Experimental and numerical investigations regarding laser drop on demand jetting of Cu alloys

Active noise reduction, structural health monitoring and energy harvesting are possible applications of active structure components. An integration of piezoceramic modules into casted Al-structures can be defined as a long term goal to achieve high functional integration and thus to address lightweight construction. Since the liquidus temperature of standard electronic solder is not sufficient to withstand the thermal loads during Al die casting processes, a suitable wire bonding process is an enabling technology to generate active Al structures. In the scope of this work, a laser based drop on demand joining process is introduced. The process consists of four main steps. First a spherical CuSn12 braze preform of 600 µm diameter with a liquidus temperature of 1233 K is inserted into a ceramic capillary and being molten by a laser pulse. The droplet is subsequently ejected by gas overpressure and impinges on the joining area, consisting of the electrode structure of the piezo element and the Cu wire, where it forms a firm joint of the Cu wire and the electrode structure. In order to evaluate time–temperature profiles of the capillary during melting and detachment of the braze preform a simulation model was set up, indicating heating and cooling rates of 22,100 K/s. Further, the impact of the capillary geometry on the velocity fields of a passing medium was evaluated. By changing the capillary geometry, the gas flow velocity could be reduced by about 10% according to the simulation model, which resulted in a reduction of droplet height deviation of 7.5% and a reduction of the droplet diameter deviation of 32.2% in the experiment.     

Study of prepolymerization complex formation in the synthesis of steroid-based molecularly imprinted polymers

The preparation of steroid-based molecularly imprinted polymers (MIPs) based upon noncovalent interaction is particularly suited for selective capture of steroid hormones in biological and environmental samples. The success of this method lies in the optimization of the interaction between steroids (template) and methacrylic acid (functional monomer) in the prepolymerization mixture. NMR techniques coupled with DFT calculations were used to evaluate the capacity of the methacrylic acid to bind a steroid for future applications. The androstane derivative steroids considered in the present study have two functional groups at C(3) and C(17), which may interact with the methacrylic acid. These can be hydroxyl or ketone groups. Experimental results show that the steroids can be divided in three groups corresponding to the ketone type at C(3), the H-bond strength increasing with the number of double bonds. DFT calculations are in very good agreement with experimental results, showing increasing binding energy from no bonds, a single bond, and two double bond steroids. For steroids holding a hydroxyl group the binding energy obtained in the solvent model is comparable to the binding energy of single bond ketone steroids.     

Degradation of Vitamin C in Spray Dryers and Temperature and Moisture Content Profiles in these Dryers

The occurrence of peak solid temperatures inside cocurrent dryers, including spray dryers, is relevant to their use for producing food powders. A numerical simulation has been used here to explore the location of the maximum degradation rates in a small-scale Buchi cocurrent spray dryer used to dry vitamin C, finding that the maximum degradation rates are likely to coincide with the peak particle temperatures. The peak particle temperatures are likely to occur shortly after the inlet of the dryer and before the outlet, irrespective of the amount of heat loss from the dryer.     

An approach for automatic sleep stage scoring and apnea-hypopnea detection

In this article we present an application of data mining to the medical domain sleep research, an approach for automatic sleep stage scoring and apnea-hypopnea detection. By several combined techniques (Fourier and wavelet transform, derivative dynamic time warping, and waveform recognition), our approach extracts meaningful features (frequencies and special patterns like k-complexes and sleep spindles) from physiological recordings containing EEG, ECG, EOG and EMG data. Based on these pieces of information, an ensemble of decision trees is constructed using the principle of bagging, which classifies sleep epochs in their sleep stages according to the rules by Rechtschaffen and Kales and annotates occurrences of apnea-hypopnea (total or partial cessation of respiration). After that, casebased reasoning is applied in order to improve quality. We tested and evaluated our approach on several large public databases from PhysioBank, which showed an overall accuracy of 95.2% for sleep stage scoring and 94.5% for classifying minutes as apneic or non-apneic.     

A general correlation for the stagnation point Nusselt number of an axisymmetric impinging synthetic jet

Whereas the heat transfer mechanisms in steady impinging jets are well understood, the available knowledge of heat transfer to impinging synthetic jets remains inconsistent. This paper provides an objective comparison of the stagnation point heat transfer performance of axisymmetric impinging synthetic jets versus established steady jet correlations. Furthermore, a general correlation for the stagnation point Nusselt number is proposed including the effect of all appropriate scaling parameters: Reynolds number (500 ? Re ? 1500), jet-to-surface spacing (2 ? H/D ? 16) and stroke length (2 ? L₀/D ? 40). Based on the ratio of stroke length to jet-to-surface spacing L₀/H, four heat transfer regimes are identified.     

Detailed nuclear analysis of ITER ELM coils

The ELM coils in ITER are intended to provide control of Edge Localized Modes (ELMs). These coils are located on the outboard side of ITER between the shield modules and vacuum vessel (VV) and are subject to high radiation levels. Detailed three-dimensional (3-D) models of the toroidal and poloidal legs of the ELM coil and surrounding region for the MCNP code were updated to reflect the latest design changes. Neutronics calculations were performed to determine a variety of radiation damage parameters for the ELM coils as well as the VV located behind them. Additionally, detailed CAD based models for the upper ELM coil region were used to perform a CAD based analysis using the DAG-MCNP5 code. The results show that the ELM coil will meet the specified material radiation limits. However, the nuclear heating on the vacuum vessel behind the poloidal multi-pipe manifolds will exceed the specified limit.     

Salmonella Inactivation During Extrusion of an Oat Flour Model Food

Little research exists on Salmonella inactivation during extrusion processing, yet many outbreaks associated with low water activity foods since 2006 were linked to extruded foods. The aim of this research was to study Salmonella inactivation during extrusion of a model cereal product. Oat flour was inoculated with Salmonella enterica serovar Agona, an outbreak strain isolated from puffed cereals, and processed using a single‐screw extruder at a feed rate of 75 kg/h and a screw speed of 500 rpm. Extrudate samples were collected from the barrel outlet in sterile bags and immediately cooled in an ice–water bath. Populations were determined using standard plate count methods or a modified most probable number when populations were low. Reductions in population were determined and analyzed using a general linear model. The regression model obtained for the response surface tested was Log (N_R/N_O) = 20.50 + 0.82T ? 141.16a_w – 0.0039T² + 87.91a_w² (R² = 0.69). The model showed significant (p < 0.05) linear and quadratic effects of a_w and temperature and enabled an assessment of critical control parameters. Reductions of 0.67 ± 0.14 to 7.34 ± 0.02 log CFU/g were observed over ranges of a_w (0.72 to 0.96) and temperature (65 to 100 °C) tested. Processing conditions above 82 °C and 0.89 a_w achieved on average greater than a 5‐log reduction of Salmonella. Results indicate that extrusion is an effective means for reducing Salmonella as most processes commonly employed to produce cereals and other low water activity foods exceed these parameters. Thus, contamination of an extruded food product would most likely occur postprocessing as a result of environmental contamination or through the addition of coatings and flavorings.     

实时在线拉曼光谱气相均相反应动力学研究中的逆命题

提出一种全新的气相均相反应动力学的研究方法. 利用实时在线拉曼光谱的点测量特点,将所测得的气相浓度和温度值通过逆命题运算对气相均相反应过程直接去卷积,确定过程的物理和化学系数. 实时在线测量得到的沿垂直射流反应器中轴线上的组分分子振动拉曼光谱被用来确定气相组分的浓度分布.同时氮气的纯转动拉曼光谱被用来确定气相温度分布.通过该方法,得到了稳定状态下TMGa-N₂二元系中组分浓度扩散系数和气相均相化学反应速度常数,所得到的结果与其他文献值相一致.     

Systematic planning to optimize investments in hydrogen infrastructure deployment

The introduction of hydrogen infrastructure and fuel cell vehicles (FCVs) to gradually replace gasoline internal combustion engine vehicles can provide environment and energy security benefits. The deployment of hydrogen fueling infrastructure to support the demonstration and commercialization of FCVs remains a critical barrier to transitioning to hydrogen as a transportation fuel. This study utilizes an engineering methodology referred to as the Spatially and Temporally Resolved Energy and Environment Tool (STREET) to demonstrate how systematic planning can optimize early investments in hydrogen infrastructure in a way that supports and encourages growth in the deployment of FCVs while ensuring that the associated environment and energy security benefits are fully realized. Specifically, a case study is performed for the City of Irvine, California – a target area for FCV deployment – to determine the optimized number and location of hydrogen fueling stations required to provide a bridge to FCV commercialization, the preferred rollout strategy for those stations, and the environmental impact associated with three near-term scenarios for hydrogen production and distribution associated with local and regional sources of hydrogen available to the City. Furthermore, because the State of California has adopted legislation imposing environmental standards for hydrogen production, results of the environmental impact assessment for hydrogen production and distribution scenarios are measured against the California standards. The results show that significantly fewer hydrogen fueling stations are required to provide comparable service to the existing gasoline infrastructure, and that key community statistics are needed to inform the preferred rollout strategy for the stations. Well-to-wheel (WTW) greenhouse gas (GHG) emissions, urban criteria pollutants, energy use, and water use associated with hydrogen and FCVs can be significantly reduced in comparison to the average parc of gasoline vehicles regardless of whether hydrogen is produced and distributed with an emphasis on conventional resources (e.g., natural gas), or on local, renewable resources. An emphasis on local renewable resources to produce hydrogen further reduces emissions, energy use, and water use associated with hydrogen and FCVs compared to an emphasis on conventional resources. All three hydrogen production and distribution scenarios considered in the study meet California's standards for well-to-wheel GHG emissions, and well-to-tank emissions of urban ROG and NO_X. Two of the three scenarios also meet California's standard that 33% of hydrogen must be produced from renewable feedstocks. Overall, systematic planning optimizes both the economic and environmental impact associated with the deployment of hydrogen infrastructure and FCVs.