Irregular Density Research Articles

Noise-Resistant Deep Learning for Object Classification in Three-Dimensional Point Clouds Using a Point Pair Descriptor

Object retrieval and classification in point cloud data is challenged by noise, irregular sampling density and occlusion. To address this issue, we propose a point pair descriptor that is robust to noise and occlusion and achieves high retrieval accuracy. We further show how the proposed descriptor can be used in a 4D convolutional neural network for the task of object classification. We propose a novel 4D convolutional layer that is able to learn class-specific clusters in the descriptor histograms. Finally, we provide experimental validation on 3 benchmark datasets, which confirms the superiority of the proposed approach.

Investigating the safety impact of roadway network features of suburban arterials in Shanghai

With rapid changes in land use development along suburban arterials in Shanghai, there is a corresponding increase in traffic demand on these arterials. To accommodate the local traffic needs of high accessibility and efficiency, an increased number of signalized intersections and accesses have been installed. However, the absence of a defined hierarchical road network, together with irregular signal spacing and access density, tends to deteriorate arterial safety. Previous studies on arterial safety were generally based on a single type of road entity, either intersection or roadway segment, and they analyzed the safety contributing factors (e.g. signal density and access density) on only that type of road entity, while these suburban arterial characteristics could significantly influence the safety performance of both intersections and roadway segments. Macro-level safety modeling was usually applied to investigate the relationships between zonal crash frequencies and demographics, road network features, and traffic characteristics, but the previous researchers did not consider the specific arterial characteristics of signal density and access density. In this study, a new modeling strategy was proposed to analyze the safety impacts of zonal roadway network features (i.e., road network patterns and road network density) along with the suburban arterial characteristics of signal density and access density. Bayesian Conditional Autoregressive Poisson Log-normal models were developed for suburban arterials in 173 traffic analysis zones in the suburban area of Shanghai. Results identified that the grid pattern road network with collector roads parallel to arterials was associated with fewer crashes than networks without parallel collectors. On the other hand, lower road network density, higher signal density and higher access density tended to increase the crash occurrence on suburban arterials.

Analysis of a Code Construction Method for Non-Binary Quasi-Cyclic Irregular Low Density Parity Check Decoder

Non-binary LDPC codes is a class of linear block code outperform in the short and moderate block length, closer to Shannon's limit. The numerical strength of the decoder is proportional to the sparsity of the parity check matrix. A Hierarchically Diagonal Parity Check Matrix (HDPCM) with better sparseness is constructed to optimize the computation complexity and decoding performance. The decoder based on the proposed matrix using FFT-SP decoding algorithm is analyzed, with different modulation schemes and channel environment. The positive impact of the constructed matrix is elaborated, concludes with the suitability of the HDPCM structure in AWGN channel and BPSK modulation environment.

Analyzing the Profile Effects of the Various Magnet Shapes in Axial Flux PM Motors by Means of 3D-FEA

Axial flux machines have positive sides on the power and torque density profile. However, the price of this profile is paid by the torque ripples and irregular magnetic flux density production. To gather higher efficiency, torque ripples should close to the zero and the stator side iron should be unsaturated. Torque ripples mainly occur due to the interaction between the rotor poles and the stator teeth. In this study, different rotor poles are investigated in contrast to stator magnetic flux density and the torque ripple effects. Since the components of the axial flux machines vary by the radius, analysis of the magnetic resources is more complicated. Thus, 3D-FEA (finite element analysis) is used to simulate the effects. The infrastructure of the characteristics which are obtained from the 3D-FEA analysis is built by the magnetic equivalent circuit (MAGEC) analysis to understand the relationships of the parameters. The principal goal of this research is a smoother distribution of the magnetic flux density and lower torque ripples. As the result, the implementations on the rotor poles have interesting influences on the torque ripple and flux density profiles. The MAGEC and 3D-FEA results validate each other. The torque ripple is reduced and the magnetic flux density is softened on AFPM irons. In conclusion, the proposed rotors have good impacts on the motor performance.

Value of Fluorine-18-fluorodeoxyglucose PET/CT examination to predict microvascular invasion of hepatocellular carcinoma

Objective To investigate the clinical value of Fluorine-18-fluorodeoxyglucose (18F-FDG) positron-emission temography/computed tomography (PET/CT) examination to predict microvascular invasion(MVI) of hepatocellular carcinoma (HCC). Methods The retrospective cohort study was conducted. The clinicopathological data of 51 HCC patients who were admitted to Changhai Hospital of the Second Military Medical University (32 patients) and Universal Medical Imaging Diagnostic Center (19 patients) from January 2013 to October 2017 were collected. Of 51 patients receiving postoperative pathological examination, 21 diagnosed with positive MVI and 30 diagnosed with negative MVI were respectively allocated into the positive and negative MVI groups. All the patients received preoperative 18F-FDG PET/CT examination and underwent surgery after related examinations. Two imaging doctors independently read films and made a semi-quantitative analysis. Observation indicators: (1) results of 18F-FDG PET/CT examination; (2) multivariate analysis and diagnostic value affecting MVI of HCC; (3) treatment and follow-up. Follow-up using outpatient examination and telephone interview was performed to detect the postoperative patients′ survival up to November 2017. Measurement data with normal distribution were represented as ±s, and comparisons between groups were evaluated with the independent-sample t test. Measurement data with skewed distribution were described as M(Qn), and comparisons between groups were analyzed using the independent-sample rank sum test. Comparisons of count data were analyzed using the chi-square test. Logistic regression analysis was performed in variables with statistical significance. The inclusion criteria was 0.05 and exclusion criteria was 0.10 according to Backward (LR) method for screening variables. Receiver Operating Characeristic (ROC) curve analysis was used to evaluate the diagnostic value using MVI as a diagnostic standard. Results (1) Results of 18F-FDG PET/CT examination: of 51 HCC patients, tumors located in the right lobe, left lobe and caudate lobe of the liver were respectively detected in 37, 12 and 2 patients. CT examinations of 51 HCC patients: HCCs showed the hypodense shadow or slightly hypodense shadow in liver and were round-like, and some of the larger lesions were irregularly conglomerate, with a relatively clear tumor-liver boundary; tumor necrosis area showed patchy and irregular lower density, with small lesions around the port of tumors. Of 51 patients, 34 were positive on PET and 17 were negative on PET, and some necrotic areas showed no uptake and located in the center of tumors. There was no abnormal 18F-FDG uptake in other parts of the whole body. The maximum diameter of tumor was (6±3)cm. The maximum standardized uptake value (SUVmax), and ratio of SUVmax of tumor to SUVmax of liver (SUVmax T/L) in all the lesions were 6.38±4.91 and 2.42±1.93, respectively. The mean standardized uptake value (SUVmean), metabolism of volume (MTV), total lesion of glycolysis (TLG) of 40 patients were 4.30±2.46, 43.82 cm3 (8.97 cm3, 219.13 cm3) and 165.73 (28.26, 794.50), respectively, and software could not automatically delineate lesions in other 11 patients due to low metabolism. Delayed imaging was found in 21 patients, and the delayed SUVmax and retention index (RI) were 7.22±6.26, 19.66% (-7.10%, 50.84%), respectively. The cases with positive and negative on PET were 18, 3 in the positive MVI group and 16, 14 in the negative MVI group, respectively, with a statistically significant difference between groups (χ2=5.829, P<0.05). The maximum diameter of tumor in the positive MVI group and negative MVI group was respectively (7.7±2.9)cm and (5.2±3.1)cm, with a statistically significant difference between groups (t=-2.930, P<0.05). (2) Multivariate analysis and diagnostic value affecting MVI of HCC: the results of multivariate analysis showed that maximum diameter of tumor was an independent factor affecting MVI of HCC (OR=1.276, 95% confidence interval: 1.028-1.585, P<0.05). The area under the ROC curve of the maximum diameter of tumor was 0.723 using MVI as a diagnostic standard. The sensitivity, specificity and Youden index were respectively 90.5%, 50.0% and 0.405, with 4.55 cm as the critical value. (3) Treatment and follow-up: all 51 patients underwent tumor resection. Twenty-two patients were followed up for 25 months (range, 12-46 months). The 1- and 2-year overall survival rates were 81.8%(18/22) and 63.6%(14/22), respectively. The 1- and 2-year tumor-free survival rates were 59.1%(13/22) and 45.5%(10/22), respectively. Conclusion The positive rate on PET of 18F-FDG PET/CT examination in HCC patients with positive MVI is higher than that in HCC patients with negative MVI, and the maximum diameter of tumor is an independent factor predicting MVI of HCC, with a certainly reference value. Key words: Liver neoplasms; Carcinoma, hepatocellular; Microvascular invasion; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose

Histological Features of the Distal Third Metacarpal Bone in Thoroughbred Racehorses, With and Without Lateral Condylar Fractures

A detailed histopathological study of the distal third metacarpal bone of Thoroughbred racehorses was undertaken to characterize lesions observed previously on magnetic resonance imaging (MRI). The bones were selected and grouped on the basis of MRI features. Representative sections in different planes were processed for histopathology. All lesions observed in the articular cartilage (AC) and subchondral bone (SCB) were recorded and graded with a scoring system, based partially on the Osteoarthritis Research Society International grading system. The scoring system included the severity of the lesion. Descriptive statistics and linear mixed effects models were performed. A positive correlation was observed between the severity of histopathological changes in the superficial and deeper osteochondral tissues, and between the number of race starts and AC score. Age was not correlated with AC or SCB score. A moderate variation in AC and SCB scores was observed between the groups; however, there were differences within individual bones. Bones with focal palmar necrosis (FPN) showed significant differences in the histological scoring of the AC compared with bones without FPN. Bones with incomplete fractures or larger areas of bone remodelling showed significant differences in SCB pathology when compared with bones with FPN. Haematoidin was detected in areas with excessive SCB and cancellous bone sclerosis and/or irregular bone density. This finding is suggestive of poor blood perfusion in these areas.

Does Poisson’s downward continuation give physically meaningful results?

The downward continuation (DWC) of the gravity anomalies from the Earth’s surface to the geoid is still probably the most problematic step in the precise geoid determination. It is this step that motivates the quasi-geoid users to opt for Molodenskij’s rather than Stokes’s theory. The reason for this is that the DWC is perceived as suffering from two major flaws: first, a physically meaningful DWC technique requires the knowledge of the irregular topographical density; second, the Poisson DWC, which is the only physically meaningful technique we know, presents itself mathematically in the form of Fredholm integral equation of the 1st kind. As Fredholm integral equations are often numerically ill-conditioned, this makes some people believe that the DWC problem is physically ill-posed. According to a revered French mathematician Hadamard, the DWC problem is physically well-posed and as such gives always a finite and unique solution. The necessity of knowing the topographical density is, of course, a real problem but one that is being solved with an ever increasing accuracy; so sooner or later it will allow us to determine the geoid with the centimetre accuracy.

Low and Midlatitude Ionospheric Plasma Density Irregularities and Their Effects on Geomagnetic Field

Earth’s magnetic field results from various internal and external sources. The electric currents in the ionosphere are major external sources of the magnetic field in the daytime. High-resolution magnetometers onboard low-Earth-orbit satellites such as CHAMP and Swarm can detect small-scale currents in the nighttime ionosphere, where plasma density gradients often become unstable and form irregular density structures. The magnetic field variations caused by the ionospheric irregularities are comparable to that of the lithospheric contribution. Two phenomena in the nighttime ionosphere that contribute to the magnetic field variation are presented: equatorial plasma bubble (EPB) and medium-scale traveling ionospheric disturbance (MSTID). EPB is formed by the generalized Rayleigh–Taylor instability over the dip equator and grows nonlinearly to as high as 2000 km apex altitude. It is characterized by deep plasma density depletions along magnetic flux tubes, where the diamagnetic effect produced by a pressure-gradient-driven current enhances the main field intensity. MSTID is a few hundred kilometer-scale disturbance in the midlatitude ionosphere generated by the coupled electrodynamics between the ionospheric $E$ and $F$ regions. The field-aligned currents associated with EPBs and MSTIDs also have significant signatures in the magnetic field perpendicular to the main field direction. The empirical discovery of the variations in the magnetic field due to plasma irregularities has motivated the inclusion of electrodynamics in the physical modeling of these irregularities. Through an effective comparison between the model results and observations, the physical process involved has been largely understood. The prediction of magnetic signatures due to plasma irregularities has been advanced by modeling studies, and will be helpful in interpreting magnetic field observations from satellites.

Development of Concentration-Dependent Diffusion Instability in Reactive Miscible Fluids Under Influence of Constant or Variable Inertia

In this work, we focus on the processes which accompany a frontal neutralization reaction occurring between two miscible fluids filling a vertical Hele-Shaw cell. We have found that chemically-induced changes of reagent concentrations coupled with concentration- dependent diffusion (CDD) can produce spatially localized low density areas which are sensitive to the external inertial field. In the case of static gravity we have demonstrated both experimentally and theoretically that it can give rise to the development of perfectly periodic convective structure. This scenario is strikingly different from the irregular density fingering, which is typically observed in the miscible systems. When the system is under the influence of the periodic low-frequency vibrations perpendicular to the reaction front, we found numerically the excitation of a mixed-mode instability combining the double-diffusion instabilities and the Rayleigh-Taylor mechanism of the convection within the low density areas.

Computed Tomographic Features of Blunt Abdominal Trauma in a Dog

A 10 months old, male Poongsan dog was referred with a history of right forelimb lameness due to hit by a car a few hours before presentation. On the physical examination, the dog showed pale mucous membrane, respiration distress, and skin abrasions. The main laboratory finding was leukocytosis, while hematocrit was normal. Abdominal radiography revealed the loss of abdominal serosal detail, which was diagnosed as peritoneal hemorrhage on ultrasonography (US) and aspiration. On computed tomography (CT), hepatic and splenic injuries were seen characterized by the discontinuity of the capsule with irregular margin and lower density lesions than parenchyma. No contrast enhancing area were shown in the laceration lesion. The accessory spleen was incidentally found by US and CT. In this case, acute intra-abdominal hemorrhage from splenic and hepatic laceration was diagnosed using CT.

Detailed structure of the outer disk around HD 169142 with polarized light in H-band

Abstract Coronagraphic imagery of the circumstellar disk around HD 169142 in H-band polarized intensity (PI) with Subaru/HiCIAO is presented. The emission scattered by dust particles at the disk surface in 0${^{\prime\prime}_{.}}$2 ≤ r ≤ 1${^{\prime\prime}_{.}}$2, or 29 ≤ r ≤ 174 au, is successfully detected. The azimuthally averaged radial profile of the PI shows a double power-law distribution, in which the PIs in r = 29–52 au and r = 81.2–145 au respectively show r−3 dependence. These two power-law regions are connected smoothly with a transition zone (TZ), exhibiting an apparent gap in r = 40–70 au. The PI in the inner power-law region shows a deep minimum whose location seems to coincide with the point source at λ = 7 mm. This can be regarded as another sign of a protoplanet in the TZ. The observed radial profile of the PI is reproduced by a minimally flaring disk with an irregular surface density distribution, an irregular temperature distribution, or with a combination of both. The depletion factor of surface density in the inner power-law region (r &amp;lt; 50 au) is derived to be ≥ 0.16 from a simple model calculation. The obtained PI image also shows small-scale asymmetries in the outer power-law region. Possible origins for these asymmetries include corrugation of the scattering surface in the outer region, and a shadowing effect by a puffed-up structure in the inner power-law region.

Analysis of Ionospheric Irregularity Observed near Suvarnabhumi International Airport in Thailand

The ionospheric irregularity is a major effect to the radio signals since the irregular electrons density can degrade the performance of the Ground-Based Augmentation System (GBAS). This work proposes the methods to calculate three parameters in the ionospheric threat model: front speed, front slope, and front width. The data of PRN9 satellite at three reference stations near Suvarnabhumi international airport, Thailand: KMITL, STFD and DPT stations, on 25th September 2012 are analyzed. The results show that the front speed is about 142.86 meters/second, the maximum front slope is-30 mm/km and the front width is higher than 25 kilometers.

Street environment change detection from mobile laser scanning point clouds

Mobile laser scanning (MLS) has become a popular technique for road inventory, building modelling, infrastructure management, mobility assessment, etc. Meanwhile, due to the high mobility of MLS systems, it is easy to revisit interested areas. However, change detection using MLS data of street environment has seldom been studied. In this paper, an approach that combines occupancy grids and a distance-based method for change detection from MLS point clouds is proposed. Unlike conventional occupancy grids, our occupancy-based method models space based on scanning rays and local point distributions in 3D without voxelization. A local cylindrical reference frame is presented for the interpolation of occupancy between rays according to the scanning geometry. The Dempster–Shafer theory (DST) is utilized for both intra-data evidence fusion and inter-data consistency assessment. Occupancy of reference point cloud is fused at the location of target points and then the consistency is evaluated directly on the points. A point-to-triangle (PTT) distance-based method is combined to improve the occupancy-based method. Because it is robust to penetrable objects, e.g. vegetation, which cause self-conflicts when modelling occupancy. The combined method tackles irregular point density and occlusion problems, also eliminates false detections on penetrable objects.

Channel Hardening-Exploiting Message Passing (CHEMP) Receiver in Large-Scale MIMO Systems

In this paper, we propose a multiple-input multiple-output (MIMO) receiver algorithm that exploits channel hardening that occurs in large MIMO channels. Channel hardening refers to the phenomenon where the off-diagonal terms of the H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sup> H matrix become increasingly weaker compared to the diagonal terms as the size of the channel gain matrix H increases. Specifically, we propose a message passing detection (MPD) algorithm which works with the real-valued matched filtered received vector (whose signal term becomes H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> Hx, where x is the transmitted vector), and uses a Gaussian approximation on the off-diagonal terms of the H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> H matrix. We also propose a simple estimation scheme which directly obtains an estimate of H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sup> H (instead of an estimate of H), which is used as an effective channel estimate in the MPD algorithm. We refer to this receiver as the channel hardening-exploiting message passing (CHEMP) receiver. The proposed CHEMP receiver achieves very good performance in large-scale MIMO systems (e.g., in systems with 16 to 128 uplink users and 128 base station antennas). For the considered large MIMO settings, the complexity of the proposed MPD algorithm is almost the same as or less than that of the minimum mean square error (MMSE) detection. This is because the MPD algorithm does not need a matrix inversion. It also achieves a significantly better performance compared to MMSE and other message passing detection algorithms using MMSE estimate of H. Further, we design optimized irregular low density parity check (LDPC) codes specific to the considered large MIMO channel and the CHEMP receiver through EXIT chart matching. The LDPC codes thus obtained achieve improved coded bit error rate performance compared to off-the-shelf irregular LDPC codes.

Irregular MDS Array Codes

In this paper, we extend the concept of maximum-distance separable (MDS) array codes to a larger class of codes, where the array columns contain a variable number of data and parity symbols and the codewords cannot be arranged, in general, in a regular array structure with equal column length. These new codes, named irregular MDS array codes, find applications in problems of distributed data storage with multiple sources of information generating data at unequal rates. We solve the problem of finding optimal parity symbol allocations that achieve minimum redundancy for a given level of protection against block erasures. We provide a classification of irregular MDS array codes according to the parameters of their parity symbol allocation and we show how regular MDS array codes are a special case of this wider class. We derive necessary and sufficient conditions for such irregular array codes to be MDS and extend the concept of the lowest density generator matrix. Finally, we show how a simple constructive method allows to design irregular lowest density MDS array codes with alphabet size independent of the size of the array columns.

A general data-driven algorithm for façade structure modeling using ground based laser data

Abstract. Façade reconstruction from laser point cloud has been an interesting subject in Photogrammetric community for the last two decades. However, due to the variety of architecture types and the nature of laser data, proposing a fully automatic modelling algorithm is still a challenge. Irregular architecture, density variation, occlusion and noise level are the main hindering factors of proposing a general model for façade reconstruction. This paper describes the sequences of an automatic data- driven method which starts from raw laser data and ends with object extraction. Statistical analysis was frequently utilized in segmentation, splitting line detection and object characterization. A rule-based modification method was employed to model the complexity of façade layout. Developed interface enables non-expert user to interact with modelling process by setting few parameters. The method was tested over a couple of datasets.

Bladder extragastrointestinal stromal tumor in an adolescent patient: A case-based review.

Extragastrointestinal stromal tumors (EGISTs) are mesenchymal tumors occurring outside the gastrointestinal tract, with histological, immunohistochemical and molecular genetic characteristics similar to those of gastrointestinal stromal tumors (GISTs). The immunohistochemical examination usually demonstrates a positive expression for CD117. GISTs are rare neoplasms and EGISTs are even less common. This is the report of a case of EGIST in the urinary bladder of a 15-year-old adolescent female patient who presented with painless gross hematuria. Pelvic computed tomography revealed an irregular soft tissue density mass, sized 5.7×4.8 cm, in the bladder. Partial cystectomy was performed in April, 2011. There was no recurrence during follow-up over the next 35 months, as determined by transabdoninal ultrasonography and cystoscopic examination. The patient in this study did not receive any molecular-targeted drugs. To the best of our knowledge, this is the first reported case of an EGIST of the urinary bladder in an adolescent patient.

Diabetes alters mechanical properties and collagen fiber re-alignment in multiple mouse tendons.

Tendons function to transfer load from muscle to bone through their complex composition and hierarchical structure, consisting mainly of type I collagen. Recent evidence suggests that type II diabetes may cause alterations in collagen structure, such as irregular fibril morphology and density, which could play a role in the mechanical function of tendons. Using the db/db mouse model of type II diabetes, the diabetic skin was found to have impaired biomechanical properties when compared to the non-diabetic group. The purpose of this study was to assess the effect of diabetes on biomechanics, collagen fiber re-alignment, and biochemistry in three functionally different tendons (Achilles, supraspinatus, patellar) using the db/db mouse model. Results showed that cross-sectional area and stiffness, but not modulus, were significantly reduced in all three tendons. However, the tendon response to load (transition strain, collagen fiber re-alignment) occurred earlier in the mechanical test, contrary to expectations. In addition, the patellar tendon had an altered response to diabetes when compared to the other two tendons, with no changes in fiber re-alignment and decreased collagen content at the midsubstance of the tendon. Overall, type II diabetes alters tendon mechanical properties and the dynamic response to load.

High performance error correction for quantum key distribution using polar codes

We study the use of polar codes for both discrete and continuous variables Quantum Key Distribution (QKD). Although very large blocks must be used to obtain the efficiency required by quantum key distribution, and especially continuous variables quantum key distribution, their implementation on generic x86 Central Processing Units (CPUs) is practical. Thanks to recursive decoding, they exhibit excellent decoding speed, much higher than large, irregular Low Density Parity Check (LDPC) codes implemented on similar hardware, and competitive with implementations of the same codes on high-end Graphic Processing Units (GPUs).

Primary abdominal wall actinomycosis

Actinomycosis is a progressive, chronic, granulomatous and suppurative disease caused by different types of actinomyces. Instead of chronic suppurative disease, sinus formation can also be seen. Cervicofascial, abdominal and thoracal involvement can occur. Abdominal wall actinomycosis is an infrequent clinical form. Isolated anterior wall actinomycosis is a very rare form of the disease. This is an interventional case report. A 62-year-old female patient with abdominal mass was referred to hospital. She had diabetes mellitus. On the examination she had abdominal tenderness. The computerized tomography revealed an irregular density sized 6.5 × 5 × 3.5 cm in the umbilical area. Surgical debridement and incisional biopsy performed. The diagnosis is confirmed by histopathological examination. The patient received parenteral crystalline penicillin treatment and recovered. Physicians should consider abdominal wall actinomycosis in the cases of abdominal masses especially in immunosuppressive patients.