• Korean Journal of Agricultural Science
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• v.47 no.3
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• pp.519-532
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• 2020

Because lotus root has a short shelf life, the quality easily deteriorates. Thus, the harvested lotus roots are processed into a variety of products. Drying is one of the simplest food preservation methods, which can increase food stability. However, the convective drying method takes a long time and requires high energy consumption. Combination drying methods have emerged to overcome the limitations of the convective drying method. This study investigated the drying characteristics of lotus root and determined the optimal drying model of lotus root depending on the microwave and hot-air combination drying conditions. The lotus root slices (5 mm in thickness and 40 mm in diameter) were dried by different drying conditions that were combined with three microwave power levels (50, 100, and 150 W) and two hot air temperatures (50 and 60℃) at a velocity of 5 m·s^-1. Eight drying models were tested to evaluate the fit to the experimental drying data, and the effective moisture diffusion (D_eff) values of the lotus root slices dried by combination drying were estimated. The combination drying time of the lotus root was significantly reduced with the high air temperature and microwave power. The effective moisture diffusion (D_eff) of lotus root was more affected by the air temperature than microwave power intensity. Logarithmic model was most suitable to describe the drying curve of lotus root in the microwave-hot air combination drying method.

• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.34-42
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• 2016

Purpose: This study was performed to improve the drying quality and drying rate of ginseng slices by combining microwave and far-infrared drying techniques. Methods: Based on single-factor experiments and analyses, a quadratic regression orthogonal rotation combination design was adopted to study the effects of the moisture content at the conversion point between the microwave and far-infrared techniques, the ginseng slice thickness and the far-infrared drying temperature on the chip drying time, the surface color difference value, the nutritional composition and the surface shrinkage rate index. Results: Compared to the far-infrared drying alone, the combined microwave and far-infrared drying resulted in an increase in the saponin content of the ginseng slices and reductions in the drying time, surface color difference, and shrinkage rate. Conclusions: We established a mathematical model of the relationships between the surface shrinkage rate index and the experimental factors using the multi-objective nonlinear optimization method to determine the optimal parameter combination, which was confirmed to be the following: microwave and far-infrared moisture contents of 65%, a ginseng slice thickness of 1 mm, and a far-infrared drying temperature of $54^{\circ}C$.

• International Journal of Highway Engineering
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• v.20 no.4
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• pp.35-46
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• 2018

PURPOSES : The purpose of this study is to compare the lane curing time of natural drying and a lane drying device when painting lines on a highway. METHODS : The painting process was carried out in July 2015 and September 2015, respectively, for the Gimcheon IC - Gimcheon JC. After the painting, measurements were obtained three times at six measurement points located at 20 m intervals on the shoulder line and the dividing line. The curing time was measured for natural drying and drying using a lane drying device, and compared for different pavement types (asphalt, concrete) and paint types (waterborne paint, methyl methacrylate paint). RESULTS : The results of the lane curing time comparison on the highway are as follows. The combination of asphalt and methyl methacrylate paint cured more rapidly during both the natural drying and drying using the lane drying device. Finally, it was cured at least 32.2% and 40.7% faster when using a drying device than in natural drying. CONCLUSIONS : The comparison of lane curing time of the highway showed that the combination of asphalt and methyl methacrylate paint cured more rapidly when using both natural drying and a lane drying device.

• Journal of Biosystems Engineering
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• v.25 no.2
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• pp.115-122
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• 2000

This study was performed to develop a prototype continuous flow ginseng dryer with which better product quality and lower drying energy consumption could be achieved compared with conventional ginseng dryers. A dryer having both far infrared ray (IR) and heated-air as the drying energy sources was designed and fabricated . Dryer performance was studied by examining energy efficiencies and dryer performance evaluation indices (DPEI) during the drying tests of medium-sized four year ginseng roots with IR radiating plate temperature and drying air temperature in the range of 80-12$0^{\circ}C$ and 22-5$0^{\circ}C$, respectively. The DPEI of IR /heated -air combined drying was 1/3 of that of the conventional heated-air drying when ginseng were dried to the same final moisture ratio. When ginsengs were dried for 12 hours in the prototype IR/heated-air combination dryer, a linear relationship was found to exist between final moisture ratio and ginseng temperature. As the drying progressed, drying air temperature inside the dryer was nearly constant but ginseng temperature was drastically increased during the first two hours and gradually increased thereafter until the end of drying. With the prototype Ir/heated-air combination dryer, the drying rate changed little but the energy efficiency increased proportionally when the amount of ginseng to be dried increased. Drying capacity, energy efficiency, and DPEI of the prototype IR/heated-air combination ginseng dryer were estimated to 1.500 roots, 65% and 3.800kJ/kg-water , respectively.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.388-395
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• 2000

This study was performed to examine the effects of infrared (IR)/heated-air combination drying on some quality attributes of Korean white ginsengs. Ginseng roots were dried in a dryer where both the far infrared ray and heated-air are available as drying energy sources. Diametral shrinkage, external color, total saponin content, and ginsenosides and free sugar composition of the IR/heated-air combination dried ginsengs were measured and compared with those of commercial white ginseng products. The external color became lower in lightness and higher in saturation as the IR radiating plate temperature increased. IR/heated-air combination dried white ginsengs at IR plate temperature of 100$^{\circ}C$ was comparable to the commercial white ginseng products in color characteristics. Diametral shrinkage ratios ranged from 20 to 36% and appeared to be independent on the different drying methods. No definite evidence could be found whether the IR/heated-air combination drying and the conventional. hot-air drying practice resulted in white ginsengs having different ginsenoside contents and compositions. No conclusion could be made on whether the various drying treatments used in the study had effects on the free sugar contents and compositions of white ginsengs.

• Journal of Biosystems Engineering
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• v.41 no.4
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• pp.389-395
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• 2016

Purpose: Drying is one of the most widely used methods for preserving agricultural products or food. The main purpose of drying agricultural products is to reduce their water content for minimizing microbial spoilage and deterioration reaction during storage. Methods: Although numerous drying methods are successfully applied to dehydrate various agricultural products with little drying time, the final quality of dried samples in terms of appearance and shape cannot be guaranteed. Therefore, based on published literature, this review was conducted to study the drying characteristics of various agricultural products when different drying methods were applied. Results: An increase in the drying power of sources-for example, increase in hot air temperature or velocity, infrared or microwave power-and the combination of drying power levels can reduce the drying time of various agricultural products. In addition, energy efficiency in drying significantly relies on the compositions of the dried samples and drying conditions. Conclusions: The drying power source is the key factor to control entire drying process of different samples and final product quality. In addition, an appropriate drying method should be selected depending on the compositions of the agricultural products.

• Journal of Biosystems Engineering
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• v.41 no.1
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• pp.43-50
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• 2016

Purpose: The present study is aimed at examining the drying characteristics of sea tangle through a combination of microwave and far-infrared drying experiment and finding the optimal drying conditions. Methods: Sea tangle was cleaned and cut into fine pieces (5mm) before they were subjected to combinational drying by microwave and far-infrared ray. The amount of specimen per drying is 2 kg. The finely cut pieces of sea tangle were preheated in a microwave dryer for three different lengths of time (10, 15, and 20 min). Subsequently, they were dried using a far-infrared dryer at tow temperatures ($90^{\circ}C$ and $100^{\circ}C$) at an air velocity of 0.8 m/s until the final moisture content reduced to 10%. Results: Sea tangle dried under the condition of 20 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. Of the drying models verified in this study, the logarithmic model showed high accuracy with the coefficient of determination $R^2>0.7825$ and RMSE<0.1095. The rehydration ratio of sea tangle was the highest (12.87 g water/g dry matter) under the condition of 15 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. The energy consumption for the combination of microwave and far-infrared drying was the lowest (4.78 kJ/kg water) under the condition of 20 min of preheating in the microwave dryer and drying at $100^{\circ}C$ by the far-infrared dryer. Conclusions: Considering the drying time, discoloration during drying, rehydration ratio, and energy consumption for the drying of sea tangle, the optimal drying conditions for high-quality sea tangle are 15 min of preheating in a microwave dryer and drying at $100^{\circ}C$ by a far-infrared dryer.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.256-260
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• 2001

This study was initially performed to investigate current red-pepper drying methods commonly being adopted on red-pepper cultivation farm area. Based on the informations obtained from the field survey, an experiment of red-pepper drying was carried out to verify the actual drying potential of plastic covered solar house similar to the conventional pipe frame greenhouses covered with one or two layer of plastic film. Some results obtained from field survey and drying experiment for red-pepper are summarized as follows; 1. Various patterns of red-pepper drying process were found; 1) complete natural drying with red-pepper exposed in outdoor air, 2) hot air drying by dry chamber only, 3) combination drying by hot air dryer together with plastic covered passive solar house, 4) drying with plastic covered solar house unit. 2. The average air temperatures of outdoor and solar house during drying experiment period were $26.9-30.8\;and\;28.6-33.8^{\circ}C$, respectively, and the maximum air temperatures of those two were $34.2-36.4\;and\;39.8\;-52.3^{\circ}C$, respectively. Horizontal solar intensity during experiment period was $18.49-23.96\;MJ/m^{2}$, and relative humidity of outdoor and experimental solar house were 56 - 66% and 64 - 70%, respectively. 3. The weight of red-pepper during drying experiment period was decreased almost linearly from initial moisture content of 85% to final moisture content of 14%.

• The Journal of Advanced Prosthodontics
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• v.1 no.2
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• pp.63-67
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• 2009

STATEMENT OF PROBLEM. Use of custom tray and tray adhesive is clinically recommended for elastomeric impression material. However there is not clear mention of drying time of tray adhesive in achieving appropriate bonding strength of tray material and impression material. PURPOSE. This study is to investigate an appropriate drying time of tray adhesives by evaluating tensile bonding strength between two types of polyvinylsiloxane impression materials and resin tray, according to various drying time intervals of tray adhesives, and with different manufacturing company combination of impression material and tray adhesive. MATERIAL AND METHODS. Adhesives used in this study were Silfix (Dentsply Caulk, Milford, Del, USA) and VPS Tray Adhesive (3M ESPE, Seefeld, Germany) and impression materials were Aquasil Ultra (monophase regular set, Dentsply Caulk, Milford, Del, USA) and Imprint II Garant (regular body, 3M ESPE, Seefeld, Germany). They were used combinations from the same manufacture and exchanged combinations of the two. The drying time was designed to air dry, 5 minutes, 10 minutes, 15 minutes, 20 minutes, and 25 minutes. Total 240 of test specimens were prepared by auto-polymerizing tray material(Instant Tray Mix, Lang, Wheeling, Il, USA) with 10 specimens in each group. The specimens were placed in the Universal Testing machine (Instron, model 3366, Instron Corp, University avenue, Nowood, MA, USA) to perform the tensile test (cross head speed 5 mm/min). The statistically efficient drying time was evaluated through ANOVA and Scheffe test. All the tests were performed at 95% confidence level. RESULTS. The results revealed that at least 10 minutes is needed for Silfix-Aquasil, and 15 minutes for VPS Tray Adhesive-Imprint II, to attain an appropriate tensile bonding strength. VPS Tray Adhesive-Imprint II had a superior tensile bonding strength when compared to Silfix-Aquasil over 15 minutes. Silfix-Aquasil had a superior bonding strength to VPS Tray Adhesive-Aquasil, and VPS Tray Adhesive-Imprint II had a superior tensile bonding strength to Silfix-Imprint II at all drying periods. CONCLUSION. Significant increase in tensile bonding strength with Silfix-Aquasil and VPS Tray adhesive-Imprint II combination until 10 and 15 minutes respectively. Tray adhesive-impression material combination from the same company presented higher tensile bonding strength at all drying time intervals than when using tray adhesive-impression material of different manufactures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.28 no.1
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• pp.274-276
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• 1999

Sardine oil was microencapsulated by spray drying method in wall systems containing corn syrup in combination with sodium casein or wheat protein. Analysis of microencapsulation yield of sardine oil was carried out by a modified soxhlet method which could reduce the extraction time of surface oil. Microencapsulation yield of sardine oil was ranged from 65.3 to 93.5 % depending on the sodium casein content.