designed to have substantial ductility and rotation capacity, more than satisfactory for beam-to-column joints of structures in seismic zones. In particular, connections with end-plate stiffeners displayed superior performance with enhanced ultimate moment and energy dissipation capacity. The recommended analytical method for M-Φ response of the joints is accurate, with an average error of less than 4% for the ultimate resistance and is robust as evidenced by its prediction of M-Φ response for models that were withheld from its initial calibration. The proposed equations provide, for the first time, a powerful analytical tool that can predict the complete moment-rotation curves of unstiffened and stiffened stainless steel extended end-plate joints, using easy-to-obtain geometric and material properties.

Experimental determination of the pull-out strength of mechanically fastened steel rods into glulam beam sections having different rod lengths and washer sizes

A new tension connection configuration utilizing threaded steel rods that are mechanically fastened into glued-laminated timber (glulam) sections has been experimentally investigated in this study. Nine different connection configurations have been examined, with each configuration being replicated four times to verify results. The glulam connection parameters studied were rod embedment length (150, 200, and 250 mm) and washer bearing area (38.1 × 38.1 mm, 50.8 × 50.8 mm, and 63.5 × 63.5 mm). Experimental results show that the largest washer (63.5 × 63.5 mm) induced wood splitting failure in the beam section more frequently as the rod embedment length decreased, creating the largest standard deviation in results among those of the three washer sizes tested in this study. Whereas the smallest washer (38.1 × 38.1 mm) induced wood crushing failure with the greater displacements into the glulam section when the rod embedment length increased. However, the dominant failure mode in the test specimens that employed the medium washer (50.8 × 50.8 mm) was rod pull-out since the washer was not too large to induce wood splitting nor too small to induce wood crushing failure in the glulam section.

Downscaling With an Unstructured Coastal-Ocean Model to the Goro Lagoon and the Po River Delta Branches

The Goro Lagoon Finite Element Model (GOLFEM) presented in this paper concentrates on the high-resolution downscaled model of the Goro Lagoon, along with five Po river branches and the coastal area of the Po delta in the northern Adriatic Sea (Italy) where crucial socio-economic activities take place. GOLFEM was validated by means of validation scores (bias – BIAS, root mean square error – RMSE, and mean absolute error – MAE) for the water level, current velocity, salinity and temperature measured at several fixed stations in the lagoon. The range of scores at the stations are: for temperature between −0.8 to +1.2°C, for salinity from −0.2 to 5 PSU, for sea level 0.1 m. The lagoon is dominated by an estuarine vertical circulation due to a double opening at the lagoon mouth and sustained by multiple sources of freshwater inputs. The non-linear interactions among the tidal forcing, the wind and the freshwater inputs affect the lagoon circulation at both seasonal and daily time scales. The sensitivity of the circulation to the forcings was analyzed with several sensitivity experiments done with the exclusion of the tidal forcing and different configurations of the river connections. GOLFEM was designed to resolve the lagoon dynamics at high resolution in order to evaluate the potential effects on the clam farming of two proposed scenarios of human intervention on the morphology of the connection with the sea. We calculated the changes of the lagoon current speed and salinity, and using opportune fitness indexes related to the clams physiology, we quantified analytically the effects of the interventions in terms of extension and persistence of areas of the clams optimal growth. The results demonstrate that the correct management of this kind of fragile environment relies on both long-term (intervention scenarios) and short-term (coastal flooding forecasts and potential anoxic conditions) modeling, based on a flexible tool that is able to consider all the recorded human interventions on the river connections. This study also demonstrates the importance of designing a seamless chain of models that are capable of integrating local effects into the coarser operational oceanographic models.

Microstructured multimaterial fibers for efficient optical detection

AbstractFlexible optoelectronic fibers are recognized as one type of important building block for the system of wearable electronics and advanced functional textiles. The thermal drawing process offers promise for scalable construction of optoelectronic fibers, while they are generally characterized by the continuous cylindrical structure and poor electrical property. Here, we report the fabrication and characterization of the flexible structured multimaterial fibers thermally drawn from the combination of metal‐semiconductor‐polymer, and control of their inner structure via fluid Plateau‐Rayleigh instability. A trapezoidal electrical connection configuration with the semiconductor spheres clamped by two metal electrodes inside the fiber is successfully achieved based on this fluid instability. The obtained structured multimaterial fiber shows better photoresponse properties than that of the as drawn multimaterial fiber. The findings open new opportunity to develop fiber devices for efficient optical detection.

Transmission delays and frequency detuning can regulate information flow between brain regions.

Brain networks exhibit very variable and dynamical functional connectivity and flexible configurations of information exchange despite their overall fixed structure. Brain oscillations are hypothesized to underlie time-dependent functional connectivity by periodically changing the excitability of neural populations. In this paper, we investigate the role of the connection delay and the detuning between the natural frequencies of neural populations in the transmission of signals. Based on numerical simulations and analytical arguments, we show that the amount of information transfer between two oscillating neural populations could be determined by their connection delay and the mismatch in their oscillation frequencies. Our results highlight the role of the collective phase response curve of the oscillating neural populations for the efficacy of signal transmission and the quality of the information transfer in brain networks.

Shaking table test of a supertall building with hinged connections connecting a gravity load resisting system to a lateral force resisting system

ABSTRACT Considering a common practical engineering structure, namely, a concrete-filled steel tube (CFST)-steel frame-core tube structure, the rigid connections between the steel beams and the columns/core are modified into hinged connections. In this manner, a 1:40 reduced scale specimen representing a real supertall building that consists of 68 storeys and four underground storeys is constructed for a shaking table test to study the seismic performance of the structure. Numerical simulations are performed to analyse the time history responses of a CFST-steel frame-core tube structural system with three different connection configurations: hinged joints, rigid joints and strengthened layers (which are defined as storeys equipped with outrigger and belt trusses to limit inter-storey drift). The results indicate that the earthquake damage to the structure mainly occurs in the lower storeys at the connections and the corners of the core tube. The seismic response of the structure under the long-period ground motion is significant. The largest inter-storey drift ratio of the core tube reaches 1/26, which exceeds the threshold of the frame-core tube structure system in the Chinese Code by a factor of 3.8. Both the rigid joints and the strengthened layers can reduce the inter-storey drift ratio of the structure.

Push-Out Behavior of Short Headed Stud Connectors in Steel-Ultra High Performance Concrete Composite Deck

A steel-ultra high performance concrete (UHPC) composite deck has good fatigue performance while the thin UHPC slab leaves a very limited space for the connector configuration. This is actually crucial to achieve the composite action. Current literatures concerning the short stud behavior are still limited for a general mechanism understanding. Therefore, a series of push-tests containing 15 specimens were conducted for investigating the mechanical behavior of short studs with various diameters and lengths in UHPC composite deck. And a parametric FEM analysis with nonlinear material constitutions was conducted as well for the bearing performance understanding. The push-out tests showed the shear fracture near stud roots is the leading dominant failure mode, and a longer stud length might introduce a higher percentage of stud shank bending deformation. It explained longer stud length could be helpful to improve the shear strength of stud in UHPC. Meanwhile, the shear stiffness of the push-out specimens were all increased with a larger stud diameter or length. On the other side, the analysis results showed that a pull-out failure could happen when the stud length was less than 25 mm in UHPC and the failure mode of stud could also be affected by the concrete strength. In addition to the tests and analysis, the safety redundancies of strength evaluations of short stud in UHPC based on several civil codes were discussed in terms of the comparison works.

Evaluation on influences of inertial mass on seismic responses and structure-soil interactions of pile-soil-piers

This research is to assess the influences of the inertial mass from the girder on the dynamic characteristic, dynamic response, and structure-soil interaction of a pile-soil-pier subsystem in a scale-model of a cable-stayed bridge. Therefore, both connection configurations between the pile-soil-pier and girder, including the sliding and fixed connections, were designed to present various inertial mass from the superstructure delivered to the pile-soil-pier. The pile-soil-pier supported by a 3 × 3 pile-group in mixed soil placed in a shear box was tested using shaking tables. The dynamic characteristics, seismic responses, inertial interactions, and pile group effects of the pile-soil-pier between the sliding and fixed connections were analyzed under three input motions with different shaking amplitudes. These results showed that more inertial mass from the girder significantly increased the reinforcement strain and bending moment at the column bottom and pile top, displacement at the column top, inertial interaction effects, and pile group effects of the pile-soil-pier due to the sliding connection changing to the fixed connection. The inertial mass increment from the girder noticeably decreased the peak accelerations of the column of the pile-soil-pier when subjected to three input motions with different amplitudes. However, the inertial mass insignificantly affected the accelerations of the pile and free-soil. Therefore, the corresponding kinematic interaction effects were almost unaffected by the inertial mass. Additionally, the evident pile group effects were observed in the sliding and fixed connections between the pile-soil-pier and girder. The numerical model could approximately reproduce the macroscopic seismic responses of the pile-soil-piers with sliding and fixed connections and capture the typical response variations induced by the connection configuration change.