• Journal of the Korean Society for Precision Engineering
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• v.4 no.3
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• pp.44-51
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• 1987

In metal cutting various types of chips are produced in consequence of cutting conditions. Flow-type chips have been studied in most cases because they are easier to be analyzed, but the actual surfaces of chips are not smooth, but crushed. This paper deals with saw-toothed chips, special types of flow-type chips, which have deep concaves and high convexes and sharp angles on the free surface. I tried to establish the theory of saw-toothed chip mechanism through experimental observation, that is, the mathmatical model of the cutting energy and cutting mechanism through the geometrical observation of the chips by using a microscope. The results obtained are as follows: 1. The mechanism of saw-toothed chips is diffenent from that of general flow-chips. 2. In the case of saw-toothed chips, the shear angle must be measured by the hypotenuse angle and the rake angle, and the shear angle is more affected by the rake angle than by the hypotenbuse angle. 3. The friction angle is represented by .beta. = . pi. /4+ .alpha./ sub n/- .phi. which is different from Merchant's equation. 4. The pitch and the slip are greatly influenced by depth of cut, but the influence of the rake angle on it is small. 5. The normal stress and the shear stress on the shear plane decrease with the increase of the cutting depth, and they are almost independent on the variation of a rake angle. 6. The unit friction energy on the tool face, the unit shear energy on the shear plane, and the total cutting energy per unit volume decrease with the increase of rake angle and cutting depth.

• Bulletin of the Korean Chemical Society
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• v.10 no.2
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• pp.191-196
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• 1989

We obtained the new complexes, $Fe{\eta}^4-R,R'-TPSCp](CO)_3$(R,R'-TPSCp = 1,1-disubstituted 2,3,4,5-Tetraphenyl-1-Silacyclopenta-2,4-diene; R = Ph, R' = Cl, R = R' = Cl) from the reaction of the corresponding R,R'-TPSCp with ironpentacarbonyl under reflux in toluene. Also, the analogous complexes with R = R' = Me and R = Me, R' = Cl were obtained in an identical manner. We have determined the crystal structure of $Fe[Ph(Cl)-TPSCp](CO_)3$ by using Mo ka, ${\lambda}$ = 0.71069${\AA}$, where the unit cell was found to be monoclinic with a = 9.042 (6)${\AA}$, b = 19.870 (9)${\AA}$, c = 17.426 (9)${\AA}$ and ${\beta}$ = 96.28(4)$^{\circ}$. The butadiene moiety of TPSCp ring is planar and the dihedral angle of the butadiene plane and C4-Si-C25 plane was opened up to 41.8$^{\circ}$. The C-C distances in the butadiene moiety were found to be 1.4346, 1.462, and 1.440 ${\AA}$, respectively. It may be said that the four ${\pi}$-electrons are delocalized over the four carbons in five membered ring through coordination with ironcarbonyl. In this complex Fe is either in distorted tetrahedron environment with the centroid of the four C-atom butadiene moiety and three carbons of the three carbonyls or in distorted square-pyramidal environment with two midpoints of double bonds of the butadiene moiety and two carbons of carbonyl defining the base of the pyramid and the carbon of remaining carbonyl the apex.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.51-61
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• 2021

In the era of the 4th industrial revolution symbolized by the Internet of Things, big data and artificial intelligence, various embedded devices are increasing exponentially. These devices have communication functions despite their low specifications, so the possibility of personal information leakage is increasing, and security threats are also increasing. Embedded devices can have security issues at most levels, from hardware to services over the network. In addition, it is difficult to apply general security techniques because it has characteristics of resource constraints such as low specifications and low power, and the related technology has not been standardized. In this study, we present vulnerabilities and possible problems and considerations in applying SDN to embedded devices in consideration of structural characteristics and real-world discovered cases. This study presents vulnerabilities and possible problems and considerations when applying SDN to embedded devices. From a hardware perspective, we consider the problems of Wi-Fi chips and Bluetooth, the problems of open flow implementation, SDN controllers, and examples of structural properties. SDN separates the data plane and the control plane, and provides a standardized interface between the two, enabling efficient communication control. It can respond to the security limitations of existing network technologies that are difficult to respond to rapid changes.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.254-259
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• 2001

In order to make clear the resistance of plane nettings u,sed widely in constructing net cages, the resistance R taken by $R=kSU^2$, where S was the wall area of nettings, U the flow velocity, and k the resistance coefficient, was measured in a circulating water channel by using nylon Raschel nettings and PE trawler-knotted nettings coated with anti-fouling paint or not and then the properties of coefficient k were investigated. The mesh size L and the angle $\phi$ between two adjacent bars was given by the function of Reynolds number ${\lambda}U/v$ in the region of ${\lambda}U/v<180$, i. e., $$k=350(\frac{\lambda U}{v})^{-0.25}$$.where $\lambda$ was the representative size of nettings expressed as $$\lambda=\frac{{\pi}d^2}{2L\;sin\;2{\phi}}$$On the other hand, the coefficient k was almost fixed between 92 and 102 ($kg{\cdot}s^2/m^4$) in the region of ${\lambda}U/v{\geq}180$ and varied according to the ratio $S_n/S$ of the total area $S_n$ of nettings projected to the plane perpendicular to the water flow to the wall area S of nettings, i.e., it was given by $$k=98.6(\frac{S_n}{S})^{1.19}$$ regardless of the coating of paint.

• ETRI Journal
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• v.32 no.2
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• pp.265-272
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• 2010

To supply a power distribution network with stable power in a high-speed mixed mode system, simultaneous switching noise caused at the multilayer PCB and package structures needs to be sufficiently suppressed. The uni-planar compact electromagnetic bandgap (UC-EBG) structure is well known as a promising solution to suppress the power noise and isolate noise-sensitive analog/RF circuits from a noisy digital circuit. However, a typical UC-EBG structure has several severe problems, such as a limitation in the stop band's lower cutoff frequency and signal quality degradation. To make up for the defects of a conventional EBG structure, a partially located EBG structure with decoupling capacitors is proposed in this paper as a means of both suppressing the power noise propagation and minimizing the effects of the perforated reference plane on the signal quality. The proposed structure is validated and investigated through simulation and measurement in both frequency and time domains.

• Proceedings of the KIEE Conference
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• 2000.11d
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• pp.650-652
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• 2000

Although Fuzzy Logic Controller(FLC) adopted three terms as input gives better performance. FLC is in general composed of two-term control because of the difficulty in the construction of fuzzy rule base. In this paper, a three-term FLC which is similar to PID control but acts as a nonlinear controller is proposed. To reduce the complexity of the rule base design and increase efficiency, a simplified fuzzy PID control is induced from a hybrid velocity/position type PID algorithm by sharing a common rule base for both fuzzy Pi and fuzzy PD parts. It is simple in structure, easy in implementation, and fast in calculation. The phase plane technique is applied to obtain the rule base for fuzzy two-term control and them. The resultant rule base is Macvicar-Whelan type. The frequency response information is used in tuning of membership functions. Also a tuning strategy for the scaling factors is Proposed based on the relationship between PID gain and them. Simulation results show better performance and the effectiveness of the proposed method.

• Journal of the Korean Applied Science and Technology
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• v.16 no.3
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• pp.249-254
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• 1999

The N-docosyl N'-methyl viologen-$(TCNQ)_2$, (DMVT) was synthesized. We investigated the ${\pi}-A$ isotherm of DMVT to find the optimal deposition condition. Temperature-dependent current-voltage characteristics of the DMVT LB films shows that there is an increase in conductivity at 330K or so. The in-plane electrical conductivity at room temperature is in the range of $10^{-7}{\sim}10^{-6}S/cm$. From the plot of logarithmic conductivity as a function of reciprocal temperature, two types of activation energies, 0.04eV and 0.73eV, were obtained depending on the temperature range. The Ohmic behaviour was observed below 0.6V and the Schottky effect was confirmed at $2.5{\sim}6V$, when the I-V characteristics was measured with Al/LB film/Al structure. I-V measurement for Al/LB film/ITO structure showed the asymmetrical I-V relationship, which resulted from the rectification property.

• Journal of Welding and Joining
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• v.6 no.2
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• pp.19-29
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• 1988

This paper reports on the elatic-plastic analysis and fracture behavior of cylinder with outer surface crack which is under external or internal pressure. For the studuty of crack length effects in cylinder, ratios of crack lengths to finite thickness (a/t) are dertermined 0.3, 0.4, 0.5. For the study of curvature effects in cylinders, ratios of mean diameter to finite thicknees (Rm/t) are determined 10.0, 15.0, 20.0. Analysis is conduceted using the theory of fracture mechanics and two dimensional finite element solution assuming the axi-symmetrical plane strain conditon. Main results of this study are as follows. 1) It is known from this paper that elastic-plastic strain is initiated near crack tip and enlarged between crack tip and inner side of cylinder. 2) $K_{1}$ of cylinder under external or internal pressure is evaluated memebrane stress .root..pi.* crack length. The results of this study are inclined to Lomacky's results and Kobayshi's result. 3) Distribution of stress near crack tip is looked higher than of other zone, as crack length of equal model is longer, and as diameter of cylinder is longer. 4) When other conditions are equal, displacemenet near crack tip is looked duller, as length is longer.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.3
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• pp.85-93
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• 2001

In this study, a computer program considering shape imperfections of arch under dynamic loading was developed. The shape imperfection of arch was assumed as higher degree polynomial expressed as $\omega$$_{i}$ = $\omega$$_{o}$ (1-(2$\chi$/L)$^{m}$ )$^n$and sinusoidal curve such as $\omega$$_{i}$ = $\omega$$_{o}$ sin(η$\pi$$\chi$/L). In finite element formulation, the material nonlinear behavior was assumed the elasto-viscoplastic model highly corresponding to the real behavior of the material and the geometrically nonlinear behavior was modeled using Lagrangian description of motion. Also, the behavior of steel was modeled by applying yield criteria of Von Mises. The developed program was applied to the analysis of the dynamic behavior for the clamped beam subjected to the concentrated load at midspan and the results were compared with those from other research to investigate accuracy of the presented finite element program. In numerical examples, the shape imperfections of L/500, L/1,000 and L/2,000 were considered and the modes of shape imperfections of the symmetric and antisymmetric were adopted. The effects of the shape imperfections on the dynamic behavior of arch were conspicuous and results of analysis indicate that the reasonable values of arch rise to arch span ratio ranged between 0.1 and 0.3.

• Journal of the Korean Vacuum Society
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• v.3 no.3
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• pp.316-321
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• 1994

Rate of mixing of Cu particles to polyimide substrate at interfaces under different thermal treatments was analyzed by Rutherford Backscattering spectroscopy using 2.0 MeV He+ ions. T he mixing rate was a function of annealing temperature and time and was constant at afioxed temperature. The amount of mixing increased linearly with time and the mixing rate increased with temperature. The activation energy for interface mixing between Cu and polyimide was 2.6 kcal/mol. The X-ray studies showed the Cu(111) plane peak changed with annealing time at fixed temperature. The mixing of Cu to polyimide was explained with segmental motion of PI chain and with interaction between functional group of the chain and metal electron donor. The comparisons were made bewteen the mixing induced by ion irradiation and by thermal treatment. The various factors affecting the interface mixing are discussed.