• ETRI Journal
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• v.37 no.3
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• pp.471-479
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• 2015

Traditional designs of cognitive radio (CR) focus on maximizing system throughput. In this paper, we study the joint overlay and underlay power allocation problem for orthogonal frequency-division multiple access-based CR. Instead of maximizing system throughput, we aim to maximize system energy efficiency (EE), measured by a "bit per Joule" metric, while maintaining the minimal rate requirement of a given CR system, under the total power constraint of a secondary user and interference constraints of primary users. The formulated energy-efficient power allocation (EEPA) problem is nonconvex; to make it solvable, we first transform the original problem into a convex optimization problem via fractional programming, and then the Lagrange dual decomposition method is used to solve the equivalent convex optimization problem. Finally, an optimal EEPA allocation scheme is proposed. Numerical results show that the proposed method can achieve better EE performance.

• Biomedical Science Letters
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• v.25 no.4
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• pp.302-312
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• 2019

The aim of this work was to investigate the effect of black tea extract (BTE) on collagen -induced platelet aggregation. In this study, BTE (10~500 ㎍/mL) was shown to inhibit platelet aggregation via thromboxane A₂ (TXA₂) down-regulation by blocking cyclooxygenase-1 (COX-1) activity. Also, BTE decreased intracellular Ca²⁺ mobilization ([Ca²⁺]_i). Additionally, BTE enhanced the levels of both cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), which are aggregation-inhibiting molecules. BTE inhibited the phosphorylation of phospholipase C (PLC) γ2 and syk activated by collagen. BTE regulated platelet aggregation via cAMP-dependent phosphorylation of vasodilator-stimulated phosphoprotein (VASP) Ser¹⁵⁷. The anti-platelet effects of BTE in high fat diet (HFD)-induced obese rats were evaluated. After eight weeks of BTE treatment (300 and 600 mg/kg), the platelet aggregation rate in the treated groups was significantly less than that in the HFD-fed control group. Also, BTE exhibited a hepatoprotective effect and did not exert hepatotoxicity. Therefore, these data suggest that BTE has anti-platelet effects on collagen-stimulated platelet aggregation and may have therapeutic potential for the prevention of platelet-mediated thrombotic diseases.

• Archives of Pharmacal Research
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• v.28 no.8
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• pp.977-982
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• 2005

The aim of this study was to compare two formulations of film-coated pellets containing c1arithromycin after single oral dose study in healthy male volunteers. Two formulations with different coating polymers were prepared: formulation-1 (F-1) was prepared by incorporating three kinds of pH-dependent gradient-release coated pellets into capsules and formulation-2 (F-2) was prepared by coated with an insoluble semiosmotic film. Release profiles of filmcoated pellets were evaluated using paddle method under different conditions. Pharmacokinetic profiles of these formulations were obtained in three healthy male volunteers and compared to commercially available immediate release (IR) tablets. The relative bioavailability based on the $AUC_{0-24h}$ was found to be $96.2\%\;and\;58.7\%$ for F-1 and F-2 compared with IR, and the $T_{max}$ was delayed.

• Journal of the Ergonomics Society of Korea
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• v.32 no.5
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• pp.459-467
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• 2013

Objective: The aim of this study is to review the studies on job rotation with various points of view and to classify the studies considering the approach methods. Background: Various work interventions were carried in order to prevent the work-related musculoskeletal disorders(WMSDs) and job rotation was considered as one of the simple and effective methods. Method: Previous studies were systematically collected with the combination of keywords such as job, task, rotation, allocation, line balancing, etc. Collected studies were classified into three categories: field study, laboratory study and optimization approach study. Results: Field studies showed that most studies focused on the evaluation of the factors causing the musculoskeletal disorder. Moreover, the effect of job rotation could be hard to identify because it required a long-period close observation. Laboratory studies covered only simple aspects of tasks or movements. Optimization approach studies showed the systematic approach to establish the job rotation scheme though many limitation and assumptions were adopted. Conclusion: This study collected and classified the previous studies on job rotation and presented the different approaches across various research areas. Application: The results of this study could help the practitioner and ergonomist how to establish the job rotation scheme.

• Structural Engineering and Mechanics
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• v.36 no.5
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• pp.545-560
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• 2010

Two or more distinct materials are combined into a single functionally graded material (FGM) where the microstructural composition and properties change gradually. Thermal post-buckling behavior of uniform slender FGM beams is investigated independently using the classical Rayleigh-Ritz (RR) formulation and the versatile Finite Element Analysis (FEA) formulation developed in this paper. The von-Karman strain-displacement relations are used to account for moderately large deflections of FGM beams. Bending-extension coupling arising due to heterogeneity of material through the thickness is included. Simply supported and clamped beams with axially immovable ends are considered in the present study. Post-buckling load versus deflection curves and buckled mode shapes obtained from both the RR and FEA formulations for different volume fraction exponents show an excellent agreement with the available literature results for simply supported ends. Response of the FGM beam with clamped ends is studied for the first time and the results from both the RR and FEA formulations show a very good agreement. Though the response of the FGM beam could have been studied more accurately by FEA formulation alone, the authors aim to apply the RR formulation is to find an approximate closed form post-buckling solutions for the FGM beams. Further, the use of the RR formulation clearly demonstrates the effect of bending-extension coupling on the post-buckling response of the FGM beams.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.600-609
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• 2016

In this paper, we propose a two-stage base station (BS) sleeping scheme to save energy consumption in cellular networks. The BS sleeping mode is divided into a light sleeping stage and a deep sleeping stage according to whether there is a user in the BS's coverage. In the light sleeping stage, a BS will retain its coverage and frequently switch between the on state and the doze state according to the service characteristics. While in the deep sleeping stage analysis, the BS will shut down its coverage, and neighbor BSs will patch the coverage hole. Several closed-form formulas are derived to demonstrate the power consumption in each sleeping stage and the stage switching conditions are discussed to minimize the average power consumption. The average traffic delay caused by BS sleeping and the average deep sleeping rate under a given traffic load have also been studied. In addition, it is shown that BS sleeping is not always possible because of the limited quality of service (QoS) requirements. Simulation results show that the proposed scheme can effectively reduce the average BS power consumption, at the cost of some extra traffic delay. In summary, our proposed framework provides an essential understanding of the design of future green networks that aim to take full advantage of different stages of BS sleeping to obtain the best energy efficiency.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.49-54
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• 2000

Conventional methods for measuring winds provide wind velocity observations over limited area and time period. The use of satellite imagery for measuring wind velocity overcomes some of these limitations by providing wide area and near condinuous coverage. And its accurate depiction is essential for operational weather forecasting and for initialization of NWP models. GMS-5 provides full disk images at hourly intervals. At four times each day - 0500, 1100, 1700, 2300 hours UTC-a series of three images is received, separated by thirty minutes, centered at the four times. The current wind system generates winds from sets of 3 infrared(IR) images, separated by an hour, four times a day. It also produces visible(VIS) and water vapor(WV) image-based winds from half-hourly imagery four times a day. The derivation of wind from satellite imagery involves the identification of suitable cloud targets. tracking the targets on sequential images, associating a pressure height with the derived wind vector, and quality control. The aim of this research is to incorporate imagery from other available spectral channels and examine the error characteristics of winds derived from these images.

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.428-432
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• 1999

As metallic surface has its unique lustrous appearance and optical reflectance in visible range of light, the metallization of plastic surface has been an essential drive toward weight reduction for fuel economy and decorations in transportation industry and has been put into practiced from wet chemical-electrochemial to dry vacuum process in view of an environmental effect. Electron-beam metallization was used in this work with an aim at improving the scratchproof surface hardness of plastic substrate with metallic finish character. Thin film of Al ($1000\AA$) and $SiO_2$($7000\AA$) were metallized on substrate of PC and PMMA and the films were evaluated by pencil test for surface hardness and by cross-cut tape test for adhesion. The ion beam treatment improved around twice as hard as non-treat surface. The ion beam is effect on its hardness and adhesion to surface hardened PC substrate.

• Journal of Technologic Dentistry
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• v.43 no.3
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• pp.93-98
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• 2021

Purpose: The aim of this study was to observe the surface roughness and surface topography of cobalt-chrome (Co-Cr) alloys with grinding time in dental barrel finishing. Methods: This study involved two types of Co-Cr alloys. Specimens were manufactured with the dimensions 10×10×2 mm. Each specimen was cast according to the manufacturer's instructions. The cast alloys were polished for 35 minutes at intervals of five minutes in an automatic barrel finishing. Specimens were imaged with a three-dimensional optical microscope to measure surface roughness. Results: BC specimens and GM specimens had the highest roughness (Ra) values in the ungrained control group, and the lowest Ra values were measured 20 minutes after grinding. Conclusion: The best conditions for grinding Co-Cr alloy using a dental barrel finishing were a weight ratio of polishing media, water, and compound of 150 g:200 g:5 g, and a rotation speed of 450 rpm. Grinding time to obtain appropriate surface roughness should be limited to 15 to 30 minutes.

• The Korean Journal of Physiology and Pharmacology
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• v.25 no.3
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• pp.189-195
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• 2021

Fluoxetine (FLX), a selective serotonin reuptake inhibitor antidepressant, exhibits various other mechanisms of action in numerous cell types and has been shown to induce cell death in cancer cells, paving the way for its potential use in cancer therapy. The aim of this study was to determine the off-target effects of the anti-depressant drug FLX, on the human ovarian granulosa tumor COV434 cells stimulated by forskolin (FSK), by measuring the real-time kinetics of intracellular cyclic AMP (cAMP), ATP level, cytoplasmic calcium ([Ca2+]cyt) and survival of COV434 cells. We show that incubating COV434 cells with FLX (between 0.6 and 10 μM) induces a decrease in intracellular cAMP response to FSK, a drop in ATP content and stimulates cytoplasmic Ca2+ accumulation in COV434 cells. Only the highest concentrations of FLX (5-10 μM) diminished cell viability. The present report is the first to identify an action mechanism of FLX in human tumor ovarian cells COV434 cells and thus opening the way to potential use of fluoxetine as a complementary tool, in granulosa tumor treatments.