GERT analysis of a single conveyor system†

Graphical Evaluation and Review Technique (GERT) has been applied to the analysis of the discrete conveyor model for service time distributions which are general but bounded and where there is no storage at work stations and no recirculation. The model is described by states with the Markovian property. The GERT analysis gives a visual representation of the conveyor system and useful information in the conveyor system design.     

Thermal conductivity of γ-irradiated LiF single crystals

The thermal conductivity of γ-irradiated lithium fluoride (LiF) single crystals has been studied using the method of stationary longitudinal heat flux in a temperature range of 50–300 K. An increase in the irradiation dose to 2 × 10⁹ rad is accompanied by a monotonic decrease in the thermal conductivity by 10% at 300 K and by a factor of 10 at 50 K. This increase in the irradiation dose also leads to an increase in the microhardness of LiF crystals from 140 to 222.5 kgf/mm².     

Recrystallisation of single crystal superalloy CMSX–4

Abstract

A series of experiments investigating the recrystallisation of single crystal superalloy CMSX-4 have been carried out. Indentation atroom temperature has been used to study the effects of annealing time and temperature, and it has been found that a very strong dependence upon temperature is evident. Annealing above the γ′ solvus temperature results in very rapid growth of recrystallised grains whereas annealing below the γ′ solvus greatly suppresses the advancing grain boundaries. Additionally experiments have been carried out using an electrothermal mechanical test (ETMT) machine, to study the effects of degree of plastic strain and the temperature at which the strain is introduced. The strain threshold for recrystallisation under various annealing conditions has been determined and it has been found that recrystallisation occurs more readily if strain is introduced above 950°C. Finally, apparent activation energies for recrystallisation have been determined by measuring the change in resistivity that occurs during recrystallisation.     

Comments on ‘vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme’

Zanoni, Mazzoldi, and Jaber [Zanoni, S., L. Mazzoldi, and M. Y., Jaber. 2014. Vendor-managed inventory with consignment stock agreement for single vendor–single buyer under the emission-trading scheme. International Journal of Production Research 52 (1): 20–31] consider a joint economic lot size problem under the vendor-managed inventory with consignment stock agreement and an emission-trading scheme. They show that the total cost of the system is a jointly convex function by simply showing that every element of the Hessian is positive. Noticing this mistake, we analyse the same problem in this technical note. We first provide a closed-form solution when the production rate is given. In order to avoid a complete search over all possible production rates, we then develop an efficient continuous approximation algorithm. Computational experiment shows that the approximation algorithm is effective and efficient.     

Extended structural defects in α-Hgl2 single crystals

Extended structural defects in both -Hgl₂ crystals grown in solution or from the vapour-phase were studied by optical microscopy, light scattering, SEM operated in cathodoluminescence and in secondary electron mode, X-ray topography, neutron, - and X-ray rocking curves and oscillating crystal X-ray diffraction. The observed dislocations were compared with theoretically calculated dislocations. Dislocation loops, having diameters ranging from 2 m to 500 m, are observed on all low index faces. Hohlstellen (lens-shaped voids) having axes along the [0 0 1] direction, less than 1 m in thickness, and diameters lying in the (001) planes, ranging from 2 m to 10 m are characteristic defects. Observed plastic deformations like glide sheets and bands, tilt and twist boundaries, kink and fatigue bands, ridges and rumplings were characterized. Growth rings, spherical void inclusions 10–30 m in diameter, orthogonal walls of forest screw dislocations parallel to 1 00 planes, and streaks (planar void sheets crossing the (001) planes) were only observed in crystals grown from the vapour-phase. Cross-penetration twins having (1 1 4) twin planes are described. The possible formation of stacking faults was analysed. The mosaicity of solution-grown crystals ranges from 1 to 6. A characteristic cellular structure, having a cell size ranging from 2 um to 10 m, was observed in all the crystals examined and correlated to local deviations from the stoichiometric composition. Solid lens-shaped inclusions, having diameters ranging from 3 m to 500 m and thicknesses ranging from 0.3 m to 50 m, respectively, are entrapped in many crystals and correlated to spiral hillocks observed on 001 growing faces.     

Self-diffusion of silicon-30 in α-SiC single crystals

The self-diffusion of³⁰Si in high purity and N-doped -SiC single crystals has been measured in the temperature range 2273 to 2573 K. The diffusion (D _Si ^* ) in N-doped crystals exceeds that in the pure crystals because of the increase in the concentration of the charged acceptor-type Si vacancies in the presence of the N species. A comparison ofD _C ^* andD _Si ^* shows that the former exceeds the latter by approximately 10², primarily because of the greater entropy of migration of C. Possible crystallographic paths of transport for both species are also discussed.     

High-performance single layered WSe₂ p-FETs with chemically doped contacts

We report high performance p-type field-effect transistors based on single layered (thickness, ～0.7 nm) WSe(2) as the active channel with chemically doped source/drain contacts and high-κ gate dielectrics. The top-gated monolayer transistors exhibit a high effective hole mobility of ～250 cm(2)/(V s), perfect subthreshold swing of ～60 mV/dec, and I(ON)/I(OFF) of >10(6) at room temperature. Special attention is given to lowering the contact resistance for hole injection by using high work function Pd contacts along with degenerate surface doping of the contacts by patterned NO(2) chemisorption on WSe(2). The results here present a promising material system and device architecture for p-type monolayer transistors with excellent characteristics.     

Andreev reflections from La2−xSrxCuO4 single crystals

Andreev reflections have been studied at the interface between a gold tip and La_2–xSr_xCuO₄ (x=0.11,0.12) single crystals, along the (110) direction. The shape of the I(V) characteristic has been analyzed within the framework of the theory of Tanaka and Kashiwaya, allowing for an anisotropic order parameter. The data cannot be fitted either to a pure isotropic s-wave or pure d-wave symmetry. The best fit is obtained for an anisotropic gap, with _max=15 meV and _min=5 meV.     

Photoinduced electric properties of Pb1−xSnxTe single crystals

It was established that the simultaneous action of laser IR radiation (ω < E_g, where E_g, is the band gap) and an external field (density of current through the crystal, j≲10²A/cm²) results in an accelerated change in electrical properties of Pb_1−xSn_xTe single crystals, which is attributed to an accelerated diffusion in the external electric field of metallic ions from associates of metal-enriched defects and dopants, arising during the crystal growth.     

Defect control for polarization switching in BiFeO₃ single crystals

BiFeO? (BFO) single crystals were grown and the effects of Zn and Mn co-doping on the polarization and leakage current properties were investigated at 25 °C for establishing materials design based on defect chemistry. Although Zn doping or Mn doping led to a deterioration in the properties, Zn-Mn co-doping led to a large remanent polarization (36 μC/ cm2), a low coercive field (19 kV/cm), and a relatively low leakage current density (~10?? A/cm2). It is proposed that defect dipoles composed of Zn2+ and Mn?+ act as effective nucleation sites for ferroelectric domains during polarization switching in BFO crystals.     

Morphology of solution-grown poly(β-propiolactone) single crystals

Single crystals of poly(-propiolactone) (PPL) with different molecular weights (M _w = 70000 and M _w = 2300) were grown from four kinds of solvents under isothermal crystallization condition. The morphologies and crystal structures of PPL single crystals were investigated by means of transmission electron microscopy and atomic force microscopy. The single crystals of high-molecular-weight PPL (HMW-PPL) grown from cyclohexanone appeared elongated with dimensions of around 0.2–0.8 m along the short and 5–10 m along the long axes. Single crystals of low-molecular-weight PPL grown from cyclohexanone showed three to five elliptical-shaped lamellae, from central nucleus like petals. The long axes of both single crystals corresponded to the crystallographic b axis. The reciprocal lattice parameters: a* = 2.045 nm^–1, b* = 1.420 nm^–1 and * = 90° could be determined from electron diffractograms. Decoration of the crystals with polyethylene suqqested that the single crystals of HMW-PPL have regular chain-folding along their long axis in the [010] direction with consecutive folds in the [110] and [1 0] directions. Accordingly, it is deduced that HMW-PPL has the anti-parallel chain-packing structure.     

Hydrogen hardening effect in heavily deformed single crystal α-Fe

Molecular dynamics simulations were performed to investigate the hydrogen interaction with edge dislocations during deformation in α-Fe. In particular, uniaxial tensile tests of a single crystal iron were conducted after the single crystal was plastically deformed to introduce high density of edge dislocations and was doped with different levels of lattice hydrogen concentration. During system relaxation, hydrogen atoms have tendency to diffuse and stay around dislocation line – a well-known hydrogen trap-site in α-Fe. Our simulations show that the yield strength of the bcc iron is very sensitive to the presence of hydrogen within edge dislocations, i.e., it increases as hydrogen concentration increases. After yielding, hydrogen atoms are de-associated with the moving dislocations, suggesting that the yield strength enhancement is caused by the hydrogen pinning effect. This direct observation of hydrogen hardening effects has confirmed the experimental findings by Matsui, etc. Additional simulations also indicate that hydrogen interaction with edge dislocations is sensitive to temperature as well as vacancies around dislocation core.     

Macrophage-targeted single walled carbon nanotubes stimulate phagocytosis via pH-dependent drug release

Atherosclerotic cardiovascular disease is the leading cause of mortality in the world.A driving feature of atherosclerotic plaque formation is dysfunctional efferocytosis.Because the“don’t eat me”molecule CD47 is upregulated in atherosclerotic plaque cores,CD47-blocking strategies can stimulate the efferocytic clearance of apoptotic cells and thereby help prevent the progression of plaque buildup.However,these therapies are generally costly and,in clinical and murine trials,they have resulted in side effects including anemia and reticulocytosis.Here,we developed and characterized an intracellular phagocytosis-stimulating treatment in the CD47-SIRPαpathway.We loaded a novel monocyte/macrophage-selective nanoparticle carrier system with a small molecule enzymatic inhibitor that is released in a pH-dependent manner to stimulate macrophage efferocytosis of apoptotic cell debris via the CD47-SIRPαsignaling pathway.We demonstrated that single-walled carbon nanotubes(SWNTs)can selectively deliver tyrosine phosphatase inhibitor 1(TPI)intracellularly to macrophages,which potently stimulates efferocytosis,and chemically characterized the nanocarrier.Thus,SWNT-delivered TPI can stimulate macrophage efferocytosis,with the potential to reduce or prevent atherosclerotic disease.     

A simple one‐dimensional model of flow through single gauzes

Abstract

This paper describes one‐dimensional simulation of the flow through single gauzes used in the regenerator of the Stirling cycle machine. The flow is modelled as a one‐dimensional core outside a boundary layer developing along the surface of the wire comprising the gauze. The simulated results show that the pressure loss coefficient, f, decreases with increasing Reynolds number, Re, and the open area ratio of gauzes, σ, for the flow in the incompressible regime. For the case of compressible flow, f increases with Mach number, M, before reaching the choking condition; the increase is sharp at choking. These tendencies are confirmed by experiment. Empirical relations between f and M, Re, and σ are then presented. They can be used for the calculation of the pressure drop of the flow through wire gauzes.     

Thermal conductivity and secondary porosity of single anatase TiO₂ nanowire

Single anatase TiO? nanowire is synthesized using the electrospinning technique with the sol-gel method and is suspended over a pre-processed 100 μm-wide TEM grid for further characterization. The diameters of the nanowires fall in the range of 250-400 nm. The transient electrothermal (TET) method is adopted to acquire the voltage-time (U-t) profile of the Ir-coated nanowire under step Joule heating. The intrinsic thermal diffusivity of single anatase TiO? nanowires varies from 1.3 to 4.6 × 10?? m2 s?1, and the thermal conductivity changes distinctly from 1.3 to 5.6 W m?1 K?1, much lower than the value of the bulk counterpart: 8.5 W m?1 K?1. The density and thermal conductivity increase significantly with the diameter, largely because at larger diameters less secondary porosity is left by decomposition of organic composites and their escape from the wire during calcination. The density of TiO? nanowires is found to be much lower than that of the bulk counterpart. This is supported by the SEM image of the secondary porous surface. High secondary porosity is observed for TiO? nanowires, ranging from 18% to 63%. This very high secondary porosity confirms that the decomposition of PVP content may distort the fibrous matrix and leave vacancies. In addition, the transition from amorphous to anatase phase could also create a porous state due to crystal particle aggregation.     

Deformation mechanism in αCu-Al single crystals with a spherical indentor

Indentation tests using a steel ball were carried out on the (0 0 1), (0 1 1) and (1 1 1) cube faces of Cu-Al single crystals in order to elucidate the plastic deformation mechanism in the surface layers. The shapes of the indent and the slip traces produced on these faces were studied in detail. In addition, the dislocation density distributions around an indent on the (1 1 1) and (¯2 1 1) faces were revealed by successively removing thin layers and developing etch pits on the exposed surfaces. Slip tends to occur in the 1 1 0 direction on the (0 0 1) and (0 1 1) faces, and in the [2 ¯1 ¯1], [¯1 2 ¯1] and [¯1 ¯1 2] directions on the (1 1 1) face. The three-dimensional slip pattern in the case of indentation on the (1 1 1) face consists of two sets of truncated triangular pyramids that diverge and converge downwards.     

Low energy laser initiation of single crystals of β-lead azide

Unfocused low energy Q-switched and non-Q-switched ruby laser irradiation of individual single crystals of-lead azide of size 40m×200m×10mm has been studied using high-speed photography. It was found that the initiation of fast reaction occurs at isolated sites which are probably defects and act as absorption centres in the dielectric which is otherwise transparent to the ruby wavelength of 694.3 nm. It has also been shown that it is the power and not the energy of the incident beam that controls the initiation under these low energy irradiation conditions. Finally, the variation of the time delay to initiation with the incident laser energy suggests a thermal mechanism of initiation.     

Observing single cell NF-κB dynamics under stimulant concentration gradient

Study of cell signaling often requires examination of the cellular dynamics under variation in the stimulant concentration. Such variation has typically been conducted by dispensing cell populations in a number of chambers or wells containing discrete concentrations. Such practice adds to the complexity associated with experimental or device design and requires substantial labor for implementation. Furthermore, there is also potential risk of missing important results due to the often arbitrary selection of discrete concentration values for testing. In this Letter, we study NF-κB activation and translocation at the single cell level using a microfluidic device that generates continuously varying concentration gradient. We use only three device settings to cover stimulant (interleukin-1β) concentrations of 4 orders of magnitude (0.001-10 ng/mL). Such device allows us to study temporal dynamics of NF-κB in single cells under different stimulant concentrations by real-time imaging. Interestingly, our results reveal that, while the percent of cells with NF-κB translocation decreases with lower stimulant concentration in the range of 0.1-0.001 ng/mL, the response time of such translocation remains constant, reflected by the single cell data.