Testing for Weak Instruments in Linear IV Regression

Weak instruments can produce biased IV estimators and hypothesis tests with large size distortions. But what, precisely, are weak instruments, and how does one detect them in practice? This paper proposes quantitative definitions of weak instruments based on the maximum IV estimator bias, or the maximum Wald test size distortion, when there are multiple endogenous regressors. We tabulate critical values that enable using the first-stage F-statistic (or, when there are multiple endogenous regressors, the Cragg-Donald (1993) statistic) to test whether given instruments are weak. A technical contribution is to justify sequential asymptotic approximations for IV statistics with many weak instruments.

Asymptotic Properties of the Hahn–Hausman Test for Weak-Instruments

This paper provides weak-instrument asymptotic representations of tests for instrument validity by Hahn and Hausman\u27s (HH) [Hahn, J., Hausman, J., 2002. A new specification test for the validity of instrumental variables. Econometrica 70, 163–189.], and uses these representations to compute asymptotic power against weak or irrelevant instruments. The HH tests were proposed as pretests, and the asymptotic properties of post-test inferences, conditional on the tests failing to reject instrument validity, are also examined

Prototipe Pembangkit Listrik Tenaga Air Memanfaatkan Teknologi Sistem Pipa Kapiler

Skripsi yang berjudul “Prototipe Pembangkit Listrik Tenaga Air Memanfaatkan Teknologi Sistem Pipa Kapiler” membahas tentang analisa dan percobaan tentang proses naiknya fluida dari bawah menuju ke atas dan pembuatan prototipe pembangkit listrik tenaga air. Proses naiknya fluida ini merujuk pada proses transportasi pada tumbuhan yang terjadi pada akar, batang dan daun. Pada percobaan yang telah dilakukan dengan memvariasikan ketinggian (75 cm, 90 cm, 105 cm, 120 cm, 135 cm, 150, 165 cm dan 180 cm) dan diameter pipa (Ф 2 mm, Ф 6 mm, Ф 8 mm) maka didapatkan hasil percobaan berupa debit, kecepatan fluida didalam pipa dan laju aliran massa fluida kemudian dilakukan perhitungan daya listrik pada alternator. Setelah percobaan dan analisa data telah dilakukan maka dilakukan perancangan prototype pembangkit listrik tenaga air

Coulomb implosion mechanism of negative ion acceleration in laser plasmas

Coulomb implosion mechanism of the negatively charged ion acceleration in laser plasmas is proposed. When a cluster target is irradiated by an intense laser pulse and the Coulomb explosion of positively charged ions occurs, the negative ions are accelerated inward. The maximum energy of negative ions is several times lower than that of positive ions. The theoretical description and Particle-in-Cell simulation of the Coulomb implosion mechanism and the evidence of the negative ion acceleration in the experiments on the high intensity laser pulse interaction with the cluster targets are presented.Comment: 4 page

PENGARUH PENGGUNAAN MEDIA PEMBELAJARAN KIMIA BERBASIS ANDROID TERHADAP PENINGKATAN MOTIVASI BELAJAR SISWA SMA

Penggunaan media berbasis ICT (Information and Comunication Technology) pada perangkat android saat ini menjadi tren dalam penelitian pendidikan sains. Penelitian ini bertujuan untuk mengetahui pengaruh penggunaan media pembelajaran kimia berbasis android dalam meningkatkan motivasi belajar siswa SMA. Desain penelitian yang digunakan adalah posttest-pretest-control group design. Subjek penelitian adalah SMAN 1 Banguntapan Yogyakarta yang terdiri atas satu kelas eksperimen dan satu kelas kontrol. Pengumpulan data menggunakan angket motivasi belajar dengan skala Likert. Data yang diperoleh dianalisis nilai gain-nya untuk mengetahui peningkatan motivasi belajar siswa SMA. Hasil penelitian menunjukkan bahwa media pembelajaran kimia berbasis android dapatmemberikan pengaruh yang signifikan terhadap peningkatan motivasi belajar siswa SMA

KAJIAN PROSES PENYULINGAN UAP MINYAK JINTAN PUTIH

ABSTRACTCumin seed  (Cuminum Cyminum Linn.) is the one of essential oil resources which is being developed for its economic value and one of the most used resources in pharmaceutical industries and flavourings. Cumin oil was able to cure some digestion problems, an antioxidants, highly anesstesive and fixative. Major component of cumin oil is cuminaldehyde,which reach 35-62%.This research aims to study cumin oil distillation character with steam distillation method and to know effect of steam pressure and bulk density to yield and physicochemical properties of cumin oil produced. Stages on this research were moisture content, essential oil content and ash content analyses, diatillation time determination, cumin oil distillation on different steam pressure and bulk density, and then analyzed. Cumin oil analyses consist of its yield, specific gravity, refractive index, optic rotation, acid number, ester value and solubility in alcohol 80%.This research used factorial complete randomized design with two factors. First factor was bulk density, which consists of two levels (0,1 and 0,2 kg/L). Second factor was steam pressure, which consists of three levels (0; 0,5; and 1 bar gauge). Analyzed data showed that its moisture content, essential oil and ash content respectively was 7,83%, 3,34% and 5,36%. Distillation time was in five hours, when 95% oil has been distillated.Steam pressure significantly affect the yield, specific gravity and ester value, which bulk density significantly affects its acid number and ester value. Interaction between these two factors significantly affects its yield and ester value. Cumin oil in this research was bright yellow to brown in color, with strong and spesific odor. Its yield was 1,23-2,65 % (bb), specific gravity was 0,9630-0,9862, refractive index was 1,497-1,504, optic rotation was +2,4°-+3,6°,  and average comparison of its solubility in alcohol 80% was 1:2.The volatile oil composition of cumin oil was investigated by gas chromatography. The highest cuminaldehyde content as the major component of cumin oil was obtained from no steam pressure gauge.Keyword : minyak jintan, cuminaldehid, penyulingan ua