• Korean Chemical Engineering Research
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• v.45 no.3
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• pp.249-257
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• 2007

The periodic square wave (PSW) model was successfully applied to the optimal design of a batch-storage network. The network structure can cover any type of batch production, distribution and inventory system, including recycle streams. Here we extend the coverage of the PSW model to multitasking semi-continuous processes as well as pure continuous and batch processes. In previous solutions obtained using the PSW model, the feedstock composition and product yield were treated as known constants. This constraint is relaxed in the present work, which treats the feedstock composition and product yield as free variables to be optimized. This modification makes it possible to deal with the pooling problem commonly encountered in oil refinery processes. Despite the greater complexity that arises when the feedstock composition and product yield are free variables, the PSW model still gives analytic lot sizing equations. The ability of the proposed method to determine the optimal plant design is demonstrated through the example of a high density polyethylene (HDPE) plant. Based on the analytical optimality results, we propose a practical process optimality measure that can be used for any kind of process. This measure facilitates direct comparison of the performance of multiple processes, and hence is a useful tool for diagnosing the status of process systems. The result that the cost of a process is proportional to the square root of average flow rate is similar to the well-known six-tenths factor rule in plant design.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.49-55
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• 2018

Under the era of energy crisis, hydrogen energy is considered as one of the most potential alternative energies. Liquid hydrogen has much higher energy density per unit volume than gas hydrogen and is counted as the excellent energy storage method. In this study, Navier-Stokes equations based on 2-phase model were solved by using a computational fluid dynamics program and the liquefaction process of gaseous hydrogen passing through a cryogenic cooling tube was analyzed. The copper with high thermal conductivity was assumed as the material for cryogenic cooling tube. For different inlet velocities of 5 m/s, 10 m/s and 20 m/s for hydrogen gas, the distributions of fluid temperature, axial and radial velocities, and volume fractions of gas and liquid hydrogens were compared. These research results are expected to be used as basic data for the future design and fabrication of cryogenic cooling tube to transform the hydrogen gas into liquid hydrogen.

• Restorative Dentistry and Endodontics
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• v.36 no.2
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• pp.98-107
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• 2011

Caries remains prevalent throughout modern society and is the main disease in the field of dentistry. Although studies of this disease have used diverse methodology, recently, X-ray microtomography has gained popularity as a non-destructive, 3-dimensional (3D) analytical technique, and has several advantages over the conventional methods. According to X-ray source, it is classified as monochromatic or polychromatic with the latter being more widely used due to the high cost of the monochromatic source despite some advantages. The determination of mineral density profiles based on changes in X-ray attenuation is the principle of this method and calibration and image processing procedures are needed for the better image and reproducible measurements. Using this tool, 3D reconstruction is also possible and it enables to visualize the internal structures of dental caries. With the advances in the computer technology, more diverse applications are being studied, such automated caries assessment algorithms.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.721-728
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• 2017

High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.

• Korean Journal of Soil Science and Fertilizer
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• v.48 no.5
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• pp.456-463
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• 2015

The objective of this study was to determine the effects of granular type of silicate fertilizer on watermelon growth, yield, and characteristics of soil in the greenhouse. Four different levels of silicate fertilizer, 0(control), 600, 1,200, $1,800kg\;ha^{-1}$ were applied for experiment. The silicate fertilizer was applied as a basal fertilization before transplanting watermelon. Compost and basal fertilizers were applied based on the standard fertilizer recommendation rate with soil testing. All of the recommended $P_2O_5$ and 50% of N and $K_2O$ were applied as a basal fertilization. The N and $K_2O$ as additional fertilization was split-applied twice by fertigation method. Watermelon (Citrullus lanatus Thunb.) cultivar was 'Sam-Bok-KKuol and main stem was from rootstock (bottle gourd: Lagenaria leucantha Standl.) 'Bul-Ro-Jang-Sang'. The watermelon was transplanted on April, 15. Soil chemical properties, such as soil pH, EC, available phosphate and exchangeable K, Mg, and available $SiO_2$ levels increased compared to the control, while EC was similar and the concentrations of soil organic matter decreased. Physical properties of soils, such as soil bulk density and porosity were not different among treatments. The growth characteristics of watermelon, such as stem diameter, fresh and dry weight of watermelon at harvest were thicker and heavier for silicate treatment than the control, while number of node was shorter than the control. Merchantable watermelon increased by 3-5% compared to the control and sugar content was 0.4 to $0.7^{\circ}Brix$ higher than the control. These results suggest that silicate fertilizer application in the greenhouse can improve some chemical properties of soils and watermelon stem diameter and dry weight, which are contributed to watermelon quality and marketable watermelon production.

• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.141-155
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• 2018

Recently, the number of ground subsidence resulting from underground cavity has been increased. Accordingly, the importance of restoration of stress release zone around the underground cavity has been emphasized. The stress release zone is composed of low density soils having extremely low stiffness and degree of compaction, which can lead to additional cavity expansion and collapse of overlying ground. Therefore, in this study, the suitability of restoration method of underground cavity using expansive material for reinforcement of stress release zone around the cavity is verified. The basic physical properties and expansion characteristics of the expansive material were examined. The experiment equipment capable simulating of stress release zone was developed and is used to investigate the effect of expanding material on stress release zone. The stress release zone was simulated using the spring in numerical analysis. The factors of the volume ratio of the underground cavity to the expansion material, the degree of stress relaxation, and the shape of the cavity were varied in numerical simulations, and the behavior of stress release zone was analyzed based on the numerical analysis results. Analysis variables are factors that affect each other. Also, filling of underground cavity and capacity of restoration of stress release zone were confirmed when the expansive material was inserted into underground cavity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.859-865
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• 2018

A construction of infrastructures and base station on the moon could be undertaken by linking with the regions where construction materials and energy could be supplied on site. It is necessary to detect craters on the lunar surface and gather their topological information in advance, which forms permanent shaded regions (PSR) in which rich ice deposits might be available. In this study, an effective method for automatic detection of lunar craters on the moon surface is taken into consideration by employing a latest version of deep-learning algorithm. A training of a deep-learning algorithm is performed by involving the still images of 90000 taken from the LRO orbiter on operation by NASA and the label data involving position and size of partly craters shown in each image. the Faster RCNN algorithm, which is a latest version of deep-learning algorithms, is applied for a deep-learning training. The trained deep-learning code was used for automatic detection of craters which had not been trained. As results, it is shown that a lot of erroneous information for crater's positions and sizes labelled by NASA has been automatically revised and many other craters not labelled has been detected. Therefore, it could be possible to automatically produce regional maps of crater density and topological information on the moon which could be changed through time and should be highly valuable in engineering consideration for lunar construction.

• Journal of the Korean Association of Geographic Information Studies
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• v.21 no.4
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• pp.26-49
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• 2018

The purpose of this study was to verify the reliability of the solar radiation model and discuss its applicability to the urban area of Seoul for summer heat stress mitigation. We extended the study area closer to the city scale and enhanced the spatial resolution sufficiently to determine pedestrian-level urban radiance. The domain was a $4km^2$ residential area with high-rise building sites. Radiance modelling (SOLWEIG) was performed with LiDAR (Light Detection and Ranging)-based detailed geomorphological land cover shape. The radiance model was evaluated using surface energy balance (SEB) observations. The model showed the highest accuracy on a clear day in summer. When the mean radiation temperature (MRT) was simulated, the highest value was for a low-rise building area and road surface with a low shadow effect. On the other hand, for high-rise buildings and vegetated areas, the effect of shadows was large and showed a relatively low value of mean radiation temperature. The method proposed in this study exhibits high reliability for the management of heat stress in urban areas at pedestrian height. It is applicable for many urban micro-climate management functions related to natural and artificial urban settings; for example, when a new urban infrastructure is planned.

• Journal of the Korean Society of Radiology
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• v.12 no.7
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• pp.833-844
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• 2018

Dual energy X-ray absorptiometry is mainly used as an X-ray test method. For equipment manufactured GE and Hologic, cross-calibration analyses (CCA) of machines from the same manufacturer and between units from different manufacturers have been conducted, but the CCA of equipment manufactured in Korea are inadequate. Through CCA, we present a formula of the intersections between the Korean medical equipment company (KEC) with GE and Hologic manufactured DXA, and among the KEC DXA. The CCA was conducted for the European Spine Phantom on DXA from four KEC and three global medical equipment company (GEC) manufacturers. We compared bone mineral density (BMD) values and calculated the CCA equation by linear regression analysis. The standard-deviations (SD) of the BMD values were highest for the Dexxum T for the low, medium, and high spine, which were 0.030, 0.029, and 0.037, respectively. The smallest SD in the low and medium vertebrae were 0.005 and 0.004 for the Horizon Ci, respectively, and 0.005 for the Osteo Pro Max in the high vertebrae. Based on the intersection equations of the KEC DXA established in this study, CCA of various KEC DXA should be established for more accurate follow-up of BMD tests in clinical environments.

• Journal of Cadastre & Land InformatiX
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• v.49 no.1
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• pp.181-195
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• 2019

This study aims to analyze the spatial context by analyzing the flow characteristics of the walking tour course and visualizing effectively using the floating population data constructed through the communication data. The floating population data refinement algorithm was developed for estimation flow population along the road and the floating population data for each walking tour courses was constructed. In order to adopt the algorithm for forming suitable for the analysis of the walking tour courses, the estimation of floating population considering the area of the road and the estimation of floating population considering the value of floating population around the road were compared. As a result, the estimation of floating population considering ambient the values of flow population was adopted, which is more appropriate to apply analysis method due to the relatively consistent data. Then, a datamining algorithm for walking tour course was constructed according to the characteristics of the floating population data, the absence of missing values. Finally, this study analyzed the flow characteristics and spatial patterns of 18 walking trails in Seoul through the floating population data according to walking tour course. To do this, the kernel density analysis and the Getis-Ord $G^*_i$ statistical hotspot analysis were applied to visualize the main characteristics of each walking tour course.