Do Hyun Kim

Nonlinear characteristics of pseudo-Y-junction single-walled carbon nanotubes

We fabricated nanoscale field-effect transistors based on Y-junction single-walled carbon nanotubes (SWCNTs) and characterized their performance. The Y-junction transistor was modulated by a metallic branch of the Y-SWCNTs and exhibited the characteristics of an ambipolar field-effect transistor (FET) at room temperature. We obtained a subthreshold swing of 700mV∕decade and an Ion∕off ratio of 105 with a low off-state leakage current of ∼10−13A. These results are of fundamental interest in nano-FET as well as CNT-mat study and may suggest reliable applications in nanoelectronics and sensors.

Pseudo Y-Junction Single-Walled Carbon Nanotube Based Ambipolar Transistor Operating at Room Temperature

A nanoscale field-effect transistor (FET) was fabricated based on pseudo Y-junction single-walled carbon nanotubes (Y-SWNTs). The Y-junction transistor was modulated by a metallic branch of the Y-SWNTs, and exhibited ambipolar FET characteristics at room temperature. A subthreshold swing of 700 mV/decade and an on/off ratio of 105 with a low off-state current of ~10-13 A were obtained. Analysis of the electrical transport of pseudo Y-SWNTs is fundamental to the study of transport properties in a carbon nanotube mat (CNT-mat)

Fabrication and Characteristics of Zinc Oxide- and Gallium doped Zinc Oxide thin film transistor using Radio Frequency Magnetron sputtering at Room Temperature

In this paper we present a bottom-gate type of zinc oxide (ZnO) and Gallium (Ga) doped zinc oxide (GZO) based thin film transistors (TFTs) through applying a radio frequency (RF) magnetron sputtering method at room temperature. The gate leakage current can be reduced up to several ph by applying thermally grown instead of using new gate oxide materials. The root mean square (RMS) values of the ZnO and GZO film surface were measured as 1.07 nm and 1.65 nm, respectively. Also, the transmittances of the ZnO and GZO film were more than 80% and 75%, respectively, and they were changed as their film thickness. The ZnO and GZO film had a wurtzite structure that was arranged well as a (002) orientation. The ZnO TFT had a threshold voltage of 2.5 V, a field effect mobility of , a on/off ratio of , a gate voltage swing of 17 V/decade and it operated in a enhancement mode. In case of the GZO TFT, it operated in a depletion mode with a threshold voltage of -3.4 V, a field effect mobility of , a on/off ratio of and a gate voltage swing of 3.3 V/decade. We successfully demonstrated that the TFTs with the enhancement and depletion mode type can be fabricated by using pure ZnO and 1wt% Ga-doped ZnO.

Effects of Three Weeks of Whole-Body Vibration Training on Joint-Position Sense, Balance, and Gait in Children with Cerebral Palsy: A Randomized Controlled Study

Purpose: To observe the effects of whole-body vibration (WBV) training in conjunction with conventional physical therapy (PT) on joint-position sense (JPS), balance, and gait in children with cerebral palsy (CP). Methods: In this randomized controlled study, 24 children with CP were randomly selected either to continue their conventional PT or to receive WBV in conjunction with their conventional PT programme. Exposure to the intervention was intermittent (3 min WBV, 3 min rest) for 20 minutes, twice weekly for 3 weeks. JPS, balance, and gait were evaluated before and after treatment. Results: Ankle JPS was improved after 3 weeks of WBV training (p=0.014). Participants in the WBV group showed greater improvements in speed (F1,21=5.221, p=0.035) and step width (F1,21=4.487, p=0.039) than participants in the conventional PT group. Conclusion: Three weeks of WBV training was effective in improving ankle JPS and gait variables in children with CP.

Effects of novel tubing gait on neuromuscular imbalance in cerebral palsy.

BACKGROUNDnGait impairments from a neuromuscular imbalance are crucial issues in cerebral palsy. The purpose of our study was to compare the effects of the assistive tubing gait (ATG) and assistive-resistive tubing gait (ARTG) on improving the vasti and hamstring muscle imbalance during the initial contact to mid-stance phases in individuals with spastic diplegic cerebral palsy (CP).nnnMETHODSnFourteen age-matched individuals including seven normal individuals (11.7 years) and seven individuals with CP (12.9 years) were recruited. All participants underwent electromyography (EMG) measurement of the unilateral vasti and hamstring muscle activity during the three gait training conditions of no-tubing gait (NTG), ATG, and ARTG. A statistical one-way repeated-measure analysis of variance (ANOVA) was used to determine differences in the vasti and hamstring activity, the vasti/hamstring ratio, and the knee joint angle across the three gait training conditions for each group.nnnRESULTSnThe initial vasti and hamstring muscle imbalance in CP was significantly improved by applying the ARTG compared with the ATG. The vasti/hamstring ratio during the ARTG was compatible with the ratio value obtained from the NTG of normal individuals. The knee joint angle in CP was not improved in this short-term intervention.nnnCONCLUSIONSnThe ARTG proportionately increased the vasti activation and reciprocally inhibited the hamstring activity, subsequently improving the neuromuscular imbalance associated with the flexed-knee gait in individuals with spastic diplegic CP.

Inhibitory effects of instrument-assisted neuromobilization on hyperactive gastrocnemius in a hemiparetic stroke patient.

An instrument-assisted soft tissue mobilization (IASTM) technique has recently been used specifically to inhibit hypertonic muscles and to lengthen muscle fiber shortness. However, it is unknown whether IASTM will show such promising inhibition effects on excessive ankle plantarflexion following stroke. Therefore, the purpose of this study was to use electromyographic (EMG) analysis to determine the ability of IASTM to reduce gastrocnemius (GCM) hypertonicity and concurrently facilitate tibialis anterior (TA) lengthening in a stroke patient. EMG activity on the patients TA and GCM was measured before and after applying IASTM. After the intervention, the GCM was deactivated by 43%, and TA activity increased by 150%, indicating IASTM-induced inhibition of the overactive GCM. The neuromobilization technique using IASTM showed a promising improvement of neuromuscular imbalance between TA and GCM activations, which can increase gait performance in a stroke case.

Effects of manual therapy with functional electrical stimulation on scoliosis curve in children with cerebral palsy

[Purpose] The purpose of this study was to investigate the effect of manual therapy with functional electrical stimulation (FES) on scoliosis curve and quality of life in children with cerebral palsy (CP). [Participants and Methods] Two children with CP performed 30 minutes of manual therapy and 30 minutes of FES three times a week for 3 months. The Cobb’s angle and Pediatric Quality of Life Inventory (PedsQL) score were assessed before and after the intervention. [Results] The Cobb’s angle and PedsQL score were improved after intervention. [Conclusion] Our results indicate that manual therapy with FES was effective for improving scoliosis curve and quality of life.

The validity and reliability of a dynamic neuromuscular stabilization-heel sliding test for core stability

BACKGROUNDnCore stabilization plays an important role in the regulation of postural stability. To overcome shortcomings associated with pain and severe core instability during conventional core stabilization tests, we recently developed the dynamic neuromuscular stabilization-based heel sliding (DNS-HS) test.nnnOBJECTIVEnThe purpose of this study was to establish the criterion validity and test-retest reliability of the novel DNS-HS test.nnnMETHODnTwenty young adults with core instability completed both the bilateral straight leg lowering test (BSLLT) and DNS-HS test for the criterion validity study and repeated the DNS-HS test for the test-retest reliability study. Criterion validity was determined by comparing hip joint angle data that were obtained from BSLLT and DNS-HS measures. The test-retest reliability was determined by comparing hip joint angle data.nnnRESULTSnCriterion validity was (ICC2,3) = 0.700 (p< 0.05), suggesting a good relationship between the two core stability measures. Test-retest reliability was (ICC3,3) = 0.953 (p< 0.05), indicating excellent consistency between the repeated DNS-HS measurements.nnnCONCLUSIONSnCriterion validity data demonstrated a good relationship between the gold standard BSLLT and DNS-HS core stability measures. Test-retest reliability data suggests that DNS-HS core stability was a reliable test for core stability. Clinically, the DNS-HS test is useful to objectively quantify core instability and allow early detection and evaluation.

Changes in gluteal pressure and center of force during sitting in children with cerebral palsy

[Purpose] The purpose of this study was to measure gluteal pressure and center of force (COF) during sitting in children with cerebral palsy (CP). [Subjects and Methods] The participants were five children with CP and five typically developing controls. We measured peak gluteal pressure and COF using the TekScan system. During the measurements, all children sat on the therapeutic table for 1 minute without back and foot support. [Results] The peak gluteal pressure and COF in children with CP were significantly higher than values in controls. [Conclusion] This study suggests that it is important to distribute hip pressure evenly and transfer COF in a forward direction during rehabilitation in children with CP.

Effects of 4 weeks of dynamic neuromuscular stabilization training on balance and gait performance in an adolescent with spastic hemiparetic cerebral palsy

[Purpose] The purpose of this study investigated the effects of 4 weeks of dynamic neuromuscular stabilization training on balance ability. [Subject and Methods] An adolescent with spastic hemiparetic cerebral palsy was recruited. The subject performed 4 weeks of dynamic neuromuscular stabilization training. We assessed the balance subtest of the Bruininks-Oseretsky Test of Motor Proficiency-Second Edition, the 10-meter walk test, and the 6-min walk test. [Results] The balance subtest scores were improved significantly after training. [Conclusion] This study suggests that 4 weeks of dynamic neuromuscular stabilization training is effective for improving balance and gait performance in spastic hemiparetic cerebral palsy.