• 대한소아치과학회지
• /
• 제23권2호
• /
• pp.347-355
• /
• 1996

The purpose of this study was to compare the bond strengths of different kinds of glass ionomer cements (GIC), which is recently increasing the clinical application in the field of pediatric dentistry and measure the repaired bond strengths in order to examine the clinical applicabilty of partial repaired cases. By using one kind of the light cured type GIC and three kinds of the chemical cured type GIC, the bond strengths of the followings were compared : unrepaired group as control, repaired conditioning group, which was treated the repaired surface using 25% polyacrylic acid and repaired non-conditioning group without surface treatment. Three point bending test was performed under Universal Testing Machine in order to measure the compressive bond strengths. The results were as follows : 1. Light cured GIC had higher bond strength than chemical cured type GIC in both of repaired and unrepaired groups. 2. In repaired cases, all of the materials decreased the bond strength when compared to the control group. In the light cured type, the bond strength of repaired conditioning group decreased 31.6%, repaired non-conditioning group decreased 40.8%. In chemical cured types, the bond strength of repaired conditining group decreased 11.8%, repaired non-conditioning group decreased 20.9%. 3. All the materials, in the case of the chemical treatment on the repaired surface using 25% polyacrylic acid had higher bond strength than untreated but, lower than control group.

• Perinatology
• /
• 제29권4호
• /
• pp.159-164
• /
• 2018

Objective: To compare neonatal respiratory morbidity of twins according to birth order related to gestational age and mode of delivery. Methods: We performed the retrospective research of the medical records of 3,224 neonates (1,612 twin pairs) born in a single center from January 2011 to December 2015. Subjects were classified into four gestational age groups: very (<32 weeks), moderate (32-33 weeks), late (34-36 weeks) preterm, and term (${\geq}37weeks$) groups. We investigated clinical characteristics and respiratory morbidity according to birth order related to gestational age group and mode of delivery. Results: We found increased risk of respiratory morbidity in second-born twin than first-born twin (P=0.039). Second-born twin was associated with increased risk of respiratory distress syndrome (RDS) in late preterm group (odds ratio [OR] 2.8, 95% confidence interval [CI] 1.30-5.95), and transient tachypnea of newborn in term group (OR 1.4, 95% CI 1.03-1.81). In vaginal delivery mode, there was no difference of respiratory morbidity between first and second-born twin in each group, but in cases of Cesarean delivery, second-born twin was related with a greater risk of RDS in late preterm group (OR 2.3, 95% CI 1.07-5.09). Birth order and Cesarean section independently increased the risk of RDS (adjusted OR [aOR] 1.69, 95% CI 1.12-2.54; aOR 2.14, 95% CI 1.25-3.66, respectively). Conclusion: Second-born twin and Cesarean delivery are associated with increased risk of RDS, especially in late preterm twins.

• 대한수학회보
• /
• 제54권6호
• /
• pp.2165-2182
• /
• 2017

Let G be a group and $\mathbb{C}$ the field of complex numbers. Suppose ${\sigma}:G{\rightarrow}G$ is an endomorphism satisfying ${{\sigma}}({{\sigma}}(x))=x$ for all x in G. In this paper, we first determine the central solution, f : G or $G{\times}G{\rightarrow}\mathbb{C}$, of the functional equation $f(xy)+f({\sigma}(y)x)=2f(x)+2f(y)$ for all $x,y{\in}G$, which is a variant of the quadratic functional equation. Using the central solution of this functional equation, we determine the general solution of the functional equation f(pr, qs) + f(sp, rq) = 2f(p, q) + 2f(r, s) for all $p,q,r,s{\in}G$, which is a variant of the equation f(pr, qs) + f(ps, qr) = 2f(p, q) + 2f(r, s) studied by Chung, Kannappan, Ng and Sahoo in [3] (see also [16]). Finally, we determine the solutions of this equation on the free groups generated by one element, the cyclic groups of order m, the symmetric groups of order m, and the dihedral groups of order 2m for $m{\geq}2$.

• 대한수학회보
• /
• 제34권4호
• /
• pp.637-643
• /
• 1997

The group $V(ZS_3)$ of units of augmentation 1 in the integral group ring $ZS_3$ is characterized as the free product of $C_2$ and $S_3$, where $C_2$ is the cyclic group of order 2.

• 한국학교수학회논문집
• /
• 제6권1호
• /
• pp.87-100
• /
• 2003

In this paper we have studied the efficiency of GSP which is widely used in the school. In order to study the efficiency of the computer aided education we divided the students into two groups in the Namwon Middle School : One group called "A" is the classes using GSP, the other called "B" is the classes not using GSP. In the three times examination group A got good marks better than group B. In the questionnaires about the interest in geometry group A is higher than group B. By the results of this study the effort on education with using various multi media can come into the utmost educational effect. Therefore it is necessary for the teachers at school to have self training continuously in order to carry a higher educational quality.

• 한국경영과학회지
• /
• 제27권2호
• /
• pp.15-31
• /
• 2002

This research suggests an interactive methodology for multiple objective linear programming problems to help the group select a compromising solution in the World Wide Web environment. Our methodology lessens the burden of group decision makers, which is one of necessary conditions of the web environment. Only the partial weak order of variables and objectives from the group decision makers are enough for searching the best compromising solution. For such a purpose, we expand the Dror and Gass algorithm to the group decision context. And we suggest the system architecture of a web-based GDSS for the Implementation of our methodology.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2000년도 하계학술대회 논문집 C
• /
• pp.2095-2097
• /
• 2000

Applications of soft X-ray which corresponds to the wavelength of the order of 1 nm and to the photon energy of the order of 1 key respectively, requires intense sources. Only synchrotron sources were available recently. The development of a new laboratory-sized source of soft X-ray radiation is required for wide applications. This paper introduces the generation of soft X-ray using laser-induced plasma.

• 한국지능정보시스템학회:학술대회논문집
• /
• 한국지능정보시스템학회 2000년도 추계정기학술대회:지능형기술과 CRM
• /
• pp.375-383
• /
• 2000

This research suggests an interactive methodology fur multiple objective linear programming problems to help the group select a compromising solution in the World Wide Web environment. Our methodology lessens the burden of group decision makers, which is one of necessary conditions of the web environment. Only the partial weak order of variables and objectives from the group decision makers are enough for searching the best compromising solution. For such a purpose, we expand the Dror and Gass algorithm to the group decision context. And we suggest the system architecture of a web-based GDSS fur the implementation of our methodology.

• 대한치과보철학회지
• /
• 제39권2호
• /
• pp.157-170
• /
• 2001

The bond strength is the most important factor in establishing long-term success of resin-retained fixed prostheses. So, various surface treatment methods have been introduced to improve the bond strength of metal surface and bonding resin till now This study was performed to compare the effect of silicoating with that of metal primer and analyze the correlation between treatment time of sandblasting and the bond strength, so that meant to find more effective surface treatment method that could enhance the bond strength of resin-retained fixed prostheses. The surfaces of all specimens made of $Verabond^{(R)}$ alloys were air abraded with $250{\mu}m\;Al_2O_3$ according to treatment time of sandblasting and they were subdivided to be treated with only sandblasting(S group), silicoating following sandblasting(SS group) and metal primer application after sandblasting(SM group). Then pairs of metal specimens (${\phi}10mm{\times}h\;2mm,\;{\phi}6{\times}h\;2mm$) were bonded with Super bond $C&B^{(R)}$. The specimens were stored in $38^{\circ}C$ water for 48 hours and shear bond strength was measured using the universal testing machine. The results were as follows, 1. In the comparison of shear bond strength according to treatment time of sandblasting, bond strength was increased in the order of 0', 15', 30', 45', 60' group. 0' group had significantly lower value than any other, while 0', 15' group were significantly different with 30', 45', 60' group(p<0.05). 2. In the comparison of shear bond strength according surface treatment methods, bond strength was increased in the order of S group. SS group and SM group. S group was significantly different with SS group and SM group(p<0.05). 3. Observing the mode of bond failure. 0', 15' group showed only adhesive failure, and 30', 45', 60' group did mostly adhesive & cohesive failure in S group. In SS group and SM group, all other groups except 0', 15' group showed mostly cohesive failure. From the above results, it is considered that sandblasting should be treated for more than 30 seconds, and metal primer be more effective and available clinically than silicoater system which is complicate, technique-sensitive and time-consuming method, when nonprecious metal surface is planning be treated with in order enhance the bond strength of resin-retained fixed prostheses.

• Toxicological Research
• /
• 제7권1호
• /
• pp.51-59
• /
• 1991

The purpose of the present study was to investigate the effects of non-watering, fasting and non-watering fasting for 16-17 hrs on haematological and biochemical parameters in SD rats. 1. Liver weight was decreased in the order of in the fasting group, non-watering fasting group and non-watering group in both sexes. 2. In fasting group and non-watering fasting group, haematologic parameters of male (HGB and MCH) and femal (MCHC) were trends to decrease compared with normal feeding & watering group. 3. In the differential leucocyte counts, there were no significant differences compared with noraml feeding % watering group.