Enhancing vibration isolation performance by exploiting novel spring-bar mechanism

This study investigates the use of a spring-bar mechanism (SBM) in a vibration suppression system to improve its performance. The SBM, comprising bars and springs, is configured with a conventional linear spring-damper isolator unit. The dynamic response, force transmissibility, and vibration energy flow behaviour are studied to evaluate the vibration suppression performance of the integrated system. It is found that the SBM can introduce hardening, softening stiffness, or double-well potential characteristics to the system. By tuning the SBM parameters, constant negative stiffness is achieved so that the natural frequency of the overall system is reduced for enhanced low-frequency vibration isolation. It is also found that the proposed design yields a wider effective isolation range compared to the conventional spring-damper isolator and a previously proposed isolator with a negative stiffness mechanism. The frequency response relation of the force-excited system is derived using the averaging method and elliptical functions. It is also found that the system can exhibit chaotic motions, for which the associated time-averaged power is found to tend to an asymptotic value as the averaging time increases. It is shown that the time-averaged power flow variables can be used as uniform performance indices of nonlinear vibration isolators exhibiting periodic or chaotic motions. It is shown that the SBM can assist in reducing force transmission and input power, thereby expanding the frequency range of vibration attenuations

Suppression of vibration transmission in coupled systems with an inerter-based nonlinear joint

This study proposes an inerter-based nonlinear passive joint device and investigates its performance in suppression of vibration transmission in coupled systems. The joint device comprises an axial inerter and a pair of lateral inerters creating geometric nonlinearity, with the nonlinear inertance force being a function of the relative displacement, velocity, and acceleration of the two terminals. Both analytical approximations based on the harmonic balance method and numerical integration are used to obtain the steady-state response amplitude. Force transmissibility and time-averaged energy flow variables are used as performance indices to evaluate the vibration transmission in the coupled system, with subsystems representing the dominant modes of interactive engineering structures. The effects of adding the proposed joint to the force-excited subsystem or to the coupling interface of subsystems on suppression performance are examined. It is found that the insertion of the inerter-based nonlinear joint can shift and bend response peaks to lower frequencies, substantially reducing the vibration of the subsystems at prescribed frequencies. By adding the joint device, the level of vibration force and energy transmission between the subsystems can be attenuated in the range of excitation frequencies of interest. It is shown that the inerter-based nonlinear joint can be used to introduce an anti-peak in the response curve and achieve substantially lower levels of force transmission and a reduced amount of energy transmission between subsystems. This work provides an in-depth understanding of the effects of inerter-based nonlinear devices on vibration attenuation and benefits enhanced designs of coupled systems for better dynamic performance

"Genotype-first" approaches on a curious case of idiopathic progressive cognitive decline

Background In developing countries, many cases with rare neurological diseases remain undiagnosed due to limited diagnostic experience. We encountered a case in China where two siblings both began to develop idiopathic progressive cognitive decline starting from age six, and were suspected to have an undiagnosed neurological disease. Methods Initial clinical assessments included review of medical history, comprehensive physical examination, genetic testing for metabolic diseases, blood tests and brain imaging. We performed exome sequencing with Agilent SureSelect exon capture and Illumina HiSeq2000 platform, followed by variant annotation and selection of rare, shared mutations that fit a recessive model of inheritance. To assess functional impacts of candidate variants, we performed extensive biochemical tests in blood and urine, and examined their possible roles by protein structure modeling. Results Exome sequencing identified NAGLU as the most likely candidate gene with compound heterozygous mutations (chr17:40695717C > T and chr17:40693129A > G in hg19 coordinate), which were documented to be pathogenic. Sanger sequencing confirmed the recessive patterns of inheritance, leading to a genetic diagnosis of Sanfilippo syndrome (mucopolysaccharidosis IIIB). Biochemical tests confirmed the complete loss of activity of alpha-N-acetylglucosaminidase (encoded by NAGLU) in blood, as well as significantly elevated dermatan sulfate and heparan sulfate in urine. Structure modeling revealed the mechanism on how the two variants affect protein structural stability. Conclusions Successful diagnosis of a rare genetic disorder with an atypical phenotypic presentation confirmed that such “genotype-first” approaches can particularly succeed in areas of the world with insufficient medical genetics expertise and with cost-prohibitive in-depth phenotyping

Neoadjuvant SBRT combined with immunotherapy in NSCLC: from mechanisms to therapy

The utilisation of neoadjuvant immunotherapy has demonstrated promising preliminary clinical outcomes for early-stage resectable non-small-cell lung cancer (NSCLC). Nevertheless, it is imperative to develop novel neoadjuvant combination therapy regimens incorporating immunotherapy to further enhance the proportion of patients who derive benefit. Recent studies have revealed that stereotactic body radiotherapy (SBRT) not only induces direct tumour cell death but also stimulates local and systemic antitumour immune responses. Numerous clinical trials have incorporated SBRT into immunotherapy for advanced NSCLC, revealing that this combination therapy effectively inhibits local tumour growth while simultaneously activating systemic antitumour immune responses. Consequently, the integration of SBRT with neoadjuvant immunotherapy has emerged as a promising strategy for treating resectable NSCLC, as it can enhance the systemic immune response to eradicate micrometastases and recurrent foci post-resection. This review aims to elucidate the potential mechanism of combination of SBRT and immunotherapy followed by surgery and identify optimal clinical treatment strategies. Initially, we delineate the interplay between SBRT and the local tumour immune microenvironment, as well as the systemic antitumour immune response. We subsequently introduce the preclinical foundation and preliminary clinical trials of neoadjuvant SBRT combined with immunotherapy for treating resectable NSCLC. Finally, we discussed the optimal dosage, schedule, and biomarkers for neoadjuvant combination therapy in its clinical application. In conclusion, the elucidation of potential mechanism of neoadjuvant SBRT combined immunotherapy not only offers a theoretical basis for ongoing clinical trials but also contributes to determining the most efficacious therapy scheme for future clinical application

Enhanced suppression of longitudinal vibration transmission in propulsion shaft system using nonlinear tuned mass damper inerter

This study proposes the use of a novel nonlinear tuned mass damper inerter device in vibration suppression of the ship propulsion shafting system and evaluates its performance. The device consists of an axial inerter and a pair of lateral inerters to create geometric nonlinearity. The system response subjected to propeller forces is determined by using the harmonic balance method with alternating-frequency-time technique and a numerical time-marching method. The force transmissibility and energy flow variables are employed to assess the performance of the device. The results show that the proposed device can reduce the peak force and energy transmission to the foundation while increase the energy dissipation within the device. Its use can lead to an improved vibration attenuation effect than the traditional mass-spring-damper device for low-frequency vibration. The configurations of the nonlinear inerter-based device can be adjusted to obtain an anti-peak at a resonance frequency of the original system, providing superior vibration suppression performance

Enhancing Vibration Isolation Performance by Exploiting Novel Spring-Bar Mechanism

This study investigates the use of a spring-bar mechanism (SBM) in a vibration suppression system to improve its performance. The SBM, comprising bars and springs, is configured with a conventional linear spring-damper isolator unit. The dynamic response, force transmissibility, and vibration energy flow behaviour are studied to evaluate the vibration suppression performance of the integrated system. It is found that the SBM can introduce hardening, softening stiffness, or double-well potential characteristics to the system. By tuning the SBM parameters, constant negative stiffness is achieved so that the natural frequency of the overall system is reduced for enhanced low-frequency vibration isolation. It is also found that the proposed design yields a wider effective isolation range compared to the conventional spring-damper isolator and a previously proposed isolator with a negative stiffness mechanism. The frequency response relation of the force-excited system is derived using the averaging method and elliptical functions. It is also found that the system can exhibit chaotic motions, for which the associated time-averaged power is found to tend to an asymptotic value as the averaging time increases. It is shown that the time-averaged power flow variables can be used as uniform performance indices of nonlinear vibration isolators exhibiting periodic or chaotic motions. It is shown that the SBM can assist in reducing force transmission and input power, thereby expanding the frequency range of vibration attenuations