Improving static resolution of dynamic class loading in Java using dynamically gathered environment information

In Java software, one important flexibility mechanism is dynamic class loading. Unfortunately, the vast majority of static analyses for Java treat dynamic class loading either unsoundly or too conservatively. We present a novel semi-static approach for resolving dynamic class loading by combining static string analysis with dynamically gathered information about the execution environment. The insight behind the approach is that dynamic class loading often depends on characteristics of the environment that are encoded in various environment variables. Such variables are not static elements; however, their run-time values typically remain the same across multiple executions of the application. Thus, the string values reported by our technique are tailored to the current installation of the system under analysis. Additionally, we propose extensions of string analysis to increase the number of sites that can be resolved purely statically, and to track the names of environment variables. An experimental evaluation on the Java 1.4 standard libraries shows that a state-of-the-art purely static approach resolves only 28% of non-trivial sites, while our approach resolves 74% of such sites. We also demonstrate how the information gained from resolved dynamic class loading can be used to determine the classes that can potentially be instantiated through the use of reflection. Our extensions of string analysis greatly increase the number of resolvable reflective instantiation sites. This work is a step towards making static analysis tools better equipped to handle the dynamic features of Java. This material is based upon work supported by the National Science Foundation under CAREER grant CCF-0546040.     

Optimizing availability and QoS of heterogeneous distributed system based on residual lifetime in uncertain environment

A notable requirement of heterogeneous parallel and distributed computing systems is to maximize their processing performance and agreed upon QoS. Lots of work in this field has been done to optimize the system performance by improving certain metrics such as reliability, robustness, security, and so on. However, most of them assume that systems are running without interruption all the time and seldom consider the system’s intrinsic characteristics, such as failure rate, repair rate, and lifetime. In this paper, we study how to achieve high availability based on residual lifetime analysis for heterogeneous distributed computational systems with considering their essential features. First, we provide an availability model taking into account system’s expected residual lifetime. Second, we propose an objective function about the model and develop a heuristic scheduling algorithm to maximize the availability with the makespan constraint. At last, we demonstrate these advantages through the extensive simulated experiments.

Oil holdup prediction of oil–water two phase flow using thermal method based on multiwavelet transform and least squares support vector machine

Oil holdup of oil–water two phase flow (OWTPF) was measured using thermocouple based on the thermal method. A new model based on least square support vector machines (LSSVM) and multiwavelet transform has been proposed for the first time, which is capable of forecasting oil holdup of oil–water two phase flow. The temperature signal of OWTPF is greatly disturbed by noises from external interference, which results in a limited measurement range of oil holdup. In order to solve the problem, a new signal processing method based on the multiwavelet transform is used. Multiwavelet transform has several scaling functions and corresponding wavelet functions, which can simultaneously achieve orthogonality, symmetry. With ideal performance, noises were removed and actual temperature signal was effectively retained. The fluctuated amplitude signal denoised and total flux of OWTPF were employed as inputs and the oil holdup was used as output of LSSVM model. In order to improve the predictive accuracy and generalization ability of the LSSVM model, a Genetic Arithmetic (GA) has been adopted to determine the optimal parameters of LSSVM model automatically. The experiment results indicate that the performance of LSSVM–GA model outperforms those of artificial neural network (ANN), LSSVM–GA model can be used for estimating the oil holdup of OWTPF with reasonable accuracy.     

Effect of passengers’ active head tilt and opening/closure of eyes on motion sickness in lateral acceleration environment of cars

This study examined the effect of passengers’ active head-tilt and eyes-open/eyes-closed conditions on the severity of motion sickness in the lateral acceleration environment of cars. In the centrifugal head-tilt condition, participants intentionally tilted their heads towards the centrifugal force, whereas in the centripetal head-tilt condition, the participants tilted their heads against the centrifugal acceleration. The eyes-open and eyes-closed cases were investigated for each head-tilt condition. In the experimental runs, the sickness rating in the centripetal head-tilt condition was significantly lower than that in the centrifugal head-tilt condition. Moreover, the sickness rating in the eyes-open condition was significantly lower than that in the eyes-closed condition. The results suggest that an active head-tilt motion against the centrifugal acceleration reduces the severity of motion sickness both in the eyes-open and eyes-closed conditions. They also demonstrate that the eyes-open condition significantly reduces the motion sickness even when the head-tilt strategy is used.

Practitioner Summary: Little is known about the effect of head-tilt strategies on motion sickness. This study investigated the effects of head-tilt direction and eyes-open/eyes-closed conditions on motion sickness during slalom automobile driving. Passengers’ active head tilt towards the centripetal direction and the eyes-open condition greatly reduce the severity of motion sickness.     

Uncertainty analysis of flash‐flood system using remote sensing and a geographic information system based on GcIUH in the Yeongdeok Basin,Korea

The current paper focuses on minimizing flood damage in the Yeongdeok basin of South Korea by establishing a flood prediction model based on a geographic information system (GIS), remote sensing and geomorphoclimatic instantaneous unit hydrograph (GcIUH) techniques. The GIS database for flash flood prediction was created using data from digital elevation models (DEMs), soil maps and Landsat satellite imagery. Flood prediction was based on the peak discharge calculated at the sub‐basin scale using hydrogeomorphologic techniques and the threshold runoff value. Using the developed flash flood prediction model, rainfall conditions with the potential to cause flooding were determined based on the cumulative rainfall for 20 min, considering rainfall duration, peak discharge and flooding in the Yeongdeok basin.     

Intercomparison of microwave remote-sensing soil moisture data sets based on distributed eco-hydrological model simulation and in situ measurements over the North China Plain

Intercomparisons of microwave-based soil moisture products from active ASCAT (Advanced Scatterometer) and passive AMSR-E (Advanced Microwave Scanning Radiometer for the Earth Observing System) is conducted based on surface soil moisture (SSM) simulations from the eco-hydrological model, Vegetation Interface Processes (VIP), after it is carefully validated with in situ measurements over the North China Plain. Correlations with VIP SSM simulation are generally satisfactory with average values of 0.71 for ASCAT and 0.47 for AMSR-E during 2007–2009. ASCAT and AMSR-E present unbiased errors of 0.044 and 0.053 m³ m^?3 on average, with respect to model simulation. The empirical orthogonal functions (EOF) analysis results illustrate that AMSR-E provides more consistent SSM spatial structure with VIP than ASCAT; while ASCAT is more capable of capturing SSM temporal dynamics. This is supported by the facts that ASCAT has more consistent expansion coefficients corresponding to primary EOF mode with VIP (R = 0.825, p < 0.1). However, comparison based on SSM anomaly demonstrates that AMSR-E and ASCAT have similar skill in capturing SSM short-term variability. Temporal analysis of SSM anomaly time series shows that AMSR-E provides best performance in autumn, while ASCAT provides lower anomaly bias during highly-vegetated summer with vegetation optical depth of 0.61. Moreover, ASCAT retrieval accuracy is less influenced by vegetation cover, as it is in relatively better agreement with VIP simulation in forest than in other land-use types and exhibits smaller interannual fluctuation than AMSR-E. Identification of the error characteristics of these two microwave soil moisture data sets will be helpful for correctly interpreting the data products and also facilitate optimal specification of the error matrix in data assimilation at a regional scale.     

Evaluation and improvement of the MODIS land surface temperature/emissivity products using ground‐based measurements at a semi‐desert site on the western Tibetan Plateau

Current MODerate‐resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST, surface skin temperature)/emissivity products are evaluated and improvements are investigated. The ground‐based measurements of LST at Gaize (32.30° N, 84.06° E, 4420 m) on the western Tibetan Plateau from January 2001 to December 2002 agree well (mean and standard deviation of differences of 0.27 K and 0.84 K) with the 1‐km Version 004 (V4) Terra MODIS LST product (MOD11A1) generated by the split‐window algorithm. Spectral emissivities measured from surface soil samples collected at and around the Gaize site are in close agreement with the landcover‐based emissivities in bands 31 and 32 used by the split‐window algorithm. The LSTs in the V4 MODIS LST/emissivity products (MYD11B1 for Aqua and MOD11B1 for Terra) from the day/night LST algorithm are higher by 1–1.7 K (standard deviation around 0.6 K) in comparisons to the 5‐km grid aggregated values of the LSTs in the 1‐km products, which is consistent with the results of a comparison of emissivities. On average, the emissivity in MYD11B1 (MOD11B1) is 0.0107 (0.0167) less than the ground‐based measurements, which is equivalent to a 0.64 K (1.25 K) overestimation of LST around the average value of 285 K. Knowledge obtained from the evaluation of MODIS LST/emissivity retrievals provides useful information for the improvement of the MODIS LST day/night algorithm. Improved performance of the refined (V5) day/night algorithm was demonstrated with the Terra MODIS data in May–June 2004.     

Investigations on characteristics of micro/meso scale gas foil journal bearings for 100–200 W class micro power systems using first order slip velocity boundary conditions and the effective viscosity model

In this paper, a modified compressible Reynolds equation for micro/meso scale gas foil journal bearings considering first order slip and effective viscosity under rarefied flow conditions is presented. The influence of rarefaction effect on the load carrying capacity, attitude angle, speed and frequency dependent stiffness and damping coefficients, modal impedance, natural frequencies and unbalance response is studied. From numerical analysis, it has been found that there is significant change in all the static and dynamic characteristics predicted by the no-slip model and model with effective viscosity. There is also a considerable difference between the values predicted by a model with effective viscosity and a model without effective viscosity. For a given eccentricity ratio, the influence of effective viscosity on load carrying capacity and attitude angle is more significant for the typical operating speed range of micro/meso scale gas turbines. The influence of effective viscosity decreases with increase in compliance of bearing structure. Similarly, the influence of effective viscosity on frequency dependent stiffness and damping coefficients increases with excitation frequency ratio. Significant change in natural frequency, modal impedance and unbalance response for model with no slip and slip with effective viscosity is observed. The influence of effective viscosity is found to be significant with increase in Knudsen number.