Presence Of Slits Research Articles

Dependence of resistivity of natural rock samples on humidity

Rock resistivity measurements under non-wet conditions are essential for interpreting subsurface shallow resistivity structure. This study investigated the resistivity of rock samples collected from several locations around the Nakadake craters of Aso Volcano, Japan. The resistivity of rock samples exhibited a logarithmically linear relationship with changes in absolute humidity, corresponding to possible seasonal variations and correlating with the porosity of rocks. As the samples maintained an identical cylindrical shape and size, the observed variations in humidity were unrelated to the external surface area but were caused by the internal pore structure of rocks. Furthermore, the external surface area of homogeneous granite was artificially varied using slits and its measured resistivity did not vary in the presence of slits. The measured distribution of electrical potential was well explained by a homogeneous model, and less so by a two-layer model, indicating that the region of resistivity change was not restricted to the surface of the sample, but rather covered the entire sample. Further, changes in resistivity in response to absolute humidity were caused by the adsorption of water molecules onto minerals at internal pore surfaces, as evidenced by the measured temporal scale of resistivity change based on a simple concentration–diffusion process of gaseous water molecules caused by humidity changes in the external environment. These findings imply significant variations in the resistivity of shallow subsurfaces owing to humidity changes; thus, the consideration of humidity is important for the interpretation of subsurface shallow resistivity structures.

The effects of rib shape and slit on fatigue properties of orthotropic steel decks

Orthotropic steel decks are composed of comparatively thin steel plates (as thin as 6 mm) that deform in the in-plane and out-of-plane directions at longitudinal-to-transverse rib connections in response to vehicle loads. Since such deformations can change as the load positions move, local stress directions can also vary such that hot spots along the weld toes are moved and the relationship between the load position and hot spot stress becomes complex. Furthermore, the deformations will differ depending on the specific type of connection. The present work investigated the effects of rib shapes and slits (that is, cut-outs) on the fatigue properties of such connections by calculating structural hot spot stresses at various connections by finite element analyses. The hot spot locations along weld toes were determined to vary depending on the load position, the longitudinal rib shape, and the presence of slits. It was also found that the load positions associated with maximum and minimum hot spot stresses at slit connections tended to be eccentric relative to the center axes of the evaluated ribs.

Investigation of thermal performance of modified vertical rectangular fin array in free convection using experimental and numerical method

Heat transfer by free convection from fin array is influenced by modification in size and shape of the fins as well as interruption in fluid flow. The objective of heat sink is the thermal management of electronic devices by removing excessive heat and improve the lifespan of the device. The paper investigates the thermal performance of free convection heat transfer with vertical heat sink by providing slits along the vertical surface of the fins. For the evaluation purpose two different arrangements viz. plain fin and slitted fin are selected. Fins are made from high thermal conductivity aluminium material and five dissimilar heat inputs are selected for study. The experimental and numerical findings are confirmed using the theoretical correlations available from the literature.The effect of number of slits and width of slits is investigated on convective heat transfer coefficient. Numerical study is used to understand the flow patterns around the vertical fin surface. It has been observed that the presence of slits on the surface appreciably improves the thermal performance of vertical fin array.

Experimental analysis of additively manufactured thin-walled heat-treated circular tubes with slits using AlSi10Mg alloy by quasi-static axial crushing test

In this study, additively manufactured aluminum thin-walled tubes with different slit dimensions are proposed to improve energy absorption efficiency. A total of 18 samples, which varied in the number of slits, slit length, slit width, and slit ends, were tested under quasi-static axial compression at a rate of 20 mm/min. The deformation and failure modes, load-displacement curves, and a number of crashworthiness factors were investigated. The factors considered included, but were not limited to, the specific energy absorption, crushing force efficiency, and energy absorbed per stroke. The results indicated that all the considered physical parameters, except for the slit ends, had an influence on the crashworthiness of the structures. The initial peak load decreases significantly as the number, width, and length of the slits increase. The bulk of the tested tubes exhibited a crushing force efficiency greater than 0.8. Overall, the presence of slits with length 15 mm and width 5 mm resulted in lower and smoother crushing forces than the straight tubes and, therefore, greater crushing force efficiency, validating them as crashworthy structures.

Study on the Cooling Effect of Attached Fins on PV Using CFD Simulation

The issue of efficiency decrease according to temperature increase is a pending problem in the PV market. Several active and passive technologies have been suggested but few quantitative studies on the estimation of the cooling effect have been carried out. In this study, a CFD (computational fluid dynamics) simulation model was developed to analyze a passive cooling technology using fins attached to the back of the PV module. Furthermore, a method to improve airflow at the back of the PV module by forming slits in the frame was analyzed. The simulation model reproduced the indoor test that uses a solar simulator and the cooling performance was analyzed according to the shape of the fins and the presence of slits. In the simulation results, the surface temperature and expected electrical efficiency without cooling were 62.78 °C and 13.24% respectively under nominal operating cell temperature conditions. Moreover, the temperature reduced by approximately 15.13 °C because the fins attached at the bottom of the PV module increased the heat transfer area with airflow. Thus, the electrical efficiency according to the PV module temperature was predicted as 14.39%. Furthermore, when slits were installed between the fins, they increased the airflow velocity and accelerated the formation of turbulence, thereby improving the cooling performance of the fins. The simulation results showed that the temperature could be further reduced by approximately 8.62 °C at a lower air velocity. As the fins and slits can also reduce the non-uniformity of the temperature, they are expected to supplement the efficiency and durability reduction of the PV modules caused by the hot spot phenomenon. In addition, it was shown that slits in the frame could further improve the cooling performance of the fins at a low-velocity airflow.

Signaling from Within: Endocytic Trafficking of the Robo Receptor Is Required for Midline Axon Repulsion.

Signaling from Within: Endocytic Trafficking of the Robo Receptor Is Required for Midline Axon Repulsion.

Maxillary sinus floor augmentation with vegetal hydroxyapatite "versus" demineralized bovine bone: A randomized clinical study with a split-mouth design

Purpose: The objective of this paper was to compare histologically and histomorphometrically a hydroxyapatite originated by algae (Algipore) versus demineralized bovine bone (Bio-Oss Geistlich Pharma, Wolhusen, Switzerland) utilised as bone substitutes in maxillary sinus floor elevation with a split-mouth design. Materials and Methods: Five healthy patients underwent a bilateral maxillary sinus floor elevation procedure under local anesthesia. In each case, residual posterior maxillary bone height was between 2 mm and 5 mm. The original bone was augmented with a split-mouth design with 100% Algipore on the test side and 100% Bio-Oss on the contralateral control side. After a healing period of 6-8 months during the re-opening surgery biopsies were retrieved and Xive Implants (Dentsply Implants, Mannheim, Germany) were placed. Results: At microscopic level both Bio-Oss and Algipore blocks resulted well osseointegrated, without inflammatory infiltrate, with an high level of mineralization, without gap between the bone and biomaterial interfaces that resulted indistinguishable. A close contact between the two faces was observed without the presence of slits. Histomorphometrical analysis showed that, on average, the percentage of medullary space was higher for the Bio-Oss compared with Algipore (38.61% ±8.90% vs. 29.23% ±7.89%). In contrast, the mean value of residual particles of biomaterials was higher in Algipore than in Bio-Oss specimens (42.86% ±18.61% vs. 22.30% ±6.40% respectively). Conclusions: The data confirmed that sinus lift carried out with Algipore performed in a similar way of that carried out with Bio-Oss and that this material is safe, predictable and without invasiveness.

レーザ超音波を用いた回転体の表面探傷

Laser ultrasound is an effective method for noncontact flaw detection, material property measurement, and temperature measurement. In this research, laser ultrasound was applied to surface flaw detection of rotating specimens, for which conventional techniques such as ultrasonic inspection using transducers cannot be applied. A SUS316 specimen with artificial slits of depth 1 mm machined in the radial and tangential directions was used. By synchronizing the rotation frequency of the specimen with the laser repetition rate, the presence of the slits could be detected from the waveform and frequency spectrum of the surface acoustic waves. The results obtained when the specimen was under rotation was in agreement with the results obtained when the specimen was at rest. Furthermore, the detection position was scanned in the tangential direction by slight desynchronization of the specimen rotation and laser irradiation. The presence of slits could be detected with high accuracy by using the ratio of different frequency components of the obtained waveform.

Taylor-Couette 유동에서 축방향 홈과 반경방향 온도구배의 영향에 대한 실험적 연구

The effect of the radial temperature gradient and the presence of slits in the wall of outer of two cylinders involved in creating a Taylor-Couette flow was investigated by measuring the velocity field inside the gap. The slits were azimuthally located along the inner wall of the outer cylinder and the number of slits used in this study was 18. The radius ratio and aspect ratio of the models were 0.825 and 48, respectively. The heating film wrapped around the inner cylinder was used for generating the constant heat flux and we ensured the constant temperature condition at the outer space of the outer cylinder. The velocity fields were measured by using the PIV(particle image velocimetry) method. The refractive index matching method was applied to remove image distortion. The results were compared with plain wall configuration of Taylor-Couette flow. From the results, the presence of slits in the wall of outer cylinder and temperature gradient increased the flow instability.

Contact-associated neurite outgrowth and branching of immature cortical interneurons.

When juvenile interneurons arrive at the cortical environment following tangential migration, they are faced with the task of positioning themselves in cortical space in preparation for local circuit wiring. This includes integration into different cortical layers and cessation of migration at various positions to ensure adequate coverage. Little is known about the signals or mechanisms that initiate a conversion from the migratory phenotype to the arborization phenotype. This study looks at the immediate changes in interneuron morphology after culturing for 24 h in a three-dimensional collagen gel. Immature interneurons taken from different stages of corticogenesis showed increased neurite branching and outgrowth after interneuronal contacts were made. These responses were suppressed in the presence of Slit and brain-derived neurotrophic factor (BDNF) if the interneurons were sourced from early to mid-stages of corticogenesis. However, interneurons taken from the late period of corticogenesis responded to Slit and BDNF by increasing branching and neurite outgrowth. These results suggest an initial interneuronal cell contact as a stimulus for propagating neuronal arborization that may lead to the formation of inhibitory neuronal circuits. In addition, we have identified the late corticogenetic period when interneurons are most sensitive to the neurite promoting effects of Slit and BDNF.

FLUKA simulations and measurements for a dump for a 250 GeV/c hadron beam

FLUKA is a Monte Carlo code, transporting hadron and lepton cascades from several TeV down to a few keV (thermal energies for neutrons). The code is widely employed in various applications, such as particle detector design, shielding, radiation therapy, high energy physics experiments. The FLUKA results were compared with experimental data of dose equivalent and spectral fluence of neutrons produced by a 250 GeV/c proton/pion beam impinging on a beam dump installed in one of the secondary beam lines of the CERN super proton synchrotron (SPS). The dump is a shielding structure made of iron/concrete, designed to absorb completely the high-energy beam. The actual geometry of the dump was modeled in the simulations and the scoring of neutron track length was performed at various locations around it. Importance sampling and Russian Roulette were used as variance reduction techniques. The simulations results were compared with experimental measurements performed with a Bonner sphere system for neutron spectrometry and various types of rem-counters, a tissue equivalent proportional counter (TEPC) and a set of bubble detectors. Some discrepancies found with the measured data can be explained by the presence of slits and openings between adjacent concrete blocks constituting the dump assembly.

The effects of the slit in orthopantomography. Report 2. Comparison between orthopantomography and ordinary tomography.

Orthopantomography for dental X-ray examinations is a kind of tomography which has a special characteristic different from any other tomographic methods. A comparative study of radiographic images formed by ordinary tomographic equipment with the attachment of slits devised by the authors and images produced by orthopantomography is presented.As a result of comparing image-formation in orthopantomography with that of ordinary tomography using the same objects, (1) hardly any blur was observed inside the contours of the orthopantomographic image, (2) a very slight blurring effect of orthopantomography was observed on the slit side, (3) the slit played an important role in limiting the tomographic effect, and (4) consequently, orthopantomography may be considered as a very special type of tomography in the presence of slits.

The extent of slits at the interfaces between luting cements and enamel, dentin and alloy

Four different cements were used to assess the presence of slits at the cement/tooth or the cement/alloy interfaces using a tooth-crown model. The model consisted of ground sections of teeth and plane plates of silver/palladium alloy. The plates were fixed with bolts between two brass plates and with three different dimensions of the cement film between tooth and alloy, i.e. 50 micrometer, 100 micrometer and 200 micrometer. The tooth-alloy specimens were sectioned and the adaption of cements was studied with an indirect technique (replica) in a scanning electron microscope. The extent of slits was expressed as the length of all slits relative to the total length of the interface in each specimen. The results showed that the zinc phosphate cement and polycarboxylate cement exhibited a slight to moderate tendency to formation of slits at the interfaces. The EBA cement had a small extent of slits adjacent to thin cement films, but more slits were observed with increasing film thickness. The composite resin cement had a marked tendency to slit formation independent of the cement film thickness.

Plasma jet deflection in magnetic fields

We investigated the motion of plasma jets in a quadripole magnetic field produced by four current conductors whose axial lines were bent through 90° (the curvature radius was 30 cm). The maximum strength of the magnetic field in the “slit” between the current conductors was 6 kOe. The plasma jet, which was produced by means of a coaxial gun, was injected along the axis of the magnetic system. The magnetic system was adequate for defecting the plasma jet, which had an initial velocity of 8×106 cm/sec and a maximum concentration before deflection of 2×1015 cm−3. The jet velocity was equal to 7×106 cm/sec. In spite of the considerable loss of particles (due to the presence of slits in the magnetic system), the ion concentration in the jet beyond the turn attained 2×1014 cm−3, while the over-all number of particles was as large as ∼1017. As a result of deflection, it was possible to eliminate completely the neutral gas accompanying the jet and to obtain virtually totally ionized plasma. The optimum value of the magnetic field's strength was ∼8 kOe.