Implementation and characterisation of a sterilisation module consisting of novel 265 nm UVC LED packages

To efficiently fight against the COVID-19 pandemic, a sterilisation module using 265 nm UVC LED packages was developed. In this paper, the performance of the sterilisation module in terms of irradiance uniformity, junction temperature increase and sterilisation efficiency were characterised. The irradiance uniformity fluctuation across the four corners and the centre point in a 130 mm × 130 mm area was below 10%, exhibiting good uniformity. Uniform irradiance was important to achieve consistent sterilisation, which was the primary difference between the UVC LED package developed and commercial UVC LED packages. Key to achieving uniform irradiance was the structure, consisting of a stacked silicon reflector and a secondary optical lens designed by ray tracing simulation. The junction temperature increase of the 265 nm UVC LED package driving at 200 mA was only 28°C, sufficiently low to exhibit better reliability and performance. A 99.99% sterilisation efficiency on E. coli bacteria was achieved within one minute with UV dosage of 2.7 mJ/cm2 at 200 mA driving current. From the results, the novel 265 nm UVC LED package was a time-efficient solution for disinfection purposes.

An advanced endoscopic surgery robotic platform for removal of early-stage gastrointestinal cancer using endoscopic submucosal dissection

Two gastrointestinal (GI) cancers, stomach and colorectal cancer, have the fifth and third highest incident rates and the fourth and second highest mortality rates among all cancers, respectively. Combined, they had 2.8 million new cases and 1.6 million deaths annually. Fortunately, early-stage GI cancer has a high five-year survival rate if the tumour can be removed completely. Endoscopic Submucosal Dissection (ESD) is the gold standard for the removal of early-stage GI cancer as it has a high rate of en-bloc resection and a low rate of recurrence. However, ESD is a very technically challenging surgical operation. It has a relatively high rate of failure, including perforation of the stomach or colon. Therefore, a surgical robotic platform with high dexterity and better ergonomics is in high demand, which can ease the technical problems induced by conventional ESD procedures. In our previous study, a prototype of an endoscopic surgery robotic platform was built and the preliminary experimental results showed that the dual flexible arm robotic platform with wire-driven continuum structure was capable of increasing the efficiency and safety in performing ESD under the master-slave controlling scheme. An advanced robotic platform was built based on this prototype to achieve higher flexibility and production requirements. The design of these two platforms and experimental results will be presented in detail.

Development of a novel design approach for rigid landslide debris-resisting barriers

Natural terrain landslides pose a global threat as they often cause casualties and economic losses. Potential impacts of climate change could further aggravate the landslide risk and robust mitigation measures such as rigid debris-resisting barriers are particularly important in protecting lives and properties. Traditionally, rigid barriers are designed based on empirical approaches which generally oversimplify the dynamic nature of debris-barrier interaction. This often results in overlyconservative designs where the barrier structures are not only bulky and environmentally intrusive, but also difficult to construct. There is thus a pressing need to optimise the design approach. In this regard, the Geotechnical Engineering Office has been endeavouring to enhance the process efficiency, in collaboration with top-notch experts, by capitalising on the latest advancement in computational simulations and physical testing, and improving the understanding of the physical process. A technical breakthrough has been achieved with respect to an improved knowledge in the debris flow dynamic and the complex debris-barrier interaction. A novel design method covering geotechnical and structural aspects has been developed for use in Hong Kong. This would bring about more cost-effective barrier designs, with enhanced design reliability and robustness.

Accuracy and precision of the CSLT measurement system: An experiment to defect diagnoses in bored piles

A new measurement system called Crosshole Sonic Logging Tomography (CSLT) provides information on the size, shape, and orientation of defects in a bored pile. The CSLT measurement system has not (yet) been accredited in Hong Kong for foundation testing. Bored piles in Hong Kong are generally wide and deep. Existing measurement accuracy studies do not consider this large type of bored piles. The objective of this research is to quantify the measurement accuracy and precision of the CSLT method for large diameter bored piles (the most common pile type for public housing projects in Hong Kong). A test pile was constructed with known defects and perform experiments with a CSLT measurement system to quantify its accuracy and precision. CSLT is found to be accurate in detecting shape, size, and location of large defects but small defects close to the tube are difficult to detect. Generally speaking, CSLT has satisfactory accuracy and precision for practical use. The use of CSLT can be considered as a feasible method in defect diagnosis of bore piles in Hong Kong.

Potential and prospects of photocatalytic disinfection: using sustainable solarenergy- driven photocatalysts

A new measurement system called Crosshole Sonic Logging Tomography (CSLT) provides information on the size, shape, and orientation of defects in a bored pile. The CSLT measurement system has not (yet) been accredited in Hong Kong for foundation testing. Bored piles in Hong Kong are generally wide and deep. Existing measurement accuracy studies do not consider this large type of bored piles. The objective of this research is to quantify the measurement accuracy and precision of the CSLT method for large diameter bored piles (the most common pile type for public housing projects in Hong Kong). A test pile was constructed with known defects and perform experiments with a CSLT measurement system to quantify its accuracy and precision. CSLT is found to be accurate in detecting shape, size, and location of large defects but small defects close to the tube are difficult to detect. Generally speaking, CSLT has satisfactory accuracy and precision for practical use. The use of CSLT can be considered as a feasible method in defect diagnosis of bore piles in Hong Kong.

A perspective of pipejacking works by tunnel boring machines in Hong Kong: part II – applications, problems encountered, cost and prospects

In this paper, application of special techniques such as pipe roof construction, retractable TBM, and rectangular TBM to address site difficulties and constraints is highlighted. Cost and prospects of TBM pipejacking works are discussed. Some observations, including problems encountered and overcome, are also highlighted. This paper should be read together with part I, which covers development, selection of design, operations and types of techniques.

Real-time object detection technology in railway operations

Development of new technology to enhance train operability, in particular during manual driving by real-time object detection on track, is one of the rising trends in the railway industry. The function of object detection can provide train operators with reminder alerts whenever there is an object detected close to a train, e.g. a defined distance from the train. In this paper, a two-stage vision-based method is proposed to achieve this goal. At first, the Targets Generation Stage focuses on extracting all potential targets by identifying the centre points of targets. Meanwhile, the Targets Reconfirmation Stage is further adopted to re-analyse the potential targets from the previous stage to filter out incorrect potential targets in the output. The experiment and evaluation result shows that the proposed method achieved an Average Precision (AP) of 0.876 and 0.526 respectively under typical scenario sub-groups and extreme scenario sub-groups of the data set collected from a real railway environment at the methodological level. Furthermore, at the application level, high performance with the False Alarm Rate (FAR) of 0.01% and Missed Detection Rate (MDR) of 0.94%, which is capable of practical application, was achieved during the operation in the Tsuen Wan Line (TWL) in Hong Kong.