Mm In Side Length Research Articles

Implications for identification of principal stress directions from acoustic emission characteristics of granite under biaxial compression experiments

The rock fracture characteristics and principal stress directions are crucial for prevention of geological disasters. In this study, we carried out biaxial compression tests on cubic granite samples of 100 mm in side length with different intermediate principal stress gradients in combination with acoustic emission (AE) technique. Results show that the fracture characteristics of granite samples change from ‘sudden and aggregated’ to ‘continuous and dispersed’ with the increase of the intermediate principal stress. The effect of increasing intermediate principal stress on AE amplitude is not significant, but it increases the proportions of high-frequency AE signals and shear cracks, which in turn increases the possibility of unstable rock failure. The difference of stress in different directions causes the anisotropy of rock fracture and thus leads to the obvious anisotropic characteristics of wave velocity variations. The anisotropy of wave velocity variations with stress difference is probable to identify the principal stress directions. The AE characteristics and the anisotropy of wave velocity variations of granite under two-dimensional stress are not only beneficial complements for rock fracture characteristic and principal stress direction identification, but also can provide a new analysis method for stability monitoring in practical rock engineering.

Application of self-made iris retractors in surgeries of cataract with small pupil

Objective To evaluate the efficacy of application of self-made iris retractors in surgeries of cataract with small pupil. Methods The data of 35 eyes of 32 cases of cataract with miosis due to glaucoma surgery, uveitis and etc from Jan. 2018 to Aug. 2018 were analyzed retrospectively. All cases underwent phacoemulsification and intraocular lens implantation with self-made iris retractors. The patients were followed up for 3-6 months. Results All the 35 eyes achieved square pupils of 5.0-6.0 mm in side length during operation, and the continuous circular capsulorhexis and phacoemulsification were successfully completed. Only 1 eye had minor iris hemorrhage during operation, but it did not affect the surgery. The pupil was nearly circular with diameter of 3.0-4.0 mm after surgery. The pupillary light reaction was normal or sluggish. Visual acuity was significantly improved after surgery. No complication such as posterior capsule rupture, pupil tear, anterior chamber hemorrhage or elevated intraocular pressure occurred. Conclusion Application of self-made iris retractors for the treatment of cataract with small pupil can enlarge the pupil and obtain favorable results. The self-made iris retractors are easy to make and simple and safe to use. Key words: Iris; Miosis; Phacoemulsification

Hydrodynamics and pressure loss of concurrent gas–liquid downward flow through sieve plate packing

Gas–liquid concurrent downward flow through a new structured packing was investigated by experiment systematically. The experimental packing consisted of 21 sieve plates. Each plate was 190mm×190mm in side length and 1mm in thickness. Three sets of packing with different sizes of sieve holes were tested. During experiment, four flow states have been observed, i.e., the trickling flow at low gas and liquid flux, the continuous flow at low gas but high liquid flux, the semi-dispersed flow at high gas flux and the completely dispersed flow as gas flux increases further. Another important phenomenon observed is the occurrence of pulsing flow, i.e., in some range of gas and liquid flow fluxes, both two phases will no longer flow smoothly through the sieve plates but flow downward in pulse regularly. Through extensive experiment, the rough boundaries for flow regime transition were obtained. Then, the pressure losses of gas flow and gas–liquid two phase flow in non-pulsing flow regime were systematically measured. The analysis for pressure differences measured at different locations show that for a given packing, the pressure loss through each plate is nearly the same. Its magnitude depends on the gas and liquid flow rates. The comparisons between pressure losses of different packings indicate that the pressure loss is associated with the hole diameter, hole pitch, free area ratio of sieve plate and the mounting distance between two adjacent plates. Finally, considering these factors, the correlations for pressure drops were developed, which approximates the experimental values with an average deviation less than 10%.

Shear resistance of reinforced concrete waffle flat slabs around the solid panel

This work presents a study on the behaviour of reinforced concrete waffle flat slabs with solid panels around internal columns and without moment transfer. Testes on 6 square waffle flat slab models were carried out, with 2400 mm in side length, 185 mm in height, 70 mm in top slab thickness, 115 mm in ribs height, 50 mm in ribs width, and 270 mm in ribs spacing, from center to center. The variables were the size of the solid panels (either 590 × 590 mm or 1130 × 1130 mm), ribs web steel ratio, type and layout. Except for one model that failed in flexure by crushing the ribs at the solid panel, all other models failed in shear by diagonal tension of the ribs. Test results were analyzed and compared with one another and with the estimations of existing expressions from codes and from other works available in the literature for punching shear of the solid panels around the column and ribs shear next to the solid panels. Finally, proposals for the design procedures for the slab region within the lines of zero moments and around the columns are given, regarding the definition of the solid panel size as a function of the ribs resistances towards shear and flexure.

Optical fiber metrology to small displacements detection

This work presents a methodology to measure deflections in the range of microns in thermo-pneumatic silicon micomembranes. This method is based on the fiber optic interferometry, which was used to study the static behavior of a silicon membrane of 10 mm in thickness, 5 mm in side length and 300 mm in bulk, which was glued to a glass slide. Static behavior is defines as the membrane deflection measurement taking into account only its response to the infrared radiation energy that drives them.

Study on Micro Reversible Electrical Discharge Machining Method for the Fabrication of Micro Structures

A reversible machining method using micro electrical discharge machining (EDM) was developed. This new method can achieve depositing or selective removing of metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one EDM machining system. In micro EDM deposition process, brass, tungsten and steel material can be deposited successfully. The deposited material has compact fine texture and combines close to workpiece. Then, micro complex structures by series deposition strategy and sub-deposition strategy were deposited. In the selective removal process, the machining effects of different working mediums were researched. Results show that the machining effect in liquid medium is better than that of in air. Finally, using the micro reversible EDM process, a micro square column with 0.070mm in side length, 0.750mm in height and a micro cylinder with 0.140mm in diameter, 1.180mm in height were fabricated.

Experimental Research of Micro Reversible Electrical Discharge Machining

Based on the principle of micro electrical discharge machining (EDM), a reversible machining method is proposed, which can achieve depositing or removing selectively metal material for the fabrication of micro structures. It is easy to transform the machining process from deposition to removal in one machining system. The characteristics of the deposited material show that the components of deposited material are almost the same as those of the tool electrode, and the metallurgical bonding has formed on the interface between the deposited material and the base. Moreover, the deposited material has well machinability in different micro EDM selective removal process, including micro EDM die-sinking and micro EDM milling. As a result, a micro square column with 0.1mm in side length, 0.88mm in height and a micro cylinder with 0.14mm in diameter, 1.18mm in height were fabricated by using the micro reversible EDM process.

Mechanical persistent current switch made of RE–Ba–Cu–O bulk with resin impregnation

We studied the possibility to construct a mechanical persistent current switch using a pair of bulk YBCO superconductors with resin-impregnation. Supercurrents could not be passed between two YBCO bulks when the currents were passed along the c-axis. In contrast, supercurrents as large as 13.5 A could be successfully passed between two YBCO cubes 8 mm in side length at the compression force of 500 N when the currents were passed along the ab-axis. The contact surfaces were observed by scanning electron microscopy after the transport measurements at 500 N load. The damage was observed on the (0 0 1) contact surface, while no damage was present on the (1 0 0) surface, reflecting superior contact characteristics.

The influence of residual stress and membrane thickness on the performance of Fe–Ni–Cr/Invar bimetal freestanding membrane for microdevices

This study attempts to demonstrate that the 75Fe–22Ni–3Cr (FNC)/64Fe–36Ni (Invar) bimetal membrane seem to be a promising candidate for the fabrication of microelectromechanical system (MEMS) devices. The performance and mechanical properties of a series of freestanding membrane under mechanical and thermal load is presented. It is found that the residual stress level and membrane thickness play an important role on the membrane performance. For membrane with thickness of 1 μm and 1 mm in side length, a 164 MPa elevation in residual stress may result in 30% reduction in membrane deflection. The increase in membrane thickness increases both the flexural rigidity of the membrane and the effective current conduction cross-section. The decrease of the flexibility of the membrane results in a reduction in deflection of about 25% as thickness varies from 0.9 to 2.0 μm. Meanwhile, the Young’s modulus also decreases quickly as membrane thickness decreased by virtue of the grain size variation, approaching the value of the bulk material of 190 GPa at about 3.2 μm thick. On the other hand, the reduction in membrane resistance may reduce the heating power. As a result, the increase in membrane thickness from 2 to 3.2 μm cause a reduction in conversion efficiency factor (CEF) of 72% from 1027 to 743 μm/W.

Mechanical persistent current switch made of resin-impregnated bulk superconductors

We studied the possibility of constructing a mechanical persistent current switch using a pair of bulk YBCO superconductors with resin-impregnation. Supercurrents could not be passed between two YBCO bulks when the currents were passed along the c axis. In contrast, supercurrents as large as 13.5 A could be successfully passed between two YBCO cubes 8 mm in side length at the compression force of 500 N when the currents were passed along the ab axis.