• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.7
• /
• pp.605-611
• /
• 2011

Shimmy is a self-excited vibration in lateral and torsional directions of a landing gear during either the take-off or landing. It is caused by a couple of conditions such as a low torsional stiffness of the strut, a free-play in the landing gear, a wheel imbalance, or worn parts, and it may make the aircraft unstable. This study was performed for an analysis of the shimmy stability on a small aircraft. A nose landing gear was modeled as a linear system and characterized by state-equations which were used to analyze the stability both in the frequency and time-domain for predicting whether the shimmy occurs and investigating a good design range of the important parameters. The root-locus method and the 4th Runge-Kutta method were used for each analysis. Because the present system has a simple mechanism using a friction to reinforce the stability, the friction, a non-linear factor, was linearized by a describing function and considered in the analysis and observed the result of the instability reduction.

• Journal of Positioning, Navigation, and Timing
• /
• v.6 no.4
• /
• pp.159-166
• /
• 2017

The position of autonomous driving vehicle is basically acquired through the global positioning system (GPS). However, GPS signals cannot be received in tunnels. Due to this limitation, localization of autonomous driving vehicles can be made through sensors mounted on them. In particular, a 3D Light Detection and Ranging (LIDAR) system is used for longitudinal position error correction. Few feature points and structures that can be used for localization of vehicles are available in tunnels. Since lanes in the road are normally marked by solid line, it cannot be used to recognize a longitudinal position. In addition, only a small number of structures that are separated from the tunnel walls such as sign boards or jet fans are available. Thus, it is necessary to extract usable information from tunnels to recognize a longitudinal position. In this paper, fire hydrants and evacuation guide lights attached at both sides of tunnel walls were used to recognize a longitudinal position. These structures have highly distinctive reflectivity from the surrounding walls, which can be distinguished using LIDAR reflectivity data. Furthermore, reflectivity information of tunnel walls was fused with the road surface reflectivity map to generate a synthetic reflectivity map. When the synthetic reflectivity map was used, localization of vehicles was able through correlation matching with the local maps generated from the current LIDAR data. The experiments were conducted at an expressway including Maseong Tunnel (approximately 1.5 km long). The experiment results showed that the root mean square (RMS) position errors in lateral and longitudinal directions were 0.19 m and 0.35 m, respectively, exhibiting precise localization accuracy.

• Journal of Korean Society of Forest Science
• /
• v.67 no.1
• /
• pp.10-16
• /
• 1984

Containerized Quercus acutissima seedlings were inoculated with vegetative mycelial inoculum of Pisolithus tinctorius and were grown in a green-house. The ectomycorrhizal fungus, P. tinctorius (Pt) increased growth of the container-grown oak seedlings. Of three treatments, Pt inoculation stimulated remarkably primary lateral roots, shoot growth, and root collar diameter and leaf area development, compared with either non-inoculated or natural soil treatment. In addition, Pt-inoculated seedlings produced ectomycorrhizae, by 71.1 percent. However, noninoculated and naturally grown seedlings were free of natural ectomycorrhizal. Ectomycorthizal roots developed more abundantly in the middle portion of the container than in the top or bottom portions.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.33 no.4
• /
• pp.704-709
• /
• 2006

Ectopic eruption should be understood as a change in the course of the normal eruption path of a dental bud at any moment in its origin. Transposition is a unique and extreme form of ectopic eruption. The treatment for ectopic eruption and transposition is various from simple observation to surgical exposure and orthodontic traction, according to direction of erupting tooth degree of developing root apex and eruption space etc. Autotransplantation is transplantation of tooth from one area of the mouth to another in the same individual or is moving a eruption tooth into extraction socket or surgically prepared socket, and autotransplantation is considered as a treatment of choice for the ectopic eruption when orthodontic traction is unable or when tooth movement is limited. These cases which were treated with autotransplantation of maxillary lateral incisor and maxillary canine were reported, and good esthetic and functional result were induced.

• Journal of Korean Society of Forest Science
• /
• v.99 no.2
• /
• pp.172-178
• /
• 2010

The status of ectomycorrhizal (ECM) fungal colonization in Pinus thunbergii seedlings was investigated 2 years after planting in an eastern coastal area of Korea. We established three $10{\times}10$ m plots at a P. thunbergii plantation in Gangneung and sampled lateral roots from 10 seedlings in each plot. ECMs were classified into morphological groups and the number of root tips of each morphotype was counted. In total, 8 ECM morphotypes were observed and fungal species that form each morphotype were identified by sequencing of the internal transcribed spacer (ITS) region of the nuclear rDNA. Suillus granulatus was the most abundant species (44.1-65.7% of relative abundance) in all plots, followed by Tomentella ellisii (14.0-37.8%) and unidentified fungus belonged to Atheliaceae (10.6-20.1%). These 3 fungal species accounted for almost all of the ECM abundance in each plot (94.9-99.8%). The remaining 5 fungal species were uncommon and rare. There was no clear difference in ECM fungal communities among plots. Community structure of ECM fungi in the young P. thunbergii plantation was simple and composed of fungal species that were also observed in mature coastal pine forests.

• Journal of Plant Biotechnology
• /
• v.5 no.4
• /
• pp.225-231
• /
• 2003

The hormonal requirement suiting micropropagation of Morus alba during any season throughout the year was studied. Sprouting frequency from axillary buds of M. alba was greatly influenced by the time of explant collection, the highest value was achieved when nodal explants were collected at the end of bud dormancy period (late in March) and cultured on Murashige and Skoog (MS) medium supplemented with low concentration (0.5 mg/L) of BAP, kinetin or IBA (85-68%). In addition, they showed higher axillary bud sprouting on growth-regulators-free medium (49%) than others collected in autumn or winter and cultured on medium supplemented with various growth regulators (47-48%). Regardless of that period, young explants with greenish buds collected in summer exhibiting high sprouting frequency (66%) on MS medium supplemented with 0.5 mg/L kinetin and 0.5 mg/L GA3. Shoot multiplication via adventitious bud formation was achieved when the nodal explants were cultured on MS medium supplemented with 2 mg/L BAP and 0.2 mg/L IBA. Further multiplication via nodal explants of in vitro grown shoots was obtained on MS medium supplemented with 0.5 mglL BAP and 0.5 mg/L GA3. While half strength MS medium supplemented with low concentration (0.5 mg/L) of IBA, IAA or 2,4-D stimulated adventitious root formation, IBA was the best. After transfer the plantlets to the soil, acclimatization for three weeks was essential prerequisite for survival in high frequency (92%). Peroxidase activity is related to break of bud dormancy where maximum enzyme activity was detected when the lateral buds were induced to commence growth under field condition (early in spring) or in vitro.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.47 no.3
• /
• pp.189-195
• /
• 2002

Soybean sprout trails were evaluated for soybeans for sprout (Glycine max) and wild soybeans (Glycine soja). Soybeans for sprout are characterized with small seed size of 10-14 grams per 100 seeds and are traditionally used only for producing sprouts. No difference was observed in hypocotyl length and sprout yield between two types of soybean. (However total length, hypocotyl hypocotyl, body weight, and the rate of good quality were greater in soybeans for sprout.) Number of lateral roots and root length were greater in wild soybeans. Contents of crude oil, oleic acid, and sucrose were higher in soybean for sprout, while that of protein and linoleic acid were higher in wild soybeans. There was no difference in sprout isoflavone content. Out of 17 amino acids analyzed, 10 amino acids such as aspartic acid, lysine, and arginine. etc. showed significantly Higher content in wild soybeans. Hypocotyl color of sprouts estimated by color meter based on the degree of L(brightness), a(red), and b(yellow) values were better in wild soybeans than soybean for sprout.

• The Journal of Korean Physical Therapy
• /
• v.21 no.3
• /
• pp.17-24
• /
• 2009

Purpose: The purpose of this study was to investigate the effects of a combination of isotonic (CI) technique on the balance, muscle fatigue and muscle activities of the quadriceps muscle in the paretic leg of hemiplegic patients. Method: All the subjects received a combined isotonic technique of proprioceptive neuromuscular facilitation (PNF) for about 30 minutes 3 times per week for 6 weeks. The root mean square (RMS) and mid frequency (MF) were recorded by surface electromyography (EMG)(EMG/EP system, OXFORD Medelec, UK) during maximal voluntary isometric contractions (MVIC). The balance ability was measured by a balance system (BIODEX, USA). Result: The RMS of the quadriceps muscle at post-treatment was significantly increased compared to that at pretreatment (p<0.05). Yet there was no significant difference among the three muscles. There were no significant difference in the MF of the vastus lateralis and rectus femoris between pre- and post-treatment, but the MF of the vastus medialis was significantly decreased (p<0.05). There was a significant difference in the vastus medialis and lateralis between pre- and post-treatment (p<0.05). Moreover, the overall stability index at post-treatment was significantly decreased compared to that at pre-treatment (p<0.05). But there was no significant difference between the anterior/posterior and medial/lateral stability indexes. Conclusion: The results of this study indicated that a CI technique of PNF had an effect to improve the balance and muscle activity in hemiplegic patients.

• Journal of the Korea Convergence Society
• /
• v.9 no.10
• /
• pp.371-376
• /
• 2018

The purpose of this study is to clarify the effects of whole-body vibration and to provide scientific basis for effective exercise by analyzing the differences in lower extremity muscle activation according to squat position during whole body vibration. In this study, muscle activation during whole-body vibration was measured in 10 healthy males in their 20s with no orthopedic conditions during standing posture, deep squat, half squat, and heel raise squat. Muscle activation was compared by measuring the root mean square (RMS) with electromyography electrodes attached to lateral gastrocnemius, tibialis anterior, vastus lateralis, and biceps femoris. The vibration intensity was applied in combinations of the volumes of 50 and 80 and the frequencies of 10, 25, and 40 Hz in each posture. The results showed that there were differences in muscle activations of external gastrocnemius, tibialis anterior, and vastus lateralis among the position(p<.05). The heal raise squat was found to have a high muscle activation effect.

• Archives of Plastic Surgery
• /
• v.39 no.3
• /
• pp.190-197
• /
• 2012

Background : This article presents long-term outcomes after correcting secondary bilateral cleft lip nasal deformities using a refined reverse-U incision and V-Y plasty or in combination with a composite graft in order to elongate the short columella. Methods : A total of forty-six patients underwent surgery between September 1996 and December 2008. The age of the patients ranged from 3 to 19 years of age. A bilateral reverse-U incision and V-Y plasty were used in 24 patients. A composite graft from the helical root was combined with a bilateral reverse-U incision in the 22 patients who possessed a severely shortened columella. The follow-up period ranged between 2 and 10 years. Results : A total of 32 patients out of 46 were evaluated postoperatively. The average columella length was significantly improved from an average of 3.7 mm preoperatively to 8.5 mm postoperatively. The average ratio of the columella height to the alar base width was 0.18 preoperatively and 0.29 postoperatively. The postoperative basal and lateral views revealed a better shape of the nostrils and columella. The elongated columella, combined with a composite graft, presented good maintenance of the corrected position with no growth disturbance. A composite graft showed color mismatching in several patients. Twenty-six patients demonstrated no alar-columella web deformity and satisfactory symmetry of the nostrils. Four patients experienced a drooping and overhanging of the corrected alar-columella web. Conclusions : A bilateral reverse-U incision with V-Y plasty or in combination with a composite graft was effective in correcting secondary bilateral cleft lip nasal deformity.