• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1339-1349
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• 2008

In this paper, a nonlinear relationship between an input complex envelope and an output complex envelope of m-th harmonic zone is theoretically analyzed, and AM/$AM_m$ and AM/$PM_m$ are defined. A scheme to extract these characteristics from measured in-phase and quadrature-phase data is suggested. The proposed analysis is verified with a fundamental-fundamental and fundamental-third harmonic measurements for a InGaP power amplifier(PA). Based on the harmonic-band nonlinear analysis and extraction scheme, a new technique to send a signal in m-th harmonic band with a harmonic signal Linearization Digital Predistortion(DPD) scheme is presented. A numerical analysis and a Look-Up Table(LUT) based DPD algorithms to linearize output signal on m-th harmonic zone are developed. For a 16- and a 64-QAM input signals, a DPD for third harmonic signal linearization is implemented, and output spectrum and signal constellation are measured. The wholly distorted signals are linearized, and thus the measured Error Vector Magnitudes (EVM) are 6.4 % and 6.5 % respectively. The results show that a proposed scheme linearizes a nonlinearly distorted harmonic band signals. The proposed nonlinear analysis and predistortion scheme can be applied to multiband transmitter in next generation software defined radio(SDR)/cognitive radio(CR) wireless system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.6
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• pp.521-530
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• 2016

Weather radar is observation equipment that transmits electromagnetic waves and receives backscattered signals from the targets. The weather radar systems of the Korea Meteorological Administration have a doppler mode that can extract the target's radial velocity. However, the radial velocity over the maximum unambiguous velocity(${\nu}_m$) for which is in a trade-off relationship with the maximum unambiguous range is folded. Therefore, a dual PRF mode of which transmits and receives signals using two different PRFs(high and low) must be used to extend the vm while maintaining the maximum unambiguous range. Using a dual PRF mode, vm can be extended to the amount of lowest common denominator of two observed vm from high and low PRF. For this extension, we have developed a velocity unfolding algorithm of which uses several criteria for classification considering observed velocity differences between high and low PRF and their error boundary. Then, correction factors are calculated for each class and are applied to unfold radial velocity. The developed algorithm was applied to the Yong-In Testbed(YIT) radar and the generated better performance of radial velocity extraction than those of the previous system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.9
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• pp.979-986
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• 2010

This paper presents an algorithm for retrieving precise radar cross sections(RCS) of various trihedral corner reflectors (TCR) which are external calibrators of synthetic aperture radar(SAR) systems. The theoretical RCSs of the TCRs are computed based on the physical optics(PO), geometrical optics(GO), and physical theory of diffraction(PTD) techniques; that is, the RCS computation includes the single reflections(PO), double reflections(GO-PO), triple reflections(GO-GO-PO), and edge diffractions(PTD) from the TCR. At first, we acquire an SAR image of the area that five TCRs installed in, and then extract the RCS of the TCRs. The RCSs of the TCRs are extracted accurately from the SAR image by adding up the power spill, which is generated due to the radar IRF(Impulse Response Function), using a square window. We compare the extracted RCSs with the theoretical RCSs and analyze the difference between the theoretical and experimental RCSs of the TCR for various window sizes and various backscattering coefficient levels of the adjacent area. Finally, we propose the minimum size of the integration area and the maximum level of the backscattering coefficients for the adjacent area.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.225-243
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• 1991

In recent years immediate implantation has been tried by a few clinicians. This study placed IMZ implants in the rabbit femur with and without bony defects around the implant for simulating fresh extraction site. And one group with bony defects used porous hydroxyapatite ganules(HA) to fill if and the other group left the bony defects around the implant. The purpose of this study was to compare the shear bond strength and the bony contact and formation around the implant. Fifteen rabbits were divided into three groups and placed 10 IMZ implants to each group. Implant sites were surgically prepared with IMZ drills kit and implants were placed(Control), artificial bony defect was created with Apaceram drills kit around the implant sites and implants were placed(Experimental I), bony defect was filled with porous hydroxyapatite granules(Experimental II). Thereafter, rabbits were sacrificed at 8th week and specimens were prepared and pushout tested for shear bond strength of bone-implant interface immediately. Undecalcified and decalcified specimens were prepared with Vilanueva and hematoxylin-eosin stain for light microscopic finding. The results of this study were as follows. 1. In the control group, mean shear strength of bone-implant interface was $2.614{\pm}0.680$ MPa, experimental I was $0.664{\pm}0.322$ MPa, and experimental II was $2.281{\pm}0.606$ MPa. There was significant difference between control and experimental I, between experimental I and experimental II, but did not show significant difference between control and experimental II statistically. 2. In the bony formation surrounding IMZ implant of the three groups, that of cortical bone is more advanced than cancellous bone area. 3. In the histological findings of undecalcified specimens, control and experimental II showed more than 50% of bony or osteoid formation at the bony-implant interface. 4. In the histological findings of undecalcified specimens, experimental I showed less than 50% of bony or osteoid formation at the interface, and observed partial bony defect in the coronal zone. 5. In the experimental II group, were observed direct bony contact to hydroxyapatite granules, and infiltration of a few giant cells. 6. No inflammatory responses were seen around the titanium implants and the hydroxyapatite granules.

• Journal of Periodontal and Implant Science
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• v.47 no.6
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• pp.352-362
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• 2017

Purpose: Furcation involvement in the molars is difficult to treat, and has been recognized as a risk factor for tooth loss. Although periodontal regenerative therapies, including guided tissue regeneration and various types of bone grafts, have been applied to furcation defects, the effects of these treatments are limited, especially in large class III furcation defects. The purpose of this pilot study was to investigate the effect of reciprocal autologous root transplantation on periodontal wound healing and regeneration in class III furcation defects in dogs. Methods: Furcation defects (7 mm wide and 6 mm high) were surgically created after root separation of the unilateral third and fourth premolars in 4 dogs. Eight furcation defects were randomized to receive either reciprocal autologous root transplantation (test) or no further treatment (control). In the test group, the mesial and distal roots were transplanted into the distal and mesial extraction sockets, respectively. The animals were sacrificed 10 weeks after surgery for histologic evaluation. Results: The healing pattern in the control group was characterized by extensive collapse of the flap and limited periodontal regeneration. New bone formation in the test group ($3.56{\pm}0.57mm$) was significantly greater than in the control group ($0.62{\pm}0.21mm$). Dense collagen fibers inserting into the residual cementum on the transplanted root surfaces were observed in the test group. Slight ankylosis was observed in 2 of the 4 specimens in the test group on the mesiodistal sides where the root-planed surfaces faced the existing bone. Root resorption (RR) was detected in both the control and test groups. Conclusions: Within the limits of this study, it can be concluded that reciprocal autologous root transplantation was effective for bone regeneration in class III furcation defects in dogs. However, further studies are required to standardize the approach in order to prevent unwanted RR prior to clinical application.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.2
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• pp.344-350
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• 2000

Incidence of crown-root fracture due to traumatic injury, have been reported 3% in the permanent dentiton, 2% in the deciduous dentition. There are two treatment methods for crown-root fractured teeth with pulp exposure, when the fracture line was located under the alveolar crest. One way is the extrusion by orthodontic force the other way is intra-alveolar transplantation which occlusally repositioning of apical fragment in the alveolar socket. Since intra-alveolar transplantation has introduced in 1970s, it was practiced as alternative to orthodontic extrusion. As the result, this method may thoughted that had a good prognosis. As a result of trauma, completely crown-root fracture was occured in the maxillary right central incisor in this case. We couldn't reposition the deepest fracture line above the alveolar crest by the conventional surgical extrusion, because apical fragment was too short. Thus, after extraction of apical fragment, we repositioned it to the socket following demineralized freezed dried bone graft, which possible to support the apical fragment. At the 15-month recall examination, the root still showed normal mobility and there was not observed any in flammatory or replacement root resorption in the periapical radiograph.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.534-547
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• 2006

Ectopic eruption and impaction of canines is a frequently encountered clinical problems. The incidence of impaction ranges between 1-3%. The cause of canine impaction can be the result of localized factors or can be a polygenic multifactorial inheritance and associated with other dental anomalies. The general dentist and pediatric dentist should know how to properly diagnose and manage potential disturbances in the eruption of maxillary canine. Diagnosis of impacted canine at age 8-10 years can significantly reduce serious ramifications, including surgical exposure and orthodontic traction as well as root resorption of the lateral incisors. Extraction of primary canine would be one of the method to prevent the impaction. The surgical procedure should be designed to minimize the destruction of periodontal tissue of impacted canine. Closed eruption technique is thought to be optimal method of surgical exposure compared with other methods. An overview of the incidence, sequela as well as the surgical periodontal, and orthodontic consideration in the management of impacted canine was presented.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.326-333
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• 2003

The appropriate treatment for eruption guide of impacted teeth necessitates the formulation of a comprehensive treatment plan, which is dependent upon a number of factors such as the condition of the deciduous teeth, dental and skeletal relationship, dental age of the patient, willingness of the patient to undergo extensive dental treatment and financial considerations. If the etiology of the eruption disturbance has been identified, the elimination of the causes and various procedures can be used for eruption guide. Particularly the transplantation is a valuable alternative to extraction of impacted teeth, where surgical exposure and subsequent orthodontic realignment are difficult or impossible. This report present three cases of autotransplantation of impacted maxillary canine. As the result in these cases, atraumatic removal of donor tooth during operation is prerequisite to an optimal clinical result. Due to a high possibility of pulp necrosis, endodontic treatment of fully developed transplanted teeth should be undertaken. In complex case, autotransplantation can save time and less expensive than orthodontic forced eruption. Recipient socket should be prepared to a size that is slightly larger than the root of the donor tooth, and can be prepared with open or close procedure depends on root size of donor tooth and buccolingual width at transplantion site.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.298-307
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• 2003

The purpose of this study was to investigate the distribution and differences of the cephalometric measurements between normal occlusion and the class III malocclusion. Kim's analysis was achieved and compared on both the 141 elementary school students with proper profile and normal occlusion and the class III malocclusion group at the age of 7 to 9, in Gwang-ju area and the results were as follows; 1. The ODI, APDI, IIA, UL showed statistically significant differences between normal occlusion and class III malocclusion(p<0.01). But, no significant difference existed in both CF and EI. 2. The mean value of ODI was 72.62, APDI 80.47 IIA 121.37 in normal occlusion. 3. The mean value of ODI was 64.45, APDI 87.31 IIA 129.89 in class III malocclusion. 4. ODI decreased as APDI increased, and the correlation coefficient was -0.576 in both normal occlusion and class III malocclusion. 5. The correlation coefficient related to EI was CF 0.777, LL -0.670, UL -0.588, IIA 0.485. It means that UL and LL were very sensitively reflected on EI.

• Journal of the korean academy of Pediatric Dentistry
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• v.36 no.4
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• pp.556-562
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• 2009

Ectopic eruption of the maxillary first permanent molar means that the molar erupts out of the normal position and is arrested in its eruption by the second primary molar. This local eruption disturbance results in a premature atypical resorption on the distal part of the second primary molar. In most irreversible cases, the second primary molar is lost prematurely, either by spontaneous exfoliation or by extraction, In cases of doubt as to whether the eruption is of the irreversible type or not, careful radiographic observation period for a few months would be valuable in evaluating the possibilities of the tooth's freeing itself. The purpose of this study was to determine the characteristics and occurrence of the ectopic eruption of the maxillary first permanent molar. A descriptive, observational, retrospective study was done using the radiographs of 25 conseutive patients, who were in the first phase of mixed dentition. A method was designed to evaluate the amount of pathologic resorption of the second maxillary primary molar and the mesial angulation of the first permanent molar. The study showed that the most important etiologic factor was the eruption path or mesial angulation of the first permanent molars relative the chosen reference lines.