Seasonal Variability of The Mixed Layer Depth in The Sulawesi Sea

The Sulawesi Sea is a semi-enclosed basin located in the Indonesian Seas and considered as the one of location in the west route of Indonesian Throughflow (ITF). There is less attention on the mixed layer depth investigation in the Sulawesi Sea. Concerning that the mixed layer plays an important role in influencing the ocean in air-sea interaction and affects biological activity, the estimation of mixed layer depth (MLD) in the Sulawesi Sea is important. Seasonal variation of the mixed layer in the Sulawesi Sea between 115°-125°E and 0°-8°N is estimated by using World Ocean Atlas 2013. Forcing elements on the mixed layer in terms of surface-forced turbulent mixing from mechanical forcing of wind stress and buoyancy forcing (from heat flux as well as freshwater flux) in the Sulawesi Sea is provided by using a reanalysis dataset. The MLD is estimated directly on grid profiles with interpolated levels based on chosen density fixed criterion of 0.03 kg.m^-3 and temperature criterion of 0.5°C difference from the surface. The results show that mixed layer depth in the Sulawesi Sea varies both spatially and temporally. Generally, the deepest MLD was occurred during the southwest monsoon (JJA), and the lowest MLD was occurred during the first transition (MAM) and second transition monsoon (SON). Strengthening and weakening MLD are influenced by mechanical forcing from wind stress and buoyancy flux. In the Sulawesi Sea, the mixed layer deepening coincides with the occurrence of a maximum in wind stress, and low buoyancy flux at the surface. This condition is the opposite when mixed layer shallowing occurs.

Effect of electrochemical modification of titanium hydride fraction on oxygen content in surface and deep layers

The paper presents a study of the microstructure and oxygen concentration in the surface and deep layers of fractions of unmodified titanium hydride and titanium hydride modified by electrodeposited layers of Ti and Cu at temperatures of 300-900 ° C. The composition of the oxide layer and the concentration of titanium and oxygen atoms are estimated. It is shown that an increase in the thickness and compaction of the oxide layer with increasing temperature prevents the penetration of oxygen into the deep layers of the unmodified fraction of titanium hydride. Modification of titanium hydride by electrochemical deposition of metallic titanium at a temperature of 700 °C reduces the oxygen concentration in titanium hydride at a layer depth of 50 μm from 35 wt% to 12.5 wt%. Electrodeposition of coatings based on titanium and copper at 700 °C reduces the oxygen concentration to 9.2 wt%, which may be due to the protective mechanism of the formed copper titanate layer. At 900 °C, in the modification layer based on titanium and copper, due to the eutectoid transformation of the β-phase of titanium, the process of contact melting occurs and a multiphase zone is formed. The oxygen concentration at a layer depth of 50 μm is no more than 12.4 wt%.

Evaluating daytime planetary boundary-layer height estimations resolved by both active and passive remote sensing instruments during the CHEESEHEAD19 field campaign

During the Chequamegon Heterogeneous Ecosystem Energy-balance Study Enabled by a High-density Extensive Array of Detectors 2019 (CHEESEHEAD19) field campaign, held in the summer of 2019 in northern Wisconsin, U.S.A., active and passive ground-based remote sensing instruments were deployed to understand the response of the planetary boundary layer to heterogeneous land surface forcing. These instruments include Radar Wind Profilers, Microwave Radiometers, Atmospheric Emitted Radiance Interferometers, Ceilometers, High Spectral Resolution Lidars, Doppler Lidars, and Collaborative Lower Atmospheric Modelling Profiling Systems that combine several of these instruments. In this study, these ground-based remote sensing instruments are used to estimate the height of the daytime planetary boundary layer, and their performance is compared against independent boundary-layer depth estimates obtained from radiosondes launched as part of the field campaign. The impact of clouds (in particular boundary layer clouds) on boundary-layer depth is also investigated. We found that while overall all instruments are able to provide reasonable boundary-layer depth estimates, each of them shows strengths and weaknesses under certain conditions. For example, Radar Wind Profilers perform well during cloud free conditions, and Microwave Radiometers and Atmospheric Emitted Radiance Interferometers have a very good agreement during all conditions, but are limited by the smoothness of the retrieved thermodynamic profiles. The estimates from Ceilometers and High Spectral Resolution Lidars can be hindered by the presence of elevated aerosol layers or clouds, and the multi-instrument retrieval from the Collaborative Lower Atmospheric Modelling Profiling Systems can be constricted to a limited height range in low aerosol conditions.

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-Ray Scattering Study

The combination of operando small- and wide-angle X-ray scattering (SAXS, WAXS) is here presented to provide insights into the changes in mean particle sizes and phase fractions in fuel cell catalyst layers during accelerated stress tests (ASTs). As fuel cell catalyst, a bimodal Pt/C catalyst was chosen that consists of two distinguishable particle size populations. The presence of the two different sizes should favor and uncover electrochemical Ostwald ripening as degradation mechanism, i.e., the growth of larger particles in the Pt/C catalyst at the expense of the smaller particles via the formation of ionic metal species. However, instead of electrochemical Ostwald ripening, the results point toward classical Ostwald ripening via the local diffusion of metal atoms on the support. Furthermore, the grazing incidence mode provides insights into the catalyst layer depth-dependent degradation. While the larger particles show the same particle size changes close to the electrolyte-catalyst interface and within the catalyst layer, the smaller Pt nanoparticles exhibit a slightly decreased size at the electrolyte-catalyst interface. During the AST, both size populations increase in size, independent of the depth. Their phase fraction, i.e., the ratio of smaller to larger size population, however, exhibits a depth-dependent behavior. While at the electrolyte-catalyst interface the phase fraction of the smaller size population decreases, it increases in the inner catalyst layer. The results of a depth-dependent degradation suggest that employing a depth-dependent catalyst design can be used for future improvement of catalyst stability.

Tracking the Catalyst Layer Depth-Dependent Electrochemical Degradation of a Bimodal Pt/C Fuel Cell Catalyst: A Combined Operando Small- and Wide-Angle X-Ray Scattering Study

The combination of operando small- and wide-angle X-ray scattering (SAXS, WAXS) is here presented to provide insights into the changes in mean particle sizes and phase fractions in fuel cell catalyst layers during accelerated stress tests (ASTs). As fuel cell catalyst, a bimodal Pt/C catalyst was chosen that consists of two distinguishable particle size populations. The presence of the two different sizes should favor and uncover electrochemical Ostwald ripening as degradation mechanism, i.e., the growth of larger particles in the Pt/C catalyst at the expense of the smaller particles via the formation of ionic metal species. However, instead of electrochemical Ostwald ripening, the results point toward classical Ostwald ripening via the local diffusion of metal atoms on the support. Furthermore, the grazing incidence mode provides insights into the catalyst layer depth-dependent degradation. While the larger particles show the same particle size changes close to the electrolyte-catalyst interface and within the catalyst layer, the smaller Pt nanoparticles exhibit a slightly decreased size at the electrolyte-catalyst interface. During the AST, both size populations increase in size, independent of the depth. Their phase fraction, i.e., the ratio of smaller to larger size population, however, exhibits a depth-dependent behavior. While at the electrolyte-catalyst interface the phase fraction of the smaller size population decreases, it increases in the inner catalyst layer. The results of a depth-dependent degradation suggest that employing a depth-dependent catalyst design can be used for future improvement of catalyst stability.

The Influence of Base Layer Thickness in Flexible Pavements

Flexible pavement design and analysis were carried out in the past with semi-experimental methods, using elastic characteristics of pavement layers. Due to the complex interferences between various layers and their time consumption, the traditional pavement analysis, and design methods were replaced with fast and powerful methods including the Finite Element Method (FEM) and the Discrete Element Method (DEM). FEM requires less computational power and is more appropriate for continuous environments. In this study, flexible pavement consisting of 5 layers (surface, binder, base, subbase, and subgrade) had been analyzed using FEM. The ABAQUS (6.14-2) software had been utilized to investigate the influence of the base layer depth on vertical stresses and displacements. Three different thicknesses were adopted (10, 20, and 30cm) with constant other pavement layer thicknesses. The results of this study showed that the stress levels at the top of the base layer increased by about 37% when the thickness of this layer increased from 10cm to 30cm, while the stress levels at the top of the subbase layer decreased by about 64%. When the base layer increased from 10 to 20, from 20 to 30, and from 10 to 30cm the vertical displacement decreased by 18%, 24%, and 37% respectively.