• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.550-554
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• 1998

We suggested the new method of thermal screen in Bridgman-Stockbarger method to control the polygrain, the internal cavities and solid-liquid (SL) interface. $CaF_2$ single crystal of 6 inch was grown perfectly when we adopted to use a graphite pipe and a ceramic warmer in the conditions of growth rate 2 mm/hr, vertical temperature of $14^{\circ}C$ for freezing and temperature of $1324^{\circ}C$ at conical tip of crucible. The light scattering phenomena occurred by internal cavities were controlled as decreasing the freezing rate to 2 mm/hr and/or as adopting the rotation of melt (7 rpm).

• Journal of Electrochemical Science and Technology
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• v.2 no.3
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• pp.168-173
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• 2011

The availability, low toxicity, and high degree of technological development make silicon the most likely material to be used in solar cells, the cost of solar cells depends entirely on cost of high purity silicon production. The present work was conducted to electrodeposite of silicon from $K_2SiF_6$, an inexpensive raw material prepared from fluorosilicic acid ($H_2SiF_6$) produced in Iraqi Fertilizer plants, and using inexpensive graphite material as cathode electrode. The preparation of potassium fluorosilicate was performed at ($60^{\circ}C$) in a three necks flask provided with a stirrer, while the electro deposition was performed at $750^{\circ}C$ in a three-electrodes configuration with melt containing in graphite pot. High purity potassium fluorosilicate (99.25%) was obtained at temperature ($60^{\circ}C$), molar ratio-KCl/$H_2SiF_6$(1.4) and agitation (600 rpm). Spongy compact deposits were obtained for silicon with purity not less than (99.97%) at cathode potential (-0.8 V vs. Pt), $K_2SiF_6$ concentration (14% mole percent) with grain size (130 ${\mu}m$) and level of impurities (Cu, Fe and Ni) less than (0.02%).

• Journal of the Semiconductor & Display Technology
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• v.10 no.1
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• pp.27-32
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• 2011

In this study, we have investigated the power conversion efficiency of organic solar cells utilizing conjugated polymer/fullerene bulk-hetero junction(BHJ) device structures. We have fabricated poly(3-hexylthiophene)(P3HT), poly[2methoxy-5-(3',7'-dimethyloctyl-oxy)-1-4-phenylenevinylene] as an electron donor, [6,6]-phenyl $C_{61}$ butyric acid methylester(PCBM-$C_{61}$)as an electron acceptor, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS) used as a hole injection layer(HIL), after fabricated active layer, between active layer and metal cathode(Al) deposited LiF interlayer(5 nm). The properties of fabricated organic solar cell(OSC) devices have been analyzed as a function of different thickness. The electrical characteristics of the fabricated devices were investigated by means J-V, fill factor(FF) and power conversion efficiency(PCE). We observed the highest PCEs of 0.628%(MDMO-PPV:PCBM-$C_{61}$) and 2.3%(P3HT:PCBM-$C_{61}$) with LiF inter-layer at the highest thick active layer, which is 1.3times better than the device without LiF inter-layer.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.591-595
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• 1989

The$^{13}C$ NMR shifts of a series of para-substituted 9-aryl-tricyclo$[3.3.1.0^{2,8}]$non-9-yl and 8-aryl-tetracyclo$[3.2.1.0^{2,7}.0^{4,6}]$-oct-8-yl cations were measured in $FSO_3H/SO_2ClF \;at\; -90^{\circ}C\; or\; -70^{\circ}C$ in order to examine whether the ${\rho}^{c+}$ values can be used to explain the mechanism for the stabilization of the geometrically rigid cyclopropylcarbinyl cations. Plots of the ${\Delta}{\delta}^{c+}$ shifts against ${\sigma}^{c+}$ reveal excellent linear correlation. The tricyclononyl systems yield a ${\rho}^{c+}$ value of -4.95 with a correlation coefficient r = 0.9948. The tetracyclo-octanyl systems give a ${\rho}^{c+}$ value of -6.39 with r = 0.9943. A fair parallelism exists between the results of $^{19}F$ nmr studies and the change of ${\rho}^{c+}$ values in these cations. Accordingly, the present study established that the ${\rho}^{c+}$ value can be used as a mearsure of the geometric influence for the charge delocalization in cyclopropylcarbinyl cations.

• Journal of the Korean Ceramic Society
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• v.46 no.5
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• pp.484-487
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• 2009

$SiC_f$/SiC composites with whiskers and pyrolytic carbon (PyC) coated whiskers in the matrix were fabricated for enhancement of the fracture behaviors by the whisker growing assisted chemical vapor infiltration (WA-CVI) process, respectively. $SiC_f$/SiC composites were also prepared by the conventional CVI process as reference material. The mechanical properties and fracture behaviors were analyzed by comparison of the two types of composites prepared by WA-CVI and conventional CVI. The densities of $SiC_f$/SiC composites were in the range of $2.6{\sim}2.65g/cm^3$. The flexural strengths of composite with whiskers and with those coated by PyC were 650 MPa and 600 MPa, respectively. The tensile strength of composites with whiskers was ${\sim}285$ MPa.

• Journal of Sericultural and Entomological Science
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• v.46 no.2
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• pp.65-71
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• 2004

Long term preservation experiment through refrigeration was conducted for 2 year on 300 lines of silkworm races preserved, as one method for the development of long term safe preservation technique. Experiment with 6 treatments was conducted for 680 days from July 1 st 2000 to May 1st 2002. Embryonic development was conducted to each treatment. There are no differences among treatments and races in 400 days preservation, the stage of whole embryonic development was Eul B and condition of eggs was good. In 650 days preservation experiment, differences were reveled among races and treatment, the level of whole embryonic development was Byeong A and condition of eggs was good. The order of embryonic development is European races >Tropical, Korean races >Japanese, Chinese races, thus European races showed fast embryonic development. Control(treatment A) and treatment C showed faster development than other treatments. And treatment D and F showed stable individual stage among all treatments. The test of shape characteristics and embryo which were conducted in hatching period showed 61% of high line succession possibility in average of 6 treatments. But treatment A and B showed no hatching, 3 lines of treatment C, 48 lines of treatment D, 1 line of treatment E, and 29 lines of treatment F showed slow development. And treatments D and F which showed stable embryo condition had highest possibility. The two treatments D and F showed good result among six treatments, and the preservation period of treatment D and F are 235 days and 310 days, and exposure period in $-2.5^{\circ}C$...was longer than other treatments. Numbers of hatched lines of treatment D and F are 48 and 29, and occupied 15.6% and 9.4% of all tested lines, respectively. Average hatching ratio of treatment D and F were 54.% and 71.6%, and average dead egg ratio were 12.6% and 2.4%, respectively. These results show that average ratio of hatching dead eggs in treatment D and F are higher than general line. Thus reconsideration of hatching condition on treatment D and F is needed.

• Korean Journal of Crystallography
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• v.6 no.1
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• pp.36-42
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• 1995

Two types of single crystals of the title compound [6-(2-pyridyl)-3, 5-hexadiyn-ol, PyHxD] were obtained by solution of n-hexane/CH2C12 and n-hexane/Et2O, and their molecular conformations are proved identical in spite of different of space groups; C22H18N2O2 (I), Mr=343.70, Monoclinic, Pa, a=14.595(2), b=5.413(2), c=12.218(2)Å, β=96.86(1)°, V=958.3Å3, Z=2, Dx=1.19 Mgm-3, λ(MoKα)=0.71069Å, μ=0.072mm-1, F(000)=360.0, T=292K, R=0.104 for 756 unique observed reflections. An asymmetric unit contains a dimer connected by two N-H…O intermolecular hydrogen bonds. C11H9NO (II), Mr=171.85, Monoclinic, P21/a, a=14.611(2), b=5.423(6), c=12.191(2)Å, β=96.89(1)°, V=959.0Å3, Z=4, Dx=1.19 Mgm-3, λ(MoKα)=0.71069Å, μ=0.072mm-1, F(000)=360.0, T=293K, R=0.066 for 824 unique observed reflection. The structural asymmetric unit contains a molecule, but two N-H…O hydrogen bonds related by controsymmetry make the molecules form a dimer. In both structure, the dihedral angle between the planar pyridyl ring and the plane defined by C(10)-C(11)-O connected by linear diyne chain is approximately normal, and the molecules are stacked along b-axis with the unit repeat of b-axis.

• Journal of the Korean Ceramic Society
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• v.37 no.6
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• pp.552-558
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• 2000

LiMn2O4 thin fiolm cathodes for Li-ion secondary battery were fabricated by r.f. magnetron sputtering technique. As-deposited films were amorphous. A spinel structure could not be obtained LiMn2O4 films by in-situ thermal annealing. After post thermal annealing over $700^{\circ}C$ in oxygen atmosphere, LiMn2O4 films prepared above 100 W r.f. power could be crystallized into a spinel structure. The electrochemical property of the LiMn2O4 film cathodes was tested in a Li/1 M LiClO4 in PC/LiMn2O4 cell. From cyclic voltammetry at scan rate of 2mV/sec of 2.5~4.5V, LiMn2O4 electrode prepared by post annealing at 75$0^{\circ}C$ showed good initial capacity. LiMn2O4 electrode prepared by post annealing at 80$0^{\circ}C$ showed the best crycling performance.

• Applied Biological Chemistry
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• v.40 no.1
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• pp.34-38
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• 1997

For the effective production of functional oligosaccharides(DP 3-5) from inulin in chicory extracts, the acid hydrolysis and enzymatic endo-inulinase reaction were compared. Acid hydrolysis was unfavorable ; the content of oligosacharides in total sugar increased to 26.0% for 12 min at $55^{\circ}C$ and 24.6% at 6 min at $65^{\circ}C$ and showed little change for 30 min. The content of high DP(DP 6) decreased from 83.5 to 49.5% and 23.0% for 30 min, repectively. Glucose, fructose and sucrose increased to 24.6% and 50.3%, respectively. Hydrolysis of chicory extracts with purified endo-inulinase from Arthrobacter sp. S37 was carried out at $40^{\circ}C$ and pH 7.5 for 44 hrs. The content of high DP($DP{\geq}6$) in total sugar decreased from 83.5 to 23.0% and that of inulobiose(F2) and DP 3-5 increased to 66.1%. Glucose, fructose and sucrose were not produced. The hydrolysis of chicory extracts without DP 1 and DP 2 with crude or with purified enzyme were also carried out. In contrast to the hydrolysate of crude enzyme, that of purified endo-inulinase did not contain glucose, fructose, sucrose, F2 and 1-kestose(GF2). The content of oligosaccharides in the hydrolysate of the purified endo-inulinase were 79.2%, composed mainly of inulotriose(F3), inulotetraose(F4) and inulopentaose(F5), which shows that the enzymatic hydrolysis using purified endo-inulinase from Arthrobacter sp. S37 is the best method for oligosaccharides production from inulin in chicory extracts.

• Resources Recycling
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• v.9 no.6
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• pp.31-35
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• 2000

The complex permeability, the complex permittivity and the reflection loss are investigated in the composite microwave absorbers which are mixed with the wasted Mn-Zn ferrite and the industrial cement. The cement has larger the complex permittivity than that of the rubber. The complex permittivity is decreasing with the increment of the mixing ratio of Mn-Zn ferrite to cement (F/C in weight) and the complex permeability is increasing with the increment of F/C. The maximum reflection loss is above -40 dB at all samples. The matching frequency is in the range of 1.3 GHz to 2.9 GHz and is decreasing with the increment of F/C from 1 to 3. The matching thickness is increasing with the increment of F/C. The wasted Mn-Zn ferrite and the cement is very useful material for the composite microwave absorber.