Optimal Pattern Research Articles

Propeller tip vortex mitigation by roughness application

In this study, the application of surface roughness on model and full scale marine propellers in order to mitigate tip vortex cavitation is evaluated. To model the turbulence, SST k−ω model along with a curvature correction is employed to simulate the flow on an appropriate grid resolution for tip vortex propagation, at least 32 cells per vortex diameter according to our previous guidelines. The effect of roughness is modelled by modified wall functions. The analysis focuses on two types of vortices appearing on marine propellers: tip vortices developing in lower advance ratio numbers and leading edge tip vortices developing in higher advance ratio numbers. It is shown that as the origin and formation of these two types of vortices differ, different roughness patterns are needed to mitigate them with respect to performance degradation of propeller performance. Our findings clarify that the combination of having roughness on the blade tip and a limited area on the leading edge is the optimum roughness pattern where a reasonable balance between tip vortex cavitation mitigation and performance degradation can be achieved. This pattern in model scale condition leads to an average TVC mitigation of 37% with an average performance degradation of 1.8% while in full scale condition an average TVC mitigation of 22% and performance degradation of 1.4% are obtained.

Study on a full-year improvement of indoor thermal comfort by different vertical greening patterns

Vertical greening is an influential element in built environment that affects the indoor thermal environment and the residents’ thermal perception. This research aims to identify the optimum vertical greening patterns for indoor thermal comfort in cold winter and hot summer areas. The general parameters of greening walls were extracted according to the constituent materials, and Envi-met model was employed to calculate the indoor thermal indexes based on the meteorological data acquired from the national meteorological station. PET isotherm was used to reveal the distribution of a year-round thermal perception. The analytical result showed that modular green walls have the highest proportion of livable PET, annually. Livable PET includes “comfortable”, “slightly cold” and “slightly hot” thermal perceptions. Linear green walls have the second highest proportion of livable PET, even though modular green walls and linear green walls extended “very cold” thermal perceptions in winter. Considering the annual PET distribution, the modular green walls and linear green walls are suitable for hot climatic regions, while the green facades pattern is preferable in the cold climate areas.

Over-the-Air Calibration of Active Antenna Arrays Using Multisine

A novel over-the-air (OTA) beamforming calibration procedure is proposed, which can be applied to different types of multiple-input multiple-output (MIMO) transmitting antennas. The method consists of using two tones on each antenna element, the main tone, and the tickle tone. The latter one operates in a different frequency for each antenna element and is used to obtain the optimum phase that needs to be set for each element to generate a beam in the desired direction, at the main tone frequency. The novel method was applied to linear, planar, 3-D antennas, and noncollocated multiantennas to validate its applicability to different antenna types. Line-of-Sight (LOS) and non-LOS experimental results demonstrate that the method can be used to retrieve the required phase to fully control the antenna radiation pattern. An optimum radiation pattern and lowest error vector magnitude (EVM) can be achieved even under high multipath effects/non-LOS conditions. A comparison between the performance and the application of the array factor (AF) theory is presented for practical indoor scenarios, demonstrating the effectiveness of the method. It is demonstrated that the method may be an alternative to the calibration of nonstandard MIMO antennas, where the AF computation is complex or not possible.

Universal response pattern of phytoplankton growth rates to increasing CO2.

Phytoplankton growth rate is a key variable controlling species succession and ecosystem structure throughout the surface ocean. Carbonate chemistry conditions are known to influence phytoplankton growth rates but there is no conceptual framework allowing us to compare growth rate responses across taxa. Here we analyse the literature to show that phytoplankton growth rates follow an optimum curve response pattern whenever the tested species is exposed to a sufficiently large gradient in proton (H+ ) concentrations. Based on previous findings with coccolithophores and diatoms, we argue that this 'universal reaction norm' is shaped by the stimulating influence of increasing inorganic carbon substrate (left side of the optimum) and the inhibiting influence of increase H+ (right side of the optimum). We envisage that exploration of carbonate chemistry-dependent optimum curves as a default experimental approach will boost our mechanistic understanding of phytoplankton responses to ocean acidification, like temperature curves have already boosted our mechanistic understanding to global warming.

Numerical simulation of heat transfer improvement of a new designed artificially roughened solar air heater using triangular ribs with semi-circular nooks

ABSTRACT The present study represents a computational analysis of two-dimensional air flow in a new designed configuration of a solar air heater (SAH). The shape of the installed ribs along the absorber plate is a combination of triangular and semi-circular nooks with variable height of three ribs simultaneously. The objective is to optimize the Thermo-Hydraulic Efficiency Parameter (THEP) of the SAH by characterizing the values of roughness height (e) and pitch (P) of the considered ribs which provides the optimum patterns. Various (e) and (P) values for varied Reynolds number (Re) between 3,800 and 18,000 are investigated. An imposed constant heat flux is considered, and governing equations describing the flow and heat transfer are solved numerically with the selected RNG k-ε for the turbulence modeling. The obtained results indicate that the THEP strongly depends on the different investigated geometric parameters and Re number. The obtimum THEP value of 1.93 could be obtained for the case C1 and Re number of 5,000.

Improvement of p-electrode structures for 280 nm AlGaN LED applications

An improvement of Ni/Au/p+-GaN p-electrode for AlGaN deep-ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength of 280 nm is proposed for both p-side-up and flip-chip structures. An interdigitated multi-finger Ni/Au was employed in p-side-up DUV LED, where the p-GaN contact layer was partially removed to improve the light extraction efficiency without a serious current-crowding effect. The 9- and 12-finger LEDs were determined to have higher thermal dissipation and lower surface temperatures and correlated well with the theoretical simulation. For the comparison of p-side-up emission LEDs, the output power of 9-finger LED is 172% higher than that of conventional LED at the current injection of 350 mA. The optimum p-electrode pattern was further applied to the flip-chip LED structure. It is determined that the output power of 9-finger flip-chip LED at 350 mA is still 14.6% higher than that of a conventional flip-chip LED. The higher output power of 9-finger flip-chip LED with a wall-plug efficiency of 1.05% is attributed to the combination of the improved current-spreading path and the higher reflection through the moderate removal of partial p+-GaN absorbing layer.

Experimental study of the optimum puncture pattern of robot-assisted needle insertion into hyperelastic materials.

The robot-assisted insertion surgery plays a crucial role in biopsy and therapy. This study focuses on determining the optimum puncture pattern for robot-assisted insertion, aiming at the matching problem of needle insertion parameters, thereby to reduce the pain for patients and to improve the reachability to the lesion point. First, a 6-degrees of freedom (DOFs) Computed Tomography (CT)-guided surgical robotic system for minimally invasive percutaneous lung is developed and used to perform puncture experiments. The effects of four main insertion factors on the robotic puncture are verified by designing the orthogonal test, where the inserting object is the artificial skin-like specimen with high transparent property and a digital image processing method is used to analyze the needle tip deflection. Next, the various phases of puncture process are divided and analyzed in detail in view of the tissue deformation and puncture force. Then, short discussion on the comparison of puncture force with different effect factors for the same beveled needle is presented. The same pattern can be observed for all of the cases. Finally, based on the experimental data, the formulations of the puncture force and needle deflection which depends on Gauge size, insertion velocity, insertion angle, and insertion depth are developed using the multiple regression method, which can be used to get an optimum puncture pattern under the constrains of minimum peak force and minimum needle tip deflection. The developed models have the effectiveness and applicability on determining the optimum puncture pattern for one puncture event, and which can also provide insights useful for the setting of insertion parameters in clinical practice.

Optimization of Output Spike Train Encoding for a Spiking Neuron Based on its Spatio–Temporal Input Pattern

A common learning task for a spiking neuron is to map a spatio–temporal input pattern to a target output spike train. There is no prescribed method for selection of the target output spike train. However, the precise spiking pattern of the target output spike train (output encoding) can affect the learning performance of the spiking neuron. Therefore, systematic methods of finding the optimum spiking pattern for a target output spike train that can be learned by spiking neurons are needed. Here, a method is proposed to adaptively adjust an initial suboptimal output encoding during different learning epochs to find the optimal output encoding. A time varying value of a local event called a spike trace is used to calculate the amount of a required adjustment. The remote supervised method (ReSuMe) learning algorithm is used to train the weights, and the proposed method is used for finding optimized output encoding (optimized desired spikes). Experimental results show that optimizing the output encoding during the learning phase increases the accuracy. The proposed method was applied to find optimized output encoding in classification tasks and the results revealed improvements up to 16.5% in accuracy compared to when using the non-adapted method. It also increases the accuracy in a classification task from 90% to 100%.

Torsional Vibration Stress and Fatigue Strength Analysis of Marine Propulsion Shafting System Based on Engine Operation Patterns

Modern merchant ships use marine propulsion systems equipped with an ultra-long-stroke diesel engine that directly drives a large slow-turning propeller. Such systems use fewer cylinders and generate greater power at slower shaft speeds, which affords improved propulsion performance as well as low repair and maintenance costs. However, this also results in higher torsional vibrations, which can lead to the fatigue of the shafting system. Tests performed on various marine propulsion systems with 5- to 7-cylinder engines have shown that engines with fewer cylinders exhibit a correspondingly wider barred speed range (BSR) and higher torsional vibration stresses. Thus, it is necessary to investigate the optimal engine operation patterns required to quickly pass the BSR with smaller torsional vibration. In this study, we carried out a series of BSR passage experiments during actual sea trials to evaluate the intermediate shaft performance under different engine operation patterns. The fractional damage accumulations due to transient torsional vibration stresses were calculated to estimate the fatigue lifetime of the shafting system. Our analysis results show that the torsional fatigue damage during BSR decelerations are small and negligible; however, the fractional damage during accelerations is a matter of concern. Our study determines the optimal main engine operation pattern for quick passage through the BSR with the smallest torsional vibration amplitudes and the least fractional damage accumulation, which can therefore extend the fatigue lifetime of the entire propulsion shafting system. Based on this analysis, we also suggest the optimum engine pattern for safe BSR passage.

Multi-objective design optimization of variable ribs composite grid plates

Grid structures are among the most lightweight elements for stiffening the plates and shells or as self-sufficient structures. There are different known grid patterns, which are composed of variable numbers of parallel ribs. Selecting an optimum pattern and geometries for a grid to achieve the minimum weight and maximum load-bearing capacity is a challenging procedure for designers. In the current study, a variable ribs model (VRM) is proposed to find the optimum architecture of a grid plate. Therefore, using a genetic algorithm process, a multi-objective optimization is implemented to maximize the axial or shear buckling loads at a minimum possible weight of a grid structure. Eleven geometrical parameters including thickness, width, and the number of ribs as well as the orientation of the grid plate are considered the design variables. The multi-objective optimization is carried out employing the e-constraint method. The buckling loads are obtained based on the first-order shear deformation plate theory using the Ritz method.

Land Suitability and Crop Pattern Model using Integrated Pollination Intelligence Algorithm and Remote Sensing

A mathematical model for crop pattern coupled with economic and environmental factors of agricultural production constructed with remote sensing and metaheuristic based algorithm is considered in this work. The model is expected to serve as a support system for farm managers' decision making process. Geographic data showing soil properties of major cities in Benue State, Nigeria using remote sensing, was integrated to the model to obtain analyzed suitability information for selected crops. A class of modern optimization algorithms was thereafter used to find optimum cropland pattern. A net production value of $1,592,107,000.00$ was obtained by using the model compared to an initial production value of $1,364,460,000.00$ recorded in the study area. The study suggests that soil properties must be considered along side with economic factors before choosing the types of crop to be planted on a piece of land. This study has shown the efficacy of optimization tools which should be dully employed by farmers in decision making process. The data used to support the findings of this study are included within the article.

Exploring Smart Growth Boundaries of Urban Agglomeration with Land Use Spatial Optimization: A Case Study of Changsha-Zhuzhou-Xiangtan City Group, China

Urban agglomeration is the main spatial organization mode used by the Chinese government to promote the policy of new urbanization strategy. Hence, a better understanding of the urban growth boundary (UGB) has profound theoretical and practical significance regarding sustainable urban development. This study devised a raster-based land use spatial optimization (LUSO) framework, and utilized ant colony optimization (ACO) algorithm to delimit the smart growth boundaries of the Changsha-Zhuzhou-Xiangtan city group (CZTCG) in China. The aim of this study is to design a LUSO model to explore an optimal pattern of urban agglomeration for sustainable growth. Multi growth scenario including a single development center, multipolar development and balanced development patterns are generated by the LUSO model for the year of 2050, and the optimum spatial pattern is chosen based on objectives comparison and the present stage of economic and social development in CZTCG. The main results are listed as the following. 1) It is feasible to identify the growth boundaries of the urban agglomeration using the land use spatial optimization model, and the optimal form of the spatial pattern can be defined. 2) With the growth trend of the urban agglomeration gradually spreads from a single center to multi-centers and even small towns, the total optimization target performance gradually increases, which means that the traditional pie-shaped development does not meet the maximum comprehensive benefit of the city group. 3) Subject to the regional social and economic development stage, absolute fair development or simply developing the central city is not conducive to promoting the coordinated development of the urban agglomeration. Gradient equalization and gradual advancement are the best choice for UGB delineation of urban agglomeration. The findings of this study would be useful to identify the UGB in CZTCG for more sustainable urban development in the future.

Self-management support activities in primary care: A qualitative study to compare provision across common health problems

ObjectiveTo explore the views of primary care teams about the provision of self-management support to patients with common health problems. MethodsSemi-structured interviews were conducted with twenty-one members of the primary care team from thirteen general practices. Interviews were transcribed verbatim, and analysed using the ‘Framework’ approach. ResultsThree categories and six sub-categories illustrating different self-management support activities across common health problems were identified from the analysis of interviews, and contributed to one major theme and one cross-cutting theme. Referral and signposting were frequently used to facilitate patient engagement with external services and resources. Practitioners faced some challenges in balancing medical management and psychosocial support and motivating patients to engage with self-management. ConclusionsPrimary care teams described providing a wide range of self-management support activities, but the pattern of use varied for different types of health problem. These patterns may have been influenced, in part, by general practices focusing upon achieving financially incentivised quality improvement goals. Practice implicationsTo improve self-management support, practitioners need a digital repository of services/resources, motivational interviewing skills, an understanding of the optimum duration and pattern of consultations, and incentivised targets that match a biopsychosocial model of care.

Tensile Characteristics of Low Density Infill Patterns for Mass Reduction of 3D Printed Polylactic Parts

Various infill patterns are introduced in 3D printing to generate low density objects that leads to reduced cost and fabrication time through mass reduction. However, as a trade-off, the strength of the 3D printed component is uncertain. Confusions arise in determining the infill pattern with highest value of tensile strength since most studies limited only to rectilinear, honeycomb, and concentric infill patterns. As consequences, there are very little information on rarely used infill patterns such as Hilbert curve, Archimedean cord and octagram spiral. Therefore, the purpose of this research is to investigate and compare the tensile strength and strain of all infill patterns in mass reduction of 3D printed components experimentally. Following ASTM D638 type III standard, ten tensile test specimens of each infill patterns with 20% density were printed with an FFF 3D printer and were then tested. It was found that Archimedean cords infill pattern had the highest specific tensile strength of 33.23×103 MPa∙mm3/g which made it as the optimum infill pattern for the mass reduction of 3D printed parts with a high tensile strength. On the other hand, having the highest specific tensile strain of 18.21×103 %∙mm3/g, concentric infill pattern was found to be more suitable for producing lightweight parts with a higher elongation before break. Additionally, Hilbert curve infill was the worst selection for mass reduction since it had the lowest values of specific tensile strength and specific strain of 19.80×103 MPa∙mm3/g and 8.34 %∙mm3/g, respectively. Nevertheless, the trends of tensile strength and strain of all six infill patterns had been obtained, especially for rarely investigated infill patterns of Archimedean cords, octagram spiral, and Hilbert curve. Specifically, the trend from the strongest to the weakest (in % compared to solid) for specific tensile strength is rectilinear (38.57%), Archimedean chords (37.29%), concentric (36.57%), octagram spiral (34.79%), honeycomb (27.84%), and Hilbert curve (22.25%), while for specific strain is concentric (102.6%), octagram spiral (83.94%), rectilinear (78.22%), Archimedean cords (77.99%), honeycomb (54.84%), and Hilbert curve (45.14%).

Investigating and Ranking Blasting Patterns to Reduce Ground Vibration using Soft Computing Approaches and MCDM Technique

The blasting method is one of the most important operations in most open-pit mines that has a priority over the other mechanical excavation methods due to its cost-effectiveness and flexibility in operation. However, the blasting operation, especially in surface mines, imposes some environmental problems including the ground vibration as one of the most important ones. In this work, an evaluation system is provided to study and select the best blasting pattern in order to reduce the ground vibration as one of the hazards in using the blasting method. In this work, 45 blasting patterns used for the Sungun copper mine are studied and evaluated to help determine the most suitable and optimum blasting pattern for reducing the ground vibration. Additionally, due to the lack of certainty in the nature of ground and the analyses relating to this drilling system, in the first step, a combination of the imperialist competitive algorithm and k-means algorithm is used for clustering the measured data. In the second step, one of the multi-criteria decision-making methods, namely TOPSIS (Technique for Order Performance by Similarity to Ideal Solution), is used for the final ranking. Finally, after evaluating and ranking the studied patterns, the blasting pattern No. 27 is selected. This pattern is used with the properties including a hole diameter of 16.5 cm, number of holes of 13, spacing of 4 m, burden of 3 m, and ammonium nitrate fuel oil of 1100 Kg as the most appropriate blasting pattern leading to the minimum ground vibration and reduction of damages to the environment and structures constructed around the mine.

Stage Specific Expression Pattern of Alpha-Hemoglobin-Stabilizing-Protein (AHSP) Portrayed in Erythroblast Chronology.

During erythropoiesis, the molecular chaperone alpha-hemoglobin-stabilizing protein (AHSP) sequesters free alpha-hemoglobin (αHb) and prevents precipitation of excess αHb. While AHSP is linked to hereditary anemia, the pattern of expression during specific erythroblast stages is poorly understood. We investigated gene and protein expressions of AHSP throughout progressive maturation stages of erythroblasts in biphasic cultures of blood and bone marrow samples from healthy donors. Differentiating erythroblasts were periodically subjected to flow cytometry, Amnis imaging and RT-qPCR analyses. We made parallel in vivo validations from naive murine bone marrow cells. Percentages of AHSP+ erythroblasts, protein expressions and AHSP gene expressions are negligible on culture day 6 (CFU-Es) and progressively increases from culture days 8–12 (peaks on day 12) and declines on day 14. Notably, sub-cellular location of AHSP is both in the cytoplasm and nucleus in the early erythroblasts while in the late stages of maturation AHSP is found predominantly in the nucleus, being expelled with it during enucleation. As both human bone marrow and peripheral blood mononuclear cells (PBMC) derived erythroblasts demonstrated similar expression patterns, sampling of erythroblasts from day 11 cultures could portray erythroblast chronology and provide optimum representative stage specific expression patterns. PBMCs may be suitable for comparison studies of AHSP expression in pathologic erythropoiesi

The role of agricultural extension in awareness of optimum crop sequences patterns in New Valley Governorate

This research aims to identify the patterns of crop sequences prevailing among the cultivated farmers during three consecutive agricultural years; determine the level of satisfaction of the respondents with the prevailing patterns of crop sequences, and the most important variables associated with it; and identify the sources of agricultural information from which the respondents derive their information in this field, and the extent to which the agricultural extension apparatus implements some extension activities in the field of educating farmers with appropriate crop sequences patterns. This research was conducted in the New Valley Governorate, where the two largest districts in the governorate were chosen namely Al-Kharjaa and Al-Dakhla districts. A simple random sample of farmers was chosen in each village by 5% of the total number of farmers in each village, where the data of this questionnaire was completed through a personal interview for respondents. A set of statistical methods were used in the analysis of field data, where these methods ranged from tabular presentation by frequency and percentages, arithmetic mean, standard deviation, and the rank correlation coefficient of Spearman. The results indicated that the most common cropping patterns among cultivated farmers in the winter season for three consecutive agricultural years were: (clover + wheat), and (clover + wheat + bean). The most common cropping patterns among cultivated farmers in the summer season for the three consecutive agricultural years were: (clover + green fodder), and (clover + Sorghum + Maize). About 11.5% of the total sample falls in the high from the degree of satisfaction with the prevailing cropping patterns. We recommend to intensify the extension efforts to provide farmers with all knowledge and information on agricultural crops, the needs of the internal and external markets, and consumers requirements.

Investigations of tip vortex mitigation by using roughness

The application of artificial roughness to mitigate tip vortex cavitation inception is analyzed through numerical and experimental investigations carried out on an elliptical foil. Different roughness configurations and sizes are tested, and effects on cavitation inception, drag, and lift are studied. Implicit Large Eddy Simulation is employed to conduct the simulation on a proper grid resolution having the tip vortex spatial resolution as fine as 0.062 mm. Two different approaches including using a rough wall function and resolving the flow around roughness elements are evaluated. New experiments, performed in the cavitation tunnel at Kongsberg Hydrodynamic Research Center, for the rough foil are presented. The vortical structures and vorticity magnitude distributions are employed to demonstrate how different roughness patterns and configurations contribute to the vortex roll-up and consequently on the tip vortex strength. It is found that the application of roughness on the leading edge, tip region, and trailing edge of the suction side is acceptable to mitigate the tip vortex and also to limit the performance degradation. This is regarded to be in close relation with the way that the tip vortex forms in the studied operating condition. The boundary layer characteristics show that roughness separation line is the reason for a more even distribution of vorticity over the tip compared to the smooth foil condition, leading to a reduction in vortex strength. For the optimum roughness pattern, both the numerical results and experimental measurements show a decrease in the tip vortex cavitation inception as large as 33% compared to the smooth foil condition with a drag force increase observed to be less than 2%.

Simulations of Tephra Fall Deposits From a Bending Eruption Plume and the Optimum Model for Particle Release

AbstractWe developed a simulation code named WT, which calculates tephra fallout from eruption plumes bent by wind. This proposed model assumes a series of radial particle sources arraying along the theoretically predicted trajectory of the plume center. To validate WT, we reconstructed the tephra dispersal during the 2011 sub‐Plinian eruption of Shinmoedake in Japan. This eruption was ideal for the validation because it was observed through various approaches; however, high‐resolution data of the fluctuating plume height made it difficult to determine a representative eruption time and plume height for running the simulations. Also, the amount of particle segregation along the plume could not be determined a priori. We thus implemented inversion calculations to study the optimum particle segregation pattern for possible ranges of time and the plume height, and the misfit between the observed and calculated mass loadings on the ground was evaluated. After this process and the following analysis, the optimum eruption time was determined for one of three major explosions (18:00 Japan Standard Time on 26 January). The optimum plume height was estimated to be 4 km above sea level, slightly lower than the estimation derived by the weather satellite (5 km). When wind shear exists, the WT model has a significant advantage in reconstructing tephra dispersal over the classical code named Tephra2, the prototype of WT. The WT inversion implies a simple segregation model from a well‐mixed plume, and further studies on particle segregation patterns will help to improve the accuracy of forward WT simulations.

An Efficient Vector Control Policy for EV-Hybrid Excited Permanent-Magnet Synchronous Motor

In this paper, a new control strategy for hybrid excited salient permanent-magnet synchronous motor (HEPMSM) is proposed, where both armature winding and DC field windings are located in the stator. The developed control strategy fulfills the required characteristics of the electric vehicles (EVs) and hybrid electric vehicles (HEVs) motors. A detailed mathematical model of the HEPMSM is presented. The field current (FC) is kept constant near its rated value for the high acceleration constant torque (CT) region. The conventional control usable method of reducing FC and reversing it on the motor performance characteristics through the constant power (CP) region is examined and evaluated. A proposed FC pattern is applied to three deferent operating modes of EV. High acceleration and wide stable constant power speed range without overdesign is the main target of this work. Based on the deduced optimum control pattern, the required EV-HEPMSM performance characteristics are developed. The required d–q control armature, field currents as well as d–q stator voltage components are provided for either current or voltage control technique availabilities. Simulation work is carried out on the commonly used method and on the proposed method. The obtained simulated characteristics effectively validate the target of the proposed steady-state presented analysis and pattern.