Perkembangan handphone khususnya smartphone yang mendukung koneksi internet dan teknologi android semakin berkembang pesat. Kurikulum 2013 menuntut guru untuk mampu mengintegrasikan pembelajaran dengan penggunaan teknologi informasi dan komunikasi (TIK). Penelitian ini bertujuan untuk mengembangkan Ulangan Berbasis Android (UBA) menggunakan aplikasi google form. Ulangan Berbasis Android (UBA) disebut juga Computer Based Test (CBT) adalah sistem pelaksanaan ulangan yang menyerupai ujian nasional dengan menggunakan android sebagai medianya. Penelitian ini merupakan penelitian pengembangan dengan model 4D dengan empat tahapan pengembangannya, yaitu define (pendefinisian), design (perancangan), development (pengembangan), dissemination (penyebaran). Hasil penelitian menunjukkan bahwa ulangan berbasis android menggunakan aplikasi google form dapat secara langsung menampilkan hasil ulangan yang telah dilakukan oleh siswa. Kata kunci: ulangan berbasis android, google form.
CNC milling strategy of EVA foam with varying hardness to provide a high degree of surface roughness of orthotic shoe insoles is presented in this work. Machining parameters (tool path strategy, spindle speed, feed rate, and step over) in addition to hardness material and wide tolerance insoles were optimized using a hybrid approach of Taguchi-Response Surface Methodology (TM-RSM). The aim of this research was to develop mathematical models and determine the optimum machining parameters which could be applied for the CNC milling of EVA foam as the insoles. Experiments were performed on a CNC milling machine with a standard milling cutter and run under dry coolants. The effects of the six parameters on the average values of surface roughness were initially analyzed by an S/N ratio of TM. Optimal conditions were established from the TM and then used to determine the optimum values in RSM modeling. The final results indicate the significant improvement of percentages (0.24% and 4.13%) in the surface roughness of the insoles obtained with TM-RSM as compared to the TM analysis. It is envisaged the present study would add to the understanding of production for orthotic shoe insoles through CNC milling.
There are several factors that influence the efforts to increase the performance of an air conditioner (AC), one of which is the selection of working fluid, environmental condition, and device components. Refrigerant is the most vital substance which determines the efficiency of the cooling machine. In addition, ambient air temperature and humidity are other important factors that affect the performance of the cooling machine. Therefore, it is extremely crucial to calculate the environmental condition, which is the air temperature, so that the cooling machine can work optimally. Currently, the refrigeration system uses R-22 refrigerant. However, the use of R-22 has a high ODP (ozone depletion potential) value, thus having a risk of damaging the ozone layer. As a safer alternative, the use of hydrocarbon refrigerants, such as R134a and R290, can solve this problem as they do not have any ODP. This study was conducted by retrofitting the synthetic refrigerant in Air Conditioner (AC) 1 HP with various types of hydrocarbon refrigerant. The outside air temperatures used were 30°C, 50°C, 60°C, and 70°C, while the airflow velocity across the condenser also varied, namely 4.8 m/s, 5.8 m. /s, 6 m/s, and 6.6 m/s. From the results of this study, it is known that retrofitting synthetic refrigerants into hydrocarbon refrigerants can increase the coefficient of performance (COP) of the air conditioner. The uses of R134a and R290 hydrocarbon refrigerants increase the COP by 19% and 24.5%, respectively. In addition, lower ambient temperature will reduce the required electrical power. R290 Refrigerant has the best COP value compared to R22 and R134a.
The role of data acquisition based measurement system in the researches is essential since it delivers many advantages compared to the manual arrangement. Nevertheless, its cost is comparatively high, then it becomes an obstacle, particularly for researchers in producing nations. The purpose of the study was to obtain a low-cost data acquisition system which has good performance when used in the research of dual-fuel engines. The study included a selection of variables, components and sensors, programming, and calibration. The Arduino based data acquisition system was chosen, which was relatively cheap and easy programming. The sensors/transducers consisted of three K-type thermocouples, three load cells, one proximity sensor, and one DHT-11 sensor. Programming of data acquisition systems was facilitated by using Arduino IDE software. The display and data recording were done in Microsoft Excel software, with the help of PLX-DAQ software. In this study, a low-cost data acquisition based measurement system had been successfully developed, which had low uncertainty, low hysteresis, and excellent repeatability. It is concluded that the system is very suitable to be used in dual fuel engine researches to measure engine speed, fuel discharge, gas fraction, torque, power, brake specific fuel consumption and brake thermal efficiency.
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