Diffraction Testbed for Use in Remote Teaching

The need for remote teaching tools in all education levels has experienced a big increase due to COVID-19 pandemic. Laboratory practical sessions have not been an exception, and many online and offline tools have been made available to respond to the lockdown of teaching facilities. This paper presents a software testbed named OPTILAB for teaching diffraction experiments to engineering students. The software simulates classical diffraction apertures (single slit, double slit, circular slit) under a wide variety of conditions. Explanation about the Physics behind the diffraction phenomenon is also included in OPTILAB to increase the students’ self-learning experience. Originally conceived as a complement to on-site teaching, due to COVID-19 pandemic OPTILAB has been adopted as the basic tool to build a brand-new, virtual laboratory session about diffraction in Physics III course (biomedical engineering) at Carlos III University of Madrid. Results obtained by the students taking this virtual lab during Fall 2020 are presented and discussed.

The Neolithic Jade Revolution in Northeast China

This chapter examines how Xinglongwa jades in the sixth millennium bce mark the beginning of nephrite’s preeminence in East Asia. Their carefully selected raw material, color, and texture, as well as established standards in form and production technologies, laid down the foundations for later jade cultures across a wide region in East Asia. In particular, the Xinglongwa jade slit rings are the early known circular slit earrings in the world. The influence of Xinglongwa jade culture on notable jade cultures across North China is evident, as key characteristics that distinguish Xinglongwa jades from other prehistoric jade traditions were preserved.

KAJIAN KOMPUTASI NUMERIK MODEL INTEGRATIF PADA DIFRAKSI CELAH LINGKARAN MENGGUNAKAN METODE PENDEKATAN SIMPSON 1/3

Abstrak Telah dilakukan penelitian tentang komputasi numerik model integratif pada difraksi celah lingkaran dengan tujuan untuk menerapkan metode simpson 1/3 untuk mencari solusi kasus difraksi celah lingkaran, menghitung nilai integrasi bessel menggunakan metode simpson 1/3, menentukan jarak antara dua intensitas pada pita terang, memperoleh grafik pola intensitas cahaya terhadap jarak pada kasus difraksi celah berbentuk lingkaran. Hasil integrasi yang diperoleh dengan metode simpson 1/3 pada tiga titik puncak intensitas yaitu 0.14352548, -0.3342371, 0.27050545 Dari hasil perhitungan pada puncak pertama untuk intensitas maksimum pada terang pusat yang berada pada jarak 0.3 cm dengan nilai intensitas 0.91553621, puncak kedua pada jarak 5.1 cm dengan nilai intensitas 0.01718022 dan pucak ketiga pada jarak 8.6 cm dengan nilai intensitas 0.00395745. Dari hasil perhitungan diperoleh grafik antara jarak dengan intensitas sehingga terdapat pola yang membentuk cincin gelap terang semakin besar panjang gelombang sumber maka semakin besar pula jarak antara suatu titik intensitas dari intensitas maksimum. Hasil perhitungan menunjukkan bahwa pendekatan integrasi simpson 1/3 hampir mendekati hasil yang telah diperoleh secara analitik. Dari hasil ini dapat dihitung nilai error dari program terhadap nilai eksak secara analitik dan diperoleh nilai pendekatan yang kecil yaitu -7.95 x 10-6, -6.07 x 10-6, 2.25 x 10-6. Sehingga hasil pendekatan dengan metode Simpson dapat diterima serta dapat dikatakan bahwa program yang dibuat telah berfungsi dengan baik. Kata kunci: Bessel; metode Simpson 1/3; difraksi celah lingkaran. Abstract [Numerical Computation Study Of Integrative Models In The Circular Aperture Diffraction With Simpson 1/3 Approach Method] Research on numerical computation of integrative models on the circular aperture diffraction with the aim to apply the Simpson 1/3 method to find a solution to the circular aperture diffraction case, calculate the integration value of the Bessel using the Simpson 1/3 method, determine the distance between two intensities on the bright band, obtain graph of the pattern of light intensity versus distance in the case of circular slit diffraction. The integration results obtained by the Simpson method at three intensity peaks are 0.14352548, -0.3342371, 0.27050545 From the results of the calculation at the first peak for maximum intensity at the center of light at a distance of 0.3 cm with an intensity value of 0.91553621, the second peak at a distance of 5.1 cm with an intensity value of 0.01718022 and a third peak at a distance of 8.6 cm with an intensity value of 0.00395745. From the calculation results obtained by the graph between the distance with intensity so that there is a pattern that forms a dark ring of light the greater the source wavelength, the greater the distance between an intensity point from the maximum intensity. The calculation results show that the Simpson 1/3 integration approach is almost close to the results that have been obtained analytically. From these results, an error value from the program can be calculated analytically and the exact value of the approach obtained is -7.95 x 10-6, -6.07 x 10-6, 2.25 x 10-6. So the results of the approach with the Simpson 1/3 method can be accepted and it can be said that the program created has functioned well. Keywords: Bessel; Simpson 1/3methods; circular aperture diffraction.

Fatigue Limit Improvement by Needle-Peening for Stainless Steel Welded Joint Containing a Crack-Like Defect

The effects of needle-peening on the bending fatigue limit of an austenitic stainless steel JIS-SUS316 welded joint containing an artificial semi-circular slit on the weld toe were investigated. Peening was applied to specimens with a semi-circular slit at depths of a = 1.0 mm and 1.5 mm. Then, plane bending fatigue tests were carried out at a stress ratio of R = 0. The fatigue limits of welded specimens containing a semi-circular slit were increased for the peened specimens. Peened specimens with slit sizes of a = 1.0 mm had high fatigue limits that were nearly equal to those of non-slit, peened specimens. We observed that a semicircular slit with a depth of less than a = 1.0 mm could be rendered harmless by peening. Additionally, the values of fatigue limit and the maximum depth of a semi-circular slit that can be rendered harmless by peening were predicted based on fracture mechanics, where we assume that a semi-circular slit is equivalent to a semi-circular crack. The prediction results were consistent with experimental results.

Effect of peening on the fatigue limit of welded structural steel with surface crack, and rendering the crack harmless

Purpose – The purpose of this paper is to investigate the effect of peening on the fatigue limit of steels for welded structure with a crack in the weld toe zone. Design/methodology/approach – An artificial semi-circular slit was created in the weld toe, and peening was conducted. Then, bending fatigue tests were carried out. Findings – First, owing to the shot peening, the maximum slit depths that can be rendered harmless were 1.0 and 1.2 mm in SUS316 and SM490, respectively. Second, during the fatigue test, the fracture of a peened specimen originated outside the slit, which indicated that peening eliminated the effect of the slit on the fatigue limit. Third, the fatigue limit of a slit specimen was improved by the enhanced residual stress distribution and the decreased stress concentration due to plastic deformation at the weld toe. Originality/value – There are very few studies about which a fatigue crack is rendered harmless by residual compressive stress, as a result the structures could be continued to use. Moreover, the study defining the concept about rendering crack harmless and systematic investigation was not able to be found.