• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.95-102
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• 2007

Purpose: To acquire high-resolution spiral-scan images at higher magnetic field, high homogeneous magnetic field is needed. Field inhomogeneity mapping and in-vivo shimming are important for rapid imaging such as spiral-scan imaging. The rapid scanning sequences are very susceptible to inhomogeneity. In this paper, we proposed a higher-order shimming method to obtain homogeneous magnetic field. Materials and Methods: To reduce measurement time for field inhomogeneity mapping, simultaneous axial/ sagittal, and coronal acquisitions are done using multi-slice based Fast Spin echo sequence. Acquired field inhomogeneity map is analyzed using the spherical harmonic functions, and shim currents are obtained by the multiplication of the pseudo-inverse of the field pattern with the inhomogeneity map. Results: Since the field inhomogeneity is increasing in proportion to the magnetic field, higher order shimming to reduce the inhomogeneity becomes more important in high field imaging. The shimming technique in which axial, sagittal, and coronal section inhomogeneity maps are obtained in one scan is developed, and the shimming method based on the analysis of spherical harmonics of the imhomogenity map is applied. The proposed technique is applicable to a localized shimming as well. High resolution spiral-scan imaging was successfully obtained with the proposed higher order shimming. Conclusion: Proposed pulse sequence for rapid measurement of inhomogeneity map and higher order shimming based on the inhomogeneity map work very well at 3 Tesla MRI system. With the proposed higher order shimming and localized higher order shimming techniques, high resolution spiral-scan images are successfully obtained at 3 T MRI system.

• Journal of Veterinary Clinics
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• v.27 no.1
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• pp.88-92
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• 2010

An 11-year-old, spayed female, weighing 10 kg miniature Schnauzer was admitted for abdominal distension, anorexia, pollakiuria, and constipation. A large, homogeneous fat opacity mass was identified in the retroperitoneum and pelvic cavity on the abdominal survey radiography. The mass displaced the descending colon peripherally and ventrally, and the urinary bladder ventrally. On the abdominal ultrasonographic examination, the mass was uniformly hyperechoic with a coarse internal echo texture and had outer hyperechoic capsule, and it showed homogeneously same attenuation (-180 ~ -110 HU) as adjacent fat on the computed tomography. There was no evidence of invasion into the surrounding structures or organs. Cytological findings from fine needle aspirates were numerous sheets and clusters of adipocytes. The dog showed complete resolution of clinical signs after surgical resection of the mass. The mass was confirmed as simple lipoma through histopathological examination.

• The Journal of the Acoustical Society of Korea
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• v.33 no.2
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• pp.102-110
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• 2014

The effect of a bonding layer on the performance of a quarter-wave (${\lambda}/4$) mode PVDF ultrasound transducer having not only a piezoelectric layer but also a non-piezoelectric layer between two electrodes was analyzed. The equivalent circuit of a transmission line model by Kikuchi et al.[Sound of IEICE, 55-A, 331-338 (1981)] was introduced for the analysis. The validity of the model was confirmed by comparison with a KLM model for three postulated adhesion cases of a $80{\mu}m$ thick piezoelectric PVDF film to a copper (Cu) backer. The pulse-echo responses of five PVDF transducers, each fabricated with a different thickness ($5{\mu}m{\sim}20{\mu}m$) of the bonding layer, were measured and the results were compared with those by simulation. The two results were in good agreement with each other and it was noted that the effect of the bonding layer on the performance of the transducer could be analyzed by the Kikuchi model. In detail, the $20{\mu}m$ bonding layer decreased the center frequency and the bandwidth by about 19.7 % and 25.0 %, respectively, and increased the insertion loss by 57.2 %.

• Journal of Climate Change Research
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• v.3 no.2
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• pp.129-142
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• 2012

This study was carried out to evaluate carbon footprint during unhulled rice production and to compare mitigation technologies of methane, main carbon source during rice production, Carbon footprint of unhulled rice was a sum of $CO_2$ emission of agri-materials manufacture, rice cultivation and waste treatment. It was emitted 1.40 kg $CO_2$ during unhulled rice production, its distribution was 71.1% by $CH_4$ emission of rice cultivation, 11.8% of $N_2O$ emission by nitrogen application and 7.6% of complex fertilizer manufacture. $CH_4$ emission could be mitigated by some technologies; cultivation of the early maturing rice variety emitted lower by 44.4% than the mid maturing variety, intermittent drainage of submerged water by 43.8% than the continuous flooding condition, direct seeding by 32.0% than transplanting cultivation, no-ploughing by 20.9% than ploughing cultivation. It means that LCA on Global Warming Potential and the statistical data on innovated technical practice are key tools to systemize Measurable-Reportable-Verifiable (MRV) system for carbon footprint and carbon emission trade in the farm base.

• Journal of the Korea Organic Resources Recycling Association
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• v.30 no.4
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• pp.85-99
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• 2022

Recently, environmental issues have become serious, and Jeju Island is promoting a pilot project of a smart collection system(waste weight-based collection system) at clean houses in Yongdam 1-dong. However, the new system faced an opposition from elderly residents who were not accustomed to using machines or smart devices. In order to solve this problem, it was intended to suggest policies related to this by conducting environmental education and identifying problems with the effect of environmental education awareness through data analysis method. The results showed positive answers in most of the satisfaction and achievement evaluations, but it is also true that most of the residents need to be educated and more information should be given. In order to vitalize education, it is important to increase the number of instructors and support them to increase their expertise. It is also important to take a practical process that strengthens public relations, shares information, and links with the local community to increase the actual participation of local residents. In addition, it is critical to secure a budget from local governments to maintain education and public awareness, and it will be helpful to link with talent donation projects in the region.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.1
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• pp.13-24
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• 2021

Tunnel boring machine (TBM) is widely used for tunnel excavation in hard rock and soft ground. In the perspective of TBM-based tunneling, one of the main challenges is to drive the machine optimally according to varying geological conditions, which could significantly lead to saving highly expensive costs by reducing the total operation time. Generally, drilling investigations are conducted to survey the geological ground before the TBM tunneling. However, it is difficult to provide the precise ground information over the whole tunnel path to operators because it acquires insufficient samples around the path sparsely and irregularly. To overcome this issue, in this study, we proposed a geological type classification system using the TBM operating data recorded in a 5 s sampling rate. We first categorized the various geological conditions (here, we limit to granite) as three geological types (i.e., rock, soil, and mixed type). Then, we applied the preprocessing methods including outlier rejection, normalization, and extracting input features, etc. We adopted a deep neural network (DNN), which has 6 hidden layers, to classify the geological types based on TBM operating data. We evaluated the classification system using the 10-fold cross-validation. Average classification accuracy presents the 75.4% (here, the total number of data were 388,639 samples). Our experimental results still need to improve accuracy but show that geology information classification technique based on TBM operating data could be utilized in the real environment to complement the sparse ground information.

• Journal of Practical Agriculture & Fisheries Research
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• v.23 no.2
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• pp.51-61
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• 2021

As a result of examining the germination rate between ginseng varieties, Jagyongjong varieties had the highest germination rate, and Yeonpung. had the lowest germination rate. In the ginseng seed germination rate experiment, the highest germination rate and growth condition were shown in artificial soil conditions of the ratio of Peatmoss 6.5: Pearlite 2: Masato 1.5. Good soil conditions require adequate soil moisture forces during the incubation period. The cultivation of ginseng medicinal crops requires optimal soil breathability, soil pH, and soil stabilization, which are important for root breathing. Microbial activity in the soil has a great influence on the growth of ginseng. The optimum pH of the soil for ginseng cultivation is 5.0-5.5 As a result of the experiment, the soil remained in an appropriate range after a month. In general, when the EC concentration value of the soil for ginseng cultivation is 0.2 mS/cm or more, growth deteriorates, and when the EC concentration value is 0.5 mS/cm or more, concentration obstacles such as root decay occur. As a result of the analysis, the higher the concentration value of EC, the more likely it is to interfere with ginseng growth.

• Korean Journal of Ecology and Environment
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• v.56 no.2
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• pp.151-160
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• 2023

Cyanobacteria Pseudanabaena strains are known to produce 2-MIB(odorous material) in freshwater systems, thereby causing problems in water use. However, their physiological responses to environmental factors in relation with 2-MIB production is not well explored. This study was conducted to evaluate the effect of temperature on the growth and 2-MIB production of Pseudanabaena redekei. The experimental cyanobacteria strains were separated from the Uiam Reservoir (North Han River) and cultured in the BG-11 medium. Temperature was set to 10, 15, 20, 25, and 30℃ for the experiment, in the reflection of the seasonal water temperature variation in situ. For each temperature treatment, cyanobacterial biomass(Chl-a) and 2-MIB concentration (intra-cellular and extra-cellular fractions) were measured every 2 days for 18 days. Both maximal growth and total 2-MIB production of P. redekei appeared at 30℃. While intra-cellular 2-MIB contents were similar (26~29 ng L^-1) regardless of treated temperatures, extra-cellular 2-MIB concentration was higher only in high temperature conditions (25~30℃), indicating that the extents of 2-MIB biosynthesis and release by P. redekei vary with temperature. The 2-MIB productivity of P. redekei was much higher in low-temperature conditions (10~15℃) than high temperature conditions (25~30℃). This study demonstrated that temperature was a critical factor contributing to 2-MIB biosynthesis and its release in cell growth (r=0.605, p<0.01). These results are important to understand the dynamics of 2-MIB in the field and thereby provide basic information for managing odorous material in drinking water resources.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.2
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• pp.45-54
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• 2010

Field study was conducted for 5 months to investigate the effect of leachate recirculation on aerobic landfill stabilization at active landfilling site. The area of field experiment was $24{\times}24m$ and 9 vertical air injection wells with screen ranging 3~9 m were installed. Aerobic landfill operation for 5 months increased average internal landfill temperature to $70^{\circ}C$ and 8 % of landfill height was settled down. $94m^3$ of leachate was recirculated for 1 month to increase moisture content of landfill to favor microbial degradation of organic matter, which resulted in temporary increase of groundwater level and anaerobic environment. But leachate recirculation triggered increase of internal landfill temperature of neighboring monitoring well. Because excessive leachate recirculation decreased internal landfill temperature by cooling effect, internal landfill temperature should be checked to avoid abrupt decrease of temperature during leachate recirculation. Also, to prevent anaerobic environment, intermittent leachate recirculation was recommended.

• Investigative Magnetic Resonance Imaging
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• v.5 no.1
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• pp.57-65
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• 2001

Purpose : $T_2$-weighted half courier Echo Planar Imaging (T2HEPI) method is proposed to reduce measurement time of existing EPI by a factor of 2. In addition, high $T_2$ contrast is obtained for clinical applications. High resolution single-shot EPI images with $T_2$ contrast are obtained with $128{\times}128$ matrix size by the proposed method. Materials and methods : In order to reduce measurement time in EPI, half courier space is measured, and rest of half courier data is obtained by conjugate symmetric filling. Thus high resolution single shot EPI image with $128{\times}128$ matrix size is obtained with 64 echoes. By the arrangement of phase encoding gradients, high $T_2$ weighted images are obtained. The acquired data in k-space are shifted if there exists residual gradient field due to eddy current along phase encoding gradient, which results in a serious problem in the reconstructed image. The residual field is estimated by the correlation coefficient between the echo signal for dc and the corresponding reference data acquired during the pre-scan. Once the residual gradient field is properly estimated, it can be removed by the adjustment of initial phase encoding gradient field between $70^{\circ}$ and $180^{\circ}$ rf pulses. Results : The suggested T2EPl is implemented in a 1.0 Tela whole body MRI system. Experiments are done with the effective echo times of 72ms and 96ms with single shot acquisitions. High resolution($128{\times}128$) volunteer head images with high $T_2$ contrast are obtained in a single scan by the proposed method. Conclusion : Using the half courier technique, higher resolution EPI images are obtained with matrix size of $128{\times}128$ in a single scan. Furthermore $T_2$ contrast is controlled by the effective echo time. Since the suggested method can be implemented by software alone (pulse sequence and corresponding tuning and reconstruction algorithms) without addition of special hardware, it can be widely used in existing MRI systems.