bluuebunny/crossref_metadata_2025 huggingface dataset:
Images of Community: Discourse and Strategy in Property Relations
Authors: Li Tania Murray
Published: October 2008

This article argues that divergent images of community result not from inadequate knowledge or confusion of purpose, but from the location of discourse and action in the context of specific struggles and dilemmas. It supports the view that ‘struggles over resources’ are also ‘struggles over meaning’. It demonstrates the ways in which contests over the distribution of property are articulated in terms of competing representations of community at a range of levels and sites. It suggests that, through the exercise of ‘practical political economy’, particular representations of community can be used strategically to strengthen the property claims of potentially disadvantaged groups. In the policy arena, advocates for ‘community based resource management’ have represented communities as sites of consensus and sustain‐ability. Though idealized, such representations have provided a vocabulary with which to defend the rights of communities vis‐à‐vis states. Poor farmers, development planners, consultants and academics can also use representations of community strategically to achieve positive effects, or at least to mitigate negative ones. Most, but not all, of the illustrations in this article are drawn from Indonesia, with special reference to Central Sulawesi.
The Politics of Economic Diversification: Reconceptualizing the Rural Informal Sector in South‐east Tanzania
Authors: Seppälä Pekka
Published: October 2008

This study examines how economic diversification is changing a Tanzanian village under economic liberalization. More specifically, it asks how different wealth groups are able to incorporate income‐generating activities into their livelihood strategies. The conclusion is that while diversification (as a division of labour) is advanced at the village level, it appears that different activities enhance the division of the village into segregated cultural spheres and increase economic differentiation. At village level the diversity of income‐generating activities reduces any single line of economic dependency either on the state or on market actors.
Income Inequality, Welfare and Poverty in Ukraine
Authors: Kakwani N.
Published: October 2008

Ukraine is now faced with economic crisis on an unprecedented scale. The country is on the brink of hyperinflation. The government has to follow rigorous demand management policies which entail lowering the standard of living of the population. To design policies which protect the poorest and most vulnerable groups in the society, it is important to understand the nature of poverty and income inequality. This study attempts to do exactly this for Ukraine for the first time. The paper demonstrates that the standard of living in Ukraine has been falling at an alarming rate. The government welfare programmes are ineffective in protecting the poorest and most vulnerable groups in the society. This article provides an empirical basis to design appropriate policies, but a lot more work needs to be done.
Foreign Aid, Structural Adjustment, and Public Management: The Mozambican Experience
Authors: Wuyts Marc
Published: October 2008

In looking at the case of Mozambique under structural adjustment, this article argues that the particular combination of fiscal restraints imposed by financial programming, and the proliferation of decentralized project‐based management, together proved to be a potent mixture which failed to reconstruct a coherent pattern of state action. The problem lies in the increasing dominance of foreign aid and in the uneasy interplay between programme aid on the one hand and project aid on the other, as competition from projects wins resources away from regular state programmes, with very little prospect of such projects becoming self‐sustainable in the absence of the continued infusion of foreign aid.
Structural Adjustment and Structural Change in Sub‐Saharan Africa: Some Provisional Conclusions
Authors: Gibbon Peter
Published: October 2008

This article reviews discussions concerning some of the main methodological difficulties surrounding the evaluation of structural adjustment policies, before suggesting a procedure to ‘save’ empirical discussion about new patterns of economic and social relations. In this light it proceeds to examine evidence gathered by the structural adjustment research programme of Nordiska Afrikainstitutet (Scandinavian Institute of African Studies) on the changing character of the ‘private sector’ and of the voluntary development sphere in contemporary Africa. The main conclusions are that, in what can be called ‘adjustment situations’, the main tendencies in these spheres are for a rise of trading capitals enjoying illicit relations to the state and for a privatization of local development. The article concludes with an argument that, had adjustment been implemented in a fuller and more consistent way, these tendencies would probably have been still more pronounced.
Coupled Flexural-Torsional Nonlinear Vibrations of Piezoelectrically Actuated Microcantilevers With Application to Friction Force Microscopy
Authors: Mahmoodi S. Nima , Jalili Nader
Published: October 2008

The problem of vibrations of microcantilevers has recently received considerable attention due to its application in several nanotechnological instruments, such as atomic force microscopy, nanomechanical cantilever sensors, and friction force microscopy. Along this line, this paper undertakes the problem of coupled flexural-torsional nonlinear vibrations of a piezoelectrically actuated microcantilever beam as a typical configuration utilized in these applications. The actuation and sensing are both facilitated through bonding a piezoelectric layer (here, ZnO) on the microcantilever surface. The beam is considered to have simultaneous flexural, torsional, and longitudinal vibrations. The piezoelectric properties combined with nonlinear geometry of the beam introduce both linear and nonlinear couplings between flexural vibration as well as longitudinal and torsional vibrations. Of particular interest is the inextensibility configuration, for which the governing equations reduce to coupled flexural-torsional nonlinear equations with piezoelectric nonlinearity appearing in quadratic form while inertia and stiffness nonlinearities as cubic. An experimental setup consisting of a commercial piezoelectric microcantilever installed on the stand of an ultramodern laser-based microsystem analyzer is designed and utilized to verify the theoretical developments. Both linear and nonlinear simulation results are compared to the experimental results and it is observed that nonlinear modeling response matches the experimental findings very closely. More specifically, the softening phenomenon in fundamental flexural frequency, which is due to nonlinearity of the system, is analytically and experimentally verified. It is also disclosed that the initial twisting in the microcantilever can influence the value of the flexural vibration resonance. The experimental results from a macroscale beam are utilized to demonstrate such twist-flexure coupling. This unique coupling effect may lead to the possibility of indirect measurement of small torsional vibration without the need for any angular displacement sensor. This observation could significantly extend the application of friction force microscopy to measure the friction of a surface indirectly.
Oscillation Effect of Impingement Surface on Two-Dimensional Impingement Heat Transfer
Authors: Ichimiya Koichi , Yoshida Yutaka
Published: October 2008

This paper describes the oscillation effect of impingement surface on two-dimensional impingement heat transfer with confined wall. The local temperature distribution on an impingement surface was measured using a thermosensitive liquid crystal sheet and an image processor. Experiments were conducted by using air as a working fluid. Experimental conditions were as follows: Reynolds number Re=1000–10,000, dimensionless distance between nozzle and impingement surface h∕B=1.0–4.0, frequency f=0–100Hz, and amplitudes a=0.5mm and 1.0mm. The local Nusselt number was improved for the comparatively low Reynolds number and low frequency and was depressed for high frequency. In the case of heat transfer enhancement, vortices on the impingement surface were renewed frequently, and on the other hand, in the case of heat transfer depression, thermal boundary layer thickness increased in appearance by the vibration of the impingement surface.
The Heat/Mass Transfer Analogy for a Simulated Turbine Endwall With Fillets
Authors: Han S. , Goldstein R. J.
Published: October 2008

Mass transfer measurements are employed as alternative methods for heat transfer measurement because of the difficulty of heat transfer measurements in thin boundary layers, complicated secondary flows, and large thermal gradients. Even though mass transfer experiments are fast and show detailed local measurement data, the conversion of mass transfer results to heat transfer data requires the heat/mass transfer analogy factors in detail. Therefore, the usefulness of mass transfer data depends on finding a simple analogy factor. The heat/mass transfer analogy on a simulated turbine endwall with fillets is evaluated in the present paper. Since the heat/mass transfer analogy factor may not be always the same, the heat/mass transfer analogy should be verified for other different geometries and experimental conditions. To utilize the heat/mass transfer analogy fully, it is necessary to check that the presence of different aerodynamic conditions caused by the fillets affects the heat/mass transfer analogy on a simulated turbine endwall with fillets. To compare heat transfer data and mass transfer data, heat transfer measurements on the endwall with fillets are conducted with a thermal boundary layer measurement technique and mass transfer measurements employing naphthalene sublimation technique on the endwall with the fillets are extracted from literature with equivalent experimental conditions and a similar geometry. As expected by heat transfer and mass transfer equations, the heat/mass transfer analogy factor is applied and shows a good agreement between heat transfer and mass transfer results on the endwall with the fillets from the leading edge to the trailing edge.
Transient Method for Convective Heat Transfer Measurement With Lateral Conduction—Part II: Application to an Isolated Spherical Roughness Element
Authors: Bons J. , Fletcher Daniel , Borchert Brad
Published: October 2008

The effect of lateral conduction on convective heat transfer measurements using a transient infrared technique over an isolated spherical roughness element (bump) is evaluated. Comparisons are made between a full 3D finite-volume analysis and a simpler 1D transient conduction model. The surface temperature history was measured with a high resolution infrared camera during an impulsively started hot-gas flow at a flow Reynolds number of 860,000. The boundary layer was turbulent with the bump heights equivalent to 0.75, 1.5, and 3 times the boundary layer momentum thickness. When considering transient conduction effects only in the bump wake, the 1D approximate method underestimates the actual Stanton number estimated with the 3D model. This discrepancy is only 10% for a 75% change in St number occurring over a surface distance of 10 mm (the half-width of the wake). When the actual bump topology is accounted for in estimating the Stanton number on the bump itself with the 3D analysis technique, the increased surface area of the finite-volume cells on the protruding bump actually decreases the predicted value of St locally. The net result is that the two effects can cancel each other, and in some cases the 1D approximate technique can provide a reasonably accurate estimate of the surface heat transfer without the added complexity of the 3D finite-volume method. For the case of the largest bump tested, with maximum surface angularity exceeding 60 deg, the correction for 3D topology yields a 1D St estimate that is within 20–30% of the 3D estimate over much of the bump surface. These observed effects are valid for transient measurement techniques while the opposite is true for steady-state measurement techniques.
Simple Explicit Equations for Transient Heat Conduction in Finite Solids
Authors: Ostrogorsky A. G.
Published: October 2008

Based on the one-term Fourier series solution, a simple equation is derived for low Biot number transient conduction in plates, cylinders, and spheres. In the 0<Bi<0.3 range, the solution gives approximately three times less error than the lumped capacity solution. For asymptotically low values of Bi, it approaches the lumped capacity solution. A set of equations valid for 0<Bi<1 is developed next. These equations are more involved but give approximately ten times lower error than the lumped capacity solution. Finally, a set of broad-range correlations is presented, covering the 0<Bi<∞ range with less than 1% error.
The Effects of Working Fluid on the Heat Transport Capacity of a Microheat Pipe
Authors: Sugumar D. , Tio Kek-Kiong
Published: October 2008

The effects of the thermophysical properties of the working fluid on the performance of a microheat pipe of triangular cross section are investigated. For this purpose, five different working fluids are selected: water, hepthane, ammonia, methanol, and ethanol. For operating temperatures ranging from 20°Cto100°C, it is found that the behavior of the heat transport capacity is dominated by a property of the working fluid, which is equal to the ratio of the surface tension and dynamic viscosity σ∕μl. This property has the same dimension as velocity and can be interpreted as a measure of the working fluid’s rate of circulation, which can be provided by capillarity after overcoming the effect of viscosity. Of the five working fluids selected, ammonia is preferable for operating temperatures below 50°C since it yields the highest heat transport capacity; however, water is the preferred working fluid for temperatures above 50°C.
Non-Newtonian Natural Convection Along a Vertical Heated Wavy Surface Using a Modified Power-Law Viscosity Model
Authors: Molla M. M. , Yao L. S.
Published: October 2008

Natural convection of non-Newtonian fluids along a vertical wavy surface with uniform surface temperature has been investigated using a modified power-law viscosity model. An important parameter of the problem is the ratio of the length scale introduced by the power-law and the wavelength of the wavy surface. In this model there are no physically unrealistic limits in the boundary-layer formulation for power-law, non-Newtonian fluids. The governing equations are transformed into parabolic coordinates and the singularity of the leading edge removed; hence, the boundary-layer equations can be solved straightforwardly by marching downstream from the leading edge. Numerical results are presented for the case of shear-thinning as well as shear-thickening fluid in terms of the viscosity, velocity, and temperature distribution, and for important physical properties, namely, the wall shear stress and heat transfer rates in terms of the local skin-friction coefficient and the local Nusselt number, respectively. Also results are presented for the variation in surface amplitude and the ratio of length scale to surface wavelength. The numerical results demonstrate that a Newtonian-like solution for natural convection exists near the leading edge where the shear-rate is not large enough to trigger non-Newtonian effects. After the shear-rate increases beyond a threshold value, non-Newtonian effects start to develop.
The Effect of Pore Size on the Heat Transfer Between a Heated Finned Surface and a Saturated Porous Plate
Authors: Schertzer M. J. , Ewing D. , Ching C. Y. , Chang J. S.
Published: October 2008

An investigation was performed to examine the effect that the pore size in a porous plate had on the heat transfer between a heated finned surface and a saturated porous plate at different gap distances between the surfaces. Experiments were performed for a porous plate with a nominal pore size of 50μm and the results were compared with previous results for a pore size of 200μm (Schertzer et al., 2006, “The Effect of Gap Distance on the Heat Transfer Performance Between a Finned Surface and a Saturated Porous Plate,” Int. J. Heat. Mass Transfer, 4, pp. 4200–4208). The plate with the smaller pore size performed better at small and intermediate gaps but not at large gaps. The maximum heat transfer coefficient was similar for both plates when compared in terms of the ratio between the gap distance and the pore size. However, the temperature distributions on the heated foil and their evolution with heat flux were dissimilar when compared in terms of the gap distance or the gap to pore ratio, suggesting that the boiling dynamics within the gap does not scale with either parameters.
The Flow of Non-Newtonian Fluids on a Flat Plate With a Uniform Heat Flux
Authors: Molla M. M. , Yao L. S.
Published: October 2008

Forced convective heat transfer of non-Newtonian fluids on a flat plate with the heating condition of uniform surface heat flux has been investigated using a modified power-law viscosity model. This model does not restrain physically unrealistic limits; consequently, no irremovable singularities are introduced into a boundary-layer formulation for power-law non-Newtonian fluids. Therefore, the boundary-layer equations can be solved by marching from leading edge to downstream as any Newtonian fluids. For shear-thinning and shear-thickening fluids, non-Newtonian effects are illustrated via velocity and temperature distributions, shear stresses, and local temperature distribution. Most significant effects occur near the leading edge, gradually tailing off far downstream where the variation in shear stresses becomes smaller.
Air Cavities in a Vibrated Bed of Visco-Elastic Glass Balls
Authors: Zamankhan Piroz
Published: October 2008

Large scale, three dimensional computer simulations of a dense aggregative bed were performed to provide insight into the physics behind bubble formation in vertically vibrated granular materials in a shaker. As the shaker acceleration exceeds a critical value, turbulent fluctuations proportional to the particle size were produced to promote fractures at the interface between the gas and particles suspended in the gas near the bottom of the shaker. As the wave fronts pass, the solid fractures took the form of sharply defined regions of very low solids fraction (air cavities) that rose through the bed with a speed that depends on their size. The nucleation of bubbles is found to be of the heterogeneous type.
A Novel Approach for Continuous Acoustic Emission Monitoring on Rotating Machinery Without the Use of Slip Ring
Authors: Loutas T. H. , Kalaitzoglou J. , Sotiriades G. , Kostopoulos V.
Published: October 2008

The acoustic emission (AE) technique is a powerful nondestructive tool for health monitoring of structures and mechanical components, especially due to its sensitivity to capture high frequency signals, which are associated with the early stages of damage development and evolution. The aim of the present work is twofold. The first is the evaluation of a new concept of transducer mounting on rotating structures without the use of the expensive solution of the slip ring. The new concept is realized in a single stage in-house built gearbox setup. The second is the evaluation of the potential of the acquired with the new concept AE signals in distinguishing between different types of artificially induced damage on the gears. Run-in tests were carried out to study the effect of gear damage on the AE recordings. The acoustic emission signature of the healthy gears is first acquired. Then artificial defects are seeded and the acquisition is repeated. The AE signals are analyzed, and their root-mean-square values are calculated. The capability of the new approach of AE acquisition in discriminating between different loading and damage states is shown and discussed. Interesting findings on the effect of the oil temperature on AE recordings only speculated theoretically so far are also presented.
Mechanical Domain Parametric Amplification
Authors: Rhoads Jeffrey F. , Miller Nicholas J. , Shaw Steven W. , Feeny Brian F.
Published: October 2008

Though utilized for more than 50years in a variety of power and communication systems, parametric amplification, the process of amplifying a harmonic signal with a parametric pump, has received very little attention in the mechanical engineering community. In fact, only within the past 15–20years has the technique been implemented in micromechanical systems as a means of amplifying the output of resonant microtransducers. While the vast potential of parametric amplification has been demonstrated, to date, in a number of micro- and nanomechanical systems (as well as a number electrical systems), few, if any, macroscale mechanical amplifiers have been reported. Given that these amplifiers are easily realizable using larger-scale mechanical systems, the present work seeks to address this void by examining a simple representative example: a cantilevered beam with longitudinal and transverse base excitations. The work begins with the systematic formulation of a representative system model, which is used to derive a number of pertinent metrics. A series of experimental results, which validate the work’s analytical findings, are subsequently examined, and the work concludes with a brief look at some plausible applications of parametric amplification in macroscale mechanical systems.
Spatial Distribution Prediction of Steady-State Sound Field With the Ray-Tracing Method
Authors: Jiang Zhong-Jin , Cui Tie-Jun
Published: October 2008

A novel two-level space volume partition (SVP) algorithm based on the ray-tracing technique is proposed to predict the spatial distribution of the steady-state sound field. The sound space is subdivided into voxels in two levels. The voxels of the level-I are of greater size and comparable to the space walls, and the ray-wall intersection points are calculated based on this level of voxels. Then each level-I voxel is hierarchically subdivided into small voxels of level-II, the size of which is determined according to the needed solution in the sound field description. The sound field spatial distribution is predicted based on this level of voxels. A three-dimensional energy matrix is set up to memorize the spatial distribution of sound energy. The numbers of the row, column, and layer of the energy matrix are equal to those of the level-II voxels, namely, each element in the energy matrix corresponds to a level-II voxel. When a sound ray enters a voxel, its sound energy is calculated and recorded in the corresponding element of the energy matrix. When all the sound rays have been traced over, the sound energy spatial distribution in the sound space has been established in the energy matrix. The sound pressure level (SPL) in a certain plane or along a certain line can be calculated and imaged directly from the energy matrix. The novel two-level SVP algorithm can finish the simulation more efficiently than the traditional SVP algorithm. Experiments were performed to measure the SPL in steady-state sound fields, and the results were consistent with the predicted results.
A Robust Semi-Analytical Method for Calculating the Response Sensitivity of a Time Delay System
Authors: Kurdi Mohammad H. , Haftka Raphael T. , Schmitz Tony L. , Mann Brian P.
Published: October 2008

It is often necessary to establish the sensitivity of an engineering system’s response to variations in the process/control parameters. Applications of the calculated sensitivity include gradient-based optimization and uncertainty quantification, which generally require an efficient and robust sensitivity calculation method. In this paper, the sensitivity of the milling process, which can be modeled by a set of time delay differential equations, to variations in the input parameters is calculated. The semi-analytical derivative of the maximum eigenvalue provides the necessary information for determining the sensitivity of the process stability to input variables. Comparison with the central finite difference derivative of the stability boundary shows that the semi-analytical approach is more efficient and robust with respect to step size and numerical accuracy of the response. An investigation of the source of inaccuracy of the finite difference approximation found that it is caused by discontinuities associated with the iterative process of root finding using the bisection method.
Convective Condensation of Vapor in Laminar Flow in a Vertical Parallel Plate Channel in the Presence of a High-Concentration Noncondensable Gas
Authors: Rao V. Dharma , Krishna V. Murali , Sarma P. K. , Sharma K. V.
Published: October 2008

The problem of laminar film condensation of a vapor from vapor-gas mixture in laminar flow in a vertical parallel plate channel is formulated theoretically. The flowing gas-vapor mixture contains a noncondensable gas in high concentration. An example of this case is the flow of humid air, in which air is present in high concentration. Vapor condenses at the dew point temperature corresponding to mass fraction of vapor in the gas-vapor mixture and the total pressure. The rate of condensation is controlled by the diffusion of the vapor through the noncondensable gas film. Thus the problem of convective condensation is treated as a combined problem of heat and mass transfer. The problem is governed by the mass, momentum and energy balance equations for the vapor-gas mixture flowing in a channel, and the diffusion equation for the vapor species. The flow of the falling film of condensate is governed by the momentum and energy balance equations for the condensate film. The boundary conditions for the gas phase and the condensate film are considered. The temperature at the gas-to-liquid interface is estimated by making use of the equations of heat and mass balance at the interface. The local condensation Nusselt number, condensation Reynolds number, and temperature at the gas-to-liquid interface are estimated from the numerical results for different values of the system parameters at the channel inlet, such as relative humidity, temperature of vapor-gas mixture, gas phase Reynolds number, and total pressure. The condensation heat transfer coefficients computed from the present theory are compared with the experimental data available in literature, and the agreement is found to be good. The present work is an extension of the earlier work, in which the problem of in-duct condensation of humid air in turbulent flow was solved theoretically. Humid air is considered as the gas-vapor mixture, since various physical and thermal properties have to be specified during the analysis.
The Efficient Iterative Solution of the P1 Equation
Authors: Hassanzadeh P. , Raithby G. D.
Published: October 2008

The P1 model is often used to obtain approximate solutions of the radiative transfer equation for heat transfer in a participating medium. For large problems, the algebraic equations used to obtain the P1 solution are solved by iteration, and the convergence rate can be very slow. This paper compares the performance of the corrective acceleration scheme of and Li and Modest (2002, “A Method to Accelerate Convergence and to Preserve Radiative Energy Balance in Solving the P1 Equation by Iterative Methods,” ASME J. Heat Transfer, 124, pp. 580–582), and the additive correction multigrid method, to that of the Gauss–Seidel solver alone. Additive correction multigrid is found to outperform the other solvers. Hence, multigrid is a superior solver for the P1 equation.
A Vector Form Exchange-Area-Based Method for Computation of Anisotropic Radiative Transfer
Authors: Jiang Yu Yan
Published: October 2008

Exchange-area-based methods (EAMs), such as the zonal method, the combined Monte-Carlo and zonal method, etc., are widely used in the numerical computation of thermal radiative transfer. In view of their inefficiency in treating with the anisotropy of radiation, researchers have been devoted to developing generalized models (GEAMs). In this article a vector form GEAM is proposed, which has concise formulations, and is found to be very efficient for handling the anisotropic scattering and reflection. In the model some vectorlike weighted-summations take account of the directional distribution of radiant energy. The summations give rise to correction coefficients to the radiosities. The heat transfer problem is solved by a coupled computation of the radiosities and the correction coefficients. The model was validated by both a one-dimensional and a three-dimensional benchmark radiation problem. The computational time is decreased to an order of that for computing isotropic radiation by conventional EAM. Such high efficency has never been achieved by the GEAMs proposed to date.
On disclosure risk analysis of anonymized itemsets in the presence of prior knowledge
Authors: Lakshmanan LAKS V. S. , Ng Raymond T. , Ramesh Ganesh
Published: October 2008

Decision makers of companies often face the dilemma of whether to release data for knowledge discovery, vis-a-vis the risk of disclosing proprietary or sensitive information. Among the various methods employed for “sanitizing” the data prior to disclosure, we focus in this article on anonymization, given its widespread use in practice. We do due diligence to the question “just how safe is the anonymized data?” We consider both those scenarios when the hacker has no information and, more realistically, when the hacker may have partial information about items in the domain. We conduct our analyses in the context of frequent set mining and address the safety question at two different levels: (i) how likely of being cracked (i.e., re-identified by a hacker), are the identities of individual items and (ii) how likely are sets of items cracked? For capturing the prior knowledge of the hacker, we propose a
belief function
, which amounts to an educated guess of the frequency of each item. For various classes of belief functions which correspond to different degrees of prior knowledge, we derive formulas for computing the expected number of cracks of single items and for itemsets, the probability of cracking the itemsets. While obtaining, exact values for more general situations is computationally hard, we propose a series of heuristics called the
O-estimates
. They are easy to compute and are shown fairly accurate, justified by empirical results on real benchmark datasets. Based on the O-estimates, we propose a recipe for the decision makers to resolve their dilemma. Our recipe operates at two different levels, depending on whether the data owner wants to reason in terms of single items or sets of items (or both). Finally, we present techniques for ascertaining a hacker's knowledge of correlation in terms of co-occurrence of items likely. This information regarding the hacker's knowledge can be incorporated into our framework of disclosure risk analysis and we present experimental results demonstrating how this knowledge affects the heuristic estimates we have developed.
Privacy-preserving decision trees over vertically partitioned data
Authors: Vaidya Jaideep , Clifton Chris , Kantarcioglu Murat , Patterson A. Scott
Published: October 2008

Privacy and security concerns can prevent sharing of data, derailing data-mining projects. Distributed knowledge discovery, if done correctly, can alleviate this problem. We introduce a generalized privacy-preserving variant of the ID3 algorithm for vertically partitioned data distributed over two or more parties. Along with a proof of security, we discuss what would be necessary to make the protocols completely secure. We also provide experimental results, giving a first demonstration of the practical complexity of secure multiparty computation-based data mining.
Whiteoak
Authors: Gil Joseph , Maman Itay
Published: October 2008

This paper presents WHITEOAK: a JAVA extension that introduces structural type equivalence and subtyping into the language. We argue that structural subtyping addresses common software design problems, and promotes the development of loosely coupled modules without compromising type safety.

We discuss language design issues, including subtyping in face of self-referencing structural types, compile-time operators for computing the new types from existing ones, and the semantics of constructors and non-abstract methods in structural types. We describe implementation techniques, including the compile-time and run-time challenges that we faced (in particular, preserving the identity of objects). Measurement indicate that the performance of our implementation of structural dispatching is comparable to that of the JVM's standard invocation mechanisms.
Contention-aware scheduler
Authors: Xian Feng , Srisa-an Witawas , Jiang Hong
Published: October 2008

In multithreaded programming, locks are frequently used as a mechanism for synchronization. Because today's operating systems do not consider lock usage as a scheduling criterion, scheduling decisions can be unfavorable to multithreaded applications, leading to performance issues such as convoying and heavy lock contention in systems with multiple processors. Previous efforts to address these issues (e.g., transactional memory, lock-free data structure) often treat scheduling decisions as "a fact of life," and therefore these solutions try to cope with the consequences of undesirable scheduling instead of dealing with the problem directly.

In this paper, we introduce
Contention-Aware Scheduler (CA-Scheduler)
, which is designed to support efficient execution of large multithreaded Java applications in multiprocessor systems. Our proposed scheduler employs a scheduling policy that reduces lock contention. As will be shown in this paper, our prototype implementation of the CA-Scheduler in Linux and Sun HotSpot virtual machine only incurs 3.5% runtime overhead, while the overall performance differences, when compared with a system with no contention awareness, range from a degradation of 3% in a small multithreaded benchmark to an improvement of 15% in a large Java application server benchmark.
Design and implementation of transactional constructs for C/C++
Authors: Ni Yang , Welc Adam , Adl-Tabatabai Ali-Reza , Bach Moshe , Berkowits Sion , Cownie James , Geva Robert , Kozhukow Sergey , Narayanaswamy Ravi , Olivier Jeffrey , Preis Serguei , Saha Bratin , Tal Ady , Tian Xinmin
Published: October 2008

This paper presents a software transactional memory system that introduces first-class C++ language constructs for transactional programming. We describe new C++ language extensions, a production-quality optimizing C++ compiler that translates and optimizes these extensions, and a high-performance STM runtime library. The transactional language constructs support C++ language features including classes, inheritance, virtual functions, exception handling, and templates. The compiler automatically instruments the program for transactional execution and optimizes TM overheads. The runtime library implements multiple execution modes and implements a novel STM algorithm that supports both optimistic and pessimistic concurrency control. The runtime switches a transaction's execution mode dynamically to improve performance and to handle calls to precompiled functions and I/O libraries. We present experimental results on 8 cores (two quad-core CPUs) running a set of 20 non-trivial parallel programs. Our measurements show that our system scales well as the numbers of cores increases and that our compiler and runtime optimizations improve scalability.
Verifying correct usage of atomic blocks and typestate
Authors: Beckman Nels E. , Bierhoff Kevin , Aldrich Jonathan
Published: October 2008

The atomic block, a synchronization primitive provided to programmers in transactional memory systems, has the potential to greatly ease the development of concurrent software. However, atomic blocks can still be used incorrectly, and race conditions can still occur at the level of application logic. In this paper, we present a intraprocedural static analysis, formalized as a type system and proven sound, that helps programmers use atomic blocks correctly. Using
access permissions
, which describe how objects are aliased and modified, our system statically prevents race conditions and enforces typestate properties in concurrent programs. We have implemented a prototype static analysis for the Java language based on our system and have used it to verify several realistic examples.
Enforcing object protocols by combining static and runtime analysis
Authors: Gopinathan Madhu , Rajamani Sriram K.
Published: October 2008

In this paper, we consider object protocols that constrain interactions between objects in a program. Several such protocols have been proposed in the literature. For many APIs (such as JDOM, JDBC), API designers constrain how API clients interact with API objects. In practice, API clients violate such constraints, as evidenced by postings in discussion forums for these APIs. Thus, it is important that API designers specify constraints using appropriate object protocols and enforce them. The goal of an object protocol is expressed as a protocol invariant. Fundamental properties such as ownership can be expressed as protocol invariants. We present a language, PROLANG, to specify object protocols along with their protocol invariants, and a tool, INVCOP++, to check if a program satisfies a protocol invariant. INVCOP++ separates the problem of checking if a protocol satisfies its protocol invariant (called protocol correctness), from the problem of checking if a program conforms to a protocol (called program conformance). The former is solved using static analysis, and the latter using runtime analysis. Due to this separation (1) errors made in protocol design are detected at a higher level of abstraction, independent of the program's source code, and (2) performance of conformance checking is improved as protocol correctness has been verified statically. We present theoretical guarantees about the way we combine static and runtime analysis, and empirical evidence that our tool INVCOP++ finds usage errors in widely used APIs. We also show that statically checking protocol correctness greatly optimizes the overhead of checking program conformance, thus enabling API clients to test whether their programs use the API as intended by the API designer.
The impact of static-dynamic coupling on remodularization
Authors: Chern Rick , De Volder Kris
Published: October 2008

We explore the concept of
static-dynamic coupling
--the degree to which changes in a program's static modular structure imply changes to its dynamic structure. This paper investigates the impact of static-dynamic coupling in a programming language on the effort required to evolve the coarse modular structure of programs written in that language. We performed a series of remodularization case studies in both Java and SubjectJ. SubjectJ is designed to be similar to Java, but have strictly less static-dynamic coupling. Our results include quantitative measures-time taken and number of bugs introduced--as well as a more subjective qualitative analysis of the remodularization process. All results point in the same direction and suggest that static-dynamic coupling causes substantial accidental complexity for the remodularization of Java programs.
Sound and extensible renaming for java
Authors: Schäfer Max , Ekman Torbjörn , de Moor Oege
Published: October 2008

Descriptive names are crucial to understand code. However, good names are notoriously hard to choose and manually changing a globally visible name can be a maintenance nightmare. Hence, tool support for automated renaming is an essential aid for developers and widely supported by popular development environments.

This work improves on two limitations in current refactoring tools: too weak preconditions that lead to unsoundness where names do not bind to the correct declarations after renaming, and too strong preconditions that prevent renaming of certain programs. We identify two main reasons for unsoundness: complex name lookup rules make it hard to define sufficient preconditions, and new language features require additional preconditions. We alleviate both problems by presenting a novel extensible technique for creating symbolic names that are guaranteed to bind to a desired entity in a particular context by inverting lookup functions. The inverted lookup functions can then be tailored to create qualified names where otherwise a conflict would occur, allowing the refactoring to proceed and improve on the problem with too strong preconditions.

We have implemented renaming for Java as an extension to the JastAdd Extensible Java Compiler and integrated it in Eclipse. We show examples for which other refactoring engines have too weak preconditions, as well as examples where our approach succeeds in renaming entities by inserting qualifications. To validate the extensibility of the approach we have implemented renaming support for Java 5 and AspectJ like inter-type declarations as modular extensions to the initial Java 1.4 refactoring engine. The renaming engine is only a few thousand lines of code including extensions and performance is on par with industrial strength refactoring tools.
Safer unsafe code for .NET
Authors: Ferrara Pietro , Logozzo Francesco , Fähndrich Manuel
Published: October 2008

The .NET intermediate language (MSIL) allows expressing both statically verifiable memory and type safe code (typically called managed), as well as unsafe code using direct pointer manipulations. Unsafe code can be expressed in C# by marking regions of code as
unsafe
. Writing unsafe code can be useful where the rules of managed code are too strict. The obvious drawback of unsafe code is that it opens the door to programming errors typical of C and C++, namely memory access errors such as buffer overruns. Worse, a single piece of unsafe code may corrupt memory and destabilize the entire runtime or allow attackers to compromise the security of the platform.

We present a new static analysis based on abstract interpretation to check memory safety for unsafe code in the .NET framework. The core of the analysis is a new numerical abstract domain, Strp, which is used to efficiently compute memory invariants. Strp is combined with lightweight abstract domains to raise the precision, yet achieving scalability.

We implemented this analysis in Clousot, a generic static analyzer for .NET. In combination with contracts expressed in FoxTrot, an MSIL based annotation language for .NET, our analysis provides
static
safety guarantees on memory accesses in unsafe code. We tested it on all the assemblies of the .NET framework. We compare our results with those obtained using existing domains, showing how they are either too imprecise (
e.g.
, Intervals or Octagons) or too expensive (Polyhedra) to be used in practice.
Typestate-like analysis of multiple interacting objects
Authors: Naeem Nomair A. , Lhotak Ondrej
Published: October 2008

This paper presents a static analysis of typestate-like temporal specifications of groups of interacting objects, which are expressed using tracematches. Whereas typestate expresses a temporal specification of one object, a tracematch state may change due to operations on any of a set of related objects bound by the tracematch. The paper proposes a lattice-based operational semantics equivalent to the original tracematch semantics but better suited to static analysis. The paper defines a static analysis that computes precise local points-to sets and tracks the flow of individual objects, thereby enabling strong updates of the tracematch state. The analysis has been proved sound with respect to the semantics. A context-sensitive version of the analysis has been implemented as instances of the IFDS and IDE algorithms. The analysis was evaluated on tracematches used in earlier work and found to be very precise. Remaining imprecisions could be eliminated with more precise modeling of references from the heap and of exceptional control flow.
Java performance evaluation through rigorous replay compilation
Authors: Georges Andy , Eeckhout Lieven , Buytaert Dries
Published: October 2008

A managed runtime environment, such as the Java virtual machine, is non-trivial to benchmark. Java performance is affected in various complex ways by the application and its input, as well as by the virtual machine (JIT optimizer, garbage collector, thread scheduler, etc.). In addition, non-determinism due to timer-based sampling for JIT optimization, thread scheduling, and various system effects further complicate the Java performance benchmarking process.

Replay compilation is a recently introduced Java performance analysis methodology that aims at controlling non-determinism to improve experimental repeatability. The key idea of replay compilation is to control the compilation load during experimentation by inducing a pre-recorded compilation plan at replay time. Replay compilation also enables teasing apart performance effects of the application versus the virtual machine.

This paper argues that in contrast to current practice which uses a single compilation plan at replay time, multiple compilation plans add statistical rigor to the replay compilation methodology. By doing so, replay compilation better accounts for the variability observed in compilation load across compilation plans. In addition, we propose matched-pair comparison for statistical data analysis. Matched-pair comparison considers the performance measurements per compilation plan before and after an innovation of interest as a pair, which enables limiting the number of compilation plans needed for accurate performance analysis compared to statistical analysis assuming unpaired measurements.
Java type inference is broken
Authors: Smith Daniel , Cartwright Robert
Published: October 2008

Java 5, the most recent major update to the Java Programming Language, introduced a number of sophisticated features, including a major extension to the type system. While the technical details of these new features are complex, much of this complexity is hidden from the typical Java developer by an ambitious type inference mechanism. Unfortunately, the extensions to the Java 5 type system were so novel that their technical details had not yet been thoroughly investigated in the research literature. As a result, the Java 5 compiler includes a pragmatic but flawed type inference algorithm that is, by design, neither sound nor locally complete. The language specification points out that neither of these failures is catastrophic: the correctness of potentially-unsound results must be verified during type checking; and incompleteness can usually be worked around by manually providing the method type parameter bindings for a given call site.

This paper dissects the type inference algorithm of Java 5 and proposes a signficant revision that is sound and able to calculate correct results where the Java 5 algorithm fails. The new algorithm is locally complete with the exception of a difficult corner case. Moreover, the new algorithm demonstrates that several arbitrary restrictions in the Java type system---most notably the ban on lower-bounded type parameter declarations and the limited expressibility of intersection types---are unnecessary. We hope that this work will spur the evolution of a more coherent, more comprehensive generic type system for Java.