Estimating cycle time and return rate distributions for returnable transport items

A return rate distribution for returnable transport items (RTI) is estimated from radio frequency identification (RFID) data. The technique is dependent on estimating a probability density function for backward fill-to-fill cycle times for the returnable containers. The cycle time distribution yields an estimate of a time period where most containers will return to the manufacturer. To obtain return rate observations, the number of returns in a production lot is observed by tracking the fill and return of uniquely tagged containers over this time period, adjusting for containers with long cycle times. The process also gives an estimate of the percentage of RTI tagged in the population or fleet of containers. The effects of estimation errors due to a partial RFID-tagging of the fleet are examined, and satisfactory results can be obtained when not all containers are tagged. The use of the cycle time and return rate distributions for creating a forecast of container returns is illustrated, and implementation of cycle time and return rate as indicators of supply chain performance is discussed.     

Relationship between impact energy and design parameters of glass bottles

Glass containers are relatively heavy. Also, glass is fragile, and breakage sometimes occurs during handling and transport. Therefore, glass bottles must be constructed to achieve maximum strength at minimum weight (wall thickness). To our knowledge, about 85% of all breakage is caused by external impact. The purpose of the present paper is to study the relationship between the shape and thickness of glass bottles and the impact loads they can resist by using linear multivariate statistical/mathematical regression (or calibration) techniques (UN-SCRAMBLER), in order to compute minimum required thickness of the bottle as a function of impact strength and vice versa. The study was based on 10 different types of bottles. Moreover, we have concentrated on measurements related to the heel of the bottle. The set of bottles used are described as follows: returnable, round body, straight side wall and without metal oxide coating. All the bottles were given a standard abusement before the impact tests. The following conclusions were reached:

• i there are strong relations between glass thickness and the resistance to external impact (as expected);
• ii multivariate calibration gave much better results than using only one variable at a time
• iii the predictive ability is not good enough (accuracy of ±10–15%). But provides useful information that would be difficult to obtain by other methods

(iii) .     

Curtailed Attribute Sampling

This paper is concerned with maximum likelihood estimation of a process (or lot) average proportion of defectives based on attribute samples that have been curtailed either with rejection of a lot on finding the kth defective or with acceptance on finding the Kth nondefective. The MLE, , based on inspections from a sequence of m lots is shown to be simply the ratio of the number of defectives found to the total number of items inspected, and the asymptotic variance of this estimator is shown to be approximately (1 — )/Σ ^m ₁ y _i , where Σ ^m ₁ y _i is the total of all items inspected.     

A Lanczos-based method for structural dynamic reanalysis problems

In this paper, a new solution method for the modified eigenvalue problem with specific application to structural dynamic reanalysis is presented. The method, which is based on the block Lanczos algorithm, is developed for multiple low rank modifications to a system and calculates a few selected eigenpairs. Given the solution to the original system Ax = λx, procedures are developed for the modified standard eigenvalue Problem (A + ΔA)x? = λ x?, where

• 1 ΔA = Σ_jBS_jB^T, where S_j = S ∈ ?^{p × p}, p ? n and B ∈ ?^{n × p} is constant for all the perturbations S_j.
• 2 ΔA = Σ_iΣ_j B_iS_jB_i^T, where B_i ∈ ?^{n × p} may vary with the pertubations S_j.

The procedures are then extended for the reciprocal and generalized eigenvalue problems so that they are directly applicable to the structural dynamic reanalysis problem. Numerical examples are given to demonstrate the applications of the method.     

An approach to the mechanism of Corrosion of tungsten in alkaline solutions

The mechanism of anodic dissolution and hence of corrosion of W in alkaline solutions (NaOH, Na₃PO₄) has been investigated by measuring anodic Tafel lines by the galvanostatic technique, and calculating both the Tafel slope b and the effect of pH on anode potential as diagnostic criteria for the mechanism. The quasi-equilibrium principle of Kabanov, Burstein and Frumkin for all reactions preceding the rate-determining (rd) step has been used to calculate the concentration of intermediates as a function of potential. Two mechanisms have been tested with this principle:

• (i) the first involving the formation and dissolution of nonstoichiometric and stoichiometric surface oxides, and
• (ii) the second deals with the formation and dissolution of hydroxide species.

     

Further development of the model of a filtration flow within the concept of the effective diameter

Extension of the concept of the effective diameter to steady-state filtration flows allows us to suggest a generalized ideal model of a porous medium combining all the existing models (models of nonintersecting cylindrical capillaries, of parallel plane pores, etc.) and possible calculation procedures based on the notions of a filtering medium in the form of longitudinal parallel channels with a certain shape of the cross section. Results of a study of a filtration flow are presented for a porous medium. The study was carried out using the calculation model suggested.Notation l length - g acceleration due to gravity - v andv _f true and fictitious average velocities - E friction losses of specific hydraulic energy along the length (or available specific potential energy) - _L and Darcy and Weisbach coefficients - Re _L =vL/v Reynolds number - v kinematic viscosity - L characteristic linear dimension - d diameter - d _h=4S/P hydraulic diameter - S cross-sectional area - P wetted perimeter - d _e=K ₁ d _h effective diameter - K ₁=(A _d/A)^0.5 shape factor - A=_LRe_L hydraulic resistance atL=d _h (A=A _d=64 atL=d andL=d _e) - K andC permeability coefficient and filtration coefficient - Re _d ^1.cr =2320 lower critical Reynolds number atL=d andL=d _e - i=E/(lg) dimensionless slope - m andn porosity (the ratio of the pore to medium volumes) and clearness coefficient (the ratio of the pore to medium areas) Izhevsk State Technical University, Izhevsk, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 4, pp. 559–563, July–August, 1995.     

UO2芯块运输容器核临界安全分析

目的 在开展二氧化铀（UO₂）芯块运输容器设计时,应进行临界安全分析,优化容器设计,并通过得出的临界安全指数（CSI）限定可运输货包的数量,确保在任何可信的运输情景下的核临界安全。方法 文中采用蒙特卡罗软件SuperMC对符合要求的国际临界安全手册中6类49个基准实验案例进行建模计算,获得本案例的次临界上限值,再基于运输容器经受正常运输条件与运输事故条件试验的结果,计算得出正常运输条件与运输事故条件下的单货包与货包阵列的最大中子增殖系数keff值。结果 该案例的次临界限值（USL）为0.91974;UO₂芯块运输容器在正常运输条件与运输事故条件下单货包的最大keff值分别为0.286 08,无限阵列货包的最大keff值为0.798 34。结论 UO₂芯块运输容器在正常运输条件与运输事故条件下的最大keff值均小于0.919 74,临界安全指数为0,容器设计临界安全性能可确保可运输安全。     

Nb3Si prepared by high-rate sputtering followed by quenching

Nb₃Si films with the A-15 structure have been prepared by sputtering onto a substrate whose temperature is about 1000 C, followed by quenching to liquid nitrogen temperature. All processes were carried out by using magnetron sputtering in a container full of liquid nitrogen. The quenching just after the deposition was achieved by thermal conduction using a sample holder in contact with the liquid nitrogen container. The highest onset temperature T _on and critical temperature (midpoint of the transition) T _c of the samples are 17.3 and 16.4 K, respectively, with a sharp transition. X-ray diffraction patterns show fine-grained A-15 structure and give a lattice constant of 5.09 Å.Work supported in part by a Grant-in-Aid for Scientific Research from the Ministry of Education.     

On size effects in helium II below 1 K

The normal fluid density _n and the specific heatc _v are calculated for helium II flowing through plane parallel slits and capillaries with a square profile at temperatures below1 K. Both functions increase over their bulk values if the thermal phonon wavelength becomes comparable to or larger than the smallest dimensiond of the container. The asymptotic expansions which are obtained in this paper have an overlapping range of validity, and therefore describe _n andc _v rather accurately for all values of /d.     

Morphology and properties of Mg2Si and Mg2(SixSn1−x) reinforcements in magnesium alloys

In this paper, the effects of Sr, Sb, Sr+Sb and Sn on Mg₂Si reinforcement phases in an Mg–Al–Zn–Si alloy are studied, and the structures and characteristics of Mg₂(Si_xSn_1?x) phases are analysed with first-principle calculations. The results show that the coarse eutectic Mg₂Si can be refined by modifying processes with Sr, Sb, and their combination. When alloying with Sn, a new reinforcement phase Mg₂(Si_xSn_1?x) forms by a substitution reaction, instead of Mg₂Si. Calculations indicate that Mg₂(Si_xSn_1?x) has a certain percentage of covalent bonds, which ensure it has sufficient hardness to act as a reinforcement phase. Calculated results for physical parameters, such as the bulk modulus and shear modulus, indicate that an Mg₂(Si_xSn_1?x) intermetallic exhibits greater ductility than Mg₂Si.

Highlights

• The coarse eutectic Mg₂Si can be refined by modifying processes.

• A new phase Mg₂(Si_xSn_1?x) forms by substitution reaction during solidification.

• Mg₂(Si_xSn_1?x) has certain covalent bound percentage.

• Mg₂(Si_xSn_1?x) has better plasticity than that of Mg₂Si.

     

The spin-up problem in Helium II

The laminar spin-up of Helium II is studied by solving the linearized equations of motion for the normal and superfluid components and the quantized vortex lines in a simple case. The fluid is taken to be confined between two parallel planes whose angular velocity increases at a small, steady rate. The vortex lines are treated as a continuum. No direct interactions between the vortex lines and the walls are included. Two mechanisms are identified for the transfer of angular momentum from the container to the interior fluid. In the first place, classical Ekman pumping occurs in the normal fluid component. Secondly, mutual friction between the normal Ekman layer and the vortex lines produces an (Ekman-like) secondary flow in the superfluid component. In both mechanisms, mutual friction in the interior couples the normal and superfluid components together, so that both components spin up. Normal-fluid Ekman pumping is found to dominate at temperatures close to the -point (T=2.17 K), while the second mechanism becomes progressively more important at lower temperatures. In the small-Ekman-number limit, when the vertical container dimension 2a is much larger than the Ekman layer thickness, the spin-up time (i.e., the time lag between the container and the interior fluid) for both components ist _spin-upf(T)a ₀ ^–1/2 , where ₀ is the angular velocity andf(T) is a decreasing function of temperature. Although some experimental spin-up times in He II have been reported in the literature, their analysis involves many uncertainties. Thus, new experiments to test this model should be highly desirable.     

Enthalpy relaxation and free volume changes in aged styrene copolymers containing a hydrogen bonding co-monomer

Enthalpy relaxation of polystyrene (PS) and four modified polystyrene copolymers containing co-monomers capable of forming hydrogen bonds of different strengths is described. Values of enthalpy lost ( H(T_a, t_a)) were calculated from experimental data plotted against log (t_a) and modelled using the Cowie-Ferguson (CF) semi-empirical model. This gives a set of values for three adjustable parameters, H(T_a), log (t_c) and . Each of the parameters defines the relaxation process, which was found to be sensitive to changes in hydrogen bond strength. The introduction of hydrogen bonding causes a slower relaxation compared with PS, with a greater overall enthalpy lost measured for the all the copolymers except the styrene-co–4-hexafluoro-2-hydrox isopropyl styrene (SHFHS). Interestingly, the free volume of this copolymer measured using Positron Annihilation Lifetime Spectroscopy (PALS) was greater than that of PS. Furthermore, the SHFHS copolymer had the lowest change in heat capacity ( C_p) of any of the systems on passing through the glass transition, T_g. All experiments indicate that the enthalpy lost by the fully relaxed glass ( H(T_a)) is less than the theoretical amount possible on reaching the state defined by the equilibrium liquid enthalpy line ( H_max(T_a)). The results are discussed with reference to the strength of interaction and free volume.     

On the anharmonic contribution to the specific heat of monatomic face-centered cubic crystals

We have presented a method for an exact calculation of the two lowest-order, cubic (F ₃) and quartic (F ₄), perturbation terms in the Helmholtz free energy (F) of an anharmonic crystal in the high temperature limit. The method is applicable to a nearest-neighbor central force model of a monatomic fcc crystal for any phenomenological two-body potential (r). The calculation of F ₃ and F ₄ requires a knowledge of the six dimensionless Brillouin zone (BZ) sums, as a function of a parameter a ₁ depending on the first and second derivatives of (r). These sums are calculated to a high degree of accuracy for a mesh size of 308,000 points in the whole BZ in the range –0.1a ₁+0.1 in steps of 0.02. The linear temperature dependent anharmonic contribution to the specific heat at constant volume, calculated for the elements Pb, Ag, Ni, Cu, Al, Ca, and Sr, from the Morse and Rydberg potentials, is found to be positive in all cases, with the exception of Pb. In this case the Morse potential gives a negative sign. The predictions of theory are in agreement with experiments where the data is available (e.g., Cu, Al, and Pb).     

The simulation of the processes of formation and decay of neutral particles in DC discharge plasma in an argon-oxygen mixture

Results are given of calculations of concentrations of fundamental neutral particles in the positive column of a dc discharge in an argon-oxygen mixture. The calculations are based on simultaneous solution of Boltzmann equation, vibrational kinetic equations for the ground state of O₂ molecule, and chemical kinetic equations for the ground and excited states of O₂ molecules and Ar and O atoms with the experimentally determined value of reduced intensity of electric field E/N. The results are compared with measured values of radiation intensities of lines of 811.5 nm (Ar) and 845 nm (OI) and of atmospheric band O₂(b ¹Σ _g ⁺ → X ³Σ _g ^? , 0-0).     

Microstructural evolution during high energy ball milling of Fe2O3-SiO2 powders

The reaction of a 25 mol% Fe₂O₃-SiO₂ (hematite-amorphous silica) powder mixture during high energy ball milling in both closed and open containers has been studied by x-ray diffraction and Mössbauer spectroscopy. After around 21 h of milling, the α-Fe₂O₃ powders with an average particle size of 15 nm have formed and no reaction between α-Fe₂O₃ and SiO₂ is found in the two types of milling containers. This demonstrates that the high energy mechanical milling technique is able to prepare a dispersion of ultrafine α-Fe₂O₃ particles. After extended milling in the open container all iron atoms are found in a hematite phase. In the closed container the hematite phase transforms into an iron-rich spinel phase and some of the iron atoms react with the amorphous SiO₂, forming a new Fe(II)-containing silicate compound.     

On Critical Velocity of Superfluid Bose Gas with Boundary Interactions

The existence of superfluidity in a 3D Bose-gas can depend on boundary interactions with container walls. We study a simple model where the dilute moving Bose-gas interacts with the walls via hard-core repulsion. Special boundary excitations are introduced, and their excitation spectrum is calculated within a semiclassical approximation. It turns out that the state of the moving Bose-gas is unstable with respect to the creation of these boundary excitations in the system gas + walls, i.e. the critical velocity vanishes in the semiclassical (Bogoliubov) approximation. Such a surface mode could exist in soft matter containers with flexible walls.     

The expansivities and the thermal degradation of some layer compounds

The thermal expansion coefficients and the decomposition products at high temperatures under vacuum have been determined for a number of layer compounds; SnS₂, SnSe₂, SnSSe, ZrS₂, HfS₂ and TiS₂, all of which have crystal structures based on that of cadmium iodide, and-GaSe. In all compounds the expansion perpendicular to the layers (c) is much greater than that parallel to the layers (c). This is ascribed to the effect of the weak van der Waal's bonding between layers. Thermal degradation at high temperatures (up to 900° C) under vacuum usually follows a route via the monochalcogenide or the sub-chalcogenide to the oxide.     

Corrections to the electronic heat capacity of metals due to finite lifetimes of the conduction electrons

The electron-phonon interaction is well known to enhance the low-temperature electronic heat capacity of metals, C _el. At high temperatures this enhancement vanishes, but the electron-phonon interaction gives the electrons a finite lifetime. That means a broadened density of states, which affects the high-temperature C _el. Starting from a many-body theory expression for the entropy, this paper presents an analytical calculation of the correction to C _el and a numerical calculation of C _el from a realistic density-of-states function, N(). The effect arising from the broadening of N() may have any sign and typically alters the heat capacity by 10% or less in transition metals.     

Containerless processing of a lithium disilicate glass

Glasses of Li₂O · 2SiO₂ (LS₂), and LS₂ doped with 0.001 wt% platinum (LS₂ + 0.001 wt% Pt) compositions were melted, cooled and reheated at controlled rates while levitated (containerless) inside an electrostatic levitator (ESL) furnace at the NASA Marshall Space Flight Center. The experiments were conducted in vacuum using spherical, 2.5–3 mm diameter, glass samples. The measured critical cooling rate for glass formation, R _c, for the LS₂ and LS₂ + 0.001 wt% Pt glasses processed at ESL were 14 ± 2 °C/min and 130 ± 5 °C/min, respectively. The values of R _c for the same LS₂ and LS₂ + 0.001 wt% Pt glasses processed in a container were 62 ± 3 °C/min and 162 ± 5 °C/min, respectively. The effective activation energy for crystallization, E, for this LS₂ glass processed without a container at ESL, was higher than that for an identical glass processed in a container. These results suggest that the glass formation tendency for a containerless LS₂ melt is significantly increased compared to an identical melt in contact with a container. The absence of heterogeneous nucleation sites that are inherently present in all melts held in containers is believed to be the reason for the increased glass forming tendency of this containerless melt.     

A dynamic multi-item two-activity problem

Summary We consider the following symmetric generalization of the well-known asset-selling problem. Assume that there are two activities, each of which must be carried out a given number of times. An example is the disposal ofi andj containers of toxic waste of two different kinds. Exactly one of the activities is performed per time period. The random rewards (possibly negative) for performing the different tasks are i.i.d. and have a known two-dimensional joint distribution. In addition, there are fixed costsc, c ₁ andc ₂ (possibly negative) per period as long as activities of both kinds, or only of the first or only of the second kind must be performed. Based on a realization of the two random rewards, each period a choice must be made which of the two activities to perform such that the expected total reward becomes maximal. We show for arbitrary discount factor the existence of an optimal control limit policy with recursively computable critical numbersd _ij . Some explicitly solvable cases are presented. Under appropriate assumptions thed _ij 's are monotone ini and/orj which allows, despite a 4-dimensional state space, to represent the optimal policy by a family of 2-dimensional monotone decision regions. And then, the limits of thed _ij 's can be used to identify large sets of states where the optimal decision can be found without numerical computations. The basic tool is the integrated distribution function of the difference of the two rewards. The paper generalizes many of the known results on asset-selling problems without recall.