Hot Arid Regions Research Articles

An Investigation on Using Passive Cooling Roofs Techniques for Improving Climatic Performance of Residential Buildings in Hot Arid Regions based on Post-Occupancy Evaluation of Inhabitants’ Thermal Comfort Appreciations

In hot dry climates, employing passive cooling roofs systems can provide cooling needs with less amount of electrical energy. Furthermore, when focusing on living spaces in terms of indoor thermal comfort and energy performance issues, occupant’s interaction with the building should not be underestimated. Recent studies with occupant-based focus have shown that human behaviour significantly impacts energy consumption, even more than building design. Likewise, understanding occupant’s interactions within buildings plays a key role in enhancing the indoor environment performance. To examine the potential for cooling load reduction and thermal comfort enhancement by using cool roofs in residential buildings, a study was performed. Considering a sample of twelve multi-story houses located in the city of Biskra (southern Algeria), thermal comfort conditions were analysed on the basis of a post-occupancy evaluation (POE) survey and in situ recorded measurements campaign. The POE household survey indicated that out of 43 respondents, 54% perceive indoor thermal conditions as “hot” during summer period, while 79.33% of them operate HVAC device day and night. Using interviews, the study also explores social acceptability toward implementing passive roofing techniques. Results showed that cool roof and cool tiles were the best accepted systems with 100% and 90% voted strongly agree. Furthermore, the potential of thermal comfort and energy-efficiency improvements due to cool roofs was investigated through a dynamic simulation using TRNSYS software. Results indicated that air temperature was reduced by an average of 4.11°C to 3.28°C, and cooling loads have decreased to 508.60kWh/m² and 384.54kWh/m² respectively during the hottest period of summer. Therefore, user-centric satisfaction as a research method would enhance future buildings design.

Effectiveness of botanicals, inorganic salts and fungicide against Fusarium wilt of muskmelon under hot arid region of Rajasthan

Investigation was undertaken to screen out the extract of botanicals viz., Neem leaf, Tumba fruit, NSKE and Aak leaf and inorganic salts against Fusarium wilt of muskmelon. This disease caused by Fusarium acuminatum is a major fungal disease causing serious losses to muskmelon growing areas in Rajasthan. The field trials were carried out on muskmelon susceptible variety ‘RM-50’ against Fusarium wilt during summer season of 2019 and 2020 at this Institute. Among 11 treatments, carbendazim (0.1%) was found the most effective treatment for management of Fusarium wilt with minimum disease incidence (PDI) of 15.83% and 60.84% disease reduction, followed by neem leaf extract @ 10% with disease incidence of 21.89% and 45.84% disease reduction. Maximum disease incidence (40.42% PDI) was found in case of control.

Environmental change alters nitrogen fixation rates and microbial parameters in a subarctic biological soil crust

Together, biological soil crust (BSC) and other cryptogamic groundcovers can contribute up to half of the global nitrogen (N) fixation. BSC also stabilizes the soil (reducing erosion and dust emissions), fixes carbon (C), retains moisture and acts as a hotspot of microbial diversity and activity. Much of the knowledge about how climate change is affecting the composition and functioning of BSC comes from hot arid and semiarid regions. The comparatively smaller body of research on BSC from cold and mesic environments has been primarily observational, for example along chronosequences after a glacier retreat. Few studies have experimentally investigated the effects of the environment on BSC from high latitudes. Such experiments allow unraveling of relationships at a resolution that can only be achieved by controlling for confounding factors. We measured short‐term (2–4 days) responses of a liverwort‐based Anthelia juratzkana BSC from the south of Iceland to a range of temperature, moisture and light conditions. Warming increased N fixation rates, especially when moisture was at a saturation level, and only when light was not limiting. A correlation analysis suggests that increases in N fixation rates were linked to cyanobacterial abundance on the BSC surface and to the rates of their metabolic activity. Warming and moisture changes also induced compositional and structural modification of the bacterial community, with consequences at the functional level. In contrast to many observations on BSC from hot drylands, the BSC from our cold and mesic study site is more limited by low temperature and light than by moisture. Our findings show possible ways in which BSC from cold and mesic ecosystems can respond to short‐term manifestations of climate change, such as increasingly frequent heat waves.

A smart grid poly-generation design for hot arid regions composed of multi-effect distillation (MED), compressed air energy storage (CAES), and parabolic trough solar collector field (PTSC)

Sustainable provision of freshwater for hot arid coastal regions with abundant solar radiation solves pivotal developmental rural and urban problems. This article presents a thermodynamic investigation of a novel poly-generation smart grid system to produce power and water in a cleaner way via the integration of a multi-effect distillation (MED), compressed air energy storage (CAES), and a parabolic trough solar collector (PTSC) field. A desalination unit is coupled with the CAES system on the charging side to prevent heat dissipation during the compression process. Also, instead of using a combustion chamber that consumes fossil fuel and causes environmental issues, a parabolic trough solar collector field has been hired on the discharge side of the CAES. The smart interconnected MED-CAES-PTSC grid system is thermodynamically tuned to increase the round-trip efficiency (RTE) of the whole system by about 33.5%. Results showed that 2068.1 m3 desalinated water is produced in 665.7 h, while 50.46 MW power is generated during the peak demand. Furthermore, a parametric analysis has been carried out and revealed that inlet motive steam mass flow rate and the maximum pressure of the air cavern have a significant effect on the production of distilled water and RTE, respectively. Total produced freshwater increases with the slope of approximately 0.6 as the inlet motive steam mass flow rate increases. Also, the RTE of the whole system for the pressure ratio of 3, increases with the rate of about 2 until the CAES inlet pressure reaches 4.5 MPa. After that, it will increase linearly with a slope of 1.2. Finally, a multi-objective analysis has been conducted to analyze the thermodynamic performance of the system alongside its economic impact and obtain the optimum value for key design variables.

Post-Occupancy Evaluation of Thermal Comfort Sensation of Pupils in School Establishments under Hot Arid Climate Conditions

School establishments have been considered the foundation of various civilizations, due to the importance of the educational process in producing future generations and shaping healthy societies. This paper aims to evaluate the thermal comfort sensation of pupils in school buildings under hostile climatic conditions in hot arid regions. The study employed the use of the post-occupancy approach with subjective assessments through questionnaires and physical measurements of the environmental physical parameters of thermal comfort: temperature, relative humidity, and air velocity as objective assessments. These measurements were in parallel with survey questionnaires that were undertaken during regular class sessions covering the hot and cold conditions of a school year, polling responses from 281 participants on their perception of the indoor climate. Finger's comfort indicators are calculated (PMV, predicted mean vote; and PPD, predicted percentage of dissatisfied people); and the actual people's clothing and metabolic rate are estimated in order to conclude the prevailing indoor thermal conditions. The investigations were carried out on three samples of school buildings in Biskra (Algeria) of different architectural styles. The study’s results revealed that the levels of temperature were the most crucial parameter that influenced the thermal sensation with an average of 35C° with a PMV of 2.48, and 15C° in winter with a PMV of -2.56, indicating more than 90% dissatisfaction. Therefore, a well-thought bioclimatic school design is needed to ensure acceptable indoors, and promote healthy and safe learning spaces, by adopting sustainable design principles and low-energy-consuming techniques.

Alternative cropping systems and optimized management practices for saving groundwater and enhancing economic and environmental sustainability

Rapid decline in groundwater table due to excessive withdrawal of water for irrigation has been posing a serious threat to sustainable agricultural production in hot arid region of India. Alternative cropping systems having low irrigation requirement have been proposed to resolve unsustainable groundwater use but trade-off with other dimensions such as yield, profitability, and environmental impacts is not well-documented. An integrated analysis of amount of groundwater use, productivity, profitability, resource-use efficiency (RUE), and environmental impacts of three cluster bean-based cropping systems [conventional cluster bean (Cyamopsis tetragonoloba)–wheat (Triticum aestivum) (CB–W), and two alternative cropping systems, namely cluster bean-Indian mustard (Brassica juncea) (CB–IM) and cluster bean–blond psyllium (Plantago ovata) (CB–BP)] under different soil management practices [two tillage types, i.e., conventional (CT), and deep tillage (DT); and three farmyard manure (FYM) application rates, i.e., 0, 5, 10 Mg ha-1] was carried out. Based on a three-year field experiment, compared to conventional CB–W, alternative cropping systems produced 28.6–47.4 % lower seed yield, but enhanced economic returns (7.6–31.1 %), while reduced amount of irrigation (− 27.9 to − 37.2 %), energy (− 22.4 to − 37.0 %), and nutrient (− 17.4 to − 46.1 %) used, global warming potential (− 20.2 to − 45.9 %) and greenhouse gas intensity (− 27.3 to − 57.7 %). Alternative cropping systems saved 1.87–2.50 × 103 m3 per year per hectare of groundwater than conventional cropping systems. Soil management practices influenced agro-economic and environmental dimensions of cropping systems. Deep tillage (DT) enhanced yield (14.0 %), economic profit (18.8 %), RUE (13.2 %, 13.8 % and 8.5 % for nutrient, water and energy use efficiency, respectively). Addition of FYM increased yield (up to 23.0 %), economic net return (up to 21.8 %), RUE (up to 22.7 %, 16.5 %, 91.0 % in water, energy and nutrient use efficiency), and reduced global warming potential (up to − 7.9 %). The CB-BP cropping system with DT and FYM addition offered the best balance of yield, profit, saving of irrigation water, energy and nutrient, while minimizing GWP. This study provides empirical evidence of the opportunities for alternative cropping systems which balance the multiple objectives of sustainable groundwater use, farmer profitability and environmental sustainability for arid region of India. The results have direct implications for sustainable utilization of underground water for similar regions of the world facing water shortage.

The Impact of Street Trees on a Typical Urban Canyon in Eastern Cairo Region

The trend of upgrading urban areas in Egypt is expanding across the region for better urban mobility patterns. Meanwhile, the concerns towards climate change and creating resilient communities are evolving to avoid the dramatic consequences on urban environments. Street trees offer great benefit in climate moderation, particularly in hot arid regions as in Cairo. In this work, different spatial arrangements and locations for evergreen, deciduous trees and palms at NW street canyon are tested using ENVI-met numerical simulation tool. It is aimed to maximize the cooling effect of tree shade on street facades and attain better pedestrian thermal comfort in peak summer times. This ultimately gives better guidance for urban planners and policymakers towards an improved planting design pattern. Comparing simulation results, it is concluded that evergreen trees located at the building edge can provide up to 6°C cooler walls and up to 3.8°C when placed at the building centre. Whilst other tree species have lower cooling effects. Also, these trees have a great role in attaining better thermal comfort levels for pedestrians at the street level. It is recommended to wisely choose suitable tree species and arrangements to maximize the cooling benefits in the urban environment.

Evaluating the thermal insulation performance of composite panels made of natural Luffa fibres and urea-formaldehyde resin for buildings in the hot arid region

ABSTRACT This study investigates the performance of thermal insulation panels composed of the natural Luffa fibres with urea-formaldehyde resin for buildings in the hot arid region. The study has been done experimentally. The work has included the collecting of Luffa fibres from local gardens in Iraq, manufacturing the specimens and measuring the thermal conductivity for different thicknesses, densities and temperatures. The results show that the thermal conductivity of Luffa/urea-formaldehyde composite ranges between 0.22 and 0.25 W/m K. Furthermore, the k-value of the panel may differ by 5–15% depending on the thickness under testing, and by 10–20% depending on the density. However, the main advantage of Luffa composites is that the k-value of the panel is not affected too much at high temperatures, where it has been increased up to 0.26 W/m K (or by 15%) as maximum by the increase of source temperature up to 80°C. This feature has encouraged the use of these panels as external insulation layers in the hot climate region. The results taken from a simulation programme have revealed that the energy saving in the cooling load due to the use of 30-mm insulated panels made of these composites and covered by reflective foils can reach up to 30%.

Characterization of thermo-physiological, hematological, and molecular changes in response to seasonal variations in two tropically adapted native cattle breeds of Bos indicus lineage in hot arid ambience of Thar Desert.

The selection of climate resilient animal is necessary to secure the future of sustainable animal production. The present investigation therefore was an effort to unravel answers to the adaptation at physiological, hematological, and molecular levels in cows of hot arid region that helps them to survive harsh environment, to continue production and reproduction. This investigation was carried out in indicine cows over a period of one year, encompassing four seasons, wherein physiological data of 50 animals, hematological data of 15 animals, and gene expression profile of 5 animals from each of Sahiwal and Kankrej breeds per season was generated. In total, 5600 physiological observations, 1344 hematological observations, and 480 molecular samples were processed. The meteorological data revealed a high diurnal variation of temperature across seasons, with THI exceeding 80 during the months of summer and hot-humid seasons, indicating significant heat stress (HS). The physiological parameters showed an increasing trend with the incremental THI, with significantly (p < 0.05) higher values of rectal temperature (RT), respiration rate (RR), pulse rate (PR), and body surface temperature (BST) at ventral (VT), lateral (LT), dorsal (DT), and frontal (FT), in both breeds recorded during HS. The hematological pictures also revealed significant (p < 0.05) seasonal perturbations in erythrocytic and leucocytic parameters. Moreover, the molecular response was driven by a significant (p < 0.05) upregulation of all the key HSPs, HSP70, HSP90, HSP60, and HSP40, except HSP27 during the hotter months of summer and hot-humid seasons. The expression of HSF1, an important transcriptional regulator ofHSP70 was also significantly (p < 0.05) upregulated during summer season in both breeds. All the molecular chaperones revealed a significant upregulation during the summer season, followed by a decreasing trend by hot-humid season. The study indicated a well-developed thermotolerance mechanism in animals of both breeds, with Kankrej cows exhibiting better thermotolerance compared to Sahiwal cows.

Notes on Grewia tenax (Forssk.) Fiori: an underutilized multipurpose shrub of hot arid region of western Rajasthan

Notes on Grewia tenax (Forssk.) Fiori: an underutilized multipurpose shrub of hot arid region of western Rajasthan

Coupling Effects of Nitrogen and Irrigation Levels on Growth Attributes, Nitrogen Use Efficiency, and Economics of Cotton.

Nitrogen (N) fertilization plays a pivotal role in physiomorphological attributes and yield formation of field-grown cotton (Gossypium hirsutum L.), but little is known of its interaction with irrigation levels. Therefore, this study was conducted with an objective of evaluating the impact of irrigation and nitrogen levels on growth attributes and nitrogen use efficiency of Bt cotton (Gossypium spp.) in the hot arid region. The experiment consisted of a factorial arrangement of three irrigation levels (200, 400, and 600 mm) and four nitrogen rates (0, 75, 150, and 225 kg ha–1) in a split-plot design with three replications. Nitrogen fertilization and irrigation levels influenced cotton growth attributes and yield. The highest leaf area index, dry matter accumulation, crop growth rate, and relative growth rate were achieved at 225 kg N ha–1 and irrigation level 600 mm as compared to other experimental treatments. Similarly, nitrogen uptake and content by seed, lint, and stalk and total nitrogen uptake recorded maximum at 225 kg N ha–1 and irrigation level 600 mm. Interestingly, the treatment of 600 mm of irrigation and 150 kg N ha–1 displayed significant increase in nitrogen use efficiency indices such as agronomic efficiency of nitrogen (AEN) and recovery efficiency of nitrogen (REN), while partial factor productivity of nitrogen (PFPN) and internal nitrogen use efficiency (iNUE) were significantly higher with application of 600 mm of irrigation and nitrogen application rate of 75 kg ha–1. Application of 600 mm of irrigation along with 225 kg N ha–1 resulted in significant increase in gross return, net return, and B:C ratio than any other treatment combinations. So, application of 600 mm of irrigation along with 225 kg N ha–1 could be recommended for achieving higher growth and yield, as well as profitability of Bt cotton under hot arid region and similar agroecologies.

Evaluation of smart irrigation systems in hot-arid climates for green roofs and walls: case of Doha, Qatar

PurposeThe study aims to develop recommendations for optimal Internet of things (IoT) based solutions for a smart precision irrigation automation platform using morphological thinking (MT). The smart irrigation system (SIS) can be applied for green roof and green wall (GRGW) design by studying the relationships and configurations that will be analyzed, listed and synthesized, representing “solutions spaces” and their possibilities.Design/methodology/approachThe research examines studying various cases of SIS; and assessing and analyzing the identified case studies through a decision support system (DSS) considering several factors regarding IoT, plant characteristics, monitoring, irrigation system and schedule, climate, cost and sensors used.FindingsTo develop recommendations for optimal IoT-based solutions for a smart precision irrigation automation platform.Originality/valueThe research paper analyzes and proposes a simultaneous solution to two conflicting problems. On the one hand, the paper proposes to apply greening of walls and roofs in hot arid regions, which will achieve greater environmental comfort. However, this is extremely difficult to implement in hot arid regions, since there is an objective problem – a lack of water. At the same time, the paper proposes the most rational approaches to organizing an irrigation system with the lowest water consumption and the highest efficiency for landscaping. Accordingly, this paper focuses on evaluating different types of SIS about the hot-arid climate in Qatar. The study aims to develop recommendations for optimal IoT-based solutions for a smart precision irrigation automation platform, which can be applied for green wall and roof design.

Comparative Analysis between Different Proposed Responsive Façade Designs for Reducing the Solar Radiation on the West Façade in the Hot Arid Region

Comparative Analysis between Different Proposed Responsive Façade Designs for Reducing the Solar Radiation on the West Façade in the Hot Arid Region

Heat Stress Responses in Small Ruminants under Arid and Semi-arid Regions of Western India: A Review

The main purpose of this review was to demonstrate the current state of the investigations on the responses of body weight, physiological and blood biochemical variables in the small ruminants (sheep and goats) reared in hot arid and semi-arid regions of western India. In recent years, scientific research has made it possible to measure how different breeds of sheep and goat respond to climatic influences and manage to be homoeothermic and adapt to various environmental conditions. The exposure of sheep and goats to heat stress leads to alterations in the physiological and biochemical profiles of blood and also affect the body weight, rectal temperature, respiratory rate, pulse rate, blood plasma properties, production, reproduction, milk quantity and its quality. There are some studies which prove that the central nervous system is susceptible to the deviations in body temperature and also that some cells are more agile in the cold than in heat. In summary, we mention that in different breeds, the rearing environment and its environmental variability can trigger the feed intake efficiency and utilization, body growth, physiological changes and biochemical changes in the blood which lead to heat increment in the body’s thermal balance.

Optimizing Shading and Thermal Performances of Vertical Green Wall on Buildings in a Hot Arid Region

Due to global concerns about energy issues, global warming, and urban quality, vertical greening systems (VGS) are receiving more attention in construction and design research. Therefore, VGS has become part of building envelope design as a passive technique for saving energy in building sectors. The current study aimed to investigate shading and energy performances of VGS in buildings in hot climate regions and to optimize VGS design as a building design element. The study was conducted through simulation and field experiments in a student housing building at a university campus (Irbid, Jordan). Field measurements were taken to assess the thermal effect of the green wall and daylight performance as well as the efficiency of the typical green wall design configuration. Furthermore, a methodology for accurately representing green walls was established and used. Both simulation and experimentation demonstrated that the thickness of the air cavity and the percentage of foliage coverage can have a substantial impact on the performance of the green wall system. Results showed that green wall systems are effective natural sunscreens and shading systems. A green wall helped to reduce the exterior wall surface temperatures by a range of 6 to 11 °C compared to the base case of the wall without a VGS on different days. In addition, it decreased the interior surface temperature of the investigated southern façade by an average of 5 °C compared to the base case. Green wall design configurations for hot climate regions, such as Jordan, will help designers to use the VGS as a design element. Our findings indicate that GW could help to improve the thermal and daylight environment and thus the results could be taken as indicative for GW wall design in other areas or buildings.

Distribution of sequestered carbon in different pools in Alfisols under long-term groundnut system of hot arid region of India

Soil organic carbon (SOC) pools are indicators of soil productivity and sustainability and provide valuable information on the pathways of carbon sequestration in soils. We analysed organic C pools of different oxidizabilities, labile pools like particulate organic carbon, permanganate-oxidisable C, and microbial biomass carbon in soils under a long-term groundnut mono-cropping system with different management practices. Among the treatments, 50% NPK+farmyard manure (FYM) maintained a proportionately higher amount of soil carbon in passive pools (48.3%) followed by 50% NPK+ groundnut shell (GNS) (46.7%), FYM (44.7%), GNS (43.8%), 100% NPK (40.6%), 50% NPK (38.3%) and the control (32.4%). Particulate organic carbon fraction was the most sensitive fraction upon application of the amendments. Carbon stabilized from GNS and FYM sources had a skewed distribution along soil profile with a ratio of 1.2:1.0:1.4 and 1.8:1.0:1.3 at 0–15, 15–30, 30–45 cm depth, respectively. A critical carbon input of 0.32 Mg ha−1y−1 was needed to maintain SOC level, and the rate of conversion of crop residue C into soil organic C was about 8.1% for the present study. Combined use of chemical fertilizers and organic manure was found to be the best for enhancing SOC sequestration in groundnut mono-cropping system under hot arid eco-regions in India.

Geothermal Energy Potential for Cooling/Heating Greenhouses in Hot Arid Regions

In arid regions, drastic seasonal variations in the climatic parameters are common; thus, a high potential of geothermal effects for heating/cooling applications is expected. However, such applications are very limited in these regions due to the lack of information about underground temperature profiles of the surface and shallow zones. Therefore, this study aims to (i) measure the underground temperature profile for one year to determine the optimum depth for burying EAHE pipes; (ii) examine the possibility of water vapour condensation occurring in the buried EAHE pipes, if the air let into the pipes was humid; and (iii) quantify the maximum cooling/heating capacity, if an EAHE was implemented. The results show that a 3-m depth is optimal to bury EAHE pipes, where the ground temperature is 32 °C in the summer and 29 °C in the winter. These temperatures would provide a maximum cooling/heating capacity of 1000/890 MJ day−1 for each 1 m3 of humid air exhausted from a greenhouse. If the EAHE were to operate in a closed loop with a greenhouse, the condensation of water vapour in the EAHE pipes would be impossible during the cooling process. The results of this study are useful for designers using geothermal effects for indoor space cooling and heating in arid regions.

When social practices produce space and create passive cooling systems in hot arid region

Abstract. Practice social of people is the key to produce space and give a possibility to maintain thermal comfort and energy efficiency. The main objective of this research is to adapt the traditional strategies in the architecture actual, to achieved a thermal comfort and improve on reducing cooling load through the using of vernacular gait. Today, it is necessary to practice these systems in the current or conventional architecture of household. The study is especially for arid cities namely the region of Saoura, in the hot and dry climatic zone in Algeria, considered for this study. Two main factors is considered such as design and urban where taken into account in order to select the appropriate and specific passive cooling strategy. The results show that the passive cooling strategy of courtyard would be appropriate for arid regions, however a high thermal mass would be suitable for construction. In conclusion, this work made it possible to choose a suitable passive cooling strategy for all types of construction in hot and dry climates. Finally, this paper puts forward a set of recommendations to improve the passive design of future buildings in hot and arid climates.

The impact of efficient insulation on thermal performance of building elements in hot arid region

The application of thermal insulation technique for buildings in hot arid region still under development and requires investigation for many aspects, especially those related to the individual elements of the construction. The present study investigates the impact of efficient insulation on the thermal performance of the following construction elements: wall, roof and foundation. The techniques used for the insulation have followed the Passive House criteria. The study introduces many benefits for passive design of the building in extreme hot climate. The work has done experimentally in Kirkuk, Iraq for two building models; one is efficiently insulated and the other is traditional. The data, which are collected in summer time, show reduction in indoor temperature of the efficient model by 8 °C in average comparing to that of traditional one. Measurements show stability in the internal wall temperatures for efficient model with an average temperature of 33 °C comparing to 42 °C for traditional one. Similarly, the insulated roof radiates less heat into the indoor than that of traditional model. Furthermore, the effect of both efficient insulated roof and canopy shading reduces the temperature of internal surface temperature of the roof by 12 °C comparing to the traditional model. A local simulation program based on ASHRAE relations has shown an energy saving in the cooling load up to 70%.

Study on wind environment of semi-open space in hot-arid and hot-humid climate zones in rural areas

To explore the coupling effect of open space temperature and air velocity in hot-arid and hot-humid climate regions in rural China, 1690 valid data were obtained by long-term field tests and questionnaires were carried out in hot-arid and hot-humid regions. Results indicated that when the operative temperature is below 33.5 °C, the mean thermal sensation decreases with the increase of air velocity in the hot-humid region. When the operative temperature rose to greater than 33.5 °C, the mean thermal sensation could be significantly reduced only when the air velocity is over 1.0 m/s. However, increasing air velocity in hot-arid regions can significantly improve the thermal sensation. In addition, residents in hot-humid regions were more willing to increase airflow than those in hot-arid regions. These results support the theory of climate adaptation and can provide a reference for the design of semi-open space buildings in rural regions.