Nonlinear principal component analysis by neural networks     

William W. Hsieh 《地球，A辑:动力气象学与海洋学》2001,53(5):599-615

Nonlinear principal component analysis (NLPCA) can be performed by a neural network model which nonlinearly generalizes the classical principal component analysis (PCA) method. The presence of local minima in the cost function renders the NLPCA somewhat unstable, as optimizations started from different initial parameters often converge to different minima. Regularization by adding weight penalty terms to the cost function is shown to improve the stability of the NLPCA. With the linear approach, there is a dichotomy between PCA and rotated PCA methods, as it is generally impossible to have a solution simultaneously (a) explaining maximum global variance of the data, and (b) approaching local data clusters. With the NLPCA, both objectives (a) and (b) can be attained together, thus the nonlinearity in NLPCA unifies the PCA and rotated PCA approaches. With a circular node at the network bottleneck, the NLPCA is able to extract periodic or wave modes. The Lorenz (1963) 3‐component chaotic system and the monthly tropical Pacific sea surface temperatures (1950–1999) are used to illustrated the NLPCA approach.  相似文献   

Reply To The Comment By Bink And Meesters     

Gabriel Katul  Cheng-I Hsieh 《Boundary-Layer Meteorology》1997,84(3):503-509

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Mass composition of the escaping plasma at Mars     

E. Carlsson  A. Fedorov  E. Budnik  H. Gunell  J.-A. Sauvaud  Y. Futaana  H. Andersson  J.D. Winningham  J.R. Sharber  A.J. Coates  D.O. Kataria  H. Koskinen  P. Riihelä  J. Kozyra  E. Roelof  S. Livi  K.C. Hsieh  M. Grande  J.-J. Thocaven  S. Orsini  M. Maggi  P. Bochsler  J. Woch  K. Asamura 《Icarus》2006,182(2):320-328

Data from the Ion Mass Analyzer (IMA) sensor of the ASPERA-3 instrument suite on Mars Express have been analyzed to determine the mass composition of the escaping ion species at Mars. We have examined 77 different ion-beam events and we present the results in terms of flux ratios between the following ion species: CO⁺₂/O⁺ and O⁺₂/O⁺. The following ratios averaged over all events and energies were identified: CO⁺₂/O⁺ = 0.2 and O⁺₂/O⁺ = 0.9. The values measured are significantly higher, by a factor of 10 for O⁺₂/O⁺, than a contemporary modeled ratio for the maximum fluxes which the martian ionosphere can supply. The most abundant ion species was found to be O⁺, followed by O⁺₂ and CO⁺₂. We estimate the loss of CO⁺₂ to be by using the previous measurements of Phobos-2 in our calculations. The dependence of the ion ratios in relation to their energy ranges we studied, 0.3-3.0 keV, indicated that no clear correlation was found.  相似文献   

The Venusian induced magnetosphere: A case study of plasma and magnetic field measurements on the Venus Express mission     

E. Kallio  T.L. Zhang  R. Jarvinen  P. Janhunen  J.-A. Sauvaud  J.-J. Thocaven  H. Andersson  K. Brinkfeldt  M. Holmström  M. Yamauchi  W. Baumjohann  A.J. Coates  D.O. Kataria  K.C. Hsieh  M. Grande  T. Säles  P. Riihelä  N. Krupp  J.G. Luhmann  S. Orsini  A. Mura  M. Maggi  P. Brandt  K. Szego  R.A. Frahm  J.R. Sharber  P. Bochsler 《Planetary and Space Science》2008,56(6):796-801

Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general picture obtained using a global numerical quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In instances where the orbit of Venus Express crossed a boundary referred to as the magnetic pileup boundary (MPB), field line tracing supports the suggestion that the MPB separates the region that is magnetically connected to the fluctuating magnetosheath field from a region that is magnetically connected to the induced magnetotail lobes.  相似文献   

Disaster risk assessment of ports based on the perspective of vulnerability   总被引：1，自引：1，他引：0  

Cheng-Hsien Hsieh 《Natural Hazards》2014,74(2):851-864

Global environmental changes have led to frequent occurrences of climatic extremes. The increasingly frequent and high-magnitude natural disasters in Taiwan have caused significant mortality, injury, and property damage. In response, there have been requests to improve the capacity to cope with extreme climatic conditions through increased awareness and identification of vulnerability. Disruptions to transportation systems affect the resilience for sustaining daily operations. Among the various types of transportation systems, ports provide substantial employment and industrial activity, contributing to national and regional development. In addition, ports integrate the functions of supply chains such as services in logistics, information, and business, becoming the location of industrial clusters. Therefore, this study examines the risk of port failures from the perspective of vulnerability. Specifically, seven vulnerable factors derived from the extant literature and lessons learned from the previous disaster cases are evaluated using geographic information systems. The results reveal that port capacity and efficiency have a significant effect on port vulnerability in which the efficiency of gantry cranes, labor productivity, free trade zone business volume, and ground access networks play crucial roles in port failure. Moreover, the risks associated with port operation are evaluated by overlapping a hazard map of areas prone to debris flows and tsunami inundation. The risk maps can assist decision makers in understanding the vulnerability and adopting appropriate strategies to minimize disaster risks.  相似文献   

A Note on the Flux-Variance Similarity Relationships for Heat and Water Vapour in the Unstable Atmospheric Surface Layer   总被引：12，自引：11，他引：1  

Gabriel G. Katul  Cheng-I Hsieh 《Boundary-Layer Meteorology》1999,90(2):327-338

Atmospheric surface layer (ASL) experiments over the past 10 years demonstrate that the flux-variance similarity functions for water vapour are consistently larger in magnitude than their temperature counterpart. In addition, latent heat flux calculations using the flux-variance method do not compare as favorably to eddy- correlation measurements when compared to their sensible heat counterpart. These two findings, in concert with measured heat to water vapour transport efficiencies in excess of unity, are commonly used as evidence of dissimilarity between heat and water vapour transport in the unstable atmospheric surface layer. In this note, it is demonstrated that even if near equality in flux-profile similarity functions for heat and water vapour is satisfied, the flux-variance similarity functions for water vapour are larger in magnitude than temperature for a planar, homogeneous, unstably-stratified turbulent boundary-layer flow.  相似文献   

Universality of a higher-order closure model for turbulent rotating flows     

A. S. Hsieh 《地球物理与天体物理流体动力学》2018,112(2):156-164

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A semi‐distributed parallel‐type linear reservoir rainfall‐runoff model and its application in Taiwan     

Lung‐Sheng Hsieh  Ru‐Yih Wang 《水文研究》1999,13(8):1247-1268

The main purpose of this paper is to introduce a semi‐distributed parallel surface rainfall‐runoff conceptual model. In this paper, a general solution of the instantaneous unit hydrograph (IUH) has been derived successfully for N linearly connected reservoirs, each having a different storage constant. The solution is a function of geomorphologic parameters, meteorologic factors and roughness coefficients. The model also takes into account the hydrologic response which is influenced by outflow downstream of a reservoir. For calibration, the shuffled complex evolution (SCE) algorithm is used to search for the global optimal parameters of the model. Because of the parallel structure, the mean roughness parameter of the channel becomes a “conceptual” parameter without a real physical meaning. To evaluate the adaptability of the model adopted, three watersheds around the city of Taipei in Taiwan were chosen to test the effectiveness of the model. The study provides an appropriate rainfall‐runoff model for planning flood mitigation in Taiwan. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Influence of strong monsoon winds on the water quality around a marine cage-culture zone in a shallow and semi-enclosed bay in Taiwan   总被引：1，自引：0，他引：1  

Huang YC  Huang SC  Meng PJ  Hsieh HJ  Chen CA 《Marine pollution bulletin》2012,64(4):851-860

Influences of marine cage culture and monsoonal disturbances, northeasterly (NE) and southwesterly (SW) monsoons on the proximal marine environment were investigated across a gradient of sites in a semi-enclosed bay, Magong Bay (Penghu Islands, Taiwan). Elevated levels of ammonia produced by the cages were the main pollutant and distinguished the cage-culture and intermediary zones (1000 m away from the cages) from the reference zone in the NE monsoon, indicating currents produced by the strong monsoon may have extended the spread of nutrient-enriched waters without necessarily flushing such effluents outside Magong Bay. Moreover, the levels of chlorophyll-a, dissolved oxygen, and turbidity were distinguishable between two seasons, suggesting that resuspension caused by the NE monsoon winds may also influence the water quality across this bay. It indicated that the impacts of marine cage culture vary as a function of distance, and also in response to seasonal movements of water driven by local climatic occurrences.  相似文献   

Does geographic location impact the survival differential between screen- and interval-detected breast cancers?     

Jeff Ching-Fu Hsieh  Susanna M. Cramb  James M. McGree  Nathan A. M. Dunn  Peter D. Baade  Kerrie L. Mengersen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):155-165

Although mammography screening programs aim to diagnose breast cancer at an early stage, not all tumours are detected during the regular screening examination. This study examines the influence of various characteristics, including geographical residence, on the survival between screen- and interval-detected breast cancers among participants of a public population-based breast screening program in Queensland, Australia. The investigation was performed using the linked population-based datasets from BreastScreen Queensland and the Queensland Cancer Registry for the period of 1997–2008 for women aged 40–89 years at diagnosis. A Bayesian spatial relative survival modelling approach that accommodates rare outcomes in small geographic regions was adopted, with the use of Markov chain Monte Carlo computation, to evaluate the relative excess risk of breast cancer. In the multivariate Bayesian spatial model, higher relative excess risk of mortality was observed in interval-detected cancer (RER = 1.59, 95 % credible interval = [1.33, 1.89]) compared to screen-detected cancer. Higher cancer survival among the study cohort was also observed among younger women (40–59 years), those of non-Indigenous ethnicity, with localised (stage I) tumour stage as well as those not in the work force. There was no independent association with marital status. Moreover, there was no substantive evidence of either measured geographical or latent random spatial inequalities in survival among screening participants across Queensland, meaning the higher survival for screen-detected breast cancer patients compared to interval-detected women was consistent across the state. These results provide suggestive evidence supporting the effectiveness of the BreastScreen Queensland screening program in reaching socio-economically disadvantaged women as well as those living in rural and remote areas of the state, but also highlights the need for any interval cancer awareness programs to be geographically widespread.  相似文献