Low Atmospheric Pressure Conditions Research Articles

Experimental investigation of flow characteristics of a jet in low atmospheric pressure conditions on the Tibetan Plateau

The indoor humidity of heated buildings on the Tibetan Plateau can be as low as 5%RH. Indoor air humidification is very important to people's life and health. Due to the low atmospheric pressure on the plateau, the air physical parameters and wet component diffusion characteristics are different from those of standard atmospheric pressure. This paper investigates experimentally the effects of horizontal and vertical wet jets with various initial velocities, pipe diameters, ambient temperatures, and moisture temperatures on the indoor temperature and humidity field. It is shown that low atmospheric pressure will lead to an increase in relative humidity nearly the jet outlet, but the effective moisture delivery distance becomes shorter and the actual moisture load increases. When the same relative humidity is reached, the specific humidity under low atmospheric pressure is about 1.5–2.5 times as that under standard atmospheric pressure. The average relative humidity of jets produced by the ultrasonic humidification source is 10% higher than the evaporative humidification source during the same time. During the actual humidification process, it is necessary to consider the balance between the initial velocity of the jet and the humidification distance and select the jet tube diameter according to the humidification space area. Additionally, choosing a jet with a temperature slightly higher than the ambient temperature can avoid reducing the indoor temperature. This study should be helpful to the plateau humidification jet characteristics and parameter selection.

Modification and verification of the PMV model to improve thermal comfort prediction at low pressure

The human body's thermal physiology changes due to atmospheric pressure, which significantly impacts the perception of thermal comfort. To quantify this effect, an improved version of the Predicted Mean Vote model (PMVp), was developed in this study to predict human thermal sensation under low atmospheric pressure conditions. The study employed environmental conditions of 0km/26°C, 3km/26°C, 4km/26°C, and 4km/21°C. Thirteen subjects were continuously monitored for exhaled CO2, inhaled O2, ambient temperature (ta), relative humidity (RH), air velocity (V), black globe temperature (tg), and altitude (H). The predictive performance of PMVp was evaluated by comparing the experimental results from this study with previous experiments. The findings demonstrate that PMVp exhibits lower root-mean-square errors (RMSE) than the original PMV model. Under the four experimental conditions, the RMSE values for PMVp were 0.311, 0.408, 0.123, and 0.375, while those for PMV were 1.251, 1.367, 1.106, and 1.716, respectively. Specifically, at a temperature range of 21∼27°C (altitude: 941m), the RMSE of PMVp (0.354) was smaller than PMV's. Furthermore, the study analyzed the sensitivity of PMVp to input parameters at an altitude of 4 km. PMVp exhibited considerable sensitivity to the metabolic rate (M) and thermal insulation of clothing (ICL). Consequently, a simple sensitivity scale was established: M>ICL>Ta≈V>Tr>H≈RH, indicating the relative importance of these parameters in influencing PMVp's response. The research findings provide comprehensive knowledge and a useful reference for developing a standard to design and evaluate indoor thermal environments in the plateau region.

Numerical analysis of the diffusion and explosion characteristics of hydrogen-air clouds in a plateau hydrogen refuelling station

The investigation of hydrogen diffusion and explosion characteristics after accidental hydrogen leaks in hydrogen refuelling stations can provide the theoretical reference of the safe application of hydrogen refuelling stations. The numerical study analyses the effects of plateau environment on the dispersion and explosion characteristics of combustible clouds, visualises the diffusion and explosion process of hydrogen-air combustible clouds and quantifies the hydrogen concentration and explosion pressure at monitoring points. Results show that combustible clouds may appear upstream of the leak hole due to the presence of obstacles. The low atmospheric pressure conditions in the plateau areas result in high hydrogen concentration near the blast wall and large combustible cloud size. The hydrogen concentration near the blast wall and combustible cloud volume are also shown a positive correlation with air temperature, which will be detrimental to fire protection in hydrogen refuelling stations. After the explosion of the hydrogen clouds, the mortality zone (explosion overpressure ≥0.69 bar) is observed near the blast wall and at high leak volumes, the hazardous zone (0.07 bar ≤ explosion overpressure ≤0.69 bar) may spread over the blast wall into the crowded area. However, the blast wall blocks the development of the high-temperature zone, which has a positive effect on preventing the spread of the explosion flame. An examination of the pressure monitoring point data reveals that there appears to be an opposite effect of atmospheric pressure on the positive and reverse overpressure. The maximum peak blast overpressure in calculated domain indicates that both higher air temperatures and atmospheric pressures promote the growth of explosion overpressure.

Вплив блокування м1-холінорецепторів асоціативної кори дорослих щурів на автономну регуляцію серцевого ритму при гіпоксичному впливі

<p>Резюме. Моделювання атмосферної гіпоксії в експерименті на щурах дозволяє більш детально дослідити участь речовин медіаторної дії у формуванні адаптації регуляторних систем мозку до гіпоксичного впливу. Метою експерименту було виявити функціональні наслідки блокування м<sub>1</sub>-холінорецепторів в асоціативній корі дорослих щурів у гіпоксичному середовищі за умов зниженого атмосферного тиску. За умов експериментальної гіпоксії спостерігали функціональну перебудову включення холінергічних структур до механізмів автономного контролю серцевого ритму. Інкубація дорослих щурів у гіпоксичному середовищі за умов зниженого атмосферного тиску, аналогічному природним умовам ІІІ типу погоди, призводить до активації холінергічної регуляції серцевого ритму.</p><p> </p><p>Ключові слова: блокування м<sub>1</sub>-холінорецепторів, асоціативна кора, знижений атмосферний тиск.</p>

The role of m1-cholinergic receptors in associative cortex of young rats in the performing autonomous regulation of heart rate during hypoxic exposure

<p>It is known that human cholinergic transmission in the cerebral cortex required for cognitive and behavioral reactions. However, in the literature there is not enough experimental data on the role of m1‑cholinergic receptors<br />in associative cortex in young rats with incubation in hypoxic environment under conditions of low atmospheric pressure, considering the functional asymmetry of the cerebral hemispheres. The aim of the experiment was to determine the functional consequences of blocking m1‑cholinergic receptors in the associative cortex in young rats with incubation in hypoxic environment under conditions of low atmospheric pressure. Functional consequences of blocking m1‑cholinergic receptors in the associative cortex in young rats with incubation in hypoxic environment under conditions of low atmospheric pressure are different in the case of right-sided and left-sided application of pirenzepin.</p>

ЗАСТОСУВАННЯ ІНФОРМАЦІЙНИХ ТЕХНОЛОГІЙ ДЛЯ ОЦІНКИ ОСОБЛИВОСТЕЙ РЕАКТИВНОСТІ ОРГАНІЗМУ МОЛОДИХ ЩУРІВ ПРИ ЕКСПЕРИМЕНТАЛЬНІЙ ГІПОКСІЇ

<p>Research of adaptation mechanisms in young body to factors such as hypoxic effect is an actual scientific problem. The aim of the experiment was to determine the functional consequences of changes in ion permeability of cell membranes in the associative cortex in young rats ufter incubation at hypoxic environment under conditions of low atmospheric pressure.<br />Incubation of rats in the hypoxic environment under conditions of moderately low atmospheric pressure leads to increased permeability of cell membranes for Na + and Cl- ions at the associative cortex. This is a functional feature of hypoxic damage to membrane structures of nerve tissue that causes compensatory limit the activity of the central contour regulation of heart rate and decrease activity of the sympathetic regulation. Peculiarities in reactivity of young rats exist due to the immaturity of fronto-thalamic brain system.</p>

Autonomous regulation of heart rate in conditions of blocking the beta 1-adrenergic receptors in associative cortex of young rats with hypoxic exposure

<p>The literature discusses modulation of beta-adrenergic receptors sensitivity of the cerebral cortex under changed<br />conditions for the functioning of the body. However, very little data on the effect of the hypoxic environment to the<br />sensitivity of beta-adrenergic receptors of the cerebral cortex in a young body, which possible to investigate in<br />experiments on rats. The aim of the experiment was to determine the functional consequences of the exclusion of<br />beta1-adrenergic receptors in the associative cortex in young rats after incubation in hypoxic environment under<br />conditions of low atmospheric pressure. Blocking the beta1-adrenergic receptors in young rat’s associative cortex<br />can significantly offset the regulatory effects on heart rate that occurred during incubation in the hypoxic environment<br />under conditions of low atmospheric pressure. Hypoxic effect in young rats resulted in a significant decrease in<br />sensitivity beta1-adrenergic receptors in the associative cortex.</p>

ДОСЛІДЖЕННЯ АВТОНОМНОЇ РЕГУЛЯЦІЇ СЕРЦЕВОГО РИТМУ МОЛОДИХ ЩУРІВ ПРИ ПОЄДНАНОМУ ВПЛИВІ ГІПОКСИЧНОЇ АТМОСФЕРИ Й МЕЛАТОНІНУ

<p>The combination of a number of adverse factors as the effect of hypoxic atmosphere, mental work and emotional stress, creates conditions for the development of maladaptive changes in the regulatory systems of the body. changes in autonomic regulation of cardiac cycle of rats under hypoxic atmosphere combined influence and melatonin were studied. The aim of the study was to identify the role of melatonin as factor of biorhythms synchronization in the impact on autonomous regulation of heart rate in young and adult rats with hypoxic incubation environment under conditions of low atmospheric pressure.</p><p>The use of melatonin drug in therapeutic doses in adults, after the completion of puberty, may be useful for the prevention of meteotropic reactions and improve the efficiency of the organism in adverse weather conditions, type III.</p>

Study on DC Pollution Flashover Performance of Various Types of Long String Insulators Under Low Atmospheric Pressure Conditions

In this paper, the dc pollution flashover performance of various types of porcelain, glass, and composite insulators is investigated. It also presents analysis of the dc flashover process of polluted insulator string at high altitude using insight from high-speed photography. The research results indicate that the relationship between the dc pollution flashover voltage and the string length of insulators is basically linear, the characteristic exponents describing the influence degree of air pressure on pollution flashover voltage vary between 0.35 and 0.77 and are related to the insulator types and pollution degree, etc., the characteristic exponents describing the influence degree of pollution on flashover voltage vary between 0.24 and 0.36 and are related to the insulator types and air pressure, etc. Based on the flashover phenomena using the insight from high-speed photography, a new physical model explaining the flashover mechanism for a polluted insulator string at high altitude is introduced, which can be expressed as an electrical circuit consisting of a surface arc of length x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> and air-gap arc of length x <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in series with a resistance representing the wet pollution layer. In addition, the exponent n describing the influence degree of air pressure on flashover voltage for the polluted insulator is discussed.

Influencia de las condiciones meteorológicas en la patología condral

Introduction In routine clinical practice, many patients attribute their joint pain to the weather. Objective To evaluate the effect of climatic conditions in patients with osteoarthritis. Methods This study was performed in patients from the Instituto Poal de Reumatología in Barcelona and the data were analyzed by Bioibérica Farma. We performed a prospective, double-blind study that included 80 patients with osteoarthritis who were compared with 42 controls. Pain evaluation (Huskisson's Visual Analogue Scale) and functional capacity (Health Assessment Questionnaire) were determined daily for 1 month. The climatic variables studied were temperature, humidity, and atmospheric pressure. Results Our data show that patients with osteoarthritis have greater joint pain when atmospheric pressure is lower, indicating that conditions of low atmospheric pressure exacerbate pain in these patients. Conclusion Our results suggest that, in future, modulation of pharmacological and nonpharmacological therapy in some osteoarthritic patients according to weather forecasts may be feasible. This could avoid, as far as possible, the joint pain and functional disability associated with the disease, thus improving quality of life in these patients.

PRACTICABILITY OF USE OF CONTACT LENSES AT LOW ATMOSPHERIC PRESSURES

Present standards for personnel of military planes require that crew members have good vision without glasses. The use of ordinary spectacles is considered impractical. Since many persons otherwise qualified are excluded from this branch of the service, in a time of great need, by reason of ametropia, the question may be fairly asked, "Can contact lenses be used practicably in planes at the altitudes commonly attained in modern warfare?" The observations here reported were made in an attempt to answer this question. Numerous studies of ocular function have been made under conditions of low atmospheric pressure, and hence low partial pressure of oxygen. These studies were reviewed by McFarland, Evans and Halperin.¹In modern flying, plane personnel need not experience lack of oxygen, since oxygen may be supplied by means of a mask. A normal supply of oxygen to the cornea via the blood stream and the intraocular fluid

A study of propagation over the ultra-short-wave radio link between Guernsey and England on wavelengths of 5 and 8 metres (60 and 37.5 Mc/s)

The paper presents a survey and analysis of field intensity measurements obtained during the years 1937–1939, over the Post Office radio-telephone link between Guernsey and Chaldon, England, on wavelengths of 5 and 8 m. (frequencies 60 and 37.5 Mc./s.). The path between the stations was almost entirely over sea and about 85 miles in length, of which some 36 miles was outside the optical range. The data recorded have been analysed in such a way as to illustrate the general and detailed variations in received signal strength, and the manner in which these are dependent on various atmospheric conditions.The results of the analysis have shown that while the fading of the signals was similar in type on the two wavelengths, there was a difference in the secular variation of the amount of fading on 5 and 8 m. No diurnal or seasonal variation of signal intensity was noted, nor was there any definite diurnal variation in the amount of fading. The fading observed took various forms, ranging from a rapid type in which the changes occurred more or less periodically every three or four minutes, to a slow type of variation extending over one or more hours. The latter type was usually accompanied by a high level of signal intensity interrupted at long intervals by rapid and deep fading lasting from 10 to 30 minutes. The field strength records show a marked correlation between periods of negligible fading and the existence of low atmospheric pressure conditions generally, including lack of appreciable temperature inversion. The occurrence of fog and snow has a similar effect to that due to the prevalence of low pressure.A consideration of these results and of similar data obtained by other workers leads to the conclusion that abrupt changes in temperature and water vapour gradients in the atmosphere give rise to signal variations in good weather, while the absence of these discontinuities in bad weather allows of steadier signal conditions.