Case Studies in Security and Resource Management for Mobile Object Systems

Mobile objects have gained a lot of attention in research and industry in the recent past, but they also have a long history. Security is one of the key requirements of mobile objects, and one of the most researched characteristics related to mobility. Resource management has been somewhat neglected in the past, but it is being increasingly addressed, in both the context of security and QoS. In this paper we place a few systems supporting mobile objects in perspective based upon how they address security and resource management. We start with the theoretical model of Actors that supports concurrent mobile objects in a programming environment. Then we describe task migration for the Mach microkernel, a case of mobile objects supported by an operating system. Using the OMG MASIF standard as an example, we then analyze middleware support for mobile objects. Mobile Objects and Agents (MOA) system, is an example of middleware level support based on Java. The active networks project, Conversant, supports object mobility at the communication protocol level. We summarize these projects, comparing their security and resource management, and conclude by deriving a few general observations on how security and resource management have been applied and how they might evolve in the future.     

湿润地区山区小流域水文模型应用与比较

将新安江模型、萨克拉门托模型及TOPMODEL应用在3个不同的湿润地区山区小流域,将洪峰相对误差及峰现时间误差作为预报精度主要评价指标,分析不同水文模型在各流域的精度及适用性。结果表明:在南阳河流域,新安江模型略优于另外两种模型,但3种模型总体精度均不高;在雾渡河流域,新安江模型精度较高,萨克拉门托模型次之,TOPMODEL精度最低;茅坪河流域资料匮乏,仅有的6场洪水全部用于模型率定,3种模型均能达到预报精度要求。综合比较后发现,新安江模型在3个研究流域预报精度最高。     

Ensemble tracking

We consider tracking as a binary classification problem, where an ensemble of weak classifiers is trained online to distinguish between the object and the background. The ensemble of weak classifiers is combined into a strong classifier using AdaBoost. The strong classifier is then used to label pixels in the next frame as either belonging to the object or the background, giving a confidence map. The peak of the map and, hence, the new position of the object, is found using mean shift. Temporal coherence is maintained by updating the ensemble with new weak classifiers that are trained online during tracking. We show a realization of this method and demonstrate it on several video sequences     

Domain adaptation–can quantity compensate for quality?

The Domain Adaptation problem in machine learning occurs when the distribution generating the test data differs from the one that generates the training data. A common approach to this issue is to train a standard learner for the learning task with the available training sample (generated by a distribution that is different from the test distribution). One can view such learning as learning from a not-perfectly-representative training sample. The question we focus on is under which circumstances large sizes of such training samples can guarantee that the learned classifier preforms just as well as one learned from target generated samples. In other words, are there circumstances in which quantity can compensate for quality (of the training data)? We give a positive answer, showing that this is possible when using a Nearest Neighbor algorithm. We show this under some assumptions about the relationship between the training and the target data distributions (the assumptions of covariate shift as well as a bound on the ratio of certain probability weights between the source (training) and target (test) distribution). We further show that in a slightly different learning model, when one imposes restrictions on the nature of the learned classifier, these assumptions are not always sufficient to allow such a replacement of the training sample: For proper learning, where the output classifier has to come from a predefined class, we prove that any learner needs access to data generated from the target distribution.     

Light polarization under water near sunrise

Dramatic and rapid changes in the intensity and spectrum of light under water at dusk and dawn are well known, but reports regarding the light's polarization at these periods are sparse. Using a rapid spectropolarimeter, we examined the spatial and spectral characteristics of the underwater polarization patterns from sunrise to midday and compared them with a Rayleigh-based model for e-vector orientation and percent polarization. With the Sun near the horizon, the underwater polarization patterns were distinctive. Unlike the polarization at small solar zenith angles, the underwater polarization at large solar zenith angles cannot be predicted by simple Rayleigh scattering, most likely because of the relatively high contribution of skylight. At sunrise, the underwater polarization pattern outside of Snell's window differed from that found during the day in percent polarization, spatial distribution, and wavelength dependence. These unique polarization characteristics may provide a polarization-sensitive animal with a distinct cue for mediating dial vertical migration performed by plankton or with another timing signal.     

Small-molecule analysis with silicon-nanoparticle-assisted laser desorption/ionization mass spectrometry

Silicon nanopowder (5-50 nm) was applied as a matrix for the analysis of small molecules in laser desorption/ionization mass spectrometry. In contrast with conventional matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry, the matrix background interference in the low mass range was significantly reduced. Effects of the particle size and sample preparation procedures on the background mass spectra and the analyte signal intensity have been investigated, and an optimized powder and sample preparation protocol was established. Several surface characterization tools have been applied as well. Both positive mode and negative mode laser desorption/ionization have been applied to different analytes including drugs, peptides, pesticides, acids, and others. Detection limits down to the low femtomole per microliter levels were achieved for propafenone and verapamil drugs. The method developed was found relatively tolerant to salt contamination, which allowed the direct analysis of morphine and propaphenone in untreated urine and triazine herbicides in a soil extract. The new silicon-nanoparticle-assisted laser desorption ionization method was found to be highly selective, which may be due to analyte-dependent precharging in solution, prior to vacuum laser desorption. Some aspects of the charge-transfer mechanism have been studied and discussed. In comparison with standard MALDI matrixes, the silicon nanopowder requires much lower laser fluence (contributing to a reduced background) has much better surface homogeneity, and is more tolerant to salt interference, which makes it an easily applicable practical tool at a potentially low cost.     

Effect of Various Gelling Cations on the Physical Properties of “Wet” Alginate Films

In this study, the physical properties of “wet” alginate films gelled with various divalent cations (Ba²⁺, Ca²⁺, Mg²⁺, Sr²⁺, and Zn²⁺) were explored. Additionally, the effect of adding NaCl to the alginate film‐forming solution prior to gelling was evaluated. Aside from Mg²⁺, all of the divalent cations were able to produce workable “wet” alginate films. Films gelled with BaCl₂ (without added NaCl) had the highest (P < 0.05) tensile strength and Young's modulus while films gelled with CaCl₂ (alone) had the highest puncture strength. The Zn‐alginate and Sr‐alginate films had the highest elongation at break values. Adding NaCl to the alginate film‐forming solution increased the viscosity of the solution. Films with added NaCl were less transparent and had lower tensile strength, elongation, and puncture strength than films formed without NaCl in the film‐forming solution. ATR‐FTIR results showed a slight shift in the asymmetric COO^? vibrational peak of the alginate when the “wet” alginate films were gelled with Zn²⁺.     

Mechanical and Microstructural Properties of “Wet” Alginate and Composite Films Containing Various Carbohydrates

Composite “wet” alginate films were manufactured from alginate–carbohydrate solutions containing 5% alginate and 0.25% pectin, carrageenan (kappa or iota), potato starch (modified or unmodified), gellan gum, or cellulose (extracted or commercial). The “wet” alginate films were used as a model to understand co‐extruded alginate sausage casings that are currently being used by several sausage manufacturers. The mechanical, optical, and microstructural properties of the calcium cross‐linked composite films were explored. In addition, the water holding capacity and textural profile analysis properties of the alginate–carbohydrate gels were studied. The results indicate that the mechanical properties of “wet” alginate films/casings can be modified by adding various carbohydrates to them. Alginate films with pectin, carrageenan, and modified potato starch had significantly (P < 0.05) greater elongation values than pure alginate films. The alginate–pectin films also had greater (P < 0.05) tensile strengths than the pure alginate films. Alginate films with extracted cellulose, commercial cellulose, and modified potato starch had lower (P < 0.05) puncture force, distance, and work values than the alginate control films. Transmission electron microscopy images showed a very uniform alginate network in the control films. Several large cellulose fibers were visible in the films with extracted cellulose, while the cellulose fibers in the films with commercial cellulose were difficult to distinguish. Despite these apparent differences in cellulose fiber length, the 2 cellulose films had similar puncture and tensile properties.     

特大型屋面与地面雨水收集系统的应用分析

以某特大型屋面及地面雨水收集系统项目为例,对特大型屋面与地面雨水收集系统进行概述,介绍了其雨水弃流过滤方式、雨水蓄水池的形式以及雨水处理工艺,探究了该系统的应用难点,并具体分析了有关雨水收集系统的应用,以保证特大型雨水收集系统的稳定运行.