pH- and Temperature-Sensitive PCL-Grafted Poly(β-amino ester)- Poly(ethylene glycol)-Poly(β-amino ester) Copolymer Hydrogels

Yongtai Zheng,Minh Khanh Nguyen,Chaoliang He,Cong Truc Huynh,이두성 한국고분자학회 2010 Macromolecular Research Vol.18 No.11

A series of poly(ε-caprolactone)-grafted poly(β-amino ester)-poly(ethylene glycol)-poly(β-amino ester)((PAE-g-PCL)-PEG-(PAE-g-PCL)) copolymers were designed and synthesized for use in injectable pH- and temperature-sensitive hydrogels. First, PEG diacrylate was synthesized and used as a macroinitiator, and the chain was extended by 4,4 trimethylene dipiperidine (TMDP), 3-amino-1-propanol and diacrylate monomers (1,4-butanediol diacrylate (BDA), and 1,6-hexanediol diacrylate (HDA)) to obtain the triblock copolymers (PAE-PEG-PAE). Poly (ε-caprolactone) was then grafted to the pendant OH groups of the resulting PAE-PEG-PAE by ring opening polymerization. The PAE-PEG-PAE and (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymers were characterized by 1H nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography. The phase diagram was measured using the tube inverting method. At pH 6.6 or higher, the (PAE-g-PCL)-PEG-(PAE-g-PCL) copolymer solutions (30 wt%) displayed sol-gel-sol transitions with increasing temperature. The viscosity of the graft copolymer solutions was determined as a function of temperature by dynamic mechanical analysis. In addition, after the subcutaneous injection of the polymer solution (30 wt%, pH 6.4) into a rat, a gel formed within a short time, suggesting biomedical applications.

Biodegradable pH- and Temperature-Sensitive Multiblock Copolymer Hydrogels Based on Poly(amino-ester urethane)s

Yongtai Zheng,Chaoliang He,Cong Truc Huynh,이두성 한국고분자학회 2010 Macromolecular Research Vol.18 No.10

A novel pH- and temperature-responsive multiblock copolymer consisting of poly(ethylene glycol) (PEG) and poly(amino-ester urethane) (PAEU) is reported. First, a biodegradable monomer, bis-1,4-(hydroxyethyl)piperazine mono-lactate (HEP mono-lactate), was synthesized by the ring-opening polymerization of D,L-lactide (LA) using HEP and Sn(Oct)2 as an initiator and catalyst, respectively. The multiblock copolymers were synthesized further from PEG, HEP, HEP mono-lactate, and 1,6-diisocyanatohexamethylene (HDI) in the presence of dibutyltin dilaurate as a catalyst. The resulting copolymers were characterized by nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). At pH 6.8 or higher, the copolymer aqueous solutions showed gel-to-sol transitions with increasing temperature, and the gel window covered the physiological conditions. After a subcutaneous injection of the multiblock copolymer solution into SD rats, a soft gel was formed in a short time. The degradability of the copolymer was adjusted by varying the LA content in the PAEU block.

INITIAL DILUTION STUDY IN STAGNANT FLOW

Chung, Yongtai 順天靑巖大學 1998 論文集-順天靑巖大學 Vol.22 No.1

본 연구에서는 해양 방류량의 여러 가지 특성 인자들에 관한 실험실의 측정치와 수학적 모형에 의한 예측치와 비교 분석하였다. 유량 및 해양조건에 따른 자료들은 다공확산관에 의한 방류량의 전형적인 유형과 관련된다. 실험실 자료들은 밀도층을 갖는 견인수조에서 얻었다. 이들 자료들은 일반적으로 이용되는 네 가지의 수학적 모형 즉, 최소희석율, 희석의 최고높이, 및 희석 폭을 위한 UM, UDKHDEN, RSB 및 CORMIX2을 이용하였다. 실험조건에 따른 변동과 불확실성으로 인하여 모형과 실측치와의 직접적인 비교를 한다는 것은 어려운 일이지만 해석결과 최소희석율에 있어서는 UM과 RSB에 의한 계산치가 잘 일치하였으며, UDKHDEN과 CORMIX2에 의한 결과치는 실측치보다 적은 값으로 나타났다. 최고위 희석영역의 최고높이에 있어서는 실측치보다 높은 계산치를 나타내는 CORMIX2를 제외한 대부분의 모형 계산치가 실측치와 잘 일치하였다. 한편 희석 폭에 대한 모형의 계산치는 실측치에 대하여 매우 흩어진 것으로 나타났다. In this study, field and laboratory measurements of various properties of ocean outfall discharges were compared with the predictions of mathematical models. The data sets cover broad ranges of discharge conditions and oceanic conditions, and are associated with a typical type of out fall discharges with multiport diffusers. The laboratory data sets were obtained in density stratified towing tanks. These data sets were used to evaluate four commonly used models: UM, UDKHDEN, RSB and CORMIS2 for minimum dilution, the height to top of wastefield, and wastefield thickness. For minimum dilution, UM and RSB predictions agree well with field data and UDKHEDN, CORMIX2 predictions underestimate dilutions. In the height to top of waste field, most of the model predictions were within measured values and agree well with measurements except CORMIX2 prediction overestimate. Likewise, the model predictions for the waste field thickness show a great deal of scatter about the measured values.

해양방류모형 CORMIX의 적용성 검토에 관한 연구

정용태,김경완 順天靑巖大學 2000 論文集-順天靑巖大學 Vol.24 No.-

The objective of a ocean outfall is to discharge wastewater such that detrimental effects to the receiving water are minimal. To design an outfall that achieves this requires understanding of a wide variety of topics in environmental hydraulics. These include the dynamics of merging turbulent jets and plumeflowing, density-stratified receiving water and their mixing and dilution; and coastal oceanography. Internal hydraulics problems are also involved, especially the dynamics of branching manifold flows and the more complex stratified flows which arise with deep tunneled outfalls. In this paper, field and laboratory studies of the behavior using three data sets(e.g., Boston, Sanfrancisco, and Sand Island) were predicated by CORMIX for minimum dilution, the height to top of wastefield, and wastefield thickness.

매립지 침출수의 색도제거

정용태,허동균 順天靑巖大學 1999 論文集-順天靑巖大學 Vol.23 No.-

응집침전법을 이용하여 침출수중의 색도제거 가능성에 대하여 검토하고, 응집반응시 색도와 유기물 제거를 위한 적합한 조건들을 규명하고자, 응집제의 종류 및 첨가량, 침출수의 농도, pH 등을 변화시키면서 색도제거 실험을 수행하였다. 무기응집제의 경우, Al_2(SO_4)_3가 FeCl_3나 PAC에 비하여 색도제거율이 가장 좋게 나타났으며, 고분자 응집제의 경우, C-486이 N-100PWG나 A-110PWG에 비하여 제거율이 좋게 나타났다. COD 제거율은 Al_2(SO_4)_3의 경우 첨가량 600 mg/l에서 44%를 나타냈고, C-486의 경우 첨가량 100 mg/l에서 47%의 제거율을 나타냈다. 본 실험에 있어서 색도제거를 위한 최적 조건을 살펴 보면, Al_2(SO_4)_3의 경우에는 pH 6, 원수색도 400 cm, 첨가량 600 mg/l이었으며, C-486의 경우에는 pH 8, 원수색도 400 cu, 첨가량 100 mg/l이었다. 이때 색도제거율은 각각 86% 및 78%이었다. This study was carried out to research the colour removal efficiency of landfill leachate by coagulation. In order to find out optimal conditions for colour removal, influential factors such as sort and dosage of coagulant, concentration of leachate, and pH were investigated with experiments. As for coagulant, Al_2(SO_4)_3 showed the highest colour removal efficiency compared with FeCl_3 or PAC. As for polymer, C-486 has the highest colour removal efficiency compared with N-100PWG or A-100PWG. When the dosage of Al_2(SO_4)_3 was 600 mg/l, the COD removal efficiency was 44%. When the dosage of C-486 was 100 mg/l, the COD removal efficiency was 47%. The optimal conditions achieved for the colour removal are as follows: the colour removal efficiency of Al_2(SO_4)_3 is 86% with a dosage of 600 mg/l at pH 6 and 400 cu, and that of C-486 is 78% with a dosage of 100 mg/l at pH 8 and 400 cu.

多變量分析法을 利用한 河川水質의 評價

丁榕泰 順天靑巖大學 1999 論文集-順天靑巖大學 Vol.23 No.-

하천수질의 오염으로 인한 문제가 점차 심각하게 대두되면서 강우시 하천으로 유입되는 오염물에 의한 하천수질변동을 평가할 수 있는 다변량해석기법을 효율적으로 이용하여 장·단기 수질관리대책에 의한 수계의 일관성 있는 해석기법의 개발이 요구되고 있다. 하천수질해석을 위한 대부분의 연구가 무강우시를 대상으로 하였다. 강우시 비점오염원의 하천으로의 유입은 상당히 복잡한 수질변동특성을 지니며, 수질반응 또한 짧은 시간에 이루어져 월 또는 연평균수질자료 등의 긴 시간간격의 수질자료에 대한 분석은 정확하지 못한 해석결과를 초래한다. 본 연구에서는 1995년 4월∼1996년 3월 일본 다마가와(多摩川)수계 4개지점의 매시간 강우와 수질자료를 대상으로 통계학적 분석방법인 다변량분석방법을 이용하여 강우시 수질항목들의 변동특성을 분석하였다. 다변량해석방법에는 주성분분석, 다중회귀분석 및 시계열분석이 포함되었다. 수질항목으로는 염화물이온, 전기전도도, 용존산소량, 수소이온농도, 탁도, 온도 등 6개 항목으로 구성되어있다. 주성분분석과 다중회귀분석에 의한 강우와 수질항목간의 정량분석결과 주성분의 순위에는 관계없이 염화물이온과 전기전도율, 탁도가 지배하는 주성분과, 수온, 용존산소량, 수소이온농도가 지배하는 주성분으로 분류되었으며, 기타 여러 항목에 의해 지배되는 주성분으로 분류되었다. 다중회귀분석에서의 변수로는 주성분 분석의 결과로부터 산출된 주성분을 종속변수로 하였으며, 독립변수로는 강우항목을 대상으로 하였다. 분석결과 선행강우일수가 수질에 미치는 영향이 가장 큰 것으로 분석되었다. 또한 다중회귀분석으로부터 선행강우일수가 2일 미만 일 때는 그 영향이 매우 미소한 것으로 나타났다. 일 평균자료의 장기변동추세를 파악하기 위해 시계열분석을 실시하였으며, 선형추세분석과 이동평균법을 사용하여 강우시 다소의 수질오염의 진행되고 있음을 알 수 있었다. The river water quality pollution problems during a rainy period become more serious, it is required development of consistent analysis method for water quality evaluation of river system through the efficient use of the multivariate analysis technique. Most of the studies for the water quality analysis in a river are performed based upon the data obtained on no-rainy period. But on rainy days, due to the inflow of nonpoint pollution loads into river, the variations of rainy water quality are very complicate and quality reaction time is relatively short. Therefore. the analysis performed based on the data collected during the long time period, which is monthly or annual average water quality data, leads to a wrong result. In this paper, in order to interpret the characteristics of rainfall and water quality variation, the hourly data at 4 monitoring stations of the Tama River at Tokyo in Japan collected from April 1995 to March 1996 was analyzed by the multivariate statistical analysis method. The multivariate analyses include principal component analysis, multiple regression analysis, and time series analysis. The data consist of 6 water quality items which are chloride, conductivity, dissolved oxygen, pH, turbidity, water temperature. However the principal component and the multiple regression analyses used to qualitatively relate the rainfall and water quality items show that a high coefficient of determination indicates that the principal components are controlled by turbidity, chloride and conductivity. These water quality items depend on rainfall. The multiple regression analysis shows a slight change of water quality when there are under two days of antecedent storm days.

Anatomical Adaptations of the Xerophilous Medicinal Plant, Capparis spinosa, to Drought Conditions

Lu Gan,Chunyu Zhang,Yongtai Yin,Zhiwei Lin,Yongwei Huang,Jun Xiang,Chunhua Fu,Maoteng Li 한국원예학회 2013 Horticulture, Environment, and Biotechnology Vol.54 No.2

Capparis spinosa is a plant that grows in dry and arid environments. As far as can be ascertained, no comprehensive studies on how the leaf, stem and root structures adapt to drought conditions have been published to date. In this paper, a study into the anatomical adaptations of the leaf, stem and root of C. spinosa to drought environments was conducted using in vitro cultured seedlings as control. The results showed that C. spinosa could change its leaf, stem, and root structures when adapting to drought conditions. The plant growing under drought conditions possessed an enlarged transit region between the stem and root where the xylem and fibro-vascular system had increased in order to enhance water absorption and storage capacity. The leaf, stem and root of C. spinosa under drought conditions were better developed than those under normal in vitro culture conditions. The leaf possessed uniform mesophyll cells and three or four layers of palisade mesophyll cells on both sides of the mature leaves. The stomata were evenly distributed across both sides of the leaf, and they remained open continually during the day throughout the summer growing period, especially those on the lower leaf surface. The xylem in the stem was extremely well developed with wide vessels and much thicker cortical layers. All these characteristics can enhance the adaptability of C. spinosa and enable it to survive in extremely dry and arid areas.

Effect of heating time on tensile properties of surface-hardened pure titanium

Chang-Lim KIM,Dong-Geun LEE,Yongtai LEE 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8

공무원의 재난관리인식에 대한 실증적 연구

김승봉(Seung-bong Kim),정용태(Yongtai Chung) 한국방재안전학회 2023 한국방재안전학회 논문집 Vol.16 No.4

본 연구는 전라남도 22개 시군의 재난관련 부서에 근무하는 공무원들의 재난안전관리업무에 대한 개인역량, 부서역량, 조직환경 및 재난교육에 대한 인식수준을 파악하기 위해 실시한 설문조사 결과를 토대로 실증적 분석을 실시하였다. 성별에 따른 개인역량, 조직 환경에 대해서는 남자가 여자보다 더 긍정적인 인식을 가진 것으로 나타났으며, 재난교육에 대해서는 여자가 남자보다 더 긍정적인 인식을 가진 것으로 나타났다. 부서역량에 대해서는 남자와 여자의 긍정적인 인식이 같은 것으로 나타났다. 개인적 특성에 따른 개인 역량, 조직환경, 부서역량 및 재난교육에 대한 응답자들이 대체로 긍정적인 인식을 가진 것으로 나타났다. This study conducted an empirical analysis based on the results of a survey conducted to determine the level of awareness of disaster safety management work of public officials working in disaster-related departments in 22 cities and counties in Jeollanam-do. Men were found to have more positive perceptions of individual competencies and organizational environments according to gender, and women were found to have more positive perceptions of disaster education than men. It was found that men and women had the same positive perception of departmental competency. Respondents to individual competency, organizational environment, departmental competency, and disaster education according to individual characteristic factors generally had positive perceptions.

Effects of pre-heat conditions on diffusion hardening of pure titanium by vacuum rapid nitriding

Dong-Geun LEE,Hyeon-Gyeong JEONG,Chang-Lim KIM,Yongtai LEE 한국진공학회 2016 한국진공학회 학술발표회초록집 Vol.2016 No.8