• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.44 no.1
• /
• pp.33-39
• /
• 2024

This study explores the utilization of common marine wastes, specifically seashells, such as oysters and cockles, as alternative fine aggregates in construction materials. The considered seashells were cleaned and pre-processed for use as a substitute for aggregate in mortar. Cement mortar specimens were prepared under different conditions, such as substitution ratios and the cleaning status of the seashells. The compressive strength of the mortars specimens was evaluated, and the solid and porous structures of each specimen were analyzed using microstructure analysis methods such as XRD, SEM, and micro-CT. The results confirmed that oyster and cockle seashells are composed of different calcium carbonate polymorphs, and their microstructural characteristics influence the mechanical properties of the cement mortar specimens.

• Nuclear Engineering and Technology
• /
• v.56 no.5
• /
• pp.1887-1894
• /
• 2024

Fatigue strength of the structural materials of lead-cooled fast reactors (LFRs) and accelerator-driven systems (ADS) may be degraded in liquid metal (Lead or lead-bismuth eutectic (LBE)) environments. The fatigue crack growth (FCG) data of structural materials in liquid LBE are necessary for damage tolerance design, safety assessment and life management of key equipment. A novel monitoring system for fatigue crack length was designed on the compliance method and the monitor technology of crack opening displacement (COD) of CT specimens by the linear variable differential transformers (LVDT) system. It can be used to predict the crack length by monitoring the COD of CT specimens in harsh high-temperature liquid LBE using a LVDT system. The prediction accuracy of this system was verified by FCG experiments in room temperature air and liquid LBE at 150, 250 and 350 ℃. The first results obtained in the FCG test for T91 steel in liquid LBE at 350 ℃ are presented.

• Journal of Welding and Joining
• /
• v.28 no.5
• /
• pp.45-50
• /
• 2010

The fatigue crack growth characteristics of base metal and weld joint of 9% Ni steel for LNG storage tank was carried out using CT specimen at room temperature and $-162^{\circ}C$. Fatigue crack growth rate of base and weld metals at RT and $-162^{\circ}C$ was coincided with a single line independent of the change of stress ratio and temperature. In the region of lower stress intensity factor range, fatigue crack growth rate at $-162^{\circ}C$ was slower than that at RT, and the slop of fatigue crack growth rate at $-162^{\circ}C$ increased sharply with propagating of fatigue crack, fatigue crack growth rate at RT and $-162^{\circ}C$ was intersected near the region of $2{\times}10-4\;mm$/cycle, and after the intersection region, fatigue crack growth rate at $-162^{\circ}C$ was faster than that at RT. The micro-fracture mechanism using SEM shows the ductile striation in the stable crack growth region. Also the defects of weld specimen after fatigue testing were detected using the A scan of ultrasonic apparatus.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2002.10a
• /
• pp.335-340
• /
• 2002

In recent years, the study of metal matrix composite has increased specially, aluminum alloy, research and development are briskly progress to find new metal matrix composite. this study is following the this purpose; This study is used metal matrix composite that was produced by matrix, AC4CH. and reinforcement $A_{18}B_4O_{33}$ metal matrix composite to add $Al_2O_3,\;TiO_2$ for strengthen of binding together among the Whisker. Each Metal matrix composite is produced using the squeeze casting method. Fracture tounghness test was in accordance with the provisions of ASTM E399; Specimen was produced half-size CT specimen W=25mm, B=12.5mm, Cross head speed 0.05mm/min in room temperature. The plane strain fracture toughness $K_{IC}$ is $8.7MPa-m^{0.5}$ for $Al_{18}B_4O_{33}$/AC4CH., $9.28MPa-m^{0.5}$ for $Al_{18}B_4O_{33}$/AC4CH added $TiO_2$. and $Al_2O_3$ but AC4CH alloy was violated the critical stipulated by ASTM standard for a valid measurement of $K_{IC}$. In case of, it was performed $I_{IC}$ test instead of $K_{IC}$ based on ASTM E 1820

• Journal of Biomedical Engineering Research
• /
• v.25 no.6
• /
• pp.519-523
• /
• 2004

This study investigates micro-structural and mechanical properties of trabecular bone in human femoral head with and without osteoporosis using Micro-CT and finite element-model. 15 cored trabecular bone specimens with 20min of diameter were obtained from femoral heads with osteoporosis (T-score > -2.5 ) resected for total hip arthroplasty, and 5 specimens were removed from femoral head of cadavers, which has no history of musculoskeletal diseases. A high-resolution micro-CT system was used to scan each specimen to obtain histomorphometry indices. Based on obtained micro-images(pixel size=21.31㎛), a FE-model was created to determine mechanical property indices. While non-osteoporosis group had increases trabecular thickness, bone volume, bone volume fraction, degree of anisotropy and trabecular number compared with those of non-osteoporotic group, the non-osteoporotic group showed decreases in trabecular separation and structure model index. Regarding the mechanical property indices, reaction force, apparent stress and young's modulus were 1ower in osteoporotic group than in non-osteoporotic group. Our data shows salient deteriorations in trabecular micro-structural and mechanical properties in human femoral head with osteoporosis.

• Journal of Chest Surgery
• /
• v.42 no.5
• /
• pp.624-629
• /
• 2009

Background: Making the histologic diagnosis of small pulmonary nodules and ground glass opacity (GGO) lesions is difficult. CT-guided percutaneous needle biopsies often fail to provide enough specimen for making the diagnosis. Video-assisted thoracoscopic surgery (VATS) can be inefficient for treating non-palpable lesions. Preoperative localization of small intrapulmonary lesions provides a more obvious target to facilitate performing intraoperative. resection. We evaluated the efficacy of CT-guided localization with using a hook wire and this was followed by VATS for making the histologic diagnosis of small intrapulmonary nodules and GGO lesions. Material and Method: Eighteen patients (13 males) were included in this study from August 2005 to March 2008. 18 intrapulmonary lesions underwent preoperative localization by using a CT-guided a hook wire system prior to performing VATS resection for intrapulmonary lesions and GGO lesions. The clinical data such as the accuracy of localization, the rate of conversion-to-thoracotomy, the operation time, the postoperative complications and the histology of the pulmonary lesion were retrospectively collected. Result: Eighteen VATS resections were performed in 18 patients. Preoperative CT-guided localization with a hook-wire was successful in all the patients. Dislodgement of a hook wire was observed in one case. There was no conversion to thoracotomy, The median diameter of lesions was 8 mm (range: $3{\sim}15\;mm$). The median depth of the lesions from the pleural surfaces was 5.5 mm (range: $1{\sim}30\;mm$). The median interval between preoperative CT-guided with a hook-wire and VATS was 34.5 min (range: ($10{\sim}226$ min). The median operative time was 43.5.min (range: $26{\sim}83$ min). In two patients, clinically insignificant pneumothorax developed after CT-guided localization with a hook-wire and there were no other complications. Histological examinations confirmed 8 primary lung cancers, 3 cases of metastases, 3 cases of inflammation, 2 intrapulmonary lymph nodes and 2 other benign lesions. Conclusion: CT-guided localization with a hook-wire followed by VATS for treating small intrapulmonary nodules and GGO lesions provided a low conversion thoracotomy rate, a short operation time and few localization-related or postoperative complications. This procedure was efficient to confirm intrapulmonary lesions and GGO lesions.

• Childhood Kidney Diseases
• /
• v.1 no.2
• /
• pp.189-194
• /
• 1997

Oligomeganephronia is a rare congenital form of bilateral renal hypoplasia histologically characterized by reduction in number and hypertrophy of nephrons. Clinically, this condition is presented in early infancy with vomiting, polyuria, polydipsia and dehydration. The problems are readily corrected, but slowly progressive renal failure follows accompanied by failure to thrive, short stature, and renal osteodystrophy. We experienced three cases of oligomeganephronia. Case 1. : A 3 2/12 years old female child was incidentally diagnosed as renal failure at age of 2 months when she was hospitalized due to pneumonia. She had open renal biopsy and was diagnosed as bilateral dysplastic kidney. On OPD follow-up, she progressed to end-stage renal failure (BUN/Cr 114/4.6 mg/dl) and had renal transplantation. The specimen was shrunk remarkably and light microscopy showed oligomeganephronia. Case 2. : A 14 8/12 years old female child with proteinuria was detected in an annual urine screening program for school children, she was diagnosed as renal failure (BUN/Cr 33.9/4.1 mg/dl), and had $5{\times}4{\times}3\;cm$ sized mass on abdominal CT scan. She had renal biopsy, and the specimen showed oligomeganephronia. She had hemodialysis for six months, and renal transplantation along with bilateral nephrectomy was performed. Case 3. : A 14 8/12 years old male child was diagnosed having chronic nephritis and chronic renal failure at 3 years old, progressed to end-stage renal failure (BUN/Cr 87/9.6 mg/dl) on OPD follow-up, and had a rephrectomy and renal transplantation. The biopsy specimen showed oligomeganephronic hypoplasia, secondary focal segmental glomerolosclerosis, and chronic interstitial nephritis. We report 3 cases of oligomeganephronia that progressed to end-stage renal failure and had successful renal transplantation with a brief review of related literatures.

• The Journal of the Acoustical Society of Korea
• /
• v.23 no.4
• /
• pp.268-273
• /
• 2004

A method of reflection-transmission type ultrasonic inverse scattering image was presented using linearly arrayed transducers in inner surface of half-cylinder. In this method, to reduce the number of data, the mirror effect using a reflector behind object and pulse wave with finite frequency band, To verify the proposed method, a computer simulation was performed for organic phantom specimen, As the results. it was verified that the reconstructed image was satisfactory even when the limitation view angle was limited to around 30 deg.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.1
• /
• pp.124-132
• /
• 1997

This paper describes an experimental and numerical study on growing ductile crack-tip behaviors. The hybrid experimental and numerical method by means of a computer image processign technique, was applied to the analysis of both base metal and weld metal CT specimens. In the weld metal specimen, the initial crack-tip was placed in front of fusion line, and the crack orientation was perpendicular to it. Finite element analysis of crack growth behaviors in both base and weld matal specimens made of A533B Class 1 steel were also performed to examine the effects of weldment on near crack-tip fields. a series of experimental studies on crack-tip behaviors have clearly shown the qualitative effects of material properties, especially a hardening exponent. The experimental and numerical results have also shown that weldment does not affect displacement and strain fields near a crack-tip while a stress field is influenced by the difference between yield stresses of both base and weld metals.

• Journal of Chest Surgery
• /
• v.35 no.4
• /
• pp.315-317
• /
• 2002

Pulmonary actinomycosis is a rare disease entity to undergo thoracic surgery. We experienced a 49-year-old man with pulmonary actinomycosis who was admitted due to recurrent hemoptysis. Prior to admission, he was diagnosed as pulmonary tuberculosis on the basis of his clinical manifestations and chest radiological findings. The plain chest x-ray and chest computed tomography(CT) showed a cavitary lesion in left upper lobe and was given anti-tuberculous medication, but the x-ray revealed no imprcovement. He underwent left upper lobe lobectomy with segmentectomy of lower lobe and the surgical specimen showed no evidence of mycobacterial infection, but revealed sulfur granules which is a typical pathological finding of actinomycosis. He was discharged uneventfully and is scheduled to receive 6 months of antibiotic treatment.