scholarly journals Integrating the Theory of Sampling into Underground Mine Grade Control Strategies: Case Studies from Gold Operations

Minerals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 238
Author(s):  
Dominy ◽  
Glass ◽  
O’Connor ◽  
Lam ◽  
Purevgerel

Grade control aims to deliver adequately defined tonnes of ore to the process plant. The foundation of any grade control programme is collecting high-quality samples within a geological context. The requirement for quality samples has long been recognised, in that these should be representative and fit-for-purpose. Correct application of the Theory of Sampling reduces sampling errors across the grade control process, in which errors can propagate from sample collection through sample preparation to assay results. This contribution presents three case studies which are based on coarse gold-dominated orebodies. These illustrate the challenges and potential solutions to achieve representative sampling and build on the content of a previous publication. Solutions ranging from bulk samples processed through a plant to whole-core sampling and assaying using bulk leaching, are discussed. These approaches account for the nature of the mineralisation, where extreme gold particle-clustering effects render the analysis of small-scale samples highly unrepresentative. Furthermore, the analysis of chip samples, which generally yield a positive bias due to over-sampling of quartz vein material, is discussed.

2015 ◽  
Vol 98 (2) ◽  
pp. 265-268 ◽  
Author(s):  
Charles A Ramsey ◽  
Claas Wagner

Abstract The concept of Sample Quality Criteria (SQC) is the initial step in the scientific approach to representative sampling. It includes the establishment of sampling objectives, Decision Unit (DU), and confidence. Once fully defined, these criteria serve as input, in addition to material properties, to the Theory of Sampling for developing a representative sampling protocol. The first component of the SQC establishes these questions: What is the analyte(s) of concern? What is the concentration level of interest of the analyte(s)? How will inference(s) be made from the analytical data to the DU? The second component ofthe SQC establishes the DU, i.e., the scale at whichdecisions are to be made. On a large scale, a DU could be a ship or rail car; examples for small-scale DUs are individual beans, seeds, or kernels. A well-defined DU is critical because it defines the spatialand temporal boundaries of sample collection. SQC are not limited to a single DU; they can also include multiple DUs. The third SQC component, the confidence, establishes the desired probability that a correct inference (decision) can be made. The confidence level should typically correlate to the potential consequences of an incorrect decision (e.g., health or economic). The magnitude of combined errors in the sampling, sample processing and analytical protocols determines the likelihood of an incorrect decision. Thus, controlling error to a greater extent increases the probability of a correct decision. The required confidence level directly affects the sampling effort and QC measures.


Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1179
Author(s):  
Camilo Wilches ◽  
Maik Vaske ◽  
Kilian Hartmann ◽  
Michael Nelles

This paper describes an automatic sampling system for anaerobic reactors that allows taking representative samples following the guidelines of Gy’s (1998) theory of sampling. Due to the high heterogeneity degree in a digester the sampling errors are larger than the analysis error, making representative sampling a prerequisite for successful process control. In our system, samples are automatically processed, generating a higher density of data and avoiding human error by sample manipulation. The combination of a representative sampling system with a commercial automate titration unit generates a robust online monitoring system for biogas plants. The system was successfully implemented in an operating biogas plant to control a feeding-on-demand biogas system.


Minerals ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 232 ◽  
Author(s):  
Simon Dominy ◽  
Hylke Glass ◽  
Louisa O’Connor ◽  
Chloe Lam ◽  
Saranchimeg Purevgerel ◽  
...  

SOIL ◽  
2015 ◽  
Vol 1 (2) ◽  
pp. 695-705 ◽  
Author(s):  
Z. Kardanpour ◽  
O. S. Jacobsen ◽  
K. H. Esbensen

Abstract. This study is a contribution to development of a heterogeneity characterization facility for "next-generation" soil sampling aimed, for example, at more realistic and controllable pesticide variability in laboratory pots in experimental environmental contaminant assessment. The role of soil heterogeneity in quantification of a set of exemplar parameters is described, including a brief background on how heterogeneity affects sampling/monitoring procedures in environmental pollutant studies. The theory of sampling (TOS) and variographic analysis has been applied to develop a more general fit-for-purpose soil heterogeneity characterization approach. All parameters were assessed in large-scale transect (1–100 m) vs. small-scale (0.1–0.5 m) replication sampling point variability. Variographic profiles of experimental analytical results from a specific well-mixed soil type show that it is essential to sample at locations with less than a 2.5 m distance interval to benefit from spatial auto-correlation and thereby avoid unnecessary, inflated compositional variation in experimental pots; this range is an inherent characteristic of the soil heterogeneity and will differ among other soils types. This study has a significant carrying-over potential for related research areas, e.g. soil science, contamination studies, and environmental monitoring and environmental chemistry.


2020 ◽  
Author(s):  
Sicong Liu ◽  
Jonathan Folstein ◽  
Lawrence Gregory Appelbaum ◽  
Gershon Tenenbaum

Although the unwanted intrusive thoughts (UITs) exist widely in human beings and show similar characteristics between clinical and nonclinical forms, its control process remains unclear. Thoughts of choking under pressure, particularly among high-achieving athletes, represent a meaningful UIT type due to their psychological and performance-related impact. Taking a dynamic view of UIT control process, this study tested the effect of thought-control strategies among sub-elite to elite athletes, applied to individualized choking thoughts. Ninety athletes recollected recent athletic choking experiences prior to being randomized into one of three thought control interventions using strategies of either acceptance, passive monitoring (control), or suppression. To control for individual differences, athletes’ working memory capacity was measured and modeled as a covariate at baseline. The activation of choking thoughts during and after the intervention was gauged through multiple measurement approaches including conscious presence in mind, priming, and event-related potentials (P3b and N400 amplitudes). Results indicated that, relative to the control, suppression led to enhanced priming and reduced conscious presence of choking thoughts, whereas acceptance resulted in an opposite pattern of reduced priming and increased conscious presence of choking thoughts. In addition, thought-related stimuli elicited less negative-going N400 amplitudes and more positive-going P3b amplitudes than control stimuli. These findings advance understandings of the control mechanism underpinning UITs, and generate applied implications regarding UIT control in high-risk populations such as those with athletic expertise.


2021 ◽  
pp. 136700692110231
Author(s):  
Mary Walworth ◽  
Amy Dewar ◽  
Thomas Ennever ◽  
Lana Takau ◽  
Iveth Rodriguez

Each of the 65 inhabited islands of Vanuatu hosts its own unique linguistic environment in which varying degrees of multilingualism are found. This paper defines various types of small-scale multilingual settings in Vanuatu and explores what sociohistorical factors have led to them. This paper is based on first-hand observations and primary data collected by the authors in four locations in the Pacific Island nation of Vanuatu since 2016: two neighboring villages of Emae Island (Makatu and Tongamea), North Malekula, and on Maewo Island. The assessments of multilingualism in these examples from Vanuatu were qualitative, based on observations of sociolinguistic practices in each of these areas, as well as data from language history and language use surveys carried out in each place. Through defining and comparing the types of multilingualism present in the four case studies, we identify patterns in the social and historical processes that lead to various kinds of multilingualism: (a) interaction of linguistic and sociocultural identities and (b) mobility of both individuals and entire speech communities. The examples described in this paper are used to highlight the diversity of multilingualism found in Vanuatu and to explore how their differing linguistic environments and histories have contributed to their varying degrees of multilingualism. This paper makes an original contribution to knowledge about the small-scale multilingual situations in Vanuatu, offering descriptions of previously undocumented and endangered multilingual environments. Through an examination of the sociocultural motivations for multilingualism, alongside historical migrations of speaker groups and marked sociolinguistic identities, this paper contributes to research on why and how small-scale multilingualism can develop. Furthermore, this paper provides the foundation for future, more rigorous investigations into the small-scale multilingual situations of this highly understudied region.


Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-18 ◽  
Author(s):  
Guolian Hou ◽  
Linjuan Gong ◽  
Xiaoyan Dai ◽  
Mengyi Wang ◽  
Congzhi Huang

The complex characteristics of the gas turbine in a combined cycle unit have brought great difficulties in its control process. Meanwhile, the increasing emphasis on the efficiency, safety, and cleanliness of the power generation process also makes it significantly important to put forward advanced control strategies to satisfy the desired control demands of the gas turbine system. Therefore, aiming at higher control performance of the gas turbine in the gas-steam combined cycle process, a novel fuzzy model predictive control (FMPC) strategy based on the fuzzy selection mechanism and simultaneous heat transfer search (SHTS) algorithm is presented in this paper. The objective function of rolling optimization in this novel FMPC consists of two parts which represent the state optimization and output optimization. In the weight coefficient selection of those two parts, the fuzzy selection mechanism is introduced to overcome the uncertainties existing in the system. Furthermore, on account of the rapidity of the control process, the SHTS algorithm is used to solve the optimization problem rather than the traditional quadratic programming method. The validity of the proposed method is confirmed through simulation experiments of the gas turbine in a combined power plant. The simulation results demonstrate the remarkable superiorities of the adopted algorithm with higher control precision and stronger disturbance rejection ability as well as less optimization time.


2016 ◽  
Vol 7 (2) ◽  
pp. 117-147 ◽  
Author(s):  
Ruth Swanwick ◽  
Sue Wright ◽  
Jackie Salter

AbstractThis paper examines the meaning of plurality and diversity with respect to deaf children’s sign and spoken language exposure and repertoire within a super diverse context. Data is drawn from a small-scale project that took place in the North of England in a Local Authority (LA) site for deaf education. The project documented the language landscape of this site and gathered five individual case studies of deaf children to examine their plural and diverse language practices at home and at school. Analysis of the language landscape and case studies from this context is undertaken in order to define and exemplify deaf children’s language plurality and diversity in terms of context and individual experience. Concepts of repertoire are explored with particular reference to the unique type of translanguaging that the plural use of sign and spoken languages affords. Implications of these preliminary insights are discussed in terms of the development of methodologies that are sensitive to the particular translanguaging practices of deaf children, and approaches to pedagogy that are appropriately nuanced and responsive to deaf children’s language plurality and diversity.


Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7485
Author(s):  
Cláudio de Andrade Lima ◽  
James Cale ◽  
Kamran Eftekhari Shahroudi

The aerospace industry is increasingly transitioning from hydraulic and pneumatic drives to power-electronic based drive systems for reduced weight and maintenance. Electromechanical thrust reverse actuation systems (EM-TRAS) are currently being considered as a replacement for mechanical based TRAS for future aircraft. An EM-TRAS consists of one or more power-electronic drives, electrical motors, and gear-trains that extend/retract mechanical members to produce a drag force that decelerates the aircraft upon landing. The use of a single (“central”) power electronic converter to simultaneously control a set of parallel induction machines is a potentially inexpensive and robust method for implementing EM-TRAS. However, because the electrical motors may experience different shaft torques—arising from differences in wind forces and a flexible nacelle—a method to implement rotor position synchronization in central-converter multi-motor (CCMM) architectures is needed. This paper introduces a novel method for achieving position synchronization within CCMM architecture by using closed-loop feedback of variable stator resistances in parallel induction machines. The feasibility of the method is demonstrated in several case studies using electromagnetic transient simulation on a set of parallel induction machines experiencing different load torque conditions, with the central converter implementing both voltage-based and current-based primary control strategies. The key result of the paper is that the CCMM architecture with proposed feedback control strategy is shown in these case studies to dynamically drive the position synchronization error to zero. The initial findings indicate that the CCMM architecture with induction motors may be a viable option for implementing EM-TRAS in future aircraft.


Author(s):  
Jane Abbiss ◽  
Eline Vanassche

A review of the field of practice-focused research in Initial Teacher Education (ITE) reveals four broad genres of qualitative research: case studies of teacher education programs and developments; research into student teacher experience and learning; inquiry into teacher educators’ own learning, identity, and beliefs; and conceptual or theory-building research. This is an eclectic field that is defined by variation in methodologies rather than by a few clearly identifiable research approaches. What practice-focused research in ITE has in common, though, is a desire on the behalf of teacher educator researchers to understand the complexity of teacher education and contribute to shifts in practice, for the benefit of student teachers and, ultimately, for learners in schools and early childhood education. In this endeavor, teacher educator researchers are presented with a challenge to achieve a balance between goals of local relevance and making a theoretical contribution to the broader field. This is a persistent tension. Notwithstanding the capacity for practice-focused research to achieve a stronger balance and greater relevance beyond the local, key contributions of practice-focused research in ITE include: highlighting the importance of context, questioning what might be understood by “improvement” in teacher education and schooling, and pushing back against research power structures that undervalue practice-focused research. Drawing on a painting metaphor, each genre represents a collection of sketches of practice-focused research in ITE that together provide the viewer with an overview of the field. However, these genres are not mutually exclusive categories as any particular research study (or sketch) might be placed within one or more groupings; for example, inquiry into teacher educators’ own learning often also includes attention to student teachers’ experiences and case studies of teacher education initiatives inevitably draw on theory to frame the research and make sense of findings. Also, overviewing the field and identifying relevant research is not as simple as it might first appear, given challenges in identifying research undertaken by teacher educators, differences in the positioning of teacher educators within different educational systems, and privileging of American (US) views of teacher education in published research, which was counteracted in a small way in this review by explicitly including voices located outside this dominant setting. Examples of different types of qualitative research projects illustrate issues in teacher education that matter to teacher educator researchers globally and locally and how they have sought to use a variety of methodologies to understand them. The examples also show how teacher educators themselves define what is important in teacher education research, often through small-scale studies of context-specific teacher education problems and practices, and how there is value in “smaller story” research that supports understanding of both universals and particularities along with the grand narratives of teacher education.


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