Judul: Analysis of the Impact of
Implementing Asymmetric Auto Rejection on Return Volatility in IDX30 Index
Stocks
Abstrak: Volatilitas return saham merupakan faktor penting dalam pengambilan keputusan investasi, dan strategi manajemen risiko yang efektif. Asymmetric Auto Rejection adalah suatu aturan atau mekanisme yang diterapkan dalam pasar saham untuk mengendalikan fluktuasi harga saham dengan cara yang tidak simetris. Penelitian ini menggunakan data volatilitas saham IDX30 pada periode Maret 2018 hingga Maret 2022. Oleh karena struktur data ini mencakup 30 emiten dalam periode tersebut, maka penelitian ini menggunakan analisis regresi data panel. Penelitian ini bertujuan untuk mengevaluasi dampak penerapan asymmetric auto rejection terhadap volatilitas return saham di pasar saham Indo-nesia selama pandemi Covid-19. Penelitian ini menunjukan bahwa model terbaik adalah model pengaruh acak dengan efek waktu. Model tersebut menunjukan bahwa tidak terdapat perbedaan volatilitas saham pada periode sebelum dan setelah penerapan kebijakan asymmetric auto rejection, artinya kebijakan tersebut dapat mengendalikan volatilitas harga saham IDX30. Trading Volume Activity (TVA) adalah jumlah total saham atau kontrak yang diperdagangkan da-lam periode waktu tertentu. TVA dan volatilitas memiliki hubungan positif, artinya ketika lebih banyak saham diperdagangkan, return saham cenderung lebih berfluktuasi. Stock return volatility is a crucial factor in investment decision-making and effective risk management strategies. Asymmetric Auto Rejection is a rule or mechanism applied in the stock market to control stock price fluctuations in a non-symmetrical manner. This study uses IDX30 stock volatility data from March 2018 to March 2022. Because this dataset includes 30 issuers over that period, this study applies panel data regression analysis. The aim of this study is to evaluate the impact of asymmetric auto rejection implementation on stock return volatility in the Indonesian stock market during the Covid-19 pandemic. The results showed that the best model was the random effects model with time effects. This model indicated that there was no difference in stock volatility before and after the implementation of the asymmetric auto rejection policy, meaning that the policy could control the return volatility of IDX30 stocks. Trading Volume Activity (TVA) is the total number of shares or contracts traded within a certain period. TVA and volatility had a positive relationship which means that the higher number of shares traded, the return tended to fluctuated more., Stock return volatility is a crucial factor in investment decision-making and effective risk management strategies. Asymmetric Auto Rejection is a rule or mechanism applied in the stock market to control stock price fluctuations in a nonsymmetrical manner. This study uses IDX30 stock volatility data from March 2018 to March 2022. Because this dataset includes 30 issuers over that period, this study applies panel data regression analysis. The aim of this study is to evaluate the impact of asymmetric auto rejection implementation on stock return volatility in the Indonesian stock market during the Covid-19 pandemic. The results showed that the best model was the random effects model with time effects. This model indicated that there was no difference in stock volatility before and after the implementation of the asymmetric auto rejection policy, meaning that the policy could control the return volatility of IDX30 stocks. Trading Volume Activity (TVA) is the total number of shares or contracts traded within a certain period. TVA and volatility
Keyword: panel data regression, asymmetric auto rejection, IDX30, random effect model, stock return volatility

Judul: Indonesian Stock Market Return Volatility and Openness: Evidence From Covid-19 Pandemic
Abstrak: Pandemi Covid-19 berdampak pada berbagai aspek ekonomi, seperti resesi global. Hal ini menyebabkan ketidakpastian pada pasar saham meningkat, termasuk pasar saham Indonesia. Keterbukaan pasar saham Indonesia dapat dicerminkan dari kepemilikian nilai saham oleh investor asing yang terus meningkat hingga Januari 2021. Penelitian ini bertujuan untuk menganalisis volatilitas return dan dampak volatilitas aliran masuk bersih oleh investor asing (Net Foreign Inflow/NFI) terhadap volatilitas return pasar saham Indonesia. Penelitian ini menggunakan data harian sejak Januari 2019 hingga Februari 2021. Metode yang digunakan ialah analisis model E-GARCH dan DCC-GARCH. Analisis model E-GARCH digunakan untuk mengetahui volatilitas return pasar saham Indonesia. Analisis DCC-GARCH digunakan untuk mengetahui dampak volatilitas NFI terhadap volatilitas return pasar saham Indonesia. Hasil penelitian menunjukkan bahwa dampak guncangan dari berita buruk dan baik lebih besar pada volatilitas return saat pandemi Covid-19. Guncangan berdampak positif terhadap peningkatan efek spillover volatilitas NFI ke volatilitas return di jangka pendek dan panjang pada periode sebelum pandemi Covid-19, namun hal tersebut tidak terjadi saat pandemi.
Keyword: E-GARCH, DCC-GARCH, net foreign inflow, return volatility

Judul: Synthesis of Apatite - Chitosan Composite Using Duck Eggshell and Chitosan with Temperature and pH Control
Abstrak: Composite of apatite-chitosan was prepared by using chitosan as polymer matrix. Calcium phosphate was prepared from CaO and (NH4)2HPO4, which the ratio Ca : P had to be 1.67. Chitosan is produced by deacetilase from biopolymer chitin. Duck eggshell (95% CaCO3) as starting material was converted to be calcium oxide (CaO) through calcinations with temperature 1000oC for 5 hours. In-situ and ex-situ methods were prepared from apatite and chitosan (dissolved with acetate acid 2%). Calcium phosphate prepared for bone implantation, but it is too fragile and brittle to be implant into the body. So addition of chitosan can decrease crystalinity and increase mechanic characteristic (tougher). Composite apatite-chitosan was resulted by fast precipitation. Fast precipitation was held in a breaker glass with nitrogen atmosphere, under controlled temperature at 37oC and pH 7, in order to increase amount of hydroxyapatite. Precipitation with CaO which was dropped by (NH4)2HPO4. Hydroxyapatite and chitosan were appearing at samples with in-situ and ex-situ methods which indicating by peak matching of XRD (closed lattice parameter, crystal size), overlapping at FTIR spectra and supporting by SEM picture (homogenous and agglomerated particle). However, it still needs further research to examine biocompatibility osteoconductive degree of sample by in-vivo and in-vitro test.
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