Cutter-path generation using multiple cutting-tool sizes for 2-1/2D pocket machining

Existing commercial CAD/CAM systems allow the user to generate the cutter-path for machining a 2-1/2D pocket by using only a single cutting-tool size. Therefore, to avoid potential problems, such as gouging and unmachined areas, the user tends to choose the size of the cutting-tool in a conservative manner. This can result in longer processing time and higher production cost than those that can be achieved by using multiple cutting-tool sizes to machine a given pocket. The key to cutter-path generation using multiple cutting-tool sizes lies in having an efficient mechanism for representing the material volumes that can be removed by a specified cutting-tool size and the unmachined material volumes that will remain after its use. In this paper, we develop a novel concept called the Voronoi mountain and describe its application to cutter-path generation using multiple cutting-tool sizes. The theoretical significance of this approach stems from its ability to: (i) to create a Voronoi mountain representation of unmachined material volumes without having to construct the corresponding Voronoi diagram; and (ii) to accommodate generalized pocket geometries.     

Efficacy trial of a brief cognitive–behavioral depression prevention program for high-risk adolescents: Effects at 1- and 2-year follow-up.

Objective: To evaluate the effects of a brief group cognitive–behavioral (CB) depression prevention program for high-risk adolescents with elevated depressive symptoms at 1- and 2-year follow-up. Method: In this indicated prevention trial, 341 at-risk youths were randomized to a group CB intervention, group supportive expressive intervention, CB bibliotherapy, or educational brochure control condition. Results: Significantly greater reductions in depressive symptoms were shown by group CB participants relative to brochure control participants by 1-year follow-up and bibliotherapy participants by 1- and 2-year follow-up but not relative to supportive expressive participants. Supportive expressive participants showed greater symptom reduction than CB bibliotherapy participants did at 2-year follow-up. Risk for onset of major or minor depression over the 2-year follow-up was significantly lower for group CB participants (14%; odds ratio = 2.2) and CB bibliotherapy participants (3%; odds ratio = 8.1) than for brochure controls (23%). Conclusions: Results indicate that this group CB intervention reduces initial symptoms and risk for future depressive episodes, although both supportive expressive therapy and CB bibliotherapy also produce intervention effects that persist long term. Indeed, CB bibliotherapy emerged as the least expensive method of reducing risk for future episodes of depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Echocardiogram in common (single) ventricle: angiographic-anatomic correlation

Common ventricle is a rare congenital anomaly in which the ventricular chamber receives blood from two separate atrioventricular (A-V) valves or a common A-V valve. Diagnosis of common ventricle was established in 55 patients aged 3 months to 33 years (mean 10 years) at cardiac catheterization in all 55 and at operation or autopsy in 24. In common ventricle with two angiographically demonstrable A-V valves (47 patients), the echocardiographic features included: (1) simultaneous recording (in the same sonic beam with the transducer held stationary) of the echoes of an anterior and a posterior A-V valve without an intervening septal echo (45 of 47 patients); (2) absence, on a base to apex scan, of the ventricular septal echo in the usual position separating the A-V valves (47 of 47 patients); (3) recording, in patients with common ventricle and outflow chamber, of this small outflow chamber anterior to the A-V valves (20 of 23 patients); and (4) recording of echographic continuity of the posterior A-V valve and great artery (27 of 31 patients). In common ventricle with a common A-V valve (8 patients), the echocardiographic features included: (1) a single demonstrable A-V valve, located posteriorly in the ventricle, which showed a large amplitude of excursion during diastole; and (2) absence of a second A-V valve echo or ventricular septal echo. Eight patients were studied postoperatively after surgical correction by ventricular septation. Echographic features included visualization of a prosthetic septum that produced a dense echo and divided the common ventricle into "right" and "left" ventricular chambers. This septum had a large excursion anteriorly during systole. Because common ventricle is now amenable to surgical correction, echocardiography should play an important role in assessment of ventricular anatomy in this complex congenital cardiac defect.     

Ce对Fe-Cr合金高温氧化行为的影响

Fe-15Cr 和 Fe-30Cr 合金在1000至1200℃空气中氧化时,表面富铁氧化伤的发展导致保护性Cr_2O_3层衰退,氧化速率增大。添加 Ce 可延迟衰退过程的发生,从而大幅度减低氧化速率。随氧化温度和合金成份变化,Cr_2O_3层衰退的开始时间和发展特征随之改变,Ce 对氧化行为的影响因而呈现出规律性的变化。研究发现,合金中 Cr 的内氧化使 Cr_2O_3层形成小舌包卷合金并使其氧化成富铁氧化物。这是Cr_2O_3层衰退的原因之一。含 Ce 合金中 Ce 的优先内氧化则降低自氧化层进入合金的氧浓度,抑制Cr 的内氧化。氧浓度降低还能促进 Si 的内氧化物在氧化层/合金界面集聚。     

Probability Models for the Splitting Algorithm in Wireless Access Networks with Multipacket Reception and Finite Nodes

In this paper, we propose an analytical approach for performance evaluation of the classic tree/stack splitting algorithm in an interference-dominating wireless access network with random traffic and finite nodes. In an interference-dominating wireless access network, a receiver could simultaneously receive multiple packets from a variety of transmitters, as long as the signal-to-interference-plus-noise ratio exceeds a predetermined threshold. We use discrete-time Markov chains and regenerative processes to derive the throughput curve, the packet blocking probability, the average system size, and the average packet delay. We show that the exact performance of the splitting algorithm depends on the total number of nodes in the network. We verify our numerical results by rigorous mathematical proof and computer simulations.     

Testing mediators of intervention effects in randomized controlled trials: An evaluation of two eating disorder prevention programs.

The authors investigated mediators hypothesized to account for the effects of 2 eating disorder prevention programs using data from 355 adolescent girls who were randomized to a dissonance or a healthy weight intervention or an active control condition. The dissonance intervention produced significant reductions in outcomes (body dissatisfaction, dieting, negative affect, bulimic symptoms) and the mediator (thin-ideal internalization), change in the mediator correlated with change in outcomes and usually occurred before change in outcomes, and intervention effects became significantly weaker when change in the mediator was partialed, providing support for the hypothesized mediators and this new approach to testing mediation in randomized trials. Findings provide somewhat less support for the hypothesis that change in healthy eating and exercise would mediate the healthy weight intervention effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aerodynamique de l'ecoulement vertical de suspensions concentrees gaz—solide—II. Chute de pression et vitesse relative gaz—solide

In the second part of this study on concentrated gas—solid flow, we analyse the pressure drop and the gas—solid slip velocity data. The particles were transported in cylindrical pipes, 3·8 cm and 5 cm dia, at volumic concentrations ranging from 0·5 per cent to 22 per cent and at gas velocities ranging from 1 m/sec to 17 m/sec. The observed phenomena are fairly different from those specific to diluted pneumatic transport usually reported in the literature.Thus for fine catalyst particles the pressure drop is in some cases only equal to a half of the weight of the suspension while the slip velocity may reach 300 times the value of the free fall velocity.     

An effectiveness trial of a selected dissonance-based eating disorder prevention program for female high school students: Long-term effects.

Objective: Efficacy trials found that a dissonance-based eating disorder prevention program in which female high school and college students with body image concerns critique the thin ideal reduced eating disorder risk factors, eating disorder symptoms, and future eating disorder onset. The present effectiveness trial tested whether this program produces effects through long-term follow-up when high school clinicians recruit students and deliver the intervention under real-world conditions. Method: Female high school students with body image concerns (N = 306; M age = 15.7 years, SD = 1.1) were randomized to the dissonance intervention or an educational brochure control condition and completed assessments through 3-year follow-up. Results: Dissonance participants showed significantly greater decreases in body dissatisfaction at 2-year follow-up and eating disorder symptoms at 3-year follow-up than controls; effects on other risk factors, risk for eating disorder onset, and other outcomes (e.g., body mass) were marginal or nonsignificant. Conclusions: Although it was encouraging that some key effects persisted over long-term follow-up, effects were on average smaller in this effectiveness trial than previous efficacy trials, which could be due to (a) facilitator selection, training, and supervision; (b) the lower risk status of participants; or (c) the use of a control condition that produces some effects. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Joint AoA and Channel Estimation for SIMO- OFDM Systems: A Compressive-Sensing Approach

Millimeter-wave (mmWave) transmission has been considered in future fifth generation (5G) communication systems. Since the pathloss in mmWave is severe, beamforming with antenna arrays, an enabling technology in the 5G era, will become a must. To conduct receive beamforming, however, we need to know the information about the angle-of-arrival (AoA). In this paper, we consider joint AoA and channel estimation for single-input-multiple-output (SIMO) OFDM systems. As known, wireless channels are sparse, and this is particularly true for mmWave environments. Conventional compressive-sensing (CS) based channel estimation methods only consider single-input-single-output systems. We propose new matching-pursuit-based CS methods for channel estimation in SIMO-OFDM systems, using frequency-domain pilots. With the estimated channels, AoA’s are then estimated by the maximum-likelihood method. Since a hidden parameter is involved in the problem, an expectation-maximization (EM) algorithm is then employed. The Cramer-Rao lower bound (CRLB) is also derived for the AoA estimation. Simulation results show that the proposed channel estimation can significantly outperform existing methods while the proposed AoA estimation attains the CRLB.