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"Inhibition is one of themechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims toinvestigate theinhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on thecorrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafelextrapolation and linear polarization techniques. The study reveals that BPTUacts as an excellent anodic inhibitor for low carbon steel in a HClsolution. The protective efficiency of the compound was found to be more than97% even at higher temperatures. The study demonstrated that BPTU gets adsorbedon the steel surface, following Temkin?s adsorption isotherm and the inhibitionis controlled by a chemisorptionmechanism. The investigation shows that the results obtained from the Tafelextrapolation and linear polarization techniques for the corrosion of mildsteel in HCl medium were in good agreement. The influence of temperatures andconcentrations of BPTU on the corrosion of low carbon steel are alsoexamined in the present work."

"Inhibition is one of the mechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims to investigate the inhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on the corrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafel extrapolation and linear polarization techniques. The study reveals that BPTU acts as an excellent anodic inhibitor for low carbon steel in a HCl solution. The protective efficiency of the compound was found to be more than 97% even at higher temperatures. The study demonstrated that BPTU gets adsorbed on the steel surface, following Temkin’s adsorption isotherm and the inhibition is controlled by a chemisorption mechanism. The investigation shows that the results obtained from the Tafel extrapolation and linear polarization techniques for the corrosion of mild steel in HCl medium were in good agreement. The influence of temperatures and concentrations of BPTU on the corrosion of low carbon steel are also examined in the present work."

"Kurang efisiennya pengeringan biji kopi dengan menggunakan sinar matahari membuat produktifitas para petani kopi di Indonesia kurang maksimal. Maka dari itu penelitian ini dilakukan untuk membuat sistem pengeringan yang lebih optimum yaitu dengan cara mengkombinasikan sistem pengeringan jenis bed drying dengan sistem refrigerasi double condensor sebagai dehumidifier. Pengujian dilakukan dengan buah kopi yang sudah dikupas dengan variasi pengujian laju aliran, temperatur dan kelembaban udara pengering. Hasil yang diperoleh dari penelitian ini adalah karakterisasi pengeringan biji kopi dengan mendapatkan nilai konstanta pengeringan dan energi aktivasi dari proses pengeringan. Yang dimana didapati dalam penelitian ini ialah besarnya nilai konstanta pengeringan dan energi aktivasi berbanding lurus dengan besarnya nilai laju aliran dan temperatur udara pengering, serta berbanding terbalik dengan kelembaban udara pengering yang dimana semakin kering udara yang digunakan selama proses pengeringan maka akan optimum hasil yang diharapkan. Dalam penelitian ini didapat nilai konstanta pengeringan tertinggi sebesar 1,8534×10-4 dan nilai konstanta pengeringan terendah sebesar 3,70079×10-5, sedangkan untuk nilai energi aktivasi tertinggi sebesar 56,117 kJ/mol dan nilai energi aktivasi terendah sebesar 44,928 kJ/mol.

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The inefficient drying of coffee beans using sunlight makes the productivity of coffee farmers in Indonesia less than optimal. Therefore, this research was conducted to make a more optimum drying system by combining a bed drying type drying system with a double condenser refrigeration system as a dehumidifier. The test was carried out with peeled coffee cherries with variations in the flow rate, temperature and specific humidity testing of the drying air. The result of this research is the characterization of coffee bean drying by obtaining the drying constant and activation energy of the drying process. What is found in this study is the value of the drying constant and activation energy is directly proportional to the value of the flow rate and temperature of the drying air, and inversely proportional to the humidity of the drying air, where the drier the air used during the drying process, the optimum results will be expected. In this study, the highest drying constant value was 1.8534×10-4 and the lowest drying constant value was 3.70079×10-5, while the highest activation energy value was 56.117 kJ/mol and the lowest activation energy value was 44,928 kJ/mol.

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"ABSTRAKPenelitian ini bertujuan untuk menghidrodearomatisasi senyawa naftalena pada fraksi gas oil dengan menggunakan katalis NiMo-P/γ-Al2O3 tersulfidasi. Pada katalis dilakukan variasi penambahan fosfor dengan kadar 0,5% dan 2,0% untuk melihat efek fosfor terhadap reaksi hidrodearomatisasi dan proses sulfidasi untuk mengganti oksida logam menjadi sulfida logam. Karakterisasi dilakukan terhadap katalis NiMo-P/γ-Al2O3 [P:0,5%] (C5P05) dan Katalis NiMo-P/γ-Al2O3 [P:2,0%] (C5P20). Karakterisasi dilakukan berdasarkan 4 parameter uji, yaitu analisa luas permukaan, volume dan diameter pori, kekuatan mekanik, fasa kristalitas, dan kadar logam yang terkandung pada katalis. Katalis C5P20 memiliki luas permukaan sebesar 184,8 m2/g yang lebih rendah dibandingkan C5P05 sebesar 188,3 m2/g, C5P20 memiliki volume pori 0,4422 cm3/g yang lebih besar dari C5P05 yaitu 0,4198 cm3/g, dan C5P20 memiliki diameter pori sebesar 9,57 nm yang lebih besar dibandingkan Katalis C5P05 yaitu 8,917 nm. Katalis C5P05 memiliki kekuatan mekanik yang lebih besar dibandingkan C5P20, nilainya berturut-turut 9,43 kg/mm dan 7,45 kg/mm. Analisa fasa kristalitas Katalis C5P05 dan C5P20 menunjukkan kristal γ-Al2O3. Analisa kadar logam terhadap katalis C5P05 dan C5P20 menunjukkan C5P05 memiliki kadar fosfor yang terikat sebesar 0,36% dan C5P20 sebesar 1,09%. Hasil aktivitas katalitik C5P05 dan C5P20 ditunjukkan berdasarkan energi aktivasi (Ea) yang didapat dari masing-masing katalis, nilai Ea berturut-turut 124,90 kJ/mol dan 92,63 kJ/mol. Pada reaksi hidrodearomatisasi menggunakan katalis C5P05 dan C5P20 tidak menunjukkan pergeseran titik didih yang signifikan antara umpan dan produk yang menandakan tidak terjadi perengkahan hidrokarbon dari hasil reaksi hidrodearomatisasi.

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ABSTRACTThis study aims to hydrodearomatization naphthalene compound on gas oil fraction by using catalyst NiMo-P/γ-Al2O3 sulphided. Phosphorus addition to the catalyst with variations levels of 0,5% and 2,0% to see the effects of phosphorus to the hydrodearomatization reaction and sulfidation process to replace the metal oxides into metal sulphides. Catalyst characterization carried out on the NiMo-P/γ-Al2O3 [P : 0,5%] (C5P05) and NiMo-P/γ-Al2O3 [P : 2,0%] (C5P20). Characterization conducted by four parameter tests, analysis of surface area, volume and pore diameter, mechanical strength, cristalline phase, and the metal content in the catalyst. C5P20 has a surface area of 184,8 m2/g lower than C5P05 is 188,3 m2/g, C5P20 has a pore diameter of 9,57 nm higher than C5P05 is 8,917 nm. C5P05 has higher mechanical strength than C5P20, respectively 9,43 kg/mm and 7,45 kg/mm. Analysis of cristalline phase on the C5P05 and C5P20 showed crystals formed γ-Al2O3. Analysis of the metal content on the C5P05 and C5P20 showed phosporus content on C5P05 is 0,36% and C5P20 is 1,09%. The result of catalytic activity C5P05 and C5P20 indicated by the activation energy (Ea) that obtained from each catalyst, the value of Ea respectively 124,9 kJ/mol and 92,63 kJ/mol. In the hydrodearomatization reaction using catalysts C5P05 and C5P20 did not show a significant shift in boiling point between the feed and product that indicates cracking of hydrocarbons is not occur from the hydrodearomatization."

"Ground granulated blast furnace slag (ggbs) is a waste material generated from iron production, and is one of the cementitious materials that can be used to replace part of the cement in concrete. The aim of this research was to determine the effects of the water-binder ratios and levels of ggbs in concrete, with regard to the activation energy, which is needed for predicting the concrete’s strength. A number of mixtures with different water-binder ratios (ranging from 0.30 to 0.51), ggbs levels, and curing temperatures were cast and tested at 0.5, 1, 2, 4, 8, 16, and 32 days. The activation energies were determined using the American society for testing and materials (ASTM) standard C1074, and the Freiesleben Hansen and Pedersen (FHP) method. The results of the experiment showed that the apparent activation energy was relatively independent of the water-binder ratio, and mainly affected by the ggbs level in the concrete. Higher ggbs levels in the concrete resulted in the higher apparent activation energies."

"Since inhibition is the simplest mechanism used for mitigating the corrosion of metals and alloys, particularly in acidic environments, the present work aims to investigate the inhibiting effect of N-benzyl-N?-phenyl thiourea (BPTU) and N-cyclohexyl-N?-phenyl thiourea (CPTU) on mild steel corrosion in 0.1M HCl medium using the Tafel extrapolation technique. Tafel experiments were conducted with ±250 mV vs. rest potential (RP) in steps of 20 mV from the cathodic side for recording the corrosion currents, and then, the Tafel plot of potential vs. current was drawn for determining the corrosion current density (icorr). The linear polarization method was also used for validating the Tafel results. It was performed by polarizing the specimen with ±20 mV vs. RP in steps of 5 mV, and the corrosion currents were noted. The plot of potential vs. current was drawn for calculating icorr. The study reveals that both BPTU and CPTU act as anodic inhibitors for mild steel in the HCl medium, and good inhibition efficiency (>97%) was evidenced from both the compounds even at elevated temperatures. The study also reveals that the investigated compounds get adsorbed quickly on the steel surface, following Temkin’s adsorption isotherm. The kinetic parameters obtained from the study indicated that the inhibition was governed by a chemisorption mechanism and the presence of inhibitors substantially reduced the metal dissolution in the studied temperature range. The investigation shows that there was a good correlation between the Tafel extrapolation and linear polarization results."

"Mampu bentuk (formability) material bukan hanya ditentukan oleh mikrostruktur dari material, temperatur, laju regangan (strain rate) dan regangan (strain), tetapi juga tahapan tegangan pada zona deformasi. Uji tarik panas merupakan salah satu metode pengujian yang dilakukan untuk mengevaluasi sifat mekanis dari material, memperoleh informasi plastisitas material dan sifat perpatahan (fracture). Pengujian dilakukan dengan menggunakan parameter dari persamaan konstitutif dimana tegangan alir merupakan fungsi dari regangan, laju regangan dan temperatur. Hal ini dapat menjelaskan karakteristik Rheologi dari material tersebut. Penelitian ini bertujuan untuk mempelajari karakteristik Rheologi dari material baja HSLA (ASTM A572 Gr 50) dengan menentukan parameter persamaan konstitutif menggunakan uji tarik panas, dengan variabel temperatur 700°C, 750°C, 800°C, dan 850°C. Dalam penelitian ini dapat dihasilkan parameter persamaan konstitutif untuk paduan Baja HSLA (ASTM A572 Gr 50), yaitu σ = K. ɛn. έm. eQ /RT, di mana dengan meningkatnya temperatur dari 700°C ke 800°C akan menurunkan nilai koefisien pengerasan regang (n) sebesar 47% dan menurunkan % elongasi sampel sebesar 26%. Pada laju regangan 0.1 s-1 dengan meningkatnya temperatur dari 700°C ke 850°C akan menurunkan tegangan luluh sebesar 42%. Pada laju regangan 0.1 s-1 dengan meningkatnya temperatur dari 750°C ke 850°C, akan meningkatkan nilai koefisien sensitifitas laju regangan (m) sebesar 96%. Pada temperatur konstan 850°C, dengan meningkatnya laju regangan dari 0.01 s-1 ke 0,1 s-1 akan menurunkan nilai energi aktivasi sebesar 2%.

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Formability not only determined by the microstructure of the material, temperature, strain rate and strain, but also stage the voltage on the deformation zone. Hot tensile test one method of testing conducted to evaluate the mechanical properties of the material, information material plasticity and fracture properties. Tests carried out by using the parameters of constitutive equations in which the flow stress is a function of strain, strain rate and temperature. This may explain the rheological characteristics of the material. This research aims to study the rheological characteristics of HSLA steel material (ASTM A572 Gr 50) by determining the parameters of the constitutive equation using hot tensile test, with variable temperature 700°C, 750°C, 800°C and 850°C.

In this study the constitutive equation can be generated parameters for HSLA steel alloy (ASTM A572 Gr 50), namely σ = K. ɛn. έm. eQ / RT, where with increasing temperature from 700°C to 800°C will lower the value of strain hardening coefficient (n) by 47% and lower % elongation of 26% of samples. At the strain rate 0.1 s-1 with increasing temperature from 700°C to 850°C will lower the yield stress by 42%. At the strain rate 0.1 s-1 with increasing temperature from 750°C to 850°C, will increase the value of strain rate sensitivity coefficient (m) of 96%. At a constant temperature of 850°C, with increasing strain rate from 0.01 s-1 to 0.1 s-1 would lower the activation energy value of 2%."