• Journal of Mechanical Science and Technology
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• v.14 no.5
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• pp.483-489
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• 2000

The purpose of this work is to investigate fatigue damage of quasi-isotropic laminates under tensile loading in different directions. Low cycle fatigue tests of $[0/-60/60]_s$ laminates and $[30/-30/90]_s$ laminates were carried out. Material systems used are AS4/Epoxy and AS4/PEEK. The fatigue damage of $[30/-30/90]_s$ is very different from that of $[0/-60/60]_s$. The experimental results are compared with the result obtained from the method for determining strain energy release rate components proposed by the authors. The analytical results were in good agreement with the experimental results. It is proved that the failure criterion based on the strain energy release rate is an appropriate approach to predict the initiation and growth of delaminations under cyclic loading.

• Journal of Biomedical Engineering Research
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• v.40 no.5
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• pp.158-164
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• 2019

The interbody fusion cage used to replace the degenerative intervertebral disc is largely composed of titanium-based biomaterials and biopolymer materials such as PEEK. Titanium is characterized by osseointergration and biocompatibility, but it is posed that the phenomenon such as subsidence can occur due to high elastic modulus versus bone. On the other hand, PEEK can control the elastic modulus in a similar to bone, but there is a problem that the osseointegration is limited. The purpose of this study was to implement titanium material's stiffness similar to that of bone by applying cellular structure, which is able to change the stiffness. For this purpose, the cellular structure A (BD, Body Diagonal Shape) and structure B (QP, Quadral Pod Shape) with porosity of 50%, 60%, 70% were proposed and the reinforcement structure was suggested for efficient strength reinforcement and the stiffness of each model was evaluated. As a result, the stiffness was reduced by 69~93% compared with Ti6Al4V ELI material, and the stiffness most similar to cortical bone is calculated with the deviation of about 12% in the BD model with 60% porosity. In this study, the interbody fusion cage made of Ti6Al4V ELI material with stiffness similar to cortical bone was implementing by applying cellular structure. Through this, it is considered that the limitation of the metal biomaterial by the high elastic modulus may be alleviated.

• Archives of Plastic Surgery
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• v.46 no.4
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• pp.365-370
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• 2019

The syndrome of the trephined is a neurologic phenomenon that manifests as sudden decline in cognition, behavior, and sensorimotor function due to loss of intracranial domain. This scenario typically occurs in the setting of large craniectomy defects, resulting from trauma, infection, and/or oncologic extirpation. Cranioplasty has been shown to reverse these symptoms by normalizing cerebral hemodynamics and metabolism. However, successful reconstruction may be difficult in patients with complex and/or hostile calvarial defects. We present the case of a 48-year-old male with a large cranial bone defect, who failed autologous cranioplasty secondary to infection, and developed rapid neurologic deterioration leading to a near-vegetative state. Following debridement and antibiotic therapy, delayed cranioplasty was accomplished using a polyetheretherketone (PEEK) implant with free chimeric latissimus dorsi/serratus anterior myocutaneous flap transfer for vascularized resurfacing. Significant improvements in cognition and motor skill were noted in the early postoperative period. At 6-month follow-up, the patient had regained the ability to speak, ambulate and self-feed-correlating with evidence of cerebral/ventricular re-expansion on computed tomography. Based on our findings, we advocate delayed alloplastic implantation with total vascularized soft tissue coverage as a viable alternative for reconstructing extensive, hostile calvarial defects in patients with the syndrome of the trephined.

• International Journal of Safety
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• v.2 no.1
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• pp.7-11
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• 2003

Structure of the counterflow nonpremixed flames were investigated by using Fire Dynamics Simulator(FDS) and OPPDIF to evaluate FDS for simulations of the diffusion flame. FDS, employed a mixture fraction formulation, were applied to the diluted axisymmetric methane-air nonpremixed counterflow flames. Fuel concentration in the mixture of methane and nitrogen was considered as a numerical parameter in the range from 20% to 100% increasing by 10% by volume at the global strain rates of $a_g = 20S^{-l} and 80S^{-1}$ respectively. In all the computations, the gravity was set to zero since OPPDIF is not able to compute the buoyancy effects. It was shown by the axisymmetric simulation of the flames with FDS that increasing fuel concentration increases the flame thickness and decreases the flame radius. The centerline temperature and axial velocity, and the peek flame temperature showed good agreement between the both methods.

• 한국기계연구소 소보
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• s.18
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• pp.163-168
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• 1988

Impregnation of molten thermoplastic resin into continuous unidirectional fiber bundles was investigated. The degree of impregnation is defined as the ratio between the number of impregnated fibers and the total number of fibers of a bundle. The degree of impregnation was modeled as a function of time, impregnation pressure, temperature and tow size assuming the radial inward flow through the fiber bundle is governed by the Darcy's law. The permeability was assumed to be constant. Experiments were performed to evaluate the validity of the medel. Today's T300 graphite fiber bundles and Polyetheretherketone(PEEK) resin was used. A fiber bundle and resin powder were put into a mold and pressure and temperature were applied. After a predetermined time, the sample was taken out and microphotographs of the cross-section were taken. From the microphotographs, the number of impregnated fibers was counted and then the degree of impregnation was determined. Experiments were also performed for different tow sizes. Good agreements were found between the model and the experiments rendering a confidence in the model.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.42
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• pp.15.1-15.8
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• 2020

Background: Reconstructing maxillofacial defects is quite challenging for most surgeons due to the region's complex anatomy and cosmetic and functional effects on patients. The use of pre-made alloplastic implants and autogenous grafts is often associated with resorption, infection, and displacement. Recent technological advances have led to the use of custom computer-designed patient-specific implants (PSIs) in reconstructive surgery. This study describes our experience with PSI, details the complications we faced, how to overcome them, and finally, evaluates patient satisfaction. Case presentation: Six patients underwent reconstruction of various maxillofacial defects arising due to different etiologies using PSI. A combined total of 10 implants was used. PEEK was used to fabricate 8, while titanium was used to fabricate 2. No complications were seen in any patient both immediately post-op and in subsequent follow-ups. All patients reported a high level of satisfaction with the final result both functionally and cosmetically. Conclusion: The use of computer-designed PSI enables a more accurate reconstruction of maxillofacial defects, eliminating the usual complications seen in preformed implants and resulting in higher patient satisfaction. Its main drawback is its high cost.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1980-1982
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• 1999

Conductive Langmuir-Blodgett(LB) films have recently attracted much interest from the viewpoint of ultrathin film conductors at the molecular level. The result shows that the Maxwell-displacement-current (MDC) measuring technique is useful in the detection of phase-transitions over the entire range of molecule areas. In this parer, electrical properties of PBDG Langmuir(L) films were investigated using a displacement current measuring technique with pressure stimulation. Displacement current was generated When the Spread volume $150{\mu}{\ell}$ and compression velocity was about 30, 40, 50 mm/min. In the result, it is known that current is generated of higher current peek as compression velocity become faster.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.4
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• pp.106-111
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• 1999

This study discusses a non-contact optical technique electronic, electronic speckle pattern interferometry(ESPI) that is well suited for in-plane and out-of-plane deformation measurement Used as specimen which has the boundary condition of two clamped parallel edges composite material AS4/PEEK[30/-30/90]s was analyzed by ESPI to determined the characteristics of tensile and vibration. These are quantitativly compared with the result of FEM analysis. Finally the results of this study are briefly summarized as follows : (1) In the in-plane strain analysis by comparison of theoretical results with experimental results qualitatively we confirmed that measurement errors are within 3 % in case of accuracy (2) From comparison of experimental vibration modes with numerical vibration mode shapes by the FEM analysis quantitatively we confirmed that vibration mode measurement by the ESPI has high accuacy.

• 대한예방의학회:학술대회논문집
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• 2005.10a
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• pp.372-372
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• 2005

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.4
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• pp.274-283
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• 1981

An inexpensive and very simple microcomputer-aided measurement system has been designed for on-line experiments, which perform simultaneously data acquisition, data recorditing, calculations with the data, and positioning of necessary sensors. Interfacting between the microcomputer and the data acquisition board which consists of A/D converter, analog multiplexer, and sample-and-holder, etc. has been done through IEEE-488 interface port and parallel user port both provided by the PET computer's main logic board. Data and control signals are transfered between devices without handshaking. By utilizing BASIC commands PEEK, POKE, SYS, USR which are offered by PET microcomputer, it is possible to link machine code subroutines into the main BASIC program. This facilitates ease of data transfer, programming, and speedy execution of the program. In addition, an X-Y scanning table has been concected to the system in order to automatically position measuring sensors along a pre-determined path of interest.