• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.104-112
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• 2014

Generally, numerical approaches of evaluation for vehicle seat comfort have been studied without considering time-dependent characteristics and the only seating moment have been considered in seat design. However, the comfort not only at the seating moment but also in the long-term should be evaluated because the passengers are sitting repeatedly on the seat to drive the vehicle for hours. So, the aim of this paper is to carry out a quantitative evaluation of the time-dependent mechanical characteristics of seat foams and to suggest a process for predicting the viscoelastic deformation of seat foam in response to long-term driving. To characterize the seat materials, uniaxial compression and tension tests were carried out for the seat foam and stress relaxation tests were performed for evaluating the viscoelastic behavior of the seat foam. A unit solid element model was used to verify the reliability of the material model with respect to the compression behavior of the seat foam. It is not straightforward to evaluate the time-dependent compression of foams using the explicit solver because the viscoelastic material model is limited. To use the explicit solver, the material model must be modified using stress-degradation data. Normalized stress relaxation moduli were added to the stress-strain curves obtained under static conditions to achieve a time-dependent set of stress-strain relations that were compatible with the implicit solver. There was good agreement between the analysis results and experimental data.

• Journal of Ginseng Research
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• v.45 no.2
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• pp.295-304
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• 2021

Background: Acute promyelocytic leukemia (APL) is a hematopoietic malignancy driven by promyelocytic leukemia-retinoic acid receptor A (PML-RARA) fusion gene. The therapeutic drugs currently used to treat APL have adverse effects. 20(S)-ginsenoside Rh2 (GRh2) is an anticancer medicine with high effectiveness and low toxicity. However, the underlying anticancer mechanisms of GRh2-induced PML-RARA degradation and apoptosis in human APL cell line (NB4 cells) remain unclear. Methods: Apoptosis-related indicators and PML-RARA expression were determined to investigate the effect of GRh2 on NB4 cells. Z-VAD-FMK, LY294002, and C 87, as inhibitors of caspase, and the phosphatidylinositol 3-kinase (PI3K) and tumor necrosis factor-α (TNF-α) pathways were used to clarify the relationship between GRh2-induced apoptosis and PML-RARA degradation. Results: GRh2 dose- and time-dependently decreased NB4 cell viability. GRh2-induced apoptosis, cell cycle arrest, and caspase3, caspase8, and caspase9 activation in NB4 cells after a 12-hour treatment. GRh2-induced apoptosis in NB4 cells was accompanied by massive production of reactive oxygen species, mitochondrial damage and upregulated Bax/Bcl-2 expression. GRh2 also induced PML/PML-RARA degradation, PML nuclear bodies formation, and activation of the downstream p53 pathway in NB4 cells. Z-VAD-FMK inhibited caspase activation and significantly reversed GRh2-induced apoptosis and PML-RARA degradation. GRh2 also upregulated TNF-α expression and inhibited Akt phosphorylation. LY294002, an inhibitor of the PI3K pathway, enhanced the antitumor effects of GRh2, and C 87, an inhibitor of the TNF-α pathway, reversed NB4 cell viability, and GRh2-mediated apoptosis in a caspase-8-dependent manner. Conclusion: GRh2 induced caspase-dependent PML-RARA degradation and apoptosis in NB4 cells via the Akt/Bax/caspase9 and TNF-α/caspase8 pathways.

• Geomechanics and Engineering
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• v.18 no.3
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• pp.299-313
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• 2019

This research investigated the nonlinear compressibility, permeability, the yielding due to structural degradation and their effects on consolidation behavior of structured soft soils. Based on oedometer and hydraulic conductivity test results of natural and reconstituted soft clays, linear log (1+e) ~ $log\;{\sigma}^{\prime}$ and log (1+e) ~ $log\;k_v$ relationships were developed to capture the variations in compressibility and permeability, and the yield stress ratio (YSR) was introduced to characterize the soil structure of natural soft clay. Semi-analytical solutions for one-dimensional consolidation of soft clay under time-dependent loading incorporating the effects of soil nonlinearity and soil structure were proposed. The semi-analytical solutions were verified against field measurements of a well-documented test embankment and they can give better accuracy in prediction of excess pore pressure compared to the predictions using the existing analytical solutions. Additionally, parametric studies were conducted to analyze the effects of YSR, compression index (${\lambda}_r$ and ${\lambda}_c$), and permeability index (${\eta}_k$) on the consolidation behavior of structured soft clays. The magnitude of the difference between degree of consolidation based on excess pore pressure ($U_p$) and that based on strain ($U_s$) depends on YSR. The parameter ${\lambda}_c/{\eta}_k$ plays a significant role in predicting consolidation behavior.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.231-236
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• 2011

In recent years, LBS(Location Based Service) is applied in many different fields. Therefore, various location-aware schemes have been studied. In the location awareness system using time dependent algorithm, TOA(Time of Arrival) or TDOA(Time Difference of Arrival) algorithm, distortion of a signal by AWGN(Additive White Gaussian Noise) and multi-path effects cause the degradation of location awareness performance. In this paper, the unexpected noise is eliminated by averaging multiple pulses in order to overcome the degradation of performance. Also, we research the technique for improving the performance of the location awareness by detecting direct-path signal with adjusting threshold.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.3
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• pp.27-34
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• 2012

This paper presents the impact of time dependent dielectric breakdown (TDDB, also called as gate oxide breakdown) failure on nanoscale digital CMOS Circuits. Recently, TDDB for ultra-thin gate oxides has been considered as one of the critical reliability issues which can lead to performance degradation or logic failures in nanoscale CMOS devices. Also, leakage power in the standby mode can be increased significantly. In this paper, TDDB aging effects on large CMOS digital circuits in the 45nm technology are analyzed. Simulation results show that TDDB effect on MOSFET circuits can result in more significant increase of power consumption compared to delay increase.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.142.3-143
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• 2003

Time-dependent PPO activity was determined at $4^\times$C and $30^\times$C. The result of activity determination, PPO extracted by phosphate buffer containing triton x-1l4(tPPO) was more stable than PPO by phosphate buffer(bPPO). The result of electrophoresis, at first a band was appeared at 48kd. After 1-3days a partial degrade band was appeared in bPPO and three partial degrade bands in tPPO. No activity band was appeared in PPOs at $30^\times$C and bPPO at $4^\times$C after 4 days. (omitted)

• Journal of Physiology & Pathology in Korean Medicine
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• v.16 no.4
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• pp.745-755
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• 2002

To examine the effects of Yunpyesan on the cell proliferation of A549 human lung carcinoma cell line, we performed various experiments such as dose-dependent effect of Yunpyesan on cell proliferation and viability, morphological changes, quantification of apoptotic cell death and alterations of apoptosis/cell cycle-regulatory gene products. Yunpyesan declined cell viability and proliferation in both a dose- and a time-dependent manner. The anti-proliferative effect by Yunpyesan treatment in A459 cells was associated with morphological changes such as membrane shrinking and cell rounding up. Yunpyesan Induced apoptotic cell death in a time-dependent manner, which was associated with degradation of poly-(ADP-ribose) polymerase (PARP), an apoptotic target protein, without alterations of the balance between Bcl-2 and Bax expressions. DNA flow cytometric histograms showed that population of G1 phase of the cell cycle was increased by Yunpyesan treatment in a dose-dependent manner. Western blot analysis revealed that cyclin D1 and A were reduced by Yunpyesan treatment, whereas cyclin dependent kinase (Cdk) inhibitor p27 was markedly increased in a time-dependent fashion. The level of tumor suppressor p53 proteins was also increased by Yunpyesan treatment and its increase might be linked to increase of Cdk inhibitor p27. In addition, Mdm2, negative regulator of p53, was down-regulated by Yunpyesan treatment. Since the expression of retinoblastome protein (pRB), a key regulator of G1/S progression, was reduced by Yunpyesan treatment, we supposed that phosphorylation of pRB might be also blocked. The present results indicated that Yunpyesan-induced inhibition of lung cancer cell proliferation is associated with the induction of apoptosis and the blockage of G1/S progression.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.10-18
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• 2016

RC(Reinfored Concrete) structures exposed to carbonation in urban city have durability degradation with extended service life and cracks in concrete causes a local accelerated carbonation. In the present work, crack effect on carbonation depth is investigated and the service life of RC structure is evaluated considering cracks from early age and time-dependent cracks based on the previous field investigation. DFP(Durability Failure Probability), safety index, and the related service life are calculated considering the time to crack width reaches to maximum crack width(0.3mm). The results with time effect on crack width show lower DFP and longer service life, which seems to be reasonable compared with conservative results from crack effect from initial stage. Furthermore, crack effect is evaluated to be insignificant on DFP and service life. The technique with time-dependent crack effect on carbonation can be effectively used for RC structure containing cracking in use.

• Earthquakes and Structures
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• v.24 no.4
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• pp.275-288
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• 2023

Based on the crucial role of high-speed railway bridges (HSRBs) in the safety of high-speed railway operations, it is an important approach to mitigate earthquake hazards by proceeding with seismic risk assessments in their whole life. Bridge seismic risk assessment, which usually evaluates the seismic performance of bridges from a probabilistic perspective, provides technical support for bridge risk management. The seismic performance of bridges is greatly affected by the degradation of material properties, therefore, material damage plays a nonnegligible role in the seismic risk assessment of the bridge. The effect of material damage is not considered in most current studies on seismic risk analysis of bridges, nevertheless. To fill the gap in this area, in this paper, a nonlinear dynamic time-history analysis has been carried out by establishing OpenSees finite element model, and a seismic vulnerability analysis is carried out based on the incremental dynamic analysis (IDA) method. On this basis, combined with the site risk analysis, the time-dependent seismic risk analysis of an offshore three-span HSRB in the whole life cycle has been conducted. The results showed that the seismic risk probabilities of both components and system of the bridge increase with the service time, and their seismic risk probabilities increase significantly in the last service period due to the degradation of the material strength, which demonstrates that the impact of durability damage should be considered when evaluating the seismic performance of bridges in the design and service period.

• 한국공간정보시스템학회:학술대회논문집
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• 2007.06a
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• pp.280-285
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• 2007

Since the human civilization, people's livelihood is dependent on natural resources primarily on forest. Human dimensions such as population, poverty, agricultural expansion and infrastructure development are some of the underlying factors and their interrelated associations which could play a vital role in deforestation and forest degradation. This process is not only related to the human population but also connected to the various socioeconomic factors. This paper focuses to link the spatio-temporal extent of population, poverty incidence and forest dependency and their severity on Terai forest of Nepal. Secondary data on censuses were used. ArcGIS and descriptive statistics were also used for data analysis. Based on analysis & literature review we concluded that population, poverty and forest dependency have largely expanded over time in Terai and their interrelated associations substantively influence on deforestation. However, the direct relationship of such factors with deforestation and forest degradation found to be incompatible, complex and hard to perceive with fragmented and inconsistency censuses data. So, deforestation and forest degradation issues intertwined with socioeconomic factors need detailed analysis to comprehend where these linkages are still unravel.