Electric-Field-Dependent Surface Potentials and Vibrational Energy-Harvesting Characteristics of Bi(Na_0.5Ti_0.5)O₃-Based Pb-Free Piezoelectric Thin Films

Cho, Ahra,Kim, Da Bin,Cho, Yong Soo American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.14

<P>The successful utilization of Pb-free piezoelectric materials is considered as critical since the piezoelectric material-based thin-film cantilever is still the preferred choice for commercial vibrational energy harvesters. Herein, we introduce a highly efficient piezoelectric energy harvester based on a Pb-free representative compound, Bi<SUB>0.5</SUB>Na<SUB>0.5</SUB>TiO<SUB>3</SUB>, which has not been explored so far. Applying a strong electric field for poling purposes brought unexpectedly huge changes in the dielectric constant and piezoelectric coefficient, which were responsible for the promising power density of 21.2 μW/cm<SUP>2</SUP>/g<SUP>2</SUP>/Hz with 537.7 mV output voltage and 2.22 μW output power for a 2 μm thick 0.94(Bi<SUB>0.5</SUB>Na<SUB>0.5</SUB>)TiO<SUB>3</SUB>-0.06BaTiO<SUB>3</SUB> thin-film cantilever. The power density value is the best so far compared with any reported values for thin-film-based harvesters. As the origin of the effects of poling, the surface potentials across the grain structure are discussed in conjunction with the defect-dipole alignment, as evidenced by the increased oxygen vacancies on the film surface under an external bias field.</P> [FIG OMISSION]</BR>

Gagamyeonryunggobon-dan(Jiājiǎnyánlínggùběn-dān) induces hair regrowth effect from activating hair follicle

Ahra Cho,홍승욱,Young-Joon Yoon 대한한방안이비인후피부과학회 2016 한방안이비인후피부과학회지 Vol.29 No.1

Objective : The purpose of this study is to report the hair regrowth effect of Gagamyeonryunggobon-dan on ICR mice from measuring the change of diverse factors. Methods : Gagamyeonryunggobon-dan was treated by oral administration with 2.5㎎/㎏/day amount for 3 weeks per mouse everyday. Hair regrowth was estimated by change of morphology, angiogenesis, hair follicle activation. The change of morphology was observed with external, internal change and sebaceous gland. Angiogenesis was estimated by image analysis, capillary distribution and angiogenic chemokine(MIP-2). Hair follicle activation was estimated by PCNA, IGF-2 and serotonin. Results : 1. Gagamyeonryunggobon-dan treated group had more and thicker hairs than the group not treated. Especially well developed sebaceous glands were seen in dermis of treated group. 2. Gagamyeonryunggobon-dan treated group had more capillaries near hair follicles of subcutaneous layer and more 2019% MIP-2 positive activity than the group not treated. 3. Gagamyeonryunggobon-dan treated group increased positive activity up to 596% in PCNA, 187% in IGF-2 and 547% in serotonin more than the group not treated. Conclusion : These results shows that Gagamyeonryunggobon-dan have the hair regrowth effect through verifying change of morphology, angiogenesis, chemokines. Consequently Gagamyeonryunggobon-dan is expected to apply to take care of extensive hair loss symptoms.

Neutralization of PEDOT:PSS with various Imidazole for stable conducting polymer films and its applications

Ahra CHO,Seyul KIM,Yunryeol KIM,Jung Hyun KIM 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Direct Correlations of Grain Boundary Potentials to Chemical States and Dielectric Properties of Doped CaCu₃Ti₄O₁₂ Thin Films

Cho, Ahra,Han, Chan Su,Kang, Meenjoo,Choi, Wooseok,Lee, Jihwan,Jeon, Jaecheol,Yu, Sujae,Jung, Ye Seul,Cho, Yong Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.18

<P>Colossal dielectric constant CaCu<SUB>3</SUB>Ti<SUB>4</SUB>O<SUB>12</SUB> has been recognized as one of the rare materials having intrinsic interfacial polarization and thus unusual dielectric characteristics, in which the electrical state of the grain boundary is critical. Here, the direct correlation between the grain boundary potential and relative permittivity is proposed for the CaCu<SUB>3</SUB>Ti<SUB>4</SUB>O<SUB>12</SUB> thin films doped with Zn, Ga, Mn, and Ag as characterized by Kelvin probe force microscopy. The dopants are intended to provide the examples of variable grain boundary potentials that are driven by chemical states including Cu<SUP>+</SUP>, Ti<SUP>3+</SUP>, and oxygen vacancy. Grain boundary potential is nearly linearly proportional to the dielectric constant. This effect is attributed to the increased charge accumulation near the grain boundary, depending on the choice of the dopant. As an example, 1 mol % Ag-doped CaCu<SUB>3</SUB>Ti<SUB>4</SUB>O<SUB>12</SUB> thin films demonstrate the best relative permittivity as associated with a higher grain boundary potential of 120.3 mV compared with 82.6 mV for the reference film. The chemical states across grain boundaries were further verified by using spherical aberration-corrected scanning transmission electron microscopy with the simultaneous electron energy loss spectroscopy.</P> [FIG OMISSION]</BR>

Ethical Guidelines for Use of Experimental Animals in Biomedical Research

Cho, Ahra,Seok, Seung Hyeok 대한미생물학회 2013 Journal of Bacteriology and Virology Vol.43 No.1

Increasing concerns on animal welfare, the discussion about the necessity and the ethical acceptability of animal experiments is getting important. In this article, we describe ethical issues between the benefits of the animal experiments and the suffering of the animals. If there are no alternatives for animal experiments, the ethical guidelines, 3Rs (Reduction, Replacement, Refinement) by Russell and Burch for humane animal experiments should be considered. Moreover, Institutional Animal Care and Use Committee (IACUC) and Institutional Biosafety Committee (IBC) assist researchers to perform animal testing humanely and safely. We point out three important aspects in support of humane animal experiments; 1) the development of diverse scientific alternatives on the animal testing, 2) the ethical education of animal experiments for researchers, 3) the productive interactions among various social groups on ethics and safety of animal experiments.

Ethical Guidelines for Use of Experimental Animals in Biomedical Research

Ahra Cho,Seung Hyeok Seok 대한미생물학회 2013 Journal of Bacteriology and Virology Vol.43 No.1

Development of a Smart Device Utilization Education Program for Senior Citizens

Ahra CHO,Chan-Woo YOO Korea Fourth Industrial Association 2024 Fourth industrial review Vol.4 No.1

Purpose: This study is based on the results of the National Information Society Agency's the Report on the Digital Divide in 2022. This study sought to develop digital literacy education programs for senior citizens, a digitally disadvantaged group, and to utilize smart devices to enhance their digital capabilities. Research design, data and methodology: Based on Gagné's nine events of instruction, a total of 7-session educational programs using smart devices were developed, and teaching-learning goals were set at a level that older learners can realistically perform. In preparation for the era of digital transformation, AI utilization methods are introduced and utilized in some sessions of the educational program. Results: Among a total of 7 sessions of the educational program, 5 sessions using KakaoTalk and Naver App, and 2 sessions using other apps were developed. There are a total of three sessions using AI. Conclusions: This study presented a digital literacy education program that combined AI, addressing the insufficiency of AI-based education programs targeting senior citizens. It is expected that this educational program will be able to improve the digital literacy skills and provide a basis for fulfilling their responsibilities as digital citizens by suggesting a direction for AI utilization education for senior citizens.

지역 참여는 우리를 더 관용적으로 만들까?

조아라(Ahra Cho),김용찬(Yong-Chan Kim),신의경(Euikyung Shin) 연세대학교 사회과학연구소 2023 社會科學論集 Vol.54 No.1

소비자의 독특성 추구경향과 과시적 소비성향이 패션 콜레보레이션 제품에 대한 태도와 구매의도에 미치는 영향

조아라 ( Cho Ahra ),이윤정 ( Lee Yoon-jung ) 한국디자인트렌드학회 2013 한국디자인포럼 Vol.38 No.-

콜레보레이션(Collaboration)은 두 개의 브랜드가 공동의 목표를 갖고, 일정기간 제휴를 맺어 다양화 된 소비자의 요구를 만족시켜주기 위한 새로운 형태의 전략이다. 본 연구는 패션 콜레보레이션 제품이 제한된 생산으로 희소성을 가진다는 점과 주로 유명 브랜드의 이미지를 활용하는 제품이 많다는 점의 두 가지 특성에 초점을 맞추어, 소비자의 독특성 추구경향과 과시적 소비성향이 패션 콜레보레이션 제품에 대한 태도와 구매의도에 미치는 영향에 관해 알아보는 것을 목적으로 한다. 본 연구의 자료는 2008년 8월 한 달간 서울의 패션 중심 거리에서 20~30대 여성을 대상으로 설문지법을 이용하여 수집하였다. 측정도구에는 소비자의 독특성 추구경향, 과시적 소비성향, 패션 콜레보레이션 제품에 대한 태도, 구매의도 등에 대한 척도와 인구통계적 특성에 대한 질문이 포함되었다. 최종 표본은 589명이었으며, 자료분석은 SPSS 12.0을 사용하여 요인분석, 상관관계분석, 회귀분석 등을 실시하였다. 본 연구의 결과는 다음과 같다. 첫째, 소비자의 독특성 추구경향의 세 가지 하위 요인 중 창의적 선택 요인은 패션 콜레보레이션 제품에 대한 태도와 구매의도에 영향을 주었다. 즉, 새롭고 디자인이 창의적인 제품을 구매하기를 원하는 성향이 높을수록 패션 콜레보레이션 제품에 대한 관심이 높은 것으로 나타났다. 둘째, 소비자의 과시적 소비성향은 패션 콜레보레이션 제품에 대한 태도와 구매의도에 영향을 주었다. 즉, 타인에게 과시하는 성향이 높은 소비자일수록 패션 콜레보레이션 제품에 대한 관심이 높은 것으로 보인다. 따라서 콜레보레이션은 소비자들에게 잘 알려진 명품 브랜드와의 협업을 통하여 제품을 생산할 경우 성공 가능성을 높일 수 있다. 그러나 독특성 추구경향 중 비대중적 선택이나 유사성 회피 요인은 패션 콜레보레이션 제품에 대한 태도에 영향을 미치지 않아, 패션 콜레보레이션 제품에 대한 소비자들의 초점이 단순한 남들과의 차별성이 아니라 디자인의 새롭고 창의적인 측면이라는 것을 알 수 있었다. 셋째, 인구 통계적 특성은 패션 콜레보레이션 제품에 대한 태도에 미치는 영향이 크지 않았다. 그러나 한 달 평균 패션 제품 지출 정도에 따른 구매의도에 대한 분석에서는 젊을수록, 그리고 지출성향이 높을수록 패션 콜레보레이션 제품을 구매할 가능성이 높은 것으로 나타났다. 본 연구는 패션 콜레보레이션 제품에 대한 태도와 구매의도에 영향을 미치는 소비자의 소비성향을 밝힘으로써 향후 콜레보레이션을 시도하려는 브랜드 간의 효과적인 마케팅 전략에 도움이 될 것이다. The purpose of this study is to examine how consumers` need for uniqueness and conspicuous consumption tendency affect their attitude toward and purchase intention of fashion collaboration products. Collaboration is a new strategy to satisfy the needs of different consumers by tying-up two different brands for the same goal for a certain period. This study focused on the fact that fashion collaboration products has scarcity due to limited production and takes advantage of the partner brands` reputation by collaborating with famous brands. A survey was conducted to women in their 20`s and 30`s who are living in Seoul area. In order to verify the validity and credibility of the instrument, a pilot study was conducted to 32 women in July 2008. The main survey was distributed to 589 women in fashion area in August 2008. The instrument included measures of need for uniqueness, conspicuous consumption tendency, attitude toward fashion collaboration products, intention to purchase fashion collaboration products, and demographics. SPSS 12.0 was used for factor analysis, correlations, and multiple regression. Conclusion of this research is as follows. First, Consumers` need for uniqueness affected to the consumption on fashion collaboration products. The creative choice factor of need for uniqueness had a positive influence on attitude toward and intention to purchase fashion collaboration products. Second, Consumers` conspicuous consumption tendency affected their attitude toward and intention to purchase fashion collaboration products. Those who have higher tendency of conspicuous consumption showed more interest in fashion collaboration products. Therefore, tying up with famous prestige brands will increase the possibility for success of collaboration products. Third, the relation between demographic characteristics and attitude toward fashion collaboration products wasn`t big. However unlike other demographic characteristics, age and average monthly expenditure on fashion items had relationships with attitude toward fashion collaboration products. Younger consumers and/or those with higher expenditure were more intended to purchase fashion collaboration products consumption. This research will help establish the marketing strategy for launching new fashion collaboration products by discovering the relationships between consumer`s consumption patterns and their attitude toward fashion collaboration products.

OpenMP 디렉티브 병렬프로그램에서의 동적 자료경합 탐지를 위한 감시 필터링 기술의 실험적 비교

조아라(Ahra Cho),하옥균(Ok-Kyoon Ha) 한국컴퓨터정보학회 2016 한국컴퓨터정보학회 학술발표논문집 Vol.24 No.2