• Journal of Communications and Networks
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• v.14 no.5
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• pp.578-587
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• 2012

One of the key elements in the emerging, packet-based long term evolution (LTE) cellular systems is the deployment of multiple femtocells for the improvement of coverage and data rate. However, arbitrary overlaps in the coverage of these femtocells make the handover operation more complex and challenging. As the existing handover strategy of LTE systems considers only carrier to interference plus noise ratio (CINR), it often suffers from resource constraints in the target femtocell, thereby leading to handover failure. In this paper, we propose a new efficient, multi-objective handover solution for LTE cellular systems. The proposed solution considers multiple parameters like signal strength and available bandwidth in the selection of the optimal target cell. This results in a significant increase in the handover success rate, thereby reducing the blocking of handover and new sessions. The overall handover process is modeled and analyzed by a three-dimensional Markov chain. The analytical results for the major performance metrics closely resemble the simulation results. The simulation results show that the proposed multi-objective handover offers considerable improvement in the session blocking rates, session queuing delay, handover latency, and goodput during handover.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5A
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• pp.339-347
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• 2012

Femtocells as home base station for indoor coverage extension and wideband data service, have been studied with significant interests. When femtocell is deployed, the existing cell structural of changes causes various technical problems. In this paper, we investigate the femto-macro cell interference mitigation in OFDMA system. We propose dynamic downlink resource management scheme which adjust the transmitted power of femtocell according to the strength of received macrocell signal and allocates subcarrier to femtocells in a dynamic manner. In this way, the interference between the macrocell users and femtocells is reduced. The simulation results show that proposed scheme enhances both macrocell and femtocell throughputs.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.1
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• pp.73-81
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• 2007

This paper analyzes the performance of the handover in an overlaid micro/macro cellular system suited for mobile communication environments. In proposed model, it is analyzed the performance of case that subscriber who move with high speed does handover to a macrocell instead of doing handover by microcell. For an easy analysis, a circle shaped cell model are assumed both in microcell and macrocell. The reservation channel scheme is adopted in microcell for a low-speed mobile while a scheme using queue is used in macrocell for a high-speed mobile. The analytic results show that the proposed scheme provides a lower handover failure relatively than in a non-overlaid cellular system with slightly increased new call blocking probability.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.3
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• pp.163-170
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• 2002

This report describes the use of a transtubular bioreactor to study the relative effects of diffusion versus perfusion of medium on antibody production by a hybridoma cell line. The study was performed with a high-density cell culture maintained in a serum-free, low-protein medium for 77 days. It was determined that the reactor possessed a macro-mixing pattern residence time distribution similar to a continuous stirred tank reactor (CSTR), However, due to the arrangement of the medium lines in the reactor, the flow patterns for nutrient distribution consist of largely independent medium path lengths ranging from short to long. When operated with cyclic, reversing, transtubular medium flow, some regions of the reactor (with short residence times) are more accessible to medium than others (with long residence times). From this standpoint, the reactor can be divided into three regions: a captive volume, which consists of medium primarily delivered via diffusion; a lapped volume, which provides nutrients through unilateral convection; and a swept volume, which operates through bilateral convection. The relative sizes of these three volumes were modified experimentally by changing the period over which the direction of medium flow was reversed from 15 min (larger captive volume) to 9 h (larger swept volume). The results suggest that antibody concentration increases as the size of the diffusion-limited (captive) volume is increased to a maximum at around 30 min with a sharp decrease thereafter. As reflected by changes in measured consumption of glucose and production of lactate, no significant difference in cellular metabolism occurred as the reactor was moved between these different states. These results indicate that the mode of operation of the transtubular bioreactor may influence antibody productivity under serum-free, low-protein conditions with minimal effects on cellular metabolism.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.393-400
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• 2013

In conventional single-tier networks, downlink based association is the best association scheme for the uplink association because all macro base stations have the same physical specification. However, in uplink heterogeneous cellular networks, a downlink based cell association cannot be the best for uplink any more because of the difference of physical specification between the different base station. In this paper, we will propose a uplink based cell association scheme, and devise performance metric for describing a uplink performance in heterogeneous cellular networks. Then, we will discuss the necessity of the uplink based association by observing outage probability, delay constraint outage probability, delay constraint outage capacity.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.18
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• pp.8271-8279
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• 2016

Background: Hepato-carcinogenesis is multifaceted in its molecular aspects. Among the interplaying agents are altered gap junctions, the proteasome/autophagy system, and mitochondria. The present experimental study was designed to outline the roles of these players and to investigate the tumor suppressive effects of curcumin with or without mesenchymal stem cells (MSCs) in hepatocellular carcinoma (HCC). Materials and Methods: Adult female albino rats were divided into normal controls and animals with HCC induced by diethyl-nitrosamine (DENA) and $CCl_4$. Additional groups treated after HCC induction were: Cur/HCC which received curcumin; MSCs/HCC which received MSCs; and Cur+MSCs/HCC which received both curcumin and MSCs. For all groups there were histopathological examination and assessment of gene expression of connexin43 (Cx43), ubiquitin ligase-E3 (UCP-3), the autophagy marker LC3 and coenzyme-Q10 (Mito.Q10) mRNA by real time, reverse transcription-polymerase chain reaction, along with measurement of LC3II/LC3I ratio for estimation of autophagosome formation in the rat liver tissue. In addition, the serum levels of ALT, AST and alpha fetoprotein (AFP), together with the proinflammatory cytokines $TNF{\alpha}$ and IL-6, were determined in all groups. Results: Histopathological examination of liver tissue from animals which received DENA-$CCl_4$ only revealed the presence of anaplastic carcinoma cells and macro-regenerative nodules. Administration of curcumin, MSCs; each alone or combined into rats after induction of HCC improved the histopathological picture. This was accompanied by significant reduction in ${\alpha}$-fetoprotein together with proinflammatory cytokines and significant decrease of various liver enzymes, in addition to upregulation of Cx43, UCP-3, LC3 and Mito.Q10 mRNA. Conclusions: Improvement of Cx43 expression, nonapoptotic cell death and mitochondrial function can repress tumor growth in HCC. Administration of curcumin and/or MSCs have tumor suppressive effects as they can target these mechanisms. However, further research is still needed to verify their effectiveness.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.268-276
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• 2013

In this paper, we introduce the technologies to handle the interference in the heterogeneous network and evaluate the performance of enhanced Inter-Cell Interference Coordination (enhanced ICIC, eICIC) techniques that are being introduced in 3GPP Release 10. In the time-domain eICIC scheme, time-domain resources are scheduled to avoid the interference by using Almost Blank Subframe (ABS) and Cell Range Expansion (CRE). To mitigate the cross-tier interference between macro and femtocell, it is important to efficiently combine the ABS and CRE in heterogeneous network. Since it is hard to evaluate the total throughput of heterogeneous network numerically, we evaluate the total throughput by using system level simulation (SLS). As a result of evaluation, the throughputs of many different cases of combination of ABS and CRE are compared.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.11
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• pp.5301-5323
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• 2017

Small cell deployment offers a low-cost solution for the boosted traffic demand in heterogeneous cellular networks (HCNs). Besides improved spatial spectrum efficiency and energy efficiency, future HCNs are also featured with the trend of network architecture convergence and feasibility for flexible mobile applications. To achieve these goals, dual connectivity (DC) is playing a more and more important role to support control/user-plane splitting, which enables maintaining fixed control channel connections for reliability. In this paper, we develop a tractable framework for the downlink SINR analysis of DC assisted HCN. Based on stochastic geometry model, the data-control joint coverage probabilities under multi-frequency and single-frequency tiering are derived, which involve quick integrals and admit simple closed-forms in special cases. Monte Carlo simulations confirm the accuracy of the expressions. It is observed that the increase in mobility robustness of DC is at the price of control channel SINR degradation. This degradation severely worsens the joint coverage performance under single-frequency tiering, proving multi-frequency tiering a more feasible networking scheme to utilize the advantage of DC effectively. Moreover, the joint coverage probability can be maximized by adjusting the density ratio of small cell and macro cell eNBs under multi-frequency tiering, though changing cell association bias has little impact on the level of the maximal coverage performance.

• JSTS:Journal of Semiconductor Technology and Science
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• v.17 no.2
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• pp.167-173
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• 2017

In this paper, the characterization of the vertical position of trapped charges in the charge-trap flash (CTF) memory is performed in the novel CTF memory cell with gate-all-around structure using technology computer-aided design (TCAD) simulation. In the CTF memories, injected charges are not stored in the conductive poly-crystalline silicon layer in the trapping layer such as silicon nitride. Thus, a reliable technique for exactly locating the trapped charges is required for making up an accurate macro-models for CTF memory cells. When a programming operation is performed initially, the injected charges are trapped near the interface between tunneling oxide and trapping nitride layers. However, as the program voltage gets higher and a larger threshold voltage shift is resulted, additional charges are trapped near the blocking oxide interface. Intrinsic properties of nitride including trap density and effective capture cross-sectional area substantially affect the position of charge centroid. By exactly locating the charge centroid from the charge distribution in programmed cells under various operation conditions, the relation between charge centroid and program operation condition is closely investigated.

• Korean Journal of Food Science and Technology
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• v.20 no.6
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• pp.742-748
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• 1988

The macro-and microstructure of Chinese cabbage used for Korean Kimchi preparation were examined and the texture characteristics of raw cabbage leaf and salted or blanched leaves were evaluated by cutting test. The length and thickness of leaf stalk increased with the order of pyllotaxis, but the thinning effect of outermost leaves was observed. The microstructure of cut-profile of stalk showed densely compacted vascular systems aligned in the center of stalk and the outer space was filled with large parenchima cells. Due to this structure, characteristic cutting curves were obtained by cutting test, composing three peaks of cutting for inner surface skin, center vascular system and outer surface skin. Salting and blanching increased the cutting force mainly due to the increase of Gutted cell wall number caused by the structure collapse.