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In a previous paper, a cost-efficient modal analysis method for the vibration of a floating roof coupled with nonlinear sloshing in a circular cylindrical oil storage tank is presented. This method is extended to the case in which the out-of-plane deformation of the roof-deck caused by the radial second mode of sloshing induces an elliptical deformation of the pontoon around the deck. First, the radial contraction of the deck is calculated from the slope of the out-of-plane deformation of the deck, and the following two points are confirmed: (i) the circumferential variation in this radial contraction results in the elliptical deformation of the pontoon, and (ii) the present theoretical prediction for the radial contraction is in good agreement with a numerical result obtained by LS-DYNA. Based on these points, the stresses arising in the pontoon are calculated by considering the contraction of the deck as an enforced displacement of the pontoon. Numerical results show that (a) the elliptical deformation of the pontoon causes a large circumferential in-plane stress, (b) reduction achieved by the increase in the thickness of the deck is larger for the radial contraction of the deck and the stresses in the pontoon than for the out-of-plane deformation of the deck, and (c) the radial contraction of the deck for a fixed value of the out-of-plane deformation of the deck increases with the decrease in the radius of the deck. [DOI: 10.1115/1.3148083]

Internal resonance in the vibration of a floating roof coupled with nonlinear sloshing in a circular cylindrical oil storage tank is investigated. The nonlinear system exhibits internal resonance when nonlinear terms of the governing equation have a dominant frequency close to a certain modal frequency of the system. Numerical results show that when internal resonance occurs, the responses of stresses in a floating roof exhibit a long-duration period of large amplitude despite a short duration of the earthquake excitation applied to the tank. Due to the presence of internal resonance, the underestimation of the stresses associated with the use of the linear theory becomes more marked, and thus the importance of nonlinearity of sloshing in the stress estimation is accentuated. It is illustrated that the magnitudes of the stresses increase with the increase in the liquid-filling level, and that the effect of internal resonance on the stresses noted in the case of sinusoidal excitation appears under real earthquake excitation. A method for reducing the stresses is proposed. [DOI: 10.1115/1.3173768]

A method of actively stabilizing a hybrid vibration absorber driven by a force proportional to the velocity detected at the attachment position of the absorber is investigated. This method can be applied to improve model-independence of robust performance while allowing for multimode controllability for the case where a hybrid vibration absorber is desired as an actuator. Robustness not only against variations in a primary structure to be controlled but also against parameter identification errors in a vibration absorber system is discussed. It is illustrated that although this method transforms the hybrid absorber equation with a spring term into the full active absorber equation, the important advantage of a hybrid absorber over a full active absorber, that is, the power-saving effect near the first resonant frequency of a primary structure can be retained. Application examples are presented also for the vibration isolation and active noise control problems. DOI: 10.2514/1.17273

A mechanical model for low-gravity sloshing in an axisymmetric tank is developed using a newly developed slosh analysis method. In this method, spherical coordinates, whose origin is at the top of the cone that is tangent to the tank at the contact line of the meniscus with the tank wall, are used to analytically determine the characteristic functions for an arbitrary axisymmetric tank for which it is customary to resort to numerical methods. By this means, fast and cost-efficient computation can be conducted. Parameters of the mechanical model are determined such that the frequency responses of the resultant force and moment to lateral excitation coincide with those of the actual sloshing system. Influences of the Bond number and the liquid-filling level on the parameters of the mechanical model are examined.

An analytical method is applied to predict the acoustic attenuation performance of expansion chambers with continuously varying cross-sectional area. A feature of the present method is the use of spherical coordinates whose origin is at the top of the cone that is tangent to the wall of the expansion chamber. By this means, the characteristic functions can be analytically determined despite the non-uniform geometry of the expansion chamber. Using the Galerkin method, a variational principle is transformed into linear algebraic equations that are solved to determine the transmission coefficient of the expansion chamber. Numerical results are provided for the case where broadband noise attenuation is achieved. [DOI: 10.1115/1.1687400]

The study uses spherical coordinates and modal analysis to model functional characteristics of an arbitrary axisymmetrical container subjected to axial excitation and analyze the low-gravity propellant sloshing. Data indicate that surface tension parameter is important in estimating the magnitude of the liquid surface oscillation.

For wave-absorbing control, the ideal controller transfer function H(s), which connects the sensor output to the control force, contains the imaginary unit i = (mathematical expression not reproducible in ASCII)- 1 explicitly. Therefore, H(s) cannot be implemented directly by convolution integration of the sensor output with the inverse Laplace transform of H(s). In this paper, this problem is solved by imposing the synchronization condition on the bases of H(s). The condition requires that the instantaneous frequencies of the control force and the incident wave be the same. In other words, the instantaneous frequency of the control force varies with time in synchronization with the frequency components of the wave that are arriving at the wave-absorbing point with different group velocities. Therefore, the condition is referred to as the synchronization condition in this paper. The solution method is applicable to various combinations of sensor and actuator. Experimental verification is presented for a simulated case. The parameters of the digital algorithm for the experiment are determined analytically by using a complex error function and a generating function expansion of the Bessel function.

A new computation scheme is presented for the response analysis of flexible frame structures with time-varying shape and attitude. The governing equations for a continuum are derived in the form of integral equations for the member joint displacements alone. The integral equations can be solved easily by transforming them into ordinary differential equations and introducing additional mass corresponding to the inertial force due to the rigid-body axial translation and rotation of members. The scheme is applied to deploying, extending, and rotating space structures and a three-dimensionally moving link-connected structure.

Biomass wastes, such as agricultural residues from rice field are generated in a large amount. Hydrothermal carbonization (HTC) treatment can convert biomass wastes into value-added product known as hydrochar, which gained researchers interests for various environmental applications. However, recent studies have shown inconsistent results for the use of hydrochar on crop production and soil improvement. Thus, the aim of this study is to understand the characteristics and potential use of rice husk and rice straw hydrochar as soil amendment. Two types of hydrochar (RHH: rice husk hydrochar, and RSH: rice straw hydrochar) produced using HTC at a pressure of 1.6 MPa, temperature at 160 – 180 °C, and reaction time of 30 min, were used to conduct pot experiment. Nutrients and morphological study of hydrochar and its raw biomass were analyzed. Five treatments (0 % hydrochar as control, 1 % RHH, 10 % RHH, 1 % RSH, and 10 % RSH (w/w)) were applied in commercial garden soil to observe the effects on soil pH and Spinach plant growth. The result from this study shows that HTC have significant effects on the hydrochar properties. The hydrochars have coarser surface and several microstructures formed on the surface. HTC significantly decreased pH, increased moisture content, and altered the nutrient compositions of the biomass. Pot experiment results showed that all hydrochar-amended treatments decreased soil pH below optimal pH of 6.0, which causes the decreased plant biomass by 60 – 67 % compared to control. This shows that these hydrochars are useful as soil amendment for dry degraded soils with pH =8. Further research is needed to reveal the mechanisms and potential modification required before using the hydrochar as soil amendment.

Prazosin (PRZ) is a type of drug used to treat hypertension. It is found to contaminate the aquatic environment, therefore has substantial threats to the ecosystem and human health. PRZ has been found to contaminate rivers in Malaysia which is presumed due to excretion and inappropriate disposal. A tropical bacterium, PR5 has been isolated from a PRZ contaminated site in Kuala Lumpur, Malaysia. It has demonstrated its capabilities to utilize PRZ as a nutrient source and efficiently degrade PRZ. UPLC-TUV is used to measure PRZ concentration during growing cell assay and the results showed that isolate PR5 able to degrade 78% of 0.01 mM PRZ within 7 days of incubation. Species identification based on the 16S rRNA gene sequence showed isolate PR5 has a 99.66% similarity with Bacillus velezensis. This study reports on the first finding of PRZ biodegradation by Bacillus velezensis.

This paper investigates the use of a sidebranch resonator subjected to active termination impedance control as a means to reduce noise transmission in a duct. The main purpose of this paper is to establish a method for controlling a broad-band noise, which is characterized by a simultaneous incidence of a large number of frequency components. To this end, a control law is expressed in terms of a controller transfer function, and a new method for accurately implementing the desired frequency characteristic of the controller transfer function over a wide frequency range is presented. In this method, the inverse Laplace transform of the controller transfer function is expressed in terms of a Fourier series. This expression leads to an online computation algorithm that allows us to update the values of base functions of the control force at each digital sampling time. The effectiveness of the algorithm is demonstrated by computer simulation. [DOI: 10.1115/1.1368118]

This paper describes a new digital algorithm for suppressing spillover-induced vibration. This algorithm can shut off the frequency components that are significantly excited by spillover with zero gain while detecting the lower modes to be controlled with gain 1 and no phase-lag, with high accuracy. Despite the noncausality of the ideal cutoff filter, a causal algorithm can be developed by utilizing the light-damping property of spillover-induced vibration. The effectiveness of the algorithm is demonstrated by computer simulation and experiment. [S0022-0434(00)01602-6]