Three-Dimensional-Printed Drill Guides for Occipitothoracic Fusion in a Pediatric Patient With Occipitocervical Instability

BACKGROUND Pediatric occipitothoracic fusion can be challenging because of small size pedicles and thin occipital bone. Three-dimensional (3D) printing technology can help with accurate screw insertion but has not been described for occipital keel plate positioning so far. OBJECTIVE To describe the novel use of 3D technology to position occipital keel plates during pediatric occipitothoracic fixation. METHODS A young boy with segmental spinal dysgenesis presented with asymmetrical pyramidal paresis in all limbs. Developmental abnormities of the cervical spine caused a thinned spinal cord, and because of progressive spinal cord compression, surgical intervention by means of occipitothoracic fixation was indicated at the age of 3 yr. Because of the small-size pedicles and thin occipital bone, the pedicle screws and occipital plates were planned meticulously using 3D virtual surgical planning technology. The rods were virtually bent in order to properly align with the planned screws. By means of 3D-printed guides, the surgical plan was transferred to the operating theater. For the occipital bone, a novel guide concept was developed, aiming for screw positions at maximal bone thickness. RESULTS The postoperative course was uneventful, and radiographs showed good cervical alignment. After superimposing the virtual plan with the intraoperative acquired computed tomography, it was confirmed that the occipital plate positions matched the virtual plan and that pedicle screws were accurately inserted without signs of breach. CONCLUSION The use of 3D technology has greatly facilitated the performance of the occipitothoracic fixation and could, in the future, contribute to safer pediatric spinal fixation procedures.

Experimental Research on Water Column Oscillations in Moonpool of a Drillship in Downtime Period

A drillship is a kind of merchant vessel with a self-propulsion unit and drilling equipment used for oil exploration. The major difference with the merchant vessel is the moonpool. A moonpool is a vertical opening from the continuous deck to the keel plate of the vessel for drilling operations and other applications like the launching of measuring instruments. This moonpool opening allowing the entry of water into the vessel. The water motion within the moonpool is mostly related to the encountering wave frequency, the geometry of the moonpool and the draft condition of the vessel. The major amplitude of the water particle motion within the moonpool, either may be in the sloshing mode or in piston mode. This water motion leads to the entry of green water on the deck during the rough weather condition. This is known as the downtime period of a drillship, during this time the operation of the drillship is in off-mode. This paper presents the study about the downtime period of drillship experimentally with rectangular moonpool.

Perhitungan laju korosi dan perancangan sistem proteksi katodik anoda korban di lambung kapal tugboat Bontang o4 PT Badak NGL Bontang

Corrosion happens differently for each point of hull plate which caused of corrosion rate differences. So that is very important to measure it for each point, which is calculated using Weight Gain Loss Method. The measurement of plate thickness that used is Ultrasonic Test Method conducted by PT BKI. To determine the condition of ship protection, then the coating and sacrificial anode system is evaluated by testing the composition and current and voltage of anode as well. Furthermore, the number and position of anode is also analyzed. So that the re-design of cathode protection is needed by referring to the PT BKI’s standards. Then the prediction of corrosion rate is calculated by using the design of cathode protection. The largest corrosion rates are in the amidships and portside for each plate lane, they are on the keel plate point K3 is 0.37 mm/years, pedestal plate point A4 is 1.05 mm/years, bilge plate point B4 is 0.62 mm/years and side plate point C5 is 0.39 mm/years. But the number of installed anode is 31 anodes with an irregular position. So in this study, done the redesign system of cathode protection based on regulations issued by PT BKI, with the result of the number of the anode is 56 units. Using the design, then carried a prediction by the result is lower, that on the keel plate is 0.073 mm/years, pedestal plate is 0.021 mm/years, bilge plate is 0.013 mm/years and the side plate is 0.014 mm/years.

Model Tests With the HVS Semisubmersible for Dry Tree Application

The global hull motion performance of the HVS semisubmersible for dry tree application is investigated with model tests. The HVS semisubmersible, which has been validated for low heave motion and VIM (Vortex Induced Motion) response, was modified for dry tree application. As a base case, the modification includes a keel plate with riser keel guides at the level of the pontoons. The keel plate is optimally designed to increase the hull heave period to compensate for the heave period reduction in the HVS semisubmersible due to the riser tensioners for the dry tree application. The plate also provides additional viscous damping that decreases the heave response at the heave natural period. The model tests were performed to investigate the in-place hull motion performance for the Gulf of Mexico environmental conditions. The pneumatic riser tensioners were modeled using a spring with dual stiffness. Because of the water depth limit in the wave basin, a truncated mooring was used to simulate the full scale prototype mooring system. An alternate modification to the HVS semisubmersible that includes pontoon plates was also tested and the measured response was compared to the response of the base case. The measured hull responses were correlated with MLTSIM, a Technip in-house nonlinear time-domain 6-DOF motion analysis program.