Value-Flow-Based Demand-Driven Pointer Analysis for C and C++

IEEE We present SUPA, a value-flow-based demand-driven flow- and context-sensitive pointer analysis with strong updates for C and C++ programs. SUPA enables computing points-to information via value-flow refinement, in environments with small time and memory budgets. We formulate SUPA by solving a graph-reachability problem on an inter-procedural value-flow graph representing a program's def-use chains, which are pre-computed efficiently but over-approximately. To answer a client query (a request for a variable's points-to set), SUPA reasons about the flow of values along the pre-computed def-use chains sparsely (rather than across all program points), by performing only the work necessary for the query (rather than analyzing the whole program). In particular, strong updates are performed to filter out spurious def-use chains through value-flow refinement as long as the total budget is not exhausted

Effect of tempering temperature on microstructure and properties of 65Mn steel for metallurgical saw blade

The continuous tempering treatment of 65 Mn steel for metallurgical saw blade was carried out in the temperature range of 200-620 °C by means of metallographic observation and mechanical property test. The results show that with the increase of tempering temperature, the strength and hardness of the pattern decrease continuously, and the impact value, section shrinkage and elongation change significantly. The experimental results provide a technical reference for preventing the failure of the saw blade during operation

Effect of tempering temperature on microstructure and properties of 65Mn steel for metallurgical saw blade

The continuous tempering treatment of 65 Mn steel for metallurgical saw blade was carried out in the temperature range of 200-620 °C by means of metallographic observation and mechanical property test. The results show that with the increase of tempering temperature, the strength and hardness of the pattern decrease continuously, and the impact value, section shrinkage and elongation change significantly. The experimental results provide a technical reference for preventing the failure of the saw blade during operation

The effect of dietary n-3 HUFA levels and DHA/EPA ratios on growth, survival and osmotic stress tolerance of Chinese mitten crab <i>Eriocheir sinensis</i> larvae

The effect of varying levels of dietary n-3 highly unsaturated fatty acid (HUFA) and docosahexaenoic acid/eicosapentaenoic acid (DHA/EPA) ratios on growth, survival and osmotic stress tolerance of Eriocheir sinensis zoea larvae was studied in two separate experiments. In experiment I, larvae were fed rotifers and Artemia enriched with ICES emulsions with 0, 30 and 50% total n-3 HUFA levels but with the same DHA/EPA ratio of 0.6. In experiment II, larvae were fed different combinations of enriched rotifers and Artemia, in which, rotifers were enriched with emulsions containing 30% total n-3 HUFA, but different DHA/EPA ratio of 0.6, 2 and 4; while Artemia were enriched with the same emulsions, but DHA/EPA ratio of 0.6 and 4. In both experiments, un-enriched rotifers cultured on baker's yeast and newly-hatched Artemia nauplii were used as control diets. Larvae were fed rotifers at zoea 1 and zoea 2 stages; upon reaching zoea 3 stage, Artemia was introduced.Experiment I revealed no significant effect of prey enrichment on the survival of megalopa among treatments, but higher total n-3 HUFA levels significantly enhanced larval development (larval stage index, LSI) and resulted in higher individual dry body weight of megalopa. Furthermore higher dietary n-3 HUFA levels also resulted in better tolerance to salinity stress. Experiment II indicated that at the same total n-3 HUFA level, larvae continuously receiving a low dietary DHA/EPA ratio had significantly lower survival at the megalopa stage and inferior individual body weight at the megalopa stage, but no negative effect was observed on larval development (LSI). The ability to endure salinity stress of zoea 3, zoea 5 and megalopa fed diets with higher DHA/EPA ratio was also improved

Event trace reduction for effective bug replay of Android apps via differential GUI state analysis

© 2019 ACM. Existing Android testing tools, such as Monkey, generate a large quantity and a wide variety of user events to expose latent GUI bugs in Android apps. However, even if a bug is found, a majority of the events thus generated are often redundant and bug-irrelevant. In addition, it is also time-consuming for developers to localize and replay the bug given a long and tedious event sequence (trace). This paper presents ECHO, an event trace reduction tool for effective bug replay by using a new differential GUI state analysis. Given a sequence of events (trace), ECHO aims at removing bug-irrelevant events by exploiting the differential behavior between the GUI states collected when their corresponding events are triggered. During dynamic testing, ECHO injects at most one lightweight inspection event after every event to collect its corresponding GUI state. A new adaptive model is proposed to selectively inject inspection events based on sliding windows to differentiate the GUI states on-the-fly in a single testing process. The experimental results show that ECHO improves the effectiveness of bug replay by removing 85.11% redundant events on average while also revealing the same bugs as those detected when full event sequences are used

Boosting the precision of virtual call integrity protection with partial pointer analysis for C++

© 2017 Association for Computing Machinery. We present, Vip, an approach to boosting the precision of Virtual call Integrity Protection for large-scale real-world C++ programs (e.g., Chrome) by using pointer analysis for the first time. Vip introduces two new techniques: (1) a sound and scalable partial pointer analysis for discovering statically the sets of legitimate targets at virtual callsites from separately compiled C++ modules and (2) a lightweight instrumentation technique for performing (virtual call) integrity checks at runtime. Vip raises the bar against vtable hijacking attacks by providing stronger security guarantees than the CHA-based approach with comparable performance overhead. Vip is implemented in LLVM-3.8.0 and evaluated using SPEC programs and Chrome. Statically, Vip protects virtual calls more effectively than CHA by significantly reducing the sets of legitimate targets permitted at 20.3% of the virtual callsites per program, on average. Dynamically, Vip incurs an average (maximum) instrumentation overhead of 0.7% (3.3%), making it practically deployable as part of a compiler tool chain

An improved calcium chloride method preparation and transformation of competent cells

Transformation is one of the fundamental and essential molecular cloning techniques. In this paper, we have reported a modified method for preparation and transformation of competent cells. This modifiedmethod, improved from a classical protocol, has made some modifications on the concentration of calcium chloride and competent bacteria solution, rotation speed in centrifugation and centrifugationtime. It was found that the optimal transformation efficiency were obtained when the concentration of CaCl2 was 75 mmol/l, OD600 of the culture meets 0.35 to 0.45, the temperature of rotation was 4°C , rotation speed was 1000 g and rotation time was 5 min. Even more, we also found out that the transformation efficiency would increase about 10 to 30 times when adding 15% glycerine into CaCl2 solution. The transformation efficiency, using our new method, reaches 108cf u/μg and higher than ultra-competent Escherichia coli method. This method will improve the efficiency in the molecular cloning and the construction of gene library.Keywords: Competent cells, CaCl2, improved method, transformation, glycerine, transformation efficienc