• Journal of Sensor Science and Technology
• /
• v.31 no.5
• /
• pp.343-347
• /
• 2022

Recently, the problem of global warming caused by greenhouse gases is getting serious due to the development of industry and the increase in transportation means. Accordingly, the need for a technology to reduce carbon dioxide, which accounts for most of the greenhouse gas, is increasing. Among them, a catalyst for converting carbon dioxide into fuel is being actively studied. Catalysts for reducing carbon dioxide are classified into thermal catalysts and photocatalysts. In particular, the photocatalyst has the advantage that carbon dioxide can be reduced only by irradiating ultraviolet rays at room temperature without high temperature or additional gas. TiO₂ is widely used as a photocatalyst because it is non-toxic and has high stability, but has a disadvantage of low carbon dioxide reduction efficiency. To increase the reduction efficiency, 1-propanol was used in the synthesis process. This prevents agglomeration of the catalyst and increases the specific surface area and pores of TiO₂, thereby increasing the surface area in contact with carbon dioxide. As a result of measuring the CO₂ reduction efficiency, it was confirmed that the efficiency of TiO₂ with 1-propanol and TiO₂ without 1-propanol was 19% and 12.3%, respectively, and the former showed a 1.5 times improved efficiency.

• Journal of Sensor Science and Technology
• /
• v.32 no.3
• /
• pp.169-173
• /
• 2023

With the increasing concern of global warming caused by greenhouse gases owing to the recent industrial development, there is a growing need for advanced technology to control these emissions. Among the various greenhouse gases, nitrogen dioxide (NO₂) is a major contributor to global warming and is mainly released from sources, such as automobile exhaust and factories. Although semiconductor-type NO₂ gas sensors, such as SnO₂, have been extensively studied, they often require high operating temperatures and complicated manufacturing processes, while lacking selectivity, resulting in inaccurate measurements of NO₂ gas levels. To address these limitations, a novel sensor using PbS quantum dots (QDs) was developed, which operates at low temperatures and exhibits high selectivity toward NO₂ gas owing to its strong oxidation reaction. Furthermore, the use of P3HT conductive polymer improved the thin film quality, reactivity, and reaction rate of the sensor. The sensor demonstrated the ability to accurately measure NO₂ gas concentrations ranging from 500 to 100 ppm, with a 5.1 times higher sensitivity, 1.5 times higher response rate, and 1.15 times higher recovery rate compared with sensors without P3HT.

• Journal of Sensor Science and Technology
• /
• v.32 no.3
• /
• pp.194-198
• /
• 2023

With the recent development of industrial technology, the problem of odor due to leakage of toxic gas discharged from industrial complexes is gradually increasing. Among them, hydrogen sulfide is a colorless representative odorous substance that can cause pain through irritation of the mucous membranes of the eyes and respiratory tract, and is a gas that can cause central nervous system paralysis and suffocation when exposed to high concentrations. Therefore, in order to improve the odor problem, research on a gas sensor capable of quickly and reliably detecting a leak of hydrogen sulfide is being actively conducted. A lot of research has been done on the existing metal oxide-based hydrogen sulfide gas sensor, but it has the disadvantage of requiring low selectivity and high temperature operating conditions. Therefore, in this study, a Pt/CNT-based electrochemical hydrogen sulfide gas sensor capable of detecting at low temperatures with high selectivity for hydrogen sulfide was developed. A working electrode capable of selectively detecting only hydrogen sulfide was fabricated by synthesizing Pt nanoparticles as a catalyst on functionalized CNT and applied to an electrochemical hydrogen sulfide gas sensor. It was confirmed that the manufactured Pt/CNT-based electrochemical hydrogen sulfide gas sensor has a current change of up to 100uA for hydrogen sulfide, and the both response time and recovery time were within 15 seconds.

• Journal of Sensor Science and Technology
• /
• v.32 no.5
• /
• pp.285-289
• /
• 2023

Recently, the demand for lidar systems for autonomous driving is increasing, and research on Shortwave Infrared(SWIR) photodetectors for this purpose is being actively conducted. Most SWIR photodetectors currently being developed are based on InGaAs, and have the disadvantages of complex processes, high prices, and limitations in research due to monopoly. In addition, current SWIR photodetectors use lasers in the 905 nm wavelength band, which can pass through the pupil and cause damage to the retina. Therefore, it is required to develop a SWIR photodetector using a wavelength band of 1400 nm or more to be safe for human eyes, and to develop a material that can replace the proprietary InGaAs. PbS QDs are group 4-6 compound semiconductors whose absorption wavelength band can be adjusted from 1000 to 2700 nm, and have the advantage of being simple to process. Therefore, in this study, PbS QDs having an absorption wavelength peak of 1415 nm were synthesized, and a SWIR photodetector was fabricated using this. In addition, the photodetector's responsivity was improved by applying P3HT and ZnO NPs to improve electron hole mobility. As a result of the experiment, it was confirmed that the synthesized PbS QDs had excellent FWHM characteristics compared to commercial PbS QDs, and it was confirmed that the photodetector had a maximum current change of about 1.6 times.

• Journal of Sensor Science and Technology
• /
• v.32 no.5
• /
• pp.290-294
• /
• 2023

Among various types of harmful gases, hydrogen sulfide is a strong toxic gas that is mainly generated during spillage and wastewater treatment at industrial sites. Hydrogen sulfide can irritate the conjunctiva even at low concentrations of less than 10 ppm, cause coughing, paralysis of smell and respiratory failure at a concentration of 100 ppm, and coma and permanent brain loss at concentrations above 1000 ppm. Therefore, rapid detection of hydrogen sulfide among harmful gases is extremely important for our safety, health, and comfortable living environment. Most hydrogen sulfide gas sensors that have been reported are electrical resistive metal oxide-based semiconductor gas sensors that are easy to manufacture and mass-produce and have the advantage of high sensitivity; however, they have low gas selectivity. In contrast, the electrochemical sensor measures the concentration of hydrogen sulfide using an electrochemical reaction between hydrogen sulfide, an electrode, and an electrolyte. Electrochemical sensors have various advantages, including sensitivity, selectivity, fast response time, and the ability to measure room temperature. However, most electrochemical hydrogen sulfide gas sensors depend on imports. Although domestic technologies and products exist, more research is required on their long-term stability and reliability. Therefore, this study includes the processes from electrode material synthesis to sensor fabrication and characteristic evaluation, and introduces the sensor structure design and material selection to improve the sensitivity and selectivity of the sensor. A sensor case was fabricated using a 3D printer, and an Ag reference electrode, and a Pt counter electrode were deposited and applied to a Polytetrafluoroethylene (PTFE) filter using PVD. The working electrode was also deposited on a PTFE filter using vacuum filtration, and an electrochemical hydrogen sulfide gas sensor capable of measuring concentrations as low as 0.6 ppm was developed.

• Korean Journal of Heritage: History & Science
• /
• v.43 no.3
• /
• pp.334-365
• /
• 2010

Mother-of-Pearl craftwork sketch involves the whole process of making a piece of work. Therefore, it includes types, forms, sizes, and patterns of the work. Some information about when and by whom those works were manufactured and who ordered them are still found in some sketches. This paper seeks to find out popular types and patterns of the works in each period and its demand and the way of supply by examining the collection of approximately 1700 Mother-of-Pearl craftwork sketches from the period of Japanese colonization up to the present time, which are owned by Mr. Song Bang-wung, Important Intangible Cultural Heritage no.10. Typical patterns of sketches are the hua-jo(花鳥 : Flowers and Birds), the Sakunja(四君子 : Four Gracious Plants), cultural treasures, figures in folk tales, 'Su-bok(壽福)' characters, and landscape. The pattern sketches have changed according to the circumstances of Korean society. During the period of Japanese colonization from the 1920s to the 1940s the manufacture and the supply and demand of Mother-of-Pearl craftworks were controled by the Japanese government. As a result, many of the patterns were adjusted to the Japanese taste. Most of its customers were also Japanese. During the 1950s after Independence the American Military Forces appeared as new customers due to the Korean War. Thus, the traditional Korean patterns to decorate accessories adored by American soldiers gained popularity. Foreign Mother-of-Perls were imported from the late 1960s to the 1970s. They were bigger and more colorful than those of Korean and it enabled the sketches bigger and the patterns more various. The most popular pattern in this period was the pattern of cultural treasures, such as an image of Buddha, metalcraft works, porcelains and pagodas. In terms of a technique, new techniques, such as engraving and rusting were introduced. There was a great demand for Mother-of-Pearl craftworks in the 1970s as people were highly interested in them. They were entirely made to order and there was a large demand from diverse organizations, furniture dealers and individuals. And the Mother-of-Pearl craftwork was in full flourish in the 1970s due to the country's economic development and the growth of national income. Mass production of the works was possible and the professional designers who drew patterns actively worked in this period. The favor of Mother-of-Pearl craftworks declined in the 1980s since the built-in furniture and the Western style of furniture became prevalent due to the change of housing into apartments. But it seemed that the manufacture of Mother-of-Pearl craftworks revived for once the technique of Kunum-jil(끊음질 : cutting and attaching) became popular in Tong-young(統營). After the 1990s, however, the making of Mother-of-Pearl craftworks gradually declined as the need of them decreased. Now it barely maintains its existence by a few artisans.

• Microbiology and Biotechnology Letters
• /
• v.44 no.2
• /
• pp.185-193
• /
• 2016

A novel proteolytic bacterium was isolated from soil at Yeungnam University, South Korea. The strain, named FBL-1, was rod-shaped with a smooth surface. Biolog and API 50CHB test results revealed that strain FBL-1 was a Bacillus species. Based on 16S rDNA sequencing and chemotaxonomic characterization, the strain was identified as Bacillus subtilis because it had the highest homology with Bacillus subtilis subsp. subtilis NCIB 3610 (99.5%). In liquid culture at 37℃ with shaking at 200 rpm, fructose and yeast extract were found to be the best carbon and nitrogen sources, respectively, for cell growth and protease production. The highest protease activity (451.640 U/ml) was obtained when the strain was cultured in medium containing 20 g/l of fructose and 5 g/l of yeast extract. Although further studies are needed to characterize the protease and enhance its activity, the newly isolated protein-degrading B. subtilis FBL-1 can be applicable for the production of peptides and for the degradation of proteins in various industries.

• Clinical and Experimental Reproductive Medicine
• /
• v.28 no.3
• /
• pp.215-223
• /
• 2001

Objective: The purpose of this study was to make a guideline of uterine artery embolization for the treatment of uterine leiomyomas accompanying with adenomyosis in Korea. Materials and Methods : We performed the retrospective study for 37 women who had uterine leiomyomas accompanying with adenomyosis. Bilateral uterine artery embolization was performed in 37 patients (age range 25-65) during 17 months with pain, hypermenorrhea, urinary frequency etc due to leiomyomas. Ultrasound imaging was performed before the procedure and at mean 6.9 months after the procedure. Results: All procedures were technically successful. Mean clinical follow-up was 12.8 months. Minor complication occurred in 82% patients after the procedure. After imaging follow-up (mean, 6.9 months postprocedure), median uterine volume decreased 34.4%, and dominant myoma volume decreased 86%. There was no statistical difference in uterine volume reduction and dominant myoma size reduction whether occluding agents was polyvinyl alcohol, polyvinyl alcohol plus gelfoam, and gelfoam, and whether ultrasound measured Resistance Index value before the procedure was low or high. Conclusion: Primary candidates for uterine artery embolization include those with symptomatic uterine leiomyomas who no longer des ire fertility but wish to avoid surgery or are poor surgical risks. To our study, uterine volume reduction and dominant myoma size reduction in patients who had adenomyosis were similar to previous other studies in patients who had not adenomyosis. Therefore adenomyosis should not be considered as a contraindication for uterine artery embolization. Because there is little data about subsequent reproductive potential after this procedure, it should not be routinely advocated for infertile women. Further investigation is warranted for occluding agents and Resistance Index.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.37 no.4
• /
• pp.395-402
• /
• 2010

The purpose of this study was to analyse the stability and validity of the related factors to the caries incidence according to the duration. The subjects were 249 elementary school students. Among them, the number of male students was 137 (55.0%). In the first year, all subjects gave the responses of the questionnaire composed of demographic variables and oral heath behaviors. They also received oral examination and tests of Dentocult SM and Dentocult LB. In the 2nd-4th year, they received second oral examination for the assessment of caries incidence on permanent teeth. The relation of oral health-related factors with caries incidence was analyzed by chi square method and adjusted Relative Risk (RR). In the caries incidence rate for 1 year, those who had 2 or higher score of dentocult LB was 2.3 times higher than those who had 1 or lower. The caries incidence rate for 2 years was highly associated with caries on deciduous molars and dentocult LB. The caries on deciduous molars showed strong association with the caries incidence for 3 years. It was suggested that the association between the caries incidence and the related factors was different according to the duration. Therefore, dentists could need to consider the visiting period in the education of the risk factors of dental caries.

• Journal of Environmental Impact Assessment
• /
• v.27 no.2
• /
• pp.139-151
• /
• 2018

This study was carried out to provide the basic information for efficient protection management of natural recreation forest in addition to providing ecological information by analysing the vascular plants in Ohdosan natural recreation forest, and conducted from September 2016 to June 2017. This study showed that the area had a total 295 taxa including 86 families, 192 genuses, 255 species, 3 subspecies, 32 variants 6 forms and the ratio of genus/family was 1.5. Korea endemic plants were 10 taxa including Aconitum austrokoreense and A. pseudolaeve. Rare plants designated by Korea Forest Service were 6 taxa including Aconitum austrokoreense and Goodyera schlechtendaliana. The floristic regional indicators plants found in this survey area were 30 taxa comprising 5 taxa of grade IV, 6 taxa of grade III, 7 taxa of gradeII and 11 taxa of gradeI. Based on the list approved for delivering overseas of plants, 42 taxa were recorded in the surveyed area. The target plants adaptable to climate change were 4 taxa such as Abies koreana, Acotinum austrokoreense and so forth. The naturalized plants were 11 taxa including Cerastium glomeratum, Oenothera biennis and so forth.