NiTi形状记忆合金在恒定应力和温度下保温过程中马氏体相变诱发的可恢复应变

研究NiTi形状记忆合金在应力下等温保温过程中的应变变化。为了研究可恢复应变,对Ni_(51)Ti_(49)和Ti_(40.7)Hf_(9.5)Ni_(44.8)Cu_(5)合金进行3种制度的保温处理,分别是:应力下冷却后在应力下保温(制度1);无应力和载荷下冷却后在应力下保温(制度2);具有双向形状记忆效应的样品在应力下保温(制度3)。结果表明,所有制度中,在应力下保温后样品均会发生应变变化。该应变在后续热处理或卸载后能恢复,因此表明应变变化是由等温马氏体相变引起的。这种等温应变取决于合金的化学成分、等温保温制度、应力和保温温度。Ti_(40.7)Hf_(9.5)Ni_(44.8)Cu_(5)合金(制度1)和Ni_(51)Ti_(49)合金(制度2)的最大等温应变分别为3.4%和6.1%。制度3中的保温伴随着较小的应变(小于0.3%)。讨论储存弹性能对等温马氏体相变的影响,结果表明,当相变伴随着较小的储存弹性能时,等温应变较大。

Influence of Particle Size Distribution on the Optical Properties of Fine-Dispersed Suspensions

Nanofluids have great potential for solar energy harvesting due to their suitable optical and thermophysical properties.One of the promising applications of nanofluids is utilization in solar collectors with the direct absorption of light(DASC).The design of a DASC requires detailed knowledge of the optical properties of nanofluids,which can be significantly affected by the particle size distribution.The paper presents the method to take into account the particle size distribution when calculating nanofluid extinction spectra.To validate the proposed model,the particle size distribution and spectral absorbance were measured for aqueous suspension with multi-walled graphite nanotubes;the minimum size of primary nanoparticles was 49 nm.The proposed model is compared with experiments demonstrating the concentration averaged and maximum discrepancies of 6.6%and 32.2%against 12.6%and 77.7%for a model assuming a monosized suspension.

XFEL and HHG interaction with matter:Effects of ultrashort pulses and random spikes

The theory of photoionization describing the interaction of x-ray free-electron laser(XFEL)pulses and high-harmonic-generated(HHG)radiation is generalized to ultrashort laser pulses,where the concept of the standard ionization probability per unit time in Fermi’s golden rule and in Einstein’s theory breaks down.Numerical calculations carried out in terms of a generalized photoionization probability for the total duration of pulses in the near-threshold regime demonstrate essentially nonlinear behavior,while absolute values may change by orders of magnitude for typical XFEL and HHG pulses.XFEL self-amplified spontaneous emission pulses are analyzed to reveal general features of photoionization for random and regular spikes:the dependences of the nonlinear photoionization probability on carrier frequency and spike duration are very similar,allowing an analytical expectation value approach that is valid even when there is only limited knowledge of random and regular parameters.Numerical simulations carried out for typical parameters demonstrate excellent agreement.

Scattering of ultrashort laser pulses on plasmons in a Maxwellian plasma

On the basis of equations obtained in the framework of second-order quantum-mechanical perturbation theory,the standard approach to the calculation of scattering radiation probability is extended to the case of ultrashort laser pulses.Weinvestigate the mechanism of the appearance of plasmon peaks in the spectrum of the plasma form factor for different parameters of the problem.For the case in which scattering on plasmons dominates over scattering on electron density fluctuations caused by chaotic thermal motion,we derive analytical expressions describing the scattering probability of ultrashort laser pulses on plasmons.Together with this,we obtain a simple expression connecting the frequency of scattered radiation and the energy transmitted from the incident pulse to plasmon,and vice versa.In considering the scattering probability,our emphasis is on the dependence on the pulse duration.Weassess in detail the trends of this dependence for various relations between pulse carrier frequency and plasmon energy.

Precise wavelength measurements of potassium He- and Li-like satellites emitted from the laser plasma of a mineral target

Atomic models of high-Zmulticharged ions are extremely complex and require experimental validation.Oneway to do so is to crosscheck the predicted wavelengths of resonance transitions in He-and Li-like ions against precise spectroscopic measurements that use the spectral lines of H-like ions for spectra calibration;these reference data can be modeled with outstanding precision.However,for elements with Z of at least 15,it is quite difficult to create a hot dense plasma with a large concentration ofH-like charge states.To mitigate this issue,the suggestion here is to use as laser targets particular minerals comprising elements with moderate(between 15 and 30)and low(less than 15)Z,with emission from the latter delivering perfect reference lines over a whole range o fHe-and Li-like moderate-Z emission under examination.This approach is implemented to measure the wavelengths of resonance transitions(1snp→1s^(2) for n=2,3)in He-likeKions and their dielectronic satellites by irradiating plates of orthoclase(KAlSi_(3)O_(8))with0.5-kJ subnanosecond laser pulses.X-ray spectra of the laser-generated plasma contain the investigated lines of highly charged K-ions together with precisely known reference lines of H-like Al and Si atoms.The K-shell spectral line wavelengths are measured with a precision of around 0.3 mA.

Search for Signatures of New Heavy Top Quark of the Fourth Generation at the Hadron Colliders

The Fourth Generation and Vector Like Quark (VLQ) models are extensions of the Standard Model of particles physics. These models predict the existence of new heavy quarks like heavy top quark t' with electric charge 2/3 and heavy bottom quark b' with electric charge -1/3. The t' and b' will act the fourth generation quarks. In current work we present a search for a pair production of a fourth generation quark, t' quark and its antiparticle, followed by their decays to Z, W bosons followed by decays to trilepton e-e-μ+ plus jets and missing transverse energy in the final state according to the process . We use Monte Carlo simulation techniques Pythia8, MadGraph5 and CalcHEP to simulate this process at both the Large Hadron Collider at CERN (proton-proton collisions) and the Fermilab Tevatron Collider (proton-antiproton collisions). We assume that the t' quark is a narrow state that always decay to a W and Z bosons plus jets. We select 2 electrons + jets+ missing energy final states with one isolated μ with high transverse momentum. The three charged leptons plus missing energy in the final state offer the best discovery potential at the hadron colliders for new heavy top quark mass of 500 GeV. We study the possible signals at both the LHC and the Tevatron of new quarks t' coupled to the third generation quarks in the context of fourth generation and vector like quark models under the assumption of a branching ratios BR(t'→Wb)=50%?and BR(t'→Zt)=50%. Heavy quark pair production gives interesting signals in final states with three charged leptons plus missing energy. Finally, from our analysis the new heavy fourth generation quark t' can be discovered at both the Tevatron and the LHC with mass 500 GeV.

Neural Networks Search for Charged Higgs Boson in Two Doublet Higgs Model at the Hadrons Colliders

In this work we present an analysis of a search for charged Higgs boson in the context of Two Doublet Higgs Model (2HDM) which is an extension of the Standard Model of particles physics where the 2HDM predicts by existence scalar sector with new five Higgs bosons;two of them are electrically charged and the other three Higgs bosons are neutral charged. Our analysis based on the Monte Carlo data produced from the simulation of 2HDM with proton antiproton collisions at the Tevatron = 1.96 TeV (Fermi Lab) and proton proton collisions at the LHC = 14 TeV (CERN) with final state includes electron, muon, multiple jets and missing transverse energy via the production and decay of the new Higgs in the hard process where the dominant background (electrons and muons) for this process comes from the Standard Model processes via the production and decay of top quark pair. We assumed that the branching ratio of charged Higgs boson to tau lepton and neutrino is 100%. We used the Artificial Neural Networks (ANNs) which are an efficient technique to discriminate the signal of charged Higgs boson from the SM background for charged Higgs boson masses between 80 GeV and 160 GeV. Also we calculated the production cross section at different energies, decay width, branching ration and different kinematics distribution for charged Higgs boson and for the final state particles.

Unveiling the early universe:Axion-like particles and their role in primordial structure formation

The groundbreaking discovery of gravitational waves(GWs)by the LIGO-VIRGO-KAGRO collaboration has revolutionized our understanding of the universe and opened up a new way of observing cosmic events. Unlike light waves, GWs allow us to probe the universe in its infancy.

Footprints of axion-like particle in pulsar timing array data and James Webb Space Telescope observations

Several pulsar timing array(PTA) collaborations have recently reported the evidence for a stochastic gravitational-wave background(SGWB), which can unveil the formation of primordial seeds of inhomogeneities in the early universe. With the SGWB parameters inferred from PTAs data, we can make a prediction of the seeds for early galaxy formation from the domain walls in the axion-like particles(ALPs) field distribution. This also naturally provides a solution to the observation of high redshifts by the James Webb Space Telescope. The predicted photon coupling of the ALP is within the reach of future experimental searches.

Chapter 5 Dark Matter and New Physics Beyond the Standard Model with LHAASO

In order to reveal the nature of dark matter,it is crucial to detect its non-gravitational interactions with the standard model particles.The traditional dark matter searches focused on the so-called weakly interacting massive particles.However,this paradigm is strongly constrained by the null results of current experiments with high precision.Therefore there is a renewed interest of searches for heavy dark matter particles above TeV scale.The Large High Altitude Air Shower Observatory(LHAASO)with large effective area and strong background rejection power is very suitable to investigate the gamma-ray signals induced by dark matter annihilation or decay above TeV scale.In this document,we review the theoretical motivations and background of heavy dark matter.We review the prospects of searching for the gamma-ray signals resulted from dark matter in the dwarf spheroidal satellites and Galactic halo for LHAASO,and present the projected sensitivities.We also review the prospects of searching for the axion-like particles,which are a kind of well motivated light pseudo-scalars,through the LHAASO measurement of the very high energy gamma-ray spectra of astrophysical sources.

Genetically encoded BRET-activated photodynamic therapy for the treatment of deep-seated tumors

Photodynamic therapy(PDT)is one of the most appealing photonic modalities for cancer treatment based on anticancer activity of light-induced photosensitizer-mediated reactive oxygen species(ROS),but a limited depth of light penetration into tissues does not make possible the treatment of deep-seated neoplasms and thus complicates its widespread clinical adoption.Here,we introduce the concept of genetically encoded bioluminescence resonance energy transfer(BRET)-activated PDT,which combines an internal light source and a photosensitizer(PS)in a single-genetic construct,which can be delivered to tumors seated at virtually unlimited depth and then triggered by the injection of a substrate to initiate their treatment.To illustrate the concept,we engineered genetic NanoLuc-miniSOG BRET pair,combining NanoLuc luciferase flashlight and phototoxic flavoprotein miniSOG,which generates ROS under luciferase-substrate injection.We prove the concept feasibility in mice bearing NanoLuc-miniSOG expressing tumor,followed by its elimination under the luciferase-substrate administration.Then,we demonstrate a targeted delivery of NanoLuc-miniSOG gene,via tumor-specific lentiviral particles,into a tumor,followed by its successful elimination,with tumor-growth inhibition(TGI)coefficient exceeding 67%,which confirms a great therapeutic potential of the proposed concept.In conclusion,this study provides proof-of-concept for deep-tissue“photodynamic”therapy without external light source that can be considered as an alternative for traditional PDT.

Eu luminescence from BaTiO_(3)/SiO_(2)multilayer xerogel structures

Sol-gel technology was applied to fabricate Eu-doped BaTiO_(3)/SiO_(2)multilayer structures by spinning on silicon and fused silica substrates.Eu photoluminescence(PL)was investigated depending on the annealing temperature of these structures.The samples demonstrate the room temperature luminescence corresponding to^(5)D^(0)→^(7)F_(J)(J=1,2,3,4)transitions of trivalent europium with the most intensive band at 615 nm.For the structure on fused silica with Eu in the BaTiO_(3)cavity,increase of the annealing temperature from 450℃to 700℃results in modification of the luminescence indicatrix and lowering of the luminescence intensity in the direction along the surface normal.For BaTiO_(3)/SiO_(2)multilayer structure generated on silicon,scanning electron microscopy(SEM)analyses reveal disordering after annealing at 1000℃.This heat treatment provides also an increase of the Eu luminescence intensity.

Testing B-violating signatures from exotic instantons in future colliders

We discuss possible implications of exotic stringy instantons for baryon-violating signatures in future colliders. In particular, we discuss high-energy quark collisions and A- transitions. In principle, the A-A process can be probed by high-luminosity electron-positron colliders. However, we find that an extremely high luminosity is needed in order to provide a （somewhat） stringent bound compared to the current data on NN→ππ,KK. On the other hand, （exotic） instanton-induced six-quark interactions can be tested in near future high-energy colliders beyond LHC, at energies around 20-100 TeV. The Super proton-proton Collider （SppC） would be capable of such measurement given the proposed energy level of 50-90 TeV. Comparison with other channels is made. In particular, we show the compatibility of our model with neutron-antineutron and NN→ππ, KK bounds.

Quantum Monte-Carlo simulation of FeAs-based superconductors

The generalized quantum Monte Carlo algorithm is developed and used to calculate the energy,occupation numbers,and correlations functions of finite FeAs clusters in the two-orbital model at finite temperatures.The coding of quantum states made it possible to take into account complex exchange terms between the orbitals.The results for the calculation of the thermodynamic characteristics of finite two-dimensional FeAs clusters simulating iron-based superconductors have been obtained.The calculated correlation functions indicate the possibility of the effective attraction of charge carriers.