• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.9
• /
• pp.1098-1106
• /
• 2007

This paper presents active antenna diplexers implemented into an ultra-wideband CPW(Coplanar Waveguide) fed monopole antennas. The proposed active antenna diplexer is designed to direct interconnect the output port of a wideband antenna to the input port of two active(HEMT) devices, where the impedance matching conditions of the proposed active integrated antenna are optimized by adjusting CPW(Coplanar Waveguide) feed line to be the length of 1/20 $\lambda_0$(@5.8 GHz) in planar type wideband antenna. The measured bandwidth of the active integrated antenna shows the range from 2.0 GHz to 3.1 GHz and from 5.25 GHz to 5.9 GHz. The measured peak gains are 17.0 dB at 2.4 GHz and 15.0 dB at 5.5 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.1
• /
• pp.1-10
• /
• 2013

In this paper, a broadband planar monopole antenna for multi-band services is proposed. The physical size of the proposed antenna is miniaturized by folding a rectangular loop. And a resonance point in the 3.9 GHz band is reduced by a coupling phenomenon with the central part of the T-shaped patch and the folded rectangular loop. In addition, the T-shaped patch is inserted to the rectangular shaped monopole antenna due to deriving the broadband frequency characteristics. The frequency characteristic is optimized by adjusting the gap and length of the folded rectangular loops and a transverse diameter of the T-shaped patch. The antenna dimensions including the ground plane are $40{\times}60{\times}1.6mm^3$. It is fabricated on the FR-4 substrate(${\epsilon}_r$=4.4) using a microstrip line of $50{\Omega}$ for impedance matching. In the measured result, the bandwidth corresponding to the VSWR of 2:1 is 162 MHz(815~977 MHz) and 2,530 MHz(1.43~3.96 GHz). For analyzing the human effect by the proposed antenna, 1 g and 10 g averaged SARs are simulated and measured. As the simulated results, 1 g-averaged SAR is 1.044 W/kg, and 10 g-averaged SAR is 0.718 W/kg. This result are satisfied by the SAR guidelines which are 1.6 W/kg(1 g-averaged) and 2.0 W/kg(10 g-averaged).

• Journal of Korean Society of Forest Science
• /
• v.96 no.4
• /
• pp.387-392
• /
• 2007

Characteristics of needle morphology and anatomy were examined in 14 populations of Abies nephrolepis (Trautv.) Maxim. and A. koreana Wilson. Additionally we studied the classification index to distinguish between the species by the method of discriminant analysis. Characteristics of needle for A. nephrolepis could be distinguished from those for A. koreana by flatten arrangement, thin and long length for needle form, many stomata row, and marginal position of resin duct Nested ANOVA showed that there were statistically significant differences among populations as well as among individuals within populations in all 9 needle traits. For the needle indices such as needle thickness, number of stomata row, and the distance between resin duct and vascular for both species, variance components among populations were larger than those among individuals within populations. The characteristics that contributed most to the separation of A. nephrolepis and A. koreana according to the discriminant analysis using stepdisc procedures were needle index and thickness of needle, needle arrangement index, distance between resin duct and vascular, and number of stomata row.

• Journal of Korean Home Economics Education Association
• /
• v.19 no.2
• /
• pp.103-114
• /
• 2007

The purpose of this study is to satisfy students in adolescent trends of school uniforms and to provide them with useful material with matching current fashions by analyzing the attitude of students toward uniform transformation in female highschool students and investigating factors influencing on behaviors of uniform transformation. The subjects of this study are 30 students in Daegu with the basic ways of investigating such as depth interview and survey. The results are as follows; First, students agree to wearing school uniforms. As the main reason for wearing school uniforms, students put emphasis on peer pressure. It is also analyzed that the figure of students' body have some influence on the attitude of students toward wearing uniform while students' appearance have no influence on the attitude of students toward wearing uniform. Second, students showed high satisfaction in school uniforms. While students are satisfied with design and color of school uniform, they are not satisfied with practicality, economic efficiency and the quality of textile. Third, the study shows most students have experience of uniform transformation as a result of depth interview about actual condition of uniform transformation. Whereas students usually wear the jacket with its width and length shortened, they tend to lengthen skirt and unstitch pleat of skirt. Fourth, there are many reasons for uniform transformation as a result of depth interview with students. Transformation for satisfying aesthetic desire tops the list, followed by transformation for matching, transformation for peer pressure. As shown by the results above, every school needs to make various efforts to satisfy students, teachers and parents by considering and using students' opinion in order to choose the better school uniforms. In addition, the study related to school uniform transformation need to have more various investigating ways to acquire more authentic results such as expanding the subjects to not only students but also teachers and parents and in-depth comparison between subjects.

• Journal of the Korean Institute of Gas
• /
• v.18 no.4
• /
• pp.63-67
• /
• 2014

Fischer-Tropsch synthesis mainly produces a wax which is a viscous liquid for long carbon chain. When a catalytic fixed-bed reactor is used for Fischer-Tropsch synthesis, the wax generated on a catalyst surface can keep adsorbing on the catalyst surface. This liquid hold-up causes significant pressure drop and clogging problems through the reactor. Thus, the model for liquid hold-up is required to design the size of reactor and catalyst particles. In this study, the liquid hold-up model considering structural and operational conditions was proposed based on empirical equations for convective mass transfer between the syngas flow and the wax-adsorbed catalyst. The developed model was validated by comparing with the experimental data from Knochen's work (2010). The influence of reactor length and coross section on the wax hold-up in reactor were analyzed and the optimal reactor size were proposed.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.6A
• /
• pp.634-639
• /
• 2006

In this paper an MMIC 2-stage power amplifier is designed and fabricated for 5GHz wireless LAN applications using $0.5{\mu}m$ gate length PHEMT transistors. The PHEMT gate width is optimized in order to meet the linearity and efficiency of the MMIC power amplifier. The $0.5{\mu}m\times600{\mu}m$ PHEMT for the drive stage and $0.5{\mu}m\times3000{\mu}m$ PHEMT for the amplification stage are the optimized sizes to achieve more than 25dBc of third order IMD at the power level of 3dB back-off from the input P1dB and more than 22dBm output power under a supply voltage of 3.3V. The two-stage MMIC power amplifier is designed to be used for the both of HIPERLAN/2 and IEEE 802.11a because of its broadband characteristics. The fabricated PHEMT MMIC power amplifier exhibits a 20.1dB linear power gain, a maximum 22dBm output power, a 24% power added efficiency under 3.3V supply voltage. The input and output on-chip matching circuits are included on a chip of $1400\times1200{\mu}m^2$.

• Journal of the Korea Institute of Building Construction
• /
• v.20 no.1
• /
• pp.83-91
• /
• 2020

The recent bridge construction projects is demanded more sophisticated risk management measures and loss forecasts to brace for risk losses from an increase in the trend of bridge construction. This study aims to analyze the risk factors that caused the loss of material in actual bridge construction and to develop a quantified predictive loss model, based on the past record of insurance payment by major domestic insurance companies for bridge construction projects. For the development of quantitative bridge construction loss model, the dependent variable was selected as the loss ratio, i.e., the ratio of insurance payout divided by the total project cost, while the independent variable adopted 1) Technical factors: superstructure type, foundation type, construction method, and bridge length 2) Natural hazards: typhoon and flood 3) Project information: construction period and total project cost. Among the selected independent variables, superstructure type, construction method, and project period were shown to affect the ratio of bridge construction losses. The results of this study can provide government agencies, bridge construction design and construction and insurance companies with the quantitative damage prediction and risk assessment services, using risk indicators and loss prediction functions derived from the findings of this study and can be used as a guideline for future basic bridge risk assessment development research.

• Journal of Digital Convergence
• /
• v.11 no.11
• /
• pp.479-490
• /
• 2013

In this research we surveyed level of textual recognition and of practice by nursing students regarding patient privacy protection. The subjects were 383 nursing students. The questionnaire developed by Lee and Park (2005) were modified and used. Data analysis was conducted through descriptive statistics, t-test, ANOVA, and Pearson correlation coefficients. The result shows that about 96.1% of the subjects received education on patient privacy protection in school or hospital but 48.0% of all received education of 10 minutes or less. Average score for recognition of patient privacy protection was a 4.13 but average practice score was 3.84. Among all areas, communication tasks showed the highest scores for both recognition and practice. There are differences according to grade in school and age of the subject, and experience with clinical practice, existence of regular educational program embedded in clinical practice at hospitals, and the length of each educational session. For both total score and score for every domain, there was a correlation between recognition and practice. The conclusions drawn from this research will help colleges of nursing and hospitals to design and develop contents of educational programs for nursing students.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.791-800
• /
• 2013

Needs for developing a better way of cost estimating process for public construction projects have been widely recognized. Those needs are mainly from the early phases of the project through the construction life cycle due to the its importance to the control process. In contrast to the traditional estimating method based on unit-price references, this research utilized this following process. The first step is analyzing the real cost data from actual cost activities (2000~2010) about the statement of P.S.C(Prestressed Concrete) Box Girder Bridge. The collected data was broken into four categories based on technical construction methods such as I.L.M(Incremental Launching Method), M.S.S(Movable Scaffolding System), F.S.M(Full Staging Method), and F.C.M(Free Cantilever Method). The second, actual design documents including the actual cost estimating documents, drawings and specifications were carefully reviewed to cluster the cost itemized statement from four categories. It was also attempted to seek the proper breakdown of standard works that are responsible for more than 95 percentage in each categories in terms of its cost. The third, this research comes up the index for standard unit materials and unit price of standard work and develops the approximate estimating model applying for the specification(length and breadth of bridges) per square area that the user takes as well as suggests the practical application plan within the original time alloted.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.19 no.5
• /
• pp.749-760
• /
• 2017

Recently, the proportion of tunnel structures in roads and railways has increased rapidly. Along with this trend, the rate of occurrence of cracks and dropouts in concrete lining of tunnel structures is increasing. Generally, maintenance of such concrete lining is normalized and managed as the core of maintenance work in tunnel maintenance. However, the maintenance of the tunnel pavement is important in securing driver in the tunnel. In the design of tunnels, the underground condition of the tunnel is designed to be in good rock condition, so there have not been many cases of cracks in the tunnel pavement in the past. Recently, the construction of tunnel structures has been rapidly increased, and the length of the tunnels has become longer.Tunnel pavement installed in these ground conditions is increasing the occurrence of cracks in the pavement due to decrease of bearing capacity of the pavement after a long time. In this study, FWD and GPR were conducted to analyze the types of cracks and the reduction of bearing capacity in the tunnel.