Civil Engineering

This study aims to build a superior strategy in the company precast concrete with a Resource Based View approach at PT. ABX, as well as generate strategies in exploiting resources, capabilities, competitive advantages to create sustainable strategies for the company. The research method used is qualitative based on phenomenology. The research results show that to improve employee performance, it is necessary to carry out work evaluations and targets. Combine the company's human resources and physical resources by placing employees who are competent and experienced in their fields. To increase the knowledge, skills and abilities of employees, companies need to conduct training. To expedite the precast concrete production process, companies need to have a batching plant. Evaluate the production process and routinely carry out material tests and concrete tests to maintain quality and quality. Promotion through digital media, such as Google, websites and other social media. Maintain...

High speed liquid jet forms when a bubble collapses near a solid boundary. The formation of the jet has both advantages and disadvantages as it causes erosion and damage in the nearby turbomachinery and can be beneficially applied in surface cleaning, fluid pumping, etc. In this paper, three-dimensional bubble oscillation between two curved rigid plates is modeled using boundary integral method (BIM). The bubble is incepted at different locations between the plates to investigate the eccentricity effects on the bubble shape, jet formation, etc. The modified Laplacian smoothing technique is implemented on the bubble surface during the jet development to reduce element distortion. The new model is validated with the Rayleigh-Plesset equation as well as with the available experimental data. It was found that the jet velocity increases, and the number of jets is reduced from two to one as the bubble is horizontally shifted away from the centroid. When the bubble is incepted on the horizontal axisymmetric line the jet is horizontal. However, the jet direction changes as the bubble is incepted closer to one of the plates. Finally, the pressure and velocity fields of the fluid surrounding the bubble are provided for better interpretation of the results.

In this paper we estimate measurement of uncertainty for determination of Fe, Pb and Zn in natural water samples by solid-phase extraction and i nductively coupled plasma optical emission spectrometry (SPE-ICP-OES). The procedure is based on the retention of analytes in the form of 8-hydroxyquinoline (8-HQ) complexes on a mini column of XAD-4 resin and subsequent elution with nitric acid. The infl uence of various analytical parameters including the amount of solid phase, pH, elution factors (concentration and volume of eluting solution), volume of sample solution, and amount of ligand on the extraction effi ciency of analytes was investigated. To estimate the uncertainty of analytical result obtained, we propose assessing trueness by employing spiked sample. Two kinds of bias (proportional bias and constant bias) estimated. We applied Nested design for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. Estimated uncertainty in Karaj water is: (1.0198 ± 0.0075) for Fe, (0.999 ± 0.010) for Pb and (1.0321 ± 0.0137) for Zn.

The face gear is used in the spinning machine to lift the spindle mechanism. The face gear are attach with the heart cam for spinning the yarn about spindle. During the working, the tangential force is acting on face gear, which may cause to break the teeth. The tangential load which is acting on the gear is from pinion. The face gear are working similar to the bevel gear and transmitting the power. The intersection axis of both the pinion and gear at right angle to each other. The failure of the gear is due to low strength of the gear material. The beam strength of the face gear is low as compare to the tangential load that why the face gear fail. By changing the material of gear we can prevent the gear from failure. The redesign involve to change the material or to chance the dimension. But in that case, by changing the dimension likes to change the module and thickness which may affect the working of machines. Similarly to change in the setup of machine, in that case it is desira...

L’articolo presenta i principali risultati di esperimenti eseguiti su nodi trave-pilastro innovativi realizzati con struttura composta acciaio e calcestruzzo. Trattasi di cinque prove in cui altrettanti nodi a due vie in scala reale sono sottoposti a spostamenti pseudo-statici di tipo ciclico tali da indurre una condizione di sollecitazione di tipo sismico. Quattro nodi hanno le travi di tipologia mista acciaio e calcestruzzo ed un nodo e interamente in calcestruzzo armato normale per stabilire utili confronti. Per quanto riguarda i primi quattro, due nodi hanno i pilastri in c.a., un nodo e realizzato con pilastro con camicia di acciaio di sezione quadrata ed infine un nodo ha anche i pilastri in struttura reticolare mista. I risultati ottenuti sono analizzati criticamente e confrontati tra loro per poter trarre utili conclusioni sulla duttilita e sulla resistenza dei nodi innovativi nei confronti delle sollecitazioni di natura sismica.

The paper presents a set of 24 lab tests on 12 composite steel truss and concrete beams with inferior precast concrete base completed by second phase concrete cast. The experiments investigate the shear and flexural strengths of the beams with different depth, width and transverse reinforcement inclination. The beams failure modes are studied focusing on the crack patterns and on the interaction between concrete cast at different times. The obtained results are compared with theoretical evaluations of typical resisting mechanisms of steel-concrete composite and reinforced concrete structures using updated European and American design Standards. The main features of the composite steel truss and concrete beams are quantitatively and qualitatively discussed.

When performing the seismic risk assessment of new or existing buildings, the definition of compact indexes able to measure the damaging and safety level of structures is essential, also in view of the economic considerations on buildings rehabilitation. This paper proposes two series of indexes, named, respectively, Global Damage Indexes (GDIs), which are representative of the overall structure performance, and Section Damage Indexes (SDIs), which assess the conditions of reinforced concrete (RC) beam‐column sections. Such indexes are evaluated by means of an efficient numerical model able to perform nonlinear analyses of the RC frame, based on the continuum damage mechanics theory and fiber approach. An improvement of a two‐parameter damage model for concrete, developed by some of the authors, which guarantees a better correlation between the Local Damage Indexes (LDIs) and the material's mechanical characteristics, is also presented. For the reinforcement, a specific LDI, nam...

Transport processes in heterogeneous media such as ionized plasmas, natural porous media, and turbulent atmosphere are often modeled as diffusion processes in random velocity fields. Using the Itô formalism, we decompose the second spatial moments of the concentration and the equivalent effective dispersion coefficients in terms corresponding to various physical factors which influence the transport. We explicitly define "ergodic" dispersion coefficients, independent of the initial conditions and completely determined by local dispersion coefficients and velocity correlations. Ergodic coefficients govern an upscaled process which describes the transport at large tine-space scales. The non-ergodic behavior at finite times shown by numerical experiments for large initial plumes is explained by "memory terms" accounting for correlations between initial positions and velocity fluctuations on the trajectories of the solute molecules.

Evolution equations for probability density functions (PDFs) and filtered density functions (FDFs) of random species concentrations weighted by conserved scalars are formulated as Fokker-Planck equations describing stochastically equivalent processes in concentration-position spaces. This approach provides consistent numerical PDF/FDF solutions, given by the density in the concentration-position space of an ensemble of computational particles governed by the associated Itô equations. The solutions are obtained by a global random walk (GRW) algorithm, which is stable, free of numerical diffusion, and practically insensitive to the increase of the number of particles. The general FDF approach and the GRW numerical solution are illustrated for a reduced complexity problem consisting of the transport of a single scalar in groundwater. Randomness is induced by the stochastic parameterization of the hydraulic conductivity, characterized by short range correlations and small variance. The objective is to infer the statistics of the random concentration sampled at the plume center of mass, integrated over the transverse dimension of a two-dimensional spatial domain. The PDF/FDF problem can therefore be formulated in a two-dimensional domain as well, a spatial dimension and one in the concentration space. The upscaled drift and diffusion coefficients describing the PDF transport in the physical space are estimated on singletrajectories of diffusion in velocity fields with short-range correlations, owing to their self-averaging property. The mixing coefficients describing the PDF transport in concentration spaces are parameterized by the trend and the noise inferred from the statistical analysis of an ensemble of simulated concentration time series, as well as by classical mixing models. A Gaussian spatial filter applied to a Kraichnan velocity field generator is used to construct coarse-grained simulations (CGS) for FDF problems. The purposes of the CGS simulations are two-fold: first to understand the significance of the FDF approach from a practical point of view and its relation to the PDF approach; second to investigate the limits of the mixing models considered here and the desirable features of the mixing models for groundwater systems.

Longitudinal dispersion coefficients in given realizations of the transport computed by two currently used approximations of the first-order in velocity variance are compared with accurate global random walk simulations. The comparisons are performed for the same ensemble of realizations of the Darcy velocity field, approximated by a quasi-periodic random field, for log-normal hydraulic conductivity with small variance and finite correlation lengths. The results show that, at finite times of about one dispersion time scale, the mean coefficient is underestimated by ≈ 20% and the fluctuations are overestimated by ≈ 80%. At larger times the errors decrease monotonously and the first-order approximations yield fairly good predictions for the mean and the fluctuations of the dispersion coefficient.

The Global Random Walk algorithm (GRW) performs a simultaneous tracking on a fixed grid of huge numbers of particles at costs comparable to those of a single-trajectory simulation by the traditional Particle Tracking (PT) approach. Statistical ensembles of GRW simulations of a typical advection-dispersion process in groundwater systems with randomly distributed spatial parameters are used to obtain reliable estimations of the input parameters for the upscaled transport model and of their correlations, input-output correlations, as well as full probability distributions of the input and output parameters.

Transport processes in heterogeneous media such as ionized plasmas, natural porous media, and turbulent atmosphere are often modeled as diffusion processes in random velocity fields. Using the Itô formalism, we decompose the second spatial moments of the concentration and the equivalent effective dispersion coefficients in terms corresponding to various physical factors which influence the transport. We explicitly define "ergodic" dispersion coefficients, independent of the initial conditions and completely determined by local dispersion coefficients and velocity correlations. Ergodic coefficients govern an upscaled process which describes the transport at large tine-space scales. The non-ergodic behavior at finite times shown by numerical experiments for large initial plumes is explained by "memory terms" accounting for correlations between initial positions and velocity fluctuations on the trajectories of the solute molecules.

Expansive soil causes problem on civil engineering structures due to its tendency to swell when it is in contact with water and shrinks when they dry out. Stabilization using chemical admixtures is the oldest and popular method of soil improvement. In this study, an investigation was conducted to explore the possibility of using termite dust as stabilizing admixture to improve clay soils. This investigation involves the determination of the swelling potential of clay soil in its natural state as well as when mixed with vary proportion of termite dust from (0 to 30%). The termite dust in this experimental work is obtained from termite mound (anthill), dried and ground followed by sieving through sieve no.36. Consistency limits, specific gravity, swelling properties were determined for the samples. Addition of termite dust decreases liquid limit, plasticity index, plastic limit. shrinkage limit, shrinkage index, specific gravity and activity. Also, the experimental results showed that the swelling percentage decreases and rate of swell increases with increasing percentage of termite dust in clay soils. The rates of swelling and swelling percentage of the stabilized specimens were also affected by curing in a positive direction such that the effectiveness of the stabilizer increases with increasing amount-of stabilizer. The CBR and UCS values obtained also increases with increased percentage of stabilizer. From the research findings, it can be deduced that termite dust at 25%-30% stabilization can be recommended for use in sub-grade pavement layer in road work.

This study has been undertaken to examine the feasibility analysis of Industrial waste unlike Foundry sand, Ferromanganese slag and Tyre Chips in Wet Mix Macadam (WMM) by partial replacement to the natural aggregates and stone dust used in WMM. Various mix designs were conducted using different proportions of the Industrial waste and aggregated mix together by partial replacement of industrial waste products to the natural aggregates especially fine aggregates and stone dust. Various laboratory tests i.e. Grain Size Analysis, Standard Proctor Test to determine the MDD and OMC of the mix, Permeability Test, California Bearing ration (CBR) were carried out to analyze the properties of the newly formulated mix in accordance with the conventional mix design of WMM. Further field applications and field results were conducted to analyze the practicability of the mix.

This research is concerned with developing passenger demand models for international aviation from/to Egypt. In this context, the aviation sector in Egypt is represented by the biggest airport, Cairo Airport, as well as by the main Egyptian international air carrier, Egyptair. The developed models utilize two variables to represent aviation demand, namely the total number of international flights originating from and attracted to Cairo Airport as well as total number of passengers using Egyptair international flights originating from and attracted to Cairo Airport. Such demand variables were related, using different functional forms, to several explanatory variables including population, gross domestic product and number of foreign tourists. Finally, two models were selected based on their logical acceptability, best fit and statistical significance. To demonstrate the usefulness of the models, they were used to forecast future demand patterns.

Ultra High Strength Concrete (UHSC) merupakan terobosan yang sedang dikembangkan dalam beberapa dekade terakhir ini. UHSC memiliki beberapa kelebihan dibandingkan Normal Strength Concrete (NSC), yaitu beton UHSC memiliki ketahanan yang lebih baik terhadap asam, kebakaran, maupun ketahanan jangka panjang. Pada tahun 2010, di Indonesia telah dapat dibuat beton UHSC dengan kekuatan mencapai 140 MPa dengan memanfaatkan material lokal dengan ukuran yang sangat halus walaupun masih di laboratorium. Dalam penelitian ini akan dicari mix design yang dapat mencapai kuat tekan UHSC, pengaruh steam curing, penambahan steel fibres, dan proses vacuum dalam pembuatan UHSC. Pencarian mix design dilakukan terebih dahulu sebelum melakukan penelitian yang lain. Kuat tekan maksimum yang dicapai adalah sebesar 115 MPa pada umur 28 hari. Perlakuan steam curing memberikan pengaruh pada kuat tekan awal dan dengan melakukan proses vacuum dalam proses pemadatan benda uji tidak memberikan pengaruh dalam kekuatan. Penambahan steel fibres memberikan pengaruh yang baik dari segi ketahan dalam mengatasi keruntuhan yang getas. KATA KUNCI: ultra high strength concrete, UHSC, steam curing, steel fibres, vacuum. Ultra High Strength Concrete (UHSC) merupakan terobosan yang sedang dikembangkan dalam beberapa dekade terakhir ini. UHSC memiliki beberapa kelebihan dibandingkan Normal Strength Concrete (NSC), yaitu beton UHSC memiliki durability yang lebih baik terhadap asam, kebakaran, maupun ketahanan jangka panjang. Penentuan komposisi yang optimum dari setiap material penyusun beton UHSC sangat diperlukan, baik dari aggregat halus, semen, supplementary cement material, air, dan metode-metode yang akan digunakan selama proses pembuatan.

Indonesia is one of the most seismically active countries in the world, and its large, vulnerable population makes reliable seismic hazard assessment an urgent priority. In 2016, the Indonesian Ministry of Public Works and Housing established a team of earthquake scientists and engineers tasked with improving the input data available for revising the national seismic hazard map. They compiled results of recent active fault studies using geological, geophysical, and geodetic observations, as well as a new comprehensive earthquake catalog including hypocenters relocated in a three-dimensional velocity model. Seismic hazard analysis was undertaken using recently developed ground motion prediction equations (GMPEs), and logic trees for the inclusion of epistemic uncertainty associated with different choices for GMPEs and earthquake recurrence models. The new seismic hazard maps establish the importance of active faults and intraslab seismicity, as well as the subduction megathrust, in d...

Rock burst and coal and gas outburst are the most serious dynamic disasters in coal mine and are affected by many factors, such as mining engineering environment. In order to accurately predict the risk area of mine dynamic disasters, a series of impact factors and events are classified, and the spatial data of these factors are managed on the basis of identifying the internal relationship between the impact factors and the disasters. A multifactor pattern recognition model is established by artificial intelligence. The risk probability prediction criteria of mine dynamic disasters and the risk probability values of each unit in the prediction area are determined by using the method of neural network and fuzzy mathematics. The dangerous area, threat area, and safety area of mine dynamic disasters are divided to evaluate the dangerous degree. The corresponding control measures for different dangerous areas are also put forward. Application of the prediction method of mine dynamic dis...

Rock burst is one of the typical dynamic disasters in coal mining. In order to reveal the mechanism of rock burst from the energy view point, the relationships between the maximum, minimum, and intermediate principal stresses and the concentration coefficients of the gravity stress k1, k2, and k3 are determined through the geostress measurement combined with engineering practice of coal mining. The coal and rock system model based on the tectonic stress is established. The relationship between energy and scale radius of the coal and rock system is determined to reveal the law of energy accumulation, release, and transfer in the coal and rock system. In view of the characteristics of the porous medium in the coal seam, the measures of water injection are put forward to relieve pressure in the coal seam, and the law of water seepage in the process of water injection in the coal seam is studied based on the seepage mechanics. The result shows that the trend of released energy of damage...

Steel fly ash silos are critical components of industrial plants, particularly in the cement and power generation industries, where fly ash is stored for further use or disposal. Due to their height, large mass, and storage capacity, these structures are subjected to various forces, with seismic conditions being one of the most significant considerations for their stability. This paper explores the impact of seismic conditions on steel fly ash silos, focusing on design considerations and guidelines as per IS 1893:2024, which provides the criteria for seismic design of structures in India.

The present study aimed to examine the prevalence and characteristics of pre-hospital injuries and fatalities involving motorcycle riders in Queensland. A retrospective analysis was undertaken of all motorcycle road traffic crashes that were attended by the Queensland Ambulance Service (QAS) over a five year period (1999)(2000)(2001)(2002)(2003). A total of 6145 motorcycle-related incidents were recorded by the QAS during the study period, of which 113 incidents involved a deceased rider. Importantly, there was a 34% increase in the total number of motorcycle injury-related cases over the 5 year period, as well as an increase in the number of pre-hospital deaths. A further comparative analysis revealed some level of disparity between QAS data and corresponding official motorcycle injury records that are predominantly utilised to inform motorcycle policy. The reasons for this discrepancy and the implications of the findings will be further examined in the paper.

In this paper, we investigate the performance of space shift keying (SSK) transmission over a generalized multiple scattering channel. This channel model provides a realistic statistical description of an intervehicular communication environment and includes as special cases the Rician, Rayleigh, and double-Rayleigh channels. We derive an accurate closed form expression for the pairwise error probability of SSK, which is used to obtain the uncoded and coded error rate performances of SSK over various propagation scenarios. An asymptotic analysis for high values of signal-to-noise ratio is carried out to determine the diversity and coding gains of the proposed system. The performance analysis reveals the impact of the number of receive antennas and the use of soft and hard decision decoding on the error rate performance of SSK transmission over multiple scattering channels. Various numerically evaluated results accompanied by Monte Carlo simulations are presented to demonstrate the correctness of the proposed analysis.

The localized corrosion behavior of Type 304L stainless steel (UNS S30400), Alloy 625 (UNS N06625), and three experimental NiCoCrMo multiprincipal element alloys (MPEA), exposed to methanol/lithium chloride solutions with different water contents, is examined in this paper. Cyclic potentiodynamic polarization tests indicated that water increased the pitting and repassivation potentials and the critical temperature at which localized corrosion occurred in chloride solutions. The effect of water on repassivation potential in methanol-chloride solution depended on the chloride concentration and alloy content. At lower chloride concentration and higher alloy content, water had a greater inhibiting effect on repassivation potential, suggesting a competitive reaction between chloride and water on the metal surface in the pit. The localized corrosion resistance of the MPEAs followed the same trend as that of commercial stainless steels and Ni-base alloys in terms of the effect of alloying ...

A two-step aging treatment is applied to nickel-base alloy 718 that has been previously surface-treated by mill finishing (MF) and machine hammer peening (MHP). As a result, a Cr-enriched oxide layer is formed along with a nano-precipitates layer that consists of high precipitate fractions of c 0 /c 00 on the top surface. Surface hardness increases after aging and the compressive residual stress is almost relaxed. The synergistic effects of MHP and aging on pitting corrosion behavior are studied. The results show that the corrosion resistance of the MHP specimens decreases after aging, although the corrosion resistance is still higher than the MF condition.

Investigations of the effects of strong vertical ground motions on structures have been gaining more attention in recent years. Many researchers have found that the assumptions in current design codes underestimate the significance of vertical excitations, especially in near-source earthquake events. Several numerical analyses have been conducted to investigate these effects. However, not many experimental works have been done. In this paper, a bridge model was excited simultaneously in the horizontal and vertical directions through a series of shake table tests. The bridge model was fixed to the base of the shake table. The seismic responses of the bridge structure in the longitudinal direction are discussed. It was found that the inclusion of vertical excitation can significantly increase the bending moment demand of the bridge deck and the development of axial force and plastic hinging in the bridge piers. However, the bending moment demand in the bridge piers have not been greatly affected by the vertical excitations.

The gravity load will reduce the shear strength of a steel shear wall (SSW) under a wind load or an earthquake load. However, this effect is not considered in practice and may lead to potential danger. In this work, three assumed distributions of vertical stress due to the gravity load, i.e. 1) cosine distribution, 2) effective width model and 3) three-segment distribution, were considered. The stress throughout the inclined tensile strip, considering the effect of different vertical stress distributions, is determined using the Von Mises yield criterion. The shear strength is calculated by integrating the shear stress along the width. To evaluate the proposed approach with different vertical stress distributions a finite element model using the software LS-DYNA is developed. The results show that the three-segment distribution is able to describe the effect of gravity load of the SSWs of different aspect ratios and slenderness ratios, while that of the cosine distribution and the effective width model will underestimate the shear strength.

Impact behaviour of FFRP-CFRC slabs were studied by experimentally. The investigation of the effectiveness of different FFRP wrapping configurations. Damage mechanisms of the FFRP-CFRC slabs have been described. The theoretical method was used to predict the maximum impact force and deflection.

Observations from past earthquake events indicate that skewed bridges are seismically vulnerable due to induced horizontal inplane rotations of the girder. To date, however, very limited experimental research has been done on the pounding behaviour of skewed bridges. In this study, shake table tests were performed on a single-frame bridge model with adjacent abutments subjected to uniform ground excitations. Bridges with different skew angles, i.e., 0 °, 30 °, and 45 °, were considered. e pounding behaviour was observed using a pair of pounding and measuring heads. e results reveal that poundings could indeed influence the responses of skewed bridges in the longitudinal and transverse directions differently and thus affect the development of the girder rotations. Ignoring pounding effects, the 30 °skewed bridges could experience more girder rotations than the 45 °skewed bridges. With pounding, the bridges with a large skew angle could suffer more opening girder displacements than straight bridges.

Rapid urbanization, demographic pressure, and sprawl of cities are key factors in the vulnerability and damage related to geo-hydrological hazards. Dysfunctional urban services that favor informal settlements are at the forefront of elements that increase vulnerability. Cases of cities that suffer from geo-hydrological hazards are increasingly reported in many regions, especially in tropical countries in the Global South. Yet, studies on such examples are rare and commonly overlook the human and societal components of hazard risks. Here, we focus on Bujumbura, a city in Africa that has experienced rapid unplanned growth and sprawl into unserviced areas because of the non-application or a lack of a valid urban planning law. After filling in the gap in data collected using high-resolution field surveys and focus group discussions, this study highlights various factors of vulnerability to geo-hydrological hazards in the urban area. Indeed, 108 events of flood and flash floods and 81 gu...

A cycling peloton is the main group of cyclists riding closely together to reduce aerodynamic drag and energy expenditure. Previous studies on small groups of in-line drafting cyclists showed reductions down to 70 to 50% the drag of an isolated rider at same speed and these values have also been used for pelotons. However, inside a tightly packed peloton with multiple rows of riders providing shelter, larger drag reductions can be expected. This paper systematically investigates the drag reductions in two pelotons of 121 cyclists. High-resolution CFD simulations are performed with the RANS equations and the Transition SST-k-ω model. The cyclist wall-adjacent cell size is 20 μm and the total cell count per peloton is nearly 3 billion. The simulations are validated by four windtunnel tests, including one with a peloton of 121 models. The results show that the drag of all cyclists in the peloton decreases compared to that of an isolated rider. In the mid rear of the peloton it reduces down to 5%-10% that of an isolated rider. This corresponds to an "equivalent cycling speed" that is 4.5 to 3.2 times less than the peloton speed. These results can be used to improve cycling strategies.

A cycling peloton is the main group of cyclists riding closely together to reduce aerodynamic drag and energy expenditure. Previous studies on small groups of in-line drafting cyclists showed reductions down to 70 to 50% the drag of an isolated rider at same speed and these values have also been used for pelotons. However, inside a tightly packed peloton with multiple rows of riders providing shelter, larger drag reductions can be expected. This paper systematically investigates the drag reductions in two pelotons of 121 cyclists. High-resolution CFD simulations are performed with the RANS equations and the Transition SST-k-ω model. The cyclist wall-adjacent cell size is 20 μm and the total cell count per peloton is nearly 3 billion. The simulations are validated by four windtunnel tests, including one with a peloton of 121 models. The results show that the drag of all cyclists in the peloton decreases compared to that of an isolated rider. In the mid rear of the peloton it reduces down to 5%-10% that of an isolated rider. This corresponds to an "equivalent cycling speed" that is 4.5 to 3.2 times less than the peloton speed. These results can be used to improve cycling strategies.

Early detection of tooth cracks is crucial for effective condition-based monitoring and decision making. The scope of this work was to bring more insight into the vibration behavior of spur gears in the presence of single and multiple simultaneous tooth cracks. The investigation was conducted in both time and frequency domains. A finite element analysis was performed to determine the variation in stiffness with respect to the angular position for different combinations of crack lengths. A simplified nonlinear lumped parameter model of a one-stage gearbox with six degrees of freedom was then developed to simulate the vibration response of faulty external spur gears. Four different multiple-crack scenarios were proposed and studied. The performances of various statistical fault detection indicators were considered and investigated. The simulation results obtained via MATLAB indicated that, as the severity of a single crack increases, the values of the time domain statistical indicator...

The earthquake attenuation behaviour is a critical part of seismic hazard modelling for regions of low and moderate seismicity. This paper presents a new approach for attenuation modelling, which does not involve the use of strong motion data, and is based on taking measurements of the shear wave velocity (SWV) in bedrock by a noninvasive technique to characterize the transmission of seismic waves. The developed filters are then applied to the generic source model for intraplate earthquakes for calculating the frequency content of seismic waves at the bedrock surface and was used as input to soil response analyses for the determination of site seismic hazard. Ground motion parameters and response spectra are then obtained from the stochastically simulated accelerograms to develop representative attenuation models for rock conditions. The described approach of obtaining a seismic attenuation relationship based on modelling the rock and soil crustal properties is not constrained to an...

We propose a direct method to compute the steady state response to cyclic loadings of elastoplastic solids with Armstrong-Frederick nonlinear kinematic hardening. The algorithm obtains the elastoplastic asymptotic cyclic response without true incremental integration. The method performs much faster than using the step-by-step procedure until stabilization. Including nonlinear kinematic hardening in this asymptotic analysis allows modeling the ratcheting phenomenon, which is important in safety assessment of structures under variable loadings. To the best of the authors knowledge, this is the first direct procedure for computing the asymptotic cyclic response of elastoplastic solids with nonlinear kinematic hardening.

Partial rootzone drying (PRD) has been reported to potentially improve crop water use efficiency (WUE crop ) compared to full irrigation in different fruit trees; however, field studies on the effect of PRD in citrus are scarce. In this field study, three irrigation strategies were tested in an orchard of mature grapefruit trees during two consecutive seasons (2013/2014 and 2014/2015): drip PRD (two drip lines, alternating irrigation between lines every month), microsprinkler irrigation, and double-line drip irrigation (control). Irrigation was applied during the fruit enlargement stage (April-August). The aims of this field study were: 1) to provide a quantitative comparison of irrigation water productivity among irrigation treatments; and 2) to study their effects on fruit quality, yield, tree growth, and flowering. Drip PRD saved 43 to 47% of irrigation water compared to control irrigation, and microsprinkler irrigation saved 12 to 18% of water compared to control irrigation PRD-irrigated trees maintained or increased yield compared to microsprinkler-irrigated and control trees, depending on the experimental season. Therefore, WUE crop in PRD-irrigated trees was significantly higher than in control and microsprinkler-irrigated trees at the end of both seasons. Fruit and juice quality parameters were statistically similar among all treatments. PRD irrigation did not reduce the flowering potential of the trees although it delayed the onset of flowering in trees relative to the other treatments in 2013/2014. There was a similar timing of flowering among treatments in 2014/2015 and there were no differences in vegetative growth among the irrigation treatments by the end of March (86 Julian data) in both experimental seasons. Our results suggest that PRD can be economically beneficial for citrus growers who use double-line drip irrigation systems, and a strategy to sustain tree growth, tree health and yield during seasons of extreme drought or when high water restrictions are placed in citrus-producing areas.

Methyl tertiary-butyl ether (MTBE), a semi volatile organic compound used as a gasoline additive, has been extensively detected in surface and groundwater and therefore became a major issue as an environmental pollutant. The removal of methyl tertiary-butyl ether (MTBE) from water by high-silica zeolite, high-silica zeolite composites, and by granular activated carbon (GAC) was investigated in suspension and by filtration. The Langmuir model yielded good simulation and prediction of MTBE removal. The removal of MTBE from water was more efficient by composites of polyacrylamide (PAM)-zeolite designed in this study than by untreated zeolite or GAC. Even in the presence of BTEX (benzene, toluene, ethyl-benzene and xylene) MTBE removal was very efficient by the PAM-zeolite composites, in comparison to its removal by the zeolite or GAC, reaching 2.5-and 75-fold higher removal, respectively. Filtration of MTBE solution through columns filled with GAC mixed with a PAM-zeolite composite (5:1 w/w ratio) demonstrated several-fold enhanced removal relative to a control which included only GAC. We suggest that the enhanced removal by the PAM-zeolite composite is attributed to (a) the displacement of water from the zeolite surface upon PAM adsorption, which promotes MTBE adsorption and (b) hydrogen binding between the polymer and MTBE.

Measuring the velocity of an arrow in flight is a task of interest to archers, but can be difficult without specialized equipment. We show how accurate velocity measurements can be made by recording the sound made by the arrow as it travels over one or more microphones. Useful recordings can be made with a data acquisition system or with the sound recorder built into most PC operating systems. Estimates of the drag coefficient of different arrows can be made using several microphones to record each shot.

Wave-driven flow over the reef flat plays an essential role in shaping the morphology of coral reefs, whose biological, ecological and geological processes are significantly affected by the water exchange between the open sea and the reef flat. In this study, detailed flow measurements are conducted to investigate the vertical flow structure in the surf zone associated with a plunging breaker over an idealized fringing reef profile with and without a reef crest. A two-dimensional vertical (2DV) numerical wave tank, which solves the Navier-Stokes equations with a buoyancy-modified k-ω SST turbulence closure, is developed to reproduce the laboratory experiments. The free surface is tracked by the Volume of Fluid (VOF) method. Laboratory measurements of the waves and the flows are used to validate the numerical model. The model is then applied to examine the mean flow field and the cross-shore variation of the radiation stress around the reef surf zone. The results suggest that the reef crest causes strong reverse mean flow in the vicinity of the reef edge, and it also blocks the flow leeside of the crest. The cross-shore radiation stress in the reef surf zone is consistently larger than that predicted by the linear wave theory.

In this study, the hydrodynamic characteristics of a novel oscillating water column (OWC) breakwater with a horizontal bottom-plate is numerically and experimentally investigated. A viscous fully nonlinear numerical wave tank (NWT) solved by the open source package OpenFOAM is established under laminar flow conditions. After comparing the numerical results with the experimental ones, the well-validated numerical model is further employed to investigate the effects of the length of horizontal bottom-plate (D), the immersion depth of backplate (d 2 ), the water depth (h) and the wave height (H) on the reflection (C r ) and transmission (C t ) coefficients, dissipation coefficient (C d ) and column-confined energy coefficient (C e ) of the breakwater. The results show that lengthening the bottom-plate can effectively increase the energy dissipation and then lead to lower reflection and transmission coefficients, and a smaller draught of the back-plate can also increase energy dissipation. The water depth has insignificant influence on the hydrodynamic coefficient of long waves, but influences the breakwater performance in short waves. The variation of wave height mainly contributes to the change of reflection coefficient.

The comprehensive utilization of floating breakwaters, specially acting as a supporting structure for offshore marine renewable energy explorations, has received more and more attention recently. Based on linear waterwave theory, the hydrodynamic performance of a T-shaped floating breakwater is semi-analytically investigated through the matched eigenfunction expansion method (MEEM). Auxiliary functions, to speed up the convergence and improve the accuracy in the numerical computations, are introduced to represent the singular behavior of fluid field near the lower salient corners of the structure. The effects of the height and installation position of the vertical screen on the reflection and transmission coefficients, dynamic response and wave forces are examined. It is found that the presence of the screen shifts the resonance frequency of RAO for both surge and pitch modes to the low-frequency area, while has no effect on heave mode. The identical added masses, damping and transmission coefficients can be obtained in the cases where the screen holds the same distance away from the longitudinal central axis of the upper box-type structure. Moreover, a relatively small pitch response can be achieved in a wide wave-frequency range, when the breakwater is Γ-shaped.

An analytical theory is developed to study the effects of a coaxial tube-sector-shaped supporting structure on the conversion efficiency of a suspended, circular OWC converter. An eigen-function expansion method is employed in a cylindrical coordinate system to study wave interaction with an OWC converter in finite depth of water. Effects of the supporting structure, OWC dimensions, wave direction on energy conversion efficiency, and optimization of power-takeoff devices are discussed. Our results show that the coaxial tubesector-shaped support with an opening in the range of π/ 2-5 π/ 4 can significantly increase the conversion efficiency and widen the frequency range over which the conversion efficiency is high.

The behaviors of microfiber-reinforced modified sulfur composites were investigated. The hybrid of steel and glass fibers was effective in improving flexural response. The post-peak toughness ratio in flexure increased according to more microfibers. The total volume of microfibers had a positive correlation with flexural strength. The compressive strength of sulfur composites was more dependent on steel fibers.