{"title":"Effects of Plasma Sintering on the Post TIG Weld Joint of Fe-15Cr-25Ni Austenitic Stainless Steel","authors":"","doi":"10.7454/mst.v26i1.1577","DOIUrl":"https://doi.org/10.7454/mst.v26i1.1577","url":null,"abstract":"","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49610404","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Enhancement of Biogas Production Through Solid-State Anaerobic Co-Digestion of Food Waste and Corn Cobs","authors":"","doi":"10.7454/mst.v26i1.1478","DOIUrl":"https://doi.org/10.7454/mst.v26i1.1478","url":null,"abstract":"","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47989030","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Control Strategy for Solar Energy-Saving Lamps for Optimized Energy Utilization and Sustainability of Operation Durability: Indonesia Case","authors":"","doi":"10.7454/mst.v26i1.1474","DOIUrl":"https://doi.org/10.7454/mst.v26i1.1474","url":null,"abstract":"","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2022-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47797435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Rankine cycle is an electricity generation system that uses water or organic fluids as high-grade or low-grade heat sources, respectively. In this paper, we present the results of our study of Rankine-cycle power generation in which we compared water and organic fluids (toluene and n-nonane) as working fluids in saturated and superheated states. We analyzed the energy and exergy of the Rankine cycle in a saturated vapor state at 300 °C and superheated states at 400 °C and 500 °C (the pressure remained the same as that at 300 °C), and assumed a constant heat input for all states. In the energy analysis, we determined the mass flow rate, heat rejection, work input of the pump, work generated by the turbine, net work output, and thermal efficiency. In the exergy analysis, we determined the exergy input, exergy loss, exergy destruction at the pump and the turbine, and the exergetic efficiency. The results show that water, categorized as a wet fluid, obtains a better performance with respect to both analyses in saturated and superheated states than toluene and nnonane, which are categorized as isentropic and dry fluids, respectively. The water realizes a higher performance in the superheated than in the saturated state, whereas the performances of toluene and n-nonane are poorer in the superheated than in the saturated state.
{"title":"Comparative Study of Rankine Cycle Power Generation using Water and Organic Fluids in Saturated and Superheated States","authors":"G. Pikra, Henny Sudibyo","doi":"10.7454/mst.v25i3.3942","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3942","url":null,"abstract":"The Rankine cycle is an electricity generation system that uses water or organic fluids as high-grade or low-grade heat sources, respectively. In this paper, we present the results of our study of Rankine-cycle power generation in which we compared water and organic fluids (toluene and n-nonane) as working fluids in saturated and superheated states. We analyzed the energy and exergy of the Rankine cycle in a saturated vapor state at 300 °C and superheated states at 400 °C and 500 °C (the pressure remained the same as that at 300 °C), and assumed a constant heat input for all states. In the energy analysis, we determined the mass flow rate, heat rejection, work input of the pump, work generated by the turbine, net work output, and thermal efficiency. In the exergy analysis, we determined the exergy input, exergy loss, exergy destruction at the pump and the turbine, and the exergetic efficiency. The results show that water, categorized as a wet fluid, obtains a better performance with respect to both analyses in saturated and superheated states than toluene and nnonane, which are categorized as isentropic and dry fluids, respectively. The water realizes a higher performance in the superheated than in the saturated state, whereas the performances of toluene and n-nonane are poorer in the superheated than in the saturated state.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48496167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since Taq polymerase was first explored and identified from thermophilic bacteria, these bacteria have become wellknown sources of thermostable enzymes. New thermophilic bacteria have been investigated to broaden biodiversity and translation research. Studies have shown interests in Indonesia because of thermophilic bacteria found in hot springs. This country is traversed by the ring of fire and has more than 70 volcanoes, resulting in the wide distribution of hot springs across the country. Although many reports have been performed, studies have yet to explore thermophilic bacteria in Tirta Lebak Buana hot springs, Java Island, Indonesia. This research was the first to examine thermophilic bacteria in Tirta Lebak Buana hot spring. Two samples from two different sampling sites were obtained and analyzed through 16srRNA analysis (sampling sites A and B). Measurements indicated that the temperature (50 °C) in sampling site A was higher than that in sampling site B (40 °C), but they had similar pH (7.0). Polymerase chain reaction (PCR) showed that the 16srRNA of the specimen was around 1465 bp. The analysis of the 16srRNA sequence revealed that the obtained bacteria have a similar sequence and close relationship with Bacillus subtilis subsp. stercoris strain N12.
{"title":"Identification of Thermophilic Bacteria from Tirta Lebak Buana Hot Spring in Serang, Banten, Indonesia","authors":"Kenny Lischer","doi":"10.7454/mst.v25i3.3993","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3993","url":null,"abstract":"Since Taq polymerase was first explored and identified from thermophilic bacteria, these bacteria have become wellknown sources of thermostable enzymes. New thermophilic bacteria have been investigated to broaden biodiversity and translation research. Studies have shown interests in Indonesia because of thermophilic bacteria found in hot springs. This country is traversed by the ring of fire and has more than 70 volcanoes, resulting in the wide distribution of hot springs across the country. Although many reports have been performed, studies have yet to explore thermophilic bacteria in Tirta Lebak Buana hot springs, Java Island, Indonesia. This research was the first to examine thermophilic bacteria in Tirta Lebak Buana hot spring. Two samples from two different sampling sites were obtained and analyzed through 16srRNA analysis (sampling sites A and B). Measurements indicated that the temperature (50 °C) in sampling site A was higher than that in sampling site B (40 °C), but they had similar pH (7.0). Polymerase chain reaction (PCR) showed that the 16srRNA of the specimen was around 1465 bp. The analysis of the 16srRNA sequence revealed that the obtained bacteria have a similar sequence and close relationship with Bacillus subtilis subsp. stercoris strain N12.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46201554","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To benefit from electronic learning (E-learning), organizations should execute considerable upfront analysis to ascertain their E-learning readiness. Studies have demonstrated a range of models that have been adapted, but they are used in developed counties for whom E-learning readiness is elevated. Thus, these models are not valid in growing countries, such as Sudan. Based on a modified model, this research was performed descriptively by applying a questionnaire-based survey method to assess the level of Sudan universities’ readiness in the employment of the E-learning system. This modified model includes social support, technology readiness, attitude toward E-learning, acceptance of E-learning, and individual learners. Furthermore, the adoption and implementation of E-learning involve numerous challenges and constraints. Therefore, in this study, the challenges that could be faced in applying E-learning in Sudan from students’ perspectives are investigated. The results show that the most prepared factor is individual learners at Sudanese universities. However, this factor still needs a few improvements for E-learning with an overall mean (3.59). Given that the learners are willing to collaborate and share information and knowledge, they can manage time for their learning, and they are also motivated and enthusiastic about using computers. Moreover, attitude toward E-learning is the least prepared factor among all factors (mean = 3.16), which means that this factor is not ready and needs some work. The study recognizes serious barriers that constrain the effective incorporation of E-learning in higher education institutes (HEIs) in developing countries.
{"title":"Assessing the E-learning Readiness of Universities in Developing Countries and Expected Obstacles","authors":"A. Ate, Samar Zaineldeenc, Cai Zhaohui, Yan Zhao","doi":"10.7454/mst.v25i3.4047","DOIUrl":"https://doi.org/10.7454/mst.v25i3.4047","url":null,"abstract":"To benefit from electronic learning (E-learning), organizations should execute considerable upfront analysis to ascertain their E-learning readiness. Studies have demonstrated a range of models that have been adapted, but they are used in developed counties for whom E-learning readiness is elevated. Thus, these models are not valid in growing countries, such as Sudan. Based on a modified model, this research was performed descriptively by applying a questionnaire-based survey method to assess the level of Sudan universities’ readiness in the employment of the E-learning system. This modified model includes social support, technology readiness, attitude toward E-learning, acceptance of E-learning, and individual learners. Furthermore, the adoption and implementation of E-learning involve numerous challenges and constraints. Therefore, in this study, the challenges that could be faced in applying E-learning in Sudan from students’ perspectives are investigated. The results show that the most prepared factor is individual learners at Sudanese universities. However, this factor still needs a few improvements for E-learning with an overall mean (3.59). Given that the learners are willing to collaborate and share information and knowledge, they can manage time for their learning, and they are also motivated and enthusiastic about using computers. Moreover, attitude toward E-learning is the least prepared factor among all factors (mean = 3.16), which means that this factor is not ready and needs some work. The study recognizes serious barriers that constrain the effective incorporation of E-learning in higher education institutes (HEIs) in developing countries.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46990866","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soil is an important and fundamental element for building and road construction. However, poor properties of soil can affect the entire construction since the soil will resist the loads transferred from the upper structures. Additives such as cement, lime, and rice husk ash (RHA) can be used as stabilization materials to increase soil strength. This study examined the behavior of stabilized plastic clay mixed with cement, lime, and RHA. The clay stabilization success rate can be measured by the California Bearing Ratio (CBR), unconfined compression strength, and swelling potential. In this study, different mixtures were prepared as samples and tested under various loads: 1, 2, 3, 4, and 5 kPa. The results indicated that the addition of cement, lime, and RHA could effectively reduce the swelling potential of clay. The mixture variations of soil–cement composite 90% + RHA 10% and soil–cement composite 90% + lime 4% + RHA 6% showed the lowest swelling rate.
{"title":"Behavior of High-plasticity Clay Stabilized with Lime and Rice Husk Ash","authors":"F. Fatnanta, Andarsin Ongko, Adnan Ihsan","doi":"10.7454/mst.v25i3.3580","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3580","url":null,"abstract":"Soil is an important and fundamental element for building and road construction. However, poor properties of soil can affect the entire construction since the soil will resist the loads transferred from the upper structures. Additives such as cement, lime, and rice husk ash (RHA) can be used as stabilization materials to increase soil strength. This study examined the behavior of stabilized plastic clay mixed with cement, lime, and RHA. The clay stabilization success rate can be measured by the California Bearing Ratio (CBR), unconfined compression strength, and swelling potential. In this study, different mixtures were prepared as samples and tested under various loads: 1, 2, 3, 4, and 5 kPa. The results indicated that the addition of cement, lime, and RHA could effectively reduce the swelling potential of clay. The mixture variations of soil–cement composite 90% + RHA 10% and soil–cement composite 90% + lime 4% + RHA 6% showed the lowest swelling rate.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44580389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shahab Khademi, I. Darus, M. Mailah, L. W. Jye, A. Khademi
Hollow fiber membrane (HFM) and related technologies have recently become highly in demand and widely used in most industries and other areas recently. HFM could be used in different functions, from water and gas treatment to blood and medical applications. The paper describes the modeling of the effects of the spinning condition of a nonporous HFM on the membrane’s characteristics with the use of an automated hollow fiber fabrication system. An integrated, systematic experimental strategy based on the design of experiments was used to elaborate the effects of each parameter on selectivity. To obtain and sustain a satisfactory, significant selectivity of HFM, an automated system controlled the parameters during the fabrication process. The parameters involved in the fabrication of HFM and used in modeling are dope flow rate, bore flow rate, draw force, and air gap, which are considered inputs to fabricate polysulfone membrane. The fabrication process is improved by automating and instrumenting fabrication systems. An empirical model of the effects of fabrication parameters on the selectivity of the membrane is extracted experimentally. The mathematical model effectively explains the selectivity of CO2/CH4 with 95% fit.
{"title":"Modeling and Optimization of Spinning Parameters on Selectivity of Polysulfone Hollow Fiber Membrane for CO2/CH4 Separation","authors":"Shahab Khademi, I. Darus, M. Mailah, L. W. Jye, A. Khademi","doi":"10.7454/mst.v25i3.3865","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3865","url":null,"abstract":"Hollow fiber membrane (HFM) and related technologies have recently become highly in demand and widely used in most industries and other areas recently. HFM could be used in different functions, from water and gas treatment to blood and medical applications. The paper describes the modeling of the effects of the spinning condition of a nonporous HFM on the membrane’s characteristics with the use of an automated hollow fiber fabrication system. An integrated, systematic experimental strategy based on the design of experiments was used to elaborate the effects of each parameter on selectivity. To obtain and sustain a satisfactory, significant selectivity of HFM, an automated system controlled the parameters during the fabrication process. The parameters involved in the fabrication of HFM and used in modeling are dope flow rate, bore flow rate, draw force, and air gap, which are considered inputs to fabricate polysulfone membrane. The fabrication process is improved by automating and instrumenting fabrication systems. An empirical model of the effects of fabrication parameters on the selectivity of the membrane is extracted experimentally. The mathematical model effectively explains the selectivity of CO2/CH4 with 95% fit.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45980300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ravena Maitsa, Q. Hafiyyan, M. Adityawan, I. Magdalena, A. A. Kuntoro, H. Kardhana
This study used the finite difference method to develop a numerical model for pollutant transport phenomenon simulation. Mathematically, the phenomenon is often described by the advection–diffusion differential equation, which is obtained from a combination of the continuity equation and Fick’s first law. The Forward Time Central Space (FTCS) scheme is one of the explicit finite difference methods and is used in this study to solve the model due to its simplicity in solving a differential equation. Yet, this method is currently unstable, which results in oscillations in the model. Thus, a numerical filter (Hansen) is added to the FTCS method to improve the stability of the model. The developed numerical model is applied to several 1D and 2D pollutant transport test cases. Simulation results are compared with those of existing analytical solutions to verify the developed model, and they show that the developed model can simulate the pollutant transport phenomenon well. Moreover, the numerical filter can increase the model stability.
{"title":"Development of A 2D Numerical Model for Pollutant Transport using FTCS Scheme and Numerical Filter","authors":"Ravena Maitsa, Q. Hafiyyan, M. Adityawan, I. Magdalena, A. A. Kuntoro, H. Kardhana","doi":"10.7454/mst.v25i3.3966","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3966","url":null,"abstract":"This study used the finite difference method to develop a numerical model for pollutant transport phenomenon simulation. Mathematically, the phenomenon is often described by the advection–diffusion differential equation, which is obtained from a combination of the continuity equation and Fick’s first law. The Forward Time Central Space (FTCS) scheme is one of the explicit finite difference methods and is used in this study to solve the model due to its simplicity in solving a differential equation. Yet, this method is currently unstable, which results in oscillations in the model. Thus, a numerical filter (Hansen) is added to the FTCS method to improve the stability of the model. The developed numerical model is applied to several 1D and 2D pollutant transport test cases. Simulation results are compared with those of existing analytical solutions to verify the developed model, and they show that the developed model can simulate the pollutant transport phenomenon well. Moreover, the numerical filter can increase the model stability.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":"86 5-6","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41292314","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study focuses on the development of a conventional oven using glass-fiber-reinforced thermoset composite sandwich panels. The design process considers the thermomechanical properties of the selected materials. The constructed rectangular box oven has the overall dimensions of 450 mm × 450 mm × 600 mm and internal heat chamber dimensions of 400 mm width, 400 mm depth, and 400 mm height with two stack trays for product placement. The sidewalls consist of inner and outer E-glass-fiber-reinforced composite panels with a sandwiched rockwool insulator. The bottom panel of the oven has an inner ceramic tile plate to suspend the electric heating element. The top panel is made of the same composite sandwich with a constructed superstructure electrical wiring compartment included for the controls. The oven can stably achieve a temperature of 150 °C and a cooking efficiency of approximately 39% when in operation and can sustain heat for more than 6 h standing time when turned off. The oven can be used for both culinary and laboratory experiments, i.e., heating, baking, drying, and curing materials, and is more affordable than alternative designs in the market.
{"title":"Economic Design, Fabrication, and Performance Evaluation of Conventional Ovens Made of Glass-Fiber-Reinforced Thermoset Composites","authors":"C. Agbo","doi":"10.7454/mst.v25i3.3853","DOIUrl":"https://doi.org/10.7454/mst.v25i3.3853","url":null,"abstract":"This study focuses on the development of a conventional oven using glass-fiber-reinforced thermoset composite sandwich panels. The design process considers the thermomechanical properties of the selected materials. The constructed rectangular box oven has the overall dimensions of 450 mm × 450 mm × 600 mm and internal heat chamber dimensions of 400 mm width, 400 mm depth, and 400 mm height with two stack trays for product placement. The sidewalls consist of inner and outer E-glass-fiber-reinforced composite panels with a sandwiched rockwool insulator. The bottom panel of the oven has an inner ceramic tile plate to suspend the electric heating element. The top panel is made of the same composite sandwich with a constructed superstructure electrical wiring compartment included for the controls. The oven can stably achieve a temperature of 150 °C and a cooking efficiency of approximately 39% when in operation and can sustain heat for more than 6 h standing time when turned off. The oven can be used for both culinary and laboratory experiments, i.e., heating, baking, drying, and curing materials, and is more affordable than alternative designs in the market.","PeriodicalId":42980,"journal":{"name":"Makara Journal of Technology","volume":" ","pages":""},"PeriodicalIF":0.2,"publicationDate":"2021-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45144246","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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