[en] Since the biggest time-dependent prestress loss of a prestressed concrete nuclear reactor containment structure is due to the creep of concrete, creep is one of the most important structural factors to be considered for the safety of a reactor containment structure during design, construction and maintenance. Creep in concrete has also recently been considered in evaluation of the crack resistance of concrete at an early-age in the durability examination of massive concrete structures like reactor containment structures. Existing empirical formulas on creep prediction show errors in their predictions due to simplified consideration of mixture proportions, and they also show large discrepancy among their predictions. In addition, they do not consider early-age behaviors of concrete and thus are mainly for the prediction of long-term creep at hardened concrete. In this paper, the creep characteristics of the reactor's both early-age and hardened reactor concrete made of type V cement are examined by carrying out both early-age and long-term creep tests. Then, the creep of the reactor concrete is predicted by using major creep-prediction equations of the AASHTO LRFD design specification, the Japanese standard specification for concrete structure, the ACI Committee 209 and the CEB/FIP model code and the Bazant and Panula's model, and the predicted results are compared with the test results. From the comparison, the applicability of the creep-prediction equations for the concrete of a reactor containment structure at both early-age and hardened stages is discussed

[en] The aspherical glass lens is required high dimensional precision such as the lack of defect. In this paper, we examined the detectable defect by using the resonant ultrasound spectroscopy (RUS). The RUS is the measurement system which is to excite the specimen and to inspect the differences of resonant frequency pattern between acceptable specimen and specimen which has some defects. In this paper, for nondestructive evaluation by using RUS, we measured the resonant frequency of a aspherical glass lens. With the results, we could evaluate the characteristic of aspherical glass lens about some flaws.

[en] The hydraulic pump of an Electro-hydrostatic Actuator should be able to quickly feed large volume of oil into hydraulic cylinder in order to reduce the response time. On the other hand, it should be also able to precisely dispense small amount of oil through low-speed operation so that the steady state position control error of the actuator can be accurately compensated. Within the scope of axial piston type hydraulic pumps, this paper is focused on the investigation how the surface treatment of their cylinder barrel with TiN plasma coating can contribute to the reduction of the friction and wear rate of valve plate in the low-speed range with mixed lubrication. The results showed that the friction torque of the valve plate mated with a TiN-coated cylinder barrel could be reduced to 22% of that with an uncoated original one when load pressure was 300 bar and rotational speed 100 rpm. It means that the torque efficiency of the test pump was expected to increase more than 1.3% under the same working condition. At the same time, the wear rate of the valve plate could be reduced to 40∼50%

[en] Our study of caldwell and water's views, most common radiological technique to delineate PNS, has verified that the ideal photographic image to diagnose PNS is, with Caldwell view, only the one whose petrous ridge coincides with the lower edge of the eye socket, and with Water's view, only the one whose petrous ridge coincides with the lower edge of maxillary sinus. With the method used hitherto, it was difficult to obtain such a ideal image diagnostically. It was made possible by changing the revolving angle formed by the central ray and the head

[en] This study was designed to evaluate the ultrasonographic (US) findings of medullary thyroid carcinoma (MTC) as compared to findings for papillary thyroid carcinoma (PTC). The study included 21 cases of MTC that were surgically diagnosed between 2002 and 2007 and 114 cases of PTC that were diagnosed in 2007. Two radiologists reached a consensus in the evaluation of the US findings. The US findings were classified as recommended by the Thyroid Study Group of the Korean Society of Neuroradiology and Head and Neck Radiology (KSNHNR) and each nodule was identified as suspicious malignant, indeterminate or probably benign. The findings of medullary and papillary carcinomas were compared with use of the chi-squared test. The common US findings for MTCs were solid internal content (91%), an ovoid to round shape (57%), marked hypoechogenicity (52%) and calcifications (52%). Among the 21 cases of MTC nodules, 17 (81%) were classified as suspicious malignant nodules. The mean size (longest diameter) of MTC nodules was 19 ±13.9 mm and the mean size (longest diameter) of PTC nodules was 11 ± 7.4 mm; this difference was statistically significant (p < 0.05). An ovoid to round shape was more prevalent for MTC lesions than for PTC lesions (p < 0.05). The US criteria for suspicious malignant nodules as recommended by the Thyroid Study Group of the KSNHNR correspond to most MTC cases. The US findings for MTC are not greatly different from PTC except for the prevalence of an ovoid to round shape

[en] To evaluate the interobserver variability and performance in the interpretation of ultrasonographic (US) findings of thyroid nodules. 72 malignant nodules and 61 benign nodules were enrolled as part of this study. Five faculty radiologists and four residents independently performed a retrospective analysis of the US images. The observers received one training session after the first interpretation and then performed a secondary interpretation. Agreement was analyzed by Cohen's kappa statistic. Degree of performance was analyzed using receiver operating characteristic (ROC) curves. Agreement between the faculties was fair-to-good for all criteria; however, between residents, agreement was poor-to-fair. The area under the ROC curves was 0.72, 0.62, and 0.60 for the faculties, senior residents, and junior residents, respectively. There was a significant difference in performance between the faculties and the residents (p < 0.05). There was a significant increase in the agreement for some criteria in the faculties and the senior residents after the training session, but no significant increase in the junior residents. Independent reporting of thyroid US performed by residents is undesirable. A continuous and specialized resident training is essential to enhance the degree of agreement and performance

[en] This study examined the yield of mammographically detected calcifications following a stereotactic vacuum-assisted biopsy (SVAB) using an upright add-on type stereotactic device. Ninety-two women underwent a SVAB between April 2002 and December 2005, and 90 calcifications obtained by the SVAB were evaluated retrospectively. The calcification retrieval rate was examined. The false negative and underestimation rates were determined by comparing the biopsy results with the results from surgery and follow-up mammography. The calcification retrieval rate was 97.8% (90/92). The histopathology of the 90 lesions was benign for 66 (73.3%), borderline for 3 (3.3%) and malignant for 21 (23.3%). A total of 22 malignancies were confirmed surgically. SVAB had a false negative rate of 4.5% (1/22). The underestimation rate of a surgically excised atypical ductal hyperplasia (ADH) and of ductal carcinoma in situ (DCIS) was 50% (1/2) and 10% (2/20), respectively. The use of SVAB with an upright add-on type stereotactic device is an efficient biopsy method for mammographically detected microcalcifications, with low false negative and high calcification retrieval rates

[en] Mammography screening has been shown to reduce breast cancer mortality and remains the primary screening method. However, the harms of false-positive results and over-diagnosis have recently been emphasized, and screening guidelines have been revised. Breast ultrasonography screening has the advantage of detecting mammographically occult breast cancers in dense breasts; however, false-positive results and rising medical costs due to increased biopsy recommendations create a problem. Till date, recommendations for breast ultrasonography screenings have not been established. Magnetic resonance imaging is recommended for women at high risk and has excellent sensitivity, but it is expensive and inferior in accessibility. This article reviews the benefits, harms, and guidelines of methods commonly used in breast cancer screening. This review also provides breast cancer screening methods according to individual breast cancer risk

[en] Three-dimensional automated breast ultrasonography (ABUS) has been approved for screening Epub ahead of print studies as an adjunct to mammography. ABUS provides proper orientation and documentation, resulting in better reproducibility. Optimal image quality is essential for a proper diagnosis, and high-quality images should be ensured when ABUS is used in clinical settings. Image quality in ABUS is highly dependent on the acquisition procedure. Artifacts can interfere with the visibility of abnormalities, reduce the overall image quality, and introduce clinical and technical problems. Nipple shadow and reverberation artifacts are some of the artifacts frequently encountered in ABUS. Radiologists should be familiar with proper image acquisition techniques and possible artifacts in order to acquire high-quality images

[en] Myoid (muscular) hamartoma is a rare subtype of hamartoma and is characterized by the presence of smooth muscle cells. We report a case of myoid hamartoma presenting as a large palpable mass in a 28-year-old patient, which was confirmed by surgical excision and pathologic diagnosis