Naval Surface Warfare Center

About: Naval Surface Warfare Center is a facility organization based out in Washington D.C., District of Columbia, United States. It is known for research contribution in the topics: Radar & Sonar. The organization has 2855 authors who have published 3697 publications receiving 83518 citations. The organization is also known as: NSWC.

Linear solvation energy relationships. Part 9.—Correlations of gas/liquid partition coefficients with the solvatochromic parameters, π*, α and β

Abstract: When referenced to an alkane solute of similar molecular volume, i.e. log (Ksolute/Kalkane), gas/liquid partition coefficients for nitromethane, methylethylketone, dioxan, toluene and ethanol solutes are well correlated by the solvatochromic parameters, π*, δ, α and β. For nitromethane and dioxan solutes the partition coefficients depend only on the dipolarity/polarizability parameters (π*, δ). For methylethylketone, there is also a measurable dependence on hydrogen-bond donor acidity (α) of protic solvents. For ethanol in aliphatic non-hydrogen-bond donor solvents the dominant effects are solvent dipolarity/polarizability and solvent hydrogen-bond acceptor basicity (β). For toluene solute there appears to be a negative or desolvation effect in protic solvents which is attributed to a ‘hydroxyphobic effect’ of weakly basic solutes in alcohol solvents.

Absorption and transport of hydrogen during gas metal arc welding of low alloy steel

Abstract: Although hydrogen induced cracking remains a major problem in the welding of steels, the present methods of managing hydrogen in the weldment are mostly empirical in nature. In recent years, numerical modelling of heat transfer and fluid flow has provided detailed insight into the physical processes in welding. However, very little effort has been made in the past to use these transport phenomena based calculations to understand the dissolution of hydrogen in the weld metal and its subsequent transport in the liquid and solid regions. The aim of the present work was to address this important need. Heat transfer, fluid flow, and hydrogen transport calculations in transient, three-dimensional form are used to predict the spatial distribution of hydrogen concentration in the weld metal during gas metal arc welding of mild steels for different welding conditions. The enhanced hydrogen solubility in the weld metal above that predicted by Sieverts law was determined from a model for the partitioning of ...

Role of sea salt aerosols in the formation of aromatic secondary organic aerosol: yields and hygroscopic properties

Abstract: Environmental context In the coastal and ocean environment, oil spills and ship movement can produce hazardous, organic aerosols. In this study, the role of sea salt in the formation processes of crude-oil-derived organic aerosols derived was explored, and it was found that sea salt can greatly increase the formation and growth of these toxic aerosols. Understanding of this process is crucial for evaluating the effect of oil spills and ship movements on air quality and human health. Abstract Dual, large (52m3), outdoor chambers were used to investigate the effect of aerosol aqueous phase chemistry on the secondary organic aerosol (SOA) yields of the photooxidation products of aromatic hydrocarbons in the coastal environment. Toluene and 1,3,5-trimethylbenzene were photochemically oxidised in the presence and absence of inorganic seeds (sea salt aerosol (SSA) or NaCl) at low NOx conditions. Overall, the presence of SSA, which was shown to contain water even at low relative humidities (RHs), led to higher SOA yields than the presence of NaCl seeds and the seedless condition. The results suggest that SOA yields in the coastal environment will be higher than those produced in terrestrial environment. To study the effect of SOA formation on the chemical composition of SSA, inorganic species were measured using a particle-into-liquid-sampler coupled to an ion chromatograph. The hygroscopic properties of the SSA internally mixed with SOA were analysed using a Fourier-transform infrared spectrometer. The fresh SSA shows a weak phase transition whereas no clear phase transition appeared in the aged SSA. The depletion of Cl– due to the accommodation of nitric acid and carboxylic acids on the surface of SSA coincides with changes in aerosol hygroscopic properties.

Microwave measurements of MgB2: implications for applications and order-parameter symmetry

Abstract: We present measurements of the microwave properties of high-quality thin films of MgB2 deposited by reactive evaporation on both dielectric and metallic substrates. The measurements include those of the surface impedance and the intermodulation distortion (IMD), both as a function of microwave power at temperatures from 1.8 to 35 K. A stripline resonator at 2 GHz is used for the measurements on dielectric substrates and a dielectric resonator at 10.7 GHz is used for the films on metallic substrates. The surface resistance of the MgB2 is lower than that of our sputtered niobium films, and no power dependence was observed up to surface radio-frequency magnetic fields of 400 Oe at 5 K. The temperature dependence of the IMD at low circulating power shows an increase at temperatures T < 10 K that cannot be explained on the basis of s-wave symmetry of the order parameter in both energy gaps. Within the gap-symmetry constraints of the hexagonal crystal symmetry of MgB2, the best fit with our IMD and penetration depth measurements is obtained for the π-gap symmetry given by Δ(, T) = Δ0(T)sin(6), where is the azimuthal angle in the ab plane, and Δ0(T) is a weakly temperature dependent amplitude at low temperatures. This symmetry entails there being six nodal lines.