Thermal Environment Research Articles

The impact of IEQ in the university lecture theatres on students’ concentration levels in London

Purpose University students’ lecture theatre concentration levels are significantly related to indoor environmental quality (IEQ). The purpose of this study is to investigate the relationship between indoor environmental quality (IEQ) and the self-reported concentration levels of university students during the winter at University College London (UCL), UK. Design/methodology/approach A questionnaire survey and physical measurements were used to assess the IEQ factors affecting students’ concentration levels. Findings The lecture theatre design factor was the most significant factor influencing students’ concentration levels, and the facility environment was more important than the thermal environment, indoor air quality, and acoustic environment in influencing students’ concentration levels in this winter investigation at UCL, UK. Additionally, students prefer a colder thermal environment. The concentration level of students was positively correlated with the indoor air quality and negatively correlated with the acoustic environment. Practical implications Based on model application, this research could provide lecture theatre IEQ design. This research additionally provides an acceptable indoor thermal environment temperature range based on a large sample, which can be used to calibrate a student performance benchmark. Originality/value As this study evaluates the IEQ factors that influence the concentration levels of university students, interior designers and engineers should consider the rational layout of these factors. Therefore, this study may provide a reference for the interior environmental design of lecture theatres in educational buildings.

A Bibliometric Analysis of the Outdoor Thermal Environment Based on CiteSpace

The outdoor thermal environment (OTE) is closely related to sustainable urban development and human living, and related research has attracted widespread attention. The research hotspots and research frontiers were obtained using CiteSpace to analyze 4473 relevant studies published in English from the Web of Science (WOS) core database from 1998 to 2023. The results show that (1) Hong Kong Polytechnic University, National University of Singapore, Chinese Academy of Sciences, Tsinghua University, and Harbin Institute of Technology are important in OTE research. China has the largest number of publications in the field of OTE, but the United States has the greatest centrality and significant influence. (2) The focus of OTE keyword clustering research is divided into four main categories: thermal environment perception, the thermal environment index, thermal environment quality, and thermal environment optimization. (3) The frontiers of OTE research have changed from focusing on environmental quality, thermal perception, numerical simulation, urban space, and thermal adaptation to thermal mitigation, energy conservation, energy consumption, and optimization strategies. Visualization research in the field of OTE helps to provide references for the direction of future research on improving climate change, human thermal comfort, urban planning, and pre-planning.

Comprehensive analysis of two-phase liquid-gas flow structures in varied channel geometries and thermal environments

Two-phase liquid-gas flows are very often used in practice. It is a branch of knowledge that has been extensively studied for many years. The extensiveness of the topic results from the fact that two-phase flows differ quite significantly, depending on the geometry, hydraulic diameter orientation of the channel, and possible thermal processes occurring in the flow. These differences affect the formation of various flow structures and thus flow resistance and heat transfer if the flow is non-adiabatic. In addition to the impact on the energy consumption of the machines in which the phenomenon occurs, the flow structures affect the stability of the equipment operation. This article presents a literature review and knowledge analysis of flow structures in both adiabatic and non-adiabatic flows in channels of different dimensions, geometry, and orientation. The authors also present the results of their research in flow structures in the liquefaction process, carried out in minichannels, as well as a summary of knowledge in the field of liquid-gas flow structures.

Effects and optimization of airflow on the thermal environment in a data center

In this research, the escalating energy consumption challenges in data centers are addressed by optimizing airflow organization designs. Through the use of computational fluid dynamics (CFD) simulations, three different airflow strategies were evaluated and improved: underfloor precision air conditioning, inter-column air conditioning, and backplane air conditioning. These cooling systems, which are usually considered in isolation, were compared in a comprehensive manner to get a full picture of their efficiency and effectiveness. The findings reveal that the implementation of cold aisle containment (CAC) or hot aisle containment (HAC) significantly improves air supply efficiency (ASE) and reduces the supply heat index (SHI), leading to a more uniform temperature distribution and enhanced cooling performance. Specifically, the ASE increased from 65.69% to 85.57% and 90.25% for underfloor precision air conditioning and from 71.29% to 92.16% and 92.17% for inter-column air conditioning, with corresponding reductions in SHI. The backplane cooling system offered consistent ambient temperatures throughout the room, eliminating thermal hotspots without the need for aisle containment. This study offers a comparative analysis of different airflow organization schemes, highlighting the benefits of aisle containment in precision and inter-column air conditioning and the suitability of backplane air conditioning for high-density cooling without the need for traditional aisle separation. The results are crucial for informing energy-efficient cooling strategies in data center design and operation.

Variations in Gender Perceptions of Summer Comfort and Adaptation in Colonial Revival-Style Homes

Past investigations have assessed gender variations in thermal comfort and adaptation in different buildings. However, no reported study has evaluated differences in gender perceptions of the thermal environment in US Colonial Revival-style homes. As a result, this study aims to provide an understanding of variations in gender perceptions of summer comfort and adaptation in the buildings. The study evaluated data collected during the field studies of thermal comfort (FSTC), including physical measurements of environmental variables and subjects’ votes. In this study, 67% females and 33% males participated in the field surveys in summertime. The mean neutral temperature of 25.5 °C and preferred temperature of 24.9 °C were noted for females. For males, the mean neutral and preferred temperatures of 25.8 °C and 25.6 °C were observed. Females feel neutral and prefer “no change” to the thermal environment at lower temperatures than males. A difference of 0.3 °C was noted between the average heat indices for females and males. Male respondents who feel warm perceive less air quality more than females. Females and males who perceive being thermally comfortable also perceive good air quality. Females and males who are thermally comfortable rated air humidity to be acceptable. There are similarities and differences between gender perceptions of the thermal environment. The investigation suggests interventions that can help users regulate their skin temperatures and use control measures that are sensitive to clothing insulation. The research also calls for policies that can promote building users’ pivotal adaptive measures to improve their indoor thermal environment. The study enhances our understanding of sustainable indoor environments and how to improve living conditions and adaptive modifications among different groups of occupants in buildings.

Thermal Environment Analysis and Optimization for Large Space Buildings with Radiant Cooling Floors: A Case Study of Xianyang International Airport

Radiant cooling floors combined with ventilation systems have been widely applied in large space buildings. However, there has been a lack of research on system control strategies for their adaptation to weather changes. This study aimed to find control strategies for radiant cooling floors combined with displacement ventilation systems used in large space buildings in order to achieve energy conservation and environmental improvement. Supply air temperature and cooling surface temperature were determined to be the control variables. It was found that cooling capacity of the combined system and the comfort index, PMV (predicted mean vote), were linear in relation to the supply air temperature and cooling surface temperature. The linear equations regarding cooling capacity and PMV were established separately using environment data, and then the optimal region was determined. A case study on Terminal 3 of Xi’an Xianyang International Airport was conducted. The thermal environment was investigated through on-site measurements, questionnaires, and numerical simulations with CFD (computational fluid dynamics). It was found that supply air temperature and cooling surface temperature had a significant impact on PMV, and less impact on the cooling capacity. Therefore, it was determined that the supply air temperature should be altered first when the indoor temperature exceeds the upper limit, and then the cooling surface temperature should be changed if the indoor environment continues to overheat with the supply air temperature set to 18 °C. Thus, the supply air temperature was kept at 18 °C, and the floor surface temperature was set to be 22 °C on a high-temperature day. The average PMV was 0.87, and the cooling capacity of the combined system was 200 W/(m2·K), according to the CFD simulation. In addition, the surface heat transfer coefficient of the cooling floor was found to be 10.26 W/(m2·K). This research provides important references for the design and operational management of radiant cooling floors in large space buildings.

Thermal Environment Monitoring and Model Development of an Enclosed Vertical-Type Composting Facility

This study focused on the development of a scaled-down model for an enclosed vertical-type composting facility designed to efficiently manage space and odors. Through thermal environment monitoring, we observed that the temperature rose to 67 °C on the first day of composting and gradually decreased to 28.9 °C as the composting progressed. Temperature variations based on height were analyzed by dividing the facility into layers. The validation of the model was conducted by comparing actual measurements with model data using contour maps, resulting in a correlation coefficient (R2) of 0.8, indicating the high reliability of the model. The findings demonstrated the effectiveness of the model in identifying and addressing issues in enclosed vertical-type composting facilities. Furthermore, it is anticipated that the model, which analyzes thermal environments, can be applied to automated operation systems for enhanced efficiency.

Decoupling the multi-drivers of urban extreme heat environment in urban agglomerations using ensemble learning

Urban extreme heat (UEH) has been imparting a formidable menace to various facets of sustainable urban and regional development. While increasing studies have examined the urban thermal environment, a gap exists in decoupling the nonlinear multi-drivers of UEH environment in intra-urban regions, especially across the urban agglomerations. In this study, we estimated UEH through the land surface temperature (LST) in the extended summer season exceeding a specific threshold computed through cross-regional statistics. Furthermore, an additive interpretable ensemble learning model enhanced via the Bayesian Optimization algorithm (BO) and Monte Carlo Simulation framework (MCS) was employed to dissect the intricate nonlinear interplay between UEH and intra-urban morphology, green-blue composition, and atmospheric determinants. Our results highlight the indispensably suppressive effect of green and blue factors on UEH, whereas urban morphological variables generally exhibit an opposite trend. Interestingly, we reveal heterogeneity responses of building heights, elevated urban structures mitigate UEH in temperate monsoon and subtropical monsoon zones and exhibit diminished marginal utility in temperate continental zones. Furthermore, the arid climatic characteristics are expected to exert an unexpectedly enhancing effect on water bodies' cooling capacity. These findings provide heterogeneous local guidance for landscape and urban planning towards the severe challenges of climate change.

Understanding individual heat exposure through interdisciplinary research on thermoception

Extreme heat events are more frequent and more intense globally due to climate change. The urban environment is an additional factor enhancing the effects of heat. Adults above 65 years old are especially at risk due to their poorer health, physiology and socio-economic situation. Yet, there is limited knowledge about their experiences of summer heat, their actual heat exposure and how they negotiate their thermal comfort through different adaptation practices. In conventional research on heat exposure and thermal comfort, very little attention is given to individual behaviour and subjective experiences. To understand how older adults feel the heat in the city we study their thermoception, which we conceptualise as an embodied knowledge about bodily sensations, thermal environments and adjustments to heat. This article stems from interdisciplinary research conducted in Warsaw and Madrid in the summers of 2021–2022. We combine and juxtapose data from ethnographic research and from physical measurements of temperature gathered in people’s homes, to show on a microscale how we can study and understand the diversity in individual heat exposure more holistically. We demonstrate that to understand the consequences of heat for vulnerable populations it is crucial to study thermoception, the subjective experiences of heat, in addition to analysing their thermal environments. With the use of a unique methodology, this article shows how similar weather conditions are experienced differently by people from the same cities, depending on the materiality of their dwellings, availability of cooling devices, as well as everyday habits and their individual bodies. We discuss the social, material and temporal adjustments participants made to deal with heat, to showcase their agency in affecting their individual heat exposure. The article emphasises the role of social sciences and qualitative methods in research on individual heat exposure and argues for the co-production of knowledge on the topic.

Study on the Impact of Design Factors of Piloti Forms on the Thermal Environment in Residential Quarters

Study on the Impact of Design Factors of Piloti Forms on the Thermal Environment in Residential Quarters

Quantitative Study on the Effects of Street Geometries and Tree Configurations on the Outdoor Thermal Environment

Global warming and the urban heat island effect has aroused the attention of research on the outdoor thermal environment. As outdoor spaces often used by citizens, streets play an important role in improving the thermal environment. In this study, six factors relating to street geometries and tree configurations in Busan are measured and quantified to form 32 typical scenarios. The degree of importance of these six factors is evaluated based on ENVI-met simulation results, and GeoDetector is introduced to evaluate the interactions between the factors and their impacts on the outdoor thermal environment. This study confirms the significantly higher impact of street geometry factors on the air temperature and physiological equivalent temperature compared to tree configuration factors. Particularly, Hb/Ws shows the most significant impact during the research period. The impact of interactions between any two factors of street geometry is much higher than that of interactions between the geometry and tree configuration factors and that of interactions between the tree configuration factors. We recommend dynamically adjusting the relationship between street geometry and tree configurations in different situations to improve the outdoor thermal environment, especially at noon and in the afternoon.

Research on Summer Indoor Air Conditioning Design Parameters in Haikou City: A Field Study of Indoor Thermal Perception and Comfort

Escalating global climate change and the intensification of urban heatwaves have led to an increase in summer air conditioning cooling energy consumption. This phenomenon is particularly critical in tropical regions, as it may trigger an energy crisis. The rational setting of indoor thermal design parameters can help conserve energy to the maximum extent while ensuring thermal comfort for occupants. This study selected Haikou City, a unique tropical city in China, as the research location. Indoor environment measurements and a questionnaire survey were conducted with participants, and the outdoor thermal environment sensitivity, population attributes and differences in thermal sensation, thermal neutral temperature, and comfort range were calculated and analyzed. The following results were obtained. Based on the overall population, long-term residence, and temporary residence classification, the indoor thermal comfort needs of residents in tropical cities in Haikou were effectively identified. The actual thermal neutral temperature of the overall population is 25.7 °C, and 90% of the acceptable thermal comfort temperature range is 23.2 °C–28.0 °C. The actual thermal neutral temperature of the regular residents is 27.3 °C, and 90% of the acceptable thermal comfort temperature range is 23.3 °C–31.4 °C. The actual thermal neutral temperature of the temporary population is 25.5 °C, and 90% of the acceptable thermal comfort temperature range is 23.0 °C–28.0 °C. These research results have an important reference value for improving the setting of the temperature of air conditioning in tropical areas in summer and further reducing energy consumption, which is conducive to sustainable development.

Bending analysis of functionally graded plates under mechanical and thermal environment using non-polynomial shear deformation theory

Bending analysis of functionally graded plates under mechanical and thermal environment using non-polynomial shear deformation theory

Efficiency Assessment on Roof Geometry and Trombe Wall Shape for Improving Buildings’ Heating Performance

It is crucial to consider structural design issues in Trombe wall (T-wall) buildings to promote more suitable indoor climates and thermal comfort standards. Therefore, the present study examined the impact of two different T-wall designs and six different roof types on the energy and operational efficiency of a building located in a low-temperature and high-humidity winter climate. Ansys-CFX 15.0 software was employed to simulate the thermal and fluid dynamics behavior of the T-wall system, and flow, thermal comfort, energy, and exergy analyses were conducted. Three-dimensional simulation results and the pertinent literature data showed a good level of agreement, and the accuracy of the model was ensured. Outcomes revealed an average air velocity variation of 0.186 m/s and maximum average indoor air temperature variation of 3.3 °C between the six roof geometries. The highest air speed (0.988 m/s) was recorded for the gambrel roof while the lowest one (0.802 m/s) was recorded for the typical flat roof. The shed roof right with a rounded T-wall was more comfortable for standing and sitting activity than the others for the two T-wall shapes, and, at Y = 0.6 m and Y = 1.1 m, the average predicted percentages of dissatisfied (PPD) values were 31 and 28%, respectively. Furthermore, it was determined in the study that solar radiation intensity and T-wall and roof geometries had a significant effect on energy and exergy efficiency, and high energy and exergy efficiencies were achieved at higher solar intensity values. The best energy and exergy efficiencies were obtained for the butterfly and shed roof configurations. This study can serve as a reference for the thermal environment design of buildings with T-walls.

Thermal response and performance evaluation of floor radiant heating system based on fuzzy logic control

The floor radiant heating system is widely used in various buildings due to its advantages such as high efficiency, comfort, and uniform heating. Generally, research on floor radiant heating systems focuses on energy saving, but the issue of slow thermal response during the heating process has not been solved. To solve the problem of slow thermal response and uneven indoor thermal environment in floor radiant heating systems, a fuzzy logic control theory based on optimal fuzzy rules was proposed. The floor radiant heating system based on fuzzy logic control was established by the TRNSYS-MATLAB integrated control platform. The study compared the thermal response and thermal comfort performance of PID control, fuzzy logic control, and optimized fuzzy control methods. The results showed that fuzzy logic control performed better than PID control in controlling the system's thermal performance and indoor thermal environment. Compared to PID control, the optimized fuzzy control reduced the thermal response time by 64.60%, and the total energy consumption of the water pump and heat pump decreased by 222 kWh and 329 kWh, respectively. The proposed fuzzy logic control demonstrates favorable thermal response characteristics and holds substantial potential for energy conservation within the increasingly prevalent floor radiant heating systems.

Morphological spatial clustering of high-density central areas and their coupling relationship with thermal environment--a case study of the wuyi road hatchback in changsha.

Intense urban development and high urban density cause the thermal environment in urban centers to deteriorate continuously, affecting the quality of the living environment. In this study, 707.49 hectares of land in the central area of Changsha were divided into 121 plots. 11 microclimate-related morphological indicators were comprehensively selected, and the K-means method was used for cluster analysis. Then, the relationship between morphological clusters and the thermal environment was explored by simulating the thermal environment of the study area with ENVI-met. First, five spatial types were found to characterize the area: high-level with high floor area ratio, low density, and low greenery; middle-level with high floor area ratio high density; medium-capacity with high density and small volume; low-level with low density and high greenery; and low floor area ratio, low density, and high greenery. Second, the building windward surface density, sky openness, building density, floor area ratio and green space rate affect the thermal environment. Third, Cluster3 had the highest average air temperature (Ta), followed by Cluster5, furthermore Clusters4, 1, and2 had relatively low Ta. The spatial vitality index and green space rate in Cluster1; the area-weighted building shape index, average building volume and sky openness in Cluster2; green space rate in Cluster3; indicators such as the floor area ratio and green space rate in Cluster4; indicators such as the impervious surface rate and green space rate in Cluster5 had greater influences on Ta. Fourthly, simply increasing the area of green space cannot maximize the cooling effect of green spaces. Instead, constructing an equalized greening network can better regulate the thermal environment. Fifthly, the results provide a scientific basis for the design and the regulation of urban centers.

Experimental Study on Thermal Environment and Thermal Comfort of Passenger Compartment in Winter with Personal Comfort System

The combined heating method of seat heating and air conditioning (A/C) was applied in the passenger compartment under different experiment conditions, using thermocouples to continuously measure the wall surfaces and air temperatures in the passenger compartment and the passengers’ skin temperatures of 17 segments. Meanwhile, a subjective evaluation questionnaire survey was conducted using a nine-point evaluation scale on the local and overall thermal sensation and thermal comfort of the passengers, and the data from the questionnaire were analyzed with the ANOVA method. The results showed that the use of the heating pad directly affected the changes in human skin temperature, which in turn affected the local and overall thermal sensation and thermal comfort. For the two thermally stimulated segments of the back and under the thighs, the skin temperature of the back was higher than that of the thighs. Using the heating pad resulted in a rapid increase in the mean skin temperature in the early period of the experiment. Thermal sensation of the back and under-thighs shifted rapidly towards the hot zone in the first 10 min, and then settled around +3, with even more significant differences between the groups. Thermal sensations in non-thermally stimulated segments changed in relation to their position on the heating pad, with slower changes in those at the “distal” end of the body, the head and the feet. Continued use of the heating pads at lower ambient temperatures maintained overall thermal comfort at a neutral level in the range of 0–1, whereas at higher ambient temperatures there was a gradual deterioration of local and overall thermal comfort.

Thermal plasticity has higher fitness costs among thermally tolerant genotypes of Tigriopus californicus

Abstract Under climate change, ectotherms will likely face pressure to adapt to novel thermal environments by increasing their upper thermal tolerance and its plasticity, a measure of thermal acclimation. Ectotherm populations with high thermal tolerance are often less thermally plastic, a trade‐off hypothesized to result from (i) a phenotypic limit on thermal tolerance above which plasticity cannot further increase the trait, (ii) negative genetic correlation or (iii) fitness trade‐offs between the two traits. Whether each hypothesis causes negative associations between thermal tolerance and plasticity has implications for the evolution of each trait. We empirically tested the limit and trade‐off hypotheses by leveraging the experimental tractability and thermal biology of the intertidal copepod Tigriopus californicus. Using populations from four latitudinally distributed sites in coastal California, six lines per population were reared under a laboratory common garden for two generations. Ninety‐six full sibling replicates (n = 4–5 per line) from a third generation were developmentally conditioned to 21.5 and 16.5°C until adulthood. We then measured the upper thermal tolerance and fecundity of sibships at each temperature. We detected a significant trade‐off in fecundity, a fitness corollary, between baseline thermal tolerance and its plasticity. Tigriopus californicus populations and genotypes with higher thermal tolerance were less thermally plastic. We detected negative directional selection on thermal plasticity under ambient temperature evidenced by reduced fecundity. These fitness costs of plasticity were significantly higher among thermally tolerant genotypes, consistent with the trade‐off hypothesis. This trade‐off was evident under ambient conditions, but not high temperature. Observed thermal plasticity and fecundity were best explained by a model incorporating both the limit and trade‐off hypotheses rather than models with parameters associated with one hypothesis. Effects of population and family on tolerance and plasticity negatively covaried, suggesting that a negative genetic correlation could not be ruled as contributing to negative associations between the traits. Our study provides a novel empirical test of the fitness trade‐off hypothesis that leverages a strong inference approach. We discuss our results' insights into how thermal adaptation may be constrained by physiological limits, genetic correlations, and fitness trade‐offs between thermal tolerance and its plasticity. Read the free Plain Language Summary for this article on the Journal blog.

An experimental study on differences in aesthetic experience according to thermal environments

Over an extended period, the art museum prioritized regulating its thermal environment solely for the preservation of artworks, without considering the visitors' aesthetic experience. However, it is no longer an exception, given the ongoing development of HVAC systems. This research aims to investigate how museums' thermal environment and the resulting thermal comfort impact visitors' aesthetic experience. The experiment was performed to examine the subjects' aesthetic experience under three temperature conditions: 18 °C, 26 °C, and 32 °C. Subjects experienced VR museum exhibition, and their physiological responses, heart rates and variability were measured. Psychological responses were gathered through thermal comfort votes, and Aesthetic Experience Questionnaire (AEQ). As a result, the thermal comfort votes were highest in the order of 26 °C, 18 °C, and 32 °C. Aesthetic experience responses, measured by AEQ, were highest at 26 °C and lowest at 32 °C. This suggests that subjects enhanced aesthetic experiences in a thermally comfortable environment, while high temperature hindered them. Beyond temperature, factors like thermal sensation and comfort were considered influential in aesthetic experiences. Thermal sensation was found to impact aesthetic experiences in a quadratic manner, and thermal comfort had a positive effect on them. Lastly, physiological responses previously associated with aesthetic experiences showed no significant impact in this study. Only thermal sensation demonstrated a significant influence, attributed to thermoregulation responding to thermal environment changes. In other words, when the thermal environment changes, the physiological response can't reliably indicate aesthetic experiences due to the thermoregulation. This study is significant in proposing unexplored aspects of thermal environments in enhancing aesthetic experiences.

The effect of synthetic grass sports surfaces on the thermal environment: A systematic review.

There are concerns regarding high surface temperatures on synthetic grass sports surfaces influencing the surrounding thermal environment, potentially increasing heat stress and impacting athlete safety. As such, studies have investigated changes to the thermal environment surrounding synthetic grass surfaces in comparison to both natural grass, and synthetic surfaces with different features, but this body of research has not been systematically reviewed. Therefore, this systematic review aimed to (i) determine if there are differences in the thermal environment surrounding synthetic grass surfaces compared with natural grass surfaces, and (ii) determine if there are differences in the thermal environment between different types of synthetic grass surfaces. A systematic review adhering to the PRISMA guidelines was performed. The eligibility criteria required investigations to report at least one of the following environmental parameters on or directly above both a synthetic surface and a comparator group of either natural grass or an alternative synthetic grass surface used in sport: Air temperature, mean radiant temperature, humidity, wind velocity, unified heat stress indices (i.e. wet-bulb-globe temperature and heat index) and/or surface temperature. Twenty-three studies were identified. The only parameters that were consistently higher on synthetic grass compared to natural grass were the air temperature (range: 0.5-1.2 °C) and surface temperature (range: 9.4-33.7 °C), while the mean radiant temperature, humidity, wind velocity and wet-bulb-globe temperature remained similar or required more data to determine if any differences exist. Synthetic grass surfaces consisting of styrene butadiene rubber infill or a shock pad had increased surface temperatures, whereas surfaces with thermoplastic elastomer infill, Cool climate turf fibres or HydroChill had lower surface temperatures. This systematic review has demonstrated that air and surface temperatures can be increased on synthetic sports surfaces, compared to natural grass surfaces. However, it is uncertain whether the differences are enough to increase an individual's heat stress risk and cause concern for athlete safety. While modifications to the turf infill or fibres can reduce synthetic surface temperatures, the effect of these features on the thermal environment as a whole is unclear. This review was prospectively registered with the Open Science Framework (Open Science Framework registration https://doi.org/10.17605/OSF.IO/BTKGE ).