ORCID Profile
0000-0003-0129-4816
Current Organisations
Kwame Nkrumah University of Science and Technology
,
University of South Australia
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Publisher: MDPI AG
Date: 15-12-2021
DOI: 10.3390/SOILSYSTEMS5040072
Abstract: No-tillage farming can improve crop productivity and the reliability of cropping compared with conventional tillage. The effects of three different seeding system configurations on surface residue handling, sunflower emergence and stand establishment, yield, and gross income were investigated over three cropping seasons. The seeding system configurations comprised of (1) turbo coulter blade, (2) notched disc row cleaner before turbo coulter blade, and (3) no residue handling unit installed in front of a double-disc opener. For all three seeding system configurations, crop residue cover on sown rows (after seeding) was greater than the minimum recommended value of 30% for no-tillage. Residue cover was best with the notched disc row cleaner in front of the turbo coulter blade compared to the other two seeding systems. Furthermore, the notched disc row cleaner in front of the turbo coulter blade produced the highest plant emergence counts and the most uniform stand establishment. Sunflower yield and gross income were highest with the notched disc row cleaner in front of the turbo coulter blade (3.16 Mg·ha−1 and 902 USD·ha−1) compared to when only the turbo coulter blade (2.38 Mg·ha−1 and 680 USD·ha−1) or no residue handling unit (1.69 Mg·ha−1 and 482 USD·ha−1) was used.
Publisher: American Society of Agricultural and Biological Engineers
Date: 2019
Publisher: MDPI AG
Date: 31-07-2023
DOI: 10.3390/AGRICULTURE13081525
Abstract: Soil-cutting forces are key indicators of root-tuber harvesters and other soil-engaging tools’ performance. To improve operational efficiency, minimise soil disturbance, and reduce fuel consumption, the draught and vertical forces involved in root and tuber crop harvesting must be minimised. Two field experiments assessed the harvester’s performance at a depth of 200 mm, varying frequencies, and travel speeds on clay and sandy loam soils. Discrete element models (DEM) were developed and subsequently used to replicate the field experiments and evaluate S-shaped and fork-shaped shovels. Linear regression and ANOVA (p 0.05) were used to analyse the data. Draught force concurrently increased with speed in both soil textures but decreased with vibration frequency. The draught force decreased by approximately 41% in clay soil and 21% in sandy loam soil when the harvester was operated between 5 Hz and 14.5 Hz and between 10 Hz and 12.5 Hz, respectively. DEM simulations had relative errors of 4% (clay) and 4.7% (sandy loam) for draught force and drawbar power compared to experimental data. The S-shaped shovel was more efficient at crushing and translocating soil–crop mass to the rear of the harvester than the fork-shaped shovel. These DEM soil–crop models are reliable for evaluating other root-tuber harvesting tools.
Publisher: Elsevier BV
Date: 05-2022
Publisher: American Society of Agricultural and Biological Engineers
Date: 2018
Publisher: American Society of Agricultural and Biological Engineers
Date: 2018
Publisher: Elsevier BV
Date: 08-2021
Publisher: Asian Agricultural and Biological Engineering Association
Date: 04-2019
Publisher: The Endocrine Society
Date: 20-09-2019
Abstract: Adrenal venous s ling (AVS) is the key test for subtyping primary aldosteronism (PA), but its interpretation varies widely across referral centers and this can adversely affect the management of PA patients. To investigate in a real-life study the rate of bilateral success and identification of unilateral aldosteronism and their impact on blood pressure outcomes in PA subtyped by AVS. In a retrospective analysis of the largest international registry of in idual AVS data (AVIS-2 study), we investigated how different cut-off values of the selectivity index (SI) and lateralization index (LI) affected rate of bilateral success, identification of unilateral aldosteronism, and blood pressure outcomes. AVIS-2 recruited 1625 in idual AVS studies performed between 2000 and 2015 in 19 tertiary referral centers. Under unstimulated conditions, the rate of biochemically confirmed bilateral AVS success progressively decreased with increasing SI cut-offs furthermore, with currently used LI cut-offs, the rate of identified unilateral PA leading to adrenalectomy was as low as & %. A within-patient pairwise comparison of 402 AVS performed both under unstimulated and cosyntropin-stimulated conditions showed that cosyntropin increased the confirmed rate of bilateral selectivity for SI cut-offs ≥ 2.0, but reduced lateralization rates (P & 0.001). Post-adrenalectomy outcomes were not improved by use of cosyntropin or more restrictive diagnostic criteria. Commonly used SI and LI cut-offs are associated with disappointingly low rates of biochemically defined AVS success and identified unilateral PA. Evidence-based protocols entailing less restrictive interpretative cut-offs might optimize the clinical use of this costly and invasive test. (J Clin Endocrinol Metab XX: 0-0, 2020)
Publisher: Springer Science and Business Media LLC
Date: 09-2013
DOI: 10.1142/S2010132513300024
Abstract: There is increasing demand for domestic and industrial refrigeration, space heating and air conditioning. Heat pump systems offer economical alternatives for recovering heat from different sources for use in these applications. As a renewable energy technology for sustainable environment, the heat pump's high efficiency and low environmental impact have already drawn a fair amount of attention all over the world. Some of these domestic and industrial applications require very low evaporating temperatures and very high condensing temperatures which induce high compressor pressure ratios beyond the practical range for single-stage heat pump cycles. These high pressure ratios also produce low coefficient of performance (COP) values and expose the compressor to high discharge temperature, low volumetric efficiency and damage. However, this challenge can be overcome by adopting two-stage heat pump cycles. In this paper, recent works on two-stage heat pump systems for various applications are reviewed. They include two-stage cycle with intercooling, two-stage cycle with refrigerant injection and two-stage cascade cycle. Research and innovative designs of systems that make use of these two-stage cycles have been able to get heat pumps to handle applications with lower and higher temperatures, while enhancing heating capacity up to 30% and COP up to 31%.
Publisher: American Society of Agricultural and Biological Engineers
Date: 2017
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 07-2021
Publisher: Association of Technology and Science
Date: 08-05-2016
Publisher: AIP Publishing
Date: 09-2013
DOI: 10.1063/1.4821509
Abstract: There is a need for hot water generation in a more efficient and environmentally friendly way for heating, ventilating, and air conditioning systems, and the heat pump is a great candidate for that. In this paper, hot water temperatures generated by ground source heat pump (GSHP) systems in Korea are analysed. It is also important to minimize the use and emission of refrigerants with high global warming potential (GWP) and ozone depletion potential (ODP) to reduce their impact on the environment. In this regard, refrigerants that are used in GSHP units in Korea are investigated. The database is composed of 86 GSHP units certified in Korea according to governmental regulation. The GSHP units are ided into three types: water-to-water, water-to-air, and water-to-air multi heat pump units. The average hot water temperature generated by the certified GSHP units is 43.8 °C with the Korean standard test conditions (NR GT 101). Temperature difference 3.8 °C between inlet and outlet of condenser is less than 5 °C as presented by the European Standard (NF EN standard). In order to replace the boiler and the conventional air conditioning unit with a highly efficient GSHP system, there is the need to increase the hot water generation temperature. With the refrigerants, 53.8% of the 78 water-to-water GSHP units use the hydro chlorofluorocarbon (HCFC) refrigerant, R22, while the others use the hydrofluorocarbon (HFC) refrigerants, R410A, R407C, and R134a. All water-to-air and water-to-air multi heat pump units use R410A refrigerant. Because R22 is a HCFC and has high GWP and ODP, it is being replaced with HFC and natural refrigerants. However, HFC refrigerants also have high GWP. It is therefore recommended to encourage the responsible use or replacement of HFC refrigerants with natural and other alternative refrigerants in Korea.
Publisher: Elsevier BV
Date: 09-2021
Publisher: American Society of Agricultural and Biological Engineers (ASABE)
Date: 2021
DOI: 10.13031/AEA.14252
Abstract: Highlights A simple frame was built to hold and apply uniaxial and biaxial loads to octagonal ring transducers for calibration. Similar results were obtained with the frame as with a universal tensile testing machine. The transducer outputs exhibited low cross-sensitivities and hysteresis (=0.4%), and R 2 = 0.9998. The frame is portable and safe, and its concept can be adapted to take a wide range of non-gravitational loads. Abstract . An extended octagonal ring transducer (EORT) is a simple, single, and compact biaxial force measuring transducer, which is ideal for soil force measurement in tillage tool research. Calibration of EORTs is needed to ascertain their sensitivities and to determine an accurate calibration equation to convert voltage output to force measurement. Typically, calibration of EORTs involves the use of universal tensile testing machines, hydraulic systems and large gravitational loads (hanging weights) to apply loads. In this study, a simple calibration frame that enables application of non-gravitational loads was evaluated and used to hold and calibrate an EORT through both uniaxial and biaxial loading. The frame was suitable for both uniaxial and biaxial application of offset coincident force up to 3000 N and centered perpendicular force up to 1500 N. The EORT exhibited a strong linear relationship (R2 = 0.9998) between applied forces and voltage outputs, low hysteresis errors (=0.4%), and low cross-sensitivities (3.61% and 1.6% for coincident and perpendicular forces, respectively). Calibration equations developed from the primary bridge output data or from the biaxial loading data using the frame produced good force predictions, which also improved when taking into account the impacts of cross-sensitivity. The results confirmed that this calibration approach can integrate the interactions of output cross-sensitivity to deliver more accurate force prediction. Coefficients of determination of the relationships between applied and predicted forces were 0.9993 to 0.9996 and 0.9877 to 0.9984 for coincident and perpendicular forces, respectively. This calibration frame presents potential for safely applying large, non-gravitational loads in a contained and portable manner and its concept can easily be adapted to suit the scale of the transducer. Keywords: Biaxial loading, Cross-sensitivity, EORT calibration, Offset coincident force, Uniaxial loading.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 11-2012
Publisher: MDPI AG
Date: 23-02-2023
DOI: 10.3390/AGRICULTURE13030541
Abstract: In agricultural machinery design and optimization, the discrete element method (DEM) has played a major role due to its ability to speed up the design and manufacturing process by reducing multiple prototyping, testing, and evaluation under experimental conditions. In the field of soil dynamics, DEM has been mainly applied in the design and optimization of soil-engaging tools, especially tillage tools and furrow openers. This numerical method is able to capture the dynamic and bulk behaviour of soils and soil–tool interactions. This review focused on the various aspects of the application of DEM in the simulation of tillage and furrow opening for tool design optimization. Different contact models, particle sizes and shapes, and calibration techniques for determining input parameters for tillage and furrow opening research have been reviewed. Discrete element method predictions of furrow profiles, disturbed soil surface profiles, soil failure, loosening, disturbance parameters, reaction forces, and the various types of soils modelled with DEM have also been highlighted. This pool of information consolidates existing working approaches used in prior studies and helps to identify knowledge gaps which, if addressed, will advance the current soil dynamics modelling capability.
Publisher: Elsevier BV
Date: 05-2020
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/SR19153
Abstract: The primary features of an effective and efficient furrow opener include controlled soil disturbance and low draught and vertical force requirements. When integrated in a no-tillage seeding system, furrow openers should also have the ability to assist, and not hinder, the functions of seeding system components – such as maintaining adequate surface residue distribution, accurate and uniform placement of seeds and fertiliser, and regular inter-plant spacing. This review highlights how these goals are affected by opener type, geometry and settings, and soil and residue conditions. Typically, tine openers cause greater soil disturbance than disc openers whereas disc openers are likely to cause residue hairpinning. Winged tine openers reduce residue interference with seed placement and support greater lateral seed spread. Inverted-T openers can achieve subsurface soil shattering, which helps conserve moisture and provides good seed–soil contact. A tine opener with concave cutting edge reduces soil disturbance relative to straight and convex cutting edges. Increasing rake angle, tine width and operating depth increase degree of soil disturbance and draught requirement. Increasing forward speed reduces residue interference with sowing but might decrease the accuracy and uniformity of depth and separation of seed and fertiliser placement. Relative to common openers, bentleg openers have lower draught and penetration force requirements while combining minimal lateral soil throw with high furrow backfill, even at speeds of up to 16 km h–1. The performance of bentleg openers need to be evaluated under residue conditions and in cohesive and adhesive soils. Recommendations for future research are presented.
Publisher: Elsevier BV
Date: 12-2022
Publisher: American Society of Agricultural and Biological Engineers
Date: 2020
No related grants have been discovered for Kojo Atta Aikins.