• Journal of the Korean Society for Nondestructive Testing
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• v.3 no.2
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• pp.28-35
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• 1984

• Journal of KIISE
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• v.44 no.2
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• pp.171-178
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• 2017

In this study, we propose an automated unit test generation technique for detecting vulnerabilities of Android kernel modules. The technique automatically generates unit test drivers/stubs and unit test inputs for each function of Android kernel modules by utilizing dynamic symbolic execution. To reduce false alarms caused by function pointers and missing pre-conditions of automated unit test generation technique, we develop false alarm reduction techniques that match function pointers by utilizing static analysis and generate pre-conditions by utilizing def-use analysis. We showed that the proposed technique could detect all existing vulnerabilities in the three modules of Android kernel 3.4. Also, the false alarm reduction techniques removed 44.9% of false alarms on average.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.16-22
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• 2010

Cast austenitic stainless steel(CASS) is used in the primary cooling piping system of nuclear power plant for it's relative low cost, corrosion resistance and easy of welding. However, the coarse-grain structure of cast austenitic stainless steel can strongly affect the inspectability of ultrasonic testing. The major problems encountered during inspection are beam skewing, high attenuation and high background noise of CASS component. So far, the best inspection performance involving CASS components have been achieved using low frequency TRL(Transmitter/Receiver side-by-side L wave) angle beam probe. But TRL technique could not detect shallow defect and it contains an uncertainty for sizing capability. Currently, most of researchers are studying to overcome these challenge issue. In this study, low-frequency phased array TRL technique used to detect and sizing the flaws in CF8A cast austenitic stainless steel.As conclusion, we could detect and size not only axial flaw but also circumferential flaw using low frequency phased array technique.

• Smart Structures and Systems
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• v.14 no.6
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• pp.1269-1289
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• 2014

With the sub-stepping technique, the numerical analysis in real-time dynamic hybrid testing is split into the response analysis and signal generation tasks. Two target computers that operate in real-time may be assigned to implement these two tasks, respectively, for fully extending the simulation scale of the numerical substructure. In this case, the integration time-step of solving the dynamic response of the numerical substructure can be dozens of times bigger than the sampling time-step of the controller. The time delay between the real and desired feedback forces becomes more striking, which challenges the well-developed delay compensation methods in real-time dynamic hybrid testing. This paper focuses on displacement prediction and force correction for delay compensation in the real-time dynamic hybrid testing with a large integration time-step. A new displacement prediction scheme is proposed based on recently-developed explicit integration algorithms and compared with several commonly-used prediction procedures. The evaluation of its prediction accuracy is carried out theoretically, numerically and experimentally. Results indicate that the accuracy and effectiveness of the proposed prediction method are of significance.

• Earthquakes and Structures
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• v.18 no.3
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• pp.337-348
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• 2020

Experimental testing has been considered as one of the most straightforward approaches to realize the structural behavior for earthquake engineering studies. Recently, novel and advanced experimental techniques, which combine numerical simulation with experimental testing, have been developed and applied to structural testing practically. However, researchers have to take the risk of damaging specimens or facilities during the process of developing and validating new experimental methods. In view of this, a small-scale structural laboratory has been designed and constructed in order to verify the effectiveness of newly developed experimental technique before it is applied to large-scale testing for safety concerns in this paper. Two orthogonal steel reaction walls and one steel T-slotted reaction floor are designed and analyzed. Accordingly, a large variety of experimental setups can be completed by installing servo-hydraulic actuators and fixtures depending on different research purposes. Meanwhile, a state-of-the-art digital controller and multiple real-time computation machines are allocated. The integration of hardware and software interfaces provides the feasibility and flexibility of developing novel experimental methods that used to be difficult to complete in conventional structural laboratories. A simple experimental demonstration is presented which utilizes part of the hardware and software in the small-scale structural laboratory. Finally, experimental layouts of future potential development and application are addressed and discussed, providing the practitioners with valuable reference for experimental earthquake engineering.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.10
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• pp.1841-1861
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• 2011

The advance in Service-Oriented Architecture (SOA) and web services has led to the development of new types of a system in which heterogeneous service components can connect and compose to solve a complex business problem. In the SOA, even though these service components are valid in their functionality, there is a need to test their behaviors when those services are composited. In recent years, WS-BPEL has received a wide acceptance as a means of integrating distributed service components. To test the composite service, the existing testing techniques have been focused on the functional features based on the WS-BPEL process. However as SOA approach is applying to real-time software development, the performance of composite service becomes one of important issues. This paper proposes a technique to the performance testing of a composite service with WS-BPEL extension which combined with the concept of aspect. Our WS-BPEL extension has been made towards annotating aspect component which is measuring the response time of the composite service. This paper also explains the procedure of performance testing with on-line transaction system. Our technique can apply to choose an adequate component in service composition with considering the performance among several candidate web service components.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.123-132
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• 2012

This paper presents a goal-oriented test data generation technique that specializes concolic testing. The proposed technique, referred to as GCT (Goal-oriented Concolic Testing) produces test inputs which execute a specific target. Concolic testing can be seen as the brute force approach to search the space of all possible paths until a required test input is found. In contrast, GCT restricts the number of program paths that are explored by using data flow information to identify statements that should be executed beforehand in order for the target to be executed. We conducted experiments to evaluate the performance of GCT with programs with flag variables to show its effectiveness.

• The KIPS Transactions:PartD
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• v.17D no.6
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• pp.423-430
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• 2010

As software becomes large-scale and complicated, the need for Quality Assurance and management is increased and software testing is becoming more important. The main aims of software testing are not only detecting and handling the defects in the system but also investigating and managing the present system. But automatic testing tools require lots of time and efforts to detect and manage the risk in the system because test-cases used in the general automatic testing tools have the simply static information. In this thesis, the dynamic management technique for weighted testcases is designed to test the high-risk testcases preferentially by giving the testcases dynamic weight.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.411-416
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• 2006

The critical subject of transverse crack detection in a rail head is treated in this paper. Conventional bulk wave ultrasonic techniques oftenfail because of shelling and other surface imperfections that shield the defects that lie below the shelling. A guided wave inspection technique is introduced here that can send ultrasonic energy along the rail under the shelling with a capability of finding the deleterious transverse crack defects. Dispersion curves are generated via a semi analytical finite element technique along with a hybrid guided wave finite element technique to explore the most suitable modes and frequencies for finding these defects. Sensor design and experimental feasibility experiments are also reported.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.6
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• pp.440-446
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• 2006

The reactor vessel body and closure head are fastened with the stud bolt that is one of crucial parts for safety of the reactor vessels in nuclear power plants. It is reported that the stud bolt is often experienced by fatigue cracks initiated at threads. Stud bolts are inspected by the ultrasonic technique during the overhaul periodically for the prevention of failure which leads to radioactive leakage from the nuclear reactor. The conventional ultrasonic inspection for stud bolts was mainly conducted by reflected echo method based on shadow effect. However, in this technique, there were numerous spurious signals reflected from every oblique surfaces of the thread. In this study, ultrasonic phased array technique was applied to investigate detectability of flaws in stud bolts and characteristics of ultrasonic images corresponding to different scanning methods, that is, sector and linear scan. For this purpose, simplified stud bolt specimens with artificial defects of various depths were prepared.