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The purpose of this study is to establish the interfacial bond-slip model for CFRP plate externally bonded to corroded steel plate. The present bond-slip models for CFRP materials bonded to uncorroded steel plate were first reviewed. Thirty-four double-lap joints were tested to investigate the effect of corrosion duration and adhesive thickness on the bond behavior between CFRP plates and corroded steel plates, and the bond-slip curves for the bonding interface with different adhesive thickness and corrosion duration were obtained combined with the CFRP plate strain distribution data. A new bond-slip model for CFRP plate externally bonded to corroded steel plate was proposed, and the expression of the characteristic parameters, which included the maximum bond resistance τ f , the relative slip at the peak bond stress s 1 , the fitting parameter α, and the interfacial fracture energy G f , were also developed based on the careful regression analysis of the present data. The influence of the corrosion duration and construction adhesive thickness on the bond-slip relationship were accounted together and expressed as a new parameter; that is, the effective adhesive thickness t eff . The comparison between the predicted values and experimental results indicated that the proposed bond-slip model can be applied to reproduce the structural response of the CFRP plate-corroded steel plate double-lap joint with reasonable accuracy. The outcome of this study can provide meaningful references and essential data for the reliable application of CFRP strengthening systems in the performance improvement of corroded steel structures. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the mechanism of improving fatigue performance and the estimation model of fatigue life for corroded steel plate strengthened with CFRP plates. A new two-stage fatigue crack propagation prediction model for the corroded steel plate strengthened with CFRP plates was proposed; moreover, the identification of critical rust pits and the equivalent method of initial cracks, and the calculation method of stress intensity factor (SIF) values at the crack tip were established. The accuracy of the proposed model was verified by comparing the predicted and tested fatigue life of the corroded steel plate strengthened with CFRP plates. Finally, the proposed two-stage crack propagation model was applied to carry out a parameter analysis to investigate the effect of weight loss rate, equivalent initial crack size, adhesive thickness, CFRP stiffness and CFRP prestress level on the fatigue crack propagation of the corroded steel plate strengthened with CFRP plates. Results showed that the maximum depth and the average width of the rust pits were suggested to be taken as the equivalent dimensions of the initial semi-elliptical surface crack for the fatigue crack propagation prediction of corroded steel plate strengthened with CFRP plates. Increasing the weight loss rate of the corroded steel plate, the initial crack size or the adhesive thickness would accelerate the crack growth and reduce the fatigue life, whereas increasing the stiffness or prestress level of the CFRP plate would significantly reduce the crack growth rate and increase the fatigue life. The smaller the initial crack size, the more sensitive the crack propagation life was to the variation of equivalent initial crack size. The influence of adhesive thickness on the fatigue life was limited and convergent, and the application of prestressing could significantly improve the utilization rate of CFRP materials and the fatigue strengthening effect of the corroded steel plate. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the stress concentration of a corroded steel plate strengthened with carbon fiber reinforced polymer (CFRP) plates. An accelerated corrosion experiment was first executed to acquire corroded steel plates, and then surface profile measurements were conducted to obtain 3D coordinate data of the corroded steel surface. Finite element models considering the surface morphology of the corroded steel plate and the interfacial bonding properties between the CFRP plate and the corroded steel plate were established to investigate the stress concentration of the corroded steel plate strengthened with and without CFRP plates. The reliability of the numerical modeling method was verified based on a mesh convergence analysis and a comparison of the fatigue test, 3D morphology scanning, and numerical analysis results. Specimens with five levels of corrosion damage, six kinds of CFRP-strengthening stiffness, five kinds of adhesive thickness, and five levels of CFRP prestress were numerically modeled. The primary indications consist of features of stress distribution, and the stress concentration factors Kt and Ktg were analyzed. Results showed that the features of stress distribution and the stress concentration factor Kt of the corroded steel plate strengthened with and without CFRP plates are only related to the shape, size, and position of rust pits, but not to the degree of uniform corrosion or the reinforcement parameters. The value of Kt for the corroded steel plate with a corrosion duration of 6~18 months and a weight loss rate of 9.16~21.78% was approximately 1.199~1.345. The converted stress concentration factor Ktg has more practical significance than the stress concentration factor Kt in describing the influence of corrosion and CFRP reinforcement on the peak tensile stress of the corroded steel plate. The value of Ktg increased linearly with the increase of the weight loss rate of the corroded steel plate and decreased appreciably with the increase of the strengthening stiffness and prestress level of the CFRP plates, and it presented a very small increasing trend with the increase of the adhesive thickness. [ABSTRACT FROM AUTHOR]

In this paper, we examine the development of the estimation models of bond strength and effective bond length for a double strap joint between carbon fiber reinforced polymer (CFRP) plate and corroded steel plate. The experimental study on the bond behavior between CFRP plate and corroded steel plate is summarized first and the analytical interfacial bond–slip model for CFRP plate externally bonded to corroded steel plate is proposed. Based on the theoretical stress analysis for the CFRP plate–corroded steel plate double-lap joint, the piecewise expressions of the interfacial shear stress and the normal peel stress of the interface between CFRP plate and corroded steel plate were established. The estimation models of the bond strength and the effective bond length for the double strap joint between the CFRP plate and the corroded steel plate were consequently developed on the basis of interfacial stress distribution equations and the stress boundary conditions. The comparison between the predicted and experimental results indicated that the proposed models could be adopted to predict the bond strength and effective bond length for the CFRP plates externally bonded to corroded steel substrates with reasonable accuracy. The proposed estimation models are expected to provide meaningful references and essential data for the reliable application of CFRP strengthening system to the performance improvement of corroded steel structures. [ABSTRACT FROM AUTHOR]

This article is aimed at discussing the combined effect of mineral admixture and servicing temperature, especially in cold environment, on the properties of magnesium phosphate repair mortar (MPM). The influence mechanism of fly ash content on the microstructure and performance of MPM were firstly investigated, and then the evolution rules in properties of fly ash modified MPM cured at − 20 °C, 0 °C, 20 °C and 40 °C were further revealed. The results show that the incorporation of fly ash has no significant effect on the setting time and fluidity of MPM. When MPM is modified with 10 wt% and 15 wt% fly ash, its mechanical properties, adhesive strength, water resistance, and volume stability are effectively improved. Fly ash reduces the crystallinity and continuity of struvite enriched in hardened MPM, and its particles are embedded among struvite and unreacted MgO. The compressive strength of MPM-10 cured for various ages increases with the elevating of curing temperature, while the flexural strength, interfacial bonding strength, strength retention and linear shrinkage exhibits the opposite laws. When cured at 0 °C and − 20 °C, MPM-10 still has good early strength, water resistance and interfacial bonding properties, which indicates that MPM-10 provides with an ability of emergency repair of cracked components served in cold environments. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the bond behaviour between CFRP plates and corroded steel plates. Double-lap joint specimens with six kinds of corrosion duration and four kinds of adhesive thickness were tested and the primary bond characteristics were analyzed together with the effect of corrosion duration on the surface characteristic. Results showed that the failure mode of the specimens mainly depended on adhesive thickness rather than corrosion duration, only when the adhesive layer take a critical thickness, the failure modes would be significantly affected by corrosion duration, furthermore, corrosion was found to have a positive effect on the ultimate load for the specimens with the same failure mode of steel/adhesive interfacial failure, and the effective bond length of the corroded specimens were obviously larger than that of the un-corroded ones. Results also indicated that as for the specimens of the same corrosion duration, the failure modes changed from the combination of steel/adhesive interfacial failure and CFRP/adhesive interfacial failure to the combination of CFRP/adhesive interfacial failure and CFRP delamination, the ultimate load increased at first and decreased afterwards, and the effective bond length progressively increased with the adhesive thickness increased from 0.5 to 1.0, 1.5 and 2.0 mm. [ABSTRACT FROM AUTHOR]

Ground heat exchanger takes the soil underground as heat source or sink to supply cooling or heating. It has been widely used in building heating and cooling systems due to high efficiency and environmental friendliness. This paper reviews the latest research on ground heat exchangers from several new perspectives and demonstrates their potentials in achieving zero energy buildings. Firstly, ground heat exchangers are classified into water-based and air-based ones based on the heat transfer medium. They can be used in a passive or active approach. Associated research and projects for each approach are introduced and analysed. Then the integration of ground heat exchangers with various cooling and heating technologies and related studies are reviewed. These technologies include solar thermal collectors, cooling towers, nocturnal radiative cooling technology, solar chimney, etc. Finally, a technical route for ground heat exchangers to help realize zero energy buildings is presented, which provides a promising solution to improve energy efficiency of buildings. [ABSTRACT FROM AUTHOR]

Pipe-embedded concrete radiant floor system has gained much popularity due to its higher energy efficiency and better thermal comfort. Simplified yet accurate heat transfer models are essential for energy simulation of this system. This study presents the development and validation of a simplified RC-network model for the pipe-embedded concrete radiant floors. A concrete radiant floor mainly consists of three parts which are the cover layer, the pipe-embedded concrete slab and the insulation layer. The cover layer and the insulation layer are simplified as one-dimensional and represented by RC models with two resistances and one capacitance (2R1C). Within the pipe-embedded concrete slab, the complex heat transfer is represented by a coupled RC model which includes two parts describing the heat transfers of the concrete slab and the water loop respectively. In the case studies, the coupled RC model for the pipe-embedded concrete slab has been validated in both numerical and experimental ways. The experimental validation results show that the average relative errors of the coupled RC model in predicting the upper and bottom surface heat fluxes are all less than 5.5%. Validation has also been conducted to demonstrate the accuracy and effectiveness of this developed simplified RC-network model in predicting the dynamic thermal performance of a multi-layer pipe-embedded concrete radiant floor. The developed simplified RC-network model can be beneficial for design and optimal control of the pipe-embedded concrete radiant floor system. [ABSTRACT FROM AUTHOR]

This study presented a systemic research to investigate the bond properties for deformed steel bar in frost-damaged concrete under monotonic and reversed cyclic loading. Specimens of three kinds of concrete strength grade and four kinds of frost damage level were tested and the primary bond response indications were analyzed. Results showed that accompanied by the increasing number of freezing-and-thawing cycles, the initial bond stiffness, the maximum bond resistance and the remaining bond strength decreased whereas the slip at peak bond stress increased, moreover, the progressive acceleration of bond stiffness degeneration as well as the more obvious bond strength decay and the worse energy dissipation capacity were also observed for the specimens of the same concrete strength grade. Results also indicated that with regard to the specimens exposed to the same freezing-and-thawing cycles, the initial bond stiffness, the slip at peak bond stress, the maximum bond resistance and the remaining bond strength increased with the increasing concrete strength grade. Thereafter, the analytical local bond stress-slip models for deformed steel bar in frost-damaged concrete under monotonic and reversed cyclic loading were presented to reproduce the bond degradation caused by loading and freezing-and-thawing. [ABSTRACT FROM AUTHOR]

Poisson-Boltzmann (PB) model is a widely used implicit solvent approximation in biophysical modeling because of its ability to provide accurate and reliable PB electrostatic salvation free energies ( as well as electrostatic binding free energy ( estimations. However, a recent study has warned that the 0.5Å grid spacing which is normally adopted can produce unacceptable errors in estimation with the solvent excluded surface (SES) (Harris RC, Boschitsch AH and Fenley MO, Influence of grid spacing in Poisson-Boltzmann equation binding energy estimation, J Chem Theory Comput 19: 3677-3685, 2013). In this work, we investigate the grid dependence of the widely used PB solver DelPhi v6.2 with molecular surface (MS) for estimating both electrostatic solvation free energies and electrostatic binding free energies. Our results indicate that, for the molecular complex and components the absolute errors of are smaller than that of , and grid spacing of 0.8Å with DelPhi program ensures the accuracy and reliability of ; however, the accuracy of largely relies on the order of magnitude of itself rather than that of or . Our findings suggest that grid spacing of 0.5Å is enough to produce accurate for molecules whose are large, but finer grids are needed when is very small. The grid dependence of the wide-used PBE solver DelPhi with molecular surface(MS) for estimating electrostatic binding free energy ( is investigated. The absolute errors of are smaller than that of , and grid spacing of 0.8 Å with DelPhi program ensures the accuracy and reliability of . The grid spacing of 0.5 Å is enough to produce accurate for molecules whose are large, but finer grids are needed when is very small. [ABSTRACT FROM AUTHOR]

Active pipe-embedded building envelope can allow for substantial heat flow for relatively small temperature difference due to the embedded pipes in the external wall/roof. This structure can directly utilize the low-grade sources for reducing building cooling/heating load and improving indoor thermal comfort by intercepting the heat gain/loss through the building envelope due to the circular water inside the embedded pipe. This paper presents the experimental validation of a semi-dynamic simplified model of the active pipe embedded building envelope. The experiment test rig consists of two environment chambers with one for simulating the ambient environment and one for indoor environment with a pipe-embedded building envelope sample separating both chambers. A small chiller and a buffer tank are installed to provide stable water temperature for the test sample. The temperatures and heat fluxes on both sides of the test sample, the inlet and outlet water temperature as well as flow rate are measured. The measured boundary conditions are used as the inputs of the semi-dynamic simplified model for calculating the thermal performance of the active structure. The results show the semi-dynamic simplified model can predict the semi-steady or pure dynamic thermal performance of the pipe-embedded building envelope very well by comparing with the measurement. [ABSTRACT FROM AUTHOR]

The study proposes a new low-grade energy utilization system, i.e. a pipe-embedded wall integrated with ground source-coupled heat exchanger, and investigates its energy saving potentials in five typical climate regions of China. The cool/hot water produced by the ground source-coupled heat exchanger is supplied to the pipe-embedded wall to intercept the heat gain/loss through the wall. A real-scale building energy simulation platform has been developed for estimating the energy saving potentials. The study results show that the energy saving potential of the proposed system varies with the climate regions. With the same sized pipe-embedded wall system, the building in warm climate regions achieves the largest energy saving percentage. It is followed by the buildings in the hot summer and cold winter climate region, the severe cold climate region, the cold climate region, and the hot summer and warm winter climate region in the declining sequence of energy saving. Meanwhile, a multi-criteria performance evaluation has been conducted to search for the optimal size of the low-grade-energy system in each climate region. The proposed system can be utilized in practice for energy saving, and the study results are helpful in guiding the practical applications of the pipe-embedded wall system in different climate regions. [ABSTRACT FROM AUTHOR]

Hollow blocks or bricks are widely used due to the good thermal insulation, lightweight, acoustic insulation, etc. This paper presents the development of a simplified heat transfer model of hollow block for simple and efficient heat flow calculation. This model is developed based on parameter identification in frequency domain by using finite element method in frequency domain. Firstly, the frequency domain finite element model (FDFEM) of the hollow block is developed by using finite element method in frequency domain to obtain the theoretical frequency characteristics of this structure. Then, the heat transfer function model in the form of s -polynomial (i.e., the s -polynomial heat transfer function model) is identified by using a parameter identification procedure based on the calculated theoretical frequency thermal characteristics. Finally, the simplified heat transfer model, i.e., the Conduction Transfer Function (CTF) coefficients, of this hollow block are derived from the identified s -polynomial heat transfer function model. A case study is presented for the prediction of the dynamic heat transfer of this hollow block by using the simplified heat transfer model. The predicted dynamic heat transfer of this block is validated by experimental data. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the seismic performance of reinforced concrete columns after freeze–thaw cycles. Based on low cyclic loading tests of eight column specimens, the failure patterns, hysteresis loops, load carrying capacity, displacement and ductility factor, skeleton curves, stiffness degradation and energy dissipation capacity of frost-damaged concrete columns were analyzed. The effect of freeze–thaw cycles and axial compression ratios were investigated in detail. Test results show that for the column specimens under the same level of axial compression, with the number of freeze–thaw cycles increasing from 0 to 300, the plastic deformation capacity decreased whereas the rate of stiffness degeneration and strength decay increased continuously. The coupling effect of the deterioration of material and loosening of bond induced the value of equivalent viscous damping coefficients to decrease at first then increase, however, the cumulative energy dissipation decreased continuously. Test results also indicate that for the column specimens with the same level of frost damage, with the increase of axial compression ratio, the load carrying capacity and initial stiffness increased, whereas the deformability capacity, the equivalent viscous damping coefficients and the cumulative energy dissipation decreased obviously, respectively. [ABSTRACT FROM AUTHOR]

Many Poisson-Boltzmann equation (PBE) solvers have been developed to calculate electrostatic energy of biomolecules, and each PBE solver has its advantages. In this study two PBE solvers - DelPhi and PBSA module in AMBER - are compared in terms of calculation results, convergence and program-running time by calculating the electrostatic solvation energy for a test set composed of 4 Kirkwood models and another test set of 25 protein structures. The protein structures were pretreated by AMBER and AMBER99SB force field parameters were used in all calculations. It is found that (i) At fine grids, both PBE solvers can produce accurate results on test set 1 and consistent results with each other on test set 2, with differences between each other varying from several to ~ 10 kcal/mol. (ii) Under convergence criterion "absolute value of relative error is less than or equal to 2% (|RE| ≤ 2%)", both PBE solvers need very fine grids to produce convergent results on small and complex Kirkwood models, while grid spacings of ≤ 0.5 Å-0.6 Å are well enough for them to achieve good convergent results on various molecular structures. We recommend users to adopt such grid spacing in using of these PBE solvers so as to get good enough convergent results. (iii) In terms of time consumption, DelPhi appears to be more time-saving than PBSA. In summary, according to our comparison, DelPhi and PBSA are paralleled good PBE solvers. The convergence of PBSA is a little better than DelPhi, while DelPhi exceeds PBSA in running speed. Poisson-Boltzmann equation (PBE) solvers DelPhi and PBSA module in AMBER are compared by calculating electrostatic solvation energies. According to the comparison, they are paralleled good PBE solvers. The convergence of PBSA is a little better than DelPhi, while DelPhi exceeds PBSA in running speed. [ABSTRACT FROM AUTHOR]

• Fatigue behavior of corroded steel plate strengthened with CFRP were tested. • Fatigue crack of strengthened specimen initiated at the bottom of rust pit. • Patching CFRP significantly strengthened fatigue behavior of corroded steel plate. This paper presents an experimental study performed to investigate the effectiveness of carbon fiber reinforced polymer (CFRP) plates in extending fatigue life of corroded steel plates. Specimens with five kinds of corrosion damage level, four kinds of strengthening configuration and four kinds of applied fatigue stress amplitude were tested and the primary fatigue behavior indications consist of failure mode, fatigue fractography, fatigue life and crack propagation were analyzed. Results showed that externally patching CFRP plates significantly strengthened the fatigue behavior of corroded steel plates, and even made the fatigue life of corroded steel plates recovered or exceeded that of the un-corroded ones, the fatigue life of the patched specimen which presented the most significant strengthening effectiveness even showed a fatigue life extension of more than 85.3 times with respect to the un-patched corroded steel plate and approximately 2 times over the un-corroded steel plate. Results also indicated that different strengthening configurations appeared to have diversity effect on the fatigue life extension and crack growth retardation of corroded steel plates, end anchorage measures effectively delayed the failure process of CFRP bonding interface and improved the fatigue strengthening effect, increasing CFRP strengthening stiffness or adopting prestressed CFRP plates significantly reduced the crack growth rate and extended the fatigue life of corroded steel plates. The outcome of the tests provided meaningful references and essential data for the reliable application of CFRP strengthening system in the fatigue performance improvement of corroded steel structures. [ABSTRACT FROM AUTHOR]

• The interaction between pits and cracks is revealed. • The K value equation of the crack tip considering the characteristics of the pit is established. • A fatigue life prediction model considering pit characteristics is proposed. • The influence of pit parameters on fatigue life is quantitatively analyzed. Pitting corrosion notably increases stress concentration, thus accelerating fatigue crack initiation and propagation at the pit base. This research quantifies the relationship between pit dimensions and fatigue crack development by introducing crack extension ratios (γ a ​ and γ c)​. Employing a series of finite element models, the influence of pit characteristics on the stress intensity factor (K) at the crack tip is assessed. Based on these assessments, a formula for computing the K -value is proposed. Furthermore, a two-stage fatigue life prediction model for both partial and complete penetration is developed using the Paris equation. Results indicate that pits substantially affect the K -value during partial penetration. Specifically, as γ a approaches zero, the K -value approaches zero, and as γ a approaches one, it aligns with the K -value of a semi-elliptical surface crack. Conversely, in the complete penetration phase, the influence of the pit on the K -value is negligible, and the K -value can be calculated according to the plate with a central penetrating crack. Experimental validation confirms that the model generally maintains a prediction error within 10%. [ABSTRACT FROM AUTHOR]

The primary aim of this paper is to assess the impact of corrosion damage on intermediate H-section steel columns subjected to combined compression and bending about the strong axis. The study conducted a comprehensive investigation into the corrosion-induced transition in the buckling behavior of steel columns through experimental and numerical analyses. Six H-section Q355 steel intermediate columns were designed, with five undergoing an artificial spray-accelerated corrosion process. The three-dimensional scanning technology was employed to quantify the general corrosion and corrosion pits. Eccentric compression tests were carried out on intermediate H-section steel columns to investigate the effect of the different corrosion levels on the failure mode and load-displacement curves, as well as to determine local buckling load based on the load-strain curves. The test results showed that the corrosion characteristic parameters of each cross-section of the steel column exhibited irregularity and variation in all locations, reflecting the heterogeneity of corrosion. The density of corrosion pits exhibited a decreasing trend with increased corrosion duration. Corrosion remarkably reduced both the ultimate carrying capacity and local buckling capacity, with the most severely corroded specimen exhibiting an average cross-sectional area loss rate of 37 %, resulting in a 43 % and 51 % reduction in ultimate load and buckling load compared to the uncorroded specimen. Furthermore, the corrosion features substantially influenced the failure mode, resulting in a transition from overall buckling to local buckling or local-global interaction buckling. A numerical methodology was developed to incorporate the actual surface morphology of corrosion, and the reliability of the modeling method was validated through comparison with experimental results, further revealing the failure mechanism of corroded intermediate H-section steel columns under compression and bending about the strong axis. • Quantitatively characterized the impact of corrosion on the geometric characteristics of steel columns. • The effect of corrosion on the buckling behavior of intermediate compression-bending corroded H-shaped steel columns. • Established a morphology-based numerical method to predict the buckling performance of corroded columns. • The failure mechanism of the corroded intermediate steel columns was observed and analyzed by tests and simulations. [ABSTRACT FROM AUTHOR]

In order to achieve low-carbon optimization in the intelligent mix ratio design of concrete materials, this work first constructs a concrete mix ratio database and performs a statistical characteristics analysis. Secondly, it employs a standard back propagation (BP) and a genetic algorithm-improved BP (GA-BP) to predict the concrete mix ratio. The NSGA-II algorithm is then used to optimize the mix ratio. Finally, the method's accuracy is validated through experiments. The study's results indicate that the statistical characteristics of the concrete mix ratio data show a wide distribution range and good representativeness. Compared to the standard BP, the fitting accuracies of each GA-BP set are improved by 4.9%, 0.3%, 16.7%, and 4.6%, respectively. According to the Fast Non-Dominated Sorting Genetic Algorithm II (NSGA-II) optimization for meeting C50 concrete strength requirements, the optimal concrete mix ratio is as follows: cement 331.3 kg/m3, sand 639.4 kg/m3, stone 1039 kg/m3, fly ash 56 kg/m3, water 153 kg/m3, and water-reducing agent 0.632 kg/m3. The 28-day compressive strength, material cost, and carbon emissions show relative errors of 2.1%, 0.6%, and 2.9%, respectively. Compared with commercial concrete of the same strength grade, costs and carbon emissions are reduced by 7.2% and 15.9%, respectively. The methodology used in this study not only significantly improves the accuracy of concrete design but also considers the carbon emissions involved in the concrete preparation process, reflecting the strength, economic, and environmental impacts of material design. Practitioners are encouraged to explore integrated low-carbon research that spans from material selection to structural optimization. [ABSTRACT FROM AUTHOR]

A non-contact three-dimensional (3 D) scanning system was first employed to capture the corrosion features of three naturally corroded steel beams and to reconstruct the 3 D geometries. A more reasonable corrosion grade parameter φ, which could comprehensively consider the effects of uniform and non-uniform corrosion, was proposed for evaluating the corrosion degree of these beams. Then, four-point bending tests were carried out on the corroded beams to investigate the effects of corrosion damage on the flexural performance. A theoretical formula and a detailed calculation process, which considered the thickness reduction and strength degradation based on the corrosion morphology, were established to evaluate the bending capacity of the corroded beams. Then, a series of parameter analyses was conducted to determine the influence of different corrosion characteristics. Finally, morphology-based numerical methodologies were also proposed to predict the flexural performance including the load and deformation of corroded beams. The research results indicated that the theoretical formula and numerical methods could both provide accurate predictions, which could supply further technical support for the non-destructive detection and assessment of existing steel structures. [ABSTRACT FROM AUTHOR]

The bond properties for plain bars in frost-damaged concrete under monotonic and reversed cyclic loading were investigated. Rapid freeze–thaw and the pull-out tests were carried out on the specimens with three kinds of concrete strength grade. The compressive strength of frost-damaged concrete and the bond stress–slip response of the specimens with different concrete strength grades and freeze–thaw cycles were obtained. The effect of concrete strength grade and of the freeze–thaw cycle on the bond behaviours between concrete and plain bars was studied. Results indicated that, with the increase in the number of freeze–thaw cycles, the bond strength, residual bond capacity, residual bond stress and the cyclic bond stress decreased while the peak slip increased, as well as there being a more obvious bond degradation rate for the specimens with the same concrete strength grade. For specimens subject to the same number of freeze–thaw cycles, the bond strength, residual bond capacity, residual bond stress and the cyclic bond stress increased with the increasing concrete strength grade. A bond–slip model for plain bars in frost-damaged concrete under monotonic and reversed cyclic loading is proposed, which can be used for performance evaluation of existing reinforced-concrete structures in cold areas. [ABSTRACT FROM AUTHOR]

Highlights • Corrosion characterizations on the surfaces of corroded connections were studied. • Degradation of seismic performances of corroded welded connections were studied. • Effects of different corrosion parameters on connection capacities were analyzed. Abstract The objective of this work is to investigate experimentally and numerically the effect of neutral salt-spray corrosion damage on the seismic capacity of welded steel connections. Firstly, the surface morphology characteristics and mechanical properties of corroded steel were discussed by testing the standard specimens fabricated from the welded connections with different exposure corrosion time. Then, the inelastic cyclic loading tests of 4 deteriorated connection specimens with different corrosion damage degrees were conducted to evaluate the changes of cyclic behavior and failure mode. Test results showed that the bearing capacities and the stiffness of corroded connections decreased due to the sectional area losses of the beam and the column, while the existence of severe pits in the welded zone accelerated the brittle fracture failure of corroded beam flange, resulting in the significant degradations of ductility and total energy dissipation. In addition, a series of parametric numerical simulation was performed to analyze the effects of different corrosion parameters on the seismic performances of connections. Analytical results indicated that the larger value could be chosen from the beam flange corrosion and the column web corrosion to estimate the remaining ultimate bearing capacity of existing connections, while the pitting damage and the uniform corrosion on the beam flange could be regarded as the main factors affecting the degradation degree of deformation capacity and energy dissipation capacity. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the changes in surface morphology and mechanical properties for carbon steel butt-welded joints by ageing in salt spray environment. The corrosion characterizations of the base metal, heat-affected zone and weld metal for the butt-welded joints were tested by employing a 3D profile measurement technology, the results showed that the pitting geometrical parameters of all three zones had a similar time-dependent evolution rule, namely mean pit depth, maximum pit depth and volume-box parameter all increased with the increasing exposure corrosion time, while pitting aspect ratio decreased. In addition, it should be noted that the pitting corrosion in the heat affected zone was more severe than that in the other two zones. Tensile tests of the corroded butt-welded joint specimens were performed, the results had shown that the strength, ductility and strain hardening of the corroded butt-welded joints decreased as the degree of pitting corrosion increased. In particular, compared with the corroded base metal specimens with the same conditions, a more significant reduction of the tensile ductility for butt-welded specimens was observed. Besides, the reasons for this above degradation phenomenon were analyzed by using the numerical simulation methods. [ABSTRACT FROM AUTHOR]

[Display omitted] • Design optimization of multi-stage tangential roller threshing unit through modelling and experimental investigations. • FEA provides a safe operating limits for structural integrity and durable performance. • Modal analysis helps to prevent resonance issues in the threshing unit. • Optimal results were achieved with a drum speed of 600 rpm, feeding rate of 1.2 kg/s, and a threshing gap of 9 mm. Rising global population of the world is resulting higher demand for buckwheat being a high-quality food crop. In this study, the multi-stage shearing drum working mode was proposed to solve the problems of easy entanglement, blockage in threshing process due to inconsistency of ripening period, decrease grain breakage rate and loss rate and increase threshing efficiency. The designed threshing unit incorporates key components: frame, feeding wheel, main and secondary threshing drums, discharge unit, and concave plate. FEA and modal analysis were integrated to assure robust structural performance and stability of the threshing components within set limits, which were validated by indoor testing that confirmed the threshing drum's working frequency did not cause resonance. Single Factor Method identifies optimal conditions: 600 rpm, 7 mm, 1.2 kg/s for minimal grain breakage; 700 rpm, 9 mm, 1.2 kg/s for lowest grain loss. A three-factor, three-level orthogonal experiment validates these findings. In conclusion, optimal results are achieved with a drum speed of 600 rpm, feeding rate of 1.2 kg/s, and a threshing gap of 9 mm thus, minimizing both grain loss and breakage rates. [ABSTRACT FROM AUTHOR]

Active pipe-embedded building envelope is a new kind of external building wall or roof which usually has pipes embedded in it to let water circulate in these pipes for heat transfer. This structure may effectively intercept the heat/coolth from the ambient environment to indoor space and provide extra space conditioning for the indoor space. Frequency-domain finite-difference (FDFD) model can predict the frequency thermal response of active pipe-embedded building envelope directly and provide some important guidelines for system control and system sizing. This paper presents the experimental validation of this model in time domain by using Fourier series analysis. An experiment test rig was developed for the thermal response measurements of the pipe-embedded building envelope under pre-defined conditions. First, the measured time series of surface temperatures are transformed into complex Fourier series by using Discrete Fourier Transform and applied into the FDFD model as the boundary condition for calculation. Then, the calculated frequency thermal responses by FDFD model can be easily transformed into time series by using Inverse Discrete Fourier Transform. Finally, the time-domain thermal responses of FDFD model are obtained. The results show that the calculated time-domain thermal responses of the active pipe-embedded building envelope by using FDFD model agree well with the experimental measurements. [ABSTRACT FROM AUTHOR]

• The biomass derived PANI/BPC composite with enhanced polarization was synthesized. • The impedance matching was optimized effectively by the regulation of permittivity. • The balance between impedance matching and attenuation was established. • The minimum RL of −40.89 dB and EAB of 4.24 GHz were achieved. Based on the strategies of heterogeneous interface construction and impedance matching optimization, the polyaniline/biomass derived porous carbon (PANI/BPC) has been synthesized. The attachment of PANI on the surface of BPC prompts a relatively amount of heterogeneous interface endowing sufficient interfacial polarization loss. Meanwhile, the coralline-like PANI acts as bridges on the surface of BPC to construct complex conductive networks enhancing conduction loss and multi-reflections & scattering. The balances between conduction loss and polarization loss, impedance matching and attenuation capability have been established. Thanks to the synergistic effect of strong dielectric loss and optimized impedance matching, the PANI/BPC composite achieves the optimal absorption capacity with the minimum reflection loss (RL) of -40.89 dB at 2.6 mm and the effective absorption bandwidth (EAB) of 4.24 GHz at 2.1 mm. This satisfactory result may provide a new approach for the effective development and utilization of biomass derived porous carbon as absorbing materials. : [Display omitted] [ABSTRACT FROM AUTHOR]

At present, the potential of natural products in new drug development has attracted more and more scientists' attention, and natural products have become an important source for the treatment of various diseases or important lead compounds. Geniposide, as a novel iridoid glycoside compound, is an active natural product isolated from the herb Gardenia jasminoides Ellis (GJ) for the first time; it is also the main active component of GJ. Recent studies have found that geniposide has multiple pharmacological effects and biological activities, including hepatoprotective activity, an anti-osteoporosis effect, an antitumor effect, an anti-diabetic effect, ananti-myocardial dysfunction effect, a neuroprotective effect, and other protective effects. In this study, the latest research progress of the natural product geniposide is systematically described, and the pharmacological effects, pharmacokinetics, and toxicity of geniposide are also summarized and discussed comprehensively. We also emphasize the major pathways modulated by geniposide, offering new insights into the pharmacological effects of geniposide as a promising drug candidate for multiple disorders. [ABSTRACT FROM AUTHOR]

Abstract: Small non-coding RNA (sRNA) plays very important role in the post transcriptional regulation in various organisms. In complex regulatory networks, highly significant relative fluctuations in RNAs copy numbers can not be neglected due to very small copy number of individual RNA molecules. Here we consider two simple regulation schemes, where one is single target gene regulated by a sRNA and the other is two target mRNAs (mRNA R and mRNA T ) regulated by one sRNA. The Fano factor (a measure of the relative size of the internal fluctuations) formulae of RNA molecules in the post transcriptional regulation are theoretically derived by using of the Langevin theory. For single target gene regulated by a sRNA, it is shown that the intrinsic noise of both mRNA and sRNA approaches the bare Poissonian limit in the regimen of both target RNA silencing and surviving. However, the strong anti-correlation between the fluctuations of two components result in a large intrinsic fluctuations in the level of RNA molecules in the regimen of crossover. For two target mRNAs regulated by one sRNA, in the regimen of crossover, it is found that, with the increasing of transcription rate of target mRNA T , the maximal intrinsic fluctuation of RNA molecules is shifted from sRNA to target mRNA R , and then to target mRNA T . The intrinsic noise intensity of target mRNA R is determined by both the transcriptional rate of itself and that of sRNA, and independent of the transcriptional rate of the other target mRNA T . [Copyright &y& Elsevier]

Modeling of the chiller performance is essential for the implementation of optimal energy-efficient control strategies in a heating, ventilation, and air conditioning (HVAC) system. Though classical data-driven chiller performance models are widely adopted in the industry, they generally suffer from poor out-of-sample generalization abilities, which refers to the model's capability to extrapolate for new data outside the range of the training dataset. In practice, however, the available chiller operation data for model development are often insufficient or collected from a few limited operating conditions, such that extrapolation is unavoidable after the model is applied for control purposes. To deal with this issue, this paper proposed a physics-guided neural network (PGNN) to model the energy performance of chillers. By adopting a new neural network architecture, modifying the loss function, and adding limited out-of-sample data, the PGNN incorporates domain knowledge into the data-driven model to achieve better out-of-sample generalization performance. Meanwhile, the convexity and monotonicity between the dependent and independent variables in the PGNN are properly addressed. The proposed PGNN is applied to model the chiller serving a high-rise building, and results show that PGNN performs much better in extrapolation than classical models and the multi-layer perceptron model. The research demonstrated the usefulness and effectiveness of the PGNN in modeling HVAC equipment. • A physics-guided neural network is developed to model chiller energy performance. • Physical constraints are added through new architecture and modified loss function. • Limited out-of-sample data are used as additional constraints for model training. • The out-of-sample generalizability of the proposed model is significantly enhanced. [ABSTRACT FROM AUTHOR]

Energy conservation and carbon reduction of existing buildings have been receiving increasing attention with the proposed carbon neutrality goals. As presented in many studies, adopting model predictive control (MPC) for building HVAC system control is an effective means to realize building energy conservation. However, existing studies rarely addressed the critical challenges for practical applications and integration of MPC in existing Building Automation Systems (BASs). This study proposes a control retrofit approach, which is lightweight and replicable, to realize the improvement of energy efficiency of the existing building HVAC systems through integrating data-driven MPC into existing BASs. The critical challenges in the practical applications of MPC strategies, including MPC strategy development, large-scale data processing, strategy deployment and integration with existing BASs are addressed. The proposed approach was applied to the existing HVAC system of an actual airport terminal and the evaluation results indicate that the control retrofit approach is effective in achieving energy efficiency and thermal comfort improvement. The system daily energy consumption was reduced by 24.5% in average and the percentage of the discomfort time was reduced from 70.2% to 5.7% in average after the control retrofit. The proposed control retrofit approach, with the help of the scalability and distributed computing capabilities of the cloud computing platform, is expected to be able to realize lightweight control retrofit of large number of existing building HVAC systems. [ABSTRACT FROM AUTHOR]

Monotonic tensile experiments and corresponding finite element (FE) analyses including a ductile fracture damage criterion have been conducted to investigate the ductility degradation behaviours of steel butt-welded joints with corrosion pits. The results showed that the ultimate elongation of welded joint samples rapidly decreased because the existence of pits led to the earlier initiation of ductile cracks after necking. Pit location was the main factor affecting ductility degradation, pits located in the weakest region of sectional stiffness were the biggest threat to the overall deformability of welded joints. In addition, both pit depth and aspect ratio had a significant effect on local ductile crack initiation and propagation, the local stress triaxiality and plastic strain accumulation increased steadily with the increase of pit size, resulting in the decrease of equivalent plastic fracture strain. Furthermore, based on the parametric numerical analyses, equivalent ductile fracture criterion considering pitting parameters was proposed to replicate the effects of actual pits on ductility degradation. [ABSTRACT FROM AUTHOR]

A deep understanding of household appliance standby energy use (SEU) and associated saving potentials in Chinese rural areas is vitally important due to the huge amounts of households and appliances. However, to date, few study has been conducted and very little is known about the SEU. Meanwhile, existing methods of estimating such saving potentials have two limitations. Firstly, they primarily evaluated it through upgrading appliances while a more practical way of improving behavior should also be considered. Secondly, they do not take the impact of its influential factors into account simultaneously, and tend to significantly decrease the estimation accuracy. To address the above issues, an investigation on the appliance SEU and its influential factors in Chinese rural homes was first conducted. Then, a data mining-based method for estimating the saving potentials was proposed, and improving occupant behavior pertaining to SEU was also considered in the estimation. The method was further applied under three typical scenarios: appliance upgrades, behavior change and the combination of both. In addition, barriers to promote standby energy reductions have been analyzed and corresponding recommendations have been made. Main contributions of this study include: (1) providing SEU of Chinese rural homes and estimating saving potentials caused by various ways including behavior change and, (2) a new method of estimating energy-saving potentials with improved accuracy. [ABSTRACT FROM AUTHOR]

The effects of corrosion on the mechanical performance of steel were investigated by conducting surface measurements and tensile tests on naturally corroded steel plates. With increasing corrosion damage, significant degradations in strength and deformation can be observed. We summarized the existing empirical formulas and elaborated a morphology based numerical method to predict the residual performance of corroded steel. With the aid of specially developed programs, it is easy to extract the pertinent evaluation indicators from the corrosion morphology and generate the finite element model of corroded surfaces. By conducting error analysis of predicted results, we found that most empirical formulas could achieve satisfying predictions in tensile strength but were unworkable in predicting the deformability. The profile based numerical method could not only achieve more reliable predictions in strength but also provide the degraded load-displacement curve of corroded steel plates. [ABSTRACT FROM AUTHOR]

Based on interactions among transcription factors, oncogenes, tumor suppressors and microRNAs, a Boolean model of cancer network regulated by miR-17-92 cluster is constructed, and the network is associated with the control of G1/S transition in the mammalian cell cycle. The robustness properties of this regulatory network are investigated by virtue of the Boolean network theory. It is found that, during G1/S transition in the cell cycle process, the regulatory networks are robustly constructed, and the robustness property is largely preserved with respect to small perturbations to the network. By using the unique process-based approach, the structure of this network is analyzed. It is shown that the network can be decomposed into a backbone motif which provides the main biological functions, and a remaining motif which makes the regulatory system more stable. The critical role of miR-17-92 in suppressing the G1/S cell cycle checkpoint and increasing the uncontrolled proliferation of the cancer cells by targeting a genetic network of interacting proteins is displayed with our model. [ABSTRACT FROM AUTHOR]