• Journal of Advanced Marine Engineering and Technology
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• v.38 no.6
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• pp.737-743
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• 2014

This paper dealt with a retrofit high power LED searchlight to replace conventional 1kW halogen searchlights. The design specification meets KDS 6230-1046-1 and KS V 8469. An optical lens with the beam angle of $6^{\circ}$ was used to meet the luminous intensity of 800,000cd at $0^{\circ}$ in horizontal line. Heat dissipation of the LED searchlight adopted a free air cooling type which does not use a fan or a heat-pipe. From the test results, power consumption of the prototype LED searchlight was 148W which was saved by 85% comparing a halogen searchlight of 1kW. Luminous intensity was 945,000cd at $0^{\circ}$ in horizontal line, satisfying KS V 8469. Luminous efficacy was improved by 4.7 times higher than that of the halogen searchlights. Beam angle, color temperature, and color rendering index(CRI) was $5.4^{\circ}$, 5,500K, and 70, respectively. Surface temperature of the LED searchlight was below $60^{\circ}C$ and surrounding temperature of the SMPS installed inside was below $50^{\circ}C$ which were satisfied with the IEC 60092-306.

• Restorative Dentistry and Endodontics
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• v.28 no.4
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• pp.354-359
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• 2003

This study evaluated the effectiveness of the light emitting diode(LED) units for composite curing. To compare its effectiveness with conventional quartz tungsten halogen (QTH) light curing unit. the microhardness of 2mm composite. Z250, which had been light cured by the LEDs (Ultralume LED2, FreeLight, Developing product Dl) or QTH (XL 3000) were compared on the upper and lower surface. One way ANOVA with Tukey and Paired t-test was used at 95% levels of confidence. In addition. the amount of linear polymerization shrinkage was compared between composites which were light cured by QTH or LEDs using a custom-made linometer in 10s and 60s of light curing, and the amount of linear polymerization shrinkage was compared by one way ANOVA with Tukey. The amount of polymerization shrinkage at 10s was XL3000 > Ultralume 2. 40. 60 > FreeLight, D1 (P<0.05) The amount of polymerization shrinkage at 60s was XL3000 > Ultralume 2, 60> Ultralume 2.40 > FreeLight, D1 (P<0.05) The microhardness on the upper and lower surface was as follows ; (equation omitted) It was concluded that the LEDs produced lower polymerization shrinkage in 10s and 60s compared with QTH unit. In addition. the microhardness of samples which had been cured with LEDs was lower on the lower surfaces than the upper surfaces whereas there was no difference in QTH cured samples.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.139-140
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• 2006

Some of novel halogen-free, elastomeric flame retardants for nylon-6 have been developed. It is found that the S-ENP and clay have a synergistic flame retardant effect on nylon-6 resulted from the formation of two barriers on the nanocomposite residue surface at the end of combustion. A novel flame retardant ternary nanocomposite of nylon-6/ENP/nano-Magnesium hydroxide was also fabricated. The new ternary composite has better flame retardancy and thermal stability than the conventional one because nano-MH can disperse much more homogeneous in the new ternary composite than in the conventional one.

• Textile Coloration and Finishing
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• v.33 no.4
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• pp.238-249
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• 2021

In this study, the effect on flame retardancy and various physical properties when TiO₂ was added with a citric acid/phosphate complex acid catalyst together with Pyrovatex CP new (N-methylol dimethylphosphonopropionamide), a phosphorus-based flame retardant, was studied on cotton fibers. SEM-EDS analysis was performed to confirm the surface characteristics and surface element analysis of the flame-retardant treated cotton fibers, and a vertical carbonization test was performed to confirm the char formation capability and flame retardancy according to the phosphoric acid ratio. By comparing the LOI index before and after washing 10 times, the washing durability of the flame retardant solution containing the phosphoric acid catalyst and TiO₂ was tested by LOI index after ten washing cycles. In addition, the influence of the flame-retardant processing on the physical properties were compared including thermogravimetric analysis (TGA), tear strength and whiteness.

• Fire Science and Engineering
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• v.16 no.1
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• pp.18-23
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• 2002

Efficiency estimation of toxicity free resistance cable experiments were conducts to understand toxicity free fire ersistance polyolefin insulation material and smoke density characteristic and combustion gas corrosion analysis. A main cause of fire-growth and generating toxic gas when it burns, should be dealt with great care in life safety design. Similar patterned fire incidents such as, Inchon Live-Hof Pub Restaurant as, Sea-land Children Resort have proven that serious loss of lives were caused by hazardous gas generated fire resistance cable materials. In this paper, Referenced documents were ASTM E662 standard test method for specific Ds genalated by solid materials. The furnace control system shall maintain the required irradiance level under steady-state condition with the chamber door closed of 2.5$\pm40.04〔w/$\textrm{cm}^2$〕for 20 min. According to the results of the smoke density analysis of NFR-8 and FR-PVC the highest decomposition flaming smoke density range of NFR-8 and FR-PVC were 25.2 to 37.5 and 51.1 respectively. Nonflaming smoke density range of NFR-8 and FR-PVC were 100.4 to 112.2 and 126.5 to 398.8. Also, the fire gases was occurred carbon monoxide and decomposition than in polyolefin due to incomplete combustion of PVC which has high content of carbon in chemical compound.

• Journal of the Korean Chemical Society
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• v.17 no.3
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• pp.154-162
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• 1973

The rates and activation parameters for the halide $(Cl^{-}, Br^{-}, I^{-})$TeX> exchange reactions of substituted benzenesulfonyl-chloride, $XC_6H_4SO_2Cl$(X:p-MeO, H, p-Cl, p-Br, p-NO$_2l$) in dry acetone at two temperatures have been determined. It was found that the ion-pair of metal halide,$M^{+}X^{-}$, have negligible reactivity compared to free halide ions. It was also found that the nucleophilic order is $Cl^{-}>Br^{-}>I^{-}$for electron-donating substituent, and $Cl^{-}>I^{-}>Br^{-}$ for electron-withdrawing substituents. These results and convex nature of the Hammett plot are interpreted in the light of simple $S_N2$mechanism with the bond breaking becoming important for compounds with the electron withdra-wing substituents.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.1
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• pp.33-41
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• 2011

The objective of this study was to compare the shear bond strengths of five dentin adhesive systems cured with three different light curing sources. Seventy five noncarious permanent teeth were collected and stored in an 0.1% thymol solution at room temperature after extraction. The tested adhesives were: Adper Scotchbond Multi-purpose Plus Adhesive (SM) Adper Single bond 2 (SB), Clearfil SE Bond (SE), Adper Prompt L-Pop (PL), G-Bond (GB). And three light curing unit systems were used: Elipar Free light 2(LED), OptiLux 501 (Halogen), Flipo (PAC). For the shear bonding test, the labial and lingual surfaces of permanent teeth were used. To obtain a flat dentin surface, the labial and lingual surfaces of the teeth were sanded on SiO2 with number 600 grit and then divided into 15 groups of 10 surfaces each. All samples were theromocycled in water $5^{\circ}C$ and $55^{\circ}C$ for 1000 cycles. The results were as follows: 1. When cured with Freelight 2, the shear bond strength of SM was significantly higher than that of PL, GB (p<0.05), whereas no significant difference was found among those of any other bonding agents. 2. When cured with Optilux 501, the shear bond strength of SM was significantly higher than those of any other bonding agents (p<0.05), whereas no singnificant difference was found among those of andy other bonding agents. 3. When cured with Flipo, the shear bond strength of SM was significantly higher than those of SB, SE, GB (p<0.05), whereas no significant differences was found among those of any other bonding agents. 4. For comparison according to three different light cure unit system, except SB and GB, each three dentin bonding agents showed no significant difference. For SB, only Freelight 2 was significantly higher than the others, with no significant difference between Optilux 501 and Flip. For GB, Statistically significant difference was found only between Freelight and Flipo.

• Clean Technology
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• v.23 no.4
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• pp.378-387
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• 2017

To obtain epoxy resin with permanently attached flame-retardant groups, phosphorus compound containing di-hydroxyl group [10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phospha phenanthrene-10-oxide, DOPO-HQ] and silicone compound containing di-hydroxyl group (polydimethylsiloxane, hydroxyl terminated, PDMS) were reacted with uncured epoxy prepolymer (diglycidyl ether of bisphenol A, DGEBA) and then cured using 4,4-diaminodiphenylmethane (DDM) as a crosslinking agent. The properties of the resulting epoxy materials were characterized using Fourier transform infrared (FTIR) spectrometer, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI) test/vertical burning test (UL 94-V test), tensile properties test and impact test. This study examined the effect of phosphorus/silicone compound contents on the thermal/mechanical properties and flame retardancy of cured epoxy resins containing phosphorus and silicone compounds. It was found that the thermal/mechanical properties of epoxy resins containing phosphorus and silicone components were higher than those of simple epoxy resin. The flame-retardancy (LOI: 29.9 ~ 31.8% and UL 94-V: V-0) of all samples containing phosphorus compound and phosphrous compound/silicone compound was found to be passed the flame-retardant requirements (LOI: > 30%, UL 94-V: V-0) of LOI and vertical burning tests. However, the flame-retardancy (LOI: 21.4% and UL 94-V: no rating) of simple epoxy resin was found to be failed the flame-retardant requirements.

• Journal of the Korean Chemical Society
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• v.17 no.4
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• pp.262-268
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• 1973

p-Phenylenediamine was tetrazotized with sodium nitrite in an excess amount of concentrated hydrochloric acid media at -10$^{\circ}$C. It was also tetrazotized almost completely in 45% perchloric acid media. The two diazo groups in the tetrazonium salt were substituted by halogen, and the degree of tetrazotization reaction was observed by dihalobenzene yielded. The result of the tetrazotization was dependent upon the stability of the tetrazonium salt, and the stability was determined by concentration and quantity of the acid media. In dilute acid media the tetrazonium salt was unstable and completely decomposed. In concentrated acid media, though the tetrazonium salt was stable, tetrazotization reaction was retarded. To harmonize the two opposing tendencies it was advisable to find the optimum acidity of media at which the salt was fairly stable. About $40{\sim}45$% of the acid media was suitable. The fact that the $H^+$ ion behaved as a negative catalyst supported the assumption that the diazotization reaction is primarily a reaction between the free amine and a nitroso group. The reaction of tetrazotization is expressed with respect to the kinetics and mechanism of diazotization.