• Journal for History of Mathematics
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• v.17 no.3
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• pp.109-120
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• 2004

This study investigated three pre-service teachers' mathematical problem solving among hand-in-write-ups and final projects for each subject. All participants' activities and computer explorations were observed and video taped. If it was possible, an open-ended individual interview was performed before, during, and after each exploration. The method of data collection was observation, interviewing, field notes, students' written assignments, computer works, and audio and videotapes of pre- service teachers' mathematical problem solving activities. At the beginning of the mathematical problem solving activities, all participants did not have strong procedural and conceptual knowledge of the graph, making a model by using data, and general concept of a sine function, but they built strong procedural and conceptual knowledge and connected them appropriately through mathematical problem solving activities by using the computer technology.

• Education of Primary School Mathematics
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• v.21 no.2
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• pp.237-260
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• 2018

This study investigated the models of four countries' elementary mathematics textbooks in Ratio and Rate and identified how multiplicative perspectives on proportional relationships and the structure of proportion situations are reflected in the textbooks. For this, textbooks of 5th and 6th grade textbooks in Korea Japan, Singapore and U.S. are compared and analyzed. As a result, we can find multiplicative perspectives on proportional relationships and the structure of proportion situations on pictorial models, ratio tables, double number lines and double tape diagrams. Also, the development of Japanese textbooks from multiple batches perspectives to variable parts perspectives and the examples of the use with two models together implied the connection and union of two multiplicative perspectives. Based on these results, careful verification and discussion for the next textbook is needed to develop students' proportional reasoning and teach some effective reasoning strategies. And this study will provide the implication for what kinds of and how visual models are presented in the next textbook.

• Journal of Advanced Navigation Technology
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• v.12 no.2
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• pp.100-108
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• 2008

In this paper, the dual-ground, high-gain and broad-band internal antenna has been designed and fabricated for 4th-generation mobile communication applications. The optimized antenna was fabricated using photolithography method. The antenna consist of the patches, antenna and system ground, and a probe. The patch and ground plane were separated by air. In order to prevent the demage due to radiator swaying, the foams(${\varepsilon}_r{\fallingdotseq}1.03$) were used to fix the patches and ground. The conductor for the radiators was 0.05 [mm] thick. The measured input return loss showed less than -10 [dB] at the broadband from 3499 to 4743 [MHz]. It's measured bandwidth was 1244 [MHz]. The radiation patterns measured at 3400, 3600, 3800, 4000 and 4200 [MHz] showed Omni-directional characteristics. The gain in the E-plane and H-plane was 4.7 ~ 6.1 and 2.1 ~ 4.3 [dBi], respectively.

• Clinical and Experimental Pediatrics
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• v.48 no.11
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• pp.1212-1218
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• 2005

Purpose : Forward pulmonary blood flow may be absent in some neonates with Ebstein's anomaly by anatomical or functional pulmonary atresia in association with the elevated pulmonary vascular resistance, patent ductus arteriosus and tricuspid regurgitation. We reviewed the presentation and outcomes of symptomatic neonates with Ebstein's anomaly focusing on the pulmonary atresia. Methods : Clinical presentation and outcome of 15 symptomatic neonates with Ebstein's anomaly seen at Asan medical center from 1998 to 2004 were reviewed. Results : Ten(67%) of 15 patients showed no forward pulmonary blood flow and 6 of them had functional pulmonary atresia. $O_2$ saturation and pH were lower and cardiothoracic(CT) ratio in chest radiography was more increased in the patients with pulmonary atresia than in the patients without pulmonary atresia(P<0.05). pH and CT ratio were not different between the anatomical and functional pulmonary atresia group, but $O_2$ saturation was lower in functional atresia group(P<0.05). 13 patients(87%) were managed with $PGE_1$. 4 of 6 patients with functional pulmonary atresia were treated with inhaled nitric oxide. Surgery was performed in 1 of 5 patients without pulmonary atresia and in 8 of 10 patients with pulmonary atresia during follow-up period(mean 37 months). 3 patients(20%) died and none of patients without pulmonary atresia died. Conclusion : We found that most symptomatic neonates with Ebstein's anomaly had functional or anatomical pulmonary atresia. The neonates with Ebstein's anomaly who had no forward pulmonary blood flow were more symptomatic and needed surgery earlier. Further studies will be needed to distinguish effectively functional and anatomical pulmonary atresia and to manage appropriately neonates with functional atresia.

• Clinical and Experimental Pediatrics
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• v.46 no.5
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• pp.484-489
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• 2003

Purpose : To understand morphologic and hemodynamic variations in patients with pulmonary atresia with intact ventricular septum(PA/IVS), and to decide the best treatment modalities, we measured right ventricular volume, inflow, and outflow valvular annulus size in these patients and compared them with those of normal newborns. Methods : Eight patients with PA/IVS diagnosed by echocardiography from January to December 2001 were enrolled in this study. Among the total eight patients, five were male and three were female. The mean age of patients was 6.9 days(1-34 days), and the mean body weight was 3,343 gm (2,970-4,000 gm). Ten fullterm newborn infants with sepsis or hyperbilirubinemia without heart disease were enrolled as a control group. Echocardiographic and Doppler studies using Acuson Aspen (7Mh probe) were recorded on super-VHS videotape and later on, with review mode. We measured volumes of right and left ventricles, aortic, pulmonic, mitral and tricuspid valvular annulus sizes using an installed program, and then these parameters were compared with those of the control group. Results : Mean Z-value of tricuspid valvular annulus in PA/IVS was $-3.69{\pm}2.80$(-8.4--0.45), and tricuspid/mitral valvular annulus size ratio $0.68{\pm}0.15$(0.43--0.84). The more the tricuspid/mitral valvular annulus size ratio, the more Z-value of tricuspid valvular annulus(P=0.003, r=0.885). Those patients who underwent pulmonary valvuloplasty(balloon or surgical) had a tendency toward larger volume of the right ventricle, more Z-value of pulmonic and tricuspid valvular annulus, and more tricuspid/mitral valvular annulus size ratio than those patients who underwent a shunt operation. Conclusion : Compared to a measurement of the volume of the right ventricle, measurements of tricuspid/mitral valvular annulus size ratio and Z-value of tricuspid valvular annulus may be easier and better parameters to decide the treatment method and to predict prognosis in PA/IVS patients.