• Macromolecular Research
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• v.15 no.6
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• pp.547-552
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• 2007

Water soluble polymer, poly(vinyl pyrrolidone) was chosen to conjugate with 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(succinyl) (N-succinyl DPPE) to make a new drug delivery system. PVP with an amine group (amino-PVP) was polymerized by free radical polymerization. The amine group of amino-PVP was conjugated with the carboxylic group of N-succinyl DPPE. The resultant conjugate could form nanoparticles in the aqueous solution; these nanoparticles were termed a lipid-polymer system. The critical aggregation concentration was measured with pyrene to give a value of $1{\times}10^{-3}g/L$. The particle size of the lipid-polymer system, as measured by DLS, AFM and TEM, was about 70 nm. Lipophilic component in the inner part of the lipid-polymer system could derive the physical interaction with hydrophobic drugs. Griseofulvin was used as a model drug in this study. The loading efficiency and release profile of the drug were measured by HPLC. The loading efficiency was about 54%. The release behavior was sustained for a prolonged time of 12 days. The proposed lipid-polymer system with biodegradable and biocompatible properties has promising potential as a passive-targeting drug delivery carrier because of its small particle size.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.3
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• pp.285-297
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• 2016

In this paper, a centralized mmWave-based multi-spot beam cellular system architecture having such a base station equipped with a plurality of beam-forming antennas, multi-layered dynamic cell configuration method as one of key concepts of this system operation and a mobility management method based on it are introduced. To estimate the performance of new system, system simulation was performed under the ideal environment without blockage. These results show the possibility that system capacity can be dramatically increased and mobility performance similar to the existing cellular system may be achieved.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.19-23
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• 2016

This paper presents a novel design for dual-band bandpass filters. The proposed filters are applicable to the carrier aggregation of the TV white space (TVWS) band and long-term evolution (LTE) band for cognitive radio applications. The lower passband is the TVWS band (470-698 MHz) whose fractional bandwidth is 40 %, while the higher passband is the LTE band (824-894 MHz) with 8 % fractional bandwidth. Since the two passbands are located very close to each other, a transmission zero is inserted to enhance the rejection level between the two passbands. The TVWS band filter is designed using magnetic coupling to obtain a wide bandwidth, and the LTE band filter is designed using dielectric resonators to achieve good insertion loss characteristics. In addition, in the proposed design, a transmission zero is placed with cross-coupling. The proposed dual-band bandpass filter is designed as a two-port filter (one input/one output) as well as a three-port filter (one common input/two outputs). The measured performances show good agreement with the simulated performances.

• Macromolecular Research
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• v.12 no.5
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• pp.501-506
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• 2004

We have investigated the spectral properties of DNA, including its electric absorption, circular and linear dichroism (CD and LD), and fluorescence emission, in the DNA-linear polyethyleneimine (LPEI) and DNA-branched polyethyleneimine (BPEI) complexes at various polymer concentrations. The spectral properties of both complexes are similar. We observed a relatively moderate change in the absorption and CD spectra at low amine/DNA phosphate (NIP) ratios (< 0.5), followed by a drastic collapse within the N/P range from 0.8 and 1.0. The absorption and CD spectra recovered as the N/P ratio increased to ca. 1.2. In contrast, the LD and emission of ethidium intercalated between the DNA bases decreased almost linearly at N/P ratios between 0.0 and 1.0. These spectra never recovered at higher N/P ratios. We believe that the moderate changes in the spectrum at low N/P ratios occurred because of electrostatic interactions between DNA and BPEI, while the collapsed spectra at N/P ratios between 0.5 and 1.5 occurred because of condensation/aggregation of the DNA. Considering the structure of the polymers, we suggest that the secondary amino group of LPEI and all three amino groups of BPEI are equally involved in DNA condensation.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.2
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• pp.245-251
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• 2016

Despite the exponential throughput improvement in mobile communications systems, their ability to satisfy requirements of state-of-the-art and future applications of advanced metering infrastructure (AMI) is still under investigation. Challenges are mainly due to the inadequacy of third generation partnership project (3GPP) networks to support large amounts of devices simultaneously, while the number of AMI end-devices and the frequency of their data transmission increase with new AMI-based applications. In this introductory survey, innovative and future AMI applications and their communication requirements are first reviewed. Then, we identify challenges of 3GPP long term evolution (LTE) in enabling future AMI applications. More importantly, the latest improvements to LTE-A standard release 12 and 13 are reviewed and analyzed with regards to their potential to improve the quality of LTE-enabled AMI. It is found that 3GPP enhancements on machine type communications (MTC) standards will significantly enhance AMI communications. Beyond MTC specifications, non-MTC-specific enhancements such as carrier aggregation and multi-connectivity for user equipment will also contribute greatly to improving reliability and availability of AMI devices. The paper's focus is towards improved backhaul support for innovative and future AMI applications, beyond traditional automatic meter reading.

• Polymer(Korea)
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• v.32 no.6
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• pp.561-565
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• 2008

Hyaluronic acid (HA) is a natural glycosaminoglycan and is used widely in the pharmaceutical field. Lipoic acid (LA) helps the regeneration of exogenous and endogenous antioxidants such as Vitamin C and Vitamin E as well as glutathione. It also acts as antioxidant indirectly. Hydrophilic HA as a biodegradable and biocompatible polymer was conjugated with hydrophobic LA as an antioxidant to form the graft copolymer. The carboxyl group of HA was modified by adipic acid dihydrazide (ADH). The synthesis of HA-g-LA graft copolymers was characterized by FT-IR, $^1H$-NMR spectroscopy. The conjugates could form the self-assembled nanoparticles in aqueous solution. The particle size and critical aggregation concentration were verified to use the nanoparticle as a carrier fur the hydrophobic material.

• Journal of Integrative Natural Science
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• v.11 no.4
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• pp.197-203
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• 2018

Long Term Evolution-Advanced (LTE-A) is the next drive in the broadband mobile communication, which allows operators to improve networks performance and service capabilities. LTE-A targets the peak data rates of 1Gbps in the downlink and 500Mbps in the uplink. This requirement is only fulfilled by a transmission bandwidth of up to 100MHz. However the accessibility of such large part of the contiguous spectrum is uncommon in practice. Therefore LTE-A uses some new features on top of the existing LTE standards to provide very high data rate transmission. Some of the most significant features introduced in LTE-A are carrier aggregation, heterogeneous network enhancement, coordinated multipoint transmission and reception, enhanced multiple input and multiple output, and development relay nodes with universal frequency reuse. This review paper presents an overview of the above mentioned LTE-A key features and functionalities. Based on this review, in the conclusion we discuss the current technical challenges for future broadband mobile communication systems.

• Journal of Microbiology and Biotechnology
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• v.21 no.1
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• pp.28-36
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• 2011

Diblock copolymers composed of poly(${\varepsilon}$-caprolactone) (PCL) and poly(N,N-dimethylamino-2-ethyl methacrylate) (PDMAEMA), or methoxy polyethylene glycol(PEG), were synthesized via a combination of ring-opening polymerization and atom-transfer radical polymerization in order to prepare polymeric nanoparticles as an antifungal drug carrier. Amphotericin B (AmB), a natural antibiotic, was incorporated into the polymeric nanoparticles. The physical properties of AmB-incorporated polymeric nanoparticles with PCL-b-PDMAEMA and PCL-b-PEG were studied in relation to morphology and particle size. In the aggregation state study, AmB-incorporated PCL-b- PDMAEMA nanoparticles exhibited a monomeric state pattern of free AmB, whereas AmB-incorporated PCL-b- PEG nanoparticles displayed an aggregated pattern. In in vitro hemolysis tests with human red blood cells, AmBincorporated PCL-b-PDMAEMA nanoparticles were seen to be 10 times less cytotoxic than free AmB (5 ${\mu}g$/ml). In addition, an improved antifungal activity of AmBincorporated polymeric nanoparticles was observed through antifungal activity tests using Candida albicans, whereas polymeric nanoparticles themselves were seen not to affect activity. Finally, in vitro AmB release studies were conducted, proving the potential of AmB-incorporated PCL-b-PDMAEMA nanoparticles as a new formulation candidate for AmB.

• Biotechnology and Bioprocess Engineering:BBE
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• v.11 no.3
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• pp.262-267
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• 2006

The objective of this study was to develop new self-organized nanogels as a means of drug delivery in patients with cancer. Pullulan (PUL) and deoxycholic acid (DOCA) were conjugated through an ester linkage between the hydroxyl group in PUL and the carboxyl group in DOCA. Three types of PUL/DOCA conjugates were obtained, differing in the number of DOCA substitutions (DS; 5, 8, or 11) per 100 PUL anhydroglucose units. The physicochemical properties of the resulting nanogels were characterized by dynamic light scattering, transmission electron microscopy, and fluorescence spectroscopy. The mean diameter of DS 11 was the smallest (approx. 100 nm), and the size distribution was unimodal. To determine the organizing behavior of these conjugates, we calculated their critical aggregation concentrations (CACs) in a 0.01-M phosphate buffered saline solution. They were $10.5{\times}10^{-4}mg/mL,\;7.2{\times}10^{-4} mg/mL,\;and\;5.6{\times}10^{-4} mg/mL$ for DS 5, 8, and 11, respectively. This indicates that DOCA can serve as a hydrophobic moiety to create self-organized nanogels. To monitor the drug-releasing behavior of these nanogels, we loaded doxorubicin (DOX) onto the conjugates. The DOX-loading efficiency increased with the degree of DOCA substitution. The release rates of DOX from PUL/DOCA nanogels varied inversely with the DS. We concluded that the PUL/DOCA nanogel has some potential for use as an anticancer drug carrier because of its low CAC and satisfactory drug-loading capacity.

• Information and Communications Magazine
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• v.30 no.12
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• pp.37-50
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• 2013

아이폰을 비롯한 새로운 스마트 기기의 도입으로 촉발된 폭발적인 데이터 트래픽의 증가는 사회.경제적으로 큰 변화를 가져 왔으며, 앞으로도 그 추세가 계속될 것으로 예측되고 있다. 국내의 경우 증가하는 데이터 트래픽을 수용하기 위해 10MHz의 LTE 시스템을 도입하여 상용 서비스를 시작한 바 있으며, 올해 하반기부터는 20MHz의 광대역 LTE 서비스와 함께 2개의 반송파를 집성하는 CA(Carrier Aggregation) 기술이 적용된 LTE-Advanced, 즉 4G 상용 서비스를 이미 개시하였다. LTE 상용 서비스가 본격화 되기 시작하면서 제조업체와 대학, 연구소 등을 중심으로 다음 세대 이동통신 기술에 대한 관심이 보다 높아졌으며, 최근 LTE-Advanced 상용 서비스 개시를 계기로 5G 이동통신에 대한 논의가 본격적으로 시작되고 있다. ITU-R WP(Working Party) 5D는 2012년 7월에 개최된 제13차 회의에서 2020년 및 그 이후의 미래 IMT 시스템을 위한 비전(Vision) 및 기술동향 연구를 수행하기로 결정하였으며, 2013년부터 본격적인 연구에 착수하여 미래 IMT 기술동향 보고서와 미래 IMT 비전 권고를 각각 2014년과 2015년까지 개발할 계획이다. 이와 관련하여 3GPP와 IEEE 802도 현재 표준화가 진행되거나 진행 예정인 최신 기술들을 중심으로 미래 IMT 기술동향 보고서에 대한 기고를 제출하였다. 향후 ITU-R WP 5D는 전례로 볼 때 현재 진행 중인 2020년 및 그 이후의 미래 IMT 시스템을 위한 비전 및 기술동향 연구 작업이 마무리하면, 4G인 IMT-Advanced의 경우와 마찬가지로 5G의 기술적 요구사항을 정의하고, 5G 후보 기술규격을 외부 표준화 기구들로부터 제안 받아 5G 기술로 승인하는 과정을 밟게 될 것이며, 이후 이 요구사항을 만족하는 시스템을 5G 이동통신 시스템이라고 명명하게 될 것이다. 5G 이동통신 시스템에 대한 요구사항은 다양한 의견 교류를 통해 큰 틀에서 컨센서스를 이루어가는 중이며, 이러한 내용이 ITU-R WP 5D의 기술적 요구사항에 반영되어 보다 구체화 될 것이다. 반면 5G에 대한 기술적 접근방법에 대해서는 여러 시각들이 존재하는 것이 사실이나, 현재 이에 대한 논의가 활발히 진행되고 있으며, 결국은 관련 표준화 기구들에서의 논의를 통해 그 접근방법이 최종적으로 결정될 것으로 보인다. 본 고에서는 먼저 5G 이동통신 요구사항과 4G 이후의 표준화 기술에 대해 살펴 본 후, 향후 이동통신 기술이 어떤 시나리오에 따라 발전할 것인지, 5G 네트워크는 어떤 구조를 갖게 될지, 그리고 어떤 기술이 적용될 지 등에 대해 개인적인 시각에서 전망해보고자 한다.