Nd:YAG laser welding of stainless steel 304 for photonics device packaging

Although pulsed Nd:YAG laser welding has been widely used in microelectronics and photonics packaging industry, a full understanding of various phenomena involved is still a matter of trials and speculations. In this research, an ultra compact pulsed Nd:YAG laser with wavelength of 1.064 µm has been used to produce a spot weld on stainless steel 304. The principal objective of this research is to examine the effects of laser welding parameters such as laser beam peak powers, pulse durations, incident angles, focus point positions and number of shots on the weld dimensions: penetration depth and bead width. The ratio of the penetration depth to the bead width is considered as one of the most critical parameters to determine the weld quality. It is found that the penetration depth and bead width increase when the laser beam peak power, pulse duration and number of shot increase. In contrast, the penetration depth decreases when the laser beam defocus position and incident angle increase. This is due to the reduction of the laser beam intensity causing by the widening of the laser spot size. These experimental results provide a reference on an optimal laser welding operations for a reliable photonics device packaging. The results obtained shows that stainless steel 304 is suitable to be used as a base material for photonics device packaging employing Nd:YAG laser welding technique

Effect of early clinical skills teaching on 3rd year medical students' learning: The student perspective

AbstractObjectivesThe main purpose of the early introduction of Clinical Skills Learning (CSL) to pre-clinical years is to allow medical students to gain experience in clinical examination skills, basic medical procedures, history-taking and clinical communication. The objective of this study was to determine the effectiveness of the early teaching of clinical skills in preparing medical students for their clinical years.MethodsA validated questionnaire assessing the value of CSL on students in their first clinical year was distributed to 3rd year medical students. The questionnaire consisted of 8 items with a five-point Likert scale and one open-ended question.ResultsThe response rate to the questionnaire was approximately 62%. Nearly 97 (70.8%) students suggested that CSL was a favourable teaching strategy. A high percentage of students (90.5%) agreed that CSL was a useful pre-clinical module to prepare them for their clinical years. The students gave positive feedback on the teaching of history-taking and physical examination, exposure to the hospital environment and acquisition of communication skills with supervisors and patients. No student perceived the CSL module as poor.ConclusionsEarly CSL was well-perceived by students in preparing them for their clinical years. CSL is a vital part of the pre-clinical curriculum and should be further enriched with frequent hospital visits to enhance students' confidence level and performance when interacting with patients during their clinical years

Association of vital pulp therapy outcomes with tooth type, arch location, treatment type, and number of surfaces destroyed in deciduous teeth: A retrospective study

There is a paucity of information concerning vital pulp treatment outcomes in the undergraduate teaching setting. This study aimed to determine which type of deciduous molar, arch location, type of vital pulp therapy, and the number of carious surfaces involved had a better prognosis when carried out by undergraduate dental students. The method used was the review of clinical records of 590 patients with 600 deciduous molars, that visited the outpatient undergraduate dental clinics for vital pulp therapy. Statistical analysis used to determine the associations of tooth type, arch location, treatment type, and the number of carious surfaces involved in successful outcomes was logistic regression analysis with significance set at p < 0.05. According to the regression analysis model results, there was a significant association based on tooth type (p < 0.05) and arch location (p = 0.003). In addition, there was a significant association based on the type of treatment performed (p = 0.036). However, there was no significant association in success rates based on the number of carious surfaces involved (p = 0.873). In conclusion, second deciduous molars and maxillary deciduous molars had a better overall prognosis, and indirect pulp therapy was revealed to be more highly associated with successful treatment outcomes in comparison to ferric sulfate pulpotomy in our setting

Patterned membrane in an energy-efficient tilted panel filtration system for fouling control in activated sludge filtration

A membrane bioreactor enhances the overall biological performance of a conventional activated sludge system for wastewater treatment by producing high-quality effluent suitable for reuse. However, membrane fouling hinders the widespread application of membrane bioreactors by reducing the hydraulic performance, shortening membrane lifespan, and increasing the operational costs for membrane fouling management. This study assesses the combined effect of membrane surface corrugation and a tilted panel in enhancing the impact of air bubbling for membrane fouling control in activated sludge filtration, applicable for membrane bioreactors. The filterability performance of such a system was further tested under variable parameters: Filtration cycle, aeration rate, and intermittent aeration. Results show that a combination of surface corrugation and panel tilting enhances the impact of aeration and leads to 87% permeance increment. The results of the parametric study shows that the highest permeance was achieved under short filtration-relaxation cycle of 5 min, high aeration rate of 1.5 L/min, and short switching period of 2.5 min, to yield the permeances of 465 ± 18, 447 ± 2, and 369 ± 9 L/(m2h bar), respectively. The high permeances lead to higher operational flux that helps to lower the membrane area as well as energy consumption. Initial estimation of the fully aerated system yields the energy input of 0.152 kWh/m3, much lower than data from the full-scale references of <0.4 kWh/m3. Further energy savings and a lower system footprint can still be achieved by applying the two-sided panel with a switching system, which will be addressed in the future

Combinación de ozono y nanopartículas magnéticas verdes para la degradación de azul de metileno en agua residual sintética textil

Trabajo de investigaciónSe usaron nanopartículas de magnetita verdes en un proceso de ozonización para remoción del colorante azul de metileno proveniente agua residual sintética textil. La concentración inicial del contaminante fue de 2mg/L. Se obtuvo una capacidad máxima de adsorción sobre el material de 0.0086mg/g debida a la modelación cinética e isotermas. Finalmente se encontró un porcentaje de remoción de 87.02 usando ozonización catalítica.RESUMEN 1. INTRODUCCIÓN 2. PLANTEAMIENTO Y FORMULACIÓN DEL PROBLEMA 3. JUSTIFICACIÓN 4. OBJETIVOS 5. ESTADO DEL ARTE 6. ANTECEDENTES 7. MARCO DE REFERENCIA 8. ALCANCE Y LIMITACIONES 9. METODOLOGÍA 10. RESULTADOS CONCLUSIONES RECOMENDACIONES REFERENCIAS ANEXOSPregradoIngeniero Civi

A comprehensive treatment of parametric effect in a silicon microring resonator

Silicon microring resonator provides a new platform to form the building block for all-optical circuits, where it could be integrated on a single chip as a passive or active components. Here, we report a comprehensive treatment of parametric effect in a symmetrical add/drop silicon microring resonator with 5 μm radius operating within telecom wavelength spectrum or C-band ranging from 1530 nm to 1565 nm. The power outputs of the system are analyzed by using transfer matrix method. The FSR and FWHM have been optimized. The results demonstrated here will pave the way towards the new on-chip and chip-to-chip architecture and structure for low power and high bandwidth applications especially for all-optical switch and optical modulator

Radio wave generation using dark and bright soliton

In this study we propose a new system for radio wave using a soliton pulse within a micro waveguide and nano-waveguide. The system consists of two micro ring resonators and a nano ring resonator that can be integrated into a single system. The input soliton power, coupling coefficients, and ring radii, are used to control the short-wave and millimeter-wave output signals being generated and filtered in a single system. The large bandwidth signal is generated using a soliton pulse within a Kerr-type nonlinear medium. The signals with broad bandwidth or wavelength can then be generated. Results obtained have shown the potential of using this system for a broad light spectra generation

Soliton pulse induces TPA effect in a silicon MRR all-optical switch

One of the critical problems in achieving a real practical all-optical switching devices is the requirement for a strong material nonlinearity. A strong material nonlinearity is crucial in order to achieve a low switching power. However, silicon-based all-optical switches require extremely high switching power due to its relatively weak nonlinear optical properties. To overcome this limitation, we have designed an all-optical switch configuration based on silicon microring resonator structure and demonstrated the switching operation based on the nonlinear effects induced by a soliton pulse. The soliton pulse induces free-carrier concentration through two-photon absorption (TPA) effect and this leads to enhance the refractive index change and enhance the nonlinearity of the silicon. Thus, the silicon microring resonator alters the nonlinear phase shift which is required for switching

A theoretical model of all-optical switching induced by a soliton pulse in nano-waveguide ring resonator

We propose a theoretical model of 1×2 all-optical switching in a silicon nano-waveguide ring resonator induced by a soliton pulse. All-optical switches made by silicon fiber or silicon waveguide have attracted much attention, because the low-absorption wavelength windows of silicon material just match optical fiber communication. However, to achieve all-optical switching in silicon is challenging owing to its relatively weak nonlinear optical properties and require high switching power, which is much higher than the signal power. Such high power is inappropriate for effective on-chip integration. To overcome this limitation, we have used a highly confined nano-waveguide ring resonator structure with soliton pulse input to enhance the nonlinearity and this leads to enhance the effect of refractive index change on the transmission response. The refractive index is changed by controlling the free-carrier concentration through two-photon absorption (TPA) effect. The result indicates that a refractive index change as small as 6.4×10−3 can reduce the switching power to 2.38 ×10−6 W. The nano-waveguide ring resonator all-optical switching described here is achieved by using the concept of strong light confinement, and the switching power is approximately three orders of magnitude lower than the available silicon optical switches. Such controllable switch is desired for achieving high performance in nanometer-size planar structures