Maximum Angular Deviation Research Articles

Fuzzy Logic based Greedy Routing (FLGR) in Multi-Hop Vehicular Ad hoc Networks

In Vehicular Ad Hoc Network (VANET), vehicles on the road provide mainly two types of services to drivers or passengers inside vehicles, namely, safety and comfort services. Safety messages are time-critical, therefore in this paper we have proposed a novel Fuzzy Logic based Greedy Routing (FLGR) protocol which assists in delivering safety messages to the destination vehicle with minimum delay. The proposed FLGR is a multi-hop routing protocol that uses multiple metrics of neighbor vehicles to decide which neighboring vehicle will be the approximate best next-hop node for further forwarding the packets. We have used the concept of fuzzy logic that helps in decision making in VANETs. Fuzzy logic deals with reasoning that is approximate rather than fixed and exact. Fuzzy logic variables may have truth values that range in degrees between 0 and 1. The fuzzy logic inference system became important and useful when the values of the decision criteria are not only vague but uncertain in nature. FLGR is used within the communication range of the current forwarding node that employs fuzzy logic for selecting the best next-hop node in multi hop VANETs. We have used the fuzzy logic tool box of MATLAB to evaluate our protocol. Metrics such as distance, speed, direction, and position of next-hop forwarding node are put into fuzzy logic system. Thus, our protocol helps in finding the approximate best next-hop node for routing the safety messages by employing fuzzy logic. It selects the next-hop node having maximum distance, speed, and progress and minimum angular deviation of nodes towards destination from current forwarding node. Further, FLGR is more suitable for safety applications in vehicular networks.

A Simplified Close‐Range Photogrammetric Technique for Soil Erosion Assessment

Surface reconstruction using digital photogrammetry offers a great advantage for soil erosion research. The technology can be cumbersome for field application because it relies on the accurate measurement of control points, often using a survey‐grade instrument. Also, even though digital photogrammetry has been used in much soil erosion research, its sensitivity in detecting soil elevation changes has rarely been assessed. This study aimed at simplifying the digital photogrammetric procedure for soil erosion research and assessing the sensitivity of this technology to detect soil erosion. To simplify the technology, we propose to combine a photogrammetric procedure for control point generation in a first step, followed by a conventional photogrammetric digital elevation model (DEM) extraction procedure. The performance of the method was assessed in the laboratory and tested in the field to digitize ephemeral gullies. In the accuracy test of photogrammetric survey step, we found that the maximum length measurement error was 3.4 mm, while the maximum angular deviation from the vertical or horizontal axes was 0.93°. The maximum error between control point coordinates generated by photogrammetry and those generated by a survey‐grade total station was 26 mm on the horizontal axes and 10 mm on the vertical axis. We also found that the sensitivity of digital photogrammetry in detecting soil surface elevation changes was similar to that of a laser scanner when the detection was performed on smooth soil surfaces and when the standard deviation of the elevation changes was approximately three times the precision of the photogrammetric DEM.

A custom-made guide-wire positioning device for Hip Surface Replacement Arthroplasty: description and first results

BackgroundHip surface replacement arthroplasty (SRA) can be an alternative for total hip arthroplasty. The short and long-term outcome of hip surface replacement arthroplasty mainly relies on the optimal size and position of the femoral component. This can be defined before surgery with pre-operative templating. Reproducing the optimal, templated femoral implant position during surgery relies on guide wire positioning devices in combination with visual inspection and experience of the surgeon. Another method of transferring the templated position into surgery is by navigation or Computer Assisted Surgery (CAS). Though CAS is documented to increase accurate placement particularly in case of normal hip anatomy, it requires bulky equipment that is not readily available in each centre.MethodsA custom made neck jig device is presented as well as the results of a pilot study.The device is produced based on data pre-operatively acquired with CT-scan. The position of the guide wire is chosen as the anatomical axis of the femoral neck. Adjustments to the design of the jig are made based on the orthopedic surgeon's recommendations for the drill direction. The SRA jig is designed as a slightly more-than-hemispherical cage to fit the anterior part of the femoral head. The cage is connected to an anterior neck support. Four knifes are attached on the central arch of the cage. A drill guide cylinder is attached to the cage, thus allowing guide wire positioning as pre-operatively planned.Custom made devices were tested in 5 patients scheduled for total hip arthroplasty. The orthopedic surgeons reported the practical aspects of the use of the neck-jig device. The retrieved femoral heads were analyzed to assess the achieved drill place in mm deviation from the predefined location and orientation compared to the predefined orientation.ResultsThe orthopedic surgeons rated the passive stability, full contact with neck portion of the jig and knife contact with femoral head, positive. There were no guide failures. The jig unique position and the number of steps required to put the guide in place were rated 1, while the complexity to put the guide into place was rated 1-2. In all five cases the guide wire was accurately positioned. Maximum angular deviation was 2.9° and maximum distance between insertion points was 2.1 mm.ConclusionsPilot testing of a custom made jig for use during SRA indicated that the device was (1) successfully applied and user friendly and (2) allowed for accurate guide wire placement according to the preoperative plan.

Complex rhombus lattice photonic crystals for broadband all-angle self-collimation

In this paper, we discuss two-dimensional photonic crystals of complexrhombus lattice structures to enable broadband, ‘all-angle’ light collimation.The proposed structures are made of complex elliptical dielectric rods (ε = 12) embedded in an air background. Based on the equi-frequency contours (EFCs) calculated bythe plane wave expansion method (PWEM), these structures show a wide range of open, nearlyflat EFCs, with the maximum angular deviation from the primary collimating direction less than2°. The broadest relative range of these open, nearly flat EFCs found is 17% of a chosencentral wavelength. For a sample element centered at 1550 nm, this range coverswavelengths from 1429 to 1695 nm; the devices can be scaled to cover alternativewavelength ranges. These structures could benefit applications that require a broadoperating wavelength range. Potential applications include collimating beam combiners,multiplexers and solar light collectors.

Multipurpose Navigation System-Based Concept for Surgical Template Production

We present a concept that uses the multipurpose navigation equipment of a university hospital for computed tomography (CT)-guided surgical template production, to improve the preclinical accuracy of the templates. Oral implants are planned on CT images with respect to the prosthodontic goal and anatomical considerations. Registration is performed via a modified Vogele-Bale-Hohner (VBH) mouthpiece (Medical Intelligence GmbH, Schwabmuenchen, Germany) and an external registration frame. In the laboratory, an optical navigation system is used to transfer the plan to the patient's registered dental stone cast for surgical template production. During preclinical evaluation, duplicated stone casts were drilled via the obtained surgical templates. Accuracy was evaluated by matching the preoperative CT to the CT of the drilled stone casts. Compared with present registration mouthpieces, the VBH mouthpiece requires only the dental impression of the patient's stone cast. In contrast to surgical navigation, an aiming device is used for navigated trajectory-alignment at the best technical level. There is no need for a positioning device, and the template can be immediately fabricated in a standard laboratory. The accuracy of 5 surgical templates showed a maximum normal deviation of 1.4 mm, and maximum angular deviations of 2.8 degrees . The presented concept allows for successful production of CT-guided surgical templates, and may show sufficient accuracy for clinical use.

Paleomagnetic constraints on the Holocene stratigraphy of the Arctic Alaskan margin

Two long Holocene piston cores (HLY0501-06JPC and -08JPC; herein after referred to as 6JPC and 8JPC) were raised from high sediment accumulation areas in the Arctic Alaskan margin in order to reconstruct the millennial- to centennial-scale behavior of Earth's magnetic field and to better constrain the regional chronostratigraphy of the Western Arctic. Paleomagnetic analyses using a u-channel cryogenic magnetometer (natural, anhysteretic and isothermal remanent magnetizations: NRM, ARM and IRM) and a vibrating sample magnetometer indicate that a strong and stable single component characteristic remanent magnetization carried by low coercivity pseudo-single domain (PSD) grains such as magnetite can be isolated in the postglacial unit of both cores, where the inclination values vary around the geocentric axial dipole (GAD) for the latitude of the coring sites and where the maximum angular deviation (MAD) values are generally lower than 5°. Apart from one interval in each core, all the derived relative paleointensity proxies (NRM/k LF, NRM/ARM and NRM/IRM) yield similar results. NRM/IRM was used as the preferred proxy because, based on cross-spectral analysis, it is not coherent with its normalizer. Based on the comparison with paleomagnetic records from Western North America, the paleomagnetic and physical analyses indicate that both sedimentary sequences have recorded some of the first reliable Arctic high-resolution records of paleomagnetic secular variation (inclination and declination) and relative paleointensity during the Holocene. In addition, full vector paleomagnetic correlations (inclination, declination and relative paleointensity) were used to constrain the chronology of core 6JPC, using core 8JPC and other previously published and independently dated sedimentary and volcanic records from Western North America. The Accelerator Mass Spectroscopy (AMS) radiocarbon-based postglacial chronology of core 8JPC indicates sedimentation rates higher than 300 cm/kyr on the continental shelf near Barrow Canyon from approximately 8000 to 5000 cal BP, followed by a major decrease in sediment deposition. In contrast, the postglacial deposition on the slope at core site 6JPC is relatively constant and sedimentation rates are nearly three times lower.

Holocene Sediment Magnetic Properties along a Transect From Ísafjardardjúp to Djúpáll, Northwest Iceland

ABSTRACTHolocene changes in terrestrial provenance and processes of sediment transport and deposition are tracked along a fjord-to-shelf transect adjacent to Vestfirdir, Iceland, using the magnetic properties of marine sediments. Magnetic susceptibility (MS) profiles of 10 cores (gravity and piston) were obtained onboard using a Bartington MS loop. Remanent magnetizations were measured at 1-cm intervals from u-channel samples taken from six cores on a cryogenic magnetometer. Between six and nine alternating field demagnetization steps were used to isolate the characteristic magnetization directions. The chronologies of the cores used in this study were determined from AMS 14C dates on mollusks and foraminifera and constrained by the regional occurrence of the 10,200 ± 60 cal yr. BP Saksunarvatn tephra. Correlative fluctuations in magnetic concentration are noted between the fjord and shelf sites, though these fluctuations are partially masked by regional variations in carbonate content. The onset of Neoglaciation is interpreted by changes in magnetic properties including an increase in mass magnetic susceptibility that began approximately 3000 cal yr. BP. The maximum angular deviation and the median destructive field (generally <20 mT) suggest that the natural remanent magnetization is carried by a coarse ferrimagnetite mineralogy, likely magnetite or titano-magnetite. Reproducible paleomagnetic inclination values are observed in several records, including a nearly vertical inclination around 8000 cal yr. BP, suggesting that the magnetic pole may have been proximal to Iceland, followed by an interval of much shallower inclination (6000–7000 cal yr. BP).

Optimizing LINAC-based stereotactic radiotherapy of uveal melanomas: 7 years’ clinical experience

Purpose: To report on the clinical outcome of LINAC-based stereotactic radiotherapy (SRT) of uveal melanomas. Additionally, a new prototype (hardware and software) for automated eye monitoring and gated SRT using a noninvasive eye fixation technique is described. Patients and Methods: Between June 1997 and March 2004, 158 patients suffering from uveal melanoma were treated at a LINAC with 6 MV (5 × 14 Gy; 5 × 12 Gy prescribed to 80% isodose) photon beams. To guarantee identical patient setup during treatment planning (CT and MRI) and treatment delivery, patients were immobilized with a BrainLAB thermoplastic mask. Eye immobilization was achieved by instructing the patient to fixate on a light source integrated into the mask system. A mini-video camera was used to provide on-line information about the eye and pupil position, respectively. A new CT and magnetic resonance (MR) compatible prototype, based on head-and-neck fixation and the infrared tracking system ExacTrac, has been developed and evaluated since 2002. This system records maximum temporal and angular deviations during treatment and, based on tolerance limits, a feedback signal to the LINAC enables gated SRT. Results: After a median follow-up of 33.4 months (range, 3–85 months), local control was achieved in 98%. Fifteen patients (9.0%) developed metastases. Secondary enucleation was performed in 23 patients (13.8%). Long-term side effects were retinopathy (<i>n</i> = 70; 44%), cataract (<i>n</i> = 30; 23%), optic neuropathy (<i>n</i> = 65; 41%), and secondary neovascular glaucoma (<i>n</i> = 23; 13.8%). Typical situations when preset deviation criteria were exceeded were slow drifts (fatigue), large sudden eye movements (irritation), or eye closing (fatigue). In these cases, radiation was reliably interrupted by the gating system. In our clinical setup, the novel system for computer-controlled gated SRT of uveal melanoma was well tolerated by about 30 of the patients treated with this system so far. Conclusion: LINAC-based SRT of uveal melanomas provides good local control. The new prototype system improves the quality of treatment and offers the possibility of movement-gated treatments. In an ongoing study, treatment-related side effects are correlated with dose levels. Such correlations can be used to further optimize linac-based SRT of uveal melanoma.

Paleomagnetism, rock-magnetism and geochemical aspects of early Cretaceous basalts of the Paraná Magmatic Province, Misiones, Argentina

Abstract The basalts of the Posadas Formation were extruded during the huge continental volcanism that affected the Paraná Basin in the Lower Cretaceous. We have carried out a paleomagnetic and rock-magnetic study on samples collected along a basalt outcrop section in Misiones, Argentina and determined that rocks classified as tholeiitic basalts and andesi-basalts are characterized by a low to intermediate content of Ti. Paleomagnetic and rock-magnetic studies suggest that the main magnetic mineral is low-Ti titanomagnetite of superparamagnetic (SP) to single-domain (SD) sizes, and very low amounts of multi-domain (MD) particles. The stable magnetic remanence enabled us to define characteristic remanent magnetizations (ChRMs) with a maximum angular deviation (MAD) &lt;5° in most cases; and in all the cases, a MAD &lt;10°. The sequence has registered at least two polarity reversions, starting from a normal polarity at the base. The calculated virtual geomagnetic poles (VGPs) present an elongated distribution similar to other distributions of VGPs published for the Paraná Magmatic Province. The elongated distribution of the VGPs could be a real feature of the geomagnetic field at a time of frequent changes of polarity.

Geometric aspects of lattice contrast visibility in nanocrystalline materials using HAADF STEM

In conventional high-resolution transmission electron microscopy (HRTEM) imaging on nanopolycrystalline materials , the surprising abundance of lattice fringe contrast has been readily explained by the geometric relationship between the Ewald sphere and the streaking of reciprocal lattice spots from small crystals. However, in high-angle annular dark field (HAADF) imaging in scanning transmission electron microscopy (STEM) the same interference considerations do not apply. We present a new method to quantify the probability of seeing lattice contrast from a set of random crystals by estimating as a function of instrumental resolution, the range of angular misorientations from each crystallographic pole, which can give rise to lattice contrast. The maximum angular deviation for common HAADF imaging conditions has been experimentally determined by tilting perfect silicon off pole. The visibility of single and multiple sets of fringes has been successfully predicted for a range of microscope resolutions and for two materials of different unit cell sizes. As many as 70% of randomly oriented nanocrystals can be expected to show fringes in an aberration-corrected STEM.

User‐friendly software for vector analysis of the magnetization of long sediment cores

New software is described that is designed for easy visualization and treatment of stepwise demagnetization of the natural remanent magnetization measured along sediment cores with pass‐through magnetometers. The software displays demagnetization diagrams (Zijderveld plots) at successive horizons for any depth interval selected by the user. Paleomagnetic directions are automatically calculated using principal component analysis, with an anchored or a free origin. The demagnetization steps to be considered for the diagram visualization and paleodirection calculations are selected by the user. Maximum angular deviation angles and median destruction fields are also calculated. All the results are stored in a single data sheet, which can be easily exported. Demagnetization diagrams can be printed and copied. This Microsoft Excel software can be used by PC or Macintosh microcomputers.

Automatic real‐time surveillance of eye position and gating for stereotactic radiotherapy of uveal melanoma

A new prototype (hardware and software) for monitoring eye movements using a noninvasive technique for gated linac-based stereotactic radiotherapy (SRT) of uveal melanoma was developed. The prototype was tested within the scope of a study for 11 patients. Eye immobilization was achieved by having the patient fixate a light source integrated into the system. The system is used in conjunction with a Head&Neck mask system for immobilization, and uses infrared tracking technology for positioning (both BrainLAB AG Heimstetten/Germany). It was used during CT and MR image acquisition as well as during all of five treatment fractions (6 MeV, 5 x 12 Gy to 80% isodose) to guarantee identical patient setup and eye rotational state during treatment planning and treatment delivery. Maximum temporal and angular deviations tolerated during treatment delivery can be chosen by the physician, the radiation then being interrupted automatically and instantaneously if those criteria are being exceeded during irradiation. A graphical user interface displays life video images of the treated eye and information about the current and previous rotational deviation of the eye from its reference treatment position. The physician thus has online access to data directly linked to the success of the treatment and possible side effects. Mean angular deviations during CT/MR scans and treatment deliveries ranged from 1.61 degrees to 3.64 degrees (standard deviations 0.87 degrees to 2.09 degrees ) which is in accordance with precision requirements for SRT. Typical situations when preset deviation criteria were exceeded are slow drifts (fatigue), sudden large eye movements (irritation), or if patients closed their eyes (fatigue). In these cases radiation was reliably interrupted by the gating system. In our clinical setup the novel system for computer-controlled eye movement gated treatments was well tolerated by all patients. The system yields quantitative real-time information about the eye's rotational state with respect to a reference position (treatment planning situation). Together with the possibility of performing movement-gated treatments of uveal melanoma, the system thus greatly improves the quality of this treatment.

Plio‐Pleistocene time‐averaged field in southern Patagonia recorded in lava flows

Paleomagnetic directions were obtained from stepwise alternating‐field or thermal demagnetization of 53 lava flows from southern Patagonia (latitudes 49.5°–52.1°S) that include the Pali‐Aike volcanic field and the Meseta Viscachas plateau lavas. In addition to previous Miocene‐late Quaternary ages of these flows, 40Ar/39Ar dates spanning from 0.1 to 15.4 Ma were obtained for 17 of the sites. All except one of the magnetic polarities coincide with the expected polarities of the magnetic polarity timescale [Cande and Kent, 1995] for the obtained 40Ar/39Ar ages. The mean direction from 33 sites (eliminating sites ≥4 Ma) that pass a selection criteria of α95 ≤ 5° is Dec = 358.7°, Inc = −68.2°, α95 = 3.5°, a value that coincides within the statistical uncertainty with the direction of the geocentric axial dipole for that area (Inc = −68.1°). Likewise, the mean virtual geomagnetic pole (VGP) coincides within the statistical uncertainty with the geographic North Pole. The secular variation described by the VGP angular standard deviation for these sites is 17.1°, a value expected for that latitude according to Model G of paleosecular variation [McFadden et al., 1988]. The characteristics of the data presented are optimum for time‐averaged field (TAF) studies because of the good age control and good quality of the paleomagnetic data: (1) primary components of magnetization were obtained using principal component analysis [Kirschvink, 1980] from at least five points and maximum angular deviation ≤5°, (2) site means were calculated with Fisher statistics using at least three samples, and (c) 38 of the 53 flows had α95 ≤ 5°. No results (five sites) or high α95 values (&gt;5°) were obtained primarily from sites affected by lightning.

On a More Restrictive Geometric Criterion for “Special” CSL Grain Boundaries

Although widely used for the characterization of grain boundaries within the coincidence site lattice (CSL) [1] framework, the application of Brandon’s criterion [2] for allowable angular deviation (i.e., Du # 15 S degrees), has often resulted in grain boundaries which do not display ‘special’ behavior being classified as low-S CSL’s; thus prompting some debate as to the overall validity of the CSL model. Other more restrictive criteria have previously been proposed; all of which being based upon the low angle approximation of the Read-Shockley relation [3], u'b/d, where u is the misorientation angle, b is the magnitude of the Burgers vector of grain boundary dislocations, and d is the dislocation spacing. The criterion of Ishida and McLean [4] considers a S dependence for Du based upon b being proportional to the two minimum Burgers vectors of the DSC lattice (i.e., S) [5], and the minimum dislocation spacing, d, being proportional to the boundary plane periodicity for symmetrical tilt grain boundaries (i.e., S). Deschamps et al [6], in attempting to generalize the criterion to all grain boundaries (i.e., symmetrical and asymmetrical tilt, twist) proposed a S dependence by considering a dislocation spacing (d) proportional to a mean edge (p) of the CSL lattice [5] (S) and a Burgers vector magnitude (b) varying on average as the mean edge of the DSC lattice [5] (S). Palumbo and Aust [7] showed that since the third Burgers vector of the DSC lattice is independent of S [5], b can only vary as S; this yielding a S dependence for the maximum allowable angular deviation. Early experimental support for the Palumbo-Aust criterion [7], Du # 15° S, was obtained by (1) a review of transmission electron microscopy studies [8] for the resolution of discrete intrinsic grain boundary dislocations [9], and (2) controlled electrochemical etching studies conducted with high purity Ni in sulphuric acid media [7]. More recently, Pan et al [10] demonstrated that Brandon’s criterion was not applicable in discerning crack-resistant grain boundaries in alloy X-750; however, in this study [10] grain boundaries classified as CSL’s using the more restrictive Palumbo-Aust criterion were indeed found to display ‘special’ cracking-resistant behaviour. With recent advances in automated electron backscatter diffraction techniques [11] and the emergence of commercial applications for ‘grain boundary engineered’ materials [12, 13], the structureproperty database upon which to evaluate the applicability of these criteria for ‘special’ behaviour has been expanded significantly. In this work, the relative applicability of the widely used Brandon criterion and the more restrictive Palumbo-Aust criterion is investigated by evaluation of experimental results pertaining to the corrosion, cracking, and creep cavitation susceptibility of several commercial metals Pergamon Scripta Materialia, Vol. 38, No. 11, pp. 1685–1690, 1998 Elsevier Science Ltd Copyright © 1998 Acta Metallurgica Inc. Printed in the USA. All rights reserved. 1359-6462/98 $19.00 1 .00 PII S1359-6462(98)00077-3

Minor influence of sialic acid on conformation of a membrane-bound oligosaccharide recognition site.

Wideline 2H NMR spectroscopy was used to assess the conformational and orientational effects of N-acetylneuraminic acid (NeuAc) (sialic acid) as a component of a particular oligosaccharide chain at a bilayer membrane surface. For this purpose, three glycosphingolipids, sharing a neutral core tetrasaccharide and differing only in the number of sialic acid residues, were compared. The starting compound was GD1A, which has terminal sialic acid attached to the second and fourth sugars of its neutral tetrasaccharide core. GD1A was probe-labeled in a non-perturbing fashion on both of these sialic acid residues and on its single GalNAc residue by replacement of -COCH3 with -COCD3 giving [(d3NeuAc)2,d3-GalNAc]GA1a. This represents the most complex glycolipid to have been studied by 2H NMR spectroscopy at a bilayer membrane surface. The sialic acid residue on the fourth sugar from the membrane was subsequently removed to produce the glycolipid [d3NeuAc,d3GalNAc]GM1, deuterated at the two remaining amino sugars. The neutral glycolipid [d3GalNAc]asialo-GM1 was then generated by removal of the second sialic acid residue, leaving an uncharged species deuterated at one (internal) oligosaccharide chain site (GalNAc). The effect of sialic acid was futher examined by selective deuteration of GM1 and asialo-GM1 at C6 of the terminal Gal residue, giving [d2Gal]GM1 and [d2Gal]asialo-GM1. Spectra of the three glycosphingolipids were compared at 7.7 mol % in unsoncicated fluid bilayers of 1-palmitoyl-2-oleoylphosphatidylcholine containing 23 mol % cholesterol. For liposomes suspend in buffered salt solutions with 2 mM Ca2+, 2H NMR spectra demonstrated the presence of well defined average conformation for each oligosaccharide chain. This preferred average conformation persisted over a wide temperature range, consistent with there being a single major oligosaccharide conformer in each case. Spectral features arising from both deuterated amino sugar (GalNAc) of asialo-GM1 could be identified, little changed, in spectra of GM1 and GD1A. Similarly, deuterons in the terminal Gal residue of asialo-Gm1 produced the same spectrum seen for this residue in GM1. Our findings indicate that certain major conformational and orientational features of this complex oligosaccharide recognition site are preserved, within maximum angular deviation + or -5 degrees or less upon addition or removal of a sialic acid residue.

Trunk and head stabilization during the first months of independent walking.

This study measured the rate of acquisition of head and trunk postural control during the two early developmental periods of independent walking, as defined by global gait parameters. Gait parameters were observed longitudinally in four children. The maximum angular deviations of the trunk and head oscillations were computed in the frontal and sagittal planes. These decreased most dramatically during the first 10-15 weeks of independent walking, during the same period when global gait parameters changed rapidly. This head and trunk stabilization may be a fundamental process that help to maintain equilibrium during walking, and may be a necessary step prior to the development of fine posturo-motor control.

A Modified Selective Precision Synthesis Technique for Planar Four-Bar Rigid-Body Guidance

The selective precision synthesis (SPS) technique is modified by adopting the displacement matrix approach and using binary links as basic elements. This modified SPS (MSPS) can thus be applied to the synthesis of slider-crank mechanisms as well. With the introduction of ‘maximum allowable angular deviation’, the mechanism construction error (MCE) at a design point can be eliminated. The link length adjustment is also found to be a useful tool for the case of infinite MCE. The proposed MSPS is shown to be logical and effective by a practical design example.

Paleomagnetism of the Brushy Basin Member of the Morrison Formation: Implications for Jurassic apparent polar wander

The paleomagnetism of the ∼147 Ma (Tithonian) Brushy Basin Member of the Morrison Formation was analyzed to obtain a Late Jurassic paleomagnetic pole for North America. A total of 200 samples were collected from 25 sedimentary horizons (sites) at Norwood Hill in southwest Colorado. At Montezuma Creek in southeast Utah, 184 samples were collected from 26 sites. Detailed thermal demagnetization (up to nine temperature steps between 600°C and 680°C) and principal component analysis were required to confidently isolate characteristic remanent magnetization (ChRM) directions carried by hematite. Demagnetization behavior for many horizons is erratic and does not allow isolation of a high unblocking‐temperature ChRM. Data selection criteria required sample ChRM directions to be defined by three or more thennal demagnetization steps and maximum angular deviations of sample ChRM directions to be ≤20°. Eight sites from the Norwood Hill location and 10 sites from the Montezuma Creek location passed these criteria. The 18 site‐mean virtual geomagnetic poles yield a paleomagnetic pole position from the Brushy Basin Member of 68.3°N, 156.2°E (A95 = 4.8°, K = 53). This pole position is within 2° of the paleomagnetic pole which Steiner and Helsley (1975a) reported for the “upper” Morrison Formation at Norwood Hill, Colorado. A second paleomagnetic pole was calculated after excluding sites with site‐mean α95 &gt; 20° and sites with fewer than three samples that passed the above selection criteria. This additional editing did not significantly change the paleomagnetic pole position at the 95% confidence level. Along with other paleomagnetic poles from the continental interior the paleomagnetic data from the Brushy Basin Member of the Morrison Formation are interpreted to indicate that the Late Jurassic part of the North American apparent polar wander path progresses from a late Middle Jurassic (∼160 Ma) position at ∼60°N, 135°E toward the mid‐Cretaceous pole position at 72°N, 191°E.

Crystal structure and mössbauer spectroscopy studies of the ferrimagnetic complex bimetallic salt hexaamminechromium (III) hexachloroferrate (III), [Cr(NH3)6][FeCl6

The crystal and molecular structures of the ferrimagnetic bimetallic complex salt hexaamminechromium(III) hexachloroferrate(III), [Cr(NH3)6][FeCl6], have been determined from single-crystal, three-dimensional x-ray diffraction counter data. The compound crystallizes as orange coloured crystals in the space groupC2/c of the monoclinic system with Z=4 and has cell dimensionsa=11.325(1) A,b=11.387(1) A,c=11.233(1) A, and β=90.83(1)A. The structure was refined by using segmented block diagonal least-squares techniques to discrepancy indices R and Rw of 0.0233 and 0.0285, respectively. The metal ions occupy sites with symmetry\(\bar 1\) and are nearly octahedrally coordinated. In the [FeCl6]3− anion there are three independent Fe−Cl distances with a mean of 2.393(2) A, and the maximum angular deviation from octahedral geometry is 1.20. In the [Cr(NH3)6]3+ cation, the mean of the three independent Cr−N distances is 2.079 (7) A, and the maximum angular deviation from octahedral geometry is 0.70. The structural data provide an explanation for the observed quadrupole splitting of 0.214 mms−1 as seen in the Mossbauer spectrum at 292.6 K and reveal superexchange pathwaysvia close amine proton-chloride anion contacts with lead to 3D-ferrimagnetic ordering near 2.8 K.

Axial transport of granular solids in rotating cylinders. Part 2: Experiments in a non-flow system

Experiments are reported here on the axial mixing of sodium carbonate and sodium bicarbonate in a batch, horizontal, rotating cylinder. The results show the effect of hold-up, particle size and speed of rotation on the axial dispersion coefficient and are interpreted in terms of the stochastic transport model recently proposed by the authors. A complementary approach invoking a surface diffusion coefficient in the thin cascade layer is also presented and applied to the data. This surface diffusivity forms a more fundamental transport parameter than the axial dispersion coefficient, and collisional theories of rapid flows of solids should provide a suitable route for its prediction. Correlations are developed here which relate the maximum angular deviation (defined in Part I), and the surface diffusion coefficient, with the characteristic translational kinetic energy and describe well the effect of variations in particle size, hold-up and speed of rotation.