Closure Criteria Research Articles

Assessment towards mine closure within IPPKH (Permit of Using Forest Area): Study case of a coal mining Licence at Taba Penanjung, Central Bengkulu, Indonesia

Mine closure is an inevitable event within the mining business; however, post-mining land use is always intended for further beneficial use for further development, mostly to reach a landscape that sustain and give further benefit after the mining operation has finished. One of the mining licence schemes is the permit of using forest area (IPPKH). One of the mining companies at Central Bengkulu has experienced phasing out production towards mine closure. The query is how the mining-affected area can be reclaimed and rehabilitated to become a healthy forest ecosystem. This study aimed to assess the closure criteria based on mine closure regulations. Data were collected from stages of operation according to assessment of mine closure, particularly from rehabilitation sites. The results indicate that rehabilitation sites showed significant re-vegetation of mining-affected areas (dumping area and in-pit backfilling area) and progression to become forested areas, as depicted by structural development of re-forested sites. The overall score is within the suitable range of “good post-mine closure” but require examination and supervision if after mining, the areas are expected to have economic value.

Charter School Closing Inequities: Do automatic closure laws target Black charter entrepreneurs and Black students?

ABSTRACT In some states, charter schools must meet inflexible, standardized performance standards to survive. Through lenses informed by Critical Race Theory, we hypothesize that charters that were established by African Americans and those which serve more African American students are more likely to close, and that state-imposed standardized closure rules exacerbate these inequities. We find that 31.9% charter schools serving predominantly African American populations close, compared to 13.7% of those serving other populations. Similarly, 31.1% of charter schools started by African Americans close compared to just 14.6% of other charters. Moreover, automatic standardized closure criteria dramatically amplify the racially disparate effects.

Stream Suspended Mud as an Indicator of Post-Mining Landform Stability in Tropical Northern Australia

Mining can cause environmental disturbances and thus mined lands must be managed properly to avoid detrimental impacts in the future. They should be rehabilitated in such a way that post mining landforms behave similarly as the surrounding stable undisturbed areas. A challenge for government regulators and mine operators is setting closure criteria for assessment of the stability of the elevated post-mining landforms. Stability of a landform is often measured by the number and incision depth of gullies. This can assess mass stability and bulk movement of coarse material. However, there is a need for a more sensitive approach to assess catchment disturbances using the concept of waves of fine suspended sediment and thus determine the dynamics of recovery of a post mining landform. A more environmentally meaningful approach would be to assess the fine suspended sediment (FSS, silt + clay (0.45 µm < diameter < 63 µm)) leaving the system and entering downstream waterways. We propose assessing stability through relationships between rainfall event loads of FSS and event discharge (Q) in receiving streams. This study used an innovative approach where, instead of using instantaneous FSS concentration, it used total FSS load in waves of sediment driven through the system by rainfall runoff events. High resolution stream monitoring data from 2004 to 2015 in Gulungul and Magela Creeks, Northern Territory, Australia, were used to develop a relationship between sediment wave and event discharge, ∑FSS α f(Q). These creeks are adjacent to and receive runoff from Ranger Mine. In 2008, a 10 ha elevated waste rock landform was constructed and instrumented in the Gulungul Creek catchment. The earthworks required to build the landform created a considerable disturbance in the catchment, making a large volume of disturbed soil and substrate material available for erosion. Between 2008 and 2010, in the first two wet seasons immediately after construction, the downstream monitoring site on Gulungul Creek showed elevated FSS wave loads relative to discharge, compared with the upstream site. From 2010 onwards, the FSS loads relative to Q were no longer elevated. This was due to the establishment of vegetation on the site and loose fine sediment being trapped by vegetation. Large scale disturbance associated with mining and rehabilitation of elevated landforms causes elevated FSS loads in receiving streams. The predicted FSS loads for the stream as per the relationships between FSS and event discharge may not show a 1:1 relation with the observed loads for respective gauging stations. When downstream monitoring shows that FSS wave loads relative to rainfall runoff event discharge reduce back to pre-construction catchment levels, it will indicate that the landform is approaching equilibrium. This approach to assess landform stability will increase the sensitivity of assessing post-mining landform recovery and assist rehabilitation engineers to heal the land and benefit owners of the land to whom it is bestowed after rehabilitation.

SEX DIFFERENCES IN PFO CLOSURE PATIENTS

BACKGROUND Although sex differences have been emphasized in stroke and congenital heart disease, there has been limited investigation on their role in patent foramen ovale (PFO). In fact, key guidelines on the management of PFO do not comment on sex or gender specific considerations in characteristics or outcomes of patients. We aimed to explore differences by sex in baseline profiles, procedural characteristics, and short-term outcomes of patients undergoing transcatheter PFO closure. METHODS AND RESULTS Data of adult patients undergoing transcatheter PFO closure at the Toronto General Hospital from 1997 to 2017 was retrospectively analyzed. Baseline information included demographic characteristics, medical history, diagnostic and procedural information, and periprocedural complications. Post-closure outcomes were captured at index hospitalization and during the first follow-up visit. From 1,032 patients in the cohort sample, 80.7% underwent closure for cryptogenic stroke and 44.8% (n=462) were females. We observed significant sex-related differences at baseline; females were younger, less likely to have a history of smoking, and less likely to have cardiovascular risk factors such as dyslipidemia and coronary artery disease (p < 0.05). No differences were observed in procedural and in-hospital outcomes between sexes. At the first follow-up, recurrent cerebrovascular events were reported in 1.5% and 1.9% of patients in the ‘cryptogenic stroke/TIA indications’ and ‘other indications’ groups respectively, with no significant differences by sex. There were significant sex differences between some symptom presentation both pre- and post-closure, with females more likely to present with migraine symptoms at both timepoints (p < 0.05). CONCLUSION Although no differences in procedural and short-term outcomes between males and females undergoing transcatheter PFO closure were observed, significant baseline differences in characteristics may justify the need for sex-specific risk assessment and PFO closure criteria. There is a critical need for long-term, systematic studies to understand sex and gender differences in the PFO population. Although sex differences have been emphasized in stroke and congenital heart disease, there has been limited investigation on their role in patent foramen ovale (PFO). In fact, key guidelines on the management of PFO do not comment on sex or gender specific considerations in characteristics or outcomes of patients. We aimed to explore differences by sex in baseline profiles, procedural characteristics, and short-term outcomes of patients undergoing transcatheter PFO closure. Data of adult patients undergoing transcatheter PFO closure at the Toronto General Hospital from 1997 to 2017 was retrospectively analyzed. Baseline information included demographic characteristics, medical history, diagnostic and procedural information, and periprocedural complications. Post-closure outcomes were captured at index hospitalization and during the first follow-up visit. From 1,032 patients in the cohort sample, 80.7% underwent closure for cryptogenic stroke and 44.8% (n=462) were females. We observed significant sex-related differences at baseline; females were younger, less likely to have a history of smoking, and less likely to have cardiovascular risk factors such as dyslipidemia and coronary artery disease (p < 0.05). No differences were observed in procedural and in-hospital outcomes between sexes. At the first follow-up, recurrent cerebrovascular events were reported in 1.5% and 1.9% of patients in the ‘cryptogenic stroke/TIA indications’ and ‘other indications’ groups respectively, with no significant differences by sex. There were significant sex differences between some symptom presentation both pre- and post-closure, with females more likely to present with migraine symptoms at both timepoints (p < 0.05). Although no differences in procedural and short-term outcomes between males and females undergoing transcatheter PFO closure were observed, significant baseline differences in characteristics may justify the need for sex-specific risk assessment and PFO closure criteria. There is a critical need for long-term, systematic studies to understand sex and gender differences in the PFO population.

Learning and Challenges of Social Action: Systematization of the Experience of the School of Psychology, University of Costa Rica

Social Action, a Latin America Public University pillar, has been developed from different models. As this theoretical and historical framework is taken as a reference, the article presents a critical systematization of the Social Action experience of the School of Psychology at the University of Costa Rica during the period 2000-2015. The research considered the systematization of experiences as a methodological approach from which a critical interpretation of the analyzed process was made. Documentary sources were consulted, and 14 interviews were conducted; these techniques allowed the construction of a timeline. Subsequently, a workshop was held, and it identified the 14 discussion axes analyzed in this article; they include political, academic, and ethical aspects of Social Action. It is concluded that Social Action had an improvement since it was defined as a priority, and a political position guiding the work was established. The main identified challenges were the dissemination, the definition of project closure criteria, the systematization and evaluation, as well as the construction of a project articulation strategy with each other and with other substantive activities of the university (teaching and research).

Establishing effective mine closure criteria for river diversion channels

Rivers are frequently relocated into new artificial channels because of mining activity. Current mine closure criteria do not adequately address river diversion practices causing an absence of guidelines and management of river diversion channels post-mining. During mine operation, river diversion channels are designed to convey large floods with an emphasis on channel stability and effective flow conveyance. After mine closure, it is now important for river diversion channels to behave more like a natural river system and imitate the characteristics of surrounding watercourses. Developing adequate closure criteria for river diversion channels is both a geomorphic and river restoration challenge. River diversion channels frequently perform poorly by creating problems during mine operation and can cause subsequent long-term legacy issues. This paper identifies the geomorphic and environmental issues of defining and implementing mine closure criteria for river diversion channels and suggests ways to improve current practices. Significant difficulties include the competing objectives of short-term channel stability and the long-term inclusion of environmentally favourable natural features, the difficulties of adequate hydrological prediction, limited understanding of regionally appropriate river characteristics and competing objectives from varied stakeholders. Effective river diversion closure criteria should include extensive hydrological, geomorphic, and ecological planning with long-term guidelines established early in the mine planning process. Lastly, river diversion closure criteria should undergo continuous revision as our understanding of river restoration develops.

Measuring savanna woody cover at scale to inform ecosystem restoration

AbstractThe maturity of remote sensing and ecosystem restoration science provides new opportunities to monitor and assess ecosystem indicators at finer resolutions and at suitable scales. A key link in joining these fields is creating a framework to apply these rich datasets to ecosystem restoration projects. Savanna woodland ecosystems have discontinuous tree cover that is an important, but potentially highly variable, structural component of these ecosystems. Woody cover in savannas is also well suited to being measured with remote sensing techniques. We extracted woody cover from a 66‐yr time series of aerial imagery covering 1718 ha of mesic savanna ecosystem in northern Australia, adjacent to the Ranger uranium mine and encompassing portions of Kakadu National Park. This ecosystem is proposed as a reference ecosystem that may be used to comparatively assess and monitor restoration trajectories of the mine site in the coming decades. The spatiotemporal patterns of change in woody cover were assessed at spatial extents similar to the mine site. We were able to construct a robust distribution of canopy cover values and associated spatial heterogeneity that can be used to set closure criteria, inform restoration trajectories, and guide monitoring activities for the restored mine site.

Incorporating Indigenous knowledge in mine closure: Ranger Uranium Mine

The Ranger Project Area, located on the lands of the Mirarr clan, is surrounded by Kakadu National Park. After 40 years of uranium production at Ranger Mine, rehabilitation has begun, with a commitment that the land will be restored to a standard such that it could be incorporated into Kakadu National Park. Historically, mine closure has not been done well in the Northern Territory, and little if any consideration has been given to the views of Aboriginal landowners. An Aboriginal perspective of country recognises the interrelationship, via local kinship and moiety systems, of all things – the rocks, plants, animals, people, stories, weather, ceremonies and tradition. There is an opportunity for this worldview to be incorporated into the rehabilitation of Ranger Mine. The mine’s operator ERA (a subsidiary of Rio Tinto) has agreed to Cultural Closure Criteria that reflect a desire of Bininj (Aboriginal people from the region) to again use the land for hunting and gathering, recreation and cultural practice. Allowing Aboriginal people to have input to rehabilitation planning demonstrates a respect for people’s knowledge and connection to country. At Ranger, where the mine was imposed against the wishes of the traditional owners, this is an important step in a return to stewardship of this land and reconnecting people to place.

Reference site selection protocols for mine site ecosystem restoration

Reference site selection associated with mining and resource development requires a comprehensive approach so that stakeholders can be confident that restoration efforts have appropriate target ecosystems. Here, we present our process to select reference sites, within a savanna ecosystem, which will be used to develop and assess closure criteria and restoration guidelines for Ranger Mine (Northern Territory, Australia). The selection of reference sites followed five steps involving desktop and field methods. We recommend that restoration projects consider inclusion criteria, randomly select sites from areas matching the chosen criteria, conduct preliminary data analysis, estimate and update sampling effort and precision at several points throughout the project, and invite stakeholder feedback and revision of the process as often as required. This detailed reference site approach appears to be the first to demonstrate how to use available data to reduce bias, address sampling effort and site selection quantitatively, involve stakeholders, and provide useful data, which can be used to calibrate ecological restoration outcomes for savanna ecosystems.

Speciation and partitioning of uranium in waterbodies near Ranger Uranium Mine

Environmental contextAs a part of the rehabilitation of Ranger Uranium Mine, Northern Australia, closure criteria for water concentrations of uranium and other contaminants in local waterbodies have been developed. Increased concentrations of uranium in the water column can result in an accumulation of uranium in the sediment and be hazardous to benthic organisms. A uranium partitioning relationship was derived to predict sediment uranium concentrations from water column concentrations. AbstractAfter almost four decades of mineral processing, the Ranger Uranium Mine (RUM) is set to cease operations in 2021. Beyond this period, rehabilitation of the Ranger Project Area (RPA) will continue into 2026. As part of the rehabilitation of RUM, water quality guideline values (WQGVs) for U and other metals in local waterbodies have been developed to protect aquatic organisms from the effects of metal toxicity. However, benthic organisms will also be exposed to U as it partitions from the water column to the sediments. This important component of the ecosystem may then be exposed to increased U concentrations through ingestion and adsorption of U from sediments. As increased concentrations of U in the water column can result in an accumulation of U in sediment, a U partitioning relationship was derived to enable prediction of sediment U concentrations when water column concentrations were at the WQGV. In this work, the effect of U counter ions and dissolved organic carbon on uranium speciation was modelled and demonstrated a high affinity for the formation of uranyl-organic complexes. Uranium partitioning was studied using experimental U-spiked sediment data as well as water/sediment data collected from multiple sites on and adjacent to the RPA. Using a Freundlich isotherm, and a water-column U concentration of 2.8µg L−1 (representing the WQGV), the acid-extractable U in sediment was calculated to be 48mg kg−1, i.e. lower than the interim sediment quality guideline value (SQGV) of 94mg kg−1. This offers assurance that a WQGV implementation of 2.8µg L−1 U will not lead to a level of U accumulation in sediment that will impact benthic communities.

A review of revegetation at mine sites in the Alligator Rivers Region, Northern Territory, and the development of a state and transition model for ecological restoration at Ranger uranium mine

Abstract Society’s expectations for mining operations are that they are undertaken using the principles of sustainable development. Numerous mines have been ‘rehabilitated’ in past decades without clear closure criteria or regulatory oversight and are characterised by less than desirable environmental outcomes. These sites provide us with information and data (in some instances) to inform future mine site restoration efforts and the sustainable development of mining resources. However, this information and data are often contained in inaccessible grey literature or have been lost over time. We used records and data on revegetation efforts and outcomes at mine sites in and around the Alligator Rivers Region (ARR) of the Northern Territory, Australia, to demonstrate the extent and currency of rehabilitation knowledge. There have been 20 mines in the region since 1950 and we found that these sites are in various deviated ecological states and that data for these mines were generally unavailable or unable to be located. A number of studies have been conducted at the largest operation, Ranger uranium mine, and there is also information from Nabarlek and South Alligator River Valley mines. We furthered the understanding of the system using available information to develop a preliminary state and transition model for eucalypt-dominated ecosystems in the region. The identification of likely desired and undesired ecological states and management requirements developed in this model could be used to actively guide future restoration and research efforts, particularly at Ranger uranium mine. Based on the lessons learned from the mine sites in the ARR, we provide recommendations for monitoring revegetation in the future.

A semi-automated approach for quantitative mapping of woody cover from historical time series aerial photography and satellite imagery

Savanna landscapes are characterised by a canopy of discontinuous tree cover overlying an understorey of shrubs and continuous grass cover. The distribution of trees (woody cover) is variable both spatially and temporally. Analysis of woody cover dynamics can provide a spatial and temporal envelope encompassing variability is useful for informing mine closure criteria. With the impending closure of Ranger uranium mine, ecologically appropriate closure criteria for ecosystem restoration are being developed through a framework of rehabilitation standards. One such closure criteria is canopy cover and historical woody cover is being used to derive the range in woody cover that can be expected over time once the mine site has been revegetated. This study reports on the development and testing of a technique for extracted woody cover from remotely sensed data (in the form of historical aerial photography and satellite imagery) in the areas adjacent to Ranger uranium mine in the World Heritage listed Kakadu National Park, northern Australia. An object-based image analysis technique was applied to four data sets from four different dates: greyscale, true colour and colour infrared aerial photo mosaics (from 1964, 1976 and 1981 respectively) and a high spatial resolution satellite image (from 2010). Overall accuracies of woody cover from each of the data sets exceeded 94%. In addition, proportional cover derived from this method displays linear relationships to cover derived from visual estimates. Due to the success of the technique, it will be applied to more data sets from different dates over the study area to assess the variability of woody cover over time to inform ecosystem restoration criteria for the mine closure.

Insertable cardiac monitor detection of silent atrial fibrillation in candidates for percutaneous patent foramen ovale closure.

An underlying atrial vulnerability or a preexisting misdiagnosed atrial fibrillation in some patients who are candidates for patent foramen ovale (PFO) closure may lead to an unnecessary percutaneous intervention. The aim of this work was to define paroxysmal atrial fibrillation rate, through a 6-month insertable loop-recorder monitoring, in patients over 55 years old with cryptogenic stroke and PFO. PFO closure criteria: significant right-to-left shunt and at least one high-risk feature (permanent right-to-left shunt, atrial septal aneurysm, prominent Eustachian valve, recurrent brain ischemia, previous deep vein thrombosis, thrombophilia). Insertable cardiac monitoring criteria: previous cryptogenic stroke, more than 55 years and at least one atrial fibrillation risk factor (heart failure, hypertension, age older than 65 years, diabetes, atrial runs, left atrium dilatation, left ventricle hypertrophy, pulmonary disease, thyroid disease, obesity). Atrial fibrillation detection threshold: arrhythmia duration longer than 5 min. From January 2008 to March 2017, 195 patients underwent to loop-recorder monitoring. A total of 70 (36%) patients were candidates for PFO closure. The 6-month silent atrial fibrillation rate was 11.4%. In the arrhythmia-free cohort, 28 patients (45.2%) underwent percutaneous foramen ovale closure (group A) and 34 (54.8%) were medically treated (group B). Atrial fibrillation detection rate was 14.3% in group A and 0% in group B. The 36-month atrial fibrillation-free survival was 76%. An occult preexisting atrial fibrillation may lead to unnecessary percutaneous foramen ovale closure in a significant proportion of patients. A 6-month loop-recorder monitoring may improve the patient oriented decision-making.

Does Risk of Paradoxical Embolism (ROPE) score correlate with PFO closure criteria? (P4.3-065)

Does Risk of Paradoxical Embolism (ROPE) score correlate with PFO closure criteria? (P4.3-065)

Depth of closure over large regions using airborne bathymetric lidar

The depth at which significant bathymetric change can be expected is an important morphological factor for science and engineering on sandy coastlines. Although most depth of closure studies have been conducted on a limited number of sites, the great quantity of airborne lidar bathymetry data collected over the past decade allows for a much wider study region. Here, we present depth of closure analysis over 600km of sandy coastline using the Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX) dataset. Improved closure predictions resulted when both extreme waves (as represented by the 12hour exceedance significant wave height over a given time interval), and more typical storm waves (as represented by the 99% significant wave height) were jointly considered. In contrast to some other studies, wave steepness terms were found to be negligible. Consideration of error terms in least-squares closure predictions was used to develop relations with different degrees of conservatism: e.g. to provide closure depth exceeded by only 10% of observations. Results are presented for four closure criteria: root-mean-square depth changes Δhclose=[20,30]cm, and relative depth changes Δhclose/h=[0.02,0.04]. Further improvements in accuracy may occur once decadal wave hindcasts include storm surge variations in water levels, and have increased nearshore resolution.

High Resolution Site Characterization as key element for proper design and cost estimation of groundwater remediation

Substantial amounts of money are spent each year on cleaning up ground water contaminations that were caused by historical industrial site activities. Too often, however, remedial objectives are not achieved within the anticipated time frame. Moreover, remedial budgets which were estimated prior to the start of remediation turn out to be largely insufficient to meet the remedial objectives. This situation, very common, creates significant troubles for all the stakeholders involved in the remediation project. The reason for not meeting remedial regulatory closure criteria or exceeding remedial budgets is often due to an incomplete conceptual site model. Having conducted high resolution site characterization programs at numerous sites where remediation was previously conducted, ERM has found several recurring themes: • Missed source areas and plumes; • Inadequate understanding of source area and plume architectures (i.e., three-dimensional contaminant distribution); • Inadequate understanding of the effects of site (hydro)geologic conditions on the ability to access contamination (i.e., via remedial additive injections of groundwater/soil gas extraction). This paper explains why remediations often fail and what the alternatives to prevent these failures (and exceeding remedial budgets) are. More specifically, it focuses on alternative investigation methods and approaches that help to get to a more complete (high resolution) conceptual site model. This more complete conceptual site model in return helps a more focused remedial design with a higher remedial efficiency. As a minimum, it will take away a lot of (financial) uncertainty during the decision making when selecting a remedial alternative. Contaminants that have a greater density then water are known to have a greater complexity in terms of both investigation as well as remediation. Therefore, they will be the main focus of this paper.

Object-based classification of semi-arid vegetation to support mine rehabilitation and monitoring

Mining activities result in significantly modified landscapes that require rehabilitation to mitigate the negative environmental impacts and restore ecological function. The aim of this study was to develop a remote sensing method suitable for monitoring the vegetation cover at mine rehabilitation sites. We used object-based image analysis (OBIA) methods and high-spatial resolution SPOT-5 imagery to identify discrete land-cover patterns that occur at fine spatial scales. These patterns relate to spatial processes that are important drivers of successful restoration of mine sites. SPOT-5 imagery of the Kidston Gold mine tailing dam in semi-arid tropical north Queensland was acquired in July 2005, comprising four 10-m spectral bands and a 2.5-m panchromatic (PAN) band. The classification scheme used in this study was adapted to the spatial scale of SPOT-5 imagery from mine closure criteria cover requirements, according to a mine rehabilitation plan. Four land-cover classes were identified: tree cover, dense grass, sparse grass, and bare ground. First, textural layers (contrast, dissimilarity, and homogeneity) were derived for each vegetation class except for bare ground from the PAN and multispectral bands. Of all textural layer combinations, homogeneity and contrast in the PAN band were identified using a Z-test as the most useful for differentiating between multiple land-cover classes. Next, an optimal segmentation scale parameter of 15 was identified using an analysis of spatial autocorrelation. Finally, the SPOT-5 image bands, derived textural layers, and normalized difference vegetation index (NDVI) were used in an OBIA fuzzy membership classification approach to map vegetation land-cover classes. The classification results were assessed with the traditional error matrix approach and the object-based accuracy assessment method. The overall classification accuracy using the error matrix was 92.5% and 81% using the object-based method. The relatively high-classification accuracy demonstrates the potential of SPOT-5 imagery for monitoring mine rehabilitation. The complete spatial coverage associated with remote sensing data at fine spatial scales has the potential to complement field-based approaches commonly used in rehabilitation monitoring. Furthermore, SPOT-5 data along with OBIA can characterize vegetation spatial patterns at spatial scales appropriate for monitoring rehabilitated landscapes, providing an important tool for landscape function analysis.

Application of the BioCondition assessment framework to mine vegetation rehabilitation

SummaryA quantitative ‘scorecard’ is essential to provide both mine regulators and managers with a robust way of assessing what is ‘good’ vegetation rehabilitation and whether it is adequate to satisfy the regulatory and legal requirements of mine closure criteria and community expectations. The BioCondition framework (Eyre et al. 2011a, http://www.ehp.qld.gov.au/ecosystems/biodiversity/biocondition.html) was applied as a scorecard to evaluate vegetation rehabilitation using largely locally native species at Meandu coal mine in Southeast Queensland. Benchmarks for vegetation condition attributes were developed from an amalgam of local reference vegetation types. To allow the appropriate, rather than aspirational evaluation of restoration for sites that were &lt; 50 years old, the scoring system was adjusted to exclude the large trees and coarse woody debris attributes. Bearing in mind that assumptions of self‐sustainability will depend on the ‘fit’ of species to the local condition and the ongoing management of the communities, the use of spider web diagrams assists mine managers and regulators to clearly see where future management intervention can increase the BioCondition score.

OCOG: A common grasp computation algorithm for a set of planar objects

This paper addresses the problem of defining a simple End-Effector design for a robotic arm that is able to grasp a given set of planar objects. The OCOG (Objects COmmon Grasp search) algorithm proposed in this paper searches for a common grasp over the set of objects mapping all possible grasps for each object that satisfy force closure and quality criteria by taking into account the external wrenches (forces and torque) applied to the object. The mapped grasps are represented by feature vectors in a high-dimensional space. This feature vector describes the design of the gripper. A database is generated for all possible grasps for each object in the feature vector space. A search algorithm is then used for intersecting all possible grasps over all parts and finding a common grasp suitable for all objects. The search algorithm utilizes the kd-tree index structure for representing the database of the sets of feature vectors. The kd-tree structure enables an efficient and low cost nearest-neighbor search for common vectors between the sets. Each common vector found (feature vector) is the grasp configuration for a group of objects, which implies the future end-effector design. The final step classifies the grasps found to subsets of the objects, according to the common vectors found. Simulations and experiments are presented for four objects to validate the feasibility of the proposed algorithm. The algorithm will be useful for standardization of end-effector design and reducing its engineering time.

Determining a pre-mining radiological baseline from historic airborne gamma surveys: A case study

Knowing the baseline level of radioactivity in areas naturally enriched in radionuclides is important in the uranium mining context to assess radiation doses to humans and the environment both during and after mining. This information is particularly useful in rehabilitation planning and developing closure criteria for uranium mines as only radiation doses additional to the natural background are usually considered ‘controllable’ for radiation protection purposes. In this case study we have tested whether the method of contemporary groundtruthing of a historic airborne gamma survey could be used to determine the pre-mining radiological conditions at the Ranger mine in northern Australia. The airborne gamma survey was flown in 1976 before mining started and groundtruthed using ground gamma dose rate measurements made between 2007 and 2009 at an undisturbed area naturally enriched in uranium (Anomaly 2) located nearby the Ranger mine. Measurements of 226Ra soil activity concentration and 222Rn exhalation flux density at Anomaly 2 were made concurrent with the ground gamma dose rate measurements. Algorithms were developed to upscale the ground gamma data to the same spatial resolution as the historic airborne gamma survey data using a geographic information system, allowing comparison of the datasets. Linear correlation models were developed to estimate the pre-mining gamma dose rates, 226Ra soil activity concentrations, and 222Rn exhalation flux densities at selected areas in the greater Ranger region. The modelled levels agreed with measurements made at the Ranger Orebodies 1 and 3 before mining started, and at environmental sites in the region. The conclusion is that our approach can be used to determine baseline radiation levels, and provide a benchmark for rehabilitation of uranium mines or industrial sites where historical airborne gamma survey data are available and an undisturbed radiological analogue exists to groundtruth the data.