• International Journal of Fluid Machinery and Systems
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• v.7 no.3
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• pp.125-129
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• 2014

The paint removal and recoating are the very important process in airplane maintenance. The traditional technology is to use the chemical way corroding the paint with paint remover. For changing the defects, corrosion & pollution & manual working, of the traditional technology, the physical process which removes the paint of airplane with 250MPa/250kW ultra-high pressure rotary water jetting though the surface cleaner installed on the six axes robot is studied. The paint layer of airplane is very thin and close. The contradiction of water jetting paint removal is to remove the paint layer wholly and not damage the surface of airplane. In order to solve the contradiction, the best working condition must be reached through tests. The paint removal efficiency with ultra-high pressure and move speed of not damaged to the surface. The move speed of this test is about 2m/min, and the paint removal efficiency is about $30{\sim}40m^2/h$, and the paint removal active area is 85-90%. No-repeat and no-omit are the base requests of the robot program. The physical paint removal technology will be applied in airplane maintenance, and will face the safety detection of application permission.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.349-354
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• 2011

Tuned mass damper is widely used in many applications of industry. The main advantage of tuned mass damper is that it can increase the damping ratio of system and reduce the vibration amplitude. Meanwhile, the natural frequency of system will be divided by two peaks, and the peak speeds are closely related to the mass and the stiffness of auxiliary mass system added. In addition, the damping ratio will also affect the peak frequency of the dynamic response. In the present research, the nonlinear mechanical characteristics of rubber is investigated and put into use, since it is usually manufactured as the spring element of tuned mass damper. By the sense of the nonlinear stiffness as well as the damping ratio which can be changed by preload applied on, the shape memory alloy is proposed to control the auxiliary mass system by self-optimizing. Supported by the experiment data of rubber, the 1 DOF theoretical model and finite element model based on computer simulation are implemented to perform the feasibility of the proposed semi-active tuned mass damper working on the drive shaft.

• Wind and Structures
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• v.31 no.6
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• pp.483-493
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• 2020

Large cylindrical floating-roof tanks, constructed as oil containers, are usually distributed regularly in open area and easily exposed to severe wind loads. However, wind pressures around these grouped squat tanks appear to have not been clearly given in design codes or thoroughly studied in existing researches. This paper conducts a detailed investigation on wind loads on the external wall of a four-tank group in square arrangement. To achieve that, wind tunnel tests are carried out on both empty and full tank groups, considering various wind angles and spacing. Results show that 3 regions in elevation can be identified on the tank shell according to the circumferential wind pressure distribution. The upper 2 regions cover a relatively small portion of the shell where excessive negative pressures are spotted, setting an alarm to the design of the top angle and stiffening rings. By comparing results on grouped tanks to those on an isolated tank, grouping effects concerning wind angle, tank position in group and spacing are discussed. Deviations on pressure distributions that will compromise structural safety are outlined, including the increase of negative pressures, the shift of maximum pressure locations as well as the change of positive pressure range. And, several potentially unfavourable wind pressure distributions are selected for further analyses.

• Geomechanics and Engineering
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• v.13 no.6
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• pp.1011-1025
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• 2017

The geological conditions surrounding the Jijiapo Tunnel of the Three Gorges Fanba Highway project in Hubei Province are very complex. In this paper, a 3-D physical model was carried out to study the evolution process of filling-type fracture water inrush and mud gush based on the conditions of the section located between 16.040 km and 16.042 km of the Jijiapo Tunnel. The 3-D physical model was conducted to clarify the effect of the self-weight of the groundwater level and tunnel excavation during water inrush and mud gush. The results of the displacement, stress and seepage pressure of fracture and surrounding rock in the physical model were analyzed. In the physical model the results of the model test show that the rock displacement suddenly jumped after sustainable growth, rock stress and rock seepage suddenly decreased after continuous growth before water inrushing. Once water inrush occured, internal displacement of filler increased successively from bottom up, stress and seepage pressure of filler droped successively from bottom up, which presented as water inrush and mud gush of filling-type fracture was a evolving process from bottom up. The numerical study was compared with the model test to demonstrate the effectiveness and accuracy of the results of the model test.

• Journal of the Korean Chemical Society
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• v.51 no.3
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• pp.279-286
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• 2007

In this study, we investigated the influences of cognitive conflict and situational interest induced by a discrepant event and an alternative hypothesis, attention and state learning strategies on conceptual change. A preconception test was administered to 486 seventh graders. They also completed the questionnaires of cognitive response and situational interest to a discrepant event before/after presenting an alternative hypothesis. After learning the concept of density with a CAI program as conceptual change intervention, the tests of attention, state learning strategies, and conceptual understanding were administered as posttests. Analyses of the results for 197 students having misconceptions about density revealed that post-cognitive conflict was significantly higher than pre-cognitive conflict. However, there was no statistically significant difference between the test scores of pre-situational interest and post-situational interest. Pre-cognitive conflict only exerted a direct effect on post-cognitive conflict, while post-cognitive conflict exerted a direct effect and Journal of the Korean Chemical Society an indirect effect via attention on conceptual understanding. Both pre- and post-situational interests were found to influence on conceptual understanding via attention. Attention had influences positively on deep learning strategy and negatively on surface learning strategy. There was a relatively small effect of state learning strategies on conceptual understanding.

• Composites Research
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• v.18 no.3
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• pp.38-46
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• 2005

In order to characterize the outstanding performance of three-dimensional (3D) composites, the low velocity impact test has been carried out. 3D fiber structures have been achieved by using the automated tape placement (ATP) process and a stitching method. Materials for the ATP and the stitching process were carbon/epoxy prepreg tapes and Kevlar fibers, respectively. Two-dimensional composites with the same stacking sequence as 3D counterparts have also been fabricated for the comparison of damage tolerance. For the assessment of damage after the impact loading, specimens were subjected to C-Scan nondestructive inspection. Compression after impact (CAI) tests were conducted to evaluate residual compressive strength. The damage area of 3D composites was greatly reduced $(30-40\%)$ compared with that of 2D composites. Although the CAI strength did not show drastic improvement for 3D composites, the ratio of retained strength was $5-10\%$ higher than 2D samples. The effect of stitching on the impact performance was negligible above the energy level of 35 Joules.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.109-115
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• 2012

In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

• Journal of Korean Neurosurgical Society
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• v.58 no.1
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• pp.14-21
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• 2015

Objective : To study the effect of early intervention and rehabilitation in the expression of aquaporin-4 and ultrastructure changes on cerebral palsy pups model induced by intrauterine infection. Methods : 20 pregnant Wistar rats were consecutively injected with lipopolysaccharide intraperitoneally. 60 Pups born from lipopolysaccharide group were randomly divided into intervention group (n=30) and non-intervention group (n=30); intervention group further divided into early intervention and rehabilitation group (n=10), acupuncture group (n=10) and consolidate group (n=10). Another 5 pregnant rats were injected with normal saline intraperitoneally; 30 pups born from the normal saline group were taken as control group. The intervention group received early intervention, rehabilitation and acupuncture treatment. The motor functions of all pups were assessed via suspension test and modified BBB locomotor score. Aquaporin-4 expression in brain tissue was studied through immunohistochemical and western-blot analysis. Ultrastructure changes in damaged brain and control group were studied electron-microscopically. Results : The scores of suspension test and modified BBB locomotor test were significantly higher in the control group than the intervention and non intervention group (p<0.01); higher in the intervention group than the non-intervention group (p<0.01). The expression of Aquaporin-4 was lower in intervention and non intervention group than in the control group (p<0.01); also lower in non-intervention group than the intervention group (p<0.01). Marked changes were observed in ultrastructure of cortex and hippocampus CAI in brain damaged group. Conclusion : Early intervention and rehabilitation training can improve the motor function in offspring with brain injury and reduce the expression of aquaporin-4 in damaged brain.

• Computers and Concrete
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• v.13 no.3
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• pp.411-421
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• 2014

A central pullout test was conducted to investigate the bonding properties between high strength rebar and reactive powder concrete (RPC), which covered ultimate pullout load, ultimate bonding stress, free end initial slip, free end slip at peak load, and load-slip curve characteristics. The effects of varying rebar buried length, thickness of protective layer and diameter of rebars on the bonding properties were studied, and how to determine the minimum thickness of protective layer and critical anchorage length was suggested according the test results. The results prove that: 1) Ultimate pull out load and free end initial slip load increases with increase in buried length, while ultimate bonding stress and slip corresponding to the peak load reduces. When buried length is increased from 3d to 4d(d is the diameter of rebar), after peak load, the load-slip curve descending segment declines faster, but later the load rises again exceeding the first peak load. When buried length reaches 5d, rebar pull fracture occurs. 2) As thickness of protective layer increases, the ultimate pull out load, ultimate bond stress, free end initial slip load and the slip corresponding to the peak load increase, and the descending section of the curve becomes gentle. The recommended minimum thickness of protective layer for plate type members should be the greater value between d and 10 mm, and for beams or columns the greater value between d and 15 mm. 3) Increasing the diameter of HRB500 rebars leads to a gentle slope in the descending segment of the pullout curve. 4) The bonding properties between high strength steel HRB500 and RPC is very good. The suggested buried length for test determining bonding strength between high strength rebars and RPC is 4d and a formula to calculate the critical anchorage length is established. The relationships between ultimate bonding stress and thickness of protective layer or the buried length was obtained.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.1832-1842
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• 2014

A novel probabilistic small signal stability analysis (PSSSA) method considering load correlation is proposed in this paper. The superiority Latin hypercube sampling (LHS) technique combined with Monte Carlo simulation (MCS) is utilized to investigate the probabilistic small signal stability of power system in presence of load correlation. LHS helps to reduce the sampling size, meanwhile guarantees the accuracy and robustness of the solutions. The correlation coefficient matrix is adopted to represent the correlations between loads. Simulation results of the two-area, four-machine system prove that the proposed method is an efficient and robust sampling method. Simulation results of the 16-machine, 68-bus test system indicate that load correlation has a significant impact on the probabilistic analysis result of the critical oscillation mode under a certain degree of load uncertainty.