• Asian Pacific Journal of Cancer Prevention
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• v.15 no.11
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• pp.4629-4635
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• 2014

Background: Diffusion-weighted imaging (DWI) makes it possible to detect malignant tumors based on the diffusion of water molecules. However, it is uncertain whether DWI has advantages over FDG-PET for distinguishing malignant from benign pulmonary nodules and masses. Materials and Methods: One hundred-forty-three lung cancers, 17 metastatic lung tumors, and 29 benign pulmonary nodules and masses were assessed in this study. DWI and FDG-PET were performed. Results: The apparent diffusion coefficient (ADC) value ($1.27{\pm}0.35{\times}10^{-3}mm^2/sec$) of malignant pulmonary nodules and masses was significantly lower than that ($1.66{\pm}0.58{\times}10^{-3}mm^2/sec$) of benign pulmonary nodules and masses. The maximum standardized uptake value (SUVmax: $7.47{\pm}6.10$) of malignant pulmonary nodules and masses were also significantly higher than that ($3.89{\pm}4.04$) of benign nodules and masses. By using optimal cutoff values for ADC ($1.44{\times}10^{-3}mm^2/sec$) and for SUVmax (3.43), which were determined with receiver operating characteristics curves (ROC curves), the sensitivity (80.0%) of DWI was significantly higher than that (70.0%) of FDG-PET. The specificity (65.5%) of DWI was equal to that (65.5%) of FDG-PET. The accuracy (77.8%) of DWI was not significantly higher than that (69.3%) of FDG-PET for pulmonary nodules and masses. As the percentage of bronchioloalveolar carcinoma (BAC) component in adenocarcinoma increased, the sensitivity of FDG-PET decreased. DWI could not help in the diagnosis of mucinous adenocarcinomas as malignant, and FDG-PET could help in the correct diagnosis of 5 out of 6 mucinous adenocarcinomas as malignant. Conclusions: DWI has higher potential than PET in assessing pulmonary nodules and masses. Both diagnostic approaches have their specific strengths and weaknesses which are determined by the underlying pathology of pulmonary nodules and masses.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.15
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• pp.6469-6475
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• 2015

Background: Diffusion-weighted magnetic resonance imaging (DWI) makes it possible to detect malignant tumors based on the diffusion of water molecules. It is uncertain whether DWI is more useful than positron emission tomography-computed tomography (PET-CT) for distinguishing benign from malignant mediastinal tumors and mass lesions. Materials and Methods: Sixteen malignant mediastinal tumors (thymomas 7, thymic cancers 3, malignant lymphomas 3, malignant germ cell tumors 2, and thymic carcinoid 1) and 12 benign mediastinal tumors or mass lesions were assessed in this study. DWI and PET-CT were performed before biopsy or surgery. Results: The apparent diffusion coefficient (ADC) value ($1.51{\pm}0.46{\times}10^{-3}mm^2/sec$) of malignant mediastinal tumors was significantly lower than that ($2.96{\pm}0.86{\times}10^{-3}mm^2/sec$) of benign mediastinal tumors and mass lesions (P<0.0001). Maximum standardized uptake value (SUVmax) ($11.30{\pm}11.22$) of malignant mediastinal tumors was significantly higher than that ($2.53{\pm}3.92$) of benign mediastinal tumors and mass lesions (P=0.0159). Using the optimal cutoff value (OCV) $2.21{\times}10^{-3}mm^2/sec$ for ADC and 2.93 for SUVmax, the sensitivity (100%) by DWI was not significantly higher than that (93.8%) by PET-CT for malignant mediastinal tumors. The specificity (83.3%) by DWI was not significantly higher than that (66.7%) for benign mediastinal tumors and mass lesions. The accuracy (92.9%) by DWI was not significantly higher than that (82.1%) by PET-CT for mediastinal tumors and mass lesions. Conclusions: There was no significant difference between diagnostic capability of DWI and that of PET-CT for distinguishing mediastinal tumors and mass lesions. DWI is useful in distinguishing benign from malignant mediastinal tumors and mass lesions.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.15
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• pp.6155-6160
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• 2014

Background: This study was conducted to investigate whether apparent diffusion coefficient (ADC) measurements by dividing the liver into left and right hepatic lobes may be utilized to improve the accuracy of differential diagnosis of benign and malignant focal liver lesions. Materials and Methods: A total of 269 consecutive patients with 429 focal liver lesions were examined by 3-T magnetic resonance imaging that included diffusion-weighted imaging. For 58 patients with focal liver lesions of the same etiology in left and right hepatic lobes, ADCs of normal liver parenchyma and focal liver lesions were calculated and compared using the paired t-test. For all 269 patients, ADC cutoffs for focal liver lesions and diagnostic accuracy in the left hepatic lobe, right hepatic lobe and whole liver were evaluated by receiver operating characteristic curve analysis. Results: For the group of 58 patients, mean ADCs of normal liver parenchyma and focal liver lesions in the left hepatic lobe were significantly higher than those in the right hepatic lobe. For differentiating malignant lesions from benign lesions in all patients, the sensitivity and specificity were 92.6% and 92.0% in the left hepatic lobe, 94.4% and 94.4% in the right hepatic lobe, and 90.4% and 94.7% in the whole liver, respectively. The area under the curve of the right hepatic lobe, but not the left hepatic lobe, was higher than that of the whole liver. Conclusions: ADCs of normal liver parenchyma and focal liver lesions in the left hepatic lobe were significantly higher than those in the right hepatic lobe. Optimal ADC cutoff for focal liver lesions in the right hepatic lobe, but not in the left hepatic lobe, had higher diagnostic accuracy compared with that in the whole liver.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.8
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• pp.3407-3412
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• 2015

Background: The aim of this study was to evaluate and compare the accuracy of diffusion-weighted imaging (DWI), apparent diffusion coefficient (ADC) value, and time-intensity curve (TIC) type analysis derived from dynamic contrast-enhanced MR imaging (DCE-MRI) in differentiating benign from malignant adnexal masses. Materials and Methods: 47 patients with 56 adnexal masses (27 malignant and 29 benign) underwent DWI and DCE-MRI examinations, prior to surgery. DWI signal intensity, mean ADC value, and TIC type were determined for all the masses. Results: High signal intensity on DWI and type 3 TIC were helpful in differentiating benign from malignant adnexal masses (p<0.001). The mean ADC value was significantly lower in malignant adnexal masses (p<0.001). An ADC value< $1.20{\times}10^{-3}mm^2/s$ may be the optimal cutoff for differentiating between benign and malignant tumors. The negative predictive value for low signal intensity on DWI, and type 1 TIC were 100%. The pairwise comparison among the receiver operating characteristic (ROC) curves showed that the area under the curve (AUC) of TIC was significantly larger than the AUCs of DWI and ADC (p<0.001 for comparison of TIC and DWI, p<0.02 for comparison of TIC and ADC value). Conclusions: DWI, ADC value and TIC type derived from DCE-MRI are all sensitive and relatively specific methods for differentiating benign from malignant adnexal masses. By comparing these functional MR techniques, TIC was found to be more accurate than DWI and ADC.

• 한국연소학회:학술대회논문집
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• 2004.11a
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• pp.231-237
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• 2004

Vacuum carburizing continues to gain acceptance as an alternative to atmosphere carburizing particularly in the car industry. The advantages of low-pressure carburization over atmospheric gas carburization is not only the creation of a surface entirely free of oxide and the environmentally friendly nature of these methods but also an improvement in deformation behaviour achieved by combining carburization with gas quenching, a reduction in batch times by increasing the carburization temperature, low gas and energy consumption and the prevention of soot to a large extent. In present study, an improved vacuum carburizing method is provided which is effective to deposit carbon in the surface of materials and to reduce cycle time. Also LPC process simulator was made to optimize to process controls parameters such as pulse/pause cycles of pressure pattern, temperature, carburizing time, diffusion time. The carburizing process was simulated by a diffusion calculation program, where as the model parameters are proposed with help the experimental results and allows the control of the carburizing process with good accordance to the practical results. Thus it can be concluded that LPC process control method based on the theoretical simulation and experimental datas appears to provide a reasonable tool for prototype LPC system.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.549-552
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• 2006

Deicing salt has been generally used for prevention of a road freezing in winter, and the amount is increasing every year. However, deicing salt may induce the decrease of bond strength, surface scaling, and environmental pollution, etc. The purpose of this paper is to suggest the fundamental data on safety and durability for concrete structures through the estimation of characteristics of chloride penetration with deicer types. According to the test results, as age of concrete is increased, chloride penetration depth is also increased independent of deicer types. However, there is no remarkable difference between deicer types. And when the estimation of chloride diffusion is carried out by immersion test, diffusion coefficient is decreased with ages, and short-term estimation may overestimate the coefficient.

• Journal of the Korean Vacuum Society
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• v.4 no.S2
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• pp.90-94
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• 1995

Defects introduced by Si, Ge preamorphization and their effects on the dopant diffusion and electrical characteristics. Good crystalline quality are obtained after the annealing of Ge ion double implanted samples. The defect clusters under the a/c interface are expected to extend up to the deep in the Si ion implanted samples. The dislocation loops near the junction absorb the interstitial Si atoms resolving from the defect cluster and result in the prevention of enhanced boron diffusion near the tail region of boron profile and show good reverse current charactristics.

• Fire Science and Engineering
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• v.26 no.4
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• pp.55-62
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• 2012

The suppression mechanisms of carbon dioxide ($CO_2$) as a representative fire suppression agent were revisited using a counterflow diffusion flame which could be applied the concept of a local application system. To end this, the low strain rate $CH_4$/air counterflow diffusions with $CO_2$ addition in either fuel or oxidizer stream were examined numerically using detailed-kinetic chemistry. Radiative heat loss due to radiating gas species including $CO_2$ added was considered by the optically thin model (OTM). As a result, the critical $CO_2$ volume fractions in the oxidizer stream required to extinguish the flame were in good agreement with the experimental data reported in the literature, while somewhat under-prediction was observed with $CO_2$ added in the fuel stream. The surrogate agents were adopted to estimate the quantitative contribution with changing in global strain rate ($a_g$) on the flame extinguishment among pure dilution effect, thermal effects including radiation heat loss and chemical effect due to the $CO_2$ fire suppression agent.

• Asia pacific journal of information systems
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• v.25 no.4
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• pp.719-745
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• 2015

Social networking services provide individuals with an easy approach for exchanging messages with others based on interpersonal relationships. However, why individuals spread marketer-generated content (MGC) in their online social circles remains unclear. Therefore, we develop a theoretical model to examine how social capital, intrinsic motivations, personal perceptions, past behavior, and personal traits influence MGC sharing behavior of social media users in micro-blogging context. Data collected from 319 social networking users support the proposed model. The results from partial least squares analyses show that enjoyment, perceived control, and outcome expectations are significant indicators of individual's MGC sharing intention in the social broadcasting environment. Results also suggest that social capital, users' intention, and past behavior positively influence the MGC sharing behavior of users. Moreover, individual prevention pride exhibits a significant interaction effect on the relationships between users' MGC sharing and its antecedents. Implications for research and practice are discussed.

• 한국태양에너지학회:학술대회논문집
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• 2011.11a
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• pp.270-273
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• 2011

Water management is important in proton exchange membrane fuel cell because the water balance has a significant impact on the overall fuel cell system performance. In fuel cell vehicle, the vehicle's power demand is dynamic; therefore, the dynamic water management system is required. This present study proposes a method to control the humidity of the input air in cathode side of the fuel cell vehicle. The simulation using several driving cycles shows the proposed air humidification control obtains a relatively good result. The liquid saturation level is seen constant at the target level although still there are small deviations at driving cycles which having averagely high power demands.