Harvest Frequency Research Articles

Pola Tanam Tumpang Sari di Desa Satar Punda Barat, Kabupaten Manggarai Timur, Provinsi Nusa Tenggara Timur


 West Satar Punda Village has horticultural farming potential that needs to be developed because it has fertile land, however most farmers are only familiar with monoculture farming system. They are not familiar with the polyculture farming system, thus farmers' income depends only on one type of crop during harvest season. The advantages of polyculture farming system are it can be planted two or more types of plants on the same land and the frequency of harvest is more than once. The purpose of this program is to introduce intercropping pattern (polyculture) by optimizing land by growing more than one type of plants (tomatoes and red chili) and increasing the welfare of farmers with the nearly simultanuous harvest time of the two types of plants. The method used were extension techniques and demonstration method in a plot of sample land. The results of the program show positive responses and increased knowledge about intercropping pattern of the members of farmers group, and also increases farmer's income.

In-situ identification of shaking frequency for adaptive vibratory fruit harvesting

The improvement of the fruit removal efficiency is important in vibratory fruit harvesting. Most relevant research has focused on the detection of dynamic parameters of the tree system by conducting experiments or simulations. The present study proposes a method of identifying multiple natural frequencies of a fruit tree in-situ during vibratory harvesting. An intelligent shaker system consisting of an eccentric shaker with adjustable speed and an acceleration signal acquisition analyzer is developed. A frequency sweeping experiment using the intelligent shaker system is carried out to measure natural frequencies by searching for extreme values of the acceleration signals. Additionally, a testing experiment for measuring acceleration responses at different shaking frequencies is performed to obtain the optimal shaking frequencies. The experiments show that the natural frequencies could be obtained effectively by the frequency sweeping experiment in-situ, and the identified natural frequencies of different branches are found to be different. All results indicate that the identified natural frequencies using the proposed method can be regarded as the optimal shaking frequencies for adaptive vibratory fruit harvesting, and that it is necessary to detect the natural frequency of each large branch of a tree during vibratory fruit harvesting.

Lowering the resonance frequency of a two-dimensional high-power piezoelectric energy harvester with reducing the stiffness of the harvester

Generating more power in lower frequencies is one of the most challenging purposes in designing cantilever beam energy harvesters. Using geometrically symmetric two-dimensional beam shapes is one of the most effective ways that has been proposed to increase the output power of harvesters. With symmetry in the geometry, torsional forces on piezoelectric elements eliminate. Consequently, the output power of the harvester increases. However, the resonance frequency of these designed harvesters is still high for some applications. In this work, we demonstrate a strategy to decrease the stiffness of a two-dimensional harvester named Elephant type, without changing in its output power. The output power and the resonance frequency of our proposed harvester are calculated using a finite element simulation. The finite element model is in a good agreement with the analytical and experimental data for the Elephant type harvester. The finite element model predicts lower resonance frequency for our model compared to Elephant type, without a major drop in the output power. Finally, we propose a dimensionless parameter to evaluate the performance of piezoelectric harvesters which have a direct relation with the output power and an inverse relation with the resonance frequency of the harvester.

System-Level Model and Simulation of a Frequency-Tunable Vibration Energy Harvester.

In this paper, we present a macroscale multiresonant vibration-based energy harvester. The device features frequency tunability through magnetostatic actuation on the resonator. The magnetic tuning scheme uses external magnets on linear stages. The system-level model demonstrates autonomous adaptation of resonance frequency to the dominant ambient frequencies. The harvester is designed such that its two fundamental modes appear in the range of (50,100) Hz which is a typical frequency range for vibrations found in industrial applications. The dual-frequency characteristics of the proposed design together with the frequency agility result in an increased operative harvesting frequency range. In order to allow a time-efficient simulation of the model, a reduced order model has been derived from a finite element model. A tuning control algorithm based on maximum-voltage tracking has been implemented in the model. The device was characterized experimentally to deliver a power output of 500 µW at an excitation level of 0.5 g at the respected frequencies of 63.3 and 76.4 Hz. In a design optimization effort, an improved geometry has been derived. It yields more close resonance frequencies and optimized performance.

Alopecia Risk and the Thickness, Number, and Frequency of Scalp Skin Harvests.

The aim of this study was to elucidate the relationships between the thickness, number, and frequency of scalp skin harvests and alopecia risk.In a PubMed search, the search terms (scalp AND graft AND alopecia) were used, resulting in 148 papers. Among 21 abstracts, 11 full papers were reviewed, and 3 papers were ultimately analyzed.The donor-site alopecia rate was significantly higher in patients who experienced hair growth on their grafts than in those who did not (odds ratio = 10.875, 95% confidence interval, 2.677-44.178; P < 0.001). The depth of the infundibulum can be estimated to be 451.8 μm at 5 years of age, 528.8 μm at 10 years, 605.8 μm at 15 years, and 682.8 μm at 20 years. Therefore, the limits of safe thickness for graft harvesting from the scalp are <18/1000 inches for 5-year olds, 21/1000 inches for 10-year olds, 24/1000 inches for 15-year olds, and 27/1000 inches for 20-year olds. The safe number of harvests (intersection of the alopecia and nonalopecia groups) was 2.7, and the safer number of harvests (limits of 2 standard deviations of the alopecia group) was 1.0. The safe time interval between harvests was 14.0 days, and the safer time interval between harvests was 15.6 days. The safe single minimal interval (SMI) between harvests was 12.7 days, and the safer SMI was 13.7 days.Since the safe thickness for graft harvesting from scalps exceeds the thickness in usual practice, following the safer SMI between harvests (13.7 days) is expected to be more important for minimizing alopecia risk.

Effect of seismic mass thickness on the resonance frequency of cantilever type piezoelectric energy harvester

Piezoelectric energy harvesters find applicability in remote area of application because of simple design and operation. Micro-electromechanical system (MEMS) process technology is utilized to fabricate these cantilever based structures. Piezoelectric layer length and thickness are the key parameters for controlling the resonance frequency. However, for further lowering the resonance frequency and having optimal output a seismic mass is introduced at the tip of the cantilever structure. In this paper, the effect of increasing the thickness of the seismic mass on the resonance frequency of the cantilever structure has been investigated. Finite Element Method (FEM) results have been obtained using Coventorware software by varying the thickness of the seismic mass 10–20 µm. It has been observed the variation of the thickness of the seismic mass has an effect on the resonance frequency of the cantilever. As the thickness increases, the volume of the seismic mass increases and the resonance frequency of the cantilever decreases. The base of the cantilever is Silicon; Aluminum Nitride (AlN) piezoelectric material has been selected of 3 µm thickness. The length of the silicon cantilever is varied from 1600 to 2500 µm and the resonance frequency is obtained. At a length of 1600 µm, variation of seismic mass thickness from 10 to 15 µm results in reduction in resonance frequency by 17.27% whereas when seismic mass is varied from 15 to 20 µm the resonance frequency is reduced by 12.63%.

Fast-Convergence Self-Adjusting SECE Circuit With Tunable Short-Circuit Duration Exhibiting 368% Bandwidth Improvement

The harvesting frequency bandwidth (HBW) of a resonant-based electromechanical harvester is inherently limited by its quality factor. Electrical tuning of the resonant frequency leveraged by a significant electromechanical coupling is a promising approach to enhance the HBW and paves the way toward industrialization of robust vibration energy harvesting system. However, it remains challenging to design a self-powered harvesting IC that includes self-tuning capabilities, especially at low vibration amplitude. This letter describes the shorted synchronous electrical charge extraction (SSECE) strategy and proposes a dedicated self-powered integrated circuit, including power stage, sensors to sequence the harvesting phases, and power sensing. An on-chip tracker dynamically maximizes the harvesting power when the piezoelectric-based harvester characteristics or excitation frequency shifts. The experimental results show a 368% HBW enlargement with the highest convergence FoM (0.213) and the lowest power-peak frequency compared to the prior art.

Mechanical-spring model on ZnO submicron rods for a steady response on vertically integrated nanogenerators at multiple harvesting frequencies

We have studied the uniaxial compression of ZnO submicron rods grown hydrothermally over Si/Cr/Au and Si/Al substrates such as mechanical springs. We used FEM simulations to find the oscillation frequency range at which the submicron rods deliver the steadiest piezopotential independently of the frequency they oscillate. A stationary and a harmonic spring-mass model were implemented for a single and multiple submicron rods. We measured dimensions and submicron rods/μm2 with our SEM/FIB image analysis. Nanoindentation was used to extract the spring constant and the Young's Modulus of the submicron rods. The steadiest piezopotentials (±3.72, ±5.16 μV) were obtained below 500 kHz. The methodology described can be helpful to design multi-frequency nanogerators.

Cacao agroforestry systems do not increase pest and disease incidence compared with monocultures under good cultural management practices

Pests and diseases threaten cacao production worldwide. Agroforestry systems are traditionally seen by farmers as one of the causes of increased pest and disease incidence, in contrast with full-sun monocultures. Cultural management practices—e.g. regular tree pruning, frequent pod harvest, regular removal of infested pods, weed management—have been reported to be crucial for pest and disease management. We performed two experiments for the purpose of assessing the effect of (i) different cacao production systems, and (ii) the frequency of harvest and removal of infested pods on the incidence of pests and diseases and on the cacao yield. The first experiment was performed in a long-term system comparison trial in Bolivia, where data on pest and disease incidence were recorded for three years in five production systems: two monocultures and two agroforestry system under organic and conventional farming, and one successional agroforestry system, i.e. a high tree density multi-strata system. Pest and disease management did not differ between systems and relied on cultural management practices. Overall, the incidence of pests and diseases did not differ between production systems, which indicated they were not the driver of yield differences between them. Across production systems, only 14% of the pods were affected by pests and diseases; 70% of these were affected by frosty pod rot. More than 80% of the pods infected by frosty pod rot were removed before the sporulation phase. In the second experiment, the effects of the frequency of harvest and removal of infected pods—every 15 days versus every 25 days—on pest and disease incidence and yield were tested in four farmers’ fields. Fortnightly harvest and diseased pod removal significantly decreased disease incidence and increased cacao yield, by 25% and 46% respectively. Our results show that cacao agroforestry systems do not increase pest and disease incidence compared with monocultures when good cultural management practices are implemented, which, in turn, can increase the productivity of the cacao plantations.

A Triple-Band High-Gain Multibeam Ambient RF Energy Harvesting System Utilizing Hybrid Combining

Overcoming the challenge of battery recharging and replacement in industry Internet-of-Things (IoT) applications is considered by proposing the design of a triple-band high-gain multibeam ambient radio frequency (RF) energy harvesting system utilizing hybrid combining. The novelty of the design is that it simultaneously exploits frequency, space, and polarization to maximize the harvested RF energy. Wideband hybrid combining is proposed, which enables the harvesting of energy at low RF power densities while maintaining the wide frequency and space coverage necessary for ambient RF energy harvesting. The antenna design consisting of 16-ports has an average area per port of 0.3λ × 0.3λ (where λ is the freespace wavelength at 1.8 GHz) and is demonstrated to achieve a wide relative bandwidth of 38.5% covering the GSM-1800, UMTS-2100, and WiFi frequency bands. Hybrid combining of the 16-port antenna provides multiple antenna beams each with up to 11 dBi antenna gain and these provide broad beam coverage. The design for the rectifiers, using multistub impedance matching, is also provided and these are shown to be efficient over the frequency bands of interest. Measurements in an anechoic chamber demonstrate that the proposed energy harvesting system can provide an output dc voltage of more than 755 mV, an output dc power of more than -6.4 dBm and RF-to-dc efficiencies greater than 40% when the power density is more than 1400 μW/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . It is also shown that the proposed system can provide output dc power of 80 μW and 7.3 μW in real outdoor and indoor ambient environments, respectively.

Phagocytosis activity of three sulfated polysaccharides purified from a marine diatom cultured in a semi-continuous system

An efficient process has been developed for bioactive polysaccharide production and purification from a local diatom isolate, Halamphora sp. AQ4. First, a semi-continuous system with fixed harvesting frequency was employed to cultivate AQ4 for the production of cell mass and polysaccharides for more than 285 days with a high yield of biomass. Six cultivation sets are performed according to different harvesting volumes per 3 days with or without Na2CO3 supplement. The addition of Na2CO3 increases both cell mass and polysaccharide production. Furthermore, three different sulfated polysaccharides (PK1~PK3) were purified from the freshly-grown AQ4 diatoms following anion-exchange chromatography. Among them, polysaccharide PK3 not only has a high content of fucose and uronic acid, but also has a strong activity to stimulate murine macrophage cells and increase their phagocytosis rate up to 170%. This study demonstrates that diatom AQ4 is an important bioresource for the production of bioactive polysaccharides.

A new design to improve bandwidth of piezoelectric energy harvester

This study proposed a unique wideband energy harvester with a spiral metal plate design which has the potential to harvest vibrational energy over a broad range of ambient frequencies. In this design, metal shim with various length was integrated with piezoceramic rings in a spiral form as the cochlea. Spiral form metal shims with various radius leaves were integrated with piezoelectric ceramic. Each metal leaves has its resonance frequency that is slightly different than its neighboring ones. Parametric studies such as split structure, the radius of the metal shim, brass thickness, and tip mass and clamped area were performed to investigate the energy harvester structure. From the results, the buzzer form energy harvesting unit is designed to split leaf form, resonance frequency shifts to lower frequency. In split structure design for various leaf radius, every leaf keeps their resonance frequencies. This designed structure was resonated on the broader frequency range. Radius difference for neighbor leaves provided wider effective energy harvesting frequency range. Thicker brass shim led to higher stress on piezoelectric ceramic, more significant peak to peak output voltage at own resonance frequency.

Solar Panels as Tip Masses in Low Frequency Vibration Harvesters

Tip masses are used in cantilevered piezoelectric energy harvesters to shift device resonance towards the required frequency for harvesting and to improve the electric power generation. Tip masses are typically in the form of concentrated passive weights. The aim of this study is to assess the inclusion of solar panels as active tip masses on the dynamics and power generation performance of cantilevered PVDF (polyvinylidene fluoride)-based vibration energy harvesters. Four different harvester geometries with and without solar panels are realized using off-the-shelf components. Our experimental results show that the flexible solar panels considered in this study are capable of reducing resonance frequency by up to 14% and increasing the PVDF power generated by up to 54%. Two analytical models are developed to investigate this concept; employing both an equivalent concentrated tip mass to represent the case of flexible solar panels and a distributed tip mass to represent rigid panels. Good prediction agreement with experimental results is achieved with an average error in peak power of less than 5% for the cases considered. The models are also used to identify optimum tip mass configurations. For the flexible solar panel model, it is found that the highest PVDF power output is produced when the length of solar panels is two thirds of the total length. On the other hand, results from the rigid solar panel model show that the optimum length of solar panels increases with the relative tip mass ratio, approaching an asymptotic value of half of the total length as the relative tip mass ratio increases significantly.

Rendimiento, perfiles nutrimental y de fermentación ruminal in vitro de pasto maralfalfa (Cenchrus purpureus Schumach.) Morrone a diferentes frecuencias de corte en clima cálido

El objetivo de este estudio fue evaluar el rendimiento, los perfiles nutrimental y de fermentación ruminal in vitro del pasto maralfalfa (Cenchrus purpureus Schumach.) Morrone, a cuatro frecuencias de corte. Los tratamientos se distribuyeron en bloques al azar en parcelas divididas con tres repeticiones. Los datos se analizaron en modelo lineal generalizado (GLM, por sus siglas en inglés) con el paquete estadístico de Statistical Analysis Software (SAS) y las medias se compararon con Tukey. El mayor rendimiento de biomasa (20.2 Mg MS ha-1), fibra detergente neutro (FDN) (66.7%), celulosa (CL) (45.4%), energía (16.3 MJ kg-1 MS) y dióxido de carbono (CO2) (89.7%) se obtuvo en la frecuencia de corte a cada 120 días (p &lt; 0.05). El contenido de proteína cruda (PC) (9.3%), hemicelulosa (HC) (17.6%), cenizas (11.7%), humedad (8.4%) y lignina detergente ácido (LDA) (4.7%), ácido acético (77.8%), propiónico (29.4%), butírico (12.6%), CH4 (11.9%) y la Digestibilidad de la materia seca (DivMS) (55.6%), fue más elevado en la frecuencia de corte a 30 días (p &lt; 0.05). El contenido de extracto etéreo (EE) (1.8%, p &lt; 0.05) fue mayor en la frecuencia de corte al día 90. El pasto maralfalfa tiene una mejor composición química y mayor contenido de ácidos grasos volátiles (AGV) en etapas tempranas de corte.

Effects of seed bed types and weed control methods on the vegetative parameters of long cayenne pepper (Capsicum frutesens L)

Effects of seed bed types and weed control methods on the vegetative parameters of long cayenne pepper (Capsicum frutesens L)

Novel tunable broadband piezoelectric harvesters for ultralow-frequency bridge vibration energy harvesting

With a nonlinear X-shaped structure connected with piezoelectric harvesters through two types of special mounting configurations (horizontal and vertical cases), novel coupled vibration energy harvesting systems are purposely constructed and investigated for exploiting nonlinearity and structural coupling effect in vibration energy harvesting. Different from concentrating on a beam harvester itself in the literature (i.e. the beneficial nonlinearity comes from the beam itself), this study focuses on exploring the nonlinear benefits that the X-shaped structure could provide, together with structural coupling effect. The novelty lies in that the coupled X-structured harvesting systems have both the advantages of the existing simple cantilevered beam harvester (harvesting power only at around the natural frequency of the beam) and the spring-mass system supported beam harvester (harvesting energy only at around the natural frequency of the supporting spring-mass system). With the proposed X-structures, the effective operation bandwidth of traditional cantilever based harvesters can be greatly enlarged and also be extended to an ultralow frequency range. This is a very special feature of the proposed X-structure based harvesting systems compared with conventionally designed cantilevered harvesters or the spring-mass supported cantilevered harvesters. The proposed devices can be regarded as advantageous versions of the cantilever-based configurations for ultralow frequency range. In addition, the X-structured harvesters can achieve very tunable harvesting bandwidth (i.e. tuning the harvesting frequency of the first peak) by adjusting several structural parameters. The experiment tests demonstrate that the proposed harvesting devices hold potentials for traffic-induced bridge vibration energy harvesting, which can be used for powering the sensors for bridge health monitoring.

A decadal multi-site study of the effects of frequency and season of harvest on biomass production from mallee eucalypts

Mallee eucalypts are hardy, woody perennials that are being developed as a short-rotation coppice crop in Australia for the production of eucalyptus oil, biofuels and other biomass products. The economic viability of this prospective crop is dependent on its ability to survive and regenerate following repeated harvesting of the above ground component. Here we report on survival and biomass yield of mallee belt plantings of Eucalyptus polybractea, E. loxophleba ssp lissophloia and E. kochii ssp plenissima, at 19 sites, under two harvest-frequencies (3–8 year cycles) and harvest seasons (autumn or spring) over a decade from 2006 to 2015. 16 sites had post-harvest mortality ranging from 1.0% to 12.2% while the remaining three sites with either shallow saline water tables or a silcrete hardpan failed. Average site dry biomass yield across treatments ranged from 2.2 to 32.8 Mg ha−1 yr−1. Higher yielding sites were generally characterised by pH between 3.8 and 8, ECe below 15.0 dS m−1 and high soil fertility. Lower yielding sites were generally near saline valley floors. After 7-years, biomass yield from unharvested treatments exceeded the average cumulative yield of harvest treatments at eight of the 16 sites, including all three E. kochii sites. For E. loxophleba, significant interactions were found between season and frequency of harvest with highest yields in long rotation spring treatments. There were also interactions between site and frequency of harvest, which were mainly driven by the variable performance of the uncut treatment. On average E. loxophleba yielded more biomass following spring harvests whereas E. kochii yielded more following autumn harvests. E. polybractea yield was unaffected by season or frequency of harvest; however, harvest treatments yielded more biomass than uncut treatments. After 10 years, at eight of the nine sites subjected to three 3-year cycles, no decline in biomass yield was observed. The site that declined in production was attributed to depletion of a sandplain aquifer by extensive mallee plantings. Overall, the results from this decadal study indicate that in warm-temperate semi-arid areas, such as the south-west of WA, mallees biomass can be harvested sustainably at most sites even in short (3-year) rotation cycles.

Efficient acoustic energy harvesting by deploying magnetic restoring force

Acoustic piezoelectric energy harvesters in quarter-wavelength resonator tubes undergo linear resonant vibration due to the external force. However, the variation of environmental conditions, such as temperature, directly alters the speed of sound in air, which in turn changes the tube resonance frequencies. This discrepancy between the tube acoustic and harvester resonance frequencies leads to reduced power generation. This paper proposes the addition of a nonlinear restoring force onto an acoustic cantilever beam piezoelectric energy harvester to tune and broaden the resonance bandwidth. The restoring force is applied by the attachment of permanent magnets at the beam tip and two external magnets. First, the nonlinear distributed parameter model of the bimorph is provided. Then, the associated dimensionless lumped-parameter model, including the magnetically coupled equations, is developed. To study the system response, an approximate-analytical solution based on the harmonic balance method is constructed. Initially, the variations of the speed of sound, and subsequently the tube resonance frequency, versus temperature, based on real statistical data, are studied. Furthermore, the effects of two scenarios of hardening and softening magnetic restoring forces are investigated. The results show that, at relatively low sound pressure levels (SPLs), the restoring forces can improve the efficiency by tuning the resonance frequency of the energy harvester. As the SPL increases, the force of the additional magnets tunes the natural frequency and broadens the resonance region. Finally, it is observed that the added magnets can change the optimum time constant ratio.

Wideband PZT energy harvesting from the wake of a bluff body in varying flow speeds

Wake-galloping flow energy harvesters vibrate linearly under fluid force which results in a narrow lock-in region. Hence, their efficiency drops significantly in variable flow speeds leading to inevitable discrepancies between the natural frequency of the energy harvester and vortex shedding frequency. This sensitive dependence on the flow speed hinders the performance of this type of energy harvesters. This paper present a novel design of a PZT energy harvester for capturing energy from a broad range of vortex shedding frequencies associated with varying wind speeds. The proposed system composed of an array of bimorphs placed in the downstream of a bluff body. First, the nonlinear partial differential equations (PDEs) governing the dynamics of aero-electromechanical system are obtained based on Euler-Bernoulli assumption and nonlinear curvature effects. Next, the ordinary forms (ODEs) of the PDEs are attained using a Galerkin's Schemes. Moreover, they are non-dimensionalized to generalize the results and analyses; a convergence analysis has been carried out to find the minimum number of modes required to the precise prediction of the response. Exploiting harmonic balance method (HBM), the approximate-analytical solutions of the ODEs are provided. Afterward, the effects of various properties of the proposed ensemble on the lock-in region are investigated. In addition, the efficiency of the energy harvester is assessed toward examining its optimal power and conversion factor. The results disclose that the proposed system has a wider lock-in region and larger conversion factor, compared to the typical wake-galloping energy harvesters. Hence, the superior performance of the proposed design is confirmed.

Biomass yield and energy efficiency of willow depending on cultivar, harvesting frequency and planting density

The study aimed at comparing the yield of dry biomass and energy efficiency of 22 willow cultivars depending on the harvesting frequency and variable plant density. The field experiment was established in 2010. The willow cultivars were planted in two densities; 13 300 and 32 500 plants per ha. Among the compared cultivars in the second year (2013) of full production, high yield of dry matter was obtained from cvs. Tordis (33.1 t/ha/year), Inger (30.4 t/ha/year) and Klara (29.0 t/ha/year). After six years of cultivation, the highest aboveground dry matter was given by cvs. Tora (27.4 t/ha/year) and Tordis (27.0 t/ha/year). The gross calorific value of willow biomass ranged from 15.2–20.1 GJ/t dry weight. Greater energy efficiency (329.3 GJ/ha/year) occurred in willow cultivars collected in a two-year cycle than in the one-year cycle (286.4 GJ/ha/year). In the two-year cycle collected in the third year after planting, energy efficiency was greater (379.5 GJ/ha/year) than in the two-year cycle harvested in the sixth year after planting (279.15 GJ/ha/year). The initial slower growth of biomass does not determine plant yielding.