Graphene Oxide is a material that has a thickness of one atom composed of carbon atoms to form a hexagonal lattice and a material that has unique properties, namely mechanical, optical, thermal, and electrical properties. Fe₂O₃ is a material that has magnetic properties and can be used for various applications such as enzyme separation, drug transport, microwave absorption, photocatalysts, biological applications, biomedicine, metal separation, and magnetic resonance imaging (MRI). In this study, the addition of graphene oxide was carried out using the coprecipitation method on Fe₂O₃ nanomaterials that had been treated with sintering and non-sintering. The coprecipitation method is the synthesis of inorganic compounds which is based on the deposition of more than one substance together when it passes the saturation point. The purpose of this study was to determine whether the addition of graphene oxide to the Fe₂O₃ material can increase the magnetic properties of the Fe₂O₃ material or vice versa. The result was that the sintering treatment on Fe₂O₃ GO did not have a transforming effect on its magnetic properties, but instead had a changing effect on its magnetic value. However, the magnetic coercivity value of Fe₂O₃ + GO 700 ºC increased to 0.038 Tesla. Thus, it can be concluded that at a temperature of 700 °C graphene oxide acts as a barrier from external magnetic fields in the opposite direction.

The air conditioning system for the Mall A building in Jakarta uses a central air conditioning system with a constant flow chiller with TES (Thermal Energy Storage). This system will be verified by measuring data regarding cooling load of the Mall A. The peak cooling load measurement results is 12,299 kW with a total cooling load of 45,733,180 kWh for 1 year. The result of the measurement data will be compared to cooling load calculation by Trace 700 software. Based on Trace 700 software, the peak cooling load is 12,594 kW with a total cooling load of 44,617,405 kWh. Furthermore, using the actual measurement data of the air conditioning system in Mall A, it will be compared with a central air conditioning system with a magnetic bearing chiller which will be equipped with VSD (Variable Speed Drive) to find out how well its energy performance and costs are for a mall building similar to Mall A, as a potential for energy and cost savings. The results of energy calculations and cost analysis, the central air conditioning system with the magnetic bearing chiller is 99 kWh/(m2.year) and the life cycle costs for 20 years, 30 years, and 50 years are 339,828,248,242 IDR, 415,994,136,400 IDR, 521,915,598,761 IDR. While the results of energy calculations and cost analysis, the TES combination constant flow chiller central air conditioning system is 141 kWh/(m2.year) and the life cycle costs for 20 years, 30 years, and 50 years are 435,150,140,059 IDR, 541,700,386,487 IDR, 690,535,151,478 IDR. Based on the foregoing, the central air conditioning system with variable flow magnetic bearing chiller is a better system than the central air conditioning system with TES combination constant flow chiller for shopping mall buildings similar to Mall A.

Corrosion engineering has taken great interest in many industries that required high cost management to overcome the serious problems. This work has investigated the role of watermelon peel extract as green inhibitor to protect carbon steel in seawater. This investigation has studied the corrosion rate and inhibition efficiency applying weight loss method. The laboratory result shows the optimum inhibition efficiency found to be 71.64% at 5% inhibitor concentration in 100 ml seawater at room temperature. The effects of temperature and immersion time on inhibition efficiency have also been examined. This study has used Arrhenius equation based on activation energy to determine type of adsorption encountered with corrosion process. The result shows a chemical adsorption justified by its high adsorption heat and strengthened by FTIR and UV-Vis examinations. The phytochemical examination of watermelon peel extract gives positive response to flavonoid, alkaloid, and saponin. The finding is useful for many industries encountered with carbon steel corrosion in corrosive medium using green inhibitor.

Introduction: Gas stations (SPBU in Indonesia) have the potency for fire and explosion hazards due to the storage and distribution of flammable liquids, one of which is Pertamax. This can be a non-military threat in the dimension of public safety because if it occurs, the resulting loss could be very large in terms of material or life. This study aims to determine the risk of fire and explosion at Indonesian gas station. Methods: The risk assessment method used is the Dow's Fire and Explosion Index in a simulated case. Results: The potential for fire and explosion or the value of the Fire Explosion Index (F&EI) in the simulated case is 110,828. The exposure radius is 28,39 m and the damage factor to the Pertamax storage tank is 63%. The large area of the Exposure is 24 m² with an area of 96 m³ of the bunker building volume. The value of the loss suffered by the company in the event of a fire and explosion in the Pertamax tank is Rp. 403.908.076,97. Conclusion: The results of the study have a risk level that is classified as Intermediate, so it is necessary to control risks such as increasing active protection and is expected to be an input in efforts to safeguard against non-military threats so as to reduce the impact of risks and losses that occur in the Pertamax storage tank.

Millscale is a large by product of metal factory. Many methods to recycled it to many applications. The aim of this research is recycled millscale to produce the iron by reduction method with graphite as reductant agent. The reduction process was deed by milled millscale and graphite powder with 4:1 weight ratio was by used High Energy Milling with 4, 6, 12 hours milling time variations. The powder then was characterized by X-Ray Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and SEM-EDS test. The XRD test result is Fe3C as a main phase then carbon, magnetite, wustite and Iron as a minor phase. The percentage of iron composition is increase during milling times amount to 6; 10.9; 13 %. The remanence for the 4, 6, and 12 hours of milling time variation, is 2.89, 3.39, and 4.98 emu/g, for the coercivity (Hc) is 209.58, 188.47, and 223.65 Oe and the magnetic saturation number is 22.59, 30.7, 39.15 emu/g, from Hc value it is concluded that the powder has superparamagnetic behavior. From SEM-EDS is knowed that the distribution of Fe is more uniform on the surface samples with the increase of milling time.

Cervical cancer is generally found in women of all ages due to virus infection on epithelial cells of female cervix. It is known that a certain type of Human Papilloma Virus (HPV) is suspected to cause cervix cancer in women from various ethnics. Several therapies have been used to cure cancer diseases like cone biopsy, laser treatment, electrosurgical excision, thermocoagulation, ablation therapy, and cryotherapy. This paper has highlighted on the role of cryogun machine applied in cryotherapy for pre-cervical cancer treatment in relation to freezing technique using liquid nitrogen to kill cancer cells on infectious area.

The use of magnetic bearing chillers in hotel air conditioning systems is an opportunity for energy or cost savings. This study will compare the electrical energy consumption and cost analysis of the centralized air conditioning system using magnetic bearing chiller that uses variable flow to another air conditioning system such as the centralized air conditioning using constant flow chiller and the VRF split air conditioning system at Hotel A in Jakarta. The calculation of energy consumption for each air conditioning system is carried out for a year. Meanwhile, the cost analysis will be carried out using the life cycle cost method for 20 years. The air conditioning system which has the least energy consumption and has the lowest life cycle cost is the best air conditioning system for this hotel building. The maximum cooling load that occurs in Hotel A is 3,281 kW. From the results of energy calculations and cost analysis, a centralized air conditioning system with magnetic bearing chiller with variable flow is the best choice to Hotel A or similar building to Hotel A, with IKE (Intensitas Konsumsi Energi) value of 84 kWh/(m2.year), and a total cost of 78,873,678,478.00 IDR for a period of 20 years.

In this research, a solid Cu/CuSO4 reference electrode has been developed. In this development process, the Cu/CuSO4 solid reference electrode provided consists of two types, namely the Cu/CuSO4 I solid reference electrode (ERP Cu/CuSO4 I) and the Cu/CuSO4 II solid reference electrode (ERP Cu/CuSO4 II). ERP Cu/CuSO4 I was prepared using two layers, namely the Cu/CuSO4 layer and the cellulose acetate layer which were placed sequentially on the surface of the planar type Cu electrode. Meanwhile, ERP Cu/CuSO4 II was prepared using three layers, namely a layer of cotton fiber/cellulose acetate, a layer of Cu/CuSO4, and a layer of cotton/cellulose acetate placed in sequence on the surface of the planar type Cu electrode, where the CuSO4 layer is between the two layers of cotton/cellulose acetate. Both types of Cu/CuSO4 solid reference electrodes were characterized by testing DmV in various concentrations of KCl solution and ERP Cu/CuSO4 II has been produced as the best reference electrode for Cu/CuSO4 solids with a DmV value of 3.3 mV. Furthermore, ERP Cu/CuSO4 II was selected for characterization using cyclic voltammetry (CV) testing, response vs Cl sensor testing, and drif testing. In CV testing, ERP Cu/CuSO4 provides a voltammogram graph pattern similar to the Ag/AgCl reference electrode as a commercial reference electrode. Meanwhile, in testing the response vs sensor Cl, ERP Cu/CuSO4 II gave a Nernstian number value of -50.1 mV/decade with a test range of 0.1-10-3 M. ERP Cu/CuSO4 II showed fairly good stability, namely with a drift value of 0.46 mV/minute which is achieved after the conditioning process after 12 minutes.

Steel is one of materials which often used on steel construction, bridge construction, and high rise building construction. Construction using welding joint is expected able to withstand construction loads for a long time. After a while weldment will be exposed to corrosion that will be construction failure in turn. One of the most important parameter in welding is heat input, however it hasn’t obtain correlation between heat input and corrosion rate on MMA (Manual Metal Arch) weldment on mild steel. This paper aims to obtain correlation between heat input and corrosion rate of low carbon steel with MMA welding. The result was show that corrosion rate tend to decrease with adding of duration, where higher corrosion rate at heat input 0,8108 kJ/mm was 68,68 gm/m2 hr at duration 5 hour.