Wear occurs in rail wheels due to varying surface contact between wheel and railway. Many materials are used to minimize the wear effect of friction, one of which is graphite. Graphite has been known having dry lubricating ability. To find out the effect of graphite lubrication on wear level of wheel and railway, an experiment-based research is important to conduct. This research started with designing the construction of disc-on-disc wear testing instrument, wheel specimen using EMS45 material and railway specimen using VCL140 material. Dry lubricant used was graphite bar polished onto wheel specimen surface. The result of research showed that graphite could adhere to wheel surface and penetrate into the fissures of contact between wheel and railway. Varying graphite polishing conducted once in 5 minutes and 10 minutes resulted in different volume of graphite filling in the fissures of wheel specimen surface. The more the graphite volume polished onto wheel specimen surface, the less is the material loss due to surface contact. Graphite’s ability of filling in this contact area fissure when administered in appropriate volume would enable graphite to be a good dry lubricant. If this graphite polishing technique is applied to rail wheels, it would be beneficial, as it can lengthen the wheel life.
Pump units with a Caterpillar C27 engine with an EUI (Electronic Unit Injector) fuel system that often has low power due to filter clogging at PT. Sapta Indra Sejati. Filter cloggingoccurs due to due to the thickened biofuel content and creates a crust. If the machine has a problem, the mining process can be disrupted because the coal loading area is flooded. This study aims to create an additional system in the form of a automatic semi-returnless where the fuel return line is changed automatically into the filter because the fuel return is clean. The movement of the return control valve is regulated by a microcontroller which is programmed according to specifications and needs. The microcontroller used is Arduino Unowith pressure and temperature sensors. Arduino Uno is programmed when the engine will experience low power with a fuel pressure of 400 kPa then the return path is changed to semi returnless. With a change in the semi returnless path, the pressure becomes stable at 380 kPa and the engine RPM is stable with power that is still maintained. The advantages of semi-returnless system are that filter replacement costs can be reduced and production time is not interrupted.
<p>Penelitian ini bertujuan untuk: (1) mengetahui karakteristik produk modul IPA terpadu yang berbasis PBL dengan tema fotosintesis, (2) mengetahui kelayakan produk modul IPA terpadu berbasis PBL dengan tema fotosintesis, (3) mengetahui peningkatan kemampuan berpikir kritis siswa setelah menggunakan modul IPA terpadu berbasis PBL dengan tema fotosintesis. Penelitian ini merupakan <em>Research</em> and <em>Development</em> (R&D). Pengembangan dilakukan dengan mengacu pada model 4-D dengan tahapan <em>Define, Design, Develop,</em> dan <em>Disseminate</em> yang dikemukakan oleh Thiagarajan. Pengembangan modul ini dinilai berdasarkan kelayakan isi, penyajian, dan bahasa oleh dosen, guru, dan <em>peer review</em>. Berdasarkan validasi kelayakan isi, penyajian, dan bahasa modul kemudian diujicobakan kecil pada 9 siswa. Setelah direvisi, modul diujicobakan ke kelas<sub>.</sub> Kemampuan berpikir kritis siswa dianalisis dengan uji nonparametrik dua sampel berhubungan dengan uji Wilcoxon menggunakan <em>software</em> PASW <em>Statistic</em> 18. Hasil penelitian ini adalah (1) modul IPA terpadu berbasis masalah dengan tema fotosintesis dikembangkan menggunakan komponen pembelajaran berbasis masalah dengan menggunakan model 4-D meliputi D<em>efine, Design, Develop,</em> dan <em>Disseminate, </em>(2) kelayakan modul IPA terpadu berbasis masalah dengan tema fotosintesis yang dikembangkan berkategori baik berdasarkan penilaian dari ahli, praktisi, dan respon siswa, dan (3) kemampuan berpikir kritis siswa setelah mengikuti proses pembelajaran menggunakan modul IPA terpadu berbasis masalah dengan tema fotosintesis mengalami peningkatan (sig.0,000). Besarnya peningkatan dilihat dari <em>gain score</em> pada 4 aspek kemampuan berpikir kritis meliputi aspek kelancaran 0,43 (sedang), aspek keluwesan 0,30 (sedang), aspek keaslian 0.35 (sedang), dan aspek memperinci 0,33 (sedang).</p>
Pump units with a Caterpillar C27 engine with an EUI (Electronic Unit Injector) fuel system that often has low power due to filter clogging at PT. Sapta Indra Sejati. Filter cloggingoccurs due to due to the thickened biofuel content and creates a crust. If the machine has a problem, the mining process can be disrupted because the coal loading area is flooded. This study aims to create an additional system in the form of a automatic semi-returnless where the fuel return line is changed automatically into the filter because the fuel return is clean. The movement of the return control valve is regulated by a microcontroller which is programmed according to specifications and needs. The microcontroller used is Arduino Unowith pressure and temperature sensors. Arduino Uno is programmed when the engine will experience low power with a fuel pressure of 400 kPa then the return path is changed to semi returnless. With a change in the semi returnless path, the pressure becomes stable at 380 kPa and the engine RPM is stable with power that is still maintained. The advantages of semi-returnless system are that filter replacement costs can be reduced and production time is not interrupted.
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