DEVELOPMENT OF THREE DIMENSIONAL SILICON MICRO- AND NANO-MACHINING

Ph.DDOCTOR OF PHILOSOPH

PRIMJENA STOHASTIČKOGA MODELA NA ODLAGALIŠTU JALOVINE KAO POTPORA DUGOROČNOJ PROIZVODNJI U OTVORENOME KOPU S CILJEM POVEĆANJA POSTOTKA RUDE U OBRADBI

This paper presents a chance-constrained integer programming approach based on the linear method to solve the longterm open pit mine production scheduling problem. Specifically, a single stockpile has been addressed for storing excess low-grade material based on the availability of processing capacity and for possible future processing. The proposed scheduling model maximizes the project NPV while respecting a series of physical and economic constraints. Differently from common practice, where deterministic models are used to calculate the average grade for material in the stockpiles, in this work a stochastic approach was performed, starting from the time of planning before the stockpile realization. By performing a probability analysis on two case studies (on iron and gold deposits), it was proven that the stockpile attributes can be treated as normally distributed random variables. Afterwards, the stochastic programming model was formulated in an open pit gold mine in order to determine the optimum amount of ore dispatched from different bench levels in the open pit and at the same time a low-grade stockpile to the mill. The chance-constrained programming was finally applied to obtain the equivalent deterministic solution of the primary model. The obtained results have shown a better feed grade for the processing plant with a higher NPV and probability of grade blending constraint satisfaction, with respect to using the traditional stockpile deterministic model.Rad prikazuje uporabu vjerojatnosnoga cjelobrojnog programiranja, temeljenoga na linearnome algoritmu, za dugoročno rješavanje proizvodnje u rudniku otvorenoga kopa. Obrađeno je jedno odlagalište jalovine sa „siromašnom” koncentracijom rude u cilju aktiviranja toga materijala u budućoj preradbi korisne sirovine. Takav projekt maksimizira trenutačnu vrijednost rudarenja uzimajući u obzir niz fizičkih i ekonomskih varijabli. Posebnost u odnosu na determinističke modele koji se danas uglavnom koriste za izračun granične prosječne vrijednosti koncentracije rude prije odlaganja kao jalovine izražena je stohastikom. Ona je uključila vjerojatnosnu analizu dvaju slučajeva, tj. za ležište željeza i zlata. U obama je dokazano kako se varijable određene na odlagalištu mogu opisati normalnom razdiobom. Stohastički model programiran je za rudnik zlata te je uzeta u obzir optimalna vrijednost rude razvrstane na različitim rudničkim razinama, a prije slanja na obradbu (mljevenje). Optimizirani model zatim je primijenjen za dobivanje usporednoga determinističkog modela. Rezultati su upozorili na to da je konačno rješenje pokazalo znatno bolji odabir granične koncentracije rude koja se mogla poslati na daljnju obradbu. Time je uvećana i ukupna vrijednost rudnika/ležišta

Self-powered cardiac pacemaker by piezoelectric polymer nanogenerator implant

Self-powered biomedical implants improve the life of patients and lower the risks associated with battery replacement. Piezoelectric energy harvesters that generate electricity from the cardiac motions are among the potential candidates to be used in self-powered implants, such as cardiac pacemakers. In this context, lead-based ceramic piezoelectric nanogenerators (PNGs) were emerged, which are toxic and susceptible to fatigue crack, causing harm to the patients. Polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE)-based films were also developed as cardiac energy harvesters. Here, we show a battery-free heart pacemaker that is powered by the generated electricity of a biocompatible and flexible piezoelectric polymer-based nanogenerator (PNG) from the cardiac motions of the left ventricle. The PNG is comprised of composite nanofibers of poly(vinylidene fluoride) (PVDF) and a hybrid nanofiller made of zinc oxide (ZnO) and reduced graphene oxide (rGO). The composite nanofiber is optimized towards achieving a large power output. In vivo implanted optimized PNG can successfully harvest 0.487 μJ from every heartbeat, which is conveniently larger than the pacing threshold energy for the human heart. The successful demonstration of a self-powered pacemaker places the polymer-based PNGs among the viable candidates for self-powered biomedical implants.</p

Porous graphene/poly(vinylidene fluoride) nanofibers for pressure sensing

Piezoelectric polymers have emerged as promising materials for application in pressure sensing devices in particular for wearable applications, where inorganic piezoelectric materials can face limitations due to their brittleness. One of the bottlenecks for the adaptation of piezoelectric polymers is their relatively weak piezoelectric voltage coefficient. Hence there have been numerous efforts to improve the performance of the comprising devices by making composites of poly(vinylidene fluoride) (PVDF), or through making porous PVDF films, or by nanostructuring. Here, we demonstrate the fabrication of porous nanofibers with graphene/PVDF composites and investigate the suitability of the fiber for motion sensing. The nanofibers are fabricated by electrospinning from the solution phase. Guided by an experimentally validated phase diagram for PVDF/solvent/non-solvent ternary system, porous graphene/PVDF nanofibers with different porosities and pore morphologies have been produced through solidifying the fibers in the binodal or spinodal regions of the phase diagram. It is found that only by solidifying the composite fibers in the spinodal region, graphene loading of 0.1 wt% promotes the formation of the electroactive phase substantially, and the resulting fibers exhibit enhanced piezoelectric output. It is further shown that the comprising sensors are biocompatible and show high sensitivity to body motion.</p

Silicon-based photonic crystals fabricated using proton beam writing combined with electrochemical etching method

A method for fabrication of three-dimensional (3D) silicon nanostructures based on selective formation of porous silicon using ion beam irradiation of bulk p-type silicon followed by electrochemical etching is shown. It opens a route towards the fabrication of two-dimensional (2D) and 3D silicon-based photonic crystals with high flexibility and industrial compatibility. In this work, we present the fabrication of 2D photonic lattice and photonic slab structures and propose a process for the fabrication of 3D woodpile photonic crystals based on this approach. Simulated results of photonic band structures for the fabricated 2D photonic crystals show the presence of TE or TM gap in mid-infrared rang

Perinatal Outcomes of Idiopathic Polyhydramnios with Normal Ultrasound: A Systematic Review and Meta-Analysis

Background: Incidence of polyhydramnios in various studies has been reported from 0.2 to 3.9%. Approximately, 50-60% of cases are idiopathic with no known etiology. We aimed to investigate perinatal outcomes of idiopathic polyhydramnios with a normal ultrasound. Materials and Methods: In this study, Persian and English databases including Barakatkns, SID, Magiran, Medline, Science Direct, Scopus, Cochran, Embase, and ProQuest were searched for articles published from 1950 to August 2018. The search procedure was conducted with keywords related to "idiopathic polyhydramnios", "perinatal outcomes", "normal ultrasound", and their equivalents in "Mesh" and PICO. In meta-analysis, first we quantified heterogeneity by using I2 statistics and tested using the Cochran’s Q test. Even when a low heterogeneity was detected, a fixed-effects model was applied, and for more than 75% of heterogeneity, random-effects model was used. The Forest Plot chart was drawn up and the relative risk (RR) estimate for each study (ES), the pooled estimate of "RR" by combining all the studies and its 95% CI, and the P-value associated with it, were indicated. Results: In this study, 13 articles involving 325,426 pregnant women were included for the Meta-analysis. The RR and 95% CI of Caesarian Section (C.S), 1.61(1.25-2.07), macrosomia, 1.84(1.40-2.42), preterm delivery, 2.45(1.29-4.64), NICU admission, 2.90(1.77-4.74), Apgar score min

A Straightforward Method to Produce Multi-Nanodrug Delivery Systems for Transdermal/Tympanic Patches Using Electrospinning and Electrospray

The delivery of drugs through the skin barrier at a predetermined rate is the aim of transdermal drug delivery systems (TDDSs). However, so far, TDDS has not fully attained its potential as an alternative to hypodermic injections and oral delivery. In this study, we presented a proof of concept of a dual drug-loaded patch made of nanoparticles (NPs) and ultrafine fibers fabricated by using one equipment, i.e., the electrospinning apparatus. Such NP/fiber systems can be useful to release drugs locally through the skin and the tympanic membrane. Briefly, dexamethasone (DEX)-loaded poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) fiber meshes were decorated with rhodamine (RHO)-loaded poly(lactic-co-glycolic acid) (PLGA) NPs, with RHO representing as a second drug model. By properly tuning the working parameters of electrospinning, DEX-loaded PHBHV fibers (i.e., by electrospinning mode) and RHO-loaded PLGA NPs (i.e., by electrospray mode) were successfully prepared and straightforwardly assembled to form a TDDS patch, which was characterized via Fourier transform infrared spectroscopy and dynamometry. The patch was then tested in vitro using human dermal fibroblasts (HDFs). The incorporation of DEX significantly reduced the fiber mesh stiffness. In vitro tests with showed that HDFs were viable for 8 days in contact with drug-loaded samples, and significant signs of cytotoxicity were not highlighted. Finally, thanks to a beaded structure of the fibers, a controlled release of DEX from the electrospun patch was obtained over 4 weeks, which may accomplish the therapeutic objective of a local, sustained and prolonged anti-inflammatory action of a TDDS, as is requested in chronic inflammatory conditions, and other pathological conditions, such as in sudden sensorineural hearing loss treatment