Connection Configurations Research Articles

Simultaneous nitrification and denitrification in the bio-cathode of a multi-anode microbial fuel cell

ABSTRACT A multi-anode microbial fuel cell (MA-MFC) was developed to investigate simultaneous nitrification and denitrification (SND) in the bio-cathode. As the chemical oxygen demand to nitrogen (COD/N) ratio of the cathode was increased from 0 to 4.5, the electricity-producing quantity ranged between 498 and 543 C and the attained total nitrogen (TN) removal rate reached 12.07 g TN·m−3·d−1, resulting in a TN removal efficiency of 78.8% under the target COD/N ratio of 3.5. The removal of pollutants in series and parallel, open-circuit and closed-circuit were compared, respectively. The removal rates of TN, , and cathode and anode COD were all higher in the parallel connection configuration than in the series configuration. In parallel connection, the TN removal rate reached 14.4 g TN·m−3·d−1, which was 1.9 times that in series connection. Compared with the open-circuit system, the removal rate of TN in the closed-circuit system was improved by 17.8%, which could be ascribed to electrochemical denitrification. The results of high-throughput sequencing confirmed and clarified the presence of autotrophic denitrification and heterotrophic denitrification, including aerobic denitrification, when the MA-MFC had been operated for 18 months.

Tai Chi Chuan exercise related change in brain function as assessed by functional near\u2013infrared spectroscopy

Early studies have shown that Tai Chi Chuan (TCC) contributes to the rehabilitation of cognitive disorders and increases blood oxygen concentration levels in the parietal and occipital brain areas; however, the mechanism of TCC training on brain function remains poorly understood. This study hypothesize that TCC has altered brain function and aims to explore the effects of TCC on functional connection and effective connection of the prefrontal cortex (PFC), motor cortex (MC), and occipital cortex (OC). The participants were 23 experienced Chen–style TCC practitioners (TCC group), and 32 demographically matched TCC–naive healthy controls (control group). Functional and effective connections were calculated using wavelet–based coherence analysis and dynamic Bayesian inference method, respectively. Results showed that beyond the intensity of activity in a particular cortical region induced by TCC, significant differences in brain activity and dynamic configuration of connectivity were observed between the TCC and control groups during resting and movement states. These findings suggested that TCC training improved the connection of PFC, MC and OC in myogenic activity, sympathetic nervous system, and endothelial cell metabolic activities; enhanced brain functional connections and relayed the ability of TCC to improve cognition and the anti–memory decline potential.

Progressive collapse resistance of precast concrete beam-column sub-assemblages with high-performance dry connections

Due to its relatively lower integrity, precast concrete structures are considered to be more vulnerable to progressive collapse than cast-in-place concrete structures. However, to date, majority of existing studies on progressive collapse focused on cast-in-place concrete structures, little attentions were paid to precast concrete structures. Among existing precast concrete structures, unbonded post-tensioning precast concrete structure is one of innovation dry connection structural systems, which no casting at the connections on site. Its excellent seismic performance was recognized by many studies, while studies on its progressive collapse resistance were very few. To fill this knowledge gaps, in this paper, eight half-scaled unbonded post-tensioning precast concrete beam-column sub-assemblages with different connection configurations were tested through pushdown tests to investigate their capacities and resistance mechanisms to prevent progressive collapse. The test results demonstrated various behaviors of beam-column sub-assemblages with different connection types. It was found that, as the longitudinal reinforcements were discontinuous across the beam-column joint region in the beams, flexural action observed in the cast-in-place concrete frames was not mobilized for the specimens with purely unbonded post-tensioning connections. When the specimens installed top-seat angles at the beam-column interfaces, considerable flexural action capacity could be mobilized for load resistance. Moreover, it was found that the failure modes of the specimens are distinctly different to that of conventional reinforced concrete frames or precast concrete frames with cast-in-place joints. The characteristic of compressive arch action and tensile catenary action in tested specimens is quite different to that of conventional reinforced concrete frames.

Feasibility study on triangular perfobond rib shear connectors in composite slab

This paper attempts to emphasize the experimental study on feasibility of Triangular perfobond rib shear connector in composite slab with cold formed steel beam. This rib shear connector is a feasible alternate to the existing type of connectors like shear studs etc., this perfoplate has triangular hole of size (30 × 50 mm) in the CFS plate of (500 × 40 mm) with two different positioning of triangular hole, one facing the flange (TR1) and the other facing opposite to flange (TR2). Vertical compressive force applied in Universal Testing Machine to find the shear capacity of the new connector in a composite slab. There is an increase in composite interaction which results in both the triangular perfobond have approximately equal load carrying capacity, but the slip behaviour is comparatively higher in the triangle head facing opposite to the flange (TR2). According to the failure phenomenon in ultimate loading state, the failure mechanism of perfobond rib shear connectors was analysed and the results indicates that brittle failure always occurs in perfobond rib connectors. The influence of the perfoplate connector configuration on the load bearing capacity and structural improvement was discussed.

Feedforward Thalamocortical Connectivity Preserves Stimulus Timing Information in Sensory Pathways.

Reliable timing of cortical spikes in response to visual events is crucial in representing visual inputs to the brain. Spikes in the primary visual cortex (V1) need to occur at the same time within a repeated visual stimulus. Two classical mechanisms are employed by the cortex to enhance reliable timing. First, cortical neurons respond reliably to a restricted set of stimuli through their preference for certain patterns of membrane potential due to their intrinsic properties. Second, intracortical networking of excitatory and inhibitory neurons induces lateral inhibition that, through the timing and strength of IPSCs and EPSCs, produces sparse and reliably timed cortical neuron spike trains to be transmitted downstream. Here, we describe a third mechanism that, through preferential thalamocortical synaptic connectivity, enhances the trial-to-trial timing precision of cortical spikes in the presence of spike train variability within each trial that is introduced between LGN neurons in the retino-thalamic pathway. Applying experimentally recorded LGN spike trains from the anesthetized cat to a detailed model of a spiny stellate V1 neuron, we found that output spike timing precision improved with increasing numbers of convergent LGN inputs. The improvement was consistent with the predicted proportionality of [Formula: see text] for n LGN source neurons. We also found connectivity configurations that maximize reliability and that generate V1 cell output spike trains quantitatively similar to the experimental recordings. Our findings suggest a general principle, namely intra-trial variability among converging inputs, that increases stimulus response precision and is widely applicable to synaptically connected spiking neurons.SIGNIFICANCE STATEMENT The early visual pathway of the cat is favorable for studying the effects of trial-to-trial variability of synaptic inputs and intra-trial variability of thalamocortical connectivity on information transmission into the visual cortex. We have used a detailed model to show that there are preferred combinations of the number of thalamic afferents and the number of synapses per afferent that maximize the output reliability and spike-timing precision of cortical neurons. This provides additional insights into how synchrony in thalamic spike trains can reduce trial-to-trial variability to produce highly reliable reporting of sensory events to the cortex. The same principles may apply to other converging pathways where temporally jittered spike trains can reliably drive the downstream neuron and improve temporal precision.

Equivalent Scheme for Calculating Short-Circuit Current in an Alternating-Current Electric Traction Network

The authors have proved the feasibility of substitution of a three-phase power-supply system with a single-phase one when calculating three-phase circuits in electric traction network irrespectively of the external power supply arrangement. In addition, calculation features have been established for particular transformer winding connection configurations (Y/Y or Y/Δ). Based on results of an analysis performed for minimizing the methodological error in calculating the short-circuit currents, a single-phase equivalent circuit has been developed for the intersubstation zone of the traction network, which takes into account the connection between two adjacent substations via an overhead transmission line of 110 (220) kV. An example of calculation in accordance with the proposed replacement scheme is given.

Reconstruction and Simulation of a Scaffold Model of the Cerebellar Network.

Reconstructing neuronal microcircuits through computational models is fundamental to simulate local neuronal dynamics. Here a scaffold model of the cerebellum has been developed in order to flexibly place neurons in space, connect them synaptically, and endow neurons and synapses with biologically-grounded mechanisms. The scaffold model can keep neuronal morphology separated from network connectivity, which can in turn be obtained from convergence/divergence ratios and axonal/dendritic field 3D geometries. We first tested the scaffold on the cerebellar microcircuit, which presents a challenging 3D organization, at the same time providing appropriate datasets to validate emerging network behaviors. The scaffold was designed to integrate the cerebellar cortex with deep cerebellar nuclei (DCN), including different neuronal types: Golgi cells, granule cells, Purkinje cells, stellate cells, basket cells, and DCN principal cells. Mossy fiber inputs were conveyed through the glomeruli. An anisotropic volume (0.077 mm3) of mouse cerebellum was reconstructed, in which point-neuron models were tuned toward the specific discharge properties of neurons and were connected by exponentially decaying excitatory and inhibitory synapses. Simulations using both pyNEST and pyNEURON showed the emergence of organized spatio-temporal patterns of neuronal activity similar to those revealed experimentally in response to background noise and burst stimulation of mossy fiber bundles. Different configurations of granular and molecular layer connectivity consistently modified neuronal activation patterns, revealing the importance of structural constraints for cerebellar network functioning. The scaffold provided thus an effective workflow accounting for the complex architecture of the cerebellar network. In principle, the scaffold can incorporate cellular mechanisms at multiple levels of detail and be tuned to test different structural and functional hypotheses. A future implementation using detailed 3D multi-compartment neuron models and dynamic synapses will be needed to investigate the impact of single neuron properties on network computation.

BOLTED CONNECTIONS FOR NON-INTERSECTING H-SECTION BEAM AND COLUMN IN STEEL MOMENT FRAMES

This research proposes connection configurations of two types for non-intersecting H-section steel beam and column. To elucidate the mechanical behavior of the proposed connections, full-scale moment connection tests and finite element analyses were conducted using T-shaped partial frame models. Comparisons between the proposed connections and regular intersecting connections demonstrate that the proposed connection is able to provide sufficient stiffness and energy-dissipation capacity if the beam and column flanges are designed to provide sufficient shear resistance. Then to understand the global behavior of frames using the proposed connections, pushover analyses of a two-story two-span frame were conducted. Because the bending moment of the beam acts on the column by a torque through the proposed connections, torsion spring models were incorporated for representing the proposed connections in 3D frame analysis. Analysis results showed that the girders and columns exhibited lower stiffness and strength than those of frames with intersecting connections because of torsion. To overcome this issue, torsion restraint by secondary beams with different configurations was discussed and optimal configuration was suggested. By utilizing the optimal configuration, torsion of girders and columns can be efficiently reduced into a similar level as that of regular intersecting connections.

Experimental performance of irregular PZs in CHS column H-shape beam steel frame

The study is aimed at clarifying the elastic and inelastic behaviour of irregular panel zones (PZs) in a steel moment-resisting frame with circular hollow section (CHS) steel columns and H-shape steel beams connected with external diaphragm under cyclic loading, where the elevations of the beams on left- and right-hand sides of the column are different. To this end, experiments were carried out on the beam-to-column steel sub-assemblage frame connected with an external diaphragm. A parametric study was conducted by considering different values of a parameter β (the ratio of the elevation difference of the beams on both sides of the column to the beam height), and different configurations of the external diaphragm in the connection. The experimental results revealed that the parameter β has a significant influence on the stiffness of the PZs, but no significant effect on the shear strength of the PZs, and the stiffness of the PZs decrease as β increases. In addition, the shape of the external diaphragm has significant influences on the energy dissipation capacity and load bearing capacity of the frame. A qualitative evaluation of the mechanical performance of the PZs is given, and a reasonable connection configuration for the structure design with the PZs is provided. The non-linear finite element analysis (FEA) method was also used to analyze the test specimens. By comparing with the experimental results, the FEA method can give a reference for quantitative analysis of the mechanical properties of the irregular PZs.

Distinguishing the Visual Working Memory Training and Practice Effects by the Effective Connectivity During n-back Tasks: A DCM of ERP Study.

Visual working memory (WM) training and practice can result in improved task performance and increased P300 amplitude; however, only training can yield N160 enhancements. N160 amplitudes are related to the spatial attention, the detection of novelty and the inhibitory control, while P300 amplitudes are related to the selective attention. Therefore, it could be speculated that the mechanisms underlying N160 and P300 production may differ to accommodate to their functions. Based on the different N160 engagements and different functional roles of N160 and P300, we hypothesized that the effects of visual WM training and practice can be dissociated by their brain effective connectivity patterns. We compared different neural connectivity configurations for the main task-related brain activities including N160 and P300 during the visual three-back task in subjects after visual WM training (the WM group) and after repetitive task practice (the control group). The behavioral result shows significantly greater improvement in accuracy after training and suggests that visual WM training can boost the learning process of this simple task. The N160 peak amplitude increased significantly after training over the anterior and posterior brain areas but decreased after practice over the posterior areas, indicating different mechanisms for mediating the training and practice effects. In support of our hypothesis, we observed that visual WM training alters the frontal-parietal connections, which comprise the executive control network (ECN) and the dorsal attention network (DAN), whereas practice modulates the parietal-frontal connections underpinning P300 production for selective attention. It should be noted that the analytic results in this study are conditional on the plausible models being tested and the experimental settings. Studies that employ different tasks, devices and plausible models may lead to different results. Nevertheless, our findings provide a reference for distinguishing the visual WM training and practice effects by the underlying neuroplasticity.

Cyclic behavior of reinforced concrete cladding panels connected with energy dissipative steel cushions

Precast concrete structures show damage after the destructive earthquakes and indicate that the connections of reinforced concrete (RC) cladding panels might be inadequate. RC cladding panels greatly increase the lateral stiffness and strength of the building when they are rigidly connected to the structural system. However, this also increases the seismic requirements. Consequently, a robust mechanical connection device with energy-dissipating capability was produced for RC cladding panels. Extensive experimental and numerical studies on an energy-dissipative steel cushion (SC) connection device were carried out in the framework of the SAFECLADDING project. Cladding panel tests were conducted with various connection configurations. The fundamental variables are the location, quantity, and thickness of SCs used in the cladding systems. The test results demonstrate that the SCs used in panel-to-panel and panel-to-support connections made large contributions to the total energy dissipation capacity. The parameters of a numerical model were also evaluated to reproduce the experimental results.

A series of fluorenone-carbazole based regioisomers as bipolar host materials for efficient organic light emitting diodes

A series of fluorenone-carbazole based regioisomers (1–4) have been synthesized and applied as host materials for red OLEDs to investigate the effect of different connection configuration on the optoelectronic properties, charge transport capability and device performance. The optoelectronic properties, thermal stability, redox behaviors and charge transport characteristics of these four compounds were fully characterized. These four hosts demonstrated high thermal stability, bipolar charge transport properties and good EL performance. Although these four compounds demonstrated similar HOMO and LUMO energy levels, the twisted structure of 1 led to the smallest singlet-triplet energy gap, which could account in part for the observation of its better EL performance.

Initial orientation of the fretting fatigue cracks in shrink-fit connection specimens

The bending configuration of shrink-fitted connection fretting fatigue tests causes a fluctuation of the contact pressure and in turn a more favourable condition for shear, rather than tensile, crack initiation. According to the classification Type I (shear) and Type II (tensile) fretting cracks, the type II was only observed for the tests with no surface enhancement, which experienced the lowest fretting strength and then a reduced pressure fluctuation effect. The crack initial direction was predicted as the critical plane orientation undergoing the maximum FS stress parameter, for the shallow type I shear cracks. If the critical plane is searched at the fretting hot-spot, the incorrect outward direction is obtained, since the orthogonal direction, with the same shear stress amplitude, experiences a more compressive maximum normal stress. On the contrary, with the application of the Point Method, taking the stress location at half the critical distance and by following the potential critical plane, a higher shear stress along the inward direction is obtained. The more compressive stress below the contact can therefore be compensated, and then the inward shallow direction is correctly predicted.

Analysis of Partial Power DC–DC Converters for Two-Stage Photovoltaic Systems

Two-stage photovoltaic (PV) configurations have become increasingly popular due to the decoupling between the inverter dc-link voltage and the PV voltage, adding flexibility to extend the maximum power point tracking range. However, the additional dc–dc converter increases the power converter losses. The concept of partial power converters (PPCs), which reduce the amount of power handled by the dc stage, can mitigate this effect. However, the type of topology, its power and voltage rating, efficiency, and an operating range can vary significantly depending on the function (boosting or reducing voltage) and type of PV application and scale (micro-, string-, or multi-sting inverter). This paper analyzes the possible configuration of connections of PPC depending on the application and scale of the PV system and introduces a new buck-type PPC. Three solutions for practical PV systems are further elaborated, including experimental validation. Results show that the PPC concept greatly improves the overall PV system efficiency with the added benefit that the dc–dc stage power ratings achieved are only a fraction of the PV system, reducing size and cost of the power converter without affecting the system performance.

Study on Electrical Tests of Superconducting Busbar Protection Insulation of ITER Feeder PF4 CFT

Poloidal field coil no. 4 (PF4) cryostat feedthrough (CFT) is a key subcomponent of ITER feeder system. The superconducting busbars of PF4 CFT have insulation protection layer, which consists of several half-overlapped pre-preg and glass Kapton for main structure. Base on the special busbar structure, how to do the electrical tests for production final acceptance was studied. In this paper, three kinds of electrical tests for PF4 CFT busbar insulation acceptance were introduced, include direct current high-voltage test, alternating current partial discharge test, and Paschen test. On-site environment control, electrodes connection configuration, and some detail processes of these electrical tests were introduced. Some test results of leakage current were showed in this paper to guarantee the high quality of PF4 CFT superconducting busbar protection insulation.

Effects of ground heat exchangers with different connection configurations on the heating performance of GSHP systems

The connection configurations of ground heat exchangers (GHEs) have a significant impact on the ground temperature and the performance of ground source heat pump (GSHP) systems. In this paper, the heating performance of a GSHP system implemented in a net zero-energy building with two different GHE connection configurations, including series and parallel connections, was experimentally and numerically investigated. A mathematical model was developed based on ANSYS fluent to analyze the thermal performance of the GHEs and the model was validated against the experimental data. The experimental results showed that the parallel configuration of the GHEs achieved a better heating performance when the mass flow rate was 2.58 kg·s−1, as compared to that of the series configuration. The system heating performance with both series and parallel configurations of the GHEs increased with the decrease in the fluid flow rate under the same heating load condition. The pressure drop between the inlet and outlet of the GHEs with the series configuration was also higher when compared to that with the parallel configuration.

Meso-to-microscale fracture porosity in tight limestones, results of an integrated field and laboratory study

Abstract The complex fluid saturation distribution and influence of microscale and mesoscale fractures on the fluid accumulation and flow properties of carbonates are still interesting challenges for petroleum geologists. For this reason, in order to know the relative role played by the aforementioned features on the storage and migration properties of tight limestones, the present work focuses on a surface analogue cropping out in southern Italy. By first applying a deterministic Discrete Fracture Network (DFN) modelling to a 1 m3 geocellular volume, an amount of 0.3% of fracture porosity and a fracture connectivity configuration above the percolation threshold are computed. In addition to mesoscale fracture porosity, in order to gather information on matrix porosity and microscale fractures, we investigate the pore type, geometry, and textural anisotropy of selected rock plugs by mean of integrated petrophysical, ultrasonic, and optical microscopy analyses experiments. Results show values of connected porosity ranging between 1% and 6%, presence of vugs localized along pre-existing structural heterogeneities, and the predominance of stiff pores within the carbonate matrix. The rare microfractures are mainly oriented orthogonal to bedding. The estimated crack density (0.19) shows that the contribution of fracture porosity at microscale (ɸ = 0.078%) is very low if compared to that of matrix porosity and also a structural configuration above the percolation. The present study therefore documents that the carbonate matrix forms an isotropic medium, which profoundly affects the storage capability of the study limestones. In fact, the amount of storage provided by carbonate matrix and microscale fractures is greater than that due to mesoscale fractures. Moreover, we document that the matrix contribution on porosity is much more significant than the contribution provided by microfractures. Finally, the present work shows the importance of integrating different methodologies on the assessment of fracture porosity at different scales of observation. In fact, a great benefit for development and production operations can be obtained by performing studies of surface analogs, which allow the detailed investigation of rock masses below seismic resolution.

Beam‐column connections of concrete‐filled double steel tubular frame structures

SummaryFour types of concrete‐filled double steel tubular (CFDST) columns were introduced in this paper, which had the advantage of higher bearing capacity, stronger stiffness, and better fire‐resistant and explosion‐resistant performance. To research a reasonable form of beam‐column connection is the top priority in CFDST frame structures. After a brief historical background concerning the development of CFDST columns, this study conducted an investigation and comparison of several existing beam‐column connections. The constructional detail and force transfer mechanism of each beam‐column connection were analyzed according to the present research achievements. Several finite element models were established to discuss the various connection configurations and main factors affecting their behaviors. In general, connection design can take full advantage of the characteristic of double tubes in CFDST structure, so a series of construction improvements for joint design parameters in CFDST frame structures was proposed to improve the seismic performance and the relevant study for the future work was also discussed.

Effect of gusset connection configurations on frame–gusset interaction in steel buckling‐restrained braced frame

SummaryAlthough buckling restrained braces (BRBs) are commonly applied in seismic buildings to mitigate structural damage, their performance was often limited by rupture of the corner gusset connections due to additional frame action. This issue may be resolved by alternative gusset connections to mitigate the frame–gusset interaction. In this study, commonly used procedures for design of the traditional gusset connection are reviewed, followed by a case study on the effect of frame action on the structural behavior of these gusset connections in steel frames with BRBs. Inspired by these analysis, two different strategies, aiming at releasing frame–gusset shear interaction using sliding gusset connection or reducing normal interaction using dual gusset plates, are tried to mitigate the frame action effects. Finite element analysis is conducted on steel frame subassemblages with/without BRBs to examine the effect of different gusset connections on the structural behavior of these framing systems. It shows that the sliding gusset connection shows beneficial effect in reducing the frame action, having much smaller stress responses on the gusset interfaces, as well as smaller shear force and plastic responses on the framing system. Thus, it becomes a promising gusset connection for improved seismic performance of the steel framing system with brace‐type dampers.

Design of Solder Connections for Self-Assembly of Optoelectronic Devices

Abstract In surface mount assembly, advantage is taken of the high surface tension of molten solder to self-align ball grid array packages and flip chip die. However, in these applications, the volume of solder applied as paste by stencil printing is not sufficiently well controlled to achieve the precise alignment required for optoelectronic devices. We believe that the requirement on solder volume control for assembly of optoelectronic devices can be relaxed by designing the bond pads so that the height or alignment of connections is controlled by the surface tension of the solder rather than its volume. Our design approach to accomplishing this is to connect auxiliary pads to the primary attachment pad, which act as solder reservoirs. Surface tension causes the solder to be redistributed among these pads to achieve a uniform pressure throughout the solder volume. This phenomena is governed by the Young-Laplace equation, ΔP = γκ, in which ΔP represents the difference in pressure within and outside the solder, γ the surface tension of the solder, and κ the local curvature of the solder surface. Thus, the design of the set of primary and auxiliary pads is critically important to realizing the desired control of joint height. In this article, we describe the use of the Surface Evolver software package in combination with analytical models, to analyze the behavior of various connection configurations with respect to variations in printed solder volume. Specifically, we calculate the equilibrium shape of the solder surface over the connected set of pads and examine how control of joint height is affected by the number, size, and geometry of auxiliary pad configurations.