Engineering Thermoelectric Performance of α-GeTe by Ferroelectric Distortion

The rhombohedralα-GeTe can be approximated as a slightly distorted rock-salt structure along its[111]direction and possesses superb thermoelectric performance.However,the role of such a ferroelectric-like structural distortion on its transport properties remains unclear.Herein,we performed a systematic study on the crystal structure and electronic band structure evolutions of Ge_(1-x)Sn_(x)Te alloys where the degree of ferroelectric distortion is continuously tuned.It is revealed that the band gap is maximized while multiple valence bands are converged at x=0.6,where the ferroelectric distortion is the least but still works.Once undistorted,the band gap is considerably reduced,and the valence bands are largely separated again.Moreover,near the ferro-to-paraelectric phase transition Curie temperature,the lattice thermal conductivity reaches its minima because of significant lattice softening enabled by ferroelectric instability.We predict a peak ZT value of 2.6 at 673 K inα-GeTe by use of proper dopants which are powerful in suppressing the excess hole concentrations but meanwhile exert little influence on the ferroelectric distortion.

A novel dual-channel thermo-optic locking method for the whispering gallery mode microresonator

Mode locking can be effectively achieved by using the thermo-optic effects in the whispering gallery mode(WGM)optical microcavity,without the help of external equipment.Therefore,it has the advantages of small size,low integration costs,and self-locking,which shows great potential for application.However,the conventional single-channel microcavity thermal-locking method that relies solely on internal thermal balance will inevitably be disturbed by the external environment.This limitation affects the locking time and stability.Therefore,in this paper,we propose a new method for closed-loop thermal locking of a dual-channel microcavity.The thermal locking of the signal laser and the thermal regulation of the control laser are carried out respectively by synchronously drawing a dual-path tapered fiber.The theoretical model of the thermal dynamics of the dual-channel microcavity system is established,and the influence of the control-laser power on the thermal locking of the signal laser is confirmed.The deviation between the locking voltage of the signal laser and the set point value is used as a closed-loop feedback parameter to achieve long-term and highly stable mode locking of the signal laser.The results show that in the 2.63 h thermal-locking test,the locking stability is an order of magnitude higher than that of the single tapered fiber.This solution addresses the issue of thermal locking being disrupted by the external environment,and offers new possibilities for important applications such as spectroscopy and micro-optical sensor devices.

Local tetragonal distortion of Pt alloy catalysts for enhanced oxygen reduction reaction efficiency

Platinum-based alloy nanoparticles are the most attractive catalysts for the oxygen reduction reaction at present,but an in-depth understanding of the relationship between their short-range structural information and catalytic performance is still lacking.Herein,we present a synthetic strategy that uses transition-metal oxide-assisted thermal diffusion.PtCo/C catalysts with localized tetragonal distortion were obtained by controlling the thermal diffusion process of transition-metal elements.This localized structural distortion induced a significant strain effect on the nanoparticle surface,which further shortened the length of the Pt-Pt bond,improved the electronic state of the Pt surface,and enhanced the performance of the catalyst.PtCo/C catalysts with special short-range structures achieved excellent mass activity(2.27 Amg_(Pt)^(-1))and specific activity(3.34 A cm^(-2)).In addition,the localized tetragonal distortion-induced surface compression of the Pt skin improved the stability of the catalyst.The mass activity decreased by only 13% after 30,000 cycles.Enhanced catalyst activity and excellent durability have also been demonstrated in the proton exchange membrane fuel cell configuration.This study provides valuable insights into the development of advanced Pt-based nanocatalysts and paves the way for reducing noble-metal loading and increasing the catalytic activity and catalyst stability.

Linear magnetoresistance and structural distortion in layered SrCu_(4-x)P_(2) single crystals

We report a systematic study on layered metal SrCu_(4-x)P_(2) single crystals via transport, magnetization, thermodynamic measurements and structural characterization. We find that the crystals show large linear magnetoresistance without any sign of saturation with a magnetic field up to 30T. We also observe a phase transition with significant anomalies in resistivity and heat capacity at T_(p)~140 K. Thermal expansion measurement reveals a subtle lattice parameter variation near Tp, i.e.,?L_(c)/L_(c)~0.062%. The structural characterization confines that there is no structure transition below and above T_(p). All these results suggest that the nonmagnetic transition of SrCu_(4-x)P_(2) could be associated with structural distortion.

Bulging Distortion of Austenitic Stainless Steel Sheet on the Partially Penetrated Side of Non-Penetration Lap Laser Welding Joint

Non-penetration laser welding of lap joints in austenitic stainless steel sheets is commonly preferred in fields where the surface quality is of utmost importance.However,the application of non-penetration welded austenitic stainless steel parts is limited owing to the micro bulging distortion that occurs on the back surface of the partial penetration side.In this paper,non-penetration lap laser welding experiments,were conducted on galvanized and SUS304 austenitic stainless steel plates using a fiber laser,to investigate the mechanism of bulging distortion.A comparative experiment of DC01 galvanized steel-Q235 carbon steel lap laser welding was carried out,and the deflection and distortion profile of partially penetrated side of the sheets were measured using a noncontact laser interferometer.In addition,the cold-rolled SUS304 was subjected to heat holding at different temperatures and water quenching after bending to characterize its microstructure under tensile and compressive stress.The results show that,during the heating stage of the thermal cycle of laser lap welding,the partial penetration side of the SUS304 steel sheet generates compressive stress,which extrudes the material in the heat-affected zone to the outside of the back of the SUS304 steel sheet,thereby forming a bulge.The findings of these experiments can be of great value for controlling the distortion of the partial penetrated side of austenitic stainless steel sheet during laser non-penetration lap welding.

Cross-section distortion and springback characteristics of double-cavity aluminum profile in force controlled stretch-bending

3D elastic-plastic FE model for simulating the force controlled stretch-bending process of double-cavity aluminum profile was established using hybrid explicit−implicit solvent method.Considering the computational accuracy and efficiency,the optimal choices of numerical parameters and algorithms in FE modelling were determined.The formation mechanisms of cross-section distortion and springback were revealed.The effects of pre-stretching,post-stretching,friction,and the addition of internal fillers on forming quality were investigated.The results show that the stress state of profile in stretch-bending is uniaxial with only a circumferential stress.The stress distribution along the length direction of profile is non-uniform and the maximum tensile stress is located at a certain distance away from the center of profile.As aluminum profile is gradually attached to bending die,the distribution characteristic of cross-section distortion along the length direction of profile changes from V-shape to W-shape.After unloading the forming tools,cross-section distortion decreases obviously due to the stress relaxation,with a maximum distortion difference of 13%before and after unloading.As pre-stretching and post-stretching forces increase,cross-section distortion increases gradually,while springback first decreases and then remains unchanged.With increasing friction between bending die and profile,cross-section distortion slightly decreases,while springback increases.Cross-section distortion decreases by 83%with adding PVC fillers into the cavities of profile,while springback increases by 192.2%.

Channel estimation in integrated radar and communication systems with power amplifier distortion

To reduce the negative impact of the power amplifier(PA)nonlinear distortion caused by the orthogonal frequency division multiplexing(OFDM)waveform with high peak-to-average power ratio(PAPR)in integrated radar and communication(RadCom)systems is studied,the channel estimation in passive sensing scenarios.Adaptive channel estimation methods are proposed based on different pilot patterns,considering nonlinear distortion and channel sparsity.The proposed methods achieve sparse channel results by manipulating the least squares(LS)frequency-domain channel estimation results to preserve the most significant taps.The decision-aided method is used to optimize the sparse channel results to reduce the effect of nonlinear distortion.Numerical results show that the channel estimation performance of the proposed methods is better than that of the conventional methods under different pilot patterns.In addition,the bit error rate performance in communication and passive radar detection performance show that the proposed methods have good comprehensive performance.

Computational Quantification of Map Projection Distortion by Fractal Dimension of Coastlines

Maps, essential tools for portraying the Earth’s surface, inherently introduce distortions to geographical features. While various quantification methods exist for assessing these distortions, they often fall short when evaluating actual geographic features. In our study, we took a novel approach by analyzing map projection distortion from a geometric perspective. We computed the fractal dimensions of different stretches of coastline before and after projection using the divide-and-conquer algorithm and image processing. Our findings revealed that map projections, even when preserving basic shapes, inevitably stretch and compress coastlines in diverse directions. This analysis method provides a more realistic and practical way to measure map-induced distortions, with significant implications for cartography, geographic information systems (GIS), and geomorphology. By bridging the gap between theoretical analysis and real-world features, this method greatly enhances accuracy and practicality when evaluating map projections.

1.55μm Fabry-Perot Thermo-Optical Tunable Filter with Amorphous-Si as Cavity

A 1.55μm Fabry-Perot (F-P) thermo-optical t unable filter is fabricated.The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique.Due to the excellent thermo-optical property of a-Si,the refractive index of the F-P cavity will be changed by heating;the transmittance resonant peak will therefore shift substantially.The measured tuning rang is 12nm, FWHM (full-width-at-half-maximum) of the transmissi on peak is 9nm,and heating efficiency is 0.1K/mW.The large FWHM is mainly due to th e non-ideal coating deposition and mirror undulation.Possible improvements to increase the efficiency of heating are suggested.

Price distortions and municipal bonds premiums:evidence from Switzerland

This study examines the pricing of municipal bonds before and after a currency shock in Switzerland.Two approaches are used to decompose the municipal to treasuries bond spreads into liquidity,maturity,and default risk premiums.The first approach is the model of the cross-sectional instrumental variables,and the second approach is the model of the instrumental variables with panel data.This study examines the composition of spreads for both approaches,in three scenarios:before,throughout,and after the currency shock.The study performed Durbin-Wu-Hausman tests for each decisive model to verify endogeneity issues,including the Lagrangian Multiplier test,the Cragg-Donald Wald F statistic to confirm the relationship of instrumental and endogenous variables,and the structural break test(Bai-Perron test)to determine the existence of structural breaks in bond distortions.This study finds that the currency price distortions of the Swiss franc in January 2015 made long-run changes in the composition of the municipal bond spreads.This research contributes to the understanding of municipal bond pricing by showing that default risk accounts for a large portion of the municipal bond spread,while maturity risk plays a lesser role.According to our empirical findings,unexpected large currency price shocks may have long-term implications on the municipal bond spreads.

Three-Dimensional Thermo-Elastic-Plastic Finite Element Method Modeling for Predicting Weld-Induced Residual Stresses and Distortions in Steel Stiffened-Plate Structures

The objective of the present paper is to develop nonlinear finite element method models for predicting the weld-induced initial deflection and residual stress of plating in steel stiffened-plate structures. For this purpose, three-dimensional thermo-elastic-plastic finite element method computations are performed with varying plate thickness and weld bead length (leg length) in welded plate panels, the latter being associated with weld heat input. The finite element models are verified by a comparison with experimental database which was obtained by the authors in separate studies with full scale measurements. It is concluded that the nonlinear finite element method models developed in the present paper are very accurate in terms of predicting the weld-induced initial imperfections of steel stiffened plate structures. Details of the numerical computations together with test database are documented.

Investigation of Induced Distortions in a-Si∶H/a-SiN_x∶H Multilayers by Raman Scattering Technique

The a-Si : H/SiN_x : H sample series are investigated by means ofRaman scattering technique(RST). The result shows that due to thestructural mismatch between a- Si: H and a-SiN_x : H, severe induceddistortions are produced in the interface of the heterojunction, andthese induced distortions tend towards a certain energy state. Theordering of the interface structure depends on the periodic number ofmuhilayer thin films.

Structural distortions and magnetisms in Fe-doped LaMn_(1-x) Fe_x O_3(0

X-ray absorption spectra （XAS） at Mn K-edge and Fe K-edge in LaMnl-xFexO3 show that with the increase of Fe substitution the chemical valence of Mn4＋ decreases, while the chemical valence of Fe3＋ remains unchanged. Structural distortions, such as the rotating and tilting for oxygen octahedron in the unit cell vary with iron content. A phase transition occurs at the Fe content values of 0.2~0.3. The evolutions of rotation and tilting angle of FeO6/MnO6 octahedral may be the vital factors to the structure and magnetism. We believe that the spin configuration of Fe3＋ may vary from the intermediate spin t2g4eg1 （S = 3/2） to the higher spin t2g3eg2 （S = 5/2） near the phase transition.

Distortions and Deformations of Metaled Meso-Substituted and Unsubstituted Porphyrins and Derivatives in Crystal Structures

Experimental crystallographic structural parameters of a range of metaled meso-substituted and unsubstituted porphyrins were reviewed to show how far the meso-substitution by any functional group and the insertion of metal in the porphyrins core macrocycle may affect the geometry. The analysis of twists and angles has shown two kinds of distortions: external [T(Cβ-Cα-Cmeso-Xn) and T(Cβ-Cα-Cmeso-Cα)] and internal [T(Nm-Cα-Cmeso-Xn) and T(Nn-Cα-Cmeso-Cα)] with averages of [+6°and –6°] and [–5°and +5°], respectively. In the meso-substituted case, the external and internal twists Cβ-Cα-Cmeso-X and N-Cα-Cmeso-X, respectively are oppositely orientated. Similar effect is observed in meso-unsubstituted of Cβ-Cα- Cmeso-H and N-Cα-Cmeso-H. However, the external distortions are more significant than internal. Considering the same order, the limit of distortions is [97°and 132°(–48°)] for external and [91°(–89°) and 52°] for internal. In the two cases, the substituents have opposite directions of distortions. The meso-substituted porphyrins have a high limit of twisting than usubstituted one, depending of the weight of substituents. The average of the bond angular deformations is 168°, almost planar. However, the limit of angular deformation is 94°.

Correction of distorted X-ray absorption spectra collected with capillary sample cell

In certain exceptional cases,capillary samples must be used to measure X-ray absorption spectra(XAS).However,the inho-mogeneous thickness of capillary samples causes XAS distortion.This study discusses the distortion and correction of the XAS curve caused by the inhomogeneous thickness of capillary samples.The relationship between the distorted XAS curveμ′d_(eq)(measured values)and the real absorption coefficientμ_(s)d_(eq)(true values)of the sample was established.The distortion was slight and negligible when the vertical size(2h)of the X-ray beam spot was smaller than 60%of the capillary tube’s inner diameter(2R_(in)).When h/R_(in)>1,X-ray leakage is inevitable and should be avoided during measurement.Partial X-ray leakage caused by an X-ray beam spot size larger than the inner diameter of the capillary tube leads to serious compressed distortion of the XAS curve.When h/R_(in)<1,the distorted XAS data were well corrected.Possible errors and their influence on the corrected XAS are also discussed.Simulations and corrections for distortions verify the feasibility and effectiveness of the corrected method.

Distortions, Growth Catch-up, and Sustainable Growth

A distortion is a departure from the allocation of economic resources from the state in which each agent maximizes his/her own welfare. Distortions can be divided into endogenous distortion(i.e. market imperfections) and policy-imposed distortion. The relationship between distortion and development is complex, thus favorable distortion would only be possible under certain conditions, where, as argued in this paper, four crucial mechanisms may play roles — advantage of backwardness, second-best principle, coordination failure and political economy perspective. Empirically, both international experience and evidence from China suggest that distortions have a positive effect on total factor productivity(TFP) in the early stages of development, but with increasing income levels this role gradually diminishes. Especially in the phases of middle and high income, the negative effects of distortions are significant and become an important factor leading to the middle-income trap. Therefore, reducing and correcting distortions is the key to achieving sustainable growth. Regarding China, it is necessary to eliminate the distortions in a clear way and let the market play the decisive role in resource allocation. Otherwise, in the name of "growth catch-up," the policy-imposed distortion will occur frequently, and the direction of market-oriented reform will become blurred and swing. Mitigating unfavorable distortions is largely a process of exploring the favorable borderline of government and market, which constitutes a major challenge for all economies.

Computerized Scheme for Histological Classification of Masses with Architectural Distortions in Ultrasonographic Images

Architectural distortion is an important ultrasonographic indicator of breast cancer. However, it is difficult for clinicians to determine whether a given lesion is malignant because such distortions can be subtle in ultrasonographic images. In this paper, we report on a study to develop a computerized scheme for the histological classification of masses with architectural distortions as a differential diagnosis aid. Our database consisted of 72 ultrasonographic images obtained from 47 patients whose masses had architectural distortions. This included 51 malignant (35 invasive and 16 non-invasive carcinomas) and 21 benign masses. In the proposed method, the location of the masses and the area occupied by them were first determined by an experienced clinician. Fourteen objective features concerning masses with architectural distortions were then extracted automatically by taking into account subjective features commonly used by experienced clinicians to describe such masses. The k-nearest neighbors (k-NN) rule was finally used to distinguish three histological classifications. The proposed method yielded classification accuracy values of 91.4% (32/35) for invasive carcinoma, 75.0% (12/16) for noninvasive carcinoma, and 85.7% (18/21) for benign mass, respectively. The sensitivity and specificity values were 92.2% (47/51) and 85.7% (18/21), respectively. The positive predictive values (PPV) were 88.9% (32/36) for invasive carcinoma and 85.7% (12/14) for noninvasive carcinoma whereas the negative predictive values (NPV) were 81.8% (18/22) for benign mass. Thus, the proposed method can help the differential diagnosis of masses with architectural distortions in ultrasonographic images.

Influence of Electrical Field Distortions Induced by Water Droplets on the Contamination Characteristics of an Insulator

When separated water droplets condense on the surface of a composite insulator,the electrical field on the insulator surface is distorted.In turn,such distortions change the trajectories of pollution particles.In this study,the COMSOL software is used to simulate such a process for the FXBW4-10/100 composite insulator with or without water droplets condensation under a 10 kV DC voltage.The influence of the wind speed and particles concentration on the contamination characteristics of the considered 110 kV insulator is analyzed.The results show that:1)in the presence of water droplets on the insulator surface,the ratio of electrical field force and gravity acting on the particles is large;2)the contamination on the insulator surface increases with the wind speed;3)when the wind speed is small,the relationship between the contamination amount and the pollution concentration is essentially linear.

Active Anomalous Transmission and Its Application in Compensating Waveform Distortions

In theoty, engineered anomalous transmission in passive materials and waveguide devices can be used to compensate for wavetorm distortions. However, they suffer from inherent dissipation. Recently, active non-Foster elements with imaginary immittance monotonically decreasing with frequency have shown important potentials in broadening bandwidths of electromagnetic devices. So far, they are implemented besed on negative impedance convertors （NICs） loaded with Foster devices. This makes them intrinsically one-port elements and thus cannot be used to compensate for distortions of signals. We construct a two-port network with a non-Foster transmission coefticient based on an unconventional use of NICs. Simulation and experiments show that it can compensate for extremely distorted signals. The proposed method can be used to broaden existing applications in different areas such as antennas, circuits and systems, and physical-layer signal processing.