Browsing by Author "Yang, CC"

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A decade bandwidth resistive FET singly balanced MIC mixer
(1999)
Chang, CY
;
Yang, CC
;
Niu, DC
;
電信工程研究所
;
Institute of Communications Engineering
A novel decade bandwidth resistive FET singly balanced MIC mixer using a broadband CPW to CPS balun is developed. The mixer uses two NEC71000 MESFETs and realized with uniplanar lines. At 17 dBm LO power and 1 GHz IF, the mixer shows a conversion loss of 5.7 to 11 dB for 2 to 20 GHz RF and 10 to 15 dB for 20 to 27 GHz RF. The IF bandwidth is from 10 MHz to 7 GHz. The signal orthogonality between RE and IF makes the IF signal may overlap the RF signal. The mixer shows an output P-1dB of 11.5 dBm (corresponding to input P-1dB of 18.5 dBm) at 8 GHz RF, 1 GHz IF and 16.5 dBm LO power. The input IF, is 24 to 37 dBm corresponding to 2.5 to 20 GHz RF and 1 GHz IF. The mixer is fabricated on a 15 mil thick Al2O3 MIC substrate.
A multioctave bandwidth rat-race singly balanced mixer
(1999-01-01)
Chang, CY
;
Yang, CC
;
Niu, DC
;
傳播研究所
;
Institute of Communication Studies
In this letter, we describe a broad-band 7.5-46 GHz rat-race ring singly balanced mixer. The rat-race ring consists of an ideal crossover phase inverter and is designed to have a Chebyshev response of order two. The mixer diodes are virtually grounded via a quarter-wavelength low-impedance FCPW (finite ground plane CPW) open circuit stubs. The mixer shows more than 5 times RF bandwidth and de to 5 GHz LF bandwidth. The circuit is realized using FCPW on 25 mil Al2O3 substrate.
A new privacy and authentication protocol for end-to-end mobile users
(2003-11-01)
Lee, CC
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this papecr. we propose a new privacy and authentication scheme for end-to-end mobile users. There are three goals in our scheme. The first allows two end-to-end mobile users to communicate privately each other. The second allows two end-to-end mobile users to distribute a session key simply. The third allows two end-to-end mobile users to mutually authenticate. Copyright (C) 2003 John Wiley Sons, Ltd.
A novel broad-band Chebyshev-response rat-race ring coupler
(1999-04-01)
Chang, CY
;
Yang, CC
;
電信工程研究所
;
Institute of Communications Engineering
A novel broad-band rat-race ring coupler with a unit element at each port and an ideal phase inverter at one of the ring arms is proposed and analyzed. Design equations based on Chebyshev equiripple functions are derived, The design curves of equal or unequal power division are also presented, Theoretical data show that the bandwidth of unequal power division with a specific return-loss value increases as the power division ratio increases or decreases from unity, For a 180 degrees hybrid with equal power division (3 dB) and 15-dB return loss, the proposed rat-race ring may have a bandwidth of 4:1. Three circuits of this novel rat-race ring are realized using finite-ground-plane coplanar waveguide. The measured results match very well with the theory.
A novel method for net-shape forming of hypereutectic Al-Si alloys by thixocasting with powder preforms
(2005-08-25)
Chen, CM
;
Yang, CC
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
This work presents a novel and feasible method for net-shape forming of hypereutectic A1-Si alloy parts. This method, briefly termed as powder thixocasting in this paper, combines the techniques of thixocasting and conventional powder metallurgy. Consolidated preforms made of gas-atomized and pre-alloyed A1-25Si-2.5Cu-1Mg-0.5Mn powder were used as the feedstock for thixocasting. The alloy powder was preheated under protection of argon atmosphere and then was compacted to form powder preforms. The powder preforms were quickly heated into semi-solid state by induction coils and were immediately thixocast using a die-casting machine. A die with a center gate, a long runner and plate-shaped cavities was designed to examine the feasibility of this process. Results demonstrated that the powder preforms exhibits very good formability by this unique process. The powder thixocast products have satisfied strength and substantial structure with uniform distribution of fine Si particles, while the processing temperature is suitably controlled. This novel process was also successfully used to fabricate compressor scrolls for demonstration. (c) 2004 Elsevier B.V. All rights reserved.
A study on characteristics of interfacial transition zone in concrete
(2004-06-01)
Liao, KY
;
Chang, PK
;
Peng, YN
;
Yang, CC
;
土木工程學系
The aim of this study was to observe the behavior of the interfacial transition zone (ITZ) of high-performance concrete that was under curing in saturated lime water. From the Scanning Electron Microscope (SEM), it was found that the pores and hydration products at the ITZ, within 100 mum between the paste and aggregate, permuted each other during the early hydration stage, and then appeared as a large lump or strip. They gradually became irregular and small lumps for the further curing age. At the curing age of 56 days, the pores almost concentrated within an area of 0-15 mum from the aggregate edge. The hydration products were much denser with the increase in its distance from the aggregate edge. (C) 2004 Elsevier Ltd. All rights reserved.
A threshold signature scheme for group communications without a shared distribution center
(2004-08-01)
Chang, TY
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this paper, we shall propose a (t, n) threshold signature with (k, l) threshold-shared verification to be used in a group-oriented cryptosystem without a shared distribution center (SDC). In this scheme, any t participants can represent a group (signing group) to sign a message, and any k participants can represent another group (verifying group) to verify the signature. We need no SDC to distribute the public and private keys to all the participants in the two groups. Hence, our scheme is more practical in real-world applications and more efficient than its predecessors in terms of communication and computational complexity as well as storage. (C) 2003 Elsevier B.V. All rights reserved.
Accuracy of the EasyTouch blood glucose self-monitoring system: a study of 516 cases
(2004-11-01)
Dai, KS
;
Tai, DY
;
Ho, P
;
Chen, CC
;
Peng, WC
Background: Self-monitoring blood glucose device is an important toot for diabetes patients to efficiently control their blood glucose concentrations. We evaluated the accuracy of EasyTouch glucose monitoring system. Methods: Capillary blood glucose concentrations measured using EasyTouch and the reference values obtained from Yellow Springs Instruments (YSI) 2300 STAT were performed in the Department of Laboratory Medicine, Wei-Gong Memorial Hospital. Results were evaluated using (1) linear regression analysis, (2) Clarke Error Grid analysis, (3) percentage of readings within a defined range of deviation from the reference value, (4) bias plots, and (5) coefficients of variation (CVs) calculated from 60 measurements in series. Results: The window of the 516 EasyTouch readings covered a range from 42 to 555 mg/dl. Linear regression analysis yielded a regression slope 0.9972, intercept 1.899 mg/dl, r(2) 0.9571, and Syx 14.89 mg/dl. A Clarke Error Grid analysis showed 100% of the EasyTouch readings in clinically acceptable zones A and B. Of the EasyTouch readings, 98.3%, 91.9%, 78.3% and 46.9% were found within +/-20%, +/-15%, +/-10%, and +/-5%, respectively, of the reference values. Further analysis showed that the percentage of EasyTouch readings within the defined intervals was similar in three glucose ranges (less than or equal to100, 101-200, and greater than or equal to201 mg/dl). The CVs for the four lots of strips (lot 1 to lot 4) ranged from 3.5 to 5.5%, 2.1 to 4.8%, 1.8 to 3.6%, and 3.0 to 5.7%, respectively. Conclusions: EasyTouch provides high accurate and precise glucose readings over a wide range of glucose concentrations. (C) 2004 Elsevier B.V. All rights reserved.
An improvement of the Yang-Shieh password authentication schemes
(2005-03-25)
Yang, CC
;
Wang, RC
;
Chang, TY
;
資訊工程學系
;
Department of Computer Science
Recently, Yang and Shieh proposed two password authentication schemes by employing smart cards. One is a timestamp-based password authentication scheme and the other is a nonce-based password authentication scheme. In 2002, Chan and Cheng pointed Out that Yang and Shieh's timestamp-based password authentication scheme was vulnerable to the forgery attack. However, in 2003, Sun and Yell pointed Out that Chan and Cheng's attack was unreasonable. At the same time, Sun and Yell pointed out that Yang and Shieh's password authentication schemes were still Vulnerable to the forgery attack. In this paper, we shall improve Yang and Shieh's schemes to resist Sun and Yell's attack. (C) 2004 Elsevier Inc. All rights reserved.
Anisotropic thermal conductivity of nano-porous silica film
(2003)
Tsui, BY
;
Yang, CC
;
Fang, KL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this work thermal conductivity of porous silica film was studied comprehensively. Silica films with porosity from 21% to 64% were spin coated. It is observed for the first time that the porous silica material has strong anisotropic characteristic. The pores in the higher porosity silica film tend to distribute horizontally. This distribution of the pores in the dielectric film is the main factor that induces the anisotropic characteristic. We proposed a Serial-Parallel Hybrid model to explain the correlation between porosity and thermal conductivity in both in-plane and cross-plane components. The anisotropic characteristic of the thermal conductivity may be accompanied by the anisotropic dielectric constant, which will greatly complicate the RC delay simulation of the circuits.
Anisotropic thermal conductivity of nanoporous silica film
(2004-01-01)
Tsui, BY
;
Yang, CC
;
Fang, KL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this paper, thermal conductivity of porous silica film with porosity from 21 to 64 % was studied comprehensively. The corresponded dielectric constant is from 2.5 to 1.5. It is observed that the porous silica material has strong anisotropic characteristic. A serial-parallel hybrid model is proposed to explain the correlation between porosity and thermal conductivity in both in-plane and cross-plane components. The pores in the higher porosity silica film tend to distribute horizontally. This distribution of the pores in the dielectric film is the main factor that induces the anisotropic characteristic. The nonuniform distribution of pores also makes the conventional two-dimensional model of 36 method inappropriate for extracting the in-plane thermal conductivity. A new method based on the hybrid model was proposed to extract the in-plane thermal conductivity successfully. The anisotropic characteristic of the thermal conductivity may be accompanied by the anisotropic dielectric constant, which will greatly complicate the thermal management and resistance-capacitance delay simulation of the circuits and should be avoided. The proposed model would be helpful on evaluation of new porous low dielectric constant materials.
Apodised fiber Bragg gratings fabricated with a uniform phase mask using Gaussian beam laser
(2000-07-01)
Yang, CC
;
Lai, YC
;
光電工程學系
;
Department of Photonics
A new exposure scheme for fabricating apodised fiber Bragg gratings by the use of a uniform phase mask and a Gaussian beam laser is demonstrated. Average refractive index is kept nearly constant along the grating to derive a side lobe suppression of 20 dB in the shorter wavelength. This scheme allows the writing of truly apodized fiber Bragg gratings. (C) 2000 Elsevier Science Ltd. All rights reserved.
Apodised fibre Bragg gratings fabricated with uniform phase mask using low cost apparatus
(2000-03-30)
Yang, CC
;
Lai, YC
;
光電工程學系
;
Department of Photonics
New exposure schemes for fabricating apodised fibre Bragg gratings using a uniform phase mask are described. A sidelobe suppression level as high as 20dB in the lower wavelength region has been successfully achieved. The schemes allow the writing of truly apodised fibre Bragg gratings using low cost and simple apparatus.
Characterization and lithographic parameters extraction for the modified resists
(1999)
Ko, FH
;
Lu, JK
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Chu, TC
;
Huang, TY
;
Yang, CC
The modification of the i-line resist structure after spiking with various amount of poly(4-vinylphenol) polymer is characterized by the spectra of ultraviolet visible (UV-VIS) and gel permeation chromatography (GPC). The chemical structure of photoactive compound is found to be unchanged after modification, while slight change in the polymer chain is observed. The resist layer coated onto the wafer is characterized by various methods including n&k analyzer, Nanospec, Fourier transform infrared red (FTIR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) to fully evaluate the film properties in terms of porosity, thickness, vibrational spectrum, and thermal stability. Our thermal analysis results show that the resists are mainly decomposed in three stages. The photoactive compound (PAC) is found to decompose during the first stage, while the polymer decomposes during the latter stages. The resist exposure parameters, namely, A, B and C at 365 mn are determined by the absorbance measurement. The extracted parameters are further used in the resist profile simulation by PROLITH/2. It is shown that the spiking of poly(4-vinylphenol) polymer into the resist can improve the resolution and linearity for dense lines. In addition, the swing effects can be reduced by up to 35 and 31 % for dense and isolated lines after resist modification, respectively.
Characterization and modeling of out-diffusion of cesium, manganese and zinc impurities from deep ultraviolet photoresist
(2000)
Ko, FH
;
Wang, MY
;
Wang, TK
;
Yang, CC
;
Huang, TY
The novel radioactive tracer technique was applied to investigate the migration of cesium, manganese and zinc impurities from deep ultraviolet photoresist into underlying substrate. Two important process parameters, viz., baking temperatures and substrate types (i.e., bare silicon, polysilicon, silicon oxide and silicon nitride), were evaluated. Our results indicated that the migration ratios were all below 6%, irrespective of baking temperatures and substrate types. The substrate types did not appear to strongly affect the metallic impurity out-diffusion from deep ultraviolet photoresist. However, solvent and/or water evaporation due to temperature change was found to have a significant effect on metal migration. The net driving force of impurity changes with temperature and the impurity diffusion can be classified into four types. Based on the proposed types, the obtained migration ratios can be realized. A new model, together with a new parameter, was proposed to describe the out-diffusion behavior of impurities from deep ultraviolet photoresist. The diffusion profile of photoresist was depicted based on diffusion equations and the migration ratios. This model could explain the migration ratios of metallic impurities in photoresist layers under various baking conditions.
Characterization and modeling of out-diffusion of manganese and zinc impurities from deep ultraviolet photoresist
(1999-09-01)
Wang, MY
;
Ko, FH
;
Wang, TK
;
Yang, CC
;
Huang, TY
The radioactive tracer technique was applied to investigate the out-diffusion of manganese and zinc impurities from deep-ultraviolet (DUV) photoresist. Two important process parameters, viz., baking temperature and the type of substrate (i.e., bare silicon, polysilicon, oxide, or nitride), were evaluated. Our results indicated that diffusion ratios were ail below 6%, irrespective of the substrate type and baking temperature. The substrate type did not appear to strongly affect the metallic impurity out-diffusion from DUV photoresist. However, solvent evaporation was found to have a significant effect on impurity diffusion. A new model, together with a new parameter, was proposed to describe the out-diffusion behavior of impurities from DUV photoresist. This model could explain the diffusion ratio of metallic impurities in photoresist layers under various baking conditions. The effectiveness of various wet cleaning recipes in removing metallic impurities such as manganese and zinc was also studied. It was found that (i) bath life due to temperature change can considerably affect the cleaning efficiency, and (ii) hot water immersion can effectively dissolve the impurities from the wafer surface. (C) 1999 The Electrochemical Society. S0013-4651(98)11-080-7. All rights reserved.
Cryptanalysis of publicly verifiable authenticated encryption
(2004-06-01)
Chang, TY
;
Yang, CC
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
Recently, Ma and Chen proposed a new authenticated encryption scheme with public verifiability. The signer can generate a signature with message recovery for a specified recipient. With a dispute, the recipient has ability to convert the signature into an ordinary one that can be verified by anyone without divulging her/his private key and the message. However, we point out that any adversary can forge a converted signature in this article.
Cryptanalysis of simple authenticated key agreement protocols
(2004-08-01)
Yang, CC
;
Chang, TY
;
Hwang, MS
;
資訊工程學系
;
Department of Computer Science
In this article, we will present a modification attack and a dictionary attack to subvert the security of the Tseng scheme and the Ku-Wang scheme. As we know, no existing schemes of simple authenticated key agreement protocols can successfully withstand our modification attack.
Cryptanalysis of the improved authenticated key agreement protocol
(2005-12-15)
Chang, TY
;
Yang, CC
;
Yang, YW
;
資訊工程學系
;
Department of Computer Science
Hsu et al. recently pointed out that the Ku-Wang scheme is vulnerable to modification attack and further proposed an improvement on their scheme. However, this article will show the improvement which they claim is still vulnerable by off-line password guessing attack. (c) 2005 Published by Elsevier Inc.
Dry sliding wear behaviors of Al-25Si-2.5Cu-1Mg alloys prepared by powder thixocasting
(2005-04-25)
Chen, CM
;
Yang, CC
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The wear performance of an Al-25Si-2.5Cu-1Mg alloy prepared by powder thixocasting was studied using a pin-on-disc machine. LM13 and an Al-25Si-2.5Cu-lMg alloy prepared by conventional ingot metallurgy were also investigated for comparison. The sliding tests were performed under ambient conditions and without lubricant. During the tests, the applied load was increased stepwise until wear seizure occurred. Experimental data reveal that the powder thixocast alloys exhibit better wear performance than that of conventional alloys, especially under heavy load conditions and following T6 treatment. This work demonstrates the potential of the new method, powder thixocasting, for fabricating hypereutectic Al-Si-X alloys with a high wear resistance. Moreover, the variation in the wear rate with the applied load for the alloy can be divided into three regions. The mechanisms associated with these wear regions were discussed based on the investigations of the worn subsurface and the wear debris. (c) 2005 Elsevier B.V. All rights reserved.