Self-tuning adaptive neurocontroller for brushless DC motors

This paper describes a self-tuning adaptive neurocontroller for brushless DC motors. Nonlinear and unknown motor dynamics are identified by using a multilayer neural network and the control input for the motor is derived from the identified model. The effect of the load torque on the control system is damped by filtering the control input. Simulation and experimental results show that the self-tuning adaptive neurocontrol has a good tracking performance but needs an adaptive filter and a parallel PI controller in the case of disturbances.     

A review of cryogenic cooling in machining processes

The cooling applications in machining operations play a very important role and many operations cannot be carried out efficiently without cooling. Application of a coolant in a cutting process can increase tool life and dimensional accuracy, decrease cutting temperatures, surface roughness and the amount of power consumed in a metal cutting process and thus improve the productivity. In this review, liquid nitrogen, as a cryogenic coolant, was investigated in detail in terms of application methods in material removal operations and its effects on cutting tool and workpiece material properties, cutting temperature, tool wear/life, surface roughness and dimensional deviation, friction and cutting forces. As a result, cryogenic cooling has been determined as one of the most favourable method for material cutting operations due to being capable of considerable improvement in tool life and surface finish through reduction in tool wear through control of machining temperature desirably at the cutting zone.     

Determination of optimal loading profiles in warm hydroforming of lightweight materials

In this study, a methodology is developed to determine proper profiles of the hydraulic pressure and the blank holder force under warm hydroforming conditions at different punch speeds. First, finite element models (2-D and 3-D) are developed and validated through comparisons with the experimental results from the literature. To determine the optimal hydraulic pressure and blank holder force profiles simultaneously, an adaptive FE analysis with fuzzy control algorithm was developed. Thinning, wrinkling, punch wall contact, die corner floating and conduction were used as criteria in the fuzzy control algorithm. The effects of the determined loading profiles are then presented in terms of thickness, strain and stress, and temperature distributions as well as success/failure of the forming process. The effect of punch speed was also investigated to reveal its impact on part formability. It was found that the optimal process conditions can be rapidly and accurately obtained with the developed adaptive FEA method coupled with fuzzy control algorithm.     

Correlates of the length of the relationship between main and specialist trade contractors in the construction industry

Although there is a growing literature on the factors associated with the length of interorganizational relationships, there seem to be few empirical studies related to the subject in project-based industries such as construction. In this study we looked for correlations among the length of the relationship between main and specialist trade contractors, control methods and the number of rival speciality contractors in the Turkish construction industry, drawing on the data provided by a study of 27 specialist trade contractors. Correlation analysis was used to investigate the relationship. The results demonstrate that the length of the relationship between main and speciality contractors is inversely related to the number of rival specialist trade contractors, but directly related to the flexibility of control exercised by the main contractor.     

Comparative pyrolysis of polyolefins (PP and LDPE) and PET

In the present study, thermal degradation of polyolefins (PP and LDPE) and PET in a tubular reactor in an inert atmosphere was conducted. Each polymer was subjected to pyrolysis at the temperatures of 673, 773, 873, and 973 K. Yields of tar, residual coke and gas, and conversion degrees were calculated. Tars which include valuable chemicals were characterized by GC–MS, ¹H-NMR, FTIR, and GPC. Pyrolysis gases (C1 + C2, C3, C4, C5, and C6 + C7) were also analyzed by GC analysis. From the comparison of data, it can be said that pyrolysis of PP and LDPE leads to the formation of tar containing mainly paraffinic structures, while aromatic structures were produced by the pyrolysis of PET.     

Investigations on thermo-mechanical fabrication of micro-scale porous surface features

In this paper, we present the preliminary results of our investigations to fabricate porous micro-feature surface structure arrays on large surface areas for fuel cell and other heat/mass transfer applications. We hypothesized that micro-channels of around 200–400 μm height and width with porosity levels of 30–50% and with strong bonding to a thin substrate could be fabricated using hot powder compaction and/or hot roll powder compaction. We investigated the effects of compaction pressure, temperature, holding time, powder size and substrate conditions on the attainable porosity and channel size. Our feasibility study findings indicate that both pressure and temperature have significant effect on the porosity level. Suggested temperature levels are around 450 °C to ensure strong bonding among powders and between powders and the thin substrate. Minimum pressure level can be around 50 MPa, but it depends on the temperature levels. Roughened substrate surface condition is found to slightly assist in achieving strong bonds and high porosity. In order to have high porosity levels, uniform powder size is preferred. Although not tested extensively, hot compacted specimens up to 450 °C temperature levels are found to be not very strong. Hence, subsequent sintering is necessary.     

Application of Markov chains on image enhancement

Stochastic image processing tools have been widely used in digital image processing in order to improve the quality of the images. Markov process is one of the well-known mathematical modeling tools in stochastic theory. In this study, a Markov chain model has been developed and applied to image denoising. The transition probabilities were obtained from Fokker–Planck diffusion equation. According to the results, the proposed Markov chain model supplies very good peak signal to noise ratio values along with low computational cost.     

以抗坏血酸作协同试剂时红土镍矿在硫酸溶液中的溶解（英文）

研究硫酸与抗坏血酸联用对恰尔达红土镍矿中镍和钴的溶解作用。作为比较,也研究柠檬酸、马来酸和硬脂酸等有机酸作为协同试剂的应用情况。结果表明,抗坏血酸和柠檬酸的使用显著改善了钴的溶解,而其他两种有机酸对浸出率的协同作用很小。对于镍的溶解,抗坏血酸是最有效的协同试剂,其次是柠檬酸、马来酸和硬脂酸。在本研究获得的最优条件下,即1 mol/L硫酸中加入4 g/L抗坏血酸、80°C、固液比1/10,浸出4 h后钴和镍的浸出率分别达到99%和98%以上。此外,浸出行为对抗坏血酸浓度的变化(2~4 g/L)较不敏感,这从操作角度来看是非常理想的。     

Determination of hydroquinone using poly(3‐methylthiophene) synthesized electrochemically on pt electrode in methylene chloride

Poly(3‐methylthiophene) (P3MT) film was synthesized by potentiodynamic method on Pt electrode in methylene chloride solution containing 0.10M tetrabuthlammonium perchlorate supporting electrolyte and used for the determination of hydroquinone (HQ) with amperometric I–t method in solution consisting of NaHSO₄/Na₂SO₄ (SBS; pH 2.0). This modified electrode has a lower working potential and good operational stability due to reducing electrode fouling when compared with the direct oxidation of HQ at the bare Pt electrode. Limit of detection, limit of quantification, and the linear response range were found to be 1.32 × 10^?5 mM, 4.41 × 10^?5 mM, and between 4.41 × 10^?5 – 50.0 mM (R² = 0.997), at 0.50 V versus saturated calomel electrode, respectively. HQ determination in complex matrix was checked using real samples to demonstrate the applicability of modified electrode. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40859.