• Weed & Turfgrass Science
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• v.4 no.1
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• pp.49-57
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• 2015

This research was initiated to analyze the periods of spring green-up and winter leaf discoloration of three ornamental grasses which have potential to be widely used with seed propagation. Two native grasses of Arundinella (Arundinella hirta var. ciliata Koidz), fountaingrass (Pennisetum alopecuroides (L.) Spreng), and switchgrass (Panicum virgatum L.) was tested. Spring green-up were evaluated after one year growth from seed propagation on April 1, 2009. Arundinella started with quick pick of spring green-up during $13^{th}$ to $20^{th}$ of May. Fountaingrass and switchgrass showed relatively slow picks of green-up during $20^{th}$ to $27^{th}$ of May. However, winter leaf discoloration started on swtichgrass and fountaingrass but Arundinella terminated relatively slowly. Swtichgrass showed the pick discoloration during $8^{th}$ to $15^{th}$ of October from the bottom to top parts of the plant. Fountaingrass showed the pick winter discoloration started from bottom to top parts during the $22^{nd}$ to $29^{th}$ of October. However, Arundinella showed relatively slow discoloration from upper to bottom parts during October $29^{th}$ to November $5^{th}$. Arundinella showed a relatively higher ornamental value with 125 days of the complete green period compared than fountaingrass and swtichgrass which maintained approximately 105 days of green period.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.620-625
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• 2018

Pyropia yezoensis is one of the most extensively cultivated seaweeds used as food in Korea. However, the quality and yield of Pyropia farms are frequently affected by outbreaks of thallus discoloration. The objective of this study was to develop a simple and rapid method to evaluate P. yezoensis discoloration caused by nutrient deficiencies. A colorimeter was used to quantify the color of P. yezoensis in nutrient deficient media over 10 days. Quantitative values of lightness (L), redness (a), and yellowness (b) measured with a colorimeter were used as indicators of P. yezoensis discoloration. The vacuoles of P. yezoensis were observed at 4 days and swelled gradually from 6 days onward. The three colorimeter parameters L, a, and b values showed significantly different values with culture period. The lightness (L) value was darker initially, and continued to lighten over culture period. The yellowness (b) value increased, but the redness (a) value decreased throughout this study. The a/b ratio and redness (a) values from the colorimeter were important P. yezoensis color change indicators. The discoloration group of P. yezoensis had quantitative values for parameters of L above 70, a below 2.6, and b above 15.0. The results of this study showed that quantitative colorimetric measurements can be used as tools for simple and rapid detection of P. yezoensis discoloration.

• Korean Journal of Heritage: History & Science
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• v.47 no.4
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• pp.58-73
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• 2014

In general, it is thought discoloration on wood is frequently found in decorative wood products. So this study was conducted focusing on white rot found lower parts of columns and baseboards of a wooden house, Hyunchungsa (shrine) to know whether microorganisms have any influence on discoloration or there is correlation with strength by investigating resistograph, occurrence of microorganisms and microscopy for analysis(SEM, tissue analysis etc.). The results obtained were as follows: (1) The result of measurement of resistograph showed there are little correlation between discoloration and strength though there was a spot indicating low resistance. (2) The moisture content of discolored part was relatively higher than that of normal parts, but occurrence of microorganisms was less in discolored parts while more kinds of microorganisms were identified in normal parts with high CFU(Colony Forming Unit). (3) The result of SEM (with a magnification of 500 times) on the surface of discolored parts, it was found out there are many kinds of particles in different sizes on the surface and those were composed of elements such as C, O, Si, Ca, and a small amount of Na and Cl (weight %) were detected in part. (4) The result of tissue analysis showed discoloration occurs limitedly to the outer surface of column. As these results, it is concluded that discoloration has nothing to do with strength, damage by microorganisms and salt.

• Journal of Welding and Joining
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• v.32 no.6
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• pp.47-55
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• 2014

The purpose of the study is to produce a mechanically improved weld and minimum variation of color through comparing unpulsed and pulsed GTAW (Gas Tungsten Arc Welding) for pure titanium (CP grade7) tube. Pulsed GTAW using 60 A peak current and 20 A background current (1:9) achieved the wider window of welding conditions having part and full penetration without burn-through than the case of unpulsed GTAW. Moreover, the pulsed welding reduced a discoloration on the back bead of the weld and the size of microstructures (basket weave and serrated ${\alpha}$). That is because the pulsed welding has it's a low heat input and severe weld flow induced from electric current variation. Furthermore, the pulsed welding improved the bending property of the welded Ti tube. The enhanced bending property for the pulsed GTAW was due to the insignificant discoloration on the weld surface with maintaining the metal polish.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.32 no.3
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• pp.48-56
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• 2000

Yellow dye-stuffs in natural plant were extracted from a gardenia, saffron, safflower, amur tree and pagoda. And then they were used to color Korean handmade paper(Hanji) on using a mordant. The results of the degree of discoloration are as follows. 1. As for a gardenia(Gardenia jasminodes Ellis for. grandiflora Makino), the effects of coloring were outstanding in the acid area. But for the preservation, it might be desirable that used a lye in a dye-stuff obtained at $40{\pm}5^{\circ}C$. 2. As for saffron(Curcuma longa L.), when used alum as a mordant, it was colored to a medium yellow color with green color. But easily discolorated and was not desirable. And, it didn't fit in a dye-stuff of Hanji. 3. For safflower(Carthamus tinctorius L.), when pH was in the low acid it was colored to the cleaner yellow color. It was the distinction of discoloration that the degree of brightness's increase was low. 4. For amur cork-tree(Phellodendron amurense Rupr.), the effects of yellow coloring were great in the areas of acidity and alkali. But, when used alum, the degree of the discoloration was high and was not effective. 5. For pagoda tree(Styphnolobium Japonica L.), using a calcium hydroxide as a mordant, enabled the more than average yellow to be gained. The degree of discoloration was good.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.1-9
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• 2007

OSP(organic solderability preservatives) finish has been considered as a very effective process for substituting the metal surface treatment of Ni/Au finish because of lower cost, interface property and environmental issue of OSP finish. However, the discoloration of OSP layer is formed during assembly process consisting of various steps of temperature. The causes of discoloration and the characterization of solder joint were investigated with a degree of discoloration and the assembly process of OSP finished products, which was also compared statistically with that of conventional Ni/Au finished products. As the results, the solution of process trouble for OSP finished products is able to be offered.

• Journal of Radiation Industry
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• v.7 no.1
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• pp.23-28
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• 2013

In this study, we fabricated high density polyethylene (HDPE) composites filled with antioxidants and UV stabilizers. The electron beam irradiation on the fabricated composites was carried out over a range of absorbed doses from 50 to 200 kGy to confirm the changes of discoloration. The changes of discoloration were characterized using a color difference meter and FT-IR for confirming the changes of the color difference and structural change. It was observed that the color difference of IRGANOX 1010-, IRGAFOS 168-, and TINUVIN 328- added HDPE was higher than that of the control HDPE by electron beam irradiation. The melting temperature of UV stabilizer-added HDPE was not significantly changed by electron beam irradiation. However, the melting temperature of phenol-containing antioxidant-added HDPE was increased with increasing the absorbed dose. And the melting temperature of phosphorus-containing antioxidant-added composite was decreased with increasing the absorbed dose.

• Journal of the Korean Wood Science and Technology
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• v.51 no.3
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• pp.173-182
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• 2023

Color is an attribute of visual perception and can be an important factor that affects the preference of customers toward bamboo and wood products. Solar radiation can discolor bamboo surfaces and initiate cracking. The purpose of this study is to investigate the effects of an ultraviolet (UV)-protective coating on the photodiscoloration of untreated and heat-treated Phyllostachys bambusoides bamboo surfaces. Artificial UVA radiators are set at a UVA irradiance of 2,000 W/m² to accelerate the aging of the outer surfaces of hot-air-dried and heat-treated bamboo samples. Half of the samples are coated with transparent UV-protective paint. As the UVA radiation progresses, the discoloration prevention efficiency (DPE) of the UV-protective coating on all samples decreases gradually. The DPEs of the hot-air-dried samples are estimated to be 31.4% and 18.8% after 21 and 72 hours of artificial UVA radiation, respectively. The heat-treated samples exhibit similar trends (29.0% after 21 hours and 10.3% after 72 hours). Recoating the UV-protective paint periodically every six months is expected to minimize the discoloration of the bamboo's outer surface.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.412-412
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• 2008

ENIG(Electroless Nickel Immersion Gold)is a surface treatment method that is used most widely at fine pitch's SMT and BGA packaging process. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. But when the discoloration occurred on the Au finish of ENIG, some key characteristics related to the quality and reliability of PCB such as bondability, solderability and electrical flowing of packaging process could be deteriorated. In this paper, we have performed the water dip test ($88^{\circ}C$ purified water) which accelerates the galvanic corrosion of Ni diffused from the Ni-P layer. That is, the excessive oxidation of the Ni layer could result in non-wetting of the solder because the flux may not be able to remove excessive oxides. Though Au discoloration have been reported to be caused by Ni oxides in many literature, it is still open to verify and discuss The microstructures and chemical compositions have been investigated using FE-SEM, TEM, FIB, EDS and XPS. As a result, authors have found that the Au discoloration in ENIG type is severely caused by the oxidation of the Ni and the mechanism of Au discoloration can be confirmed through the experiment result of water dip test.

• Journal of the korean academy of Pediatric Dentistry
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• v.41 no.4
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• pp.335-343
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• 2014

Regenerative endodontic treatment has the potential to heal a necrotic pulp, which can affect root development in immature teeth. However, several drawbacks and unfavorable outcomes are associated with regenerative endodontic treatment, of which the most significant is coronal discoloration due to the presence of minocycline in triple antibiotic paste and mineral trioxide aggregate (MTA). To prevent tooth discoloration following pulp treatment, the modified triple antibiotics (ciprofloxacin, metronidazole, clindamycin) were used as canal disinfectants and Retro MTA, a $ZrO_2$-containing calcium aluminate cement, was used to seal the canal. Following access cavity acquisition, the canal was copiously irrigated with 2.5% sodium hypochlorite. A modified triple antibiotic paste was then applied to the canal. Once the tooth was asymptomatic (after between 3 and 8 weeks), Retro MTA was carefully placed over the blood clot or a collagen plug. Follow-up radiographs revealed normal periodontal ligament space and root development. In two cases, successful regenerative endodontic treatment of the infected immature tooth, without discoloration, was achieved with disinfection using modified triple antibiotics and Retro MTA sealing.