• Journal of Magnetics
• /
• v.9 no.1
• /
• pp.17-22
• /
• 2004

We studied the magnetotransport properties of tunnel junctions with AlO and AlN barriers fabricated using microwave-excited plasma. The plasma nitridation process provided wider controllability than the plasma oxidization for the formation of MTJs with ultra-thin insulating layer, because of the slow nitriding rate of metal Al layers, comparing with the oxidizing rate of them. High tunnel magnetoresistance (TMR) ratios of 49 and 44% with respective resistance-area product $(R{\times}A) of 3 {\times} 10^4 and 6 {\times} 10^3 {\Omega}{\mu}m^2$ were obtained in the Co-Fe/Al-N/Co-Fe MTJs. We conclude that AlN is a hopeful barrier material to realize MTJs with high TMR ratio and low $R{\times}A$ for high performance MRAM cells. In addition, in order to clarify the annealing temperature dependence of TMR, the local transport properties were measured for Ta $50{\AA} /Cu 200 {\AA}/Ta 50 {\AA}/Ni_{76}Fe_{24} 20 {\AA}/Cu 50 {\AA}/Mn_{75}Ir_{25} 100 {\AA}/Co_{71}Fe_{29} 40 {\AA}/Al-O$ junction with $d_{Al}= 8 {\AA} and P_{O2}{\times}t_{0X}/ = 8.4 {\times} 10^4$ at various temperatures. The current histogram statistically calculated from the electrical current image was well in accord with the fitting result considering the Gaussian distribution and Fowler-Nordheim equation. After annealing at $340^{\circ}C$, where the TMR ratio of the corresponding MTJ had the maximum value of 44%, the average barrier height increased to 1.12 eV and its standard deviation decreased to 0.1 eV. The increase of TMR ratio after annealing could be well explained by the enhancement of the average barrier height and the reduction of its fluctuation.

• Journal of the Korean Magnetics Society
• /
• v.18 no.4
• /
• pp.142-146
• /
• 2008

The angular dependence of the exchange bias($H_{ex}$) and coercivity($H_c$) in multilayer $[Pt/Co]_N-IrMn$ with applied measuring field rotated toward in-plane at angle $\theta$ from perpendicular-to-plane, has been measured. Multilayer films consisting of $Si/SiO_2/Ta(50)/Pt(4)/[Pt(15)/Co(t_{Co})]_N/IrMn(50)/Ta(50)(in\;{\AA})$ were prepared by magnetron sputtering under typical base pressure below $2{\times}10^{-8}$ Torr at room temperature. Magnetization measurements were performed on a vibrating sample magnetometer and extraordinary Hall voltage measurement systems after cooling from 550 K under a field of 2 kOe applied along the perpendicular to film direction. The hysteresis loop shifts from the origin not only along the field axis but also along the magnetization axis. $H_{ex}$ and $H_c$ show a $1/cos{\theta}$ and $1/|cos{\theta}|$ dependence on the angle($\theta$) between the applied measuring field and the perpendicular-film direction, respectively. This $1/cos{\theta}$ dependence can be accounted for by considering the angular dependence of strong out-of-plane magnetic anisotropy introduced during the field cooling.

• Journal of Environmental Science International
• /
• v.12 no.4
• /
• pp.497-501
• /
• 2003

The new tridentate ligands of nitrogen donor atoms N,N-Bis(2-amino-ethyI)-benzyl-amine 2HCI(BABEA. 2HCI) and 2,6-Bis(amino-methyl)-pyridien. 2HCI(BAMP. 2HCI) were synthesized as their dihydrochloride salts and characterized by TA, IR. Mass and NMR spectroscopy. The protonation constants of the ligands and stability constants for Cd$^{2+}$, Pb$^{2+}$, Zn$^{2+}$and Cu$^{2+}$ ions were determined by potentiometric titration in aqueous solutions and compared with those of analogous ligands. The effect stability constants of ligands and metal ions for removal of heavy metals in aqueous solution were described.

• Bulletin of the Korean Mathematical Society
• /
• v.55 no.6
• /
• pp.1667-1690
• /
• 2018

We consider the minimum order of a graph G with a given lazy cop number $c_L(G)$. Sullivan, Townsend and Werzanski [7] showed that the minimum order of a connected graph with lazy cop number 3 is 9 and $k_3{\square}k_3$ is the unique graph on nine vertices which requires three lazy cops. They conjectured that for a graph G on n vertices with ${\Delta}(G){\geq}n-k^2$, $c_L(G){\leq}k$. We proved that the conjecture is true for k = 4. Furthermore, we showed that the Petersen graph is the unique connected graph G on 10 vertices with ${\Delta}(G){\leq}3$ having lazy cop number 3 and the minimum order of a connected graph with lazy cop number 4 is 16.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.43 no.6
• /
• pp.958-964
• /
• 1994

To study on the superconducting properties with cooling conditions, silver-sheathed Bi-Pb-Sr-Ca-Cu-O wires fabricated by the powder-in-tube method. The wires cooled down in the furnace, air and liquid NS12T after sintering at 840$^{\circ}C$ Critical current density of sample cooled in the furnace is 5.1${\times}$10S03TA/cmS02T and sample cooled in the air is 40A/cmS02T at 77K, zero magnetic field. The latter is very low critical current density of Bi system. 2223 high-Tc superconducting phase of sample cooled in the air was distroyed. Properties of sample cooled down in the liquid nitrogen is the same as cooled in the furnace.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.10 no.6
• /
• pp.535-539
• /
• 2005

The thermoacidophilic archaeon Thermoplasma acidophilum has long been known to utilize D-glucose via the non-phosphorylated Entner-Doudoroff (nED) pathway. We now report the identification of a gene encoding 2-keto-3-deoxy-D-gluconate (KDG) kinase. The discovery of this gene implies the presence of a glycolysis pathway, other than the nED pathway. It was found that Ta0122 in the T. acidophilum genome corresponded to KDG kinase. This enzyme shares no similarity with known KDG kinases, and belongs to a novel class of sugar kinases. Of the five sugars tested only KDG was utilized as a substrate.

• Journal of Korean Physical Therapy Science
• /
• v.24 no.2
• /
• pp.36-44
• /
• 2017

Background: To determine the effect of proprioceptive exercise(PE) on muscle activation and balance of healthy subjects. Methods: 20 subjects were randomly assigned to proprioceptive exercise(PE, n=10) and general exercise group(GE, n=10). To measure muscle activation of the lower limb and balance. For evaluation of muscle activation(Tibialis anterior, Gastrocnemius lateral and medial head), the Electromyogram was used, and balance was measured using the one-leg standing test, OLST. Results: Tibialis anterior(TA), Gastrocnemius medial head(GM) and Gastrocnemius lateral head(GL) muscle activations were significantly (p<0.05) improved in PE group and GE group. and significantly difference between groups(p<0.05). Regarding balance, eye open and close OLST were significantly (p<0.05) increased in PE group and GE group. and significantly difference between groups(p<0.05). Conclusion: Proprioceptive exercise can improve muscle activation of the lowe limb and balance in subjects.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.21 no.9
• /
• pp.2514-2525
• /
• 1996

This paper presents the possibility of the satellite broadcasting reception as a means of microstrip antenna of the planar structure. The paper discusses the design of the optimal KOREASAT DBS(Direct Broadcasting Satellite) reception microstrip antenna. Experimental results for ta 16*16 array antenna of size 35*35cm are also described. Itsgain is over 28dB in the frequency range of 11.7~12.0GHz DBS band. The measured NHK broadcasting C/N ratio of 16816 array antenna is over 10dB in Pusan. It is expected that good picture quality of C/N .GEQ. 12dB can be obtained for domestic use if this microstrip antenna is used in KOREASAT broadcasting receiving system.

• Bulletin of the Korean Mathematical Society
• /
• v.58 no.6
• /
• pp.1341-1354
• /
• 2021

Let r ≥ 2, and let k_i ≥ 2 for 1 ≤ i ≤ r. Mixed van der Waerden's theorem states that there exists a least positive integer w = w(k₁, k₂, k₃, …, k_r; r) such that for any n ≥ w, every r-colouring of [1, n] admits a k_i-term arithmetic progression with colour i for some i ∈ [1, r]. For k ≥ 3 and r ≥ 2, the mixed van der Waerden number w(k, 2, 2, …, 2; r) is denoted by w₂(k; r). B. Landman and A. Robertson [9] showed that for k < r < $\frac{3}{2}$(k - 1) and r ≥ 2k + 2, the inequality w₂(k; r) ≤ r(k - 1) holds. In this note, we establish some results on w₂(k; r) for 2 ≤ r ≤ k.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.25 no.1
• /
• pp.53-59
• /
• 2009

The purpose of this study was to clarify the clinical efficiency of tungsten carbide/carbon coating on obtaining optimal preload of abutment screw compared with non-coated screw in external-hex implant system. In the present work, rotational value and the compressive force between abutment and fixture of abutment screws without coating and with coating tightened to 30Ncm were measured. Mean compressive force of coated screw was 504.6N. Then uncoated screw was tightened to clamping the abutment and the implant to 504.6N, and the tightening torque value and the rotational value was recorded. The following conclusions were drawn within the limitation of this study. Compressive force of coated screw was higher than that of uncoated screw after tightening at 30Ncm. The tightening torque that was nedeed to clamping the uncoated screw equal to coated screw tightened to 30Ncm was 55.6Ncm. In case of equal compressive force, there was no significant difference in rotation value between coated and uncoated screw.