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Продемонстровано підхід до концептуального проєктування турбіни низького тиску авіаційного турбогвинтового двигуна на базі єдиного газогенератора. Підхід цікавий тим, що крім коефіцієнта корисної дії, у якості критерію оптимального проєктування використана маса турбіни і маса пального, а також кількість аеродинамічних профілів. Отримано залежність цих параметрів від коефіцієнта аеродинамічного навантаження турбіни, який змінюється шляхом зміни діаметра турбіни в заданих обмеженнях. An approach to the conceptual design of the low pressure turbine for the aviation turbopropeller engine has been shown. The engine is created on the basis of the single gas generator for the two-engine power plant intended for the average transport aircraft. This approach is of great interest because in addition to the efficiency factor, the mass of the designed turbine, the fuel mass and the number of aerodynamic profile were used as optimal design criteria. The designed turbine includes the two stages and the interturbine transition channel of a diffuser type arranged in front of them. Consideration was given to the four flow parts of the turbine that differ by the diameter and the height selected in the preset limitation range. The gas dynamic efficiency of the interturbine transition channel, gas dynamic efficiency of the after-turbine channel, the strength of the turbine blade of the last stage were taken as the limitations. The dependencies of the efficiency factor, the turbine mass and the number of turbine blades on the turbine aerodynamic load factor were obtained for the four turbine options. The turbine efficiency factor was determined using our own method of one-dimensional gas-dynamic computation. The fuel flow rate was determined using the mathematical engine model. The turbine mass was determined using the parametric method as a function of the aerodynamic load factor and the turbine flow rate factor. The number of aerodynamic profiles was defined using the Zweifel parameter. It was shown that the use of heavy loaded and less loaded low pressure turbines can reduce the take-off weight of the aircraft in spite of an increased fuel flow rate.

he purpose of this research is to study and substantiate the possibility of the use of two options of the technology to manufacture blades in order to provide an optimal variant of the flow part for the high pressure cylinder (HPC) turbine K-330-23.5. The methods of comparative analysis have been used for the comprehensive estimation of the advantages and drawbacks of each technology in question used for the design and manufacture of blades. To solve optimization problems we used the methods of multiparametric multicriterion and multilevel optimization of complex engineering objects. These methods are based on the use of the algorithms of experimental design theory, LPτ-sequence, "bee swarm", nonlinear programming, etc. The computation of steam flow in the turbine flow part and water steam properties has been based on the use of the methods of numerical solution of appropriate equation systems. CFD-methods have been used to estimate the efficiency of rotors assembled using the blades that were manufactured based on the technologies of a different level of complexity. The calculated analysis and the optimization research showed that contemporary optimization methodologies used to get optimal flow parts for the HPC of К-330-23.5 turbine allow us to provide highly efficient flow parts for the HPC using the two types of technologies suggested for the manufacture of blades and blades cascades. At the same time, the research done proved that the use of more expensive technology for the manufacture of blades combined with the solution of multiparametric optimization problem provides a high gain both in the efficiency factor and the cylinder power in comparison with a simpler technology used for the manufacturing of blades. The use of contemporary optimization algorithms allows for a considerable increase in the efficiency of the flow parts of steam turbines even if simplified technologies are used to manufacture rotor blades.

At the section of sinter grading and cooling of JSC “Ural steel” sinter plant, lamellar conveyors are used for transportation of return products. The conveyors have an open cylinder tooth gear, the working surface of which are quickly worn out because of abrasive particles of dust and sinter, which got into the gearing. It was proposed to substitute the lamellar conveyors drives, consisting of electric motor, coupling, cylinder two-step gear, open cylinder tooth gear, to the drives, consisting of motor-gear. The advantages of the motor-gear were demonstrated, as follows: they are compact, and have a high efficiency factor. The motor-gear has a block structure, which enables to replace it quickly in case of failure, therefore reducing the downtime of equipment. As a result of modernization of drives of CA-5 and CA-6 lamellar conveyors, their reliability will increase, the expenses for repair and technical maintenance will decrease resulting the sinter cost decreasing. The payback time of the drives modernization project of CA-5 and CA-6 lamellar conveyors will make two years.

In this paper, yield analysis of a 186 kWth parabolic trough collector (PTC) system for medium-temperature heat process applications, is conducted under a semi-arid climate (Benguerir, Morocco). For this purpose, a PTC model is simulated and validated using experimental data from a PTC test loop, installed at the Green Energy Park research facility. Following, the studied system is simulated using high-quality meteorological data measured at ground level for three years. The impact of soiling on the system’s heat production is studied, considering it as a time-dependent parameter. Finally, an economic analysis is conducted considering as indicators the Levelized cost of heat (LCOH) and the payback time. According to the results, the used model for PTC simulation is accurate, where the daily average deviation is around 4.8% under clear sky conditions. Furthermore, and based on the simulation results, integration of PTC in the Moroccan industrial processes can be very beneficial, where the proposed 186 kWth PTC plant can produce about 388 Tons of saturated steam at 5 bars, annually. Nevertheless, soiling is a limiting efficiency factor especially during the dry period of the year, where the solar field daily average thermal losses can reach 354 kWthh, which is equivalent to a drop of 27% in the production. Economic evaluation results showed that for a low-cost PTC (

The use of lightweight concrete (LC) represents a great challenge due to the reduction of the mechanical properties caused by the substitution of conventional aggregate for light aggregate. In view of the above, this paper aimed to verify the effect of the addition of 10% of silica fume (SF) in mixtures of concrete with replacement of 50% and 100% of the volume of crushed stone by expanded clay (EC). In the fresh state, the content of superplasticizer additive needed to obtain a consistency of 100±20 mm was analyzed using the slump test. In the hardened state, tensile and compressive strengths were analyzed at 3, 7 and 21 days of hydration. A decrease in the mechanical performance of the concrete was observed when the gravel was replaced by EC. Despite this decrease, lightweight concretes resulted in greater strength/weight ratios. It was observed that the addition of SF significantly improved the mechanical properties of lightweight concrete. Thus, it is possible to conclude that the addition of SF can compensate for the loss of mechanical performance caused by the replacement of conventional coarse aggregate with expanded clay, without the need to increase the amount of cement in the mixture A utilização de concreto leve (CL) representa grande desafio devido a redução das propriedades mecânicas causadas pela substituição do agregado convencional por agregado leve. Frente ao exposto, este trabalho objetivou verificar o efeito da adição de 10% de sílica ativa (SA) em traços de concretos com substituição de 50% e 100% do volume de brita por argila expandida (AE). No estado fresco, foi analisado o teor de aditivo superplastificante necessário para obter a consistência de 100±20 mm através do ensaio de slump test. No estado endurecido, foram analisadas as resistências à tração e à compressão aos 3, 7 e 21 dias de hidratação. Foi observada diminuição do desempenho mecânico do concreto quando a brita foi substituída por AE. Apesar dessa diminuição, os concretos leves resultaram em maiores relações resistência/peso. Foi observado que a adição de SA melhorou significativamente as propriedades mecânicas dos concretos leves. Dessa forma é possível concluir que a adição de SA pode compensar a perda de desempenho mecânico provocado pela substituição do agregado graúdo convencional pela argila expandida, sem ser necessário aumentar a quantidade de cimento da mistura.

This work presents green lightweight reactive powder concrete (GLRPC) as a novel lightweight composite with improved properties by incorporating modified expanded polystyrene beads (MEPS) i...

Recent evidence suggests that the stability performance of footings can be greatly enhanced using a granular trench. Therefore, this paper sets out to study the bearing capacity of strip footing on a two-layered soil system that is composed of overlying granular fill above the undrained clay with an inclusion of a granular trench. The study also considers reinforced as well as unreinforced conditions at the interface of a two-layered soil system. An efficiency factor (ξ) of bearing capacity is defined by the ratio of the improved bearing capacity (pum) of strip footing in a two-layered soil system to the bearing capacity of strip footing over the original clay soil (pu). Numerical formulations are implemented by employing lower bound finite element limit analysis to study the bearing capacity of strip footing using LINPROG in MATLAB. The numerical models are validated with available results in the literature. Several parametric studies were performed for various settings, such as with or without granular trench and/or reinforced granular fill. The produced charts should, therefore, be of use to practitioners.

The long-term prosperity of oil and gas companies requires a constant influx of new volumes of producible oil and gas that can be developed to replace existing production. Without such activity it is inevitable that production will eventually fall as the resource base is gradually consumed The attractiveness of achieving more barrels from existing discovered fields has always been strong as it has long been recognized that such opportunities can be economically attractive and rapidly brought to fruition. It is also recognized however that such opportunities may be more complex relying both upon excellent subsurface understanding and successful brownfield project execution. It is therefore not surprising that in many cases actual recovery factors (produced volume/initial in-place volume) in oil and gas fields can be significantly less than what should be technically achievable. Identification of economically robust brownfield opportunities remains an industry challenge. In this paper we address this challenge by reporting a new workflow for brownfield opportunity identification leading to recovery factor improvement. Shell's Recovery Factor Improvement (RFI) Workflow was developed to address these issues and builds upon the existing best practice workflows to better explore and define the activities that would be required to achieve top quartile recovery factor performance. The workflow combines elements of various existing published approaches: (1) Shell's TQ-EUR Tool is an internal database that allows current and forecast recovery factor to be compared with that of analogue reservoirs using a reservoir complexity factor and key reservoir performance parameters as comparison criteria across the Shell portfolio. (2) An efficiency factor-based analysis of recovery factor; (3) a structured workshop to elicit new recovery factor improvement activities by addressing each individual efficiency factor in turn; (4) Consistent reporting of results. The combination of these approaches creates a powerful workflow to improve brownfield field opportunity identification and maturation. The RFI Workflow is intended to provide asset teams with a practicable and repeatable process that can be completed without specialist technical support or software to enable the identification of robust new opportunities. Experience with using the new workflow has demonstrated that it is able to bring new understanding to asset teams, consistently identify new opportunities and highlight common portfolio-wide opportunity types that would benefit from further central technology development funding.

We report the fabrication process and performance characterization of a fully integrated ferroelectric gate stack in a WSe2/SnSe2 Tunnel FETs (TFETs). The energy behavior of the gate stack during charging and discharging, together with the energy loss of a switching cycle and gate energy efficiency factor are experimentally extracted over a broad range of temperatures, from cryogenic temperature (77 K) up to 100 °C. The obtained results confirm that the linear polarizability is maintained over all the investigated range of temperature, being inversely proportional to the temperature T of the ferroelectric stack. We show that a lower-hysteresis behavior is a sine-qua-non condition for an improved energy efficiency, suggesting the high interest in a true NC operation regime. A pulsed measurement technique shows the possibility to achieve a hysteresis-free negative capacitance (NC) effect on ferroelectric 2D/2D TFETs. This enables sub-15 mV dec−1 point subthreshold slope, 20 mV dec−1 average swing over two decades of current, ION of the order of 100 nA µm−2 and ION/IOFF > 104 at Vd = 1 V. Moreover, an average swing smaller than 10 mV dec−1 over 1.5 decades of current is also obtained in a NC TFET with a hysteresis of 1 V. An analog current efficiency factor, up to 50 and 100 V−1, is achieved in hysteresis-free NC-TFETs. The reported results highlight that operating a ferroelectric gate stack steep slope switch in the NC may allow combined switching energy efficiency and low energy loss, in the hysteresis-free regime.

Робота знайшла своє застосування при конструюванні малогабаритних літальних апаратів, де як рушійну силу використовують п’єзокерамічні пластини. При конструюванні малогабаритних апаратів на основі п’єзокераміки є вкрай важливим вплив співвідношення довжини та ширини п’єзокерамічної пластини на її резонансну частоту. В результаті досліджень отримано математичні залежності для прогнозування частоти коливань залежно від геометричних розмірів п’єзоелектричної пластини. Адекватність отриманих чисельних розрахунків підтверджено експериментальними дослідженнями. In the article the attention is paid to the peculiarities of the construction of small-sized aircraft flying into the air with the help of wings based on the bionic principle – copying movements birds or insects. Micro devices of such size and type have a wide range of applications and a number of tasks set before them, such as: pollination of crops, search and rescue operations, observation, as well as monitoring of weather, climate and environment with high resolution. The work has found its application in the design of small-sized aircraft, where piezoceramic plates are used as a driving force. The piezoceramics becomes much more relevant than that of an electric motor, since with the reduced design of a small-sized flying machine built on the basis of an electric motor, it will have to reduce the electromagnetic engine itself, that will lead to a loss in the efficiency factor of the engine and the aircraft in general. The piezoceramic engine is capable of converting electric energy into a mechanical one with a very high operating coefficient, which in some cases amounts to more than ninety percents. In addition, the use of piezoactuators has a number of advantages: operating speed, the development of large forces, the absence of a magnetic field, low energy consumption, no tendency to wear, the ability to work in extreme conditions. When constructing small-sized devices based on piezoceramics, the ratio of the length and width of the piezoceramic plate to its resonant frequency is extremely important. As a result of the research, mathematical dependences have been obtained for predicting the oscillation frequency, depending on geometric dimensions of the piezoelectric plate. The adequacy of the obtained numerical calculations is confirmed by experimental studies

In order to find effective confining pressure in concrete members externally wrapped with Fiber Reinforced Polymer (FRP) jackets, different values of the so-called strain efficiency factor have been suggested by several researchers. In this paper, the durability of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets in aggressive marine environment is assessed, and the effect of such environments on the strain efficiency factor in compressive members is investigated. A set of 3D finite element analyses (FEA) are performed to find the strain efficiency factor. The strain efficiency factor of GFRP jackets is lower than that of CFRP jackets in different environmental conditions. Furthermore, the strain efficiency factor decreases as the exposure time increases, which is more evident in GFRP-wrapped concrete. After 3000 and 9000 h of marine exposure, the strain efficiency factors decrease by 11% and 43%, respectively, in GFRP jackets. In CFRP-wrapped members, the reduction is about 18% and 25%, respectively.

Introduction. The existing methods of assessing the technical condition of power hydraulic cylinders do not allow one to conclude about the need to restore worn surfaces of parts. The data on limit values of wear of parts (wear and tear value at which a decision is made to repair) in technical requirements to overhaul and other technical documentation of hydraulic cylinders are not currently available. The aim of the study is to determine limit values of wear of working surfaces of hydraulic cylinder parts of C series. Materials and Methods.To assess the technical condition of hydraulic cylinders used, the authors developed a device on the basis of the stand KI-28097M-GOSNITI, equipped with an independent hydraulic station and load hydraulic cylinder, at which bench tests were carried out in the operation of С series hydraulic cylinders to determine overall efficiency values. Results. Results of bench and micrometer tests of the former hydraulic cylinders of the С series (С75/30, С90/30, С100/40) are presented. The regression model of the relationship between total efficiency of C series hydraulic cylinders (С75/30, С90/30, С100/40) and wear of working surfaces of parts was obtained. According to this regression model obtained using the method of steep ascent, limit values of wear of the working surfaces of C series hydraulic cylinder parts (С75/30, С90/30, С100/40) were determined. Discussion and Conclusion.19,5 % of hydraulic cylinders of С series (С75/30, С90/30, С100/40) were operated in an out-of-limit condition. In case of technical service companies carrying out the input control of to-be-repaired hydraulic cylinders, limit values of wear for hydraulic cylinder surfaces, determined by the method of steep ascent, allow for making proper decisions on the need of their restoration.

The mass fraction burned (MFB) of the gas mixture in combustion process as the function of the combustion duration time, reflects the percentage of fuel consumed at the every moment in the combustion process, and is an important factor for analysing of the fuel combustion performance, and it has high engineering value for evaluating engine design parameters and operating performance and for improving the combustion process in-cylinder combustion process. The ion current signal directly originated from the fuel combustion process in the cylinder, and contained much information about the combustion process; the MFB of fuel in combustion process can be obtained based on the correlation between the MFB and ion current signal. In this paper, the ion current method is constructed to calculate the MFB of fuel in combustion process under different initial conditions (initial pressure from 1 bar to 3 bar, equivalence ratio from 0.8 to 1.2, hydrogen mass fraction from 0% to 10%, and CO2 dilution ratio from 0% to 10%), the method based on the waveform parameters of ion current signal for obtaining the efficiency factor and the form factor of Wiebe function, and further to slove the mass fraction burned of combustion process. The mass fraction burned is obtained through ion current method reduced assumptions error and improved the calculation accuracy compared with the well-known Rassweiler–Withrow method, and the ion current method has an advantage that not requires an high-cost sensor and some rather complex measuring instruments. The ion current method is a simple but powerful calculation model that provide a new technical path for analysing and online obtaining the MFB of fuel in combustion process.

The article presents a method of quantitative assessment of the oil transportation efficiency through the trunk pipelines’ segments, considering the flow performance of the line section. In accordance with the methodology, the assessment of the oil pipelines’ energy performance parameters is performed according to the data recorded by built-in tools of supervisory control and data acquisition (SCADA) system, including: • efficiency factor of the oil pumping station – according to readings of pressure gauges installed at the pump station inlet and in the discharge header; • control factor of the automated pressure control system (APCS) – according to the readings of the pressure gauges installed in the discharge header and in the pumping station outlet line; • flow performance of the oil pipeline segment – according to the readings of the pressure gauges at the inlet/outlet of the oil pumping station and at the end of the technological segment of the oil pipeline. Using the example of the oil pipeline operation data analysis, it is shown that the proposed comparison criterion, the performance factor of the technological segment, enables to determine all the traditionally used criteria for assessing the actual operating conditions of the trunk oil pipelines, to identify the characteristic features of each mode, to compare the operation parameters of the pipelines with various diameters and designs.

There are a lot of the parameters which affect pile group behavior in soil. One of these factors is the distance of piles from each other. The impact of distance on pile groups in sand has been investigated through some researches, whereas most of them have not represented an exact estimation according to the continuous change of the distance in sand. Moreover, most of previous investigations have considered two piles as a perfect group. Since two-pile group has the least interaction effect among piles, it cannot suitably demonstrate the influence of spacing. In this lecture, several 4-pile groups modeled with different spacing were subjected to axial loading in laboratory. The pile groups were free-head with length to diameter ratio of 13.5. The piles are designed in a way which the shaft resistance of piles can be completely mobilized through the test. Then, the bearing capacities of pile groups are measured and compared with the single pile's resistance in order to calculate the efficiency coefficient of the groups. It is revealed that the distance is noticeably effective in efficiency factor and this effectiveness, non-linearly decreases by increase of spacing. The results show that the efficiency coefficient is changing between almost 1 and 1.4.

A novel work conducted upon three sides concave dimple roughened SAHs is presented here. Exhaustive experimental investigations were carried out in Feb-May 2017 upon one and three sides roughened solar air heaters on test setup installed at terrace of Mechanical Engineering Dept., NIT Jamshedpur and results are presented as rise in heat transfer and thermal performance of three sides over one side roughened duct against corresponding frictional losses. The experimental setup was validated using Nusselt number and friction factor correlation derived by Saini and Verma (2008) using one side roughened similar duct model. The geometrical parameters were used as dimensionless ratio as relative dimple pitch (p/e), relative dimple height (e/Dh) and relative dimple depth (e/d) in the range of 8–15, 0.018–0.045 and 1–2 respectively. The range of Reynolds number covered during experimentation was 2000–13500. Heat transfer augmentation for three sides over one side roughened ducts was appreciable considering rise in frictional losses. The thermal efficiency was measured in terms of collector heat removal factor (FR) and collector efficiency factor (F') and the collector’s performance parameters were given as F R τ α and ( F R U L ). The optimum roughness parameter was found to be p/e = 12, ‘e/Dh’ = 0.036 and ‘e/d’ = 1.5. For m = 0.0293 kg/s and Cp = 1.005 kJ/kg K, F R τ α and F R U L comes out equal to 0.7346 and 8.85 W/m2 K, respectively. Three sides roughened SAHs have high thermal efficiency of the order of 44–67% more than that of one side roughened SAH for the range of flow and roughness parameters investigated.

Compressive strength is an important and pertinent property for the characterization of concrete. It is known that compressive strength of hardened concrete depends on the efficiency factor (K) of silica fume and its percentage replacement (%SF). Consequently, the ultrasonic pulse velocity (UPV) is also an important factor for predicting compressive strength. The article examines the capability of relevance vector machine (RVM) and emotional neural network (ENN) for determination of compressive strength using the efficiency factor, percentage silica fume replacement and UPV as an input parameter. A comparative study has been carried out for the developed model using RVM and ENN. The analysis confirms that both RVM and ENN are a robust model for the prediction of compressive strength of hardened concrete.

Carbon fibre-reinforced polymer (CFRP) was introduced over three decades ago to the field of structural engineering. The goal of this study is to investigate the effects of different types of sands...

Concrete pipes are widely used in municipal structures and vulnerable to cracking and leakage when subjected to external load. To improve the mechanical properties and hence increase the cracking resistance of the pipe, steel fiber reinforced cement-based composite pipe specimens with steel fibers annularly distributed along the circumferential direction of the pipe were prepared. In the preparation of the annularly aligned steel fiber reinforced cement-based composite (ASFRC) pipe specimens, an external circular magnetic field was applied to the fresh mixture of the steel fiber reinforced cement-based composite to drive the steel fibers rotating to the circumferential direction of the pipe when the mixture was compacted. The three-edge-bearing strength and ductility of the ASFRC and ordinary steel fiber reinforced cement-based composite (SFRC) pipes were tested and compared. The results showed that annularly aligned steel fibers can effectively improve the load carrying capacity and ductility of the pipe specimens, which can be attributed to the higher orientation efficiency factor of the steel fibers and the increase in the number of steel fibers on fractured section of ASFRC pipe specimens.

Home-based health care applications are rapidly gaining popularity, enabling a renewed focus on the design of low-power and low-noise front-end circuitry. In this context, the evaluation of low-frequency biomedical signals, such as the respiration pattern, benefits from the design of a front-end amplifier with reduced power consumption and low noise. Continuous efforts on improving the performances of respiration-monitoring devices have resulted in the reduction of noise and motion artefacts by increasing complexity (e.g. complex algorithms or high precision filtering) at the expense of increased power consumption. This study is focused on the design of a fully integrated charge amplifier for respiration monitoring based on a pyroelectric sensor. Simulation and test results show a power consumption of 1.8 µW, an active die area of 0.085 mm 2 , a bandwidth in the range from 10 mHz to 13 kHz, and a remarkable noise efficiency factor of ∼2.79, which fits well with the development of an energy efficient wearable device.

In this study, an experimental investigation of the interference effect of two closely spaced strip footings resting on the surface of a layered sand deposit was conducted through a number of laboratory scaled model tests. The influence of the footing's length and spacing ratio and the thickness of the first layer on the efficiency factor were examined. The results are presented in terms of efficiency factors, and their variation was computed with respect to the change in the spacing ratio between the two footings. The results revealed that the efficiency factor depended significantly on the upper layer's thickness and strength.

Fibre reinforced cementitious matrix (FRCM) systems are mostly externally bonded (EB) for the strengthening of reinforced concrete (RC) and masonry structures. In this paper, the relatively new concept of near-surface embedded (NSE) FRCM, has been introduced for the flexural strengthening of beams. The process of the application of NSE-FRCM strengthening technique involves the removal of the concrete layer at beam soffit, being the most deteriorated in actual practices. Experimental evidence of the flexural strengthening efficacy of this technique is provided here. Fourteen RC beams were prepared and tested under four-point loading with the consideration of three test parameters: (a) FRCM material (polyparaphenylene benzobisoxazole (PBO)/carbon/glass); (b) strengthening technique (NSE and EB); and (c) the reinforcement ratio (0.5% representing flexure-deficient beams and 1.28% representing typical under-reinforced beams). The strengthening led to gains in ultimate loads that ranged between 30.1% and 93.3%. The strengthening techniques are compared based on an introduced strengthening efficiency factor. This paper was made possible by NPRP grant # NPRP 7-1720-2-641 from the Qatar National Research Fund (a member of Qatar Foundation) Scopus

This paper experimentally investigated the thermal performance of the developed solar box cooker with different reflector configurations. All tests were carried out under Bahir Dar (Ethiopia) prevailing weather condition. Two standard tests, namely stagnation test and sensible heat test were adopted in order to evaluate the thermal performance of the cooker. The highest maximum plate temperature of 148.7 °C can be achieved by the cooker with tracking reflector at optimal angle. In order to evaluate the performance of the cooker, the following performance indexes were employed, thermal efficiency, cooking power and two figures of merit, namely the ratio of optical efficiency to heat loss factor (F1) and the product of heat exchange efficiency factor and optical efficiency (F2). According to the experimental data, the highest computed value F1 of 0.154°C m2/W, can be obtained from the cooker with tracking reflector at optimal angle. The thermal efficiencies achieved by Cooker I, II and III are 37.24%, 32.27% and 33.89%, respectively. Thermal efficiency of the cooker was improved by 9.6% by tracking reflector at optimal angle instead of with fixed reflector. Furthermore, the thermal efficiency was also improved by 15.4% by using aluminum cooking vessel in place of using stainless steel vessel. It can be concluded from the experiments that effective utilization of all solar radiation intercepted on the reflector, and the use of cooking vessel having a reasonably good thermal diffusivity contribute significant roles to improve the cooking performance of the cooker.

The effective functioning of a railway track under operating conditions depends largely on the performance of various rail track interfaces (e.g. ballast-subballast interface, subballast-subgrade interface). In this context, a series of large-scale direct shear tests were conducted to investigate the shear behavior of unreinforced and geogrid-reinforced ballast-subballast interfaces at different normal stresses (σn) and rates of shearing (Sr). Fresh granite ballast and subballast having average particle size (D50) of 42 mm and 3.5 mm respectively, and five geogrids with different aperture shapes and sizes were used in this study. Tests were performed at different normal stresses (σn) ranging from 20 to 100 kPa and shearing rates (Sr) ranging from 2.5 to 10.0 mm/min. The laboratory test results confirmed that the shear strength of ballast-subballast interface was highly influenced by the applied normal stress (σn) and rate of shearing (Sr). The friction angle (φ) of unreinforced ballast-subballast interface was found to decrease from 63.24° to 47.82° and dilation angle (ψ) from 14.56° to 5.23° as the values of σn and Sr increased from 20 to 100 kPa and 2.5–10.0 mm/min, respectively. Further, the breakage of ballast (Bg) was found to increase from 2.84 to 6.69%. However, geogrid inclusions enhanced the shear strength of the ballast-subballast interface and also reduced the extent of Bg. The results indicate that it is possible to establish a relationship between the friction angle (φ) and breakage of ballast (Bg), wherein the friction angle (φ) of both unreinforced and geogrid-reinforced interfaces reduces with the increase in breakage (Bg). The interface efficiency factor, defined as the ratio of the shear strength of the geogrid-reinforced ballast-subballast interface to the original shear strength of ballast-subballast interface varies from 1.04 to 1.22. Moreover, the current study revealed that the shear behavior of ballast-subballast interface was influenced by geogrid aperture size (A).

The paper presents the study of wireless channel over-the-air channels of the family of 802.11х standards within the 5GHz frequency band, taking into account the influence of architectural obstacles within premises. The following parameters have been selected as the main parameters in the course of the study: an efficient rate of information transmission, signal power at the receiver input, as well as channel carrying capacity. As a result of the experimental study, the author has found out relevant mathematical expression for estimation of the efficiency criterion of wireless channels of the family of 802.11х standards for the 5GHz frequency band, taking into account relevant architectural obstacles within premises.

This research develops a parameter defined as the equivalent void ratio, est, which is able to accurately describe the dependence of the mechanical properties of cementitious material-clay...

In this study, a graphite-powder-based heating and cooling processing method (GP-HCPM) was used to produce carbon-based nanofluids (CBNFs) as working fluid for a brazed plate heat exchanger (BPHE) system. Sodium dodecyl benzenesulfonate (SDBS) was added to CBNFs as a dispersant to enhance their stability, and the CBNF concentration was adjusted to 0.2 wt% (S1) and 0.6 wt% (S2). The thermal conductivity, viscosity, density, specific heat, and contact angle of the CBNFs were measured and analyzed. Finally, the CBNFs were tested in a BPHE system to evaluate the average heat exchange capacity ( Q ex , a v g ), pumping power consumption (Pp), and system efficiency factor (SEF) under various temperatures (35, 40, and 45 °C) and laminar flow conditions. Results show that the Q ex , a v g of S1 and S2 was higher than water under all experimental parameters, indicating that CBNFs exhibit a higher heat exchange performance than water. The Pp of S1 was slightly lower than that of water. The maximum Q ex , a v g and SEF enhancement ratio of S1 and S2 was 7.54% and 7.98% and 9.19% and 7.28%, respectively. Considering the overall system efficiency of experimental parameters of the BPHE system, S1 was deemed more suitable than S2.

Issues of technological systems modes optimization for streaming raw materials processing have a significant impact on the enterprises profitability in the chemical, food and metallurgical industries. At present, the task of moving from the profitability requirements to control actions remains actual. The task requires the development of specialized methods. Such methods should use an efficiency factor with evaluating of a technological operation results by a combination of cost estimates of the output product, costs and time. In the paper it is shown the structure of the channel system for raw materials processing should contain blocks for calculating the consumption costs of raw materials, resources and energy for the processing and transporting parts of the station and for calculating the overall efficiency factor. An example of a production line for drying a granular product in a drum furnace with zone and axial burners using different types of fuel is considered. The mutual influence of the line components on its productivity, quality and costs is taken into account. The non-linear form of the efficiency factors expression required modification for use in the dynamic programming method. For optimal mode searching we chose a dynamic programming method that determines the optimal phase trajectory with maximizes the additive criterion formulated for this method. Cost estimation of the trajectory sections was carried out using a computational model. The model describes the dynamic processes in the station. The search for optimal controls was carried out from the end of a possible trajectory to the beginning in a discretized space of phase coordinates. The phase coordinates are the position of the product portion inside the drum, the moisture content of the product; control variables: drum angular velocity, fuel consumption in each burner. A comparison of the efficiency factor values for the found optimal trajectory and efficiency factor values for trajectories with deviations showed the validity of the chosen approach.

A low-power and low-noise bioamplifier for multichannel electrode arrays (MEA) is presented. Reduction in area and power is achieved (1) by means of active-integration using a small capacitor, (2) implementation of a high-pass filter without using large DC-blocking capacitors, and (3) by sharing the common parts of bioamplifiers of different channels. This bioamplifier, as the main building block of a neural recording system, has been designed to record neural signals, amplify them, filter out the unwanted signals, and extract the action potentials. Theoretical analysis on noise specification, crosstalk between the channels due to sharing parts, and power reduction has been presented and a design trade-off is achieved. Following the theoretical analysis, a 4-channel bioamplifier has been designed and simulated in 0.18 μm CMOS technology, in total layout area of 0.0976 mm2 and the current consumption of 3.2 μA per channel from ±1.2 V power supply. Based on post-layout simulation results, the power and noise specifications of the proposed design are comparable with the best specifications reported to date based on noise efficiency factor (NEF). The bioamplifier achieves a mid-band gain of 60 dB and a -3 dB bandwidth from 100 Hz to 10.2 kHz. The input-referred noise is 3.87μVrms corresponding to a NEF of 2.65, for the mentioned -3 dB bandwidth.

Використано спеціальні дерев’яні конструкції «кашиці» та синтетичний носій типу «Вія» для створення очисної конструкції, що діє за принципом «біореактора». Показано, що очисна конструкція здатна нагромаджувати на своїй поверхні (перифітоні) значну кількість бактерій та безхребетних гідробіонтів. Вивчення динаміки нагромадження бактерій на синтетичному носії «Вія», за період літнього сезону, вказує на сигмоїдний характер даного процесу. Так, на першій фазі процес адсорбції мікроорганізмів на синтетичному носію протікає повільно, особливо в заповідній зоні природоохоронного об’єкту, де мікробне число знаходиться в межах 1600±65 колонієутворюючих одиниць / мл, що значно нижче існуючих санітарних норм. В подальшому має місце логарифмічна залежність та насичення поглинальної поверхні мікроорганізмами. Показано, що незалежно від рівня забруднення водного середовища спостерігається певна кратність насичення синтетичного носія, що характеризується коефіцієнтом нагромадження рівним 14-16 одиниць. В перифітоні, застосованого нами волокнистого носія «Вія», створюється специфічна мікроекосистема, в якій волокнистий носій служить свого роду моделлю штучно створеного живильного ланцюга. Критерієм ефективності роботи очисної конструкції служили санітарно-гігієнічні показники поверхневих вод. Після проходження через «біореактор» забруднені поверхневі води очищаються від органічних компонентів, про що свідчать величини санітарно-гігієнічних показників (розчинений кисень, біохімічне споживання кисню, хімічне споживання кисню). Застосування очисних конструкцій типу «біореактор» призвело до суттєвого покращення якості води, особливо на територіях традиційних господарських ландшафтів, про що свідчить незначне перевищення гранично допустимої концентрації за основними санітарно-гігієнічними показниками. Впродовж літнього сезону (від червня до початку вересня) має місце підтримання динамічного балансу видового різноманіття перифітону «біореактора» при збереженні високого рівня коефіцієнту ефективності очисної споруди., It were used special wooden constructions "kashytsia" and synthetic carrier "Vija" type for the creation of a purifying structure, acting on the principle of "bioreactor". It has been shown that the purifying structure is capable of storing a significant amount of bacteria and invertebrates in their periphery (peryphiton). Study of the dynamics of accumulation of bacteria on the synthetic carrier "Vija", during the summer season, indicates the sigmoid nature of this process. Thus, in the first phase, the process of adsorption of microorganisms on the synthetic carrier proceeds slowly, especially in the protected area of the protected object, where the microbial number is within the limits of 1600 ± 65 colony forming units / ml, which is much lower than the existing sanitary norms. In the future there is a logarithmic dependence and saturation of the absorbing surface by microorganisms. It is shown that regardless of the level of pollution of the aqueous medium, a certain multiplicity of saturation of a synthetic carrier is observed, which is characterized by a accumulation coefficient equal to 14-16 units. In the peryphiton, applied by us fiber carrier "Vija", creates a specific microecosystem, in which the fibrous carrier serves as a kind of model of artificially created nutritional chain. The sanitary-hygienic indicators of surface water served as a criterion for the effectiveness of the treatment structure. After passing through the "bioreactor", contaminated surface water is cleared of organic components, as evidenced by the values of sanitary and hygiene indices (dissolved oxygen, biochemical oxygen consumption, chemical oxygen consumption). Application of purifying structures such as "bioreactor" has led to a significant improvement in water quality, especially in the territories of traditional economic landscapes, as evidenced by a slight excess of the maximum permissible concentration in the main sanitary and hygiene indicators. During the summer season (from June to the beginning of September), maintaining a dynamic balance of the species diversity of the peryphiton "bioreactor" occurs while maintaining a high level of efficiency of the treatment plant.

Finding the optimal fleet composition under uncertainties is crucial for the economic success of a business. This paper presents the Fleet Efficiency Factor, a decision support tool for fleet size and mix problems and fleet composition problems. The method is based on a particle swarm optimisation algorithm combined with a stochastic model to include uncertainties into the decision-making progress. This combination allows selecting the best option out of a pool of available vessels, vehicles and aircrafts. Additionally, the FEF is based on the classical ship merit factor and thus capable of comparing different fleet compositions according to their economic efficiency, by describing the efficiency in a simple factor. A case study for the supply of an offshore platform in the high North is conducted. The approach proved to be flexible and applicable to different strategical and tactical planning problems in maritime transportation.

In order to well predict mean explosive particle size effects on the shock-to-detonation transition (SDT) process of a plastic bonded explosive (PBX), some improvements to a previous three-term mesoscopic reaction rate model that consists of a hot-spot ignition term, a hot-spot growth term, and an overall reaction term are made: A set of new switch conditions, which depend on mean explosive particle size, is proposed for the operations of the three terms; a new expression is obtained for the hot-spot growth term by combining an ignition efficiency factor which depends on mean explosive particle size and replacing the original burning topology geometric factor, which merely describes the characteristic of the outward pore surface burning reaction, by a more reasonable one, which combines the characteristic of inward particle surface burning reaction and that of outward pore surface burning reaction. Furthermore, for verification, the improved reaction rate model is incorporated into the DYNA2D code to simulate numerically the SDT process of three formulations of PBXC03 having the same density but different mean particle sizes, and the numerical results of pressure histories at different Lagrangian locations in the explosive are found to be in good agreement with previous experimental data.