bluuebunny/crossref_metadata_2025 huggingface dataset:
OPTIMIZING OF NEW APPROACH SINTERING METHOD ON CARBONATED HYDROXYAPATITE BIOCERAMIC
Authors: Noor Ahmad Fauzi Mohd , Wong Wai Yee , Ching Kee Chia , Htun Zaw Linn , Othman Radzali
Published: June 2024

Synthetic carbonated apatite ceramics are considered as alternative to autograft and allograft materials for bone substitute. This study was to investigate and compare the effect of carbonation introduced during cooling down of sintering of dense CHA with two kind of wet CO2 atmosphere (direct wet CO2 and dry CO2 flow through water). Pelletized samples were sintered to 800°C and soaked for 120 minutes. Upon cooling down to 150, 200, 250 and 300°C, carbonation with wet CO2 in desiccators were performed. The sintered CHA after carbonation at the various cooled temperatures was found to retain as B-type CHA. Carbonation of sintered CHA by dry CO2 through water showed an overall better results as compared to carbonation by direct wet CO2. Sample D200 with carbonation temperature of 200oC has the highest carbonate content (3.35%) and relative density (94%) while D250 with carbonation temperature of 250oC has the highest DTS value (18MPa). In vitro testing using SBF solution showed that apatite layer formed on the sintered CHA surface after one week of immersion, thus indicating the bone-forming ability. This indicated that the CHA synthesized in this study has sufficient biocompatibility to be applied as bone substitutes.
NANO CORE-SHELL PHOTOCATALYSTS FOR TREATMENT OF WATER POLLUTANTS
Authors: Tu Le Anh , Le Nguyen Thi My , Long Nguyen Quang , Salim Chris , Phuong Nguyen Thi Ngoc , Mariquit Eden , Hinode Hirofumi
Published: June 2024

Nano-materials are considered as a part of nanotechnology which is expected to provide many applications in the future. However, separation and reuse of the nano materials are challenging for catalysis application in liquid phase reactions. In this research, nano core-shell containing TiO2 which possess magnetic property have been synthesized using two methods: sol-gel method and modified sol-gel method. The materials have been characterized using different techniques such as X-ray Diffraction (XRD), Transmission electron microscopy (TEM). TiO2 anatase structure of the catalysts have been verified from XRD patterns. The potential application for the treatment of water contaminated by organic pollutants has been investigated via the photocatalytic degradation of methyl orange (MO) and p-nitrophenol (NP) as models using the as-synthesized materials. The magnetic photocatalyst which was synthesized by the sol-gel method, exhibited comparable activity as the commercial TiO2 (P25) after three hours reaction. However, the catalyst prepared by the modified sol-gel method performed high recyclability.
REGRESSION-BASED OPTIMIZATION OF THE PARTIAL OXIDATION OF METHANA ON Ni-MgO/α-ALUMINA MONOLITH CATALYST IN A REVERSE-FLOW REACTER
Authors: Nguyen Trung Kim , Razon Luis , Tan Raymond , Tran Hai-Ung , Hinode Hirofumi , Aida Takashi
Published: June 2024

This study describes the use of statistical optimization techniques on a laboratory scale reverse flow reactor for the catalytic partial oxidation of methane on Ni-MgO/α-alumina monolith catalyst. The effects of initial temperature (Tini), switching time (τ), total flow rate (F), mole fraction of methane (M), and catalyst length on hydrogen yield and methane conversion are investigated using systematic experimental design. In the first experimental phase, the steepest ascent path was established by ridge analysis to determine the stationary point. The optimum operating conditions were determined in the second experimental phase. The following interactions were found to be significant for methane conversion: M*τ, F*τ and M*F. The interaction of F*τ also affected the hydrogen yield. The third-order interaction of F*τ*M was also found to be statistically significant. The optimum methane conversion value of 57.36% could be obtained by setting switching time, total flow rate and a mole fraction of methane of 4.24 minutes, 543ml/min and 0.6043, respectively. The optimum value of hydrogen yield of 36.73% was reached by setting total flow rate, mole fraction of methane and switching time of 540ml/min, 0.5845 and 4.15 minutes, respectively. The analysis of reactor operation showed that optimization of the system required changing more than one factor and that there is a complex interplay of the different experimental factors. The influence of the factors may all be interpreted in terms of heat release and heat loss in the system.
ANALYSIS OF 3D PLANAR CRACKS WITH CONSIDERATION OF SURFACE STRESS EFFECTS
Authors: Nguyen Thai Binh , Rungamornrat Jaroon , Senjuntichai Teerapong , Wijeyewickrema Anil
Published: June 2024

An efficient numerical procedure for modeling planar cracks in three-dimensional, linear elastic, infinite media accounting for the surface stress effect is presented in this paper. The concept of surface stresses, which has been widely employed in the modeling of nano-scale problems, is considered in the present study to derive a suitable mathematical model capable of simulating nano-sized cracks. An infinitesimally thin layer of material on the crack surface is modeled by a surface with zero-thickness and perfectly adhered to the bulk material, with its behavior governed by the Gurtin-Murdoch constitutive law. In the formulation, the classical theory of isotropic linear elasticity is utilized to establish the governing equation of the bulk material in terms of completely regularized boundary integral equations for the displacements and tractions on the crack surface. For the zero-thickness layer, the final governing equation incorporating the surface stress effect is obtained in a weak form following the standard weighted residual technique. Solutions of the fully coupled system of equations are then obtained by the FEM-SGBEM coupling numerical procedure. Owing to the weakly singular feature of all involved boundary integral equations, standard C0 interpolation functions are used everywhere in the approximation of crack-face data and only special quadrature for evaluating nearly singular and weakly singular integrals is required. Once the implemented numerical scheme is validated with available benchmark solutions, it is applied to investigate the nano-scale influence of nano-sized cracks. Results from an extensive parametric study reveal that, the presence of surface stresses not only increases the near-surface material stiffness but also introduces size-dependent behavior of predicted solutions and the reduction of stresses in the region ahead of the crack front
ASSESSING THE IMPACTS OF SEA LEVEL RISE ON SAND EXPLOITATION IN THE CAN GIO COASTAL AREA (VIETNAM)
Authors: Huyen Dang Thuong , Vinh Bui Trong , Tin Huynh Trung , Phong Le Thanh , Aoki Shinichi , Deguchi Ichiro
Published: June 2024

In recent years, due to the demand for economic development in Ho Chi Minh as well as the Key Economic Zone of Southern Vietnam, the requirement for construction materials has increased rapidly. There are about 10 sand mines which are reserved and licensed in the Can Gio coastal area. The exploitation of these mines is affecting this area. According to the climate change scenario for 2011 prepared by the Ministry of Natural Resources and Environment (Vietnam) and tidal observation, sea level is rising up in Can Gio area. Sea level rise will enhance the potential of coastal erosion, flooding, saline intrusion and increase fishing activities, as well as other artificial beach projects in the Can Gio area. To assess the impacts of sea level rise and sand exploitation activities in the Can Gio coastal area as well as artificial beaches, this research carries out. Numerical modelling was carried out to assess the effects of sand exploitation coupled with sea level rise on the Can Gio coastal area. The research showed that sand exploitation activities have led to erosion in the study area.
DEVELOPMENT OF AN ASSESSMENT METHOD FOR HAZARDOUS SUBSTANCES VALUE IN AUTOMOTIVE COMPONENTS FOR SUPPORTING GREEN MANUFACTURING
Authors: Martawirya Yatna Yuwana , Raharno Sri , Setiawan Wiki Yuanditra
Published: June 2024

This aim of this research is to develop an assessment method for hazardous substances value in automotive components for supporting green manufacturing. Basically, the green manufacturing focuses on reducing environmental risks and impacts of industrial activities through elimination of resource waste, pollution and use of material containing hazardous substances. In this research, the method will be used to assess the hazardous substances contained in automotive components quantitatively. Based on the values, the hazard level of components could be compared relatively. This research has retrieved hazardous substances information from the Material Safety Data Sheet (MSDS) of the component. After that the hazardous substances were assessed based on the Hazardous Materials Identification System (HMIS). Furthermore, the information would be processed using a weighting method to obtain a single value. This research has assessed several automotive components by using the method as case studies. The results of assessments are brake pad 6.6, brake pad with asbestos 7.6, brake shoe 7.0, brake shoes with asbestos 13.2, clutch disc 9.2, and clutch disc with asbestos 8.6.
REDUCING WELDLINE IN PLASTIC INJECTION MOLDING
Authors: Hong Minh Nguyen Thi
Published: June 2024

Weldlines in plastic injection molding occur at the point where two different flow fronts meet, which can be caused by inserts, lattices, or multi-point gates. The presence of weld lines in areas of stress concentrations may lead to strength problems, and therefore, countermeasures should be implemented in advance. This paper addresses a method of reducing weldline problems which takes into account the important process parameters that impact the weldlines such as the mold and the melt temperature, as well as the injection speed. Using experimental approach, quantifying the weldline in parts produced under different conditions reveals that it is possible to reduce the weldline size by adapting the process parameters, where the melt temperature plays the most important role. Such data has been used to optimize the injection condition which can offer minimal weldline width of 0.8 µm for a specific case.
EFFECT OF AIR LUBRICATION METHOD ON FRICTIONAL RESISTANCE REDUCTION OF SHIP
Authors: Liem Hoang Cong , Toda Yasuyuki , Sanada Yugo
Published: June 2024

Air lubrication method is a method in that air bubble is introduced into the turbulent boundary layer developing downstream along the solid surface in water flow. Effect of air lubrication on reducing frictional resistance is proved from the experiment results. Obtained results show that maximum total resistance reduction can be reduced 11% in ballast condition and 6% in full load condition with the assumption that thrust deduction is constant for with and without bubble injection. Effect of air bubble in reducing frictional resistance persists for the whole bottom area. Reduction rate of shear stress under the bottom of ship seems to be larger up stream and smaller toward the side of the ship. The mean propeller inflow velocity is increased for with air lubrication from no air condition due to the viscous resistance reduction. Estimation of wake fraction or advance speed of propeller based on viscous resistance reduction when bubble was injected is also considered.
ROLLING BEARING DAMAGE DETECTION AT LOW SPEED USING VIBRATION AND SHOCK PULSE MEASUREMENTS
Authors: Abidin Zainal , Mahyuddin Andi Isra , Kurniawan Wawan
Published: June 2024

This paper describes a study on damage detection of a rolling bearing at low speed. In this study, an NTN N204 cylindrical roller bearing with an artificial local damage was tested under various operating speed and load levels. During the testing, two methods of measurement are employed to detect the damage. The first method is vibration measurement while the second is shock pulse measurement. For vibration data, RMS (Root Mean Square) and CF (Crest Factor) values are utilized to evaluate the bearing condition. For shock pulse data, dBc (dB carpet), dBm (dB maximum), LR (Low Rate), HR (High Rate), HDm (High Definition maximum), HDc (High Definition carpet) are utilized to evaluate the bearing condition. The results show that the shock pulse measurement is capable of detecting local bearing damage at lower speed than vibration measurement. For shock pulse measurement, HDm/HDc method of analysis is capable of detecting bearing damage at lower speed than either dBm/dBc or LR/HR method. For vibration measurement, the CF value is a better parameter for detecting bearing damage at low speed than the RMS value.
SUPERCRITICAL FLUID EXTRACTION OF α - MANGOSTIN FROM MANGOSTEEN FRUIT RIND (GARCINIA MANGOSTANA LINN.)
Authors: Phung Le Thi Kim , Nam Hoang Minh , Tuyet Nguyen Thi Ngoc
Published: June 2024

The extraction of α-mangostin from mangosteen fruit rind Garcinia mangostana Linn cultivated in Vietnam using supercritical carbon dioxide with ethanol as a modifier was studied in this work. Experimental design was used to investigate the effect of operating pressure (20-30MPa), temperature (313-333 K), and solvent flow rate (10-20g/min) on the recovery and the selectivity of α-mangostin. Statistical analysis of experiments indicated that pressure and flow rate of solvent affected on the recovery of α-mangostin; with the selectivity of α-mangostin, pressure, solvent flow rate, temperature and interaction between these factors significantly affected. The central composite design showed that the polynomial regression models were in good agreement with the experimental results with the coefficients of determination from 0.9037 to 0.9666. Based on the proposed model, the optimal condition for extraction that was within the experimental range was found to be at lowest temperature 313 K, highest pressure 30 MPa and the nearly lowest flow rate of solvent 12.71 g/min. It was proved that the model equation developed can be used for predicting the extraction of α-mangostin from Garcinia mangostana Linn. The maximum recovery and selectivity of α-mangostin achieved at the optimal conditions was 22.83 mg/g material and 32.77%.
EFFECT OF NORFLOXACIN ON ANTIBIOTIC RESISTANCE OF ESCHERICIA COLI: COMPARISON BETWEEN SEQUENCING BATCH REACTOR AND SEQUENCING BATCH MEMBRANE BIOREACTOR
Authors: Chiemchaisri Wilai , Deerut Phanida , Watanabe Toru , Honda Ryo , Chiemchaisri Chart
Published: June 2024

Seven antibiotics including norfloxacin (NOR) were tested via disk susceptibility test on E. coli culture isolated from the MLSS of the two types of lab-scale sequencing batch reactors (SBR): a common SBR and an SBR with microfiltration membrane (SB-MBR) for treatment of synthetic municipal wastewater. The same experiment treating the NOR-added wastewater to examine the possible induction of resistance to itself and the other antibiotics. The MLSS from Bangkok’s municipal wastewater treatment plant was employed as an initial seed and the susceptible E. coli culture (TISTR780) were spiked daily into both reactors. The reactors were continuously operated under 2hr/2hr of aeration/non-aeration cycle and resistances to antibiotics of E. coli in MLSS were monitored. When NOR was not added, the SB-MBR showed lower percentages of resistant E. coli than the SBR did to amoxicillin/clavulanic acid, amikacin, nalidixic acid, tetracycline and chloramphenicol. Oppositely, the SB-MBR treating the NORadded wastewater appeared to promote resistances of E. coli to nalidixic acid, sulfamethoxasole and tetracycline probably due to a long SRT and low DO compared to that of SBR. Although its mechanism should be analyzed with molecular techniques in further studies, this NOR-induced expression of resistance resulted in a higher occurrence of multidrug resistant E. coli in the SBMBR than that in the SBR.
UNDERGROUND WATER IN OPEN PIT MINING AT MAE MOH MINE OF THAILAND
Authors: Touch Samphors , Pongpanlarp Pornchai , Pipatpongsa Thirapong , Takemura Jiro
Published: June 2024

The groundwater problem at Mae Moh mine has drawn attention as the mining excavation goes deeper, thus resulting in detailed investigation of hydrogeological condition. One of the problems facing the mining is floor heave influenced by groundwater. The control of groundwater pressure in deep-seated aquifers with high elevation becomes important in the mining. In addition, the underground water at Mae Moh mine is naturally contaminated by arsenic. Therefore, the developments of 3D groundwater model of deep pit mine using Modflow simulation and the studies of underground water treatment are needed for the future planning. The predictive simulations were carried out for eight years (2007 to 2015). Because stability of the Mae Moh mine shows how can be closely linked to the water environment, this paper aims to report the field visits to the water related facilities of the mine, which were conducted during 2010-2013. The result reveals that the potentiometric head level is strongly increased, which might be a potential risk for the floor heave; thus, depressurization is required. Field measurements reveal pH level at 8 and a range of total dissolved solid (TDS) at 870-2020 ppm. Treatment efficiency shows that more than 95% of the arsenic can be successfully removed using ferric chloride.
SYNTHESIS, ADSORPTION ABILITY AND ACTIVITY OF MOF-199 IN THE REACTION OF METHANOL SYNTHESIS FROM CARBON OXIDES
Authors: Loc Luu Cam , Van Nguyen Thi Thuy , Tri Nguyen , Cuong Hoang Tien , Ha Huynh Ky Phuong
Published: June 2024

Metal-organic framework (MOF) is a material which can be applied in many fields. In this research MOF-199 was synthesized using solvothermal method. Based on this product, ZnO@MOF-199 and Cu,ZnO@MOF-199 were synthesized and their properties were characterized. The adsorption capacity of CO2 and CH4 on MOF-199 were investigated and results show that adsorption capacity of CO2 is higher than that of CH4 at 30 bar and 30 oC, reaching 277.25 cm3/g and 170.38 cm3/g, respectively. The catalytic activity of MOF-199, Cu,ZnO@MOF-199 and ZnO@MOF-199 were also tested for methanol production from synthesis gas at atmospheric pressure and 200 oC. Methanol yield after 1 h for MOF-199 and Cu,ZnO@MOF-199 reached 157.9 and 27.63 μmol.gcat-1.h-1 , respectively. Meanwhile, the methanol yield for catalyst ZnO@MOF-199 is not significant. However, the structure of MOF-199 collapsed after 60 minutes of reaction.
EAF STEEL SLAG AS SUPPLEMENTARY CEMENTING MATERIAL
Authors: Son Nguyen Khanh , Phuoc Nguyen Vinh , Hanh Le Thi Duy , Minh Huynh Ngoc , Son Le Minh , Hoa Nguyen Thai
Published: June 2024

Large scale recycling of steel slag as a cementitious additive to cement mortar and/or concrete was investigated in this paper. As the material component of steel slag is highly variable, this EAF slag is gathered from plant site of Dong Tien steelmaker in Ba Ria-Vung Tau province. Chemical compositions of slag consist almost the high content of free CaO, MgO and iron, FexOy. Lower content of cementitious mineral C3S, C2S endorses relative low hydraulic reactivity in comparing with Portland cement. After grinding slag to particle size < 90 μm (Blaine 3400 cm2/g), blended cement–steel slag with 10 to 40% by mass of slag were formulated. Both steel slag-cement Portland and steel slag-granulated blast furnace slag (GBFS)-cement Portland system were introduced to analyze early age and later age property of mortar sample. Preliminary results of resistance remark appropriate formulation of 20% of slag. By adding 20% GBFS in such product, practical application could be considered due to the typical enhancement of durability property of cement mortar in severe condition (sulfate, chlorhydric acid). Others, by considering an approach of slag treatment to improve hydraulic reactivity as the GBFS materials model present. The mineralogical composition and some cementitious properties of obtained product would be discussed for a perspective of new clinker steel slag.
PROPERTIES OF HIGH STRENGTH CONCRETE USING STEEL SLAG COARSE AGGREGATE
Authors: Tran Mien Van , Nguyen Chanh Van , Nawa Toyoharu , Stitmannaithum Boonchai
Published: June 2024

Steel slag, which has low CaO content, is a by-product of steel processing. The steel slag consisting iron oxides is ground into sizes as coarse aggregates used for concrete. In this paper, the steel slag was characterized by chemical, physical and mineralogical analysis, and then the steel slag was used to replace 100% coarse aggregates in high strength concrete which has various compressive strengths as 60, 70 and 80MPa. Results showed that the strength of the concrete using steel slag aggregate was equivalent to that of the conventional concrete, whereas, the durability of the steel slag aggregate concrete was better than that of the conventional concrete in terms of chloride penetration resistance and resistivity. Moreover, dimensional stability of the steel slag cement mortar was detected.
ARSENIC ADSORPTION PERFORMANCE OF LIGNITE IN LABORATORY COLUMN EX PERIMENTS UNDER SATURATED FLOW CONDITIONS
Authors: Mar Kyu Kyu , Karnawati Dwikorita , Putra Doni Prakasa Eka , Sarto  , Igarashi Toshifumi , Tabelin Carlito Baltazar
Published: June 2024

This paper presents the adsorption behavior of arsenic (As) onto lignite in saturated column experiments under various flow rates and adsorbent thicknesses. The lignite sample originated from Indonesia is predominantly composed of organic matter with minor amounts of pyrite (FeS2). Arsenic content of lignite is 1.8 mg/kg with high sulfur content of 10.8 wt. %. The experiments were performed at room temperature using a glass column with an inner diameter of 2.4 cm and total length of 30 cm. Different lignite bed thicknesses (6 and 12 cm) at a constant flow rate of 0.85 cm3/min and a fixed lignite bed thickness of 12 cm with different flow rates (0.85 and 0.22 cm3/min) were conducted. All effluents had acidic pH (1.04 to 3.36) and were under oxidizing conditions (Eh: +554 – +629 mV) regardless of the flow rate and lignite bed thickness. The breakthrough of As indicated both leaching and adsorption regions. The leaching of As could be attributed to very high concentration of dissolved organic carbon (DOC) that competes with As for Adsorption sites. Leaching region occurs until ca. 69 mL (ca. 1.35 h) at a thinner lignite bed. After this, the concentration of As in the effluent slowly increased and then reached the influent As concentration. In contract, the retardation of As observed until ca. 159 mg/L (ca. 3.15 h) at a thicker lignite bed, indicating that the As adsorption increased substantially at thicker lignite bed. Decreasing the flow rate (0.22 cm3/min) had a similar effect with case 2, that is, the As adsorption increased substantially. Based on these results, As removal efficiency under flow-through conditions is strongly influenced by thickness of adsorbent but not the flow rate.
THE POTENTIAL OF LAHARIC FLOWS DISASTER ALONG GENDOL AND OPAK RIVERS, YOGYAKARTA, INDONESIA
Authors: Surjono Sugeng S , Wijaya Erlangga , Yufianto Andreas , Firmansyah Arfian
Published: June 2024

Gendol River flows from the south slope of Merapi Volcano meets Opak River to form a wider river, namely Opak River. In the upper stream of Opak and Gendol Rivers area, volcanic material accumulated from the 2010 Merapi Volcano eruption that ready to flow downstream through both rivers. The total amount of volcanic material in the Merapi’s peak area is predicted as much as 140 million cubic meters, part of it is distributed in the upper stream of both rivers. In the downstream area, the Opak River flows nearby the great Prambanan Temple and across the main road of Yogyakarta-Surakarta capital cities.To know the laharic flow disaster potential of both rivers, collecting of primary data along the river flows is needed in order to understand the characteristic and mechanism of laharic flows. DEM analysis combined with ArcGIS 9.3 tools are applied to know the additional volume of volcanic material after 2010 Merapi Volcano eruption. The triggering factor of laharic flows in the study area including the runoff, soil water saturation rate, rainfall and soil water saturation time are mathematically calculated based on data analysis on soil mechanics.Based on the calculation of thickness and distribution in the Merapi Peak area, the mass volcanic material that is ready to be transported as the laharic flows through Gendol and Opak Rivers is around 14,745,496 m3. The volcanic material can transform into laharic flows by initial runoff if the soil water saturation column reach at least 5.96 m. With the rainfall average in the southern part of Merapi Volcano is 17.32 mm/day, that saturation value can be reached by 21.8 hours in the upper stream area and 17.67 hours in the lower part area. If the laharic flows occurred, the damage would happen in villages along the rivers, Prambanan Temple, and Opak River’s Bridge connecting Yogyakarta-Surakarta main road.
A FRAMEWORK FOR DISASTER MITIGATION NETWORKS
Authors: Kok Gin-Xian , Chow Chee-Onn , Ishii Hiroshi , Utsu Keisuke
Published: June 2024

The existing communication infrastructure could be destroyed during a disaster and this could lead to the disruption of communication activities. Communication is extremely important during disasters; therefore, it is vital that a temporary network is quickly setup to restore communication activities. Temporary networks could be setup using programmable sensor nodes. In this paper, we present SafeNet, a framework for disaster mitigation networks using programmable sensor nodes. We discussed several aspects such as: i) placement of sensor nodes, ii) modes of operation, and iii) the required components.
LEVERAGING ON NEIGHBOUR INFORMATION FOR OPTIMIZING NETWORK SELECTION
Authors: Pedrasa Jhoanna Rhodette , Seneviratne Aruna
Published: June 2024

Current operating systems rely on Received Signal Strength (RSSI) to choose which network to connect. However, RSSI is not a good measure of actual network performance and requires the interfaces to be turned on, which can significantly drain the battery of the mobile node. This work revisits how network discovery is performed in a multi-radio, mobile environment. The current method of basing decisions on physical-layer characteristics cannot adequately capture network service parameters. Going beyond radio properties allows users to make better choices as to which is the "best'' network and Point of Attachment to connect to. In this work we extend MOBIX, a system for managing MOBility using Information eXchange, which allows nodes to exchange information in a peer-to-peer manner in addition to leveraging on a centralized server. We performed simulations to study the performance of MOBIX with and without the map server and show that our enhanced system strikes a balance of providing a scalable, updated network performance information in densely populated areas and relying on a network server in less urbanized areas with lower number of nodes.
STRUCTURAL ANALYSIS OF SANDWICH THIN-WALLED HOLLOW CYLINDRICAL TUBES WITH ALUMINUM FOAM FILLER SUBJECTED TO LOW VELOCITY AXIAL LOAD USING NUMERICAL SIMULATION
Authors: Ly Hung Anh , Nguyen Van Nhat Vu , Thai-Quang Thinh , Nguyen Hiep Hung
Published: June 2024

Impact safety and weight-saving are two important criteria for energy-absorbing structures in train, car and aircraft design. Innovations in light-weight material such as metallic cellular material, aluminum foam have developed significantly; it opens many researches to enhance capability of energy absorber. Research on structure of sandwich thin-walled cylindrical tubes with aluminum foam filler has been conducted much; however, the number of researches focusing on sandwich thin-walled hollow cylindrical tubes with aluminum foam filler is limited. This paper presents numerical analyses of sandwich thin-walled hollow cylindrical tubes with aluminum foam filler subjected to low velocity axial loading using a non-linear finite element method. The objective is to predict and compare the behavior of these structures in absorbing energy.
RESEARCH AND APPLICATION OF FUNCTIONAL ELEMENTS AND NEWLY DEFINED FUNCTION SYMBOLS FOR MECHANICAL HANDLING SYSTEMS
Authors: Dang Tan Nguyen , Berger Maik
Published: June 2024

The assembly and handling technology guideline VDI 2860 mentions concepts, definitions and symbols in a handling technology. However, in this document there are limitations which make it more difficult to describe and outline a handling flowchart. The method of this study is based on assembling and manufacturing equipment, parameters and functions effecting the handling process, as well as methods used in assembling techniques to establish new concepts. The introduced function symbols are checked by application examples in a virtual assembly line. As the result of this study, necessary parameters are added to the existing elementary and compound functions. Moreover, new function symbols are formed and gathered in new function symbols of handling. The theoretical concept and the final application of these elementary and compound functions can be used for computer-aided planning (CAP) of handling systems.
STUDY OF ENTRANCE CONFIGURATION EFFECT ON STREAMWISE VORTICES IN WAVY CHANNEL
Authors: Budiman Alexander Christantho , Mitsudharmadi Hatsari , Bouremel Yann , Low Hong Tong , Winoto Sonny Handojo
Published: June 2024

Two different entrance configurations of a channel with wavy (sinusoidal) surface, namely cosine entrance and negative cosine entrance configuration, were numerically and experimentally investigated to study the downstream development of the induced counterrotating streamwise vortices. The study is limited to the laminar boundary layer flow. The negative cosine entrance configuration has a “blockage effect” which subjects to large pressure penalty. However, under a certain amplitude and wavelength of the sinusoidal surface, this configuration might have lower hydraulic channel gap than the other configuration due to the formation of separation bubbles at the valley of the sinusoidal surface which makes the stream lifted-up and behaves like a flow in a smooth channel. As such, the flow in the negative cosine entrance configuration is more stable than that in the cosine configuration. This is indicated by the evolution of streamwise vortices at Re = 2700 that are preserved farther downstream prior to its breakdown into turbulence.
PETALLING DAMAGE ANALYSIS OF METALLIC PLATE STRUCTURES UNDER LOCALIZED IMPACT LOADING - A REVIEW
Authors: Nam Pham Hoang , Widagdo Djarot , Santosa Sigit , Putra Ichsan Setya
Published: June 2024

The main objective of this paper is to review the theoretical predictions on the petalling damage of plate structures against highly localized load. There are three existing methods to solve petalling problem. First method of Zaid and Paul (1958) used momentum conservation to calculate high speed projectile perforation of a plate structure. The magnitude and direction of forces and velocities were considered as a function of penetration distance. This method used hole enlargement models, a rather simple method to calculate the momentum conservation of the two impacting bodies. Second method of Landkof and Goldsmith (1983) predicted petalling damage of a plate structure during penetration by using cylindro-conical projectile. This work showed that petalling damage is combination of bending and tearing process. Bending process was calculated due to the action of plastic hinges. The tearing process was formulated by Mode I fracture mechanics. Limitation of the method by Landkof and Goldsmith is in the calculation of all energies such as dishing, bending and tearing energy that was done independently. The third method, which was done recently by Wierzbicki (1999) and Lee (2004) gave a new method to describe petalling problem based on energy conservation. This method showed that tearing and bending process are related through the local radius of petal, while bending process and dishing process are related through the circumferential curvature of the dish. Tearing process was described more proper than before by using crack opening displacement (COD) criterion. In these works of Wierzbicki and Lee, there are some places which could be improved such as consideration of shearing process and modification of tearing model.
AVERAGE CHANNEL CAPACITY OF FREE-SPACE OPTICAL MIMO SYSTEMS OVER ATMOSPHERIC TURBULENCE CHANNELS
Authors: Trung Ha Duyen , Ai Duong Huu , Pham Anh Tuan
Published: June 2024

In this paper, we theoretically analyze the performance of multiple-input multiple-output (MIMO) free-space optical (FSO) systems. The MIMO/FSO average channel capacity (ACC), which is expressed in terms of average spectral efficiency (ASE) is derived taking into account the atmospheric turbulence effects on the MIMO/FSO channel. They are modeled by log-normal and the gamma-gamma distributions for the cases of weak-to-strong turbulence conditions. We quantitatively discuss the influence of turbulence strength, link distance, and different MIMO configurations on the system ASE. Numerical and computer simulation results are presented in order to verify the validity of the mathematical analysis.
POLY (2-METHYL-2-OXAZOLINE) (PMOXA) AND ANTIMICROBIAL PEPTIDE GKH17 AS POTENTIAL ANTIMICROBIAL COATINGS FOR CONTACT LENSES
Authors: Pidhatika Bidhari , Ridwan Nur Fathurahman , Rakhmawati Anna
Published: June 2024

Microbial contamination on contact lens surfaces can occur during handling, storage, and even cleaning with contaminated solutions. Several severe consequences of this event include microbial keratitis, contact lens-induced peripheral ulcer, and inflitrative keratitis. In this study we used SiO2 as a model substrate for silicon-based contact lenses. The antimicrobial activities of two polymers, poly(2-methyl-2-oxazoline) (PMOXA) and antimicrobial peptide GKHKNKGKKNGKHNGWK (GKH17), on surfaces, were tested against two types of bacteria, Gram-positive Staphlyococcus sp. and Gram-negative Neisseria sp., isolated from used contact lenses. The inhibition activity of the polymers was first tested using the Kirby-Bauer method, and the properties of the polymers immobilized on SiO2 surface were investigated by means of viable plate count and DNA absorbance measurements. Our results show that both types of bacteria are susceptible to both PMOXA and GKH17, however with a different degree of susceptibility. Both polymers are thus potential antimicrobial coatings for contact lenses.
MAPPING THE EFFECTS OF STARTER CULTURE ADDITION ON COCOA BEAN FERMENTATION
Authors: Kresnowati Made Tri Ari Penia , Febriami Hanny
Published: June 2024

Fermentation is an essential step in the formation of aroma and flavour of cocoa beans. During the fermentation, cocoa bean pulp is degraded to form metabolic products, one of which functions as the precursor for the aroma and flavour of cocoa beans. Previous research suggested that the addition of starter culture on the cocoa bean fermentation process can improve the fermentation performance. In this research the effects of various starters culture combinations, including Saccharomyces cerevisiae var. Chevalieri, Lactobacillus plantarum, and Acetobacter aceti were studied. The addition of starter culture was confirmed by analysis of microbial population during the fermentation. Fermentation performances were measured as fermentation index and cocoa bean pH, as well as sugar and metabolic product concentration. The obtained results showed that in general the addition of starter culture accelerated sugar consumption and increased metabolites production. The highest fermentation index was 1.38±0.07, obtained from fermentation added with starter culture combination containing Saccharomyces cerevisiae var. Chevalieri and Lactobacillus plantarum. This fermentation advanced faster and was completed at 4 days, or shortened the overall fermentation time. On the other hand fermentation added with starter culture containing only Acetobacter aceti gave the lowest fermentation index, 0.96±0.04
ON THE PERFORMANCE OF VERTICAL AXIS WIND TURBINES IN STEADY WIND UNDER VARIOUS BLADE CAMBER LEVELS
Authors: Bausas Michael De Los Santos , Danao Louis Angelo
Published: June 2024

Vertical axis wind turbine (VAWT) has been shown to be more suited to small scale power production in the urban environment due to distinct advantages over its horizontal counterpart. Over the last few years, continuous improvement on its aerodynamic performance, either through experimental or numerical analysis, have been carried out by numerous researchers. VAWT performance was investigated using Computational Fluid Dynamics modeling. The influence of camber on steady wind performance was analyzed and the most efficient of all levels of blade camber studied for VAWT application was determined. Various levels of camber were imposed on to a NACA XX25 blade profile, namely: 0.5%; 1.5% (cambered close to the path of rotation); and 2%. Results revealed positive effect of incorporating a positive level of blade camber to VAWT design. The most favorable configuration for the VAWT under study was determined to be the camber level that causes the camber line to coincide with the path of the rotor rotation. The paper presents an in-depth discussion of the flow physics and wake dynamics, for the two wind cases of VAWTs, through flow visualizations and blade force analysis.
PRE-FEASIBILITY STUDY OF WIND ENERGY RESOURCES IN MYANMAR
Authors: Soe Thi Thi , Zheng Maosheng , Sreevalsan Eripurath
Published: June 2024

In this study, the wind power density of MERRA analysis data for weather and the ASTER DEM 30m enhanced with satellite data for terrain elevation are employed as input data to get wind resources distribution in Myanmar with the simulation of ArcMap 10, ArcGIS software. The simulated result shows that Yakhine State, Ayeyarwaddy, Yangon and Tanintharyi Regions are the best wind resource regions in Myanmar from the output color-coded wind power density map at 50m above ground level, of which the wind power density ranges from 80-126W/m2 in some part of these regions; while the better wind resource regions are: Sagaing, Mandalay, Magway Regions and Mon State, the wind power density ranges from 20 to 80 W/m2 . The overall output of wind power density map shows the highest in the south and southwest coastal area in Myanmar.
PARAMETRIC ANALYSIS ON OFF-SHORE DREDGING PROCESS USING CUTTER SUCTION DREDGERS
Authors: Setiawan Rachman
Published: June 2024

Nowadays, cutter-suction dredgers are widely used in off-shore tin mining around South East Asia region, especially in Indonesia. So far, the effectiveness of the dredging process is arguably due to the skills and experience of individuals who operate the dredgers. No sufficient guidelines, standard operating procedures exist on how to operate the dredgers effectively based on scientific facts and factual data on the mining environment. This paper discusses the effectiveness of the dredging process in a cutter suction dredger (CSD). The influence of various parameters is studied through parametric simulation based on theoretical approach developed by Miedema and Vastbloom, with a number of adaptations from the original model in order to obtain a better approximation. A specific CSD design is used as a case study. From the parametric analysis, it is found that, dredging capacity is highly affected by the cutting thickness and swing speed, rather than the dredging depth. With the limit of pump capacity and dredge power, the optimum cutting thickness is approximately 75% for the dredger in question, adjustable through the swing speed during operation. Moreover, the dredging forces are highly affected by the cutter rotational speed and soil type, whilst lightly affected by the dredging depth. For dredging harder soils, the dredge forces increase by up to 68%, for the dredger in question, hence the operational parameters must be adjusted, i.e. by lowering the swing speed, however maintaining higher rotational speed, in order to have a safe and optimum operation.
A COMPUTATIONAL STUDY OF AERODYNAMIC NOISE ALLEVIATION ON A GENERIC CAR MODEL
Authors: Kim Dung Hoang Thi , Phu Khanh Nguyen
Published: June 2024

The aerodynamic noise is referred to the noise generated by unsteady flow, which the turbulent flow is connected to the noise sources. In this paper, the aerodynamic noise on a generic car was carried out by using numerical method. First, the turbulent flow on and around the car, when the car moved at velocity 100 km/h, was found out by using CFD method in ANSSYS FLUENT software. Then, Fast Fourier Transform tools in ANSYS FLUENT software was applied to estimate the sound pressure level from the fluctuation of pressure on and around the car. With the aim of alleviating the aerodynamic noise on the cars, four different car shapes were studied. The results remarked that the worse car shape had, the more complex turbulent pressure was found and the higher aerodynamic noise was found as well.
EFFECT OF CORE CUTTING TOPOLOGY AND MATERIAL OF THREE PHASE TRANSFORMER ON MAGNETIZATION CURVE AND INRUSH CURRENT: EXPERIMENTAL APPROACH
Authors: Negara I Made Yulistya , Fahmi Daniar , Asfani Dimas Anton , Cahyadiputra Rahman
Published: June 2024

This study conducts the core cutting topology effect in three phase transformer on magnetization curve and inrush current. Core cutting topology effect on magnetization curve and magnetic field is analyzed using Finite-Element Method (FEM) simulation at the points of connection between the core pieces. The magnetization curves are used to determine inrush current of each transformer. Therefore, calculated inrush current was then compared to experimental measurements of inrush currents. The existence of residual flux or remnant flux is considered in inrush current measurement, thus demagnetization method is used to obtain the real inrush current value. Simulation and experimental results show that the topology of the transformer core cutting affects the magnetization curves and inrush currents. These are proven by differences in the magnetization curve and inrush current of both topology transformer core cutting. It was also suggested that quality of core material affected the magnetization curve and inrush current.
CONTINUOUS ADSORPTION REFRIGERATION PERFORMANCE OF ACTIVATED CARBON–R134A PAIR FOR ICE-MAKING APPLICATION USING TRANSIENT CFD SIMULATION
Authors: Purnomo Dwi Marhaendro Jati , Astina I Made
Published: June 2024

The new system and refrigerant were introduced in heat driven adsorption refrigeration system. Adsorption refrigerator’s capability to be operated by relatively low temperature heat source has drawn considerable attention. This system can be driven by utilizing waste heat and solar energy. Positive gauge operating pressure has been pursing R-134a as the most suitable refrigerant due to its saturated temperature on high pressure and other considerations including health factor, safety, and environment. The continuous system was designed to obtain higher cooling capacity. The optimization was conducted on temperature for each process undergoing in the reactor to approximate the highest possible COP (Coefficient of Performance). The cooling capacity of the system was estimated by transient simulation on CFD software. The cooling capacity acquired by employing CFD transient simulation is 18.36 W, whereas the highest possible COP which could be attained is 0.1047 for ice-making application.
STUDY ON ROBOT MANIPULATOR USING (REAL-TIME) NONLINEAR CONTROL-SIMULATION OF ROBOT MANIPULATOR UNDER DISTURBANCE
Authors: Bakar Elmi Abu , Umar Siti Nur Hanisah
Published: June 2024

Robot manipulator is currently essential as human assistant. While performing their tasks, the robot leaved its well structured environment and confronted with unexpected disturbances. The conventional linear control system is insufficient to guarantee the prescribe performance of the robot manipulator when unknown external disturbance is considered. Thus, implementing a nonlinear control system is essential to guarantee the performance of the desired tasks. Firstly, the proportional, integral and derivative (PID) controller will be tested and the restriction of the linear control system is studied. Then, two type of nonlinear controller the PID computed torque control (PIDCTC) and Sliding mode computed torque control (SMCTC) are implemented. From the result, the optimal variable value is determined and performances of three controllers are compared.
Importance of Artificial Intelligence in Achieving SDGs in India
Authors: Gupta Shivani , Gupta Satinder Bal , Gupta Monika
Published: June 2024

Sustainable Development Goals (SDGs) represents the 2030 Agenda defined by the United Nations to attain sustainable development. It comprises outlines 17 goals that cover a range of issues. These goals focus on addressing the globe's most crucial economic, communal, and environmental challenges to provide a more sustainable future for every individual. In India, the government has initiated several schemes and programmes for attaining the targets set for different SDGs, but addressing the complex challenges associated with sustainable development requires continued efforts and collaborations from multiple stakeholders including governments, individuals, public and private sectors. Achieving the SDGs is a continuous process, and some targets may need more time and effort to get achieved. Regular monitoring and evaluation are significant for tracking progress and addressing the gaps or challenges that may arise. The COVID-19 pandemic put a critical impact on the advancement towards attaining the targets set for all the SDGs globally. India has been found to be off track for 19 out of the 33 SDG indicators and there is an urgent need to accelerate the momentum of achieving the targets by 2030. AI presents significant opportunities to address these challenges in India. Overall, in India, Artificial Intelligence is seen as valuable tool to achieve the targets set for different goals in the coming years. In this paper, the authors have discussed the schemes and programmes initiated by the Government of India to attain these SDGs and the role of Artificial Intelligence in attaining the targets by the year 2030
Effects of Different Conditioning Activities on the Sprint Performance of Elite Sprinters: A Systematic Review With Meta-Analysis
Authors: Loturco Irineu , Pereira Lucas A. , Moura Túlio B.M.A. , McGuigan Michael R. , Boullosa Daniel
Published: June 2024

Purpose: Postactivation performance enhancement (PAPE), which refers to the phenomena associated with the attainment of enhanced performance in sport-specific tasks after a conditioning activity, is an important objective of warming-up practices in many sports. This is even more relevant for sprinters, as potential increases in sprinting speed will directly influence their competitive results. This systematic review with meta-analysis evaluated the effects of different PAPE protocols (ie, using plyometrics, strength-power exercises, and resisted/assisted sprints) on the sprinting performance (ie, sprint time or sprint speed) of competitive sprinters. Methods: Initially, 1205 records published until last December 18 were identified, using the following databases: PubMed/MEDLINE, Scopus, and Clarivate Web of Science. After removing duplicates and screening titles and abstracts, 14 high-quality studies met the inclusion criteria for the meta-analysis. Results: Overall, there were no significant changes in sprint performance after implementing various types of conditioning activities (standardized mean difference [SMD] = 0.16 [95% CI, −0.02 to 0.33]; Z = 1.78; P = .08; I2 = 0%). In addition, when comparing prechanges and postchanges between experimental, control, and other conditions, no significant differences were found in sprint speed or time across all studies (SMD = 0.09 [95% CI, −0.10 to 0.28]; Z = 0.92; P = .36; I = 0%). Conclusions: Results revealed that different types of conditioning activities may not be capable of acutely enhancing the sprint speed of competitive sprinters. This aligns with previous observations indicating that sprinting is a highly stable physical capacity, a phenomenon that is even more consistent among elite sprinters. Coaches and sport scientists should collaborate to develop more efficient PAPE protocols for these highly specialized athletes, with special attention to study design and individualization, while considering their effects on acceleration versus top speed.