• 한국정보과학회:학술대회논문집
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• 한국정보과학회 2006년도 한국컴퓨터종합학술대회 논문집 Vol.33 No.1 (D)
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• pp.217-219
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• 2006

4G mobile networks are expected to support various multimedia services over IP networks and also satisfy high spectral efficiency requirement. In cellular systems including 4G networks, hotspot cells can occur when available wireless resources at some location are not enough to sustain the needs of users. The hotspot cell can potentially lead to blocked and dropped calls, which can deteriorate the service quality for users. In a 4G mobile network, a band of users enjoying multimedia services can move around, which may generate heavy flows of traffic load. This situation can generate the hotspot cell which has a short life span of only a few minutes. In this paper, we propose a handover-based scheme which can effectively manage hotspot cells in 4G mobile networks. With the scheme, the current serving cell can recognize the load status of the target cell in advance before handover execution. Adaptive handover time control according to the amount of traffic load of cells can effectively and flexibly manage the hotspot cell in the network. And, through our hotspot cell management scheme, acceptable service quality can be supported as users continuously maintain connections with the network. In the simulation results, we find that our scheme generates smaller number of hotspot cells and supports higher service quality than the compared schemes.

• Journal of Communications and Networks
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• 제6권3호
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• pp.216-225
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• 2004

In a cellular network, if there are too many data users in a cell, data may suffer long delay, and system's quality-of-service (QoS) will degrade. Some traditional schemes such as dynamic channel-allocation scheme (DCA) will assign more channels to hot (or overloaded) cells through a central control system (CC) and the throughput increase will be upper bounded by the number of new channels assigned to the cell. In mobile-assisted data forwarding (MADF), we add an ad-hoc overlay to the fixed cellular infrastructure and special channels-called forwarding channels- are used to connect mobile units in a hot cell and its surrounding cold cells without going through the hot cell's base station. Thus, mobile units in a hot cell can forward data to other cold cells to achieve load balancing. Most of the forwarding-channel management work in MADF is done by mobile units themselves in order to relieve the load from the CC. The traffic increase in a certain cell will not be upper bounded by the number of forwarding channels. It can be more if the users in hot cell are significantly far away from one another and these users can use the same forwarding channels to forward data to different cold neighboring cells without interference. We find that, in a system using MADF, under a certain delay requirement, the throughput in a certain cell or for the whole net-work can be greatly improved.

• Asian Pacific Journal of Cancer Prevention
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• 제13권12호
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• pp.6363-6368
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• 2012

Objective: The study aim was to prepare poly-DL-lactide-poly (PELA) microspheres encapsulating recombinant tissue inhibitors of metalloproteinase-1 (TIMP-1) in an adenovirus to investigate its inhibition on the proliferation of hepatocellular carcinoma cells HepG2. Methods: Microspheres were prepared by encapsulating the recombinant TIMP-1 adenovirus into biodegradable PELA. The particle size, viral load, encapsulation efficiency and in-vitro release were measured. Microspheres were used to infect HepG2 cells, then infection efficiency was examined under a fluorescent microscope and ultrastructural changes assessed by TEM. Expression of TIMP-1 mRNA in HepG2 cells was examined by semi-quantitative RT-PCR and proliferation by MTT and cell growth curve assays. Results: We successfully prepared microspheres encapsulating recombinant TIMP-1 adenovirus with a diameter of $1.965{\mu}m$, an encapsulation efficiency of 60.0%, a viral load of $10.5{\times}10^8/mg$ and approximate 60% of virus release within 120 h, the total releasing time of which was longer than 240 h. The microspheres were confirmed to be non-toxic with blank microspheres. Infected HepG2 cells could stably maintain in-vitro expression of TIMP-1, with significantly effects on biological behaviour Conclusion: PELA microspheres encapsulating a recombinant TIMP-1 adenovirus can markedly inhibit the proliferation of HepG2 cells, which provides an experimental basis for polymer/chemistry-based gene therapy of hepatocellular carcinomas.

• 한국기계가공학회지
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• 제15권6호
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• pp.64-69
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• 2016

Vehicle clutch measurement for disc cushion variation was developed for the production of high quality Dual clutch transmissions. The developed device is composed of load cells for load measurement and LVDT for measuring the distance variation measurement in cushion variation. The servo motor-driven electric press for flexible loads that was developed was controlled by a PC-based HMI system, LabVIEW, and the device was able to continuously record real time measurement data with the accuracies of ${\pm}0.1\;kgf$ load and ${\pm}5{\mu}m$ cushion amount, which is far above the requirements of commercial vehicle standards.

• IMMUNE NETWORK
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• 제21권1호
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• pp.3.1-3.16
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• 2021

Coronavirus disease 2019 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been spreading worldwide since its outbreak in December 2019, and World Health Organization declared it as a pandemic on March 11, 2020. SARS-CoV-2 is highly contagious and is transmitted through airway epithelial cells as the first gateway. SARS-CoV-2 is detected by nasopharyngeal or oropharyngeal swab samples, and the viral load is significantly high in the upper respiratory tract. The host cellular receptors in airway epithelial cells, including angiotensin-converting enzyme 2 and transmembrane serine protease 2, have been identified by single-cell RNA sequencing or immunostaining. The expression levels of these molecules vary by type, function, and location of airway epithelial cells, such as ciliated cells, secretory cells, olfactory epithelial cells, and alveolar epithelial cells, as well as differ from host to host depending on age, sex, or comorbid diseases. Infected airway epithelial cells by SARS-CoV-2 in ex vivo experiments produce chemokines and cytokines to recruit inflammatory cells to target organs. Same as other viral infections, IFN signaling is a critical pathway for host defense. Various studies are underway to confirm the pathophysiological mechanisms of SARS-CoV-2 infection. Herein, we review cellular entry, host-viral interactions, immune responses to SARS-CoV-2 in airway epithelial cells. We also discuss therapeutic options related to epithelial immune reactions to SARS-CoV-2.

• Asian Pacific Journal of Cancer Prevention
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• 제15권12호
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• pp.4915-4918
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• 2014

Background and Aims: Advances in the treatment of cervical cancer over the last decade have predominantly involved the development of genes directed at molecular targets. Gene therapy is recognized to be a novel method for the treatment of cervical cancer. Genes can be administered into target cells via nanocarriers. This study aimed to develop systemically administrable nano-vectors. Floate (Fa) containing gene loaded nanoparticles (NPs) could target HeLa human cervical cancer cells through combination with receptors on the cells to increase the nuclear uptake of genetic materials. Methods: Fa was linked onto Poly (ethylene glycol)-b-poly (D, L-lactide) (PEG-PLA) to form Fa-PEG-PLA, and the resulting material was used to load plasmids of enhanced green fluorescence protein (pEGFP) to obtain gene loaded nanoparticles (Fa-NPs/DNA). Physical-chemical characteristics, in vitro release and cytotoxicity of Fa-NPs/DNA were evaluated. The in vitro transfection efficiency of Fa-NPs/DNA was evaluated in HeLa cells and human umbilical vein endothelial cells (HUVEC). PEG-PLA without Fa was used to load pEGFP from NPs/DNA as a control. Results: Fa-NPs/DNA has a particle size of 183 nm and a gene loading quantity of 92%. After 72h of transfection, Fa-NPs/DNA displayed over 20% higher transfection efficiency than NPs/DNA and 40% higher than naked DNA in HeLa cells. However, in HUVECs, no significant difference appeared between Fa-NPs/DNA and NPs/DNA. Conclusions: Fa-PEG-PLA NPs could function as excellent materials for gene loading. This nano-approach could be used as tumor cell targeted medicine for the treatment of cervical cancer.

• 한국전기전자재료학회논문지
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• 제28권11호
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• pp.737-742
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• 2015

This paper is designed to find out where power reaches the highest point as the load of solar cells varies. In addition, the current and power were measured when irradiation changes, and the correlation between current and power was investigated. On top of that, experiments were conducted with the light volume kept constant and with the incoming light angle changing in order to figure out the incoming light angle that produces the most power and to conduct analyses. It was ascertained that if the load increases, the current decreases and the voltage increases. Since the power of 0.9828[W] was the highest when measurements were done, it can be said that when a load of 30[%] is applied to the solar cells, they are the most efficient.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.754-758
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• 2002

According to the enlargement of production facilities and structures, the requirements of high-capacity load cells are increased for monitoring the process conditions in many fields. Generally, however, the accuracy of the column-type high-capacity load cells is not enough due to the geometric nonlinearity. It is supposed to result from the fact that the whole spring element is under high-level stress for the uniform strain field. In this paper, a new shape of spring element is developed which utilizes the stress concentration. As a design criterion, an object function which quantifies the degree of nonlinearity is defined and optimized by use of response surface modeling. As a result, the weight of the spring element is reduced shout 50% in comparison to the conventional shape. The bonding positions of stain gages are found. which show theoretically zero geometrical nonlinearity, while the ratio of overload protection is reduced from 130% to 125% Also it is shown that the response surface method is very efficient in the optimization approach by use of FEM.

• The Journal of the Acoustical Society of Korea
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• 제20권3E호
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• pp.31-37
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• 2001

Finite element model of a cMUT is constructed using the commercial code ANSYS to analyze the cross talk mechanism. Calculation results of the complex load impedance seen by single capacitor cells are presented, and then followed by a calculation of the plane wave real load impedance seen by a parallel combination of many cells that are used to make a transducer. Cross talk between 1-D array elements is found to be due to two main sources: coupling through a Stoneley wave propagating at the transducer-water interface and coupling through Lamb waves propagating in the substrate. To reduce the cross talk level, the effect of various structural variations of the substrate are investigated, which include a change of its thickness and etched trenches or polymer walls between array elements.

• Journal of information and communication convergence engineering
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• 제14권2호
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• pp.122-128
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• 2016

In the future, hybrid power management systems using fuel cells (FCs) and batteries will be used as the driving power systems of ships. These systems consist of an FC, a converter, an inverter, and a battery. In general, an FC provides steady-state energy; a battery provides the dynamic energy in the start state of a ship for enabling a smooth operation, and provides or absorbs the peak or dynamic power when the load varies and the FC cannot respond immediately. The FC voltage range is very wide and depends on the load; Therefore, the FC cannot directly connect to the inverter. In this paper, we propose a power management strategy and design process involving a unidirectional converter, a bidirectional converter, and an inverter, considering the ship's operating conditions and the power conditions of the FC and the battery. The presented experimental results were verified through a simulation.