MAXIMIZING OUTPUT VOLTAGE OF A PIEZOELECTRIC ENERGY HARVESTER VIA BEAM DEFLECTION METHOD FOR LOW-FREQUENCY INPUTS

In micro-scale energy harvesting, piezoelectric (PZT) energy harvesters can adequately convert kinetic energy from ambient vibration to electrical energy. However, due to the random motion and frequency of human motion, the piezoelectric beam cannot efficiently harvest energy from ambient sources. This research highlights the ability of piezoelectric energy harvester constructed using a PZT-5H cantilever beam to generate voltage at any input frequency from human motion. An eccentric mass is used to convert the linear motion of human movement to angular motion. Then, using a magnetic plucking technique, the piezoelectric beam is deflected to its maximum possible deflection each time the eccentric mass oscillates past the beam, ensuring the highest stress is induced and hence the highest current is generated. For testing works, the frequency of oscillation of the eccentric mass is controlled using an Arduino Uno microcontroller. In this work, it is found that when given any input frequencies, the energy harvester produced a consistent AC voltage peak around 5.8 Vac. On the other hand, the DC voltage produced varies with respect to the input frequency due to the number of times the peak AC signal is generated. The highest DC voltage produced in this work is 3.7 Vdc, at 5 Hz, which is within the frequency range of human motion. This research demonstrated that energy can still be effectively harvested at any given low-frequency input, in the condition that the piezoelectric beam is being deflected at its maximum. ABSTRAK: Piezoelektrik dapat mengubah tenaga kinetik daripada getaran persekitaran kepada tenaga elektrik melalui penjanaan tenaga berskala mikro. Namun, PZT tidak dapat menjana tenaga dengan berkesan dari sumber persekitaran kerana pergerakan dan kekerapan pergerakan manusia adalah rawak. Kajian ini adalah mengenai keupayaan penuai tenaga piezoelektrik menggunakan bilah kantilever PZT-5H bagi menjana voltan pada sebarang frekuensi menerusi gerakan manusia. Jisim eksentrik digunakan bagi menukar gerakan linear manusia kepada gerakan putaran. Kemudian, teknik penjanaan piezoelektrik secara magnetik digunakan bagi memesongkan bilah piezoelektrik ke tahap maksimum. Bagi memastikan tenaga tertinggi dihasilkan, jisim eksentrik perlu berayun melepasi bilah PZT. Ayunan frekuensi jisim eksentrik ini dikawal melalui kawalan mikro Arduino Uno. Dapatan kajian menunjukkan bagi setiap frekuensi input, PZT ini dapat menghasilkan voltan AC yang konsisten, iaitu sekitar 5.8 Vac. Namun, voltan DC maksimum yang terhasil adalah berbeza-beza bagi setiap frekuensi input, iaitu berdasarkan bilangan kekerapan maksimum isyarat AC yang terhasil. Voltan DC tertinggi ialah 3.7 Vdc, pada 5 Hz, iaitu pada kadar frekuensi gerakan manusia. Ini menunjukkan bahawa tenaga masih dapat dihasilkan secara berkesan pada frekuensi rendah, dengan syarat bilah piezoelektrik terpesong pada tahap maksimum.

The investigation on the AC to DC voltage multiplier

This paper investigates the topic of voltage multiplication, which converts a low AC voltage source to a high DC voltage source. Several designs are evaluated, such as the voltage doubler, the voltage tripler, and the voltage quadrupler. It is discovered that the input frequency and the capacitance do not affect the output voltage. This design can be extended to any integer multiples of the input voltage.

Fuzzy Lexical Representations in Adult Second Language Speakers

We propose the fuzzy lexical representations (FLRs) hypothesis that regards fuzziness as a core property of nonnative (L2) lexical representations (LRs). Fuzziness refers to imprecise encoding at different levels of LRs and interacts with input frequency during lexical processing and learning in adult L2 speakers. The FLR hypothesis primarily focuses on the encoding of spoken L2 words. We discuss the causes of fuzzy encoding of phonological form and meaning as well as fuzzy form-meaning mappings and the consequences of fuzzy encoding for word storage and retrieval. A central factor contributing to the fuzziness of L2 LRs is the fact that the L2 lexicon is acquired when the L1 lexicon is already in place. There are two immediate consequences of such sequential learning. First, L2 phonological categorization difficulties lead to fuzzy phonological form encoding. Second, the acquisition of L2 word forms subsequently to their meanings, which had already been acquired together with the L1 word forms, leads to weak L2 form-meaning mappings. The FLR hypothesis accounts for a range of phenomena observed in L2 lexical processing, including lexical confusions, slow lexical access, retrieval of incorrect lexical entries, weak lexical competition, reliance on sublexical rather than lexical heuristics in word recognition, the precedence of word form over meaning, and the prominence of detailed, even if imprecisely encoded, information about LRs in episodic memory. The main claim of the FLR hypothesis – that the quality of lexical encoding is a product of a complex interplay between fuzziness and input frequency – can contribute to increasing the efficiency of the existing models of LRs and lexical access.

Some puzzling findings regarding the acquisition of verbs

On the whole, children acquire frequent words earlier than less frequent words. However, there are other factors at play, such as an early "noun bias" (relative to input frequency, toddlers learn nouns faster than verbs) and a "content-word bias" (content words are acquired disproportionately to function words). This paper follows up reports of a puzzling phenomenon within verb-learning, where "experiencer-object" emotion verbs (A frightened/angered/delighted B) are lower frequency but learned earlier than "experiencer-subject" emotion verbs (A feared/hated/loved B). In addition to the possibility that the aforementioned results are a fluke or due to some confound, prior work has suggested several possible explanations: experiencer-object ("frighten-type") verbs have higher type frequency, encode a causal agent as the sentential subject, and perhaps describe a more salient perspective on the described event. In three experiments, we cast doubt on all three possible explanations. The first experiment replicates and extends the prior findings regarding emotion verbs, ruling out several possible confounds and concerns. The second and third experiments investigate acquisition of chase/flee verbs and give/get verbs, which reveal surprising findings that are not explained by the aforementioned hypotheses. We conclude that these findings indicate a significant hole in our theories of language learning, and that the path forward likely requires a great deal more empirical investigation of the order of acquisition of verbs.

Transcranial magnetic stimulation entrains alpha oscillatory activity in occipital cortex

Parieto-occipital alpha rhythms (8–12 Hz) underlie cortical excitability and influence visual performance. Whether the synchrony of intrinsic alpha rhythms in the occipital cortex can be entrained by transcranial magnetic stimulation (TMS) is an open question. We applied 4-pulse, 10-Hz rhythmic TMS to entrain intrinsic alpha oscillators targeting right V1/V2, and tested four predictions with concurrent electroencephalogram (EEG): (1) progressive enhancement of entrainment across time windows, (2) output frequency specificity, (3) dependence on the intrinsic oscillation phase, and (4) input frequency specificity to individual alpha frequency (IAF) in the neural signatures. Two control conditions with an equal number of pulses and duration were arrhythmic-active and rhythmic-sham stimulation. The results confirmed the first three predictions. Rhythmic TMS bursts significantly entrained local neural activity. Near the stimulation site, evoked oscillation amplitude and inter-trial phase coherence (ITPC) were increased for 2 and 3 cycles, respectively, after the last TMS pulse. Critically, ITPC following entrainment positively correlated with IAF rather than with the degree of similarity between IAF and the input frequency (10 Hz). Thus, we entrained alpha-band activity in occipital cortex for ~ 3 cycles (~ 300 ms), and IAF predicts the strength of entrained occipital alpha phase synchrony indexed by ITPC.

Non-volatile artificial synapse based on a vortex nano-oscillator

In this work, a new mechanism to combine a non-volatile behaviour with the spin diode detection of a vortex-based spin torque nano-oscillator (STVO) is presented. Experimentally, it is observed that the spin diode response of the oscillator depends on the vortex chirality. Consequently, fixing the frequency of the incoming signal and switching the vortex chirality results in a different rectified voltage. In this way, the chirality can be deterministically controlled via the application of electrical signals injected locally in the device, resulting in a non-volatile control of the output voltage for a given input frequency. Micromagnetic simulations corroborate the experimental results and show the main contribution of the Oersted field created by the input RF current density in defining two distinct spin diode detections for different chiralities. By using two non-identical STVOs, we show how these devices can be used as programmable non-volatile synapses in artificial neural networks.

Analisis Pengaruh Sudut Penyalaan TRIAC terhadap Pengaturan Kecepatan Motor Induksi Satu Fasa Menggunakan Cycloconverter

ABSTRACTA single-phase induction motor is one type of electric motor that is most widely used in everyday’s life, especially for running small loads. The application of this single phase induction motor is not only in households but also in shops, shopping centers, and industry. In its operation, single-phase induction motors can be operated with constant speed and variable speed. The operation of a single-phase induction motor at a constant speed can be done by inputting the nominal voltage and frequency of the motor. Meanwhile, the operation of a single-phase induction motor with varying speeds can be done by adjusting the input frequency of the motor. In this study, an induction motor speed control was carried out using a cycloconverter to regulate the speed of a single-phase induction motor by changing the input frequency of the motor into three variations, namely f / 1, f / 2 and f / 3 at the base frequency of 50 Hz. The cycloconverter switching was designed using TRIAC and then a study was carried out on the effect of the TRIAC’s firing angle on the speed, voltage and output power of the motor by varying firing angles by 0?, 30?, 45?, 60? and 90?. The result show, it is found that increasing the firing angle, the motor output voltage decrease, the motor output power also decrease, except at the angle of 60 ? rises then at the angle of 90 decrease again, while the motor speed increases at the same frequency. Keyword: cycloconverter, firing angle, TRIAC.