• Computers and Concrete
• /
• v.8 no.2
• /
• pp.207-227
• /
• 2011

In flexural strength design of unconfined reinforced concrete (RC) members, the concrete compressive stress-strain curve is scaled down from the uni-axial stress-strain curve such that the maximum concrete stress adopted in design is less than the uni-axial strength to account for the strain gradient effect. It has been found that the use of this smaller maximum concrete stress will underestimate the flexural strength of unconfined RC members although the safety factors for materials are taken as unity. Herein, in order to investigate the effect of strain gradient on the maximum concrete stress that can be developed in unconfined flexural RC members, several pairs of plain concrete (PC) and RC inverted T-shaped specimens were fabricated and tested under concentric and eccentric loads. From the test results, the maximum concrete stress developed in the eccentric specimens under strain gradient is determined by the modified concrete stress-strain curve obtained from the counterpart concentric specimens based on axial load and moment equilibriums. Based on that, a pair of equivalent rectangular concrete stress block parameters for the purpose of flexural strength design of unconfined RC members is determined.

• Ocean Systems Engineering
• /
• v.2 no.2
• /
• pp.159-171
• /
• 2012

Reinforced concrete structures in cold coastal regions are subjected to coupled effects of service load, freeze-thaw cycles and seawater corrosion. This would significantly degrade the performance and therefore shorten the service life of these structures. In the current paper, the mechanical properties of concrete material and the structural behaviour of eccentrically loaded reinforced concrete columns under multiple actions of seawater corrosion, freeze-thaw cycles and persistent load have been studied experimentally. Results show that when exposed to alternating actions of seawater corrosion and freeze-thaw cycles, the compressive strength of concrete decreases with the increased number of freeze-thaw cycles. For reinforced concrete column, if it is only subjected to seawater corrosion and freeze-thaw cycles, the load resistance capacity is found to be reduced by 11.5%. If a more practical service condition of reinforced concrete structures in cold coastal regions is simulated, i.e., the environmental factors are coupled with persistent loading, a rapid drop of 15% - 26.9% in the ultimate capacity of the eccentrically loaded reinforced concrete column is identified. Moreover, it is observed that the increase of eccentric load serves to accelerate the deterioration of column structural behavior.

• Korean Journal of Applied Biomechanics
• /
• v.24 no.1
• /
• pp.59-66
• /
• 2014

The purpose of this study was to investigate the effects of knee joint muscle fatigue and overweight on shock absorption during single-leg landing of adult women. Written informed consent forms, which were approved by the human subject research and review committee at Dong-A University, were provided to all subjects. The subjects who participated in this study were divided into 2 groups: a normal weight group and an overweight group, consisting of 15 young women each. Both the normal weight group and the overweight group showed that use soft landing and ankle dominant strategy. The peak vertical ground reaction force, the knee joint absorption power, and eccentric work done, as the increase of knee joint muscle fatigue level, showed a decrease. And the hip joint absorption power and eccentric work done, as the increase of weight, was less than the overweight group showed the normal weight group. In conclusion, the accumulation of the knee joint muscle fatigue and the increase of body weight may lead to an increased risk of injury during landing.

• Steel and Composite Structures
• /
• v.37 no.4
• /
• pp.405-418
• /
• 2020

The application of double-skin composite wall should meet different layout plans. However, most available research focused on the rectangular section with uniform axial compression. In this research, the structural behavior of double-skin composite wall with L section was studied. Due to the unsymmetric geometric characteristics, the considered loading condition combined the axial compression and biaxial bending. Five specimens were designed and tested under eccentric compression. The variables in the test included the width of the web wall, the truss spacing, the thickness of the steel faceplate, and the thickness of the web wall. The test results were discussed in terms of the load-displacement responses, buckling behavior, stiffness, ductility, strength utilization, strain distribution. Two modern codes were employed to predict the interaction between the axial compression and the biaxial bending. The method to calculate the available bending moment along the two directions was proposed. It was found that CECS 159:2004 offers more suitable results than AISC 360.

• Journal of Institute of Control, Robotics and Systems
• /
• v.10 no.12
• /
• pp.1202-1209
• /
• 2004

This paper presents a design methodology of a Digital Servo Signal Processor for high speed CD-RW drive systems. The proposed Digital Servo Signal Processor enables us to develop CD-related systems for the very high speed applications and is one of the key components of the CD-RW systems. The proposed center compensation servo control is newly built for an actuator shaking due to the fast response of a step motor when it jumps to a long distance. A control method compensating for eccentricity of a disc is implemented for operating robustly at a higher rotational speed. This servo mechanism is more size efficient and less power consumed because it is implemented using a ARM7 embedded processor and hardware digital filters. Furthermore, it is convenient to upgrade firmware for the future required functions. From experimental results, we can see that the performance of the control system is improved greatly. The proposed servo algorithm shows a shorter setting time including a pull-in time and a faster access time. It can be applied easily to the DVD-ROM and the DVD-RAM which have the same optical structure.

• Journal of Mechanical Science and Technology
• /
• v.16 no.12
• /
• pp.1576-1582
• /
• 2002

Vibration of a BLDC motor is a coupled phenomenon between mechanical characteristics and magnetic origins which takes place through the motor airgap. When relative misalignment of a rotor in the airgap is introduced during assembly, the dynamic characteristics of the motor system are affected. The rotor-motor system used in a washing machine is modeled using FETM and magnetic forces in a BLDC motor with radial rotor eccentricity are determined analytically The transient whirl responses of a rotor system supported on two roller bearings with relative misalignment in the motor airgap are investigated by considering mechanical and magnetic coupling effects. Results show that rotor misalignment in the airgap considerably affects the vibration of the rotor-motor system.

• Journal of The Korean Society of Integrative Medicine
• /
• v.2 no.3
• /
• pp.31-37
• /
• 2014

Purpose : Delayed onset muscle soreness(DOMS) is a common problem that can interfere with rehabilitation as well as activities of daily living. The purpose of this study was to compare the effect of both trascutaneous electrical nerve stimulation(TENS) Micro current(MC) and only normal Therapy on Delyed Onset Muscle Soreness(DOMS). Method : The Methods ten untrained and male volunteer subjects were randomly assigned to one of two treatment groups: 1) a group that received TENS (60Hz) MC($60{\mu}A$, 3pps) a control group that received no MC treatment. Subjects performed repeated eccentric exercise of the non-dominant forearm flexor muscle with submaximal intensity by the simply designed eccentric exercise devices. Treatments were applied after 24hours and 48hours. Subjects attended on two consecutive days for treatment and measurement of paining(visual analogue scale: VAS) and CK(Creatine kinase) on a daily basis. Measurements were taken after treatment. Results : 1) There were no significant differences between TENS and MENS by two-way repeated ANOVA. The Results that t-test for VAS revealed significant differences within TENS group. 3) The t-test for VAS, and Creatine Kinase of time revealed significant differences within MC group. Conclusion : These findings suggest that both TENS and MENS had effect on DOMS.

• The Journal of Korean Physical Therapy
• /
• v.13 no.2
• /
• pp.273-280
• /
• 2001

The purpose of this study was to analyze the effect of quadriceps setting exercise(N= 10) and electrical stimulation(N= 10) on improvement of quadriceps muscle strength. The experiment were performed for 6weeks. The subject of this study was 20 college students(male) who had not any medical problems. The quadriceps muscle strength was evaluated by make use of the KIN COM(Isokinetic dynamometer). The electrical stimulator was used to stimulate the quadriceps muscle. The results were as follows: 1. The mean increment ratio was 29.6% for concentric muscle strength and 36.4% for eccentric muscle strength after quadriceps setting exercise(p<0.05). 2. The mean increment ratio was 21.2% for concentric muscle strength and 24.3% for eccentric muscle strength after electrical stimulation, but did not significantly higher than pre-electrical stimulation In this study, we have found that quadriceps setting exercise on left side affect the improvement of the muscle strength in college students(male). However, electrical stimulation did not affect on the muscle strength.

• The KSFM Journal of Fluid Machinery
• /
• v.8 no.3 s.30
• /
• pp.26-32
• /
• 2005

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fall has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control the size and position, is the important cause of performance decrease. In this study, experiments we carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spiral, which is the important factor having an effect on it.

• The Journal of Korean Medicine
• /
• v.26 no.4
• /
• pp.39-45
• /
• 2005

Objectives: The study investigated the efficacy of oral Korean red-ginseng (RG) on sCRP response mediated by eccentric contraction-induced muscle damage and discussed its mechanism. Methods: Nineteen healthy young subjects (aged 24.4$\pm$2.07 yr) volunteered for this double blind test. They were classified into either the RG group (N=10) or placebo (P) group (N=9) during the 10-d experimental protocol. Blood samples were collected on T1 (baseline), T1 (1h), T2 (1d), T3 (2d) and T4 (3d) after eccentric contraction-induced injury on the seventh day. Statistical analyses were conducted using nonparametric methods (p<0.05). Results: The RG group increased sCRP more than P group and didn't increase soreness peak at T2, not significant. There were no correlations between soreness intensity and sCRP. Oral RG had little efficacy for reducing sCRP at the muscle damage-mediated acute phase; rather, it increased because of its proinflammatory cytokine production. Conclusions: Oral RG could stimulate proinflammatory cytokine production, and occasionally bal-pyo-beob could be helpful for the efficient recovery of muscle injury.