Pengaruh Penambahan Serat Ijuk Terhadap Stabilitas Campuran Aspal Emulsi Dingin

Serat ijuk merupakan serat alami yang mudah ditemukan, tetapi belum dimanfaatkan secara optimal. Penelitian ini dilakukan untuk mengetahui pengaruh penambahan serat ijuk terhadap stabilitas Campuran Aspal Emulsi Dingin (CAED). CAED adalah campuran antara agregat bergradasi menerus dan aspal emulsi sebagai bahan pengikat. Aspal emulsi adalah aspal berbentuk cair yang dihasilkan dengan mendispersikan aspal keras ke dalam air atau sebaliknya dengan bantuan bahan pengemulsi sehingga diperoleh partikel aspal yang bermuatan listrik positif atau negatif atau tidak bermuatan listrik. Pengujian Marshall dilakukan pada CAED tanpa dan dengan tambahan serat ijuk dengan waktu curing selama 0 dan 7 hari untuk mendapatkan nilai stabilitas. Hasil penelitian menunjukkan semakin banyak kadar serat ijuk yang ditambahkan maka stabilitas meningkat. Stabilitas CAED dengan serat ijuk umur curing 0 hari meningkat pada kadar ijuk 0,1% - 0,3% lalu mengalami penurunan pada kadar ijuk 0,4%. Stabilitas kadar ijuk 0,3% lebih tinggi daripada CAED tanpa serat ijuk. Stabilitas CAED dengan serat ijuk umur curing 7 hari meningkat pada kadar ijuk 0,1% - 0,4% dan masih bisa terus naik. Stabilitas kadar ijuk 0,4% lebih tinggi daripada CAED tanpa serat ijuk. Panjang serat ijuk antara 0,1 – 0,25 cm. Waktu curing selama 7 hari meningkatkan stabilitas CAED tanpa dan dengan tambahan serat iju

A Validation Study on Mechanical Properties of Foam Concrete with Coarse Aggregate Using ANN Model

The usage of foam concrete (FC) was extended from being used as a filler material to an alternative concrete due to the effect of conventional concrete on global warming. The diversified perspective on FC as an alternative to conventional concrete is due to its low density (400–1800 kg/m3) and good thermal conductivity, which also results in the reduction of costs in production, labor, and transportation. Generally, FC is produced by adding a pre-made foam to the cement slurry consisting of cement and aggregates. Here, the study was carried out by the addition of a coarse aggregate and foaming agent (i.e., 12%, 6%, 3%, 2%, 1%) at varying percentages in FC to improve the strength characteristics. FC was tested for its physical and mechanical properties. From the experimental results, an Artificial Neural Network (ANN) was developed to predict the strength of FC. The results from training and testing of the Polynomial Regression Analysis model (PRA) through ANN have shown great potential in predicting compression, split tensile, and flexural strength of FC. It was found that the strength of FC is increased with the reduction of foam volume and increase in coarse aggregate volume. However, a strength of 25.6 N/mm2 is achieved when 1% foam and 50% coarse aggregate is used

Exploring the non-equilibrium fluctuation relation for quantum mechanical tunneling of electrons across a modulating barrier

We study the validity of the fluctuation relation for a non-equilibrium quantum mechanical system, viz., electrons quantum mechanically tunneling across a periodically modulating barrier. Experimentally this system is realized by measuring the fluctuation in the tunneling current between an STM tip and a vibrating gold film deposited on a piezo crystal. The long time series of tunneling signal shows large positive and negative fluctuations. The analysis shows that over finite observation time intervals, the probability distribution of the average rate of work done has a positive mean. About this mean, the distribution is broad and it is spread over not only positive but also negative values. These positive and negative values correspond to work done either on the electron by the external drive or work done by the electron against the drive, as it tunnels across the modulating barrier, respectively. For different driving frequencies, we show that the probability distribution satisfies the non-equilibrium fluctuation relation (NEFR). Thus, we prove that the NEFR is valid for a driven quantum mechanical system. For this tunneling process, we determine the large deviation function (LDF), which is related to NEFR. We see changes in the shape of the LDF as a function of the drive frequency, although NEFR is valid at all these frequencies. Measuring dissipation associated with microscopic irreversible trajectories in non-equilibrium quantum mechanical systems is a challenging task. Here we use NEFR also to obtain a measure of the dissipation associated with the electron tunneling across the modulated barrier