• Journal of Institute of Control, Robotics and Systems
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• v.20 no.2
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• pp.218-222
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• 2014

In this paper, we introduce an autonomous calibration method for a 2D laser displacement sensor (e.g. laser vision sensor and laser range finder) by matching a single point on a flat structure. Many arc welding robots install a 2D laser displacement sensor to expand their application by recognizing their environment (e.g. base metal and seam). In such systems, sensing data should be transformed to the robot's coordinates, and the geometric relation (i.e. rotation and translation) between the robot's coordinates and sensor coordinates should be known for the transformation. Calibration means the inference process of geometric relation between the sensor and robot. Generally, the matching of more than 3 points is required to infer the geometric relation. However, we introduce a novel method to calibrate using only 1 point matching and use a specific flat structure (i.e. circular hole) which enables us to find the geometric relation with a single point matching. We make the rotation component of the calibration results as a constant to use only a single point by moving a robot to a specific pose. The flat structure can be installed easily in a manufacturing site, because the structure does not have a volume (i.e. almost 2D structure). The calibration process is fully autonomous and does not need any manual operation. A robot which installed the sensor moves to the specific pose by sensing features of the circular hole such as length of chord and center position of the chord. We show the precision of the proposed method by performing repetitive experiments in various situations. Furthermore, we applied the result of the proposed method to sensor based seam tracking with a robot, and report the difference of the robot's TCP (Tool Center Point) trajectory. This experiment shows that the proposed method ensures precision.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.11_12
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• pp.557-565
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• 2005

This paper presents the development and implementation of a zero-copy file transfer mechanism that improves the efficiency of file transfers for PC cluster systems using hardware-based VIA(Virtual Interface Architecture) network adapters. VIA is one of the representative user-level communication interfaces, but because there is no library for file transfer, one copy occurs between kernel buffer and user boilers. Our mechanism presents a file transfer primitive that does not require the file system to be modified and allows the NIC to transfer data from the kernel buffer to the remote node directly without copying. To do this, we have developed a hardware-based VIA network adapter, which supports the PCI 64bit/66MHz bus and Gigabit Ethernet, as a NIC, and implemented a zero-copy file transfer mechanism. The experimental results show that the overhead of data coy and context switching in the sender is greatly reduced and the CPU utilization of the sender is reduced to $30\%\~40\%$ of the VIA send/receive mechanism. We demonstrate the performance of the zero-copy file transfer mechanism experimentally. and compare the results with those from existing file transfer mechanisms.

• Korean Journal of Materials Research
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• v.14 no.12
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• pp.893-899
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• 2004

Even though Ti-6Al-4V has gained popularity as an implant material, the possible dissolution of Al and V ions in body fluids remains a matter of concern. Though commercially pure Ti (Cp-Ti) overcomes this problem, the mechanical strength of pure titanium remains very low. Thus, in this experiment Cp-Ti was processed by Equal channel angular processing (ECAP), in order to increase the mechanical strength. The biocompatibility of ECAP-Ti, Cp-Ti and Ti-6Al-4V was examined by the apatite formation on each sample surface, after treating the surface with 5M NaOH and soaking in Simulated body fluids (SBF). Initially, the samples were mechanically polished on silicone carbide paper (#2000). The polished samples were treated with 5M NaOH solution at $60^{\circ}C$ for 24 hours. The NaOH treated samples were washed gently with distill water and dried at $40^{\circ}C$ for 1 day. The dried samples were heat treated in air at $600^{\circ}C$ for 1 hour. The surface morphology of these samples were studied using SEM and XRD. The SEM studies showed network of pores in all samples. The XRD showed oxide layer formation on Cp-Ti and Ti-6Al-4V. samples. However the oxide layer in ECAP-Ti was not substantial. These samples were immersed in SBF, kept at $36.5^{\circ}C$ for seven days period. At the end of 7 days, the apatite formation was confirmed only on Cp-Ti and was not observed in Ti-6Al-4V and ECAP-Ti. These observations of apatite formation relate to the fact that Cp-Ti showed greater oxide layer than other samples. The apatite examined was confirmed as tricalcium phosphate (TCP) using EDS and XRD.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.6
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• pp.34-51
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• 2008

Today, the Internet is a part of our life. For that reason, we regard revealing characteristics of Internet traffic as an important research theme. However, Internet traffic cannot be easily manipulated because it usually occupy huge capacity. This problem is a serious obstacle to analyze Internet traffic. Many researchers use various sampling techniques to reduce capacity of Internet traffic. In this paper, we compare several famous sampling techniques, and propose efficient sampling scheme. We chose some sampling techniques such as Systematic Sampling, Simple Random Sampling and Stratified Sampling with some sampling intensities such as 1/10, 1/100 and 1/1000. Our observation focused on Traffic Volume, Entropy Analysis and Packet Size Analysis. Both the simple random sampling and the count-based systematic sampling is proper to general case. On the other hand, time-based systematic sampling exhibits relatively bad results. The stratified sampling on Transport Layer Protocols, e.g.. TCP, UDP and so on, shows superior results. Our analysis results suggest that efficient sampling techniques satisfactorily maintain variation of traffic stream according to time change. The entropy analysis endures various sampling techniques well and fits detecting anomalous traffic. We found that a traffic volume diminishment caused by bottleneck could induce wrong results on the entropy analysis. We discovered that Packet Size Distribution perfectly tolerate any packet sampling techniques and intensities.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.41.1-41.1
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• 2009

Aerosol Deposition (AD) is anovel way to fabricate bioactive ceramic coatings in biomedical implants and prostheses applications. In the present work, silicon-substituted hydroxyapatite (HA) coatings on commercially pure titanium were prepared by aerosol deposition using Si-HA powders. The incorporation of silicon in the HA lattice is known to improve the bioactivity of the HA, makingsilicon-substitute HA an attractive alternative to pure HA in biomedical applications. Si-HA powders with the chemical formula $Ca_{10}(PO_4)_6-x(SiO_4)x(OH)_2-x$, having silicon contents up to x=0.5 (1.4 wt%), were synthesized by solid-state reaction of $Ca_2P_2O_7$, $CaCO_3$, and $SiO_2$. The Si-HA powders were characterized by X-ray diffraction (XRD), X-ray fluorescence spectrometry (XRF), and Fourier transform infrared spectroscopy(FT-IR). The corresponding coatings were also analyzed by XRD, scanning electron microscopy (SEM), and electron probe microanalyzer (EPMA). The results revealed that a single-phase Si-HA was obtained without any secondary phases such as $\alpha$- or $\beta$-tricalcium phosphate (TCP) for both the powders and the coatings.The Si-HA coating was about $5\;{\mu}m$ thick, had a densemicrostructure with no cracks or pores. In addition, the proliferation and alkaline phosphatase (ALP) activity of MC3T3-E1 preosteoblast cells grown on the Si-HA coatings were significantly higher than those on the bare Ti and pure HA coating. These results revealed the stimulatory effects induced by siliconsubstitution on the cellular response to the HA coating.

• Journal of Mushroom
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• v.18 no.3
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• pp.208-213
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• 2020

Burkholderia contaminans PSB-A and Burkholderia ambifaria PSB-B were isolated from button mushroom bed to estimate their phosphate solubility. The phosphate-solubilizing abilities of these strains were assessed by measuring the phosphorus content in a single and co-inoculation medium for 7 days. The co-inoculation of these two strains released the highest content of soluble phosphorus (166.3 ㎍ mL^-1) into the medium, followed by single inoculation of B. contaminans PSB-A (143.73 ㎍ mL^-1) and B. ambifaria PSB-B (127.1 ㎍ mL^-1). The highest pH reduction, organic acid production, and glucose consumption were also observed in the co-inoculation medium. According to the plant growth promotion bioassay, co-inoculation enhanced the growth of romaine lettuce much more than the single inoculation (20.4% for leaf widths and 16.6% for root lengths). Although no significant difference was noted between single and co-inoculation of bacterial strains in terms of phosphorous release and plant growth, co-inoculation of PSB may have a beneficial effect on crop growth due to a synergistic effect between the strains.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.2
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• pp.93-100
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• 2010

The calcium to phosphate ratio (Ca/P) in biphasic calcium phosphates powders using X-ray diffraction analysis (XRD) was characterized. The BCP powders with various stoichiometric Ca/P molar ratio were synthesized with coprecipitation process and calcination. Compositions of the powders with Ca/P molar ratio between 1.5 and 1.67 were subjected to starting Ca/P molar ratio, pH = 10, and thermal treatment up to $900^{\circ}C$. The structural, morphological and chemical characterizations for BCP powders with stoichiometric Ca/P ratio were carried out with scanning electron microscope (SEM) and inductively coupled plasma atomic emission spectroscopy (ICP-AES) and a phase quantification was investigated by XRD. The solubility of HAp, $\beta$-TCP, and BCP powders was tested in the phosphate buffer solution (PBS) at $36.5^{\circ}C$ and pH = 7.4.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.109-117
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• 2010

Building a large-scale testbed for Future Internet is very important to evaluate a new protocol and new network architecture designed by clean-slate approach. In Korea, new Future Internet testbed project, called FIRST (Future Internet Research for Sustainable Testbed), has been started since Mar. 2009 to design and test new protocols. This project is working together with ETRI and 5 universities. The FIRST@PC is to implement a virtualized hardware-accelerated PC-node by extending the functions of NetFPGA card and build a Future Internet testbed on the KOREN and KREONET for evaluating newly designed protocols and interesting applications. In this paper, we first briefly introduce FIRST@PC project and explain a 'MAC in IP Capsulator' user-space program using raw-socket in Linux to interconnect OpenFlow enabled switch sites on the KOREN and KREONET. After that, we address test results for TCP throughput performance for varying packet size. The test results show that the software based capsulator can support a reasonable bandwidth performance for most of applications.

• Journal of the Institute of Convergence Signal Processing
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• v.15 no.1
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• pp.15-22
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• 2014

This paper presents the implementation of a control system of pellet boiler using wood pellet as carbon neutral material. The system also has the additional features to provide remote controlling and monitoring based on home networking technology through either public switched telephone networks or mobile communication networks. It consists of three kinds of sub-modules; a main controller provides basic and additional features such as a setting of temperature, a supplying of wood pellet, a controlling of ignition and fire-power, and a removing of soot. The second is temperature controller of individual rooms which is connected to the main controller through RS-485 links. And interface modules with PSTN and mobile networks can support remote controlling and monitoring the functions. The test results under the heating area of $172m^2$ show a thermal efficiency of 93.6%, a heating power of 20,640kcal/hr, and a fuel consumption of 5.54kg/hr. These results are superior to those of the conventional pellet boilers. In order to obtain the such high performance, we newly applied a 3-step ignition flow, a flame detection by $C_dS$ sensor, and a fire-power control by fine controlling of shutter to our pellet boiler.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.262-269
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• 2020

Recently, many attempts have been made to reduce the time required for payment in various shopping environments. In addition, for the Fourth Industrial Revolution era, artificial intelligence is advancing, and Internet of Things (IoT) devices are becoming more compact and cheaper. So, by integrating these two technologies, access to building an unmanned environment to save people time has become easier. In this paper, we propose a smart shopping cart system based on low-cost IoT equipment and deep-learning object-detection technology. The proposed smart cart system consists of a camera for real-time product detection, an ultrasonic sensor that acts as a trigger, a weight sensor to determine whether a product is put into or taken out of the shopping cart, an application for smartphones that provides a user interface for a virtual shopping cart, and a deep learning server where learned product data are stored. Communication between each module is through Transmission Control Protocol/Internet Protocol, a Hypertext Transmission Protocol network, a You Only Look Once darknet library, and an object detection system used by the server to recognize products. The user can check a list of items put into the smart cart via the smartphone app, and can automatically pay for them. The smart cart system proposed in this paper can be applied to unmanned stores with high cost-effectiveness.