Azzah Dyah Pramata | Indonesian Capital Market and Financial Institution Supervisory Agency (Bapepam-LK) (original) (raw)

Papers by Azzah Dyah Pramata

Research paper thumbnail of Facial synthesis of colloidal stable magnetic nanoparticles coated with high hydrophilic negative charged poly(4‐styrenesulfonic acid co‐maleic acid) sodium for water remediation

Polymers for Advanced Technologies

Research paper thumbnail of Light‐Stimulated Luminescence Control of Lead Halide‐Based Perovskite Nanocrystals Coupled with Photochromic Molecules via Electron and Energy Transfer

Research paper thumbnail of Sintesis dan Karakterisasi Minyak Cashew Nut Shell Liquid (CNSL) dari Limbah Kulit Biji Mete Desa Blaru, Badas, Kediri dengan Metode Press Panas

Sewagati

Desa Blaru, Kecamatan Badas, Kabupaten Kediri, terkenal sebagai sentra produksi kacang mete. Kaca... more Desa Blaru, Kecamatan Badas, Kabupaten Kediri, terkenal sebagai sentra produksi kacang mete. Kacang mete yang diproduksi memiliki kualitas yang bagus, renyah, gurih, serta tahan lama. Pangsa pasarnya bahkan sampai keluar Jawa Timur, termasuk Kalimantan.Selama ini, masyarakat hanya mengolah bijinya saja sebagai makanan ringan, sementara kulit bijinya dibuang sebagai limbah atau sebagai kayu bakar. Padahal, di dalam kulit biji jambu mete terdapat minyak yang apabila di ekstrak bisa dijual dengan harga yang mahal. Minyak hasil ektraksi dari kulit biji jambu mete biasanya disebut sebagai Cashew Nut Shell Liquid (CNSL), yang sering digunakan sebagai campuran bensin, cat genteng, hingga untuk industri minyak rem. Proses pembuatan minyak CNSL dilakukan dengan menggunakan metode pengepresan panas. Sebanyak 2 kg limbah biji mete dimasukkan ke dalam alat pengepresan, ditutup, kemudian kulit mete dipress dengan menggunakan poros ulir. Kemudian selanjutnya adalah pemanasan. Kulit mete dipanaska...

Research paper thumbnail of Review Pengaruh Konsentrasi dan Sifat Permukaan Dikorelasikan dengan Rasio Si/Al Katalis Silika-Alumina dalam Cracking Sampah Plastik Polypropylene untuk Produksi Bahan Bakar Cair

Penelitian ini bertujuan untuk menganalisis pengaruh konsentrasi dan sifat permukaan yang dikorel... more Penelitian ini bertujuan untuk menganalisis pengaruh konsentrasi dan sifat permukaan yang dikorelasikan dengan rasio Si/Al katalis silika-alumina dalam cracking sampah plastik polypropylene untuk produksi bahan bakar cair. Penelitian ini menggunakan komparasi beberapa telaah jurnal dengan metode literature review berdasarkan penelitian eksperimental yang selanjutnya didesain menjadi penelitian cross-sectional. Dari penelitian ini, ditemukan bahwa konsentrasi dan sifat permukaan katalis pada cracking sangatlah penting. Konsentrasi yang sedikit (berdasarkan nilai modus dan rata-rata optimum sebesar 10% wt dan 6,42% wt) dan sifat permukaan berupa area permukaan dan ukuran pori yang bernilai tinggi dirasa efektif (berdasarkan nilai rata-rata optimum sebesar 394 m2g-1 dan 0,94 cm3g-1). Jika dikorelasikan dengan rasio Si/Al, konsentrasi yang sedikit mampu menghasilkan jumlah relatif Si/Al yang sedang (35/65) untuk produksi liquid yang efektif. Terkait dengan sifat permukaan, semakin tingg...

Research paper thumbnail of Effect of stearic acid treatment for calcium carbonate on morphology and tensile strength of recycled HDPE/Calcium carbonate composites for 3D printer filament

THE 4TH INTERNATIONAL CONFERENCE ON MATERIALS AND METALLURGICAL ENGINEERING AND TECHNOLOGY (ICOMMET) 2020, 2021

Research paper thumbnail of Morphologically stable and controlled shape of CsPbBr3 perovskite nanoparticle synthesized at room temperature with curing time

THE 4TH INTERNATIONAL CONFERENCE ON MATERIALS AND METALLURGICAL ENGINEERING AND TECHNOLOGY (ICOMMET) 2020, 2021

Research paper thumbnail of Numerical Simulation of Effects of Number of Beds and Presence of Aerosol Flow from Sanitation Machine to Air Circulation in Hospital Isolation Room of COVID-19 Patients

MATERIALS RESEARCH COMMUNICATIONS, 2021

Coronavirus Disease (Covid-19) becomes a serious attention because the virus can spread from huma... more Coronavirus Disease (Covid-19) becomes a serious attention because the virus can spread from human-to-human rapidly. By the first case at December 2019, Covid-19 was making the outbreak all over the world just in few months, especially since February 2020 until now. As a result, the pandemic makes hospital occupancy really high. Hospital must make strategy to make sure the isolation rooms are sterile. By knowing the best configuration for the isolation room and sanitizing machine for spreading disinfectant aerosol, modelling can be used to minimize the high risk from the virus inside the room, as the virus can be transmitted in the airborne. In this study, CFD modelling is used to answer this problem by modelling 3 rooms with different amount of beds. Room 1 contains of 2 beds, room 2 contains of 3 beds and room 3 contains of 6 beds. SST k-ε equation is used to model the flows. It is observed that the room with 6 beds has the biggest turbulence kinetic energy and high turbulence will be the best effective way to distribute aerosol from sanitizer to entire room.

Research paper thumbnail of Informative Bounds of Neural Networks Prediction for Composite Fatigue Life Under Variable Amplitude Loading

MATERIALS RESEARCH COMMUNICATIONS, 2021

In this study, the informative bounds of neural networks (NN) prediction with respect to the util... more In this study, the informative bounds of neural networks (NN) prediction with respect to the utilization of less fatigue data for fatigue life assessment of composite material covering a wide range of stress ratios R was examined and investigated. Fiberglass reinforced polyester of [90/0/±45/0]S lay-up with fatigue data of various stress ratios (R = 0.1, 0.5, 0.7, 0.8, 0.9,-0.5,-1,-2 and 10) was examined in the present paper. Multi-layer Perceptrons (MLP) trained with Levenberg-Marquardt algorithm was utilized to result in fast and efficient NN model and Bayesian regularization technique was incorporated to deal with limited training data chosen for the model. The developed NN model was trained with fatigue data from only two stress ratios, where three sets of two stress ratio values were formed and used as the training sets, namely R = 0.1 and 0.5, R = 0.1 and-1, and R = 0.1 and 10, respectively. It was obtained that fatigue data from R = 10 produced the widest bounds of prediction, namely having the highest estimated standard deviation value from the fatigue lives predicted. Furthermore, it is revealed in the current study knowing the fact that fatigue data from R = 10 have the highest estimated standard deviation and subsequently including the fatigue data as one of the training data set, the NN model trained could produce the lowest mean squared error (MSE) value for the results of fatigue life prediction. This is justifying also the selection of training set of R = 0.1 and 10 as best training set in the previous study, which is based on the stress ratios' better relative positions in the corresponding constant life diagram (CLD). Finally, taking the highest estimated standard deviation value from fatigue data of R = 10 as the conservative estimated bounds of NN prediction, it was shown that for the NN prediction of fatigue life whose noticeable discrepancies with the experimental data, the discrepancies were well confined within the conservative bounds of prediction.

Research paper thumbnail of The Effects of Annealing on the Morphology and Luminescence Stability of an Inorganic Perovskite CsPbBr3 Synthesized Using the Ligand Assisted Reprecipitation (LARP) Method

Materials Science Forum, 2022

The inorganic perovskite CsPbBr3 is a promising candidate for photovoltaic and light-emitting dev... more The inorganic perovskite CsPbBr3 is a promising candidate for photovoltaic and light-emitting devices, but stability concerns hinder its commercial application. The purpose of this study is to investigate the effect of annealing temperature on the morphology and luminescence stability of inorganic CsPbBr3 perovskite at 90°C, 100°C, 110°C, and 120°C. The CsPbBr3 was prepared by Ligand Assisted Reprecipitation (LARP). The TEM images revealed the formation of nanoplatelets of inorganic CsPbBr3 perovskite with an average particle size of 35 nm. The morphological stability of as-synthesized CsPbBr3 after annealing at a defined temperature was demonstrated using X-Ray Diffraction characterization and SEM imaging. The crystal structure remains stable with a cubic structure even when heated to 120°C. UV-Vis absorbance and photoluminescence intensity spectra confirmed the luminescence stability of the as-prepared CsPbBr3 after annealing process.

Research paper thumbnail of The Effect of Cu2O Synthesis Method on its Optical Properties

Materials Science Forum, 2022

Cuprous Oxide (Cu2O) is a semiconductor material with excellent photocatalytic properties, a broa... more Cuprous Oxide (Cu2O) is a semiconductor material with excellent photocatalytic properties, a broad range of applications, low fabrication costs, and is non-toxic. We concentrated on the impact of two different synthesis methods in this study. Cu2O synthesis was carried out using two different techniques, which are chemical deposition and hot-soap method. The chemical deposition (CD) method used a copper sulfate pentahydrate precursor in a room temperature reaction. Hot-soap (HS) method employed copper acetylacetonate with reaction at higher temperature. The X-Ray Diffraction analysis reveals a sharp peak with a size of 53.8 nm and a broaden peak with a size of 26.24 nm for particles synthesized by (Cu2O-CD) and (Cu2O-HS), respectively. Using the Tauc Plot method, the band gap of Cu2O-HS is estimated to be 2.65 eV and that of Cu2O-CD to be 1.7 eV. Cu2O-HS emits a noticeable photoluminescence peak at 425 nm, whereas Cu2O-CD emits no peaks in photoluminescence spectra analysis. These f...

Research paper thumbnail of Effect of Perovskite CsPbBr3 Concentration and Coating Method on Thin Film Morphology and its Photovoltaic Performance

Materials Science Forum, 2022

Perovskite CsPbBr 3 has a band gap energy of 2.3 eV which has the potential for solar cell applic... more Perovskite CsPbBr 3 has a band gap energy of 2.3 eV which has the potential for solar cell applications. The issue regarding the relationship between the different coating methods and the concentration has not been studied further. Therefore, this study focuses on analyzing the effect of variations in the concentration of CsPbBr 3 20 mM and 40 mM as well as d ifferent coating methods, spin-coating, dip-coating and drop-c asting on the morphology of the thin film. The ligand assisted reprecipitation LARP method was used to synthesize CsPbBr3 using control ligands, octylamine and oleic acid to obtain CsPbBr3 orthorhombic.Scanning Electron Microscopy (SEM) observations show that increasing the concentration resulted in larger particle size, and the Drop Casting method resulted in a more fully coverage on thin film. Drop Casting and a 40 mM solution produced the highest solar cell efficiency of 1.4 %.

Research paper thumbnail of Efficient Fatigue Life Assessment of Composite Materials by Using a Hybrid Surrogate Modeling

MATERIALS RESEARCH COMMUNICATIONS, 2021

In this study, hybrid surrogate and nonlinear autoregressive with exogenous inputs (NARX) model i... more In this study, hybrid surrogate and nonlinear autoregressive with exogenous inputs (NARX) model is developed and presented as data-driven based predictive model for efficient fatigue life assessment of composite materials. Surrogate modeling based upon wavelet neural networks (WNN) is employed to efficiently unveil mathematical pattern in S-N data, but costly to get from experiments. Moreover, the NARX architecture is chosen in order to enable multi-step ahead prediction in fatigue life assessment of multivariable amplitude loadings. By observing fatigue data as dynamic data of stress ratio series, it is shown that the hybrid model produces reasonably accurate fatigue life prediction by using fatigue data from two stress ratio values only. The use of two stress ratio values also allows usage of more limited fatigue data in the lifetime prediction. The WNN-NARX surrogate model is tested with well-known fatigue data in literature. Several composite materials examined in this study show the efficacy and robustness of the proposed model.

Research paper thumbnail of Photochemistry in CuInS2 Quantum Dots/Polyoxometalate System

Energy transfer involving semiconductor quantum dots (QDs) has received increased attention in re... more Energy transfer involving semiconductor quantum dots (QDs) has received increased attention in recent years because of high photostability and size-tunable optical properties. Here, we study photochemistry in quantum dot/polyoxometalate (POMs) systems and utilize quantum dots as light antenna that captures visible light to sensitize wide band gap POMs. We also demonstrate the photoenergy storage properties of CuInS 2 QD/POM systems. The PL quenching and the decrease in PL lifetime are clear indication that the excited electron of CuInS 2 was deactivated by electron transfer to POM such as PMo 12 O 40 , W 10 O 32 and SiW 10 O 36 that were hybridized with a cationic surfactant and dispersed together in an organic solvent. The quantum yields of CuInS 2 QDs were 2.32% with 3.9 nm in particle size. Irradiating QD/POM systems with visible light generates a one-electron reduced form of POMs, suggesting the reduction of POMs. Photoenergy can be stored as reduced POM under deaerated conditio...

Research paper thumbnail of Reversible ON/OFF switching of photoluminescence from CsPbX3 quantum dots coated with silica using photochromic diarylethene

Chemical Communications, 2019

Highly luminescent silica-coated CsPbX3 quantum dots (QDs) with good photostability were synthesi... more Highly luminescent silica-coated CsPbX3 quantum dots (QDs) with good photostability were synthesized and coupled with photochromic diarylethene to modulate the QDs’ photoluminescence (PL).

Research paper thumbnail of Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect-Related Photoluminescence Using Polyoxometalates as Quenchers

Advanced Functional Materials, 2017

Colloidal semiconductor nanocrystals (NCs), called quantum dots (QDs), have been intensively stud... more Colloidal semiconductor nanocrystals (NCs), called quantum dots (QDs), have been intensively studied because of their excellent photoluminescence (PL) quantum yields. However, commercial QDs such as CdSe and InP contain toxic or expensive rare elements, limiting their sustainable use. This study focuses on nontoxic, stable, and cheap tin oxides, and synthesized luminescent SnO 2 NCs of ≈2 nm in size by a heating-up method. Tin precursors and diols in a high-boiling point solvent with oleylamine as the surfactant are heated at 240 °C. SnO 2 NCs show defect-related photoluminescence at 400-460 nm by excitation at 370 nm, achieving a high quantum yield of more than 60%. The PL intensity is stable even when the NCs are stored in atmospheric air at room temperature for over 1 year. The defect-related emissions of the SnO 2 NCs are studied using polyoxometalates (POMs) as the PL quencher. POMs efficiently quench the PL emissions by extracting excited electrons from the conduction band and shallow surface defects. The results reveal that PL emissions from SnO 2 NCs are associated with radiative charge recombination via shallow defect levels on the surface and in the bulk, demonstrating the effectiveness of the PL quenching technique using POMs in studying the PL emission mechanism in QDs.

Research paper thumbnail of Visible Light-Driven Photoenergy Storage and Photocatalysis Using Polyoxometallates Coupled with a Ru Complex

The Journal of Physical Chemistry C, 2017

Polyoxometallates (POMs) have been attracting much attention as homogeneous molecular catalysts b... more Polyoxometallates (POMs) have been attracting much attention as homogeneous molecular catalysts because of their excellent photocatalytic activities. However, the poor sensitivities of POMs to visible light limit their utilization of solar energy. Here, we studied photoinduced electron transfer (PET) from a Ru complex to POMs such as SiW 10 O 36 8-, W 10 O 32 4-, SiW 12 O 40 4-, and PMo 12 O 40 3to use them for photoenergy storage and photocatalysis driven by visible light. A hydrophobic Ru complex ([Ru(nbpy) 3 ] 2+ ; nbpy = 4,4'-dinoyl-2,2'-bipyridyl) was coupled with POMs that were hybridized with dioctadecyldimethylammonium (DODA) in chloroform. Photoluminescence (PL) quenching and lifetime measurements indicate that PET efficiently occurred from the Ru complex to the POMs/DODA hybrids in chloroform by excitation with visible light. The PET led to the formation of one-electron reduced POMs that store photoexcited electrons. The stored/charged electrons can be discharged in a subsequent reaction that can proceed under dark conditions. The Ru complex-POM hybrid system in chloroform was used to reduce metal ions in a water phase at a liquid/liquid interface under visible light irradiation. The one-electron reduced POM that was formed by PET could reduce metal ions to produce metal particles, suggesting the applicability of this system for photocatalytic reactions under visible light irradiation.

Research paper thumbnail of Efficient solution route to transparent ZnO semiconductor films using colloidal nanocrystals

Journal of Asian Ceramic Societies, 2016

ZnO nanocrystals (NCs) were synthesized by heating Zn (II) acetylacetonate in oleic acid/oleylami... more ZnO nanocrystals (NCs) were synthesized by heating Zn (II) acetylacetonate in oleic acid/oleylamine in the presence of 1,2-hexadecanediol at 220 • C. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed the formation of monodispersed ZnO NCs of ca. 7 nm. ZnO NC assembled films were fabricated on a glass substrate by deposition with the colloidal ZnO NCs dispersed in toluene. The film composed of the NCs showed good optical transparency in the visible to near-infrared region. A device coupling the ZnO NC film with a p-type Cu 2 ZnSnS 4 (CZTS) NC film exhibited an obvious diode-like current-voltage behavior. The results suggest that the transparent ZnO film has a potentiality to be used for an n-type window layer in some optoelectronic applications.

Research paper thumbnail of Visible-Light Sensitization and Photoenergy Storage in Quantum Dot/Polyoxometalate Systems

Chemistry - A European Journal, 2015

Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals... more Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals, called quantum dots (QDs), to other semiconductors has attracted much attention and has potential application in solar energy conversion (i.e., QD-sensitized solar cells). Sensitization of wide band gap polyoxometalates (POMs) to visible light by using CuInS 2 QDs dispersed in an organic solution is demonstrated herein. Photoluminescence quenching and lifetime studies revealed efficient electron transfer from the CuInS 2 QDs to POMs, such as SiW 12 O 40 and W 10 O 32 , that were hybrid-ized with a cationic surfactant. CuInS 2 QDs function as an antenna that absorbs visible light and supplies electrons to the POMs to enable certain photocatalytic reactions, including noble-metal-ion reduction. The photoenergy storage capabilities of the QD-POM system, in which electrons photogenerated in QDs by visible-light excitation are trapped and accommodated by POMs to form reduced POM, are also demonstrated. Electrons stored in the POM can be later discharged through reductive reactions, such as oxygen reduction, in the dark.

Research paper thumbnail of Synthesis and Characterization of Semiconducting Boron-doped Amorphous Carbon Materials Using an Organic Boron Compound as a Precursor

Chemistry Letters, 2011

Boron-doped amorphous carbon was synthesized by polymerizing naphthalene and triphenylborane with... more Boron-doped amorphous carbon was synthesized by polymerizing naphthalene and triphenylborane with subsequent heat treatment by spark plasma sintering. The boron-doped carbon material has negative Seebeck coefficient (¹0.22 mV K ¹1), which indicates the carbon material functions as an n-type semiconductor.

Research paper thumbnail of Photoluminescence: Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect‐Related Photoluminescence Using Polyoxometalates as Quenchers (Adv. Funct. Mater. 4/2018)

Advanced Functional Materials, 2018

Research paper thumbnail of Facial synthesis of colloidal stable magnetic nanoparticles coated with high hydrophilic negative charged poly(4‐styrenesulfonic acid co‐maleic acid) sodium for water remediation

Polymers for Advanced Technologies

Research paper thumbnail of Light‐Stimulated Luminescence Control of Lead Halide‐Based Perovskite Nanocrystals Coupled with Photochromic Molecules via Electron and Energy Transfer

Research paper thumbnail of Sintesis dan Karakterisasi Minyak Cashew Nut Shell Liquid (CNSL) dari Limbah Kulit Biji Mete Desa Blaru, Badas, Kediri dengan Metode Press Panas

Sewagati

Desa Blaru, Kecamatan Badas, Kabupaten Kediri, terkenal sebagai sentra produksi kacang mete. Kaca... more Desa Blaru, Kecamatan Badas, Kabupaten Kediri, terkenal sebagai sentra produksi kacang mete. Kacang mete yang diproduksi memiliki kualitas yang bagus, renyah, gurih, serta tahan lama. Pangsa pasarnya bahkan sampai keluar Jawa Timur, termasuk Kalimantan.Selama ini, masyarakat hanya mengolah bijinya saja sebagai makanan ringan, sementara kulit bijinya dibuang sebagai limbah atau sebagai kayu bakar. Padahal, di dalam kulit biji jambu mete terdapat minyak yang apabila di ekstrak bisa dijual dengan harga yang mahal. Minyak hasil ektraksi dari kulit biji jambu mete biasanya disebut sebagai Cashew Nut Shell Liquid (CNSL), yang sering digunakan sebagai campuran bensin, cat genteng, hingga untuk industri minyak rem. Proses pembuatan minyak CNSL dilakukan dengan menggunakan metode pengepresan panas. Sebanyak 2 kg limbah biji mete dimasukkan ke dalam alat pengepresan, ditutup, kemudian kulit mete dipress dengan menggunakan poros ulir. Kemudian selanjutnya adalah pemanasan. Kulit mete dipanaska...

Research paper thumbnail of Review Pengaruh Konsentrasi dan Sifat Permukaan Dikorelasikan dengan Rasio Si/Al Katalis Silika-Alumina dalam Cracking Sampah Plastik Polypropylene untuk Produksi Bahan Bakar Cair

Penelitian ini bertujuan untuk menganalisis pengaruh konsentrasi dan sifat permukaan yang dikorel... more Penelitian ini bertujuan untuk menganalisis pengaruh konsentrasi dan sifat permukaan yang dikorelasikan dengan rasio Si/Al katalis silika-alumina dalam cracking sampah plastik polypropylene untuk produksi bahan bakar cair. Penelitian ini menggunakan komparasi beberapa telaah jurnal dengan metode literature review berdasarkan penelitian eksperimental yang selanjutnya didesain menjadi penelitian cross-sectional. Dari penelitian ini, ditemukan bahwa konsentrasi dan sifat permukaan katalis pada cracking sangatlah penting. Konsentrasi yang sedikit (berdasarkan nilai modus dan rata-rata optimum sebesar 10% wt dan 6,42% wt) dan sifat permukaan berupa area permukaan dan ukuran pori yang bernilai tinggi dirasa efektif (berdasarkan nilai rata-rata optimum sebesar 394 m2g-1 dan 0,94 cm3g-1). Jika dikorelasikan dengan rasio Si/Al, konsentrasi yang sedikit mampu menghasilkan jumlah relatif Si/Al yang sedang (35/65) untuk produksi liquid yang efektif. Terkait dengan sifat permukaan, semakin tingg...

Research paper thumbnail of Effect of stearic acid treatment for calcium carbonate on morphology and tensile strength of recycled HDPE/Calcium carbonate composites for 3D printer filament

THE 4TH INTERNATIONAL CONFERENCE ON MATERIALS AND METALLURGICAL ENGINEERING AND TECHNOLOGY (ICOMMET) 2020, 2021

Research paper thumbnail of Morphologically stable and controlled shape of CsPbBr3 perovskite nanoparticle synthesized at room temperature with curing time

THE 4TH INTERNATIONAL CONFERENCE ON MATERIALS AND METALLURGICAL ENGINEERING AND TECHNOLOGY (ICOMMET) 2020, 2021

Research paper thumbnail of Numerical Simulation of Effects of Number of Beds and Presence of Aerosol Flow from Sanitation Machine to Air Circulation in Hospital Isolation Room of COVID-19 Patients

MATERIALS RESEARCH COMMUNICATIONS, 2021

Coronavirus Disease (Covid-19) becomes a serious attention because the virus can spread from huma... more Coronavirus Disease (Covid-19) becomes a serious attention because the virus can spread from human-to-human rapidly. By the first case at December 2019, Covid-19 was making the outbreak all over the world just in few months, especially since February 2020 until now. As a result, the pandemic makes hospital occupancy really high. Hospital must make strategy to make sure the isolation rooms are sterile. By knowing the best configuration for the isolation room and sanitizing machine for spreading disinfectant aerosol, modelling can be used to minimize the high risk from the virus inside the room, as the virus can be transmitted in the airborne. In this study, CFD modelling is used to answer this problem by modelling 3 rooms with different amount of beds. Room 1 contains of 2 beds, room 2 contains of 3 beds and room 3 contains of 6 beds. SST k-ε equation is used to model the flows. It is observed that the room with 6 beds has the biggest turbulence kinetic energy and high turbulence will be the best effective way to distribute aerosol from sanitizer to entire room.

Research paper thumbnail of Informative Bounds of Neural Networks Prediction for Composite Fatigue Life Under Variable Amplitude Loading

MATERIALS RESEARCH COMMUNICATIONS, 2021

In this study, the informative bounds of neural networks (NN) prediction with respect to the util... more In this study, the informative bounds of neural networks (NN) prediction with respect to the utilization of less fatigue data for fatigue life assessment of composite material covering a wide range of stress ratios R was examined and investigated. Fiberglass reinforced polyester of [90/0/±45/0]S lay-up with fatigue data of various stress ratios (R = 0.1, 0.5, 0.7, 0.8, 0.9,-0.5,-1,-2 and 10) was examined in the present paper. Multi-layer Perceptrons (MLP) trained with Levenberg-Marquardt algorithm was utilized to result in fast and efficient NN model and Bayesian regularization technique was incorporated to deal with limited training data chosen for the model. The developed NN model was trained with fatigue data from only two stress ratios, where three sets of two stress ratio values were formed and used as the training sets, namely R = 0.1 and 0.5, R = 0.1 and-1, and R = 0.1 and 10, respectively. It was obtained that fatigue data from R = 10 produced the widest bounds of prediction, namely having the highest estimated standard deviation value from the fatigue lives predicted. Furthermore, it is revealed in the current study knowing the fact that fatigue data from R = 10 have the highest estimated standard deviation and subsequently including the fatigue data as one of the training data set, the NN model trained could produce the lowest mean squared error (MSE) value for the results of fatigue life prediction. This is justifying also the selection of training set of R = 0.1 and 10 as best training set in the previous study, which is based on the stress ratios' better relative positions in the corresponding constant life diagram (CLD). Finally, taking the highest estimated standard deviation value from fatigue data of R = 10 as the conservative estimated bounds of NN prediction, it was shown that for the NN prediction of fatigue life whose noticeable discrepancies with the experimental data, the discrepancies were well confined within the conservative bounds of prediction.

Research paper thumbnail of The Effects of Annealing on the Morphology and Luminescence Stability of an Inorganic Perovskite CsPbBr3 Synthesized Using the Ligand Assisted Reprecipitation (LARP) Method

Materials Science Forum, 2022

The inorganic perovskite CsPbBr3 is a promising candidate for photovoltaic and light-emitting dev... more The inorganic perovskite CsPbBr3 is a promising candidate for photovoltaic and light-emitting devices, but stability concerns hinder its commercial application. The purpose of this study is to investigate the effect of annealing temperature on the morphology and luminescence stability of inorganic CsPbBr3 perovskite at 90°C, 100°C, 110°C, and 120°C. The CsPbBr3 was prepared by Ligand Assisted Reprecipitation (LARP). The TEM images revealed the formation of nanoplatelets of inorganic CsPbBr3 perovskite with an average particle size of 35 nm. The morphological stability of as-synthesized CsPbBr3 after annealing at a defined temperature was demonstrated using X-Ray Diffraction characterization and SEM imaging. The crystal structure remains stable with a cubic structure even when heated to 120°C. UV-Vis absorbance and photoluminescence intensity spectra confirmed the luminescence stability of the as-prepared CsPbBr3 after annealing process.

Research paper thumbnail of The Effect of Cu2O Synthesis Method on its Optical Properties

Materials Science Forum, 2022

Cuprous Oxide (Cu2O) is a semiconductor material with excellent photocatalytic properties, a broa... more Cuprous Oxide (Cu2O) is a semiconductor material with excellent photocatalytic properties, a broad range of applications, low fabrication costs, and is non-toxic. We concentrated on the impact of two different synthesis methods in this study. Cu2O synthesis was carried out using two different techniques, which are chemical deposition and hot-soap method. The chemical deposition (CD) method used a copper sulfate pentahydrate precursor in a room temperature reaction. Hot-soap (HS) method employed copper acetylacetonate with reaction at higher temperature. The X-Ray Diffraction analysis reveals a sharp peak with a size of 53.8 nm and a broaden peak with a size of 26.24 nm for particles synthesized by (Cu2O-CD) and (Cu2O-HS), respectively. Using the Tauc Plot method, the band gap of Cu2O-HS is estimated to be 2.65 eV and that of Cu2O-CD to be 1.7 eV. Cu2O-HS emits a noticeable photoluminescence peak at 425 nm, whereas Cu2O-CD emits no peaks in photoluminescence spectra analysis. These f...

Research paper thumbnail of Effect of Perovskite CsPbBr3 Concentration and Coating Method on Thin Film Morphology and its Photovoltaic Performance

Materials Science Forum, 2022

Perovskite CsPbBr 3 has a band gap energy of 2.3 eV which has the potential for solar cell applic... more Perovskite CsPbBr 3 has a band gap energy of 2.3 eV which has the potential for solar cell applications. The issue regarding the relationship between the different coating methods and the concentration has not been studied further. Therefore, this study focuses on analyzing the effect of variations in the concentration of CsPbBr 3 20 mM and 40 mM as well as d ifferent coating methods, spin-coating, dip-coating and drop-c asting on the morphology of the thin film. The ligand assisted reprecipitation LARP method was used to synthesize CsPbBr3 using control ligands, octylamine and oleic acid to obtain CsPbBr3 orthorhombic.Scanning Electron Microscopy (SEM) observations show that increasing the concentration resulted in larger particle size, and the Drop Casting method resulted in a more fully coverage on thin film. Drop Casting and a 40 mM solution produced the highest solar cell efficiency of 1.4 %.

Research paper thumbnail of Efficient Fatigue Life Assessment of Composite Materials by Using a Hybrid Surrogate Modeling

MATERIALS RESEARCH COMMUNICATIONS, 2021

In this study, hybrid surrogate and nonlinear autoregressive with exogenous inputs (NARX) model i... more In this study, hybrid surrogate and nonlinear autoregressive with exogenous inputs (NARX) model is developed and presented as data-driven based predictive model for efficient fatigue life assessment of composite materials. Surrogate modeling based upon wavelet neural networks (WNN) is employed to efficiently unveil mathematical pattern in S-N data, but costly to get from experiments. Moreover, the NARX architecture is chosen in order to enable multi-step ahead prediction in fatigue life assessment of multivariable amplitude loadings. By observing fatigue data as dynamic data of stress ratio series, it is shown that the hybrid model produces reasonably accurate fatigue life prediction by using fatigue data from two stress ratio values only. The use of two stress ratio values also allows usage of more limited fatigue data in the lifetime prediction. The WNN-NARX surrogate model is tested with well-known fatigue data in literature. Several composite materials examined in this study show the efficacy and robustness of the proposed model.

Research paper thumbnail of Photochemistry in CuInS2 Quantum Dots/Polyoxometalate System

Energy transfer involving semiconductor quantum dots (QDs) has received increased attention in re... more Energy transfer involving semiconductor quantum dots (QDs) has received increased attention in recent years because of high photostability and size-tunable optical properties. Here, we study photochemistry in quantum dot/polyoxometalate (POMs) systems and utilize quantum dots as light antenna that captures visible light to sensitize wide band gap POMs. We also demonstrate the photoenergy storage properties of CuInS 2 QD/POM systems. The PL quenching and the decrease in PL lifetime are clear indication that the excited electron of CuInS 2 was deactivated by electron transfer to POM such as PMo 12 O 40 , W 10 O 32 and SiW 10 O 36 that were hybridized with a cationic surfactant and dispersed together in an organic solvent. The quantum yields of CuInS 2 QDs were 2.32% with 3.9 nm in particle size. Irradiating QD/POM systems with visible light generates a one-electron reduced form of POMs, suggesting the reduction of POMs. Photoenergy can be stored as reduced POM under deaerated conditio...

Research paper thumbnail of Reversible ON/OFF switching of photoluminescence from CsPbX3 quantum dots coated with silica using photochromic diarylethene

Chemical Communications, 2019

Highly luminescent silica-coated CsPbX3 quantum dots (QDs) with good photostability were synthesi... more Highly luminescent silica-coated CsPbX3 quantum dots (QDs) with good photostability were synthesized and coupled with photochromic diarylethene to modulate the QDs’ photoluminescence (PL).

Research paper thumbnail of Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect-Related Photoluminescence Using Polyoxometalates as Quenchers

Advanced Functional Materials, 2017

Colloidal semiconductor nanocrystals (NCs), called quantum dots (QDs), have been intensively stud... more Colloidal semiconductor nanocrystals (NCs), called quantum dots (QDs), have been intensively studied because of their excellent photoluminescence (PL) quantum yields. However, commercial QDs such as CdSe and InP contain toxic or expensive rare elements, limiting their sustainable use. This study focuses on nontoxic, stable, and cheap tin oxides, and synthesized luminescent SnO 2 NCs of ≈2 nm in size by a heating-up method. Tin precursors and diols in a high-boiling point solvent with oleylamine as the surfactant are heated at 240 °C. SnO 2 NCs show defect-related photoluminescence at 400-460 nm by excitation at 370 nm, achieving a high quantum yield of more than 60%. The PL intensity is stable even when the NCs are stored in atmospheric air at room temperature for over 1 year. The defect-related emissions of the SnO 2 NCs are studied using polyoxometalates (POMs) as the PL quencher. POMs efficiently quench the PL emissions by extracting excited electrons from the conduction band and shallow surface defects. The results reveal that PL emissions from SnO 2 NCs are associated with radiative charge recombination via shallow defect levels on the surface and in the bulk, demonstrating the effectiveness of the PL quenching technique using POMs in studying the PL emission mechanism in QDs.

Research paper thumbnail of Visible Light-Driven Photoenergy Storage and Photocatalysis Using Polyoxometallates Coupled with a Ru Complex

The Journal of Physical Chemistry C, 2017

Polyoxometallates (POMs) have been attracting much attention as homogeneous molecular catalysts b... more Polyoxometallates (POMs) have been attracting much attention as homogeneous molecular catalysts because of their excellent photocatalytic activities. However, the poor sensitivities of POMs to visible light limit their utilization of solar energy. Here, we studied photoinduced electron transfer (PET) from a Ru complex to POMs such as SiW 10 O 36 8-, W 10 O 32 4-, SiW 12 O 40 4-, and PMo 12 O 40 3to use them for photoenergy storage and photocatalysis driven by visible light. A hydrophobic Ru complex ([Ru(nbpy) 3 ] 2+ ; nbpy = 4,4'-dinoyl-2,2'-bipyridyl) was coupled with POMs that were hybridized with dioctadecyldimethylammonium (DODA) in chloroform. Photoluminescence (PL) quenching and lifetime measurements indicate that PET efficiently occurred from the Ru complex to the POMs/DODA hybrids in chloroform by excitation with visible light. The PET led to the formation of one-electron reduced POMs that store photoexcited electrons. The stored/charged electrons can be discharged in a subsequent reaction that can proceed under dark conditions. The Ru complex-POM hybrid system in chloroform was used to reduce metal ions in a water phase at a liquid/liquid interface under visible light irradiation. The one-electron reduced POM that was formed by PET could reduce metal ions to produce metal particles, suggesting the applicability of this system for photocatalytic reactions under visible light irradiation.

Research paper thumbnail of Efficient solution route to transparent ZnO semiconductor films using colloidal nanocrystals

Journal of Asian Ceramic Societies, 2016

ZnO nanocrystals (NCs) were synthesized by heating Zn (II) acetylacetonate in oleic acid/oleylami... more ZnO nanocrystals (NCs) were synthesized by heating Zn (II) acetylacetonate in oleic acid/oleylamine in the presence of 1,2-hexadecanediol at 220 • C. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed the formation of monodispersed ZnO NCs of ca. 7 nm. ZnO NC assembled films were fabricated on a glass substrate by deposition with the colloidal ZnO NCs dispersed in toluene. The film composed of the NCs showed good optical transparency in the visible to near-infrared region. A device coupling the ZnO NC film with a p-type Cu 2 ZnSnS 4 (CZTS) NC film exhibited an obvious diode-like current-voltage behavior. The results suggest that the transparent ZnO film has a potentiality to be used for an n-type window layer in some optoelectronic applications.

Research paper thumbnail of Visible-Light Sensitization and Photoenergy Storage in Quantum Dot/Polyoxometalate Systems

Chemistry - A European Journal, 2015

Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals... more Recently, the process by which energy is transferred from photoexcited semiconductor nanocrystals, called quantum dots (QDs), to other semiconductors has attracted much attention and has potential application in solar energy conversion (i.e., QD-sensitized solar cells). Sensitization of wide band gap polyoxometalates (POMs) to visible light by using CuInS 2 QDs dispersed in an organic solution is demonstrated herein. Photoluminescence quenching and lifetime studies revealed efficient electron transfer from the CuInS 2 QDs to POMs, such as SiW 12 O 40 and W 10 O 32 , that were hybrid-ized with a cationic surfactant. CuInS 2 QDs function as an antenna that absorbs visible light and supplies electrons to the POMs to enable certain photocatalytic reactions, including noble-metal-ion reduction. The photoenergy storage capabilities of the QD-POM system, in which electrons photogenerated in QDs by visible-light excitation are trapped and accommodated by POMs to form reduced POM, are also demonstrated. Electrons stored in the POM can be later discharged through reductive reactions, such as oxygen reduction, in the dark.

Research paper thumbnail of Synthesis and Characterization of Semiconducting Boron-doped Amorphous Carbon Materials Using an Organic Boron Compound as a Precursor

Chemistry Letters, 2011

Boron-doped amorphous carbon was synthesized by polymerizing naphthalene and triphenylborane with... more Boron-doped amorphous carbon was synthesized by polymerizing naphthalene and triphenylborane with subsequent heat treatment by spark plasma sintering. The boron-doped carbon material has negative Seebeck coefficient (¹0.22 mV K ¹1), which indicates the carbon material functions as an n-type semiconductor.

Research paper thumbnail of Photoluminescence: Synthesis of Highly Luminescent SnO2 Nanocrystals: Analysis of their Defect‐Related Photoluminescence Using Polyoxometalates as Quenchers (Adv. Funct. Mater. 4/2018)

Advanced Functional Materials, 2018