• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.41.2-42
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• 2020

Understanding how the filamentary structure plays a role in the formation of the prestellar cores and stars is a key issue to challenge. We have observed two prestellar cores in surrounding filamentary environments in 13CO, C180 (3-2) and HCO+ (4-3) molecular lines with the Heterodyne Array Receiver Program (HARP) of the James Clerk Maxwell Telescope (JCMT), in order to search for the evidence related to the possible flow motions along the filament and/or the radial accretion (or infalling motions) of gas material toward the dense cores from their surrounding filamentary cloud. In L1544, the velocity gradient of 1.6 km s-1 pc-1 toward the core was measured in a small branch of filament lying on a radial direction of main filament while no velocity gradient along the main axis of filament in both 13CO and C18O lines. In L694-2, we found the velocity gradient of 0.6 km s-1 pc-1 along the filament in only 13CO lines. The projected accretion rate of ~6 M◉ Myr-1 was estimated in both cases. The infall (or radially contracting) velocity of gas material was measured ~0.16 km s-1 in both 13CO and HCO+ lines and in both L1544 and L694-2, which leads to estimate a mass infall rate of ~20 M◉ Myr-1. Our analysis suggests that our targets are at a stage where the gravitational contraction dominates the mass accretion through the surrounding filamentary cloud. This is consistent with the fact that our targets are highly evolved prestellar cores on a verge of star formation. More detailed results will be presented at the meeting.

• Smart Structures and Systems
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• v.15 no.2
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• pp.469-488
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• 2015

Thermal loads, especially thermal gradients, have a considerable effect on the behaviors of large-scale bridges throughout their lifecycles. Bridge design specifications provide minimal guidance regarding thermal gradients for simple bridge girders and do not consider transversal thermal gradients in wide girder cross-sections. This paper investigates the three-dimensional thermal gradients of arch bridge girders by integrating long-term field monitoring data recorded by a structural health monitoring system, with emphasis on the vertical and transversal thermal gradients of wide concrete-steel composite girders. Based on field monitoring data for one year, the time-dependent characteristics of temperature and three-dimensional thermal gradients in girder cross-sections are explored. A statistical analysis of thermal gradients is conducted, and the probability density functions of transversal and vertical thermal gradients are estimated. The extreme thermal gradients are predicted with a specific return period by employing an extreme value analysis, and the profiles of the vertical thermal gradient are established for bridge design. The transversal and vertical thermal gradients are developed to help engineers understand the thermal behaviors of concrete-steel composite girders during their service periods.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.599-602
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• 2003

A new technique is presented to construct predictive models of plasma etch processes. This was accomplished by combining a backpropagation neural network (BPNN) and a random generator (RC). The RG played a critical role to control neuron gradients in the hidden layer, The predictive model constructed in this way is referred to as a randomized BPNN (RG-BPNN). The proposed scheme was evaluated with a set of experimental plasma etch process data. The etch process was characterized by a 2$^3$ full factorial experiment. The etch responses modeled are 4, including aluminum (Al) etch rate, profile angle, Al selectivity, and do bias. Additional test data were prepared to evaluate model appropriateness. The performance of RC-BPNN was evaluated as a function of the number of hidden neurons and the range of gradient. for given range and hidden neurons, 100 sets of random neuron gradients were generated and among them one best set was selected for evaluation. Compared to the conventional BPNN, the proposed RC-BPNN demonstrated about 50％ improvements in all comparisons. This illustrates that the RG-BPNN of multi-valued gradients is an effective way to considerably improve the predictive ability of current BPNN of single-valued gradient.

• Journal of Korean Neurosurgical Society
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• v.30 no.3
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• pp.381-383
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• 2001

Neurological symptoms may develope when the blood urea nitrogen is lowered too rapidly by hemodialysis. It is known that these symptoms, known as dialysis disequilibrium are associated with cerebral edema. However, the pathogenesis of brain swelling and neurological deterioration after rapid hemodialysis is controversial. The reverse urea hypothesis suggests that hemodialysis removes urea more slowly from the brain than from the plasma, creating an osmotic gradient that results in cerebral edema. The idiogenic osmole hypothesis proposes that an osmotic gradient between brain and plasma develops during rapid dialysis because of newly formed brain osmoles. Authors report a such case and discuss the possible mechanism and preventive methods.

• Korean Journal of Microbiology
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• v.30 no.6
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• pp.524-527
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• 1992

Synechococcus sp. cyanophage was isolated from Baekwoon reservoir located in KyonggiDo. The cyanophage was purified by employing ultrafiltration. differential centrifugation. and sucrose density gradient centrifugation. Electron microscopic observation indicated that the sizes of its isometric head and contractile tail are 89 nm and] II nm. respectively. which means that the isolated cyanophage is included in the group. Myoviridae. The cyanophage maintained the stability of more than 50 percent from $20^{\circ}C$ to $40^{\circ}C$ and from pH 5 to 8. and had the maximal infectivity at $30^{\circ}C$ and pH 9 implying its ecological significance.

• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.908-912
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• 2014

Microgratings whose diffracted field at a fixed angle generate IR spectra of $SF_6$ or $NH_3$ were fabricated by MEMS techniques for the purpose of IR correlation spectroscopy. Each micrograting was composed of 1441 reflecting lines in the area of $19.2{\times}19.2mm^2$. The depth profile of the line elements was determined with a gradient searching method that was described in our previous publication (J. Mod. Opt. 2013, 60, 324-330), and was discretized into 16 levels between 0 and $6.90{\mu}m$. The diffraction field from a given depth profile was calculated with Fraunhofer equation. The fabricated microgratings showed errors in the depth and the width within acceptable ranges. As the result, the diffracted IR spectrum of each micrograting matched well with its target reference spectrum within spectral resolution of our optical setup.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.1 s.256
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• pp.129-138
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• 2007

In this paper, a modified sensitivity control for the semi-active suspension system with a magneto-rheological (MR) damper is investigated. A 2-d.o.f quarter-car model together with a 6th order polynomial model for the MR damper is considered. For the purpose of suppressing the vertical acceleration of the sprung mass, the square of the vertical acceleration is defined as a cost function and a modified sensitivity control that updates the current input in the negative gradient of the cost function is proposed. The implementation of the proposed algorithm requires only the measurement of the relative displacement of the suspension deflection. The local stability of equilibria of the closed loop nonlinear system is proved by investigating the eigenvalues of the linearized ones. Through simulations, the passive suspension, the skyhook control, and the proposed modified sensitivity control are compared.

• Journal of the Korea Institute of Building Construction
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• v.8 no.4
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• pp.115-121
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• 2008

The present study performed low-pressure steam curing with mortar specimens in order to examine the temperature profile and strength development of steam curing in high-strength specimens of 100MPa. In addition, as a basic research to utilize PC products, we examined the effects of curing temperature and time in steam curing cycle on strength development resulting from the hydration of cement within the range of high strength by changing four factors affecting the quality of PC displacement time, peak curing temperature, peak temperature duration, and ascending and descending gradient of temperature - in various patterns, and analyzed the optimal strength development characteristic based on the relation between temperature profile and strength development. With regard to the high-temperature curing characteristic of PC, we performed an experiment on the strength characteristic according to the temperature profile of high-strength mortar, and from the results of the experiment according to curing characteristic, displacement time, peak curing temperature, peak temperature duration, and ascending and descending gradient of temperature, we drew conclusions as follows.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10C
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• pp.1000-1009
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• 2007

This paper presents a content adaptive interpolation (CAI) for intra deinterlacing. The CAI consists of three steps: pre-processing, content classification, and adaptive interpolation. There are also three main interpolation methods in our proposed CAI, i.e. modified edge-based line averaging (M-ELA), gradient directed interpolation (GDI), and window matching method (WMM). Each proposed method shows different performances according to spatial local features. Therefore, we analyze the local region feature using the gradient detection and classify each missing pixel into four categories. And then, based on the classification result, a different do-interlacing algorithm is activated in order to obtain the best performance. Experimental results demonstrate that the CAI method performs better than previous techniques.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.8
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• pp.423-431
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• 2000

This paper presents a systematic approach to the input-output data-based fuzzy modeling for the complex and uncertain nonlinear systems, in which the conventional mathematical models may fail to give the satisfying results. To do this, we propose a new method that can yield a successful fuzzy model using a mGA hybrid schemes with a fine-tuning method. We also propose a new coding method fo chromosome for applying the mGA to the structure and parameter identifications of fuzzy model simultaneously. During mGA search, multi-purpose fitness function with a penalty process is proposed and adapted to guarantee the accurate and valid fuzzy modes. This coding scheme can effectively represent the zero-order Takagi-Sugeno fuzzy model. The proposed mGA hybrid schemes can coarsely optimize the structure and the parameters of the fuzzy inference system, and then fine tune the identified fuzzy model by using the gradient descent method. In order to demonstrate the superiority and efficiency of the proposed scheme, we finally show its applications to two nonlinear systems.