• IMMUNE NETWORK
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• v.12 no.6
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• pp.240-246
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• 2012

Natural killer (NK) cells play a pivotal role in early surveillance against virus infection and cellular transformation, and are also implicated in the control of inflammatory response through their effector functions of direct lysis of target cells and cytokine secretion. NK cell activation toward target cell is determined by the net balance of signals transmitted from diverse activating and inhibitory receptors. A distinct feature of NK cell activation is that stimulation of resting NK cells with single activating receptor on its own cannot mount natural cytotoxicity. Instead, specific pairs of co-activation receptors are required to unleash NK cell activation via synergy- dependent mechanism. Because each co-activation receptor uses distinct signaling modules, NK cell synergy relies on the integration of such disparate signals. This explains why the study of the mechanism underlying NK cell synergy is important and necessary. Recent studies revealed that NK cell synergy depends on the integration of complementary signals converged at a critical checkpoint element but not on simple amplification of the individual signaling to overcome intrinsic activation threshold. This review focuses on the signaling events during NK cells activation and recent advances in the study of NK cell synergy.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.79.1-79.1
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• 2016

We investigated the dynamical properties of the K2-3 multi-planet system. Recently three transiting planets are discovered using the extended Kepler2 (K2) mission (Crossfield et al. 2015). We extended their preliminary stability study by considering a substantial longer integration time. Since planet mass is not known from photometry we calculated exoplanets masses using empirical mass-radius relations (Weiss & Marcy 2014). Forward numerical integration was done using the MERCURY integration package (Chambers 1999). Our results demonstrate that this system is stable over a time scale of $10^8years$. Furthermore, we investigated the dynamical effects of a hypothetical planet in the semi-major axis vs eccentricity space. For stable orbits of the hypothetical planet we calculated transit-timing variation (TTV) and radial velocity signals. We find that for a hypothetical perturber with mass 1-13 Mjup, semi-major axis 0.2 - 0.8 AU and eccentricity 0.00-0.47 the following timing signals for the planet K2-3 b is ~ 5 sec, K2-3 c is ~ 130 sec and for K2-3 d is ~ 190 sec. The radial velocity signal of the hypothetical planet is ~ 4 m/s. Using typical transit-timing errors from the K2 mission, we find that the above hypothetical planet would not be detectable. Its radial velocity signal, however, would be detectable using the APF 2.4m telescope or HARPS at the ESO/La Silla Observatory in Chile.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.4B no.4
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• pp.170-179
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• 2004

The paper presents technical issues which integrated sensors must address to be implemented in the next generation of power electronics and motor drives. The underlying goal of the sensor integration will be to improve reliability of power conversion systems while making the power converter and motor drive become the primary source of diagnostic signals for the application. The paper focuses on design methodologies that will allow this integration to succeed in meeting the technical demands for both reliability and for application level diagnostics.

• Proceedings of the Acoustical Society of Korea Conference
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• 1993.06a
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• pp.259-262
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• 1993

In this paper, a new pitch beginning point detection method by extracting the G-peak, is proposed. By the speech production model, the area of the first peak on a pitch interval of speech signals is emphasized. By using the above characteristics, this method have more advantages than the others for pitch beginning point detection. The defective decision caused by an impulsive noise is minimized and the pre-filtering is not necessary for this method, because the integration of signals takes place in the process.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.189-192
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• 2000

In this paper, we consider a code acquisition of W-CDMA signals over multipath Rayleigh fading channel when double-dwell serial search code acquisition is used for initial synchronization. We derive the detection and false alarm probability, and mean acquisition time mathematically by taking into account of multiple H$\_$l/ cells and double-dwell serial search. It is noteworthy that the more the number of the post-detection integration, the shorter the mean acquisition time in low SNR.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.233-236
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• 2000

In this paper, we consider a code acquisition of W-CDMA signals over multipath Rayleigh fading channel when double-dwell serial search code acquisition is used for initial synchronization. We derive the detection and false alarm probability, and mean acquisition time mathematically by taking into account of multiple H$_1$ cells and double-dwell serial search. It is noteworthy that the more the number of the post-detection integration, the shorter the mean acquisition time in low SNR.

• Korean Journal of Transplantation
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• v.28 no.3
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• pp.113-120
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• 2014

Two-signal models are useful in explaining various types of immune responses. In particular, secondary, so-called costimulatory, signals are critically required for the process of T-cell activation, survival, differentiation, and memory formation. Early studies in rodent models showed that targeting T-cell costimulatory pathways elicits immunological tolerance, providing a basis for development of costimulatory therapeutics in allograft rejection. However, as the classic definition of T-cell costimulation continues to evolve, simple blockade of costimulatory pathways has limitations in prevention of allograft rejection. Furthermore, functions of costimulatory molecules are much more diverse than initially anticipated and beyond T cells. In this mini-review, we will discuss CD137-CD137L bidirectional signals as examples showing that two-signals can be applicable to multiple phases of immune responses.

• Journal of Institute of Control, Robotics and Systems
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• v.16 no.7
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• pp.720-725
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• 2010

In AGPS method, user position can be obtained even in the shadow region by improving signal sensitivity. A hybrid long integration scheme employing both coherent and non-coherent integration method is commonly used in AGPS receivers. Because coherent loss increases as residual frequency become large, residual frequency should be minimized to maximize coherent integration gain. This paper presents performance analysis of residual frequency estimator using FFT in fine-time assistance AGPS method. Considering the hardware complexity and the estimation accuracy, optimal length of FFT is proposed for GPS L1 C/A signal. Signal sensitivity for estimating the residual frequency is also analysed. By field experimental results, it is found that the residual frequency can be successfully estimated using 1 second snap-shot data when GPS signal strength is larger than -150 dBm and its RMS error is 3Hz.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2011.06a
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• pp.329-330
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• 2011

This paper concerns to the acquisition of Global Positioning System L1 C/A coded signals. It specifically addresses the issues of acquiring very low power signals which are attenuated due to special circumstances such as indoor environment or forest canopy etc. The proposed post-processing algorithm applies modified signal folding coherent integration scheme on weak signal record. It dynamically compensates the doppler effect on the length of C/A code before integrating the signal power. Experimental results show effectiveness of the algorithm on weak GPS signals recorded in a real environment.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.254-257
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• 2007

This paper presents an examination of the spatial integration method for extracting the RCS of a trihedral corner reflector from SAR images for SAR external calibration. An exact external radiometric calibration technique is required for extracting an exact calibration constant. Therefore, we examine the accuracy of the spatial integration method, which is commonly used for the SAR external radiometric calibration. At first, an SAR image for a trihedral corner reflector is simulated with a high-resolution SAR impulse response with a known theoretical RCS of the reflector, and a background clutter image for the high resolution SAR system is also generated. Then, a SAR image in a high resolution is generated for a trihedral comer reflector located on a background clutter by superposition of the two SAR images. The radar cross section of a trihedral corner reflector in the SAR image is retrieved by integrating the radar signals of the pixels adjacent to the reflector for various size of the integration area. By comparison of the measured RCS by the integration method and the theoretical RCS of the reflector, the effect of the size of the integration area on the extraction of the calibration constant is examined.