Operating Zones Research Articles

In-field characterization of key performance parameters for bifacial photovoltaic installation in a desert climate

Abstract To address the main challenges inhibiting the adoption of bifacial PV technology in hot desert environment, continuous performance monitoring and comprehensive analyses are timely required. Therefore, for strengthening its bankability, this techno-economic study presents an in-field bifacial parametric analysis for the environment of Middle-East. Impacts of ground coverage ratio (GCR), stand-alone/in-array mounted losses, albedo, module temperature, mounting height, tilt, and azimuth angle were quantified. To highlight the bifacial potential, economic analysis as a function of energy gain and investment premium was carried out for demarcating profitable operating zones. Moreover, multi-variable analysis for rear irradiance was performed using ground coverage ratio, height, albedo and array size, specifically:1 × 1 (free-standing module), 3 × 3 and 5 × 5. It was found that for systems where the land costs are significant, high GCR coupled with increased mounting height would result in a better energy yield per area. Module with a bifacial gain of 8.6% was found to be profitable provided that the bifacial premium investment doesn’t exceed 10% of monofacial. Thermally, bifacial power gain was found to determine the cell temperature under different irradiation conditions. The study reveals vital insights that will allow engineers and researchers to optimize bifacial PV performance in hot and sunny desert climates.

Parametric Study of a Plunging NACA0012 Airfoil

Natural flight has always been the source of imagination for the Human being, but reproducing the propulsive systems used by animals is indeed complex. New challenges in today’s society have made biomimetics gain a lot of momentum because of the high performance and versatility these systems possess when subjected to the low Reynolds numbers effects. The main objective of the present work is the computational study of the influence of the Reynolds number, frequency and amplitude of the oscillatory movement of a NACA0012 airfoil in the aerodynamic performance for a constant angle of attack over time. The thrust and power coefficients are obtained which together are used to calculate the propulsive efficiency. The simulations were performed using ANSYS Fluent with a RANS approach for Reynolds numbers between 8,500 and 34,000, reduced frequencies between 1 and 5, and Strouhal numbers from 0.1 to 0.4. The aerodynamic parameters were widely explored as well as their interaction, obtaining optimal operational condition zones for the different Reynolds numbers studied.
 Keywords: Plunging, Airfoil, CFD, Aerodynamic coefficients, Biomimicry

Composteando el digestato de la fracción orgánica de residuos sólidos urbanos

A biosolid was produced from the composted digestate of the organic fraction of urban solid wastes (OFUSW). During a first hydrolytic-acidogenic stage, the milled OFUSW mass is transformed into volatile fatty acids and other soluble or suspended substances in the leachate while the residual solids constitute the digestate. A biosolid was produced from the composted digestate of the organic fraction of urban solid wastes (OFUSW). During a first hydrolytic-acidogenic stage, the milled OFUSW mass is transformed into volatile fatty acids and other soluble or suspended substances in the leachate while the residual solids constitute the digestate. To obtain a composting mass (CM) with a C/N between 25 and 35 and a matrix to allow aeration, mixtures of digestate (fD), OFUSW (fF) and sawdust (fS) were prepared using a simplex centroid design. Results were adjusted to a multiple regression model with volatile solids degradation efficiency (ηVS) as a response variable. It was found that the operation zone with the highest ηVS, were CM with the following compositions: fD: 0.425-0.625, fF: 0.275-0.450; and fS: 0.1-0.15. Three assays were carried out in a bench scale reactor, the final biosolids had a pH = 7.5, a C/N = 15 and a germination index (GI) = 84%. A linear correlation between ηvs and CO2 production was proposed for process control. A rapid CM stabilization was reached, up to ηVS = 35% in 12 days and the biosolids with high GI, can be used to improve soils.

Influence of Timber Harvesting Operations and Streamside Management Zone Effectiveness on Sediment Delivery to Headwater Streams in Appalachia

Disturbances created by timber harvesting equipment and associated haul roads and skid trails can create overland sediment flows (sediment paths), especially in steeply sloping terrain, leading to stream sedimentation. This study investigated the effect of variables associated with GPS tracked harvest equipment movement, skid trail development and retirement, topography, and streamside management zone (SMZ) width and tree retention on sediment delivery to streams. While the intensity of harvest equipment traffic was not correlated with sediment path development, the presence and location of skid trails were. All of the sediment paths were found to originate at water control structures, influenced by microtopographic features, on the skid trails directly adjacent to SMZs. Mesic slopes were associated with increased sediment path development across all SMZ configurations. Two factors, the accumulation of coarse logging debris in the SMZ and the increased distance of skid trails to streams, were both correlated with decreased sediment path development. The study provides insight into how these variables interact and can be used to develop site-specific guidelines for SMZs in steeply sloping terrain that could improve their efficiency and effectiveness.

Relationship between follow-up periods and the low-dose ranges with statistically significant radiation-induced risk of all solid cancers in the Russian cohort of Chernobyl emergency workers.

Radiation-induced risks for all solid cancer incidence and mortality were studied in the cohort of Russian Chernobyl emergency workers. The cohort included 69,440 persons with documented individual radiation dose accrued over the time of working in the Chernobyl zone. The mean age at entry into the zone of recovery operations was 33.9years and accumulated radiation dose was 132.9mGy. A total of 6981 solid cancer incident cases and 4272 deaths occurred in this cohort from 1992 to 2017. Three follow-up periods were studied: 1992-2009, 1992-2013, and 1992-2017. For each follow-up period, the lowest dose range with statistically significant (p < 0.05) radiation-induced risk of all solid cancer incidence and mortality were obtained. For the incidence of all solid cancer during the follow-up period 1992-2009, this lowest dose range was estimated to be 0-250mGy with an excess relative risk per dose of ERRGy-1 = 0.51 and 95% confidence interval (CI) (0.02; 1.05) Gy-1. For the period 1992-2013, the lowest dose range was 0-175mGy with ERRGy-1 = 0.85 (95% CI 0.03; 1.78), while for the whole follow-up period 1992-2017, it was 0-175mGy with ERRGy-1 = 0.81 (95% CI 0.08; 1.62). For mortality from all solid cancers during the follow-up period 1992-2009, the lowest dose range with statistically significant radiation-induced risk was estimated to be 0-225mGy with ERRGy-1 = 1.07 (95% CI 0.31; 0.97). For the period 1992-2013, the lowest dose range was 0-225mGy with ERRGy-1 = 0.86 (95% CI 0.23; 1.58), while for the whole follow-up period 1992-2017, the lowest dose range was 0-200mGy with ERRGy-1 = 0.82 (95% CI 0.10; 1.65). Thus, it was found that the minimal level of significant exposure (Dmin), for which a statistically significant radiation-induced risk of all solid cancers was obtained for Russian emergency workers (with individual doses of 0 - Dmin), decreases with increasing duration of cohort observation, both for cancer incidence and mortality.

Comparison of interaction mechanisms of lead phthalocyanine and disodium phthalocyanine with functionalized 1,4 dihydropyridine for optoelectronic applications

In the current work, the compound 2-methyl-N-octadecyl-2-(1-((trifluoromethyl)sulfonyl)-1,4-dihydropyridin-4-yl) propanamide was synthesized and characterized. Subsequently, its structure was optimized by DFT (Density Functional Theory) and its interaction with the chosen phthalocyanines: lead phthalocyanine (PbPc) and disodium phthalocyanine (Na2Pc) were also theoretically studied. The energy values of the HOMO (Highest Occupied Molecular Orbital) and the LUMO (Lowest Unoccupied Molecular Orbital), as well as the band gap were obtained from the resulting complex and a semiconductor behavior was found. Based on the theoretical results, bulk heterojunction films were manufactured with the aim of using them as semiconductor active layers in optoelectronic devices. In those films, the bandgap was determined through their absorption coefficients and the energy values of the photon, the results were compared to the theoretical bandgap previously calculated. Finally, the electrical behavior of the electronic donor-acceptor active layers was evaluated in form of simple devices with a heterojunction arrangement. The evaluation of the current-voltage (I–V) was carried out under the presence of different lighting conditions and the devices showed the curve of a typical semiconductor. No variations between the forward and reverse operation zones were shown by the devices, not even when they were exposed to different illumination sources. In general, an ohmic behavior was observed. Results demonstrated that 2-methyl-N-octadecyl-2-(1-((trifluoromethyl)sulfonyl)-1,4-dihydropyridin-4-yl) propenamide can be used as an electron acceptor species for the manufacture of semiconductor active layers of optoelectronic devices.

Implementation of Intelligent Controlling Mechanism to Improve Conversion Efficiency of Solar PV Module

The research article aims at an intelligent control method to improve conversion efficiency of solar photovoltaic module by tracking maximum operating point irrespective of variations in temperature and irradiance. A novel hybrid maximum power point based on learning automata is proposed. The algorithm works in two stages, first the learning automata detects the temperature and irradiation of light incidenting on PV module, second it identifies the zone of operation and adjusts the duty cycle of DC-DC converter. This implementation is done by designing the learning automata using artificial neural network and the adjustment of duty cycle is implemented with fuzzy logic controller. The design is verified using matlab/simulink environment.

Enhanced power generation, faster transient response and longer durability of HT-PEMFC using composite polybenzimidazole electrolyte membrane with optimum rGO loading

Here we report enhanced power generation, faster transient response and longer durability of HT-PEMFC by employing a composite membrane of PBI with reduced graphene oxide (rGO) at an optimum loading of 1%. Easy and low cost synthesis of the composite membranes at different loading of rGO is achieved using methane sulfonic acid (MSA) as solvent that resolves the long-standing issue of poor solubility of PBI in the conventional solvents. Property and performance mapping with respect to rGO loading not only leads to attain the optimum but also identifies the window of feasible operating zone. It is observed that with very low (1%) rGO content, composite PBI membrane (rGO-PBI-1) offers the maximum enhancement of all properties viz water uptake, acid uptake, proton conductivity, ion exchange capacity, acid retention capacity, chemical stability, yield strength, while beyond a threshold/critical loading (~4%) deterioration of electrochemical and mechanical properties occur. Steady state performance analysis reveals almost two times peak power enhancement of HT-PEMFC using rGO-PBI-1 electrolyte membrane at an operating temperature of 170 °C; insitu impedance analysis during fuel cell operation reveals sharp decay in charge transfer resistance. Multiple step response analysis confirms (~2 times) faster transient response of fuel cell using rGO-PBI-1 while compared to that with pristine PBI membrane. Fuel cell stability analysis ensures longer durability of operation with negligible decay in voltage.

The influence of the internally displaced persons forced migration on the dynamics of regional social and economic security indicators

The processes of forced internal migration, which became significant in 2014 as a result of the armed conflict in the east of the country, caused significant demographic and social changes in the regions performance. Particularly large changes have been taken place in the areas directly adjacent to the joint forces operation zone. The study is devoted to the research of the impact of the described processes on certain aspects of social and economic security of the regions. Impact assessment was performed on the basis of cluster analysis. In particular, the author constructed a neural network such as the Kohonen map. The model divided the neural sample from 25 regions (24 regions and the city of Kyiv) into six clusters according to the level of four indicators of social and economic security. This allowed assessing the impact of forced internal migration on some aspects of social and economic security of the regions. Based on the obtained map, it has been depicted that Donetsk and Luhansk regions, which directly border the joint forces operation zone, had a dramatic increase in the demographic burden and unemployment rate during the study period. The obtained results allowed assessing the impact of the processes of forced internal migration on the dynamics of certain indicators of social and economic security of the territories.

Determination of the safe operation zone for a turbine-less and solid oxide fuel cell hybrid electric jet engine on unmanned aerial vehicles

Solid oxide fuel cell (SOFC) hybrid electric jet engines without turbines in which compressors are powered by fuel cells instead of the turbines are promising and developmental aero-engines for unmanned aerial vehicles. The hybrid electric jet engine combines the merits of turbo-electric engines and fuel cell engines. To avoid component malfunctions and engine performance deterioration, the determination of the safe operation zone is necessary. In this study, a performance analysis model of the hybrid electric jet engine is built and the main conclusions are as follows. The safe operating zone of the hybrid engine is not restricted by turbine inlet temperature. Under low fuel flow rate and low air flow rate, zones of too low reforming temperature or too low SOFC open voltage exist. An unbalanced energy zone exists under high fuel flow rate and low air flow rate. The power produced by the SOFC is above that consumed by the compressor. The lower boundary of the safe zone is determined by the choke zone of the compressors. In the safe zone, the hybrid engine has properties of high specific thrust (837.6 N/(kg.s−1)) and high thermal efficiency (70.4%) at high fuel low and air flow rate.

Feasibility of targeted fishing in mesoscale oceanic eddies: a study from commercial fishing grounds of Andaman and Nicobar Islands, India

ABSTRACT Mesoscale eddies are important ocean phenomena that enhance biological productivity by mixing of water column and influence fishery catches, especially in stratified seas such as Bay of Bengal and Andaman Sea. The current study was conducted around the Andaman and Nicobar Islands (ANI), India located in the Eastern Indian Ocean. The study tested the feasibility of targeted fishing in eddies, by characterizing the mesoscale eddies in the region, towards developing operational altimetry-based fishery advisories for the fishers. We analysed fish catch data from 15,370 commercial fishing trips from the Islands using five fishing gears during 2014–17 spatially vis-à-vis the eddies delineated from Maps of Sea Level Anomaly (M-SLA). We show that 5-24% of the routine commercial catches occurred in eddies, fishery catches are positively influenced by different eddy zones and the fish catch using different fishing gear are significantly higher in some of the eddy zones. We generated experimental advisories showing locations of eddies and their zones, identified using Near Real-Time M-SLA data and guided the commercial fishers for targeted fishing in eddies. The fish Catch Per Unit Effort (CPUE) from the experimental fishing within the eddy zones was significantly (p < 0.01) higher than that from the traditional fishing grounds in the non-eddy areas. The spatio-temporal analysis of eddies around ANI during 2009–16 showed the occurrence of higher number of anticyclonic eddies, majority of which move westward and have a lifespan of less than 2 weeks and amplitude less than 4 cm. In the current study, the areas around ANI with frequent eddy occurrence and eddy density have been identified, which could aid in increasing the fishing intensity by targeting the pelagic fishes, using longlines, gillnets and ringnets. Thus, we show the possibility of using eddy fishing advisories generated from altimeter data, for augmenting the currently operational Potential Fishing Zone (PFZ) advisories that are generated using optical/thermal remote sensing data and disseminated to the coastal fishers in India. This will be helpful especially for the regions with and during periods of persistent cloud cover.

Service replanning in urban rail transit networks: Cross-line express trains for reducing the number of passenger transfers and travel time

Reducing the number of transfers and improving the operating speed are key factors in enhancing the competitiveness of urban rail transit (URT) systems. This paper proposes an integrated optimization with tactical cross-line planning and an operational express train mode to fully utilize line capacities and reduce the total trip time without additional operating costs and investments. In this paper, a new mixed integer non-linear programming (MINLP) model is proposed for systemically exploring the benefits of cross-line express trains to achieve both passenger travel time and operation cost savings; in this model, the frequencies, stopping patterns and operation zones of cross-line express trains and local trains are simultaneously optimized. The characteristics of same-line trips (SLT) and cross-line trips (CLT) under various stopping patterns are investigated. Additionally, a genetic algorithm (GA) is developed based on the MINLP model. Finally, the effectiveness of the proposed model and heuristic algorithm is verified through a set of real-life instances based on the Beijing URT network. The results show that the number of transfers can be reduced by 78%, with a 3.34% savings of travel time and a 4.66% savings of operating costs, when the cross-line express operating mode is properly adjusted.

The study of the wear of the control knives of the straw chopper

The article considers the topical task of studying the wear rate of steel parts in the course of agricultural work. The wear of the knives of chopper-cum-spreaders used in agricultural works is determined and compared with control samples. Within the scope of the study, the relative linear and weight wear was being determined. The results of the study of dimensional parameters are given in the article. The dependence of wear on the operating time and zones of various wear of the part is determined. A graphic illustration of these dependencies is provided. The mechanism of wear of these parts is proposed. It was established that it is necessary to change the design of the hardsurfacing overlay used in order to maintain the acceptable cutting properties of the knife until it reaches its limit state, more specifically: firstly, to refuse applying hardening strips of hard alloy on the reverse side of the cutting edges by 1/3 of their length located at a distance of 65-70 mm from the flat end; secondly, to make the width of the strips variable, gradually increasing it to a size 1.5 to 2 times exceeding the blade width when approaching the flat end of the knife, i.e. give them triangular or curvilinear shape that is close to and/or overlapping the boundaries of the wear outline; thirdly, the triangular shape of the strips can be achieved due to the excessive material released from the unhardened 1/3 of the blade length.

Two-phase thermo-hydraulic model of a 210 MW thermal power plant boiler for designing the riser-downcomer circuit

In the present work, a natural circulation boiler of a typical 210 MW thermal power plant is investigated with an objective to provide the feasible, reliable, and safe design solution of the riser-downcomer circuit. A thermo-geometric analysis of a riser-downcomer circuit of a typical subcritical boiler is carried out for a specified steam generation rate, based on a two-phase flow model. The developed model is validated with the available experimental/numerical data, satisfactorily. The model takes care of a detailed flow regime map, is capable of identifying DNB and CHF points, and can estimate a typical temperature rise of riser tubes under any flow regimes. The safe and unsafe zones of operations of heated riser tubes have been identified quantitatively and accordingly a range of feasible design solutions are demonstrated in a tabular form. The tube numbers, lengths, and especially the diameters and thicknesses are provided in compliance with the ASME boiler code. We would like to emphasize that the objective of this work is not to select a single design, rather provide a number of flexible solutions, which can be utilized by researchers, manufacturers, and practicing engineers, according to their needs.

Bioresorption and biodegradation of the 3D-printed gene-activated bone substitutes based on octacalcium phosphate

Gene-activated materials are getting translated to the clinical practice that is the result of increased research activity in this area. There is significant success in development of gene-activated materials for bone grafting procedures. In our study, we made the gene-activated bone substitute based on octacalcium phosphate and plasmid DNA with VEGFA gene using three-dimensional printing technologies (discs, size of 10x2 mm). During the subcutaneous test in rats, the dynamics of bioresorption of materials was evaluated in comparison with the control that was presented by the scaffold without gene constructs. 60-90 days after surgery, volumes of the implants twicely decreased while the diameter declined by 20% at 180 days, and there were no significant differences between the groups related to these parameters. According to a histological examination, no signs of pronounced inflammation were found in the operation zone, the materials were surrounded by a connective tissue capsule. Further studies are needed to evaluate the effect of gene-activated materials produced with the developed technology on reparative osteogenesis.

The state of phosphorus balance on 58 Virginia dairy farms.

Managing a sustainable dairy farm requires balancing phosphorus (P) imports and exports that enter and leave through the farm gate. Over the long term, P surpluses will elevate soil-test P concentrations above crop requirements through routine land applications of manure. The objectives of this study were aimed at Virginia dairy farms (a) to determine P mass balances, (b) to define potential guidelines for a sustainable and feasible zone of operation based on P balance and P use efficiency, and (c) to assess risk factors driving P surplus and P use inefficiencies. Data on farm-gate P imports and exports via feed, manure, crops, fertilizers, bedding, animals, and milk were collected for 58 dairy farms in Virginia. There was no relationship between farm P balance and milk production, indicating that a P surplus was not necessary for good milk productivity. A feasible P balance limit was calculated below which 75% of farms could operate, and this was 18.7kg P ha-1 . Two risk factors were identified for farms having a P balance above this limit: (a) land application of poultry litter and (b) excessive import of P through feed. Combined dairy and beef operations generally had more land and a lower P balance, whereas having combined dairy and poultry did not raise the P balance as long as poultry litter was exported. Dairy farms in Virginia can operate with a sustainable P balance as long as they avoid using excessive poultry litter and pay attention to P imported through purchased feed.

Device-to-device communications under transceiver impairments in OFDMA cellular networks

Device to Device communication (D2D) would be a part of 5G to cater variety of services along with cellular offloading. In order to leverage the benefits of D2D communication it needs be adapted for robust conditions. In physical layer we use OFDM for cellular and D2D communication. OFDM based systems are inherently associated with transceiver impairments. Using OFDM for D2D communication thereby involves the impact of these transceiver impairments on D2Ds and their feasibility zone of operation. As the D2D transmitter power is small, the transceiver impairments effect becomes predominant and hence it becomes important to study D2D performance under transceiver impairments. As there is limited literature on the effect of transceiver impairments onto the performance of D2D enabled cellular networks, it becomes essential to analyse this aspect. We analysed the impact of these impairments on the cellular and the D2D modes and the zone where D2Ds can be operated under these impairments. Our conclusion is that due to transceiver impairments there is fall in throughput of both cellular and D2D mode. D2D communication which is beneficial at the cellular edges loses its operational advantage. Besides we also conclude that under the effect of transceiver impairments the switch-over distance to D2D mode moves towards eNB. We also analyse that D2D communication could be harnessed even under the case of transceiver impairments if we do threshold adjustment in the physical layer. We get an advantage of approximately 5 Mbps in throughput at distance 150 metres from eNB after threshold adjustment.

Automatic generation control of a large hydropower plant with head‐sensitive forbidden and restricted zones

Head-sensitive forbidden and restricted zones of large hydropower units are challenging the automatic generation control (AGC) as admissible operating zones are discontinuous and variational. This study focuses on the AGC of such a large hydropower plant to ensure the stability, security and timeliness of power grids. A methodology is developed to solve the unit commitment (UC) and load distribution in AGC. This methodology identifies in advance all feasible unit combinations under different water heads and determines admissible operating zones using combinatorial mathematics techniques. A fast strategy that includes the accurate estimation of varying water heads helps to eliminate infeasible unit combinations. Minimising the number of units working in restricted zones and times of unit output passing through forbidden zones is used to optimise the UC, where priority orders of units are introduced to evaluate UC schemes with the same objective value. Finally, a dynamic programming based model is formulated to solve an economic load distribution among operating units. The methodology is applied to the AGC of the Nuozhadu with nine 650 MW units of two different types. Three cases indicate that the number of units working in restricted zones and times of unit output passing through forbidden zones is significantly reduced.

Проблемні питання організації медичного забезпечення Збройних Сил України в антитерористичній операції на сході країни

У статті проаналізовані проблеми медичного забезпечення ЗС України в зоні антитерористичної операції. Акцентовано увагу на основних напрямах удосконалення медичного забезпечення Збройних Сил України в зоні АТО, необхідності організації взаємодії медичних служб різних міністерств і відомств в єдиному медичному просторі держави, формуванні сучасної системи лікувально-евакуаційного забезпечення з метою своєчасного надання медичної допомоги, проведення якісного лікування військовослужбовців до кінцевого результату.

A Fully Self-Powered Vibration Monitoring System Driven by Dual-Mode Triboelectric Nanogenerators.

Vibration sensor is very necessary for monitoring the structural health of constructions. However, it is still a major challenge to meet simultaneously real-time monitoring, continuous assessment, and early incident warning in a simple device without a complicated power and analysis system. Here, we report a self-powered vibration sensor system to achieve real-time and continuous detection of the vibration characteristics from a dual-mode triboelectric nanogenerator (AC/DC-TENG), which can produce either alternating current (AC) or direct current (DC) within different operation zones. Within the vibration-safe region, the AC/DC-TENG with AC output not only can continuously assess the vibration characteristics but also can power the signal transmission. More importantly, once the vibration amplitude crosses the danger threshold, the AC converts immediately to DC, meanwhile triggering the alarm system directly to accurately predict the danger of construction. Our self-powered vibration sensor system can serve as a facile tool for accurately monitoring the structural health of constructions.