• Title/Summary/Keyword: Rejection property

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A Study on the Simulator for the fabrication of bandpass filter for the Wide-band Codeless Division Multiple Access (광 대역 통과 필터 제작을 위한 모의 실험기)

  • 유일현
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.8 no.3
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    • pp.686-693
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    • 2004
  • We have studied a method to fabricated a Surface Acoustic Waves (SAW) filter for Wide band Codeless Division Multiple Access(WCDMA) was formed on the Langasite substrate and was evaporated by Aluminum-Copper alloy and then we developed a simulator using the mathematica package. And, we can design and fabricate the Slanted finger Inter-digital Transducer (SFIT) for the purpose to decreased the ultimate rejections on side of the electrodes, and performed computer-simulation by simulator. Also, we have employed that the block weighted type Inter-digital Transduce(IDT) as input transduce of the filter and the withdrawal weighted type IDT as an output transducer of the filter in order to minimize effect of diffractions. We have employed that the number of pairs of the input and output IDT are 50 pairs and the thickness and the width of reflector are $5000\AA$, and $1\lambda/4(\cong3.6{\mu}m)$, respectively. Also the width of IDT' finger and the space between IDT' finger and reflector are $1\lambda$/16 and 1\lambda$/8, respectively. Frequency response of the fabricated SAW bandpass filter has the property that center frequency is about 190MHz, bandwidth at the 3dB is probably 4MHz and out-band attenuation is -60dB approximately.

A study on membrane technology for surface water treatment: Synthesis, characterization and performance test

  • Haan, Teow Yeit;Shah, Mubassir;Chun, Ho Kah;Mohammad, Abdul Wahab
    • Membrane and Water Treatment
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    • v.9 no.2
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    • pp.69-77
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    • 2018
  • The use of membrane as an innovative technology for water treatment process has now widely been accepted and adopted to replace the conventional water treatment process in increasing fresh water production for various domestic and industrial purposes. In this study, ultrafiltration (UF) membranes with different formulation were fabricated via phase inversion method. The membranes were fabricated by varying the polymer concentration (16 wt%, 18 wt%, 20 wt%, and 21 wt%). A series of tests, such as field emission scanning electron microscope (FESEM), pore size and porosity, contact angle, and zeta potential were performed to characterize the membranes. The membrane performance in terms of permeation flux and rejection were evaluated using a laboratory bench-scale test unit with mine water, lake water and tube well as model feed solution. Long hour filtration study of the membranes provides the information on its fouling property. Few pore blocking mechanism models were proposed to examine the behaviour of flux reduction and to estimate the fouling parameters based on different degree of fouling. 21 wt% PVDF membrane with smaller membrane pore size showed an excellent performance for surface water treatment in which the treated water complied with NWQS class II standard.

A Study on Developing the Adolescent Anger Provocation Scale(AAPS) for Korean Adolescents (한국 청소년 분노유발요인 척도개발연구)

  • Lee, Jee-Sook
    • The Journal of the Korea Contents Association
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    • v.22 no.3
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    • pp.261-272
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    • 2022
  • The aim of the study is to develop the Adolescent Anger Provocation Scale(AAPS) for Korean adolescents. In order to develop the scale, two research processes were conducted. First, a total of 130 items were derived from various related research. After analyzing 130 items by a research team(2 related field professors and 2 Ph.D. students), a total of 54 items reconstructed based on redundancy, cultural relevancy, and appropriateness. Second, a survey was administered among 252 Korean adolescents. After analyzing an exploratory factor analysis, 12 items of poor factor loading were deleted. Thus, seven factors and 42 items were extracted. Seven factors were as follows: (1) threat to self-esteem, (2) uncontrollable situations, (3) violation of personal property, (4) incidents associated with rejection, (5) violation of regulation or rules, (6) disrespectful treatment, (7) unfair treatment due to age. The internal consistency and convergence validity of the scale were supported. The results of confirmatory factor analysis were also reported. In addition, study limitations and recommendations of future research were discussed.

Preparation and Anti-fouling Properties of PVDF Mixed Matrix Asymmetric Membranes Impregnated with 𝛽-cyclodextrin (𝛽-사이클로덱스트린을 함침시킨 PVDF 혼합기질 비대칭막의 제조와 내오염성 평가)

  • Shin, Sung Ju;Lee, Jong Sung;Lee, Jeong Gil;Youm, Kyung Ho
    • Membrane Journal
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    • v.31 no.6
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    • pp.434-442
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    • 2021
  • Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m2·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

The Evaluation of the Packaging Properties and Recyclability with Modified Acrylic Emulsion for Flexible Food Paper Coating (유연 종이 식품 포장재의 개질 아크릴 에멀젼 코팅 특성 및 재활용성 평가)

  • Myungho Lee;In Seok Cho;Dong Cheol Lee;Youn Suk Lee
    • KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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    • v.29 no.3
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    • pp.153-161
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    • 2023
  • The worldwide effects of COVID-19 have led to a surge in online shopping and contactless services. The consumption pattern has caused the issues such as the environmental pollution together with the increase of plastic waste. Reducing the reliance on the petroleum based plastic use for the package and replacing it with environmentally friendly material are the simple ways in order to solve those problems. Paper is an eco-friendly product with high recyclability as the food packaging materials but has still poor barrier properties. A barrier coating on surface of the paper can be achieved with the proper packaging materials featuring water, gas and grease barrier. Polyethylene (PE) or polypropylene (PP) coatings which are generally laminated or coated to paper are widely used in food packaging applications to protect products from moisture and provide water or grease resistance. However, recycling of packaging containing PE or PP matrix is limited and costly because those films are difficult to degrade in the environment. This study investigated the recyclability of modified acrylic emulsion coating papers compared to PE and PP polymer matrixes as well as their mechanical and gas barrier properties. The results showed that PE or modified acrylic emulsion coated papers had better mechanical properties compared to the uncoated paper as a control. PE or PP coating papers showed strong oil resistance property, achieving a kit rating of 12. Those papers also had a significantly higher percentage of screen reject during the recycling process than modified acrylic coated paper which had a screen rejection rate of 6.25%. In addition an uncoated paper had similar value of a screen rejection rate. It may suggest that modified acrylic emulsion coating paper can be more easily recycled than PE or PP coating papers. The overall results of the study found that modified acrylic emulsion coating paper would be a viable alternative to suggest a possible solution to an environmental problem as well as enhancing the weak mechanical and poor gas barrier properties of the paper against moisture.

The Design and Measurements of 100/150 GHz Band Single Side Band Filters by Using Rotated Polarization (편파 회전을 이용한 100/150 GHz 대역용 단측파대 여파기의 제작 및 성능측정)

  • Park, Jong-Ae;Han, Seog-Tae;Kim, Tai-Seong;Kim, Kwang-Dong;Kim, Hyo-Ryong;Chung, Hyun-Su;Cho, Se-Hyung;Yang, Jong-Man
    • Journal of the Korean Institute of Telematics and Electronics D
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    • v.36D no.2
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    • pp.20-30
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    • 1999
  • We have made the single side hand filter for the dual channel receiver which is a heterodyne receiver to observe the cosmic radio waves with 100GHz band ranged from 85GHz to 115GHz and 150GHz band ranged from 125GHz to 175GHz simultaneously. We have introduced the filter theory using the principle of the Martion-Puplett interferometer, which has the characteristics of rotated polarization. To reduce the loss of the transmission and beam coupling which are caused from the path difference associated with the intermediate frequency the design and the implementation have been intensely considered. The receiver needs two filters with different characteristics each other. Because each of them has the optimum positions as a function frequency at which the signal frequency is fed to mixer and the image frequency is rejected to the image termination load. The intermediate frequency and its band width have been also evaluated. We have measured the property of two filters using the vector network analyser and the beam measurement system which is made by us. The responses of the filter as a function of the position and the frequency are compared with the theory. It is shown that not only the measured values are very close to the theoretical values, but also the image rejection ratios are better than 22dB for both filters. Through successful observation using a dual channel receiver with two manufactured filters, the performance of the filters has finally verified.

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Characterization and Seawater Filtration Performance of Commerical Microfiltration and Ultrafiltration Membranes (상업용 정밀여과/한외여과막의 특성 분석 및 해수 여과 성능 평가)

  • Choi, Changkyoo;Kim, In S.
    • Journal of Korean Society of Environmental Engineers
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    • v.39 no.9
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    • pp.542-547
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    • 2017
  • This paper was to analyze the membrane characterization of hydrophilicity, surface morphology and membrane chemical anlysis of three commercial microfiltration/ultrafiltration membranes, and evaluate the filtration performance of a seawater to assess the availability for pretreatment of desalination process. From the results of contact angle, Mem-3, fabricated with polyacrylonitrile, was highly hydrophilic. It find out that Mem-3 has more anti-biofouling property. In Field emission scanning electron microscope (FESEM), Mem-1 (polyethylene) and Mem-2 (Polyvinylidenefluoride) showed the sponge-like shape and Mem-3 showed finger-like shape. Membrane chemical analysis by energy dispersive spectrometer (EDS) presented that Mem-2 was mostly fluoride and Mem-3 had s high ratio of N (32.47%) due to the nitrile group. The permeation flowrate per time on suction pressures using deionized water (D.I. water) tends that permeation rate of Mem-3 more increased when the pressure was increased compared to other membranes. From the results of turbidity and total suspended solids (TSS) removal, turbidity of permeate was 0.191 NTU to 0.406 NTU and TSS was 2.2 mg/L to 3.0 mg/L in all membranes, indicating that it was not suitable for the pretreatment of seawater desalination by short-term experiments.

Architecture and Transport Properties of Membranes out of Graphene (그래핀에 기초한 막의 구조와 물질 전달 성질 개관)

  • Buchheim, Jakob;Wyss, Roman M.;Kim, Chang-Min;Deng, Mengmeng;Park, Hyung Gyu
    • Membrane Journal
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    • v.26 no.4
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    • pp.239-252
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    • 2016
  • Two-dimensional materials offer unique characteristics for membrane applications to water technology. With its atomic thickness, availability and stackability, graphene in particular is attracting attention in the research and industrial communities. Here, we present a brief overview of the recent research activities in this rising topic with bringing two membrane architecture into focus. Pristine graphene in single- and polycrystallinity poses a unique diffusion barrier property for most of chemical species at broad ambient conditions. If well designed and controlled, physical and chemical perforation can turn this barrier layer to a thinnest feasible membrane that permits ultimate permeation at given pore sizes. For subcontinuum pores, both molecular dynamics simulations and experiments predict potential salt rejection to envisage a seawater desalination application. Another novel membrane architecture is a stack of individual layers of 2D materials. When graphene-based platelets are chemically modified and stacked, the interplanar spacing forms a narrow transport pathway capable of separation of solvated ions from pure water. Bearing unbeknownst permeance and selectivity, both membrane architecture - ultrathin porous graphene and stacked platelets - offer a promising prospect for new extraordinary membranes for water technology applications.