• Journal of Korean Society of Forest Science
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• v.89 no.5
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• pp.564-575
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• 2000

This study was carried out to reveal characteristics of long-term runoff by using HYCYMODEL in a small forested watershed. From May to September in 1998 and in 1999, the fitness of HYCYMODEL and runoff characteristics were estimated by HYCYMODEL using rainfall and discharge at the experimental watershed. The function of stage and discharge in the experimental watershed was determined as following equation $Q=11.148H^{2.5867}$($R^2=0.9956$). From May to September in 1998 and in 1999, the runoff rates were 57.7% in 1998 and 87.1% in 1999 at the experimental watershed. The discharge was assumed to be increased because of rainfall intensity difference and thinning. By applicability test, the HYCYMODEL showed good estimation of runoff by optimized fifteen parameters. Comparing runoff characteristics before and after thinning by calculating through HYCYMODEL, direct runoff and base runoff increased 4%, 7%, respectively as evapotranspiration decreased 11%. Parameters $D_{50}$ and $K_h$, which were related to the direct run, and a parameter $K_u$, which was related to the baseflow, were assumed to indicate that forest was changed by the effect of thinning and weathering process of bed rock.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.10-20
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• 2007

For spacecraft attitude control, reaction wheel (RW) steering laws with more than three wheels for three-axis attitude control can be derived by using a control allocation (CA) approach.1-2 The CA technique deals with a problem of distributing a given control demand to available sets of actuators.3-4 There are many references for CA with applications to aerospace systems. For spacecraft, the control torque command for three body-fixed reference frames can be constructed by a combination of multiple wheels, usually four-wheel pyramid sets. Multi-wheel configurations can be exploited to satisfy a body-axis control torque requirement while satisfying objectives such as minimum control energy.1-2 In general, the reaction wheel steering laws determine required torque command for each wheel in the form of matrix pseudo-inverse. In general, the attitude control command is generated in the form of a feedback control. The spacecraft body angular rate measured by gyros is used to estimate angular displacement also.⁵ Combination of the body angular rate and attitude parameters such as quaternion and MRPs(Modified Rodrigues Parameters) is typically used in synthesizing the control command which should be produced by RWs.¹ The attitude sensor signals are usually corrupted by noise; gyros tend to contain errors such as drift and random noise. The attitude determination system can estimate such errors, and provide best true signals for feedback control.⁶ Even if the attitude determination system, for instance, sophisticated algorithm such as the EKF(Extended Kalman Filter) algorithm⁶, can eliminate the errors efficiently, it is quite probable that the control command still contains noise sources. The noise and/or other high frequency components in the control command would cause the wheel speed to change in an undesirable manner. The closed-loop system, governed by the feedback control law, is also directly affected by the noise due to imperfect sensor characteristics. The noise components in the sensor signal should be mitigated so that the control command is isolated from the noise effect. This can be done by adding a filter to the sensor output or preventing rapid change in the control command. Dynamic control allocation(DCA), recently studied by Härkegård, is to distribute the control command in the sense of dynamics⁴: the allocation is made over a certain time interval, not a fixed time instant. The dynamic behavior of the control command is taken into account in the course of distributing the control command. Not only the control command requirement, but also variation of the control command over a sampling interval is included in the performance criterion to be optimized. The result is a control command in the form of a finite difference equation over the given time interval.⁴ It results in a filter dynamics by taking the previous control command into account for the synthesis of current control command. Stability of the proposed dynamic control allocation (CA) approach was proved to ensure the control command is bounded at the steady-state. In this study, we extended the results presented in Ref. 4 by adding a two-step dynamic CA term in deriving the control allocation law. Also, the strict equality constraint, between the virtual and actual control inputs, is relaxed in order to construct control command with a smooth profile. The proposed DCA technique is applied to a spacecraft attitude control problem. The sensor noise and/or irregular signals, which are existent in most of spacecraft attitude sensors, can be handled effectively by the proposed approach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.4
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• pp.23-32
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• 1988

The rates of infiltration contributed to the flow fo water in an unconfined aquifer under the partially penetrated stream at an ungaged station and the corresponding base flow in channel are coupled by using the hydraulic and/or hydrologic characteristics obtained from the geomorphologic and soil maps. For the determination of groundwater flow, the linearized model which is originally Boussinesq's nonlinear equation is applied in this study. Also, a stream flow routing model for base flow in channel is based on a simplification of the Saint-venant. The distributed runoff model with piecewise spatial uniformity is presented for obtaining its solution based on a finite difference technique of the kinematic wave equations. The method developed in this study was tested to the Bocheong watershed(area : $475.5km^2$) of the natural stream basin which is one of tributaries in Geum River basin in Korea. As a result, it is suggested that the rationality of hydro-graph separation according to a wide variability in hydrogeologic properties be worked out as developing the physically based subsurface model. The results of the present model are shown to be possible to simulate a base flow due to an arbitrary rate of infiltration for ungaged basins.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.221-232
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• 2011

Applicability of three soil erosion models for burnt hillslopes was evaluated. The models were estimated with the data from plots established after tremendous wildfire occurred in the east coastal region. Soil erosion and surface runoff were simulated by the Water Erosion Prediction Project (WEPP) and the Revised Universal Soil Loss Equation (RUSLE) of application mode for disturbed forest areas and the Soil Erosion Model for Mountain Areas (SEMMA) developed for burnt hillslopes. Simulated sediment yield and surface runoff were compared with the measured those. In maximum value of sediment yield, three models was under-predicted and RUSLE and WEPP had difference of over two times. SEMMA showed the best model response coefficient, determination coefficient and the model efficiency. In application of models to the soil erosion according to the elapsed year after wildfire, all models were underestimated in initial stage disturbed by wildfire. Evaluation of models in this burnt hillslopes was shown the tends to under-predict soil erosion for larger measured values. Although a lot of sediment can be generated in small rainfall event as fine-grained soil of the high water repellency was exposed excessively right after wildfire, this under-prediction was shown that those models have a limit to estimate the weighted factors by wildfire.

• Journal of KSNVE
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• v.8 no.5
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• pp.964-973
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• 1998

In this paper we propose a levitation and imbalance compensation controller design methodology of magnetic bearing system. In order to achieve levitation and elimination of unbalance vibartion in some operation speed we use the discrete-time Q-parameterization control. When rotor speed p = 0 there are no rotor unbalance, with frequency equals to the rotational speed. So in order to make levitatiom we choose the Q-parameterization controller free parameter Q such that the controller has poles on the unit circle at z = 1. However, when rotor speed p $\neq$ 0 there exist sinusoidal disturbance forces, with frequency equals to the rotational speed. So in order to achieve asymptotic rejection of these disturbance forces, the Q-parameterization controller free parameter Q is chosen such that the controller has poles on the unit circle at z = $exp^{ipTs}$ for a certain speed of rotation p ( $T_s$ is the sampling period). First, we introduce the experimental setup employed in this research. Second, we give a mathematical model for the magnetic bearing in difference equation form. Third, we explain the proposed discrete-time Q-parameterization controller design methodology. The controller free parameter Q is assumed to be a proper stable transfer function. Fourth, we show that the controller free parameter which satisfies the design objectives can be obtained by simply solving a set of linear equations rather than solving a complicated optimization problem. Finally, several simulation and experimental results are obtained to evaluate the proposed controller. The results obtained show the effectiveness of the proposed controller in eliminating the unbalance vibrations at the design speed of rotation.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.15-26
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• 2014

This study focus on a economic value of the Big Data technologies by real options model using big data technology company's stock price to determine the price of the economic value of incremental assessed value. For estimating stochastic process of company's stock price by big data technology to extract the incremental shares, Generalized Moments Method (GMM) are used. Option value for Black-Scholes partial differential equation was derived, in which finite difference numerical methods to obtain the Big Data technology was introduced to estimate the economic value. As a result, a option value of big data technology investment is 38.5 billion under assumption which investment cost is 50 million won and time value is a about 1 million, respectively. Thus, introduction of big data technology to create a substantial effect on corporate profits, is valuable and there are an effects on the additional time value. Sensitivity analysis of lower underlying asset value appear decreased options value and the lower investment cost showed increased options value. A volatility are not sensitive on the option value due to the big data technological characteristics which are low stock volatility and introduction periods.

• The Korean Journal of Nuclear Medicine Technology
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• v.16 no.2
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• pp.156-161
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• 2012

Purpose : IRMA method for the experimental reagents, as set out in the manual settings for doing and reporting the test results should, in principle. But many of the reagents allows for the setting of the plot does not have a lot of information. Depending on the angle setting of the table make a difference in test results and what settings are best suited to investigate. Materials and Methods : The hospital has Boramae DREAM10, Cobra, SR-300's using the Immunotech TSH reagents have been compared with the measurements. Since then there using EXCEL calculation of the equipment compared with the measurement. Results : In the comparison between each piece of equipment 1.SR-300: DREAM 10 y = 1.1376x - 0.046 (LOG-LOGIT), 2.SR-300: COBRA y = 1.0985x + 0.042 (LOG-LOG) 3.DREAM10: COBRA y = 0.965x + 0.0887 (LOG-LOG) was the result. In all charts the same X, Y axis, X values were good in general when you have. Linear-Logit value of Cobra Dream10 and Excel tends to match the calculated values provided. Conclusion : Is to guide the B / max, B / Total Logit Y axis of the chart is set to draw a look at the value equation when the X-axis LOG a high concentration are disadvantages rising urgently toward the slope. Linear-Logit plots close to the straight line has a curve. If you have a chart to guide on setting AS setting and therefore, set to guide the absence of information on the need to set up the experiment are thought to pass through.

• Progress in Superconductivity and Cryogenics
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• v.15 no.2
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• pp.34-38
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• 2013

AC Losses for face to face stacks of four identical coated conductors (CCs) were numerically calculated using the H-formulation combined with the E-J power law and the Kim model. The motive sample was the face to face stack of four 2 mm-wide CC tapes with 2 ${\mu}m$ thick superconducting layer of which the critical current density, $J_c$, was $2.16{\times}10^6A/cm^2$ on IBAD-MgO template, which was suggested for the mitigation of ac loss as a round shaped wire by Korea Electrotechnology Research Institute. For the calculation the cross section of the stack was simply modeled as vertically aligned 4 rectangles of superconducting (SC) layers with $E=E_o(J(x,y,t)/J_c(B))^n$ in x-y plane where $E_o$ was $10^{-6}$ V/cm, $J_c$(B) was the field dependence of current density and n was 21. The field dependence of the critical current of the sample measured in four-probe method was employed for $J_c$(B) in the equation. The model was implemented in the finite element method program by commercial software. The ac loss properties for the stacks were compared with those of single 4 cm-wide SC layers with the same critical current density or the same critical current. The constraint for the simulation was imposed in two different ways that the total current of the stack obtained by integrating J(x,y,t) over the cross sections was the same as that of the applied transport current: one is that one fourth of the external current was enforced to flow through each SC. In this case, the ac loss values for the stacks were lower than those of single wide SC layer. This mitigation of the loss is attributed to the reduction of the normal component of the magnetic field near the SC layers due to the strong expulsion of the magnetic field by the enforced transport current. On the contrary, for the other case of no such enforcement, the ac loss values were greater than those of single 4cm-wide SC layer and. In this case, the phase difference of the current flowing through the inner and the outer SC layers of the stack was observed as the transport current was increased, which was a cause of the abrupt increase of ac loss for higher transport current.

• The Journal of Korean Academy of Prosthodontics
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• v.27 no.2
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• pp.11-36
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• 1989

Mandibular movements are guided mainly by three determinants, namely the two posterior controls (the Temporomandibular joints) and the anterior control (the incisal guidance). The aim of this study was to evaluate the incisal guide angle in effort to reconcile a patient's condylar guide angle and incisu guide angle, to develop criteria for incisal guidance in clinical practice. 48 subjects (male 33, female 15) with intact intercuspation, without past history and symptoms of stomatognathic system, were selected for this study. All of the subjects had not anterior prostheses. The sagittal condylar guide angles and incisal guide angles were measured and estimated statistically by cephalogram and articulator (Whip-Mix 8500A). The results of this study were as follows: 1. Average of condylar guide angle was 43.33 degree by cephalogram, and was 35.18 degree by articulator. 95% confidence interval was from 40.43 to 46.23 degrees in cephalogram and was from 32.98 to 37.38 degrees in articulator. 2. Average of incisal guide angle was 51.51 degree by cephalogram, and was 44.11 degree by articulator. 95% confidence interval was from 49.12 to 54.95 degrees in cephalogram and was from 40.67 to 47.56 douses in articulator. 3. Difference between condylar and incisal guide angle was 8.18 degree by cephalogram, and was 8.94 degree by articulator. 95% confidence interval was from 4.61 to 11.74 degrees in cephalogram and was from 4.90 to 12.98 degrees in articulator. 4. In case of the incisal guide angle steeper than condylar guide angle, subjects were 69% (33 of 48) in cephatogram and 75% (36 of 48) in articulator. 5. By the multiple regression equation, condylar guide angle was more influenced by the anterior teeth. 6. When the mandible protrudes from the intercuspal position to the edge to edge position the incisal linear movement was 4.18mm (S.D.:1.30mm) and the condylar linear movement was 4.38mm (S.D.:1.26mm).

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.15 no.5
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• pp.203-220
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• 2020

The purpose of this study is to examine the importance of entrepreneurs' well-being, and to propose several ways to improve it. First, the factors influencing entrepreneurs' well-being were explored via previous literature review, and positive psychological capital based on positive psychology was selected as the main factor. In addition, the hypotheses were formulated and the research model was constructed by selecting authentic leadership, mastery goal orientation, and social support as the antecedents predictably associated with positive psychological capital. To empirically analyze the proposed model, a questionnaire survey was conducted for the entrepreneurs who fulfilled the training/coaching/consulting programs offered by the Youth Startup Academy. By using the collected 133 responses, PLS-Structural Equation Analysis, PLS-Multi Group Analysis(MGA), and PLS-Importance-Performance Map Analysis(IPMA) were performed. As a result, it was found that positive psychological capital had a high causal relationship with the well-being of entrepreneurs; and authentic leadership and mastery goal orientation had a positive effect on positive psychological capital. However, the statistical significance of the impact of social support has not been verified. While differences in causality between early and growing stages of start-ups only acted as sub-factors of positive psychological capital, the aforementioned three antecedents showed a significant difference for hope and optimism, respectively. This study expanded the topic of entrepreneurship-related research, which mostly focuses on identifying the performance factors of start-ups. It is meaningful in that it empirically verified the causality model constructed by exploring the factors with respect to the mental well-being of entrepreneurs, which is a main theme in the entrepreneurship-related research. These results found in the current study will render practical insights to entrepreneurs, researchers, and educators.