• Journal of Multimedia Information System
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• v.5 no.4
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• pp.235-244
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• 2018

Potential maximum soil moisture retention (S) is a dominant parameter in the Soil Conservation Service (SCS; now called the USDA Natural Resources Conservation Service (NRCS)) runoff Curve Number (CN) method commonly used in hydrologic modeling for event-based flood forecasting (SCS, 1985). Physically, S represents the depth [L] soil could store water through infiltration. The depth of soil moisture retention will vary depending on infiltration from previous rainfall events; an adjustment is usually made using a factor for Antecedent Moisture Conditions (AMCs). Application of the method for continuous simulation of multiple storms has typically involved updating the AMC and S. However, these studies have focused on a time step where S is allowed to vary at daily or longer time scales. While useful for hydrologic events that span multiple days, this temporal resolution is too coarse for short-term applications such as flash flood events. In this study, an approach for deriving a time-variable potential maximum soil moisture retention curve (S-curve) at hourly time-scales is presented. The methodology is applied to the Napa River basin, California. Rainfall events from 2011 to 2012 are used for estimating the event-based S. As a result, we derive an S-curve which is classified into three sections depending on the recovery rate of S for soil moisture conditions ranging from 1) dry, 2) transitional from dry to wet, and 3) wet. The first section is described as gradually increasing recovering S (0.97 mm/hr or 23.28 mm/day), the second section is described as steeply recovering S (2.11 mm/hr or 50.64 mm/day) and the third section is described as gradually decreasing recovery (0.34 mm/hr or 8.16 mm/day). Using the S-curve, we can estimate the hourly change of soil moisture content according to the time duration after rainfall cessation, which is then used to estimate direct runoff for a continuous simulation for flood forecasting.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.77-80
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• 1999

This paper deals with a design of a symbol timing recovery circuit of QAM using the interpolation in AWGN channel. To reduce timing jitter and the amount of processing data, we employ MGA (Modified Gardner Algorithm) as a symbol timing error detector which is called NDA(Nondecision Directed Algorithm). We show the characteristics (S-curve and the variance) of timing error detector with the roll-off factor of a shaping filter, which are compared with GA. Also, we compare the BER curve of interpolation method with that of ideal case. The performance of the STR is shown to be close to that of ideal case. This result shows that this method can be useful to implement symbol timing recovery circuit for multi-level modulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11A
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• pp.1864-1871
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• 2001

In this paper, new symbol timing recovery algorithm is proposed, which is suitable for the digital communication system with Multi-level PAM signals. In the newly proposed symbol timing recovery algorithm, the timing error function is derived by compensating the several difference values between sampled symbol and neighboring symbol every symbol period with mid samples and decided symbol values. Conventional symbol timing recovery methods did not work well in Multi-level PAM signals, but the newly proposed method can be applied to Multi-level PAM signals as well as QPSK. For the performance analysis, the derived variance of the timing error function and the timing error characteristics of S-curve show that the proposed method has better performance than Gardner method and the modified Gardner method.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.33 no.4
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• pp.167-177
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• 2010

Recent competitive and technological changes during the past decade have accelerated the need for better capital recovery methods. Competition and technology have together shortened the expected lives of property which could not have been forecasted several years ago. Since the usage of technological growth models has been prevalent in various technological forecasting environments, the various forms of growth models have become numerous. Of six such models studied, some models do significantly better than others, especially at low penetration levels in predicting future levels of growth. A set of criteria for choosing an appropriate model for technological growth models was developed. Two major characteristics of an S-shaped curve were elected which differentiate the various models; they are the skewness of the curve and underlying assumptions regarding the variance of error structure of the model.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.107-114
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• 2017

The performance of polymer electrolyte membrane fuel cell (PEMFC) could be deteriorated when fuel contains contaminants such as carbon monoxide (CO) or hydrogen sulfide ($H_2S$). Generally, $H_2S$ is introduced in hydrogen by steam reforming of hydrocarbon which has mercaptan as odorant. $H_2S$ poisoning effect on PEMFC performance was examined on this study. Pure hydrogen injection, voltage cycling and water circulation methods were compared as performance recovery methods. The PEMFC performance was analyzed using electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Pure hydrogen injection and voltage cycling methods showed low recovery ratio, however, water circulation method showed high recovery ratio over 95%. Because anode was directly poisoned by $H_2S$, anode water circulation showed higher recovery ratio compared to the other methods. Water circulation method was developed to recover PEMFC performance from $H_2S$ poisoning. This method could contribute to PEMFC durability and commercialization.

• Transactions of Materials Processing
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• v.22 no.8
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• pp.470-476
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• 2013

The aim of the current study was to predict shape recovery behavior of Ni-Ti shape memory alloy (SMA) wire after loading-unloading and after wire drawing. The superelasticity of SMA was analyzed by a hyper-elastic model for the Mullins effect using ABAQUS. Firstly, tensile tests and loading-unloading tests of the Ni-Ti SMA wire with a diameter 1.0 mm were performed using an MTS servo-hydraulic tester. The parameters for the Mullins effect were computed by ABAQUS based on curve-fitting of the loading-unloading test data. The proposed FE-model predicted the shape recovery of Ni-Ti SMA after wire drawing. Finally, the effectiveness of the model was verified by drawing experiments. The wire drawing experiments using the Ni-Ti SMA were conducted on a drawing machine(1ton, 50mm/s). In order to evaluate the shape recovery of Ni-Ti SMA, the drawn wires are annealed for 30min at $450^{\circ}C$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.11
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• pp.1299-1310
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• 1992

Recently, digital realizations of timing recovery circuits for digital data transmission are of growing interest. As a result of digital realization of timing recovery circuits, new digital algorithms for timing error detection are required. In this paper, we present a new digital Angular Form(AF) algorithm which can be directly applied to QPSK modulation technique. AF algorithm is basically developed on the concepts of detected angle form and transition logic table. We evaluated the performance of this algorithm by Monte-Carlo simulation method under Gaussian and Impulsive noise environments. From the performance evaluation result, we show that the performance of AF Algorithm is better than that of Gardner in BER, RMS jitter, S-curve.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.11
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• pp.1-10
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• 1993

A Study on New Digital In this paper, we propose a new Angular Form Carrier Recovery Loop(AFCR loop) for PSK modulation technique. AF CR loop includes detected angle symbol and Multi Level Hardlimiter. Using zero crossing DPLL, we model 1st 2nd AF CR loop, and also derive SCurve. In order to prove steady state operation of AF CR loop, we evaluate performance of this loop by Monte-Carlo and analytical simulation method. We also compare the performance of AF CR loop to that of other loop in terms of acquisition, S-Curve, and RMS jitter. From the comparison result, we verify that the performance of AF CR loop operates well in steady state.

• Proceedings of the Korean Magnestics Society Conference
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• 2000.09a
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• pp.397-406
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• 2000

Hopkinson effect in the HDDR-treated Nd$\sub$15/Fe$\sub$77/B$\sub$8/ alloy was examined in detail by means of a thermomagnetic analysis with low magnetic field (600 Oe). The emergence and magnitude of maximum in magnetisation in the thermomagnetic curve due to the Hopkinson effect was correlated to the grain structure and coercivity of the HDDR-treated material. the HDDR-treated materials showed clear Hopkinson effect (maximum in magnetisation just below the Curie temperature of the Nd$\sub$2/Fe$\sub$14/B phase) on heating in the thermomagnetic curve. Magnitude of the magnetisation rise due to the Hopkinson effect became smaller as the recombination time increased. The magnetisation recovery at room temperature on cooling from above the Curie temperature became smaller as the recombination time increased. The HDDR-treated materials with shorter recombination time, finer grain size and higher coercivity showed larger magnetisation maximum due to Hopkinson effect in the thermomagnetic curve.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.6
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• pp.619-628
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• 2021

In order to compare numerical analyses made by Song and Kim needed for predicting gas and water filling with experimental results we conducted an experiment to recover a test projectile (43.7 kg with a 155 mm diameter) at a velocity of 775 m/s in a soft recovery system with a length of 179 m using pressurized gas and filled water. The soft recovery system consisting of a series of pressure tubes had a diaphragm, piston, and water plug for filling the pressurized gas and water. We installed a continuous wave Doppler radar system for velocity measurements of the test projectile travelling in the pressure tubes and pressure transducers for measuring the pressure in the soft recovery system. Continuous wave Doppler radar has the advantage of achieving real-time measurements of the velocity of a test projectile. The velocity-time curve of the test projectile, measured using the continuous wave Doppler radar, and the pressure profile were compared with the numerical analysis results. The experiment results show good agreement with the numerical analysis results based on the one-dimensional Euler equation with an HLL Riemann solver.