• Smart Structures and Systems
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• v.25 no.2
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• pp.155-167
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• 2020

This paper demonstrates a real-time hybrid substructuring (RTHS) shake table test to evaluate the seismic performance of a base isolated building. Since RTHS involves a feedback loop in the test implementation, the frequency dependent magnitude and inherent time delay of the actuator dynamics can introduce inaccuracy and instability. The paper presents a robust stability and performance analysis method for the RTHS test. The robust stability method involves casting the actuator dynamics as a multiplicative uncertainty and applying the small gain theorem to derive the sufficient conditions for robust stability and performance. The attractive feature of this robust stability and performance analysis method is that it accommodates linearized modeled or measured frequency response functions for both the physical substructure and actuator dynamics. Significant experimental research has been conducted on base isolators and dampers toward developing high fidelity numerical models. Shake table testing, where the building superstructure is tested while the isolation layer is numerically modeled, can allow for a range of isolation strategies to be examined for a single shake table experiment. Further, recent concerns in base isolation for long period, long duration earthquakes necessitate adding damping at the isolation layer, which can allow higher frequency energy to be transmitted into the superstructure and can result in damage to structural and nonstructural components that can be difficult to numerically model and accurately predict. As such, physical testing of the superstructure while numerically modeling the isolation layer may be desired. The RTHS approach has been previously proposed for base isolated buildings, however, to date it has not been conducted on a base isolated structure isolated at the ground level and where the isolation layer itself is numerically simulated. This configuration provides multiple challenges in the RTHS stability associated with higher physical substructure frequencies and a low numerical to physical mass ratio. This paper demonstrates a base isolated RTHS test and the robust stability and performance analysis necessary to ensure the stability and accuracy. The tests consist of a scaled idealized 4-story superstructure building model placed directly onto a shake table and the isolation layer simulated in MATLAB/Simulink using a dSpace real-time controller.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.2
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• pp.60-67
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• 2000

When the eigenvalues of the input covariance matrix of an array system spread by orders of magnitude, conventional adaptive arrays can't remove all the interference signals effectively In this paper, an Applebaum array adopting an adaptive gain controller (AGC) in the feedback loop of the array is proposed When eigenvalue spreaded interferences are incident to an array, a high power interference is removed easily in several iterations while a relative low power interference which is a cause of eigenvalue spread is still remained In the array output After some initial iterations, the proposed array increases the correlation between the low power interference and the array output by amplifying the output signal of the array As a result, the weights vector adapts to the direction of the low power interference as well as that of the high power interference Computer simulation results show that the proposed array gives high output signal to interference plus noise ratio (SINR) and a fast convergence speed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.597-604
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• 2006

An ultrawideband(UWB) $3.1{\sim}5.15$ GHz low-noise amplifier employing a novel input matching circuit and feedback topology are presented. The proposed UWB amplifier is Implemented in $0.18{\mu}m$ RF CMOS technology. Measurements show a NF of $3.4{\sim}3.9$ dB, a power gain of $12.8{\sim}14$ dB, better than -9.4 of input matching and, an input IP3 of -1 dBm, while comsuming only 14.5 mW of power.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.3
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• pp.283-291
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• 2015

In this paper, a negative impedance converter, the key element of non-Foster matching to enhance the bandwidth of matching high Q-factor passive element, is presented. Proposed negative impedance converter is implemented by the topology of Linvill's transistor negative impedance converter circuit. It is hard to forecast the operation of negative impedance circuit, because it is composed of gain element and positive feedback. Therefore the negative impedance circuit is implemented by hybrid type beforehand to check out the feasibility and it is designed by integrated circuit. The integrated circuit is fabricated by commercial $0.18{\mu}m$ SiGe BiCMOS process, and non-Foster matching is observed at 700~960 MHz band by cancelling the target reactance.

• Toxicological Research
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• v.11 no.1
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• pp.9-14
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• 1995

The immune system is partially under the control of the sympathetic and parasymphathetic nervous systems through the regulatory feedback loop. Methamphetamine (MA) is a neurotoxic chemical which affects the neurotransmitter system. The objective of this study was to investigate the immunotoxic effect of MA on the major immune target organ and lymphocyte proliferation to the various mitogens. Female Balb/C mice, 15 to 20 g, were injected subcutaneously with 0, 0.5, or 5 mg MA/kg for 14 consecutive days. In MA treated mice, the body weight gain and relative spleen and thymus weight were decreased in doserelated manner. Histopathologically, there was a paucity of lymphold follicles and germinal centers in the spleen, and thymic cortical atrophy with lymphophagocytosis was prominent. Apoptosis also occurred in germinal centers of spleen and thymic cortex. The threshold and peak of lymphocyte proliferation at various concentration of mitogens showed similar patterns. However, the response to lipopolysaccaride (LPS) and pokeweed mitogen (PWM) in the 5 mg MA/kg treated group showed threshold and peak proliferation at high concentration of mitogens (25${\mu}g$ LPS/ml for MA vs 15${\mu}g$ LPS/ml for control; 60${\mu}g$ PWM/ml for MA vs 45${\mu}g$ PWM/ml for control), which suggest that MA impairs T cell dependent-B cell function. This preliminary study indicated that MA affected the lymphold organs and immune function.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3917-3922
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• 2010

In this paper, 3 stage amplifier MMIC was designed and fabricated with U-band optimized epitaxal pHEMT that produced by large signal characterization and modeling for 60 GHz band. The pHEMT used in this paper, the gate $0.12\;{\mu}m$ length and total gate width of $100\;{\mu}m$, $200\;{\mu}m$ has been modeled using the large signal designed with negative feedback and MCLF instead of MIM capacitor for improving stability. Fabricated MMIC $2.5{\times}1.5mm^2$ size, current about 40 mA, operating frequency 59.5~60.5 GHz, gain 19.9~18.6 dB, input matching characteristics -14.6~-14.7 dB, output matching characteristics -11.9~-16.3 dB and output -5 dBm characteristics were obtained.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.787-790
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• 2003

A 4-wavelength optical transceiver system is designed and implemented by using 4 OADMs (optical add-drop multiplexers), WDMs, and optical transceivers. In this new system, the wavelengths of 1510 nm and 1530 nm are used for upload and download signals, respectively, as well as the wavelengths of 1550 nm and 1310 nm which have been utilized in a 2-wavelength optical transceiver systems. The 4-wavelength optical module shows very encouraging pass characteristics of about - 5 dB and isolation characteristics of less than -40 dB, which is configured with two OADMs, 4 couplers, and WDM couplers by fusion splicing. Noise figure (NF) of the one-stage balanced amplifier designed and fabricated for receiver module is 0.38 dB and the amplifying gain is 14.2 dB. S$_{11}$, S$_{22}$ and input, output VSWR are -28.81 dB, -32.08 dB, 1.05 : 1, 1.08 : 1, respectively.y.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.304-306
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• 2007

In this paper, we presents a scheme for the parameter estimation and optimal control scheme for apparatus of container crane system. For parameter estimation, first, we construct the open loop of the container crane system and estimate its parameters based on input-output data, a real-coded genetic algorithm(RCGA) and the model adjustment technique. The RCGA plays an important role in parameter estimation as an adaptive mechanism. For controller design, state feedback gain matrix is searched by another RCGA and the estimated model. The performance of the proposed methods are demonstrated through a set of simulation and experiments of the experimental apparatus.

• Atmosphere
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• v.22 no.1
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• pp.117-128
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• 2012

Does snow depth initialization have a quantitative impact on sub-seasonal to seasonal prediction skill? To answer this question, a snow depth initialization technique for seasonal forecast system has been implemented and the impact of the initialization on the seasonal forecast of surface air temperature during the wintertime is examined. Since the snow depth observation can not be directly used in the model simulation due to the large systematic bias and much smaller model variability, an anomaly rescaling method to the snow depth initialization is applied. Snow depth in the model is initialized by adding a rescaled snow depth observation anomaly to the model snow depth climatology. A suite of seasonal forecast is performed for each year in recent 12 years (1999-2010) with and without the snow depth initialization to evaluate the performance of the developed technique. The results show that the seasonal forecast of surface air temperature over East Asian region sensitively depends on the initial snow depth anomaly over the region. However, the sensitivity shows large differences for different timing of the initialization and forecast lead time. Especially, the snow depth anomaly initialized in the late winter (Mar. 1) is the most effective in modulating the surface air temperature anomaly after one month. The real predictability gained by the snow depth initialization is also examined from the comparison with observation. The gain of the real predictability is generally small except for the forecasting experiment in the early winter (Nov. 1), which shows some skillful forecasts. Implications of these results and future directions for further development are discussed.

• Development and Reproduction
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• v.14 no.1
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• pp.35-41
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• 2010

Mammalian reproduction is regulated by a feedback circuit of the key reproductive hormones such as GnRH, gonadotropin and sex steroids on the hypothalamic-pituitary-gonadal axis. In particular, the onset of female puberty is triggered by gain of a pulsatile pattern and increment of GnRH secretion from hypothalamus. Previous studies including our own clearly demonstrated that genistein (GS), a phytoestrogenic isoflavone, altered the timing of puberty onset in female rats. However, the brain-specific actions of GS in female rats has not been explored yet. The present study was performed to examine the changes in the activities of GnRH neurons and their neural circuits by GS in female rats. Concerning the drug delivery route, intracerebroventricular (ICV) injection technique was employed to eliminate the unwanted actions on the extrabrain tissues which can be occurred if the testing drug is systemically administered. Adult female rats (PND 100, 210-230 g BW) were anaesthetized, treated with single dose of GS ($3.4{\mu}g$/animal), and sacrificed at 3 hrs post-injection. To determine the transcriptional changes of reproductive hormone-related genes in hypothalamus, total RNAs were extracted and applied to the semi-quantitative reverse transcription polymerase chain reaction (RT-PCR). ICV infusion of GS significantly raised the transcriptional activities of enhanced at puberty1 (EAP-1, p<0.05), glutamic acid decarboxylase (GAD67, p<0.01) which are known to modulate GnRH secretion in the hypothalamus. However, GS infusion could not change the mRNA level of nitric oxide synthase 2 (NOS-2). GS administration significantly increased the mRNA levels of KiSS-1 (p<0.001), GPR54 (p<0.001), and GnRH (p<0.01) in the hypothalami, but decreased the mRNA levels of LH-$\beta$ (p<0.01) and FSH-$\beta$ (p<0.05) in the pituitaries. Taken together, the present study indicated that the acute exposure to GS could directly activate the hypothalamic GnRH modulating system, suggesting the GS's disrupting effects such as the early onset of puberty in immature female rats might be derived from premature activation of key reproduction related genes in hypothalamus-pituitary neuroendocrine circuit.