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임지호,이상엽,신동원 제어·로봇·시스템학회 2024 제어·로봇·시스템학회 논문지 Vol.30 No.1
This study investigated a mobile robot capable of navigating unbalanced road surfaces solely via its mechanical structure, utilizing an unbalanced road adaptation device. This adaptation device was designed by introducing a height adaptor to the existing suspension mechanism, with each component consisting of links and shock absorbers. With these components, the robot excelled in adapting to unbalanced road surfaces. To validate the performance of the designed robot, a degree-of-freedom analysis was conducted, and the robot’s driving stability was evaluated through driving simulations.
과 액상 형성에 의한 비납계 압전 (Na,K)NbO<sub>3</sub>-Ba(Cu,Nb)O<sub>3</sub> 결정립의 비정상 성장 거동 및 전기적 특성
임지호,이주승,이승희,정한보,박춘길,안철우,유일열,조경훈,정대용,Lim, Ji-Ho,Lee, Ju-Seung,Lee, SeungHee,Jung, Han-Bo,Park, Chun-kil,Ahn, Cheol-Woo,Yoo, Il-Ryeol,Cho, Kyung-Hoon,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.4
$Pb(Zr,Ti)O_3$ (PZT) is used for the various piezoelectric devices owing to its high piezoelectric properties. However, lead (Pb), which is contained in PZT, causes various environment contaminations. $(K,Na)NbO_3$ (NKN) is the most well-known candidate for a lead-free composition to replace PZT. A single crystal has excellent piezoelectric-properties and its properties can be changed by changing the orientation direction. It is hard to fabricate a NKN single crystal due to the sodium and potassium. Thus, $(Na,K)NbO_3-Ba(Cu,Nb)O_3$ (NKN-BCuN) is chosen to fabricate the single crystal with relative ease. NKN-BCuN pellets consist of two parts, yellow single crystals and gray poly-crystals that contain copper. The area that has a large amount of copper particles may melt at low temperature but not the other areas. The liquid phase may be responsible for the abnormal grain growth in NKN-BCuN ceramics. The dielectric constant and tan ${\delta}$ are measured to be 684 and 0.036 at 1 kHz in NKN-BCuN, respectively. The coercive field and remnant polarization are 14 kV/cm and $20{\mu}C/cm^2$.
동적 물성치를 고려한 진공 인터럽터 충격특성의 영향인자 분석
임지호,송정한,허훈,박우진,오일성,안길영,최종웅,Lim, Ji-Ho,Song, Jeong-Han,Huh, Hoon,Park, Woo-Jin,Oh, Il-Seong,Ahn, Gil-Young,Choe, Jong-Woong 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.5
Vacuum interrupters in order to be used in various switch-gear components such as circuit breakers, distribution switches, contactors, etc. spread the arc uniformly over the surface of the contacts. The electrodes of vacuum interrupters are made of sinter-forged Cu-Cr materials for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain rate at that velocity, the dynamic behavior of the sinter-forged Cu-Cr is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain rate is obtained from the split Hopkinson pressure bar test using disc-type specimens. Experimental results from both quasi-static and dynamic compressive tests are Interpolated to construct the Johnson-Cook model as the constitutive relation that should be applied to simulation of the dynamic behavior of the electrodes. The impact characteristics of a vacuum interrupter are investigated with computer simulations by changing the value of five parameters such as the initial velocity of a movable electrode, the added mass of a movable electrode, the wipe spring constant, initial offset of a wipe spring and the virtual fixed spring constant.
상온분말분사공정을 이용한 고밀도 폴리머-세라믹 혼합 코팅층 제조 및 에너지 저장 특성 향상
임지호,김진우,이승희,박춘길,류정호,최두현,정대용,Lim, Ji-Ho,Kim, Jin-Woo,Lee, Seung Hee,Park, Chun-kil,Ryu, Jungho,Choi, Doo hyun,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.3
This study examines paraelectric $Bi_{1.5}Zn_{1.0}Nb_{1.5}O_7$ (BZN), which has no hysteresis and high dielectric strength, for energy density capacitor applications. To increase the breakdown dielectric strength of the BZN film further, poly(vinylidene fluoride) BZN-PVDF composite film is fabricated by aerosol deposition. The volume ratio of each composition is calculated using dielectric constant of each composition, and we find that it was 12:88 vol% (BZN:PVDF). To modulate the structure and dielectric properties of the ferroelectric polymer PVDF, the composite film is heat-treated at $200^{\circ}C$ for 5 and 30 minutes following quenching. The amount of ${\alpha}-phase$ in the PVDF increases with an increasing annealing time, which in turn decreases the dielectric constant and dielectric loss. The breakdown dielectric strength of the BZN film increases by mixing PVDF. However, the breakdown field decreases with an increasing annealing time. The BZN-PVDF composite film has the energy density of $4.9J/cm^3$, which is larger than that of the pure BZN film of $3.6J/cm^3$.
상온분사분말공정에 의해 SrTiO<sub>3</sub> (100), (110) Seed에 코팅된 BaTiO<sub>3</sub>의 고온 성장 거동 분석
임지호,이승희,김기현,지성엽,정승운,박춘길,정한보,정대용,Lim, Ji-Ho,Lee, Seung Hee,Kim, Ki Hyun,Ji, Sung-Yub,Jung, Suengwoon,Park, Chun-kil,Jung, Han-Bo,Jeong, Dae-Yong 한국재료학회 2019 한국재료학회지 Vol.29 No.11
Single crystals, which have complexed composition, are fabricated by solid state grain growth. However, it is hard to achieve stable properties in a single crystal due to trapped pores. Aerosol deposition (AD) is suitable for fabrication of single crystals with stable properties because this process can make a high density coating layer. Because of their unique features (nano sized grains, stress inner site), it is hard to fabricate single crystals, and so studies of grain growth behavior of AD film are essential. In this study, a $BaTiO_3$ coating layer with ${\sim}9{\mu}m$ thickness is fabricated using an aerosol deposition method on (100) and (110) cut $SrTiO_3$ single crystal substrates, which are adopted as seeds for grain growth. Each specimen is heat-treated at various conditions (900, 1,100, and $1,300^{\circ}C$ for 5 h). $BaTiO_3$ layer shows different growth behavior and X-ray diffraction depending on cutting direction of $SrTiO_3$ seed. Rectangular pillars at $SrTiO_3$ (100) and laminating thin plates at $SrTiO_3$ (110), respectively, are observed.
2D영상을 이용한 자동 시기능 훈련기구의 시기능 개선 효과
임지호,설고은,최정은,장민화,강혜원,임수민,김민지,정현빈,서유영,김하경,신철근,이석주 대한시과학회 2017 대한시과학회지 학술대회 Vol.2017 No.11
목적: 2D 영상이 재생되는 자동 시기능 훈련기구를 이용하여 훈련 전과 후의 시기능의 개선효과를 알아보고자 하였다. 방법: 성인 남녀 20명을 대상으로 자동 시기능 훈련기기(WISDOM社, China)를 이용하여 30분 간 재생되는 영상을 보면서 시기능 훈련을 실시하였으며, 훈련 전과 후의 폭주력, 조절력, 버전스 용이성(3△BI/12△BO), 조절용이성(±2.00D)검사를 시행하였다. 자동 시기능 훈련기구는 0.00~6.00D 범위의 조절과 0~6 M·A 범위의 버전스 훈련을 자동으로 하도록 설계되어 있다. 결과: 시기능 훈련 30분 전과 후의 시기능 변화를 확인한 결과, 양안 조절력은 12.63 ± 4.17D에서 15.02 ± 5.96D로 2.39 ± 2.89D 증가하였으며(p<0.05), 폭주력은 13.96 ± 4.99D 에서 16.02 ± 6.03D로 2.05 ± 2.85D 증가하였다(p<0.05). 양안 조절용이성은 16.58 ± 6.52 CPM에서 20.65 ± 6.51 CPM으로 4.07 ± 4.59 CPM으로 증가하였으며(p<0.05), 버전스 용이성은 16.40 ± 6.49 CPM에서 23.2 ± 6.95 CPM으로 4.8 ± 2.98 CPM으로 증가하였다 (p<0.05). 결론: 본 연구를 통해 2D 영상을 이용한 자동 시기능 훈련기구의 시기능 개선효과를 알 수 있었다. 이는 평소 좋아하는 영화나 드라마 등의 콘텐츠를 활용하여 훈련의 몰입도를 높일 수 있으므로 기존의 단조로운 시기능 훈련에서 벗어난 새로운 훈련방법중의 하나가 될 수 있다.