Hardness Levels Research Articles

Mechanical properties of FDM 3D printed component using self-made PLA-titanium filament: hardness perspective

3D printing, also known as additive layer manufacturing, is a technique that creates three-dimensional objects or any shape from a digital model. It works by building objects layer-by-layer, similar to how a laser printer operates. Fused Deposition Modeling (FDM) is a widely used technique in 3D printing because it is easy to use, cost-effective in production, and environmentally friendly. This study focuses on a self-made filament made of a PLA-titanium mixture. PLA is a biodegradable thermoplastic polymer sourced from plants, whereas titanium is a strong, lightweight, and corrosion-resistant metal. To measure the hardness of different materials, there are several methods available. In this study, the Shore D hardness test, specifically designed for polymer materials, was used. Data were collected using the Taguchi method, specifically L4 (23), and the data were analysedusingAnalysis of Variance (ANOVA). The variations in print parameters examined in this study include nozzle temperature (230°C and 240°C), layer height (0.2 mm and 0.3 mm), and print speed (30 mm/s and 40 mm/s). The aim of this study was to determine whether there were any changes in the hardness of the specimens. The ANOVA results revealed that the most influential parameter was print speed, with a contribution value of 56.01%. The results demonstrated that the printing parameters affected the hardness of the printed specimens. The highest hardness level of 56.3 Shore D was obtained with a nozzle temperature of 240°C, a layer height of 0.3 mm, and a print speed of 30 mm/s. The application of this study was demonstrated through the creation of dentures made from PLA-titanium.

A State of the Art on Cryogenic Cooling and Its Applications in the Machining of Difficult-to-Machine Alloys.

Cryogenic cooling has gathered significant attention in the manufacturing industry. There are inherent difficulties in machining materials that are difficult to machine because of high levels of hardness, abrasiveness, and heat conductivity. Increased tool wear, diminished surface finish, and reduced machining efficiency are the results of these problems, and traditional cooling solutions are insufficient to resolve them. The application of cryogenic cooling involves the use of extremely low temperatures, typically achieved by employing liquid nitrogen or other cryogenic fluids. This study reviews the current state of cryogenic cooling technology and its use in machining difficult-to-machine materials. In addition, this review encompasses a thorough examination of cryogenic cooling techniques, including their principles, mechanisms, and effects on machining performance. The recent literature was used to discuss difficult-to-machine materials and their machining properties. The role of cryogenic cooling in machining difficult materials was then discussed. Finally, the latest technologies and methods involved in cryogenic cooling condition were discussed in detail. The outcome demonstrated that the exploration of cryogenic cooling methods has gained prominence in the manufacturing industry due to their potential to address challenges associated with the machining of exotic alloys.

Estimation of Hardness Level and Total Dissolved Solids in Ground Water at Shendi Town, River Nile State, Sudan

Water is life but hardness in water is harmful to human health. This descriptive and analytical study was conducted to determine the levels of hardness and concentration of Total Dissolved Solids (TDS) in drinking water in Shendi town of Sudan. The drinking water samples of 150 (50 samples for each season) were collected from wells, distribution channels and storage facilities and tested per season. The analysis of these samples was done using photometer device to determine the water hardness and result is displayed as mg/l CaCO3, while for estimation of TDS Conductivity / TDS meter and results were noted in parts per million (PPM). The results of this study found that water hardness is found in 48%, 56% and 50% of tested samples during Summer, Autumn and Winter seasons respectively. While Water Quality Index (WQI) base on TDS showed that water quality is excellent and good in autumn and winter seasons, but unacceptable for drinking during the summer season. Based on the findings, the study recommends that Civil Water Corporation should improve the quality of drinking water by treating the water before supplying to the community.

General investigations on the heat treatment and thermal fatigue behavior of an experimental hot work tool steel tailored for laser powder bed fusion

An experimental hot work tool steel with a leaner chemistry compared to the standard AISI-H13 grade, aimed at enhanced processability, was gas atomized and processed using laser powder bed fusion (L-PBF) to >99.8 % relative density. The lower carbon content (∼0.25 wt% vs. ∼0.4 wt% in H13) resulted in a softer as-built (AB), and quenched martensite (∼485 HV1 vs. 625 HV1 in H13), higher martensite-start temperature (∼360 °C vs. 280–320 °C), and about ∼18 % reduction in dilatation, ascribed to the volume expansive martensitic transformation. Charpy V-notch impact toughness in AB condition (>30 J) was higher than those reported for AB H13. These features account for the improved L-PBF processability. The tempering response in comparison with a wrought H13, was characterized by a larger precipitation of thermally stable Mo- and V-rich secondary hardening alloy carbides at the expense of the easy-to-coarsen Cr-rich ones, attributed to the higher Mo and lower Cr content in experimental alloy. The combination of lower C- and V-contents in experimental alloy, reduced the driving force for the precipitation of coarse vanadium rich carbides during austenitization, as confirmed by electron diffraction spectroscopy (EDS) and synchrotron X ray diffraction. This led to a stronger fine secondary hardening alloy carbide precipitation during tempering, and enhanced temper resistance. As elaborated by isochronal tempering, as well as tempering curves, reduction of the elements Si, and Cr shifted the secondary hardness peak to higher tempering temperatures. Consequently, tempering, and thermomechanical softening resistance was significantly enhanced in the new steel with a maximum hardness of ∼550 HV1 in over-tempered condition (i.e., slightly above secondary hardness peak). Thermal fatigue (TF) tests revealed a denser and finer TF crack network with a larger oxidation in experimental steel. Thereby, the TF crack penetration depth scaling with the local plastic yielding of the matrix was evidently shorter in the new steel compared with wrought H13, thanks to significantly improved hot hardness, thermal conductivity, and enhanced thermomechanical softening resistance. Finally, a proof of concept is demonstrated by processing a relatively large injection molding die (150 mm × 110 mm × 30 mm) with promising tensile and impact toughness properties after direct double tempering to 51 HRC, and 45 HRC hardness levels.

Pembangunan Game Edukasi Interaktif Pelajaran Bahasa Jawa Indramayu pada SDN 1 Margadadi

This research aims to improve the abilities of students at Elementary School 1 Margadadi in reading and writing the Javanese language of Indramayu. The process involved conducting observations and data collection, followed by analyzing the existing issues by gathering grade data from Class V for the past 2 years in the subjects of writing and reading in Indramayu Javanese language.. It was found that many students were not achieving the Minimum Competency Criteria. To address this issue, As a solution, an educational game for learning the Indramayu Javanese language was developed. The research methodology consisted of five stages, including problem analysis, game analysis, system design, system implementation and testing, and finally, conclusions and recommendations. This educational game utilizes the Visual, Audio, and Kinesthetic (VAK) learning method within its content. Results from testing the game with 10 student respondents showed that the average time for writing Javanese script was 13.63 seconds, which was faster than manual writing that took 27.03 seconds. The longest time recorded was 16 seconds for the letter "Nyo," as only 7 respondents were able to complete this task. Furthermore, the testing of understanding the Javanese language of Indramayu revealed that the average scores exceeded the Minimum Competency Criteria, with an average score of 84.6% for the normal level in the game and 81.4% for the hard level in the game.

The effect of water hardness on the development of embryo and larvae of silver carp (Hypophthalmychthis molitrix)

This study aimed to investigate the effect of water hardness on the fertilization rate, hatching rate, survival rate, and deformity rate of common carp larvae. In the experiment, fertilized eggs of silver carp were incubated in different water hardness levels of 70, 100, 130, 160, & 190 mg CaCO3/L, with a stocking density of 400 eggs/L. The experimental results showed that the fertilization rate was high (78.0 - 79.3%) and did not show significant differences between the treatments (P > 0.05). The hatching rate ranged from 41.0 to 54.0% and larvae stage had the highest survival rate of 54.0% at 70 mg CaCO3/L. The deformity rate of larvae ranged from 5.7 to 74.3% with the lowest observed at the 70 mg CaCO3/L. From the results of the study, it can be assumed that silver carp eggs should be incubated in an aquatic environment with a water hardness of 70 mg CaCO3/L.

Estimation of friction and wear properties of additively manufactured recycled-ABS parts using artificial neural network approach: effects of layer thickness, infill rate, and building direction

Abstract This investigation aims to elucidate friction and wear features of additively manufactured recycled-ABS components by utilizing neural network algorithms. In that sense, it is the first initiative in the technical literature and brings fused deposition modeling (FDM) technology, recycled filament-based products, and artificial neural network strategies together to estimate the friction coefficient and volume loss outcomes. In the experimental stage, to provide the required data for five different neural algorithms, dry-sliding wear tests, and hardness measurements were conducted. As FDM printing variables, layer thickness (0.1, 0.2, and 0.3 mm), infill rate (40, 70, and 100 %), and building direction (vertical, and horizontal) were selected. The obtained results pointed out that vertically built samples usually had lower wear resistance than the horizontally built samples. This case can be clarified with the initially measured hardness levels of horizontally built samples and optical microscopic analyses. Besides, the Levenberg Marquard (LM) algorithm was the best option to foresee the wear outputs compared to other approaches. Considering all error levels in this paper, the offered results by neural networks are notably acceptable for the real industrial usage of material, mechanical, and manufacturing engineering areas.

Effect of energy distribution on laser cleaning quality of 30Cr3 ultra-high strength steel

30Cr3 is a novel ultra-high strength steel (UHSS) with excellent strength and plastic toughness, which has been mainly used in aerospace shells and stressed parts. Currently, there is still a lack of systematic research and comprehensive evaluation on the laser cleaning of this particular material. In this study, a nanosecond pulsed laser was employed for the cleaning process. First, the energy distribution model was derived, the influence of the spatial and temporal distribution of laser energy on the cleaning quality was discussed, and the cleaning experiment was conducted. The results showed that a laser energy density of 15 J/cm2, combined with the beam overlap rate 52% in the x-direction and 61% in the y-direction, can effectively remove the oxide layer and thoroughly expose the natural metal matrix. Then, under the optimum parameters, the oxygen content decreased from 22.3% to 3.4%, the Fe content increased from 54.5 to 83.4%, the Fe3+ peak disappeared in the X-ray photoelectron spectroscopy (XPS), a remelted layer of only 1 μm was observed. Last, the roughness was slightly reduced from 3.573 μm to 2.985 μm, the hardness was restored to the original hardness level of the substrate (∼260 HV), and the electron back scatter diffraction (EBSD) showed that the structure hardly changed after cleaning, the grain size was comparable to that of the matrix. These findings indicated that laser cleaning can effectively remove the oxide layer of 30Cr3 UHSS without damaging the properties of the base material, which has promising application in the cleaning of UHSS.

Application of bioassays and physicochemical analysis for assessing groundwater quality of selected tube wells in a CKDu impacted area

Groundwater from tube and dug wells are primarily used for drinking purposes by rural communities inhabiting Chronic Kidney Disease of unknown aetiology (CKDu) impacted areas in Sri Lanka. Groundwater safety assessment using targeted physicochemical analysis alone is not adequate to capture interactive effects of chemical mixtures in the groundwater. This study explored for the first time combined use of physicochemical analysis and bioassays with root meristems of Allium cepa and erythrocytes of Cyprinus carpio to assess groundwater quality of selected tube wells in Medawachchiya (a CKDu impacted area), Sri Lanka covering pre-monsoon, monsoon and postmonsoon seasons. The pH, turbidity, arsenic, cadmium, lead, mercury, fluoride, chloride, nitrate and nitrite levels in the groundwater complied with Sri Lanka standards for potable drinking water in all seasons. Yet, alkalinity and total hardness levels in the groundwater exceeded national drinking water standards (nearly up to two folds) mostly in the monsoon season. Bioassays revealed genotoxic effects of the groundwater of some tube wells in pre-monsoon and monsoon seasons. Observed genotoxicity may be associated with synergistic effects of contaminants including undetected and unknown chemicals in the groundwater depending on the season. The results support the use of bioassays as complementary tools for evaluating groundwater quality of CKDu hotspots considering consumer safety.

Studying the possibility of using butter produced by the method of converting high fat cream in the production of puff products

The article presents comparative studies of the composition, physico-chemical and structural-mechanical characteristics of butter samples produced by the method of converting high-fat cream from domestic raw materials, and foreign-made but- ter by churning cream in continuous buttermakers, as well as their influence on the process of puff pastry formation and the organoleptic properties of finished products made from puff pastry. The purpose of the research is to assess the suitability of butter produced by the method of converting high-fat cream for the production of puff pastry and products made from it. New Zealand butter samples produced by the method of churning cream in continuous butter makers and often used in the manufacture of puff pastry products in cafes served as control samples. Typical samples of Russian-made butter produced by the method of converting high-fat cream were used as experimental samples. Based on the research results, differences in the fatty acid composition of the studied butter samples were established in terms of the content of lauric, myristic, palmitic and linoleic acids. It was revealed that in the range from 20 to 30 °, i. e., in conditions under which the dough rolling and proofing operations take place, the experimental butter samples were characterized by relatively higher levels of solid triglycerides and hardness. This caused a decrease in the plasticity of the butter and its ability to roll out. Based on comparative studies of the structural and mechanical properties of the butter, it was established that in order to improve its characteristics necessary for uniform rolling of the butter layer, it is advisable to lower the hardness value while simultaneously increasing the value of the butter structure recoverability. It has been concluded that such characteristics for butter produced by the method of convert- ing high-fat cream can be obtained by adjusting the composition of the butter and its production modes, and a decrease in the solid triglycerides can be achieved by active influence of the diet of animals in different periods of the year.

Optimising polyurethane/CNTs piezoresistive pressure sensors by varying the modulus of the polymer matrix

Varying the elastic modulus of the thermoplastic polyurethane (TPU) matrix on the sensing behaviour of pressure sensors made from TPU/carbon nanotubes (CNTs) elastomeric composites was studied. Piezoresistive sensors have a wide range of applications in wearable devices such as smart shoe insoles. Compounds were prepared using different grades of TPU with various levels of hardness, ranging from 37 to 98 Shore A, using a melt extrusion technique. The percolation threshold of CNTs was about 2 wt%, with the best sensing performance being at a weight fraction above this, at 2.5 wt% CNTs. The elastomeric nanocomposites were characterised for their pressure sensing behaviour. Sensors were constructed by assembling the composite films and an interdigitated silver electrode, and their sensing properties were characterised using a voltage divider circuit under cyclical loading. This work evaluates the reference resistor-dependency, test frequency-dependency and the long-term stability under cyclic loading. The results indicate that the polymer modulus has a significant impact on the sensing performance and piezoresistive hysteresis value for each sensor. As the modulus increases, the hysteresis value between loading-unloading is reduced and the sensor displays a much more stable response during longer cyclical loading tests.

Phosphorus-nitrogen synergistic transparent UV-curable coatings to enhance the flame retardancy of polycarbonate

There is an urgent demand for flame retardant treatment of polycarbonate (PC) with as little adverse impact on the inherent advantages of PC as possible, especially the high transparency. Herein, a flame-retardant coating with high transparency was successfully prepared on PC via a two-step ultraviolet-curing (UV-curing) process with tri(acryloyloxyethyl) phosphate and melamine acrylate resin. All the coated PC composites showed high transparency and excellent pencil hardness levels (6H). The coupling effect of the combustion behaviours of the UV-cured coatings and the PC substrates was particularly investigated to give insight into a holistic picture of the combustion of the coated composite systems. Specifically, all the composite UV-cured coating samples (T2M1, T1M1 and T1M2) formed highly expanded char with honeycomb-like inner structure due to the phosphorus-nitrogen synergistic effects, which could efficiently suppress mass and heat transfer, thereby protecting the PC substrates from the harsh conditions of high temperature and realizing significantly enhanced flame retardancy of the PC samples. Improving the thermal and mechanical stabilities of the intumescent carbon layers may be a practical strategy to achieve further improved flame retardant capabilities of the PC samples. Additionally, the PC-T2M1 composite exhibited the optimal flame retardant effect, realizing significantly suppressed heat release in the cone calorimeter tests, reaching UL94 V-0 rating and showing long fire resistance time thanks to the intumescent char. The UV-cured coating method introduced in this work had great potential in spawning new strategies for designing advanced flame retardant coatings for polymer substrates.

The Tensile Properties of Functionally Graded Materials in MSLA 3D Printing as a Function of Exposure Time

Functionally graded additive manufacturing (FGAM) emerged from the combination of Functionally Graded Materials into additive manufacturing. This work involved the production of FGAM specimens to alter the characteristics of both the outer and inner zones of tensile specimens. This was achieved by adjusting the exposure time without additional costs or equipment. During the assessment, the tensile specimen was separated into three zones. The exterior layers were initially created with a 3-second exposure time, followed by the interior layers with a 15-second exposure time. Then, the process was reversed, with the outer layers exposed for 15 seconds and the inner layers exposed for 3 seconds. Subsequently, all layers were generated using exposure durations of 3 seconds and 15 seconds, respectively, without any alterations, resulting in a total of 4 distinct samples. The hardness and tensile tests were conducted on all specimens, both with and without post-curing, in order to assess the impact of post-curing. The outcomes indicate that the levels of hardness and maximum tensile strength rise as the final curing process progresses, but the elongation capability diminishes. The highest ultimate tensile strength, achieved after 15 seconds of exposure time with post cure, was measured at 46.46 ± 0.9 MPa. The green FGAM specimens have a greater ultimate tensile strength (35.85 ± 0.4 MPa) when created with an exposure time of 15-3-15 s. However, the specimen produced with an exposure time of 3-15-3 s demonstrates a higher ultimate tensile strength (38.77 ± 0.7 MPa) following post curing.

Fretting wear behavior on LPBF processed AlSi10Mg alloy for different heat treatment conditions

To widen the industrial application of additively manufactured (AM) parts, the study of fretting wear behavior is essential, as it ensures the safety and reliability that drive innovation in design and materials. This study explores the fretting wear behavior of the as-built and heat-treated state of AlSi10Mg alloy fabricated, viz., laser powder bed fusion (LPBF). Initially, the as-built and T5, T6, and stress-relieved (SR) heat-treated samples were examined using scanning electron microscopy (SEM) to gain insights into the microstructural changes. The as-built samples exhibited a higher hardness level (135 HV) primarily due to the presence of very fine microstructure of the α-Al cellular matrix with embedded Si. The α-Al cellular structure dissolved with various heat treatments, and Si particles coarsened. The hardness decreased to 85, 79, and 67 HV for the T5, T6, and SR conditions, respectively. Subsequently, fretting tests were conducted on the samples, applying various normal loads of 10, 50, and 100 N. Further, the samples were characterized by the coefficient of friction (COF), worn surface morphology, and wear volume loss. The investigation showed that the as-built material showed less wear volume loss under all loading conditions than the heat-treated conditions. Furthermore, the T5 heat treated sample had a lower wear volume when compared to the T6 and SR heat-treated samples. The heat-treated sample exhibits compressive stress, whereas the LPBF processed, the as-built sample shows tensile stress.

Germination effects on the physicochemical properties and sensory profiles of velvet bean (Mucuna pruriens) and soybean tempe.

Previous studies have shown that the velvet bean, an indigenous legume in Indonesia, possesses high protein content and bioactive compounds. However, the utilization of velvet beans in tempe production remains underexplored. This study aims to address this research gap by investigating the physicochemical properties and sensory profiles of tempe made from velvet beans, both individually and in combination with soybean. The study involved the production of tempe using germinated and non-germinated velvet bean, soybean, and a soy-velvet bean combination (61:39% ratio). Physicochemical analyses, including hardness, firmness, colour, antioxidant capacity, proximate, pH, and titratable acidity, were conducted. Hedonic rating and Check-All-That-Apply (CATA) tests were also performed to assess the sensory attributes of fresh and fried tempe. Germination treatment of velvet bean resulted in tempe with reduced hardness, firmness, antioxidant capacity, and pH levels compared to non-germinated velvet bean tempe. However, velvet bean tempe exhibited a darker colour, higher antioxidant capacity, higher pH levels, and lower titratable acidity compared to soybean tempe and soy-velvet bean combination tempe. The protein content in velvet bean tempe was found to be below the required threshold of 15%. Hedonic rating tests revealed that fresh and fried velvet bean tempe received lower scores than other samples. CATA tests identified specific sensory attributes essential for fresh and fried tempe, including beany aroma, white colour, nutty aroma, golden brown colour, solid and crunchy texture, umami taste, and nutty aftertaste. These findings provide valuable insights into the potential applications of velvet beans in tempe production and emphasize the significance of considering germination as a factor affecting the quality and sensory attributes of tempe.

ОЦІНКА НАПРУЖЕНОГО СТАНУ РОБОЧОГО ШАРУ ВАЛКІВ КОЕРЦИТИМЕТРИЧНИМ ЕКСПРЕС-МЕТОДОМ

The purpose of the work is the problem of researching the influence of chemical composition and structure on the indicators of operational stability of centrifugal two-layer rolling rolls made of high chromium cast iron by the coercimetric express method. In order to ensure the achievement of this goal, the following tasks were set and solved: conducting an analysis of the causes of the destruction of the surface layer of rolls; building a mathematical model for studying the influence of the chemical composition and structure of cast iron on the level of hardness and coercive force; using the coercimetric method to analyze the quality of rolled rolls. Conclusions. Forecasting the behavior of the rolls during operation is inextricably linked to the analysis of the main factors on which the level of properties and operational stability of the working layer depend. The properties of high-chromium alloys are closely related to the type of phases formed and their ratio. The amount of residual austenite and martensite in the structure of the alloy has the greatest influence on the properties of the alloy (in the studied interval of changes in the proportion of phases). The operational layer of two-layer high-chromium rolls is characterized by a high level of residual stresses. Exceeding the permissible level of stresses or their unfavorable distribution can cause premature destruction during the operation of the roll. With the help of the coercimetric express method, it is possible to solve a fairly wide range of tasks of quality control of rolls, related to the determination of the level and distribution of residual stresses in the working layer of the rolls. This is because the intensity of the process of formation of thermal cracks under conditions of thermo-cyclic loading largely depends on the level of residual compressive stresses. Too high a level of stresses or their unfavorable distribution can cause premature destruction of the working layer of the roll, because the typical type of destruction due to an unbalanced distribution of stresses is cracking. A local increase in the level of coercive force can be the basis of the prediction of crack formation.

Phase composition, structure and properties of B<sub>4</sub>C–TiB<sub>2</sub> ceramics produced by hot pressing

Composite ceramic materials based on B4C with the addition of TiB2 in amounts of 0, 10, 20, 25 and 30 mol. % have been studied. Titanium diboride was synthesized from TiO2 powder and nanofibrous carbon using the boron carbide method in an induction furnace at 1650 °C in an argon atmosphere. The samples were produced by hot pressing at 2100 °C and 25 MPa in an argon environment. The phase composition was determined, and the apparent density and open porosity of the experimental materials were measured. The microstructure was assessed using optical and scanning electron microscopy. The investigations revealed that an increase in the TiB2 content reduces the open porosity while concurrently enhancing the relative density of the boron carbide ceramics. For a sample containing 30 mol. % TiB2 , the open porosity and relative theoretical density were 1.6 and 99 %, respectively. Using XRD and XRS analyses established that the synthesized materials are comprised of two phases: B4C and TiB2 . The average grain size of TiB2 was 0.85 ± 0.02 µm for the sample with 10 mol. % TiB2 and 8.90 ± 0.25 µm for the material with 30 mol. % TiB2 . It was found that at higher TiB2 concentrations, large clusters of grains are formed. The destruction pattern of B4C grains is intragranular, while TiB2 grains are characterized by intergranular destruction. For a sample containing 30 mol. % TiB2 , the fracture toughness was 4.97 ± 0.23 MPa∙m0.5, and the hardness was 3320 ± 120 HV0.5 . Therefore, the addition of TiB2 at these specified concentrations facilitated a 30 % enhancement in fracture toughness relative to single-phase B4C while preserving a high level of hardness.

Decision Intelligence-Based Predictive Modelling of Hard Rock Pillar Stability Using K-Nearest Neighbour Coupled with Grey Wolf Optimization Algorithm

Pillar stability is of paramount importance in ensuring the safety of underground rock engineering structures. The stability of pillars directly influences the structural integrity of the mine and mitigates the risk of collapses or accidents. Therefore, assessing pillar stability is crucial for safe, productive, reliable, and profitable underground mining engineering processes. This study developed the application of decision intelligence-based predictive modelling of hard rock pillar stability in underground engineering structures using K-Nearest Neighbour coupled with the grey wolf optimization algorithm (KNN-GWO). Initially, a substantial dataset consisting of 236 different pillar cases was collected from seven underground hard rock mining engineering projects. This dataset was gathered by considering five significant input variables, namely pillar width, pillar height, pillar width/height ratio, uniaxial compressive strength, and average pillar stress. Secondly, the original hard rock pillar stability level has been classified into three types: failed, unstable, and stable, based on the pillar’s instability mechanism and failure process. Thirdly, several visual relationships were established in order to ascertain the correlation between input variables and the corresponding pillar stability level. Fourthly, the entire pillar database was randomly divided into a training dataset and testing dataset with a 70:30 sampling method. Moreover, the (KNN-GWO) model was developed to predict the stability of pillars in hard rock mining. Lastly, the performance of the suggested predictive model was evaluated using accuracy, precision, recall, F1-score, and a confusion matrix. The findings of the proposed model offer a superior benchmark for accurately predicting the stability of hard rock pillars. Therefore, it is recommended to employ decision intelligence models in mining engineering in order to effectively prioritise safety measures and improve the efficiency of operational processes, risk management, and decision-making related to underground engineering structures.

Trusting My Predictions: On the Value of Instance-Level Analysis

Machine Learning solutions have spread along many domains, including critical applications. The development of such models usually relies on a dataset containing labeled data. This dataset is then split into training and test sets and the accuracy of the models in replicating the test labels is assessed. This process is often iterated in a cross-validation procedure for obtaining average performance estimates. But is the average of the predictive performance on test sets enough for assessing the trustfulness of a Machine Learning model? This paper discusses the importance of knowing which individual observations of a dataset are more challenging than others and how this characteristic can be measured and used in order to improve classification performance and trustfulness. A set of strategies for measuring the hardness level of the instances of a dataset is surveyed and a Python package containing their implementation is provided.

Drinking water quality in Cooch Behar Municipality, West Bengal, India: Assessment using WQI and public perception

AbstractEffective assessment and management of groundwater quality are essential for safeguarding the integrity of freshwater resources. Cooch Behar Municipality of West Bengal has been chosen for the present study due to its reliance primarily on groundwater for drinking water. The study focuses on assessing groundwater quality in the study area, a planned city with a long history of urbanization. The primary objective is to analyze various parameters relevant to drinking water and compute the Water Quality Index (WQI) with the residents' perception. Forty water samples were collected from Cooch Behar Municipality's Public Health Engineering (PHE) department, encompassing all 20 wards. Each ward provided one sample from a Deep Tube Well (DTW) and a Shallow Tube Well (STW). EC, Fe, TH, Mn, pH, TDS, Turbidity, Ca, and Mg levels were determined using standard instruments and methods, and analyzed geospatial techniques and statistical methods were employed. Results revealed concerning levels of manganese (Mn) and total hardness (TH), exceeding permissible limits in 82.5% and 75% of samples, respectively. While some parameters remained within acceptable limits, computed WQI values ranged from 63.28 to 162.67, indicating significant overall water quality concerns. Alarmingly, 45% of samples were unsuitable for drinking, with an additional 40% classified as very poor. Notably, demographic factors such as household income and education level correlated with perceptions of poor water quality. Policy implications suggest the urgent need for a well‐structured management system to address these findings and ensure safe drinking water for residents.