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Combined inter- and intra-band spectroscopy studies are presented on structurally well-characterized InAs/GaAs(001) self-assembled quantum dots grown via conventional continuous deposition and the innovative punctuated island growth approach. Temperature and power dependent photoluminescence (PL) and PL Excitation (PLE) on these remarkably uniform quantum dot based samples (with typical PL linewidth 25 meV), reveal details of size-dependent electronic structure. These studies are complemented with systematic near- and middle-infrared photocurrent spectroscopy for interband through electron intra-band transitions as a function of temperature and applied electric field.

Photothermal ionization spectroscopy (PTIS) measurements were carried out on a free-standing, high purity and high quality 4H–SiC epitaxial layer at various temperatures. The two step photothermal ionization process is clearly reflected in the temperature dependence of the photoconductivity. The PTI spectrum at a temperature of 25.6 K exhibits one order of magnitude higher energy resolution than the infrared absorption spectra of 4H–SiC bulk material. It reveals five strong, well resolved electronic transition lines associated with the shallow nitrogen donor. The ionization energy of the shallow nitrogen donor is deduced to be 60.2±0.5 meV based on experimental results. Furthermore, PTI magnetospectroscopy measurements were performed to investigate the symmetry properties of these transitions in Faraday configuration. No linear Zeeman splitting is observed, however, these lines show a diamagnetic shift. It indicates that the excited states of the shallow nitrogen donor are nondegenerate at zero magnetic field, which is consistent with the fact that the effective mass tensor of 4H–SiC has three different diagonal components.

We report on a comprehensive study of the ZnSe(100)-c(232)-Na interface using x-ray and UV photoemission, and x-ray-induced Auger spectroscopy. Spectra were taken after stepwise Na deposition onto a clean c(232)-reconstructed ZnSe~100! surface at room temperature up to a saturation coverage of about 1 ML of Na and after annealing. Based on the analysis of Auger parameters and of the relative intensity evolution of various Na, Zn, and Se species, we present the following model for the ZnSe(100)-c(232)-Na interface: below a coverage of 0.5 ML, Na is adsorbed on Zn vacancy sites; above 0.5 ML, a cation exchange reaction occurs between Na and Zn atoms; Zn atoms segregate on top of the Na overlayer forming metallic Zn. In addition, band-bending, surface dipole, valence-band and surface states will be discussed. @S0163-1829~99!02336-X#

Direct and detailed information about the surface of differently sized CdS nanoparticles has been obtained from high-resolution X-ray photoelectron spectroscopy using tunable synchrotron radiation. We identify up to four distinct components in the S 2p core level spectra. Two of them are assigned to bulk and surface S-species of the nanoparticles, the latter arising from a surface core level shift due to their S-termination. The remaining S 2p components stem from S-atoms of the stabilizer thiol group bound to Cd and to S–S-bonds formed by thiol groups which are attached to surface S-atoms. In the latter case, the oxidation of the nanoparticle surface is drastically reduced.

We have investigated the valence band offset (ΔE VBO ) of the molecular beam epitaxially grown heterostructure HgTe/CdTe(001) by k-resolved ultraviolet (UPS) and X-ray (XPS) photoemission. Our angle-dependent UPS measurements at two different photon energies demonstrate that the dispersion of the valence band (VB) must be checked carefully in order to find the true position of the VB maximum in the Brillouin zone. With this information the valence band discontinuity was determined as (0.53 ± 0.03) eV, which is different from previously found photoemission values but now agrees well with magneto-optical investigations. In addition, we have determined the energy gap of CdTe(001) and HgTe(001) by a combination of UV and inverse photoemission. The energy gap of CdTe is determined to (1.57 ± 0.06) eV and that for HgTe as (0.0 ± 0.06) eV. We therefore conclude that HgTe is a semi-metal with inverted band structure in agreement with other results.

The thermal behaviour of CdS nanoparticles and especially of their surfaces has been investigated by high resolution photoelectron spectroscopy. Different annealing characteristics were observed for particles of different sizes. From the changes of surface core-level shifts in the S 2p and Cd 3d 5/2 spectra we derive that the nanoparticle surface, which is S-terminated at room temperature, changes after annealing by removal of S atoms and segregation of Cd atoms. Furthermore, we observe that the temperature at which this process takes place depends on the particle size.

The influence of humidity on the electronic structure of Na-containing polycrystalline Cu(In,Ga)Se2 thin films on soda-lime glass substrates has been investigated by x-ray and UV photoemission as well as by Auger electron spectroscopy. Different interactions between coadsorbed Na, H2O, and the Cu(In,Ga)Se2 surface are revealed at low temperatures and upon annealing at room temperature. Both, reversible and irreversible interactions such as a H2O-induced reduction of the Na surface content and the formation of a Na–O–Cu(In,Ga)Se2 complex are observed. Our findings can be correlated with the influence of ambient conditions on Cu(In,Ga)Se2 solar cell adsorbers and demonstrate the importance of adequate encapsulation of Na-containing Cu(In,Ga)Se2-based thin-film solar cells.

Far infrared magnetophotoconductivity performed on high purity GaAs reveals the existence of fine structures in the resonant magnetopolaron regions. The fine structures are attributed to the presence of bound phonons due to multiphonon processes. We demonstrate that the magnetopolaron energy spectrum consists of bound phonon branches and magnetopolaron branches. Our results also indicate that different phonons are bound to a single impurity, and that the bound phonon in Si-doped GaAs is a quasilocalized mode.

Poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) nanotubes, an excellent adsorbent, were successfully synthesized by an in situ template method and used for the removal of methylene blue (MB) from aqueous solution. The morphology and structures of as-synthesized PZS nanotubes were characterized by scanning electron microscopy, transmission electron microscope, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The effects of temperature, concentration, pH and contact time on MB adsorption were studied. It was favorable for adsorption under the condition of basic and high temperature. The pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to fit adsorption data in the kinetic studies. And results showed that the adsorption kinetics were more accurately described by the pseudo-second-order model. The equilibrium isotherms were conducted using Freundlich and Langmuir models. It has been demonstrated that the better agreement was Langmuir isotherm with correlation coefficient of 0.9933, equilibrium absorption capacity of 69.16 mg/g and the corresponding contact time of 15 min. Thermodynamic analyses showed that MB adsorption onto the PZS nanotubes was endothermic and spontaneous and it was also a physisorption process.

Background Only 2%-3% of patients with acute ischemic stroke receive thrombolysis. The aim of this study was to identify the reasons for exclusion from thrombolysis in patients admitted within the therapeutic time window. Methods Patient data in the hospital stroke registry between January 2012 and September 2013 were retrospectively examined. All cases with a diagnosis of ischemic stroke were screened, and those admitted to the neurology wards within 4.5 hours of symptom onset were analyzed. The reasons for exclusion from thrombolysis were examined. Logistic regression analysis was used to find independent predictors of thrombolysis treatment. Results Of the 1579 cases of ischemic stroke, 234 patients were admitted to the neurology ward within 4.5 hours of symptom onset. A total of 57 patients received thrombolysis. The thrombolysis rate was 3.6% of all ischemic stroke patients. Of the 177 patients who were excluded from thrombolysis, 36.2% (n = 64) had stroke of insufficient severity to warrant thrombolysis, and 24.9% (n = 44) were older than 80 years. Logistic regression analysis showed that the interval between symptom onset and admission (odds ratio 20.24, 95% confidence interval 3.75-109.24) and history of ischemic stroke (odds ratio .11, 95% confidence interval .04-.34) affected the likelihood of thrombolysis. Conclusions Mild stroke and advanced age were the major reasons for exclusion from thrombolysis in patients admitted within 4.5 hours of symptom onset. Patients who were admitted early and those without a history of ischemic stroke were more likely to receive thrombolysis.

For aerospace composite materials and structures, damage due to impact events may not be visible to surface inspection but still can cause significant loss of structural integrity. Therefore, an investigation was performed to develop a real-time health monitoring system for the identification and prediction of the location and force history of foreign object impact on composite panel structures with distributed built-in piezoceramic sensors. The smart health monitoring system is composed of two main subsystems: a measurement subsystem and an identification subsystem. The measurement subsystem with distributed built-in sensor network was used to collect and preprocess sensor data, and then the identification subsystem was implemented to reconstruct the force history and determine impact location with the acquired prefiltered sensor data. Thereupon, the identification subsystem consists of a structure system model, an inverse model operator (IMO) and a response comparator. The identification subsystem was created to identify the impact location and reconstruct the force history on composite structures without the need for the information about actual mechanical properties, geometries and boundary conditions of a structure, and without building a specific neural network with exhaustive training such as neural-network techniques, also without the need of constructing a full-scale accurate structural model. Consequently, a novel dynamic mechanical model based time-series model structure approach is used into the identification subsystem, where the entire impact identification procedure is much faster than that of the traditional model-based techniques. The smart health monitoring system was tested with various impact situations, for all of the cases considered, which verified the accuracy of impact load and position predictions, and the estimation errors fell well within the prespecified limit.

Helical structure is a sophisticated ubiquitous motif found in nature, in artificial polymers, and in supramolecular assemblies from microscopic to macroscopic points of view. Significant progress has been made in the synthesis and structural elucidation of helical polymers, nevertheless, a new direction for helical polymeric materials, is how to design smart systems with controllable helical chirality, and further use them to develop chiral functional materials and promote their applications in biology, biochemistry, medicine, and nanotechnology fields. This review summarizes the recent progress in the development of high-performance systems with tunable helical chirality on receiving external stimuli and discusses advances in their applications as drug delivery vesicles, sensors, molecular switches, and liquid crystals. Challenges and opportunities in this emerging area are also presented in the conclusion.

A total of six beams have been tested to investigate the influence of FRP sheet on the mechanical behavior of concrete beam with different FRP sheet width. In addition, the failure mode of the concrete beam and FRP reinforced concrete beams were also studied by numerical simulation method named Realistic Failure Process Analysis (RFPA). The results indicate that, the loading capacity is increased and maximum deflection of the concrete beam is also increased with the increasing of the FRP sheet width. Moreover, the interfacial debonding easily propagates along the interfacial concrete layer at a load that is below the estimated maximum strength of the FRP-strengthened structure. The maximum strength of the FRP sheet in the experiment was not achieved due to the adhesive layer between the concrete and FRP sheet was not strong enough compared with the numerical simulation result. It showed that the FRP sheet width was considered to be an important factor influence the failure mode and load capacity. So does the interface between the concrete and FRP plate.

The failure mode of the FRP reinforced concrete beam with different sheet length was investigated by experiments. The results indicate that, more cracks distributed on the bottom of the beam in the failure process of the FRP reinforced concrete structure. The effect of the FRP sheet length is considered to be an important factor not only to significantly influence the loading capacity but also to control the maximum deflection of the concrete beam. In addition, the loading capacity is increased and maximum deflection of the concrete beam is also increased with the increasing of the FRP sheet length. It showed that FRP strengthened beams failed prematurely in a brittle and sudden manner due to debonding between FRP and concrete substrate and therefore the full strength of the FRP sheet cannot be sufficiently utilized.

We report noise characteristics, carrier capture probability, and photoconductive gain of InAs quantum-dot infrared photodetectors with unintentionally doped active regions. At 77 K, a photoconductive gain of 750 was observed at a bias of 0.7 V. The high gain is a result of the low carrier capture probability: p=0.0012.

A new synchronization acquisition method based on the power spectrum analysis was studied and the theory analysis proved that the new algorithm has better synchronization performance than the traditional algorithm of sliding correlation acquisition. Also, the best band was got by discussing the center frequency of band-pass filter. At last, the whole simulation was given and the result showed that the new algorithm is fit for the real Spread Spectrum System.

To further the objective of controlled manipulation of the electronic states in epitaxial island quantum dots (QDs), we introduce the notion of a lateral potential confinement layer (LPCL) whose judicious placement during island capping allows selective impact on ground and excited electron and hole states. The energy states of InAs/In0.15Ga0.85As QDs are manipulated using 10-monolayer-thick In0.15Al0.25Ga0.60As LPCLs positioned at the bottom, upper, and top region of the QDs. The changes in the photoluminescence (PL) and PL excitation spectra reveal the nature of the electronic transitions impacted selectively through the spatial charge distributions of the states involved.

We report a bias-controllable multiwavelength quantum dot infrared photodetector (QDIP). The active region of the QDIP consisted of five layers of InAs quantum dots with InGaAs cap layers. Photoresponse peaks at 5.5, 5.9, 8.9, and 10.3–10.9 μm were observed. The relative response of these peaks could be controlled through the applied bias. For 5.9 μm detection, a peak detectivity, D*, of 5.8×109 cm Hz1/2/W at 77 K and 0.3 V was achieved.

We present experimental evidence for the existence and directionality of dipoles induced by intraband transitions from the electron ground states to high, bound excited states in self-assembled InAs/GaAs quantum dots (QDs). Moreover, the orientation of the interband transition induced dipoles is also determined for the same QDs. The findings indicate the potential use of intraband dipoles in asymmetric QDs in proposed quantum gates.

We report the realization of electron intraband absorption based middle- (∼5.6 μm) and long- (∼10 μm) wavelength infrared (IR) photoresponse for normally incident radiation on InGaAs-capped GaAs(001)/InAs quantum dots (QDs) in a n–i(QD)–n structure. The relative photoresponse in this dual-wavelength structure is tunable up to two orders of magnitude with bias. The full width at half maximum of the long-wavelength IR intraband photocurrent peak at 80 K is as narrow as 8.2 meV.

Guangdong walk in the forefront of reform and opening up, sustained economic growth in the nearly 30 years, adjustment of the industrial structure and upgrade at a key time. However,Eastern, Northern and Western of Guangdong and the Pearl River Delta region Lack of coordination issues such as restricting the industrial structure of Guangdong industrial economic development. In recent years, the state and the Guangdong provincial government enacted a series of coordinated industrial policy, the Guangdong government at all levels to guide the industrial structure adjustment, but can not reach the budget targets, the same industrial structure still existed, or even more serious. In this paper, to study this issue Inquiry. First, Accordingly, the author discuss why the local government's plight game caused the same of the Guangdong's industrial structure, and what the main means, the causes of this results in the industrial structure of Guangdong. Secondly, the author have one study way base on the plight of local governments' Game to adjust the industrial structure.

We report on tailoring detection bands of InAs quantum-dot infrared photodetectors (QDIPs) using InxGa1−xAs strain-relieving capping layers that also act as quantum wells (QWs). QDIPs with InAs QDs capped by a 20 ML In0.15Ga0.85As QW show a sharp photoresponse at ∼9 μm, while the counterpart QDIPs without QWs show broad photoresponse in the 5–7 μm range. The excited states involved in the intraband transitions in QDIPs with the In0.15Ga0.85As QW appear to be coupled QD and QW electron excited states.

The synchronous carrier is difficult to extract in low SNR power line communication environment by traditional spread-spectrum demodulation method. To solve this problem, a novel design of DSSS (Direct Sequence Spread Spectrum) receiver, based on Software radio structure and band-pass sampling theorem is proposed in this paper. The designed receiver consists of A/D converter and digital low-pass filter, which can demodulate information without carrier synchronization. Moreover, spread-spectrum demodulation can be realized in base band. Both theoretical analysis and simulation results prove that the novel receiver structure has low system spending and high anti-noise performance and it can be applied in rough communication environment.

In this paper, a complex wireless sensing unit is designed for application in structural health monitoring systems. Fabricated from advanced embedded system technologies, the fundamental building block of the system is a wireless sensing unit capable of employing a spread-spectrum wireless modem for peer-to-peer communication between sensing units and a complex 32-bit computational core for local data interrogation in real time. The computational capabilities of the prototype structural health monitoring system design can be utilized for execution of embedded engineering analyses such as damage detection and system identification. To illustrate the computational capabilities of the system, methods for fitting auto-feedback time series models are executed as algorithms embedded in the units of the system. The research goal is that the important techniques embedment support the collaborative processing of real-time measurement data for the identification of potential damage in a structural system, and suggest strong potential for unit installation in automated structural health monitoring systems.

The system complexity, detection probability and average acquisition time are the most important performances. This paper proposes a novel method to reduce false-alarm probability and improve these performances, which utilizes the changes of power spectral density between in-sync and out-of-sync, and uses the difference of signals in-band and out-of-band instead of the signals in-band as the inputs of threshold comparator. What is more, this paper also proposes an adaptive threshold adjustment technology, which bases on the average power spectral density of received signals. At last, the simulation results are given.

This paper presents a BFSK demodulation method using discrete short-time Fourier transform (DSTFT). The method discusses the BFSK signal in time-frequency domain, which is different from conventional demodulation methods. The principle of demodulation and a new code synchronization algorithm are given in the paper, different window functions are tried during the simulation, which bring different demodulated performance. And the test results indicates the demodulation is all right.

Methods 20 SD patients with thoracic kyphosis aged 10 to 18 years were included in this study. 30 healthy volunteers were recruited to serve as controls. Computed tomography 3D reconstruction of the total sternum in supine position was performed. The length, width, thickness of manubrium and mesosternum was measured respectively. Meanwhile, the angle (a) between the axis of manubrium and that of mesosternum were also measured. The size of sternum and angle a were compared between SD patients and normal controls using the Studenst test.

This paper reviews recent progresses in developing self-assembled InAs/GaAs quantum dots based infrared photodetectors, especially, with n-i(QDs)-n configuration. These significant progresses indicate a realistic hope that QDIPs can be exploited for mid-infrared imaging application.

Fourier transform infrared photoconductivity spectra of Si donors in GaAs under magnetic field are presented in this paper. Four new spectral lines corresponding to the transitions from hydrogen-like ground state to the metastable states (510), (610), (710), and (810) under nonzero magnetic field were observed. The variational calculation model proposed by Barmby et al. was applied to the high-lying metastable states. The experimental data of the transition energies agree well with the variational results under high magnetic field and below the resonant polaron region. Deviations due to omitting the bound Landau continuum coupling in the trial wave function were found in the comparison at the low field region for the metastable states with higher Landau index. The ionization energies of the high-lying metastable states were also determined.

Far infrared photoconductivity spectra of B‐doped Si1−xGex grown by Czochralski technique have been investigated in the temperature region from 4.2 to 34 K as well as under high magnetic fields. The photo ionization transition from the ground state of boron acceptor to P3/2 valence band and that related to spin‐orbit splitting valence band (P1/2) are observed. The experimental results show that the ionization energy of boron acceptor in Si1−xGex decreases fast and linearly with the increase of Ge concentration for lower Ge composition, and 4% Ge contents make a decrease of 14 meV for the ionization energy of boron in Si0.96Ge0.04. The photoconductivity spectra hardly change with magnetic field up to 11 T.

We report a series of InAs quantum dots infrared photodetectors. By using InGaAs cap layers and InAIGaAs lateral potential confinement layers, the peak absorption can be manipulated in from /spl sim/5.6 /spl mu/m to /spl sim/9 /spl mu/m.

In this paper, we present a study of a series of InAs quantum dot infrared photodetectors (QDIPs) with unintentionally doped active regions. The wavelength tunability will be demonstrated by changes of the content of In and Al in the InGaAs cap layers and InAlGaAs lateral potential confinement layers. The samples were grown on semi-insulating GaAs(001) substrates by solid-source molecular beam epitaxy (MBE). Fourier transformation infrared (FTIR) spectroscopy measurement demonstrated peak photoresponses at the wavelength ranging from /spl sim/ 5.6 /spl mu/m to /spl sim/ 9 /spl mu/m. The dark current and noise of the QDIP samples were measured at various temperature.

The temperature dependence of the orientation of intraband-transition-induced dipoles in self-assembled InAs/GaAs(001) quantum dots (QDs) embedded in n-i(QDs)-n configuration was reported.

A method was developed to measure the tetramine in plasma by liquid-liquid extraction and GC-NPD with the limit of detection (LOD) 1.5 pg and the limit of quantity 10 ng/ml. The linear range was 0.1-5 micrograms/ml with a correlation coefficient of 0.999. Recoveries for three concentrations of tetramine were 96.0%, 107.0%, 106.8%. The intra-day precision were 9.6%, 9.8%, 7.8%, the inter-day precision were 6.6%, 8.5%, 6.2%. Tetramine in plasma was stable up to 5 months at -4 degrees C.

We report on normal-incidence single and dual-wavelength intraband infrared photodetectors (with contacts in the vertical configuration) based on epitaxial InAs/InAlGaAs quantum dots.

This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, high-power photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).

This paper surveys recent work in several photodetector areas including high-speed, low-noise avalanche photodiodes, solar-blind ultra-violet PIN photodiodes, and quantum dot infrared photodetectors (QDIPs).

Manipulation and control of the electronic structure of quantum dots (QDs) is of central importance to their applications in electronics and optoelectronics. Such tuning is typically carried out by varying the QD average size and shape, or the capping layer, or annealing QDs thermally. Most these approaches do not allow selective tuning some QD states but not others. In this report, we introduce and demonstrate a mean of achieving selective tuning of energy levels through the use of a thin layer, called here the lateral potential confinement layer (LPCL), positioned at the bottom, upper, or top regions of the QDs.

The progress of detection method of four forbidden rodenticides, including fluoroacetamide, sodium fluoroacetate, gliftor and tetramine is reviewed in this paper. The technique of sample preparation and gas chromatography are emphasized.

The FTIR photoconductivity measurements and theoretical comparison of the magnetic field induced metastable states of the hydrogen-like donors in GaAs are reported in this paper. The transitions from the ground bound Is state to the high-lying metastable states of Si donors are observed and identified. A simplified trial wave-function is applied to these high-lying metastable states and the variational calculations are in good agreement with our experimental data. The electron-phonon interaction related with the metastable states are investigated. Integrated energy spectra consist of the resonant magneto-polaron branches and the bound phonon branches, which corresponding to the multiple phonon process, are obtained for the first time.

InAs quantum dot infrared photodetectors based on bound-to- bound intraband transitions in undoped InAs quantum dots are reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 micrometers . At 77 K and -0.7 V bias the responsivity was 14 mA/W and the detectivity, D*, was 1010 cmHz1/2/W. By introducing InGaAs cap layers, a QDIP with bias-controllable two-color characteristic was demonstrated.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

InAs/AlGaAs quantum dot infrared photodetectors based on bound-to-bound intraband transitions in undoped InAs quantum dots are reported. AlGaAs blocking layers were employed to achieve low dark current. The photoresponse peaked at 6.2 μm. At 77 K and –0.7 V bias the responsivity was 14 mA/W and the detectivtiy, D*, was 1010 cmHz1/2/W.

Photoelectron spectroscopy (XPS, UPS) has been employed to study the influence of humidity on external and internal surfaces of RTP-processed polycrystalline Cu(In,Ga)Se/sub 2/ thin films for solar cells. Various interactions of deliberately deposited or segregated Na with adsorbed H/sub 2/O have been found. The Na content at the CIGS surface is changed by an H/sub 2/O-induced segregation of Na at low temperatures (100 K) and by reaction and desorption at higher temperatures. Further reactions, such as the passivation of as-deposited "metallic" Na and the formation of a Na-O-CIGS complex influence the electronic structure (i.e. the workfunction and band bending) and are thus of great importance for the electrical performance of corresponding solar cells.

Summary form only given. Magneto-optical effect has been attracting more and more attention because of its theoretical and practical values. The Faraday magneto-optical rotation characteristics of polyaniline film has been studied in this paper. It is demonstrated experimentally that there is fine linear relationship between the Faraday rotation angle and magnetic field intensity at the case of low magnetic field, which can be explaned according to the classical Faraday magneto-optical theory, and the Faraday rotation angle increases and decreases alternately with the increase of magnetic field intensity at the case of high magnetic field which can be explaned according to the quantum theory of Faraday magneto-optical effect. Since the Faraday magneto-optical property is dependent on the change rate of the refractive index with wave length of light, the peak of Faraday rotation spectrum and the peak of absorption spectrum are accompanied but do not coincide with each other for Polyaniline film. The effective mass of charge carrier in poyaniline film can be obtained from the experimental results of Faraday magnetic rotation. The effective mass of charge carrier is importent physical parameter of material.