Local Loading Effects Research Articles

Destabilization of Cylindrical Shells Coupling Effect of Local Impact Load and Circumferential Pressure

Destabilization of Cylindrical Shells Coupling Effect of Local Impact Load and Circumferential Pressure

A Comparative Examination of the Electricity Saving Potentials of Direct Residential PV Energy Use in European Countries

The increasing global penetration of photovoltaic (PV) technology creates not only enormous opportunities for clean energy production but also poses challenges that put energy systems to the test. Although there are many ways of dealing with the rising share of PV energy, most of these solutions require substantial funding, time, and effort to implement, which highlights the importance of solving some of the issues at their source, i.e., through the direct use of the electricity generated at PV power plants, many of which are owned and operated by households. In recent decades, PV technology has experienced an unprecedented growth in Europe due to a range of reasons, including the nations’ policies and supporting schemes. The goal of the present research was to determine the annual consumption of electricity per capita in the households of certain European countries and how much of this can be covered by the direct use of PV energy in the case of an on-grid PV system and to show what the annual potential of the direct use of PV energy is compared to the annual energy production of the PV systems. The significance and novelty of this research is justified by the lack of comparative scientific studies related to the annual potential of the direct household use of PV energy, which could alleviate some of the problems facing electricity networks with high shares of PV energy. The novel practical benefit of the study was determining, for the examined European countries, the extent to which direct household PV energy use could lower annual electricity consumption from the grid, in the case of on-grid PV systems of different capacities. In addition, these findings also provide information related to the grid’s macro-energy systems in terms of local network load effects related to given investment sizes.

Phase transition by nanoindentation in a relaxor ferroelectric single crystal PMN-0.3PT: A phase-field investigation

Nanoindentaiton testing has revealed pop-in events in load–displacement curves of relaxor single crystal PMN-0.3PT ferroelectric materials that occur when the indentation depth is small (e.g., dozens of nanometers). Although there has been speculation of an occurrence of phase transition, there is a relative lack of investigation on the domain evolution associated with the phase transition when the pop-in events appear. In the present study, nanoindentation of this material was systematically modeled using phase-field simulations, which capture the domain and phase evolution of a PMN-0.3PT ferroelectric single crystal. The results, qualitatively similar to the experimental results, revealed details of the contribution of phase transformations to pop-in events. The influence of indenter shape, size, and external electric field on the pop-in event was also examined. This work provides a computational evaluation of the effects of the phase transition mechanism in ferroelectric materials under nanoindentation and gives insight into local mechanical loading effects on these electromechanically coupled crystals.

Investigation of the Effect of External Local Sealing Loads on the Well Support

The article presents the definition of problems in the well support from external local sealing loads. The conditions of local sealing loads are identified. The calculations were carried out according to the equations. A model of the stress-strain state in the well support has been created. The parameters of the effect of compression on the absolute value of strength are determined.

Characterisation of local damage in pultruded GFRP road bridge decks with random fibre mat misalignments

The extent to which random, manufacturing-induced fibre mat misalignments compromise the structural integrity of pultruded GFRP road bridge decks is not fully understood. The problem is often critical at the web-flange junctions, which frequently contain the most severe misalignments and are subjected to high moment-shear (M−V) combinations due to local tyre load effects. To that end, in the presently reported experimental study, determinate M−V combinations were applied at the junctions of a pultruded GFRP bridge deck, without artificially restraining (e.g. by clamping, which spuriously strengthens) these junctions. For any given M−V ratio, significant scatter was observed in the damage patterns and loads up to ultimate, owing to random fibre mat misalignments which have been digitally documented in a previous paper. Damage occurred mostly within the junctions, and sometimes in the adjoining flanges. Relative to misalignment-free specimens, the first fracture moments dropped by 19% and 21% for junctions containing flip and wrinkle misalignments respectively. 19% of tests showed higher tangent stiffnesses after damage, probably due to beneficial changes in load-carrying mechanism. A three-pronged approach, based on the load-response, acoustic emission and video data, enables the definition of damage indices, thereby paving the way for integrity assessment of pultruded decks under local tyre load effects.

"Investigation of the Effect of External Local Sealing Loads on the Well Support"

"Investigation of the Effect of External Local Sealing Loads on the Well Support"

Influence of Local Frequent Dynamic Disturbance on Micro-structure Evolution of Coal-Rock and Localization Effect

This study aimed to investigate the influence of local frequent dynamic disturbance on micro-structure evolution in different zones of coal-rock. To do so, we carried out a systematic experimental research on the micro-structure evolution of briquette and raw coal samples under local impact load by using self-developed pendulum hammer dynamic impact loading test device of coal-rock and ultrasonic testing equipment, and analyzed the localization effect of local impact load. The results show that Mn (micro-structure cumulative change factor) of briquette coal samples presents an inclined M-shaped four-stage evolution mode along and perpendicular to impact direction with cyclic impact times under conventional full impact load, whereas it shows more obvious anisotropy and localization under local impact load. Mn for both conventional full impact and local impact shows a nonlinear increasing trend with the increase in impulse, but their increasing gradients are different. The critical zone is the most affected, the impact zone comes next, and the non-impact zone is the least affected with the increase in impulse under local impact load. Mn in the impact zone and critical zone decreases exponentially with the increase in the impact loading area, while it increases exponentially in the non-impact zone. The micro-structures evolution in briquette and raw coal samples is similar, but the anisotropy and localization effect of micro-structure evolution for raw coal samples are more significant and more sensitive to the impact loading area. The micro-structure evolution of coal-rock under local impact load shows obvious localization effect. Mn in the critical zone is usually the largest, Mn in the impact zone is slightly less than that in the critical zone, and Mn in the non-impact zone is the least. The larger the impact loading area, the wider the influence enhancement area, and the smaller the non-influence area, yet the smaller the impact zone and critical zone are affected by local impact load.

CONTROL TECHNIQUE OF LOCAL AND GENERAL STABILITY OF THE LOADING CRANE’S TELESCOPIC BOOM

Introduction . The paper examines the overall and local stability of a telescopic boom (TS). Materials and methods . The author uses methods for analytical research of oscillatory systems with a finite number of degrees and methods of the Deformable Solid Mechanics, such as Material Resistance. Moreover, the author applies Solid Edge Simulation as finite element analysis program based on FEA Femap analysis technology and the NX Nastran solver. Results . As a result, the author develops a methodology for monitoring the overall and local stability of the vehicle. The usage of the calculation for the overall stability of the vehicle allows to determine the load-height characteristics, parameters of the working equipment that ensure the steady state of the system, and also to track the overall steady state of the vehicle as a function of the vehicle characteristics. In addition, the usage of local stability calculation allows to track the maximum stress state of the vehicle, which is a criterion of local stability and provides the ability to monitor the stability of the most loaded shelves and walls. The proposed method for calculating the stress state takes into account the combined effect of external and local horizontal and vertical loads. Discussion and conclusions . The usage of methods of monitoring the overall and local stability of the vehicle allows to set automatically the most optimal characteristics of the working equipment, including the developed method in the crane safety system, and to increase the level of safe operation of load- lifting cranes equipped with vehicles.

Development and Application of the TUM-WelChem Cell Model for Prediction of Liquid Distribution in Random Packed Columns

Liquid maldistribution is, next to the prediction of interfacial phase area and mass transfer coefficients, one of the bigger uncertainties in random packed column design. In a joint project, “Cell Model for Packed Column and Liquid Distributor Design” supported by the Bavarian Research Foundation, liquid maldistribution experiments were conducted in three packed columns with diameters of 0.4, 1.2 and 2.0 m at Technical University of Munich (TUM), RVT Process Equipment GmbH and Linde AG. Experiments covered varying experimental and operating parameters – gas/liquid system, type of packing, packing height, type of liquid distributor, liquid load, and gas load. An evaluation of the acquired database provided insight into influencing factors on liquid distribution (Hanusch et al., 2017). In 2007, Wild and Engel first presented their WelChem Cell Model. The original model predicted liquid distribution in random packing from cell layer to cell layer based on directional dispersion coefficients, deduced from virtual 3D irrigation simulations with a CAD model of one random packing element (Wild and Engel, 2007). Further development at TUM included implementation of the influencing factors liquid load and gas load, considering local loading effects and increasing liquid dispersion. Wall effects were refined by distinction of packing elements and voids at the column wall. Liquid distribution profiles predicted with the TUM-WelChem Cell Model are in good agreement with experimental data.WelChem GmbH implemented the TUM-WelChem Cell Model in their column design software TrayHeart, thus making the research results directly accessible for TrayHeart users. Application of the TUM-WelChem Cell Model ranges from prediction of maldistribution in random packed columns, through liquid distributor design, considering interactions with random packing, to process simulation, considering maldistribution in parallel column models (Schultes, 2000).

High-uniformity centimeter-wide Si etching method for MEMS devices with large opening elements

We propose a compensated mesh pattern filling method to achieve highly uniform wafer depth etching (over hundreds of microns) with a large-area opening (over centimeter). The mesh opening diameter is gradually changed between the center and the edge of a large etching area. Using such a design, the etching depth distribution depending on sidewall distance (known as the local loading effect) inversely compensates for the over-centimeter-scale etching depth distribution, known as the global or within-die(chip)-scale loading effect. Only a single DRIE with test structure patterns provides a micro-electromechanical systems (MEMS) designer with the etched depth dependence on the mesh opening size as well as on the distance from the chip edge, and the designer only has to set the opening size so as to obtain a uniform etching depth over the entire chip. This method is useful when process optimization cannot be performed, such as in the cases of using standard conditions for a foundry service and of short turn-around-time prototyping. To demonstrate, a large MEMS mirror that needed over 1 cm2 of backside etching was successfully fabricated using as-is-provided DRIE conditions.

Study of improved load sharing methodologies for distributed generation units connected in a microgrid

In this paper, an improved load sharing strategy is proposed for distributed generation units (DGs) connected in a microgrid. Conventional frequency and voltage droop control result in unacceptable active and reactive power sharing. The proposed method formulates a suitable algorithm for load sharing in the islanded microgrid. The feeder power loss and the line impedance voltage drops are minimized so as to regulate the voltage at the point of common coupling (PCC) at its nominal value. The desired DG output voltages are calculated and a linear relationship is obtained between the shared active and reactive powers and the DG output voltages. A master DG controller sets the frequency which is followed by other DG units. The reference powers for the DG units are adjusted so as to maintain the rated PCC voltage. The proposed strategy is verified taking into account the DG ratings, unequal line impedance drops, feeder losses, change in system impedance and effect of DG local loads and formulates an improved power sharing strategy that also facilitates PCC voltage regulation under variable loading conditions. Simulation and experimental results are presented to verify the effectiveness of the proposed method.

Analysis of the Effect of Local Loads on Thick-Walled Cylindrical Shells with Different Boundary Conditions

Two approaches to the analysis of the stress–strain state of thick-walled cylindrical shells with different boundary conditions under local loads are proposed. These approaches involve the division of a thick shell into several coaxial shells. One approach uses polynomials to approximate the unknown functions in plan and over the thickness. In the other approach, the unknown functions are approximated by linear polynomials in plan, and their distribution over the thickness is found from the analytical solution of the corresponding system of differential equations. The stress–strain state of the shell in the area of local loading is analyzed for different boundary conditions. It is shown that the effect of the boundary conditions on the stress–strain state is very weak for shells of high curvature and strong for shells of low curvature

Lateral gas phase diffusion length of boron atoms over Si/B surfaces during CVD of pure boron layers

The lateral gas phase diffusion length of boron atoms, LB, along silicon and boron surfaces during chemical vapor deposition (CVD) using diborane (B2H6) is reported. The value of LB is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the boron deposition temperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the boron deposition is investigated on the micro scale. A LB = 2.2 mm was determined for boron deposition at 700 °C, while a LB of less than 1 mm was observed at temperatures lower than 500 °C.

船底局部荷重を考慮したコンテナ船の縦曲げ最終強度解析に関する研究

This paper is the first of two companion papers dealing with ultimate longitudinal strength analysis of a container ship considering local loads effects. The purpose of this paper is to clarify the effect of bottom local loads on the longitudinal bending collapse behavior of a large container ship. An important problem is a bending deformation of the double bottom due to upward bottom local loads that may reduce the hull girder ultimate strength.

Evaluation of Po River water quality in Torino (Italy): Effects of diffuse and local point loads

The aim of this paper is to examine the Po River water quality in a small stretch in Piedmont (northern Italy). In this stretch a large pollution load, derived from the wastewater treatment plant of Torino area (more than 2 million inhabitants), is discharged and diluted in the water. In this study this load has been quantified and modeled in order to understand the sources, destinations and effects of the emitted pollutants. The objective was to determine the impact produced by the Torino Wastewater Treatment Plant on the quality of the water, based on various hydrological conditions and the possible intervention on the point and diffuse loads.

(Invited) Fabrication of Pure-GaB Ge-on-Si Photodiodes for Well-Controlled 100-pA-Level Dark Currents

The selective epitaxial growth of Ge-on-Si followed by in-situ deposition of a nm-thin Ga/B layer stack (PureGaB) has previously been shown to be a robust CMOS-compatible process for fabrication of Ge-on-Si photodiodes. In this paper, strategies to improve the control and reproducibility of PureGaB Ge-on-Si photodiode fabrication by reducing the local loading effects during the depositions are presented. As compared to the earlier PureGaB devices, the elimination of parasitic Ge and concomitant in-situ As-doping from oxide regions surrounding the deposition windows leads to a well-controlled process flow that improves photodiode electrical and optical characteristics. For micrometer-sized diodes, ideality factors of less than 1.1 and dark current densities in the range of 15 µA/cm2 at room temperature are now achieved. Moreover, improvements in the flatness of the Ge-island surface facilitated a process flow for contacting the diode perimeter while leaving a large oxide-covered PureGaB-only light-entrance window on the central photosensitive region. The optical characteristics of the photodiodes at the low temperature of 180 K display dark current densities of less than 150 pA/cm2 and increased sensitivity towards infrared wavelengths.

(Invited) Fabrication of Pure-GaB Ge-on-Si Photodiodes for Well-Controlled 100-pA-Level Dark Currents

In this paper the influence of PureGaB Ge-on-Si photodiode (PD) design strategies that aim to reduce local loading effects during Ge deposition are presented. As compared to our earlier devices, the elimination of parasitic Ge and concomitant As-doping deposition from oxide regions surrounding the deposition windows also leads to an improved diode ideality. For micrometer-sized diodes, ideality factors of less than 1.1 and dark currents in the range of 100 pA are now achieved, which to our knowledge are by far the lowest values reported in the literature. Moreover, improvements in the flatness of the Ge-island surface facilitated a process flow for contacting the diode perimeter while leaving a large oxide-covered PureGaB-only light entrance window on the central photosensitive region.In Fig.1 the basic process flow is illustrated for fabricating the improved PureGaB Ge PDs. First a 1-µm-thick SiO2 layer is deposited and patterned on the Si surface. In contrast to earlier flows, the windows destined to be filled with Ge for PD realization are surrounded by another ring-shaped window where Ge also is deposited. After this patterning, the wafers are loaded into a CVD reactor and in one deposition cycle the n-type Ge and nm-thin Ga/B layer-stack (PureGaB) is grown. It was found that a 5-µm-thick ring was sufficient to absorb most of the Ge and As atoms that otherwise would reach the main PD window by lateral diffusion across the SiO2 as a local loading effect. After Ge deposition, the wafers are transferred to a PECVD reactor for deposition of a second SiO2layer which is subsequently patterned and etched with a soft-landing to give access to the perimeter regions of the Ge-PDs. Then the metallization is sputtered on both sides of the wafer to give access to the anode and cathode of the Ge-PDs. Finally the front-side metal is patterned and removed from the center of the Ge-PDs.Top-view SEM images of the fabricated PureGaB Ge PD before and after the metal removal, are shown in Fig.2.a and Fig.2.b, respectively. It is shown that this extra metal removal step on the surface of the Ge-PD, creates a clean oxide-covered PureGaB-only front-entrance window with no indication of damage to PureGaB surface.The diode quality was checked by I-V measurements of PureGaB Ge-PDs with various sizes. In Fig.3 the I-V curves are shown for 3 different sizes. An area/perimeter analysis reveals that the current is area-dependent which means that the perimeter leakage that usually is present in Ge diodes is eliminated in the PureGaB PD’s. The exact reason for this behavior is yet unknown since several factors are counteracting each other. Effects that may play a role are: the Ge does not attach to the sidewalls of the SiO2window; the PureGaB deposition is conformal over the Ge surface; the depletion and associated electric field at the perimeter are modified by the presence of the oxide and any increase of the As-doping at the perimeter due to the local loading effect. The n-doping of the Ge-islands is determined by Capacitance-Voltage (C-V) profiling, some results of which are shown in Fig.4. From the almost perfect area-dependent behavior of the I-V characteristics it is expected that the n-doping is similar in all cases. In fact the doping goes from about 3×1015 cm-3 to 1016 cm-3 when going from a PD area of 26×26 µm2 to 11×11 µm2. This increase in doping with PD area can possibly be accorded to an increasing, but small, local loading effect due to an increase in oxide area around the smaller devices. This is layout dependent and can be corrected for future designs.All in all, the suppression of local loading effects significantly improves the electrical diode characteristics and also the yield: an almost 100% yield has been achieved for arrays of 300×1 PDs of varying sizes.

Data-Enabled Design and Optimization (DEDOpt): Tall steel building frameworks

Recent increases in computational resources and speed have opened the door to the possibility of integrating informational databases into the design process of civil structures. The aim of this paper is twofold. Firstly, efficient time/frequency domain procedures for the estimation of local and global load effects are presented with focus on the use of proper orthogonal decomposition of the spectral and covariance matrices. Secondly, a procedure is presented that fully automates the design procedure through the rigorous discrete member size optimization of the structural system subject to multiple performance constraints on both the local and global load effects.

Local-Loading Effects for Pure-Boron-Layer Chemical-Vapor Deposition

The so-called local-loading effect is studied for pure boron (PureB) depositions from B2H6 in a chemical-vapor deposition (CVD) reactor. This effect occurs because the boron is not deposited on oxide and this increases the deposition rate (DR) of boron in open Si areas in the oxide. Experiments are performed for wide range of local-oxide ratio (LOR). Three regions can be distinguished. For LOR < 0.1 the oxide areas are too small to have any significant influence on the DR and for 0.1 < LOR < 1 the DR increases as the oxide area increases. An empirical model is developed to describe this behavior in the latter region and it is experimentally verified. This formulation can be used to model the lateral diffusion component of the boron atoms and to develop a comprehensive model to predict the PureB deposition rate on any 2-D uniform or non-uniformly patterned wafer. For LOR > 1, the experimental data deviates from the model, showing saturation of DR as the oxide area increases. In this region the gas phase diffusion of the boron atoms across the oxide is limited by their diffusion length. Conditions that allow reliable deposition of 2-nm-thick PureB layers are found.

Hydrological deformation induced by the West African Monsoon: Comparison of GPS, GRACE and loading models

Three‐dimensional ground deformation measured with permanent GPS stations in West Africa was used for investigating the hydrological loading deformation associated with Monsoon precipitation. The GPS data were processed within a global network for the 2003–2008 period. Weekly station positions were retrieved with a repeatability (including unmodeled loading effects) of 1–2 mm in the horizontal components and between 2.5 and 6 mm in the vertical component. The annual signal in the vertical component for sites located between 9.6°N and 16.7°N is in the range 10–15 mm. It is consistent at the 3 mm‐level with the annual regional‐scale loading deformations estimated from GRACE satellite products and modeled with a combination of hydrological, atmospheric, and nontidal oceanic models. An additional 6 month transient signal was detected in the vertical component of GPS estimates at most of the West African sites. It takes the form of an oscillation occurring between September and March, and reaching a maximum amplitude of 12–16 mm at Ouagadougou (12.5°N). The analysis of in situ hydro‐geological data revealed a strong coincidence between this transient signal and peak river discharge at three sites located along the Niger River (Timbuktu, Gao, and Niamey). At Ouagadougou, a similar coincidence was found with the seasonal variations of the water table depth. We propose a mechanism to account for this signal that involves a sequence of swelling/shrinking of clays combined with local loading effects associated with flooding of the Niger River.