Abstract This study proposes an extended generalized conditional intensity measure (EGCIM)‐based approach to selecting aftershock ground motions that match the target aftershock EGCIM distributions. ...The main purposes of the proposed methodology are threefold: (a) to consider the multiple characteristics of aftershock ground motions (e.g., amplitude, frequency contents, cumulative effects, and duration), (b) to account for the correlations between mainshocks (MS) and aftershocks (AS) as well as cross‐correlations between AS IMs, and (c) to associate with the conventional mainshock GCIM approach to enforce mainshock‐consistency for practical applications. For these purposes, three components of the EGCIM methodology for aftershock ground motion selection are utilized: (1) the multivariate aftershock EGCIM distributions of any vector of aftershock intensity measures (IMs) are constructed conditioned on two MS‐AS IMs, (2) the correlations between mainshocks and aftershocks as well as the cross‐correlations between AS IMs are considered, and (3) the random realizations of aftershock IMs are generated as a target using the aftershock EGCIM distributions to select aftershock ground motions from the specific database. The proposed methodology is applied to a case study in the LPCC station in New Zealand, whose aftershock EGCIM distributions of the considered 18 IMs are constructed for the case scenario. Among them, the correlations between mainshocks (MS) and aftershocks (AS) as well as the cross‐correlations between AS IMs are determined using the total residuals (epsilons) based on 662 real MS–AS ground‐motion pairs. Several examples are then discussed to illustrate the application of the proposed aftershock EGCIM approach, including the comparison of the aftershock acceleration spectrum with the ASK14 model and the effects of different components of the aftershock IM weight vector. Then, the proposed approach is compared with the conventional aftershock synthesis methods. It is observed that the conventional methods perform biased representations of different aftershock characteristics, of which the limitations are improved in the proposed approach. Moreover, a sensitivity study is performed for a typical midrise structure to investigate the effects of aftershock ground motion selection on the aftershock fragility analysis. The results indicate that the selection of aftershock records considering different AS characteristics has a notable impact on the aftershock fragility assessment. The uncertainties associated with record‐to‐record variations in aftershock fragility analysis can be effectively reduced by using the proposed selection approach that incorporates the comprehensive ground motion characteristics. The findings in this study promote the extension of the existing methods for aftershock ground motion selection, which can be applied to structural design or seismic risk analysis considering the aftershock effects.
The direct functionalization of C-H bonds has drawn the attention of chemists for almost a century. C-H activation has mainly been achieved through four metal-mediated pathways: oxidative addition, ...electrophilic substitution, σ-bond metathesis and metal-associated carbene/nitrene/oxo insertion. However, the identification of methods that do not require transition-metal catalysts is important because methods involving such catalysts are often expensive. Another advantage would be that the requirement to remove metallic impurities from products could be avoided, an important issue in the synthesis of pharmaceutical compounds. Here, we describe the identification of a cross-coupling between aryl iodides/bromides and the C-H bonds of arenes that is mediated solely by the presence of 1,10-phenanthroline as catalyst in the presence of KOt-Bu as a base. This apparently transition-metal-free process provides a new strategy with which to achieve direct C-H functionalization.
The approximation of seismic hazard curve H(x) affects the determination of risk-targeted design ground motion SaR significantly. The traditional first-order approximation of H(x) for obtaining SaR ...may result in a relatively large error. Therefore, this study employs a second-order approximation of H(x) with three parameters to define the fitted parabolic functions. Three scenarios are proposed to determine the second-order approximation of H(x). Scenario 1 utilizes the ground motion intensity values of the three points along with their corresponding annual exceedance probabilities. Scenario 2 is essentially the same as scenario 1, with the difference that scenario 2 uses the tangent of the parabola at the frequent-level earthquake when the ground motion intensity is less than that of the frequent-level earthquake. Scenario 3 involves the utilization of two points and a symmetry axis. The suitability of the three scenarios is verified by comparing the risk-targeted maximum considered earthquake (MCER) obtained from the approximated H(x) with that from the actual H(x). The suitability is further examined by studying the ground motion intensity interval which significantly affects the determination of SaR through the lower and upper integration limits. Subsequently, the maps of MCER, collapse risk, and risk coefficient (i.e., the ratio of MCER to MCE) for mainland China are developed, and the sensitivity analysis is studied. It is shown that the ranges of the collapse risk in 50 years and risk coefficients for mainland China are 0.86%–1.03 % and 0.94–1.01, respectively. Therefore, only minor adjustments to the MCE in the current Chinese seismic design code are required to achieve the target collapse risk of 1 % in 50 years.
•Three scenarios are proposed for second-order seismic hazard curve approximation.•Ground motion intensity interval that significantly impacts RTGM is determined.•Sensitivity analysis for RTGM is conducted with various decision parameters.
Sugars play important roles in plant growth and development, crop yield and quality, as well as responses to abiotic stresses. Abscisic acid (ABA) is a multifunctional hormone. However, the exact ...mechanism by which ABA regulates sugar accumulation is largely unknown in plants. Here, we tested the expression profile of several sugar transporter and amylase genes in response to ABA treatment. MdSUT2 and MdAREB2 were isolated and genetically transformed into apple (Malus domestica) to investigate their roles in ABA-induced sugar accumulation. The MdAREB2 transcription factor was found to bind to the promoters of the sugar transporter and amylase genes and activate their expression. Both MdAREB2 and MdSUT2 transgenic plants produced more soluble sugars than controls. Furthermore, MdAREB2 promoted the accumulation of sucrose and soluble sugars in an MdSUT2-dependent manner. Our results demonstrate that the ABA-responsive transcription factor MdAREB2 directly activates the expression of amylase and sugar transporter genes to promote soluble sugar accumulation, suggesting a mechanism by which ABA regulates sugar accumulation in plants.
•Cyclic loading tests were conducted for the ACE and ECE technologies corroded RC columns.•Appearance, corrosion crack, corrosion characteristics of corroded columns using ACE and ECE were ...compared.•The corrosion products due to ACE and ECE were analyzed using X-ray diffraction.•Specimen’s failure mode, hysteresis curve, backbone curve, and seismic performance indexes were compared.
Corrosion of reinforcement bars can cause reinforced concrete (RC) columns more vulnerable under seismic loads. In this study, the seismic behavior of corroded RC columns was experimentally studied with a focus on the comparison between two different accelerated corrosion techniques by using artificial climate environment (ACE) and electrochemical chloride extraction (ECE). To do this, six RC square columns were designed and fabricated as the test specimens. The test specimens were categorized into two groups with a low level and a high level of axial compression ratio (i.e., 0.1 and 0.45), respectively, and each group includes three test specimens, i.e., an uncorroded column and two corroded columns under ACE and ECE techniques. An X-ray diffraction approach was used to examine the major ingredients of corrosion products attached on the corroded reinforcement bars under ACE and ECE techniques. The column specimens were subjected to repeated cyclic loadings, and the failure modes, hysteresis and backbone curves, stiffness degradation, ductility level and energy dissipation of the specimens corroded under different techniques were compared. The results show that, under a consistent target corrosion level, the ECE corrosion technique can cause more significant damage to the corroded RC columns than the ACE corrosion technique, leading to a change of failure mode and worse hysteretic performance.
Seismic design under the paradigm of uniform hazard only considers the seismic hazard of building sites, which will lead to inconsistent collapse risks of buildings in different areas. To achieve ...uniform collapse risk, the paradigm of conventional seismic design with uniform hazard should be shifted to the new framework of uniform risk, which accounts for both seismic hazard of sites and collapse fragility of buildings. In this study, based on the principle of risk targeting, parametric sensitivity analyses of risk-targeted ground motions for mainland China are performed considering different risk categories and site classes. Then, the risk-targeted peak ground accelerations and the uniform-risk seismic design spectra are obtained for mainland China. Seismic risk assessment is conducted for an 8-story reinforced concrete frame structure using the ground motions selected based on the uniform-risk seismic design spectra. The results indicate that the influence of logarithmic standard deviation of the target collapse fragility function on the risk-targeted maximum considered earthquake gradually increases with risk category. The impact of target collapse risk on risk-targeted maximum considered earthquake of a hard site is more remarkable than that of other sites. The effects of the logarithmic standard deviation and the conditional collapse probability under the maximum considered earthquake on the collapse risk gradually increase with the site class. In addition, the construction of uniform-risk seismic design spectra takes into account both seismic hazard and structural fragility. It is reasonable to select ground motions based on uniform-risk seismic design spectra for conducting seismic risk assessment of structures.
•Risk-targeted PGA corresponding to three levels of seismic design are obtained.•Parametric sensitivity considering risk categories and site classes are investigated.•The risk-targeted seismic design spectra are constructed for mainland China.•Seismic risk assessments are conducted based on risk-targeted design spectra.
Pyridines and related N-heteroarenes are commonly found in pharmaceuticals, agrochemicals and other biologically active compounds
. Site-selective C-H functionalization would provide a direct way of ...making these medicinally active products
. For example, nicotinic acid derivatives could be made by C-H carboxylation, but this remains an elusive transformation
. Here we describe the development of an electrochemical strategy for the direct carboxylation of pyridines using CO
. The choice of the electrolysis setup gives rise to divergent site selectivity: a divided electrochemical cell leads to C5 carboxylation, whereas an undivided cell promotes C4 carboxylation. The undivided-cell reaction is proposed to operate through a paired-electrolysis mechanism
, in which both cathodic and anodic events play critical roles in altering the site selectivity. Specifically, anodically generated iodine preferentially reacts with a key radical anion intermediate in the C4-carboxylation pathway through hydrogen-atom transfer, thus diverting the reaction selectivity by means of the Curtin-Hammett principle
. The scope of the transformation was expanded to a wide range of N-heteroarenes, including bipyridines and terpyridines, pyrimidines, pyrazines and quinolines.
In the context of structural integrity management (SIM), effective utilization of real-time structural health monitoring (SHM) information is crucial for minimizing the expected value of life-cycle ...costs. To enhance the benefits of real-time SHM information for SIM, this paper introduces a framework aimed at optimizing the utilization of real-time SHM information from a life-cycle perspective, grounded in Bayesian posterior decision analysis. In addressing this issue, the paper utilizes a robust probabilistic model that is intimately connected with real-time SHM information. This model plays a crucial role in quantifying how the availability of real-time SHM data impacts the benefits of SIM. Following this quantification in the proposed analytical framework, the paper conducts a comprehensive comparative analysis of various utilization strategies, highlighting their respective efficiencies and effectiveness in the context of SIM. Through a case study centered on a weld exposed to fatigue loading, the paper not only showcases the proposed framework but also demonstrates its efficacy in identifying the optimal strategy for real-time SHM information utilization.
•Bayesian preposterior decision analysis is used to optimize the information utilization.•A probabilistic model of real-time SHM information is proposed.•Identification of optimal utilization strategy of real-time SHM information are discussed.
•A phenomenological hysteretic model for corroded RC columns was developed.•The parameters of the phenomenological hysteretic model were calibrated based on test data.•Empirical prediction equations ...were generated for the parameters of the developed hysteretic model.
A phenomenological hysteretic model is developed for corroded RC columns in this study. To this end, the test data of 77 corroded rectangular RC columns and 26 uncorroded ones under repeated cyclic loads are collected to establish a database. A polygonal hysteretic model that can well incorporate the degradation of stiffness and strength is adopted to describe the hysteretic behavior of corroded columns. The hysteretic model parameters related to monotonic backbone (i.e., yield moment My, yield rotation θy, pre-capping rotation θp, post-capping rotation θpc, the ratio of capping moment to yield moment k) and cyclic deterioration (i.e., cyclic deterioration parameter λ) are identified for each of the test specimens in the database after a careful calculation with the experimental data. The backbone parameters identified for the corroded columns are compared to those for the uncorroded columns to quantify the corrosion-induced deterioration coefficients (CIDCs). Multivariate-linear-type empirical relationships are then developed to relate each of the CIDCs to the corrosion rate and critical structural design variables using stepwise regression analysis. A multilinear empirical relationship is also proposed for the cyclic deterioration parameter. The developed hysteretic model together with the predictive equations for the model parameters are proved of high accuracy through simulating the intra-database tests considering varying corrosion levels. They are further applied to the corroded columns beyond the database, those without data on uncorroded counterparts provided in particular, also indicating a desirable accuracy.
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