• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1993.11a
• /
• pp.124-127
• /
• 1993

In this paper, the magnetic properties of Ni-Zn ferrite powders dependent on pH have been studied. Ni-Zn ferrite powders were synthesized by coprecipitation method(pH were 7. 9. 11 and 13. respetively) using FeCl$_3$$.$ 6H$_2$O, NiCl$_2$$.$6H$_2$O and ZnCl$_2$as starting materials and its powders were calcined at 1,000($^{\circ}C$). The saturated magnetizations of the Ni-Zn ferrite powders dependent on various pH. such as 7, 9, 11 and 13 were 11.44, 29.77, 69.62 and 66.75(emu/g), respetively.

• Bulletin of the Korean Mathematical Society
• /
• v.39 no.1
• /
• pp.123-131
• /
• 2002

Let A(p, k) (p, k$\in$N) be the class of functions f(z) = $z^{p}$ + $a_{p+k}$ $z^{p+k}$+… analytic in the unit disk. We introduce a subclass H(p, k, λ, $\delta$, A, B) of A(p, k) by using the Ruscheweyh derivative. The object of the present paper is to show some properties of functions in the class H(p, k, λ, $\delta$, A, B). B).

• Communications of the Korean Mathematical Society
• /
• v.13 no.2
• /
• pp.233-242
• /
• 1998

Let $k = Q(\sqrt{m})$ be a real quadratic field. In this paper, the following theorems on p-divisibility of the class number h of k are studied for each prime pp. Theorem 1. If the discriminant of k has at least three distinct prime divisors, then 2 divides h. Theorem 2. If an odd prime p divides h, then p divides $B_{a,\chi\omega^{-1}}$, where $\chi$ is the nontrivial character of k, and $\omega$ is the Teichmuller character for pp. Theorem 3. Let $h_n$ be the class number of $k_n$, the nth layer of the $Z_p$-extension $k_\infty$ of k. If p does not divide $B_{a,\chi\omega^{-1}}$, then $p \notmid h_n$ for all $n \geq 0$.

• Korean Journal of Environmental Agriculture
• /
• v.13 no.3
• /
• pp.346-358
• /
• 1994

In this paper, the current knowledge on the formation of acid rain and its effect on vegetation are reviewed. The pollutants which were emitted into the air are oxidized by photochemical reaction and affect the vegetation by dry and wet deposition. Acid rain at pH 4.0 affected sensitive plants and when it was below pH 3.0, visible symptoms developed in most of the crops. The acid rain treatment at pH 2.0 decreased dry weight, leaf area and chlorophyll contents in soybean but it increased rate of photosynthesis and respiration rate. Rain treatment at pH 2.8 increased ethylene production, but it’s not a suitable indicator of sensitivity to acid rain. At pH 2.0 treatment, the contents of soluble Mn and Al were increased but the cultivated soil pH at upper layer(0-5cm) was significantly decreased. The pertubation of glandular trichome which is existed along the vein was developed at all treatment except the control(pH 6.0) and non-treatment. Histological pertubation of spiked trichome and disintegration of chloroplast were developed only on the leaves of sesame treated with SAR(simulated acid rain) of pH 2.0.

• Tribology and Lubricants
• /
• v.20 no.2
• /
• pp.97-101
• /
• 2004

This paper reports the studies on the wear-corrosion behavior of Al-Mg alloy in various pH environments. In various pH of sea water, corrosion and wear-corrosion loss of Al-Mg alloy were investigated. Also, the polarization test of Al-Mg alloy using potentiostat/galvanostat was carried out. And the rubbed surface of Al-Mg alloy using scanning electron micrographs after wear-corrosion test was examined in various pH values of sea water. The main results are as following : The polarization resistance of Al-Mg alloy in pH 4 solution is higer than that in pH 6.7 solution, and the corrosion current density in pH 4 is controlled than in pH 6.7 solution. The wear-corrosion loss of Al-Mg alloy with lowering pH becomes sensitive. As the oxide product of Al-Mg alloy appears granular structure and exholiation phenomenon, wear-corrosion loss of Al-Mg alloy increases.

• Journal of Institute of Control, Robotics and Systems
• /
• v.12 no.12
• /
• pp.1178-1183
• /
• 2006

This paper is concerned with the modeling and identification of pH neutralization process as nonlinear chemical system. The pH control has been applied to various chemical processes such as wastewater treatment, chemical, and biochemical industries. But the control of the pH is very difficult due to its highly nonlinear nature which is the titration curve with the steepest slope at the neutralization point. We apply SVM which have become an increasingly popular tool for machine teaming tasks such as classification, regression or detection to model pH process which has strong nonlinearities. Linear and radial basis function kernels are employed and each result has been compared. So SVH based on kernel method have been found to work well. Simulations have shown that the SVM based on the kernel substitution including linear and radial basis function kernel provides a promising alternative to model strong nonlinearities of the pH neutralization but also to control the system.

• Corrosion Science and Technology
• /
• v.10 no.5
• /
• pp.175-179
• /
• 2011

The transportation and deposition of iron corrosion products are important elements that affect both the steam generator (SG) integrity and secondary system in pressurized water reactor (PWR) nuclear power plants. Most of iron corrosion products are generated on carbon steel materials due to flow accelerated corrosion (FAC). The several parameters like water chemistry, temperature, hydrodynamic, and steel composition affect FAC. It is well established that the at-temperature pH of the deaerated water system has a first order effect on the FAC rate of carbon steels through nuclear industry researches. In order to reduce transportation and deposition of iron corrosion products, increasing pH(t) tests were applied on secondary system of A, B units. Increasing pH(t) successfully reduced flow accelerated corrosion. The effect of increasing pH(t) to inhibit FAC was identified through the experiment and pH(t) evaluation in this paper.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.8
• /
• pp.616-621
• /
• 2011

In this paper, CdS thin films, which were widely used window layer of the CdTe and the Cu(In,Ga)$Se_2$ thin film solar cell, were grown by chemical bath deposition, and effects of pH of reaction solution on the structural and optical properties were investigated. For pH<10.5, as the pH of reaction solution was higher, the deposition rate of CdS films was increased by improving ion-by-ion reaction in the substrate surface and the crystallinity of the films was improved. However, when the pH was higher than 10.5, the deposition rate was decreased because of smaller $Cd^{2+}$ ion concentration in the reaction solution. Also, the crystallinity of the films were deteriorated. The CdS films deposited at lower pH showed poor optical transmittance due to adsorbed colloidal particles, while the transmittance was improved for higher pH.

• Journal of Korean Society of Archives and Records Management
• /
• v.1 no.1
• /
• pp.177-200
• /
• 2001

The causes which affects the deterioation of paper arc paper structure, papermaking process, temperature and rative humidity, light and biological agents. Paper made from cllulose fibers by the wood and the nonwood, This paper structure is further hydrolyzed by acidic additive such as the sizing agents during the manufacturing process. These additives leave residual acids in the paper, which break the cellulose clown to simper molecules. The results is weak paper and bas caused most of the damage to book. This study was carried out to investigate the presevation and the deacidification for the permanenece by the book. The deacidification and the chemical agents aims to nutralized the aicd in paper and add alkaline to it as a buffer to withstand future acid attacks. By applying the system to the acid paper with a pH of 4.5 neutralized a pH of 8.5. The expected of alkaline reserved paper extend about 2times and 3times than acidic paper.

• Bulletin of the Korean Mathematical Society
• /
• v.55 no.6
• /
• pp.1835-1843
• /
• 2018

In this paper, finite p-groups G satisfying $N_G(H){\leq}H^G$ for every non-normal subgroup H of G are completely classified. This solves a problem proposed by Y. Berkovich.