• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.9-14
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• 2022

Silica aerogel is a porous material with a very low density and high specific surface area. Still, its application is limited due to its weak mechanical properties due to structural features. To solve this problem, a method of complexing it with various polymers has been proposed. We synthesized polyimide cross-linked silica aerogel by the sol-gel process to obtain high mechanical properties. Tetraethyl orthosilicate (TEOS) was used as a precursor to make silica aerogel, and 3- aminopropyltriethoxysilane (APTES) was used as a coupling agent for cross-linking polyimide. Polyimide was synthesized using pyromellitic dianhydride and 3,5-diaminobenzoic acid, and mechanical properties were improved by crosslinking polyimide with 10 repeating units in the polyimide chain using the reaction formula ${\frac{n_1}{n_2}}={\frac{n}{n+1}}$ To realize silica aerogel, polyimide having various weight ratios was added before gelation, resulting in a 19-fold or greater increase in maximum compressive strength compared to pure silica aerogel. From this study, an enhancement of silica aerogel could be enhanced through polymer cross-linking bonds.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.15-20
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• 2022

Aerogel is a material having a nanopore structure based on a high porosity. Due to this high porosity, it has excellent properties not found in conventional materials, but its application has been limited due to low mechanical strength. Therefore, to improve the mechanical strength of the aerogel, polyurea crosslinking was introduced and a precursor having an amine group essential for polyurea polymer formation was selected to synthesize a polyurea crosslinked aerogel composite. In addition, the crosslinking of polyurea was adjusted according to the number of amine groups present in aminosilane. It was confirmed through various analyses that the nanopore structure of the aerogel was maintained to have mesopores. The aerogel thus formed was able to improve the mechanical strength by about two times, and it was confirmed through field emission scanning electron microscope analysis that a one-dimensional polymer was formed on the silica aerogel surface through the introduction of ethylene diamine. The one-dimensional polymer thus formed has improved mechanical properties, resulting in securing an elastic modulus of about 2.66 MPa.

• Korean Journal of Remote Sensing
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• v.39 no.5_2
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• pp.743-754
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• 2023

The global occurrence of myriad natural disasters and incidents, catalyzed by climate change and extreme meteorological conditions, has engendered substantial human and material losses. International organizations such as the International Charter have established an enduring collaborative framework for real-time coordination to provide high-resolution satellite imagery and geospatial information. These resources are instrumental in the management of large-scale disaster scenarios and the expeditious execution of recovery operations. At the national level, the operational deployment of advanced National Earth Observation Satellites, controlled by National Geographic Information Institute, has not only catalyzed the advancement of geospatial data but has also contributed to the provisioning of damage analysis data for significant domestic and international disaster events. This special edition of the National Disaster Management Research Institute delineates the contemporary landscape of major disaster incidents in the year 2023 and elucidates the strategic blueprint of the government's national disaster safety system reform. Additionally, it encapsulates the most recent research accomplishments in the domains of artificial satellite systems, information and communication technology, and spatial information utilization, which are paramount in the institution's disaster situation management and analysis efforts. Furthermore, the publication encompasses the most recent research findings relevant to data collection, processing, and analysis pertaining to disaster cause and damage extent. These findings are especially pertinent to the institute's on-site investigation initiatives and are informed by cutting-edge technologies, including drone-based mapping and LiDAR observation, as evidenced by a case study involving the 2023 landslide damage resulting from concentrated heavy rainfall.

• Phonetics and Speech Sciences
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• v.15 no.3
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• pp.27-35
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• 2023

This study aimed to investigate the effect of Chinese on the production of Korean rhythm. Korean and Chinese are typologically classified into different rhythmic categories; because of this, the phonological properties of Korean and Chinese are similar and different at the same time. As a result, Chinese can exert both positive and negative influences on the realization of Korean rhythm. To investigate the influence of the rhythm of the native language of L2 learners on their target language, we conducted an acoustic analysis using acoustic metrics like of the speech of 5 Korean native speakers and 10 advanced Chinese Korean learners. The analyzed material is a short paragraph of five sentences containing a variety of syllable structures. The results showed that KS and CS rhythms are similar in %V, VarcoV, and nPVI_S. However, CS, unlike KS, showed characteristics closer to those of a stress-timed language in the values of %V and VarcoV. There was also a significant difference in nPVI_V values. These results demonstrate a negative influence of the native language in the realization of Korean rhythm. This can be attributed to the fact that all vowels in Chinese sentence are not pronounced with the same emphasis due to neutral tone. In this sense, this study allowed us to observe influences of L1 on L2 production of rhythm.

• Journal of Advanced Navigation Technology
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• v.28 no.4
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• pp.559-565
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• 2024

Research on autonomous vehicles is being actively conducted. As autonomous vehicles emerge, there will be a transitional period in which traditional and autonomous vehicles coexist, potentially leading to a higher accident rate. Currently, when a traffic accident occurs, the fault ratio is determined according to the criteria set by the General Insurance Association of Korea. However, the time required to investigate the type of accident is substantial. Additionally, there is an increasing trend in fault ratio disputes, with requests for reconsideration even after the fault ratio has been determined. To reduce these temporal and material costs, we propose a deep learning model that automatically determines fault ratios. In this study, we aimed to determine fault ratios based on accident video through a image classification model based on ResNet-18 and video action recognition using TSN. If this model commercialized, could significantly reduce the time required to measure fault ratios. Moreover, it provides an objective metric for fault ratios that can be offered to the parties involved, potentially alleviating fault ratio disputes.

• Nuclear Medicine and Molecular Imaging
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• v.42 no.1
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• pp.29-38
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• 2008

Purpose: The aim of this study was to investigate the feasibility of 3 ' -[F-18]fluoro-3 ' -deoxythymidine positron emission tomography(FLT-PET) for the detection of locally advanced breast cancer and to compare the degree of FLT and 2' -deoxy-2 ' -[F-18]fluoro-d-glucose(FDG) uptake in primary tumor, lymph nodes and other normal organs. Material & Methods: The study subjects consisted of 22 female patients (mean age; $42{\pm}6$ years) with biopsy-confirmed infiltrating ductal carcinoma between Aug 2005 and Nov 2006. We performed conventional imaging workup, FDG-PET and FLT PET/CT. Average tumor size measured by MRI was $7.2{\pm}3.4$ cm. With visual analysis, Tumor and Lymph node uptakes of FLT and FDG were determined by calculation of standardized uptake value (SUV) and tumor to background (TB) ratio. We compared FLT tumor uptake with FDG tumor uptake. We also investigated the correlation between FLT tumor uptake and FDG tumor uptake and the concordant rate with lymph node uptakes of FLT and FDG. FLT and FDG uptakes of bone marrow and liver were measured to compare the biodistribution of each other. Results: All tumor lesions were visually detected in both FLT-PET and FDG-PET. There was no significant correlation between maximal tumor size by MRI and SUVmax of FLT-PET or FDG-PET (p>0.05). SUVmax and $$SUV_{75} (average SUV within volume of interest using 75% isocontour) of FLT-PET were significantly lower than those of FDG-PET in primary tumor (SUVmax; $6.3{\pm}5.2\;vs\;8.3{\pm}4.9$, p=0.02 /$SUV_{75};\;5.3{\pm}4.3\;vs\;6.9{\pm}4.2$, p=0.02). There is significant moderate correlation between uptake of FLT and FDG in primary tumor (SUVmax; rho=0.450, p=0.04 / SUV75; rho=0.472, p=0.03). But, TB ratio of FLT-PET was higher than that of FDG-PET($11.7{\pm}7.7\;vs\;6.3{\pm}3.8$, p=0.001). The concordant rate between FLT and FDG uptake of lymph node was reasonably good (33/34). The FLT SUVs of liver and bone marrow were $4.2{\pm}1.2\;and\;8.3{\pm}4.9$. The FDG SUVs of liver and bone marrow were $1.8{\pm}0.4\;and\;1.6{\pm}0.4$. Conclusion: The uptakes of FLT were lower than those of FDG, but all patients of this study revealed good FLT uptakes of tumor and lymph node. Because FLT-PET revealed high TB ratio and concordant rate with lymph node uptakes of FDG-PET, FLT-PET could be a useful diagnostic tool in locally advanced breast cancer. But, physiological uptake and individual variation of FLT in bone marrow and liver will limit the diagnosis of bone and liver metastases.

• Journal of Chest Surgery
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• v.31 no.12
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• pp.1147-1158
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• 1998

Background: Portable cardiopulmonary bypass(CPB) technique has been used increasingly as a potent and effective option for emergency cardiopulmonary resuscitation(CPR) because it can maintain more stable hemodynamics and provide better survival than conventional CPR techniques. This study was designed to develop a prototype of Korean portable CPB system and, by applying it to CPR, to discriminate whether it would be superior to standard open-chest CPR. Material and Method: By using adult mongrel dogs, open-chest CPR(OCPR group, n=4) and portable-CPB CPR(CPB group, n=4) were compared with respects to restoration of spontaneous circulation(ROSC), hemodynamics, effects on blood cells, blood gas patterns, biochemical markers, and survivals. Ventricular fibrillation-cardiac arrest(VF-CA) of arrest(VF-CA) of 4 minutes followed by basic life support(BLS) of 15 minutes was applied in either group, which was standardized by the protocol of American Heart Association. Then, advanced life support(ALS) was applied to either group under the support of internal cardiac massage or CPB. ALS was maintained until ROSC was achieved but not longer than 30 minutes regardless of the presence of ROSC. All of the measured values were expressed as means±SD percent change from baseline. Result: During the early ALS, higher mean arterial pressure was maintained in CPB group than in OCPR group(90±19 vs. 71±32 %; p<.05) and lower mean pulmonary arterial pressure was also maintained in CPB group than in OCPR group(105±24 vs. 146±6%; p<.05). ROSC was achieved in all dogs. Post-ROSC levels of hematocrit, RBC, and platelet were decreased and plasma free hemoglobin was increased significantly in CPB group compared to OCPR group(p<.05). Changes in blood gas patterns, lactate, and CK-MB levels were not different between groups. Early mortality was seen in 3 dogs in OCPR group(survival time 31±36 hours) and 2 in CPB group(228±153 hours, p=ns). The remainders in both groups showed prolonged survival. Conclusion: These findings indicate that portable CPB can be effective to maintain stable hemodynamics during cardiac arrest, to achieve ROSC and to prolong survival. Further study is needed to refine the portable CPB system and to meet clinical challenges.

• Journal of Chest Surgery
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• v.43 no.4
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• pp.375-380
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• 2010

Background: Primary cardiac tumors are extremely rare. The most common type are benign myxomas, and these are almost completely curable with early surgery. Malignant tumors, however, such as sarcomas, are difficult to remove surgically, and their prognosis is known to be poor. In this study, data on patients who had undergone surgical treatment of cardiac tumor in the authors' hospital were collected and analyzed. Material and Method: The subjects included 28 patients who had undergone surgical treatment of cardiac tumor from August 1993 to December 2008. Their medical records were reviewed and retrospectively analyzed. Result: The patients were aged from 20 to 76 years (mean age: $54.2{\pm}15.6$), and 11 were male (39%) and 17 female (61%). Fifteen of them (54%) underwent emergency surgery to improve heart failure symptoms. The most common preoperative symptom was dyspnea (15 cases, 54%). Preoperative echocardiography was performed on all the patients. The average size of the tumor as measured during the operation was $7.0{\pm}6.9cm$ (the average length of the long axis was 2∼40 cm), and the sites of tumor attachment were the interatrial septum (18 cases, 64%), the left atrium (9 cases, 32%), the mitral valve annulus (2 cases, 7%), and the left ventricle (2 cases, 7%). The operation was performed with an incision through both atria in all the patients, and a complete excision was made in 25 cases (89%). According to the biopsy results, there were 4 cases of sarcoma (14%), 1 case of lipoma (4%), and 23 cases of myxoma (82%). The three cases in which the tumors were not completely excised were sarcomas. No operative deaths occurred after the operations. Outpatient follow-up was possible for 24 cases (86%), with a mean follow-up period of $46.8{\pm}42.7$ months. Late death occurred in 3 of the 24 patients; each of these patients had sarcomas. Of these patients, the first had undergone two repeat surgeries, the second had metastatic sites removed, and the last had only chemotherapy. The average recurrence time was $12.7{\pm}10.8$ months, and the average metastasis time was $20.5{\pm}16.8$ months. Conclusion: Most cardiac tumors are benign myxomas. In principle, they should be surgically treated because they can create risks such as embolism, and can be radically treated when surgically removed. In most cases, however, malignant sarcomas are already considerably advanced with severe infiltration into the neighboring tissues at the time of diagnosis. The surgical removal of malignant sarcomas is known to be difficult because of the advanced stage and degree of infiltration. We suggest that excision of the removable portion of the tumor sites to alleviate symptoms such as heart failure can improve quality of life.

• Journal of Chest Surgery
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• v.35 no.11
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• pp.799-806
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• 2002

In spite of the establishment of chemotherapy and the gradual decrease in prevalence, pulmonary tuberculosis is still mainly treated with an operation. Through analyzing and examining some cases of surgical treatment, we hope to provide some help in treating of pulmonary tuberculosis in the future. Material and Method: By comparing four journals previously published in our department with 144 cases of lung surgery during ten years from January of 1991 to December of 2000 performed by the department of thoracic and cardiovascular surgery of the National Medical Center, we analyzed and reviewed the most recent trends and the results of the surgical treatment. Annual frequency of the operation, distribution of age, examination of sputum, adaptability and types of techniques, complications, and results of the postoperative follow-up were used as methods. Result: It was found that the annual frequency of operations had decreased. The ratio of men to women, 2:1 indicates that there are more incidences in men. Aging of patients could be speculated by the .results that the decrease in the incidence rate in the 20s age range and increase rate in the 50s age range. The range of preoperative lesions belonged mostly to far advanced and moderately advanced tuberculosis. By monitoring the period of use in preoperative antituberculosis drugs, cases for more than 3 years remarkably increased from 16.0 % to 55.6 %. The positive reactive rate for preoperative sputum examinations were drastically decreased from 91 % to 27 %. Total pulmonary destruction and partial destruction were the most common cases in terms of adaptability to the operations and there were significant increases in forming empyema accompanied by parenchymal lesions from 4.0 % to 20.1 %. Pneumonectomy and pulmonary lobectomy were the major type of operations. Especially, there were increases in the incident rate of empyema and recurrence of tuberculosis resulted. Post operative follow-up indicates that the rate of complete recovery was more than 70 % and the rate of gradual increase in treating with persistent antituberculosis drug was from 5.8 % to 18.0 %. Conclusion: In recent cases, there is an increasing number of patients showing tolerance to chemotherapy. Patients with pleural tuberculosis and severe lesions were typically increased. It is important to accurately analyze those complaints accurately that are mostly difficult to be treated medically. Surgical treatment is strongly recommended Before multiple drug resistance occurs.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.479-489
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• 2008

Statement of the problem: Under anatomical limitations on maxillary posterior region, a poor crown-to root ratio acting on dental implants can result in undesirable stress in surrounding bone, which in turn can cause bone defects and eventual failure of implants. Purpose: The purpose is to compare stress distribution due to different crown-root ratio and effect of splinting between natural teeth and implants in maxillary molar area under different loads. Material and methods: Analysis of stress arising supporting bone of the natural teeth and the implant was made with 3-dimensional finite element method. The model simulated naturel teeth was made with 2nd premolar and 1st molar in the maxillary molar region (Model T). The model simulated implants placed on same positions with two parallel implants of Straumann Dental Implant cemented abutment (Model I). Each model was designed in different crown-root ratio (0.7:1, 1:1, 1.25:1) and set cement type gold crown to make it non-splinted or splinted. After that, 300 N force was loaded to each model in five ways (Load 1: middle of occlusal table, Load 2: middle of buccal cusp, Load 3: middle of lingual cusp, Load 4: horizontal load to buccal cusp of anterior abutment only, Load 5: horizontal load to middle of buccal cusp of each abutment), and stress distribution was analyzed. Results and conclusion: On all occasions, stress was concentrated at the cervical region of the implant. Under load 1, 2 and 3, stress was not increased even when crown-root ratio increases, but under load 4 and 5, when crown-root ratio increases, stress also increased. There was difference in stress values between natural teeth and implants when crown-root ratio gradually increases; In case of natural teeth, splinting decreased stress under vertical and horizontal loads. In case of implants, splinting decreased stress under vertical loads 1,2 and 3, but increased maximal stress under loads 2 and 3. Under horizontal loads, splinting decreased stress, however the effect of splinting decreased under load 5 than load 4. Furthermore, the stress was increased, when crown-root ratio is 1.25:1. Clinical implications: This limited finite element study suggests that the stress on supporting bone may be increased under non-axial loads and poor crown-root ratio. Under poor crown-root ratio, excessive stress was generated at the cervical region of the implant, and decreased splinting effect for stress distribution, which can be related to clinical failure.