Judul: Wire electroplating sludge sebagai katalis pembakaran batu bara
Abstrak: A fuel additive (combustion catalyst) can improve the combustion efficiency by promoting complete oxidation of fuel. Combustion catalyst in this research was composed of wire electroplating sludge dispersed in a mixture of vegetable oil, water, and surfactant. Four types of catalyst suspensions were prepared, namely A (2% sludge); B (3% sludge); C (2% sludge, 3% oxalyc acid); and D (3% sludge, 3% oxalyc acid). Addition of oxalyc acid in catalyst suspension C and D showed significant effects on combustion efficiency. Each suspension was applied in coal having caloric value of 5235.09 cal/g. The concentration of catalyst suspension in coal was about ±0.1% w/w. The results of activity test by using differential thermal analyzer showed that the energy efficiency from catalyst A was 62.21%, B: 97.19%, C: 77.96%, and D: 97.54%. Catalyst D (3% sludge, 3% oxalyc acid) is the best catalyst suspension that can be used as coal combustion catalyst.
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Judul: Meta-Analysis of the Effectiveness of Shell-based Calcium Oxide Catalysts on Biodiesel Transesterification
Abstrak: Katalis kalsium oksida (CaO) dari cangkang kerang telah banyak diteliti dengan beragam proses dan mempengaruhi transesterifikasi biodiesel. Penelitian bertujuan untuk menentukan efektivitas katalis heterogen CaO berbasis cangkang kerang untuk transesterifikasi biodiesel dari sejumlah penelitian terkait dengan metode meta-analisis. Prosedur penelitian meliputi penelusuran literatur, seleksi sumber pustaka, pembuatan database, dan analisis data kelompok berdasarkan perlakuan katalis CaO. Screening jurnal diperoleh 1308 jurnal ilmiah, 6 jurnal diinklusi kedalam meta-analisis dengan total 20 studi. Meta-analisis memiliki nilai rerata effect size seluruh studi dengan 11,494 berkorelasi positif atau perlakuan katalis CaO berpengaruh pada transesterifikasi biodiesel. Efektivitas katalis CaO pada transesterifikasi biodiesel disertai estimasi rerata effect size secara berturut-turut adalah proses perlakuan kalsinasi-hidrasi-dehidrasi (1114,047) > impregnasi KBr diaktivasi (363,675) > impregnasi fly ash (23,855) > kalsinasi (7,465) > impregnasi Zn, Al diaktivasi (0,087). Kesamaan pola persebaran data melalui funnel plot memperlihatkan distribusi yang simetris atau tidak dipengaruhi oleh bias publikasi., Calcium oxide (CaO) catalysts from shells have been widely studied with various processes and affect the transesterification of biodiesel. The aim of the study was to determine the effectiveness of a shell-based CaO heterogeneous catalyst for biodiesel transesterification from a number of studies related to the meta-analysis method. The research procedure included literature search, selection of library sources, database, and analysis of group data based on CaO catalyst treatment. Screening obtained 1308 scientific journals, 6 journals were included in the meta-analysis with a total of 20 studies. The meta-analysis had a mean effect size for all studies with 11.494 positive correlations or the CaO catalyst treatment had an effect on biodiesel transesterification. The effectiveness of CaO catalyst in biodiesel transesterification with the estimation of the mean effect size respectively were calcination-hydration-dehydration process (1114.047) > activated KBr impregnation (363.675) > fly ash impregnation (23.855) > calcination (7.465) > activated Zn, Al impregnation (0.087). The similarity of data distribution patterns through funnel plots showed a symmetrical distribution or was not influenced by publication bias.
Keyword: energi terbarukan, impregnasi, transesterifikasi, impregnation, renewable energy, transesterification

Judul: igenvalues and Eigenvectors of Tridiagonal Matrix with Non Constant and Recurrent Diagonal Entries.
Abstrak: Matriks tridiagonal adalah suatu matriks yang mempunyai entri-entri bernilai nol kecuali pada diagonal utama, di bawah diagonal utama (subdiagonal) dan di atas diagonal utama (superdiagonal). Entri pada diagonal utama tidak konstan dan berulang. Setiap entri pada matriks tridiagonal ini adalah bilangan kompleks. Dalam karya ilmiah ini, akan dibuktikan 3 teorema untuk menentukan nilai eigen dengan 2 kasus dan 1 teorema untuk menentukan vektor eigen. Teorema pertama menentukan polinomial karakteristik dari matriks tridiagonal. Polinomial karakteristik dari matriks tridiagonal tersebut digunakan untuk menentukan nilai eigen pada teorema kedua dan ketiga serta menentukan vektor eigen pada teorema keempat
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