• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.4
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• pp.1-7
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• 2010

Large quantity of bending deformation as well as irregular rotating torque fluctuation are the main struggles of the balance shaft module during a high speed rotation. Since two issues are much sensitive to the location of both supporting bearing and unbalance mass at a balance shaft, it is recommended to construct a design strategy on balance shaft at the early stage so as to save developing time and effort before approaches to the detailed design process. In this paper, an optimal design formulation is proposed to minimize the elastic strain energy due to bending as well as the kinematic energy of polar moment of inertia in rotation. Case studies of optimal design are conducted for different mass ratio as well as linear combination of objective function and its consequence reveals that global optimum of balance shaft model is existed over possible design conditions. Simulation shows that best locations of both supporting bearing and unbalance are globally 20% and 80%, respectively, over total length of a balance shaft.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.1
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• pp.54-61
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• 2014

This paper proposes a driver supportive device with haptic cue function which can transmit optimal gear shifting timing to a driver without requiring the driver's visual attention. Its performance is evaluated under vehicle model considering automotive engine, transmission and vehicle body. In order to achieve this goal, a torque feedback device is devised and manufactured by adopting the MR (magnetorheological) fluid and clutch mechanism. The manufactured MR clutch is then integrated with the accelerator pedal to construct the proposed haptic cue device. A virtual vehicle emulating a four-cylinder four-stroke engine, manual transmission system of a passenger vehicle and vehicle body is constructed and communicated with the manufactured haptic cue device. Control performances including torque tracking and fuel efficiency are experimentally evaluated via a simple feed-forward control algorithm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.11 no.2
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• pp.279-286
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• 1987

An numerical and experimental study has been performed on natural convection heat transfer from a horizontal heat exchanger tube with a fin. At s bare tube, by increasing $C_{T}$ (tube conduction parameter), mean Nusselt number and outer wall temperature are apparently increased at $C_{T}$.leq.300, slightly increased at $C_{T}$>300 and they can be represented in an exponential function of $C_{T}$. Natural convection heat transfer characteristics for the tube with a fin at given Rayleigh number are well agreed by those for an isothermal cylinder at a modified Rayleigh number. The local fin Nusselt number of the tube with a downward fin is much higher than that of the tube with an upward fin. The comparisons between numerical and experimental results showed good agreement.reement.

• Journal of Drive and Control
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• v.14 no.4
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• pp.45-50
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• 2017

The gas spring is a hydropneumatic adjusting element, consisting of a pressure tube, a piston rod, a piston and a connection fitting. The gas spring is filled with compressed nitrogen within the cylinder. The filling pressure acts on both sides of the piston and because of area difference it produces an extension force. Therefore, a gas spring is similar in function compare to mechanical coil spring. Conversely, optimization is a process of finding the best set of parameters to reach a goal while not violating certain constraints. The AMESim software provides NLPQL (Nonlinear Programming by Quadratic Lagrangian) and GA (genetic algorithm) for optimization. The NLPQL method builds a quadratic approximation to the Lagrange function and linear approximations to all output constraints at each iteration, starting with the identity matrix for the Hessian of the Lagrangian, and gradually updating it using the BFGS method. On each iteration, a quadratic programming problem is solved to find an improved design until the final convergence to the optimum design. In this study, we conducted optimization design of the gas spring reaction force with NLPQL.

• The Journal of Korea Robotics Society
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• v.16 no.3
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• pp.223-231
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• 2021

In this paper describes the research and development of a pipe robot for pipe rehabilitation construction of old water pipes. After the water supply pipe construction, the pipe is leaking, damaged, and aging due to corrosion. Eventually, resistance to the flow of water in lower supply efficiency and contaminated water such as rusty water, finally in various consumer complaints. In order to solve this problem, rehabilitation construction robot technology is required to secure the construction quality of pipe rehabilitation construction and restore the function of the initial construction period. The developed pipe rehabilitation construction robot required a hydraulic actuator for high traction and was equipped with a small hydraulic supply device. In addition, we have developed a hydraulic cylinder and a link system that supports the pipe inner diameter to develop a single pipe robot corresponding to 500 to 800mm pipe diameter. The analysis and experimental verification of the driving performance and unit function of the developed pipe reconstruction robot are explained, and the result of the integrated performance test of the pipe reconstruction robot at the water supply pipe network site is explained.

• Korean Journal of Mathematics
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• v.30 no.4
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• pp.593-601
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• 2022

Let C(Q) denote Yeh-Wiener space, the space of all real-valued continuous functions x(s, t) on Q ≡ [0, S] × [0, T] with x(s, 0) = x(0, t) = 0 for every (s, t) ∈ Q. For each partition τ = τ_m,n = {(s_i, t_j)|i = 1, . . . , m, j = 1, . . . , n} of Q with 0 = s₀ < s₁ < . . . < s_m = S and 0 = t₀ < t₁ < . . . < t_n = T, define a random vector X_τ : C(Q) → ℝ^mn by X_τ (x) = (x(s₁, t₁), . . . , x(s_m, t_n)). In this paper we study the conditional integral transform and the conditional convolution product for a class of cylinder type functionals defined on K(Q) with a given conditioning function X_τ above, where K(Q)is the space of all complex valued continuous functions of two variables on Q which satify x(s, 0) = x(0, t) = 0 for every (s, t) ∈ Q. In particular we derive a useful equation which allows to calculate the conditional integral transform of the conditional convolution product without ever actually calculating convolution product or conditional convolution product.

• Korean Journal of Mathematics
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• v.30 no.2
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• pp.239-247
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• 2022

Let C₀[0, T] denote the Wiener space, the space of continuous functions x(t) on [0, T] such that x(0) = 0. Define a random vector $Z_{\vec{e},k}:C_0[0,\;T] {\rightarrow}{\mathbb{R}}^k$ by $$Z_{\vec{e},k}(x)=({\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^T}\;e_1(t)dx(t),\;{\ldots},\;{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^T}\;ek(t)dx(t))$$ where e_j ∈ L₂[0, T] with e_j ≠ 0 a.e., j = 1, …, k. In this paper we study the conditional Fourier-Feynman transform and a conditional convolution product for a cylinder type functionals defined on C0[0, T] with a general vector valued conditioning functions $Z_{\vec{e},k}$ above which need not depend upon the values of x at only finitely many points in (0, T] rather than a conditioning function X(x) = (x(t₁), …, x(t_n)) where 0 < t₁ < … < t_n = T. In particular we show that the conditional Fourier-Feynman transform of the conditional convolution product is the product of conditional Fourier-Feynman transforms.

• Journal of Korean Society of Forest Science
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• v.97 no.1
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• pp.61-70
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• 2008

This study was conducted to develop a mobile tower-yarder with tractor for agriculture and forestry that is the efficient yarder in steep terrains, thinning operation and small scale logging operation. It was designed and manufactured that the power source of tower-yarder is equiped three hydraulic pump connected to PTO of tractor, and three hydraulic pump is used to operate the four motor for drum, the cylinder for clutch of interlocker, the cylinder for tower expanding and the out-rigger cylinder. It was to adopt the running skyline system and the inter-lock function, and to equip the double capstan drum, the storage drum and the clutch for interlock in the development of tower-yarder. It was to develop the tower-yarder which the winch torque of double-capstan drum, the traction force of double-capstan drum, the number of rotation of double-capstan drum and the line speed is $191kg{\cdot}m$, 1,910 kgf, 220.5 rpm and 138.5 m/min, respectively. And it was known that the optimum flange diameter of the main and haulback storage drum is about 360 mm and about 460 mm in order to storage the main line length of 250m and the haulback line length of 450 m. The carriage was made to adopt the running skyline system and to equip the lock function in order to the convenience of chocking and the fall down preventing of tree. It was provided to develop the wire remote controller for the inter-lock function, the convenience of control and the efficiency of yarding. In development process, this tower-yarder was attached the 3-point linkage hitch equipment and the tire wheel for the traction and moving of tower-yarder. Also, it was equipped that the out-rigger and the guy line in order to raise the safety and efficiency of yarding of tower-yarder.

• Journal of the Korea Institute of Building Construction
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• v.15 no.6
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• pp.589-595
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• 2015

This study evaluated the in-site compressive strength development of high-strength concrete developed for the mass structures under cold weather condition. Two mock-up wall specimens with $2.0{\times}1.2{\times}1.0m$ in dimension were cured under an average temperature of $5^{\circ}C$. Core strengths measured at different locations of the mock-up walls were compared with the companion standard cylinder strengths. Test results revealed that the core strength of mock-up walls at an age of 3 days is higher by approximately 30% than the companion cylinder strength because of the high curing temperature effect generated from the heat of hydration of cementitious materials. Furthermore, comparisons with the prediction models based on maturity function confirmed that the effect of hydration heat on the curing temperature increase needs to be reflected to reasonably evaluate the on-site compressive strength development of concrete for mass elements.

• Journal of Dental Rehabilitation and Applied Science
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• v.17 no.4
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• pp.307-314
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• 2001

To evaluate the effect of misfit in two implant-supported fixed partial dentures in the posterior of the mandible, variations of the standard finite element models were made by changing the location of the gap as follows: 1) no gap present; 2) located between the gold cylinder and the abutment on the distal implant; 3) gap located between the gold cylinder and the abutment on the mesial implant. The results of this study were as follows: 1. When the location of the gap was close to the load applied on the prosthesis, the stress in the prosthesis, implant components and surrounding bone increased. 2. The presence of cantilever increased the stress in the prosthesis, implant and surrounding bone significantly, regardless of the presence of the gap. 3. When there was a gap between the prosthesis and abutment, the stress in the bone around the implant increased. 4. When passive fit was achieved, the stress was distributed widely in each component with less peak stress in each component. 5. The inner structures of the implant components, the gold screw and the abutment screw bear more stress when the prosthesis did not exhibit passive fit with the abutments than when passive fit was present.