• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.12 no.3
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• pp.42-52
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• 2013

In this study, value of VMS (Variable Message Sign) traffic information is estimated by using CVM (Contingent Valuation Method), which is developed to quantify the value of non-marketable goods in environmental economics. CVM is used to estimate the value of goods provided by a project under consideration and then the project feasibility can be indirectly examined on the basis of the estimated value. This study focuses on estimating to estimate value of traffic information provided through VMS, a part of the transportation system enhancement project by Korea Expressway Corporation which is aimed at mitigating traffic problems on expressways. In particular, this study analyzes value of information separately by trip purpose, information type, and traffic flow condition. A state preference survey was designed to estimate the value of non-marketable traffic information. To maximize reliability of the survey results, a pilot survey was taken before the main survey. The open-ended question method was adopted in capturing users' willingness-to-pay. Both Tobit and binary Probit models were applied in estimating the value of VMS traffic information and their parameters were estimated using the maximum likelihood estimation. The estimation results suggests that the value of traffic information perceived by users is 518.28 KRW.

• Journal of the Ergonomics Society of Korea
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• v.35 no.5
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• pp.371-381
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• 2016

Objective:This study aims to evaluate the features of heart rate variability (HRV) and respiratory signals as indices for a driver's drowsiness and waking status in order to develop the classification model for a driver's drowsiness and waking status using those features. Background: Driver's drowsiness is one of the major causal factors for traffic accidents. This study hypothesized that the application of combined bio-signals to monitor the alertness level of drivers would improve the effectiveness of the classification techniques of driver's drowsiness. Method: The features of three heart rate variability (HRV) measurements including low frequency (LF), high frequency (HF), and LF/HF ratio and two respiratory measurements including peak and rate were acquired by the monotonous car driving simulation experiments using the photoplethysmogram (PPG) and respiration sensors. The experiments were repeated a total of 50 times on five healthy male participants in their 20s to 50s. The classification model was developed by selecting the optimal measurements, applying a binary logistic regression method and performing 3-fold cross validation. Results: The power of LF, HF, and LF/HF ratio, and the respiration peak of drowsiness status were reduced by 38%, 22%, 31%, and 7%, compared to those of waking status, while respiration rate was increased by 3%. The classification sensitivity of the model using both HRV and respiratory features (91.4%) was improved, compared to that of the model using only HRV feature (89.8%) and that using only respiratory feature (83.6%). Conclusion: This study suggests that the classification of driver's drowsiness and waking status may be improved by utilizing a combination of HRV and respiratory features. Application: The results of this study can be applied to the development of driver's drowsiness prevention systems.

• Fire Science and Engineering
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• v.30 no.6
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• pp.31-36
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• 2016

The flash point is one of the most important properties for characterizing the fire and explosion hazard of liquid solutions. In this study, the flash points of two flammable binary mixtures, n-pentanol + n-propanol and n-pentanol + n-heptanol systems were measured using a Seta flash closed cup tester. The flash point was estimated using the methods based on Raoult's law and multiple regression analysis. The measured flash points were also compared with the predicted flash points. The absolute average errors (AAE) of the results calculated by Raout's law were $1.3^{\circ}C$ and $1.3^{\circ}C$ for the n-pentanol + n-propanol and n-pentanol + n-heptanol mixtures, respectively. The absolute average errors of the results calculated by multiple regression analysis were $0.4^{\circ}C$ and $0.3^{\circ}C$ for the n-pentanol + n-propanol and n-pentanol + n-heptanol mixtures, respectively. According to the AAE, the calculated values based on multiple regression analysis were better than those based on Raoult's law.

• Fire Science and Engineering
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• v.25 no.3
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• pp.113-118
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• 2011

The flash point is an important indicator of the flammability of a chemical. The minimum flash point behaviour (MFPB) is exhibited when the flash point of a mixture is below the flash points of the individual components. The identification of this behaviour is critical, because a hazardous situation results from taking the lowest component flash point value as the mixture flash point. In this study, the flash points for the n-butanol + n-decane and n-octane + n-propanol systems which exhibit MFPB, were measured by Tag open-cup apparatus. The experimental data were compared with the alues calculated by the Raoult's law, the van Laar equation and the Wilson equation. The calculated values based on the van Laar and Wilson equations were found to be better than those based on the Raoult's law. It was concluded that the van Laar and Wilson equations were more effective than the Raoult' law at describing the activity coefficients for non-ideal solution such as the n-butanol + n-decane and n-octane + n-propanol systems. The predictive curve of the flash point prediction model based on the Wilson equation described the experimentally-derived data more effectively than was the case when the prediction model was based upon the van Laar equation.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.1
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• pp.47-52
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• 2010

For cryptographic systems, nonlinearity is crucial since most linear systems are easily decipherable. C.Bracken, Z.Zhaetc., propose the APN(Almost Perfect Nonlinear) functions with the properties similar to those of the bent functions with perfect nonlinearity. We design two kinds of new code sequence generating algorithms using the above APN functions. And we find that the out of phase ${\tau}\;{\neq}\;0$, autocorrelation functions, $R_{ii}(\tau)$ and the crosscorrelation functions, $R_{ik}(\tau)$ of the binary code sequences generated by two new algorithms over GF(2), have three values of {-1, $-1-2^{n/2}$, $-1+2^{n/2}$}. We also find that the out of phase ${\tau}\;{\neq}\;0$, autocorrelation functions, $R_{p,ii}(\tau)$ and the crosscorrelation functions, $R_{p,ik}(\tau)$ of the nonbinary code sequences generated by the modified algorithms over GF(p), $p\;{\geq}\;3$, have also three values of {$-1+p^{n-1}$, $-1-p^{(n-1)/2}+p^{n-1}$, $-1+p^{(n-1)/2}p^{n-1}$}. We show that these code sequences have the characteristics of the correlation functions similar to those of Gold code sequences.

• Smart Media Journal
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• v.7 no.1
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• pp.37-44
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• 2018

Utilizing sequence control and numerical computing, embedded devices are used in a variety of automated systems, including those at industrial sites, in accordance with their control program. Since embedded devices are used as a control system in corporate industrial complexes, nuclear power plants and public transport infrastructure nowadays, deliberate attacks on them can cause significant economic and social damages. Most attacks aimed at embedded devices are data-coded, code-modulated, and control-programmed. The control programs for industry-automated embedded devices are designed to represent circuit structures, unlike common programming languages, and most industrial automation control programs are designed with a graphical language, LAD, which is difficult to process static analysis. Because of these characteristics, the vulnerability analysis and security related studies for industry automation control programs have only progressed up to the formal verification, real-time monitoring levels. Furthermore, the static analysis of industrial automation control programs, which can detect vulnerabilities in advance and prepare for attacks, stays poorly researched. Therefore, this study suggests a method to present a discussion on an industry automation control program designed to represent the circuit structure to increase the efficiency of static analysis of embedded industrial automation programs. It also proposes a medium term translation technology exploiting LLVM IR to comprehensively analyze the industrial automation control programs of various manufacturers. By using LLVM IR, it is possible to perform integrated analysis on dynamic analysis. In this study, a prototype program that converts to a logical expression type of medium language was developed with regards to the S company's control program in order to verify our method.

• Polymer(Korea)
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• v.32 no.1
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• pp.63-69
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• 2008

The mechanical properties and morphologies of cellulose blends with two different additives were compared. Poly (vinyl alcohol) (PVA) of ethylene glycol (EG) were used as additives in the formation of cellulose blends through the solution blending. The properties of blends were varied with the additive content in the polymer matrix. The ultimate tensile strength and initial modulus of the cellulose blends were highest for a blend PVA content of 30 wt% and for a blend EG content of 10 wt%, respectively. Ternary blended systems of composition of cellulose/PVA (70/30=w/w)/EG were also prepared by the solution blending method with different EG contents. The mechanical properties of these systems were found to be optimal for EG contents of up to 40 wt%. The mechanical properties of the cellulose ternary blend films were superior to those of the cellulose binary blend films. The oxygen permeability transmission rate ($O_2TR$) monotonically decreased with increasing EG content in the ternary blend films. Overall, the mechanical properties of the cellulose blend films were found to be better than those of pure cellulose films.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.169-179
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• 2010

The aim of this study was to investigate occupational and individual risk factors and working conditions in relation to musculoskeletal symptoms in street cleaners. Investigation was conducted through a survey of 395 male street cleaners employed by the government office in Seoul, Gyeonggi and Chung-Nam from July to August of 2009. The control group was comprised of 143 male drivers and security guards. Risk factors for musculoskeletal symptoms in street cleaners were investigated by multiple logistic regression analysis and also evaluated ergonomic risk factors by assessing working conditions of 4 street cleaners. As a result of symptom questionnaires, all of the prevalent rates of musculoskeletal symptoms in street cleaners had significantly higher results than those of the control group(p<0.05). On binary logistic regression analysis of musculoskeletal symptoms, street cleaners showed significant higher odds ratio as 18.84(95%CI: 6.56-54.12) in the arm/elbow, 10.49(95%CI: 4.29-25.65) in the hand/wrist compared to the control group. Both absence of rest breaks and exposure to ergonomic risk factors showed to be important internal risk factors of musculoskeletal symptoms among street cleaners. The exposure levels of QEC(Quick exposures checklist) in street cleaners were revealed to be higher on the shoulder/arm, wrist/hand, and neck than back, or from stress. The findings appear to show that street cleaners were high-risk group of work-related musculoskeletal disorders. Therefore street cleaners require a holistic interventional strategy, including adequate arrangement of rest breaks, improvement of working tools and control of individual risk factors such as obesity and smoking.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.292-299
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• 2012

We made 8 wt% silica dispersion system with fumed silica and photo curable acrylic monomer by beads mill process. These dispersions could be applied in organic/inorganic hybrid coating systems. These dispersions could be applied in organic/inorganic hybrid coating systems. The 4 species of photo curable acrylic monomer which was presence of hydroxyl group, different solubility parameter, and different molecular size were used in the silica dispersions. Stability of polar solvent, isopropyl alcohol, in silica dispersions was investigated. We investigated the stability of silica dispersions by using steady-state and dynamic rheology. As the monomer has hydroxyl group increased in mono and binary monomer silica dispersions, they showed non flocculated stable sol (loss modulus (G")> storage modulus (G')). When polar solvent IPA was added into slightly flocculated silica dispersions, they changed to non flocculated stable sol.

• Journal of Software Assessment and Valuation
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• v.16 no.1
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• pp.65-79
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• 2020

As Programmable Logic Controllers (PLCs), popular components in industrial control systems (ICS), are incorporated with the technologies such as micro-controllers, real-time operating systems, and communication capabilities. As the latest PLCs have been connected to the Internet, they are becoming a main target of cyber threats. This paper proposes two sanitizers that improve the security of uC/OS-II based firmware for a PLC. That is, we devise BU sanitizer for detecting out-of-bounds accesses to buffers and UaF sanitizer for fixing use-after-free bugs in the firmware. They can sanitize the binary firmware image generated in a desktop PC before downloading it to the PLC. The BU sanitizer can also detect the violation of control flow integrity using both call graph and symbols of functions in the firmware image. We have implemented the proposed two sanitizers as a prototype system on a PLC running uC/OS-II and demonstrated the effectiveness of them by performing experiments as well as comparing them with the existing sanitizers. These findings can be used to detect and mitigate unintended vulnerabilities during the firmware development phase.