Organic Brick

Clay is one of the earliest known material used in construction, and the most widely used building material on the planet. Our ancestors have performed the tasks of mixing water with dust to make clay, then shaping it into bricks, bricks into buildings, and buildings into cities for more than ten thousand years. In recent years, 3D printing technology has become increasingly popular thanks to its ability to manufacture complex morphologies and to optimize physical and mechanical properties for specific applications. This study investigates customized 3D clay bricks as a new building material (building component) by employing resources that are eco-friendly, locally available, inexpensive, and driven from recycled sources or waste streams. In this experiment, four different fiber types have been investigated with different clay treatment. The specimens were fabricated in the laboratory and tested with unconfined compression loading. The strength and ductility of the clay specimens were then analyzed based on the experiment results. Several experiments have been conducted during the study for understanding the effects of different fibers when mixed with clay in order to identify which type of fibers and which size has the most effective influence on its compression strength. Furthermore, it has been tested also the water absorption of the 3D printed brick. A case study has been developed to show the actual potential of 3D printed clay bricks for a small housing complex. The project is located in a village near to Abuja, Nigeria, at a time of exponential population increase and associated lack of affordable housing. The 3D printed blocks embed a cooling function, thanks to their geometry and the presence of cooling pipes directly in the wall. The result is a highly flexible envelope, designed to be resilient and energy efficient.

Nonrelativistic Electron–Ion Bremsstrahlung: An Approximate Formula for All Parameters

The evaluation of the electron–ion bremsstrahlung cross section—exact to all orders in the Coulomb potential—is computationally expensive due to the appearance of hypergeometric functions. Therefore, tabulations are widely used. Here, we provide an approximate formula for the nonrelativistic dipole process valid for all applicable relative velocities and photon energies. Its validity spans from the Born to the classical regime and from soft-photon emission to the kinematic endpoint. The error remains below 3% (and widely below 1%) except at an isolated region of hard-photon emission at the quantum-to-classical crossover. We use the formula to obtain the thermally averaged emission spectrum and cooling function in a Maxwellian plasma and demonstrate that they are accurate to better than 2%.

Cooling and instabilities in colliding flows

Collisional self-interactions occurring in protostellar jets give rise to strong shocks, the structure of which can be affected by radiative cooling within the flow. To study such colliding flows, we use the AstroBEAR AMR code to conduct hydrodynamic simulations in both one and three dimensions with a power law cooling function. The characteristic length and time scales for cooling are temperature dependent and thus may vary as shocked gas cools. When the cooling length decreases sufficiently rapidly the system becomes unstable to the radiative shock instability, which produces oscillations in the position of the shock front; these oscillations can be seen in both the one and three dimensional cases. Our simulations show no evidence of the density clumping characteristic of a thermal instability, even when the cooling function meets the expected criteria. In the three-dimensional case, the nonlinear thin shell instability (NTSI) is found to dominate when the cooling length is sufficiently small. When the flows are subjected to the radiative shock instability, oscillations in the size of the cooling region allow NTSI to occur at larger cooling lengths, though larger cooling lengths delay the onset of NTSI by increasing the oscillation period.

A Comparative Analysis of Thermoelectric Modules for the Purpose of Ensuring Thermal Comfort in Protective Clothing

In recent times, more and more workers are exposed to thermal stress due to climate changes and increased ambient temperature. Demanding physical activities and the use of protective clothing are additional sources of thermal load for workers. Therefore, recent research has focused on the development of protective clothing with a cooling function. Phase change materials, air or liquid, were mainly used for this purpose; only a few publications were concerned the use of thermoelectric modules. This publication analyzes the influence of such factors as supplied current, ambient temperature, and the type of heat sink on the amount of heat flux transferred by a thermoelectric cooler (TEC) and the electric power consumed by it. In the course of laboratory tests, a flexible thermoelectric module and three heat sink variants were tested. For this purpose, a polymer TEGway heat sink, a metal one, and a self-made one based on a superabsorbent were used. The research showed that at a temperature of 30 °C and above, the amount of the heat flux transferred by a TEC with a total area of 58 cm2, and an active area of 10 cm2 should be expected to be from 1 W to 1.5 W. An increase in ambient temperature from 20 to 35 °C caused a significant reduction in the heat flux by about 1 W. The results obtained indicated that the type of heat sink affects the heat flux drawn by the TEC to a statistically significant extent. The heat sink using the evaporation effect turned out to be the most efficient.

Thermal Analysis of Heating–Cooling Mat of Textile Incubator for Infants

On the medical device market there are several types of stationary and portable incubators that can be used in the care of infants. The prototype of a textile incubator made as part of this work consists of five material layers. The textile incubator is equipped with a functional heating and cooling mat, which is made on the basis of 3D channeled weft-knitted fabric. Its function is to generate heat and maintain it inside the textile incubator or to cool the baby's body while using therapeutic hypothermia. The mat is equipped with hoses transporting the heating or cooling medium. The mat, depending on variable input parameters, can emit heat in the range from 1.15 W to 86.88 W. In case of the cooling function, it can receive heat in the range from −4.32 to −27.96 W. This indicates a large adjustment range of the amount of heat supplied and received, which is a positive feature, and enables programming the heat balance to ensure comfort for the baby. The analysis of temperature measurements on the mat surface confirmed that maximum temperature differences do not exceed 1.6°C.

Shatter or not: role of temperature and metallicity in the evolution of thermal instability

ABSTRACT We test how metallicity variation (a background gradient and fluctuations) affects the physics of local thermal instability using analytical calculations and idealized, high-resolution 1D hydrodynamic simulations. Although the cooling function (Λ[T, Z]) and the cooling time (tcool) depend on gas temperature and metallicity, we find that the growth rate of thermal instability is explicitly dependent only on the derivative of the cooling function relative to temperature (∂ln Λ/∂ln T) and not on the metallicity derivative (∂ln Λ/∂ln Z). For most of 104 K ≲ T ≲ 107 K, both the isobaric and isochoric modes (occurring at scales smaller and larger than the sonic length covered in a cooling time [cstcool], respectively) grow linearly, and at higher temperatures (≳107 K) the isochoric modes are stable. We show that even the non-linear evolution depends on whether the isochoric modes are linearly stable or unstable. For the stable isochoric modes, we observe the growth of small-scale isobaric modes but this is distinct from the non-linear fragmentation of a dense cooling region. For unstable isochoric perturbations we do not observe large density perturbations at small scales. While very small clouds (∼min[cstcool]) form in the transient state of non-linear evolution of the stable isochoric thermal instability, most of them merge eventually.

Experimental Study of Thermal Comfort Based on Driver Physiological Signals in Cooling Mode under Summer Conditions

In this study, electroencephalogram (EEG), photo-plethysmography (PPG), and surface temperature measurements of subjects were taken while performing a driving simulation when the cabin and vent discharge air temperature in summer were changed from discomfort to comfort conditions. Additionally, subjective questionnaires were used to analyze the subject’s thermal comfort under the various driving environments. As a result, the surface temperatures of the forehead, left hand, right hand, and abdomen of the subject during driving were reduced by 2, 0.97, 2.18, and 5.86 °C, respectively, by operating a 12.5 °C vent cooling function at a cabin temperature of 35 °C. As a comprehensive analysis of the subjective survey, PPG, and EEG results, total power (TP), the standard deviation of N-N interval (SDNN), and the root mean square of successive differences (RMSSD) of subjects increased and stress index decreased at cabin and vent discharge air temperatures of 30–27.5 °C and 16.5–18.5 °C, respectively. Furthermore, the relative sensory motor rhythm (SMR) wave and concentration index (CI) of the frontal lobe tended to increase under the same temperature conditions. Accordingly, it was confirmed that these temperature conditions provided a pleasant driving environment for the driver and increased concentration on driving.

INFLUENCE OF THE EFFECT OF THE URBAN HEAT ISLAND ON THE CITIES SUSTAINABLE DEVELOPMENT

The result of the action of the urban heat island on the layout of the city of Hanoi is considered. It is stated that the formation and development of sustainable urban development creates optimal conditions for the life and work of citizens, is a guarantee of safety and comfortable living, and guards the natural environment. In a scientifi c study, such a remote sensing method was used as a means of analyzing the surface temperature in a city with environmental problems due to the eff ect of the “urban heat island” (UHI. The analysis was performed using satellite images Landsat-5, Landsat-7, Landsat-8. This study confi rmed the existence of the urban heat island eff ect in the center of Hanoi and examined the role of city confi guration on a macro scale. The effi ciency of using green spaces on the roofs of megacities is estimated. It is emphasized that thanks to the transpiration process, green spaces contribute to reducing the negative eff ects of UHI and gas contamination. It is established that the use in the city’s architecture of light surfaces of buildings and planes (roads, sidewalks, platforms) favorably aff ects the mesoclimate, performing the cooling function. At the macro level, the orderly introduction of green spaces in large cities helps to resolve serious environmental problems such as global warming and the greenhouse eff ect.

Effect of knitting structure and yarn composition on thermal comfort properties of bi-layer knitted fabrics

In this work, nine bi-layer knitted samples with varied knitting structures and made up of different yarn compositions were fabricated, and their thermal comfort properties were investigated. The thermal comfort properties were evaluated by breathability, water transfer properties, thermo-physiology properties and dynamic cooling properties, and their relationship with fabric knitting structure and yarn composition were investigated statistically. It was observed that bi-layer knitted fabrics with meshes at one side had better air permeability, moisture management properties, drying performance, thermo-physiological properties and dynamic cooling function, but lower wicking height than bi-layer knitted fabrics with trim and symmetrical structure (without meshes). The composition of nylon and polyester filaments with varied wettability as outer and inners layer of bi-layer knitted fabrics, respectively, improved the water one-way transport capacity significantly. In particular, bi-layer fabrics with asymmetric structure and made up of yarns with varied hydrophilicity as each layer have excellent moisture management capacity. Moreover, fabrics made up of yarns with finer fibers exhibited better thermal comfort properties.