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( Shaha Nur Kabir ),( Sun Ok Chung ),( Yong Joo Kim ),( Sung Hyun Shin ) 한국농업기계학회 2014 바이오시스템공학 Vol.39 No.3
Purpose: The objective of this paper was to compare test standards regarding the performance and safety of agricultural tractors to identify the differences in test conditions, measurement tolerances, and test procedures. Based on the comparison, some recommendations were proposed for possible revisions or improvements to current tractor test standards. Methods: The test standards and codes of major standards development organizations (SDOs), such as the Organization for Economic Co-operation and Development (OECD), the International Organization for Standardization (ISO), the American Society of Agricultural and Biological Engineers (ASABE), EC type approval, and the board of actions of the Nebraska Tractor Test Laboratories (NTTL), were selected and analyzed. Comparison of the test standards: The ISO provides references for fuel and lubricants for tractor tests, and the OECD provides additional measurements for calculating fuel consumption characteristics during the power take-off (PTO) tests. The ISO, EC type approval, and the ASABE provide PTO protective device and the safety requirements. During drawbar power tests, seven transmission ratios are selected for fully automatic transmissions, according to the OECD. In case of hydraulic lift tests, ISO 789-2 and OECD Code 2 advise the use of a static lift force, while SAE J283 advises the use of additional dynamic lift capacity tests for a better representation of in-field operations. The OECD, the ISO, and EC type approval determine the seat index point (SIP), whereas the ASABE determines the seat reference point (SRP) for roll-over protective structure (ROPS) tests. Diversified measurement tolerances were among the braking performance test standards. The European Union (EU) has developed daily limits for vibration exposures with adaptations from ISO 2631-1. Electromagnetic compatibility evaluations are emerging of high-efficiency tractors due to the long-term conformance to electromagnetic emissions and interferences.
Spatiotemporal variation of Van der Burgh's coefficient in a salt plug estuary
Shaha, Dinesh Chandra,Cho, Yang-Ki,Kim, Bong Guk,Sony, M. Rafi Afruz,Kundu, Sampa Rani,Islam, M. Faruqul Copernicus GmbH 2017 Hydrology and earth system sciences Vol.21 No.9
<P><p><strong>Abstract.</strong> Salt water intrusion in estuaries is expected to become a serious global issue due to climate change. Van der Burgh's coefficient, <i>K</i>, is a good proxy for describing the relative contribution of tide-driven and gravitational (discharge-driven and density-driven) components of salt transport in estuaries. However, debate continues over the use of the <i>K</i> value for an estuary where <i>K</i> should be a constant, spatially varying, or time-independent factor for different river discharge conditions. In this study, we determined <i>K</i> during spring and neap tides in the dry (&lt;<span class='thinspace'></span>30<span class='thinspace'></span>m<sup>−3</sup><span class='thinspace'></span>s<sup>−1</sup>) and wet (&gt;<span class='thinspace'></span>750<span class='thinspace'></span>m<sup>−3</sup><span class='thinspace'></span>s<sup>−1</sup>) seasons in a salt plug estuary with an exponentially varying width and depth, to examine the relative contributions of tidal versus density-driven salt transport mechanisms. High-resolution salinity data were used to determine <i>K</i>. Discharge-driven gravitational circulation (<i>K</i><span class='thinspace'></span>∼ 0.8) was entirely dominant over tidal dispersion during spring and neap tides in the wet season, to the extent that salt transport upstream was effectively reduced, resulting in the estuary remaining in a relatively fresh state. In contrast, <i>K</i> increased gradually seaward (<i>K</i><span class='thinspace'></span>∼ 0.74) and landward (<i>K</i><span class='thinspace'></span>∼<span class='thinspace'></span>0.74) from the salt plug area (<i>K</i><span class='thinspace'></span>∼<span class='thinspace'></span>0.65) during the dry season, similar to an inverse and positive estuary, respectively. As a result, density-driven inverse gravitational circulation between the salt plug and the sea facilitates inverse estuarine circulation. On the other hand, positive estuarine circulation between the salt plug and the river arose due to density-driven positive gravitational circulation during the dry season, causing the upstream intrusion of high-salinity bottom water. Our results explicitly show that <i>K</i> varies spatially and depends on the river discharge. This result provides a better understanding of the distribution of hydrographic properties.</p> </P>
( Shaha Nur Kabir ),( Myong Jin Ryu ),( Sun Ok Chung ),( Yong Joo Kim ),( Chang Hyun Choi ),( Soon Jung Hong ),( Je Hoon Sung ) 한국농업기계학회 2014 바이오시스템공학 Vol.39 No.1
Background : Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO`s) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.
Visibility Evaluation for Agricultural Tractor Operators According to ISO 5006 and 5721-1 Standards
( Shaha Nur Kabir ),( Ming Zhang Song ),( Sun Ok Chung ),( Yong Joo Kim ),( Su Chul Kim ),( Jong Kyou Ha ) 한국농업기계학회 2015 바이오시스템공학 Vol.40 No.1
Purpose: A system to measure the visibility of agricultural tractor operators was designed and evaluated according to ISO standards, and a blind area diagram around the tested tractor was created based on the manual method recommended by the National Institute for Occupational Safety and Health (NIOSH). Methods: A visibility measurement system was designed and evaluated based on the ISO 5006 and ISO 5721-1 standards. Two bulbs used to simulate the operator``s eyes were mounted on a bar with a supporting frame. A wooden frame was used to determine the seat index point position. The 12-mvisibility test circle was divided into six sectors of vision, and the test tractor was placed at the center of the circle. Artificial light was supplied in the darkened environment, and shadow or masking effects were measured manually around the 12-mcircle. Results: When the bulbs were placed at the operator’s eye level, front visibility was good; no masking was found in the “A” vision sector, but larger masking widths were found in the “B” and “C” vision sectors. Since the masking width exceeded 700 mm, additional tests, such as movement of the light sources to both sides of the operator’s eye level, were performed. Less than six masking effects were found in the semi-circle of vision to the front, and more than one masking was found in the “B” and “C” visual fields. The minimum distance between the centers of two masking effects exceeded 2500 mm when measured as a chord on the semi-circle of vision. A blind area diagram was created to define the exact nature of the blind spots and mirror visibility. Conclusions: Visibility evaluation is an effective way to enable proper and safe operation for agricultural tractor operators. Inclusion of this visibility evaluation test in the general testing process might aid tractor manufacturers.
Sneha Shaha,Yinglin Gao,Jiahao Peng,Kendrick Che,John J. Kim,Wasseem Skef 대한소화기내시경학회 2023 Clinical Endoscopy Vol.56 No.5
Background/Aims: We aimed to study the effects of sedation on endoscopic ultrasound-guided tissue acquisition. Methods: We conducted a retrospective study evaluating the role of sedation in endoscopic ultrasound-guided tissue acquisition bycomparing two groups: anesthesia care provider (ACP) sedation and endoscopist-directed conscious sedation (CS). Results: Technical success was achieved in 219/233 (94.0%) in the ACP group and 114/136 (83.8%) in the CS group (p=0.0086). Inmultivariate analysis, the difference in technical success between the two groups was not significant (adjusted odds ratio [aOR], 0.5;95% confidence interval [CI], 0.234–1.069; p=0.0738). A successful diagnostic yield was present in 146/196 (74.5%) in the ACP groupand 66/106 (62.3%) in the CS group, respectively (p=0.0274). In multivariate analysis, the difference in diagnostic yield between thetwo groups was not significant (aOR, 0.643; 95% CI, 0.356–1.159; p=0.142). A total of 33 adverse events (AEs) were observed. The incidenceof AEs was significantly lower in the CS group (5/33 CS vs. 28/33 ACP; OR, 0.281; 95% CI, 0.095–0.833; p=0.022). Conclusions: CS provided equivalent technical success and diagnostic yield for malignancy in endoscopic ultrasound-guided tissueacquisition. Increased AEs were associated with anesthesia for the endoscopic ultrasound–guided tissue acquisition.