• Journal of Chest Surgery
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• v.52 no.4
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• pp.232-235
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• 2019

A 2.5-kg neonate with coarctation of the aorta and a small left ventricle experienced a severe pulmonary hypertensive crisis. An emergency pulmonary artery-to-systemic artery shunt was placed to break the positive feedback loop caused by pulmonary hypertension and functional mitral stenosis. This shunt provided immediate relief of suprasystemic pulmonary hypertension and the resultant low cardiac output.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.104-110
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• 2006

A design and control of electrostatic suspension system for flexible objects is presented. A number of electrode pairs of which the number depends on the object flexibility are positioned above the object and the voltages applied to each electrode pair are controlled, independently on the others, on the basis of the gap length. To implement the system with low cost and compactness, switched-voltage control scheme that is based on the relay feedback control is utilized. Relay feedback control method deploys only a single high-voltage power supply that can deliver a DC voltage of positive and/or negative polarity and thus high voltage amplifiers that are costly and bulky are not needed any more. It is shown that despite the inherent limit cycle property of the relay feedback based control, an excellent performance in vibration suppression is attained due to the presence of a relatively large squeeze film damping originating from the electrodes and levitated object. Employing fourteen electrode pairs, a thin aluminum plate with a thickness of 0.1 mm has been suspended at a gap length of 0.75mm.

• Journal of the Korean Institute of Telematics and Electronics
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• v.21 no.6
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• pp.42-50
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• 1984

The method of increasing the bandwidth of distributed amplifier by the feedback loop is presented in this paper. In this method, it is tried to increase the gain of the amplifier in the high frequency range by giving a positive feedback on the device, while giving no influence in the low frequency range. For the simplicity of the amplifier design the transmission line theory of periodical structure with a unilateral divice is used in the design, and the 2-ports cascade network theory developed by K.B. Niclas is used in computer analysis for the purpose of precise results. In this simulation, the bandwidth of the amplifier is increased from 16 [GHz] without feedback loop to about 20 [GHz] with the feedback loop.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.6
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• pp.16-23
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• 2003

In this paper, we propose an efficient bias circuit of discrete BJT component for hearing aid. The collector feedback bias circuit, widely used for the hearing aid, has a resistor for negative feedback. As the resistor affects AC and DC simultaneously, it is quite difficult to adjust amplifier gain without changing DC bias point. The previous bias circuit also has weak point to be oscillated by the positive feedback of power noise if gain of hearing aid is high. In the proposed circuit, we can reduce the two weak points of the previous circuit by adding a resistor to the collector feedback bias circuit between base and power supply which is $\beta$ times target than the collector resistor. Thus. we can change amplifier gain without changing DC bias point, and reduce power noise gain about 18.5% compare to that of tile previous circuit in the simulation.

• Communications of Mathematical Education
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• v.31 no.4
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• pp.409-432
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• 2017

The purpose of this study is to find out the importance of process - based evaluation and to find a way to set up and operate the formative assessment which is getting attention. As one of the ways, we investigated the effect of formative assessment through student's interactive feedback on mathematics achievement and attitude of fourth grade students in elementary school. In order to conduct the study, two groups of homogeneous grades were selected. In the experimental group, formative assessment was conducted through student's interactive feedback. In comparison group, formative assessment was conducted through self - confirmation feedback. Statistical analysis of the results after the experiment showed that the formative assessment through student's interactive feedback was found to have a positive effect on the improvement of mathematics achievement. In addition, the formative assessment through student's interactive feedback positively changed the mathematics attitude. Therefore, this suggests that applicability of formative assessment through student's interactive feedback in elementary school classroom instruction, as well as implications for follow - up study for effective implementation of formative assessment.

• Fire Science and Engineering
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• v.26 no.2
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• pp.32-39
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• 2012

This research focuses on finding the way of improving creativity in fire stations by scrutinizing the factors influencing and enhancing creativity in organizations. As environmental changes including the needs of citizens as well as the climate change are moving culminated today, fire stations should be changed appropriately to get the legitimacy of existence not to mention their own mission accomplishments. In this respect, the creativity can be expected as the main factor for fire stations' going concern. This research provided 5 hypotheses to find whether the chosen factors such as vision, learning/unlearning and positive feedback affect the creativity in fire stations. To prove hypotheses are valid, we employed survey as a method in which 155 firemen in Seoul responded, ending up with getting the result that the vision formulation and sharing, unlearning activities and positive feedback improve organizational creativity. In conclusion, this paper suggests that fire stations establish useful policies for the creativity based on these research findings.

• BMB Reports
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• v.50 no.1
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• pp.1-2
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• 2017

Acquiring a selective growth advantage by breaking the proliferation barrier established by gatekeeper genes is a centrally important event in tumor formation. Removal of the mammalian Hippo kinase Mst1 and Mst2 in hepatocytes leads to rapid hepatocellular carcinoma (HCC) formation, indicating that the Hippo signaling pathway is a critical gatekeeper that restrains abnormal growth in hepatocytes. By rigorous genetic approaches, we identified an interacting network of the Hippo, Wnt/${\beta}$-catenin and Notch signaling pathways that control organ size and HCC development. We found that in hepatocytes, the loss of Mst1/2 leads to the activation of Notch signaling, which forms a positive feedback loop with Yap/Taz (transcription factors controlled by Mst1/2). This positive feedback loop results in severe liver enlargement and rapid HCC formation. Blocking the Yap/Taz-Notch positive feedback loop by Notch inhibition in vivo significantly reduced the Yap/Taz activities, hepatocyte proliferation and tumor formation. Furthermore, we uncovered a surprising inhibitory role of Wnt/${\beta}$-catenin signaling to Yap/Taz activities, which are important in tumor initiation. Genetic removal of ${\beta}$-catenin in the liver of the Mst1/2 mutants significantly accelerates tumoriogenesis. Therefore, Wnt/${\beta}$-catenin signaling, known for its oncogenic property, exerts an unexpected function in restricting Yap/Taz and Notch activities in HCC initiation. The molecular interplay between the three signaling pathways identified in our study provides new insights in developing novel therapeutic strategies to treat liver tumors.

• The Journal of the Korea Contents Association
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• v.15 no.12
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• pp.185-192
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• 2015

This study analyzed the spatial interrelation between living wages and economic variables and how they operate based on systems thinking theory to understand what value living wages have as policy instruments and why they are necessary. Results from this study can be summed as follows. First, the relationship between living wages and economic variables shows close interaction at a considerable level. In particular, mutual feedback which connects to laborers' standards of living, consumption, business, and economy was operating closely. Second, largely three positive (+) feedback loops were operating in the feedback structure of living wages and economic variables. This can be interpreted to mean that positive economic variables which are associated with living wages have the possibility of growth. Also, it can mean that the minimum wage system did not fully fulfill its role. Through these study results, it can be learned that living wages have sufficient value as a policy means and that it is advisable to allow living wages to exceed simple application levels in the public sector to expand into the private sector, to bring positive change to the economic system.

• Proceedings of the National Institute of Ecology of the Republic of Korea
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• v.1 no.1
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• pp.58-67
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• 2020

Terrestrial ecosystems influence climate change via their climate regulation function, which is manifested within the carbon, water, and energy circulation between the atmosphere and surface. However, it has been challenging to quantify the climate regulation of terrestrial ecosystems and identify its regional distribution, which provides useful information for establishing regional climate-mitigation plans as well as facilitates better understanding of the interactions between the climate and land processes. In this study, a land surface model (LSM) that represents the land-atmosphere interactions and plant phenological variations was introduced to assess the contributions of terrestrial ecosystems to atmospheric warming or cooling effects over East Asia over the last half century. Three main climate-regulating components were simulated: net radiation flux, carbon exchange, and moisture flux at the surface. Then, the contribution of each component to the atmospheric warming or cooling (negative or positive feedback to the atmosphere, respectively) was investigated. The results showed that the terrestrial ecosystem over the Siberian region has shown a relatively large increase in positive feedback due to the enhancement of biogeochemical processes, indicating an offset effect to delay global warming. Meanwhile, the Gobi Desert shows different regional variations: increase in positive feedback in its southern part but increase in negative one in its eastern part, which implies the eastward movements of desert areas. As such, even though the LSM has limitations, this model approach to quantify the climate regulation is useful to extract the relevant characteristics in its spatio-temporal variations.

• Journal of Power Electronics
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• v.11 no.3
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• pp.360-368
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• 2011

This paper proposes an active frequency with a positive feedback in the d-q frame anti-islanding method suitable for a robust phase-locked loop (PLL) algorithm using the FFT concept. In general, PLL algorithms for grid-connected PV PCS use d-q transformation and controllers to make zero an imaginary part of the transformed voltage vector. In a real grid system, the grid voltage is not ideal. It may be unbalanced, noisy and have many harmonics. For these reasons, the d-q transformed components do not have a pure DC component. The controller tuning of a PLL algorithm is difficult. The proposed PLL algorithm using the FFT concept can use the strong noise cancelation characteristics of a FFT algorithm without a PI controller. Therefore, the proposed PLL algorithm has no gain-tuning of a PI controller, and it is hardly influenced by voltage drops, phase step changes and harmonics. Islanding prediction is a necessary feature of inverter-based photovoltaic (PV) systems in order to meet the stringent standard requirements for interconnection with an electrical grid. Both passive and active anti-islanding methods exist. Typically, active methods modify a given parameter, which also affects the shape and quality of the grid injected current. In this paper, the active anti-islanding algorithm for a grid-connected PV PCS uses positive feedback control in the d-q frame. The proposed PLL and anti-islanding algorithm are implemented for a 250kW PV PCS. This system has four DC/DC converters each with a 25kW power rating. This is only one-third of the total system power. The experimental results show that the proposed PLL, anti-islanding method and topology demonstrate good performance in a 250kW PV PCS.