George Yu

Rogue access point detection using temporal traffic characteristics

As the cost of IEEE 802.11 hardware continues to fall, the appeal of inserting unauthorized wireless access into enterprise networks grows. These rogue access points (AP) expose the enterprise network to a barrage of security vulnerabilities in that they are typically connected to a network port behind the firewall. Most of the current approaches to detecting rogue AP are rudimentary and are easily evaded by hackers. We propose the use of temporal traffic characteristics to detect rogue AP at a central location. This detection is independent of the wireless technology (IEEE 802.11a, 802.11b, or 802.11g), is scalable, does not possess the inefficiencies of the current solutions, and is independent of the signal range of the rogue AP.

CMOS Electro-Chemical DNA-Detection Array with On-Chip ADC

We report on a CMOS-based microsensor array, featuring 576 electrodes and 24 channels, for label-free electrochemical detection of DNA hybridization. Each channel comprises a potentiostatic circuit that keeps the electrode at a defined potential and measures the respective electrical current. The readout channels rely on a first-order delta-sigma architecture, where the electrode-electrolyte capacitance is used as the integrator. This results in a very compact recording circuit inclusive of A/D conversion; the circuit consists of only the measurement electrode, a comparator, a feedback capacitance and a few switches. Biological experiments with short DNA samples and DNA extracted from human immunodeficiency virus (HIV) are presented.

Development of a magnetic quartz crystal microbalance.

A new technique for measurement of magnetic properties of materials is demonstrated. It can be used for the measurement of thin magnetic films during their chemical modification. The resonance frequency of a quartz crystal microbalance (QCM) with conducting polymer (polyaniline) suspension in poly(ethylene glycol) was observed to increase with increasing the externally applied uniform dc magnetic field. Slowly sweeping the magnetic field between 0 and 3.1 T results in a frequency-field response curve. Chemical doping was done by exposing the polyaniline-emeraldine base film to HCl vapor. The change in population of free spins is reflected in increased frequency-field curve magnitude after HCl doping. Two working hypotheses explaining this observation are offered to explain how frequency of QCM with deposited magnetic film shifts with increasing intensity of the magnetic field.

Evaluation of fall risk for post-stroke patients using bluetooth low-energy wireless sensor

The widespread need to assess fall risk has generated need for a reliable, inexpensive, and quantifiable clinical measure. In this paper, we propose mStroke, a practical, accurate, and mobile health system that remotely measures fall risk estimation for post stroke patients. Our proposed system is delivered as an application (App) running on our hardware system consisting of two bluetooth low energy (BLE) modular sensor devices and a smartphone. This system uses accelerometer, gyroscope, and magnetometer to measure fall risk within the functional reach test, an accurate single-tasked clinical tool for fall risk assessment. The proposed system has been extensively tested using emulated and real data from Physical Therapy students as well as stroke patients.

Magnetic quartz crystal microbalance: A multilayer gold/nickel stack

A stack of alternating layers of nickel and gold was electroplated on a quartz crystal microbalance (QCM). When external magnetic fields of up to 10 kG were applied, changes in the QCM admittance magnitude and phase were observed. A mass-equivalent stack of continuous consecutive layers of nickel and gold was also exposed to magnetic field, but no admittance magnitude and phase changes were observed. The Butterworth–van Dyke model was used to mimic the observed effects by varying only the equivalent resistor component. Since the resistor component changes are attributed to internal shear friction effects, it indicates that the friction at the nickel/gold interface is modulated by the magnetic field.

Magnetic quartz crystal microbalance: Magneto-acoustic parameters

Magnetic quartz crystal microbalance is a new instrument that allows determination of magneto-acoustic parameters of thin magnetic films. The analysis in this paper is based on simple Butterworth-van-Dyke oscillator model. To demonstrate the use of the new instrument, CuNi magnetic alloy has been electroplated on a gold electrode of a quartz crystal microbalance substrate. The magneto-acoustic admittance and magneto-acoustic capacitance of the alloy film were measured in the static magnetic field between 0 and 10.00 kG, at room temperature.