Stabilization of discrete-time systems with stochastic parameters

This letter presents a solution to the problem of stabilization by a constant feedback of a linear system whose system and control matrices are multiplied by scalar correlated noise sequences.     

Railway track geometry determination using adaptive Kalman filtering model

The Kalman filter has been widely used to solve different filtering problems especially in tracking and estimation applications. Besides its simplicity, robustness and optimality, the application of Kalman filter to nonlinear systems can be complicated. The most common method is to use extended Kalman filter which linearizes the nonlinear model so that the standard Kalman filter can be applied. In this paper, a new adaptive Kalman filtering algorithm is designed and applied to a railway track geometry surveying system which has been designed in the scope of a research project at Yildiz Technical University/Turkey. Track gauge, super-elevation, gradient and track axis coordinates which are the railway geometrical parameters can be instantly determined while making measurements by using adaptive Kalman filtering algorithm integrated surveying system.     

Effects of ultraviolet light and ultrasound on microbial quality and aroma-active components of milk

BACKGROUND: Heat treatment is the most common way to extend the shelf life of milk. However, alternative technologies such as ultraviolet (UV) light and ultrasound (US), which are non‐thermal methods for processing milk, have been developed to replace heat treatment. These technologies do not have any adverse effects on the quality of milk. The major purpose of this study was to investigate the effects of UV and US on different micro‐organism groups and aroma compounds in milk. RESULTS: Heat pasteurisation at 65 °C for 30 min was used as thermal control treatment. The growth of total coliform group bacteria, Escherichia coli and Staphylococcus spp. was completely reduced by UV treatment. Application of US was not sufficient to reduce the numbers of yeasts and moulds. In neutral/basic fractions, 3‐methylthiophene (plastic), hexanal (grass) and 1‐hexen‐3‐one (floral) were major volatiles in milk samples. CONCLUSION: UV had a major effect on total coliforms, E. coli and Staphylococcus spp., but US was not as effective as UV and heat treatment in reducing certain groups of micro‐organisms. No major differences were observed in terms of aroma‐active compounds and flavour of milk following the different treatments. However, some new volatiles and change in rheological properties were generated by UV and US treatments. Copyright © 2011 Society of Chemical Industry     

Time-optimized hole sequence planning for 5-axis on-the-fly laser drilling

On-the-fly laser drilling requires the use of acceleration continuous trajectories, which are typically planned using time parameterized spline functions. In this operation, the choice of hole drilling sequence, and positioning timings in between the holes, play a critical role in determining the achievable cycle time. This paper presents a new algorithm for sequencing 5-axis on-the-fly laser drilling hole locations and timings. The algorithm considers machine tool and process constraints, as well as the temporal nature of the final commanded spline trajectory. The achievable productivity and motion smoothness improvement are demonstrated in the production of a gas turbine combustion chamber panel.     

Thermal stability and mechanical properties of nanocrystalline Fe–Ni–Zr alloys prepared by mechanical alloying

The thermal stability of nanostructured Fe_100?x?y Ni _x Zr _y alloys with Zr additions up to 4 at.% was investigated. This expands upon our previous results for Fe–Ni base alloys that were limited to 1 at.% Zr addition. Emphasis was placed on understanding the effects of composition and microstructural evolution on grain growth and mechanical properties after annealing at temperatures near and above the bcc-to-fcc transformation. Results reveal that microstructural stability can be lost due to the bcc-to-fcc transformation (occurring at 700 °C) by the sudden appearance of abnormally grown fcc grains. However, it was determined that grain growth can be suppressed kinetically at higher temperatures for high Zr content alloys due to the precipitation of intermetallic compounds. Eventually, at higher temperatures and regardless of composition, the retention of nanocrystallinity was lost, leaving behind fine micron grains filled with nanoscale intermetallic precipitates. Despite the increase in grain size, the in situ formed precipitates were found to induce an Orowan hardening effect rivaling that predicted by Hall–Petch hardening for the smallest grain sizes. The transition from grain size strengthening to precipitation strengthening is reported for these alloys. The large grain size and high precipitation hardening result in a material that exhibits high strength and significant plastic straining capacity.     

Torsional oscillations of an infinite cylindrical elastic tube under large internal and external pressure

This study is concerned with the small amplitude torsional oscillations of a hyperelastic infinite circular cylindrical thick tube made of a rubber-like material subjected to a large static internal and external pressure. The material is represented by a Mooney-type strain energy relation. The governing differential equation is first solved by the Frobenius method then a variational approach, which is more suitable for numerical calculations, is developed. Several values for the natural frequencies are obtained.     

Synthesis and Properties of Novel Selenium containing Polyimides with Various Dianhydrides

Novel selenium-containing polyimides were prepared from bis(1,3-di-p-dimethylaminobenzylpyrimidine- 2-selenon) and bis(1,3-di-p-dimethylaminobenzyldiazepane-2-selenon) and with various aromatic dianhydrides in a one-stage polycondensation at high temperature in N-methyl-2-pyrrolidone. The polyimides have inherent viscosities that range from 1.55 to 2.05 dL/g in NMP at 30°C. These polymers showed glass transition temperatures between 188 and 268°C, and an initial decomposition temperature from 421 to 502°C with a 10% mass loss occurring from 480 to 547°C in air.     

Block-Based Methods for the Reconstruction of Finite-Length Signals From Nonuniform Samples

Two novel block-based algorithms are presented for the reconstruction of uniform samples given the nonuniform samples. The first algorithm uses a sinc interpolator whereas the second one uses a DFT-based interpolator. It is shown that the proposed algorithms are stable and the error due to noise and sampling jitter is bounded by the corresponding error norms of noise and jitter, respectively. We show that both of the block-based algorithms provide nearly perfect reconstruction for a class of practically time and bandlimited signals. Boundary effects are considered and single and multiblock processing is discussed. A modified block-based algorithm is developed by using the windowing technique in order to improve the mean-squared error (MSE) performance for nonbandlimited signals. It is shown that this algorithm performs better than a group of alternative algorithms, including Yen's third algorithm, for a variety of signal, noise, and sampling grids     

板类零件数控切割的自动编程

利用ＣＡＤ系统与ＮＣ连接自动编程的方法，研究了工业锅炉板类零件数控切割。通过对ＡｕｔｏＣＡＤ状态下的零件图形进行处理，读取图形交换ＤＸＦ文件中的几何信息，可以自动确定切割路线和自动编制数控加工程序。结果表明，该方法可以大大提高编程的可靠性、数控切割效率及自动化水平。     

An enhanced scanning-based MPPT approach for DMPPT systems

In this paper, an improved maximum power point tracking (MPPT) approach being low parameter dependency, simple structure and limited search interval has been presented for distributed MPPT photovoltaic (PV) systems. Basically, this approach is based on scanning of power–voltage (P-V) characteristic curve of PV modules in a limited duty ratio interval which makes tracking operation simple, fast and efficiently available in both uniform irradiance and partial shading conditions (PSCs). By limiting the scanning interval of maximum and minimum values of duty ratio via some analyses related to P-V characteristic for PSCs, global MPPT (GMPPT) is achieved in an efficient way. So as to validate performance of the proposed approach, a single-ended primary inductance converter has been used in both simulation and experimental studies. PV simulator has been used as a PV source to obtain different module characteristics with different number of bypass diodes and PV power levels. Both simulation and experimental results clarify that improved MPPT approach realises GMPPT effectively. Due to the high performance results, this approach can be an alternative technique in module-integrated converters, smart modules and PV power optimisers in which single module is used.