Constant Flow System Research Articles

Two-stage stochastic robust optimization scheduling of electric–thermal microgrid with solid electric thermal storage

During the periods of high heat load (HL) demand in winter, the increased heat output of combined heat and power units (CHPs) can significantly compress the electric power regulation range, thereby posing a threat to the safety of the power system. The solid electric thermal storage (SETS) can be employed as the regulating resource for both electric and thermal systems, expanding the dispatch space of microgrids to promote renewable energy consumption. In this paper, a two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is proposed, and the electric–thermal bi-directional regulation characteristics of SETS are considered. First, a SETS operation model based on the heat transfer characteristics of the homogeneous material-type thermal storage unit is established. Second, a regional thermal inertia model under a constant-flow variable-temperature system is established, which integrates HL at different locations to the heat source, avoiding the calculation of variation in water temperature, thus reducing the calculation difficulty. Finally, the two-stage stochastic robust optimization scheduling model of an electric–thermal microgrid with SETS is established. The model decouples the power and heat generation of CHP through the bi-directional regulation function of SETS. Case studies demonstrate the validity and effectiveness of the proposed scheduling model.

Simulation of gravity- and pump-driven perfusion techniques for measuring outflow facility of ex vivo and in vivo eyes.

Aqueous humor dynamics are commonly assessed by infusing fluid into the eye and measuring intraocular pressure (IOP). From the pressure-flow relationship, conventional outflow facility is estimated to study glaucomatous processes that lower facility or identify therapeutics that enhance facility in hopes of restoring healthy IOP levels. The relative merits and limitations of constant flow (CF), gravity-driven constant pressure (CPg), and pump-driven constant pressure (CPp) infusion techniques were explored via simulations of a lumped parameter viscoelastic model of the eye. Model parameter values were based on published perfusion system properties and outflow facility data from rodents. Step increases in pressure or flow were simulated without and with IOP noise recorded from enucleated eyes, anesthetized animals, and conscious animals. Steady-state response levels were determined using published window and ratio criteria. Model simulations show that all perfusion techniques estimate facility accurately and that ocular fluid dynamics set a hard limit on how fast measurements can be taken. This limit can be approached with CPg and CPp systems by increasing their gain but not with CF systems, which invariably take longest to settle. Facility experiment duration is further lengthened by inclusion of IOP noise, and data filtering is needed for steady-state detection with in vivo noise. The ratio criterion was particularly affected because noise in the flow data is amplified by the higher gain of CPg and CPp systems. A recursive regression method is introduced, which can ignore large transient IOP fluctuations that interfere with steady-state detection by fitting incoming data to the viscoelastic eye model. The fitting method greatly speeds up data collection without loss of accuracy, which could enable outflow facility measurements in conscious animals. The model may be generalized to study response dynamics to fluid infusion in other viscoelastic compartments of the body and model insights extended to optimize experiment design.

Development of a Contactless Conductivity Sensor in Flowing Micro Systems for Cerium Nitrate

Impedance spectroscopy has a high potential to detect chemical reactions in flowing systems. In this work, the approach using impedance spectroscopy as a possible analytical tool for a continuous hydrothermal syntheses (CHTS) is presented. With the CHTS-process, it is possible to produce metalloxide nanoparticles with a close particle size distribution and specific surface properties. For this, it is necessary to evaluate the electrode geometry, frequency and other factors influencing the impedance with respect to concentration measurements. In case of frequency-sweep measurements possible electrode geometries for C4D-Sensors (capacitively coupled contactless conductivity detection) are evaluated. Then distinguishability and reproducibility are tested applying titration measurements to show the ability for concentration detection in constant flow systems. The possibility to measure concentration changes in flowing systems in a reproducible and fast manner as well as with high distinguishability for the test solution cerium nitrate will be presented. Furthermore, the major influencing-factors like electrode geometry, frequency etc. could be determined. It has been shown that with increasing electrode spacing and electrode width, the distinguishability of the concentrations increases and shifts them to lower frequencies.

Long-Term Variability of Wind Speed and Direction in the Mediterranean Basin

In this work, the ERA5 reanalysis dataset, with its fine spatial and temporal resolution, is used to study the wind speed and direction characteristics in the Mediterranean basin from 1979 to 2020. Their variability, trend and mean values, as well as their association, are examined in the monthly, annual and interannual/decadal time scales. The long-term variability of the wind direction is assessed using the angular variance, while the mean annual and interannual variability are used for the wind speed. The most characteristic and constant flow systems appear in the Gulf of Lion (Mistral) and the Aegean Sea during the summer (Etesian winds). The mean annual variability maximizes in the northern part of the basin, while the western part appears to have the most variable wind directions, while the fastest increasing wind speeds appear in the southwestern Levantine sub-basin. The long-term linear trend for the mean, the 95th and 99th quantiles of annual wind speed and the number of occurrences of extreme wind events have been also assessed. For particular areas, there is an increasing tendency in both intensity and frequency of occurrence of extreme wind events. Τhe linear-circular correlation coefficient has been implemented in order to quantify the linear association between the wind direction and the wind speed. This parameter demonstrates higher annual values for the Mistral wind in the Gulf of Lion and the Etesian winds in the Aegean Sea during the summer. Finally, the comparison of the results of ERA5 with the results of ERA-Interim highlighted significant differences in the Mediterranean wind speed and direction characteristics.

Power Train System Control of Electric Loader Based on Positive Flow System

Energy conservation and emission reduction have drawn more and more attention in the world. Loaders are widely used in various earthworks. However, traditional loaders with high energy consumption and poor emission cannot meet the needs of sustainable development. Electric loaders can achieve zero emission by replacing the engine with the electric motor, which is considered to be one of the main trends in future development. However, the existing electric loader only uses the electric motor to simulate the operation of the engine without fully considering the characteristics of the hydraulic system, resulting in the inability to optimize the energy efficiency and control performance of the system. In this paper, an electric motor with excellent speed regulation was employed. A positive flow system based on variable speed for constant displacement pump was studied. The efficiency of the power train system was analyzed. The relationships of the opening area of the main valve core, the system demand flow, and the pilot pressure were studied. A variable speed control strategy based on the pilot pressure control was put forward. In order to verify the feasibility of the proposed system and control strategy, simulation and experiments were carried out. The results showed that the proposed system has better energy saving and maneuverability than the traditional constant flow system.

Enhanced extracellular polymeric substances production and aggravated membrane fouling potential caused by different disinfection treatment

Extracellular polymeric substances (EPS) were the main cause of membrane biofouling in advanced treatment of wastewater. Disinfection was usually used to reduce microbial concentration in the feed water and prevent biofouling. However, the disinfection residual bacteria (DRB) could regrow to produce EPS, and there was still a paucity of information on EPS productivity and properties from DRB and their further interaction with membranes. In this study, three commonly-used disinfection methods (free chlorine, chloramine and ozone disinfection) were used to investigate their effects on microbial EPS production and the further effects on membrane fouling. It was found all the disinfection treatment increased the relative abundance of typical bacterial genus with high EPS production ability, and thus significantly enhanced EPS volumetric productivity (by 26%–82%). The molecular weight and fluorescence intensity of EPS produced by DRB also increased. The fouling potential of these EPS on ultrafiltration (UF) membranes and reverse osmosis (RO) membranes was then tested. EPS of DRB showed significantly higher fouling potential. Compared with the control group, the time for transmembrane pressure (TMP) increased to 3 bar decreased by 43%–49% in the constant-flow UF system in the disinfection groups. As for the constant-pressure RO systems, the final flux decreased by 33%–41% in the disinfection groups compared with the control group. The thickness of foulants on UF and RO membranes in the disinfection groups was all higher than that in the control group. The extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory further showed that the EPS of DRB had significantly higher interaction energy with membranes than that in the control group. Therefore, caution should be exercised when oxidizing disinfection was used as pre-treatment for membrane filtration in the wastewater reclamation process.

Impact of the worldwide trends on the development of the digital economy

The aim of the article is to develop a new model of the digital economy as a new scientific direction of the philosophy of economics. Analysis methodology is the use of methods such as cross-cultural, systemic, synergetic, informational, axiological, cybernetic to develop a new model of the digital economy as a new scientific direction, in the context of which a new information space is being formed. The problems of solving the digital economy are taking place against the backdrop of new trends - globalization 4.0, Industry 4.0, Enlightenment 2.0, Agile management, in the context of which there is a transition from simple interconnection to hyperconnection and the spread of Moore's law, according to which there is a doubling of information. The results of the study. 1) The development of the digital economy as a new scientific field, which is based on a combination of concepts of informatization, digitalization, robotics, developing under the influence of global trends is studied. 2) It has been established that the digital economy contributes to technological progress and, under the pressure of global trends, develops a variety of economic models of scientific, technical and digital progress, which are based on the solution of problems of man, science, society. 3) The problematic issues of the digital economy and the conditions for its solution are identified. Conclusions. The prospects that the digital economy opens up thanks to modern technologies representing a technological breakthrough are analyzed. The digital technology network is designed so that it moves with the least loss and the smallest pieces of calculus are at the heart of this new constant flow system. All this indicates that in the context of globalization and the BIG DATA era, humanity is entering a new stage of calculus, when information doubles in accordance with Moore's law.

Comparison of the technological background of aquaponic systems

Aquaponics is the combined culture of fish and plants in recirculating aquaculture systems, an ecologically sustainable horticultural production technique with long traditions.
 The objective of this study is to compare flood-and- drain, and the water crossflow system and examine the differences in the water quality, fish yield and plant growth parameters for Common carp (Cyprinus carpio) and basil (Ocimum basilicum). During the study, water quality parameters of two treatments were compared in temperatures, pH, EC and NO3¯N were significantly different (p <0.05). Leaf area of the basil plants grew to an average of 20.37 cm2 (± 9.02 cm2). The plants’ biomass production was significantly different (p< 0.05) in the two systems. The biomass production showed lower yield, 458.22 g (± 214.59 g) in the constant flow system that in the flood- and- drain system 692.9 g (± 175.82 g). Fish Growth parameters were better in constant flow system (FCR 5.48 g/g ± 0.19). However, the specific growth rate (SGR) demonstrated that fish grew faster in flood- and- drain system 1.38 %/day (± 0.29).

Effect of methylxanthines, cytochalasin B and FMLP on neutrophil filterability in a constant flow system

Effect of methylxanthines, cytochalasin B and FMLP on neutrophil filterability in a constant flow system

Efficiency Improved Load Sensing System—Reduction of System Inherent Pressure Losses

Although more efficient than e.g., constant flow systems, hydraulic load sensing (LS) systems still have various losses, e.g., system inherent pressure losses (SIPL) due to throttling at pressure compensators. SIPL always occur whenever two or more actuators are in operation simultaneously at different pressure levels. This paper introduces a novel hydraulic LS system architecture with reduced SIPL. In the new circuit, each actuator section is automatically connected either to the tank or to a hydraulic accumulator in dependence of its individual and the systems load situation via an additional valve. When connected to the accumulator, the additional pressure potential in the return line increases the load on the actuator and thus reduces the pressure difference to be throttled at the pressure compensator. The new circuit was developed and analyzed in simulation. For this, the hydraulic simulation model of a hydraulic excavator was used. To validate the sub-models of both machine and new circuit, two separate test rigs were developed and used. Both valid sub-models then were combined to the model of the optimized system. The final simulation results showed, that under the applied conditions, the novel hydraulic circuit was able to decrease SIPL of the examined system by approximately 44% and thus increasing the machines’ total energy efficiency. With the successful completion of the project, the gathered knowledge will be used to further develop the proposed circuit and its components.

A systematic approach for the accurate and rapid measurement of water vapor transmission through ultra-high barrier films.

Flexible organic electronic devices are often protected from degradation by encapsulation in multilayered films with very high barrier properties against moisture and oxygen. However, metrology must be improved to detect such low quantities of permeants. We therefore developed a modified ultra-low permeation measurement device based on a constant-flow carrier-gas system to measure both the transient and stationary water vapor permeation through high-performance barrier films. The accumulation of permeated water vapor before its transport to the detector allows the measurement of very low water vapor transmission rates (WVTRs) down to 2 × 10-5 g m-2 d-1. The measurement cells are stored in a temperature-controlled chamber, allowing WVTR measurements within the temperature range 23-80 °C. Differences in relative humidity can be controlled within the range 15%-90%. The WVTR values determined using the novel measurement device agree with those measured using a commercially available carrier-gas device from MOCON®. Depending on the structure and quality of the barrier film, it may take a long time for the WVTR to reach a steady-state value. However, by using a combination of the time-dependent measurement and the finite element method, we were able to estimate the steady-state WVTR accurately with significantly shorter measurement times.

Formaldehyde preparation methods for pressure and temperature dependent laser-induced fluorescence measurements.

Formaldehyde is an excellent tracer for the early phase of ignition of hydrocarbon fuels and can be used, e.g., for characterization of single droplet ignition. However, due to its fast thermal decomposition at elevated temperatures and pressures, the determination of concentration fields from laser-induced fluorescence (LIF) measurements is difficult. In this paper, we address LIF measurements of this important combustion intermediate using a calibration cell. Here, formaldehyde is created from evaporation of paraformaldehyde. We discuss three setups for preparation of formaldehyde/air mixtures with respect to their usability for well-defined heating of formaldehyde/air mixtures. The "basic setup" uses a resist heater around the measurement cell for investigation of formaldehyde near vacuum conditions or formaldehyde/air samples after sequential admixing of air. The second setup, described for the first time in detail here, takes advantage of a constant flow formaldehyde/air regime which uses preheated air to reduce the necessary time for gas heating. We used the constant flow system to measure new pressure dependent LIF excitation spectra in the 343 nm spectral region (41 (4) absorption band of formaldehyde). The third setup, based on a novel concept for fast gas heating via excitation of SF6 (chemically inert gas) using a TEA (transverse excitation at atmospheric pressure) CO2 laser, allows to further minimize both gas heating time and thermal decomposition. Here, an admixture of CO2 is served for real time temperature measurement based on Raman scattering. The applicability of the fast laser heating system has been demonstrated with gas mixtures of SF6 + air, SF6 + N2, as well as SF6 + N2 + CO2 at 1 bar total pressure.

A critical comparison of constant and pulsed flow systems exploiting gas diffusion

Considering the beneficial aspects arising from the implementation of pulsed flows in flow analysis, and the relevance of in-line gas diffusion as an analyte separation/concentration step, influence of flow pattern in flow systems with in-line gas diffusion was critically investigated. To this end, constant or pulsed flows delivered by syringe or solenoid pumps were exploited. For each flow pattern, two variants involving different interaction times of the donor with the acceptor streams were studied. In the first one, both the acceptor and donor streams were continuously flowing, whereas in the second one, the acceptor was stopped during the gas diffusion step. Four different volatile species (ammonia, ethanol, carbon dioxide and hydrogen sulfide) were selected as models. For the flow patterns and variants studied, the efficiencies of mass transport in the gas diffusion process were compared, and sensitivity, repeatability, sampling frequency and recorded peak shape were evaluated. Analysis of the results revealed that sensitivity is strongly dependent on the implemented variant, and that flow pattern is an important feature in flow systems with in-line gas diffusion.

An optimal control strategy based on virtual flow measuring for variable flow primary pumping

A virtual flow measuring is integrated with the best efficiency staging and the loop differential pressure (DP) reset method to unleash pump power saving potentials from a variable flow primary pump system. Based on the measured pump head, speed, and power, the virtual measuring determines the pump operation condition in an accurate and fast way. The pump operation parameters are then used to realize the best efficiency staging and the loop DP reset control, which calculate the optimal number of operating pumps and each pump's speed respectively. Simulation shows that this control strategy is most energy efficient, and it saves on pump energy consumption by 74.8% compared with a constant flow pumping system. The experiment from a retrofitted two-pump system also shows that the control strategy provided 64.5% pump energy saving over the original constant flow system. In addition, this control strategy requires a lower initial cost, simplifies the implementation process, makes system operation more reliable and stable, and reduces maintenance demands.

Energy and Sustainability in Museums. The Plant Refurbishment of the Medieval Building of Palagio di Parte Guelfa in Florence

This paper presents a performance-based design of a HVAC plant and controller system of the “Palagio di Parte Guelfa” Palace, a medieval building converted into a museum in the city of Firenze. Transient simulations to evaluate the internal microclimate conditions during the year for the building and the different system plant were carried out. A comparison between the indoor microclimatic parameters obtained and the values suggested by the standards on protection and conservation of historical works of art, suggested a non-invasive and reversible plant system solution. The MuseumofHistorical Footballbuilding portion is the case study. The proposed plant, a constant air flow system coupled with radiant panels dry mounted above the existing flooring, was simulated throughout the year under transient conditions to evaluate its energy performance. This solution ensures indoor temperature and humidity values suitable for the conservation of works of art and visitor comfort. It is an example of a possible course of action for a plant refurbishment in a historic building converted into a museum, located in climatic regions characterized by high thermal and solar loads. The present paper concerns the study of an integrated and reversible architectural-plant solution proposed: reversibility of the proposed system is understood as the possibility for the present conditions being easily restored.

Application of Fieldbus and Frequency Conversion Technology in Air-Condition VWV System

This paper presents a method which uses LonWorks control system and frequency converter in Central Air-Condition chilled water variable flow system. In this system, the output of frequency converter can be altered by augmenter PID control rule which is used in control of invariable difference in temperature between water supply and backwater, and the rotating speed of water pump can be changed correspondingly, so when the user load is small ,the electric energy consume can be reduced. The effect of energy-saving was visible comparing with the conventional Air-Condition chilled water constant flow system.

Effects of iloprost on blood rheology and tissue perfusion in patients with intermittent claudication: Results of a double-blind placebo-controlled study

The effects of an infusion of a single dose of Iloprost (from 0.5 up to a maximum of 2 ng/kg/min for six hours) in patients with stage II peripheral vascular disease (PVD) on blood rheology and tissue perfusion were determined in a double-blind placebo-controlled study using repeated treadmill exercise test to stress leg circulation. Blood viscosity (BV) at low shear, soluble P-selectin levels (expression of platelet activation), unfractioned leukocyte and erythrocyte filterability rates (using a constant-flow positive-pressure system), plasma fibrinogen concentration, haematocrit, leukocyte and platelet counts were measured in two matched groups of 8 PVD patients before and after treatment. Transcutaneous oxygen pressure (TcPO2) during controlled ischaemia was also measured. Controlled peripheral ischaemia generated an impaired haemorheological profile. Iloprost reduced the impairments in BV and the filterability rates of unfractioned leukocytes, inhibited platelet activation and improved erythrocyte deformability. These improvements were associated with significant shortening of the TcPO2 half recovery time, indicating that ischaemic damage had been contained.

Microinjecting Cells Using a Constant-Flow Microinjection System

INTRODUCTIONThe efficient delivery of exogenous DNA to cells for expression and function studies is an essential technique of modern cell biology, and direct delivery of genetic material by microinjection remains a reliable means of transfection. In the system described here a constant flow of sample is delivered from the tip of the pipette, and the amount of sample injected into the cell is determined by how long the pipette remains in the cell. The system can be assembled at relatively low cost using commercially available components: Typically, a pressure regulator that can be adjusted for two pressures (back pressure and injection pressure), a capillary holder, and coarse and fine micromanipulators. A constant-flow system, by design, injects less reproducible cell volumes than does a pulsed-flow system. However, with practice, this difference can be made negligible.

THE ANALYSIS OF BALANCING WATER COOLING SYSTEMS AND MAKING MANAGEMENT DECISIONS REGARDING OFFICE BUILDINGS

The paper analyses a cooling system installed using 268 fan coils and having an area of 7900 m2 in a public building situated in Vilnius city. A comparison between a constant flow system having three way valves, a variable flow system having manually balanced valves and a variable flow system having automatically balanced control valves is made. The analysis has been performed to find out initial investments, installation costs and operating costs during 10 year period. Calculation has showed advantages of the variable flow. The overall cost of the system having manually balanced and two way control valves is 20% lower than that of the constant flow system. The overall cost of the system having automatically balanced control valves is 37% lower than that of the constant flow system. The marked differences may increase in case of growth in electricity price.

The impact of subchronic cadmium poisoning on the vascular effect of nitric oxide in rats

The aim of this study was to evaluate the impact of poisoning with cadmium in hypertensive doses (50 or 200 ppm in drinking water for three months) on the basal and stimulated release NO effect in the isolated and perfused rat mesenteric bed. Mesenteric artery preparation preconstricted by norepinephrine (0.5 microg/mL) was used to determine changes in its vascular resistance induced by e-NOS synthase blocker, N-omega-nitro-L-arginine (L-NOARG) injected in increasing doses from 1.0 to 200.0 microg or acetylcholine (ACh) administered in doses from 0.05 x 10(-10) to 5.0 x 10(-10) mol before and during L-NOARG infusion (1.0 microg/mL). Vascular reactivity was measured as an increase or decrease in perfusion pressure in the constant flow system. Rats poisoned with 50 or 200 ppm of cadmium demonstrated a significant decrease (P <0.05) in vascular response to L-NOARG used in doses of 50 or 100 microg. The dose-response curve obtained for L-NOARG was shifted to the right and ED50 value was greater in the group of rats given cadmium in a dose of 200 ppm than in the controls (70.3 +/- 10.7 versus 25.7 +/- 4.8 microg, P <0.01). These rats reacted with lower expressed vasodilatation to ACh in doses to 0.2 x 10(-10) mol. In all poisoned rats, L-NOARG enhanced the effect of ACh used in doses from 0.05 to 0.5 x 10(-10) mol, whereas in the control group this effect was only achieved at 0.1 x 10(-10) mol. The serum nitric oxide concentration was decreased (P <0.05) in both groups of cadmium-treated rats. These results suggest that cadmium in hypertensive doses modifies the vascular effect of NO in basal conditions and after stimulation by ACh.