Judul: Aplikasi Lampu LED dengan Variasi Warna sebagai Alternatif Pengganti Sinar Matahari dalam Pertumbuhan Tanaman Pakcoy (Brassica sinensis L.)
Abstrak: Penelitian ini untuk mengetahui perbedaan pertumbuhan pakcoy dalam kondisi pencahayaan berbeda dan mencari perlakuan yang dapat memberikan hasil optimum. Terdapat empat perlakuan yaitu P1 dengan lampu LED grow light 60 watt + LED hijau 3 watt, P2 dengan lampu LED putih 63 watt (dua ukuran besar 30 watt + satu ukuran kecil 3 watt), P3 dengan matahari tidak langsung, dan P4 dengan matahari langsung. Media tanam dengan polybag 25 cm x 25 cm. Proses penyiraman kurang lebih 375 ml setiap perlakuan per tiga polybag serta pada P1 dan P2 mendapat pengaruh cahaya lampu LED sekitar 12 jam. Terdapat dua faktor yang mempengaruhi pertumbuhan pakcoy dalam penelitian ini yaitu intensitas cahaya dan faktor lingkungan (suhu dan kelembababan serta kandungan unsur hara dan air). Perlakuan yang paling optimal terdapat pada P3 dengan hasil rata-rata diameter batang sebesar 0,180 cm, rata-rata jumlah daun sebanyak tujuh helai daun, rata-rata tinggi tanaman sebesar 1,870 cm, rata-rata lebar daun sebesar 5,030 cm, rata-rata akar tanaman sebesar 14,100 cm, dan rata-rata bobot basah sebesar 4,00 gram.
Keyword: Humidity, LED, Light Intensity, Pakcoy, Temperature

Judul: Pakcoy Plant Growth (Brassica rapa L. subsp. chinensis (L.) Hanelt) under some Artificial Lighting in a Wick Hydroponic System
Abstrak: Cahaya merupakan faktor yang sangat penting bagi pertumbuhan tanaman, namun cuaca yang fluktuatif di Indonesia mempengaruhi penerimaan sinar matahari oleh tanaman. Pencahayaan buatan, seperti light emitting diode (LED) surface mounted device (SMD), dapat berfungsi sebagai sumber cahaya alternatif. Penelitian ini bertujuan untuk melihat pengaruh jenis pencahayaan buatan yaitu pencahayaan alami (sinar matahari), LED SMD 5050, LED SMD 5730 dengan lama waktu pencahayaan buatan tunggal yaitu 20 jam, serta lama waktu pencahayaan buatan tambahan yaitu 8 jam pada tanaman pakcoy. Pakcoy dibudidayakan dengan sistem hidroponik sumbu (wick). Parameter tanaman yang dievaluasi meliputi jumlah daun, tinggi tanaman, luas kanopi tanaman, dan berat total biomassa selain akar. Hasil penelitian menunjukkan bahwa tanaman yang dipapar LED SMD 5730 selama 20 jam menunjukkan rata-rata tinggi tanaman, jumlah daun, berat biomassa selain akar, dan luas kanopi tertinggi. Namun hasil ini tidak lebih baik dari tanaman yang diberikan pencahayaan matahari saja (kontrol). Hasil tanaman yang paling buruk merupakan tanaman yang diberikan perlakuan pencahayaan buatan dengan LED SMD 5050 selama 20 jam. Sehingga, berdasarkan hasil penelitian yang dilakukan LED SMD 5730 merupakan sumber pencahayaan buatan yang lebih baik daripada LED SMD 5050., Light is a crucial factor for plant growth, but the fluctuating weather in Indonesia affects the reception of sunlight by plants. Artificial lighting, such as SMD LEDs, can serve as an alternative light source. This study aims to assess the effects of different artificial lighting types, including natural lighting (sunlight), LED SMD 5050, and LED SMD 5730. The lighting durations tested were twenty hours of continuous artificial lighting and eight hours of supplementary artificial lighting on pakcoy plants grown using a wick hydroponic system. Several plant parameters were evaluated, including the number of leaves, plant height, plant canopy area, and total biomass weight excluding roots. Results showed that the plants exposed to SMD 5730 LEDs for twenty hours exhibited the highest average plant height, number of leaves, total biomass weight excluding roots, and canopy area. However, these outcomes did not surpass the control group exposed only to sunlight. Conversely, the plants treated with 5050 SMD LED for twenty hours demonstrated the lowest yields. Consequently, the research findings suggest that SMD 5730 LEDs are a superior artificial lighting source compared to 5050 SMD LEDs.
Keyword: artificial lighting, LED SMD, pakcoy, wick hydroponic

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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