Electrical and Computer Engineering

WORD MAP is the ultimate vocabulary builder which accumulates all words from Barron's, Word Smart and other test-prep books combined, with Bangla meanings. The words are not arranged in monotonous alphabetical order, rather they are grouped using synonyms, antonyms, etymology and derivatives, making the book's design unique, which eventually improves the skills of GRE verbal. For the first time 'mathematical expressions of words' has been used. And the gripping sentences from world-class literatures will keep one absorbed throughout the journey.

Organization of the Book The book is divided into three parts. Every part has its own distinctive style of story-telling and covers a particular range of subjects. Majority of the first part talks about human mind, body and its needs. The part starts with the chapter Joy accompanied by Sorrow, then Love and Hate, Anger and Fear, and finally Confusion, all of these being primary or basic emotions. The next few chapters describe complex emotions or feelings like Annoyance, Calmness and Pride followed by Boasting, which is an outcome of pride. After discussing about emotions, we start talking about senses or Perceptions, Facial Expressions, followed by Body Types and physical fitness, and finally gestures and Motions. The next two chapters are about human needs like Sex and Money, accompanied by War and destruction, Religions and doctrines. We end this part by discussing about Deception. Part 2 is about society, professions and fields of study. The sequence of progression is like: it starts with Social Classes, followed by Apparel and Behavior, then Professions along with working Tools and Instruments. The remaining chapters of the part discusses about diverse fields of study. Our discussion on scientific disciplines starts with life sciences (Biology and Medical Science), then Earth Science, Agricultural Science, and then Physics and Chemistry, all being parts of natural sciences; followed by Politics, Economics and Anthropology under social sciences. Then we talk about the humanistic disciplines as Jurisprudence, Fine Arts (architecture), Literature, Drama, Music, and conclude this part discussing few other similar topics. The third part is organized in a slightly different manner. It's a collection of contrasting couples, meaning each chapter consists of a pair of words having opposite meanings, such as Energetic-Lethargic, Diligent-Negligent, Astute-Asinine, Accord-Discord , Approve-Reject and so on. However the last chapter, Appraise-Apprise, is not perfectly a contrasting pair, rather it has more properties of a diabolic duo, which we will define shortly.

In this paper, an unconditionally stable finitedifference time-domain (FDTD) method in cylindrical coordinates is developed to analyze electromagnetic responses under axially symmetric measure-while-drilling/logging-while-drilling (MWD/LWD) environments. The method is based on the application of the Crank-Nicholson scheme to the FDTD method in cylindrical coordinates. To accelerate the solution of this approach, an algebraic multigrid method is applied. For several MWD/LWD electromagnetic simulations, it is observed that the proposed method can be close to 20 times faster than the conventional FDTD method.

In this paper, we study the performance of a technique called time reversal for cooperative communication in a mobile wireless environment. To put the work in context, a brief introduction to timereversal communication (TRC) in general and cooperative TRC in particular is presented. Performance of a proposed cooperative TRC scheme is evaluated numerically via a simulated indoor environment containing multiple wireless communication nodes. We characterize the behavior of the peak power received at a target node as a function of the number of cooperating transmitting nodes and as a function of the distance of the target from its predicted location within the simulated environment. The results demonstrate that the performance of cooperative TRC is less sensitive to uncertainty in the target position than might be expected from standard assumptions regarding the relationship between signal wavelength and spatial channel correlation in a complex multipath environment.

We propose an efficient algorithm for the simulation of densely sampled biological objects. This technique is based on an algebraic multi-grid (AMG) accelerated Crank-Nicholson (CN) finite-difference time-domain (FDTD) method. Using this scheme, simulation time step sizes are no longer limited by the Courant-Friedrich-Levy (CFL) number. A practical guideline on how to choose appropriate timestep sizes for accurate bioelectromagnetic applications is also presented. Numerical examples are used to demonstrate the effectiveness of this technique.

ABSTRACT: A new technique for generating millimeter-wave signals from a semiconductor laser is presented. A 32-GHz signal is generated using a multi-section semiconductor laser, which is operated under continuous-wave conditions and by injecting optical pulses at a repetition rate equal to the fourth subharmonic (8 GHz). The generated millimeter-wave signal exhibits a large subharmonic suppression ratio (Ͼ17 dB), a large-frequency detuning range (Ͼ300 MHz), low levels of phase noise (Ϫ77.5 dBc/Hz), and large locking (Ͼ400 MHz).

We demonstrate our Raman chemical imaging capability using microalgae cells which are representative living cells currently we have. Carotenoids and different lipids can be clearly identified. Most carotenoids (1155cm -1 , 1520cm -1 ), saturated lipid (1440cm -1 ) and liquid hydrocarbon oils (1639cm -1 -1670cm -1 ) are in the cell membranes and colony extracellular matrix. 1639cm -1 ,1647cm -1 ,1647cm -1 bands are specific for indicating methylated liquid hydrocarbons (C 31 ,C 32 ,C 33 and C 34 ).

Monolithic hierarchical nanoporous gold disks, 500 nm in diameter, 75 nm in thickness and 3.5 nm in pore radius, have been fabricated by hybrid processes. A surface-enhanced Raman scattering enhancement factor of at least 10 8 has been obtained on individual disks using benzenethiol self-assembled monolayer with 785 nm laser excitation. † Electronic supplementary information (ESI) available: Detailed fabrication process, large area SERS mapping with corresponding SEM and optical micrographs, as well as discussion of the detection limit in terms of integration time and CCD temperature. See

The purpose of this experiment was to determine the internal resistance of consumer-grade AA batteries of two different chemical types. The chemical types chosen were alkaline and lithium. The approach consisted of simultaneously connecting three new batteries of the same type to three separate circuits measuring 1.22 [Ω] each. The circuits were made up of 12 carbon-film resistors measuring 13.3 [Ω] each. The three identical meters used to measure the voltage drop were the Fluke 45 dual-display multi-meters. The meter was connected via the RS-232 port to a computer and recorded voltage measurements at constant intervals of 25 seconds over a period of 5 hours. The average internal resistance of the alkaline batteries increased non-linearly from 0.00 [Ohms] at t=0 [m] to 36.67±2.95 [Ohms] at t=300 [m] at a 99% confidence for future trials. The average internal resistance of the alkaline batteries increased non-linearly from 0.00 [Ohms] at t=0 [m] to 67.22±3.86 [Ohms] at t=300 [m] at a 99% confidence for future trials.

The purpose of this experiment is to calculate the potential, charge density, and capacitance of a non-symmetrical surface using a finite difference approximation of Laplace’s Equation. Microsoft Excel was used to construct a nodal grid scheme to simulate the structure at five exponentially increasing levels of precision. The first case used a nodal grid of dimensions 23 by 11 cells and the most precise case used dimensions of 353 by 161 cells. The potential used towards the bottom of the structure was 1 [V] and 0 [V] around the perimeter of the structure. The potential distribution was found to be symmetrical about the length of the structure, but not the height. A plot of the flux lines is included to show the behavior across each equipotential region of the structure. The total surface charge density near the edges of the structure was calculated to be 257.0887[pC/m2] and 56.463 [pC/m2] in the middle of the structure. The capacitance per unit length for the most precise nodal grid was calculated to be 72.1322 [pF].

The purpose of this experiment was to implement and analyze an eight band analog vocoder with an audible output using only fixed and adjustable resistors, capacitors, operational amplifiers, BJTs, and LEDs. The design involved a modified version of a fourteen band vocoder schematic taken from a DIY project website. The operational amplifiers used were the Texas Instruments TL-074 (Qty: 18), which were chosen for their lownoise characteristic. The design requires a bi-polar power supply at ± 15 [VDC]. The total current required to run the circuit can up to 625 [mA] with all LEDs fully illuminated. Instead of soldering, the project was mounted on prototyping boards for efficiency. The noise induced by the breadboards was minimal. Our main specifications were to achieve ±5 [dB] at the center frequency for each of the eight band pass filters and ensure that no output is generated when no modulator input is received by the circuit. These specifications were met successfully and the vocoder worked as expected.

In this paper, we have proposed ultra-broadband terahertz absorber with three layers of periodic graphene disks arrays (PGDAs). A gold layer was utilized as backside reflector and TOPAS as dielectric spacers. Circuit model of PGDAs and the developed Transmission Line Model (TLM) for the absorber is utilized to design the structure using impedance matching concept. The validity of the results of the device was confirmed by Finite Element Method (FEM). The structure absorbs both TE and TM polarizations. Furthermore, the obtained normalized absorption bandwidth is 148% with a bandwidth of 2.64 THz in 1.78 THz central frequency which is to best of our knowledge the best report in two-dimensional graphene-based structures.

In this research paper, an unsophisticated configuration of the ultra-wideband THz absorber for transverse electric (TE) and transverse magnetic (TM) modes of the incident THz wave is proposed. The mentioned absorber consists of two layers of graphene disks and one kind of dielectric that is utilized for substrates. Graphene disks with periodic structure have been recently equalized to the analytical circuit model. So, this circuit model is considered for developing the equivalent transmission line model for the whole of the absorber structure. Therefore, the input impedance of the designed absorber is obtained by the equivalent transmission line theory. And also, the real part of the input impedance is approximately regulated to be matched to the free space impedance while the imaginary part of it is closely adjusted to zero around the central frequency of the THz absorber. Using only just two layers of periodic arrays of graphene disks (PAGDs) with one kind of dielectric as the ma...

In this paper, we analytically design a simple configuration of a broadband THz and polarization-insensitive absorber. The mentioned absorber consists of two layers of graphene disks, and the transmission line model is considered for the whole of the proposed absorber’s structure to design it accurately. Therefore, the input admittance of the designed absorber is obtained by the transmission line model. Also, the real part of the input admittance is approximately tuned to be matched to the free space admittance. In contrast, the imaginary part of it is closely adjusted to zero around the central frequency of the THz absorber. Using only just two layers of Periodic Arrays of Graphene Disks (PAGDs) with one kind of dielectric as the material of substrates, it causes that the absorption of the structure can be achieved higher than 90% by the Finite Element Method (FEM). Normalized bandwidth has reached up to 75.4% in 5 THz as the central frequency of the device. As the next step, we us...

Optical sensors getting widespread usage in almost every field, especially industries. A high thermal optical sensor is proposed to predict and prevent the environmental temperature in power plants. A high sensitivity, accuracy, low cost, compact size, linear operation, and suitable transmission coefficient optical sensor in a wide thermal range is achieved that changing the surrounding temperature has a severe effect on the conductivity of graphene which changes the transmission power of the sensor. In this article, the position of the graphene sheet affects the interaction of light and graphene, effectively. The Cylindrical diameter of the optical sensor is 4.1 lambda which is the smallest in size among the references checked and has the desired performance from room temperature to 2000 degrees Kelvin, indicating the suitable efficiency of the sensor and the fiber optic sensor with graphene coating has great potential in the field of measurement, especially in the temperature of t...

Stroke remains a leading cause of disability, limiting independent ambulation in survivors, and consequently affecting quality of life (QOL). Recent technological advances in neural interfacing with robotic rehabilitation devices are promising in the context of gait rehabilitation. Here, the X1, NASA's powered robotic lower limb exoskeleton, is introduced as a potential diagnostic, assistive, and therapeutic tool for stroke rehabilitation. Additionally, the feasibility of decoding lower limb joint kinematics and kinetics during walking with the X1 from scalp electroencephalographic (EEG) signals-the first step towards the development of a brain-machine interface (BMI) system to the X1 exoskeleton-is demonstrated.

We present a mobile brain-body imaging (MoBI) dataset acquired during treadmill walking in a braincomputer interface (BCI) task. The data were collected from eight healthy subjects, each having three identical trials. Each trial consisted of three conditions: standing, treadmill walking, and treadmill walking with a closed-loop BCI. During the BCI condition, subjects used their brain activity to control a virtual avatar on a screen to walk in real-time. Robust procedures were designed to record lower limb joint angles (bilateral hip, knee, and ankle) using goniometers synchronized with 60-channel scalp electroencephalography (EEG). Additionally, electrooculogram (EOG), EEG electrodes impedance, and digitized EEG channel locations were acquired to aid artifact removal and EEG dipole-source localization. This dataset is unique in that it is the first published MoBI dataset recorded during walking. It is useful in addressing several important open research questions, such as how EEG is coupled with gait cycle during closed-loop BCI, how BCI influences neural activity during walking, and how a BCI decoder may be optimized. Design Type(s) observation design • replicate design Measurement Type(s) brain activity measurement • Gait Technology Type(s) electroencephalography • goniometer Factor Type(s)

Recent mobile brain/body imaging (MoBI) techniques based on active electrode scalp electroencephalogram (EEG) allow the acquisition and real-time analysis of brain dynamics during active unrestrained motor behavior involving whole body movements such as treadmill walking, over-ground walking and other locomotive and non-locomotive tasks. Unfortunately, MoBI protocols are prone to physiological and non-physiological artifacts, including motion artifacts that may contaminate the EEG recordings. A few attempts have been made to quantify these artifacts during locomotion tasks but with inconclusive results due in part to methodological pitfalls. In this paper, we investigate the potential contributions of motion artifacts in scalp EEG during treadmill walking at three different speeds (1.5, 3.0, and 4.5 km/h) using a wireless 64 channel active EEG system and a wireless inertial sensor attached to the subject's head. The experimental setup was designed according to good measurement practices using state-of-the-art commercially available instruments, and the measurements were analyzed using Fourier analysis and wavelet coherence approaches. Contrary to prior claims, the subjects' motion did not significantly affect their EEG during treadmill walking although precaution should be taken when gait speeds approach 4.5 km/h. Overall, these findings suggest how MoBI methods may be safely deployed in neural, cognitive, and rehabilitation engineering applications.