Small-scale Experimental Results Research Articles

Vehicle routing for customized on-demand bus services

This study investigates a variant of the Vehicle Routing Problem (VRP) for customized on-demand bus service platforms. In this problem, the platform plans customized bus routes upon receiving a batch of orders released by passengers and informs the passengers of the planned pick-up and drop-off locations. The related decision process takes into account some passenger-side time window-related requirements, walking limits, the availability and capacities of various types of buses. A mixed-integer linear programming model of this new VRP variant with floating targets (passengers) is formulated. To solve the model efficiently, a solution method is developed that combines the branch-and-bound and column generation algorithms and also includes embedded acceleration techniques such as the multi-labeling algorithm. Experiments based on real data from Dalian, China are conducted to validate the effectiveness of the proposed model and efficiency of the algorithm; the small-scale experimental results demonstrate our algorithm can obtain optimal results in the majority of instances. Additionally, sensitivity analysis is conducted, and model extensions are investigated, to provide customized bus service platform operators with potentially useful managerial insights; for example, a platform need not establish as many candidate stops as possible, a wide range of walking distance may not bring early arrival at destinations for customers, more mini-buses should be deployed than large buses in our real-world case. Moreover, the rolling horizon-based context and zoning strategies are also investigated by extending our proposed methodology.

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Embracing Anisotropy – Opportunities and Challenges to the Functional Application of Advanced Manufacturing of Energetic Materials

Influence of girth welding material on thermal and residual stress fields in welded lined pipes

An experimental and numerical investigation on the thermal and mechanical response of a lined pipe (compound pipe) under welding is presented. The welding process consists of a single-pass overlay welding (inner lap-weld) and a two-pass girth welding (outer butt-weld). The influence of the filler material of the girth welding has been examined thermally and mechanically as it is a key factor that can affect the quality of lined pipe welding. To this end, a three-dimensional non-linear finite element model based on the ABAQUS code has been developed and successfully validated against small-scale experimental results. This study was conducted on two specimens of lined pipe joined together by a girth welding deposited either by mild steel or by austenitic stainless steel. Furthermore, in this study, a pre-heat treatment required to produce lined pipe specimens has been taken into account. Strains and residual stresses have been measured by means of high temperature strain gauges, residual stress gauges and the X-ray diffraction technique along the inner and outer surfaces of the welded lined pipe whereas the thermal history has been recorded by thermocouples. The findings point out that replacing the girth welding mild steel by austenitic stainless steel has a significant effect on the residual stress results but no influence on the thermal history results.

A Robustness-Aware Real-Time SFC Routing Update Scheme in Multi-Tenant Clouds

In multi-tenant clouds, requests need to traverse a set of network functions (NFs) in a specific order, referred to as a service function chain (SFC), for security and business logic issues. Due to workload dynamics, the central controller of a multi-tenant cloud needs to frequently update the SFC routing, so as to optimize various network performance, such as load balancing. To achieve effective SFC routing update, we should consider two critical requirements: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">system robustness</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">real-time update</i> . Without considering these two requirements, prior works either result in fragile clouds or suffer from large update delay. In this paper, we propose a robustness-aware real-time SFC routing update (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -UA) scheme which takes both requirements into consideration. R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -UA pursues robustness-aware real-time routing update through two phases: robust NF instance assignment update and real-time SFC routing update. Two algorithms with bounded approximation ratios are proposed for these two phases, respectively. We implement R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -UA on a real testbed. Both small-scale experimental results and large-scale simulation results show the superior performance of R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> -UA compared with other alternatives.

A Robust Service Mapping Scheme for Multi-Tenant Clouds

In a multi-tenant cloud, cloud vendors provide services ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">e.g.</i> , elastic load-balancing, virtual private networks) on service nodes for tenants. Thus, the mapping of tenants’ traffic and service nodes is an important issue in multi-tenant clouds. In practice, unreliability of service nodes and uncertainty/dynamics of tenants’ traffic are two critical challenges that affect the tenants’ QoS. However, previous works often ignore the impact of these two challenges, leading to poor system robustness when encountering system accidents. To bridge the gap, this paper studies the problem of robust service mapping in multi-tenant clouds (RSMP). Due to traffic dynamics, we take a two-step approach: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">service node assignment</i> and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">tenant traffic scheduling</i> . For service node assignment, we prove its NP-Hardness and analyze its problem difficulty. Then, we propose an efficient algorithm with bounded approximation factors based on randomized rounding and knapsack. For tenant traffic scheduling, we design an approximation algorithm based on fully polynomial time approximation scheme (FPTAS). The proposed algorithm achieves the approximation factor of 2+ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon $ </tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\epsilon $ </tex-math></inline-formula> is an arbitrarily small value. Both small-scale experimental results and large-scale simulation results show the superior performance of our proposed algorithms compared with other alternatives.

A Neural Network Inverse Optimization Procedure for Constitutive Parameter Identification and Failure Mode Estimation of Laterally Loaded Unreinforced Masonry Walls

A new Neural Network Optimization (NNO) algorithm for constitutive material parameter identification based on inverse analysis of experimental tests of small-scale masonry prisms under compressive loads is presented. The Concrete Damaged Plasticity (CDP) constitutive model is used for the brick and mortar of the Unreinforced Masonry (URM) walls. By comparisons with experimental data taken from laboratory tests, it is demonstrated that the constitutive parameters calibrated by application of the proposed inverse optimization procedure on the small-scale (prism) experimental results are sufficiently accurate to allow for the prediction of the mechanical response of large-scale URM walls subject to compressive and lateral loads. This eliminates the need for large-scale URM wall experimental tests for the identification of their material properties, making the calibration process more economic. After verifying the accuracy of the calibrated constitutive parameters based on the above comparisons, a numerical parametric study is performed for the investigation of the effect of material behavior and geometrical aspect ratios on the failure mechanisms of large-scale URM walls.

Stabilizing Control of an Unmanned Surface Vehicle Pushing a Floating Load

In this paper, the automatic control of a single unmanned surface vehicle (USV) pushing a floating load is developed and theoretically analyzed. This represents a challenging control problem, since the manipulated load is underactuated and its open-loop dynamics is inherently unstable. Thus, a stabilizing controller must be designed. To this end, a scheme that combines partial feedback linearization with local linearization of the remaining nonlinear terms is proposed. Such scheme simplifies the design of a variable structure controller, that has robustness characteristics to parametric uncertainties and matched disturbances. The proposed closed-loop control system has local stability properties. Small-scale experimental results in calm waters, and simulation results, illustrate the performance of the proposed control system.

Relating a Small-Scale Experiment to a Full-Scale Railgun Using Simulation and Similarity Theory

In this paper, a small-scale experimental method for the study of the dynamic performance of an electromagnetic railgun is proposed. A silicon-based microbeam under electrostatic force was used to simulate the electromagnetic railgun. An experimental model was developed for a set of railgun parameters. On the basis of similarity theory, the natural frequency similarity ratio between the railgun and the experimental model was determined. The excitation and detection circuits of the experimental model were designed and fabricated. Using the experimental model, the natural frequency for the railgun was obtained and compared with the real full-scale one. Results revealed that the small-scale experimental results agreed well with the experimental result of the full-scale railgun. The proposed method can be used to predict the dynamic performance of the full-scale railgun system.

Trait-based responses of seven annual crops to elevated CO2and water limitation

AbstractBy potentially disrupting crop production, climate change has been implicated as a threat to global food security. We focus on two elements of climate change: elevated atmospheric carbon dioxide concentration, or e[CO2], and reduced water availability, as caused by drought. Both variables have been shown to have effects on crop physiology, although there is considerable evidence of interactions and moderation by species-specific differences. Measuring traits helps scale environmental effects up to functional responses, and we focused on traits connected to photosynthesis, which has a close association with crop yield. We measured the response of four physiological traits—quantum photosynthetic yield, chlorophyll content, root:shoot ratio and leaf area—across a diverse set of seven annual crop species grown under three levels of e[CO2] (450, 575 and 700 ppm) and two levels of water availability (minimum ~45 and ~15% VWC) in a growth chamber. Species included barley, durum wheat, maize, oats, sorghum, pinto bean and sunflower. Our regression analysis focused on testing for interactions between e[CO2] and water limitation and determining relative effect sizes of climate change impacts across species, data that can be used for species-specific modeling or determining appropriate levels of environmental variables in free-air CO2enrichment studies designed to extend small-scale experimental results to the field. Across all species and all traits, the strongest effect of e[CO2] occurred from 450 to 575 ppm, with only marginal differences from 575 to 700 ppm. We found substantial declines in leaf area across all species as a result of e[CO2] and wide variability in leaf area responses to water limitation. Other traits showed weak and variable responses to both e[CO2] and water limitation. While our data confirm that elements of global change, especially increased atmospheric CO2concentration, do affect traits related to photosynthesis, we found no discernible pattern to suggest which crops might be more resistant to e[CO2].

A parametric study of thermal and residual stress fields in lined pipe welding

Welded lined cylindrical structures such as boilers, pressure vessels and transportation pipes are widely used in the oil and gas industries because an inexpensive outer layer is protected from corrosion by a thinner expensive layer, which is made of a corrosion resistant alloy (CRA). Welding in the lined pipe is of two different types, where the first one, so called weld overlay (lap-weld), is deployed to seal the liner with the outer pipe whilst the other one, known as girth welding (butt-weld), is deposited to join two specimens of lined pipe together. Therefore, the precise prediction of the thermal and residual stress fields due to the combination of two different types of circumferential welding is a major concern regarding welded lined pipes to avoid sudden failure during service. Six parametric studies have been conducted primarily to examine the influence of welding properties (weld overlay and girth welding materials), geometric parameters (weld overlay and liner) and welding process parameters (heat input) on the thermal and residual stress fields. All predicted results obtained from a 3-D FE model based on the ABAQUS code are validated against small-scale experimental results. Furthermore, in this study, the effect of mesh size has been investigated.

Wireless structural control using stochastic bandwidth allocation and dynamic state estimation with measurement fusion

Wireless sensor networks are becoming more popular for structural monitoring because of their low installation costs; in addition, coupling structural control with wireless data acquisition can also yield advantages. However, these systems have limited communication bandwidth, limiting their effectiveness as the number of devices in control networks grows large if centralized control approaches are used. Traditional methods for collocating data in wireless structural control network rely on time-budgeted bandwidth or spatial decentralization, where the network is divided into smaller subnetworks. These methods are largely static and typically do not take into account any measure of data quality to prioritize transmissions. This study presents a dynamic approach for bandwidth allocation in wireless structural control networks that relies on an application-specific, autonomous, and controller-aware, carrier sense multiple access with collision detection protocol. Stochastic parameters are derived to strategically alter back-off times in the carrier sense multiple access with collision detection algorithm based on nodal observability and output estimation error. Inspired by data fusion approaches, this paper presents 2 different methods for neighborhood state estimation using a dynamic form of measurement-only fusion. Upon receiving data from the contended wireless medium, each wireless unit fuses incoming data using a precalculated static Kalman gain matrix for the corresponding dynamic neighborhood. Onboard, each wireless unit contains a library of Kalman gain matrices, to accommodate any possible set of communicated data. Both numerical simulations and small-scale laboratory experimental results are presented.

Hydraulic experiments of urban river meandering method and fish habitat revitalization

Recently, the number of urban river restoration projects that use artificial spurs to create ecologically sound rivers has steadily increased. In this study, the effect of spur placement on improving the ecological environment of rivers is investigated for an optimal riverbank spur design based on small-scale experimental results. The experiments were conducted by varying the placement of the spur formations, the spur types, and the dimensionless Froude Numbers. Stone mattress, wickerwork, and combinations of these materials were used as spurs. The experimental results show that the spur placement helped create a gentle meandering river and secured the fish habitat. A combination of stone mattress and wickerwork (wickerwork beneath a stone mattress) resulted in the most effective type of spur for achieving a gentle meandering and sound fish habitat. The average water flow velocities in front of the spurs decreased by roughly 30%, while the average water flow velocities behind the stone mattress decreased by approximately 70%. Consequently, it is concluded that the well-implementation of spurs could induce an ecologically favorable habitat for fish and fish spawning.

Invariant representation for rectilinear rulings

Ruling gap ratios are an affine-invariant characterization of parallel ruling configurations in scanned documents. This report quantifies the advantage of simultaneous extraction of horizontal and vertical rulings. It demonstrates that every ruling gap ratio can be derived from a minimal set of basis ratios. The effect on the basis ratios of noise on the radial coordinates of individual rulings is analyzed and the dependence of basis-ratio variability on random-phase sampling noise is determined as a function of the spatial sampling rate. The analysis provides insight into already-presented small-scale experimental results on form classification and guidance for future work that requires the extraction of parallel lines from scanned or photographed images.

Passive Force–Deflection Behavior for 0° and 30° Skewed Abutments

Accounting for seismic forces and thermal expansion in bridge design requires an accurate passive force–deflection relationship for the abutment wall. Current design codes make no allowance for skew effects on passive force; however, small-scale experimental results indicate a significant reduction in peak passive force as skew angle increases for plane-strain cases. To explore this issue further, large-scale field tests were conducted at skew angles of 0° and 30° with unconfined backfill geometry. The abutment back wall was 11 ft (3.35 m) wide by 5.5 ft (1.68 m) high, and backfill material consisted of dense, compacted sand. The peak passive force for the 30° skew was found to be 58% of the peak passive force for the 0° skew case, which was in good agreement with the available laboratory and numerical results; however, the small difference between field and available laboratory results suggests that backfill geometry may have some effect on the reduction in peak passive force with respect to skew angle. Longitudinal displacement of the back wall at the peak passive force was found to be between 3% and 5% of the back wall height for field tests of both the 0° and 30° skew, which was consistent with previously reported values for large-scale passive force–deflection tests. For both tests, the failure geometry extended approximately 4 to 5 ft (1.22 to 1.52 m) beyond the edge of the pile cap and 16 to 18 ft (4.88 to 5.49 m) from the face of the cap when measured perpendicular to the back wall.

厚みの薄い煙層内を流動する天井流温度に関する実験的研究

In the case of fires occurred in a huge shop and a factory, which have a large floor area, a smoke layer with relatively thin thickness is formed by hanging smoke barriers which are installed in each constant area to prevent the spread of smoke layer. Some studies on ceiling jet temperature property which flows through the smoke layer with thick thickness accumulated in a compartment were presented. However few study on ceiling jet temperature which flows through the smoke layer with thin thickness formed by hanging smoke barriers. Using both the small-scale fire experimental results, which were conducted with varying heat release rate, depth of hanging smoke barrier and ceiling height with a horizontal ceiling, and the idea of Yamauchi's correlation, which can estimate temperature of ceiling jet in arbitrary radial position in the space where smoke layer with thick thickness is formed, a new correlation which can estimate the ceiling jet temperature which flows through the smoke layer with thin thickness is presented.

Numerical study on the initial expansion of two-phase cloud from an instantaneous release

In industries some dangerous liquefied gases may accidentally release and it may form a flammable or toxic mixture after mixing with air. One tool that is being developed in industry for two-phase cloud dispersion modeling is computational fluid dynamics (CFD). In this paper, the dispersion processes of different dangerous materials including liquefied chlorine, liquefied ammonia and liquefied petroleum gas were simulated in the same condition to analyze the characteristics of the initial expansion processes by CFD tool. The heat and mass transfer between droplets and the vapor after an instantaneous release event was calculated by using the Eulerian–Lagrangian method. The results from a number of 3-D CFD based studies were compared with the available small-scale experimental results. The results show that the present model and numerical simulation are reliable.

Kinetic metabolic modelling for the control of plant cells cytoplasmic phosphate

A previously developed kinetic metabolic model for plant metabolism was used in a context of identification and control of intracellular phosphate (Pi) dynamics. Experimental data from batch flask cultures of Eschscholtiza californica cells was used to calibrate the model parameters for the slow dynamics (growth, nutrition, anabolic pathways, etc.). Perturbation experiments were performed using a perfusion small-scale bioreactor monitored by in vivo 31P NMR. Parameter identification for Pi metabolism was done by measuring the cells dynamic response to different inputs for extracellular Pi (two pulse-response experiments and a step-response experiment). The calibrated model can describe Pi translocation between the cellular pools (vacuole and cytoplasm). The effect of intracellular Pi management on ATP/ADP and phosphomonoesters concentrations is also described by the model. The calibrated model is then used to develop a control strategy on the cytoplasmic Pi pool. From the identification of the systems dynamics, a proportional-integral controller was designed and tuned. The closed-loop control was implemented in the small-scale NMR bioreactor and experimental results were in accordance with model predictions. Thus, the calibrated model is able to predict cellular behaviour for phosphate metabolism and it was demonstrated that it is possible to control the intracellular level of cytoplasmic Pi in plant cells.

Thermal Conductivity of Gypsum at High Temperatures – A Combined Experimental and Numerical Approach

Performance of gypsum board based systems in fire is highly influenced by the temperature-dependant thermal conductivity of gypsum boards, yet there is a wide difference in the thermal conductivity values used in literature. Presented here is a hybrid method to determine the effective thermal conductivity of gypsum boards at high temperatures, based on using small-scale experimental results and a thermal conductivity model which includes the effects of radiation in voids.

掘削体積比エネルギーを用いた岩石強度の寸法効果の推定

It is well known that rock strength decreases with increasing of specimen size. Accurate knowledge for the size or scale effects in rock strength is very important to apply the small-scale experimental results to the large-scale underground space design. However, the investigation of the size effects requires tremendous efforts and expenses in most cases. In this study, a new method to estimate the size effects of rock based on the specific energy in excavation was proposed. The method needs minimum efforts without extra equipments. Through the careful examination of eleven excavation methods, it was found that the specific energy decreases with the excavation scale following the equation:(Specific energy) ∝ (Excavation scale)-2α with α=0.2.Cutting spacing, penetration or geometrical mean of the two was found to be appropriate as excavation scale. Specific energy is roughly proportional to square of strength. Then, the following equation stands:(Rock strength) ∝ (Excavation scale)-α.This result is very conformable to the size effects deduced by the results of the compression tests. The size of cuttings in excavation was examined and the close relation was found between the excavation scale and the size of cuttings. Relation between the specific energy and the work index in comminution was also discussed.

Attrition of porous glass particles in a fluidised bed

Fluidisation is frequently accompanied by unwanted attrition of the bed material. This paper focuses on the mechanical aspects of fines creation by attrition in fluidised beds supported by multi-orifice distributor plates. The attrition rates of low-density porous glass particles were measured; these particles show abrasive wear behaviour rather than breakage. Positron emission particle tracking (PEPT) was used to follow particle motion in three dimensions within the fluidised bed. For a single orifice distributor with background fluidisation, the attrition rate increased exponentially with increasing orifice gas velocity. For a multi-orifice distributor, however, attrition rates were roughly proportional to excess gas velocity, except near to a critical ratio of particle to orifice diameter; as this ratio approached 2, attrition was observed to increase by an order of magnitude. A method is proposed for estimating attrition rates from a combination of small-scale experimental results and theoretical calculations of distributor jet entrainment rates.