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In the machining of carbon fiber–reinforced plastic by abrasive waterjet, the surface morphology of the cutting front directly reflects the processing quality. So in this study, the changes in the topography and surface roughness of the cutting front as a result of variations in five operational parameters, namely, the traverse speed, abrasive mass flow rate, waterjet pressure, standoff distance, and sample thickness, were experimentally studied with the aid of μscan laser confocal microscopy. It was found that periodic stripes and grooves appeared in the traverse direction from observations of three-dimensional surface morphology. And the analysis of the surface roughness revealed that there were three distinct cutting regions along the penetration direction, namely, an initial damage region at the jet entry, a smooth cutting region in the intervening cutting area, and a rough cutting region near the jet exit. According to the three distinct regions in the penetration direction, a three-zone cutting front model was proposed. A high-quality machined surface could be obtained by extending the smooth cutting zone through the appropriate choice of process parameters. Therefore, the influences of the above five parameters on the length of the smooth cutting zone were also investigated, and recommendations are proposed for process control.

The jet fish pump is a potentially valuable tool for fish transport. Though jet fish pumps have been shown to cause the least damage to fish, cavitation as a commonly encountered flow phenomenon can lead to injury or death of fish. Experiments were conducted to investigate damage to tissue of Carassius auratus caused by different cavitation stages in a jet fish pump. Mortality was assessed for 48 h after the fish passed through the device. Tissues from swim bladders, livers and gills were examined. Fish were also examined for several important enzymes that are indicators of tissue injury. The results showed that cumulative mortalities of fish in cavitation operating conditions were higher than those in non-cavitation operating conditions at each sampling time. The cumulative mortality in the stable cavitation condition reached 55% within 48 h after the experiment. Two types of swim bladder damage, crumpling and rupturing, were found in 60% of the dead fish. The damage rate of swim bladders rose with the increase of cavitation, and broken swim bladders were found only in cavitation operating conditions. In addition, liver damage was found in those dead fish experiencing intensive cavitation operating conditions, and significantly high serum ALT and AST activity verified this damage. Free bubbles, an essential symptom of the gas bubble disease, were found in the gill filament of those fish experiencing intensive cavitation operating conditions. The significantly high serum LDH activity indicated that fish experienced intense anaerobic respiration during intensive cavitation operating conditions. Judging from the significant serum Cr content, cavitation in the jet fish pump also posed a potential risk for the kidneys of fish. Moreover, a pressure damage experiment showed that rupturing of swim bladders occurred in the recompression process; environmental pressure between 40 kPa and 58 kPa was a transition area for pressure damage to swim bladders in vitro. Swim bladders in vitro were safe when environmental pressure was above 58 kPa, yet they were broken when environmental pressure was less than 40 kPa. This study illustrates that intensive cavitation is a dangerous flow phenomenon for fish in a jet fish pump and should be avoided in practical applications.

Replacing the batteries of wearable medical devices is an inconvenience to the user. Wireless power transfer (WPT) could be a solution for this problem. However, the structure should be compact to satisfy the wearable device requirements and the power efficiency should be as high as possible for prolonging the user experience. Besides, as algorithms embedded in these devices become more complex, the device power consumption also increases. Fulfilling these specifications in a compact structure with better efficiency is the aim of this research paper. This paper proposes a power processing module for WPT applications. This module is embedded within the WPT path to convert receiving end ac power to dc power, and to simultaneously provide multiple dc–dc power conversion for wearable medical devices. The ac–dc circuit is specifically designed using a compact topology to convert wireless ac power to stable dc power. The dc power is further regulated by different mode controls either to perform battery charging or to provide independent voltage supplies to dc loads. The integrated circuit occupies an area of 1.9 × 2.3 mm when implemented on a 0.25 μm high voltage CMOS process.

The present paper describes a jet fish pump designed to safely convey fish in the aquatic industry due to its simple structure and reduced tendency to cause mechanical injury. High-speed imaging, physiology investigations and CFD simulations are used to demonstrate the impacts of the flow on the grass carp during transport in the jet fish pump for various operating conditions. The results show that none of the tested fish were dead, had organ injuries or had swimming problems after passing through the jet fish pump. The respiratory rates and most of the blood indexes of the tested fish were affected by the flow field in the pump, but they were able to recover to normal levels after just 24 h. The surface injuries such as descaling and operculum injuries were mainly caused by recirculation flows, shear flows and pressure gradients. Further analyses indicated that bruising was caused by the flow direction changes, with cavitation potentially causing eye injuries. A deflection number, C d , was proposed to describe the amount of flow direction changes for various operating conditions in the jet fish pump. The results show that, even though shear flows and pressure gradients are inevitable, the jet fish pump operating conditions can be optimized to reduce the risk of fish injuries. Recirculation regions and intensive cavitation should be avoided since they may cause serious injuries in the fish, reduce the fish transport rate and reduce the flow efficiency. These results provide a basis for improved jet fish pump designs.

We consider the classification of sparse functional data that are often encountered in longitudinal studies and other scientific experiments. To utilize the information from not only the functional trajectories but also the observed class labels, we propose a probability-enhanced method achieved by weighted support vector machine based on its Fisher consistency property to estimate the effective dimension reduction space. Since only a few measurements are available for some, even all, individuals, a cumulative slicing approach is suggested to borrow information across individuals. We provide justification for validity of the probability-based effective dimension reduction space, and a straightforward implementation that yields a low-dimensional projection space ready for applying standard classifiers. The empirical performance is illustrated through simulated and real examples, particularly in contrast to classification results based on the prominent functional principal component analysis.

Objective High channel count electrode arrays allow for the monitoring of large-scale neural activity at high spatial resolution. Implantable arrays featuring many recording sites require compact, high bandwidth front-end electronics. In the present study, we investigated the use of a small, light weight, and low cost digital current-sensing integrated circuit for acquiring cortical surface signals from a 61-channel micro-electrocorticographic (μECoG) array. Approach We recorded both acute and chronic μECoG signal from rat auditory cortex using our novel digital current-sensing headstage. For direct comparison, separate recordings were made in the same anesthetized preparations using an analog voltage headstage. A model of electrode impedance explained the transformation between current- and voltage-sensed signals, and was used to reconstruct cortical potential. We evaluated the digital headstage using several metrics of the baseline and response signals. Main results The digital current headstage recorded neural signal with similar spatiotemporal statistics and auditory frequency tuning compared to the voltage signal. The signal-to-noise ratio of auditory evoked responses (AERs) was significantly stronger in the current signal. Stimulus decoding based on true and reconstructed voltage signals were not significantly different. Recordings from an implanted system showed AERs that were detectable and decodable for 52 d. The reconstruction filter mitigated the thermal current noise of the electrode impedance and enhanced overall SNR. Significance We developed and validated a novel approach to headstage acquisition that used current-input circuits to independently digitize 61 channels of μECoG measurements of the cortical field. These low-cost circuits, intended to measure photo-currents in digital imaging, not only provided a signal representing the local cortical field with virtually the same sensitivity and specificity as a traditional voltage headstage but also resulted in a small, light headstage that can easily be scaled to record from hundreds of channels.

Conventional wearable medical devices need batteries to sustain reliable power for the circuits. Battery replacement is usually inconvenient to the user experience. Wireless power transfer (WPT) could be the solution for this problem. However, wearable medical devices have their intrinsic specifications that could be challenges to the WPT. Their structures should be concise for the wearable needs. Power efficiency should be made as high as possible for prolonging the user experience. Besides, more computing based algorithms embedded in these devices would require more power consumption. How to fulfill these specifications is the aim of this research work. This paper proposes a wireless power processing module that integrate AC-DC and multi- DC-DC power circuits together for wearable medical devices. The AC-DC circuit is specifically designed using a concise topology to enhance power conversion efficiency. The DC power is further regulated by different mode controls to facilitate battery charging or to provide multiple voltage outputs. The integrated circuit is implemented by a 0.25 µm high voltage CMOS process with 1.9 µm × 2.3 µm circuit dimensions.

In this paper, the performance of a code-division multiple-access (CDMA) cellular system with various traffic types is examined. Traffic integration and resource management are two major issues in the design of the next generation of wireless networks with integrated services. To provide design guidelines for traffic integration, the impact of the line rate (actual transmission bit rate in the radio channel) selection on the system capacity is examined. Since in a CDMA system the signal from one specific user is spread over the entire available bandwidth, the actual bandwidth resource occupied by a user depends on the amount of the transmission power of the user. In this paper, we also address how to assign suitable power levels to the different traffic types. A method for optimizing the power assignment for multiple traffic types is developed.

The minimum description length (MDL) principle originated from data compression literature and has been considered for deriving statistical model selec- tion procedures. Most of the existing methods that use the MDL principle focus on models with independent data, particularly in the context of linear regression. This paper considers data with repeated measurements and studies the selection of fixed effect covariates for linear mixed effect models. We propose a class of MDL procedures that incorporate the dependence structure within individual or clus- ter and use data-adaptive penalties that suit both finite and infinite dimensional data generating mechanisms. Theoretical justifications are provided from both data compression and statistical perspectives, where the covariance of random effects is treated as known or estimated by maximum likelihood. Numerical experiments are conducted to demonstrate the usefulness of the proposed MDL procedure and the influence of the estimated covariance, and an application to U.S. EPA data for air quality control is provided.

The viability of device to device (D2D) communication on uplink resources [1] as also the benefits accruing from network control over such communication, on licensed spectrum [2], are quite well understood today. We investigate the merits of a particular system instantiation based on these two tenets. The challenge of scheduling communication between two devices using remote schedulers at one or more base stations is addressed with minimal changes to the current signaling mechanisms in a 3GPP LTE based framework. This system maintains as tight a control over device to device communication as is currently maintained over device to infrastructure communication. Furthermore the benefits of such a system range from optimized routing and resource allocation to metered charging for data exchanged on the D2D link to lawful intercept to dynamic local broadcast. We also provide a comparison of this system with the available option of D2D communications over unlicensed spectrum using Wi-Fi.

In this paper, we analyze multi-cell multi-user interference through a new approach. The area averaged probability density function (PDF) of interference power from one active user is evaluated. Differing from the distance membership determination, the statistical effect of hand-off is considered. The Gamma distribution is proposed to model the area averaged PDF of the interference power of an active user. An efficient method for evaluating system performance is developed. Differing from the Gaussian approximation, this method is very effective and accurate for both a large number and a small number of users. The performance of a CDMA cellular system with high quality requirements and mixed traffic is evaluated.

The authors identify a new limiting factor, hop timing error, in regard to the phase coherence for coherent frequency hopped spread spectrum (C-FHSS) communications. A phase-lock system model and the Fokker-Planck equation are applied to examine the phase acquisition process for every hop. The acquisition time in certain cases, including the worst cast, is obtained for evaluating whether the C-FHSS system is practical. The relationship between the system error performance and the acquisition time is established through the phase error tolerance bound. It is shown that the hopping rate is substantially restricted by the acquisition time. >

Most conventional optimum or good bias schemes of importance sampling may be over biased for the simulation of a class of communication systems with information feedback. A new concept of the whole estimator is introduced. In addition to the estimation variance, the confidence interval and confidence level are mainly considered as the criteria of optimizing bias schemes. The nature of new optimum bias schemes is found through rigorous analysis. >

Analyzes the multi-cell multi-user interference through a new approach. The statistical effect of hand-off is considered. Differing from the Gaussian approximation, an efficient method for evaluating the performance of a system with small number of users is developed.

We obtain both the mean and variance of multicell multiuser interference power in a CDMA cellular system with non-ideal handoff and power control. We investigate the effects of handoff operation and choice of line rate (bit transmission rate through the channel) on the Erlang capacity. We consider the call arrival statistics, user membership statistics and finite number of channels available at a base-station in our evaluation of the call dropping rate. The minimum number of channels required at a base-station to ensure a specified quality of service at a given capacity requirement is determined. System capacity is further evaluated considering both the outage probability limited by interference and call dropping rate limited by the finite number of channels.