Influence of magnetorheological elastomer on tool vibration and cutting performance during boring of hardened AISI4340 steel

During boring process, tool vibration is a major concern due to its overhanging length, which results in high cutting force, poor surface finish, and increase in tool wear. To suppress tool vibration and improve cutting performance, a novel technique in rheological fluid was designed and developed. In this work, a magnetorheological elastomer (MRE) was developed, and parameters, such as piston location, current intensity, and coil winding direction, were considered. Cutting experiments were conducted to obtain a set of parameters that can efficiently control vibration during boring of hardened AISI 4340 steel. Taguchi method was used to optimize the cutting condition, and findings show that the cutting tool embedded with the MRE reduced tool vibration and effectively increased cutting performance.

     

A dual-purpose positioner-fixture for precision six-axis positioning and precision fixturing: Part II. Characterization and calibration

The kinematics, stiffness, and repeatability of a moving groove, dual-purpose positioner-fixture were determined experimentally. A dual-purpose positioner-fixture is an alignment device that may be operated in a fixture mode or a six-axis nanopositioning mode. When operated in fixture mode, experiments show standard deviation in repeatability of 11, 11, and 38 nm in x, y, and z; and 0.7, 0.3, and 0.3 μrad in θ_x, θ_y, and θ_z. The stiffness characteristics were shown to match predictions within 5%. When operated in nanopositioner mode, the device demonstrated 4 nm resolution and a range, of 40 μm × 40 μm × 80 μm in translation and 800 μrad × 800 μrad × 400 μrad in rotation. The fixture possesses a load capacity of 450 N and a natural frequency of 200 Hz when the fixture is preloaded to 225 N.     

Single-well "push-pull" partitioning tracer test for NAPL detection in the subsurface

Previous environmental applications of partitioning tracer tests to detect and quantify nonaqueous phase liquid (NAPL) contamination in the subsurface have been limited to well-to-well tests. However, theory and numerical modeling suggests that single-well injection-extraction ("push-pull") partitioning tracer tests can also potentially detect and quantify NAPL contamination. In this type of test, retardation factors for injected partitioning tracers are estimated from the increase in apparent dispersion observed in extraction-phase breakthrough curves in the presence of NAPL. A series of laboratory push-pull tests was conducted in physical aquifer models (PAMs) packed with natural aquifer sediment prepared with and without the presence of trichloroethene (TCE) NAPL. Field tests were conducted in an aquifer contaminated with petroleum hydrocarbon NAPL. Injected test solutions contained a suite of partitioning and conservative (nonpartitioning) alcohol tracers. Laboratory push-pull partitioning tracer tests were able to detect and quantify sorption of partitioning tracers to aquifer sediment (in the absence of NAPL) and to detect NAPL when it was present. NAPL saturations computed from estimated retardation factors bracketed those computed from known volumes of emplaced NAPL in the sediment pack. However, numerical modeling with assumed homogeneous NAPL distribution and linear equilibrium partitioning of tracers between aqueous and NAPL phases was unable to reproduce all features of observed breakthrough curves. Excavation of the sediment pack after all tests indicated that a portion of the emplaced NAPL had sunk to the bottom of the PAM invalidating the modeling assumption of homogeneous NAPL distribution. Moreover, the apparent dispersion in extraction-phase breakthrough curves decreased when the injection-extraction pumping rate was decreased, suggesting that mass transfer limitations existed during laboratory tests. Field push-pull partitioning tracer tests were able to detect NAPL in a portion of the aquifer known to contain NAPL; computed NAPL saturations were comparble to those obtained from sediment coring and the results of a partitioning interwell tracer test conducted in the same location. This study clearly demonstrates that the single-well partitioning tracer test can detect NAPL under both laboratory and field conditions. However, additional research is needed to verify the ability of the test to quantify NAPL saturations.     

Constitutive Modeling of a Schistose Rock in the Himalaya

Strain‐controlled triaxial tests have been conducted using servo‐controlled loading system on three schistose rocks from a hydropower project in the Himalaya. A constitutive model based on the disturbed state concept is used to model the behavior of the rocks. Predictions are made using a single point method and finite element method. The constitutive model is found to provide satisfactory predictions. The DSC model is used to predict observed behavior of a powerhouse cavern; the relevant paper, “Analysis of a Powerhouse Cavern in the Himalaya,” appears in this issue.     

Traffic Aware Congestion Control Priority Based Efficient Adaptive Multipath Routing in Wired Networks with New Queuing Technique

Wireless Personal Communications - This paper proposes a novel technique for data transmission from source to destination by using adaptive multipath routing with route adaptability. In this...     

Microfluidic generation of transient cell volume exchange for convectively driven intracellular delivery of large macromolecules

Efficient intracellular delivery of target macromolecules remains a major obstacle in cell engineering and other biomedical applications. We discovered a unique cell biophysical phenomenon of transient cell volume exchange using microfluidics to rapidly and repeatedly compress cells. This behavior consists of brief, mechanically induced cell volume loss followed by rapid volume recovery. We harness this behavior for high-throughput, convective intracellular delivery of large polysaccharides (2000?kDa), particles (100?nm), and plasmids while maintaining high cell viability. Successful proof of concept experiments in transfection and intracellular labeling demonstrated potential to overcome the most prohibitive challenges in intracellular delivery for cell engineering.     

Admission control by implicit signaling in support of voice over IP over ADSL

Voice over DSL (VoDSL) is a technology that enables the transport of data and multiple voice calls over a single copper-pair. Voice over ATM (VoATM) and Voice over IP (VoIP) are the two main alternatives for carrying voice over DSL. ATM is currently the preferred technology, since it offers the advantage of ATM’s built-in Quality of Service (QoS) mechanisms. IP QoS mechanisms have been maturing only in recent years. However, if VoIP can achieve comparable performance to that of VoATM in the access networks, it would facilitate end-to-end IP telephony and could result in major cost savings. In this paper, we propose a VoIP-based VoDSL architecture that provides QoS guarantees comparable to those offered by ATM in the DSL access network. Our QoS architecture supports Premium and Regular service categories for voice traffic and the Best-Effort service category for data traffic. The Weighted Fair Queuing algorithm is used to schedule voice and data packets for transmission over the bottleneck link. Fragmentation of large data packets reduces the waiting time for voice packets in the link. We also propose a new admission control mechanism called Admission Control by Implicit Signaling. This mechanism takes advantage of application layer signaling by mapping it to the IP header. We evaluate the performance of our QoS architecture by means of a simulation study. Our results show that our VoIP architecture can provide QoS comparable to that provided by the VoATM architecture.