• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.2
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• pp.17-24
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• 2004

In end milling process, undeformed chip thickness and cutting forces vary periodically with phase change of the tool. Recently, a model has been proposed to simulate the shear and friction characteristics of an up-end milling process in terms of the equivalent oblique cutting to this. In the current study, a down-end milling process has been replaced with the equivalent oblique cutting process. And shear and tool-chip friction characteristics variation of SM45C steel has been studied using the end-mills of different helix angles. The specific shear and friction energy consumed with helix angle of $50^{\circ}$ is somewhat larger than those of$30^{\circ}$ and $40^{\circ}$. The specific shear energy consumed is about 76-77% of the specific cutting energy regardless the helix angles.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.10
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• pp.1520-1527
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• 2001

In end milling process the undeformed chip thickness and the cutting force components vary periodically with phase change of the tool. In this study, up end milling process is transformed to the equivalent oblique cutting. The varying undeformed chip thickness and the cutting force components in end milling process are replaced with the equivalent average ones. Then it can be possible to analyze the chip-tool friction and shear process in the shear plane of the end milling process by the equivalent oblique cutting model. According to this analysis, when cutting SM45C steel, 72% of the total energy is consumed in the shear process and the balance is consumed in the friction process.

• International Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.14-21
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• 2016

This paper presents research on predicting the possible intercept time for a Nodong missile based on its flight trajectory. North Korea possesses ballistic missiles of various ranges, and nuclear warhead miniaturization tests and ballistic missile launch tests conducted last year and in previous years have made these missiles into a serious security threat for the international community. With North Korea's current miniaturization skills, the range of the nuclear capable Nodong missiles can be adjusted according to their use goals and operating environment by using a variety of adjustment methods such as payload, fuel mass, Isp, loft angle, cut-off, etc., and therefore precise flight trajectory prediction is difficult. In this regards, this research performs model simulations of the flight trajectory of North Korea's domestically developed Nodong missiles and uses these as a basis for predicting the possible intercept times for major ballistic missile defense systems such as PAC-3, THAAD, and SM-3.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.512-518
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• 2001

In this paper, the geometrical properties of the optical system for Head Mounted Display (HMD) were investigated. Also, this work deals with the concept for an optical system design bated on Diffractive Optical Elements (DOE). In designing the optical system for HMD, it is considered that the optical system should have compact, high performance, and comfortable properties while user sees the picture. In order to satisfy these requirements, we applied DOE and aspheric surfaces to the lens so that correction of color and monochromatic aberrations could be obtained. Also, the design and evaluation for the optical system were carried out using the generalized model of the human eye. Finally, it was expected to fulfill all the requirements of an HMD system.

• Archives of Pharmacal Research
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• v.19 no.3
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• pp.183-190
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• 1996

There are a wide variety of semi-solid ointments used for healing the skin diseases, whose therapeutic and skin penetration abililties may greatly differ from one another depending on the compositions of ointment vehicles. A computer optimization technique was applied to obtain the optimum formula of o/w type ointment giving the in vitro maximum absorption rate through hairless rat skin membrane. Some of the formulations were selected to find out a relationship between skin penetration of ointment and its Theological characteristics. The experimental value of absorption rate obtained from the ointment by optimum formula agreed well with the theoretical value obtained from a polynomial regression analysis, Three kinds of ointments selected among 15 formulations were obtained with a concentric cylinder type rheometer (Model; Rheolab SM-HM Physica, Germany) at 20, 30, 40 and $50^{\circ}C$ for rheograms of rhelolgical properties of o/w type ointments. As the temperature was raised, all products showed a decrease in both shear stress and yield values. The higher skin penetration, the lower shear stress showed.

• Bulletin of the Korean Chemical Society
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• v.18 no.4
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• pp.395-401
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• 1997

The substituent effects in the gas-phase rearrangement of carbenes to ketenes involved in the Wolff reaction have been investigated theoretically using the AM1 method. In the initial state, carbene, there is a relatively strong vicinal n-σ* interaction between the lone pair (n) and carbonyl group (σ*). In the bridged transition state (TS), electronic charge is transferred from the migrating ring (Z-ring) toward the nonmigrating ring (Y-ring). The carbenes are stabilized by an electron donor Y (δσY < 0) whereas the TS is stabilized by an electron acceptor Y (δσY > 0). Multiple regression analysis of log (kYZ/kHH)(=-δΔG≠/2.3RT) leads to a relatively large negative cross-interaction constant, ρYZ=-0.53, log (kYZ/kHH)=2.96 σY--1.40 σZ-0.53 σY-σZ reflecting an extensive structural change in the transition state due to the stabilization of the initial state by the vicinal n-σ* overlap. When the solvent (water) effects are accounted for by the SM2.1 model of the Cramer and Truhlar method, the magnitude of all the selectivity parameters, ρY-, ρZ and ρYZ (=-0.66) are increased.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.287-304
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• 2022

With the development of quantum computers, ring signature schemes based on large integer prime factorization, discrete logarithm problem, and bilinear pairing are under threat. For this reason, we design a ring signature scheme based on lattice with a fixed verification key. Compared with the previous ring signature scheme based on lattice, our design has a fixed verification key and does not disclose the signer's identity. Meanwhile, we propose an anonymous electronic voting scheme by using our ring signature scheme based on lattice and (t, n) threshold scheme, which makes up for the lack of current anonymous electronic voting that cannot resist attacks of the quantum computer. Finally, under standard model (SM), we prove that our ring signature scheme based on lattice is anonymous against the full-key exposure, and existentially non-forgeable against insider corruption. Furthermore, we also briefly analyze the security of our anonymous electronic voting scheme.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.9
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• pp.2223-2233
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• 1993

An engineering method is suggested to calculate the applied load versus crack extension in the elastic-plastic fracture. The condition for an increment of crack extension is set by a critical increment of crack-up opening displacement(CTOD). The ratio of the CTOD increment to the incremental crack extention is a critical crack-tip opening angle(CTOA), assumed to be constant for a material of a given thickness. The Dugdale model of crack-tip deformation in an infinite plate is applied to the method, and a complete solution for crack extension and crack instability is obtained. For finite-size specimens of arbitrary geometry in general yielding, an approximate generalization of the Dugdale model is suggested so that the approximation approaches the small-scale yielding solution in a low applied load and the finite-element solution in a large applied load. Maximum load is calculated so that an applied load attains either a limit load on an unbroken ligament or a peak load during crack extension. The proposed method was applied to three-point bend specimens of a carbon steel SM45C in various sizes. Reasonable agreements are found between calculated maximum loads and experimental failure loads. Therefore, the method can be a viable alternative to the J-R curve approach in the elastic-plastic fracture analysis.

• Archives of design research
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• v.19 no.3 s.65
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• pp.143-154
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• 2006

The primary purpose of this study was to investigate the influence of Cognitive Factors (CF) on the Creative Abilities (CAs) in design. We set up a model of Cognitive Design Process (CDP), which consists of four domains: Concepts, Experience, Five Senses (FS), and Thinking Modes (TM). Here, experience is first perceived by the five senses, and then recognized by intelligence. We regard design as a transforming process from concept to experience. For this study, two major Sensory Modalities (Visual and Kinesthetic), four Thinking Modes (Brain Dominance Profile), and four Creative Abilities (Fluency, Flexibility, Originality, and Elaboration) were reviewed. We hypothesized that idea generation is influenced by different Sensory Modalities (Visual Sense vs. Kinesthetic Sense) and Thinking Modes, and that these have a close relationship with the attributes of CAs. Firstly, we have examined the cognitive thinking model in design. Then, we adapted the Test of Creative Abilities of Design Thinking (TCADT) for measuring CAs. We surveyed the CAs under CF in particular. Finally, we have investigated the influences of the different Sensory Modalities (Visual Sense vs. Kinesthetic Sense) on CAs. It was found that a close relationship between Brain Dominance and CAs, and Sensory Modalities (SM) have different influence on these creative abilities. As a result, a tool for the Test of CAs and a framework for creative idea generation with the effective CF will be presented. These provide the basis for a new approach to creative idea generation in Experience Design.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1683-1696
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• 2018

Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.