• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.173-186
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• 1999

To utilize diffuse sampling of formaldehyde in air, a new sampler was designed. A glass fiber filter was impegnated with 2,4-dinitrophenylhydrazine(DNP) and phosphoric acid and mounted 37mm cassette. The formaldehyde vapor was sampled in the dynamic chamber and measured by high performance liquid chromatograph and compared with solid sorbent tube. The results were as follows ; 1. The desorption efficiencies of diffusive sampler between 97.0% and 100%. 2. the sampling rate is constant as in $58{\sim}61.8m{\ell}/min$ when sampling times are between 120 and 360 min. 3. There was a significant relationship between concentrations of diffusive samples and active samples with the coefficient of determination(R2) of 0.92. 4. Desorbed amount of formaldehyde diffusive sampler was increased by high relative humidity. 5. Wheth diffusive samplers were stored at room temperature or at refrigerator there was no statistically significant difference in the accuracy of result. 6. When the diffusive samplers, which collected formaldehyde vapor, were exposed to clean air for three hours, there was no significant loss of formaldehyde due to reverse diffusion. In conclusion, this study suggest that developed diffusive samplers will be a reasonable substitute for the solid sorbent tube for sampling formaldehyde and practical comparative study of developed diffusive sampler should be performed at workplaces of manufacturing industry.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.639-646
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• 2000

It is important to estimate the mechanical properties of clay since it is directly related to the design and the construction of geotechnical structures. Site exploration, which is composed of boring, sampling, in-situ, or laboratory tests, is preformed to estimate the mechanical properties. However, mechanical properties of clay measured from laboratory test may be different from in-situ properties due to disturbances occurred during sampling, transportation, storage, and trimming. In this study, the degree of disturbance according to sampling method was estimated with the test results of CK/sub o/U triaxial compression test on Yangsan clay. The soil samples were obtained by three types of sampling method, j.e., 76mm-tube sampler, 76mm-piston sampler, and block sampler. In order to evaluate the quality of samples, volumetric strain, undrained shear strength, secant Young's modulus, and pore pressure coefficient at peak measured from each sample were compared with one another. From the test results, it was observed that mechanical properties of the block and piston samples were more reliable than those of tube samples. But it was observed that the water content of piston was similar to that of tube samples at given depths while the water content of block samples was 14.3∼15.8% smaller than that of piston and tube samples. In addition to the evaluation of the quality of samples, relationship between c/sub u// σ/sub vc/'and OCR was established from the results of the CK/sub o/U triaxial compression tests, which were carried out using SHANSEP method. And also undrained shear strength was analyzed using the in-situ test data such as Cone Penetration Test(CPT), Dilatometer Test(DMT), and Field Vane Test(FVT) and was compared with that evaluated from CK/sub o/U triaxial compression test.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.4 no.2
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• pp.208-223
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• 1994

The purpose of this study was to evaluate the efficiency of diffusive(or passive) sampler in measuring airbone organic solvents. Diffusive samplers are generally simple in construction and do not require power for operation. The efficiency of the diffusive samplers has not sufficiently been investigated in Korea. Three types of samplers were studied in this study. The sampling and analytical results by passive samplers were compared with results by charcoal tube method recommended by NIOSH(National Institute for Occupational Safty and Health). The following characteristics are identified and studied as critical to the performance passive monitors; recovery, reverse diffusion, storage stability, accuracy and precision, face velocity and humidity, n-Hexane, TCE(trichloroethylene) and toluene were used as test vapors. A dynamic vapor exposure system consisting of organic vapor generator and sampling chamber for evaluating diffusive samplers are made. The results of the study are summarized as follows. 1. NIOSH recommands that the overall accuracy of a sampling method in the range of 0.5 to 2.0 times the occupational health standard should be ${\pm}25$ percent for 95 percent confidence level. Among three types of diffusive samplers, sampler A has permeation membrane and samplers Band C have diffusive areas, samplers A and B met the criterion that overall accuracy for 95% confidence level of the samplers were within ${\pm}25$ percent of the reference value. Sampler C had overall accuracy ${\pm}9.6%$ and ${\pm}11.8%$ in hexane and TCE, respectively. The concentration of toluene was overestimated in sampler C with overall accuracy of ${\pm}43.9%$. 2. The desorption efficiencies of diffusive samplers were 96-107%. 3. There was no significant sampe loss during four weeks of storage both with and without refrigeration. 4. There was no significant reverse diffusion, when the samplers were exposure to clean air for 2 hours after sampling for 2 hours at the level of 2 TLY. 5. In case of 8 hours sampling, relative differences(RD) of concentrations between charcoal tube method and diffusive method were 15-39%, 13-46%, and 4-35% for sampler A, B and C, respectively. The performance was poor in 8 hours sampling for multiple substance monitors. 6. At high velocity(100 cm/sec), samplers B and C overestimated the concentrations of organic vapors, and sampler A with permeation membrance gave better results. 7. At 80% relative humidity, samplers showed no siginificant effect. Low humidity also did not affect the diffusive samplers.

• Journal of Technologic Dentistry
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• v.11 no.1
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• pp.95-102
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• 1989

This study was performed to study the efficiency of a local ventilation system, installed in dental laboratories, and of two types of protecting face masks. The dust originating from the workpiece as well as from the wheels and stones was collected on air filters in the cutting cycle during coarse and fine grinding, and in the subsequent polishing procedures of each specific dental material. The efficiency of the ventilation system was measured on the basis of weight reduction of dust in the breathing air at a distance about 20-40 cm from workpiece. The results were as follows: 1. Use of the local ventilation system reduced the amounts of respirable dust to an average level of 21.4%, although the efficiency of the local ventilation system varied depending upon materials used. 2. Mounting a nozzle on the tube improved the efficiency of the ventilation system considerably. The efficiency of the local ventilation system also increased as the workpiece was closing to the tube inlet. 3. With or without the local ventilation system, the distance between the position of the workpiece and sampler greatly affected the dust level. 4. The face masks covering the sampler improved the efficiency of the ventilation system considerably.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.7 no.1
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• pp.33-48
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• 1997

Korean diffusive sampler (KDS) and charcoal tube (CT) were used for sampling n-hexane, trichloroethylene and toluene in air KDS was made by Department of Environmental Health, SNU-SPH in 1995. Surveys were conducted at ten industrial plants with organic solvents. The relationship between two sampling methods was examined by linear regression analysis, and concentrations by two sampling methods were compared using paired t-test. The results are as follows: 1. The geometric means by CT and KDS methods were 3.26ppm and 3.32ppm for n-hexane, 5.07ppm and 6.34ppm for toluene, and 7.18ppm and 7.90ppm for toluene, respectively. There was no significant difference between results by CT and KDS methods in three organic vapors (p>0.05). When linear regression analysis was performed, two sampling methods were highly related ; correlation coefficients were 0.98, 0.90 and 0.96 for n-hexane, toluene and trichloroethylene, respectively. 2. Airborne concentrations of n-hexane (n=21) were below 0.5 TLV level. The GM by two methods were almost same (3.09 ppm). And there was no significant difference between results by two methods (p>0.05). 3. Since toluene and trichloroethylene concentrations showed several levels, appropriate sampling rates were applied for each level. The GM of toluene concentrations by two methods at 0.5 TLV level were 3.75ppm and 5.48ppm. The KDS method overestimated the toluene concentrations at 0.5 TLV level (p<0.05). The GM values of toluene concentrations at 1 TLV level were 31.80ppm and 25.38ppm and at 2 TLV level were 64.13 ppm and 51.37 ppm. The KDS method underestimated concentration at both level (p<0.05). For trichloroethylene, the GM at 0.5 TLV level were 4.97 ppm and 7.11ppm. The KDS method overestimated the concentration of trichloroethylene (p<0.05). In conclusion, concentrations of three organic vapors measured by CT and KDS were not significantly different and results by two methods were highly related. But at contain concentrations, the levels by method were significantly different. Therefore, it is suggested that sampling rate of KDS should be studied simultaneously using CT method for organic vapors.

• Journal of Intelligence and Information Systems
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• v.28 no.4
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• pp.329-346
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• 2022

Recently, as the market for short form videos (Instagram, TikTok, YouTube) on social media has gradually increased, research using them is actively being conducted in the artificial intelligence field. A representative research field is Video to Shop, which detects fashion products in videos and searches for product images. In such a video-based artificial intelligence model, product features are extracted using convolution operations. However, due to the limitation of computational resources, extracting features using all the frames in the video is practically impossible. For this reason, existing studies have improved the model's performance by sampling only a part of the entire frame or developing a sampling method using the subject's characteristics. In the existing Video to Shop study, when sampling frames, some frames are randomly sampled or sampled at even intervals. However, this sampling method degrades the performance of the fashion product search model while sampling noise frames where the product does not exist. Therefore, this paper proposes a sampling method MF (Missing Fashion items on frame) sampler that removes noise frames and improves the performance of the search model. MF sampler has improved the problem of resource limitations by developing a keyframe mechanism. In addition, the performance of the search model is improved through noise frame removal using the noise detection model. As a result of the experiment, it was confirmed that the proposed method improves the model's performance and helps the model training to be effective.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.95-102
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• 1999

It is important to estimate the magnitude of settlement and the time of primary consolidation in geotechnical engineering projects. For these purposes, site explorations and laboratory tests are usually performed. However, the mechanical properties determined from laboratory tests on the samples obtained by different sampling techniques show different trends. In this study, three types of consolidation test were carried out on the soil samples obtained by three different sampling techniques (76mm tube, 76mm piston, and block samples), to verify the effect of sample disturbance on consolidation properties. It was found that sampling methods have influence on the $\varepsilon$ - log $\sigma$'$_{v}$ relationship. While insignificant difference of compression indices from the samples obtained by different sampling techniques was observed in compression region, these values showed a different trend in precompression region. The values of $c_{v}$ and k of block samples had a tendency to be larger than those of piston and tube samples. At consolidation pressure larger than $\sigma$'$_{p}$, however, these properties became similar regardless of sampling methods. The block and piston samples gave slightly higher values of $C_{a/}$ $C_{c}$ than tube samples. In the results of I $L_{EOP}$ and CRS test, it was observed that the values of $\sigma$'$_{p measured}$/$\sigma$'$_{p best estimated}$ of Yang-San clay decreases when strain becomes larger than 1.0% and that precompression strain of block samples is in the range of 1.5~2.0% while those of piston and tube samples are 1.75~3.75%. It was also shown that the values of $\sigma$'$_{p}$ of block samples exceed those of piston and tube samples by about 6~10%.6~10%.%.%.%.%.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.206-211
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• 2001

This article describes identification and quantification of benzene in the casting process. Air samples around the casting process were taken by using personal air sampler attached charcoal tube and desorbed by carbon disulfide. The identification and quantitative analysis of benzene have been performed by GC-MS and GC-FID. Calibration range of standard solutions for benzene was prepared in range from 0.1 to 2 times of TLVs concentrations($1.4{\sim}28{\mu}g/1m{\ell}$ CS2) and the limit of detection was $0.11{\pm}0.002{\mu}g/1m{\ell}$ CS2. Benzene detected in airborne was ranged in 4.0ppb~104.7ppb.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.43-53
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• 2003

To get improved soil parameters in the laboratory tests, the effects of sample disturbance should be excluded as much as possible. A collaborative research between Dong-A University and PHRI (Japan) was conducted to investigate the effects of sample disturbance due to sampling techniques and samplers on Pusan clays. The results of unconfined compression and consolidation tests performed on the clay samples taken by them have been compared in terms of soil parameters and sample disturbance. As the result of the study, it was found that when the Korean sampler was used with a different technique of cleaning the borehole bottom and removing slime before inserting and penetrating the sampler tube, similar to the one commonly used in Japanese practice, the quality of samples could be greatly improved. Furthermore, the CRS test with the rate of 0.02%/min yielded larger values of consolidation parameters and better degree of sample disturbance than those of oedometer test, due to the difference in testing method.

• Geotechnical Engineering
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• v.8 no.3
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• pp.23-36
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• 1992

The flat dilatometer(DMT) has been practically used as an in-situ test equipment. It is a simple, rapid and cost-effective tool to characterize the in-situ stress-strain-strength properties of various types of ground materials. However, the results of flat DMT should be validated with considerable data with respect to the known reference values for a specific site. In this study, the applicability of existing relationships which were established for other local deposits is verified by performing the tests in several clay deposits. To compare with the DMT results, field vane tests and cone penetration tests were also carried out in the same field as reference tests, and unconsolidated undrained tests, oedometer tests, and other fundamental material properties tests were conducted on the thin-walled tube samples in the laboratory. The results of the flat DMT combined with empirical correlations are used to estimate soil types, unit weights, coefficients of lateral earth pressure at rest, overconsolidation ratios, constrained moduli and undrained shear strengths of three clay local deposits. It was found that various geotechnical properties estimated from the flat DMT generally well agree with those from the reference tests.