• Journal of the Korean Wood Science and Technology
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• v.35 no.5
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• pp.7-15
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• 2007

To evaluate the durability of finger-jointed woods according to change of humidity conditions, four types of finger-jointed woods glued with different kinds of adhesives and finger pitches were made with Sitka spruce, and the effect of humidity conditions on creep performances was investigated. The shape of creep curves differed among humidity conditions, and the inclination of creep curves was greatest in 85%RH, and lowest in 65%RH. Their creep curves showed a linear behavior beyond approximately one hour, regardless of humidity conditions. The A values of the creep curves fitted to power law increased with increasing relative humidity, whereas the A' values were in order of 30 > 85 > 65%RH unlike the A values. The initial deformation increased with increasing relative humidity, whereas the creep deformation unlike the initial deformation was in order of 85 > 30 > 65%RH, and it was found that the creep deformation of finger-jointed woods indicated the smaller amount in air-dry moisture content rather than in a low moisture content less than 30%RH. Finger-jointed woods with 6.8 mm (L) pitch had the greater creep amount than in those with 4.4 mm (S) pitch in all humidity conditions. The difference of creep amount between both adhesives in all humidity conditions was small. Relative creep at 240 hr was greatest as 62.2~71.9% in 85%RH, and the values indicated 2.1~2.6 times that of 30%RH and 3.0~3.6 times that of 65%RH and were equal or slightly greater than that of solid spruce.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.461-466
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• 1999

The humidity sensor containing ammonium salt was prepared from the copolymer of 2-methacryloxyethyl dimethyl 2-hydroxyethyl ammonium bromide (MDHAB)/MMA/DAEMA = 6/3/1. The humid membrane was fabricated on the gold/alumina electrode by dipping. The impedances were $298k{\Omega},\;11k{\Omega}$, and $2.3k{\Omega}$ at 40%RH, 70%RH and 90%RH, respectively, at $5^{\circ}C$ and the humidity-sensitive characteristics were suitable for low temperature humidity sensor. The temperature-dependent coefficient between $5^{\circ}C$ and $20^{\circ}C$ was found to be $-0.80%RH/^{\circ}C$ and the hysteresis falled in the ${\pm}2%RH$ range. The response time was found to be 38 sec for the relative humidity ranging from 34%RH to 88%RH at $20^{\circ}C$. The reliabilities such as temperature cycle, humidity cycle, high temperature and humidity resistance, electrical load stability, stability of long-term storage and water durability were measured and evaluated for the application as a humidity sensor.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.6 no.1
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• pp.125-137
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• 1996

This study was designed to investigate effects of relative humidity on the breakthrough of charcoal tubes at a fixed vapor concentration and sampling time during mixed organic vapor sampling. A vapor generator was used to generate three different concentrations of mixed organic vapor and a stainless steel chamber was fabricated and utilized to maintain three different percentages of relative humidity while maintaining a constant temperature. The results were as follows; 1. At high relative humidity, breakthrough of mixed organic vapor occurred quickly at low vapor concentration than at high vapor concentration because of the reduced adsorption volume of charcoal tube due to humidity. 2. Breakthrough by competitive adsorption of vapors onto charcoal tube was observed at first from n-hexane having the lowest boiling point and highest vapor pressure among the three organic vapors investigated, followed by TCE. No breakthrough was observed from toluene under all experimental conditions. 3. For n-hexane, breakthrough was observed after 2 hours of sampling and breakthrough rates were increased as relative humidity increased. For TCE, breakthrough was found after 3 hours of sampling and breakthrough rates by sampling time were increased as vapor concentration increased. 4. The adsorbed amount of mixed organic vapor at breakthrough was shown to have statistically significant correlations with sampling time, relative humidity, and vapor concentration in descending order of correlation. Relative humidity and sampling time for n-hexane and sampling time and concentration for TCE were both statistically significantly correlated. 5. Relative humidity was found to affect the amount of breakthrough of mixed organic vapor and n-hexane. Among three percentages of relative humidity investigated, the amount of breakthrough at 85 % relative humidity was significantly larger than those of at lower percentages of relative humidity. No statistically significant difference was found between 25 % and 55 % relative humidity. 6. The results of multiple regression analysis between breakthrough and relative humidity, vapor concentrations showed that the coefficient of determination of mixed organic vapor was 0.263 and those of n-hexane and TCE were 0.275 and 0.189, respectively. 7. Flow rates of sampling pumps used were found to be affected by relative humidity present. At 25 %, 55 %, and 85 % relative humidity, the relative errors of sampling pump were 1.4 %, 13.4 %, and 18.6 %, respectively. In conclusion, the results of this study showed that high relative humidity could reduce the adsorption volume of charcoal tubes and subsequently increase breakthrough rates. Therefore, to prevent breakthrough when sampling mixed organic vapors, it is suggested that either sampling volume be reduced on the flow rate be lowered so as to minimize breakthrough of the most volatile organic vapor in the mixture. In addition, since the flow rates of a sampling pump can be adversely affected by high relative humidity, it is recommended to use a constant flow mode pump when sampling in the highly humid environment.

• Journal of Environmental Science International
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• v.13 no.9
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• pp.767-777
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• 2004

This study evaluated the technical feasibility of the application of $TiO_2$ photocatalysis for the removal of volatile hydrocarbons(VHC) at low ppb concentrations commonly associated with non-occupational indoor air quality issues. A series of experiments was conducted to evaluate five parameters (relative humidity (RH), hydraulic diameter (HD), feeding type (FT) of VHC, photocatalytic oxidation (PCO) reactor material (RM), and inlet port size (IPS) of PCO reactor) for the PCO destruction efficiencies of the selected target VHC. None of the target VHC presented significant dependence on the RH, which are inconsistent with a certain previous study that reported that under conditions of low humidity and a ppm toluene inlet level, there was a drop in the PCO efficiency with decreasing humidity. However, it is noted that the four parameters (HD, RM, FT and IPS) should be considered for better VHC removal efficiencies for the application of $TiO_2$ photocatalytic technology for cleansing non-occupational indoor air. The PCO destruction of VHC at concentrations associated with non-occupational indoor air quality issues can be up to nearly 100%. The amount of CO generated during PCO were a negligible addition to the indoor CO levels. These abilities can make the PCO reactor an important tool in the effort to improve non-occupational indoor air quality.

• Journal of Environmental Science International
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• v.31 no.4
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• pp.311-318
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• 2022

In this study, we analyzed the relationships between weather factors and photosystem II activity (F_v/F_m), as a measure of photochemical efficiency, in three cool-season turfgrasses commonly planted on golf courses in Jeju, South Korea: perennial ryegrass (Lolium perenne L.), Kentucky bluegrass (Poa pratensis L.), and creeping bentgrass (Agrostis palustris Huds.). In all three turfgrasses, F_v/F_m was higher during late summer than during early summer. However, in late summer, F_v/F_m was significantly lower in perennial ryegrass than in the other two species. In early summer, F_v/F_m in perennial ryegrass and Kentucky bluegrass was positively correlated with mean low temperature and extreme minimum temperature, whereas, in late summer, this parameter in Kentucky bluegrass and creeping bentgrass was positively correlated with relative humidity, and in creeping bentgrass was negatively correlated with mean high temperature, mean low temperature, and extreme maximum temperature. These results indicate that raising low temperatures is favorable for perennial ryegrass and Kentucky bluegrass in early summer, whereas, in late summer, the lowering of high temperatures proves to be beneficial for creeping bentgrass, and raising relative humidity is conducive to the growth of Kentucky bluegrass and creeping bentgrass. These findings will contribute to improving the selection and management of turfgrasses on golf courses and sports fields.

• Particle and aerosol research
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• v.18 no.4
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• pp.109-127
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• 2022

Recently, low-cost particulate matter (PM) sensors have been widely used in monitoring mass concentration. Maintaining the accuracy of the sensors is important and requires rigorous performance evaluation and calibration. In this study, two commercial low-cost PM sensors(LCS), Plantower PMS3003 and Plantower PMS7003, were evaluated in the laboratory and field with a reference-grade PM monitor (GRIMM 11-D). Laboratory evaluation was conducted with single/mixed particles of PSL (Poly Styrene Latex) in an acrylic chamber at 20℃ and relative humidity of 20%. Field evaluation was conducted inside a building of Yonsei University (Shinchon) from February 12 to March 31, 2022. In both evaluations, LCS measured values became different from reference measured values when the relative humidity was high or the outdoor air PM10/PM2.5 ratio was high. Based on the field evaluation, the LCS measured values were corrected through four different regression analysis models. As a result, the multivariate polynomial regression analysis model showed highest matching with the reference PM monitor (PM2.5 >0.9, PM10 >0.85). In this model, the PM10/PM2.5 ratio and relative humidity were chosen as independent variables.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.55 no.1
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• pp.26-30
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• 2006

For the purpose of developing capacitive humidity sensor having interdigital electrodes, interdigital electrode was modeled and simulated to obtain capacitance and sensitivity as a function of geometric parameters like the structural gap and thickness. For the development of ASIC, switched capacitor signal processing circuits for capacitive humidity sensor were designed and simulated by Cadence using $0.25{\mu}m$ CMOS process parameters. The signal processing circuits are composed of amplifier for voltage gain control, and clock generator for sensor driving and switch control. The characteristics of the fabricated sensors are; 1) sensitivity is 9fF/%R.H., 2) temperature coefficient of offset(TCO) is $0.4%R.H./^{\circ}C$, 3) nonlinearity is 1.2%FS, 4) hysteresis is 1.5%FS in humidity range of $3%R.H.{\sim}98%R.H.$. The response time is 50 seconds in adsorption and 70 seconds in desorption. Fabricated process used in this capacitive humidity sensor having interdigital electrode are just as similar as conventional IC process technology. Therefore this can be easily mass produced with low cost, simple circuit and utilized in many applications for both industrial and environmental measurement and control system, such as monitoring system of environment, automobile, displayer, IC process room, and laboratory etc.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.6
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• pp.1080-1086
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• 2007

The aim of this paper is to establish the optimum fabrication condition of specimens, using the Vapor Deposition Polymerization Method(VDPM), which is one of modesto prepare functional organic thin films using a dry process, and to develop a thin film type humidity sensor which has good humidity sensitive characteristics. The inner part of the film became denser and roughness of the film surface eased as curing temperature increased so that thickness of the film could be made uniform. This also shows the appropriate curing temperature was $250^{\circ}C$. The basic structure of the humidity sensor is a parallel capacitor which consists of three layers of Aluminum/Polyimide/Aluminum. The result of SEM and AFM measurement shows that the thickness of PI thin films decreased and the refraction increased as curing temperature increased, which indicates that a capacitance-type humidity sensor utilizing polyimide thin film is fabricated on a glass substrate. The characteristics of fabricated samples were measured under various conditions, and the samples had linear characteristics in the range of 20-80 %RH, independent of temperature change, and low hysteresis characteristic.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.34 no.1
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• pp.46-53
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• 2002

This study was carried out to analyze the effects of preservation temperature and relative humidity to the physical properties of corrugated fiberboard boxes for fruit and vegetable packaging. The preservation temperature did not affect severely to physical properties of corrugated fiber-board. Relative humidity was a major cause of corrugated fiberboard box quality deterioration. The burst and compressive strengths of experimental boxes measured with Mullen high pressure tester and tong crush tester were decreased gradually as relative humidity increased from 55% to 75%. But, the strength properties slightly decreased relative humidity at 75% or higher. This tendency was the greater for single wall (SW) corrugated fiberboard box than that for double wall (DW). It is suggested that development of the water-resistant corrugated fiberboard and box be needed that can be used under the condition of low temperature and high moisture content, which are being employed in the cold chain system.

• Journal of the Korean Ceramic Society
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• v.48 no.4
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• pp.293-297
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• 2011

The thermodynamic behavior of phenolic resin was investigated to verify the relation between the properties of porous ceramics with $ZrO_2$-C system for submerged entry nozzle and the characteristics of phenolic resin with various relative humidity. The green and the sintered density were decreased between 25% and 50% relative humidity, whereas they were gradually enhanced above 50% relative humidity. The highest value of apparent porosity was 20.1% and the minimum compressive strength was 69MPa in the specimen using the powder exposed to 50% relative humidity. As a result of thermal analysis for phenolic resin, the shift of endothermic peak to low temperature and the reduction of exothermic peak were observed, and the peaks corresponded to melting and curing of phenolic resin, respectively. The melting and the curing of phenolic resin generate the change of green density, and it can affect the properties of submerged entry nozzle.