• Journal of the Korean Society of Industry Convergence
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• v.23 no.6_2
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• pp.1103-1110
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• 2020

In this study, a segmented model with Upside-Down bathtub shaped failure intensity for a repairable system are proposed under the assumption that the occurrences of the failures of a repairable system follow the Non-Homogeneous Poisson Process. The proposed segmented model is the compound model of S-PLP and LIP (Segmented Power Law Process and Logistic Intensity Process), that fits the separate failure intensity functions on each segment of time interval. The maximum likelihood estimation is used for estimating the parameters of the S-PLP and LIP model. The case study of system A shows that the S-PLP and LIP model fits better than the other models when compared by AICc (Akaike Information Criterion corrected) and MSE (Mean Squared Error). And it also implies that the S-PLP and LIP model can be useful for explaining the failure intensities of similar systems.

• Convergence Security Journal
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• v.11 no.4
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• pp.85-91
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• 2011

Due to the large-scale application software syslmls, software reliability, software development has animportantrole. In this paper, software truncated software reliability growth model was proposed based on log-logistic distribution. According to fixed time, the intensity function, the mean value function, the reliability was estimated and the parameter estimation used to maximum likelihood. In the empirical analysis, Poisson execution time model of the existiog model in this area and the log-logistic model were compared Because log-logistic model is more efficient in tems of reliability, in this area, the log-logistic model as an alternative 1D the existiog model also were able to confim that you can use.

• Proceedings of the Technology Innovation Conference
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• 2005.08a
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• pp.5-28
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• 2005

This paper estimates the effect of networks on innovative performance at the firm level , using Korean Innovation Survey (KIS) dataset Product innovation, product improvement , and process innovation are used as proxies for innovative activity. The explanatory variables such as firm size, market concentration ratio, lagged profitability, foreign ownership, export ratio, firm's age, formal R&D activity, and industrial R&D intensity are yet other considerations. With two year-long (2000 and 2001) data from 1,124 Korean manufacturing firms, we estimated the logistic regression model. The research finding indicates that the external networks have a strong positive effect on innovative output regardless of type of innovation. However, the network effects by partner (other firms or research institutions) vary across the type of innovation. Especially, we found that the user-supplier linkage plays an important role in product ion innovation, product improvement, and process innovation.

• Journal of Korea Technology Innovation Society
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• v.12 no.3
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• pp.564-581
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• 2009

The paper investigates the determinants of firm's standardization activity in the Korean manufacturing industry. Standardization variables as dependent ones are standardization management at the firm level, accreditation activity, domestic standards utilization, and international standards utilization. The independent variables include innovative activities(R&D intensity and patent application), firm size, export ratio, networks, and firm's organization characteristics. We estimated the logistic regression model, using the data from 636 Korean manufacturing firms. The empirical findings are as follows. First, R&D intensity doesn't have any influence on standardization activities, except the utilization of international standards. Second, patent application has a positive effect on standardization management at the firm level and accreditation activity, respectively. Third, the inverse U-shape hypothesis relating firm size is accepted for standardization management and accreditation, respectively. Fourth, the level of chief executive officer's interest on standardization is a very important factor in determining firms' efforts to participate standardization process, regardless of types of standardization activity.

• Management & Information Systems Review
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• v.28 no.2
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• pp.95-112
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• 2009

The paper investigates the determinants of firm's standardization activity in the Korean service industry. Standardization variables as dependent ones are standardization management at the firm level, domestic standardization activity, and international standardization activity. The independent variables include innovative activities(R&D intensity and patent application), firm size, export ratio, network, and firm's organization characteristics. We estimated the logistic regression model, using the data from 102 Korean service firms. The empirical findings are as follows. First, R&D intensity has a positive effect on international standardization activity, but not on the standardization management at the firm level and domestic standardization activity. Second, patent application has a negative effect on the standardization management at the firm level. Third, firm size doesn't have any influence on firms' standardization activities in the service sector. Fourth, the level of chief executive officer's interest on standardization is a very important factor in determining firms' efforts to participate standardization process, regardless of types of standardization activity.

• Journal of Digital Convergence
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• v.11 no.9
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• pp.159-166
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• 2013

In this paper, make a study decision problem called an optimal release policies after testing a software system in development phase and transfer it to the user. When correcting or modifying the software, finite failure non-homogeneous Poisson process model, presented and propose release policies of the life distribution, half-logistic property model which used to an area of reliability because of various shape and scale parameter. In this paper, discuss optimal software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement. In a numerical example, the parameters estimation using maximum likelihood estimation of failure time data, make out estimating software optimal release time. Software release time is used as prior information, potential security damages should be reduced.

• Journal of Korean Academy of Nursing
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• v.49 no.3
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• pp.329-339
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• 2019

Purpose: The purpose of this study was to investigate the frequency, patterns, and factors of reversals in decisions about life-sustaining treatment (LST) among older patients with terminal-stage chronic cardiopulmonary disease. Methods: This was a retrospective correlational descriptive study based on medical chart review. De-identified patient electronic medical record data were collected from 124 deceased older patients with terminal-stage cardiopulmonary disease who had made reversals of LST decisions in an academic tertiary hospital in 2015. Data were extracted about the reversed LST decisions, LST treatments applied before death, and patients' demographic and clinical factors. Multivariate logistic regression analysis was used to identify the factors associated with the reversal to higher intensity of LST treatment. Results: The use of inotropic agents was the most frequently reversed LST treatment, followed by cardiopulmonary resuscitation, intubation, ventilator therapy, and hemodialysis. Inconsistency between the last LST decisions and actual treatments occurred most often in hemodialysis. One-third of the reversals in LST decisions were made toward higher intensity of LST treatment. Patients who had lung diseases (vs. heart diseases); were single, divorced, or bereaved (vs. married); and had an acquaintance as a primary decision maker (vs. the patients themselves) were significantly more likely to reverse the LST decisions to higher intensity of LST treatment. Conclusion: This study demonstrated the complex and turmoil situation of the LST decision-making process among older patients with terminal-stage cardiopulmonary disease and suggests the importance of support for patients and families in their LST decision-making process.

• Journal of Technology Innovation
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• v.13 no.3
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• pp.77-100
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• 2005

This paper analyzes the determinants of firm's innovative activity, using Korean Innovation Survey (KIS) dataset. Especially, we focused on the role of external networks by partners(other firms or research institutions) in performing innovative activities. The product innovation, product improvement, and process innovation are used as proxies for innovative activity. The explanatory variables such as market concentration ratio, lagged profitability, foreign ownership, export ratio, firm's age, formal R&D activity, and industrial R&D intensity are also considered. With data from 1,124 firms for the two years (2000-2001), we estimated the logistic regression model. The finding is that the determinants of firm's innovative activities differ by type of innovations. We also found that the innovative behavior of SMEs differs from that of large firms. The result confirms that external networks have a strong positive effect on innovative activity. However, the network effects by partners vary across both firm size and type of innovations.

• The Plant Pathology Journal
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• v.33 no.5
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• pp.441-449
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• 2017

Citrus canker is an important bacterial disease of citrus in several regions of the world. Strains of Xanthomonas citri type-A (Xc-A) group are the primary pathogen where citrus canker occurs. After Xc-A entered the Northeast of Argentina in 1974, the disease spread rapidly from 1977 to 1980 and then slowed down and remained moving at slow pace until 1990 when it became endemic. Citrus canker was detected in Northwest Argentina in 2002. This paper presents the main steps in the fight of the disease and the management strategies that have been used to control citrus canker at this time. We think the process might be usefull to other countries with the same situation. Results from more than 40 years of research in Northeast (NE) Argentina indicate that we are at the limit of favorable environment for the disease. The severity of citrus canker is greatly affected by the environment and El $Ni{\tilde{n}}o$ Southern Oscillation (ENSO) phenomenon which causes cyclic fluctuations on the disease intensity in the NE region. Weather-based logistic regression models adjusted to quantify disease levels in field conditions showed that the environmental effect was strongly modulated by the distance from a windbreak. Production of healthy fruits in citrus canker endemic areas is possible knowing the dynamics of the disease. A voluntary Integrated Plan to Reduce the Risk of Canker has been in place since 1994 and it allows growers to export unsymptomatic, uninfested fresh fruit to countries which are free of the disease and require healthy, pathogen free fruits. The experience from Argentina can be replicated in other countries after appropriate trials.

• Investigative Magnetic Resonance Imaging
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• v.24 no.1
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• pp.38-45
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• 2020

Background: Differentiation of cerebellopontine angle (CPA) schwannoma from meningioma is often a difficult process to identify. Purpose: To identify imaging features for distinguishing CPA schwannoma from meningioma and to investigate the usefulness of susceptibility-weighted imaging (SWI) in differentiating them. Materials and Methods: Between March 2010 and January 2015, this study pathologically confirmed 11 meningiomas and 20 schwannomas involving CPA with preoperative SWI were retrospectively reviewed. Generally, the following MRI features were evaluated: 1) maximal diameter on axial image, 2) angle between tumor border and adjacent petrous bone, 3) presence of intratumoral dark signal intensity on SWI, 4) tumor consistency, 5) blood-fluid level, 6) involvement of internal auditory canal (IAC), 7) dural tail, and 8) involvement of adjacent intracranial space. On CT, 1) presence of dilatation of IAC, 2) intratumoral calcification, and 3) adjacent hyperostosis were evaluated. All features were compared using Chi-squared tests and Fisher's exact tests. The univariate and multivariate logistic regression analysis were performed to identify imaging features that differentiate both tumors. Results: The results noted that schwannomas more frequently demonstrated dark spots on SWI (P = 0.025), cystic consistency (P = 0.034), and globular angle (P = 0.008); schwannomas showed more dilatation of internal auditory meatus and lack of calcification (P = 0.008 and P = 0.02, respectively). However, it was shown that dural tail was more common in meningiomas (P < 0.007). In general, dark spots on SWI and dural tail remained significant in multivariate analysis (P = 0.037 and P = 0.012, respectively). In this case, the combination of two features showed a sensitivity and specificity of 80% and 100% respectively, with an area under the receiver operating characteristic curve of 0.9. Conclusion: In conclusion, dark spots on SWI were found to be helpful in differentiating CPA schwannoma from meningioma. It is noted that combining dural tail with dark spots on SWI yielded strong diagnostic value in differentiating both tumors.