Showing papers in "Journal of Engineering and Technological Sciences in 2016"
TL;DR: In this paper, an overview of different types of brine effluents, their sources and characteristics are discussed, as well as impacts of brines on the environment and management options related to their characteristics.
Abstract: Brine discharge is one of the largest sources of wastewater from industrial processes. Because of the environmental impacts arising from improper treatment of brine discharge and more rigorous regulations of pollution control, industries have started to focus on waste minimization and improving the process of wastewater treatment. Several approaches have been proposed to provide a strategy for brine handling by recovering both brine and water or to remove pollutant components so it complies with environmental regulations when discharged. One of the most promising alternatives to brine disposal is reusing the brine, which results in reduction of pollution, minimizing waste volume and salt recovery. The brine may also contain valuable components that could be recovered for profitable use. Also, water recovery from brine effluent is generally performed to save water. In the case of rejected brine from desalination plants, water recovery from higher brine concentrations has huge potential for salt production. This paper gives an overview of different types of brine effluents, their sources and characteristics. Also discussed are impacts of brine on the environment and management options related to their characteristics.
50 citations
TL;DR: In this paper, a modification of polysulfone ultrafiltration membrane was conducted by blending polysolfone with PEG400 and acetone as additives. And the influence of each additive on the resulted membrane morphology and fouling characteristics were investigated.
Abstract: Modification of polysulfone ultrafiltration membrane was conducted by blending polysulfone with PEG400 and acetone as additives. The influence of each additive on the resulted membrane morphology and fouling characteristics were investigated. The experimental results showed that the hydrophilicity of the polysulfone membrane was improved by the increase of PEG400 in the polysulfone membrane. The water contact angle of the membrane was decreased from 76.1° to 38.31° when 35 %wt of PEG400 was added into the polysulfone solution, while the water content of the membrane was increased by around 38%. The high concentration of PEG400 in the polysulfone solution led to the formation of longer finger-like cavities in the membrane structure and resulted in a thicker membrane skin layer. The high concentration of PEG400 also contributed to the increase in hydraulic resistance of the membrane due to organic matter fouling. This problem could be minimized by the addition of acetone into the polysulfone solution, which resulted in a lower fouling resistance of organic matter during up to five hours of peat water filtration.
34 citations
TL;DR: In this article, a mixed matrix anion exchange membrane (AEM) was synthesized using dry-wet phase inversion, and the casting solutions were prepared by dispersing finely ground anion-exchange resin particles in DMAc solutions of polysulfone (PSf).
Abstract: Mixed matrix anion exchange membranes (AEMs) were synthesized using dry-wet phase inversion. The casting solutions were prepared by dispersing finely ground anion-exchange resin particles in N,N-dimethylacetamide (DMAc) solutions of polysulfone (PSf). Subsequently, nanosilica particles were introduced into the membranes. The results show that evaporation time ( t ev ) and solution composition contributed to membrane properties formation. A longer t ev produces membranes with reduced void fraction inside the membranes, thus the amount of water adsorbed and membrane conductivity are reduced. Meanwhile, the permselectivity was improved by increasing t ev , since a longer t ev produces membranes with a narrower channel for ion migration and more effective Donnan exclusion. The incorporation of 0.5 %-wt nanosilica particles into the polymer matrix led to conductivity improvement (from 2.27 to 3.41 mS.cm -1 ). This may be associated with additional pathway formation by hydroxyl groups on the silica surface that entraps water and assists ion migration. However, at further silica loading (1.0 and 1.5 %-wt), these properties decreased (to 1.9 and 1.4 mS.cm -1 respectively), which attributed to inaccessibility of ion-exchange functional groups due to membrane compactness. It was found from the results that nanosilica contributes to membrane formation (increases casting solution viscosity then reduces void fraction) and membrane functional group addition (provides hydroxyl groups).
26 citations
TL;DR: In this paper, the authors presented a new intelligent computation method, called the Thunderstorm Algorithm (TA), for searching the optimal solution of the integrated economic and emission dispatch (IEED) problem as the operational assessment for determining unit commitment.
Abstract: Solving the unit commitment problem is an important task in power system operation for deciding a balanced power production between various types of generating units under technical constraints and environmental limitations. This paper presents a new intelligent computation method, called the Thunderstorm Algorithm (TA), for searching the optimal solution of the integrated economic and emission dispatch (IEED) problem as the operational assessment for determining unit commitment. A simulation using the IEEE-62 bus system showed that TA has smooth convergence and is applicable for solving the IEED problem. The IEED’s solution is associated with the total fuel consumption and pollutant emission. The proposed TA method seems to be a viable new approach for finding the optimal solution of the IEED problem.
20 citations
TL;DR: In this paper, the authors present the physical properties of sand soils related to their resistance to vibration using a shaking table and the acceleration and settlement of the samples were recorded during shaking.
Abstract: Liquefaction due to strong earthquakes often occurs in sandy soil under low water table conditions with certain physical properties. The physical properties of sandy soil that give effect to liquefaction resistance include grain size and relative density. This paper presents the physical properties of sand soils related to their resistance to vibration. Vibration tests were conducted by using a shaking table. The acceleration and settlement of the samples were recorded during shaking. The tests were conducted with variation of soil density and mean grain size. The test results showed that average grain size and relative density of sand have a unique effect on liquefaction resistance. It can be concluded that there is a density limit with respect to the mean grain size of the sand particles associated with the liquefaction resistance for a certain acceleration.
17 citations
TL;DR: In this paper, a 10-MeV proton beam generated from a typical CS-30 cyclotron was used to produce 56 Co radionuclide layers on iron surfaces via a 56 Fe(p,n) 56 Co nuclear reaction.
Abstract: The laboratory-scale erosion-corrosion testing facility at BATAN’s Center for Radioisotope and Radiopharmaceutical Technology (PTRR) in Serpong was employed to simulate flow-induced corrosion of iron surfaces. Surface loss rates were measured by a nuclear technique called thin layer activation (TLA) analysis. A 10-MeV proton beam generated from a typical CS-30 cyclotron was used to produce 56 Co radionuclide layers on iron surfaces via a 56 Fe(p,n) 56 Co nuclear reaction. The labeled iron specimens were then exposed to circulating seawater simulated in BATAN’s flow-induced corrosion test facility. The experimental results indicated that the TLA technique was able to measure a very low flow-induced erosion rate of 0.91±0.3 µm/hr. There was no significant difference in the measured surface loss rates between the remaining activity method and the concentration method. The iron surface loss in seawater was lower than that of the same material in HCl solution observed in earlier studies.
15 citations
TL;DR: In this paper, a risk-targeted ground motions (RTGM) with 1% probability of building collapse in 50 years was developed by integrating the hazard curve with the structural capacity distribution.
Abstract: In 2010 a national team (Team 9) developed the hazard curve and maximum considered earthquake (MCE) for the whole Indonesian area. The results were further applied in this study. Risk-targeted ground motions (RTGM) with 1% probability of building collapse in 50 years were developed by integrating the hazard curve with the structural capacity distribution. Parametric study on various variables that affect the log-normal standard deviation suggests a value of 0.7. In the effort to obtain the RTGM for the whole Indonesian region, integration was carried out using definite integration in which the curves are split into thin vertical strips and the areas below each curve are multiplied and summed. Detailed procedures and verification are given in this paper. An example of RTGM calculation was carried out for Jakarta City and then applied to the whole Indonesian region. Risk coefficients defining the ratio between RTGM and MCE were eventually developed and mapped. Risk coefficient development was generated for two periods of interest, i.e. a short time period (T = 0.2 seconds) and a 1-second period, respectively. Based on the results, for the period of 1.0 seconds 55% of Indonesian cities/districts have a risk coefficient in the range of 0.9 to 1.1 and about 37% in the range of 0.7 to 0.9, with only 5% in the range of 1.1 to 1.25.
11 citations
TL;DR: It was observed that the cell concentration in the inoculum and the initial pH affect cell growth and xylitol production, and pH 5 was observed to give the best fermentation performance.
Abstract: Considering its high content of hemicellulose, oil palm empty fruit bunch (EFB) lignocellulosic biomass waste from palm oil processing has the potential to be utilized as the raw material for the production of xylitol, a low calorie, low GI, and anti cariogenic alternative sugar with similar sweetness to sucrose. This research explored the possibility of converting EFB to xylitol via green microbial fermentation, in particular the effects of inoculum and initial pH on the fermentation performance. It was observed that the cell concentration in the inoculum and the initial pH affect cell growth and xylitol production. pH 5 was observed to give the best fermentation performance. Further, the fermentation tended to yield more xylitol at higher initial cell concentration. It was also observed that no growth or fermentation inhibitory compounds were found in the EFB hydrolysate obtained from enzymatic hydrolysis of EFB. Thus it can be used directly as substrate for xylitol fermentation.
10 citations
TL;DR: In this article, the effects of desulfurization temperature and Ca/S ratio (Ca = calcium content in adsorbent; S = sulfur content in coal and biomass) on coal and bio-briquettes were studied.
Abstract: Presently, biomass is mostly utilized as co-fuel in coal combustion in view of energy diversification and emission reduction. However, since the coal content of bio-briquettes is high (up to 80% in this study), gas emissions such as those of SO x still occur. Therefore, the introduction of SO 2 adsorbent is common in coal briquette or bio-briquette combustion. A calcium-based material is usually used for this goal. The aim of this study was to observe the effects of desulfurization temperature and Ca/S ratio (Ca = calcium content in adsorbent; S = sulfur content in coal and biomass) on desulfurization efficiency and kinetics. The ratio of coal to biomass (palm kernel shell/PKS) was fixed at 90:10 (wt/wt) and the ratios of Ca to S were varied at 1:1, 1.25:1, 1.5:1, 1.75:1 and 2:1. The mixtures of coal, PKS and adsorbent were briquetted at a molding pressure of 6 ton/cm 2 with Jatropha curcas seeds and starch mixture as binding agents. Desulfurization was performed within a temperature range of 300 to 500°C for 720 seconds at an airflow rate of 1.2 L/min. The results showed that the highest desulfurization efficiency (90.6%) was associated with the Ca/S ratio of 2:1 and temperature of 400°C. Moreover, the highest reaction rate constant of desulfurization was 0.280 min -1 .
10 citations
TL;DR: In this article, the effects of controlled parameters on the CO 2 absorption such as gas flow rate, solution concentration, height to diameter ratio of the column were considered, and an empirical equation of the methane enrichment with the related parameters was developed.
Abstract: Biogas upgrading with carbon dioxide absorption in a column of monoethanolamine (MEA) solution was carried out. The effects of controlled parameters on the CO 2 absorption such as gas flow rate, solution concentration, height to diameter ratio of the column were considered. High CH 4 concentration could be achieved at low gas flow rate and high MEA concentration. The CH 4 concentration could be up from 70-75% to 92-95% by volume for 0.2 M MEA. A set of breakthrough curves was obtained to determine the absorption characteristics, such as the absorption constant ( k ), the absorption time when the CO 2 concentration at the outlet was 50% of the concentration at the inlet ( t ), and the absorption period ( t * ) when the CH 4 concentration was over 90%. An empirical equation of the methane enrichment with the related parameters was developed.
10 citations
TL;DR: In this paper, the authors investigated the hysteretic performance of partially pre-stressed-reactive powder concrete (RPC) for both interior and exterior beam-column joint sub-assemblages.
Abstract: Reactive powder concrete (RPC) is an alternative to normal concrete (NC) allowing for significantly higher strength of partially pre-stressed concrete structures. In the Indonesian national standard SNI 03-2847-2013 (2013) and the American standard ACI 318-14 (2014), the partial pre-stressed ratio (PPR) is limited to a maximum of 25.0 percent to ensure that pre-stressed concrete structures remain ductile and capable to dissipate seismic energy sufficiently. The objective of this experimental study was to investigate the hysteretic performance of partially pre-stressed-RPC (PP-RPC) for both interior and exterior beam-column joint sub-assemblages. Four specimens with different levels of PPR were tested with a combination of constant axial compression and cyclic lateral loads. The PPR used for the first and the second two specimens were 22.8% and 33.8%, respectively. The strength of the RPC was 101.60 MPa for all specimens. The results showed that increasing the PPR of PP-RPC improves its hysteretic performance. The best performing specimen, with a PPR of 33.8%, had a ductility that was 1.97 times that of the specimen with a PPR of 22.8%.
TL;DR: In this article, the authors analyzed the rainfall-discharge relationship and its implications for water quality conditions at Limboto Lake, Gorontalo, Indonesia, and found that higher average rainfall in May (184.5 mm) gave a higher average total sediment load (4.41 g/L/day).
Abstract: Problems of high turbidity, sedimentation, water pollution and siltation occur at Limboto Lake, Gorontalo, Indonesia. The objective of this study was to analyze the rainfall-discharge relationship and its implications for water quality conditions. Secchi disk (water transparency), chlorophyll- a (chl- a ), and total organic matter (TOM) were measured in May 2012, September 2012 and March 2013 at three sites of the lake (L-1, L-2 and L-3) to observe the impacts on the surrounding catchment. Based on representative stations for rainfall data from 2004 to 2013, monthly averages of rainfall in March-May (166.7 mm) and September (76.4 mm) were used to represent the wet and dry period, respectively. Moreover, sediment traps at these three sites were installed in September 2012. Based on the analysis it is suggested that rainfall magnitude and land use change at the Alopohu River catchment influenced the amount of materials flowing into the lake, degrading the water quality. Specifically, the higher average rainfall in May (184.5 mm) gave a higher average total sediment load (4.41 g/L/day). In addition, water transparency decreased with increasing chl- a . This indicates that the concentrations of sediment and nutrients, reflected by the high amount of chl- a , influenced the water quality conditions.
TL;DR: In this article, the authors describe the research activity related to VIV that has taken place at NTNU and MARINTEK in Trondheim during the last years.
Abstract: This paper describes the research activity related to VIV that has taken place at NTNU and MARINTEK in Trondheim during the last years. The overall aim of the work has been increased understanding of the VIV phenomenon and to improve the empirical basis for prediction of VIV. The work has included experiments with flexible beams in sheared and uniform flow and forced motions of short, rigid cylinders. Key results in terms of hydrodynamic coefficients and analysis procedures have been implemented in the computer program VIVANA, which has resulted in new analysis options and improved hydrodynamic coefficients. Some examples of results are presented, but the main focus of the paper is to give an overview of the work and point out how the new results can be used in order to improve VIV analyses.
TL;DR: In this paper, the effect of the addition of carbon nanotube (CNT) composite to porous graphene-like nanosheets (PGNS) as the electrode on a hybrid supercapacitor was studied.
Abstract: Electric vehicles are set to become a most attractive alternative transportation mode due to their high efficiency and low emission. Electric vehicles require an efficient energy storage system, e.g. a supercapacitor. Coconut shells have high lignocellulosic content and are not being fully utilized in Indonesia. The lignocellulose could be converted into activated carbon for use as the electrode on a hybrid supercapacitor. This research focused on studying the effect of the addition of carbon nanotube (CNT) composite to porous graphene-like nanosheets (PGNS) as the electrode on a hybrid supercapacitor. The PGNS and CNT composite were synthesized via simultaneous activation and carbonization. Nickel oxide was used as the counter electrode. The CNT composite had a large surface area of 1374.8 m 2 g -1 , pore volume of 1.1 cm 3 g, and pore size of 3.2 nm. On the other hand, the PGNS had a surface area of 666.1 m 2 g -1 , pore volume of 0.47 cm 3 g, and pore size of 2.8 nm. The electrode pair between the NiO and the activated carbon achieved 5.69 F/g and 94.1% cycle durability after 10 charging and discharging cycles. The composite had an energy density of 0.38 W h kg -1 . The aim of this research was to provide an alternative formula for producing high-performance supercapacitor materials.
TL;DR: In this paper, thin microporous silica membranes were prepared on a porous alumina tube by sol-gel method using tetraethyl orthosilicate (TEOS) as the silica precursor.
Abstract: Silica membranes were developed and tested for the separation of acetic acid and water by pervaporation. Thin microporous silica membranes were prepared on a porous alumina tube by sol-gel method using tetraethyl orthosilicate (TEOS) as the silica precursor. Colloidal and polymeric silica sols were prepared by hydrolysis of TEOS. The pervaporation experiment results revealed that the silica membranes showed water selectivity towards acetic acid. The permeate flux and the separation factor were strongly influenced by the composition of the silica sols. For a feed concentration of 90 wt% acetic acid, the permeate flux varied between 0.016 to 0.91 kg/m 2 h, with the separation factor varying between 3.7 and 324.
TL;DR: In this article, the authors evaluated consumers' purchasing decisions of their present cars and investigated their awareness of ASEAN NCAP, and found that safety was considered as one of the top three factors by the respondents when purchasing their new cars.
Abstract: In Malaysia, the car safety level has been elevated through regulations and a consumer-based approach, i.e. the New Car Assessment Program in Southeast Asian Countries (ASEAN NCAP). Nevertheless, the availability of information on consumers’ car purchasing decisions towards safety is still limited in Malaysia. Thus, this study was aimed at evaluating consumers’ purchasing decisions of their present cars and investigating their awareness of ASEAN NCAP. Self-administered questionnaires were distributed among consumers visiting different car showrooms and dealer shops. The findings suggest that safety was considered as one of the top three factors by the respondents when purchasing their present cars. Awareness of ASEAN NCAP has increased as compared to a previous study. This information is essential for policy makers, manufacturers and other stakeholders to assist in setting priorities with regard to the promotion of car safety in the country.
TL;DR: In this article, the effectiveness of the use of blinding agents, ionic exchanger resins and the combination of them in improving gold extraction from simulated preg-robbing ore is discussed.
Abstract: In the present paper, the effectiveness of the use of blinding agents, ionic exchanger resins and the combination of them in improving gold extraction from simulated preg-robbing ore is discussed. The blinding agents used were kerosene, diesel oil and pine oil, while the ion exchange resins used were Lewatit Monoplus MP 800, Lewatit AF 5 and guanidine. Preg-robbing conditions were simulated by blending fine activated carbon with ore sample. The investigation results show that the presence of artificial carbonaceous materials at 2% (w/w) in the gold ore significantly reduces gold recovery. Pretreatment of artificial preg-robbing ore prior to cyanidation by mixing with kerosene, diesel oil and pine oil for 0.5h improved gold recovery up to 25.4%. A combination of pre-treatment using blinding agent and a resin in leach (RIL) test using Lewatit MP 800 resin demonstrated a synergistic effect that improves gold recovery up to a level of 99.5%,which is significantly higher than using activated carbon and without pretreatment.
TL;DR: In this paper, a double-arch tunnel was modeled using data from an actual excavation of a highway tunnel and the skewed distribution of the surrounding rock pressure varied with changes in stress state, construction sequence and excavation size.
Abstract: It is of great importance to reasonably estimate the surrounding rock load of a double-arch tunnel for the design, construction and stability evaluation of the tunnel. Currently, the basic theory on surrounding rock pressure of double-arch tunnels is insufficient for properly making the design and calculations. Generally, simplified calculations based on experience are used, such as the calculation method of Protodyakonov’s theory, the building code method and others. Considering the fact that the surrounding rock pressure of double-arch tunnels has skewed distribution characteristics, a computational model of a double-arch tunnel was built using data from an actual excavation of a highway tunnel. Taking some factors into consideration, such as different stress states, different construction methods and different sizes of double-arch tunnels, the pressure evolution of the surrounding rock was analyzed during step-by-step excavation of the double-arch tunnel. The results showed that in each condition the surrounding rock pressure of the double-arch tunnel displayed skewed distribution characteristics. The skewed distribution of the surrounding rock pressure varied with changes in stress state, construction sequence and excavation size. The skewed pressure of the double-arch tunnel was converted to equivalent load. The conversion method and distribution characteristics of the equivalent load are specified. They have important theoretical significance and practical value for similar engineering practices.
TL;DR: The results showed that the water quality in the stabilization pond system of Bojongsoang WWTP supported rapid growth of microalgae, where most rapid microbial growth occurred in the anaerobic pond.
Abstract: The Bojongsoang Wastewater Treatment Plant (WWTP) serves to treat domestic wastewater originating from Bandung City, West Java, Indonesia. An abundant amount of nutrients as a result of waste decomposition increases the number of microalgae populations present in the pond of the wastewater treatment plant, thereby causing a population explosion of microalgae, also called algal blooming. In a stabilization pond system, the presence of algal blooming is not desirable because it can decrease wastewater treatment performance. More knowledge about the relationship between the nutrients concentration and algae blooming conditions, such as microalgae diversity, is needed to control and maintain the performance of the wastewater treatment plant. Therefore this study was conducted, in order to reveal the diversity of microalgae in the stabilization pond system and its relationship with the water characteristics of the comprising ponds. The results showed that the water quality in the stabilization pond system of Bojongsoang WWTP supported rapid growth of microalgae, where most rapid microbial growth occurred in the anaerobic pond. The microalgae diversity in the stabilization ponds was very high, with various morphologies, probably affiliated with blue-green algae, green algae, cryptophytes, dinoflagellates and diatoms. This study has successfully produced information on microalgae diversity and abundance profiles in a stabilization pond system.
TL;DR: In this article, the thermal performance of an SWH system using a V-shaped absorber plate was investigated experimentally and two SWH systems with different absorber plates, i.e., a flat-plate and a Vshaped plate, were installed and tested at a low flowrate of 0.5 L/min and at a high flow rate of 2L/min.
Abstract: Solar energy is known as an environmentally friendly energy source with a wide range of applications. This energy can be utilized in various applications such as domestic and industrial water heating using solar water heating (SWH) systems. The thermal performance of an SWH system using a V-shaped absorber plate is presented in this study. Two SWH systems with different absorber plates, i.e. a flat-plate and a V-shaped plate, have been investigated experimentally. First, the absorptivity of the absorber plates was calculated analytically. The optimum V-shaped configuration with angle at β = 21° (V-shaped dimensions t = 4 cm and l = 4 cm) was determined from various V-shaped plate absorbers based on their absorptivity and applied in the experimental study. Two SWH systems were installed and tested at a low flowrate of 0.5 L/min and at a high flowrate of 2 L/min. The results showed that the SWH system with V-shaped plate absorber had a 3.6-4.4% better performance compared with that of the system with flat-plate absorber.
TL;DR: In this article, a sand filtration-dielectric barrier discharge (DBD) system was investigated as an alternative process for treating POME, which can reduce land usage, processing time and costs compared to conventional systems.
Abstract: In the palm oil industry, open ponding, aerobic and anaerobic digestion, physicochemical treatment and membrane filtration are generally applied as conventional treatments of palm oil mill effluent (POME). In this study, a sand filtration-dielectric barrier discharge (DBD) system was investigated as an alternative process for treating POME. This system can reduce land usage, processing time and costs compared to conventional systems. The removal efficiency of chemical oxygen demand (COD), biological oxygen demand (BOD 5 ), and oil-grease in relation to the applied voltage were studied. Furthermore, the pH and temperature profiles were investigated. The obtained results indicate that the removal efficiency of COD, BOD 5 , and oil-grease increased with an increase of the applied voltage. The electrical energy consumption needed is about 10.56 kWh/L of POME.
TL;DR: In this article, a prediction model of the influence function on mining subsidence was used to establish the relationship between surface curvature and wall deformation, which provided the basis for a damage evaluation method for buildings in coalmine areas.
Abstract: Ground curvature caused by underground mining is one of the most obvious deformation quantities in buildings. To study the influence of surface curvature on buildings and predict the movement and deformation of buildings caused by ground curvature, a prediction model of the influence function on mining subsidence was used to establish the relationship between surface curvature and wall deformation. The prediction model of wall deformation was then established and the surface curvature was obtained from mining subsidence prediction software. Five prediction lines were set up in the wall from bottom to top and the predicted deformation of each line was used to calculate the crack positions in the wall. Thus, the crack prediction model was obtained. The model was verified by a case study from a coalmine in Shanxi, China. The results show that when the ground curvature is positive, the crack in the wall is shaped like a “V”; when the ground curvature is negative, the crack is shaped like a “∧”. The conclusion provides the basis for a damage evaluation method for buildings in coalmine areas.
TL;DR: In this paper, the interaction among piles, pile cap and soil of a piled raft system on medium and stiff clays was studied and the effects of various distances between piles (s/d) in affecting load transfer mechanisms and deformation were considered.
Abstract: Piled raft foundation designs consider the contribution of the pile cap in transferring load to the ground and distributing load over the piles. The concept of a piled raft foundation requires a comprehensive evaluation of a number of factors that affect the performance of the foundation system. In this research the interaction among piles, pile cap and soil of a piled raft system on medium and stiff clays was studied. The effects of various distances between piles (s/d) in affecting load transfer mechanisms and deformation were considered. The study was performed by utilizing the 3D finite element method with a professional software package called Plaxis3D Foundation. A case study of the piled raft foundation performances of a foundation design for a high-rise building based on the soil stratification in Jakarta was also performed and is presented in this paper.
TL;DR: In this paper, a large-scale ocean hydrodynamics and sediment transport model MuSed3D was applied to the North Java Sea to simulate suspended sediment transport at the study site.
Abstract: The morphology of the Cimanuk Delta at the North Java Sea has changed rapidly over the last two decades. The annual sediment deposition is about two million cubic meters (Yuanita and Tingsanchali, [1]). The large-scale ocean hydrodynamics and sediment transport model MuSed3D (Muin, [2]) was applied to the North Java Sea to simulate suspended sediment transport at the study site. A potential offshore structure was positioned at approximately 30 km from the Cimanuk Delta. The result of the large-scale model was calibrated using observation data and Landsat satellite image interpretation. The agreement between the modeling results and the observations was excellent. It was found that the critical shear stresses for erosion and deposition were 0.1 Pa and 0.05 Pa respectively. An empirical formula was further utilized to assess the local scouring at the potential offshore structure site in a small-scale domain and under extreme conditions.
TL;DR: In this article, the effects of temperature exposure on the growth of the TiAl 2 interdiffusion zone layer on two-phase α 2 -Ti 3 Al/γ-TiAl alloys with a chemical composition of Ti-47Al-2Nb-2Cr-0.5Y 0.5Zr are presented.
Abstract: Lower density materials of TiAl based intermetallic alloys have recently attracted intensive attention for the replacement of nickel-based superalloys used at high temperatures. As aluminium-rich titanium aluminide intermetallic compounds are normally brittle, two-phase α 2 -Ti 3 Al/γ-TiAl alloys have been developed. To increase the corrosion resistance of these alloy systems, an aluminide coating of TiAl 3 layer is normally applied. During operation at high temperatures, however, interdiffusion between the coating and the alloy substrate can occur and decrease the TiAl 3 layer thickness of the coating. The effects of temperature exposure on the growth of the TiAl 2 interdiffusion zone layer on two-phase α 2 -Ti 3 Al/γ-TiAl alloys with a chemical composition of Ti-47Al-2Nb-2Cr-0.5Y-0.5Zr are presented in this paper. The exponents for kinetics and rate constant of the TiAl2 interdiffusion layer growth of this multi-component system were found under variation of temperature. The results were compared with those from other researchers.
TL;DR: In this paper, an evaluation of the mechanical properties of glulam wood sourced from native Indonesian timber: Bengkirai wood, Kamper wood, and Nyatoh wood is presented.
Abstract: Wood is a natural resource that is renewable and available in various species in tropical countries. Its abundancy in nature makes it easy to obtain, thus making it a nature friendly material for use in construction. Indonesia is the most important source of tropical wood in the world after Brazil, making the use of wood for structural elements very desirable. It is estimated that 4000 different varieties of wood exist in Indonesia. This estimate is based on the herbarium species collected by the Forestry Research Institute, currently counting nearly 4000 types of trees with a diameter of more than 40 cm. In the Indonesian wood structure code, the strength of woods is divided into 3 grades (grade I, II and III). This paper presents an evaluation of the mechanical properties of glulam wood sourced from native Indonesian timber: Bengkirai wood (grade I), Kamper wood (grade II), and Nyatoh wood (grade III), thus proving the potential for Indonesian wood as industrial structural elements in wooden constructions.
TL;DR: In this article, experiments on four specimens of reinforced concrete slab-column connection sub-assemblages using reactive powder concrete (RPC) were conducted and the results showed that up to 5.0 percent drift all specimens had stable hysteresis loops without any significant degradation of strength and stiffness.
Abstract: Experimental work on four specimens of reinforced concrete slab- column connection sub-assemblages using reactive powder concrete (RPC) was conducted. The specimens were subjected to a combination of gravity and cyclic loading. The gravity loading was represented by a number of concrete cubes hung on the slab bottom surface and the cyclic lateral loading was applied on the upper end of the columns. The specimens consisted of two variables, i.e tensile flexural reinforcement ratio (0.65% and 1.8%) and slab span (2.0 m and 3.0 m). Shear reinforcement was not used in the slab. The displacement history consisted of three repeated cycles, starting from 0.07 to 5.00 percent drift ratio, covering the elastic and the inelastic response of the specimens. The RPC mixture proportion for the specimen’s material was developed using local materials and normal concrete technology methods. The average RPC compression tests results were 136.0 MPa at 28 days and 141.0 MPa at the time of the first specimen, tested at 56 days. The tests results showed that up to 5.0 percent drift all specimens had stable hysteresis loops without any significant degradation of strength and stiffness. The specimen with a larger tensile flexural reinforcement ratio developed more strength, stiffness and energy dissipation.
TL;DR: In this article, the effects of tablet compared to laptop usage postures on the development of fatigue, discomfort and pain were investigated and the results indicated that the effect of portable device placement was significant with varied effects across measurements.
Abstract: The number of people using online tablets in public places has increased dramatically. Their postures are dominantly characterized by non-neutral and awkward positions that in the long term may lead to a higher risk of musculoskeletal disorders. The purpose of this study was to investigate the effects of tablet compared to laptop (i.e. netbook) usage postures on the development of fatigue, discomfort and pain. A total of 12 participants accomplished email typing tasks for 2 hours with four different usage configurations: 1) Netbook-on-table, 2) Netbook-on-lap, 3) Tablet-on-table, and 4) Tablet-on-lap. Changes in fatigue, discomfort, and pain were monitored based on pinch grip strength (tip pinch, key pinch, and palmar pinch), rating of perceived discomfort, and Phalen’s & Reverse Phalen’s tests, respectively. The results indicated that the effect of portable device placement was significant (p < 0.05), with varied effects across measurements. No effect of portable computer type was found. The interactive effect of portable computer type and placement was only significant for right tip pinch (p < 0.05). The findings of this study can hopefully be used to increase the awareness of tablet users about associated fatigue, discomfort and pain while using a tablet in public places that may lead to a higher risk of musculoskeletal disorders.
TL;DR: In this paper, a smart prognostic method for photovoltaic module health degradation was developed based on two approaches to achieve more accurate predictions: online diagnosis and data-driven prognosis.
Abstract: All industrial systems and machines are subjected to degradation processes, which can be related to the operating conditions. This degradation can cause unwanted stops at any time and major maintenance work sometimes. The accurate prediction of the remaining useful life (RUL) is an important challenge in condition-based maintenance. Prognostic activity allows estimating the RUL before failure occurs and triggering actions to mitigate faults in time when needed. In this study, a new smart prognostic method for photovoltaic module health degradation was developed based on two approaches to achieve more accurate predictions: online diagnosis and data-driven prognosis. This framework of forecasting integrates the strengths of real-time monitoring in the first approach and relevant vector machine in the second. The results show that the proposed method is plausible due to its good prediction of RUL and can be effectively applied to many systems for monitoring and prognostics.
TL;DR: In this article, the authors proposed a simulation model for a separate spare parts ordering schedule, where the spare parts for replacement can be classified as stochastic demand for failure replacement and deterministic demand for block replacement.
Abstract: A block replacement schedule can be optimized simultaneously with a spare parts ordering schedule, since all items are replaced at a constant interval. The solution of joint optimization for spare parts ordering time and block replacement gives lower costs compared to separate optimization of ordering time and replacement time. The spare parts for replacement can be classified as stochastic demand for failure replacement and deterministic demand for block replacement. In this paper, we propose a simulation model for a separate spare parts ordering schedule. The solution was compared to the solution for a model with common spare parts for both failure and block replacement. The system has N identical components, each with a Weibull lifetime distribution. The costs of failure and block replacements, and also the costs of ordering, holding and shortage of spare parts are given. The proposed model was shown to perform better than the common order model. Also, compared to the age replacement model, the solution of the proposed model is relatively similar, yet the economies of scale would be an advantage for the block replacement over age replacement.