• Smart Structures and Systems
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• 제31권1호
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• pp.13-27
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• 2023

Fatigue crack is a fatal problem for steel structures. Early detection and maintenance can help extend the service life and prevent hazards. This paper presents the ultrasonic guided waves-based (UGWs-based) fatigue crack detection of a steel I-beam. The semi-analytical finite element model has been built to obtain the wave propagation characteristics. Damage indices in both time and frequency domains were analyzed by considering the characteristic variations of UGWs including the amplitude, phase angle, and wave packet energy. The pulse-echo and pitch-catch methods were combined in the detection scheme. Lab-scale experiments were conducted on welded steel I-beams to verify the proposed method. Results show that the damage indices based on the characteristic variations in the time domain can identify and localize the fatigue crack before it enters the rapid growth stage. The damage severity can be reasonably evaluated by analyzing the time-domain damage indices. Two nonlinear damage indices in the frequency domain give earlier warnings of the fatigue crack than the time-domain damage indices do. The identification results based on the above two nonlinear indices are found to be less consistent under various excitation frequencies. More robust nonlinear techniques needed to be searched and tested for early crack detection in steel I-beams in further study.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.361-370
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• 2017

Through the use of finite element analysis and acoustic emission techniques we have evaluated the interfacial failure of a carbon fiber reinforced polymer (CFRP) repair patch on a notched aluminum substrate. The repair of cracks is a very common and widely used practice in the aeronautics field to extend the life of cracked sheet metal panels. The process consists of adhesively bonding a patch that encompasses the notched site to provide additional strength, thereby increasing life and avoiding costly replacements. The mechanical strength of the bonded joint relies mainly on the bonding of the adhesive to the plate and patch stiffness. Stress concentrations at crack tips promote disbonding of the composite patch from the substrate, consequently reducing the bonded area, which makes this a critical aspect of repair effectiveness. In this paper we examine patch disbonding by calculating the influence of notch tip stress on disbond area and verify computational results with acoustic emission (AE) measurements obtained from specimens subjected to uniaxial tension. The FE results showed that disbonding first occurs between the patch and the substrate close to free edge of the patch followed by failure around the tip of the notch, both highest stress regions. Experimental results revealed that cement adhesion at the aluminum interface was the limiting factor in patch performance. The patch did not appear to strengthen the aluminum substrate when measured by stress-strain due to early stage disbonding. Analysis of the AE signals provided insight to the disbond locations and progression at the metal-adhesive interface. Crack growth from the notch in the aluminum was not observed until the stress reached a critical level, an instant before final fracture, which was unaffected by the patch due to early stage disbonding. The FE model was further utilized to study the effects of patch fiber orientation and increased adhesive strength. The model revealed that the effectiveness of patch repairs is strongly dependent upon the combined interactions of adhesive bond strength and fiber orientation.

• 한국수산과학회지
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• 제28권4호
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• pp.383-391
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• 1995

출산 전후의 황점볼락 및 조피볼락 어미의 뇌 조직에서 GtH 분비를 자극하는 신경호르몬으로 알려진 NPY를 검출하기 위해, 면역조직화학을 실시하고 뇌하수체내 GtH 분비세포의 활성을 서로 비교하였다. 두 어종 모두에서 뇌 조직중 NPY 양성반응을 나타내는 세포는 후각망울, 종뇌 및 중뇌에서, 신경섬유는 후각망울, 종뇌, 시각신경, 시상하부, 중뇌 및 시각엽에서 각각 관찰되었다. 뇌하수체내에서 NPY 양성반응을 나타내는 신경섬유는 성숙에 관계없이 두 어종 모두 앞원위부분의 AF 음성세포에 인접한 신경엽에 분포하였고, 성장 및 성숙기의 난모세포를 가진 어체에서는 앞원위부분의 신경엽과 중간원위부분의 GtH 분비세포에 인접한 신경엽에서 관찰되었다. 뇌하수체내의 GtH 분비세포는 출산전의 황점볼락 및 성숙기의 조피볼락 개체에서는 AF 염색성이 약했으나, 출산후 황점볼락 및 조피볼락의 GtH 분비세포는 출산전 및 성숙기에 비해 AF 염색성이 증가하였다. 두 어종에서 출산전 난소를 가진 개체들의 GtH 분비세포와 핵경의 크기는 출산후(황점볼락)이거나 출산 이후 휴지기의 난소를 가진 개체(조피볼락) 보다 유의하게 컸다(P<0.01).

• Asian Pacific Journal of Cancer Prevention
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• 제15권21호
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• pp.9143-9146
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• 2014

Background: The aim of this study was to investigate the general characteristics of patients with deep vein thrombosis (DVT) and pancreatic cancer as well as evaluate the relationship between mean platelet volume (MPV), DVT and survival. Materials and Methods: Seventy-seven patients with pancreatic cancer, who were admitted to Cukurova University Medical Faculty, Department of Medical Oncology, were enrolled in the study Results: The mean age was $59{\pm}20$. Forty-nine (63.6%) were men and 28 women (36.4%). Sixty-eight (88.3%) patients had adenocarcinoma and 9 (11.7%) had a malignant epithelial tumor. Thirty-six (46.7%) had liver metastasis at diagnosis. Twenty-six (33.8%) patients were alive, 20 (26%) were dead and in 31 (40.2%) the status was unknown. Only 14 (18.1%) patients had DVT. In 42 (54.5%) patients MPV values were normal, in 28 (36.4%) patients they were above normal, and in 7 (9.1%) patients they were below normal. There was no statistically significant difference between gender, tumour localization, chemotherapy and survival rates (p:0.56, p:0.11, p:0.21). There was no significant difference between DVT, gender, localisation, histological subtype, the presence of metastasis, stage and if the patient had been treated with chemotherapy (p:0.5, p:0.6, p:0.2, p:0.32, p:0.1, p:0.84). There was also no significant difference between MPV and DVT (p:0.57) but there was a significant difference between liver metastasis and DVT (p:0.02). Age, stage, the presence of metastasis and DVT were prognostic in pancreatic cancer patients. Conclusions: Cases of pancreatic cancer with liver metastasis should be studied more carefully as thrombosis is more common in these patients.

• Parasites, Hosts and Diseases
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• 제54권4호
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• pp.385-391
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• 2016

The discovery and understanding of antigenic proteins are essential for development of a vaccine against malaria. In Plasmodium falciparum, Pf92 have been characterized as a merozoite surface protein, and this protein is expressed at the late schizont stage, but no study of Pv92, the orthologue of Pf92 in P. vivax, has been reported. Thus, the protein structure of Pv92 was analyzed, and the gene sequence was aligned with that of other Plasmodium spp. using bioinformatics tools. The recombinant Pv92 protein was expressed and purified using bacterial expression system and used for immunization of mice to gain the polyclonal antibody and for evaluation of antigenicity by protein array. Also, the antibody against Pv92 was used for subcellular analysis by immunofluorescence assay. The Pv92 protein has a signal peptide and a sexual stage s48/45 domain, and the cysteine residues at the N-terminal of Pv92 were completely conserved. The N-terminal of Pv92 was successfully expressed as soluble form using a bacterial expression system. The antibody raised against Pv92 recognized the parasites and completely merged with PvMSP1-19, indicating that Pv92 was localized on the merozoite surface. Evaluation of the human humoral immune response to Pv92 indicated moderate antigenicity, with 65% sensitivity and 95% specificity by protein array. Taken together, the merozoite surface localization and antigenicity of Pv92 implicate that it might be involved in attachment and invasion of a merozoite to a new host cell or immune evasion during invasion process.

• Parasites, Hosts and Diseases
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• 제54권6호
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• pp.725-732
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• 2016

Plasmodium vivax produces numerous caveola-vesicle complex (CVC) structures beneath the membrane of infected erythrocytes. Recently, a member helical interspersed subtelomeric (PHIST) superfamily protein, $PcyPHIST/CVC-81_{95}$, was identified as CVCs-associated protein in Plasmodium cynomolgi and essential for survival of this parasite. Very little information has been documented to date about $PHIST/CVC-81_{95}$ protein in P. vivax. In this study, the recombinant $PvPHIST/CVC-81_{95}$ N and C termini were expressed, and immunoreactivity was assessed using confirmed vivax malaria patients sera by protein microarray. The subcellular localization of $PvPHIST/CVC-81_{95}$ N and C termini in blood stage parasites was also determined. The antigenicity of recombinant $PvPHIST/CVC-81_{95}$ N and C terminal proteins were analyzed by using serum samples from the Republic of Korea. The results showed that immunoreactivities to these proteins had 61% and 43% sensitivity and 96.9% and 93.8% specificity, respectively. The N terminal of $PvPHIST/CVC-81_{95}$ which contains transmembrane domain and export motif (PEXEL; RxLxE/Q/D) produced CVCs location throughout the erythrocytic-stage parasites. However, no fluorescence was detected with antibodies against C terminal fragment of $PvPHIST/CVC-81_{95}$. These results suggest that the $PvPHIST/CVC-81_{95}$ is localized on the CVCs and may be immunogenic in natural infection of P. vivax.

• 한국발생생물학회지:발생과생식
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• 제2권1호
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• pp.53-62
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• 1998

리소솜 acid phosphatase(LAP)를 포함하는 리소솜 산성 가수 분해 효소는 세포 내,외 성분의 분해에 중요한 기능을 수행하며, 유미 양서류의 다리 재생 과정에서 LAP의 효소 활성도는 탈분화시기에 특이적으로 증가하는 것으로 알려져 있다. 본 연구에서는 멕시코산 도룡뇽의 일종인 axolotl(Ambystoma mexicanum)의 다리 재생 가정에서 정상적인 다리 재생 조직과 retinoic acid (RA)가 처리된 다리 재생 조직에서 LAP의 분포 및 발현을 면역 화학적 방법으로 조사하였다. Axolotl의 다리 재생 조직에서 한국산 도룡뇽(Hynobius leechii)의 LAP에 대한 단일 항체를 이용한 면역 반응도는 줄 탈분화시기에 있는 wound epidermis와 미분화된 중배엽성 세포인 blastema 세포, 탈분화 상태의 근육과 연골 부위 세포에서 나타나는 것으로 조사되었다. 또한 LAP의 면역 반응도는 재생단게의 초기에 점차 증가하여 탈분화시기 동안 최대치에 도달하였으며, 재분화가 시작되면서 basal level 까지 서서히 감소하는 것으로 나타나\ulcorner. 유미 양서류의 다리 재생 과정에서 골격 패턴의 복제를 유발시키는 것으로 알려져 있는 RA 처리는 LAP의 면역 반응도를 강화시키는 것으로 나타나\ulcorner. 즉, RA가 처리된 다리 재생 조직에서 LAP의 면역 반응도는 정상적인 다리 재생 조직에서 보다 강하게 나타났으며, 면역 반응도가 나타나는 시기 또한 연장되는 것으로 조사되었다. 이와 같은 결과는 다리 재생 조직에서 RA 처리가 탈분화시기의 연장에 관여한다는 것을 시사하고 있다.

• 대한수의학회지
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• 제46권3호
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• pp.177-184
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• 2006

Experimental autoimmune encephalomyelitis (EAE) is a disease model of multiple sclerosis (MS) that is characterized by remittance and relapse of the disease and autoimmune and demyelinating lesions in the central nervous system (CNS). Autoimmune inflammation is maintained by secretion of a large number of protein. Previous studies have suggested that transcripts encoding osteopontin (OPN) are frequently detected in the mRNA population of MS plaques. To elucidate the functional role of OPN in initiation and development of EAE, we examined the expression and localization of OPN in the spinal cord during acute EAE. We demonstrated that OPN significantly increased at the early stage of EAE and slightly declined thereafter by western blot analysis. An immunohistochemical study revealed that OPN was constitutively expressed in some glial cells (microglia, astrocytes) of white matter and neurons in the CNS of control rats. OPN expression was shown to be increased in the same cells at the early and peak stage of EAE. To identity cells expressing OPN by double-immunofluorescence labeling, we labeled rat spinal cord sections for OPN with a monoclonal OPN antibody and with mAbs for astrocyte (GFAP), microglia/macrophage (OX42)-specific markers. The major cell types of OPN-expressing cells were activated astrocytes and microglia in the adjacent inflammatory lesions. Interestingly, OPN was mainly expressed in the end feet of astrocytes around vascular cell adhesion molecule-1 (VCAM-1) expressing endothelial cells of CNS blood vessel. These findings suggest that increased levels of OPN in activated glial cell may play an important role in the recruitment of inflammatory cells into the CNS parenchyma during EAE.

• 전자공학회논문지
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• 제51권7호
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• pp.60-68
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• 2014

최근 전자전 지원 시스템 분야에서는 TDOA(time difference of arrival)와 FDOA(frequency difference of arrival) 정보를 활용한 고 정밀 위치 추정 방법에 대한 연구가 활발히 진행되고 있다. TDOA/FDOA 위치 추정 시스템은 TDOA와 FDOA 정보를 추출하는 단계와 추출한 정보로부터 신호원의 위치를 추정하는 두 단계로 나뉘며, 정보 추출 단계에서 보편적으로 사용하는 알고리즘으로 CAF(complex ambiguity function) 기반 방법이 알려져 있다. 하지만 기존의 CAF 기반 알고리즘은 VHF 대역의 통신 신호로부터 TDOA 및 FDOA 정보를 추출하는 경우, 많은 연산량으로 인해 제한된 시간에 처리하기 어려운 단점이 있다. 따라서 본 논문에서는 통신 신호 기반 TDOA/FDOA 정보 추출을 연산량 측면에서 효율적으로 수행하기 위해 개선된 CAF 기반 순차 추정 알고리즘을 제안하고, 기존 CAF기반 알고리즘과 연산량을 비교 분석한다. 또한 제안한 알고리즘의 추출 성능을 검증하기 위해 CRLB(Cramer-Lao lower bound)를 이용해 유도된 이론적 한계 성능과 비교 분석한다.

• 전자공학회논문지
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• 제52권4호
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• pp.37-45
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• 2015

TDOA (time difference of arrival)와 FDOA (frequency difference of arrival) 정보를 활용한 고 정밀 위치 추정 방법에 대한 연구는 최근 전자전 시스템 분야의 핵심 주제이다. TDOA/FDOA 위치 추정 시스템은 TDOA와 FDOA 정보를 추출하는 단계와 추출한 정보로부터 신호원의 위치를 추정하는 두 단계로 나뉘며, 정보 추출 단계에서 CAF (complex ambiguity function) 기반의 다양한 알고리즘이 제안되었다. 미상 신호원과 수신단간의 이격이 수백km인 전자전 지원 시스템 환경에서 기존의 CAF 기반 알고리즘을 사용하여 통신 신호로부터 TDOA 및 FDOA 정보를 추출하는 경우, 고 정밀 위치 추정을 위해서는 수신단에서 장시간의 수집시간이 요구된다. 이러한 수집시간의 증가는 신호처리를 위해 수신단으로부터 중앙처리장치로 데이터를 전송하는 데 소요되는 시간을 수용할 수 없을만큼 늘어나게 할뿐만 아니라, 데이터량의 증가로 인한 연산량의 증가까지 야기하게 된다. 따라서 본 논문에서는 전자전 환경에서 통신 신호 기반 TDOA/FDOA 정보의 정밀 추정에 요구되는 수집시간을 CRLB (Cramer-Lao lower bound)를 이용하여 이론적으로 분석하고, 고 정밀 추정을 위해 장 시간동안 수집된 대용량의 데이터를 이용하였을 때, 기존의 알고리즘과 정확도는 유사하면서 전송시간 및 연산량을 최소화하는 2-단계 전역 최적화 알고리즘을 제안한다. 또한 제안한 알고리즘을 기존 CAF 기반 알고리즘과 연산량을 비교 분석하고, CRLB를 통해 유도된 한계 성능과 비교 분석하여 알고리즘의 성능을 검증한다.