• 전자공학회논문지D
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• 제34D권12호
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• pp.14-21
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• 1997

This study was conducte dto fabricate 2GHz circulator using Ca,Sn substituted UIG(yttrium iron garnet)ceramics. When the electric, magnetic and microwave properties were measured in Ca, Sn substituted YIG, the measured perimittivity and perfmeability in microwave frequencies were 16.25, 0.8964. For $Y_{2.4}$C $a_{0.3}$A $n_{0.3}$F $e_{3.5}$A $l_{1.5}$ $O_{12}$ garnet ceramics sintered at 1400.deg. C, the ferrimagnetic resonance line width (.DELTA.H) at 10GHz was 53 Oe and saturation magnetization was 375G. The strip-line circulator was simulated with 3-D FEM (finite element method) software and designed at the center frequency of 2GHz. The fabricated strip-line junction circulator using above YIG ceramics had insertion loss of 1.271dB, return loss of 23.843dB, isolation of 21.751dB at the center frequency 1.855GHz.z.z.z.z.z.z.

• 한국세라믹학회지
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• 제34권2호
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• pp.163-170
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• 1997

대표적인 무기계 지연제인 규불하마그네슘(MgSiF6.6H2O)을 시멘트 수화반응시 첨가했을 때의 수화반응의 지연 효과 및 특성과 수용액 이온농도 변화 고찰하기 위하여 규불화마그네슘을 시멘트 질랴의 0.3wt%에서 5wt%까지 변화시키면서 그 영향을 연구 검토하였다. 시멘트 모르타르의 flow는 지연제의 첨가에 따라 감소하는 경향이 있으며 응결 시간은 지연제의 첨가량에 따라 지연되었다. 모르타르의 압축 강도는 지연제의 첨가량에 따라 3일, 7일까지는 지연제를 첨가하지 않은 plain mortar에 비하여 약간 낮은 강도를 나타내나, 시간이 지남에 따라 회복되어 28일이 지나면 plain 모르타르와 같은 강도를 나타낸다. 규불화마그네슘이 첨가되면 수화 초기 단계에서 시멘트로부터 용출된 알카리 이온과 반응하여 K2SiF6의 생성이 일어나며 그와 동시에 Ca++와 F++와의 반응에 따라 CaF2화합물이 생성됨을 확인하였다. 이때 생성된 K2SiF6 및 CaF2생성물의 비표면적은 대단히 컸으며 이들 물질이 수화반응 초기에 미수화 시멘트시 입자 표면에 생성되어 시멘트의 수화가 지연되는 것으로 검토된다. 또한 수화초기의 수화용액의 Ca++ 및 K+이온 농도의 저하 역시 포틀랜드 수화반응속도를 지연시켜 주는 이유가된다.

• 한국재료학회지
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• 제33권10호
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• pp.400-405
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• 2023

Tb³⁺-doped CaNb₂O₆ (CaNb₂O₆:Tb³⁺) thin films were deposited on quartz substrates at a growth temperature of 300 ℃ using radio-frequency magnetron sputtering. The deposited thin films were annealed at several annealing temperatures for 20 min and characterized for their structural, morphological, and luminescent properties. The experimental results showed that the annealing temperature had a significant effect on the properties of the CaNb₂O₆:Tb³⁺ thin films. The crystalline structure of the as-grown CaNb₂O₆:Tb³⁺ thin films transformed from amorphous to crystalline after annealing at temperatures greater than or equal to 700 ℃. The emission spectra of the thin films under excitation at 251 nm exhibited a dominant emission band at 546 nm arising from the ⁵D₄→⁷F₅ magnetic dipole transition of Tb³⁺ and three weak emission bands at 489, 586, and 620 nm, respectively. The intensity of the ⁵D₄→⁷F₅ (546 nm) magnetic dipole transition was greater than that of the ⁵D₄→⁷F₆ (489 nm) electrical dipole transition, indicating that the Tb³⁺ ions in the host crystal were located at sites with inversion symmetry. The average transmittance at wavelengths of 370~1,100 nm decreased from 86.8 % at 700 ℃ to 80.5 % at an annealing temperature of 1,000 ℃, and a red shift was observed in the bandgap energy with increasing annealing temperature. These results suggest that the annealing temperature plays a crucial role in developing green light-emitting CaNb₂O₆:Tb³⁺ thin films for application in electroluminescent displays.

• 한국광물학회지
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• 제2권1호
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• pp.8-10
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• 1989

Sphene from the McDonald pegmatite near Bancroft, Ontario, Canada was analyzed using EPMA. It contains 4.3 to 6.3 weight percent of Nb2O5 with an average formula Ca1.02(Ti0.62Al0.22Nb0.07Fe0.06Ta0.01)Si0.99(O4.85F0.16). Three types of subtitutions are possible; 1)2Ti4+=(Nb, Ta)5+ + (Al, Fe3+), 2) Ti + O = (Al, Fe3+) + (F, OH), and 3) 2Ti + O = Fe2+ + (Nb, Ta)5+ + (F, OH). T재 different schemes of substitutions for balancing the analysis are considered when the iron is either all ferric or all ferrous. Assuming stoichiometry fo Ca and Si, a general formula derived from the two different schemes is Ca(Ti0.64Al0.22Fe3+0.06-X {{{{Fe_{x}^{2+} }} Nb0.01)Sio4.80-XF0.16(OH)0.04+x.

• 한국세라믹학회지
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• 제15권1호
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• pp.9-15
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• 1978

The possiblity of mullitization from the domestic alunite by adding of $Fe_2O_3-MnO_2$, $Fe_2O_3-MnO_2-TiO_2$, $Fe_2O_3-MnO_2-CaF_2$, and $Fe_2O_3-MnO_2-CaF_2-TiO_2$ mixtures as mineralizers was studied at the temperature range between $1, 250^{\circ}C$~$1, 430^{\circ}C$. The modifying method of domestic alunite was performed by calcination, wet ballmilling, and washing with water. The following results were obtained; 1) When added of 3.0% $Fe_2O_3$ plus 1.0-1.5% $MnO_2$ to modified alunite, the appropriate temperature range of mullite-forming was $1, 350^{\circ}C$-$1, 400^{\circ}C$. 2) When added of $TiO_2$ as mineralizer, the mullite-forming temperature was higher than not added. 3) When added of $CaF_2$ as mineralizer, the synthesized mullite was resolve at the temperature above $1, 350^{\circ}C$.

• 한국재료학회지
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• 제22권5호
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• pp.215-219
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• 2012

Red phosphors $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ were synthesized with different concentrations of $Eu^{3+}$ ions by using a solid-state reaction method. The crystal structure of the red phosphors was found to be a tetragonal system. X-ray diffraction (XRD) results showed the (112) main diffraction peak centered at $2{\theta}=28.71^{\circ}$, and the size of crystalline particles exhibited an overall decreasing tendency according to the concentration of $Eu^{3+}$ ions. The excitation spectra of all the phosphors were composed of a broad band centered at 275 nm in the range of 230-310 nm due to $O^{2-}{\rightarrow}W^{6+}$ and a narrow band having a peak at 307 nm caused by $O^{2-}{\rightarrow}Eu^{3+}$. Also, the excitation spectrum presents several strong lines in the range of 305-420 nm, which are assigned to the 4f-4f transitions of the $Eu^{3+}$ ion. In the case of the emission spectrum, all the phosphor powders, irrespective of $Eu^{3+}$ ion concentration, indicated an orange emission peak at 594 nm and a strong red emission spectrum centered at 615 nm, with two weak lines at 648 and 700 nm. The highest red emission intensity occurred at x = 0.10 mol of Eu3+ ion concentration with an asymmetry ratio of 12.5. Especially, the presence of $Eu^{3+}$ in the $Ca_{1-1.5x}WO_4:{Eu_x}^{3+}$ shows very effective use of excitation energy in the range of 305-420 nm, and finally yields a strong emission of red light.

• Journal of Korean Biological Nursing Science
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• 제3권2호
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• pp.51-61
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• 2001

This study was done to investigate the effect of the first experience of the clinical experience for psychiatric nursing on urinary $Na^+$, $Cl^-$, $K^+$, $Ca^{++}$ of the nursing students. We analyzed the urine of 36 students on curriculum who were students of D college in K city. The data were analyzed with SAS Statistical analysis was performed by using paired t-test, GLM. The second day group increased 18.56 at 8AM, 31.90 at 4PM in case of $Na^+$(p=0.004). The second day group increased 27.61 at 8AM, 45.53 at 4PM in a case of $Cl^-$(p=0.009). The first day group increased 2.62 at 8AM, 7.09 at 4PM in case of $K^+$(p=0.018). The second day group increased 3.69 at 8AM, 5.19 at 4PM in a case of $K^+$(p=0.013). The second day group increased 20.65 at 8AM, 14.07 at 4PM in a case of $Ca^{++}$(p=0.033). There was a significant difference in $Na^+$ according to group at 8AM(F=4.17, p=0.024) and 4PM(F=3.58, p=0.040). There was a significant difference in $Cl^-$ according to group at 8AM(F=4.38, p=0.020) and 4PM(F=6.29, p=0.003). There was a significant difference in $K^+$ according to group at 8AM(F=5.03, p=0.012). In conclusion, $Na^+$, $Cl^-$, $K^+$, $Ca^{++}$ may be used as a indicator of the amount of stress to improve the educational environment for the students.

• 한국세라믹학회지
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• 제37권12호
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• pp.1229-1233
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• 2000

(1-x)NdAlO$_3$-xCaTiO$_3$세라믹스의 결정구조와 마이크로파 유전특성을 조사하였다. 시편의 결정구조는 조성에 따라서 변화하였는데, 그 결정구조는 x$\leq$0.1일 때는 능면정(rhombohedral) 구조를, 0.3$\leq$x$\leq$0.7에서는 정방정 (tetragonal) 구조를 그리고, x$\geq$0.7일 때 다시 사방정 (orthorhombic) 구조로 바뀌었다. 또한 (1-x)NdAlO$_3$-xCaTiO$_3$세라믹스에서 이차상의 두 종류가 발견되었다. x$\leq$0.5인 시편에서는 Nd$_4$Al$_2$O$_{9}$상이, x$\geq$0.7인 시편에서는 Al-rich상이 발견되었다. x가 증가함에 따라, 유전율 ($\varepsilon$$_{r}$)과 공진주파수의 온도계수 ($ au$$_{f}$ )가 증가하였고, Q$\times$f 값은 x의 증가에 따라 증가하며, x=0.5일 때 최대값을 얻었다. 그리고 0.3NdAlO$_3$-0.7CaTiO$_3$에서 Q$\times$f=46,000, $\varepsilon$$_{r}$=45 그리고 $\tau$$_{f}$ =-1.5 ppm/$^{\circ}C$의 우수한 마이크로파 유전특성을 얻을 수 있었다.

• 한국산학기술학회논문지
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• 제18권4호
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• pp.608-613
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• 2017

본 연구에서는 저품위인 35wt% 금합금에 대해 80.0wt% 이상의 Au를 얻기 위한 건식 정련 공정을 제안하였다. Au35wt%-Ag5wt%-Cu60wt%의 조성을 가진 금합금에 대해 PbO/(PbO+CaO)의 혼합비를 각각 0~1로 변화시키고 플럭스/금합금의 무게비는 1/2로 하여 $1200^{\circ}C$-5시간의 열처리를 진행하였다. 이때 공정 전, 후 시료의 조성 변화는 energy dispersive X-ray spectroscopy(EDS)로 확인하고, 공정이 완료된 후 분리된 플럭스 금속 원소 성분은 time of flight secondary ion mass spectromerty(ToF-SIMS)로 확인하였다. EDS분석 결과 플럭스의 비율이 1(PbO 단일)인 경우 Au의 함량이 35.0wt%에서 86.7wt%로 가장 크게 향상되었고, 다른 플럭스 조성의 경우도 84wt% 이상으로 정련이 가능하였다. 또한 2/3 혼합비의 플럭스에서 Ag가 플럭스부로 빠져나가는 손실이 가장 적었다. 플럭스부의 ToF-SIMS 분석 결과 플럭스의 비율이 1, 0 일 때 $Au^+$의 특성 피크의 강도가 각각 349, 37로 측정되었다. Au의 손실을 고려하였을 때 CaO 단일 플럭스의 사용이 더 유리할 수 있었으나, 이 정도의 신호강도는 무시할 수 있는 정도로 판단되었다. 따라서 혼합플럭스를 이용한 건식 열처리를 통해 효과적인 금의 정련이 가능하여 경제적인 습식제련의 전처리 공정으로 사용될 수 있음을 확인하였다.

• Journal of Veterinary Science
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• 제21권6호
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• pp.85.1-85.6
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• 2020

A cold-adapted porcine reproductive and respiratory syndrome virus (CA-VR2332) was generated from the modified live virus strain VR2332. CA-VR2332 showed impaired growth when cultured at 37℃ with numerous mutations (^S731^F, ^E819^D, ^G975^E, and ^D1014^N) in the hypervariable region of the NSP2, in which the mutation ^S731^F might play a vital role in viral replication at 30℃. Conserved amino acid sequences of the GP5 protein suggests that CA-VR2332 is a promising candidate for producing an effective vaccine against PRRSV infection. Further studies on replication and immunogenicity in vivo are required to evaluate the properties of CA-VR2332.