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OBJECTIVES In addition to the association between positive fluid balance (FB) and acute kidney injury (AKI) after cardiac surgery reported by former studies, this study examined the relationship between FB and progressive AKI. DESIGN A retrospective, observational study. SETTING University teaching, grade A tertiary hospital in Shanghai, China. PARTICIPANTS Adult patients after cardiac surgery from July-December 2016. INTERVENTIONS Perioperative data relating to postoperative fluid intake and output were collected. AKI progression was defined as a worsening of AKI stage. FB was calculated as (fluid intake [L] - fluid output [L]/body weight [kg] × 100%). MEASUREMENTS AND MAIN RESULTS The study comprised 1,522 patients. The incidences of AKI and progressive AKI were 33.1% (n = 504) and 18.1% (n = 91), respectively. There was an exponential increase between 24-hour FB and AKI occurrence, and an approximate "U"-shape association between 48-hour FB and AKI progression. Multivariate logistic regression showed that 24-hour FB ≥5% was an independent risk factor for AKI incidence (odds ratio [OR] 3.976; p < 0.001) and 48-hour FB

Composite laminates are usually made of anisotropic viscoelastic materials with layer-dependent properties. Although such structures are advantageous over the traditional single-material structure, their interfacial damage/failure is a great concern. In this paper, we present the general formulation and the corresponding solution to enhance our understanding on the guided waves in such laminates with imperfect interfaces. The formulation is based on the modified dual variable and position (DVP) method combined with a powerful and accurate root-finding algorithm. While the former overcomes the numerical instability when handling layered structures, the latter finds all the roots of the dispersion equation in a complex domain providing the full three-dimensional (3D) dispersion curves. After the proposed formulation is validated by the semi-analytical finite-element (SAFE) method for the perfect interface case, the present solution is applied to analyze the dispersion curves and mode shapes for a bilayer laminate with imperfect interface. Numerical examples demonstrate the detailed evolution mechanisms on wave features from perfect interface to complete delamination in the bilayer with imperfect interface. The results presented in this paper provide important insight to guide the in-situ monitoring of the evolution processes of the wave mode shapes and dispersion curves from perfect interface to complete delamination.

Objectives Stroke volume variation (SVV) has been used to predict fluid responsiveness. The authors hypothesized the changes in SVV induced by passive leg raising (PLR) might be an indicator of fluid responsiveness in patients with protective ventilation after cardiac surgery. Design A prospective single-center observational study. Setting A single cardiac surgery intensive care unit at a tertiary hospital. Participants A total of 123 patients undergoing cardiac surgery with hemodynamic instability. Tidal volume was set between 6 and 8 mL/kg of ideal body weight. Interventions PLR maneuver, fluid challenge. Measurements and Main Results SVV was continuously recorded using pulse contour analysis before and immediately after a PLR test and after fluid challenge (500 mL of colloid given over 30 min). Sixty-three (51.22%) patients responded to fluid challenge, in which PLR and fluid challenge significantly increased the SV and decreased the SVV. The decrease in SVV induced by PLR was correlated with the SV changes induced by fluid challenge. A 4% decrease in the SVV induced by PLR-discriminated responders to fluid challenge with an area under the curve of 0.90. The gray zone identified a range of SVV changes induced by PLR (between –3.94% and –2.91%) for which fluid responsiveness could not be predicted reliably. The gray zone included 15.45% of the patients. The SVV at baseline predicted fluid responsiveness with an area under the curve of 0.72. Conclusions Changes in the SVV induced by PLR predicted fluid responsiveness in cardiac surgical patients with protective ventilation.

Although energy piles are widely used worldwide as green foundations, currently no approach is available to quantify the design uncertainties in their long-term performance. Based on the cyclic load-transfer curves, this paper presents a probabilistic model for life-cycle analysis of energy piles under seasonal thermal loading. For computational efficiency, the subdomain sampling method is adopted for estimating the failure probability due to excessive settlement, and is compared with Monte Carlo simulation. This probabilistic analysis approach for energy piles is illustrated through a case study. The life-cycle failure probability of energy piles for various mechanical loading and thermal loading scenarios is investigated.

In this study, the effects of soil spatial variability in braced excavations are investigated by focusing on three structural responses: wall bending moments, wall shear forces, and strut forces. The soil spatial variability is modeled using random field theory, and the generated soil parameters are mapped onto a finite element model. A procedure for automating the Monte Carlo simulation, which is used for probabilistic analysis, is described. A case study demonstrates that the soil spatial variability has a considerable effect on the excavation-induced structural responses. Furthermore, a reliability analysis is performed to estimate the failure probability for three structural failure modes. The results demonstrate the importance of considering soil spatial variability in the structural assessment of braced excavations. Keywords: Braced excavations, Soil spatial variability, Random field modeling, Finite element method

Objective To compare outcomes between intensivist-directed and cardiac surgeon-directed care delivery models. Design This retrospective, historical-control study was performed in a cohort of adult cardiac surgical patients at Zhongshan Hospital (Fudan University, China). During the first phase (March to August 2015), cardiac surgeons were in charge of postoperative care while intensivists were in charge during the second phase (September 2015–June 2016). Both phases were compared regarding successful extubation rate, intensive care unit (ICU) length of stay (LOS), and in-hospital mortality. Setting Tertiary Zhongshan Hospital (Fudan University, China). Patients Consecutive adult patients admitted to the cardiac surgical ICU (CSICU) after heart surgery. Interventions Phase I patients treated by cardiac surgeons, and phase II patients treated by intensivists. Main variables of interest Successful extubation, ICU LOS and in-hospital mortality. Results A total of 1792 (phase I) and 3007 patients (phase II) were enrolled. Most variables did not differ significantly between the two phases. However, patients in phase II had a higher successful extubation rate (99.17% vs. 98.55%; p = 0.043) and a shorter median duration of mechanical ventilation (MV) (18 vs. 19 h; p 48 h, those in phase II had a comparatively higher successful extubation rate (p = 0.033), shorter ICU LOS (p = 0.038) and a significant decrease in in-hospital mortality (p = 0.039). Conclusions The intensivist-directed care model showed improved rates of successful extubation and shorter MV durations after cardiac surgery.

This paper presents a new pavement design approach based on the concept of robust design. Robust pavement design is capable of minimizing the influence of various uncertainties (such as uncertain material properties) on the designed pavement rutting life and fatigue life through a rational adjustment of the design parameters. In this new approach, the signal-to-noise ratio is used to quantify the design robustness, and a genetic algorithm is employed to determine the Pareto front. Using a marginal utility function, the knee point on the Pareto front is selected and is recommended as the optimal design that simultaneously best meets the requirements of safety, robustness and cost. A case study is performed to illustrate this new design approach.

Given the increasing prevalence of smart grids, the introduction of demand-side participation and distributed energy resources (DERs) has great potential for eliminating peak loads, if incorporated within a single framework such as a virtual power plant (VPP). In this paper, we develop a data mining-driven incentive-based demand response (DM-IDR) scheme to model electricity trading between a VPP and its participants, which induces load curtailment of consumers by offering them incentives and also makes maximum utilization of DERs. As different consumers exhibit different attitudes toward incentives, it is both essential and practical to provide flexible incentive rate strategies (IRSs) for consumers, thus respecting their unique requirements. To this end, our DM-IDR scheme first employs data mining techniques (e.g., clustering and classification) to divide consumers into different categories by their bid-offers. Next, from the perspective of VPP, the proposed scheme is formulated as an optimization problem to minimize VPP operation costs as well as guarantee consumer’s interests. The experimental results demonstrate that through offering different IRSs to categorized consumers, the DM-IDR scheme induces more load reductions; this mitigates critical load, further decreases VPP operation costs and improves consumer profits.

Energy piles are sustainable green foundations. Although several geotechnical design methods have been proposed, no methods have yet been developed to quantify the uncertainty propagation in thermo-mechanical pile-soil interactions. The probabilistic model proposed in this paper, which is based on load-transfer curves, considers the effects of spatial variability for energy pile design. The developed random finite difference method is used to address the effects of vertical spatial variability on the ultimate limit state design and serviceability limit state design. This study points to the necessity of modeling the soil spatial variability in the thermo-mechanical pile-soil interactions in energy piles.

This case study presents the effect of spatial variability of soft clays on the geotechnical serviceability assessment of braced excavations. Finite element modeling is performed to predict the excavation-induced wall and ground movement. The spatial variations in two key soil parameters are modeled as two correlated lognormal random fields. The system reliability-based serviceability assessment conducted in this case study shows that the system probability of serviceability failure is greater than or equal to that for each single failure mode, indicating that serviceability assessment considering an individual failure mode can result in unsafe predictions.

Generalized stacking-fault energies (GSFEs) of basal-plane stacking faults I1 and I2 in Mg alloys have been studied based on first-principles calculations, where 43 alloying elements were considered. It is found that the most contributing features of alloying elements to GSFEs are bulk modulus, equilibrium volume, binding energy, atomic radius and ionization energy. Both bulk modulus and ionization energy exhibit positive relationships with GSFEs, and the others show opposite relationships. Multiple regressions have been performed to offer a quantitative prediction for basal-plane GSFEs in Mg-X systems. GSFEs, alloying effects of elements and the prediction model established within this work may provide guidelines for new Mg alloys design with better ductility.

This paper focuses on the influence of Y3+ donor doping on optimizing dielectric properties of CaCu3Ti4O12 (CCTO) ceramics by controlling electrical properties of grains and grain boundaries (GBs). The Y3+ ions donor-doped Ca1-xYxCu3Ti4O12 (CYCTO, x = 0, 0.01, 0.02, 0.03, 0.05 and 0.07) ceramics were prepared by the conventional solid state reaction method. The influence of doping content on phase structure, morphologies and dielectric properties of CYCTO ceramics was investigated. It was found that Y3+ donor doping scarcely influenced the phase structure of CYCTO, but grain growth in CYCTO ceramics was depressed by Y3+ ions. Interestingly, although the grain size of CCTO was depressed, an enhancing value in dielectric constant (er) with simultaneously reducing dielectric loss tangent (tanδ) was successfully achieved as Y3+ doping content x increased from 0.01 to 0.03. Impedance spectroscopy analysis further revealed that Y3+ donor doping can improve conductivity of semiconducting grain in CYCTO ceramics with x increasing up to 0.05, which was well consistent with the rising tendency of er. The resistance of insulating GBs was improved with x increasing up to 0.03, which resulted in a considerable reduction in tanδ. The donor doping type of using Y3+ substitution for A site Ca2+ into CCTO in this work should provide an effective route for further optimizing properties of CCTO ceramics by reducing resistance of grains (Rg) and simultaneously enhancing resistance of GBs (Rgb).

This paper presents an efficient system reliability approach for the internal instability of mechanically stabilized earth walls in a heavy haul railway. The first-order reliability method is adopted to assess the wall failures due to rupture and pullout. The effects of uncertainties in the backfill unit weight, the friction angle of backfill and the friction along the soil-reinforcement interface, as well as the width, thickness and tensile strength of steel strips are explicitly explored. Moreover, the system reliability analysis clearly demonstrates the impact of steel corrosion on the life-cycle retaining wall stability.

In this study, a three-dimensional vehicle-track-tunnel-soil model for evaluating the dynamic response of a double-line metro tunnel in a poroelastic half-space is developed. The model development consists of two steps. In the first step, the vehicle-track-tunnel-soil model in a full-space is developed. In the second step, based on the full-space model, the dynamic response of the poroelastic half-space is solved by using the 2.5-dimensional boundary integral equation and the Green’s function. The developed vehicle-track-tunnel-soil model is validated against existing tunnel models and is demonstrated through a case study of the dynamic response induced by one-way and two-way train loads.

The influences of solute atoms (Li, Al, Mn, Zn, Fe, Ni, Cu, Y, Zr) and Cl adsorption on the anodic corrosion performance on Mg (0001) surface have been investigated based on first-principles calculations, which might be useful for the design of corrosion-resistant Mg alloys. Work function and local electrode potential shift are chosen as descriptors since they quantify the barrier for charge transfer and anodic stability. We found that at 25% surface doping rate, Y decreased the work function of Mg, while the impact of remaining doping elements on the work function of Mg was trivial due to the small surface dipole moment change. The adsorption of Cl destabilized the Mg atoms at surface by weakening the bonding between surface Mg atoms. We find that a stronger hybridization of d orbits of alloying elements (e.g. Zr) with the orbits of Mg can greatly increase the local electrode potential,which even overbalances the negative effect introduced by Cl adsorbates and hence improves the corrosion resistance of Mg alloys.

This study is devoted to developing an efficient system reliability-based mechanistic-empirical pavement design procedure to address the uncertain material property. This procedure consists of the following four components: 1) mechanics-based layered elastic analysis for computing the tensile strain and the compressive strain, 2) empirical models for predicting fatigue life and rutting life, 3) first-order reliability method (FORM) for estimating the probability of pavement failure, and 4) an updated spreadsheet tool for estimating the system probability of pavement failure. The proposed procedure can efficiently estimate the probability of pavement failure without requiring the engineers to have a detailed knowledge of theoretical mechanics and reliability simulations.

In this paper, a probabilistic assessment of supported excavations in spatially varied sands is presented. Random finite element modelling (RFEM) is performed to simulate excavation-induced responses. A procedure for automating the Monte Carlo simulation is developed to facilitate the RFEM. The effects of soil vertical spatial variability on several major geotechnical and structural failure modes, including geotechnical ultimate failure, geotechnical serviceability failure, wall bending failure, wall shear failure, and strut buckling failure, are explicitly investigated. This study demonstrates the importance of addressing the spatial variation of soil properties by considering multiple failure modes for complicated soil-structural interaction problems.

This study explores the influence of rotated anisotropy of soil property on the bearing capacity of embedded strip footings using the random finite element method. An extensive parametric study was carried out considering the different scales of fluctuations, embedded depths, and rotation angles of the random fields. Results show that for various footing embedded depths considered in this study, the major scale of fluctuation has a large influence on the probability of bearing capacity failure in all cases. Furthermore, the mean bearing capacity remains almost constant regardless of the change of rotation angle, while the probability of bearing capacity failure decreases with the increase of rotation angle. The significant role of rotation angle in probabilistic analysis highlights the need to understand and consider the soil layer orientation in geotechnical foundation design to achieve safety and reliability.

Based on laser scanning technique and discrete element program, the fine mesoscopic model of irregular ballast particles was simulated well by series of bonded disc clusters, then the large-scale static and cyclic loading tests were used to determine the parameters of the discrete element model. On this basis, the plastic deformation and shakedown behaviors of ballast samples under cyclic loading were studied, and the effects of cyclic loading amplitude, confining pressure and loading frequency were discussed. The results show that, in plastic shakedown state, broken ballast particles were rare and the strain rate of the sample decreased rapidly with the increase of the number of load cycles; in plastic creep state, ballast particles were broken at the beginning of cyclic loading and then appeared stable deformation; in incremental collapse state, ballast particles were broken in initial cyclic loading, but the plastic deformation of the sample was mainly due to the rapid shear failure. The stress limits of ballast samples for different shakedown states increased with raising the confining pressure, but the influence of the loading frequency on the stress limits related to the stress levels of confining pressure, and accordingly, the empirical exponential models of the relationships between the stress limits (i.e. maximum principal stress) and the ratios of corresponding maximum principal stress to minimum principal stress were established.

Objective This study aimed to evaluate the outcomes of high-flow nasal cannula (HFNC) oxygen therapy compared with noninvasive ventilation (NIV) for the treatment of acute hypoxemic respiratory failure in renal transplant recipients. Methods Data were retrospectively collected from a tertiary intensive care unit (ICU) from July 1, 2011, to September 31, 2015. All renal recipients who had acute respiratory failure at that period of time were classified into the HFNC or NIV group depending on the initial form of respiratory support. Results A total of 38 patients were enrolled in this study. Twenty patients received HFNC and the other 18 received NIV as the initial respiratory support. The ICU mortality in the HFNC group was 5% (1 patient), compared with 22.2% (4 patients) in the NIV group ( P = .083). The median length of the ICU stay was 12 days in the HFNC group, compared with 14 days in the NIV group ( P = .297). The number of ventilator-free days at day 28 was significantly higher in the HFNC group than in the NIV group (26 ± 3 vs 21 ± 3; P P = .042) and skin breakdown (0% vs 22.2%; P = .042) were significantly lower in the HFNC group. Conclusions In renal transplant recipients with acute hypoxemic respiratory failure secondary to severe pneumonia, HFNC achieved outcomes similar to NIV. In addition, HFNC was associated with an increased number of ventilator-free days at day 28 and fewer complications.

Although the CaCu 3 Ti 4 O 12 ceramics have colossal dielectric constants, their relative high dielectric losses are one of the limiting factors for commercial applications. Various doping elements and additive compounds have been extensively used to reduce their dielectric losses with only limited success. Instead of using such doping elements, this work shows that a facile air quenching technique can considerably reduce the dielectric losses of the CaCu 3 Ti 4 O 12 ceramics over a wide frequency range. In the meantime, their colossal dielectric constants can be simultaneously enhanced. It was found that the dielectric loss of the air-quenched CaCu 3 Ti 4 O 12 ceramics is as low as 0.03 at 12 kHz, and the dielectric constant is over 1×10 4 across the frequency range up to 1 MHz.

Second phase strengthening has been widely applied in Mg alloy designs, many of which however have been reported to aggravate the galvanic corrosion of Mg alloys. In this study, the hydrogen evolution reaction (HER) on MgZn2 Laves phase, which serves as a local cathode, is investigated by first-principles calculations based on density functional theories. We first calculated the surface energy of MgZn2 and found (0001) surface with Mg-rich termination to be the most stable one, and the favored adsorption sites for relevant molecule species were further identified. By using Nudged Elastic Band (NEB) method, the reaction pathway and energy barriers of H2O molecule decomposition, H adatom diffusion, and H2 molecule recombination were obtained, among which hydrogen recombination is thermodynamically unfavored. This study provides fundamental insights into the cathodic reaction on Mg alloys, from determining the cathode, identifying the most stable surface, obtaining reaction energy barrier, to comparing corrosion property among different intermetallics, which may be a guidance to the corrosion-resistant Mg alloys design.

Recently, the pit-in-pit braced excavations are frequently adopted in the geotechnical engineering projects in China due to the large demand of urban underground space utilization. In this study, a simplified approach for basal-heave stability analysis of pit-in-pit braced excavations in soft clays is developed based on the limit equilibrium method. The configuration of failure surfaces is obtained by using finite element method with the shear strength reduction technique. The factors of safety computed with the simplified approach are comparable to those from the finite element simulation. This simplified approach is demonstrated through a case study of pit-in-pit excavations in Shanghai.

This study proposes an improved tunnel model for evaluating train-induced dynamic stress in saturated soils, which can consider multiple moving loads, grouting layer and pore-water pressure. Using Shanghai Metro’s actual parameters for train speed, tunnel, grouting layer and soils, the analysis of the spatial distribution of dynamic stress for soils and stress state of various locations under moving train loads shows that neglecting effects such as pore-water pressure can lead to underestimating dynamic normal stress and overestimating dynamic shear stress in the soils below tunnel. This model can be further extended to investigate principal stress axes rotations and tunnel settlement.

This paper presents a probabilistic approach for seismic stability analysis of a slope at a given site in a specified exposure time. For a probabilistic seismic stability analysis, the ground motion parameter, in terms of the peak ground acceleration (PGA), at a given site in a specified exposure time of interest (say, 30 years) is treated as a random variable, and the PGA distribution at the given site is derived based on the USGS National Seismic Hazard Maps data. Further, the spatial variability of the soil property is simulated herein by a random field, and the fluctuation of the groundwater level is simulated by a random variable. Within the probabilistic framework, a deterministic model for evaluating the slope stability is required; here, a pseudo-static analysis is adopted and implemented through 2D finite difference program FLAC version 7.0. In the face of the uncertainties in the input parameters, the performance or safety of the slope is expressed as a failure probability; within the proposed probabilistic analysis framework, a recently developed sampling method is adopted for the uncertainties propagation through the deterministic solution model. This probabilistic analysis framework is demonstrated with an illustrative example of a two-layer earth slope. Finally, a parametric study is undertaken to investigate how the failure probability of the slope (at a given site in a specified exposure time) is affected by the uncertain factors such as the earthquake-induced ground motion and the spatial variability of soil property. The study results demonstrate the versatility and effectiveness of the proposed framework for probabilistic seismic stability analysis of slope at a given site in a specified exposure time.

Background The optimal timing of renal replacement therapy (RRT) initiation in patients undergoing cardiac surgery remains controversial. This study aimed to determine whether preemptive RRT or standard RRT was associated with hospital mortality in cardiac surgical patients with acute kidney injury (AKI). Methods Data were retrospectively collected from patients who underwent cardiac surgery and experienced postoperative AKI requiring RRT at Zhongshan Hospital of Fudan University from September 1, 2006 to December 31, 2013. The patients were divided into two groups according to the RRT strategy applied. Results A total of 213 patients were enrolled in this study; 59 patients were categorized into the preemptive RRT group and 154 into the standard RRT group. The preemptive RRT group exhibited significantly lower mortality (33.90% versus 51.95%, P = 0.018) and time to recovery of renal function than the standard RRT group (15.34 ± 14.46 versus 22.88 ± 14.08 d, P = 0.022). Moreover, the preemptive RRT group showed significantly lower serum creatinine levels and higher proportions of recovery of renal function and weaning from RRT at death or discharge than the standard RRT group. There was no significant difference in the duration of mechanical ventilation, RRT, intensive care unit stay, or hospital stay between the two groups. Conclusions In patients after cardiac surgery, preemptive RRT was associated with lower hospital mortality and faster and more frequent recovery of renal function than standard RRT. However, preemptive RRT did not affect other patient-centered outcomes including mechanical ventilation time, RRT time, or length of intensive care unit or hospital stay.

Energy piles provide clean energy in lieu of non-renewable energy resources such as petroleum and coal. The current geotechnical design of energy piles is merely realized through enlarging the factor of safety. The factor of safety used for energy piles is at least twice that used for traditional piles, which can lead to considerable additional costs and inconsistent levels of safety. Although the performance of existing energy pile technology is satisfactory and recent investigators have significantly advanced the understanding of the load-transfer mechanisms of energy piles, it is still necessary to quantify the uncertainty in the thermal–mechanical analysis and to develop reliability-based designs for energy piles. This paper presents a pioneering probabilistic study on the geotechnical design of energy piles. The critical soil parameters for ultimate limit state (ULS) and serviceability limit state (SLS) are identified through sensitivity study. The point estimate method is adopted to understand the uncertainty propagation and to estimate the probability of ULS failure and the probability of SLS failure. The adverse effects of thermal loading in the geotechnical design of energy piles are explicitly demonstrated through a case study.

The influence of vertical spatial variability of sands on the excavation-induced lateral wall deflection and bending moment of excavations supported by cantilever retaining walls is investigated in this paper. Herein, the random finite element method (RFEM) is adopted to explicitly study the effect of one-dimensional spatial variability of internal friction angle of sands on the predicted wall and ground responses. The RFEM analysis consists of three components: (1) finite element method for analyzing lateral wall deflection and bending moment, (2) random field theory implemented with Monte Carlo simulation (MCS), and (3) statistical interpretation of MCS results through confidence intervals. This study reveals the importance of random field modeling in coping with the spatial variability of sands in the problem of supported excavations: (1) neglecting spatial variability of soil property will cause an overestimation of the variation in the predicted wall deflection and bending moment; (2) the estimated probability of failure based on a well-established serviceability limit state may be overestimated or underestimated depending on the chosen limiting lateral wall deflection. This study further investigates the effect of the number of MCS on the confidence intervals of the predicted statistics of the maximum lateral wall deflection and the maximum bending moment. The results also demonstrate that the confidence interval analysis of the predicted statistics of the maximum lateral wall deflection and the maximum bending moment provides a rational tool for interpreting the statistical data from RFEM. (C) 2016 Elsevier Ltd. All rights reserved.

This study investigates the long-term settlement of Nanjing Metro Line 10 in China. A maximum settlement of 240 mm was measured within 5.75 years after the track system was constructed. Four settlement troughs were observed along the longitudinal direction of the railway line. The settlement of the tunnel developed rapidly in the first two years and then the rate of settlement gradually decreased. The excessive settlement and large differential settlement of the tunnel were primarily caused by the deep and non-uniform distribution of the underlying soft soil. The long-term tunnel settlement mainly consists of two components, including recompression settlement following construction and secondary consolidation settlement of the foundation. Each component of settlement was analyzed and estimated in this study. The computed results correspond well with the measured data, and the recompression deformation and the secondary consolidation deformation represents approximately 78.0–100% and 0–22.0% of the total tunnel settlement, respectively. The measured data and calculated results revealed that the lengths of the cement mixing piles used to improve the tunnel foundation are insufficient to reduce the long-term settlement. Piles entirely penetrating the soft silty clay layer are recommended.

Although numerical models have been widely used in the geotechnical profession, their applications for reliability analysis are still rather limited mainly because most geotechnical numerical programs lack the probabilistic function. In this study, an efficient response surface method is suggested for geotechnical reliability analysis using existing numerical programs. The developed approach can effectively avoid the occurrence of negative values for positive random parameters, and thus it solves the key limitation of the classical response surface method in geotechnical applications. To facilitate its application, a procedure is designed for automating reliability analysis with the commercially available program, FLAC3D. The developed method and procedure are demonstrated in detail using a slope example. The versatility of the suggested procedure is illustrated through the serviceability reliability analysis of a soft ground improved with deep mixing columns. For the reinforced ground studied in this paper, the reliability is mainly governed by the uncertainties in Young’s moduli of the soil and reinforced columns. The suggested method can be conveniently used for reliability-based design of deep mixing columns.

Differential settlements of the shield tunnel along the longitudinal direction can significantly affect the circumferential behavior of segmental lining, degrading both the structure safety and serviceability. In this paper, the authors introduce both the shearing effect and flattening effect on the tunnel cross section, which was caused by the longitudinal differential settlement, into an existing analytical model of jointed shield tunnels. An example is then presented to illustrate the variation of the circumferential behavior of segmental lining, including both the structure safety and serviceability, along the longitudinal position. Finally, a series of parametric studies are performed to investigate how factors such as tunnel longitudinal settlement, property of surrounding ground, and the design parameters of segmental lining affect the circumferential behavior of the segmental lining.

An efficient approach for reliability-based mechanistic-empirical pavement design considering fatigue and rutting failures is developed in this study. This efficient approach relies on the first-order reliability method (FORM) and is implemented in a spreadsheet. The gamma sensitivity study is performed to identify the key input parameters in the reliability analysis. This study investigates the effect of the uncertainty in elastic modulus, layer thickness, design traffic as well as the model error of a three-layered pavement system on the reliability analysis. Comparison study shows that this efficient approach using FORM can yield results that are comparable with those obtained using Monte Carlo simulation. The advantages of this efficient approach include: it requires much less computational effort to determine probability of failure; it can be readily adapted for other mechanistic-empirical models for pavement design; it is easy to be adopted in the engineering practice and thus has the potential to become a practice tool in the reliability-based mechanistic-empirical pavement design.

Excessive settlement caused by tunneling during construction often damages adjacent infrastructures and utilities. Such excessive settlement can also present a challenge in the maintenance of subways during their operation. Thus, it is important to be able to accurately predict tunneling-induced settlement. The uncertainties in geotechnical parameters, however, can lead to either an overestimation or an underestimation of the tunneling-induced settlement. Such uncertainties can arise from many sources such as spatial variability, measurement error, and model error; in this paper, the focus is on the geotechnical parameters characterization from site exploration. The goal here is to determine an optimal level of site exploration effort so that effective predictions of the tunneling-induced settlement in clays can be achieved. To this end, a Monte Carlo simulation-based numerical model of site exploration is first established to generate artificial test data. Then, a series of parametric analyses are performed to investigate the relationship between the level of site exploration effort and the accuracy of the tunneling-induced ground settlement prediction. Through the assumed different levels of site exploration effort, statistics of soil parameters are estimated using the maximum likelihood method and the tunneling-induced ground settlement is then analyzed using the probabilistic method, and finally the effect of site exploration effort is assessed. The knowledge generated from this series of analyses is then used to develop the proposed framework for selecting an optimal site exploration program for improved prediction of the tunneling-induced ground settlement in clays. Examples are presented to illustrate the proposed framework and demonstrate its effectiveness and significance.

Energy piles have been adopted worldwide as a green foundation technology. The current geotechnical design methods for energy piles — factor-of-safety-based design and reliability-based design — mainly focus on the safety and cost, while design robustness is usually ignored. This paper presents a robust design model for energy piles that is based on the load-transfer method. A fuzzy set-based point estimate method is adopted to quantify the uncertainty in the ultimate limit state design and serviceability limit state design. This robust design approach is intrinsically a multi-objective optimization, in which the optimal design can be determined by simultaneously meeting the requirements for safety, cost and robustness. The proposed robust design approach for energy piles is demonstrated through a case study.

The ZnO:B (BZO) films with different boron doping levels have been prepared by low pressure chemical vapor deposition (LPCVD) technique. The electrical and optical properties of the BZO films have been systematically investigated through a post annealing treatment in hydrogen atmosphere, as well as in vacuum for comparison. It is found that conductivity of BZO films, especially with a low boron doping level, can be enhanced significantly after annealing in hydrogen, and moreover, the total transmittance (TT) and haze factor of the H2-annealed BZO films were still almost unchanged simultaneously, which were attributed to phenomena of an increase in carrier mobility with an almost constant of free carrier concentration. The conversion efficiency of a-Si:H/μc-Si:H tandem solar cell incorporating H2-annealed lowly doped BZO film as front electrode was confirmed to be improved remarkably by 1.10% due to the enhancement of TT and haze factor, as compared to that using an as-grown heavily doped BZO film as front electrode. The results indicate that H2-annealing is a quite attractive and alternative technique to optimize properties of BZO film as TCO for further enhancing conversion efficiency of a-Si:H/μc-Si:H tandem solar cells.

In this paper, the authors present a probabilistic back-analysis of a recent slope failure at a site on Freeway No. 3 in northern Taiwan. Post-event investigations of this failure found uncertain strength parameters and deteriorating anchor systems as the most likely causes for failure. Field measurement after the event indicated an average slip surface of inclination 15°. To account for the uncertainties in input parameters, the probabilistic back analysis approach was adopted. First, the Markov Chain Monte Carlo (MCMC) simulation was used to back-calculate the geotechnical strength parameters and the anchor force. These inverse analysis results, which agreed closely with the findings of the post-event investigations, were then used to validate the maximum likelihood (ML) method, a computationally more efficient back-analysis approach. The improved knowledge of the geotechnical strength parameters and the anchor force gained through the probabilistic inverse analysis better elucidated the slope failure mechanism, which provides a basis for a more rational selection of remedial measures.

In this paper, the fatigue life of rubberized asphalt concrete mixtures containing reclaimed asphalt pavement is investigated through probabilistic analysis. The simple traditional empirical models updated with a reliable database are employed to predict the fatigue lives of various mixtures containing crumb rubber and/or reclaimed asphalt pavement. The effects of model uncertainty and input parameter uncertainty on the fatigue life are interpreted with the probability of fatigue failure, this is defined herein as the probability that the predicted fatigue life fails to satisfy the minimum requirements of fatigue life. The probabilistic analysis of fatigue failure is estimated with a simple reliability-based approach, known as point estimate approach (PEM). Comparison study shows that the probability of fatigue failure obtained with PEM is identical with that obtained with the Monte Carlo simulation (MCS). The results indicated that the probabilistic analysis using PEM and MCS methodologies can be used for exploring the fatigue life probability effectively, requires very limited computational effort, and thus has the potential and ease as a practical tool to employ in pavement engineering.

This paper develops and compares various models for probability of liquefaction using standard penetration tests. These probabilistic models are developed using the most recently updated database of liquefaction case histories by Idriss and Boulanger. Rigorous theories, including the principles of Maximum Likelihood and the Information Theory, are employed in the model development. The developed probabilistic models are compared with existing models. The results show superior capability of the developed models. Furthermore, application of the developed models is presented with provisions for consideration of input parameter uncertainty. Examples are presented to demonstrate the developed models.

Salmonella enterica serovar Typhi (S. Typhi) causes a human-restricted systemic infection called typhoid fever. It invades intestinal epithelial cells requiring expression of genes located at SPI-1. QseC is a regulator of quorum sensing that initiates transcription of a series of flagellar genes in reponse to AI-3 in Escherichia coli. By sequencing analysis, we have found that the homolog of the putative qseBC (t3098, t3099) in a wild-type strain of S. Typhi shares 98% and 99% identity with that of S. enterica serovar Typhimurium (S. Typhimurium), respectively. Glucose is not only an energy source compound but also an important environmental signaling molecule for enteropathogenic bacteria. In this study, we found that a series of invasion-associated genes in SPI-1 were downregulated in the qseC mutant of S. Tyhpi compared to the wild-type in the presence of glucose, by the genomic microarray assay. Results of qRT-PCR were consistent with the microarray data and suggest that the transcriptional regulation of invasion-associated genes by QseC is glucose-dependent and the regulation is not dependent on QseB. A qseC mutant cultured in the presence of glucose condition was impaired in invasion of epithelial cells. These data indicate that QseC can promote invasion in S. Typhi in the presence of glucose.

This paper aims to apply a preference method for selecting optimal city distribution reloading locations in urbanized areas. The focus in the optimization is on trucks entering the urbanized area where the truck can choose between at least two locations with similar distances determined by a specified integer value generated randomly by a given interval. Results from a numerical example show that a sorting order of city distribution reloading locations with similar distance can be effectually obtained with this approach.

A simplified approach to consider the effect of spatial variability in a two-dimensional (2-D) random field for reliability analysis of basal-heave in a braced excavation in clay is presented. In contrast to the random field modeling (RFM) approach, which necessitates use of Monte Carlo simulation (MCS), the proposed approach employs the equivalent variance technique to consider the effect of spatial variability so that the analysis for probability of basal-heave failure can be performed using well-established first-order reliability method (FORM). Case study shows that this simplified approach yields results that are nearly identical to those obtained from the MCS-based RFM approach. The proposed approach is shown to be effective and efficient for probabilistic analysis of basal-heave in a braced excavation in a 2-D random field.

A simplified framework is proposed for evaluating the probability of “serviceability failure” in a braced excavation in a spatially random field. Here, the “serviceability failure” is said to occur when the excavation-induced wall or ground movement exceeds specified limiting values. Knowledge of this probability can aid in engineering decision-making to prevent damage to adjacent infrastructures. The proposed framework consists of five elements: (1) finite element method (FEM) for analyzing wall and ground responses in a braced excavation, (2) fuzzy set modeling of parameter uncertainty, (3) spatial averaging technique for handling spatial variability, (4) vertex method for processing fuzzy input through FEM model, and (5) interpretation of fuzzy output. The proposed framework is demonstrated through a well-documented case history. The results show the proposed framework is simple and effective for assessing the probability of serviceability failure in a braced excavation in a spatially random field. To focus on the proposed fuzzy FEM approach, the scope of this paper is limited to one-dimensional modeling of spatial variability with an assumed exponential autocorrelation function.

This paper presents a framework for assessing the probability of exceeding a specified liquefaction-induced settlement at a given site in a given exposure time. This framework deals not only with the effect of liquefaction (in terms of settlement) but also with probabilistic characterization of all possible ground motions at a given site (in terms of a joint distribution of a max and M w ). Additionally, a new concept, referred to herein as liquefaction-induced settlement hazard curve , is introduced for assessing the annual rate of settlement exceedance at a given site. This settlement hazard curve concept has the potential to be a very useful tool in the field of geotechnical earthquake engineering. Satisfactory results are obtained in the demonstration examples analyzed with the proposed framework. Whereas the proposed framework is simple and effective, further refinements to this framework, especially on the treatment of epistemic uncertainty, are warranted.

A new stochastic method named hybrid generalized extremal optimization (HGEO) is proposed in this paper. It combines genetic algorithms (GAs) and generalized extremal optimization (GEO). In order to extend GEO’s mutation operator to accelerate convergence speed and be easily incorporated into HGEO, the real coded GEO is first developed to population-base GEO (PGEO), and then incorporated into the HGEO in the paper. Constraints consideration for using the HGEO and the effects of related operators are also investigated. Finally, the performance of the HGEO is fully investigated compared with other related algorithms to find the optimal power consumption for the semi-track air-cushion vehicle (STACV). The results show that the HGEO has better performance than GAs or other related simpler algorithms.

This paper describes the design principle for a semi-track air-cushion vehicle working on soft terrain. A novel structure, i.e., a flexible joint mechanism is designed for the semi-track air-cushion vehicle suspension system. Focusing on optimizing the total power consumption of the vehicle, three main issues were studied in this paper. First, a theoretical model for minimizing the total power demand of the vehicle is developed. The effects of load distribution on total rolling resistance and total power requirement are calculated which are compared with the prototype experiment data. Second, the optimization procedure is presented. Third, a control scheme is proposed to minimize the power consumption by using a self-tuning PID fuzzy controller and the feasibility was examined by the simulations performed in Matlab/Simulink software environment.