Column Length Research Articles

A microchip gas chromatography column assembly with a 3D metal printing micro column oven and a flexible stainless-steel column

In this work, a microchip gas chromatography (GC) column assembly utilizing a three-dimensional (3D) printed micro oven and a flexible stainless steel capillary column was developed. The assembly's performance and separation capabilities were characterized. The key components include a 3D printed aluminum plate (7.50 × 7.50 × 0.16 cm) with a 3-meter-long circular spiral channel, serving as the oven, and the column coiled on the channel with an inner diameter of 320 μm and a stationary phase of OV-1. A heating ceramic plate was affixed on the opposite side of the plate. The assembly weighed 40.3 g. The design allows for easy disassembly, or stacking of heating devices and columns, enabling flexibility in adjusting column length. When using n-C13 as the test analyte at 140 °C, a retention factor (k) was 8.5, and 7797 plates (2599 plates/m) were obtained. The assembly, employing resistance heating, demonstrated effective separation performance for samples containing alkanes, aromatics, alcohols and ketones, with good reproducibility. The reduction in theoretical plates compared to oven heating was only 2.95 %. In the boiling point range of C6 to C18, rapid temperature programming (120 °C/min) was achieved with a power consumption of 119.512 W. The assembly was successfully employed to separate benzene series compounds, gasoline and volatile organic compounds (VOCs), demonstrating excellent separation performance. This innovative design addresses the challenges of the complexity and low repeatability of the fabrication process and the high cost associated with microchip columns. Furthermore, its versatility makes it suitable for outdoor analysis applications.

Hyphenation of Thermodesorption into GC × GC-TOFMS for Odorous Molecule Detection in Car Materials: Column Sets and Adaptation of Second Column Dimensions to TD Pressure Constraints

Vehicle interior air quality is an issue of growing interest among car manufacturers and customers. GC-MS is the benchmark method for the analysis of indoor air or material emissions. It is suitable for the quantification of target pollutants and the most abundant compounds. It fails, however, to uncover the true molecular complexity of these samples. In the present study, we describe the development of a TD-GC × GC-TOFMS method designed to detect polar and potentially odorous molecules in car material emissions. Attention is paid to the hyphenation of the thermodesorber and the gas chromatograph, both at software and hardware levels, and the constraints due to pressure limitations on the thermodesorber (evaluated at 414 kPa/60 psi at the end of the temperature ramp and at 138 kPa/20 psi at rest). A compromise was made for the 2D column length and diameter to balance separation and pressure (50 × 0.18 × 0.18 cm × mm × µm + 60 cm transfer line selected). On various materials, we were able to observe several hundreds of polar molecules, among them were between 75 and 150 odorants per material. This work lays the foundation for the widespread screening of potential odorants in car material emissions.

Improving the stability of a planar tape-spring hyper-redundant manipulator

The planar tape-spring hyper-redundant manipulator presented in this paper is mainly constructed from tape springs, fixed-drive components, and mobile-drive components. It not only has high robustness and excellent transformability, but also high packaging efficiency. However, when the manipulator extends to a long range in motion experiments, some segments of the tape springs buckle. To address this drawback, a kinematic model of the planar tape-spring hyper-redundant manipulator is established, and, a configuration planning method based on a virtual spring model is proposed to solve the inverse kinematics problem. To enhance stability, the column stability is then incorporated into the configuration planning model. This approach relies on only configuration planning to prevent buckling. An alternative approach of adding auxiliary rods into the manipulator is also proposed. With this method, extra intermediate supports have been added to the manipulator. The effective column length of some segments is shortened, which effectively increases the critical buckling load of those segments of the tape spring. Finally, a prototype was subjected to motion and stability experiments to validate the presented approaches and analysis.

Experimental Investigation and Numerical Analysis of the Axial Load Capacity of Circular Concrete-Filled Tubular Columns

This paper focuses on the experimental investigation of the axial load capacity of CFT (concrete-filled steel tube) columns under actual construction conditions during building reconstruction. A total of four samples were loaded up to failure. The varied parameters were the column length and absence/presence of the concrete infill within the steel tube. Further, the analysis is extended to developing a numerical model in the finite element-based software ABAQUS version 6.9. This numerical model includes material and geometrical nonlinearities and was validated with the experimental results. The contribution of the concrete core to the column capacity and the concrete core confinement effect are discussed. Finally, the column capacity was calculated according to several design codes: the Eurocode 4 with and without considering the confinement effect, American specifications, Australian standards, the American Institute of Steel Construction, and the Architectural Institute of Japan. The Eurocode 4 considering the confinement effect provides the closest results to those obtained in the tests.

Collapse analysis of restrained concrete-filled steel tubular columns in fire conditions

This paper presents numerical analyses of the thermo-mechanical behavior of restrained square concrete-filled steel tubular (CFST) columns subjected to standard fire. It is found that the behavior is significantly influenced by the load ratio and axial restraint level. The collapse of restrained columns in fire conditions can be defined as the axial force in columns reaching 0 or the axial contraction deformation reaching a hundredth of column length. Three collapse modes are discovered, i.e., the expansion deformation collapse mode, contraction deformation collapse mode, and load-bearing capacity loss collapse mode. Under a low load ratio, three distinct modes of collapse are possible. Conversely, at a high load ratio, only the contraction deformation collapse mode and the load-bearing capacity loss collapse mode are observed. Through analytical and numerical approaches, a method for identifying the collapse mode based on geometric dimensions, axial restraint level, and load ratio has been established. This identification method can significantly contribute to optimizing fire protection strategies for CFST columns in structural designs.

Safety First: Stability and Dissipation of Line-tied Force-free Flux Tubes in Magnetized Coronae

Magnetized plasma columns and extended magnetic structures with both footpoints anchored to a surface layer are an important building block of astrophysical dissipation models. Current loops shining in X-rays during the growth of plasma instabilities are observed in the corona of the Sun and are expected to exist in highly magnetized neutron star magnetospheres and accretion disk coronae. For varying twist and system sizes, we investigate the stability of line-tied force-free flux tubes and the dissipation of twist energy during instabilities using linear analysis and time-dependent force-free electrodynamics simulations. Kink modes (m = 1) and efficient magnetic energy dissipation develop for plasma safety factors q ≲ 1, where q is the inverse of the number of magnetic field line windings per column length. Higher-order fluting modes (m > 1) can distort equilibrium flux tubes for q > 1 but induce significantly less dissipation. In our analysis, the characteristic pitch μ˜0 of flux-tube field lines determines the growth rate ( ∝μ˜03 ) and minimum wavelength of the kink instability ( ∝μ˜0−1 ). We use these scalings to determine a minimum flux tube length for the growth of the kink instability for any given μ˜0 . By drawing analogies to idealized magnetar magnetospheres with varying regimes of boundary shearing rates, we discuss the expected impact of the pitch-dependent growth rates for magnetospheric dissipation in magnetar conditions.

Numerical simulation of bending characteristics of geosynthetic encased stone column

A numerical model of the cantilever bending structure of a geosynthetic encased stone column (GESC) of length 3 m and diameter 0.3 m was established using Z-Soil. The aim was to analyze the stress distribution and bending characteristics of the GESC under a bending load and to investigate the impact of encasement strength, encasement stiffness, gravel friction angle, and diameter on the bending characteristics of the GESC. The maximum bending moment of the GESC under bending conditions occurs at the anchored end. The dividing line of tensile and compressive stresses on the gravel in the anchored end section after bending failure appears at a radius of 0.5 of the column above the section centerline. The geosynthetic sleeve exhibits good resistance to tensile stress. The dividing line between the tensile and compressive stresses is located at the centerline of the section. The mechanical properties of the encasements and gravel has a significant impact on bending characteristics of the GESC. Increasing the strength of the encasement and friction angle of the gravel may significantly improve the bending capacity of the GESC, whereas an increase in the stiffness of encasement and diameter of the column decreases the bending deformation of the GESC.

Gas-driven triboelectric nanogenerator for mechanical energy harvesting and displacement monitoring

Gas as an energy carrier has been widely studied, ranging from small bubble motions to steam strike turbines. Despite the remarkable results, fewer studies have investigated the gas-driven liquid column movement commonly used in hydraulic systems, oil extraction, and other fields. Herein, we proposed a gas-driven triboelectric nanogenerator (GD-TENG) with liquid column motion for mechanical energy harvesting and displacement monitoring. When the gas drives a single liquid column to move inside a polytetrafluoroethylene (PTFE) tube, the solid-liquid interface of the GD-TENG can achieve efficient sliding friction and generate an open-circuit voltage of 15.9 V. Meanwhile, the influence of some critical parameters such as liquid column length, PTFE tube wall thickness and liquid column motion speed on the output performance of the GD-TENG were systematically investigated. Furthermore, the GD-TENG can successfully harvest mechanical energy to power microelectronic devices. A sensing system was designed based on the GD-TENG device for displacement monitoring of moving objects. This work provides a new research path in the field of mechanical energy harvesting and self-powered displacement monitoring.

Study on trapping behaviour of SiO2-containing droplets on the solid surface

The dynamic behaviour of droplets impacting solid surfaces exists in nature, production, and life. In this paper, for the first time, the molecular dynamics method is used to simulate capturing the behaviour of nanodroplets containing SiO2 on solid surfaces. The dynamic behaviour of nanodroplets impacting solid surfaces is analysed when the initial falling velocity v0 of the droplet is 0.3–1.5 nm·ps−1 and for different particle size ds, mass fraction φs of SiO2, and solid surfaces with various wettability. The contact angles of droplets containing SiO2 nanoparticles on the solid surface were measured, and the simulated values closely matched experimental results. The results show that the droplets on the smooth solid surface are completely captured after impact when v0 = 0.3–1.1 nm·ps−1. When v0 = 1.2–1.5 nm·ps−1, the droplet is fragmented, and the fragmentation ratio ns increases with the mass fraction φs. The droplet fragments when v0 = 1.4–1.5 nm·ps−1 on the rough solid surface when the ratio of the side length of the square column to the droplet diameter is 0.07, while the pure water droplet directly bounces and does not fragment. There is a linear relationship between the minimum height of the centre of mass and the mass fraction in the process of droplet impact. The maximum droplet’s spreading factor value in the spreading stage βmax increases with mass fraction φs and v0. When the spreading factor of droplets increases to βc ≈ 3.02, the droplet fragments. The droplet spreading presents the Wenzel state on the rough solid surface. Moreover, the pinning effect affects the droplet falling into the square column gap surface, hindering droplet spreading. Therefore, the rough surface has better catching ability for the droplet than the smooth surface, while the speed range that can be caught is larger. These results provide a theoretical basis for related engineering applications.

C@MOF composite material for rapid and efficient capture of gaseous iodine

In addressing the urgent challenge of mitigating gaseous iodine, a highly volatile and hazardous element in nuclear incidents, this study synthesized composite adsorbents with diverse C/Zn molar ratios using MOF and carbon powder. The saturated iodine adsorption at 75 °C exhibited the sequence: CZ-3 (1.15 g g−1) > CZ-2 (1.08 g g−1) > CZ-1 (0.93 g g−1) > C (0.79 g g−1), displaying 2.3–10.1 times increase in adsorption rate compared to carbon powder and Zn-MOF-2. At an elevated temperature of 95 °C, it achieved saturated adsorption of 1.29 g g−1(CZ-3). The adsorbed iodine primarily manifested in the forms of I2, I3-, and I5-. The dynamic maximum iodine adsorption capacity under specific conditions (75 °C, 300 ppm, 100 mL min−1, 0.5 MPa, 4 cm column length, and 6 mm diameter) reached 1077 mg g−1. Leveraging the Levenberg-Marquardt backpropagation neural network (LM-BPNN) algorithm, a superior fit was achieved. This research provides a theoretical foundation for the rapid and efficient treatment of gaseous iodine in nuclear scenarios.

Matching relationship of low-cycle fatigue life and fatigue design method of concentrically braced frames with H-section steel

Simulations on 192 concentrically braced frames with H-section steel (Q355B) are carried out to investigate their low-cycle fatigue performance. The fatigue life of a steel-braced frame is predicted using a multiaxial fatigue damage parametric model. To depict the fatigue failure sequence and the matching relationship of the fatigue life between the two components in the braced frame, the fatigue life ratio (β) is introduced. This ratio represents the gusset plate's fatigue life to the brace's fatigue life. Simulated results are analyzed, and β is found to be positively correlated with four influencing factors, the width-to-thickness ratio of the brace flange, connection coefficient, ratio of the column length to beam length, and slenderness ratio of the gusset plate. Also, β is found to be negatively correlated with the slenderness ratio of the brace. Based on the Bayesian updating method, a probabilistic model is formulated to predict β of a steel-braced frame. Accordingly, a fatigue design method is proposed, which contributes to avoiding the in-coordination of seismic capacity caused by the significant difference between the brace’s and gusset plate’s fatigue life within the steel braced frame. The proposed fatigue design method has the potential to serve as a reference for improving design specifications.

Satin bowerbird optimizer-neural network for approximating the capacity of CFST columns under compression

Concrete-filled steel tube columns (CFSTCs) are important elements in the construction sector and predictive analysis of their behavior is essential. Recent works have revealed the potential of metaheuristic-assisted approximators for this purpose. The main idea of this paper, therefore, is to introduce a novel integrative model for appraising the axial compression capacity (Pu) of CFSTCs. The proposed model represents an artificial neural network (ANN) supervised by satin bowerbird optimizer (SBO). In other words, this metaheuristic algorithm trains the ANN optimally to find the best contribution of input parameters to the Pu. In this sense, column length and the compressive strength of concrete, as well as the characteristics of the steel tube (i.e., diameter, thickness, yield stress, and ultimate stress), are considered input data. The prediction results are compared to five ANNs supervised by backtracking search algorithm (BSA), earthworm optimization algorithm (EWA), social spider algorithm (SOSA), salp swarm algorithm (SSA), and wind-driven optimization. Evaluating various accuracy indicators showed that the proposed model surpassed all of them in both learning and reproducing the Pu pattern. The obtained values of mean absolute percentage error of the SBO-ANN was 2.3082% versus 4.3821%, 17.4724%, 15.7898%, 4.2317%, and 3.6884% for the BSA-ANN, EWA-ANN, SOSA-ANN, SSA-ANN and WDA-ANN, respectively. The higher accuracy of the SBO-ANN against several hybrid models from earlier literature was also deduced. Moreover, the outcomes of principal component analysis on the dataset showed that the yield stress, diameter, and ultimate stress of the steel tube are the three most important factors in Pu prediction. A predictive formula is finally derived from the optimized SBO-ANN by extracting and organizing the weights and biases of the ANN. Owing to the accurate estimation shown by this model, the derived formula can reliably predict the Pu of concrete-filled steel tube columns.

Buckling strengths of cold-formed built-up cruciform section columns under axial compression

This paper describes experiments addressing the buckling and collapse behaviour of cold-formed stainless steel cruciform section columns. Doubly symmetrical flanged cruciform section columns were built using six individual press-braked plain channels made of austenitic grade EN 1.4307 assembled back-to-back. Three different column lengths were tested – namely, short (600 mm), intermediate (1200 mm) and long (2400 mm) lengths, and two channel geometries were used in all tests – with cross-section depths of 200 mm and 100 mm. Tests were carried out under pure axial compression and with fixed end support conditions. Tests were repeated two times for each length. It was observed that the buckling patterns were affected both by the global slenderness and by the spacing between the fasteners. Stocky columns experienced local buckling of the individual channel sections. The plastic failure mechanism was dependent on the fasteners spacing. Intermediate slenderness columns were characterised by interaction between global torsional buckling and local buckling whereas more slender columns failed predominantly through torsional buckling. For the latter, the spacing between the fasteners had a minor influence on the ultimate capacity.

Evaluation of the rotational stiffness of precast reinforced concrete beam-column connections

Usually, beam-column connections with steel dowels are treated as hinged connections. This approach overlooks the rotational restraining effect of the dowels. To study the behaviour of these types of connections, an experimental campaign was carried out. Three full-scale beam-column connections were tested, subjected to monotonic and cyclic displacements. The specimens were also simulated numerically to study the influence of the bond quality between the steel dowel and the grout on the stiffness of the connection. The numerical models were calibrated using the experimental results. The results showed that the restraining effect is not negligible and affects the effective length of columns, leading to smaller second-order effects.

A Lagrangian theory of equatorial upwelling

An explicit expression is derived for the speed of equatorial upwelling by filtering out the inertial oscillations from the wind-forced, Lagrangian, dynamics north and south of the equator. The derivation focuses on the poleward motion of the steady states of the meridional dynamics of water columns of unit zonal length forced by a uniform, westward directed, wind stress. A significant advance is achieved by substituting the pseudo angular momentum for the zonal velocity in all equations. The derived expression for the speed is independent of the Ekman layer's depth and varies linearly with the wind stress. Its only free parameter is the initial meridional extent of the water column that straddles the equator. The theoretical speed matches available observations of the upwelling speed when the column's meridional extent is 350–400 km on each side of the equator.

Nonlinear analysis and design of high-strength concrete filled steel tubular columns under nonuniform fires

The main objective of this study is to investigate the behaviour of concrete-filled steel tubular (CFST) columns with ultra-high strength concrete (UHSC) and high strength steel (HSS) under fires through finite element method (FEM). High-strength materials can be used in CFST columns to reduce member dimensions, lowering material consumption and foundation loads. However, their fire behaviour has been insufficiently examined, especially under nonuniform fire exposure. In this study, thermal-structural models of the composite columns are developed using the SAFIR software. The numerical results are compared with published test data on temperature distribution, axial displacement, lateral displacement, failure modes and failure time. Then, parametric analyses are conducted to investigate the influence of various factors such as concrete strength, steel strength, different fire exposures, column length and load ratio on the fire performance of the CFST columns. In addition, the tabular design approach in European code EN1994–1-2 and Australian/New Zealand code AS/NZS 2327:2017 for designing uniformly exposed CFST columns is evaluated. It is observed that the prescribed design values in the table for R30 and R60 fire ratings under load ratio lower than 0.47 appear insufficient for the allowable slenderer columns. The applicability of the tabulated data for a load ratio up to 0.47 is further checked for the columns with UHSC of 120 MPa and HSS of 690 MPa, which is the strength limits recommended in AS/NZS 2327:2017.

Plastic hinge behavior of rectangular CFRP-confined RC columns: Meso-scale modelling and formulation

The ultimate rotation capacity, depending on the plastic hinge length, is a vital factor in the seismic design of flexural members. This paper focuses on the investigation of the plastic hinge length and size effect of rectangular carbon fiber-reinforced polymer (CFRP)-confined reinforced concrete (RC) columns. Firstly, considerable scatter and evident bias of the calculation results were found after evaluating existing models for calculating the plastic hinge length of FRP-confined RC columns. Accordingly, a meso-scale numerical approach was developed, with concrete heterogeneity considered, to investigate the influences of the confinement ratio and corner radius on the plastic hinge length and size effect of rectangular CFRP-confined RC columns. Results show that columns having different cross-sectional sizes exhibit similar failure patterns, and the region of lateral crack propagation for columns with lower confinement ratios is larger than that for columns with higher confinement ratios. The actual plastic hinge length is determined based on the yielding zone of reinforcement, the crushing zone of concrete, and the localization zone of curvature, while the localization zone of curvature is employed to determine the real plastic hinge zone. The size effect is found to exist in the plastic hinge length ratio, and it is weakened with the increase of the corner radius, which can be attributed to the fact that columns with higher corner ratios have more effective confinement. Taking into account the size effect, a new model for calculating the ultimate drift ratio of CFRP-confined RC columns was proposed based on an assumption of curvature distribution and presented accurate predictions.

Axial compression tests on CFRP strengthened CFS plain angle short columns

A comprehensive test program was performed to experimentally investigate the effect of CFRP strengthening on the axial strength and stability of CFS plain angle short columns subjected to monotonic axial compression. A total of 28 specimens were tested by varying the CFRP strengthening configurations for different column heights. Both uni-directional (CF_UD) and bi-directional (CF_BD) CFRP were considered. The influence of various parameters such as the type of CFRP, fiber orientation, and number of CFRP layers was investigated and discussed in detail. For single layer (ply) of CFRP, CF_UD-0° strengthening configuration resulted in maximum increase of axial capacity by 58.33% and 45.72% (in comparison to bare steel specimens), corresponding to 0.5 m and 1.0 m column lengths respectively. All the bare steel and skin-strengthened specimens failed predominantly due to torsional–flexural buckling mode. Additional layer of CFRP wrapping was found to enhance the axial capacity further and CF_UD-0°/BD was found to possess greater capacity in the case of double layer of CFRP. Adopting cardboard in-fill in addition to CF_UD-0° wrap has prevented the torsional mode of buckling and resulted in a peak increase of axial capacity by 192.55% and 240.61% corresponding to 500 mm and 100 mm long specimens, respectively.

Lunate Shift Index (LSI): A New Parameter for the Evaluation of Residual Ulnar Side Wrist Pain in Patients with Wrist Osteoarthritis Undergoing Three-Corners Arthrodesis vs. Four-Corners Arthrodesis-A Retrospective Comparative Study with Minimum 2Years of Follow-up.

Both scaphoid non-union advanced collapse wrist (SNAC) and scapho-lunate advanced collapse wrist (SLAC) at stage II-III are common indications for limited wrist fusions including four-corners fusion (4CF) and three-corners fusion (3CF). The aim of this study was to assess the clinical and radiological outcomes in patients undergoing 3CF vs. 4CF. A new radiological index called Lunate Shift Index (LSI) was devised to evaluate the importance of the lunate displacement relative to the radiolunate joint. Twenty-eight patients undergoing 3CF and 40 patients undergoing 4CF were clinically evaluated. The radiolunate angle, the carpal height, and the LSI were recorded radiographically. The LSI corresponds to the ratio between the distance from the lunate centre to the middle of the intermediate column and the length of the intermediate column of the distal radius. A statistically significant correlation was observed between LSI and clinical outcomes. The lunate displacement was associated with an increased incidence of wrist ulnar pain.No statistically significant differences were observed between 3 and 4CF in all parameters compared. The osteoarthritis of piso-triquetral joint has been identified as the cause of wrist ulnar pain in patients undergoing 4CF. The lunate correct positioning allows to maintain the carpal height and to increase the contact area at the level of the radiolunate joint. A good reduction of the lunate could be obtained with the 3CF compared to 4CF. This study showed how proper realignment of the lunate following midcarpal arthrodesis correlates with a better clinical outcome. Level III, Retrospective comparative study.

Effect of the column design and fabrication method on the reverse recovery characteristics of 1.2 kV SiC-superjunction-MOSFETs

We investigated the effects of the column length and fabrication method of the superjunction (SJ) structure on the reverse recovery characteristics of 1.2 kV silicon carbide (SiC) SJ metal–oxide–semiconductor field-effect transistors (MOSFETs). The voltage slope (dV/dt) and reverse recovery current slope (dir/dt) values during the reverse recovery of the SJ-MOSFETs with the SJ structure formed by Aluminum (Al) ion implantation were comparable to the values of MOSFETs without SJ structure at room temperature (RT), but they increased markedly with temperature. This is caused by the reduced p-column carrier concentration at RT during short recovery transient time due to the deep hole trap (DI center) introduced by ion implantation. At 175 °C, a softer reverse recovery waveform was obtained by shortening the SJ columns. Besides, Al ion implanted SJ-MOSFETs exhibited a weaker current dependence of the reverse recovery charge Qrr at 175 °C indicating a lower carrier injection level compared to the SJ-MOSFETs with the SJ structure formed by trench formation and epitaxial growth. This is caused by the short carrier lifetime of the SJ columns due to the Al ion implantation defects. The short and Al ion implanted SJ columns are effective for soft reverse recovery characteristics in SiC-SJ-MOSFETs.