• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.439-446
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• 2011

Frequency is an important operating parameter for the protection, control, and stability of a power system. Thus, it must be maintained very close to its nominal frequency. Due to the sudden change in generation and loads or faults in a power system, however, frequency deviates from its nominal value. An accurate monitoring of the power frequency is essential for optimum operation and prevention of wide area blackout. Most conventional frequency estimation schemes are based on the DFT filter. In these schemes, the gain error could cause defects when the frequency deviates from the nominal value. We present an advanced frequency estimation technique using gain compensation to enhance the DFT filter-based technique. The proposed technique can reduce the gain error caused when the frequency deviates from the nominal value. Simulation studies are performed using both the data from EMTP-RV software and the user-defined arbitrary signals to demonstrate the effectiveness of the proposed algorithm. Results show that the proposed algorithm achieves good performance under both steady state tests and dynamic conditions.

• Reproductive and Developmental Biology
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• v.39 no.2
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• pp.37-41
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• 2015

The oocyte undergoes various events during maturation and requires many substances for the maturation process. Various intracellular organelles are also involved in maturation of the oocyte. During the process glucose is essential for nuclear and cytoplasmic maturation, and adenosine triphosphate is needed for reorganization of the organelles and cytoskeleton. If mitochondrial function is lost, several developmental defects in meiotic chromosome segregation and maturation cause fertilization failure. The endoplasmic reticulum, a store for $Ca^{2+}$, releases $Ca^{2+}$ into the cytoplasm in response to various cellular signaling molecules. This event stimulates secretion of hormones, growth factors and antioxidants in oocyte during maturation. Also, oocyte nuclear maturation is stimulated by growth factors such as epidermal growth factor. This review summarizes roles of organelles with focus on the Golgi apparatus during maturation in oocyte.

• Archives of Craniofacial Surgery
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• v.21 no.1
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• pp.73-76
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• 2020

Cranial implant removal is recommended if implants become exposed owing to scalp necrosis after cranioplasty. However, it carries the risk of extensive bleeding, and the resultant cranial defects can cause both aesthetic and functional problems. We present a case of a scalp defect exposing a cranial prosthetic implant that was reconstructed with a local flap and salvaged using an indwelling antibiotic irrigation system. A 73-year-old man presented with scalp necrosis after undergoing cranioplasty due to intracranial hemorrhage. The cranial implant was exposed through the scalp defect. Methicillin-resistant Staphylococcus aureus was detected in the culture from the open wound. After debridement of the necrotic tissue and burring of the superficial layer of the implant, a transposition flap was used to cover the defect and an indwelling antibiotic irrigation system was installed. Continuous irrigation with vancomycin was conducted for 5 days, and intravenous vancomycin was continued for 4 weeks. The flap was in good condition at 4 months postoperatively, with no infection. The convex contour of the scalp was well maintained. The patient's neurological status was stable. Exposed cranial implants can be salvaged with continuous antibiotic irrigation as an alternative to implant removal; thus, the risk of bleeding and possible disfigurement may be avoided.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.327-330
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• 2004

Because of its effectiveness for the PD(partial discharge) pattern recognition, PSA(Pulse Sequence Analysis) has been considered as a new analytic method instead of conventional PRPDA(Phase Resolved Partial Discharge Analysis). However, PSA has a big problem that can misanalyze patterns in case of data missing resulting from poor sensitivity because it analyses the correlation between sequential pulses, which leads to hesitate to apply it to on-site. Therefore, in this paper, the problems of PSA such as data missing and noise adding cases were investigated. For the purpose, PD data obtained from various defects including noise adding data were used and analysed, The result showed that both cases can cause fatal errors in recognizing PD patterns. In case of the data missing, the error depends on the kinds of defect and the degree of degradation. Also, it could be noticed that the error due to adding noises was larger than that due to some data missing.

• Journal of the Korean Wood Science and Technology
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• v.37 no.3
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• pp.231-238
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• 2009

Red pine (Pinus densiflora) has been used for structural wood members of Korean traditional residence (HANOK) and historic wooden structures. For these constructions, generally, natural drying has conducted for long time; however, unless drying is conducted sufficiently, it could cause several drying defects such as check or warping. Shrinkage changes of red pine species for small clear specimens and big-size specimens according to the conditions of moisture contents, were examined. For the estimation of volumetric shrinkage at a special moisture content, it was more precise to divide the range of moisture contents into two groups, green to air-dry and air-dry to oven-dry. The volumetric shrinkage had no difference with specimen sizes in sapwood, but decreased as specimen size increased in heartwood.

• The Journal of Korea Assosiation for Disability and Oral Health
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• v.10 no.1
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• pp.31-37
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• 2014

The general local cause of gingival bleeding is the vessel engorgement and erosion by odontogenic infection. Abnormal gingival bleeding is also associated with systemic causes. Bleeding disorders in which continuous gingival bleeding is encountered include the followings : vascular abnormalities, platelet disorders, hypoprothrombinemia and other coagulation defects. There are classic methods for gingival bleeding control, such as, direct pressure, electrocoagulation, suture, crushing and application of hemostatic agents. If the continuous gingival bleeding is not stopped in spite of the conventional methods, the life of patient is threatened owing to upper airway obstruction, syncope, vomiting and hypovolemic shock. Therefore, the rapid and correct hemostatic method is very important in the emergency condition. This is a case report of continuous gingival bleeding control by primary endodontic drainage & suture in a disabled patient with systemic bleeding disorders.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.612-621
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• 2006

Drawing is a mechanical operation attenuating material thickness to an appropriate level for the next processing or end usage. When the input material has a form of bundle or bundles made of very thin and long shaped wires or fibers, this attenuation operation is called 'bundle drawing' or 'drafting'. Bundle drawing is being used widely in manufacturing micro sized wires or staple yarns. However, the bundle processed by this operation has more or less defects in the evenness of linear density. Such irregularities cause many problems not only for the product quality but also for the efficiency of the next successive processes. In this research a mathematical model for the dynamic behavior of the bundle fluid is to be set up on the basis of general physical laws containing physical variables, i.e. linear density and velocity as the dynamic state variables of the bundle fluid. The governing equations resulting from the modeling show that they appear in a slightly different form from what they do in a continuum fluid. Then, the governing equations system is simplified in a steady state and the bundle dynamics is simulated, showing that the shape of the velocity profiles depends on two model parameters. Experiments confirm that the model parameters are to be well adjusted to show a coincidence with the theoretical analysis. The higher the drawing ratio and drawing speed we, the more sensitive becomes the bundle flow to exogenous disturbances.

• Archives of Reconstructive Microsurgery
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• v.16 no.1
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• pp.14-22
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• 2007

Perforator free flap (PFF) is currently a major reconstructive option for soft tissue reconstruction in adults. Although PFFs have been used commonly, most reconstructive surgeons still hesitate to perform PFFs in children. The main cause of concern is the perceived high failure rate related to the small diameter of children's perforator vessels. We present 8 consecutive cases of successful transfer of thoracodorsal artery (TDA) & anterolateral thigh (ALT) perforator flap in children. Between 2003 and 2005, 8 children(4 to 13 years old) with soft tissue defects of the extremities were reconstructed with TDA & ALT PFFs. All flaps completely survived. There were no problems relating to vascular spasm or occlusion. Range of motion of reconstructed extremities were fully recovered. Among 8 patients, only 1 patient was performed an additional flap thinning procedure. 8 cases of TDA & ALT perforator flaps were successfully transferred in children. PFF is an excellent option in reconstruction of children as well as in adults because of its thinness, long pedicle length, least donor site morbidity and acceptable donor site scar.

• The Journal of Korean Association of Computer Education
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• v.18 no.4
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• pp.11-18
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• 2015

A person with defects and the lack of hearing, has very difficult problems to listen to the sound of conversation or environment, and these problems cause wrong directions in the linguistic sense and character. We designed and implemented an application to practice and correct pronunciation of a hearing-impaired person specially. This is made as a mobile app without the limitation of time and space, and this provides practices with the level of difficulty in learning of pronunciation, taking into consideration of remedial status in pronunciation. The hearing-impaired person can train the basic pronunciation and the word pronunciation. He or she can practice basic skills in pronunciation and check the record on the practice rate and the success rate. Also, the person can improve pronunciation by self-correction function using the front camera of a smart phone.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.45-50
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• 2021

In the recent fourth industrial revolution, the demand for additive processes has emerged rapidly in many mechanical industries, including the aircraft and automobile industries. Additive processes, in contrast to subtractive processes, can be used to produce complex-shaped products, such as three-dimensional cooling systems and aircraft parts that are difficult to produce using conventional production technologies. However, the limitations of additive processes include nonuniform surface quality, which necessitates the use of post-processing techniques such as subtractive methods and grinding. This has led to the need for hybrid machines that combine additive and subtractive processes. A hybrid machine uses additional additive and subtractive modules, so product deformation, for instance, deflection, is likely to occur. Therefore, structural analysis and design optimization of hybrid machines are essential because these defects cause multiple problems, such as reduced workpiece precision during processing. In this study, structural analysis was conducted before the development of an additive/subtractive hybrid processing machine. In addition, structural optimization was performed to improve the stability of the hybrid machine.