• Journal of Powder Materials
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• v.19 no.4
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• pp.247-252
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• 2012

Effect of Cu and $DyF_3$ powder mixing with Cu-free (Nd, Dy)-Fe-B jet-milled powder on the magnetic properties of sintered magnets was investigated. The coercivity of a magnet prepared from the Cu-free (Nd, Dy)-Fe-B powder was about 10 kOe even though the alloy powder already contained some Dy (3.5 wt%). When small copper powder was blended, however, the coercivity of the magnet increased almost 100%, exhibiting about 20 kOe. On the contrary, the coercivity enhancement was moderate, about 4 kOe, when dysprosium content in the sintered magnet was simply increased to 4.9 wt% by the addition of small $DyF_3$3 powder.

• Journal of Periodontal and Implant Science
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• v.40 no.4
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• pp.201-205
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• 2010

Purpose: The purpose of this study was to evaluate the clinical effectiveness of and patient's satisfaction with treatment of gingival melanin hyperpigmentation with a Nd:YAG laser and a high speed rotary instrument. Methods: Three patients with melanin hyperpigmentation in the anterior parts of the gingiva were chosen for this case study. Clinical photographs were taken at the preoperative state and three patients were treated under local anesthesia. In the maxilla, the gingival deepithelization was conducted with a high speed diamond bur, whereas, in the mandible with a Nd:YAG laser. Clinical photographs were taken immediately after the procedures and at the 1st, 2nd, and 4th week to evaluate clinical color changes. A week after the procedure, the patients filled out a questionnaire about any pain or discomfort. At the 4th week after the procedure, the patients filled out questionnaires about esthetic aspects of the results of treatment. Results: In all cases, both anterior gingival areas were depigmented with satisfaction and the patients did not complain of severe pain or discomfort. At the 1st week of healing, the gingiva showed moderate to fast epithelization. Two weeks after the procedure, clinically, the gingiva showed almost complete healing. Four weeks after the procedure, there was significant improvement in gingival melanin hyperpigmentation. Conclusions: The Nd:YAG laser and the high speed rotary instruments seem to be effective for the esthetic treatment of gingival melanin hyperpigmentation.

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.635-645
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• 1993

This study was perfomed to investigate the prosthodontic and periodontal status of the abutment teeth in distally extending bridges(DEBs) (78 cases) and removable partial dentures(RPDs) (43 cases) for 122 patients (55 males and 57 females) visiting department of Periodontology, Seoul National University Hospital. The average wearing periods were 67.8 months for DEBs and 66.4 months for RPDs. 38.4% of the patients in DEBs and 35.9% in RPDs complainted of chewing discomfort and 22.6% and 24.4% were not chewing on the prosthodontically - treated sides, respectively. In DEBs, when the restoration for 2nd molar supported by 1st molar & 2nd premolar was grouped to type 1, 1st molar supported by 1st & 2nd premolars was type 2, and 1st & 2nd molars supported by 1st & 2nd premolars was type 3, there was a significant differences only in the tooth mobility score among clinical parameters (type 2>type 1>type 3). In RPDs, when bilateral free-end case was grouped to type 1, and unilateral case was type 2, there was a significant difference in the Gingival index (type 1>type 2). In DEBs, 62.8% of restoration were overcontoured, 72% had interproximal space closures, 30.5% overextended pontics and 86.6% overhanging margins. In RPDs, 24.4% of the restorations were overcontoured, 45.5% had interproxinal space closures and 58.3% overhanging margins. From these results of this study, periodontal problems caused by prosthodontic defects were considered to be contributing factors in chewing discomfort.

• Economic and Environmental Geology
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• v.37 no.2
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• pp.245-253
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• 2004

The 36km-long Daebo-Campo coast has a well-developed marine terraces divided to six steps by elevation of paleoshoreline : 0.5 m(T1), 10 m(T2), 30 m(T3), 40 m(T4), 60 m(T5) and 75 m(T6). The 2$^{nd}$ and 3$^{nd}$ platforms in Daebo to Guryongpo are wider and more distinctive than those of Guryongpo to Gampo. The 3$^{nd}$ terrace of 30 m high is subdivided to two flights as lower(T3b) and upper(T3a) by old sea cliff. Platform age is unclear because of coral fossil free. However, the terrace age could be determined with convergent OSL ages from beach sediments on 2$^{nd}$ step(T2). OSL ages of the terrace of 10 m high range in 60-70 ka. It reveals that the 2$^{nd}$ -step platform correlates to Oxygen Isotope Time scale, substage 5a(ca. 80 ka), and that uplift rate is ca. 0.19 m/ka for 2$^{nd}$ terrace at Daebo-Campo coast. If considering equivalent uplift rate for all terraces since the Late Pleistocene, the 3$^{rd}$ and 4$^{th}$ terraces would be 5e substage and 7 stage. The 30 m-high terrace provides a good indicator for uplift at Daebo-Gampo coast since 125,000 yrs(MIS 5e). It suggests that the local neotectonic deformation might cause an optional uplift rate of ca. 0.19 m/ka along the SE coast of Korea.

• Journal of Oral Medicine and Pain
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• v.25 no.1
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• pp.129-144
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• 2000

The purpose of this study was to examine dentin surface changes of extracted sound third molar specimens which were etched with 10% maleic acid and irradiated at $7-140J/cm^2$ with $CO_2$ and at $156-280J/cm^2$ with Nd:YAG laser. The results were as follows. 1. Dentin surfaces etched with 10% maleic acid and then irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the retentive morphology for resin restoration. 2. Dentin surfaces irradiated at below of $42J/cm^2$ with $CO_2$ laser showed the increased acid-resistance. 3. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser showed the retentive morphology. 4. Dentin surfaces irradiated at $218-280J/cm^2$ with Nd:YAG laser and etched 10% maleic acid and then $218-280J/cm^2$ with Nd:YAG laser showed the increased acid-resistance.

• Korean Journal of Optics and Photonics
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• v.11 no.4
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• pp.294-298
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• 2000

The output characteristics of intracavity frequency doubling of laser-diode end-pumped Nd:S-VAP laser were investigated. Nd:S-VAP is suitable for a microchip laser medium, which has a low threshold property because of a very high value of the stimulated emission cross-section and lifetime product. The threshold energy measured was 81 J.ll. The second harmonic output energy measured was $126\mu\textrm{J}$at a pump energy of $2\mu\textrm{J}$. We described for intracavity frequency doubling by using theoretical calculations. Q-switched second harmonic energy measured was $15\mu\textrm{J}$per pulse with a pulse-width of 26 ns. at a pump energy of 2 mJ and an $M^2$ of 1.47 represented a good beam quality. ality.

• Korean Journal of Materials Research
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• v.4 no.5
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• pp.535-540
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• 1994

Thin film magnet was fabricated by radio frequency magnetron sputtering using $Nd_13/(Fe.Co)_{70}B_{17}$ alloy target and magnetic properties were investigated according to sputtering conditions from the metallurgical point of view. we could obtain the best preferred orientation of $Nd_2Fe_{14}B$ phase at substrate temperatures between $450^{\circ}C$ and $460^{\circ}C$ with the input power 150W, and thin films had the anisotropic magnetic properties. But, as the thickness of thin film increased, the c-axis orientation gradually tended to be disordered and magnetic properties also become isotropic. Just like Nd-Fe-B meltspun ribbon, the microstructure of thin film magnet was consisted of very find cell shaped $Nd_2Fe_{14}B$ phase and the second phase along grain boundary. While, domain structure showed maze patterns whose magnetic easy axis was was perpendicular to film plane of thin film. It was concluded from these results that the perpendicualr anisotropy in magnetization was attributed to the perpendicular alignment of very find $Nd_2Fe_{14}B$ grains in thin film.

• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.66-68
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• 1994

강유전체 박막과 마이크로 가공기술을 이용하여 초전형 적외선 센서를 제작하였다. 초전형 적외선 센서는 $Pb_{1-x}La_xTi_{1-x/4}O_3$ (x=0.05) (PLT) 강유전체 박막 커패시터를 RF 마그네트론 스퍼터링 방식으로 백금 전극이 증착된 MgO 기판상에 결정 성장시킨 구조를 갖고 있다. 스퍼터링된 PLT 바닥은 높은 c-축 결정 구조를 가지므로 센서로 사용하기 위한 poling 처리 과정이 필요하다. 이는 적외선 이미지 센서를 구현함에 있어서 수율 향상에 필수적인 요소이다. 마이크로 가공 기술을 사용하여 센서의 열용량을 극소화 함으로서 센서의 효율을 최대화하였다. 제작된 센서의 상부에 폴리이미드를 코팅하고 MgO 기판을 선택적으로 식각하여 코팅된 폴리이미드가 강유전체 박막 커패시터를 지지하고 있는 구조를 구현하였다. 이렇게 제작된 센서의 감도는 상온에서 $8.5{\times}10^8cm{\cdot}{\sqrt}{Hz/W}$로 측정되었으며 이는 마이크로 가공 기술을 사공하지 않은 경우보다 약 100 때의 감도 향상을 가져왔다.

• Journal of Magnetics
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• v.4 no.2
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• pp.46-51
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• 1999

A solid-HDDR characteristics of the Nd-Fe-B-type alloys magnetic properties of the solid-HDDR treated materials have been investigated using three types of alloys; $Nd_{15}Fe_{77}B_8 (alloy A), Nd_{16}Fe_{75.9}B_8Zr_{0.1}(alloy B), and Nd_{12.6}Fe_{68.7}Co_{11.6}B_8Ga_{1.0}Zr_{0.1} $(alloy C). It has been found that the four-components alloy B and six-components alloy C have showed higher hydrogenation temperatures than the ternary alloy A. The alloys A and B appeared to absorb more hydrogen gas more rapidly as well compared to the alloy C. The disproportionation temperature of hydrogenated materials was exhibited no significant difference among the alloys. The thermal stability of the hydrided materials of the three types of alloys was found to become more stable in order of number of components. The disproportionation and the recombination kinetics were significantly sluggish in the solid-HDDR manner with respect to the conventional manner. Some degree of anisotropic nature was found to exist in the ingot and this anisotropic nature was retained even after the solid-HDDR treatment. It was suggested the solid-HDDR treatment may possibly be used for a preparation of an isotropic or anisotropic Nd-Fe-B-type cast magnets.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.12 no.1
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• pp.57-61
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• 1982

The author has made a study on the classification of the mandibular 3rd molars of Korean youths through dental radiography by means of Pell & Gregory's classification and on the prevalence of the dental caries of distal surface of the mandibular 2nd molar adjacent to the mandibular 3rd molars turned anteriorly. The results are as follow; 1. It was found that the largest case number was class I (272 cases, 52.9%) in the relation of the tooth to the ramus of the mandible and 2nd molar. 2. The mesio-angular position was the largest number (239 cases, 46.5%) in the relation of the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 3. The mesio-angular position of class I was the largest number (140 cases, 27.2 %) in the relation of the tooth to the ramus of the mandible and 2nd molar and the long axis of the impacted mandibular 3rd molar to the long axis of the 2nd molar. 4. The average angle of the long axis of mandibular 3rd molar in mesioangular position or horizontal position to the occlusal plane was 143° 5. Mandibular 3rd molar with lesion such as dental caries or pericoronitis was 73 cases (14.2). 6. The caries incidence rate of the distal surface of the 2nd molar was about 3.1%.