Z-axis Coordinates Research Articles

Applicability of RANS models and pressure drop in edge subchannels for 19-pin wire-wrapped fuel bundle channel in CiADS

The accelerator-driven subcritical system has a strong transmutation ability and high inherent safety, and it is internationally recognized as the most promising long-life nuclear waste disposal device. This study involves the construction of a Visual Hydraulic ExperimentaL Platform (VHELP) for the purpose of evaluating the applicability of Reynolds-averaged Navier–Stokes (RANS) models and analyzing the pressure distribution within the fuel bundle channel of China initiative accelerator-driven system (CiADS). Measurements of thirty differential pressures in edge subchannels within a 19-pin wire-wrapped fuel bundle channel were obtained under different conditions using deionized water. The pressure distribution in the fuel bundle channel at Reynolds numbers of 5000, 7500, 10,000, 12,500, and 15,000 was simulated using Fluent. The results show that RANS models obtained accurate results, and the shear stress transport k-ω model provided the most accurate prediction of the pressure distribution. The difference between the results of the Shear stress transport (SST) k-ω model and experimental data was the smallest, and the maximum difference was ±5.57%. Moreover, the error between the experimental data and numerical results of the axial differential pressure was smaller than that of the transverse differential pressure. The pressure periodicity in axial and transverse directions (one pitch) and a relatively three-dimensional pressure measurements were studied. The static pressure fluctuated and decreased periodically as the z-axis coordinate increased. These results can facilitate research on the cross-flow characteristics of liquid metal-cooled fast reactors.

STERNOCLAVICULAR JOINT OSTEOARTHRITIS: IS SHORTER CLAVICULAR LENGTH A RISK FACTOR?

Osteoarthritis (OA) is the most common disorder of the Sternoclavicular Joint (SCJ). In our case-control study, we evaluated the relationship between clavicular length and OA at the SCJ.CT scans of adults presenting to the Emergency Department of our hospital were examined to look for OA, defined as the presence of osteophytes, subchondral cysts, or cortical sclerosis at the SCJ. Medial-most and lateral-most points of the clavicle were marked on the slices passing through the SC and AC joints respectively. Using x, y, and z-axis coordinates from the DICOM metadata, clavicular length was calculated as the distance between these two points with 3D geometry.Preliminary data of 334 SCJs from 167 patients (64% males, 36% females) with a mean age of 48.5 ± 20.5 years were analysed. Multivariate regression models revealed that age and clavicular length were independent risk factors for OA while gender did not reach statistical significance. A 1mm increase in length was associated with 9% and 7% reduction in the odds of developing OA on the left and the right respectively. Comparing the mean clavicular length using t-test showed a significantly shorter clavicle in the group with OA (145.8 vs 152.7, p=0.0001, left and 144.2 vs 150.3, p=0.0007, right).Our data suggest that the risk of developing OA at the SCJ is higher for shorter clavicles. This could be of clinical relevance in cases of clavicular fracture where clavicular shortening might lead to a higher risk of developing OA. Biomechanical studies are needed to find out the mechanism of this effect.

Computerized three-dimensional cephalometric template for Thai adults

Cephalometry is essential in several fields of study. These include health science, anthropology, and forensic studies. Furthermore, cephalometric norms are essential for numerous disciplines in the health sciences, such as clinical anatomy, plastic surgery, pediatrics, pediatric dentistry, orthodontics, oral and maxillofacial surgery, and forensic medicine. Three-dimensional (3D) cephalometric templates offer an advanced but simple method for these specialties. This study aimed to establish cephalometric norms by developing 3D templates for Thai adults, based on cephalometric landmark coordinates obtained from skull cone-beam computed tomography (CBCT) scans of individuals with normal skeletal patterns. Full-head CBCT scans of 45 individuals (20 men and 25 women) were obtained from the archive. All had a Class I molar relationship with minor crowded teeth. The scans were captured in a normal head position, and the coordinates of 21 important cephalometric landmarks were identified using Slicer 4.10.2 software. Manual affine transformation of all landmarks was used to transfer medical image coordinates (Digital Imaging and Communications in Medicine [DICOM] or Right-Anterior-Superior [RAS] systems) to Cartesian universal coordinates. Intraclass correlation coefficients (ICC) and Bland-Altman (BA) plots were used to assess inter- and intra-examiner reliability (ICC = 0.961–1.000, BA mean errors = −0.1 mm). Important cephalometric measurements were compared to the most relevant and recent study with a sample size of 200. Most measurements showed no statistical difference (one-sample t-test, p > 0.05). Independent samples t-tests revealed that there was no statistically significant difference in the X and Y axes; however, most mean coordinates between men and women in the Z-axis coordinates were statistically significant. Consequently, 3D cephalometric templates were generated separately for adult Thai men and women using landmark coordinates. Although they are available for all disciplines at no cost through QR codes, these templates should be used with care, especially for the upper and lower incisor angulation. The application and future development of each specialty are also described here.

Digital map and probability compensation model for repeated positioning error of feed axis

The randomness of the repeated positioning error of feed shaft is the main reason for the difficulty to address this error. The previous repeated loading and unloading suppression methods will easily do damages to parts. This paper sets out to investigate the probability distribution of all possible error values while feed shaft is at different positions, and determine the maximum value of probability error from the random errors. With feed axis at a certain position, first of all, we count the probability of each error based on a large number of random errors. We also draw the digital map of the repeated positioning error of this error with the error of positive and negative stroke measurement as the x-axis and y-axis coordinates and the probability of each error value as the z-axis coordinates. Secondly, based on the digital map of each position on the feed axis and combined with the dynamic optimization algorithm, we find the highest point on the map and take the coordinate point of this point as the starting point of each position compensation. Then, we set the error probability threshold to control the possibility of compensation errors and output the size and direction of the final compensation value. Finally, we start the compensation command and detect the compensated error. The error data that fail to meet the requirements will enter the probability statistics again, redraw the digital map and update the map. Through real-time detection and feedback, the digital map is dynamically improved to adapt to the changing environment. This probability compensation model of repeated positioning error can end the suppressing repeated positioning errors brought by repeatedly disassembling parts.

Deformation Monitoring and Shape Reconstruction of Flexible Planer Structures Based on FBG

To reduce the dependence of real-time deformation monitoring and shape reconstruction of flexible planar structures on experience, mathematical models, specific structural curvature (shape) sensors, etc., we propose a reconstruction approach based on FBG and a data-driven model; with the aid of ANSYS finite element software, a simulation model was built, and training samples were collected. After the machine learning training, the mapping relationship was established, which is between the strain and the deformation variables (in three directions of the x-, y-, z-axis) of each point of the surface of the flexible planar structure. Four data-driven models were constructed (linear regression, regression tree, integrated tree, and BP neural network) and comprehensively evaluated; the predictive value of the BP neural network was closer to the true value (R2 = 0.9091/0.9979/0.9964). Finally, the replication experiment on the flexible planar structure specimen showed that the maximum predictive error in the x-, y-, and z-axis coordinates were 2.93%, 35.59%, and 16.21%, respectively. The predictive results are highly consistent with the expected results of flexible planar structure deformation monitoring and shape reconstruction in the existing test environment. The method provides a new high-precision method for the real-time monitoring and shape reconstruction of flexible planar structures.

Correlation between Electrode Location and Anxiety Depression of Subthalamic Nucleus Deep Brain Stimulation in Parkinson's Disease.

Objectives: our group explored the correlation between postoperative coordinates of the electrode contacts, VTA, and anxiety and depression symptoms in Parkinson’s disease (PD) patients after subthalamic nucleus deep brain stimulation (STN-DBS). Methods: STN-DBS was conducted on PD patients (n = 57) for six months with follow-up. Clinical outcomes were explored using the unified Parkinson’s disease rating scale Part III (UPDRS-III), the Hamilton Anxiety Rating Scale (HAM-A), and the Hamilton Depression Rating Scale (HAM-D) before and after surgery. At the Montreal Neurological Institute (MNI), the location of active contacts and the volume of tissue activated (VTA) were calculated. Results: patient evaluations took place preoperatively and follow-ups took place at 1 month, 3 months, and 6 months. The average patient improvement rates for HAM-A and HAM-D scores at the 6-month follow-up were 41.7% [interquartile range (IQR) 34.9%] and 37.5% (IQR 33.4%), respectively (both p < 0.001). In medication-off, there were negative correlations between the HAM-A improvement rate and the Z-axis coordinate of the active contact (left side: r = −0.308, p = 0.020; right side: r = −0.390, p = 0.003), and negative correlations between the HAM-D improvement rate and the Z-axis coordinate of the active contact (left side: r = −0.345, p = 0.009; right side: r = −0.521, p = 0.001). There were positive correlations between the HAM-A and HAM-D scores improvement rate at 6 months after surgery and bilateral VTA in the right STN limbic subregion (HAM-A: r = 0.314, p = 0.018; HAM-D: r = 0.321, p = 0.015). Conclusion: bilateral STN-DBS can improve anxiety and depression symptoms in PD patients. The closer the stimulation to the ventral limbic region of the STN, the more significant the improvement in anxiety and depression symptoms of PD patients.

3D MSSD: A multilayer spatial structure 3D object detection network for mobile LiDAR point clouds

Point cloud-based object detection is vital and essential for many real-world applications, such as autonomous driving and robot vision. The PointPillars model has achieved the efficient detection of objects in front of a vehicle. However, the algorithm does not consider the spatial structures semantic information stored in the three-dimensional point cloud for a given spatial structure, thus leading to missed or false detections for objects with complex spatial structures or singular structures. We propose an approach based on PointPillars, which considers the spatial structure characteristics of 3D point clouds to enhance the detection accuracy. First, based on the specified range of the z-axis coordinates, the entire point cloud scene is divided into several layers so that the point cloud areas in the same height interval form one layer. Data from several layers are obtained. Second, the point clouds of several layers are processed with Pillar Feature Net to obtain several pseudoimages. Each pseudoimage represents the semantic information from the corresponding level of the point cloud. Third, the obtained pseudoimages from each level are merged with the pseudoimages of the entire scene to obtain a feature map with spatial structure characteristics. We apply a Region Proposal Network, and an object detection operator processes the feature map and obtains the result of object detection. Experiments show that the proposed method has a highly accurate detection effect for objects with complex spatial structures. In addition, the proposed method does not erroneously detect objects with similar semantic information after vertical dimension projection.

Relationship between electrode position of deep brain stimulation and motor symptoms of Parkinson\u2019s disease

BackgroundTo investigate the relationship between the position of bilateral STN-DBS location of active contacts and the clinical efficacy of STN-DBS on motor symptoms in Parkinson’s disease (PD) patients.MethodsRetrospectively analyze the clinical data of 57 patients with PD who underwent bilateral STN-DBS from March 2018 to December 2018. Unified Parkinson’s Disease Rating Scale-Part III (UPDRS-III) score, levodopa equivalent day dose (LEDD), Parkinson’s Disease Quality of Life Scale (PDQ-39) before operation and within 6 months after operation, determine the location of activated contacts and volume of tissue activated (VTA) in the Montreal Neurological Institute (MNI) space, and analyze their correlation with the improvement rate of motor symptoms (UPDRS-III score improvement rate).ResultsAfter 6 months of follow up, the UPDRS-III scores of 57 patients (Med-off) were improved by 55.4 ± 18.9% (P<0.001) compared with that before operation. The improvement rate of PDQ-39 scores [(47.4 ± 23.2)%, (P < 0.001)] and the reduction rate of LEDD [(40.1 ± 24.3)%, (P < 0.01)] at 6 months postoperation were positively correlated with the improvement rate of motor symptoms (Med-off)(PDQ-39:r = 0.461, P<0.001; LEDD: r = 0.354, P = 0.007), the improvement rate of UPDRS-III (Med-off) and the Z-axis coordinate of the active contact in the MNI space were positively correlated (left side: r = 0.349,P = 0.008;right side: r = 0.369,P = 0.005). In the MNI space, there was no correlation between the UPDRS-III scores improvement rate (Med-off) at 6 months after operation and bilateral VTA in the STN motor subregion, STN associative subregion and STN limbic subregion of the active electrode contacts of 57 patients (all P > 0.05). At 6 months after surgery, the difference between the Z-axis coordinate in the different improvement rate subgroups(<25, 25 to 50%, and>50%) in the MNI space was statistically significant (left side: P = 0.030; right side: P = 0.024). In the MNI space, there was no statistically significant difference between the groups in the VTA of the electrode active contacts (all P > 0.05).ConclusionSTN-DBS can improve the motor symptoms of PD patients and improve the quality of life. The closer the stimulation is to the STN dorsolateral sensorimotor area, the higher the DBS is to improve the motor symptoms of PD patients.

Less interference tool-path planning method for quarter revolution penetration and retraction trajectories in internal cylindrical thread helical milling

Critical interference error can be mostly resulted from illogical tool-path generations in the penetration and retraction segments of internal cylindrical thread helical milling. Therefore, a less interference tool-path planning method is proposed for the quarter revolution penetration and retraction trajectories in internal cylindrical thread helical milling. Firstly, the parametric expression of the complete tool path of internal cylindrical thread helical milling is established; after that, a definition of eccentricity parameter m is given to adjust the radius of the penetration and retraction trajectories, and Z-axis coordinate of any point on the tool path is defined as a function of the θ; thus, the planned penetration and retraction trajectories in internal cylindrical thread helical milling with the m are derived; finally, the proper eccentricity parameter m is decided to improve the machining accuracy of thread by exploring the influence of the m on the interference error. Taking the experimental of milling, an M20 × 1.5 thread using a φ8 × 1.5 cutter as one of the examples that indicate the maximum interference error of the planning method (m = 0.4) can be reduced by 30.93%, compared with the original trajectory, and can dramatically improve the precision of internal cylindrical thread helical milling.

UAV swarm autonomous control based on Internet of Things and artificial intelligence algorithms

At present, the UAV swarm positioning solution has the problems of poor positioning accuracy and instability. Therefore, it is necessary to design a sliding mode formation controller to realize formation. This study analyzes the self-service control strategy of the UAV swarm and establishes the behavior-based formation control strategy as the main research point of this article. This paper combines the Internet of Things and artificial intelligence algorithms to build an autonomous control model for the UAV swarm and designs the UAV formation control law from the disturbed and undisturbed conditions respectively. With reference to the basic architecture of the Internet of Things, this study imitates ZigBee’s self-organizing network to propose an adaptive networking scheme based on the Internet of Things by using the AP+STA working mode of the Internet of Things module in the node device. The results of the experiment show that the positioning accuracy of the UAV is high, which can meet the needs of cluster flight. Based on the Z-axis coordinates of the UAV, the accuracy of the laser distance measurement and the barometer value is significantly improved, the root mean square error is reduced, and the positioning result is significantly better than the data of direct traditional positioning.

A Novel Stereo Vision Measurement System Using Both Line Scan Camera and Frame Camera

In the product surface defect detection system, the detection accuracy can be greatly improved if the surface grayscale image and depth image can be adopted simultaneously. Existing 3-D cameras have the problem in precise registration of 2-D images and 3-D data, which results in inflexibility and inevitable error in practical vision tasks. Hence, we propose a novel stereo vision measurement system which is able to simultaneously acquire registered scan grayscale images and depth images without special data registration algorithm as well as the calibration method. The proposed measurement system mainly consists of a line laser system, a line scan camera, and a frame camera. The line scan camera captures clear images of objects illuminated by the line laser. In addition, the line scan camera and the frame camera form a stereo vision sensor. In this case, the line laser stripe provides location feature of the matching point for frame camera. The epipolar constraint implements the matching process between the line scan camera and the frame camera. Finally, the stereo vision measurement model is utilized to realize the 3-D coordinate reconstruction, and the z-axis coordinate is used to generate depth image. The proposed system can simultaneously obtain the image and depth information corresponding to each pixel by means of a push sweep. In the experiment, the measurement system can achieve the accuracy of 0.13 mm within a measurement range of $500\,\,\text {mm} \times 300\,\,\text {mm}\times \,\,200$ mm.

An isogeometric multimesh design approach for size and shape optimization of multidirectional functionally graded plates

This article firstly presents a novel numerical methodology to concurrently optimize material distribution (size) and thickness variation (shape) of multidirectional functionally graded (MFG) plates under free vibration within the isogeometric analysis (IGA) framework. An isogeometric multimesh design (IMD) approach is proposed to generate two distinct non-uniform rational B-spline (NURBS) surfaces via the k-refinement strategy. A finer analysis one relied upon a combination of the IGA and a generalized shear deformation theory (GSDT) is utilized for the unknown solution approximation in finite element analyses (FEAs). Whilst the other coarser design one is employed for the exact geometry representation as well as the optimal material and thickness depiction. Size and shape design variables are in turn the ceramic volume fraction and z-axis coordinate of the top side of the MFG plate coincidentally assigned to each of control points on this surface. Flexibly utilizing such two surfaces helps diminish a large number of design variables and considerably save the computational cost in optimization problems, yet still appropriately manifesting optimal material and thickness profiles. Additionally, this definition accurately simulates mechanical behavior of MFG plates in analysis ones as well. A recently developed derivative-free adaptive hybrid evolutionary firefly algorithm (AHEFA) is used to solve constrained frequency maximization problems. Several numerical examples are executed to verify the effectiveness and robustness of the present paradigm.

Enhanced 3D localisation accuracy of body‐mounted miniature antennas using ultra‐wideband technology in line‐of‐sight scenarios

This study presents experimental investigations on high-precision localisation methods of body-worn miniature antennas using ultra-wideband (UWB) technology in line-of-sight conditions. Time of arrival data fusion and peak detection techniques are implemented to estimate the three-dimensional (3D) location of the transmitting tags in terms of x, y, z Cartesian coordinates. Several pseudo-dynamic experiments have been performed by moving the tag antenna in various directions and the precision with which these slight movements could be resolved has been presented. Some more complex localisation experiments have also been undertaken, which involved the tracking of two transmitter tags simultaneously. Excellent 3D localisation accuracy in the range of 1–4 cm has been achieved in various experiment settings. A novel approach for achieving subcentimetre 3D localisation accuracy from UWB technology has been proposed and demonstrated successfully. In this approach, the phase centre information of the antennas in a UWB localisation system is utilised in position estimation to drastically improve the accuracy of the localisation measurements to millimetre levels. By using this technique, the average localisation error has been reduced by 86, 31, and 72% for the x-, y-, and z-axis coordinates, respectively.

Precision of manual landmark identification between as-received and oriented volume-rendered cone-beam computed tomography images.

The objective of this study was to evaluate the effect of the orientation of cone-beam computed tomography (CBCT) images on the precision and reliability of 3-dimensional cephalometric landmark identification. Ten CBCT scans were used for manual landmark identification. Volume-rendered images were oriented by aligning the Frankfort horizontal and transorbital planes horizontally, and the midsagittal plane vertically. A total of 20 CBCT images (10 as-received and 10 oriented) were anonymized, and 3 random sets were generated for manual landmark plotting by 3 expert orthodontists. Twenty-five landmarks were identified for plotting on each anonymized image independently. Hence, a total of 60 images were marked by the orthodontists. After landmark plotting, the randomized samples were decoded and regrouped into as-received and oriented data sets for analysis and comparison. Means and standard deviations of the x-, y-, and z-axis coordinates were calculated for each landmark to measure the central tendency. Intraclass correlation coefficients were calculated to analyze the interobserver reliability of landmark plotting in the 3 axes in both situations. Paired t tests were applied on the mean Euclidean distance computed separately for each landmark to evaluate the effect of 3-dimensional image orientation. Interobserver reliability (intraclass correlation coefficient,>0.9) was excellent for all 25 landmarks for the x-, y-, and z-axes on both before and after orientation of the images. Paired t test results showed insignificant differences for the orientation of volume-rendered images for all landmarks except 3: R1 left (P=0.0138), sella (P=0.0490), and frontozygomatic left (P=0.0493). Also midline structures such as Bolton and nasion were plotted more consistently or precisely than bilateral structures. Orientation of the CBCT image does not enhance the precision of landmark plotting if each landmark is defined properly on multiplanar reconstruction slices and rendered images, and the clinician has sufficient training. The consistency of landmark identification is influenced by their anatomic locations on the midline, bilateral, and curved structures.

Influence of electrode position on cardioversion energy requirements during transvenous electrical cardioversion in horses

To evaluate influence of electrode position on cardioversion energy (CE; energy delivered in the shock at which cardioversion was achieved) during transvenous electrical cardioversion (TVEC) in horses with atrial fibrillation. 37 horses with atrial fibrillation (41 cardioversion events). Records were reviewed to identify horses that underwent TVEC for treatment of atrial fibrillation. Signalment and CE were recorded. Electrode positions in the right atrium and pulmonary artery were identified on intraoperative radiographs. An orthogonal coordinate space was created, and electrode y- and z-axis coordinates and shadow lengths were determined. Trigonometric modeling was used to estimate x-axis electrode positions that resulted in observed shadows. Postmortem casts of catheterized horses were used to assess electrode paths and anatomic relationships. Model assumptions were tested by use of these and a theoretical data set. Relationships between signalment, electrode position, and CE were assessed via multivariate analysis. Sex and y-axis differences between electrode positions were significant predictors of CE. Population stratification based on examination of residuals improved model strength; populations differed in z-axis variables and in CE. Decreasing distance between electrodes and pulmonary artery electrode positions ventral to the right atrium were associated with increased CE. Agreement between estimated and actual x-axis coordinates was poor. Optimal electrode positioning can reduce the energy requirement for successful TVEC and may eventually support application of TVEC under short-term IV anesthesia and potentially increase chances of treatment response. Further investigation into these relationships is warranted.

COMPARISON OF INTERFRACTIONAL VARIATION IN CANINE HEAD POSITION USING PALPATION AND A HEAD-REPOSITIONING DEVICE

Radiation treatment planning is performed on images that do not take variation in patient position into account. To compensate for expected variations in position of the patient, a three-dimensional expansion of the clinical target volume, or set-up margin, is added. Variations in patient position can be decreased through use of an immobilization device, allowing selection of a smaller set-up margin. The objective of this prospective study was comparison of interfractional variation in patient position between set-ups of the canine head region using palpation of bony landmarks and set-ups using a head-repositioning device. Fiducial markers were attached to the skull bones of three research dogs, and the dogs were positioned as for a typical radiation treatment of the head region using both set-up methods. A kilovoltage on-board imager was used to acquire orthogonal images and the difference between the x-, y-, and z-axis coordinates of each fiducial marker relative to the initial reference isocenter was measured. The difference in patient position for each axis coordinate was significantly lower for set-ups using the head-repositioning device than for set-ups using bony landmarks (P < 0.05). Ninety-five percent of the absolute values of the displacement vector differences were < 4.62 mm for set-up using bony landmarks, and < 1.93 mm for set-up using the head-repositioning device. A minimum set-up margin of 5-6 mm is recommended when patient set-up is based on bony landmarks and of 2-3 mm when the head-repositioning device is used.

A new method to quantify wear using implant supported restorations

Objectives: To design a novel technique to assess the wear of prosthodontic veneering materials. Further to determine whether accurate transfer between the oral cavity and the measuring device is achievable and assess the reproducibility of the coordinates generated by the measuring system. Methods: The system is based on the repositioning capacity of an octagonal connector of the ITI ® implant system. The same type of connector was screwed onto the clinical implants that supported the experimental restorations and secured to the x– y table of the measuring device. The measuring setup also comprised a z-axis LVDT displacement gauge that allowed the entire surface of the restorations to be profiled and digitized. The system was under the control of a PC equipped with custom-made software that set the position of the stepping motors, lifted and lowered the z-axis probe, and registered and wrote the x-, y- and z-axis coordinates. Final numerical adjustments and analyses were performed using a commercial array-oriented software package. Validation procedures were performed using a specially designed calibration surface. Results: On repeated profile tracings, the measurement error was less than 2 μm. When the calibration surface was removed between measurements as during clinical trials, the measurement error increased to ca. 5 μm. Significance: The measurement error of the testing procedure including transfer to and from the mouth is ±5 μm.

Stereo Photogrammetric Errors in Determining the Surface Area of a Small Pig Model with Non-Metric Cameras.

A small pig model was made with plaster and plastic from the mold of a female pig of 27 days old. Surface area of the pig model was estimated with 2 non-metric cameras by stereo photogrammetry, and the error of surface area was analyzed. Error consists of optical error in determining the space coordinates of the pig model and shape error in tracing the complex shape of the object. Optical error was estimated with 28 control marks set around the pig model to calculate the space coordinates of about 300 object marks on it from stereo pairs of photographs. The objects marks were used for drawing cross sectional shape and contour lines of the pig model and estimating the surface area. Shape error was evaluated in comparison with the measured surface area by counting the numbers of a 1mm square section of the graph paper covering the pig model.The errors in the X- and Y-axes coordinates of the control marks were within 1mm. The errors in the Z-axis coordinates were in less than 3mm, distributing nearly equally in positive and negative. These errors were no more than theoretical limits. The error would give rise to about 5% of optical error, when estimating the surface area of a part in the body, formed with neighboring cross sections and assumed a truncated cone, 70mm and 66mm in radiuses and 27mm in slant length. Optical error could be neglected when the significant figures of surface area was limited to minimum.The difference between the measured and estimated total surface area of the pig model was 34cm2, which was only 1.2% on a relative basis. This means that the shape error was very small and the stereo photographs using the non-metric cameras was accurate enough.

A truly three-dimensional vectorcardiographic display

The future clinical use of vectorcardiography is dependent upon a standardization of measurement procedures and an effective display of the vector loop. Conventional two-dimensional displays of the three-dimensional loop may not adequately demonstrate certain cardiac abnormalities. This paper describes a method for visualizing the complete vector loop on a cathode ray screen or plotter. Transformation of the three coordinates for each point of the display is effected by an algorithm which allows for manual rotation of the loop about the orthogonal axes and provides depth perception by intensity modulation of the z-axis coordinates.