• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.9
• /
• pp.1518-1523
• /
• 2016

In this study, in order to understand the degradation characteristics of oil-paper insulation for power transformers and OF cables, tan delta was measured using cable model specimens with long-term accelerated thermal and electrical aging. In addition, to find out the degradation level due to the accelerated aging, tensile strengths of aged papers were measured. As a result, tan ${\delta}$ showed the characteristics of slight decrease at the first stage and then increase with the aging time, which could be analyzed due to the evaporation of remaining moisture and the change of aging rate with time. Also, the trend of tensile strengths with aging temperature and time was appeared to be exponentially decreased and by use of these data equivalent calculated lifetimes and accelerated aging factors were derived for each aging temperatures. After then, tan ${\delta}$ was analyzed with the equivalent operating years. For all different aging temperatures, the aged data were very well fit to the equivalent operating years and it is shown that tan ${\delta}$ was increased with the decrease of tensile strength.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.1
• /
• pp.41-47
• /
• 2001

Ruminal degradation characteristics of dry matter (DM), neutral detergent fiber (NDF) and crude protein (CP) in fresh leaves of two Japanese native grasses (Zoysia japonica and Miscanthus sinensis) and one sown temperate grass (Dactylis glomerata) were investigated by an in sacco method in spring (mid-May), summer (mid-July) and autumn (mid-September). Japanese native grasses had higher NDF and lower CP concentrations than D. glomerata, and the CP concentration in native grasses decreased in autumn. Ruminal degradability of DM, NDF and CP was lower in native grasses than in D. glomerata (p<0.05) in all seasons. DM and NDF degradability decreased in summer for Z. japonica and D. glomerata, while it decreased in autumn for M. sinensis. CP degradability in Z. japonica was constant throughout the seasons, whereas that in M. sinensis greatly decreased in summer and autumn (p<0.05). It was concluded that Z. japonica could stably supply ruminally digestible nutrients for grazing animals in Japanese native pasture. However, the degradation characteristics of freshly chopped native grasses did not fit the exponential model of $D=a+b(1-e^{-ct})$ proposed by Ørskov and McDonald.

• Journal of the Korean Ceramic Society
• /
• v.52 no.1
• /
• pp.23-27
• /
• 2015

Recently, the use of ion-exchange strengthened glass has increased sharply, as it is now used as the cover glass for smart phone devices. Therefore, many researchers are focusing on methods that can be used to strengthen ion-exchange glass. However, research on how the improved strength can be maintained under thermal environment of device manufacturing is still insufficient. We tested the degradation of the characteristics of ion-exchange soda-lime glass samples, including their surface compressive stress characteristics, the depth of the ion-exchange layer (DOL), flexural strength, hardness, and modulus of rupture (MOR) values. Degradation of the characteristics of the ion-exchange glass samples occurred when they were heat-treated at a temperature that exceeded $350^{\circ}C$.

• Proceedings of the KIEE Conference
• /
• 1996.07c
• /
• pp.1765-1768
• /
• 1996

It is well known that the degradation transformer oil is mainly effected to the failure of transformer. In this paper it is discussed the characteristics of the degradation sensor checking transformer oil condition in live line. The degadation sensor composed with base ring, electrodes and porous ceramic passed through the transformer oil and checked the transformer oil condition with sensor's leakage current. It is important to minimize the leakage current of base ring and connection parts. To investigate the leakage current of base ring and connection parts it is examined the characteristics of V-T-I and DC 2 KV and other examinations. It is verified that ionized transformer caused by the expansion of oil temperature increase in the leakage current of porous ceramic sensor. It is certificated that the leakage current of other parts of porous ceramic is very small (about 2 %) than the porous ceramic and it is confirmed that the leakage current in porous ceramic is changed sensitively according to the new oil(NO) and and the degradation oil(DO).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.05a
• /
• pp.333-336
• /
• 1999

The relationship between the DC degradation characteristics of the $ZnO-Bi_2O_3$ varistor and post-annealing is investigated in this study. $ZnO-Bi_2O_3$ varistors containing $SiO_2$ range 0.3 mol% were fabricated by standard ceramic techniques. The post- annealing is performed at $550^{\circ}C$ for 0, 1.5 and 5h. A little phase transition is found according to the analysis of X-ray diffraction. DC degradation tests were conducted at $115\pm3^{\circ}C$ for periods up to 22h. Current-voltage analysis was used to determine nonlinear coefficients($\alpha$). Capacitance-voltage analysis enable the donor density($N_d$) and the barrier height($E_B$) to be determined. From above analysis, it is found that the past-annealing for 5h improved degradation characteristics in $ZnO-Bi_2O_3$ with Si additive.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.05a
• /
• pp.116-119
• /
• 1994

The characteristics of the Si-SiO$_2$ interface and the degradation in the short channel(L${\times}$W=1.7$\mu\textrm{m}$${\times}$15$\mu\textrm{m}$) SONOSFET nonvolatile memory devices, fabricated on the basis of the existing n-well CMOS processing technology for 1 Mbit DRAM with the 1.2$\mu\textrm{m}$ m design rule, were investigated using the charge pumping method. The SONOSFET memories have the tripple insulated-gate consisting of 30${\AA}$ tunneling oxide 205${\AA}$ nitride and 65${\AA}$ blocking oxide, The acceleration method which square voltage pulses of t$\_$p/=10msec, Vw=+19V and V$\_$E/=-22V continue to be alternatly applied to gale, was used to investigate the degradation of SONOSFET memories with the write/erase cycle. The degradation characteristics were ascertained by observing the change in the energy and spatial distributions of the interface trap density.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.13 no.3
• /
• pp.194-199
• /
• 2001

The turbulent flow resistance of water solution with polymer is reduced as compared with that of pure water. This effects is named th drag reduction and offers the significant reduction of the pumping power and the energy consumption. But the intense shear forces and the high temperature experienced by the polymer solution when passing through the pipes cause the degradation a loss of drag reduction effectiveness. Especially, the degradation behavior is found to be strongly dependent on temperature. This mechanical and thermal degradation can be avoided by adding materials such as surfactant to the polymer solution, which enhance the bonding force between molecules. In the present study, Copolymer and SDS were utilized and they were mixed in 10 different mixture ratios, while total concentration was fixed as 100wppm. Degradation of Copolymer-SDS mixture solutions was investigated experimentally in closed loop at the temperature of $10^{\circ}C\; and\; 80^{\circ}C$ with various flow average velocities of 1.5 m/sec, 3.0m/sec, and 4.5m/sec. Degradation characteristics of polymer solution without surfactant show a radical loss of drag reduction effectiveness at high temperature. Degradation alleviation ability of surfactant is especially effective at high temperature. Consequently, this results show that the addition of surfactant to the polymer solution can control unfavorable degradation phenomena for high temperature systems.

• Asian-Australasian Journal of Animal Sciences
• /
• v.11 no.5
• /
• pp.503-509
• /
• 1998

Whole faba beans (WFB) were dry roasted at different temperatures of 110, 130 and $150^{\circ}C$ for 15, 30 and 45 minutes (min) to determine the optimal heating conditions to increase bypass starch as glucose source which may be a limiting nutrient in high producing dairy cattle. Ruminant degradation characteristics of starch (St) of WFB were determined using in sacco method in 6 dairy cows fed 60% hay and 40% concentrate. Measured characteristics of St were soluble (washable) fraction (S), potentially degradation fraction (D) and the rate of degradation (Kd) of the insoluble but degradable St fraction. Based on measurement of these characteristics, percentage bypass starch (%BSt) and bypass starch (BSt) were calculated. Degradability of starch in the rumen was reduced by dry roasting at temperature of 130 and $150^{\circ}C$ and increased at $110^{\circ}C$. S varied from 50.0% in the raw whole faba beans (RWFB) and 53.7% in $110^{\circ}C$/15 min to 18.2% in $150^{\circ}C$/45 min. D varied from 49.9% in RWFB and 46.3% in $110^{\circ}C$/15 min to 81.8 % in $150^{\circ}C$/45 min. Kd varied from 9.8% in RWFB and 11.0% in the $110^{\circ}C$/30 min to 4.2 in $150^{\circ}C$/45 min. All these effects resulted in increasing %BSt from 22.1% in the $110^{\circ}C$/45 min and 23.9% in RWFB to 49.9% in the $150^{\circ}C$/45 min. Therefore BSt increased from 91.4 g/kg and 98.4 g/kg to 199.9 g/kg respectively. Dry roasting at $110^{\circ}C$ increased the starch rumen degradation. Treatment at higher temperature (130 and $150^{\circ}C$) decreased rumen degradation of starch and seemed to be linear up to highest values tested. No optimal dry roasting conditions of treatment could be determined at this stage. It may be concluded that dry roasting at temperatures of 130 and $150^{\circ}C$ was effective in shifting starch degradation from rumen to intestine to increase bypass starch.

• Progress in Superconductivity and Cryogenics
• /
• v.7 no.3
• /
• pp.29-33
• /
• 2005

Critical current$(I_c)$ degradation of High $T_c$ Superconducting(HTS) tapes and AC loss under mechanical load is one of the hottest issues in HTS development and application. Mechanical load reduces the critical current of superconducting wire, and the $I_c$ degradation affects the AC loss of the wire. We measured the $I_c$ degradation and AC loss under tension and bending of Bi-2223 tapes made by 'Powder-in-Tube' technique at 77K with self-field. Also, we have studied the frequency characteristics on self-field AC loss in multi-filamentary Bi-2223/Ag tape at 77K. The measurement results and discussions on the relationship between $I_c$ degradation and AC loss are presented.

• Asian-Australasian Journal of Animal Sciences
• /
• v.15 no.7
• /
• pp.974-981
• /
• 2002

Faba beans (vicia faba) (FB) and lupin seeds (Lupinus Albus) (LS) were dry roasted at three temperatures (110, 130, $150^{\circ}C$) for 15, 30 or 45 min to determine the effects of dry roasting on rumen degradation of crude protein and starch free organic matter ($^{PSF}OM$). Rumen degradation characteristics of $^{PSF}OM$ were determined by the nylon bag incubation technique in dairy cows fed 60% hay and 40% concentrate. Measured characteristics of $^{PSF}OM$ were undegradable fraction (U), degradable fraction (D), soluble fraction (S), lag time (T0), and the rate of degradation (Kd). Based on the measured characteristics, rumen availability ($RA^{PSF}OM$) and bypass $^{PSF}OM$ ($B^{PSF}OM$) were calculated. Dry roasting did not have a greater impact on rumen degradation characteristics of $^{PSF}OM$ (p>0.05). S varied from 32.1 (raw) to 30.0, 27.8, 30.8% (LS) and 15.4 (raw) to 14.4, 20.8, 20.9% (FB); D varied from 65.4 (raw) to 66.3, 66.9, 55.9% (LS) and 54.9 (raw) to 55.0, 51.0, 64.7% (FB); U varied from 2.6 (raw) to 7.3, 7.0, 7.7% (LS) and 29.7 (raw) to 30.6, 28.2, 14.4% (FB); Kd varied from 6.0 (raw) to 7.3, 7.0, 7.7% (LS) and 22.4 (raw) to 24.4, 21.1, 7.9% (FB); $B^{PSF}OM$ varied from 35.5 (raw) to 33.8, 36.6, 38.2% (LS) and 41.3 (raw) to 41.5, 39.7, 47.6% (FB) at 110, 130 and $150^{\circ}C$, respectively. Therefore dry roasting did not significantly affect $RA^{PSF}OM$, which were 353.7, 367.9, 349.6, 336.9 (g/kg DM) (LS) and 12.82, 127.0, 133.7, 117.1 (g/kg DM) (FB) at 110, 130 and $150^{\circ}C$, respectively. These results alone with our previously published reports indicate dry roasting had the differently affected pattern of rumen degradation characteristics of various components in LS and FB. It strongly increased bypass crude protein (BCP) and moderately increased starch (BST) with increasing temperature and time but least affected $^{PSF}OM$. Such desirable degradation patterns in dry roasted LS and FB might be beneficial to the high yielding cows which could use more dry roasted $^{PSF}OM$ as an energy source for microbial protein synthesized in the rumen and absorb more amino acids and glucose in the small intestine.