Browsing by Author "Yu, HC"

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1.3 mu m quantum dot vertical-cavity surface-emitting laser with external light injection
(2005-10-27)
Peng, PC
;
Chang, YH
;
Kuo, HC
;
Tsai, WK
;
Lin, G
A 1.3 mu m quantum dot vertical-cavity surface-emitting laser (QD VCSEL) with external light injection is presented, having been experimentally demonstrated. The QD VCSEL is fabricated on GaAs substrate. The 3 dB frequency response of the QD VCSEL based on the TO-Can package is enhanced from the free-running 1.75 to 7.44 GHz with the light injection technique.
1.3-mu m InAs-InGaAs quantum-dot vertical-cavity surface-emitting laser with fully doped DBRs grown by MBE
(2006-01-01)
Yu, HC
;
Wang, JS
;
Su, YK
;
Chang, SJ
;
Lai, FI
We report InAs-InGaAs quantum-dot vertical-cavity surface-emitting lasers (VCSELs) grown by molecular beam epitaxy with fully doped n- and p-doped AlGaAs distributed Bragg reflectors and including an AlAs layer to form a current and waveguiding aperture. The metal contacts are deposited on a topmost p(+) (GaAs)-Ga-. contact layer and on the bottom surface of the n(+)-GaAs substrate. This conventional selectively oxidized top-emitting device configuration avoids the added complexity of fabricating intracavity or coplanar ohmic contacts. The VCSELs operate continuous-wave at room temperature with peak output powers of 0.33 mW and differential slope efficiencies up to 0.23 W/A. The peak lasing wavelengths are near 1.275 mu m, with a sidemode suppression ratio of 28 dB.
A Litterman BVAR approach for production forecasting of technology industries
(2003-01-01)
Hsu, PH
;
Wang, CH
;
Shyu, JZ
;
Yu, HC
;
統計學研究所
Forecasting the production of technology industries is important to entrepreneurs and governments, but usually suffers from market fluctuation and explosion. This paper aims to propose a Litterman Bayesian vector autoregression (LBVAR) model for production prediction based on the interaction of industrial clusters. Related industries within industrial clusters are included into the LBVAR model to provide more accurate predictions. The LBVAR model possesses the superiority of Bayesian statistics in small sample forecasting and holds the dynamic property of the vector autoregression (VAR) model. Two technology industries in Taiwan, the photonics industry and semiconductor industry are used to examine the LBVAR model using a rolling forecasting procedure. As a result, the LBVAR model was found to be capable of providing outstanding predictions for these two technology industries in comparison to the autoregression (AR) model and VAR model. (C) 2002 Elsevier Science Inc. All rights reserved.
A preliminary report on the Phase-I ATSC field test results in Taiwan
(2000)
Tsai, JF
;
Lin, CC
;
Hang, HM
;
Tarng, JH
;
Yu, HC
In May 1998, Taiwan formally adopted the ATSC Digital Television (DTV) as its local digital terrestrial broadcasting standard. In order to define the DTV service area and specify the transmission parameters, we like to know the characteristics of the DTV signal over the local irregular terrain, the impact of interference, and the relationship between the signal power and video quality. me measured the DTV signal and compared the DTV and the NTSC service availability. We selected 100 test sites in Taipei city and its vicinity including three types of environment: urban, suburban and rural areas. In general, the DTV system has a clear advantage over the NTSC system in reception quality.
A study of alternative broadcasting technologies for the extension of DTV coverage in Taiwan
(2000-12-01)
Yu, HC
;
Tarng, JH
;
Hang, HM
;
Lee, ZY
;
電子工程學系及電子研究所
In Taiwan. there are six major NTSC terrestrial broadcasting stations and 129 relay stations, which cover about 98% of Taiwan's population. This paper addresses the planning of DTV broadcasting in Taiwan. DTV signals will be broadcast from the same six major transmitting sites and are expected to provide similar coverage. To extend DTV coverage beyond the major transmitting sites, only the existing 9 NTSC relay stations with over 100W transmitting power would relay DTV signals. Residences living beyond the above coverage areas could rely on CATV or DTH to receive terrestrial DTV programs.
A variable P value rolling Grey forecasting model for Taiwan semiconductor industry production
(2005-06-01)
Chang, SC
;
Lai, HC
;
Yu, HC
;
科技管理研究所
;
Institute of Management of Technology
The semiconductor industry plays an important role in Taiwan's economy. In this paper, we constructed a rolling Grey forecasting model (RGM) to predict Taiwan's annual semiconductor production. The univariate Grey forecasting model (GM) makes forecast of a time series of data without considering possible correlation with any leading indicators. Interestingly, within the RGM there is a constant, P value, which was customarily set to 0.5. We hypothesized that making the P value a variable of time could generate more accurate forecasts. It was expected that the annual semiconductor production in Taiwan should be closely tied with U.S. demand. Hence, we let the P value be determined by the yearly percent change in real gross domestic product (GDP) by U.S. manufacturing industry. This variable P value RGM generated better forecasts than the fixed P value RGM. Nevertheless, the yearly percent change in real GDP by U.S. manufacturing industry is reported after a year ends. It cannot serve as a leading indicator for the same year's U.S. demand. We found out that the correlation between the yearly survey of anticipated industrial production growth rates in Taiwan and the yearly percent changes in real GDP by U.S. manufacturing industry has a correlation coefficient of 0.96. Therefore, we used the former to determine the P value in the RGM, which generated very accurate forecasts. (c) 2003 Elsevier Inc. All rights reserved.
An analysis and comparison of different types of electronic payment systems
(2001)
Lee, ZY
;
Yu, HC
;
Kuo, PJ
;
科技管理研究所
;
Institute of Management of Technology
Two parties that conduct a business transaction through the Internet do not see each other face-to-face; nor do they exchange any document or currency hand-to-hand. When electronic money is transferred from a buyer to a seller over telecommunications networks, accuracy and security is critical. This paper explores the advantages and limitations of four types of electronic payment systems: namely, the online credit card payment system, the electronic-cash payment system, the electronic-check payment system, and the smart-card-based electronic-cash payment system. Each payment system was assessed from four perspectives: the technological aspect, the economic aspect, the social aspect, and the regulatory aspect. The requirements of merchants and consumers, the appropriate business environments for each of them to function, and the potential for future expandability were analyzed. The findings of this research could be useful for companies who are planning to adopt or to devote R & D into an electronic payment system.
Analysis of ATSC field test results in Taiwan
(2002-03-01)
Lin, CC
;
Chen, CM
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Tarng, JH
;
Hang, HM
;
Yu, HC
Field tests of the transmission performance of the ATSC DTV system have been conducted in Taiwan. The test results as well as comparisons against the NTSC system performance are reported and analyzed. From the measured results the reception characteristics of the DTV can be deduced and can provide guidelines for television stations to design transmission system, schedule equipment deployment, plan service coverage areas, and improve the reception quality of the digital signal.
Anti-competition issues between Taiwan's cable TV system operators and channel providers - new rules of engagement?
(2001-08-01)
Yu, HC
;
科技管理研究所
;
Institute of Management of Technology
Taiwan's cable TV system operators have formed multiple system operators (MSOs), while channel providers have formed multiple channel providers (MCPs). Through horizontal and vertical integration, the mergers have formidable market bargaining power in the channel- licensing market. The Fair Trade Act does not prevent unfair channel licensing trade in Taiwan. This paper recommends an open channel-licensing mechanism, which can be used to remedy the "concerted purchasing actions" of the MSOs and the "concerted selling actions" of the MCPs. (C) 2001 Elsevier Science Ltd. All rights reserved.
Applied hybrid grey model to forecast - Seasonal time series
(2001-06-01)
Tseng, FM
;
Yu, HC
;
Tzeng, GH
;
科技管理研究所
;
Institute of Management of Technology
The grey forecasting model has been successfully applied to finance, physical control, engineering, economics, etc. However, no seasonal time series forecast has been tested. The authors of this paper proved that GM(1,1) grey forecasting model is insufficient for forecasting time series with seasonality. This paper proposes a hybrid method that combines the GM(1,1) grey forecasting model and the ratio-to-moving-average deseasonalization method to forecast time series with seasonality characteristics. Three criteria, i.e., the mean squares error (MSE), the mean absolute error (MAE), and mean absolute percentage error (MAPE) were used to compare the performance of the hybrid model against other four models, i.e., the seasonal time series ARIMA model (SARIMA), the neural network back-propagation model combined with grey relation, the GM(1,1) grey model with raw data, the GM(1,N) grey model combined with grey relation. The time series data of the total production value of Taiwan's machinery industry (January 1994 to December 1997) and the sales volume of soft drink reported from Montgomery's book were used as test data sets. Except for the out-of-sample error of the Taiwan machinery production value time series, the MSE, the MAE, and the MAPE of the hybrid model were the lowest. (C) 2001 Elsevier Science Inc.
Combining neural network model with seasonal time series ARIMA model
(2002-01-01)
Tseng, FM
;
Yu, HC
;
Tzeng, GH
;
科技管理研究所
;
Institute of Management of Technology
This paper proposes a hybrid forecasting model, which combines the seasonal time series ARIMA (SARIMA) and the neural network back propagation (BP) models, known as SARIMABP. This model was used to forecast two seasonal time series data of total production value for Taiwan machinery industry and the soft drink time series. The forecasting performance was compared among four models, i.e., the SARIMABP and SARIMA models and the two neural network models with differenced and deseasonalized data, respectively. Among these methods, the mean square error (MSE), the mean absolute error (MAE), and the mean absolute percentage error (MAPE) of the SARIMABP model were the lowest. The SARIMABP model was also able to forecast certain significant turning points of the test time series. (C) 2002 Elsevier Science Inc. All rights reserved.
Design of a voice coil motor used in the focusing system of a digital video camera
(2005-10-01)
Yu, HC
;
Lee, TY
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Wang, SJ
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Lai, ML
;
Ju, JJ
This paper raises a valid method to design a voice coil motor (VCM) used in the focusing system of a digital video camera (DVC). A better VCM performance, such as lower battery consumption, higher efficiency, and shorter focusing time, can be achieved by turning the diameter of a winding coil, the thickness of the magnet, and the winding spaces in a VCM.
Effect of annealing on low-threshold-current large-wavelength InGaAs quantum well vertical-cavity laser
(2006-02-01)
Chen, IL
;
Hsu, WC
;
Kuo, HC
;
Sung, CP
;
Chiou, CH
An emission wavelength record emission wavelength of 1245 nm in double InGaAs/GaAs quantum wells without a strain-compensated barrier is obtained by metalorganic chemical vapor deposition (MOCVD). The effect of annealing on highly strained InGaAs quantum wells is analyzed using phtoluminanescence spectra. By comparing devices p-type distributed Bragg reflector (p-DBR) growth temperatures, the preliminary results indicate that a device with a low p-DBR growth temperature of 670 degrees C exhibits a low threshold current and a high light output power. A threshold current of 6.7 mA in an InGaAs vertical-cavity surface emitting laser (VCSEL) in CW operation is realized with an emission spectrum up to 1.26 mu m.
Evolution of conduction and interface states of laterally wet-oxidized AlGaAs with oxidation time
(2006-01-15)
Chen, JF
;
Hsiao, RS
;
Hung, WK
;
Wang, JS
;
Chi, JY
The conduction and interface states of laterally wet-oxidized GaAs-AlGaAs-GaAs structures after various oxidation times are investigated. Effective current blocking is achieved after 150 min oxidation and the conduction of current through the oxidized AlGaAs layer is controlled by the Poole-Frenkel mechanism, from which a relative dielectric constant of 7.07 is obtained. At an oxidation time of 15 min, capacitance-voltage spectra exhibit capacitance dispersion over frequency, implying the presence of an interface state. The intensity of the dispersion increases with increasing the oxidation time and admittance spectroscopy reveals a significant interface state at similar to 0.28 eV at 45 min. Further increasing the oxidation time to 150 min broadens the interface state to a set of continuous interface states from 0.19-0.31 eV with decreasing densities from 3x10(11) to 0.9x10(11) eV(-1) cm(-2) and generates fixed charges of about 9.1x10(11) cm(-2) in the oxidized layer. By comparison to a similar trap in a relaxed InGaAs/GaAs, the interface state is tentatively assigned to the interaction of residual As with dislocations. (c) 2006 American Institute of Physics.
Exploring the interaction between incubators and industrial clusters: the case of the ITRI incubator in Taiwan
(2003-01-01)
Su, PH
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Shyu, JZ
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Yu, HC
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Yuo, CC
;
Lo, TH
This article aims to explore the interaction between incubators and industrial clusters, which is an important linkage for local development but has not been analyzed in the literature. A model is proposed to describe this interaction. The Industrial Technology Research Institute (ITRI) Incubator within the Hsinchu industrial cluster,. the core of Taiwan's technology industries, is considered to be an empirical cage. This case is investigated with the proposed model and methods including data analysis, in-depth interviews, manager surveys and stakeholder analysis. It was found that the clustering effect in the Hsinchu industrial cluster is a main factor in the ITRI Incubator's development. The ITRI Incubator in turn reinforces the cluster in some aspects as feedback. This result confirms the existence and importance of this interaction in local development. It is recommended that government officials and incubator managers take account of this interaction in operating an incubator program and utilize the proposed model to analyze the incubator's contributions to its industrial cluster.
Fabrication of high speed and reliable 850nm oxide-confined VCSELs for 10Gb/s data communication
(2005)
Kuo, HC
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Chang, YH
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Chang, YA
;
Tseng, KF
;
Laih, LH
In this paper, we demonstrate high performance 850 nm InGaAsP/InGaP strain-compensated MQWs vertical-cavity surface-emitting lasers (VCSELs). These VCSELs exhibit superior performance with threshold currents of similar to 0.4 mA, and slope efficiencies of similar to 0.6 mW/mA. High modulation bandwidth of 14.5 GHz and modulation current efficiency factor of 11.6 GHz/(mA)(1/2) are demonstrated. We have accumulated life test data up to 1000 hours at 70 degrees C/8mA. In addition, we also report a high speed planarized 850nm oxide-implanted VCSELs process that does not require semiinsulating substrates, polyimide planarization process, or very small pad areas, therefore very promising in mass manufacture.
Fuzzy ARIMA model for forecasting the foreign exchange market
(2001-02-16)
Tseng, FM
;
Tzeng, GH
;
Yu, HC
;
Yuan, BJC
;
管理學院
Considering the time-series ARTMA (p,d,q) model and fuzzy regression model, this paper develops a fuzzy ARIMA (FARIMA) model and applies it to forecasting the exchange rate of NT dollars to US dollars. This model includes interval models with interval parameters and the possibility distribution of future values is provided by FARIMA. This model makes it possible for decision makers to forecast the best- and worst-possible situations based on fewer observations than the ARIMA model. (C) 2001 Elsevier Science B.V. All rights reserved.
Fuzzy MCDM approach for IC company's strategy in the semiconductor industry
(2001)
Lee, ZY
;
Tzeng, GH
;
Yu, HC
;
科技管理研究所
;
Institute of Management of Technology
In this paper the impacts of Global Competition on the IC corporate strategies for the semiconductor industries are studied. This research seeks to blend strategic competition with global development by addressing challenges for deterministic attitudes. It also examines critical environmental factors, technological systems and governmental policy on IC companies in the changes of the semiconductor industries. The need for a new strategy paradigm for IC companies, which comes out of new trends of the global competition, are also examined. The impacts of IC corporate strategy for the semiconductor industry are discussed and a hierarchical fuzzy multicritiria decision-making (Fuzzy MCDM) method for evaluating the propagating IC companies' strategies is proposed. Finally, an example is provided in order to show the practicability and usefulness of this method. From the results of practical applications in evaluating the IC corporate strategies, the proposed method is appropriate and appears to be ideal for a fuzzy environment.
High speed (> 13 GHz) modulation of 850 nm vertical cavity surface emitting lasers (VCSELs) with tapered oxide confined layer
(2005-06-01)
Chang, YH
;
Kuo, HC
;
Lai, FI
;
Tzeng, KF
;
Yu, HC
Improved oxide-implanted VCSELs utilising the tapered oxide layer are presented. The VCSELs exhibited similar static performance, but superior modulation bandwidth up to 13.2 GHz, compared with conventional blunt oxide VCSELs. The damping rate was reduced two times in the tapered oxide VCSEL and therefore enhanced the maximal modulation bandwidth. A very clean eye was demonstrated from the improved VCSEL with a rising time of 26 ps, falling time of 40 ps and jitter of less than 20 ps, operating at 10 Gbit/s with 6 mA bias and 6 dB extinction ratio. A comprehensive small signal measurement and analysis was conducted. Based on the equivalent circuit model, the extrinsic bandwidth limitation of the tapered oxide VCSELs was determined.
High temperature stability 850-nm In0.15Al0.08Ga0.77As/Al0.3Ga0.7As vertical-cavity surface-emitting laser with single Al0.75Ga0.25As current blocking layer
(2005)
Chang, YA
;
Lai, FI
;
Yu, HC
;
Kuo, HC
;
Laih, LW
In this paper, we employed a high bandgap Al0.75Ga0.25As layer acting as an electronic blocking layer in the upper In0.15Al0.08Ga0.77As/Al0.3Ga0.7As active region before the growth of p-type layers of 850-nm vertical-cavity surface-emitting lasers (VCSELs). A threshold current of 1.33mA and slope efficiency of 0.53W/A at 25 degrees C were obtained, and the temperature dependent light output and voltage versus current (L-I-V) characteristics showed that the VCSELs with a high bandgap Al0.75Ga0.25As layer were more stable when the substrate temperature was in a range of 25-95 degrees C. The threshold current increased with temperature up to 95 degrees C was less than 21% and the slope efficiency dropped only 24.5%.