GREEN SYNTHESIS NANOPARTIKEL GRAPHENE DENGAN AGEN PEREDUKSI URIN MANUSIA DAN APLIKASINYA SEBAGAI ADITIF BIONANOLUBRICANT BERBASIS CPO (CRUDE PALM OIL)

Graphene is a nanomaterial that has been widely applied to various fields because of the uniqueness of the material, therefore this material is very interesting to be developed as an additive in lubricant. This study aims to determine the optimum additive weight ratio and obtain optimum operating conditions in the graphene dispersion process in base oil. This research is divided into 2 stages: preliminary research and main research. The preliminary study aims to transform the chemical structure of crude palm oil (CPO) through a three-stage reaction into a polyol as a base oil. The main research is the process of making bionanolubricant. Graphene is synthesized using a combination technique with a human urine as reducing agent. The formulations are known by varying the weight of the additive and the time of the dispersion. Variation of additive weight was 0% (A1), 0.25% (B1), 0.5% (C1), 1% (D1) while for dispersion time variation ranged from 0 min (A2), 60 min (B2), 90 minutes (C2) and, 120 minutes (D2). Based on the SEM-EDX test results, the SEM image formed graphene and spectrum layers on EDX show that the oxide in graphene has been successfully reduced. Bionanolubricant was tested for quality with 7 parameters. The composition of base oil formula 250 gr and graphene nanoparticles 0.5% w / w is the optimum additive weight ratio for C1 sample code whereas the economical dispersion time is 60 minutes. The result of the viscosity index test is 121,72, its pour point is 10,4oC, flash point equal to 228oC with lubrication capability tested through four ball tester got scar diameter equal to 0,87 mm. This Bionanolubricant belongs to the SAE 250 class and is classified as a GL-4 lubricant based on the quality level of API (American Petroleum Institute) performance test

Standard errors estimation in the presence of high leverage point and heteroscedastic errors in multiple linear regression

In this study, the Robust Heteroscedastic Consistent Covariance Matrix (RHCCM) was proposed in order to estimate standard errors of regression coefficients in the presence of high leverage points and heteroscedastic errors in multiple linear regression. Robust Heteroscedastic Consistent Covariance Matrix (RHCCM) is the combination of a robust method and Heteroscedasticit Consistent Covariance Matrix (HCCM). The robust method is used to eliminate the effect of high leverage points while HCCM is mainly used to eliminate the effect of heteroscedastic errors. The performance of RHCCM was assessed through an empirical study and compared with results obtained when the original Heteroscedastic Consistent Covariance Matrix was used

Identification of discrete-time dynamic systems using modified genetic algorithm

The purpose of this study is to investigate the application of genetic algorithm (GA) in modelling linear and non-linear dynamic systems and develop an alternative model structure selection algorithm based on GA. Orthogonal least square (OLS), a gradient descent method was used as the benchmark for the proposed algorithm. A model structure selection based on modified genetic algorithm (MGA) has been proposed in this study to reduce problems of premature convergence in simple GA (SGA). The effect of different combinations of MGA operators on the performance of the developed model was studied and the effectiveness and shortcomings of MGA were highlighted. Results were compared between SGA, MGA and benchmark OLS method. It was discovered that with similar number of dynamic terms, in most cases, MGA performs better than SGA in terms of exploring potential solution and outperformed the OLS algorithm in terms of selected number of terms and predictive accuracy. In addition, the use of local search with MGA for fine-tuning the algorithm was also proposed and investigated, named as memetic algorithm (MA). Simulation results demonstrated that in most cases, MA is able to produce an adequate and parsimonious model that can satisfy the model validation tests with significant advantages over OLS, SGA and MGA methods. Furthermore, the case studies on identification of multivariable systems based on real experimental data from two systems namely a turbo alternator and a continuous stirred tank reactor showed that the proposed algorithm could be used as an alternative to adequately identify adequate and parsimonious models for those systems

Identification of discrete-time dynamic systems using modified genetic algorithm

The purpose of this study is to investigate the application of genetic algorithm (GA) in modelling linear and non-linear dynamic systems and develop an alternative model structure selection algorithm based on GA. Orthogonal least square (OLS), a gradient descent method was used as the benchmark for the proposed algorithm. A model structure selection based on modified genetic algorithm (MGA) has been proposed in this study to reduce problems of premature convergence in simple GA (SGA). The effect of different combinations of MGA operators on the performance of the developed model was studied and the effectiveness and shortcomings of MGA were highlighted. Results were compared between SGA, MGA and benchmark OLS method. It was discovered that with similar number of dynamic terms, in most cases, MGA performs better than SGA in terms of exploring potential solution and outperformed the OLS algorithm in terms of selected number of terms and predictive accuracy. In addition, the use of local search with MGA for fine-tuning the algorithm was also proposed and investigated, named as memetic algorithm (MA). Simulation results demonstrated that in most cases, MA is able to produce an adequate and parsimonious model that can satisfy the model validation tests with significant advantages over OLS, SGA and MGA methods. Furthermore, the case studies on identification of multivariable systems based on real experimental data from two systems namely a turbo alternator and a continuous stirred tank reactor showed that the proposed algorithm could be used as an alternative to adequately identify adequate and parsimonious models for those systems

The Implementation Of Maintenance Works For Historical Buildings – A Review On The Current Scenario

The conservation of historical buildings is a method on preserving structures which are historically and culturally important to the nation

Multi-layer micro channels system: interpretation and developments

During the last three decades the concept of the traditional cooling systems was modified to include single, double, and multi-layer micro channels. The new studies, applications, fabrication, and research focus on four main areas: the geometrical shape of the micro channels, the number of stacked layers, the type of the coolants, and the heat performance optimization. The previous studies have shown a significant reduction in the power consumption as the optimization is accomplished. In this paper, a semi-review for the previous works is provided, an attempt to interpret the nature of the work done, and show another trial for optimization. In this study, water was used as a coolant agent, stacked multi-channel was adopted, and thermal resistance network was calculated.The heat sink under consideration is a rectangle of width ?? and length ??. The thickness ???????? of the base of the micro-channel is 100 [?m] while the depth ????of the micro-channel is 500[?m], both kept constant for all future optimization cases

Single-objective optimization of a thermoacoustic refrigerator

Optimization of energy-related systems with by-products that involve environmental degradation has never been so crucial today with depleting resources and global concerns over negative impacts on our environment. This paper reports the results of an optimization scheme on the coefficient of performance (COP) of a standing wave thermoacoustic refrigerator based on genetic algorithm. The environmentally friendly refrigerator operates without any CFCs, which has been associated with the depletion of ozone, a substance that prevents uv light from reaching the earth’s atmosphere. A single- objective optimization to maximize the COP of a thermoacoustic refrigerator has been completed. The variables investigated include the length of the stack, Lsn, center position of the stack, xsn, blockage ratio, B and drive ratio, DR. The results show that a COP of up to 1.64 is achievable which provides promise for future improvements in the present systems

High potential of magnet on the performance of dual piezoelectric fans in electronics cooling system

Recently, piezoelectric fan has gained attention as potential active cooling method for electronics devices. Even though the piezoelectric requires high voltage, there are findings to overcome the shortcomings. Adding on a magnet at the tip of the piezoelectric fan to activate other magnetic passive fans is one of the methods to increase the total amplitude generated by the fans. This paper will discuss on the performance of integrated piezoelectric fan with passive fans (later refer to magnetic fans) to enhance the heat transfer in cooling system. A repulsive force produced by the magnets will cause the magnetic blades to oscillate together with the piezoelectric fan. The paper will focus on the optimization parameters of the magnets for selected dimension of piezoelectric fan. The parameters under investigation are the position of the magnet on the piezoelectric fan, number of magnets on each blades and orientation of blades with respect to adjacent blade. Results show that the magnet at middle location of extensive blade with double magnets generate the largest amplitude, 80% better than fan without magnet and for dual integrated piezoelectric fan with magnetic fan, radial orientation gives better result by 25%. By increasing the total amplitude using magnetic force, power consumption can be reduced while the heat transfer performance can be enhanced. it shows a good agreement for positive heat transfer and thermal resistance improvement compared to natural convection

Derivative Proportional – Integral Controller Using Nelder-Mead Optimization for Glycerine Purification Heating Process

It is important to purify the crude glycerine before to convert them into value-added products. Such dark colored crude have high free fatty acid content that can be removed via heating process. This paper focuses mainly on the heating control system, which has contributed to the improvement of the glycerine purification process system. The design of Derivative Proportional – Integral controller for the glycerine temperature control loop system could demonstrate some improvement of the glycerine heating process control response in term of process settling time and percent overshoot. Derivative Proportional – Integral is a proposed controller where Proportional and Derivative control actions operate on process variables rather than error signals. Meanwhile, the integral mode is connected to the forward path where the error signal is used as an input to the control mode. The output of the two control modes is then subtracted to drive the process. The Derivative Proportional – Integral controller was designed using the Nelder-Mead optimization algorithm with objective function of the Integral Time Absolute Error criteria calculated using Simpson's one-third rule. The control performance of the proposed controller was analyzed by comparing the rise time, percent overshoot and settling time of the response with that of the conventional PID controller. The simulation results show that the Nelder-Mead optimization algorithm can be used and can produce a good control system with zero percent overshoot and shorter heating time compared to the achievements of the PID control system. In addition, the robustness test of the controller has shown that the proposed control system can effectively detect changes in the operating temperature. The control performance shown by the proposed controller is excellent. The Derivative Proportional – Integral control system designed based on optimization algorithm techniques can improve the performance of the glycerine purification process heating system to meet the purified glycerine requirements