This paper aims to analyze the vibration characteristics of functionally graded material (FGM) double layered floating raft structures under various boundary conditions. The artificial virtual spring ...technique is introduced to simulate the boundary conditions and coupling effect between the FGM plates by adjusting the spring stiffness. The spectro-geometric method is used to describe the displacement admissible function, which overcomes the discontinuity or jump phenomenon at the boundary for the conventional Fourier series. Based on the unified Rayleigh-Ritz energy framework, the dynamic equations of the FGM double layered floating raft structure are derived, and the corresponding vibration characteristics are obtained. The correctness of the presented method is verified by some numerical examples of comparisons with the calculation results obtained from the finite element method. After that, parametric analysis is carried out to investigate the effects of material parameters, geometric parameters, coupling spring stiffness, and coupling damping on the steady-state response of the FGM double layered floating raft with various boundary conditions.
Aquaponics, the integrated multi-trophic fish and plants production in quasi-closed recirculating system, is one of the newest sustainable food production systems. The hydroponic component of the AP ...directly influences water quality (in turn influencing fish growth and health), and water consumption (through evapotranspiration) of the entire system. In order to assess the role of the design and the management of the hydroponic component on the overall performance, and water consumption of the aquaponics, 122 papers published from 1979 to 2017 were reviewed. Although no unequivocal results were found, the nutrient film technique appears in several aspects less efficient than medium-based or floating raft hydroponics. The best system performance in terms of fish and plant growth, and the highest nutrient removal from water was achieved at water flow between 0.8 L min-1 and 8.0 L min-1. Data on water consumption of aquaponics are scarce, and no correlation between the ratio of hydroponic unit surface/fish tank volume and the system water loss was found. However, daily water loss was positively correlated with the hydroponic surface/fish tank volume ratio if the same experimental conditions and/or systems were compared. The plant species grown in hydroponics influenced the daily water loss in aquaponics, whereas no effect was exerted by the water flow (reciprocating flood/drain cycle or constant flow) or type (medium-based, floating or nutrient film technique) of hydroponics.
•The power transmissibility of a floating raft system was investigated.•Stop bands of periodic structures were utilized to decrease power flow.•A practical design approach for optimization of ...periodic structures was developed.•A genetic algorithm and the transfer matrix method were utilized.
This paper presented a theoretical study of the vibration control of a floating raft system using periodic structures. The band gap properties of the periodic structures, the power flow and the power transmissibility of the floating raft system were investigated by using the transfer matrix method. To minimize the power flow through periodic structures in a floating raft system, the geometrical parameters of the periodic structures were optimized by using a genetic algorithm. The numerical results demonstrated that the optimum periodic structure can provide broader stop band regions. The stop band regions of the optimum periodic structure contained all the harmonic frequencies of the force excitation in the floating raft system. The numerical results validated that the proposed optimization approach is sufficiently capable for the design of periodic structures. The proposed optimization approach has potential use for the development of vibration and shock isolation systems such as floating raft systems.
Sistem hidroponik rakit apung merupakan salah satu sistem yang biasa digunakan dalam hidroponik. Sistem ini menggunakan bak penampung dan menggenangkan tanaman dengan campuran air dan nutrisi. ...Meskipun banyaknya sistem hidroponik menggunakan rakit apung, tetapi masih kurang dalam pengendalian dan pengontrolan, untuk mengembangkan sistem ini dibutuhkan sistem kontrol penambahan nutrisi AB mix otomatis berbasis Internet Of Things (IoT). Penggunaan sistem IoT dalam hidroponik adalah untuk memudahkan dan memanipulasi hasil panen yang memuaskan dan juga memberikan kemudahan dalam penggunaan hidroponik. Tujuan dari penelitian ini adalah untuk memudahkan Penambahan sistem kontrol dan membuat petani hidroponik lebih mudah untuk mengontrol serta memonitoring nutrisi Ab mix. Sensor yang digunakan untuk mendeteksi nilai ppm dari campuran air dan nutrisi adalah sensor TDS. Sensor TDS membaca nilai ppm pada sistem hidroponik rakit apung. Pembacaan yang diberikan sensor TDS dikirim ke aplikasi blynk dengan bantuan NODEMCU. Sensor membaca data menggunakan rentang nilai ppm. Rentang nilai yang diberikan dari 600-800 ppm. Jika nilai ppm kurang dari 600 ppm maka nutrisi akan bertambah secara otomatis dengan bantuan pompa peristaltik. Nutrisi bertambah sampai dengan rentang nilai ppm yang telah diperintahkan. Data pengamatan dilakukan sekali tiga hari dari jam 08.00 WIB sampai dengan 18.00 WIB. Pada penelitian ini didapatkan perbandingan signifikan antara penggunaan IoT dalam hidroponik. Penggunaan IoT memberikan kemudahan pada hidroponik dalam memenuhi kebutuhan nutrisi apabila nutrisi yang dibutuhkan berkurang.
Acoustic black holes have good application prospects in the field of vibration and noise reduction. Based on engineering practice, this study proposes a systematic process method for the application ...of acoustic black hole structure in raft structure, which provides new ideas and references for improving the vibration isolation performance of floating raft system and reducing the level of ship vibration and noise. The influence law of each parameter on structural vibration and the recommended value range of each parameter are given, which provides support for the systematic method and process of the application of acoustic black holes in the raft structure. Then, the acoustic black hole process is applied to a floating raft system. According to the characteristics of the raft structure, an application scheme of the acoustic black hole in the raft structure is formed, and the vibration level drop of the floating raft vibration isolation system before and after the acoustic black hole is embedded, calculated, and analyzed. The changes further improve the vibration reduction and isolation performance of the raft system and effectively reduced the mechanical noise level of the ship’s cabin.
Marine floating raft aquaculture (FRA) monitoring is significant for marine ecological environment and food security assessment. Synthetic aperture radar-based monitoring is considered to be an ...effective means of FRA identification because of its capability for all-weather applications. Considering the poor generalization and extraction accuracy of traditional monitoring methods, a semantic segmentation model called D-ResUnet is proposed to extract FRA areas from Sentinel-1 images. The proposed model has a U-Net-like structure but combines the pre-trained ResNet34 as the encoder and adds dense residual units into the decoder. For this model, the final layer and cropping operation of the original U-Net model are removed to eliminate the model parameters. The mean and standard deviation of Precision, Recall, Intersection over Union (IoU), and F1 score are calculated under a five-fold training strategy to evaluate the model accuracy. The test experiments indicated that the proposed model performs well with the F1 of 92.6% and IoU of 86.24% in FRA extraction tasks. In particular, the ablation experiments and application experiments proved the effectiveness of the improvement strategy and the portability of the proposed D-ResUnet model, respectively. Compared with the other three state-of-the-art semantic segmentation models, the experiments demonstrate a clear accuracy advantage of the D-ResUnet model. For the FRA extraction task, this paper presents a promising approach that has refined extraction capability, high accuracy, and acceptable model complexity.
In view of the excellent performance of a single quasi-zero-stiffness (QZS) device in vibration attenuation, this paper presents a study on a vibration isolation floating raft system constructed with ...a double-layer QZS mechanism. A QZS device is a typical nonlinear isolator, hence the floating raft system is a coupled highly nonlinear isolation system. To understand the behaviors and its performance in vibration attenuation, an analytical approach is developed to describe the characteristics including the mathematical relationship between amplitude–frequency, force transmissibility, and the effects of the mass ratio and damping ratios on attenuation performance. The outcomes show that the two-degree-of-freedom QZS–QZS system is superior for vibration isolation when compared to the traditional linear system and the two other types of QZS systems. The effective vibration isolation frequency region of the QZS–QZS system is expanded to the low-frequency region by 72%. The QZS system is sensitive to the damping ratio, which decreases the resonance peak significantly. The mass ratio is a crucial design parameter in low-frequency vibration isolation design.
Floating raft vibration isolation (FRVI) systems employing isolators with high-static-low-dynamic stiffness (HSLDS) characteristics offer excellent large-scale and multidirectional vibration ...attenuation performance ideally suited to stealth applications in ocean faring vessels. However, the rolling motions of vessels in heavy seas can produce large displacements and induce instability in HSLDS-FRVI systems, and our present state of understanding of these systems is insufficient to facilitate the design of more stable systems. The present work addresses this issue by establishing an accurate analytical model of a double-layer FRVI system with 12 degrees of freedom to facilitate detailed rolling stability analyses when adopting HSLDS isolators. This model is also adapted to obtain a simplified single-layer HSLDS-FRVI system model and a corresponding single-layer equivalent linear system (ELS) model for investigating the factors contributing to FRVI system stability. The results demonstrate that the single-layer HSLDS-FRVI system obtains increasingly superior rolling stability compared to that of the corresponding ELS as the system loading increases. Also, good rolling stability can be maintained by applying proper mounting locations for the isolators. Additional factors contributing to FRVI system stability are deduced by comparing the results obtained for double-layer HSLDS-HSLDS, HSLDS-ELS, ELS-HSLDS, and ELS-ELS systems. The results demonstrate that the use of isolators with HSLDS characteristics is most beneficial for improving the rolling stability of double-layer FRVI systems when applied between the ground and bottom layers, and maximum rolling stability is obtained when the mass of the lower level is close to that of the upper level.
Introduction: The aim of the present study was to develop and to characterize the Floating raft system (FRS) of Amoxicillin to enhance gastric residence time and drug release to target Helicobacter ...pylori effectively. Method: In the present study, guar gum, Glyceryl Monostearate (GMS), Calcium carbonate were selected as factors. Gelation duration (h), floating lag time (min), and % Cumulative drug release (CDR) were selected as responses. 23 factorial design with replicates was selected for experimentation. Results: It was observed that Guar gum and GMS were the major factors affecting gelation duration, increase in the quantity of both Guar gum and GMS increased gelation duration i.e., sustained gelation period (24 h). Floating time increased with an increase in the amount of guar gum and calcium carbonate, whereas an increase in the quantity of GMS decreased floating time. Guar gum, calcium carbonate, and GMS exhibited an antagonistic effect on % CDR. Contour plots were used to identify design space; further numerical analysis yielded 12 best solutions based on desirability. FRS exhibited greater AUCo-t, Cmax, tmax, and t1/2 when compared to marketed formulation approximately 2.30 folds enhancement and prolongation with a sustained release for greater than 24 h that might be due to better gelation. Conclusions: It can be concluded that the floating raft system was successfully developed by the Design of experiment (DoE) application with fewer trails and by utilizing easily available excipients for better floating, gelation, and sustained delivery of the drug.
Abstract
This study was done to assess the effect of two hydroponics cultivation (media bed (MB) and floating raft (FR)) on the performance of striped snakehead fish (SSF) (
Channa striata
Bloch, ...1793) and mint (
Mentha arvensis
Linnaeus, 1953), and water quality parameters in the aquaponic system. Fish were cultured at a density of 500 fingerlings per m
3
for 130 days. Mints were planted at densities of 40 and 34 lettuce m
−2
in the MB and FR treatments, respectively, and had two cutting harvests. During the experimental period, levels of most water quality parameters analysed in the two treatments were in the optimal range for SSF and mint. After 130 days, all the growth performances and survival rates of fish in the FR treatment were higher than those in the MB treatment, but these differences were not statistically significant (
P
> 0.05). Fish growth performance was similar to those reported in other RAS and aquaponics studies, whereas FCR was lower. For mint, the plant height and diameter in the MB were significantly higher than those in the FR, but the fresh biomass in the FR was significantly greater than that in the MB (
P
< 0.05). In general, these results implied that the FR unit is more effective than the MB for culturing SSF (
C. striata
) with mint (
M. arvensis
) in aquaponics.
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