Preferred temperature with standing and treadmill workstations

Prolonged sedentary behavior has been shown to increase chronic diseases. Using standing and treadmill desk reduces sitting time, increases metabolic rate and thus has potential to improve health. There is little existing guidance on how to keep thermal comfort when using standing and treadmill desk. It is unknown what are the suitable ambient temperatures for occupants at elevated office activity levels. This experiment investigated thermal sensation and preferred temperature at elevated office activity levels, including sitting (SED), standing (STD), and two slow-walk speeds: walking at 1.2 km/h (TRD1) and walking at 2.4 km/h (TRD2). Comfort votes were obtained from 20 subjects under personal controlled ambient temperature. The active workstation significantly increased human metabolic level and reduced preferred temperature. The measured metabolic rates were 1.0, 1.1, 1.9 and 2.5 met for SED, STD, TRD 1 and TRD 2. The preferred ambient temperature reduced from 25.85 °C for SED, to 25.0, 24.1 and 23.2 °C for STD, TRD 1 and TRD 2 respectively. All subjects were comfortable at their preferred temperatures. PMV model was found to predict too cool temperature than needed for higher metabolic rates

Preferred temperature with standing and treadmill workstations

Prolonged sedentary behavior has been shown to increase chronic diseases. Using standing and treadmill desk reduces sitting time, increases metabolic rate and thus has potential to improve health. There is little existing guidance on how to keep thermal comfort when using standing and treadmill desk. It is unknown what are the suitable ambient temperatures for occupants at elevated office activity levels. This experiment investigated thermal sensation and preferred temperature at elevated office activity levels, including sitting (SED), standing (STD), and two slow-walk speeds: walking at 1.2 km/h (TRD1) and walking at 2.4 km/h (TRD2). Comfort votes were obtained from 20 subjects under personal controlled ambient temperature. The active workstation significantly increased human metabolic level and reduced preferred temperature. The measured metabolic rates were 1.0, 1.1, 1.9 and 2.5 met for SED, STD, TRD 1 and TRD 2. The preferred ambient temperature reduced from 25.85 °C for SED, to 25.0, 24.1 and 23.2 °C for STD, TRD 1 and TRD 2 respectively. All subjects were comfortable at their preferred temperatures. PMV model was found to predict too cool temperature than needed for higher metabolic rates

Field study on human thermal comfort and indoor air quality in university dormitory buildings

Field studies on the environmental conditions and occupant thermal comfort were carried in air-conditioned buildings and no air-conditioned building in Xi’an, China. The present study aimed to explore the effect of indoor thermal history on the thermal adaptation and indoor air quality of occupants. Based on a field study, 550 and 580 data sets were obtained in naturally ventilated (NV) and spilled air-conditioned dormitory buildings (SAC), respectively. The physical environment parameters and subjective responses were explored. Most of the environment in NV mode were warmer than the current standard upper limit (28 °C). The neutral temperature of the NV group was 26.7 °C, 1.5 higher than that of the SAC group (24.6 °C). The upper limit of 80% acceptable temperature range was 29.2 °C for the NV group, 1.7 °C higher than that of the SAC group (27.5 °C). Compared to the SAC group, a warm indoor thermal history of the NV group produced a shift to higher neutral temperature and higher acceptable temperature. Differences were found in the indoor environment quality and in the occupant’s subjective satisfaction between the two groups. Compared to PMV model, the adaptive model was more applicable to spilt air-conditioned building

Experimental Research on Cavitation Evolution and Movement Characteristics of the Projectile during Vertical Launching

Aiming at the problem of unsteady cavitation during a projectile’s vertical water-exit process, scaled model experiments were carried out based on the self-designed underwater launch platform and high-speed cameras, which focus on changes in cavitation shape and projectile posture. In this paper, the general process of the cavitation evolution and projectile’s movement is described; the relationship between the re-entry jet, local cavitation number and cavitation stability is discussed. Meanwhile, the effect of head forms and launch speeds on the cavitation evolution and movement characteristics is analyzed, including 60° cone, 90° cone and hemispherical head with velocity of 16.8 m/s, 18.5 m/s and 20.0 m/s, whose launch cavitation number is 0.714, 0.589 and 0.504. The results show that the attached cavities fall off from the bottom up under the influence of the end-re-entry jet and the shedding frequency declines when the launch cavitation number decreases. The cavitation growth of 60° cone is easily disturbed by the air mass near the launcher, the cavitation development of 90° cone is characterized by small-scale and high-frequency growth and shedding, while the hemispherical head is not prone to cavitation. Moreover, increasing the speed can improve the stability of cavitation development and the projectile’s movement

Carbon dioxide generation rates and subjects’ perception of air quality of office activities under various ambient temperatures

Indoor carbon dioxide (CO2) concentration is an important parameter that has been used to characterize and design indoor air quality and building ventilation. In indoor spaces, the primary source of CO2 is occupants, and the rate is always related to occupants’ activities intensity. However, the CO2 generation rates required by many applications were currently calculated by metabolic rates using equations given in the ASHRAE Handbook, which were based on the average of adults from Europe and North America that are several decades old. In addition, the ambient temperatures may also affect CO2 generation rates by affecting human metabolic reactions but were not considered. There is little systematic experimental determination of human CO2 generation rates at different activity levels and various ambient temperatures. This study experimentally determines Chinese office people’s CO2 generation rates by 28 college students (14 women and 14 men) aged 20~30, while conducting office tasks (sitting and typing, standing and typing, walking at 1 km/h, and walking at 2 km/h) at 20, 23, 26, and 29 ℃. CO2 generation rates increase significantly as activity levels increase, and slightly increased with increasing ambient temperature. With activity intensity increases, the gender and temperature differences also grow

Experimental Research on Cavitation Evolution and Movement Characteristics of the Projectile during Vertical Launching

Aiming at the problem of unsteady cavitation during a projectile’s vertical water-exit process, scaled model experiments were carried out based on the self-designed underwater launch platform and high-speed cameras, which focus on changes in cavitation shape and projectile posture. In this paper, the general process of the cavitation evolution and projectile’s movement is described; the relationship between the re-entry jet, local cavitation number and cavitation stability is discussed. Meanwhile, the effect of head forms and launch speeds on the cavitation evolution and movement characteristics is analyzed, including 60° cone, 90° cone and hemispherical head with velocity of 16.8 m/s, 18.5 m/s and 20.0 m/s, whose launch cavitation number is 0.714, 0.589 and 0.504. The results show that the attached cavities fall off from the bottom up under the influence of the end-re-entry jet and the shedding frequency declines when the launch cavitation number decreases. The cavitation growth of 60° cone is easily disturbed by the air mass near the launcher, the cavitation development of 90° cone is characterized by small-scale and high-frequency growth and shedding, while the hemispherical head is not prone to cavitation. Moreover, increasing the speed can improve the stability of cavitation development and the projectile’s movement

Field Study of thermal comfort of indoor fitness places in cold region

A healthy body is the foundation of everything. The indoor environment comfort of fitness places has been paid more and more attention. However, there is a lack of relevant standards for the thermal environment of indoor sports and fitness venues in China, especially the research on the indoor thermal environment in different seasons. Therefore, in our study, physical environment parameters such as indoor temperature and humidity, black ball temperature, air flow rate and CO2 concentration in 9 indoor fitness places in Xi ‘an in different seasons were measured on site. At the same time, a subjective questionnaire survey was conducted on thermal sensation and acceptability of the people who were exercising in the fitness places. Through subjective questionnaire analysis, respondents generally have a high degree of satisfaction and acceptance of temperature, and the average thermal comfort vote is the highest when the indoor temperature is 17.9-23.9°C. In addition, the thermal comfort of different sports in the same space also has certain differences. The fitness people indoor have lower satisfaction with air flow and air quality. Based on the study of the factors affecting indoor thermal comfort, this paper puts forward the improvement strategies for improving indoor thermal comfort, and provides scientific basis for the design and operation of fitness venues

Aeolian sand cover affects the soil hydrothermal state and permafrost degradation on the Qinghai-Tibet Plateau

Aeolian sand significantly affects permafrost degradation, but the effect of the aeolian sand on the permafrost on the Qinghai-Tibet Plateau remains unknown. The sand layer thickness is critical to its role. However, little quantitative research has been conducted on the effect of the sand layer thickness on its role. In this study, using CoupModel, we investigated the differences in the impact of the aeolian sand cover on the hydrothermal state of permafrost with 20 different sand layer thicknesses (10 ∼ 200 cm, 10 cm increment) and analyzed the mechanisms that explain the different impacts. The results reveal that the active layer is where the aeolian sand has the most impact on the permafrost. The aeolian sand layer accumulates precipitation into the soil below the sand, thereby significantly drying the shallow soil layer of the current stratum. Moreover, the thicker the sand layer, the more water accumulates in the underlying soil layer. In the middle-upper active layer, the initial soil heat storage, soil heat flow interception, and liquid water and ice contents govern the soil temperatures that increase in cold seasons and decrease in warm seasons as the sand layer thickens. Near the bottom of the active layer, the initial soil heat storage and soil heat flow interception control the soil temperatures that increase in cold seasons but fluctuate between sand layer thicknesses of 50 cm, 70 cm, and 120 cm in warm seasons as the sand layer thickens. Permafrost degradation is enhanced by sand layers thinner than 150 cm and retarded by sand layers thicker than 150 cm, respectively. The thermal state, soil properties, and accumulation process of the aeolian sand also contribute to this effect of the aeolian sand on the permafrost. In the plateau aeolian deserts, the sparse vegetation promotes permafrost degradation and the thinner seasonal snow cover protects permafrost. Moreover, under the different climate during the geological history period, the island or discontinuous permafrost might be formed due to the pluvial-radiation talik caused by the thicker sand layer or dunes

Research on the properties of peat soil and foundation treatment technology

In the infrastructure construction of my country and the countries along the “Belt and Road”, there are many projects involving peat soil foundation treatment, but there is a lack of in-depth research on the properties of peat soil and foundation treatment technology, and there is no complete set of relevant foundation treatment technical specification systems. However, the traditional replacement method for ground treatment characteristics cannot meet the needs of energy saving, environmental protection and green development concepts. This article adopts the method of literature research, taking Sri Lanka (CKE project) as an example to introduce the engineering foundation treatment technology of peat soil in detail, and provide a reference for the construction and treatment of peat soil foundation. How to realize the technical problem of peat soil-based treatment needs to be solved urgently, so the understanding of peat soil requirements is beneficial in the long term

The Chinese thermal comfort dataset

Abstract Heating and cooling in buildings accounts for over 20% of total energy consumption in China. Therefore, it is essential to understand the thermal requirements of building occupants when establishing building energy codes that would save energy while maintaining occupants’ thermal comfort. This paper introduces the Chinese thermal comfort dataset, established by seven participating institutions under the leadership of Xi’an University of Architecture and Technology. The dataset comprises 41,977 sets of data collected from 49 cities across five climate zones in China over the past two decades. The raw data underwent careful quality control procedure, including systematic organization, to ensure its reliability. Each dataset contains environmental parameters, occupants’ subjective responses, building information, and personal information. The dataset has been instrumental in the development of indoor thermal environment evaluation standards and energy codes in China. It can also have broader applications, such as contributing to the international thermal comfort dataset, modeling thermal comfort and adaptive behaviors, investigating regional differences in indoor thermal conditions, and examining occupants’ thermal comfort responses