Judul: Gagasan Awal Material Struktur Sarang Lebah Belangkas dari Asia (Tachypleus tridentatus) dan Amerika (Limulus polyphemus)
Abstrak: The honeycomb structure serves as a catalyst for future advancements in biomaterial development due to the integration of bioinspired designs and the study of renewable materials. The prosoma, a distinctive feature of horseshoe crabs resembling a horseshoe-shaped plate, have not been developed in terms of its material specifications and role in the honeycomb structure. This study aimed to determine the physical-chemical characteristics of honeycomb structure materials from the prosoma of Tachypleus tridentatus (TT) and Limulus polyphemus (LP). The study included the identification and morphometric analysis of the species, macro and microstructure appearance. Mechanical physical properties included compressive strength, tensile strength, elasticity, and thermal properties, while chemical properties included composition, elements or components, functional groups, and the estimation of honeycomb structure with acoustic impulse. The prosoma structure of horseshoe crabs exhibited a twisted plywood network with a Bouligand pattern. The compressive strength of prosoma TT and LP is 108 kPa and 115 kPa, while tensile strength is 62 kPa and 64 kPa. Thermal properties showed the same phase range value and component decomposition occurred at 350°C. Chemically, high protein content with functional groups suitable for chitin was present. The density and amplitude of the acoustic wave differed at a frequency of 5000 Hz.
Keyword: bioinspiration material, chitin, non destructive testing, superior material

Judul: Material Medis Penambal Membran Timpani Berbasis Komposit Chitosan Melalui Pendekatan Mekanoakustik
Abstrak: Perforation patch scaffold organic model-based on chitosan through mechano-acoustical approach to assess the perforation enclosure quality in terms of sound pressure quantity is the new inspiration of perforation closure method. The objectives of this research was to develop a model of composite chitosan as medical patch material of tympanic membrane through mechanoacoustical approach. Chitosan composite membrane formulated with polyvinyl alcohol (PVA) only (A00), 3% chitosan-3% glycerol (B33), and 5% chitosan-1% glycerol (C51). Optimum formulation is obtained on a composite chitosan, glycerol, and PVA with 3%/4%/5% ratio (B33) had characteristics of 622,29 kg/m3 in density, 160,70 μm in thickness, 1.43×10-2 g/mm a day in water vapour transmission rate. Its formed varied pores, granule, and hygroscopic condition on composite membrane due to the addition of chitosan and glycerol on varied ratio. Mechanoacoustical test results of composite membranes with the formula had 0,30×106.N/m2 in Young's modulus; 0,18 cm-1 in sound absorption coefficient; 0,22×102 m/s in velocity on medium; 203,52 dBSPL in membrane sensitivity; and 94% of sound attenuation rate.
Keyword: tympanic membrane perforation., mechanoacoustical, composite, chitosan

Judul: Fluktuasi Curah Hujan DKI Jakarta Tahun 1876 – 1975 Menggunakan Analisis Spektral.
Abstrak: Curah hujan DKI Jakarta selama tahun 1876 – 1975 dianalisis dengan menggunakan analisis spektrum dan analisis spektrum silang. Hasil analisis spektrum basis bulanan adalah curah hujan dengan periodisitas 12 dan 6 bulan. Hal ini menunjukkan bahwa curah hujan DKI Jakarta dalam basis bulanan dipengaruhi oleh sirkulasi monsun dan osilasi setengah tahunan. Untuk melihat pengaruh ENSO low pass filter dengan cut off filter 1 4 siklus/tahun diperoleh hasil curah hujan dengan periodisitas 4 tahun pada bulan Januari, Februari, April, Mei, Juni, Juli, Agustus, September, dan Oktober. Semua bulan tersebut memiliki rentang nilai koherensi 0.4 – 0.8. Analisis grafik garis untuk data Nino 3.4 dan anomali curah hujan yang telah di filter terlihat bahwa kedua memiliki hubungan yang berbanding terbalik. Hasil analisis spektrum dan spektrum silang dari data bilangan sunspot dan anomali curah hujan adalah periodisitas curah hujan 11 tahun di bulan Mei, September, dan Oktober. Nilai koherensi ketiga bulan tersebut berturut – turut 0.6, 0.28, dan 0.59. Dengan analisis grafik garis data bilangan sunspot dan curah hujan terlihat bahwa siklus 11 tahunan aktivitas matahari mempengaruhi curah hujan secara spontan.
Keyword: analisis spektral, analisis spektral silang, ENSO, sunspot