• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.197-199
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• 2002

The invention of VHDL(Very High Speed Integrated Circuit Hardware Description Language), Technical language of Hardware, is a kind of turning point in digital circuit designing, which is being more and more complicated and integrated. Because of its excellency in expression ability of hardware, VHDL is not only used in designing Hardware but also in simulation for verification, and in exchange and conservation, composition of the data of designs, and in many other ways. Especially, It is very important that VHDL is a Technical language of Hardware standardized by IEEE, intenational body with an authority. The biggest problem in modern circuit designing can be pointed out in two way. One is a problem how to process the rapidly being complicated circuit complexity. The other is minimizing the period of designing and manufacturing to survive in a cutthroat competition. To promote the use of VHDL, more than a simple use of simulation by VHDL, it is requested to use VHDL in composing logical circuit with chip manufacturing. And, by developing the quality of designing technique, it can contribute for development in domestic industry related to ASIC designing. In this paper in designing SMPS(Switching mode power supply), programming PWM by VHDL, it can print static voltage by the variable load, connect computer to chip with byteblaster, and download in Max(EPM7064SLCS4 - 5)chip of ALTER. To achieve this, it is supposed to use VHDL in modeling, simulating, compositing logic and product of the FPGA chip. Despite its limit in size and operating speed caused by the specific property of FPGA chip, it can be said that this method should be introduced more aggressively because of its prompt realization after designing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.781-785
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• 2015

In this study, a newly developed ultrasonic fatigue test was performed for durability assessment of polyoxymethylene engineering plastic, which has a high crystallization rate and degree of crystallization. Fatigue strength of POM (polyoxymethylene) was performed on a piezoelectric UFT developed by Mbrosia Co., Ltd(1), operating at a high frequency of 20 kHz. The test results showed a fatigue limit of 5.0~6.0 MPa under fatigue testing at R = -1, 20kHz; and, electron microscopy revealed the size effect by risk volume and fractured dimple structure after the coalescence of micro-voids through the crazing effect, which occurs during the failure of a polymer.

• Journal of Korea Society of Industrial Information Systems
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• v.21 no.2
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• pp.21-29
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• 2016

Capstone design course in current domestic software education environment has been opened in undergraduate courses in order to improve student's practical skills. However, the capstone design course is hardly applied the software convergence trend. We opened the capstone design course in not only the students in certain department, but also the students in other departments in order to solve this problem, and then we analyzed the operating results of this capstone design course. In the analyzed result, we find that operation of the convergence capstone design course is enough satisfactory, but we find that the operation of the convergence capstone design course has the limit that the certain department operates individually the convergence capstone design project. Hence, we need that the convergence capstone design course is preferably operated as the department-integration.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.1-11
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• 2005

This study applied EK method to remediate contaminated soil by lead (Pb), tried increasing efficiency of remediation using adsorbent (apatite and zeolite) as enhanced EK remediation method to overcome the limit of traditional EK remediation method. Adsorption tests on Pb were practiced to extract EK, making different concentration of contaminated soil, voltage condition, operating time etc., transferring Pb-ion into the position of adsorbent, then tried immobilization. On this results, the efficiency of remediation is different on its test conditions. In addition, the efficiency of remediation was not only improved by adding electrode revεrsal and install position of adsorbent but also satisfied TCLP regulation of EPA in USA through the whole sample range. Finally, absorption and immobilization capacity of apatite and zeolite proved on its excellence and confirmed the possibility of application of apatite and zeolite as enhanced EK remediation method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.797-803
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• 2012

Proportional solenoid valves are a modulating type that can control the displacement of valves continuously by means of electromagnetic forces proportional to the solenoid coil current. Because the solenoid-type modulating valves have the advantages of fast response and compact design over air-operated or motor-operated valves, they have been gaining acceptance in chemical and power plants to control the flow of fluids such as water, steam, and gas. This paper deals with the auto tuning of the position controller that can provide the proportional and integral gain automatically based on the dynamic system identification. The process characteristics of the solenoid valve are estimated with critical gain and critical period at a stability limit based on implemented relay feedback, and the controller parameters are determined by the classical Ziegler-Nichols design method. The auto-tuning algorithm was verified with experiments, and the effects of the operating point at which the relay control is activated as well as the relay amplitude were investigated.

• Korean Journal of Materials Research
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• v.22 no.5
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• pp.237-242
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• 2012

We report on the NO gas sensing properties of Al-doped zinc oxide-carbon nanotube (ZnO-CNT) wire-like layered composites fabricated by coaxially coating Al-doped ZnO thin films on randomly oriented single-walled carbon nanotubes. We were able to wrap thin ZnO layers around the CNTs using the pulsed laser deposition method, forming wire-like nanostructures of ZnO-CNT. Microstructural observations revealed an ultrathin wire-like structure with a diameter of several tens of nm. Gas sensors based on ZnO-CNT wire-like layered composites were found to exhibit a novel sensing capability that originated from the genuine characteristics of the composites. Specifically, it was observed by measured gas sensing characteristics that the gas sensors based on ZnO-CNT layered composites showed a very high sensitivity of above 1,500% for NO gas in dry air at an optimal operating temperature of $200^{\circ}C$; the sensors also showed a low NO gas detection limit at a sub-ppm level in dry air. The enhanced gas sensing properties of the ZnO-CNT wire-like layered composites are ascribed to a catalytic effect of Al elements on the surface reaction and an increase in the effective surface reaction area of the active ZnO layer due to the coating of CNT templates with a higher surface-to-volume ratio structure. These results suggest that ZnO-CNT composites made of ultrathin Al-doped ZnO layers uniformly coated around carbon nanotubes can be promising materials for use in practical high-performance NO gas sensors.

• Nuclear Engineering and Technology
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• v.39 no.6
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• pp.747-752
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• 2007

The Proton Engineering Frontier Project (PEFP) has designed and developed a proton linear accelerator facility operating at 100 MeV - 20 mA. The radiological effects of such a nuclear facility on the environment are important in terms of radiation safety. This study estimated the production rates of radionuclides in the soil around the accelerator facility using MCNPX. The groundwater migration of the radioisotopes was also calculated using the Concentration Model. Several spallation reactions have occurred due to leaked neutrons, leading to the release of various radionuclides into the soil. The total activity of the induced radionuclides is approximately $2.98{\times}10^{-4}Bq/cm^3$ at the point of saturation. $^{45}Ca$ had the highest production rate with a specific activity of $1.78{\times}10^{-4}Bq/cm^3$ over the course of one year. $^3H$ and $^{22}Na$ are usually considered the most important radioisotopes at nuclear facilities. However, only a small amount of tritium was produced around this facility, as the energy of most neutrons is below the threshold of the predominant reactions for producing tritium: $^{16}O(n,\;X)^3H$ and $^{28}Si(n,X)^3H$ (approximately 20 MeV). The dose level of drinking water from $^{22}Na$ was $1.48{\times}10^{-5}$ pCi/ml/yr, which was less than the annual intake limit in the regulations.

• Korean Journal of Materials Research
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• v.22 no.11
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• pp.609-614
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• 2012

We report on the NO gas sensing properties of non-directional ZnO nanofibers synthesized using a typical electrospinning technique. These non-directional ZnO nanofibers were electrospun on an $SiO_2$/Si substrate from a solution containing poly vinyl alcohol (PVA) and zinc nitrate hexahydrate dissolved in distilled water. Calcination processing of the ZnO/PVA composite nanofibers resulted in a random network of polycrystalline ZnO nanofibers of 50 nm to 100 nm in diameter. The diameter of the nanofibers was found to depend primarily on the solution viscosity; a proper viscosity was maintained by adding PVA to fabricate uniform ZnO nanofibers. Microstructural measurements using scanning electron microscopy revealed that our synthesized ZnO nanofibers after calcination had coarser surface morphology than those before calcination, indicating that the calcination processing was sufficient to remove organic contents. From the gas sensing response measurements for various NO gas concentrations in dry air at several working temperatures, it was found that gas sensors based on electrospun ZnO nanofibers showed quite good responses, exhibiting a maximum sensitivity to NO gas in dry air at an operating temperature of $200^{\circ}C$. In particular, the non-directional electrospun ZnO nanofiber gas sensors were found to have a good NO gas detection limit of sub-ppm levels in dry air. These results illustrate that non-directional electrospun ZnO nanofibers are promising for use in low-cost, high-performance practical NO gas sensors.

• Korean Journal of Materials Research
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• v.24 no.3
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• pp.152-158
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• 2014

We report the effect of the fabric of the surface microstructure on the CO gas sensing properties of $SnO_2$ thin films deposited on self-assembled Au nanodots ($SnO_2$/Au) that were formed on $SiO_2/Si$ substrates. We characterized structural and morphological properties, comparing them to those of $SnO_2$ thin films deposited directly onto $SiO_2/Si$ substrates. We observed a significant enhancement of CO gas sensing properties in the $SnO_2$/Au gas sensors, specifically exhibiting a high maximum response at $200^{\circ}C$ and quite a low detection limit of 1 ppm level in dry air. In particular, the response of the $SnO_2/Au$ gas sensor was found to reach the maximum value of 32.5 at $200^{\circ}C$, which is roughly 27 times higher than the response (~1.2) of the $SnO_2$ gas sensor obtained at the same operating temperature of $200^{\circ}C$. Furthermore, the $SnO_2/Au$ gas sensors displayed very fast response and recovery behaviors. The observed enhancement in the CO gas sensing properties of the $SnO_2/Au$ sensors is mainly ascribed to the formation of a nanostructured morphology in the active $SnO_2$ layer having a high specific surface-reaction area by the insertion of a nanodot form of Au nucleation layer.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.181-186
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• 2015

With the rapid growth of semiconductor technologies, small-sized devices with powerful computing abilities are becoming a reality. As this environment has a limit on power supply, NVM storage that has a high density and low power consumption is preferred to HDD or SSD. However, legacy software layers optimized for HDDs should be revisited. Specifically, as storage performance approaches DRAM performance, existing I/O mechanisms and software configurations should be reassessed. This paper explores the challenges and implications of using NVM storage with a broad range of experiments. We measure the performance of a system with NVM storage emulated by DRAM with proper timing parameters and compare it with that of HDD storage environments under various configurations. Our experimental results show that even with storage as fast as DRAM, the performance gain is not large for read operations as current I/O mechanisms do a good job hiding the slow performance of HDD. To assess the potential benefit of fast storage media, we change various I/O configurations and perform experiments to quantify the effects of existing I/O mechanisms such as buffer caching, read-ahead, synchronous I/O, direct I/O, block I/O, and byte-addressable I/O on systems with NVM storage.