Experimental Model Tests Research Articles

Experimental test of the geometric model of image formation in bright-field microscopy.

In the geometric optics approximation, an image formed by an objective lens replicates the distribution of intensity at the front focal plane of the objective. Although this fact represents a fundamental optical principle, its application to analysis of bright-field microscopic images was developed only recently and has not been tested experimentally. In this paper, we applied simple ray tracing to compute an image of a glass cylinder at various positions of the objective and to compare it to the experiment. We obtained a close match between theory and observation, except for a slight underestimation of the intensity in the middle part of the cylinder. The likely reason for this minor difference was constructive interference due to lens-like properties of a cylinder, which could not be accounted for by geometric approximation. We expect that such artefacts would be negligible in imaging of live cells, and the geometric approach would successfully complement the existing quantitative phase methods.

Analytical and Experimental Study of Pile Capacity in Unsaturated Sandy Clay

The design of pile foundation in technical practice is based on saturated soil mechanic or empirical procedure that ignores the influence of matric suction. Understanding the pile behavior and predicting the capacity of pile in unsaturated soil are important topics in foundation design. An experimental model test has been conducted on a single concrete pile model with a diameter of 16 mm and L/d ratios of 6, 10, 15 and 20. Model pile has been driven into sandy clay in the test box and is subjected to compression and uplift loading. The tensiometer instrument has been used to measure matric suction and the SoilVision has been used to get an estimate of the entire Soil Water Characteristic Curve (SWCC). The shear strength of sandy clay has been examined using a series of unconsolidated undrained triaxial tests to identify the relationship between cohesion, internal friction angle, and matric suction. The result has shown that end bearing pile capacity, skin friction capacity and total capacity of single piles are significantly influenced by the contribution of matric suction. Based on the experimental result, end bearing capacity and skin friction capacity of pile in saturated soil equation have been modified to calculate total capacity of pile in unsaturated soils by considering the influence of matric suction.

Experimental and numerical study on hydraulic characteristics of multi-level intake for diversion project

Multi-level intake as an inlet of diversions has the advantage of selective withdrawal. To further understand the hydraulic characteristics of this inlet hydraulic structure, experimental model test and numerical simulation were carried out. The results of this study show that the water flow in the diversion channel is stable, and the flow pattern in the lock chamber section is disordered. In addition, the pressure near the entrance of the tunnel is linear, and the water head loss of the upper layer is the largest. Further, the formation of potential vortex flow can be prevented by controlling and scheduling. The results presented in the current work provide new insights into the hydraulics of flow in stratified intake structure and can be used in the design and operation of similar hydraulic projects.

Like Me, You Say? a Model and Experiment on Supporting In-Group Bias through Cheaptalk

This paper presents a simple application and experimental test of a theoretical model of discriminatory social preferences. First, it establishes conditions under which a specification of “defection aversion” can support an equilibrium in which costless messages engender cooperative strategies in a one-shot Prisoners’ Dilemma (PD) game. The main result is a signaling equilibrium with full separation of signals, and cooperation whenever the social distance is less than a certain threshold level. The second part of the paper is an experimental application and test of a discrete version of the theory. Using the minimal group paradigm, subjects are put into a set of interlocking groups. 116 subjects played 4 games each (within-subjects) under different informational (treatment) contexts. Results are broadly consistent with the theory: people cooperate more when faced with group members. They are also less “honest” with their messages when messages are sequential than when they are simultaneous, which suggests a strategic motivation to the messages. A somewhat unexpected empirical result shows that the threshold social distance supporting cooperation is lower when the group information is based on simultaneous cheap talk than when it is exogenously revealed. Noting that the empirical rates of honest messaging are also rather far from the 100% predicted by the model, a theoretical extension shows that smaller social neighborhoods are in fact a straightforward prediction when the truth of messages is uncertain.

Experimental and Numerical Investigation of Green Water Occurrence for KRISO Container Ship

The occurrence of green water on the deck of Korea Research Institute of Ships & Ocean Engineering (KRISO) container ship is investigated using model test experiments and a fully coupled impulse response function (IRF)–computational fluid dynamics (CFD)–based numerical approach. In the experimental study, green water pressure over the deck and superstructure is investigated for different regular head wave conditions (wavelength/ship length ratio: .8–1.5) and vessel speeds (Froude number: .055–.166). The impact pressure on the deck is found to be highest at a wavelength/ ship length ratio of 1.2 and increases drastically with the increase in Froude number. The variation of green water pressure with wave steepness is linear for points on the forward deck and quadratic for the superstructure. In the second part, a coupled IRF-CFD–based numerical method is developed in which the global hydrodynamic forces such as radiation–diffraction and Froude–Krylov force are computed using a potential flow solver, whereas the local pressure due to the shipping water impact is computed using CFD and added as an external force. Comparisons of vessel motions and green water pressures with experiments indicate that the coupled IRF-CFD method can be a robust and efficient tool to predict shipping water loads on ships. Introduction The prediction of green water shipped on the deck and the resulting impact on ships and offshore structures have been an important research topic in the last couple of decades because it is directly related to the safety of the structure at sea. Historically, shipping of water on the deck had caused many serious damages to the bow and superstructure, and some of them have even capsized; e.g., the Schiehallion Floating Production Storage and Offloading (FPSO) was damaged severely in November 1998 because of steep waves. These incidents resulted in considerable research on this topic in the past two decades. The primary focus has been on the understanding of critical aspects and the accurate prediction of green water loading which requires proper modeling of green water occurrence. Also, accurate calculation of the green water loads on the deck and superstructure is very important for structural design load calculation. However, this is a nontrivial task because it depends on many physical and geometrical factors such as wave steepness, the wavelength- to-ship length ratio, hull shape around the bow region, and vessel speed. Hence, efforts have been made to develop suitable numerical models that may consider most of these aspects under necessary underlying assumptions.

Performance of timber girders with end-notch: Experimental and numerical investigation

Many bridges built during the colonial times in Australia have timber girders as load transferring elements and they are still in service with increased traffic loads and consistent deterioration. Most of the timber girders in those bridges are notched at the ends for better seating arrangement. Therefore, it is necessary to quantify the strength characteristics of notched girders in order to ensure structural safety and make necessary intervention to extend their service lives. Hence experimental tests were conducted on the notched rectangular timber girder samples with three different notch depths (i.e.10%, 15% and 30% of the depth of beam) having the notched angle of 1:4. Consequently, detailed finite element models were developed for notched timber girders, and the models were validated with experimental results. The validated model was used to predict the shear and flexural strengths and stiffnesses of typical circular and rectangular timber girders with two different spans (i.e. 6 m and 9 m), three different notch angles (i.e. 1: 0, 1:2 and 1:4) and three depths (i.e.15%, 30% and 45% o of the depth of beam). Strength data developed for notched timber were used to compare the applicability of the design provisions in various timber design standards. Experimental and finite element model test results show that when the notch depth increased from 15% to 45%, the load carrying capacity of rectangular timber girder was reduced by 50%. Whilst, the reduction of the load carrying capacity of the corresponding circular timber girder was slightly low (i.e. 37%). Further, when the notched angle changes from 1:0 to 1:4, the load carrying capacity of circular and rectangular girders increased about 50%, 69% and 110% for the notch depths 15%, 30% and 45%, respectively.

Uncertainty analysis of a WEC model test experiment

Ocean wave energy has significant technical potential but limited full-scale deployments and technology convergence. Consequently, guidelines for developing wave energy converters (WECs) are still developing themselves, especially around experimental uncertainty analysis (UA). To develop a comprehensive WEC-specific UA methodology, we conducted a 1:30 scale experiment of a case study oscillating water column (OWC) WEC. This paper presents the methodology, which describes UA principles and means to identify parameters causing uncertainty, and demonstrates new WEC-specific UA methods: general uncertainty analysis (GUA), the Monte Carlo method (MCM) for uncertainty propagation, and Type A and Type B uncertainty evaluation. Results show the expanded uncertainty averaged ± 16% for capture width ratio and ± 6% for wave loads; Type B uncertainty tended to be slightly larger than Type A uncertainty; and uncertainty in regular waves slightly larger than irregular waves. The MCM was found to be effective and efficient in uncertainty propagation. In general, given WECs tend to maximise motions, use a power take-off system, and must survive storms, WEC model tests may be especially susceptible to uncertainty due to nonlinearities and modelling complexities. In conclusion, UA should be carried out in WEC model test experiments. We close with recommendations for refining relevant international guidelines.

Subsea manifold installation: Operational windows estimation based on hydrodynamic model testing

In this paper, added mass and drag coefficients for typical subsea manifolds installation conditions are determined through experimental model tests. The forced oscillation test results show that the equipment has large drag coefficients in the low Keulegan-Carpenter (KC) region, which leads to higher damping. The results also show that the added mass increases with higher KC number values and is appreciably larger than those found in the literature for flat plates, even when extrapolated to a prism. With the experimentally obtained hydrodynamic coefficients, a series of analytical and numerical simulations are conducted for a typical installation operation for various sea states. The results show that the operational windows for subsea equipment installation are expanded when compared to the current conventional approach.

Formation of Readiness for Command Activity of Courses of Military Institutions

Problem and Aim. The author of the article investigated the study of the problem of formation of readiness for command activity of cadets of military institutes. This article examines the phenomenon of formation of readiness for command activity of cadets of military institutes as a pedagogical problem. The article describes the approbation of the pedagogical program and pedagogical technology of formation of readiness for command activity of cadets of military universities. The model of formation of readiness for command activity of cadets of military institutions presented in the article is a toolkit in which the optimal range of the value of active readiness of cadets is operationally presented, within which their training is seen as the most effective. The purpose of the article is consideration of the problem of preparedness for command activities of graduates of military institutes of the troops of the National Guard of the Russian Federation and the prospects for the implementation of a pedagogical program in the learning process at a military institute as a special branch of pedagogical knowledge on the problem of improving the sphere of scientific substantiation of innovations and experimental testing of models for improving pedagogical activity. Methodology. Methods of organizing and implementing educational and cognitive activities, stimulating and motivating to master educational and cognitive activities, teaching methods, teaching methods in the course of the practical application of knowledge by developing skills and abilities, methods of testing and evaluating learning outcomes.. The article considers the problem of the implementation of such a pedagogical phenomenon as the formation of readiness for command activity of cadets of military institutes, which is based on a pedagogical program based on the content-technological component of the structural-functional model of the formation of readiness for command activity of cadets of military institutes and the pedagogical technology of formation of readiness for command activities

Theoretical and experimental study of the free hydroforming of egg-shaped shell

ABSTRACT This study investigated the free hydroforming of a stainless-steel egg-shaped shell. An egg-shaped shell is a promising geometry for deep pressure hulls. The length and width of the egg-shaped shell were 512.40 and 356.25 mm, respectively. The wall thickness of the egg-shaped shell were 0.844 mm. The equivalent stress, yielding load, internal capacity, and surface area of the egg-shaped shell and its inscribed segmented preform were investigated analytically and experimentally. The hydroforming performance of the egg-shaped shell was analysed using the nonlinear finite element method, and the results were validated by experimental model tests. The results indicated that free hydroforming can be an effective technique for fabricating egg-shaped pressure hulls and can yield highly symmetric shells of revolution regardless of the large geometric deviation of the segmented preform.

Numerical and Experimental Investigation on the Free-surface Flow and Total Resistance of the DTMB Surface Combatant

Starting with the initial design stage, the ship resistance constitutes one of the most important hydrodynamic aspects. In order to generate and optimize the body lines plan, the ship resistance performance must be considered. In this case, both numerical and experimental methods must be applied to obtain the minimum ship resistance controlled by the speed domain. In the last years, numerical studies based on the Computational Fluid Dynamic (CFD) were implemented in the initial ship design stage in order to analyse the free-surface flow and to predict the ship resistance. The numerical optimization process of the hull forms must be validated by means of the experimental model tests in the specific towing tanks. The constant evolution of the numerical and experimental methodologies can be noted. As a consequence, the accuracy level of the ship resistance prediction is increased; though, difficult numerical problems can occur in case of the unconventional hull forms. Taking into account this aspect, a complex numerical and experimental investigation of the ship resistance problem and free-surface topology was performed in the case of the DTMB surface combatant. A parallel numerical simulation was carried out by using the viscous flow solver ISIS–CFD of the software FINETM/Marine provided by NUMECA. The solver is based on the finite volume method to build the spatial discretization of the transport equation to resolve the Reynolds-Averaged Navier Stokes (RANS) equation. Closure to turbulence is achieved by making use of the k-ω SST model, while the free-surface is captured through an air-water interface based on the Volume of Fluid (VOF) method. For the validation purpose, the tank conditions are reintroduced in the numerical model to account for any banking effect, especially for the high speed cases. Experimental model tests were performed in accordance with the ITTC standard procedures, while the extrapolation process to the full-scale was obtained by using an in-house code, based on the ITTC 57 method. The experimental results are compared through with some internationally recognized towing tank experiments that have been performed for a similar ship model, showing a good agreement. Also, the numerical results are validated against the experimental data and showed to be within a satisfactory congruence.

The Effect of Crib Installation with Placement Variations in River Bends Using Laboratory Model Tests

Scour or landslide is a problem that occurs at river bends. Many methods are used for scouring or landslide protection. One of the protections for scouring construction is crib model by using gabions and current-aligning bamboo. The purpose of this study is to determine of the effect of variations in the placement of the crib by using of gabions model and the current-aligning bamboo on the river bends. This research is an experimental test of the hydraulic model using river flume model with 5m on bend length, 0.8m width, 0.5m height and a constant discharge of 7.07lt/sec. The test consists of testing control, that is a bend without reinforcement and testing with reinforcement at the bends. The reinforcement at the bends using placement variation was twice carried out with the variation 1 consisted of 3 current-aligning bamboo, 4 gabions, 3 current-aligning bamboo and the variation 2 contains the opposite. The test results showed that the maximum scouring occurs in variation 1 with -5.4cm, -5.2cm on landslides and 0.61cm on scour. The results of the Surfer App and cross sections of stations P00 until P07 are more effective using gabions, while P08 through P24 are more effective using current-aligning bamboo.

New Method for Estimating Roughness Coefficient for Debris Flows

Flow resistance is a fundamental control of flow hydraulics in streams and rivers. In this paper, five dimensionless factors affecting the Manning roughness coefficient n and attributed to the external roughness coefficient n1 and the internal roughness coefficient n2 were analyzed comprehensively. And then, dimensionless factors affecting n1 and n2 with precise physical meanings were proposed. With a calculation method for roughness coefficient fitted and analyzed based on observation data from published research papers, the analysis results showed that the external resistance coefficient is closely related to the dimensionless factor D84/R. The correlation between the dimensionless factor (D16/D50) and the internal roughness coefficient n2 was not significant. While the factors H/D50, J, and Sv showed significant correlation. In addition, the expression of external roughness n1 is calibrated based on the observation data of 102 cross-sections listed in previous works, while the internal roughness n2 is calibrated by 20 experimental model tests. Finally, an equation describing the Manning’s roughness coefficient is presented and verified based on 24 groups of observation data from Dongchuan Debris Flow Observation Station (DDFORS) in China. This study is contributing toward a comprehensive model for the Manning coefficient, which provide a scientific reference for the research on disaster prevention and mitigation of debris flow.

Daylight autonomy improvement in buildings at high latitudes using horizontal light pipes and light-deflecting panels

Horizontal light pipes (HLP) have shown the potential to convey daylight deeper into buildings. The wide variation in incident angles of sunlight rays and the resulting numerous interreflections of light rays within the pipe are the main reasons for the limited light transmittance of such light pipes during certain daylight periods. This paper presents a research study on different configurations of acrylic laser-cut panels (LCP) applied at the entrance of horizontal pipes as light collectors to increase the transmittance of HLPs and improve daylight autonomy in spaces equipped with HLPs. This study required the development of a suitable methodology. The study begins with an experimental laboratory test of a HLP scale model to determine the light transmittance efficiency (standard daylight guide characteristic) of HLPs with several LCP configurations. The results from the laboratory test are combined with the statistical data for both the direct and diffuse illuminance on the vertical south-oriented surface (Satel-Light database) for the location selected for the analyses (Oslo, Norway). The analyses are discussed via the application of a theoretical model of an office space equipped with a HPL as well as through the concept of daylight autonomy (DA) in an indoor space. The paper shows that a certain static LCP configuration has the potential to increase DA100 and DA300 to 10% and 19%, respectively, at a 2.1 m distance from the façade, and 8.75% and 16%, respectively, at a 4.5 m distance. This paper also contributes to lighting science with its data on the light transmittance efficiency of each LCP configuration, which can be applicable in further research.

Stabilizer Cell Gene Therapy: A Less-Is-More Strategy to Prevent Cardiac Arrhythmias.

In cardiac gene therapy to improve contractile function, achieving gene expression in the majority of cardiac myocytes is essential. In preventing cardiac arrhythmias, however, this goal may not be as important since transduction efficiencies as low as 40% suppressed ventricular arrhythmias in genetically modified mice with catecholaminergic polymorphic ventricular tachycardia. Using computational modeling, we simulated 1-, 2-, and 3-dimensional tissue under a variety of conditions to test the ability of genetically engineered nonarrhythmogenic stabilizer cells to suppress triggered activity due to delayed or early afterdepolarizations. Due to source-sink relationships in cardiac tissue, a minority (20%-50%) of randomly distributed stabilizer cells engineered to be nonarrhythmogenic can suppress the ability of arrhythmogenic cells to generate delayed and early afterdepolarizations-related arrhythmias. Stabilizer cell gene therapy strategy can be designed to correct a specific arrhythmogenic mutation, as in the catecholaminergic polymorphic ventricular tachycardia mice studies, or more generally to suppress delayed or early afterdepolarizations from any cause by overexpressing the inward rectifier K channel Kir2.1 in stabilizer cells. This promising antiarrhythmic strategy warrants further testing in experimental models to evaluate its clinical potential.

Experimental test of Leggett's inequalities with solid-state spins

Bell's theorem states that no local hidden variable model is compatible with quantum mechanics. Surprisingly, even if we release the locality constraint, certain nonlocal hidden variable models, such as the one proposed by Leggett, may still be at variance with the predictions of quantum physics. Here, we report an experimental test of Leggett's nonlocal model with solid-state spins in a diamond nitrogen-vacancy center. We entangle an electron spin with a surrounding weakly coupled $^{13}C$ nuclear spin and observe that the entangled states violate Leggett-type inequalities by more than four and seven standard deviations for six and eight measurement settings, respectively. Our experimental results are in full agreement with quantum predictions and violate Leggett's nonlocal hidden variable inequality with a high level of confidence.

A Qualitative Study of the Critical Conditions for the Initiation of Mine Waste Debris Flows

Mine waste debris flows are a type of man-made debris flow that commonly lead to major disasters. In this study, the Xiaotong Gully, which is located in the Xiaoqinling gold mining area in China and contains a typical mine waste debris flow gully, was selected as the study area. Since a debris flow can be classified as either a geotechnical debris flow or hydraulic debris flow based on its initiation mode, we conducted 46 experimental model tests to explore the initiation conditions of these two different types of debris flows. According to our tests, the initiation conditions of hydraulic debris flows were mainly affected by the flume gradient, the water content of the mine waste, the inflow discharge, the water supply modes, and the clay particle content. A larger flume gradient and higher mine waste water content were more conducive to initiating a hydraulic debris flow. However, the influence of the water supply mode on the initiation of a hydraulic debris flow was complex (influenced by factors such as water content of mine waste, runoff discharge rate and rainfall intensity). The critical runoff of a hydraulic debris flow, which starts with a parabolic relationship to the clay particle content of the mine waste, decreased with increasing clay particle content and then increased. There was a minimum critical runoff when the clay content of the mine waste was 30%. The initiation conditions of a geotechnical debris flow were mainly affected by the flume gradient, the water content, and the clay particle content. The critical gradient of a geotechnical debris flow decreased with increasing water content and had a parabolic relationship to the clay particle content. In tests 31–46 of this study, the second and third critical slopes both decreased and then increased with increasing clay particle content. These preliminary research results provide a scientific reference for subsequent research on the prevention and mitigation of mine waste debris flows.

Quantum Phases of SrCu_{2}(BO_{3})_{2} from High-Pressure Thermodynamics.

We report heat capacity measurements of SrCu_{2}(BO_{3})_{2} under high pressure along with simulations of relevant quantum spin models and map out the (P,T) phase diagram of the material. We find a first-order quantum phase transition between the low-pressure quantum dimer paramagnet and a phase with signatures of a plaquette-singlet state below T=2 K. At higher pressures, we observe a transition into a previously unknown antiferromagnetic state below 4K. Our findings can be explained within the two-dimensional Shastry-Sutherland quantum spin model supplemented by weak interlayer couplings. The possibility to tune SrCu_{2}(BO_{3})_{2} between the plaquette-singlet and antiferromagnetic states opens opportunities for experimental tests of quantum field theories and lattice models involving fractionalized excitations, emergent symmetries, and gauge fluctuations.

Battling Neurodegenerative Diseases with Adeno-Associated Virus-Based Approaches.

Neurodegenerative diseases (NDDs) are most commonly found in adults and remain essentially incurable. Gene therapy using AAV vectors is a rapidly-growing field of experimental medicine that holds promise for the treatment of NDDs. To date, effective delivery of a therapeutic gene into target cells via AAV has been a major obstacle in the field. Ideally, transgenes should be delivered into the target cells specifically and efficiently, while promiscuous or off-target gene delivery should be minimized to avoid toxicity. In the pursuit of an ideal vehicle for NDD gene therapy, a broad variety of vector systems have been explored. Here we specifically outline the advantages of adeno-associated virus (AAV)-based vector systems for NDD therapy application. In contrast to many reviews on NDDs that can be found in the literature, this review is rather focused on AAV vector selection and their testing in experimental and preclinical NDD models. Preclinical and in vitro data reveal the strong potential of AAV for NDD-related diagnostics and therapeutic strategies.

Novel numerical method to simulate hydrodynamic characteristic of moving body through free surface and stratified-fluid interface

In order to solve the difficult physical problem of moving structures through free surface and stratified fluid interface, the paper presents and develops a new method based on surface capturing method and Cartesian cut cell mesh to handle transient density interface and moving boundary. Therein, quad-tree data storage structure, adaptive grid techniques, and high-resolution reconstruction limiter are introduced to improve computational efficiency and precision. Hybrid mesh systems of structural and Cartesian cut cell mesh are extended to be applied in the laminar flow problem at low Reynolds number. On this basis, a series of experimental tests of cylindrical models falling through air-water, air-oil and oil-water interfaces are carried out respectively, then several cases are taken to validate the numerical method. Sequentially, the characteristics of interface variation and closure shape versus different density ratios are compared, and the effect of stratified fluid interface on the hydrodynamic force of moving body is mainly discussed. In summary, this paper unifies free surface and stratified fluid interface together as density interface, which can be handled and studied by the same numerical method. Thus, by combining water entry with stratified fluid problem, the influence of various density interfaces on moving body can be better analyzed.