• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.88-93
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• 2005

Ti-AI-Si-N coating layers were deposited on WC-Co substrates by a hybrid system of arc ion plating and sputtering techniques. The coatings were prepared with different Si contents to investigate the effect of Si content on their mechanical properties and microstructures. The dry sliding wear experiments were conducted on Ti-AI-Si-N coated WC-Co discs at constant load, 3N, and sliding speed, 0.1 m/s with two different counterpart materials such as steel ball and zirconia ball using a conventional ball-on-disc sliding wear apparatus. In the case of steel ball, the friction coefficient of Ti-AI-Si-N coating layers became lower than that of Ti-AI­N coating layers. The friction coefficient decreased with increasing of Si content due to adhesive wear behavior between coating layer and steel ball. On the contrary, in the case of zirconia ball, the friction coefficient increased with increasing of Si content, indicating that abrasive wear behavior was more dominant when the coating layers slid against zirconia ball.

• Wind and Structures
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• v.20 no.4
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• pp.549-564
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• 2015

The three-dimensional unsteady incompressible Reynolds-averaged Navier-Stokes equations and k-${\varepsilon}$ double equations turbulent model were used to investigate the effect on the measurements of anemometers due to a passing high-speed train. Sliding mesh technology in Fluent was utilized to treat the moving boundary problem. The high-speed train considered in this paper was with bogies and inter-carriage gaps. Combined with the results of the wind tunnel test in a published paper, the accuracy of the present numerical method was validated to be used for further study. In addition, the difference of slipstream between three-car and eight-car grouping models was analyzed, and a series of numerical simulations were carried out to study the influences of the anemometer heights, the train speeds, the crosswind speeds and the directions of the induced slipstream on the measurements of the anemometers. The results show that the influence factors of the train-induced slipstream are the passing head car and tail car. Using the three-car grouping model to analyze the train-induced flow is reasonable. The maxima of horizontal slipstream velocity tend to reduce as the height of the anemometer increases. With the train speed increasing, the relationship between $V_{train}$ and $V_{induced\;slipstream}$ can be expressed with linear increment. In the absence of natural wind conditions, from the head car arriving to the tail car leaving, the induced wind direction changes about $330^{\circ}$, while under the crosswind condition the wind direction fluctuates around $-90^{\circ}$. With the crosswind speed increasing, the peaks of $V_X,{\mid}V_{XY}-V_{wind}{\mid}$ of the head car and that of $V_X$ of the tail car tend to enlarge. Thus, when anemometers are installed along high-speed railways, it is important to study the effect on the measurements of anemometers due to the train-induced slipstream.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.157-157
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• 2017

To minimize the damage by wild birds and acquire the benefits such as protection against weeds and maintenance of water content in soil, the mulching black color vinyl after seeding should be carried out. Non-contact and non-destructive methods that can continuously determine the locations are necessary. In this study, a crop position detection method was studied that uses infrared thermal image sensor to determine the cotyledon position under vinyl mulch. The moving system for acquiring image arrays has been developed for continuously detecting crop locations under plastic mulching on the field. A sliding mechanical device was developed to move the sensor, which were arranged in the form of a linear array, perpendicular to the array using a micro-controller integrated with a stepping motor. The experiments were conducted while moving 4.00 cm/s speed of the IR sensor by the rotational speed of the stepping motor based on a digital pulse width modulation signal from the micro-controller. The acquired images were calibrated with the spatial image correlation. The collected data were processed using moving averaging on interpolation to determine the frame where the variance was the smallest in resolution units of 1.02 cm. Non-linear integral interpolation was one of method for analyzing the frequency using the normalization image and then arbitrarily increasing the limited data value of $16{\times}4pixels$ in one frame. It was a method to relatively reduce the size of overlapping pixels by arbitrarily increasing the limited data value. The splitted frames into 0.1 units instead of 1 pixel can propose more than 10 times more accurate and original method than the existing correction method. The non-integral calibration method was conducted by applying the subdivision method to the pixels to find the optimal correction resolution based on the first reversed frequency. In order to find a correct resolution, the expected location of the first crop was indicated on near pixel 4 in the inversion frequency. For the most optimized resolution, the pixel was divided by 0.4 pixel instead of one pixel to find out where the lowest frequency exists.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.4
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• pp.968-980
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• 1995

Al/Al$_{2}$O$_{3}$/C hybrid metal matrix composites are fabricated by the direct squeeze infiltration method. From the microstructure of Al/Al$_{2}$O$_{3}$/C composites, uniform distribution of reinforcements and good bondings are found. Optimum processing conditions for preforms and squeeze castings are suggested. Mechanical properties, such as elastic modulus, elongation, 0.2% offset yield strength and ultimate tensile strength are obtained. Through the abrasive were test and wear surface analsis, wear behavior and its mechanism of AC2B aluminum and Al/Al$_{2}$O$_{3}$/C composites can be characterized under various sliding speed conditions. Tensile strenght elongation of Al/Al$_{2}$O$_{3}$/C composites are decreased with increasing the addition of carbon fiber. On the contrary, elastic modulus of Al/Al$_{2}$O$_{3}$/C composites is slightly improved compared with that of the unreinforced matrix alloy. The addition of carbon fiber to al/al$_{2}$O$_{3}$/C composites gives rise to improvement of the wear resistance. Specially, carbon chopped fibers play an important role in interfering sticking between the counter material and metal matirix composites. Al/Al$_{2}$O$_{3}$/C composites are suitable to high speed due to solid lubication of carbon. And wear model of Al/Al$_{2}$O$_{3}$/C composites is suggested by the examination of worn surfaces.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.102-109
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• 1994

The thick and hard alloyed layer was formed on the surface of Aluminum Cast Alloy(AC2B) by PTA overlaying process with Cr, Cu and Ni metal powders under the condition of overlaying current 150A, overlaying speed 150mm/min and different powder feeding rate 5-20g/min. The characteristics of hardening and were resistance of alloyed layer have been investigated in relation to microstructure of alloyed layer. As a result, it was made clear that Cu powder was the most superier one in three metal powders used due to an uniform hardness distribution of Hv 250-350, good wear resistance and freedom from cracking in alloyed layer of which microstructure consisted of hypereutectic. On the contrary, irregular hardness distribution was usually obtained in Cr or Ni alloyed layers of which hardness was increased as Cr or Ni contents and reached to maximum hardness of about Hv 400-850 at about 60wt% Cr or 40wt% Ni in alloyed layer. However the cracking occurred in these alloyed layers with higher hardness than Hv 250-300 at more than 20-25wt% of Cr or Ni contents in alloyed layer. Wear rate of alloyed layer was decreased to 1/10 in Cu alloyed layer and 1/5 or 1/3 in Cr or Ni alloyed layer with same hardness of about Hv 300 in comparison with that of base metal at higher sliding speed.

• Journal of IKEEE
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• v.21 no.4
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• pp.358-367
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• 2017

Advanced Driver Assistance Systems(ADAS), such as Front Collision Warning System (FCWS) are currently being developed. FCWS require high processing speed because it must operate in real time while driving. In addition, a low-power system is required to operate in an automobile embedded system. In this paper, FCWS is implemented in CPU-FPGA architecture in embedded system to enable real-time processing. The lane detection enabled the use of the Inverse Transform Perspective (IPM) and sliding window methods to operate at fast speed. To detect the vehicle, a Convolutional Neural Network (CNN) with high recognition rate and accelerated by parallel processing in FPGA is used. The proposed architecture was verified using Intel FPGA Cyclone V SoC(System on Chip) with ARM-Core A9 which operates in low power and on-board FPGA. The performance of FCWS in HD resolution is 44FPS, which is real time, and energy efficiency is about 3.33 times higher than that of high performance PC enviroment.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.48-57
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• 1984

To analyze the grain transport velocity, which is valuable for optimizing the separation losses, an oscillating appratus for sieve was designed. The grain transport velocity was measured in each combination of three amplitude levels, three rpm levels and four projection angle levels. To analyze the grain transport velocity theortically, two computer programs were developed. And the results from experiment and theoretical analysis were compared. 1. The grain transport velocity was increased with the projection angle of oscillating sieve. Especially when the projection angle is higher than $45^{\circ}$ the grain transport velocity on the flat-plate was not increased but on the racked surface was increased persistently. 2. The grain transport velocity was increased linearly with the frequency of oscillating motion. The speed of driving link must be higher than 350 rpm at 24mm amplitude, 250 rpm at 36 mm amplitude to transport the grain efficiently. 3. The grain transport velocity was increased with the amplitude of oscillating motion. But if the amplitude was smaller than interval of racks, the grain on the racked surface was not transported, even though the projection angle or the speed of revolutionary link was increased. 4. The transport characteristics of a grain varied with the amplitude and projection angle. Especially in the range of 1.5 < K < 2.3 at $45^{\circ}$ projection angle the transportation of grain was successful and the grain motion consisted of sliding movement (forward, backward) and jumping movement, which is considered recommendable for separating process of a combine sieve. 5. The results from theoretical analysis were approximately in accord with that from experiment.

• Tribology and Lubricants
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• v.30 no.6
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• pp.330-336
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• 2014

Sintered metallic brake pads and low alloy heat resistance steel disks are applied to mechanical brake systems in high energy moving machines that are associated with recently developed 200km/h trains. This has led to the speed-up of conventional urban rapid transit. In this study, we use a lab-scale dynamometer to investigate the effects of the composition of friction materials on the tribological characteristics of sintered metallic brake pads and low alloy heat resistance steel under dry sliding conditions. We conduct test under a continuous pressure of 5.5 MPa at various speeds. To determine the optimal composition of friction materials for 200 km/h train, we test and the evaluate frictional characteristics such as friction coefficients, friction stability, wear rate, and the temperature of friction material, which depend on the relative composition of the Cu-Sn and Fe components. The results clearly demonstrate that the average friction coefficient is lower for all speed conditions, when a large quantity of iron power is added. The specimen of 25 wt% iron powder that was added decreased the wear of the friction materials and the roughness of the disc surface. However when 35 wt% iron powder was added, the disc roughness and the wear rate of friction materials increased By increasing the amount of iron powder, the surface roughness, and temperature of the friction materials increased, so the average friction coefficients decreased. An oxidation layer of $Fe_2O_3$ was formed on both friction surfaces.

• Journal of IKEEE
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• v.25 no.4
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• pp.664-671
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• 2021

This paper proposes a GPGPU structure that can reduce the number of operations and memory access by effectively applying a data reuse method to a convolutional neural network(CNN). Convolution is a two-dimensional operation using kernel and input data, and the operation is performed by sliding the kernel. In this case, a reuse method using an internal register is proposed instead of loading kernel from a cache memory until the convolution operation is completed. The serial operation method was applied to the convolution to increase the effect of data reuse by using the principle of GPGPU in which instructions are executed by the SIMT method. In this paper, for register-based data reuse, the kernel was fixed at 4×4 and GPGPU was designed considering the warp size and register bank to effectively support it. To verify the performance of the designed GPGPU on the CNN, we implemented it as an FPGA and then ran LeNet and measured the performance on AlexNet by comparison using TensorFlow. As a result of the measurement, 1-iteration learning speed based on AlexNet is 0.468sec and the inference speed is 0.135sec.

• Tribology and Lubricants
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• v.23 no.6
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• pp.298-300
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• 2007

Frictional characteristics of mesoporous $SiO_2$ thin films were evaluated with different pore sizes. The films were manufactured by sol-gel and self-assembly methods to have a porous structure. The pores on the surface may play as the outlet of wear particle and the storage of lubricant so that the surface interactions could be improved. The pores were exposed on the surface by chemical mechanical polishing (CMP) or plasma-etching after forming the porous films. The ball-on-disk tests with mesoporous $SiO_2$ thin films on glass specimen were conducted at sliding speed of 15 rpm and a load of 0.26 N. The results show considerable dependency of friction on pore size of mesoporous $SiO_2$ thin films. The friction coefficient decreased as increasing the pore size. CMP process was very useful to expose the pores on the surface.