Research on the Method of Heat Preservation and Heating for the Drilling System of Polar Offshore Drilling Platform

This study investigates the heat dissipation mechanism of the insulation layer and other plane insulation layers in the polar drilling rig system.Combining the basic theory of heat transfer with the environmental requirements of polar drilling operations and the characteristics of polar drilling processes,we analyze the factors that affect the insulation effect of the drilling rig system.These factors include the thermal conductivity of the insulation material,the thickness of the insulation layer,ambient temperature,and wind speed.We optimize the thermal insulation material of the polar drilling rig system using a steady-state method to measure solid thermal conductivity.By analyzing the distribution of temperature in space after heating,we optimize the distribution and air outlet angle of the heater using Fluent hydrodynamics software.The results demonstrate that under polar conditions,polyisocyanurate with stable thermodynamic properties is selected as the thermal insulation material.The selection of thermal insulation material and thickness significantly affects the thermal insulation effect of the system but has little effect on its heating effect.Moreover,when the air outlet angle of the heater is set to 32.5°,the heating efficiency of the system can be effectively improved.According to heat transfer equations and heat balance theory,we determine that the heating power required for the system to reach 5°C is close to numerical simulation.

Special issue “Photoacoustic imaging: microscopy, tomography, and their recent applications in biomedicine” in visual computation for industry, biomedicine, and art

Photoacoustic(PA)imaging is a promising non-invasive and non-ionizing biomedical imaging modality that emerged in recent years.The articles presented in this special issue describe some of newest progress in this field.We are extremely grateful to all contributing authors.The first part of the issue covers new laser source devel-opment,including fiber lasers and laser diodes.The sec-ond part is dedicated to improving the image resolution through chronic cranial window techniques,virtual-point concept,fast polygon scanning,and Fabry Perot sensing.The third part shows the basic principles of photoacous-tic/ultrasound imaging and its applications.

Micro-rocket robot with all-optic actuating and tracking in blood

Micro/nanorobots have long been expected to reach all parts of the human body through blood vessels for medical treatment or surgery.However,in the current stage,it is still challenging to drive a microrobot in viscous media at high speed and difficult to observe the shape and position of a single microrobot once it enters the bloodstream.Here,we propose a new micro-rocket robot and an all-optic driving and imaging system that can actuate and track it in blood with microscale resolution.To achieve a high driving force,we engineer the microrobot to have a rocket-like tripletube structure.Owing to the interface design,the 3D-printed micro-rocket can reach a moving speed of 2.8 mm/s(62 body lengths per second)under near-infrared light actuation in a blood-mimicking viscous glycerol solution.We also show that the micro-rocket robot is successfully tracked at a 3.2-μm resolution with an optical-resolution photoacoustic microscope in blood.This work paves the way for microrobot design,actuation,and tracking in the blood environment,which may broaden the scope of microrobotic applications in the biomedical field.

Five-wavelength optical-resolution photoacoustic microscopy of blood and lymphatic vessels

Optical-resolution photoacoustic microscopy(OR-PAM)has been developed for anatomical,functional,and molecular imaging but usually requires multiple scanning for different contrasts.We present five-wavelength OR-PAM for simultaneous imaging of hemoglobin concentration,oxygen saturation,blood flow speed,and lymphatic vessels in single raster scanning.We develop a five-wavelength pulsed laser via stimulated Raman scattering.The five pulsed wavelengths,i.e.,532,545,558,570,and 620∕640 nm,are temporally separated by several hundreds of nanoseconds via different optical delays in fiber.Five photoacoustic images at these wavelengths are simultaneously acquired in a single scanning.The 532-and 620∕640-nm wavelengths are used to image the blood vessels and dye-labeled lymphatic vessels.The blood flow speed is measured by a dual-pulse method.The oxygen saturation is calculated and compensated for by the Grüneisen-relaxation effect.In vivo imaging of hemoglobin concentration,oxygen saturation,blood flow speed,and lymphatic vessels is demonstrated in preclinical applications of cancer detection,lymphatic clearance monitoring,and functional brain imaging.

Confocal visible/NIR photoacoustic microscopy of tumors with structural, functional, and nanoprobe contrasts

Distinguishing early-stage tumors from normal tissues is of great importance in cancer diagnosis.We report fiberbased confocal visible/near-infrared(NIR)optical-resolution photoacoustic microscopy that can image tumor microvasculature,oxygen saturation,and nanoprobes in a single scanning.We develop a cost-efficient single laser source that provides 532,558,and 1064 nm pulsed light with sub-microseconds wavelength switching time.Via dual-fiber illumination,we can focus the three beams to the same point.The optical and acoustic foci are confocally aligned to optimize the sensitivity.The visible and NIR wavelengths enable simultaneous tumor imaging with three different contrast modes.Results show obvious angiogenesis,significantly elevated oxygen saturation,and accumulated nanoparticles in the tumor regions,which offer comprehensive information to detect the tumor.This approach also allows us to identify feeding and draining vessels of the tumor and thus to determine local oxygen extraction fraction.In the tumor region,the oxygen extraction fraction significantly decreases along with tumor growth,which can also assist in tumor detection and staging.Fiber-based confocal visible/NIR photoacoustic microscopy offers a new tool for early detection of cancer.