Recommendations from the commercialization of government-sponsoredtelecommunications R&D with multiple development cycles inKorea

A number of government-sponsored large-scale R&D projects in the telecommunications sector have been carried out in Korea. Among them is the time division exchange (TDX) project that lasted for more than 15 years. The project has two characteristics: the commercialization of government-sponsored R&D and the commercialization of R&D with multiple development cycles. This paper describes these characteristics of the project from various viewpoints: product development strategy, the role of each organization, success factors of each product, the classification of commercial products by commercialization model, and technology transfer strategies encouraging participation of manufacturing firms. We conclude with several recommendations     

A three-phase current-fed dc/dc converter with a three-leg high frequency transformer for fuel cells

In this paper, a three-phase current-fed dc/dc converter with an active clamp is introduced, and a new three-phase three-leg high frequency transformer is proposed for the converter. The three-phase dc/dc converter transfers power through transformer leakage inductances in the discontinuous current mode; a single common active clamp branch is employed for zero-voltage switching (ZVS) in all active switches. Further, the converter's three-phase power configuration increases power transfer, and it reduces the rms current per phase, thus reduces conduction losses. Moreover, a delta–delta connection on the three-phase transformer provides parallel current paths and reduces conduction losses in the transformer windings. A three-phase transformer can be constructed by connecting three discrete single-phase transformers, but this process results in a higher volume and higher material costs. Therefore, a new three-phase three-leg high frequency transformer is designed with three discrete cores integrated into a single transformer core. The proposed transformer is analyzed according to the several operating modes of the converter, and its design rules are determined. Experimental results are obtained on a 500-W prototype unit; the design is fully verified and analyzed.     

Thermal Properties of Anisotropic and/or Inhomogeneous Suspended Thin Films Assessed via Dual-Side Time-Domain Thermoreflectance: A Numerical Study

Time-domain thermoreflectance (TDTR) is a powerful method for measuring thermal properties, such as thermal conductivity and thermal boundary resistance, of a broad variety of thin-film materials and interfaces. Dual-side TDTR, in which measurements are performed on the top and bottom sides of a suspended region of a thin film of interest, has recently emerged as an effective way to investigate the thermal properties of a film that is thermally anisotropic and/or inhomogeneous. Despite its experimental versatility, dual-side TDTR has yet to be fully interrogated. In this work, we examine the thermal conductivity and boundary resistance of anisotropic and/or inhomogeneous suspended thin films, extracted by dual-side TDTR on these films via numerical simulation. We start from a simple case of an anisotropic or inhomogeneous suspended membrane and then consider the combined case where the suspended membrane is both anisotropic and inhomogeneous. Taken together with analysis of measurement sensitivity, we aim to provide a general guideline for data extraction methodologies for dual-side TDTR on anisotropic and/or inhomogeneous suspended thin films.     

Integrated remote control of the process capability and the accuracy of vision calibration

This study aims at jointly controlling two critical process parameters from a remote site, of which include the process capability of robotic assembly operations and the accuracy of vision calibration. The process capability is regarded as the indication of robot positioning accuracy. When the robot is driven by the vision camera, the process capability becomes mainly dependent on the calibration accuracy of vision-guided robot system. Even though newly commissioned, high precision assembly robots typically display excellent positioning accuracies under normal working conditions, the imperfect mathematical conversion of vision coordinates into robot coordinates imparts the accuracy problems. In this study, a novel vision calibration method is proposed that effectively rectifies the inherent complications associated with lens distortions. Our analysis shows that the degree of lens distortion appears very differently along the vision field of view. Because of this non-uniform distortion, a single mathematical equation for vision calibration is deemed ineffective. The proposed methodology significantly improves the positioning accuracy, which can be performed over the network from a remote site. This is better suited for today?s global manufacturing companies, where fast product cycles and geographically distributed production lines dictate more efficient and effective quality control strategies.     

Reliability design and case study of refrigerator parts subjected to repetitive loads under consumer usage conditions

When newly designed refrigerator parts failed due to repetitive loads under consumer usage conditions in the field, a general method for reliability design was proposed. A newly designed refrigerator compressor system that brings greater energy efficiency to side-by-side (SBS) refrigerators was studied. The laboratory failure mode and mechanism of the compressor was a stopping nose due to design flaws. The data on the failed products in the field, accelerated life tests (ALT) and corrective action plans were used to identify the key control parameters for the mechanical compressor system. The missing controllable design parameters of the compressor system in the design phase were the gap between the frame and the upper due to the stator frame shape. After a tailored series of accelerated life tests with corrective action plans, the B₁ life of the new compressor system is now guaranteed to be over 10 years with a yearly failure rate of 0.1%.     

Site calibration for the wind turbine performance evaluation

The accurate wind speed information at the hub height of a wind turbine is very essential to the exact estimation of the wind turbine power performance testing. Several methods on the site calibration, which is a technique to estimate the wind speed at the wind turbine’s hub height based on the measured wind data using a reference meteorological mast, are introduced. A site calibration result and the wind resource assessment for the TaeKwanRyung test site are presented using three-month wind data from a reference meteorological mast and the other mast temporarily installed at the site of wind turbine. Besides, an analysis on the uncertainty allocation for the wind speed correction using site calibration is performed.     

Thickness-dependent thermal conductivity of ultrathin (< 100 nm) barium titanate films

Thin film barium titanate (BaTiO₃) is a promising material in the electronics and ceramics industry owing to its compelling dielectric properties. A number of works have investigated its dielectric and structural properties, but less studied are its thermal properties particularly at sub-100?nm thicknesses. Here, we measure the room-temperature thermal conductivity of ultrathin (< 100?nm), pulsed laser deposited BaTiO₃ films. The measured thermal conductivities are thickness-dependent, and this trend is consistent with the thickness-dependent crystallinity of the films. Transmission electron microscopy analysis of the films reveals the presence of an initial amorphous layer ~?60?nm thick from the growth interface and the subsequent formation of columnar grains of width ~ 12?nm that are embedded within an amorphous matrix. For a region that incorporates grains with columnar morphology, we find that cross-plane heat conduction may be favored by 30–40% over in-plane heat conduction due to the columnar morphology of grains.     

Thermal conductivity of yttria-stabilized zirconia thin films grown by plasma-enhanced atomic layer deposition

Zirconia doped with yttrium, widely known as yttria-stabilized zirconia (YSZ), has found recent applications in advanced electronic and energy devices, particularly when deposited in thin film form by atomic layer deposition (ALD). Although ample studies reported the thermal conductivity of YSZ films and coatings, these data were typically limited to Y₂O₃ concentrations around 8 mol% and thicknesses greater than 1 μm, which were primarily targeted for thermal barrier coating applications. Here, we present the first experimental report of the thermal conductivity of YSZ thin films (∼50 nm), deposited by plasma-enhanced ALD (PEALD), with variable Y₂O₃ content (0–36.9 mol%). Time-domain thermoreflectance measures the effective thermal conductivity of the film and its interfaces, independently confirmed with frequency-domain thermoreflectance. The effective thermal conductivity decreases from 1.85 to 1.22 W m⁻¹ K⁻¹ with increasing Y₂O₃ doping concentration from 0 to 7.7 mol%, predominantly due to increased phonon scattering by oxygen vacancies, and exhibits relatively weak concentration dependence above 7.7 mol%. The effective thermal conductivities of our PEALD YSZ films are higher by ∼15%–128% than those reported previously for thermal ALD YSZ films with similar composition. We attribute this to the relatively larger grain sizes (∼23–27 nm) of our films.     

Shock tube measurements of species time-histories in monomethyl hydrazine pyrolysis

The first measurements of NH₂ and NH₃ time-histories in monomethyl hydrazine (MMH) pyrolysis were performed behind reflected shock waves in a shock tube using laser absorption techniques. An improved measurement of MMH using IR laser absorption is also presented. MMH concentrations of ∼1% in Ar were employed, over the temperature range 941–1252 K, at pressures near 2 atm. NH₂ was measured at the peak of the overlapping doublet lines at 16739.90 cm⁻¹ (597.4 nm). NH₃ and MMH were measured using direct absorption of CO₂ laser lines at 9.22 and 10.22 μm, respectively. These measurements were then compared to a current comprehensive MMH pyrolysis mechanism based on the work of Sun et al. (2009) and Zhang et al. (2010). Based on the measurements of NH₂ and NH₃, it was possible to measure rate coefficients for two key reactions in the MMH pyrolysis system:(1)CH₃NHNH₂→CH₃NH+NH₂(2)CH₃NHNH₂+NH₂→CH₃NNH₂+NH₃These rates combined with the measured overall MMH decomposition rate strongly imply that Reaction (1) is the dominant MMH decomposition channel. The following rate coefficients (2 atm, 900–1300 K) were uniquely determined:Based on the MMH measurement, the value of the CH₃ decomposition channel is 0–20% of the NH₂ channel, and a value of 1.64 × 10⁵⁸ * T^−12.84 exp(−39580/T) s⁻¹ is recommended for the overall unimolecular decomposition of MMH. Further analysis of the NH₂ measurements indicate that the rate of the following reaction used in the Princeton mechanism should also be significantly increased:(4)CH₃NNH+NH₂→CH₃NN+NH₃The changes to the MMH pyrolysis mechanism recommended in this work result in greatly improved agreement between measured and modeled NH₂, NH₃, and MMH time-histories over the entire range of the study.     

Design and evaluation of disturbance observer algorithm for cable-driven parallel robots

Recently, a cable-driven parallel robots (CDPRs) has been applied to radio telescope as the accurate actuator, that is the five-hundred-meter aperture spherical telescope. It can be affected by the disturbances such as wind, earthquake and so on. Therefore, this paper developed a disturbance observer (DOB)-based control suitable for CDPR. The propose of the control is to reduce the effects of disturbance while the end-effectors maintains the same position even though the disturbance affects it. The key component of the DOB controller is a disturbance observer, which includes inverse nominal plant for each cable. So, a system identification test was carried out firstly. Then, the simulation and experiment were also carried out to evaluate the performance of the algorithm in CDPR. The results showed that the designed DOB algorithm could effectively reduce disturbances.