Hydraulic Characteristics of the New Type Bulb Turbine With Micro-Head

The head of low-head hydropower stations is generally higher than 2.5m in the world, while micro-head hydropower resources which head is less than 2.5m are also very rich. In the paper, three-dimensional CFD method has been used to simulate flow passage of the micro-head bulb turbine. The design head and unit flow of the turbine was 1m and 3m3/s respectively. With the numerical simulation, the bulb turbine is researched by analyzing external characteristics of the bulb turbine, flow distribution before the runner, pressure distribution of the runner blade surface, and flow distribution of the outlet conduit under three different schemes. The turbine in second scheme was test by manufactured into a physical model. According to the results of numerical simulation and model test, bulb turbine with no guide vane in second scheme has simpler structure, lower cost, and better flow capacity than first scheme, which has traditional multi-guide vanes. Meanwhile, efficiency of second scheme has just little decrease. The results of three dimensions CFD simulation and test results agree well in second scheme, and higher efficiency is up to 77% which has a wider area with the head of 1m. The curved supports in third scheme are combined guide vanes to the fixed supports based on 2nd scheme. By the water circulations flowing along the curved supports which improve energy transformation ability of the runner, the efficiency of the turbine in third scheme is up to 82.6%. Third scheme, which has simpler structure and best performance, is appropriate for the development and utilization of micro-head hydropower resources in plains and oceans.

Development of an Adaptive Human-Machine-Interface to Minimize Driver Distraction and Workload

The original use of the vehicle dashboard was to provide enough sensory information to inform the driver of the current engine and vehicle status and performance. Over time, it has evolved into an entertainment system that includes person-to-person communication, global positioning information, and the Internet, just to name a few. Each of these new features adds to the amount of information that drivers must absorb, leading to potential distraction and possible increases in the number and types of accidents. In order to provide an overview of these issues, this paper summarizes previous work on driver distraction and workload, demonstrating the importance of addressing those issues that compete for driver attention and action. In addition, a test platform vehicle is introduced which has the capability of assessing modified dashboards and consoles, as well as the ability to acquire relevant driving performance data. Future efforts with this test platform will be directed toward helping to resolve the critical tug-of-war between providing more information and entertainment while keeping drivers and their passengers safe. The long-term goal of this research is to evaluate the various technological innovations available for inclusion in the driving environment and determining how to optimize driver information delivery without excessive distraction and workload. The information presented herein is the first step in that effort of developing an adaptive distraction/workload management system that monitors performance metrics and provides selected feedback to drivers. The test platform (1973 VW Beetle converted to a plug-in series hybrid) can provide speed, location (GPS), 3-D acceleration, and rear proximity detection. The test drive route was a 2 km × 3 km city street circuit which took approximately 25 minutes to complete. Data is provided herein to demonstrate these capabilities. In addition, the platform has driver selectable layouts for the instrument cluster and console (LCD screens). The test platform is planned for use to determine driver preferences (e.g., dashboard/console configurations) and attention performance in addition to identifying optimal real-time feedback for drivers with different demographics.

Size-Dependent Antibacterial Behavior of Graphene Quantum Dots

In this study, the antibacterial behavior of differing sized graphene quantum dots (GQDs) was studied. The gram negative bacteria, Escherichia coli (E. coli), were used as the bacteria mode. Different sized GQDs with tunable fluorescent colors were acquired by a gel-filtration method. The size, surface chemistry, and photoluminescence properties of GQDs were characterized, respectively. The viability of GQDs treated bacteria was determined by the standard plate counting method. Moreover, the reactive oxidative species (ROS) level was detected by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) method. The integrality of the bacteria membrane was observed under the scanning electron microscopy (SEM). The experimental results indicated that GQDs demonstrated size-dependent and surface chemistry-dependent antibacterial behaviors. This research provided insightful guidelines in the selection of suitable GQDs for their potential bioapplications.

Understanding Temperature Profiles Experienced by Biological Samples During a Hybrid Vitrification Technique

From thermodynamic point of view, vitrification is considered as a superior preservation technique in comparison with the traditional slow-cooling cryopreservation techniques, due to formation of the glassy state in both intra and extracellular environment. While vitrification of biological samples are difficult to achieve, recently a hybrid technique involving partial desiccation of the cell samples prior to cryogenic exposure has been successfully employed to achieve vitrification. In this technique cells in monolayer attached to a substrate was suspended in a trehalose solution and then rapidly and uniformly desiccated to a low moisture content (<0.12 g of water per g of dry weight) using a spin-drying technique. The spin-dried samples were stored in liquid nitrogen (LN2) at a vitrified state (Fig. 1). It was shown that following re-warming to room temperature and re-hydration with a fully complemented cell culture medium, 51% of the spin-dried and vitrified cells survived and demonstrated normal growth characteristics. The current study further investigates the temperature profiles experienced by the cell samples during partial desiccation and cryogenic exposure to identify possible ways to improve this novel vitrification strategy. Physical Vapor Deposition technique was employed to develop glass substrate having thermocouples (2×2×2 μm) at four radial positions across the substrate to record the thermal history of the cell samples during the entire process. Efforts are undertaken to understand the uncertainties related temperature measurement spatially and with respect to time. These temperature characterization studies are important to optimize the newly developed hybrid vitrification technique for vitrification of cellular samples.

Implications of Increased Lower Extremity Movement Variability on Fall Susceptibility at Increased Stride Lengths During Locomotion

The purpose of this examination was to explore the effects of stride length (SL) perturbations on walking gait, relative to preferred walking (PW) and running (PR), via lower extremity range of motion (ROM) variability. ROM variability at the hip, knee, and ankle joints, in the sagittal and frontal planes were used in evaluating motor control of gait, where increased gait variability has been previously implicated in fall susceptibly. Nine participants (5 male, 4 female; mean age 23.11±3.55 years, height 1.72±0.18m, mass 72.66±14.37kg) free from previous lower extremity injury were examined. Kinematic data were acquired using a 12-camera system (Vicon MX T40-S; 200Hz). Data filtering and interpolation included a low pass, 4th order, Butterworth filter (15Hz cutoff) and cubic spline. Five gait trials were completed for PW and PR, with subsequent SL manipulations computed as a percentage of leg length (LL). SL perturbations included 60%, 80%, 100%, 120%, and 140% of LL. Kinematic analysis involved one stride (two steps) during each gait trial, assessing ROM at the hip, knee, and ankle from heel contact to toe-off for each limb, in the sagittal and frontal planes. Variability was expressed using coefficient of variation (%). Comparisons were made using 3×7 (joint × stride condition) mixed model ANOVAs, with repeated measures on stride condition (α = 0.05), using SPSS 20.0. Differences in lower extremity ROM variability were detected among stride conditions in the frontal and sagittal planes (F[3.185,76.451] = 3.004, p = .033; F[4.595,110.279] = 2.834, p = .022, respectively). Greater ROM variability was observed at, and in excess of SLs of 100%LL relative to PW in the frontal plane (PW: 9.2±4.2%; 100%LL: 11.8±3.6%, p = .014; 120%LL: 13.5±5.8%, p = .046; 140%LL: 13.8±6.5%, p = .016), and between SLs of 80%LL and 120%LL in the sagittal plane (4.9±3.0%; 7.8±4.7%, p = .046, respectively). From this, PW appeared to occur within SLs of 60%LL to 80%LL, while SLs exceeding 100%LL resulted in increased lower extremity ROM variability. This may have consequences for fall susceptibility at increased stride lengths during walking. PR did not reveal significant variability differences (p>.05) compared to walking conditions in either the sagittal or frontal plane (7.5±5.0%; 12.8±7.7%, respectively), suggesting that running represents a separate, but stable gait pattern. In the sagittal plane, ROM variability was significantly lower at the hip (3.9±1.5%), relative to the ankle (8.4±1.6%, p<.001) and knee joints (7.4±2.6%, p = .001), suggesting that gait control may be more active at the ankle and knee joints. Future investigations should examine kinetic changes in gait when altering stride length.

Preliminary Performance Test of Mechanical Pump for a Stella-1

In the process of sodium-cooled fast reactor (SFR) design, it is very important to verify thermo-hydraulic performance of each component in the sodium environment. In KAERI (Korea Atomic Energy Research Institute) STELLA (Sodium Integral Effect Test Loop for Safety Simulation and Assessment) project is under a Mid- and Long-term Nuclear R&D Program. The STELLA project is composed of two stages. In the 1st stage the performance for heat exchangers such as DHX (Decay heat exchanger) and AHX (Air heat exchanger) and for PHTS (Primary heat transport system) mechanical pump will be evaluated. The detailed design of each component is based on that of a 600MWe demonstration reactor. Since full-scale components could not be installed in STELLA-1 [1], the model pump is designed to be scaled-down based on the scaling law. Various pump tests have been done in water environment by using model pump. In this study the design features of model pump were described and the scaling parameters were examined. The results of pump performance tests have been also introduced which is essential to perform safety analysis.

Pressure Drop Analysis of a Pressure-Channel Type SuperCritical Water-Cooled Reactor

Pressure drop calculation and temperature profiles associated with fuel and sheath are important aspects of a nuclear reactor design. The main objective of this paper is to determine the pressure drop in a fuel channel of a SuperCritical Water-cooled Reactor (SCWR) and to calculate the temperature profile of the sheath and the fuel bundles. One-dimensional steady-state thermal-hydraulic analysis was conducted. In this study, the pressure drops due to friction, acceleration, local losses, and gravity were calculated at supercritical conditions.

Enhancing Infeasibility Detection Method for Mechanical Design Problems

This paper presents the application of the Multistart point technique in order to enhance a previous existing infeasibility detection method based on Sequential Quadratic Programming (SQP) used for detecting modeling errors by finding the Minimum Intractable Subsystem (MIS) of constraints. This new method showed a great potential in detecting infeasibility without countering the problems of the initial starting point faced by many methods for Nonlinear Programming Problems. The real performance of the anticipated method is demonstrated by solving complex mechanical systems were inconsistency constraints are presented. The proposed method succeeded to find the MIS set of constraints that cause infeasibility in the these models while direct Nonlinear Programming solver, based on Sequential Quadratic Programming only, failed to detect the correct inconsistent constraints.

Optimal Design of Worm Gear System Usage in CVVL for Automobiles

Gearing with a ZK worm and an involute helical gear is used in the motor drive system of automotive continuous variable valve lift (CVVL) because of production cost. Since the geared system does not satisfy the meshing condition, transmission error (TE) and teeth interference (TI) are inevitable. This paper introduces a method for reducing TE and eliminating TI. Transmission error function is derived mathematically and used in checking TI. The first prototype for an automobile shows a lot of NVH problem, which is simply combined by coinciding with the helix/lead angles of two gears at the pitch point. By an optimal process with alternating the pressure and helix angles of worm gear system, an prototype of CVVL worm drive of which NVH problem is acceptably solved is designed.

Investigation of Conjugate Heat Transfer in Microchannels Using Variable Thermophysical Property Nanofluids

We report the results of a study on heat transfer in microchannels. The fluid used is a nanofluid whose properties are temperature dependent. The energy dissipation is evaluated for various solid fraction contents along with the cooling effectiveness of this modern type of heat exchangers. The shape of the channels is also investigated. The evaluation parameter used for thermal energy dissipation is the Nusselt number while that used for cooling effectiveness is the static pressure drop between the inlet and the outlet of the microchannel. Conjugate convection-conduction energy conservation equations have been solved along with mass and momentum conservation equations in order to determine these parameters. The results obtained showed important heat transfer augmentation with solid fraction at the expense of an increased pressure drop, i.e high pumping cost (therefore low cooling effectiveness). The microchannel inlet section geometry was also found to contribute to the values of the Nusselt number and pressure drop. Among the tested geometries (elliptical, rectangular, trapezoidal) the rectangular section provided the best compromise between heat transfer augmentation and pumping cost. At the end of the study, a comparison was made between the results obtained by assuming Newtonian rheology and those obtained with non-Newtonian rheological behavior of the same nanofluid sample. It was found that the assumption of non-Newtonian rheological behavior of nanofluids gives higher Nusselt number values and much lower pressure drops.