Mm For Test Research Articles

Experimental research on the thermal hydraulic characteristics of liquid sodium flowing in annuli with low Peclet number

Thermal hydraulic characteristics of liquid sodium flowing in annuli with low Peclet number are experimentally studied. Two test sections are used: the inner and outer diameters are 6mm and 10mm, respectively for test section No. 1, and 8mm and 12mm for test No. 2. Both the two annuli are 1100mm long. In the experiment, the heat flux ranges from 50 to 210kW/m2, Reynolds (Re) number from 0 to 18,000 and average fluid temperature from 200 to 500°C. Experimental data show that the flow regime of liquid sodium flowing in annuli can be divided into three regions, i.e. laminar flow (Re<2000), transition flow (2000<Re<4000) and turbulent flow (Re>4000). The effects of heat flux, Re number and average fluid temperature on the heat transfer coefficients are investigated separately. Correlations for the friction coefficient and for the Nusselt (Nu) number are obtained based on the experimental data in the three flow regions.

An Experimental Investigation on Strength Properties of Metakaolin Based Light Weight Aggregate Concrete Reinforced With Steel Fibers

At present all the constructions are executed with conventional granite aggregate concrete. If the granite aggregate is reduced by replacing it partially and fully by Metakaolin pellets as aggregate, the behavior and strength properties are interesting to be investigated. In this study an attempt has been made to use the Metakaolin as the basic ingredient in preparation of artificial pelletized metakaol in aggregate using lime and cement as binders. In the present experimentation, addition of Metakaolin pellets replacing the conventional granite aggregate in percentages of 0, 25, 50, 75 and 100% by volume of concrete and also adding the crimped steel fibre in percentages of 0.50, 1.00, 1.50 and 2.00% by weight. The properties such as compressive strength, split tensile strength, modulus of elasticity and flexural strength are studied by casting and testing around 240 samples consisting of 60 numbers of plain cube specimens of size 150x150x150 mm, 120 numbers of cylinders of size 150mm diameter and 300mm height and 60 numbers of plain beams of size 500x100x100 mm for testing after 28 days of curing.

Finite Element Analysis Comparison of Plate Designs in Managing Fractures Involving the Mental Foramen

Introduction The aim of the study was to propose an ideal plating design for fractures running through the mental foramen. Methods The study compared three plating designs-two four-hole miniplates, 2 × 2-hole three-dimensional (3D) plate, and modified 2 × 2-hole 3D plate (posterior strut removed)-using finite element analysis. Von Mises stresses generated around the plates and bone were measured, as well as the mobility that is generated between the fracture fragments by applying muscle forces to generate bite force in one test and applying a force of 500 N over the premolars and first molar region in the second test. Results Von Mises stress in bone with miniplates measured 9.24 MPa in test 1 and 131.99 MPa in test 2. The stress with unmodified 3D plates measured 34.9 MPa in test 1 and150.03 MPa in test 2. The stress with modified 3D plates measured 24.98 MPa in test 1 and 150.59 MPa in test 2. Von Mises stress on the plates and screws measured 28.23 MPa, 95.97 MPa, 72.93 MPa in test 1 and 458.63 MPa, 779.01 MPa, 742.39 MPa in test 2 on miniplates, unmodified 3D plates, and modified 3D plates, respectively. The fracture mobility generated in the model with miniplates measured 0.001 mm in test 1 and 0.01 mm in test 2 and 0.007 mm and 0.02 mm in the model with unmodified 3D plates in test 1 and in test 2, respectively. In the model with modified 3D plates, the value was 0.001 mm and 0.01 mm in tests 1 and 2, respectively. Conclusion The ideal plate design is the two-plate technique with minimal stress generation on the bone and the hardware. The modified 3D plate has adequate strength to be used in the region but needs to be studied in detail.

Nano‑crystalline hydroxyapatite bone graft combined with bioresorbable collagen membrane in the treatment of periodontal intrabony defects: A randomized controlled clinical trial

Aim:To evaluate the clinical outcome of nanocrystalline hydroxyapatite (NcHA) bonegraft (Sybograf®) in combination with collagen membrane (PerioCol®) compared with open flap debridement (OFD) only in the treatment of intrabony periodontal defects.Materials and Methods:Eighteen intrabony defects in 16 systemically healthy patients aged between 25-65 years, were randomly assigned to test and control groups. The Plaque index, gingival index, probing pocket depth (PPD), clinical attachment level (CAL), and gingival recession were recorded at baseline, and were reevaluated at 6 months. In addition to this, radiographic bone fill was assessed using digital software. At the test site NcHA bone graft and collagen membrane was placed, whereas at the control site only, OFD was done. Recall appointments were made at 7th day, 1st month, 3rd month, and 6th month.Results:The data were subjected to statistical analysis using the Mann-Whitney ‘U’ Test and Wilcoxon signed rank sum test. In the control group, the mean reduction of PPD was 3.22±1.09 mm and CAL gain was 2.78±1.09 mm. In the test group, the mean PPD reduction of 4.33±0.5 mm and mean gain in CAL was 3.78±0.66 mm at 6 months. The mean increase in gingival recession was 0.55±0.72 mm in test and 0.44±0.52 mm in control group.Conclusion:The NcHA bone graft in combination with collagen membrane demonstrated better clinical outcomes compared with OFD alone.

Silica–silica polyimide buffered optical fibre irradiation and strength experiment at cryogenic temperatures for 355 nm pulsed lasers

A controlled UV-light delivery system is envisioned to be built in order to study the stability properties of superconducting strands. The application requires a wave guide from room temperature to cryogenic temperatures. Hydrogen loaded and unloaded polyimide buffered silica–silica 100 μm core fibres were tested at cryogenic temperatures. A thermal stress test was done at 1.9 K and at 4.2 K which shows that the minimal mechanical bending radius for the fibre can be 10 mm for testing (transmission was not measured). The cryogenic transmission loss was measured for one fibre to assess the magnitude of the transmission decrease due to microbending that takes place during cooldown. UV-irradiation degradation measurements were done for bent fibres at 4.2 K with a deuterium lamp and 355 nm pulsed lasers. The irradiation tests show that the fibres have transmission degradation only for wavelengths smaller than 330 nm due to the two photon absorption. The test demonstrates that the fibres are suitable for the cryogenic UV applications with 355 nm and 70 μJ pulsed lasers.

Implants Inserted with Low Insertion Torque Values for Intraoral Welded Full‐Arch Prosthesis: 1‐Year Follow‐Up

The aim of the present study is to evaluate the osteointegration and crestal bone remodeling after 1 year around implants for intraoral welded immediate full-arch prosthesis inserted with low insertion torque (IT) values. The study was conducted from June 2008 to September 2010. Patients were eligible for the study if they needed an immediate intraoral welded implant-supported full-arch fixed prosthesis and received three or more implants with an IT ≤ 20 Ncm and two or more implants with IT ≥ 25 and ≤ 50. For each implant, peak IT was recorded during insertion surgery; periapical x-rays were taken at the time of surgery and again after 12 months. Finally, it was recorded whether an implant was lost or removed (within 12 months from insertion surgery). Thirteen patients were included in the study; the prosthesis presented the following number of implants: nine with six implants and four with seven implants. A totand al of 82 implants were inserted: 51 implants presented an IT ≤ 20 Ncm (test group), 31 implants presented an IT ≥ 25 and ≤ 50 Ncm (control group). Each prosthesis presented at least three test implants and two control implants. The survival rate after 1 year was 98% for the test and 100% for the control group. The mean distance between the fixture-abutment junction and the bone crest was 0.1 ± 0.8 mm for test and 0.2 ± 0.5 mm for control group at implant insertion. After 12 months, it was 0.7 ± 0.9 mm for test group and 0.8 ± 0.6 mm for control group. The differences were not statistically significant. Within the limitations of this study, the results suggested that rigid framework splinting can be a viable technique to improve success rate of implants with low primary stability using immediate loading protocols for full-arch prosthesis.

Effect of plasma rich in growth factors on the healing of intrabony defects in human: a comparative clinical trial

Background and aims. A combination of guided tissue regeneration (GTR), bovine porous bone mineral (BPBM), and platelet rich plasma has been already applied for the regeneration of intrabony defects. The aim of this study was to determine the role of plasma rich in growth factor (PRGF) alone in the periodontal regeneration of intrabony defects in humans as compared with BPBM/GTR Technique. Materials and methods. In this split-mouth clinical trial, nine advanced periodontal patients with 20 intrabony defects were randomly treated with a combination of either BPBM/GTR (control) or PRGF (test). Periodontal parameters including gingival recession, probing depth (PD), gingival index (GI), plaque index (PI), and relative clinical attachment level (CAL) were evaluated at baseline and 6 months post-operatively. Results. No difference was observed at baseline between the two groups. At 6-month post-treatment, both techniques demonstrated significant reduction in CAL, PD and GI. The mean pocket depth reduction in control group was 4.1 ± 1.52 mm and 4.5 ± 1.5 mm on buccal and lingual sites, respectively (P < 0.0001); and 3.6 ± 0.9 mm in the test group. The changes in CAL in the deepest part of the defect were 3.06 ± 1.79 mm and 2.33 ± 0.78 mm for test and control groups, respectively. No statistically significant difference was detected between the two groups after 6 months. Conclusion. According to the results, the use of PRGF alone, similar to BPBM/GTR improves clinical parameters and plays a significant role in PD reduction and CAL gain.

Effect of neonatal clomipramine in the pathogenesis of ligature-induced periodontitis in Lewis rats

Objective. The aim of this study was to verify the association between an endogenous depression model and the development of ligature-induced periodontitis in rats. Material and methods. Nine male Lewis rats received 30 mg/kg clomipramine from neonatal day 8 to day 21 (depressed group), while 13 control Lewis rats were left untouched (control group). On day 150, ligatures were placed around the 2nd upper molars in both groups, i.e. the contralateral molar of the intra-group control. On day 190, the rats were killed and the maxillae were defleshed. The distance between the cemento-enamel junction and the alveolar bone crest was measured by a blinded examiner using standardized digital photographs. Results. The depressed rats showed hyperactivity in open field on day 142 and greater attempts to escape on day 143 compared to controls. The other behavioral data did not show statistically significant differences between the groups (Mann-Whitney, p>0.05). In teeth with ligature, mean alveolar bone loss varied from 0.51 to 0.60 and from 0.63 to 0.64 mm for tests and controls, respectively (t-test, p>0.05). In teeth without ligature, these values varied from 0.38 to 0.43 and 0.42 to 0.45 mm in the test and control groups, respectively (t-test, p>0.05). Conclusion. Induced depression did not alter ligature-induced bone loss in Lewis rats.

A retrospective clinical, radiographic and microbiological study of periodontal conditions of teeth with and without crowns

The aim of this study was to evaluate retrospectively the periodontal conditions of teeth with fixed crowns that had been in place from 3 to 5 years before the study was conducted. Forty individuals were recalled for a follow-up visit. Full-mouth clinical examinations were carried out and Visible Plaque Index (VPI), Gingival Bleeding Index (GBI), Probing Pocket Depth (PPD), and clinical attachment level (CAL) were assessed in 6 sites per tooth. Parallel radiographs were also taken and blindly analyzed by a digital caliper (distance between the apex and the bone crest). BANA tests were performed. A contra-lateral sound tooth was considered the control. Mean values were obtained and Wilcoxon and paired sample t tests were used to compare the test and control sites. Crowns had a mean VPI value of 30.42% as compared to 49.17% for sound teeth. The GBI was 33.33% and 26.25% for test and control teeth respectively. Assessment of PPD revealed values of 2.30 and 2.14 mm, and assessment of CAL revealed averages of 2.02 and 1.89 mm for test and control teeth respectively. The mean values for radiographic distances were 12.73 and 13.67 mm, and for the BANA test, 67.50 and 50.00 for sound and crowned teeth, respectively. Statistically significant differences were observed for all parameters except for CAL and for the BANA test. It may be concluded that, with the methods used in the present study, crowns may be associated with more signs of inflammation, however not with periodontal breakdown.

A new thread tear test using silicone tubing.

I have already reported the development of a method for measuring tear volume using a cotton thread (No. 82/3, about 0.2 mm in diameter). While this previous testing method proved useful, both in the diagnosis of lacrimal deficiencies, and in cases of slight to medium epiphora, it could not accurately measure the high volume of lacrimation produced in cases of strong epiphora because of the low absorption capacity of the thread. To overcome this shortcoming, I have developed a new system which utilizes a cotton thread enclosed in a soft, calibrated, silicone tubing. In subsequent testing of this new technique, eyes that exhibited a strong epiphora state gave a wetted length of 226.9 +/- 56.0 mm (mean +/- SD) in a 5- to 10-second test. This compares with 41.0 +/- 8.9 mm in tests using thread alone in a 5- to 10-second test (p less than 0.001).

熱処理による表面形状の変化について

The change in dimensions after heat treatment, in most cases, has been expressed by elongation or shrinkage obtained by measuring the distance between two sides of the specimen.In this paper, change in dimensions and change in profiles on sections and cubic surfaces after heat treatment by oil cooling, air cooling, marquenching, etc. were studied by using micrometer and surface roughness gauge.Three kinds of tool steels (SKS 2, SKD 11, and SKS 31+Mo in JIS) were selected and worked into rectangular parallelopipeds of 150×45×22mm for test pieces.The results obtained were as follows.(1) The surface profile of each face changed in three dimensions. For example, after SKS 2 was oil cooled, two corrugated ranges of mountains appeared in one direction and only one range in the perpendicular direction on 150×22mm face. However, on 150×45 face, there appeared V shaped corrugations in one direction and one range of mountains in the perpendicular direction.(2) Change in dimensions was the largest in SKS 2, and next in order were SKS+Mo and SKD 11.(3) SKS 2 showed the best results among the test pieces on which profiles were symmetrically distorted. The surface profiles were more accurately measured with roughness gauge than micrometer.