Judul: Pengaruh Penambahan Polivinil Alkohol dan Perbedaan Rasio Campuran Ampok Jagung dan Tapioka Terhadap Karakter Fisik Biodegradable Foam
Abstrak: Biodegradable foam is a packaging materials made from renewable resources which very prospective to substitute synthetic polystyrene foam. Starch is now dominantly use as a promising material to produce biodegradable foam due to its superior characteristic and availability. However, starch is preferable as food source so that an alternative material such as corn hominy feed can be used for producing this foam. Corn hominy is a by product of corn milling which has high content of starch and fibre which is possibly to improve the physical properties of this foam. This research is aimed to study the influence of adding PVOH and different ratio of corn hominy and cassava starch on physical properties of biodegradable foam. The corn hominy and cassava starch were mixed in rheocor mixer in 65 rpm speed at 90-100-90oC. Then the extrudat were expanded in a microwave oven at 100% power level for 45 seconds. The physical analysis result showed that the composition of corn hominy feed and cassava starch affected physical properties of biodegradable foam. The foam that consisted of corn hominy : cassava starch (80:20) gave the highest expantion ratio and water absorption index. PVOH also affected the physical properties of biodegradable foam which improved the hardness index of the foam. However, interaction between ratio of cassava starch: corn hominy feed and adding of PVOH does not show significant influence to the physical characteristic of biodegradable foam.
Keyword: 

Judul: Product developmentof cassava and corn hominy based biodegradable foam
Abstrak: Starch based foam is a packaging material made from renewable resources which are very prospective to substitute synthetic polystyrene foam. Tapioca is one of potential materials for starch based foam production due to availability and cheap price compared to other starch. Unfortunately, the foam produced only with starch is brittle, poor mechanical properties and highly sensitive to moisture. Fiber reinforcement and blending with synthetic polymer and hydrophobic materials are the way to improve foam’s properties. Corn hominy, a by product of corn dry milling industry, is a potential source to be used as fiber reinforcement due to its composition that still contained high fiber, starch, protein and fat that needed for producing starch-based foam. The objective of this research wasto develop biodegradable foam made from tapioca and corn hominy. Four steps formulation was conducted to get the best characteristics of biodegradable foam. Starch, corn hominy, modified starch, PVOH and other dry materials were mixed with various concentration. Water, plasticizer and other liquid materials were added to get total solid 50-60% and then baked with thermopressing machine at 150-1700C for 2-3 minutes. The results showed that, addition of corn hominy increased hydrophobicity and biodegradability of biofoam. On the other hand, increasing corn hominy proportion also decreased mechanical properties and brightness of biofoam and increased density. Addition of PVOHincreasedhydrophobicity and mechanical properties of biofoam but decrease biodegradability and increased density. Addition of hydrophobic starch did not make satisfying improvement on hydrophobicity or mechanical properties of biofoam, but decreased biodegradability of biofoam. Starch acetate and sizing agentaddition could increase hydrophobicity, marked by increasing of contact angle value. Meanwhile, addition of plasticizer not only improved viscoelasticity of biofoam but also increased biofoam’s hydrophobicity. Utilization of tapioca and corn hominy as biodegradable materials could increase value added of tapioca by 14,33% meanwhile for corn hominy almost71,44%.
Keyword: 

Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf