• Journal of the Korean Physical Society
• /
• v.73 no.9
• /
• pp.1225-1229
• /
• 2018

The Drosophila auditory system consists of four large basal segments: the arista, the funiculus, the pedicel, and the scape. When an acoustic stimulus is applied to the arista and the funiculus their mechanical vibrations are transmitted to chordotonal neurons in Johnston's organ where mechanoelectric transduction arises. We study the mechanotransduction mechanism in the Drosophila auditory system by using a laser Doppler vibrometer (LDV) and extracellular electrophysiology. We find that large and small peaks appear alternatively and that the antenna vibration is asymmetric depending on whether the pedicel and the scape are fixed. Interestingly, we find that this asymmetric vibration accompanies the alternating neural peak structure. Here, we propose a mathematical model to explain the alternating peak structure by using a model consisting of two opposing neurons that are modeled as strings. Generally, strings have tension only when they are elongated. This property allows the alternating neural peaks for asymmetric antenna motion.

• Korea-Australia Rheology Journal
• /
• v.19 no.3
• /
• pp.99-107
• /
• 2007

A nanofluid is a mixture of solid nanoparticles and a common base fluid. Nanofluids have shown great potential in improving the heat transfer properties of liquids. However, previous studies on the characteristics of nanofluids did not adequately explain the enhancement of heat transfer. This study examined the distribution of particles in a fluid and compared the mechanism for the enhancement of heat transfer in a nanofluid with that in a general microparticle suspension. A theoretical model was formulated with shear-induced particle migration, viscosity-induced particle migration, particle migration by Brownian motion, as well as the inertial migration of particles. The results of the simulation showed that there was no significant particle migration, with no change in particle concentration in the radial direction. A uniform particle concentration is very important in the heat transfer of a nanofluid. As the particle concentration and effective thermal conductivity at the wall region is lower than that of the bulk fluid, due to particle migration to the center of a microfluid, the addition of microparticles in a fluid does not affect the heat transfer properties of that fluid. However, in a nanofluid, particle migration to the center occurs quite slowly, and the particle migration flux is very small. Therefore, the effective thermal conductivity at the wall region increases with increasing addition of nanoparticles. This may be one reason why a nanofluid shows a good convective heat transfer performance.

• Journal of Biomedical Engineering Research
• /
• v.36 no.6
• /
• pp.271-275
• /
• 2015

The aim of this study was to develop a multi-nozzle based bioprinting system for fabrication of three-dimensional (3D) biological structure. In this study, a thermoplastic biomaterial that has relatively high mechanical stability, polycaprolactone (PCL) was used to make the 3D structure. A multi-nozzle bioprinting system was designed to dispense thermoplastic biomaterial and hydrogel simultaneously. The system that consists of 3-axes of x-y-z motion control stage and a compartment for injection syringe control mounted on the stage has been developed. Also, it has 1-axis actuator for position change of nozzle. The controllability of the printed line width with PCL was tested as a representative performance index.

• Journal of Biomedical Engineering Research
• /
• v.39 no.6
• /
• pp.278-283
• /
• 2018

Nowdays, many people suffer from the neck pain due to forward head posture(FHP) and text neck(TN). To assess the severity of the FHP and TN the craniovertebral angle(CVA) is used in clinincs. However, it is difficult to monitor the neck posture using the CVA in daily life. We propose a new method using the cervical flexion angle(CFA) obtained from a wearable sensor to monitor neck posture in daily life. 15 participants were requested to pose FHP and TN. The CFA from the wearable sensor was compared with the CVA observed from a 3D motion camera system to analyze their correlation. The determination coefficients between CFA and CVA were 0.80 in TN and 0.57 in FHP, and 0.69 in TN and FHP. From the monitoring the neck posture while using laptop computer for 20 minutes, this wearable sensor can estimate the CVA with the mean squared error of 2.1 degree.

• Proceedings of the KOSOMBE Conference
• /
• v.1994 no.05
• /
• pp.111-114
• /
• 1994

Three component velocity measurements with a refractive index-matching technique was used to investigate the flow characteristics in the atrio-pulmomnary (AP) Fontan connection under the steady flow condition. A strong swirl was observed in the extra-cardiac conduit and the main pulmonary artery (MPA). Maximum velocity magnitude in the MPA was about 0.8 m/s near the posterior wall at 6 liter/min. Swirling motion of the flow as well as geometric abnormalities of the connection are important factors in energy loss across Fontan connections.

• Journal of Biomedical Engineering Research
• /
• v.8 no.2
• /
• pp.111-116
• /
• 1987

In this study, basilar membrane motions and neural tuning responses are analysed with I-dimensional equations for cochlear fluid mechanics and an active cochlear model. The results are as follows. (1) The differences between basilar membrane motions in an active cochlear model and in an passive cochlear model are explained. (2) The basilar membrane motion curves and the neur'at tuning curves which are in accordance with physiological measurements ave obtained. (3) It is proved that the active mechanism makes cochlear highly frequency sensitive.

• Journal of the Korean Society for Precision Engineering
• /
• v.29 no.7
• /
• pp.717-722
• /
• 2012

This paper presents the design and dynamic model of the finger exoskeleton actuated by Ionic Polymer Metal Composites (IPMC) to assist a tip pinch task. Although this exoskeleton will be developed to assist 3 degree-of-freedom motion of each finger, it has been currently made to perform the tip pinch task using 1 degree-of-freedom mechanism as the first step. The six layers of IPMC were stacked in parallel to increase the low actuation force of IPMC. In addition, the finger dummy was manufactured to evaluate the performance of the finger exoskeleton. The pinch task experiments, which were performed on the finger dummy with the developed exoskeleton, showed that the pinch force close to the desired level was obtained. Moreover, the dynamic model of the exoskeleton and finger dummy was developed in order to perform the various analyses for the improvement of the exoskeleton.

• Journal of Korean Neurosurgical Society
• /
• v.59 no.6
• /
• pp.647-649
• /
• 2016

The device for intervertebral assisted motion (DIAM) is a dynamic implant that consists of a silicone bumper enveloped by a polyethylene terephthalate (PET) fiber sack. Silicone and PET were used because of their biological inertness, but repetitive motion of the spine can cause wear on the implant nonetheless. The purpose of this study is to report a case of foreign body reaction (FBR) against a DIAM. A 72-year-old female patient presented with lower back pain and both legs radiating pain. She had undergone DIAM implantation at L4-5 for spinal stenosis 5 years previously. The intervertebral disc space of L4-5, where the DIAM was inserted, had collapsed and degenerative scoliosis had developed due to left-side collapse. MRI showed L3-4 thecal sac compression and left L4-5 foraminal stenosis. The patient underwent removal of the DIAM and instrumented fusion from L3 to L5. During surgery, fluid and granulation tissue were evident around the DIAM. Histopathology showed scattered wear debris from the DIAM causing chronic inflammation due to the resulting FBR. A FBR due to wear debris of a DIAM can induce a hypersensitivity reaction and bone resorption around the implant, causing it to loosen.

• Journal of Biomedical Engineering Research
• /
• v.29 no.2
• /
• pp.139-145
• /
• 2008

Many recent studies suggest that the posterior dynamic stabilization(PDS) can be a more physiologically-relevant alternative to the rigid fixation for the patients suffering from low back pain. However, its biomechanical effects or clinically proven efficacies still remain unknown. In this study, we evaluated kinematic behaviors of the lower lumbar spine with the PDS system and then compared to those of the rigid fixation system using finite element (FE) analysis. A validated FE model of intact lumbar spine(L2-L5) was developed. The implanted model was then constructed after modification from the intact to simulate two kinds of pedicle screw systems (PDS and the rigid fixation). Hybrid protocol was used to flex, extend, laterally bend and axially rotate the FE model. Results showed that the PDS systems are more flexible than rigid fixation systems, yet not flexible enough to preserve motion. PDS system allowed $16.2{\sim}42.2%$ more intersegmental rotation than the rigid fixation at the implanted level. One the other hand, at the adjacent level it allowed more range of motion ($2.0%{\sim}8.3%$) than the rigid fixation. The center of rotation of the PDS model remained closer to that of the intact spine. These results suggest that the PDS system could be able to prevent excessive motion at the adjacent levels and restore the spinal kinematics.

• Journal of Biomedical Engineering Research
• /
• v.41 no.3
• /
• pp.121-127
• /
• 2020

The purpose of this paper is to review the validation on the application of low frequency IMU(Inertial Measurement Unit) sensors by replacing high frequency motion analysis systems. Using an infrared-based 3D motion analysis system and IMU sensors (22 Hz) simultaneously, the gait cycle and knee flexion angle were measured. And the accuracy of each gait parameter was compared according to the statistical analysis method. The Bland-Altman plot analysis method was used to verify whether proper accuracy can be obtained when extracting gait parameters with low frequency sensors. As a result of the study, the use of the new gait assessment system was able to identify adequate accuracy in the measurement of cadence and stance phase. In addition, if the number of gait cycles is increased and the results of body anthropometric measurements are reflected in the gait analysis algorithm, is expected to improve accuracy in step length, walking speed, and range of motion measurements. The suggested gait assessment system is expected to make gait analysis more convenient. Furthermore, it will provide patients more accurate assessment and customized rehabilitation program through the quantitative data driven results.