Browsing by Author "Hsu, YC"

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An optional operation organization of Chiang Kai-Shek International Airport rail link project in Taiwan
(2005)
Hsu, YC
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Chou, YH
;
Chen, YN
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
With CKS International Airport remains one the important gateways to Taiwan, the CKS International Airport rail link system would serve as a most crucial mass transportation tool that would poise to excel the competitiveness of the international airport and its adjacent metropolises. In light of which, how best to locate an optimal operating organization that offers a sustainable management would emerge as a pressing concern. Taking into account urban transit and airport rail link service, the study, upon analyzing using the FAHP and TOPSIS methods, has chosen the Taipei Mass Rapid Transit Corporate alternative as the optimized alternative, together with the alternative of setting up a new private-run company as the second best alternative. As derived from analyses conducting on various decision-making groups, an operator with actual transportation operations would emerge as a crucial determining factor to become the future airport rail link operator. The study findings are not only intended as references to government departments but also to recommend the government to expeditiously finalize the operator as an urgent mission to facilitate subsequent implementation in light of the complexity in the rail system's interfacing logistical implementation.
Bandwidth brokers of instantaneous and Book-ahead requests for Differentiated Services networks
(2001)
Lin, YD
;
Chang, CH
;
Hsu, YC
;
資訊工程學系
;
Department of Computer Science
The Quality of Service (QoS) reservations in Differentiated Service (DiffServ) networks can be classified into two sets; Book-ahead (BA) requests and Instantaneous Requests (IRs). When an admitted BA request becomes active, some ongoing IRs are dropped when the bandwidth is insufficient for supporting both IRs and BA requests. The admission control should predict the lifetime, i.e. look-ahead time, of the IRs to prevent the admitted IRs from being dropped. The control should then check whether the available bandwidth during the look-ahead time is sufficient for the incoming IRs. We propose an application-aware look-ahead admission control for IRs, which determines the look-ahead time for specific types of IR applications. An admitted BA request might block subsequent ones that could bring more effective revenue. Thus, we propose the deferrable model of the admission control for BA requests. Simulation results indicate that the application-aware look-ahead admission control successfully reduces the dropping probability and wasted revenue of IRs by up to 10 times and 30%, respectively. Besides, the deferrable model indeed results in more BA effective revenue.
Bandwidth brokers of instantaneous and book-ahead requests for differentiated services networks
(2002-01-01)
Lin, YD
;
Chang, CH
;
Hsu, YC
;
資訊工程學系
;
Department of Computer Science
The Quality of Service (QoS) reservations in Differentiated Service (DiffServ) networks can be classified into two sets: Book-ahead (BA) requests and Instantaneous Requests (IRs). When an admitted BA request becomes active, some ongoing IRs is dropped when the bandwidth is insufficient for supporting both IRs and BA requests. The admission control should predict the lifetime, i.e. look-ahead time, of the IRs to prevent the admitted IRs from being dropped, The control should then check whether the available bandwidth during the look-ahead time is sufficient for the incoming IRs. We propose an application-aware look-ahead admission control for IRs, which determines the lookahead time for specific types of IR applications. An admitted BA request might block subsequent ones that could bring more effective revenue. Thus, we propose the deferrable model of the admission control for BA requests, Simulation results indicate that the application-aware look-ahead admission control successfully reduces the dropping probability and wasted revenue of IRs by up to 10 times and 30%, respectively. Besides, the deferrable model indeed results in more BA effective revenue.
Base-centric routing protocol for multihop cellular networks
(2002)
Hsu, YC
;
Lin, YD
;
資訊工程學系
;
Department of Computer Science
This paper presents base-centric routing (BCR) protocol, which is designed for Multihop Cellular Networks (MCNs) for wireless data communications. MCN, in which packets are multi-hopped to their destination, is hybrid of traditional Singlehop Cellular Networks (SCNs) and ad-hoe networks architecture. Because the existing routing protocols designed for ad-hoc networks are not suitable for MCN, herein, a hybrid of table-driven and demand-driven protocols with base-centric computing is designed. The base tracks network topology by the table-driven method and can thus compute paths for MSs, constituting base-centric computing. When paths are needed by MSs, when is demand-driven, the path query messages are unicast to the base. If MSs do not obtain paths from the base, then path query messages will be flooded as in AODV. Simulation yields the following conclusions. The throughput of MCN increases as radio distance decreases and is higher than that of SCN. When the radio distance in MCN is the same as that in SCN, the throughput in MCN is about twice that in SCN. Moreover, the improvement can be by up to a factor of three when the radio distance in MCN is 1/4 of that in SCN. The hybrid protocol outperforms AODV because with base-centric computing, path query messages can be unicast to the base and the overhead is greatly reduced. Without mobility, UDP outperforms TCR However, with mobility, TCP outperforms UDP.
Electromigration in pb-free SnAg3.8Cu0.7 solder stripes
(2005-08-01)
Hsu, YC
;
Chou, CK
;
Liu, PC
;
Chen, C
;
Yao, DJ
Electromigration behavior in the eutectic SnAg3.8Cu0.7 solder stripes was investigated in the vicinity of the device operation temperature of 100 degrees C by using the edge displacement technique. Measurements were made for relevant parameters for electromigration of the solder, such as drift velocity, threshold current density, activation energy, as well as the product of diffusivity and effective charge number (DZ(*)). The threshold current densities were estimated to be 4.3x10(4) A/cm(2) at 80 degrees C, 3.2x10(4) A/cm(2) at 100 degrees C, and 1.4x10(4) A/cm(2) at 120 degrees C. These values represent the maximum current densities that the SnAg3.8Cu0.7 solder can carry without electromigration damage at the three stressing temperatures. The electromigration activation energy was determined to be 0.45 eV in the temperature range of 80-120 degrees C. The measured products of diffusivity and the effective charge number, DZ(*), were -1.8x10(-10) cm(2)/s at 80 degrees C, -5.0x10(-10) cm(2)/s at 100 degrees C, and -7.2x10(-10) cm(2)/s at 120 degrees C. (c) 2005 American Institute of Physics.
Electromigration induced failure in SnAg3.8Cu0.7 solder joints for flip chip technology
(2002)
Hsu, YC
;
Shao, TL
;
Chen, C
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Electromigration of SnAg3.8Cu0.7 Solder was investigated in flip chip solder bump. An under-bump metallization (UBM) of Cr/Cr-Cu/Cu tri-layer was deposited on the chip side and electroless Cu/Ni/Au pad was deposited on the BT board side. Electromigration damage was observed under the current density of 2 x 10(4) A/cm(2) at 100 degreesC. Voids were found at cathode side and crack was observed at solder/thin film UBM interface after current stressing, and the bump failed after 168-hour stressing. Copper atoms were found to move in the direction of electron flow. Intermetallic compounds of Cu-Sn an Ni-Cu-Sn were also observed to spread into the solder bump due to current stressing.
Electromigration study in SnAg3.8Cu0.7 solder joints on Ti/Cr-Cu/Cu under-bump metallization
(2003-11-01)
Hsu, YC
;
Shao, TL
;
Yang, CJ
;
Chen, C
;
材料科學與工程學系
This paper investigates the electromigration-induced failures of SnAg3.8Cu0.7 flip-chip solder joints. An under-bump metallization (UBM) of a Ti/Cr-Cu/Cu trilayer was deposited on the chip side, and a Cu/Ni(P)/Au pad was deposited on the BT board side. Electromigration damages were observed in the bumps under a current density of 2 x 10(4) A/cm(2) and 1 x 10(4) A/cm(2) at 100 degreesC and 150 degreesC. The failures were found to be at the cathode/chip side, and the current crowding effect played an important role in the failures. Copper atoms were found to move in the direction of the electron flow to form intermetallic compounds (IMCs) at the interface of solder and pad metallization as a result of current stressing.
Inter-working and integration of messaging services in a heterogeneous wireless environment
(2005)
Tsao, SL
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Chou, JC
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Hsu, YC
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資訊工程學系
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Department of Computer Science
Messaging service such as email, short message, instant messaging and etc. has become one of the most important applications in both Internet and personal communication systems. Unfortunately, most of the messaging systems are not interoperable, and users using different systems might not be able to communicate with each other. Besides the message inter-working issue, to facilitate users accessing their messages through the preferred devices, networks and messaging systems at anytime and anywhere is also an important feature for a future messaging system. In this paper, we present a generic inter-working and integration architecture of messaging systems in a heterogeneous wireless environment. By employing the architecture, different messaging systems can be easily integrated, and provide users a pervasive messaging service. A prototype system based on this concept is thus implemented to demonstrate the correctness of the proposed architecture and design.
Interfacial reaction and shear strength of Pb-free SnAg2.5Cu0.86b0.5 and SnAg3.0Cu0.5Sb0.2 solder bumps on Au/Ni(P) metallization
(2006-06-29)
Hsu, YC
;
Huang, YM
;
Chen, C
;
Wang, H
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材料科學與工程學系
This study investigates the metallurgical reaction and shear strength of Pb-free SnAg2.5Cu0.8Sb0.5 and SnAg3.0Cu0.5Sb0.2 solder bumps on Au/Ni(P) metallization pads. It is found that (Cu,Ni)(6)Sn-5 intermetallic compound (IMC) formed at the interface between the Sn2.5Ag0.8Cu0.5Sb solder and the metallization pad; whereas (Cu,Ni)(6)Sn-5 and (Ni,Cu)(3)Sn-4 IMCs formed when the SnAg3.0Cu0.5Sb0.2 reacted with the Au/Ni(P) metallization pad. The difference in the Cu concentration in the two solders may be responsible for the different interfacial IMC formation. The shear strengths for the SnAg2.5Cu0.8Sb0.5, SnAg3.0Cu0.5Sb0.2, SnAg3.0Cu0.5, and SnAg4.0Cu0.5 solders were also measured. The shear strength test revealed that the SnAg2.5Cu0.8Sb0.5 solder has the highest shear strength, which may be due to the solid-solution strengthening of the Sb atoms. (c) 2005 Elsevier B.V. All rights reserved.
Measurement of electromigration parameters of lead-free SnAg3.5 solder using U-groove lines
(2005-10-01)
Hsu, YC
;
Chen, DC
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Liu, PC
;
Chen, C
;
材料科學與工程學系
Measurement of electromigration parameters in the lead-free solder SnAg3.5 was carried out by utilizing U-groove solder lines and atomic force microscopy in the temperature range of 100-150 degrees C. The drift velocity was measured, and the threshold current densities of the SnAg3.5 solder were estimated to be 4.4 x 10(4) A/cm(2) at 100 degrees C, 3.3 x 10(4) A/cm(2) at 125 degrees C, and 5.7 x 10(3) A/cm(2) at 150 degrees C. These values represent the maximum current densities that the SnAg3.5 solder can carry without electromigration damage at the three stressing temperatures. The critical products for the SnAg3.5 solder were estimated to be 462 A/cm at 100 degrees C, 346 A/cm at 125 degrees C, and 60 A/cm at 150 degrees C. In addition, the electromigration activation energy was determined to be 0.55 eV in the temperature range of 100-150 degrees C. These values are very fundamental for current carrying capability and mean-time-to-failure measurement for solder bumps. This technique enables the direct measurement of electromigration parameters of solder materials.
Multihop cellular: A novel architecture for wireless data communications
(2002-03-01)
Hsu, YC
;
Lin, YD
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資訊工程學系
;
Department of Computer Science
This work presents a novel architecture, Multihop Cellular Network (MCN), for wireless communications. MCN preserves the benefit of conventional single-hop cellular networks (SCN) where the service infrastructure is constructed by fixed bases or access points (APs), and it also incorporates the flexibility of ad-hoe networks where wireless transmission through mobile stations in multiple hops is allowed. MCN can reduce the required number of bases or APs and improve the throughput performance, while limiting path vulnerability encountered in ad-hoc networks. In addition, MCN and SCN are analyzed, in terms of mean hop count, hop-by-hop throughput, end-to-end throughput, and mean number of channels (i.e., simultaneous transmissions) under different traffic localities and transmission ranges. Numerical results demonstrate that throughput of MCN exceeds that of SCN and the former also increases as the transmission range decreases. The above results can be accounted for by the different orders, linear and square, at which mean hop count and mean number of channels increase, respectively.
Multihop wireless IEEE 802.11 LANs: A prototype implementation
(2000-12-01)
Lin, YD
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Hsu, YC
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Oyang, KW
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Tsai, TC
;
Yang, DS
In this paper; we present a prototype for a new architecture, MCN (Multihop Cellular Network) implemented over a wireless LAN platform. MCN preserves the virtue of traditional single-hop cellular networks where the service infrastructure is constructed bl; many BSs (Ease Stations) but it also adds the flexibility of ad hoc networks where wireless transfer through mobile stations in multiple hops is allowed. MCN can reduce the number of required BSs or improve the throughput performance, In the prototype of MCN, a bridging protocol, BRIEF (Base-driven Multihop Bridging Protocol) runs between mobile stations and access points to enable multihop routing and roaming. Demonstration show that MCN is a feasible architecture for wireless LANs.
Nonparametric identification of a building structure from experimental data using wavelet neural network
(2003-09-01)
Hung, SL
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Huang, CS
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Wen, CM
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Hsu, YC
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土木工程學系
This study presents a wavelet neural network-based approach to dynamically identifying and modeling a building structure. By combining wavelet decomposition and artificial neural networks (ANN), wavelet neural networks (WNN) are used for solving chaotic signal processing. The basic operations and training method of wavelet neural networks are briefly introduced, since these networks can approximate universal functions. The feasibility of structural behavior modeling and the possibility of structural health monitoring using wavelet neural networks are investigated. The practical application of a wavelet neural network to the structural dynamic modeling of a building frame in shaking tests is considered in an example. Structural acceleration responses under various levels of the strength of the Kobe earthquake were used to train and then test the WNNs. The results reveal that the WNNs not only identify the structural dynamic model, but also can be applied to monitor the health condition of a building structure under strong external excitation.
QoS routing in multihop packet radio environment
(1998)
Hsu, YC
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Tsai, TC
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Lin, YD
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資訊工程學系
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Department of Computer Science
In this paper, we present a method to compute the path bandwidth for the DSDV-based routing algorithm The addressed network does not necessarily have a cellular structure and could have no fired infrastructure. This network can be either stand-alone, or connected to the wired network. Each mobile station has to relay packets for others, thus achieving multihop routing. To calculate the available bandwidth of a path in this environment, it is incorrect to simply compute the minimum bandwidth of the links along the path. There are two crucial steps in the path bandwidth computation process of this multihop environment: (I) intersecting the sets of common free slots of two adjacent links, and (2) dividing the intersection for the adjacent links to share. We present two bandwidth computation rules including the Half rule and the Floating rule. Numerical results are given to evaluate the performance of applying these rules to the DSDV-based QoS routing algorithm.
Threshold current density of electromigration in eutectic SnPb solder
(2005-05-16)
Yeh, YT
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Chou, CK
;
Hsu, YC
;
Chen, C
;
Tu, KN
Electromigration has emerged as an important reliability issue in the microelectronics packaging industry since the dimension of solder joints has continued to shrink. In this letter, we report a technique that enables the precise measurement of the important parameters of solder electromigration, such as activation energy, critical length, threshold current density, effective charge numbers, and electromigration rate. Patterned Cu/Ti films in a Si trench were employed for eutectic SnPb solder to be reflowed on, and thus solder Blech specimens were fabricated. Atomic force microscope was used to measure the depletion volume caused by electromigration on the cathode end. The threshold current density is estimated to be 8.5x10(3) A/cm(2) at 100 degrees C, which relates directly to the maximum allowable current that a solder joint can carry without electromigration damage. This technique facilitates the scientifically systematic investigation of electromigration in solders. (c) American Institute of Physics.
Tool replacement for production with a low fraction of defectives
(2006-06-15)
Pearn, WL
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Hsu, YC
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Wu, CW
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工業工程與管理學系
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Department of Industrial Engineering and Management
In manufacturing industry, the tool replacement cost is, in many cases, a significant portion of the production cost. Early tool replacement increases the production cost. Overdue tool replacement, however, results in poor production quality. Accordingly, improving production quality while maintaining a low production cost is essential. The index C-pk is regarded as a yield-based index. For a fixed C-pk value, the production yield and fraction of defectives can be calculated. In this paper, we present an analytical approach using C-pk to determine the optimal tool replacement time. An accurate process capability must be calculated, particularly when the data contain assignable cause variation. Tool wear is a dominant and inseparable component in many machining processes (a systematic assignable cause), and ordinary capability measures become inaccurate because process data are contaminated by the assignable cause variation. Considering process capability changes dynamically, an estimator of C-pk is investigated. The closed form of the exact sampling distribution is derived. An effective tool management procedure for determining the optimal tool replacement time is presented for processes with a low fraction of defectives. For illustrative purposes, an application example involving tool wear is presented.
Two-stage dynamic uplink channel and slot assignment for GPRS
(2003-09-01)
Hsu, YC
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Lin, YD
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Chiang, MY
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資訊工程學系
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Department of Computer Science
General packet radio service (GPRS) uses a two-stage mechanism to allocate uplink radio resource to mobile stations (MSs). In stage-1, the base station (BS) assigns several packet data channels (PDCHs) to an MS. Furthermore, a PDCH may be assigned to multiple MSs. In stage-2, therefore, the BS selects one of the multiplexed MSs in a PDCH to use the radio resource. In this paper, maintaining a load balance between PDCHs in stage-1 is examined and several selection schemes to lower the mis-selection rate in stage-2 are proposed. From our simulation results, the cost deduced from the poor load balancing and selection schemes render a lower system throughput and a non-negligible increase in packet queuing delay. Among the various stage-2 selection policies, round robin with linearly-accumulated adjustment (RRLAA) has the lowest mis-selection rate and outperforms the one without any heuristic by up to 50%.
Two-stage dynamic uplink channel and slot assignment for GPRS
(2001)
Lin, YD
;
Hsu, YC
;
Chiang, MY
;
資訊工程學系
;
Department of Computer Science
General Packet Radio Service (GPRS) uses a two-stage mechanism to allocate uplink radio resource to Mobile Stations (MSs). In stage-1, the Base Station (BS) assigns several Packet Data CHannels (PDCHs) to an MS. Furthermore, a PDCH may be assigned to multiple MSs. In stage-2, therefore, the BS selects one of the multiplexed MSs in a PDCH to use the radio resource. In this work, maintaining a load balance between PDCHs in stage-1 is examined and several selection schemes to lower the mis-selection rate in stage-2 are proposed. From our simulation results, the cost deduced from the poor load balancing and selection schemes render a lower system throughput and a non-negligible increase In packet queuing delay. Among the various stage-2 selection policies, Round Robin with Linearly-Accumulated Adjustment (RRLAA) has the lowest mis-selection rate and outperforms the one without any heuristic up to 50%.
Visual metaphor interface and cognitive style: A study for on-line learning
(2004)
Lee, JJ
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Hsu, YC
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傳播研究所
;
Institute of Communication Studies
Individual characteristics in virtual environments have stimulated considerable interests. An understanding of various cognitive style learners as they respond to different information representation approaches may provide practical information for on-line learning. The proper application of user interface metaphors may significantly impact the degree to which hypermedia learners construct their mental models. This study will report the empirical results of how cognitive style and metaphorical interface affect the on-line learning performance of undergraduate college students.