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Normal shock trains are a flow phenomenon of significance to ramjet engines, but it remains unclear what its structure is decided by and how it evolves with the incoming Mach number. To seek a theoretical explanation, the minimum entropy production principle is generalized to the quasi-steady behavior of normal shock trains in two-dimensional straight channels with uniform incoming flow. Numerical simulations are also performed to validate the model together with the data collected from public literature. The analysis suggests that the flow parameters of a normal shock train depend on the inviscid shock-shock interactions rather than the local boundary-layer separations, though the angles of two incident shocks should still be equal as similar to the case that complies with the free-interaction theory. The shock feet’s positions, meanwhile, are allowed to be coincident or not, free from the entropy restriction. This freedom of position explains why both symmetric and partially asymmetric normal shock trains could be found previously. Further theoretical calculations reveal the inclinations of two incident shocks increase first and then decrease with the incoming Mach number, peaking at 48.570 degrees when the Mach number reaches 1.753. It is also indicated that the Mach number range allowing for a normal shock train is 1.652 to 2.254, giving evidence for past observations. [ABSTRACT FROM AUTHOR]

A compact and lightweight sensor is always expected to be embedded with the traditional micro-vibration isolator in spacecraft. It helps to detect the subtle disturbances the isolator encounters and alerts for potential harm. In this work, we developed a self-sensing micro-vibration isolator using an electret transducer. The theoretical models of the electret-based self-sensing isolator are derived from Hamilton's principle to investigate the coupled dynamics of the system and guide a model-based design. Simulations via the finite element method were also conducted to verify and extend the effectiveness of the proposed model. The results show that the electret transducer is an excellent candidate for the embedded sensor of the micro-vibration isolator. With the proper size and appropriate deployment pattern, the electret sensors can precisely detect the translation and rotation of the unsprung load. [ABSTRACT FROM AUTHOR]

In this article an 8-port annular ring-shaped MIMO antenna for 5G and 5G advanced applications is presented. An annular ring on the radiating plane and novel isolator structure on the ground plane are etched over a Rogers RT/Duorid (5870 tm) substrate to achieve high performance antenna for mm wave applications. A systematic study is performed, and an optimized single port antenna (Design-4) is selected among Designs (1-4). The intended 8-port MIMO antenna resonates at 36.4 GHz and exhibits 6.1 GHz (34.2-40.3 GHz) wide bandwidth and 40 dB high isolation level. The proposed antenna covers a complete band of 5G NR-n260 which supports time division duplexing (TDD) mode. Moreover, a unique design of suggested antenna attains a high-level gain of 8.3 dB at 39 GHz and more than 85.2 % radiation efficiency. MIMO characteristics such as ECC, TARC, MEG and CCL are studied and found them in acceptable limit. Additionally, an approach toward massive antenna with 16-port for mmWave applications is also demonstrated. The proposed 16-port massive antenna with more than 22 dB isolation exhibits two bands: first band in 30-33 GHz for ports P9-P16 and second band in 33.5-40.9 GHz for ports P1-P8. A prototype of suggested 8-port antenna is fabricated, tested and validated and found it in close agreement of simulated results. [ABSTRACT FROM AUTHOR]

Magnetorheological elastomers (MREs) are smart materials. Their rheological properties can be controlled by applying an external magnetic field. MRE is a solid rubbery material that can change its modulus through the application of a magnetic field. This article presents the research on the simulation, manufacturing, and testing of vibration insulators. The first step in MRE vibration isolator design. A sufficient magnetic field for the stiffness change is considered in the material selection of the vibration isolator. The effectiveness of electromagnetic circuits in generating magnetic fields to minimize vibration is demonstrated using finite element method magnetics software. A vibration isolator test rig is installed as a second step. Lastly, different effects of current input on MRE isolators have been examined. The higher current input is more effective in eliminating vibration using the MRE isolation system. [ABSTRACT FROM AUTHOR]

This paper reports on a new type of multi-functional bandpass filtering (BPF) architecture with center frequency tunability, switching-off, and isolator functionality. The proposed filter, isolator, and switch (FIS) combines frequency-tunable passive resonators with unilateral frequency-selective stages (UFSs) to achieve tunable, fully-directional, quasi-elliptic transfer functions. The UFS, consists of a transistor-based path and a tunable feedback network, enabling frequency-selective transmission in the forward direction, RF signal cancellation in the reverse direction, and reconfigurability in terms of center frequency and intrinsic switching-off. It is demonstrated that by cascading UFSs and tunable resonators, highly selective frequency-tunable FISs can be developed. The proposed FIS also offers a reconfigurable switch-off mode capability with high isolation that is obtained by adjusting transmission zeros and reconfiguring the UFSs. In this paper, two types of UFSs are analyzed using circuit schematic simulations and coupling routing diagram (CRD)-based synthesis. Scalability to high-order transfer functions is also demonstrated by CRD-synthesized examples, design examples and manufactured prototypes. For experimental validation, two tunable UFSs and four tunable FISs were manufactured and measured at the L band.

In scramjet，the isolator plays a crucial role as a transitional component between the combustor and the inlet. Within the isolator，complex flow phenomena such as shock wave/boundary layer interactions，flow separation，and shock trains are observed under the influence of high back-pressure from the combustor. In this study，the self-adaptive turbulence eddy simulation（SATES）is used to numerically study the shock train characteristics in a cylindrical isolator. The primary focus is to analyze the potential challenges faced when the isolator is coupled with the combustor，including the effects of constant or pulsating back-pressure at the isolator exit and wall temperature on the shock train characteristics within the isolator. The results indicate that an increase in the exit back-pressure of the isolator，a decrease in the frequency of pulsating back-pressure，and an elevation in wall temperature can all cause the shock train to move towards the inlet，leading to potential unstart risks. Therefore，in practical engineering applications，particular attention should be paid to the high back-pressure and low-frequency oscillations induced during the combustor combustion process，as well as the wall heat conduction effects，to prevent the shock train from being expelled from the isolator，which could result in the unstart of not only the isolator but also the entire engine.

Isolator tegangan tinggi memainkan peran penting dalam memastikan keamanan sistem listrik yang beroperasi pada tegangan tinggi. Isolator memiliki fungsi sebagai pemisah tegangan antara konduktor fase dan konduktor fase lainnya dan juga antara konduktor fase dengan ground. Dalam perancangan sistem tenaga listrik, basic insulation level (BIL) tidak dapat diabaikan. BIL merupakan batas operasional tegangan maksimum sebelum isolator mengalami flashover. Selain harus mampu menahan tegangan, isolator juga harus mampu menahan kondisi lingkungan, seperti suhu, kelembapan, dan polusi, yang dapat memengaruhi kinerja isolator. Pada penelitian ini, dilakukan pengujian untuk melihat kinerja isolator kaca bekas PLTU Adipala ketika dipengaruhi oleh kondisi lingkungan dan dibandingkan dengan nilai BIL. Pengujian dilakukan dengan empat skema, yaitu pengujian dalam kondisi baik, pengujian dengan kondisi basah, pengujian dengan kondisi diberikan polutan, dan pengujian dengan kondisi ketika isolator dengan polutan berada pada kondisi lembap. Berdasarkan pengujian, didapatkan hasil bahwa kondisi yang sangat memengaruhi kinerja isolator adalah kondisi basah dan juga kondisi berpolutan dan lembap. Pada kondisi isolator bersih yang terkena hujan, penurunan kinerja isolator sebesar 19% sampai 25%, sedangkan pada kondisi diberikan polutan dengan equivalent salt deposit density (ESDD) 0,113816 mg/cm2 dan non-soluble deposit density (NSDD) 1,309962 mg/cm2 serta berada pada kelembapan 90%, terjadi penurunan kinerja sebesar 41% hingga 53%. Penurunan yang sangat signifikan ini tentunya mengakibatkan kinerja isolator berada jauh di bawah standar BIL.

The interaction between light and the magnetization of a material is called the magneto–optical effect. It was used in magneto–optical recording such as MO disks and has been applied to optical isolators etc. with the development of optical communications. The magneto–optical properties of magnetic garnets and their applications are briefly reviewed in this article. In the first half, after a brief overview of the phenomenology of the magneto–optical effect, the effects of element substitution on properties such as Faraday rotation and optical absorbance of magnetic garnets are shown. In the second half, some interesting applications such as imaging technologies and other novel applications using the magneto–optical effect of magnetic garnets are also introduced. [ABSTRACT FROM AUTHOR]

The epsilon‐near‐zero (ENZ) frequency regime of transparent conducting oxide materials is known to yield large enhancements in their optical nonlinearity and electro‐optic response. Here, Faraday rotation is investigated in Gd and In‐doped CdO films and it is found that the Verdet constant peaks at values >3 105 deg T−1 m−1 near the ENZ frequency, which is tunable in the wavelength range 2 < λ< 10 µm by varying the doping concentration. These results are among the highest reported to date in the mid‐infrared spectral range and are in good agreement with the Drude model, which confirms that the magneto‐optic response of doped CdO derives from its free carriers. The combination of a tunable Verdet constant, low optical loss compared to other plasmonic materials, and the ability to deposit CdO on Si with no loss in performance make this material a promising platform for integrated magneto‐optic and magnetoplasmonic devices that operate across the mid‐infrared. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a new type of isolator based on one-way surface magnetoplasmons (SMPs) at microwave frequencies, and it is the first time that an experimental prototype of isolator with wideband and ultra-high isolation is realized using SMP waveguide. The proposed model with gyromagnetic and dielectric layers is systematically analyzed to obtain the dispersion properties of all the possible modes, and a one-way SMP mode is found to have the unidirectional transmission property. In simulation and experiment with metallic waveguide loaded with yttrium–iron–garnet (YIG) ferrite, the scattering parameters and the field distributions agree well with the analysis and verify the one-way transmission property. The isolation is found to be as high as 80 dB and the typical value of insertion loss is 1 dB. Besides, the one-way transmission band can be controlled by changing the magnetic bias. From theoretical analysis and simulation, it is found that with a tiny value of 10 Oe of the magnetic bias, the relative bandwidth can be tuned to be greater than 50%. Compared with conventional isolators, this one-way SMP isolator has the advantages of ultra-high isolation, wide relative frequency band, and requires much smaller bias field, which has promising potential in non-reciprocal applications.

This study proposes a novel semi-active vibration control technique for mechanical transmission systems. The backbone of current research technology is the adaptive stiffness and damping properties of metal rubber (MR) which plays the role of tuning to the vibrational system eigenmodes. The adaptive properties of MR material were proved by a previous study, but the present research investigates the effect of this feature on the structural response and designs an MR-based semi-active vibration controller for industrial application. For this purpose, the semi-active control strategy is created based on an optimal tuning using experimental harmonic test results. The control strategy is applied in practice using a linear actuator controlled by a double pole double throw (DPDT) relay, and National Instruments hardware and software for reading data and writing the control task. The isolator attachment position is defined through the analysis of eigenmode shapes that are predetermined by numerical simulation. A maximum isolation rate of 55.17% is measured near the vibration isolator position. It is observed that the isolation position has a prominent effect on structure vibration behavior where the elastic wave has been reduced in amplitude by passing the isolator position. The effectiveness of the MR-based semi-active control approach is eminent and its application for vibration isolation of commercial mechanical transmission systems could be studied in the future. [ABSTRACT FROM AUTHOR]

Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Understanding aeroelastic issues related to isolators is pivotal for the structural design and flow control of scramjets. However, research on fluid–structure interactions (FSIs) between thin-walled structures and the isolator flow remains limited. This study delves into the FSIs between thin-walled panels and the isolator flow, as characterized by an oblique shock train, by quantitatively analyzing 11 flow parameters assessing the structural response, separation zones, shock structures, flow symmetry, and performance. The results reveal that an FSI triggers panel flutter under oblique shock train conditions, with the panel shapes exhibiting a combination of first- and second-mode responses, peaking at 0.75 of the panel length. Compared to rigid wall conditions, isolators with a flexible panel at the bottom wall experience downstream movement of the separation zones and shock structures, reduced flow symmetry, and minor changes in performance. Transient fluctuations occur due to the panel flutter. Two flexible panels at the top and bottom walls have a comparatively lesser influence on the averaged parameters but exhibit more violent transient fluctuations. Furthermore, the FSI effects under oblique shock train conditions are contrasted with those under normal shock train conditions. The flutter response under normal shock train conditions is more pronounced, with a larger amplitude and higher frequency, driven by the heightened participation of the first-mode response. The effects of FSIs under normal shock train conditions on the averaged parameters are the opposite (with a larger influence) to those under oblique shock train conditions, with significantly more drastic transient fluctuations. Overall, this study sheds light on the complex and substantial influence of FSIs on the isolator flow, emphasizing the necessity of considering FSIs in future isolator design and development endeavors. [ABSTRACT FROM AUTHOR]

Many vibration isolators, such as passive vehicle mounting devices, have an inflexible stiffness. This article presents the development of a smart material vibration isolator based on magnetorheological elastomer (MRE), which has adjustable stiffness to minimize unwanted vibrations. The objective of this research is to first create a design for the vibration isolator, and then simulate a magnetic circuit. The Finite Element Method Magnetics (FEMM) software was employed to simulate the effectiveness of the electromagnetic circuit in generating a magnetic field through the vibration isolator by employing MRE samples. Pure iron was chosen as the material for the housing of the vibration isolator test rig. To attain an optimal magnetic field, an inventive design of the magnetic circuit, including examination of the wire type, size, and coil turn number, along with the housing material of the test rig, was performed. The study analyzed the performance of the MRE vibration isolator concerning different current inputs in the coil. The results indicate that the stiffness value of the MRE-based isolator system can be more effectively modified by increasing the current inputs. Therefore, a larger current input leads to a greater change in stiffness.

The interaction between light and the magnetization of a material is called the magneto–optical effect. It was used in magneto–optical recording such as MO disks and has been applied to optical isolators etc. with the development of optical communications. The magneto–optical properties of magnetic garnets and their applications are briefly reviewed in this article. In the first half, after a brief overview of the phenomenology of the magneto–optical effect, the effects of element substitution on properties such as Faraday rotation and optical absorbance of magnetic garnets are shown. In the second half, some interesting applications such as imaging technologies and other novel applications using the magneto–optical effect of magnetic garnets are also introduced.

This work presents a rigorous design and experimental validation of a non-reciprocal bandpass filter (NBPF) employing time-modulated resonators with progressive phase shift sinusoidal modulation signal to achieve low forward transmission insertion loss (IL) and ultrawide high reverse isolation bandwidth. Analytical design equations have been derived for numerical design of NBPF asl well as providing insights of nonreciprocal frequency response. Additionally, these proposed analytical spectral S-parameters offer the flexibility to design NBPFs with arbitrary termination port impedances. This work also demonstrates a systematic approach to find modulation parameters without relying on optimization methods. It has established empirical relationships between the modulation parameters and the filters specifications to achieve low forward transmission IL and reverse isolation exceeding 15 dB at entire frequency range. The accuracy of the proposed NBPF design has been confirmed by comparing with harmonic balance simulation results of microstrip line NBPF. For experimental validation, three prototypes of NBPF with different termination port impedances are designed, implemented, and manufactured. In experimental results, the frequency of NBPFs can be continously tuned from 1.62 GHz to 1.94 GHz (17.98 %) with maximum forward transmission IL (|S21|) of 5.40 dB and input/output return loss higher than 12 dB. For each frequency tuning state, the reverse isolation (|S12|) exceeds higher than 20 dB across the entire frequency range.

This research aims to determine the flashover voltage on the surface of porcelain insulators on 150 kV transmission lines located in Payakumbuh, where the insulators are contaminated with dust and moss due to the effects of temperature and humidity. The experiment is carried out with only up to seven insulator plates due to the limitations of the available apparatus. For the further testing, a trend analysis is applied. According to the experimental results, a rise in temperature around the insulator will increase the flashover voltage value and accelerate the potential for a flashover event. This happens because high temperatures can reduce the insulator's dielectric strength and insulation resistance and increase the risk of flashover. The dielectric strength values decreased with an average decrease of 44.62% per insulator plate for dusty insulators and 45.08% for each plate for mossy insulators. The results aim to minimize flashover on transmission lines in hilly areas with relatively high contamination. [ABSTRACT FROM AUTHOR]

This article deals with the operational behavior of barium hexaferrite (BHF) disc when incorporated in microwave substrates for wireless applications. A microstrip line printed on a Rogers substrate (35 mm × 35 mm × 1.6 mm) has been used in the design to observe the effect of BHF material. A BHF circular‐shaped disc of radius 4.5 mm and thickness 1 mm is inserted in the middle of the microstrip line. The ferrite is biased using miniature lightweight neodymium magnets stacked one over the other to obtain desired magnetic field strength. The proposed microstrip line inserted with a BHF disc exhibits wide band isolation properties in the K‐band (15–21 GHz) with an average isolation of 20 dB and peak isolation of 51 dB centered at 18.5 GHz. It is observed that the same circuit is behaving as a phase shifter showing a 45° ± 3° phase shift in the band ranging from 12 to 14 GHz. The proposed compact microstrip‐line circuit can be used as both ferrite phase shifter and isolator in consecutive bands (Ku‐ and K‐bands) with ease of integration and biasing. [ABSTRACT FROM AUTHOR]

Purpose: Detection of deformation of devices in high voltage electricity transmission line systems is an important issue in terms of economy and reuse. This study is aimed to detect devices that are deformed or thought to have suffered due to environmental and electrical reasons. Design/methodology/approach: In this experimental study, it was ensured that the sound and deformed insulators used in energy transmission lines were determined by the analysis of the sounds obtained by using the impact method. Equal intensity impact was applied to the isolator using the pendulum and the resulting sound noise signal analyses were made using power spectral density (PSD), magnitude scalogram (MS), multitape power spectrum density (MPSD) and continuous wavelet transform (CWT) methods in the study. In the analysis results, the isolators that are not visible to the eye and have certain damage were successfully separated from the intact insulators. Especially, MPSD and CWT analysis results are quite satisfactory. Findings: Damage analysis of insulators used in electricity transmission lines has been made. A total of 40 insulators were examined in two categories in their group, both damaged and not damaged. Data collection system was established. The data obtained from the data collection system were analysed and compared using four analysis methods. PSD, MS, MPSD and CWT analyses were made in the study. All the analyses carried out generally contain features that distinguish damaged and undamaged insulators from each other, the most successful results are MS and CWT results. CWT results are very successful in terms of time and amplitude, and it has been proposed as a method that can be used to separate damaged and undamaged insulators. Originality/value: It can be suggested as a result of experimental tests that the results of CWT analysis can be used in the pulse noise method in isolators to be tested for reuse in electrical power transmission lines.

Two types of elastomeric vibration isolators used for equipment vibration isolation in aerospace vehicles are considered for the present study. These isolators are constructed using elastomers mounted in steel encasings. These isolators are initially deformed statically and dynamic loads are applied on the deformed configuration. To capture the static deformation, equivalent static load corresponding to its load rating and specified displacements are created. Static deformation is computed using Finite Element methods with four node axi-symmetric element which include the geometric non-linear effect for steel and with standard Yeoh hyper-elastic material model for elastomers (Muhammed and Zu, 2012) [1]. Yeoh material constants are derived from uni-axial tension test data of the elastomer specimen. These isolators are subjected to harmonic and random excitations in the pre-deformed state. For numerical analysis, elastomeric constants at dynamic conditions are obtained as complex function of frequency using Dynamic Mechanical Analyzer (DMA) for a range of frequencies. The standard material model of Yeoh is modified incorporating frequency dependant material characteristics and damping in the range of frequencies of interest. A multiplicative non-separable variables law is derived for Yeoh material model to include the effect of static pre-stress, based on the methodology given in literature (Nashif et al., 1985; Beda et al., 2014) [2,3]. The modifications of Yeoh model suitable for frequency domain analysis is the novelty in the present study. In the analysis, while dynamic loads are applied, the configuration is updated considering initial static loading. The frequency response of the isolators is computed using material properties evaluated at progressive dynamic strains until a match in natural frequency is observed. Appropriate damping corrections are then incorporated to match the test observed transmissibility. Then updated material properties are used to compute the random response which showed good agreement with results of experiments, validating the approach taken for the development of this model.

For a further understanding on 3D shock train structure and correlation between 3D and 2D shock trains at Mach 1.5 and 3.0, the SST turbulence model based on Reynolds average algorithm was employed to simulate the 3D and 2D structures of the shock trains in the isolator respectively, of which the mesh sizes were 18 million and 200 thousand, respectively. First, when the full flow state of the nozzle was completely converged, the shock train structure was induced by a linearly increasing back pressure at the outlet. Then, the 3D shock train simulation results in xy-plane and zx-plane perspectives were analyzed. Finally, structures of the 3D shock train in different slices and structures of the 2D shock train were analyzed for comparison. It is found that the shock train at Mach 1.5 is symmetrical in xy-plane and zx-plane perspectives, which is highly similar to the 2D simulation results. However, the shock train at Mach 3.0 is symmetrical in the xy-plane perspective, while it is asymmetrical in the zx-plane perspective. The asymmetrical structure is highly similar to 2D simulation results. Therefore, there is a ″quasi-2D area″ in the 3D shock train. For the shock train at Mach 1.5, the structures in the areas including the central position and a certain range on both sides of the xy-plane and zx-plane perspectives can be approximated as 2D structures (The proportion of ″quasi-2D area″ is about 40%); for the shock train at Mach 3.0, the structures in the areas including the central position and a certain range on both sides of the symmetrical viewing angle can be approximated as 2D structures (The proportion of ″quasi-2D area″ is about 60%).

Understanding aeroelastic issues related to isolators is pivotal for the structural design and flow control of scramjets. However, research on fluid–structure interactions (FSIs) between thin-walled structures and the isolator flow remains limited. This study delves into the FSIs between thin-walled panels and the isolator flow, as characterized by an oblique shock train, by quantitatively analyzing 11 flow parameters assessing the structural response, separation zones, shock structures, flow symmetry, and performance. The results reveal that an FSI triggers panel flutter under oblique shock train conditions, with the panel shapes exhibiting a combination of first- and second-mode responses, peaking at 0.75 of the panel length. Compared to rigid wall conditions, isolators with a flexible panel at the bottom wall experience downstream movement of the separation zones and shock structures, reduced flow symmetry, and minor changes in performance. Transient fluctuations occur due to the panel flutter. Two flexible panels at the top and bottom walls have a comparatively lesser influence on the averaged parameters but exhibit more violent transient fluctuations. Furthermore, the FSI effects under oblique shock train conditions are contrasted with those under normal shock train conditions. The flutter response under normal shock train conditions is more pronounced, with a larger amplitude and higher frequency, driven by the heightened participation of the first-mode response. The effects of FSIs under normal shock train conditions on the averaged parameters are the opposite (with a larger influence) to those under oblique shock train conditions, with significantly more drastic transient fluctuations. Overall, this study sheds light on the complex and substantial influence of FSIs on the isolator flow, emphasizing the necessity of considering FSIs in future isolator design and development endeavors.

In biomedical research, germ-free and gnotobiotic mouse models enable the mechanistic investigation of microbiota-host interactions and their role on (patho)physiology. Throughout any gnotobiotic experiment, standardized and periodic microbiological testing of defined gnotobiotic housing conditions is a key requirement. Here, we review basic principles of germ-free isolator technology, the suitability of various sterilization methods, and the use of sterility testing methods to monitor germ-free mouse colonies. We also discuss their effectiveness and limitations, and share the experience with protocols used in our facility. In addition, possible sources of isolator contamination are discussed and an overview of reported contaminants is provided. [ABSTRACT FROM AUTHOR]

A two-degree-of-freedom (2DOF) vibration isolation structure with an integrated geometric nonlinear inerter (NI) device is proposed. The device is integrated into an inertial nonlinear energy sink (INES), and its vibration suppression performance is examined by the Runge-Kutta (RK) method and verified by the harmonic balance method (HBM). The new isolator is compared with a traditional vibration isolator. The results show a significant improvement in the vibration suppression performance. To investigate the effects of the excitation amplitude and initial condition on the dynamics of the system, a series of transmissibility-frequency response analyses are performed based on the displacement transmissibility. The energy flow of the system is analyzed, and numerous calculations reveal a series of ideal values for the energy sink in the NI-INES system. This study provides new insights for the design of vibration isolators. [ABSTRACT FROM AUTHOR]

Applications of the American Seismic Isolator Standard "SIS" are summarized. The SIS is the only construction standard that specifies design criteria for retaining the functionality of hospitals after earthquakes. The SIS specifies limits for in-structure accelerations and deformations. Earthquake data shows that the SIS limits are the maximum that can be tollerated and retain the functionaluity of hospitals after earthquakes. The Adana and Elazig hospital complexes retained 100% functionality after the severe earthquakes that occurred in Turkey in 2023 and 2020. These earthquakes resulted in 55,000 fatalities and 236 health care facilities losing functionality. Since the 1989 California earthquake, 18 structures with SIS isolators have retained 100% functionality after major earthquakes that caused over 800,000 deaths, and over 700,000 structures to be demolished. The functionality of these SIS structures saved many lives by enabling post-earthquake emergency services. Since 1985, SIS isolators have been implemented in over 40 million square meters of important buildings, bridges, and industrial facilities, in 34 countries. The cost to build these 40 million square meters of important structures with SIS isolators was about the same as constructing ductile moment frames for only collapse avoidance without isolators. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Southeast University / Dongnan Daxue Xuebao is the property of Journal of Southeast University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Arrester merupakan sebuah perangkat yang berfungsi untuk melindungi peralatan dari kegagalan dielektrik yang disebabkan oleh impuls petir, switching surge, ataupun lonjakan tegangan yang melebihi kemampuan dielektrik suatu peralatan. Pada sebagian besar arrester dipasang alat penghitung kerja arrester (event counter) yang berfungsi untuk menghitung frekuensi arrester telah bekerja. Di kondisi lingkungan lembap dan polusi tinggi, pada bagian isolator sangat mudah terjadi surface discharge. Surface discharge merupakan discharge yang terjadi pada suatu daerah yang berhubungan langsung dengan permukaan dielektrik yang memiliki medan listrik berlebih, sehingga memicu terjadinya discharge. Surface discharge yang berlangsung secara terus-menerus dapat mengakibatkan flashover. Flashover yang mengenai bagian dari event counter dapat membuat event counter mengalami error sehingga tidak menunjukkan angka yang benar. Di samping itu, kinerja event counter akan terganggu. Untuk itu, perlu dilakukan pengujian isolator arrester dengan tiga skema, yaitu isolator kondisi bersih, isolator kondisi lembap, serta isolator dengan kondisi lembap dan berpolutan. Pada pengujian ini, digunakan polutan dengan nilai equivalent salt deposit density (ESDD) sebesar 4,69 mg/cm2 dan nilai nonsoluble deposit density (NSDD) sebesar 1,8841 mg/cm2. Berdasarkan hasil pengujian, diketahui bahwa terjadi penurunan kemampuan isolasi arrester dalam menahan tegangan yang diakibatkan oleh kelembapan dan polutan. Kelembapan memberikan penurunan breakdown voltage (BDV) sebesar 5,8 kV setiap kenaikan kelembapan 5%, sedangkan polutan memberikan penurunan BDV sebesar 59 kV ketika isolator diberi polutan.

The current work investigates the relationship between the shape of an isolator of a concentric rotary piston compressor and the secondary peak pressure developed during each operating cycle. This peak pressure is developed when the piston passes through the isolator cavity, and it is negative for compressor efficiency. The aim of this paper is to identify the isolator cavity shape that minimizes this secondary peak to improve compressor efficiency. This study covers five different cavities that may be used in such compressors. Contrary to our expectations, the conclusion is that the best geometry is the one that can be manufactured with CNC machining. The geometry that can be manufactured with 3D printing also produces a significantly lower secondary peak pressure, but it is not cost-efficient. Another limitation of the 3D printing design is the thin walls that this cavity creates. Very thin walls may cause significant deformation during the compression cycle. The conclusion is that there is a CNC machining design that is cost-efficient and allows for higher compressor performance.

In this contribution, we simulate, design, and experimentally demonstrate an integrated optical isolator based on spatiotemporal modulation in the thin-film lithium niobate on an insulator waveguide platform. We used two cascaded travelling wave phase modulators for spatiotemporal modulation and a racetrack resonator as a wavelength filter to suppress the sidebands of the reverse propagating light. This enabled us to achieve an isolation of 27 dB. The demonstrated suppression of the reverse propagating light makes such isolators suitable for the integration with III-V laser diodes and Erbium doped gain sections in the thin-film lithium niobate on the insulator waveguide platform.

This paper reports on the RF design and practical development of GaAs MMIC multi-functional RF isolators and quasi-circulators with embedded filtering functionality. They are based on cascaded arrays of non-reciprocal resonators (NRRs), passive resonators, and impedance inverters. A unique transistor-based architecture is used for the realization of the NRR that exhibits an one-pole type bandpass response in the forward direction and RF signal cancellation in the reversed one. By controlling the number and type of resonators within cascaded resonator arrays, different levels of gain, out-of-band selectivity and in-band isolation can be obtained. The operating principles of the multi-functional isolator/filtering and quasi-circulator/filtering concepts are presented through synthesized and linear circuit-simulated examples. Practical design aspects using a commercially available GaAs MMIC process are also discussed. For proof-of-concept demonstration purposes, four prototypes were designed and experimentally validated at X-band. They include: i) a NRR, ii) a two-resonator based frequency selective isolator (FSI), iii) a five-resonator based FSI, and iv) a two-pole/two-TZ frequency selective quasi-circulator (FSQC).

In traditional non-reciprocal metasurfaces based on antenna-circuit-antenna structure, the radiation module and the non-reciprocal circuit module are coplanar, which occupies extra surface area and has the inherent defect of narrow operating bandwidth. Therefore, a new 2.5D non-reciprocal metasurface based on the aperture coupling structure is proposed to realize the separate design and broad operating bandwidth, in which the non-reciprocal circuit module is perpendicular to the radiation module. In addition, this work improves isolation to over 35 dB without affecting the radiation mode and resonance frequency. Based on multimode resonance theory, a broadband microstrip antenna is further presented to obtain a broader operating bandwidth. By exciting multiple resonant modes with similar frequencies in the resonant cavity, the relative bandwidth reaches up to 38.2%. The experimental results coincide well with the simulation results, which fully demonstrate the validity of the proposed design.

In biomedical research, germ-free and gnotobiotic mouse models enable the mechanistic investigation of microbiota-host interactions and their role on (patho)physiology. Throughout any gnotobiotic experiment, standardized and periodic microbiological testing of defined gnotobiotic housing conditions is a key requirement. Here, we review basic principles of germ-free isolator technology, the suitability of various sterilization methods, and the use of sterility testing methods to monitor germ-free mouse colonies. We also discuss their effectiveness and limitations, and share the experience with protocols used in our facility. In addition, possible sources of isolator contamination are discussed and an overview of reported contaminants is provided.

Two types of elastomeric vibration isolators used for equipment vibration isolation in aerospace vehicles are considered for the present study. These isolators are constructed using elastomers mounted in steel encasings. These isolators are initially deformed statically and dynamic loads are applied on the deformed configuration. To capture the static deformation, equivalent static load corresponding to its load rating and specified displacements are created. Static deformation is computed using Finite Element methods with four node axi-symmetric element which include the geometric non-linear effect for steel and with standard Yeoh hyper-elastic material model for elastomers (Muhammed and Zu, 2012) [1]. Yeoh material constants are derived from uni-axial tension test data of the elastomer specimen. These isolators are subjected to harmonic and random excitations in the pre-deformed state. For numerical analysis, elastomeric constants at dynamic conditions are obtained as complex function of frequency using Dynamic Mechanical Analyzer (DMA) for a range of frequencies. The standard material model of Yeoh is modified incorporating frequency dependant material characteristics and damping in the range of frequencies of interest. A multiplicative non-separable variables law is derived for Yeoh material model to include the effect of static pre-stress, based on the methodology given in literature (Nashif et al., 1985; Beda et al., 2014) [2,3]. The modifications of Yeoh model suitable for frequency domain analysis is the novelty in the present study. In the analysis, while dynamic loads are applied, the configuration is updated considering initial static loading. The frequency response of the isolators is computed using material properties evaluated at progressive dynamic strains until a match in natural frequency is observed. Appropriate damping corrections are then incorporated to match the test observed transmissibility. Then updated material properties are used to compute the random response which showed good agreement with results of experiments, validating the approach taken for the development of this model. [ABSTRACT FROM AUTHOR]

In various applications such as plant mines or mechanical systems, machines in operation generate significant vibrations which are transmitted from the foundation to the surrounding environment and precision instruments. In order to minimize these vibrations, they must be either isolated, absorbed, or damped. The current study investigates the effects of an oil damper, passive vibration isolator, and absorbers (single and double) on the vibration frequency of a composite beam made of Al6061 (with 90% weight fraction) and SiC (with 10% weight fraction) produced through the stir casting process. Experimental analysis was conducted on the fabricated composite beam to investigate the frequencies of the fundamental vibration modes under hinged-hinged, fixed-free, and fixed-hinged boundary conditions. Results indicate that the absorber, damper, and isolator have a significant effect in reducing the amplitude of vibrations, resulting in lower frequencies compared to the main frequency. Furthermore, as the number of holes in the beam increases, the frequencies decrease due to a decrease in stiffness. The frequencies are higher for fixed-free end conditions without holes compared to other conditions. The oil damper was found to be more effective in reducing vibrations compared to absorbers and isolators. [ABSTRACT FROM AUTHOR]

The current work investigates the relationship between the shape of an isolator of a concentric rotary piston compressor and the secondary peak pressure developed during each operating cycle. This peak pressure is developed when the piston passes through the isolator cavity, and it is negative for compressor efficiency. The aim of this paper is to identify the isolator cavity shape that minimizes this secondary peak to improve compressor efficiency. This study covers five different cavities that may be used in such compressors. Contrary to our expectations, the conclusion is that the best geometry is the one that can be manufactured with CNC machining. The geometry that can be manufactured with 3D printing also produces a significantly lower secondary peak pressure, but it is not cost-efficient. Another limitation of the 3D printing design is the thin walls that this cavity creates. Very thin walls may cause significant deformation during the compression cycle. The conclusion is that there is a CNC machining design that is cost-efficient and allows for higher compressor performance. [ABSTRACT FROM AUTHOR]