• Journal of Internet Computing and Services
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• v.16 no.1
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• pp.57-65
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• 2015

As information technology fusion is accelerated, the researches to improve the quality and productivity of crops inside a plant factory actively progress. Advanced growth environment management technology that can provide thermal environment and air flow suited to the growth of crops and considering the characteristics inside a facility is necessary to maximize productivity inside a plant factory. Currently running plant factories are designed to rely on experience or personal judgment; hence, design and operation technology specific to plant factories are not established, inherently producing problems such as uneven crop production due to the deviation of temperature and air flow and additional increases in energy consumption after prolonged cultivation. The optimization process has to be set up in advance for the arrangement of air flow devices and operation technology using computational fluid dynamics (CFD) during the design stage of a facility for plant factories to resolve the problems. In this study, the optimum arrangement and air flow of air circulation fans were investigated to save energy while minimizing temperature deviation at each point inside a plant factory using CFD. The condition for simulation was categorized into a total of 12 types according to installation location, quantity, and air flow changes in air circulation fans. Also, the variables of boundary conditions for simulation were set in the same level. The analysis results for each case showed that an average temperature of 296.33K matching with a set temperature and average air flow velocity of 0.51m/s suiting plant growth were well-maintained under Case 4 condition wherein two sets of air circulation fans were installed at the upper part of plant cultivation beds. Further, control of air circulation fan set under Case D yielded the most excellent results from Case D-3 conditions wherein air velocity at the outlet was adjusted to 2.9m/s.

• Korean Journal of Food Science and Technology
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• v.35 no.5
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• pp.905-913
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• 2003

The physicochemical properties of rice flour roasted at various temperatures and times were analyzed, and the quality characteristics of tarakjuk made from these roasted rice flours were investigated. As roasting temperature and time increased, rice flour showed decreasing moisture, protein content, and glucose the major reducing sugar of rice flour. Total amino acid content did not show any significant changes, but the amount of free amino acids and individual amino acids, such as lysine, tryptophane, and tyrosine, decreased. A decrease in L value and increases in a and b values from both roasted rice flour and tarakjuk was observed. Reduced crystallinity and gelatinization temperatures of roasted rice flour were investigated with X-ray diffractogram and DSC, respectively. The thermal transitions between $100.6{\sim}127.6^{\circ}C$ of tarakjuk by DSC are considered to be due to the melting of amylose-lipid complex. As the roasting temperature and time of rice flours increased, tarakjuk showed lower viscosity and higher spreadability. Sensory characteristics, such as nutty flavor, color intensity, and gritty texture increased significantly. Tarakjuk made from rice flour roasted at $185^{\circ}C$ for 25min showed the highest score on overall preference. From the above results, roasted rice flour produced more preferable tarakjuk than nonroasted flour in terms of sensory quality.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.1
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• pp.60-68
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• 2015

The study of waste activated sludge (WAS) solubilization has been increased for sludge volume reduction and enhancing the efficiency of anaerobic digestion. Microwave (MW)-assisted solubilization is an effective method for the solubilization of WAS because this method can lead to thermal, nonthermal effect and ionic conduction by dielectric heating. In this study, the solubilization of WAS by MW heating and conductive heating (CH) was compared and to enhance the MW-assisted solubilization of WAS at low MW output power, chemical agents were applied such as $H_2SO_4$ as the strong acid and $CaCl_2$, NaCl as the ionic materials. Compared to the COD solubilization of WAS by CH, that by MW heating was approximately 1.4, 6.2 times higher at $50^{\circ}C$, $100^{\circ}C$, respectively and the highest COD solubilization of WAS was 10.0% in this study of low MW output power condition. At the same MW output power and reaction time in chemically agents assisted experiments, the COD solubilization of WAS were increased up to 18.1% and 12.7% with the addition of $H_2SO_4$ and NaCl, however, that with the addition of $CaCl_2$ was 10.7%. This result might be due to the fact that the precipitation reaction occurred by calcium ion ($Ca^{2+}$) and phosphate ion (${PO_4}^{3-}$) produced in WAS after MW-assisted solubilization. In this study, $H_2SO_4$ turned out to be the optimal agent for the enhancement of MW efficiency, the addition of 0.2 M $H_2SO_4$ was the most effective condition for MW-assisted WAS solubilization.

• Korean Journal of Optics and Photonics
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• v.20 no.5
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• pp.266-271
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• 2009

We designed a thermo-optic switch based on a directional coupler with not only a high extinction ratio but also significantly low power consumption. The switch operates by using the thermo-optic effect of the polymer which the refractive index changes by heating the electrode. If the electrode is not powered (OFF), the input light will be coupled completely to the other waveguide. When the electrode is powered at a certain level (ON), input light launched into the input waveguide will remain in that waveguide due to the lower index adjusted in the other waveguide. The switch based on the directional coupler was designed using the generalized extinction ratio curve and the lateral shift of the input waveguide. The coupling length is 1,610 ${\mu}m$ and the extinction ratios are -28 and -30 dB for ON and OFF states, respectively. The electrode structures were optimized by thermal analysis. The transported heat into the waveguide is increased, as the electrode width (w) is increased and the center distance between the electrode and the waveguide (d) is decreased. Also, because the heat generated in the electrode affects the other waveguide, the temperature difference between two waveguides is varied as the given w and d. There are specific conditions which have the maximum of the temperature difference. That of the temperature difference is increased as the width and the temperature of the electrode are increased. Especially, when the switch is designed using the condition with the maximum of the temperature difference for switching, the temperature of the electrode can be decreased. We expect this condition will be the novel method for the reduction of the power consumption in a thermo-optic switch.

• Journal of Bio-Environment Control
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• v.31 no.3
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• pp.143-151
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• 2022

This study was carried out to investigate quantitative characteristics of the cooling effect in a single-span arch greenhouse with roll-up side vents depending on operation of circulation and exhaust fans during ventilation, in order to suggest a practical strategy regarding installation or operation of forced ventilation systems. The examination was conducted under 3 different ventilation conditions (side vents only, side vents + circulation fans, and side vents + circulation fans + exhaust fans). In each condition, variations of internal and external air temperatures and exogenous environmental factors were recorded during ventilation, and the cooling effects were investigated by comparing the normalized temperature difference (NTD) of each ventilation condition. In the morning time (11:00-12:00), a temporary peak in the temperature difference was observed at the beginning of ventilation regardless of ventilation methods. The time taken to the maximum NTD was decreased from 340 s to 110s, and the NTD was dropped from 1.158 to 1.037 as the more forced ventilation systems were operated. The more operations caused the passing time over specific NTD values reduced by 60% as the time was reduced from 1,030 s to 550 s at NTD = 0.8, 1,610 s to 915 s at NTD = 0.6, and 2,315 s to 1,360 s at NTD = 0.4. The temporary peak in NTD was not observed in the afternoon time (14:00-15:00) but it was dropped as quickly as the ventilation started. Also the more operations resulted in the passing time over specific NTD values reduced by 70% as the time was reduced from 560 s to 345 s at NTD = 0.8, from 825 s to 540 s at NTD = 0.6, and from 1,145 s to 810 s at NTD = 0.4. Conclusively, the intervention of the forced ventilation system is recommended in the morning time or in high thermal conditions to achieve more effective and economical ventilation.

• Journal of Bio-Environment Control
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• v.5 no.2
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• pp.215-235
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• 1996

The thermal analysis by mathematical model simulation makes it possible to reasonably predict heating and/or cooling requirements of certain greenhouses located under various geographical and climatic environment. It is another advantages of model simulation technique to be able to make it possible to select appropriate heating system, to set up energy utilization strategy, to schedule seasonal crop pattern, as well as to determine new greenhouse ranges. In this study, the control pattern for greenhouse microclimate is categorized as cooling and heating. Dynamic model was adopted to simulate heating requirements and/or energy conservation effectiveness such as energy saving by night-time thermal curtain, estimation of Heating Degree-Hours(HDH), long time prediction of greenhouse thermal behavior, etc. On the other hand, the cooling effects of ventilation, shading, and pad ||||&|||| fan system were partly analyzed by static model. By the experimental work with small size model greenhouse of 1.2m$\times$2.4m, it was found that cooling the greenhouse by spraying cold water directly on greenhouse cover surface or by recirculating cold water through heat exchangers would be effective in greenhouse summer cooling. The mathematical model developed for greenhouse model simulation is highly applicable because it can reflects various climatic factors like temperature, humidity, beam and diffuse solar radiation, wind velocity, etc. This model was closely verified by various weather data obtained through long period greenhouse experiment. Most of the materials relating with greenhouse heating or cooling components were obtained from model greenhouse simulated mathematically by using typical year(1987) data of Jinju Gyeongnam. But some of the materials relating with greenhouse cooling was obtained by performing model experiments which include analyzing cooling effect of water sprayed directly on greenhouse roof surface. The results are summarized as follows : 1. The heating requirements of model greenhouse were highly related with the minimum temperature set for given greenhouse. The setting temperature at night-time is much more influential on heating energy requirement than that at day-time. Therefore It is highly recommended that night- time setting temperature should be carefully determined and controlled. 2. The HDH data obtained by conventional method were estimated on the basis of considerably long term average weather temperature together with the standard base temperature(usually 18.3$^{\circ}C$). This kind of data can merely be used as a relative comparison criteria about heating load, but is not applicable in the calculation of greenhouse heating requirements because of the limited consideration of climatic factors and inappropriate base temperature. By comparing the HDM data with the results of simulation, it is found that the heating system design by HDH data will probably overshoot the actual heating requirement. 3. The energy saving effect of night-time thermal curtain as well as estimated heating requirement is found to be sensitively related with weather condition: Thermal curtain adopted for simulation showed high effectiveness in energy saving which amounts to more than 50% of annual heating requirement. 4. The ventilation performances doting warm seasons are mainly influenced by air exchange rate even though there are some variations depending on greenhouse structural difference, weather and cropping conditions. For air exchanges above 1 volume per minute, the reduction rate of temperature rise on both types of considered greenhouse becomes modest with the additional increase of ventilation capacity. Therefore the desirable ventilation capacity is assumed to be 1 air change per minute, which is the recommended ventilation rate in common greenhouse. 5. In glass covered greenhouse with full production, under clear weather of 50% RH, and continuous 1 air change per minute, the temperature drop in 50% shaded greenhouse and pad ＆ fan systemed greenhouse is 2.6$^{\circ}C$ and.6.1$^{\circ}C$ respectively. The temperature in control greenhouse under continuous air change at this time was 36.6$^{\circ}C$ which was 5.3$^{\circ}C$ above ambient temperature. As a result the greenhouse temperature can be maintained 3$^{\circ}C$ below ambient temperature. But when RH is 80%, it was impossible to drop greenhouse temperature below ambient temperature because possible temperature reduction by pad ||||&|||| fan system at this time is not more than 2.4$^{\circ}C$. 6. During 3 months of hot summer season if the greenhouse is assumed to be cooled only when greenhouse temperature rise above 27$^{\circ}C$, the relationship between RH of ambient air and greenhouse temperature drop($\Delta$T) was formulated as follows : $\Delta$T= -0.077RH＋7.7 7. Time dependent cooling effects performed by operation of each or combination of ventilation, 50% shading, pad ＆ fan of 80% efficiency, were continuously predicted for one typical summer day long. When the greenhouse was cooled only by 1 air change per minute, greenhouse air temperature was 5$^{\circ}C$ above outdoor temperature. Either method alone can not drop greenhouse air temperature below outdoor temperature even under the fully cropped situations. But when both systems were operated together, greenhouse air temperature can be controlled to about 2.0-2.3$^{\circ}C$ below ambient temperature. 8. When the cool water of 6.5-8.5$^{\circ}C$ was sprayed on greenhouse roof surface with the water flow rate of 1.3 liter/min per unit greenhouse floor area, greenhouse air temperature could be dropped down to 16.5-18.$0^{\circ}C$, whlch is about 1$0^{\circ}C$ below the ambient temperature of 26.5-28.$0^{\circ}C$ at that time. The most important thing in cooling greenhouse air effectively with water spray may be obtaining plenty of cool water source like ground water itself or cold water produced by heat-pump. Future work is focused on not only analyzing the feasibility of heat pump operation but also finding the relationships between greenhouse air temperature(T$_{g}$ ), spraying water temperature(T$_{w}$ ), water flow rate(Q), and ambient temperature(T$_{o}$).

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.1
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• pp.1-17
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• 2002

The purpose of this study is to examine the possibility of thermal injury to bone tissues during an implant site preparation under the same condition as a typical clinical practice of $Br{\aa}nemark$ implant system. All the burs for $Br{\aa}nemark$ implant system were studied except the round bur The experiments involved 880 drilling cases : 50 cases for each of the 5 steps of NP, 5 steps of RP, and 7 steps of WP, all including srew tap, and 30 cases of 2mm twist drill. For precision drilling, a precision handpiece restraining system was developed (Eungyong Machinery Co., Korea). The system kept the drill parallel to the drilling path and allowed horizontal adjustment of the drill with as little as $1{\mu}m$ increment. The thermocouple insertion hole. that is 0.9mm in diameter and 8mm in depth, was prepared 0.2mm away from the tapping bur the last drilling step. The temperatures due to countersink, pilot drill, and other drills were measured at the surface of the bone, at the depths of 4mm and 8mm respectively. Countersink drilling temperature was measured by attaching the tip of a thermocouple at the rim of the countersink. To assure temperature measurement at the desired depths, 'bent-thermocouples' with their tips of 4 and 8mm bent at $120^{\circ}$ were used. The profiles of temperature variation were recorded continuously at one second interval using a thermometer with memory function (Fluke Co. U.S.A.) and 0.7mm thermocouples (Omega Co., U.S.A.). To simulate typical clinical conditions, 35mm square samples of bovine scapular bone were utilized. The samples were approximately 20mm thick with the cortical thickness on the drilling side ranging from 1 to 2mm. A sample was placed in a container of saline solution so that its lower half is submerged into the solution and the upper half exposed to the room air, which averaged $24.9^{\circ}C$. The temperature of the saline solution was maintained at $36.5^{\circ}C$ using an electric heater (J. O Tech Co., Korea). This experimental condition was similar to that of a patient s opened mouth. The study revealed that a 2mm twist drill required greatest attention. As a guide drill, a twist drill is required to bore through a 'virgin bone,' rather than merely enlarging an already drilled hole as is the case with other drills. This typically generates greater amount of heat. Furthermore, one tends to apply a greater pressure to overcome drilling difficulty, thus producing even greater amount heat. 150 experiments were conducted for 2mm twist drill. For 140 cases, drill pressure of 750g was sufficient, and 10 cases required additional 500 or 100g of drilling pressure. In case of the former. 3 of the 140 cases produced the temperature greater than $47^{\circ}C$, the threshold temperature of degeneration of bone tissue (1983. Eriksson et al.) which is also the reference temperature in this study. In each of the 10 cases requiring extra pressure, the temperature exceeded the reference temperature. More significantly, a surge of heat was observed in each of these cases This observations led to addtional 20 drilling experiments on dense bones. For 10 of these cases, the pressure of 1,250g was applied. For the other 10, 1.750g were applied. In each of these cases, it was also observed that the temperature rose abruptly far above the thresh old temperature of $47^{\circ}C$, sometimes even to 70 or $80^{\circ}C$. It was also observed that the increased drilling pressure influenced the shortening of drilling time more than the rise of drilling temperature. This suggests the desirability of clinically reconsidering application of extra pressures to prevent possible injury to bone tissues. An analysis of these two extra pressure groups of 1,250g and 1,750g revealed that the t-statistics for reduced amount of drilling time due to extra pressure and increased peak temperature due to the same were 10.80 and 2.08 respectively suggesting that drilling time was more influenced than temperature. All the subsequent drillings after the drilling with a 2mm twist drill did not produce excessive heat, i.e. the heat generation is at the same or below the body temperature level. Some of screw tap, pilot, and countersink showed negative correlation coefficients between the generated heat and the drilling time. indicating the more the drilling time, the lower the temperature. The study also revealed that the drilling time was increased as a function of frequency of the use of the drill. Under the drilling pressure of 750g, it was revealed that the drilling time for an old twist drill that has already drilled 40 times was 4.5 times longer than a new drill The measurement was taken for the first 10 drillings of a new drill and 10 drillings of an old drill that has already been used for 40 drillings. 'Test Statistics' of small samples t-test was 3.49, confirming that the used twist drills require longer drilling time than new ones. On the other hand, it was revealed that there was no significant difference in drilling temperature between the new drill and the old twist drill. Finally, the following conclusions were reached from this study : 1 Used drilling bur causes almost no change in drilling temperature but increase in drilling time through 50 drillings under the manufacturer-recommended cooling conditions and the drilling pressure of 750g. 2. The heat that is generated through drilling mattered only in the case of 2mm twist drills, the first drill to be used in bone drilling process for all the other drills there is no significant problem. 3. If the drilling pressure is increased when a 2mm twist drill reaches a dense bone, the temperature rises abruptly even under the manufacturer-recommended cooling conditions. 4. Drilling heat was the highest at the final moment of the drilling process.

• Korean Journal of Agricultural and Forest Meteorology
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• v.15 no.2
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• pp.76-84
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• 2013

An adequate downscaling of the official forecasts of Korea Meteorological Administration (KMA) is a prerequisite to improving the value and utility of agrometeorological information in rural areas, where complex terrain and small farms constitute major features of the landscape. In this study, we suggest a simple correction scheme for scaling down the KMA temperature forecasts from mesoscale (5 km by 5 km) to the local scale (30 m by 30 m) across a rural catchment, especially under temperature inversion conditions. The study area is a rural catchment of $50km^2$ area with complex terrain and located on a southern slope of Mountain Jiri National Park. Temperature forecasts for 0600 LST on 62 days with temperature inversion were selected from the fall 2011-spring 2012 KMA data archive. A geospatial correction scheme which can simulate both cold air drainage and the so-called 'thermal belt' was used to derive the site-specific temperature deviation across the study area at a 30 m by 30 m resolution from the original 5 km by 5 km forecast grids. The observed temperature data at 12 validation sites within the study area showed a substantial reduction in forecast error: from ${\pm}2^{\circ}C$ to ${\pm}1^{\circ}C$ in the mean error range and from $1.9^{\circ}C$ to $1.6^{\circ}C$ in the root mean square error. Improvement was most remarkable at low lying locations showing frequent cold pooling events. Temperature prediction error was less than $2^{\circ}C$ for more than 80% of the observed inversion cases and less than $1^{\circ}C$ for half of the cases. Temperature forecasts corrected by this scheme may accelerate implementation of the freeze and frost early warning service for major fruits growing regions in Korea.

• Korean Chemical Engineering Research
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• v.50 no.4
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• pp.684-689
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• 2012

Poly(acrylic acid) (PAA) microspheres is one of the widely-used polymeric materials for the bio-field application and the electric materials. For the synthesis of PAA microspheres, the polymerization technique using surfactants is applied. After the synthesis, the purification and separation processes are required for the removal of surfactant. When general organic solvents were used, many problems, such as huge amount of waste solvent, additional separation processes, and the possibility of residual media, were occurred. Thus, High-pressure Soxhlet extraction using liquid $CO_2$ was developed to solve these problems. In this study, High-pressure Soxhlet extraction of the synthesized PAA microspheres using liquid $CO_2$ was conducted for the removal of Monasil PCA which is used for the dispersion polymerization of acrylic acid in compressed liquid Dimethyl ether (DME). The morphology of the extracted PAA particles was checked by field emission scanning electron microscopy (FE-SEM) and the residual concentration of Monasil PCA was analyzed by inductively coupled plasma - Optical Emission Spectrometer (ICP-OES). For studying the effect of the solvent effect, Soxhlet extraction was conducted using n-hexane, liquid DME, and liquid $CO_2$. In case of n-hexane, some extracted PAA microspheres were produced. However, deformation was also occurred due to the high thermal energy of n-hexane vapor. Liquid DME could not remove Monasil PCA. When using liquid $CO_2$, the extracted PAA microspheres which were free for the residual solvent were produced without deformation. For finding the optimum operating condition, high-pressure Soxhlet extraction was conducted for 8 hours with changing the temperature of reboiler and condenser. When the extractor temperature is $19.6{\pm}0.2^{\circ}C$ and the pressure is $51.5{\pm}0.5$ bar, the best removal efficiency was obtained.

• Journal of the Korea Organic Resources Recycling Association
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• v.16 no.2
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• pp.47-56
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• 2008

The objective of this research is to evaluate the optimum recycling methods for the sewage sludge cakes at different microwave power-settings and for different periods of time. The dehydrated sewage sludge cakes used in this study was obtained from N wastewater treatment plan in the P City. The beginning drying processes were carried out in a microwave oven with 2,450 MHz frequency and power ranges of 1kW to 4 kW. The continuous conveyer drying system was also operated with 2,450 MHz frequency and power setting, ranging from of 1 kW to 6 kW. Initial moisture content of the sewage cake is 78~80%, and the moisture content decreased rapidly up to 0.2~2(wt%) within short periods due to breaking the cell walls. This study is also conducted to evaluate the characteristics of sewage sludge cakes with respect to important physical parameters effect on the thermal kinetics for evaporation water in the sludge which are operation times, moisture contents, drying rates, input amounts, flow rates and calorific values. It takes 60 minutes and 120 minutes to reach the critical moisture contents with power setting of 4 kW for 3kg/min and 6kg/min of the flow rates respectively. It takes 120 minutes and 110 minutes to reach the critical moisture contents with flow rates of 2.5 cm/min and sludge input of 6kg/min for the power settings of 4 kW and 6 kW respectively. The most effective value of the power for drying the sludge is 4 kW. Operation with 6kg/min and 4kW on 2cm of the sludge thickness can be effectively and inexpensively to reach the critical moisture contents, when you compare 2cm of the sludge thickness with 1cm and 3cm of the sludge thickness.