Judul: Determination of Harvest Index of Crystal Guava Fruit Non-Destructively with NIR Spectroscopy
Abstrak: Buah jambu kristal merupakan buah klimakterik yang umumnya dipanen oleh petani berdasarkan pengalaman budidaya sehingga memiliki potensi tingkat kematangannya kurang akurat. Penelitian ini bertujuan untuk memprediksi parameter indeks panen buah jambu kristal secara non destruktif dengan spektroskopi NIR. Parameter yang diukur adalah total padatan terlarut (TPT), acidity, rasio TPT dengan acidity, dan kekerasan daging buah. Bahan yang digunakan adalah buah jambu kristal sejumlah 150 buah dengan lima umur panen yang berbeda, masing-masing 30 buah untuk setiap umur panen. Alat yang digunakan adalah spektrometer NIRFlex N-500 fiber optic solid dan dipilih panjang gelombang 1300-2500 nm. Hasil penelitian menunjukkan bahwa model terbaik penentuan indeks panen buah jambu kristal secara non destruktif dengan spektroskopi NIR yaitu berdasarkan TPT dan kekerasan daging buah menggunakan metode PLS, sedangkan parameter acidity dan rasio TPT dengan acidity tidak layak digunakan. TPT dapat diprediksi menggunakan data reflektan dengan pre-treatment Smoothing Moving Average 3 Point pada faktor 13 (r = 0.84, CV = 7.85%, RPD = 1.78). Kekerasan daging buah dapat diprediksi menggunakan data reflektan dengan pre-treatment Standard Normal Variate pada faktor 15 (r = 0.88, CV = 13.72%, RPD = 1.89). Evaluasi parameter model menunjukkan metode PLS memberikan performa lebih baik dibandingkan JST untuk semua parameter fisikokimia yang diukur. Kata kunci: indeks panen, jambu kristal, NIRS, parameter kimia, Crystal guava fruit is a climacteric fruit that is generally harvested by farmers based on cultivation experience so that it has the potential for less accurate maturity levels. This study aims to predict the harvest index parameters of crystal guava fruit non-destructively with NIR spectroscopy. Parameters measured were total soluble solids (TSS), acidity, ratio of TSS to acidity, and fruit pulp hardness. The material used is 150 pieces of crystal guava fruit with five different harvest ages, 30 each for each harvest age. The instrument used is a NIRFlex N-500 spectrometer fiber optic solid and the wavelength is 1300-2500 nm. The results showed that the best model for determining the harvest index of crystal guava fruit non-destructively with NIR spectroscopy was based on TSS and pulp hardness using the PLS method, while the parameters acidity and the ratio of TSS to acidity were not feasible to use. TSS can be predicted using reflectance data with pre treatment Smoothing Moving Average 3 Points at a factor of 13 (r = 0.84, CV = 7.85%, RPD = 1.78). Flesh hardness can be predicted using reflectance data with pre-treatment Standard Normal Variate at a factor of 15 (r = 0.88, CV = 13.72%, RPD = 1.89). Evaluation of model parameters showed that the PLS method gave better performance than ANN for all measured physicochemical parameters. Keywords: chemical parameters, crystal guava, harvest index, NIRS
Keyword: chemical parameters, crystal guava, harvest index, NIRS

Judul: Prediction Quality “Crystal” Guava Non-Destructive Using Portable Near Infrared spectrometer NIRS
Abstrak: Jambu biji “Kristal” (Psidium guajava L.) merupakan buah non klimakterik yang memiliki pola respirasi yang stabil dan tidak menunjukkan adanya puncak klimaterik atau meningkatnya kecepatan produksi CO2 secara signifikan. Petani selama ini memeriksa indek panen buah berdasarkan pengalaman budidaya yaitu seperti warna kulit buah jambu, tekstur atau kekerasan pada buah jambu yang dilakukan secara kronologi (perhitungan hari setelah anthesis). Meskipun para petani pada umumnya memiliki pengalaman budidaya yang cukup namun potensi petani untuk memanen jambu “Kristal” kadang tidak sesuai dengan permintaan konsumen. Pengukuran indeks panen buah jambu “Kristal” masih dilakukan secara manual sehingga membuat hasil dari pengukuran tersebut kurang akurat dan kurang objektif akibat keterbatasan visual manusia, serta dapat berpotensi merusak badan buah (destruktif). Dalam penelitian ini, portable near-infrared spectrometer dengan panjang gelombang 740-1070 nm digunakan untuk memprediksi dengan cepat indeks panen jambu biji “Kristal” melalui pendekatan non-kontak dan non-destruktif. Sampel buah jambu biji diambil pada umur panen 91, 94, 97, dan 100 hari setelah anthesis (HSA). Jumlah sampel masing-masing 30 buah. Kekerasan, kandungan padatan terlarut, acidity dan rasio gula asam dievaluasi sebagai parameter kualitas. Metode Partial Least Square (PLS) digunakan untuk pengolahan data. Ditemukan bahwa Standard Normal Variate (SNV) menghasilkan pretereatment terbaik untuk semua parameter kualitas indeks panen. Hasil dari penelitian ini berupa performa terbaik ditunjukkan oleh koefisien korelasi (r), Standard Error of Calibrasi (SEC) dan Standar Error of Prediksi (SEP), yang masing-masing adalah 0,88, 6,21, 5,92 untuk prediksi kekerasan, 0,74, 0,84, 0,79 untuk prediksi kandungan total padatan terlarut, 0,59, 0,19, 0,26 untuk prediksi acidity, dan 0,71, 1,21, 1,58 untuk model prediksi rasio gula asam yang menentukan kualitas indeks panen jambu “Kristal” serta dapat berkontribusi untuk pengembangan sortasi buah secara tidak merusak., “Crystal” guava (Psidium guajava L.) is a non-climacteric fruit that has a stable respiration pattern and does not show any lyateric peaks or significantly increased co2 production speed. Farmers have been checking the index of fruit harvest based on cultivation experience such as the skin color of guava fruit, texture or hardness in guava fruit carried out chronologically (calculation of the day after anthesis). Although farmers in general have sufficient cultivation experience, the potential for farmers to harvest "Crystal" guava sometimes does not match consumer demand. Measurement of the harvest index of guava fruit "Crystal" is still done manually so as to make the results of these measurements less accurate and less objective due to human visual limitations, and can potentially damage the fruit body (destructive). In this study, a portable 740-1070 nm near-infrared spectrometer was employed to rapidly predict harvest indices of “crystal” guava, by means of non-contact and non-destructive approach. Samples of guava fruit were collected at days after anthesis (DAA) of 91, 94, 97, and 100. The total number of each sample were 30 fruits. The firmness, soluble solid content, acidity and sugar acid ration were evaluated as quality parameters. Partial least square (PLS) method was utilized for data processing. It was found that Standard Normal Variate (SNV) resulted in the best pre-processing for all quality parameters. The results of this study in the form of best performance are indicated by correlation coefficient (r), Standard Error
Keyword: “Crystal” guava, harvest indices, Partial Least Square (PLS), portable near-infrared spectrometer

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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