Secondary Columns Research Articles

Development of a Standardized Protocol for the Classification of Column Sets in Comprehensive Two-Dimensional Gas Chromatography

One-dimensional gas chromatography (1D-GC) stationary phases are generally classified according to their relative polarity into non-polar, semi-polar, and polar columns. In comprehensive two-dimensional gas chromatography (GC×GC), it is the polarity difference between the two tandem-assembled stationary phases that determines the selectivity of the column ensemble. This polarity difference is called orthogonality, and GC×GC column sets can be broadly categorized into four groups based on the direction of the serial coupling between the primary and secondary columns. A significant portion of the GC×GC column sets in use today are operated in forward-orthogonality mode, which means that the secondary column is more polar than the primary column. A growing number of reported GC×GC applications operate in reversed-orthogonality configurations, where the secondary column is less polar than the primary column. Very few examples exist of non-orthogonal column sets because of the fact that there is limited additional selectivity that the secondary column can offer over the separation that has already been achieved in the primary column when the two phases are either identical or close in polarity. The fourth group of GC×GC column sets, called hybrid orthogonality, involves the coupling of stationary phases with peculiar selectivity differences that manifest themselves in the bi-dimensional separation plots. In this work, we are presenting a normalized approach to GC×GC column set characterization that is based on the use of a reference mixture of standards called the Century Mix. The Century Mix contains 100 chemical probes of different functionalities that span a reasonable range of volatilities and polarities to capture the selectivity profile of any GC×GC column set. The Century Mix also contains important chemical probes that are used for 1D-GC column characterization (such as the Grob mix and the Rohrschneider/McReynolds compounds) to make some connections between the 1D-GC building block columns and the GC×GC column sets. We finally also outline some other important metrics of comparison that should be taken into consideration to assess the overall performance of a GC×GC system.

Shear resistance design of semi-supported buckling-restrained steel plate shear walls: Analytical and numerical investigation

Buckling-restrained steel plate shear wall (BRSPSW) rises as an excellent energy-dissipating lateral force-resisting component. Semi-supported BRSPSW is more flexible in structural configuration than the conventional BRSPSW owing to its independent vertical boundary elements (VBEs). In this paper, the shear resistance and the VBEs effect of the semi-supported BRSPSW were studied by the analytical and numerical methods. A simplified model was developed for simulating the semi-supported BRSPSWs. A minimum sectional area of the VBEs, namely, Acr was suggested for the BRSPSW to fully develop its shear field. Meanwhile, the ultimate shear resistance formula of the semi-supported BRSPSW was proposed. Furthermore, a general finite element (FE) model of the BRSPSWs with two-sided, semi-supported, and four-sided connections was established and applied for parametric analyses. It was found that the semi-supported BRSPSW under the shear could be divided into one middle region with the shear field and two vertical edge regions with local stress fields. The edge regions acted as the additional VBEs for the middle region, whose span decreased with the rise in the sectional area of the VBEs, i.e, secondary columns. The hysteretic behavior of the BRSPSW could be improved by increasing the sectional area of the VBEs when the section area of the VBEs was smaller than Acr. The shear field could be utilized more efficiently in the semi-supported BRSPSW with a larger sectional area of the VBEs and a higher span-to-height ratio of the steel plate. Finally, the equations for predicting the ultimate shear resistance and shear field distribution of the BRSPSW were verified by the test and FE results.

Modal analysis and harmonic response analysis of energy-absorbing and anti-scouring columns

Many field observations have found that damage to the support did not increase with the magnitude of the impact ground pressure. To enhance the impact protection performance of “support and surrounding rock” system. From the perspective of preventing the resonance of the “support and surrounding rock” system, the dynamic response of energy-absorbing and anti-scouring column is studied. Using the block theory, a dynamic model of the roadway enclosure-absorbing anti-scouring column under impact loading was established, and the dynamic response equation of the rock block at the support end was obtained. Based on the structural dynamics and Love shell theory, the characteristic equations of the energy-absorbing and anti-scouring column were derived, and the theoretical equations for the natural frequency and vibration mode function of the energy-absorbing and anti-scouring column were obtained. The ABAQUS numerical simulation method was used to carry out pre-stress modal analysis and harmonious response analysis of energy-absorbing and anti-scouring columns and conventional columns. We obtained the natural frequencies and vibration modes of the two columns and analyzed the effect of the setting load on the modalities of the columns. The column dynamic response law was determined by monitoring the displacement and velocity response curves at different positions. The results show that the natural frequency and vibration mode of the energy-absorbing and anti-scouring column are related to the density, elastic modulus, and length. The vibration of the energy-absorbing and anti-scouring column has two forms: beam vibration mode and cylindrical shell vibration mode, and the first four orders of vibration mode are transverse bend. The setting load has a small effect on the natural frequency and vibration mode of both types of columns, where the natural frequency decreases as the setting load increases. When the excitation frequency is close to the vibration frequency of the surrounding rock, the radial, axial, and circumferential response amplitudes of the primary and secondary columns of the energy-absorbing and anti-scouring column are the largest. Reinforcement and strengthening measures should be implemented to reduce the column deformation amplitude.

Influence of modulator injection width on comprehensive two-dimensional gas chromatography peak dimensions.

This study examines how the height and width of peaks exiting the secondary column of a comprehensive two-dimensional gas chromatography (GC × GC) separation are affected by the width of the pulse introduced to the secondary column. A flow-modulated GC × GC apparatus was assembled that allowed input pulse widths to be controlled precisely over a range of 10 to 70ms. GC × GC chromatograms were obtained using secondary columns containing a polyethylene glycol stationary phase with internal diameters of 0.25 and 0.32mm. The area, height, and width of peaks emerging from the secondary column were found to be accurately modeled by the convolution of a rectangular function with a Gaussian distribution. The rectangular function represents the input pulse, and the Gaussian distribution represents the broadening that occurs in the secondary column. The minimum peak width that could be produced by the secondary column was determined for a wide range of compounds. Injection pulse widths that matched a compound's minimum peak width produced peaks that were 25% wider than the minimum width and had heights that were 76% of the maximum possible peak height. Increasing the injection width significantly above the minimum width yielded substantially broader peaks with only a modest increase (< 25%) in peak height.

On the behavior of an innovative four-layer semi-supported steel plate shear wall

Observations of past earthquakes as well as numerical and experimental studies have confirmed the acceptable performance of Steel Plate Shear Walls (SPSW). Although the SPSW has a number of advantages, it has two major flaws: low elastic-buckling capacity of the infill plate and significant stresses generated by the infill plate on the boundary columns. There are some techniques to overcome these shortcomings. Among them, using the semi-supported SPSW is the most effective one. However, the weak point of this system is the reduction of stiffness and strength of the system in comparison with the conventional SPSW. To resolve this issue, an innovative four-layer semi-supported SPSW has been introduced recently. The system is composed up of the main frame, secondary columns, two corrugated infill plates, and two flat infill plates. Since there is no connection between the infill plates and the mainframe, there is no stress transmission from plates to columns. This fact, in turn, reduces the ductility demand. As a result of the combination of the corrugated and flat plates, the buckling capacity of the wall increases nearly up to the yielding point. This results in a more cost-effective system. The current study presents the results of a comprehensive numerical study to investigate the effect of plate thickness, wall length, and aspect ratio on the behavior of this system under the monotonic lateral load. To obtain the pushover curves, the finite element (FE) software package ABAQUS was utilized. The findings showed that, as the aspect ratio of the wall increases, the wall capacity increases and exceeds the capacity of the frame. Furthermore, the relevant equations for achieving the pushover curve were proposed without the need for FE simulation. Finally, the results showed a good match between the FE results and the intended relations.

Analysis of Key Points of Formwork-free Construction Technology for Secondary Structural Columns

Analysis of Key Points of Formwork-free Construction Technology for Secondary Structural Columns

Comprehensive two-dimensional gas chromatography using direct flow modulation to extend the secondary dimension separation time

A simple direct flow modulator has been constructed and evaluated. This modulator employs a tee to connect the primary and secondary columns so that a negative pulsed flow can be introduced through the third leg of the connector into the joint between the columns. The modulation gas pressure can be adjusted to allow a longer recovery time for the primary column flow after the reversal initiated at the beginning of a modulation period, resulting in a longer secondary separation time. In this study, a 120 s secondary separation time has been achieved. That is long enough for use with a longer secondary column and secondary temperature ramping. Factors which affect the secondary peak width at base (2Wb), including modulation pulse width, modulation period, and inlet/modulation pressure differential, have also been investigated. Our results indicate that all three of these factors have a large impact on 2Wb, since they all affect the amount of primary effluent loaded onto the secondary dimension. Various sizes of tee connectors – 360 µm, 1/32″, and 1/16″ – have been investigated as well. Out of those three, the 360 µm tee gives the best performance in terms of less peak tailing and narrower 2Wb. The time needed to switch from one dimension GC to GC×GC for this method is discussed, and several methods to shorten the waiting time have been proposed. Applications of this method on gasoline and reference gas oil standard have been demonstrated.

Two-Dimensional Gas Chromatographic and Mass Spectrometric Characterization of Lipid-Rich Biological Matrices-Application to Human Cerumen (Earwax).

Earwax is a readily accessible biological matrix that has the potential to be used in disease diagnostics. However, its semisolid nature and high chemical complexity have hampered efforts to investigate its potential to reveal disease markers. This is because more conventional methods of analysis such as gas chromatography–mass spectrometry (GC–MS) and liquid chromatography–mass spectrometry yield unsatisfactory results due to the presence of many nonvolatile and/or coeluting compounds, which in some cases have very similar mass spectrometric profiles. In addition, these routine methods often require the sample to be saponified, which dramatically increases the complexity of the analysis and makes it difficult to determine which compounds are actually present versus those that are produced by saponification. In this study, two-dimensional GC mass spectrometry (GC × GC–MS) was successfully applied for the characterization of the chemical components of earwax from healthy donors using nonpolar (primary) and midpolar (secondary) columns without saponification. Over 35 of the compounds that were identified are reported for the first time to be detected in unsaponified earwax. The resulting GC × GC–MS contour plots revealed visually recognizable compound class clusters of previously reported groups including alkanes, alkenes, fatty acids, esters, triglycerides, and cholesterol esters, as well as cholesterol and squalene. The application of GC × GC–MS revealed results that provide a foundation upon which future studies aimed at comparing healthy donor earwax to that from individuals exhibiting various disease states can be accomplished.

Development and Validation of an LC-MS/MS Method for the Ultra-Trace Analysis of Pacific Ciguatoxins in Fish.

BackgroundCiguatera fish poisoning (CFP) poses a serious threat to both public health and the use of aquatic resources from the various warm‐water regions of the world. Hence, a process for the efficient determination of the relevant toxins is required.ObjectiveWe sought to develop and validate the first LC-MS/MS method to quantify the major toxins prevalent in fish from the Pacific Ocean.MethodToxins were extracted from fish flesh (2 g) using a methanol–water mixture (9:1, v/v). The extract was heated at 80°C, and low-polarity lipids were eliminated using hexane, initially from the basic solution and later from the acidic solution. The cleanup was performed using solid-phase extraction, Florisil, silica, reversed-phase C18, and primary secondary amine columns. A validation study was conducted by spiking fish flesh with two representative toxins having different skeletal structures and polarities and was calibrated by NMR (qNMR) spectroscopy.ResultsThe validation parameters for the ciguatera toxins CTX1B and CTX3C at spiked levels of 0.1 µg/kg were as follows: repeatabilities of 2.3–3.5% and 3.2–5.3%; intermediate precisions of 6.3–9.8% and 6.0–7.4%; recoveries of 80–107% and 95–120%, respectively. The lowest detection levels were 0.004 µg/kg for CTX1B, 0.005 µg/kg for 51-hydroxyCTX3C, and 0.009 µg/kg for CTX3C.ConclusionsThe described method practically clears the international action level of 0.01 µg/kg CTX1B equivalents set by the U.S. Food and Drug Administration and the European Food Safety Authority and satisfies the global standards set by Codex and AOAC INTERNATIONAL.HighlightsA validation study for an LC-MS/MS method for ciguatoxin detection was completed for the first time using calibrated toxin standards.

Representation of the Diurnal Distribution of Organic Aerosol by Multidimensional Liquid Chromatography Systems

Aerosols have various effects on human health, climate, and ecosystems. Aerosols also have an important role in climate change by altering the radiation balance and lifetime and properties of clouds. Organic aerosol (OA) is composed of a mixture of hundreds to thousands of organic compounds that varies geographically, diurnally, and seasonally according to several factors, such as type and concentration of precursor, type and concentration of oxidants, temperature, relative humidity, among others. The type and number of functional groups composing individual organic species influence their interaction with water vapor and sunlight, therefore affecting both the water cycle and radiation balance. Great efforts have been made to develop analytical techniques that allow the identification and quantification of individual species composing this complex mixture of organic matter and decrease the uncertainty of models to accurately predict OA formation and evolution. It was found that most of the column combinations were not adequate and the best system was provided by methanol: water (1:1). The combination of columns that provided the best separation of the standard compounds was provided by Cyclohexyl and Methyl as primary and secondary columns. However, when this combination of columns was used to represent the evolution of ambient air organic aerosols, significant co-elution was observed. The positive outcome of this study was helpful to evaluate 2D-LC as a potential technique for more accurate determination of organic aerosol components and to understand organic aerosol formation and transformation pathways that can be used in secondary organic aerosol production models.

Cuckoo index

In modern data warehousing, data skipping is essential for high query performance. While index structures such as B-trees or hash tables allow for precise pruning, their large storage requirements make them impractical for indexing secondary columns. Therefore, many systems rely on approximate indexes such as min/max sketches (ZoneMaps) or Bloom filters for cost-effective data pruning. For example, Google PowerDrill skips more than 90% of data on average using such indexes. In this paper, we introduce Cuckoo Index (CI), an approximate secondary index structure that represents the many-to-many relationship between keys and data partitions in a highly space-efficient way. At its core, CI associates variable-sized fingerprints in a Cuckoo filter with compressed bitmaps indicating qualifying partitions. With our approach, we target equality predicates in a read-only (immutable) setting and optimize for space efficiency under the premise of practical build and lookup performance. In contrast to per-partition (Bloom) filters, CI produces correct results for lookups with keys that occur in the data. CI allows to control the ratio of false positive partitions for lookups with non-occurring keys. Our experiments with real-world and synthetic data show that CI consumes significantly less space than per-partition filters for the same pruning power for low-to-medium cardinality columns. For high cardinality columns, CI is on par with its baselines.

Quasi-Stop-Flow Modulation Strategy for Comprehensive Two-Dimensional Gas Chromatography.

An easy-to-implement strategy of differential flow modulation for comprehensive two-dimensional gas chromatography was innovated. With this approach, an independent auxiliary pneumatic control device for flow modulation was not a prerequisite. The strategy involved splitting the carrier gas stream into two separate streams before reaching the inlet embodiment. One stream was employed as a mobile phase for chromatographic separation. The other stream, for flow modulation, was routed to one of the ports of a three-way solenoid valve. The modulation stream flowed onward to a fluidic path and a T-junction that joined the primary and secondary dimension columns. With this arrangement and depending on the configuration of the three-port valve, the analytical platform can be operated in three different modes: bypass stop-flow, vent stop-flow, and quasi-stop flow. Quasi-stop-flow mode was demonstrated to have a significantly better chromatographic performance, as demonstrated in various types of real-life petroleum samples such as gasoline and light cycle oil. In the light cycle oil sample, a respectable separation between compound classes was achieved with peak width at half height of 34 ms or less for alkanes on a second dimension with polyethylene glycol stationary phase. Excellent repeatability was shown with normal alkanes standards of nC8-nC25. Relative standard deviations for retention times are almost zero in 1D, less than 0.2% in 2D, and less than 3.5% for peak areas (n = 9).

Bilinear Load–Displacement Curve of Semi-supported Steel Shear Walls

Elastic stiffness and ultimate shear capacity are two main parameters of a structural system to obtain its ideal bilinear load–displacement. In the previous studies, the ultimate shear capacity of semi-supported steel shear walls (SSSW) which are a new lateral resisting system, has been determined. In this system, wall plates do not have any direct connection to the main columns of structure and they are connected to secondary columns which do not carry the gravity loads. The used thin plate in the SSSW elastically buckles at low levels of lateral loads and the wall plate stays on a fairly vast region with elastic post-buckling behavior (elastic stiffness). In this study, the Von-Karman plate equations are solved by the Galerkin method to find displacement field of the wall plate in the elastic post-buckling region as well as the maximum shear load after which the plasticity expand in the wall plate. Thus, the elastic stiffness of system is calculated. As the analytical procedure is complicated, the method is applied on 144 examples with different material and geometrical properties. Using linear regression technique, a concise formula is proposed to predict the elastic stiffness of system. The dimensions of wall plate are only the effective parameters in the suggested formula and the elastic stiffness is independent of the overturning moment, section of secondary columns and yield stress of material. Using the ultimate shear capacity and elastic stiffness, an ideal bilinear curve is obtained for the lateral load versus the horizontal displacement. The shear capacity at the end of elastic post-buckling region and out of plane displacement are acceptably validated with those of FE analysis for some examples.

Improving behavior of semi-supported steel plate shear walls

In spite of the good performance of the steel plate shear wall (SPSW) in recent earthquakes and experimental studies, the need for huge columns to surround the infill plate is a major shortcoming of the system. This shortcoming can be resolved by using semi-supported SPSW. The semi-supported SPSW has secondary columns that prevent the transfer of stress from the infill plate to the main columns. In spite of extensive experimental and numerical investigations on SPSWs, there are many ambiguities regarding the behavior of the semi-supported SPSW. Although stress in the columns is reduced, incomplete diagonal tension field action is formed in the infill plate that creates new problems. In this paper, a new type of semi-supported SPSW is presented in which the steel plate and the secondary columns are angled. The creation of the angle of the plate and the secondary column makes it possible to use the full capacity of the steel plate as well as the capacity of the secondary columns. Numerical results showed that the wall with a 60° angle has a favorable performance relative to the semi-supported wall. Moreover, with the 60° angle, stiffness, strength and energy absorption is increased. The angle of the secondary columns has little effect on the non-elastic stiffness. Nevertheless, using a wall with an angle of more than 90° can neutralize the wall’s behavior relative to conventional walls. Therefore, the wall with a 60° angle as an optimal angle is recommended.

Column selection approach to achieve a high peak capacity in comprehensive three-dimensional gas chromatography

The separation power of comprehensive three-dimensional gas chromatography (GC3) is substantially enhanced through proper selection of the phase volume ratio, β, of each column relative to each other on successive dimensions. Consideration and application of the ratio of phase volume ratios, βr, or β ratio, between successive dimensions has been a relatively un-studied approach to maximize separating power in comprehensive multidimensional GC instrument design. Herein, proper selection of βr in multidimensional GC is shown to control the elution temperature, Te, of analytes throughout a 40 min primary (1D) column separation, and thus better control width-at-base, W, on all three dimensions. Specifically, between the 1D and secondary (2D) columns, a βr of 0.45 was applied, and between the 2D and tertiary (3D) columns a βr of 1.0 was applied. A total ideal peak capacity of 30,600, or a peak capacity production of ~770 peaks/min, was accomplished with the GC3 instrument with the reconfigured parameters. Additionally, due to the complex nature of this three-dimensional data, a novel approach to “slicing” the chromatographic run into user-defined time intervals is shown. This novel way to view the data still elicits a traditional GC×GC chromatograms, but with the focus on 2D × 3D separations. Moreover, due to proper βr selection, every 2 s window (i.e. every 1D modulation period) is shown to have a peak capacity of ~50–100 for each 2D × 3D separation. This high overall peak capacity (30,600) and peak capacity per 1D modulation (~50–100), courtesy of proper column selection, is demonstrated to hold great promise to physically separate truly complex mixtures.

A comprehensive two-dimensional gas chromatography valve modulation method using hold-release primary column flow for long secondary separation time with 100% transfer

A valve modulator with a hold-release primary column flow method has been proposed. This method uses a valve plumbed so that the head and tail of the primary column are connected during the secondary separation, to reverse, slow down, and finally stop the primary column flow. This keeps the sample in the primary column longer, gaining more time for secondary separation. Applying this method, a 60-second secondary retention time with 100% transfer, 133 ms secondary peak width at base, and no primary peak profile loss has been achieved. A standard sample with 19 compounds in 3 groups has been tested. The relative standard deviations for the retention time of this standard mixture are <0.26% for primary dimension and <0.94% for secondary dimension. A gasoline sample analysis with 5, 15, and 30-meter-long secondary columns has been demonstrated. With the secondary column length increase, the secondary separation has greatly improved even though the total run time increases to 45, 110, and 120 min and the toluene primary peak width at base increases to 0.51, 1.81, and 1.85 min respectively. A diesel samplerun by this method has also been demonstrated.

Experimental and numerical studies of instability mechanism and load resistance of rhombic grid hyperboloid-latticed shells under vertical load

This paper presents the instability mechanism of an innovative Rhombic Grid Hyperboloid-Latticed Shell (RGHLS) under vertical load through experimental and numerical investigations. The RGHLS is only composed of bidirectional inclined primary and secondary columns without any circumferential members or lateral braces in its radial direction along its height. Therefore it would likely fail by out-of-plane multi-column interaction instability and the corresponding load-carrying capacity should be predicted. The experimental investigation of a reduced-scale test model of RGHLS was firstly performed to study its vertical load-carrying capacity and the multi-column interaction instability. A special spatial beam-string device for vertical multi-point loading of the test model has been initially designed and fabricated to precisely distribute the concentrated load to the top of the columns according to proportional distribution of loads required by designers. The experimental results revealed that the inclined columns indeed exhibited strong mutual restraining actions, and the ratio of the actual ultimate load-carrying capacity of the test model to its design load was 3.37, indicating a reasonable safety margin. In addition, FE numerical results of the test model corresponded well with the experimental results. Ultimately, additional FE numerical analyses have been conducted on the test model. Accordingly the effects of the ratio of stiffness between the secondary and primary columns, overall initial geometric imperfection, in-plane stiffness of top ring beam, and dimensions of portal columns on the load-carrying capacity and failure mode of RGHLS have been investigated extensively. As a result, the ratio of stiffness between the secondary and primary columns has been particularly recommended within a range of 0.46–0.70, so as to eliminate premature failure of X-joints prior to the instability of columns in the prototype of RGHLS.

Microstructural evolution of plasma spray physical vapor deposited thermal barrier coatings at 1150 °C studied by impedance spectroscopy

Plasma spray physical vapor deposition (PS-PVD) is a new promising technology for processing thermal barrier coatings (TBCs). In this study, the microstructural evolution of PS-PVD yttria-stabilized zirconia (YSZ) TBCs at 1150 °C was investigated by scanning electron microscopy, electron backscattered diffraction, and impedance spectroscopy. Bridging is observed between the secondary columns of the coatings during the first 8 h of heat treatment, while sintering necks are observed between the quasi-columns over the heat-treatment interval of 12–20 h. As the heat-treatment time increases to 100 h, the nanogaps between the secondary columns disappear and a large number of shrinkage pores are observed in the columns, leading to a typical cellular structure. Besides, the average grain size of the YSZ coatings increases from 0.20 (as-deposited) to 0.55 µm (after 50 h of heat treatment). The resistance of the YSZ grains increases while that of the YSZ grain boundaries decreases because of grain coarsening. During the first 4 h of heat treatment, the resistance of the thermally grown oxide (TGO) scale increases because of its thickening. However, its resistance decreases during the next 4 h of heat treatment mainly because of the change in its composition (from pure alumina to mixed oxides).

Experimental and numerical investigation into the load resistance and hysteretic response of rhombic grid hyperboloid-latticed shells

The rhombic grid hyperboloid-latticed shells (RGHLSs) in the China Comic and Animation Museum (CCAM) are located on the ground floor, and they sustain enormous vertical and horizontal loads induced from upper building structures on top of them. Each RGHLS consists of numerous bidirectional inclined major and secondary columns that intertwine with one another to form a rhombic grid with X-shaped joints. Without both horizontal circumferential members and horizontal lateral braces in the radial direction of the RGHLS, as well as the existence of significant difference of compressive stiffness between major and secondary columns, the RGHLS would ultimately fail in a complicated form of in-plane and out-of-plane multi-column interaction instability in addition to its overall twist deformation under relatively low vertical loads. Currently, no design method for estimating its design strength and safety is available. Therefore, the load-carrying capacity of the RGHLS must be examined experimentally. This paper selects the RGHLS denoted by Y4 in the structure of the CCAM as the prototype, and presents an experimental investigation of its reduced scale (1:1/4) test model. A loading protocol consisting of six loading phases has been devised in order to predict the static vertical and horizontal load resistance, and horizontal hysteretic response of the RGHLS by keeping the amplitudes of the vertical load constantly as 1.0, 1.4 and 1.6 times the vertical design load of the reduced-scale test model, respectively. The experimental results obtained indicate that the test model remains elastic under 1.8 times its design loads, which is commonly adopted as static structural strength limit in practical design in China. In addition, horizontal cyclic load test indicated that the reduced-scale test model demonstrated sufficiently large horizontal load-carrying capacity as well as exhibited stable and ample hysteretic curves even under 1.6 times vertical load actions without any obvious stiffness reductions. This study comprehensively introduces the experimental test schemes and deeply analyzes the experimental results, thus forming an important basis for designing the load-carrying capacity of such RGHLSs. Ultimately, according to the experimental loading protocol, numerical simulations and analyses of the test model have been conducted by adopting ANSYS 12.1. The interaction strength design curve of the test model under a combination of vertical and horizontal loads is also proposed by carrying out additional numerical simulations of the model. The FE and experimental results have been compared, and they correspond well to one another, indicating that the results of the reduced-scale test model are accurate enough and reliable.

Routine quantification of 54 allergens in fragrances using comprehensive two‐dimensional gas chromatography‐quadrupole mass spectrometry with dual parallel secondary columns. Part I: Method development

AbstractThe forthcoming extension of the regulated fragrance allergen number is raising a challenge: the previously developed quantification methods need to be drastically improved in terms of rapidity, without altering their reliability. This work describes a procedure based on comprehensive bidimensional gas chromatography, hyphenated with a low‐cost quadrupole mass spectrometer (GCxGC‐QMS). The second chromatographic dimension was operated in a dual configuration, consisting of two parallel secondary columns, one being connected to the QMS, the other to a flame ionization detector (FID). This not only allowed optimization of the chromatographic gas flows when compared to the usual single second dimension, but it also enabled the use of the FID signal to extend the quantification range from 2 to 10,000 mg/kg. The QMS was used at a low level (2‐100 mg/kg), where coelutions are frequent, and the FID was used for the most abundant analytes (100‐10,000 mg/kg) with a low risk of significant interferences. To assess the identity and purity of the analyte peak at low level, we propose a strategy and summarize it in a decisional tree. To our knowledge, this represents the first fully developed quantification method based on a GCx2GC‐QMS/FID system. In contrast to other methods, it enables the quantification of a wide variety of analytes in fragrances in a single run, without requiring a series of sample dilutions to match the calibration range.