Flat Component Research Articles

Effects of curved geometry on residual stress in laser peening

Prevention of failure in materials has been extensively researched for centuries by people all over the world. Sustained or cyclic loading is a major cause of failure in many situations. There can be other contributing factors, such as manufacturing defects and the presence of unfavorable residual stresses. But residual stresses can also play a positive role and can enhance the life of the component, if applied properly. Laser peening (LP) is a surface enhancement technique that can impede crack initiation and propagation by inducing favorable compressive residual stresses in the peened components. Laser peening can generate deeper compressive stresses compared with other surface enhancement techniques, such as shot peening, and it has been used to improve the fatigue life of components in aerospace, automotive and medical applications. In this work, the effects of laser peening are studied by using two dimensional finite element simulation models created with ABAQUS©. Crack initiation often occurs along the curved regions or fillets of structural components because of the presence of high stress concentrations. These critical regions are modeled as a curved geometry to capture the curvature effects using simulation models. Concave and convex simulation models are created and compared with flat geometry to investigate the effects of curvature in a laser peening problem. A mechanism of residual stress generation in curved models is used to explain the residual stress results obtained from finite element models. The results predict that increasing the radius of curvature in a concave model decreases the compressive residual stress generated in the component while increasing the radius of curvature of a convex model increases the compressive residual stress induced in the material when compared with a flat component.

Micro-scanning system using flat optics for resolution improvement of infrared images

There are some problems in the traditional micro-scanning approach which is based on flat optical component (FOC). For example, the scanning germanium glass of Archimedes spiral is hard to be manufactured and there is image distortion (we called it as image-rotating) which makes the infrared images blurry. These problems limit the ability of ascending the spatial resolution of infrared images. In this paper, we brought forward a new micro-scanning approach based on FOC. We improved the shape of scanning germanium glass from Archimedes spiral to arc and adopted quasi-discrete scanning motion (acceleration motion–deceleration motion–uniform motion) to the micro-scanner. Both the subjective images and the objective data indicate that the new micro-scanning approach based on FOC raised in this paper improve the spatial resolution of infrared images more effectively than traditional micro-scanning approach.

Low Warpage Flip-Chip Under-Fill Curing

Mechanical stress in flip-chip assemblies continues to be a significant problem both for the reliability of the component and for the assembly of a flat component to the next board-level assembly. This paper describes the combination of unique low-temperature multi-step curing profiles with the use of variable frequency microwaves (VFM) to produce lower warpage components both on the die side of the package as well as on the board carrier side. This lower warpage compared to standard convection cure is maintained even after three sequential lead-free solder reflow conditions. Statistical data support this improved co-planarity by Shadow Moire measurements at various stages of processing from as-received parts through prebake, cure, and three reflow cycles. Typical co-planarity improvement in the 12-65 percent range is observed and verified by confirmation sample sizes used for microwave cured parts and conventional box oven cured parts. Thinned and larger die, and reduced thickness substrate boards showed the most warpage improvement with VFM. Two under-fill chemistries show the same effect despite lower cure temperatures and faster cure cycle times.

Blue-black rule: a simple dermoscopic clue to recognize pigmented nodular melanoma

Dermoscopy improves melanoma recognition, but most criteria were described in the context of superficial spreading melanoma. To test whether pigmented nodular melanoma could be recognized dermoscopically by the presence of a combination of blue and black colour within the lesion. Dermoscopic images of histopathologically diagnosed pigmented nodular tumours with no (or only minimal) flat component were evaluated for the presence of standard melanoma criteria and for the presence of a new feature named blue-black (BB) colour. Sensitivity, specificity, positive predictive value and negative predictive value were calculated for standard criteria and BB feature in relation to the diagnosis of melanoma and to diagnosis of malignancy. Of 283 lesions, 160 were malignant, including 78 (27·6%) melanomas, and 123 were benign. The BB feature and the standard criteria had 78·2% and 43·6% sensitivity for melanoma, respectively, whereas a combined method based on the presence of either the BB feature or one (or more) of the standard criteria reached 84·6% sensitivity, with 80·5% specificity and 93·2% negative predictive value. Sensitivity values for malignant lesions were only 24·4%, 56·9% and 60% for standard criteria, BB feature and the combined method, respectively. However, the combined method gave 91·9% specificity and 90·6% positive predictive value for malignancy. Using a method based on the BB feature or one of the standard melanoma criteria, only 9·4% of positive pigmented nodular lesions were found to be benign and only 6·8% of negative lesions were found to be melanoma histopathologically.

ACCELERATION OF PARTICLES AT THE TERMINATION SHOCK OF A RELATIVISTIC STRIPED WIND

The relativistic wind of obliquely-rotating pulsars consists of toroidal stripes of opposite magnetic field polarity, separated by current sheets of hot plasma. By means of two- and three-dimensional particle-in-cell simulations, we investigate particle acceleration and magnetic field dissipation at the termination shock of a relativistic striped wind. At the shock, the flow compresses and the alternating fields annihilate by driven magnetic reconnection. Irrespective of the stripe wavelength "lambda" or the wind magnetization "sigma" (in the regime sigma>>1 of magnetically-dominated flows), shock-driven reconnection transfers all the magnetic energy of alternating fields to the particles, whose average Lorentz factor increases by a factor of sigma with respect to the pre-shock value. The shape of the post-shock spectrum depends primarily on the ratio lambda/(r_L*sigma), where r_L is the relativistic Larmor radius in the wind. The spectrum becomes broader as the value of lambda/(r_L*sigma) increases, passing from a relativistic Maxwellian to a flat power-law tail with slope around -1.5, populated by particles accelerated by the reconnection electric field. Close to the equatorial plane of the wind, where the stripes are symmetric, the highest energy particles resulting from magnetic reconnection can escape ahead of the shock, and be injected into a Fermi-like acceleration process. In the post-shock spectrum, they populate a power-law tail with slope around -2.5, that extends beyond the flat component produced by reconnection. Our study suggests that the spectral break between the radio and the optical band in Pulsar Wind Nebulae can be a natural consequence of particle acceleration at the termination shock of striped pulsar winds.

Trigger Board for the Auger Surface Detector With 100 MHz Sampling and Discrete Cosine Transform

The surface detector array of the Pierre Auger Observatory contains 1600 water Cherenkov detectors spread over an area of 3000 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The Cherenkov light is detected by three 9-inch photomultiplier tubes from which the signals of the anode and last dynode are digitized by 10 bit ADCs. The currently used Front-End Boards equipped with the ACEX <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> and Cyclone <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> FPGA are sampled with 40 MHz. New requirements from the Auger North (100 MHz) and AMIGA (80 MHz) specification as well as the proposal of new spectral triggers based on the 16-point Discrete Cosine Transform (DCT) impose a new Front End Boards with more powerful FPGA chip with a sufficient amount of DSP blocks. The DCT trigger allows recognition of ADC traces with a very short rise time and fast exponential attenuation related to a narrow, flat muon component of very inclined extensive air showers generated by hadrons and starting their development early in the atmosphere. Ten prototype boards equipped with Altera <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> Cyclone <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> III FPGA have been fabricated and successively tested in the lab and in real pampas conditions in six test surface detectors within April 19 - July 26, 2009. Boards contain only a single FPGA chip, which implements also the slow channel, in previous three generations supported by the external Dual-Port RAM. Tests confirmed full stability and high reliability of the digital part. Both lab and field tests confirm a high efficiency of the recognition of expected patterns of ADC traces.

UNIFYING A BOXY BULGE AND PLANAR LONG BAR IN THE MILKY WAY

It has been known for sometime that the Milky Way is a barred disk galaxy. More recently several studies inferred from star count observations that the Galaxy must contain a separate, new, flat long bar component, twisted relative to the barred bulge. Here we use a simulation with a boxy bulge and bar to suggest that these observations can be reproduced with a single structure. In this simulation, a stellar bar evolved from the disk, and the boxy bulge originated from it through secular evolution and the buckling instability. We calculate star count distributions for this model at different longitudes and latitudes, in a similar way as observers have done for resolved star counts. Good agreement between the simulation and the observations can be achieved for a suitable snapshot, even though the simulation has a single boxy bulge and bar structure. In this model, part of the long bar signature is due to a volume effect in the star counts, and another part is due to choosing a snapshot in which the planar part of the boxy bulge and bar has developed leading ends through interaction with the adjacent spiral arm heads. We also provide predictions from this model for the line-of-sight velocity distributions at the longitudes with the long bar signature, for comparison with upcoming surveys.

Structural advantages of rectangular-like channel cross-section on electrical characteristics of silicon nanowire field-effect transistors

We have experimentally demonstrated structural advantages due to rounded corners of rectangular-like cross-section of silicon nanowire (SiNW) field-effect transistors (FETs) on on-current ( I ON), inversion charge density normalized by a peripheral length of channel cross-section ( Q inv) and effective carrier mobility ( μ eff ). The I ON was evaluated at the overdrive voltage ( V OV) of 1.0 V, which is the difference between gate voltage ( V g) and the threshold voltage ( V th), and at the drain voltage of 1.0 V. The SiNW nFETs have revealed high I ON of 1600 μA/μm of the channel width ( w NW) of 19 nm and height ( h NW) of 12 nm with the gate length ( L g) of 65 nm. We have separated the amount of on-current per wire at V OV = 1.0 V to a corner component and a flat surface component, and the contribution of the corners was nearly 60% of the total I ON of the SiNW nFET with L g of 65 nm. Higher Q inv at V OV = 1.0 V evaluated by advanced split-CV method was obtained with narrower SiNW FET, and it has been revealed the amount of inversion charge near corners occupied 50% of all the amount of inversion charge of the SiNW FET ( w NW = 19 nm and h NW = 12 nm). We also obtained high μ eff of the SiNW FETs compared with that of SOI planar nFETs. The μ eff at the corners of SiNW FET has been calculated with the separated amount of inversion charge and drain conductance. Higher μ eff around corners is obtained than the original μ eff of the SiNW nFETs. The higher μ eff and the large fractions of I ON and Q inv around the corners indicate that the rounded corners of rectangular-like cross-sections play important roles on the enhancement of the electrical performance of the SiNW nFETs.

Influencing factors of microscanning performance based on flat optical component

To decrease the performance difference between the actual microscanning thermal imager and the theoretical value, a germanium lens (placed at a certain angle between the infrared focal plane array and infrared lens) dip angle model of flat optical component microscanning is introduced in this letter. The model is the basis for choosing the dip angle of the germanium lens, which is used in the microscanning thermal imager. In addition, the actual dip angle of the germanium lens is chosen according to the model, the infrared lens parameters of the thermal imager, and the germanium lens parameters of manufacture and installation. Only in this manner can the optimal performance of the microscanning thermal imager based on the flat optical component be obtained. Results of the experiments confirm the accuracy of the conclusions above.

Environmental Tax and the Distribution of Income among Heterogeneous Workers

This paper analyzes the environmental tax policy issues when labor is heterogeneous. The objective is to assess whether an environmental tax policy could be Pareto improving, when the revenue of the pollution tax is recycled by a change in the labor tax properties. We show that, depending on the heterogeneity characteristics of labor and on the initial structure of the tax system, a policy mix could be designed in order to leave each class of workers unharmed. It consists of an increase in progressivity together with a decrease in the flat rate component of the wage tax.

The universal distribution of halo interlopers in projected phase space

When clusters of galaxies are viewed in projection, one cannot avoid picking up foreground/background interlopers (FBIs), that lie within the virial cone (VC), but outside the virial sphere. Structural & kinematic deprojection equations are not known for an expanding Universe, where the Hubble flow (HF) stretches the line-of-sight (LOS) distribution of velocities. We analyze 93 mock relaxed clusters, built from a cosmological simulation. The stacked mock cluster is well fit by an m=5 Einasto DM density profile (but only out to 1.5 virial radii [r_v]), with velocity anisotropy (VA) close to the Mamon-Lokas model with VA radius equal to that of density slope -2. The surface density of FBIs is nearly flat out to r_v, while their LOS velocity distribution shows a dominant gaussian cluster-outskirts component and a flat field component. This distribution of FBIs in projected phase space is nearly universal in mass. A local k=2.7 sigma velocity cut returns the LOS velocity dispersion profile (LOSVDP) expected from the NFW density and VA profiles measured in 3D. The HF causes a shallower outer LOSVDP that cannot be well matched by the Einasto model for any k. After this velocity cut, FBIs still account for 23% of DM particles within the VC (close to the observed fraction of cluster galaxies lying off the Red Sequence). The best-fit projected NFW/Einasto models underestimate the 3D concentration by 6+/-6% (16+/-7%) after (before) the velocity cut, unless a constant background is included in the fit. Assuming the correct mass profile, the VA profile is well recovered from the measured LOSVDP, with a slight bias towards more radial orbits in the outer regions. These small biases are overshadowed by large cluster-cluster variations caused by cosmic variance. An appendix provides an analytical approximation to the surface density, projected mass and tangential shear profiles of the Einasto model.

Fee for Service, Outperformance or Assets Under Management? Indications from Generalized Log Utility

We investigate efficient fee structures for actively managed funds when both the investor-principal and the prospective manager-agent have utility functions of the generalized log variety. Efficient fees include a fixed component that reflects the manager’s protected consumption. This is a new rationale for a flat component of fees analogous to fee-for-service. Also new is our result that participation is not all or nothing. Specifically, the amount placed with the active manager is equal to the investor’s wealth less the present value of the total protected consumption of the investor and the manager. Efficient fees also include variable components reflecting total assets under management and performance relative to a passive benchmark.

Evidence for supernova-synthesized dust from the rising afterglow of GRB 071025 at z∼ 5

We present observations and analysis of the broadband afterglow of Swift GRB 071025. Using optical and infrared (RIYJHK) photometry, we derive a photometric redshift of 4.4 < z < 5.2; at this redshift our simultaneous multicolour observations begin at ~30 s after the GRB trigger in the host frame and during the initial rising phase of the afterglow. We associate the light curve peak at 580 s in the observer frame with the formation of the forward shock, giving an estimate of the initial Lorentz factor Gamma_0 ~ 200. The red spectral energy distribution (even in regions not affected by the Lyman-alpha break) provides secure evidence of a large dust column. However, the inferred extinction curve shows a prominent flat component between 2000-3000 Angstroms in the rest-frame, inconsistent with any locally observed template but well-fit by models of dust formed by supernovae. Time-dependent fits to the extinction profile reveal no evidence of dust destruction and limit the decrease in the extinction column to Delta A_3000 < 0.54 mag after t = 50 s in the rest frame. Our observations provide evidence of a transition in dust properties at z~5, in agreement with studies of high-z quasars, and suggest that SN-formed dust continues to dominate the opacity of typical galaxies at this redshift.

The evolution of chaos in active galaxy models with an oblate or a prolate dark halo component

AbstractThe evolution of chaotic motion in a galactic dynamical model with a disk, a dense nucleus and a flat biaxial dark halo component is investigated. Two cases are studied: (i) the case where the halo component is oblate and (ii) the case where a prolate halo is present. In both cases, numerical calculations show that the extent of the chaotic regions decreases exponentially as the scale‐length of the dark halo increases. On the other hand, a linear relationship exists between the extent of the chaotic regions and the flatness parameter of the halo component. A linear relationship between the critical value of the angular momentum and the flatness parameter is also found. Some theoretical arguments to support the numerical outcomes are presented. An estimation of the degree of chaos is made by computing the Lyapunov Characteristic Exponents. Comparison with earlier work is also made (© 2010 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Generalized D-Forms Have No Spurious Creases

A convex surface that is flat everywhere but on finitely many smooth curves (or seams) and points is a seam form. We show that the only creases through the flat components of a seam form are either between vertices or tangent to the seams. As corollaries we resolve open problems about certain special seam forms: the flat components of a D-form have no creases at all, and the flat component of a pita-form has at most one crease, between the seam’s endpoints.

Malignant Transformation of Congenital Hypertrophy of the Retinal Pigment Epithelium

To report a clinicopathologic correlation of an adenocarcinoma that arose from solitary congenital hypertrophy of the retinal pigment epithelium (CHRPE). Case report with clinicopathologic correlation. A 56-year-old black woman was referred for an asymptomatic fundus lesion in her left eye. It had features typical of CHRPE, but there was a small elevated nodule within the flat component, and the diagnosis was adenoma of the retinal pigment epithelium (RPE) arising from CHRPE. The lesion was observed periodically. The nodule slowly enlarged, and increasing amounts of lipoproteinaceous exudation accumulated in the adjacent retina. Thirteen years after the initial diagnosis, the patient returned with severe visual loss and no view of the fundus resulting from cataract and posterior synechia. Ultrasonography revealed a total retinal detachment and a pedunculated tumor measuring 7.5 mm in thickness. The eye was enucleated and studied histopathologically. Clinical evaluation and correlation of clinical findings with histopathologic results of the enucleated eye. Histopathologically, the mass was composed of a proliferation of atypical RPE cells with a marked infiltration of benign plasma cells. Typical features of CHRPE were present at the base of the tumor. The final diagnosis was adenocarcinoma arising from CHRPE. Congenital hypertrophy of the retinal pigment epithelium, once considered to be a benign and stationary lesion, may spawn a malignant neoplasm.

On the stabilizability of a structural acoustic model which incorporates shear effects in the structural component

In this paper we consider a linear three-dimensional structural acoustic model which takes account of displacement, rotational inertia and shear effects in the flat flexible structural component of the model. Thus the deflections of the structural component of the structure are governed by the Reissner–Mindlin plate equations. We show strong stabilization of the coupled model without incorporating viscous or boundary damping in the equations for the gas dynamics and without imposing geometric conditions. It turns out that damping is needed in the interior of the plate, to which end Kelvin–Voigt damping is introduced in the plate equations. As our main tool we use a resolvent criterion for strong stability due to Tomilov.

A spectral 1st level FPGA trigger for detection of very inclined showers based on a 16-point discrete cosine transform for the Pierre Auger Observatory

The paper describes a new spectral trigger based on the 16-point discrete cosine transform (DCT) algorithm that was implemented into an FPGA. The DCT trigger allows recognition of FADC traces with a very short rise time and fast exponential attenuation related to a narrow, flat muon component of very inclined extensive air showers generated by hadrons and starting their development early in the atmosphere. The discrete cosine transform, based on only real coefficients in the frequency domain, provides much more sensitive trigger conditions and a simpler interpretation in comparison to a discrete Fourier transform (DFT) that is based on complex coefficients or their absolute values. It also offers a scaling feature. The ratio of the DCT coefficients to the 1st harmonics depends only on the shape of signals, not on their amplitudes. However, an implementation of the DCT into an FPGA requires more resources than DFT even based on an FFT algorithm.

Langzeitergebnisse nach zementiert und zementfrei verankerter S.T.A.R.-Prothese beim Rheumapatienten

We report the clinical and radiological results of 65 S.T.A.R. prosthesis that were performed be-tween 1993 and July 2000 in our two institutions. Cementless fixation was used in 38 prosthesis and cement fixation in 27. Rheumatoid arthritis was the main diagnosis, with females dominating. The average follow-up was 9.3 years for cemented S.T.A.R. prostheses and 11.3 years for cementless S.T.A.R. prostheses. The follow-up was based on the Kofoed ankle score, which consists of three tests, one subjective dealing with pain and two objective parts about ankle function and mobility. 23 patients (77.4%) with cementless fix-ation achieved good and excellent results. The Kofoed ankle score improved from preoperatively 44.7 to an average of 80.7 points at final examination. The cemented S.T.A.R. prosthesis gained an average score of 76,3 postoperatively, representing 16 (64%) implants with good and excellent result. The mobility score showed a moderate rise in range of motion for extension and flexion (+8.5°), while a decrease in subtalar joint movement has been noted. This is due to additional subtalar and talonavikular arthrodesis. For cemented S.T.A.R.-prosthesis we had to recognise progressive radiolucent lines of the tibial component in 11 (44%) patients and talar subsidence in eight (32%). We had three tibial exchange arthroplasties and six arthrodesis due to prosthesis loosening. The radiographic analysis showed radiolucent lines of the flat tibial component in seven cases (22.5%) of the cementless prosthesis. Five (16%) times we had to recognise talar subsidence. We had to perform six (19.3%) revisions because of meniscal breakage or insufficient meniscal height. An exchange of the talar component was necessary twice. Three prosthesis had to be revised with arthrodesis due to symp-tomatic loosening. In conclusion, cementless ankle arthroplasty using the cementless S.T.A.R.-prosthesis proved excellent clinical and radiological long-term results, especially for rheumatoid patients. The success of ankle arthroplasty depends on careful indication, cementless fixation of a second generation total ankle arthroplasty and appropriate rehabilitation. Cement fixation in total ankle arthroplasty should be abandoned.

Strong stabilization of a structural acoustic model, which incorporates shear and thermal effects in the structural component

In this paper we consider the question of stabilization of a linear three-dimensional structural acoustic model, which incorporates displacement, rotational inertia, shear and thermal effects in the flat flexible structural component of the model. We show strong stabilization of the coupled model without incorporating viscous or boundary damping in the equations for the gas dynamics and without imposing geometric conditions. It turns out that damping is needed in the interior of the plate. Our main tool is an abstract resolvent criterion due to Y. Tomilov. Copyright © 2009 John Wiley & Sons, Ltd.