• Journal of the Korean Society of Industry Convergence
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• v.4 no.3
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• pp.267-273
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• 2001

In this study, the survival rate of fiber is investigated by nozzle size difference in injection/mold sides. The survival rate of fiber is influenced about the nozzle size differ. Also, The mechanical properties of short carbon glass fiber reinforced polypropylene are experimentally measured as functions of fiber volume fraction and nozzle size difference. These mechanical properties are compared with the survival rate of fiber and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber as well as fiber volume fraction is influenced by injection processing condition, the used materials, mold conditions and nozzle sides difference, etc, In particular, the survival rate of fiber is great influenced when injection/mold nozzle sides are different more than that of the same. Consequently, the mechanical properties of short carbon/glass fiber reinforced polypropylene arc improved as the nozzle sides are the same in injection mold sides.

• Communications for Statistical Applications and Methods
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• v.24 no.4
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• pp.325-337
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• 2017

In this paper, we proposed a new long-term lifetime distribution with four parameters inserted in a risk competitive scenario with decreasing, increasing and unimodal hazard rate functions, namely the Weibull-Poisson long-term distribution. This new distribution arises from a scenario of competitive latent risk, in which the lifetime associated to the particular risk is not observable, and where only the minimum lifetime value among all risks is noticed in a long-term context. However, it can also be used in any other situation as long as it fits the data well. The Weibull-Poisson long-term distribution is presented as a particular case for the new exponential-Poisson long-term distribution and Weibull long-term distribution. The properties of the proposed distribution were discussed, including its probability density, survival and hazard functions and explicit algebraic formulas for its order statistics. Assuming censored data, we considered the maximum likelihood approach for parameter estimation. For different parameter settings, sample sizes, and censoring percentages various simulation studies were performed to study the mean square error of the maximum likelihood estimative, and compare the performance of the model proposed with the particular cases. The selection criteria Akaike information criterion, Bayesian information criterion, and likelihood ratio test were used for the model selection. The relevance of the approach was illustrated on two real datasets of where the new model was compared with its particular cases observing its potential and competitiveness.

• Journal of Applied Reliability
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• v.18 no.2
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• pp.130-142
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• 2018

Purpose: The purpose of this study is to introduce regression method in the presence of competing risks and to show how you can use the method with hypothetical data. Methods: Survival analysis has been widely used in biostatistics division. But the same method has not been utilized in reliability division. Especially competing risks, where more than a couple of causes of failure occur and the occurrence of one event precludes the occurrence of the other events, are scattered in reliability field. But they are not utilized in the area of reliability or they are analysed in the wrong way. Specifically Kaplan-Meier method is used to calculate the probability of failure in the presence of competing risks, thereby overestimating the real probability of failure. Hence, cumulative incidence function is introduced. In addition, sample competing risks data are analysed using cumulative incidence function along with some graphs. Lastly we compare cumulative incidence functions with regression type analysis briefly. Results: We used cumulative incidence function to calculate the survival probability or failure probability in the presence of competing risks. We also drew some useful graphs depicting the failure trend over the lifetime. Conclusion: This research shows that Kaplan-Meier method is not appropriate for the evaluation of survival or failure over the course of lifetime in the presence of competing risks. Cumulative incidence function is shown to be useful in stead. Some graphs using the cumulative incidence functions are also shown to be informative.

• Communications for Statistical Applications and Methods
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• v.26 no.3
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• pp.239-259
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• 2019

The transmuted generalized extreme value (TGEV) distribution was first introduced by Aryal and Tsokos (Nonlinear Analysis: Theory, Methods & Applications, 71, 401-407, 2009) and applied by Nascimento et al. (Hacettepe Journal of Mathematics and Statistics, 45, 1847-1864, 2016). However, they did not give explicit expressions for all the moments, tail behaviour, quantiles, survival and risk functions and order statistics. The TGEV distribution is a more flexible model than the simple GEV distribution to model extreme or rare events because the right tail of the TGEV is heavier than the GEV. In addition the TGEV distribution can adjusted various forms of asymmetry. In this article, explicit expressions for these measures of the TGEV are obtained. The tail behavior and the survival and risk functions were determined for positive gamma, the moments for nonzero gamma and the moment generating function for zero gamma. The performance of the maximum likelihood estimators (MLEs) of the TGEV parameters were tested through a series of Monte Carlo simulation experiments. In addition, the model was used to fit three real data sets related to financial returns.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.4
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• pp.564-573
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• 2001

The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.

• Communications for Statistical Applications and Methods
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• v.14 no.1
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• pp.93-109
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• 2007

In this paper we study a number of new exponentiated distributions. The survival function, failure rate and moments of the distributions have been derived using certain special functions. The behavior of the failure rate has also been studied.

• The Korean Journal of Applied Statistics
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• v.22 no.3
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• pp.595-606
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• 2009

Two tests were introduced for comparing several survival functions with doubly interval-censored data and illustrated with data surveyed by Korean Cancer Prevention Study (Jee et al., 2005). The test which extended Kim et al. (2006)'s test to the doubly interval-censored data has an advantage over Sun (2006)'s test in terms of saving computation time because the proposed test only depends on the size of risk set, and also the proposed test is applicable to continuous failure time data as well as discrete failure time data unlike Sun's test. Comparing male with female groups on the incubation time of diabetes was highly different and the survival of female group was longer than that of male one. Regardless of gender, the difference in survival functions of four age groups was highly significant with p-value of less than 0.001. This trend was more remarkable for female group than for male one. Simulation results showed that the significance level of both tests was well controlled and the proposed test was better than Sun's test in terms of power.

• Biomedical Science Letters
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• v.19 no.2
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• pp.118-123
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• 2013

Tumor necrosis factor-alpha (TNF-${\alpha}$) is a proinflammatory cytokine that mediates the inflammatory response and immune functions, and modulates the proliferation, differentiation and cell death of cancer cells. The differential functions of TNF-${\alpha}$ in various human cells due to the formation of different stimulating pathway upon the binding of TNF-${\alpha}$ to its receptors. In the present study, we examined the different effects of TNF-${\alpha}$ on the survival and apoptosis between normal granulocytes and human myeloid leukemia HL-60 cells. Although TNF-${\alpha}$ did not affect on the constitutive apoptosis of granulocytes, TNF-${\alpha}$ strongly induced the apoptosis of HL-60 cells in a dose- and a time-dependent manner. TNF-${\alpha}$-induced apoptosis was occurred via the activation of caspase 8, caspase 9 and caspase 3/7 and the induction of ROS production in HL-60 cells. Also, BAY-11-7085, a NF-${\kappa}B$ inhibitor, blocked the TNF-${\alpha}$-induced apoptosis in HL-60 cells. NF-${\kappa}B$ may be involved in TNF-${\alpha}$-induced apoptotic signaling pathway in HL-60 cells. These results suggest that TNF-${\alpha}$ activates apoptotic pathways and its process depends on cell type and many cellular factors. A better understanding of the differential effect of TNF-${\alpha}$ on cell apoptosis and survival may provide important information that can be used to elucidate the specific inhibitory effect of TNF-${\alpha}$ on the cancer dis.

• Biomolecules & Therapeutics
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• v.20 no.1
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• pp.68-74
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• 2012

Anthocyanins have received growing attention as dietary antioxidants for the prevention of oxidative damage. Astrocytes, which are specialized glial cells, exert numerous essential, complex functions in both healthy and diseased central nervous system (CNS) through a process known as reactive astrogilosis. Therefore, the maintenance of glial cell viability may be important because of its role as a key modulator of neuropathological events. The aim of this study was to investigate the effect of anthocyanin on the survival of glial cells exposed to oxidative stress. Our results demonstrated that anthocyanin extracts from black soybean increased survival of U87 glioma cells in a dose dependent manner upon oxygen-glucose deprivation (OGD), accompanied by decrease levels of reactive oxygen species (ROS). While treatment cells with anthocyanin extracts or OGD stress individually activated autophagy induction, the effect was signifi cantly augmented by pretreatment cells with anthocyanin extracts prior to OGD. The contribution of autophagy induction to the protective effects of anthocyanin was verifi ed by the observation that silencing the Atg5 expression, an essential regulator of autophagy induction, reversed the cytoprotective effect of anthocyanin extracts against OGD stress. Treatment of U87 cells with rapamycin, an autophagy inducer, increased cell survival upon OGD stress comparable to anthocyanin, indicating that autophagy functions as a survival mechanism against oxidative stress-induced cytotoxicity in glial cells. Our results, therefore, provide a rationale for the use of anthocyanin as a preventive agent for brain dysfunction caused by oxidative damage, such as a stroke.

• Journal of the Korean Data and Information Science Society
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• v.14 no.3
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• pp.561-570
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• 2003

We propose a nonparametric test procedure for checking the proportionality assumption between hazard functions using a functional equation. Because of the involvement of censoring distribution function, we consider the large sample case only and obtain the asymptotic normality of the proposeed test statistic. Then we discuss the rationale of the use of the functional equation, give some examples and compare the performances with Andersen's procedure by computing powers through simulations.