Judul: Prediksi kualitas pepaya pada umur petik dan waktu penyimpanan yang berbeda dengan spektroskopi NIR
Abstrak: Pepaya biasa dipanen pada kondisi masih hijau tetapi sudah tua. Tingkat ketuaan pepaya saat panen ditentukan berdasarkan tujuan pasar. Pengetahuan tentang tingkat ketuaan pepaya dan pengaruhnya terhadap perubahan kualitas pascapanen selama penyimpanan sangat penting berkaitan dengan tujuan pasar. Perubahan kualitas pepaya meliputi perubahan fisik dan kandungan kimia. Namun perubahan kandungan kimia biasa diukur dengan metode kimia yakni secara destruktif, membutuhkan waktu lama, dan biaya mahal. Oleh karena itu metode nondestruktif perlu dikembangkan untuk mengetahui kandungan kimia pepaya. Tujuan dari penelitian ini adalah untuk memprediksi kualitas pepaya dengan spektroskopi NIR dan menganalisis pengaruh umur petik pepaya varietas IPB9 terhadap perubahan kualitas dan masa simpannya. Sampel buah pepaya dipanen pada umur petik 114, 121, 128, 131, dan 135 hari setelah bunga mekar. Setelah dipanen, pepaya diperam dalam alat pemeram buatan dengan perlakuan penambahan gas etilen ±50 ppm selama 24 jam pada suhu 20 °C. Setelah proses pemeraman, sampel buah pepaya diletakkan di suhu ruang. Hasil pengukuran dengan spektroskopi NIR nilai reflektan sampel berkisar 1000-2500 nm. kemudian diolah dengan metode PLS untuk memperoleh hasil kalibrasi dan validasi terbaik. Enam perlakuan data spektra yakni normalisasi antara 0 dan 1 (n01), turunan pertama (dg1), turunan kedua (dg2), rataan tiga titik (sa3), multiple scatter correction (msc), dan standard normal variate (snv). Transformasi data hasil pengukuran sifat fisik dan kimia dengan metode standar. Hasil pengukuran, buah pepaya dengan umur petik 128 hari memiliki kandungan pati tertinggi dan nilai total padatan terlarut tertinggi pada hari kelima setelah pemeraman sebesar 6.7 °Brix, serta memiliki umur simpan terlama. Umur petik pepaya 135 dan 131 hari memiliki nilai total padatan terlarut tertinggi sebesar 8.3 °Brix dan 7.5 °Brix pada hari ketiga setelah pemeraman dan memiliki umur simpan yang lebih pendek dari 128 hari. Umur petik pepaya 121 dan 114 hari memiliki nilai total padatan terlarut yang masih rendah. Prediksi nilai kandungan pati terbaik dengan transformasi data dan pra perlakuan kombinasi (msc, dg1) dengan nilai R, SEC, SEP, CV, dan RPD berturut-turut 0.90, 0.17 %, 0.16 %, 10.95 %, dan 2.15. Prediksi nilai total padatan terlarut terbaik dengan transformasi data dan pra perlakuan msc dengan nilai R, SEC, SEP, CV, dan RPD berturut-turut 0.90, 0.124 %, 0.123 %, 4.85 %, dan 2.27. Prediksi nilai kadar air terbaik dengan transformasi dan pra perlakuan dg1 dengan nilai R, SEC, SEP, CV, dan RPD berturut-turut 0.84, 0.03 %, 0.04 %, 0.43 %, dan 1.85. Prediksi nilai kekerasan terbaik dengan transformasi dan pra perlakuan snv dengan nilai R, SEC, SEP, CV, dan RPD berturut-turut 0.88, 0.28 %, 0.30 %, 12.67 %, dan 2.09. Spektroskopi NIR dapat memprediksi kualitas pepaya dengan baik secara nondestruktif.
Keyword: papaya cv IPB9, different picking date,, nondestructive by NIR, starch content

Judul: Prediksi Umur Panen Pepaya Berdasarkan Total Padatan Terlarut, Kandungan Protein dan Kadar Air dengan NIR Spektroskopi
Abstrak: Papaya is a climacteric fruit that usually harvested in green mature. The method of determination of papaya’s picking time can help the farmer to determine the harvest time. NIR (near infrared) can measure the content of an organic and non organic materials without affect them. Maturation level of papaya is correlated to the content of materials in the papaya. The objective of this experiment was to develop the method of determination of papaya’s picking time using NIR. Water content, protein and total soluble solid were used as internal parameter quality. Spectra of papaya was measured using NIR spectroscopy. Data of spectra were then used to develop calibration and validation model of NIR spectroscopy measurement based on the reference method. Partial Least Square (PLS) is a method used to determine the relation between chemistry composition of papaya and reflectant spectra and the absorbance. Spectra NIR was analyzed using 5 treatments: smooth average 3 points, normalization between 0 to 1, second derivative Savitzky-Golay 9 points, combination between smooth average 3 points and normalization between 0 to 1 and combination of smooth average 3 points, normalization between 0 to 1 and second derivative Savitzky-Golay every 9 points. The best model was selected according to coefficient of determination (R2), standard of error (SE), coeficient of variability (CV), ratio of standard error prediction to standard deviation (RPD) and model consistency (SEC/SEP). The best calibration models that selected based on the high accuration and consistency value by validation models with coefficient of determination (R2), SEC and SEP of 0.900 0.62 and 0.76 for water content; 0.837, 0.1 and 0,1 for protein content and 0.876, 0.90 and 1.06 for total soluble solid.
Keyword: water content, validation, total soluble solid, protein content, papaya, NIR, calibration

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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