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Characteristics of changes in the level of resistance of mixed martial arts athletes to a stress stimulus in the conditions of different force load regimes

The presented article is devoted to the study of the problem of developing effective strength training regimens for mixed martial arts athletes, taking into account the specifics of this sport and determining the level of resistance of their body and the manifestation of processes of long-term adaptation to a stressful stimulus of the appropriate nature. The purpose of the study was to study the characteristics of the change in the level of resistance of the body of mixed martial arts athletes under the conditions of the use of power load regimes with different parameters of volume and intensity. 75 athletes aged 19±0.7 years, who were divided into 3 groups, took part in the research. The following research methods were used: theoretical and methodological analysis of data from scientific and methodological literature, control testing of the development of maximum muscle strength of athletes, a method of quantitative assessment of the level of physical exertion in power sports, biochemical methods of controlling the concentration of cortisol in the blood serum of participants, a pedagogical experiment, mathematics - statistical methods of processing results. The results of the study indicate that mainly in the athletes of group 3, who during the 12 weeks of the study used a regime of high-intensity loads (Rа=0.72) under the conditions of anaerobic-lactate type of energy supply of muscle activity, we observe the most accelerated growth rates of the power capabilities of the pectoral m muscles on the background of the lowest load volume indicators in a separate set among the groups. At the same time, under the given conditions of training activity, the level of the body's resistance to such a stress stimulus of a force orientation is maximally increased in such a short period of time among athletes of the 3rd group. At the same time, in the athletes of the first group under the conditions of using the mode of low-intensity power loads (Rа=0.53), not only a minimal shift in relation to the investigated problem was detected, but also a fixed manifestation of compensatory reactions to the stressful stimulus.

Diffusion tensor imaging and voxel-based morphometry in differentiating multiple sclerosis and its mimics

BackgroundThe discrimination between multiple sclerosis (MS) and other white matter lesions in adults is still problematic as multiple diseases have similar clinical and radiological findings, especially at the disease onset. This case–control study aimed to evaluate the efficacy of diffusion tensor imaging (DTI) and brain morphometry in the differentiation between adult MS and its magnetic resonance imaging (MRI) mimics.MethodsFifty-eight patients (49 women and 9 men; mean age 35.74 ± 11.86 years, range 18–50 years) with clinically suspected MS and age- and sex-matched fifteen healthy subjects were included. All study subjects underwent MRI using 3D FLAIR, 3D T1 MPRAGE, axial T2WI fast spin echo, and DTI sequences. The included patients were classified into MS and mimics groups according to MC Donald’s criteria 2017. Image post-processing using the region of interest (ROI) analysis for DTI parameters and automated voxel brain morphometry and segmentation was done for all study groups. Statistical comparison between the two patient groups and between them and the control group was performed regarding DTI indices (fractional anisotropy [FA], mean diffusivity [MD], and relative anisotropy [RA]) and brain morphometry parameters (including white matter volume (WMV), grey matter volume (GMV), cerebrospinal fluid volume (CSFV), T2 lesion load and deep grey matter volume).ResultsA statistically significant difference was observed between the MD, FA, and RA values of the patients and control groups. The MD values were significantly higher in the MS than in its mimics with a cut-off value of > 1.058 × 10−3 mm2/s (p < 0.001). Compared to the mimics group, the MS patients showed significantly lower WMV (33.31 ± 4.40 versus 35.71 ± 4.58; p = 0.047) and higher CSFV (16.38 ± 5.93 versus 13.06 ± 3.09; p = 0.012) with no significant difference regarding the GMV.ConclusionsMD analysis of DTI, WMV, and CSFV are useful quantitative measurements in confirming the diagnosis of MS and differentiating it from its imaging mimics.

Platinum loading and electrolyte volume fraction simultaneous gradient distributions in a proton exchange membrane fuel cell: Improving electrical performance and mass transfer

Platinum loading and electrolyte content affect the surface area of electrochemical reaction and proton conductivity, respectively, and protons and oxygen are not uniformly distributed in the catalyst layer. Therefore, platinum loading and electrolyte content can be set to be simultaneous non-uniform distributions to further enhance the species utilization and cell performance. In this study, a non-isothermal, two-dimensional, two-phase fuel cell model is set up and coupled with the catalyst layer agglomerate model. The electrolyte content and platinum loading uneven distributions influence on products and reactants transmission and electrical property is explored. Results indicate that electrolyte volume fraction and platinum loading coinstantaneous graded distribution is more helpful in the species transfer and electrical property improvement. The maximum power density of coinstantaneous graded distribution of platinum content and electrolyte loading along the channel direction is increased by 3.40% compared with the uniform distribution, and is 2.94% higher than the superposition of the maximum power density when the graded distributions of electrolyte volume fraction and platinum loading are separately set. Moreover, the platinum content and electrolyte content gradient distributions do not make liquid water saturation present an evident segment variation along the channel direction, while the opposite is true for oxygen concentration.

The effect of incorporating magnetic fly ash in asphalt binders with respect to permanent deformation and fatigue

The search for efficient and environmentally viable materials to improve the quality and durability of asphalt binders used in roadways has been growing in recent years. This is especially true giving the increase in the volume and magnitude of traffic loads, as well as the changes in the earth's temperature that cause frequent pavement distresses, such as permanent deformation and fatigue. In this context, the objective of this work is to evaluate the potential of magnetic particles from fly ash, as a residual resource with high added value and low-cost raw material for modifying asphalt binders. Magnetic particles were incorporated into the asphalt binder at 2%, 4%, 6% and 8%, content by weight. The materials were characterized by chemical, empirical and rheological tests, specifically the Multiple Stress Creep and Recovery and the Linear Amplitude Sweep test. X-ray Fluorescence data revealed silicon, aluminum and iron as the main elements present in the fly ash, as well as the increase in iron concentration after magnetic separation in the magnetic particle sample. A homogeneous dispersion of magnetic particles in the asphalt binder observed by Scanning Electron Microscopy and shifts in infrared bands characteristic of iron (ca. 450 cm-1) and of asphalt binder (ca. 1456 cm-1) clearly indicated a significative interaction between the magnetic particles and the asphalt binder. The rheological results indicated that the incorporation of particles provide better performance to the binder in terms of both permanent deformation and fatigue. The modified binders were less susceptible to permanent deformation than the neat binder, and this is reflected in the increase in adequate traffic levels, moving from standard traffic to heavy traffic at a temperature of 64 °C. This economical, easy, and sustainable approach to using magnetic particles in hot asphalt binders can contribute to producing asphalts that are more efficient with changes in temperature and traffic.

Estimation of the Water Level in the Ili River from Sentinel-2 Optical Data Using Ensemble Machine Learning

Monitoring of the water level and river discharge is an important task, necessary both for assessment of water supply in the current season and for forecasting water consumption and possible prevention of catastrophic events. A network of ground hydrometric stations is used to measure the water level and consumption in rivers. Rivers located in sparsely populated areas in developing countries of Central Asia have a very limited hydrometric network. In addition to the sparse network of stations, in some cases remote probing data (virtual hydrometric stations) are used, which can improve the reliability of water level and discharge estimates, especially for large mountain rivers with large volumes of suspended sediment load and significant channel instability. The aim of this study is to develop a machine learning model for remote monitoring of water levels in the large transboundary (Kazakhstan-People’s Republic of China) Ili River. The optical data from the Sentinel-2 satellite are used as input data. The in situ (ground-based) data collected at the Ili-Dobyn gauging station are used as target values. Application of feature engineering and ensemble machine learning techniques has achieved good accuracy of water level estimation (Nash–Sutcliffe model efficiency coefficient (NSE) &gt;0.8). The coefficient of determination of the model results obtained using cross-validation of random permutations is NSE = 0.89. The method demonstrates good stability under different variations of input data and ranges of water levels (NSE &gt; 0.8). The average absolute error of the method ranges from 0.12 to 0.18 meters against the background of the maximum river water level spread of more than 4 meters. The obtained result is the best current result of water level prediction in the Ili River using the remote probing data and can be recommended for practical use for increasing the reliability of water level estimation and reverse engineering of data in the process of river discharge monitoring.

Подвижные игры как компонент воспитания физических качеств студентов-борцов

Martial arts classes offer the involvement of students in the pedagogical process aimed at mastering knowledge, skills and abilities, the development of model characteristics reflecting the properties and the athlete’s level of readiness, and allowing to achieve the best results. Model characteristics are based on the most significant in training of wrestlers goals and targets that reflect the sportsmen’s objective level, a logically correct theory of sports training, methods of teaching techniques at different stages of training athletes. The modern model of an athlete-wrestler includes the following indicators: characteristics of the training process (intensity and volume of loads), and the level of preparedness (tactical, technical, physical and psychological). Not the least role in the development of modern wrestlers’ physical qualities is played by properly selected outdoor games included in the plan of the training process. An important component in the selection of outdoor games is the development of such physical qualities as strength, endurance, agility, flexibility, speed. It is proved experimentally in the article.

Hygienic assessment of sanitary and epidemiological well-being in modern urban educational institutions

Introduction. The restructuring of general education has led to the problem of overcrowding of schools, which in turn has caused the formation of a number of hygiene problems. Despite the active material and technical equipment of urban schools, the relevance of maintaining safe teaching conditions remains in general education. &#x0D; Materials and methods. The assessment of sanitary and epidemiological well-being in ten urban educational institutions was carried out according to the methodology of the Federal State Educational Institution ROSHUMZ-34-2016 “Algorithm for determining the level of sanitary and epidemiological &#x0D; well-being of an educational institution”. The intensification of the educational process was assessed according to the Federal Law ROSHUMZ-16-2015 “Hygienic assessment of the intensity of students’ learning activities”. &#x0D; Results. The leading factors that worsen the sanitary and epidemiological state of urban educational institutions were non-compliant with the hygienic requirements of the school environment and its premises, material and technical equipment, microclimate, lighting and the mode of management of training. The duration of extracurricular activities exceeded the standards by 1.8 times. In urban schools, the intensity of the educational process (class 3.1) was formed due to intellectual, sensory loads, monotony and the mode of academic work (class 3.1). It is necessary to regulate the volume of the academic load and introduce methods that allow quantifying the intensification of the educational process by analyzing the intensity of educational work. &#x0D; Limitations. The study on the assessment of the sanitary and epidemiological well-being in urban educational institutions was limited by the fact that the sample was represented by 10 urban schools, which does not allow them to be fully extrapolated to the total population of urban students. At the same time, the new type of schools included in the research with a design capacity of 1300 people could improve the indicators of sanitary and epidemiological safety, since modern newly built schools had good and new equipment, whereas in cities there are schools of the old type, where the learning conditions, the material and technical fund can be much worse. &#x0D; Conclusion. The data obtained emphasize the urgency of the need for continuous monitoring of educating conditions and the management of the educational process, taking into account modern risks that contribute to reducing the sanitary and epidemiological well-being in urban schools.

Phytoremediation Process of Textile Industry Effluent by Eichhornia Crassipes and Pistia Stratiotes

In the world, a large part of the wastewater is not previously treated, resulting in the contamination of water resources. Textile wastewater contains large volume of pollution load. In the present study, the removal of pH, COD, TS, TDS, TSS, Sulphate and Chloride has been studied by using Eichhornia crassipes and Pistia stratiotes. A lab scale study was conducted to test the feasibility of Eichhornia crassipes and Pistia stratiotes for treating textile wastewater. pH was reduced from alkaline to nearly neutral in all dilution. The maximum percentage reduction was observed after treatment with Eichhornia crassipes and it was 25.62% for pH, 69% for COD, 25.71% for TS, 34.61% for TDS, 68% and 45% for Sulphate and Chloride respectively. Aftrer treatment with Pistia stratiotes percentage removal efficiency was pH 23%, COD 45%, TS 20%, TDS 17.53%, Sulphate 64% and Chloride 39.51%. Hence, the efficiency for removal of pollutants of textile wastewater by Eichhornia Crassipes is more than Pistia stratiotes.

Modeling and simulation of the negative angle cutting with a combined constitutive model for U71Mn rail steel

Due to the increasing train axle load, running speed and traffic volume, rails are prone to severe rolling contact fatigue (RCF) defects. Repairing the rail profile by milling is the latest technology to solve the above hidden problems, but there are few related studies in recent years. In this paper, the milling maintenance process of rails is studied by using finite element method(FEM). This study examines the fracture behavior of U71Mn steel rail under various stress triaxiality conditions, temperatures, and strain rates. An electronic universal testing machine is utilized to conduct the experiments, and a Johnson-Cook (J-C) failure model for U71Mn steel rail is developed. A 3D cutting simulation model was developed using the Johnson-Cook (J-C) combined constitutive model. The accuracy and reliability of the numerical simulation model were confirmed by comparing the cutting force and chip morphology obtained from both simulation and experimental results. The cutting simulation model had an error rate of within 10 % when predicting the cutting force. Following that, the fracture zone and chip portion of the tensile specimen were metallographically analyzed. The applicability of the ductile failure criterion in describing the observed failure in the U71Mn rail has been proven.

Rapid recovery in a patient with severe COVID-19 after a low-load, high-frequency rehabilitation program using an ergometer in the supine position.

Background Rehabilitation therapy for patients with severe coronavirus disease 2019 (COVID-19) is crucial; however, studies regarding rehabilitation strategies for intensive care unit (ICU) patients with COVID-19 are limited. We report a case of severe COVID-19 in an ICU patient whose physical function and basic movement ability rapidly improved after the initiation of active aerobic exercise in the supine position.Case A 70-year-old man with hypertension and obesity was admitted to the ICU and managed with a ventilator because of severe COVID-19. Physical therapy started on postadmission day 34. Problems encountered during physical therapy included low saturation of percutaneous oxygen (SpO2; <90%), dyspnea with a light exercise load, advancing muscle weakness, and endurance decline. The rehabilitation program included getting out of bed and resistance training of the upper and lower limbs twice daily while maintaining SpO2 at ≥90%. After ventilator weaning, we initiated aerobic training using a supine ergometer with varying load volume. On discharge from the ICU on postadmission day 45, the patient' s physical function (handgrip strength, Medical Research Council score, and Borg scale) and basic movement ability (Functional Status Score for ICU) rapidly improved.Conclusion Rehabilitation therapy involving aerobic cycling training based on a quantitative load setting may be effective in treating COVID-19.

Temporal changes in intensity and volume of external training loads during a 1 × 1 short-bout, small-sided games in elite youth soccer players

This study compared external training load (ETL) and its temporal changes across repetitions during a speed endurance production (SEP) training comprised of 1 × 1 short-bout, small-sided games (SSGs) in elite youth soccer players. Twenty U18 players were divided into two groups (SEP1 and SEP2) performing six 30 s and 45 s bouts of SSG (work-to-rest ratio 1:4) on a 10 by 15 m field. ETL was characterized by the total distance covered, Player Load, the total number of accelerations/decelerations, and their relative values (per minute). Significant overall decreases in the ETL parameter values across six repetitions in both SSG groups were observed relative to the measurement in the first set beginning in 3rd (SEP1) or 4th (SEP2) repetitions. Significant greater decreases in Player Load (F(5.90) = 2.99, p < 0.05, η P2 = 0.14), Player Load per minute (F(5,90) = 11.32, p < 0.001, η P2 = 0.39), total distance per minute (F(3.43,61.73) = 7.72, p < 0.001, η P2 = 0.30) and accelerations per minute (F(5,90) = 2.59, p < 0.05, η P2 = 0.13) were observed in the 30-s games than in the 45-s games. In conclusion, the use of SSGs in SEP training is associated with a decrease in the effectiveness of physical work performed across repetitions. In practice, due to the decrease in the measured ETL indicators already in the 3rd or 4th repetition (especially in the SEP1 group), the work-to-rest ratio could be increased from the applied 1:4 to 1:6.

Fast Estimation of Loader’s Shovel Load Volume by 3D Reconstruction of Material Piles

Fast and accurate measurement of the volume of earthmoving materials is of great significance for the real-time evaluation of loader operation efficiency and the realization of autonomous operation. Existing methods for volume measurement, such as total station-based methods, cannot measure the volume in real time, while the bucket-based method also has the disadvantage of poor universality. In this study, a fast estimation method for a loader’s shovel load volume by 3D reconstruction of material piles is proposed. First, a dense stereo matching method (QORB–MAPM) was proposed by integrating the improved quadtree ORB algorithm (QORB) and the maximum a posteriori probability model (MAPM), which achieves fast matching of feature points and dense 3D reconstruction of material piles. Second, the 3D point cloud model of the material piles before and after shoveling was registered and segmented to obtain the 3D point cloud model of the shoveling area, and the Alpha-shape algorithm of Delaunay triangulation was used to estimate the volume of the 3D point cloud model. Finally, a shovel loading volume measurement experiment was conducted under loose-soil working conditions. The results show that the shovel loading volume estimation method (QORB–MAPM VE) proposed in this study has higher estimation accuracy and less calculation time in volume estimation and bucket fill factor estimation, and it has significant theoretical research and engineering application value.

TECHNOLOGICAL BASIS OF THE PROCESS OF ZIRCONIUM AND HAFNIUM SEPARATION

The paper presents the results of industrial testing of the process and equipment for the extraction separation of zirconium and hafnium in a single technological cycle with the production of high-purity nitrate compounds and pure nitric acid solutions as raw materials for the production of sodium nitrate. It is shown that the efficiency of the extraction process is determined primarily by the purity of the nitric acid solution by the content of a critical impurity – silicic acid, which causes an undesirable emulsification process and disrupts the stability of the process. Optimal conditions have been determined under which the formation of non-extractable forms of zirconium and hafnium is excluded. The replacement of pulsating columns with centrifugal extractors reduced operating costs by reducing the volume of a one-time load of a flammable extractant and its losses as a result of hydrolysis. This increased the degree of separation of zirconium and hafnium. Centrifugal extractors provided high process kinetics, reduced production areas, and increased labor productivity and product quality.

Dynamics of Accommodative Asthenopia in Patients with Visually Intense Work after LASIK with Different Degrees of Myopia

Purpose — to study the dynamics of accommodative asthenopia (AA) in patients with visually stressful labor (VLT) after laser keratomileusis in situ (LASIK) with different degrees of myopia. Patients and methods. There were 300 patients with VLT under supervision, divided into three groups of equal age and gender, corresponding to weak (up to 3.0 diopters, 100 patients, 200 eyes), medium (3.25–6.0 diopters, 100 patients, 200 eyes) and high (6.25–8.0 diopters, 100 patients, 200 eyes) degrees of myopia. All patients underwent objective accommodation using the Righton Speedy-I device (Japan) with further calculation of the coefficient of microfluctuations of the ciliary muscle of the eye (CMF). Diagnosis of the type of AA was carried out according to the following indicators: with CMF less than 53.0 rel. un. — asthenic form of accommodative asthenopia (AFAA); at CMF from 53.0 to 58.0 rel. un. — NORM; at CMF more than 58.0 rel. un. — habitual excess tension of accommodation (PINA). The survey was carried out before and three months after the operation. Statistical analysis of the results of the study was performed on the basis of the rate of occurrence (in % of the total number of eyes) of different dynamics (before-after surgery) AA (NORM-NORM; PINA-PINA; AFAA-AFAA; NORM-AFAA; NORM; PINA-AFAA; AFAA-NORM; AFAA-PINA). Results. The change in the form of AA varied from 2 % (APAA-PINA) to 18 % (PINANORM), averaged 15 % and was not statistically significant. The results obtained naturally reflect the state of AA as an adequate physiological response of the accommodative system of the eye to long-term, intense visual work with a fairly high level of responsibility for the result. Based on the above situation and the patient’s desire to maintain (in some cases even increase) the volume of daily visual load after the operation, it is unlikely to expect a significant improvement in the state of accommodation. Conclusion. LASIK with different degrees of myopia in patients with VLT has practically no effect on the dynamics of AA and requires a complex of therapeutic and restorative measures based on the development of methodological principles from the standpoint of a differentiated approach to the form of AA and the basic provisions of medical rehabilitaton.

Dynamics of TP, HF-, LF-, and VLF-Waves of the Cardiointervalogram (in Clinostasis Conditions) of an Elite Ski Racer in the Preparatory, Competition, and Transition Periods Depending on the Volume and Intensity of Training Loads

Dynamics of TP, HF-, LF-, and VLF-Waves of the Cardiointervalogram (in Clinostasis Conditions) of an Elite Ski Racer in the Preparatory, Competition, and Transition Periods Depending on the Volume and Intensity of Training Loads

AUTOMOBILE CRANES QUANTITY DETERMINATION FOR MAIN GAS PIPELINES CONSTRUCTION AND REPAIR

Russia’s dominance in the global energy market is predetermined by the scale and development prospects of gas transmission infrastructure to ensure a continuous cycle of gas supply from fields to end consumers. Operating conditions of gas production, processing, transportation, storage and distribution facilities are associated with the influence of environmental factors, which varies greatly due to the length of pipelines covering all climatic regions of the country. The growth in the length of new pipelines and the need to repair existing pipelines based on the results of in-line diagnostics contribute to an increase in the volume of loading and unloading operations and the storage of pipes, therefore, studies on improving methods for determining the need for truck cranes when for constructions organizing technological processes and repair of main gas pipelines are relevant.&#x0D; The purpose of the study is to determine the efficiency of truck cranes operation in the process of main gas pipelines overhaul and construction.&#x0D; The scientific novelty is formed by the patterns of formation of the cost and labor intensity of loading, depending on the load capacity of a truck crane and the unloading pipes parameters.&#x0D; The research methodology is based on a systematic approach, methods for analyzing the technical operation of vehicles and proven data processing techniques.&#x0D; The recommendations made as a result of this study have been implemented to organize preparatory work at major main gas pipelines overhaul facilities and construction, which increases the efficiency of processes, optimizes the structure of special vehicles and reduces the cost of technological operations.

Heterogeneously catalyzed palm biodiesel production in intensified fruit blender

This research investigated palm biodiesel production via solid base-catalyzed transesterification in an intensified kitchen fruit blender. Studied parameters included methanol to palm oil molar ratio, CaO catalyst loading, reaction temperature, and reaction volume. XRD analysis showed a pure CaO phase after calcination while other characteristics illustrated good functionality of the catalyst. An optimal condition was achieved with 15:1 of methanol to palm oil molar ratio, 5 wt% of CaO dosage, 60 °C of reaction temperature, and 1,000 mL of reaction volume, obtaining the highest FAME production of 97.58% and yield efficiency of 1.47 × 10−3 g/J. The FT-IR illustrated an alteration of various functional groups through a reusability experiment demonstrating exceptional activity stability. The catalyst activity was decreased by only 15.8% in the 5th consecutive cycle. Properties of produced biodiesel conformed to international standards. This proved that biodiesel production using the CaO catalyst in the intensified kitchen fruit blender provides a positive effect on reuse, reduces wastewater from the washing process, lowers production costs, and is environmentally responsible to achieve high FAME yield due to the cavitation phenomena inside the reactor to generate fine emulsion of oil and methanol which could be easier to reach the active site of the CaO catalyst.

Dynamics of TP, HF-, LF- and VLF- Waves of the Cardiointervalogram (in Clinostasis Conditions) of an Elite Ski Racer in the Preparatory, Competitive and Transitional Periods, Depending on the Volume and Intensity of Training Loads

In order to study the mechanisms of adaptation to loads requiring high endurance, the 27-year-old master of Sports of Russia in cross-country skiing repeatedly recorded a cardiointervalogram (CIG) under clinostasis conditions, estimating TP, absolute power (mc2) of LF-, HF- and VLF-waves and the relative (as a percentage of TP) power of these waves, i.e. LF%, HF% and VLF%. They were compared with the volume (Vkm, Vmin) and intensity (Nhr) of training loads. The volume of loads was maximum in the preparatory period (21 km/day) and it is minimal in the transition period (18 km/day), and their intensity throughout the annual cycle was stable (working pulse – 120–121 beats/min). With the change in the volume of loads, the values of the KIG indicators also changed. So, in the preparatory period, the medians of TP, the power of HF-, LF- and VLF-waves, as well as VLF% increase; in this period, with an increase in the volume of loads (Vkm), the values of VLF% increase. In the competitive period, the medians of TP, the power of HF-, LF- and VLF-waves and VLF% remain at a high level. In the transition period, the median of TP, the power HF-, LF- and VLF-waves, as well as LF% and VLF%, but the median of HF% increases. For the annual cycle, a direct dependence of the median of TP on the volume of loads (Vkm) and the median power of VLF waves on the volume (Vkm) and intensity (Nhr) of the load was revealed. It is postulated that the values of TP, HF-, LF-, and VLF-waves, as well as VLF% (in clinostasis) reflect the influence of the Cholinergic system on the heart, while VLF% probably reflects the intensity of synthesis of non-neuronal heart’s acetylcholine, and the values of LF% and HF% reflect the formation of anxiety in connection with upcoming starts.

Dynamic testing of a new integrated collector storage solar water heater (ICSSWH) according to standard ISO 9459‐5: Use of a numerical approach for long‐term prediction in different climatic conditions

AbstractThis work analyzes the performance of a new Integrated Collector Storage Solar Water Heater (ICSSWH) by using Dynamic System Testing (DST) method according to Standard ISO 9459‐5. The long‐term performance study of the system in different climatic conditions has been achieved by a coupling model between DST results and a numerical approach based on the system transient behavior. Results of the experimental dynamic system evaluation showed that the total store heat capacity Cs, the useful collector surface Ac* and the storage tank heat losses coefficient Us are, respectively, 0.87 MJ/K, 1.21 m2 and 10 W/K. In Tunisian climatic conditions, the ICSSWH system allows covering until 79.3% from a typical family need for a daily consumption of 170 L. The results found allow optimizing the energy gain of the ICSSWH as well as selecting a specific load volume according to the location. Especially, investigations showed that in Stockholm and Riadh climatic conditions, the ICSSWH's solar fraction reached 27% and 83%, respectively, for a daily load volume of 250 L. More importantly, the experimental effort of DST identification can be minimized by coupling DST data with a robust numerical approach.

Strategies on Enabling High Areal Sulfur Loading in Lithium Sulfur Batteries

Needs for energy storage devices in modern-day applications such as electric vehicles and other high energy consuming portable electronics make the Lithium sulfur batteries (LSBs) to be one of the most attractive types since they offer a high theoretical energy density (2600 Wh kg-1), which is about an order of magnitude higher than the theoretical specific capacity of the lithium ion batteries. In addition, Sulfur is one of the most abundant materials in nature and moreover, a non-toxic element which makes the lithium sulfur battery a suitable candidate for commercialization. However, obstacles to overcome include the loss of active sulfur due to various phenomena mainly represented by polysulfide diffusion and reactivity on the lithium anode. Another serious issue observed in so many ways is the low electronic conductivity of Sulfur and its products such as Li2S as a result of cycling. These problems are often exacerbated at higher sulfur loading and lower electrolyte to sulfur ratios (E/S). One way to increase the sulfur loading is to increase the thickness of the cathode which in return increases the risk of low utilization of active material because of the high thickness and low wettability by electrolyte. Another way is to increases the ratio of the sulfur in respect to conductive host material without increasing the thickness of the cathode. By doing so, sulfur is going to fill all the pores existing in the host material and therefore, this structure cannot provide enough volume expansion during discharge process and as a result, the cathode structure may collapse and the whole cell fail. Therefore, to come up with a high performance and stable battery during cycling, there is no doubt that we have to focus on the structure of the cathode and the host material to effectively confine the sulfur and produced polysulfide and at the same time, alleviate the way of the electron transfer through the conductive network.In this research, we investigate some of the most influential parameters mainly associated with the morphology of the cathode to improve capacity retention. Optimizing the sulfur loading, E/S content, pore structure and pore volume, and the thickness of the cathode lead to an overarching understanding of the physical transitions that occur during the discharge and charge operation of the battery. In addition, various electrochemical testing to evaluation the loss of activity of the cathode surface is also carried it to correlate to the proposed physical model.