• Electrical & Electronic Materials
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• v.10 no.6
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• pp.555-561
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• 1997

The passivation of n-GaAs(100) surface has investigated by photoreflectance(PR). The surface of the sample was treated with the 0.001 N solution Se/NH$_4$OH. After the surface treatment, the samples were annealed between 400 to $700^{\circ}C$ in a $N_2$atmosphere for 10 min. The intensity of PR signal and period of Franz-Deldysh oscillation(FKO) gradually decreased as the annealing temperature increased. The surface electric field(E$_{s}$) of the sample annealed at $600^{\circ}C$ is obtained 1.34$\times$10$^{5}$ V/cm. This value is 1.97 times less than that of unannealed sample. It has found that the passivation of surface occurred when the surface of the sample had been treated with Se/NH$_4$OH solution and annealed from 500 to $600^{\circ}C$. This result could be due to activation of elemental Se on the surface. It has also found that the elemental Se of the surface diffused about 100 $\AA$ into the bulk GaAs when Se-treated sample was annealed at $600^{\circ}C$.>.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.43-48
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• 1993

A laboratory study was cunducted to obtain fundamental informations on environmental-conservative treatment technique of soiled animalwaste. The release rate of inorganic nitrogen which mineralized from solid pigwaste and the effect of nitrification inhibitor(Dicyandiamide, DCD) on nitrate concentration of fresh or fermented pigwaste were weekly checked for ten weeks under incubation condition. Average pH of soild pigwaste was maintained over 8 unit during all incubation periods with no difference by nitrification inhibitor addition and the pHs of fresh- or fermented pigwaste without DCD were elevated by passing time 0.04, 0.058 pH unit/week (P<0.05) during incubation. While $NH_4-N$ concentration of fermented pigwaste until two week was nearly the same as it before incubation, $NH_4-N$ concentration of fresh pigwaste was remarkably increased upto 3,732 ppm for 1 week after incubation and the portion of increased $NH_4-N$ concentration, 2,473 ppm was 20.1% of indigenous organic nitrogen of fresh pigwaste. By the passing incubation time, $NH_4-N$ concentration began to lower linearly at not only fresh- but fermented pigwaste after 1 or 2 week, respectively and the $NH_4-N$ concentration loss rate at fresh pigwaste was 61.8 ppm/week with DCD addition and 72.3ppm/week with no DCD. There was positive relationship between $NO_3-N$ concentrations of fresh pigwaste by the addition of DCD or not and $NO_3-N$ concentraion was significantly lowered with DCD treatment($r=0.79^{**}$).

• Journal of Korean Society of Environmental Engineers
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• v.22 no.6
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• pp.1093-1101
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• 2000

The object of this study was to develop new BNR process using fixed-biofilm which could be applied to retrofit the existing wastewater treatment plant or to introduce as tertiary treatment plant. To achieve complete denitrification from typical raw sewage in Korea, external carbon source must be supplied because $SCOD_{cr}/T-N(NH_4{^+}-N+NOx-N)$of raw sewage was lower than other countries. In this study, the ratio of $SCOD_{cr}/NH_4{^+}-N$ was 2.49 and the influent $NH_4{^+}$-N concentration during the experimental period was varied from 25 to 37 mg/L. To enhance nitrogen removal from the sewage, the two processes using fixed biofilm were adopted as R-Hanoxic/mid.settler/aerobic/anoxic/ aerobic) and R-2(aerobic/mid.settlerlanoxic/anoxic/aerobic), respectively. In the comparison of $NH_4{^+}$-N, T-N effluent quality and T-N removal efficiency in both processes without external carbon source, R-1 process was better than R-2 process for nitrogen removal from raw sewage. With respect to $SCOD_{cr}$/NOx-N ratio and total nitrogen removal in each anoxic reactor of two processes, R-1's was more effective than R-2's for distributing organic matters of raw sewage. In the both processes using fixed biofilm, the amount of required alkalinity to remove unit $NH_4{^+}$-N were 5.18 and 5.76($g{\cdot}CaCO_3/g{\cdot}NH_4{^+}-N_{removed}$), respectively and were lower than activated sludge BNR process(7.14).

• Nuclear Engineering and Technology
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• v.4 no.4
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• pp.306-321
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• 1972

Molecular reorientation in (NH$_4$)$_2$SO$_4$, has been studied by cold neutron scattering. For T=300$^{\circ}$K data, the isolated quasielastic spectra and form-factors at various scattering angles are compared with four reorientational models based on SKOLD theory. Front these, it is concluded that the NH$_4$ions are performing either 3-fold four axes or 2-fold three axes reorientation with $\tau$$_{c}$=2.0$\times$10$^{-11}$ sec. The temperature dependence of f. is studied over 100$^{\circ}$K-413$^{\circ}$K and for the high-temperature phase, the widths of composite spectra are compared with the results from NMR relaxation measurements. All the results have shown that the neutron scattering method is capable of giving detalis of the reorientational modes in solids and therefore some discussions are given on the application of this method. A study of the form-factor is applied for NH$_4$I (Phase I) by comparing the measurement with the calculation based on free rotation approximation and proposed a reorientation model of NH$_4$ ions in the octahedral potential cage with $\tau$$_{c}$$\leq$10$^{-12}$ sec. Also a brief theoretical prediction for the effect of reorientational motions on the inelastic spectrum is discussed.sed.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1994.11a
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• pp.96-97
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• 1994

국내에서 가장 많이 소비되는 양념채소 중 하나인 잎파는 계절별 재배면적의 변동때문에 가격파동이 극심한 작물로서 안정적인 생산체계가 요구되고 있다. 따라서 greenhouse내에서의 수경재배를 통한 잎파의 생산은 계절적 요인에 의한 재배환경 변화 대처에 용이하다는 측면에서 안정적 생산을 기하는데 유리하다. 따라서 수경재배를 통한 주년생산을 위하여 양액내 NO3$^{-}$ : NH4$^{+}$ 비가 잎파의 생육에 미치는 영향을 조사하고자 본 실험을 수행하였다. (중략)

• Korean Journal of Soil Science and Fertilizer
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• v.32 no.3
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• pp.223-231
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• 1999

This study was carried out to investigate the factors influencing water quality of the river (Mankyeong River) and groundwater in controlled horticulture region from 1994 to 1998. Water quality of Mankyeong River was monitored at 13 sites along main stream for 6 months from April to September from 1994 to 1997. Monthly average concentrations of $NH_4-N$, $SO{_4}^{2-}$ and $Cl^-$ were highest in April, while that of $NO_3-N$ was highest in August. Monthly average concentrations of COD was highest in September Concentrations of $NH_4-N$ and $SO{_4}^{2-}$ in many sites of Mankyeong River exceeded the water quality criteria of agricultural water for irrigation. Water quality of Mankyeong River was not suitable for the irrigation source excepted the sites such as Hari, Gosan and Soyang stream. The floodgates of Mokcheon, Yocheon, Jeonju and Samcheon streams were rapidly polluted by the municipal sewage, otherwise the Iksan stream was rapidly polluted by the sewage of swine. The sum of inorganic ion concentrations in Mankyeong River was highest at floodgate of Yocheon due to the sewages municipal and industrial. The order of the major anions and canons concentration in Mankyeong River- stream were $SO{_4}^{2-}$ > $Cl^-$ > $NO{_3}^-$ > $PO{_4}^{3-}$ and $Na^+$ > $Ca^{2+}$ > $NH{_4}^+$ > $Mg^{2+}$ > $K^+$, respectively. The geoundwater quality at controlled horticulture region was surveyed 4 sites from 1994 to 1998. Concentrations of $NH_4-N$ and $NO_3-N$ were lower at the deeper groundwater. However there was no difference between the concentrations of $SO{_4}^{2-}$ and $Na^+$, and the groundwater depth below 15m. Contents of $NH_4-N$, $NO_3-N$, $PO{_4}^{3-}$, $SO{_4}^{2-}$, $Na^+$ and $Cl^-$ in groundwater were the highest at dry season. Nitrate-N level, exceeded $20mg\;l^{-1}$, the critical level for agricultural usage, at Yongjinmyeon Wanju and $PO{_4}^{3-}$ concentration were higher at Seogtandong Iksan than the other places.

• Journal of The Korean Society of Grassland and Forage Science
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• v.44 no.2
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• pp.133-139
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• 2024

This study aimed to evaluate the efficiency of combining acidification with adsorbents (zeolite and biochar) to mitigate the environmental impacts of pig slurry, focusing on ammonia (NH₃) emission and nitrate (NO₃^-) leaching. The four treatments were applied: 1) pig slurry (PS) alone as a control, 2) acidified PS (AP), 3) acidified pig slurry with zeolite (APZ), and 4) acidified pig slurry with biochar (APB). The AP mitigates NH₃ emission and NO₃^- leaching compared to PS alone. Acidification reduced the cumulative NH₃ emission and its emission factor by 35.9% and 12.5%, respectively. The APZ and APB increased NH₄⁺-N concentration, with the highest level in APB, compared to AP. The NH₄⁺ adsorption capacity of APB (0.90 mg g^-1) was higher than that of APZ (0.63 mg g^-1). The APB and APZ treatments induced less NH₃ emission compared to AP. The cumulative NH₃ emission was reduced by 12.2% and 27.6% in APZ and APB, respectively, compared to AP treatment. NO₃^- leaching began to appear on days 12 and 13, and its peak reached on days 16 and 17, which were later than AP. The cumulative NO₃^- leaching decreased by 17.7% and 25.0% in APZ and APB, respectively, compared to AP treatment. These results suggest that combining biochar or zeolite with acidified pig slurry is an effective method to mitigate NH₃ emission and NO₃^- leaching, with biochar being particularly effective.

• Advances in pediatric surgery
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• v.7 no.2
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• pp.95-104
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• 2001

Biliary atresia (BA) is very difficult to distinguish from neonatal hepatitis (NH) and its prognosis depends on the age at the time of Kasai operation. Therefore early differentiation between these two conditions is very important. Although various clinical and laboratory tests have been reported to differentiate between them, they are still of limited value. From 1980 to 1999, forty-five infants were referred to our pediatric surgical unit for operation for suspected BA. Eight patients underwent Kasai operation immediately because of late diagnosis. These were excluded from the study. The clinical history, physical findings. radiologic and laboratory examinations of 37 cases were analyzed retrospectively. The average age of BA (n=20) was $55.1{\pm}16.7$ days, and that of NH (n=17) was $55.8{\pm}15.6$ days. The sex ratio of BA was 13:7, and that of NH was 14:3. All the patients had obstructive jaundice and acholic stool except 4 BA and 6 NH patients. Acholic stool with yellow component was more frequent in NH. Onset of jaundice was within 2 weeks after birth in 85 % of BA, and in 65% of NH. The onset of acholic stool was within 2 weeks after birth in 60 % of BA, and in 23.5 % of NH. The duration of jaundice and acholic stool of BA were $50.9{\pm}16.6$ days and $41.3{\pm}18.4$ days and those of NH were $40.1{\pm}23.1$ days and $26.6{\pm}25.4$ days respectively. The ultrasonogram and hepatobiliary scan were useful, but not a definitively reliable method for the differentiation of these two diseases. There was no difference in laboratory data. Seventeen cases had NH among 45 referred cases for Kasai operation with the clinical impression of BA, and 4 cases of 17 NH cases needed to be explored to rule out BA. In conclusion. false positive rate of clinical impression of BA was 37.8 %. and negative exploration rate was 8.9 %, Therefore. careful clinical observation for 1-2 weeks by an experienced pediatric surgeon was very important to avoid unnecessary operation to rule out NH up to the age of 8 - 10 weeks. so long as the stool had yellow component.

• Applied Biological Chemistry
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• v.29 no.2
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• pp.159-163
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• 1986

The optical properties of monocationic zeolite suspension adsorbed with each of $Na^+$, $NH_4^+$, $Ca^{2+}$, and $Al^{3+}$ were studied in the wavelength range $200{\sim}800nm$. The results were as follows. 1. The optical density of zeolite suspension seemed to be affected by the light absorption of zeolite particles at the wavelength range of $200{\sim}300nm$ and by the light scattering of zeolite particles at wavelength of $300{\sim}800nm$. 2. At the wavelength range of $380{\sim}800nm$, the optical densities of monocationic zeoliteg differed mutually according to adsorbed cations and increased in the order of $Al-\;>\;Ca-\;>\;NH_4->\;Na-zeolite$ suspension. 3. It was convenient that at the wavelength range of $380{\sim}800nm$, the diluted suspension of zeolite was measured in the short wavelength and the concentrated suspension of zeolite was measured in the long wavelength. 4. Zeolite particles in zeolite suspension were aggregated and the size of aggregation size was larger in the order of $Al-\;>\;Ca-\;>\;Na-\;>\;NH_4-zeolite$.

• Journal of Surface Science and Engineering
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• v.55 no.1
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• pp.24-31
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• 2022

This study investigated the effect of pre-treatment on the PEO film formation of AZ91 Mg alloy. The pre-treatment was conducted for 10 min at room temperature in 0.5 M oxalic acid (C₂H₂O₄) solution containing various ammonium fluoride (NH₄F) concentrations. The pre-treated AZ91 Mg specimens were anodized at 100 mA/cm² of 300 Hz AC for 2 min in 0.1 M NaOH + 0.4 M Na₂SiO₃ solution. When AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with NH₄F concentration less than 0.3 M, continuous dissolution of the AZ91 Mg alloy occurred together with the formation of black smuts and arc initiation time for PEO film formation was very late. It was noticed that corrosion rate of the AZ91 Mg alloy became faster if small amount of NH₄F concentration, 0.1 M, is added. The fast corrosion is attributable to fast formation of porous fluoride together with porous oxides in the reaction products. On the other hand, when AZ91 Mg alloy was pretreated in 0.5 M oxalic acid with sufficient NH₄F more than 0.3 M, a thin and dense protective film was formed on the AZ91 Mg alloy surface which resulted in faster initiation of arcs and formation of PEO film.