• Knee surgery & related research
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• v.30 no.4
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• pp.311-318
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• 2018

Purpose: The purpose of this study was to evaluate changes in the coronal alignment of the knee and ankle joints after open wedge high tibial osteotomy (OWHTO) to determine factors related to the recurrence (R) of the varus deformity by serial analysis. Materials and Methods: Sixty-four OWHTOs were enrolled in this study. The weight bearing line (WBL) ratio, joint line convergence angle (JLCA), knee joint inclination, mechanical axis-tibial plateau angle, talar inclination (TI), and distal tibia articular angle (DTAA) were serially assessed. Serial correlation analysis between all parameters was performed. Patients were divided into R group and no recurrence (NR) group according to the WBL ratio (55%) at postoperative one year. Results: The preoperative WBL ratio showed significantly negative correlation with serial changes of JLCA, TI, and DTAA (p<0.05). The JLCA, TI, and DTAA as well as WBL ratio showed a significantly larger degree of varus alignment in the R group than in NR group at postoperative 6 weeks and 1 year after OWHTO (p<0.05). Conclusions: Sufficient correction of the WBL and restoration of the JLCA during OWHTO are essential to prevention of the R of varus deformity after the surgery because they are the only modifiable factors during surgery. Level of Evidence: IV, Case series.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.3
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• pp.285-291
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• 2017

Micro-needles are used as transferring devices for sampling of tiny constitute substances from biological bodies. Typically, nickel is used as a coating to improve the rigidity of micro-needles. This study introduces the methodology to manufacture a WC needle with very high hardness and toughness. Micro-EDM technology was used to manufacture micro-needles with holes $130{\mu}m$ in diameter and $2300{\mu}m$ in length. A micro-needle was aligned to the micro-EDM electrode using a custom two degree-of-freedom alignment system. A three-step manufacturing technique was developed to drill a micro-hole using a WC electrode. In the first process, an electrode $105{\mu}m$ in diameter was used to make a hole. Electrodes of 90 and $105{\mu}m$ diameters were used in the second and third process, respectively. Consequently, a WC micro-needle with an inner hole of $135{\mu}m$ diameter, length of $2300{\mu}m$, and outer diameter of $300{\mu}m$ was developed.

• Design & Manufacturing
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• v.13 no.4
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• pp.1-9
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• 2019

In-mold Coating is a method that can simultaneously perform injection molding and surface coating in injection mold. The material used for coating is two-component polyurethane which is composed of polyol and isocyanate. L-type mixing head can be used to mix polyol and isocyanate uniformly, and inject them inside the mold cavity. The surface quality of the injection molded products by using in-mold coating depends on the mixing uniformity between main agent and hardener. In this study, flow analysis was performed to design a mixing head for uniform mixing of two-component polyurethane. Especially the effects of design parameters of mixing head on mixing uniformity and nozzle pressure were investigated. The parameters of mixing head were mixing chamber diameter, cleaning cylinder diameter, nozzle alignment angle in the horizontal and vertical direction, and cleaning piston position. It was found that optimal design values were mixing chamber diameter of 3.5 mm, cleaning cylinder diameter of 5.0 mm, nozzle horizontal/vertical alignment angles of 140°/160°, and cleaning piston position of 1.8 mm. The optimal values would be used to develop a two-component mixing head achieving an uniform mixing for in-mold coating.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.10
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• pp.48-53
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• 2019

A water jet propeller is a key component that generates propulsion during the start of a naval vessel. When failure or breakage occurs, the vessel cannot operate. Recently, a flow analysis and structural analysis were conducted to understand the cause of damage to a bolt on a water jet. In particular, the stress and strain acting on the fastening bolt (impeller shaft and tail shaft) were examined to determine the extent of misalignment between the impeller shaft and the tail shaft of the water jet propeller. The study determined that stress and strain were concentrated on the impeller shaft and the tail shaft bolt. The alignment of the propeller impeller shaft and the tail shaft increased significantly in response to the tail shaft bolt. Failure of the tail shaft bolt fastening can lead to misalignment between the impeller shaft and the tail shaft.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.2
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• pp.55.4-56
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• 2018

Linear Astigmatism Free - Three Mirror System (LAF-TMS) is the linear astigmatism free off-axis wide field telescope with D = 150 mm, F/3.3, and $FOV=5.51^{\circ}{\times}4.13^{\circ}$. We report the design and analysis results of its mirrors and optomechanical structures. Tolerance allowance has been analyzed to the minimum mechanical tolerance of ${\pm}0.05mm$ that is reasonable tolerance for fabrication and optical alignment. The aluminum mirrors are designed with mounting flexure features for the strain-free mounting. From Finite Element Analysis (FEA) results of mounting torque and self-weight, we expect 33 - 80 nm RMS mirror surface deformations. Shims and the L-bracket are mounted between mirrors and the mirror mount for optical alignment. The mirror mount is designed with four light-weighted mechanical parts. It can stably and accurately fix mirrors, and it also suppresses some of stray light.

• Journal of Korean Neurosurgical Society
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• v.67 no.2
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• pp.137-145
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• 2024

In adult spinal deformity (ASD) surgery, mechanical failure (MF) has been a significant concern for spine surgeons as well as patients. Despite earnest endeavors to prevent MF, the absence of a definitive consensus persists, owing to the intricate interplay of multifarious factors associated with this complication. Previous approaches centered around global spinal alignment have yielded limited success in entirely forestalling MF. These methodologies, albeit valuable, exhibited limitations by neglecting to encompass global balance and compensatory mechanisms within their purview. In response to this concern, an in-depth comprehension of global balance and compensatory mechanisms emerges as imperative. In this discourse, the center of gravity and the gravity line are gaining attention in recent investigations pertaining to global balance. This narrative review aims to provide an overview of the global balance and a comprehensive understanding of related concepts and knowledge. Moreover, it delves into the clinical ramifications of the contemporary optimal correction paradigm to furnish an encompassing understanding of global balance and the current optimal correction strategies within the context of ASD surgery. By doing so, it endeavors to furnish spine surgeons with a guiding compass, enriching their decision-making process as they navigate the intricate terrain of ASD surgical interventions.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.1
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• pp.42-46
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• 2006

This paper presents a method for deposition an individual carbon nanotube (CNT). The alignment of a single CNT is very useful to perform studies related to applications in FET (Field Emitted Transistor), SET (Single Electron Transistor) and to make chemical sensor as well as bio sensors. In this study, we developed the deposition method of a CNT individualized in a solution. Using the electrokinetic method, we found the optimum conditions to assemble the nanotube and discussed about plausible explanation for the assembling mechanism. These results will be available to use for making the CNT sensor device.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.6 s.261
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• pp.644-650
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• 2007

Mechanical property evaluation of micrometer-sized structures is necessary to help design reliable microelectromechanical systems(MEMS) devices. Most material properties are known to exhibit dependence on specimen size and such properties of microscale structures are not well characterized. This paper describes techniques developed for tensile testing of thin film used in MEMS. Epi-polycrystalline silicon is currently the most widely used material, and its tensile strength has been measured as 1.52GPa. We have developed a tensile testing machine for testing microscale specimen using electro-magnetic actuator. The field magnet and the moving coil taken from an audio-speaker were utilized as the components of the actuator. Structure of specimen was designed and manufactured for easy handling and alignment. In addition to the static tensile tests, it is described that new techniques and procedures can be adopted for high cycle fatigue test of a thin film.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.8
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• pp.3301-3306
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• 2012

In LED chip packaging, die bonding is a very important process which fixes the LED chip on the lead frame to provide enough strength for the next process. Conventional pick-up device of the die bonder is simply operated by up and down motion of a collet and an ejector pin. However, this method may cause undesired problems such as position misalignment and/or severe die damage when the pick-up device reaches the die. In this study, to minimize the position alignment error and die damage, a die bonder is developed by adopting a new pick-up head for precise alignment and high speed feeding. To evaluate structural stability of the designed system, required finite element model of the die bonder is generated, and structural analysis is performed. Vibration analysis of the pick-up head is also performed using developed finite element model at operation frequency range. As a result of the analysis, deformation, stress, and natural frequency of the die bonder are investigated.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.47-56
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• 2018

In this paper, the structural analysis of the Geostationary Korea Multi-Purpose Satellite-2 (GEO-KOMPSAT-2) tubing system is discussed, and the structural integrity of the tubing system is assessed by comparative analysis with the results of overseas partner AIRBUS. Securing structural reliability of the tubing system is a very important key element of the propulsion system of the GEO-KOMPSAT-2 satellite. Therefore, FE modeling of the propulsion tubing was carried out directly using the CAE program, and structural analysis was performed to evaluate the stress state under launch conditions. Hoop stress, axial stress, bending stress, and torsion stress were calculated according to diverse load conditions by using pressure stress analysis, thruster alignment analysis, sine qualification load analysis, and random qualification load analysis. From the results, the Margin of Safety (MoS) of the tubing system is evaluated, and we can verify the structural integrity of the tubing system when subjected to various launch loads.