RMT: Rule-based Metamorphic Testing for Autonomous Driving Models

Deep neural network models are widely used for perception and control in autonomous driving. Recent work uses metamorphic testing but is limited to using equality-based metamorphic relations and does not provide expressiveness for defining inequality-based metamorphic relations. To encode real world traffic rules, domain experts must be able to express higher order relations e.g., a vehicle should decrease speed in certain ratio, when there is a vehicle x meters ahead and compositionality e.g., a vehicle must have a larger deceleration, when there is a vehicle ahead and when the weather is rainy and proportional compounding effect to the test outcome. We design RMT, a declarative rule-based metamorphic testing framework. It provides three components that work in concert:(1) a domain specific language that enables an expert to express higher-order, compositional metamorphic relations, (2) pluggable transformation engines built on a variety of image and graphics processing techniques, and (3) automated test generation that translates a human-written rule to a corresponding executable, metamorphic relation and synthesizes meaningful inputs.Our evaluation using three driving models shows that RMT can generate meaningful test cases on which 89% of erroneous predictions are found by enabling higher-order metamorphic relations. Compositionality provides further aids for generating meaningful, synthesized inputs-3012 new images are generated by compositional rules. These detected erroneous predictions are manually examined and confirmed by six human judges as meaningful traffic rule violations. RMT is the first to expand automated testing capability for autonomous vehicles by enabling easy mapping of traffic regulations to executable metamorphic relations and to demonstrate the benefits of expressivity, customization, and pluggability

Cross-Layer Handover Scheme for Multimedia Communications in Next GenerationWireless Networks

ROC NSC [97-2221-230 E-018-020-MY3, 98-2218-E-151-004-MY3]In order to achieve seamless handover for real-time applications in the IP Multimedia Subsystem (IMS) of next generation network, a multiprotocol combined handover mechanism is proposed in this paper. We combine SIP (Session Initiation Protocol), FMIP (Fast Mobile IPv6 Protocol), and MIH (Media Independent Handover) protocols by cross-layer design and optimize those protocols' signaling flows to improve the performance of vertical handover. Theoretical analysis and simulation results illustrate that our proposed mechanism performs better than the original SIP and MIH combined handover mechanism in terms of service interruption time and packet loss

Testing of Autonomous Driving Systems: where are we and where should we go?

Autonomous driving shows great potential to reform modern transportation. However, its reliability and safety have drawn a lot of attention and concerns. Compared with traditional software systems, autonomous driving systems (ADSs) often use deep neural networks in tandem with logic-based modules. This new paradigm poses unique challenges for software testing. Recently, the software engineering (SE) community has devoted significant effort to developing new testing techniques for autonomous driving systems. However, it is not clear to what extent those techniques have addressed the needs of industrial practitioners. To fill this gap, we present the first comprehensive study to identify the current practices and needs of testing autonomous driving systems in industry. We conducted semi-structured interviews with developers from 10 autonomous driving companies and surveyed 100 developers who have worked on autonomous driving systems. Through systematic analysis of interview and questionnaire data, we identified eight common practices and four common needs of testing autonomous driving systems from industry. We further surveyed 98 highly relevant papers from 28 SE conferences, journals, and workshops to find solutions to address those needs. Finally, we analyzed the limitations of existing testing techniques and proposed several future directions for SE researchers

Numerical and experimental investigation on the effect of the two-phase flow pattern on heat transfer of piston cooling gallery

To study factors affecting the formation and conversion of two-phase flow pattern as well as the heat transfer of piston cooling gallery, a transient visual target test bench was set up to research the oscillatory flow characteristics in the cooling gallery under idle condition of the engine. The computational fluid dynamics (CFD) was employed while dynamic mesh technology, SST k–ω turbulence model and volume of fluid (VOF) two-phase flow model were applied to simulate the flow process of piston cooling gallery so as to predict the distribution pattern of two-phase flow. Simulation results were in good agreement with that experimentally obtained. It was observed that in the reciprocating movement of the piston, the action of two-phase flow oscillation was severe, forming some unstable wave flows and slug flows. Results show that under the same pipe diameter, the increase of fluid viscosity results in the decrease of amplitude and the increase of the liquid slugs number as well as the enhancement on heat transfer effect. In addition, it was revealed that injection pressure has little effect on the two-phase flow pattern. However, when the pressure is reduced, the change of the liquid phase is weakened and the locations of flow pattern transition move towards to the behind, thus the impact on the heat transfer is also faint

Prediction of Residual Stress Distribution in NM450TP Wear-Resistant Steel Welded Joints

This study developed a thermo-metallurgical-mechanical simulation method to calculate the temperature field and residual stress distribution in the NM450TP wear-resistant steel welded joints. During the simulation, the solid-state phase transformation and softening effect of NM450TP wear-resistant steel was considered. The simulation results were compared with the experimental results, which verified the feasibility of this method. The influences of solid-state phase transformation and softening effect on the welding residual stress distribution were discussed. The numerical simulation results showed that the solid-state phase transformation had a more significant effect on the magnitude and distribution of the longitudinal residual stress than that of the transverse residual stress. The softening effect had a significant influence on the peak value of the longitudinal residual stress and had little influence on the transverse residual stress. Comparing the numerical simulation results with the experimental results, it could be seen that the calculation results of the welding residual stress were in the best agreement with the experimental measurement results when the solid-state transformation and softening effects were considered at the same time

Bacterial diversity in Bohai Bay solar saltworks, China

The microbiota in solar salterns plays an important role in salt production quantitatively and qualitatively. Bohai Bay coast is the major sea salt producing area in China. However, few ecological characterization studies of the Bohai Bay salt ponds, particularly of their microbial diversity, have been conducted. This study investigated the structure and diversity of the bacterial community in Hangu saltworks in response to environmental factors. The brine water was sampled from five selected saltponds within a salinity range of 5.0-19.3 % in May, July, and October, 2012. Phylogenetic analysis based on the denaturing gradient gel electrophoresis (DGGE) patterns of the PCR-amplified 16S rRNA gene fragment showed that, rather than pond salinity, especially the month of sampling influenced the structure of the bacterial community in the saltponds, which may be related to the water temperature or other factors fluctuating over the months. Moreover, canonical correspondence analysis of biological and physico-chemical parameters indicated that especially other environmental factors such as nitrogenous and phosphorous nutrient contents and pH structured the microbial community. The relatively high range-weighted richness index and Shannon-Wiener index (H') observed in this study reflect the high level of richness and biodiversity present, though there were substantial fluctuations over the months and salinities of sampling. The fragment of 16S rRNA gene sequence recovered from DGGE bands indicated that the bacterial assemblage in Hangu Saltworks was dominated by members of gamma-Proteobacteria (34 % of total sequences obtained), followed by Firmicutes (14 %) and Bacteroidetes (9 %)

Effect of poly-β-hydroxybutyrate on growth, enzyme activity and intestinal microbial community of Chinese mitten crab, Eriocheir sinensis (Milne-Edwards) juveniles

Poly-beta-hydroxybutyrate (PHB) is microbial carbon and energy storage polymer, which can be degraded into water-soluble beta-hydroxybutyric acid in the gastrointestinal tract of aquatic animals. A 60-day culture experiment was performed using Chinese mitten crab, Eriocheir sinensis (Milne-Edwards) juveniles with an average initial body weight of 0.74 +/- 0.06 g which were fed a diet supplemented with 0%, 0.5%, 1%, 3% or 5% PHB. A PHB dietary supplementation of 1% and 3% significantly improved the body weight gain, moulting frequency and concomitantly reduced 2nd-3rd moulting intervals of the crabs (P < 0.05). The dietary PHB level positively related to hepatopan-creatic pepsin, trypsin and lipase activity (P < 0.05). Increasing the dietary PHB also improved total superoxide dismutase activity, but reduced alkaline phosphatase and acid phosphatase activity in the serum of hemolymph (P < 0.05). A 16S rRNA gene analysis by denaturing gradient gel electrophoresis indicated that PHB supplementation led to a significantly higher range-weighted richness, diversity and evenness of the gut bacterial community when dosed at 3% in the feed. The beneficial effects of PHB are discussed in terms of immune defense, metabolism and gut microbiota of the crabs