• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.49 no.5
• /
• pp.556-563
• /
• 2016

We examined the removal of hazardous heavy metals (Cd, Cr, and Pb) from laver Pyropia sp. using citric, hydrochloric, and nitric acids. Under the same conditions, the quality of the laver samples was also evaluated using the variation in absorbance and major mineral levels. The heavy metals that accumulated in raw laver samples after 3 days in seawater included Pb (117.79 μg/g), Cr (33.53 μg/g), and Cd (10.54 μg/g) in descending order. The rate of heavy metal removal from laver was higher at lower pH for all acids used. However, its color changed unsatisfactorily at pH 2.0. After 10 min in seawater at pH 2.5, the heavy metals in laver were eliminated in the order Cd (68.7–81.6%), Pb (57.7–67.0%), and Cr (31.9–49.4%) using the three acids. The differences in heavy metal removal among acid types were not significant. The laver quality was not affected after 20 min at the pH range of 2.5–4.0. The maximum removal of heavy metals was from laver soaked for 10 min in seawater at pH 2.5 using the organic acid, citric acid.

• Korean Journal of Materials Research
• /
• v.11 no.4
• /
• pp.272-277
• /
• 2001

NiO-doped $WO_3$ thick films were prepared by a screen printing technique. The electrical Property and microstructure of the films were investigated with the partial pressure of oxygen and the amount of NiO. The grain size of NiO-doped $WO_3$ was smaller than that of undoped $WO_3$ but the grain sixte of 0.1, 1, 10 mol% NiO-doped$ WO_3$ were nearly the same. The electrical conductance of the $WO_3$ thick films decreased with the oxygen partial pressure, and increased with the amount of NiO to the limit of solid solution. The variation of the electrical conductance with temperature is not so large in the extrinsic region, but it changed rapidly in the intrinsic region. The conductance decreased with adsorption of oxygen in the intermediate range between the extrinsic and intrinsic region.

• Journal of Sensor Science and Technology
• /
• v.1 no.2
• /
• pp.131-145
• /
• 1992

This paper has been described a process technology for the fabrication of Si-on-insulator(SOI) transducers and circuits. The technology utilizes Si-wafer direct bonding(SDB) and mechanical-chemical(M-C) local polishing to create a SOI structure with a high-qualify, uniformly thin layer of single-crystal Si. The electrical and piezoresistive properties of the resultant thin SOI films have been investigated by SOI MOSFET's and cantilever beams, and confirmed comparable to those of bulk Si. Two kinds of pressure transducers using a SOI structure have been proposed. The shifts in sensitivity and offset voltage of the implemented pressure transducers using interfacial $SiO_{2}$ films as the dielectrical isolation layer of piezoresistors were less than -0.2% and +0.15%, respectively, in the temperature range from $-20^{\circ}C$ to $+350^{\circ}C$. In the case of pressure transducers using interfacial $SiO_{2}$ films as an etch-stop layer during the fabrication of thin Si membranes, the pressure sensitivity variation can be controlled to within a standard deviation of ${\pm}2.3%$ from wafer to wafer. From these results, the developed SDB process and the resultant SOI films will offer significant advantages in the fabrication of integrated microtransducers and circuits.

• Journal of Veterinary Clinics
• /
• v.11 no.2
• /
• pp.561-566
• /
• 1994

Serum $\alpha$-tocopherol was measured in cattle to evaluate normal range and to investigate the difference of $\alpha$-tocopherol levels between healthy cattle and diseased cattle. Seventy two heads of 1 year old beef Cattle have 429.9$\pm$77.2 $\mu\textrm{g}$/100ml of Serum $\alpha$-tocopherol. The Serum $\alpha$-tocopherol values of calves with diarrhea(8 heads), pneumonia(6 heads) and piroplasmosis(4 heads) were 87.1$\pm$19.2, 126.3$\pm$45.7 and 106.3$\pm$30.9$\mu\textrm{g}$/100ml, respectively. But that of calves in good health (S heads) was 357.t$\pm$68.4 $\mu\textrm{g}$/100m1. And the values of diseased calves are significantly lower an that of calves in good health(p<0.05). Seasonaly, serum $\alpha$-tocopherol levels of dairy Holstein cows were 529.9$\pm$ 120.3(March), 540.2$\pm$127.2(June), 566.9$\pm$149.5(September) and 550,0$\pm$ 125.4(December)$\mu\textrm{g}$/100m1, respectively. The values on autumn was the highest than that of othor seasons. Serum H-tocopherol level of cows with retained placenta was 262.2$\pm$40.6$\mu\textrm{g}$/100m1. And the level of retained placenta was significantly lower than that of healthy cattle regardless seasonal variation(p<0.05).

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.19 no.2
• /
• pp.106-110
• /
• 1983

As the first step to investigate the effect of ship's motion when detecting target with an echo sounder, variations in the incident sound level at the optional position within the sound beam due to roll motion of the transmitter have been measured and calculated. In this experiment, the transmitter (75 KHz) was mounted to the bottom of a FRP model of the 2,275 G. T. stern trawler and the receiver (75 KHz) was installed at each measuring point within the transmitter's beam. Then, the incident sound level was measured for the roll angles from the free roll test on the model ship. For a range of roll angle of $\pm$20$^{\circ}$from the vertical, the measuring values of the incident sound level at each measuring point were rapidly fluctuated from 12.9% to 78.1 depending on the roll angle, and agreed well with the caculated ones. Consquently, we concluded that the effect of ship's motion when detecting target with an echo sounder should be sufficiently considered.

• Nuclear Engineering and Technology
• /
• v.38 no.4
• /
• pp.375-382
• /
• 2006

Characterization tests (load vs. displacement curve) are conducted for the springs of Zirconium alloy spacer grids for an advanced LWR fuel assembly. Twofold testing is employed: strap-based and assembly-based tests. The assembly-based test satisfies the in situ boundary conditions of the spring within the grid assembly. The aim of the characterization test via the aforementioned two methods is to establish an appropriate assembly-based test method that fulfills the actual boundary conditions. A characterization test under the spacer grid assembly boundary condition is also conducted to investigate the actual behavior of the spring in the core. The stiffness of the characteristic curve is smaller than that of the strap-wised boundary condition. This phenomenon may cause the strap slit condition. A spacer grid consists of horizontal and vertical straps. The strap slit positions are differentiated from each other. They affords examination of the variation of the external load distribution in the grid spring. Localized legions of high stress and their values are analyzed, as they may be affected by the spring shape. Through a comparison of the results of the test and FE analysis, it is concluded that the present assembly-based analysis model and procedure are reasonably well conducted and can be used for spring characterization in the core. Guidelines for improving the mechanical integrity of the spring are also discussed.

• Journal of Korean Ophthalmic Optics Society
• /
• v.13 no.2
• /
• pp.59-62
• /
• 2008

Purpose: This study was designed to investigate the time-dependent changes of visual acuity after alcohol ingestion. Methods: Both the subjective and objective refraction, distant contrast sensitivity, and three needle tests were carried out at 1 and 3 hours after alcohol ingestion. Results: It was found that the degree of myoptization increased as the blood alcohol level increased in the range of average -0.25D ~ -0.35D when tested 1 and 3 hours after alcohol ingestion. Under the same test conditions the increase in blood alcohol resulted in the reduction in the function of dynamic stereopsis. However, the variation in contrast sensitivity was found to be insignificant for all spatial frequencies. Conclusions: The optician has to be well aware of the fact that alcohol could affect the visual acuity and functional tests, therefore inquiring of the alcohol ingestion prior to visual test can be necessary.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.1
• /
• pp.27-38
• /
• 2005

An experimental investigation of the gas-phase photooxidation of toluene-NO$_{x}$-air mixtures at sub-ppm concentrations has been carried out in a 6.9 ㎥, indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NO$_{x}$ experiments included aerosol, $O_3$, NO, NO$_2$, NO$_{x}$ CO, SO$_2$ toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NO$_{x}$ in ppbC/ppb was in the range of 5～20. It was found that the variation of aerosol number concentration with irradiation time caused by the photooxidation of toluene-NO$_{x}$-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NO$_{x}$. The dependency of initial toluene concentration on the photooxidation of toluene-NO$_{x}$-air mixtures for toluene/NO$_{x}$= 5～6 seemed to be opposite to that for toluene/NO$_{x}$=10～11. The maximum number concentration of aerosols formed by photooxidation and the aerosol yield depended on both initial toluene concentration and initial concentration ratio of toluene/NO$_{x}$. In this study, the aerosol yield, defined as aerosol formed per unit toluene consumed, was found to be 0.01～0.16.und to be 0.01～0.16.

• Journal of Biomedical Engineering Research
• /
• v.18 no.1
• /
• pp.25-36
• /
• 1997

To regulate cardiac output of the Total Artificial Heart(TAH) physiologically, the hemodynamic information must be toed back to the controller. So far, our group has developed an automatic cardiac output control algorithm using the motor current waveform, It is, however difficult to detect the preload level such as a filling status of ventricular inflow and the variation of atrial pressures within normal physiologic range(0-15 mmHg) by analyzing the motor current which simultaneously reflects the afterload effect. On the other hin4 the interventricular volume pressure(IVP) which is not influenced by arterload but by preload is a good information source for the estimation of preload states. In order to find the relationship between preload and IVP waveform, we set up the artificial heart system on the Donovan type mock circulatory system and measured the IVP waveform, right and left atrial pressures, inflow and outflow waveforms and the signals represented the information of moving actuator's position. We shows the feasibility of estimating the hemodynamic changes of inflow by using IVP waveform. fife found that the negative peak value of IVP waveform is linearly related to atrial pressures. And we also found that we could use the time to reach the negative peak in IVP waveform, the time to open outflow valve, the area enclosed IVP waveform as unfu parameters to estimate blood filling volume of diastole ventricle. The suggested method has advantages of avoiding thrombogenesis, bacterial niche formation and increasing longterm reliability of sensor by avoiding direct contact to blood.

• Journal of Environmental Health Sciences
• /
• v.45 no.6
• /
• pp.658-667
• /
• 2019

Objective: This study was designed to compare construction types and seasonal radon concentrations in dwellings in Jeollabuk-do Province in Korea. Methods: The measurement of indoor radon concentrations in 79 dwellings using alpha-track detectors was performed every three months (seasonally) over one year between 2015 and 2016. Also, Radon concentrations in soil were measured in spring to investigate the correlations between the concentrations in soil and indoor air. Results: The annual average concentration of indoor radon for dwellings was 89.7±72.1(GM: 72.4) Bq/㎥, with a range (min-max) of 17.2 to 505.4 Bq/㎥. The highest indoor radon concentration was measured in winter and the lowest was shown in summer. The geometric mean of radon concentration in winter was 1.03-2.58 times higher than other seasons. Radon concentrations in soil were investigated at the depth of 1 m, and the concentrations ranged from 1,780 Bq/㎥ to 123,264 Bq/㎥. This showed low correlations with indoor radon concentrations.