According to new findings, the use of clean energy sources such as solar energy to supply energy (both electricity and heat) to human societies is essential. On the other hand, choosing the appropriate technology to convert solar energy into useful energy in the form of individual or combined systems is a fundamental issue. Individual solar energy systems have inherently low performance. However, their use in hybrid energy systems with other energy generation devices is key solution and shows high performance. The present work provides the performance of a new combined energy system composed of the parabolic dish solar collector (PDC), Stirling engine (SE) and thermoelectric device (TD) under various parameters. Sun is the main source of energy in this system, where, sunlight is focused on the PDC focal point by the parabolic shaped mirrors. Thus, the useful thermal power is produced by PDC and then feeds to the SE. The operating fluid of the engine is heated by this heat and converted into mechanical energy. Then, the mechanical energy is converted into electricity by a generator connected to the SE and the excess heat is lost from the engine. The exhaust of the SE transferred to the TEG hot end and produces further electricity. In addition, the TEC module absorbs the cooled environment heat and produces cooling energy (by consuming electricity from the TEG). Therefore, the proposed combined process provides the electricity, heat and cooling. The paper is based on the following three scenarios: (1) the system performance is evaluated under constant climatic conditions, (2) climate data from five various cities in Europe and Asia are used for system operation and (3) this scenario presents the general comparison between the two different hybrid energy systems driven by PDC and linear Fresnel reflector (LFR). In addition, multi-objective optimization is provided to obtain the optimal performance of the developed hybrid system. The optimization results showed that, the optimum total output electricity and overall efficiency were 26.21 kW and 39.17%, respectively. It was also found that, average daily useful power generated by PDC in Moscow on 14-June is 373.97 W/m2, which is about 11.1%, 1.55%, 33.3% and 14.23% more than Tehran, Beijing, Geneva and Kiev, respectively. Furthermore, increasing the temperature of PDC absorber improves the performance of SE and TD and subsequently improves the overall operation. Also, in terms of the PDC numbers, the system in the cities of Tehran, Beijing and Moscow has a better justification compared to the other two cities (Geneva and Kiev).
In this paper, we have exploited the first-order sliding mode control method to track the ECG data of the human heart by three different nonlinear control laws. In order to lessen the intrinsic chattering of the classic sliding mode control system, smooth function approximations of the control input, by means of the hyperbolic tangent and the saturation function, were used. The fast Fourier transform was used to evaluate the average chattering frequency of the control inputs. The synthesized control schemes namely SMC-sign, SMC-tanh, and SMC-sat, were able to track the real-world ECG signal with an average root mean square error of 0.0306 and a chattering frequency of 92.7 Hz. The findings show that the sliding mode controllers can be implemented in electronic artificial pacemakers to provide the intended results successfully. Based on today's electronics, the involved frequency range (556.4 Hz for the worst case) is quite acceptable and practical.
Mechanical properties are important parameters in preparation of nanocomposites. Analyzing the trends on mechanical properties gives information about the effect of compatibilizing agent , nanoclays , and processing method. MA and GMA have higher compatibilizing effect than AA because of their different polarity promoting a better mechanical performance specially in Young,s modulus and impact strength and tensile strength and produce a less drastic reduction of the deformation properties. addition of clay to pp improves the tensile modulus and tensile strength, but reduces the elongation at break, regardless of the coupling agent used. In pp/clay, nanocomposites prepared with cloisite 15A and PP-g-MA, tensile strength is decreased , while Young,s modulus is increased.The solvent resistant of these nanocomposites decreased, when clay loading increased. In pp/clay nanocomposites prepared with oligomerically modifiedclay, this clay has plasticising effect on the polymers that the tensile strength is slightly decreased compared with the virgin polymers, while Young,s modulus is slightly increased.It is worth nothing that the elongation at break for most nanocomposites does not drop as severely as usually seen with the typical organically modified clay.
Breakthrough curves for citric acid adsorption from aqueous solution onto ion-exchange resin at 20, 35, and 55°C have been investigated. To predict breakthrough curves, three mathematical models have been analyzed based on the values of the least square method parameters, Durbin-Watson test, and mean relative percent error and, finally, appropriate models have been achieved. Models are in good agreement with experimental data based on the results. To examine models reliabilities and accuracy, models have been compared by various breakthrough curve data obtained by other investigators. The results show appropriate agreement and in some cases regression errors have been reduced to less than 1.0 percent.
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