Kyung-min Lee

A Miniaturized Tadpole Robot Using an Electromagnetic Oscillatory Actuator

In this paper, we propose a miniaturized tadpole-like robot using an electromagnetic oscillatory actuator. The electromagnetic actuator has a simple structure with a moving-magnet type and the body size is 13 mm (length) × 11 mm (height) × 10 mm (width). A tail has the thickness of 100 μm and the length of 20 mm which is twice of the body-length (BL). The tail attached to the oscillatory actuator generates undulatory propulsion for the forward swimming. Moreover, the tadpole robot enables the change of the direction by controlling input signal patterns applied to the oscillatory actuator. Prototypes of the tadpole robot have been manufactured and the thrust force and swimming speed are measured to evaluate the performance of the biomimetic robot in water at various tail-beat frequencies. The maximum thrust force is 42 mN at the tail-beat frequency of 30 Hz with voltage of 3 V, enabling the tadpole robot to swim at the speed of 210 mm·s−1 (6 BL·s−1). The tadpole robot can also change its moving direction with the angular velocity of 21 deg·s−1 at the half pulse pattern of 30 Hz.

Coxsackievirus B Infection Is Highly Related with Missed Abortion in Korea

Purpose This study investigated the possible relationship between viral infection and first trimester pregnancy loss. Materials and Methods A prospective study was performed on 51 gravidas with missed abortion, fetal anomaly, pre-term delivery, and full-tem delivery at Hanyang University Hospital. Enteroviruses were detected by semi-nested reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry in abortive tissues and placentas. Enterovirus serotypes were confirmed by genome sequencing. Herpesviruses were detected by PCR. Results Coxsackievirus B3 (CVB3) was detected in 8 of 14 missed abortion cases, 1 of 27 full-term cases, and none of the 9 pre-term cases. Coxsackievirus B1 (CVB1) was detected in an encephalocele case. Herpes simplex virus type 1 was found in 4 full-term cases, 3 pre-term cases, and none of the missed abortion cases. Conclusion The prevalence of CVB3 was significantly higher in missed abortion cases compared to full-term or pre-term delivery cases. CVB infection may therefore be an important etiological agent of missed abortion.

Seroepidemiologic Survey of Varicella-Zoster Virus in Korean Adults Using Glycoprotein Enzyme Immuno Assay and Fluorescent Antibody to Membrane Antigen Test

BACKGROUNDnHerpes zoster (HZ) occurs mainly in the elderly and Korea is rapidly becoming an aging society. Therefore, it is important to know the immune status against varicella-zoster virus (VZV) in Korean adults to prevent the disease.nnnOBJECTIVEnThe aim of this study was to survey the immune status of Korean adults over 40 years of age against VZV.nnnMETHODSnAntibody titer was measured using a VaccZyme™ VZV glycoprotein enzyme immunoassay (gpEIA) (Binding Site, UK). Fluorescent antibody to membrane antigen (FAMA) test was performed to measure the seropositive rate.nnnRESULTSnHZ incidence in the 214 adults enrolled in this study was 10.3%. The gpEIA geometric mean titer (GMT) was 490 mIU/ml and 90.2% of the subjects had a protective level of gpEIA antibody titer against varicella. The average gpEIA GMT of adults who previously had HZ was 1,122 mIU/ml, which was higher than the average gpEIA GMT of 457 mIU/ml in adults who had not had HZ. The FAMA positive rate was 98.6%.nnnCONCLUSIONnMost (90.2%) Korean adults ≥40-years-of-age have a protective level of gpEIA antibody against varicella and 98.6% were FAMA seropositive. The GMT of gpEIA antibody was significantly increased with age, and was higher in adults with a history of HZ.

Clawed Miniature Inchworm Robot Driven by Electromagnetic Oscillatory Actuator

In this research we propose a novel inchworm robot, which is composed of an Electromagnetic Oscillatory Actuator (EOA) and claws. The EOA consists of a yoke, a magnet, and a coil. The overall robot size is 12.2 mm × 11 mm × 9 mm (length × height × width). The locomotion of the robot is achieved by different amounts of slips when the robot stretches and contracts its front leg. To realize locomotion, the working conditions were calculated theoretically and the calculated input signal was applied to the robot. The performance of the inchworm robot was evaluated experimentally with varying input voltages and frequencies. A simple op-amps based driving circuit was used to provide a square-wave input. Travel speed, average distance per step of the robot, and moving distance of the leg and body at each step were measured. The maximum travel speed was 36 mm·s−1 at 30 Hz, which validates our simple locomotion strategy experimentally.

A compact stair-climbing wheelchair with two 3-DOF legs and a 1-DOF base

Purpose – The purpose of this paper is to describe a compact wheelchair, which has two 3-degrees of freedom (DOF) legs and a 1-DOF base (the total DOF of the leg system is 7) for stair-climbing, and wheels for flat surface driving. Design/methodology/approach – The proposed wheelchair climbs stairs using the two 3-DOF legs with boomerang-shaped feet. The leg mechanisms are folded into the compact wheelchair body when the wheelchair moves over flat surfaces. The authors also propose a simple estimation method of stair shape using laser distance sensors, and a dual motor driving system to increase joint power. Findings – The proposed wheelchair can climb arbitrary height and width stairs by itself, even when they are slightly curved. During climbing, the trajectory of the seat position is linear to guarantee the comfort of rider, and the wheelchair always keeps a stable condition to ensure the stability in an emergency stop. Originality/value – The wheelchair mechanism with foldable legs and driving wheels ...

Power-Assisted Wheelchair With Gravity and Friction Compensation

In this paper, a gravity compensated power-assisted wheelchair (GCPAW) is proposed, which will climb a hill, and stop, and make as a delicate movement in the middle of the hill as it can do on a flat surface. To climb the hill, the proposed GCPAW compensates for the parallel component of the force of gravity (the force that causes acceleration or deceleration) on a hill. A tilt sensor measures the angle of the inclined plane and electric clutches automatically connect and disconnect drive mechanisms with the wheels. The GCPAW also compensates for friction in the drive mechanism that would cause additional resistance. The rider propels the GCPAW in the same way that he/she would propel a manual wheelchair, but the mechanism compensates for both gravity and the friction. Additionally, overcompensation for the friction helps the riders propulsion, so that with the same propulsion force the rider travels further than in a manual wheelchair, resulting in an easier movement for the rider.

Pregnancy loss following coxsackievirus b3 infection in mice during early gestation due to high expression of coxsackievirus-adenovirus receptor (CAR) in uterus and embryo.

Coxsackieviruses are important pathogens in children and the outcomes of neonatal infection can be serious or fatal. However, the outcomes of coxsackievirus infection during early gestation are not well defined. In this study, we examined the possibility of vertical transmission of coxsackievirus B3 (CVB3) and the effects of CVB3 infection on early pregnancy of ICR mice. We found that the coxsackievirus and adenovirus receptor (CAR) was highly expressed not only in embryos but also in the uterus of ICR mice. CVB3 replicated in the uterus 1 to 7 days post-infection (dpi), with the highest titer at 3 dpi. The pregnancy loss rate in mice infected with CVB3 during early gestation was 38.3%, compared to 4.7% and 2.7% in mock-infected and UV-inactivated-CVB3 infected pregnant mice, respectively. These data suggest that the uterus and embryo, which express abundant CAR, are important targets of CVB3 and that the vertical transmission of CVB3 during early gestation induces pregnancy loss.

Design of Rotating Moving-Magnet-Type VCM Actuator for Miniaturized Mobile Robot

A voice coil actuator with a rotating moving magnet has been developed for a miniaturized mobile robot. The actuator has simple structure comprising a magnet, a coil, and a yoke. Actuator performance is predicted using a linearized theoretical model, and dynamic performance based on the air-gap between the magnet and the coil is predicted using motor constant and restoring constant obtained through finite element simulations. The theoretical model was verified using a prototype with 60 Hz resonance and 80 Hz bandwidth. We found that an input of 1.5 V can make the actuator rotate by statically. The driving configuration of the proposed actuator can be simplified because of its implementation of open-loop control.

Design of a high-speed, short-stroke xy-stage with counterbalance mechanisms

In many cases, the moving speed of xy-stages influences the productivity of industrial machines; thus, it is very important to develop high speed xy-stages. This paper presents a high-speed/short-stroke xy-stage mechanism, which is used on a long-stroke stage and which performs high-speed xy-motions in a short range. To reduce the weight of the moving part, the proposed xy-stage transfers the motion of two actuators to the stage through two perpendicularly-installed linear motion guides. The dump force applied to the base frame is also greatly reduced by adding the counterbalance mechanism. A prototype design and its simulation results are presented.

Coxsackievirus B3 infection reduces female mouse fertility.

Previously we demonstrated coxsackievirus B3 (CVB3) infection during early gestation as a cause of pregnancy loss. Here, we investigated the impacts of CVB3 infection on female mouse fertility. Coxsackievirus-adenovirus receptor (CAR) expression and CVB3 replication in the ovary were evaluated by immunohistochemistry or reverse transcription-polymerase chain reaction (RT-PCR). CAR was highly expressed in granulosa cells (GCs) and CVB3 replicated in the ovary. Histological analysis showed a significant increase in the number of atretic follicles in the ovaries of CVB3-infected mice (CVBM). Estrous cycle evaluation demonstrated that a higher number of CVBM were in proestrus compared to mock mice (CVBM vs. mock; 61.5%, 28.5%, respectively). Estradiol concentration in GC culture supernatant and serum were measured by an enzyme-linked immunosorbent assay. Baseline and stimulated levels of estradiol in GC were decreased in CVBM, consistent with significantly reduced serum levels in these animals. In addition, aromatase transcript levels in GCs from CVBM were also decreased by 40% relative to the mock. Bone mineral density evaluated by micro-computed tomography was significantly decreased in the CVBM. Moreover, the fertility rate was also significantly decreased for the CVBM compared to the mock (CVBM vs. mock; 20%, 94.7%, respectively). This study suggests that CVB3 infection could interfere with reproduction by disturbing ovarian function and cyclic changes of the uterus.