• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.276-290
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• 2024

A study of the transition from transitory state to steady state in DSSCs based on natural dyes is presented; cochineal was used as dye and Li⁺, Na⁺, and K⁺ were the ions added to the electrolyte. The photocurrent profiles were obtained as a function of time. Several DSSCs were prepared with different cations and their role and the transitory-to-steady transition was determined. A novel hybrid charge carrier source model based on the Heaviside function H(t) and the Lambert-Beer law, was developed and applied to analysis of the transient response of the output photocurrent. Additionally, the maximum effective light absorption coefficient α and the electronic extraction rate κ for each ion were determined: ${\alpha}_{Li^+,Na^+,K^+}\,=\,(0.486,\,0.00085,\,0.1126)\,cm^{-1}$, and also the electronic extraction rate ${\kappa}^{Li^+,Na^+,K^+}_{ext.}\,=\,(1410,\,19.07,\,19.69)\,cm\,s^{-1}$. The impedance model using Fick's second law was developed for carrier recombination to characterize the photocurrent.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.3
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• pp.109-121
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• 2004

This paper presents an optimal design method for structure-borne durability of a vehicle body structure. Structure-borne durability design requires a new design that can increase fatigue lives of critical areas in a structure and must prohibit transition phenomenon of critical areas that results from modification of the structure at the same time. Therefore, the optimization problem fur structure-borne durability design are consists of an objective function and design constraints of 2 types; type 1-constraint that increases fatigue lives of the critical areas to the required design limits and type 2-constraint that prohibits transition phenomenon of critical areas. The durability design problem is generally dynamic because a designer must consider the dynamic behavior such as fatigue analyses according to the structure modification during the optimal design process. This design scheme, however, requires such high computational cost that the design method cannot be applicable. For the purpose of efficiency of the durability design, we presents a method which carry out the equivalent static design problem instead of the dynamic one. In the proposed method, dynamic design constraints for fatigue life, are replaced to the equivalent static design constraints for stress/strain coefficients. The equivalent static design constraints are computed from static or eigen-value analyses. We carry out an optimal design for structure-borne durability of the newly developed bus and verify the effectiveness of the proposed method by examination of the result.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.10
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• pp.47-55
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• 1999

In this paper, a new function hazard elimination algorithm is proposed for asynchronous circuit synthesis. In previous approach, function hazard is eliminated by using state graph which is obtained from the state assignment on STG(signal transition graph) representing transition relationship among signals. These algorithms can use conventional hazard removal and synthesis method applied in synchronous system, but it has much computational complexity and takes much time to handle the state graph. Although some hazard elimination algorithm from STG were proposed, it could not reduce the area overhead due to the addition of new signals. The proposed algorithm eliminate function hazard directly on STG and also control the number of minterms and product-term of added signal in order to minimize the area overhead. Experimental results on benchmark data shows that overall circuit area after hazard elimination is decreased about 15% on the average than that of previous method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2310-2316
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• 2010

This paper presents an application of retiming to model checking, a branch of formal verification. Retiming can change the transition relation of a circuit without changing its input-output behaviour by relocating its registers. With the retiming, a given circuit can have a different structure more adequate for model checking. This paper proposes a cost function to reflect the number of registers and the characteristic of its transition relation and develops a heuristic annealing algorithm to search efficiently the circuit structures obtained by retiming. Experimental results show that the proposed method can improve the model checking performance.

• Korean Institute of Interior Design Journal
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• v.15 no.4 s.57
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• pp.37-45
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• 2006

The purpose of this study is to stand assembly the meaning and function of entry space with analysing their social and cultural characteristic. The entry space is the linkable place between inner space and out space, and that is the transition place to be experienced two opposing characteristic. Till now the entry space has not taken effect as symbol needed to the resident and observer, and that has been a tendency to shrink as the minimal sign of entrance. So thus, it is in need of studying the entry space's specific and characterizing structurally as expanded function. For the purpose, this study define newly the meaning, function and composition of entry space in an apartment building, and try to find how to reinforce a resident identity. This study propose justification that the entry space isn't boxing space minimally but enforcing symbol presented clearness of composition and vital character.

• Journal of the Korean institute of surface engineering
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• v.51 no.3
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• pp.185-190
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• 2018

Dopant-free silicon heterojunction solar cells using Transition Metal Oxide(TMO) such as Molybdenum Oxide($MoO_X$) and Vanadium Oxide($V_2O_X$) have been focused on to increase the work function of TMO in order to maximize the work function difference between TMO and n-Si for a high-efficiency solar cell. One another way to increase the work function difference is to control the silicon wafer resistivity. In this paper, dopant-free silicon heterojunction solar cells were fabricated using the wafer with the various resistivity and analyzed to understand the effect of n-Si work function. As a result, it is shown that the high passivation and junction quality when $V_2O_X$ deposited on the wafer with low work function compared to the high work function wafer, inducing the increase of higher collection probability, especially at long wavelength region. the solar cell efficiency of 15.28% was measured in low work function wafer, which is 34% higher value than the high work function solar cells.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.45.3-46
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• 2015

Space weathering agents such as micrometeoroids and solar wind particles continuously age the uppermost regolith of the lunar surface by comminuting as well as darkening and reddening. Among several maturity indices, we investigate median grain size () and optical maturity (OMAT) of the crater rim walls. Crater rim wall is the most immature place among the impact crater features because the vertical mixing process by mass-movement can enhance the gardening of regolith and the supply of immature materials in the deeper layer to the surface. More than 140 simple and complex craters were considered. Both and OMAT values of the inner rim wall initially increase as the crater size increases until ~10-20 km, then decrease. This transition crater size happens to correspond to the transition diameter from simple to complex craters. For larger craters, i.e., complex craters, it is clear that the inner rim wall of the craters formed in recent eras tend to remain fresh and become mature along with time. For the simple crater case, smaller craters are more mature, which is opposite to the case of complex craters. This is thought to be because smaller craters become flattened more quickly, thus have smaller vertical mixing in the regolith due to mass-movement. We will also discuss on the maturity indices of the crater rim walls at high latitudes as a function of the position angle to see the latitude dependence of the space weathering process.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.46-52
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• 2010

Derivative analysis, based on the derivative of the drawdown as a function of time (i.e., rate of drawdown change), was applied to the evaluation of hydraulic parameters of the aquifer as an aid of the aquifer test interpretation based on the Theis solutions. Pumping tests were conducted at a coastal fractured aquifer in Muan county, Korea, of which the drawdown data, measured at the two observation wells, were used for derivative analysis. Wellbore storage and transition period were hard to identify at conventional log-log and semi long plots, but was easily recognized by distinctive curves of positive unit slope, hump and negative unit slope in the derivative plot. For the observation well of OW-2 at which wellbore storage and transition lasted over an hour, conventional aquifer analysis would suffer from the uniqueness problems and in further result in erroneous hydraulic parameters. Derivative analysis was found to be effective for distinguishing the drawdown data directly reflecting the aquifer property from those reflecting non aquifer effects such as wellbore storage and transition, which offers a unified methodology to yield correct hydraulic parameters from aquifer test data.

• Archives of design research
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• v.19 no.2 s.64
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• pp.251-260
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• 2006

Rapid development of electronic technology has made it possible to perform various function. But this technology made it increase it's complexity. Therefore, It was important to identify usability problem in interface design. The quality of interface to promote the efficient interaction should be evaluated with regard to users' cognitive characteristics. So, in this paper, washing machine, that is one of the most useful electronic home application was studied menu structure on interface and it's operational states transition. At first, an cognitive menu structure is identified with users' conceptual similarity of the main function of washing machine. Then three washing machines was selected to compare with the cognitive menu structure. And, we were analyzed how operational state of the washing machine was transfered. As a result, we can be revealed that menu operational method based on the cognitive structure was consistent with the user's preferred operational method during the experimental tasks and the users and designers had a different knowledge of an it's function structure. These results will be useful to design the washing machine interface.

• International Journal of Control, Automation, and Systems
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• v.6 no.1
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• pp.109-118
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• 2008

We present two estimators for discrete non-Gaussian and nonstationary probability density estimation based on a dynamic Bayesian network (DBN). The first estimator is for off line computation and consists of a DBN whose transition distribution is represented in terms of kernel functions. The estimator parameters are the weights and shifts of the kernel functions. The parameters are determined through a recursive learning algorithm using maximum likelihood (ML) estimation. The second estimator is a DBN whose parameters form the transition probabilities. We use an asymptotically convergent, recursive, on-line algorithm to update the parameters using observation data. The DBN calculates the state probabilities using the estimated parameters. We provide examples that demonstrate the usefulness and simplicity of the two proposed estimators.