• Journal of the Korean Society for Marine Environment & Energy
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• v.9 no.4
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• pp.216-224
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• 2006

To clarify the formation process and characteristics of oxygen deficient water mass in Gamak Bay, oxygen deficiency was weekly observed from 17 June to 12 September 2005. Surface water temperature was significantly lower in the outer bay than in the inner bay, whereas the bottom water temperature was higher in the central area of bay than in the outer and inner bay. The vertical stratification of water mass was strongly formed during the period, and thermocline was observed between 3 and 5m deep. The oxygen deficiency in the bottom layer began to appear at early July in the inner bay and gradually spread to the center area of the bay in early August. The mean transparency and light attenuation coefficient($K_d$) in water mass was 4.0m and 0.47, respectively. Average concentrations of nutrient and chlorophyll ${\alpha}$ in the bottom layer were significantly higher than those in surface, and those concentrations were significantly higher in the inner bay than in the outer bay. During the formation of oxygen deficiency in the bottom layer, oxygen penetration depth in the bottom sediment were extremely shallow, and oxygen consumption rate in the bottom sediment were lower than that in the area where oxygen deficient water mass disappeared. Dissolved oxygen concentrations in the bottom layer are negatively correlated with nutrient concentrations, whereas those in the surface layer did not show a significant relationship with nutrient concentrations. Elevated loss of oxygen in the bottom water mass was attributed to the increase of the oxygen consumption rates in sediments and the decomposition of organic matter by microorganism.

• Journal of Digital Convergence
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• v.13 no.9
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• pp.431-437
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• 2015

This convergence study analyzed the effectiveness of contrast agent reduction by normal saline solution dilution in the computed tomography of arteries of lower limb. 48 patients of 125 cc contrast agent and 30 patients of the same amount divided at a ratio of 7:3 for the contrast agent and normal saline solution were studied. The average attenuation coefficient(HU) and signal to noise ratio(SNR) of abdominal aorta, femoral artery, popliteal artery and posterior tibial artery at each image were evaluated quantitatively and the four criteria in the five point scale was conducted qualitatively by two radiologists and four radiological technologists. In the quantitative evaluation, both HU and SNR had high average score before dilation but there were no statistical significance by independent t-test(p>0.05). In the qualitative evaluation, there were a little differences in the average scores between 4.86~4.77 of original contrast agent and 4.83~4.67 of dilated contrast agent but there were no statistical significance(p>0.05). In the computed tomography of arteries of lower limb, the dilated contrast agent doesn't influence image quality and reduces overall contrast agent and lowers iodine content per unit of molecular therefore will contribute to decrease side effect of contrast agent.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.1
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• pp.13-19
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• 2009

A 440MHz wireless and passive surface acoustic wave (SAW) based chemical sensor was developed on a $41^{\circ}YX\;LiNbO_3$ piezoelectric substrate for simultaneous measurement of $CO_2$ gas and relative humidity (RH) using a reflective delay line pattern as the sensor element. The reflective delay line is composed of an interdigital transducer (IDT) and several shorted grating reflectors. A Teflon AF 2400 and a hydrophilic $SiO_2$ layer were used as $CO_2$ and water vapor sensitive films. The coupling of mode (COM) modeling was conducted to determine optimal device parameters prior to fabrication. According to simulation results, the device was fabricated and then wirelessly measured using the network analyzer. The measured reflective coefficient $S_{11}$ in the time domain showed high signal/noise (S/N) ratio, small signal attenuation, and few spurious peaks. In the $CO_2$ and humidity testing, high sensitivity ($2^{\circ}/ppm$ for $CO_2$ detection and $7.45^{\circ}/%$RH for humidity sensing), good linearity and repeatability were observed in the $CO_2$ concentration ranges of $75{\sim}375ppm$ and humidity levels of $20{\sim}80%$RH. Temperature and humidity compensations were also investigated during the sensitivity evaluation process.

• Journal of radiological science and technology
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• v.25 no.2
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• pp.47-55
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• 2002

We came to the following conclusion as the results of experiment on the image quality of mammography and the average glandular dose using 4 apparatuses at 3 hospitals in Seoul. 1. Whereas the measurement of half value layer showed no differences among the apparatuses, the measurement by an attenuation curve method showed some differences by 5.9%. There were 9.1% differences in the measurement by aluminum conversion method. 2. The basic density of an automatic exposure control unit must be D = 1.40, but there was no automatic exposure unit adjusted precisely at any hospitals. The unit at the B hospital exceeded the allowable limit by ${\pm}0.15$. 3. In the photographing using an automatic exposure control unit and the management of an automatic film processor using a sensitometer, most automatic film processors were well kept. But in some cases the mean value of a fluctuation coefficient exceeded the allowable limit. There is a need for more cautious management. 4. The image quality of breast phantom photography was affected by the screen/film system among the hospitals. 5. The average glandular dose at a breast of 4.2 cm thickness depended on the tube voltage, In the case of Mo/Mo, it was measured $0.26{\sim}1.39\;mGy$ less than ACR standard 3.0 mGy.

• Journal of radiological science and technology
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• v.29 no.2
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• pp.63-69
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• 2006

In diagnostic ultrasound, the quality of image affect to diagnose. To maintain suboptimal imaging uniformly, Quality Assurance of Ultrasound equipment should take periodically. This is article about examination the quality of image in diagnostic ultrasound to understand conditions of probes in hospitals. There is comparative study of convex and linear probes on ultrasound using tissue-mimicking phantom included simulated cysts, echogenic structures. The ultrasonic attenuation coefficient versus frequency of 0.5 dB is representative of normal liver and 0.7 dB is representative of fatty liver condition in ultrasound phantom. There are results of convex probe, 0.5 dB, vertical group, cystic masses, high contrast masses are mostly shown but 0.7 dB, mid level in vertical group, cystic masses and high contrast masses are nearly visible. In linear probe, 0.5 dB, mid level in vertical group, two or four of them are shown in cystic masses and high contrast masses but there are not visible in 11 of cases. 0.7 dB, there are mostly appear under 6 in vertical group, two or four of them show in cystic masses and high contrast masses and there are not shown in 40 of cases, besides. Linear probes in fatty liver condition of ultrasound instrument are not good in the quality of image practically. So there needs to be replace and fix of probes. Actually management of ultrasound probes is inadequate in hospitals. So if there are program of evaluation to check probes periodically in hospitals from establishment of the ultrasound equipment, there will get better image and have a suitable condition of instruments further more.

• Journal of radiological science and technology
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• v.39 no.1
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• pp.71-79
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• 2016

The purpose of this study is computed tomography contrast agent at low concentrations and low tube voltage technique to evaluate the usefulness on the phantom image. By varying the degree of mixture by the contrast medium concentration it was inserted in phantom. It was taken by changing the tube voltage and tube current step by step, and to evaluate the dose and the CT value obtained from the phantom image. As a result, low-contrast, low tube voltage(300 mgI/ml, 100 kV) was reduced by an average 21%(CTDIvol; computed tomography dose indexvol) more standard condition(350 mgI/ml, 120 kV). SNR was increased at all depths of the phantom, respectively 1:10 and 1:20(by diluting a contrast agent and normal saline) 12.2(26%) 6.2(17%). CNR was increased at all depths of the phantom, respectively 1:10 and 1:20(by diluting a contrast agent and normal saline) 11.5(32%), 6.3(26%). Research work on the CT scan is necessary in a variety of studies on the low contrast concentration and low tube voltage techniques for dose reduction and reducing of side effects the contrast agent.

• The Korean Journal of Nuclear Medicine
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• v.21 no.2
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• pp.175-182
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• 1987

For measurement of ventricular performance, ejection fraction (EF) has gained wide acceptance. But EF is influenced not only by changes in muscle function but also by changes in cardiac loading conditions. In case of valvular heart disease which is variable in loading conditions, EF cannot be reliable as an index of myocardial contractility. The end systolic pressure (ESP)-end systolic volume (ESV) relation, howver, is known to represent myocardial contractility, independent of changes in loading conditions. Similar results can be obtained by using peak-systolic pressure (PSP) instead of ESP. To evaluate the utility of the peak systolic pressure-end systolic volume index (PSP-ESVI) relation as an index of myocardial function, we measured $PSP&ESVI$ in 19 partents with coronary artery disease before $(PSP_1\;&\;ESVI_1)$ and after $(PSP_2\;&\;ESVI_2)$ sublingual administration of nitroglycerin. PSP was measured with standard mercury sphygmomanometer during gated blood pool scintigraphic study. ESVI was measured by count derived method after attenuation correction. $PSP_2\;&\;ESVI_2$ measurement was started when the fall of PSP was greater than 5 mmHg after 7-14 minutes post-administration of nitroglycerin. Mean values $({\pm}S.D.)$ of $PSP_1\;&\;ESVI_1$ was $124.9({\pm}20.7)mmHg\;&\;59.4({\pm}39.9)ml/M^2$. Mean values $({\pm}S.D)$ of $PSP_2\;&\;ESVI_2$, was $113.2({\pm}19.9)mmHg\;&\;37.5({\pm}26.1)ml/M^2$. There was a significant difference between mean values of $PSP_1\;&\;PSP_2$, (p<0.01), and mean values of $ESVI_1\;&\;ESVI_2$, (p<0.01). $PSP_1-PSP_2/ESV_1-ESVI_2,\;PSP_1/ESVI_1$ and EF were in the range of 0.14-5.19 mmHg/ml/$M^2$, 0.67-7.68 mmHg/ml/$M^2$ and 10.8%-74.5% respectively. $PSP_1-PSP_2/ESVI_1-ESVI_2$, and EF showed exponential correlation (r=0.85, P<0.01). The correlation coefficient between $PSP_1/ESVI_1$ and EF was 0.73(p<0.01). With the above results, we suggest that $PSP_1-PSP_2/ESVI_1-ESVI_2$, and $PSP_1/ESVI_1$, can be used as an index of myocardial function.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.2
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• pp.127-141
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• 1995

The distribution of water mass in Deukryang Bay was investigated using observational data obtained on July 12 (spring tide) and 19 (neap tide) in 1994. In characteristics of water mass at the bay the area is divided into three ones by a vertical attenuation coefficient k and a stratification parameter, log sub (10) (H/U super (3)), was H is depth, and U mean velocity in the bay. The contour of k=0.6 has a similar distribution to the isobath of 10m depth in spring tide, and of 5m depth in neap tide, respectively. This indicates that the water mass in the area between the isobath of 5m and 10m depth is changed by tidal periods. The stratification parameter corresponding to k=0.6 was 2.1~2.2. In the shallow water of 5m depth the characteristics of water mass was distributed in temperature of 25.5~31.$0^{\circ}C$ and salinity of 32.8~33.8PSU(Practical Salinity Unit), the temperature was high and the salinity distributed widely. In the deep water of 10m depth it was the temperature of 22.0~29.5$^{\circ}C$ and the salinity of 33.0~33.6PSU, the temperature was low and the salinity distributed narrowly. In the middle depth water of 5m to 10m depth, the temperature of 22.0~30.$0^{\circ}C$ and the salinity of 32.8~33.5PSU, its values showed the middle between the values of the deep area and the values of the shallow area.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.575-584
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• 2021

The aim of this study was to achieve optimal portal phase while reducing contrast medium by applying weight-based dose protocol compared to standard fixed dose protocol to performing of pediatric abdominal CT examination. Discovery 750HD (General Electric Medical Systems, Milwaukee, USA) was used, and a total of 167 children consisting of 85 men and 82 women under the age of 18 were studied. The group in which the 300 mgI/ml(Xenetix, Guerbet, France) contrast medium was fixedly injected at twice body weight and the group injected with physiological saline while gradually decreasing the injection amount by 10% while applying the weight-based protocol were distinguished. Also, the CT number and SNR of abdominal organs were compared and evaluated while changing the scan delay time. Subjective image quality of enhancement and beam-hardening artifacts of around the heart was assessed with five-point criterion. The group adapted weight-based protocol with 20% reduction in contrast medium was most similar in contrast enhancement in the group with fixed injection at twice body weight. Furthermore, the group with a delay time of 20% had the highest contrast enhancement effect, and the difference in CT attenuation coefficient from the group scanned immediately after injection of the contrast media. Therefore, the appropriate delay time after injection of the contrast agent increased the contrast enhancement of the parenchymal organ. In addition, the weight-based injection protocol with normal saline reduced artifacts around the heart, and the effect of contrast enhancement could be maintained. In conclusion, it is possible to reduce dosage of contrast media through the application of weight-based injection protocols and appropriate latency, and to characterize optimal portal phase imaging on pediatric abdominal CT.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.603-615
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• 2020

The design factors of artificial recharge are determined by considering the hydrogeological characteristics of the aquifer. The optimal design factors for artificial recharge were derived after performing the injection tests step by step for each injection type (vertical well, ditch and mixed type), which were built in the test site of the study area. It was analyzed that the difference in the injection effect according to the diameter of the injection well was not large, and the 100 mm well was evaluated as appropriate in consideration of the availability and economy of land use. Since the injection effect was well maintained even in the upper rock, the depth of the injection well was proposed for the alluvial layer and the upper rock layer. On the other hand, in four cases of filter media in the ditch, it was analyzed that the penetration efficiency and the hydraulic interference effect indicated excellent injection performance when a filter medium of 10 to 30 mm diameter was filled in the ditch. In addition, the proper spacing of the injection wells was analyzed as 9~12 m considering the interference efficiency. The interference efficiency attenuation coefficient per 1 m of hole spacing was calculated to be 1.75% in this area. In the future study, the artificial recharge design factors obtained in this stage are applied and verified on site construction and operation. Also it is expected to contribute to securing water in areas where there is always a lack of water.