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작교이방성 판이론을 적용한 바닥판 활하중 모멘트 산정식 개발
안예준(Ahn Ye Jun),남석현(Nam Suk Hyun),박장호(Park Jang Ho),신영석(Shin Yung Seok) 대한토목학회 2007 대한토목학회논문집 A Vol.27 No.5A
교축과 교축직각 방향의 철근비가 다른 철근콘크리트 바닥판은 두 방향의 휨 강성이 다르기 때문에 직교이방성의 재료성질을 가진다. 이러한 철근콘크리트 바닥판의 직교이방성 성질은 교량의 바닥판 휨모멘트에 영향을 미친다. 2004년 개정된 AASHTO LRFD Bridge Desi맑 Specification은 활하중에 의해 바닥판에 작용하는 휨모멘트를 산정하는데 휨 강성비를 고려하고 있지만, 국내의 도로교설계기준(건설교통부, 2005)는 휨강성비를 고려하지 않고 있다. 또한 도로교 표준시방서 하중저항계수 설계편(대한토목학회, 1996)의 활하중 모멘트 값은 휨강성비를 고려하고 있으나, 단일 하중만을 고려하고 있기 때문에 안전한 값으로 보기 힘들다. 본 연구에서는 국내 설계기준에 제시된 트럭 하중모델과 승용차 전용 고가도로 설계용 활하중모델에 대하여 휨 강성비와 다수의 윤하중을 고려한 바닥판 활하중 모멘트 산정식을 제안하고자 한다. 직교이방성 판이론을 이용하여 철근콘크리트 바닥판에 작용하는 휨모멘트를 산정하였다. 바닥판 활하중 모멘트 산정식에는 국내 설계기준 및 시방서에 제시된 하중계수, 동시재하계수, 및 트럭하중모델을 각각 적용하였다. Because of the orthotropic elastic properties and a significant two-way bending action, orthotropic plate theory may be suitable for describing the behavior of concrete-filled steel grid decks. In AASHTO LRFD Bridge Design Specification(2004), the equations for live load moment consider a ratio of flexural rigidity between longitudinal and transverse directions, but not in the Korea design specification of highway bridge (2005). The Korea LRFD bridge standard specification of highway(1996) includes an orthotropic plate model with single load to estimate effects induced by live load moments of concrete-filled steel grid decks. However, the orthotropic plate model considering only single patch load may not be conservative. This paper presents live load moment equations for truck and passenger car, based on the classical orthotropic plate theory, which includes multiple patch loads. Design factors and live load models of Korea standard specification of highway bridge is applied to proposed formulations.
Ahn, Cheol Hyoun,Kang, Won Jun,Kim, Ye Kyun,Yun, Myeong Gu,Cho, Hyung Koun American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.24
<P>Highly repeatable and recoverable phototransistors were explored using a 'multifunctional channels' structure with multistacked chalcogenide and oxide semiconductors. These devices were made of (i) photoactive CdS (with a visible band gap), (ii) fast charge transporting ZnO (with a high field-effect mobility), and (iii) a protection layer of Al2O3 (with high chemical durability). The CdS TFT without the Al2O3 protection layer did not show a transfer curve due to the chemical damage that occurred on the ZnO layer during the chemical bath deposition (CBD) process used for CdS deposition. Alternatively, compared to CdS photo transistors with long recovery time and high hysteresis (del V-th = 19.5 V), our 'multi-functional channels' phototransistors showed an extremely low hysteresis loop (del V-th = 0.5V) and superior photosensitivity with repeatable high photoresponsivity (52.9 A/W at 400 nm). These improvements are likely caused by the physical isolation of the sensing region and charge transport region by the insertion of the ultrathin Al2O3 layer. This approach successfully addresses some of the existing problems in CdS phototransistors, such as the high gate-interface trap site density and high absorption of molecular oxygen, which originate from the polycrystalline CdS.</P>
Ahn Jee Hyun,Go Jieon,Lee Suk Jun,Kim Jee Ye,Park Hyung Seok,Kim Seung Il,Park Byeong-Woo,Park Vivian Youngjean,Yoon Jung Hyun,Kim Min Jung,Park Seho 대한영상의학회 2023 Korean Journal of Radiology Vol.24 No.5
Objective: Mammographic density is an independent risk factor for breast cancer that can change after neoadjuvant chemotherapy (NCT). This study aimed to evaluate percent changes in volumetric breast density (ΔVbd%) before and after NCT measured automatically and determine its value as a predictive marker of pathological response to NCT. Materials and Methods: A total of 357 patients with breast cancer treated between January 2014 and December 2016 were included. An automated volumetric breast density (Vbd) measurement method was used to calculate Vbd on mammography before and after NCT. Patients were divided into three groups according to ΔVbd%, calculated as follows: Vbd (post-NCT − pre-NCT)/pre-NCT Vbd x 100 (%). The stable, decreased, and increased groups were defined as -20% ≤ ΔVbd% ≤ 20%, ΔVbd% < -20%, and ΔVbd% > 20%, respectively. Pathological complete response (pCR) was considered to be achieved after NCT if there was no evidence of invasive carcinoma in the breast or metastatic tumors in the axillary and regional lymph nodes on surgical pathology. The association between ΔVbd% grouping and pCR was analyzed using univariable and multivariable logistic regression analyses. Results: The interval between the pre-NCT and post-NCT mammograms ranged from 79 to 250 days (median, 170 days). In the multivariable analysis, ΔVbd% grouping (odds ratio for pCR of 0.420 [95% confidence interval, 0.195–0.905; P = 0.027] for the decreased group compared with the stable group), N stage at diagnosis, histologic grade, and breast cancer subtype were significantly associated with pCR. This tendency was more evident in the luminal B-like and triple-negative subtypes. Conclusion: ΔVbd% was associated with pCR in breast cancer after NCT, with the decreased group showing a lower rate of pCR than the stable group. Automated measurement of ΔVbd% may help predict the NCT response and prognosis in breast cancer.
Ye Ji Ahn,Wan Su Yun,최진실,김우철,Su Hoon Lee,Dong Jun Park,박정은,Jaehong Key,서영준 대한의용생체공학회 2021 Biomedical Engineering Letters (BMEL) Vol.11 No.1
Recently, application of stem cell therapy in regenerative medicine has become an active field of study. Mesenchymal stem cells (MSCs) are known to have a strong ability for homing. MSCs labeled with superparamagnetic iron oxide nanoparticles (SPIONs) exhibit enhanced homing due to magnetic attraction. We have designed a SPION that has a cluster core of iron oxide-based nanoparticles coated with PLGA-Cy5.5. We optimized the nanoparticles for internalization to enable the transport of PCS nanoparticles through endocytosis into MSCs. The migration of magnetized MSCs with SPION by static magnets was seen in vitro. The auditory hair cells do not regenerate once damaged, ototoxic mouse model was generated by administration of kanamycin and furosemide. SPION labeled MSC’s were administered through different injection routes in the ototoxic animal model. As result, the intratympanic administration group with magnet had the highest number of cells in the brain followed by the liver, cochlea, and kidney as compared to those in the control groups. The synthesized PCS (poly clustered superparamagnetic iron oxide) nanoparticles, together with MSCs, by magnetic attraction, could synergistically enhance stem cell delivery.
Jun, Yong Woong,Kim, Hye Rim,Reo, Ye Jin,Dai, Mingchong,Ahn, Kyo Han Royal Society of Chemistry 2017 Chemical Science Vol.8 No.11
<▼1><P>We have developed a new class of two-photon absorbing dyes that are far-red emitting, water-soluble, and very bright inside cells as well as in tissue. The significant autofluorescence from yellow wavelength region in tissue imaging can be addressed by deep-red emitting dyes.</P></▼1><▼2><P>The fluorescence imaging of tissue is essential for studying biological events beyond the cellular level. Two-photon microscopy based on the nonlinear light absorption of fluorescent dyes is a viable tool for the high resolution imaging of tissue. A key limitation for deep tissue imaging is the autofluorescence from intrinsic biomolecules. Here, we report a systematic study that discloses relative autofluorescence interference, which is dependent on the type of tissue and the excitation and emission wavelengths in two-photon imaging. Among the brain, kidney, liver, lung, and spleen mouse tissues examined, the kidney tissue exhibited prominent autofluorescence followed by the liver and others. Notably, regardless of the tissue type, prominent autofluorescence is observed not only from the green emission channel but also from the yellow emission channel where common two-photon absorbing dyes also emit, whereas there is minimal autofluorescence from the red channel. The autofluorescence is slightly influenced by the excitation wavelength. Toward minimal autofluorescence, we developed a new class of two-photon absorbing dyes that are far-red emitting, water-soluble, and very bright inside cells as well as in tissue. A comparative assessment of the imaging depth, which is dependent on the three selected dyes that emit in the blue-green, yellow, and far-red regions, shows the importance of far-red emitting dyes for deep tissue imaging.</P></▼2>