• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.1
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• pp.57-62
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• 2017

The purpose of this study is to develop a method for diagnosing the degree of gradual degradation of a reciprocating pump caused by continuous use as a water supply pump in a nuclear power plant. Normally, the progress of such degradation is too slow to be noticed. Hence, it is difficult to determine the degree of degradation using the existing diagnostic methods. In this paper, we propose a new method by which the normal state and the degraded state of the pump can be differentiated, so that the degree of degradation can be identified. First, an emulator was developed using FPGA by providing the parameters of the pump under normal state, so that the emulator generates the information of the pump in the healthy state. Then, by comparing this information with the parameters received from various output sensors of the emulator during the current state, it is possible to identify and measure the degree of gradual degradation. This paper presents some of the results obtained during the development process, and results that show how the emulator operates, by comparing the data collected from an actual pump.

• Journal of Aerospace System Engineering
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• v.13 no.6
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• pp.26-35
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• 2019

In this paper, progressive failure analysis is performed on composite joints widely used in various industries such as the aerospace industry. The analysis was conducted on single bolted joints to confirm its reliability and in succession on double-bolted composite joints as well to study the characteristics of progressive failure. Hashin failure criteria and EGDM (energy based gradual degradation model) were used for the analysis. Failure variables are defined by four failure modes, respectively. According to the variables, stiffness degradation has been calculated. As a result of comparing the test and analysis results of single-bolted joints, the error was below 5% and it showed that the analytical results are rather credible. Also, the parametric analysis consequences were obtained conducting the process-progressive failure analysis on the double-bolted composite joints considering edge-distance ratio (e/d ratio) and bolt spacing.

• The Journal of the Acoustical Society of Korea
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• v.18 no.6
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• pp.38-43
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• 1999

The EVRC vocoder is a toll quality coder, but it shows significant degradation or the quality in weak RF environment. In this paper, the speech quality degradation phenomenon of the EVRC is analyzed, and two methods are proposed as the solution - the pitch prediction and the gradual increase. The preference tests for various Rf environment are performed for speech quality assessments and both the methods show better performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.93-94
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• 2006

The $I_c$ degradation behavior of YBCO CC tapes due to torsional deformation has been investigated. Particularly, the influence of torsion angle on the $I_c$ in HTS tapes was examined at 77K (self-field). At low torsional angles or shear strains, the $I_c$ degradation was small and gradual. Also, a good consistency of the $I_c$ degradation behaviors was found along the longitudinal direction under torsion when multiple voltage terminals were adopted for investigating the homogeneity of the $I_c$ degradation.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.87-95
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• 1992

Recently, the robot actuator worked by the driving recovery-force of the thermo elastic martensitic transformation of shape memory alloys(SMA) has been studied. In general, such a SMA actuator necessitates a number of cyclic repeated motion, so that the investigation of gradual decrease of recovery force with repeated motion cycle as well as the prevention of such a degradation of shape memory effect(SME) are very important for the actual use of a robot actuator. However, such research and discussions about the degradation of SME are very few up to the present. Therefore, in this study, the characteristics of the cyclic deformation and degradation of SME of Ti-Ni alloy would be investigated and discussed in detail by current heat type fatigue tester, which is a newly designed fatigue tester by author. In addition, we will establish a new design concept for robot actuator from these result.

• Journal of the Korean Applied Science and Technology
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• v.24 no.3
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• pp.278-286
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• 2007

As a part of enhancing the performance of wood-plastic composites (WPC), polypropylene (PP)/ nanoclay (NC)/ wood flour (WF) nanocomposites were prepared using melt blending and injection molding process to evaluate their thermal stability. Thermogravimetric analysis (TGA) was employed to investigate thermal degradation kinetics of the nanocomposites both dynamic and isothermal conditions. Dynamic scans of the TGA showed an increased thermal stability of the nanocomposites at moderate wood flour concentrations (up to 20 phr, percentage based on hundred percent resin) while it decreased with the addition of 30 phr wood flour. The activation energy $(E_a)$ of thermal degradation of nanocomposites increased when nanoclay was added and the concentration of wood flour increased. Different equations were used to evaluate isothermal degradation kinetics using the rate of thermal degradation of the composites, expressed as weight loss (%) from their isothermal TGA curves. Degradation occurred at faster rate in the initial stages of about 60 min., and then proceeded in a gradual manner. However, nanocomposites with wood flour of 30 phr heated at $300^{\circ}C$ showed a drastic difference in their degradation behavior, and reached almost a complete decomposition after 40 min. of the isothermal heating. The degree of decomposition was greater at higher temperatures, and the residual weight of isothermal degradation of nanocomposites greatly varied from about 10 to 90%, depending on isothermal temperatures. The isothermal degradation of nanocomposites also increased their thermal stability with the addition of 1 phr nanoclay and of wood flour up to 20 phr. But, the degradation of PP100/NC1/MAPP3/WF30 nanocomposites with 30 phr wood flour occurs at a faster rate compared to those of the others, indicating a decrease in their thermal stability.

• Journal of Conservation Science
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• v.2 no.2 s.2
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• pp.15-24
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• 1993

To understand the morphological change of ancient woods, samples classified by cell type, burial environment and species were collected and observed using microscopy. Decay of wood by cell type could classified into two types. First, degraded secondary wall was formed granular residues in $S_2$ layer and was remained $S_3$ layer and compound middle lamella. Second, the cell wall was slightly degraded and cracked in secondary wall. A gradual thinning of cell wall was occured. The compound middle lamella was separated from secondary wall. The resistance of degradation is increased at vessels, parenchyma, and tracheid and wood fiber in the order named. The type of degradation by species could be classified into four types. Overall degradation type; the degradation of cell wall is usually heavy and the extent of degradation Varies by part of the same sample. Partial degradation type ; this type shows severely different decay type by part of the sample. Nondegraded cells were mixed with degraded cells on the same sample. Erose degradation type ; thinning of the cell wall was occoured and the degradation type was different by part. Slight degradation types ; secondary wall was slightly degraded, cracked and separated from compound middle lamella. Considering different type of burial environment, dry wood was similiar to sound wood and slightly decayed. Waterlogged and peat burial wood was heavilydecayed. Between species of under the same environment, decay type and extent were diferentiated from each other.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.24-28
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• 2013

In this study, the homogeneity of critical current, $I_c$, along the lengthwise direction in the coated conductor (CC) tape under uniaxial tension was investigated using a multiple voltage tap configuration. Initially, a gradual and homogeneous $I_c$ degradation occurred in all subsections of the tape up to a certain strain value. This was followed by an abrupt $I_c$ degradation in some subsections, which caused scattering in $I_c$ values along the length with increasing tension strain. The $I_c$ degradation behaviour was also explained through n-value as well as microstructure analyses. Subsections showed $I_c$ scattering corresponding to damaged areas of the CC tape revealed that transverse cracks were distributed throughout the gauge length. This homogeneous $I_c$ degradation behaviour under tension is similar with the case under torsion strain but different with the case under hard bending which were previously reported. This behaviour is also different with the case using Bi-2223 HTS tapes under tension strain.

• Preventive Nutrition and Food Science
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• v.10 no.4
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• pp.378-381
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• 2005

Actin and myosin solutions and fresh ground pork were irradiated with the electron beam (e-beam) at a dose of 0, 1.5, 3.0, 5.0 and 10 kGy. The changes in SDS-PAGE pattern of 2 proteins and the salt-soluble proteins extracted from ground pork after e-beam irradiation were monitored. When the myosin solution was irradiated with e-beam, myosin was degraded completely. Complete myosin degradations were observed even with the lowest dose (1.5 kGy) of e-beam treatment. Actin was degraded with the irradiation, but to a less extent than myosin was. The degradation of actin increased as the e-beam treatment increased from 1.5 to 10.0 kGy. Among the salt-soluble proteins extracted from ground pork, myosin was degraded gradually when the e-beam dose increased from 1.5 up to 10.0 kGy. Similar gradual increase in the degradation of actin also occurred with the increase of irradiation. Increases of 2 low molecular weight compounds (<29 kDa) were observed when the irradiation dose increased from 1.5 to 10.0 kGy. These 2 molecules are thought to be the breakdown products produced from the degradation of major salt-soluble proteins, myosin and actin. The salt-soluble protein content of ground pork did not change with the e-beam irradiation.

• Applied Chemistry for Engineering
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• v.17 no.1
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• pp.100-105
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• 2006

The photocatalytic activity of phenol degradation was investigated with the variation of operating parameters in $UV/TiO_2$ honeycomb reactor. In the comparison of phenol degradation rates among various $TiO_2$, Ishihara (STS-02)-coated honeycomb exhibited a slightly higher photocatalytic activity than Degussa P25-coated honeycomb. On the other hand, honeycomb coated by alcohol-mixed $TiO_2$ (N Co.) did not exhibit any photocatalytic activity on phenol degradation. With the increase of Degussa P25 coating amounts, the honeycomb reactor exhibited the gradual increase of phenol degradation rates. The degradation rate of phenol over $UV/TiO_2$ (Degussa P25) honeycomb reactor was asymptotically increased up to 500 mL/min, subsequently followed by a slight decrease as the recirculation rate (100~700 mL/min) was increased. UV absorption at 269 nm was high due to partial degradation of phenol at initial reaction time because the honeycomb surface was pre-adsorbed by phenol prior to UV irradiation.