Judul: Estimation of Physico-chemical Characteristics of Apple Fruit Using Near Infrared Spectroscopy
Abstrak: Apel (Malus sylvestris.) merupakan buah yang memiliki nilai ekonomi cukup tinggi di Indonesia. Apel banyak digemari oleh masyarakat Indonesia karena memiliki cita rasa yang khas dan menimbulkan efek segar pada orang yang mengonsumsinya. Cita rasa apel terbaik diperoleh ketika buah sudah matang sempurna dan apel merupakan buah klimaterik sehingga tingkat kematangan dipengaruhi oleh ketuaan buah saat dipanen. Namun penentuan ketuaan apel masih dilakukan secara visual tanpa alat bantu sehingga hasilnya kurang akurat, kurang objektif sehingga berpotensi kematangan tidak sempurna. Metode spektroskopi NIR (Near Infrared Spectroscopy) memberikan alternatif dalam menentukan tingkat ketuaan buah apel tanpa merusak bagian buah tersebut. Penelitian ini bertujuan untuk menduga sifat fisiko-kimia buah apel manalagi dengan tiga umur panen berbeda (130, 140, dan 150 hari setelah bunga mekar, HSBM) secara nondestruktif dengan menggunakan metode spektroskopi NIR. Sifat atau kandungan fisiko-kimia buah apel terkait dengan tingkat ketuaan buah apel. Parameter yang diuji untuk menentukan kandungan fisiko-kimia buah apel adalah total padatan terlarut, kekerasan daging, dan kadar air. Hasil penelitian menunjukkan hasil terbaik untuk pendugaan total padatan terlarut buah apel didapatkan menggunakan pra-pengolahan data Smoothing Savitzky-Golay (SGs) dengan nilai koefisien korelasi sebesar 0.93; standard error of calibration (SEC) sebesar 0.81 %brix; standard error of prediction (SEP) sebesar 0.86 %brix dan ratio of standard error of prediction to deviaton (RPD)sebesar 2.61. Untuk parameter kekerasan buah hasil terbaik didapatkan dengan pra-pengolahan data Multiplicative Scatter Correction (MSC) dengan nilai koefisien korelasi sebesar 0.78; SEC sebesar 0.47 N; SEP sebesar 0.45 N dan RPD sebesar 1.53. Untuk parameter kadar air didapatkan hasil terbaik dengan pra-pengolahan data Standard Normal Variate (SNV) dengan nilai koefisien korelasi sebesar 0.75; SEC sebesar 0.92%; SEP sebesar 0.85% dan RPD sebesar 1.50., Apple (Malus sylvestris.) is a fruit with high economic value in Indonesia. Apples are much favored by people in Indonesia because they have a distinctive taste and have a fresh effect on people who consume them. The best apple taste is obtained when the fruit is fully ripe and the apple is a climacteric fruit so that the level of maturity is influenced by the age of the fruit when it is harvested. However, the determination of the aging of apples is still done visually without any tools so that the results are less accurate, less objective so that the potential for ripeness is not perfect. The NIRS (Near Infrared spectroscopy) method provides an alternative to determine the level of maturity of apples without damaging the fruit. This study aims to estimate the physico-chemical properties of manalagi apples with three different harvest ages (130, 140, and 150 days after blooming, DAB) nondestructively by using the NIR spectroscopy method. The properties or physicochemical properties of apples are related to the level of maturity of apples. The parameters tested to determine the physico-chemical content of apples were total dissolved solids, flesh hardness, and moisture content. The results showed that the best results for estimating total soluble solids of apples were obtained using Smoothing Savitzky-Golay (SGs) data pre-processing with a correlation coefficient of 0.93; standard error of calibration (SEC) of 0.81 %brix; standard error of prediction (SEP) is 0.86 %brix and ratio
Keyword: Apple, flesh hardness, moisture content, NIRS, total dissolved solids

Judul: Prediction of Chemical Content of ‘Citra’ Water Apple Using Near Infrared Spectroscopy (NIRS)
Abstrak: Jambu air citra termasuk salah satu buah lokal yang menjadi unggulan dan memiliki nilai komersial tertinggi dibandingkan dengan jenis jambu air lainnya. Penentuan kualitas jambu air citra didasarkan pada permintaan pasar dengan pertimbangan kualitas internal dan eksternal buah. Kandungan buah seperti kadar air, kandungan gula, dan total asam menjadi kriteria mutu internal yang penting. Pada umumnya untuk mengetahui kandungan internal di dalam buah dilakukan pengukuran secara destruktif yang bersifat merusak buah. Dengan kemajuan teknologi, penentuan kandungan kimia internal suatu bahan dapat dilakukan secara non-destruktif menggunakan teknologi Near Infrared Spectroscopy (NIRS). Penelitian ini bertujuan untuk menduga kadar air, total padatan terlarut dan total asam buah jambu air citra secara non-destruktif menggunakan NIRS. Bahan yang digunakan adalah buah jambu air citra dengan tiga umur panen yang berbeda. Alat yang digunakan adalah NIR spektrometer tipe NIRFlex N-500 fiber optik solid yang bekerja pada panjang gelombang 1000-2500 nm. Metode pengolahan data yang digunakan dalam kalibrasi dan validasi data spektra NIR dengan data referensi adalah metode kemometrik Partial Least Squares (PLS) dengan pre-treatment data spektra Normalisasi, Standard Normal Variate (SNV), De-Trending (DT), Multiplicative Scatter Correction (MSC), dan Smoothing Savitzky-Golay (SSG). Perlakuan terbaik dalam menduga kadar air diperoleh dengan pre-treatment data SSG pada faktor PLS 16 dengan nilai r = 0,90; SEC = 0,86%; SEP = 1,00%; CV = 1,11%; RPD = 1,83; dan konsistensi = 85,73%. Pengolahan data spektra terbaik dalam menduga total padatan terlarut diperoleh dengan pre-treatment data SSG pada faktor PLS 16 dengan nilai r = 0,94; SEC = 0,72 °Brix; SEP = 0,75 °Brix; CV = 8,44%; RPD = 2,57; dan konsistensi = 95,69%. Perlakuan terbaik dalam menduga total asam diperoleh dengan pre-treatment data De-Trending pada faktor PLS 8, dengan nilai r = 0,70; SEC = 0,10%; SEP = 0,11%; CV = 24,15%; RPD = 1,21; dan konsistensi = 94,86%. Hasil ini menunjukkan bahwa NIRS dapat digunakan untuk menduga kadar air dan total padatan terlarut buah jambu air citra, namun belum mampu menduga secara akurat kandungan total asam pada buah jambu air citra., Citra water apple is one of the leading local fruits and has the highest commercial value compared to other types of water apple. The quality of citra water apple determined based on market demand with consideration of the internal and external quality of the fruit. The content of the fruit such as moisture content, sugar content, and total acid are important criteria for internal quality. In general, to determine the internal content in the fruit, destructive measurements are made which damage the fruit. With technological advances, determination of the internal chemical content of a material can be done non-destructively using Near Infrared Spectroscopy (NIRS) technology. This study aims to estimate the water content, total soluble solids and total acid of water apple fruit non-destructively using NIRS. The materials used were citra water apple fruits with three different harvest ages. The tool used is NIR spectrometer type NIRFlex N-500 solid optical fiber that works at a wavelength of 1000-2500 nm. The method used in the calibration and validation of NIR spectra data with reference data is the Partial Least Squares (PLS) chemometric
Keyword: citra water apple, non-destructive, NIRS, PLS

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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