• 한국해양학회지
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• v.24 no.1
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• pp.52-61
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• 1989

The daily net primary production by phytoplankton and ammonium excretion by macrozooplankton (> $350{\mu}m$) were measured to understand the nitrogenous nutrient dynamics in the southern part of the East Sea of Korea. At most of the staions, water columns were well stratified and strongly developed pycnoclines and matching nutriclines could be found near the 20-60m. Total chlorophyll ranged between $1.22-3.24{\mu}g$ ChI/l and nano-fractions of chlorophyll ranged from 43.2 to 99.6% in the surface layer. The daily net primary production by phytoplankton ranged from 0.75 to 2.04 gC/$m^2$/d and averaged to be 1.5 gC/$m^2$/d. 1t is evidenced that the primary production and chlorophyll content are relatively high in frontal waters where the North Korean Cold Water meets with the East Korean Warm Water. The turnover time of nitrate in the euphotic zone ranged from 0.2 day to 1.6 day and averaged to be 0.8 day. The N:P ratio of the study area shows on the average 13.4 which indicates nitrogenous nutrient to be the limiting factor for phytoplankton growth. Ammonium excretion by macrowoplankton averaged out to 1.3mg at-N/$m^2$/d, and contributed 7.3% of daily total nitrogen requirement by phytoplankton in this area. Calculation of upward flux of nitrate to the surface mixed layer from the lower layer approximates 7% of nitrogen requirement by phytoplankton.

• Journal of the Korean Regional Science Association
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• v.38 no.2
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• pp.3-20
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• 2022

The purpose of this study is to explore the heterogeneity of compensating wage differentials for outdoor workers, under the threat of climate change and heatwave, by region and by wage quantile. This study conducted Oaxaca-Blinder decomposition, multiple regression analysis by region, and unconditional quantile regression analysis using the Korean Working Conditions Survey, which provides individual-level information on the working environment and worker's characteristics. The implications derived from the results of the study are as follows: For most variables, the endowment effect and the price effect were greater for indoor workers, while experience and gender played a role in narrowing the wage gap; The compensating wage differentials for outdoor workers were confirmed to be 2.4% nationwide, depending on the region however, the compensating wage differentials varied from 5 times of national average to nothing statistically significant; The higher the wage quantile, the greater the compensating wage differentials for outdoor workers, and statistically significant monetary compensation was not identified for some low-level outdoor workers. This study is meaningful as an early study that revealed the heterogeneity of compensating wage differentials for outdoor workers and suggested further research on the topic.

• Journal of the Korean Chemical Society
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• v.63 no.6
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• pp.453-458
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• 2019

Synthesis of ZnCo₂O₃ oxide is performed by sol-gel method via nitrate-citrate route. Powder X-ray diffraction (XRD) study shows monoclinic unit cell having lattice parameters: a = 5.721(1) Å, b = 8.073(2) Å, c = 5.670(1) Å, β = 93.221(8)°, space group P_2/m and Z = 4. Average crystallite sizes determined by Scherrer equation are the range ~14-32 nm, whereas SEM micrographs show nano-micro meter size particles formed in ZnCo₂O₃. Endothermic peak at ~798 K in the Differential scanning calorimetric (DSC) trace without weight loss could be due to structural transformation and the endothermic peak ~1143 K with weight loss is due to reversible loss of O₂ in air atmosphere. Energy Dispersive X-ray (EDX) analysis profile shows the presence of elements Zn, Co and O which indicates the purity of the sample. Magnetic measurements in the range of +12 kOe to -12 kOe at 10 K, 77 K, 120 K and at 300 K by PPMS-II Physical Property Measurement System (PPMS) shows hysteresis loops having very low values of the coercivity and retentivity which indicates the weakly ferromagnetic nature of the oxide. Observed X-band EPR isotropic lineshapes at 300 K and 77 K show positive g-shift at g_iso ~2.230 and g_iso ~2.217, respectively which is in agreement with the presence of paramagnetic site Co²⁺(3d⁷) in the oxide. DC conductivity value of 2.875 ×10^-8 S/cm indicates very weakly semiconducting nature of ZnCo₂O₃ at 300 K. DRS absorption bands ~357 nm, ~572 nm, ~619 nm and ~654 nm are due to the d-d transitions ⁴T_1g(⁴F)→²E_g(²G), ⁴T_1g(⁴F)→⁴T_1g(⁴P), ⁴T_1g(⁴F)→⁴A_2g(⁴F), ⁴T_1g(⁴F)→⁴T_2g(⁴F), respectively in octahedral ligand field around Co²⁺ ions. Direct band gap energy, E_g~ 1.5 eV in the oxide is obtained by extrapolating the linear part of the Tauc plot to the energy axis indicates fairly strong semiconducting nature of ZnCo₂O₃.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.749-754
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• 2011

It is common that basic unit and model of fuel consumption have been used to evaluate effectiveness analysis of transportation infrastructure investment programs. However they could not reflect vehicle characteristics such as loading capacity and types of heavy vehicles. For these reasons, this study reviews convention fuel consumption model which is widely used and conducts a field experiment for 5 classes of heavy vehicles. To develop the fuel consumption quadratic model the field data are used and we develop each model by classes, and then compare with convention fuel consumption model. As a result, between convention and suggested model, there are considerable differences, which have a similar pattern between an 11-ton cargo of convention model and a 25-ton cargo type dump truck of the suggested model. Likewise we identify that there is an approximately 26% gap between convention model result and the result which is calculated a weighted average by registered number of heavy vehicles based on 5 types of fuel consumption model suggested in this study. This result implies that convention fuel assumption model has a realistic limitation.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.497-504
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• 1993

Effects of $Ta_2O_5,ZrO_2$ and $SiO_2$ addition on magnetic properties of 0.02wt%$Bi_2O_3$ and 0 . 0 5 wt%$CaCO_3$ doped Mn-Zn ferrites(58.5mol% $Fe_2O_3$, 25.5 mol% ZnO) were investigated. E:lectrlcal resistivity and magnetic properties such as the initial permeability($\mu_i$), loss factor(tan$\delta$), coercive force Hc(m0c) were measured. With lncreasing $Ta_2O_5$ and $ZrO_2$ addition, the following effects were observed: I ) Decreasing of the average grain size; 2) lncreasing of the electrical resistivity and initial permeability; 3) Ilecreasmg of loss factor values. (very low loss esprcially at high frequency region) ; 4 ) Fine and uniform microsrructures were obtamed at O.lwt% nddecl samples. In case of $SiO_2$ addition, anomalous grain growth and degradation of magnetic properties were observed. The obtained maximum initial permeability value was 6260 at IOkHz. $25^{\circ}C$ from 0.02wt%$Bi_2O_3$. 0.05wt%$CaCO_3$, 0.lwt%$Ta_2O_5$ added sample, the corresponded relative loss factor (tan$\delta /\mu_i$)for the sample was $4.2 \times 10^{-6}$.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.1
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• pp.103-107
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• 2000

Traditionally, EPT and thermal tests were used as diagnostic methods for pulp vitality test. The thermal and electrical stimulation tests are the methods to determine the vitality of a tooth based on its neuronal response. These have certain limitations, one of them is the difficulty of approaching the correct result in case of treatment of children. The reason is management problem caused by the unpleasant stimulation. Also, the response from patients are not objective, and false positive or false negative could be happened. Recently, laser doppler flowmetry and pulse oximeter which evaluate vascular integrity are introduced in an effort of overcoming to limitation of traditional methods. The principle of pulse oximeter is to and out level of oxygen saturation by ratio of the two pulses between emitted light and detected light penetrating them to the termination of body, such as ears or fingers. From this point of view, it can be applied to a tooth to determine its vitality. The objective of this study lies mainly on varifying pulse oximeter as a method of determining tooth vitality and providing basic data of its clinical implementation. The result of the research showed that level of oxygen saturation in vital teeth was average of 96.3% and 0.0% in pulpless teeth. As a comprehensive result, pulse oximeter could be an useful diagnostic equipment in determining of tooth vitality.

• Journal of Korea Water Resources Association
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• v.43 no.6
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• pp.583-595
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• 2010

Virtual water is defined as the volume of water to produce commodities and provide services, which has been developed by Tony Allan since the early 1990s. This research aims to evaluate a volume of virtual water trade in Korea from 1998 to 2007 by applying the evaluation method of unit virtual water volume to agricultural, live stock and industrial products, which is developed by Chapagain and Hoekstra (2004). Also, the concept of water footprint is deployed to quantify the volume of virtual water trade between countries. The study attempts to assess the appropriateness of the evaluation method of unit virtual water volume by employing the method to calculate the total amount of agricultural products in Korea and comparing this with the amount of agricultural water demand in the Korea Water Vision 2006. The research outcome shows that Korea has a net virtual water import of 32 billion $m^3$ on average in the form of agricultural, live stock and industrial commodities whose volume gradually increases. The gap between the volume of virtual water import of agricultural and live stock commodities and the total volume of agricultural water use reaches approximately 600 million $m^3$. This figure can be negligible considering the total volume of water demand in Korea, around 16 billion $m^3$, which demonstrates the validity of the evaluation method in terms of analyzing water balance.

• Journal of Yeungnam Medical Science
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• v.3 no.1
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• pp.361-366
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• 1986

Fracture of the carpal scaphoid bone is the most common fracture of the carpus. Unfortunately. nonunion are common since the symptoms do not alert patients to seek early medical treatment and the diagnosis is easily missed. Fracture of the scaphoid is a common condition whose management remains controversial. The conservative treatment has many complications, these include inability to work while in plaster, stiffness of the wrist afterwards, muscle wasting, weakness and malunion. So various operative treatments of scaphoid fracture have been developed. Open reduction by use of screws suggested by Maclaughlin first in 1954. In 1984 a new and simple operative technique has been developed to provide rigid internal fixation for all types of fractures of the scaphoid by T.J. Herbert. This involves the use of a double-treaded bone screw which provides good fixation that, after operation, a plaster cast is rarely required and most patients are able to return to work within a few weeks. Authors have experienced 10 cases of scaphoid fracture and accomplished good result in all cases by internal fixation using Herbert screw. The results are as follows : Of these 10 fractures, 2 were fresh fractures and 8 were non unions of scaphoid fracture. In nonunion cases, the time interval between fracture and operation was from 5 months to 5 years. The postoperative immobilization period was average of 4 weeks. Short period of immobilization achieved early functional recovery of the wrist. The bony unions in roentgenogram were seen from 3 months to 9 months after operation. In 2 cases the fracture gap was seen after 9 months. But in these cases the symptoms such as pain and range of motion of wrist were improved.

• Korean Journal of Materials Research
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• v.12 no.8
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• pp.624-633
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• 2002

In order to improve the hydrogen storage capacity and the activation properties of the hydrogen storage alloys, the rare-earth metal alloy series, MmN $i_{4.5}$M $n_{0.5}$Z $r_{x}$(x=0, 0.025, 0.05, 0.1), are prepared by adding excess Zr in MmN $i_{4.5}$M $n_{0.5}$ alloy. The various parts in hydrogen storage vessel consisted of copper pipes reached the setting temperature within 4~5 minutes after heat addition, which indicated that storage vessel had a good heat conductivity required in application. The performance test on storage vessel filled with rare-earth metal alloys of 1000 gr was also conducted after hydrogen charging for 10 min at $18^{\circ}C$ under 10 atm. It showed that the average capacity of discharged hydrogen volume was found to be for $MmNi_{4.5}$ $Mn_{0.5}$ and $MmNi_{4.5}$ $Mn_{x}$ 0.5/$Zr_{samples}$ indicated that the released amount of hydrogen for this $AB_{5}$ type alloys was more than 92 % of theoretic value, and also it was found that the optimum discharging temperature for obtaining an appropriate pressure of 3 atm was determined to be $V^{\circ}C$ for $MmNi_{4.5}$ $Mn_{0.5}$$Zr_{x}$(x=0, 0.025, 0.05, 0.1) hydrogen storage alloys. The released amount of these hydrogen storage samples was 125 $\ell$ , 122.4 $\ell$ and 108.15 $\ell$/kg for $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{0.025}$ $MmNi_{4.5}$M $n_{0.5}$Z $r_{0.05}$, and MmN $i_{4.5}$ Mn_0.5$Zr_{0}$, at $70^{\circ}C$ respectively. Amount of the 2nd phases increase with increase on Zr contents in $MmNi_{4.5}$$Mn_{0.5}$ $Zr_{ 0.1}$/ alloy. This phenomenon indicates that$ ZrNi_3$ in $MmNi_{4.5}$ $Mn_{0.5}$ $Zr_{x}$ / phase, which shows the maximum storage capacity and the strong resistance to intrinsic degradation, is considered as a proper alloy for hydrogen storage. As the Zr contents increase, the activation time and the plateau pressure decreases and sloping of the plateau pressure increases.creases.eases.s.

• Journal of The Korean Association For Science Education
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• v.35 no.5
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• pp.907-917
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• 2015

Response to Intervention (RTI), which is focused on the gap between pre-interventions and post-interventions, provides an effective intervention program. This study takes under-achievement factors into consideration to determine the overall characteristics of underachievers. The under-achievement factors include cognitive learning factors, affective factors, and environmental factors. This study conducted curriculum-based assessments, achievement tests, and assessments on attitudes toward science and science learning motivation to verify the effects of individually tailored teaching according to the types of under-achievement in science. The experimental group was composed of six students in fourth grade, and the comparison group had 23 students. The findings of the study were as follows. First, the performance and progress of underachievers in the first-stage showed little progress and did not reach grade-level performance. Second, the underachievers in the second-stage greatly improved. In particular, the average of eight sessions in the second-step demonstrated performance beyond that of the regular child. Third, individually tailored teaching according to the types of under-achievement in science positively affected attitudes toward science and science learning motivation. This study will contribute to the improvement of the underachiever by applying individually tailored teaching according to the types of under-achievement in science.