• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.361-365
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• 2002

Advancements in silicon phase control (SCR) technologies provide an arc welding power supply that has the capability to allow the alteration of the Alternating Current (AC) welding output. These technologies provide a square wave output involving sixteen frequency selections and multiple balance selections. While an AC out put is known to minimize magnetic disturbances associate with Direct Current (DC), the potentials of a non-sinusoidal waveform have not been explored. The focus of the paper is to determine the effects that the frequency and balance of an AC wave form output will have upon a high speed Submerge Arc (SAW) application. The test matrix of the project includes welding .250" steel plate. Joint type is square groove with a travel speed of 65 IPM. Each of the weld parameters was held constant, only the frequency and/or balance were altered between welds. Each frequency/balance combination involved three-gap spacing. Upon completion of the welds the bead profiles were measured and recorded. A relationships/trends were observed with various frequency and balance values. Optimum frequency and balance values were found for the .250" square groove application which permit consistent weld sizing, ease of slag removal, and minimal plate distortion.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.385-388
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• 1999

A new frequency-variant equivalent circuit model of power/ground plane is presented. The equivalent circuit is modeled with grid cells. The circuit parameters of each cell were extracted by using Fasthenry. To verify the developed circuit model, its s-parameters are compared with the measured s-parameters 〔2〕 and the full-wave simulation-based s-parameters. Consequently, it is shown that our frequency-variant equivalent circuit model can accurately predict imperfect ground effects under the high frequency operation of electronic package.

• Structural Engineering and Mechanics
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• 제89권6호
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• pp.589-599
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• 2024

This study presents the usability of the high-rate single-frequency Precise Point Positioning (SF-PPP) technique based on 20 Hz Global Positioning Systems (GPS)-only observations in detecting dynamic motions. SF-PPP solutions were obtained from post-mission and real-time GNSS corrections. These include the International GNSS Service (IGS)-Final, IGS real-time (RT), real-time MADOCA (Multi-GNSS Advanced Demonstration tool for Orbit and Clock Analysis), and real-time products from the Australian/New Zealand satellite-based augmentation systems (SBAS, known as SouthPAN). SF-PPP results were compared with LVDT (Linear Variable Differential Transformer) sensor and single-frequency relative positioning (SF-RP) solutions. The findings show that the SF-PPP technique successfully detects the harmonic motions, and the real-time products-based PPP solutions were as accurate as the final post-mission products. In the frequency domain, all GNSS-based methods evaluated in this contribution correctly detect the dominant frequency of short-term harmonic oscillations, while the differences in the amplitude values corresponding to the peak frequency do not exceed 1.1 mm. However, evaluations in the time domain show that SF-PPP needs high-pass filtering to detect accurate displacement since SF-PPP solutions include trends and low-frequency fluctuations, mainly due to atmospheric effects. Findings obtained in the time domain indicate that final, real-time, and MADOCA-based PPP results capture short-term dynamic behaviors with an accuracy ranging from 3.4 mm to 8.5 mm, and SBAS-based PPP solutions have several times higher RMSE values compared to other methods. However, after high-pass filtering, the accuracies obtained from PPP methods decreased to a few mm. The outcomes demonstrate the potential of the high-rate SF-PPP method to reliably monitor structural and earthquake-induced ground motions and vibration frequencies of structures.

• 경영과학
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• 제33권1호
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• pp.17-33
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• 2016

This study investigated the relationships among proper types of e-commerce, patterns of inter-organizational information flow (IIF), benefits of e-commerce, and supply-chain performance. In IIF, it was empirically observed that environmental competition positively influences the frequency of IIF, and environmental uncertainty has a positive impact on the quality of IIF. It was also empirically confirmed that only quality of IIF has effects on the usage levels of e-procurement as well as e-partnerships. Through regression analyses and cluster analysis, it was found that under high degrees of the frequency and quality of IIF, the benefits of e-commerce are vastly realized in the firms that highly utilize e-partnerships. The results of this study also showed that when the degrees of quality of IIF are high, the levels of benefits of e-commerce are increased in the firms that employ e-procurement. The moderating effects of buyer and supplier firms' abilities on the relationships between patterns of IIF and usage levels in various types of e-commerce were empirically examined. According to the results, the moderating roles of buyer firms' capabilities and suppliers' abilities were partially demonstrated. Finally, it was found that the realization of benefits of e-commerce can lead to the improvement of supply-chain performance.

• Journal of Acupuncture Research
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• 제26권2호
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• pp.79-89
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• 2009

Objectives : The aim of this study was to observe the effect of acupuncture and high frequency electroacupuncture at $ST_{39}$ on intestinal motility in rats. Methods: We made over-activated state of intestinal motility with carbachol and suppressed state of intestinal motility with loperamide in rat and carried out needle retention acupuncture and high frequency electroacupuncture at $ST_{39}$ or sham point in rat divided into pre-treatment group and post-treatment group. We fed charcoal to them after the treatment and measured the travel rate of charcoal in the gastrointestinal tract to observe intestinal motility. Results : Examining intestinal motility of normal rat treated with needle retention acupuncture at $ST_{39}$ significantly suppressed intestinal motility. Pre-treatment of needle retention acupuncture significantly suppressed intestinal motility in rat which over-activated with carbachol. Pre-treatment and post-treatment of high frequency electroacupuncture significantly suppressed intestinal motility in rat which over-activated with carbachol. All of the pre-treatment and post-treatment of needle retention acupuncture, high frequency electroacupuncture showed no significant effect than control group on intestinal motility of rat which was suppressed with loperamide. Conclusions : These results suggest that acupuncture and high frequency electroacupuncture at $ST_{39}$ have preventive and therapeutic effects on over-activated intestinal motility, and high frequency electroacupuncture is more effective.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.326-328
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• 2005

In order to reduce the capital and overall operating cost of a fuel-cell system, a high-efficiency fuel-cell power inverter with a simple framework is required. The high-order two-inductance two-capacitance (LLCC) resonant technique is adopted in this study to implement a low-frequency 60-Hz sine wave voltage inverter utilized in the proton exchange membrane fuel-cell (PEMFC) system. The methodology for inverting dc voltage into low-frequency ac boltage is usually generated by the pulse-width-modulation (PWM) technique. However, the PWM-type inverter output has high-frequency harmonic components. Although an adequately designed filter could be utilized to overcome this problem, there are still some undesirable effects introduced by the high-frequency switching loss, electromagnetic-interference, harmonic current, and load variation. A novel power inverter via the LLCC resonant technique is designed for inverting dc voltage into 60-Hz ac sine wave voltage in the PEMFC system. This circuit scheme has the merits of low harmonic components, soft switching, high efficiency, and simplified implementation. The effectiveness of the proposed resonant inverter used for the PEMFC system is verified by numerical simulations and experimental results.

• 한국가구학회지
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• 제17권2호
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• pp.25-34
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• 2006

This experiment was carried out to investigate the high-frequency gluing characteristics of poly vinyl acetate emulsion adhesive(PVAc) on MDF edge-glued boards. The edge-glued boards were glued lengthwise with butt, scarf, or finger joint. The wastes of MDF boards were reused as board materials. The obtained results are summarized as follows; the bending strength of edge-glued MDF increased slightly with the HF heating time, but the economically desirable heating time was 6 minutes. The bending and tensile strength of edge-glued MDF were high with scarf, finger and butt joint, in order. The strength of finger jointed MDF showed 80% of scarf jointed MDF. The effects of location of finger joints on the bending strength of edge-glued MDF were larger than those of the numbers of finger joints. The bending strength of edge-glued MDF with one joint on the middle position showed 40% decrease in comparison with non-jointed MDF.

• 한국문헌정보학회지
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• 제23권
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• pp.165-205
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• 1992

The purpose of this research is to verify the hypothesis that the serious ness of barriers may have significant relevance to barrier components expressing the extent of barrier, e. g. their frequency of occurrence, effect of the barrier on the acquisition of information and on the research project and trend of the barrier. Major conclusions made in this research are summarized as follows: 1. Barriers that their frequency of occurrence are high, show high seriousness of barriers. This indicates that frequency of barriers affects the seriousness of barriers. 2. Barriers that their effects on the acquisition of information and on the research project are large, show high seriousness of barriers. This indicates that the effect of the barrier on the acquisition of information and on the research project affects the seriousness of barriers. 3. Barriers that their trends are increasing, show high seriousness of barriers. This indicates that the trend of the barrier affects the seriousness of barriers.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.924-925
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• 2006

In this study, hydroxyapatite (HAp) and hydroxyapatite-yttria stabilized zirconia (HAp-3YSZ) with 20 vol.%-($ZrO_2+3%mol\;Y_2O_3$) nanopowders were consolidated very rapidly to full density by High-frequency induction heat sintering (HFIHS). Effects of temperature and the addition of 3YSZ on the toughness, hardness and microstructure properties have been studied. 3YSZ second phase toughening HAp composites with higher toughness were successfully developed at relatively low temperatures through this technique. Compared with hardness and toughness obtained for pure HAp, the hardness and toughness for HAp-20vol. % 3YSZ were much higher.

• Journal of information and communication convergence engineering
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• 제3권1호
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• pp.28-32
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• 2005

In this paper, we propose a novel test method to effectively detect hard and soft faults in CMOS 2-stage op-amps. The proposed method uses a very high frequency sinusoidal signal that exceeds unit gain bandwidth to maximize the fault effects. Since the proposed test method doesn't require any complex algorithms to generate the test pattern and uses only a single test pattern to detect all target faults, therefore test costs can be much reduced. The area overhead is also very small because the CUT is converted to a unit gain amplifier. Using HSPICE simulation, the results indicated a high degree of fault coverage for hard and soft faults in CMOS 2-stage op-amps. To verify this proposed method, we fabricated a CMOS op-amp that contained various short and open faults through the Hyundai 0.65-um 2-poly 2-metal CMOS process. Experimental results for the fabricated chip have shown that the proposed test method can effectively detect hard and soft faults in CMOS op-amps.