bluuebunny/crossref_metadata_2025 huggingface dataset:
Steady State and Transient Experimentally Validated Analysis of Hybrid Data Centers
Authors: Gao Tianyi , Sammakia Bahgat , Samadiani Emad , Schmidt Roger
Published: November 2014

Data centers consume a considerable amount of energy which is estimated to be about 2% of the total electrical energy consumed in the U.S. in the year 2010, and this number continues to increase every year. Thermal management is becoming increasingly important in the effort to improve the energy efficiency and reliability of data centers. The goal is to keep the information technologies (IT) equipment temperature within the allowable range in high power density data centers while reducing the energy used for cooling. In this regard, liquid and hybrid air/water cooling systems are alternatives to traditional air cooling. In particular, these options offer advantages for localized cooling higher power racks which may not be manageable using the room level air cooling system without requiring significantly more energy. In this paper, a hybrid cooling system in data centers is investigated. In addition to traditional raised floor, cold aisle-hot aisle configuration, a liquid–air heat exchanger attached to the back of racks is considered. First of all, the paper presents a review of literature of the study of this heat exchanger strategy in the thermal management of a data center. The discussion focus on rear door heat exchanger (RDHx) performance, both the steady state and transient impact are analyzed. The studies show that under some circumstances, this hybrid approach could be a viable alternative to meet the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommended inlet air temperatures, while at the same time reducing the overall energy consumption in high density data centers. The hybrid design approach can also significantly improve the dynamic performance during rack power increases or computer room air conditioner (CRAC) unit failure. And then, additional parametric steady state and dynamic analyses, are presented in detail for the different scenarios.
Experimental Study of the Type VI Stilling Basin Performance
Authors: Sobhan Aleyasin Seyed , Fathi Nima , Vorobieff Peter
Published: November 2014

Understanding the estuarine turbulent flow from dams, channels, and pipes, as well as the river flow are very important due to the potential to cause damage to the bed of the river or channel and cause scouring of structures such as the saddles of bridges, because of the huge amount of the kinetic energy carried by the flow. One of the most efficient yet simple ways to dissipate this energy is to install a stilling basin at the discharge point to calm the flow. Turbulence data were recorded using acoustic Doppler velocimetry (ADV) for type VI2 of stilling basins for pipe outlets. During the study, various splitters and a cellular baffle were placed in the stilling basin, and the baffle locations were changed to assess the effect on the energy dissipation. Velocity at several locations in the basin was measured for different Froude numbers to investigate the effect of flow rate. Based on the findings of the experiments, several suggestions regarding the efficiency and geometry of stilling basins were made.
A Computational Study on the Influence of Surface Roughness Lay Directionality on Micropitting of Lubricated Point Contacts
Authors: Li Sheng
Published: November 2014

This study focuses on the influence of roughness lay directionality on micropit crack formation, using a computational approach. A mixed lubrication model is implemented to find the surface tractions, which are used in a stress model to compute the near surface stress concentrations. With the stress amplitudes and means determined, the crack formation lives are assessed according to a fatigue criterion. It is found when the roughness lays of the two surface are parallel to the rolling direction and are out-of-phase, the resulted micropitting area percentage is minimum. The most severe micropitting activity is observed on the surface whose roughness lay is parallel to the rolling direction, while the roughness lay of its counterpart is normal to the rolling direction.
Ghost Image Suppression Based on Particle Swarm Optimization-MVDR in Sound Field Reconstruction
Authors: Li Min , Wei Long , Fu Qiang , Yang Debin
Published: November 2014

In sound field reconstruction, spurious sources called ghost images always appear around the position of the real sound source in the sound pressure distribution map because of the grating and side lobes, thus resulting in an incorrect identification of the sound source. To solve this problem, a method for suppressing ghost images is proposed in this paper; such method is based on particle swarm optimization (PSO) and minimum variance distortionless response (MVDR) beamforming. In this method, the elements distribution of a microphone array is first optimized by the PSO algorithm to acquire the optimal design of an unequal spacing microphone array. With this array, the grating lobe is suppressed, and the increscent value of the inherent side lobe value is reduced. Second, MVDR algorithm is used to weaken the effect of the side lobes and to obtain a sound pressure distribution map in which the ghost images are suppressed. The advantage of this method is the combination of the unequal spacing array, which suppresses the grating lobe, and the MVDR algorithm, which has excellent performance in spatial filtering. Through this method, a microphone array with a few number of elements can achieve ghost image suppression. Experiments on sound field reconstruction in an anechoic chamber for a single-tone sound source are conducted to validate the proposed method. Moreover, some extra sound field reconstructions for a single-tone sound source and double sound sources with broadband in a normal room with different parameters such as the array shape and distance from the sources to the array are conducted to discuss their influences on the effectiveness of the proposed method.
Modeling and Stability of a Hydraulic Load-Sensing Pump With Investigation of a Hard Nonlinearity in the Pump Displacement Control System
Authors: Wagner Zachary D. , Fales Roger
Published: November 2014

Certain types of Load-sensing (LS) pumps utilize a hydro-mechanical control system designed to regulate the pressure difference, or margin pressure, between the inlet and outlet of a flow control valve. With a constant margin pressure, predictable flow control can be achieved by controlling the orifice area of the flow control valve. In this work, the stability of the pressure control system will be investigated. A combination of linear analysis and nonlinear analysis is employed to assess the stability of a particular LS pump system. Among many nonlinearities present in the hydro-mechanical system, of particular interest is the saturation inherent in the actuator that is used to displace the pump swash plate and the saturation within the 3-way spool valve that permits flow to reach the actuator. This saturation nonlinearity has been isolated from the rest of the system to enable stability analysis. Analysis of model characteristics is used to make conclusions about the stability of the system consisting of interconnected linear and nonlinear portions. The stability analysis is compared to results obtained through a simulation study using a nonlinear model based on first principles.
Modelling and Simulating the Pump of an Aerospace Electro-Hydrostatic Module for Fault Detection and Identification Purposes
Authors: Mare Jean-Charles , Vinson Garance , Prado Thomas , Combacau Michel
Published: November 2014

This communication deals with the modelling and simulation of a fixed-displacement axial-piston pump used in aerospace electro-hydrostatic actuators. The pump model is developed in the LMS-AMESim simulation environment to support the development of fault detection and identification features. The model-based fault diagnosis method is introduced first and the modelling needs are addressed. Then, a system-level pump model is proposed with special considerations to model architecture. The different ways to improve the model’s realism are reviewed, in particular concerning energy losses (bearing friction, leakages in gaps), barrel force balance, piston back pumping, piston eccentricity and pump loading for tests. Finally, directions of research in system-level modelling of hydraulic effects are suggested.
Hydraulic Actuator Internal Leakage Detection Using Cross-Correlation Time Series Analysis
Authors: May Morgan , Sepehri Nariman , Kinsner Witold
Published: November 2014

As a hydraulic actuator is used over time, the piston seal that closes the gap between the moveable piston and the cylinder wall wears. This results in the fluid to eventually being able to flow across the piston and between the cylinder chambers. Although no fluid is lost from the circuit, the dynamic performance of the system is affected since only a portion of the flow delivered to the actuator is available to move the piston against the load. Leakage across the piston introduces a flow deadband, which can lead to servoing errors. This paper presents an approach based on the cross-correlation time-series analysis to determine the health of hydraulic actuator internal seals. Pressure signals obtained directly from routine operations are analyzed using the cross-correlation function. The method presented in this paper is shown to be capable of detecting leakages as small as 0.069 l/min.
Performance of a Pump Controlled Asymmetric Actuator: A Comparison of Different Control Methods
Authors: Kukkonen Sami , Mäkinen Esa
Published: November 2014

This paper discusses different stabilizing pump control methods to improve and optimize the damping of a pump controlled asymmetric linear actuator response. The main purpose of the paper has been to study the redeeming features and drawbacks of influencing the actuator response by pump control without direct position, velocity or pressure feedback from the actuator. To the author’s knowledge, this type of stabilizing method is novel to pump controlled hydraulic drives. Pole placement techniques with both pump speed and displacement control are discussed and finally the system performance is compared by simulation with a system where dynamic pressure feedback has been used. Preliminary optimal tuning rules for the pump speed controller and pump volumetric displacement value have been derived and their applicability to high, varying inertial loading application has been assessed. Results indicate clear improvements of the actuator response damping level with the suggested rules but also raise the demands for pump torque and displacement range.
Single Edge Meter Out Control for Mobile Machinery
Authors: Vukovic Milos , Murrenhoff Hubertus
Published: November 2014

To decrease throttling losses in mobile hydraulic systems a number of new system architectures have been introduced in recent years. The concept of independent metering (IM), developed in the seventies, shows a lot of promise [1]. By allowing the meter-in as well as meter-out edges to be controlled separately, additional operating modes are created allowing a more efficient adaptation of system pressure to load pressure [2, 3]. Despite these advantages IM circuits have yet to find their way into industrial applications. This is mainly due to the related increase in component costs and more demanding control strategies. Additionally, the effect of mode switching on actuator motion and operator comfort is still unclear and considered to be a challenge.

The STEAM mobile hydraulic system currently being developed in Aachen, Germany uses a number of new features to improve total machine efficiency [4]. Among others is the use of a new independent metering circuit called single edge meter-out control. Unlike other IM configurations, only one proportional valve is used to control cylinder motion. This paper introduces the new concept and discusses its advantages.
Fatigue Life Improvement of the Roller Swashplate Bearing of an Axial Swashplate Type Piston Pump
Authors: Du Hongliu , Carlson David J.
Published: November 2014

The roller swashplate bearing in hydraulic piston pumps is very unique in applications of roller element bearings. The main advantages of this type of bearings are low friction, very small difference between start torque and steady state torque, and no additional pressure source is required for their functioning. Therefore, better control performance and higher efficiency can be expected from piston pumps with roller swashplate bearings, compared with pumps with hydrostatic or plain ones. However, it is particularly challenging to design a roller swashplate bearing to meet the very demanding and widely varying load requirements for heavy duty off-highway machine operations, considering cost and pump size limitations. Quite different from most other roller bearing applications, a roller swashplate bearing for heavy duty hydraulic piston pumps is subject to (a) extremely high contact pressure between rollers and races due to high system pressure, (b) high frequency oscillating forces in three dimensions caused by the torque ripple and discharge pressure ripple inherent in pump rotating group, (c) very unfavorable local lubrication conditions when the pump is operated with no or little displacement change, and (d) sliding between rollers and races because of frequent sudden pump displacement changes. Based on the observed failure modes of bearings in this application, this paper discusses several measures to improve the fatigue life of the swashplate roller bearing for an axial swashplate type piston pump used in a heavy duty off-highway machine. Analyses, simulation results, and machine operation results are provided to show the effectiveness of the proposed measures.
A Power Recovery Type Pressure Reducer in the High Pressure Pneumatic System
Authors: Xu Qiyue , Sun Junpeng , Cai Maolin , Shi Yan , Fu Xiangheng
Published: November 2014

Pressure reducing devices are the essential and critical components of a pneumatic system. But the energy lose due to the pressure reducing process is considerably huge when there is a high pressure difference. Aiming at this issue, firstly, the mechanism and quantification method of the energy loss in the throttling reducing process is analyzed based on pneumatic power theory. Then, a power recovery type (PRT) pressure reducer which can output shaft power during the reducing operation is proposed. The basic mechanical structure and the working principle of the PRT reducer are described. For evaluating the feasibility of the design, a thermodynamic model of the PRT reducer is established. And under specific parameter settings, simulations on the PRT reducer’s power output characteristics and the pressure regulating ability are carried out. On this basis, the principle structure of an energy recycling high pressure pneumatic system is proposed. This research is the theoretical foundation of the prototype design of a PRT high pressure reducing device.
Modeling and Simulation of the Swing System of Crawler-Type Medium Hydraulic Excavator Using Dynamic Friction Model
Authors: Lee Ji-Min , Cho Jae-Hong , Yoo Jae-Hyeong
Published: November 2014

An analysis model is presented in this paper to simulate the dynamics of the swing system of crawler-type medium hydraulic excavator. It is found from experiments that the static friction model cannot simulate actual friction phenomena such as the Stribeck effect which can be observed in real swing system. A dynamic friction model, i.e., the simplified LuGre model, has been implemented for more accurate simulation in the theoretical analysis. The validity of the simulation model adopting the dynamic friction model has been verified by comparing in time domain the simulated swing angle with that from actual swing test. Cross-correlation between the simulated and measured swing angles turned out to be 0.92. It can be concluded, therefore, that the proposed dynamic friction model considerably improves the simulation accuracy.
Process-Adapted Control to Maximize Dynamics of Speed- and Displacement-Variable Pumps
Authors: Willkomm Johannes , Wahler Matthias , Weber Jürgen
Published: November 2014

Within the last years, speed-variable pump drives were investigated in numerous applications. In combination with a variable displacement pump, the volume flow and the drive speed can be decoupled. In this paper the resulting degree of freedom will be used to maximize the dynamics of so called “Hydro-Gear” drive systems. By means of a novel process-adapted control concept, a dynamic model of all drive components will be transformed to a mathematical optimization problem. It will be shown that the optimum use of the two control variables depends on the actual system and process conditions. In comparison to known control strategies of speed- and displacement-variable pumps the new process-adapted approach can exemplary double the maximum volume flow gradient while reducing the necessary motor speed by over 40% at the same time.
Investigation of Different Methods to Measure the Entrained Air Content in Hydraulic Oils
Authors: Schrank Katharina , Murrenhoff Hubertus , Stammen Christian
Published: November 2014

The fluids used as pressure media in fluid power systems are often polluted with undesired air bubbles. This entrained air affects the system behaviour, stability and safety. Knowledge of the amount of entrained air inside a hydraulic fluid plays a decisive role in predicting the system behaviour. In addition, this information is necessary when a system or components should be optimised to obtain better air release properties. The content of entrained air highly depends on the static pressure as air is always dissolved in hydraulic pressure fluids up to a certain equilibrium condition.

In this paper, different physical principles (optical, mechanical and electrical) are presented to determine the amount of entrained air in an oil-hydraulic system. Starting from these theoretical ideas, different methods are selected and corresponding test devices are designed and built up. These devices are experimentally investigated by including entrained air into a commonly used mineral oil in a hydraulic system. The tested devices are based on different physical principles. In the end, the methods are compared against each other in terms of accuracy of the results and effort to perform these measurements.
Experimental Investigation of a Switched Inertance Hydraulic System
Authors: Pan Min , Robertson James , Johnston Nigel , Plummer Andrew , Hillis Andrew
Published: November 2014

This article reports on experimental investigations of a switched inertance hydraulic system (SIHS), which is designed to control the flow and pressure of a hydraulic supply. The switched system basically consists of a switching element, an inductance and a capacitance. Two basic modes, a flow booster and a pressure booster, can be configured in a three-port SIHS. It is capable of boosting the pressure or flow with a corresponding drop in flow or pressure respectively. This technique makes use of the inherent reactive behaviour of hydraulic components. A high-speed rotary valve is used to provide sufficiently high switching frequency and minimise the pressure and flow loss at the valve orifice, and a small diameter tube is used to provide an inductive effect. In this article, a flow booster is introduced as the switched system for investigation. The measured steady state and dynamic characteristics of the rotary valve are presented, and the dynamics characteristics of the flow booster are investigated in terms of pressure loss, flow loss and system efficiency. The speed of sound is measured by analysis of the measured dynamic pressures in the inertance tube. A detailed analytical model of a SIHS is applied to analyse the experimental results. Experimental results on a flow booster rig show a very promising performance for the SIHS.
Investigations on Pulsation-Reduction Characteristics of Hydraulic Attenuator Based on Experimental Method
Authors: Zhu Jiabin , Zhou Hua , Yang Huayong
Published: November 2014

Three types of hydraulic attenuators are designed and investigated to study the pulsation-reduction characteristics in hydraulic system. Attenuator test rig is established to obtain pressure signals in time domain and frequency domain (5 Hz to 1200 Hz), respectively. Influences of changing source impedance and loading impedance to the attenuation rate (Ka) and pressure ratio of inlet and outlet (Pio) are discussed.

Experiment results show that expansion chamber attenuator (ECA) is a better choice for a wide frequency range of pulsation reduction. Two types of perforated tube attenuators (PTA) have better performances in some certain frequency range. The performance of PTA can have further improvements by designing the damping holes diameters. The performance of the attenuator is mainly influenced by pump character and rotating speed. The system loading has limited influence on the performance comparing to source impedance.
Investigations on Position Estimation and Motion Manipulation of Electromagnetic Driven Dosing Pumps Using Co-Simulation
Authors: Kramer Thomas , Petzold Martin , Richter Sören , Weber Jürgen , Ohligschläger Olaf , Müller Axel
Published: November 2014

Uncontrolled magnetically driven dosing pumps cause noise when the armature reaches the mechanical end stops. The reason for this is the impulse of the armature, which depends on the armature speed. A speed reduction before reaching the end stops could reduce the noise level. This requires a special modification of the time-dependent armature motion using variable energy supply. In order to control the armature motion independently from various inputs such as supply voltage, outlet pressure and liquid properties, the position has to be known. Sensorless position estimation is used, since it offers the determination of the armature position without modifying the simple pump design. The estimation is based on the evaluation of electrical values.

In order to show feasibility of position estimation in dosing pumps considering different control strategies, simulation based preliminary investigations are performed and validated with experimental results. For this purpose, a co-simulation of controller, electrical and mechanical system simulation and magnetic FEM simulation is used.
Actuator Speed Control Using Digital Hydraulics
Authors: Locateli Cristiano Cardoso , Belan Henri Carlo , De Pieri Edson Roberto , Krus Petter , De Negri Victor Juliano
Published: November 2014

In the last few years, the energetic efficiency of hydraulic systems has been widely discussed. One approach that has a particular potential is digital hydraulics. According to recent research, digital hydraulics has several potential advantages when compared with traditional technology, such as improved energy efficiency and the simplicity and robustness of its components. In this context, the main objective of this paper is to discuss the speed control of symmetrical actuators using digital hydraulic principles. It is proposed a hydraulic circuit configuration based on use of several fixed displacement units instead of one pump, on/off directional valves replacing flow control valves, and a specific control strategy. An energy management device is also proposed. This device allows the digital hydraulic system to operate in motor mode as well as store energy, therefore, improving the efficiency. The modelling of the hydraulic system is carried out by AMESim software and the control is implemented in the MATLAB software. The simulations were carried out using a co-simulation technique. Initially, the speed behaviour of the digital hydraulic system, using different delay times applied to on/off valves, is analyzed. The cases where the smallest power loss and the best dynamic behaviour take place are identified. Based on this, the actuator speed behavior, flow rate on the on/off valves and actuators and the pressure in the fixed displacement units for different speed steps are studied. The preliminary results showed a small power loss in the digital hydraulic system when compared with the average efficiency of other hydraulic systems. The speed transitions had small oscillations and adequate dynamic behavior.
Comparison of Proportional Control and Displacement Control Using Digital Hydraulic Power Management System
Authors: Heikkilä Mikko , Karvonen Matti , Linjama Matti , Tikkanen Seppo , Huhtala Kalevi
Published: November 2014

The Digital Hydraulic Power Management System (DHPMS) is a solution based on the digital pump-motor technology and has shown to be a promising approach to improve the energy efficiency of hydraulic systems. The DHPMS is controlled by active on/off valves, but unlike the digital pump-motors the DHPMS has multiple independent outlets; hence, the DHPMS can operate also as a transformer. In this experimental study, a proportional control of a mobile boom is compared with a displacement control when a six-piston DHPMS is used. In the proportional control, the system pressure is controlled by the DHPMS and a lift cylinder with a proportional valve. In the displacement control, the cylinder fluid volumes are controlled directly using the DHPMS. Firstly, the systems under study are presented along with the control methods. Then the control performance of the DHPMS is studied and finally, the energy losses in the systems are analysed. The results show the versatility of the DHPMS; it is capable of fast and accurate pressure control but also handles the direct flow control. According to the measurements, the losses are significantly smaller in the displacement controlled system thanks to the minimised throttling losses and the energy recovery. Nevertheless, the energy losses in the prototype DHPMS are rather high due to the leakage in the control valves and their low flow capacity, and therefore improvements in the design are needed.
System Dynamic Model and Design of a Stirling Pump
Authors: Winkelmann Anna , Barth Eric J.
Published: November 2014

This paper presents the design and dynamic modeling of a second generation prototype combined Stirling engine pump. The Stirling pump is intended to fill the technological gap of a compact high energy density power supply for untethered fluid power applications in the 50W to 500W range. Specifically, this prototype is intended as a compact and quiet, untethered, hydraulic power supply for an ankle foot orthosis testbed associated with the Center for Compact and Efficient Fluid Power. The energy source for the unit is flexible and can include propane, butane, methane, natural gas, or other high energy density hydrocarbon source of heat. The target output pressure of 7 MPa (1000 psig) is obtained from a pumping stage that is driven by a sealed engine stage that utilizes high pressure helium as the working fluid. The separate pumping stage utilizes the differential pressure swing inside the engine section to pump hydraulic fluid to the desired output pressure. This paper presents the system dynamic model of the Stirling pump, and includes (1) heat transfer from the heat source to the working fluid in the hot space of the engine, (2) heat transfer from the working fluid in the cold space of the engine to the heat sink, (3) energetically derived pressure dynamics in the hot and cold spaces, (4) mass flow around the displacer piston in between the hot and cold sides, (5) work output to the pump driving section, (6) pumping piston inertial dynamics, (7) flow losses through the pump’s check valves, and (8) hydraulic power output. This dynamic model allows components of the Stirling pump to be sized. The paper includes results from the dynamic model.
Advanced Strain Energy Accumulator: Materials, Modeling and Manufacturing
Authors: Cummins Joshua J. , Pedchenko Alexander , Barth Eric J. , Adams Douglas E.
Published: November 2014

Energy efficiency is a prominent target in cost reduction efforts in a variety of machinery including manufacturing equipment and hybrid vehicles. In the course of developing a proof of concept strain energy accumulator on an Ankle Foot Orthosis (AFO) device, several technical barriers have been quantified in this device. Due to the hyperelastic nature of the material, the identification of an appropriate elastomer and the characterization of the strength properties and energy density of this elastomer are challenging tasks. Another technical barrier is the manufacturability of these elastomers including the high cost of fabrication and the limited elastomer formulations with high strength and large energy density. A quantitative analysis of these technical barriers is needed. A comprehensive modeling effort for the strain energy accumulator in 2-D and 3-D using the hyperelastic Mooney-Rivlin model was performed to validate the behavior of the strain energy accumulator. Additionally, various multiscale modeling methods, including the Mori-Tanaka, Hashin-Shtrikman, Lielens, Voigt and Reuss Methods were investigated to estimate the homogenized elastic modulus of carbon nanotube rubber resulting in homogenized modulus estimates ranging anywhere from a few times to almost 80 times the elastic modulus of rubber.
State Estimation and Fault Detection of an Electrohydrostatic Actuator
Authors: Gadsden S. A. , Habibi S. R.
Published: November 2014

The electrohydrostatic actuator (EHA) is an efficient type of linear actuator commonly found in aerospace applications. It consists of an external gear pump (fluid), an electric motor, a closed hydraulic circuit, a number of control valves and ports, and a linear actuator. An EHA, built for experimentation, is studied in this paper. Two types of estimation strategies, the popular Kalman filter (KF) and the smooth variable structure filter (SVSF), are applied to the EHA for kinematic state and parameter estimation. The KF strategy yields the statistical optimal solution to linear estimation problems. However, the KF becomes unstable when strict assumptions are violated. The SVSF is an estimation strategy based on sliding mode concepts, which brings an inherent amount of stability to the estimation process. Recent advances in SVSF theory include a time-varying smoothing boundary layer. This method, known as the SVSF-VBL, offers an optimal formulation of the SVSF as well as a method for detecting changes or faults in a system. In addition to the application of the KF and SVSF for state estimation, the SVSF-VBL is applied to the EHA for the purposes of fault detection. The EHA is operated under various operating conditions (normal, friction fault, leakage fault, and so on), and the experimental results are presented and discussed.
An Investigation of Piezoelectric Ring Benders and Their Potential for Actuating Servo Valves
Authors: Bertin M. J. F. , Plummer A. R. , Bowen C. R. , Johnston D. N.
Published: November 2014

This paper describes the deformation of a piezoceramic disc shaped actuator due to two effects: inner edge mechanical loading and electrical excitation. A 2D axisymmetric coupled-field finite element model was constructed to represent the piezoceramic ‘ring bender’. The model was used to predict actuator displacement due to a force applied to the inner edge, and also the piezoelectric induced strain due to an electric field applied in the poling direction of the piezoceramic. Results are compared with theoretical calculations of the deformation of a uniform thickness disc under mechanical load, and the displacement-voltage characteristics reported by the manufacturer. Experimental results for the displacement of the piezoelectric actuator, under a variety of constraint conditions, are also compared.

The research presented provides an understanding of how the ring bender deforms under combined mechanical load and electric field. Each of these effects is considered and results show that the shape formed is different depending on whether the load is mechanical or electrical. This result provides an insight into how the actuator may be mounted for use as an actuator in servo valve pilot stage.
Feed-Forward Control of an Arbitrary Pressure Pulsation Generator and its Application to Testing an Orifice-Type Flow Meter
Authors: Kato Tomonori , Hirakawa Tetsuma , Nakao Mitsuhiro , Oowaku Takashi , Sakuma Hirohisa , Kagawa Toshiharu
Published: November 2014

This paper presents a compact arbitrary pressure pulsation generator for assessing the characteristics of flow meters and sensors, particularly around their zero points. In this study, a compact arbitrary pressure pulsation generator was created using some pneumatic components, such as a high-precision quick-response pneumatic pressure regulator (HPR) and a spool-type servo-valve. The feed-forward compensation of the controller provided the desired pressure pulse to the tested flow meter by controlling the spool-type servo valve; 30 Hz was achieved.

In order to validate the effectiveness of the developed generator, we evaluated the dynamic characteristics around the zero point of an orifice-type flow meter in the range from 1 Hz through 30 Hz.
Microwave ablation energy delivery: Influence of power pulsing on ablation results in an ex vivo and in vivo liver model
Authors: Bedoya Mariajose , del Rio Alejandro Muñoz , Chiang Jason , Brace Christopher L.
Published: November 2014

Purpose:

The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models.

Methods:

A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5–20 mm from the ablation antenna, with values over 60 °C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post‐hoc pairwise tests.

Results:

No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm3). At 25 W average, pulsed‐power ablation volumes were larger than continuous‐power ablations (67.4 ± 34.5 cm3 versus 23.6 ± 26.5 cm3, P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and pulsed ablations were again slightly more circular.

Conclusions:

Pulsed energy delivery created larger ablation zones at low average power compared to continuous energy delivery in the presence of blood perfusion. Shorter duty cycles appear to provide greater benefit when pulsing.
The Influence of the Internship on Students’ Career Decision Making
Authors: Odio Michael , Sagas Michael , Kerwin Shannon
Published: November 2014

The internship experience is generally recognized for its educational and career-related benefits (Gault, Leach, & Duey, 2010); however, scholars are beginning to question the merit and expected benefits of undergraduate internships in sport management (King, 2009; Schneider & Stier, 2006). Further research has found evidence that the internship experience may negatively influence students’ intent to enter the profession (Cunningham, Sagas, Dixon, Kent, & Turner, 2005). The current study uses a longitudinal approach and qualitative analysis to examine the influence of the internship on students’ career-related decision making. Findings show that the internship plays a major role in shaping students’ career trajectory; however, many students come away more confused about their career path than before their internship. Further findings reveal issues related to intern supervision and the type of learning opportunities available to students.
Allosteric Activation of Bacterial Response Regulators: the Role of the Cognate Histidine Kinase Beyond Phosphorylation
Authors: Trajtenberg Felipe , Albanesi Daniela , Ruétalo Natalia , Botti Horacio , Mechaly Ariel E. , Nieves Marcos , Aguilar Pablo S. , Cybulski Larisa , Larrieux Nicole , de Mendoza Diego , Buschiazzo Alejandro
Published: November 2014

Response regulators are proteins that undergo transient phosphorylation, connecting specific signals to adaptive responses. Remarkably, the molecular mechanism of response regulator activation remains elusive, largely because of the scarcity of structural data on multidomain response regulators and histidine kinase/response regulator complexes. We now address this question by using a combination of crystallographic data and functional analyses
in vitro
and
in vivo
, studying DesR and its cognate sensor kinase DesK, a two-component system that controls membrane fluidity in
Bacillus subtilis
. We establish that phosphorylation of the receiver domain of DesR is allosterically coupled to two distinct exposed surfaces of the protein, controlling noncanonical dimerization/tetramerization, cooperative activation, and DesK binding. One of these surfaces is critical for both homodimerization- and kinase-triggered allosteric activations. Moreover, DesK induces a phosphorylation-independent activation of DesR
in vivo
, uncovering a novel and stringent level of specificity among kinases and regulators. Our results support a model that helps to explain how response regulators restrict phosphorylation by small-molecule phosphoryl donors, as well as cross talk with noncognate sensors.

IMPORTANCE
The ability to sense and respond to environmental variations is an essential property for cell survival. Two-component systems mediate key signaling pathways that allow bacteria to integrate extra- or intracellular signals. Here we focus on the DesK/DesR system, which acts as a molecular thermometer in
B. subtilis
, regulating the cell membrane’s fluidity. Using a combination of complementary approaches, including determination of the crystal structures of active and inactive forms of the response regulator DesR, we unveil novel molecular mechanisms of DesR’s activation switch. In particular, we show that the association of the cognate histidine kinase DesK triggers DesR activation beyond the transfer of the phosphoryl group. On the basis of sequence and structural analyses of other two-component systems, this activation mechanism appears to be used in a wide range of sensory systems, contributing a further level of specificity control among different signaling pathways.
Tuberculous granuloma: a rare cause of a non-healing ulcer
Authors: Graham George Edward Alexander , Jones Rupert , Derry David
Published: November 2014

A 78-year-old woman on ciclosporin for aplastic anaemia presented to her general practitioner with a 2 cm cystic swelling on the right side of her forehead. After a period of 8 months the lesion ruptured and, despite good wound care, failed to heal over a period of seven further months. Imaging demonstrated an invasive process and a biopsy was taken, which showed granulomatous inflammation that stained positively for mycobacteria. Further investigation with cross-sectional imaging revealed no other sites of disease. The only history of exposure to tuberculosis was 64 years prior to presentation. Differential diagnoses of mycetoma, autoimmune disease and non-tuberculous mycobacterial infection were considered, but culture confirmed tuberculosis. This case demonstrates an unusual presentation of isolated cutaneous tuberculosis in a patient with suppressed immune function.
Wait and see: a 5 year history of ‘recurrent dementia’
Authors: D'Angelo Roberto , Rinaldi Rita , Parchi Piero , Cirignotta Fabio
Published: November 2014

Rapid evolving cognitive impairment can be the onset of either a progressive or a treatable dementia. We describe a case of a man in whom the clinical and laboratory presentation suggested a diagnosis of Creutzfeldt-Jakob disease, which subsequently turned into a diagnosis of voltage-gated potassium channel complex antibodies limbic encephalitis. The natural history and an increased knowledge of limbic encephalitis and the related antibodies led us to the correct diagnosis.
Vertebral osteomyelitis in an immunosuppressed patient with rheumatoid arthritis
Authors: Giri Upama , Thavalathil Berry Cheriyan , Varghese Roy
Published: November 2014

We report a case of spontaneous osteomyelitis of the cervical spine complicated by epidural abscess due to methicillin-resistantStaphylococcus aureus(MRSA) in a patient with rheumatoid arthritis with no obvious focus of infection or bacteraemia. The patient was on immunosuppressants and complete blood count revealed neutropaenia. He was successfully treated with intravenous antibiotics and surgery.
Large intraperitoneal lipoma in pregnancy
Authors: Mathen Stephy , Nockolds Claire , Arutchelvam Satthiyabama
Published: November 2014

Intraperitoneal lipomas causing high-grade bowel obstruction in advanced pregnancy are rare. We report an unusual case which presented at 33 weeks with faecal vomitus and abdominal pain. Lipomas are benign adipose tissue tumours that are usually asymptomatic. The constraints of diagnosis, investigation and treatment of such tumours in pregnancy are also discussed.
The relationship of adiposity and mortality among people with diabetes in the US general population: a prospective cohort study
Authors: Menke Andy , Casagrande Sarah S , Cowie Catherine C
Published: November 2014

Objective

Several studies have found a U-shaped association between body mass index (BMI) and mortality in the general population. In similar studies among people with diabetes, the shape of the association is inconsistent. We investigated the relationship of BMI and waist circumference with mortality among people with diabetes.

Setting

The Third National Health and Nutrition Examination Survey (NHANES III) and the 1999–2004 NHANES Mortality Studies were designed to be representative of the US general population. Baseline data were collected in 1988–2004.

Participants

2607 adults ≥20 years of age with diabetes.

Primary Outcome Measure

Participants were followed through 31 December 2006 for mortality (n=668 deaths).

Results

Compared with people with a BMI 18.5–24.9 kg/m2, the HRs (95% CI) of mortality were 0.85 (0.60 to 1.21) for 25–29.9 kg/m2, 0.87 (0.57 to 1.33) for 30–34.9 kg/m2and 1.05 (0.72 to 1.53) for ≥35 kg/m2after adjustment for age, sex, race-ethnicity, smoking status, education, income and diabetes duration. Compared with people in the lowest sex-specific quartile of waist circumference, the adjusted HRs (95% CI) of mortality were 1.03 (0.77 to 1.37) for the second quartile, 1.02 (0.73 to 1.42) for the third quartile and 1.12 (0.77 to 1.61) for the highest quartile of waist circumference. When modelled as a restricted quadratic spline with knots at the 10th, 50th and 90th centiles, BMI and waist circumference were not associated with mortality. Several sensitivity analyses were conducted and most found no significant association between measures of adiposity and mortality, but there were significant results suggesting a U-shaped association among people in the highest tertile of glycated haemoglobin (≥7.1%), and there was an inverse association between BMI and mortality among people 20–44 years of age.

Conclusions

In a nationally representative sample of the non-institutionalised US population with diabetes, BMI and waist circumference were not associated with risk of mortality.
Research protocol: a realist synthesis of cross-border patient mobility from low-income and middle-income countries
Authors: Durham Jo , Blondell Sarah J
Published: November 2014

Introduction

People are increasingly mobile for numerous reasons, including healthcare. Patient mobility has vast implications for individuals, communities and whole populations and yet, to date, research on patient mobility has been quite limited. Only a small body of evidence exists on patient mobility between low-income and middle-income countries, instead having focused primarily on cross-border movement between high-income and low-income countries. In this paper, we present a protocol for examining this under-studied phenomenon.

Methods and analysis

We propose to examine patient mobility between low-income and middle-income countries using a realist synthesis approach. Specifically, we aim to document why patients from low-income and middle-income countries cross international borders for healthcare, by identifying the mechanisms through which patients decide to cross-borders, and the contextual characteristics of domestic health markets that influence this choice. An underlying theory was established, based on the lead author's experience and a brief literature review, which will provide the basis to analyse search results in a subsequent paper. Search results will be obtained from databases (Ovid Medline, EMBASE, Scopus, EconLit, Web of Science) and the grey literature. An expert committee will be enlisted, prior to screening results, to review search results to ensure comprehensiveness. Based on this preliminary theory, we propose that, in some low-income and middle-income country markets, the interaction between demand-side and supply-side determinants results in market imperfections that, in turn, lead to patient movement across borders.

Ethics and dissemination

The study does not involve primary research and, therefore, does not require formal ethical approval; we do, however, follow the relevant standards of utility, usefulness, feasibility, propriety, accuracy and accountability. The standards of realist and meta-narrative evidence synthesis (RAMESES) will be adhered to in reporting the findings of the review. Once completed, the findings of the resulting manuscript will be published in a peer-reviewed journal.

Trial registration number

This protocol has been registered with PROSPERO, registration number CRD42014014391.
Spectra of graphene nanoribbons with armchair and zigzag boundary conditions
Authors: Freitas Pedro , Siegl Petr
Published: November 2014

We study the spectral properties of the two-dimensional Dirac operator on bounded domains together with the appropriate boundary conditions which provide a (continuous) model for graphene nanoribbons. These are of two types, namely, the so-called armchair and zigzag boundary conditions, depending on the line along which the material was cut. In the former case, we show that the spectrum behaves in what might be called a classical way; while in the latter, we prove the existence of a sequence of finite multiplicity eigenvalues converging to zero and which correspond to edge states.
Bounded properties of curvatures of perturbed Ricci metric on curve moduli
Authors: Zhu Xiaorui
Published: November 2014

As is well-known, the Weil–Petersson metric ωWP on the moduli space ℳg has negative Ricci curvature. Hence, its negative first Chern form defines the so-called Ricci metric ωτ. Their combination [Formula: see text], C > 0, introduced by Liu–Sun–Yau, is called the perturbed Ricci metric. It is a complete Kähler metric with finite volume. Furthermore, it has bounded geometry. In this paper, we investigate the finiteness of this new metric from another point of view. More precisely, we will prove in the thick part of ℳg, the holomorphic bisectional curvature of [Formula: see text] is bounded by a constant depending only on the thick constant and C0 when C ≥ (3g - 3)C0, but not on the genus g.