A study on the building of a new “output–output model” and its usefulness: based on a comparative analysis of the input–output model

This paper describes the building of a new open static “output–output” (O–O) model in comparison to the open static input–ouput (I–O) model developed by Leontief (Rev Econ Stat 18:105–125, 1936). While the I–O model can be characterized as a system that relates final demand to gross output, the O–O model relates gross output for final demand (endogenous or exogenous) to gross output for output (endogenous). We perform a comparative analysis between the two models in structure and characteristics and illustrate the usefulness of the O–O model, for example, by formulating I–O multipliers that can accept output as an initial change. The comprehensive analysis conducted in this paper, including a numerical illustration with an example, shows that the two models form a mutually supplementary relationship and could give rise to a fundamental framework for the analyses of various regional and national economic activities.     

Investigation of the effects of wetting–drying and freezing–thawing cycles on some physical and mechanical properties of selected ignimbrites

This study was performed to investigate the changes in the physical and mechanical parameters of ignimbrites of different colors (black, red, yellow, gray) from Central Anatolia under the influence of wetting–drying and freezing–thawing cycles. For this purpose, 96 NX-size core samples were prepared. The unit weight, specific gravity, apparent porosity, water absorption by weight, slake durability index, uniaxial compressive strength, and P-wave velocity of each ignimbrite sample before conversion were determined. All of these parameters were then redetermined every 10 cycles (for a total of 50 cycles) for each sample. The changes in the values of the parameters after these set numbers of cycles were evaluated statistically. The petrographic and chemical compositions of the volcanic rocks influence their physical and mechanical properties, so some changes were also observed in the ignimbrite samples after these physical processes. Freezing and thawing cycles were observed to have an obvious impact on the physical and mechanical properties of the samples. The greatest changes were observed in black ignimbrite (with ferromagnesian minerals).     

Effect of chemical erosion and freeze–thaw cycling on the physical and mechanical characteristics of granites

Bulletin of Engineering Geology and the Environment - Rocks in nature are very often subjected to weathering processes. The physical and mechanical properties of granites exposed to chemical...     

Investigation of pro-oxidant agents’ effects on the ageing of polypropylene bags

ABSTRACT

In this work, the effects of calcium, aluminium and zinc stearates as pro-oxidant agents on the degradation of polypropylene (PP) bags were studied under natural weathering of Mediterranean climate. Samples were taken off periodically and characterised. Tensile properties, structural modifications, morphological and thermal properties were investigated. All the considered properties were affected by the presence of the three pro-oxidant agents. The pro-oxidants can be classified as follows: Zinc stearate > Calcium stearate>Aluminium stearate.     

Rate and acceleration effects on residual strength of kaolin and kaolin–bentonite mixtures in ring shearing

Rate effects on residual strength play an important role in predicting and evaluating the behaviour of reactivated landslides and in the application of test results and procedures. Although the rate dependency of residual strength has been investigated extensively, there is a lack of consistency in the experimental results. In particular, the effect of the shear rate on the residual strength of high-plasticity, low-permeability soils is not well understood. Additionally, field observations suggest that the sliding velocity of a soil block in the residual state is not constant and that its acceleration may affect the residual strength of the soil. However, the effect of acceleration changes on the residual strength of soil has not yet been investigated. The main objectives of this study are to elucidate the rate dependency of the residual strength of high-plasticity soils and investigate the effect of acceleration. In addition, the effect of the test procedure on the rate effect is also examined. A number of kaolin and kaolin–bentonite samples were tested using the Bishop-type ring shear device. The single-stage procedure which the shear rate was not changed during shearing, was conducted on individual specimens with shear rates from 0.02 to 20?mm/min to investigate the rate effect. The accelerations of 0.028 and 0.014?mm/min² were applied in multi-stage procedure with shear rates increasing gradually from 0.002 to 20?mm/min to examine the acceleration effect. The test results show that the bentonite content significantly affects the rate effect on the residual strength of kaolin–bentonite mixtures. For instance, in the single-stage procedure, the presence of just 10% bentonite changes the rate effect from positive to negative. This may be due to the generation of unknown excess pore water pressure under fast shearing. Furthermore, the test results also show that the type of rate effect observed depends on the test procedure. For mixture samples of 90% kaolin and 10% bentonite, the rate effect is negative in the single-stage procedure but positive in the multi-stage procedure. The analysis of the experimental results suggests that the effect of acceleration can be neglected in determining the residual strength.     

Effect of the vertical earthquake component on permanent seismic displacement of soil slopes based on the nonlinear Mohr–Coulomb failure criterion

In the present study, a model is developed to calculate the upper bound of the seismic displacement of a slope based on the sliding rigid block model. In this model, it is assumed that the geotechnical materials satisfy the nonlinear Mohr–Coulomb (M–C) failure criterion, and the instantaneous shear strength parameters are introduced by the “external tangent method”. A sequential quadratic program, based on the nonlinear iteration procedure, is also employed to obtain the optimal solution for the objective function. Using the upper bound method and the Newmark sliding rigid block model, the effect of the vertical earthquake component on the permanent displacement of slopes is studied under the following two conditions: (1) It is assumed that the vertical acceleration is in phase with the horizontal acceleration; (2) Actual vertical ground motion records are used (i.e., the vertical and horizontal accelerations are mutually independent). The results show that the nonlinear parameter m significantly affects the permanent displacement of slopes, and that the effect of the vertical earthquake component on permanent displacement cannot be ignored. The impact of the vertical earthquake component on slope stability will be overestimated if the vertical acceleration is in phase with the horizontal acceleration.     

Market structure of China’s construction industry based on the Panzar–Rosse model

The structure–conduct–performance (SCP) paradigm posits that market structure determines market performance, and the generally low productivity of China’s construction industry is a reflection of the irrationality of its market structure. Currently, the main approaches for measuring market structure can be classified as either structural approaches or non-structural approaches. Because the statistical data on structural approaches is one-sided, the indicators for the Panzar–Rosse model (a non-structural approach) for the construction industry can be selected by examining the Panzar–Rosse model and comparing the characteristics of the construction industry with those of the banking industry. The Panzar–Rosse model is employed to assess the market structure of 21 listed companies in China’s construction industry during the period from 2009 to 2011. The analysis revealed that China’s construction industry operates under conditions of monopolistic competition with free-entry equilibrium. The methods and results of the research are expected to contribute to the advancement of theories related to and methods of analysing the market structure of industries other than the banking industry.     

Investigation of geotextile–soil interaction under a cyclic vertical load using the discrete element method

Geotextiles are often used in roadway construction as separation, filtration, and reinforcement. Their performance as reinforcement in geotextile-reinforced bases depends on geotextile–soil interaction. This paper investigates the geotextile–soil interaction under a cyclic wheel load using the Discrete Element Method (DEM). In this study, soil was modeled as unbonded particles using the linear contact stiffness model, and the geotextile was modeled as bonded particles. The micro-parameters of the soil and the geotextile were determined using biaxial tests and a tensile test, respectively. The influence of the placement depth and the stiffness of the geotextile on the performance of the reinforced base was investigated. The DEM results show that the depth of the geotextile significantly affected the degree of interaction between the geotextile and the soil. Under the applied cyclic vertical load, the geotextile developed a low tensile strain. The effect of the stiffness of the geotextile on the deformation was more significant when the geotextile was placed at a shallower location than when placed at a deeper location.     

Model testing of the spatial–temporal evolution of a landslide failure

Bulletin of Engineering Geology and the Environment - This paper outlines the spatial–temporal evolution of a landslide. A multiple monitoring system that consists of a three-dimensional (3D)...     

Effects of water content and interface roughness on the shear strength of silt–cement mortar interface

Although the shear behaviors of silt–structure interfaces are critical in engineering practice, they have not been extensively investigated systematically. In this study, the influence of the silt water content and interface roughness on the shear behaviors of silt–cement mortar interfaces is investigated. Forty–eight silt–cement mortar structure interface tests and 18 silt direct shear tests were carried out. The results indicated that as the water content of the silt gradually increased to saturation, the interface shear stress–displacement curves changed from strain softening to strain hardening, and the interface shear strength decreased significantly. The shear strength of the rough interface was found to be significantly greater than of the silt, and the shear strength of the smooth interface was found to be lower than that of the silt. The interface shear strength gradually increased with the surface roughness, but the increase tended to be gentle. A large shear deformation was observed, and this increased with the decrease in soil water content and the increase (up to a point) in interface roughness. A model of the interface shear strength between unsaturated soil and structures considering the influence of water content and interface roughness was established and verified.     

A numerical investigation into the effects of slamming impulsive loads on the elastic–plastic response of imperfect stiffened aluminium plates

Nowadays stiffened aluminium panels have been widely used for marine applications such as building high speed vessels. The panels of high speed vessels are subjected to different in plane and out-of-plane loads. One of the most important out-of-plane loads is the impulse caused by bottom slamming. In the present study, the transient large deflection elastic–plastic responses of a number of stiffened aluminium panels subject to slamming impulsive loads are investigated. The impulsive loads are exerted on the finite element models of aluminium panels proposed by Ultimate Strength Committee of ISSC 2003. Several impact conditions are considered to study the influence of several structural factors such as heat affected zone (HAZ) arrangement, boundary conditions, thickness of plating, number of transverse frames and in-plane fixation. Based on these studies, several design-oriented conclusions are issued. Moreover, this paper outlines the various aspects of the influence of the HAZ presence on the strength of the slam-loaded panels with respect to loading time ratio.     

Analysis of seismically-isolated two-block systems using a multi–rocking-body dynamic model

A novel multibody rocking model is developed to investigate the dynamic response of two stacked rigid blocks placed on a linear base isolation device. The model is used to investigate the dynamic response of a realistic statue-pedestal system subject to pulse-like ground motions. The analysis shows that, in general, base isolation increases the safety level of the rocking system. However, for large period pulses or small size blocks, the isolator can amplify the ground motion, resulting in a lower minimum overturning acceleration than for the nonisolated system. Further, the amplification or shock spectrum of a linear mass-dashpot-spring oscillator, was found to be the reciprocal of the minimum nondimensional overturning acceleration of the investigated rocking system. Novel rocking spectra are obtained by normalizing the frequency of the pulse by the frequency of the isolator. The analysis also demonstrates how the dynamic response of the two stacked blocks is equivalent to that of a single-block configuration coincident with the whole system assumed monolithic or the upper block alone, whichever is more slender.     

Project management and burnout: Implications of the Demand–Control–Support model on project-based work

Project-based work has long been characterized as frenetic, fast-paced, and dynamic. The often competing constraints imposed by schedules, stakeholders, and budgetary restrictions make project activities conflict-laden and highly conducive to work-related stress. Stress is not an end unto itself but instead, is often a precursor for burnout. Burnout is a psychological syndrome of emotional exhaustion, cynicism, and reduced personal accomplishment. This paper reports on the results of a study of burnout among project management personnel. Using the Demand–Control–Support model as our conceptual framework, we analyzed a sample of respondents from four project-intensive organizations. Our findings demonstrated that women tend to experience emotional exhaustion to a greater extent than their male counterparts. Further, control and social support do serve as moderators for the burnout dimensions of emotional exhaustion and cynicism, suggesting limited support for the Demand–Control–Support model. Implications of this study for project management and workplace burnout are discussed.     

Estimation of radiance reflectance and the concentrations of optically active substances in Lake Mälaren, Sweden, based on direct and inverse solutions of a simple model

A semi-analytical model which predicts radiance reflectance just below the water surface (Lu/Ed 0-) has been developed and used to predict the spectral variability of radiance reflectance in Lake M?laren, Sweden. Radiance reflectance is predicted as a function of the optically active substances in the water, which include the concentrations of chlorophyll-a + phaeophytin-a, suspended particular inorganic material (SPIM), suspended particulate organic material (SPOM), and dissolved yellow substances. These substances are linked to the absorption and backscattering coefficients through a series of empirical relationships, and ultimately radiance reflectance is estimated as a function of the ratio of backscattering to absorption. Parameterization of the model, i.e. the development of the empirical relationships linking the optically active substances to the inherent optical properties (IOPs), is based on both in situ measurements and laboratory analyses. We have collected data that allowed us to examine the potential variability in radiance reflectance, as predicted by our model, due to both variations in the optically active substances, and in the model parameterization. Simulations based on a data set collected during the fall of 1997 from 12 sites, which span a large range in water quality (secchi depth 0.8-5.0 m), suggest that, with the proper parameterization, the model can accurately predict the spectra of radiance reflectance as a function of the concentration of optically active substances. Variations in the concentrations of optically active substances accounted for a large portion of the total simulated variability in radiance reflectance (i.e. that resulting from variations in parameterization and in the concentrations of optically active substances). However, the measured variability in parameterization could account for up to 50% of the total variability in simulated radiance reflectance. This suggests that variability in the model parameterization, arising from both real variability and experimental error, will limit the use of this model for interpreting remote sensing data. Nevertheless, inverse solutions of the model are able to estimate the concentrations of chlorophyll, suspended inorganic material (SPIM) and the absorption of yellow substances from measured radiance reflectance spectra The average error for the 12 sites was a -0.07 for chlorophyll, -0.15 for dissolved yellow substances (measured as the absorption at 400 nm) and 0.07 for SPIM, even though individual errors could be as great as 50%.     

Dynamic analysis of three-dimensional bridge–high-speed train interactions using a wheel–rail contact model

A formulation of three-dimensional dynamic interactions between a bridge and a high-speed train using wheel–rail interfaces has been developed. In the interface, contact loss is allowed, the vertical contact is represented by finite tensionless stiffness and the lateral contact is idealized by finite contact stiffness and creepage damping. Such stiffness and damping are nonlinearly dependent on normal contact force. The relative rotations of a wheelset to the rails about its vertical and longitudinal axes are included. Bridge eccentricities and deck displacement due to torsion are accounted for in bridge deck modeling. A numerical algorithm using separate integrations for bridges and trains, and iterations for interface compatibilities is established. A case study of a ten-car train passing over a two-span continuous bridge at various speeds and rail irregularity wavelength ranges is analyzed. The responses of the bridge, car-bodies and wheelsets are investigated for their behavior, acceptability and relations with the wavelengths. Analytical and numerical evaluations of resonant speeds are in good agreement, and the exit span vibration is more amplified than the entrance one at those speeds. The computed relative displacements of all wheelsets to the rail facilitate an explicit assessment for derailment risk.     

The effect of weak interlayer on the failure pattern of rock mass around tunnel – Scaled model tests and numerical analysis

Weak interlayer is one of unfavorable geological discontinuities often encountered in underground engineering. Many failures of underground openings were reported to be closely related to the existence of weak interlayer nearby. For the purpose of exploring the effect of weak interlayer on failure pattern of rock mass around tunnel, both physical model tests and numerical analysis were carried out to simulate tunnel excavation near an interlayer. In the model tests, by comparison of the failure patterns between homogenous ground and ground with a weak interlayer, it was found that the weak interlayer affected the stability of tunnel by increasing the failure zones and causing asymmetrical stress distribution. The results of model tests were then verified by numerical analysis. Furthermore, based on the numerical analysis results, the location, dip and thickness of the interlayer as well as the distance from the interlayer to the tunnel were proved to be important factors influencing tunnel stability, and the relationships of the induced damage zones with these parameters of the weak interlayer were established. These results can provide a useful guidance for support design and safe excavation of tunnel near or crossing through a weak interlayer.     

Experimental verification of parameter m in Hoek–Brown failure criterion considering the effects of natural fractures

Hoek–Brown failure criterion is one of the widely used rock strength criteria in rock mechanics and mining engineering. Based on the theoretical expression of Hoek–Brown parameter m of an intact rock, the parameter m has been modified by crack parameters for fractured rocks. In this paper, the theoretical value range and theoretical expression form of the parameter m in Hoek–Brown failure criterion were discussed. A critical crack parameter B was defined to describe the influence of the critical crack when the stress was at the peak, while a parameter b was introduced to represent the distribution of the average initial fractures. The parameter m of a fractured rock contained the influences of critical crack (B), confining pressure (σ₃) and initial fractures (b). Then the triaxial test on naturally fractured limestones was conducted to verify the modification of the parameter m. From the ultrasonic test and loading test results of limestones, the parameter m can be obtained, which indicated that the confining pressure at a high level reduced the differences of m among all the specimens. The confining pressure σ₃ had an exponential impact on m, while the critical crack parameter B had a negative correlation with m. Then the expression of m for a naturally fractured limestone was also proposed.     

Investigation of BTEX removal efficiency using the electrolytic oxidation and Fenton’s reaction

The removal of benzene, toluene, ethyl benzene, and xylene (BTEX) using the electrolytic oxidation or Fenton’s reaction has been studied. The value of current and pH value were shown to produce a significant effect on electrolytic oxidation of BTEX. More than 95% of BTEX could be removed at 500 mA current within 8 hours. In the case of Fenton’s reaction it was established that more than 95% of BTEX could be removed at pH 4 with an addition of hydrogen peroxide in the amount of 12 mg/dm³. The treatment cost based on electrolytic oxidation amounted to between $0.04 and $5.1 USD/m³. For Fenton’s reaction, the treatment cost was between $0.16 and $0.65/m³. The costs of electrolytic oxidation and Fenton’s reaction were similar to the cost of electrodialysis and cheaper than the freeze–thaw and evaporation; however, these costs were higher than for air flotation and the use of anoxic/aerobic granular activated carbon.     

Particle shape effects on the cyclic shear behaviour of the soil–geogrid interface

The accurate determination of the interface shear strength is essential in the design of geosynthetic-reinforced soil structures. The particle geometries of three types of soil materials and a spherical granular medium are imaged and quantified using binary image-based methods and described in terms of regularity. Cyclic direct shear tests are conducted to investigate the effects of particle regularity on the interface shear strength, stress–displacement relationship, shear stiffness, and damping ratio. The results reveal that the interface shear strength and deformation strongly depend on particle regularity. The vertical displacement ratio is found to increase with particle regularity under the same cycle number. The interface stiffness is observed to increase with the cycle number for particle regularities of 0.453, 0.565, and 0.672 but decreases with the cycle number for a particle regularity of 0.971. For a given regularity, the trend of damping ratio with the increasing cycle number is contrary to the that of shear stiffness. Finally, it is observed that the cyclic friction angle decreases with increasing particle regularity, the relationship of which is determined using linear regression. Thus, the systematic quantification of particle shape characteristics can lead to a better understanding of soil–geogrid interface behaviour.