1,724,321 research outputs found
XU, CHEN-HONG
No full text本篇論文的目的，主要在發展一套交談式的電腦輔勵設計系統(Interactive Freeform
Modeling CAD System)m同時發展一套小型的繪圖核心系統(Graphical Kernel System)
簡稱G.K.S.做為電腦輔助設計的繪圖工具。
在電腦輔勵設計方面，則先以Bezier Curve With Fitting Points 的方式建立曲線，
而曲線Fitting Point 的輸入與修改，則以系統提供的Point Editor 來執行。我們先
以Point Editor 來產生一些剖面(Profiles) 曲線與切面曲線(Crosssections) ，再
以剖面曲線和怍面曲線為基本圖元，應用到曲面旋轉(Surface of Reveolution) ，
直軸設計(Rectilinear Axis Design) 及自然軸設計(Natural Axis Design) 三種設
計技巧上。使用者可利用系統提供的資料結構建立與修改副系統，輸入模式實體的組
合方式興組合物體的型態及相關的資料，讓系統製造出模式的圖形，使用者可依其圖
形加以修改，直到產生滿意，合乎理想的模式為止。此套系統很適合於機械上的零件
組合設計，亦可用來畫一些蓋術品，如花瓶、杯子……等。
在繪圖核心系統方面，G.K.S. 是一套圖際標準局(I.S.O.) 所定立的標準繪圖系統，
具有完整的繪圖功能，這些功能乃用來表現二度空間的觀視圖形。同時也提供了程式
與使用者間交談作用的功度，使用G.K.S. 將很容易地發展一些特殊用途及一般用途
的應用系統來，如資料繪圖、機械、建築的電腦輔助設計及一般的商業報表、製圖等
。繪圖核心系統之發展大致分為六大部分，分別設計，即一、繪圖輸出元件功能(Gr
aphic Output Primitives)；二、工作站(Work Station)；三、座標系統(Coordina
te System)；四、節段控制(Segment Control)；五Metafile 及六、輸出／入控制(I
/O Control)，六大部分。
此電腦輔助設計部分及繪圖核心系統統部分，均已在IBM 16 Bits 微電腦上發展成功
Revision of the Stegana nigrolimbata species group (Diptera: Drosophilidae) from the Oriental Region
No full textCao, Hua-Zhi, Chen, Hong-Wei (2008): Revision of the Stegana nigrolimbata species group (Diptera: Drosophilidae) from the Oriental Region. Zootaxa 1848: 27-36, DOI: 10.5281/zenodo.18334
Cross-layer operation aided wireless networks
No full textIn this thesis, we propose several cross-layer operation aided schemes conceived for wireless networks. Cross layer design may overcome the disadvantages of the network's layered architecture, where layering is most typically represented by the Transport Control Protocol (TCP) / Internet Protocol (IP) suite.We invoke Fountain codes for protecting file transfer at the application layer, since they are suitable for erasure channels. They are also often referred to as rateless codes. When implementing Fountain code aided file transfer, the file will be firstly partitioned into a number of blocks, each of which contains K packets. Fountain codes randomly select several packets from a block and then combine them using exclusive- OR additions for generating an encoded packet. The encoding continues until all blocks are successfully received. Considering an 802.11 Wireless Local Area Network (WLAN) scenario, the packet size has to be appropriately chosen, since there exists a trade-off between the packet size and the transmission efficiency, which is defined as the number of primary information bits to the total number of all transmitted bits including headers, control packets and retransmitted replicas. In order to find the optimum packet size, the transmission efficiency is formulated as a function of the Packet Loss Ratio (PLR) at the application layer and of the total load imposed by a single packet. The PLR at the application layer is related both to the packet size, as well as to the 802.11 MAC retransmission mechanism and to the modulation scheme adopted by the physical layer. Apart from its source data, the total load imposed by an information packet also contains the control packets of the 802.11 Media Access Control (MAC) protocol such as the Request To Send (RTS) / Clear To Send (CTS) messages, the retransmitted replicas and the Acknowledgement (ACK) messages. According to these relations, the transmission efficiency may finally be expressed as a function of packet size. Based on the numerical analysis of this function, the optimum packet size may be determined. Our simulation results confirmed that indeed the highest transmission efficiency may be achieved, when using the optimum packet size.Since turbo codes are capable of achieving near capacity performance, they may be successfully combined with Hybrid Automatic Repeat reQuest (HARQ) schemes. In this thesis, the classic Twin Component Turbo Codes (TCTCs) are extended to Multiple Component Turbo Codes (MCTCs). In order to apply classic two-dimensional Extrinsic Information Transfer (EXIT) charts for analyzing them, we divided an N-component MCTC into two logical parts. This partitioning was necessary, because otherwise an N-component scheme would require an N-dimensional EXIT chart. One of the parts is constituted by an individual Bahl, Cocke, Jelinek and Raviv (BCJR) decoder, while the other so-called composite decoder consists of the remaining (N-1) components. The EXIT charts visualized the extrinsic information exchange between these two logical parts of MCTCs. Aided by this partitioning technique, we may find the so-called 'open tunnel SNR threshold' for MCTCs, which is defined as the minimum SNR for which the EXIT chart at the specific coding rate used has an open tunnel. It may be used as a metric to compare the achievable performance to the Discrete-input Continuous-output Memoryless Channel's (DCMC) capacity. Our simulation results showed that the achievable performance of MCTCs is closer to the DCMC capacity than that of non-systematic TCTCs, but a bit further than that of systematic TCTCs, if generator polynomials having an arbitrary memory length - and hence complexity - are considered. However, for the lowest-memory octally represented polynomial (2; 3)o, which implies having the lowest possible complexity, MCTCs outperform non-systematic and systematic TCTCs. Furthermore, MCTC aided HARQ schemes using the polynomial of (2; 3)o exhibit significantly better PLRs and throughput performances than systematic as well as non-systematic TCTC aided HARQ schemes using the same polynomial. If systematic TCTC aided HARQ schemes relying on the polynomial of (17; 15)o are used as benchmarkers, MCTC aided HARQ schemes may significantly reduce the complexity, without a substantial degradation of the PLR and throughput.When combining turbo codes with HARQ, the associated complexity becomes a critical issue, since iterative decoding is immediately activated after each transmission. In order to reduce the associated complexity, an Early Stopping (ES) strategy was proposed in this thesis to substitute the fixed number of BCJR operations invoked for each iterative decoding. By observing the EXIT charts of turbo codes, we note that the extrinsic information increases along the decoding trajectory of an open or closed tunnel. The ES aided MCTC HARQ scheme curtails iterative decoding, when the Mutual Information (MI) increase becomes less than a given threshold. This threshold was determined by an off-line training in order to achieve a trade-off between the throughput and complexity. Our simulation results verified that the complexity of MCTC aided HARQ schemes may be reduced by as much as 80%, compared to that of systematic TCTC aided HARQ schemes using a fixed number of 10 BCJR operations.Moreover, the complexity of turbo coded HARQ schemes may be further reduced by our Look-Up Table (LUT) based Deferred Iteration (DI) method. The DI method delays the iterative decoding until the receiver estimates that it has received sufficient information for successful decoding, which may be represented by the emergence of an open tunnel in the EXIT chart corresponding to all received replicas. Therefore, the specific MI that a 'just' open tunnel appears when combining all previous (i-1) MIs will be the threshold that has to be satisfied by the ith reception. More specifically, if the MI received during the ith reception is higher than this threshold, the EXIT tunnel is deemed to be open and hence the iterative decoding is triggered. Otherwise, iterative decoding will be disabled when the tunnel is deemed to be closed. This reduces the complexity. The LUT stores all possible MI thresholds for N-component MCTCs, which results in a large storage requirement, if N becomes high. Hence, an efficient LUT design was also proposed in this thesis. Our simulation results demonstrated the achievable complexity reduction may be as high as 50%, compared to the schemes operating without the DI method
Stegana (Oxyphortica) Nigripennis Species-Group, With Descriptions Of Four New Species From Southeast Asia (Insecta: Diptera: Drosophilidae)
No full textChen, Hong-wei, Wang, Bao-cheng (2004): Stegana (Oxyphortica) Nigripennis Species-Group, With Descriptions Of Four New Species From Southeast Asia (Insecta: Diptera: Drosophilidae). Raffles Bulletin of Zoology 52 (1): 29-36, DOI: http://doi.org/10.5281/zenodo.461888
Discovery Of The Genus Luzonimyia Malloch (Insecta: Diptera: Drosophilidae) In China, With Descriptions Of Two New Species
No full textCao, Hua-Zhi, Chen, Hong-Wei (2008): Discovery Of The Genus Luzonimyia Malloch (Insecta: Diptera: Drosophilidae) In China, With Descriptions Of Two New Species. Raffles Bulletin of Zoology 56 (2): 251-254, DOI: 10.5281/zenodo.534027
FIGURE 10. Leucophenga striatipennis Okada, 1989 in The genus Leucophenga (Diptera, Drosophilidae), part V: the mutabilis species group from East Asia, with morphological and molecular evidence
No full textFIGURE 10. Leucophenga striatipennis Okada, 1989, male: A. Epandrium, surstylus and cercus (lateral view); B. hypandrium, paramere, aedeagus and aedeagal apodeme (lateral view). Scale bar = 0.1 mm.Published as part of Zhou, Lan & Chen, Hong-Wei, 2015, Zootaxa 4006 (1), DOI: 10.11646/zootaxa.4006.1.2, http://zenodo.org/record/24406
A new species of tonguefish (Pleuronectiformes: Cynoglossidae) from Taiwanese waters
No full textLee, Mao-Ying, Munroe, Thomas A., Chen, Hong-Ming (2009): A new species of tonguefish (Pleuronectiformes: Cynoglossidae) from Taiwanese waters. Zootaxa 2203: 49-58, DOI: 10.5281/zenodo.27512
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