• 한국전기전자재료학회논문지
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• 제14권7호
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• pp.572-577
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• 2001

The electrical properties of Pr$_{6}$ O$_{11}$ -based ZnO varistors consisting of ZnO-Pr$_{6}$ O$_{11}$ -CoO-Cr$_2$O$_3$-Er$_2$O$_3$ ceramics were investigated with sintering temperature in the range of 1325~f1345$^{\circ}C$. As sintering temperature is raised., the nonlinear exponent was increased up to 1335$^{\circ}C$, reaching a maximum 70.53, whereas raising sintering temperature further caused it to decrease, reaching a minimum 50.18 and the leakage current was in the range of 1.92~4.12 $\mu$A. The best electrical properties was obtained from the varistors sintered at 1335$^{\circ}C$, exhibiting a maximum (70.53) in the nonlinear exponent and a minimum (1.92 $\mu$A) in the leakage current, and a minimum (0.035) in the dissipation factor. On the other hand, the donor concentration was in the range of (0.90~1.14)x10$^{18}$ cm$^{-3}$ , the density of interface states was in the range of (2.69~3.60)x10$^{12}$ cm$^{-2}$ , and the barrier height was in the range of 0.77~1.21 eV with sintering temperature. With raising sintering temperature, the variation of C-V characteristic parameters exhibited a mountain type, reaching maximum at 134$0^{\circ}C$. Conclusively, it was found that the V-I, C-V, and dielectric characteristics of Pr$_{6}$ O$_{11}$ -based ZnO varistors are affected greatly by sintering temperature.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.640-646
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• 2001

The electrical stability for DC stress of Pr$_{6}$O$_{11}$-based ZnO varistos consisting of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Er$_2$O$_3$-based ceramics were investigated with sintering temperature in the range of 1325~1345$^{\circ}C$. A the sintering temperature is raised, the nonlinear exponent of varistors was decreased, whereas the stability was markedly improved. The density of ceramics was found to greatly affect the electrical stability for DC stress. The varistors sintered at 13$25^{\circ}C$ were completely degraded because of thermal runaway attributing to low density. The varistors sintered at 1335$^{\circ}C$ exhibited the highest nonlinearity, with a nonlinear exponent of 70.53 and a leakage current of 1.92$\mu$A, whereas they did not exhibit relatively high stability. On the contrary, the varistors sintered at >134$0^{\circ}C$ exhibited not only a high nonlinearity marking the nonlinear exponent above 50 and the leakage current below 3$\mu$A, but also a high stability marking the variation rate of the varistor voltage below 2%, even under DC stress such as (0.80V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85V$_{1mA}$/115$^{\circ}C$/12h)+(0.90V$_{1mA}$/12$0^{\circ}C$/12h)+(0.95V$_{1mA}$/1$25^{\circ}C$/12h)+(0.95V$_{1mA}$/15$0^{\circ}C$/12h). In particular, ti was found that the varistors sintered at 134$0^{\circ}C$ were more nonlinear and more stable, compared with that of 1345$^{\circ}C$.EX>.}C$.EX>.

• 농약과학회지
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• 제12권1호
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• pp.82-87
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• 2008

우리나라에서 사용되고 있는 벼재배용 제초제인 butachlor의 담수조류에 대한 생장영향을 알아보고자 녹조류 Selenastrum capriconutum, Scenedesmus subspicatus, Chlorella vulgaris 3종과 규조류 Nitzschia palea 1종에 대해 72시간 생장저해시험(growth inhibition test)을 수행하였다. 시험결과 butachlor에 대한 S. capricornutum, S. subspicatus, C. vulgaris, 그리고 N. palea의 생장율 기준 반수영향농도($EC_{50}$)는 각각 0.0022, 0.019, 8.67 그리고 $4.94\;mg\;L^{-1}$이었고, 무영향농도(NOEC)는 0.0008, 0.0016, 5.34 그리고 $2.92\;mg\;L^{-1}$로 나타나 S. capricornutum가 가장 높은 감수성을 보였다. 양성대조물질인 $K_2Cr_2O_7$에 대한 S. capricornutum, S. subspicatus, C. vulgaris 그리고 N. palea의 생장율 기준 $EC_{50}$은 각각 0.91 0.78, 0.85 그리고 0.57 mg $EC_{50}$이었고, NOEC는 각각 0.2, 0.2, 0.2 그리고 0.18 mg $EC_{50}$였다. butachlor를 논에 살포하였을 때 논물에 전량 용해된 후 배수로를 통해 농수로에 배출될 때를 가정한 환경추정농도(Predicted Environmental Concentration; PEC)에 따른 생장저해율을 계산한 결과, S. capricornutum와 S. subspicatus는 각각 100%와 75%의 생장율 저해를 보였으나 C. vulgaris와 N. palea는 영향이 없었다.

• 대한환경공학회지
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• 제22권10호
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• pp.1799-1808
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• 2000

본 연구에서는 구입이 용이한 황토를 이용하여 축산폐수외 화학적 응집 처리제로서의 적용가능성과 최적 응집조건을 찾고 기존에 사용되어 왔던 고분자 응집제(PAC, PACS, LAS)와 응집성능을 비교하였다. 연구 결과 황토와 생석회의 최적 혼합비율은 3:7이었으며, 이 혼합 응집제의 적정 주입량은 30 g/L이었다. 기존 응집제와 비교실험에서는 loess : lime = 3 : 7의 경우 탁도, SS, BOD, $COD_{er}$, T-P, TKN의 제거효율이 각각 95.8%, 92.5%, 71.6%, 71.1%, 98.2%. 32.5%를 나타내었다. Loess : lime = 3 : 7은 응집제로서 사용할 수 있으며, 생산된 슬러지는 토양개량제로서의 사용 가능성을 확인할 수 있었다.

• The Journal of Advanced Prosthodontics
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• 제12권4호
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• pp.189-196
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• 2020

PURPOSE. The aim of the present study was to investigate the effects of surface treatments on the bond strengths between polymer-containing restorative materials and two dual-cure resin cements. MATERIALS AND METHODS. In the present study, rectangular samples prepared from Lava Ultimate (LU) and Vita Enamic (VE) blocks were used. The specimen surfaces were treated using CoJet sandblasting, 50 ㎛ Al₂O₃ sandblasting, % 9 HF (hydrofluoric) acid, ER,Cr:YSGG laser treatment, and Z-Prime. Dual-cure resin cements (TheraCem and 3M RelyX U 200) were applied on each specimen's treated surface. A micro-tensile device was used to evaluate shear bond strength. Statistical analysis was performed using the SAS 9.4v3. RESULTS. While the bond strength using TheraCem with LU or VE was not statistically significant (P=.164), the bond strength using U200 with VE was statistically significant (P=.006). In the TheraCem applied VE groups, Z-Prime and HF acid were statistically different from CoJet, Laser, and Sandblast groups. In comparison of TheraCem used LU group, there was a statistically significant difference between HF acid and other surface treatments. CONCLUSION. The bonding performance between the restorative materials and cements were material type-dependent and surface treatment had a large effect on the bond strength. Within the limitations of the study, the use of both U200 and TheraCem may be suggested if Z-prime was applied to intaglio surfaces of VE. The cementation of LU using TheraCem is suitable after HF acid conditioning of the restoration surfaces.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1996년도 The 9th KACG Technical Annual Meeting and the 3rd Korea-Japan EMGS (Electronic Materials Growth Symposium)
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• pp.258-292
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• 1996

In the last year great interest appears to YBCO thin films preparation on different substrate materials. Preparation of epitaxial film is a very difficult problem. There are many requirements to substrate materials that must be fullfilled. Main problems are lattice mismatch (misfit) and similarity of structure. From paper [1] or follows that difference in interatomic distances and angles of substrate and film is mire important problem than similarity of structure. In this work we present interatomic distances and angle relations between substrate materials belonging to ABCO4 group (where A-Sr or Ca, B-rare earth element, C-Al or Ga) of different orientations and YBCO thin films. There are many materials used as substrates for HTsC thin films. ABCO4 group of compounds is characterized by small dielectric constants (it is necessary for microwave applications of HTsC films), absence of twins and small misfit [2]. There most interesting compounds CaNdAlO4, SrLaAlO4 and SrLaGaO4 were investigated. All these compounds are of pseudo-perovskite structure with space group 14/mmm. This structure is very similar to structure of YBCO. SLG substrate has the lowest misfit (0.3%) and dielectric constant. For preparation of then films of substrates of this group of compound plane of <100> orientation are mainly used. Good quality films of <001> orientations are obtained [3]. In this case not only a-a misfit play role, but c-3b misfit is very important too. Sometimes, for preparation of thin films substrates of <001> and <110> orientations were manufactured [3]. Different misfits for different YBCO faces have been analyzed. It has been found that the mismatching factor for (100) face is very similar to that for (001) face so there is possibility of preparation of thin films on both orientations. SrLaAlO4(SLA) and SrLaGaO4(SLG) crystals of general formula ABCO4 have been grown by the Czochralski method. The quality of SLA and SLG crystals strongly depends on axial gradient of temperature and growth and rotation rates. High quality crystals were obtained at axial gradient of temperature near crystal-melt interface lower than 50℃/cm, growth rate 1-3 mm/h and the rotation rate changing from 10-20pm[4]. Strong anisotropy in morphology of SLA and SLG single crystals grown by the Czochralski method is clearly visible. On the basics of our considerations for ABCO4 type of the tetragonal crystals there can appear {001}, {101}, and {110} faces for ionic type model [5]. Morphology of these crystals depend on ionic-covalent character of bonding and crystal growth parameters. Point defects are observed in crystals and they are reflected in color changes (colorless, yellow, green). Point defects are detected in directions perpendicular to oxide planes and are connected with instability of oxygen position in lattice. To investigate facets formations crystals were doped with Cr3+, Er3+, Pr3+, Ba2+. Chromium greater size ion which is substituted for Al3+ clearly induces faceting. There appear easy {110} faces and SLA crystals crack even then the amount of Cr is below 0.3at.% SLG single crystals are not so sensitive to the content of chromium ions. It was also found that if {110} face appears at the beginning of growth process the crystal changes its color on the plane {110} but it happens only on the shoulder part. The projection of {110} face has a great amount of oxygen positions which can be easy defected. Pure and doped SLA and SLG crystals measured by EPR in the<110> direction show more intensive lines than in other directions which allows to suggest that the amount of oxygen defects on the {110} plane is higher. In order to find the origin of colors and their relation with the crystal stability, a set of SLA and SLG crystals were investigated using optical spectroscopy. The colored samples exhibit an absorption band stretching from the UV absorption edge of the crystal, from about 240 nm to about 550 m. In the case of colorless sample, the absorption spectrum consists of a relatively weak band in the UV region. The spectral position and intensities of absorption bands of SLA are typical for imperfection similar to color centers which may be created in most of oxide crystals by UV and X-radiation. It is pointed out that crystal growth process of polycomponent oxide crystals by Czochralski method depends on the preparation of melt and its stoichiometry, orientation of seed, gradient of temperature at crystal-melt interface, parameters of growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth (rotation and pulling rate) and control of red-ox atmosphere during seeding and growth. Growth parameters have an influence on the morphology of crystal-melt interface, type and concentration of defects.

• 아시안잔디학회지
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• 제3권1호
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• pp.39-52
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• 1989

Native Kerean lawngrass (Zeysia japonica steud.) and Manilagrass ( Zeysia matrella Merr.) are frequently used as sport turf and lawn in Kerea and ether Asian countries because of its excellent summer qualities and superior winter-hardiness compared to ether warm-season turfgrass . The objective of this study was to investigate the effect of the plant growth retardants ( PGR ) en the inhibition (d the growth of the two Kerean native turfgrasses. Kerean lawngrass and Manilagrass were treated with [2 RS , 3 RS] -1- [4- chlorophenyl ] -4, 4-dimethyl -2- [1 H -1, 2, 4- tiazol -1- y] pentan -3- ol ( PP -333) at 93 and 930 gha -j ; 5-[4- chlorphenyl ]-3, 4, 5, 9, 10- peiitaaza - tetracyclo [5, 4, 1, 0 2 6 . o ~'~I -3, 9- diene ( BAS -106) at 16 and 160 gha ; [ E I-] - cyclohexyl -4, 4- dimethyl -2- [1, 2, 4- triazol -1- yl ]-1-pentene - 3- ol ( NTN -821) at 56 and 560 gha ', and 4- chloro -2- [$\alpha$- hydrozybenzy I isonicotin anilide ( CGR -811) at 92 gha in pot study . All PGR treatments were effective in reducing the plant height, with the exception of BAS -106 at 16 gha for Korean lawngrass ; however , all increased quality to some degree , with the exception of PP -333 at 93 gha . The low PGR rates significantly increased Korean lawngrass height during late jtily aitd mid-August . On the other hand , BAS -106 significantly increased Manilagrass height {rom 24 Septeml)er onwards . All PGR treatments haol higher turfgrass quality than untreatments , and also the high rates of PGIt treatments were more effective in increasing quality than the low rates observed on 8 October . Meanwhile , Manilagrass quality was increased to some extent than Korean lawegrass . PP - 333 was significantly effective in reducing clipping yield and the same results were found with the application of NTN -821 at 560 gha -l for both Korean lawngrass and Manilagrass , BAS -106 at 160 gha for Korean lawegrass , and CGR -811 at 92 gha for Manilagrass . The high PGR rates had higher turfgrass shoot weight observed on 8 October than the low rates , and there were little increases obtained with the low rates of PP -333 for Korean lawngrass and BAS - 1 06 for Manilagrass . Effeets on stolon growth varied between growth retardants , and between retardant treatments ; the high rates of PGR as well as the low rate of NTN -821 elongated stolon of Korean lawngrass and manoilagrass . However , PP -333 at 93 gha and BAS -106 at 16 gha - shortened stolons of Korean lawugrass , resulting in inhibition or little difference of stolon dry weight . NTN -821 at 560 gha and CGR -811 had no positive effect on the stolon length of Manilagrass . 101) -333 and the low rate of BAS -106 and NTN -821 decreased root weight of Korean lawng - rass All PGR rates had negative effect on the root weight of Manilagrass with the exception of BAS -106 CR -811 and the high rate of NTN -821 which made no difference in root weight between retarolant treatments and the control .