An investigation of the use of heat pipes for machine tool spindle bearing cooling

The results of an experimental investigation into the practicality of using a heat pipe installed in the spindle of a milling machine to remove the heat produced in the spindle bearings which is capable of causing thermal distortion and cutting error are presented in the paper. Measurements of the variation of bearing temperature with time are reported at four different spindle speeds when there was no heat pipe installed, when the heat pipe was cooled by air and when the heat pipe was cooled by an ice/water mixture. Analysis of the results by a simple heat transfer model indicates that the particular heat pipe used was capable of removing up to 160 W with a corresponding 50% reduction in the rise of the bearing temperature above the temperature of the surrounding air at steady operating conditions.     

Binary polymer blend of ArPTU/PI with advanced comprehensive dielectric properties and ultra-high thermally stability

Flexible high-temperature polymeric dielectrics with advanced dielectric properties are urgently demanded in various applications. In this work, series of polymer blend films were prepared from aromatic polythiourea (ArPTU) and polyimide (PI). The experimental results revealed that the blend films were properly engineered to achieve higher breakdown strength, greater dielectric constant, and larger energy density than pure PI film. For instance, the optimum property was obtained from the blend film with 10 wt% ArPTU, exhibiting prominent dielectric properties (K = 4.52, E_b = 443 MV/m), enhanced energy density (4.00 J/cm³) as well as excellent heat resistance (T_g = 419°C). In addition, stable dielectric properties at broad temperature range from −50 to 250°C were also acquired. It is deduced that the good compatibility from ArPTU and PI with similar polarity are responsible for the improved properties. The superior comprehensive properties which combine the advantages of ArPTU and PI suggest the potential applications of ArPTU/PI blend film in high-temperature dielectric areas.     

Mechanical and high velocity impact performance of a hybrid long carbon/glass fiber/polypropylene thermoplastic composite

This research explores mechanical and high velocity impact response of hybrid long carbon/glass fiber-reinforced polypropylene thermoplastic composites (HLFT) with different fiber lengths. The work examines three hybrid long fiber thermoplastic composites, i.e., 5, 10 and 20 mm. The HLFTs were prepared by a combination of extrusion and pultrusion processes and using a cross-head die. Tensile and Izod impact tests were carried out to evaluate the mechanical performance of each HLFT compound. A gas gun with a spherical projectile was used to conduct high velocity impact tests at three velocities of 144, 205 and 240 m/s. The results showed that internal mixing operation caused extensive reduction in fiber length of all three LFT lengths. Tensile strength, modulus and Izod impact test results were the indications of higher values with increase in HLFT length. Comparison of these results for the HLFT with that of corresponding glass/PP LFTs, adopted from earlier work by Shayan Asenjan et al. (J Compos Mater 53:353–360, 2019), showed better performance of HLFT. The high velocity impact results showed a steady higher impact performance with the increase in HFLT fiber length for all impact velocities tested. Comparison of HLFT high velocity impact performance revealed better results for all impact velocities tested with that of the corresponding glass/PP LFT composite.     

Application of transmission FT-IR spectroscopy for the trans fat determination in the industrially processed edible oils

The amount of trans fatty acids (TFA) in fourteen industrially hydrogenated and deodorized oils was determined. To achieve better sensitivity 200 μm KCl cell was used in transmission Fourier transform infrared (FT-IR) spectroscopy. The results of transmission FT-IR spectroscopy were evaluated by gas chromatography (GC) with flame ionization detector (FID), and found to be comparable. All analyzed cooking oil samples had a lower trans content of 0.4–1.8%. Trans fatty acid contents of partially hydrogenated oil samples were relatively higher as comparable to those of the cooking oils. Among the samples examined, the highest level was found to be at 26.5% and 25.7% by the GC–FID and FT-IR spectroscopy, respectively. Due to harmful effects, high amounts of trans fatty acids in partially hydrogenated oils is an alarming issue for the consumer’s health and quality control authorities.     

A new analytical/iterative approach to statistical delay characterization of cmos digital combinational circuits

This paper is believed to be one of the first attempts to statistically characterize signal delays of basic CMOS digital building blocks. Analytic expressions in terms of the transistor geometries and technological process variations are provided for fast delay computations, to be used for manufacturing yield optimization, delay variability reduction and general VLSI circuit design for quality. the proposed approach is novel in several ways: (1) It is a combination of an accurate, semi-empirical MOS transistor model with the use of an efficient interpolation technique to link the non-physical model parameters to the ‘designable’ and ‘noise’ factors. (2) It uses several newly developed analytical delay formulae where possible and simple iterative solutions where direct analytical solutions do not exist. (3) the resulting hybrid analytical/iterative models are tuned, if necessary, to enhance the overall statistical accuracy. (4) Local delays are combined together for the analysis of complex combinational VLSI circuits. (5) C-code is generated for specific delay paths to further increase efficiency (improvement in analysis times by two to four orders of magnitude with respect to SPICE, with about 5%-10% accuracy). Examples of statistical delay characterization are used to illustrate the high accuracy of the proposed approach in modelling the influence of the ‘noise’ parameters on circuit delay relative to direct SPICE-based Monte Carlo analysis. the important impact of the proposed approach is that statistical evaluation and optimization of delays in much larger VLSI circuits will become possible.     

A decision support framework for metrics selection in goal-based measurement programs: GQM-DSFMS

Software organizations face challenges in managing and sustaining their measurement programs over time. The complexity of measurement programs increase with exploding number of goals and metrics to collect. At the same time, organizations usually have limited budget and resources for metrics collection. It has been recognized for quite a while that there is the need for prioritizing goals, which then ought to drive the selection of metrics. On the other hand, the dynamic nature of the organizations requires measurement programs to adapt to the changes in the stakeholders, their goals, information needs and priorities. Therefore, it is crucial for organizations to use structured approaches that provide transparency, traceability and guidance in choosing an optimum set of metrics that would address the highest priority information needs considering limited resources. This paper proposes a decision support framework for metrics selection (DSFMS) which is built upon the widely used Goal Question Metric (GQM) approach. The core of the framework includes an iterative goal-based metrics selection process incorporating decision making mechanisms in metrics selection, a pre-defined Attributes/Metrics Repository, and a Traceability Model among GQM elements. We also discuss alternative prioritization and optimization techniques for organizations to tailor the framework according to their needs. The evaluation of the GQM-DSFMS framework was done through a case study in a CMMI Level 3 software company.     

Effects of seawater on AAR expansion of concrete

Recently, AAR was identified in submerged piles of some bridges in tidal waters. Microstructural examination detected chloroaluminate salts in some cracks. To clarify whether seawater had influenced the deterioration an experimental program was planned to examine the effects of sodium chloride on AAR under various curing conditions.Concrete prisms containing either of highly-reactive, slowly-reactive or nonreactive aggregate, and either low or high alkali contents, were stored in saltwater (representing seawater) or at 100% RH, at temperatures of 38, 60 and 80 °C, for expansion measurement over 600 days, after which the temperature for those stored in saltwater was lowered to 23 °C, to check its effect on further expansion, which could be attributed to precipitation of ettringite and/or Ca-chloroaluminate.The results indicate that the type of aggregate and concrete alkali content had the greatest effect on AAR expansion. Exposure to saltwater did not have any significant effect on the AAR expansion.