bluuebunny/crossref_metadata_2025 huggingface dataset:
Research on the distribution mechanism of fault alarm information for power grid fault diagnosis
Authors: Zhang Ziqi , Du Mingxuan , Wang Zirui , Zhang Xu
Published: May 2023

Power grid fault diagnosis aims to locate faulty components quickly and accurately. The alarm information generated by the SCADA system of the grid is the data basis for power grid fault diagnosis. The existing research lacks mechanical analysis of the alarm information, so the models and algorithms are difficult to be used in engineering applications. The established power grid fault diagnosis models are somewhat different from the actual grid, and the alarm information timing characteristics are difficult to express. In this paper, we analyze the correlation and characteristics of the data related to the number of voltages, number of stations, and duration of faults for each period, and analyze the spatial and temporal distribution mechanism of the alarm messages in conjunction with the characteristics of the equipment that issued the alarm messages during the fault events. It also compares the differences in the distribution patterns of the alarm information when the data sources are different. The research can lay the foundation for establishing fault diagnosis models and provide theoretical support for model design and algorithm research.
Research on the Balance Control Method of Instantaneous Power for the Converter in D-PMSG
Authors: Feng Ruming , A Minfu , Gao Chen , Yan Xu , Liu Taowei , Yang Zaixin , Zhang Wei
Published: May 2023

This paper establishes a numerical model of wind power generation system. The low voltage ride-through characteristics of direct-driven wind turbines in case of grid failure are studied. By comparing the measured data with the numerical data, the correctness, validity and the numerical simulation results for the grid-connected operation of the direct-drive wind turbine generator set proposed in this paper are verified.
A Temperature Control Method of Electric Heating Furnace Based on Fuzzy PID
Authors: Hu Dawei , Liu Hengyu , Zhu Yidong , Li Qingxin , Wang Jun , Zhang Zhongrui , Sun Jiazheng , Yang Luyu , Zhang Zhe , Yuan Jingwei
Published: May 2023

The traditional PID control method has a series of problems such as overshoot or static error. This paper takes the electric heating furnace temperature control system as the background, combines the fuzzy algorithm to design the fuzzy PID system, and uses the MATLAB fuzzy control box to set up the fuzzy reasoning system and the fuzzy rule table., and use the Simulink platform to build the temperature control system simulation model of ordinary PID and fuzzy PID, and verify the influence of parameters on the system.
Preliminary study of topside ionospheric variations using SWARM satellites over the Malaysia Region
Authors: Bahari S A , Husin S R S , Abdullah M , Ghamry E
Published: May 2023

The European Space Agency (ESA) launched a satellite constellation mission called Swarm in 2013. The Swarm satellites named A, B and C are equipped with Global Positioning System (GPS) receivers which can be used to study the topside of the ionosphere. In Malaysia, the use of ionospheric data from the Swarm satellites is still new as most researchers previously used GPS receivers on the Earth. This paper presents the preliminary result of topside-ionosphere parameter, Total Electron Content (TEC) over Malaysia using the Swarm satellite data. TEC from the Swarm data were analyzed during quiet and disturbed geomagnetic days. The results showed that the Swarm satellites passed through Malaysia twice in 24 hours and the variations of TEC over Malaysia ranged from 2 to 20 TECU. Analysis of the topside ionosphere during a geomagnetic storm showed a sudden decreased of TEC compared to the quiet days. The findings indicate that the variations of topside TEC using Swarm are in agreement with those found in previous studies.
The comparison of indoor and outdoor pyranometer calibration method in Jakarta
Authors: Saputro R D , Handoko D , Hidayah Q A , Nugraha H A , Sail A , Lukito I S
Published: May 2023

The increasing energy crisis motivated people to develop renewable energy, one of the promising renewable energies is solar energy. Considering that Indonesia has the potential for sunlight throughout the year, this country should be able to take full advantage of this solar radiation energy. To discover potential area in Indonesia, good and calibrated equipment are needed such as pyranometer, pyrheliometer etc. The objective of this study is to compare developed method of outdoor and indoor pyranometer calibration responsivity. There are 4 pyranometer calibration methods, one of them is called Continuous Sun and Shade Method (CoSSM). However, this method has never been carried out before, so it is going to be developed by the Agency for Meteorology, Climatology, and Geophysics (BMKG) Indonesia. The CoSSM method utilizes two standard components consist of direct and diffuse irradiance to obtain new responsivity values from calibrated global radiation sensor or so called Unit Under Test (UUT). This experiment used 4 UUT and carried out for 12 days. The new responsivity values then compared with the responsivity value that had been obtained from BMKG indoor calibration accredited by National Accreditation Committee (KAN). The results obtained from calibration process provided the highest percentage difference of 6.2% and the smallest 0.2%. This shows that outdoor calibration in cloudy and polluted conditions in Jakarta still give quite good result.
Distance pattern and spacing of the multiplanet systems in TESS data
Authors: Geraldo L D , Bautista R A B
Published: May 2023

Titius-Bode’s Law is a well-known formulation that describes the distances of the planets in the Solar System. It had a significant role in the discovery of dwarf planet Ceres. Since then, there are studies that attempted to apply it in other planetary systems using the original or modified form of the Law. This is done to examine their distances and possibly find another planet. However, those studies were few and the growing number of discovered planets and planetary systems continues due to the different missions. In this paper, we focused on the planetary systems mainly discovered by the Transiting Exoplanet Survey Satellite (TESS) and we tried to use exponential regression to determine the equations that will express the best fit for the distance pattern of the planets. We only included planetary systems with at least 2 planets. In addition, we explored the trends in the distances or spacing of the planets using ANOVA. Overall, we were able to get the necessary equations and there is a high value of R2 that indicates a good fit. The distances and spacing of the planets in each planetary system, there is no significant difference which indicates that planets have close spacings.
A study of the effect of open biomass burning aerosol on rainfall event over Malaysia by using EOF analysis
Authors: Chen Y , Chan A , Yenn T F , Ooi C. G. , Li L
Published: May 2023

Significant biomass burning aerosols resulted from biomass burning activities from Sumatra and Kalimantan Island transported to Malaysia every year from August to October by the southeast monsoon. These transboundary haze changes the precipitation pattern by aerosol interaction with radiation and cloud which affects the solar radiation budget and cloud condensation nuclei properties. In this work, empirical orthogonal function (EOF) was used to assess the effect of biomass burning aerosol on rainfall pattern over Malaysia from both a spatial and a temporal perspective. Over Peninsular Malaysia, regional rainfall activities tend to be suppressed by concentrated biomass burning aerosols and produce another heavy rain over the downwind areas after 30-60 days (60 days) under highly (less) populated condition. Similar precipitation pattern has been indicated over Sarawak and Sabah where biomass burning aerosols suppress rainfall in the southwestern area while leads to a more intensified rainfall event in the northeast area with 30-60 days (60 days) interval under highly (less) populated condition.
Analysis of trends in extreme temperature indices over selected areas in Peninsular Malaysia from 1991-2020
Authors: Rosli M A M , Ash’aari Z H
Published: May 2023

This study investigates the temporal variations of extreme temperature trends across three stations in Peninsular Malaysia with different settings, Petaling Jaya represents urban station, while Kluang and Batu Embun represent rural areas from 1991-2020. Eleven extreme warm and cold indices trends were analysed using the Mann-Kendall test, with Sen’s slope as a magnitude estimator. The findings revealed that the annual daily mean temperature, daily mean maximum temperature, and daily mean minimum temperature increased significantly at all stations by 0.04°C yr–1, 0.02°C yr–1, and 0.05°C yr–1, respectively. The station in the rural area shows a significant increment of an average of 0.03°C yr–1 for mean and warm extreme indices. Despite that, there were no changes in the total number of warm days and nights and cold days and nights for all settings. For the cold temperature indices, there were significant decreasing trends for the annual minimum of maximum temperature in rural areas, while urban station did not exhibit changes. All stations also exhibit similar annual patterns when compared although significantly higher readings were observed during El Niño events.
Methanogenic archaea community in relation to methane production in oil palm planted on tropical peatland
Authors: Ayob Z , Kusai N A , Jantan N M , Murdi A A , Law M C , Khairuddin N S K , Idris A S
Published: May 2023

Understanding the microbial processes that regulate methane emissions in the tropical peatlands can facilitate their future management. However, the microbiota of Malaysian tropical peatlands specifically the methanogens (methane producers) and methanotrophs (methane consumers) remains poorly characterised. This study aimed to determine the key players in methane production and to assess their spatial distribution in different oil palm management zones (i.e., avenue, cover crop, frond pile, and weeded circle) across depths namely 0–15 cm, 15–30 cm, and 30–45 cm in an 11-year-old oil palm plantation that was established on the peatland of Sarawak. Based on high-throughput Illumina sequencing targeting the 16S hypervariable V4–V5 regions of archaeal rRNA amplicon, the diversity indices (Shannon and Simpson) and richness (Chao1 and ACE) were highest in the upper peat layers across management zones, and the microbial diversity and composition are influenced by depths. Taxonomic profiling revealed that the domain Archaea was dominated by Halobacteriota, Thermoproteota, and Thermoplasmatota that increased with depth across management zones. Meanwhile, the order Methanomassiliicoccales was predominant, with Methanomethylophilus sp002495325 as the most abundant species in the upper peat layers in the frond pile zone due to a high decomposition rate of organic matter. The key players of methanogenic archaea belonging to Methanomassiliicoccales, Methanosarcinales, Methanomicrobiales, and Methanobacteriales were detected in oil palm peat soils, providing indirect genetic evidence for the biogeochemical processes associated with methane production in the oil palm plantation. Having established the feasibility of utilising high-throughput sequencing to characterise the archaeome of Malaysian oil palm plantation, future works in correlating the relative abundance of methanogens and methanotrophs with methane production will be instrumental in providing valuable insights for prediction and mitigation of methane emissions in oil palm cultivation on peat.
The integration of cattle grazing activities as potential best sustainable practices for weeding operations in oil palm plantations.
Authors: Umar Y , Syakir M I , Yusuff S , Azhar B , Tohiran K A
Published: May 2023

Oil palm agriculture depends heavily on the use of herbicides to preserve crop output against competing weeds. Rising concerns about the impact of herbicides and carbon emissions on biodiversity and ecosystems require an urgent transformation in weed management. The 45% increase in global oil palm production area has resulted in increased agrochemical inputs in oil palm producing countries. Currently, estimated herbicide usage in Malaysia is reported to have increased by 18%. In fact, the use of herbicides may destroy understory vegetation that serves as critical habitat for certain species that are essential for the biodiversity of the oil palm. Hence, without any effort for innovation and sustainable weeding practices, this may lead to excessive use of herbicides, which reduce microbial activity, alter soil organic matter, and consequently influence soil CO2 emissions. The integrated cattle grazing system in oil palm plantations can be seen as a land-sharing method. Potentially, the livestock integration can improve productivity of the land while minimizing the impact of pollution and resource degradation. So, any reduction in the use of herbicides should be balanced by innovative, sustainable weed control methods such as the integration of cattle grazing. This will help reduce pollution, restore soil carbon (C) sequestration, and protect the oil palm ecosystem’s biodiversity. This review demonstrates that modern livestock systems can be redesigned to better exploit cattle and buffaloes’ ecological niches as sustainable best practices to regenerate oil palm plantation landscapes and contribute to faunal conservation initiatives in Malaysia’s oil palm plantation ecosystem.
Industrial wastewater treatment methods employed in Southeast Asian countries
Authors: Razman K K , Hanafiah M M , Ramli A N , Harun S N
Published: May 2023

Wastewater pollution from industrial sector has tremendously increased in recent years and has posed severe environmental and health problems in many countries worldwide. Humans and other living organisms need clean water to sustain life and performing other daily activities, such as growing crops in agriculture, mining, and manufacturing. However, lack of effective water treatment and poor management of water sources caused by wastewater discharge to the environment without sufficient treatment have contributed to the high concentration of organic matter and hazardous compounds. In Southeast Asian countries, several treatments are employed in treating wastewater such adsorption, advanced oxidation process and membrane filtration reactor. As there are limited data demonstrating the most efficient and cost-effective way for wastewater treatment in the Southeast Asia’s industrial sector, this paper aims to examine the existing and advanced methods for treating industrial wastewater in Southeast Asian countries and assess its efficacy in removing contaminants from the industrial wastewater. PRISMA approach was used to conduct the review of this study with 64 articles making the final selection from 5 Southeast Asian countries (Malaysia, Singapore, Indonesia, Thailand and Vietnam). The review found that the anaerobic aerobic-wetland sequential system and a convective sludge dryer removed the highest number of contaminants eliminating almost 99% of chemical oxygen demand (COD), volatile suspended solid (VSS), and volatile fatty acid (VFA) with an added benefit of being cost effective, environmentally friendly and sustainable.
Assessing Forest Carbon Accumulation Potential Across Different Treatments using Field Inventory Data
Authors: Mazlan S M , Wan Mohd Jaafar W S , Omar H , Teh Y A , Cutler M E J
Published: May 2023

Deforestation and forest degradation lead to an increase in the level of carbon in the atmosphere and disrupted the global carbon cycle. The tropical forest has received a lot of interest since it contributes around 60% of the total global forest carbon. By enhancing carbon sink, tropical forests have a great potential in mitigating climate change. Assessing aboveground biomass (AGB) and carbon stock through field inventories is crucial for this purpose as it provides the most accurate result. The research was conducted at Danum Valley Conservation Area and INFAPRO in Sabah, Malaysia. An earlier study over 35 years ago at this site suggests that restored forests accrue AGB at twice the rate of regenerating forests, though the cause of this difference between treatments is unclear. Thus, this study will focus on three principal study sites which are restored, naturally regenerating and old-growth forests to determine the forest’s potential to sequester and store carbon in the forest ecosystem. These three sites were chosen because it is a well-established plot from the earlier inventory over the last seven years. The field measuring method is a non-destructive methodology. Tree parameters such as diameter at breast height (DBH), tree height and tree species diversity were collected for calculating AGB using a species-specific allometric equation. Results showed a positive correlation between tree species, diameter at breast height, and biomass/carbon stock across three different forest treatments. The active restoration increases up to 151% carbon stock whilst the old-growth forest increased by 34% and natural regeneration increased by 73%, which active restoration can be the best solution for forest treatment. The outcome of this study will increase the ability of forest authorities and the Malaysian government to effective monitoring of carbon stock for establishing reliable standard guidelines in measuring deforestation and forest degradation toward achieving sustainable forest management.
Developing an IoT-Based Digital Climate Station at Dramaga Climate Observational Station
Authors: Aditama G K L , Wijaya S K , Siagian S B , Nugroho W
Published: May 2023

A climatological station has several obligations to conduct climatological observations over a long-term time range, with the observed parameters consisting of air temperature, relative humidity, solar radiation, air pressure, wind, rainfall, and soil temperature. At the moment, the BMKG (Indonesia Meteorological Administration) Climate Station manages to do the task conventionally with the observer on duty. By utilizing state-of-the-art technology, an internet-based automatic climate monitoring system was designed to ease the data users’ ability to conduct real-time climate monitoring anywhere connected to the Internet. Dramaga Climatological Station is one of BMKG's observational stations to be used as a sample for digital instrument monitoring. The Digital Climatological Station (DCS) was a system capable of measuring elements of climate automatically that was designed using the Campbell CR1000X datalogger for data acquisition, multiple meteorological sensors, and a solar-based power system. The sensors in this system were a combination of sensors with voltage output and serial (SDI-12) output, so that all the sensors could match the number of logger ports. The overall industrial-grade sensors had a maximum error of 2.38%. Acquired data from the logger was sent via the Amazon AWS IoT Core MQTT Broker using the MQTT protocol. Subscribing was carried out on the server by Node-Red, stored in a MySQL database, and displayed using Grafana on a desktop or mobile phone. The system managed to transmit the data with more than 97% completion out of 1440 daily records. The mentioned instrument is expected to be a pioneer in observation automation in order to assist the observer while improving accuracy.
Synthesis, characterization, photoluminescent properties of carbon quantum dots and its applications in wastewater treatment
Authors: Nizam N U M , Hanafiah M M
Published: May 2023

Carbon-based nanomaterials are currently gaining attention in wastewater treatment. They have gained a prime position in membrane filtration to degrade pollutants. One of the most recent additions to the field of carbon-based nanomaterials is quantum dots (QDs). Due to their exceptional qualities, QDs are among the most promising carbon-based nanomaterials at the forefront of the wastewater treatment research field. Nonetheless, most quantum dots were not sustainably fabricated. Therefore, this study aims to evaluate the carbon-based carbon quantum dots derived from biomass wastes (rubber seed shells) where the properties, behaviour and photoluminescence characteristics were evaluated through several characterization analyses. The QDs were characterized using Fourier-transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), field emission scanning electron microscope (FESEM) equipped with energy-dispersive X-ray spectroscopy (EDX), photoluminescence spectroscopy, zeta potential analyser and Raman spectroscopy. The morphological analysis revealed multi-layered planes with highly porous and uneven surfaces, consisting of a large number of oxygen-functional groups (hydroxyl, carboxyl, carbonyl). The mapping results showed a large uniform distribution of carbon and oxygen elements on the surface of QDs with a more signified composition of wt% carbon (72.4%) compared to oxygen elements, with 23.6%. The spectroscopic and photoluminescence studies confirmed the fabrication of high-quality carbon quantum dots with blue-greenish fluorescence emissions. These results have shown promising biomass-based QDs that can be applied in wastewater treatment based on their unique characteristics. Thus, the derived biomass-based QDs can be viewed as a promising and cost-effective adsorbent for wastewater and water treatment.
Oil Palm Health Estimation Using Low Altitude Remote Sensing
Authors: Jefri N S M , Ahmad A , Darwin N , Rasib A W
Published: May 2023

Unmanned Aerial Vehicle (UAV), Unmanned Aerial System (UAS), or drones are small autonomous airplane that does not need a pilot on board (CAR, 2016). UAS is increasingly becoming widely known for its capability to bring many innovations to the world. UAVs are also utilized as geospatial technology tools, providing benefits to environmental monitoring. Therefore, this study aims to estimate oil palm health using UAV payload remote sensing compact sensors. Two remote sensing compact sensors were used in this study which is visible (RGB) and Near Infrared (NIR) to get the reflectance curve of the oil palm. Analysing oil palm condition from reflectance curve by using a spectroradiometer are the first objective while analysing extraction oil palm condition by using sensors is the second objective. Some policy and regulation were involved to follow the guideline that has been implemented by the agency. Instead of using a UAV, the spectroradiometer was used to visualize the spectral response curve of an oil palm. As a result, the oil palm condition at study area is in healthy condition where the reflectance curve for multispectral compact sensors (0.84) and spectrometer (0.82) which are above healthy indicator (0.5) whereby favourable to determine the growth stability of oil palm trees. As a summary, these techniques are potential to support the development of modernization technology in environmental monitoring for oil palm plantations and give an alternative way to give good result on oil palm health condition.
Preliminary soil characteristics and growth performance of selected shrub plants for bio-engineering technique
Authors: Aznan M E , Rahman Z A , Tarmidzi S N A , Idris W M R , Lihan T , Khamis S , Kadir A A , Jalil N A A , Rahman M R A
Published: May 2023

This study presents the preliminary results of the physicochemical characteristics of the soil taken from the slope bio-engineering study. The soil would be used as a medium for the growth of selected shrub species namely Strobilanthes crispa (SC), Pseuderanthemum carruthers (PC), Tabernaemontana divaricata (TD), and Hibiscus rosa-Sinensis (HR). Soil medium was prepared in a 3:2:1 ratio (soil: organic fertilizer: sand). The plant-cutting technique was adopted and planted in polybags. The growth performance (height, number of leaves, chlorophyll, and leaf area) of these species was monitored on monthly basis up to three months. The result showed that the pH, organic matter and moisture content ranged from 4.15 to 5.23, 4.29% to 7.96% and 16.1% to 62.93%, respectively. The specific gravity and porosity of the soil ranged from 2.66 to 2.70 and 58.48% to 60.83%, respectively with clay loam and loam textures. SC and TD showed high mortality rates, with only 28% and 50% of the species still alive. However, the PC and HR had low mortality rates, with 98% and 96% of cuttings surviving, respectively. TD recorded the highest plant with 30.63 cm followed by HR (27.94 cm), PC (25.32 cm) and SC (22.36 cm). TD also recorded the highest number of leaves with 23 individuals. SC showed the highest leave area with a mean of 23.61 cm2 followed by PC (23.2 cm2), HR (14.43 cm2) and TD (13.28 cm2). HR recorded the highest chlorophyll content with a mean value of 46.62 followed by TD (45.23), SC (35.87) and PC (32.79). In conclusion, HR showed a good growth performance among the studied species. These preliminary findings suggested that all species have the potential to be used as biological material for slope erosion protection, with some soil treatment required for better growth outcomes.
Utilization of low-density emulsion to increase blasting efficiency and safety environment
Authors: Lubis J F , Handayana R H
Published: May 2023

The low-density emulsion was developed to replace ANFO, an explosive with weak resistance to water and tends to produce fume in the blasting process. Hanwha Mining Service Indonesia has developed low-density products with the brand Himex 70 LD. The base chemical emulsion uses the addition of a chemical as a gassing agent and a control gassing which can maximize the density of the emulsion up to 0.85 gr/cc. The stability of the emulsion is maintained by increasing the product’s viscosity. This study aimed to determine the performance of using low-density emulsion Himex 70 LD on the fragmentation, digging time, use of powder factor, and product stability against fumes. Based on project data, Himex 70 LD can produce optimal blasting results with a detonation value velocity reaching more than 4500 m/s. Himex 70 LD also reduces powder factor usage by up to 0.17 compared to pf usage in normal density emulsion with an average pf of 0.19. The resulting fragmentation size reaches 586.56 mm at 80% passing and digging time in the average range of 9.2 to 11.8 seconds. The low-density emulsion is also effectively stable even in wet holes and produces no yellow fume or zero NOX detonation.
Study of Flyrock to Reduce Safe Radius from 500 m to 300 m on Blasting Quarry at PT Vale Indonesia, Sorowako, Luwu Timur, South Sulawesi
Authors: Eko M R , Haris R H , Lubis J , Deri N P
Published: May 2023

Flyrock exceeding the safe radius can cause harm to equipment and humans. In recent years there has been frequent flyrock exceeding 500 m which has caused a significant impact on the environment in addition to several quarries adjacent to the population at a distance of 500 meters. Data collection at PT. Vale Indonesia uses Leica GS and GoPro with an analysis method using Tracker 5.1.5 to observe blasting activities. The estimated maximum flyrock trajectory distance is determined using empirical and dimensional analysis methods. It is done to obtain accurate and precise results on the conditions of the blasting sites. The empirical method is based on the theories of Lundborg (1981) and Richard and Moore (2005), while the dimensional analysis method is based on the theory of Ebrahim Ghasemi (2012). A comparison of the actual flyrock trajectory deviation between the dimensional analysis method of Ebrahim Ghasemi and the empirical method of Richard and Moore shows that Ebrahim Ghasemi’s method is closer to the deviation percentage, which is 7.76%. From the estimated distance, the flyrock closest to the actual flyrock dimension analysis method has a deviation of 4.89m with a factor of safety value against flyrock hazards of 1.5. A trial was conducted based on the dimensional analysis method to determine the appropriate safe radius.
The comparison of physical and mechanical properties of sand in Sedau and Obel-Obel Village
Authors: Firaz M F , Isfanari
Published: May 2023

The research was conducted in two regencies: Sedau Village in West Lombok Regency and Obel- Obel Village in East Lombok Regency. The two research sites are areas with potential sand wealth, with many sand mining companies operating. The sand mining company at the research site is expected to implement good mining practices which pay attention to mining design safety. Geotechnical recommendations on slope dimensions with a good safety factor value are required in making a mining design. Several factors affect a rock’s geotechnical properties. These factors are physical and mechanical. In this study, a comparison was made between the physical and mechanical properties of sand at two locations, which aims to compare rock characteristics and become a reference for geotechnical recommendations in the area. The research method used was sampling and testing in the laboratory. The results showed that the porosity value in Sedau Village was 0.102 and Obel-obel Village’s was 0.09. The average water content value in Sedau Village was 6.567%, and the average water content value in Obel-Obel Village was 8.233%. The specific gravity value of sand in Sedau Village was 3.75 gr/cm3, and that in Obel-obel Village was 3.75 gr/cm3. The compressive strength of sand in Sedau Village was 0.137 Mpa, and the compressive strength of sand in Obel-obel Village was 2.32 MPa. Based on the laboratory testing results, the influencing factors were analyzed, namely the location of its formation and the different processes of sand sedimentation in Sedau Village and Obel-obel Village.
Legal Protection for the Community Around the Sand Mining In Ijobalit Village, East Lombok Regency
Authors: Hartati W , Alpiana  , Ariyanto
Published: May 2023

Sand mining in Ijobalit Village, East Lombok district, is a mining activity carried out by people who own hilly land containing quarry materials such as sand. With this background, the community carries out mining by renting excavators to support their purposes. However, these activities come with many issues. This paper aims to determine the conception and provisions of mining in Indonesia and the legal protection for the community who carry out mining activities. The method used in this paper is normative legal research. The study results show that the conception and provisions of mining in Indonesia are inseparable from the utilization of natural resources and the sustainability of human and natural ecosystems. The sustainability of natural resources and human resources, can be assessed through licensing regulations and authorities as well as preventive protection. Licensing regulations and authorities means granting the community rights to natural resources use and management that are mutual control by taking damages caused by sand mining into account. And repressive protection means management efforts to more responsible sand mining businesses by developing an independent local business sector with guaranteed occupational safety. Occupational safety needs to be regulated technically through a permit to manage sand mining management.
General expressions for heat distribution, pressure, and current density in argon welding arcs
Authors: Villarreal-Medina R. , Delgado-Álvarez A. , Murphy A. B. , Méndez P. F. , Ramirez-Árgaez M. A.
Published: May 2023

In welding and wire-arc additive manufacturing (WAAM), a mobile arc is the heat source that enables the deposition of metals and the resulting properties of the final product. Because the arc involves temperatures of 20 000 K, and gas velocities of the order of 300 m/s, there are only a few experiments and models available to determine optimal, or at least acceptable, parameters for the operation such as current, voltage, and arc length. On the other hand, there is a lack of engineering guidance to optimize the processes resulting in costly and time-consuming trial-and-error optimization methods, which also involve wasteful use of energy and scrap parts. In this work, a numerical model of the gas-tungsten arc welding (GTAW) arc was created and validated against experiments. The model considers the arc interactions between a non-consumable electrode and the weld pool and accounts for multiple coupled heat transfer mechanisms: Joule heating, conduction, advection, radiation, and Thomson effect. The conditions considered cover the vast majority of GTAW welding operations. The results are generalized in the form of engineering expressions suitable to be embedded in metamodels, in which the heat source is just a part. Applications include penetration and width of welds and deposition rate in external-wire WAAM.
Understanding the inoculation of aluminium grains during welding under the influences of high cooling rate and high temperature gradient
Authors: Xu Yijiang , Kvam-Langelandsvik Geir , Bunaziv Ivan , Li Yanjun
Published: May 2023

Inoculation is an important method to generate fine equiaxed grain structures in alloys during solidification, which is widely used in shape casting and direct chill casting processes of aluminium alloys. Different from the normal casting processes, welding and additive manufacturing can have ultrahigh cooling rate and temperature gradient during solidification. This makes the grain refinement by inoculation method more difficult. Therefore, a deeper understanding on the influences of cooling rate and temperature gradient on the nucleation and growth of grains is necessary. In this work, a numerical model is developed to quantitatively address the above influences. The model has been successfully applied to predict the grain size in the welding of aluminium alloys as a function of locations.
Laser welding of dissimilar materials - simulation driven optimization of process parameters
Authors: Serdeczny M S
Published: May 2023

Laser welding can be used to join dissimilar materials to produce lightweight structures, and electric vehicle battery systems, which are important means of limiting the carbon emissions in the transport industry. Due to the differences in melting temperatures, thermal conductivities, and mutual solubility of dissimilar materials, it is still challenging to create defect-free joints with high mechanical strength, or low contact electrical resistance. In this work, we present a state-of-the-art numerical model of laser welding, developed within the Computational Fluids Dynamics (CFD) paradigm. The multi-physics model simulates melting, flow, and solidification of the alloys and accounts for the laser-material interactions, phase change, temperature and alloy-dependent thermophysical properties, recoil pressure, buoyancy force, and Marangoni effect. The simulation predicts weld penetration depth and width, alloy mixing, as well as the temperature gradient and cooling rate during the solidification that can be further fed into a micro-structure prediction model. The model is coupled with an optimization tool, which iterates over different process parameters to optimize the joint. The methodology is presented for steel to aluminium welding in lap configuration, but it can be used for other materials such as steel-copper, aluminium-copper, or steel-nickel, and in arbitrary geometrical configuration.
Enhancement of a quasi-analytical solution for modelling additive manufacturing processes
Authors: Cooke S. , Sinclair C. , Maijer D.
Published: May 2023

Numerical modelling methods (e.g. finite element) can provide accurate descriptions of long-range temperature fields in laser or electron-beam melting processes, however the high computational costs at part-scale make them unsuitable for process modelling in additive manufacturing (AM). Alternative methods such as semi-analytical solutions based on a moving heat source reduce the computational expense but at the cost of unrealistic assumptions. Radiation, temperature-dependent physical properties and latent heat are not considered in the semi-analytical approach but can have a significant effect on the thermal history. In this study, the error associated with each of these contributions are assessed against the conduction-only semi-analytical solution for a range of processing parameters for surface melting on solid Ti-6Al-4V. The semi-analytical model is then “enhanced” using results from finite element simulations to better account for the heat transfer in the AM process.
Measurements of deposition rate and droplet temperature in GMAW of aluminum alloys
Authors: Ramgopal Rishiekesh , Yan Zhaoyang , Scott Kevin S. , Chen Shujun , Mendez Patricio F.
Published: May 2023

This article explores the reason behind the higher deposition rate in Mg-containing aluminum alloys in gas metal arc welding (GMAW). Experiments performed on ER1100 (Mg-free alloy) and ER5183 (high Mg alloys) measured current, wire feed speed, and droplet temperature. A non-linear analysis of Joule heating at the electrode extension and an analysis of the power needed to heat the consumable to the droplet temperature were performed. Analysis revealed that Joule heating is two orders of magnitude smaller than what was necessary for the higher wire feed speed. The droplet temperature measurements were done for the first time for both consumables under identical conditions, which revealed that ER5183 had a lower droplet temperature than ER1100 by almost 350 K.
Arc length behaviour and voltage predictions for GMAW-Sp aluminum procedures in the Lincoln Procedure Hand Book
Authors: Eduardo Alvarez Rocha J. , Mendez Patricio F.
Published: May 2023

Heat input is a key component of a welding procedure, which is dependent on the several fall voltages composing a total voltage loss. As current practice is primarily reliant on trial and error to determine voltage settings for a desired heat input, a means to understand and predict the voltage loss is of interest to welding engineers. Voltage, amperage, and arc length measurements using ER4043 1.2 mm at varying voltages were used to break down fall voltage constituents for a given weld with GMAW-Sp. Arc length was defined as the distance from the weld pool to the point where the metal vapour and ionized gas boundary attach to the consumable, and measured over 5 droplet cycles to obtain a time average. Aluminum procedures in the Lincoln Procedure Hand Book (LPHB) with 1.2, 1.6, and 2.4 mm consumables were analyzed to predict the individual fall voltage constituents using experimental results. Expected arc lengths ranged from 13-26 mm depending on voltage prescribed in the procedure, and agreed with comparative experiments. Combined anode/cathode, and the arc column were major contributors to overall fall voltage with 64±3%, and 34±3%, respectively. Contact tip, electrode extension, and lead cables were minor contributors, each contributing less than 1.2% to the overall voltage loss.
Combined defect prediction for large-area die-cast components using high-resolution multi-phase simulation
Authors: Jakumeit J. , Behnken H , Laqua R , Gänz J. , Becker L. , Fehlbier M. , Middelmann O.
Published: May 2023

In the automotive industry there is a trend towards large components that are manufactured using high pressure die casting process (HPDC), in particular when many previously welded individual parts are to be replaced with one cast part to save costs and energy. In the case of large components, incipient solidification during mold filling cannot be ruled out. Casting defects due to cold running, air pockets and porosity cannot be separated spatially and temporally and influence each other. This stronger linking of the defects requires a realistic depiction of the casting process in the simulation, since the interactions between effects are more difficult to depict through approximations. The multi-phase approach presented here offers various options for this: The air is calculated as a compressible gas that is separated from the melt by a sharp boundary surface. Reduced melt flow due to solidification is represented by a porous media approach, followed by a complete flow stop at high solids. The formation of porosity due to volume shrinkage is coupled with a gas evaporation model. The multi-phase approach was validated by casting trials using a specially designed test geometry for thin-walled aluminum HPDC applications. First results of an industrial application are shown.
Predicting the local solidification time using spherical neural networks
Authors: Erber Maximilian , Rosnitschek Tobias , Bauer Constantin , Ali Güldali Muhammet , Alber-Laukant Bettina , Tremmel Stephan , Volk Wolfram , Hartmann Christoph
Published: May 2023

Castings are predestined for the application of structural optimization, but to date, the integration of process simulation into structural optimization is limited due to high computational cost and is therefore often neglected at the beginning of the design process. This leads to the need for surrogate models, which allow a fast and simplified evaluation of design proposals during the optimization in order to improve the integration. This article introduces a novel approach that estimates the solidification time of randomly created geometries solely based on the casting geometry. The approach uses ray-tracing methods to calculate the distance function along preset directions. The estimated solidification time is calculated using a Spherical Convolutional Neural Network (CNN). The training data is obtained by several thousand solidification simulations using the optimization toolkit of a commercial casting simulation software combined with further data augmentation. The model is experimentally validated for five different geometries in the sand casting process.
Meshless simulation of a macrosegregation benchmark considering the solid motion
Authors: Govže Viktor , Vušanović Igor , Šarler Božidar
Published: May 2023

We have extended the existing two-dimensional rigid solid phase benchmark for binary substance with the solid phase motion in the present paper. Incompressible laminar Newtonian flow is assumed, and a standard mixture formulation is used for the mass, momentum, energy, and solute transport. A coherency solid motion model accounts for the free-floating grains, assuming that the solid velocity is proportional to the mixture velocity and the liquid fraction. The lever rule is used to describe the mass fractions of the phases. A two-dimensional benchmark is solved using the semi-implicit meshless diffuse approximate method with an adaptive subdomain upwinding strategy. The results of the meshless method are compared to the finite volume method results with a reasonable agreement. The new benchmark results show that the solid motion has an essential effect on the macrosegregation pattern.
Droplet temperature measurement in GMAW
Authors: Sánchez Vicente Núñez , Yan Zhaoyang , Chen Shujun , Mendez Patricio F.
Published: May 2023

This work presents measurements of the droplet temperature for the Gas Metal Arc Welding process. Four different aluminium electrodes were used for experiments performed under the same conditions. The approach used yielded higher droplet temperatures than were obtained in previous experiments with the same raw data because the energy balance approach differed. However, trends were similar, with a minimum value close to the transition current and a tendency to increase with the current. Anode fall voltages behaved similarly, increasing with the current. Differences in temperature were found between the four electrodes. This can be explained by the different alloying elements present on the electrodes, which evaporate and take energy out of the droplet.
Modelling microstructure formation in TiAl by isomorphic inoculation
Authors: Kennedy J.R. , Boukellal A.K. , Založnik M. , Daloz D. , Zollinger J.
Published: May 2023

Ti-Al alloys have replaced Ni-based superalloys in the last stages of some aircraft engines to improve fuel efficiency. In order to improve their properties, grain refinement has been investigated via isomorphic inoculation with Ti-Al-Nb particles. This inoculation method is orders of magnitude more efficient on a particle-by-particle basis than traditional inoculation, rather than multiple inoculant particles added to form a solidified bulk phase grain, in isomorphic inoculation each particle added results in the formation of multiple grains. As the particles are indistinguishable from the matrix after solidification, a model was used to elucidate this mechanism. Two phenomena were considered to calculate the number of particles acting during solidification: particle breakup along grain boundaries and complete particle dissolution. The grain size of the particles was calculated with an empirical model from initial TKD analysis of the particles and high temperature molten salt heat treatments. Particle dissolution was estimated via mass transport of the slowest diffusing Nb species. This showed the population of isomorphic inoculant particles which can act during solidification is near a 1:1 ratio with the number of grains formed, confirming the mechanism of grain refinement by direct epitaxial growth from the particles.
A study of the complex dynamics of dendrite solidification coupled to structural mechanics.
Authors: Soar P , Kao A , Djambazov G , Pericleous K A
Published: May 2023

The impact of structural mechanics is often overlooked when modelling the solidification of dendritic microstructures, despite experimental observations that the interaction between these processes can be a factor leading to the development of crystal mosaicity throughout the microstructure which can itself lead to more serious defects. When considered at all, the structural mechanical behaviour of columnar dendrites is often considered as being analogous to a cantilever beam both in interpretations of experimental results and in existing numerical modelling. While this is not an unreasonable assumption when considering a dendrite in isolation, this is a scenario that infrequently occurs. In this paper a parametric study is presented using a Cellular Automata solidification solver coupled to a Finite Volume Structural Mechanics solver. These results highlight the complex non-linear behaviour that arises when considering dendrite interaction, demonstrating the significantly different microstructures that can be obtained by varying only the force experienced by the system.
CA-LBM studies on the grain formation process of aluminum alloy under convection
Authors: Zhang Yanying , Dou Ruifeng , Wang Junsheng , Tian Yuzhu , Liu Xunliang , Wen Zhi
Published: May 2023

A cellular automata-lattice Boltzmann coupled model was established to simulate the grain formation process of aluminum alloy under convection conditions. The influence of flow on crystal grain growth was simulated. Results show that the existence of convection prevents the crystal from growing symmetrically compared with the pure diffusion condition. Moreover, the growth of dendrite at the upstream side is promoted, whereas that at the downstream side is inhibited because of solute segregation. The greater the flow velocity is, the stronger the asymmetry of the grain is. The greater the undercooling is, the greater the dendritic growth driving force is, the faster the dendritic growth is, the dendrite arms coarsen, and the secondary dendrite arms become increasingly developed, thereby increasing the solute concentration at the solid-liquid interface at the tip of the dendrite and aggravating the solute segregation.