楔形砌块溢道上的水流分析

世界各国的试验数据、研究成果和原型测试已明确表明，混凝土楔形砌块是一种理想的土坝溢洪道、堆石坝溢洪道或过水围堰等的保护材料。混凝土楔形块不仅便于制作安装，而且经济、安全、可靠。作者首先提出使用出口突然放大能量损失的理论对作用在楔形块溢洪道上的沿程阻力进行分析，推导出准均匀流状态下的无量纲的Ｃｈｅｚｙ系数Ｃ０、水流深度ｈ０和水流流速Ｖ的求解方式。计算成果与模型、原型试验成果进行了对比，证明了公式的实用性。     

A Shift-Invariant Neural Network for the Lung Field Segmentation in Chest Radiography

We have developed a computerized method using a neural network for the segmentation of lung fields in chest radiography. The lung is the primary region of interest in routine chest radiography diagnosis. Since computer is expected to perform disease pattern search automatically, it is important to design appropriate algorithms to delineate the region of interest. A reliable segmentation method is essential to facilitate subsequent searches for image patterns associated with lung diseases. In this study, we employed a shift invariant neural network coupled with error back-propagation training method to extract the lung fields. A set of computer algorithms were also developed for smoothing the initially detected edges of lung fields. Our preliminary results indicated that 86% of the segmented lung fields globally matched the original chest radiographs. We also found that the method facilitates the development of computer algorithms in the field of computer-aided diagnosis.     

CPU bugs, CPU backdoors and consequences on security

In this paper, we present the security implications of x86 processor bugs or backdoors on operating systems and virtual machine monitors. We will not try to determine whether the backdoor threat is realistic or not, but we will assume that a bug or a backdoor exists and analyze the consequences on systems. We will show how it is possible for an attacker to implement a simple and generic CPU backdoor in order—at some later point in time—to bypass mandatory security mechanisms with very limited initial privileges. We will explain practical difficulties and show proof of concept schemes using a modified Qemu CPU emulator. Backdoors studied in this paper are all usable from the software level without any physical access to the hardware.     

Development of a Wireless Sensor Glove for Surgical Skills Assessment

Laparoscopic surgery is a challenging task in minimally invasive surgery, which involves complex instrument control, extensive manual dexterity, and hand-eye coordination. This requires a greater attention to training and skills evaluation. In order to provide a more objective skills assessment method, this paper presents a wireless sensor platform for the capture of laparoscopic hand gesture data and a hidden-Markov-model-based analysis framework for optimal sensor selection and placement. Detailed experimental validation is provided to illustrate how the proposed method can be used to assess surgical performance improvement over repeated training.     

A Post-fire Survey on the Pre-evacuation Human Behavior

A delay in the pre-evacuation reaction may be one of the reasons causing occupants to be ‘trapped’ in a dangerous zone. Under fire situations, people are found to behave differently in that some may start evacuation immediately, some may ignore the fire alarms and engage in their activities and some others may participate in fighting the fire. These behavioral reaction patterns are influenced by some factors, such as occupant characteristics, building characteristics and fire characteristics. The purpose of this study is to investigate the pre-evacuation behavior of occupants under fire and explore the associations between these factors and the human behavior. To obtain the human behavioral information in real fire, a post-fire survey for a multi-storey office building fire in a major city in Mainland China was carried out with the assistance of local fire professionals. Some of the possible factors that might influence the occupants’ actions at recognitions and response stage were examined. It was reckoned that the behavioral reaction at recognition and response stage was mainly dependent on the human characteristics and building characteristics except the fire characteristics. The results also implied that pre-evacuation time was typically influenced by the occupant characteristics.     

Enhanced Vertical Light Extraction From Ultrathin Amorphous Si–Si$_{3}$ N$_{4}$ Multilayers With Photonic Crystal Patterns

We have investigated the significant enhancement of light extraction from amorphous Si-Si₃N₄ multiple-quantum-well structures, in which two-dimensional hexagonal-lattice air-hole photonic crystals (PCs) were integrated. The vertical spectral integrated intensity of light emission around 674 nm was enhanced up to times due to strong coupling to the inherent leaky modes or radiation modes near Gamma point of PC's band structure. The experimental observations also suggested that coupling to leaky modes should be more beneficial for light extraction enhancement.     

Alterations in K+ evoked profiles of neurotransmitter and neuromodulator amino acids after focal ischemia-reperfusion

e present evidence that nestmate discrimination in the eusocial paper wasp, Polistes dominulus, is context dependent. We compared aggression levels between nestmates and non-nestmates in dyads consisting of a pair of either nestmates or non-nestmates, and triads consisting of either three nestmates, three non-nestmates, or two nestmates and a non-nestmate. In 130 of the 237 total trials, a nest fragment (containing both brood and eggs) from the nest of some, all or none of the interactants was placed into the interaction arena. Polistes dominulus workers recognized and discriminated nestmates from non-nestmates, familiar from unfamiliar nest material and neighbours from non-neighbours. These findings suggest that nestmate and neighbour discrimination are context dependent: discrimination occurs when either the presence of a nestmate or a familiar nest fragment indicate the proximity of the colony. The context-dependent variation in aggression levels is best described by multiple, context-dependent shifts in an acceptance threshold. Thus this study provides the most extensive, critical support yet obtained for Reeve's (1989, American Naturalist, 133, 407-435) optimal acceptance threshold model. Copyright 1998 The Association for the Study of Animal Behaviour     

Cascade self-induced holography: a new grating fabricationtechnology for DFB/DBR lasers and WDM laser arrays

A method of fabricating submicron gratings for optoelectronic devices from a glass mask was proposed and demonstrated. The glass mask has gratings on both sides with a period of at least four times the final feature size. By introducing an offset to the grating periods on the mask, one can achieve multiple-period gratings with a very fine period spacing for advanced wavelength-division multiplexing (WDM) devices. In this paper, we demonstrated 0.5-μm second-order gratings for 1.55-μm DFB lasers and gratings with a 6-Å period difference for a four-channel WDM laser array using only optical sources. The Moire pattern caused by the spatial frequency beating was also observed and discussed. The Moire pattern could serve as an effective tool to measuring wavelength channel spacing between devices with an unprecedented (0.1 Å) resolution     

Interface trap generation by FN injection under dynamic oxide fieldstress

Interface trap generation under dynamic (bipolar and unipolar) and dc oxide field stress has been investigated with the charge pumping technique. It is observed that regardless of stress type, whether dc or dynamic (bipolar or unipolar), and the polarity of stress voltage, interface trap generation starts to occur at the voltage at which Fowler-Nordheim (FN) tunneling through the oxide starts to build up. For positive voltage, interface trap generation is attributed to the recombination of trapped holes with electrons and to the bond breaking by the hydrogen (H and H⁺) released during stressing. For negative voltage, in addition to these two mechanisms, the bond breaking by energetic electrons may also contribute to interface trap generation. The frequency dependence of interface trap generation is also investigated. Interface trap generation is independent of stressing frequency for unipolar stress but it shows a frequency dependence for bipolar stress