Effect Of Loading Research Articles

Study of a mechano-electrochemical model: a numerical and experimental approach

The mechanochemical effects of elasticity and plasticity are introduced into a peridynamic (PD) corrosion model. A PD equation that couples the mechanics and kinetics of electrochemistry is proposed for the first time. This clarifies the influence of the mechanical load in governing the occurrence of diffusion during corrosion. The phase changes experienced by a material are used to characterize the movement of the corrosion boundary, and the concentration of material points is used to characterize the degree and extent of damage caused to the chosen metal. Immersion tests and in situ electrochemical tests are carried out, and the results are used to explore the effects of stress and/or load on the kinetics of environment-induced damage to an aluminum alloy. The model predictions are in good agreement with the experimental observations. The results of this study demonstrate that a coupled mechano-electrochemical PD corrosion model can capture corrosion-induced damage and can be used to study damage propagation upon exposure to an aggressive environment.

An improved golden jackal optimization algorithm for combined economic emission dispatch problems

In this research paper, a new improved golden jackal optimization (IGJO) algorithm is applied to address the combined economic emission dispatch (CEED) problem, along with various thermal generator constraints such as valve point loading (VPL) effect, generator limits (GL) in power system. The hunting behavior of the golden jackals is mimicked in the golden jackal optimization (GJO) algorithm. The main aim of the CEED problem is to find the best optimal generation scheduling while minimizing both fuel cost and emission besides meeting the different power system constraints. The original GJO algorithm faces challenges when dealing with high-dimensional optimization problems, as it tends to get trapped in local optima. To address this issue the opposition-based learning (OBL) method was adopted in this GJO algorithm to obtain the global optimal solution and ensure enhanced performance in finding the solution for the CEED problems. To assess the competitiveness of the IGJO algorithm, it is used for various CEED test problems available in the literature, and results are contrasted with other recent heuristic optimization algorithms. Simulation results show that the proposed IGJO performs more effectively than the other compared algorithms in terms of solution quality, and robustness.

Running-in Period During Sliding Wear of Austenitic Steels

The running-in period during dry sliding wear might determine the evolution to steady-state wear behaviour. To this end, the running-in period during sliding wear of austenitic stainless steel, AISI 316L stainless steel, and Hadfield steel were studied through the testing pin (flat-ended)-on-disk configuration. The effects of the normal load, sliding speed, and alloy type were assessed, and the specific wear rate and strain hardening characteristics were determined. The wear rate was correlated with wear mechanism, friction coefficient, hardening, and roughness to characterize the changes occurring during the running-in period. These changes could influence the responses of these materials to wear during the steady-state period. The stabilization of the specific wear rate and hardness was noted to align with the end of the running-in period.Graphical

Examining the effects of cognitive load on information systems security policy compliance

PurposeEnforcing employee compliance with information systems security policies (ISSP) is a herculean task for organizations as security breaches due to non-compliance continue to soar. To improve this situation, researchers have employed fear appeals that are based on protection motivation theory (PMT) to induce compliance behavior. However, extant research on fear appeals has yielded mixed findings. To help explain these mixed findings, the authors contend that efficacy formation is a cognitive process that is impacted by the cognitive load exerted by the design of fear appeal messages.Design/methodology/approachThe study draws on cognitive load theory (CLT) to examine the effects of intrinsic cognitive load, extraneous cognitive load and germane cognitive load on stimulating an individual’s efficacy and coping appraisals. The authors designed a survey to collect data from 359 respondents and tested the model using partial least squares.FindingsThe analysis showed significant relationships between cognitive load (intrinsic, extraneous, and germane) and fear, maladaptive rewards, response costs, self-efficacy and response efficacy.Originality/valueThis provides support for the assertion that fear appeals impact the cognitive processes of individuals that then in turn can potentially affect the efficacy of fear and coping appraisals. These findings demonstrate the need to further investigate how individual cognition is impacted by fear appeal design and the resulting effects on compliance intention and behavior.

The Effect of Thermocycling and Mechanical Loading on the Fracture Resistance of Graphene and All-Ceramic Anterior Crowns

The Effect of Thermocycling and Mechanical Loading on the Fracture Resistance of Graphene and All-Ceramic Anterior Crowns

Tribological evaluation of thermoplastic polyurethane-based bearing materials under water lubrication: Effect of load, sliding speed, and temperature

AbstractPolymers are widely used in bearing applications. In the case of water-lubricated stern tube bearings, thermoplastic polyurethane (TPU)-based composites are used due to their excellent wear resistance, corrosion resistance, and tunable mechanical properties. Their tribological performance, however, depends on operating conditions. In this work, TPU was blended with carbon fiber, graphene platelet, and ultra-high molecular weight polyethylene (UHMWPE). Friction tests of TPU based-composites against copper countersurface were carried out in water to mimic the actual operating conditions of the bearing. Most of the resulting contacts were in the boundary lubrication regime, in which friction was attributed to both contact mechanics of asperities as well as water lubrication. Our results show that the viscoelasticity of TPU has a considerable impact on its tribological performance. Water lubrication at 50 °C promotes the softening of polymer surface material during sliding, resulting in higher fluctuation in the coefficient of friction and wear loss. This is attributed to the reduced thermomechanical properties. In addition, Schallamach waviness is observed on worn surface. The tribological properties of TPU are significantly improved by the inclusion of carbon fiber, graphene platelet, and UHMWPE. The formation of graphene transfer-layers and UHMWPE transfer film reduces friction and wear loss, while the inclusion of carbon fiber enhances wear resistance due to improved mechanical properties and load bearing capacity.

Freeze‐Casting of Arbitrary‐Shaped Porous Ceramics

Porous ceramics hold the great potential in the field such as bone tissue engineering, superinsulation material, and energy storage. However, it is quite challenging to fabricate them with arbitrary shape using conventional processes. Herein, a method to fabricate arbitrary‐shaped porous ceramic structure is presented by combining traditional freeze‐casting process and indirect three‐dimensional printing technology. Various polydimethylsiloxane (PDMS) soft molds are prepared for freeze‐casting, and diverse‐shaped porous ceramics are fabricated. It proves that PDMS molds are ideal choices for freeze‐casting of porous ceramics with complex geometries. The freeze‐casting process of a complex‐shaped model with PDMS is simulated by finite element analysis. The effect of the solid loading of the alumina suspension on the microstructure and compressive strength of the as‐fabricated porous ceramics are investigated. The present study provides a strategy to fabricate complex‐shaped porous ceramic structure that can be used in a wide variety of applications.

Fluid Structure Interaction Analyses of Elevated Storage Tank under Seismic Load

Elevated storage tanks are used to store fresh and waste water, cereal, oil and petrochemical materials. Therefore they serve in a wide area of utilization in this day and age. Analysis of a half full with water elevated storage tank is performed in the scope of this study. The structure is composed of a steel circular storage tank and frame typed steel stager. The structure is under the effect of earthquake loads as well as operational ones. Numerical model is generated by Finite Elements Analysis (FEA) software including fluid and structure parts. The interaction of the parts is provided by Coupled Eulerian Lagrangian (CEL) technique. While the structure constitutes the Lagrangian part, the fluid constitutes the Eulerian part. Interaction of Eulerian and Lagrangian parts are provided by general contact algorithms. Free surface movement of the water, maximum displacements and natural frequency values with related mode shapes of the structure are obtained after numerical analysis. Numerical results are verified by semi-analytical model, where the structure is modelled as single degree of freedom system. The accordance between results is numerically and visually obtained. The turbulent movement of water under the influence of an earthquake is modelled by utilizing the CEL technique. So, the effect of the dynamic pressure induced by the turbulence on the tank and the structural system has been taken into consideration.

Optimization of the Traffic Load Model for Suspenders of a Super-Long-Span Suspension Bridge Considering Influence Line Geometry and Extreme Load Effect Scenarios

Optimization of the Traffic Load Model for Suspenders of a Super-Long-Span Suspension Bridge Considering Influence Line Geometry and Extreme Load Effect Scenarios

Numerical Simulation of Structural Performance in a Single-Tube Frame for 12 m-Span Chinese Solar Greenhouses Subjected to Snow Loads

To address the structural concerns of a 12.0 m-span landing assembled single-tube frame (LASF) for Chinese solar greenhouses subjected to snow loads, the internal forces and deformations of LASF and its reinforced counterpart (RLASF) were numerically simulated to determine the ultimate bearing capacities (Lu) and the failure loads (Lf). During the simulations, steel tubes were modeled as beam188 elements and cables as link180 elements. The frame constraints and the connections were assumed to be fixed supports and rigid, respectively. The loads were determined according to the Chinese standard (GB51183-2016). Simulations revealed that the LASF and RLASF primarily withstand bending moments and are prone to strength failures under snow loads. Both exhibited lower Lu and Lf under non-uniform snow loads than under uniform snow loads. The results also indicated that crop loads could deteriorate the structural safety of the LASF and RLASF. Lu and Lf were found to be proportional to the section modulus of the tubes. The effects of wind loads and initial geometry imperfections on Lf of the LASF and RLASF can be neglected. Furthermore, the RLASF exhibited higher Lf compared to the LASF. Steel usage of the RLASF could be further reduced by replacing circular tubes with rectangular tubes, making the RLASF a feasible option for constructing Chinese solar greenhouses.

Motion and mooring load responses of a novel 12 MW semi-submersible floating wind turbine: An experimental study

Abstract Due to the complexity of the integrated Floating Wind Turbine (FWT) system, obtaining reliable results necessitates extensive experiments. This paper conducts a comprehensive study on the motion performance and mooring load responses of a novel 12 MW semi-submersible FWT through model tests carried out in a wave basin. A multi-blade large-scale wind generation system, equipped with a rectifier network, was enhanced and constructed to provide a dependable wind field. And a flexible tower was designed and fabricated, achieving an accurate simulation of the tower's stiffness characteristic and its impact on the overall dynamic response. The marine environmental conditions encompass various combinations of wind, waves, and currents. Rigorous calibration and identification tests were undertaken to validate the environmental conditions and the model system. The findings reveal that, under mild wave parameters, the mooring load is primarily influenced by the resonance response with platform motions, particularly surge resonance. The load effect of wind and current induces mean surge and pitch motions, while their damping effect reduces the standard deviation of responses, notably suppressing the pitch response peak at its natural motion frequency. Wave loads predominantly dictate the vibration range of motion responses. When the current velocity reaches a sufficient magnitude, the coupling effect between current and wave in the wave-frequency region significantly amplifies the mooring response. Notably, motions and mooring loads in the 60° and 90° directions surpass those in the 0° direction, with the maximum responses occurring at 60°.

PAU Smart Seeder: a novel way forward for rice residue management in North-west India

In winter, the paddy residues become wet during morning and late evening due to dew, which restricts the operation of sowing machines (Happy Seeder and Super Seeder) into paddy residues, as wet residues do not slide on furrow openers/tines. A PAU Smart Seeder (PSS) was developed and evaluated for a four-wheel tractor that can sow wheat with optimum crop establishment in combined harvested rice fields. The PSS were evaluated for its performance under varying straw load, forward speed, and rotor speed in terms of fuel consumption, field capacity, seed emergence, and grain yield. The crop establishment and wheat yield of PSS was also compared with the existing straw management machines Happy Seeder (HS) and Super Seeder (SS) under heavy paddy residue conditions. The effect of the straw load was more pronounced on dependent variables than the effect of the speed index. PSS performance was best at a forward speed of 2.6 km h−1, rotor speed of 127.5 rpm, and a straw load of 6 t ha−1. Average fuel consumption using PSS was lower than SS but higher than HS. Wheat emergence was higher by 15.6 and 25.7% on the PSS plots compared to HS and SS, respectively. Average wheat grain yield in PSS plots was significantly higher by 12.7 and 18.9% than SS and HS, respectively in one experiment, while the grain yield was similar for both PSS and HS in other experiments. PSS has a novel mechanism to manage paddy straw and simultaneously sow wheat into a heavy straw load (> 8 t ha−1) mixture of anchored and loose straw. In conclusion, PSS showed promise for in-situ management of rice straw as it eliminates most of the operational problems encountered by the existing seeders (HS and SS).

#2268 Dialysis patients survival in HD centres from Belgium, Estonia, Spain, and Sweden—association with BMI and hypocalcemia

Abstract Background and Aims Several factors are known to influence the morbidity and mortality of ESKD patients, among them cardiovascular disease, nutritional status, delivered dialysis dose, uremic toxins levels, and infectious diseases. This observational study aimed to analyse factors that impact the survival of ESKD patients on haemodialysis. Method We analysed 3- and 5-year survival of 76 patients during the period of 2018-2023 (17 females, 59 males, aged 63.6 ± 15.9 years) from four separate dialysis centres from countries with diverse life expectancies, renal replacement therapy incidences, and kidney transplant rates: North Estonia Medical Centre, Tallinn, Estonia (21 patients); Linköping University Hospital, Linköping, Sweden (21 patients); Ghent University Hospital, Ghent, Belgium (14 patients) and Fundación Jiménez Díaz University Hospital Health Research Institute, Madrid, Spain (20 patients). We included stable chronic haemodialysis patients receiving three times per week post-dilution ol-HDF treatment. Patients with central dialysis catheter, acute coronary syndrome or stroke within three months were excluded. Cox proportional-hazard regression analysis was used to detect the factors affecting the survival of patients. In the Cox model, the 3-year survival was set as a dependent parameter. Age, gender, BMI, and serum levels of creatinine, phosphate, calcium, total protein, and uric acid were set as independent parameters. Kaplan-Meier survival analysis was performed to study survival in the subgroups of patients. Results Out of 76 patients, 22 died in 3-years and 34 in five years (Fig. 1a and b). Our Cox model (adjusted with the age, gender, creatinine, phosphate, total protein, and uric acid serum levels) indicated patients' body mass index (BMI, p = 0.014) and calcium (p = 0.033) levels as statistically significant factors in 3-year survival. Kaplan-Meier survival analysis showed statistically significant increased survival in the group where BMI was higher than 27.6 kg/m2 (Fig. 2a) and in the group where serum calcium levels were higher than 2.25 mmol/L (Fig. 2b). Conclusion This study shows that among prevalent haemodialysis patients 3-year survival is about 65% and 5-year survival 45%, and a higher risk of mortality could be associated with low BMI and low serum calcium levels. Our findings are in accordance with previous studies, where survival benefit for haemodialysis patients with higher BMI is shown [1, 2]. It is proposed that this phenomenon among advanced CKD patients with higher BMI could be due to better nutritional reserve that helps resist chronic inflammation and wasting. The negative effects of excess calcium load for haemodialysis patients are well known, and nowadays, non-calcium-based phosphorus binders, calcimimetics, and low-calcium concentrates in haemodialysis are used more often, thus putting the patients at risk of hypocalcaemia. Though less studied, long-term hypocalcaemia is shown to increase mortality among haemodialysis patients [3], as concurs with our results. Safe calcium concentration limits for these patients are still debatable and need further investigation.

A comprehensive evaluation on particles breakage characteristics of waste argillaceous gangue as subgrade filler

Reutilising waste argillaceous gangue (AG) in road engineering is crucial to reducing its environmental pollution. To effectively control settlement and long-term performance of subgrade filled with AG, the effects of humidification and loading on the particle crushing evolution of AG were investigated. The effects of dry-wet cycles, compaction work, and initial coarse grain content (CGC) on the breakage characteristics were evaluated. The relationship among fractal dimension D and compaction work, initial CGC, and breakage index Bg was established. The results show that the initial CGC and compactness are essential factors affecting the breakage characteristics of AG. It is recommended that the CGC be controlled at 50% when AG is used as subgrade filler. The fractal dimension increases logarithmically with the increase of compaction work and decreases linearly with the rise of CGC. Fractal dimensions D and Bg can effectively evaluate the breaking process of AG and the gradation after compaction.

Bio-based composite from chitosan waste and clay for effective removal of Congo red dye from contaminated water: Experimental studies and theoretical insights

Water pollution due to dyes in the textile industry is a serious environmental problem. During the finishing stage, Congo red (CR) dye, water-soluble, is released into wastewater, polluting the water body. This study explores the effectiveness of utilizing a composite composed of Safi raw clay and chitosan to remove an anionic dye from synthetic wastewater. The chitosan was extracted from crab shells. Its removal performance was compared to that of natural clay. Both the composite and raw clay were used to remove target pollutant. The effects of the chitosan load in the composite, size particles, initial dye concentration, contact time, pH, and temperature on the dye's elimination were tested in batch modes. The composite with 30% (w/w) of chitosan exhibited the highest dye removal. At pH 2, an adsorption capacity of 84.74 mg/g was achieved, indicating that the grafting of the polymer onto clay surface enhances its efficacity and stability in acidic environments. This finding was supported by characterization data obtained from X-ray diffraction (XRD), scanning electron microscopy (SEM), dispersive X-ray spectroscopy (EDX), and Fourier transform infrared (FT-IR) analyses. Under optimized conditions of 20 mg dose, pH 2, 30 min of reaction time, and 20 mg/L of dye concentration, about 92% of dye removal was achieved. The Langmuir isotherm model represents dye adsorption by the composite, while dye removal was controlled by pseudo-second-order model. Thermodynamic data of the adsorption (ΔH = +8.82 kJ/mol; ΔG <0) suggested that the dye adsorption was spontaneous and endothermic. The findings provide insights into the dye elimination by the adsorbent, indicating that the removal occurred via attractive colombic forces, as confirmed by density functional theory (DFT) analysis. Overall, the composite of natural clays and chitosan waste is a promising and innovative adsorbent for treating wastewater containing recalcitrant dyes.

Fracture resistance of additively or subtractively manufactured resin-based definitive crowns: Effect of restorative material, resin cement, and cyclic loading

ObjectiveTo evaluate how restorative material, resin cement, and cyclic loading affect the fracture resistance of resin-based crowns fabricated by using additive or subtractive manufacturing. MethodsA right first molar crown standard tessellation language (STL) file was used to fabricate 120 crowns from one subtractively manufactured polymer-infiltrated ceramic network (SM) and two additively manufactured resin composites (AM-B and AM-S) (N = 40). These crowns were randomly divided into 4 groups within each material according to the dual-polymerizing resin cement to be used (RX and PN) and the aging condition (n = 10). After cementation, the crowns without cyclic loading were subjected to fracture testing, while the others were first cyclically loaded (1.7 Hz, 1.2 million cycles, and 49-N load) and then subjected to fracture testing. Data were analyzed with generalized linear model analysis (α = .05). ResultsFracture resistance of the crowns was affected by material, resin cement, and cyclic loading (P ≤ .030). However, none of the interactions significantly affected fracture resistance of tested crowns (P ≥ .140). Among tested materials, SM had the highest fracture resistance, whereas AM-B had the lowest (P ≤ .025). RX led to higher fracture resistance, and cyclic loading decreased the fracture resistance (P ≤ .026). SignificanceTested materials can be considered reliable in terms of fracture resistance in short- or mid-term (5 years of intraoral simulation) when used for single molar crowns with 2 mm occlusal thickness. In the long term, polymer-infiltrated ceramic network crowns cemented with RelyX Universal may provide promising results and be less prone to complications considering higher fracture resistance values obtained.

Experimental Study on Shear Lag Effect of Long-Span Wide Prestressed Concrete Cable-Stayed Bridge Box Girder under Eccentric Load

Based on the engineering background of the wide-width single cable-stayed bridge, the shear lag effects of the cross-section of these bridge box girders under the action of the eccentric load were experimentally studied. The behavior of shear lag effects in the horizontal and longitudinal bridge directions under eccentric load in the operational stage of a single cable-stayed bridge was analyzed by a model testing method and a finite element (FE) analytical method. The results showed that the plane stress calculation under unidirectional live load was similar to the results from spatial FE analysis and structural calculations performed according to the effective flange width described in the design specification. At the position of the main beam near the cable force point of action, the positive stress at its upper wing edge was greatest. At a distance from the cable tension point, the maximum positive stress position trend showed that from the center of the top flange to the junction of the top flange and the middle web to the junction of the top flange and the middle web and the side web. Under eccentric load, the positive and negative shear lag effects on the end fulcrum existed at the same time, and the shear lag coefficient on the web plate was larger than the shear lag coefficient on the unforced side. Due to the influence of constraint at the middle fulcrum near the middle pivot point, positive and negative shear lag effects were significant, and the coefficient variation range was large, resulting in large tensile stress on the roof plate in this area. According to FE analytical results, stress and shear forces of a single box three-chamber box girder under eccentric load were theoretically analyzed, the bending load decomposed into the accumulation of bending moment and axial force, using the bar simulation method, and the overall shear lag effect coefficient λ was obtained and verified.

Experimental Study on the Microfabrication and Mechanical Properties of Freeze-Thaw Fractured Sandstone under Cyclic Loading and Unloading Effects.

A series of freeze-thaw cycling tests, as well as cyclic loading and unloading tests, have been conducted on nodular sandstones to investigate the effect of fatigue loading and freeze-thaw cycling on the damage evolution of fractured sandstones based on damage mechanics theory, the microstructure and sandstone pore fractal theory. The results show that the number of freeze-thaw cycles, the cyclic loading level, the pore distribution and the complex program are important factors affecting the damage evolution of rocks. As the number of freeze-thaw cycles rises, the peak strength, modulus of elasticity, modulus of deformation and damping ratio of the sandstone all declined. Additionally, the modulus of elasticity and deformation increase nonlinearly as the cyclic load level rises. With the rate of increase decreasing, while the dissipation energy due to hysteresis increases gradually and at an increasing rate, and the damping ratio as a whole shows a gradual decrease, with a tendency to increase at a later stage. The NRM (Nuclear Magnetic Resonance) demonstrated that the total porosity and micro-pores of the sandstone increased linearly with the number of freeze-thaw cycles and that the micro-porosity was more sensitive to freeze-thaw, gradually shifting towards meso-pores and macro-pores; simultaneously, the SEM (Scanning Electron Microscope) indicated that the more freeze-thaw cycles there are, the more micro-fractures and holes grow and penetrate each other and the more loose the structure is, with an overall nest-like appearance. To explore the mechanical behavior and mechanism of cracked rock in high-altitude and alpine areas, a damage model under the coupling of freeze-thaw-fatigue loading was established based on the loading and unloading response ratio theory and strain equivalence principle.

Parafoveal Processing of Orthography, Phonology, and Semantics during Chinese Reading: Effects of Foveal Load.

The foveal load hypothesis assumes that the ease (or difficulty) of processing the currently fixated word in a sentence can influence processing of the upcoming word(s), such that parafoveal preview is reduced when foveal load is high. Recent investigations using pseudo-character previews reported an absence of foveal load effects in Chinese reading. Substantial Chinese studies to date provide some evidence to show that parafoveal words may be processed orthographically, phonologically, or semantically. However, it has not yet been established whether parafoveal processing is equivalent in terms of the type of parafoveal information extracted (orthographic, phonological, semantic) under different foveal load conditions. Accordingly, the present study investigated this issue with two experiments. Participants' eye movements were recorded as they read sentences in which foveal load was manipulated by placing a low- or high-frequency word N preceding a critical word. The preview validity of the upcoming word N + 1 was manipulated in Experiment 1, and word N + 2 in Experiment 2. The parafoveal preview was either identical to word N + 1(or word N + 2); orthographically related; phonologically related; semantically related; or an unrelated pseudo-character. The results showed robust main effects of frequency and preview type on both N + 1 and N + 2. Crucially, however, interactions between foveal load and preview type were absent, indicating that foveal load does not modulate the types of parafoveal information processed during Chinese reading.

Design and Tensor Impedance Analysis of 4×4 Isotropic Homogeneous Metasurface-Backed Slotted Dual-Layered Bio-Superstrate-Loaded MPA

A 4×4 Isotropic Homogeneous Metasurface (IHM) backed, rectangular slotted dual-layered triband microstrip patch antenna (MPA) is proposed in this article. A detailed mathematical way to analyze the tensor surface impedance matrix (TSIM) of the proposed 4×4 IHM and slotted patch is demonstrated. The proposed IHM-backed MPA has a triband even-mode resonance at fr0=2.45 GHz, 2fr0=5.4 GHz, and 4fr0=7.7 GHz. A better and more accurate estimation of bio-superstrate loading effect for triband resonance is employed using the human skin (εr=52.79, σs=1.39) and blood (εr=52.8, σs=1.23) layer on the top of dual-layered metasurface-backed slotted MPA. TSIM characterization is observed for both blood- and skin layer-loaded dual-layered metasurface-backed slotted MPA. Chicken breast (εr=55.2, σs=1.49, and tanδ=0.325) with blood (εr=58.2, σs=2.59, and tanδ=0.364) is loaded onto fabricated dual-layered structure to verify numerically modeled estimation. A closed form triband, even-order resonance mode (i.e., fr0, 2fr0, and 4fr0) estimation based on dielectric superstrate thickness (Hs) is numerically established using MATLAB solver. Complete measurement setup with simulated vs. measured results is compared in this article.