• Journal of the Korean Mathematical Society
• /
• v.42 no.4
• /
• pp.749-759
• /
• 2005

We apply a cone theoretic fixed point theorem and obtain conditions for the existence of positive periodic solutions of the system of functional differential equations $$x'(t)\;=\;A(t)x(t)+{\lambda}f(t,\;x(t-\tau(t))$$.

• Bulletin of the Korean Mathematical Society
• /
• v.42 no.1
• /
• pp.169-177
• /
• 2005

A Hilbert Space operator T is of class Q if $T^2{\ast}T^2-2T{\ast}T + I$ is nonnegative. Every paranormal operator is of class Q, but class-Q operators are not necessarily normaloid. It is shown that if a class-Q contraction T has no nontrivial invariant subspace, then it is a proper contraction. Moreover, the nonnegative operator Q = $T^2{\ast}T^2-2T{\ast}T + I$ also is a proper contraction.

• Bulletin of the Korean Mathematical Society
• /
• v.42 no.3
• /
• pp.571-577
• /
• 2005

In this paper we prove that if T is a k-th root of a p­hyponormal operator when T is compact or T$^{n}$ is normal for some integer n > k, then T is (generalized) scalar, and that if T is a k-th root of a semi-hyponormal operator and have the property $\sigma$(T) is contained in an angle < 2$\pi$/k with vertex in the origin, then T is subscalar.

• Mycobiology
• /
• v.39 no.3
• /
• pp.182-186
• /
• 2011

Four Trichoderma strains (CH2, SH16, PQ34, and TN42) were isolated from soil samples collected from Quang Tri and Thua Thien Hue provinces in Vietnam. The strains exhibited high chitinolytic secretion. Strain PQ34 formed the largest zone of chitinase-mediated clearance (> 4 cm in diameter) in agar containing 1% (w/v) colloidal chitin. Analysis of the internal transcribed spacer regions of these strains indicated that they were Trichoderma asperellum. The molecular weights of the chitinases were approximately 42 kDa. Chitinase genes (chi42) of T. asperellum strains TN42, CH2, SH16, and PQ34 were 98~99% homologous to the ech42 gene of T. harzianum CB-Pin-01 (accession No. DQ166036). The deduced amino acid sequences of both T. asperellum strains SH16 and TN42 shared 100% similarity.

• Proceedings of the SAREK Conference
• /
• 2007.06a
• /
• pp.42-42
• /
• 2007

• Journal of the Korean Society of Food Culture
• /
• v.20 no.2
• /
• pp.214-220
• /
• 2005

Seasoning oil (SO) for Chinese dish was manufactured from the combination of Maillard reaction for methionine and xylose with autoclaving method. Volatile compounds were determined by GC, GC-MSD for this SO and 3 kinds of seasoning jajang samples which was obtained from restaurant. From this SO 61 kinds-404.92ppm volatile compounds were separated and identified. And from 3 samples of restaurant, 39 kinds-333.52ppm, 42 kinds-330.01ppm, 42 kinds-393.18ppm obtained respectively. Major volatile components of SO were diallyl disulfide, pentane, diallyl trisulfide, t,t-2,4-decadienal and zinngiberene. Those contents were 40.15ppm, 32.32ppm, 19.57ppm, 15.06ppm and 13.23ppm, respectively. Major volatile components in 3 kinds samples were pentane, propenal, hexanal, t-2-heptanal, 2,4-heptadienal, t,t-2,4-decadienal and unknown components. The volatile components of SO were very similar to 3 samples,

• Korean Journal of Environmental Agriculture
• /
• v.8 no.2
• /
• pp.103-118
• /
• 1989

In order to investigate the uptake of the systemic insecticide, carbofuran, 2,3-dihydro-2,2-dimethyl-7-benzofuranyl-N-methyl(arbamate) residues, fresh and aged, by rice plants, they were grown for 42 days in soils containing freshly treated (T-1), 3-month-aged (T-2), and 6-month-aged residues (T-3). The amounts of $^{14}CO_2$ evolved from $^{14}C-carbofuran$ during the 3-and 6-month aging in soil (temp. $22{\pm}1^{\circ}C$ ; moisture, 50% of the maximum water-holding capacity) were 8.9 and 26.7% of the original radioactivity applied, respectively. Mineralization of $^{14}C-carbofuran$ in soil to $^{14}CO_2$ during 42 days of rice growing was 4.4% (T-1), 11.0% (T-2), and 15.7 (T-3). The methanol extract of the 3-and 6-month-aged soils revealed that 3-keto carbofuran phenol (2,3-dihydro-2,2-dimethyl-3-oxo-7-benzofuranol) was the major metabolite, where as 3-hydroxy carbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxy-7-benzofuranyl-N-methylcarbamate) turned out to be the major metabolite in the shoots by the enzymatic cleavage of the possible conjugate present in the methanol extract. Volatilization of $^{14}C-carbofuran$ in soil during 3-and 6-month-aging, and 42 days of rice growing was 0.026, 0.05, and 0.012-0.018% of the applied radioactivity, respectively. The $^{14}C-radioactivity$ which was absorbed from the soils by rice plants during 42 days of the growing period and persisted in rice plant tissues was 26.8, 21.4, and 10.3% in T-1, T-2, and T-3, respectively. The non-extractable bound residues were 8.3, 37.9, and 54.6% of the originally applied carbofuran in T-1. T-2, and T-3, respectively. The small translocation of $^{14}C-radioactivity$ in T-3 upwards suggests that major metabolite 3-keto carbofuran phenol is conjugated in roots and the low recovery in T-1 indicates the loss of carbofuran from the shoots.

• Journal of the Korean Mathematical Society
• /
• v.42 no.2
• /
• pp.255-268
• /
• 2005

We use Krasnoselskii's fixed point theorem to show that the nonlinear neutral difference equation with delay x(t + 1) = a(t)x(t) + c(t)${\Delta}$x(t - g(t)) + q(t, x(t), x(t - g(t)) has a periodic solution. To apply Krasnoselskii's fixed point theorem, one would need to construct two mappings; one is contraction and the other is compact. Also, by making use of the variation of parameters techniques we are able, using the contraction mapping principle, to show that the periodic solution is unique.

• Honam Mathematical Journal
• /
• v.42 no.4
• /
• pp.667-680
• /
• 2020

Our paper deals with the following neutral nonlinear Levin-Nohel integro-differential with variable delay $${\frac{d}{dt}x(t)}+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_{t-r(t)}}^t}a(t,s)x(s)ds+{\frac{d}{dt}}g(t,x(t-{\tau}(t)))=0.$$ By using Krasnoselskii's fixed point theorem we obtain the existence of periodic and positive periodic solutions and by contraction mapping principle we obtain the existence of a unique periodic solution. An example is given to illustrate this work.

• Korean Journal of Poultry Science
• /
• v.29 no.4
• /
• pp.265-270
• /
• 2002

This study was conducted to determine the effect of aluminum sulfate[Al$_2$(S0$_4$)$_3$$.$14H$_2$O], commonly referred to as ALUM, addition to broiler litter on 3 and 6 week old broiler performance and the nitrogen content of the litter at 6 weeks of age. The two treatment groups were 134 identical diets with the same protein levels, but one group(T$_1$) had ALUM added as a top dressing to the litter at a rate of 200 g ALUM / kg of rice bran, while T$_2$ did not have ALUM added to the litter. Feed consumption for T$_1$ was higher in the 22 to 42 day-old and 0 to 42 day-old periods (P<0.05). Body weight in T$_1$ was also higher in the 0 to 42 day -old period (P<0.0l). There was no difference, however, in the feed : gain ratio between T$_1$ and T$_2$ During the first 5 weeks, T$_1$ had significantly less(P<0.05 or 0.01) ammonia emission from the litter than T$_2$ but at 6 weeks there was no difference in ammonia concentration between the two groups. At 6 weeks, T$_1$ had a lower litter pH than Ta (P<0.05) and total Kjeldahl nitrogen(TKN) was higher far T$_1$ than T$_2$ (P<0.05). However,71 did not show any difference from T$_2$ in the content of NH4-N and NO3-N. In summary, the addition of ALUM to broiler litter improved broiler performance at 6 weeks, while increasing nitrogen content from the litter used as the nitrogen fertilizer although ammonia emission was increased in T$_1$ at 6 weeks.