ABSTRACT
Multiforce nickel-titanium (NiTi) orthodontic archwires release progressively increasing forces in a front-to-back direction along their length. The properties of NiTi orthodontic archwires depend on the correlation and characteristics of their microstructural phases (austenite, martensite and the intermediate R-phase). From a clinical and manufacturing point of view, the determination of the austenite finish (Af) temperature is of the greatest importance, as in the austenitic phase, the alloy is most stable and exhibits the final workable form. The main purpose of using multiforce orthodontic archwires is to decrease the intensity of the applied forces to the teeth with a small root surface area, such as the lower central incisors, and also provide forces high enough to move the molars. With the optimally dosed forces of multiforce orthodontic archwires in the frontal, premolar and molar segments, the feeling of pain can be reduced. This will contribute to the greater cooperation of the patient, which is of utmost importance to achieve optimal results. The aim of this research was to determine the Af temperature at each segment of as-received and retrieved Bio-Active® and TriTanium® archwires with dimensions of 0.016 × 0.022 inches, investigated by the differential scanning calorimetry (DSC) method. A classical Kruskal-Wallis one-way ANOVA test and multi-variance comparison based on the ANOVA test statistic using the Bonferroni corrected Mann-Whitney test for multiple comparisons were used. The incisor, premolar and molar segments have different Af temperatures, and they decrease from the anterior to posterior so that the posterior segment has the lowest Af. Bio-Active® and TriTanium® with dimensions of 0.016 × 0.022 inches can be used as first leveling archwires by additional cooling and are not recommended for use on patients with mouth breathing.
ABSTRACT
Heterostructures of Ga[Formula: see text]O[Formula: see text] with other materials such as Si, SiC or diamond, are a possible way of addressing the low thermal conductivity and lack of p-type doping of Ga[Formula: see text]O[Formula: see text] for device applications, as well as of improving device reliability. In this work we study the electrical and thermal properties of Ga[Formula: see text]O[Formula: see text]-SiO[Formula: see text] heterostructures. Here, thin-film gallium oxide with thickness ranging between 8 and 30 nm was deposited onto a silicon substrate with a thermal oxide by means of oxidised liquid gallium layer delamination. The resulting heterostructure is then characterised by means of X-ray photoelectron spectroscopy and transient thermoreflectance. The thin-film gallium oxide valence band offset with respect to the SiO[Formula: see text] is measured as 0.1 eV and predicted as [Formula: see text] eV with respect to diamond. The thin-film's out-of-plane thermal conductivity is determined to be 3 ±0.5 Wm[Formula: see text] K[Formula: see text], which is higher than what has been previously measured for other polycrystalline Ga[Formula: see text]O[Formula: see text] films of comparable thickness.
ABSTRACT
Multiforce orthodontic archwires are thermodynamic wires made of nickel-titanium alloy (Ni-Ti). They release biologically tolerable forces along their length, progressively increasing from front to back. The frontal archwires' segments distribute the weakest force: the premolar, the greater, and the molar, the greatest. The aim of the present study was to determine the influence of clinical use on the mechanical properties of two types of multi-force orthodontic archwires (TriTanium®, American orthodontics; Bio-Active®, GC) with dimensions of 0.016 × 0.022 inches for periods of up to 8 weeks and over 8 weeks of in-vivo use. A three-point bending test was used, and the data gained is statistically analyzed through a multi-variance comparison Mann-Whitney test. We found that after uses of up to 8 weeks and over 8 weeks, the shape memory effect and superelasticity are preserved, as well as the tendency for differential force release along the length of the archwires is kept.
ABSTRACT
Photoelectrochemical water splitting is a promising method of clean hydrogen production for green energy uses. Here, we report on a tin-based oxide perovskite combined with an overlayer that shows enhanced bifunctional hydrogen and oxygen evolution. In our first-principles study of tin-based perovskites, based upon density functional theory, we investigate how the formation of a surface affects the electronic properties of these materials. We show that the best candidate, SrSnO3, possesses hydrogen and oxygen overpotentials of 0.75 and 0.72 eV, respectively, which are reduced to 0.35 and 0.54 eV with the inclusion of a ZrO2 overlayer. Furthermore, this overlayer promotes charge extraction, stabilizes the reaction pathways, and improves the band gap such that it straddles the overpotentials between pH 0 and pH 12. This result indicates that SrSnO3 with a ZrO2 overlayer has significant potential as a highly efficient bifunctional water splitter for producing hydrogen and oxygen gas on the same surface.
ABSTRACT
The significant issue of the classic multiangle data-processing technique is that the height up to which this technique allows the reliable profiling of the searched atmosphere is always significantly less than the maximum operative range of the scanning lidar signals. The existing multiangle inversion methodology does not allow for the proper inversion into optical profiles of the distant range signals measured in and close to zenith. In this study, a data-processing technique is considered which allows for increasing the maximal heights when profiling the atmosphere with scanning lidar; it is achieved by using the auxiliary backscatter near-end solution and the assumption of a constant lidar ratio over high altitudes. Simulated and experimental data are presented that illustrate the specifics of such a combined technique.
ABSTRACT
The direct multiangle solution is considered, which allows improving the scanning lidar-data-inversion accuracy when the requirement of the horizontally stratified atmosphere is poorly met. The signal measured at zenith or close to zenith is used as a core source for extracting optical characteristics of the atmospheric aerosol loading. The multiangle signals are used as auxiliary data to extract the vertical transmittance profile from the zenith signal. Details of the retrieval methodology are considered that eliminate, or at least soften, some specific ambiguities in the multiangle measurements in horizontally heterogeneous atmospheres. Simulated and experimental elastic lidar data are presented that illustrate the essentials of the data-processing technique. Finally, the prospects of the utilization of high-spectral-resolution lidar in the multiangle mode are discussed.
ABSTRACT
The upper height of a region of intense backscatter with a poorly defined boundary between this region and a region of clear air above it is found as the maximal height where aerosol heterogeneity is detectable, that is, where it can be discriminated from noise. The theoretical basis behind the retrieval technique and the corresponding lidar-data-processing procedures are discussed. We also show how such a technique can be applied to one-directional measurements. Examples of typical results obtained with a scanning lidar in smoke-polluted atmospheres and experimental data obtained in an urban atmosphere with a vertically pointing lidar are presented.
ABSTRACT
The methodology of using mobile scanning lidar data for investigation of smoke plume rise and high-resolution smoke dispersion is considered. The methodology is based on the lidar-signal transformation proposed recently [Appl. Opt. 48, 2559 (2009)]. In this study, similar methodology is used to create the atmospheric heterogeneity height indicator (HHI), which shows all heights at which the smoke plume heterogeneity was detected by a scanning lidar. The methodology is simple and robust. Subtraction of the initial lidar signal offset from the measured lidar signal is not required. HHI examples derived from lidar scans obtained with the U.S. Forest Service, Fire Sciences Laboratory mobile lidar in areas polluted by wildfires are presented, and the basic details of the methodology are discussed.
ABSTRACT
We present an alternative method for determining the total offset in lidar signal created by a daytime background-illumination component and electrical or digital offset. Unlike existing techniques, here the signal square-range-correction procedure is initially performed using the total signal recorded by lidar, without subtraction of the offset component. While performing the square-range correction, the lidar-signal monotonic change due to the molecular component of the atmosphere is simultaneously compensated. After these corrections, the total offset is found by determining the slope of the above transformed signal versus a function that is defined as a ratio of the squared range and two molecular scattering components, the backscatter and transmittance. The slope is determined over a far end of the measurement range where aerosol loading is zero or, at least, minimum. An important aspect of this method is that the presence of a moderate aerosol loading over the far end does not increase dramatically the error in determining the lidar-signal offset. The comparison of the new technique with a conventional technique of the total-offset estimation is made using simulated and experimental data. The one-directional and multiangle measurements are analyzed and specifics in the estimate of the uncertainty limits due to remaining shifts in the inverted lidar signals are discussed. The use of the new technique allows a more accurate estimate of the signal constant offset, and accordingly, yields more accurate lidar-signal inversion results.
