A survey on wireless ATM technologies and standardization

Growing emphasis on multimedia traffic has underlined the importance of broadband asynchronous transfer mode (ATM) networks which are capable of supporting demanding applications such as audio/video playback, image browsing, real-time voice/video transmission and interactive data exchange in a unified manner. However, the extension of ATM from wireline to wireless creates a new set of challenging issues. ATM standards are developed based on high data rates and reliable transmission links. This is in contrast to wireless channels where bandwidth is limited and error rates are high. Furthermore, existing ATM specifications are designed primarily to provide services to fixed end-terminals with little ability to adapt to mobile connections and the highly time-varying conditions associated with wireless networks. This paper surveys the major technical and service issues related to the deployment of ATM in third-generation wireless networks. It will also cover how international standards are progressing in this important area. This revised version was published online in August 2006 with corrections to the Cover Date.     

The approximate swap and mismatch edit distance

There is no known algorithm that solves the general case of the approximate edit distance problem, where the edit operations are insertion, deletion, mismatch, and swap, in time o(nm), where n is the length of the text and m is the length of the pattern.In the effort to study this problem, the edit operations have been analyzed independently. Karloff [10] showed an algorithm that approximates the edit distance problem with only the mismatch operation in time . Amir et al. [4] showed that if the only edit operations allowed are swap and mismatch, then the exact edit distance problem can be solved in time .In this paper, we discuss the problem of approximate edit distance with swap and mismatch. We show a randomized time algorithm for the problem. The algorithm guarantees an approximation factor of (1+?) with probability of at least .     

Calculation of heat transfer in fire test furnaces with specific interest in the exposure of steel structures. A technical note

The equations for radiactive transfer in a compartment are outlined for a uniform gray gas. The incident radiation towards a test structure is related to the incident radiation from a black gas by the parameter φ.

φ increases with time as the compartment walls are heated. φ values are plotted in a figure, which makes manual calculation possible. In computer programmes time dependence of gas- and wall surface emissivities can be accounted for.

In general the ε_res approach is incorrect. For steel structures in a uniform test furnace a comparison is made between the two approaches, and it is shown that the ε_res approach overestimates the thermal exposure. The “overfiring” of test furnaces due to the fact that the ISO curve is specified for a thermocouple (and not the true gas temperature) partly compensates this error.     

Digging below the surface: Secondary analysis of TIMSS data for Hong Kong and its implications for educational reform

Abstract:

Hong Kong students outperform their counterparts in most other countries’ in mathematics in the Third International Mathematics and Science Study Repeat (TIMSS‐R) project, while their science performance is marginally above the international average. In order to probe below the surface of these achievement results, secondary analysis of the TIMSS‐R Hong Kong data was performed to identify factors that affect student achievement. Results of the secondary analysis relating to curriculum provision, teacher characteristics, and classroom conditions and climate are reported in this paper. Based on the results, some recommendations are proposed to meet the need for quality education in the new era.     

Prevention of defects in castings using back propagation neural networks

Defects in castings often lead to rejection, which would ultimately result in loss of productivity for a foundry. Expert systems developed by some researchers mostly act as postmortem tools, discussing and analyzing a defect after it has occurred. Though some investigators have attempted to predict a few important defects, a tool that could predict all the possible defects just before the castings are made has not yet been developed. Hence in the present work, an attempt has been made to predict major casting defects like cracks, misruns, scabs, blowholes and air-locks using back-propagation neural networks from the data collected from a steel foundry. The neural network was trained with parameters like green compression strength (GCS), green shear strength (GSS), permeability, moisture percent, composition of the charge and melting conditions as inputs and the presence/absence of defects as outputs. After the training was over, the set of inputs of the casting that is going to be made was fed to the network and the network could predict whether the casting would be sound or defective. If defective, the nature of the defect was also specified by the neural network. The neural network could predict cracks, misruns and air-locks accurately in most of the cases. The neural network could also predict other defects successfully. Investigating the causes followed by altering the moulding parameters and appropriate treatment of the molten metal can prevent the defects that were predicted by the backpropagation neural network.     

Dynamic fracture and spall in aluminum with helium bubbles

Investigation of the dynamic properties of aluminum targets with helium bubbles is presented. The targets were obtained by melting pure aluminum with 0.15% wt.¹⁰B powder. The solid targets were neutron irradiated to get homogeneous helium atoms inside the aluminum boron 10 matrix according to the reaction ¹⁰B + n → ⁷Li+⁴He. Helium atoms further accumulated into bubbles by diffusion in the bulk aluminum. Shock wave experiments were performed by accelerating the aluminum impactor into different targets: (1) pure aluminum, (2) Al-¹⁰B, and (3)Al-¹⁰B with different radii and concentrations of helium bubbles. The spall strength was calculated and analyzed from the free surface velocity measurements. It was found that the addition of ¹⁰B in pure aluminum reduces the spall strength of the material by 25–32%. However, irradiated sample with helium bubbles was found to have higher spall strength compared to samples without bubbles. This finding was reconstructed by numerical simulations. The impacted targets were collected after the impact experiments and examined by TEM. These targets were compared to TEM pictures before the impact. The number of helium atoms in the bubbles was calculated from the electron energy loss spectrum (EELS). TEM comparison between the pre-impacted and the impacted targets shows bubbles coalescence and EELS measurements demonstrate a reduction of the helium atoms concentration in the bubbles from ~10²⁸ m^?3 before the impact to ~10²⁷ m^?3 after the impact.     

Allocation of quality control stations in multistage manufacturing systems

The allocation of quality control stations (AQCS) in multistage manufacturing systems has been studied extensively over the decades. This paper reviews the existing approaches, models comparison and solution techniques applied in AQCS. The relevance of the models and the effectiveness of the inspection strategies are examined by developing a generalised model. The conducting simulation experiments show that as the number of workstation increases the processing time to solve the problem increases significantly. This led to the development of a heuristic algorithm with local search. The performance the heuristic was compared with the optimization method based on complete enumeration method (CEM). It was found that the heuristic method can derive an acceptable solution significantly faster than the CEM. The review has shown that the most common techniques used are dynamic programming and non-linear programming. The paper suggests some biologically inspired optimisation algorithms can be of interest for further study.     

Forever Do心蝶让爱，从心开始

在生活的道路上，经历众多过往以后，邂逅爱情最初的迷恋才能真正成为生命中最珍贵的诗篇。本季，潮宏基为在爱情森林中寻觅芳心的人们．倾心打造神圣、璀璨的爱之铭证：Forever Do“心蝶”系列。     

Quantifying PPCP interaction with dissolved organic matter in aqueous solution: combined use of fluorescence quenching and tandem mass spectrometry

The documented presence of pharmaceuticals and personal care products (PPCPs) in water sources has prompted a global interest in understanding their environmental fate. Dissolved organic matter (DOM) can potentially alter the fate of these contaminants in aqueous systems by forming contaminant-DOM complexes. In-situ measurements were made to assess the interactions between three common PPCP contaminants and two distinct DOM sources: a wastewater treatment plant (WWOM) and the Suwannee River, GA (SROM). Aqueous DOM solutions (8.0 mg L⁻¹ C, pH 7.4) were spiked with a range of concentrations of bisphenol-A, carbamazepine and ibuprofen to assess the DOM fluorophores quenched by PPCP interaction in excitation-emission matrices (EEM). Interaction effects on target analyte (PPCP) concentrations were also quantified using direct aqueous injection ultra high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). At low bisphenol-A concentration, WWOM fluorescence was quenched in an EEM region attributed to microbial byproduct-like and humic acid-like DOM components, whereas carbamazepine and ibuprofen quenched fulvic acid-like fluorophores. Fluorescence quenching of SROM by bisphenol-A and carbamazepine was centered on humic acid-like components, whereas ibuprofen quenched the fulvic acid-like fluorophores. Nearly complete LC-MS/MS recovery of all three contaminants was obtained, irrespective of analyte structure and DOM source, indicating relatively weak PPCP-DOM bonding interactions. The results suggest that presence of DOM at environmentally-relevant concentration can give rise to PPCP interactions that could potentially affect their environmental transport, but these DOM-contaminant interactions do not suppress the accurate assessment of target analyte concentrations by aqueous injection LC-MS/MSMS.