Judul: Studi pustaka hama sengon (Paraserianthes falcataria (L) Nielsen)
Abstrak: Pohon sengon (Paraserianthes falcataria (L) Nielsen) tergolong jenis pohon cepat tumbuh (fast growing species) sehingga dapat dipanen dalam waktu 5 – 8 tahun. Pengusahaan hutan sengon, baik berupa hutan milik atau hutan negara, tidak terlepas dari gangguan berbagai jenis hama. Karena itu diperlukan pengetahuan mengenai hama-hama tersebut. Pengentahuan tersebut dapat diperoleh melalui penelusuran pustaka (studi pustaka). Studi pustaka tentang hama sengon ini dilakukan di berbagai perpustakaan selama tiga bulan, mulai dari Mei - Juli 2010. Sumber-sumber pustaka yang dipelajari di tiap perpustakaan di Bogor, Jakarta, Bandung, Yogyakarta, Solo dan Malang, berupa majalah ilmiah, jurnal, laporan penelitian, skripsi, tesis dan desertasi tentang hama sengon.
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Judul: Sebaran diameter pohon sengon, Paraserianthes falcataria (L>) Nielsen yang mendapat serangan Xystocera festiva Pascoe pada berbagai umur tegakan
Abstrak: Pohon sengon [Paraserianthes falcataria (L) Nielsen] merupakan salah satu jenis pohon unggulan dalam program pembangunan hutan tanaman dan hutan rakyat di Indonesia khususnya di Pulau Jawa. Salah satu masalah dalam pengusahaan hutan sengon adalah adanya serangan hama pengerek batang Xystrocera festiva Pascoe (Coleoptera; Cerambycide) yang banyak dikenal dengan nama boktor sengon. Adanya sejumlah lubang gerek pada batang menyebabkan penurunan kualitas dan kuantitas kayu pertukangan yang dihasilkan. Penelitian ini bertujuan untuk menentukan pola serangan Xystrocera festiva Pascoe menurut diameter pohon pada berbagai umur tegakan sengon [Paraserianthes falcataria (L) Nielsen]. Hasil penelitian ini diharapkan dapat digunakan dalam pelaksanaan penjarangan tegakan sengon yang telah mengalami serangan boktor sengon (Xystrocera festiva Pascoe).
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Judul: Which one use to overcome multicollinearity ? Ridge regression or principal component regression
Abstrak: In multiple linear regression the effect of nonorthogonality of the prediction vectors is to pull the least squares estimates of the regression coefficient away from the true coefficient that one is trying to estimate. Separating the effects of each factor of the regressors has been found to be difficult because of high correlation among independent variables. Although the multicollinearity problem has been recognized by many ways, ordinary least squares is still the main technique used in many fields, but the estimation of regression coefficient can present problems when the data vectors for the predictors are not orthogonal, or in this case are multicollinear. In using ordinary least squares, the regression coefficient may be unstable, too large in absolute value, and incorrect with respect to sign. Introduced biased estimation refer to unbiased one that measure the average closeness to the parameter being estimated corresponding to its mean square error (MSE). Ridge regression and principal component can produce better estimates by its own way than those given by ordinary least squares. It may well be preferred estimator since it will have larger probability of being close to true parameter value. Two of the biased regression methods, ridge regression and principal component regression will be applied into this research and discuss briefly for each of its properties. These methods have its particular idiosyncrasy. The biased regression methods attack the collinearity problem by computationally suppressing the effects of the collinearity. Ridge regression does this correctly by modifying the correlation matrix adding a biased constant driving through nonsingular matrix. Principal component regression attacks the problem by regressing Y on the important principal component and then parceling out the effect of the principal component variables to the original variables. Finally translated back the obtained variables into original variables yield the same sign and nearly the same coefficients for both methods.
Keyword: Regresssion analysis