Notes on “single-machine scheduling with a time-dependent deterioration”

The aim of this paper is to show by an example that Theorem 3 and Corollary 2 in Wang et al. (Int J Adv Manuf Technol 43:805–809, 2009) are incorrect.     

A note on “Single-machine scheduling problems with release time of jobs depending on resource allocated”

A result in a recent paper reported by Zhang et al. (Int J Adv Manuf Technol 57:1175–1181) is incorrect because job processing times are variable due to both deteriorating jobs and learning effects, which is not taken into account by the authors. In this note, we show by a counter-example that the published result is incorrect and provide the corrected result.     

Comments on “A bicriteria parallel machine scheduling with a learning effect”

The purpose of this paper is to point out that if there are some machines that do not process any job then the mathematical programming model provided by Eren and Güner (Int J Adv Manuf Technol 40:1202–1205, 2009) may not be a valid one.     

Notes on “minimizing the earliness/tardiness costs on parallel machine with learning effects and deteriorating jobs: a mixed nonlinear integer programming approach”

The aim of this paper is to point out that the mixed nonlinear integer programming model proposed by Toksar? and Güner (Int J Adv Manuf Technol 38:801–808, 2008) is incorrect. We present a mixed nonlinear 0–1 programming model for the same scheduling problem based on their model.     

Methodology for evaluating effects of material characteristics on machinability—theory and statistics-based modelling applied on Alloy 718

The potential machinability for Alloy 718 (Inconel 718) is examined in terms of five material characteristics considered to play a key role in the machinability: ductility (elongation to fracture), strain hardening (ultimate tensile strength over yield strength), thermal conductivity, yield strength and abrasiveness (amount of carbides). The material characteristics are simulated with the software JMatPro from Sente software. The effects of composition, grain size, hardness (size of the precipitated intermetallic particles for given volume fraction), heat treatment, temperature and strain rate have been modelled and statistically evaluated. Combining thermodynamics-based modelling (JMatPro), design of experiments and statistical analysis (Minitab), and machinability polar diagram, a concept on methodology to assess variations in material specifications and to optimise these specifications with respect to potential machinability has been developed. The mechanical properties, predicted from the meta-modelling are found to be affected by the same parameters: hardness (intermetallic particles characteristics), grain size, amount of aluminium, strain rate and temperature. The abrasiveness should only be affected by the amount of carbon. Simulated material characteristics for two different types of turbine discs were compared with measured tool wear from production environment machining experiments. Variations in material characteristics between the discs were small as well as the critical tool wear, revealing a robust metal cutting process.     

Temperature effects on the tensile strength of brazed Fe-Cr-Al alloy (Fecralloy®) with Ni-based filler metal and corresponding image processing based analysis

Journal of Mechanical Science and Technology - Brazing bonding of iron-chromium-aluminum alloy (Fecralloy) with nickel based filler metal (MBF20) were performed at different maximum temperatures,...     

Stability and dynamics of rotor system with 45° slant crack on shaft

Crack on a shaft is one of the common damages in a rotor system. In this paper, transverse vibrations are calculated to compare the influences of transverse crack and slant crack on the rotor system. Results show that the vibration amplitude of the rotor system with a 45° slant crack on the shaft is larger than that with a transverse crack when the two types of crack have the same depth and the rotor system runs in the same condition. Stability and dynamic characteristics of the rotor system with a 45° slant crack on the shaft under torsional excitation are analyzed by considering opening and closing of the crack. It is shown that the instability of the transverse vibration of the rotor system increases with increasing difference between the bending stiffness in two main directions, and the vibration is stable when the two bending stiffness are identical. The spectrum analysis of the steady-state response reveals that the gravity and the eccentricity produce different frequency components, and when the two bending stiffness are identical, the multiple frequency components of the torsional excitation disappear. Further investigation shows that the vibration amplitudes in combined frequencies increase rapidly in transversal, torsional, and axial vibration with increasing slant crack depth. The results are helpful for the understanding the dynamic behavior of a rotor system with a slant crack on a shaft and can be used for the detection of the slant crack on a shaft.     

The effects of nickel and carbon concentrations on the wear resistance of Fe–Ni–C austenitic alloys

The effects of nickel and carbon concentrations on the wear resistance of Fe–xNi–yC (x = 14–20 wt.%, y = 0.6–1.0 wt.%) were investigated with respect to strain energy initiation of the martensitic transformation and hardness. The strain energy needed to initiate the martensitic transformation increased with increasing carbon and nickel concentrations, except in 1.0 wt.% C alloys. The wear resistance of the material decreased with increasing carbon concentration up to 0.9 wt.% C. This effect is most likely due to decrement of the martensite volume fraction with increasing carbon concentration induced by the incremental strain energy required to begin the martensitic transformation. In the case of 1.0 wt.% C, the improved wear resistance may be due to carbide precipitation.     

Surface roughness and roundness of bearing raceway machined by floating abrasive polishing and their effects on bearing’s running noise

As the two most important indexes of bearing raceway, surface roughness and roundness have significant influence on bearing noise. Some researchers have carried out studies in this field, however, reason and extent of the influence of raceway surface geometric characteristics on bearing running noise are not perfectly clear up to now. In this paper, the raceway of 6309 type bearing＇s inner and outer ring is machined by floating abrasive polishing adopting soft abrasive pad. Surface roughness parameters, arithmetical mean deviation of the profile Ra, the point height of irregularities Rz, maximum height of the profile Rmax and roundness fof raceways, are measured before and after machining, and the change rules of the measured results are studied. The study results show that the floating abrasive polishing can reduce the surface geometric errors of bearing raceway evidently. The roundness error is reduced by 25%, Rm~x value is reduced by 35.5%, Rz value is reduced by 22% and Ra value is reduced by 5%. By analyzing the change of the geometrical parameters and the shape difference of the raceway before and after machining, it is found that the floating abrasive polishing method can affect the roundness error mainly by modifying the local deviation of the raceway＇s surface profile. Bearings with different raceway surface geometrical parameter value are assembled and the running noise is tested. The test results show that Ra has a little, Rmax and Rz have a measurable, and the roundness error has a significant influence on the running noise. From the viewpoint of controlling bearings＇ running noise, raceway roundness error should be strictly controlled, and for the surface roughness parameters, R,n~x and Rz should be mainly controlled. This paper proposes an effective method to obtain the low noise bearing by machining the raceway with floating abrasive polishing after super finishing.     

A study on the energy efficiency improvement of greenhouses — with a focus on the theoretical and experimental analyses

Most greenhouses in Korea are made according to European weather conditions, which leads to very low solar energy efficiency under the domestic weather conditions. Thus, greenhouses in Korea should be adapted to the regional weather conditions to improve their energy efficiency. This paper investigates the current greenhouses in Korea. It also analyzes the problems arising from the greenhouses and offers alternatives for improving their energy efficiency based on measurements and a theoretical analysis. The elements of greenhouses were also investigated. When using a partially non-transparent insulation with heat storage mass between the indoor and outdoor air, the temperature difference became greater than 20°C during the daytime and greater than 5°C during the night, which will reduce the cost of fossil fuels.     

Comments on “Second-order sliding mode control with experimental application”

In this paper, some points to the stability analysis of the paper [Eker I, Second-order sliding mode control with experimental application, ISA Trans 2010;50:394–405] are presented. It is illustrated that the way the author in [1] proves stability, suffers lack of correct justification. A modification to the stability analysis is presented and the stability conditions are restated. Moreover, some other flaws in the original paper are addressed.     

Hyperthermal atomic oxygen interaction with MoS<Subscript>2</Subscript> lubricants and relevance to space environmental effects in low earth orbit – effects on friction coefficient and wear-life

Wear-life of the MoS₂ film was evaluated by in situ tribological testing under 5 eV atomic oxygen exposures which simulated atomic oxygen environment in low Earth orbit. A combination of a laser-detonation atomic oxygen source and a conventional pin-on-disk friction tester was used to perform tribological tests. It was confirmed that the friction coefficient was not affected by atomic oxygen exposure when atomic oxygen fluence was low; however, the friction coefficient increased with increasing atomic oxygen fluence and it reached as high as 0.05 at the atomic oxygen fluence of 3.4 × 10¹⁶ atoms/cm²/cycle (nine times larger than the normal value). Effect of atomic oxygen on the wear-life of the film has much more drastic. With atomic oxygen fluence of 1.7 × 10¹⁶ atoms/cm²/cycle, wear-life of the film was reduced less than one-tenth of that during ex situ testing result of the same film. It was also observed that the wear-life of the film was inversely proportional to the atomic oxygen fluence between sliding passes.     

Comments on “Overflow characteristics of streamlined weirs based on model experimentation” by Bagheri S. and Kabiri-Samani A

In this paper the stage-discharge equation of a streamlined weir is theoretically deduced applying the Π-Theorem of dimensional analysis and the self-similarity theory. The coefficients of the new stage-discharge relationship are estimated using the experimental results by Bagheri and Kabiri-Samani.     

Studies on extreme pressure films — reactions of sulphurized vegetable oils and alkyl phenols with iron

The reaction products of sulphurized Mohwa oil and sulphurized pentadecyl phenol (hydrogenated cardanol) with iron powder in hydrocarbon medium at 150°C for 8 h were studied to investigate the type of lubricant films formed during their application as antiwear and extreme pressure additives. Three main reaction products were isolated on the basis of their solubilities in chloroform and dimethyl formamide. An examination of their elemental analysis and infrared absorption data reveals that there is progressive reduction in the length of the alkyl chains and carbonyl ester group in the case of sulphurized Mohwa oil, with subsequent formation of inorganic iron sulphides, on the one hand, and polymerized products with a number of ketonic and aldehydic groups containing iron and sulphur in the polymeric films, in the form of unsaturated cyclic rings. The alkyl phenol, on similar studies, gave polymerized products with elimination of the long alkyl chain and containing cyclized rings with sulphur present in the form of sulphide bridges and in the heterocyclic ring structures, with progressive elimination of iron as iron sulphide. The films formed are organo-inorganic in nature, rather than the purely inorganic iron sulphide type. The load-carrying characteristics of these products are strongly influenced by the type of the film formed on the iron surfaces.     

Study of the slow-fast preamplifier input parameter’s effects on output image for LYSO scintillator with PS-PMT based animal PET

We developed a small animal positron emission tomography with four detector heads, each one composed of 2 × 2 cm² of pixilated LYSO matrix of 10 × 10 crystals, 2 × 2 mm wide and 10 mm deep coupled to position sensitive photomultiplier (PS-PMT, Hamamatsu R8900U-00-C12). Anger-type logic discretized positioning circuit (DPC) multiplexed readout connected to PMT of each head. The fast-slow preamplifier is used in the fabricated animal PET. We showed that the input capacitance of the preamplifier (the capacitance in the output node of the resistive network) has a direct effect on output image. Image broadening, peak to valley ratio and the geometry distortion of crystal illustration are studied for different input capacitance of preamplifier. The input capacitance of 1 nF resulted in the best image by keeping all the parameters at the proper level with no geometry distortion at the edge of the image.