• Knowledge Management Research
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• v.13 no.3
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• pp.55-77
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• 2012

Selecting promising technology is becoming more and more difficult due to the increased number and complexity. In this study, we propose hybrid AHP/DEA-AR method and hybrid AHP/DEA-AR-G method to evaluate efficiency of technology alternatives based on ordinal rating data collected through survey to technology experts in a certain field and select efficient technology alternative as promising technology. The proposed method normalizes rating data and uses AHP to derive weights to improve the credibility of analysis, then in order to avoid basic DEA models' problems, use DEA-AR and DEA-AR-G to evaluate efficiency of technology alternatives. In this study, we applied the proposed methods to clean technology and compared with the basic DEA models. According to the result of the comparison, we can find that the both proposed methods are excellent in confirming most efficient technology, and hybrid AHP/DEA-AR method is much easier to use in the process of technology selection.

• Journal of Hydrogen and New Energy
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• v.27 no.2
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• pp.182-191
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• 2016

In the present work, a solar assisted heat pump (SAHP) system with a hybrid collector was analyzed. For this, a simplified thermodynamic model was developed. Based on the proposed model, the heat transfer rate, COP, and the annual operating hour of the SAHP system were estimated. The effect of the variation of system design parameters on the performance of the system was also examined. From the results, the performance was improved with increasing the effectiveness of heat exchangers and decreasing the difference between the evaporation temperature and the outlet brine temperature of the hybrid collector loop. Finally, the performance of SAHP system with a hybrid collector was compared with that of conventional serial and parallel SAHP systems. The SAHP system with a hybrid collector was substantially better than a series system and slightly worse than a parallel system for both the yearly averaged heat transfer rate and COP. However, the annual operating hour of the SAHP system with a hybrid collector was much better than that of a parallel system.

• Structural Engineering and Mechanics
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• v.57 no.1
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• pp.141-159
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• 2016

Bearing joint dynamic parameter identification is crucial in modeling the high speed spindles for machining centers used to predict the stability and natural frequencies of high speed spindles. In this paper, a hybrid method is proposed to identify the dynamic stiffness of bearing joint for the high speed spindles. The hybrid method refers to the analytical approach and experimental method. The support stiffness of spindle shaft can be obtained by adopting receptance coupling substructure analysis method, which consists of series connected bearing and joint stiffness. The bearing stiffness is calculated based on the Hertz contact theory. According to the proposed series stiffness equation, the stiffness of bearing joint can be separated from the composite stiffness. Then, one can obtain the bearing joint stiffness fitting formulas and its variation law under different preload. An experimental set-up with variable preload spindle is developed and the experiment is provided for the validation of presented bearing joint stiffness identification method. The results show that the bearing joint significantly cuts down the support stiffness of the spindles, which can seriously affects the dynamic characteristic of the high speed spindles.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.4
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• pp.475-483
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• 2012

This paper presents new type of the hybrid supply modulator for the next reconfigurable transmitters. The efficiency of the hybrid supply modulator is one of the most important performance. For enhancement the efficiency, multi-switching structure in the hybrid supply modulator is employed. Additionally, input envelope signal sensing stage is employed for implementation multi-mode operation. To compare the performance of the proposed hybrid supply modulator, the conventional hybrid supply modulator is also designed. The measured efficiency of the proposed hybrid supply modulator is 85 %/84 %/79 % for EDGE/WCDMA/LTE signals which have 384 kHz/3.84 MHz/5 MHz bandwidth, respectively. The efficiency of the proposed hybrid supply modulator is higher than the conventional hybrid supply modulator. Therefore, this structure shows good candidate for the reconfigurable transmitters.

• Macromolecular Research
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• v.17 no.12
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• pp.950-955
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• 2009

The physical and rheological properties of thermoplasticized irradiation-crosslinked polyethylene foam using supercritical methanol treatment were investigated by GPC, FTIR, DSC, WAXS, DMTA and UDS. The polyethylene foam was selectively decrosslinked into thermoplasticized polyethylene in an appropriate supercritical methanol condition without any undesirable side reactions such as oxidation and disproportionation. The thermoplasticization was promoted with increasing reaction temperature to reach completion above $380^{\circ}C$. The supercritical reaction condition affected the crystallization behavior, and mechanical and rheological properties of the decrosslinked polyethylene foam, but not its crystallographic structure or crystallinity.

• Carbon letters
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• v.11 no.2
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• pp.90-95
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• 2010

Carbon materials such as graphite and graphene exhibit high electrical conductivity. We examined the electrical conductivity of synthetic and natural graphene powders after the chemical reduction of synthetic and natural graphite oxide from synthetic and natural graphite. The trend of electrical conductivity of both graphene (synthetic and natural) was compared with different graphite materials (synthetic, natural, and expanded) and carbon nanotubes (CNTs) under compression from 0.3 to 60 MPa. We found that synthetic graphene showed a marked increment in electrical conductivity compared to natural graphene. Interestingly, the total increment in electrical conductivity was greater for denser graphite; however, an opposite behavior was observed in nanocarbon materials such as graphene and CNTs, probably due to the differing layer arrangement of nanocarbon materials.

• Journal of Electrochemical Science and Technology
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• v.4 no.1
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• pp.19-26
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• 2013

Graphene/Ni-Al layered double hydroxide (LDH) hybrid materials were synthesized by a hydrothermal reaction. Hexagonal Ni-Al LDH particles nucleated and grew on graphene sheets, thus preventing restacking of the graphene sheets and aggregation of the Ni-Al LDH nanoparticles upon drying. Electrode made from the graphene/Ni-Al LDH hybrid materials showed a substantial improvement in electrochemical capacitance relative to those made with pure Ni-Al LDH nanoparticles. In addition, the graphene/Ni-Al LDH hybrid composite materials showed remarkable stability after 4000 cycles with over 100% capacitance retention. These materials are thus very promising for use in electrochemical capacitor electrodes.

• Journal of Hydrogen and New Energy
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• v.34 no.1
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• pp.32-37
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• 2023

In this study, in order to propose a integrity evaluation for type IV high aspect ratio hydrogen storage vessel, a numerical analysis of the hoop tensile test and pressure test was performed using FEM software, and the results of the actual physical property test were reviewed. The property test and numerical analysis were compared, and very similar results were obtained with deviations of maximum tensile strength of 4.75% and fiber direction stress of 5.39%.

• Journal of the Semiconductor & Display Technology
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• v.22 no.4
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• pp.38-47
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• 2023

Three dimensional (3D) packaging is a next-generation packaging technology that vertically stacks chips such as memory devices. The necessity of 3D packaging is driven by the increasing demand for smaller, high-performance electronic devices (HPC, AI, HBM). Also, it facilitates innovative applications across another fields. With growing demand for high-performance devices, companies of semiconductor fields are trying advanced packaging techniques, including 2.5D and 3D packaging, MR-MUF, and hybrid bonding. These techniques are essential for achieving higher chip integration, but challenges in mass production and fine-pitch bump connectivity persist. Advanced bonding technologies are important for advancing the semiconductor industry. In this review, it was described 3D packaging technologies for chip integration including mass reflow, thermal compression bonding, laser assisted bonding, hybrid bonding.

• Journal of Internet Technology
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• v.21 no.3
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• pp.849-859
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• 2020

High-performance computing (HPC) systems provide huge computational resources and large memories. The hybrid memory is a promising memory technology that contains different types of memory devices, which have different characteristics regarding access time, retention time, and capacity. However, the increasing performance and employing hybrid memories induce more complexity as well. In this paper, we propose a roofline-based data migration methodology called HyDM to effectively use hybrid memories targeting at Intel Knight Landing (KNL) processor. HyDM monitors status of applications running on a system and migrates pages of selected applications to the High Bandwidth Memory (HBM). To select appropriate applications on system runtime, we adopt the roofline performance model, a visually intuitive method. HyDM also employs a feedback mechanism to change the target application dynamically. Experimental results show that our HyDM improves over the baseline execution the execution time by up to 44%.