Model Checking of Distributed Multi-Threaded Java Applications

In this dissertation, we focus on the verification of distributed Java applications composed of communicating multithreaded processes. We choose model checking as the verification technique. We propose an instance of the so-called centralization approach which allows for model checking multiple communicating processes. The main challenge of applying centralization is keeping data separated between different processes. In our approach, this issue is addressed through a new class-loading model. As one of our contributions, we implement our approach within an existing model checker, Java PathFinder (JPF). To account for interactions between processes, our approach provides the model checker with a model of interprocess communication. Moreover, our model allows for systematically exploring potential exceptional control flows caused by network failures. We also apply a partial order reduction (POR) algorithm to reduce the state space of distributed applications, and we prove that our POR algorithm preserves deadlocks. Furthermore, we propose an automatic approach to capture interactions between the system being verified and external resources, such as cloud computing services. The dissertation also discusses how our approach is superior to existing approaches. Our approach exhibits better performance which is mainly due to the POR technique. Furthermore, our approach allows for verifying a considerably larger class of applications without the need for any manual modeling, and it has been successfully used to detect bugs that cannot be found using previous work

MESA: Message-Based System Analysis Using Runtime Verification

In this paper, we present a novel approach and framework for run-time verication of large, safety critical messaging systems. This work was motivated by verifying the System Wide Information Management (SWIM) project of the Federal Aviation Administration (FAA). SWIM provides live air traffic, site and weather data streams for the whole National Airspace System (NAS), which can easily amount to several hundred messages per second. Such safety critical systems cannot be instrumented, therefore, verification and monitoring has to happen using a nonintrusive approach, by connecting to a variety of network interfaces. Due to a large number of potential properties to check, the verification framework needs to support efficient formulation of properties with a suitable Domain Specific Language (DSL). Our approach is to utilize a distributed system that is geared towards connectivity and scalability and interface it at the message queue level to a powerful verification engine. We implemented our approach in the tool called MESA: Message-Based System Analysis, which leverages the open source projects RACE (Runtime for Airspace Concept Evaluation) and TraceContract. RACE is a platform for instantiating and running highly concurrent and distributed systems and enables connectivity to SWIM and scalability. TraceContract is a runtime verication tool that allows for checking traces against properties specified in a powerful DSL. We applied our approach to verify a SWIM service against several requirements.We found errors such as duplicate and out-of-order messages

Effect of Mobile Cell Phone Ringing on Function of Gamma Camera

Abstract: After the start of renal scintigraphy in a 32-year-old woman, there was an abnormal view in frame 6 that was simultaneous with the start of ringing of a mobile cell phone that was in the patient’s trousers pocket. In frame 6 of the flow phase, some bright dots were observed, suggesting photomultiplier tubes. Immediately after that frame, in spite of continued ringing of the mobile cell phone (up to 1–2 minutes), the imaging frames came back to a normal situation. In the case, electromagnetic interference from the mobile cell phone may disrupt the photoelectric functioning of photomultiplier tubes during scintigraphy

« The electromagnetic interference of mobile phones on the function of a gamma camera »

Purpose: The aim of the present study is to evaluate whether or not the electromagnetic field generated by mobile phones interferes with the function of a single-photon emission computed tomography (SPECT) gamma camera during data acquisition. Methods and materials: We tested the effects of seven models of mobile phones on one SPECT gamma camera. The mobile phones were tested when making a call, in ringing mode, and in standby mode. The gamma camera function was assessed during data acquisition from a planar source and a point source of technetium-99m with activities of 10 mCi and 3 mCi, respectively. A significant decrease in count number was considered to be electromagnetic interference (EMI). Results: The percentage of induced EMI with the gamma camera per mobile phone was in the range of 0–100%. The incidence of EMI was mainly observed in the first seconds of ringing and then mitigated in the following frames. Conclusion: Mobile phones are portable sources of electromagnetic radiation, and there is interference potential with the function of SPECT gamma cameras leading to adverse effects on the quality of the acquired images. Keywords: Electromagnetic interference (EMI), mobile phones, gamma camera, single-photon emission computed tomography (SPECT

Detection of human herpes viruses 1-5 in miscarriage: A case-control study

Background: Miscarriage is the spontaneous pregnancy loss before 24 wk of gestation. The incidence rate of miscarriage over the past few decades has shown steady or even growing trends. Viral intrauterine infections are one of the probable etiological causes of miscarriage. Previous evidence have shown that human herpes viruses (HHVs) could be considered as the potential reasons for intrauterine infections and adverse pregnancy outcomes. Objective: This case-control study aimed to detect HHV1-5 DNAs in placental tissues and assess their association with miscarriage during the first 24 wk of pregnancy in spontaneous and therapeutic abortions. Materials and Methods: Placental tissues from 83 women with spontaneous abortions during the first and the second trimesters of pregnancy and 81 women with therapeutic abortion during the same gestational age were collected. The DNA extraction was performed by the phenol/chloroform method. A part of the DNA polymerase gene of HHVs was amplified with multiplex nested-polymerase chain reaction. The polymerase chain reaction products were subjected to sequencing. Results: The results showed the presence of human cytomegalovirus genome in the placenta of both spontaneous (8.4%) and therapeutic (4.9%) abortions. No statistically significant differences were found between these two groups. The other investigated viruses were not detected here. Conclusion: In conclusion, like some other studies, no correlation was detected between the HHVs placental infections and the increased risk of spontaneous abortions. In order to find the actual role of HHVs infections in miscarriage, further investigations should be performed on a larger sample size in different areas. Key words: Spontaneous abortion, Therapeutic abortion, Infections, Human herpes viruses

jpf−concurrent: an extension of Java PathFinder for java.util.concurrent

One of the main challenges when verifying multi-threaded Java applications is the state space explosion problem. Due to thread interleavings, the number of states that the model checker has to verify can grow rapidly and impede the feasibility of verification. In the Java language, the source of thread interleavings can be the system under test as well as the Java Development Kit (JDK) itself. In our paper, we propose a method to minimize the state space explosion problem for applications verified under the Java PathFinder (JPF) model checker. Our method is based on abstracting the state of the application to a smaller domain and implementing application behavior using the Model Java Interface (MJI) of JPF. To show the capabilities of our approach, we have created a JPF extension called jpf-concurrent which abstracts classes from the Java Concurrency Utilities. Several benchmarks proved the usefulness of our approach. In all cases, our implementation was faster than the JDK implementation when running under the JPF model checker. Moreover, our implementation led to significantly smaller state spaces

Management of gastrointestinal complaints in differentiated thyroid cancer patients treated with

Comparison of the efficacy of pantoprazole, metoclopramide, and ondansetron – a randomized clinical tria

Tools to generate and check consistency of model classes for Java PathFinder

Java PathFinder (JPF) is a model checker for Java applications. Like any other model checker, JPF has to combat the notorious state space explosion problem. Since JPF is a JVM, it can only model check Java bytecode and needs to handle native calls differently. JPF tackles the state space explosion problem and handles native calls by means of so-called model classes and native peers. In this paper we focus on model classes. For a class that either causes a state space explosion or that contains native calls, one can introduce a model class that either abstracts away particular details or implements the native call in Java. Rather than model checking the original class, JPF model checks the model class instead. Writing such model classes is time consuming and error prone. In this paper we propose two tools to assist with the development of model classes. The one tool generates a skeleton of a model class. The other tool checks whether a model class is consistent with the original class