total efficiency
Recently Published Documents

A multiple-input-multiple-output (MIMO) antenna array for triple-band 5G metal-frame smartphone applications is proposed in this paper. Each single antenna element consists of an S-shaped feeding strip and an L-shaped radiation strip on the metal frame. The dimension of the antenna element is only 6.5 mm × 7 mm (0.076 λ0 × 0.082 λ0, λ0 is the free-space wavelength at the frequency of 3.5 GHz). The −6 dB impedance bandwidth of the proposed eight-antenna array can cover 3.3–3.8 GHz, 4.8–5 GHz, and 5.15–5.925 GHz. The evolution design and the analysis of the optimal parameters for a single antenna element are derived to investigate the principle of the antenna. The measured total efficiency is larger than 70%. The measured isolation is better than 13 dB. The measurements of the prototype agree well with the simulation results.

This work proposes the use of a specialized algorithm based on evolutionary computation to the global MPPT regulation of panel of thermoelectric modules connected serially in numerous string sections. Each section of the thermovoltaic panel is equipped with local DC/DC converter controlled by the proposed algorithm and finally this allows the optimization of the total efficiency of conversion. Evolutionary computations adjust PWM signals of switching waveforms of DC/DC sectional simple boost converters, which have outputs configured in parallel. It gives the chance to obtain the highest level of electric energy harvested, i.e., thanks to boost converting operational points precise adaptation to the system temperature profile as well as electric load level. The simulation results of the proposed evolutionary technique confirmed the high speed of the MPPT process that is much better than for perturbation and observation, as well as incremental conductance methods, and it assures concurrent optimization of numerous PWM signals. Next, the work shows practical optimization results achieved by the proposed algorithm implemented to microcontroller module controlling the DC/DC converter during thermal to electric conversion experiment. A laboratory thermovoltaic panel was constructed from a string of Peltier modules and radiator that assured passive cooling. The measurements obtained once more proved the MPPT evolutionary regulation properness and its adaptation effectiveness for different resistive test loads.

Giant squid hydrolysate (GSH) elaborated from different batches from a fishing company was evaluated for cadmium removal. Fixed-bed column packed with iminodiacetic resin as adsorbent was used. GSH solution at different cadmium concentrations were fed in the fixed-bed column and breakthrough curves were evaluated. A high degree of metal removal from the solution was achieved and the saturation point (Ce/C0 ≤ 0.8) was achieved more quickly at higher concentrations of cadmium. The maximum capacity of adsorption (q0) was obtained using the Thomas model, where 1137.4, 860.4, 557.4, and 203.1 mg g−1 were achieved using GSH with concentrations of 48.37, 20.97, 12.13, and 3.26 mg L−1, respectively. Five cycles of desorption of the resin with HCl (1 M) backflow and regeneration with NaOH (0.5 M) were also evaluated, where no significant differences (p-value > 0.05) were observed between each cycle, with an average of 935.9 mg g−1 of qmax. The in-series columns evaluated reached a total efficiency of 90% on average after the third column in GSH with a cadmium concentration of 20.97 mg L−1. This kind of configuration should be considered the best alternative for cadmium removal from GSH. Additionally, the chemical composition of GSH, which was considered a quality parameter, was not affected by cadmium adsorption.

This paper presents a novel antenna with its array and MIMO configuration for the 5G sub-6 GHz applications. The proposed antenna element operates at the central frequency of 5.57 GHz dedicated for Sub-6 GHz 5G communication applications. The antenna element holds a circular-shaped radiating portion with an inner-circular slot, plus a rectangular slot at its right edge to make the proposed design resonate at the desired frequency band. The RT5880 substrate is used with a thickness of 0.787 mm, and the low-loss tangent of 0.0009. To achieve a desired gain of 12 dB, a four-element array configuration is adopted, which improved a bore side gain to 12.4 dB from 6.66 dB. Then, the two-port configuration is adopted such that the isolation achieved between them is more than −30 dB. The total efficiency of the proposed antenna array is observed to be more than 80% within the operating bandwidth. Moreover, the Specific Absorption Rate (SAR) analysis is also presented for the proposed MIMO configuration, obeying the standard value (i.e., <2 W/kg for any 10 g of tissue). The measured results are in good agreement with the simulated results. All the simulations of the proposed design are performed in the CST MWS software.

Abstract In this work, a circular patch antenna is designed and a parametric study in terms of different geometrical parameters is conducted. As a second step, a parasitic chip is introduced on top of the proposed circular patch antenna in the aim to enhance the gain and antenna efficiency. The proposed antenna operates at 25.61 GHz (With a frequency range between24.383 GHz and 27.7 GHz), suitable for 5G applications. The antenna modelling with and without parasitic chip, along with the performance analysis is conducted with CST Studio Electromagnetic (EM) simulator software. A compact size of 10×10×1.547 mm3, easy to fabricate, broadband characteristics up to 3.31 GHz with a high gain up to 6.87 dB, total efficiency of 95 % and a minimum return loss low than -68.02 dB covering the operating frequency range. Lastly, to investigate and validate the antenna overall performance, both frequency and time domain-based simulation is performed, and a good agreement is obtained.

Abstract A new microwave energy reception method is proposed for the wireless energy transmission needs of lunar rovers combined with the lunar environment, i.e. collecting thermal energy through microwave absorbing materials, and then converting thermal energy into direct current by using temperature difference power generation devices. The article analyses the two conversion processes, microwave-thermal and thermal-DC, separately. Under the approximate condition that the temperature at both ends of the absorbing material is regarded as equal, the two conversion processes are linked by energy conservation, which theoretically leads to the temperature and total efficiency of the system at steady state. The temperature and total efficiency of the system are initially obtained by numerical simulation with respect to the thickness of the absorbing material, the receiving area and the input power density by selecting the parameters of the carbon and iron composite material at 10 GHz. The results show that there is an optimum thickness of absorbing material for a certain input power density and receiving area, which results in the highest system efficiency. The larger the receiving area and input power density in a certain range, the higher the efficiency, but beyond a certain range the system efficiency shows a decreasing trend. Also the theory and the actual will produce a large deviation when temperature is high. The article concludes that this energy receiving method has great potential for application in the space environment based on the excellent wave absorbing materials and thermoelectric components but further research is needed.

Purpose of this work is to study modes and conditions that make it possible to excite the highest type of microwave oscillations, the frequency of which is a multiple of the frequency of the main type, in a monotron with a three-band resonator. Method of the investigation is a numerical 3D modeling, used to calculate the dimensions and electrodynamic parameters of the resonator (characteristic impedance, coupling coefficient, relative electronic conductivity); operation modes of the monotron are considered, which are characterized by excitation of oscillations in the highest type oscillations. Result. In the resonator under consideration, it is possible to achieve a multiple (equal to three) ratio between the frequency of the 25th highest type of oscillations and the frequency of the π/2-type. It was shown that in such resonator simultaneous excitation of electromagnetic field on those frequencies can be made. The maximum of an output power achieved at 100.22 GHz is 15.4 W with an accelerating voltage of 7825 V and an electronic beam microperveance 0.36 µA/V3/2 . The maximal efficiency on a third harmonic is 0.83% while the total efficiency (generating electromagnetic waves of the first and the third harmonics) is up to 17%. Conclusion. It was set that the described method of generation of terahertz range radiation is promising for further investigation, as it solves problem that orthodox microwave devices meet in the millimeter wavelength range, such as small linear dimensions of the components and critical current density of the electronic beam.

Introduction. Nowadays, the development of an enterprises social responsibility (SR) strategy is one of the integral components of its successful functioning as it transfers the relationship between the enterprise and society to a higher level and becomes one of the most important factors on the way to the economic development of both an individual enterprise and our country as a whole. Modern business cannot consider itself separately from its most important stakeholders, therefore, the implementation of corporate social responsibility concept is the indirect factor that provides the link SR – stakeholders – enterprise total efficiency increasement. Purpose. The theoretical basis of the study is the works of leading domestic and foreign scientists, as well as international and national legislative and regulatory acts in the field of the enterprise’s social responsibility concept formation and development. In the process of performing the work and reflecting the results, such general scientific research methods were applied as etymological, comparable, systematical, synthesis and analysis, generalization, statistical comparison, etc. Results. The essence of the “social responsibility” concept is viewed through the prism of its key elements (economic, legal, moral, philanthropic and environmental), only a comprehensive implementation of which allows you to verify that the company is making progress towards sustainable development. The article analyzes the successful experience of applying the concept of social responsibility among world famous companies of different industry sectors, and also clarifies how the management systems of domestic enterprises are adapted to the principles of corporate social responsibility and sustainable development in general. As a result, the advantages of introducing social responsibility in Ukrainian companies are outlined, and problematic issues accompanying this process are highlighted and general recommendations for their effective elimination are presented. Conclusion. The SR management system is a set of interrelated functions of analysis, planning, organization and control that ensure a continuous process of interaction between enterprise management and stakeholders. At the same time, only well-coordinated actions of business entities and the state towards the development of applied tools for socially responsible company management will allow us to bring the concept of social responsibility in Ukraine to a qualitatively new level, ensuring the intensification of our society development in the direction of sustainable development.

The purpose of this study is to analyze the efficiency and productivity of the Korean ship parts manufacturing industry. To this end, the manufacturing process was divided into two stages (operating activities, financial activities), and the Dynamic Network SBM model and Malmquist Productivity Index were used. We collected analysis data from KIS-VALUE, and analyzed 40 companies from 2014 to 2020. As a result of the analysis, from 2014 to 2017, the average operating efficiency was 0.7825, the average financial efficiency was 0.5208, and the average total efficiency was 0.4537. It was found that improving efficiency requires improving both activities simultaneously, rather than focusing on a specific activity. Operating activities DMI was 1.0025, financial activities DMI was 0.9236, and OMI was 0.9464. In order to improve OMI, it is necessary to improve the financial activities DMI, which is the cause of the decrease in productivity. In order to improve financial activities DMI, government policy or technology change to improve DFS was found to be necessary. Finally, the effect of environmental factors on efficiency was analyzed by tobit regression. It was found that Firm Size had a negative (−) effect on efficiency, and Firm Age had a positive (+) effect on efficiency. The analysis results of this study will help to understand the relationship between input and output, which has been treated as a black box in the manufacturing industry, in two stages; and this will serve as a guideline for those working in Korea’s ship parts manufacturing industry to establish policies.

This article reports on technological mastery assistance in three small metal forming industries in Indonesia. Problems in the blangking and piercing separately process caused increased production time which resulted in inefficiency cost. Therefore, the expert team aided in metal forming technology through participatory action research (PAR) methods and experimental methods through reverse engineering for several products. The PAR method involves optimal contribution and participation from the industry. Assistance in mastering technology in small metal-forming industries reduces the manufacturing process from seven to three stages, increasing efficiency. The press machine's tonnage capacity must balance with the force blanking/piercing requirement. The minimum press machine requirement is 6.7 tons, and based on the availability of existing press machines, the expert team recommends a 20-ton capacity press machine. Total efficiency can be further increased by implementing full progressive die technology by combining piercing, blanking, and bending processes.