• Journal of Biosystems Engineering
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• v.31 no.1 s.114
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• pp.16-23
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• 2006

Depth and working load control is one of the most important technique in control system for tractor rotary implement automation. Keeping the depth consistent is critical to bring along crops and to improve the efficiency and quality of the following operations. Keeping the load of engine consistent is an essential factor for the efficiency of operation and engine protection of tractor. In this study we investigated the possibility of application of depth and working load control system for tractor using a proportional valve through field tests. Depth control was implemented by the ascent and descent of 3 point linkage for the change of setting depth. There were 4 mm and 5.2 mm control deviations for setting depths of 50mm and 100mm, respectively. Load control was operated appropriately by the ascent and of descent of 3 point link for the change of setting working load. The standard deviations between setting load and engine load were 171 rpm at 1.3 km/h and 164 rpm at 2.3 km/h tractor travel velocity. The results of experiment showed that the characteristics of response was sufficient to be used as the implement depth and working load control system for tractor using proportional valve.

• Korean Journal of Agricultural Science
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• v.47 no.4
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• pp.1123-1134
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• 2020

The goal of this study was to develop an accelerated life test for an implement working pump for an agricultural tractor. The field experiments were conducted to measure the load of an implement working pump during major agricultural operations such as plow tillage, rotary tillage, baler operations, and wrapping operations. The measurement system for an implement working pump load was constructed using a pressure sensor, the engine rotational speed, and the hitch pump displacement. The measured implement working pump load was calculated as an equivalent load for each agricultural operation using the Palmgren-Miner rule, which is a cumulative damage method. The equivalent load was calculated using the total load data and peak load data when the total data included the operation of an implement working. The annual usage time of the agricultural tractor was applied to develop two integrated equivalent loads. The acceleration factor was calculated to develop an accelerated life test and was calculated from the two integrated equivalent loads, the maximum pressure, and the flow rate conditions of the hitch pump. In Korea, the warranty life of a tractor is 2,736 hours, and the time required for the test to guarantee the operational life of tractors was calculated as 7,561 hours. The acceleration factors were calculated as 453.6 and 38.3, respectively, from the total load data and peak load data. The fatigue test time can be shortened by 16.7 and 197.4 hours according to the result of the acceleration factors.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.27-35
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• 2021

This study investigated the change in stiffness and deflection of a scaffold working plate caused by damage to a cross-beam in the plate. Experiments were conducted considering various load and damage conditions of cross-beams. A cross-beam falling off from the working plate was considered damaged. The load-displacement curves of specimens at the center of the uniform load showed that the working plate stiffness decreased by 14.66%-1.89%, depending on the load interval due to the damage of one cross-beam. A reduction in the stiffness of 33.94%-40.76% resulted from the damage of two cross-beams. Moreover, the displacement increased by an average of 25% when one cross-beam was damaged and an average of 65% when two cross-beams were damaged. Therefore, damage to the cross-beam in the working plate can potentially cause accidents and harm workers. As the load increases, the risk of an accident due to the aforementioned damage also increases because the stiffness remarkably decreases with the load increase. Further, the damage to the cross-beam mainly reduces the stiffness but increases the displacement rather than the strength of the working scaffold plate.

• Journal of Biosystems Engineering
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• v.42 no.4
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• pp.251-257
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• 2017

Purpose: A chisel mounted on working implement, such as agricultural machinery used in irregular farming conditions, is subjected to highly variable fatigue loading during work. To ensure the safety of the chisel on a working implement for the duration of its service life, fatigue testing must be performed with the proper fatigue test load conditions. In this study, working loads for a chisel were developed by reconstructing loads from strain gage data collected during field tests and used to conduct fatigue tests on the chisel component. Methods: FE analysis with nCode software was utilized to select the proper quantity and locations of strain gages for load measurements. A fatigue test was performed to experimentally verify the fatigue strength of the chisel and to evaluate the validity of the load history developed with the load reconstruction technique. Results: A strain history for the chisel was obtained from data collected during field tests. The data was filtered for the 14-16 km/h speed range, connected, and merged. The chisel load history was developed using the load reconstruction technique. The resulting load history was expressed as a load spectrum using the rain-flow counting method. Conclusions: A fatigue test was conducted on a chisel under a constant load condition with an equivalent load amplitude and number of cycles, as calculated by Miner's Rule for linear damage accumulation. During the fatigue test, there were no cracks at any position. It is concluded that the fatigue test method proposed in this study can be utilized successfully as a durability evaluation method for the chisel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.3
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• pp.567-571
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• 2009

This study was conducted in order to investigate the role of working memory in word recognition. As a preliminary step in tackling this topic, word frequency and working memory load were manipulated in a naming task. The results showed that word frequency is significantly involved with the working memory load. The effects of working memory load were greater in low-frequency word processing than in high-frequency word processing. These results indicat that working memory is involved more in the processing of low-frequency words. The implications for the teaching of children at the early reading acquisition stage are discussed in this paper.

• Journal of Navigation and Port Research
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• v.32 no.9
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• pp.737-742
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• 2008

In this paper, we deal with an allocation model of vertical type container yard for minimizing the total ATC (Automated Transfer Crane) working time and the equivalence of ATC working load in each block on automated container terminal. Firstly, a layout of automated container terminal yard is shown The characteristic of equipment which work in the terminal and its basic assumption are given Next, an allocation model which concerns with minimizing the total working time and the equivalence of working load is proposed for effectiveness of ATC working in automated container terminal. Also, a weight values on critical function are suggested to adjust the critical values by evaluating the obtained allocation plan. For ATC allocation algorithm, we suggest a simple repeat algorithm for on-line terminal operation.

• Anxiety and mood
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• v.18 no.1
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• pp.32-37
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• 2022

Objective : Impaired working memory has been known to play an important role in the pathophysiology of obsessive-compulsive disorder (OCD) with growing evidence. Delayed matching-to-sample task (DMST) is a working memory task which have an advantage in analyzing several different working memory processes in one task. However, most of the studies have failed to reveal the working memory impairment with the DMST. The aim of this study was to identify whether working memory deficit in OCD can be evaluated with the DMST. Methods : The participants included 20 OCD patients and 20 healthy volunteers. Working memory was evaluated with the DMST with two different working memory loads. Accuracy of response and mean response time were measured. Results : OCD patients showed a significantly longer reaction time and lower accuracy in DMST compared to healthy controls in the task with high working memory loads. Moreover, the difference in accuracy showed interaction with the working memory load. Conclusion : The present results indicate that working memory deficit in patients with OCD can be evaluated with the DMST. The findings also suggest that previous negative behavioral results using the DMST were from low working memory load of the task.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.283-305
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• 2001

The purpose of this study was to analyze the stress distribution of condylar regions and edentulous mandible with implant-supported cantilever prostheses on the certain conditions, such as amount of load, location of load, direction of load, fixation or non-fixation on the condylar regions. Three dimensional finite element analysis was used for this study. FEM model was created by using commercial software, ANSYS(Swanson, Inc., U.S.A.). Fixed model which was fixed on the condylar regions was modeled with 74323 elements and 15387 nodes and spring model which was sprung on the condylar regions was modeled with 75020 elements and 15887 nodes. Six Br${\aa}$nemark implants with 3.75 mm diameter and 13 mm length were incorporated in the models. The placement was 4.4 mm from the midline for the first implant; the other two in each quardrant were 6.5 mm apart. The stress distribution on each model through the designed mandible was evaluated under 500N vertical load, 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. The load points were at 0 mm, 10 mm, 20 mm along the cantilever prostheses from the center of the distal fixture. The results were as follows; 1. The stress distribution of condylar regions between two models showed conspicuous differences. Fixed model showed conspicuous stress concentration on the condylar regions than spring model under vertical load only. On the other hand, spring model showed conspicuous stress concentration on the condylar regions than fixed model under 250N horizontal load linguobuccally, buccal 20 degree 250N oblique load and buccal 45 degree 250N oblique load. 2. Fixed model showed stress concentration on the posterior and mesial side of working and balancing condylar necks but spring model showed stress concentration on the posterior and mesial side of working condylar neck and the posterior and lateral side of balancing condylar neck under vertical load. 3. Fixed model showed stress concentration on the posterior and lateral side of working condylar neck and the anterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior sides of working and balancing condylar necks under horizontal load linguobuccally. 4. Fixed model showed stress concentration on the posterior side of working condylar neck and the posterior and lateral side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 20 degree oblique load. 5. Fixed model showed stress concentration on the anterior and lateral side of working condylar neck and the posterior and mesial side of balancing condylar neck but spring model showed stress concentration on the anterior side of working condylar neck and the anterior and lateral side of balancing condylar neck under buccal 45 degree oblique load.. 6. The stress distribution of bone around implants between two models revealed difference slightly. In general, magnitude of Von Mises stress was the greatest at the bone around the most distal implant and the progressive decrease more and more mesially. Under vertical load, the stress values were similar between implant neck and superstructure vertically, besides the greatest on the distal side horizontally. 7. Under horizontal load linguobuccally, buccal 20 degree oblique load and buccal 45 degree oblique load, the stress values were the greatest on the implant neck vertically, and great on the labial and lingual sides horizontally. After all, it was considered that spring model was an indispensable condition for the comprehension of the stress distributions of condylar regions.

• Journal of the Ergonomics Society of Korea
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• v.26 no.1
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• pp.39-46
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• 2007

The purpose of this study was to develop a comprehensive posture classification scheme considering the effects of external load and motion repetition as well as those of working posture. The scheme was developed based on a series of existing empirical studies dealing with postural classification scheme, effects of external load and motion repetition. Ranges of joint motions, external load and motion repetition were divided into the groups with the same degree of discomforts. Each group was assigned a numerical relative discomfort score of code on the basis of discomfort values for the neutral position of elbow flexion. The criteria for evaluating stress of working postures were proposed based on the four distinct action categories, in order to enable practitioners to apply appropriate corrective actions. The proposed scheme was compared with OWAS, RULA and REBA. The comparison revealed that while the proposed scheme and RULA showed similar results for the working postures with light external load and non-repetitive postures, the former overestimated postural load for postures with moderate or heavy external load and repetitive postures than the latter.

• 제어로봇시스템학회:학술대회논문집
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• 1988.10b
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• pp.869-874
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• 1988

The operational control of the rotary snowplow is considered to improve its working efficiency. The speed of the rotary snowplow is controlled, so that the load to the rotary snowplow is kept constant. As the load can not directly be detected, some items considered for the controlled variable are, for example, the engine revolution, the load pressure and etc. In order to examine these, the working simulation of the rotary snowplow was considered by introducing the experimental equation of the load. The control methods were examined by means of the simple digital control using the personal computer. These control methods were compared with simulations and experiments. Consequently, the working efficiency is improved about 20% than the manual operation.