• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.11
• /
• pp.1157-1162
• /
• 2011

The parking brake is an essential unit embedded in the track-driving motor of an excavator. The parking brake plays an important role in keeping the excavator in place not only when it is parked, but also during the digging operation. In fact, the load placed on the parking brake during the digging operation is significantly higher than the parking load, because the impact and rating loads caused by the bucket digging force cycle frequently and have very high load ranges. Therefore, the load conditions during the digging operation should be taken into account in the parking brake certification test. In this study, a series of experiments was carried out in which various operating pressures were applied to the parking brake, where repeated loads were reciprocally placed on the brake by locking the multifriction disc and releasing the hydraulic cylinder. The characteristics of the parking brake were investigated by comparing the obtained experimental results and the theoretical design specifications.

• Journal of Information Technology Services
• /
• v.17 no.4
• /
• pp.101-117
• /
• 2018

Companies are responding appropriately to the rapidly changing business environment and striving to lead those changes. As part of that, we are meeting our strategic goals through IT projects, which increase the number of simultaneous projects and the importance of project portfolio management for successful project execution. It also strives for efficient deployment of human resources that have the greatest impact on project portfolio management. In the early stages of project portfolio management, it is very important to establish a reasonable manpower plan and allocate performance personnel. This problem is a problem that can not be solved by linear programming because it is calculated through the standard deviation of the input ratio of professional manpower considering the uniformity of load allocated to the input development manpower and the importance of each project. In this study, genetic algorithm, one of the heuristic methods, was applied to solve this problem. As the objective function, we used the proper input ratio of projects, the input rate of specialist manpower for important projects, and the equal load of workload by manpower. Constraints were not able to input duplicate manpower, Was used as a condition. We also developed a program for efficient application of genetic algorithms and confirmed the execution results. In addition, the parameters of the genetic algorithm were variously changed and repeated test results were selected through the independent sample t test to select optimal parameters, and the improvement effect of about 31.2% was confirmed.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.63 no.4
• /
• pp.13-21
• /
• 2021

The feasibility of HWS for agricultural use was analyzed through a crop cultivation test to utilize the hydroponic waste solution (HWS) generated from the nutriculture greenhouse. The fertilizing effect of HWS was assessed on the basis of the inorganic nitrogen (N) mostly existed in HWSs, and nitrogen (urea) fertilizer. Lettuce was selected as the target crop influenced by the soil treatment and also for the crop cultivation test. Thus, the change in growth characteristics of lettuce and that in chemical characteristics of the soil were investigated. In terms of the growth of lettuce, the C control group with 70% nitrogen (urea) fertilizer and 30% HWS and the D control group with 50% nitrogen (urea) fertilizer and 50% HWS were more effective than the practice control group (B) with 100% nitrogen (urea) fertilizer. The results of this study confirmed the combined applicability of the chemical fertilizer and HWS for crop cultivation. Because NO₃-N present in HWS has a high possibility of leaching into the soil, its applicability as a fertilizer has been considered to be relatively low in Korea. However, if an appropriate mixing ratio of urea fertilizer and HWS could be applied, the problems associated with leaching of nitrate nitrogen could be reduced with beneficial effects on crop cultivation. Thus, future studies are required on the treatment effect of HWS with repeated cultivation, impact assessment on the surrounding environment, and appropriate fertilization methods using nitrogen (urea) fertilizer and HWS. These studies would facilitate the sustainable recycling of HWS.

• Steel and Composite Structures
• /
• v.38 no.2
• /
• pp.151-164
• /
• 2021

During the pipe forming process, a steel plate undergoes inelastic behavior multiple times under a load condition repeating tension and compression in the circumferential direction. It derives local reduction or increase of yield strength within the thickness of steel pipes by the plastic hardening and Bauschinger effect. In this study, a combined hardening model is proposed to effectively predict variations of yield strength in the circumferential direction of API-X65 and X70 steel pipes with relatively low t/D ratio during the forming process, which is expected to experience accumulated plastic strain of 2~3%, the typical Lüder band range in a low-carbon steel. Cyclic tensile tests of API-X65 and X70 steels were performed, and the parameters of the proposed model for the steels were calibrated using the test results. Bending-flattening tests to simulate repeated tension and compression during pipe forming were followed for API-X65 and X70 steels, and the results were compared with those by the proposed model and Zou et al. (2016), in order to verify the process of material model calibration based on tension-compression cyclic test, and the accuracy of the proposed model. Finally, parametric analysis for the yield strength of the steel plate in the circumferential direction of UOE pipe was conducted to investigate the effects of t/D and expansion ratios after O-forming on the yield strength. The results confirmed that the model by Zou et al. (2016) underestimated the yield strength of steel pipe with relatively low t/D ratio, and the parametric analysis showed that the t/D and expansion ratio have a significant impact on the strength of steel pipe.

• Earthquakes and Structures
• /
• v.26 no.1
• /
• pp.77-86
• /
• 2024

To investigate the seismic performance of steel pipe-aeolian sand recycled concrete columns, this study designed and produced five specimens. Low-cycle repeated load tests were conducted while maintaining a constant axial compression ratio. The experiment aimed to examine the impact of different aeolian sand replacement rates on the seismic performance of these columns. The test results revealed that the mechanical failure modes of the steel pipe-recycled concrete column and the steel pipe-aeolian sand recycled concrete column were similar. Plastic hinges formed and developed at the column foot, and severe local buckling occurred at the bottom of the steel pipe. Interestingly, the bulging height of the damaged steel pipe was reduced for the specimen mixed with an appropriate amount of wind-deposited sand under the same lateral displacement. The hysteresis curves of all five specimens tested were relatively full, with no significant pinching phenomenon observed. Moreover, compared to steel tube-recycled concrete columns, the steel tube-aeolian sand recycled concrete columns exhibited improved seismic energy dissipation capacity and ductility. However, it was noted that as the aeolian sand replacement rate increased, the bearing capacity of the specimen increased first and then decreased. The seismic performance of the specimen was relatively optimal when the aeolian sand replacement rate was 30%. Upon analysis and comparison, the damage analysis model based on stiffness and energy consumption showed good agreement with the test results and proved suitable for evaluating the damage degree of steel pipe-wind-sand recycled concrete structures.

• The Journal of Korean Academy of Prosthodontics
• /
• v.49 no.4
• /
• pp.324-332
• /
• 2011

Purpose: The purpose of this study was to compare the stress distribution of teeth and jaw on load by differentiating property of materials according to each layer of widely used mouthguard. Materials and methods: A Korean adult having normal cranium and mandible was selected to examine. A customized mouthguard was constructed by use of DRUFOMAT plate and DRUFOMAT-TE/-SQ of Dreve Co. according to Signature Mouthguard system. The cranium was scanned by means of computed tomography with 1mm interval. It was modeled with CANTIBio BIONIX/Body Builder program and simulated and interpreted using Alter HyperMesh program. The mouthguard was classified as follows according to the layers. (1) soft guard (Bioplast)(SG) (2) hard guard (Duran)(HG) (3) medium guard (Drufomat)(MG) (4) soft layer + hard layer (SG + HG) (5) hard layer + soft layer (HG + SG) (6) soft layer + hard layer + soft layer (SG + HG + SG) (7) hard layer + soft layer + hard layer (HG + SG + HG) The impact locations on mandible were gnathion, the center of inferior border, and the anterior edge of gonial angle. And the impact directions were oblique ($45^{\circ}$). The impact load was 800 N for 0.1 sec. The stress distribution was measured at maxillary teeth, TMJ and maxilla. The statistics were conducted using Repeated ANOVA and in case of difference, Duncan test was used as post analysis. Results: In teeth and maxilla, the mouthguard contacting soft layer of mandibular teeth presented lowest stress measure and, in contrast, in condyle, the mouthguard contacting hard layer of mandibular teeth presented lowest stress measure. Conclusion: For all impact directions, soft layer + hard layer + soft layer, the mouthguard with three layers which the hard layer is sandwiched between two soft layers, showed relatively even distribution of stress in impact.

• Korean Journal of Health Education and Promotion
• /
• v.26 no.5
• /
• pp.97-113
• /
• 2009

Objectives: This study was conducted to identify the intervention effects on health efficacy and health knowledge related to health behaviors for improving cardiovascular health in elementary school children. Methods: A repeated measure, pre-post-test design was used to identify the intervention effect on health efficacy and health knowledge among 5th grade school children. Intervention consisted of a curriculum classroom intervention and parent intervention. Health efficacy, health knowledge, and perceived parental monitoring were measured for testing intervention effect. A sample of 219 participants completed a baseline pre-test and two tests during intervention and after intervention from March to July 2004. Results: Mental health efficacy improved significantly from baseline test to the test after intervention (F = 32.88, p < 0.0001). Physical health efficacy also significantly increased during intervention (F = 50.51, p < 0.0001), but did not significantly change after parent intervention. Health knowledge increased significantly from baseline test to the test after education (F =10.23, p < 0.0001), but decreased after parent intervention. Perceived parental monitoring had a significant impact on mental health efficacy and physical health efficacy. Conclusion: The findings support school-based cardiovascular health promotion intervention as effective in improving health efficacy and health knowledge. Parental influence should also be considered to maintain improved health efficacy and health knowledge by thinking process in the intervention for elementary school children.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.6
• /
• pp.10-15
• /
• 2017

The refraction expansion joints have been newly developed by complementing the problems of shock, noise, replaceability, displacement in the direction perpendicular to bridge, vertical difference, which are problems of existing expansion joints. The Refraction expansion joints are characterized by continuous surfaces with small impact and low noise. The behavior of the Refraction expansion joints performs the bridge expansion behavior by rotation of the link. In the rotational behavior of the link, the bolt is the central axis of the behavior. Therefore, it can be said that the durability of the bolt is very important. However, the theoretical and experimental verification of the bolt durability of the Refraction expansion joint is lacking. In this paper, to verify the fatigue durability of the bolt, test specimens with a 300 mm Refraction expansion joint were fabricated. A strain gauge dedicated to the bolt was installed inside the manufactured test specimen bolt. The test method was applied in accordance with KS F 4425. The fatigue durability of the bolts assembled inside the diaphragm expansion joint was confirmed by the repeated fatigue test of 2,000,000 cycles.

• The Journal of Korean society of community based occupational therapy
• /
• v.3 no.1
• /
• pp.33-42
• /
• 2013

Objective : The purpose of this study is to assess effects of Robot-assisted therapy on function of upper extremity in stroke patients. Method : A total of 11 patients suffered from stroke participated in this study. Inpatients of 4 people and outpatients of 7 people divided by 12 months conducted Robot-assisted therapy for 5~6 weeks. Therapists selected appropriate exercise mode to patients, and patients Patients performed the reaching exercise was repeated with looking monitor provided 3-dimensional feedback. Before and after treatment of upper extremity functions was compare by Wolf Motor Function(K-WMFT), Box & Block Test(BBT), Dynamometer, average execution time. Result : Grip power, K-WMFT, BBT, average performance times were promoting in all subjects, and only showed statistically significant changes in outpatients. But outpatients did not show statistically significant changes in inpatients. Conclusion : Robotic-assisted therapy in stroke patients have a positive impact on upper extremity function that could confirm that. In the future, Robots-assisted therapy is expected to be useful for stroke patients in the area of occupational therapy.

• Child Health Nursing Research
• /
• v.7 no.1
• /
• pp.21-34
• /
• 2001

The impact of childhood experience has lifelong significance on subsequent health and development. Especially, the experience of infant is mostly affected by the quality of parental care and rearing environment. But the new mothers usually do not know what to do because of the lack of experience in these days. Therefore, an educational program regarding maternal role would be necessary. This study was conducted to evaluate the effectiveness of the maternal role education program for mother-infant interaction, child-rearing environment, and infant development. Non-equivalent control group time-series design was used, and Barnard's mother-infant interaction model was used as a conceptual framework of this study. The subjects were the healthy infants weighing over 2,500gm at birth, whose gestational age was more than 37 weeks, and their mothers. The final sample consisted of 19 mother-infant dyads for intervention group and 18 dyads for control group. Data were collected from March 15th to September 3rd in 1999. For the intervention group, programmed education which focused on mother-infant interaction, breast feeding, and infant care was provided before discharge. Telephone counselling was provided within one week after discharge. Home visiting for maternal role education was provided twice, one month and three months postpartum. For the control group, home visiting was also conducted but only for data collection. The data were analyzed using chi-square test and t-test to test the equivalence of two groups, and the effectiveness of intervention program was determined with repeated measure ANCOVA and t-test. The results were as follows: 1. Significant differences were found in mother-infant interaction between two groups(p=.000). It indicates that intervention program was effective in improving mother- infant interaction. In subscale analysis, four out of six subscale showed significant differences between the groups: sensitivity to cues (p=.000), social-emotional growth fostering (p=.000), cognitive growth fostering(p=.000) in mothers, and responsiveness to caregiver (p=.019) in infants. 2. The difference in the mean score of childrearing environment (HOME) between the intervention group and control group was significant(p=.003). When each subscale of HOME was examined individually, intervention group showed significantly higher scores in the diversity of stimulation(p=.000), and mother's involvement(p=.001). 3. Three-month-Infants of the intervention group showed higher GQ in the Griffiths mental development scale(p=.026). In subscale analysis, significant differences were found in the personal-social(p=.005), and the hearing and speech(p=.003). In conclusion, the maternal role education program proved to be effective in promoting the mother-infant interaction, organizing the childrearing environment, and fostering the infant development. These results are very meaningful that we found maternal role education necessary for normal infants' mothers, and that nurses can make a great contribution in promoting health of infants and mothers.