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PENGGUNAAN INDEKS KENYAMANAN UNTUK MENGEVALUASI KESESUAIAN WILAYAH UNTUK PROSES REPRODUKSI TERNAK DOMBATHE USE OF COMFORT INDEX TO EVALUATE REGION SUITABILITY FOR SHEEP REPRODUCTION Rohman, Lutfi; Boer, Rizaldi
Agromet Vol. 15 No. 1 & 2 (2000): DECEMBER 2000
Publisher : PERHIMPI (Indonesian Association of Agricultural Meteorology)

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1264.526 KB) | DOI: 10.29244/j.agromet.15.1 & 2.01-10

Abstract

Abstract is available in the full text (pdf format)
Molecular Dynamics Study for Inhibition of Iron Corrosion in High-Temperature Liquid PbBi with Nobel Gas Inhibitors Arkundato, Artoto; Rohman, Lutfi; Sa’adah, Umi
Jurnal ILMU DASAR Vol 17 No 2 (2016)
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1057.906 KB) | DOI: 10.19184/jid.v17i2.2690

Abstract

Molecular dynamics is a popular method to observe the movement of interacting molecules. In this study molecular dynamics method was used to observe the phenomenon of iron corrosion and analyze effect of noble gases as a corrosion inhibitor for iron in liquid metal PbBi. Physical quantities are evaluated from the results of this study including: Mean Square Displacement (MSD), the diffusion coefficient, and for the crystal structure is visualized using Ovito program. The ron is placed in the middle high temperature liquid PbBi, the noble gases is injected into the liquid metal. Based on the three kinds of the noble gases (helium, neon, and argon) thhat injected into the molten metal PbBi, it obtained that Argon is the most effective in inhibiting the corrosion of iron. Argon is able to reduce the corrosion rate of 80.29% iron for temperature of 1023K. One reason to use the noble gas because these gases are difficult to react with other elements. Keywords: Molecular Dynamics, Corrosion in Liquid metals, Nobel Gases, Inhibitors
Studi Resonansi Feromagnetik BaFe12O19 Menggunakan Simulasi Mikromagnetik Wicaksono, Angga; Rohman, Lutfi; Supriyanto, Edy
BERKALA SAINSTEK Vol 6 No 1 (2018)
Publisher : Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/bst.v6i1.7771

Abstract

Barium Hexaferit (BaFe12O19) adalah magnet keramik golongan ferit. Ferit diaplikasikan sebagai magnet permanen dan mempunyai struktur hexagonal close-pakced (HCP). Kurva histerisis magnet permanen jenis ini memiliki koersivitas yang relatif tidak besar sehingga senyawa tersebut juga berpeluang cukup baik untuk diaplikasikan sebagai media penyimpanan data (magnetic recording) berupa patterned media. Penelitian ini mengkaji sifat-sifat magnetik bahan BaM berbentuk hexagonal terhadap kurva histerisis dan sifat resonansi feromagnetik pada berbagai variasi ukuran (meliputi : ketebalan dan diagonal hexagonal). Running simulasi mikromagnetik dilakukan untuk mendapatkan kurva histerisis dan frekuensi resonansi bahan BaM. Frekuensi resonansi meningkat (heksagonal diagonal tetap pada 12 nm) dengan bertambahnya ketebalan bahan BaM (misal pada ketebalan 24 nm diperoleh frekuensi resonansi sebesar 21,7 GHz dan pada ketebalan 36 nm diperoleh frekuensi resonansi sebesar 22,4 GHz), hal ini dikarenakan dengan bertambahnya ukuran ketebalan bahan BaM posisi spin terlihat sangat teratur. Sedangkan hubungan frekuensi resonansi dengan diagonal hexagonal yaitu kebalikannya.Kata Kunci: BaFe12O19, Simulasi mikromagnetik, Frekuensi resonansi
Study of A Phenomenon STT (Spin Transfer Torque) on the Material La0.7Sr0.3MnO3 Shaped Nanowire Using Micromagnetic Simulation Rohman, Lutfi; Musyarofah, L.; Purwandari, Endhah
Jurnal ILMU DASAR Vol 18 No 2 (2017)
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1209.742 KB) | DOI: 10.19184/jid.v18i2.5911

Abstract

STT (Spin Transfer Torque) can be referred to as a process of manipulation and control of spin current in the field of spintronics. When the material is ferromagnetic nanowire La0.7Sr0.3MnO3injected currents will move the domain wall with accompanying changes of spin currents. In mikromagnetik simulation shows that the application is capable of producing flow velocity or pressure of domain wall in the direction of electron flow. The domain wall pressure generating magnetization changes with increasing current density occurs. To that end, the simulation research was done in order to obtain the effect of the injection of electric current to the magnetization of the material. This phenomenon is simulated by modeling the material into the 3D geometry. The greater the current density is given the domain wall velocity or pressure on the nanowire faster so that the magnetization process is also faster. Changes in the velocity of the fastest domain wall is obtained when the material is injected with a current density as well as M-t get a graph showing oscillation pattern that is denser when the current is increased. Furthermore, the total energy analysis with variations in size diameter of 10 nm, 20 nm and 30 nm. The results show that with increasing diameter, total energy tends to increase. Keywords: spin transfer torque, La0.7Sr0.3MnO3, magnetisation, domain wall, ferromagnetic
Simulation of Formation of Icosahedral Structure in Solid-Liquid-Solid Phase Change Using Molecular Dynamics Methods Hauwali, Nikodemus Umbu Janga; Arkundato, Artoto; Rohman, Lutfi
Jurnal ILMU DASAR Vol 17 No 1 (2016)
Publisher : Fakultas Matematika dan Ilmu Pengetahuan Alam Universitas Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (279.395 KB) | DOI: 10.19184/jid.v17i1.2661

Abstract

It has successfully conducted research to study the structure of the icosahedral formation in the event of change of the solid phase - liquid-solid using molecular dynamics method . The result showed that the percentage of the maximum icosahedral structure is obtained when the simulation is run at the start of the cooling temperature of 2875 K at a rate of temperature decrease of 0.064 K /step and at the beginning of the cooling temperature of 3000 K at a rate of temperature decrease 0.12 K/step. While icosahedral minimum percentage obtained when the simulation is run at a temperature of 2750 K with the initial cooling rate of temperature decrease of 0.069 K/step. Based on these results we can conclude that there is a relationship between the initial temperature of the cooling and the rate of temperature decrease of the icosahedral structure is formed. Keywords: Icosahedral, phase change, molecular dynamics
Temperatur Curie dan Medan Koersivitas Material Co0,8Ni0,2 dalam Struktur Random Alloy dan Double Layers Rohman, Lutfi; Novitasari, Suci; Supriyadi, Supriyadi
INDONESIAN JOURNAL OF APPLIED PHYSICS Vol 10, No 01 (2020): IJAP Volume 10 ISSUE 01 YEAR 2020
Publisher : Department of Physics, Sebelas Maret University

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (598.215 KB) | DOI: 10.13057/ijap.v10i01.31346

Abstract

Material Kobalt Nikel (CoNi) merupakan paduan penting karena memiliki sifat kemagnetan yang baik diantaranya yaitu temperatur curie dan koersivitas yang tinggi. komposisi, struktur alloy dan ukuran sisi kubus bahan berpengaruh terhadap temperatur Curie dan koersivitas. Simulasi mikromagnetik dilakukan pada material Co0,8Ni0,2 dengan struktur random alloy dan double layers untuk menentukan nilai temperatur Curie dan analisis kurva histerisis. Simulasi material Co0,8Ni0,2 dilakukan menggunakan software Vampire dengan variasi ukuran sisi kubus yang digunakan yaitu 5 nm, 8 nm, 10 nm, 12 nm, dan 15 nm. Hasil simulasi menunjukkan nilai temperatur Curie semakin meningkat dengan bertambahnya ukuran sisi kubus. Pada material Co0,8Ni0,2 double layers diperoleh nilai temperatur Curie lebih tinggi dari pada material Co0,8Ni0,2 random alloy. Karakteristik kurva histerisis pada material Co0,8Ni0,2 random alloy dan double layers menunjukkan bahwa nilai koersivitas meningkat seiring bertambahnya ukuran sisi kubus. Namun pada material Co0,8Ni0,2 random alloy ketika ukuran bahan yang diberikan 12 nm dan 15 nm nilai medan koersivitasnya semakin menurun, dibandingkan saat ukuran 10 nm. Pada ukuran sisi kubus 10 nm dikatakan sebagai ukuran terbaik dari material Co0,8Ni0,2 random alloy ditinjau dari nilai medan koersivitas yang besar.
Analysis Curie Temperature and Hysteresis La0,7Sr0,3MnO3 with Micromagnetic Simulation Febiantoro, Muhamad Rony; Rohman, Lutfi; Sutisna, Sutisna
Computational And Experimental Research In Materials And Renewable Energy Vol 3 No 2 (2020): November
Publisher : Physics Department, Faculty of Mathematics and Natural Sciences, University of Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/cerimre.v3i2.23545

Abstract

Simulation reseach has been carried out to obtain the characteristic of material La0,7Sr0,3MnO3. The simulation method used atomistic of magnetic materials. Simulations were carried out using Vampire software Micromagnetic simulation were determine Curie temperature and Hysterisis Curve. The monte carlo algorithm was used in this reseach. Simulation were carried out by variation nanocube size 22 nm, 27 nm, and 32 nm. The simulation result show, Curie temperature show in 27 nm have the biggest value and stuck in that value. The characteristics of the Hysterisis curve 32 nm bigger than the others.From the simulation, it is found that the between the temperature and Hysteris curve. More temperature value, the smaller the Hysterisis curve.
Study of Phenomenon STT (Spin Transfer Torque) on Permalloy NiFe Material Shaped Nanowire Using Micromagnetic Simulation Ni’mah, Khiptiatun; Rohman, Lutfi; Purwandari, Endhah
Computational And Experimental Research In Materials And Renewable Energy Vol 2 No 1 (2019): May
Publisher : Physics Department, Faculty of Mathematics and Natural Sciences, University of Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/cerimre.v2i1.20555

Abstract

STT is a process of controlling the spin currents in spintronic. This simulation aims to know the properties of NiFe permalloy materials' properties by studying STT phenomenon-shaped nanowire that can be applied in storage devices, like MRAM. The material's magnetic properties include magnetization value, energy in the ferromagnetic system, and the speed of the domain wall movement, obtained by injecting the electric current density through a micromagnetic simulation using the NMAG program. This simulation's result is that the domain wall's position will shift faster along the nanowire when we inject current density to the nanowire. Current density injection will produce a domain wall pressure on the domain structure, resulting in a change in the material's magnetization value. The graph of magnetization relation to time (M-t), shown along with the increasing electric current density, we obtain oscillation magnetization change will increase. The larger the given diameter, the total energy generated will increase, demagnetization energy tends to be greater than the energy exchange. The greater the polarization of the material provided at the same diameter, the speed of the domain wall movement will be greater too.
Analysis of Tensile Strenght and Shear Modulus of GRE Pipe using Ansys Puspita, Dita; Arofah, Siti Lailatul; Hidayah, Elok; Rohman, Lutfi; Syarifah, Ratna Dewi
Computational And Experimental Research In Materials And Renewable Energy Vol 1 No 1 (2018): November
Publisher : Physics Department, Faculty of Mathematics and Natural Sciences, University of Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/cerimre.v1i1.19544

Abstract

Composite materials (GRE pipe) had been applied in various industries. These kind application are based on the advantages of composite properties, that are lightweight, high corrosion resistance and low cost. In order to make a lightweight and strong materials, some materials that light and stiff had been widely used, lie fiber glass, epoxy and the other. These materials (fiber glass and epoxy) are synthetic and non-biodegradable, but give some advantages in composite to make composite more stiff, light and strong. Mechanical properties of fiber glass composites had been doing based on theory through modeling. Theoretical results obtained showed that maximum stress and shear modulus value of GRE pipe are less than each components (glass fiber and epoxy resin). Each value of maximum stress and shear modulus are 584,57 MPa and 46,15 MPa.
Study of Vortex Generator Effect on Airfoil Aerodynamics Using the Computational Fluids Dynamics Method Ayudia, Siti Aisyah; Arkundato, Artoto; Rohman, Lutfi
Computational And Experimental Research In Materials And Renewable Energy Vol 3 No 2 (2020): November
Publisher : Physics Department, Faculty of Mathematics and Natural Sciences, University of Jember

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.19184/cerimre.v3i2.23547

Abstract

The lift force is one of the important factors in supporting the aircraft flying capabilities. The airplane has a section called the aircraft wing. In particular, the wing section of aircraft is called the airfoil. One of the efforts to increase the lift force is to make the flow of air fluid at the top of the airfoil more turbulent. Turbulent flow can attract momentum from the boundary layer, the result of this momentum transfer has energy that is more resistant to the adverse pressure gradient which can trigger the flow separation. Efforts that can be made to reduce separation flow and increase lift force are the addition of a turbulent generator on the upper surface of the airfoil, one type of turbulent generator is a vortex generator, a vortex generator can accelerate the transition from the laminar boundary layer to the turbulent boundary layer. This study was conducted with the aim of knowing the effect of the vortex generator on the aerodynamics of NACA-4412 using the computational fluid dynamics method. The main thing that will be investigated is the effect of the straight type vortex generator application on the lift coefficient, by comparing the plain airfoil and airfoil that has been applied to the vortex generator to vary the angle of attack. The variation of the angles of attack are 0º, 5º, 10º, 15º and the placement of the vortex generator is 24% of the leading edge. The results obtained that the lift coefficient changes with increasing angle of attack and the application of a vortex generator to an airfoil can increase the lift coefficient than a plain airfoil. The optimum increase in lift coefficient is at the angle of attack of 5º as much as 13%.