Middle Cross Research Articles

Facial alveolar bone wall width – a cone‐beam computed tomography study inAsians

The width of the facial alveolar bone wall is crucial for long-term successful esthetic outcomes of implants immediately placed into extraction sockets. A threshold of 2 mm is recommended to minimize buccal vertical bone resorption. To assess the width of the facial alveolar bone wall using cone-beam computed tomography images (CBCT). Retrospective CBCT images were acquired from a representative sample of Asians using the i-CAT classic system with a 0.4-mm voxel size. At random, 200 CBCT images were selected according to predefined criteria. The DICOM file was imported into the i-CAT Vision software. In the panoramic screen, the middle of each tooth was selected, and in the sagittal window, the middle cross section was selected for performing the measurements using a computer. The vertical distance from the alveolar crest (BC) - cemento-enamel junction (CEJ) was measured. The width of the facial alveolar bone wall was measured at three locations: 1, 3, and 5 mm apical to BC. Descriptive statistics, frequency analyses, and multi-level comparisons were performed. The sample consisted of 74 men and 126 women (mean age of 37.2 years; range 17-82 years). A total of 3618 teeth were assessed. There was no significant difference between the values of right and left sides, or between genders. However, statistically significant differences were observed between age groups at all levels. The distance from CEJ to BC varied from 0.4 to 4 mm, with an overall tendency to increase with age. The mean width of the facial alveolar bone wall at anterior teeth was 0.9 mm and increased toward posterior regions. Rarely, a width of 2 mm was yielded (0.6-1.8% for anterior teeth, 0.7-30.8% for posterior teeth). At a 5-mm distance from BC, minimal widths of facial alveolar bone were identified for the anterior teeth. The frequency of dehiscence ranged from 9.9% to 51.6% for anterior and 3.1% to 53.6% for posterior teeth, respectively. A thin facial alveolar bone wall was usually present in both jaws. Hence, for most patients, adjunctive bone augmentation may be needed when installing implants in areas of esthetic concern.

Finite Element Analysis of the Hydraulic Pressure in a Large Heat Exchanger

By the use of ANSYS common finite element software, the finite element entity model for the heat exchanger is built. The strength analysis of the heat exchanger in the Hydraulic pressure condition is done. The analysis results show that the maximum stress concentrates at the transition the sharp corner of the saddle and the maximum displacement location is the middle cross section of the heat exchanger. According to JB4732-1995, the surplus of material needed is large, the design is safe and meet the strength requirement. The analysis results can be used as useful reference data to design and manufacture in the large heat exchanger.

Influence of Rheological Behaviour on Load-Carrying Capacity of Timber-Concrete Composite Beams Under Long Term Loading

Wood and concrete are materials with different time dependent behaviour and both have different reactions to thermal and humidity changes of environment. In timber-concrete composite beams it results in generation of inelastic strains and redistribution of stress in cross-section.To determine load carrying capacity of composite wood-concrete element is possible according to Additions B of EN 1995-1-1, Design of Timber Structures. But this calculation technique does not consider the influence of rheological properties of composite materials as shrinkage, eventually bulking of materials, the influence of composite on creep coefficient and the influence of environmental changes. In this paper, the analytical calculation model of long term behavior of the timber-concrete composite beams is presented, which considers the most significant rheological phenomena such as: viscous-elastic creep of concrete and wood, mechano-sorptive creep of wood, creep of shear connection, concrete shrinkage and strains due to thermal and relative humidity changes of environment. This model is applicable for simple beams with linear material properties and allows determining the final deflection in the middle span and stressing distribution in the middle cross- section of the composite beams affected by long term loading. Applying the presented calculation model and results of experimental tests, the analysis of rheological behavior influence on long term load carrying capacity of timber-concrete beams is described as well.

A Graph Optimization Algorithm for Warehouses with Middle Cross Aisles

This paper considers picker routing problem where the picking area consists of vertical and middle cross aisles, and has picking locations at some cross aisles. A graph optimization algorithm is developed to minimize total traveling distance for the unique layout. Because the dynamic programming-based graph optimization algorithm is very sensitive to the layout, it is not directly applicable to our aisle structure where has openings also in some cross aisles. Representing the rectangular picking layout as a graph of edges and vertices, the algorithm enumerates all picking tours by the principle of dynamic programming. We investigate the performance of the proposed algorithm through a practical case study in consumer packaged goods industry. For the given set of orders, the algorithm significantly reduces total distances than the current method. Its computing times are no longer than a second in spite of its apparent complexity.

Numerical simulation on the effect of jet nozzle position on impingement cooling of gas turbine blade leading edge

In this paper, Computational Fluid Dynamics (CFD) simulations are performed to investigate the impingement cooling on internal leading edge region which is stretched by the middle cross section of the first stage rotor blade of GE-E 3 engine high pressure gas turbine. The simulations are carried out for a blade with a single row of circle jets at five different positions and seven different inlet flow Mach numbers. The results indicate that the global area weighted average Nusselt number at the blade leading edge increases with the increase of jet Mach number, and increases with the decrease of the distance between the jet nozzle and the pressure side. The correlation for the area weighted average Nusselt number as a function of the parameters is derived for the range of the parameters considered. The streamwise length weighted average Nusselt number and the spanwise length weighted average Nusselt number also increase with the decrease of the spacing between the jet nozzle and the pressure side, and increase with the increase of jet Mach number. The side entry jet is desirable to improve the performance of impingement cooling on turbine leading edge, but the arrangement of the jet nozzle and the shape of the internal cooling passage should be further optimized to improve the distribution of the heat transfer coefficient.

Experimental Research on the New Method of Complex Reinforcement for Steel Beam

A new type of complex reinforcement method for steel structure seldom used in pratical engineering mainly due to lack of theoretic and experimental support. The experiment with this method for H-section steel beams and the results of that are introduced in this paper. The mechanical properties of the steel and CFRP material are given. The carrying capacity and the load-displacemengt curves of each specimen beams are obtained as well as the stress and strain of every feature points on the middle cross section of the beams. The results may provided reference for practical engineering.

Stock assessment and management implications of inland fishery in the floodplain of the Cross River, Nigeria

Fishery assessment was conducted monthly between January, 2004 and December, 2006 in 3 zones of inland wetlands of Cross River, Nigeria. Zone I was upper Cross River (savanna wetlands), Zone II: middle Cross River (savanna/forest wetlands) and Zone III was the lower Cross River (forest wetlands)]. Forty six fish species belonging to 28 genera and 16 families were observed. These included; Bagridae (25.7%), Cichlidae (16.9%), Clariidae (11.5%) Clupeidae (10.2%), Mochokidae (8.7%), Mormyridae (5.8%), Cyprinidae (2.9%), Osteoglossidae (2.8%), Protopteridae (2.6%), Denticeptidae (2.4%), Hepsetidae (2.4%), Distichodontidae (2.3%), Malapteruridae (2.2%), Polypteriidae (2.2%), Schilbeidae (2.0%) and Characidae (2.0%). 2768 artisanal fishermen consisting of 500 (Zone I), 887 (Zone II) and 1381 (Zone III) were enumerated. Four hundred and seventeen were found to be full-time fishermen, 893 part-time, 969 shoreline and 489 assistants. Common gears were hook and line constituting 30%, cast net (20.1%) bailing method (15%), gill nets (13.3%), seine net (11%) Traps (10.5%), lift net (6.7%) Dip nets (5%), poisoning (4.8%), cutlass (3.3%) and spear (1%). Four hundred and forty two operational boats were encountered. Significant differences were observed in the percentage of operational boats between the three zones (F = 5.67; P< 0.05) (Zone I: 19%, Zone II: 31% and Zone III: 50%) and the average catch per boat in the different zones (F = 7.84; P < 0.05) (Zone I: 31.9kg, Zone II: 64.8kg and Zone III: 106.3kg), with highest production occurring in Zone III and lowest in Zone I. Estimated catch per annum was 14,670MT. The study shows that there was no sustainable management practice in place. There were high incidences of bad fishing methods. Community based management system that establishes participatory involvement of fishermen in the conservation and rational exploitation of fisheries resources was therefore recommended.

Implicación clínica de la lesión iatrogénica de la cuerda del tímpano en la cirugía de la otosclerosis

Introduction: Damage to the chorda tympani nerve is frequent during otologic surgery. This article studies the clinical outcomes of the nerve's section versus its conservation in otosclerosis surgery.Material and method: Retrospective observational study using our department's otosclerosis database and a validated questionnaire on symptoms associated with the chorda tympani nerve. The sample was divided into two groups: section and conservation (patients whose nerve was anatomically conserved). We studied the presence and duration of symptoms, the surgical technique and the audiometric results.Results: 78 patients (88 ears): section group (18 ears; 20 %) and conservation group (70 ears; 80 %). Overall, gustatory symptoms appear in 35 % (39 % section group; 34 % conservation group). Differences between groups are not statistically significant in relation to presence and duration of symptoms, surgical technique or audiometric results. Only 1 patient in each group reports long-term symptoms. Our results suggest there are no major clinical differences following section versus conservation of the chorda tympani nerve. A wide range of factors such as age, presence of previous middle ear pathology, cross innervation and gastronomic culture may play a role in the appearance of symptoms.Conclusions: Symptoms appearing after iatrogenic damage to the chorda tympani nerve have, in general, little clinical relevance, especially in the long term, regardless of whether the nerve is dissected or manipulated to various degrees.

Clinical implications of iatrogenic lesion in the chorda tympani nerve during otosclerosis surgery

IntroductionDamage to the chorda tympani nerve is frequent during otologic surgery. This article studies the clinical outcomes of the nerve's section versus its conservation in otosclerosis surgery. Material and methodRetrospective observational study using our department's otosclerosis database and a validated questionnaire on symptoms associated with the chorda tympani nerve. The sample was divided into 2 groups: section and conservation (patients whose nerve was anatomically conserved). We studied the presence and duration of symptoms, the surgical technique, and the audiometric results. ResultsSeventy-eight patients (88 ears): section group (18 ears; 20%) and conservation group (70 ears; 80%). Overall, gustatory symptoms appear in 35% (39% section group; 34% conservation group). Differences between groups are not statistically significant in relation to presence and duration of symptoms, surgical technique, or audiometric results. Only 1 patient in each group reports long-term symptoms. Our results suggest there are no major clinical differences following section versus conservation of the chorda tympani nerve. A wide range of factors such as age, presence of previous middle ear pathology, cross innervation, and gastronomic culture may play a role in the appearance of symptoms. ConclusionsSymptoms appearing after iatrogenic damage to the chorda tympani nerve have, in general, little clinical relevance, especially in the long term, regardless of whether the nerve is dissected or manipulated to various degrees.

ANALYSIS OF COLLISION BETWEEN DRILLSTRING AND WELL SIDEWALL

Drillstring is the most important tool in petroleum drilling engineering. Alternating stress has been found to be responsible for the premature failure of drillstring. Propagation of stress wave, induced by collision between tool-joints of drillstring and borehole wall, is studied in this paper. The condition that all the tool-joints of drill pipes (DPs) strike borehole wall at the same time has been considered. Because of symmetry, the middle cross section of the DP is simplified as fixed end, and mechanical model is established as the beam with both ends fixed. Propagation of lateral displacement wave and stress wave in the DP is investigated by means of Eigen-frequency method and the Finite Element Analysis software ANSYS. The theoretic results coincide with those obtained from numerical modeling very well and also explain the drillstring accidents in gas fields.

Improvement order picking in mobile storage systems with a middle cross aisle

Mobile automated storage/retrieval system (M-AS/RS) is more efficient than mobile storage system (MSS). However, the problems of huge rack row movement and long travel distance have not been effectively solved, especially for heavy items. This study proposes the middle cross aisle model (MCAM) based on the perspective of warehouse layout of M-AS/RS. By designing the layout of cross aisle from front to middle, the warehouse was divided into two small blocks. Picker travel distance could thus be reduced significantly, reducing the huge rack row and making rack row movement more economic and safe. This study formulates the MCAM operation and decomposes the order picking process into three stages, integrating with routing algorithms to achieve better picking routes. Simulation results showed that the MCAM model outperformed the M-AS/RS model. It is suitable for application to lower order density, heavy items with deep racks rows. The optimal ratio for simulation experiment rack shape is 0.6 to 1. Finally, the authors compared typical M-AS/RS and MCAM and also raised some practical concerns regarding its application to industry and addressed future research directions.

An analysis of dual-command operations in common warehouse designs

In a warehouse that uses dual-command operations, workers travel loaded from the pickup and deposit (P&D) point first to a location to store a pallet, then to a second location from which they pick a pallet and return to the P&D point. We develop expected travel distance expressions for such operations and use them to analyze three common warehouse designs. Our results indicate that the best of the three is – in our experience – the one least commonly found in practice. We also show that the optimal placement of a “middle cross aisle” in the most common design is, in fact, not in the middle.

Numerical simulation of gas-liquid two-phase jet flow in air-bubble generator

Air-bubble generator is the key part of the self-inspiration type swirl flotation machines, whose flow field structure has a great effect on flotation. The multiphase volume of fluid (VOF), standard k-ɛ turbulent model and the SIMPLE method were chosen to simulate the present model; the first order upwind difference scheme was utilized to perform a discrete solution for momentum equation. The distributing law of the velocity, pressure, turbulent kinetic energy of every section along the flow direction of air-bubble generator was analyzed. The results indicate that the bubbles are heavily broken up in the middle cross section of throat sect and the entrance of diffuser sect along the flow direction, and the turbulent kinetic energy of diffuser sect is larger than the entrance of throat sect and mixing chamber.

Investigation on Mechanisms of Polymer Enhanced Oil Recovery by Nuclear Magnetic Resonance and Microscopic Theoretical Analysis

Polymer flooding is an efficient technique to enhance oil recovery over water flooding. There are lots of discussions regarding the mechanisms for polymer flooding enhancing oil recovery. The main focus is whether polymer flooding can increase sweep efficiency alone, or can increase both of sweep efficiency and displacement efficiency. We present a study on this problem. Oil displacement experiments on 4 natural cores show that polymer flooding can increase oil recovery efficiency by more than 12% over water. Moreover, photos are taken by the nuclear magnetic resonance (NMR) method both after water flooding and after polymer flooding, which show remaining oil saturation distribution at the middle cross section and the central longitudinal section. Analyses of these photos demonstrate that polymer flooding can increase both sweep efficiency and displacement efficiency.

Diet, size and reproductive biology of the silver catfish, Chrysichthys nigrodigitatus (Siluformes: Bagridae) in the Cross River, Nigeria

The silver catfish, Chrysichthys nigrodigitatus (Lacépède: 1803) is a highly valued food-fish included among the dominant commercial catches exploited in major rivers of Africa. To provide useful biological data for management, samples were collected monthly between January (2005) and December (2007) in three zones: I: Upper Cross River (grassland), II: Middle Cross River (mixed forest and grassland), and III: Lower Cross River (rainforest)] along 200 km length of the Cross River, Nigeria. Data from 1 248 specimens were processed using: allometric coefficient (b), gonado-somatic index, Fulton's condition factor and diversity indices. Male dominance was observed in all populations; C. nigrodigitatus reached maturity at 11.5 cm (male) and 16.7cm (female) total length. Gonado-somatic index was higher for females with a peak in the early rains. The breeding period was between April and August with mean fecundity ranging between 4522 +/- 1924 eggs and 20321 +/- 5543 eggs. This was directly related to total length and weight by the regression models: F = 2365.88 + 560.22 log L and F = 5025.81 +56.34 log W respectively. Exponential equations for length-weight relationships were Wt = -1.997 Lt(2.206) (Zone I), W = -2.831 Lt(3.040) (Zone II) and Wt = -2.245 Lt(2.995) (Zone III). The mean allometric coefficient (b) showed significant departure from cubic value (negative allometry) for Zone I while Zones II and III showed no difference, indicating isometry. Dominant items in the diet were fish and fish parts constituting 21.6% with Food Richness and Gut Repletion Index of 18 and 100% respectively, in all zones. Diet Breadth of 0.802 (Zone 1), 0.922 (Zone II) and 0.910 (Zone III) indicate a high trophic flexibility that enables switching from one diet to another according to availability. Mean condition factor for males varied from 0.718 +/- 0.117 minimum in Zone I to 0.996 +/- 0.062 maximum in Zone III. Forest inland wetlands (Zone II and III) of Cross River provided better condition for C. nigrodigitatus.

English

Biological assessment of&nbsp;Oreochromis niloticus&nbsp;was conducted monthly between January, 2004 and December, 2006 in 3 zones [(Zone I: upper Cross River (savanna wetlands) Zone II: middle Cross River (savanna/forest wetlands) and Zone III: lower Cross River (forest wetlands)] along 200 km length of the inland wetlands of Cross River, Nigeria. Major items in the diet of&nbsp;O. niloticus&nbsp;were algae and plant 38 and 20.4% (Zone I), 21.7 and 18.0% (Zone II), 20.2 and 26.9% (Zone III), respectively. Diet breadth ranged from 0.820 - 0.913. Food richness and Gut Repletion Index were 12 and 100%, respectively. Sex ratio was 1: 1 (Zone1), 1:0.78 (Zone II) and 1: 0.89 (Zone III). Mean allometric coefficients (b) of the length-weight relationship were 2.194 &plusmn; 0.215 (Zone I), 2.935 &plusmn; 0.333 (Zone II) and 3.03 &plusmn; 0.202 (Zone III). Fecundity varied from 70 eggs for fish (total length (TL) = 11.00cm and weight (W) = 37.9 g) to 502 eggs (TL = 25.8cm and W = 198.8g) in Zone I, 60 eggs (TL = 13.3cm and W = 19.8g) to 709 egg (TL = 26.5, W= 317.0) in Zone II and 110 eggs (TL = 13.7cm, W = 24.0g) to&nbsp; 811 eggs (TL = 22.8cm, W = 278.8g) in Zone III. Relationship exists between fecundity and body size. Mean condition index ranged from 0.770 &plusmn; 0.128 minimum for males at Zone I to 1.188 &plusmn; 0.157 maximum also for males at Zone III. Therefore, male&nbsp;O. niloticus&nbsp;were in better condition than females and the forest wetlands of Cross River (Zone III) offered more favourable living conditions for the species than the savanna wetlands (Zone I and II). &nbsp; Key words:&nbsp;Biological assessment, Cross River, inland wetlands,&nbsp;Oreochromis niloticus

Numerical and Experimental Analyses of Magnetic Convection of Paramagnetic Fluid in a Cylinder

The magnetic convection of paramagnetic fluid in a cylindrical enclosure is studied experimentally and numerically. The upper side wall of the cylinder is cooled and the lower side wall heated, an unstable configuration. The whole system is placed coaxially in a bore of a superconducting magnet in the position of the minimum radial component of magnetic buoyancy force at the middle cross section of the enclosure. The stable configuration— when the whole system is placed inversely and the horizontal axial case are also considered. As a paramagnetic fluid an aqueous solution of glycerol with the gadolinium nitrate hexahydrate is used. The isotherms in the middle-height cross section are visualized by thermochromic liquid crystal slurry. For the unstable configuration the magnetic buoyancy force acts to assist the gravitational buoyancy force to give multiple spoke patterns at the mid cross section. The stable configuration gives an almost stagnant state without the magnetic field. Application of the magnetic field induces the convective flow similar to the unstable configuration. For the horizontal configuration a large roll convective flow (without the magnetic field) is changed under the magnetic field to the spoke pattern. The numerical results correspond to the experimental results.

Comparative Analysis of the Vortex Heat Exchange in Turbulent Flows around a Spherical Hole and a Two-Dimensional Trench on a Plane Wall

The vortex heat exchange in turbulent flows around a spherical hole and a transverse trench, identical in depth and in the shape of the middle cross section, on a plane wall has been numerically investigated using multiblock computational technologies. A factorized, implicit multiblock algorithm and a Menter's model of shear-stress transfer were tested in the process of comparative analysis of calculation and experimental data on flows around isolated holes.

X-Ray Source Based on Electron Cyclotron Resonance Discharge in a Magnetic Mirror Trap

A new concept of the x-ray source based on a low-pressure microwave discharge that is confined in a magnetic mirror trap and heated at electron cyclotron resonance conditions is described. It is demonstrated that the energetic electrons accelerated on the resonance hyperboloid of one sheet surface type, form a rotating ring, which is located in the middle cross section of the trap. When the ring strikes a metal target, an x-ray radiation is produced. A 100 keV radiation is obtained by using 2.45 GHz microwaves of 150 W.

Improvement of bloom casting and high reduction breakdown process

In May 1998, Muroran Works installed a near-net shape casting and compact high reduction (NCR) process in its steelmaking plant. The No.3 continuous casting machine was rearranged to cast middle cross section blooms, and a reheating furnace and a 2-passes high reduction breakdown mill were newly equipped. No.3 CCM casts square 220 mm mould size blooms and the breakdown mill reduces their cross section to square 162 mm. This combined process improved the quality of the cast billets and achieved high productivity.