Judul: The Optimization of Temperature and Voltage on  Thickness, Hardness, and Corrosion Rate of Hard Chrome Plating
Abstrak: Baja karbon AISI 1045 merupakan jenis baja karbon sedang yang banyak dimanfaatkan diberbagai bidang. Namun, kerentanan sifat logam terhadap korosi mendorong peningkatan kualitas sifat logam. Pelapisan hard chrome merupakan salah satu teknik perlindungan material yang memiliki banyak keunggulan. Selain memberikan perlindungan korosi, pelapisan hard chrome meningkatkan sifat kekerasan material yang berdampak pada meningkatnya ketahanan aus material. Tujuan penelitian ini adalah menentukan kondisi optimum suhu dan tegangan dalam proses pelapisan hard chrome terhadap kekerasan, ketebalan dan laju korosi sampel baja karbon AISI 1045. Pelapisan dilakukan dalam larutan hard chrome dengan kadar CrO3 282,56 g/L dengan ragam suhu, yaitu 45, 55, dan 65 °C serta ragam tegangan 6, 8, dan 12 V. Berdasarkan hasil pengamatan secara visual dan kuantitatif, kondisi optimum diperoleh pada suhu 55 °C tegangan 8 V dengan ketebalan 0,0041 cm, kekerasan 37 HRC, dan laju korosi 0,0412 mm/tahun., AISI 1045 carbon steel is medium carbon steel widely used in various fields. However, the metal susceptibility to corrosion encourages the increase in metal quality. Hard chrome plating is one of the material protection techniques which has a lot of advantages. It does not only protect against corrosion, but it also increases the hardness of material increase of material wear resistance. The study aimed to determine the optimum conditions of temperature and voltage in the hard chrome plating process on thickness, hardness, and corrosion rate of AISI 1045 carbon steel. The plating was conducted in a hard chrome solution containing CrO3 282,56 g/L with temperature variations of 45, 55, and 65 °C as well as voltage variations of 6, 8, and 12V. The result of visual and quantitative observation indicated that the optimum plating condition is obtained at a temperature of 55 °C voltage 8 V with a thickness of 0,0041 cm, hardness of 37 HRC, as well corrosion rate of 0,0412 mm/year.
Keyword: carbon steel 1045, hard chrome plating, optimum condition

Judul: Characterizations of low alloy steel sae 4422  plated with chromic acid (Cro3)
Abstrak: Characterizations of low alloy steel SAE 4422 plated with chromic acid (CrOrO3) was use Optical Microscopy (OM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), RD),Energy Dispersive Analysis of X-Ray (EDAX), Hardness Test and Roughness Test. Microstructures analysis exhibits cracks and grain boundaries microcracks as a characteristics of chrome metal found at plating metal. Perlite and Ferrite as grains of steel found at base metal with grain boundaries around it. Phase analysis of plating metal appropriate to chrome metal with lattice constant (a) is 2.559 Å and phase analysis of base metal appropriate to iron ferrite with lattice constant (a) is 3.318 Å. Both plating and base metal have cubic system. Chemical analysis of plating metal at surface section exhibits that cracks area have highest value of carbon element compare with grains and grains boundaries area. While chemical analysis of base metal at cross section exhibits that perlite have highest value of carbon element compare with ferrite and grain boundaries. The hardness value of plating metal at surface section and cross section are 753 and 637 VHN. While, the hardness value of base metal and interface area at cross section are 205 and 373 VHN. The roughness value at measurement points of chrome surface for as received sample are 0.445 μm. Observation used Optical Microscopy and Scanning Electron Microscopy exhibits surface irregularities combine to form surface texture of plating metal at surface section.
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Judul: Zero-inflated negative binomial models in small area estimation.
Abstrak: The problem of over-dispersion in Poisson data is usually solved by introducing prior distributions which lead to negative binomial models. Poisson data sometime is also suffered by excess zero problems, a condition when data contains too many zero or exceeds the distribution's expectation. Zero Inflated Negative Binomial (ZINB) method can be utilized to solve such problems. This paper demonstrates the adaption of ZINB methods in Small Area Estimation with excess zero data. It is shown that the excess zero problem has substantially influenced the Empirical Bayes (EB) estimates, and the adaption of ZINB methods has improved the precision and reliability of the estimates. Key Words: Small Area Estimation, Zero-Inflation, Poisson-Gamma, Negative Binomial Regression, Empirical Bayes
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