An Elementary Study on the Combustion Mechanism of Levitated Droplet Clusters by Ultrasonic Wave

Combustion is a kind of important reaction that affects people's daily lives and the development of aerospace. Exploring the reaction mechanism contributes to the understanding of combustion and the more efficient use of fuels. Ab initio quantum mechanical (QM) calculation is precise but limited by its computational time for large-scale systems. In order to carry out reactive molecular dynamics (MD) simulation for combustion accurately and quickly, we develop the MFCC-combustion method in this study, which calculates the interaction between atoms using QM method at the level of MN15/6-31G(d). Each molecule in systems is treated as a fragment, and when the distance between any two atoms in different molecules is greater than 3.5 Å, a new fragment involved two molecules is produced in order to consider the two-body interaction. The deviations of MFCC-combustion from full system calculations are within a few kcal/mol, and the result clearly shows that the calculated energies of the different systems using MFCC-combustion are close to converging after the distance thresholds are larger than 3.5 Å for the two-body QM interactions. The methane combustion was studied with the MFCC-combustion method to explore the combustion mechanism of the methane-oxygen system.

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Pengaruh Variasi Waktu Paparan Gelombang Ultrasonik dalam Mengurangi Jumlah Bakteri coliform pada Sampel Air Sungai Kahayan

Risalah Fisika ◽

10.35895/rf.v4i1.168 ◽

2020 ◽

Vol 4 (1) ◽

pp. 9-13 ◽

Cited By ~ 1

Author(s):

Neny Kurniawati, Kerelius, Sunariyati ◽

Luqman Hakim, Dyah Ayu Pramoda Wardani, Widya Krestina ◽

Dwi Tyas Setiawan, Ferry Purwanto, Diah K. Fatmala

Keyword(s):

Water Treatment ◽

River Water ◽

Ultrasonic Wave ◽

Exposure Time ◽

Water Samples ◽

Sampling Technique ◽

Wave Exposure ◽

Test Results ◽

Time Data ◽

Grab Sampling

Abstrak – Penelitian ini bertujuan untuk mengkaji pengaruh waktu paparan gelombang ultrasonik terhadap pengurangan jumlah koloni bakteri coliform pada sampel air sungai Kahayan. Pengambilan sampel air sungai dilakukan dengan teknik Grab Sampling menggunakan alat Kemmerer Sampler. Sampel air yang didapatkan diberikan paparan gelombang ultrasonik secara langsung, tanpa merubah kondisi lingkungan awal. Waktu paparan divariasikan pada 1 jam, 2 jam, 3 jam, 4 jam, dan 5 jam dengan frekuensi 40 kHz untuk memperoleh data waktu optimum. Uji coliform dilakukan dengan metode MPN, dengan tahapan uji pendugaan, uji penegasan, dan perhitungan koloni. Hasil uji MPN 24 jam setelah paparan menunjukkan bahwa penggunaan ultrasonik sebagai antibateri dapat optimum ketika diberikan paparan dengan waktu 3 jam, dengan efisiensi 96%. Kata kunci: antibakteri, coliform, ultrasonik, water treatment, sungai Kahayan Abstract – This study aims to examine the effect of ultrasonic wave exposure time on reducing the number of coliform bacterial colonies in the Kahayan river water samples. River water sampling is done using the Grab Sampling technique using the Kemmerer Sampler tool. The water samples obtained were given direct ultrasonic wave exposure, without changing the initial environmental conditions. The exposure time is varied in 1 hour, 2 hours, 3 hours, 4 hours and 5 hours with a frequency of 40 kHz to obtain optimum time data. Coliform test was carried out by the MPN method, with the stages of the estimation test, affirmation test, and colony calculation. The MPN test results 24 hours after exposure showed that the use of ultrasonic as an antibody can be optimum when given exposure with a time of 3 hours, with an efficiency of 96%.Keywords : antibakterial, coliform, ultrasonic, water treatment, Kahayan river

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