• Journal of Biosystems Engineering
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• v.32 no.6
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• pp.448-454
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• 2007

This study was conducted to develop a 100 kPa soil tensiometer mainly consisted of a porous ceramic cup, water-holding tube, and a digital vacuum gauge, through theoretical design analysis and experimental performance evaluation. Major findings were as follows. 1. Theoretical analysis showed that air entry value of a porous media decreased as the maximum effective size of the pore increased, and the maximum diameter of the pores was $2.9\;{\mu}m$ for measuring up a 100 kPa of soil-water tension. 2. Property analysis of tensiometer porous cups supplied in Korean domestic market indicated that main components were $SiO_2$ and $Al_2O_3$ with a porosity range of $33.8{\sim}49.3%$. 3. The porous cup selected through sample fabrication and air-permeability tests showed weight ratios of 87% and 11% for $Al_2O_3$ and $SiO_2$. The analysis of SEM (scanning electron microscope) images showed that the sample was sintered at temperatures of about $1150^{\circ}C$, which consisted of pores with sizes of up to 25% of those for commercial porous cups. 4. The prototype soil tensiometer was fabricated using the developed porous cup and a digital vacuum gauge that could measure water tension with a pressure of 85 kPa in air tests. 5. In-soil tests of the prototype conducted during a period of 25-day drying showed that soil-water tension values measured with the prototype and commercial units were not significantly different, and soil-water characteristic curves could be established for different soils, confirming accuracy and stability of the prototype.

• Clinical and Experimental Pediatrics
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• v.63 no.9
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• pp.361-367
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• 2020

Background: Length of stay is a significant indicator of care effectiveness and hospital performance. Owing to the limited number of healthcare centers and facilities, it is important to optimize length of stay and associated factors. Purpose: The present study aimed to investigate factors associated with neonatal length of stay in the neonatal intensive care unit (NICU) using parametric and semiparametric models and compare model fitness according to Akaike information criterion (AIC) between 2016 and 2018. Methods: This retrospective cohort study reviewed 600 medical records of infants admitted to the NICU of Bandar Abbas Hospital. Samples were identified using census sampling. Factors associated with NICU length of stay were investigated based on semiparametric Cox model and 4 parametric models including Weibull, exponential, log-logistic, and log-normal to determine the best fitted model. The data analysis was conducted using R software. The significance level was set at 0.05. Results: The study findings suggest that breastfeeding, phototherapy, acute renal failure, presence of mechanical ventilation, and availability of central venous catheter were commonly identified as factors associated with NICU length of stay in all 5 models (P<0.05). Parametric models showed better fitness than the Cox model in this study. Conclusion: Breastfeeding and availability of central venous catheter had protective effects against length of stay, whereas phototherapy, acute renal failure, and mechanical ventilation increased length of stay in NICU. Therefore, the identification of factors associated with NICU length of stay can help establish effective interventions aimed at decreasing the length of stay among infants.

• Korean Journal of Veterinary Research
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• v.44 no.2
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• pp.171-177
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• 2004

The regional distributions and frequencies of argentaffin endocrine cells in gastrointestinal (GI) tract of osteoporotic Sprague-Dawley rat induced by ovariectomy were studied by Masson-Hamperl silver stain. The experimental animals were divided into two groups, one is non-ovariectomized group (Sham) and the other is ovariectomized group (OVX). Samples were collected from each part of GI tract (fundus, pylorus, duodenum, jejunum, ileum, cecum, colon and rectum) at 10th week after ovariectomy or sham operation. Argentaffin cells were detected throughout the entire GI tract with various frequencies regardless of ovariectomy except for the rectum of OVX in which no cells were detected. Most of these argentaffin cells in the mucosa of GI tract were generally spherical or spindle in shape (open type cell) while cells showing round in shape (close type cell) were rarely found in gland regions. Significant decrease of argentaffin cells was detected in OVX compared to that of Sham except for the fundus and jejunum. However, in the fundus and jejunum, argentaffin cells in OVX showed similar frequency compared to that of Sham. In conclusion, the endocrine cells are the anatomical units responsible for the production of gut hormones that regulate gut motility and digestion including absorption, and a change in their density would reflect the change in the capacity of producing these hormones and regulating gut motility and digestion. Ovariectomy induced severe quantitative changes of GI argentaffin endocrine cell density, and the abnormality in density of GI endocrine cells may contribute to the development of gastrointestinal symptoms in osteoporosis such as impairments of calcium and some lipids, frequently encountered in patients with postmenopausal osteoporosis.

• Biomolecules & Therapeutics
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• v.9 no.4
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• pp.277-281
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• 2001

Chromium is an essential nutrient and participates in glucose and lipid metabolism in human beings and animals. The present study was conducted to assess the effects of chromium picolinate (Cr-pic) on glucose tolerance and insulin sensitivity in type I and ll diabetic rats. The experimental groups were type I diabetic (streptozotocin-induced: 40 mg/kg, i.p.) and type II diabetic (Goto-Kakizaki rats) models. Each group was subdivided into control. low-dose and high-dose of Cr-pic treated groups. The Cr-pic was orally administered with Cr-pic (100 mg/kg for low dose group and 200 mg/kg for high dose group) for 4 weeks. And then we performed intraperitoneal glucose tolerance test (IPGTT) and insulin sensitivity test (ITT). The glucose tolerance test was carried out by inection of glucose (2 g/kg, i.p.). The peripheral insulin sensitivity test was con- ducted by injection of insulin (5 units/kg, s.c.) and glucose. We performed determining of blood glucose concentration at 0, 10, 30, 60, 90, and 120 min using automated glucose analyzer. The plasma insulin concentration was determined by rat insulin EIA kit. Administration of Cr-pic improved weight gain in all group s with higher significant in the low-dose group. There was no significance between the control and the Cr-pic treated groups in the area under the blood glucose curve and serum insulin concentration plots of IPGTT and peripheral ITT in type I diabetic rats. But Cr-pic treated groups showed significantly lower levels of the area under the blood glucose currie during IPGTT and ITT and the high-dose group showed less effects compared with the low-dose group in the type II diabetic rats. The plasma insulin concentration of both diabetic groups was not influenced by Cr-pic supplementation. We can conclude that chromium picolinate may improve the endogenous and exogenous insulin action and peripheral insulin sensitivity in type II diabetic rats.

• Journal of Elementary Mathematics Education in Korea
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• v.14 no.1
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• pp.135-151
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• 2010

The purpose of this study is to investigate the effect of learner-centered instructions using instructional materials which are developed in the light of constructivism and implementing practices of the instruction. According to the result of Recall Test, experimental group and comparing group have not statistically meaningful difference. However, in the result of Generation Tests which include the contents not dealt with during the experiment treatments, the two groups have statistically meaningful difference. It can be drawn from the result that students who take learner-centered instruction are in a good readiness for learning of the contents which will be addressed in future.

• Journal of Elementary Mathematics Education in Korea
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• v.15 no.1
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• pp.121-139
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• 2011

This study conducted experimental problem posing activities using real-life materials. This study investigated the changes on students' mathematical thoughts and attitudes through the activities. This study is conducted via participation of students in a 5th grade class of N elementary school located in Daegu city. As a qualitative case study, this study focused on processes of problem posing rather than results. The problems applying new situations appear, and the used mathematical terms, units, and figures became more practical. The numbers of problems made are increased gradually, and more complex conditions are added as activities are performed. Most of the students revealed interests about problem making activities.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.5
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• pp.694-700
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• 1999

In this paper, we studied the design of power divider using the slow-wave effect of Photonic Bandgap structure, which is etched on the ground plane. The proposed PBG structure can provides the changing of the characteristic impedance of the transmission line and the group delay velocity characteristic. Therefore we can make wider width than the width of conventional transmission line and decrease the length of transmission line. We presented the application for power divider using the characteristic impedance and electrical length extracted from scattering parameter. As adding proposed defect units, the effect of defect is studied. The experimental results show good agreements with the simulated results.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.1
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• pp.84-93
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• 2018

In this paper, we propose an Elman recurrent neural network to predict and analyze a time series of power energy consumption. To this end, we consider the volatility of the time series and apply the sample variance and the detrended fluctuation analyses to the volatilities. We demonstrate that there exists a correlation in the time series of the volatilities, which suggests that the power consumption time series contain a non-negligible amount of the non-linear correlation. Based on this finding, we adopt the Elman recurrent neural network as the model for the prediction of the power consumption. As the simplest form of the recurrent network, the Elman network is designed to learn sequential or time-varying pattern and could predict learned series of values. The Elman network has a layer of "context units" in addition to a standard feedforward network. By adjusting two parameters in the model and performing the cross validation, we demonstrated that the proposed model predicts the power consumption with the relative errors and the average errors in the range of 2%~5% and 3kWh~8kWh, respectively. To further confirm the experimental results, we performed two types of the cross validations designed for the time series data. We also support the validity of the model by analyzing the multi-step forecasting. We found that the prediction errors tend to be saturated although they increase as the prediction time step increases. The results of this study can be used to the energy management system in terms of the effective control of the cross usage of the electric and the gas energies.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.4
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• pp.245-251
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• 2008

The cooling load in winter is significant in buildings and hotels because of the usage of office equipments and the high efficiency of wall insulation. Hence, the development of a multi-heat pump that can cover heating and cooling simultaneously for each indoor unit is required. In this study, the operating characteristics and performance of a simultaneous heating and cooling heat pump in the heating-main operating mode were investigated experimentally. The system adopted a variable speed compressor with four indoor units and one outdoor unit with R-410A. In the heating-main mode, the cooling capacity was lower than the design cooling capacity due to the reduction of the flow rate in the indoor unit for the cooling, with the increase of the heating capacity. To solve these problems, the performance characteristics of the simultaneous heating and cooling heat pump in the heating-main mode were investigated by varying the flow rate to the indoor unit for the cooling and the compressor rotating speed. In addition, the adequate control methods were suggested to improve the system efficiency.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.13-19
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• 2000

The blind segmentation method, which segments input speech data into recognition unit without any prior knowledge, plays an important role in continuous speech recognition system and corpus generation. As no prior knowledge is required, this method is rather simple to implement, but in general, it suffers from bad performance when compared to the knowledge-based segmentation method. In this paper, we introduce a method to improve the performance of a blind segmentation of Korean continuous speech by postprocessing the segment boundaries obtained from the blind segmentation. In the preprocessing stage, the candidate boundaries are extracted by a clustering technique based on the GLR(generalized likelihood ratio) distance measure. In the postprocessing stage, the final phoneme boundaries are selected from the candidates by utilizing a simple a priori knowledge on the syllabic structure of Korean, i.e., the maximum number of phonemes between any consecutive nuclei is limited. The experimental result was rather promising : the proposed method yields 25% reduction of insertion error rate compared that of the blind segmentation alone.