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"Pembuatan sistem eksperimen impuls berbasis PC telah berhasil dilakukan. Sistem eksperimen impuls ini terdiri dari sensor Piezoresistive (Flexiforce), rangkaian pengkondisi sinyal, dan DAQ. Sensor diletakkan pada modul mekanik untuk mengamati perubahan gaya akibat diberikan beban pada modul mekanik. Rangkaian pengkondisi sinyal menghasilkan tegangan yang dibaca oleh PC melalui perangkat SST DAQ. Perancangan perangkat lunak menggunakan program visual basic dan macromedia flash. Eksperimen impuls dilakukan dengan menggunakan bola tenis dengan massa 32,2 gram, dan ketinggian bervariasi dari 10 cm sampai 50 cm. Hasil nilai impuls yang didapatkan untuk variasi tersebut dihitung dengan menggunakan dua metode, pertama dengan selisih momentum awal dan momentum akhir. Kedua, dengan menghitung luas kurva pulsa impuls kedua. Nilai impuls yang didapatkan untuk variasi ketinggian dengan metode pertama yaitu antara 0,065 Ns sampai 0,014 Ns. Dan untuk metode kedua, yaitu antara 0,051 Ns sampai 0,079 Ns. Pada eksperimen ini ketinggian dibatasi hanya sampai ketinggian 50 cm, karena tegangan sensor untuk impuls yang terjadi pada ketinggian tersebut sudah maksimal. Dari eksperimen ini dapat diamati bahwa ketinggian berpengaruh terhadap perubahan momentum yang terjadi saat tumbukkan.

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The impulse experiment based on PC has successfully done. This impulse experiment consist of Piezoresistive sensor, signal conditioning circuit, and DAQ. The sensor put in mechanical module which detect force changing on module. The signal conditioning circuit gives an output voltage that will be read by PC using SST DAQ device. Design of software use Visual Basic and Macromedia Flash programme. The impulse experiment has been done using tennis ball with 32,2 gram of mass, and height variation from 10 cm to 50 cm. The impulse calculated using two method, calculate momentum difference before and after collision, and calculate area under impulse curve. The result from the first method is between 0,065 Ns to 0,014 Ns, and from the second method is between 0,051 Ns to 0,079 Ns. In this experiment, the height limited until 50 cm, because the output sensor has reach its maximum value. From this experimen, we can observe that the height influence momentum changing."

"ABSTRAKTelah dilakukan proses surface treatment Thermal Reactive Deposition (TRD) dalam pembentukan lapisan tipis karbida pada substrat baja SUJ2 . Pada proses ini menggunakan metode pack cementation menggunakan campuran serbuk Ferrovanadium dan Ferrochromium sebagai carbide former . Serbuk carbide former dan susbtrat dicampur bersama NH4Cl dan Al2O3 untuk diproses selama 6 jam dalam furnace. Dilakukan 3 variasi temperatur yaitu 900, 950 dan 1000 C untuk mengetahui pengaruh temperatur terhadap ketebalan, kehomogenan, kekerasan dan laju keausan lapisan karbida yang terbentuk. Hasil pengamatan pada mikroskop optik menunjukkan bahwa semakin tinggi temperatur proses, maka semakin tebal lapisan karbida yang terbentuk pada permukaan substrat disertai membesarnya butir baja pada subtrat. Hasil linescan mikroskop elektron SEM juga menunjukkan bahwa semakin tinggi temperatur ,proses laju difusi dari carbide former Vanadium lebih tinggi dibandingkan Krom pada tiap temperatur. Hasil lapisan dikarakterisasi menggunakan difraksi sinar-X XRD menunjukkan bahwa lapisan terdiri dari karbida vanadium dan juga karbida krom. Pada pengujian keras mikro Vickers, dihasilkan kekerasan rata-rata yaitu sekitar 2100 HV dan menghasilkan laju keausan yang hampir identik pula yaitu sekitar 3 x 10-4 mm3/m, yang artinya campuran serbuk FeCr dan FeV mendekati nilai kekerasan lapisan dengan penggunaan FeV sebagai carbide former tunggal yang memiliki kekerasan rata-rata lapisan sekitar 2400 HV.

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ABSTRAKIn the present study, surface treatment on SUJ2 steel by thermal reactive Deposition TRD method was studied. Two different carbide former powders, ferrovanadium and ferrochromium were used with pack cementation method. The process was carried out on steel substrate at temperatures of 900, 950 dan 1000 C for 6 hours. The effects of temperature on layer thickness, homogenity and hardness were studied. The result showed that the higher temperature the thicker layer that formed on substrate surface and it is followed by enlargement of substrate grains. Scanning Electron Microscope SEM linescan shows that at higher temperature, diffusion rate of vanadium and chromium are increase with the note that vanadium has higher diffusion rate than chromium. XRD results shows that layer that formed with this process consists of vanadium carbide and chromium carbide. The average micro hardness of coatings for 3 temperature variations was about 2100 HV and wear rate was about 3 x 10 4 mm3 m. This hardness was approaching hardness value of FeV as single carbide former with a hardness value of about 2400 HV. "

"ABSTRAKSintesis LiFe1-0.5Mn0.5PO4/V/C sebagai katode baterai ion litium telah berhasil dilaksanakan. Material LiFe1-0.5Mn0.5PO4/V/C disintesis dengan prekursor intermediat garam besi yang terdiri dari FeSO4.7H2O, dan NH4H2PO4, prekursor LiOH, prekursor MnSO4.H2O, prekursor NH4VO3, serta prekursor C6H8O7. Prekursor intermediat garam besi disintesis dengan variasi kondisi pH meliputi suasana asam (pH 2), netral (pH 7), dan basa (pH 10), metode pemanasan yang digunakan, serta penambahan perlakuan ultrasonik. Hasil penelitian menunjukkan bahwa kondisi pH sintesis akan mempengaruhi morfologi serta struktur kristal senyawa intermediat yang dihasilkan. Morfologi partikel dari seri asam cenderung berbentuk bulat ataupun oktahedral, seri netral cenderung berbentuk persegi panjang, sementara dari seri basa cenderung berbentuk lembaran. Struktur kristal seri asam menyerupai mineral lipscombite, sedangkan struktur kristal seri netral dan basa memiliki struktur garam besi fosfat. Perlakuan ultrasonik juga memberikan pengaruh terhadap morfologi serta struktur kristal senyawa intermediat yang dihasilkan. Morfologi dari sampel yang dikenai perlakuan ultrasonik cenderung berbentuk oktahedral, sementara durasi perlakuan ultrasonik mempengaruhi ukuran kristalit material. Proses pemanasan mempengaruhi morfologi serta struktur kristal senyawa intermediat yang dihasilkan. Proses pemanasan tanpa metode hidrotermal menghasilkan partikel yang cenderung beragregat. Hasil pengujian memperlihatkan sampel katode yang memiliki konduktivitas optimum didapatkan dari sampel LiFe1-0.5Mn0.5PO4/V/C yang disinter dengan tube furnace sebesar 5.6870 x10-5 S.cm-1, dengan tegangan kerja serta kapasitas pengisian optimum dalam sistem baterai R2032 dengan susunan [Li|1 M LiPF6/EC-DMC| LiFe1-0.5Mn0.5PO4/V/C] masing-masingnya 4.7 V dan 5.6 mAh.g-1.

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ABSTRACTSynthesis and characterization of LiFe1-0.5Mn0.5PO4/V/C used as lithium ion battery cathode has been successfully conducted. The LiFe1-0.5Mn0.5PO4/V/C composite was synthesized using iron salt intermediate precursors, which consist of FeSO4.7H2O, and NH4H2PO4, LiOH precursor, MnSO4.H2O precursor, NH4VO3 precursor and C6H8O7 precursor. Iron salt intermediate precursors were synthesized at various variable including variations in pH conditions acidic atmosphere (pH 2), neutral (pH 7), and alkaline (pH 10), heat treatments, and the use ultrasonic treatment. The results show that the pH synthesis conditions affect the morphology and crystal structure of the intermediate compounds produced. The morphology of iron salt intermediates in acidic condition was round and octahedral, in neutral condition is rectangular, and in alkaline condition is in sheet form. The crystal in acidic condition favored lipscombite structures, while the neutral and alkaline conditions favored phosphate iron salt structure. The ultrasonic treatment affected morphology and crystal structure of the intermediate compounds produced. The samples subjected to ultrasonic treatment formed an octahedral structure. Heat treatment also affected the morphology and crystal structural of the intermediate compounds produced. Heat treatment without hydrothermal treatment produced aggregated particles. In this work, the best conductivity of the cathode was obtained from LiFe1-0.5Mn0.5PO4/V/C sintered with tube furnace at 5.6870 x10-5 S.cm-1 and a working voltage and charge discharge in R2032 coin cell battery [Li|1 M LiPF6/EC-DMC| LiFe1-0.5Mn0.5PO4/V/C] of 4.7 V and 5.6 mAh.g-1, respectively."

"This volume contains the proceedings of the XIX International Colloquium on Mechanical Fatigue of Metals, held at the Faculty of Engineering of the University of Porto, Portugal, 5-7 September 2018. This International Colloquium facilitated and encouraged the exchange of knowledge and experiences among the different communities involved in both basic and applied research in the field of the fatigue of metals, looking at the problem of fatigue exploring analytical and numerical simulative approaches.Fatigue damage represents one of the most important types of damage to which structural materials are subjected in normal industrial services that can finally result in a sudden and unexpected abrupt fracture. Since metal alloys are still today the most used materials in designing the majority of components and structures able to carry the highest service loads, the study of the different aspects of metals fatigue attracts permanent attention of scientists, engineers and designers."

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Logam transisi dichalgogenides (TMDs) memperlihatakan sifat-sifat yang unik pada fase struktur monolayernya, yaitu celah pita langsung, yang menjadikannya kandidat menjanjikan dalam penerapannya dalam optoelektronik. Diantara TMDs tersebut, WS₂ memperlihatkan interaksi spin-orbit yang kuat sehingga dalam uji eksperimen dapat memisahkan pita-pita energi pada band valensinya hingga sebesar ~400 meV. Tidak seperti TMDs lainnya, puncak eksitonik pertamanya A berbentuk sangat tajam, sedangkan puncak eksitonik keduanya berbentuk lebih lebar dengan intensitas yang relatif lebih kecil jika dibandingkan puncak pertama. Untuk mendapatkan nilai eksitoniknya secara teori, khususnya puncak B, kami menerapkan metode Double-Grid. Efek-efek interaksi elektron-hole sendiri dibahas dengan membandingkannya terhadap yang dihitung pada level partikel independen. Perhitungan first principle yang kami lakukan dengan menerapkan efek interaksi spin-orbit menunjukkan terjadinya pergeseran celah pita energi ke wilayah energi yang lebih rendah sebesar 0.36 eV jika dibandingkan dengan perhitungan tanpa menggunakan efek spin-orbit. Lebih lanjut, efek spin-orbit ini juga menyebabkan pemisahan pada pita energi valensi tertingginya sebesar 410 meV. Dari sisi struktur eksitoniknya, interaksi spin-orbit menyebabkan terpecahnya puncak-puncak eksiton WS₂ monolayer menjadi dua bagian, khususnya pada puncak kedua dan ketiga

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Transition metal dichalcogenides (TMDs) display unique properties in their monolayer structures, namely a direct band-gap transition, which becomes a promising candidate for optoelectronics applications. Among them, WS₂ exhibits strong spin-orbit (SO) interaction which splits the electronic valence band as observed in the experimental data up to 400 meV. Unlike the other TMDs, the first excitonic peak A is very sharp for WS₂, while the secondary peak B is broader with smaller relative intensity. In this study, we perform first-principles calculations on the electronic band structure and solve the Bethe-Salpeter equation (BSE) for the complex dielectric function of monolayer WS₂ to study the effects of spin-orbit coupling on its excitonic structures. To resolve the excitonic peaks, in particular the B peak, we implement the double-grid method. We discuss the effects of electron-hole interaction on the absorption spectrum by comparing it with that calculated at the independent-particle level. Our first principle with spin-orbit calculation band structure shows spin-orbit coupling induce red-shifting of 0.36 eV compare to one without spin-orbit interaction. It also induces splitting of 400 meV on the valence band structure. From perspective of exitonic structure, spin-orbit coupling induces peak splitting on the second and third peak of WS₂ monolayer absorption optical spectra.

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"The research described here develops and applies novel, ultra-wideband (UWB) antipodal Vivaldi antennas for high-resolution detection of defects and damages in composite construction materials and structures using their microwave and millimeter wave imaging. The author examines the challenges of applying the UWB microwave technique in that the technique is dependent on the operating frequency used for the specified material under test. In this context, the objectives of this research volume include, but are not limited to, development of a small UWB antenna at frequency range from 5 GHz-50 GHz for microwave and millimeter wave imaging of wide range of low loss construction materials, design of a small UWB antenna operating for microwave and millimeter wave imaging of low loss and high loss materials for the purpose of detection of surface damages of concrete under low loss materials, and development of a UWB antenna at frequency range from 2 GHz-27 GHz for microwave imaging of low loss and high loss materials such as concrete structures and layered structures for the purpose of detection of cavities inside concrete.;"

"This volume contains many state-of-the-art applications for the development of new materials and technologies. It discusses computer-based engineering tools which are widely used and related to the simulation, evaluation of data and design processes. For example, modern joining technologies can be used to fabricate new compound or composite materials, even composed of dissimilar materials. Such materials are many times exposed to harsh environments and must reveal specific properties. Technologies in this context are mainly related to the transportation technologies in their wider sense. This means automotive and marine technology, i.e., ships, amphibious vehicles, docks, offshore structures, and even robots. Typically, finite element and finite volume methods are used in the context of engineering simulations and this volume highlights their importance."