• Journal of Microbiology and Biotechnology
• /
• v.19 no.10
• /
• pp.1085-1091
• /
• 2009

A phytase with high activity at low temperatures has great potential for feed applications, especially in aquaculture. Therefore, this study used a degenerate PCR and TAIL PCR to clone a phytase gene from Erwinia carotovora var. carotovota, the cause of soft rot of vegetables in the ground or during cold storage. The full-length 2.5-kb fragment included an open reading frame of 1,302 bp and encoded a putative phytase of 45.3 kDa with a 50% amino acid identity to the Klebsiella pneumoniae phytase. The phytase contained the active site RHGXRXP and HD sequence motifs that are typical of histidine acid phosphatases. The enzyme was expressed in Escherichia coli, purified, and displayed the following characteristics: a high catalytic activity at low temperatures (retaining over 24% activity at $5^{\circ}C$) and remarkably thermal lability (losing >96% activity after incubation at $60^{\circ}C$ for 2 min). The optimal phytase activity occurred at pH 5.5 and ${\sim}49^{\circ}C$, and the enzyme activity rapidly decreased above $40^{\circ}C$. When compared with mesophilic counterparts, the phytase not only exhibited a high activity at a low temperature, but also had a low $K_m$ and high $k_{cat}$. These temperature characteristics and kinetic parameters are consistent with low-temperature-active enzymes. To our knowledge, this would appear to be the first report of a low-temperature-active phytase and its heterogeneous expression.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.7 no.5
• /
• pp.139-150
• /
• 2007

As computer technology has been rapidly advanced, geographic information system (GIS) is recently used in many disciplines. In this study, for a model area in Seoul, seismic hazard potential relating to site effects, which are influenced by the subsurface geotechnical conditions, was estimated using the GIS tool. The distribution of pre-existing borehole drilling data in Seoul metropolitan area was examined for the regional estimation of site-specific seismic responses at the model area. Spatial geo-layers across the entire model area were predicted by constructing a GIS-based geotechnical information system (GTIS). A microzonation of site period $(T_G)$ for estimating site-specific seismic responses at the model area was performed within the GTIS. The spatial microzoning map of $T_G$ indicated seismic vulnerability of two- to four-storied buildings in the model area. Furthermore, a site classification map for determining the design ground motion was established based on the $T_G$ within the GTIS. This informed that most of location in the model area was categorized into current site classes C and D. This seismic microzonation framework for the model area could be applicable particularly in the entire Seoul metropolitan area based on the pre-existing borehole data.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.4 no.2
• /
• pp.25-34
• /
• 2001

/sup 226/Ra and /sup 228/Ra analysis were carried out at the representative station of Masan Bay from May to August, 1999. The high activities of /sup 226/Ra and /sup 228/Ra in the surface water were appeared in rainy season (August, 1). However, there is no significant variation in concentrations in the other season. A high negative linear correlation between /sup 226/Ra activities and salinity in the surface water suggests that /sup 226/Ra activity in the surface water was controlled by simple mixing between the two end-members low salinity high /sup 226/Ra activity water of inner Bay and a high salinity low /sup 226/Ra activity water of the continental shelf water out of Bay. /sup 226/Ra activities below the surface mixed layer were higher than those of expected level from the /sup 226/Ra versus salinity. And also /sup 228/Ra//sup 226/Ra ratios in the bottom water were lower compared to those in surface water due to the presence of potential source of /sup 226/Ra below the surface mixed layer. However, it is known that /sup 228/Ra compared to /sup 226/Ra is enriched in bottom sediments and pure water. Therefore, the most probable sources for low /sup 228/Ra//sup 226/Ra activity ration is submarine ground water discharge. Further studies are required to quantify the various sources of /sup 226/Ra and /sup 228/Ra and their relative contributions.

• Journal of Biomedical Engineering Research
• /
• v.25 no.5
• /
• pp.335-342
• /
• 2004

This paper describes a trans-admittance scanner for breast cancer detection. A FPGA-based sinusoidal waveform generator produces a constant voltage. The voltage is applied between a hand-held electrode and a scan probe placed on the breast. The scan probe contains an 8x8 array of electrodes that are kept at the ground potential. Multi-channel precision digital ammeters using the phase-sensitive demodulation technique were developed to measure the exit current from each electrode in the array. Different regions of the breast are scanned by moving the probe on the breast. We could get trans-admittance images of resistor and saline phantoms with an anomaly inside. The images provided the information on the depth and location of the anomaly. In future studies, we need to improve the accuracy through a better calibration method. We plan to test the scanner's ability to detect a cancer lesion inside the human breast.

• Geophysics and Geophysical Exploration
• /
• v.23 no.3
• /
• pp.117-130
• /
• 2020

Noises can distort acquired geophysical data, leading to their misinterpretation. Potential noises sources include anthropogenic activity, natural phenomena, and instrument noises. Conventional denoising methods such as wavelet transform and filtering techniques, are based on subjective human investigation, which is computationally inefficient and time-consuming. Recently, many researchers attempted to implement neural networks to efficiently remove noise from geophysical data. This study aims to review and analyze different types of neural networks, such as artificial neural networks, convolutional neural networks, autoencoders, residual networks, and wavelet neural networks, which are implemented to remove different types of noises including seismic, transient electromagnetic, ground-penetrating radar, and magnetotelluric surveys. The review analyzes and summarizes the key challenges in the removal of noise from geophysical data using neural network, while proposes and explains solutions to the challenges. The analysis support that the advancement in neural networks can be powerful denoising tools for geophysical data.

• Journal of the Mineralogical Society of Korea
• /
• v.27 no.3
• /
• pp.115-124
• /
• 2014

In order to leach Au and Ag from gold-silver bearing sulfide concentrate, the sulfide concentrate was ground in a ball mill for a dry pre-treatment and a wet pre-treatment process. Mineralogical studies and thiourea leaching experiments were carried out with the pre-treated sulfide concentrate. The results of the pre-treatment with the concentrate samples showed the mean particle size and iso-electrical potential was smaller in the dry pre-treatment sample than in the concentrate sample, and the contents was lower in the wet pre-treatment sample than in the dry pre-treatment sample. In XRD analysis, amorphous properties were only shown in the wet pretreatment sample. The results of the concentrate sample leaching experiments showed that the best Au, Ag leaching parameters were when the addition of thiourea was at a 1.0 g concentration, ferric sulfate was 1.0 M, sulfuric acid was 2.0 M and the leaching temperature was at $60^{\circ}C$. The Au, Ag leaching rate was always much greater and faster with the wet pre-treatment samples than with the dry pre-treatment samples. Accordingly, it is expected that more Au, Ag can be leached in an eco-friendly methodology using wet pre-treatment. The pre-treatment could be improved with an optimized grinding additive reagent and through researching grinding time in future non-cyanide processes.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.11 no.1 s.53
• /
• pp.45-57
• /
• 2007

The mean shear wave velocity to the depth of 30 m (Vs30) derived from the western Vs is the current site classification criterion for determining the design seismic ground motion taking into account the site amplification potential. In order to evaluate the Vs30 at a site, a shear wave velocity (Vs) Profile extending to at least 30 m in depth must be acquired from in-situ seismic test. In many cases, however, the resultant depth of the Vs profile may not extend to 30 m, owing to the unfavorable field condition and the limitation of adopted testing techniques. In this study, the Vs30 and the mean shear wave velocity to a depth shallower, than 30 m (VsDs) were computed from the Vs profiles more than 30 m in depth obtained by performing various seismic tests at total 72 sites in Korea, and a correlation between Vs30 and VsDs was drawn based on the computed mean Vs data. In addition, a method for extrapolating the Vs profile from shallow depth to 30 m was developed by building a shape curve based on the average data of all Vs profiles. For evaluating the Vs30 from the shallow Vs profiles, both the methods using VsDs and shape curve result in less bias than the simplest method of extending the lowermost Vs equally to 30 m in depth, and are usefully applicable particularly in the cases of the Vs profiles extending to at least 10 m in depth.

• Journal of the Korean Geographical Society
• /
• v.45 no.1
• /
• pp.11-25
• /
• 2010

Green Growth was declared as a national development agenda in 2008. There are many contributing concepts and factors in the process of molding the agenda, such as climate change, sustainable development, globalization, the so-called 747 campaign pledges by President Lee in 2007, and the hunger for economic growth in Asia and the Pacific. Green Growth is rather growth-oriented and pays less attention to environmental conservation and social justice. Green Development would fit better as the name of the agenda, dealing with the weaknesses of Green Growth. Climate change itself is a testing ground for geographic knowledges, whose demand is growing rapidly. The contemporary issue increasingly bears complexity that Earth System Science and Sustainability Science have emerged as a research and applications program. Geography is widely recognized as a portal to these programs, where inter- and trans-disciplinary studies are required. Regional potentials should be evaluated from a holistic view so that proper development goals are chosen. Different development trajectory should be taken, depending on the amount of potential a region bears. Material loop should be closed for environmentally sound regions. Green way of life is essential for low carbon society. In the circumstances of climate change in Korean Peninsula and needing of energy efficiency, geographic insight or imagination is urgent for Green Development.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.47 no.6
• /
• pp.45-52
• /
• 2019

As international criteria and standards are required in the fields of design and construction, landscape performance must also be considered not only for the value of the landscape but also for providing quality assurance and sustainability. Given the lack of research on landscape performance, the present research was purposed to analyze the importance of potential assessment categories and items using an analytical network process. A list of assessment items, which is composed of 20 items and 6 categories, was derived through a literature review and a preliminary survey of 11 landscape professionals. An ANP model was established and a survey was conducted among 30 landscape practitioners to determine the weight of priorities considering the criteria. The results of ANP showed that the categories of site selection, preservation and health, and convenience had high priorities while materials had the lowest importance score. For the assessment items, a monitoring plan was the highest importance, followed by cultural/ historic preservation, management cost reduction, and natural ground areas. Despite the difficulties in quantifying landscape achievements, most respondents agreed that there needs to be an evaluation system for landscape performance in order to assure the quality and sustainability of landscape development. More research and discussion are needed to develop an assessment system for landscape performance that is applicable to Korean context.

• Journal of the Korean Geographical Society
• /
• v.48 no.4
• /
• pp.497-508
• /
• 2013

The objective of this study is to determine the spatiotemporal influences of climatic factors and atmospheric aerosol on phenological cycles of the Korea Peninsular on a regional scale. High temporal-resolution satellite data can overcome limitations of ground-based phenological studies with reasonable spatial resolution. Study results showed that phenological characteristics were similar among evergreen forest, deciduous forest, and grassland, while the inter-annual vegetation index amplitude of mixed forest was differentiated from the other forest types. Forest types with high VI amplitude reached their maximum VI values earlier, but this relationship was not observed within the same forest type. The phase of VI, or the peak time of greenness, was significantly influenced by air temperature. Aerosol optical thickness (AOT) time-series showed strong seasonal and inter-annual variations. Generally, aerosol concentrations were peaked during late spring and early summer. However, inter-annual AOT variations did not have significant relationships with those of VIs. Weak relationships between AOT amplitude and EVI amplitude only indicates that there would be potential impacts of aerosols on vegetation growth in the long run.