Matching sender and receiver: poikilothermy and frequency tuning in a tree cricket

Animals communicate in non-ideal and noisy conditions. The primary method they use to improve communication efficiency is sender-receiver matching: the receiver's sensory mechanism filters the impinging signal based on the expected signal. In the context of acoustic communication in crickets, such a match is made in the frequency domain. The males broadcast a mate attraction signal, the calling song, in a narrow frequency band centred on the carrier frequency (CF), and the females are most sensitive to sound close to this frequency. In tree crickets, however, the CF changes with temperature. The mechanisms used by female tree crickets to accommodate this change in CF were investigated at the behavioural and biomechanical level. At the behavioural level, female tree crickets were broadly tuned and responded equally to CFs produced within the naturally occurring range of temperatures (18 to 27 degrees C). To allow such a broad response, however, the transduction mechanisms that convert sound into mechanical and then neural signals must also have a broad response. The tympana of the female tree crickets exhibited a frequency response that was even broader than suggested by the behaviour. Their tympana vibrate with equal amplitude to frequencies spanning nearly an order of magnitude. Such a flat frequency response is unusual in biological systems and cannot be modelled as a simple mechanical system. This feature of the tree cricket auditory system not only has interesting implications for mate choice and species isolation but may also prove exciting for bio-mimetic applications such as the design of miniature low frequency microphones.

Dynamically Reconfigurable Regular Expression Matching Architecture

Regular Expressions are generic representations for a string or a collection of strings. This paper focuses on implementation of a regular expression matching architecture on reconfigurable fabric like FPGA. We present a Nondeterministic Finite Automata based implementation with extended regular expression syntax set compared to previous approaches. We also describe a dynamically reconfigurable generic block that implements the supported regular expression syntax. This enables formation of the regular expression hardware by a simple cascade of generic blocks as well as a possibility for reconfiguring the generic blocks to change the regular expression being matched. Further,we have developed an HDL code generator to obtain the VHDL description of the hardware for any regular expression set. Our optimized regular expression engine achieves a throughput of 2.45 Gbps. Our dynamically reconfigurable regular expression engine achieves a throughput of 0.8 Gbps using 12 FPGA slices per generic block on Xilinx Virtex2Pro FPGA.

Efficient Regular Expression Pattern Matching for Network Intrusion Detection Systems using Modified Word-based Automata

Network Intrusion Detection Systems (NIDS) intercept the traffic at an organization's network periphery to thwart intrusion attempts. Signature-based NIDS compares the intercepted packets against its database of known vulnerabilities and malware signatures to detect such cyber attacks. These signatures are represented using Regular Expressions (REs) and strings. Regular Expressions, because of their higher expressive power, are preferred over simple strings to write these signatures. We present Cascaded Automata Architecture to perform memory efficient Regular Expression pattern matching using existing string matching solutions. The proposed architecture performs two stage Regular Expression pattern matching. We replace the substring and character class components of the Regular Expression with new symbols. We address the challenges involved in this approach. We augment the Word-based Automata, obtained from the re-written Regular Expressions, with counter-based states and length bound transitions to perform Regular Expression pattern matching. We evaluated our architecture on Regular Expressions taken from Snort rulesets. We were able to reduce the number of automata states between 50% to 85%. Additionally, we could reduce the number of transitions by a factor of 3 leading to further reduction in the memory requirements.

A Simple Label Switching Algorithm for Semisupervised Structural SVMs

In structured output learning, obtaining labeled data for real-world applications is usually costly, while unlabeled examples are available in abundance. Semisupervised structured classification deals with a small number of labeled examples and a large number of unlabeled structured data. In this work, we consider semisupervised structural support vector machines with domain constraints. The optimization problem, which in general is not convex, contains the loss terms associated with the labeled and unlabeled examples, along with the domain constraints. We propose a simple optimization approach that alternates between solving a supervised learning problem and a constraint matching problem. Solving the constraint matching problem is difficult for structured prediction, and we propose an efficient and effective label switching method to solve it. The alternating optimization is carried out within a deterministic annealing framework, which helps in effective constraint matching and avoiding poor local minima, which are not very useful. The algorithm is simple and easy to implement. Further, it is suitable for any structured output learning problem where exact inference is available. Experiments on benchmark sequence labeling data sets and a natural language parsing data set show that the proposed approach, though simple, achieves comparable generalization performance.

A Simple and Convenient One Step Method for the Reductive Deoxygenation of Aryl Ketones to Hydrocarbons

A one step, clean and efficient, conversion of arylaldehydes, ketones and ketals into the corresponding hydrocarbon using ionic hydrogenation conditions employing sodium cyanoborohydride in the presence of two to three equivalents of BF3. OEt(2) is described.

Simple Method of Preparing Graphene Flakes by an Arc-Discharge Method

Arc discharge between graphite electrodes under a relatively high pressure of hydrogen yields graphene flakes generally containing 2-4 layers in the inner wall region of the arc chamber. The graphene flakes so obtained have been characterized by X-ray diffraction, atomic force microscopy, transmission electron microscopy, and Raman spectroscopy. The method is eminently suited to dope graphene with boron and nitrogen by carrying out arc discharge in the presence of diborane and pyridine respectively.

The Use of Two Nematic Solvents in the Determination of Molecular Structure of Systems Providing Deceptively Simple Spectra

The use of two liquid crystals as solvents in the determination of molecular structure has been demonstrated for systems which do not provide structural information from studies in a single solvent owing to the fact that the spectra are deceptively simple, with the result that all the spectral parameters cannot be derived with reasonable precision. The specific system studied was 2-(p-bromophenyl)-4,6-dichloropyrimidine, for which relative inter-proton discances have been determined from the proton NMR spectra in two nematic solvents.

A simple circuit to aid direct measurement of capture cross sections of deep level impurities

An inexpensive and simple circuit to aid the direct measurement of majority carrier capture cross sections of impurity levels in the band gap of a semiconductor by the variable width filling pulse technique is presented. With proper synchronisation, during the period of application of the pulse, the device is disconnected from the capacitance meter to avoid distortion of the pulse and is reconnected again to the meter to record the emission transient. Modes of operation include manual triggering for long emission transients, repetitive triggering for isothermal and DLTS measurements and the DLTS mode which is to be used with signal analysers that already provide a synchronising pulse for disconnection.

Small-amplitude cyclic voltammetry: Part I. A simple fourier synthesis approach

Current-potential relationships are derived for small-amplitude periodic inputs for linear electrochemical systems using a Fourier synthesis procedure. Specific results have been obtained for a triangular potential waveform for two simple model systems.

Simple new PWM patterns for thyristor three-phase AC/DC convertors

Thyristor forced commutated AC/DC convertors are useful for improving the power factor and waveform of AC-side line current. These are controlled through pulse-width modulation schemes for best performance. However, the 3-phase versions impose restrictions on the PWM strategies that can be implemented for excellent harmonic rejection. This paper presents new PWM control strategies for the 3-phase converters and compares them along with the conventional 4-pulse PWM strategy for harmonic elimination. Finally, two new PWM strategies are shown to be the best, for which oscillograms are presented from actual implementation.

Simple Coding Scheme For Modular Arithmetic

A dual representation scheme for performing arithmetic modulo an arbitrary integer M is presented. The coding scheme maps each integer N in the range 0 <= N < M into one of two representations, each being identified by its most significant bit. The encoding of numbers is straightforward and the problem of checking for unused combinations is eliminated.

The ethyl, 1- and 2-propyl, and other simple alky carbanions do not exist

A combination of experimental data and theoretical calculations has been used to estimate the electron affinities of simple primary, secondary, and tertiary alkyl radicals and the proton affinities of the corresponding anions. With the exception of cyclopropyl, such carbanionsâ are indicated to be unstable towards loss of an electron and are not expected to exist as long-lived species in the gas phase.

A Simple Multiple Pulsewidth Modulated AC Choppe

A simple multiple pulsewidth modulated (MPWM) ac chopper using power transistors for 3-ý power control is discussed. 120ý chopping period is used for main transistors so that the circuit can accommodate resistive and lagging or leading power factor loads. Only 1-ý sensing is used for 3-ý control. An alternate economical power and control schemes for 3-ý MPWM ac choppers suitable only for resistive loads is also suggested. The experimental results for 12 choppings per cycle are given.

A simple vibrating reed apparatus for use at low temperatures

The authors report the design and construction of a very simple vibrating reed apparatus with automatic frequency locking capability where the resonance frequency and the internal friction can be recorded continuously as a function of temperature. The apparatus is particularly suitable for studies down to liquid helium temperatures or below.

Firing characteristics of a simple coaxial triggeredva cuum gap

The firing and delay characteristics of a simple coaxial type of triggered vacuum gap (TVG) are described and compared with the planar type. The designs are new and differ from those reported earlier. By analogy with gaseous breakdown the statistical and formative time lags have been determined.