• Journal of Positioning, Navigation, and Timing
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• v.2 no.2
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• pp.115-121
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• 2013

For the auto-landing operation of an air vehicle, the possibility of auto-landing operation should be first evaluated by testing the navigation performance through a flight test. In general, navigation performance is tested by analyzing north/east/down (NED) errors relative to reference equipment whose precision is about 8~10 times higher than that of a navigation system. However, to evaluate the auto-landing operation of an air vehicle, whether the air vehicle approaches a glide path aligned with the runway, within a specific error, needs to be examined rather than examining the north/east errors of the navigation system. Therefore, the longitudinal/lateral errors of air vehicle heading need to be analyzed. In this study, a method for analyzing the longitudinal/lateral errors of a navigation system was proposed as the navigation performance test method for evaluating the safety during the auto-landing of an air vehicle. Also, flight tests were performed six times, and the safety of auto-landing was examined by analyzing the performance using the proposed method.

• Physical Therapy Korea
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• v.21 no.2
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• pp.8-17
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• 2014

The purpose of this study was to examine the effects of hip joint mobilization (HJM) on walking ability, balance ability, and the joint range of motion in stroke patients to minimize the problems of the musculoskeletal system in patients with central nervous system diseases. All volunteers were randomly assigned to the HJM group ($n_1=14$) and the general neurodevelopment therapy (NDT) group ($n_2=16$). The HJM procedure involved applying Maitland mobilization techniques (distraction, lateral gliding, inferior gliding, and anterior gliding) by grade 3 to both hip joint. The mobilization process included mobilization and NDT for 15 min/day, 3 days a week for 4 weeks. The outcome measures were evaluated, including the hip joint passive range of motion (ROM) test and femur head anterior glide test (FHAG) using prone figure four test, dynamic and static balance abilities [timed up and go (TUG) test and center of pressure (COP) analysis], and walking ability [10-meter walking test (10MWT) and 6-min walking test (6MWT)]. Both the groups showed significant post-training differences in the hip joint ROM (FHAG and degree of hip extension) and 10MWT. The post-training improvements in the TUG test were significantly greater in patients of the HJM group than in the NDT group; however, there were no post-training improvements in COP in both groups. Patients in the HJM group showed post-training improvement in the 6MWT; however, statistically significant differences were not observed. Patients in the NDT group showed post-training improvements in the 6MWT. These results suggest that HJM improves hip joint ROM, dynamic balance ability, and walking speed in stroke patients. However, further studies are required to evaluate the long-term therapeutic efficacy of HJM in stroke patients.

• Journal of the Korean institute of surface engineering
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• v.38 no.6
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• pp.207-211
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• 2005

In this work a multi-layered nanostructured TiAIN/CrN superlattice coatings was synthesized using closed-field unbalanced magnetron sputtering method and the relationships between their superlattice period (1), micro-structure, hardness and elastic modulus were investigated. In addition, wear test at $500^{\circ}C$ and oxidation resistance test at $900^{\circ}C$ were performed to investigate high temperature properties of these thin films. The coatings were characterized in terms of microstructure and mechanical properties by transmission electron microscopy (TEM) and nano-indentation test. Results from TEM analysis showed that superlattice periods was inversely proportional to the jig rotation speed. The maximum hardness and elastic modulus of 37 GPa and 375 GPa were observed at superalttice period of 6.1 nm and 4.4 nm, respectively. An higher value of microhardness from TiAIN/CrN thin films than either TiAIN (30 GPa) or CrN (26 GPa) was noted while the elastic modulus was approximately an average of TiAIN and CrN films. These enhancement effects in superlattice films could be attributed to the resistance to dislocation glide across interface between the CrN and TiAIN layers. Much improved plastic deformation resistance ($H^3/E^2$) of 0.36 from TiAIN/CrN coatings was observed, compared with 0.15 and 0.16 from TiAIN and CrN, respectively. Also the wear resistance at $500^{\circ}C$ was largely increased than those of single TiAIN and CrN coatings and TiAIN/CrN coatings showed much reduced weight gain after exposure at $900^{\circ}C$ for 20 hours.

• Transactions of Materials Processing
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• v.17 no.1
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• pp.46-51
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• 2008

Polycrystalline materials such as steels(BCC) and aluminum alloys(FCC) show the strain hardening and the strain rate hardening during the plastic deformation. The strain hardening is induced by deformation resistance of dislocation glide on some crystallographic systems and increase of the dislocation density on grain boundaries or inner grain. However, the phenomenon of the strain rate hardening is not demonstrated distinctly in the rage of $10^{-2}$ to $10^2/sec$ strain rate. In this paper, tensile tests for various strain rates are performed in the rage of $10^{-2}$ to $10^2/sec$ then, specimens are extracted on the same strain position to investigate the microscopic behavior of deformed materials. The extracted specimens are investigated by using the electron backscattered diffraction(EBSD) and transmission electron microscopy(TEM) results which show the effect of texture orientation, grain size and dislocation behavior on the strain rate hardening.

• Korean Journal of Materials Research
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• v.33 no.6
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• pp.251-256
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• 2023

This study aims to examine the correlation between microstructures and the mechanical properties of two high-strength API X70 linepipe steels with different specimen directions and Moaddition. The microstructure of the Mo-added steel has an irregularly shaped AF, GB matrix with pearlite because of the relatively large deformation in the non-recrystallization temperature region, while that of the Mo-free steel shows a PF matrix with bainitic microstructure. In the Mo-added steel, the M/A (martensite-austenite) in granular bainite (GB) and pearlite act as crack initiation sites with decreased upper shelf energy and an increased ductile to brittle transition temperature (DBTT). Regardless of Mo addition, all of the steels demonstrate higher strength and lower elongation in the T direction than in the L direction because of the short dislocation glide path and ease of pile-up at grain boundaries. In addition, the impact test specimens with T-L direction had a lower impact absorbed energy and higher DBTT than those with the L-T direction because the former exhibit shorter unit crack path compared to the latter.

• Physical Therapy Korea
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• v.23 no.4
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• pp.1-8
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• 2016

Background: Various methods are used for recovery of knee flexion range of motion (ROM) due to a tightened rectus femoris muscle (RFM) or limited inferior glide of the patella. Stretching methods are common interventions for restoring the tightened RFM length. Also patellar inferior gliding (PIG) technique can recover tightened RFM length too. However, effect of applying the PIG to passive knee flexion (PKF) has not been studied. Objects: The purpose of this study was to investigate the effect of combining PIG with RFM stretching for improving knee flexion ROM in subjects with RFM tightness. Methods: Twenty-six subjects with RFM tightness were recruited. Two different methods of knee stretching were tested: 1) PKF during modified Thomas test (MTT) and 2) PKF with PIG during MTT. The passive stretching forces was controlled by hand-held dynamometer. The knee flexion ROM angle was measured by a MTT with ImageJ software. Differences between the conditions with and without PIG were identified with a paired t-test. Results: The knee flexion ROM was significantly greater for PKF with PIG ($114.44{\pm}9.33$) than for PKF alone ($108.97{\pm}9.42$) (p<.001). Conclusion: A combination of passive knee flexion exercise and PIG can be more effective than PKF in increasing knee flexion ROM in individuals with RFM tightness.

• Physical Therapy Korea
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• v.29 no.1
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• pp.70-78
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• 2022

Background: Individuals with calf muscle shortening may have decreased dynamic balance. Objects: This study aimed to investigate the effect of mobilization with movement (MWM) and myofascial release (MFR) on kinematic changes in dynamic balance in individuals with calf muscle shortening. Methods: Thirteen participants were randomly assigned to the MWM or the mobilization with movement added myofascial release (MWM-MFR) group. The MWM group received treatment with only MWM, whereas the MWM-MFR group was treated with MWM and MFR. Pre- and post-intervention passive range of motion (PROM), maximum reaching lengths, and modified star excursion balance test (MSEBT) results were compared for all participants. Wilcoxon signed-rank test and Mann-Whitney U test were used for statistical analysis. Results: The results showed significant within-group differences in ankle PROM, but no significant between-group differences. The maximum reaching length in the MWM-MFR group in the posterolateral direction was significantly different before and after the intervention (p = 0.005). This group also showed significantly reduced ankle abduction in MSEBT during the posteromedial direction section 3 (p = 0.007) and posterolateral direction section 5 (p = 0.049) compared with the MWM group. Conclusion: Combined MWM and MFR intervention improves ankle stability in the coronal plane during the posteromedial and posterolateral forward movement in dynamic balance compared with only MWM in individuals with calf shortening.

• The Journal of the Korean dental association
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• v.56 no.5
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• pp.254-262
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• 2018

Objectives: This study aimed to compare the postoperative pain and clinical performance after applying three different intracanal medicaments and root canal sealers. Materials and Methods: Sixty-five patients requiring root canal treatment due to symptomatic apical periodontitis were included in this study. After a glide path preparation by using PathFile, each canal was shaped with ProTaper Next file system. After the canal cleaning and shaping procedure, the canal was dried and each intracanal medicaments were adjusted (Calcipex II, TRC-paste, Metapaste). At the next visit, the patients were requested to answer the absence of the pain after the procedure. Once the patients showed no symptom, the canal was obturated with each corresponded root canal sealers (AH plus, Radic-sealer, ADseal). The patients were recalled after 1 week, 1, 3, and 6 months to check the postoperative pain or unexpected clinical signs. One-way ANOVA and Duncan's post hoc comparison, and Chi-square test were used for statistical analysis to evaluate any differences among tested materials. Results: The average number of visits for intracanal medication was 2.69, 2.65, and 2.61 for Calcipex II, TRC-paste, and Metapaste. There were no statistically differences in post-obturation pain among three groups obturated with different root canal sealers (P > 0.05). Conclusions: Under the limitations of this study, three tested intracanal medicaments and epoxy resin root canal sealers showed clinically acceptable similar results.

• Nuclear Engineering and Technology
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• v.8 no.4
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• pp.203-207
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• 1976

Strain rate dependence of the flow stress of cold-worked and annealed Zircaloy-4 was studied by stress relaxation test in temperature range of 20$0^{\circ}C$ to 45$0^{\circ}C$. The In $\sigma$-ln i curves for various temperatures were straight in the eirange of 10$^{-5}$ to 10$^{-3}$ sec$^{-1}$ . From the slope of a curve strain rate sensitivity m was obtained. The m in cold-worked Zircaloy-4 had a minimum value at 30$0^{\circ}C$, while m in annealed Zircaloy-4 had two minimum values, one at 30$0^{\circ}C$ and the other at 45$0^{\circ}C$. It was found that the temperatures of the minimum m are consistent with the temperatures of strain ageing peaks. The minimum m at 30$0^{\circ}C$ is considered to be due to strain ageing owing to the pinning of glide dislocations by oxygen atoms, while the minimum m at 45$0^{\circ}C$ for annealed specimen is attributed to iron atoms.

• Journal of Dental Rehabilitation and Applied Science
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• v.28 no.4
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• pp.371-383
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• 2012

Shaping the root canal system to maintain original canal curvature is essential to clinical success in endodontic treatment. Opposed to most root canals that are curved, endodontic instruments are made from straight metal blanks. They have a tendency of straightening the root canal during preparation and frequently result in procedural errors. A new treatment method to maintain original canal curvature during shaping has been introduced for preventing procedural errors. The aim of this study was to compare the ability of instruments to maintain original canal curvature of continuous rotary system and single file system. Thirty ISO 15, 0.02 taper, Endo Training Blocks(Dentsplay Maillefer) were used. Specimens were assigned to 1 of 3 groups for shaping: specimens in group 1 were shaped with ProFile #20/.06 at the WL. Specimens in group 2 were shaped with Mtwo #35/.04 at the WL. Specimens in group 3 were shaped with WaveOne Primary reciprocating files at the WL after the glide path was achieved with PathFile. Pre- and postinstrumentation digital images were superimposed and processed with Matlab r2010b(The MathWorks Inc, Natick, MA) software to analyze the curvature-radius ratio(CRr), representing canal curvature modification. Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file were analyzed with 1-way ANOVA(P<.05). Data for comparison on the ability of instruments to maintain original canal curvature depending on each Ni-Ti file system were analyzed with independent t-test(P<.05). A statistically significant difference(P<0.05) was noted on each Ni-Ti file. ProFile and WaveOne instrumentations maintained the original canal curvature significantly better(P<0.05) than Mtwo file. There were no significant difference(P>0.05) between continuous rotary system and single file system. Under the conditions of this study, ProFile and WaveOne instruments maintained the original curvature significantly better than Mtwo file and were less modification of the canal curvature compared. There was no significant difference between continuous rotary system and single file system in shaping of simulated canals. As clinical practitioners, it may be advantages to use hybrid approach when root canal shapes depending on the design and usage of Ni-Ti files.