Spray drying with a two-fluid nozzle to produce fine particles: Atomization,scale-up,and modeling

This article presents experimental and modeling work to complete previously reported work on spray drying. Back-calculated droplet sizes have been verified by measurements with a laser imaging rig. Flow patterns in a cylindrical spray chamber have been simulated by computational fluid dynamics and demonstrated that droplet residence times are much shorter than expected. A droplet tracking population balance model has been implemented in gSOLIDS and shows how drying times vary with droplet diameter. Particle collection by cyclone and bag filter have also been compared experimentally.     

Temperature Dependence of Efficiency in GaInN/GaN Light‐Emitting Diodes with a GaInN Underlayer

The temperature dependence of the efficiency (i.e., temperature‐mediated efficiency droop) in blue light‐emitting diodes (LEDs) is investigated. A GaInN/GaN LED with a GaInN underlayer having an indium mole fraction of 8% shows less temperature dependence of efficiency, compared to the LED without an underlayer. Better carrier confinement in the active region of the LED with a GaInN underlayer is proposed to reduce carrier leakage from the active region at high temperature. The results indicate that the insertion of an underlayer leads to an improvement of the LED's radiative efficiency and its high‐temperature‐tolerant performance.     

Influence of strain histories on liquefaction resistance of sand

The liquefaction resistance of sand increases with cyclic pre-shearing and pre-shaking as a result of earthquakes if the strain level in the pre-shearing is small. When larger shear strains are imposed, liquefaction resistance decreases. These complicated effects of pre-shearing histories on the liquefaction resistance are investigated in this study through a series of cyclic triaxial tests. Various combinations of cyclic stress amplitude and number of cycles of pre-shearing are examined. The tested sand is Toyoura Sand at 45% relative density, under a confining pressure of 50 kPa. Test results indicate that for the range of shear strain amplitude in pre-shearing smaller than 0.35%, the liquefaction resistance increases with pre-shearing. The increase in the liquefaction resistance depends strongly on the volumetric strain in the pre-shearing, and several effects of the shear stress amplitude and number of cycles can be negligible. Small volumetric strain of the order of 1% doubled the liquefaction resistance. Meanwhile, in the range of shear strain amplitude larger than 0.6%, the liquefaction resistance decreases. The liquefaction resistance decreases as the shear strain amplitude increases. Shear strain amplitude is one of the factors dominating this degrading effect, and the volumetric strain exerts beneficial effects to a certain extent. In this study, another series of tests are conducted to investigate the combined effects of small and large strain amplitude pre-shearing. It is observed that small shear strain pre-shearing cycles subsequent to large shear strain cycles erased the degrading effect of the latter. However, a large shear strain pre-shearing after small strain cycles degrades the beneficial effect of the small shear strain pre-shearing cycles previously applied to the specimens; however, the effects of the former small strain pre-shearing remains.     

Mechanical and Tribological Properties of Ca/P-Doped Titanium Dioxide Layer Produced by Plasma Electrolytic Oxidation: Effects of Applied Voltage and Heat Treatment

Plasma electrolytic oxidation (PEO) is a technique that produces a hard oxide layer on the titanium surface where its properties can be tailored by changing the process parameters or by a posterior heat treatment (HT). In this work, a TiO₂ layer with different crystallinity was produced by PEO with different applied voltages (250 to 400 V) and post-HT at 600°C. Our aim was to evaluate the influence of the PEO voltage and HT on the mechanical and tribological properties of anodized Ti. There is an increase in pore size, oxide thickness, and Ca/P ratio for the oxide layer with the applied voltage during the PEO process. X-ray diffraction (XRD) results indicated an increase in the crystalline rutile phase in the oxide layer with voltage and HT. Nanoindentation shows an increase in the oxide hardness and elastic modulus with increased voltage and HT, leading to an improvement in the wear resistance.     

Detonation Products as a Function of Initiation Strength,ambient gas and binder systems of explosives charges

The way of initiating an insensitive high explosive can influence the start of a detonation reaction remarkably. In order to study the extent of this influence, different boosters and different booster structures for the initiation of explosive mixtures containing TNT and nitroguanidine (NQ) have been used. The experiments have been conducted in a 1.5 m³ containment from which the detonation products could be taken and analyzed. In those cases where we only used a 10 g RDX booster together with a detonation cap no. 8, we had not a complete detonation reaction by initiating cylindrical charges of TNT/NQ and TNT/AN. This means that unreacted TNT was analyzed in the solid residue, mainly consisting of carbon soot. On the other hand, we had a complete detonation using an additional booster of about 18 g detonation sheet, placed on the front side of the cylindrical explosive, having the same diameter as the explosive charge. Another part of the investigations deals with the determination of the influence of different argon pressures on the composition of the detonation gas and the solid residue. Between vacuum and one bar argon a strong change not only of the gas but also of the soot residue was measured. A stronger influence on the products was found using a confinement with glass tubes. The investigation of Al-containing charges exhibited a very different behavior compared with charges without Al. No more influence of vaccum or of different ambient gas pressure could be observed. By investigation of two composite explosive charges (PBX) containing binder systems of different energies and different oxygen balances, a great influence on the reaction of Al was found. The PBX charges with the better O₂-balance containing the energetic GAP-binder reacted nearly completely with the Al, opposite to the charge containing the polyisobutylene (PIB) binder system.     

Boron nitride-reinforced polysilazane-derived ceramic composites via direct-ink writing

In this study we investigate the use of hexagonal boron nitride (hBN) as a rheology modifier in polysilazane resin to enable direct-ink writing (DIW) of polysilazane-derived boron nitride-reinforced ceramic composites. hBN is shown to effectively modify the flow properties of the resin by imparting strong shear thinning and yield stress behavior, and to reduce the mass loss and shrinkage associated with the polymer-to-ceramic conversion process, when compared with unfilled polysilazane resin. DIW inks are formulated with 40 vol.% hBN and used print flexural specimens and complex structures with high resolution. Mechanical properties of the resulting polymer-derived ceramic composites were evaluated by 3-pt. flexure and Vickers microhardness. The printed composites exhibit flexural strength of 56.4 MPa and microhardness of 111.4 HV2.     

Synthesis of Alkyl Fructosides

The anomeric alkylation of D-fructose is efficiently catalyzed by mild acid catalysts. Degradation of fructose is negligible under the conditions applied.     

Aging Behavior of Propellants investigated by heat generation,stabilizer consumption,and molar mass degradation

Four double-base rocket propellants and a single-base gun propellant were tested to find out stabilizer consumption molar mass degradation, and heat generation between 50 °C and 90 °C and between 40 °C and 110 °C, respectively. Stabilizer depletion was measured by high performance liquid chromatography (HPLC), molar mass degradation by gel permeation chromatography (GPC), and heat generation by microcalorimetry. The conditioning times at different temperatures were determined with one of the rocket propellants, and the influence of the long-term storage on heat generation at 60 °C for 2191 dys was investigated. A correlated experiment between stabilizer consumption and heat generation showed that heat production does not increase substantially until the stabilizer has been consumed almost completely. The experimental data of molar mass degradation are described by a kinetic model based on statistical chain scission, and the stabilizer decrease by a first order reaction. For the gun propellant the Arrhenius plots of the reaction rate constants show two temperatures of teh stabilizer consumption, molar mass degradation and heat generation were determined.     

Milk fatty acids as possible biomarkers to early diagnose elevated concentrations of blood plasma nonesterified fatty acids in dairy cows

Most cows encounter a state of negative energy balance during the periparturient period, which may lead to metabolic disorders and impaired fertility. The aim of this study was to assess the potential of milk fatty acids as diagnostic tools of detrimental levels of blood plasma nonesterified fatty acids (NEFA), defined as NEFA concentrations beyond 0.6 mmol/L, in a data set of 92 early lactating cows fed a glucogenic or lipogenic diet and subjected to 0-, 30-, or 60-d dry period before parturition. Milk was collected in wk 2, 3, 4, and 8 (n = 368) and blood was sampled weekly from wk 2 to 8 after parturition. Milk was analyzed for milk fatty acids and blood plasma for NEFA. Data were classified as “at risk of detrimental blood plasma NEFA” (NEFA ≥0.6 mmol/L) and “not at risk of detrimental blood plasma NEFA” (NEFA <0.6 mmol/L). Concentrations of 45 milk fatty acids and milk fat C18:1 cis-9-to-C15:0 ratio were subjected to a discriminant analysis. Milk fat C18:1 cis-9 revealed the most discriminating variable to identify detrimental blood plasma NEFA. A false positive rate of 10% allowed us to diagnose 46% of the detrimental blood plasma NEFA cases based on a milk fat C18:1 cis-9 concentration of at least 230 g/kg of milk fatty acids. Additionally, it was assessed whether the milk fat C18:1 cis-9 concentrations of wk 2 could be used as an early warning for detrimental blood plasma NEFA risk during the first 8 wk in lactation. Cows with at least 240 g/kg of C18:1 cis-9 in milk fat had about 50% chance to encounter blood plasma NEFA values of 0.6 mmol/L or more during the first 8 wk of lactation, with a false positive rate of 11.4%. Profit simulations were based on costs for cows suffering from detrimental blood plasma NEFA, and costs for preventive treatment based on daily dosing of propylene glycol for 3 wk. Given the relatively low incidence rate (8% of all observations), continuous monitoring of milk fatty acids during the first 8 wk of lactation to diagnose detrimental blood plasma NEFA does not seem cost effective. On the contrary, milk fat C18:1 cis-9 of the second lactation week could be an early warning of cows at risk of detrimental blood NEFA. In this case, selective treatment may be cost effective.     

Consequences of dietary energy source and energy level on energy balance,lactogenic hormones,and lactation curve characteristics of cows after a short or omitted dry period

Omitting the dry period (DP) generally reduces milk production in the subsequent lactation. The aim of this study was to evaluate the effect of dietary energy source—glucogenic (G) or lipogenic (L)—and energy level—standard (std) or low—on milk production; energy balance (EB); lactogenic hormones insulin, insulin-like growth factor 1 (IGF-1), and growth hormone (GH); and lactation curve characteristics between wk 1 and 44 postpartum in cows after a 0-d or 30-d DP. Cows (n = 110) were assigned randomly to 3 transition treatments: a 30-d DP with a standard energy level required for expected milk yield [30-d DP(std)], a 0-d DP with the same energy level as cows with a 30-d DP [0-d DP(std)], and a 0-d DP with a low energy level [0-d DP(low)]. In wk 1 to 7, cows were fed the same basal ration but the level of concentrate increased to 6.7 kg/d for cows fed the low energy level and to 8.5 kg/d for cows fed the standard energy level in wk 4. From wk 8 postpartum onward, cows received a G ration (mainly consisting of corn silage and grass silage) or an L ration (mainly consisting of grass silage and sugar beet pulp) with the same energy level contrast (low or std) as in early lactation. Cows fed the G ration had greater milk, lactose, and protein yields, lower milk fat percentage, greater dry matter and energy intakes, and greater plasma IGF-1 concentration compared with cows fed the L ration. Dietary energy source did not affect EB or lactation curve characteristics. In cows with a 0-d DP, the reduced energy level decreased energy intake, EB, and weekly body weight gain, but did not affect milk production or lactation curve characteristics. A 30-d DP resulted in a greater total predicted lactation yield, initial milk yield after calving, peak milk yield, energy intake, energy output in milk, days to conception [only when compared with 0-d DP(low)], plasma GH concentration [only when compared with 0-d DP(std)], and decreased weekly body weight gain compared with a 0-d DP. A 30-d DP decreased both the increasing and the declining slope parameters of the lactation curve and the relative rate of decline in milk yield (indicating greater lactation persistency) compared with a 0-d DP, and decreased plasma insulin and IGF-1 concentration, and EB. In conclusion, feeding a G ration after wk 7 in milk improved energy intake and milk production, but did not affect EB compared with an L ration. For cows without a DP, a reduced dietary energy level did not affect milk production and lactation curve characteristics, but did decrease EB and weekly body weight gain. A 30-d DP increased milk yield and lactation persistency, but decreased milk fat and protein content, EB, and plasma insulin and IGF-1, compared with a 0-d DP.