• Education of Primary School Mathematics
• /
• v.25 no.1
• /
• pp.81-100
• /
• 2022

The purpose of this study is to develop a framework for analyzing the solution spaces of open-ended task and to explore their usefulness and applicability based on the analysis of solution spaces constructed by students. Based on literature reviews and previous studies, researchers developed a framework for analyzing solution spaces (OMR-framework) organized into subspaces of outcome spaces, method spaces, representation spaces which could be used in structurally analyzing students' solutions of open-ended tasks. In our research, we developed open-ended tasks which had various outcomes and methods that could be solved by using the concepts of factors and multiples and assigned the tasks to 181 elementary school fifth and sixth graders. As a result of analyzing the student's solution spaces by applying the OMR-framework, it was possible to systematically analyze the characteristics of students' understanding of the concept of factors and multiples and their approach to reversible and constructive thinking. In addition to formal mathematical representations, various informal representations constructed by students were also analyzed. It was revealed that each space(outcome, method, and representation) had a unique set of characteristics, but were closely interconnected to each other in the process. In conclusion, it can be said that method of analyzing solution spaces of open-ended tasks of this study are useful for systemizing and analyzing the solution spaces and are applicable to the analysis of the solutions of open-ended tasks.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.7 s.98
• /
• pp.681-689
• /
• 2005

This paper presents an ultra wide band(UWB) mixer using anti-parallel diode pair(APDP) with simulation and measurement results. The proposed mixer adopts the even-harmonic direct conversion mixing, which consists of a couple of filter, in-phase wilkinson power divider, wideband $45^{\circ}$ power divider, and APDP. The m mixer is operating over 3.1 to 4.8 GHz and producing quadrature(I/Q) outputs with a conversion loss of 18 dB and input third order intercept point($IIP_3$) of 15 dBm. I/Q outputs also have difference of about 0.5 dB and phase difference of ${\times}3^{\circ}$ and $P_{1dB}$ of 2 dBm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.16 no.9 s.100
• /
• pp.957-963
• /
• 2005

This paper presents technique of wideband TIA for optical communication systems using TSMC 0.25 ${\mu}m$ CMOS RF-Mixed mode. In order to improve bandwidth characteristics of an TIA, we use active inductor shunt peaking to cascode and common-source configuration. The result shows the 37 mW and 45 mW power dissipation with 2.5 V bias and 61 dB$\Omega$ and 61.4 dB$\Omega$ transimpedance gain. And the -3 dB bandwidth of the TIA is enhanced from 0.8 GHz to 1.45 GHz in cascode and 0.61 GHz to 0.9 GHz in common-source. And the input noise current density is $5 pA/\sqrt{Hz}$ and $4.5 pA/\sqrt{Hz}$, and -10 dB out put return loss is obtained in 1.45 GHz. The total size of the chip is $1150{\times}940{\mu}m^2$.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.38 no.7
• /
• pp.7-13
• /
• 2001

The wirebonding is a common interconnection technique for modern microwave devices because of rather simple and reliable processes involved. At millimeter-wave frequencies, however, the bondwire parasitics are significant and consequently limit the external performance of packaged devices. In this paper, we represent wideband characterization of multiple bondwires and ribbon in a frequency range from 20 to 35 GHz. From these results, the double bondwire shows very small insertion loss less than 0.55 dB up to 35 GHz and its performance is comparable to that of the ribbon in the millimeter-wave frequencies. Therefore, the wirebonding is very suitable for millimeter wave packaging in terms of performance and manufacturing cost.

• KDI Journal of Economic Policy
• /
• v.19 no.1
• /
• pp.105-149
• /
• 1997

이 논문에서는 남북한 관계를 중심으로 분쟁해소와 협력관계 구축에 있어서 신뢰(信賴)가 할 수 있는 역할(役割)에 대해 검토해 보았다. 이 논문의 모델은 Kreps-Wilson(1982)의 신규진입 게임을 협력관계 구축이라는 새로운 상황에 맞게 변환시킨 순차적 게임모델로서 유한반복(有限反復) 게임구도와 비대칭적(非對稱的) 정보소유(情報所有)를 그 근간으로 한다. 북한이 남한정부가 진보적이라고 믿는 확률을 남한에 대한 '신뢰(信賴)'라고 정의할 때, 신뢰는 크게 나누어 다음과 같은 역할을 한다. 북한이 남한에 대해 작은 규모의 신뢰감만 가지고 있어도 피의자(被疑者)의 딜레마 (Prisoner's Dilemma) 상황을 피할 수 있으며 상당한 기간동안 남북협력관계(南北協力關係)가 지속될 수 있다. 왜냐하면 보수적 성향의 남한정부도 북한이 개혁정책을 추진할 때 대북(對北) 압박정책 대신 포용정책(包容政策)을 통해 얻을 수 있는 수익이 적지 않은 점을 고려하여 상당기간동안 포용정책을 선택할 동기가 있기 때문이다. 하지만 이와 같이 자신의 성향을 은폐하는 위장행동의 가능성이 높은 동안 신뢰(信賴)는 쉽게 증진되지 않는다. 다만 남북한이 협력을 통해 실질적인 수익을 얻을 수 있을 뿐이다. 남북협력관계를 구축하기 위해 남한이 할 수 있는 일은 정책대응에 소요되는 시간을 줄이는 한편, 개혁정책을 통해 북한이 얻을 수 있는 기대수익(期待收益)을 늘리고 남한에 배신당할 경우 입는 피해를 줄여주는 것이다. 특히 장기적인 관점에서 북한의 기대수익을 점진적으로 늘려 '신뢰도(信賴度)가 넘어야 할 문턱'을 낮추는 것이 효과적인 정책이다. 따라서 남북관계를 진전시키기 위해서는 북한의 지속적인 개혁을 조건으로 북한의 기대수익이 점진적으로 증가하는 KEDO식의 장기적 경협사업(經協事業)을 고안하여 추진해야 한다. 이에 반해 인도주의적 명분하에 일과성의 식량지원을 북한에 제공하는 것은 북한의 구조적(構造的) 경제난(經濟難) 해소나 남북관계의 지속적 진전에 별 도움이 안되는 정책이다. 북한은 북한 나름대로 남한을 한번 믿어볼 필요가 있다. 왜냐하면 상대방에 대한 불신(不信)은 결국 협력관계가 유지될 수 있는 기간을 감축시켜 비효율적인 결과를 초래하기 때문이다.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.12
• /
• pp.4854-4862
• /
• 2010

Twenty five compounds isopropylmethylphenyl benzenesulfonate derivatives of thymol (1), 4-isopropyl-3-methylphenol (2), 5-isopropyl-3-methylphenol (3), 4-isopropylphenol (4), and 2-isopropylphenol (5) derivatives were synthesized. These compounds were analyzed for their structural confirmation with IR, GC/MS, and $^1H$-NMR. Synthetic compounds were tested against phytopathogenic fungi activities such as Pyrcularia grisea, Rhizoctonia solani, Phytophthora infestans, Colletotrichum orbiculare, and Sphaerotheca fusca. 2-Isopropyl-5-methylphenyl o-toluenesulfonate (1a), 2-isopropylphenyl 2,4,5-trichloro-benzenesulfonate (5b) and 2-isopropylphenyl 2-methyl-5-nitrobenzenesulfonate (5e) showed a potent in vivo antifungal activity against Pyrcularia grisea, Phytophthora infestans and Sphaerotheca fusca.

• The Journal of the Acoustical Society of Korea
• /
• v.21 no.2
• /
• pp.134-141
• /
• 2002

In this paper, a free wake analysis based on the curved vortex element and CVC wake model is used to predict the aerodynamic performance and noise for HAWT. Also for prediction of RPM, a maximum value through a quadratic regression was suggested. And for a noise prediction, the broadband noise prediction method based on experimental equation was used. The curved vortex element uses a BCVE and an SIVE instead of a straight vertex element. In the CVC wake model, the vortex strengths are assumed to be constant along a span and a vortex filament. The free wake structure made by the curved vortex element and CVC was substituted for a vortex lattice, so it has an advantage for the less calculation time and a depiction of accurate wake structure. For the verification of this program, calculated results are compared with Mr. Kim's experiment model and Zond Z-40FS for performance and with WTS-4 and USWP models for noise. Good agreements are obtained between the predicted and the measured data for the performance and far-field noise spectra.

• Journal of Korean Library and Information Science Society
• /
• v.48 no.4
• /
• pp.259-282
• /
• 2017

There is a strong need to develop a training program for specialized personnel called mental health librarian. The study examines the necessity of ongoing education as series of steps to be considered in actual curriculum development, by looking at the features of bibliotherapy through a literature review and through an analysis to the requirements of a qualified mental health librarian and its training system. The result shows that, in order to train librarian in mental health, it is necessary to establish courses corresponding to the bibliotherapy field within the subject of library and information sciences and to strengthen the specialization in the its curriculum. It is desirable to establish the mental health librarian educational programs in library and information science graduate programs in Korea. The results of this study, as fundamental data for future research, will promote the role of the specialized mental health librarian and guidelines for developing and expanding the qualities and training of specialized librarian to resolve the immediate problem of the Korean library scene and academia.

• Journal of the Korean Society for information Management
• /
• v.18 no.3
• /
• pp.29-40
• /
• 2001

In this paper, we suggest a query optimization algorithm to select the optimal processing method of an extended boolean query on inverted files. There can be a lot of methods for processing an extended boolean query according to the processing sequence oh the keywords con tamed in the query, In this sense, the problem of optimizing an extended boolean query it essentially that of optimizing the keyword sequence in the query. In this paper, we show that the problem is basically analogous to the problem of finding the optimal join order in database query optimization, and apply the ideas in the area to the problem solving. We establish the cost model for processing an extended boolean query and develop an algorithm to filled the optimal keyword-processing sequence based on the concept of keyword rank using the keyword selectivity and the access costs of inverted file. We prove that the method selected by the optimization algorithm is really optimum, and show, through experiments, that the optimal method is superior to the others in performance We believe that the suggested optimization algorithm will contribute to the significant enhancement of the information retrieval performance.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.1
• /
• pp.81-88
• /
• 2011

This paper presents a design of spiral antenna with broad bandwidth for non-linear junction detector(NLJD). An elliptical patch as radiating element located on center position of radiating surface, as well as the spiral elements on radiating surface was designed for broad bandwidth of spiral antenna. An antenna ground structure generating the multi resonance by spiral slit inserted on ground surface was also proposed. In order to realize high directivity and high gain of the proposed antenna, the cavity wall made of Fr4-epoxy and the metal cap were considered in design. As a result, the calculated gain of antenna with metal cap was improved about 3 dB with comparison of antenna without metal cap and the measured main beam directivity toward -z axis direction agreed well with calculation result. The measured axial ratio satisfied the circular polarization within -z axis ${\pm}45^{\circ}$ at design frequency bands and showed reasonable agreement with prediction.