ABSTRAK. Penggunaan wafer ransum komplit mengandung limbah kopi pada itik peking dilakukan dengan tujuan untuk mengetahui berat akhir dan persentase karkas. Materi penelitian yang digunakan adalah itik peking umur 1 hari (DOD) sebanyak 96 ekor dibagi dalam 4 perlakuan dan 3 ulangan. Ransum yang digunakan satu bulan pertama adalah ransum komersil, dan satu bulan terakhir wafer ransum komplit mengandung limbah kopi. Ransum perlakuan yang diberikan adalah: P0 = Wafer ransum komplit 0% limbah kopi (kontrol), P1 = Wafer ransum komplit 2,5% limbah kopi, P2 = Wafer ransum komplit 5% limbah kopi, dan P3 = Wafer ransum komplit 7,5% limbah kopi. Parameter yang diamati: bobot hidup, bobot karkas, bobot potongan karkas, persentase karkas, dan persentase potongan karkas. Penelitian ini menggunakan Rancangan Acak Lengkap. Data dianalisis dengan analysis of variance dan dilanjutkan dengan Uji Duncan. Hasil penelitian menunjukkan penggunaan limbah kulit kopi sebagai bahan penyusun ransum itik peking dalam bentuk wafer ransum komplit berpengaruh nyata terhadap bobot akhir. Penggunaan limbah kulit kopi 2,5% dalam ransum secara signifikan (P<0.05) meningkatkan bobot karkas dan potongan karkas. Dapat disimpulkan penggunaan limbah kulit kopi sebanyak 2,5% sebagai bahan penyusun wafer ransum komplit tidak memberi pengaruh negatif terhadap bobot badan akhir, persentase karkas dan potongan karkas itik peking.  (Carcass percentage of peking duck feed wafer complete ration containing of coffee waste) ABSTRACT. This research was conducted to study the effectiveness of wafer complete ration containing coffee waste on the final body weight and carcass percentage. The study used 96 DOD Peking duck. Completely Randomized Design (CRD) consisting of 4 treatments and 3 replications. Rations used during the first month was a commercial ration, and then subsequently wafer complete ration of coffee waste given as treatments; P0 = wafer complete ration contained 0% of coffee waste (control), P1 = wafer complete ration 2,5% of coffee waste, P2 = wafer complete ration 5% of coffee waste, and P3 = Wafer complete ration 7,5% of coffee waste. The observed variables were: final body weight, carcass weight, carcass percentage, carcass component weight, and carcass component percentage. Collected data was analyzed by ANOVA and followed by Duncan’ Multiple Range Test if there was a significant different between treatments. The results showed wafer complete ration containing coffee waste was significantly (P< 0.05) effect on  final body weight. Feed containing 2,5 % of coffee waste significantly (P<0.05) effect on carcass weight and carcass percentage. It is concluded that no negatif effect of wafer complete ration containing 2,5 % coffee waste on final body weight and carcass percentage of peking duck.

An experimental method for estimating the tangential contact stiffness of contact interface with controlled contact asperities is discussed. The tangential contact stiffness is analyzed from the shift of certain eigenmode frequency of the system resulting from the changes in the density of contact asperities and the application of normal force. The results show that for the case of contact combination with 189 contact asperities, the corresponding eigenmode frequency shifted from 1.01 kHz at normal force of 19 N to 1.64 kHz at normal force of 148 N. This shift corresponds to the increase of tangential contact stiffness from 34.08 MN/m at normal force of 19 N to 67.44 MN/m at normal force of 148 N. It is found that the corresponding eigenmode frequency and its shift were affected by the density of contact asperities as well as the normal force. In the case of contact combination with 397 contact asperities, the corresponding eigenmode frequency shifted from 2.36 kHz at normal force of 49 N to 3.9 kHz at normal force of 153 N, indicating the increase of the tangential contact stiffness from 93.91 to 140.73 MN/m. A simple power relationship is proposed to explain the quantitative relationship between the eigenmode frequency shift and the tangential contact stiffness value.

In this work, a novel anti-corrosion water-based lubricant is prepared. Carboxymethyl cellulose and Uncaria Gambir Extract, all in powder form, were dispersed in water. Corrosion, stability, and tribology test with pin-on-disk reciprocating tribometer were studied. The newly obtained lubricants were designated as Uncaria Gambir (UG), i. e. UG0 (0% volume Uncaria Gambir extract in Carboxymethyl cellulose, UG1 (1% volume Uncaria Gambir extract in Carboxymethyl cellulose, and UG2 (2% volume Uncaria Gambir extract in Carboxymethyl cellulose). The addition of Uncaria Gambir Extract into Carboxymethyl cellulose solution delivered good stability, low corrosion rate, and stable friction coefficient. UG1 has the best stability (no sedimentation), corrosion, and tribological performance. After a one-hour friction test, UG2showed the best performance in terms of CoF, indicated by a 7.6% CoF reduction, compared to UG0. This finding indicates the potential of Uncaria Gambir Extract as an additive for an anticorrosive water-based lubricant for machining application.

In this paper, a fundamental mechanism for creep-groan generation is investigated by adopting a simple yet effective caliper-slider experimental model. Contact condition, which is a function of three parameters, namely normal force, contact roughness, and material combination, is connected with the creep-groan phenomenon in terms of contact stiffness. Creep-groan generation is determined by analyzing the frequency characteristic of the generated vibration acceleration when the sliding commences due to a simultaneous application and release of force in the tangential and normal directions, respectively. As per the obtained results, creep-groan occurrence or absence in the employed experimental model may be classified into three regions based upon the value of the contact stiffness, i.e., occurrence, non-occurrence, and mixed regions. The results also indicate that creep-groan occurrence in this caliper-slider experimental model can be avoided by controlling the value of contact stiffness in an effective manner.