Dynamic software update(DSU)patches programs on the fly.It often involves the critical task of object transformation that converts live objects of the old-version program to their semantically consistent counterparts ...Dynamic software update(DSU)patches programs on the fly.It often involves the critical task of object transformation that converts live objects of the old-version program to their semantically consistent counterparts under the new-version program.This task is accomplished by invoking an object transformer on each stale object.However,a defective transformer failing to maintain consistency would cause errors or even crash the program.We propose TOAST(Test Object trAnSformaTion),an automated approach to detecting potential inconsistency caused by object transformers.TOAST first analyzes an update to identify multiple target methods and then adopts a fuzzer with specially designed inconsistency guidance to randomly generate object states to drive two versions of a target method.This creates two corresponding execution traces and a pair of old and new objects.TOAST finally performs object transformation to create a transformed object and detects inconsistency between it and the corresponding new object produced from scratch by the new program.Moreover,TOAST checks behavior inconsistency by comparing the return variables and exceptions of the two executions.Experimental evaluation on 130 updates with default transformers shows that TOAST is promising:it got 96.0%precision and 85.7%recall in state inconsistency detection,and 81.4%precision and 94.6%recall in behavior inconsistency detection.The inconsistency guidance improved the fuzzing efficiency by 14.1%for state inconsistency detection and 40.5%for behavior inconsistency detection.展开更多
The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The vali...The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.展开更多
A YDC type hydraulic hammer is a new valve-type double action hydraulic hammer suitable for oil and gas well drilling.It is hard to find out the optimal matching relationship among various factors based on experience ...A YDC type hydraulic hammer is a new valve-type double action hydraulic hammer suitable for oil and gas well drilling.It is hard to find out the optimal matching relationship among various factors based on experience and experiments,for the matching relationships of inner pressure is complex and the impact performance is influenced by many factors.In this paper,the operating principle of a YDC type hydraulic hammer was investigated,the force applied to the main moving components(valve core and hammer)was analyzed and a dynamic model of valve core and hammer in each operating stage was established.Then,a hydraulic hammer performance optimization design software was developed on the Matlab software platform,and the performance parameters calculated by the software were compared with the laboratory test results.The following research results were obtained.Firstly,single impact energy,impact frequency and impact power increase with the increase of pump displacement or the decrease of flow bean diameter,and they increase firstly and then decrease with the increase of area difference between the upper and lower chambers.Secondly,with the increase of hammer weight,single impact energy and impact power increase,but the impact frequency decreases slowly.Thirdly,with the increase of hammer travel,single impact energy presents an increasing trend,impact frequency presents a decreasing trend and impact power basically remains unchanged.Fourthly,with the increase of valve core weight,single impact energy presents an increasing trend,while both impact frequency and impact power decrease.Fifthly,the parameter combination corresponding to the optimal single impact energy and impact power is A5B1C5D4E3F2,and the effect of displacement on single impact energy and impact power is the greatest.It is concluded that under the existing displacement and pressure of drilling pumps,the impact performance of the hydraulic hammer can be increased effectively by improving the structure of the hydraulic hammer and thus increasing its work displacement.展开更多
Repackaging brings serious threats to Android ecosystem.Software birthmark techniques are typically applied to detect repackaged apps.Birthmarks based on apps'runtime graphical user interfaces(GUI)are effective,es...Repackaging brings serious threats to Android ecosystem.Software birthmark techniques are typically applied to detect repackaged apps.Birthmarks based on apps'runtime graphical user interfaces(GUI)are effective,especially for obfuscated or encrypted apps.However,existing studies are time-consuming and not suitable for handling apps in large scale.In this paper,we propose an effective yet efficient dynamic GUI birthmark for Android apps.Briefly,we run an app with automatically generated GUI events and dump its layout after each event.We divide each dumped layout into a grid,count in each grid cell the vertices of boundary rectangles corresponding to widgets within the layout,and generate a feature vector to encode the layout.Similar layouts are merged at runtime,and finally we obtain a graph as the birthmark of the app.Given a pair of apps to be compared,we build a weighted bipartite graph from their birthmarks and apply a modified version of the maximum-weight-bipartite-matching algorithm to determine whether they form a repackaging pair(RP)or not.We implement the proposed technique in a prototype,GridDroid,and apply it to detect RPs in three datasets involving 527 apks.GridDroid reports only six false negatives and seven false positives,and it takes GridDroid merely 20 microseconds on average to compare a pair of birthmarks.展开更多
基金supported by the National Natural Science Foundation of China under Grant Nos.62025202 and 61690204。
文摘Dynamic software update(DSU)patches programs on the fly.It often involves the critical task of object transformation that converts live objects of the old-version program to their semantically consistent counterparts under the new-version program.This task is accomplished by invoking an object transformer on each stale object.However,a defective transformer failing to maintain consistency would cause errors or even crash the program.We propose TOAST(Test Object trAnSformaTion),an automated approach to detecting potential inconsistency caused by object transformers.TOAST first analyzes an update to identify multiple target methods and then adopts a fuzzer with specially designed inconsistency guidance to randomly generate object states to drive two versions of a target method.This creates two corresponding execution traces and a pair of old and new objects.TOAST finally performs object transformation to create a transformed object and detects inconsistency between it and the corresponding new object produced from scratch by the new program.Moreover,TOAST checks behavior inconsistency by comparing the return variables and exceptions of the two executions.Experimental evaluation on 130 updates with default transformers shows that TOAST is promising:it got 96.0%precision and 85.7%recall in state inconsistency detection,and 81.4%precision and 94.6%recall in behavior inconsistency detection.The inconsistency guidance improved the fuzzing efficiency by 14.1%for state inconsistency detection and 40.5%for behavior inconsistency detection.
基金the National Natural Science Foundationof China(No.60375033)
文摘The 3D model of flapping wing mechanism and veins is constructed in 3D computer aided design (CAD) software UG.Then the co-simulation model is established by using multibody dynamics software ADAMS and MATLAB.The validation of this co-simulation model is verified by comparing the simulation results with final experiments.The simulation results and experiments reveal that the relation between flapping frequency and driving voltage of motor is approximately linear under various wingspans.The variance of flapping frequency among different wingspans augments gradually with increasing voltage.Furthermore,the simulation results suggest that flapping frequency is sensitive to wingspan and decreases with increasing wingspan of veins,and the relation between flapping frequency and moment of inertia of veins is also approximately linear for various voltages.
基金supported by CNPC Scientific Research and Technology Development Project“Study on New Drilling Techniques and Methods”(No.2014A-4211).
文摘A YDC type hydraulic hammer is a new valve-type double action hydraulic hammer suitable for oil and gas well drilling.It is hard to find out the optimal matching relationship among various factors based on experience and experiments,for the matching relationships of inner pressure is complex and the impact performance is influenced by many factors.In this paper,the operating principle of a YDC type hydraulic hammer was investigated,the force applied to the main moving components(valve core and hammer)was analyzed and a dynamic model of valve core and hammer in each operating stage was established.Then,a hydraulic hammer performance optimization design software was developed on the Matlab software platform,and the performance parameters calculated by the software were compared with the laboratory test results.The following research results were obtained.Firstly,single impact energy,impact frequency and impact power increase with the increase of pump displacement or the decrease of flow bean diameter,and they increase firstly and then decrease with the increase of area difference between the upper and lower chambers.Secondly,with the increase of hammer weight,single impact energy and impact power increase,but the impact frequency decreases slowly.Thirdly,with the increase of hammer travel,single impact energy presents an increasing trend,impact frequency presents a decreasing trend and impact power basically remains unchanged.Fourthly,with the increase of valve core weight,single impact energy presents an increasing trend,while both impact frequency and impact power decrease.Fifthly,the parameter combination corresponding to the optimal single impact energy and impact power is A5B1C5D4E3F2,and the effect of displacement on single impact energy and impact power is the greatest.It is concluded that under the existing displacement and pressure of drilling pumps,the impact performance of the hydraulic hammer can be increased effectively by improving the structure of the hydraulic hammer and thus increasing its work displacement.
基金supported by the Leading-Edge Technology Program of Jiangsu Natural Science Foundation of China under Grant No.BK20202001the National Natural Science Foundation of China under Grant No.61932021.
文摘Repackaging brings serious threats to Android ecosystem.Software birthmark techniques are typically applied to detect repackaged apps.Birthmarks based on apps'runtime graphical user interfaces(GUI)are effective,especially for obfuscated or encrypted apps.However,existing studies are time-consuming and not suitable for handling apps in large scale.In this paper,we propose an effective yet efficient dynamic GUI birthmark for Android apps.Briefly,we run an app with automatically generated GUI events and dump its layout after each event.We divide each dumped layout into a grid,count in each grid cell the vertices of boundary rectangles corresponding to widgets within the layout,and generate a feature vector to encode the layout.Similar layouts are merged at runtime,and finally we obtain a graph as the birthmark of the app.Given a pair of apps to be compared,we build a weighted bipartite graph from their birthmarks and apply a modified version of the maximum-weight-bipartite-matching algorithm to determine whether they form a repackaging pair(RP)or not.We implement the proposed technique in a prototype,GridDroid,and apply it to detect RPs in three datasets involving 527 apks.GridDroid reports only six false negatives and seven false positives,and it takes GridDroid merely 20 microseconds on average to compare a pair of birthmarks.
