Composite production riser assessment

The performance of a deep water composite production riser from a system perspective is presented, and its advantages are articulated through comparisons with a typical steel riser under identical service conditions. The composite riser joints in this study were considered to be a part of a single Tension Leg Platform (TLP) riser string to be installed at a depth of 6000 ft in Gulf of Mexico. A series of numerical analyses âÂÂburst, collapse, fatigue, global and local â have been performed, and the capacities of the composite riser have been determined utilizing long-term strength properties. The capacities associated with the hoop direction, i.e., burst and collapse, are limited by the presence of a steel internal liner whose function is to ensure pressure and fluid tightness. The collapse capacity of the riser can be drastically impaired by the presence of a debond between the liner and composite. Due to the high strength to weight ratio of the carbon/epoxy composite, its response under combined axial tension and bending moment showed great safety margins, favoring pursuits of greater water depths. The study also constructed damage envelopes associated with axial tension and bending moment, which facilitate feasibility checks for expanding the use of the composite joints to other locations or systems. The fatigue life of the composite body is expected to greatly exceed its design life, and the most critical element is the welds between the liner and metal end pieces. Since there is wide dispersion of S-N relationships for carbon/epoxy composites depending on the combinations of constituent materials, a parametric study was carried out in this study to suggest the range of acceptable S-N relationships. The composite riser is estimated to offer only moderate damping, due primarily to its specially orthotropic lay-up. The study also demonstrates that the use of Rayleigh stiffness proportional damping may not be suitable for deep water risers. A series of forced excitation analyses show that the system in sea water does not show notable resonance due to fluid drag. When compared with the steel riser, vibration amplitudes at low elevations are much lower

Symmetry-breaking motility of penetrable objects in active fluids

We investigate how a symmetric penetrable object immersed in an active fluid becomes motile due to a negative drag acting in the direction of its velocity. While similar phenomena have been reported only for active fluids that posses polar or nematic order, we demonstrate that such motility can occur even in active fluids without any preexisting order. The emergence of object motility is characterized by both continuous and discontinuous transitions associated with the symmetry-breaking bifurcation of the object's steady-state velocity. Furthermore, we also discuss the relevance of the transitions to the nonmonotonic particle-size dependence of the object's diffusion coefficient.Comment: 14 pages, 9 figure

Emergency microsurgical embolectomy in acute ischemic stroke with diffusion-negative MRI

Although diffusion-weighted imaging (DWI) is highly sensitive and specific for the detection of acute ischemic injury, there are increasing reports that it may fail to demonstrate an acute stroke. Here, we present a case involving an acute ischemic stroke with a false-negative DWI in a 64-year-old woman who had undergone an emergency microsurgical embolectomy for an occluded middle cerebral artery (MCA). Although the endovascular mechanical embolectomy failed in treating the occluded MCA, we were able to successfully treat our patient with the second treatment option of a microsurgical embolectomy. Microsurgical embolectomy might be the treatment of choice, especially if the mechanical catheter is expected to not be able to access the target artery due to tortuous vascular structures

Effect of Feeding Whole Crop Barley Silage on Growth Performance, Carcass Trait and Meat Quality of Hanwoo Steer

Hanwoo steers are one of the major sources of meat, required for increasing consumer demands in Korea, Japan, and China. Beef contained high levels of saturated fat, and it contains appreciable quantities of linolenic acid, eicosapentaenoic acid and docosahexaenoic acid. Optimum growth can obtain with appropriate combination of concentrate and forage. Fattening of Hanwoo on concentrate-based feeds resulted in faster, more efficient growth and heavier carcasses. However, feed costs represent the largest single variable in beef production in Korea and Japan. The grass is generally the cheapest source of feed available for beef production, which provides high yields with quality herbage. Grass-feed based production systems are low-input methods that are particularly suitable to meet the demand of meat retailers and consumers. Therefore, in Korea, the combination of roughage and concentrates are commonly available in the market is used for rearing Hanwoo. Especially, the study of manufacturing silage using whole crop barley or whole crop rye was carried out to expand the usage of roughage. Barley is an important crop cultivated for the production of high-quality forage in Korea and Japan. However, the benefits of feeding diet combinations of concentrate and barley silages from growing period to finishing the period of Hanwoo steer have not been evaluated. The objectives of this study were to compare the growth performance, meat quantity and quality characteristics in Hanwoo steers fed barley silage/concentrate and rice straw/concentrate diet

Two-point discrimination values vary depending on test site, sex and test modality in the orofacial region: a preliminary study

The two-point discrimination (TPD) test is one of the most commonly used neurosensory tests to assess mechanoperception in the clinical settings. While there have been numerous studies of functional sensibility of the hand using TPD test, there have been relatively not enough reports on TPD in the orofacial region. Objective The aims of the present study were to determine the normal values of TPD in the six trigeminal sites (the forehead, cheek, mentum, upper lip, lower lip, and the tongue tip) and to investigate the effect of the site, sex, and test modality on the TPD perception. Material and Methods Forty healthy volunteers consisting of age-matched men (20) and women (20) with a mean age of 27.1 years were recruited. One examiner performed the TPD test using a simple hand-operated device, i.e., by drawing compass with a blunt or sharp-pointed tip. The static TPD with a blunt-pointed tip (STPDB), moving TPD with a blunt-pointed tip (MTPDB), and static TPD with a sharp-pointed tip (STPDS) were measured. The predictors were the site, sex, and test modality, and the outcome variable was the TPD value. Three-way ANOVA was used for statistics. Results The analysis showed a significant effect of the site, sex and test modality on the TPD values. Significant differences between the test sites were observed with the descending order from the forehead and cheek>;mentum>;upper lip and lower lip>;tongue tip and index finger. Women showed lower TPD values than those of men. The STPDS measurements were consistently lower than those of the STPDB and MTPDB. Conclusions The normal values of TPD in this study suggest that the cheek and forehead were less sensitive than other regions evaluated and women were more sensitive than men. The STPDS was the most sensitive test modality