• Journal of Astronomy and Space Sciences
• /
• v.30 no.1
• /
• pp.25-32
• /
• 2013

We statistically investigated the properties of low-latitude Pi2 pulsations using Bohyun (BOH, Mlat = $29.8^{\circ}$, L = 1.35) ground magnetometer data in 2008. For this 1-year interval, 582 Pi2 events were identified when BOH was in the nightside from 1800 to 0600 local times. We found the following Pi2 characteristics. (1) The occurrence distribution of Pi2s is relatively constant in local times. (2) The Pi2 frequency varies in local times. That is, Pi2 pulsations in postmidnight sector had higher frequency than in premidnight sector. (3) Pi2 power in premidnight sector is stronger than in postmidnight sector. (4) Pi2 frequency has positive correlation with solar wind speed and AE index. (5) Pi2 power has not a clear correlation with solar wind parameters. This indicates that Pi2 power is not controlled by external sources. (6) It is found that the most probable-time between Pi2 onsets is ${\Delta}t$ ~ 37.5 min: This is interpreted to be the period between Pi2 pulsations when they occur cyclically. We suggest that ${\Delta}t$ ~ 37.5 min is the occurrence rate of reconnection of open field lines in the tail lobe.

• Journal of the Microelectronics and Packaging Society
• /
• v.29 no.2
• /
• pp.43-48
• /
• 2022

Effect of temperature/humidity (T/H) treatment conditions on the peel strength of screen-printed Ag/polyimide (PI) structures was evaluated by peeling PI films in 90° peel test. Initial peel strength was 25.99±1.47 gf/mm, and then decreased to 6.05±0.54 gf/mm after 500 h at 85℃/85% relative humidity T/H condition. And, the peeled locus was changed from Ag/PI interface to shallow cohesive inside PI near interface. X-ray photoelectron spectroscopy analysis on the peeled surfaces showed that the long-term moisture penetration into the Ag/PI interface during T/H treatment led to hydrolytic degradation of PI to form weak boundary layer inside PI near Ag/PI interface, which are responsible for large decrease in peel strength.

• Current Research on Agriculture and Life Sciences
• /
• v.8
• /
• pp.35-44
• /
• 1990

Sixty two lines of pepper including Korean local cultivars and introductions were planted out to the experiment farm of Kyungpook National University for seed increase, and 16 plant and fruit characters including days to flower were recorded. In days to flower, KC85(Chilgok Dongmyung) and KC116(PI308791), KC154(Cherry Sweet), and KC185(Choseongochu) were the earliest with 83 days, and KC139(Serrano chili) and KC103(PI297488) were the latest with 126 days. In fruit detachment force, KC85(Chilgok dongmyung) was the tenderest with 0.45kg and KC162(PI22444) was the toughest with 3.34kg. In powdery mildew incidence, KC10(Pimiento), KC23(PI224423), KC51(PI257044), KC56(PI257053), KC126(PI358812), KC119(PI322719), KC143(Emerald Giant), KC148(VR-2), KC163(PI224445), KC163(Papari Mild) were the least diseased. Anthracnose was least on KC39(Serrano Chili). Collection and introduction of pepper germplasm was continued. Fourteen Korean local cultivars and 25 foreign cultivars including 2 wild species were additionally collected or introduced.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.2
• /
• pp.33-38
• /
• 2020

In the photoelectrochemical (PEC) water splitting, GaN is one of the most promising photoanode materials due to high stability in electrolytes and adjustable energy band position. However, the application of GaN is limited because of low efficiency. To improve solar to hydrogen conversion efficiency, we introduce a Cobalt Phosphate (Co-pi) catalyst by photo-electrodeposition. The Co-pi deposition GaN were characterized by SEM, EDS, and XPS, respectively, which illustrated that Co-pi was successfully decorated on the surface of GaN. PEC measurement showed that photocurrent density of GaN was 0.5 mA/㎠ and that of Co-pi deposited GaN was 0.75 mA/㎠. Impedance and Mott-Schottky measurements were performed, and as a result of the measurement, polarization resistance (R_p) and increased donor concentration (N_D) values decreased from 50.35 Ω to 34.16 Ω were confirmed. As a result of analyzing the surface components before and after the water decomposition, it was confirmed that the Co-pi catalyst is stable because Co-pi remains even after the water decomposition. Through this, it was confirmed that Co-pi is effective as a catalyst for improving GaN efficiency, and when applied as a catalyst to other photoelectrodes, it is considered that the efficiency of the PEC system can be improved.

• Journal of the Korean Mathematical Society
• /
• v.32 no.3
• /
• pp.371-387
• /
• 1995

Let X be a compact polyhedron, H a normal subgroup of the fundamental group $\pi_1(X)$ of X and $f : X \longrightarrow X$ a selfmap such that $f_piH \subset H$, where f_\pi : \pi_1(X) \longrightarrow \pi_1(X)$ is the induced homomorphism by f.

• Communications of Mathematical Education
• /
• v.11
• /
• pp.307-319
• /
• 2001

대학수학에서, 멱급수의 전개를 배우는 단원에서 관심을 끄는 수 ${\pi}$에 대하여 고찰함으로써, ${\pi}$값의 계산 과정에 있어서의 발달을 이해하고, Mathematica를 이용하여 수학자들이 만든 공식을 통해 ${\pi}$값을 구체적으로 계산하여 보며, 또한 수학에 흥미를 느끼도록 하여 학생들 스스로가 ${\pi}$값을 계산해 볼 수 있는 기회를 갖도록 유도한다.

• Current Research on Agriculture and Life Sciences
• /
• v.9
• /
• pp.127-133
• /
• 1991

PI201232, a pepper line resistant to Phytophthora capsici Leonian, was crossed with PI2713222 and P1163192, resistant to Xanthomonas campestTis pv. vesicatoria (Doidge) Dye and inheritance of the resistance to each disease and genetic relationship between the two disease resistances was studied. Non-hypersensitive resistance to race 3 of X. c. pv. vesicatoria of PI271322 was inherited in a quantitative mode. Resitance to P. capsici of PI201232 was inherited in a mode close to two dominant alleles. Hypersensitive resistance to race 1 of X. c. pv. vesicatoria of PI271322 was inherited in a mode of single dominant allele. PI 163192 was consistently resistant to both race 1 and race 3 of X c. pv. vesicatoria and the resistance was inherited in a quantitative mode with high dominance effect. Resistance to X. c. pv. vesicatoria was inherited independently from resistance to P. capsici.

• Communications of Mathematical Education
• /
• v.29 no.1
• /
• pp.91-110
• /
• 2015

The purpose of this study is to investigate the understanding of pi of elementary gifted students and explore improvement direction of teaching pi. The results of this study are as follows. First, students understood insufficiently the property of approximation, constancy and infinity of pi from the fixation on 'pi = 3.14'. They mixed pi up with the approximation of pi as well. Second, they had a inclination to understand pi as algebraic formula, circumference by diameter. Third, few students understood the property of constancy and infinity of pi deeply. Lastly, the discussion activity provided the chance of finding the idea of the property of approximation of pi. In conclusion, we proposed several methods which improve the teaching of pi at elementary school.

• Bulletin of the Korean Mathematical Society
• /
• v.53 no.1
• /
• pp.91-102
• /
• 2016

A chief factor H/K of G is called F-central in G provided $(H/K){\rtimes}(G/C_G(H/K)){\in}{\mathfrak{F}}$. A normal subgroup N of G is said to be ${\pi}{\mathfrak{F}}$-hypercentral in G if either N = 1 or $N{\neq}1$ and every chief factor of G below N of order divisible by at least one prime in ${\pi}$ is $\mathfrak{F}$-central in G. The symbol $Z_{{\pi}{\mathfrak{F}}}(G)$ denotes the ${\pi}{\mathfrak{F}}$-hypercentre of G, that is, the product of all the normal ${\pi}{\mathfrak{F}}$-hypercentral subgroups of G. We say that a subgroup H of G is ${\pi}{\mathfrak{F}}$-embedded in G if there exists a normal subgroup T of G such that HT is s-quasinormal in G and $(H{\cap}T)H_G/H_G{\leq}Z_{{\pi}{\mathfrak{F}}}(G/H_G)$, where $H_G$ is the maximal normal subgroup of G contained in H. In this paper, we use the ${\pi}{\mathfrak{F}}$-embedded subgroups to determine the structures of finite groups. In particular, we give some new characterizations of p-nilpotency and supersolvability of a group.

• Journal of the Korean Mathematical Society
• /
• v.47 no.6
• /
• pp.1269-1282
• /
• 2010

We in this note consider a new concept, so called $\pi$-McCoy, which unifies McCoy rings and IFP rings. The classes of McCoy rings and IFP rings do not contain full matrix rings and upper (lower) triangular matrix rings, but the class of $\pi$-McCoy rings contain upper (lower) triangular matrix rings and many kinds of full matrix rings. We first study the basic structure of $\pi$-McCoy rings, observing the relations among $\pi$-McCoy rings, Abelian rings, 2-primal rings, directly finite rings, and ($\pi-$)regular rings. It is proved that the n by n full matrix rings ($n\geq2$) over reduced rings are not $\pi$-McCoy, finding $\pi$-McCoy matrix rings over non-reduced rings. It is shown that the $\pi$-McCoyness is preserved by polynomial rings (when they are of bounded index of nilpotency) and classical quotient rings. Several kinds of extensions of $\pi$-McCoy rings are also examined.