219 research outputs found
Masquerader Detection Using OCLEP: One-Class Classification Using Length Statistics of Emerging Patterns
We introduce a new method for masquerader detection that only uses a user’s own data for training, called Oneclass Classification using Length statistics of Emerging Patterns (OCLEP). Emerging patterns (EPs) are patterns whose support increases from one dataset/class to another with a big ratio, and have been very useful in earlier studies. OCLEP classifies a case T as self or masquerader by using the average length of EPs obtained by contrasting T against sets of samples of a user’s normal data. It is based on the observation that one needs long EPs to differentiate instances from a common class, but needs short EPs to differentiate instances from different classes.
OCLEP has two novel features: for training it uses EPs mined from just the self class; for classification it uses the length statistics instead of the EPs themselves. Experiments show that OCLEP can achieve very good accuracy while keeping the false positive rate low, it achieves slightly better area-under-ROC-curve than SVM, and it can achieve good results when other approaches can not. OCLEP requires little effort in choosing parameters; the SVM requires significant tuning and it is hard to reach the theoretical optimal result. These features imply that OCLEP is a good complementary component for a robust masquerader detection system, even though its average performance in false positive rate is not as good as SVM’s
A Three Phase Interleaved Boost Converter with L & C Voltage Extension Mechanism
In this paper a high step-up dc-dc voltage converter is proposed. The proposed converter employs coupled inductors and voltage extension capacitors for obtaining a high voltage gain. The coupled inductors and extension capacitors are merged in traditional interleaved boost converters to get the additional advantage of high step-up voltage conversion ratio and reduced voltage stress on switches along with existing features of interleaved boost converters. The main operating principle of the proposed converter is discussed and the key principle waveforms and equations are analysed. A simulation in PSIM is carried out for the proposed converter as well as traditional interleaved boost converter for the same parameters which shows that the proposed converter has better performance as compared to the traditional interleaved boost converter. Finally, an experiment is carried on a 32 W, 20 V input, 160 V output prototype in the laboratory for experimental validation of the proposed converter. Important future directions have also been given for future research on the proposed topology
Tunable Quantum Beam Splitters for Coherent Manipulation of a Solid-State Tripartite Qubit System
Coherent control of quantum states is at the heart of implementing
solid-state quantum processors and testing quantum mechanics at the macroscopic
level. Despite significant progress made in recent years in controlling single-
and bi-partite quantum systems, coherent control of quantum wave function in
multipartite systems involving artificial solid-state qubits has been hampered
due to the relatively short decoherence time and lacking of precise control
methods. Here we report the creation and coherent manipulation of quantum
states in a tripartite quantum system, which is formed by a superconducting
qubit coupled to two microscopic two-level systems (TLSs). The avoided
crossings in the system's energy-level spectrum due to the qubit-TLS
interaction act as tunable quantum beam splitters of wave functions. Our result
shows that the Landau-Zener-St\"{u}ckelberg interference has great potential in
the precise control of the quantum states in the tripartite system.Comment: 24 pages, 3 figure
Detection of small single-cycle signals by stochastic resonance using a bistable superconducting quantum interference device
We propose and experimentally demonstrate detecting small single-cycle and
few-cycle signals by using the symmetric double-well potential of a radio
frequency superconducting quantum interference device (rf-SQUID). We show that
the response of this bistable system to single- and few-cycle signals has a
non-monotonic dependence on the noise strength. The response, measured by the
probability of transition from initial potential well to the opposite one,
becomes maximum when the noise-induced transition rate between the two stable
states of the rf-SQUID is comparable to the signal frequency. Comparison to
numerical simulations shows that the phenomenon is a manifestation of
stochastic resonance.Comment: 5 pages 3 figure
Demystifying RCE Vulnerabilities in LLM-Integrated Apps
In recent years, Large Language Models (LLMs) have demonstrated remarkable
potential across various downstream tasks. LLM-integrated frameworks, which
serve as the essential infrastructure, have given rise to many LLM-integrated
web apps. However, some of these frameworks suffer from Remote Code Execution
(RCE) vulnerabilities, allowing attackers to execute arbitrary code on apps'
servers remotely via prompt injections. Despite the severity of these
vulnerabilities, no existing work has been conducted for a systematic
investigation of them. This leaves a great challenge on how to detect
vulnerabilities in frameworks as well as LLM-integrated apps in real-world
scenarios.
To fill this gap, we present two novel strategies, including 1) a static
analysis-based tool called LLMSmith to scan the source code of the framework to
detect potential RCE vulnerabilities and 2) a prompt-based automated testing
approach to verify the vulnerability in LLM-integrated web apps. We discovered
13 vulnerabilities in 6 frameworks, including 12 RCE vulnerabilities and 1
arbitrary file read/write vulnerability. 11 of them are confirmed by the
framework developers, resulting in the assignment of 7 CVE IDs. After testing
51 apps, we found vulnerabilities in 17 apps, 16 of which are vulnerable to RCE
and 1 to SQL injection. We responsibly reported all 17 issues to the
corresponding developers and received acknowledgments. Furthermore, we amplify
the attack impact beyond achieving RCE by allowing attackers to exploit other
app users (e.g. app responses hijacking, user API key leakage) without direct
interaction between the attacker and the victim. Lastly, we propose some
mitigating strategies for improving the security awareness of both framework
and app developers, helping them to mitigate these risks effectively
Observation of coherent oscillation in single-passage Landau-Zener transitions
Landau-Zener transition (LZT) has been explored in a variety of physical
systems for coherent population transfer between different quantum states. In
recent years, there have been various proposals for applying LZT to quantum
information processing because when compared to the methods using ac pulse for
coherent population transfer, protocols based on LZT are less sensitive to
timing errors. However, the effect of finite range of qubit energy available to
LZT based state control operations has not been thoroughly examined. In this
work, we show that using the well-known Landau-Zener formula in the vicinity of
an avoided energy-level crossing will cause considerable errors due to coherent
oscillation of the transition probability in a single-passage LZT experiment.
The data agree well with the numerical simulations which take the transient
dynamics of LZT into account. These results not only provide a closer view on
the issue of finite-time LZT but also shed light on its effects on the quantum
state manipulation.Comment: 10 pages,5 figure
Landau-Zener-St\"{u}ckelberg Interference of Microwave Dressed States of a Superconducting Phase Qubit
We present the first observation of Landau-Zener-St\"{u}ckelberg (LZS)
interference of the dressed states arising from an artificial atom, a
superconducting phase qubit, interacting with a microwave field. The dependence
of LZS interference fringes on various external parameters and the initial
state of the qubit agrees quantitatively very well with the theoretical
prediction. Such LZS interferometry between the dressed states enables us to
control the quantum states of a tetrapartite solid-state system with ease,
demonstrating the feasibility of implementing efficient multipartite quantum
logic gates with this unique approach.Comment: 6 pages, 3 figures To appear in Physical Review B(R
Quantum interference induced by multiple Landau-Zener transitions in a strongly driven rf-SQUID qubit
We irradiated an rf-SQUID qubit with large-amplitude and high frequency
electromagnetic field. Population transitions between macroscopic distinctive
quantum states due to Landau-Zener transitions at energy-level avoided
crossings were observed. The qubit population on the excited states as a
function of flux detuning and microwave power exhibits interference patterns.
Some novel features are found in the interference and a model based on rate
equations can well address the features.Comment: 6 pages, 3 figures, comments are welcom
Simulation of self-pressurization in cryogenic propellant tank
In order to predict the pressure and investigate the
interrelation among the physical processes in cryogenic
propellant tanks, a 2D axial symmetry Volume-of-Fluid (VOF)
computational fluid dynamic (CFD) model including a liquid
propellant phase and a mixture real gas phase is established.
The propellant phase change model is based on the assumption
of thermodynamic equilibrium. Two comparisons between the
simulation results and the self-pressurization tests of two
different liquid hydrogen tanks are made to validate the model.
And the deviations of pressure in the tanks are 2.7%~6.1%. The
results indicate that the evaporation induced by the initial
overheat is the key factor of the pressure rising in the liquid
hydrogen tank at the beginning of self-pressurization, but has
less influence when the tank becomes saturated.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
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