Large Amplification Research Articles

Enhanced Amplification and Fan-Out Operation in an All-Magnetic Transistor.

Development of all-magnetic transistor with favorable properties is an important step towards a new paradigm of all-magnetic computation. Recently, we showed such possibility in a Magnetic Vortex Transistor (MVT). Here, we demonstrate enhanced amplification in MVT achieved by introducing geometrical asymmetry in a three vortex sequence. The resulting asymmetry in core to core distance in the three vortex sequence led to enhanced amplification of the MVT output. A cascade of antivortices travelling in different trajectories including a nearly elliptical trajectory through the dynamic stray field is found to be responsible for this amplification. This asymmetric vortex transistor is further used for a successful fan-out operation, which gives large and nearly equal gains in two output branches. This large amplification in magnetic vortex gyration in magnetic vortex transistor is proposed to be maintained for a network of vortex transistor. The above observations promote the magnetic vortex transistors to be used in complex circuits and logic operations.

SERS optical fiber probe with plasmonic end‐facet

SERS optical fiber probe with plasmonic end‐facet

Modeling and Simulation of Negative Capacitance Gate on Ge FETs

In this work, a polysilicon-ferroelectric (FE) gate capacitor is proposed to be stacked on the Ge-MOSFET to simultaneously maintain the stability and the potential amplification in the sub-threshold region of a Negative Capacitance Field Effect Transistor (NCFET). Hence, the non-hysteresis ID-VG characteristics with sub-60mV/dec subthreshold slope (SS) can be designed. Based on the simulation results, a small signal capacitance model (Fig.1(b)) which includes the effects of gate-to-source/drain overlap, interface trap states at oxide/Ge, and polysilicon/FE/metal is presented. In the sub-threshold region, the value of -CFE should be as close (but larger) to CMOS as possible to achieve large potential amplification. However, when the strong inversion of the MOS occurs and CMOS increases rapidly, -CFE > CMOS is still required to stabilize the NCFET.[1] The desirable properties can be achieved by utilizing the polysilicon capacitance (Cpoly) which is a function of the applied voltage. The magnitude of the effective CFE’ (=1/(1/CFE + 1/Cpoly)) approaches to CMOS capacitance closely at the subthreshold region and increases when strong inversion of Ge-MOSFET occurs (Fig.2(a)). Hence, a hysteresis-free steep SS NCFET is obtained. The optimized hysteresis-free polysilicon-FE NCFET achieves SS as low as 43mV/dec in the simulation (Fig.2(b)). Its optimized SS is further improved when the direct S/D overlap with floating metal of Ge-MOSFET increases (Fig.2(b)). On the other hand, the trapped charges in the FE interface will compensate the polarization of the ferroelectric material, and thus degrade the negative capacitance. By tuning the FE thickness and adding fixed charges, its effect on CFE can be balanced through our optimization approach. Reference: [1] S. Salahuddin and S. Datta, Nano letters, vol. 8, no. 2, pp. 405–410 (2008). Figure 1

Co-seismic response of water level in the Jingle well (China) associated with the Gorkha Nepal (Mw 7.8) earthquake

Changes in co-seismic water levels associated with the Gorkha Nepal earthquake (25 April 2015, Mw 7.8) were recorded in the Jingle well in Shanxi Province China (longitude E112.03°, latitude N38.35°, about 2769km from epicenter). Based on the observed water levels, we clearly identified signals relating to P, S and surface waves. However, the water temperature recorded at a depth of 350m shows no co-seismic changes. A spectrum analysis of co-seismic variations of water level shows that the oscillation frequency and amplitude of water level in the borehole are determined by the natural frequency of the borehole, which is not associated with the propagation of seismic waves. The borehole-aquifer system shows a large amplification associated with ground vibrations generated by earthquakes. Considering the local hydro-geological map and the temperature gradient of the Jingle well, a large volume “groundwater reservoir” model can be used to explain these processes. Due to seismic wave propagation, the volume of a well-confined aquifer expands and contracts forming fractures that change the water flow. In the well-confined aquifer, water levels oscillate simultaneously with high amplitude ground shaking during earthquakes. However, the water in the center of the “underground reservoir” remains relatively stationary, without any changes in the water temperature. In addition, a possible precursor wave is recorded in the water level at the Jingle well prior to the Gorkha earthquake.

Novel e8a2 BCR/ABL Fusion Transcript in Case of a Myeloproliferative Neoplasm.

Main objective of this work was to confirm the occurrence of rare BCR-ABL fusion variant involving the a2 region of the ABL gene and e8 of BCR gene in a patient of Myeloproliferative neoplasm positive for t(9;22) translocation but negative for common major and minor breakpoint cluster regions. A patient with elevated white blood cell count was subjected to classical cytogenetics, FISH as well as RT-PCR testing using commercial kits as well as published primers and in house testing protocol. The translocation event in chromosome 9 and 22 could be successfully detected. BCR/ABL dual color, dual fusion probe generated a classical balanced translocation scenario within the nucleus. In RT-PCR we found an unexpectedly large amplification band around 1700bp, which is consistent with e8a2 transcript. Nine metaphases showed 46,XY,t(9;22)(q34;q11.2)[9] by cytogenetic. A rare e8a2 break point in the BCR-ABL gene in myeloproliferative neoplasm disease detected in India. It also emphasizes the utility of cytogenetic and FISH for primary diagnosis of any neoplasm in blood. Our Patient detected rare BCR-ABL fusion variant e8a2 was on imatinib 400mg since last 3months. After 3months fluorescent in situ analysis and reverse transcriptase pcr analysis showed negative results.

Transient growth in Poiseuille-Rayleigh-Bénard flows of binary fluids with Soret effect

The transient growth due to non-normality is investigated for the Poiseuille-Rayleigh-Benard problem of binary fluids with the Soret effect. For negative separation factors such as ψ = −0.1, it is found that a large transient growth can be obtained by the non-normal interaction of the two least-stable-modes, i.e., the upstream and downstream modes, which determine the linear critical boundary curves for small Reynolds numbers. The transient growth is so strong that the optimal energy amplification factor G(t) is up to 102 ~ 103. While for positive separation factors such as ψ = 0.1, the transient growth is weak with the order O(1) of the amplification factor, which can even be computed by the least-stable-mode. However, for both cases, the least-stable-mode can govern the long-term behavior of the amplification factor for large time. The results also show that large Reynolds numbers have stabilization effects for the maximum amplification within moderate wave number regions. Meanwhile, much small negative or large positive separation factors and large Rayleigh numbers can enlarge the maximum transient growth of the pure streamwise disturbance with the wavenumber α = 3.14. Moreover, the initial and evolutionary two-dimensional spatial patterns of the large transient growth for the pure streamwise disturbance are exhibited with a plot of the velocity vector, spanwise vorticity, temperature, and concentration field. The initial three-layer cell vorticity structure is revealed. When the amplification factor reaches the maximum Gmax, it develops into one cell structure with large amplification for the vorticity strength.

Stability analysis of unstructured finite volume methods for linear shallow water flows using pseudospectra and singular value decomposition

The discretization of the shallow water system on unstructured grids can lead to spurious modes which usually can affect accuracy and/or cause stability problems. This paper introduces a new approach for stability analysis of unstructured linear finite volume schemes for linear shallow water equations with the Coriolis Effect using spectra, pseudospectra, and singular value decomposition. The discrete operator of the scheme is the principal parameter used in the analysis. It is shown that unstructured grids have a large influence on operator normality. In some cases the eigenvectors of the operator can be far from orthogonal, which leads to amplification of solutions and/or stability problems. Large amplifications of the solution can be observed, even for discrete operators which respect the condition of asymptotic stability, and in some cases even for Lax–Richtmyer stable methods. The pseudospectra are shown to be efficient for the verification of stability of finite volume methods for linear shallow water equations. In some cases, the singular value decomposition is employed for further analysis in order to provide more information about the existence of unstable modes. The results of the analysis can be helpful in choosing the type of mesh, the appropriate placements of the variables of the system on the grid, and the suitable discretization method which is stable for a wide range of modes.

Design of novel multidirectional magnetized permanent magnetic adsorption device for wall-climbing robots

A multidirectional magnetized permanent magnetic adsorption device (PMAD) for wall-climbing robots is proposed. The novel PMAD can significantly increase the adsorption force under the same mass. Firstly, the magnetic circuit of the novel PMAD was optimized based on the design theory proposed in this paper. The novel PMAD contains multiple closely arranged permanent magnets with different magnetizing directions. The magnets can be divided into several component units by the arrangement regulation of the magnetizing directions. In every component unit, the magnetizing directions distribute along a semi-circle. Secondly, Finite element analysis software Ansys Workbench was used for parameterized modeling, structural characteristic analysis, magnetic circuit simulation, adsorption force calculation and parameter optimization of the novel PMAD. Then, The novel and the Halbach type of PMADs with the same material and volume were trial-produced. The adsorption force was measured under different air gap thicknesses. The experimental results proved that the adsorption force of the novel PMAD doubled averagely compared with the Halbach type of PMAD under the same mass, and the largest amplification was 2.3 times. Finally, the novel PMADs were applied in a wall-climbing robot for ultrasonic testing, and provide steady and reliable adsorption.

Scattering of gravity waves in subcritical flows over an obstacle

We numerically study the scattering coefficients of linear water waves on stationary flows above a localized obstacle. We compare the scattering on trans- and subcritical flows, and then focus on the latter which have been used in recent analog gravity experiments. The main difference concerns the magnitude of the mode amplification: whereas transcritical flows display a large amplification (which is generally in good agreement with the Hawking prediction), this effect is heavily suppressed in subcritical flows. This is due to the transmission across the obstacle for frequencies less than some critical value. As a result, subcritical flows display high- and low-frequency behaviors separated by a narrow band around the critical frequency. In the low-frequency regime, transmission of long wavelengths is accompanied by non-adiabatic scattering into short wavelengths, whose spectrum is approximately linear in frequency. By contrast, in the high-frequency regime, no simple description seems to exist. In particular, for obstacles similar to those recently used, we observe that the upstream slope still affects the scattering on the downstream side because of some residual transmission.

Large Brillouin amplification in silicon

Strong Brillouin coupling has only recently been realized in silicon using a new class of optomechanical waveguides that yield both optical and phononic confinement. Despite these major advances, appreciable Brillouin amplification has yet to be observed in silicon. Using a new membrane-suspended silicon waveguide we report large Brillouin amplification for the first time, reaching levels greater than 5 dB for modest pump powers, and demonstrate a record low (5 mW) threshold for net amplification. This work represents a crucial advance necessary to realize high-performance Brillouin lasers and amplifiers in silicon.

Design and Control of a Compliant Microgripper With a Large Amplification Ratio for High-Speed Micro Manipulation

The design and control of a novel piezoelectric actuated compliant microgripper is studied in this paper to achieve fast, precise, and robust micro grasping operations. First, the microgripper mechanism was designed to get a large jaw motion stroke. A three-stage flexure-based amplification composed of the homothetic bridge and leverage mechanisms was developed and the key structure parameters were optimized. The microgripper was manufactured using the wire electro discharge machining technique. Finite element analysis and experimental tests were carried out to examine the performance of the microgripper mechanism. The results show that the developed microgripper has a large amplification factor of 22.6. Dynamic modeling was conducted using experimental system identification, and the displacement and force transfer functions were obtained. The position/force switching control strategy was utilized to realize both precision position tracking and force regulation. The controller composed of an incremental proportional-integral-derivative control and a discrete sliding mode control with exponential reaching law was designed based on the dynamic models. Experiments were performed to investigate the control performance during micro grasping process, and the results show that the developed compliant microgripper exhibits good performance, and fast and robust grasping operations can be realized using the developed microgripper and controller.

Galaxy bispectrum, primordial non-Gaussianity and redshift space distortions

Measurements of the non-Gaussianity of the primordial density field have the power to considerably improve our understanding of the physics of inflation. Indeed, if we can increase the precision of current measurements by an order of magnitude, a null-detection would rule out many classes of scenarios for generating primordial fluctuations. Large-scale galaxy redshift surveys represent experiments that hold the promise to realise this goal. Thus, we model the galaxy bispectrum and forecast the accuracy with which it will probe the parameter fNL, which represents the degree of primordial local-type non Gaussianity. Specifically, we address the problem of modelling redshift space distortions (RSD) in the tree-level galaxy bispectrum including fNL. We find novel contributions associated with RSD, with the characteristic large scale amplification induced by local-type non-Gaussianity. These RSD effects must be properly accounted for in order to obtain un-biased measurements of fNL from the galaxy bispectrum. We propose an analytic template for the monopole which can be used to fit against data on large scales, extending models used in the recent measurements. Finally, we perform idealised forecasts on σfNL—the accuracy of the determination of local non-linear parameter fNL—from measurements of the galaxy bispectrum. Our findings suggest that current surveys can in principle provide fNL constraints competitive with Planck, and future surveys could improve them further.

An Experimental Study of Tsunami Amplification by a Coastal Cliff

ABSTRACT Sim, S.Y. and Huang, Z., 2016. An experimental study of tsunami amplification by a coastal cliff. There is a general lack of understanding of the effects of coastal cliffs or other complex topography features on tsunami run-ups and tsunami heights onshore. We experimentally investigated several factors that might influence the amplification of onshore tsunami heights in the presence of a coastal cliff through a set of wave flume tests. The cross-shore bed profile used in the experiment was modeled using a composite slope made of three sections, with the gentlest section onshore to replicate the beach. A structure with an adjustable foreslope was mounted onto the beach section to model a coastal cliff. From our experimental results, a critical angle of about 45° was identified: the amplification factor increased with the cliff slope for cliffs gentler than 45°, and cliffs steeper than 45° gave more or less constant amplification factors for a given wave condition. The largest amplification factor ...

Assemble of high-density gold nanodots on TiO2 substrate for surface-e nhanced Raman spectroscopy

The cost-effective assemble of Au nanodots on TiO2 substrate over a large domain for high-sensitivity and reproducible surface enhanced Raman spectroscopy (SERS) is demonstrated. Au nanoparticles of defined size are immobilized on TiO2 to form high-density Au nanodots with removal of surface ligand meanwhile. The Au nanodots exhibit pronounced surface Plasmon resonance (SPR) due to strong interparticle coupling and hot spots formed in these gaps which enable large amplification of SERS signals. Using the Au nanodots (3.8nm) assemble a 5 times stronger SERS enhancement than larger Au nanoparticles (NPs) of same Au amount is experimentally demonstrated. The facile fabrication of SERS-active substrate over a large area and cost-effective character enable this high-density Au nanodots on TiO2 substrate practical application for SERS detection of trace amount of molecule of interest.

(Invited) Synthesis and Photoswitching Tunability of GHz Dielectric Property at e-Polarizable [60]Fullerosomic Surface of Hybrid Core-Shell Nanoparticles

We fabricated highly magnetic γ-FeOx@AuNP core-shell nanoparticles with deposition of fullerosome array of C60(>DPAF-C9) at the outer shell. It formed a configuration of three-layered core-shell (γ-FeOx@AuNP)@[C60(>DPAF-C9)]n 1. These surface-stabilized soluble NPs were found to be capable of photoinducing surface plasmonic resonance (SPR) effect in the inner Au layer by white LED light and subsequently transfer the accumulated PR energy at the interface to the outer, partially bilayered 1-derived fullerosome membrane layer in a near-field (~1.5 nm). The phenomena led to large amplification of dielectric properties associated with the photoswitching effect and the new unusual phenomenon of delayed photoinduced capacitor-like (i.e. electric polarization) behavior at the frequency range of 0.5‒4.0 GHz. The effect may be suitable for designing photoresponsive dielectric-switchable nanomaterial toward applications of GHz frequency devices.

Self-consistent model for the saturation mechanism of the response to harmonic forcing in the backward-facing step flow

Certain flows denominated as amplifiers are characterized by their global linear stability while showing large linear amplifications to sustained perturbations. As the forcing amplitude increases, a strong saturation of the response appears when compared to the linear prediction. However, a predictive model that describes the saturation of the response to higher amplitudes of forcing in stable laminar flows is still missing. While an asymptotic analysis based on the weakly nonlinear theory shows qualitative agreement only for very small forcing amplitudes, the linear response to harmonic forcing around the mean flow computed by direct numerical simulations presents a good prediction of the saturation also at higher forcing amplitudes. These results suggest that the saturation process is governed by the Reynolds stress and thus motivate the introduction of a simple self-consistent model. The model consists of a decomposition of the full nonlinear Navier–Stokes equations in a mean flow equation together with a linear perturbation equation around the mean flow, which are coupled through the Reynolds stress. The full fluctuating response and the resulting Reynolds stress are approximated by the first harmonic calculated from the linear response to the forcing around the aforementioned mean flow. This closed set of coupled equations is solved in an iterative manner as partial nonlinearity is still preserved in the mean flow equation despite the assumed simplifications. The results show an accurate prediction of the response energy when compared to direct numerical simulations. The approximated coupling is strong enough to retain the main nonlinear effects of the saturation process. Hence, a simple physical picture is formalized, wherein the response modifies the mean flow through the Reynolds stress in such a way that the correct response energy is attained.

Near‐fault effects on residual displacements of RC structures

SummaryResidual displacements of single‐degree‐of‐freedom systems due to ground motions with velocity pulses or fling step displacements are presented as a function of period T and of its ratio to the pulse period Tp. Four hysteretic behaviors are considered: bilinear elastoplastic, stiffness‐degrading with cycling, stiffness‐cum‐strength degrading, with or without pinching. When expressed in terms of T/Tp, peak inelastic and residual displacements due to motions with a pulse or fling appear similar to those due to far‐fault motions, if the response to far‐field records are expressed in terms of the ratio of T to the record's characteristic period. However, as the latter is usually much shorter than the pulse period of motions with fling, the range of periods of interest for common structures becomes a short‐period range under fling motions and exhibits very large amplification of residual and peak inelastic displacements. Similar, but less acute, are the effects of motions with a velocity pulse. Wavelets of different complexity are studied as approximations to near‐fault records. Simple two‐parameter wavelets for fling motions overestimate peak inelastic displacements; those for pulse‐type motions overestimate residual displacements. A more complex four‐parameter wavelet for motions with a velocity pulse predicts overall well residual and peak displacements due to either pulse‐ or fling‐type motions; a hard‐to‐identify parameter of the wavelet impacts little computed residual displacements; another significantly affects them and should be carefully estimated from the record. Even this most successful of wavelets overpredicts residual displacements for the periods of engineering interest. Copyright © 2016 John Wiley & Sons, Ltd.

Strong ground motion in the Kathmandu Valley during the 2015 Gorkha, Nepal, earthquake

On 25 April 2015, a large earthquake of Mw 7.8 occurred along the Main Himalayan Thrust fault in central Nepal. It was caused by a collision of the Indian Plate beneath the Eurasian Plate. The epicenter was near the Gorkha region, 80 km northwest of Kathmandu, and the rupture propagated toward east from the epicentral region passing through the sediment-filled Kathmandu Valley. This event resulted in over 8000 fatalities, mostly in Kathmandu and the adjacent districts. We succeeded in observing strong ground motions at our four observation sites (one rock site and three sedimentary sites) in the Kathmandu Valley during this devastating earthquake. While the observed peak ground acceleration values were smaller than the predicted ones that were derived from the use of a ground motion prediction equation, the observed peak ground velocity values were slightly larger than the predicted ones. The ground velocities observed at the rock site (KTP) showed a simple velocity pulse, resulting in monotonic-step displacements associated with the permanent tectonic offset. The vertical ground velocities observed at the sedimentary sites had the same pulse motions that were observed at the rock site. In contrast, the horizontal ground velocities as well as accelerations observed at three sedimentary sites showed long duration with conspicuous long-period oscillations, due to the valley response. The horizontal valley response was characterized by large amplification (about 10) and prolonged oscillations. However, the predominant period and envelope shape of their oscillations differed from site to site, indicating a complicated basin structure. Finally, on the basis of the velocity response spectra, we show that the horizontal long-period oscillations on the sedimentary sites had enough destructive power to damage high-rise buildings with natural periods of 3 to 5 s.

Microzonation of Seismic Hazards and Assessment of Potential Human Fatality in the Chianan Area, Taiwan

The purpose of this study is to assess seismic hazards in the 57 administration districts of the Chianan area (Chiayi County, Chiayi City, and Tainan City), Taiwan, in the form of ShakeMaps, as well as to estimate potential human fatalities from scenario earthquakes on the three type I active faults in this area. The resultant ShakeMap patterns of maximum ground motion show two regions with high modified Mercalli intensity (MMI; greater than IX). One is in the Chiayi area around Minsyong, Dalin, and Meishan due to presence of the Meishan fault and large site amplification factors. The other is in the Tainan area around Jiali, Madou, Siaying, Syuejia, Jiangjyun, and Yanshuei. The projected probabilities in 10, 30, and 50 yr periods with seismic intensity exceeding MMI VIII in these areas are greater than 45%, 80%, and 95%, respectively. Furthermore, from the distribution of probabilities, high values of greater than 95% over a 10 yr period with seismic intensity corresponding to Central Weather Bureau intensity V and MMI VI are found in central and northern Chiayi and northern Tainan. Finally, from estimation of potential human fatalities for scenario earthquakes on three active faults in Chianan area, it is noted that potential fatalities increase rapidly for people above age 45. Total fatalities reach high peaks in two age groups, ages 60–64 and 75–79, respectively, from scenario earthquakes on the Meishan and Chukou faults. On the other hand, total fatalities peak at ages 55–64 in the case of Hsinhua fault; this is probably because more people in this age group live in the nearby densely populated urban areas (>5000 persons/km2) such as the Yongkang District. We urge the local and central governments to pay special attention to seismic‐hazard mitigation in this urbanized area, with its large number of old buildings. Online Material: Maps of probabilities of exceeding Central Weather Bureau intensity (CWBI) V, VI, and VII and modified Mercalli intensity (MMI) VI and VII of ground shaking over 10, 30, and 50 yr periods.

Preliminary assessment of seismic site effects in the fluvio-lacustrine sediments of Kathmandu valley, Nepal

Seismic site effects are predicted adopting ground response analysis for the fluvio-lacustrine deposits of Kathmandu Valley using available geotechnical data. Equivalent linearization of nonlinear soil model has been analyzed for the study area with the geotechnical database up to the engineering bedrock level. The amplification ratio has been estimated to be varying from 1.9 to 7.8. As the peak spectral acceleration and predominant period largely contribute in the damage of structures, higher values of these parameters are consistent with the damage during 1934 Bihar–Nepal earthquake. The peak spectral acceleration for Kathmandu Valley has been estimated in a close range of 1.2725–1.2826 g. Meanwhile, the predominant period of valley soil varies from 0.27 to 0.61 s, representing the possible resonance, as 3–6 stories structures are the majority constructions in the study area. It has been contemplated that the upper 30 m of Kathmandu Valley soil would undergo large amplification with higher spectral acceleration and the predominant period shows the higher possibility of resonance with the construction trend of the buildings. Past events have shown the severity of damage level during earthquake events in Kathmandu Valley; as the capital city with the highest population density is residing in this area, similar scenario of damage may be witnessed in future events as well, so incorporating the local site effects is must. Thus, the present study provides insights on the level of risk and possible geotechnical basis for the mitigation of inherited earthquake risk in the valley.