Lubrication condition monitoring of journal bearings in diesel engine based on thermoelectricity

There is still a lack of effective lubrication condition monitoring methods in the field of diesel engines.The paper proposes a novel thermoelectric approach to divide the lubrication state of bearings.First,the generation mechanism of thermoelectric potential on bearings is clarified.Then,both experimental and simulation studies are done,and a strong correlation between lubrication and thermoelectric potential is shown.The film thickness and temperature are further confirmed as significant factors influencing thermoelectric potential.Generally,the thermoelectric potential increases with temperature.However,a small film thickness ratio(when the film thickness ratio is less than 4)will suppress the thermoelectric potential.Three typical lubrication states of bearings are distinguished through thermoelectric potential and supported by the Stribeck curve results.Moreover,the significant influence of lubrication on the bearing is confirmed through the analysis of surface morphology and composition.

Inverse design of digital nanophotonic devices using the adjoint method

A high-efficiency inverse design of"digital"subwavelength nanophotonic devices using the adjoint method is proposed.We design a single-mode 3dB power divider and a dual-mode demultiplexer to demonstrate the efficiency of the proposed inverse design approach,called the digitized adjoint method,for single-and dual-object optimization,respectively.The optimization comprises three stages:1)continuous variation for an"analog"pattern;2)forced permittivity biasing for a"quasi-digital"pattern;and 3)a multilevel digital pattern.Compared with the conventional brute-force method,the proposed method can improve design efficiency by about five times,and the performance optimization can reach approximately the same level.The method takes advantages of adjoint sensitivity analysis and digital subwavelength structure and creates a new way for the efficient and high-performance design of compact digital subwavelength nanophotonic devices,which could overcome the efficiency bottleneck of the brute-force method,which is restricted by the number of pixels of a digital pattern,and improve the device performance by extending a conventional binary pattern to a multilevel one.

Ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers

We propose and experimentally demonstrate a novel ultracompact dual-mode waveguide crossing based on subwavelength multimode-interference couplers for a densely integrated on-chip mode-division multiplexing system.By engineering the lateral-cladding material index and manipulating phase profiles of light at the nanoscale using an improved inverse design method, a subwavelength structure could theoretically realize the identical beat length for both TE_0 and TE1, which can reduce the scale of the device greatly. The fabricated device occupied a footprint of only 4.8 μm× 4.8 μm. The measured insertion losses and crosstalks were less than 0.6 d B and-24 d B from 1530 nm to 1590 nm for both TE0 and TE1 modes, respectively. Furthermore, our scheme could also be expandedto design waveguide crossings that support more modes.

On-chip cyclic-AWG-based 12 × 12 silicon wavelength routing switches with minimized port-to-port insertion loss fluctuation

With the rapidly increasing bandwidth requirements of optical communication networks, compact and low-cost large-scale optical switches become necessary. Silicon pbotonics is a promising technology due to its small footprint, cost competitiveness, and high bandwidth density. In this paper, we demonstrate a 12 × 12 silicon wavelength routing switch employing cascaded arrayed waveguide interconnection network on a the switch＇s footprint. We single chip. We optimize develop an algorithm based gratings （AWGs） connected by a silicon waveguide the connecting strategy of the crossing structure to reduce on minimum standard deviation to minimize the port-to- port insertion loss （IL） fluctuation of the switch globally. The simulated port-to-port IL fluctuation decreases by about 3 dB compared with that of the conventional one. The average measured port-to-port IL is 13.03 dB, with a standard deviation of 0.78 dB and a fluctuation of 2.39 dB. The device can be used for wide applications in core networks and data centers.