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Optimization of Bioethanol Production From Chlorella Vulgaris With Ca2+,Mg2+, and Zn2+ Ion Suplements Through Separated Hydrolysis and Fermentation Using Respon Surface Methodology
Full text linkIndonesia, with its wealth of natural resources, has the potential to develop bioethanol as an alternative to diminishing fossil energy sources. Third-generation bioethanol is a form of renewable energy and an environmentally friendly fuel derived from non-conventional biomass resources, particularly from microorganisms such as algae and cyanobacteria. This study focuses on optimizing the bioethanol production process from the microalga Chlorella vulgaris using the Separated Hydrolysis and Fermentation (SHF) method, with the addition of Ca2+, Mg2+, and Zn2+ ions to enhance bioethanol yield and concentration. The research procedure includes raw material pretreatment, acid hydrolysis, liquefaction, saccharification, fermentation, and distillation. The distillate samples are analyzed for bioethanol concentration using a refractometer and bioethanol density with a pycnometer. The effect of added medium components on the fermentation process is statistically analyzed using Analysis of Variance (ANOVA) in MINITAB Statistical Software and Response Surface Methodology (RSM) in DESIGN EXPERT 13. Statistical optimization of the fermentation process is performed using Central Composite Design (CCD). ANOVA analysis reveals significance with a P-Value <0.0001 for bioethanol yield and concentration. Optimization results indicate an optimal yield of 17.087% with a concentration of 165.592 g/L, achieved with the addition of Ca2+ at 164.755 ppm, Mg2+ at 146.279 ppm, and Zn2+ at 38.516 ppm
Risk Evaluation Of The Shipyard Supply Chain Process On Ship Repair With The House Of Risk Matrix Method
Full text linkOne of the keys to the success of ship repair is the supply chain (SC) process of materials that arrive on time. However, delays in its implementation were still found due to poor SC risk management. The purpose of the study is to identify risk factors for SC delay, measure risk factors and evaluate risk factors. This study uses the HOR (House of Risk) method which identifies risk variables (risk events and risk agents) and designs mitigation actions. The results of the HOR phase 1 study show an assessment score in the form of Aggregate Risk potential (ARP) which has a high influence on KM repair. Lintas Damai 1 includes: Supplier's unpreparedness in fulfilling orders with a score of 225, the forwarder experienced a delay in scoring 116 and Needs rejuvenation of facilities and transportation with a score of 120 and KM. Shinpo19 includes the quality of materials from suppliers that are of poor quality with a score of 280, materials that are difficult to obtain in the area with a score of 138 and the layout of poorly organized storage warehouses with a score of 92. The results of HOR phase II include mitigation actions to handle risk agents in KM. Lintas Damai 1 includes finding trusted supplier partners, increasing networking with other suppliers, holding tenders with suppliers who are ready and conducting service and checks every month. Meanwhile, KM. Shinpo19 has mitigation actions to handle risk agents, namely replacing materials with the same specifications but still of quality, having supplier connections with quality standards, supervising suppliers so that they comply with quality standards and structuring materials based on their type
Effect of Inhibitor Addition, pH, and Current Density on the Corrosion Rate of Fe Metals
Full text linkCorrosion significantly impacts public safety and the economy, causing substantial financial losses, infrastructure damage, and hazardous incidents across various industries. Researchers investigated the effects of pH, current density, and corrosion inhibitors (potassium chromate and potassium nitrate) on iron corrosion by measuring weight loss of iron samples immersed in sulfuric acid over time. The addition of inhibitors showed that KNO₃ was more effective in reducing the corrosion rate, with values of 4.992068, 3.744051, 2.736034, 1.728017, and 0.608008 mpy, compared to K₂CrO₄, which resulted in 9.728132, 7.296099, 5.472066, 3.648033, and 1.216017 mpy. Corrosion rate increased as pH decreased, with Fe showing corrosion at pH 6.21, 5.18, 4.26, 3.85, and 3.22. The relationship between current density and corrosion rate was found to be proportional, with voltage values of 1.31, 2.24, 3.16, 5.11, and 7.1 A/m². This study confirms that inhibitor type, acidity (pH), and current density significantly influence corrosion behavior, where increasing pH and current density can accelerate corrosion, and potassium nitrate (KNO3) demonstrates superior corrosion inhibition compared to potassium chromate (K2CrO4)
Compressive Strength Performance of High-Volume Fly Ash Concrete with CaCO3 Addition
Full text link This study investigates the compressive strength performance of High-Volume Fly Ash (HVFA) concrete with added CaCO₃ as a sustainable alternative to Ordinary Portland Cement (OPC) for infrastructure applications. The experimental research replaces a significant portion of cement with fly ash—a byproduct of coal combustion—aiming to reduce greenhouse gas emissions associated with concrete production. Two HVFA concrete mixtures were developed, substituting 37% and 47% of cement content with fly ash and adding 3% CaCO₃ to enhance mechanical properties. Material characterization, including XRF and XRD analysis, confirmed the suitability of fly ash for concrete production based on ASTM C618-19 standards. Aggregate gradation, moisture content, and specific gravity tests were conducted to optimize the mix design. Compressive strength tests were performed at 7, 14, and 28 days, showing that HVFA concrete with 37% fly ash substitution achieved higher strength values, reaching 25.92 MPa at 28 days, compared to the 47% mix, which reached 24.68 MPa. Slump tests indicated sufficient workability, with a measured slump of 10 cm for FA37C3 and 12 for FA47C3. These findings suggest that HVFA concrete with moderate fly ash substitution, complemented by CaCO₃ addition, can achieve compressive strength and workability comparable to OPC, supporting the development of environmentally friendly concrete solutions.
Implementation Of Fuzzy Logic in The Dissolved Oxygen and pH Control System to Reduce the Risk of Death of Cyprinus Carpio Fish
Full text linkCultivation of Cyprinus carpio, commonly known as the goldfish, in aquariums requires strict monitoring of water quality to maintain the fish's health and ensure its survival. Key parameters such as dissolved oxygen and pH greatly affect the aquatic environment, where imbalances can lead to stress or death. This study aims to design and implement a dissolved oxygen and pH control system using fuzzy logic as an alternative to traditional PID-based or rule-based systems commonly used in aquaculture. The proposed system automatically detects water conditions (LOW, NORMAL, HIGH) and activates appropriate control responses. It integrates an SEN0237 dissolved oxygen sensor, an E-201C pH sensor, aerators, dosing pumps, and an Arduino-based microcontroller. Sensor data is processed via fuzzy inference to operate actuators—either to increase oxygen levels or inject buffer solutions for pH normalization. Unlike previous studies that focus on single-parameter control or fixed-response systems, this system offers a dual-parameter adaptive control approach. Experimental validation shows that the system maintains pH at 6–7 and DO at 3–4 mg/L, with sensor accuracy exceeding 95%. Over 10 days, fish survival improved in the controlled aquarium (7/10) compared to the uncontrolled aquarium (5/10). The system demonstrates potential to reduce water quality fluctuations, offering hope for a more stable aquaculture environment. This work contributes to the application of fuzzy logic in small-scale innovative aquaculture systems, highlighting its potential advantages over conventional methods
Numerical Analisys of Segmental Box Girder’s Stress with Eccentric Tendon Anchoring on Balanced Cantilever Box Girder Bridge
Full text linkDiagonal crack damage on the web of balanced cantilever box girder bridges has frequently occurred worldwide, including in Indonesia. Previous studies have shown that these cracks can result from additional shear stress caused by prestressed tendon anchoring. In this study, an analysis was conducted using a 2D element model verified through a numerical approach. The evaluation of box girder web stress values was used to assess the potential for cracking and confirm the results of crack mapping conducted on site. The research found that shear stress from prestressed tendon anchoring increases the total shear stress on the box girder web by up to 46.6% of the total shear stress value. The distribution of shear stress from prestressed tendon anchoring is concentrated in the anchoring areas on the top slab and bottom slab sides of the box girder web. The evaluation of principal tensile stress shows that the observed crack locations in the field correspond to areas where the principal tensile stress values exceed the allowable design limit
Comparative Risk Prioritization in the Initiation Phase of the Pagerungan Besar Photovoltaic Plant: A Failure Mode and Effect Analysis (FMEA) and Risk Matrix Approach
Full text linkPhotovoltaic (PV) power plant projects in East Java often face challenges during the initiation phase due to inadequate risk assessments. This phase is crucial for ensuring the project's long-term success; however, suboptimal risk identification has caused project delays. In the risk assessment process, high-priority risks need to be mitigated, but differences in the methods used can result in varying risk priority outcomes. One of the methods that can be used is Failure Mode and Effect Analysis (FMEA), while according to internal regulations at PT PLN (Persero), the Risk Matrix is applied. By using these two methods, the differences in the resulting risk priority rankings can be identified. Both tools rely on evaluations from experts experienced in decision-making during the initiation phase of PV power plant projects. From the analysis, 12 risks were identified during the initiation phase of the Pagerungan Besar PV power plant project. The highest-priority risks identified include Suboptimal feasibility study (Risk Priority Number/RPN: 74.27), unfavorable outcomes for the organization/company (RPN: 68.96), lack of budget (RPN: 64.00), and stakeholder Intervention (RPN: 53.69). Meanwhile, by plotting the Severity Level and Occurrence Level of each risk on the Risk Matrix according to PT PLN (Persero) regulations, the highest-priority risks identified include Suboptimal feasibility study (Extreme Risk Level, Zone E5), location-related issues (Extreme Risk Level, Zone E5), non-compliance with regulations (Extreme Risk Level, Zone E5), and suboptimal project team (Very High Risk Level, Zone D5). The two risk assessment methods produced different prioritizations, potentially impacting mitigation strategy decisions. This variation highlights the need for further analysis to ensure accurate and reliable risk prioritization, which is critical for project success and efficient resource allocation. Future studies should focus on evaluating prioritization methods to support effective decision-making and ensure timely project implementation in line with the targeted Commercial Operation Date (COD)
Effect of Flow Rate NaOH on CO₂ Absorption Efficiency Using a Column Tray Absorber
Full text linkCO₂ in industrial gas streams reduces process efficiency, corrodes equipment, and affects product quality. Additionally, CO₂ emissions contribute to climate change and global warming. To mitigate these effects, CO₂ removal through absorption is essential. Absorption involves contacting a gas mixture with a liquid absorbent to dissolve the gas component. This study examines the effect of CO₂ flow rate (V) and NaOH flow rate (L) on CO₂ absorption efficiency. The experiment involved preparing 33 liters of 0.1N NaOH and 250 ml of 0.1N HCl, followed by solution standardization using methyl orange. CO₂ was introduced through valve V-4 while NaOH was pumped into the absorption column. Samples were taken after steady state was reached, and titration with 0.1N HCl determined residual NaOH concentration. Flow rate variations of 1, 3, 5, 7, and 9 L/min were tested. Results align with literature, indicating that as CO₂ flow rate increases, NaOH flow rate also rises. However, the L/V ratio and absorbed CO₂ amount decrease due to reduced contact time, lowering absorption efficiency. This study highlights the importance of optimizing flow rates to enhance CO₂ capture
Comprehensive Study on Cr(VI) Adsorption and Regeneration Behavior of Alkali-Treated Wood Charcoal: Isotherms and Kinetics Models
Full text linkThe present study considers the adsorption and regeneration behavior of alkali-treated wood charcoal (WC-NaOH and WC-KOH) for Cr(VI) removal. Adsorption isotherms (Langmuir, Freundlich, Temkin, and Dubinin-Raduskevich) and kinetics (Pseudo-first-order and Pseudo-second-orderare being investigated utilizing a non-linear method that provides precise parameter prediction and mechanism elucidation. The outcomes suggested that both WC-NaOH and WC-KOH exhibit good Cr(VI) removal efficiency, with the Langmuir model best explaining the adsorption phase, indicating single-layer adsorption. The kinetic study revealed that the Pseudo-second-order model aligns remarkably well with the data, thereby affirming that chemical adsorption is the predominant mechanism in consideration. A comparative analysis revealed that WC-KOH exhibits a higher amount of adsorption than WC-NaOH, attributable to its enhanced larger surface area as well as micro-porous structure.. Regeneration studies showed the possibility of reuse of both adsorbents. It shows the efficiency of alkali-treated wood charcoal for Cr(VI) decontamination and the advantages of non-linear modeling in adsorption experiment
Computational Study on Urea Concentration Profiles in Hemodialysis Hollow Fiber Membranes Under Different Blood Flow Conditions
Full text linkKidney failure significantly impairs physiological functions, primarily due to the accumulation of urea in the bloodstream. When renal function drops below 75%, hemodialysis becomes a crucial therapeutic intervention. This study investigates the performance of a hollow fiber dialyzer, consisting of a shell-side dialysate flow, a semi-permeable membrane, and internal capillaries for blood flow. The main objective is to develop a theoretical model describing urea mass transfer through the membrane during hemodialysis. The analysis focuses on the effect of blood flow rate on urea concentration distribution across the tube, membrane, and shell regions in both axial and radial directions. Additionally, the influence of membrane length and dialysate flow rate on urea clearance is examined. Simulation results indicate that higher blood flow rates lead to elevated urea concentrations at the tube outlet, suggesting reduced diffusion into the dialysate compartment. In contrast, increasing membrane length enhances urea clearance. Interestingly, the dialysate flow rate shows minimal impact on clearance efficiency. Under a fixed dialysate flow rate of 500 mL/min and a membrane length of 27 cm, the calculated urea clearance values were 21.95%, 17.06%, 14.31%, and 12.52% for blood flow rates of 200, 300, 400, and 500 mL/min, respectivel