• Ocean and Polar Research
• /
• v.43 no.2
• /
• pp.53-63
• /
• 2021

Changes in a marine environment have a broad socioeconomic implication on fisheries and their relevant industries so that there has been a growing demand for the medium-range (months to years) prediction of the marine environment Using a medium-range ocean prediction model (Ocean Mid-range prediction System, OMIDAS) for the northwest Pacific, this study attempted to assess seasonal difference in the mid-range predictability of the sea surface temperature (SST), focusing on the Korea seas characterized as a complex marine system. A three-month re-forecast experiment was conducted for each of the four seasons in 2016 starting from January, forced with Climate Forecast System version 2 (CFSv2) forecast data. The assessment using relative root-mean-square-error was taken for the last month SST of each experiment. Compared to the CFSv2, the OMIDAS revealed a better prediction skill for the Korea seas SST, particularly in the Yellow sea mainly due to a more realistic representation of the topography and current systems. Seasonally, the OMIDAS showed better predictability in the warm seasons (spring and summer) than in the cold seasons (fall and winter), suggesting seasonal dependency in predictability of the Korea seas. In addition, the mid-range predictability for the Korea seas significantly varies depending on regions: the predictability was higher in the East Sea than in the Yellow Sea. The improvement in the seasonal predictability for the Korea seas by OMIDAS highlights the importance of a regional ocean modeling system for a medium-range marine prediction.

• Journal of Korean Society of Environmental Engineers
• /
• v.39 no.3
• /
• pp.112-117
• /
• 2017

Ion exchange fiber, PADD was synthesized by the reaction between PAN based acrylic fiber and DETA with $AlCl_3{\cdot}6H_2O$, and was analyzed by FT-IR and SEM to investigate its characteristics. The experimental results of Cr(VI) removal by PADD were better fitted with Langmuir adsorption isotherm, and the maximum uptake value ($Q_{max}$) was calculated to be 6.93 mmol/g. The kinetic data can be well described by Lagergen pseudo-second order rate model. The Cr(VI) adsorption capacity of PADD was 4.11 mmol/g at pH 2, which shows the effect of pH changes on the removal of Cr(VI). The adsorption selectivity of Cr(VI) was higher than phosphate and As(V). Total ion exchange capacity of PADD was 4.70 mmol/g, which was measured by acid-base back titration.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.26 no.2
• /
• pp.446-452
• /
• 1999

Ectopic eruption of the first permanent molar means the first permanent molar assumes an atypical path of eruption resulting in premature atypical resorption of the second primary molar. If the reversible eruption does not occur, early loss of the second primary molars results in space loss, mesial tipping of the first permanent molar, impaction of the second premolar, buccal segment crowding and overeruption of opposing tooth. The main objectives of treatment are (1) to prevent loss of the second deciduous molars so it can continue to serve as a space maintainer and (2) to regain lost arch length, allowing the second premolar to erupt into normal position. The optimal treatment approach depends on a number of factors including the clinical eruption status of /6/, the change in position of /6/, the amount of enamel ledge of /E/ entrapping /6/, the mobility of /E/, and the presence of pain or infection. Unilateral appliance to correct the mesial angulation of ectopic permanent first molars, as in the majority of the appliance designs, would produce a resultant force that would further enhance the space loss. A bilateral support similar to the holding arch design is recommended to maximize the anchorage. These case reports present the successful result of preserving space for the second premolar in treatment of ectopic eruption of the first permanent molar using Halterman appliance with bilateral anchorage on patients visiting department of pediatric dentistry in Samsung Medical Center.

• Journal of the Korean Chemical Society
• /
• v.42 no.1
• /
• pp.84-91
• /
• 1998

Random copolymers of N-isopropyl acrylamide (NIPAAm) and acrylic acid (AAc) which exhibit temperature- and pH-responsive behavior were synthesized by free-radical polymerization. The copolymers were characterized by means of FT-IR spectrometry and titration. The influence of polyelectrolyte on the lower critical solution temperature (LCST) of pH/temperature-sensitive polymers was investigated in the pH range of 2-12. The LCSTs of PNIPAAm/water in poly(NIPAAm-co-AAc) were determined by cloud-point measurements. A polyelectrolyte complex was prepared by mixing poly(NIPAAm-co-AAc) with poly(allylamine) (PAA) or poly(L-lysine) (PLL) solutions as anionic and cationic polyelectrolytes, respectively. Back titration was performed to determine the content of AAc and to study the effect of comonomer ionization on the LCST. The LCSTs of PNIPAAm/water in the copolymers were strongly affected by pH, presence of polyelectrolyte, AAc content, and charge density on the polymer. The polyelectrolyte complexes were formed at neutral condition. The influence of more hydrophobic PLL as polyelectrolyte on the cloud-point of PNIPAAm/water in the copolymer was stronger than that of poly(allylamine) (PAA).

• Applied Chemistry for Engineering
• /
• v.28 no.1
• /
• pp.73-79
• /
• 2017

Maleic anhydride (MAH) grafted polypropylene (PP-g-MAH) copolymers were prepared by changing MAH and styrene monomer (SM) content, using a twin screw extruder at $190^{\circ}C$. The grafting degree was measured by non-aqueous back titration method. The grafting degree of PP-g-MAH-SM copolymer was higher than that of PP-g-MAH at the same MAH content. PP-g-MAH-SM/kenaf fiber (KF) composites were also prepared by using a PP-g-MAH as a matrix at $200^{\circ}C$ and the KF content was fixed at 20 wt%. Based on the degradation temperature investigated by TGA, the thermal stability of PP-g-MAH-SM/KF composites was more enhanced than that of PP-g-MAH only. Mechanical properties of the composites were also improved when MAH and SM applied together. The adhesion degree between the copolymer and KF was confirmed by both SEM pictures of the fractured surface and contact angles.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.275-282
• /
• 2021

High-molecular-weight maleic anhydride-grafted polylactic acids (HMMA-g-PLA) compatibilizers were prepared by melt grafting in a twin screw extruder using di(tert-butyl-perxoyisopropyl)benzene (PK-14; as initiator), maleic anhydride (MA), and divinylbenzene (DVB). To determine the properties of the prepared HMMA-g-PLA compatibilizers, Fourier transform infrared (FTIR), Melt index (MI), and back-titration analyses were performed. On increasing DVB concentration, grafting yield of HMMA-g-PLA increased but MI decreased because 𝛽-scission of PLA was restrained by the DVB, and thus, the molecular weight of HMMA-g-PLA increased. PLA-based wood-plastic composites (WPCs) were prepared using HMMA-g-PLA by melt blending through a single screw extruder. The flexural and impact strengths of WPCs compatibilized with HMMA-g-PLA were greater than those of WPCs produced without HMMA-g-PLA. Scanning electron microscope (SEM) studies indicated that increased mechanical properties were caused by excellent interfacial adhesion between PLA and wood fibers due to the addition of HMMA-g-PLA. However, rather high contents of HMMA-g-PLA reduced the mechanical properties of WPCs. We believe that lower molecular-weight of HMMA-g-PLA added as an compatibilizer, compared with PLA polymer, caused the reduction of mechanical properties.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.10 no.1
• /
• pp.72-86
• /
• 2006

A technical review of current ramjet propulsion is presented. In addition to summarize the current status of ramjet technology, new key techniques like Boosting technique easily adapting total impulse of booster, flame stabilization technique with minimized ramjet combuster length, variable nozzle-inner-surface technique realizing wide flight-envelop, and thermal protection technique for long operating time are identified. Actually various Ramjet propulsion technology has been matured and expanding to both military and combined cycle application. Yet many opportunities remain to be challenged by future generations of explorers to utilize s typical ramjet propulsion system for multi-purpose(multi-platform and multi-target) missiles, for example, American JSSCM and Russian Yakhont missiles, improving both reliability of techniques and downsizing development cost of new propulsion system.

• Applied Microscopy
• /
• v.36 no.1
• /
• pp.17-23
• /
• 2006

The pregnant rats were given a drinking water administration of the sodium fluoride and normal saline for control animals. The sodium fluoride produced cellular changes of odontoblast with consistent response. Compare to control group, the odontoblasts that were administrated by sodium fluoride, showed significantly ultrastructural differences including large number of free ribosomes and swelled mitochondria in dose-dependent manner (300 ppm). From fine structural and morphological investigations of the changes in odontoblast, there were three distinctive structural changes: (1) destruction of the endoplasmic reticulum, (2) swelling of the mitochondria, and (3) severe cellular derangement of the endoplasmic reticulum and mitochondria. From this consecutive structural change, we observed that sodium fluoride temporarily affects the cell organelles in odontoblasts (100, 200 ppm), suggesting it is important that optimal concentration of the sodium fluoride in developing fetus of the rat.

• Korean Journal of Labor Studies
• /
• v.24 no.3
• /
• pp.73-107
• /
• 2018

The purpose of this study is to shed light on the characteristics of the social relations of migrant workers in the Ansan area and the factors for the construction of those characteristics. The social relations of migrant workers in the Ansan area are affected by the Korean government's policy of EPS, a short-term rotation policy and its ban on the settlement of migrant workers. These workers are likely to form a temporary and bounded social relationship. The bounded social relationship of migrant workers to society is one of the major factors that put them in social poverty. Ethnic communities, support organizations for migrant workers, and local government agencies have assumed the task of helping build the network among migrant workers of various ethnic backgrounds as well as aiding their participation in local social activities. The status of a temporary resident is the prime reason for spatial exclusion and social poverty among migrant workers. To prevent the exacerbation of these phenomena, this study suggests that the government reconsider its short-term work permit policy for less skilled workers.

• Journal of Korean Medical classics
• /
• v.20 no.2
• /
• pp.231-268
• /
• 2007

재일본규주황한의학적전통의학지전신취시중국전통의학적지식(在日本叫做皇漢醫學的傳統醫學之前身就是中國傳統醫學的知識). 16세기이래(16世記以來), 일본불단수도이개조중국의학적최신성과(日本不斷收到而改造中國醫學的最新成果), 동양원류우부동홍류적한방의학체계점점형성적과정전후(同樣源流又不同洪流的漢方醫學體系점점形成的過程前后), 출현료4개학문유파(出現了4個學問流派). 저취시(저就是)"후세파(后世派)"."고방파(古方派)"."절충파(折衷派)"."고증파(考證派)". 소우호세파(소于호世派), 논자이경재대한한의학원전학회지적제19권3호상보고료(논者已경在大한한의학原典학회紙的第19卷3호上보告了), 본논문시연속적연구성과(本논文是연속的硏究成果). 종이재본논문상(종而在本논文上), 이한국적이정환(以한국的李政桓), 백유상(白裕相), 정창현등적연구여중국양영적연구위기초(丁彰炫等的硏究與中國梁嶸的硏九爲基礎), 요개략지보고일본의학방면상적‘고방파’(要槪略地報告日本의학方面上的'古方派'). "고방파"지칭부정근세송명의학이지지지한대장중경적"상한잡병론"지일본의가("古方派"指稱否定近世宋明醫學而只支持漢代張仲景的"傷寒雜病論"之日本醫家). 일반"상한론"전파우일본적실정시대(一般"傷寒論"傳播于日本的室町時代), 명응년간(明應年間)(1492${\sim}$1500)판정운재명유학후(阪淨運在明留학후), 타회도일본적시후(他回到日本的시候), 종명수입(종明수入)"상한잡병론(傷寒雜病論)", 이후일본후세한의칭송료이관동지역적영전덕본(以후日本후世漢醫칭송了以關東地域的永田德本)(1513-1603)위(爲)"고방파적선구자(古方派的先구者)". 도강호시대재일본학술계출현료복고사조(到江戶時代在日本學術係出現了復古思潮). 이등인제(伊藤仁劑)(1627${\sim}$1705)앙망료유학적경전(仰望了儒學的經典), 이차적극지주장료의학적복고(而且積極地主張了醫學的復古), 이후적생조래(以후荻生組徠)(1666${\sim}$1728)대우복여성인적학문부단노력(對于復與聖人的學問不斷努力). 인차복고적학문재덕천시대성위일대학파(因此復古的學問在德川時代成爲一代學派), 18세기상반기시전성시기(18世紀上半期是全盛시期). 주요의가시명고옥현의(主要醫家是名古屋玄議)(1628${\sim}$1696), 후등양산(後藤양山)(1659${\sim}$1733), 산협동양(山脅東洋), 병하천민(병河天民)(1679${\sim}$1719), 송원유악(松原維嶽)(1689${\sim}$1765), 향천수암(香川修庵)(1683${\sim}$1755), 타문복고적유학영향도흔다의학방면(他문復古的儒學影향到흔多의학方面). 중요의가길익동동(重要醫家吉益東洞)(1702${\sim}$1773)도후대피평위고방적'태두'(到后代被평위古方的'泰斗'), 동시'마귀'(同시'魔鬼'). 인차본논문소우황한의학지중"후세파"여반대후세파적"고방파"(因此本論文소于皇漢醫學之中"后世派"與反대后世派的"古方派"), 통과학파명칭여역사지위(通過學派名稱與歷史地位), 주요의가적생애(主要醫家的生涯), 학술적요지(學術的要旨), 저서등(著書等), 이연구병보고타문적학문주장(以硏究병報告他們的學問主張). 이차진저차궤회(而且진저次机회), 상회고아문한의학연착여하역사적궤적(想回고我문韓醫學沿着如何歷史的軌跡).