Добірка наукової літератури з теми "Blocking moment"

In this paper, we provide a new technique for analyzing the nonstationary Erlang loss queueing model with abandonment. Our method uniquely combines the use of the functional Kolmogorov forward equations with the well-known Gram-Charlier series expansion from the statistics literature. Using the Gram-Charlier series expansion, we show that we can estimate salient performance measures of the loss queue such as the mean, variance, skewness, kurtosis, and blocking probability. Lastly, we provide numerical examples to illustrate the effectiveness of our approximations.

In this paper we research the process of magnetization of iron-containing coatings obtained on aluminum and titanium plasma electrolytic oxidation. It is shown that the formation of a remnant magnetic moment mainly determined by the magnetostatic interaction particles (phases). This interaction leads to a decrease of the blocking volume of particles (phases). Thus, a large number of superparamagnetic particles (phases) obtain stable magnetic moments and are involved in creating of the remnant magnetization of the sample.

This study introduces a method for measuring the blocking force of a shape memory polymer composite hinge to quantify the performance of a shape memory polymer composite hinge for space deployable structure applications. A detailed design of how to select heating elements for a self-deployable configuration is also suggested. The shape memory polymer composite hinge consists of two reverse carpenter shape memory polymer composite tapes that were made from carbon-epoxy fabric, shape memory polymer resin, and two heating elements. The heating elements were attached to the shape memory polymer composite tape using the composite manufacturing method, and they were used as the heating source in the deployment test. The blocking force and moment of the hinge were measured using a pulley–mass system setup to examine the mechanical performance of the hinge. During the test, the shape change was recorded with a camera to calculate the moment arms. While the blocking force was 7.21 N in the initial test, it decreased slightly with the working cycle and was 6.27 N in the repeated test. The maximum hinge moment was 0.47 N m in the repeated test. In addition, the results revealed that a pop-up phenomenon occurred at the middle period of deployment. These results confirm that the shape memory polymer composite hinge works well with heating elements and provide a guideline for performance evaluation of the shape memory polymer composite hinge.

Nuclear structure data plays an important role in nuclear physics studies and applications such as nuclear power generation. This article presents evaluations of a mean-field approach to describe two nuclear structure quantities namely the electric and magnetic moments. The Hartree-Fock-plus-pairing approach was employed with pairing correlations treated within the Bardeen-Cooper-Schrieffer (BCS) framework. The Skyrme SIII parametrization and seniority force are chosen to approximate the effective nucleon-nucleon and pairing interactions, respectively. Calculated results show that the self-consistent blocking procedure which takes into account time-reversal symmetry breaking is important to reproduce experimental magnetic moment

In this paper, we propose an enhanced file transfer mechanism for a communication framework (CM) for Internet of Things (IoT) applications. Our previous file transfer method uses a basic non-blocking communication channel and thread for the CM (non-blocking method), but this method has a cost of adding additional bytes to each original file block. Therefore, it is not suitable for the transfer of large-sized files. Other existing file transfer methods use a separate channel to transfer large-sized files. However, the creation of a separate channel increases the total transmission delay as the transfer frequency increases. The proposed method uses a dedicated blocking communication channel in a separate thread (blocking method). The blocking method uses a separate channel and thread which are dedicated to transferring file blocks. As it creates the separate channel in advance before the file transfer task, the proposed method does not have an additional channel creation cost at the moment of the file transfer. Through file transfer experiments, the blocking method showed a shorter file transfer time than the non-blocking method, and the transmission delay was increased as the file size grew. By supporting both non-blocking and blocking methods, an application can flexibly select the desirable method according to its requirement. If the application requires the transfer of small-sized files infrequently, it can use the non-blocking method. If the application needs to transfer small-sized or large-sized files frequently, a good alternative is to use the blocking method.

Nanoclusters and nanocrystals of the room temperature magnetic spinel CuCr2S4 synthesized using a facile solution-based method were examined by magnetic resonance in a wide frequency range 9.6÷80 GHz and at temperatures down to 4.2 K. Decreasing of the resonance field and broadening of the resonance lines are found below ∼ 50 K for both the nanocluster and nanocube samples due to the freezing of magnetic moments of nanocubes and nanocrystalline particles constituting nanoclusters. Additional blocking temperature Tb≅300 K appears in nanoclusters due to the freezing of the magnetic moment of the entire cluster as a whole. Below this temperature, an additional low-field resonance line is found in the resonance spectra of nanoclusters at X-band.

Nanosized particles of AFe2O4(A = Mn, Co, Ni, or Zn) spinel ferrites were synthesized by coprecipitation from nonaqueous solutions using nitrate salts as starting reagents. The particles were characterized by X-ray diffraction, transmission electron microscopy, and magnetic measurements. Quasistatic magnetic measurements show superparamagnetic behavior with blocking temperature below room temperature for cobalt, nickel, and zinc spinel ferrite nanoparticles. Characteristic magnetic parameters of the particles including average magnetic moment of an individual nanoparticle and blocking temperature have been determined. The specific loss power which is released on the exposure of an ensemble of synthesized particles to a magnetic field is calculated and measured experimentally. It is shown that among all nanoferrites under study, the ZnFe2O4nanoparticles demonstrate the highest heating efficiency in AC magnetic fields. The key parameters responsible for the heating efficiency in AC magnetic field have been determined. The directions to enhance the SLP value have been outlined.

Дисертація на здобуття наукового ступеня доктора філософії за спеціальністю 255 "Озброєння та військова техніка" (25 – Воєнні науки, національна безпека, безпека державного кордону). – Національний технічний університет "Харківський політехнічний інститут", Харків, 2020. Актуальність теми. Потреба в міжколісних диференціалах (МКД) виникла відразу ж після появи перших автомобілів із приводом на два колеса однієї осі. Найбільш відчутно ця потреба проявлялася при проходженні автомобілем поворотів і їзді по дорогах з нерівностями. Відсутність МКД у таких трансмісіях приводило до появи циркуляції потужності, невиправдано великого додаткового навантаження на ведучу вісь і колеса, підвищення витрати палива, великого зношування шин. З винаходом класичного конічного симетричного МКД ці проблеми були вирішені. Однак з'явилися інші проблеми, пов'язані з явищем буксування у важких дорожніх умовах. Природно, що на цей виклик найшлася велика кількість технічних рішень, які так чи інакше згладжували проблему, але не вирішували її комплексно. В останні десятиліття з'явилися конструктивні рішення, у яких величина блокування диференціала контролюється електронікою по заданому алгоритму, а також приводи, у яких система контролю тяги управляє безпосередньо крутним моментом, що підводиться до ведучого колеса. Особливо ефективно такі рішення працюють у випадку застосування електричних або гідростатичних мотор-коліс. Однак, не дивлячись на достаток технічних рішень в області диференціального привода ведучих коліс, ефективної конструкції МКД для військових колісних машин (КМ) і повнопривідних автомобілів багатоцільового призначення (ПАБП) отримано поки не було. Існуючі конструкції або як і раніше використовують повне блокування з ручним керуванням, або базуються на диференціалах, що самоблокуються, підвищеного тертя, які не в змозі одночасно забезпечити і високу прохідність, і гарну керованість. Тому, не дивлячись на бурхливий розвиток електронних систем керування та індивідуального електроприводу, для військових КМ і ПАБП розробка ефективного МКД із внутрішньою автоматичністю є актуальною. Метою дисертаційної роботи є збільшення тягової динаміки колісних бронетранспортерів і ПАБП в складних дорожніх умовах при високих показниках економічності і керованості шляхом розробки і застосування МКД із гідростатичним блокуванням на базі шестеренного насосу. Для досягнення поставленої мети необхідно вирішити такі завдання: – методами чисельного моделювання провести дослідження впливу структури і параметрів МКД на динаміку розгону машини в складних дорожніх умовах; – методами чисельного моделювання провести дослідження впливу структури і параметрів МКД на опір криволінійному руху і керованість; – оцінити теоретично і експериментально можливість реалізації гідростатичного блокування без додаткових фрикційних дисків для МКД бронетранспортера БТР-4 і визначити його необхідні технічні параметри; – оцінити експериментально характеристики штатного кулачкового МКД бронетранспортера БТР-4 при повному вивішуванні одного з коліс; – визначити параметри МКД із гідростатичним блокуванням і методами чисельного моделювання провести дослідження обраних параметрів рухливості бронетранспортера БТР-4, укомплектованого запропонованими МКД. Наукова новизна отриманих результатів. Основними науковими результатами, які виносяться на захист, являються: – вперше науково обґрунтована можливість створення МКД з гідростатичним блокуванням без додаткових фрикціонів на основі шестеренного насосу для колісного бронетранспортера; – вперше запропонований енергетичний метод оцінки ефективності МКД, який на відміну від існуючих спирається на втрати не при сталому русі, а при розгоні машини в складних дорожніх умовах до заданої швидкості; – вперше запропонований метод оцінки впливу структури і параметрів МКД на спротив криволінійному руху по дорогах з твердим покриттям, який на відміну від існуючих спирається на оцінку не тільки втрат в МКД при криволінійному русі, а й на втрати при проковзуванні коліс по дорозі і збільшення дійсного радіусу повороту за рахунок уводу коліс і їх проковзування; – вперше експериментально отримана залежність блокувального моменту від швидкості буксування для двохрядного кулачкового МКД бронетранспортера БТР-4. Практичне значення одержаних результатів. Проведені дослідження надали можливість розрахувати параметри шестеренного насосу для гідростатичного блокування МКД, що з незначними доробками монтується в картер головної передачі бронетранспортера БТР-4 і в змозі замінити покупний російський вузол з гіршими експлуатаційними характеристиками. Розроблені методи оцінки ефективності диференціалів при прямолінійному розгоні в складних дорожніх умовах і при криволінійному русі по дорогах з твердим покриттям надають можливість проводити структурно-параметричний синтез не тільки МКД, а й міжосьових диференціалів для військових КМ та ПАБП з механічною трансмісією. Практичне значення результатів дисертаційного дослідження підтверджується актами про впровадження в розрахункову практику запропонованих методів оцінки ефективності МКД в ДП "Харківське конструкторське бюро з машинобудування ім. О.О. Морозова" та ТОВ "Машгідропривод", а також актом про впровадження в навчальний процес методів оцінки ефективності МКД в НТУ "ХПІ" при підготовці студентів за спеціальністю 133 – Галузеве машинобудування, спеціалізації 133.02 – Автоматизоване проектування транспортних засобів високої прохідності. Висновки по роботі: 1) З аналізу літературних джерел був зроблений висновок про відсутність технічного рішення в області МКД, яке б забезпечувало високу прохідність (у тому числі при повному вивішуванні ведучих коліс), не погіршувало керованість, мало внутрішню автоматичність, було досить простим і дешевим у виготовленні і надійним в експлуатації. 2) Для КМ, експлуатація яких припускає можливість вивішування при русі одного або декількох коліс, у МКД для забезпечення прохідності необхідно використовувати або повне блокування, або протибуксовочні системи на базі АБС, або диференціали, що самоблокуються, з моментом, що блокує, залежним від різниці або квадрата різниці частот відносного обертання півосей і корпуса диференціала. Використання повного блокування в існуючих конструкціях вимагає або повної зупинки машини перед блокуванням / розблокуванням диференціалів або використання фрикційних дисків, блокування яких вимагає додаткового відбору потужності для їхнього втримання в замкнутому стані і які при активній експлуатації машини в складних дорожніх умовах інтенсивно зношуються. Для використання протибуксовочних систем на базі АБС на даний момент, на жаль, ми не маємо відпрацьованих достатньо надійних в умовах військового застосування вітчизняних АБС, які могли б лягти в основу створення противобуксовочной системи. Тому доцільним є використання МКД із гідростатичним блокуванням без використання додаткових фрикційних дисків. 3) З наведеного аналізу витікає, що найбільш ефективним вхідними параметрами для більшості підходів по забезпеченню автоматичного розподілу потужності між колесами є кінематична неузгодженість швидкостей обертання ведучих коліс і положення керованих коліс. 4) При аналізі прохідності КМ, які припускають можливість вивішування при русі одного або декількох коліс, необхідно оперувати поняттям блокувального моменту диференціала, а не коефіцієнта блокування. 5) У результаті математичного моделювання і розрахунків на прикладі бронетранспортера БТР-4 були отримані значення максимальної відносної частоти обертання півосі і корпусу МКД, що може виникнути через різницю у швидкостях обертання коліс різних бортів при маневруванні на дорогах із твердим покриттям, а також залежності необхідного для забезпечення прохідності блокувального моменту МКД від частоти відносного обертання півосі і корпусу МКД. Виявлено, що оптимально блокувальний момент повинен зростати від нуля до максимального значення в 3000 Нм відповідно при зростанні відносної частоти обертання півосі і корпусу диференціалу від 80 до 115 хв⁻¹. 6) З розглянутих конструкцій МКД по динаміці розгону в складних дорожніх умовах для середніх значень коефіцієнтів пропорційності перевагу мають МКД, у яких ступінь блокування залежить від навантаження. 7) При обраних коефіцієнтах пропорційності системи для малих кутів повороту керованих коліс (до 8) у перших трьох чвертях діапазону безпечних швидкостей і по опору повороту, і по зростанню радіуса повороту перевагу мають МКД, у яких ступінь блокування залежить від квадрата різниці швидкостей півосей. 8) Для більших кутів повороту керованих коліс у першій половині діапазону безпечних швидкостей також перевагу мають МКД, у яких ступінь блокування залежить від квадрата різниці швидкостей півосей. Але при швидкостях, близьких до перекидання, для будь-яких кутів повороту керованих коліс їх випереджають по показниках МКД, у яких ступінь блокування залежить від навантаження. 9) Диференціали із ПБС на базі АБС найбільше доцільно використовувати при відносно невеликих значеннях дисбалансу коефіцієнтів зчеплення по бортах машини і інтегрувати їх із системами підтримки курсової стійкості, які дозволяють залежно від ситуації легко змінювати значення коефіцієнтів пропорційності (настроювання системи). 10) Для автомобілів підвищеної прохідності, експлуатація яких не припускає режими з повним вивішуванням ведучих коліс можливо ефективне використання МКД, у яких ступінь блокування залежить від навантаження. 11) Для автомобілів високої прохідності і військових КМ, при експлуатації яких можливо повне вивішування ведучих коліс, доцільне використання МКД із фрикційним моментом, що залежить від квадрата різниці швидкостей обертання півосей. Вони можуть мати високі енергетичні показники при розгоні з мінімальним негативним впливом на керованість машини і при цьому опиратися не на електронні системи керування, а на власну внутрішню автоматичність. 12) Проведені випробування показали, що сила тяги ведучого мосту із дворядним кулачковим диференціалом при повному вивішуванні одного з коліс (правого) істотно залежить від частоти обертання колеса, що буксує, і досягає максимальної величини в 1091 Н при частоті обертання колеса, що буксує, 399 хв-1. Ця частота обертання відповідає обертанню вхідного фланця ведучого мосту для руху бронетранспортера зі швидкістю 11 м/с (39,6 км/год) після чого наступає заклинювання диференціала. 13) Отримані значення для сили тяги ведучого мосту із дворядним кулачковим диференціалом при повному вивішуванні одного з коліс (правого) недостатні для впевненого подолання бронетранспортером перешкод типу «яр» або «бархан» з діагональним вивішуванням і перешкод типу «рів» з послідовним вивішуванням мостів. 14) На основі шестеренного насоса із внутрішнім зачепленням можна реалізувати МКД із гідростатичним блокуванням без використання додаткових дисків тертя. Даний диференціал має квадратичну залежність блокувального (гальмівного) моменту від різниці кутових швидкостей півосі і корпусу диференціала. Це дозволяє, з одного боку, одержати практично повне блокування диференціала при буксуванні і, з іншого боку, чинити мінімальний опір повороту при маневруванні на дорогах із твердим покриттям. 15) Для бронетранспортера БТР-4 робочий об'єм шестеренного насоса із внутрішнім зачепленням, що дозволяє при блокуванні реалізувати максимальне зчеплення з дорогою колеса, яке не буксує, становить 415 см3. Такий насос успішно компонується в габаритах штатної головної передачі при заміні існуючого кулачкового диференціала на класичний відкритий диференціал з конічними шестірнями. 16) Оптимальний розрахунковий діаметр дроселюючого отвору становить 2 мм. Однак залежно від точності виготовлення елементів шестеренного насоса і сукупних об'ємних втрат ця величина повинна коректуватися експериментальним шляхом в бік зменшення. 17) Героторні насоси із циклоїдальним зачепленням були зняті з розгляду по причині складності реалізації в них високого тиску через низький коефіцієнт перекриття профілів зубів. Для синтезу МКД із внутрішньою автоматичністю, який би задовольняв вимогам і до тягової прохідності, і до динаміки машини і одночасно не перешкоджав її криволінійному руху, остаточно прийнятий диференціал, у якому величина блокувального моменту залежить від квадрата різниці кутових швидкостей півосей. 18) МКД із моментом блокування, що залежить від навантаження (у тому числі і штатний дворядний кулачковий диференціал) досить успішно конкурують із розглянутими диференціалами з гідростатичним блокуванням по ефективності роботи в складних дорожніх умовах, але без повного вивішування одного з коліс. 19) Для МКД із гідростатичним блокуванням досить мати діаметр дроселюючого отвору більше 3 мм для безперешкодного входу бронетранспортера в поворот і криволінійного руху без істотного збільшення енерговитрат і погіршення керованості в усьому діапазоні швидкостей руху. 20) З метою одержання необхідної прохідності і динаміки руху в складних дорожніх умовах для МКД з гідростатичним блокуванням необхідно мати діаметр дроселюючого отвору не більше 1 мм. 21) Для ліквідації отриманого протиріччя пропонується ставити в шестеренний насос керований електромагнітний клапан, що у важких дорожніх умовах буде дозволяти по команді водія в будь-якому режимі руху зменшувати прохідний перетин до діаметра менш 1 мм або взагалі повністю його закривати з розрахунком на запобіжний клапан по тиску і об’ємні втрати.
Thesis for a PhD Degree in Technical science: Specialty 255 – Armament and military equipment (25 – Military sciences, national security, state border security). – National Technical University “Kharkiv Polytechnic Institute”, the Ministry of Education and Science of Ukraine, Kharkiv, 2020. Relevance of the topic. The need for inter-wheel differentials (IWD) arose immediately after the appearance of the first two-wheel drive cars. Most notably, this need was manifested during turning and driving on rough roads. The absence of IWD in such transmissions caused power circulation, unreasonably large additional loads on the drive axle and wheels, increased fuel consumption and high tire wear. With the invention of the traditional symmetric bevel gear IWD, these problems were solved. However, there were other problems associated with the phenomenon of slipping in difficult road conditions. Naturally, this challenge has found a large number of technical solutions that somehow smoothed out the problem, but did not solve it comprehensively. In recent decades, design solutions have emerged in which the differential lock is controlled electronically by a given algorithm, as well as drives in which the traction control system directly controls the input torque of the drive wheel. These solutions are especially effective for electric or hydrostatic motor wheels. However, despite the abundance of technical solutions in the field of differential wheel drive, there is no effective IWD design for military wheeled and multi-purpose full-wheel drive vehicles. The existing designs either still use complete manual lock, or are based on SLLSD that are not able to provide high cross-country ability and good handling at the same time. Therefore, despite the rapid development of electronic control systems and individual electric drives, the development of an efficient, internally automated IWD is topical for military wheeled and multi-purpose full-wheel drive vehicles. The aim of the dissertation is to increase the traction dynamics of wheeled armored personnel carriers and multi-purpose full-wheel drive vehicles in difficult road conditions with high rates of economy and controllability by developing and using IWD with hydrostatic locking based on a gear pump. To achieve this aim it is necessary to solve the following tasks: – to study the influence of the structure and parameters of IWD on the dynamics of acceleration of the car in difficult road conditions using methods of numerical simulation; – to study the influence of the structure and parameters of IWD on the resistance to curvilinear motion and controllability using numerical simulation methods; – to evaluate theoretically and experimentally the possibility of implementing hydrostatic blocking without additional friction disks for the IWD of the BTR-4 armored personnel carrier and determine its necessary technical parameters; – to evaluate experimentally the characteristics of the standard cam IWD of the BTR-4 armored personnel carrier with the full hanging of one of the wheels; – determine the parameters of the IWD with hydrostatic blocking and conduct a study of the selected mobility parameters of the armored personnel carrier BTR-4, equipped with the proposed IWD, using numerical simulation. The scientific novelty of the results. The main scientific results that are submitted to the public defense are: – for the first time, the possibility of creating an IWD with hydrostatic locking without additional friction disks based on a gear pump for a wheeled armored personnel carrier has been scientifically substantiated; – for the first time, an energy method has been proposed for assessing the efficiency of IWD, which, unlike the existing ones, is based on losses not with constant movement, but when the vehicles is accelerated in difficult road conditions to a given speed; – for the first time, a method is proposed for assessing the influence of the structure and parameters of IWD on the resistance to curvilinear movement on paved roads, which, in contrast to existing methods, is based not only on the assessment of losses in the IWD during curvilinear movement, but also on losses due to wheel slippage along the road and an increase in the actual radius turning due to the deviation of the wheels rolling direction and their slipping; – The dependence of the locking moment on the slipping speed for a two-row cam IWD of the BTR-4 armored personnel carrier was experimentally obtained. The practical significance of the results. The studies made it possible to calculate the parameters of the gear pump for hydrostatic locking of the IWD, which, with minor changes, is mounting in the main gear housing of the BTR-4 armored personnel carrier and is able to replace the purchased Russian unit with the worst performance characteristics. The developed methods for evaluating the effectiveness of differentials in straight-ahead acceleration in difficult road conditions and in curved motion on paved roads provide the opportunity to carry out structural-parametric synthesis of not only IWD, but also center differential for military vehicles and multi-purpose full-wheel drive vehicles with mechanical transmission. The practical significance of the dissertation research results is confirmed by acts on the implementation of the proposed methods for evaluating the effectiveness of IWD in the design practice in the State enterprise “Kharkov Machine Building Design Bureau named after A.A. Morozov” and LLC “Mashhydroprivod”. An act was also received on the introduction of methods for evaluating the effectiveness of IWD into the educational process of the NTU “KhPI” when preparing students for specialty 133 – Sectoral Engineering, specializations 133.02 – Automated design of cross-country vehicles. Conclusions on the work: 1) From the analysis of literary sources, it was concluded that there is no technical solution in the field of IWD that would ensure high crossability (including with full hanging of the drive wheels), do not impair handling, have internal automatism, was quite simple and cheap to manufacture and reliable in operation. 2) For wheeled vehicles, the operation of which allows the possibility of hanging one or several wheels when moving, in the IWD, to ensure patency, it is necessary to use either full blocking, or anti-slip systems based on ABS, or self-locking differentials with a blocking moment depending on the difference or square of the difference in the frequency of relative rotation axle shafts and differential housings. The use of complete locking in existing structures requires either a complete stop of the machine before locking (unlocking) differentials or the use of friction discs, the locking of which requires additional power take-off to keep them closed and which, when the machine is actively used in difficult road conditions, wear out intensively. Unfortunately, for the use of traction control systems based on ABS, we do not have well-tested domestic ABS systems that could form the basis for the creation of a traction control system in conditions of military use. Therefore, it is advisable to use IWD with hydrostatic locking without the use of additional friction discs. 3) From the above analysis it follows that the most effective input parameter for most approaches to ensure automatic power distribution between the wheels is the kinematic inconsistency of the rotational speeds of the drive wheels and the position of the steered wheels. 4) When analyzing the patency of wheeled vehicles that allow the possibility of hanging one or several wheels when moving, it is necessary to operate with the concept of the differential locking moment, and not the blocking coefficient. 5) As a result of mathematical modeling and calculations using the BTR-4 armored personnel carrier as an example, the values of the maximum relative rotational speed of the half-axle and the IWD housing were obtained, which can occur due to the difference in the rotational speeds of the wheels of different sides when maneuvering on paved roads. Also obtained are the dependences of the blocking moment of the IWD, necessary to ensure high crossability, on the frequency of the relative rotation of the axle shaft and the housing of the IWD. It was found that the optimum blocking moment should increase from zero to a maximum value of 3000 Nm, respectively, with an increase in the relative rotational speed of the half-axle and differential housing from 80 to 115 min-1. 6) Of the considered constructions of IWD on the dynamics of acceleration in difficult road conditions for average values of the proportionality coefficients, IWD have an advantage in which the degree of blocking depends on the load. 7) With the selected proportionality coefficients of the system for small steering angles (up to 8) in the first three quarters of the safe speed range and in terms of turning resistance and increasing turning radius, IWDs have an advantage, in which the degree of blocking depends on the square of the difference in speed of the half-axles. 8) The IWD, in which the degree of blocking depends on the square of the difference of the speeds of the axle shafts, also have an advantage for large steering angles of the steered wheels in the first half of the safe speed range. But at speeds close to turning over, they are behind from IWD, in which the degree of blocking depends on the load, for any angle of rotation of the steered wheels. 9) The IWD with a traction control system based on ABS are most suitable for use with relatively small values of the imbalance of adhesion coefficients on the sides of the car and integrate them with directional stability systems that allow you to easily change the value of the proportionality coefficients (system setting) depending on the situation. 10) For off-road vehicles, the operation of which does not imply modes with full hanging of the drive wheels, it is possible to use IWD effectively, in which the degree of blocking depends on the load. 11) For off-road vehicles and military wheeled vehicles, during operation of which full hanging of the drive wheels is possible, it is advisable to use an IWD with a locking moment, which depends on the square of the difference in the speeds of rotation of the axle shafts. They can have high energy performance during acceleration with minimal negative impact on the controllability of the machine and at the same time rely not on electronic control systems, but on their own internal automation. 12) The tests showed that the traction force of the drive axle with a double-row cam differential when one of the wheels (right) is fully hung out substantially depends on the speed of the slipping wheel. It reaches a maximum value of 1091 N at a rotational speed of a slip wheel of 399 rpm. This speed corresponds to the rotation of the input flange of the drive axle for the movement of the armored personnel carrier at a speed of 11 m / s (39.6 km / h), after which the differential is jammed. 13) The obtained values for the traction force of the drive axle with a double-row cam differential with full hanging of one of the wheels (right) are insufficient for the armored personnel carrier to overcome obstacles of the “ravine” type or “dune” type with diagonal hanging and obstacles of the “moat” type with sequential suspension of bridges. 14) Based on a gear pump with internal gearing, it is possible to realize a IWD with hydrostatic locking without the use of additional friction disks. This differential has a quadratic dependence of the locking (braking) moment on the difference in the angular velocities of the half-axle and the differential housing. This allows, on the one hand, to obtain almost complete differential blocking during slipping and, on the other hand, to provide minimal turning resistance when maneuvering on paved roads. 15) For the BTR-4 armored personnel carrier, the working volume of the gear pump with internal gearing, which allows maximum grip on the road when locking on a non-skid wheel, is 415 cm3. Such a pump is successfully assembled in the dimensions of the standard main gear (final drive) when replacing the existing cam differential with a classic open differential with bevel gears. 16) The optimum design diameter of the droselling hole is 2 mm. However, depending on the accuracy of manufacture of the gear pump elements and the total volume losses, this value should be experimentally adjusted downward. 17) Cycloidal gear gerotor pumps have been discontinued due to the difficulty of realizing high pressure in them due to the low coefficient of overlap of tooth profiles. For the synthesis of IWD with internal automaticity, which would satisfy the requirements for both traction and vehicle dynamics and at the same time not impede its curvilinear movement, the differential is finally adopted, in which the value of the blocking moment depends on the square of the difference in the angular velocities of the half-axles. 18) MKD with the moment of blocking, which depends on the load (including the standard two-row cam differential), quite successfully compete with the considered differentials with hydrostatic locking in terms of operating efficiency in difficult road conditions, but without fully hanging one of the wheels. 19) For MCD with hydrostatic locking, it is enough to have a diameter of a throttling hole of more than 3 mm for an unhindered start of rotation of the armored personnel carrier and its curvilinear movement without a significant increase in energy consumption and deterioration of controllability over the entire range of travel speeds. 20) In order to obtain the necessary cross-country ability and driving dynamics in difficult road conditions, for a MCD with hydrostatic locking, it is necessary to have a diameter of the droselling hole of not more than 1 mm. 21) To eliminate the contradiction, it is proposed to put a controlled solenoid valve in the gear pump, which in difficult road conditions will allow, at the command of the driver, in any driving mode to reduce the bore to a diameter of less than 1 mm or even completely closing it with the pressure relief valve in mind and volumetric losses in the pump.

Alterations in respiratory function and gas exchanges are frequently seen in patients during anaesthesia and in the post-operative period. Mechanical ventilation and drugs such as neuromuscular blocking agents can alter normal function of the respiratory system and cause damage to lungs. Protective ventilation strategies should always be adopted intra-operatively in mechanically-ventilated patients. A neuromuscular monitoring-guided use of decurarizating agents and post-operative adequate analgesia techniques are recommended to avoid post-operative residual curarization and pain. Pneumonia is the most frequent infective complication, but at the moment there are no recommended clinical tools (scoring systems) to identify patients at high. A fast-track surgical approach and early can decrease the risk. Early mobilization and prophylactic low molecular weight heparins use have a well-documented efficacy on prevention of pulmonary embolism. There is still no general consensus on the widespread use of early NIV in post-operative patients, although in selected high-risk patients it could help respiratory recovery and reduce complications.

This article discusses the magnetic properties of nanoparticles. It first considers magnetic domains and the critical size for single-domain behavior of magnetic nanoparticles before providing an overview of magnetic anisotropy in nanoparticles. It then examines magnetic dynamics in nanoparticles, with particular emphasis on superparamagnetic relaxation and the use of Mössbauer spectroscopy, dc magnetization measurements, and ac susceptibility measurements for studies of superparamagnetic relaxation. It also describes magnetic dynamics below the blocking temperature, magnetic interactions between nanoparticles, and fluctuations of the magnetization directions. Finally, it analyzes the magnetic structure of nanoparticles, focusing on magnetic phase transitions and surface effects, non-collinear spin structures, and magnetic moments of antiferromagnetic nanoparticles.

Relational Inequalities focuses on the organizational production of categorical inequalities, in the context of the intersectional complexity and institutional fluidity that characterize social life. Three generic inequality-generating mechanisms—exploitation, social closure, and claims-making—distribute organizational resources, rewards, and respect. The actual levels and contours of the inequalities produced by these three mechanisms are, however, profoundly contingent on the historical moments and institutional fields in which organizations operate. Organizational inequality regimes are comprised of the resources available for distribution; the task-, class-, and status-based social relations within organizations; formal and informal practices used to accomplish goals and tasks; and internal cultural models of people, work, and inequality, often adapted from the society at large to fit local social relationships. Legal and cultural institutions as they are filtered through workplace inequality regimes steer which groups are exploited and excluded, blocking or facilitating the conditions that lead to exploitation and closure. Sometimes exploitative and closure claims-making are naked and open for all to see; more often, they are institutionalized, taken for granted, and legitimated, sometimes even by those being exploited and excluded. The implications of RIT for social science and equality agendas are discussed in the conclusion. Case studies examine historical and contemporary workplace inequality regime variation in multiple countries. The role of intersectionality in producing regime variation is explored repeatedly across the book. Many occupations and industries are examined in depth, with particular attention given to engineers, CEOs, financial service, airlines, and information technology industries.

Prayer on stage might, at points, have been felt to be real. Private prayer was made in the wider context of a domestic performance culture, in which people sang, danced, played, and read aloud to each other. Such prayer was seen as a dialogue, not a charm, so, when it came to staged prayer, the actor and audience were primed to understand that God was listening with them to a character speak to him. Passages of solitary prayer would have got the same rehearsal, under the same conditions, as a real private prayer. A moment of prayer in a play lets actors revive a sense of the options open to their character (blocking out for the moment their knowledge of what subsequently happens), thus aiding the blending of actor into character. Prayer that is worded conventionally, in particular, may encourage audiences to respond as they do to such signals off stage.

Plastic surgery can be considered an art form, molding and shaping areas of the body to provide enhancement and visual improvements. During this process, anesthesia is a key role player, for both local and general aspects. Proper combinations of local and general anesthesia can provide not only great pain relief and the ability to perform the artwork of plastic surgery, but can also lead to better and faster postoperative recovery of patients. Take a moment to imagine doing our skills without anesthesia, not only would it be barbaric, but also unethical. The method of using fan-shaped anesthesia application will be explored as a technique to improve patient recovery. This, instead of the classic straightforward areal injection application, seems to provide improved anesthetic distribution, penetrates layers better, and offers a swifter and more efficient way of blocking pain receptors. Choosing an appropriate anesthetic from the various ones available today is very important for pain control and postoperative recovery, as well as combining it with other drugs to increase its duration of action. This medley of drug combinations provides patient satisfaction and enhanced recovery.

Highlights how the negotiators were able to work collaboratively to successfully reach agreement, while blocking the efforts of various spoilers who wished to derail the water negotiations. Dealing with Spoilers tells the story of how this was achieved, as the negotiators utilized political power, built relationships of trust across the negotiating table, and strategically managed communications with the press and the media. Leading through Ingenuity underscores the importance of facilitative leadership, as the key players on each side read the negotiation proceedings in real time to improvise, reassess, caucus, and clarify with each other in small informal settings, to refocus and redefine their delegation’s negotiation strategies. Finally, Testing the Ways to Agreement explains how the negotiating parties used points of provisional accord in order to maintain momentum, creatively propose options without committing, evaluate multiple packages, and move toward consensus, to the ultimate success of the Colorado River binational negotiation process.

To develop low-pollution burners, the effect of inlet blocking on NO formation in a swirl coal combustor is studied by numerical simulation. An algebraic unified second-order moment turbulence-chemistry model and a simplified Solomon model of HCN release for NO formation are proposed. These models are incorporated into a full two-fluid model of reacting gas-particle flows and coal combustion. The sub-models are the k-ε-kp two-phase turbulence model, the EBU-Arrhenius volatile and CO combustion model, the six-flux radiation model, coal devolatilization model and char combustion model. The effect of inlet blocking position on NO formation in a swirl coal combustor is studied. The predicted temperature, turbulence intensity, coal concentration and NO concentration were obtained. The prediction results for typical cases are in good agreement with the experimental results reported in references, indicating that the numerical models are appropriate. The prediction results indicate that the blocking between the primary-air flow and the secondary-air flow will increase the turbulence intensity, but increase the coal concentration and reduce the temperature in the near-inlet zone, hence can remarkably reduce the NO formation.

Origami-inspired active structures have important characteristics such as reconfigurability and the ability to adopt compact flat forms for storage. A self-folding shape memory alloy (SMA)-based laminated sheet is considered in this work wherein SMA wire meshes comprise the top and bottom layers and a thermally insulating compliant elastomer comprises the middle layer. Uncertainty in various parameters (e.g. material properties) may affect the performance of the sheet, which is explored here. Different modeling approaches are studied in order to compare their accuracy and computational cost. A numerical approach based on the Euler-Bernoulli beam theory is selected due to its accuracy when compared to higher fidelity finite element simulations and its low computational cost, necessary to perform a large number of design evaluations as required for uncertainty analysis. Optimization is performed considering uncertainty in the material properties. Failure probabilities under mechanical constraints and expected values of fold curvature and blocking moment are considered during optimization of the self-folding sheet. The multiobjective genetic algorithm for technology characterization P3GA is used to obtain the Pareto dominant designs. Most designs forming the Pareto frontier have the same values for certain design parameters such as the distance between the wires in the SMA meshes non-dimensionalized by SMA wire thickness, elastomer layer thickness non-dimensionalized by SMA wire thickness, and applied temperature. The design parameter deciding the trade-off between fold curvature and blocking moment is found to be the SMA wire thickness.

Reactive precipitation in micro- and minichannels currently draws attention of both, chemists and engineers in the field of micro process engineering. Due to intensified mixing and improved heat and mass transfer, fast chemical and thermodynamical processes involved in precipitation can be controlled readily in micro or mini structures. Particularly microchannels are a promising technology for particulate processes allowing continuous operation along with little or no backmixing. However, the sensitivity of microscale channels to blocking and fouling requires careful design and appropriate peripheral equipment. This study presents experimental results of barium sulfate precipitation from barium chloride solution and sulfuric acid in both, T-shaped and injection micromixers. The measured particle size distributions (PSD) are characterized by their first and second moment, reflecting the correlation between fluidic mixing and precipitation: faster mixing results in smaller mean particle sizes (1st moment of the PSD). The homogeneity of the mixing process on the other hand should have impact onto the width of the distribution (2nd moment of the PSD) due to superposition of locally formed particles to the global size distribution. The experimental particle size distributions are compared with simulations based on reduced-order modeling of the diffusive mixing process, coupled with the population balance for particle nucleation and growth. While the simulated size distributions have mean diameters between 40 nm and 68 nm, experimental data are between 90 nm and 130 nm.

In this research, the two-phase slug regime is investigated analytically with an engineering approach. due to the velocity gradient in the layers of the two-phase flow, numbers of waves form and grow in the liquid phase and may block the duct which in this case is called slug. Blocking the flow, it causes higher pressure accumulation which is the main reason of slug’s momentum through the duct. Simplifying the slug’s geometry and using basic physics laws yielded an equation between the slug’s back pressure and its length.

The proton-exchange membrane (PEM) fuel cell works under low temperatures and hence is suitable for the automotive industry. The produced water vapor in the vicinity of the membrane may condense into liquid water, if the water mass fraction is higher than the saturation value corresponding to the local temperature. In this case the flowing fluid inside the layers of the PEMFC is a 2-phase flow. The locally homogeneous flow (LHF) model has been previously used for modeling the 2-phase flow in PEM fuel cells, with limited success. This model could not predict the blocking effect of the liquid phase, since both phases flow locally with the same velocity, according to the LHF model. In contrast to complete coupling of the two phases, assumed by the LHF model, a blocking model was used by some investigators where the liquid is totally uncoupled to the gas phase. This assumption causes the liquid to become essentially stationary inside the pores of the GDL and catalyst layers and hence only the gas phase equations need to be considered. Both of these extreme models were only successful to a limited extent. The present work considers a two-fluid mathematical model for the gas-liquid flow in PEM fuel cells. One fluid represents the continuous gas phase flow through the layers of the fuel cell. For this fluid, the governing equations of momentum, energy, mass continuity and species mass fractions, are considered with additional inter-fluid exchange source terms. The second fluid represents the dispersed liquid phase that is formed from the condensed water vapor inside the layers of the PEM fuel cell. For this fluid only the momentum, energy and mass continuity equations need to be included, as no electrochemical reactions are essentially possible. The dispersed fluid is made up of small droplets in the gas channel. However, in the porous layers of the fuel cell, the flowing layers of water represent the dispersed fluid over the solid matrix. The thickness of the creeping water layers is controlled by the wetability of the solid matrix of the porous layers of the PEM fuel cell. Numerical computations are carried out for a typical proton exchange membrane fuel cell that has experimental data. In order to obtain complete performance results, the computations are repeated for increasing fuel cell electric current densities until the limiting current is reached. The obtained two-fluid and single-phase simulations are compared with the corresponding experimental and numerical data available in the literature. The 2-fluid model shows that the blocking effect of the liquid phase starts to dominate, for cell voltage less than 0.65 V; in this case, the flowing 2-phase flow produces faster drop in cell voltage as the loading electric current increases. This phenomenon was partially hindered by the LHF model but essentially completely bypassed by the single-phase simulations. The 2-fluid simulations show that most of the liquid dispersed phase is concentrated in the cathode, reaching maximum value near the cathode catalyst layer- membrane interface. This behavior results from the lack of mobility of the liquid water inside the pores.

This paper presents results from adjoint-based optimization processes applied to an inlet pipe of an exhaust gas recirculation cooler in a diesel engine. The boundary conditions applied resemble those of a truck at cruising speed. Three implementations are considered for the gradient calculations with the objective of minimizing the total pressure drop through the pipe. In the first implementation the gradients are evaluated with respect to the motion of the center of the cell using a newly presented implementation based on the ALE formulation of the Navier-Stokes equations. The results are compared to the surface sensitivities, where the gradient of the cost function is evaluated with respect to the normal motion of the surface of the pipe. In the last approach a topological optimization is performed where the gradients are evaluated with respect to a momentum loss in each cell. This gives information that is used when blocking the cells.

A usage of multi-legged structures in ice conditions involves some peculiarities that should be taken into account both while designing the platform and while planning technological operations nearby it. In 2010–2013 a range of theoretical and experimental studies were performed at the Krylov State Research Centre, St. Petersburg, Russia. The work aimed to investigate main peculiarities of multi-legged structure interaction with ice, such as 1). mutual influence on ice action on each leg, 2) jamming of the inner space between legs and blocking the space between the front legs with ice floes, and 3) arisen yaw moments about the platform vertical axis due to unsymmetrical ice action on the legs. Three series of model tests with various multi-legged structures models were carried out in the Ice Basin. The presented in the paper main results show effect of key parameters on the interaction processes and on the ice action. During the tests the following parameters were varying: distance between the legs, ice drift speed and direction, broken ice concentration and the ice pieces size. Also, the paper contains results of numerical simulations of some tested scenarios in broken ice conditions. The numerical model is based on discrete element method, and it enables to extend a range of the investigations.

A three-dimensional, multi-component, two-fluid model developed in the commercial CFD package CFX 13 (ANSYS inc.), is used to investigate the effect of porous media compression on transport phenomenon of a PEM Fuel cell (PEMFC). The PEMFC model only consist of the cathode channel, gas diffusion layer, micro-porous layer and catalyst layer, excluding the membrane and anode. In the porous media liquid water transport is described by the capillary pressure gradient, momentum loss via the Darcy-Forchheimer equation and mass transfer between phases by a non-equilibrium phase change model. Furthermore, the presence of irreducible liquid water is taken into account. In order to account for compression, porous media morphology variations are specified based on the GDL throughplane strain and intrusion which are stated as a function of compression. These morphology variations affect gas and liquid water transport, and hence liquid water distribution and the risk of blocking active sites. Hence, water transport is studied under GDL compression, in order to investigate the qualitative effects. Two simulation cases are compared; one with and one without compression.

We consider a stress-assist chemical reaction front propagation in a deformable solid undergoing a localized chemical reaction between solid and gas constituents. The reaction is sustained by the diffusion of the gas constituent through the transformed solid material. We introduce a chemical transformations strain tensor that relates two reference configurations of solid constituents. Then mass, momentum and energy balances are written down for the open system considered and the expression of the entropy production due to the reaction front propagation in a solid with arbitrary constitutive equations is derived. As a result, the expression of the chemical affinity tensor is obtained. Kinetic equation for the chemical reactions front propagation is formulated in a form of the dependence of the front velocity on normal components of the chemical affinity tensor. The locking effect — blocking the reaction by stresses is demonstrated. Finally the kinetic equation for the bulk chemical reaction is derived in a form of the dependence of the reaction rate on the first invariant of the chemical affinity tensor.

An experimental study was conducted to investigate the film cooling performance on the suction side of a first stage turbine vane. Tests were conducted on a nine times scale vane model at density ratios of DR = 1.1 and 1.6 over a range of blowing conditions, 0.2 ≤ M ≤ 1.5 and 0.05 ≤ I ≤ 1.2. Two different mainstream turbulence intensity levels, Tu∞ = 0.5% and 20%, were also investigated. The row of coolant holes studied was located in a position of both strong curvature and strong favorable pressure gradient. In addition, its performance was isolated by blocking the leading edge showerhead coolant holes. Adiabatic effectiveness measurements were made using an infrared camera to map the surface temperature distribution. The results indicate that film cooling performance was greatly enhanced over holes with a similar 50° injection angle on a flat plate. Overall, adiabatic effectiveness scaled with mass flux ratio for low blowing conditions and with momentum flux ratio for high blowing conditions. However, for M < 0.5 there was a higher rate of decay for the low density ratio data. High mainstream turbulence had little effect at low blowing ratios, but degraded performance at higher blowing ratios.

This short pedagogical movie illustrates an effect in nuclear physics called backbending which was first observed in the study of the rotational behavior of rapidly rotating rare-earth nuclei in Stockholm, Sweden in 1971. The video contains a mechanical analog utilizing rare-earth magnets and rotating gyroscopes on a turntable along with some historic spectra and papers associated with this landmark discovery together with its explanation in terms of the Coriolis induced uncoupling and rotational alignment of a specific pair of particles occupying high-j intruder orbitals. Thus backbending represents a crossing in energy of the groundstate, or vacuum, rotational band by another band which has two unpaired high-j nucleons (two quasi-particles) with their individual angular momenta aligned with the rotation axis of the rapidly rotating nucleus. Backbending was a major surprise which pushed the field of nuclear structure physics forward but which is now sufficiently well understood that it can be used as a precision spectroscopic tool providing useful insight for example, into nuclear pairing correlations and changes in the latter due to blocking effects and quasi-particle seniority, nuclear deformation, the excited configurations of particular rotational structures and the placement of proton and neutron intruder orbitals at the Fermi surface.