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A crack opening stress equation for in-phase and out-of-phase thermomechanical fatigue loading
(2016)
In this paper, a crack opening stress equation for in-phase and out-of-phase thermomechanical fatigue (TMF) loading is proposed. The equation is derived from systematic calculations of the crack opening stress with a temperature dependent strip yield model for both plane stress and plane strain, different load ratios and different ratios of the temperature dependent yield stress in compression and tension. Using a load ratio scaled by the ratio of the yield stress in compression and tension, the equation accounts for the effect of the temperature dependent yield stress and the constraint on the crack opening stress. Based on the scaling relation established in this paper, Newman's crack opening stress equation for isothermal loading is enabled to predict the crack opening stress under TMF loading.
The aim of this study was to develop a biomechanically validated finite element model to predict the biomechanical behaviour of the human lumbar spine in compression.
For validation of the finite element model, an in vitro study was performed: Twelve human lumbar cadaveric spinal segments (six segments L2/3 and six segments L4/5) were loaded in axial compression using 600 N in the intact state and following surgical treatment using two different internal stabilisation devices. Range of motion was measured and used to calculate stiffness.
A finite element model of a human spinal segment L3/4 was loaded with the same force in intact and surgically altered state, corresponding to the situation of biomechanical in vitro study.
The results of the cadaver biomechanical and finite element analysis were compared. As they were close together, the finite element model was used to predict: (1) load-sharing within human lumbar spine in compression, (2) load-sharing within osteoporotic human lumbar spine in compression and (3) the stabilising potential of the different spinal implants with respect to bone mineral density.
A finite element model as described here may be used to predict the biomechanical behaviour of the spine. Moreover, the influence of different spinal stabilisation systems may be predicted.
In this paper, the influence of the material hardening behavior on plasticity-induced fatigue crack closure is investigated for strain-controlled loading and fully plastic, large-scale yielding conditions by means of the finite element method. The strain amplitude and the strain ratio are varied for given Ramberg–Osgood material properties representing materials with different hardening behavior. The results show a pronounced influence of the hardening behavior on crack closure, while no significant effect is found from the considered strain amplitude and strain ratio. The effect of the hardening behavior on the crack opening stress cannot be described by existing crack opening stress equations.
Given the looming threats of climate change and the rapid worldwide urbanization, it is a necessity to prioritize the transition towards a carbon-free built environment. This research study provides a holistic digital methodology for parametric design of urban residential buildings with regard to the Mediterranean semi-arid climate zone of Morocco in the early design phase. The morphological parameters of the urban residential buildings, namely the buildings’ typology, the distance between buildings, the urban grid’s orientation, and the window-towall ratio, are evaluated in order to identify the key combinations of passive and active solar design strategies that determine the high energy performing configurations, based on the introduced Energy Performance Index (EPI), which is the ratio between solar BIPV production to maximum available installed BIPV capacity and the normalized thermal energy needs. Through an automated processing of 2187 iterations via Grasshopper, we simulate daylight autonomy, indoor thermal comfort and solar rooftop photovoltaic and building integrated photovoltaic (BIPV) energy potential. Then, we analyze the conflicting objectives of energy efficiency measures, active solar design strategies, and indoor visual comfort in the decision-making process that supports our goal of getting closer to net zero urban residential buildings. The digital workflow showed interesting trends in reaching a balanced equilibrium between performance metrics influenced by the contrasting impact of solar exposure on indoor daylight autonomy and thermal energy demand. Furthermore, the study’s findings indicate that it is possible to achieve an annual load match exceeding 66,56 % while simultaneously ensuring an acceptable visual indoor comfort (sDA higher than 0.4). The findings also highlight the important role of the BIPV system in shifting towards the net zero energy goal, by contributing up to 30 % of the overall solar energy output and covering up to 20 % of the yearly self-consumption. Moreover, the energy balance evaluation on an hourly basis indicates that BIPV system notably enhances the daily load cover factor by up to 5.5 %, particularly in the case of slab SN typology, throughout the different seasons. Graphical representations of the yearly, monthly and hourly load matches and the hourly energy balance of the best performing configurations provide a thorough understanding of the potential evolution of the urban energy system over time as a result of the gradual integration of active solar electricity production.
In this paper, the multiaxial formulation of a mechanism-based model for fatigue life prediction is presented whichcan be applied to low-cycle fatigue (LCF) and thermomechanical fatigue (TMF) problems in which high-cycle fa-tigue loadings are superimposed. The model assumes that crack growth is the lifetime limiting mechanism and thatthe crack advance in a loading cycleda/dNcorrelates with the cyclic crack-tip opening displacement ΔCTOD.The multiaxial formulation makes use of fracture mechanics solutions and thus, does not need additional modelparameters quantifying the effect of the multiaxiality. Furthermore, the model includes contributions of HCF on ΔCTODand assesses the effect of the direction of the HCF loadings with respect to LCF or TMF loadings inthe life prediction. The model is implemented into the finite-element program ABAQUS. It is applied to predictthe fatigue life of a thermomechanically loaded notched specimen that should represent the situation between theinlet and outlet bore holes of cylinder heads. A good correlation of the predicted and the measured fatigue lives isobtained.
High temperature components in internal combustion engines and exhaust systems must withstand severe mechanical and thermal cyclic loads throughout their lifetime. The combination of thermal transients and mechanical load cycling results in a complex evolution of damage, leading to thermomechanical fatigue (TMF) of the material. Analytical tools are increasingly employed by designers and engineers for component durability assessment well before any hardware testing. The DTMF model for TMF life prediction, which assumes that micro-crack growth is the dominant damage mechanism, is capable of providing reliable predictions for a wide range of high-temperature components and materials in internal combustion engines. Thus far, the DTMF model has employed a local approach where surface stresses, strains, and temperatures are used to compute damage for estimating the number of cycles for a small initial defect or micro-crack to reach a critical length. In the presence of significant gradients of stresses, strains, and temperatures, the use of surface field values could lead to very conservative estimates of TMF life when compared with reported lives from hardware testing. As an approximation of gradient effects, a non-local approach of the DTMF model is applied. This approach considers through-thickness fields where the micro-crack growth law is integrated through the thickness considering these variable fields. With the help of software tools, this method is automated and applied to components with complex geometries and fields. It is shown, for the TMF life prediction of a turbocharger housing, that the gradient correction using the non-local approach leads to more realistic life predictions and can distinguish between surface cracks that may arrest or propagate through the thickness and lead to component failure.
Quantifying the midsole material characteristics of athletic footwear is a standard task in footwear research and development. Current material testing protocols primarily focus on the determination of cushioning properties of the heel region or the quantification of the midsole properties as one assembly. However, midsoles possess different spatial material properties that have not been quantified from previous methodologies. Therefore, new material testing methods are required to quantify the local material response of athletic footwear. We developed a cyclical force-controlled material testing protocol for the determination of non-homogeneously distributed material stiffness with a high spatial resolution. In five prototype shoes varying in their stiffness distribution, we found that the material properties can be reliably measured across the midsole. Furthermore, we observed a characteristic non-linear material response regardless of the midsole location. We found that the material stiffness increased with an increase of the applied force and that this effect is further intensified by higher testing cycles. Additionally, the obtained midsole stiffness depends on the geometry of the midsole. We explored different approaches to reduce the measurement time of the testing protocol and found that the number of measurements can be reduced by 70% using 2 D-interpolation procedures. Determining the spatial material properties of midsoles needs to be considered to understand foot-shoe interactions. Furthermore, this measurement protocol can be used for quality control within the footwear and can be adapted for considering the effects of different running styles or speeds on ground force application characteristics.
Uptakes of 9.2 mmol g−1 (40.5 wt %) for CO2 at 273 K/0.1 MPa and 15.23 mmol g−1 (3.07 wt %) for H2 at 77 K/0.1 MPa are among the highest reported for metal–organic frameworks (MOFs) and are found for a novel, highly microporous copper‐based MOF (see picture; Cu turquoise, O red, N blue). Thermal analyses show a stability of the flexible framework up to 250 °C.
Metal–organic frameworks (MOFs) as highly porous materials have gained increasing interest because of their distinct adsorption properties.1–3 They exhibit a high potential for applications in gas separation and storage,4 as sensors5 as well as in heterogeneous catalysis.6 In the last few years, the H2 storage capacity of MOFs has been considerably increased. Mesoporous MOFs show high adsorption capacities for CH4, CO2, and H2 at high pressures.2, 3, 7–10 To increase the uptake of H2 and CO2 by physisorption at ambient pressure, adsorbents with small micropores as well as high specific surface areas and micropore volumes are required.11, 12 Such microporous materials seem to be more appropriate for gas‐mixture separation by physisorption than mesoporous materials. For gas separation in MOFs the interactions between the fluid adsorptive and “open metal sites” (coordinatively unsaturated binding sites) or the ligands are regarded as important.13 Industrial processes, such as natural‐gas purification or biogas upgrading, can be improved with those materials during a vapor‐pressure swing adsorption cycle (VPSA cycle) or a temperature swing adsorption cycle (TSA cycle).14 The microporous MOF series CPO‐27‐M (M=Mg, Co, Ni, Zn), for example, shows very high CO2 uptakes at low pressures (<0.1 MPa).15, 16 Concerning H2 adsorption, the microporous MOF PCN‐12 offers with 3.05 wt % the highest uptake at ambient pressure and 77 K reported to date.17
Herein, we present a novel microporous copper‐based MOF equation image[Cu(Me‐4py‐trz‐ia)] (1; Me‐4py‐trz‐ia2−=5‐(3‐methyl‐5‐(pyridin‐4‐yl)‐4H‐1,2,4‐triazol‐4‐yl)isophthalate) with extraordinarily high CO2 and H2 uptakes at ambient pressure, the H2 uptake being similar to that in PCN‐12. The ligand Me‐4py‐trz‐ia2−, which can be obtained from cheap starting materials by a three‐step synthesis in good yield, combines carboxylate, triazole, and pyridine functions and is adopted from a recently presented series of linkers,18 for which up to now only a few coordination polymers are known.
The durability of polymer electrolyte membrane fuel cells (PEMFC) is governed by a nonlinear coupling between system demand, component behavior, and physicochemical degradation mechanisms, occurring on timescales from the sub-second to the thousand-hour. We present a simulation methodology for assessing performance and durability of a PEMFC under automotive driving cycles. The simulation framework consists of (a) a fuel cell car model converting velocity to cell power demand, (b) a 2D multiphysics cell model, (c) a flexible degradation library template that can accommodate physically-based component-wise degradation mechanisms, and (d) a time-upscaling methodology for extrapolating degradation during a representative load cycle to multiple cycles. The computational framework describes three different time scales, (1) sub-second timescale of electrochemistry, (2) minute-timescale of driving cycles, and (3) thousand-hour-timescale of cell ageing. We demonstrate an exemplary PEMFC durability analysis due to membrane degradation under a highly transient loading of the New European Driving Cycle (NEDC).
An algorithm is presented that has successfully been utilized in practice for several years. It improves data analysis in chromatography. The program runs in an extremely reliable way and evaluates chromatographic raw data with an acceptable error. The algorithm requires a minimum of preliminaries and integrates even unsmoothed noisy data correctly.
We report improved separation of the highly toxic contact herbicides paraquat, diquat, difenzoquat, mepiquat, and chloromequat by HPTLC. Quantification was based on a new derivatization reaction using sodium tetraphenylborate. Measurements were in the wavelength range from 440 to 480 nm or from 440 to 590 nm. An LED emitting very intense light at 365 nm was used for excitation. The quantification limits of paraquat and diquat in water, using improved solid-phase extraction, was in the low ng L −1 range. The linear range covered more than two orders of magnitude. Recovery was investigated for all the compounds, and was insufficient, ranging from 11 to 92%, but the method is inexpensive, rapid, and works reliably.
Synthesis and crystal structure of a novel copper-based MOF material are presented. The tetragonal crystal structure of [ ∞ 3 ( Cu 4 ( μ 4 -O ) ( μ 2 -OH ) 2 ( Me 2 trz p ba ) 4 ] possesses a calculated solvent-accessible pore volume of 57%. Besides the preparation of single crystals, synthesis routes to microcrystalline materials are reported. While PXRD measurements ensure the phase purity of the as-synthesized material, TD-PXRD measurements and coupled DTA–TG–MS analysis confirm the stability of the network up to 230 °C. The pore volume of the microcrystalline material determined by nitrogen adsorption at 77 K depends on the synthetic conditions applied. After synthesis in DMF/H2O/MeOH the pores are blocked for nitrogen, whereas they are accessible for nitrogen after synthesis in H2O/EtOH and subsequent MeOH Soxhleth extraction. The corresponding experimental pore volume was determined by nitrogen adsorption to be V Pore = 0.58 cm 3 g - 1 . In order to characterize the new material and to show its adsorption potential, comprehensive adsorption studies with different adsorptives such as nitrogen, argon, carbon dioxide, methanol and methane at different temperatures were carried out. Unusual adsorption–desorption isotherms with one or two hysteresis loops are found – a remarkable feature of the new flexible MOF material.
Linear acceleration is a key performance determinant and major training component of many sports. Although extensive research about lower limb kinetics and kinematics is available, consistent definitions of distinctive key body positions, the underlying mechanisms and their related movement strategies are lacking. The aim of this ‘Method and Theoretical Perspective’ article is to introduce a conceptual framework which classifies the sagittal plane ‘shin roll’ motion during accelerated sprinting. By emphasising the importance of the shin segment’s orientation in space, four distinctive key positions are presented (‘shin block’, ‘touchdown’, ‘heel lock’ and ‘propulsion pose’), which are linked by a progressive ‘shin roll’ motion during swing-stance transition. The shin’s downward tilt is driven by three different movement strategies (‘shin alignment’, ‘horizontal ankle rocker’ and ‘shin drop’). The tilt’s optimal amount and timing will contribute to a mechanically efficient acceleration via timely staggered proximal-to-distal power output. Empirical data obtained from athletes of different performance levels and sporting backgrounds are required to verify the feasibility of this concept. The framework presented here should facilitate future biomechanical analyses and may enable coaches and practitioners to develop specific training programs and feedback strategies to provide athletes with a more efficient acceleration technique.
The newly synthesized Zn4O-based MOF 3∞[Zn4(μ4-O){(Metrz-pba)2mPh}3]·8 DMF (1·8 DMF) of rare tungsten carbide (acs) topology exhibits a porosity of 43% and remarkably high thermal stability up to 430 °C. Single crystal X-ray structure analyses could be performed using as-synthesized as well as desolvated crystals. Besides the solvothermal synthesis of single crystals a scalable synthesis of microcrystalline material of the MOF is reported. Combined TG-MS and solid state NMR measurements reveal the presence of mobile DMF molecules in the pore system of the framework. Adsorption measurements confirm that the pore structure is fully accessible for nitrogen molecules at 77 K. The adsorptive pore volume of 0.41 cm3 g−1 correlates well with the pore volume of 0.43 cm3 g−1 estimated from the single crystal structure.
The formation and analysis of ten microporous triazolyl isophthalate based MOFs, including nine isomorphous and one isostructural compound is presented. The compounds 1 M – 3 M with the general formula [ M ( R 1 - R 2 - trz - ia ) ] ∞ 3 ·x H 2 O (M 2+ = Co 2+ , Cu 2+ , Zn 2+ , Cd 2+ ; R 1 = H, Me; R 2 = 2py, 2pym, prz (2py = 2-pyridinyle; 2pym = 2-pyrimidinyle; prz = pyrazinyle)) crystallize with rtl topology. They are available as single crystals and also easily accessible in a multi-gram scale via refluxing the metal salts and the protonated ligands in a solvent. Their isomorphous structures facilitate the synthesis of heteronuclear MOFs; in case of 2 M , Co 2+ ions could be gradually substituted by Cu 2+ ions. The Co 2+ :Cu 2+ ratios were determined by ICP-OES spectroscopy, the distribution of Co 2+ and Cu 2+ in the crystalline samples are investigated by SEM-EDX analysis leading to the conclusions that Cu 2+ is more favorably incorporated into the framework compared to Co 2+ and, moreover, that the distribution of the two metal ions between the crystals and within the crystals is inhomogeneous if the crystals were grown slowly. The various compositions of the heteronuclear materials lead to different colors and the sorption properties for CO 2 and N 2 are dependent on the integrated metal ions.
A Simple and Reliable HPTLC Method for the Quantification of the Intense Sweetener Sucralose®
(2003)
This paper describes a simple and fast thin layer chromatography (TLC) method for the monitoring of the relatively new intense sweetener Sucralose® in various food matrices. The method requires little or no sample preparation to isolate or concentrate the analyte. The Sucralose® extract is separated on amino‐TLC‐plates, and the analyte is derivatized “reagent‐free” by heating the developed plate for 20 min at 190°C. Spots can be measured either in the absorption or fluorescence mode. The method allows the determination of Sucralose® at the levels of interest regarding foreseen European legislation (>50 mg/kg) with excellent repeatability (RSD = 3.4%) and recovery data (95%).
HPTLC on amino plates, with simple heating of the plates for derivatization, has been used for quantification of glucosamine in nutritional supplements. On heating the plate glucosamine reacts to form a compound which strongly absorbs light between 305 and 330 nm, with weak fluorescence. The reaction product can be detected sensitively either by absorption of light or by fluorescence detection. The detection limit in absorption mode is approximately 25 ng per spot. In fluorescence mode a detection limit of 15 ng is achievable. A calibration plot for absorption detection is linear in the range 25 to 4000 ng glucosamine. The derivative formed from glucosamine by heating is stable for months, and the relative standard deviation is 1.64% for 600 ng glucosamine. The amounts of glucosamine found in nutritional supplements were in agreement with the label declarations.
We present an improved quantification method for urethane found in spirits. The quantification is based on a derivatization reaction using cinnamaldehyde in combination with phosphoric acid. Measurements were carried out in the wavelength range from 445 to 460 nm using a diode-TLC device. An LED was used for illumination purposes. It emits very dense light at 365 nm. The quantification range of urethane is in the lower ng range. By applying 20 µL of sprits, the urethane quantification range is from 320 µg/L to 8.1 mg urethane per litre of spirit. The range of linearity covers nearly two magnitudes. The method is cheap, fast and reliable, and is able to monitor all European legislation limits without time-consuming sample pre-treatments.
The DMFC is a promising option for backup power systems and for the power supply of portable devices. However, from the modeling point of view liquid-feed DMFC are challenging systems due to the complex electrochemistry, the inherent two-phase transport and the effect of methanol crossover. In this paper we present a physical 1D cell model to describe the relevant processes for DMFC performance ranging from electrochemistry on the surface of the catalyst up to transport on the cell level. A two-phase flow model is implemented describing the transport in gas diffusion layer and catalyst layer at the anode side. Electrochemistry is described by elementary steps for the reactions occurring at anode and cathode, including adsorbed intermediate species on the platinum and ruthenium surfaces. Furthermore, a detailed membrane model including methanol crossover is employed. The model is validated using polarization curves, methanol crossover measurements and impedance spectra. It permits to analyze both steady-state and transient behavior with a high level of predictive capabilities. Steady-state simulations are used to investigate the open circuit voltage as well as the overpotentials of anode, cathode and electrolyte. Finally, the transient behavior after current interruption is studied in detail.
A Validated Quantification of Sudan Red Dyes in Spicery using TLC and a 16-bit Flatbed Scanner
(2018)
We present a video-densitometric quantification method for Sudan red dyes in spices and spice mixtures, separated by TLC. Application was done band-wise in small dots using a 5 μL glass pipette. For separation, the RP-18 plates (20 × 20 cm with fluorescent dye; Merck, Germany, 1.05559) were developed in a vertical developing chamber without vapor saturation from the starting point to a distance of 70 mm by using acetonitrile, methanol, and aqueous ammonia solution (25%; 8 + 1.8 + 0.2, v/v) as mobile phase. The quantification is based on direct measurements using an inexpensive 16-bit flatbed scanner for color measurements (in red, green, and blue). Evaluation of only the green channel makes the measurements very specific. For linearization, an extended Kubelka-Munk expression for data transformation was used. The range of linearity covers more than two magnitudes and lies between 20 and 500 ng. The extraction from a 2 g sample with acetonitrile, evaporation, and reconstitution to 200 μL with methanol and the band-wise application (7 mm) of a 10 μL sample allows a statistically defined LOD of less than 500 ppb of Sudan red dyes. To perform the analysis, a separation chamber, RP-18 plates, 5 μL glass pipettes, and a 16-bit flatbed scanner for 105 € are needed; therefore, the separation method is inexpensive, fast, and reliable.
Background
To assess the in-field walking mechanics during downhill hiking of patients with total knee arthroplasty five to 14 months after surgery and an age-matched healthy control group and relate them to the knee flexor and extensor muscle strength.
Methods
Participants walked on a predetermined hiking trail at a self-selected, comfortable pace wearing an inertial sensor system for recording the whole-body 3D kinematics. Sagittal plane hip, knee, and ankle joint angles were evaluated over the gait cycle at level walking and two different negative slopes. The concentric and eccentric lower extremity muscle strength of the knee flexors and extensors isokinetically at 50 and 120°/s were measured.
Findings
Less knee flexion angles during stance have been measured in patients in the operated limb compared to healthy controls in all conditions (level walking, moderate downhill, steep downhill). The differences increased with steepness. Muscle strength was lower in patients for both muscle groups and all measured conditions. The functional hamstrings to quadriceps ratio at 120°/sec correlated with knee angle during level and downhill walking at the moderate slope in patients, showing higher ratios with lower peak knee flexion angles.
Interpretation
The study shows that even if rehabilitation has been completed successfully and complication-free, five to 14 months after surgery, the muscular condition was still insufficient to display a normal gait pattern during downhill hiking. The muscle balance between quadriceps and hamstring muscles seems related to the persistence of a stiff knee gait pattern after knee arthroplasty. LoE: III.
There is a growing trend for the use of thermo-active building systems (TABS) for the heating and cooling of buildings, because these systems are known to be very economical and efficient. However, their control is complicated due to the large thermal inertia, and their parameterization is time-consuming. With conventional TABS-control strategies, the required thermal comfort in buildings can often not be maintained, particularly if the internal heat sources are suddenly changed. This paper shows measurement results and evaluations of the operation of a novel adaptive and predictive calculation method, based on a multiple linear regression (AMLR) for the control of TABS. The measurement results are compared with the standard TABS strategy. The results show that the electrical pump energy could be reduced by more than 86%. Including the weather adjustment, it could be demonstrated that thermal energy savings of over 41% could be reached. In addition, the thermal comfort could be improved due to the possibility to specify mean room set-point temperatures. With the AMLR, comfort category I of the comfort norms ISO 7730 and DIN EN 15251 are observed in about 95% of occasions. With the standard TABS strategy, only about 24% are within category I.
Adaptive predictive control of thermo-active building systems (TABS) based on a multiple regression algorithm: First practical test. Available from: https://www.researchgate.net/publication/305903009_Adaptive_predictive_control_of_thermo-active_building_systems_TABS_based_on_a_multiple_regression_algorithm_First_practical_test [accessed Jul 7, 2017].
Adsorption of N2 and CO2 on Activated Carbon, AlO(OH) Nanoparticles, and AlO(OH) Hollow Spheres
(2015)
Adsorption behaviors of nitrogen and CO2 on Norit R1 Extra and AlO(OH) nanoparticles and hollow spheres were measured under different temperature and pressure conditions using a magnetic suspension balance. Independent from the substrate investigated, all isotherms increase at lower pressure, reach a maximum, and then decrease with increasing pressure. In addition, selected experimental data were correlated with different model approaches and compared with reliable literature data. In case of CO2 on AlO(OH), capillary condensation was observed at two defined temperatures. The results suggest that the conversion of the liquid into a supercritical adsorbate phase does not take place suddenly.
A systematic toxicological analysis procedure using high-performance thin layer chromatography in combination with fibre optical scanning densitometry for identification of drugs in biological samples is presented. Two examples illustrate the practicability of the technique. First, the identification of a multiple intake of analgesics: codeine, propyphenazone, tramadol, flupirtine and lidocaine, and second, the detection of the sedative diphenhydramine. In both cases, authentic urine specimens were used. The identifications were carried out by an automatic measurement and computer-based comparison of in situ UV spectra with data from a compiled library of reference spectra using the cross-correlation function. The technique allowed a parallel recording of chromatograms and in situ UV spectra in the range of 197–612 nm. Unlike the conventional densitometry, a dependency of UV spectra by concentration of substance in a range of 250–1000 ng/spot was not observed.
Membrane distillation (MD) is a thermal separation process which possesses a hydrophobic, microporous
membrane as vapor space. A high potential application for MD is the concentration of hypersaline brines, such as
e.g. reverse osmosis retentate or other saline effluents to be concentrated to a near saturation level with a Zero
Liquid Discharge process chain. In order to further commercialize MD for these target applications, adapted MD
module designs are required along with strategies for the mitigation of membrane wetting phenomena. This
work presents the experimental results of pilot operation with an adapted Air Gap Membrane Distillation
(AGMD) module for hypersaline brine concentration within a range of 0–240 g NaCl /kg solution. Key performance
indicators such as flux, GOR and thermal efficiency are analyzed. A new strategy for wetting mitigation
by active draining of the air gap channel by low pressure air blowing is tested and analyzed. Only small reductions
in flux and GOR of 1.2% and 4.1% respectively, are caused by air sparging into the air gap channel.
Wetting phenomena are significantly reduced by avoiding stagnant distillate in the air gap making the air blower
a seemingly worth- while additional system component.
Am 1. Juli 2022 trafen sich im Rahmen des Abschlusskolloquiums des Projekts ACA-Modes rund 60 Teilnehmende aus Forschung, Lehre und Industrie zu einer internationalen Konferenz an der Hochschule Offenburg. Hier wurden die Projektergebnisse rund um die erfolgreiche Implementierung modellprädiktiver Regelstrategien vorgestellt, aktuelle Fragestellungen diskutiert und Entwicklungspfade hin zu einem netzdienlichen Betrieb von Energieverbundsystemen skizziert.
Hintergrund
In diesem Artikel wird ein Überblick und Vergleich der am häufigsten verwendeten zementierten Hüftschäfte, gruppiert in die verschiedenen Schafttypen und Zementmanteldicken, gegeben, um zu sehen, welche Kombination gut abschneidet.
Methodik
Aus dem Endoprothesenregister Deutschland wurden die Revisionsraten zementierter Schaftarten kategorisiert und die Revisionsraten von 3 und 5 Jahren erfasst und analysiert. Für die Recherche lag die Konzentration auf den Schäften Exeter, C‑Stem, MS-30, Excia, Bicontact, Charnley, Müller Geradschaft, Twinsys, Corail, Avenir, Quadra und dem Lubinus SP II. Ein wichtiger Aspekt lag darin, welcher Schaft favorisiert implantiert wird und welche Zementiertechnik in Hinblick auf die geplante Zementmanteldicke angewendet wird. Um einen Trend in der zementierten Hüftendoprothetik herauszufinden, wurden zusätzlich die Daten des dänischen, schwedischen, norwegischen, schweizerischen, neuseeländischen, englischen und australischen Endoprothesenregister verglichen.
Ergebnisse und Schlussfolgerung
Die meisten Länder nutzen zementierte Prothesen nach dem Kraftschlussprinzip (Exeter, MS30, C‑Stem etc.) oder dem Formschlussprinzip (Charnley, Excia, Bicontact), welche mit einer Zementmanteldicke von 2–4 mm implantiert werden. Jedoch hat sich in Deutschland und der Schweiz ein Trend zur Line-to-Line-Technik, mit einer geplanten Zementmanteldicke von 1 mm (Twinsys, Corail, Avenir, Quadra) aufgezeigt, dem Prinzip der Müller-Geradschaft-Prothese und der Kerboul-Charnley-Prothese folgend, auch wenn diese an sich als „french paradoxon“ postuliert werden. In den EPRD-5-Jahres-Ergebnissen scheinen die neueren Line-to-Line-Prothesen etwas schlechter abzuschneiden. Die besten Ergebnisse erzielt der „MS 30“ in Deutschland und der „Exeter“ in England. Hierbei handelt es sich um polierte Geradschäfte mit Zentraliser und Subsidence-Raum an der Spitze mit einem 2–4 mm Zementmantel in guter Zementiertechnik.
Running footwear is continuously being modified and improved; however, running-related overuse injury rates remain high. Nevertheless, novel manufacturing processes enable the production of individualized running shoes that can fit the individual needs of runners, with the potential to reduce injury risk. For this reason, it is essential to investigate functional groups of runners, a collective of runners who respond similarly to a footwear intervention. Therefore, the objective of this study was to develop a framework to identify functional groups based on their individual footwear response regarding injury-specific running-related risk factors for Achilles tendinopathy, Tibial stress fractures, Medial tibial stress syndrome, and Patellofemoral pain syndrome. In this work, we quantified the footwear response patterns of 73 female and male participants when running in three different footwear conditions using unsupervised learning (k-means clustering). For each functional group, we identified the footwear conditions minimizing the injury-specific risk factors. We described differences in the functional groups regarding their running style, anthropometric, footwear perception, and demographics. The results implied that most functional groups showed a tendency for a single footwear condition to reduce most biomechanical risk factors for a specific overuse injury. Functional groups often differed in their hip and pelvis kinematics as well as their subjective rating of the footwear conditions. The footwear intervention only partially affected biomechanical risk factors attributed to more proximal joints. Due to its adaptive nature, the framework could be applied to other footwear interventions or performance-related biomechanical variables.
An Extraction Method for 17α-Ethinylestradiol from Water using a new kind of monolithic Stir-bar
(2015)
We present a video-densitometric high-performance thin-layer chromatography (HPTLC) quantification method for patulin in apple juice, developed in a vertical chamber from the starting point to a distance of 50 mm, using MTBE, n-pentane (9 + 5, v/v) as mobile phase. After separation the plate is sprayed with methyl-benzothiazolinone hydrazone hydrochloride monohydrate (MBTH) solution (40 mg in 20 mL methanol) and heated at 105 °C for 15 min. Patulin zones are transformed into yellow spots. The quantification is based on direct measurements using an inexpensive 48-bit flatbed scanner for color measurements (in red, green, and blue). Evaluation of the blue channel makes the measurements very specific. Quantification in fluorescence was also done by use of a 16-bit CCD-camera and UV-366 nm illumination as well as using a HPTLC DAD-scanner. For linearization the extended Kubelka–Munk expression for data transformation was used. The range of linearity covers more than two magnitudes and lies between 5 and 800 ng patulin. The extraction of 20 g apple juice and an extract application on plate up to 50 µL allows statistically defined checking the limit of detection (LOD) of 50 ng patulin per track, which is equivalent to 50 µg patulin per kg apple juice.
An isomorphous series of 10 microporous copper-based metal–organic frameworks (MOFs) with the general formulas ∞3[{Cu3(μ3-OH)(X)}4{Cu2(H2O)2}3(H-R-trz-ia)12] (R = H, CH3, Ph; X2– = SO42–, SeO42–, 2 NO32– (1–8)) and ∞3[{Cu3(μ3-OH)(X)}8{Cu2(H2O)2}6(H-3py-trz-ia)24Cu6]X3 (R = 3py; X2– = SO42–, SeO42– (9, 10)) is presented together with the closely related compounds ∞3[Cu6(μ4-O)(μ3-OH)2(H-Metrz-ia)4][Cu(H2O)6](NO3)2·10H2O (11) and ∞3[Cu2(H-3py-trz-ia)2(H2O)3] (12Cu), which are obtained under similar reaction conditions. The porosity of the series of cubic MOFs with twf-d topology reaches up to 66%. While the diameters of the spherical pores remain unaffected, adsorption measurements show that the pore volume can be fine-tuned by the substituents of the triazolyl isophthalate ligand and choice of the respective copper salt, that is, copper sulfate, selenate, or nitrate.
Soot particles emitted from a light duty (LD) Volkswagen diesel engine running at different operating points (speed and torque levels) are analyzed for mean size determination using a laser‐based three Wavelength Extinction Method (3‐WEM). For this reason, collected soot samples are suspended using an appropriate sample preparation technique with optimized conditions of sonication as it revealed its effect on the soot mean particle size measured by 3‐WEM.
An online Scanning Mobility Particle Analyzer (SMPS) is also used to measure soot emission at identical engine operating points. Size values obtained from SMPS are lower than those of suspended soot samples obtained from 3‐WEM. The size discrepancies are mainly related to the required sample preparation procedure employed for 3‐WEM measurements. The engine operating points affect, differently, the size measurements obtained from SMPS and 3‐WEM.
Sedimentation Field‐Flow Fractionation (SdFFF) is used for density determination of soot samples based on size measurements of fractions collected at peak maxima of fractograms using the off‐line hyphenation with 3‐WEM. It is assumed that a size dependent separation of soot particles occurred with a uniform particle density over the whole size distribution. An average density value is used for the conversion of soot fractograms to size distributions. Discrepancies are also found with size distribution profiles obtained from SMPS for the same engine operating points, due to the sample preparation procedure employed for SdFFF measurements.
In der Planungs- und Betriebspraxis herrscht im Bereich der Betriebsführung von thermisch aktivierten Bauteilsystemen und insbesondere der thermisch trägen Bauteilaktivierung noch große Unsicherheit. Trotz einer weiten Verbreitung dieser Systeme im Neubau von Nichtwohngebäuden hat sich bis heute keine einheitliche Betriebsführungsstrategie durchgesetzt. Vielmehr kritisieren Bauherren und Nutzer regelmäßig zu hohe bzw. niedrige Raumtemperaturen in den Übergangsjahreszeiten und bei Wetterwechsel sowie generell eine mangelhafte Regelbarkeit. Demgegenüber weisen Monitoringprojekte immer wieder einen hohen thermischen Komfort in diesen Gebäuden nach. Offensichtlich unterscheiden sich hier subjektiv empfundene Behaglichkeit und objektiv gemessener Komfort. Gleichzeitig sind Heiz- und Kühlkonzepte mit Flächentemperierung dann besonders energieeffizient, wenn das Regelkonzept auf deren thermische Trägheit angepasst ist. Eine gute Regelung gewährleistet also einen hohen thermischen Komfort und sorgt für einen möglichst niedrigen Energieeinsatz. Das Rechenverfahren mit Anlagenaufwandszahlen (in Anlehnung an DIN V 18599) bietet eine gute Möglichkeit, Anlagenkonzepte inklusive deren Betriebsführungsstrategie zu bewerten. Damit ist es möglich, eine auf das Gebäude angepasste Betriebsführungsstrategie für die Bauteilaktivierung zu finden und einheitlich zu bewerten.
In the present study, in vitro toxicity as well as biopersistence and photopersistence of four artificial sweeteners (acesulfame, cyclamate, saccharine, and sucralose) and five antibiotics (levofloxacin, lincomycin, linezolid, marbofloxacin, and sarafloxacin) and of their phototransformation products (PTPs) were investigated. Furthermore, antibiotic activity was evaluated after UV irradiation and after exposure to inocula of a sewage treatment plant. The study reveals that most of the tested compounds and their PTPs were neither readily nor inherently biodegradable in the Organisation for Economic Co-operation and Development (OECD)-biodegradability tests. The study further demonstrates that PTPs are formed upon irradiation with an Hg lamp (UV light) and, to a lesser extent, upon irradiation with a Xe lamp (mimics sunlight). Comparing the nonirradiated with the corresponding irradiated solutions, a higher chronic toxicity against bacteria was found for the irradiated solutions of linezolid. Neither cytotoxicity nor genotoxicity was found in human cervical (HeLa) and liver (Hep-G2) cells for any of the investigated compounds or their PTPs. Antimicrobial activity of the tested fluoroquinolones was reduced after UV treatment, but it was not reduced after a 28-day exposure to inocula of a sewage treatment plant. This comparative study shows that PTPs can be formed as a result of UV treatment. The study further demonstrated that UV irradiation can be effective in reducing the antimicrobial activity of antibiotics, and consequently may help to reduce antimicrobial resistance in wastewaters. Nevertheless, the study also highlights that some PTPs may exhibit a higher ecotoxicity than the respective parent compounds. Consequently, UV treatment does not transform all micropollutants into harmless compounds and may not be a large-scale effluent treatment option.
Cooling towers or recoolers are one of the major consumers of electricity in a HVAC plant. The implementation and analysis of advanced control methods in a practical application and its comparison with conventional controllers is necessary to establish a framework for their feasibility especially in the field of decentralised energy systems. A standard industrial controller, a PID and a model based controller were developed and tested in an experimental set-up using market-ready components. The characteristics of these controllers such as settling time, control difference, and frequency of control actions are compared based on the monitoring data. Modern controllers demonstrated clear advantages in terms of energy savings and higher accuracy and a model based controller was easier to set-up than a PID.
In this paper fatigue crack closure under in-phase and out-of-phase thermomechanical fatigue (TMF) loading is studied using a temperature dependent strip yield model. It is shown that fatigue crack closure is strongly influenced by the phase relation between mechanical loading and temperature, if the temperature difference goes along with a temperature dependence of the yield stress. In order to demonstrate the effect of the temperature dependent yield stress, the influence of in-phase and out-of-phase TMF loading is studied for a polycrystalline nickel-base superalloy. By using a mechanism based lifetime model, implications for fatigue lives are demonstrated.
As a basis for the evaluation of hydrogen storage by physisorption, adsorption isotherms of H2 were experimentally determined for several porous materials at 77 K and 298 K at pressures up to 15 MPa. Activated carbons and MOFs were studied as the most promising materials for this purpose. A noble focus was given on how to determine whether a material is feasible for hydrogen storage or not, dealing with an assessment method and the pitfalls and problems of determining the viability. For a quantitative evaluation of the feasibility of sorptive hydrogen storage in a general analysis, it is suggested to compare the stored amount in a theoretical tank filled with adsorbents to the amount of hydrogen stored in the same tank without adsorbents. According to our results, an “ideal” sorbent for hydrogen storage at 77 K is calculated to exhibit a specific surface area of >2580 m2 g−1 and a micropore volume of >1.58 cm3 g−1.
Automatic Identification of Travel Locations in Rare Books - Object Oriented Information Management
(2017)
The digital content of the Internet is growing exponentially and mass digitization of printed media opens access to literature, in particular the genre of travel literature from the 18th and 19th century, which consists of diaries or travel books describing routes, observations or inspirations. The identification of described locations in the digital text is a long-standing challenge which requires information technology to supply dynamic links to sources by new forms of interaction and synthesis between humanistic texts and scientific observations.
Using object oriented information technology, a prototype of a software tool is developed which makes it possible to automatically identify geographic locations and travel routes mentioned in rare books. The information objects contain properties such as names and classification codes for populated places, streams, mountains and regions. Together, with the latitudes and longitudes of every single location, it is possible to geo-reference this information in order that all processed and filtered datasets can be displayed by a map application. This method has already been used in the Humboldt Digital Library to present Alexander von Humboldt’s maps and was tested in a case study to prove the correctness and reliability of the automatic identification of locations based on the work of Alexander von Humboldt and Johann Wolfgang von Goethe.
The results reveal numerous errors due to misspellings, change of location names, equality of terms and location names. But on the other hand it becomes very clear that results of the automatic object detection and recognition can be improved by error-free and comprehensive sources. As a result an increase in quality and usability of the service can be expected, accompanied by more options to detect unknown locations in the descriptions of rare books.
Cyclic micro-bending tests on fcc single crystal Ni-base Alloy 718 cantilevers with different crystal orientations were performed to analyze the influence of activated slip systems on dislocation plasticity, latent hardening and the Bauschinger effect. The investigations indicate that plasticity in single crystal micro-cantilevers is significantly influenced by two phenomena - dislocation interaction and dislocation pile-up at the neutral plane. Both phenomena occur at the same time. Their ratio seems to be determined by the activated slip systems. Slip trace analysis indicates that the activation of only one slip system leads to a strong localization of plasticity to a limited number of parallel slip bands. This results in low dislocation interaction and consequently pronounced pile-ups at the neutral plane. In multi slip orientation, the second slip system leads to activation of significantly more dislocation sources, causing a much earlier and more homogeneous elastic-plastic transition zone. In stress-strain hysteresis loops during bending, pronounced dislocation interaction in multi slip orientation leads to a more pronounced latent hardening. The results suggest that on a microstructural length scale, plasticity behavior is strongly affected by activated slip systems, which determine local dislocation phenomena. Based on the results presented in this paper, a finite element analysis of latent hardening and the Bauschinger effect using a single crystal plasticity model with latent kinematic hardening is presented in Part II.
In this paper, the Bauschinger effect and latent hardening of single crystals are assessed in finite element calculations using a single crystal plasticity model with kinematic hardening. To this end, results of cyclic micro-bending experiments on single crystal Alloy 718 in different crystal orientations (single slip and multi slip) with respect to the loading direction are used to determine the slip system related material properties of the single crystal plasticity model. Two kinematic hardening laws are considered: a kinematic hardening law describing latent hardening and a kinematic hardening law without latent hardening. For the determination of material properties for both hardening laws, a gradient-based optimization method is used. The results show that the different strength levels observed for micro-bending tests on different crystal orientations can only be described with latent kinematic hardening well, whereas the pronounced Bauschinger effect is described well by both kinematic hardening laws. It is concluded that cyclic micro-bending experiments on single crystals using different crystal orientations give an appropriate data base for the determination of the slip system related material properties of the single crystal plasticity model with latent kinematic hardening.