• Polymer(Korea)
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• v.37 no.6
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• pp.677-684
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• 2013

Zinc alginate films were prepared by a film maker from sodium alginate solutions of different weight ratios and then they solidified into 3 wt% content $ZnCl_2$ coagulation solution and washed and dried at a $60^{\circ}C$ oven for 20 min. The characteristics were measured by several methods (antimicrobial activity, viscosity, FTIR, TGA, SEM, EDS, contact angle, tensile strength and solubility) and the film properties were investigated. The antimicrobial test showed that the zinc alginate films result in excellent antimicrobial activity in the two strains (Klebsiella pneumonia, Staphylococcus). The surface of zinc alginate film from the solution of 9 wt% sodium alginate showed more uniform shape than any other films and the cross-section were hard and rough when the films were well-solidified by the $ZnCl_2$ solution. The tensile strength of zinc alginate films increased along with the concentration of sodium alginate solution due to the cross-linking, and the initial thermal decomposition temperature increased gradually.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.83-90
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• 2010

Composite materials can be used economically and efficiently in civil engineering applications when standards and procedure for analysis, design, construction and quality control are to be established. Bridge systems, including the girders and cross-beams, and concrete decks behave as the specially orthotropic plates. For such systems with sections, boundary conditions other than Navier solution types, it is very difficult to obtain its analytical solution. To design the bridge made by the composite materials, cross-section was used as the form-core shape for economical reason and finite difference method was used for output of the stress value. The Tsai-Wu failure criterion for stress space is used. In this paper, the rate of tensile strength reduction due to increased size was considered. And also numerical study is made for these cases.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.5
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• pp.789-798
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• 2021

In this study, for the purpose of collecting and analyzing target-specific RCS data of target signals simulator for verification/improvement of radar system performance, VHF band monostatic/bistatic RCS of civil aircraft(B-747, B-737) and fighter(F-16) models were analyzed by EM simulation tool. In order to reduce the RCS analysis time, the analysis time and RCS data were compared and cross-verified. Also, the analysis range was selected by examining the interpolation error according to the analysis angle resolution. The RCS data obtained for each model were analyzed separately by the incident/reflection elevation angle and frequency. The RCS characteristics according to the shape of the aircraft and the incident/reflection azimuth angle were described. Finally, the statistical RCS distribution value of each model is presented through RCS distribution histogram analysis. In the future, the RCS database obtained by this study will be used for the target signals simulator of the VHF band radar system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.3
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• pp.66-73
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• 2019

Recently, FDM-type 3D printer technology has been developed, and efforts have been made to improve the output formability and characteristics further. Through this, 3D printers are used in various fields, and printer technologies are suggested according to usage, such as FDM, SLA, DLP, and SLM. In particular, the FDM method is the most widely used, and the FDM method technology is being developed further. The characteristics of the output are produced by the FDM-type 3D printer, which is determined by various factors, and particularly the perspective of the Inter-Layer Fill Factor, which is the volume ratio of the laminated material that exerts a direct influence. In this study, the Inter-Layer Fill Factor is theoretically obtained by presenting the internal space between each layer according to the laminate thickness as a cross-sectional shape model, and the cross section of the actual laminated sample is compared with the theoretical model through experiments. Then, the equation for the theoretical model is defined, and the strength change according to each condition (tensile strength of material, reduction slope, strength reduction rate, and output strength) is confirmed. In addition, we investigated the influence on the correlation and strength between laminate thickness and the Inter-Layer Fill Factor.

• The Korea Journal of Herbology
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• v.33 no.3
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• pp.11-18
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• 2018

Objectives : Saururus chinensis and Houttuynia cordata (Saururaceae) are perennial herbs using for medicinal purposes in Korea. The objectives of this study are to compare anatomical key characters between two medicinal plants and to provide fundamental information for the identification of two herbal medicines by using anatomical features. Methods : Cross-sections of root, rhizome, stem, petiole, and leaf for each species were observed in this study. Materials were analyzed through dehydration, paraffin embedding and micro-sectioning, and double staining with Safranin O and Fast-Green FCF. Observations of permanent preparation were conducted using light microscope. Results : S. chinensis and H. cordata were distinguished with anatomical differentiations; Idioblasts with essential oil were scattered in the parenchyma cell of cortex, pith, and phloem of S. chinensis, on the other hand, in H. cordata, idioblasts were distributed ring-shaped in the cortex of the root. S. chinensis had two cycles of vascular bundles in the stem while H. cordata had one cycle. Hypodermis layer was conspicuous in a stem of H. cordata, crystals were observed the only parenchyma in a stem of S. chinensis, and epidermal oil cells were developed in the epidermis of H. cordata. S. chinensis had air cavity at the cortex and pith of the stem. The shape of cross-section was polygonal in the stem of S. chinensis and was circular in the stem of H. cordata. Conclusions : We investigated anatomical study of Korean S. chinensis and H. cordata. To identify two herbal medicines, we considered main anatomical features and provided identification key here.

• Composites Research
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• v.25 no.2
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• pp.46-53
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• 2012

Using pultrusion process, FRP composite structural members having various cross-section shapes can be produced with unlimited lengths. Because of such reasons, these members are suitable for the application in the construction field. Especially, this material is highly appreciated if the material is to be used in the corrosive environments such as aquatic or oceanic environments due to its high corrosion resistance. However, design criteria for the FRP structural member are not developed yet. So, the research on the development of design guideline is needed ungently. In order to use the pultruded structural FRP member efficiently, the members are composed of thin plate components, and thus, the member is prone to buckle easily and the buckling is one of the governing strength limit states for the design. In this paper, we present the analytical study results pertaining to the buckling behavior of I-shape FRP compression member. In addition, design procedure and flow-chart are also proposed based on the study results including previous experimental results. Proposed design procedure is similar to that in ANSI/AISC 360-10 with minor modification. Therefore, it is convinced that the structural design of pultruded FRP compression member could be done easily by following design procedure proposed in this paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.128-133
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• 2015

This paper describes the construction of a static 3D ultrasonography image by tracking the radiation beam position during the handy operation of a 1D array probe to enable point-of-care use. The theoretical model of the transformation from the translational and rotational information of the sensor mounted on the probe to the reference Cartesian coordinate system was given. The signal amplification and serial communication interface module was made using a commercially available sensor. A test phantom was also made using silicone putty in a donut shape. During the movement of the hand-held probe, B-mode movie and sensor signals were recorded. B-mode images were periodically selected from the movie, and the gray levels of the pixels for each image were converted to the gray levels of 3D voxels. 3D and 2D images of arbitrary cross-section of the B-mode type were also constructed from the voxel data, and agreed well with the shape of the test phantom.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.247-255
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• 2008

According to "A guide Book to Highway Design", most road elements are chosen based on a certain design speed in order to ensure obtaining safe and smooth traffic operating. However, road safety in practical way is corelative to not only all element of roads but also road shape, for example, between straight line and curves line and between curved lines. Also, it is relates to alignments such as horizontal alignment, vertical alignment, and cross section. That is, the practical road design should be examined in both sides of 3 dimension and consecutiveness as the practical road is a 3-dimensional successive object. The paper presents a concept for acceleration to evaluate consistency of road considering actual road shape on 3-dimension. Acceleration of vehicle is influential to road consistency based on running state of vehicle and state of drivers. Especially, the magnitude of acceleration is a quite influential element to drivers. Based on above, the acceleration on each point 3-D road can be calculated and then displacement can be done. Computation of acceleration means total calculation on each axis.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.179-190
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• 2011

The swirling flow developing in Francis turbine draft tube under part load operation leads to pressure fluctuations usually in the range of 0.2 to 0.4 times the runner rotational frequency resulting from the so-called vortex breakdown. For low cavitation number, the flow features a cavitation vortex rope animated with precession motion. Under given conditions, these pressure fluctuations may lead to undesirable pressure fluctuations in the entire hydraulic system and also produce active power oscillations. For the upper part load range, between 0.7 and 0.85 times the best efficiency discharge, pressure fluctuations may appear in a higher frequency range of 2 to 4 times the runner rotational speed and feature modulations with vortex rope precession. It has been pointed out that for this particular operating point, the vortex rope features elliptical cross section and is animated of a self-rotation. This paper presents an experimental investigation focusing on this peculiar phenomenon, defined as the upper part load vortex rope. The experimental investigation is carried out on a high specific speed Francis turbine scale model installed on a test rig of the EPFL Laboratory for Hydraulic Machines. The selected operating point corresponds to a discharge of 0.83 times the best efficiency discharge. Observations of the cavitation vortex carried out with high speed camera have been recorded and synchronized with pressure fluctuations measurements at the draft tube cone. First, the vortex rope self rotation frequency is evidenced and the related frequency is deduced. Then, the influence of the sigma cavitation number on vortex rope shape and pressure fluctuations is presented. The waterfall diagram of the pressure fluctuations evidences resonance effects with the hydraulic circuit. The influence of outlet bubble cavitation and air injection is also investigated for low cavitation number. The time evolution of the vortex rope volume is compared with pressure fluctuations time evolution using image processing. Finally, the influence of the Froude number on the vortex rope shape and the associated pressure fluctuations is analyzed by varying the rotational speed.

• Korean Institute of Interior Design Journal
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• v.18 no.3
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• pp.74-83
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• 2009

This study is subway station canopy evaluation to improve the landscape of a street furniture design. From a survey of the professional abstracted the design elements of subway station canopy in Daegu. And then, it practiced a canopy design appreciation by the analysis of appreciation items. The results are as follows. First, this research analyzes each quality a classified by the four characteristics at the subway station. In general station case, the slope roof was consistent in used to be unified. If the symbol of the express station wasn't common in cross-section or material. In addition, the design evaluation in the lower canopy were evaluated. Therefore, in case of the city installed in the canopy, the characteristic of city gateway and the symbolic characteristic of a design that is required. Second, subway station canopy existed in widely opened site come out a lower rating about safety. Therefore, considering the safety light device or system need to do. Third, if the horizontal or sloping roof shape come out in a lower rating, the highly evaluated curve shape is considered to apply. Forth, a structure material of the canopy was highly evaluated the aluminum composite panels and structural steel pipes. Therefore, to improve a beauty of the city, to give rhythm to a structure material of the canopy of the aluminum composite panels and structural steel pipes will be desirable to use as the main ingredient.