An integral approach to lifting wing theory at Mach one

Summary An approach to lifting wing theory at Mach one is presented that utilizes an integral method similar to the Karman-Pohlhausen method in boundary layer theory. As in any integral method the results obtained are approximate in nature. Nonetheless, comparison with experimental data shows good agreement in cases for which experimental data are available. The method can easily be used to determine the lift on wings of finite aspect ratio and also to solve transient lifting problems. The method is demonstrated by solving for the pressure distribution on a lifting airfoil of arbitrary symmetric cross-section, the lift on a wing of rectangular planform, and the transient lift on an airfoil due to a sudden change in angle of attack. These cases were chosen to illustrate the versatility of the method and are not meant to be exhaustive of all possibilities. The computational time required to obtain numerical results is very small in all cases considered.List of symbols A parameter associated with Guderley airfoil, defined in equation (28) - AR aspect ratio - AR reduced aspect ratio=AR ^1/3( + 1)^1/3 - c chord of airfoil - C _l sectional lift coefficient - C _L lift coefficient - C _p pressure coefficient - M Mach number - p Laplace transform variable - s span of wing (in units ofc) - t time (in units ofc/U) - U free stream velocity - x streamwise coordinate (in units ofc) - x ^* distance from leading edge to sonic point (in units ofc) - y spanwise coordinate (in units ofc) - z coordinate normal to plane of wing (in units ofc) - angle of attack - y/2s - ratio of specific heats (=1.4 in all calculations) Research sponsored by the Air Force Office of Scientific Research/AFSC, United States Air Force, under Contract No. F44620-72-C-0079. The United States Government is authorized to reproduce and distribute reprints for governmental purposes notwithstanding any copyright notation hereon.     

Inferential Queueing and Speculative Push

Communication latencies within critical sections constitute a major bottleneck in some classes of emerging parallel workloads. In this paper, we argue for the use of two mechanisms to reduce these communication latencies: Inferentially Queued locks (IQLs) and Speculative Push (SP). With IQLs, the processor infers the existence, and limits, of a critical section from the use of synchronization instructions and joins a queue of lock requestors, reducing synchronization delay. The SP mechanism extracts information about program structure by observing IQLs. SP allows the cache controller, responding to a request for a cache line that likely includes a lock variable, to predict the data sets the requestor will modify within the associated critical section. The controller then pushes these lines from its own cache to the target cache, as well as writing them to memory. Overlapping the protected data transfer with that of the lock can substantially reduce the communication latencies within critical sections. By pushing data in exclusive state, the mechanism can collapse a read-modify-write sequences within a critical section into a single local cache access. The write-back to memory allows the receiving cache to ignore the push. Neither mechanism requires any programmer or compiler support nor any instruction set changes. Our experiments demonstrate that IQLs and SP can improve performance of applications employing frequent synchronization.     

Software transactional memories for Scala

Transactional memory is an alternative to locks for handling concurrency in multi-threaded environments. Instead of providing critical regions that only one thread can enter at a time, transactional memory records sufficient information to detect and correct for conflicts if they occur. This paper surveys the range of options for implementing software transactional memory in Scala. Where possible, we provide references to implementations that instantiate each technique. As part of this survey, we document for the first time several techniques developed in the implementation of Manchester University Transactions for Scala. We order the implementation techniques on a scale moving from the least to the most invasive in terms of modifications to the compilation and runtime environment. This shows that, while the less invasive options are easier to implement and more common, they are more verbose and invasive in the codes using them, often requiring changes to the syntax and program structure throughout the code.     

Book Reviews and Lists

Burdell, Edwin Sharp. A method of investigating the administration of the zoning ordinance in Columbus, Ohio, 1923-31. Reprinted from Abstracts of Doctors' Dissertations, No. 17, The Ohio State University Press, 1935; pp. 33-49.

A Hundred New 'Towns for Britain: a scheme of national reconstruction proposed by J47485; rev. and enlarged ed. London, Simpkin Marshall, Ltd., Nov. 1934. illus. Price 3s.6d.

James, Harlean, Ed. American planning and civic annual: a record of recent civic advance, including the Proceedings of the Conference on City, Regional, State, and National Planning, 1935. Washington, American Planning and Civic Association, Inc., 1935. 356p. illus, plans. Price $3.00.

Lambie, Morris B., Ed. Training for the public service: the report and recommendations of a conference sponsored by Public Administration Clearing House. Chicago, Public administration Service, 1935. 49p. (Publication no. 49.) Price 50 cents.

Malcher, Fritz. The steadyflow traffic system. Cambridge, Harvard University Press, 1935. 91p. illus., diagrs. (Harvard City Planning Studies, Vol. IX.) Price $1.00.

Merrill, Harold, and others, Comps. Some re-cent references (since 1928) on national and state planning in the United States, compiled by Harold Merrill, James T. Rubey, and William H. Heers. Washington, National Resources Committee, Oct. 1935. 24p. (U.S. Geological Survey Library, Bibliographical List No. 5.) Mimeographed.

U.S. National Resources Board. State planning: a review of activities and progress, June 1935. Washington, Govt. Printing Office, 1935. 310p. maps, plans, charts, tables. Price 75 cents (paper cover).

U. S. National Resources Committee. Regional factors in national planning and development. Washington, Govt. Printing Office, Dec. 1935. 223p. illus., maps, charts.     

Treatment of Critical Size Femoral Bone Defects with Biomimetic Hybrid Scaffolds of 3D Plotted Calcium Phosphate Cement and Mineralized Collagen Matrix

To treat critical-size bone defects, composite materials and tissue-engineered bone grafts play important roles in bone repair materials. The purpose of this study was to investigate the bone regenerative potential of hybrid scaffolds consisting of macroporous calcium phosphate cement (CPC) and microporous mineralized collagen matrix (MCM). Hybrid scaffolds were synthetized by 3D plotting CPC and then filling with MCM (MCM-CPC group) and implanted into a 5 mm critical size femoral defect in rats. Defects left empty (control group) as well as defects treated with scaffolds made of CPC only (CPC group) and MCM only (MCM group) served as controls. Eight weeks after surgery, micro-computed tomography scans and histological analysis were performed to analyze the newly formed bone, the degree of defect healing and the activity of osteoclasts. Mechanical stability was tested by 3-point-bending of the explanted femora. Compared with the other groups, more newly formed bone was found within MCM-CPC scaffolds. The new bone tissue had a clamp-like structure which was fully connected to the hybrid scaffolds and thereby enhanced the biomechanical strength. Together, the biomimetic hybrid MCM-CPC scaffolds enhanced bone defect healing by improved osseointegration and their differentiated degradation provides spatial effects in the process of critical-bone defect healing.     

In situ measurement of free radical formation during the thermal decomposition of grape seed oil using “spin trapping” and electron paramagnetic resonance spectroscopy

The generation of free radical intermediates as a result of the oxidative degradation of lipid molecules during the heating of grape seed oil has been established by a combination of “spin trapping” and electron paramagnetic resonance spectroscopy. The effects of temperature on the rates of formation and decomposition of the adduct with the spin trapN-t-butyl-α-phenylnitrone (PBN) have been investigated over the temperature range 105–180°C. The results show that PBN can be used for studies of free radical processes in oils in situ in the spectrometer cavity at temperatures up to 180°C.     

Acetylene Hydrogenation on Au-Based Catalysts

Hydrogenation of acetylene has been investigated on Au/TiO₂, Pd/TiO₂ and Au-Pd/TiO₂ catalysts at high acetylene conversion levels. The Au/TiO₂ catalyst (avg. particle size: 4.6 nm) synthesized by the temperature-programmed reduction-oxidation of an Au-phosphine complex on TiO₂ showed a remarkably high selectivity to ethylene formation even at 100% acetylene conversion. Au/TiO₂ prepared by the conventional incipient wet impregnation method (avg. particle size: 30 nm), on the other hand, showed negligible activity for acetylene hydrogenation. Although the Au catalysts showed a high selectivity for ethylene, the acetylene conversion activity and catalyst stability were inferior to the Pd-based catalysts. Au-Pd catalysts prepared by the redox method showed high acetylene conversions as well as high selectivity for ethylene. Interestingly Au-Pd catalysts prepared by depositing Pd via the incipient wetness method on Au/TiO₂ showed very poor selectivity (comparable to mono-metallic Pd catalysts) for ethylene. High-resolution transmission electron microscopy (TEM) studies coupled with energy dispersive X-ray spectroscopy (EDS) showed that while the redox method produced bimetallic Au-Pd catalysts, the latter method produced individual Pd and Au particles on the support.     

Simulating the Complexities of Heterogeneous Catalysis with Model Systems: Case studies of SiO2 Supported Pt-Group Metals

Model catalyst surfaces, consisting of vapor-deposited metal nanoparticles supported on a planar oxide support, can help to link reactivity studies on well-defined single crystal surfaces with those conducted on high-surface area supported catalysts. When coupled with near atmospheric pressure kinetic and spectroscopic techniques, these well-defined model catalyst surfaces represent a useful approach to combine the power of surface analytical techniques with reactivity studies under relevant reaction conditions. Here, we review recent results of our investigations characterizing the physical and catalytic properties of Pt/SiO₂ and Rh/SiO₂ model catalyst surfaces. As will be discussed, the model catalyst approach can help simulate the complexities of catalytic reactions on supported catalysts, helping to provide insights into the role of particle size, particle morphology, and surface adsorbates in dictating the observed structure-sensitivity (activity and selectivity) during reactions at near atmospheric pressures.