• Journal of Ecology and Environment
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• v.34 no.2
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• pp.193-202
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• 2011

We studied temperature sensitivity characteristics of soil respiration during periods of rising and falling temperatures within a common temperature range. We measured soil respiration continuously through two periods (a period of falling temperature, from August 7, 2003 to October 13, 2003; and a period of rising temperature from May 2, 2004 to July 2, 2004) using an open-top chamber technique. A clear exponential relationship was observed between soil temperature and soil respiration rate during both periods. However, the effects of soil water content were not significant, because the humid monsoon climate prevented soil drought, which would otherwise have limited soil respiration. We analyzed temperature sensitivity using the $Q_{10}$ value and $R_{ref}$ (reference respiration at the average temperature for the observation period) and found that these values tended to be higher during the period of rising temperature than during the period of falling temperature. In the absence of an effect on soil water content, several other factors could explain this phenomenon. Here, we discuss the factors that control temperature sensitivity of soil respiration during periods of rising and falling temperature, such as root respiration, root growth, root exudates, and litter supply. We also discuss how the contribution of these factors may vary due to different growth states or due to the effects of the previous season, despite a similar temperature range.

• Journal of Korean Society on Water Environment
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• v.35 no.4
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• pp.308-315
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• 2019

The objective of this study was to investigate mountain stream water and air temperatures, area, latitude, altitude, and forest coverage in headwater catchments located in Kangwon-do, Mid-eastern Korea from 2015 to 2017. Daily mean value of mountain stream water temperature was approximately $6^{\circ}C$ lower than the daily mean value of air temperature on the monitoring sites during the observation period. Monthly mean value of mountain stream water temperature increased with increasing monthly mean value of air temperature from May to August during the observation period. Seasonal variations of mountain stream water temperature were dependent on air temperature rising and falling periods. Correlation analysis was conducted on mountain stream water temperature to investigate its relationship with air temperature, area, latitude, altitude, and forest coverage of air temperature rising and falling periods. The correlation analysis showed that there exists a relationship (Correlation coefficient: -0.581 ~ 0.825; p<0.05), particularly the air temperature showed highest correlation with mountain stream water temperature. Regression equations could be developed due to contribution of air temperature to affect mountain stream water temperature (Correlation coefficient: 0.742 and 0.825; p<0.01). Therefore, a method using various parameters based on air temperature rising and falling periods, could be recommended for predicting mountain stream water temperature.

• Clean Technology
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• v.7 no.2
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• pp.151-159
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• 2001

Mathematical modeling and numerical simulation studies have been conducted for a falling film type absorber of the ammonia absorption heat pump. A rigorous absorber model has been developed by considering temperature effects on physical properties and its predictability proved far superior to that of existing models, which has been confirmed by the experimental data. Using the developed model, effects of cooling water condition - temperature and flow rate - on the efficiency of absorber has been examined. As the result of simulation, the efficiency of absorber has increased as the cooling water temperature has decreased and flow rate has increased.

• Laser Solutions
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• v.6 no.1
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• pp.1-8
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• 2003

A molten metal droplets are deposited onto solid substrate for solid freeform fabrication, Collision dynamic and substrate heat transfer associated with solidification determine the final shape of molten metal droplets. In this study, the experimental model, based on the variational condition with substrate temperature and falling height, was produced reliable optimal data of droplet pattern.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.342-356
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• 2016

Purpose: The drying of a thin layer of native cassava starch in a tray dryer was modeled to establish an equation for predicting the drying behavior under given conditions. Methods: Drying tests were performed using samples of native cassava starch over a temperature range of $40-60^{\circ}C$. We investigated the variation in the drying time, dynamic equilibrium moisture content, drying rate period, critical moisture content, and effective diffusivity of the starch with temperature. The starch diffusion coefficient and drying activation energy were determined. A modification of the model developed by Hii et al. was devised and tested alongside fourteen other models. Results: For starch with an initial moisture content of 82% (db), the drying time and dynamic equilibrium moisture content decreased as the temperature increased. The constant drying rate phase preceded the falling rate phase between $40-55^{\circ}C$. Drying at $60^{\circ}C$ occurred only in the falling rate phase. The critical moisture content was observed in the $40-55^{\circ}C$ range and increased with the temperature. The effective diffusivity of the starch increased as the drying temperature increased from 40 to $60^{\circ}C$. The modified Hii et al. model produced randomized residual plots, the highest $R^2$, and the lowest standard error of estimates. Conclusions: Drying time decreased linearly with an increase in the temperature, while the decrease in the moisture content was linear between $40-55^{\circ}C$. The constant drying rate phase occurred without any period of induction over a temperature range of $40-55^{\circ}C$ prior to the falling rate period, while drying at $60^{\circ}C$ took place only in the falling rate phase. The effective diffusivity had an Arrhenius relationship with the temperature. The modified Hii et al. model proved to be optimum for predicting the drying behavior of the starch in the tray dryer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3D
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• pp.271-278
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• 2010

Semi rigid pavement is a pavement type using advantages of both flexibility of asphalt pavement and rigidity of concrete pavement by infiltrating cement paste into voids of open graded asphalt mixtures. The semi rigid pavement has better smoothness and smaller driving vibration or noise comparing to the concrete pavement, and has smaller permanent deformation and has temperature falling effect comparing to the asphalt pavement. The temperature falling effect were investigated at a semi rigid overlay pavement test section, and the temperature falling and water retaining effects were verified by measuring the temperature and weight of specimens at a housetop. Horizontal and vertical stresses and strains were compared by structural analysis of the semi rigid pavement and asphalt pavement using the Abaquser o, a commercial 3D finite element analysis program. The results were verified by Bisar 3.0, a multi-layered elastic analysis program. Performance of the semi rigid pavement and asphalt pavement were compared by predicting fatigue cracking based on the structural analysis results.

• The Korean Journal of Malacology
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• v.29 no.4
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• pp.303-311
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• 2013

This study investigated survival, falling and structural changes of foot in Haliotis discus hannai with various water temperature and salinity. Experimental conditions were composed of control with $20^{\circ}C/33.5$ psu, higher temperature group with 23, 26, 29 and $32^{\circ}C$, lower temperature group with 3, 6, 9 and $12^{\circ}C$, and different salinities group with 33.5, 26.8, 20.1, 13.4, 6.7 and 3.3 psu. Experimental period was 7 days. Survival and falling rate of the abalone exposed to 7 days at control and experimental condition of $12^{\circ}C$ and $23^{\circ}C/33.5$ psu were 100% and 0%, respectively. Mortality and falling rate of the abalone exposed to the different temperature and salinity were dose dependent by experimental condition. Histopathological changes in epithelial and muscular layer of foot showed more obvious with experimental condition of salinity decrease than different temperature condition.

• Journal of the Korean Chemical Society
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• v.16 no.2
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• pp.106-116
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• 1972

The universality of the pseudo wet bulb temperature has been established in the drying of macroporous inerts, microporous inerts, and microporous swellable materials using water and methyl alcohol as the liquids. The pseudo wet bulb temperature is a new constant temperature intermediate between the wet bulb and dry bulb temperatures of the air during the second falling rate period. This temperature is calculated from consideration of the heat transfer to, and vapor diffusion from, liquid evaporating at the liquid-air boundary. The experimental results agree with that calculated from the equation proposed by Nissan, Bolles and George.

• Journal of Biosystems Engineering
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• v.40 no.3
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• pp.232-237
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• 2015

Purpose: In Korea, wheat is dried using circulating cross-flow grain dryers. However, there is no research on wheat drying which can be utilized for the dryers. Therefore, this study developed and evaluated a simulation of the circulating cross-flow dryer, and examined the effects of various factors on drying performance. Methods: The simulation program was developed using drying models and was evaluated against wheat-drying experiments with a dryer having a 30-ton capacity. The influence of drying temperature, air volume, and grain falling rate on drying performance were examined through the simulation. Results: The experimental results validated the simulation program by showing the same root mean square error (RMSE) for moisture content (0.286%) and drying rate (0.056%/h) in both the experimental data and the simulation values. The appropriate wheat-drying parameter values, considering drying conditions, were determined to be $50^{\circ}C$ for drying temperature, $500m^3/min$ for air volume, and a grain falling rate of $36.0m^3/h$. Conclusions: The developed simulation program for circulating cross-flow dryers analyzed the influences of performance factors such as drying temperature, air volume, and falling rate on drying performance.

• Korean Journal of Food Science and Technology
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• v.25 no.5
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• pp.558-564
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• 1993

The drying characteristics of fluidized bed drying with different drying conditions using naked barley were carried out. This fluidized drying mechanism of naked barley was consisted of consecutive two falling rate parts, first falling rate period and second falling rate period without showing constant rate period. The drying rate constant was increased with decreasing charged amount and relative humidity and increasing air temperature and air velocity. Since the drying rate constant expressed by Arrhenius type equation in the falling rate period showed good linearity, the falling rate period was considered as the controlling step. The activation energy of first falling step was 1,900 cal/gmol, while for second falling step the values showed 2,500 cal/gmol.