Balance Of Flows Research Articles

The impact of diversification on the balance of cash flows of an engineering organization

The impact of diversification on the balance of cash flows of an engineering organization

Multiple jets in a rotating annulus model with an imposed azimuthal magnetic field

Zonal flows driven by rotation and convection are found commonly within astrophysical and geophysical bodies. Multiple jets are most famously observed on the surface of Jupiter, with prograde and retrograde zonal flows making up part of its banded structure of zones and belts. Non-magnetic studies of convection in a rotating annulus model have previously been shown to produce multiple jet structures, similar to those observed in atmospheres of giant planets such as Jupiter. These giant planets have strong magnetic fields which impact on convection in the electrically conducting regions of their atmospheres. Therefore the effect of a magnetic field on the multiple jet solutions of the annulus model is of astrophysical interest. In this work we impose a uniform azimuthal magnetic field to the annulus model and vary its strength and other control parameters to determine the parameter space where multiple jets exist. Zonal flows and multiple jet solutions are found at weak magnetic field strength and, indeed, the magnetic field can promote the production of these features. Simulations with a weak magnetic field or no magnetic field are also found to match well with the Rhines scaling theory. For cases with multiple jets, a strong inertial force must be present, combined with either a weak Lorentz force, or a Lorentz force entering the main balance with increased contributions from the viscous force. At strong magnetic field strengths two regimes are found. For weak magnetic diffusion zonal flows can be retained, albeit without the multiple jet structure. For larger magnetic diffusion non-axisymmetric solutions without clear bands are found. In these regimes, the Lorentz force appears in the primary balance of forces and zonal flows are only retained at strong driving when inertia is able to also enter the balance at leading order.

Computational substantiation of technological characteristics of the closure stage of nuclear fuel cycle using code VIZART

There exist different variants of organizing the closure of nuclear fuel cycle (CNFC) depending on fast reactor type, fuel types, station or centralized allocation of closed nuclear fuel cycle stages. One of the ways to verify and estimate engineering solution is mathematical modeling of radiochemical technology which in the end will allow to optimize composite technological process in order to increase effectiveness and reduce cost. In order to calculate the balance of material flows of process circuits and individual production sections in the stationary and dynamic modes, with taking into account the isotopic composition evolution, a software package VIZART (Virtual Plant of Radiochemical Technologies) was developed, allowing the user to assemble the required sequence of operations for any part of the process scheme and perform the calculation of material balance for all flows of the circuit, as well as to optimize the equipment operating modes and provide the necessary data to justify the safety of certain limits and the entire process circuit. The following capabilities of code VIZART for computational substantiation of CNFC technology design and characteristics are considered: material balance calculation, cyclogram creation, determination of the most loaded parts of processing lines, estimation of fissile materials accumulating in devices and intermediate vessels, optimization of productivity of nodes and devices.

MATHEMATICAL MODELS OF THE NODE OF TECHNOGENIC INFLUENCE, TAKING INTO ACCOUNT THE MAIN DIRECTIONS OF MATERIAL FLOWS IN THE LOGISTICS OF MINING ENTERPRISES

ABSTRACT. The aim of the work is to create a mathematical model of liquid waste storage that accumulates processed products and mine waters simultaneously from many mining and processing plants, taking into account technological constraints on waste volumes and climatic factors depending on the season. The proposed mathematical model of node of technogenic influence is based on the balance of material flows in and out the node. A typical node of technogenic influence is an accumulation node. In the problem considered in this paper, the accumulation node is a waste storage facility where liquid man-made deposits are stored. The model of this node includes a system of equations describing the height of the water mirror and the bottom level depending on the volume of placers and water in and out for the analysed period of operation, taking into account the geometric features of the storage. The main directions of material flows can be formed from two or three nodes of technogenic influence. The first case is typical for underground mining, and the second one is typical for open pit mining. In the second case, the main direction is formed from the node of extraction of primary deposits, the node of processing or separation, and the node of accumulation or the node of storage of man-made deposits. The mathematical model makes it possible to determine the level of the free surface mirror in any month of the year, as well as to calculate the change in the current height of the water mirror in storage for any period of the year, such as spring months or all year round.

Methodological approaches to analyzing cash funds of enterprises

Conducting economic activities without attracting cash funds is not possible, as money plays a direct role in a variety of enterprise operations, whether it's paying rent, and salaries, providing the enterprise with fixed assets, purchasing raw materials, distributing dividends to shareholders, or paying for construction and installation work. The success of a business entity's activities and its ability to finance current operations while timely repaying debts to creditors and accumulating funds for further investment in production expansion depend on the balanced size of cash inflows and outflows. Therefore, the analysis of cash funds is an important component of economic analysis at every enterprise, aimed at finding ways to optimize based on evaluating the sufficiency of formation, effectiveness of application, as well as the balance of inbound and outbound cash flows. This article identifies the stages of analyzing the existing cash flows of a business entity and clarifies the information base used during its implementation. Relative liquidity indicators have gained the widest use among financial condition indicators. The article provides a characterization of liquidity indicators and summarizes scholars' views on determining their normative values. It is proven that the main difficulties arise during the interpretation of the analysis results, as there are no uniform standards even for liquidity ratios in economic literature, which leads to ambiguity in assessing the level of cash management success and their sufficiency to ensure the company's solvency. It is noted that achieving a balance between positive and negative cash flows is one of the main directions of optimizing cash flow. The article describes the composition of indicators characterizing the state and effectiveness of cash flow formation and the efficiency of cash fund utilization. It is emphasized that a reasoned and comprehensive economic analysis of cash funds creates conditions for rational cash management, as it helps to track key development trends of the enterprise, identify the main factors influencing it, and make further forecasts.

Разность потенциалов в стволах березы повислой (Betula pendula ROTH): особенности процессов релаксации при изменении температуры окружающей среды

The daily dynamics of the potential difference arising in the wood of the trunk of the hanging birch (Betula pendula Roth) at ambient temperature changes makes it possible to simulate the dynamics of the processes of redistribution of salt ions in the pores. An analysis of the results of measuring the potential difference in the wood of the model tree trunk showed that its dynamics is of a relaxation nature and tends to a certain stationary value. On the basis of the data of full-scale measurements of the potential difference in the framework of classical electrodynamics, a formalized model of the dynamics of the relative potential difference was constructed, containing three parameters. As a result of a computational experiment using an optimization procedure based on the Nash-Sutcliffe criterion, the parameters of the relaxation process of formation of a stable potential difference along the birch trunk caused by a change in the ambient temperature were calculated. It was revealed that the dynamic balance of the charge redistribution flows is determined by the factors of stimulating and stabilizing processes inside the trunks of woody plants. It is shown that a competent combination of the results of monitoring the potential difference in tree trunks and a computational experiment will make it possible to form an extensive database of parameters for the processes of formation of a stable dynamic equilibrium of salt ion fluxes in them, depending on the characteristics of growth, daily and seasonal changes in ambient temperature and soil composition. The study of changes in the state of trees due to the response to the impact of various environmental factors makes it possible to expand the range of tools for predicting the occurrence of catastrophic situations in forest ecosystems.

The role of fiscal instruments in the implementation of low-carbon agriculture

Purpose. The study purpose is to determine the aspects for improving the fiscal toolkit as an economic lever for regulating agricultural land use with the optimized approach to the selection of areas of introduction of the low-carbon development for the formation of organizational and economic management conditions towards the ensuring of restoration and preservation of agricultural resource potential.
 Methodology / approach. In this work, we used the following research methods: monographic, statistical analysis, graphic, correlation and regression analysis. The national and international documents of legal framework for regulating the processes of agricultural land use, materials of the State Statistics Service of Ukraine were used.
 Results. Based on the ecological and economic efficiency analysis of agricultural land use, the priority of obtaining profits in contrast to the problems of the restoration and preservation of the agricultural resource potential was demonstrated, thanks to which Ukraine took the lead in many commodity crops export. The soil fertility decline is a reason of formed threat to agroecological and food security. Based on the assessment of the nitrogen balance flows, the amount of removal of nutrients from the soil cover was estimated.
 Originality / scientific novelty. The expediency of using an improved tax instrument for land use as an economic lever for the formation of organizational and economic conditions of management with a focus on the introduction of the principles of the green economy is substantiated. This improvement consists in the correction factor proposed for the first time to the calculated volumes of tax collections. This coefficient allows taking into account the characteristics of the land use effectiveness in combination with the coefficients of carbon stock changes of the internationally recognized methodology UN Intergovernmental Panel on Climate Change (IPCC). Based on the improvement of the target agroecological zoning approach (on the example of the Odesa region), an approach to establishing the priority of land plots from the point of view of the perspective of introducing low-carbon land use is proposed.
 Practical value / implications. The proposed approach opens the possibility to optimize efforts to introduce low-carbon land use and therefore to restore and preserve agro-resource potential. The national crop production competitiveness is ensured by this. Therefore, this approach can be taken as a basis for the introduction of the latest green economy tools for the agricultural land use sector at the level of territorial communities.

When health services research becomes important

‚Dear health services researchers, we have finally achieved what we have been working for.‘ With these enthusiastic words, Prof Dr Wolfgang Hoffmann, Chairman of the German Network for Health Services Research (DNVF), opened the 22nd DKVF, which took place at the Urania in Berlin at the beginning of October. The reason for his delight was the fact that - Hoffmann continued - the Innovation Committee recommends the transfer to standard care for 17 projects from the first and second funding waves of the new forms of care, but above all that the results of care research - including those of the ‚WiZen‘ innovation fund project, which was able to demonstrate the superiority of initial therapy in the primary treatment of cancer patients in certified centres - form an evidence base for the recommendations of the government commission for hospital reform. However, this is also precisely what the DNVF Chairman reminded the research community gathered at the German Congress for Health Services Research. Since health services research is now systemically relevant, this not only entails growing responsibility, but also has serious consequences: ‚Health services research now has critics.‘ Because, according to Hoffmann: ‚Our results, recommendations and priorities are now more likely to have consequences, they affect care providers, shift the balance of power and change financial flows.‘

Phase Transformation Under High Pressure Radiates as a Double Couple Deep Earthquake

AbstractDeep‐focus earthquakes (DFEs) originating at the Mantle‐Transition‐Zone (MTZ) (400–700 km) have a Double Couple (DC) radiation pattern similar to crustal earthquakes; however, their mechanism is different and governed by high pressures (15–25 GPa) at nucleation depths. We present a model of nucleation and growth of regions of phase transformation, undergoing a sudden reduction in volume (5%–10%), “volume collapse.” Successive symmetry‐breaking instabilities minimize the energy spent to move the boundary of phase discontinuity and a collapsing volume expands as a flattened pancake‐like self‐similarly expanding Eshelby ellipsoidal inclusion. At the vanishing of the M integral, expressing the balance of flows of energy across the inclusion boundary, at a critical value of the pressure, an arbitrarily small inclusion nucleates and grows at constant potential energy driven by the pressure acting on the change in volume. The inclusion develops shear eigenstrains that decompose into two DC, placing one on the basal plane to radiate without energy losses. The symmetric volume collapse radiates out as an anti‐symmetric DC, and the radiated energy is obtained as the “excess energy,” of the ambient pressure acting on the “volume collapse,” reduced by the energy consumed for the growth of the pancake surfaces, with a “pressure drop” (p0 − pcr) driving the expansion emitting a DC, even under full isotropy. The solution explains some features of the DFEs, (a) the DC radiation, (b) their large energies (the Mw 8.3 Okhotsk earthquake [2013]), (c) the absence of volumetric radiation, and (d) why they can originate in the MTZ, a long‐standing open problem.

Mapping Urban Water Balance to support the integrated design of water cycles in the peri-urban areas

The paper tests the effectiveness of a methodology used to analyze the water element in the urban context, in supporting design choices oriented toward sustainable water management. In particular, it presents a mapping technique of the variables used for calculating the UWB (Urban Water Balance) using the open data available for Milan. The methodology is applied to a peri-urban area of the city’s southern outskirts, the Corvetto/Chiaravalle district. The availability of the data has allowed identifying the minimum spatial area on which to carry out a balance of water flows using open-source GIS in the census block (CB). The methodology’s effectiveness in supporting the design choices was verified on two specific census blocks, the first representing the diffuse residential built area, the second an existing farmhouse no longer productive with residential functions. The main design strategy’s goal was to reduce water withdrawal from the aqueduct and reuse part of the outgoing water to limit the discharge into the sewage system as much as possible.

Green technologies in smart city multifloor manufacturing clusters: A framework for additive manufacturing management

Abstract The development of smart sustainable megapolises is associated with the formation of city multifloor manufacturing clusters (CMFMCs) in them directly in the residential area in order to reduce the supply chain from the manufacturer to consumers. Additive technologies (ATs) belong to green technologies because they are considered environmentally sustainable due to less production waste and the ability to reuse of product materials within the circular economy concept. Sustainable development of ATs and additive manufacturing management has become a priority sphere for scientific research, and the use of ATs in the city manufacturing has become any daily reality. Nevertheless, the issues of additive manufacturing management within the CMFMCs have not yet been sufficiently studied. The primary goal of this study was to examine the possibilities of additive manufacturing management in the CMFMCs of the megapolis due to the rational facilities multi-floor layout in production buildings, considering the structure of city manufacturing and business process reengineering related to the needs of the production services market. This paper presents a novel model of facilities multi-floor layout in the production buildings of the CMFMCs, considering the structure of city manufacturing, morphological analysis of the additive manufacturing equipment (AME) used, the balance of material and energy flows under infrastructure capacity limitations of megapolis. The model was verified based on a case study for various options of the floor-by-floor grouping of AME in a building of the CMFMCs. Management solutions for maintaining the flow balance of material, energy and water resources in the CMFMCs are discussed. The results may be useful for additive manufacturing management in an urban environment, taking into account the needs of the production services market in the megapolis.

Asymmetry of tensile versus compressive elasticity and permeability contributes to the regulation of exchanges in collagen gels.

The Starling principle describes exchanges between blood and tissues based on the balance of hydrostatic and osmotic flows. However, the permeation properties of the main constituent of tissues, namely, collagen, in response to the stress exerted by blood pressure remain poorly characterized. Here, we develop an instrument to determine the elasticity and permeability of collagen gels under tensile and compressive stress based on measuring the temporal change in pressure in an air cavity sealed at the outlet of a collagen slab. Data analysis with an analytical model reveals a drop in the permeability and enhanced strain stiffening of native collagen gels under compression versus tension, both effects being essentially lost after chemical cross-linking. Furthermore, we report the control of the permeability of native collagen gels using sinusoidal fluid injection, an effect explained by the asymmetric response in tension and compression. We lastly suggest that blood-associated pulsations could contribute to exchanges within tissues.

Spontaneous near-inertial wave generation from mesoscale eddy: Nonlinear forcing mechanism

The spontaneous generation of near-inertial waves (NIWs) from quasi-geostrophic mesoscale eddies in a stratified fluid is investigated and the process and mechanism clarified by numerical modeling and a theoretical analysis. Mesoscale eddies, as slow balance flows, are inevitably accompanied by unbalanced near-inertial oscillations (NIOs) in their long period evolution. A mesoscale eddy supplies kinetic energy to NIOs through its interaction with perturbations, which exist universally in the world oceans. Afterward, NIWs are generated spontaneously via the nonlinear coupling of the eddy and NIOs. The baroclinicity of mesoscale eddies is an essential condition of this spontaneous NIW generation mechanism. The resonance of the NIWs and NIOs enables the internal wave continuum to be dominated by NIWs, which share the same horizontal wavenumbers with the eddy. After generation, the NIWs radiate energy toward the eddy center and remain stationary as a whole, relative to the propagating eddy. Generally, an anticyclonic mesoscale eddy can emit much stronger NIWs than does a cyclonic eddy. The NIW intensity strengthens exponentially with the Rossby number. The essence of this spontaneous NIW generation mechanism is the nonlinear interaction between slow balance flows and the accompanying fast motions. It represents an effective pathway for mesoscale eddy energy sinks and makes a non-negligible contribution to the global NIW energy.

Impacts of Foreign Trade on the Economy of Wood-Based Sectors Generating Different Levels of Value Added in the Slovak and Czech Republics

Foreign trade belongs among the main sources of economic growth as classical theories of international trade affirm. The aim of the paper is to evaluate the impact of trade balance flows on sectors generating different value-added in the wood-based industries (WBI) of the Czech and Slovak Republics. The multivariate regression method (MLR) was applied to identify the relationship between foreign trade and economic indicators and also specific indicators assessing impacts of foreign trade on the economy of wood-based industries. The results showed that the performance of high value-added production is only slightly affected by foreign trade. It means that both monitored countries do not utilize raw wood so intensively that the positive effects of foreign trade are manifested. Growth in net exports represents a positive influence on the economy of the sector regardless of the value-added rate only if the increase in imports is smaller than in exports. The contribution of the study to existing knowledge is in using specific indicators evaluating trade impacts on the industry’s economy. The article provides new empirical insights into the influence of foreign trade balance flows on the economy of wood-based sectors with a different value-added rate.

Towards Positive Energy Districts: Energy Renovation of a Mediterranean District and Activation of Energy Flexibility

The paper presents the analysis of energy retrofitting, integration of renewable energy and activation of energy flexibility in a cluster of buildings in the surroundings of a port on the Mediterranean Sea in Southern Italy, with the aim of checking the potential for it to achieve the status of positive energy district (PED). The objective of this study is to improve the contemporaneity between local energy generation and energy demand and reduce CO2eq emissions by considering signals that reflect the environmental variability of the electricity grid, through flexibility solutions applied to the HVAC system. The proposed scenarios are based on the dynamic simulation of the district and analyze the effect of actions that activate the energy flexibility of buildings through advanced control strategies of the air conditioning system. The results show that the joint action of energy efficiency strategies, integration of solar energy and energy flexibility improves the environmental sustainability of the district and the balance of energy flows. Specifically, the activation of energy flexibility contributes to a 10% reduction in operational CO2eq emissions and increases in self-consumption of energy per year. The operational emissions of the district vary from the base value of 33.37 tons CO2eq/y to 19.52 tons CO2eq/y in the scenario based on the integration of solar energy systems and energy efficiency measures, and to 17.39 tons CO2eq/y when also the demand-side energy flexibility is activated.

Assessing Potential Effects of Nature-Based Solutions (NBS) on Water Ecosystem Service in the Interurban Micro-Watershed Río Torres, Costa Rica

The implementation of green infrastructure (GI) as Nature-Based Solutions (NBS) generates positive effects on the water ecosystem service in an urban context. Practices such as bioretention cells, green roofs, rain gardens, permeable pavements, and infiltration trenches contribute to treating large volumes of runoff and providing safe spaces for populations living in highly urbanized areas. With the aim to simulate these effects, a hydrological modeling was carried out using the i-Tree Hydro Plus model, which quantified the runoff generated from precipitation events and effective transformations (NBS) to cope with runoff. Eight scenarios were developed: a baseline scenario, five future scenarios with green infrastructure, a scenario with increased tree coverage, and a scenario with increased urbanization. Our hypothesis is that NBS would reduce runoff and increase permeable flow. The analysis of the feasibility of implementing the modeled green infrastructures was carried out through consultation with local stakeholders in the micro-watershed. We found that bioretention cells decrease runoff by 5%, green roofs by 4%, rain gardens by 4%, permeable pavements by 4.5%, and infiltration trenches by 7.5% compared to the baseline scenario where runoff accounts for 32% of water balance flows. The scenario of increased tree coverage had a similar behavior to the baseline scenario, indicating that efforts in this alternative would generate a limited impact on the reduction of runoff. With increased urbanization, impermeable flow increases up to 78%, which would generate floods. Implementing NBS would be feasible since this type of initiative is included in the agenda of many regulatory instruments of urban planning in Costa Rica.

Hemodynamic performance evaluation of neonatal ECMO double lumen cannula using fluid-structure interaction.

Extra corporeal membrane oxygenation (ECMO) is an artificial oxygenation facility, employed in situations of cardio-pulmonary failure. Some diseases i.e., acute respiratory distress syndrome, pulmonary hypertension, corona virus disease (COVID-19) etc. affect oxygenation performance of the lungs thus requiring the need of artificial oxygenation. Critical care teams used ECMO technique during the COVID-19 pandemic to support the heart and lungs of COVID-19 patients who had an acute respiratory or cardiac failure. Double Lumen Cannula (DLC) is one of the most critical components of ECMO as it resides inside the patient and, connects patient with external oxygenation circuit. DLC facilitates delivery and drainage of blood from the patient's body. DLC is characterized by delicate balance of internal and external flows inside a limited space of the right atrium (RA). An optimal performance of the DLC necessitates structural stability under biological and hemodynamic loads, a fact that has been overlooked by previously published studies. In the past, many researchers experimentally and computationally investigated the hemodynamic performance of DLC by employing Eulerian approach, which evaluate instantaneous blood damage without considering blood shear exposure history (qualitative assessment only). The present study is an attempt to address the aforementioned limitations of the previous studies by employing Lagrangian (quantitative assessment) and incorporating the effect of fluid-structure interaction (FSI) to study the hemodynamic performance of neonatal DLC. The study was performed by solving three-dimensional continuity, momentum, and structural mechanics equation(s) by numerical methods for the blood flow through neonatal DLC. A two-way coupled FSI analysis was performed to analyze the effect of DLC structural deformation on its hemodynamic performance. Results show that the return lumen was the most critical section with maximum pressure drop, velocity, shear stresses, and blood damage. Recirculation and residence time of blood in the right atrium (RA) increases with increasing blood flow rates. Considering the structural deformation hasled to higher blood damage inside the DLC-atrium system. Maximum Von-Mises stress was present on the side edges of the return lumen that showed direct proportionality with the blood flow rate.

External Balance and Financialization: An Interpretation of the Evolution of the Brazilian Economy Since 2000

Brazil experienced a complete economic cycle with an ascending phase in the 2000s, followed by a decline during the following decade. Using the national accounts, the objective of this article is to trace the growth path of the Brazilian economy from the 2000s onwards through a detailed analysis of the financial balance and income flows of the institutional sectors. It will be shown that the economy has two relevant points of inflection: the first was the external shock occasioned by the 2008 global financial crisis, and the second was the change in domestic economic policy after 2015 following an austerity agenda. The article compares the financial balance of the institutional sectors at the two historical moments. It sheds new light on why the Brazilian economy entered the descending phase of the economic cycle and is stagnating and deepening its financialization process.

FORMATION OF HYDROGEOLOGICAL CONDITIONS OF THE CHELYABINSK COAL BASIN AT THE POST-OPERATIONAL STAGE

Completion of the development of mineral deposits requires the development of new methods for managing areas disturbed by mining. The closure of mining facilities, especially those with a long history of mining forms a difficult environmental situation. This is determined by several factors. The development of deposits is accompanied by drainage measures changing the balance and structure of surface and groundwater flows, and new chemical agents are involved in the formation of the qualitative composition of the hydrosphere. The use of mined-out space during the development of schemes with roof collapse induces geomechanical processes forming the zones of collapse and displacement accompanied by disturbances of the Earth’s surface. The cessation of mine operation means the stop of drainage, which leads to the gradual filling of the depression funnel, the formation of flooding areas and mine water outlets to the surface. Unstable rocks in the quarry sides, on which there were landslides even during drainage, become especially dangerous areas when the water level rises. Taking in consideration that residential and industrial buildings are often historically located in close proximity to mines (sometimes even within the mining allotment), the hydrogeoecological problems of old industrial areas at the post-operational stage become very acute. At the same time, in many cases it is difficult to determine, which factors, natural (features of the geological structure, geomorphological conditions, water content of the period) or technogenic (cessation of drainage) are responsible for territory flooding, especially in the areas distant from the objects of completed mining. This gives rise to numerous speculations and leads to irrational technical solutions. By the example of the Chelyabinsk coal basin, the ecological and hydrogeological problems are considered that arise after mining completion and drainage termination. The measures for reducing their negative impact on the hydrogeoecological conditions of the territory are proposed.

Temporal variation of wall flow and its influences on energy balance of the building wall

The characteristics of energy balance and heat transfer on building walls are important for building energy consumption and outdoor thermal/wind environment. The in-situ measurement of energy balance and wall flows during clear days on a 16-story building in Guangzhou, China is introduced and analyzed in this paper. The velocity along the wall was measured by 3D ultrasonic anemometers. The surface temperature was measured by infrared camera and thermal couples. The ambient temperature, relative humidity, wind velocity and solar radiation were recorded by weather stations. The Rayleigh number of wall flows reached as high as 1.44 × 1014. We found that the different kinds of heat flux reach their maximum value in a day cycle at different times. The transmittance of the atmosphere keeps decreasing from sunrise to sunset on Guangzhou’s typical clear days thus inducing different incoming solar radiation. The wall surface temperature and air flow were visualized by infrared videos. The diurnal change of energy balance on the south facing wall was calculated based on the solar radiation, long wave radiation and heat transfer caused by natural convection adjacent to the wall.