• Metals and materials international
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• v.28
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• pp.1778-1782
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• 2021

This study examines the insulation coating technology of Fe-Si-Cr powder via selective oxidation annealing, which oxidizes elements selectively by controlling the oxidation potential. The study calculated the oxidation driving force of Fe, Si, and Cr, and conducted a thermodynamic analysis of oxidation and reduction conditions according to temperature and oxidation potential. Based on the results, a selective oxidation annealing was performed in an atmosphere in which Fe is reduced and only Si and Cr are selectively oxidized. The oxidation potential was controlled through the partial pressure ratio of hydrogen and water vapor. The XPS analysis results confirmed that a Si and Cr complex oxide layer formed on the powder surface after the selective oxidation annealing. Afterward, withstanding voltages were analyzed to evaluate the insulation property. Then, the withstanding voltage of the powder applying the selective oxidation annealing increased significantly compared to that of the initial powder. Further analysis showed that the powder annealed in an air atmosphere had a significantly lower saturation magnetic flux density than the initial powder, while the powder applying the selective oxidation annealing had only a slightly reduced saturation magnetic flux density.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1664-1667
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• 2005

The main function of Ball-Stop part is to operate power shift for vehicle with more than 5 ton when a driver changes gear using suitable force. This paper presents the implementation of a DFSS(Design For Six Sigma) for robust design of Ball-Stop part of power shift. The factors influencing Ball-Stop part performance is derived to find control factor. Based on this factor, contact force between head and detent pin analysis is performed to get optimal factor is analyzed and compared with contact force test result to verify reliability of design. This makes clear the reason why the proposed one is necessary and the role of DFSS.

• Physical Therapy Korea
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• v.10 no.2
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• pp.1-10
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• 2003

This study was carried out to help the comprehensive rehabilitation of spinal cord injuries by measuring propulsion force and endurance exerted on wheelchair handrims, and predicting the differences among three different rear axle positions. The BTE (Baltimore Therapeutic Exerciser) work simulator was used on 9 paraplegia to test the force and endurance during wheelchair propulsion. The 141 large wheel of the BTE work simulator and a standard wheelchair with removed handrims were used for simulating wheelchair propulsion. The neurological and demographical characteristics of the patients were collected by personal interviews and direct examinations. The Kruskal-Wallis test was used to compare force and endurance among the groups. The strongest maximum isometric strength was produced when the rear axle of the wheelchair and the acromion process were on the same coronal plane. Although there were no significant differences statistically, moving the rear axle forward did result in greater isotonic strength. The research suggests that better functional activity of persons with paraplegia is possible when the rear axle of the wheelchair is appropriately adjusted.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.198-203
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• 2004

In these days, the orthodontic surgery including lingual orthodontics has attracted a person' attention due to its functional and esthetic appreciation. The delivery of the optimal orthodontic treatment is greatly influenced by clinician' ability to predict and control the tooth movement by applying force system to dentition. The skeletal anchorage system with the miniscrew has been used recently in the lingual orthodontics to assist the anchorage control. Precise understanding of the force system produced from the various orthodontic appliances is necessary. However, the qualitative and quantitative effect of the miniscrew has not been identified well. In this paper, three dimensional finite element analysis is introduced on the lingual orthodontics to investigate the effect of anterior retraction force on the miniscrew and transpalatal arch wire. The purpose of this study is to determine the location of the miniscrew and the point of force application of the anchorage system in the lingual orthodontics. The analysis results indicate the efficient position of the miniscrew and the transpalatal arch wire in the lingual orthodontics.

• Integrative Medicine Research
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• v.5 no.3
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• pp.176-181
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• 2016

Recent studies have focused on evidence-based interventions to prevent mobility decline and enhance physical performance in older adults. Several modalities, in addition to traditional strengthening programs, have been designed to manage age-related functional decline more effectively. In this study, we reviewed the current relevant literatures to assess the therapeutic potential of eccentric exercises for age-related muscle atrophy (sarcopenia). Age-related changes in human skeletal muscle, and their relationship with physical performance, are discussed with reference to in vitro physiologic and human biomechanics studies. An overview of issues relevant to sarcopenia is provided in the context of the recent consensus on the diagnosis and management of the condition. A decline in mobility among the aging population is closely linked with changes in the muscle force-velocity relationship. Interventions based specifically on increasing velocity and eccentric strength can improve function more effectively compared with traditional strengthening programs. Eccentric strengthening programs are introduced as a specific method for improving both muscle force and velocity. To be more effective, exercise interventions for older adults should focus on enhancing the muscle force-velocity relationship. Exercises that can be performed easily, and that utilize eccentric strength (which is relatively spared during the aging process), are needed to improve both muscle force and velocity.

• Structural Engineering and Mechanics
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• v.77 no.6
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• pp.721-734
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• 2021

The seismic analysis of structures without applying the effects of soil can undermine functional objectives of structure so that it can affect all the desired purposes at the design and control stages of the structure. In this research, employing OpenSees and MATLAB software simultaneously and developing a definite three-dimensional finite element model of a high-rise concrete structure, designed using performance-based plastic design approach, the performance of Tuned Mass Damper (TMD) and Active Mass Damper (AMD) is both examined and compared. Moreover some less noted aspects such as nonlinear interaction of soil and structure, uplift, nonlinear behavior of structure and structural torsion have received more attention. For this purpose, the analysis of time history on the structural model has been performed under 22 far-field accelerogram records. Examining a full range of all structural seismic responses, including lateral displacement, acceleration, inter-story drift, lost plastic energy, number of plastic hinges, story shear force and uplift. The results indicate that TMD performs better than AMD except for lateral displacement and inter-story drift to control other structural responses. Because on the one hand, nonlinear structural parameters and soil-structure interaction have been added and on the other hand, the restriction on the control force applied that leads up to saturation phenomenon in the active control system affect the performance of AMD. Moreover, the control force applied by structural control system has created undesirable acceleration and shear force in the structure.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.425.1-425.1
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• 2014

Thermal transport in nanomaterials is not only scientifically interesting but also technological important for various future electronic, bio, and energy device applications. Among the various computation approaches to investigate lattice thermal transport phenomena in nanoscale, the atomistic nonequilibrium Green's function approach based on first-principles density functional theory calculations appeared as a promising method given the continued miniaturization of devices and the difficulty of developing classical force constants for novel nanoscale interfaces. Among the nanometerials, carbon atomic chains, namely the cumulene (all-doulble bonds, ${\cdots}C=C=C=C{\cdots}$) and polyyne (alternation of single and triple bonds, ${\cdots}C{\equiv}C-C{\equiv}C{\cdots}$) can be considered as the extream cases of interconnction materials for nanodevices. After the discovery and realization of carbon atomic chains, their electronic transport properties have been widely studied. For the thermal transport properties, however, there have been few literatures for this simple linear chain system. In this work, we first report on the development of a non-equilibrium Green's function theory-based computational tool for atomistic thermal transport calculations of nanojunctions. Using the developed tool, we investigated phonon dispersion and transmission properties of polyethylene (${\cdots}CH2-CH2-CH2-CH2{\cdots}$) and polyene (${\cdots}CH-CH-CH-CH{\cdots}$) structures as well as the cumulene and polyyne. The resulting phonon dispersion from polyethylene and polyene showed agreement with previous results. Compared to the cumulene, the gap was found near the ${\Gamma}$ point of the phonon dispersion of polyyne as the prediction of Peierls distortion, and this feature was reflected in the phonon transmission of polyyne. We also investigated the range of interatomic force interactions with increase in the size of the simulation system to check the convergence criteria. Compared to polyethylene and polyene, polyyne and cumulene showed spatially long-ranged force interactions. This is reflected on the differences in phonon transport caused by the delicate differences in electronic structure.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.113-121
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• 2012

The purpose of this study was to evaluate the effects of forefoot rocker shoes equipped with a metatarsal bar on lower extremity muscle activity and plantar pressure distribution. Ten healthy women in the age of twenties were participated in this study as the subjects. All subjects walked on a treadmill(Gait Trainer, BIODEX, USA) wearing normal shoes and metatarsal bar shoes, during which the plantar pressure distribution and muscle activity were measured. Using Pedar-X system(Novel Gmbh, Germany), the plantar pressure was measured for six regions of the foot: forefoot, midfoot, rearfoot, 1st metatarsal, 2-3th metatarsal, and 4-5th metatarsal, and for each sub-region, 4 features such as maximum force, contact area, peak pressure, and mean pressure were analyzed based on the plantar pressure. EMG(Electromyography) activity was measured by attaching surface electrodes to the rectus femoris, biceps femoris, tibialis anterior, and gastrocnemius medial head, and magnitude of muscle contraction was analyzed in IEMG(Integrated EMG) value. The results show that the maximum force, contact area, peak pressure, and mean pressure in the midfoot all increased while maximum force, peak pressure, contact area, mean pressure in the 1st metatarsal and 2-3th metatarsal all decreased when wearing functional shoes. Also, muscle activities in the four muscles were all decreased when wearing the functional shoes. This paper suggests that forfoot rocker shoes equipped with a metatarsal bar can help disperse the high pressure and absorb the shock to the foot as well as give positive influence on gait pattern and postural stability by reducing muscle fatigue during walking.

• Journal of Periodontal and Implant Science
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• v.54 no.3
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• pp.189-204
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• 2024

Purpose: This pilot study was conducted to develop a novel test setup for the in vitro assessment of the primary stability of dental implants. This was achieved by characterising their long-term behaviour based on the continuous recording of micromotions resulting from dynamic and cyclic loading. Methods: Twenty screw implants, each 11 mm in length and either 3.8 mm (for premolars) or 4.3 mm (for molars) in diameter, were inserted into the posterior region of 5 synthetic mandibular models. Physiological masticatory loads were simulated by superimposing cyclic buccal-lingual movement of the mandible with a vertically applied masticatory force. Using an optical 3-dimensional (3D) measuring system, the micromotions of the dental crowns relative to the alveolar bone resulting from alternating off-centre loads were concurrently determined over 10,000 test cycles. Results: The buccal-lingual deflections of the dental crowns significantly increased from cycle 10 to cycle 10,000 (P<0.05). The deflections increased sharply during the first 500 cycles before approaching a plateau. Premolars exhibited greater maximum deflections than molars. The bone regions located mesially and distally adjacent to the loaded implants demonstrated deflections that occurred synchronously and in the same direction as the applied loads. The overall spatial movement of the implants over time followed an hourglass-shaped loosening pattern with a characteristic pivot point 5.5±1.1 mm from the apical end. Conclusions: In synthetic mandibular models, the cyclic reciprocal loading of dental implants with an average masticatory force produces significant loosening. The evasive movements observed in the alveolar bone suggest that its anatomy and yielding could significantly influence the force distribution and, consequently, the mechanical behaviour of dental implants. The 3D visualisation of the overall implant movement under functional cyclic loading complements known methods and can contribute to the development of implant designs and surgical techniques by providing a more profound understanding of dynamic bone-implant interactions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.246-250
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• 2003

In this study, two new types of micro-grippers in which micro-fingers are actuated by piezoelectric multi-layer benders and stacks are introduced for the manipulation of micrometer-sized objects. First, we constructed a 3-chopstick-mechanism tungsten gripper, which is composed of three chopsticks: two are designed to grip micro-objects, and tile third is used to help grasp and release the objects through overcoming especially electrostatic force among some surface effects including electrostatic, van der Waals forces and surface tension. Second, a 2-chopstick-mechanism silicon micro-gripper that uses an integrated force sensor to control the gripping force was developed. The micro-gripper is composed of a piezoelectric multilayer bender for actuating the gripper fingers, silicon fingertips fabricated by use of silicon-based micromachining, and supplementary supports. The micro-gripper is referred to as a hybrid-type micro-gripper because it is composed of two main components; micro-fingertips fabricated using micromachining technology to integrate a very sensitive force sensor for measuring the gripping force, and piezoelectric gripper finger actuators that are capable of large gripping forces and moving strokes. The gripping force signal was found to have a sensitivity of 667 N/V. To the design of each of components of both of the grippers. a systematic design approach was applied, which made it possible to establish the functional requirements and design parameters of the micro-grippers. The micro-grippers were installed on a manual manipulator to assess its performance in tasks such as moving micro-objects from one position to a desired position. The experiment showed that the micro-grippers function effectively.