Judul: Turbulence Intensity in Two Palm Oil Plantation (Case Study : Pompa Air village and PTPN VI Jambi
Abstrak: Angin mempengaruhi pertumbuhan, perkembangan, dan produksi tanaman melalui mekanisme pertukaran bahang, CO2 , serta momentum antara tanaman dengan lingkungan. Terjadinya gerakan acak atau perturbasi arah dan kecepatan angin disebut dengan turbulensi. Analisis data yang dilakukan pada dua lokasi perkebunan kelapa sawit yaitu desa Pompa Air (umur tanaman 2.5 tahun) dan PTPN VI Jambi (umur tanaman 10.5 tahun) untuk menentukan perbedaan intensitas turbulensi di kedua lokasi. Perhitungan dan analisis menghasilkan karakteristik kekasapan permukaan berupa perpindahan bidang nol (d), panjang kekasapan (zo) dan kecepatan kasap (u*) meningkat seiring bertambahnya umur tanaman. Nilai parameter kekasapan permukaan yaitu d, zo dan u* di perkebunan desa Pompa Air berturut-turut yaitu 1.67 m, 0.004 m dan 0.03 m/s lebih rendah dibandingkan dengan PTPN VI yaitu 7 m, 0.03 m dan 0.08 m/s. Karakteristik kekasapan dan stabilitas atmosfer sangat besar pengaruhnya terhadap pembentukan turbulensi di suatu lokasi. Secara umum, pada kondisi atmosfer tidak stabil, proses pemanasan permukaan oleh radiasi matahari menyebabkan terbentuknya pengangkatan massa udara keatas (bouyancy) yang mencapai nilai tertinggi pada tengah hari (12.00-14.00 WIB). Variasi diurnal stabilitas atmosfer di PTPN VI menunjukkan periode stabil yang lebih panjang dibandingkan desa Pompa air yang berkorelasi positif dengan turbulensi. Nilai intensitas turbulensi sebanding dengan rasio antara standar deviasi dari kecepatan angin dengan kecepatan angin rata-rata pada ketinggian tertentu. Variasi diurnal intensitas turbulensi pada perkebunan perkebunan PTPN VI berturut-turut terhadap ketinggian yaitu 0.89, 0.97, 0.98. Nilai tersebut lebih tinggi dibandingkan di perkebunan desa Pompa Air yaitu berkisar 0.5, 0.64 dan 0.68. Nilai intensitas turbulensi meningkat dengan pertambahan ketinggian. Semakin tinggi intensitas turbulensi maka masukan CO2 ke permukaan kanopi semakin banyak dan mengakibatkan semakin efektif proses fotosintesisnya.
Keyword: Intensitas turbulensi,, kecepatan kasap, kekasapan permukaan, panjang kekasapan, perpindahan bidang nol.

Judul: The dynamics of surface boundary layer characteristics above oil palm plantation
Abstrak: Penelitian yang dilakukan di dua lokasi perkebunan sawit, yaitu di Desa Pompa Air, Jambi (umur 2 tahun) dan di PT. Perkebunan Nusantara VIII, Cimulang, Jawa Barat (umur 8-10 tahun) menunjukkan bahwa karakteristik kekasapan (perpindahan bidang nol (𝑑��), kecepatan kasap (𝑢��∗), dan panjang kekasapan (𝑧��0)) meningkat dengan bertambahnya umur tanaman. Parameter kekasapan ini menentukan dinamika profil-vertikal kecepatan angin, intensitas turbulensi, energi kinetik turbulensi (TKE), dan juga transfer momentum serta bahang (terasa dan uap air). Berdasarkan hasil yang diperoleh pada kedua lokasi perkebunan, kecepatan angin di dekat permukaan akan mengalami disturbansi dan menurun secara logaritmik karena gesekan dengan permukaan yang berkorelasi positif dengan koefisien drag (𝐶��𝐷��). Nilai 𝐶��𝐷�� sebanding dengan kuadrat rasio antara kecepatan tangensial parsel udara karena turbulensi mekanik dengan kecepatan angin rata-rata pada ketinggian tertentu. Nilai koefisien drag pada kondisi netral 𝐶��𝐷�� cenderung menurun terhadap pertambahan kecepatan angin. Pada kondisi atmosfer tidak stabil, proses pemanasan permukaan oleh radiasi matahari mendorong terbentuknya pengangkatan massa udara ke atas (buoyancy) yang mencapai puncak pada tengah hari (12.00-14.00 WIB). Semua mekanisme ini menyebabkan gerakan acak aliran massa udara dan mengubah energi kinetik serta potensial aliran pada suatu ketinggian menjadi TKE. Analisis menunjukkan TKE memiliki korelasi yang tinggi dengan transfer bahang terasa dan uap air. Hal ini menunjukkan bahwa turbulensi lebih efektif dalam proses pencampuran dibanding melalui proses difusi molekular., The research conducted in two separated oil palm plantation sites, i.e. in Pompa Air Village, Jambi (2 years old of oil palm) and in PT. Perkebunan Nusantara VIII, Cimulang, West Java (8-10 years old of oil palm) showed that the roughness parameters including zero-plane displacement (𝑑�), friction velocity (𝑢�∗), and roughness length (𝑧�0) increase with the rise of the age of plants. These parameters play a crucial role in affecting the dynamics of wind vertical-profile, turbulence intensity, turbulence kinetic energy (TKE), as well as momentum and heat (sensible and latent) transport mechanisms. Based on the results, above the plant canopies of both of plantation sites, the wind speed will be disturbed by and logarithmically decreased downward to just above the roughness elements by the surface shear stress which has postitive correlation with the drag coefficient (𝐶�𝐷�). Value of 𝐶�𝐷� is equivalent to square of ratio between the tangential velocity of air flow generated by mechanical turbulence and wind speed at certain height. Above both of plantation sites in neutral atmospheric condition 𝐶�𝐷� tended to decrease with the increase of wind speed. In addition, in unstable atmospheric condition, surface heating process by short wave radiation generates buoyancy reaching its peak at mid-day (12 am - 2 pm). All of these mechanisms cause chaotic air flow and convert kinetic and potential energy of stratified mean flow into TKE. Based on result, TKE had high correlation with sensible heat flux and latent heat flux as well. It showed that turbulence has more efficient mixing mechanism than molecular diffussion process. Keywords: roughness parameters, zero-plane displacement, friction velocity, roughness length, turbulence, TKE, drag coefficient, momentum flux, heat flux
Keyword: kekasapan permukaan, perpindahan bidang nol, kecepatan kasap, panjang kekasapan, turbulensi, TKE, koefisien drag, transfer momentum, transfer bahang

Judul: Algorithm Construction of HLI Hash Function
Abstrak: Cryptography is a study of mathematical techniques related to aspects of information security regarding on confidentiality, data integrity, entity authentication, and data origin authentication. Data integrity is a service, which is associated with the conversion of data carried out by unauthorized parties. To maintain data integrity, one can use hash functions. An hash function is a computationally efficient function to map an arbitrary length bitstring to a fixed length bitstring called as hash value. The use of hash function in maintaining the information integrity and authentication is in digital signatures, virus protection, and software distribution. Illustration of the hash function in the integrity and authentication of information that is emailed as follow. The sender sends the information and hash value to the recipient. If the hash value of the information is equal to the hash value that is sent by the sender, then information has not been changed. Otherwise the information has been changed. An hash function has two properties, one way and collision resistance. An hash function is called one way if it is computationally infeasible to find any input such that when given any hash value . Meanwhile an hash function is called collision resistant if it is computationally infeasible to find any two inputs where such that . The purpose of this study is to construct a HLI hash function algorithm, to analyze the speed and security of the hash functions as a results of construction. Furthermore, it is to compare it with SWIFFT. Hash function is constructed based on the result of algebraic operations on modular polynomial ringwith . Modular polynomial ring noted as is a set of all polynomials of degree at most with coefficients in . can be represented as a set of integer vector of modulo in dimension . So, it is simple to implement in a computer. In vector operations, is lattice . Furthermore, alattice that is defined from certain polynomial ring is called ideal lattice. HLI hash function is consists of addition and multiplication algorithm in the ring. Addition algorithm consists of sumation operations of modulo and multiplication consists of multiplication operations of modulo . Generally, algorithm of HLI hash function consists of multiplication operations of modulo and addition operations of modulo . However, if the input is binary number then multiplication algorithm only consists of multiplication operation of modulo , so algorithm of HLI hash function consists of multiplication operations of modulo and addtion operations of modulo . An hash function is secured if it has two properties, i.e., one way and collision resistance. HLI hash function hash is one way, it is following the proof of Micciancio. It is has collision resistant because of polynomial is irreducible over and monic. Moreover, it is proved that for every unit vector , the vector is small vector. If the input of hash function is a binary number then HLI hash function only involves addition operations of modulo . So the time that used almost same with SWIFFT. The excellence of HLI hash function is the key size smaller than SWIFFT. This effect on
Keyword: hash function, modular polynomial ring, lattice