Theoretical considerations on the penetration of powdered metal jets

This paper explores some of the theoretical issues encountered when interpreting the penetration behavior of an oilwell perforating charge, whose jet forms from an unsintered powdered metal (PM) liner. Appropriate treatments of the jet's porous compressible nature fill the gap between classical “continuous” and “fully particulated” jet penetration models. Within certain constraints, increasing a penetrator's length (even if by distension) increases its hydrodynamic penetration depth, while reducing its impact pressure; and a porous penetrator penetrates deeper than a non-porous penetrator of the same density, length, and velocity. Dynamic target pressure considerations lead to the conclusion that highly distended, low-velocity, PM jets should penetrate moderate-strength geologic targets effectively. After demonstrating that initial transient shock pressures may be much higher than steady-state penetration pressures, we suggest that initial penetration rates may be higher than the steady-state rates. This, in conjunction with the well-known “residual penetration” phenomenon, indicates that a non-continuous jet's penetration may be strongly influenced by transient effects.     

Validation and calibration of a lateral confinement model for long-rod penetration at ordnance and high velocities

In designing targets for laboratory long-rod penetration tests, the question of lateral confinement often arises, “How wide should the target be to exert enough confinement?” For ceramic targets, the problem is enhanced as ceramics are usually weak in tension and therefore have less self-confinement capability. At high velocities the problem is enhanced even more as the crater radius and the extent of the plastic zone around it are larger. Recently we used the quasistatic cavity expansion model to estimate the resistance of ceramic targets and its dependence on impact velocity [1]. We validated the model by comparing it to computer simulations in which we used the same strength model. Here we use the same approach to address the problem of lateral confinement.

We solved the quasistatic cavity expansion problem in a cylinder with a finite outside radius “b” at which σ_r (b) = 0 (σ_r = radial stress component). We did this for three cases: ceramic targets, metal targets, and ceramic targets confined in a metal casing. Generally, σ_r (a) is a decreasing function of “a” (“a” = expanding cavity radius, and σ_r (a) = the stress needed to continue opening the cavity). In the usual cavity expansion problem b → ∞, σ_r (a) = const., R =−σ_r (a) (R = resistance to penetration). For finite “b” we estimate R by averaging σ_r (a) over a range o ≤ a ≤ a_r, (where a_r, the upper bound of the range, is calibrated from computer simulations).

We ran 14 computer simulations with the CTH wavecode and used the results to calibrate a_r for the different cases and to establish the overall validity of our approach.

We show that generally for D_t/D_p > 30, the degree of confinement is higher than 95% (D_t = target diameter; D_p = projectile diameter; and degree of CONFINEMENT = R/R_∞; R∞ = resistance of a laterally infinite target). We also show the tensile strength of ceramic targets (represented by the spall strength P_min) has a significant effect on the degree of confinement, while other material parameters have only a minor effect.     

X-ray imaging with “edge-on” microchannel plate detector: first experimental results

A novel scanning slit X-ray imaging system based on an “edge-on” microchannel plate detector was developed and tested. Images were acquired at 50 kV(p) X-ray tube voltage with a limiting spatial resolution of 7 lp/mm. The pixel noise was measured to be 0.3 count/pixel/s for a 50×70 μm² pixel size. This photon counting detector can be considered to be virtually noise free.     

Rents, Rights N'Rhythm: Cooperation, Conflict and Capabilities in the Music Industry

The need for better informed copyright policy and management is a huge problem because of the enormous and growing size and scope of the creative industries. In this paper we challenge the prevailing thinking dominating the theoretical literature on the economics of copyrights. By integrating the very real effect of cooperation (strategic interaction and creative interdependence) and conflict (asymmetric relationships in terms of interests, financial dominance, power and capabilities) throughout the economic system in generating value and appropriating rent from music copyrights, we argue how prevailing theory on copyright can be improved by integrating it into a framework of New Institutional Economics. Focus is on the interplay between (i) the “institutional environment” (or “rules of the game”) with respect to the regulation of copyrights underpinned by the economic rationales; and (ii) the “institutions of governance” (or the “play of the game”) with respect to the specific institutional mechanisms in organizing the creation and distribution of value and revenue from music copyrights, and with respect to royalty management.     

A fission-fragment-sensitive target for X-ray spectroscopy in neutron-induced fission

A fission-fragment-sensitive detector built for low-energy photon spectroscopy applications at the WNR “white” neutron source at Los Alamos is described. The detector consists of eight layers of thin photovoltaic cells, onto which 1 mg/cm² of pure ²³⁸U is deposited. The detector serves as an active target to select fission events from background and other reaction channels. The fairly small thickness of the detector with respect to transmission of 20–50 keV photons permits the measurement of prompt fission-fragment X-rays. Results with the GEANIE photon spectrometer are presented.     

An Exploratory Study on Stopping a Paced Line When Incompletions Occur

This is an exploratory study of “hybrid” lines, i.e., “paced” lines whose cycle time can be extended (something like an “unpaced” line) when some task incompletions occur. Such a line should have its tasks classified into two categories; only the tasks in the first category have sufficiently high incompletion costs to justify extending the cycle time to ensure their completion. A heuristic procedure is developed to perform this classification, and we found that such hybrid lines may have a lower total cost (i.e. sum of labor and incompletion costs) than standard paced lines.     

Stability and characterization of phospholipid Langmuir-Blodgett films

The regularity of the bilayer structure was compared between dipalmitoylphosphatidic acid (DPPA) Langmuir-Blodgett (LB) films and “oriented multilayers” of DPPA, using X-ray diffraction and electron spectroscopy for chemical analysis (ESCA). The angular variation of the (001) Bragg spot due to the irregularity of the lamellar repeat was remarkable in the system of oriented multilayers. In contrast, the spot of DPPA LB films exhibited only a slight angular variation, suggesting a regular structure of this film. The take-off angle dependence of the phosphorus:carbon ratio obtained by ESCA indicates that the regular layered structure in DPPA LB film is maintained after 49 layers are deposited.     

Improvement of Heater Surface Flatness and Uniformity of TiN Film Deposition

The deposition rate and the thickness uniformity of chemical vapor deposition (CVD) titanium nitride films depend on wafer temperatures. The heater surface conditions, such as flatness, roughness, and surface imperfections, can greatly affect heat transfer efficiency from the heater surface to the wafer, and the process performance. Because heater surface imperfections or “hot spots” that caused poor uniformity had to be eliminated, the origin of “hot spots” was identified by a detailed study of heater surface profiles. A better visualization of “hot spots” could be obtained by comparing wafer-chucking patterns with deposition patterns. Thus, the time needed to locate “hot spots” could be shortened. The manufacturing process was revised to prevent “hot spots” and improve heater performance.     

Physical characterization of polyurethanes reinforced with the in situ-generated silica-polyphosphate nano-phase

A series (SPUN) of segmented polyurethanes reinforced with the in situ-generated sodium silica-polyphosphate nano-phase (SSP) was characterized by thermogravimetry, differential calorimetry, wide-angle and small-angle X-ray diffraction and stress–strain relationships.

Cross-over from the rubber-like to the solid-like mechanical behavior of the SPUN above the apparent percolation threshold w ≈ 40% was considered as evidence for the onset of the “infinite clusters” of SSP nano-domains spanning the entire volumes of initial (i.e., undeformed) samples. The infinite clusters of SSP nano-domains crossed over from the mass fractal-like to the surface fractal-like behavior at the composition-dependent, characteristic X-ray scattering vectors q*. A continuous nano-phase of the polyurethane coexisting with a continuous nano-phase (infinite cluster) of the SSP is likely to be expanded due to the “negative pressure” effect.     

Qualitative Ordinal Scales: The Concept of Ordinal Range

Many practical problems of quality control involve the use of ordinal scales. Questionnaires planned to collect judgments on qualitative or linguistic scales, whose levels are terms such as “good,” “bad,” “medium,” etc., are extensively used both in evaluating service quality and in visual controls for manufacturing industry. In an ordinal environment, the concept of distance between two generic levels of the same scale is not defined. Therefore, a population (universe) of judgments cannot be described using “traditional” statistical distributions since they are based on the notion of distance. The concept of “distribution shape” cannot be defined as well. In this article, we introduce a new statistical entity, the so-called ordinal distribution, to describe a population of judgments expressed on an ordinal scale. We also discuss which of the traditional location and dispersion measures can be used in this context and we briefly analyze some of their properties. A new dispersion measure, the ordinal range, as an extension of the cardinal range to ordinal scales, is then proposed. A practical application in the field of quality is developed throughout the article.     

A mechanistic model for the effect of stress ratio on the LEFM fatigue crack growth behavior of metals and alloys—II. Crack-brittle materials

A recently proposed mechanistic model for the effect of stress ratio, R, on the LEFM (long) fatigue crack growth behavior of “crack-ductile” materials is extended here to explain and predict similar behavior under similar conditions of “crack-brittle” materials characterised by the presence of “static” modes of fatigue fracture in stages II and III. It is shown that in these materials the stage I behavior is similar, but the stages II and III behave differently from crack-ductile materials. Mechanism-based existence of two types of stage II curves characterised respectively by “ pure shear mode ” (SM-II) and “mixed-mode” (MM-II), both plotting linear but having different slopes, is introduced. It is shown that while stage SM-II is insensitive, stage MM-II is significantly sensitive to R, in the same material. Similar to stage I, another “ moving pivot-point ” exists at the transition from SM-II to MM-II, which slides down the “ master shear-curve ” with increasing R. Assuming a critical K_max for the initiation of static modes, a critical R for saturation of these modes, and Paris-type growth relations, a quantitative predictive model containing growth equations for stages SM-II and MM-II, has been developed. Stage III is discussed only qualitatively. Reasonably good agreement was found between predicted curves at selected R-values and a relatively large volume of experimental data for steels, Al-alloys and Ti-alloys. This simple, alternative model may be used for obtaining quick, fairly accurate and conservative estimates of R-influenced crack growth rates for design applications in preference to crack-closure which frequently requires elaborate and tedious experimental procedures.     

Effect of Cryogrinding on Physico-Chemical Properties of Drugs. II. Cortisone Acetate: Particles Sizes and Polymorphic Transition

The low temperature grinding (at 78 K) of cortisone acetate was carried out. From electron microscopy data, there were determined a form, mean linear sizes of particles and then specific surface was calculated. From X-ray data, a part of microcrystalline fraction in cryogrinded samples was calculated. As was indicated by X-ray data, the mechano-induced phase transition from “monoclinic” phase (form F_I) to “orthorhombic” one (form F_II) takes place as a result of I0-min grinding. The transition is confirmed by IR-spectroscopy results too. The local pressures induced by the mechanical stress seems to be the main cause of the phase transition observed.     

Combining cost-based and rule-based knowledge in complex resource allocation problems

A major challenge in the formulation of optimization models for large-scale, complex operational problems is that some data are impossible or uneconomical to collect, producing a cost model that suffers from incomplete information. As a result, even an optimal solution may be “wrong” in the sense that it is solving the wrong problem. In many operational settings, knowledgeable experts will already know, at least approximately, how a model should behave, and can express this knowledge in the form of low dimensional patterns: “high powered locomotives should pull intermodal trains” (because they need to move quickly) or “loaded C-141s should not be flown into Saudi Arabia” (for maintenance reasons). Unlike the literature on inverse optimization which uses observed actions to train the parameters of a cost model, we used exogenous patterns to guide the behavior of a model using a proximal point term that penalizes deviations from these patterns. Under the assumption that the patterns are derived from rational behaviors, we establish the conditions under which incorporating patterns will reduce actual costs rather than just the engineered costs. The effectiveness of the approach is demonstrated in a controlled, laboratory setting using data from a major railroad.     

Guides “bimorphes” d''ondes ultrasoniques “bimorph” ultrasonic wave guides”

An analysis of the dispersion of elastic waves is presented for two types of long ultrasonics wave-guides that we qualify of “bimorph”: (i) a “three-layer” guide made of two different materials and (ii) a “clad core” guide built up of a rectangular core surrounded by a cladding, the materials of the rod and cladding having different properties. An analytical model is proposed to describe the extensional, flexural and torsional motions in “bimorph” wave guides having two geometrical and material symmetry axes. The asymptotic behaviour of the model allows one to select the material properties which lead to modes guided essentially either in the central layer or in the core of the bimorph guide. Moreover, the dispersive properties of a “bimorph” can be controlled through the choice of geometrical and material parameters.     

Theoretical study of the interactions of carbon monoxide with Rh-decorated (8,0) single-walled carbon nanotubes

Recent laboratory studies have shown that metal nanoparticles-decorated single-walled carbon nanotubes (SWCNTs) can be used to detect carbon monoxide (CO) gases at room temperature, which is known not able to be adsorbed on pure SWCNTs. In this paper, we investigated the Rh-decorated (8,0) SWCNT and its interaction with CO gases by using density functional theory (DFT) methods. Upon Rh atom adsorption, the conductivity of the (8,0) SWCNT and the atomic charges of some carbon atoms around Rh atom are enhanced dramatically. The Rh-adsorption may be thought of as providing “activated” carbon-sites of adsorbing foreign species. Both the Rh-site and the “activated” C-sites are considered as reactivity sites for the adsorption of CO gases. The binding energy is larger for CO-adsorption on the Rh-site than on the “activated” C-sites. Since the interaction between CO gases and the Rh-site is very strong, the Rh-decorated SWCNT is not reusable for CO gases detecting due to the large binding energy. On the other hand, the CO gases can also be adsorbed on the “activated” C-site with the binding energy of about −0.80 eV and 0.12 electrons transfer. The electronic properties have changed dramatically upon the CO gases. These calculation results are useful not only to explain the sensing mechanisms but also to evaluate the potential for SWCNTs-based sensing materials at room temperature.     

A mechanistic model for the influence of stress ratio on the LEFM fatigue crack growth behavior of metals and alloys—I. Crack-ductile materials

Concentrating on local behavior of a highly stressed zone ahead of the crack tip, a recent mechanistic approach to analyse LEFM fatigue crack growth behavior in three stages at stress ratio R = 0 is extended here to include the effect of a positive stress ratio. This paper is limited to analysing primarily the stages I and II of “crack-ductile” materials, characterised by a purely “reversed shear” (or ductile “striation”) growth mechanism in stage II. It is shown that in these materials stage I is R-sensitive and stage II is insensitive, and these can, without invoking crack closure arguments, be rationalised alternatively by considering the dominance of a K_max-controlled “Submicroscopic Cleavage” and a ΔK-controlled “ reversed shear ” fracture mechanism, respectively. Assuming Paris type power relations to hold, a predictive model is developed that contains separate growth equations with R-effect for stages I and II and shows the existence of a characteristic “master shear-curve” and a “moving pivot-point” on this curve for a class of materials. Good agreement was found between quantitatively predicted growth curves at selected R-values and a relatively large volume of available experimental data for low strength steels, aluminum alloys and titanium alloys. Besides providing more physical explanations for the observed growth behavior, the model may also be useful as a convenient alternative to crack closure for obtaining fairly accurate and conservative estimates of fatigue life for design applications.     

X-ray imaging with parametric X-rays (PXR) from a lithium fluoride (LiF) crystal

X-ray imaging produced by parametric X-rays (PXR) is reported. The PXR are generated using an electron beam with energy of 56 MeV and currents up to 6.4 μA, that interacted with a 1.5-mm thick lithium fluoride (LiF) crystal target in Laue geometry. The LiF (2 2 0) crystallographic plane was used with a Bragg angle (θ_B) near 15° to produce PXR with energy 16.6 keV and FWHM of 3%. This intense, directional, and tunable X-ray source was then used to image a small fish, an integrated circuit, and an electrical switch with an intensified CCD camera. The bremsstrahlung from the target crystal is characterized as a source of noise and compared to the PXR.     

Centering of the ion trajectory in the cyclotron

In this paper we present the theory of the horizontal motion ions through the acceleration gap in the case of a static magnetic field and time-varying electric field. It also describes the motion of the center of the ion trajectory through the acceleration gap and also during the acceleration process. The result also describes analytically the angle through which the ion passed (so called “flying angle”) between two acceleration gaps. That angle can be measured from the center of the ion trajectory or from the center of the cyclotron. The analysis shows that the “flying angle” of the ions measured in these two reference systems is not same. Namely, the “flying angle” of the ion measured from the center of its trajectory is bigger than in the case when the “flying angle” is measured from the center of the cyclotron. It shows that difference between “flying angle” in these two reference systems becomes less and less during acceleration process.     

Deposition and etch processes: continuum film evolution in microelectronics

Aspects of modeling and simulation of topography evolution during deposition and etch processes used in the fabrication of integrated circuits are discussed. Overall, we hope to demonstrate that combined simulation and experimental studies of film profiles and composition profiles inside features is a valuable tool in efforts to arrive at useful kinetic and transport models. In particular, conformality limitations and film composition variations inside features for films deposited at low pressures are explained using examples of studies that combine transport and reaction simulations of deposition processes and carefully designed experimental work. The technical presentation is divided into three major parts. In the first section, we demonstrate that thermal systems can be modeled without “calibrating” the transport and reaction models used, though calibration can still be useful. The process considered in this section is the thermal deposition of SiO₂ from TEOS (tetraethoxysilane). We discuss the use of film profile information to decide between two kinetic models for the deposition process, then we discuss one way to integrate reactor scale and feature scale models in order to capture “microloading” due to changes in local pattern density. The second section demonstrates the state of topography simulation for plasma processes. We demonstrate the use of physically motivated models that in general require calibration from experimental data for a given set of operating conditions. As our first plasma example, we use the sputter deposition of Ti–W to demonstrate the existence of composition profiles inside features. We then use etch simulations to show how simulations can be used to test proposed chemical and/or physical phenomena. The last major section is a case study on plasma enhanced deposition of SiO₂ from TEOS and oxygen (PETEOS) that demonstrates the roles of “3d/2d” and “3d/3d” (transport dimensionality/surface dimensionality) topography simulators in “virtual wafer fabs”. The same methodology would apply to most topography relevant processes, including thin film flow processes.     

Stereoselective release behaviors of imprinted bead matrices

In this work, the stereoselective release behaviors of “low”-swelling molecularly imprinted polymer (MIP) bead matrices in pressed-coat tablet type were studied. Either R-propranolol selective MIP or S-propranolol selective MIP was combined with excipients and racemic propranolol and fabricated into the matrix. Subsequently, the release of different propranolol enantiomers from the matrices was examined. Also, the microscopic structure of the hydrated “low”-swelling MIP matrix was determined using a cryogenic scanning electron microscope in order to compare with that of the hydrated “high”-swelling MIP matrix. In vitro release profiles of the “low”-swelling matrices showed a difference in the release of enantiomers, in that the non-template isomer was released faster than the template isomer. However, in the last phase of dissolution this difference reduced and later reversed, resulting at last in the type of specificity being similar to that obtained previously with “high”-swelling MIP matrices.

n summary, MIP beads can be fashioned into matrices and incorporated into different formulations to regulate the resultant stereoselectivity. From the behaviors of stereoselective release observed in MIP matrices, we can conclude that the enantioselective-controlled delivery mechanism of MIPs via formulations depends on the relative affinity of the enantiomer for the template sites, as well as the nature of the polymer, such as hydrophobicity and swellability.